Industrial & Engineering Chemistry Research, Vol.49, No.4, 1848-1858, 2010
Experimental Study of a Dual Reflux Enriching Pressure Swing Adsorption Process for Concentrating Dilute Feed Streams
A dual reflux (DR) enriching pressure swing adsorption (PSA) process with two beds and an intermediate feed located at z/L = 0.5 was studied experimentally for concentrating a dilute feed of ethane in N-2 using MeadWestvaco BAX-1500 activated carbon. A five-step cycle was used with feed, light reflux, and heavy reflux steps carried out simultaneously, and cocurrent depressurization and heavy product pressurization steps carried out simultaneously during different segments of the cycle. A parametric study showed that the light reflux flow rate, feed/heavy reflux step time, heavy product flow rate, and ethane feed mole fraction all had significant effects on the process performance in terms of purity and recovery. It also showed that it was relatively easy to concentrate ethane using a pressure ratio of only 7. The average of 19 runs with an ethane feed concentration of 1.38 vol % gave an ethane enrichment of 45.8 (63.2 vol %) and ethane recovery of 84%, while producing N-2 at high purity (99.8 vol %) and recovery (>99%). Overall, this study showed that a DR enriching PSA process is well suited for concentrating dilute hydrocarbon feed streams and producing the light component at both high purity and recovery.