Industrial & Engineering Chemistry Research, Vol.47, No.9, 3138-3149, 2008
Separation of dilute binary gases by simulated-moving bed with pressure-swing assist: SMB/PSA processes
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 degrees out of phase to form a continuous SMB/PSA process. With no additional nitrogen carrier gas (D/F = 0), the SMB/PSA produced products having a maximum average purity of similar to 86% and a maximum average recovery of similar to 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 attainable at DIF = 15.0. Further decreases in molar desorbent requirements were realized by increasing the number of beds per zone and employing bed coupling during purge.