Comparison of extractive distillation and pressure-swing distillation for acetone/chloroform separation

Two of the most common methods for separating a binary homogeneous azeotrope are pressure-swing distillation and extractive distillation. The former is effective if the composition of the azeotrope changes significantly with pressure. The latter method is effective if a suitable solvent can be found. This paper compares the steady-state design and the dynamic control of these two methods when applied to the acetone-methanol binary system. The minimum-boiling azeotrope at 1 atm contains 77.6 mol % acetone at 328 K. At 10 atm the azeotropic composition is 37.5 mol % acetone at 408 K, so pressure-swing separation is feasible. Extractive distillation is also feasible using water as the solvent. Both systems require two distillation columns. Purities of the two products are set at 99.5 mol %. Results show that the extractive distillation system has a 15% lower total annual cost. However, a third component (water) is introduced that appears as trace impurities in both the acetone and methanol products. It is al...