Simulation Of Olefin Copolvmerization Process Based On Simultaneous Approach

Nowadays, polymers are in large demand for their good performance, such as high strength, good toughness, high temperature resistant and easy processing. Copolymer is the product of polymerization with two or more monomers, which can significantly improve the performance of the product because of the optimal combination of different polymers. Olefin copolymerization is such an important process to produce copolymer. The modeling and simulation of this process contains four major aspects, modeling of copolymerization mechanism, thermodynamic properties of copolymerization system, the quality of copolymer and efficient process simulation method. Due to the complex copolymerization mechanism, population balances of different chain must be considered to establish the reaction model, leading to the rapid expansion of the model scale. The suitable thermodynamic model, PC-SAFT, involves a complicate sequential solving process. It is difficult to be used in equation-oriented approach. Chain length distribution (CLD) and chemical composition distribution (CCD) are the most important microcosmic quality index of the copolymer. The whole model of copolymerization process will be a large-scale model with heavily coupled variables and strong nonlinearity.To solve the model efficiently and accurately, an equation-oriented approach (EO) is developed in this project. Based on the EO approach, the studies on modeling and simulation of the olefin copolymerization process are conducted. The contributions of this thesis include the following four aspects.1. Reaction kinetics of copolymerization reaction of olefins is derived by using the moment method. The CLD and CCD of copolymer for multi-site catalyst are derived. A model of HDPE slurry process is developed.2. To overcome the modeling complexity and solving difficulty of PC-SAFT, surrogate models based on Kriging method are developed to describe the relationship between the physical conditions and the material properties.3. Different operating conditions of copolymerization are simulated by using the EO approach. The good simulation results show the accuracy of the kinetic models, Kriging models, CLD models and CCD models.4. Simultaneous approach based on orthogonal collocation finite elements is used for the dynamic simulation of grade transition of the copolymerization.