Inhibition of insoluble HgS and HgO generation and promotion of easy-soluble HgCl2 production for the solution washing regeneration of mercury adsorbent in syngas

Abstract

Inhibiting the generation of insoluble HgO and HgS, as well as promoting the generation of HgCl2 can significantly contribute to the solution washing regeneration of adsorbent for Hg removal in syngas. In this study, CeO2-MnO2/TiO2(Ce-Mn/Ti) was chosen as the Hg adsorbent, the fixed-bed test, Hg-TPD, and characterization test (including BET, SEM-EDS, and XPS) were conducted. Firstly, the effects of different concentrations of CO, H2, NH3, and HCl on the generation of HgS, HgO, and HgCl2 on adsorbent was investigated. Although the increase of CO, H2, and NH3 concentration can inhibit the generation of HgS and HgO to different extents, and the increase of HCl concentration can promote the production of HgCl2, but they will also lead to the increase in Hg concentration to varying degrees, indicating the adjustment on syngas components and concentrations is not a feasible method. Subsequently, the effects of different concentrations of modification reagent with CuCl2 were studied. The optimal impregnation ratio of CuCl2 was determined as 10%, in which the Hg removal efficiency in H2S atmosphere could reach over 97%, and almost of the Hg-containing product was easy-soluble HgCl2. The great advantage of impregnation modification of CuCl2 is attributed to the uniform and dense distribution of CuCl2, as well as the strong activity of CuCl2 itself towards Hg0 oxidation to HgCl2. The impregnation modification of CuCl2 can significantly improve the Hg removal efficiency, inhibit the generation of HgS and HgO, and promote the generation of HgCl2, which is verified as a feasible method to improve the solution washing regeneration of Hg adsorbent.