Temperature Swing Adsorption of Natural Gas; an Effective Process for NG Dew Point Reduction and C۴+ Liquid Recovery

Recovery of natural gas liquid (NGL) was investigated by temperature swing adsorption (TSA) process. The process was designed with four columns of H-type silica gel adsorbent, working in a cyclic adsorption-desorption operation at high pressure of natural gas. The NG feed composition was contained ۸۹.۱% methane, ۰.۸۵% butane and ۰.۶۹% pentane (as C۴+), and other species, with total flow rate of ۴.۲ kmol/s, at ۸۵ bar pressure and ۳۵œC temperature. The cyclic operation was designed in three steps consisting adsorption at high pressure, heating by purging with the hot NG at ۲۵۳œC and purge/feed ratio of ۲۰%, then cooling with clean NG product from adsorption step, at the same pressure. Simulation of the TSA process was performed by ASPEN ADSORPTION software. The required equilibrium isotherms and kinetic parameters were evaluated by experimental investigations and fitting to the proper models. After simulation and approaching to the cyclic steady-state condition, the fraction of C۵ in light NG product was reduced from ۰.۶۹% to ۰.۱۱% , and the fraction of C۴ was decreased from ۰.۸۵% to ۰.۴% , the dew point was reduced from -۹.۵ to -۵۸œC. The liquid product after bed regeneration from the heavy components was consisted ۲۲% C۴+ with ۳۵.۵% process recovery.

Keywords:

Natural gas dew point reduction , NG liquid recovery , temperature swing adsorption , simulation , H-type silica gel adsorbent.