Abstract: The employed feed element in a grinding body feed apparatus of a grinding mill is the grinding bodies supply tank proper, in which the grinding bodies are charged from a ball hopper or storage. In connection with the supply tank, there is provided a grinding bodies discharge element, by means of which the grinding bodies are conducted to a duct serving as a feed chute and leading to the grinding mill, and via said duct, to the grinding mill proper. The opening and closing of the supply tank is carried out by external, opposing control elements that encircle the drum element of the supply tank in relation to its frame. By means of the feed device, it is possible to feed one ball at a time to the mill, in which case a correct number of balls can be supplied.

Abstract: A method and an apparatus for heating devices of a mineral material processing unit, said devices in said method being heated with electric heating means, whereby said devices are heated with heating means attached to or in the immediate vicinity of parts getting into contact with the feed material, and/or said devices are heated with heating means attached to or substantially in the immediate vicinity of parts most essential for the cold starting of said devices. The invention further relates to a mineral material processing unit.