An eloquent optimization method was recently proposed and tested on the separation of tetrahydrofuran and water using pressure-swing distillation. The purpose of this paper is to compare the results of this rigorous optimum design with the design presented in a 1985 paper, which used heuristic engineering optimization. The new design uses more feed preheating in the low-pressure column and a higher pressure with more trays in the high-pressure column. Simulation results show that the old design has a 14% lower energy cost. (C) 2018 Elsevier Ltd. All rights reserved.