Digester Gas Conditioning for CHP Engines
Conditioning trains that scrub, dry, polish and boost sewage digester gas for CHP engines.
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Engine-ready gas from sewage digesters
CRA's conditioning trains take digester gas from the gas holder, remove its H₂S, water and siloxanes and deliver it to CHP engines at a steady pressure.
Stages
Scrubbing, drying, polishing, boosting
End use
CHP engines
Also removes
Siloxanes and VOCs
Supply
Skid-mounted package
What does a digester gas conditioning train do?
Digester gas leaves the gas holder wet, sour and at a low pressure, and at a sewage works it also carries siloxanes. The train removes the hydrogen sulphide in a scrubber, cools the gas so that the water condenses and drains, adsorbs siloxanes and residual H₂S on activated carbon and raises the pressure with a booster. The CHP engines then receive clean, dry gas at a steady pressure.
How it works
The train sits between the gas holder and the CHP engines, with a branch to the flare for gas the engines cannot take.
A biological scrubber, or a chemical scrubber with biological regeneration, removes the hydrogen sulphide.
Refrigerated cooling condenses the water, which drains away automatically.
Activated carbon adsorbs siloxanes and residual H₂S.
The booster lifts the gas to the supply pressure of the engines.
Clean, dry gas flows to the CHP engines, with surplus gas sent to the flare.
Key Benefits
Activated carbon adsorbs the siloxanes that would otherwise coat engine parts in silica.
Clean gas cuts the deposits and corrosion that take engines out of service.
Refrigerated drying stops water condensing in the gas lines and engines.
The booster holds the gas at the pressure the CHP engines need.
Scrubbing, drying, polishing and boosting share one design basis.
Projects That Push Boundaries
Complete gas conditioning train transforming raw digester gas into clean, usable fuel for a city utility.
Removes H2S and acidic contaminants for safe, reliable biogas use in municipal infrastructure.
The CRA Edge
CRA has more than 30 years of experience in gas handling and flare engineering.
Design, R&D and manufacturing are carried out under one roof.
ISO 9001 certified through TÜV NORD, with designs aligned with ASME, API and CE.
Designs are customised to the process needs and the regulations that apply at site.
Applications
Built to help you specify.
Sizing tools, decision guides, and technical references. Use them before, during, and after your evaluation.
Frequently Asked Questions
Why does sewage digester gas need conditioning before a CHP engine?
Sewage digester gas carries hydrogen sulphide, water and siloxanes. H₂S corrodes the engine and sours the lube oil, water condenses in the gas lines, and siloxanes burn to silica deposits. Conditioning removes them before the gas reaches the engine.
What are siloxanes and where do they come from?
Siloxanes are silicon compounds used in soaps, shampoos and other personal care products. They reach the sewage works with the wastewater, collect in the sludge and pass into the digester gas.
How are siloxanes removed from digester gas?
CRA removes siloxanes on activated carbon, which adsorbs them along with residual H₂S and other trace compounds. Drying the gas first protects the carbon.
What data does CRA need to size a CHP gas conditioning train?
CRA needs the digester gas flow range, its composition including H₂S and siloxanes, the engine make and fuel gas specification, and the site conditions.
Can the train be added to an operating sewage works?
Yes. CRA builds the train as a package that ties into the existing gas line ahead of the engines.