Biotrickling filter for H2S treatment of a biogas fed fuel cell: field test results

The presence of significant amounts of hydrogen sulphide is a critical issue in fuel cell power systems fed with biogas from anaerobic digestion. The concentration of this contaminant in the digester output biogas varies over the time, but it should be kept below the ppm level at the fuel cell system inlet, to minimize the reformer catalyst poisoning and cell component degradation. This work was aimed to analyse, into a real case, the entire anaerobic digestion process, highlighting the parameters that govern the hydrogen sulphide production, and to study the behaviour of a biotrickling filter for fine desulphurisation of real biogas to be fed into a laboratory scale HT-PEM (High Temperature Proton Exchange Membrane) fuel cell system. The amount of hydrogen sulphide in biogas resulted to be an important instantaneous indicator of the proper digestion process. The biotrickling filter showed high hydrogen sulphide removal efficiencies and proved to be a quite robust system, satisfactorily performing also in off-design conditions.