Elemental mercury capture from flue gas by magnetic recyclable Fe6Mn1-xCexOy sorbent. Part 1. Performance evaluation and regeneration

Abstract

A series of Ce doped Fe-Mn magnetic sorbents (Fe6Mn1-xCexOy) were prepared by using the co-precipitation method. The mercury removal performance evaluation and thermal regeneration of Fe6Mn1-xCexOy sorbent was conducted in a fixed-bed system. Combining with the characterization of N2 adsorption, X-ray diffraction (XRD), vibrating sample magnetometer (VSM), and X-ray photoelectron spectroscopy (XPS), the structure–activity relationship and the mechanism of circulating mercury removal by Fe6Mn1-xCexOy sorbent was analyzed. The results show that the Fe6Mn0.8Ce0.2Oy sorbent displays the best mercury removal capability, because Ce doping modifies the pore structure of sorbent, but excessive Ce addition reduces the active component of Mn. Both O2 in flue gas and low temperature are beneficial to mercury removal by Fe6Mn0.8Ce0.2Oy sorbent, because O2 can supplement the consumed lattice oxygen and Ce doping promotes the oxidation activity of lattice oxygen at low temperature. During mercury removal process, gas phase Hg0 is oxidized to Hg2+ by Mn4+ reducing to Mn3+, and combining with adsorbed O to form HgO. During thermal regeneration, part of Mn3+ is re-oxidized to Mn4+ by O2 in flue gas as well as Ce3+. After 6 cycles of mercury removal and thermal regeneration, the Fe6Mn0.8Ce0.2Oy sorbent still keep stable magnetism and high mercury removal capability. Therefore, the Fe6Mn0.8Ce0.2Oy sorbent is a promising sorbent for cyclic mercury removal from coal-fired flue gas.