Kola Mining and Metallurgical Company JSC, Monchegorsk, Russia:

V. D. Zhidovetskiy, Principal Specialist, Automation Office, Tel.: +7 (81536) 7-98-07

Soyuztsvetmetavtomatika JSC, Moscow, Russia:
A. V. Kuzyakov, Senior Researcher

An automatic system has been developed and implemented for optimum control over converter matte grinding in a ball mill. This work provided a step to a new level of control: from automated control (when a process person assigns tasks to controllers) to automatic control (when the optimum control system itself calculates and assigns tasks to local controllers). It is shown that control inputs are generated amid uncontrolled disturbance and the lack of full information about the grinding process status. However, when using methods of direct search for optimum process parameters, even limited information available from process monitoring instruments make the system invariant with respect to uncontrolled disturbance, and it is almost always stable within a broad range of all variables governing the grinding process. The implementation of the automatic optimum control system included introduction of a granulometer PIK-074P designed to continuously monitor the concentration of 45 μm product and finer (20 μm) particles in the slurry discharged from the spiral classifier. The difficulty lay in the fact that the slurry contains foreign objects, such as wood chips, pieces of plastic, rubber, polyethylene film, and pebbles. Besides, the solid part of the slurry tends to settle and accumulate in the discharge box, in which the granulometer is installed. A new design solution was found for the discharge box, which proved effective. As a result, the right environment was created to ensure failure-free operation of the PIK-074P granulometer installed where the slurry flows over the baffle of the spiral classifier. To prevent the slurry from sticking to the working surfaces of the granulometer that look on the slurry flow, a spray system was installed to spray the bottom of the granulometer with filtered water. The transfer to automatic optimum control of the grinding process opens up new opportunities for downstream optimization.

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