The sulfur in biogas mainly exists in the form of H2S and contains less organic sulfur. There are many methods for removing hydrogen sulfide, which can generally be divided into dry desulfurization, wet desulfurization, and biological desulfurization.
Dry desulfurization is commonly used for low sulfur gas treatment, especially for fine gas desulfurization. Most dry desulfurization processes cannot continue to operate due to the need to replace the desulfurizer. There are also some dry methods such as manganese ore method, zinc oxide method, iron oxide, activated carbon, etc. The desulfurizer cannot be regenerated or the regeneration frequency is very small. After desulfurization saturation, it needs to be discarded. This will cause environmental problems on the one hand and increase desulfurization costs on the other hand.
Wet desulfurization is the process of using a specific solvent to remove H2S through countercurrent contact with gas. The solvent is regenerated and reabsorbed, which can be further divided into chemical absorption, physical absorption, physicochemical absorption, and wet oxidation based on different absorption mechanisms. Wet oxidation method has high desulfurization efficiency, recyclable elemental sulfur, simple process, most desulfurizers can be regenerated, and low operating cost; At the same time, this method has a complex process, high investment, and is suitable for situations with large gas processing capacity and high H2S content.
The biological desulfurization system is based on the capacity of various microorganisms, utilizing their life activities to transform organic pollution into compounds that are harmless to human health and the ecological environment. Sulfides are commonly produced in wastewater treatment projects through biological methods. Biological desulfurization technology includes biological filtration, biological adsorption, and biological drip filtration, all of which belong to open systems, and their microbial populations change with environmental changes. In the process of biological desulfurization, oxidized sulfur-containing pollutants must first undergo biological reduction to generate sulfides or H2S, and then undergo biological oxidation to generate elemental sulfur in order to be removed.
Compared with the traditional processes mentioned above, biological purification processes have advantages such as low operating costs, mild reaction conditions, low energy consumption, and effective reduction of environmental pollution. However, desulfurization microorganisms require oxygen, and the addition of oxygen or air may lead to an increase in oxygen content in biogas, affecting the safety of biogas. Therefore, the use of biological desulfurization requires constant monitoring of the oxygen content in the reactor.
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