Coal mill
The coal mill is a special form of the mill and is used for grinding of stone and brown coal for a coal power plant . Coal dust is also used as a reducing agent in pig iron manufacture (blast furnace). Inside the mill, the fuel is crushed to such an extent that specific surfaces of a few 1000 m² per kg of fuel are achieved in order to reliably ignite the coal in the combustion chamber .
When grinding, the coal is dried and inerted at the same time inside the mill with exhaust gases from the associated dust furnace or other furnaces . The fineness of the grinding is ensured by downstream classifiers . Most coal mills are designed as tube or vertical mills . The power requirement of all coal mills used in a coal-fired power station block can be up to 2% of the total installed power .
The same machine types of a coal mill (the tube or ball mill, the vertical roller mill, the classifier or separator ) are also used in the grinding of minerals (for copper and gold ore grinding) and in cement works . On the other hand, due to the flammability of coal dust, the requirements for a coal mill are higher than for the grinding of ores or the materials in the cement works: Many machine components have to pass demanding explosion protection tests in the EU . However, today it is also possible to operate the systems in a self-inerting manner, so that the design effort is considerably reduced. Because of this effort, there are only a few machine suppliers for coal mills.
Reuter West thermal power station
Dismantled impact wheel in the Schwarze Pump power plant
Opened coal mill in a black pump
See also vertical mill .