Experimental study on H2S adsorption on gasification char under different operative conditions

Char is the solid by-product of biomass gasification. It usually represents a cost for plant owners, who have to dispose of it at a cost. However, its high carbon content and surface area could make it suitable for further applications, such as adsorption. In this work, we studied its potential for the adsorptive removal of hydrogen sulphide (H2S), a common pollutant present in the producer gas of gasification, as well as in biogas from anaerobic digestion. Different samples of char collected from commercial gasification plants in South Tyrol (Italy) were tested. The adsorption was reproduced in a lab-scale tubular fixed-bed reactor. The results highlight that all samples could capture hydrogen sulphide, showing different adsorption performances. The materials' specific surface area and metal and oxygen content seem to affect the removal capacity. After these tests, we selected the best-performing char, and tested its adsorption performance in different operative conditions, i.e. at different inlet concentrations of H2S and temperatures.