洁净煤技术

2020, v.26;No.130(06) 189-195

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基于热力学平衡计算的燃煤电厂烟气中SO_3形态研究
Reseach on SO_3 morphological characteristics in flue gas of coal-fired power plants based on thermodynamic equilibrium calculation

于伟静;马超;谭闻濒;崔磊;李昌浩;
YU Weijing;MA Chao;TAN Wenbin;CUI Lei;LI Changhao;China Huadian Engineering Co.,Ltd.;

摘要(Abstract):

SO_3是燃煤电厂烟气排放常见污染物之一,对系统设备稳定运行和大气环境质量有较大影响。为深化相关研究,基于热力学及酸露点理论建立了SO_3形态转化计算模型,计算了不同烟气温度、湿度和SO_3浓度的形态特征,确定了常规燃煤电厂烟气中SO_3形态的分布特征,结果表明:燃煤电厂烟气中SO_3主要以SO_3气体、H_2SO_4气体和H_2SO_4气溶胶3种形态存在,形态转化基于化学反应和物理反应2个过程,化学反应指气态SO_3与H_2O结合形成气态H_2SO_4的过程,物理反应指在烟气温度降至酸露点以下时气态H_2SO_4通过均相或非均相成核形成H_2SO_4气溶胶的过程。此外,假设烟气湿度为8%,烟气温度低于202℃时,全部以H_2SO_4形态存在;烟气温度高于495℃时,全部以SO_3形态存在;烟气温度低于95℃时,基本以H_2SO_4气溶胶的形态存在。结合常规燃煤电厂烟气湿度和温度的分布情况,则SO_3形态的分布特征为:烟气脱硝装置前段,主要以SO_3气体形态存在;脱硝装置至空预器段,SO_3气体和H_2SO_4气体共同存在;空预器至脱硫装置段,H_2SO_4气体和H_2SO_4气溶胶共同存在;脱硫装置后段主要以H_2SO_4气溶胶形态存在,粒径<0.1μm。
SO_3 is one of the common pollutants discharged from coal-fired power plants,which has a great impact on the stable operation of system equipment and the quality of atmospheric environment. In order to deepen the relevant research,SO_3 morphologic transformation calculation model was established based on thermodynamics and acid dew point theory. The morphologic characteristics of different flue gas temperature,humidity and SO_3 concentration were calculated,and the distribution characteristics of SO_3 morphologic characteristics in flue gas from conventional coal-fired power plants were determined. The results show that SO_3 in flue gas of coal-fired power plants is mainly composed of SO_3 gas,H_2SO_4 gas and H_2SO_4 aerosol. The transformation of SO_3 is based on chemical reaction and physical reaction. The chemical reaction is that SO_3 gas reacts with H_2O gas to H_2SO_4 gas and the physical reaction is that H_2SO_4 gas condenses to H_2SO_4 aerosol by homogeneous and heterogeneous nucleation when flue gas temperature is lower than dew point,respectively. In addition,assuming the valve of humidity is 8%,when the flue gas temperature is lower than 202 ℃,higher than 495 ℃ and lower than 95 ℃,SO_3 exists in the form of H_2SO_4 gas,SO_3 gas and H_2SO_4 aerosol,respectively. Furthermore,combined with the distribution of flue gas humidity and temperature in conventional coal-fired power plants,the distribution characteristics of SO_3 are as follows: SO_3 gas,SO_3 gas and H_2SO_4 gas,H_2SO_4 gas and H_2SO_4 aerosol,H_2SO_4 aerosol exist the section ahead denitrification device,between denitrification device and air preheater,between air preheater and rear section of desulfurization unit,respectively. What is more,the particle size of H_2SO_4 aerosol is less than 0.1 μm.

关键词(KeyWords): 燃煤电厂;热力学平衡;SO_3;硫酸气体;硫酸气溶胶
coal-fired power plant;thermodynamic equilibrium;SO_3;H_2SO_4 gas;H_2SO_4 aerosol

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基金项目(Foundation): 中国华电集团重点科技研发项目(CHDKJ19-01-34)

作者(Author): 于伟静;马超;谭闻濒;崔磊;李昌浩;
YU Weijing;MA Chao;TAN Wenbin;CUI Lei;LI Changhao;China Huadian Engineering Co.,Ltd.;

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DOI: 10.13226/j.issn.1006-6772.19071301

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