gas treatmentReading time:
In addition to methane 70-80 % and CO2 20-30%, the gas often contains H2S generated from the reduction of sulphates and sulphur forms in raw effluents.
Depending on the COD concentration for certain untreated industrial effluents diluted with more than 200 mg · L–1 in SO4, H2S can increase. A concentration of H2S of more than 2% in the gas can compromise its utility (corrosive nature of condensates, corrosion affecting burners, excessive SOx content in flue gases…). Biogas desulpherisation may then be necessary:
- either using pressurized water (~ 10 bar);
- or by inducing controlled biological oxidation to produce elementary sulphur that can be settled (an Azurair type attached growth system that is well suited to this particular case); please refer to the San Miguel brewery system (Spain);
- or by fixing the S2- onto iron oxides.