Performance of CuCl2 solution on washing regeneration of activated carbon for mercury removal in syngas

Abstract

Mercury pollution in syngas has received increasing attention. Regeneration of AC can reduce the cost and avoid Hg secondary release effectively. The performance of CuCl2 solution on AC regeneration was studied combining fixed-bed reactor, Hg-TPD, and characterization tests (BET, SEM-EDS, XPS, and FT-IR). Hg adsorption on AC in N2 mainly followed physisorption. There was a synergistic contribution of HCl and H2S on Hg removal, in which HCl promotion was stronger than H2S. The main Hg-containing compounds on AC in HCl were HgCl2 and HgO, in H2S were HgO and HgS. The well-developed pore structure of AC enhanced Hg adsorption while inhibited the elution of Hg-containing compounds. CuCl2 solution exhibited an excellent synergy in the elution of Hg-containing compounds and the impregnation modification of AC, which not only eluted the Hg-containing compounds, restored the well-developed pore structure, and recovered the reactive oxygen-containing functional groups effectively, but also brought in Cu and Cl for promoting Hg removal by generating Hg-Cu and HgCl2 respectively. The best impregnation content of CuCl2 was 10% that exhibited higher (above 99%) and more stable Hg removal efficiency than raw AC, and the dominant Hg-containing compound was easy-soluble HgCl2, proving the practicability of CuCl2 solution on AC regeneration.