Siloxane Sources
Natural biogas is a mixture of various gases. In addition to the main components of methane (50% to 70%) and carbon dioxide (30% to 40%), there are many other impurity gases, including water vapor, nitrogen, oxygen, hydrogen sulfide, mercaptan, chlorinated hydrocarbons, siloxanes, etc. Siloxanes in biogas mainly come from compounds that are not decomposed during anaerobic digestion. These compounds mainly come from cosmetics, detergents, building materials, paper coatings, textiles, medicines, etc.Since these consumables are often discharged into sewage treatment plants or landfills, the biogas produced by anaerobic digestion of agricultural waste and most industrial waste generally does not contain or contains a small amount of siloxanes, while the siloxane content in landfill gas and sludge biogas is higher.
Siloxane hazards
The hazards of siloxane are mainly reflected in three aspects:1. Environmental impact: Untreated siloxane emissions will cause air pollution;
2. Equipment clogging: Under low temperature conditions, siloxane is viscous and easily clogs filters and pipeline systems;
3. Equipment damage: When siloxane is burned, it will be converted into microcrystalline silicon dioxide, which has properties similar to glass and can cause multiple hazards:
• Deactivate fuel catalysts and lubricants
• Formation of deposits on engine inner walls and surfaces of key components
• Significantly reduces heat transfer efficiency
• Accelerated equipment wear
• Significantly shorten equipment maintenance cycle and service life
How does activated carbon remove siloxane?
Activated carbon can effectively remove siloxanes from biogas due to its unique physical and chemical properties. The surface of activated carbon has a large number of micropores, mesopores and macropores, forming a complete multi-level pore system, making it an ideal choice for removing siloxanes.Non-impregnated activated carbon
Non-impregnated activated carbon mainly removes siloxanes by physical adsorption, and its developed pore structure provides a large number of adsorption sites. Micropores (<2nm) are mainly responsible for capturing small molecular siloxanes, mesopores (2-50nm) are suitable for adsorbing large molecular siloxanes, and macropores (>50nm) serve as transmission channels to ensure that the gas can quickly reach the internal pores. The hydrophobicity of the activated carbon surface is also conducive to the adsorption of organosilicon compounds, but the adsorption capacity of ordinary activated carbon for siloxanes is relatively limited.Impregnated activated carbon
Impregnated activated carbon is based on ordinary activated carbon and modified by adding specific chemical reagents (such as KOH, NaOH, KI etc.), which significantly improves the removal efficiency of siloxane. Impregnated activated carbon not only retains the physical adsorption effect, but also increases the chemical adsorption mechanism, allowing the siloxane molecules to form a stronger binding force with the activated carbon surface. This modified activated carbon has higher adsorption capacity and longer service life. It is especially suitable for processing high concentrations of siloxane and is currently the most popular choice in industrial applications.Conclusion
Activated carbon has become the preferred solution for removing siloxanes from biogas due to its excellent adsorption performance, especially the dual action mechanism of impregnated modified activated carbon. With the continuous improvement of the requirements for the use of renewable energy, the standards for biogas purification are also constantly improving.Zhulin Carbon Industry has been deeply engaged in the research and development and production of activated carbon for years, and has always been committed to providing customers with the best gas purification solutions. If you are troubled by the problem of siloxanes in biogas, contact us. Our technical team will provide the most suitable solution according to your specific needs.
