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Biogas Upgrading

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Biogas Upgrading

Biogas from landfills, digesters, etc mainly comprises of methane (CH4), Carbon dioxide (CO2), Nitrogen (N2), Oxygen (O2), Hydrogen Sulfide (H2S) and Water (H2O). The raw biogas has low calorific value as it contains the above mentioned impurities. Hence it is significant to upgrade the biogas so as to use it for transportation fuel, grid injection or industrial heating purpose in order to match the composition and qualities of LPG and CNG. B-Sustain use activated carbons and molecular sieves for the removal of these impurities. B- Sustain's advanced technology of biogas upgrading system to upgrade raw biogas to bio-methane increases the fuel efficiency above 95% using the best-in-class machineries.

Steps involved in biogas upgrading

  1) Hydrogen sulphide removal

Biogas is compressed at 1 bar and fed into the Biogas upgrading system. Biogas upgradation starts with H2S removal unit. In the Biogas upgrading process the first and the foremost step is the removal of H2S from the Biogas. H2S content in biogas is typically below 1%. But it may vary based upon the raw material used for biogas generation. B-Sustain use activated carbon with catalyst to achieve the H2S content below 20 ppm.

  2) Moisture removal

After the removal of the hydrogen sulphide from biogas, the next component to be removed is moisture (H2O). Initially the biogas contains moisture content from 5 to 8%. B-Sustain removes the moisture from the biogas by cooling the biogas below 5°C. It is necessary to remove H2O before removing CO2 in VPSA.

  3) Carbon-di-oxide removal

B-Sustain use VPSA technology for removal of Carbon-di-oxide (CO2). CO2 is adsorbed on a molecular sieve with the aim of achieving the Natural gas quality, in other words improving the methane percentage in biogas. After many cycles duration, the adsorber vessel will be saturated and requires regeneration. B-Sustain achieves regeneration by reducing the pressure below the atmospheric pressure. At this pressure, CO2 will be desorbed from the molecular sieve and is blown to the atmosphere. B-Sustain introduces one or two pressure equalisation steps in order to improve the methane. B-Sustain’s VPSA technology achieves the maximum methane purity level of 98%.

  4) Gas analyser

B-Sustain uses online gas analyser to monitor the inlet biogas composition & outlet gas purity. The major components under analysis are CH4, CO2, H2O & H2S. B-Sustain use NDIR & Electro chemical method in gas analyser.

  5) Odourizing unit

For safety reasons, B-Sustain adds an odorant since biomethane is an odourless gas. Different types of odorants are available for Biomethane odorising. B-Sustain use Ethyl Mercaptan as odorant.

  6) Compression of Upgraded Biomethane

CNG Cascade filling

B-Sustain fills the upgraded biomethane in the CNG cascade or Tube trailer at 250 bar pressure. After filling, CNG cascade or the tube trailer is supplied to the industries, Hotels & colleges for Thermal application, Power generation and Transportation fuel. Biogas fuelled vehicles can reduce CO2 emissions by 75% to 200% compared with other fuels.

Grid Injection. The upgraded biomethane can also be injected into the national or regional level grid network. This can either be a high pressure gas transmission grid or a local low pressure gas distribution network.