Subambient temperature swing adsorption utilizing cold energy from liquefied natural gas

Abstract

This study proposes a CO2 capture process by temperature swing adsorption (TSA) using latent heat of evaporation for liquefied natural gas (LNG) as a cold energy source, which is currently unused and discarded into seawater. The proposed subambient process has several advantages: (1) the total energy cost can be saved by the LNG cold energy; (2) the equilibrium capacity of CO2 at subambient temperature can be increased substantially; and (3) water in the flue gas which would lead to deterioration of the adsorbent can be removed by a pretreatment step utilizing LNG cold energy. For the adsorbent in the TSA system, zeolite 13X, MIL-101, UiO-66, and CPL-1, which are considered effective for CO2 adsorption in the subambient, were considered and adsorption isotherm data were obtained at subambient conditions. Comparisons of these adsorbents were carried out using a rigorous dynamic model of the TSA process. It was found that CPL-1 gives a high recovery rate of 70% and purity of 95%. It was also found that the proposed system has the potential to capture up to 6% of the CO2 emitted from Japan.