Research On The Scheduling And Optimization Algorithm For The Polypropylene Multi-Grade Problem

Production scheduling is the core content and the key technology in enterprises production management. A good scheduling program can distribute the tasks and resources reasonably, reduce the production costs, and improve the production operation efficiency and the rapid response capability of enterprises, and thus enhance the competitiveness of enterprises. Therefore, it is of great significance to carry out the study on the production scheduling problems, and to provide scientific and efficient production scheduling programs for enterprises. A market-oriented short-term scheduling model is established for the polypropylene continuous multi-grade process. Based on the obtained system model, the optimization algorithms are investigated for the scheduling problem. The main work and contribution in this dissertation are as follows:1. At first the motivations and the meanings of the studied content are discussed. The status quo of worldwide products and supply/demand of polypropylene both at home and abroad are summarized in detail. From the technical points of polypropylene production, the paper introduces the requests of technical process and control in polypropylene production, and the Spheripol process was also briefly introduced.2. The grade transition and production scheduling problems for polypropylene continuous multi-grade process is analyzed, and existing results on these problems are summarized. The significance of the production scheduling problem is illustrated by the studies on the existing results. Then the interrelated problems and the future developments of production scheduling are analyzed.3. Based on the internal supply chain model of a polypropylene company, the short-term scheduling problem is investigated for the polypropylene continuous multi-grade process. Moreover, a short-term scheduling optimization model which is aimed at gaining the maximum economic benifit is presented. 4. Based on the obtained scheduling optimization model, the optimal scheduling problem for the polypropylene multi-grade process is described as a mixed-integer programming problem. A hybrid method called DESimplex is proposed to handle the nonlinear constraint more effectively. Moreover, the calculation burden is significantly reduced by utilizing the cluster analysis. We verify the feasibility and efficiency of the proposed algorithm by lots of numerical experiments.5. Finally, the summary is presented, some problems to be solved and the possible directions on the development of polypropylene production scheduling are point out.