含K成分形成初始沉积层的数学模型及烟气条件影响分析
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摘要
针对积灰初始沉积层形成的两种主要机理即凝结和热泳机理,建立了含K成分形成初始沉积层的数学模型,采用文献中的实验结果检验了模型,表明考虑沉积层厚度、表面温度随位置和时间的变化对模型预测有合理的改善。应用该模型研究含K气体成分和气溶胶颗粒在受热面上的沉积过程,并考察烟气中含K成分组成、烟温和烟速等因素的影响。研究表明,由于烟气中含K气体成分和气溶胶颗粒相对浓度的差异,凝结和热泳在沉积过程开始时都可能对初始沉积层的形成起主要作用,而在沉积过程后期热泳沉积则占据主导地位;烟温和烟速对含K成分沉积过程的影响相似,即较高的烟气温度和速度,其初期沉积速率高,而后期沉积速率相对低,形成的沉积层厚度较低。
Aiming at the two main mechanisms of initial deposition layer of ash deposition, namely, condensationand thermophoresis mechanism, a mathematical model for the formation of initial deposition layer by K-containingspecies was established. The rationality of the model was validated by the experimental results in the literaturewhich indicates that considering the changes of the thickness of the deposition layer and the surface temperaturehave a reasonable improvement. The model was used to study the deposition process of K-containing gas andaerosol particles on the heating surface, and to investigate the effects of K-containing species composition, flue gastemperature and velocity. The results show that, because of the difference in the relative concentrations of K-containing gas and aerosol particles, both condensation and thermophoresis deposition may play a major role in theformation of the initial deposition layer at the beginning of the deposition process, while thermophoretic depositiondominates the later stage. The effects of flue gas temperature and velocity on the deposition process is similar, thatis, the higher flue gas temperature and velocity, the higher the initial deposition rate, the lower the later depositionrate, and the lower the thickness of the deposited layer.
Aiming at the two main mechanisms of initial deposition layer of ash deposition, namely, condensationand thermophoresis mechanism, a mathematical model for the formation of initial deposition layer by K-containingspecies was established. The rationality of the model was validated by the experimental results in the literaturewhich indicates that considering the changes of the thickness of the deposition layer and the surface temperaturehave a reasonable improvement. The model was used to study the deposition process of K-containing gas andaerosol particles on the heating surface, and to investigate the effects of K-containing species composition, flue gastemperature and velocity. The results show that, because of the difference in the relative concentrations of K-containing gas and aerosol particles, both condensation and thermophoresis deposition may play a major role in theformation of the initial deposition layer at the beginning of the deposition process, while thermophoretic depositiondominates the later stage. The effects of flue gas temperature and velocity on the deposition process is similar, thatis, the higher flue gas temperature and velocity, the higher the initial deposition rate, the lower the later depositionrate, and the lower the thickness of the deposited layer.
引文
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[2]胡理乐,李亮,李俊生.生物质能源的特点及其环境效应[J].能源与环境, 2012,(1):47-49.Hu L L, Li L, Li J S. Characteristics of biomass energy and its environmental effects[J]. Energy and Environment, 2012,(1):47-49.
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[8]徐明厚.燃煤可吸入颗粒物的形成与排放[M].北京:科学出版社, 2009.Xu M H. Formation and Discharge of Inhalable Particulate Matterby Burning Coal[M]. Beijing:Science Press, 2009.
[9]张志潮,刘晶,杨应举,等.燃煤锅炉烟气中Na2SO4生成的化学动力学研究[J].化工学报, 2018, 69(8):3643-3650.Zhang Z C, Liu J, Yang Y J, et al. Study on chemical kinetics ofNa2SO4formation in coal fired flue gas[J]. CIESC Journal, 2018,69(8):3643-3650.
[10]刘涛,陈雪莉,李德侠,等.生物质与煤混合灰的熔融及黏温特性[J].化工学报, 2012, 63(4):1217-1225.Liu T, Chen X L, Li D X, et al. Blending ash fusion and viscosity-temperature characteristics of biomass and coal[J]. CIESC Journal,2012, 63(4):1217-1225.
[11] Baxter L L. Ash deposition during biomass and coal combustion:amechanistic approach[J]. Biomass&Bioenergy, 1993, 4(2):85-102.
[12] Xu M, Yu D, Yao H, et al. Coal combustion-generated aerosols:formation and properties[J]. Proceedings of the CombustionInstitute, 2011, 33(1):1681-1697.
[13] Zhan Z, Wendt J O L. Role of sodium in coal in determiningdeposition rates[J]. Energy&Fuels, 2017, 31:2198-2202.
[14] Huang L Y, Norman J S, Pourkashanian M, et al. Prediction of ashdeposition on superheater tubes from pulverized coal combustion[J]. Fuel, 1996, 37(3):271-279.
[15] Zhan Z, Fry A, Zhang Y, et al. Ash aerosol formation from oxy-coal combustion and its relation to ash deposit chemistry[J].Proceedings of the Combustion Institute, 2015, 35(2):2373-2380.
[16] Zhan Z, Fry A R, Wendt J O L. Deposition of coal ash on avertical surface in a 100 kW downflow laboratory combustor:acomparison of theory and experiment[J]. Proceedings of theCombustion Institute, 2017, 36(2):2091-2101.
[17] Li J, Zhu M, Zhang Z, et al. Characterisation of ash deposits on aprobe at different temperatures during combustion of a Zhundonglignite in a drop tube furnace[J]. Fuel Processing Technology,2016, 144:155-163.
[18] Kleinhans U, Rück R, Schmid S, et al. Alkali vapor condensationon heat exchanging surfaces:laboratory-scale experiments and amechanistic CFD modeling approach[J]. Energy&Fuels, 2016,30:9793-9800.
[19] Zhan Z, Fry A R, Wendt J O L. Relationship between submicronash aerosol characteristics and ash deposit compositions andformation rates during air-and oxy-coal combustion[J]. Fuel,2016, 181:1214-1223.
[20] Capablo J. Formation of alkali salt deposits in biomass combustion[J]. Fuel Processing Technology, 2016, 153:58-73.
[21] Hansen S B, Jensen P A, Frandsen F J, et al. Mechanistic modelfor ash deposit formation in biomass suspension-firing(1):Modelverification by use of entrained flow reactor experiments[J].Energy&Fuels, 2017, 31:2771-2789.
[22] Hansen S B, Jensen P A, Frandsen F J, et al. Mechanistic modelfor ash deposit formation in biomass suspension-firing(2):Modelverification by use of full scale tests[J]. Energy&Fuels, 2017, 31:2790-2802.
[23] Capablo J, SalvadóJ. Estimating heat transfer losses caused byalkali salt deposits in biomass combustion[J]. Renewable Energy,2017, 105:449-457.
[24] Hansen S B. model for deposition build-up in biomass boilers[D].Copenhagen:Technical University of Denmark, 2015.
[25]耶菲莫夫.无机化合物性质手册[M].西安:陕西科学技术出版社, 1987.ЕфимовАИ. Handbook of Inorganic Compounds Properties[M].Xi’an:Shaanxi Science and Technology Press, 1987
[26]伊赫桑·巴伦.纯物质热化学数据手册[M].北京:科学出版社, 2003.Barin I. Pure Substance Thermochemical Data Manual[M].Beijing:Science Press, 2003.
[27] Knacke O, Kubaschewski O, Hesselmann K. ThermochemicalProperties of Inorganic Substances[M]. 2nd ed. Verlag Stahleisen,1991.
[28] Zhou H, Jensen P A, Frandsen F J. Dynamic mechanistic model ofsuperheater deposit growth and shedding in a biomass fired grateboiler[J]. Fuel, 2007, 86(10/11):1519-1533.
[29] Brock J R. On the theory of thermal forces acting on aerosolparticles[J]. Journal of Colloid Science, 1962, 17(8):768-780.
[30] Davies C N. Definitive equations for the fluid resistance of spheres[J]. The Proceedings of the Physical Society, 1945, 57:259-270.
[31] Kassman H, B?ver L,?mand L E. The importance of SO2and SO3for sulphation of gaseous KCl—an experimental investigation ina biomass fired CFB boiler[J]. Combustion and Flame, 2010, 157:1649-1657.
[32] Kassman H, Pettersson J, Steenari B M, et al. Two strategies toreduce gaseous KCl and chlorine in deposits during biomasscombustion-injection of ammonium sulphate and co-combustionwith peat[J]. Fuel Processing Technology, 2013, 105:170-180.
[2]胡理乐,李亮,李俊生.生物质能源的特点及其环境效应[J].能源与环境, 2012,(1):47-49.Hu L L, Li L, Li J S. Characteristics of biomass energy and its environmental effects[J]. Energy and Environment, 2012,(1):47-49.
[3]喻火明.电站锅炉受热面积灰结渣在线监测的研究[D].北京:华北电力大学, 2006.Yu H M. Researches of on-line monitoring of heating surfacefouling and slagging in power plant boiler[D]. Beijing:NorthChina Electric Power University, 2006.
[4] Bryers R W. Fireside slagging, fouling, and high-temperaturecorrosion of heat-transfer surface due to impurities in steam-raising fuels[J]. Progress in Energy&Combustion Science, 1996,22(1):29-120.
[5] Hansen L A, Nielsen H P, Frandsen F J, et al. Influence of depositformation on corrosion at a straw-fired boiler[J]. Fuel ProcessingTechnology, 2000, 64:189-209.
[6]黄海珍,于秀敏,陈海波,等.煤与生物质混合燃烧特性实验研究[J].化工进展, 2006, 25(s1):599-603.Huang H Z, Yu X M, Chen H B, et al. Experimental study oncombustion characteristics of co-firing by coal and biomass[J].Chemical Industry and Engineering Progress, 2006, 25(s1):599-603.
[7] Zheng Y, Jensen P A, Jensen A D, et al. Ash transformationduring co-firing coal and straw[J]. Fuel, 2007, 86:1008-1020.
[8]徐明厚.燃煤可吸入颗粒物的形成与排放[M].北京:科学出版社, 2009.Xu M H. Formation and Discharge of Inhalable Particulate Matterby Burning Coal[M]. Beijing:Science Press, 2009.
[9]张志潮,刘晶,杨应举,等.燃煤锅炉烟气中Na2SO4生成的化学动力学研究[J].化工学报, 2018, 69(8):3643-3650.Zhang Z C, Liu J, Yang Y J, et al. Study on chemical kinetics ofNa2SO4formation in coal fired flue gas[J]. CIESC Journal, 2018,69(8):3643-3650.
[10]刘涛,陈雪莉,李德侠,等.生物质与煤混合灰的熔融及黏温特性[J].化工学报, 2012, 63(4):1217-1225.Liu T, Chen X L, Li D X, et al. Blending ash fusion and viscosity-temperature characteristics of biomass and coal[J]. CIESC Journal,2012, 63(4):1217-1225.
[11] Baxter L L. Ash deposition during biomass and coal combustion:amechanistic approach[J]. Biomass&Bioenergy, 1993, 4(2):85-102.
[12] Xu M, Yu D, Yao H, et al. Coal combustion-generated aerosols:formation and properties[J]. Proceedings of the CombustionInstitute, 2011, 33(1):1681-1697.
[13] Zhan Z, Wendt J O L. Role of sodium in coal in determiningdeposition rates[J]. Energy&Fuels, 2017, 31:2198-2202.
[14] Huang L Y, Norman J S, Pourkashanian M, et al. Prediction of ashdeposition on superheater tubes from pulverized coal combustion[J]. Fuel, 1996, 37(3):271-279.
[15] Zhan Z, Fry A, Zhang Y, et al. Ash aerosol formation from oxy-coal combustion and its relation to ash deposit chemistry[J].Proceedings of the Combustion Institute, 2015, 35(2):2373-2380.
[16] Zhan Z, Fry A R, Wendt J O L. Deposition of coal ash on avertical surface in a 100 kW downflow laboratory combustor:acomparison of theory and experiment[J]. Proceedings of theCombustion Institute, 2017, 36(2):2091-2101.
[17] Li J, Zhu M, Zhang Z, et al. Characterisation of ash deposits on aprobe at different temperatures during combustion of a Zhundonglignite in a drop tube furnace[J]. Fuel Processing Technology,2016, 144:155-163.
[18] Kleinhans U, Rück R, Schmid S, et al. Alkali vapor condensationon heat exchanging surfaces:laboratory-scale experiments and amechanistic CFD modeling approach[J]. Energy&Fuels, 2016,30:9793-9800.
[19] Zhan Z, Fry A R, Wendt J O L. Relationship between submicronash aerosol characteristics and ash deposit compositions andformation rates during air-and oxy-coal combustion[J]. Fuel,2016, 181:1214-1223.
[20] Capablo J. Formation of alkali salt deposits in biomass combustion[J]. Fuel Processing Technology, 2016, 153:58-73.
[21] Hansen S B, Jensen P A, Frandsen F J, et al. Mechanistic modelfor ash deposit formation in biomass suspension-firing(1):Modelverification by use of entrained flow reactor experiments[J].Energy&Fuels, 2017, 31:2771-2789.
[22] Hansen S B, Jensen P A, Frandsen F J, et al. Mechanistic modelfor ash deposit formation in biomass suspension-firing(2):Modelverification by use of full scale tests[J]. Energy&Fuels, 2017, 31:2790-2802.
[23] Capablo J, SalvadóJ. Estimating heat transfer losses caused byalkali salt deposits in biomass combustion[J]. Renewable Energy,2017, 105:449-457.
[24] Hansen S B. model for deposition build-up in biomass boilers[D].Copenhagen:Technical University of Denmark, 2015.
[25]耶菲莫夫.无机化合物性质手册[M].西安:陕西科学技术出版社, 1987.ЕфимовАИ. Handbook of Inorganic Compounds Properties[M].Xi’an:Shaanxi Science and Technology Press, 1987
[26]伊赫桑·巴伦.纯物质热化学数据手册[M].北京:科学出版社, 2003.Barin I. Pure Substance Thermochemical Data Manual[M].Beijing:Science Press, 2003.
[27] Knacke O, Kubaschewski O, Hesselmann K. ThermochemicalProperties of Inorganic Substances[M]. 2nd ed. Verlag Stahleisen,1991.
[28] Zhou H, Jensen P A, Frandsen F J. Dynamic mechanistic model ofsuperheater deposit growth and shedding in a biomass fired grateboiler[J]. Fuel, 2007, 86(10/11):1519-1533.
[29] Brock J R. On the theory of thermal forces acting on aerosolparticles[J]. Journal of Colloid Science, 1962, 17(8):768-780.
[30] Davies C N. Definitive equations for the fluid resistance of spheres[J]. The Proceedings of the Physical Society, 1945, 57:259-270.
[31] Kassman H, B?ver L,?mand L E. The importance of SO2and SO3for sulphation of gaseous KCl—an experimental investigation ina biomass fired CFB boiler[J]. Combustion and Flame, 2010, 157:1649-1657.
[32] Kassman H, Pettersson J, Steenari B M, et al. Two strategies toreduce gaseous KCl and chlorine in deposits during biomasscombustion-injection of ammonium sulphate and co-combustionwith peat[J]. Fuel Processing Technology, 2013, 105:170-180.
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