The aim of this work is to develop a sliding mode control scheme to keep the operation of a flash distiller in the feasible operating region. Flash distillation is characterized as a simple single-phase separation system but operationally complex because it has a strong nonlinear behavior due to the thermodynamic equilibrium, obligatory to reach the required component separation. Control of flash distillation processes must guarantee a good performance and robustness to achieve preseparation quality before entering to next fractional distillation processes. A phenomenological-based semiphysical model is used here to represent the flash distillation process. The proposed control structure tries to avoid the biggest problem of the flash distiller: its recurrent restart due to temperature disturbances in the feed flow. The suggested control schemes, applied to a given separation, allow regulation of the pressure and the liquid level of the flash drum, keeping also the concentration of propylene glycol at the flash vapor outlet near its set point, rejecting temperature disturbances. The simulation results show the features of the proposed controllers, which overcome some of the disadvantages of typical flash distiller controllers operating in design conditions.

中文翻译：

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使用可行操作区域的闪蒸蒸馏控制：滑模控制方法

这项工作的目的是开发一种滑模控制方案，以使闪蒸蒸馏器的运行保持在可行的工作区域内。闪蒸的特征是简单的单相分离系统，但操作复杂，因为由于热力学平衡，它具有很强的非线性行为，必须达到所需的组分分离。控制闪蒸过程必须保证良好的性能和耐用性，以在进入下一个分馏过程之前达到预分离质量。这里使用基于现象学的半物理模型来表示闪蒸过程。所提出的控制结构试图避免闪蒸蒸馏器的最大问题：由于进料流中的温度扰动，其经常性重启。建议的控制方案，在给定的分离条件下使用时，可以调节闪蒸罐的压力和液位，并使闪蒸蒸气出口处的丙二醇浓度也保持在其设定点附近，从而避免温度干扰。仿真结果表明了所提出控制器的特性，克服了典型的闪蒸蒸馏器控制器在设计条件下运行的一些缺点。