Abstract
In this study, a solvent dehydration column of purified terephthalic acid (PTA) plant was used as the research object. Based on a dynamic model of the solvent dehydration column, a dynamic sensitivity analysis of the key parameters was carried out using Aspen Dynamics. After the dynamic model reached stability, the reflux rate, methyl acetate concentration, and reflux temperature of the solvent dehydration column were adjusted and the changes of the key separation indexes under the corresponding disturbance were analyzed. According to the analysis results, a sensitive plate temperature controller was added to carry out the dynamic sensitivity analysis. In addition, the acetic acid (HAc) concentration of the bottom of the column was found to be unstable in the dynamic sensitivity analysis. Considering the HAc concentration controller of the column bottom, two control strategies were designed. By analyzing the dynamic response of the feed flow disturbance under different control strategies, a more suitable control strategy under different conditions was obtained. From this, a reasonable method could be derived to design the control strategy, thereby providing a theoretical basis for further real-time optimization and advanced control of solvent dehydration in a PTA plant.
Highlights
Purified terephthalic acid (PTA) is an important raw material in the polyester and textile industries
For control strategy 1 (CS1), considering that the water content in F1 was the highest, it exerted a great influence on the heating capacity of the column
CS2 had a better performance than CS1 proven to control the HAc dehydration column well
Summary
Purified terephthalic acid (PTA) is an important raw material in the polyester and textile industries. Some studies were conducted on the design of dynamic modeling and control strategies for HAc dehydration systems, no dynamic sensitivity analysis has ever been performed. HAc dehydration with NPA as the entrainer was studied, considering the influence and recycling of the unreacted precursor, PX, and the byproduct, MA, in the solvent, HAc. The steady-state model of the five-component mixture described in our previous research [24] was used as the basis. The obtained dynamic sensitivity analysis results better described the performance of the solvent dehydration column in real time, and provided a more accurate basis for the design of the dynamic model’s control strategies. The theoretical basis and method guidance were provided to design the control scheme and to achieve further real-time optimization and advanced control for solvent dehydration in the PTA plant, and even for the industrial HAc dehydration process
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