Biogas upgrading to biomethane

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.

BIOupgrade^CH4 biogas upgrading system is an automatic, easily monitored and remotely controlled refining system, that utilizes membrane technology from world’s leading membrane supplier, Air Products. BIOupgrade^CH4 enables efficient gas upgrading to over 99 % methane content.

With the reliable membrane and PSA upgrading technologies represented by Biovoima, even the highest gas quality requirements are met without any chemical or water utilization.

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Flexible operating capacities with membrane-based upgrading

Membrane is a biogas refining method where the gas to be purified flows through hundreds of thin, spaghetti-like tubes. Carbon dioxide and biomethane are separated based on their different permeabilities. Purification usually occurs in two or three stages, meaning the gas is recycled within the process. This achieves high product quality and minimal methane loss.

Biovoima´s BIOupgrade^CH4 has been designed with expertise to meet the needs and requirements of customers. The upgrading unit enables customization not only for biogas upgrading to biomethane, but also injecting biomethane into the natural gas grid. BIOupgrade^CH4 can be integrated to Biovoima`s grid injection unit, BIOadapter^CH4. In this case, upgrading unit will take care of not only biogas upgrading, but also of measuring the quantity and quality of the gas, ensuring monitoring and billing for the produced biomethane.

To ensure the highest possible utilization rate and decades-long lifecycle, Biovoima takes care of scheduled maintenance of the equipment and also provides remote support. Biovoima handles maintenance of its solutions with its expertise and also ensures that spare parts are available on time, even up to 24/7 emergency services.

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Flexible operating capacities with membrane-based upgrading

The advantages of 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

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PSA technology for large scale biomethane production

PSA technology is a frequently used way to upgrade biogas into biomethane (PSA = Pressure Swing Adsorption) in large scale biomethane production. 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.

Biovoima represents the PSA technology based upgrading units by Carbotech GmbH.

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