Simulation of Cement Grinding Process for Optimal Control of SO3 Content

D. Tsamatsoulis

Abstract
The control of cement grinding/mixing process in an industrial mill regarding SO3 content has been effectively simulated taking into account all its fundamental sides and particularities. Based on a simulator, two controllers of different philosophy have been studied: A classical proportional-integral (PI) controller as well as a nonlinear one (step changes, SC) consisting of certain classes of SO3 output ranges that result in certain levels of discrete corrections of gypsum feed. Initially, the simulator was implemented for grinding of a single cement type each time. Totally, three cement types were investigated. The controllers have been parameterized and compared using the minimal standard deviation of SO3 as a criterion. Both provided satisfactory SO3 consistency, but PI was more efficient against SC as with the double sampling period, the same minimum standard deviation was obtained leading to equal results with half the sampling actions. The simulation was also realized in milling of several cement types. A feedforward part was added to the feedback loop to face the case of cement type changing. The results of operation of this kind of controller in an industrial milling system contribute greatly to the improvement in cement quality.

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Keywords
Regulation, cement, sulphates, dynamics, mill, grinding, uncertainty, simulation