Design and control of a pressure-swing distillation process with vapor recompression

Pressure-swing distillation is widely used to separate minimum-boiling azeotropes when the azeotropic composition has significant pressure dependence. The two columns operate at different pressures with distillate streams having compositions close to their respective azeotropes. Heat integration is typically used since column temperatures are sufficiently different to permit heat transfer. A novel modification to achieve process intensification has recently been proposed that uses vapor recompression on both columns. The study developed a complex heat exchanger network along with the design of the two columns. Dynamic controllability was not studied. The purpose of this paper is to develop a robust control structure for this process. A novel control scheme features the flowrate of the distillate recycle from the high-pressure column as the throughput manipulator with the fresh feed brought in on level control.