碱基吸收剂对燃煤烟气SO_(3)脱除机制研究

Study on the Removal Mechanism of Alkaline Absorbent for SO_(3) in Coal-Fired Flue Gas

燃煤烟气中SO_(3)的生成与排放严重威胁着电厂的安全经济运行与大气环境,本文探究了K_(2)CO_(3)、Na_(2)CO_(3)与Ca(OH)_(2)三种碱基吸收剂对SO_(3)的脱除性能及速率控制机制。结果表明,吸收剂对SO_(3)脱除性能为K_(2)CO_(3)>Na_(2)CO_(3)>Ca(OH)_(2),温度与化学当量比的增加均有利于SO_(3)的脱除。随着SO_(3)脱除反应的进行,吸收剂表面形成的硫酸盐覆盖物会影响SO_(3)向未反应界面的扩散,导致反应速率下降。SO_(3)脱除反应速率受外扩散过程控制,但在Na_(2)CO_(3)与Ca(OH)_(2)脱除SO_(3)的反应后期,反应速率由外扩散与内扩散共同控制。

The generation and emission of SO_(3)in coal-fired flue gas seriously threaten the safe and economic operation of power plants and the atmospheric environment.The removal performance and rate control mechanism of SO_(3)by three alkaline absorbents,K_(2)CO_(3),Na_(2)CO_(3),and Ca(OH)_(2),were investigated in this study.The results show that the SO_(3)removal performance of the absorbent is K_(2)CO_(3)>Na_(2)CO_(3)>Ca(OH)_(2),and the increase of temperature and stoichiometric ratio is beneficial to the removal of SO_(3).With the process of reaction,the sulfate coating formed on the surface of the absorbent will affect the diffusion of SO_(3)to the unreacted interface,resulting in a decrease in the reaction rate.SO_(3)removal reaction rate is controlled by external diffusion.For the absorbents of Na_(2)CO_(3)and Ca(OH)_(2),the reaction rate in the later stage of the reaction is controlled by both external diffusion and internal diffusion.