BULK GAS SEPARATION OF BINARY AND TERNARY MIXTURES BY PRESSURE SWING ADSORPTION.

The PSA (pressure swing adsorption) cycle steps and the principles of operation are different in purification and bulk separation. Experimental and theoretical results for bulk separation of two binary and two ternary mixtures, where all components are desired products, are presented. The cocurrent blowdown step is crucially important to the purity of the heavy product. The effects of this step, as well as that of the fractional bed coverage during the adsorption step, can be understood through a bed loading analysis. An optimal purge/feed ratio and repressurization by the light component are important to the purity of the light product. Large temperature excursions during each PSA cycle are observed in bulk separation, and have detrimental effects on the separation results. However, thses detrimental effects can be alleviated by heat exchange between beds. Three models are developed for the PSA processes: pore diffusion, equilibrium, and linear- driving-force. The mass transfer resistance is not important for activated carbon and moderately long cycle times. Nonetheless, all experimental data are successfully predicted or simulated by these models.