Improved LNG production through the advancement of CH4 + N2 separations using pressure swing adsorption

Abstract

The majority of global energy analysts predict the demand for LNG is set to grow substantially during the next 3-4 decades, particularly in the Asia-Pacific region. Impurities in the natural gas feedstock used to produce LNG pose a significant challenge to its efficient production, especially if high-quality natural gas fields are depleted and sub-quality gas needs to be used. One of the most challenging contaminants to remove from unrefined natural gas is N2 as its inert properties make it difficult to separate from CH4-dominant gas streams. Although a small number of N2 + CH4 separation technologies exist for this purpose, economies of scale dictate that cryogenic distillation, although costly, is the only technique economically viable for flows of more than 25 MMSCFD at this point. This paper examines the present state of commercial N2 + CH4 separation technologies with respect to LNG production and the present opportunities for improvement. The potential that pressure swing adsorption (PSA) has compared with competing technologies through using the low-temperature conditions available in an LNG gas processing facility is illustrated. Finally, the challenges associated with developing the proposed low-temperature PSA process and the status of the research underway to address them is discussed.