(49b) Improved Pressure Swing Adsorption Cycles for Ethanol PSA-Distillation Systems

Pressure swing adsorption (PSA) has been the customary approach for azeotrope breaking and ethanol drying in the corn-ethanol industry.  This PSA process is typically carried at 4 atm and 440 K using zeolite 3A as the adsorbent and a relatively simple 2-bed 4-step pressure vacuum swing process (PVSA). The question addressed in this work was: Is it possible to improve the PSA process performacne by adding more complexity to the PVSA cycle schedule in terms of the number of beds and additional cycle steps? The work done to date tends to indicate that the answer to this question is, yes. In this presentation the role of four different, continuous feed, PSA cycle schedules on the performance of ethanol drying will be evaluated. The PSA variables to be discussed include the number of beds, the number of equalization steps and cycle time. The performance will be judged in terms of the ethanol purity, ethanol recovery and separations cost.