Optimal Control Problem in Batch Distillation Using Thermodynamic Efficiency

Abstract

In this work we have optimized a batch distillation column as an optimal control policy problem. We used the optimal constant reflux policy for the process, and the objective function is to maximize the thermodynamic efficiency for a fixed time given a product concentration. The simulation model of the column considers its complete dynamics, and it has been formulated as a nonlinear programming problem for the solution of the thermodynamic efficiency. We use a SQP based dynamic optimization technique in this work. The procedure is shown for the separation of a binary mixture Benzene + Toluene. The achieved accumulated thermodynamic efficiency was close to 80%. Also we have compared with the optimal control problem of the maximum distillate for the same separation above, and we can observe that in the problem we proposed, less reflux is required, and even when thermodynamic efficiency in the problems is quite close, the energetic requirement in the problem we propose herein is smaller.

From modeling to virtual laboratory development of a continuous binary distillation column for engineering education using MATLAB and LabVIEW

“…The LabVIEW language was chosen, which is able to deliver the required user experience, and it is frequently used by chemical engineers [22]. Three code implementation methods were evaluated: (a) the "Formula Node" (C language), (b) the "Mathscript Node" (MATLAB language) and (c) equation reading from dll file using the "Call Library Function Node".…”

Missing Components in Multicomponent Batch Distillation and Optimal Control

“…The optimization problems in batch distillation mostly involve optimal control problem where the time-dependent reflux profile is determined by optimizing some performance index. These problems are described below. Maximum Distillate Problem–where the amount of distillate of a specified concentration for a specified time is maximized − Thermodynamic Efficiency Problem–where the thermodynamic efficiency for a specified concentration of distillate at a specified time is maximized − Minimum Time Problem–where the batch time needed to produce a prescribed amount of distillate of a specified concentration is minimized − , Maximum Profit Problem–where a profit function for a specified concentration of distillate is maximized ,,, …”

“…Thermodynamic Efficiency Problem–where the thermodynamic efficiency for a specified concentration of distillate at a specified time is maximized − …”

Batch Distillation: Thermodynamic Efficiency

“…According to Equations (44), (45), (46) and (47), the thermodynamic efficiency not only depends on the reflux ratio but on the concentration of components in both phases and the kind of mixture. A convenient way to express thermodynamic efficiency is the average thermodynamic equation used by Zavala Loría (2004), Zavala et al (2007), Zavala and Coronado (2008). and Zavala et al (2011) to solve the maximum thermodynamic efficiency problem:…”

“…The analysis of thermodynamic efficiency in a batch distillation column has been presented by Kim and Diwekar (2000), Zavala-Loría (2004), Zavala et al (2007), Zavala & Coronado (2008) and Zavala et al (2011). The first work only developed expressions to calculate thermodynamic efficiency while the rest of the works developed expressions to calculate thermodynamic efficiency and have applied them to a new problem of optimal control: Maximum thermodynamic efficiency.…”