Simulation Of Purified Terephthalic Acid Process

Purified terephthalic acid (PTA), one of the main feedstock of polyester, is usually produced by liquid oxidization of p-xylene (PX). The byproduct, 4-carboxybenzaldehyd (4-CBA) is reduced by hydrogenating so that the purity of the product can achieve the industrial requirement. About this process, the mechanisms in reaction, phase equilibrium, gas-liquid mass transfer have been researched and mastered by our group. With all the knowledge, this paper will develop the software to simulate the whole process including oxidation and hydrogenation, and provide a basical platform for industrial application.Basical databases is supplied in this paper, mechanism models of all the units and the whole process are constructed which agree well with the industrial data. Advanced simultaneous equations method and parallel calculating are applied to simulate different PTA processes, and the interface of the program is developed, too.The thesis includes mainly following four parts.The Thermodynamic Databases of PTA ProcessThe thermodynamic databases are significant for mechanism models of units, while the thermodynamic equlibria of PTA process are complicated, including Vapor-Liquid\Gas-Liquid\Solid-Liquid\Liquid-Liquid equlibria in the same time. With HOC and UNIQUAC models, this paper provides databases to calculate all kinds of equilibria and enthalpy of PTA process which considers 13 materials. Necessary parameters are correlated and a good agreement is obtained.Mechanism Models of Units in PTA ProcessIn order to deal with the difficulty in reusing units models for different processes, with the mass conservation equations, energy conservation equations, and the thermodynamical equibria equations, etc, this paper conduct units models in the same uniform. Data structure is discussed to difine the function of units in process simulation, freedom is considered, too.PTA Whole Process SimulationBased on simultaneous equations, Newton-Raphson method is used to solve the large-scale nonlinear equations of the whole process. An advanced algorithm is also developed to calculate different processes, which with special structure of Client/Server/Models. Solution for sparse matrix and parallel calculating are applied, too.Interface of PTA process simulation programIn this part, the interface of the process simulation program is built to visualize the program, which is developed with Visual Basic. Visual input/output systems are constructed.