Design and control of distillation processes for methanol-chloroform separation

The binary mixture of methanol-chloroform exhibits a minimum-boiling azeotrope with ~34. mol% methanol at 327. K under atmospheric pressure. In this paper, design and control of alternative distillation processes for separation of methanol-chloroform azeotropic mixture are explored. The steady-state and dynamic simulations are carried out with Aspen Plus and Aspen Dynamics. The comparison in terms of steady-state design is done between homogeneous extractive distillation and pressure-swing distillation processes. The pressure-swing distillation process is found significantly more economical than the homogeneous extractive distillation process. Based on results, a heat-integrated pressure-swing distillation process is considered, and found economically feasible. Thus, the dynamic comparison is done between pressure-swing distillation systems with and without heat integration. The pressure-swing distillation process without heat integration can be controlled using a basic control structure, while the heat-integrated pressure-swing distillation system requires a pressure-compensated temperature control structure. Results show that dynamic controllabilities of both processes are quite similar.