Abstract: In this method according to the invention for extracting metals, starting ore material is subjected to material bed comminution and then leached by the addition of leaching fluid. In order to be able to ensure an optimal yield of metals even in the case of greatly differing particles sizes of the comminuted ore material, the comminuted ore material is divided into oversize material and fine material, whereupon oversize material is delivered to a heap leaching and fine material to a tank leaching.

Abstract: The invention relates to a grinding plant and to a method of grinding and classifying brittle material for grinding, in which two classifiers are used. The finer fraction from the first classifier is delivered to a second classifier which separates it into coarse material and fine material. The coarse material passes into a fine grinding mill and from there is conveyed back to the second classifier by way of a mechanically transporting conveyor arrangement.

Abstract: The invention relates to a method and apparatus for the comminution of brittle material for grinding, particularly send-like material such as metallurgical sand in the roller gap of a material bed roller mill. In order to create an optimum capacity for drawing in the material for grinding in the roller gap, the material for grinding at the inlet to the roller gap is set to a (mixed) moisture content of approximately 0.3 to 3.0%, preferably approximately 0.5 to 2.0%.

Abstract: The invention relates to a method and a grinding plant for reduction of brittle material for grinding, in which material which has undergone primary reduction from a first grinding stage is delivered as fresh material to the second mill of a second grinding stage and finished product is removed from this second grinding stage, and in which the quantity of feed material of this second mill is kept constant when the quantity of finished product alters by altering the quantity of fresh material. This first grinding stage contains an air separator from which the fines are fed as fresh material to the second mill. In the event of alteration in the quantity of fresh material for the second grinding stage the quantity is kept constant by corresponding alteration of the fineness of separation of the separator of the first grinding stage.

Abstract: The invention relates to a material bed roller mill for crushing brittle material to be ground in the gap between two driven rollers which are pressed against one another with a high grinding force with a filling shaft for the delivery of material provided above the rollers. The width of the stream of material delivered to the roller gap can be altered with the aid of vertical guide walls which are adjustable at right angles to the vertical central plane of the roller mill while maintaining their vertical position. The column of material which is aligned vertically above the rollers creates pressure which is introduced fully into the material bed crushing and if required the column of material can be moved in the cross direction with respect to the rollers.

Abstract: The invention relates to a separator with a rotor and a material distributor which are driven separately. Such a separator is particularly suitable for grinding plants which are equipped with a high-pressure grinding roll mill. The scabs discharged from such a roll mill can be broken up in a simple manner in the separator which acts simultaneously as a disagglomerator.

Abstract: A method and apparatus for the two-stage crushing of brittle material comprising a roll mill and a mill connected downstream thereof, the output of the second mill being delivered to a sifter in which a second branch stream of the grit obtained in the sifting operation is returned to the roll mill and a further branch stream is returned to the second mill. A first control circuit keeps the sum of the quantity of fresh material and the quantity of grit constant, while a second control circuit divides the quantity of grit into two branch streams in such a way that the drive power of the roll mill remains constant.

Abstract: A method and apparatus for the two-stage crushing of brittle material comprising a roll mill and a second mill downstream thereof, the output of the second mill being delivered to a sifter. The quantity of grit obtained in the sifting operation is divided between the roll mill and the second mill in such a way that the sum of the quantity of fresh material and the quantity of grit delivered to the roll mill remains constant.

Abstract: The invention relates to a method and to apparatus for the crushing of material to be comminuted by means of a material bed roll mill, in which such material is forcibly delivered in a regulable mass flow to the roll gap. In this way even materials which tend to slip on the rolls can be crushed satisfactorily. It is also possible to keep the nature of the product constant over a wide range of variations in the throughput.

Abstract: The invention relates to a tube mill in which the cylinder of the drying chamber and the transition wall which it supports are divided centrally or a number of times in the axial direction so that this cylinder and the transition wall can be replaced without the grinding elements having to be removed from the grinding chamber.