Abstract
In this study, to simulate a biogas desulfurization process, a modified Monod-Gompertz kinetic model incorporating a dissolved oxygen (DO) effect was proposed for a sulfur-oxidizing bacterial (SOB) strain, Acidithiobacillus thiooxidans, under extremely acidic conditions of pH 2. The kinetic model was calibrated and validated using experimental data obtained from a bubble-column bioreactor. The SOB strain was effective for H2S degradation, but the H2S removal efficiency dropped rapidly at DO concentrations less than 2.0 mg/L. A low H2S loading was effectively treated with oxygen supplied in a range of 2%–6%, but a H2S guideline of 10 ppm could not be met, even with an oxygen supply greater than 6%, when the H2S loading was high at a short gas retention time of 1 min and a H2S inlet concentration of 5000 ppm. The oxygen supply should be increased in the aerobic desulfurization to meet the H2S guideline; however, the excess oxygen above the optimum was not effective because of the decline in oxygen efficiency. The model estimation indicated that the maximum H2S removal rate was approximately 400 ppm/%-O2 at the influent oxygen concentration of 4.9% under the given condition. The kinetic model with a low DO threshold for the interacting substrates was a useful tool to simulate the effect of the oxygen supply on the H2S removal and to determine the optimal oxygen concentration.
Highlights
Research and industrial interests in renewable energy sources have increased due to the depletion of natural resources
The growth rate of the sulfur-oxidizing bacterial (SOB) strain and the H2S removal rate were measured as a function of the concentrations of H2S and oxygen introduced into the bioreactor
The dual growth kinetic model was proposed for the SOB stain, A. thiooxidans capable of degrading H2S under the extremely acidic condition of pH 2, and the model parameters for the removal of H2S in biogas were determined using the experimental data obtained from the short-term bioreactor operation
Summary
Research and industrial interests in renewable energy sources have increased due to the depletion of natural resources. Biogas is the most reliable and feasible alternative [1,2]. Biogas is commonly generated by anaerobic digestion using organic wastes such as wastewater sludge, food waste, livestock manure, and agricultural by-products. The main components of biogas are methane (CH4) and carbon dioxide (CO2), and other trace compounds [3]. In order to utilize biogas as an energy source, it needs to be pretreated before use to increase its methane fraction and to remove impurities. Biogas commonly contains trace gases such as hydrogen sulfide (H2S), ammonia, siloxanes, and so on. The trace components can frequently cause malfunctions and failures in biogas utilization facilities [4]; the trace components must be eliminated for the effective use of biogas [5]
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