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如何超越你的对手英语作文Title: Surpassing Your Competitors: Strategies and Perspectives.In the realm of competition, the desire to excel and surpass one's opponents is inherent. Whether it's a sports match, a business battle, or any other form of contest, the quest for victory is always exciting and challenging. However, achieving this feat requires more than just raw talent or brute force. It involves a combination of strategic planning, continuous learning, innovation, and a laser-sharp focus on personal and team development.1. Understand Your Competitors.To surpass your competitors, the first step is to truly understand them. This involves a thorough analysis of their strategies, products, services, market positioning, and customer base. Understanding their strengths and weaknesses will help you identify areas where you can differentiateyourself and provide a better offering.2. Innovate and Differentiate.In today's era of hyper-competition, differentiation is key. Find ways to innovate and provide something uniquethat your competitors cannot offer. This could be a new product feature, a better customer experience, or a more efficient operational model. Innovation not only helps you stand out but also acts as a barrier against模仿, as it's difficult for others to replicate something entirely new and original.3. Leverage Your Core Strengths.Every organization or individual has their unique strengths. Identify what you do best and double down on it. Leverage your core strengths to create a competitive edge and use them to outmaneuver your competitors. This could be a particular skill set, a patented technology, or a strong brand reputation.4. Continuous Learning and Adaptability.The business world is constantly evolving, and so are your competitors. Staying ahead requires a culture of continuous learning and adaptability. Be open to new ideas, technologies, and market trends. Embrace change and be willing to pivot when necessary.5. Build a Strong Team.No individual can achieve sustained success alone. Building a strong team of like-minded individuals with diverse skills and perspectives is crucial. Encourage collaboration, provide opportunities for growth, and create a culture of mutual respect and support. A strong team will help you stay focused, motivated, and innovative.6. Execute with Excellence.In the end, it's all about execution. Having a great strategy is one thing, but delivering on it with excellence is another. Ensure that you and your team have thenecessary skills, resources, and processes to execute your plans flawlessly. Attention to detail, discipline, and a focus on continuous improvement are essential for sustainable success.7. Maintain a Long-Term Perspective.Success in competition is not a sprint but a marathon. Avoid getting caught up in short-term gains and focus on building sustainable competitive advantages that will last over time. Invest in research and development, brand building, and talent development to ensure a robust foundation for future growth.In conclusion, surpassing your competitors requires a multi-faceted approach that combines strategic planning, innovation, continuous learning, team building, and execution excellence. By staying focused, adapting to change, and continuously improving, you can create a competitive edge that will help you stand out and achieve sustained success.。
超临界二氧化碳萃取英语1. **定义与释义**1.1 **词性**：名词1.2 **释义**：一种利用超临界二氧化碳作为溶剂来提取物质的技术1.3 **英文解释**：A technique that uses supercritical carbon dioxide as a solvent to extract substances.1.4 **相关词汇**：supercritical fluid extraction（超临界流体萃取）2. **起源与背景**2.1 **词源**：超临界二氧化碳萃取技术是随着现代科技的发展而逐渐兴起的。
2.2 **趣闻**：超临界二氧化碳萃取技术在食品、医药等领域有着广泛的应用，它的出现为许多行业带来了创新和突破。
3. **常用搭配与短语**3.1 **supercritical carbon dioxide extraction process**：超临界二氧化碳萃取过程例句：The supercritical carbon dioxide extraction process is widely used in the food industry.翻译：超临界二氧化碳萃取过程在食品行业被广泛应用。
3.2 **extraction efficiency of supercritical carbon dioxide**：超临界二氧化碳的萃取效率例句：The extraction efficiency of supercritical carbon dioxide is relatively high.翻译：超临界二氧化碳的萃取效率比较高。
4. **实用片段**（1）. "I'm really interested in the supercritical carbon dioxide extraction technology. It's amazing how it can extract valuable compounds from plants."翻译：我对超临界二氧化碳萃取技术真的很感兴趣。
Coal liquefaction using supercritical toluene–tetralinmixture in a semi-continuous reactorS.Sangon,S.Ratanavaraha,S.Ngamprasertsith,P.Prasassarakich *Department of Chemical Technology,Faculty of Science,Chulalongkorn University,Bangkok 10330,ThailandReceived 21February 2005;received in revised form 29June 2005;accepted 1July 2005AbstractLiquefaction of Banpoo coal and Mae Moh coal using supercritical toluene–tetralin mixture was performed in a semi-continuous apparatus at a temperature ranging from 370to 490-C and under pressures up to 12.2MPa.The addition of tetralin to toluene increased the coal conversion and the liquid yield by the stabilization of radical fragments and inhibition of radical recombination.The effect of solvent pre-swelling treatment and catalyst impregnation on conversion and liquid yield was also examined.The combination effects of catalyst and swelling enhanced conversion and the liquid yield of sub-bituminous coal.The yield of coal liquid at the condition of 490-C and 10MPa with toluene–tetralin reached a maximum 45wt.%(in daf coal)with THF as the swelling agent and ZnCl 2as the catalyst.The coal residue,after extraction,maintained most of its heating value and had a lower sulfur content.D 2005Elsevier B.V .All rights reserved.Keywords:Coal;Supercritical fluid;Liquefaction;Co-solvent;Catalyst1.IntroductionIntense efforts have been made to liquefy coal in the past.Processes such as pyrolysis,solvent extraction and catalytic liquefaction have had varying degrees of success.Such processes have indicated that a significant coal conversion and coal liquid yield may be obtained.Presently,supercritical fluid extraction is increasingly of interest because of its low viscosity and controllable solvent power.Supercritical fluid extraction (SCFE)has the advantage of a high mass transfer rate allowing easy separation of the extract (coal liquid and solvent)from the coal residue,thus overcoming a major problem of the conventional liquefaction process [1,2].Supercritical fluids such as toluene have previously been reported as good media for extraction of coal.Though a lower conversion is achieved in supercritical fluid extraction,the addition of a co-solvent such as tetralin or ethanol improves coal conversion and liquid yield [3].The co-solvent should have a hydrogen-donor capability to stabilize the free radicals generated and therefore reduce considerably the repolymerization reaction.Hydrogenating SCFE has also been studied using toluene with different combinations of molecular hydrogen,a hydro-gen-donor solvent and catalyst;molecular hydrogen had a negative effect on coal conversion and coal liquid yield [4].The effect of the extraction conditions and solvent type (hexane,benzene,toluene and toluene–tetralin mixture)on liquid yield and properties was studied to clarify the relation between the coal yield,the solvent power of supercritical fluid and the reaction occurring during extraction [5].The effect of temperature and solvent density on the characteristic of extracts (saturated HC,aromatics,resins and asphaltenes)was also studied for SCFE with toluene.Lighter compounds were found to increase with increasing temperature and with the addition of 5mol%ethanol [6].It was reported that,for liquefaction using supercritical toluene and co-solvent (methanol and ethanol),extraction conditions affected the elemental composition,thermogravimetric character and group composition of extracts and their fractions.The liquefaction of coal using supercritical alcohol has been reported [7,8].Recently,when supercritical alcohols (ethanol and isopropanol)were used in coal liquefac-tion,an increase in either temperature or pressure was found to increase liquid yield.Additionally,the extracts were charac-terized for eight discrete fractions with well-defined chemical functionality [9].0378-3820/$-see front matter D 2005Elsevier B.V .All rights reserved.doi:10.1016/j.fuproc.2005.07.007*Corresponding author.Tel.:+6622187517;fax:+6622555831.E-mail address:ppattara@chula.ac.th (P.Prasassarakich).Fuel Processing Technology 87(2006)201–207/locate/fuprocImprovement in coal liquefaction can be achieved by impregnating the catalyst into the coal rather than mixing with the coal as powder.Besides improving catalyst behavior by dispersion,the activity of the catalyst may affect the structure of the coal causing the weakened structure that is more susceptible to depolymerization reaction.One method to modify coal structure is solvent swelling.The swelling may facilitate the impregnation by the catalyst,thus the pretreatment can increase conversion[10–12].The beneficial effects depend on the nature of the catalyst and swelling agent and the coal rank[13].Although much is known about supercritical extraction and catalytic liquefaction,the system is complex and more remains to be discovered.Maximizing liquid yield requires a balance between temperature,pressure,residence time and the addition of appropriate catalysts.This work examines the use of hydrogenated solvent under supercritical condition,catalyst and coal swelling prior to extraction.Coal liquefaction using a toluene–tetralin mixture in a semi-continuous reactor was studied and the effects of various parameters on coal conversion and liquid yield were investigated.The extracts were characterized by the simulated distillation chromatogra-phy method and the coal residue was also analyzed.2.Experimental2.1.Impregnation of swollen coal with the catalyst prior to liquefactionThe coal used in this study was sub-bituminous coal from the Banpoo mine and lignite from the Mae Moh mine in Lampang province,northern Thailand.The coal samples were ground,sieved(particle size:<1mm,1–2mm and4–5mm) and air-dried.Proximate and ultimate analyses and sulfur distribution are presented in Table1.The coal samples were predried at110-C in an oven.For pre-swelling experiments, coal was mixed with the swelling solvent to give a solvent to coal ratio of approximately3:1and was stirred for18h at room temperature.The solvent was removed by evaporation under reduced pressure and the coal was dried as described previously.For impregnation,the catalyst was loaded onto the swollen coal at0.5%metal loading on daf basis.The swollen coal was impregnated with a water solution of ZnCl2 or pentane solution of Mo(CO)6overnight and then dried in an oven.2.2.Coal liquefactionThe liquefaction experiments were carried out in a50-ml stainless steel reactor.A schematic diagram of the semi-continuous reactor is given in Fig.1.For each experiment,20g of air-dried coal were loaded in the reactor.The nitrogen was charged into the reactor and the heater was turned on to reach the desired temperature and pressure.The solvent was pumped to the reactor at a rate of2ml/min with the exit closed to permit the build-up of the desired pressure and temperature.The reactor pressure was controlled by a back-pressure regulator valve.The weight hourly space velocity(WHSV)of the toluene–tetralin mixture(70/30v/v)was estimated as5.38hÀ1 in the reactor.At the end of each experiment,the furnace was withdrawn and the reactor was cooled down to room temperature.The coal residue was recovered by filtration and dried for4h in an oven at100-C.The weight loss of the coal sample after extraction on daf basis defined the degree of coal conversion.The extract product was collected,the solvent was removed by rotary evaporation under vacuum and the coal liquid was analyzed.The coal conversion and liquid yield were calculated by the following expressions:%Conversion¼W sample;dryÀW residueÀÁsample;dafÂ100ð1Þ%Liquid yield¼W liquidW sample;dafÂ100ð2Þwhere W liquid and W residue is the mass of coal liquid and coal residue,respectively.W sample,dry and W sample,daf is the mass of starting sample at dry basis and dry ash free basis,respectively.2.3.Extract and residue analysisIn this study,the coal liquid was analyzed by Simulated Distillation Gas Chromatography(Varian Model CP-3800) according to ASTM D2887.Star Simulated Distillation version 5.5software was used for data collection and processing.The coal liquid was dissolved in CS2(1%v/v).CP-SIL5CB15 mÂ0.25mm was used for separation.The oven temperature was raised from30-C to370-C at a constant heating rate of20 Table1Proximate and ultimate analyses of coalBanpoo1Banpoo2Mae Moh Proximate analysis(wt.%db)Ash 5.410.340.2V olatile matter42.738.835.4 Fixed carbon51.950.924.4Ultimate analysis(wt.%daf)C73.067.656.5H 5.8 4.79.5N 1.00.9 2.5S 1.90.6 1.3O(by diff.)18.326.230.2 Heating value(dry,MJ/kg)24.522.710.8Ash constituent(wt.%)SiO2NA0.4025.31Al2O3NA 2.1914.68Na2O NA– 1.06K2O NA0.27 2.29 CaO NA27.2212.85 MgO NA 4.19 2.78Fe2O3NA14.2618.05 SO3NA50.6321.98 TiO2NA–0.39 BaO NA0.730.19 Others NA0.110.42S.Sangon et al./Fuel Processing Technology87(2006)201–207 202-C/min.The distillation curve was evaluated to fractions as follows:IBP—200-C,naphtha;200–250-C,kerosene;250–350-C,light gas oil;350–370-C,gas oil;and 370-C—FBP,long residue.The raw and leached coal was analyzed for proximate analysis and total sulfur by ASTM methods D2492and D3177.The heating value of raw coal and coal residue was determined according to ASTM D2015.Carbon,hydrogen and nitrogen analyses were performed using a CHN analyzer (Perkin Elmer PE 2400Series II).3.Results and discussion 3.1.Effect of solvent typeIn liquefaction,radicals are produced through the thermal decomposition of the coal.Some radicals recombine with each other or with the coal while others decompose to small molecules.In the presence of tetralin,most of the radicals are stabilized by abstracting hydrogen from the tetralin which inhibits both the recombination with coal and the further decomposition of the radicals.For tetralin addition (10–70%)to toluene,coal liquid yield increased with tetralin content until it remained unchanged when tetralin content was above 30vol.%[3].Thus,tetralin content of about 30vol.%may be sufficient to inhibit the recombination of radicals.During the liquefaction with toluene–ethanol mixture,ethanol molecule or active chemical species produced by the reaction between ethanol and coal altered the coal structure.Thus,the addition of about 10%ethanol promoted the alteration of the coal structure and the coal liquid because supercritical alcohol can act as a hydrogen donor [14].The supercritical coal liquefaction was carried out using various solvents at 450-C and 10MPa for 90min.Fig.2shows the result of %conversion and %liquid yield.Toluene–tetralin solvent resulted in a %conversion (47–62%)and %liquid yield (25–28%)that was double the rate of the one solvent (conversion =24–28%,liquid yield =9–12%).Thetoluene–tetralin mixture for this composition had critical properties calculated by the HYSYS program as follows:T c =361.1-C,P c =4.07MPa.Thus,toluene–tetralin at a ratio of 70:30v/v was chosen for liquefaction of Banpoo coal.3.2.Effect of coal particle sizeThe effect of varying particle size on %conversion and %liquid yield of coal liquefaction using toluene–tetralin (70/30v/v)is shown in Fig.3.The condition was kept constant at a temperature of 450-C,pressure of 10MPa and time of 90min.For both lignite and sub-bituminous coal,the conversion and liquid yield increased as the particle size decreased.Varying the particle distribution affected initial particle size area for contact with the solvent which increased rapidly with decreasing particle size.Lignite gave slightly higher liquid yield (26–33%)than sub-bituminous coal (22–30%)since lignite has a weak structure which is susceptible todepolymerization.TolueneEthanolToluene- 20% Ethanol Toluene- 10% Tetralin Toluene- 30% Tetralin%w t (d a f )Fig.2.Effect of solvent type on liquid yield and coal conversion for non-catalytic liquefaction of Banpoo2(1–2mm).T =450-C,P =10MPa,time=90min.Temperature controllerTCPTSolvent reservoirNitrogen cylinderHPLC pumpPreheaterCoolerTubular furnaceReactorBack pressure regulatorSampling vesselTrapVentIce bathPressure TransducerFig.1.Schematic diagram of the semi-continuous reactor system.S.Sangon et al./Fuel Processing Technology 87(2006)201–207203However,lignite yielded lower conversion (37–53%)than sub-bituminous coal (54–70%)due to the high ash in lignite.High ash lignite (40%ash)has more inactive sites,due to the presence of inorganic matters,than sub-bituminous coal (10%ash)and thus the solvent could penetrate and convert only the organic matter to liquid and gas.It might also be found that the sub-bituminous coal gives a higher gas yield than bined effects of swelling and catalyst impregnation Via the modification of the coal structure by solvent swelling,dissolution activity of the catalyst can be promoted and the weakened structure would be more susceptible to depolymer-ization.The swollen coal network would lead to pore expansion with the swelling facilitating impregnation by the catalyst and diffusion of the toluene–tetralin mixture to the reactive sites of the coal.From the study of the solvent types and particle size effects,the following liquefaction experiments were performed using toluene–tetralin (70/30v/v)and a coal particle size of 1–parative conversion and liquid yield for catalyst impregnation-swollen lignite and sub-bituminous coal are given in Table 2.For the non-catalytic liquefaction of sub-bituminous coal,THF and pyridine swelling provided a greater conver-sion (75–78%)but the liquid yield remained unchanged (27–29%).The deposition of ZnCl 2with THF swelling increased the conversion and liquid yield substantially to 89%and 37%,respectively.This suggests that swelling introduces macroscopic cracks and fission in the coal matrix which aid the dispersion of ZnCl 2on the coal surface.The beneficial effects depend on the nature of the swelling agent and the coal rank.When the coal matrix expands because of swelling,the internal surface of the coal macromolecule becomes more accessible to reagent and coal reactions are facilitated.In contrast,ZnCl 2with pyridine did not have any advantage (80%conversion and 29%liquid yield).Though pyridine was the most effective swelling solvent,pyridine actually sup-pressed coal conversion and liquid yield.It is postulated that too high pyridine in the coal network (swelling ratio =1.68)lowered the ZnCl 2concentration in coal and ZnCl 2activity decreased in high swollen coal.The surface area for catalyst/coal contact resulting from swelling in THF was appropriate for sub-bituminous coal liquefaction which yielded high conversion and liquid yield.To examine the effects of coal rank and catalyst,lignite was examined in the same manner as sub-bituminous coal.The results are summarized in Table 3.The non-catalytic liquefac-tion with THF and pyridine swelling gave 45–52%conversion and 33–36%liquid yield.Swelling of lignite with THF or pyridine slightly improved conversion and liquid yield compared with the non-swelling coal liquefaction (30%liquid yield).It can also be noted that the conversion of lignite is much lower than that of sub-bituminous coal.One reason is that lignite with high ash exhibited a lower swelling ratio (1.16in THF)than sub-bituminous coal (1.35in THF)because the high ash lignite has less organic matter for swelling and a high crosslink structure among acidic functional groups while sub-bituminous coal has an aromatic structure with fewer cross-links.The sub-bituminous coal swelled very well in polar solvents such as THF and pyridine.For catalytic ZnCl 2liquefaction with pre-swelling,the conversion remained unchanged but the oil yield actually decreased compared with non-catalytic liquefaction.In con-trast,the deposition of Mo(CO)2increased the conversion to 56%and the oil yield increased substantially to 42%.These beneficial effects depend on the nature of the swelling agent and coal rank.ZnCl 2is an efficient catalyst for low ash coal containing low Na and K.For Mae Moh coal with high ash,the alkaline metal in the coal reacted with the ZnCl 2catalyst,so the catalyst concentration in the system was decreased and resulted in an inefficient catalytic process.Thus,ZnCl 2is not an efficient catalyst for high ash coal [15].3.4.Effects of pressure and temperatureTHF is the only solvent capable of effectively dispersing the catalyst in Banpoo coal.For the catalytic process,ZnCl 2was used as the catalyst and THF as the swelling solvent.Fig.4shows liquid yield and coal conversion as a function ofTable 2Effect of pre-swelling and catalyst on supercritical liquefaction using toluene –tetralin (70/30v/v)CoalSwelling solvent Catalyst Conversion (wt.%daf)Liquid yield (wt.%,daf)Banpoo2(1–2mm)sub-bituminousNone None 6228THF None 7527Pyridine None 7829None ZnCl 26327THF ZnCl 28937Pyridine ZnCl 28029Mae Moh (1–2mm)ligniteNone None 4430THF None 4536Pyridine None 5233None ZnCl 24426THF ZnCl 24428PyridineMo(CO)65642Condition:T =450-C,P =10MPa,time =90min.Banpoo 2:swelling ratio=1.35in THF,1.68in pyridine.Mae Moh:swelling ratio=1.16in THF,1.33in pyridine.62%54%30%28%53%44%37%33%30%26%Particle size (mm)%w t (d a f )Liquid yield Liquid yield22%Banpoo 2:Mae Moh:Fig.3.Effect of coal particle size on liquid yield and coal conversion for non-catalytic liquefaction using toluene–tetralin (70/30v/v).T =450-C,P =10MPa,time=90min.S.Sangon et al./Fuel Processing Technology 87(2006)201–207204pressure for catalytic and non-catalytic liquefaction using toluene–tetralin (70/30v/v).It can be seen that a rise in pressure causes an increase in liquid yield as a result of the increase in solvent power (or solvent density).To compare the performance with regard to liquid yield,liquefaction was conducted resulting in 39%for ZnCl 2catalytic and 30%for non-catalytic process at 450-C and 12MPa.The coal conversion and liquid yield of catalytic liquefaction was higher than that of non-catalytic liquefaction for all pressures.Interestingly,the conversion of catalytic liquefaction increased with pressure up to 10MPa and then decreased at 12MPa.The reason for this discrepancy in the coal conversion is not clear at this time.One possible reason is that at very high pressure,the impregnated catalyst in coal may be disrupted or loosened due to an increase in fluid density and consequently the catalyst activity decreases.However,the liquid yield still increases slightly in the pressure range between 10and 12MPa due to high diffusivity of the supercritical solvent.The effect of temperature on liquid yield and coal conversion for catalytic and non-catalytic liquefaction usingtoluene–tetralin (70/30v/v)is illustrated in Fig.5.The coal conversion and liquid yield of catalytic liquefaction was higher than that of non-catalytic liquefaction at all temperatures.For ZnCl 2catalytic liquefaction,the liquid yield was a maximum of 45%(daf)at 490-C and 10MPa;the corresponding coal conversion was 33%.As expected,an increase in temperature resulted in an increase in the coal conversion and liquid yield.It should also be observed that the temperature has a more pronounced effect than the pressure on the liquid yield.Another interesting effect is that for catalytic liquefaction,the coal conversion increased with temperature approaching a maximum value (89%)and then slightly decreased.At high temperature,the thermal decomposition drastically accelerated.However,the liquid yield increased slightly in the temperature range of 450and 490-C due to the pronounced ability of the supercritical solvent.Table 3shows the comparison of supercritical liquefaction results from this work with previous investigations.The coal conversion and liquid yield depend on process conditions,swelling solvent,catalyst,catalyst type and coal rank.Our results compare well with those that others obtained athigherPressure (MPa)%w t (d a f )Non-Catalytic, Banpoo 1:ZnCl 2 Catalytic, Banpoo 2:Fig.4.Effect of pressure on liquid yield and coal conversion for non-catalytic and catalytic liquefaction using toluene –tetralin (70/30v/v).Coal particle size =1–2mm,T =450-C,time=90min.%w t (d a f )Temperature (o C)Non-Catalytic, Banpoo 1:ZnCl 2 Catalytic, Banpoo 2:Fig.5.Effect of temperature on liquid yield and coal conversion for non-catalytic and catalytic liquefaction using toluene–tetralin (70/30v/v).Coal particle size=1–2mm,P =10MPa,time=90min.Table 3Comparison of coal liquefaction from this work and other investigation InvestigatorSupercritical fluid Swelling solvent Catalyst Coal class Condition Coal conversion (wt.%,daf)Liquid yield (wt.%,daf)Shishido et al.(1991)Toluene–tetralin ––Sub-bituminous 380-C,20MPa 6459Toluene–ethanol 5854Canel et al.(1990)Toluene ––Bituminous Supercritical 2814Toluene–H 2Lignite 550-C 5017Toluene–tetralin 10MPa 5923Pinto et al.(1999)–THF ZnCl 2Sub-bituminous 400-C 916727TBAHH 27.9MPa 56Artok et al.(1992)–Mo(CO)6Lignite 275-C NA 7THF Mo(CO)6Bituminous H 27MPa NA 15TBAH ATTM Sub-bituminous NA 19Joseph J.T.(1991)–TBAH Mo(CO)6Bituminous 400-C8737THF Sub-bituminous H 21100psig 8848This workToluene–tetralin––Sub-bituminous 490-C,10MPa 6333THFMo(CO)6Lignite450-C,10MPa 5642ZnCl 2Sub-bituminous490-C,12MPa8545TBAH=tetrabutylammonium hydroxide,ATTM=ammonium tetrathiomolybdate,(NH 4)2MoS 4.S.Sangon et al./Fuel Processing Technology 87(2006)201–207205temperature and pressure.The oil yield might also be related to the ash and oxygen content of the coal[3].One advantage of the semi-continuous reactor is the separation of toluene–tetralin and coal extract from the coal residue.The supercritical fluid stream was passed through a bed of coal particles,and the extracted oil was carried with the solvent thus effecting a complete separation between the extracted coal liquid and the coal(Fig.1).Finally,the coal liquid was separated from the continuous stream of pared with the previous work by various investigators,the liquefaction in a batch reactor has one disadvantage which is that the separation of the liquid extract from coal and solvent requires a tedious procedure to achieve any accuracy.In this work,the toluene–tetralin mixture was separated from coal liquid by vacuum evaporation and recovered about96%of solvent feed.For process development,the loss of solvent could be minimized to less than1%by an optimal process engineering design.3.5.Analysis of coal liquidThe coal liquid was the product of ZnCl2catalytic liquefaction using toluene–tetralin.It was divided into naphtha,kerosene,light gas oil,heavy gas oil and long residue by using Simulated Distillation Chromatography.In this study, the oil yield increased with temperature.Fig.6illustrates the effect of temperature and pressure on the yields of distillation fractions of liquid from THF pre-swelling Banpoo coal.It can be seen that the content of naphtha and kerosene increased while light gas oil and gas oil decreased with increasing temperature.At a constant pressure of10MPa,the long residue had a high value(45–59%)at400–490-C and increased with temperature.At high temperature(490-C),naphtha was not found.The reason is that repolymerization probably occurred due to insufficient hydrogen from tetralin to stabilize the large amount of free radicals occurring when the maximum liquid yield of45%was achieved.As pressure increased,long residue decreased and naphtha increased and the oil distribution at this condition(450-C,12 MPa)had similar characteristics to Thai crude oil from Lankrabue,northeastern Thailand.It can be concluded that high temperature and pressure would benefit the formation of lighter components,e.g.naphtha,kerosene and light gas oil. The increase in temperature and pressure,leading to more severe thermolysis of the coal structure,results in an increase in the amount of lighter and intermediate compounds at the expense of the higher MW compounds.The coal extract at optimum process conditions included naphtha14%,kerosene 21%,light gas oil27%,gas oil5%and long residue33%by weight.These values became the foundation for turning the oil of Banpoo coal into liquid fuel as well as raw chemical materials.3.6.Effects of variables on coal residue propertiesThe proximate analysis of coal residue from catalytic liquefaction using toluene–tetralin was studied.Table4shows the effect of temperature and pressure on coal residue properties in terms of sulfur reduction and the increase in heating value.The coal residue was the product of ZnCl2 catalytic liquefaction with THF pre-swelling.As temperature increased,the volatile matter deceased and fixed carbon increased which resulted in an increase in heating value.A similar trend was observed for the pressure effect in that the volatile matter decreased and fixed carbon increased with increasing pressure.It was also found that the increase in heating value ranges from33%to45%and sulfur reduction from7%to39%was dependent on the process conditions.The coal residue from catalytic liquefaction at450-C and10MPa which had lower sulfur content(0.29%)and higher heating value(32.6MJ/kg)will be considered for use subsequently in a gasification process.Furthermore,the coal residue or char can be used in fluidized combustion,in gasification or for hydrogen production since such residues are essentially composed of porous low temperature char which has no agglutinating tendency and releases little or no tarry matter during heating.4.ConclusionsSupercritical toluene is effective for coal extraction at high pressure in a relatively short time.Besides this,a hydrogenTable4Proximate analysis of coal residue from catalytic liquefaction a using toluene–tetralin(70/30v/v)for Banpoo2(1–2mm)10MPa7MPa12MPa400-C450-C490-C450-C450-C Proximate analysis(db)Ash7.811.110.511.911.1V olatile matter22.518.015.530.214.9 Fixed carbon69.770.974.057.974.0 Sulfur(%)0.450.340.290.420.31 Sulfur reduction(%)7.229.539.413.537.2 Heating value(dry,MJ/kg)32.132.632.630.332.9a THF as swelling agent,ZnCl2as catalyst.Time=90min.400 C 10 MPa450 C 10 MPa490 C 10 MPa450 C 12 MPa Crude%wt(28%)(37%)(45%)(39%)Fig.6.Effect of temperature and pressure on oil distribution of coal liquid forZnCl2catalytic liquefaction using toluene–tetralin(70/30v/v)for Banpoo2(1–2mm).Time=90min,the value of liquid yield is in parenthesis.S.Sangon et al./Fuel Processing Technology87(2006)201–207206donor such as tetralin is required for suppressing the aromatization of coal.Temperature,pressure and catalyst are the main determinates of liquid yield and coal conversion.The results indicated that coal conversion and liquid yield increased with increasing temperature and pressure.Up to45%liquid yield can be achieved in catalytic liquefaction using a semi-continuous reactor with a toluene–tetralin mixture at high temperature and pressure.The coal residue after extraction maintains most of its heating value and has lower sulfur content.AcknowledgementsFinancial support for this research by ADB through the Ministry of University Affairs is gratefully acknowledged.The authors express their gratitude to TJTTP of the Japan Bank for International Corporation(JBIC)for providing the equipment used in the present study.The authors also thank Prof.Yoshito Oshima for his assistance in equipment operation.References[1]J.C.Whitehead,D.F.Williams,Solvent extraction of coal by supercriticalgases,Inst.Fuel Lond.(1975)182.[2]N.Gangoli,G.Thodos,Ind.Eng.Chem.Prod.Res.Dev.16(1977)208.[3]M.Shishido,T.Mashiko,K.Arai,Fuel70(1991)545.[4]M.Canel,K.Hedden,A.Wilhelm,Fuel69(1990)471.[5]S.R.P.Rocha,J.V.Oliveira,S.G.Avila,D.M.Pereira,ncas,Fuel76(1997)93.[6]Q.Yaun,Q.Zhang,H.Hu,S.Guo,Fuel77(1998)1237.[7]N.P.Vasilakos,J.M.Dobbs,A.S.Parisi,Ind.Eng.Chem.Process Des.Dev.24(1985)121.[8]L.A.Amestica,E.E.Wolf,Fuel63(1984)227.[9]C.Dariva,J.V.Oliveira,M.G.R.Vale,E.B.Caramao,Fuel76(1997)585.[10]J.T.Joseph,Fuel70(1991)459.[11]R.M.Baldwin,D.R.Kennar,O.Ngaunprasert,ler,Fuel70(1991)429.[12]F.Pinto,I.Gulyurtlu,L.S.Lobo,I.Cabrita,Fuel78(1999)629.[13]L.Artok,A.Davis,G.D.Mitchell,H.H.Schobert,Fuel71(1992)981.[14]D.S.Ross,J.E.Blessing,Fuel58(1979)433.[15]C.Y.Wen,E.S.Lee,Coal Conversion Technology,Addison-Wesley Pub.Co.,1979.S.Sangon et al./Fuel Processing Technology87(2006)201–207207。
Ultra trace determination of fluorobenzoic acids in tap and reservoir water using solid-phase extraction and gas chromatography–mass spectrometry（利用固相萃取-气相色谱-质谱来检测自来水和水库中的水中微量的乙酸）AbstractA method for the ultra trace analysis of 21 fluorobenzoic acids (FBAs) via GC–MS based on solid-phase extraction (SPE) and derivatization with BF3·MeOH is described. All fluorobenzoic acids were enriched and determined simultaneously. Solid-phase extraction on hydrophilic–lipophilic-balanced reversed-phase cartridges containing a poly(divinylbenzene-co-N-vinylpyrrolidone) polymer allowed a 250-fold enrichment of the acids if 100 mL sample volume is used with extraction efficiencies between 71% and 94%. The method enables the determination of fluorobenzoic acid methyl esters (FBAMEs) down to the range of 6–44 ng L−1combined with a fast and easy sample-preparation (pH-adjusting prior to SPE and derivatization within 24 h at 64 °C directly in the vial样品瓶). It uses low amounts of chemicals and is adaptable to larger and smaller sample volumes. Simultaneous extraction and determination of 21 fluorinated aromatic acids in reservoir samples with high salinity（高盐度）confirmed the applicability and reproducibility of the method.本文描述了利用固相萃取，气相色谱串联质谱的方法检测超21种超衡量氟化芳香酸，同时对三氟化硼和甲醇结合物来衍生化。
英语作文a step towardA Step Toward: Embracing Challenges and Seizing Opportunities迈向：拥抱挑战，抓住机遇In life"s journey, taking a step toward something new and unknown can be both daunting and exciting.It requires courage to venture into the uncharted territories of life, where challenges lurk around every corner, yet opportunities also abound.在人生的旅程中，迈向未知的新领域既令人畏惧又充满激动。
这需要我们勇敢地踏入生活的未知领域，在那里挑战无处不在，但机遇也同样丰富。
From the moment we decide to learn a new language, like English, we embark on a transformative journey.Each vocabulary learned, every sentence constructed, and every conversation attempted is a step toward mastery.当我们决定学习一门新的语言，比如英语，那一刻起，我们就踏上了一段变革之旅。
每一个学习的词汇，每一个构建的句子，以及每一次尝试的对话，都是通往精通的一步。
However, the path to proficiency is never smooth.It is filled with moments of frustration and doubt.But, it"s in these moments that we must remind ourselves to persevere, for a step backward can sometimes be the push needed to take two steps forward.然而，通往熟练的道路从未平坦。
与其仰望高楼,不如拾级而上英语作文英文回答：In life's arduous journey, we often have to make a choice between lofty ambitions and practical, incremental steps. While it's alluring to set our sights on towering skyscrapers, the most prudent path may lie in taking the proverbial staircase, one step at a time.Aspiring to achieve grandiose goals can be a source of motivation, but it can also lead to discouragement if our expectations aren't met. By breaking down our objectives into manageable chunks, we reduce the likelihood of feeling overwhelmed and increase our chances of success. Each small victory along the way serves as a stepping stone,propelling us forward with a sense of accomplishment.Furthermore, focusing on the immediate steps within our reach allows us to navigate the present moment more effectively. When our minds are preoccupied with distantobjectives, we may neglect the important tasks that need our attention now. By embracing the principle of "one step at a time," we can prioritize our efforts and make the most of every opportunity.While it's essential to dream big and set ambitious goals, it's equally important to recognize that the journey to the summit is a gradual process that requires patience and perseverance. By choosing the staircase over the skyscraper, we acknowledge the reality of our limitations and adopt a more realistic approach to achieving our aspirations.In Chinese literature, there is a famous idiom that epitomizes this philosophy: "一步一个脚印，走稳才能走远." It translates to "Take one step at a time; by walking steadily, you can travel far." This adage reminds us that the path to success is paved with small, consistent steps, and that true progress is made through persistent effort rather than sporadic bursts of enthusiasm.中文回答：在人生的艰苦跋涉中，我们常常不得不在远大理想和脚踏实地的渐进步骤间做出选择。
如何赶上时代进步的英语作文范文模板In a world propelled by rapid advancements, keeping pace with the relentless march of progress can feel like a perpetual challenge. Whether it’s technological innovations, societal shifts, or cultural transformations, the landscape of our era is in constant flux, leaving many grappling with how to stay relevant and adaptable. This essay endeavors to explore strategies for embracing and even harnessing the momentum of progress in the modern age.Understanding the Need for Adaptation:The first step in catching up with the pace of progress is acknowledging the necessity of adaptation. In today’sfast-evolving world, clinging to outdated methods and perspectives can quickly render one obsolete. Recognizing that change is inevitable and often beneficial lays the foundation for embracing progress rather than resisting it.Continuous Learning and Self-Improvement:At the heart of keeping up with the times lies a commitment to lifelong learning and self-improvement. This involves actively seeking out new knowledge, skills, and experiences that broaden one’s horizons and enhance adaptability. Whether through formal education, self-study, or experiential learning, the pursuit of growth is essential for staying relevant in an ever-changing world.Embracing Technology and Innovation:Technology serves as a driving force behind much of the progress in the modern era. Embracing technological advancements not only facilitates efficiency and productivity but also opens doors to new opportunities for growth and development. From mastering digital tools to leveraging emerging technologies, integrating technology into daily life is crucial for staying connected and competitive in the digital age.Cultivating Critical Thinking and Creativity:In a world inundated with information and ideas, theability to think critically and creatively is indispensable. Navigating complex issues and solving novel problemsrequires a nimble mind capable of discerning truth from falsehood and generating innovative solutions. Cultivating these skills through reflection, analysis, and experimentation empowers individuals to adapt and thrive in an ever-changing landscape.Fostering Adaptability and Resilience:Adaptability and resilience are perhaps the most essential qualities for keeping pace with progress. As the world evolves at an unprecedented pace, the ability to adapt to new circumstances and bounce back from setbacks becomes increasingly valuable. Cultivating resilience through adversity and embracing change with an open mind enables individuals to not only survive but thrive in an eradefined by flux.Conclusion:In conclusion, catching up with the progress of our timesrequires a proactive approach centered on continuous learning, embracing innovation, cultivating critical thinking, and fostering adaptability. By embracing change rather than shying away from it, individuals can position themselves to navigate the complexities of the modern era with confidence and resilience. As we journey forward into an uncertain future, let us embrace the opportunities for growth and transformation that progress affords, knowing that the only constant in life is change.。
In the realm of dreams and aspirations,the concept of legacy plays a pivotal role.It is the thread that weaves through generations,connecting the past with the present and the future.A legacy is not merely a collection of possessions or achievements it is the embodiment of values,knowledge,and experiences that are passed down from one generation to the next.This essay will explore the significance of legacy in shaping dreams and the importance of preserving and building upon it.The Power of LegacyLegacy is a powerful force that shapes our dreams and ambitions.It is the foundation upon which we build our lives.The dreams we hold dear are often influenced by the stories and lessons passed down from our ancestors.These narratives inspire us to aim higher,to strive for greatness,and to contribute positively to the world.The legacy of great leaders,innovators,and thinkers serves as a beacon,guiding us towards our own aspirations and dreams.Cultural and Historical LegaciesEvery culture and society has its own rich tapestry of legacy.This includes the oral traditions of indigenous peoples,the architectural wonders of ancient civilizations,and the literary works of great writers.These legacies are not just historical artifacts they are living,breathing testaments to the dreams and achievements of those who came before us. They inspire us to dream big and to work towards a future that honors the past.The Role of Education in LegacyEducation is a crucial component in the transmission of legacy.It is through education that we learn about the world,our place in it,and the dreams of those who have shaped it. Schools and educational institutions play a vital role in preserving and passing on the knowledge,values,and dreams of previous generations.By learning from the past,we can better understand our present and shape our future.Preserving and Building Upon LegacyIn order to build upon the legacy of our predecessors,we must first understand and appreciate it.This involves a deep respect for the achievements and sacrifices of those who have come before us.It also requires a commitment to preserving and promoting the values and ideals that have been passed down through generations.Moreover,building upon legacy means taking what has been handed down to us andadding our own unique contributions.It is about innovating and creating new dreams that are rooted in the wisdom of the past but are also forwardlooking and adaptive to the changing world.The Future of LegacyAs we look to the future,the importance of legacy in shaping our dreams cannot be overstated.The dreams we hold today will become the legacy of tomorrow.It is our responsibility to ensure that the dreams we pass on are ones that inspire future generations to continue the cycle of传承,building upon the dreams and achievements of those who came before them.In conclusion,legacy is a vital component in the tapestry of our lives.It is the bridge that connects our past,present,and future.By understanding,appreciating,and building upon the legacy of our predecessors,we can shape our dreams in a way that honors the past and paves the way for a brighter future.It is through this传承of dreams and aspirations that we can truly make a lasting impact on the world.。
超越自我，勇攀六级英语高峰In the journey of life, every step forward is a leap of faith and courage. The Six-level English exam is no exception. It stands as a challenging milestone, demanding not just knowledge and skills, but also perseverance and dedication. As we embark on this journey, let us remember that the destination is not merely a certificate or a score; it is a testament to our hard work and perseverance.The road to the Six-level English exam is often fraught with difficulties. Vocabulary and grammar tests our memory and comprehension. Listening and reading sections challenge our attention to detail. Writing and speaking sections require us to express our thoughts clearly and coherently. However, these challenges are not obstacles; they are stepping stones to our growth and progress.To excel in the Six-level English exam, we mustcultivate a positive mindset. Believing in ourselves andour abilities is crucial. We must also develop a habit of regular practice, honing our skills through constant repetition and revision. Additionally, seeking help fromteachers, peers, or online resources can greatly enhanceour learning experience.Moreover, we should embrace the process of learning, rather than focusing solely on the outcome. Enjoying the journey, discovering new words, and understanding different cultures will make the process more enjoyable and rewarding. By doing so, we not only improve our English proficiencybut also broaden our horizons.Remember, the Six-level English exam is not a destination; it is a stepping stone to furtheropportunities and adventures. By working hard, staying focused, and maintaining a positive attitude, we can overcome any challenges and achieve our desired results.Let us embrace the challenge,超越自我，勇攀六级英语高峰，and together, we will reach the summit of our dreams.**超越自我，勇攀六级英语高峰**在人生的旅途中，每一次向前迈进都是对信仰和勇气的考验。
A MAJOR STEP FORWARD---THESUPERCRITICAL CFB BOILERRagnar Lundqvist, Foster Wheeler Energia OyAndre Schrief, Siemens Power GenerationPertti Kinnunen Foster Wheeler Energia OyKari Myöhänen, Foster Wheeler Energia OyMani Seshamani, Foster Wheeler Power Group, Inc.ABSTRACTSince the start-up of a coal-fired, 30 MW e bubbling fluidized bed boiler in the US at Rivesville, West Virginia in 1977, fluidized bed boilers have grown steadily in size, matured into a circulating fluidized bed (CFB) configuration, and now offer utilities enhanced performance, high reliability, and the ability to burn a wide variety of fuels. Having built the Rivesville demonstration unit and the world’s largest CFB boilers, Foster Wheeler has been a pioneer in this effort. The largest units now in operation, with a nominal 300 MW e capacity, are located at Jacksonville Electric Authority’s Northside Generating Station These began operation in 2002 and can fire coal or petroleum coke in varying proportions.Although CFB technology was previously viewed by some as being limited to relatively small sizes and serving only a niche ‘hard-to-burn’ fuel market, it is obvious that CFBs have grown to meet the power industry’s need for large-scale power generation, minimum stack gas emissions, and fuel flexibility.The next step in the evolution of CFB technology has been the move to advanced steam cycle conditions to maximize plant efficiencies. In February 2003, the Polish utilityPoludniowy Koncern Energetyczny S.A. awarded Foster Wheeler a contract to build the world’s first CFB boiler operating at supercritical steam conditions---a 460 MWe unit to be built at their Lagisza station. In addition to operating at supercritical pressure (27.50 MPa/3989psig main steam throttle pressure) with superheat and reheat steam temperatures of 560°C and 580°C (1040°F and 1076°F) respectively, the CFB will incorporate BENSON Vertical Low Mass Flux Once-Through Technology developed by Siemens Power Generation of Erlangen, Germany. This technology allows the boiler to operate with reduced pressure drop, thus minimizing auxiliary power demand and increasing plant efficiency. In addition, tube flow characteristics are typical of drum-type units, where an increase in heat flux translates automatically into an increase in tube side flow rate. The latter is very important, as it protects tubes against over-temperature under the worst upset conditions, without having to resort to mechanically complex, high pressure drop designs.This paper describes the 460 MW e supercritical CFB boiler, Siemens Low Mass Flux Once Through Technology and its advantages for a CFB design, and presents the results of design analyses investigating the effects of varying furnace conditions, both steady-state and loss of fuel feed, on tube water/steam flow distributions and evaporator outlet temperatures.INTRODUCTIONThe Kyoto Protocol, regardless whether it is fully ratified or not, has been the catalyst for a number of changes in the energy generation industry. Debate on future energy management for power stations and what types of energy should be used continues to be quite intensive, and has resulted in a lot of new research and development work. One focus of this debate has been on carbon dioxide (CO2) emissions and how to reduce them. As a result, coal remains somewhat unpopular, due to the perception that coal-fired plants pollute the atmosphere and generate higher emissions of CO2 than gas-fired technology. Flue gas cleaning technologies have made major improvements here. The capture and sequestration of CO2 is not yet an economic technology when burning coal. The industry nevertheless needs to use coal as one of its fuel sources; and the only feasible method ofreducing CO2 in the near and medium term when utilizing coal is to emit as little CO2 as possible, by increasing plant efficiency.Modern power plants are designed for high efficiency, not only for economical reasons but also for environmental reasons, such as reducing fuel usage, the quantity of ash generated, and cutting the level of pollutants emitted. Increasing efficiency also means lower emissions of CO2. Supercritical steam parameters have been applied as a first step to achieving these goals. Most of the large European thermal power plants fired on fossil fuels, such as coal and brown coal, that have been commissioned over the last decade have incorporated supercritical steam parameters In order to achieve even higher efficiencies, steam temperatures and pressures are being continuously increased as much as the metals used in boiler tubes and turbine blades allow.The larger plants built recently have been based on pulverized coal (PC) technology, and much development of this technology has taken place. However, circulating fluidized bed (CFB) technology has emerged as a growing challenger. CFB boiler technology based on natural circulation has reached utility scale over the last decade. The largest units in operation at the moment are two 300 MW e boilers operated by Jacksonville Electric Authority (JEA) in Jacksonville, Florida, capable of burning either 100% coal or 100% petroleum coke or any combination of the two.For CFB technology to be considered a viable technology for meeting the power generation guidelines established by the United States Department of Energy Road Map , it has to be designed with supercritical steam parameters. This step has now been reached by Foster Wheeler, following the award of a contract by the Polish utility, Poludniowy Koncern Energetyczny S. A. (PKE), in February 2003 to build the world’s first CFB boiler operating at supercritical steam conditions, a 460 MWe unit to be built at their Lagisza station.Prior to winning the contract, Foster Wheeler had carried out extensive development work on the mechanical design issues involved and understanding the process conditions affecting heat transfer, flow dynamics, carbon burnout, gaseous emission suppression, hydraulic flows, etc.. Various methods and equipment, such as bench-scale test rigs, pilotplants, field testing at operating units, model development, design correlations for conventional boiler design, and simulation employing semi-empirical models or more theoretical models have been used for developing and successfully implementing design criteria for larger units.The Foster Wheeler supercritical once-through boiler (OTU) employs a licensed application of Siemens’ low mass-flux BENSON vertical once-through technology. It also employs the results of work performed under an EU-funded program aimed at further developing OTU CFB technology; that program known as High Performance Boiler (HIPE), began in 2002 under the Community’s 5th Framework , and involves Foster Wheeler Energia Oy from Finland, Siemens AG from Germany, the Technical Research Center of Finland, and Energoprojekt Katowice from Poland. The BENSON system, together with some test results from the HIPE program, along with a design description of Foster Wheeler’s 460 MW e unit, are discussed below. The advantages of using low mass-flux OTU technology for a CFB boiler are described in general.SIEMENS BENSON LOW MASS-FLUX VERTICAL ONCE-THROUGH (OT) TECHNOLOGYWith a total of more than 1,000 units delivered over many years to the power generation industry, the BENSON boiler is the most commonly used type of once-through boiler. It operates at power levels up to 1,300 MW e, steam pressures up to 350 bar, and steam temperatures up to well over 600°C. More than a quarter of units operate at supercritical pressure.BENSON technology is centered on an evaporator design and has been licensed by Siemens since 1933. It is a once-through design suitable for sub- and supercritical pressure and variable pressure operation. Steam generators using the BENSON design incorporate features that are critical to economic success on today’s competitive power markets. These features include:Ø a highly efficient water/steam cycle, as a result of supercritical pressures and high steam temperaturesØ insensitivity of steam output and steam temperature to fluctuating fuel properties Ø the capability for rapid load changes, due to variable-pressure operation and short start-up times, thanks to thermoelastic design.The extensive worldwide use of the BENSON boiler is the result of ongoing efforts to develop the technology. The expanded knowledge base obtained through detailed studies, particularly of the heat transfer mechanisms within furnace tubes, has made an important contribution to this effort. New evaporator designs will continue to improve operating behavior and make boiler manufacturing more cost-effective.The BENSON Low Mass Flux design is unique. Earlier furnaces were designed with spiral-wound tubes, and operating experience has been built up with several hundred boilers extending over more than 30 years. A new development started in the 1980s in the form of vertical evaporator tubing with low mass flux, based on the use of rifled tubes, as shown in Figure 1. Figure 1 BENSON Boilers – Concepts for Water Walls.Heat transfer in a rifled tube is very good, especially during evaporation, since centrifugal forces transport the water fraction of the wet steam to the tube wall. The resulting wall Spiral-wound tubing and support straps Vertical tubingwith rifled tubeswetting results in excellent heat transfer from the wall to the fluid. This has the following advantages over smooth tubes:Ø No deterioration of heat transfer, even in the range of high steam qualityØ Very good heat transfer, even at low mass fluxØ Only a slight increase in wall temperature in the case of film boiling near critical pressureØ Potential for increased heat transfer by optimizing rifling geometry.The Siemens high-pressure test rig – the largest in the world, with an electrical heater capacity of about 2,000 kW – was used to generate more than 200,000 data points in an investigation of standard commercial rifled tubes and tubes with modified rifling geometry. Changes to the rifling geometry permit significant improvements in heat transfer to be achieved, as can be seen in Figure 2.A vertical tube arrangement on the one hand, and rifling on the other, allow a design with very low mass flux. This low mass flux changes the flow characteristics of a once-through system. Increased heat input to an individual tube leads to increased throughput for the tube concerned, instead of reduced throughput, as might be expected. This flow behavior – typical of drum boilers – is known as a natural circulation or positive flow characteristic. The advantages of a vertically tubed furnace can be summarized as follows:Ø Mass flux reduction from 2,000 to 1,000 kg/m²s, with a similar flow characteristic to that of drum boilersØ Cost-effective fabrication and assemblyØ Low minimum load and simple start-upØ Reduced slagging and erosion on furnace wall due to parallel gas flowØ Reduced evaporator pressure drop.The BENSON low mass flux design was first tested in the Farge 420 MW e supercritical power plant, using a few small test sections. The first coal-fired boiler with an evaporator based on the Siemens low mass flux design was built in Yaomeng, China, and has now been in successful operation since mid-2002. The boiler – a repowering project at a 300MW power plant – incorporates the special challenge of a center water wall with heat input from both sides and configured parallel to the water walls. Despite the large variations in heat input between the outer water walls and the center water wall, the temperature variations at the outlet of the water wall heat exchange surfaces are negligible.CFB plants incorporating once-through boilers rated up to 100 MW e have been in operation for many years. The state of the art when these plants were constructed featured a relatively elaborate riser–downcomer system for the water walls. The largest CFB plants to date, rated in the 300 MW e range, are designed with drum boilers. However, once-through operation and elevated steam conditions up to approximately 600°C and 300 bar are required to make CFB technology a real competitor to pulverized coal firing for large plants.Figure 2 Rifled tubes reduce wall temperatures or allow mass flux reduction.Table 1 shows the references for CFB BENSON boilers with vertical riser-downcomer systems and PC BENSON Boilers with low mass flux installations.1 8 0 02 0 0 0 P r e s s u r e 2 1 2 b a r P e a k h e a t f l u x3 1 0 k W /m 2 2 2 0 0 24 0 0 1 8 0 0 3 6 0 3 8 0 4 0 0 4 4 0 2 0 0 0 2 2 0 0 2 4 0 0 F l u i d e n t h a l p y I n n e r w a l l t e m p e r a t u r e 3 6 0 3 8 0 4 0 0 ° C 4 4 0 S m o o t h t u b e M a s s f l u x 1 0 0 0 k g / m 2 s S t a n d a r d r i f l e d t u b e M a s s f l u x 1 0 0 0 k g /m 2s O p t i m i z e d r i f l e d t u b e M a s s f l u x 1 0 0 0 k g / m 2s S m o o t h t u b e M a s s f l u x 15 0 0 k g /m 2 s S t a n d a r d r i f l e d t u b e M a s s f l u x 1 0 0 0 k g /m 2 s O p t i m i z e d r i f l e d t u b e M a s s f l u x 7 7 0 k g /m 2 s k J / k g ° C k J / k gAs part of the EU HIPE research program, an evaporator concept for a 460 MW e CFB plant was elaborated, based on the Siemens low mass flux design. Fluid mechanics analysis have been performed, as well as heat transfer measurements in the BENSON test rig using rifled tube, such as that used in the intermediate water walls (wing walls) of a combustor subject to heat input from both sides.Due to the differing geometries and heat inputs involved, the evaporator had to be subdivided into a number of systems, configured in parallel. The individual mass flows and the corresponding outlet temperatures from the water wall sections were then determined. The effects of variations in heat input and the loss of a fuel feeder on the temperatures were also investigated.Power Plant Type Flow(kg/s)Temp.(°C)Pressure(bar)Contrac-tual DateManufacturerSW Duisburg* CFB 75 535 140 1983 Babcock Borsig Bayer Leverkusen 1 CFB 2 x 39 580 140 1984 Burmeister+Wain Bayer Leverkusen 2 CFB 2 x 39 580 140 1988 Burmeister+Wain Berlin Moabit CFB 91 540 190 1986 Burmeister+Wain KW Farge TestLoopPC 300 535 250 1996 Babcock Borsig Yaomeng (China) PC 278 545 164 2001 Mitsui BabcockTable 1 BENSON references for CFB with a vertical riser-downcomer-system and PC boilers with vertical tubing. Note that SW Duisburg* has horizontal evaporatortubing .The selection of a relatively low design mass flux – between 400 kg/m²s and 700 kg/m²s depending on the type of tube – yields a good positive flow characteristic for all tubes, for the smooth tubes in the front, rear, and side walls, as well as for the rifled tubes in the intermediate walls (wings walls).This means that even large variations in heat input are evened out by the adjustment of individual mass flows, which takes place automatically as a result of the self-regulating characteristic. At full load, the differences between the highest and lowest individual tubetemperatures at the evaporator outlet are only 35 K, even in the event of the loss of a fuel feeder, as shown in Figure 3. Further investigations performed for partial load conditions (75% and 40%) yielded even lower temperature differences.Thanks to the low mass fluxes, the evaporator pressure drop between the point of distribution to the individual systems and the separator inlet only amounts to 2.7 bar at full load. This makes a major contribution to reducing the auxiliary power requirement.Figure 3 Outlet temperatures of the evaporator tube segments. Note that only one half ofthe furnace is shown.CFB technology imposes stringent requirements on water wall tubing. The high ash loading in the combustor requires the use of tubing running parallel to the flue gas/ash flow. Wound tubing, such as that usually implemented in the furnaces of pulverized coal-fired boilers, is not feasible for the combustor. In addition, some variations in heat input must be assumed. The combustor walls feature zones of greatly differing heat input, especially in the upper section. As a result, several sections in the ash discharge area are provided with lining. Higher-output plants require intermediate water walls, with heat input to both sides, where necessary.In the CFBs constructed to date as once-through boilers, the combustor has been implemented using a system of risers and downcomers, each featuring a complex 480390400420430440450460470Temperature °Credistribution of the water/steam mixture after each pass. Thanks to the BENSON low mass flux design, an evaporator concept is now available that fulfills the above requirements and is cost-effective, thanks to its inherent simplicity. Medium flows take place in parallel through all tubes in one pass, and no distribution of water/steam mixture is required. There are only negligible variations in temperature between the tubes at the outlet from the combustor, as variations in heat input are evened out by the positive flow characteristic. The relatively low heat flux in the combustor compared to that in the furnace of pulverized coal-fired boilers allows smooth tubes to be used for the water walls subject to single-sided heat input. In addition, the suitability of the evaporator system for variable-pressure operation meets all power plant requirements with regard to operating flexibility.COMBUSTION-SIDE STUDIES WITH THE LOW MASS-FLUX OTU CFBThe CFB process also has a number of other merits when applying supercritical OTU technology. The nature of CFB combustion results in low and uniform heat flux throughout the entire furnace, due to relatively low combustion temperatures, no distinct flame with high temperature and high radiation, and uniformity of furnace temperature resulting from the circulating solids acting as a buffer. In pulverized coal firing, the burner flames cause a high temperature zone, resulting in high heat fluxes locally and higher temperatures in the boiler tubes. Figure 4 illustrates the heat flux for a CFB boiler compared to a PC boiler, and the difference is significant. Figure 4 also shows how the heat flux develops along the height of a furnace.Understanding heat flux characteristics is of utmost importance, and requires a thorough understanding of the combustion process in a furnace, including the release of heat in the combustion process, heat transfer, and gas and flow dynamics. Foster Wheeler has concentrated on testing and measuring these issues in bench-scale test rigs, pilot plants, and operational units, and developing empirical and semi-empirical models for use in combination with more theoretical models to create simulation tools to assist in CFB furnace design.Figure 4 Heat flux versus height in a CFB and PC furnace.Boiler combustion behavior and its influence on heat flux and heat transfer can now be modeled accurately in a three-dimensional model. The model combines fundamental balance and momentum equations and empirical correlations. Theoretical equations are used for those phenomena for which the governing equations are defined and acceptable. Empirical correlations are used for phenomena for which the theoretical equations are not known or the theory is too complex, resulting in unacceptable computing times.The most important phase in the development of these models and correlations has been validation, using measurements taken in real conditions. For validating a three-dimensional model, the standard measurements for defining overall mass and energy balance areAverage heat flux over height forPC and CFB furnaces50,40,35,30,25,20,15,10,5,0,45,0100 200300 400F u r n a c e H e i g h tHeat flux (average) [kW/m²]PCCFBrequired, but are insufficient in themselves. Profile measurements have been carried out in various parts of the furnace, and measurement locations extended well inside the furnace. It is also essential to know more about fuel and limestone behavior in areas such as attrition and fragmentation.An extensive program has been conducted to measure heat transfer and heat fluxes, combustion profiles, and other issues in large-scale units. One part of the total program has been the measurements carried out under an EU-supported project, ‘In Furnace Process in a 235 MW e CFB Boiler’, in one of the units at the Turów power station in Bogatynia, Poland. The partners in the project have been the plant, Technical University Hamburg-Harburg, Czestochowa Technical University, the Technical University of Ostrava, Chalmers University of Technology, and Foster Wheeler Energia Oy. A more detailed description of the development of the models is presented in /1/.The heat flux is relatively uniform in the furnace, as seen in Figure 4. This also applies for the temperature. However, as there are occasional inconsistencies in operation, such as feeder trips, it is of interest to investigate these situations. If a boiler is sensitive to such disturbances, some partial overheating or imbalance could occur. This has been studied extensively for a CFB boiler in the 400-500 MW e size range. In the case of a corner feeder tripping, as described in Table 2, when the other feeders have to pick up the load, not very much happens to the heat flux or the combustion temperature. Figure 5 shows the heat flux and the differences, while Figure 6 shows the temperature distribution and the difference. For illustrative purposes, the colors show a large difference, but in fact the numerical changes are very small.Case 1: Basic case.Uniform fuel feeding to all the feeding points.Case 2: Fuel feed stopped to feeding point at front-right corner.Feed rate to other feeders increased equally.Table 2 Heat flux distribution cases.Figure 5 Heat flux comparison between Case 1 and Case 2, front and right wallCase 1 Case 2 Scale [kW/m2] Change in heat flux:Difference Case 2 – Case 1 [kW/m2] Percentage change [%]Figure 6 Gas temperature comparison between Case 1 and Case 2Case 1 Case 2 Scale [°C] Difference in gas temperature [°C] (Case 2 – Case 1):Case 1 – Case 2 Scale [ºC]The difference in gas temperature is close to 25 ºC at its maximum point, but this does not have a very significant influence on heat flux. Figure 7 presents the percentage change at different horizontal locations on the furnace walls at an elevation of approximately 6 meters from the grid. The heat flux changes gradually from the front to the back of the furnace. Such percentage changes have no significant impact on wall metal temperatures. The change is in the order of a few degrees.Figure 7 Percentage change in heat flux in the horizontal direction when one fuel feeder trips.Various kinds of operational modes, as well as the overall sensitivity of a boiler and its combustion process, can be studied using this kind of tool, as has been done, and is still being done in respect of the Lagsiza project.ADVANTAGES OF A SUPERCRITICAL OTU CFB BOILEROne general feature of Siemens’ low mass-flux BENSON OTU technology is that it results in a lower water/steam side pressure drop. This reduces feed water pump power consumption, thereby reducing the plant net heat rate.Other advantages of an OTU CFB include the fact that a low and uniform heat flux makes boiler tubes insensitive to overheating, as earlier discussed. As the combustion temperatureis relatively low in a CFB, i.e. 850-880 ºC (1562-1616 ºF), there is no slagging or fouling of the furnace water walls and, hence, no deterioration of heat transfer.In addition, the following general advantages should be mentioned:Ø fuel flexibilityØ multi-fuel capabilityØ low emissions without the need for secondary clean-upOne inherent feature of a CFB boiler is its insensitivity to variations in fuel composition. In many cases, coal or brown coal from the same mine varies widely in terms of heat value, ash content, and moisture. Such variations do not materially affect the combustion temperature, due to the thermal wheel that the circulating solids create, i.e. the solids act as a buffer against any variations in fuel characteristics andthe amount of fuel present in the unit is only a few percent of the total amount of bed material.. The relatively uniform combustion temperature provided by the CFB results in a uniform heat flux and even temperatures in the boiler tubes.Multi-fuel operation is another inherent feature of a CFB unit. When firing several different fuels, heat fluxes will also be low and uniform, due to the buffer characteristics of the circulating solids. These are clear advantages for a plant owner, as fuel property variations and fuel availability will not become an issue, giving owners a larger degree of freedom to use the most economical fuel source. This is increasingly important, as many plant owners rely on imported coal or coal from various mines.A CFB boiler generates low levels of gaseous emissions without the use of additional flue gas cleaning equipment. The cost of flue gas desulfurization (FGD) and selective catalytic reduction (SCR) systems can be very significant. In addition, an SCR system requires ammonia injection, and the catalyst must be replaced on a regular basis. A CFB produces more ash, since in-furnace sulfur reduction is not as efficient as an FGD. On the other hand, limestone can be used directly and lime is not required. The cost of lime is typically several times higher than the cost of limestone. The end-product of a CFB is always dry and there are no wet discharge streams.Even though the CFB operates at a much lower temperature than a pulverized coal-fired unit, the high particle residence time and turbulent mixing provided by the hot circulating solids to enhance carbon burnout and in, practice, the two units operate with similar combustion efficiencies.. The CFB, however, can operate with a lower flue gas exit temperature which enhances boiler efficiency. The reason for this lower flue gas temperature is the economizer, which can be used more effectively in a CFB. The water temperature can be raised in the economizer while still maintaining the appropriate steam/water ratio by weight in the furnace tubes, as the heat fluxes are lower than in a pulverized coal-fired unit. The SO2 content in CFB flue gas is also significantly lower than in a PC, since sulfur capture takes place in the furnace. This results in a lower acid dew point and flue gas can be colder without cold end corrosion.While more auxiliary power is needed for fluidization, no mills are required and there is no additional flue gas pressure drop due to FGD and SCR units, and no water consumption, as in a FGD. The power demand of these components are more or less equal to the power needed for fluidization.Overall, CFB boiler technology offers so many advantages that it can be expected to be utilized more and more in future large-scale power generation based on coal or brown coal.THE 460 MW e ONCE-THROUGH CFB LAGISZA PROJECTThe first company to benefit from utilizing a OTU CFB with supercritical steam parameters will be the Polish utility, Poludniowy Koncern Energetyczny S.A. (PKE). Located in southern Poland, PKE is the largest utility in Poland, operating eight power plants within a 50 km radius from Katowice. The company has installed capacity of over 4,795 MW e, which is approximately 17% of Poland’s total generating capacity. In addition, the company has over 2,000 MW th of district heating capacity, which accounts for 16% of the local heat generating requirements of the Katowice area.PKE solicited quotations for a 460 MW e once-through supercritical, coal-fired boiler plant in October 2001. The bidding process was split into two phases and specified for two。
