Activated Carbon for Biogas Purification

I. Importance
Hydrogen sulfide (H₂S) is a common corrosive pollutant in biogas that damages generators, pipelines, and fuel cells, while its combustion produces sulfur dioxide (SO₂), leading to environmental pollution. To ensure equipment operation and meet emission standards, H₂S must be removed before biogas enters downstream processes.

II. Detailed Process
XingSen columnar activated carbon effectively removes H₂S through a combination of chemical and physical adsorption, with the following steps:
1. System Design:
①Biogas passes through a fixed-bed adsorption tower filled with XingSen impregnated columnar activated carbon (typically impregnated with alkaline substances like potassium hydroxide or sodium hydroxide).
②Single or multi-tower configurations ensure continuous operation and high removal efficiency.

2. Adsorption Process:
① H₂S molecules are captured by the carbon’s porous structure and react with the impregnated chemicals to form sulfides or sulfates (e.g., K₂S or K₂SO₄), which are fixed on the carbon surface.
② The high surface area (typically >800 m²/g) and optimized pore distribution enhance H₂S adsorption capacity.
③ Physical adsorption also captures trace VOCs and other impurities.

3. Operating Conditions:
① Biogas flow is controlled to ensure sufficient contact time (a few seconds to tens of seconds).
② Temperature is maintained at 20-50°C, with humidity optimized at 40-70% to enhance adsorption.

4. Monitoring and Replacement:
① H₂S sensors monitor outlet concentrations, and replacement or reactivation occurs when H₂S breakthrough is detected.
② Saturated carbon can be processed through XingSen’s thermal reactivation service.

5. Reactivation: At 800-1000°C, adsorbed sulfides are decomposed to restore adsorption capacity, reducing carbon emissions by approximately 80% compared to new carbon production.

III. Advantages
1. High H₂S adsorption capacity (20-30% w/w) extends service life and reduces replacement frequency.
2. Low dust characteristics minimize equipment wear, making it suitable for various biogas sources.

I. Importance
Siloxanes, prevalent in landfill gas and wastewater treatment plant biogas, form silicon dioxide (SiO2) deposits upon combustion, increasing wear and maintenance costs for generators and turbines. Removing siloxanes is essential to protect equipment and ensure biogas quality.

II. Detailed Process
XingSen columnar activated carbon efficiently removes siloxanes through physical adsorption, following these steps:

1. System Design:
An independent fixed-bed adsorption tower filled with non-impregnated columnar activated carbon is used, which can be connected in series with the H2S tower or deployed as a mobile filter.

2. Adsorption Process:
① Siloxane molecules (e.g., D4, D5) are captured by the carbon’s porous structure, with optimized mesopore distribution providing an adsorption capacity of 5-10% w/w.
② The columnar shape ensures low powdering and maintains low pressure drop during prolonged operation.

3. Operating Conditions:
Temperature is controlled at 20-40°C, with humidity below 70%, and gas flow velocity set at 0.1-0.5 m/s.

4. Monitoring and Replacement:
① Gas chromatography-mass spectrometry (GC-MS) or siloxane sensors ensure outlet concentrations remain below 0.1 mg/m³.
② Saturated carbon can be reactivated or replaced.

5. Reactivation:
At approximately 800°C, organic silicon compounds are decomposed to restore adsorption capacity.

III. Advantages
1. High adsorption efficiency protects CHP equipment and reduces maintenance costs.
2. Uniform particles suit high-flow systems and support sustainable operations.