Research On Optimization Approaches For Production Planning And Scheduling In Steel-Making & Continuous-Casting With Applications

The iron and steel enterprises are facing stronger and stronger challenges as the global completion in market is enhanced. Meanwhile, the customers demand small lot with different varieties and strict delivery time windows. Therefore, more and more attentions are paid to the issues such as production planning, productivity forecast and quality management in the iron and steel corporations. The steelmaking and continuous-casting (SCC) production is very important in all the processing stages of steel production. As a result, many types of production planning problems in the SCC production are researched in the literature. However, the majority of the results in the literature cannot be applied and only be referenced in actural application because the SCC production process is very complex. In spite of variety approaches that are developed for the production planning problems in the SCC process, the application of the simulation based optimization (SBO) has not been found until now.Therefore, several key problems in the SCC process planning are researched using the approaches including the SBO approach in this thesis. The main researches are as follows:(1) A large quantity of monographs, journal articles, proceeding papers and reports are carefully checked. The following related fields are reviewed:the whole sequence of processing stages in the iron and steel productin; the existing management modes; the management problems in the iron and steel production such as materials purchase and optimization, production quality management and particularly production planning and scheduling. Also, the related approaches, especially the development, theoretical and applied researches of the SBO approach are summarized.(2) A multi-objective mathematical model of the charge batching problem in steclmaking is proposed with its solution algorithm developed. The model minimizes the open ordered slabs and the total costs including the substitute costs between grades respectively with the assumption that the weight of a single customer is perhaps greater than a charge. A heuristic algorithm with an embedded tabu list is developed after the analyses and simplification of the model. The final experiments indicate the validity of the algorithm. Also, the relationship between the obtained open ordered slabs and the given customer weights is analyzed. The Pareto solutions scatter well, which provides great space for the decision makers.(3) A graph-based mathematical model for the cast batching problem is built and solved based on the genetic algorithm (GA). It is assumed that all the charges must be assigned, that number of casts is unknown, and that all the casters (tundishes) are homogeneous. The problem is formulated as a multi-city-type asymmetric multiple traveling salesmen problem, which minimizes both the total traveling distances and the number of involved traveling salesmen with the constraint of maximum number of cities that can be visited by one salesman. A GA based algorithm is developed. The algorithm uses an ordered encodeing with separators and ordered crossover with single corss point. The GA algorithm is tested based on a number of randomly generated instances with the valuing method of parameters discussed. Finally, the effects of paremeters on the results and the necessity and feasibility of introducing the SBO method are analyzed.(4) A simulation based GA algorithm for the job scheduling problem is developed. With the help of mathematical model, the job scheduling problem in SCC process is formulated, the objective function of which minimizes the maximum gap between the earliest available time and starting casting time of casters. The problem is solved based on the SBO method. The optimizer of the SBO is a segmented ordered encoding GA, which is easy for genetic operation. The simulator of the SBO simulates not only the actual system but also the operators, which runs fast. Finally the experiments show that it is convenient to consider the uncertain factors in this method and that the obtained scheduling is much closer to the actual system.(5) An integrated scheduling system for the SCC process is designed, developed and applied. The system is based on the three-layer architecture as client, middle ware, and server. The middle ware is realized using TUXEDO. The main modules of the system consist of scheduling and re-scheduling, match and optimization of planning, and the handling of abnormal logistics. The core algorithm is the hybrid of optimization and human-interactive method. The system has such features as friendly human-machine interface, seamlessly integration with the MES system, and easy maintenance. Furthermore, the author proposes a research frame work of SBO for the medium- or long-term planning in the SCC production, including the division of planning period, the interface between plans and the evaluation system.