Separation of Dilute Binary Gases by Simulated-Moving Bed with Pressure-Swing Assist: SMB/PSA Processes

Abstract

Hybrid simulated-moving bed/pressure-swing adsorption (SMB/PSA) cycles are developed to achieve the relatively difficult separation of dilute enantiomeric enflurane in a nitrogen carrier gas. SMB/PSA decreases molar desorbent requirements by taking advantage of gas expansion at low pressure and the desorbent (carrier gas) present in the dilute feed. The most practical SMB/PSA configuration is a pair of two-zone SMB/PSA trains operating 180° out of phase to form a continuous (1,1)−(1,1) SMB/PSA process. With no additional nitrogen carrier gas (D/F = 0), the (1,1)−(1,1) SMB/PSA produced products having a maximum average purity of ∼86% and a maximum average recovery of ∼86%. By manipulating the recycle ratio (RR) and the bed purge ratio (BPR) at D/F = 0, either the raffinate or extract product could be produced with purity greater than or equal to 95%. To produce purer products simultaneously, pure nitrogen was added as desorbent. A maximum average purity of 99% and a maximum average recovery of 99% were att...