APPLICATION OF IRON-BASED ADSORBENT (FEOOH) TO REMOVE HYDROGEN SULFIDE (H2S) FROM BIOGAS

Abstract

Biogas generated during the anaerobic digestion of piggery wastes is considered as one of the renewable energy sources. This biogas is methane-rich, based on a typical composition of 60 - 70 % methane (CH4). However, trace amounts of undesirable compounds, such as hydrogen sulfide (H2S) is also present, which hinder their use as it is very toxic and corrode the equipment. In this study, a lab-scale adsorption system was conducted to removal H2S from biogas collected at Thanh Hung pig farm (Thanh Oai district, Hanoi). The initial biogas contained high CH4 concentration of 72 %, and the H2S concentration was about 1995 ppm. The iron-based adsorbent (FeOOH) with the particle size of 0.50-1.18 mm was used for H2S purification. The system was operated continuously at various biogas flow rates from 0.5 to 3 L/min. Breakpoint of FeOOH appeared after 1,038 min. The adsorption capacity was estimated up to 0.18 g H2S/g FeOOH. A longer empty bed contact time increased the amount of H2S that was adsorbed up until the time of breakpoint. During operation, the temperature in the air and in biogas was varied insignificantly in the range of 29 to 32 oC. However, the humidity was much different between in the ambient air (56 %) and in biogas (87 %). In conclusion, FeOOH has high capacity for H2S purification to produce high quality purified biogas with H2S concentration of below 100 ppm which could be used for electrical generation.