Influence of grinding media movement on the throughput of dry grinding circuit with electromagnetic mill

The paper investigates how the movement of grinding media affects the throughput of dry grinding circuit with the innovative electromagnetic mill. General structure of the grinding circuit, control system and its advantages are presented. Three air flows are critical for determining material throughput and providing proper operating conditions of the installation: flow through the working chamber of the mill, through the main classifier and in the recycle stream. They are affected by the moving grinding media. To assess this influence, air speed measurements were taken for different positions of dampers in air streams, for several masses of grinding media and frequencies of the rotating electromagnetic field. For each air stream, a set of polynomial models was identified. Control scheme for the air flows was proposed, including compensation for grinding media movement. Introduction of hierarchical control and distribution of particular control tasks on different layers was necessary.