Styrene Industrial-grade Body Thermal Polymerization Process Modeling And Simulation

Developing a mathematic model that can be successfully applied to predict molecular properties for polymerization processes depends on well understanding the whole process in physical and chemical aspects and on deriving functions of mass balance, energy balance and momentum balance accurately.On the basis of thoroughly analyzing the industrial bulk polymerization process of styrene, modeling is carried out by the way of theoretical analysis.First of all, the flow behaviors in the industrial reactors are investigated, and the results indicate that the pre-polymerization reactors might be simplified as CSTR models, and that the post-polymerization might be simplified as CSTR and PFR models in series. As for kinetics mechanism, a kinetic model, with third-initiation order, with termination by both combination and disproportionation, and with chain transfer to solvent is developed after summing up a number of correlative materials. The kinetic parameters are determined by comparing simulation results, such conversion, average molecular weight and molecular distribution with industrial data.On the one hand, the simulation results of conversion, average molecular weight and molecular weight distribution are in good agreement with industrial data, with simulation values provided by the supplier, and with the data of material balance sheets for a variety of GPPS grades. On the other hand, a model for HIPS polymerization process is also developed, and correlative kinetic parameters are studied preliminarily.As for industrial polymerization process, modeling is only the first step to go. In fact, analyzing, optimizing steady-state operation parameters, developing new products, designing new reactors, optimizing transition strategies might be put into practice.On the scale of the whole polymerization process, the influence caused by changing steady-state operation parameters, including temperature, volume flow rate and the intake fraction of monomer is investigated. As a result, the most sensitive parameter is temperature, and the most inactive parameter is volume flow rate.The feasibility of manufacturing GPPS with high molecular weight by using presentreactors is studied, and operation parameters are gained by optimization analysis; The size of new reactors and related operation parameters are put forward to meet the requirement of high molecular weight.The tool of SIMULINK model is borrowed to simulate the dynamic states. The traces of conversion, average molecular weight and polydispersity are obtained during dynamic states, such as the processes of start-up, end-up, duty change and grade transition. The simulation results are also successful.Moreover, two policies of grade transition for pre-polymerization reactors are compared, and the transition time of industrial way might be shortened 23% as compared with that of the original way provide by the supplier. Again, according to sensitivity analysis, various policies are brought forward and the simulation results showed that the transition time might be shortened 81%. This policy could be introduced and might benefit for the improvement on profit.This model might be helpful to determine the kinetic constants for HIPS, to perform on-line state estimation on conversion, average molecular weight, and melt index, and to optimize control strategy.