Empirical modeling of H2S removal from biogas by chemical absorption in electrochemically prepared solutions containing iron ions

Abstract

For the energy use of biogas, it is important to remove hydrogen sulfide (H₂S) as it is highly corrosive. Chemical absorption is a technology that has proven to be effective for H₂S removal. Based on the principle of this technology, the objective of this research was to evaluate the removal of H₂S from biogas via chemical absorption using solutions containing Iron III ions (Fe³⁺). These solutions were produced electrochemically based on experimental designs that had pH and electrolysis time as independent variables, as well as the solution deactivation time as a response variable. The Fe³⁺ ion solutions were prepared in the laboratory and subsequently used in biogas purification tests, which were carried out using biogas from a poultry slaughtering agro-industry biodigester. The results indicated a good performance of the solutions for H₂S removal when compared with distilled water. It was possible to observe that better results for the deactivation time can be found when higher pH values are used in the solutions, within the range applied in this study. The solution prepared under pH 7.4 and electrolysis time of 22.1 min provided a deactivation time 83% greater than water one. In addition, it was possible to find a significant mathematical model that describes the solution deactivation time as a function of pH.