Advanced Control Systems for Grinding

Abstract

Composition control serves to ensure the desired average chemical composition of the raw meal, i.e. to keep the oxide variables (C, S, A, F), or their relative rates represented by the moduli, to prescribed values. The main problem of composition control derives from the time needed for measurement of the oxide content which causes considerable delay in the closed-loop control system. Its value may be so large (from 30 minutes to one hour) that several experts advocate improvements in the quality of control by decreasing this dead-time rather than by using the most advanced control algorithms. Previously chemical analysis was performed by manual sampling and laboratory procedures. Now, representative sampling is performed automatically and the oxide content is analyzed by an X-ray fluorescence analyzer (RFA). As the time delay caused by the measuring method cannot be significantly reduced further at an acceptable level of cost, so effective control algorithms play a more important role.