Study On Solvent Recovering Process With Azeotropic Distillation In TA Production

Purified terephthalic acid (PTA) was an important feedstock in production of polyester. Usually in the first step of the process, crude terephthalic acid (CTA) was obtained via catalytic oxidation of liquid p-xylene with air. And then CTA was purified by hydrogenation. The energy consumed in solvent recovery unit was mostly in PTA production process, reducing energy consumption in solvent recovery unit was very important to PTA production, which was also beneficial to reduce the production cost and improve market competition. So this paper paid attention to a study for solvent recovering process with azeotropic distillation in TA production. Binary interaction parameter was obtained by LLE experiment data measure and regression, and then the solvent recovering process with azeotropic distillation was calculated by using the process simulation software. On this basis, the influence of some operating parameters of the solvent recovering process was analyzed. Mainly including:LLE data of methyl acetate-water, butyl acetate-water, methyl acetate-butyl acetate-water, methyl acetate-butyl acetate-water-acetic acid-p-xylene under normal pressure were obtained by experiments. The reliability of experiment method was verified through test measurement of regular system. The binary interaction parameters of NRTL equation were regressed by using LLE experiment data of methyl acetate, butyl acetate, water systems. LLE data of binary and much components of the system were estimated by obtained NRTL equation. The results showed that the model calculation values were in agreement with the experiment data. Results also showed that experiment data, selected model and regression method were reliable. The binary interaction parameters of NRTL equation in database of the process simulation software were replaced by regressed parameter values, and the solvent recovering process with azeotropic distillation was simulated again. Compared to operation data and analysis data, simulated values were basically in agreement with the practice data, therefore, the reliability of the simulation method further was verified. Based on the simulation method, the influence of some process parameters change to operation performance was studied for the solvent recovery process in TA production unit, the parameters including:theoretical plate number, feed position and side stream location etc. The research provided basic data and feasibility for energy saving, capacity expansion, and new process design of the solvent recovery unit in the PTA plant .