Heat Integration and Control of a Triple-Column Pressure-Swing Distillation Process

Abstract

Heat integration and dynamic characteristics are critical for the triple-column pressure-swing distillation (TCPSD) processes that are used to separate ternary or multicomponent systems. In this study, rigorous steady-state simulations of heat-integrated TCPSD processes are optimized using Aspen Plus, and dynamic strategies for the different TCPSD processes are explored using Aspen Dynamics. When ±20% feed flow rates and composition disturbances are introduced, the composition/temperature cascade control structure (CSB), which uses stage 19 as the temperature-sensitive stage in the second column, exhibits better controllability than the CSA, which uses stage 4 as the temperature-sensitive stage. Three cases of partial heat integration are studied, and the first case, which uses an auxiliary condenser, is the most economic. The dynamic control strategies of the first and second cases handle ±10% feed disturbances well; however, the CSE can attain good controllability when ±20% feed disturbances are introduced. For the fully heat-integrated TCPSD process, the CSG exhibits good controllability for ±20% feed disturbances. The time that the control structures require to reach new steady states varies greatly for different heat-integrated processes.

Design and control of pressure‐swing distillation for separating ternary systems with three binary minimum azeotropes

“…Total annual cost (TAC) is often used as the objective function in the process design such as design of extractive distillation and pressure‐swing distillation, which is calculated using the following correlation from Douglas (see Eq. ). …”

“…A plant‐wide control structure with feedforward and dual temperature difference strategy is proposed in Figure based on the basic control strategy in the Supporting Information Figure S11 for the triple‐column pressure‐swing distillation to effectively reduce deviations and offsets of products purities . The detailed information (e.g., column diameter and side weir length) of three columns are given in the Supporting Information Table S21.…”

“…There are three most common and important nonconventional distillations including pressure‐swing, azeotropic, and extractive distillations that have been well developed for the separation of ternary nonideal mixtures in continuous modes. These distillations involve either changing operating pressures (i.e., pressure‐swing distillation) or at another location instead (i.e., extractive distillation) or adding an entrainer together with the feed (i.e., azeotropic distillation) . Although extractive distillations and azeotropic distillations can change the relative volatility of azeotropic mixtures by introducing an entrainer, some important characteristics of the entrainer such as solubility, toxicity, and stability require to be carefully investigated.…”

“…All these efforts are limited to pressure‐swing batch distillation without providing detailed analysis of operating pressures, which may not be widely applicable to continuous pressure‐swing distillation. Zhu et al reported a continuous triple‐column pressure‐swing distillation for separating acetonitrile/methanol/benzene nonideal azeotropic system and then they studied heat integration and control of a triple‐column pressure‐swing distillation process. Luyben also investigated the plant‐wide dynamic controllability of this complex, nonideal interacting process.…”

Process design, evaluation and control for separation of 2,2,3,3‐tetrafluoro‐1‐propanol and water by extractive distillation using ionic liquid 1‐ethyl‐3‐methylimidazolium acetate

“…5 It is difficult to separate TFP with high purity by conventional distillation. Generally, for separating azeotropic mixtures, special separation technologies are usually considered, such as azeotropic distillation, 6 extractive distillation, [7][8][9] pressure-swing distillation, [10][11][12] and membrane technology. 13 To separate TFP from its aqueous solution, Shi et al 5,14 adopted azeotropic distillation to separate TFP and water with chloroform and p-xylene as azeotropic agents.…”