Homepage > Gas Processing Systems > Landfill Gas Upgrading

Landfill Gas Upgrading

While digesters normally require only carbon dioxide removal from the product gas, landfills generally have issues with both carbon dioxide (CO₂) and nitrogen (N₂) in the feed gas.  Guild Associates' approach to landfill gas upgrading has included pairing the Molecular Gate^TM N₂ rejection technology with CO₂ membranes, as well as a dual-Pressure Swing Adsorption (PSA) systems, the first to primarily remove CO₂ and the second to remove N₂.  

The unique dual-PSA approach results in a simplified system that is easy to maintain and operate.  The feed gas is compressed to 110 psig, then cooled in order to remove the bulk of the moisture in a condensate trap.  The resulting feed gas is then re-heated using the waste heat of the compressor and fed to the CO₂ PSA.  The CO₂ PSA is filled with Molecular Gate^TM adsorbent that has been pore-sized controlled to preferentially adsorb CO₂, letting the methane and nitrogen pass.  In the CO₂ PSA step, CO₂ is removed from a typical 30% range down to less than 0.5%.  Also removed in this step is residual moisture (to <150 ppm), siloxanes, VOCs and hydrogen sulfide (H₂S).  

The product gas from the CO₂ PSA is fed to the N₂ PSA which removes the nitrogen to pipeline quality.  THe resulting product gas of the N₂ PSA is injected in to the local natural gas grid at 90 PSIG.  In order to improve the overall methane recovery, about 15% of the feed gas is recycled back to the N₂ PSA feed, which increases the methane recovery of the N₂ PSA to 88%.  The overall plant methane recovery is about 81%.  The N₂ tail gas is fed to a generator for local power use.

The Guild Associates' Molecular Gate^TM technology enables the system to be efficient, easy to operate and maintain.  There is no media to replace on a regular basis, as the Molecular Gate^TM media is regenerable and will last the lifetime of the equipment.  

The video below describes the operation of the Guild Associates dual-PSA system at the Billings City Landfill in Billings, Montana.  





Do you have a project in mind?  Download our CUSTOMER QUESTIONNAIRE and send the completed form to Guild Associates.  If you have questions or want to discuss your specific application, contact Paul Baker at 614-760-8013 or email to at Information Requests.