Design And Process Simulation For Purified Isophthalic Acid Manufacture

In this thesis, the process for the production of purified isophtalic acid (PIA) was studied systematically by means of experimentations and computer simulations. The dissertation presented a novel method and scheme about the separation of mixed xylene, which was proved to be an effective way to reduce prices of highly purified m-xylene (MX) feedstock. The solid-liquid equilibrium thermodynamic data at high temperature for the production of PIA was greatly enriched. The computational model of the reactor for liquid phase oxidation of MX to isophtalic acid (IA) was built, the simulation calculation was conducted and the model validation was performed. The whole process for the production of PIA which included the oxidation and purification sections was simulated. The result could provide theoretical basis for setting up manufacturing equipment and instructing practical operation for the production of PIA. The main works can be summarized as follows:(1) On the basis of the crystallization thermodynamic analysis, the dissertation brought forward a scheme using mixed xylenes as feedstock for producing mixed PX and MX, and developed the mathematic models for every unit throughout the entire process using Matlab software. Finally, the implementation scheme and feasibility analysis about the process were discussed. It turned out that this novel method about the separation of mixed xylene could produce mixed PX-MX with high purity as the final products which could be used in the subsequent process of oxidation.(2) Through the refining working section in the process for the production of PIA, a self-developed pilot equipment based on the solid-liquid equilibrium theory was used to measure the solid-liquid equilibrium thermodynamic data in a wide range of temperature. More than anything, dissolubility of PIA in water at high temperature (473.15-523.15K) which had not been reported at present was measured for the first time in this thesis. The Apelbalt empirical equation was applied to correlate the experimental data and then predict the dissolubility of PIA in water at different temperature which could be used in the modeling and simulation of the purification section of PIA.(3) The model of continous gas-liquid-solid stirred tank reactor-four condensors for the oxidation of MX is established, validated and scaled-up by using Aspen_Custom_Modeler software. The results showed that the model has the advantages of high accuracy and predictability. On this basis, an annual 250kt PIA oxidation equipment of size-enlarged plant is designed with investigating influence of various factors on reaction process by computor, which provides thoeral support for expansion of existing installations and process optimization.(4) The whole process for the production of PIA containing oxidation and purification sections was modeled and calculated by Aspen_Custom_Modeler and Aspen_Plus. The thesis simulated the whole production process of PIA with the scale of 250kt annually, determined the main technology parameters in each unit and investigated the factors that influenced the process. By giving out the main simulation process and simulation results, this dissertation provided theoretical guidance and data support for improving the present equipment and design of new equipment for the production process of PIA.