摘要
低热值气体是指发热量小于6.28MJ/m3的气体燃料,由于热值低、成分复杂,难以被处理而直接排放。这些低热值气体中含有甲烷,甲烷的温室效益是二氧化碳的21倍,将甲烷高效转化为二氧化碳将产生巨大的环境和经济效益。本文利用燃烧段与蓄热段分离往复多孔介质燃烧技术处理此类低热值气体,并研究拓展系统燃烧极限、增大系统处理低热值气范围的方法。低热值气体是由可燃成分和不参与燃烧的惰性成分组成的无氧混合气,本文将利用氮气稀释天然气模拟低热值气体,并研究此类气体在往复多孔介质燃烧器中的燃烧和污染物排放特性。本文研究工作主要包括两个部分:
第一部分,低热值气体在往复多孔介质燃烧器中燃烧极限拓展实验研究。主要考察蓄热段对系统温度波动和分布特性的影响,系统由稳定燃烧过渡到过滤燃烧轴向温度分布的变化特性,以及系统燃烧极限特性。结果表明,蓄热段能显著的降低系统温度波动,提高系统燃烧温度和燃烧效率;当量比降低使得轴向温度分布形状从“马鞍形”、“梯形”、“椭圆形”,变化到系统达到燃烧极限时形成的“三角形”分布;在实验研究范围内,半周期缩短,热负荷降低、截面流速增大,系统燃烧极限先降低后升高,蓄热段蓄热能力增大能较小幅降低系统燃烧极限。系统贫燃极限为当量比0.07,混合气热值264kJ/m3。
第二部分,无氧低热值气体往复多孔介质燃烧实验研究。主要考察混合燃气(指天然气与氮气混合气)热值、氧含量和空气当量比对燃烧特性和污染物排放特性的影响,并与单向多孔介质燃烧技术相对比,分析往复多孔介质燃烧技术的优势。研究结果表明:混合燃气热值降低,高温段长度缩短,平均温度和燃烧温度升高;氧含量、空气当量比降低,燃烧温度先升高后降低,排烟温度降低,且不同空气当量比使最大燃烧温度对应的氧含量不同,空气当量比越高对应氧含量越低;相比单向燃烧系统,往复式燃烧系统T/Tad=1对应空气当量比低于单向多孔介质燃烧系统,T/Tad随空气当量比变化的变化趋势大于单向系统,且NOx和CO排放浓度都要低于单向燃烧系统,更加适合低热值混合气燃烧。燃烧效率主要由天然气与氧气接触的几率和高温区宽度决定,随着氧含量、空气当量比降低而降低。空气当量比降低,混合燃气极限热值先降低后升高,系统稳定燃烧极限对应氧含量不断升高。系统混合燃气极限热值为447.35kJ/m3,氧化气氧含量为3.5%,预混气热值为373.2 kJ/m3。在较佳的燃烧工况下,CO排放浓度低于15ppm,NOx排放浓度低于5ppm。
Due to low heat value and complex composition, low calorific gases whose heat value is below 6.28MJ/m3 are not exploited and directly discharged. They contain large amounts of methane, greenhouse effects of which are 21 times more than carbon dioxide. The efficient transformation of methane to carbon dioxide will bring us huge environmental and economic benefits. In this thesis, combustion technology in porous media with reciprocating is used to deal with these low calorific gases, and some studies have been done to expend the system's flammability limit. Some low calorific gases are made up of combustible components and inert components, and don't contain oxygen. In order to study these gases'combustion and pollutant emission characteristics in porous media combustor with reciprocating flow, the mixture of nitrogen and natural gas is used to simulate these gases. The work done by this article mainly includes two parts:
First, experimental studies of flammability limit of low calorific gases combustion in porous media with reciprocating flow system. Effects of regenerator section on temperature fluctuation and distribution, variation characteristics of axial temperature distribution and flammability limits were investigated experimentally. The results show that adding regenerative sections leads to reduction of temperature fluctuation amplitude and increase of combustion temperature and efficiency; With the increasing of equivalence ratio, the shape of axial temperature distribution has continuous changes, from saddle-shaped, ladder-shaped, oval-shaped to triangle-shaped when the system works on flammability limit; With the reducing of half-period, thermal load and inlet gas velocity, the system's flammability limit firstly decreases and then increases; With increasing of heat storage capacity of regenerator section, the flammability limit is slight lower. The flammability limit can be extended to the low equivalence ratio of 0.07, corresponding to the heat value of 264kJ/m3.
Second, experimental studies of anaerobic gases in porous media with reciprocating flow system. The effects of the heat value of mixed fuel gases (the mixture of nitrogen and natural gases)、oxygen content and air equivalence ratio on combustion and pollutant emission characteristics are investigated experimentally; Compared with simple porous media burner, analysis the advantages of reciprocating flow system. The results show that:With the reducing of heat value of mixed fuel gases, the length of high-temperature zone shortens, the average temperature and combustion temperature increases; with the reducing of oxygen content and air equivalence ratio, the combustion temperature firstly increases and then decreases, the exhaust gas temperature decreases, and oxygen contents of the maximum combustion temperature on certain air equivalence ratio are different, the air equivalence ratio higher, the oxygen content lower; Compared with simple porous media burner, the air equivalence ratio is lower when T/Tad=1, and the emission concentration of NOx and CO is lower; With the reducing of air equivalence ratio, the heat value of flammability mixed fuel gases firstly decreases and then increases, the oxygen content of flammability limit rise. The flammability limit can be extended to the mixed fuel gases heat value of 447.35kJ/m3, the oxygen content of the oxidizer of 3.5%, corresponding to the premixed gases heat value of 373.2 kJ/m3. In better combustion condition, the CO emission concentration is below 15ppm and the NOX mission concentration is below 5ppm.
引文
[1]BP世界能源数据统计2008.NO.2008.6.
[2]IPCC第四次评估报告.《气候变化2007》[R],NO.2007.
[3]何英.国际移民组织称将达10亿“气候难民”.中国能源报.2009.12.14;09.
[4]温家宝.凝聚共识加强合作推进应对气候变化历史进程.In:哥本哈根世界气候大会(ed).哥本哈根,2009-12-18.
[5]国家电力监管委员会.中国面对酸雨威胁.2005.
[6]娄马宝.低热值气体燃料(高炉煤气)的利用[J].燃气轮机技术,2000,13(3):16-18.
[7]王海凤,刘永启.高炉煤气发电技术[J].农业装备与车辆工程,2006,183(10):6-8.
[8]谢祖琪,刘建.发展秸秆气化技术是我国秸秆能源化利用的有效途径[J].当代农机,2007(9):11-13.
[9]昝林森.我国农作物秸秆资源综合利用现状和对策[C]//2008中国国际秸杆综合利用高峰研讨会暨秸杆产业化新产品新技术推介会.2008.5,
[10]陈家军.垃圾填埋气(LFG)的净化及利用前景[J].新材料产业,2007(5):41-44.
[11]煤层气抽采国家标准将出台-可利用量有望倍增.中国证券报.2008-12-11.
[12]节能中长期规划.In:国家发改委(ed),2004.2.
[13]周红军,吴全贵.垃圾填埋气的回收利用[J].环境保护,2001,8:44-46.
[14]Katsunori Hanamura, Kiyoshi Bohda, Yukio Miyairp. A study of super-adiabatic combustion engine[J]. Energy Convers,1997,38(10):1259-1266.
[15]Egerton A, Gugan K, Weinberg F.J. The mechanism of smoldering in cigarettes[J]. Combustion and Flame,1963,7:73.
[16]Weingerg F.J. Combustion temperatures:the future[J]. Nature,1971,233:239-241.
[17]Takeno T, Sato K, Hase K. A theoretical study on an excess enthalpy flame. In:Institute T. C. (ed). Eighteenth Symposium (International) on combustion. Pittsburgh,1980:465-471.
[18]王恩宇.气体燃料在渐变型多孔介质中的预混燃烧机理研究[D].浙江大学,2004.
[19]李姮.多孔介质预混燃烧中的气固温度分布及传热特性研究[D].浙江大学,2006.
[20]杜礼明..稀薄预混气体在多孔介质中超绝热燃烧的研究[D].大连理工大学,2003.9.
[21]李昊.往复式多孔介质燃烧器的实验研究[D].浙江大学,2004.
[22]马世虎.往复流动下预混合气体在多孔介质中超绝热燃烧的数值模拟[D].大连理工大学,2004.
[23]G. BRENNER, K. PICKENA CKER, O. PICKENA CKER, D.TRIMIS, K. WAWRZINEK, T. WEBER. Numerical and experimental investigation of matrix-stabilized methane/air combustion in porous inert media[J]. Combustion and Flame,2000,123(1-2):201-213.
[24]Tseng C-J, Li C-H. Thermally-enhanced combustion in a porous medium burner[J]. Journal of the Chinese Society of Mechanical Engineers,2001,22(3):217-224.
[25]Wang En-Yu, Cheng Le-Ming, Luo Zhong-Yang, Xing Shou-Xiang, Cen Ke-Fa. Stability of flames in the gradually-varied porous meida. Proceedings of International Conference on Energy and the Environment. Shanghai,2003:977-982.
[26]杜礼明,解茂昭.预混气体在多孔介质中往复流动下超绝热燃烧的理论探讨[J].Energy Engineering,2003,5:6-11.
[27]何贤昶.陶瓷材料概论.上海:上海科学普及出版社,2005:220-222.
[28]朱玉梅,靳正国,吕楠.多孔碳化硅陶瓷的抗热震性研究[J].陶瓷学报,1998,19(4):213-216.
[29]吕琴谊.泡沫陶瓷成孔性能对热震性的影响[J].江苏陶瓷,2000,33(3):13-14,16.
[30]包亦望.氧化铝、氮化硅和碳化硅的疲劳特性与寿命预测[J].硅酸盐学报,2001,29(1):21-25.
[31]包亦望,王毅敏,金宗哲.Al2O3/SiC复相陶瓷的高温蠕变与持久强度[J].硅酸盐学报,2000,28(4):348-351,356.
[32]卜景龙,张存满.结构陶瓷高温蠕变的影响因素[J].河北理工学院学报,2000,22(3):72-74.
[33]林明通,王连洲,施剑林.陶瓷高温蠕变寿命的估计[J].硅酸盐学报,1999,27(5):618-621.
[34]周洋.陶瓷基复合材料疲劳特性的研究[D].武汉:华中理工大学,1996.
[35]... A new method of destroying organic pollutants in exhaust air[R], NO.1990.
[36]S Zhdanok, A Lawrence, Kennedy, G Koester. Superadiabatic Combustion of Methane Air Mixtures under Filtration in a Packed Bed[[J]. Combustion and Flame,1995,100:221-231.
[37]Y. Huang, C.Y.H Chao, P. Cheng. Effects of preheating and operation conditions on combustion in a porous medium[J]. International Journal of Heat and Mass Transfer,2002,45:4315-4324.
[38]Sumrerng Jugjai, Viriya Nungniyom. Cyclic operation of porous combustor-heater (PCH) [J].Fuel,200810,4:1-7.
[39]Sumrerng Jugjai, Amorn Somjetlertcharoen. Multimode heat transfer in cyclic flow reversal combustion in a porous medium[J]. International Journal of Energy Research,1999,23(3):183-206.
[40]J.GHoffmann, R. Echigo, H.Yoshida, S.Tada.:. Experimental Study on Combustion in Porous Media with a Reciprocating Flow System[J]. Combustion and Flame,1997,111:32-46.
[41]邓洋波,解茂昭.多孔介质内预混合超绝热燃烧的排放特性.大连理工大学学报.2004;24(3):392-397.
[42]Katsunori Hanamura, R Echigo. Super adiabatic combustion in a porous medium[J]. International Journal of Heat and Mass Transfer,1993,36:3201-3209.
[43]Katsunori Hanamura, Kiyoshi Bohda, Yukio Miyairi. A study of super-adiabatic combustion engine[J]. Energy Convers,1997,38(10):1259-1266.
[44]Ryozo Echigo, Katsunori Hanamura, Hideo Yoshida. Sophisticated thermoelectric conversion device of materials by super-adiabatic combustion of reciprocating flow and advanced power generation system[C]//XI international conference on thermo electrics.1992,Ⅲ-2:45-50.
[45]杜礼明,解茂昭.多孔介质的热物性对往复流动下超绝热火焰的影响[J].热能动力工程,2005,20(2):148-152.
[46]Fabiano Contarin, V Alexei, Saveliev. A reciprocal flow filtration combustor with embedded heat exchangers:numerical study[J]. International Journal of Heat and Mass Transfer,2003,46 949-961.
[47]C.L Hackert, J.L Ellzey, O.A Ezekoye. Combustion and heat transfer in model two-dimensional porous burners[J]. Combust Flame,1999,116:177.
[48]G. Brenner, K. Pickenacker, O. Pickenacker, D. Trimis, K. Wawrzinek, T. Weber. Numerical and experimental investigation of matrix-stabilize methane/air combustion in porous inert media[J]. Combust Flame 2000,123:201.
[49]S.C Mishra, M Steven, S Nemoda. Heat transfer analysis of a two-dimensional rectangular porous radiant burner[J]. International Communications in Heat and Mass Transfer,2006,33467-474.
[50]史俊瑞,解茂昭.往复流多孔介质燃烧器的二维数值模拟与结构改进[J].燃烧科学与技术,2007,13(3):280-285.
[51]K.V. Dobrego, I.M. Kozlov, V.I. Bubnovich, C.E. Rosas. Dynamics of filtration combustion front perturbation in the tubular porous media burner[J]. International Journal of Heat and Mass Transfer,2003,46:3279-3289.
[52]Nelson O. Moraga, Cesar E. Rosas, Valeri I. Bubnovich, Nicola A. Solari. On predicting two-dimensional heat transfer in a cylindrical porous media combustor[J]. International Journal of Heat and Mass Transfer,2008,51:302-311.
[53]T.C. Hayashi, I. Malico, J.C.F. Pereira. Three-dimensional modelling of a two-layer porous burner for household applications[J]. Computers and Structures,2004,82:1543-1550.
[54]T. W Tong, S. B Sathe. Heat Transfer Characteristic of Porous Radiant Burners[J]. ASME JOURNAL OF HEAT TRANSFER,1991,113:423-428.
[55]F Andersen. Heat Transport Model for Fibre Burners[J]. Progress in Energy and Combustion Science,1992,18:1-12.
[56]Katsunori Hanamura, Kiyoshi Bohda, Yukio Miyairp. A STUDY OF SUPER-ADIABATIC COMBUSTION ENGINE[J]. Energy Convers,1997,38:1259-1266.
[57]Fabiano Contarin, Alexei V. Saveliev, Alexander A. Fridman. A reciprocal flow filtration combustor with embedded heat exchangers:numerical study[J]. International Journal of Heat and Mass Transfer 2003,46:949-961.
[58]Jun-Rui Shi, Mao-Zhao Xie, Hong Liu, Gang Li, Lei Zhou. Numerical simulation and theoretical analysis of premixed low-velocity filtration combustion[J]. International Journal of Heat and Mass Transfer,2007:1-12.
[59]M.A.A Mendes, J.M.C Pereira, J.C.F Pereira. On the stability of ultra-lean H2/CO combustion in inert porous burners[J]. international Journal of Hydrogen Energy,2008:1-9.
[60]R.J Kee, J. F Grcar, M. D Smooke, J. A Miller. A Fortran Program for Modeling Steady Laminar One-Dimensional Premixed Flames[R], Sandia National Laboratories Report. NO. SAND85-8240.1985.
[61]P.F Hsu, J. R Howell, R.D Matthews. A numerical investigation of premixed combustion within porous inert media[J]. Transactions of the ASME,1993,115:744-750.
[62]Amanda J. Barra, Guillaume Diepvens, Janet L. Ellzey, Michael R. Numerical study of the effects of material properties on flame stabilization in a porous burner [J]. Combustion and Flame,2003,134:369-379.
[63]M. Frenklach, H. Wang, M. Goldenberg, G.P. Smith, D.M. Golden, C.T. Bowman, R.K. Hanson, W.C. Gar-diner, V. Lissianski. GRI-Mech—an optimized detailed chemical reaction mechanism for methane combustion[R], Gas Research Institute Topic. NO. GRI-95/0058.1995.
[64]C.T Bowman, R.K Hanson, D.F Davidson. http://www.me.berkeley.edu/gri_mech/2.11.
[65]G.P Smith, D.M Golden, M. Frenklach, N.W Moriarty. http://www.me.berkeley.edu/gri_mech/version30/.
[66]赵平辉.惰性多孔介质内预混燃烧的研究[D].合肥:中国科学技术大学,2007.
[67]K.V.Dobregoa, N.N.Gnesdilov a, S.H.Lee b, H.K.Choi. Lean combustibility limit of methane in reciprocal flow filtration combustion reactor[J]. International Journal of Heat and Mass Transfer,2008:1-9.
[68]Amanda J. Barra, Guillaume Diepvens. Numerical study of the effects of material properties on flame stabilization in a porous burner [J]. Combustion and Flame, 2003,134:369-379.
[69]赵平辉,朱曼明.双层多孔介质燃烧器的数值模拟[J].计算物理,2006,23(6):679-684.
[70]T.C. Hayashi, I. Malico, J.C.F. Pereira. Three-dimensional modeling of a two-layer porous burner for household applications[J]. Computers and Structures,2004,82:1543-1550.
[71]F S.R.Khatami, B. Safavisohi, E. Sharbati. Porosity and Permeability Effects on Centerline Temperature Distributions, Peak Flame Temperature, Flame Structure and Preheating Mechanism for Combustion in Porous Media. Transactions of the ASME.2007;129:54-65.
[72]岑可法,程乐鸣,骆仲泱,方梦祥,倪明江,施正伦,王勤辉,高翔,周劲松,王树荣,余春江.渐变型多孔介质燃烧器.2001;ZL01226080.0.
[73]王恩宇,程乐鸣,褚金华,施正展,骆仲泱,岑可法.渐变型多孔介质中燃气燃烧特性实验研究.工程热物理学报.2005;26(6):1037-1040.
[74]王恩宇,程乐鸣,骆仲泱,岑可法.渐变型多孔介质中预混燃烧温度分布试验[J].热科学与技术,2003,2(1):64-69.
[75]王恩宇,程乐鸣,骆仲泱,倪明江,岑可法.天然气在渐变型多孔介质中的预混燃烧[J].燃烧科学与技术,2004,10(1):1-6.
[76]K.V.Dobrego, N.N.Gnesdilov, I.M.Kozlov. Numerical investigation of the new regenerator-recuperator scheme of VOC oxidizer[J]. International Journal of Heat and Mass Transfer,2005,48:4695-4703.
[77]J.P. Bingue. Filtration combustion of mathane and hydrogen sulfide in inert porous media: Theory and Experiments[D]. Chicago:University of Illinois,2003.
[78]J.P. Bingue, A.V. Saveliev, Lawrence A. Kennedy. Optimization of hydrogen production by filltration combustion of methane by oxygen enrichment and depletion[J]. International Journal of Hydrogen Energy,2004,29:1365-1370.
[79]李吴,程乐鸣,王恩宇,褚金华,骆仲泱,岑可法.往复式多孔介质燃烧器温度分布的试验研究.浙江大学学报.2005;39(8):1185-1188.
[80]王关晴.往复式热循环多孔介质燃烧系统特性研究与数值模拟[D].杭州:浙江大学,2008.
[81]李昊,程乐鸣,王恩宇,褚金华,骆仲泱,岑可法.往复式多孔介质燃烧器流动特性的试验研究[J].能源工程,.2004,4:1-5.
[82]王关晴,程乐鸣,杨春,郑成航,骆仲泱,岑可法.往复式热循环多孔介质燃烧系统冷态阻力特性.中国电机工程学报.2007;27(26):52-58.
[83]史俊瑞,解茂昭,周磊.往复流多孔介质燃烧器的二维数值模拟与结构改进[J].燃烧科学与技术,2007,13(3):280-285.
[84]景思睿,张鸣远.流体力学.西安:西安交通大学出版社,2001:181-189.
[85]J. L. Lage, B. V. Antohe, D. A. Nield. Two types of non-linear pressure drop versus flow rate relation observed for saturated porous media[J]. ASME Journal of Fluids Engineering,1997,119:701-706.