摘要
近年来,由于燃煤电厂的大量建立,以及煤在今后一段时间内依然是极为重要的能源,因而继SO_x、NO_x、CO_2等污染物之后,燃煤排放中重金属污染问题在世界范围内引起了广泛的关注,尤其是汞元素,会对人类的健康和生态环境产生严重的危害。如何找到即经济又高效的脱除硫硝以及重金属汞的方法,目前这方面的研究还处于探索阶段,其中利用选择性催化还原法(SCR,Selected Catalytic Reductation)对NOx脱除的高效,在通过合适的催化剂将Hg~0氧化然后通过湿法烟气脱硫装置将NOx、SOx以及重金属汞脱除不失为一种行之有效的联合脱除方法,因此,本文就这一流程中的若干问题进行了有益的探讨。
本文首先综合国内外最新资料,对燃煤烟气中汞的控制脱除技术进行归纳总结,并对选择性催化还原法脱除硝的过程中汞的氧化机理以及脱除的研究进行科学描述归纳,明确自己的研究思路。然后为了研究在SCR反应过程中不同因素对汞氧化的影响,我们利用自己制备的六种不同的催化剂(V_2O_5/SiO_2、V_2O_5/TiO_2<浸渍法制备>、V_2O_5/TiO_2<溶胶凝胶法制备>、WO_3/TiO_2、V_2O_5-WO_3/TiO_2、CuO/γ-Al_2O_3)在模拟部分烟气的情况下对汞在反应后催化氧化情况进行了实验,重点考查了氨气浓度、温度、以及不同催化剂对其形态变化的影响,然后在随后的实验中还考察了上述六种催化剂对汞的吸附性能。结果表明,HCl可以显著促进SCR反应过程中汞单质的氧化和催化剂的吸附性能,氨气浓度的增大则会使汞的氧化效率和催化剂对其的吸附效率都下降。然后,为了对不同汞催化氧化的机理进行深入探讨,我们对SCR反应过程中汞的氧化和吸附的模型进行了分析,并将模型模拟结果与实验结果进行对比分析,两者都互相符合的很好。
In recent years, because of a great deal of establishment of the coal-burning power station, and in a period of time the coal is still an extremely important energy of the world. As a result of pollutant such as SO_x, NO_x, CO_2 etc., the problem of coal-burning that caused an extensive concern in the scope of the world, particularly the mercury pollution, will produce serious bane to the mankind's health and the ecosystem environment. How to find economic and effective method to take off the pollution of the SOx,NOx and the heavy metals ? The research of this aspect is still placed on the road. Making use of the selectivity catalyst Reductation method(SCR) can reduce NOx in the coal-fired flue gas. And it is also reported that SCR system can oxidize mercury as well, so this thesis paid attention on the mercury oxidation in the SCR system.
This text firstly synthesized lately data at home and abroad, then took off to the control of the mercury in the coal-fired flue gas. Then in the purpose of studying the influence of the different factor upon the mercury species’variety in the SCR process, we made use of six kinds of different catalysts (V_2O_5/SiO_2, V_2O_5/TiO_2, V_2O_5/TiO_2< sol-gel>, WO_3/TiO_2, V_2O_5-WO_3/TiO_2, CuO/γ-Al_2O_3) in the experiments. The point is to investigate the influence on mercury oxidation and catalysts’adsorbtion of ammonia concentration, SCR temperature, and different catalysts, and in the addition, we carry on an evaluation to the different catalysts.
Then, in order to carry on the deep discussion for the mercury catalysis oxidized mechanism, we analyzed some mercury catalysis oxidized and adsorbed model in SCR process, and compare the results with experimental results. The final result shows that they match well.
引文
[1]世界环境与发展委员会.我们共同的未来.北京:世界知识出版社,1989
[2]郑楚光.洁净煤技术.武汉:华中理工大学出版社,1996
[3]陈鹏.中国煤的分类、性质和用途.北京:化学工业出版社, 2001, 379-3
[4] Thomas D. Brown, Dennis N. Smith, Richard A. Hargis, Winian J. O’Dowd, Mercury measurement and its control: What we know, Have learned, and Need to further investigate, Journal of the air & waste management association, 1999,49:628-640
[5] UNEP.Report of the global mercury assessment working group on the work of its first meeting[R].Geneva:UNEP,2002
[6]党民团,刘娟.中国汞污染的现状及防治对策.应用化工, 2005,34(7): 395
[7]毛健雄,毛健全,赵树民,编著,煤的清洁燃烧,北京:中国科学出版社,2000.
[8] Gerald H. Luttrell, Jaisen N. Kohmuench, Roe-Hoan Yoon, An evaluation of coal preparation technologies for controlling trace element emissions, Fuel Processing Technology, 2000, 65-66: 407-422
[9] Akers David, Dosphy Robert, Role of coal cleaning in control of air toxic, Fuel Processing Technology, 1994, 39: 73-80
[10] Keating M H, Mahaffey K R, R.Schoeny, Rice G. E, Bullock O R, Ambrose R B, Mercury Study Report to Congress, Volume II. EPA -452/R-97-004b, Office of Air Quality Planning and Standards and Office of Research and Development, Research Triangle Park, NC. December 1997
[11] Ferris D D.,Engineering development of advanced physical fine coal cleaning technologies—Froth flotation.ICF Kaiser engineers final report for DOE contract.
[12] Akers D J., Raleigh C E.,The mechanisms of trace element removal during coal cleaning.Coal Preparation.1998,(19),3 4.
[13]赵毅,马双忱,华伟,庞庚林.电厂燃煤过程中汞的迁移转化及控制技术研究.环境污染治理技术与设备, 2003,11(4): 59-63.
[14] Livengood C D., Huang H S., Mendelsohn M H.,J M.Wu,1996,Enhancement of Mercury Control in Flue Gas Cleanup Systems,Proc.U.S.DOE/PETC First Joint Power&Fuel Systems Contractors Conference,Pittsburgh,Penn.,July 9 11.
[15] Miller S J., Laudal D H., Dunham B E.,K.Walker,H.Krigmont,Advanced Hybrid particulate collector,A new concept for air toxics and fine particulate control,the EPRI DOE EPA combined utility air pollutant control symposium, Washington D.C.,August 1997.
[16] [16] Kilgroe J D., Srivastava R K., Control of mercury emission from coal fired electric utility boilers,Technical memorandum,October 2000.
[17] An Assessment of Mercury Emissions from U.S. Coal-Fired Power Plants [R]. 1000608, EPRI, 2000.
[18] Chow W. Managing air toxics under the new clean air actamendments. Power Engineering, 1995, 80: 209-215.
[19]刘晶,陆晓华.煤中痕量砷和汞的形态分析.华中理工大学学报, 2000, 28(7): 71-73.
[20] Lesley Sloss. Mercury-emissions and control. International Energy Agency (IEA) Coal Research—the Clean Coal Centre, 2002
[21] Meij R.,The fate of mercury in coal fired power plants and the influence of wet flue gas desulphurization,Water,Air,and Soil Pollution,1991;56:21 33.
[22] Chang J R., Owens D.,EPRI J.1994,July/Aug,46.
[23] Chang R, Hargrove B, Carey T, Richardson C, Meserole F, Power Plant Mercury Control Options and Issues, Proc. POWER-GEN '96 International, Conference Orlando, Fla., Dec. 4-6, 1996.
[24] Huang,H S.,Wu,J M.,Livengood,C D.,Development of Dry Control Technology for Emissions of Mercury in Flue Gas.Proc.The Fourth International Congress on Toxic Combustion Byproducts.Berkeley,Calif.June, l995,5-7.
[25] Ghorishi S B., Lee C W., Kilgroe J D.,Mercury Speciation in Combustion Systems:Studies with Simulated F1ue Gases and Model FLY Ashes.Paper#99 651 Presented at the 92nd Annual meeting of Air and Waste Management Association,June 20-24,St.Louis, MO,1999.
[26] Livengood C D, Mendelsohn M H., Progress for combined control of mercury andnitric oxide EPRI-DOE-EPA Combined Utility Air Pollution Control Symposium, 1999, Atlanta, Georgia.
[27] Mendelsohn M H, Harkness J B L, Enhanced Flue-Gas Denitrification Using Ferrous?EDTA and a Polyphenolic Compound in an Aqueous Scrubber System. Energy & Fuels, 1991, 5(2): 244-247.
[28] McDermott Technologies, Inc. Advanced Emissions Control Development Program Phase III¨C Approved Final Report, prepared for the U.S. Department of Energy (U.S. DOEFETC contract DE-FC22-94PC94251.22) and Ohio Coal Development Office (grant agreement CDO/D-922-13), July 1999, Available at: http://www.osti.gov/dublincore/servlets/purl/756595-LACvcL/webviewable/756595.pd >.
[29] Pavlish, Sondreal E A, Mann M D, et al. Status review of mercury control option for coal-fired power plants [J]. Fuel Processing Technology, 2003, 82: 89~165.
[30] Senior C L, Helble J J, Sarofim A F. Predicting the speciation of mercury emissions from coal-fired power plants [A]. Proceedings of the Air Quality II: Mercury, Trace Elements, and Particulate Matter Conference [C]. McLean, VA, 2000. A5-2.
[31] Laudal D. Pilot-Scale Evaluation of the Impact of Selective Catalytic Reduction for NO, on Mercury Speciation [R]. 1000755, EPRI, 2000.
[32] U.S. Department of Energy, National Energy Technology Laboratory. Full-Scale Testing of Enhanced Mercury Control in Wet FGD, November 2001, Available at < http://www.fetc.doe.gov/coalpower/environment/mercury/index.html >.
[33] J Alix F.,Neister S.and McLarnon C.,Barrier Discharge Conversion of SO2 and NOx to Acids,U.S.Patent No.5,871,703,February,1999.
[34] McLarnon J C.,Nitrogen Oxide Decomposition By Barrier Discharge,Dissertation for Doctor of Philosophy Degree in Chemical Engineering,University of New Hampshire,May 1996.
[35] McLarnon C R, Horvath M L, Boyle P D, " Electro -Catalytic Oxidation Technology Applied to Mercury and Trace Elements Removal from Flue Gas," presented at Conference on Air Quality II ,McLean , VA. September 20, 2000.
[36] McLarnon C R, Jones M D, " Electro - Catalytic Oxidation Process for Multi– Pollutant Control at First Energy’s R. E. Burger Generating Station," presented at Electric Power 2000, Cincinnati , OH. April 5, 2000.
[37]钟秦,燃煤烟气脱硫脱硝技术及工程实例,化学工业出版社,2002:296-299
[38]刘今.发电厂烟气脱硝技术-SCR法,江苏电机工程,1996,15(1),52
[39] Lee, C.; Srivastava, R.; Ghorishi, S. B.; Karwowski, J.; Hastings,T. W.; Hirschi, J. Presented at the Combined Power Plant Air PollutantControl Mega Symposium, Washington, DC, August 30-September2, 2004; Paper No. 7.
[40] Lee, C.W.; Srivastava, Ravi K.; Ghorishi, S. Behrooz; Hastings, Thomas W.; Stevens, Frank M. Investigation of selective catalytic reduction impact on mercury speciation under simulated NOx emission control conditions. Presented at Journal of the Air and Waste Management Association, v 54, n 12, December, 2004, p 1560-1566
[41] Standard test method for mercury from coal-fired stationary sources (Ontario Hydro Method),July7,1999,EPA USA
[42] Sandhya Eswaran; Harvey G. Stenger. Understanding Mercury Conversion in Selective Catalytic Reduction (SCR) Catalysts. Presented at Energy & Fuels 2005, 19, p2328-2334
[43] Galbreath, K. C.; Zygarlicke, C. J.; Olson, E. S.; Pavlish, T. J.; Toman, D. L. Sci. Total Environ. 2002, 261 (1-3), 149-155.
[44] Galbreath, K.; Zygarlicke, C. Fuel Process. Technol. 2002, 65/66, 289-310
[45] Bock, J.; Hocquel, M. J. T.; Unterberger, S.; Hein, K. R. G. Presented at the Combined Power Plant Air Pollutant Control MegaSymposium, Washington, DC, May 19-22, 2003.
[46] Stein E , et al . Environmental distribution and transformation of mercury compounds [J] .Crit Rev Environ Sci Technol, 1996 , (26) :1 - 431
[47] Pacyna J .M, Munch J., Anthropogenic mercury emission in Europe, Water, Air and Soil Pollution, 56, 1991, 51-61.
[48] Thomas D. Brown , Dennis N. Smith , Richard A. Hargis J r. , and Winiam J . O’Dowd. Mercury Measurement and Its Control : What We Know , Have Learned , and Need to Further Investigate[J ] . Journal of the air & waste management association , 1999 ,6.
[49]王起超,沈文国,麻壮伟,中国燃煤汞排放量估算,中国环境科学,1999; 194,318-321.
[50] Lee Y H , Jung W S , Choi Y R , et al . Application of pulsed corona induced plasma chemical process to an industrial incinerator. Environmental Science and Technology , 2003 , 37 ( 1 ) :2563~2567
[51] Laudal D, Brown T, Nott B. Effects of flue gas constituents on mercury speciation [J ]. Fuel processing technology, 2000 (65-66) : 157~165.
[52] QM201G荧光测汞仪说明书
[53] Sandhya Eswaran; Harvey G. Stenger. Understanding Mercury Conversion in Selective Catalytic Reduction (SCR) Catalysts. Presented at Energy & Fuels 2005, 19, p2328-2334
[54]高洪亮,周劲松,骆仲泱,午旭杰,倪明江,岑可法.氯化氢对燃煤烟气中汞形态分布影响的实验研究.浙江大学学报(工学版),2004,38(6):765~769.
[55] Lee, C.W.; Srivastava, Ravi K.; Ghorishi, S. Behrooz; Hastings, Thomas W.; Stevens, Frank M. Investigation of selective catalytic reduction impact on mercury speciation under simulated NOx emission control conditions. Presented at Journal of the Air and Waste Management Association, v 54, n 12, December, 2004, p 1560-1566
[56]毛金波.溶胶凝胶法制备CuO/γ-Al2O3催化吸附剂及其脱硫脱硝研究.[硕士学位论文].武汉,华中科技大学研究生院,2006
[57]任建莉.燃煤过程汞析出及模拟烟气中汞吸附脱除试验和机理研.[博士学位论文].杭州,浙江大学研究生院,2003
[58] Carey T., Hargrove O., Richardson C., Factors Affecting Mercury control in utility flue gas using activated carbon, Journal of Air & Waste management association, 1998, (48), 1166-1174
[59] Withum J A.,Mercury Emissions from Coal-Fired Facilities with SCR-FGD Systems,DOE/NETL’s Mercury Control Technology Conference,December 12, 2006
[60] Stephen Niksa,Naoki Fujiwara. A Predictive Mechanism for Mercury Oxidation On SCR Catalysts Under Coal-Derived Flue Gas. Presented at JOURNAL OF THE AIR & WASTE MANAGEMENT ASSOCIATION,v55,n12,December,2005,p1866-1875
[61] Flora J.R., Vidic R.D., W.Liu, Modeling powered activated carbon injection for the uptake elemental mercury vapors, Journal of air &waste management association, 1998 (48), 1051-1059
[62] Tai-Gyu Lee,Study of mercury kinetics and control methodologies in simulates combustion flue gas, dissertation, University of Cincinnati,1999
[63] Thomas H.C., J.Am/Chem/Soc,1944,(66),1664
[64] Hall B., Lindqvist O., Mercury chemistry in simulated flue gases related to waste incineration conditions,Environmental Science and technology, 1990, 24(1), 108-111
[65] Senior, C.L. ,L.E., et.al. A Fundamental Study of Mercury Partitioning in Coal Fired Power Plant Flue Gas, Annual Meeting of Air & Waste Mgmnt Assoc., Paper 97-WP72B. 08, Toronto, Canada (1997)
[66] Tronconi, E., Forzatti, P., Gomez Martin, J. P., and Malloggi, S.,“Selective catalytic removal of NOX : A mathematical model for design of catalyst and reactor,“Chem. Eng. Sci., 47(9-11), 2401-06 (1992a).
[67] Senior,C. Oxidation of mercury across selective catalystic reduction catalysts in coal-fired power-plants. J. Air Waste Manage. Assoc. 2006, 56, 23
[68]柳正辉,王果庭,杨孔璋编译,吸附的动力学特性,科学出版社,1964
[69]章燕豪编著,吸附作用,上海科学技术文献出版社,1975
[70] Oliver Malerius,Joachim Werther,Modeling the adsorption of mercury in the flue gas of sewage sludge incineration,Chemical Engineering Journal,96 (2003) 197-205
[71]高洪亮,周劲松,骆仲泱,午旭杰,倪明江,岑可法.氯化氢对燃煤烟气中汞形态分布影响的实验研究.浙江大学学报(工学版),2004,38(6):765~769.】
[72] Albert.A. , Presto, Evan J.Granite, Survey of Catalysts for Oxidation of Mercury in Flue Gas, Environmental Science & Technology, v40, n.18, 2006,p5601-5609