Performance of commercial and modified activated carbons for hydrogen sulfide removal from simulated biogas

In Thailand, biogas is one of a renewable energy that can be utilized for fuel and electricity generator. It contains methane (CH₄), carbon dioxide (CO₂), nitrogen (N₂), Oxygen (O₂) and a contaminant; hydrogen sulfide (H₂S). H₂S is toxicity and high corrosion for engine. H₂S can be removed from biogas by adsorption over activated carbon, which can be produced from agricultural waste in Thailand. The purpose of this work is to test performance of commercial and modified activated carbons on H₂S removal from simulated biogas at 30 °C. Activated carbons were modified by steam activation, potassium hydroxide (KOH) impregnation and the combination of steam activation and KOH impregnation (S_KOH). Simulated biogas contain 3000 ppmv H₂S, 40% CO₂, 2% O₂ and 70% humidity. It was found that modified activated carbons have adsorption capacity significantly higher than commercial activated carbon (in the range of 2-6 times higher depending on modification method). In detail, 1 gram of S_KOH can adsorb 84.75 mg of H₂S. Furthermore, S_KOH removed H₂S from 3000 ppmv into 0 ppmv for 100 minutes. It can be concluded that modified activated carbons are highly applicable for H₂S removal in biogas at room temperature. Therefore, purified biogas is safe for using in household and industry.