Biogas upgrading unit refines raw biogas to biomethane that can be injected into the natural gas grid or used as transport fuel.
In addition to methane, raw biogas typically contains about 35-40 % carbon dioxide, as well as small amounts of water, nitrogen, oxygen and impurities. For biogas to be used, for example, in a car engine, most of these gases must be removed before being pressurized and used as transport fuel.
Biogas upgrading unit is a solution to produce high-quality biomethane out of raw biogas. Upgraded biomethane is similar to natural gas and it can be used as vehicle fuel and injected into the natural gas grid.
With the robust and market-leading PSA and membrane upgrading technologies represented by Biovoima, even the highest gas quality requirements are met without any chemical or water utilization.
PSA technology is a frequently used way to upgrade biogas into biomethane (PSA = Pressure Swing Adsorption). It is based on Pressure Swing Adsorption principle, where a carbon dioxide selective molecular sieve captures the raw gas CO2 in certain pressures and releases it in another. Moisture and impurities of the raw gas (such as hydrogen sulfides or siloxanes) are removed in the pre-treatment phase before the upgrading process.
With a bit different variation, PSA technology is suitable for refining biogas, landfill gas or pyrolysis gas. Feasible PSA upgrading unit sizes start from 350 Nm3/h capacities, and they can be scaled upwards nearly limitlessly.
Membrane biogas upgrading technology is based on gas flow through hundreds of spaghetti-like thin fiber tubes with selective wall material. The separation of carbon dioxide occurs because of its diffusivity through the fiber wall material that is different compared to methane. As carbon dioxide “escapes” through the walls, methane travels to the other end of the tubes and is collected without CO2. This cycle is then repeated typically in two or three process steps to gain high enough quality of the end gas.
Advantages of membrane-based upgrading technology are the following:
The PSA units that Biovoima represents are developed and manufactured by Carbotech GmbH. Carbotech is one of the most advanced PSA developers in the world, and they have more than 800 established gas treatment plants, of which more than 100 pcs are installed in connection with biogas plants.
The advantages of Carbotech PSA technology are: