Experimental and Adsorption Kinetics Study of Hg0 Removal from Flue Gas by Silver-Loaded Rice Husk Gasification Char

Abstract

Coal holds a significant position in China’s energy consumption structure. However, the release of Hg0 during coal combustion poses a serious threat to human health. Traditional activated carbon for Hg0 removal is expensive; finding efficient, inexpensive and renewable adsorbents for Hg0 removal has become a top priority. Rice husk gasification char (RHGC) is a solid waste generated by biomass gasification power generation, which, loaded with silver to remove Hg0, could achieve the purpose of waste treatment. This paper examines the Hg0 removal performance of silver-loaded rice husk gasification char (SRHGC) under different operating conditions through experimental analysis. This study employed quasi-first-order, quasi-second-order, and internal diffusion kinetics adsorption equations to model the amount of Hg0 removed by SRHGC at different temperatures, thereby inferring the reaction mechanism. The results indicate that Hg0 removal efficiency of SRHGC increased by about 80%. The Hg0 removal ability was directly related to silver load, and the amount of Hg0 removed by SRHGC did not a exhibit a simple inverse relationship with particle size. Additionally, the Hg0 removal efficiency of SRHGC declined with increasing adsorption temperature. The removal of Hg0 by SRHGC conformed to the quasi-second-order kinetic equation, with the adsorption rate constant decreasing as the temperature rose, consistent with experimental observations. This paper provides both experimental and theoretical references for future modification and optimization of RHGC for coal-fired flue gas treatment, and also offers valuable insights into Hg0 removal by carbon-based adsorbents.