Effect of the Side-Stream Location and the Side-Stream Value on the Optimal Entrainer Flowrate in Thermally Coupled Extractive Distillation Columns

The extractive distillation of three binary mixtures (acetone–chloroform, acetone–methanol, and allyl alcohol–allyl acetate) in traditional two-column schemes and in sequence with partially coupled heat and material flows is considered. The optimal scheme parameters according to the criterion of total energy costs in column boilers are determined. It is shown that the use of sequence with partially coupled heat and material flows provides energy cost savings of 4.4–29.2% compared to the traditional scheme. It is found that during the extractive distillation of the allyl alcohol–allyl acetate mixture, the optimal values of the extractive agent flowrate for the two-column scheme and the scheme with partially coupled heat and material flows coincide; the optimal flowrate of the extractive agent in the scheme with partially coupled heat and material flows in the separation of an acetone–chloroform mixture is 1.28 times lower, and in the separation of an acetone–methanol mixture, it is 1.27 times higher than in the two-column scheme. The reasons for these differences are established.