Acceleration of the reaction of H2S and SO2 by non-thermal plasma to improve the mercury adsorption performance of activated carbon

Abstract

Activated carbon (AC) loading sulfur can improve mercury adsorption performance. Fine sulfur clusters can be generated by the H2S and SO2 reaction, but the reaction is extremely slow at ambient temperatures. This study proposes a cost-effective and efficient method for non-thermal plasma (NTP) to accelerate the reactions between H2S and SO2 on AC to improve elemental mercury (Hg0) removal performance. The NTP treatment experiment was carried out on a laboratory-scale dielectric barrier discharge system. The Hg0 adsorption experiment was conducted via the Tekran Hg CEMS online monitoring device. The results showed that NTP treatment accelerated the reaction of H2S and SO2. The specific surface area and surface morphology of the AC had no significant changes after NTP treatment. However, the surface of AC was enriched with more sulfur in a very short time. H2S and SO2 presented an optimum mixing ratio of 2:1. NTP exhibited an optimum treatment time and voltage of 1 min and 3 kV, respectively. The Hg0 removal efficiency was increased by approximately 70% as compared to AC. In addition, the effects of the adsorption temperature and individual flue gas composition were explored. Further X-ray photoelectron spectroscopy analysis and temperature programmed desorption were also performed. Hg0 adsorption was mainly controlled by chemisorption, wherein the elemental sulfur loaded on AC was the main active site for Hg0 conversion to mercuric sulfide (HgS).