Thermodynamic design of methane liquefaction system based on reversed-Brayton cycle

Cryogenic Heat-Exchanger Design for Freeze-out Removal of Carbon Dioxide from Landfill Gas

“…1. Since the saturation (sublimation) pressure of CO 2 at LNG temperature (112 K) is 0.57 Pa, the mole fraction of CO 2 can be made less than 6 ppm at the point where CH 4 begins to condense, if the mixture is at atmospheric or higher pressure. For a long term operation, two identical heat exchangers are installed in parallel so that they can alternately capture or release CO 2 by periodically switching the flow directions.…”

“…A number of standard gas separation methods are applicable to the removal of CO 2 , including membrane, physical or chemical scrubbing, temperature or pressure swing adsorption (TSA or PSA), and distillation. The pilot-scale systems under recent development in U.S.A. (1,2) , China (3) , and Korea (4) have an LNG production rate at 160~2,350…”

“…For continuous production of LNG from LFG, CO 2 should be removed, because its deposition as solid or frost would increase the flow resistance of passage and might cause a blockage after a period of operation. As the required CO 2 fraction for LNG production is typically given at 50 ppm or less (5) , an efficient and convenient separation of CH 4 and CO 2 is one of the key techniques in the LFG-to-LNG conversion process. A number of standard gas separation methods are applicable to the removal of CO 2 , including membrane, physical or chemical scrubbing, temperature or pressure swing adsorption (TSA or PSA), and distillation.…”

“…Over the past decade, there have been efforts to purify and liquefy methane into liquefied natural gas (LNG) for high energy-density storage and transportation at a moderate pressure (1)(2)(3)(4) . For continuous production of LNG from LFG, CO 2 should be removed, because its deposition as solid or frost would increase the flow resistance of passage and might cause a blockage after a period of operation.…”

“…Landfill gas (LFG) is a useful resource of renewable energy whose major components are methane (CH 4 : 50~70% by volume) and carbon dioxide (CO 2 : 20~40% by volume). Over the past decade, there have been efforts to purify and liquefy methane into liquefied natural gas (LNG) for high energy-density storage and transportation at a moderate pressure (1)(2)(3)(4) .…”