A New Matrix Simulation Method of Closed-Circuit Grinding Systems

Abstract

A new matrix simulation method of closed-circuit grinding systems is proposed. This method can be effectively applied to even such grinding systems as closed-circuit ball mills, in which mean residence time and classifier characteristics are seriously affected by total flow-rate of materials in mills.In this method, the Modified Molerus' Model is adopted for expressing the classifier performance, and it is assumed that the parameter s, expressing the sharpness of classification, is not affected by operating conditions of the classifier, while the ratio of partition towards the coarser products β is seriously affected by the solid concentration in the classifier. Moreover, it is assumed that the mean residence time of materials in the mill is inversely proportional to total flow-rate of materials in the mill F, and that the grinding matrix per unit time is independent of F.The procedure of calculation is as follows.i) A value for F is assumed.ii) The cut size of classifier is determined by the trial-and-error method from the restriction that the fineness of fine products must meet the prerequisite conditions.iii) Steady-state flow-rate and particle size distribution of fine products are calculated.iv) Procedures i)-iii) are repeated for several F values.v) Results are compared and the optimal level for F is determined.This method has an advantage over the existing procedures that the time for calculation can be remarkably reduced without injuring the accuracy of simulation.By using this simulation method, various problems encountered in grinding plants can be effectively solved. Analysis of steady-state characteristics of grinding systems, investigation of the cause of difference between the efficiency of two grinding systems, examination whether one more classifier should be added to an existing plant or no, investigation of the optimum flow-schema in a grinding system and optimization of design variables of grinding systems are some of examples.