Advanced VSA for Renewable Biomethane (AVSAR-Biomethane^TM)

Biogas is one of the renewable energy sources with favorable CO₂ balance. It can be formed by biological transformation of large variety of organic wastes. It primarily consists of methane (CH₄), carbon dioxide (CO₂) and small amounts of H₂S and water. The typical composition of bio-gas is Methane (CH₄): (55-65%); Carbon Dioxide (CO₂): 30-45%; Hydrogen Sulfide (H₂S): 0-3%; Moisture (Saturated). The bio-gas needs to be upgraded to increase its calorific value (Bio-gas: 21.5 MJ/m³  vis a vis Natural gas: 35.8 MJ/m³); to improve flame speed (Bio-gas: 25 cm/s  vis a vis LPG: 38 cm/s) and also to remove toxic and corrosive H₂S. The upgraded bio-gas can be used as fuel for gas-engines, boilers, fuel cells, vehicle etc.

CSIR-Indian Institute of Petroleum (IIP) has developed a Vacuum Swing Adsorption (VSA) process for producing high purity methane gas from simulated biogas at laboratory scale. Based on the process developed at laboratory scale, a pilot study was carried out at  500m³/day raw biogas feed throughput at an anaerobic digester site, run by a municipal corporation. The technology was further demonstrated at commercial scale (2.5 TPD compressed biogas meeting BIS 16087 specs. for pipeline quality biomethane).

Important parameters unique to the development:

• Process is based on simple VSA cycle configuration.
• The process is designed to operate at low pressure considering availability of biogas at low pressure.
• The process operates with low cost commercially available adsorbent.
• The process simultaneously produces high purity methane and carbon dioxide streams.
• Methane purity of >97% with over 98% recovery is obtained.
• High purity CO₂ is also simultaneously produced (Purity >95 %).
• The productivity of VSA process is 3-4 times higher than similar process reported for biogas upgradation.