Dynamics and control of vapor recompression distillation

Vapor recompression distillation is an energy integrated distillation configuration which works on the principle of a heat pump. The tight material and energy integration in such columns shows a potential for intricate dynamics. In this paper, a systematic modeling framework is developed which explicitly captures the discrepancies between different material and energy flows present in such columns. This feature is documented to lead to stiff dynamic equations and multiple time-scale dynamics. Through a nested application of singular perturbations, reduced order non-stiff models are derived which capture the dynamics in each time-scale. A hierarchical control strategy is then proposed exploiting this timescale multiplicity. A case of propane-propylene separation is considered to illustrate these results and demonstrate the effectiveness of the proposed control strategy via a simulation case study. (C) 2009 Elsevier Ltd. All rights reserved.