Effect of pressure ratio on the separation performances of different DRPSA configurations under equilibrium conditions

Abstract

Dual reflux pressure swing adsorption is a peculiar application of pressure swing adsorption with relevant separation potential. In a proper range of operating parameters, high separation performances are achieved in many applications, including complete separation in the case of binary mixtures. In this work, a new representation of the design parameters suitable for complete separation based on the semi-analytical solution of the corresponding Equilibrium Theory model is proposed for the four basic process configurations. Namely, given feed position, feed composition, and adsorbent separation selectivity, the combinations of the remaining process parameters ensuring complete separation are identified in a 3D plot. Furthermore, the same model equations have been solved numerically to explore conditions of incomplete separation, where the semi-analytical solution is not available. In particular, the sensitivity of the separation performances of each configuration to the pressure ratio has been explored. More specifically, given the region of operating conditions suitable for complete separation, selected operating conditions outside this region have been explored aimed to recover/improve the separation quality. Even though the different configurations exhibit different behaviors, the general dependence of the product purity upon the pressure ratio is quite limited and only minor improvements can be obtained with a few exceptions.

On the Design of a Dual Reflux Pressure Swing Adsorption Process

“…Before discussing the results, it is worth noting that the purity of the light component has not been considered in the optimization procedure since the heavy product stream flow rate has been set equal to that required by complete separation (that is, the feed flow rate times the CO 2 mole fraction in the feed stream, ṅ HP = ṅ feed y feed ). This way, a relationship between heavy component purity in the heavy product stream and light component purity in the light product stream is enforced through the material balance over a cycle, as discussed elsewhere . Moreover, the values of all of the plant-related parameters, such as the lateral feed position, the solid sorbent, or the bed volume, have been kept constant; therefore, this is the typical rating problem where the plant is given and only some operating parameters can be changed to improve the process performances.…”

“…This way, a relationship between heavy component purity in the heavy product stream and light component purity in the light product stream is enforced through the material balance over a cycle, as discussed elsewhere. 46 Moreover, the values of all of the plant-related parameters, such as the lateral feed position, the solid sorbent, or the bed volume, have been kept constant; therefore, this is the typical rating problem where the plant is given and only some operating parameters can be changed to improve the process performances.…”