(320am) An Algebraic Modeling of Dual Reflux Psa Process for High Enrichment and Recovery of Dilute Adsorbate

Pressure Swing Adsorption (PSA) is a widespread technology for gas separation and purification. However, high enrichment and recovery of dilute adsorbate are incompatible with each other in conventional PSA processes. Also, the enrichment ratio of dilute adsorbate cannot exceed the pressure ratio of the PSA process due to adsorption equilibrium relationship, which is known as a thermodynamic limitation. In order to overcome this limitation, Dual Reflux PSA process was proposed by Diagne et al., (1994). This process has two refluxes at both ends of adsorption column and the feed gas is supplied at an intermediate position of the column. This process configuration is much like that of a distillation process. Hence the enrichment ratio is no longer limited by the pressure ratio and it is determined simply by mass balance. This fact has been demonstrated experimentally and theoretically by recent studies. However, published studies on theoretical analysis of the Dual Reflux PSA considering effects of finite mass transfer rate and non-linear adsorption isotherm are few. Therefore, we analyzed the Dual Reflux PSA theoretically by means of a method called ?the short cycle time approximation? which is a highly simplified PSA model considering finite mass transfer rate and non-linear isotherm. The principal objectives of this paper are to demonstrate theoretically that the Dual Reflux PSA process exceeds the limitation and to investigate the effects of operation parameters such as feed inlet position and reflux ratios. Some results of the analysis based on the short cycle time approximation are mentioned here. The enrichment of dilute adsorbate beyond the pressure ratio is achieved when the operation parameters are properly configured. The optimum feed inlet position, where the enrichment becomes the maximum, is found to be a point in which gas concentration in the column equals the feed concentration. This fact has been proved algebraically, not numerically and agrees with findings reported in previous works on Dual Reflux PSA. This algebraic analysis was extended to explaining influences of reflux ratios and the other parameters on the process performance.