Mineral processing – Milling
Practical Action
i.e. more than 50 tonnes per hour and have a power requirement ranging from 40 kW up to
hundreds of kW.
Iron ore
Phosphate
Limestone
Bauxite
Copper ore
Slags
Uranium
Table 4: Material Suitable for Autogenous Mills
Niobium ores
Rod Mills
Description:
The rod mill is another tumbling mill but having a large percentage of its volume (30 - 40%)
loaded with steel rods. The rods are placed axially in the mill and are loose and free to move
within the mill. The internal lining of the drum has a series of lifters which raise the rods and
drop them at a predetermined point. The mineral is fed in at one end with a maximum size of
about 25mm. The rods crush the rock and as the charge passes through the mill it is reduced
in size to between 2mm and 0.1mm. The mill can be fed from one end with the product
removed from the other end or, alternatively, the mill can be fed from both ends with the
discharge at the centre. The process can be wet or dry but is more commonly carried out wet.
Maximum rod length is about 6 to 7 metres, otherwise there is a risk of the rods bowing. The
drum diameter is limited to 0.6 or 0.7 times the length of the mill.
Characteristics:
Rod mills are used for grinding hard minerals. This type of mill is usually used as the first
stage of a milling process to provide a reduced size feedstock for a further milling process.
Coke
Cement clinker (needs to be dry)
Table 5: Material Suitability for Rod Mills
Products for the glass industry
Figure 2: Rod Mill
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