Simulation And Study On Acetic Acid Recovery System For The Production Of PTA

Purified terephthalic acid (PTA) is useful in a diverse variety of industrial applications. For example, PTA is starting material for producing polyesters including polyethylene terephthalate. PTA is typically produced by a reaction of paraxylene with molecular oxygen in the presence of catalysts. During the production process, acetic acid is used as a solvent of terephthalic acid. Presently, there are mainly three patent technologys have been employed in the PTA plants. They are Amoco technology, ICI technology and MPC technology.This paper focuses attention on the research and analysis of the recovery of acetic acid coming from oxidation section. The model of the flow process which was industrialized was set up using chemical software tool. The simulation result shows that the selected method suits the system well. Based on that, a new process scheme of acetic acid dehydration system was put forward for certain domestic plant which produces PTA 50t/a. Optimum process design and operating condition were ascertained. Investment and energy consumption of two methods were compared.First of all, the acetic acid dehydration process with normal butyl acetate as entrainer simulated for certain domestic plant which product PTA 25t/a. The decanter, the solvent azeotropic distillation tower and the recovery tower were calculated respectively using DECANTER and RADFRAC models. Due to the non-ideal behavior, NRTL-HOC and UNIQUAC-HOC model was used to depict vapor-liquid phase equilibrium behavior of this system. In addition, another acetic acid dehydration system was simulated. In that, normal propyl acetate was entrainer. UNIQUAC-HOC model as the global property methods was used to calculate the DECANTER and RADFRAC models. The appropriate convergence method and order were selected. The results of simulation accord with the operating data well, which proved that the calculation method and the software are credible.On the basis of that, a new acetic acid dehydration process, in that normal butyl acetate as entrainer, was simulated. The output and hydraulics character were calculated. Another, a new acetic acid dehydration process, in that normal propyl acetate as entrainer, was designed. The optimum results are gotten by simulation of changing the value of some variable such as feed position and theoretical stages.The optimum value can be used to guide industrial design.Both normal propyl acetate and normal butyl acetate as azeotropic agent are contrast to each other according to operational data.