Correlations between adsorbent characteristics and the performance of pressure swing adsorption separation process

In the pressure swing adsorption (PSA) technique for gas separation, the working performance of the adsorbent determines the efficiency of the separation unit. Excellent kinetic performance, high adsorption capacity, and selectivity are all critical for the utilization of adsorbents. This work presents a 4-bed PSA model for H2/CO2 separation to evaluate the real-time H2 purification capability of adsorbents with different kinetic performance, adsorption capacity, and selectivity. The experimental data on a test-scale PSA apparatus were used for model validation. The purity of H2 at the outlet was exactly 99% and the H2 recovery rate ranged from 70% to over 95%; hence, the extent of gas recovery was representative of the working performance. Theoretical analysis of the PSA process indicates that H2 is discharged at the blow-down and purge steps, and that the amount of H2 wasted in these steps is inversely proportional to the adsorption capacity and selectivity. This inverse relation was demonstrated by simulation, in which the correlation coefficient reached 0.99. When the kinetic performance was poor, the kinetic parameter ka-CO2 was less than 0.1, and separation was highly dependent on the adsorption and desorption rate. When ka-CO2 > 0.3, the dependency was not evident. The simulation results were used to analyze the limitations of the kinds of CO2 adsorbents, identify areas of improvement, and thus achieve better working performance.