Dynamic modeling, simulation, and optimization of hydropurification reactor and crude terephthalic acid purification system troubleshooting
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Date
2014
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Publisher
Universiti Teknologi Malaysia
Abstract
Purified terephthalic acid (PTA) is a raw chemical utilized in polyester production plants. In the PTA production process, para-xylene is oxidized to crude terephthalic acid (CTA), which has to be purified. The CTA hydropurification process is carried out in a fixed-bed catalytic reactor consisting of palladium supported on carbon (0.5 wt. % Pd/C) catalyst. The purpose of this study is to dynamically model, simulate, and optimize the hydropurification reactor and troubleshoot the CTA purification system. In the first step, first principle model (FPM) was developed incorporating Pd/C classical catalyst deactivation equation to model the initial reactor system. However, the classical catalyst deactivation equation does not reflect the actual plant catalyst deactivation performance. Hence, in the second step a hybrid model which combines the FPM with artificial neural network capable of predicting a more accurate catalyst deactivation mechanism was established. In the third step, the reactor performance was optimized by manipulating the critical impurity to increase the rate of production. Finally, an expert system to troubleshoot the CTA purification system was established employing fuzzy logic in order to ensure the system could be run at its optimal conditions as suggested by the models. All models were coded into Matlab 2010b environment. The four models were validated by applying the data of an industrial hydropurification reactor and verifying the results with the plant owners. The result of the hybrid model gave 32 percent more accuracy as compared to the FPM. 4- carboxybenzaldehyde (4-CBA) was found to be the major contributor to the catalyst deactivation affecting the reactor performance. Uncontrolled 4-CBA also led to higher benzoic acid and carbon monoxide (CO) being produced as side reaction, where CO might become a poison to the palladium catalyst. Increase of feed flowrate, feed concentration, and production rate was also found to adversely influence the reactor operation.
Description
Thesis (PhD. (Chemical Engineering))
Keywords
Chemicals—Purification, Terephthalic acid, Catalyst poisoning