SBIR-STTR Award

A combination pressure swing adsorption (PSA)/temperatureswing adsorption (TSA) process will be developed for removingnitrogen from low quality natural gas in order to produce pipelinequality natural gas on a small scale. Nitrogen rejection remainsthe major technoeconomic hurdle for utilizing major resources oflow-quality natural gas. This will provide a methodology forproducing a valuable fuel resource out of gas resources which arecurrently either being thrown away or are left unused in thegeologic formations in which they were discovered. This projectwill develop a potentially patentable process for nitrogenrejection applied on a small scale, allowing the matching ofprocessing capabilities to the scale of low-quality gasproduction. The Phase I project will include laboratory testingof PSA parameters for different adsorbents, review and selectionof possible sites, and will define the variables and optimize thePSA process. A team has been established which will develop theapplicable technologies. The team will have access to numeroussites where low-quality gas resources are available.Anticipated Results/Potential Commercial Applications as described by the awardee:Nominally, 25% of the nation's gas reserves are lowquality. This is a resource of about 250 trillion cubic feet (TCF)of natural gas. The successful development of a nitrogen rejectionprocess provides economic, environmental, and national securitybenefits. Initial economic assessments show the pricecompetitiveness of the process. Environmental benefits arise fromthe potential capture of methane emissions (a greenhouse gas). Thelow-quality gas resources base is domestic, providing the nationwith an improved energy balance and security.

The technical and economic feasibility of the pressure swing adsorption (PSA) process was demonstrated in Phase I. The laboratory work showed that activated carbons (AC) affect the desired separation between methane and nitrogen. Some commercially available ACs were shown to have a selectivity of methane to nitrogen of three or more. A kinetics test showed that these materials adsorb methane very rapidly, a major unexpected positive result. Because the PSA process can be cycled so quickly, the AC adsorbents are much better than more expensive carbon molecular sieve materials (CMS) used by other developers. Based on lab test results and on mathematical modeling, a conceptual PSA process was developed and a preliminary demonstration plant was designed. The plant is expected to produce pipeline quality methane gas (exceeding 97% methane) from a feed stream containing only 83% methane. The plant recovers 57% of the feed methane. Some of the unrecovered methane is used as fuel for the necessary compressors, and the balance is reinjected into the producing formation at some distance from the producing well. The demonstration plant, planned for Phase II, could process 300 MCFD (thousands of cubic feet per day) of feed gas. This should yield 149 MCFD of product gas at a cost of $1.40 per MCF. Even this small plant should produce an economically competitive product since present day natural gas prices at the wellhead are generally in excess of $2.00 per MCF. A larger plant, capable of producing 1 MMCFD of pipeline gas, should have a processing cost of only $0.70-1.00/MCF. The Phase II process demonstration unit (PDU) should provide the foundation for rapid commercial deployment of this technology in Phase III. Anticipated Results /Potential Commercial Applications as described by the awardee:The Nation has nearly 250 trillion cubic feet (TCF) of sub-quality natural gas. Successful development of this process should provide economic, national security, and environmental benefits. Cost estimates show that this process could provide gas at lower prices than current levels. It uses a domestic resource - not an imported one. Environmental benefits arise from the capture of greenhouse gas: methane.