Modeling Of Liquid Bulk Polypropylene Processes Using POLYMERS PLUS

Developing a mathematic model of industrial polymerization processes, which can be successfully applied to predict both the process based on reaction kinetics mechanism and the process industrial performance, is not only helpful to master the inherence of the polymerization process, but also the basis of optimizing the production process and enhancing the process benefit. Due to its complexity of the polymerization kinetics mechanism and the practical industrial polymerization processes, modeling of a polymerization process becomes a major branch of polymer reaction engineering, and it's also an unsolved and chanllenging problem.In this paper, an industrial bulk polymerization process of propylene was considered. Based on the thoroughly analysis, modeling and optimization of the propylene polymerization on plant scale was carried out with the Polymers Plus software tool. The main work was listed ans follows:The plant of propylene polymerization is made up of four reactors in series (D201, D202, D203, D204). The first two reactors (D201, D202) were liquid-phase synthesis of polypropylene using stirred reactors, and the later two were gas-phase using fluidized bed reactors. All the reactors were simulated with one CSTR module. We characterize a Ziegler-Natta catalyst by assuming the existence of multiple catalyst site types, and deconvoluting data from gel permeation chromatography (GPC) to determine the most probable chain-length distributions and relative amounts of polymer produced at each site type. The model contains a single set of kinetic and thermodynamic parameters that accurately predicts the polymer production rate, molecular weight, and polydispersity index. The steady-state model accurately predicts the major polymer properties and key process variables for two polymer grades.The effect of kinetic parameters to the conversion and the molecular weight of polypropylene were carried out with the tool of sensitivity analysis in Aspen. The kinetic parameters were propagation parameter (kp), catalyst active by hydrogen (kaH),catalyst active by sponse (kas), transfer to hydrogen (ktH), and transfer to propylene (ktm). The fluence to conversion of propylene is in following order: kp> kaH > kas, the fluence of ktH and ktm are almost neglectable. In the case of molecular weight of polypropylene, the order is following: kp > ktm > ktH .We demonstrate the application of our dynamic model and process control by comparing grade-transition strategies. We can use the dynamic model to explore grade-change strategies, to minimize the transition time and the production of off-specification polymer. Morever considered the production of the second reactor is less than others; the policy could be introduced and migh benefit for the improvement on profit.