Performance of polydimethylsiloxane membrane contactor process for selective hydrogen sulfide removal from biogas

H₂S in biogas affects the co-generation performance adversely by corroding some critical components within the engine and it has to be removed in order to improve the biogas quality. This work presents the use of polydimethylsiloxane (PDMS) membrane contactor for selective removal of H₂S from the biogas. Experiments were carried out to evaluate the effects of different pH of absorption liquid, biogas flowrate and temperature on the absorption performances. The results revealed that at the lowest loading rate (91mg H₂S/m²·h) more than 98% H₂S and 59% CO₂ absorption efficiencies were achieved. The CH₄ content in the treated gas increased from 60 to 80% with nearly 5% CH₄ loss. Increasing the pH (7-10) and loading rate (91-355mg H₂S/m²·h) enhanced the H₂S absorption capacity, and the maximum H₂S/CO₂ and H₂S/CH₄ selectivity factors were 2.5 and 58, respectively. Temperature played a key role in the process and lower temperature was beneficial for intensifying H₂S absorption performance. The highest H₂S fluxes at pH 10 and 7 were 3.4g/m²·d and 1.8g/m²·d with overall mass transfer coefficients of 6.91×10^-6 and 4.99×10^-6m/s, respectively. The results showed that moderately high H₂S fluxes with low CH₄ loss may be achieved by using a robust and cost-effective membrane based absorption process for desulfurization of biogas. A tubular PDMS membrane contactor was tested for the first time to remove H₂S from biogas under slightly alkaline conditions and the suggested process could be a promising for real scale applications.