Methane Enrichment of Biogas Using Rapid Cycle Pressure Swing Adsorption

Sean Mezei¹ and Andrew Hall^2
1 QuestAir Technologies Inc, Burnaby, BC
² QuestAir Technologies Inc, Burnaby, NF

Substantial opportunities for the use of anthropogenic methane currently exist. The most common method of harnessing the energy is through on site electric power generation and heat production. However, the margins in small scale power generation are thin, and very few sites have useful heat sinks in close proximity. In order to transport the methane so it can be utilized at another location, the cost effective removal of high levels of CO2 is an essential step needed for utilizing existing natural gas distribution grids. QuestAir Technologies, Inc. has developed proprietary gas purification technology using Pressure Swing Adsorption (PSA) systems to economically remove CO2 from biogas.

The main sources of biologically generated gas streams (biogas) are landfill gas (LFG) and anaerobic digester gas (ADG). In both cases, the methane content of these gas streams is relatively low (35-65% CH4) and the carbon dioxide levels is relatively high (35-55%). Also, LFG and ADG gas streams are usually relatively small (0.1 to 5 MMSCFD), and contain trace levels of many impurities, such as siloxanes, halides, etc. The gases are also collected at roughly ambient pressure. These factors make conventional CO2 removal systems, such as amine, solvent, cryogenic or membrane plants difficult to justify due to the high, compression and/or gas pretreatment costs.

Conventional PSA systems have been proven to reliably upgrade biogas in Europe, but the economics of performing the same separation in North America are more difficult, due to the lower prices of natural gas and the absence of significant subsidies. QuestAir has utilized its unique rotary valve PSA technology to upgrade biogas at a much lower cost than previously possible, and is developing next generation technology to make another cost reduction. This paper will compare technology alternatives for making pipeline grade natural gas.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005