Design and scale-up of an oxidative scrubbing process for the selective removal of hydrogen sulphide from biogas

Reliable and selective removal of hydrogen sulphide (H2S) is an essential part of the biogas upgrading procedure in order to obtain a marketable and competitive natural gas substitute for flexible utilisation. A promising biogas desulphurisation technology has to ensure high separation efficiency regardless of process conditions or H2S load without the use or production of toxic or ecological harmful substances. Alkaline oxidative scrubbing is an interesting alternative to existing desulphurisation technologies and is investigated in this work. In experiments on a stirred tank reactor and a continuous scrubbing column in laboratory-scale, H2S was absorbed from a gas stream containing large amounts of carbon dioxide (CO2) into an aqueous solution prepared from sodium hydroxide (NaOH), sodium bicarbonate (NaHCO3) and hydrogen peroxide (H2O2). The influence of pH, redox potential and solution aging on the absorption efficiency and the consumption of chemicals were investigated. Because of the irreversible oxidation reactions of dissolved H2S with H2O2, high H2S removal efficiencies were achieved while the CO2 absorption was kept low. At an existing biogas upgrading plant an industrial-scale pilot scrubber was constructed, which efficiently desulfurises 180 m3/h of raw biogas with an average removal efficiency of 97%, even at relatively high and strongly fluctuating H2S contents in the crude gas.

Authors: Krischan, J.; Makaruk, A.; Harasek, M. ;Full Source: Journal of Hazardous Materials 2012, 215-216, 49-56 (English) ;