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Selection of biogas desulfurization processes ① Dry desulfurization: The common method in dry desulfurization is the atmospheric-pressure iron oxide desulfurization method. At normal temperature and pressure, biogas passes through a desulfurization agent bed; the hydrogen sulfide in the biogas comes into contact with active iron oxide, resulting in the formation of iron sulfide and ferrous sulfide. Then regeneration takes place: the desulfurizer containing sulfides comes into contact with oxygen in the air, and in the presence of water, the iron sulfides are converted back into iron oxide and elemental sulfur. This desulfurization and regeneration process can be repeated multiple times until most of the pores on the surface of the iron oxide desulfurizer are filled with sulfur or other impurities, causing it to lose its activity. Once the desulfurizer loses its activity, it must be removed from the tower and spread out on an open area. Then, a small amount of dilute ammonia water is sprayed evenly over the desulfurizer, and natural regeneration takes place using the oxygen in the air. Once the sulfur agent is loaded, no maintenance is required in normal operation; however, when the sulfur content in the biogas at the outlet exceeds the specified limit, the desulfurization agent should be replaced. The desulfurizer that has been replaced can be regenerated, and the number of times it can be regenerated depends on the quality of the desulfurizer; generally, it can be regenerated 2 to 3 times. ②Wet flue gas desulfurization includes the direct oxidation method, chemical absorption method, and physical absorption method. Currently, the commonly used method in China is direct oxidation desulfurization, which involves oxidizing hydrogen sulfide to elemental sulfur in a liquid phase; the process is relatively simple, allowing for the direct production of elemental sulfur. This method is mainly used to treat gases with low hydrogen sulfide concentrations and high carbon dioxide concentrations. The disadvantage of this desulfurization method is the low sulfur capacity of the solution to absorb hydrogen sulfide; as a result, a large volume of solution must be circulated, and a large amount of recovered sulfur has to be processed. Applicable to desulfurization amount