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Catalytic CO 2hydration by immobilized and free human carbonic anhydrase II in a laminar flow microreactor –Model and simulationsIon Iliuta,Maria Cornelia Iliuta,Faical Larachi ⇑Department of Chemical Engineering,Laval University,Québec,Canada G1V 0A6a r t i c l e i n f o Article history:Received 2April 2012Received in revised form 9November 2012Accepted 9January 2013Available online 26January 2013Keywords:Laminar flow microreactor CO 2hydrationHuman carbonic anhydrase II Modeling Simulationa b s t r a c tEx vivo applications of human carbonic anhydrase II (HCA II)for its potential in CO 2capture technologies are emerging owing to the formidably large hydration turnover number Nature endowed this enzyme with to catalyze aqueous hydration of CO 2near diffusion limits.In this work,we investigated the CO 2hydration process catalyzed by solution-phase or immobilized HCA II enzyme in a laminar flow microreactor with the purpose to simulate the reaction–transport of HCA II in microchannels.The effects of operating condi-tions as well as the contribution of carbonic anhydrase on the performances of the CO 2hydration process are presented.Numerical simulations indicate that in laminar flow microreactor with HCA II immobilized on the inner surface of the tube,interpreting the data as a one-dimensional plug flow results will lead to significant error.Therefore,coupling of transport phenomena and surface enzymic reaction necessitates the use of a two-dimensional analysis.Simulations reveal that hydrodynamic and diffusional constraints do not permit reasonable utilization of the immobilized HCA II enzyme in a laminar flow microreactor,even if HCA II has a very high hydration turnover and the uncatalyzed bulk CO 2hydration is the dominant pro-cess.In the microreactor with solution-phase HCA II enzyme ‘‘plug flow’’is achieved under laminar flow conditions and the contribution of uncatalyzed CO 2hydration process is not considerable.Ó2013Elsevier B.V.All rights reserved.1.IntroductionThe reversible hydration of carbon dioxide catalyzed by human carbonic anhydrase II (HCA II)in aqueous solutions has been exten-sively investigated,mainly from a biochemistry and catalytic standpoint [1–4].HCA II-catalyzed CO 2=HCO À3inter-conversion plays a significant role in a multitude of physiological processes such as pH homoeostasis,respiratory gas exchange,photosynthe-sis,ion transport,as well as it is a fairly important reaction for drug design [5]and has been thoroughly investigated and described in a number of reviews [6–9].Emerging ex vivo applications of HCA II for its potential use in CO 2capture and sequestration technologies have recently at-tracted the researchers’attention [10,11].The main incitement to this interest is the very high hydration turnover,k h %106s À1,and 2nd-order rate constant,k h =K CO 2%108M À1s À1,that Nature endowed this enzyme with to effectuate catalytic hydration of CO 2near the limits imposed by diffusion encounters in aqueous media [12].Unfortunately,application of free HCA II enzyme in solution-phase is not always suitable and optimal because of the large volume of enzyme required.Binding of HCA II enzyme on a solid support is an attractive modification of its application having several advantages,including easier separation of the reaction products without catalyst contamination,ability to recover and re-use the enzyme,increase of the enzyme stability and operational lifetime,continuous operation of enzymatic processes and flexibil-ity of the reactor design [13,14].However,attaching HCA II to a so-lid macrosurface may lead the enzyme to behave differently [14]because:(i)the immobilization may cause the enzyme molecules to adopt a different conformation;(ii)the immobilized enzyme ex-ists in an environment different from that when it is in solution-phase;(iii)there is a partitioning of substrate between the solution and support,with the result that the substrate concentration in the neighborhood of the enzyme may be significantly different from that in the bulk solution;and (iv)diffusional effects play a more important role with immobilized enzymes.The present contribution focuses on the CO 2hydration process catalyzed by solution-phase or immobilized HCA II enzyme in a laminar flow microreactor –which allows strict control of reaction conditions in time.The objective lies on exploring the possibility to use this micro enzyme reactor system as a tool for further under-standing and development of CO 2hydration process with a view to elaborate a comprehensive theoretical framework of these sys-tems and to apply it for experimental data reduction.The behavior of CO 2hydration laminar flow microreactor with human carbonic anhydrase attached to the inner surface of the tube was explored using a detailed kinetic model developed for reversible CO 2hydra-tion catalyzed by solution-phase HCA II (pseudo random Quad1383-5866/$-see front matter Ó2013Elsevier B.V.All rights reserved./10.1016/j.seppur.2013.01.006⇑Corresponding author.E-mail addresses:ion.iliuta@gch.ulaval.ca (I.Iliuta),maria.iliuta@gch.ulaval.ca (M.C.Iliuta),rachi@gch.ulaval.ca (rachi).Quad Iso Ping Pong mechanism with one transitory complex[15]). Particular attention has been given to the following items:(i)util-ity of the numerical simulations for refining the reactor operating conditions when determining the catalyzed CO2hydration kinetics data in a laminarflow microreactor with immobilized human car-bonic anhydrase,(ii)numerical identification of conditions,if any, to approximate plugflow operation,and(iii)evaluation of the ef-fects of uncatalyzed CO2hydration and two-dimensionality of the flow on laminarflow microreactor performance.Finally,we reveal the difficulties that result in interpreting the data obtained when HCA II is immobilized on the microreactor wall.minarflow microreactor modelThe system considered consists of a circular tube with solution-phase HCA II enzyme or with HCA II enzyme uniformly attached on its inner surface.The microreactor is isothermal.The entireflow in the tube may be viewed as consisting of three sections[13]:the so-called hydrodynamic inlet section,the concentration inlet section, and the fully developed section.In the hydrodynamic inlet section the initiallyflat liquid velocity profile evolves toward a parabolic velocity profile which remains translationally invariant in the downstream direction.The hydrodynamic inlet section is esti-mated to be fairly short(less than1mm)compared to the total length of the tube(0.1m)and we may consider that the laminar flow with a parabolic velocity profile is developed from the en-trance of the tube.Owing to the enzymatic reaction in solution-phase or on the tube wall and the diffusion of substrate towards the wall,the initiallyflat concentration profile changes gradually and becomes fully established in the third region.Flat entrance velocity profile would tend to shorten residence time of liquid lay-ers nearby the wall.In the presence of the chemical reaction,this leads to radial reactant concentration gradients which are larger than those with parabolic velocity profiles.Hence,‘‘all-through’’parabolic velocity profiles are expected to lead to lesser conver-sions thanflat entrance velocity profiles evolving towards para-bolic.However,it is reasonable to assume that our simulations lead to conservative estimation of CO2conversion in the presence of solution-phase HCA II enzyme or HCA II immobilized enzyme.The pseudo random Quad Quad Iso Ping Pong mechanism with one transitory complex,which implies a possible competitive in-ter-molecular proton transfer step by the CO2=HCOÀ3pair with re-spect to external buffer(B),was used to describe the reversible hydration of carbon dioxide catalyzed by human carbonic anhy-drase II[15]:CO2þZnOHÀðEÞ¢ZnHCOÀ3ðESÞð1ÞH2OþZnHCOÀ3ðESÞ¢HCOÀ3þZnH2OðE WÞð2ÞE W¢H Eð3ÞBþZnH2OðH EÞ¢BHþþZnOHÀðEÞð4ÞHCOÀ3þZnH2OðH EÞ¢CO2þH2OþZnOHÀðEÞð5ÞThe mechanism of uncatalyzed hydration of CO2and dehydra-tion of H2CO3under the conditions used in enzymatic process was described in the following way[16]:H2OþCO2¢k31k13HþþHCOÀ3ð6ÞHþþHCOÀ3¢k12k21H2CO3ð7ÞH2OþCO2¢k32k23H2CO3ð8Þ2.1.Model for CO2hydration laminarflow microreactor with immobilized HCAII enzymeThe unsteady-state mass balance equations for a chemical species j in the liquid phase are formulated taking into account that in laminarflow regime the transport in the lateral direction occurs as a result of molecular diffusion only and the transport in the longitudinal direction occurs by both advection and diffusion:@C CO2@tþ2m‘1ÀrR2@CCO2@z¼D CO2@2C CO2þD CO21@r@C CO2ÀR ucCO2ðC jÞð9Þ@C HCOÀ3þ2m‘1Àr 2@CHCOÀ3¼D HCOÀ3@2C HCOÀ3þD HCOÀ31@r@C HCOÀ3þR ucCO2ðC jÞð10Þ@C B@tþ2m‘1ÀrR2@CB@z¼D B@2C B@z2þD B1r@@rr@C B@rð11Þ@C BHþ@tþ2m‘1ÀrR2@CBHþ@z¼D BHþ@2C BHþ@z2þD BHþ1r@@rr@C BHþ@rð12ÞTo complete the description of the system,the following initial and boundary conditions are written:t¼0C jð0;z;rÞ¼C injð13Þz¼0C jðt;0;rÞ¼C injð14Þz¼L@C j@zðt;L;rÞ¼0ð15ÞNomenclaturea s specific surface area,m2=m3reactorC E0enzyme load,kmol=m3reactorC j concentration of species j in liquid phase,kmol/m3D j molecular diffusion coefficient in liquid phase,m2/s L microreactor length,mr radial position within microreactor,mR microreactor radiusR j reaction rate,kmol/m3s t time,sv‘liquid velocity,m/s z axial coordinate,m Subscripts/Superscriptsc catalyzedin microreactor inlet uc uncatalyzed62I.Iliuta et al./Separation and Purification Technology107(2013)61–69r¼0@C j@rðt;z;0Þ¼0ð16Þr¼RÀD j @C jðt;z;RÞa s¼R cjðC j jr¼RÞð17ÞThe boundary condition selected for the outlet does not set any restrictions except that convection dominates transport out of the reactor.Thus this condition keeps the outlet boundary open with-out restrictions on the concentration.2.2.Model for CO2hydration laminarflow microreactor with solution-phase HCAII enzymeThe unsteady-state mass balance equations for a chemical spe-cies j in the liquid phase are:@C CO2 @t þ2m‘1ÀrR2@CCO2@z¼D CO2@2C CO2@z2þD CO21r@@rr@C CO2@rÀR ucCO2ðC jÞÀR cCO2ðC jÞð18Þ@C HCOÀ3þ2m‘1Àr 2@CHCOÀ3¼D HCOÀ3@2C HCOÀ3þD HCOÀ31@r@C HCOÀ3þR ucCO2ðC jÞþR cCO2ðC jÞð19Þ@C B @t þ2m‘1ÀrR2@CB@z¼D B@2C B@z2þD B1r@@rr@C B@rÀR cCO2ðC jÞð20Þ@C BHþ@t þ2m‘1ÀrR2@CBHþ@z¼D BHþ@2C BHþ@z2þD BHþ1r@@rr@C BHþ@rþR cCO2ðC jÞð21ÞThe initial and boundary conditions are:t¼0C jð0;z;rÞ¼C injð22Þz¼0C jðt;0;rÞ¼C injð23Þz¼L@C j@zðt;L;rÞ¼0ð24Þr¼0@C jðt;z;0Þ¼0ð25Þr¼R@C jðt;z;RÞ¼0ð26ÞThe boundary condition selected for r=R makes sure that nomaterialflow through the reactor wall.2.3.Uncatalyzed CO2hydration kineticsThe overall rate of uncatalyzed conversion of dissolved CO2tobicarbonate developed by Ho and Sturtevant(1963)was used[16]:R ucCO2¼k031C CO2Àk013C HþC HCOÀ3where k031¼k31þk32;k013¼k13þk23=K H2CO3ð27ÞThe rate constants at25°C are:k031¼0:037sÀ1andk013¼5:5Â104m3=kmol s[16].Table1The rate constant aggregates,turnover,apparent Michaelis and inhibition constants [15].Rate constant aggregates Turnover,apparent Michaelis and inhibitionconstantsk3k1¼9:5Â10À3M k h¼1:1Â106sÀ1;k d¼9:4Â104sÀ1 K Ea1k1þk5¼8:4Â106MÀ1sÀ1K CO2¼9:5mMk1kÀ1¼1:11Â103MÀ1K B1¼5:2mM;K BHþ1¼0:23mMK HCOÀ3¼22:2mMK i HCOÀ3;1¼14:8mM;K i HCOÀ3;2¼127:9mM;K i HCOÀ3;3¼37:5mM;K i HCOÀ3;4¼61:9mM;K i HCOÀ3;5¼12:2mMTable2The equilibrium constants[15].Equilibrium constant ValueCO2þH2O¢HCOÀ3þHþKa1¼½HCOÀ3 ½Hþ2;mol=l p K a1=5.97Proton-transfer group acid dissociationH E¢EþHþKE¼½E ½Hþ½H E;mol=l p K E=7.1Catalytic group acid dissociationE W¢EþHþKE ¼½E ½Hþ½E W;mol=l p K E%7.1BþHþBHþKa2¼½B ½Hþ½BHþ;mol=lBuffer:Na2HPO4p K a2=7.2 1,2-Dimethylimidazole(1,2-DMI)p K a2=8.2I.Iliuta et al./Separation and Purification Technology107(2013)61–69632.4.Catalyzed CO2hydration kineticsThe pseudo random Quad Quad Iso Ping Pong mechanism with one transitory complex,which implies a possible competitive in-ter-molecular proton transfer step by the CO2=HCOÀ3pair with re-spect to external buffer,B,was used to describe the reversible hydration of carbon dioxide catalyzed by HCA II[15]:In addition to enzyme isomerization,the model takes into ac-count the intermolecular CO2=HCOÀ3-subtended proton transfer viaa½CO2 Á½HCOÀ3coupling,the CO2=HCOÀ3-subtended proton transfervia½HCOÀ32and½CO2 Á½HCOÀ32couplings,and the enzyme-substratetransitory complex via½CO2 Á½HCOÀ3Á½B coupling.The hydration and dehydration turnover rate constants,k h and k d,the apparent Michaelis constants,K CO2,K HCOÀ3,K B,KþBH,and the apparent bicarbon-ate inhibition constants,K i HCOÀ3;jare defined as follows:k h%K a1K Ek3k1K EK a1k1þk5;k d%K a1K Ek3k1K EK a1k1þk51þk3À1ð29ÞK CO2%k3k1;K HCOÀ3%21þk3kÀ1K a1K Ek3k1;K B¼K B1K EþK a2K E;K BHþ¼K BHþ1K EþK a2K a2ð30ÞTable3Laminarflow microreactor operating conditions.Operating conditions DataChannel diameter 2.0mmMicroreactor length0.1mActive HCA II loading4:32Â10À7kmol=m3reactor Microreactor temperature298KInlet CO2concentration0.017mol/lInlet superficial liquid velocity0.0025–0.0.005m/sR c CO2¼k h C CO2C BÀK a2a1C HCOÀ3C BHþ1þC HCOÀ3i HCOÀ3;3C E0K B C CO2þK CO2C BþK B2K EK a1C HCOÀ3þ2K CO2K a2K EC BHþþC CO2C Bþ2K CO2K HCOÀ3K a2K EC HCOÀ3C BHþþK BK i HCOÀ3;1C CO2C HCOÀ3Â1K CO2K i HCOÀ3;2C B C HCOÀ3þ12K BK i HCOÀ3;3K EK a1C HCOÀ32þK BK i HCOÀ3;1K i HCOÀ3;4C CO2C HCOÀ32þ1K i HCOÀ3;5C CO2C B C HCOÀ3ð28Þ64I.Iliuta et al./Separation and Purification Technology107(2013)61–69K i HCOÀ3;1%2K a1K Ek1kÀ1þ2k1k3k5K Ea1k1þk5!À1;K i HCOÀ3;2¼K a1EK CO2;K i HCOÀ3;3¼K a1Ek31K EK a1k1þk55ð31ÞK i HCOÀ3;4¼K2i HCOÀ3;3K i HCOÀ3;3ÀK i HCOÀ3;1;K i HCOÀ3;5¼121K i HCOÀ3;1À1K i HCOÀ3;3!À1ð32ÞThe rate constant aggregates with the inferred turnover and apparent Michaelis constant and inhibition constants are tabulated in Table1.The equilibrium constants are given in Table2.The ki-netic model was developed for reversible hydration of carbon diox-ide in the presence of solution-phase human carbonic anhydrase II. However,the kinetic model is expected to be suitable under immo-bilization enzyme conditions taking into account the comparable CO2removal efficiency of the immobilized HCA II and the soluble counterpart for extended periods[17].2.5.Method of solutionIn order to solve the system of partial differential equations,we discretized in space and solved the resulting set of ordinary differential equations.The spatial discretization was performed using the standard cell-centeredfinite difference scheme.The GEAR integration method for stiff differential equations was em-ployed to integrate the time derivatives.The relative error toler-ance for the time integration process in the present simulations was set at10À6for each time step.3.Results and discussionThe model was initially used to compare the performance of the laminarflow microreactor with solution-phase or immobilized HCA II enzyme under the same HCA II loading.Both catalyzed and uncat-alyzed CO2hydration processes were considered.Figs.1and2show typical CO2and HCOÀ3radial and axial steady-state concentration profiles obtained under the same operating conditions(Table3).Dif-fusional effects are more important with immobilized HCA II en-zyme(Fig.1a)and the result is a lower CO2conversion(Fig.2a). On the other side,with solution-phase HCA II enzyme,the species concentration is nearly uniform in the radial direction(Fig.1b) and this is close to the ideal‘‘plugflow’’conditions[18].Numerical simulations indicate that in laminarflow microreactor with the HCA II immobilized on the inner surface of the tube the coupling of transport phenomena and chemical reaction necessitates the use of two-dimensional analysis in processing the experimental data.I.Iliuta et al./Separation and Purification Technology107(2013)61–6965Interpreting the data as one-dimensional plugflow results will leadto significant error.It is of interest to investigate the behavior of CO2hydration pro-cess by forcing artificially silencing of the uncatalyzed conversion of dissolved CO2to bicarbonate(Figs.3and4).As expected,with solution-phase HCA II enzyme the contribution of uncatalyzed CO2hydration is reduced and the overall reaction rate is dominated by the enzymatic process(Fig.4b).On the other side,the uncata-lyzed CO2hydration is the prevailing process when HCA II enzyme is immobilized on the inner surface of the tube.Due to consider-able diffusional limitations(Fig.3a),a relatively small amount of HCOÀ3is produced by catalyzed CO2hydration process(Fig.4a). Therefore,the hydrodynamic and diffusional constraints in laminar flow microreactors do not permit a reasonable utilization of HCA II enzyme immobilized on the inner surface of the tube.It is antici-pated that such behavior will generate difficulties in interpreting experimental data obtained with immobilized HCA II enzymes.Un-der these conditions,the microreactor configuration must be se-lected accurately to exploit the absorption potential of HCA II enzyme(e.g.,enhanced mixing to disrupt adjacent laminarfluid streams by adding internals in the microchannel).In laminarflow microreactors,an important parameter which dictates mixing in the radial direction is the molecular diffusion coefficient.The influence of the diffusion coefficients on the CO2 hydration process under immobilized HCA II enzyme conditions is illustrated in Figs.5and6where both catalyzed and uncatalyzed CO2hydration processes were considered.It is evident that an in-crease in the molecular diffusion coefficient(a10-fold increase with respect to estimated values with Frank et al.[19]and Wil-ke-Chang(Reid et al.[20])correlations)leads to higher mass trans-ferfluxes transported between the liquid and the catalytic solid surface(Fig.5)and the result is a higher CO2conversion(Fig.6a). Theoretically,as the molecular diffusion coefficient continues to increase,the mixing in the radial direction will become faster as well as theflux of CO2toward the walls will be promoted.The high degree of mixing in the radial direction will lead to a more uniform distribution of mass across the cross section and a higher CO2 conversion.Figs.7and8show CO2and HCOÀ3axial and radial steady-state concentration profiles obtained for two values of liquid velocity in the laminarflow microreactor with immobilized HCA II enzyme. Two cases were simulated:(i)catalyzed CO2hydration process was considered only,and(ii)both catalyzed and uncatalyzed CO2 hydration processes were considered.As expected,CO2conversion increases with the decrease of liquid velocity due to higher resi-dence time(Fig.7).At lower liquid velocity,diffusional limitation continues to be considerable(Fig.8a)and the uncatalyzed CO2 hydration becomes more important(Figs.7and8b).The perfor-mance of the laminarflow microreactor with solution-phase HCA II enzyme increases slowly(not shown)with the decrease of liquid velocity.66I.Iliuta et al./Separation and Purification Technology107(2013)61–69Figs.9and10show the effect of the inlet buffer(Na2HPO4)con-centration on the axial and radial steady-state concentration pro-files without uncatalyzed CO2hydration in the laminarflow microreactor with solution-phase or immobilized HCA II,under the same HCA II loading.Buffers in solution participate as pro-ton-transfer agents in the catalyzed CO2hydration process.Low buffer concentration displaces the hydration into a regime where the inter-molecular proton transfer is rate determining and CO2 hydration rate is small.On the contrary,sufficiently high buffer concentrations ensures that inter-molecular proton transfer is not rate limiting and CO2hydration rate is large.This behavior ex-plains the raise of CO2conversion with the increase of inlet buffer concentration(Figs.9and10a).The enhancement is less important with immobilized HCA II enzyme because of the lower mass trans-ferfluxes of buffer transported between the liquid and the immo-bilized HCA II enzyme due to the diffusional limitation(Fig.9b). Fig.10b shows,once more,that the solution-phase HCA II enzyme system is a non-diffusion limited system and‘‘concentration’’plug flow is achieved in laminarflow.Fig.11shows the influence of the type of buffer(characterized by the equilibrium constant K a2)on the radial steady-state concen-tration profiles in the laminarflow microreactor with immobilized HCA II enzyme.Both catalyzed and uncatalyzed CO2hydration processes were considered.The buffers used in simulations are: Na2HPO4and1,2-dimethylimidazole.CO2conversion increases with the decrease of equilibrium constant K a2due to the higher CO2hydration driving force.The raise is less important with immo-bilized HCA II enzyme due to diffusional limitation(Fig.11).In the laminarflow microreactor with immobilized HCA II en-zyme–a diffusion limited system as mention above–the cata-lyzed CO2hydration process is largely dictated by the diffusive fluxes between the liquid and the immobilized HCA II enzyme. Therefore,the system is not very sensitive to the increase of cata-lyzed CO2hydration kinetic parameters.A10-fold increase in the reactor HCA II loading and hydration turnover does not have a sig-nificant effect on the CO2hydration process.So,because of diffu-sion limitations,the laminarflow microreactor with immobilized HCA II enzyme on the internal surface is not suitable for kinetic studies,unless a method to enhancefluid mixing is employed. On the contrary,in laminarflow microreactor with solution-phase HCA II enzyme,non-diffusion limited system,the catalyzed CO2 hydration process is largely dictated by the kinetics.A10-fold in-crease in molecular diffusion coefficients values does not have a significant effect on the CO2hydration process.4.ConclusionThe behavior of CO2absorption enhanced by the enzyme car-bonic anhydrase in a laminarflow microreactor was studied withI.Iliuta et al./Separation and Purification Technology107(2013)61–6967the purpose to understand the mechanism of HCA II enzyme reac-tions in a microchannel for further development of this process. The effects of operating conditions as well as the contribution of carbonic anhydrase on the performances of CO2hydration are pre-sented.Numerical simulations indicate that in laminarflow mic-roreactor with the HCA II immobilized on the inner surface of the tube the coupling of transport phenomena and chemical reaction necessitates the use of a two-dimensional analysis for data inter-pretation as a one-dimensional plugflow description will lead to significant error.The laminarflow microreactor with immobilized HCA II enzyme is a diffusion limited system and hydrodynamic and diffusional constraints do not permit a reasonable utilization of the immobilized HCA II enzyme even if HCA II has a very high hydra-tion turnover(a better mixing is necessary to disrupt adjacent lam-inarfluid streams).The uncatalyzed CO2hydration is the dominant process and this behavior will generate difficulties in interpreting the experimental data.Because of diffusion limitations,the laminar flow microreactor with immobilized HCA II enzyme on the internal surface is not suitable for kinetic studies,unless a method to en-hancefluid mixing is employed.In the microreactor with solu-tion-phase HCA II enzyme–a non-diffusion limited system,‘‘concentration plugflow’’is achieved under laminarflow condi-tions,the enzymatic contribution to the overall reaction rate is large and therefore the contribution of uncatalyzed CO2hydration process is not considerable.Any future modeling studies of mixing in capillaries equipped with internals to enhance mass transfer must benchmark or com-pare the enzymatic performance results with the present empty capillary case.A branch which can take advantage of presentfind-ing is the design of reliable‘‘kinetic study’’devices more appropri-ate for immobilized enzymes.Our present contribution is on the right direction to help elucidating diffusion–reaction couplings for high-turnover enzymes.References[1]S.H.Koenig,R.D.Brown,H2CO3as substrate for carbonic anhydrase in thedehydration of HCOÀ3,Proc.Nat.Acad.Sci.69(1972)2422–2425.[2]D.N.Silverman,S.Lindskog,The catalytic mechanism of carbonic anhydrase:implications of a rate-limiting protolysis of water,Acc.Chem.Res.21(1988) 30–36.[3]S.Lindskog,Structure and mechanism of carbonic anhydrase,Pharmacol.Ther.74(1997)1–20.[4]D.N.Silverman,R.McKenna,Solvent-mediated proton transfer in catalysis bycarbonic anhydrase,Acc.Chem.Res.40(2007)669–675.[5]V.M.Krishnamurthy,G.K.Kaufman,A.R.Urbach,I.Gitlin,K.L.Gudiksen,D.B.Weibel,G.M.Whitesides,Carbonic anhydrase as a model for biophysical and physical–organic studies of proteins and protein–ligand binding,Chem.Rev.108(2008)946–1051.[6]Y.Pocker,S.Sarkanen,Carbonic anhydrase:structure,catalytic versatility,andinhibition,Adv.Enzymol.47(1978)149–274.[7]S.Lindskog,Carbonic anhydrase,Adv.Inorg.Biochem.4(1982)115–170.68I.Iliuta et al./Separation and Purification Technology107(2013)61–69。
MBA英语阅读精讲汇粹（8）Passage Eight(The Development of Cities)Mass transportation revised the social and economic fabric of the American city in three fundamental ways. It catalyzed physical expansion, it sorted out people and land uses, and it accelerated the inherent instability of urban life. By opening vast areas of unoccupied land for residential expansion, the omnibuses, horse railways, commuter trains, and electric trolleys pulled settled regions outward two to four times more distant form city centers than they were in the premodern era. In 1850, for example, the borders of Boston lay scarcely two miles from the old business district; by the turn of the century the radius extended ten miles. Now those who could afford it could live far removed from the old city center and still commute there for work, shopping, and entertainment. The new accessibility of land around the periphery of almost every major city sparked an explosion of real estate development and fueled what we now know as urban sprawl. Between 1890 and 1920, for example, some 250,000 new residential lots were recorded within the borders of Chicago, most of them located in outlying areas. Over the same period, another 550,000 were plotted outside the city limits but within the metropolitan area. Anxious to take advantage of the possibilities of commuting, real estate developers added 800,000 potential building sites to the Chicago region in just thirty years – lots that could have housed five to six million people.Of course, many were never occupied; there was always a huge surplus of subdivided, but vacant, land around Chicago and other cities. These excesses underscore a feature of residential expansion related to the growth of mass transportation: urban sprawl was essentially unplanned. It was carried out by thousands of small investors who paid little heed to coordinated land use or to future land users. Those who purchased and prepared land for residential purposes, particularly land near or outside city borders where transit lines and middle-class inhabitants were anticipated, did so to create demand as much as to respond to it.Chicago is a prime example of this process. Real estate subdivision there proceeded much faster than population growth.1. With which of the following subjects is the passage mainly concerned?[A] Types of mass transportation.[B] Instability of urban life.[C] How supply and demand determine land use.[D] The effect of mass transportation on urban expansion.2. Why does the author mention both Boston and Chicago?[A] To demonstrate positive and negative effects of growth.[B] To exemplify cities with and without mass transportation.[C] To show mass transportation changed many cities.[D] To contrast their rate of growth.3. According to the passage, what was one disadvantage of residential expansion?[A] It was expensive.[B] It happened too slowly.[C] It was unplanned.[D] It created a demand for public transportation.4. The author mentions Chicago in the second paragraph as an example of a city,[A] that is large.[B] that is used as a model for land development.[C] where the development of land exceeded population growth.[D] with an excellent mass transportation system.V ocabulary1. revise 改变2. fabric 结构3. catalyze 催化，加速4. sort out 把……分门别类，拣选5. omnibus 公共汽车/马车6. trolley （美）有轨电车，（英）无轨电车7. periphery 周围，边缘8. sprawl 建筑物无计划延伸，蔓延，四面八方散开9. lot 小片土地10. underscore 强调，在下面划横线11. transit lines 运输线路12. subdivision （出售的）小块土地，再划分小区写作方法与文章大意文章论述了“公共交通从三方面改变了城市的社会和经济结构。
第12卷第4期 化学反应工程与工艺 V o l 12,N o 41996年12月 Chemica l Reac tio n Enginee ring and Technolog y Dec,1996专题讲座气固下行流化床反应器Ⅲ气、固混合魏 飞(清华大学化工系,北京100084)祝京旭(Departm ent of Chemical and Bioch emical Engineering Univ ersityof W es tern Ontario,London ,N6A5B9,Canada)摘 要 与气固并流上行提升管反应器相比,气固并流下行管反应器的轴向气固返混明显降低,而径向气固混和仍然相当大,因而有利于提高气固快速反应的转化率及选择性。
本文在分析下行流化床反应器内气、固混合机理的基础上,比较了有关气、固混合的研究方法及结果,并比较了提升管和下行管的不同混合现象,旨在促进对这一课题更加深入系统地研究,以适应循环床下行管反应器设计、放大和模型化的迫切要求。
关键词:下行流化床反应器 气、固混合 返混 停留时间分布1 前 言气固混合行为的研究不仅对于深入认识下行管作为一种通用的化工及物理加工设备有重要的学术意义,而且对于它作为反应器有特别重要的意义。
气固逆重力场流态化过程一直以良好的气固混合及传热性能而引人瞩目,但同时,它较大的气体及颗粒轴向返混对于反应转化率及选择性的提高都是极为不利的。
对于一个串联反应过程,特别是对于转化率及选择性均要求较高的反应过程,要得到尽可能多的中间产品,最大限度地减少气体返混是十分重要的。
催化裂化工艺从传统流化床过渡到提升管反应器所产生的质的飞跃,就是由于提升管有效地降低了气固返混,减少了反应生成的油气向下返混而过度裂化为气体及焦碳的可能性。
然而,由于颗粒的浓度及速度在提升管中的径向分布不均匀,提升管反应器内的气固返混仍然很严重。
从上一文(讲座Ⅱ)中介绍的下行管流体力学特性的研究结果可以看到,下行管给人们带来了一个希望:形成一种新型的流化床反应器,它不仅具有良好的气固传递特性,而且能使气固轴向返混比现有流化床反应器大大地降低。
基于DPM模型的旋风分离器内颗粒浓度场模拟分析高助威;王娟;王江云;冯留海;毛羽;魏耀东【摘要】To study the distribution of the particle concentration in cyclone,the RSM model and the particle stochastic trajectory model were used to simulate the gas-solid flow of the cyclone.The top ash ring and erosion of the wall were analyzed from particle concentration distribution and residence time.The results showed that the concentration of particles in the wall were distributed in a spiral gray band,and the width and pitch of the gray bands were different.Along radial direction,the particle concentration near the wall was high while other regions were low.Along axial direction,the particle concentration was larger in the bottom of the separation space,and the width of the spiral gray band increased but the pitch decreased.There was top ash ring under the roof of annular space,where a lot of particles gathered.The top ash ring was unevenly distributed,with obvious non-axisymmetric characteristics.Furthermore,the top ash ring had a certain periodicity shedding phenomenon.The performance would not only cause the escape of particles and reduce the separation efficiency of cyclone,but also cause erosion wear of the wall.In severe cases,the wall of the cyclone separator would be worn out,causing the equipment to failure.%为了研究旋风分离器内部颗粒浓度场的分布规律,采用RSM模型和颗粒随机轨道模型,对旋风分离器进行气-固两相流动数值模拟,并从浓度分布和停留时间两方面对顶灰环及壁面磨损现象进行分析.结果表明,壁面处的颗粒浓度呈螺旋状灰带分布,灰带的宽度和螺距不同;从径向看,除壁面附近浓度较高外,其他部位浓度较低;从轴向上看,在分离空间下部,螺旋灰带的宽度加大,螺距减小,颗粒浓度增大.在环形空间顶板下方有大量颗粒聚集,存在顶灰环现象,而且顶灰环分布不均匀,具有一定的准周期脱落特性.这不仅造成颗粒的逃逸,降低旋风分离器的分离性能,而且也会对壁面造成冲蚀磨损,严重时能够使分离壁面磨穿,造成设备失效.【期刊名称】《石油学报（石油加工）》【年(卷),期】2018(034)003【总页数】8页(P507-514)【关键词】旋风分离器;数值模拟;DPM;颗粒浓度;顶灰环;壁面磨损【作者】高助威;王娟;王江云;冯留海;毛羽;魏耀东【作者单位】中国石油大学重质油国家重点实验室,北京102249;过程流体过滤与分离技术北京市重点实验室,北京102249;中国石油大学重质油国家重点实验室,北京102249;过程流体过滤与分离技术北京市重点实验室,北京102249;中国石油大学重质油国家重点实验室,北京102249;过程流体过滤与分离技术北京市重点实验室,北京102249;北京低碳清洁能源研究院,北京102209;中国石油大学重质油国家重点实验室,北京102249;中国石油大学重质油国家重点实验室,北京102249;过程流体过滤与分离技术北京市重点实验室,北京102249【正文语种】中文【中图分类】TQ051.8旋风分离器是气-固分离过程的重要设备，因其结构简单，处理量大，维修方便等优点，在工业除尘、石油化工、煤炭发电等领域应用广泛[1]。
Greerco High ShearDivision125 Flagship DriveNorth Andover, MA 01845Phone: (978) 687-0101 Fax: (978) 687-8500High Shear Pipeline Mixer Installation,Operation and Maintenance Manual Model:In-Line Pipeline MixerUnit Serial Number:Customer:Purchase Order:For Service and Information Contact:We at Chemineer, Inc would like to take this opportunity to thank you for choosing us for your processing equipment needs.Whether you are one of our many repeat customers or a brand new customer, our goal is to supply you with a piece of equipment that is superior in both design and ease of operation. By following the instructions in this manual and performing regular maintenance, we trust you will receive years of trouble – free operation from this machine.If you have any questions at all, or require additional information, do not hesitate to contact your local Chemineer representative or our Customer Service Department.THIS MACHINE SHOULD ONLY BE OPERATED BY QUALIFIED PERSONNEL WHO HAVE READ THIS MANUAL & UNDERSTAND HOW THE MACHINE OPERATES.T ABLE OF C ONTENTSE QUIPMENT D ESCRIPTION 2P RINCIPLE OF O PERATION 2I NLET F LANGE CAUTION 3S INGLE VS.T ANDEM S HEAR C ONFIGURATIONS 3P RODUCT O UTLET 4D IRECTION OF R OTATION 4M ACHINE I NSTALLATION &S TART-UP G UIDELINES 5M ECHANICAL S EALS 6M AINTENANCE 7 M IXING H EAD D ISASSEMBLY 8B EARING H OUSING D ISASSEMBLY 10M ACHINE R EASSEMBLY 12A XIAL A DJUSTMENT OF R OTOR-S TATOR G AP 13S PARE P ARTS 13E QUIPMENT D ESCRIPTIONYou have just purchased a Greerco® In-Line, Industrial Pipeline Mixer. This pipeline mixer is a high speed, high shear mixer for full-scale continuous in-line processing. The machine will blend, emulsify, de-agglomerate and produce a thorough wetting of dispersed substances resulting in a completely homogeneous product. However, a pipeline mixer will NOT dry grind and should never be considered a “pump”.P RINCIPLE OF O PERATIONThe Greerco® Pipeline Mixer employs a high-speed turbine running in close proximity to a fixed stator to perform its shearing operation. Product is processed as it passes through one (single) or two (tandem) of these shear zones, where intense shear and hydraulic forces result in a product that has been broken down into its primary particle size or the dispersion of the dispersed phase throughout the continuous, carrier phase.You will note that the inlet to your pipeline mixer is of a smaller line size than the mixer body itself. This design ensures that the mixer will draw the fluid into the shear zone. Though the mixer design will pump certain water-like fluids, the mixer should never be considered a “pump”. In many cases it will be desirable and even necessary to use a pump to pressure feed the mixer. It is recommended that the system pump be placed upstream of the mixer to ensure that the mixer is never starved.Should additional retention time be required, throttling a valve at the mixer outlet will reduce flow through the mixer and increase residence time for more thorough mixing. If the supply pump speed is reduced to obtain this result, be aware that cavitation may result and be certain that the mixing chamber is kept fluid full at all times. (See comments about dry operation under “Common Damage” on page 7 and parts 7 & 10 on page 9).P IPELINE M IXER I NLET C ONFIGURATIONAll industrial pipeline mixers are supplied with a blind inlet flange drilled with an NPT process connection. This flange is integral to proper operation of the equipment. Do not operate this mixer without the blind flange in place.Consult factory for custom inlet configuration designs.S INGLE VS.T ANDEM S HEARGreerco offers two styles of Sanitary Pipeline Mixers: the single shear and the tandem shear. The single shear consists of a single rotor-stator combination and the tandem shear consists of two rotor-stator combinations. In tandem shear configurations, the secondary stator is a multi-port stator consisting of several rows of smaller holes, where the primary consists of a single row of large holes.NOTE:All Pipeline Mixers can be converted to or from atandem shear configuration as required. However,stators and turbines from the two configurations areNOT interchangeable.P RODUCT O UTLETThe mixer head assembly is bolted to the bearing housing utilizing a common ANSI flange. By rotating the head assembly at this joint, the mixer may be installed with the discharge in any position that meets the needs of the piping scheme.The factory standard configuration is for the product outlet to be towards the right side when facing the inlet of the mixer.D IRECTION OF R OTATIONA red arrow (affixed to the bearing housing or the coupling halves and may be hidden by the coupling guard) indicates proper rotational direction for operation of your Industrial Pipeline Mixer. O PERATING DIRECTION IS COUNTERCLOCKWISE WHEN FACING THE INLET PORT OF THE MIXER (MOTOR IS AWAY FROM YOU).DO NOT OPERATE YOUR MIXER IN REVERSE CATASTROPHIC DAMAGE CAN OCCUR WITH ONLY MOMENTARY OPERATION IN THE WRONG DIRECTION ******************************************************* MOTOR COUPLING IS DISENGAGED TO PREVENT DRY-RUNNING WHILE VERIFYING OPERATING DIRECTIONM ACHINE I NSTALLATION &S TART-UP G UIDELINESThe Industrial Pipeline Mixer is shipped assembled and ready to connect and operate after the motor is wired and the motor coupling is engaged.1.Make sure that the base is bolted to a flat surface and is not twisted.Any distortion in the base will misalign the motor coupling, which may cause excessive stress and failure of the mixer shaft.2.Do not operate this mixer without first checking that the shaft spinsfreely and that no foreign material has been lodged in the mixing head during transport and piping.3.Stock Industrial Pipeline Mixers are supplied with 3600rpm, 3-phase,60Hz, 230/460Volt Explosion-Proof Motors. Follow the motor’s wiring directions. The mixer is shipped with the coupling disengaged to prevent “dry-running” damage to the mixer upon start-up. Once wired, confirm that the motor turns in the required direction to properly drive the mixing head in a counterclockwise direction (when facing inlet port) prior to engaging coupling. This will prevent the turbine from unscrewing, becoming disengaged and causing major damage to inlet port and mixing head components.4.After the motor has been wired and proper rotational direction isconfirmed, the mixer can be connected to the motor for operation.NOTE: The 2” Industrial Pipeline Mixer is equipped with a Belt Driven Motor to achieve higher mixer head rotation speeds.It is shipped with the belt disconnected. When installing orre-installing the timing belt, do not over-tighten or bearingfailure may result. Proper tension will allow deflectionapproximately equal to the thickness of the belt (includingthe teeth) without exerting excessive pressure.5.Do not remove the blind flange on the mixer inlet. This is NOT an“extra” piece or adapter. Consult the factory for alternate connections.6.The mixing head must always be supplied with product (water issufficient) and be “fluid full” to lubricate the sleeve and bushing in the mixing head. If operating at the low-end of the unit’s operating capacity and/or processing low viscosity product, it may be necessaryto apply backpressure (20 PSIG) with a down-stream valve. This will ensure a full mixing head and prevent cavitation that may cause a “dry-running” condition and damage the stellite sleeve and bushing. M ECHANICAL S EALSThe Industrial Pipeline Mixer can be supplied with either a single or double mechanical seal. Both seal options are self-contained and preloaded.Single Mechanical Seals∙Do not require a separate seal flush, but MUST be immersed ina liquid at all times when operating. Seal is lubricated byprocess fluid and mixer must be flooded prior to operation.∙Factory Stock Model is a John Crane 81T for a 2” machine anda John Crane 5610 for the larger models.Double Mechanical Seals∙Need to be flushed with a barrier fluid to lubricate and clean seal faces. The fluid should be compatible with process fluidsand should be at a pressure approximately 20psi higher than theprocess pressure.∙Seal is supplied with pipe nipples, pressure gauge, and ball valve for regulation of barrier fluid flow and pressure. A lubesystem or “ lube pot” may require piping changes; follow themanufacturer’s installation and operation instructions carefully.∙Factory Stock Model is a John Crane Type 88T for a 2”machine and a John Crane 5620 for the larger models.****************CAUTION**************** SEAL CHAMBER MUST BE FLOODED PRIOR TO OPERATION.FOLLOW ALL SEAL & LUBE SYSTEM INSTALLATION & OPERATION INSTRUCTIONS FOR PROPER SEAL PERFORMANCE Standard Factory Seal Construction (unless specified at time of order): Viton Elastomers, 316SS Hardware, and Carbon vs. Silicon Carbide Faces.Alternate seal faces and seal manufacturers are available – Please consult the factory for cost and/or designs.M AINTENANCE OF THE I NDUSTRIAL P IPELINE M IXER Maintenance requirements on the pipeline mixers are minimal. However, proper care and maintenance are essential to optimal service life.“Normal Wear” – Normal wear is confined to the turbine sleeve and the stator bushing. Both parts are constructed of wear-resistant Stellite. If you are processing abrasive materials, wear may also be seen on the turbine and stator. The rate of abrasive wear will be different for every product and processing condition.Common Damage – The most common cause of damage to mixing head components is physical. Contamination of product fluid with hard objects such as tramp metal or stones may cause catastrophic damage to the mixing head. It is imperative that hard objects be kept out of the mixer, as the operating speed is so high that there is a low probability that rigid objects will pass the moving parts without causing damage. Foreign objects will result in irreparable damage to the turbine and either superficial or catastrophic damage to the stator. Depending on the length of operation under such a condition, the shaft and bearings could also be damaged.The second most common mode of failure is running the machine dry. Even a momentary dry operation (jogging the motor for instance) will lead to damage. The stellite sleeve on the turbine requires the process fluid for lubrication. Failures of this sort could be limited to sleeves and bushings or could be as catastrophic as the welding of the mixing head to the shaft.Last are failures caused by reverse operation, the results of which are obvious. Operation in the reverse direction will allow the turbine to unthread, back off the shaft, and into the inlet cap. Minor cases result in a damaged turbine and superficial inlet cap damage. Major cases result in severe bending of the turbine blades, and damage to the inlet cap and stator. Before you begin any maintenance procedures on this machine, be sure to…∙Note any exterior damage to unit.∙Make a note of product and operating conditions.∙If failure has occurred, make a note of important information that may assist in diagnosing the problem (product temperature, productpressure, viscosity, noise, excessive heat, or process changes, etc.).M IXING H EAD D ISASSEMBLY1.Disengage the motor coupling.2.Unbolt the blind flange from the inlet flange of the mixer.3.Remove the Inlet Gasket4.Inspect the exposed turbine area for anything unusual (productbuild-up or damage, etc)If possible, measure the turbine-stator gap - Especially if theturbine blades are worn and there is a noticeable or uneven gapwhere the turbine blades meet the stator.In the field, we recommend using Mylar feeler gaugesto determine if the gap is within the 0.008-0.012”factory setting. The gap setting should be checkedalong the entire length of each turbine blade. This willprovide a more accurate “lowest point” measurement.5.Rotate the primary turbine counter-clockwise while holding thecoupling stationary. Turbine should freely unscrew.6.Inspect primary turbine for damage, corrosion or worn edges (lackof sharpness). Turbine edges should be sharp. The turbine should “stand” on the blade ends and have all the blades rest solidly on a flat surface, without any wobble or misalignment.Note that the turbine blades are (should be) sharp and care should be taken not to damage the edge or cut the technician’s hands.7.Inspect turbine sleeve around neck of turbine for excess wear.Mild, consistent scuffing is normal. Gouges or uneven wear is abnormal.▪If Stellite sleeve has ripples or gouges in the surface it should immediately be replaced. These marks areindications of dry operation or abrasion. Wear like this willcreate escalating damage to the mixing head components ifallowed to continue operating in this condition.▪If uneven wear is present, put a dial indicator on the end of the shaft and rotate the shaft at the coupling end. Optimaloperation requires less than 0.003” shaft run-out.8.Remove the primary stator. Hole edges should be sharp. Take carenot to cut yourself.(Do not lose the pin that holds the stator in place.)9.Check the primary stator for wear or corrosion.10.I nspect the stator bushing for wear.▪If worn, note the position and pattern of the wear. The bushing will need to be replaced by pressing the componentout of the stator from the rear side of the stator.▪If the Stellite sleeve has ripples or gouges in the surface it should immediately be replaced. These marks areindications of dry operation or abrasion. Wear like this willcreate escalating damage to the mixing head components ifallowed to continue operating in this condition.11.I f a tandem shear unit, a second turbine and stator will now berevealed. The secondary turbine should now easily slid off theshaft and the secondary stator slid out of the body. Inspect thesecomponents as you would the primary pair.12.R emove and save any shims; note the position, thicknesses andquantity used (reference the drawing at the beginning of thissection).B EARING H OUSING D ISASSEMBLY1.From backside of seal chamber, remove any seal anchor screws.2.The mixer housing can now be unbolted and removed from theshaft and bearing housing assembly. Note orientation of outlet portso that machine is properly configured during reassembly.ing care, slide mechanical seal off the shaft.Refer to your seal manual for guidelines on inspectingand repairing the mechanical seal.∙Check the shaft surface area under the seal. If there are any defects note the type and location. Shaftdefects may cause seal leakage or damage.4.Spin the mixer shaft by hand to inspect the bearings. Shaftshould spin smoothly with no rumbling and very little“play”. Be sure to replace/grease any bearings exhibitingsigns of wear.5.If the bearings and/or shaft need replacement, use the followingprocedure and consult the equipment drawings at the back of this manual for part identification:∙Loosen the setscrew and remove the mixer coupling.∙Unbolt the thrust cap from the motor end of the bearing housing and remove.∙Inspect the motor end shaft seal (located within the thrust cap) for damage, oxidation, cracking or simple dryness andinflexibility. Replace if damaged.∙Pull the shaft and bearing assembly out of the bearing housing.∙Remove the Locknut (Locknuts should not be re-used more than twice)∙Bearings and bearing spacer can now be pulled from the shaft.∙Inspect mixer end shaft seal (located in bearing housing) for damage, oxidation, cracking or simple dryness andinflexibility. Replace if damaged.R EASSEMBLY OF I NDUSTRIAL P IPELINE M IXERThe industrial pipeline mixer may be reassembled by simply reversing the procedure outlined above. Keep in mind the following.∙ Be sure all components are clean and free of debris before reassembly. ∙ Lubricate o-rings prior to installation∙ Ensure that shaft run out is less than 0.003” before installing shaft.∙Check all surfaces for burrs before sliding seals or o-rings over rough surfaces that may damage integrity of the seal.∙ It is possible to inadvertently cause damage to the shaft during machine reassembly. This damage of this type is evident in extreme run-out after assembly that was not seen when the individual shaft is inspected. When the bearings are pressed into place on the shaft, be careful not to use the shoulder at the threads as a point of applied force. Utilize a fixture that allows pressure to be applied at the main shoulder of the shaft so that forces are applied to the thicker cross section rather than at the thinner, threaded shoulder.∙ It is also possible to cause damage to the turbine(s) while pressing the turbine sleeve into place. Support the turbine as shown in the following drawing:∙ Be sure to follow all motor, seal, and coupling precautions when installing.Apply constant pressure on this shoulder.∙Jog motor to ensure proper direction of rotation prior to coupling to mixer.∙Rotate the shaft by hand to ensure free movement before coupling machine to motor.∙Use common sense and safety at all times.A XIAL A DJUSTMENT OF R OTOR-S TATOR G APFor optimal performance, your pipeline mixer should be operating with a 0.008-0.012” gap between the rotor(s) and stator(s). Thin metal (washer-like) shims are used to create this gap. The gap should be measured at the lowest point along each of the rotor blades.S PARE P ARTSIncluded, at the back of this manual, is a complete assembly drawing of the pipeline mixer you have just purchased. Recommended spare parts are denoted with an asterisk on this drawing. These are parts that over time will need replacement. It is recommended that the customer maintain an inventory of these parts as protection against down time due to wear or accidental damage such from foreign objects. For your convenience, we offer multiple discounted spare parts kits for use in the maintenance of this machine.Consumable Spares KitAvailable for any shaft seal configuration, this kit contains all lip seals, bearings, shaft seals, gaskets and retaining ring. Please specify machine serial number at time of quote/order. – Mechanical Seal is NOT included in this kit.Machine Rebuild KitAvailable for any shaft seal configuration, this kit contains all wearing parts including shaft, rotor, o-rings, bearings, seals and locknuts. The stator(s) are NOT included in this kit. Please specify machine serial number at time of quote/order.Should you need to order parts, please contact your local Chemineer-Kenics/Greerco representative, as listed on the front of this manual, or our factory at (978) 687-0101.。
Maritime transportation,commonly referred to as sea freight,is one of the oldest and most widely used modes of transport in the world.It involves the movement of goods and passengers across bodies of water,typically oceans and seas,using various types of vessels such as cargo ships,tankers,and container ships.Here is an introduction to this significant mode of transport:Historical Significance:Maritime transport has been a cornerstone of global trade for centuries.It was the primary means of moving goods and people across long distances before the advent of air travel and modern land transportation.The development of maritime routes and the expansion of shipbuilding technologies have played a crucial role in shaping the worlds economy and cultural exchanges.Types of Vessels:1.Cargo Ships:These are designed to carry general cargo,which can include a wide range of items from raw materials to manufactured goods.2.Tankers:Specialized for the transportation of liquids,particularly oil and chemicals.3.Container Ships:Carry standardized shipping containers,which are easy to load and unload,making them highly efficient for bulk cargo transport.4.Rollon/Rolloff RoRo Vessels:Allow vehicles and other wheeled cargo to be driven on and off the ship on their own power.5.Ferries:Primarily used for the transportation of passengers and their vehicles across bodies of water.Advantages of Maritime Transport:1.CostEffectiveness:Sea freight is generally cheaper than air freight,making it ideal for bulk goods and longdistance transport.2.Capacity:Ships can carry massive amounts of cargo,making them suitable for largescale trade.3.Reliability:Established shipping lanes and schedules provide a predictable and reliable service.4.Low Carbon Footprint:Sea transport has a lower carbon footprint compared to air transport,making it a more environmentally friendly option.Disadvantages of Maritime Transport:1.Slower Speeds:Ships are slower than air and land transport,which can be a disadvantage for timesensitive goods.2.Limited Accessibility:Not all locations have direct access to a seaport,which may require additional transportation to reach the final destination.3.Weather Dependent:Sea transport can be affected by weather conditions,leading todelays and potential damage to cargo.Modern Developments:The maritime industry is continuously evolving with the introduction of advanced technologies such as automation,improved navigation systems,and the use of cleaner fuels to reduce environmental impact.Additionally,the expansion of global trade has led to the development of larger and more efficient vessels.Regulations and Safety:International maritime transport is governed by a set of laws and regulations,primarily overseen by the International Maritime Organization IMO,which ensures safety,security, and environmental protection standards are met.Conclusion:Maritime transport remains a vital component of the global supply chain,offering a costeffective and reliable means of moving goods around the world.As the industry continues to innovate and adapt to changing demands,its importance in facilitating international trade is unlikely to diminish.。
整个注射过程:（四个油缸作用）clamp cylinder nozzle cylinder鳗一（低压模保）一整前（喷嘴进I 行程开关injection start ）— injection cylinder注射（螺杆进一保压一储料（预塑/螺杆转）一（料自料斗进，料满后推动 螺杆退，背压）一防流涎一同时冷却—整后（有时无）一开模一ejector cylinder顶出（产品通过光电开关/电眼自动掉下）一顶退.TECHNICAL TERMSpan-head screw:圆头螺丝 screwdriver:螺丝刀 locknut:紧定螺帽/螺母，紧母/迫母 tie rod nutwasher:调模丝母垫 tie rod nut holder:调模丝母压盖bolt: n.螺钉/螺栓;v,栓住，定位 stud bolt:模具压板螺栓 hold-down bolt:压紧装置/螺栓jack bolt:调节螺栓 eye bolt:吊环螺栓countersink screw:沉头螺钉 fundation bolt:地脚螺栓Mold mounting bolt:模具安装螺栓 fastening bolt:紧固螺钉anchoring hole/ foundation bolt hole:地脚螺栓孔 flight:螺齿 /导程 secondary flight:次螺槽 primary flight:主螺槽 channel:槽，通道 screw land:螺棱 land:台面 flute:槽 trough:槽 chute:滑槽 coolant reservoir:冷却液槽 T-slot: T 型槽screw axis:螺轴 pitch:螺距（沥青），螺牙（螺距=lead ） screw speed:螺杆转速opposed semi-circular grooves:对置式半环形键槽Tangential groove:切向键槽 axial groove:轴向键槽 Remedial groove:修复式键槽 stripping tank:洗提槽Spline:花键 key:键 membrane:薄膜键 steel wadge:钢契口 grinding wheel:砂轮 emery cloth:砂布 main machine:整机 machine frame:机器框架 /机架 barrel base cover:前板盖 screw barrel:机筒 end cap:前机筒flat-head screw:平头螺丝fixing screw:托脚 fullthread:全螺纹 tie rod nut:调模丝母end platen:终端压板 screw barrel base:射台前板screw drive base:射台后板 deflector:偏转器/挡板throttle pin:节流/减压销钉 split pin:开口销 retaining pin:定位 销link pin:连杆销 radial pin:径向销钉 link tie bar:连杆拉杆tie bar:拉杆 push-rod:（阀）推拉杆adjustable rod /scotch bar:机械保险杆 safety lever:（液压）保险撞块 drop bar:机械保险挡板 safety pawl:机械保险挡块/安全制动掣pawl:挡块 location block:定位挡块（block 意为“压块”） Dog:撞（挡）块 snap ring:挡圈（板） press ring:压圈 O-ring: O 型密封圈 rod-packing: Y 型密封圈 cap ring:盖圈wiper:密封圈（刮水器） scraper:防尘圈/铲刀seal holder:防尘（圈）压盖 spring washer:弹簧垫圈gasket:垫圈，密封衬垫 heel block:垫块 cushion :衬垫，软垫 pad:垫板（座） cross head collar:垫片 parallel:垫板/垫片mallet:槌子 adjustable mount:机器调整垫块vibration-proof block 防震垫块（铁）limit switch:行程开关 stopper:限位块plugging switch:反接制动开关key operated switch:钥匙操作开关 switching device:开关器件 access code:通路编码 access:通道，接近通路communications network or link:通信网或数据链saddle strap:鞍形板Guiding bar holder 导杆支座 guide pin / leader pin:导杆 /导柱 front （rear ） plate link:（前）后支架 brace and bracket:支架/托架（支承物） barrel support:机筒支架 rack:（电子）槽/支架bracket: 灯架screw-shell:灯头螺口 stroboscopic effect:频闪效应 cable tray:电缆托架 撑板，托板backing plate /supporting plate: 托板/支架板slab:厚板 plate:金属板 subpanel:配电连接板 mold lifting bracket:吊模架 suspension hook:吊钩 hook:起吊架脚 bracket stay / brace:托架撑脚 rear （main ） link:后连杆 front link:前连杆 sub link:小连杆guide rod support:夹板 support tie rod:夹板紧固杆 cross head guide rod:夹板拉杆 cross head:直角机头limit switch cam:顶出开关杆knockout pin （center ）:顶出杆（主） knockout pin / ejector pin:顶出杆 knockout bar:顶出板assembled weights:平衡块balancer:轻重块 plate:底板/压板 baffle:挡板（作用类似“压盖”）shelf:搁板 lampholder:灯头座 reflector:反光罩 carrier:托架，载体adapter plate:连接板，stationary/ fixed platen:定模板（头板） movable platen:动模板（二板） mold height adj. Platen/ back platen:尾板 shoulder:轴肩 coupling:联轴节/器 flexible coupling:弹性联轴节head cover:前盖 rear cover:后盖 mold cavity:模腔 air ring:气环collar seat / back ring:止逆环 screw collar/ Thrust ring:推力环 split collar:半环 cover ring:套环 adapter ring:嵌入环/接口 套locating ring:定位环/接口套 positioning steel ball:定位钢珠 split mold:组合模 tube connector:管接rotation center:转心 recess: n.孑L,凹槽；v.退回counterbore:扩口内孔（钻孑L/扩孑L ）sink: through hole:通孔 air pocket:气孔 opening:通孔 drain hole:排泄孔 tapping hole:钻孑Lscavenging port:放油孔open clear sp=====an channel:开口式光亮通孔evenly spaced notch:切割均匀的切口 （凹痕） porous: adj.有孔的，能渗透的（porosity:n.孔） air vent:排气孔 vent: v.排出，发泄n.排气孔 ejector transducer:顶出电子尺platen moving transducer:移模电子尺position transducer:位移传感器/电子尺photoelectric sensor / presence-sensing device:光电开关/ 电眼 proximity switch/sensor:接近开关 flip switch:急扳开关gear:（调模）齿轮/介轮 mold height adj. gear:调模大齿圈 core of the bar:钢筋型心 retainer:套板（止退座）risk:危险 hazard:危害/险情guard:防护装置 enclosing guard:封闭体 barrier sheet:隔板casing:箱 safeguard:安全防护装置 safeguarding:安全防护（措施guide yoke:导套 adaptor:接套（连接器） bushing:衬套/套管/钢套 shoe:套架/固定板 loading bush:安装套（吹塑机上） steel liner:钢衬垫（lining:衬垫）toggle bushing with oil:曲肘含油肘衬（衬套）front seal and bushing:前盖钢套 hub / boss:轴套sprue bushing:主流道衬套/浇道衬套/ （模具）注入口钢套mold bushing:模具定位钢套copper bushing / cross head bushing:铜套｝rod cover:机械保险罩 tie rod cover :拉杆护罩sheath/ shell:外罩（外壳，外皮，护套） outer shell:（机筒）外罩 outer tube:（机筒）管状防护罩 reinforcing tubing:加固管purge guard of nozzle/purge cover:清机罩 purging:清洗nozzle cover:注射防护罩 column covering:立柱外罩pulley holder:滑轮套 enclosure:护壳 housing:护罩 enclose:封装 tie-bar location recess:定位孑L缩孔 blind hole:盲孔 knockout:出砂孔 damping port:阻尼孔transducer:传感器 sensor:传感器sleeve:（机筒）套筒 jacket: 护套chase: 模套locks:拉杆闸cylinder tube:（锁模）油缸筒piston rod:油缸杆small-bore traverse cylinder:小口径快速移动油缸｝（是直压式机器上的两种large-bore cylinder:大口径锁模油缸｝油缸）single-acting toggle cylinder:单作用锁模油缸cylinder flange:锁模缸底座cover base:支柱flange:法兰connection tube flange:接管底板trash can:垃圾桶washing machine tub:洗衣机桶seating:坐具bedding:卧具defroster:除霜机energy absorber:减能器armrest:扶手headrest:头垫toilet seat:马桶座圈shower stall:淋浴房bathtub:浴缸faucet:水龙头cock: n.（排气孔的）开关,（水）龙头clutch:离合器bumper fascias:（汽车）保险杠cross head link:推力座main link pin:大锁轴cross head link pin:小锁轴bearing box:轴承箱eject:顶出/脱模emergency stop:紧急制动器brake:制动器reverse current braking:反接制动plug-reverse:反接制动plug-stop:制动停止ejector advance:顶出ejector retract:顶退ejector forward/return:脱模进（顶出）/ 顶退ejector force/ ejector tonnage:顶出力Carriage:射（整）移pull-back cylinder:整移油缸carriage connection base:射移铰座nozzle retract:整移后退screw retract device:螺杆倒索器件（螺杆退）nozzle advance/forward/:整移进nozzle touch molding:整前（动作）nozzle touch force:整前力nozzle return force: 整后力preplasticize/ screw rotate/ charge/pre-suck:预塑（化）plasticize:储料injection unit return/ forward stop:（注射）座台退/进终，即喷嘴退/进注射座台指:从喷嘴开始，包括料筒，螺杆，料斗,射台前板和射台后板的一整套装置. Screw drive assembly / injection housing:注射座injection seat / screw drive assembly / screw driving unit: 注射（预塑）座微压马达熔胶装置/整移结构screw forward end position:螺杆进终止位置（注射到底位置） Injection unit return/forward Device:液压座台进退装置balancing twin-cylinder injection system: 双缸平衡式注射系统=液压平衡注射装置adjusting “air gap” devi调整气隙装置Separable structure for machine seat:机座分体式结构Logic valve hydraulic system:插装式液压系统shift out of position:（模具）移位dislodgement:挪位，移位orientation / be held in place:定位clamp:移模/锁模，夹紧clamp station:锁模位置clamp block valve:锁模块阀（即锁模阀板上的阀） mold clamp （assembly）:模具压板（组件） T-Slot auxiliary platen: T 型槽模具辅助板clamp front interlock:合模前连锁hydraulic crank interlock:液压曲柄连锁daylight :模板间距toggle stroke:开模/移模行程clamping force:合模力air blast in stationary platen:母模吹气air blow:气顶pneumatic open-door booster:气动开门助力器air leaking:放气inert gas:惰性气体bubble:气泡void: n.空隙（空缺）air gap:空气隙air cap:空气帽air duct:空气管convex: adj+n.凸状物，凸面的concave: adj+n.凹状物，凹面的splay:银条（出现在成品表面的气泡）sharp edge:锐棱flash:焊渣burr:毛刺hairline crack:细裂纹block:毛坯weep: v.（液体）渗出stress crack:应力裂纹die height:模具厚度die: n.模具;v.压five-point double-toggle locking mechanism:五支点双肘杆锁模机构split-caliper locking arrangement:对开卡钳式锁模机构pneumatic operation with mechanic clamping:气动机械式锁模的操作结构toggle linkage:曲肘连接/关节装置toggle machine:曲肘式机器straight hydraulic machine:直压式机器low-pressure mold protection device:低压模保装置insufficient filling:制品充模不足inadequately packs mold cavities:充模不足fill: v.注模（充模）high internal stress:过高内应力hold pressure: v.保压back pressure:储料背压medium pressure:中压pneumatic pressure:气压pack pressure: v.填充压力，充气no pressure:不起压pressurize:加压pressure drop:压降（压降低=压力损失小）reload:取资料clamp ultra high speed close:超高速关模差动（功能）open link:开模连动high speed injection:射出快速（差动高速）accumulator:射出增速（此功能实为蓄能器）mold close stop:关模停accumulator pressure switch:蓄能充足感应器accumulator release valve:射出增压阀（放能阀）accumulator charge valve:蓄能阀core （pull ）:中子 double hydraulic core pulling:双抽芯core-out / in 1 stop:中子退/进一终，抽芯/插芯一终single Hydraulic core-out / in Device:单组液压抽插芯装置closed loop control:闭环控制 hydraulic unscrew device:铰牙 collar cooling:环冷却 mold cooling manifold:模具冷却分水块 recovery rate:（螺杆）回复/退回率 plasticizing opacity:塑化能力shot capacity:注射量 injection weight:注射量（射胶量） throughput: n.生产量（注射量/容许能力） inventory:库存量 high molecular weight:高分子量auto cycle pause time:自动循环暂停时间 duty cycle:工作循环 short-time:短期工作pot life:（油漆）存罐期/储放期/适用期 working life:可用时间 shelf life / storage life:适用期production cycle time:生产周期 downtime:停工期lead time:订货至交货期的时间（产品设计至实际投产的时间）residence time:（塑料在机筒内）停留时间good response time:（液压中）响应时间短 curing time:熟化期 injection time set:注射时间 cushion monitor:注射监测over move to the point registed: 移动超程 follow the same step:同步 synchronous:同步的,共振的 induction （motor ）:异步/感应（电动机） molded part:制模成品 end product:最终产品shot count reset function:产品计数归零 reading: n.读数 test pattern molding:试模the trial/ test run:试车 run （to ）:敷入（导线）/运转 initiate:启动，开动运转 start:起动 tap:分接出 reset:复位 reclose:（变压器）重合闸 commission: v.试车（trialoperation ）,试投产，启动，使用 out of commission:不能使用（一般指PC 中断） decommission:中止操作 wrap-round:卷绕状的 illuminated dot:亮点（点状） bar:划条（条 状） spiral:螺旋状 helical valley:螺旋谷 worm:蜗杆 shaft mounting:安装轴（均指齿轮电机的类型） front and trailing edges:前缘和尾缘 leading edge:螺旋边缘compression intensity:抗压强度 tensile yield strength:抗拉屈服强度 shot size:理论容量shot:物料量/注射产量output:生产/输出量（率） mold capability:容模量real-time: 实时 inverse time:反时限torsional strength:扭转强度 度）interference radiation:干扰辐射 interference immunity:抗扰性 high noise-reduction:抗干扰性强parallelism:平行度，对应性，一致性alignment:排成直线，校直，校准（度） centering: n.对中性loading capacity: （土壤）承载力 geometric accuracy:几何精度 angle position change:角位置变化sweep torque:间歇扭矩 bending force:弯曲力（扭矩） magnifying ratio:（锁模力）扩大比率percent fill of raceway:导线槽满率 shear rate:剪切/切变速率 |送） weight /performance ratios:重量性能比positive force:（液压中）正（遮盖）力 stress:应力reference point:基准 sliding friction:滑动摩擦（力） thermal expansion /contraction rate:热膨胀 / 收缩率flash point / fire point / ignition point:燃点ductile: adj.有韧性的（易拉长的何锻的） hypersonic speed:特超音速的速度 speed shift / variable speed:变速 ultrasonic:超声波viscosity index:粘性指数long service life:使用寿命长 durability /endurance:耐用性（耐久性/强 度）lasting durability:经久耐用electromagnetic compatibility:电磁相容性（协调性/适合性/共存性/兼容性/配伍性）extreme porosity:极端透气 conductive:导电的，传导的heat conductance:热传导性 thermal conductivity:导热性（导热系dielectric strength:绝缘强度（介质强 gate width:浇道阔度hot runner:热流道direct gate: 直浇口 jet width:（喷漆）射流宽度fixing surface:安装表面承面deformation property:变形性 straightness:直线性 hot-short:热脆的 repeatability:重复精度 metal-to-metal bearing surface:金属间支 integrity:整体性 concentricity:同轴度 tilting moment:倾覆力矩bending moment:弯矩curvatures:弯曲度（曲pump ratio:输送速率（pump: v.输 positive mold:正压塑模detent point:止动点compation:压缩spherical radius:球面半径 bulk density:容积密度 specific gravity:比重 radii: 半径rigidity:刚性（硬度）specific heat: 比热 toughness:韧性，坚固度 velocity: 速度 slow-down: n.减速 resultant velocity:合速度 viscosity:粘性（度）数）heating capability:热容量（热值）thermal efficiency:热效率conduction:传导 convection:对流 radiation:辐射thermoset :热固性（adj ） thermoplastic:热塑性（adj ）heat-sensitive resin:热敏性树脂 epoxy resin:环氧树脂solid plastic:密实塑料 （high solids :固体含量高）solid color:颜色一 致blown film:吹塑薄膜 melt film:熔融膜 melt pool:熔融液流melt front:熔融前锋 melt penetration:熔融渗透 solid bed:固态（凝固）层 laminar flow:层流 back flow:倒流 turbulent flow:紊流dispersion disc:分流盘 unmelted pellet:未熔（塑料）团粒 crystalline:晶粒（晶体）coloration: n.（塑料）着色 pastel shade:轻淡优美的色彩 homogeneous melt:熔融均化 overdilute:过度稀释（thin:v ）uniformity:均匀性 homogenization:均质化tumbling and messaging action:（塑料）翻滚和挪动（动作）metering section:（螺杆）均化/计量段 conical transition:（螺杆）锥形转 化段involute transition:（螺杆）渐开转化段 nose cone angle:前锥角 helix angle:螺旋角 chamfer:倒角 edge chamfer:边倒角 included angle:夹角 bevel:斜角undercut:陷槽/底切部,根切，截槽，倾角 corner:内角 elongation:对角线（距角） taper:锥度single-stage:单阶式（螺杆） reciprocating:往复式的爆杆） flex flight mixing screw:曲槽混炼螺杆 one-line screw: 一线式螺杆 foam screw:泡沫螺杆 frothing:发泡plasticate:塑炼 plasticize:增塑 plastify:塑化 plasticating screw:塑炼螺杆 barrier screw:屏障型份离型）螺杆interlocked screw tip / “castle” desigi 联锁式螺杆头/ “城堡”式设计（槽形设计）slide ring valve:滑动环形螺杆头（阀）static mixer:静态混合器vent bleeding: n.排气（放气） vent stack:通风管vented conversions:排气转换装置 converting equipment:换能装置 exhaust: n.排气,废气 contaminant:污染物 soil: v.弄污 entrapped volatiles:截留挥发物 devolatilization:冷凝伽）PID programmed barrel heating system: PID 程式料管加热系统 Multiple molding data memorizing system:多组塑料成型参数记忆系统 Rotativeleakage flow:漏流 pressure flow:回流/逆流 back flush:回洗（回流洗涤） distribution:分流atomize /fogging （n ）:雾化 particle:（塑料）粒子deposit:（镇）沉淀块color dispersion:色散scale:旋转编码器encoder:编码器linker:连接器floppy disk:软盘firmware:固件（微程序语言）Subroutine:子程序back up: v,备份Debug: v.（计）调试Prepare:调试prepared:调制好的，处理过的feature: n.功能部件configuration:配置，结构（configure:v.） arrangement: n 配置connectivity:连通性intuitive script language:直观描述正本语言built-in transaction logging:内置式处理记录mirrored remote viewing:镜像远程观测distributed I/O fieldbus:分布式输入/输出总线serial link:串行连接be series connected:串联Interaction:交互作用operator interface（OI）:用户（使用者）界面interface:平台Color pentium OI:彩色用户界面，内置奔腾芯片PC Control runtime engine: PC 控制驱动Active matrix display:激活点阵显示Autotune function:自整定功能electrical cabinet/ host controller/ distribution box:配电箱U.L.panel/ distribution panel / switchboard / switch panel /control panel: 配电盘operator's control station:操作控制站operating station:操作工位control enclosure:控制电柜/护壳compartment:隔间raceway:电缆通道wireway:电线槽wiring channel:行线槽data highway:数据总栈solid state relay（SSR）:固体继电器overload relay:过载继电器voltage relay:电压继电器timer:时间继电器interrelay:内部继电器surge killer:突波吸收器（控制电压用）arcing relay:灭弧继电器surging: n.大量涌出，冒料，电涌，突波Concurrent:联合引发in conjunction with:以联合形式galvanic action:电位差腐蚀作用short circuit:短路open circuit:开路电路power circuit:动力电路parallel circuit:并联电路incoming / outgoing supply circuit:引入/接出电源电路printed circuit board:印刷电路板control circuit of heating band:电热短路short circuit protection:短路保护earth leakage breaker:漏电保护器（开关） electric shock:触电direct contact:直接触电load-sensing circuit:载荷感知式电路capacitor:电容器Amp. Level:电流表ampacity:载流容locked-rotor current:（电机）堵转电流 inrush current:注入电流 steady-state current:稳态电流 overcurrent:过电流interrupting capacity:（电流）切断能力 impedance:阻抗 speed regulator:稳速器 current regulator:稳流器transformer:变压器 voltage stablizer /regulator / manostat: 稳压 器 AC/ DC:交流（直流）电 convertor:变频器 regulator:调节器main power supply:主变压器 thermostat:恒温器 armature:电 枢 tachometer generator:测速发电机 varistor:可变电阻 resistor:电阻 （器） Trimpot:电位器 Trimmer capacitor:微调电容器Elco UF:电容 IC （Integrate Circuit ） / molectron /chip:芯片（集成电 路） contactor （unit ）:触头，触点/开关（电流接触器） quick fuse:快速熔丝 slow-blow fuse:耐燃熔丝fuse holder:熔丝座 receptacle / socket / jack/ socket-outlet: 插座attachment plug and receptacle:插销插座组合附件 fuse breaker:熔丝断路器 fuse link:熔丝接线main circuit breaker:空气开关/断路器 disconnecting switch:断开器（切断开关）central processor unit:中央处理器装置 （CPU ）wiring terminal:接线端子 control voltage terminal:控制电压接线柱（端 子）terminals of Y-starter:星型起动接头 termination:接线端，端接wiring:电热接线，配线，布线 panel wiring:电柜内配线powering:电源接通disc earthing:接地盘 line lug:接线片 conduit:导线管 oversized conductor:导线加粗 strand:绞（合）线flex:折弯，挠曲 kinking:折弯 bend:弯头/折弯fray:磨损 strain:绷紧solid copper conductor:实心铜导线 shielded conductor:屏蔽导线 flexible cord:软线 annealed copper wire:软铜线bus:母线 feeder:馈电线/馈电电路 lead:导线仁conductor ） grounding conductor: 保护接地导线 grounded conductor: 接地导 线grounding pole: 接地极 current-carrying pole: 带电极polarize:极化 transmission cable:传动电缆reel:电缆盘 multiconductor cable:多芯电缆 gauge:电线直径 grounding/earthing:电源接地（方式）knit line:密接线 fuse socket:熔丝盒no-fuse breaker:无熔丝开关 main disconnection:主断路 supply switch:断火开关terminal board:接线板 terminal block:接线座splitter block:分流器 pull box:分线盒terminal box / junction box:接线盒 heater box:电热接线盒 stackedconnector:接线头 signal transfer board:信号输送板 memory card:贮存板 main connection:主接线 jumper wire:控制线（跨连线/连接线/跳线） reflector:反射电 field:（电磁）场 field loss detection:失磁检 测electrode:电极 electrostatic charge:静电电荷 brush discharge:刷型放电 corona discharge:电晕放电worklight:工作照明 lighting:照明 stationary lights:固定照明（装 置）flame: v.引燃analog port:模拟口 analog input:模拟输入simulate: v.模拟，仿 真packages:程序（模块） procedure:步骤（程序/流程）diode DC:二极管直流电 limit diode:限流二极管LED ：发光二极管 Transistor:晶体管HZ:赫兹 HP:功率 volt-Amperes:伏安 foot pound:尺磅 kcmil:圆密耳（导线尺寸单 wire rope/steel cable:钢缆 （in ） 3-phase 4-wire:三相四线 handle for the breaker:带门锁手柄 alarm lamp:报警灯 infrared lamp:红外线灯automotive multicolored taillight:汽车多色尾灯alarm-sound:声报警 alarm-light:光报警panel switch:按钮开关 master switch:总开关 signal lamp:信号灯 command signal:指令信号 discrete signal:离散信号push-button （with lock ）:按钮开关（带锁）changeover switch:变化（转换） 开关rapid traverse changeover switch:快速变动voltage spike:（电压）峰值 peak value:（电压）峰值keyboard connector:键盘连接线motor delta check:电机三角形接法检查 ground machine frame:接地 机架cable hose:电缆软管 3-pole protector:三极保护器extended nozzle:力口长喷嘴 Spring-operated shut off nozzle:弹簧喷嘴 shut nozzle:液压喷嘴（hydraulic-operated shut off valve ）flex conductor:软（弯曲）导线 electronic beam:电子射线 fluid conductor:液体引流器 neutral:中线polarity:极性megohm:兆欧位）BSP:英制（in ） English unit:英制 metric unit:公（米）制 bulb:灯泡 interval:n.间隔flash:闪光片（飞片）shut off option:喷嘴选择shut off nozzle time:射出喷嘴计时nozzle centering alignment device:喷嘴对中微调装置（inching switch:微调开关）inch:缓慢地移动inching:延缓闭模/降速闭模brillant-flat jet tip:（喷漆枪）光亮平喷嘴round jet tip:（喷漆枪）圆喷嘴multi-channel swirl nozzle:（喷漆枪的）多槽旋涡式喷嘴reverse-taper nozzle:反向圆锥喷嘴barrel:料筒screw tip:料嘴头heating band for nozzle:喷嘴电热段数resistance heater band:电阻加热圈mica heater band:云母电热圈ceramic heater band:陶瓷电热圈cast aluminum heater:铸铝电热圈thermocouple:热电偶（flush melt thermocouple:奔涌式熔融热电偶??immersion melt thermocouple:浸没式熔融热电偶|outlet / orifice / discharge end:落料口，出口，放料嘴for easy access:容易触及flared entry:扩口式入口inlet / feed:加料口inlet plate:料口开关fixed feed:固定加料controlled feeding device:可控加料器automatic purge:自动清料nozzle temperature controller:电热恒温嘴insulator / insulation:绝缘体（隔热体）heat expansion:加热膨胀heater zone:电热区spare part:备件option:选择件rigid:硬质negative:负片safety gate:安全门（栅栏）electric-mechanical double safety device:电气机械双保险装置hopper dryer:（加料斗）干燥机auto loader:上料机hopper magnet:磁力架hopper throat:上料口hopper car:漏底车poppet:提动阀芯valve stem:气门杆（阀门芯）（valve） tappet:（阀）推杆cartridge hydaulics:插装液压系统cartridge:插装阀）proportional valve:比例阀limit valve:进水阀directional valve:方向阀press & flow valve:压力流量比例阀gauge valve:（压力）表阀sol.（enoids） relief valve:电磁溢流阀valve of release:排气阀moisture removal valve:排湿阀（水汽吸收器，用在液压系统油箱内）plastic dehumidifying machine:塑料除湿机（用于除去塑料桶内的湿气,与前者不同）angle check valve / non-return valve:单向阀sol.（enoid） pilot valve:电磁换向阀limit pilot valve:行程换向阀pathfinder control:导航式控制器valve driver board:阀输出板Manual pilot valve:手动阀air blast valve:吹气阀water saver valve:冷却水节流阀pump relief valve:油泵安全（溢流）阀screw torque selector valve:螺杆力矩选择阀/背压阀water control valve for oil cooler:油冷却器水控制阀water control valve for feeding throat:（料筒）进料口冷却水控制阀hydraulic motor:液压马达reducer housing:液压马达座electric motor:电机DC motor:直流电机pump motor: 油泵马达hydraulic screw drive motor:预塑马达radial-piston motor:径向柱塞马达fixed-displacement vane pump:定排量叶片泵mud pump:（油田）抽泥泵hydraulic pipe / hose:高压软管relief setting on proportional valve:比例阀溢流设定screw/suck back:射退suck-back pressure:防流涎压力decompression （suck-back）:防流涎no-load:空载（转），无载side load:横载荷（边载）bypass oil filter:旁路滤油oil level:油位计heat exchanger:油冷却器pressure gauge:压力表（面板式）level gauge:液位计potentiometer:电位计moisture level:湿度位temperature gauge / thermometer:温度计surveyor’s level:水准仪indicator:百分表dashboard indicator:（汽车）仪表盘指示针magnetic gauge:磁性表座micrometer:千分尺caliper:游标卡尺/卡钳mike bar:测微棒feeler gage:测隙规digital bore gage:数字式口径量规cylinder gage:量缸表（surface） profilometer:表面光度仪grating ruler:光栅尺measure head:测头scanning head:扫描头probe:测头jaw:（游标卡尺的）卡口square:直角尺/矩尺angle iron:角铁oil gun:牛油枪portable / hand-held spray gun:手提式/ 轻便型喷漆枪robot out:机械手出feeding / discharging robot:力口料/取瓶（卸产品）机械手universal spanner:活络扳头universal plier:活动钳hexagon wrench:内六角扳头（管子钳）mesh:滤眼（网眼）suction filter:滤油器suction:空气滤清器full-time filter:不间断/全天候滤清器push-in filter:嵌入式过滤网electrostatic precipitator:静电滤尘器（除尘器）dust precipitator:集尘器vapor condenser:蒸气冷凝器noncondensing:无冷凝水unscrambler:清理器preform tank:瓶坯箱parison:型坯funnel:漏斗chip conveyor:排屑器interface port:接口fitting:装置叩pliance:用具device:器件tooling:（工序件）刀具fixture:器具apparatus:仪器vault-type hardware:拱形器具assembly / subassembly:组件 （heating ） element:（发热）元件conductive part:导体件 live part:带电体actuator:操作件/执行机构 machine actuator:机械执行机构 extended operator:伸缩操作件 activator:激活器wobble-stick:手摇杆 palm type:掌揿式 mushroom-head type:蘑菇头式 wire-clip type:线夹式rod-operated type:杆式 self-latching type:自锁式manifold: n.复式接头/复合管/多支管/组合件/分水块 adj.多种多样的，多功能的piping, fitting & connetion:管路接头 expansion fitting:膨胀管接头 connector / joint:接头 splice:拼结点/接头fittings:垫片，附件/配件outfit(s): n.配备，全套装备；v.配备，得到装备 interference fit:干涉配合 captive fastener:系留紧固件fixing element:固定件 be snug on ：紧贴….hold closed:紧密固紧 shrink fit:热装 shrink over:趁其热胀时套上steam turbine:汽轮 chain block (=derrick / crane /jack ):起重机chain:挂链 hinge:较链 handle:手柄knob:旋钮 roller:滚轮/滚辊woven wire armor:编织线网铠装 nip rolls:夹辊/牵引辊solenoid coil:电磁铁 coil:线圈 shunt coil magnetic device:电磁器件工作线圈 delayed no-voltage device:延时无电压器件prewired device:预接引出线的器件 axial winding:轴向缠绕winding:绕组 secondary winding:二次绕组line side:进线边load side:负载边derate:减载运行 engage: v.接合/啮合 disconnect / deenergize:切断（电源 primary:（变压器）原线圈，原边，原电压secondary:副/次线圈，副边，副电压undervoltage:欠电压 PELV （protective extra low voltage ）:保安特低电 压residual voltage:残余电压 line voltage:线电压breakdown voltage:击穿电压ripple:波纹电压 nominal voltage:额定/常规电压voltage impulse:电压冲击 （impact / shock:冲击）voltage dip:电压降 voltage level:电平harmonic distortion:谐波畸变 r.m.s.:有效值sequence of states:状态序列 jogging / inching:点动voltage of the negative sequence component:电压负序成分 detector:测压器/检测器collective set:组合体secondary circuit:二级电路 rating:额定值trip:跳闸/脱扣energize:通电，接通electronic beam:电子射线electromagnetic clutch:电磁离合器 factor:系数（因素） coefficient:系数 tolerance:公差 allowance for …：公差differential: n.差动deflect: v.倾斜，转向，弯曲 deflection:偏差，挠度 heating calibration:力口热偏移 formula:公式label:指示标签 nameplate:铭牌 identification tag:识别标 牌 item:功能项 designation:项目代号identification :识别标志 group identification:组合标示graphical symbol:图示符号 legend:图例/图示set up:装配（机器） layout:布局/装配/分布图schematic diagram:示意图 block diagram:框图/立体图interconnection diagram:互连接线图cross-referencing scheme:相互对照图front view:正面图 sectional drawing:剖面图temperature profile:温度剖面（温度分布线图）section:截（剖）面 （cross ） longitudinal section:（横）纵截面 circular cross section:环形截面 sectional point:分段处 overview:整体外观，概观 outline:外形 video out:屏幕图象输出 temperature conditions page:温度状况屏幕页 text:文本graphic:绘图式 LCD:液晶示屏animation:动画 overlay: n.夕卜层 elastic layer:弹性层intersect （with ）:与…相交 intersection:交叉（点）in a circumferential direction:以圆周方向 bolt circle （pattern ）:螺旋圆周（状）in cross direction:横向（断面方向） longitudinal:纵向（水平方向）lengthwise: adj.纵向的 lateral:横向的 horizontal:水平的,卧式 vertical:垂直的（+3） （be ） perpendicular to/ （be ） vertical:垂直于 heat-resistant grease:耐热润滑脂 grease nipple:滑脂嘴 anti-wear/wear resistance hydraulic oil:抗磨液压油corrosion resistance:耐蚀（性） abrasion resistance:磨蚀强度abrasive resistance:耐研磨性（研磨磨损）abrasive blasting:磨蚀喷抛清 理abrasive finishing:打磨修整 blast finishing:喷砂修整adhesive resistance:耐粘合性（粘合磨损）chemical resistance:耐化学 性 resistance to diffusion:防扩散性 hydroscopic: adj.吸湿性的leak-free hydraulic system:防漏液压系统 moisture-proof:防潮的extraction system:（喷漆）排雾系统parameter:参数clearance:间隙（孑L隙） deviation:偏差anti-rusted / rustproof:防锈的 antiseize:防卡塞 dustproof:防尘 的 anti-shock / vibration-proof:防震的 spill-resistance:防溢性splash-proof:防溅的（splatter / spatter / sprinkle : v.激溅）spark:（擦出）火花（〜off:导致…）；n.火花good dead head resistance:流动性好edible oil:食用油 potable water:饮用水remainder cold material:残余冷料 scrap:下脚料/残次废料composite:复合材料 compound:配料sheet:片材/板材/薄片 overlay sheet:贴面材料composite laminate:复合层压制件 laminate: n.层压材料lamination:薄片制作 reinforcement:增强材料 polymer:聚合 物VOC （ volatile organic compound ）:挥发性有机化合物 Fumes of acids:酸性气体 alkali:碱（性的）fresh water:生水molding compounds:成型调和物 compound:混合物virgin / feedstock:原料 backing material:衬料 base material:基料colorant: n.颜料 padding / filler:填料 coating material:涂料 thermal spray coating:热喷涂层 intermediate coat:中间层（漆） textured paint:膨松漆 enamel:釉漆 flux:焊剂 coolant:冷却剂/冷却液 cure:熟化 curing agent:熟化剂 度 thinner:稀释剂 additive:添加剂 extender:补充剂 retarder:阻滞剂燃剂finish:整饰剂/抛光剂 finishing:整饰 good finish:光洁度良好 （semi-gloss:不完全光滑） reinforcing agent:增强剂 cleaning agent / solvent:清洗剂/溶剂 detergent:洗涤剂 clarifier:澄清剂additive:添加剂 pigment:颜料/色素（涂剂） adhesive : n.粘合剂 binder:结合剂electrical tape:绝缘胶布 adhesive strip:胶粘条backing: n.衬垫（unbacked: adj.无衬的） foreign object ：无关的物 品inlay: n+v.镶入（物） insert:插片，插塞/嵌件carbon brush （holder ）:碳刷 stone:油石 textile:织物 paper-backed wood veneer laminate:纸衬胶合薄木片talc:滑石（云母） mica:云母 PMP:电木粉polyolefins:聚烯烃 styrene:苯乙烯 rosin:松香oil seal:骨架式橡胶油封 oil cover:油封盖oil-tight connections:油密封连接 soldered connection:锡焊连接solderless wrap:无锡焊卷绕 wire-wraped connection:金属绕丝连接substrate:底层 galvanizing:电镀（层）primer: 底漆 lubricant:润滑剂 degree of cure: 固化程flame retardant:火焰阻wave soldered:波焊 pretine:预镀锡 linear oven:线性烘箱 vertical furnace:立式熔炉 plasma spray coating technique:等离子喷涂 HIP （hot isostatic pressure ）:热均衡压力 precipitation hardening:弥散（沉淀）硬化 dispersion hardening:弥散硬 化hardsurface: v.硬表面化 point / local / selective hardening:局部淬火 carbon case hardening:渗碳硬化 shell hardening:渗碳（表面淬火） case:渗碳层/淬火层（先渗碳后淬火） heat harden:淬火anneal:退火 negative hardening: n.低温退火bake: v.烘焙 after-bake:后烘 sulphurize: v.硫化carbonize:碳化调质处理：thermal refiningor:调质=先淬火+后高温回火quenching followed by tempering at high temperature（或 quenching prior to tempering at high temperature ） magnetic flux reversal:磁通量转换 centrifugally cast:离心式浇铸 centrifugal casting:离心铸塑（法） centrifugal molding:离心模制 flow molding:流动模制 molding:模塑bath lubrication:浸油润滑plastic injection molding machine:注塑机 plastic extruding machine:挤塑机 （pipe-, profile-, sheet-lines:管状-，异型状-，片状生产线） Reheat Stretch Blow Molding machine:再热式拉伸吹塑机（吹瓶机） aircompressor:空压机 die casting machine:压铸机 machine tools:机床/金属加工机械 metal forming tools:金属成形机 械 tool post:刀架 copy milling machine:仿形铳床grinding machine:磨床 boring machine:镗床clicker press / punching machine:冲床 drilling machine:钻床 planing machine:刨床 shaping machine:牛头刨床horizontal machining center:卧式加工中心 CNC （Computerized Numerical Control ）:电脑数值控制（数控） pelletizer:造粒机 cutting machine:切削机 size reduction equipment:粉碎机 /磨碎机 laminating machinery:层 压机 plastic mashing machine:破碎机 plastic mixing machine:混料机coordinate measuring machine:坐标测量机 In-process gaging machine:加工过程中的测量装置 machine shop:金工车间 钣金件：metal sheet dip soldered:浸焊spray booth:喷漆间spinning oven:旋转炉ion nitride:离子氮化法 （技术）。
英文版导游词（优秀4篇）作为一名可信赖的导游人员，时常需要编写导游词，导游词的主要特点是口语化，此外还具有知识性、文学性、礼节性等特点。
那么一遍条理清晰的`导游词应该怎么写呢？下面是牛牛范文整理的4篇英文版导游词，希望可以启发、帮助到大朋友、小朋友们。
英文的导游词篇一Good morning! Ladies and gentlemen:Today we will go and visit the Nanyue Temple, Nanyue Temple is situated on the northern tip of Nanyue Township and at the southern foot of Chidi Peak. In a layout of nine rows, It is the largest and best-preserved ancient palatial architectural complex of south China. Magnificent and splendid with resplendent upturned eaves. Inside the east in parallel to eight Buddhist palaces on the west, It is indeed a wonder in the history of religion that Taoism. Buddhism and Confucian culture can co-exist within a single temple.The exact time of the construction of Nanyue Temple is unknown. It existed asearly as in the Qin and Han Dynastis. Originally Located on the summit of Zhurong Peak, The temple was later moved to the mountain foot to facilitate the religious activities. The beginning of the Tang Dynasty witnessed the formal construction of the Heavenly Lord Huo"s Temple" the "Heavenly Master Temple"。
Review:Continuous hydrolysis and fermentation for cellulosic ethanol productionSimone Brethauer,Charles E.Wyman *Center for Environmental Research and Technology and Chemical and Environmental Engineering Department,University of California,Riverside,CA 92507,United Statesa r t i c l e i n f o Article history:Received 31August 2009Received in revised form 2November 2009Accepted 3November 2009Available online 14December 2009Keywords:Continuous fermentation Enzymatic hydrolysis Fuel ethanolLignocellulosic biomassSimultaneous saccharification and fermentation (SSF)a b s t r a c tEthanol made biologically from a variety of cellulosic biomass sources such as agricultural and forestry residues,grasses,and fast growing wood is widely recognized as a unique sustainable liquid transporta-tion fuel with powerful economic,environmental,and strategic attributes,but production costs must be competitive for these benefits to be realized.Continuous hydrolysis and fermentation processes offer important potential advantages in reducing costs,but little has been done on continuous processing of cellulosic biomass to ethanol.As shown in this review,some continuous fermentations are now employed for commercial ethanol production from cane sugar and corn to take advantage of higher vol-umetric productivity,reduced labor costs,and reduced vessel down time for cleaning and filling.On the other hand,these systems are more susceptible to microbial contamination and require more sophisti-cated operations.Despite the latter challenges,continuous processes could be even more important to reducing the costs of overcoming the recalcitrance of cellulosic biomass,the primary obstacle to low cost fuels,through improving the effectiveness of utilizing expensive enzymes.In addition,continuous pro-cessing could be very beneficial in adapting fermentative organisms to the wide range of inhibitors gen-erated during biomass pretreatment or its acid catalyzed hydrolysis.If sugar generation rates can be increased,the high cell densities in a continuous system could enable higher productivities and yields than in batch fermentations.Ó2009Elsevier Ltd.All rights reserved.1.IntroductionAccording to the recent report of the Intergovernmental Panel on Climate Change (IPCC)warming of the world’s climate system is unequivocal and is very likely due to the observed increases in anthropogenic greenhouse gas concentrations.Atmospheric con-centrations of carbon dioxide (CO 2),the dominant greenhouse gas,have increased from a pre-industrial value of about 280ppm to 379ppm in 2005,primarily as a result of fossil fuel use (IPCC,2007).Overall,petroleum is the source of about 170quadrillion (1015)BTUs or quads of energy of the total of more than 460quads the world uses,far more than derived from coal,natural gas,hydroelectric power,nuclear energy,geothermal,or other sources.Over half of petroleum in this total is used for transportation,and demand is projected to grow rapidly as vehicle traffic increases throughout the world and even accelerates in Asia.Besides the negative global warming impact of fossil fuels,volatile oil prices and dependency on politically unstable oil exporting countries re-sulted in a significant increase in international interest in alterna-tive fuels and led policy makers in the EU and the US to issue ambitious goals for substitution of alternative for conventional fuels (Galbe and Zacchi,2002;Wyman,2007).Ethanol made biologically by fermentation from a variety of bio-mass sources is widely recognized as a unique transportation fuel with powerful economic,environmental and strategic attributes.First generation ethanol made from starch-rich materials such as corn and wheat or from sugar feedstock is a mature commodity product with a worldwide annual production of over 13billion US gallons in 2007.However,these raw materials are insufficient to meet the increasing demand for fuels,and concerns have heightened recently that competition between the use of agricultural commod-ities for fuel production is driving up food costs.Furthermore,the use of food crops for fuel production may lead to environmentally detri-mental indirect land use changes,e.g.the deforestation of tropical rainforest to gain more farmland.In addition,the reduction of green-house gases resulting from use of starch-based ethanol is not as high as desirable (Farrell et al.,2006;Hahn-Hägerdal et al.,2006).Alter-natively,ethanol can be produced from lignocellulosic materials such as agricultural residues,wood,paper and yard waste in muni-cipal solid waste,and dedicated energy crops,which constitute the most abundant renewable organic component in the biosphere (Cla-assen et al.,1999).Regardless of the feedstock,the final ethanol selling prize must be competitive with that for gasoline,but gasoline benefits from over a century of learning curve improvements and largely paid for capital.Thus,profit margins in ethanol production processes are low,and returns on capital are uncertain due to the tremendous0960-8524/$-see front matter Ó2009Elsevier Ltd.All rights reserved.doi:10.1016/j.biortech.2009.11.009*Corresponding author.Tel.:+19517815703;fax:+19517815790.E-mail address:charles.wyman@ (C.E.Wyman).Bioresource Technology 101(2010)4862–4874Contents lists available at ScienceDirectBioresource Technologyjournal homepage:www.elsevier.c o m /l o c a t e /b i o r t echprice swings in petroleum prices.In this context,costs must be kept as low as possible,and continuous fermentation of cellulosic bio-mass to ethanol can offer important advantages in terms of greater productivity and lower costs.Unfortunately,although process designs have been conceptualized based on continuous enzymatic hydrolysis and fermentations to take advantage of their low cost potential,limited studies have actually been reported from which to design or advance the technology.Thus,more information is sorely needed on this subject to guide the advancement of lower cost approaches to making ethanol and overcome the significant cost barriers to market entry.In this paper,we will provide a short introduction to concepts and characteristics of continuous fermentations.Then a summary is presented of experiences and research activities withfirst gener-ation industrial continuous ethanol fermentations as these provide the foundation for second generation cellulose-based processes. Following that,we review current knowledge of continuous fer-mentation of lignocellulosic material,including those based on chemical and enzymatic hydrolysis of cellulose to glucose.2.Concept of continuous fermentationsIn a true continuous fermentation system,substrate is con-stantly fed to the reaction vessel,and a correspondingflow of fer-mented product broth is discharged to keep the reactor volume constant.Furthermore,the balance between feed and discharge is maintained for long enough times to achieve steady state oper-ation with no changes in the conditions within the -pared to a batch reaction,this mode of operation offers reduced vessel down time for cleaning andfilling providing improved vol-umetric productivity that can translate into smaller reactor vol-umes and lower capital investments plus ease of control at steady state.Two basic types of continuous reactors can be employed:the continuous stirred tank reactor(CSTR)or the plugflow reactor (PFR).In an ideally mixed CSTR,the composition in the reactor is homogenous and identical to that for the outgoingflow.In an ideal PFR,the reactants are pumped through a pipe or tube with a uni-form velocity profile across the radius,and the reaction proceeds as the reagents travel through the PFR with diffusion assumed to be negligible in the axial direction.Consequently,PFR operations imply that inoculum has to be constantly fed to the reactor for fer-mentation processes.Cascading a large number of CSTRs in series will have similar performance to a PFR.In a system with constant overall reaction stoichiometry that can be described by a single kinetic equation,performing the reac-tion in two or more bioreactors may lead to a higher product con-centration,a higher degree of conversion,a higher volumetric productivity,or a combination of these factors compared to opera-tion of a single CSTR.One approach to optimizing a continuous pro-cess is to determine the reactor configuration that gives the lowest residence time to achieve a certain degree of conversion.If the kinetics are known,a plot of the reciprocal rate against the dimen-sionless substrate concentration S/S feed can be employed to esti-mate the reaction residence time and therefore the reaction volume(de Gooijer et al.,1996).For a CSTR,the area corresponding to a rectangle whose height equals the reciprocal of the rate at the desired conversion will equal the residence time for reaction to this conversion,whereas the residence time for a PFR will corre-spond to the area under the curve(see Fig.1).If the desired conver-sion is higher than the minimum in the curve,a combination of reactors will require less reaction volume.Thus,for the situation depicted in Fig.1,the combination of a CSTR followed by a PFR will be preferred if a conversion of98%is targeted.An important performance criteria is the productivity of the fer-mentation system,i.e.,the amount of product formed per unit of time and reactor volume,which depends on several factors includ-ing substrate concentration,cell concentration,and dilution rate. We used a simple model based on Monod growth kinetic that in-cludes terms for product and cell inhibition(Lee et al.,1983)to illustrate the influence of some operational parameters.Generally, the productivity in a continuous fermentation system is higher than in a batch reactor.In the model example,a productivity of 3.57g LÀ1hÀ1was calculated for a batch process inoculated with 1g LÀ1yeast cells.In a standard single stage CSTR without cell retention,where the biomass concentration would befixed,a max-imum productivity of4.24g LÀ1hÀ1was calculated for a dilution rate of0.136hÀ1,however,the substrate conversion was only 83%.Generally it is desirable to achieve almost complete substrate conversion at the highest possible productivity to avoid loss of sub-strate or the need for recycle.In a two stage system with properly designed unequal reactor sizes(see Fig.2a),the maximum possible overall productivity would be lower than in a single stage system, but the substrate conversion at identical productivities would be higher.In the two stage system,a maximum overall productivity of4.16g LÀ1hÀ1was calculated at a substrate conversion of92% (Fig.2b).If a substrate conversion of99%were the goal,the pro-ductivity in a single stage CSTR would be 2.77g LÀ1hÀ1but 3.94g LÀ1hÀ1for a two stage system.Generally,a cascade of fer-mentors would be superior to a single vessel for autocatalytic reac-tions such as cell growth which are product-inhibited,but for situations with substrate inhibition,a single stage CSTR is often more favourable to remove as much reactant as possible(de Goo-ijer et al.,1996).3.Continuous ethanol production from starch and sugar feedstocks3.1.Industrial continuous ethanol production from sugar caneSugar cane is a tropical and subtropical crop that is the primary feedstock for ethanol production in Brazil,India,and Colombia.It contains mainly sucrose,a dimer of glucose and fructose,which is readily assimilated by Saccharomyces cerevisiae(Sanchez and Cardona,2008).Both sugar cane juice and molasses normally con-tain sufficient minerals and nutrients for S.cerevisiae to ferment1.00.80.60.40.20.0CSTRPFRS.Brethauer,C.E.Wyman/Bioresource Technology101(2010)4862–48744863them directly to ethanol(Wheals et al.,1999).In Brazil,70–80%of the distilleries employ fed-batch processes(Melle-Boinot Process) for fermentors with outputs ranging from400to2000m3ethanol per day.Typically,high yeast cell concentrations of between8% and17%achieve fermentation times of only6–10h andfinal etha-nol concentrations of up to11%v/v,corresponding to an average ethanol yield of91%.After each fermentation cycle,the yeast cells are separated,treated with dilute sulphuric acid to kill contaminat-ing bacteria,and then recycled to start a new fermentation.This se-quence can be repeated up to200times and minimizes carbon consumption for yeast growth while providing very high ethanol productivities(Dorfler and Amorim,2007;Godoy et al.,2008; Wheals et al.,1999;Zanin et al.,2000).Thefirst continuous ver-sions of the Melle-Boinot process appeared in the1970s,but sev-eral operational problems were detected,such as a high level of contamination,low productivity,low yields,and problems with solidsflow.Today’s continuous fermentation processes are opti-mized based on kinetic models to achieve high productivities(typ-ically10mL LÀ1hÀ1),high processflexibility and stability,and low consumption of chemicals and are considered to be less expensive for ethanol production than batch processes(Zanin et al.,2000).An important feature of state-of-the-art continuous processes is the use of multiples stages(typically four orfive)of variable sizes.The sugar substrate is fed to the top of thefirst reactor together with the recycled yeast cream and leaves through the bottom,flowing then by gravity to the middle of the next stage.Each reac-tor typically uses an external plate-type heat exchanger for cooling of the fermentation broth,with the kinetic energy of the liquid leaving the heat exchanger outlet used to agitate the reactor.The yeast cells produced are separated from the‘‘wine”by disk-bowl centrifuges,forming a yeast cream,which is then sent to acid treat-ment prior to being recycled back to thefirst reactor(Zanin et al., 2000).Guerreiro et al.(1997)described an expert system for the de-sign of such an industrial continuous fermentation plant which combines expert knowledge and industrial practices with kinetic modelling.As parameters are taken from industrial fermentations, differences between theoretical calculations and practical results are claimed to be minimal.In the example presented,an input medium containing170–190g LÀ1sugar was fed at a rate of 143m3hÀ1to a four stage reactor train with volumes of215, 274,324,and213m3to maximize performance.In this case,the steady state concentrations in thefirst and last stages were54 and1g LÀ1of sugar,42and66g LÀ1of ethanol,and29and 31g LÀ1of yeast biomass,respectively,and the process productiv-ity was given as7.7g LÀ1hÀ1.Generally,the volumes of the tanks influence the productivity which varied from6.1to7.9g LÀ1hÀ1. Through optimization,it was possible to replace a previous fed-batch plant that consisted of24fermenters of200m3volume each (total4800m3)producing400m3of96%ethanol per day with a continuous plant with a total volume of2500m3producing about 440m3of96%ethanol per day(Guerreiro et al.,1997).However, larger continuous plants exist with capability to produce up to 600m3ethanol per day(Zanin et al.,2000).In some Brazilian distilleries,processes based onflocculent yeast strains are employed,with cell separation in settlers to avoid costly centrifuges.Yeastflocculation is a reversible,asexual,cal-cium dependent process of self-aggregation in which cells adhere to formflocs consisting of thousands of cells.Because of their macroscospic size and mass,the yeastflocs rapidly settle out of the fermenting medium,thus providing natural cell immobiliza-tion(Verbelen et al.,2006).Compared to the classical Melle-Boinot process,it is claimed that up to1.5%higher fermentation efficiency is obtained,ethanol production costs are ca.$7/m3lower,and con-sumption of chemicals such as antifoam is reduced(Zanin et al., 2000).Despite such desirable attributes,there are also critical opinions about replacing batch fermentations with continuous processes.In one study of the advantages and disadvantages of continuous and batch fermentation processes for62distilleries over a time span of 9years(1998–2007),batch processes with yeast recycle were shown to be less susceptible to bacterial contamination and the corresponding loss in productivity(Godoy et al.,2008).Lactobacil-lus contaminations,in particular,are regarded as the major factor that can reduce ethanol yield and also impair yeast centrifugation, and greater quantities of antibiotics are needed to address this is-sue for continuous processes.Also,slightly more sulphuric acid was consumed in continuous processes.Yet,continuous processes have the advantages of lower installation costs due to smaller fer-mentor volumes and less heat exchanger demands as well as lower costs due to greater automation(Godoy et al.,2008).3.2.Continuous ethanol production from cornUp to now,corn is the major feedstock for ethanol production in the US,which surpasses Brazil as the largest ethanol producer. Corn kernels contain about70%by weight starch on a dry weight basis.Starch is a D-glucose polymer,consisting of about30%amy-lose,a linear chain of a-1,4linked glucose units with ahelical 4864S.Brethauer,C.E.Wyman/Bioresource Technology101(2010)4862–4874structure and70%amylopectin,a highly branched polymer with additional a-1,6glycolytic bonds.Ethanol from corn can be pro-duced by either a dry grind(67%of the fuel ethanol)or wet mill (33%)process with recent growth in the industry mostly with dry grind plants due to their lower capital costs(Bothast and Schli-cher,2005).In the wet mill process,the grain is separated into its four basic components of starch,germ,fiber,and protein to recover higher value co-products including corn oil,corn gluten meal,corn gluten feed,and germ.On the other hand,the dry grind process is much simpler in that the entire corn kernel is ground and mixed with water to form a mash.The isolated starch from wet-milling and the mash from the dry grind process are treated identically to produce ethanol.First,a thermostable alpha-amylase,which breaks down the starch poly-mer to soluble dextrins by hydrolyzing a1–4bonds,is added. The mixture is heated to over100°C to liquefy the mash over a holding time of at least30min.Then,glucoamylase is added, which converts liquefied starch to glucose at an optimal tempera-ture of65°C.In thefinal fermentation step,which is performed either coupled(simultaneous saccharification and fermentation, SSF)or subsequent to glucoamylase treatment(separate hydrolysis and fermentation,SHF),the mash is cooled to32°C,and yeast is added as well as ammonium sulphate or urea as a nitrogen source. Alternatively,proteases are added to break down corn protein to free amino acids for use as a nitrogen source.Fermentation is com-pleted in48–72h to afinal ethanol concentration of10–12%v/v and higher.Over the course of fermentation,the pH drops to4.0 or lower,which helps to prevent bacterial contamination.Many plants use simultaneous saccharification and fermentation,be-cause it lowers the risk of contamination,lowers the initial osmotic stress on the yeast,and is generally more energy-efficient(Bothast and Schlicher,2005).According to a United States Department of Agriculture(USDA) survey in2002,27%of the dry grind distilleries in the US employ continuous fermentation processes which are more common in large plants producing more than400m3ethanol per day(Shapo-uri and Gallagher,2005).To the best of our knowledge,no perfor-mance data for industrial continuous corn ethanol fermentations are published.However,Bai et al.(2008)described in their review a commercial plant employing a self-flocculating yeast with a pro-duction capacity of680m3per day which started operation in 2005in China.In this system,six fermentors with volumes of 1000m3each were arranged in a cascade,and corn meal hydroly-zate,with a sugar concentration of200–220g LÀ1,was fed to the fermentation system at a dilution rate of0.05hÀ1.Thefinal ethanol concentration was reported to be11–12%v/v.Yeastflocs were re-tained within the fermentor by baffles to effectively immobilize them,and the yeast concentration within the fermentors was maintained at40–60g DCW LÀ1.4.Continuous production of second generation ethanol from lignocellulosic materialsAlthough composition of lignocellulosic materials varies in dif-ferent plants,the three main components are cellulose(36–61%), hemicellulose(13–39%),and lignin(6–29%)(Olsson and Hahn-Hägerdal,1996).Cellulose is a D-glucose polymer,where the sub-units are linearly linked by b-1,4glycosidic bonds and exists in crystalline and amorphous forms.Hemicellulose is composed of linear and branched heteropolymers of pentoses(i.e.,xylose and arabinose)and hexoses(i.e.,mannose,glucose,and galactose).Lig-nin is a polymer that can consist of three different phenylpropane units(p-coumaryl,coniferyl and sinapyl alcohol)that bind the plant together.In order to release fermentable sugar monomers,cellulose and hemicellulose are hydrolyzed chemically,enzymati-cally,or by their combination(Gray et al.,2006;Hendriks and Zee-man,2009;Wyman et al.,2004).Lignocellulosics can be hydrolyzed chemically by addition of acids,with sulphuric acid most often preferred based on price and toxicity,and acid hydrolysis can be divided in two categories: concentrated acid hydrolysis and dilute acid hydrolysis.Concen-trated acid processes operate at low temperatures,e.g.,40°C,and give high sugar yields,e.g.,90%of theoretical glucose yield.How-ever,acid consumption is high,a lot of energy is consumed for acid recovery and recycle,the equipment can suffer from corrosion,and reaction times of2–6h are required.The dilute acid process is characterized by a low acid consumption and very short reaction times at high temperatures.Hemicellulose is generally much more susceptible to acid hydrolysis than cellulose,and yields of more than85%can be obtained at relatively mild conditions,with only a small part of the cellulose converted to glucose.More severe con-ditions required to achieve high glucose yields from cellulose, however,lead to degradation of hemicellulose sugars,resulting in low yields and unwanted side-products that are also strong fer-mentation inhibitors.Potential inhibitors that can be formed or re-leased from hemicellulose,cellulose,and lignin during such thermochemical routes include furfural,5-hydroxymethylfurfural (HMF),levulinic acid,acetic acid,formic acid,uronic acid,4-hydroxybenzoic acid,vanillic acid,vanillin,phenol,cinnamalde-hyde,and formaldehyde.To reduce degradation of monosaccha-rides at high temperature,dilute acid hydrolysis is typically carried out in two stages,with hemicellulose solubilized in thefirst under relatively mild conditions and the residual solids hydrolyzed in the second under the more severe conditions needed to break-down cellulose.With this procedure,hemicellulose derived sugar yields are in the range of90%,while glucose yields are only about 40–60%at realistic residence times.However,it has been reported that alternative reactor configurations to classic batch reactors, such as a shrinking-bed reactor give glucose yields of up to90% (Taherzadeh and Karimi,2007).Cellulase enzymes from the fungus Trichoderma reesei can hydrolyze biomass to sugars at near ambient temperatures,result-ing in little degradation.However,because sugar yields from raw biomass are very low,the biomass is subjected to a pretreatment step.Numerous pretreatment methods have been developed including pretreatment with steam,liquid hot water,dilute acid, lime,ammonia,and wet oxidation and are discussed in more detail elsewhere(Hendriks and Zeeman,2009;Mosier et al.,2005;Wy-man et al.,2005,2009).Effective pretreatments are thought to en-hance enzymatic digestibility of biomass due to several effects: disruption of the lignocellulosic structure by loosening the hemi-cellulose lignin entanglement,hemicellulose hydrolysis,lignin sol-ubilisation and disruption,decrystallization of cellulose,and increased accessible surface area(Lynd et al.,2002;Zhang and Lynd,2004,2006).During many pretreatments,fermentation inhibitors such as acetic acid,lignin breakdown products,and fur-fural are released.After pretreatment,several process configura-tions are possible,as recently reviewed in detail(Cardona and Sanchez,2007).In the separate hydrolysis and fermentation (SHF)approach,the liquid and solid phases are separated after pre-treatment,and the solid phase may be subjected to additional washing steps.The solids,in case of dilute acid and steam pretreat-ment,contain most of the lignin and cellulose from the raw bio-mass,with the latter hydrolyzed to glucose by addition of cellulolytic enzymes that are comprised of endo-and exoglucanase and b-glucosidase activities,often supplemented with additional b-glucosidase derived from Aspergillus niger.The resulting hexose solution is then fermented to ethanol using conventional yeast or other suitable microorganisms.A suitable pentose fermenting strain can convert the liquid stream from pretreatment containingS.Brethauer,C.E.Wyman/Bioresource Technology101(2010)4862–48744865solubilized hemicellulose to ethanol in a separate unit usually after a detoxification step such as overliming to reduce fermentation inhibitors and make the hydrolyzate fermentable.Hydrolysis and fermentation were initially separated to better match the pH and temperatures to those that are optimal for each step,with about 50°C preferred for enzymatic hydrolysis and about32°C often best for fermentations.Alternatively,enzymes could be added to the whole pretreatment slurry without separation of the liquid from the solids,followed by fermentation of pentoses and hexoses to ethanol,a process which we call separate hydrolysis and co-fer-mentation(SHcF).This more integrated approach is economically very attractive,but the fermentation step is much more challeng-ing than in SHF and complicates hydrolyzate conditioning to re-move inhibitors due to the presence of the solids(Cardona and Sanchez,2007).Because cellulases are inhibited by their hydrolysis products cellobiose and glucose,a favoured processing mode is to combine hydrolysis and the fermentation,a process termed simultaneous saccharification and fermentation(SSF),thereby keeping sugar concentrations low(Gauss et al.,1976;Spindler et al.,1987;Takagi et al.,1977;Wright et al.,1987;Wyman et al.,1986).Although ini-tial applications subjected only the washed solids fraction from pretreatment to SSF with the liquid pentose stream processed sep-arately,these two steps can be combined in what is termed simul-taneous saccharification and co-fermentation(SScF)(Wooley et al., 1999).Despite the need to reduce the temperature for SSF from the optimal levels for enzymes to accommodate fermentative organ-isms available to date,SSF was shown to achieve higher rates, yields,and concentrations than SHF by overcoming the major ef-fects of end-product inhibition(Spindler et al.,1987;Wright et al.,1987).In addition,SSF,and even more so SScF,reduces fer-mentation equipment demands,and the presence of ethanol im-pedes invasion by unwanted organisms.Thus,until enzymes are found that can overcome end-product inhibition,SSF or SScF are likely to be preferred in terms of productivity,yields,and ethanol concentrations.In the following sections,results for continuous fermentations with hydrolzates from acid and enzymatic hydroly-sis and for SSF applications are summarized.4.1.Fermentation of hexoses in enzymatic hydrolyzatesFermentation of hexose sugars derived from enzymatic hydro-lysis of washed pretreated lignocellulosic material generally does not pose special difficulties(see Table1),as the inhibitor concen-tration should be very low.However,compared to starch and sug-arcane fermentations,the sugar concentration after hydrolysis are often low with values approaching typically not more than70g LÀ1 due to challenges in feeding solids concentrations higher than about10%by weight to the fermentors and end-product inhibition of cellulase enzymes by the sugars released.Thus,a concentration step,e.g.,vacuum evaporation,might be needed to achieve higher concentrations,with additional extra costs possibly counterbal-anced by savings in thefinal distillation step(Maiorella et al., 1984).In one study,sugar cane bagasse was delignified by autoclaving in1%NaOH for1h,and the solids were washed several times prior to hydrolysis by T.reesei cellulases.In a single stage continuous fer-mentation of S.cerevisiae with a16%glucose feed,several dilution rates were tested tofind a maximum ethanol productivity of 4.1g LÀ1hÀ1at a dilution rate of0.13hÀ1.At this point,steady state concentrations of90g LÀ1glucose,31g LÀ1ethanol,and 3.8g LÀ1biomass were measured.To avoid washout of large amounts of unfermented glucose,a continuous single stage cell re-cycle fermentation system was set up,and the maximal productiv-ity reached18.3g LÀ1hÀ1at a dilution rate of0.3hÀ1with a steady state glucose concentration of22g LÀ1(Ghose and Tyagi,1979).Lee et al.(2000)employed an enzymatic hydrolyzate derived from washed steam exploded oak chips(3min at215°C).To re-duce fermentation inhibitors,the hydrolyzate was sterilized for 120min at60°C,rather than at a typical temperature of121°C. Continuous cultures were performed in a reactor equipped with an internal membranefiltration module to retain cells inside the reactor.At a dilution rate of0.22hÀ1and a feed glucose concentra-tion of180g LÀ1,77g LÀ1ethanol was produced,corresponding to a productivity of16.9g LÀ1hÀ1and a yield of0.43g gÀ1.In a batch fermentation in a similar medium containing170g LÀ1glucose, only57g LÀ1ethanol was produced in210h,with35g LÀ1glucose not utilized,leading to a very low productivity of0.3g LÀ1hÀ1.No problems were experienced with bacterial contamination despite the low sterilization temperature.When the solid–liquid separation and solids washing steps are omitted and the whole slurry is enzymatically hydrolyzed,fermen-tations are much more difficult,as exemplified by the work of Palmqvist et al.(1998)who employed a hydrolyzate of spruce pre-treated by steam explosion for5min at215°C after sulphur diox-ide impregnation.Two different batches of hydrolyzate were used, containing25–50g LÀ1glucose and approximately10g LÀ1man-nose,that were both supplemented with mineral media.S.cerevi-siae ATCC96581,a strain isolated from a spent sulphite liquor(SSL) fermentation plant running since1940and showing a7-fold high-er maximum growth rate on SSL than bakers yeast,was employed for the study.At a pH of4.6in a batch system,cells metabolizedTable1Fermentation of hexoses in enzymatic hydrolyzates.Medium Sugar concentration(g LÀ1)Reactor type Dilutionrate(hÀ1)Ethanol(g LÀ1)cell dryweight(g LÀ1)Ethanolyield(g gÀ1)Ethanolproductivity(g LÀ1hÀ1)ReferencesSugar cane bagasse pretreated with NaOH;washed solids enzymatically hydrolyzed,concentration by vacuum evaporation;addition of‘‘cheapnitrogen source”,CaCl2,MgSO4Reducing sugars:160Single stage CSTR0.1331 3.80.19 4.1Ghose andTyagi(1979)Single stage CSTRwith cell recycle0.358300.3618.3Steam exploded oak chips,washed solids enzymatically hydrolyzed,concentrated by vacuum evaporation,sterilizationfor120min at60°C Glucose:180Single stage CSTRwith cell retention bymembrane module0.2277n.d.0.4316.9Lee et al.(2000) Glucose:170Batch–570.340.3(fermentationtime of210h)Steam exploded spruce,whole slurry enzymatically hydrolyzed,addition of complete mineralmedium salts Glucose:25–50,mannose:10Single stage CSTR0.05200.90.320.5Palmqvistet al.(1998)0.1WashoutSingle stage CSTRwith cell recycle0.123Maximum260.51 2.34866S.Brethauer,C.E.Wyman/Bioresource Technology101(2010)4862–4874。
Designing Microreactors in ChemicalSynthesis –Residence-time Distributionof Microchannel DevicesKLAUS GOLBIGANSGAR KURSAWEMICHAEL HOHMANNSHAHRIYAR TAGHAVI-MOGHADAMTHOMAS SCHWALBECPC-Cellular Process Chemistry Systems GmbH,Mainz,GermanyThis contribution deals with the application of numerical methods in CPC-Systems’microreaction development process and demonstrates the feasibility and significantbenefits for the suggested design method.It is focused on the design of capillary resi-dence tubes,which is necessary if the residence time provided by the original micro-reactor is not sufficient to complete the reaction.The residence time distribution iscalculated from a straightforward numerical model based on the common assump-tion that axial gradients can be neglected.The results can be adapted easily to othercapillary diameters or reaction conditions.As an example,the method is applied tothe case of sequential synthesis.Keywords :Microreactor;Residence time distribution;Sequential synthesis;Dispersion;Fluid dynamicsIntroductionSynthesis via MicroreactorsMicroreaction devices are beneficial innovative tools in the improvement and opti-mization of reactions as well as in fast supply of sufficient quantities of target com-pounds.This exciting new technology improves control of reaction parameters such as temperature and concentration equipartition and thus allows in many cases higher yields,fewer by-products,and higher selectivities.Therefore it has become increas-ingly interesting for small-scale production and mobile reaction systems,e.g.,for automotive applications (Wegeng and Drost,1998).In order to realize these benefits a proper design of the microreaction system is crucial:heat transfer area,mixing channel dimensions,and flow capillaries must be sized very carefully to achieve,for example,reasonable mixing,pressure drops,andReceived 2March 2001;in final form 19June 2003.Address correspondence to Klaus Golbig,CPC-Systems GmbH,Hanauer Landstrasse 526,G58III,Frankfurt,Mainz 60343,Germany.E-mail:wille@620m.,192:620–629,2005Copyright #Taylor &Francis Inc.ISSN:0098-6445print =1563-5201onlineDOI:10.1080=00986440590495197Designing Microreactors in Chemical Synthesis621 flow equipartition(Ehrfeld et al.,1997).To open the field of general application of microreactors in chemical synthesis,a comprehensive analysis of the requirements for such a microreactor has to be performed.Such an analysis identifies the design parameters for multipurpose microreactors,based on a feed rate corresponding to a typical bench-scale synthesis.The resulting solution should be suitable for a variety of applications with reactions or transformations of miscible liquids.Microreactor Approach to a Better ChemistryCPC-Systems,Cellular Process Chemistry Systems GmbH,located in Mainz (Germany),is engaged in the development and optimization of standardized modu-lar microreaction systems as well as in their application to organic synthesis.This approach is based on the idea of shortening development periods of new active substances by consequent numbering-up.This means that the same microreactor units are used in laboratory and in pilot plant,thus avoiding the scale-up risk.Numerous microreactor applications are stated in the current literature that can be considered as proof of the principle of microreaction technology in general. Microreactors have been used in commodity synthesis,i.e.,ethylene oxide(Richter et al.,1998),the preparation of hydrocyanic acid(Hessel et al.,1999)and for poly-merizations.CPC-Systems’modular microreaction system,based on the CYTOS1 microreactor,can be applied to promising fields in drug discovery and development processes.For instance,chemical syntheses of different targets like quinoline acid derivates(Ciprofloxacin1)and the Paal-Knorrpyrrole synthesis have been investi-gated(Taghavi-Moghadam et al.,2001).Further examples from our day-to-day microreactor lab experience could be found in Schwalbe et al.(2002)and Autze et al.(2000);they cover the complete range from common nitrations over rearrange-ments to Suzuki couplings and Wittig-Horner reactions.Furthermore,the CYTOS1 modular microreaction system can be used in a setup for sequential synthesis to generate compound libraries.In comparison to conventional parallel synthesizers,sequential synthesis offers higher flexibility because the reaction conditions can be controlled independently and individually for each reaction pared to the limited reaction vol-ume in a reaction block of a parallel synthesizer,access to variable amounts of target compounds is ensured by a system running continuously,even if the reaction sequence is demanding or divergent.The automation of the system,which can be established by using an auto-feed-sampler and a fraction collector,leads to perform-ing a maximum of chemistry with minimum effort.The automated microreaction system also opens up an easy way to automatic reaction optimization.For this purpose a mathematical software generates a statisti-cal design of experiments and evaluates the results automatically via inline analytical sensors.Therefore CPC-Systems’microreaction systems are suited for the pro-duction of specimens as well as for the process development.Design Model for Capillary FlowsThe ProblemCPC-Systems’CYTOS1microreaction system,shown in Figure1,is composed of a pumping module,an exchangeable microreaction unit,and an optionalresidence-time providing module,all connected by a convenient bayonet coupling.The residence-time providing unit,for example,a stainless steel capillary,is required for realization of larger reaction times.For sequential operations the residence-time distributions (RTD)of the micro-reactor and the residence module have to be considered carefully because they may suffer from the laminar flow regime in the capillary tubing,especially if dead volumes are present.On the other hand,diffusive mixing can be very fast on a small scale,so that laminar flow is not necessarily considered a drawback.If more than one capillary is operated in parallel,flow equipartition also becomes an important issue.However,laminar flow regime is known to be modeled very precisely with minor effort.In our microreaction system corrosion-resistant ceramic piston pumps are used,in contrast to some micro-analytic devices,e.g.,electrophoresis,which are based on electroosmotically driven flows.The velocity profiles differ in both cases.In a pressure-driven capillary,the laminar velocity profile in Figure 2shows a pro-nounced parabolic shape,where the liquid at the wall is nearly stagnant.Influenced by such a velocity profile a concentration peak injected at the inlet will soonbeFigure 1.CYTOS 1microreaction system,the first commercial turn-key microreaction system.622K.Golbig et al.dispersed,yielding a broad residence-time distribution at the outlet.Nevertheless,the molecular diffusion in radial direction limits this peak broadening.In this article design rules consider both effects.ModelingThere are only a few sources available on this particular problem.In the engineering literature usually only an axial dispersion process is considered (Levenspiel,1958,1999),which was shown first by Taylor (1953)to be sufficient.He developed an analytical solution of the interaction between radial diffusion and axial convection in tubes.On the assumption that axial concentration gradients can be neglected in comparison to radial gradients and the introduction of a relative coordinate system moving with the mean velocity of the fluid,he was successful in reformulating the original problem into a simpler unidimensional axial dispersion process.The role of this process in the case of heterogeneous gas-phase reactions was investigated by Matlosz and coworkers (Commenge et al.,2001).In order to uncover the details of this peak-broadening phenomenon,a numerical approach was developed that is more flexible regarding geometry and boundary con-ditions.The model uses finite volume balances as well as the following assumptions:.Fully developed parabolic velocity profile .Restriction to radial diffusion .Conservation of mass (no reaction).Discretization in axial and radial direction .Limitation of maximum concentration change to 10%by appropriate choice of D t .Length of one axial discretization element D lD l ¼D t Áu maxThe program computes the diffusivec i ;j ;k þ1¼c i ;j ;k þD n i À1;k ÀD n i ;j ;k p D l ðr i Àr i À1Þwith D n i ;k ¼2p D D l r i c i ;j ;k Àc i þ1;j ;k r i þ1Àr iand the convectional mass transport from cell i,j À1to cell i,jc i ;j ;k þ1¼ð1Àg i Þc i ;j ;k þg i c i ;j À1;kin an alternating mode.In the equations n denotes amount of moles,c the cell concen-tration,D the diffusion coefficient,r i the outer radial position of the cell i ,and g itheFigure 2.Velocity profile and peak broadening inside a capillary tube due to combination of axial convection and radial diffusion.Designing Microreactors in Chemical Synthesis 623velocity weighting factor of cell i.The velocity weighting factor g i represents the ratio of fluid leaving cell i,j À1into the next cell i,j downstream during the time period D t .g i ¼1Àr 2i þr 2i À12R 2where R denotes to the inner radius of the capillary.The subscripts contain infor-mation about the radial and axial position of the cell,and the last subscript indicates the numeric operation step.Simulation ResultsAs presented in Figure 3,the resulting residence-time distribution of a short capillary for each individual radial position clearly shows that material is short cutting through the center whereas the RTD curves near the wall are delayed.Generalized RTD Diagram.To avoid time-consuming calculations,the fact is used that,simply put,the calculation procedure is just computing the same figures of dimensionless concentrations in each run.Only the scaling of the time steps differs depending on the diffusion time constants d 2=D .Thus,the resulting dimensionless RTD curve is dependent on only one parameter,the dimensionless diffusion time or Fourier number Fo d :Fo d ¼t mean Dd where t mean is mean residence time,D is diffusivity,and d 2is tube diameter is1.Figure 3.Residence-time distribution for capillary with 5min mean residence time and1.75mm inner diameter (D ¼6.9Á10À10m 2=s).624K.Golbig et al.Thus,previously generated output data can be reused for other conditions.Examples for dimensionless RTD curves are illustrated in Figure 4.Each curve represents a set of many different cases that are analogous from a physical point of view.For the required case,only the Fourier number Fo d has to be determined,and the corresponding calculation run can be taken from the output database,which should be arranged in terms of Fo d number.Dimensionless Dispersion Curve.This straightforward numerical model was vali-dated by experiments with capillaries and toluene as tracer,which was analyzed by gas chromatography (GC).The double logarithmic plot in Figure 5reflects the width of the RTD curve peaks at half of their height showing a minor deviation between the experimental results (plotted as dots)and the numerical calculated dis-persion curve (dashed line),but we found excellent agreement between the theory of Taylor (Levenspiel,1999;Taylor,1953)(gray line)and our calculated dispersion curve.During the evaluation it became apparent that there is a need for faster solvers that give results for high Fourier numbers Fo d greater than three.One possibility to reach this aim is to exploit the fact that the dispersion process in the laminar flow regime can be regarded as a linear signal transmission process.Thus,the trans-fer functions of two capillaries,which have to be determined first,can be convo-luted.Then the convolution is done from each inlet radial position of the first capillary to each outlet position of the second one by averaging over all possible combinations.The advantage of such a procedure is that it proceeds exponentially in time or capillary length.Although convolutions are very time-consuming calculations,they offer a speed advantage for high Fo dnumbers.Figure 4.Generalized RTD curves.Designing Microreactors in Chemical Synthesis 625Application to Sequential SynthesisOne major application of microreaction systems is the generation of a variety of substances by automatically exchanging the starting materials (and if necessary also modifying the reaction conditions).A photo of such a sequential synthesis setup using the SEQUOS 2Lab System is given in Figure 6.An auto-sampler and a fraction collector complete the setup of the CYTOS 1microreaction system.The individual substances are separated by short purge-flushes of solvents.The intensity of these purge-flushes can be modified in order to optimize the process.While too long flushes waste operating time,too short flushes may result in cross-contamination of the different substances.Figure 7illustrates an example with short pumping and purging periods.Reac-tant A is pumped over a time period of t ¼4min 30s,the spacer over 2min 20s.Because of the RTD,the resulting response at the system’s exit after 9min 40s is slightly broadened.The product is collected directly after the elapse of the mean residence time for the adjusted pumping time.While collecting the first reactant A,the next reactant B is already fed into the reactor separated by the spacer.It can be clearly seen that both reactant peaks are nevertheless separated.An inte-gration of the RTD signal yields that 85%of the fed reactants are collected,slightly diluted by spacer solvent.This example clearly demonstrates that the residence-time distribution of the system –microreactor and residence tubing –has to be taken into account and is a crucial part of the system’s functionality.In the example of Figure 8a longer pumping time was applied in order to obtain a sample of higher quality (i.e.,lessFigure 5.Dimensionless dispersion curve.626K.Golbig et al.dilution with spacing solvent),slightly increasing the spacing time from 140s up to 270s and improving the separation of both sequences.This setup allows the collect-ion of 77%of the whole pulse with only 1.3%dilution by spacing solvent.Theore-tically,it is possible to gather all spent material if the purging time is as long as the total peak width from the Diracpulse.Figure 7.Short cycle times for high throughput (SEQUOS 2microstructured residence time modules having 9min 40s mean residence time,pumping time 270s,spacing time 140s).Figure 6.Sequential synthesis with SEQUOS 2microreaction system.Designing Microreactors in Chemical Synthesis 627Conclusion and OutlookThus it can be stated that.CPC-Systems has successfully implemented a realistic numerical model for residence-time distribution of capillaries.Residence capillaries have been designed with adjusted trade-off between peak-broadening and pressure drop demands.Calculated data can be converted easily to actual conditions.Experiments can be planned accurately inadvance.Figure 8.Sequential synthesis with longer cycle times for overall higher product quality and better sequence separation (SEQUOS 2microstructured residence time modules having 9min 40s mean residence time,9min 40s pumping time,and 4min 30s spacingtime).Figure 9.Temperature distribution in a flat microchannel setup (70m m wide capillary gap)with neutralization reaction (55kJ =mol,concentration 4800mol =m 3).628K.Golbig et al.Designing Microreactors in Chemical Synthesis629 This method will be used as a pre-optimization tool for future microreactor projects at CPC-Systems.Future work aims at the extension to more complex cases and flow structures.An example for this is presented in Figure9,where the tempera-ture distribution in a flat rectangular channel is shown.The channel is fed with strong acid and strong base from the left.Instantaneous release of reaction heat(55kJ=mol)is presumed as well as isothermal wall condition.Due to micro dimensions of the channel,the hot spot is limited to4.2K in this case.LiteratureAutze,V.,Kleemann,A.,Golbig,K.,and Oberbeck,S.(2000).Nachr.Chem.,48,p.683–685. Commenge,J.M.,Falk,L.,Corriou,J.P.,and Matlosz,M.(2001).In5th International Conference on Microreaction Technology:Book of Abstracts,143.Ehrfeld,W.,Golbig,K.,Hessel,V.,Lo¨we,H.,and Richter,Th.(1997).In VDI-GVC Jahrbuch,102–116,VCH,Weinheim.Hessel,V.,Ehrfeld,W.,Golbig,K.,and Wo¨rz,O.(1999).GIT Lab.-Fachz.,10,1100–1103. Levenspiel,O.(1958).Ind.Eng.Chem.,50,343.Levenspiel,O.(1999).Chemical Reaction Engineering,3d ed.,ch.13,296–301,John Wiley, New York.Richter,Th.,Ehrfeld,W.,Gebauer,K.,Golbig,K.,Hessel,V.,Lo¨we,H.,and Wolf,A.(1998).In2nd International Conference on Microreaction Technology:Process Miniaturization, Topical Conference Preprints,146–151,American Institute of Chemical Engineers, New York.Taghavi-Moghadam,S.,Kleemann,A.,and Golbig,K.(2001).Microreaction technology as a novel approach to drug design,process development and reliability,Org.Process Res.&Dev.,5,652–658.Taylor,G.I.(1953).Proc.Roy.Soc.,219A,186.Schwalbe,T.,Autze,V.,and Wille,G.(2002).Chimia,56,636–646.Wegeng,R.S.and Drost,M.K.(1998).In2nd International.Conference on Microreaction Technology:Process Miniaturization,3–11.。
气相法PE装置脱挥单元的数值模拟及应用吴文清【摘要】基于费克扩散定理、亨利定律、质量守恒定律等，结合气相法工艺聚乙烯（PE）装置脱挥单元中脱气仓的运行情况，建立了脱气仓的数学模型。
运用该模型定量分析了N2流量、停留时间、压力等操作条件对脱气仓操作曲线和脱挥性能的影响，模拟分析了300kt/a气相法PE装置脱挥单元，确定了优选操作条件：操作点应同时位于出口处组分的质量分数与N2流量关系曲线的转折点，以及N2流量与停留时间关系曲线的转折点附近；N2流量与PE流量之比为0.010~0.040。
%The resin degassing unit mathematical model of gas-phase fluidized bed polyethylene process was established based on Fick's diffusion law, Henry's law, mass conservation equation and so on. Then the model was applied to quantitatively analyzing the impact of the operating conditions such as nitrogen flow rate, residence time and pressure on the operation curve of purge bin and degassing performance curve, and simulation analysis of resin degassing unit in a 300 kt/a gas-phase polyethylene installations was performed to determine the preferred operating conditions. Specific conditions: operating point should be located at the turning point on outlet mass percentage of the components-nitrogen flow curve and at the turning point on nitrogen flow-residence time curve, and the flow ratio of nitrogen to polyethylene ranged from 0.010 to 0.040.【期刊名称】《合成树脂及塑料》【年(卷),期】2014(000)004【总页数】5页(P43-47)【关键词】聚乙烯;气相法;脱挥单元;数学模型【作者】吴文清【作者单位】中国石油化工股份有限公司天津分公司，天津市 300270【正文语种】中文【中图分类】TQ325.1+2;TQ021.8聚乙烯（PE）脱挥是气相法工艺生产PE的一个重要单元，目的是脱除PE粉料中的单体、共聚单体、冷凝介质和其他组分，并且使残留的催化剂失活，在满足环境保护的要求、保证下游工序安全和产品质量的同时，可以降低生产成本。
Transportation Advances and Applications Transportation has always been a crucial aspect of human civilization, enabling the movement of people and goods from one place to another. Over the years, there have been significant advances and applications in transportation, revolutionizing the way we travel and transport goods. These advancements have not only improved the efficiency and speed of transportation but have also had a profound impact on various aspects of our lives, including the economy, environment, and social dynamics.One of the most notable advances in transportation is the development of electric and autonomous vehicles. Electric vehicles have gained popularity due to their environmentally friendly nature, as they produce zero emissions and reduce the reliance on fossil fuels. The widespread adoption of electric vehicles has the potential to significantly reduce air pollution and mitigate the impact of climate change. Additionally, the emergence of autonomous vehicles has the potential to revolutionize the way we travel, making transportation safer, more efficient, and accessible to a wider population, including individuals with disabilities and the elderly.Another significant advancement in transportation is the development of high-speed rail systems. These systems have the potential to drastically reduce travel times between cities, making long-distance travel more convenient and efficient. High-speed rail also has the potential to alleviate traffic congestion and reduce the reliance on air travel for short to medium-distance trips, thereby reducing greenhouse gas emissions. Furthermore, high-speed rail systems can stimulate economic development in the regions they connect, creating new opportunities for business, tourism, and cultural exchange.The advent of ride-sharing and car-sharing services has also transformed the way we think about transportation. These services have provided a more flexible and cost-effective alternative to traditional car ownership, reducing the number of vehicles on the road and alleviating parking and congestion issues in urban areas. Additionally, ride-sharing and car-sharing services have the potential to improve access to transportation for individuals who may not have the means to own a car, thereby promoting social equity and inclusion.Furthermore, advancements in transportation technology have led to the development of smart transportation systems, which leverage data and connectivity to optimize the flow of traffic and improve the overall efficiency of transportation networks. These systems have the potential to reduce travel times, fuel consumption, and emissions, while also enhancing the safety and reliability of transportation infrastructure. Additionally, smart transportation systems can provide real-time information to travelers, enabling them to make more informed decisions about their routes and modes of transportation.In conclusion, the advances and applications in transportation have had a profound impact on our lives, reshaping the way we travel, commute, and transport goods. These advancements have not only improved the efficiency and sustainability of transportation but have also contributed to economic development, environmental conservation, and social inclusion. As we continue to innovate and invest in transportation technology, it is essential to consider the broader implications of these advancements and ensure that they benefit society as a whole. By embracing these advancements and harnessing their potential, we can create a more sustainable, accessible, and efficient transportation system for future generations.。
Axial transport and residence time of MSW in rotary kilnsPart I.ExperimentalS.-Q.Li a,b,*,J.-H.Yan a ,R.-D.Li a ,Y .Chi a ,K.-F.Cen aa Department of Energy Engineering,Zhejiang University,Hangzhou 310027,PR China bDepartment of Thermal Engineering,Tshinghua University,Beijing,100084,PR ChinaReceived 17October 2000;received in revised form 28December 2001;accepted 31December 2001AbstractExperiments on the influences of operational variables on the axial transport of both heterogeneous municipal solid waste (MSW)and homogenous sand are conducted in a continuous lab-scale rotary kiln cold pared with sand,the residence time of MSW has a relatively large discrepancy with the ideal normal distribution due to the trajectory segregation of MSW components.The residence time at different axial zone is quite different due to the varied bed depth profile along the kiln length.MSW has a longer mean residence time (MRT)and a lower material volumetric flow (MVF)than sand because of the higher h d than sand.The increment of both rotating speed and kiln slope reduces MRT,and increases MVF.Exit dam has a significant impact on the MRT and the influence of internal structure group consisting of various axial ribs and circular ribs is mainly determined by the height of circular ribs.Inside wall roughness also has effect on MRT through changing the bed regimes.For a case with the certain inlet and exit bed depths,the product of MRT and MVF holds at a constant within the limits of experimental errors in spite of the changing experimental variables.D 2002Published by Elsevier Science B.V .Keywords:Rotary kiln;MSW;Axial transport;Mean residence time;Material volumetric flow1.IntroductionRotary kilns have been widely employed in chemical and metallurgical industries as heterogeneous noncatalytic gas–solid reactors.The typical applications include drying or heating of wet solids,mixing or grinding of powders,calcining of limestone,clinkering of cementitious materials,reducing of iron ore or ilmenite,etc.[1–3].Rotary kilns continue to find new applications in such gas–solid reac-tions,despite challenges from newer and more specialized reactors such as fluidized bed and spouted bed.In recent years,rotary kilns have played an important role in the thermochemical treatment of municipal solid wastes (MSW).Rotary kiln system is one of the most promising incineration processes since it can simultane-ously treat wastes as liquids or solids of various shapes and sizes and easily achieve the flexible adjustment by altering kiln inclination,rotational speed,etc.Rotary kiln as a primary gasification chamber,followed by a secon-dary combustion chamber,can fulfil the complete destruc-tion and detoxification of hazardous wastes,meanwhile minimize emissions of dioxins and heavy mental.All these unique features enable rotary kiln irreplaceable in MSW incineration.‘Siemens Schwelbrenn’,‘Noell Conversion’and ‘Westinghouse O’Connor’processes are updated rep-resentatives of rotary kiln incinerators [4,5].Pyrolysis,on the other hand,is an attractive alternative to incineration as a waste treatment option with respect to minimum environmental emissions and maximum resource recovery [6,7].Rotary kiln pyrolyser also has many unique advantages over other types of reactors.For instance,slow rotation of inclined kiln enables the well mixing of wastes,thereby the more uniform pyrolytic products.Also,the flexible adjustment of residence time can make pyrolysis reaction perform at a perfectly optimum condition conven-iently.With a view to different resource recovery option,rotary kiln can be properly designed to yield mainly the synthesis gas,e.g.,‘Landgard’Process [8],or to make the high calorific tars as well as porous carbon black,e.g.,‘Kobe Steel’Process [9].Mean residence time (MRT)of solids through rotary kiln is one of the most important parameters,which not only directly influences mass and heat transfer,but also deter-0032-5910/02/$-see front matter D 2002Published by Elsevier Science B.V .PII:S 0032-5910(02)00014-1*Corresponding author.Tel.:+86-10-62782108.E-mail address:lishuiqing@ (S.-Q.Li)./locate/powtecPowder Technology 126(2002)217–227mines chemical reaction degree of gas and solid phase.In order to optimize the design and operation of rotary kiln,it is necessary to develop the simplified empirical expressions to enable the proper predicting of the volumetric flow of material(MVF)as well as MRT.Sullivan et al.[10] originally conducted the experimental research on the sol-ids’MRT in rotary cylindrical kiln and derived the empirical equation of MRT correlating various operational variables, kiln geometry parameters and material properties.Subse-quently,Va`hl and Kingma[11]and Kramers and Kroock-ewit[12]made further experiments on the holdup as well as MRT in a horizontal or inclined cylinder,respectively.The effect of internal structures is one of remarkable research community.Chatterjee et al.[13]studied the effect of ring formation,Matchett and Sheikh[14]studied the effect of both number and angle of axial flight,and Rutgers[15] considered the influences of shapes of kiln entrance and exit end faces.Furthermore,the residence time distribution (RTD)in rotary drums were researched by Abouzeid and Fuerstenau[16]and Sai et al.[17]adopting tracer stimulus-response techniques,or by Wes et al.[18]using atomic absorption spectroscopy methods.In addition,as the prac-tical field-scale rotary kiln was concerned,Groen et al.[19] performed corresponding investigations in a high-temper-ature kiln,while Schofield and Glikin[20]studied them in an intensive gas-flow fleeting kiln.More recently,Wightman and Muzzio[21]emphasized that a research community focusing on the segregation of multimixed particles in rotary cylinder.Donald and Rosse-man[22]firstly performed experimental studies in a hori-zontal system and identified three patterns of segregation: radial,axial and end longitudinal.Gupta et al.[23]described qualitative mechanisms of axial segregation,stating that a difference in the dynamic reposing angles of two pure components is a necessary(though not sufficient)condition of band formation.Nakagawa et al.[24]recently employed magnetic resonance imaging to study axial segregation. Boateng and Barr[25]and Bridgewater et al.[26]studied the mechanism of radial segregation,respectively.However,previous researches on axial transport in rotary kilns are mostly concentrated on the studies of small cementitious and metallurgical particles,which are rela-tively homogeneous in nature.Although rotary kilns have been extensively used as reactors for MSW incineration or pyrolysis,so far,there have been few attempts on extrap-olating the experiences and correlation developed from homogeneous materials to heterogeneous MSW.In this part,comparative studies are conducted between homoge-neous sand and irregular MSW in a rotary kiln cold simulator(I.D.0.3Â1.8m).Impacts of material character-istics(in terms of the dynamical angle of repose),kiln geometry characteristics(i.e.,roughness of kiln wall,exit-end dam and internal structures)and operational parame-ters(i.e.,kiln inclination and rotational speed)on both MRT and MVF are examined.Simplified formulas of MRT and MVF are proposed on the basis of the experiment results in Part II of this work.2.Experimental2.1.SetupA cold simulator of rotary kiln,0.3mm in diameter and1.8mm in length,shown schematically in Fig.1,was employed for the experiments.The cylinder was made of plexiglass so that the solid motion can be viewed.The rotational speed is variable within the range of0.5–10rpm (revolution per minute).The angle of kiln inclination can be easily adjusted between0j and5j by altering the height of the supporter at kiln inlet end.The feed rate of materials was adjusted to a certain amount that keeps the inlet depth of the solids on a desired value during each run.That is,the inlet depth of solid bed responds to the feed rate of materials, which is practically equal to the flow rate of materials under the steady state,one to one,under the same operational conditions.Therefore,the inlet bed depth instead of material feed rate were selected as one of the operating parameters, which was kept at70mm in all runs.In order to study the impact of internal structures on solid material motion,axial ribs and circular ribs were specially designed,as shown in Fig.2.The grouped typesand Fig.1.Schematic of rotary kiln cold simulator((1)Funnel,(2)Belt conveyor,(3)Tracer addition point,(4)Feed chute,(5)Rotary cylinder,(6)Position plate,(7)Belt wheel,(8)Position wheel,(9)Jockey wheel,(10)Slope angle adjustor,(11)Supportor,(12)Varible motor,(13)Exit chute,(14)Sample collector).S.-Q.Li et al./Powder Technology126(2002)217–227218geometric factors of the different kinds of axial ribs and circular ribs are listed in Table1.2.2.MaterialsTwo categories of materials were employed for experi-ments.One was reconstituted MSW consisting of49.9wt.% wood chips,17.0wt.%paper plates and33.1wt.%waste tyres.The mixture has irregular shape,size and heteroge-neous property.Also,homogeneous sand was used as another category for a contrast,which has higher density, regular shape and similar size.The physical properties of both kinds of materials are given in Table2.As was reported in earlier literatures[11–20],the bulk characteristics of solids in terms of the dynamic angle of repose,h d,exert significant influences on the transport and mixing of the solids in the kiln.Here h d is measured according to the Rotating Drum-Method(Henein et al.[27]).This measurement is done under one of the most general bed rotation cases of the kiln,rolling regime,and it can reflect the real dynamical bulk characteristics of solids in kiln.For all h d measuring of various materials,the kiln rotates at4rpm and fill ratio of solids in the kiln is about 15%–20%.h d of sand is about29.7j while that of MSW mixture is48.5j.In order to study the influence of wall roughness on MRT and MVF,the inside kiln wall are covered by the finer or coarser emery cloths.The wall friction factor of solids is defined as the tangent function of the wall friction angle.The latter is measured by a special shear-plate-analyzer with an easy adjusting shear angle.A plate,which has the same roughness with the tested wall,is fixed on the adjustable shear plate.A layer of tested solids is laid on the plate.Then,the plate is gradually tilted until the solids begin to fall along it.At that time,the slope of the plate with respect to the horizontal line is just the wall friction angle of solids.As shown in Table2,compared to the smooth inside wall,the friction coefficient,f,increased dramatically(69–243%)with finer emery cloth setting. However,f increased only about6–25%from the finer emery cloth to the coarser one.2.3.Experimental methodsTo determine MRT and MVF,the system must be adjusted to achieve the steady state,which is reached when the output of materials is equal to the feed rate of materials. The steady-state flow rate of materials,volumetric or molar, was measured by collecting sample successively within a certain time and quantifying it.As is widely known,the residence time of solids through rotary kiln is not a constant, but a probability distribution.Hence,the mean and variance of residence time are experimentally obtained by the stim-ulus-response techniques of tracers.Generally,the method for RTD measurement of MSW is hardly available in current literatures,though that of homogeneous sand has been described in detail[16–18].In this work,experiments were taken by introducing the dyed tracers consisting of9wood chips,15paper plates and36waste tyres.The ratios of three kinds of tracers are47.9,16.9and35.2wt.%,which are quite similar to those of original mixed wastes(i.e.,49.9 wt.%wood chips,17.0wt.%papers and33.1wt.%tyres).In fact,it is difficult to feed all tracers to kiln inlet end at the same time.Also,it is infeasible to label every tracer and measure its time one by one in such a short time interval. Thus,all tracers are divided into three groups and dyed red, white and yellow(each of which consists of3wood chips,5 papers and12tyres).As the steady state is reached,three groups of tracers are successively fed to the kiln inlet and the corresponding inlet time for each group is recorded.At the kiln outlet,they were collected after a certain time interval,until all tracers finished their excursion through the kiln.Meanwhile,the residence time of tracers in each sample interval was recorded(here,the inlet-time differ-ences of three group were taken into account).The mean and variance of residence time of the tracers are expressed below:MRT cX Ii¼1t i EðD t iÞ;ð1Þr2cX Ii¼1ðt iÀMRTÞ2EðD t iÞ;ð2ÞTable1The grouped types and geometric factors of internal structuresGroup No.Axial ribs Circular ribsNumber Height(mm)Number Height(mm) Exit dam1––130 Exit dam2––15012b-4n122043012b-7n122073012n-4n121043012b-4b1220450 Fig.2.Schematic of internal structures((1)Cylinder,(2)Circular ribs,(3)Longitudinal ribs).S.-Q.Li et al./Powder Technology126(2002)217–227219where I is the sequence of sampling interval,D t i is the interval of the i st sampling interval,and t i is the retention time of tracers in the i st interval.E (D t i )can be expressed as the ratio of the number of tracers in i st sampling interval to that of the total tracers,i.e.:E ðD t i Þ¼N ðD t i Þ=X I i ¼1N ðD t i Þ:ð3ÞUsually,the relative variance is used to express thedispersing extent of RTDs,which satisfies the relation:r 2r ¼r 2=MRT 2:ð4Þ3.Results and discussionsTable 3summarizes the detailed experimental results for MRT (together with r and r r )and MVF of the MSW in rotary kiln simulator with various rotating speeds,kiln slopes,exit-end dams,internal structures and walls of different roughness.In the following sections,the effect of each variable both on MRT and MVF will be discussed accordingly.3.1.Residence time distribution of MSW and sand The previous studies on residence time of solids in rotary kiln are scarcely concentrated on the heterogeneous MSW,but on the homogeneous particles instead.For instance,Abouzeid and Fuerstenau [16]concluded that residence time of dolomites in rotary kiln is approximately subjected to a normal distribution by employing the axial dispersion model.The comparison between experimental results and theoretical calculation for RTD of both sand and MSW are shown in Figs.3and 4,respectively.As for sand,the probability of tracers by experiment in each sample interval (D t i )fits well with the theoretical normal distribution function.However,it is noted that,for MSW,there exists a relatively large discrepancy between exper-imental value and theoretical curve,other than r r 2of MSW is much larger than that of sand under the samecondition.It can be explained that,as tracers consist of three components with various shapes,sizes and densities,the variance in residence time would arise from axial segregation instead of axial mixing (particle collision).In fact,the axial segregation causes the deviation of meas-ured RTD from the normal distribution (this view will be further verified in Part II of this work).In addition,the alternate band formation of the various components (i.e.,the visible axial segregation)that has been studied and emphasized in a batch kiln system by some investigators [21–24]does not occur in this experiment.According to Donald and Rosseman [22],the alternate band formation in batch system may not arise in continuous system where the length of system is not adequate for particles to demix.Gupta et al.[23]stated that a difference in h d of all pure components at a particular rotation speed is one of the necessary (though not sufficient)conditions of band formation.From Table 2,the h d difference among three components of MSW is not significant.The rotating speed is only an order of magnitude smaller than that in the study of Gupta et al.Thus,it is induced that the axial segregation of MSW in kiln won’t be violent enough to form alternate bands,especially for such a system with a limited ratio of length to diameter (L /D =6).The detailed r and r r of RTD of MSW under various rotating speeds,kiln slopes,exit-end dams,internal struc-tures and wall roughness are given in Table 3.Much valuable information can be obtained as follows.(1)Increasing rotating speed or kiln slope leads to relatively slight increment of r ,while r r varies or keeps in a narrow range from 0.02to 0.05.(2)The usage of exit dam can also increases r or r r ;but the impact on variance is less appreciable than that on MRT.(3)Employment of internal structures promotes both r and r r remarkably by one order of magnitude (e.g.,r r from range [0.02,0.05]to range [0.2,0.4]).However,it must be stated that the measuring error of RTD’s r and r r is quite high due to the segregation of MSW properties.Meanwhile,the measuring precision of both MRT and MVF can doubtlessly reach an expected level because of their statistical averaged characteristics.Therefore,more attention is paid to discussions on MRT/MVF rather than r /r r in the following paper.Table 2Summary of properties,bulk characteristic and wall friction factors of materials Materials Shapes Bulk density (kg/m 3)True density (kg/m 3)Sizes (mm)h d (j )f 1f 2f 3**Wood chips Cylindrical 371.5646.0U 25Â3047.30.5250.9020.941Paper plates Tabulate 104.5691.730Â30Â351.90.563 1.930 2.331Waste tyre Arcuate 278.71020.010Â5Â3052.90.4210.941 1.102Mixed MSW *–225777.6–48.50.480 1.003 1.251SandNodular134226601.0–2.029.70.4070.7240.768*Mixed MSW consist 49.9wt.%woods,17.0wt.%papers and 33.1wt.%tyres.**f 1,f 2,f 3are wall friction factor of solids with none,finer and coarser emery cloth setting on inside wall.S.-Q.Li et al./Powder Technology 126(2002)217–2272203.2.Axial velocity distribution along kiln lengthFor end-open system,as the bed depth and the fill ratio of solids in cross-section are different at the different axial position,the axial cascading velocity of solids is not constant along the kiln axis.That is,the residence time in different zone along kiln length is quite different.Figs. 5and6give the axial velocity of sand and MSW under different axial points,respectively.It can be seen that the axial velocity of particles increases along the axial direc-tion.It is due to the decrement of the bed depth or the fill ratio along the kiln axis.Thus,according to the mass conservation theory,d(q uA)/d x=0,the axial velocity along kiln length increases gradually.By the way,as for the practical rotary kiln reactor,it has various reaction zones along the axis and the solids have different properties in every zone.Thus,it is essential to know the detailed residence time of the solids in each zone.However,up to now,nearly all the experimental/theoretical works of solid transport are concentrated on the overall residence time through the kiln inlet to outlet.The residence time of solid passing a special reaction zone can be obtained by integration of the bed axial velocity along the age of this zone,t i¼m z i ziÀ1d z=uðzÞwhere z represents kiln axis and iTable3Overall experimental data for MRT and MVF of MSW with different variablesRun number Internal structure Rotated rate(rpm)Inclination(j)MRT(min)MVF(l/min)r r r1Smooth wall2 2.4011.53 1.560.260.023 23 2.408.25 2.620.200.024 34 2.40 5.58 3.730.180.026 44 1.817.05 2.530.230.043 540.6211.28 2.180.540.049 66 2.40 4.07 4.240.160.042 78 2.40 3.27 5.500.120.037 8Finer emery cloth setting3 2.4010.98 2.04 2.650.24 94 2.408.87 3.09 2.020.23 104 1.818.78 2.09 1.750.20 1140.6216.80 1.16 3.840.24 126 2.40 6.20 4.58 1.190.19 138 2.40 4.20 4.620.850.20 14Coarser emery cloth setting3 2.4011.83 1.60 2.100.18 154 2.408.40 2.80 1.700.20 164 1.819.47 1.96 2.230.24 1740.6212.30 1.69 3.820.23 186 2.40 6.15 3.82 1.430.23 198 2.40 4.95 4.270.970.20 20Exit dam1(30mm)3 2.4013.15 1.640.430.033 214 2.409.93 2.440.370.037 224 1.8112.27 1.470.370.030 238 2.40 5.92 4.220.300.051 24Exit dam24 2.4014.80 1.560.670.045 2512b-4n2 2.4019.67 1.27 4.480.23 263 2.4013.90 1.71 3.290.24 274 2.409.75 2.16 2.260.23 284 1.8112.67 2.00 3.560.28 2940.6224.67 1.188.260.34 3012b-7n2 2.4016.95 1.02 4.360.26 313 2.4015.90 1.69 4.110.27 324 2.4011.62 2.33 2.450.21 334 1.8115.12 2.13 4.340.29 3440.6221.670.987.320.33 3512n-4n2 2.4019.67 1.33 5.570.28 363 2.4012.08 1.84 3.240.27 374 2.409.78 2.71 2.140.22 384 1.8115.20 1.91 4.670.31 3940.6222.37 1.20 6.890.33 4012b-4b2 2.4024.920.87 6.270.25 413 2.4015.85 1.47 2.940.19 424 2.4012.03 2.04 2.610.22 434 1.8115.95 1.38 3.920.25 4440.6226.750.847.650.27 *The inlet depth of solid bed in all runs is70mm(23%of inner diameter).S.-Q.Li et al./Powder Technology126(2002)217–227221the zone’s sequence.Axial velocity,u (x ),can be calculated through the empirical correlations (Lebas et al.[28],Perron and Bui [29]).3.3.Influences of particle characteristics on MRT and MVFThe comparison of MRT and MVF between sand and MSW under the same conditions is shown in Figs.7and 8,respectively.The MRT of MSW is greater than that of sand for all runs.From the regress curve in Fig.7,it is obtained that the former is about 1.43times of the latter.Contrarily,MVF of MSW is less than that of sand with the multiple of 0.625(1/1.48).From Table 2,it can be seen that sin h d of MSW is 1.50times of that of sand.Thus,the conclusion is drawn:the material’s characteristics exerts its influences on the MRT and MVF mainly in terms of h d ;MRT increases approximately in linear fashion as sin h d of material increases,while MVF is subjected to the inverse proportional function of sin h d .These conclusions will beverified subsequently by the theoretical analysis in Part II of this work.3.4.Influences of rotating speed and kiln slopeThe impact of rotating speed on the MRT and MVF of heterogeneous MSW is shown in Fig.9.As rotational speed increases from 2to 8rpm,MRT decreases nearly in inverse proportional fashion of rotating speed,while MVF increases gradually.These conclusions are consistent with those acquired from the homogenous small particles by others [11,30].It may be explained that the axial transport of solids mainly occurs in the active layer of bed surface,while solids in the stagnant region under bed surface only turn around the kiln axis without any axial displacement.As the rotational speed increases,the times of a particle entering the active layer per unit time increases,which further results in the increase of the particle’s axial displacement per unit time (namely,particle’s axial velocity)[18,31].Therefore,MRT decreases and MVFincreases.Fig.3.Residence time distribution ofsand.Fig.4.Residence time distribution ofMSW.Fig.5.Axial speed distribution of sand along kilnaxis.Fig.6.Axial speed distribution of MSW along kiln axis.S.-Q.Li et al./Powder Technology 126(2002)217–227222Fig.10indicates the effect of kiln slope on the transport behavior of MSW.When kiln slope angle increases from 0.62j to 2.40j ,the MRT decreases in an approximately linear fashion from 11.28to 5.58min,while MVF rises from 2.18to 3.73l/min.It is possible that the increasing kiln inclination causes the increment of the gravitational force component in the axial direction of individual particle during its cascading,i.e.,the increment of the solid axial velocity,which finally causes MRT to decrease and MVF to increase.3.5.Influences of exit-end damsThe exit-end dam exerts significant influences on the MRT and MVF of solids in a rotary kiln.As shown in Fig.11,MRT of MSW and sand with the 30-mm dam (about 10%of inner kiln diameter)are 78.0%and 71.4%longer than that with no end constriction,respectively.As for a higher 50-mm dam (about 16.7%of inner diameter),thecorresponding augment is 165%and 138%for MSW and sand,respectively.The higher height of dam has,the more remarkable effect it has on MRT.The affecting extent made by the 50-mm dam is almost twice of that made by the 30-mm dam.The reasons for above conclusions lie in two aspects.First,the usage of exit dam reduces the slope of the solid bed and then the axial cascading velocity of particles.On the other hand,it causes the increment of bed depth in kiln.This increment of flow area in cross-section will decrease axial cascading velocity,either.Finally,the combi-nation of two reasons above cause the remarkable increase of MRT.In addition,MVF decreases when employing exit-end dam.As for the 30-mm dam,the reduction of MVF of MSW and sand are 34.5%and 27.9%,respectively,and for the 50-mm dam,the corresponding reduction is 58.3%and 35.2%(shown in Fig.12).It is doubtless that the usage of exit dam is an effective method to control the MRT and MVF of solids.However,it is noted that exit dam has no such apparent impacts on relative variance r r as it has on MRT,as seen from Table 3.parison of MRT between MSW andsand.parison of MVF between MSW andsand.Fig.9.Effect of rotational speed on MSW transportbehavior.Fig.10.Effect of kiln slope angle on MSW transport behavior.S.-Q.Li et al./Powder Technology 126(2002)217–2272233.6.Influences of the internal structuresThe internal structures inevitably affect the axial trans-port of solids [13,14].The impacts of internal structures on MRT are different with various groups consisting of a certain number of axial ribs or circular ribs.Figs.13and 14illustrate the influences of four groups of internal structures (listed in Table 2)on the MRT of MSW and sand,respectively.It is found that all these four kind of internal structures seriously increase MRT of solids.The detailed conclusions are drawn:as the number of circular ribs in an internal structure group increases (12b-4n !12b-7n),the MRT in 12b-7n case is slightly longer than that in 12b-4n case for both MSW and sand;as the height of circular ribs increases from 30to 50mm (12b-4n !12b-4b),the incre-ment of MRT from 12b-4n to 12b-4b case is more remark-able.However,with the increasing height of axial ribs from 10to 20mm (12n-4n !12b-4n),the MRT changing ten-dency of MSW and sand is inconsistent or inexplicit.According to above,it is concluded that influences of the internal structure group on MRT are dependent on the height of circular ribs,while the impacts of the height of axial ribs is inexplicit.The influence of circular ribs on MRT can be explained by their similarity to the exit dam whose influence has been already tested to be remarkable.The impact of axial ribs on MRT is quite complicated,which not only changes the solid’s dynamic angle of repose,but also kicks up some particles from the bed surface to the freeboard space.These conclusions can be verified by the experi-ments.For instance,the 30-mm exit dam promotes MRT with 78.0%;however,the internal structure groups labeled 12b-4n,12b-7n and 12n-4n,whose circular ribs is also 30-mm height,only promote the MRT in range of 75%to 108%with MSW under an condition of rotating speed at 4rpm and inclination at 2.40j (Fig.14).Since the exit dam (regarded as one special circular rib)does not exert the same apparent effects on r r as it does on MRT,here,the great promotion by one-order ofmagni-Fig.11.Effect of exit end dam onMRT.Fig.12.Effect of exit end dam onMVF.Fig.13.Effect of various internal structures on MRT ofMSW.Fig.14.Effect of various internal structures on MRT of sand.S.-Q.Li et al./Powder Technology 126(2002)217–227224。
