NO_x空气氧化与碱液吸收工艺实验研究

烟气污染治理NO x空气氧化与碱液吸收工艺实验研究乔军师胡金榜宗润宽常明坤(天津大学化工学院,天津300072)摘要根据我国NO x废气治理技术的特点与现状,分析了用空气氧化NO,用烧碱溶液对氧化后的气体进行吸收工艺的可行性。

并对该工艺中模拟废气中NO x的浓度、氧化时间、氧化度以及吸收率之间的关系进行了实验研究和分析,为其工业应用提供了实验依据。

关键词空气氧化法NOx氧化度吸收率1前言NO x主要由NO和NO2组成,此外还包括N2O、N2O3等,统称为氮氧化物。

现在全世界NO x年排放量约为86@106t[1],从而引起了酸雨、光化学烟雾等破坏地球生态环境和损害人体健康的一系列问题。

NO x中NO2的体积百分数称为NO x的氧化度,含NO x废气是一种较难处理的工业废气,其中的NO x的氧化度一般都很低,NO除了生成络合物外,几乎不被水或碱液吸收。

为了有效地治理含NO x废气,需将其中的NO氧化为NO2,调节NO x的氧化度至50%~ 60%,然后再用吸收剂进行吸收。

在低浓度下,NO的氧化速率是非常缓慢的,因此提高NO的氧化速率就成为脱除NO x的决定性因素。

对于治理NO x废气,以提高环境质量为目的,综合考虑各种氧化方法的氧化效率和成本,本实际研究选用空气氧化法[2]。

利用空气作为氧化剂氧化NO,空气来源丰富且成本低,通过氧化提高NO x到一定的氧化度,能促进含NO x废气的脱除。

根据我国经济技术的现状,吸收法治理含NO x 废气,是化学工业生产过程中普遍采用的方法。

在众多的吸收方法中,碱液吸收法较为常用。

但综合考虑原料价值、操作费用和吸收效率等因素,工业上以NaOH和Na2CO3使用较多,其中NaOH溶液的吸收效果更好些。

因此本实验选用NaOH作为吸收剂。

当NO x废气的氧化度为50%~60%时,吸收速率最大,吸收效率也最高[3]。

2实验设计211实验流程与设备实验流程如图1所示。

图1实验流程图1)氮气钢瓶;2)NO钢瓶;3)流量计;4)气体混合器;5)氧化塔;6)采样点;7)吸收塔;8)碱液罐;9)碱液泵;10)抽气泵。

实验中使用的主要设备参数为:吸收塔直径为3015mm,高为1200mm;氧化塔直径为200mm,塔高为750mm。

212实验与检测方法实验时,采用转子流量计来控制N2和NO的流量,进而得到所需的模拟工业废气。

N2和NO经气体混合器充分混合后,从氧化塔顶端进入,与同样从氧化塔顶端进入的空气进行混合。

在氧化塔内停留一定时间,NO与空气中的氧气发生氧化反应生成NO2,从而提高NO x的氧化度。

氧化后的气体由底部进入吸收塔,NaOH水溶液从塔顶由计量泵送入。

在吸收塔内完成NaOH水溶液对NO x的吸收操作,处理后的废气从吸收塔顶由抽气泵排出。

为了测试氧化塔对NO的氧化效果以及检测吸收塔的吸收效率,分别在吸收塔的进口和出口处设置采样点,采用盐酸萘乙二胺分光光度法,对NO x废气进行浓度监测,其优点在于能同时准确测量NO2和NO x的浓度。

213实验条件实验条件如表1所示。

37环境工程2005年4月第23卷第2期表1 实验条件N 2流量P m 3#h -1氧化时间P s 操作温度P e 补充空气与模拟废气摩尔流量比NaO H 溶液质量分数%017601612~18191B 16016701612~18191B 16015841612~18191B 163 实验数据分析与讨论311 氧化时间对NO 转化率的影响实验测得当NO 的浓度在3500~5500mg P m 3范围内变化时,氧化时间与NO 的转化率的对应关系如图2所示。

图2 NO 转化率与NO 浓度及氧化时间的关系由图2可知,当NO 浓度一定时,NO 的转化率随着氧化时间的延长而增大。

312 氧化度对NO x 吸收效率的影响实验测得当吸收塔进口的NO x 浓度([NO x ]进口)为3700mg P m 3时(统计值3700mg P m 3?10%),NO x 氧化度和NO x 吸收率的关系曲线,如图3所示。

图3 NO x 吸收率和NO x 氧化度的关系在此还对一定NO x 进口浓度下NO x 氧化度对NO x 吸收率的影响进行了实验研究,实测数据见表2。

由图3和表2可知,当[NO x ]进口一定时,随着NO x氧化度的升高,NO x 吸收率也相应提高。

313 NO x 进口浓度对NO x 吸收效率的影响实验测得当NO x 氧化度一定时NO x 吸收率和[NO x ]进口的关系如表3所示。

表2 [NO x ]进口一定时NO x 吸收率和NO x 氧化度的关系[NO x ]进口P mg #m -3NO x 氧化度%NO x 吸收率%20001511~16154418~511425001612~24185115~631530001912~25185614~671937002311~32156515~741445002715~34166917~761555003013~42117013~8512表3 N O x 氧化度一定时NO x 吸收率和[NO x ]进口的关系NO x 氧化度%[NO x ]进口P mg #m -3NO x 吸收率%151860~22804418~5312202248~30235511~6016252748~44286315~6917303588~51066917~7414353992~58017119~8113405801~61407518~8512由表3可知,当NO x 氧化度一定时,随着[NO x ]进口的升高,NO x 吸收率也相应提高。

由此可见,用吸收法治理NO x 废气时,对于NO x氧化度较低的工业NO x 废气,提高NO x 的氧化度对NO x 废气的治理是十分必要而且非常有效的。

4 结论使用空气作为NO 的氧化剂,把氧化后的气体用NaOH 溶液进行吸收。

该工艺成本低,经济性好,工艺流程简单,对NO x 浓度较大的工业废气还可对副产品亚硝酸钠进行回收利用。

本实验为该工艺的工业应用提供了实验依据。

参考文献1 郑惠榕.简析氮氧化物的污染及工业治理.福州师范高等专科学校化学系,2000.(1):28~30.2 常明坤,胡金榜,宗润宽,王晋刚.利用空气氧化NO x 的技术探讨.化学工业与工程,2003.20(6):518~522.3 童志权.工业废气净化与利用.北京:化学工业出版社,2001.297~314.作者通讯处 乔军师 300072 天津大学化工学院化机系电话 (022)27408812E -mail qi aojunshi@si na.c om2004-06-17收稿38环 境 工 程2005年4月第23卷第2期APPLIATION OF UPFLOW AN AER OBIC SLUDGE BED -CON TACT OXIDATION PROCESS IN TREATMENT OF ETHANOL WASTEWATER Fan Xinsheng et al (21),,,,,,,,,,,,,,,,,Abstract The application of UASB -contact oxidation process in treating ethanol was tewater is presen ted.The operating resul ts have shown that when the influent COD Cr ,B OD 5and SS are in range of 18000~21000mg P L,10500~12000mg P L and 16000~18500mg P L respectively ,the effluent of the system is good enough to meet the class Òguided by National Was tewater Integrated Discharge Standard (GB8978-96).Keywords ethanol wastewater,UASB reactor and contact oxidation STUDY ON TREATMEN T OF PH OSPHOR IC COATING WASTEWATERWu Juzhen et al (23),,,Abstract The defatted was tewater was pretreated by heating or demulsi fied by acidification;then the phosphorized wastewater was expreienced advanced treatmen t by coagulation -flocculation -sedimentation -airfloat process.The combination of suitable chemicals,inorganic coagulant and high polymer flocculant can reduced remarkably the contents of COD Cr ,oil and SS of the wastewater.The tests show that the process can reduce COD Cr from 900~2200mg P L to below 50mg P L,the oil content from 300~800mg P L to below 5mg P L and SS less than 45mg P L.All the index es meet the second -order of /National Wastewater Discharge Standard 0(GB8978-1996).Keywords flocculan t,phosphorized wastewater,wastewater treatment,emulsified oi-l bearing wastewater and demusi ficationAPPLICATION OF LKM TYPE FLOCCU LANT IN TREATMEN T OF OILY WASTEWATERSong Yongji et al (26),,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,Abstract LKM type flocculant possesses of hi gh -ant-i emulsificaton ability,good water solubility,good stability and usability.The cost of its mul tiple prescription LKM -5715is low and its flocculation result is perfect.The insitu industrial experi ments indicated that at similar deoiling efficiency,i ts consu mption was 1P 2~1P 5amount of poly -aluminum chloride.The production of scum was little and easy to dispose and utilize.Instead of poly -alminum chloride,LKM -5715type flocculant can be widely utilized in the treatment of oily wastewater.Keywords wastewater treatmen t,flocculant and application studyEN GINEERING EXAMPLE OF TREATING HOTEL SEWAGE BY A 2P O PR OCESSYu Xiuhua et al (28),,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,Abstract The designed treating capacity of a wastewater treatment plant for a hotel was 800m 3P d.The A 2P O process was used and the running results of two years showed that when C OD Cr ,B OD 5,SS,NH 3-N and animal &plan t oil of the influent were 250~300mg P L,100~150m P L ,120~140mg P L,25mg P L and 50mg P L respecti vely,the quality of the effluent could meet the firs -t order during second period of /Discharge Limits of Water Pollutants 0(DB44P 26-2001)in Guangdong Province.Keywords hotel wastewater,A 2P O process and fully embedded structureOPERATION MAN AGMENT OF A -A P O PR OCESS IN COKING WASTE WATER TREATMENT SYSTEM Xing Xiangjun et al (29),,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,Abstract According to the actual circumstance of constructi on and operation of wastewater treatment project in Bei Gang Group Company,biological denitrogenation theory,A -A P O technological process,domes tication sludge and operation managment were discussed in this paper.The factors influenci ng the biolog ical denitrogenation and nitrogenation were also explored.Keywords coking waste water,nitrification -deni trification process and operation managmentAPPLICATION OF SIMPLIFIED ACTIVATED SLUDGE MODEL TO UR BAN WASTEWATER TREATMENT PLANT Liu Fang et al (33),,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,Abstract Simplified activated sludge model (ASM -CN)is proposed based on the activated sludge model No.1(AS M1).This model describes the carbon oxidation process and nitrati on process.The amount of components,processes and parameters of ASM -CN is fewer than that of AS M1,so the practicability of ASM -CN model is enhanced.The measurement of components and parameters is also studied.Finally,AS M -C N model is applied to si mulate the operation of actual wastewater treatent plants and good results are achieved.Keywords activated sludge model,simplificai ton,urban wastewater treatment plant and simulati onEXPER IMENTAL RESEARCH ON PROCESS OF AIR OXIDATION AND ABSOR PTION OF N O X WITH ALKALINE SOLUTION Qiao Junshi et al (37),,,,,,,,,,,,,,,,,,,,,,,,,,,Abstract According to the character i stics of current technology of disposing NO X i n waste gas in China,the possibility of the process of air oxidation of NO and absorp tion of NO X waste gas wi th sodium hydroxide soluti on i s analyzed.For the simulated waste gas in this process,the relation of NO X concentration,oxidation ti me,ratio of oxidation and NO X absorptivity was studied and analyzed,which provides an experimental basi s for its industrial application.3ENVIR ONMENTAL ENGINEERINGVol 123,No 12,Apr.,2005Keywords air ox idation,NO X ,ratio of ox idation and absorptivi tyDEN ITRIFICATION OF NO IN WASTE GAS STREAMS USING AGED -REFUSE -BASED BIOREACTOR Zhang Hua et al (39),,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,Abstract Stabilized or aged refuse i s a good media for bioreactor and can be used to treat NO X in waste gas s boratory study shows that an aged -refuse -based bi oreactor can effecti vely remove NO from waste gas streams.The empty bed retention time (EBRT)is the key parameter effecting the removal efficiency of NO which decreases with the shortening of EBRT.The removal efficiency of NO is 90%with the EBRT of 3.8min and 96%at 7.5min.T he removal efficiency of NO under anaerobic condition is better than that of aerobic condition.Denitrification of NO is preferable to the biological ni trification of NO.Keywords aged refuse,nitrogen oxides,ni tric oxide,biofiltration and deni trificationTREATIN G VOLATILE ORGANIC COMPOUND S -BEARIN G EXH AUST GAS IN PAC KING PRIN TING HOUSE Qiao Huixian et al (42),,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,Abstract T he paper introduced that VOCs exhaust gas in packing printing house was treated by FCJ organic gas purification eq uip ment,which is based on adsorption and catalytic combustion principle.The technical process and detecting result on treating VOCs exhaust gas were described in detail.The resul ts showed that it is efficient to treating VOCs exhaust gas in packi ng printing house by FCJ technique and eq uip ment.The treating result meets the second -order of the national emission standard.Keywords printing,VOCs,adsorption,catalytic combustion and treatment of exhaust gasNEW EXPLORATION OF C LEANING TECHNIQU E FOR C ATERING OIL FUMEZhang Jinping et al (45),,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,Abstract On the 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attenuation,width and visibility is obtained.The spectrum analysis of the noise attenuation is also done,which provides a basis for the desi gn of forest belts of highway for noise reduction.Keywords traffic noise,green belts,effect of noise attenuation and design of fores t beltsRESEAR CH ON ACOUSTIC DESIGN AND C ALCULATION OF RESISTANCE LOSS OF NOISE CON TROL FOR COLLIERY AIR SHAFT Zhang Chi (52),,,,,,,,,,,,,,,,,,,,,,,Abstract Due to a high air flow rate and a strong moise radiation in a colliery ai r shaft,i t is the key to controlling noise successfully that the ri ght and reasonable acoustic design for muffler and the calculation of resistance loss.Keywords colliery air shaft,centrifugal fan,noise control,acoustic design and resistance lossCHARAC TERIZATION OF RIVER DREDGING SILT AND ITS FEASIBILITY STU DY AS COVERIN G MATERIALS FOR REFUSE LAN DFILL Zhao Aihua et al (56),,,,,,,,,,,,,,,Abstract It is studied systematically that various parameters,such as penetration coefficien t,leaching toxicity and the con ten t of heavy metals etc of river dredging silt,as well as its feasibility of a covering material for refuse land fill.The results show that it possesses of better slope stability when used as a covering material for refuse land fill,which can basically meet the technical requirements of the covering material.There is no extra burden to the treatment of the leachate.So this sort of use can not only solve the problem of lackings of soil for a plain type landfill,but also make a way out for the dredging sil t.Keywords dredging silt,covering material and researchEXPER IMENTAL STUDY ON PRODU CING MASONRY CEMEN T BY FLY -ASH OF CIRCULATING FLUIDIZED BED BOILER Zhao Ming et al (59),,,,,,,,,,,,,,,,,,,,,Abstract Because circulating fluidized bed combustion (CFB)is the advanced technology of combustion,it is developing widely at home4ENVIR ONMENTAL ENGINEERINGVol 123,No 12,Apr.,2005。