What are the methods of biogas desulfurization?
Aug 07, 2025
Biogas, as an emerging energy source, is becoming increasingly widely used. In China's environmental standards, it is strictly stipulated that the H2S content in biogas gas should not exceed 20mg/m3 when using biogas energy. H2S must be removed as much as possible in both industrial and civilian gases.
When biogas is produced from anaerobic fermentation equipment, especially during medium or high temperature fermentation, it carries a large amount of H2S. Due to the presence of a large amount of water vapor in biogas, the combined action of water and H2S in biogas accelerates the corrosion and blockage of metal pipelines, valves, and flow meters. In addition, the SO2 generated after the combustion of H2S combines with the water vapor in the combustion products to form sulfurous acid, which corrodes the metal surface of the equipment and also causes pollution to the atmospheric environment, affecting human health. Therefore, before using biogas, H2S must be removed from it.
The commonly used biogas desulfurization methods in the industry include dry desulfurization, wet desulfurization, and biological desulfurization.
1) Dry desulfurization
Dry desulfurization is a simple, efficient, and relatively low-cost desulfurization method, which is generally suitable for desulfurization of biogas with small biogas volume and low hydrogen sulfide concentration. The basic principle of the equipment for dry removal of hydrogen sulfide (H2S) from biogas gas is a method of oxidizing H2S to sulfur or sulfur oxides using O2, also known as dry oxidation method. The composition of the dry process equipment is to put fillers in a container, and the filler layer includes activated carbon, iron oxide, etc. The gas passes through the packing layer inside the container at a low flow rate, and hydrogen sulfide (H2S) is oxidized to sulfur or sulfur oxides, remaining in the packing layer. After purification, the gas is discharged from the other end of the container.
2) Wet desulfurization
Wet desulfurization can be classified into three types: physical absorption method, chemical absorption method, and oxidation method. There is a problem of hydrogen sulfide reprocessing in physical and chemical methods. The oxidation method uses alkaline solution as the absorbent and oxygen carrier as the catalyst to absorb H2S and oxidize it into elemental sulfur. The wet oxidation method dissolves the desulfurizer in water, and the liquid enters the equipment and mixes with biogas. The hydrogen sulfide (H2S) in biogas reacts with the liquid to produce elemental sulfur. The liquids that absorb hydrogen sulfide include sodium hydroxide, calcium hydroxide, sodium carbonate, ferrous sulfate, etc. The mature oxidation desulfurization method can achieve a desulfurization efficiency of over 99.5%.
In large-scale desulfurization projects, the wet method is generally used for coarse desulfurization first, and then the dry method is used for fine desulfurization.
3) Biological desulfurization
The working mechanism of biological desulfurization is described as follows: a certain amount of air is introduced into biogas containing hydrogen sulfide, and a large amount of biological packing is installed in the reactor, which provides sufficient space for bacterial reproduction. The tower body adopts a drip filtration form, and the system water and nutrient solution (NPK) are continuously circulated and drip filtered to keep the packing moist and supplement the nutrients needed for bacterial growth and reproduction. Exclusive silk sulfur bacteria and sulfur bacteria absorb hydrogen sulfide during metabolism, convert it into elemental sulfur, and further oxidize it into sulfuric acid.
When biogas is produced from anaerobic fermentation equipment, especially during medium or high temperature fermentation, it carries a large amount of H2S. Due to the presence of a large amount of water vapor in biogas, the combined action of water and H2S in biogas accelerates the corrosion and blockage of metal pipelines, valves, and flow meters. In addition, the SO2 generated after the combustion of H2S combines with the water vapor in the combustion products to form sulfurous acid, which corrodes the metal surface of the equipment and also causes pollution to the atmospheric environment, affecting human health. Therefore, before using biogas, H2S must be removed from it.
The commonly used biogas desulfurization methods in the industry include dry desulfurization, wet desulfurization, and biological desulfurization.
1) Dry desulfurization
Dry desulfurization is a simple, efficient, and relatively low-cost desulfurization method, which is generally suitable for desulfurization of biogas with small biogas volume and low hydrogen sulfide concentration. The basic principle of the equipment for dry removal of hydrogen sulfide (H2S) from biogas gas is a method of oxidizing H2S to sulfur or sulfur oxides using O2, also known as dry oxidation method. The composition of the dry process equipment is to put fillers in a container, and the filler layer includes activated carbon, iron oxide, etc. The gas passes through the packing layer inside the container at a low flow rate, and hydrogen sulfide (H2S) is oxidized to sulfur or sulfur oxides, remaining in the packing layer. After purification, the gas is discharged from the other end of the container.
2) Wet desulfurization
Wet desulfurization can be classified into three types: physical absorption method, chemical absorption method, and oxidation method. There is a problem of hydrogen sulfide reprocessing in physical and chemical methods. The oxidation method uses alkaline solution as the absorbent and oxygen carrier as the catalyst to absorb H2S and oxidize it into elemental sulfur. The wet oxidation method dissolves the desulfurizer in water, and the liquid enters the equipment and mixes with biogas. The hydrogen sulfide (H2S) in biogas reacts with the liquid to produce elemental sulfur. The liquids that absorb hydrogen sulfide include sodium hydroxide, calcium hydroxide, sodium carbonate, ferrous sulfate, etc. The mature oxidation desulfurization method can achieve a desulfurization efficiency of over 99.5%.
In large-scale desulfurization projects, the wet method is generally used for coarse desulfurization first, and then the dry method is used for fine desulfurization.
3) Biological desulfurization
The working mechanism of biological desulfurization is described as follows: a certain amount of air is introduced into biogas containing hydrogen sulfide, and a large amount of biological packing is installed in the reactor, which provides sufficient space for bacterial reproduction. The tower body adopts a drip filtration form, and the system water and nutrient solution (NPK) are continuously circulated and drip filtered to keep the packing moist and supplement the nutrients needed for bacterial growth and reproduction. Exclusive silk sulfur bacteria and sulfur bacteria absorb hydrogen sulfide during metabolism, convert it into elemental sulfur, and further oxidize it into sulfuric acid.
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