Energy efficient distillation by optimal distribution of heating and cooling requirements

Abstract In this paper investigations regarding optimal placement and duty distribution of internal heat exchangers in distillation columns have been carried out based on simulations. In particular the effect of adding 2, 4 and 19 internal heat exchangers to a 19 tray distillation column separating 2-propanol and methanol was studied. It is concluded that the minimum entropy production placement of the heat exchangers depends strongly on the degree of separation. The optimum is however rather flat, which indicates that optimal placement for a nominal operating point may remain nearly optimal in terms of entropy production even for significant changes in feed and product compositions. When compared to a conventional column run under the same operating conditions, entropy production for an optimally operating column with four thermally active stages (4TA) is reduced by 25% as compared to 37% for a column with six thermally active stages (6TA) column and 49% for a column in which all the trays are equipped with heat exchangers.