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CO2 Removal Biogas Systems

Solutions:
         Media
         Membrane
         Non hazardous reusable chemicals

RemovalTechnologies:

Water scrubbing
Carbon dioxide is soluble in water. Water scrubbing uses the higher solubility of CO2 in water to separate the CO2 from biogas. This process is done under high pressure and removes H2S as well as CO2. The main disadvantage of this process is that it requires a large volume of water that must be purified and recycled.

Polyethylene glycol scrubbing
This process is similar to water scrubbing; however, it is more efficient. It also requires the regeneration of a large volume of polyethylene glycol.

Carbon molecular sieves
The carbon molecular sieve method uses differential adsorption characteristics to separate CH4 and CO2. This adsorption is carried out at high pressure and is also known as pressure swing adsorption. For this process to be successful, H2S should be removed before the adsorption process.

Membrane separation
There are two membrane separation techniques:
        High pressure gas separation
         Gas-liquid adsorption

The high pressure separation process selectively separates H2S and
CO2 from CH4. Usually, this separation is performed in three stages and produces 96 per cent pure CH4.

Gas liquid adsorption is a new development and uses micro porous hydrophobic membranes as an interface between gas and liquids. The CO
2 and H2S dissolve while the methane (in the gas) is collected for use.

Activated carbon
Activated carbon impregnated with potassium iodide can catalytically react with oxygen and H2S to form water and sulfur. The reaction is best achieved at 7 to 8 bar (unit of pressure) and 50 to 70 C. Activated carbon beds also need regeneration or replacement when saturated.

Scrubbing and membrane separation
As discussed in the section on
CO2 removal, the CO2 and H2S can be scrubbed by water, polyethylene glycol solutions or separated using the membrane technique.