Temperature Swing Adsorption of Natural Gas; an Effective Process for NG Dew Point Reduction and C4+ 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 89.1% methane, 0.85% butane and 0.69% pentane (as C4+), and other species, with total flow rate of 4.2 kmol/s, at 85 bar pressure and 35°C temperature. The cyclic operation was designed in three steps consisting adsorption at high pressure, heating by purging with the hot NG at 253°C and purge/feed ratio of 20%, 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 C5 in light NG product was reduced from 0.69% to 0.11% , and the fraction of C4 was decreased from 0.85% to 0.4% , the dew point was reduced from -9.5 to -58°C. The liquid product after bed regeneration from the heavy components was consisted 22% C4+ with 35.5% process recovery.