Investigation on the removal of H2S from microwave pyrolysis of sewage sludge by an integrated two-stage system.

In this study, an integrated two-stage system, including the in-situ catalytic microwave pyrolysis (ICMP) and subsequent catalytic wet oxidation (CWO) processes, was proposed to remove H2S released from microwave-induced pyrolysis of sewage sludge. The emission profile and H2S removal from the pyrolysis of raw sewage sludge (SS) and sewage sludge spiked with conditioner CaO (SS-CaO) were investigated. The results showed that CaO played a positive role on sulfur fixation during the pyrolysis process. It was found that SS-CaO (10 wt.%) contributed to about 35% of H2S removal at the first stage (ICMP process). Additionally, the CWO process was demonstrated to have promising potential for posttreatment of remaining H2S gas. At the Fe3+ concentration of 30 g/L, the maximum H2S removal efficiency of 94.8% was obtained for a single Fe3+/Cu2+ solution. Finally, at the pyrolysis temperature of 800 °C, 99.7% of H2S was eliminated by the integrated two-stage system meeting the discharge standard of China. Therefore, the integrated two-stage system of ICMP + CWO may provide a promising strategy to remove H2S dramatically for the biomass pyrolysis industry.