Biogas upgrading unit – clean biomethane from biogas

Upgrading unit refines biogas into pure biomethane

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. It means that the gas treatment is needed.

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.

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PSA technology converts biogas into vehicle fuel and biomethane that is injected into the grid

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 gas pre-treatment phase before the upgrading process, i.e. gas treatment 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.

Gas purification: PSA technology flowchart. © Suomen Biovoima — Gas purification: PSA technology flowchart.

PSA-technology to convert biogas into vehicle fuel and gas grid form

PSA technology is a common way to upgrade biogas into biomethane. (PSA = Pressure Swing Adsorption). It is based on Pressure Swing Adsorption, 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 upgrading unit sizes start from 350 Nm3/h capacities, and they can be scaled upwards nearly limitlessly.

Partner: leading PSA manufacturer Carbotech

The PSA units that Biovoima represents re 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 80 pcs installed in European biogas plants.

The advantages of Carbotech PSA technology are:

Low energy consumption, 0.16-0.24 kWh/Nm3 (depending on the installed capacity)
High-quality product gas
Small (less than 1%) methane slip
Reliability: developed and robust technology
No need for water or chemical utilization
Compact plant size; modular, containerized solution
Easy, continuous operation
Automated and remote-controllable process

Flexible operating capacities with membrane upgrading technology

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 its diffusivity through the fiber wall material 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 product gas quality.

Advantages of membrane-based upgrading technology are for example the following:

Suitable for even small project, starting from 50 Nm3/h of input biogas
High product gas quality, very low methane slip
Robust and widely used technology
Lower investment cost
No need for water or chemical utilization
Easy, automated and remote-controlled operation