Comparison of Separation Alternatives for Two Industrial C6-C7 Aliphatic Hydrocarbon Mixtures Including Stacked Complex Sequences

Distillation configurations are optimized and compared for two industrially relevant C6-C7 aliphatic hydrocarbon mixtures: methylcyclopentane/cyclohexane/methylcyclohexane (MCM), which is formed during the rectification of hydrocracked coal tar, and lights/methylcylopentane/cyclohexane (LMC), which is a byproduct in the manufacture of caprolactam. Design alternatives considered include conventional and complex sequences with and without column stacking (CS) and dividing-wall columns (DWCs). The results show that stacked complex sequences (SCSs) outperform DWCs in both cases, reducing cost relative to the conventional sequence by 13.1% (MCM) and 17.1% (LMC) compared with 1.7% (MCM) and 7.1% (LMC) for DWCs. This suggests that SCSs should be considered to be a strong candidate for saving energy and reducing cost in multicomponent distillation.