Capacity Allocation Of Plant-wide Production Processes Considering Production Changeover In Steel Industry

The production processes in iron&steel companies involve multiple stages including steelmaking,hot rolling and acid rolling.Each production line has multiple suppliers,while it also supplies materials to multiple production lines.The requirements of the customers are various,while each production line expects to make plans in larger batches.From the plant-wide perspective,the companies should make reasonable plan to decide the production volume and variety of each production line in each stage and each time slot,so as to ensure that the supply of each production line is steady,and that the productivity are utilized sufficiently.This thesis studies the capacity allocation planning of steel enterprises considering the production changeover from the plant-wide view,which is derived from the whole production process of the iron and steel enterprises.Then a mixed-integral linear programming model is formulated with consideration of productivity utilization,production changeover etc.Moreover,a two-phase heuristic is developed,and column generation algorithm is designed to obtain the lower bound of the problem.Finally,a decision support system is developed.The main research contents are as follows:1)For the capacity allocation planning of steel enterprises considering the production changeover,a mathematical programming model is formulated,which considers the production capacity limit of each production line,the inventory capacity,logistics and inventory flow constraints,and takes the objective of minimizing the penalties incurred by insufficient production capacity,inventory,transportation and production changeover.The model is linearized and solved by CPLEX.Finally,the experiments are conducted to test the performance of the model.2)Since the above model cannot be solved within reasonable time,a two-phase heuristic approach is developed,in which the production volume of each order in production line in each time slot is decided in the first stage,while the order sequence in each production line in each time slot are decided in the second phase.To test the performance,a column generation algorithm is designed.The problem is decomposed by the Dantzig-Wolfe decomposition method.The dynamic programming algorithm with relaxed state space is developed to solve the sub-problem.Finally,the efficiency of the algorithms is evaluated by experiments.3)Based on the above models and algorithms,a decision support system for steel plant capacity allocation is designed and developed,which considers the production changeover and can provide a human-computer interaction platform to steel enterprises.