SO2-Na2S-H2O体系热力学分析

摘要

利用Na<,2>S溶液吸收SO<,2>是湿法烟气脱硫中具有良好应用前景的新方法.为了能更好地利用Na<,2>S溶液进行烟气深度脱硫,文中通过热力学计算,对Na<,2>S溶液吸收SO<,2>烟气所构成的SO<,2>-Na<,2>S-H<,2>O体系中气液固三相组成与pH值的关系进行了分析.结果表明,pH值大于6时,SO<,2>-Na<,2>S-H<,2>O体系中主要存在S<,2>O<,3><'2->,HS<'->,H<,2>S气体和单质硫;pH值在4-6时,体系中基本上只存在S<,2>O<,3><'2->和单质硫;pH值小于4时,体系中主要存在S<,2>O<,3><'2->,HSO<'-><,3>,H<,2>SO<,3>,SO<,2>气体和单质硫.因此,为了保证较好的吸收效果,溶液pH值应控制在4以上.%The new method of absorbing SO2 with Na2S solution is of good prospects. In order to better use Na2S in the deep desulfurization of flue gas, the variable relations between the contents of gas phase, liquid phase and solid phase in SO2-Na2S-H20 system and pH values were analyzed by thermodynamic calculation. The result shows that when pH value is higher than 6, there are S2032-, HS-, H2S gas and sulfur in SO2-Na2S-H2O system; when pH value changed from 4 to 6, there are only S2O32- and sulfur in the system; when pH value is lower than 4, there are S2O32- , HSO3- , H2SO3, SO2 gas and sulfur in the system. Therefore, the pH value of solution should be higher than 4 to reach good efficiency in absorption.