1. Rod Mill
During grinding, steel rods replace steel balls and rod mills are divided into three types: overflow rod mills, rod mills near the end of the head and rod mills around the center.
The process of the rod mill is characterized by more uniform particle sizes, fewer coarse particles and less sludge. It is mainly applied to gravity separation or magnetic separation plant of tungsten-tin ore and other rare metal ore, in order to prevent damage caused by over-comminution. In the process of two-stage grinding, if in the first stage the ore of 20-6 mm is grinded to 3-1 mm, a rod mill is recommended and has a larger production capacity and a higher efficiency. For the fact that a rod has a smaller surface area than a ball of equal wieght, the rod-grinding mill has a lower productivity and efficiency than the ball-milling during the second-stage fine grinding. In some cases, it can substitute a short-head cone crusher.
2. Grate Ball Mill
In multi-stage grinding, the grate mill is usually used in first stage grinding in the light of grate forced drainage, long service life and easy maintenance. The application scope covers metallurgy, mining, building materials, chemical industry and etc.
Grate type ball mill’s cylinder body is equipped with a liner made of manganese steel, chrome steel, wear-resistant cast iron or rubber and other materials. The high manganese steel is widely used. The mill has a hollow journal end cap at the end of the discharge line equipped with internal bearing inner sleeve and ore discharge grate. The ore-discharging grate consists of a center liner, a grate liner and a dome-shaped liner. On the inner wall of the end cap 8 bars are installed in a radial order, dividing the cap into eight fan-shaped chambers. A dome-shaped lining plate is installed in each fan-shaped chamber and fixed on the end cap by screws. Then the grate plate is installed on each fan chamber formed by a dome-shaped lining plate.
3. Overflow-type ball mill
In multi-stage grinding, the overflow ball mill is often used in the second and third-stage grinding. The overflow natural discharge has a long service life and simple maintenance. Its application scope covers metallurgy, mining, building materials, chemical and other fields.
The main part of the wet overflow ball mill is a cylinder body of a small diameter and large length has no heavy grate plate, supported by the rolling bearing and runned by the drive machine. The fed material is grinded by the steel balls and the force from the fall and autogenous grinding of the material. The fed material in the cylinder moves from the feed end to the discharge end under the effect of pressure and the slurry overflows from the lower edge of the hollow shaft of the ore-discharging end. Hollow shafts is equipped with anti-helical blades which carry spilled-out steel balls and coarse ores to the mill.
4. Wet autogenous mill
The application of the autogenous mill has shortened the existing crushing and grinding processes and reduced the metal consumption, which is often used in coarse crushing. It is suitable for coarse crushing of ore with A×b value higher than 30 and ball work index less than 15.
In the process of autogenous mill, the grinded material itself functions as a grinding medium and the material is continuously impacted and milled in the cylinder as to powder the material. In some cases, to increase the processing capacity, a small amount of steel balls may be added, usually only accounting for 2-3% of the effective volume of the mill. The scope of application of the autogenous mill has been expanded from the treatment of non-metallic ores to ferrous metals, non-ferrous metal copper ore, molybdenum ore, lead-zinc ore, and rare metal ores.