The Model Study Of Product Mix And Appropriate Backlog For Rare Earth Plants

The theory research of production planning and application system have been widely applied in the petrochemical, steel industry and other fields. The optimization of production planning improve the production efficiency and economic benefits. Because of the problems of that the joint cost of production is hard to allocate, the RE material partition (weight ratio of some kind of ReO in all ReO) were not balanced with the market share of various elements and the correlation between products price and so on, the production plan model has become the difficulty and hot topic in the recent years. At present,a model of product mix, developed by He and Lu, solved the questions of the joint cost of production.In view of the problem of the correlation between products price and the imbalance between the RE material partition and the market share of various elements, the production plan model of RE plants was perfected. First by introducing the constrained of the fuzzy relations between products price, a products mix model price (M1) was established in the paper. By comparing the result of the calculation example and the optimization results of the original model that assumed that the demands and prices of various RE elements was independent random variables, the gap of optimistic solution and pessimistic solution was narrowed, and helped policy makers to make scientific decisions.The imbalance between the RE material partition and the product demand possibly leaded to"double—low effect", orders and capacity utilization would maintain low levels or the other extreme: the serious backlog problem of unsalable RE elements. A model of appropriate backlog (M2) was established in this paper. Considering expectant sale price, inventory holding cost and interest rates, the present value of the backlog products was calculated. With the rare earth price fluctuation, the present value of the backlog products could be higher than, equal to or lower than current price, so the objective function become piecewise linear function. The model was solved by the iterative linear program. Accordingly, the model can address the maximum of cash income or profits at the appropriate amount of backlog.The production planning optimization software was designed using Matlab, which has been put into practice in the Bao Tou Steel Rare Earth Plant and operates normally.