Nitrogen rejection continues to be the major technological and economic hurdle for producing pipeline quality gas from low-quality gas resources. Numerous types of processes have been proposed for nitrogen rejection, but pressure swing adsorption is one of two that have been technically demonstrated. Unfortunately, it has not been proven economically competitive. This project involves exploration of the technical and economic viability of a continuous pressure swing adsorption (CPSA) process. In Phase I, it was demonstrated that activated carbons (AC) and zeolites can effect the desired separation of nitrogen from methane. A significant discovery during Phase I was that 4A zeolites exhibited nitrogen selectivity in the process because of the kinetics of nitrogen versus methane adsorption. This provides the potential option of using either a methane-selective adsorbent, AC, or a nitrogen-selective adsorbent, 4A zeolite, in the CPSA process. Even though the simple CPSA cycle is constrained in its upgrading capabilities, the addition of process engineering unit operation enhancements provides the potential for upgrading a wide variety of sub-quality gases to pipeline quality natural gas. In Phase II, a demonstration plant will process 300 MCFD (thousands of cubic feet per day) of feed gas, which at this small scale, can cost less than one dollar per MCF of product. The building of a larger plant, capable of producing three million cubic feet per day of pipeline gas, could have a processing cost of only $0.48/MCF of product.Anticipated Results/Potential Commercial Applications as described by the awardee: The Nation has nearly 250 trillion cubic feet of sub-quality natural gas. Successful development of this process should provide economic, national security, and environmental benefits. Cost estimates show that this process can provide gas at lower prices than current levels and uses a domestic resource. Environmental benefits also arise from the capture of methane, a greenhouse gas.
