Studies On The Process Simulation And Optimization Of P-Xylene High-temperature Oxidation Process

Purified terephthalic acid(PTA), one of the most important feedstocks of polyester, is produced by p-xylene(PX) liquid phase oxidation. According to the difference of oxidation temperatures, current related patents and techniques can be classified as high-temperature oxidation technology(191~205℃), mid-temperature oxidation technology(185℃), and low-temperature oxidation technology(160℃). High-temperature oxidation technology is adopted by most PTA production, and it is also the base of other PX oxidation technology. In order to better understand the process operation and develop the novel PTA techniques, a comprehensive research that follows the methodologies of chemical engineering and process system engineering was carried out to study high-temperature oxidation process units' modeling and develop a process simulator, which could contribute to PX oxidation process design and rebuild. At First, through compare and investigation of PX oxidation processes, comprehended character and design principles of high- temperature oxidation technology. Second, appropriate physical properties methods were provided. The impact of property calculation on the simulation result is great. Equilibrium calculation and the bases of property calculation have been mainly explained. Equilibrium calculation includes vapor-liquid equilibrium of association mixture containing acetic acid, vapor-liquid-liquid equilibrium of acetic acid-water-butyl acetate, solid-liquid equilibrium and gas-liquid equilibrium. Other physical properties such enthalpy, transport property est. were took into account too. Furthermore, Mathematic models of oxidationprocess key units based on the first principle have been developed, and the effects of units' operation conditions were studied. Based on these, a sequential modular method was employed to simulate a specified high-temperature oxidation process, simulation results were tested with industrial data. At last through process simulation and pointing out bottlenecks of the process, several optimal improvements of this high-temperature process were proposed. The optimized flowsheet and process operation parameters were also completed by process simulation. Studies on PX high-temperature oxidation are meaningful fundamental work. The simulation and optimization of PX high-temperature oxidation process completed in this research has great value of current process rebuilding and new PX oxidation process development.