The Importance of Work Index in Mineral Processing
| Understand the Relationship Between Energy and Size
Mineral processing is concerned with the relationship between; The amount of energy put into a rock or particle of a known size and, the reduced particle size after the comminution (the action of reducing a material) process has taken place. ‘Work Index’ is the amount of energy required to do this work. It is a measurement of how hard the rock is and an expression of the resistance that a material has to crusher.
Shown in the table below is typical Work Index, reflecting the different rock characteristics. It shows for example, that their is more energy required to crush Basalt then Iron Ore.
Work Index:
The size fraction when rocks are reduced in size
| Typical Values for Crushing Work Indices
Crushing Work Index
Material
8
Clay
13
Coal
22
Basalt
Crushing Work Index
Material
17
Iron Ore
14
Copper Ores
3
Glass
Crushing Work Index
Material
14
Quartz
13
Limestone
16
Gold Ores
The kilowatt-hours per tone (kWh/t) will work out your work index. The number of kittowatts consumed in a hour divided by the tonnes of rock gives you your work index.
Remember, the higher the Work Index the more work required to crush the rock. This will impact the equipment chosen for your project.
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