Biological removal of hydrogen sulfide H2S

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This post was last edited by modekiller on 2009-9-17 at 14:52. Having just seen a post where the discussions were limited to dry and wet methods, I will introduce the biological desulfurization process. Biological desulfurization is a new type of biogas desulfurization technology that has become popular in countries and regions such as Europe and Japan. The principle of biological desulfurization is similar to that of odor removal in pumping stations; it relies on bacteria from the genera Thiobacillus and Thiospirillum to absorb sulfur during their metabolic processes, thereby achieving desulfurization. A typical biological desulfurization tower is shown in the figure below. A certain amount of air is introduced into biogas containing hydrogen sulfide, and the mixed gas passes through a biological desulfurization tower to remove hydrogen sulfide. Special plastic fillers are installed inside the tower, providing ample space for the growth of desulfurization bacteria. The circulation of the nutrient solution keeps the filler moist and supplies the nutrients required for the growth and reproduction of desulfurization bacteria. Under normal circumstances, nutrients can be obtained naturally, for example through: · digested wastewater · the supernatant from digested or dewatered sludge · leachate from landfills · or synthetic fertilizers (NPK886). Thiobacillus and Thiothrix species begin to reproduce in the filler using these nutrients. Under these conditions, they absorb hydrogen sulfide from the mixed biogas and convert it into elemental sulfur, which is then transformed into sulfuric acid. The chemical reactions are as follows: H2S + 2O2 ----> H2SO4 (1) 2H2S + O2 ----> 2S + 2H2O (2) S + H2O + 1.5O2 ----> H2SO4 (overall). The resulting sulfuric acid, along with the nutrient solution, is discharged from the system due to the buffering effect of the nutrient solution; this process repeats continuously. The hydrogen sulfide concentration in the incoming gas can reach 20,000 ppm, and the efficiency of hydrogen sulfide removal depends on its concentration in the incoming gas, with efficiencies ranging from 90% to 98%. The disadvantage of biological desulfurization is that the period required for microbial stabilization during the initial operation is long, at 2–3 weeks, and it demands a high level of operational management as well as good technical support from suppliers. The biological desulfurization equipment produced by Austrian EnvironTec (represented by our company ZCIC) is one of the more mature solutions of this kind; to date, it has been used in hundreds of projects across Europe, Japan, South America, China, and other regions. The process flow is as follows: The gas passes through a plastic container installed within the reaction tower, which serves as a growth area for bacteria, and is then mixed with the gas to be treated at the inlet. The air flow rate will be controlled by the gas flow rate and oxygen concentration. The bacterial culture solution will be sprayed onto the top of the container and automatically refreshed. 1. Gas inlet 5, Bacterial culture solution 9, Circulation pump 2. Reaction tower with container 6, Dilution water 10, Heat exchanger 3. Gas outlet 7, Waste bacterial culture solution 11, Control panel 4. Air supply 8, Air control unit. Based on our current experience, the biological desulfurization process is the most cost-effective compared to other washing systems. Furthermore, the biological hydrogen sulfide removal process can convert most of the hydrogen sulfide into sulfates, which will prevent the formation of unpleasant odors resulting from the emission of oxidation products. The oxidation products (sulfates) generally go directly to the wastewater treatment facility and/or sewer system. The processing process requires only a small amount of nutrient solution. It was posted in the gas purification section; it’s also posted here for the biomass section for everyone’s reference