The challenge

At Rumpke, raw landfill gas contains methane, roughly 50% carbon dioxide, water, and hydrogen sulfide. Vertical wells across the landfill collect the gas and carry it through a 24-inch pipe to a pretreatment site, where hydrogen sulfide and volatile organics are removed.

CO₂ removal is the key step in achieving pipeline quality.

In 2006, Montauk began planning another upgrading plant. Rather than conventional options at the time, it evaluated newer gas purification technologies that could provide greater capacity in a smaller footprint while meeting Duke Energy’s pipeline specifications.

The solution

In 2007, Montauk selected the M-3100 PSA system, and Rumpke became the first landfill to install IVYS (formerly XEBEC) PSA technology. Located downstream of pretreatment, the landfill gas upgrading system removes CO₂ and remaining contaminants to produce pipeline-grade biomethane.

The system’s proprietary rapid-cycle technology operates at much higher cycle speeds than conventional PSA. Because faster cycling requires less adsorbent, the equipment is up to 10 times smaller than conventional PSA units. Proprietary rotary valves replace the bulky piping and switching valves used in conventional systems. These compact, low-maintenance valves reduce operating costs and the plant’s total cost of ownership over its lifetime.

Results

The utility has never shut down the IVYS PSA because of off-specification gas. It delivers product gas with purity above 96% directly into Duke Energy’s distribution system, supplying about 25,000 homes and businesses in the Cincinnati area.

Together with the existing equipment, the Rumpke landfill site processes 15 million scf/d of landfill gas at the plant inlet, making it one of the world’s largest landfill gas-to-pipeline facilities.