Integrated Technologies for Coal Mine Methane Utilization

摘要

Northwest Fuel Development, Inc. (NW Fuel) has developed an integrated system of nitrogen rejection and power generation technologies to optimally recover and utilize waste methane from coal mines. This integrated approach applies separate processes to methane waste streams based on their suitability as a feed for the given process. A waste methane stream that is close to natural gas pipeline quality would be processed in a nitrogen rejection unit in order to produce pipeline quality gas. In contrast, waste methane streams that are too high in nitrogen would be used directly as a power generation fuel. By combining the two processes, one can take advantage of a synergism that will yield optimal methane utilization systems. Waste methane-fueled power generating sets fabricated and operated by NW Fuel are based on modular units of 75 kW. These are aggregated for larger installations. In contrast to conventional wisdom of "economies of scale", these units benefit from economies of mass production. NW Fuel's nitrogen rejection technology utilizes pressure swing adsorption (PSA) - based processes, which are also economically competitive on a relatively small scale. Methane streams of less than one million cubic feet per day (1 MMCFD = 20 m~3/min) can be economically processed with one of NW Fuel's two PSA systems. NW Fuel has prepared the detailed design of an integrated gas processing / power generating system for a coal mine in West Virginia. A demonstration plant will be built there in 2001. The plant will have the capacity to produce 500 MCFD (10m~3/min) of pipeline quality gas and 1.2 MW of electricity.