Grade Transition Research Of Continuous Polypropylene Production Process

Based on the Spheripol process, this thesis studied the grade transition problem of polypropylene's continuous production process, including modeling and optimizing. On this basis, the optimal strategy's application in industrial production devices was introduced and online revision was discussed.Firstly, a great deal of papers on the field of grade transition were reviewed and discussed. After a brief introduction, this thesis illuminated the assortment, objective, important factors and mathematical descriptions of grade transition, then summarized the general framework of solving this problem, reviewing the progress made in this area during the last decades, and finally pointed out the development trends in the future.Secondly, both the catalyst system and propylene's polymerization mechanism were introduced, Spheripol process was also briefly introduced. Based on the polymerization mechanisms, model framework was developed and something about polymerization's soft measurement was studied. In the study, the main consideration ingredients include temperature, hydrogen concentration, ethylene concentration and propylene concentration. With the application of production data collected from a factory to curve fitting, the half experience half mechanism models were developed, while the soft measurement model of melt index was validated. By the way, these models were composed of Melt Index, Isotactic Index and Ethylene Content.Thirdly, the research on optimization strategy of grade transition process was concerned. As an example, the grade transition between homopolymerization grades was detailed discussed, the transition process was modeled, the target function was built and calculated so as to get the optimal grade transition trajectories. The causes of changes in the state variables were analyzed and the significant means of research results was proved.Finally, the grade transition problem in industrial production was discussed. Because of the tremendous losses of grade transition, companies were badly in needof an optimal grade transition strategy to guild the production operation. According to his own experiences, the author detailed introduced the theory basis and practical application of grade transition, which was integrated in the computer monitoring system. Further more, the problem on how to implement grade transition's closed loop control on the real production process was analyzed and answered. The scheme seems absolutely feasible.