The Air-X process is a pressure swing adsorption process that uses a natural zeolite as the adsorbent. The process operates at low pressures, from 30 to 60 psia, and is able to remove air and/or nitrogen from methane economically in small volume plants, ranging from 1 to 5 million cubic feet per day. Applications include landfill gas, gob gas from coal mines, and small conventional natural gas fields. Conventional cryogenic nitrogen removal processes are typically designed for volumes of 50 million cubic feet per day and up, and are uneconomic for these small applications.
The process has not yet been proven beyond bench scale testing, but estimated economics are that the process will have a significant cost advantage over competitive processes.
The graphs below show estimated capital and operating costs for the Air-X process for two different feed gas streams at atmospheric pressure, one containing 15% air and 85% methane, and the other 40% air and 60% methane. Costs are estimated for a plant operating at 15 psig, with the product gas coming off at that pressure. Costs do not include additional compression for insertion into a pipeline, for example. Operating costs include one full time operator, maintenance, power at 6¢ per kWhr, and process royalties, expressed in cost per million BTU in the product gas.