Research Of Two-Step Chemotrophic Microbial Reactor Removing Hydrogen Sulfied From Biogas

Hydrogen sulfide in biogas is one of the most influencing factors on utilization of biogas. The bio-desulfurization of biogas is focused because of its advantages, such as low expense, no specific catalyst, simple process and serviceability, which the dry process and wet process do not possess. However, the bio-desulfurization is still at the experimental mimic stage in domestic. There are few reports about bio-desulfurization of biogas in engineering applications. To popularize and apply biogas in our country, developing a high effective and low cost bio-desulfurization process is imperative.Biological oxidation and absorption of H2S is the key of enhancing the efficiency of desulfurization. This paper mainly made a systematic study on the two parts.Firstly, a bio-desulfurization reactor and a domestication process which can get Colorless Sulfur Bacteria (CSB) of bio-desulfurization through domesticating the sludge of sewage treatment plant were established. The main factors, such as DO, volume loading, pH, temperature, HRT and salinity in the biological contact oxidation process were investigated systematically.1. At a given initial concentration of S2-, DO was the key factor to control the production of sulfur, and there was an optimum DO to maximize sulfur production rate. The sulfide volume loading was also influence the sulfate production. Bio-desulfurization was operated reasonably well when the volume loading was below 100 mg/h·L. At the S2- initial concentration of 85～90 mg/L, the sulfur production rate was various from 26% to 90% when DO increased gradually from 0.3 mg/L to 1.3 mg/L, and the main product was elemental sulfur with few sulfate. With the continuous increase of DO (DO>1.3 mg/L), sulfur production rate dropped and stabilized at 67% at the DO concentration 2.5 mg/L2. There is a distinct relationship between the volume loading and optimal DO. While the sulfide volume loading is between 70 mg/h·L and 300 mg/h·L, Sulfide volume loading had a certain function to the optimum DO: DO=10-6Fv3-0.0006 Fv2+0.1328 Fv-6.175.3. The salinity of biological desulfurization should be controlled below 1.5%. Growth and metabolism of CSB would be inhibited at a high salinity.Secondly, at the absorption tower, the influences of absorption liquid pH, absorption liquid temperature and gas-to-liquid ratio on absorption of H2S were investigated through a experimental scale desulfurization equipments with the daily biogas treatment capacity of 100 cubic meter. And the removal rate of H2S reached 95% by optimizing the above three factors.Lastly, based on the above study results, through adding backwashing device and semi-soft filler, adding rich sulfide solution tank and poor sulfide solution sank, and some other methods, the techniques process was optimized to surmount certain difficulties, such as instability absorption efficiency of absorption tower, the instability of reactor's running, and the reduced absorption rate of H2S when the reactor was scaled up; etc. According to above adjustment, a pilot scale bio-desulfurization device with the biogas treatment capacity of 1000～1500 cubic meter per day was designed and established. When the initial concentration of H2S was 3000～4000 mg/m3, the average H2S concentration after desulfurization was 108 mg/m3 and desulfurization rate achieved at 95%. Sulfur produce rate was above 85%, and sulfate produce rate was below 2%. Treatment cost of 1m3 biogas was Y0.03～0.06.