Selection of in-situ Desulfurizers for Chicken Manure Biogas and Prediction of Dosage

摘要

The hydrogen sulfide (H2S) in biogas is poisonous and corrosive, so it is usually removed in the early stage of biogas upgrading. Dosing iron compounds directly into the anaerobic fermenter is an in-situ method for rough desulphurization. But it is difficult to estimate the appropriate amount of iron compound to add and overdosing is usually inevitable. Five kinds of iron compounds (FeCl2, FeCl3, Fe(OH)(3), Fe2O3, and FeSO4) were applied as in-situ desulfurizers in chicken manure fermentation to reduce H2S emissions. Biogas yield, CH4 concentration, and H2S concentration were examined to evaluate the performance of these desulfurizers. Among these five desulfurizers, FeCl2, FeCl3, and Fe(OH)(3) showed better performance; the desulfurization rates were all above 98.5% when the addition was 16 mmol L-1. In order to establish the prediction model of the required amount for in-situ desulfurizer, it is assumed that the dosage of desulfurizer could be simply divided into two parts: one part for consumption of released H2S, and the other part for guaranteeing a certain desulfurizing level. Under this assumption, the prediction formulas were fitted based on the bottle experiments and applied in a 5 L fermentation system. The required desulfurization levels (H2S concentration) when adding FeCl2, FeCl3, and Fe(OH)(3) were set to 120, 200, and 100 ppmv, respectively. After adding the calculated dosage of the three in-situ desulfurizers, the actual H2S concentrations were 163.0, 180.3, and 89.4 ppmv, respectively, which were relatively closed to the required desulfurization levels.