The hydrogen sulfide in biogas has a strong corrosive effect on pipelines and equipment. At the same time, it will produce harmful gases such as sulfur dioxide during combustion, which will pollute the environment. Therefore, the use of biogas for power generation must be desulfurized. At present, the commonly used methods for biogas desulfurization are dry desulfurization and wet desulfurization, biological desulfurization, etc.
1.Dry desulfurization
Dry desulfurization has the advantages of simple process, mature and reliable, and low cost. It is often used for the treatment of low-sulfur gas. Dry desulfurizers include activated carbon, zinc oxide, manganese oxide and iron oxide. Considering the operating time, use temperature, pollution, and price, the most commonly used desulfurizer is iron oxide.
2, wet desulfurization method
The process of wet desulfurization is complicated and the investment is large. It is suitable for projects with large gas processing capacity and high hydrogen sulfide content. In the wet desulfurization method, alkaline liquid is generally used to absorb hydrogen sulfide. The biogas to be purified enters the tower from the bottom, reacts in countercurrent contact with the absorbent, and is then discharged from the top of the tower.
3, biological desulfurization technology
Biological desulfurization is the use of various microorganisms in the fermentation broth, such as Thiobacillus denitrificans, Thiobacillus thiooxidans, Thiobacillus ferrooxidans, Thiobacillus thiobacillus, etc. to oxidize H2S into elemental S and H2SO4 under micro-oxygen conditions. The gas derived from the fermentation tank enters the biological desulfurization tower, and at the same time, a part of the fermentation liquid is drawn from the fermentation tank, and the fermentation liquid is pumped from the bottom of the biological desulfurization tower to the top for spraying. The use of biological desulfurization must meet several conditions: 1. It has reliable efficiency; 2. It requires less nutrients; 3. The elemental sulfur in biomass is easily separated.
4, other desulfurization methods
In addition, there are naphthoquinone oxidative desulfurization technology, HAPS oxidative desulfurization technology, PDS desulfurization technology, etc., which can be applied to biogas desulfurization. The PDS desulfurization technology has been tested with a desulfurization efficiency of more than 90%. The depth of H2S in the desulfurized gas is much smaller than that of the engine. The H2S concentration standard required in fuel gas, but because the used catalyst PDS needs to be synthesized, the desulfurization cost is correspondingly high, which limits the promotion and application of its desulfurization technology.