Study of combining rusty scrap iron with micro-oxygen to enhance biogas in-situ deep desulfurization
RUAN Ren-jun1,2, XIANG Jing-wei1, ZHAO Jun-jie1, ZHAO Chang-shuang1,2, SUN Jun-wei1, ZHAO Wei1, CAO Jia-shun2
1. School of Architecture and Civil Engineering, Anhui Polytechnic University, Wuhu 241000, China; 2. College of Environment, Hohai University, Nanjing 210098, China
Abstract:To achieve biogas in-situ deep desulfurization of waste-activated sludge (WAS) anaerobic digestion. An integrated rusty scrap iron-micro-oxygen (RSI-MO) anaerobic digestion process was constructed embedding optimal RSI dosage (20g/L) and providing micro-oxygen condition to explore the influence of RSI-MO process on anaerobic digestion in-situ desulfurization performance. This semi-continuous anaerobic/microaerobic experiment was carried out in seven stages (P1~P7). The first stage (P1) was set as a control group. RSI was added in the second stage (P2). And increasing O2 levels were introduced stepwise in P3~P7stages. The results showed that supplementary O2 induced sulfur-oxidizing bacteria microbial oxidation of sulfide to elemental sulfur and chemical oxidative corrosion of iron to form ironic sulfide precipitate. It promoted the sulfide solidification by coupling of biological desulfurization with chemical desulfurization. From P3 to P7, the content of H2S in biogas decreased and residual oxygen increased with rising of O2 dose, respectively. The optimum performance was considered on the basis of anaerobic digestion efficiency and desulfurization property, which was obtained in P6. The methane yield was 301.1mL/gCOD, and the H2S concentration was 113mg/m3. The average methane yield increased by 37.65% comparing with P1. What’s more, the H2S removal efficiency in biogas decreased by 99.40%. According to the analysis of sulfur balance, it was found that the sulfur contents in solid-liquid-gas three phases accounted for 84.0, 11.9 and 0.21 percent of total sulfur in P6, respectively. It is indicated that the integrated process of RSI-MO anaerobic digestion could benefit biogas in-situ deep desulfurization.
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