生物质气化与混燃过程研究
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摘要
随着全球经济的飞速发展,人类对能源的需求量快速增加,世界各国开始面临资源枯竭,环境恶化的严峻现实。为了实现经济与环境的协调和可持续发展,人们寄希望于寻求化石燃料的代替能源。生物质能以其永不枯竭、绿色洁净的特点受到全世界的关注,成为化石燃料的良好替代品。本文以生物质能的高效利用为核心,对生物质气化技术以及生物质气与煤粉混合燃烧过程进行研究。主要研究内容如下:
1.选择松木、玉米秸秆和木屑三种生物质作为气化原料,建立了以空气为气化剂,常压循环流化床的生物质气化模型。并利用ASPEN流程模拟软件对生物质气化的情况进行了数值模拟。
2.利用exergy分析方法,对生物质气化过程性能进行了评估。得到气化合成气成分、气化炉运行温度、合成气低位热值、碳转化率、气化效率和exergy效率随空燃比的变化,最终得到松木、玉米秸秆和木屑的最佳气化参数。
3.对生物质气化过程进行了优化研究。分析了生物质种类、生物质含水率和气化剂温度对气化过程exergy效率的影响,通过改善生物质气化操作条件,确定了干燥生物质原料、提高气化剂温度等方案,对原有生物质气化过程进行优化,从而提高气化过程exergy效率以及合成气的热值。
4.建立了生物质气与煤混合燃烧模型。采用建立在热力学第一定律基础上的热平衡分析方法和建立在热力学第一、二定律基础上的exergy分析方法对混燃过程进行热平衡计算和exergy平衡计算。通过对各项热损失和exergy损失的对比分析找到影响锅炉效率的主要因素。计算了纯煤粉燃烧、以及混燃5%~30%生物质气化气时锅炉的热效率、exergy效率、燃烧所需理论空气量和产生的理论烟气量。
结果表明,玉米秸秆气化合成气与煤混燃同单独燃煤发电相比,燃烧所需理论空气量减少,燃烧产生的理论烟气量增加,锅炉热效率和exergy效率均减小。随着混燃比例的增加理论空气量逐渐减小,理论烟气量逐渐增大,锅炉热效率和exergy效率逐渐减小。
生物质气化技术在我国已有良好的基础,通过气化可以高效地利用生物质能。生物质气与煤混燃技术充分地利用了现有燃煤发电厂的巨额投资和基础设施,不仅可以利用生物质替代化石燃料,改善环境质量,而且在一定程度上还可以提高电厂的经济效益。我国生物质资源丰富,生物质气化技术和混燃发电技术,非常符合我国的国情,在绿色电力的开发以及新能源技术的推广方面都具有很现实的意义。
With the rapid development of the global economy, Human’s demand for energy is growing very fast. The world has begun to face the grim reality of resource exhaustion and environmental degradation. In order to achieve the coordination and sustainable development of economic and environmental, people hope there is some renewable resource that can replace fossil fuels for energy. Biomass with its inexhaustible, clean and green features has attracted worldwide attention and become a good alternative to fossil fuels. Based on the efficient utilization of biomass energy, the biomass gasification and co-combustion process has been studies in this paper. The main research contents are as followings:
1. The model of biomass gasification was established under the conditions of air as gasification agent and in atmospheric circulating fluidized bed. Pine, cornstalk and sawdust were selected as gasification raw materials. The numerical simulation of biomass gasification process was carried out though ASPEN process simulation software.
2. The performances of the gasification process were evaluated by exergy analysis, which were syngas molar fraction, gasifier temperature, syngas low heating value, carbon conversion, gasification efficiency and exergy efficiency. The optimal gasification parameters of biomass gasification were acquired.
3. Biomass gasification processes were optimized to enhance the process exergy efficiency. The influence factors on the exergy efficiency are the types of biomass, biomass moisture content and gasifying agent temperature. Optimization schemes were determined though improving biomass gasification operating conditions, such as preheating biomass raw material, increasing gasifying agent temperature and so on. It shows that both preheating biomass raw material and increasing gasifying agent temperature could improve the gasifier’s exergy efficiency obviously.
4. The models of co-combustion of coal and biomass-gas were established. The thermal equilibrium analysis method based on the first law of thermodynamics and the exergy equilibrium analysis method based on the first and the second 1aw of thermodynamics were adopted. The thermal balanceable calculation and exergy equilibrium calculation of boiler were done. Main factors that influenced boiler efficiency were found though comparing heat losses with exergy losses. Heat efficiency, exergy efficiency, theoretical burned gas mass flow and theoretical air mass flow were calculated in pure coal burning process and co-combustion process with 5%~30% biomass-gas.
By comparing co-combustion with pure coal burning, it shows that the theoretical burned gas mass flow will reduce and the theoretical air mass flow will increase and both boiler heat efficiency and exergy efficiency will decrease when there is more biomass gas co-combustion.
In China, biomass gasification technology has a good foundation. Through gasification, biomass energy can be efficiently developed. The syngas co-combustion with coal in a traditional type of coal burning boiler can make the most utilization of the substantive investment and infrastructures of a modern coal burning power plant. Co-combustion is suitable for the transformation of coal-fired power plant in China. Developing biomass gasification technology and co-combustion technology in china can not only improve the environment quality, but also increase economic benefits to some extent. Accordingly, biomass gasification technology and co-combustion technology accord with our country national condition, and have very realistic significance to the development of green power and the promotion of new energy technologies.
1.选择松木、玉米秸秆和木屑三种生物质作为气化原料,建立了以空气为气化剂,常压循环流化床的生物质气化模型。并利用ASPEN流程模拟软件对生物质气化的情况进行了数值模拟。
2.利用exergy分析方法,对生物质气化过程性能进行了评估。得到气化合成气成分、气化炉运行温度、合成气低位热值、碳转化率、气化效率和exergy效率随空燃比的变化,最终得到松木、玉米秸秆和木屑的最佳气化参数。
3.对生物质气化过程进行了优化研究。分析了生物质种类、生物质含水率和气化剂温度对气化过程exergy效率的影响,通过改善生物质气化操作条件,确定了干燥生物质原料、提高气化剂温度等方案,对原有生物质气化过程进行优化,从而提高气化过程exergy效率以及合成气的热值。
4.建立了生物质气与煤混合燃烧模型。采用建立在热力学第一定律基础上的热平衡分析方法和建立在热力学第一、二定律基础上的exergy分析方法对混燃过程进行热平衡计算和exergy平衡计算。通过对各项热损失和exergy损失的对比分析找到影响锅炉效率的主要因素。计算了纯煤粉燃烧、以及混燃5%~30%生物质气化气时锅炉的热效率、exergy效率、燃烧所需理论空气量和产生的理论烟气量。
结果表明,玉米秸秆气化合成气与煤混燃同单独燃煤发电相比,燃烧所需理论空气量减少,燃烧产生的理论烟气量增加,锅炉热效率和exergy效率均减小。随着混燃比例的增加理论空气量逐渐减小,理论烟气量逐渐增大,锅炉热效率和exergy效率逐渐减小。
生物质气化技术在我国已有良好的基础,通过气化可以高效地利用生物质能。生物质气与煤混燃技术充分地利用了现有燃煤发电厂的巨额投资和基础设施,不仅可以利用生物质替代化石燃料,改善环境质量,而且在一定程度上还可以提高电厂的经济效益。我国生物质资源丰富,生物质气化技术和混燃发电技术,非常符合我国的国情,在绿色电力的开发以及新能源技术的推广方面都具有很现实的意义。
With the rapid development of the global economy, Human’s demand for energy is growing very fast. The world has begun to face the grim reality of resource exhaustion and environmental degradation. In order to achieve the coordination and sustainable development of economic and environmental, people hope there is some renewable resource that can replace fossil fuels for energy. Biomass with its inexhaustible, clean and green features has attracted worldwide attention and become a good alternative to fossil fuels. Based on the efficient utilization of biomass energy, the biomass gasification and co-combustion process has been studies in this paper. The main research contents are as followings:
1. The model of biomass gasification was established under the conditions of air as gasification agent and in atmospheric circulating fluidized bed. Pine, cornstalk and sawdust were selected as gasification raw materials. The numerical simulation of biomass gasification process was carried out though ASPEN process simulation software.
2. The performances of the gasification process were evaluated by exergy analysis, which were syngas molar fraction, gasifier temperature, syngas low heating value, carbon conversion, gasification efficiency and exergy efficiency. The optimal gasification parameters of biomass gasification were acquired.
3. Biomass gasification processes were optimized to enhance the process exergy efficiency. The influence factors on the exergy efficiency are the types of biomass, biomass moisture content and gasifying agent temperature. Optimization schemes were determined though improving biomass gasification operating conditions, such as preheating biomass raw material, increasing gasifying agent temperature and so on. It shows that both preheating biomass raw material and increasing gasifying agent temperature could improve the gasifier’s exergy efficiency obviously.
4. The models of co-combustion of coal and biomass-gas were established. The thermal equilibrium analysis method based on the first law of thermodynamics and the exergy equilibrium analysis method based on the first and the second 1aw of thermodynamics were adopted. The thermal balanceable calculation and exergy equilibrium calculation of boiler were done. Main factors that influenced boiler efficiency were found though comparing heat losses with exergy losses. Heat efficiency, exergy efficiency, theoretical burned gas mass flow and theoretical air mass flow were calculated in pure coal burning process and co-combustion process with 5%~30% biomass-gas.
By comparing co-combustion with pure coal burning, it shows that the theoretical burned gas mass flow will reduce and the theoretical air mass flow will increase and both boiler heat efficiency and exergy efficiency will decrease when there is more biomass gas co-combustion.
In China, biomass gasification technology has a good foundation. Through gasification, biomass energy can be efficiently developed. The syngas co-combustion with coal in a traditional type of coal burning boiler can make the most utilization of the substantive investment and infrastructures of a modern coal burning power plant. Co-combustion is suitable for the transformation of coal-fired power plant in China. Developing biomass gasification technology and co-combustion technology in china can not only improve the environment quality, but also increase economic benefits to some extent. Accordingly, biomass gasification technology and co-combustion technology accord with our country national condition, and have very realistic significance to the development of green power and the promotion of new energy technologies.
引文
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[10] Magin Lapuerta, Juan J, Hernandez et al. Gasification and co-gasification of biomass wastes: Effect of the biomass origin and the Gasifier operating conditions[J]. Fuel processing technology, 2008,89(9):828-837
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[2] Arvind Joshi Kulbhushan. Effects of blending, staging and furnace temperature on co-firing of coal and biomass-bagasse[D]. Mechanical Engineering Master's Theses. Boston, Massachusetts, Northeastern University, 2008.8
[3]中国电力科学研究院生物质能研究室编.生物质能及其发电技术[M].北京:中国电力出版社,2008,1-5
[4] HaU D O, Grassi G Scheer H. Biomass for Energy and Industry[J]. 7th E.C.Conference, Ponte Press, Germany, l994:67～71
[5]尹忠东,朱永强.可再生能源发电技术[M].北京:中国水利水电出版社,2010.5, 214
[6]国外生物质发电产业化大发展,中国经贸导刊,2007,12:49~49
[7] Energy Visions 2030 for Finland. VTT Energy, ISBN-951-37-3596-6.2001
[8]张巍,侯勇.生物质发电前景广阔[M].中国电力企业管理,2007,4:30-32
[9] Larry Baxter, Jaap Koppejan. Biomass Coal Co-Combustion: Opportunity for Affordable Renewable Energy
[10] Magin Lapuerta, Juan J, Hernandez et al. Gasification and co-gasification of biomass wastes: Effect of the biomass origin and the Gasifier operating conditions[J]. Fuel processing technology, 2008,89(9):828-837
[11]杨睿,四角切圆煤粉炉生物质气与煤粉混燃数值模拟[D].华北电力大学硕士论文,北京,华北电力大学热能工程系2009.03
[12]张建安,刘德华.生物质能源利用技术[M].北京:化学工业出版社,2010.3,40-41
[13]杨勇平,董长青等.生物质发电技术[M].北京:中国水利水电出版社,2007.4
[14]刘荣厚.生物质能工程[M].北京:化学工业出版社,2009.9 221-222
[15]姚兴佳,刘国喜.可再生能源及其发电技术[M].北京:科学出版社,2010.7, 220-223
[16]田宜水.生物质发电[M].北京:化学工业出版社,2010.6 121-123
[17] Lars Waldheim. Heating value of gases from biomass gasification[R].IEA Bioenergy Agreement,Task 20-Thermal Gasification of Biomass, May 2001.
[18]布罗章斯基BM著.王加璇等译.用方法及其分析[M].北京:中国电力出版社,1996
[19]王松平,华贲,陈清林等.用损失的机理研究[J].华南理工大学学报(自然科学版),1999,27(4):53-59
[20]华贲.工艺过程用能分析与综合[M].北京:中国石化出版社,1995,40-42
[21]朱明善.能量系统的用分析[M].北京:清华大学出版社,1988,55-58
[22] Higman, Cvan der Burgt. M. Gasification[M].Elsevier:New York,2003.
[23] Sjaak van loo, Jaap Koppejan. Handbook of Biomass Combustion and Co-firing [M]. Beijing: Chemical Industry Press, 2008, 16-32.
[24] Kotas TJ. The exergy method of thermal plant analysis. London: Butterworths;1985
[25]严家騄,王永青.工程热力学[M].北京:中国电力出版社,2004,96-98
[26]吕鹏梅,常杰,熊祖鸿等.生物质废弃物制氢技术[J].环境保护,2002,(8):4 3-4 5
[27] Padban Nader, Wang Wu-yin, Ye Zhi-cheng, et a1. Tar for motioning pressurized fluidized bed air gasification of woody biomass [J]. Energy and Fuels,2000,14(3):603-611
[28] Keiichi Tomishige, Mchammed Asadullah, Kimio Kunimofi. Novel catalysts for gasification of biomass with high conversion efficiency [J]. Catalysis Surveys from Asia, 2003,12:219-233
[29] Ong'iro A, Ugursal V.I. , Taweel A.M.A, et al. Thermodynamic simulation and evaluation of a steam CHP plant using aspen plus[J]. Applied Thermal Engineering, 1996, 16(3): 263-271
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