Control of heat-integrated extractive distillation processes

Pressure in many distillation columns is set such that cooling water can be used in the condenser. Pressure selection is more involved in some columns such as reactive distillation in which there is a trade-off-between temperatures favorable for reaction kinetics and temperatures favorable for vapor-liquid equilibrium. In azeotropic systems, pressure selection is critical in achieving the desired separation by consideration of distillation boundaries and isovolatility curves. A recent paper presented a striking example of pressure selection in extractive distillation. Operation at 1 atm required a solvent-to-feed (S/F) ratio of 3.52 while operating at 10 atm cut the S/F to only 0.717. The purpose of this paper is to explore the dynamic controllability of this low S/F extractive distillation system. Results show that the control structure must be modified from the conventional configuration used in most extractive distillation processes. (c) 2017 Elsevier Ltd. All rights reserved.