The heart of our system is the membrane separation unit. Membrane technology for biogas processing is a relatively new technology, but it has already proven itself. The gas treatment market has already recognized the advantages of membrane technology over other separation systems such as water scrubbing, amine scrubbing and pressure swing (PSA) systems.

Membranes for gas separation
To make an efficient CO₂/ CH₄ separation possible, the impurities must first be removed. One of the most important techniques for doing this is the use of activated carbon that absorbs undesirable substances. The membranes separate the two major gas components: CH₄ and CO₂. The separation is accomplished through the pressure difference over the membrane surface.

The high-pressure biogas is fed into the membrane and the CO₂ passes through the membrane surface to the permeate - the low-pressure side - much quicker than CH₄. The membranes are mainly pressure-driven, so the higher the pressure the more CO₂ will pass through the membrane surface.

The discharge from the membrane (the retentate) contains mainly CH₄ as the CO₂ has been pushed through the membrane surface. The CO₂-rich gas will leave the membrane on the low-pressure side of the membrane (permeate).

Multistage solutions
Pentair provides a two-stage membrane system together with a cryogenic system. This system provides two valuable products: biomethane and 100 % liquid CO₂.