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EPO grants Evonik patent for three-stage membrane biogas purification process

The European Patent Office (EPO) has granted Evonik Fibres GmbH, an Austria-based subsidiary of global speciality chemical major Evonik Industries AG, a patent for a three-stage process for membrane-based purification of biogas and natural gas. In addition to the patents granted in the relevant markets in America and Asia, Evonik's three-stage membrane process now has legal protection in all key European markets.

A SEPURAN Green membrane cartridge consists of several thousand hollow fibres manufactured from high-performance polymers and bundled in a stainless steel vessel. The ends are embedded in a resin. The membrane cartridge is contained in a closed housing unit.(photo courtesy Evonik Fibres).

In the gas separation process – also developed by Evonik – binary gas mixtures such as raw biogas, which consists primarily of biomethane and carbon dioxide (CO2), can be separated very efficiently and cost-effectively. In addition to increased yields and lower equipment and energy requirements – a second compressor is no longer required – the membrane process eliminates the need for additional purification so that the enriched gas can be fed directly into the natural gas network.

Gas separation with hollow-fibre membranes

At the core of the separation process are the innovative hollow fibre membranes of the company’s SEPURAN Green brand. Introduced to the market for biogas upgrading in 2011, these consist of a high-performance plastic, developed by Evonik, which can withstand extreme pressure and temperatures.

According to the company, the membranes also have excellent selectivity. In combination with the three-stage separation process, recycling streams can be minimized which helps to optimize the energy costs of biogas processing plants.

With the purchase of the SEPURAN Green membranes, contract partners – plant engineering companies – also receive a license to use this three-stage separation process. In turn, when a company buys a biogas processing plant with these membranes that has been constructed by the said contract partners, the plant can be operated using the patent-protected process.

Deployed in over 100 biogas plants worldwide, the product family includes membranes for biogas processing, nitrogen generation, and helium and hydrogen processing.

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