Simulation Of Bubble Column Reactor For P-Xylene Oxidation

Purified terephthalic acid (PTA) is the important feedstock in production of polyester. In the industrial process, crude terephthalic acid (CTA) is produced by p-xylene (PX) liquid phase oxidation with air. Then CTA is purified by hydrogenation obtaining purified terephthalic acid. The oxidation reactor is one of the most important equipments in the whole process. The bubble column oxidation reactor with a dehydration column was studied in this paper and the model of oxidation reactor was developed.First, the reaction of p-xylene oxidation was analyzed. Based on the theory of gas-liquid reaction, the feature number of macro kinetics was calculated. The results show that the oxidation reaction, a slow one, mainly happened in the main body of liquid phase. The reaction influenced the gas-liquid mass transfer slightly. Also the transmission properties of the bubble column were studied. According to the bubble size distribution, the gas phase in the churn-turbulent regime can be separated into two classes: large bubbles and small bubbles. Correlations for the estimation of fluid dynamics parameters were employed using two-bubble classes model.The flow field in bubble column was investigated. Backmixing was strong in the slurry phase so the slurry phase can be regard as well-mixing. Large bubbles traveled up through the column at high velocities which resulted short residence time, in a more or less plug-flow manner. Small bubbles were entrained in the slurry phase and as a good approximation had the same backmixing characteristics of the slurry phase. Base on these, the model was developed to simulate the oxidation part of the reactor and the computer program for it was also developed. The model of the dehydration column was set up using Aspen Plus as software tool. Linked this two modes in the environment of Visual Basic using software's ports, the simulation of the whole reactors was completed. The numerical results agreed with the real industrial values.The axial dispersion model of the reactor was developed and the non-idea behavior of the slurry phase was taken into account. The comparison between the computational values and the real ones presents a good agreement. The results showed that the temperature was lower at the bottom of the column and higher at the top. It caused by the rigid evaporation of the acetic acid and water near the bottom where the...