Four-Bed Vacuum Pressure Swing Adsorption Process for Propylene/Propane Separation

A vacuum pressure swing adsorption (VPSA) using zeolite 5A was studied experimentally and theoretically. An equimolar mixture of propylene/propane was used as a feed gas for an eight-step, four-bed VPSA process. Isotherm data of zeolite 5A at various temperatures and breakthrough curves of propylene and propane for both adsorption and regeneration steps were obtained to acquire the input parameters for the test runs with the pilot plant. Experimental measurements by the pilot plant have been obtained between a maximum pressure of PH = 5.8-6.4 bar and a minimum pressure of PL = 0.1-0.05 bar at a constant temperature of 70 (degree)C. The effects of feed rate and dilution with H2, purge rate, and vacuum pressure on the product purity and recovery were also investigated via experimentation. Using a feed rate of 320 NL/h of a mixture of 50% propylene/propane at 70 (degree)C, a purity of 92% propylene and a recovery of 29% were obtained. Comparison of the results from the experiments and the simulation gave a reasonable agreement.