Gas goes green

Jon Lawson

Breakthrough process uses biogas to produce bio-LNG and bioCO2, and lower biomethane tariffs

Cryo Pur has selected the UK AD & BIOGAS tradeshow held July to be its official launch into the British biogas industry. With its innovative technology, the company can produce bio-LNG (Liquid Natural Gas) using an energy-efficient process that effectively minimises polluting emissions. The breakthrough in this approach is in how it recovers the CO2 by-product in liquid form, thereby creating a high level of purity that can be reused industrially.

Cryo Pur is a company that specialises in the design and manufacturing of systems for cryogenic biogas upgrading and biomethane liquefaction. The Cryo Pur system generates two products from biogas: liquid biomethane (or bio-LNG) and BioCO2. The system treats biogas generated by all kinds of waste: agricultural waste, industrial waste, sewage sludge and household waste.

There are three primary advantages of the system: cryogenic biogas upgrading and biomethane liquefaction combined in a single energy-efficient process; the separation of CO2 at a grade of purity high enough for industrial valorization; and the separation of air gases (nitrogen and oxygen) during biomethane liquefaction.

The advantage of bio-LNG itself is that it allows efficient biomethane transportation, beyond the reach of the natural gas grid. It represents a sustainable supply of renewable fuel for heavy goods vehicles, characterised by: reduced greenhouse gas emissions; reduced emissions of fine particles; reduced NOx emissions; and reduced noise pollution.

The technology

Cryo Pur technology is adapted for biogas flow rate of 70 to 2,000 Nm3/hr. The undesirable components contained within biogas (H2O, H2S, COV, siloxanes, CO2) are captured through cryo-condensation, freezing each component for optimal biogas upgrading.

The CO2 is retrieved in liquid form, the extremely high level of purity enabling revalorization. Once purified, the biomethane fulfills the characteristics necessary to be injected into the natural gas grid. To be transported to a valorization site or for use as fuel for HGVs, biomethane is liquefied in the form of bio-LNG.

The key to Cryo Pur technology is that it performs all of these functions with minimal electric energy consumption, in the area of 0.5 kWh/Nm3 of raw biogas, for both upgrading and liquefaction.

There are a number of benefits associated with this cryogenic upgrading. First is zero loss of biomethane and optimal availability of the installation. Next, the solution is adaptable to high variations of biogas flow rate. Heat recovered from the refrigeration units is reused for the digester. Finally, the solution creates a pure biomethane product and pure bioCO2 product.

There are two key advantages of the Cryo Pur biomethane liquefaction: the separation of air gases (nitrogen and oxygen), allowing the valorization of landfill biogas; and minimal consumption of electric energy through the association of cryogenic upgrading and liquefaction

Real-world reference

An industrial demonstrator was built in partnership with Suez-Environnement as part of the BioGNVal project, and partially funded by the ‘Invest in the Future’ programme run by the ADEME (French Environment and Energy Management Agency).

The demonstrator performs biogas upgrading and biomethane liquefaction on biogas from sewage sludge, as well as the separation of bioCO2. The demonstrator is dimensioned for a nominal debit of 120 Nm3/h of biogas.

During 2014, the demonstrator successfully performed all of its functions at the CNPP public utility site at Vernon: cryogenic CO2 capture; biomethane liquefaction; and nitrogen and oxygen separation.

In 2015, the demonstrator was installed at the Valenton water treatment plant, the second biggest in France, run by the SIAAP (public society serving the Paris region).

GNVert (Engie) and IVECO are also partners in the BioGNVal project, providing the Bio-LNG distribution station and the heavy goods vehicle Flex Fuel gas/Bio-LNG respectively.

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