Combined removal of SO3 and HCl by modified Ca(OH)2 from coal-fired flue gas.

Abstract

As treatments for mainstream pollutants in coal-fired power plants have been established, the control of non-conventional pollutants, such as SO3 and HCl, is gradually gaining attention. In this study, combined SO3 and HCl removal is proposed based on SO3 removal by absorber injection. However, it is challenging to selectively absorb SO3 and HCl from SO2-rich atmospheres. Therefore, Ca(OH)2 was modified via ball milling and doping with CuO for the combined removal of SO3 and HCl. The results showed that ball milling reduced the particle and grain sizes of Ca(OH)2, which increased the active sites of Ca(OH)2 and prolonged reaction time. After modification by ball milling, SO3 absorption per mg of Ca(OH)2 increased by 40 %. However, HCl removal efficiency was difficult to improve by modifying Ca(OH)2 using only ball milling under SO3 and SO2 atmospheres. Therefore, the dechlorination capacity of Ca(OH)2 was improved by adding ions during the ball milling process. Doping of Ca(OH)2 with Cu2+ changed its crystal structure, weakened the diffusion resistance of HCl, and improved Ca(OH)2 utilization. Additionally, it increased the energy of Ca(OH)2 to adsorb HCl.