Three Factors Affecting Tungsten Ore Electrical Selection
Electrical selection method is an important auxiliary way of ore processing, when tungsten ores are under electrical selection, tungsten ores and cassiterite need to be separated.
With high voltage electrical selection machine, wolframite and scheelite can successfully separated, sulfide ores and wolframite can successfully separated as well. Because wolframite and sulfide ores are with conductivity, scheelite and tin ores are not with conductivity.
The effect of electrical selection method is not only determined by the conductivity of tungsten, also by three major factors: temperature, structure, and surface states.
1. Temperature: For conductors, the conductivity decreases when temperature increases. For semiconductors like tungsten ores, as the temperature goes high, the bound charge is released by the heat energy, the free electron increases and the conductivity increases. Therefores, proper heating befores electrical selection can improve the effect of electrical selection and is mores benificial to ore selection.
2. Crystalline Structures: Modern solid physics has proved that any of the excess atoms in a semiconductor that deviate from the chemical composition, defects in foresign impurities and lattice structure can significantly change the electrical conductivity. The purer the component, the better the electrical selection.
3. Surface States of Ores: The surface state of ores determines the surface conductivity of ores, including surface moisture and porosity.
Based on the above three factors, we can change the external conditions when tungsten ores under electrical selection so that we can get better ores.
For ores with small electrical conductivity, a change in the chemical composition of the ore surface is enough to change its surface conductivity, in some cases, a proper addition of certain agents enables the ore surface to be covered with a new layer of conductive film to enhance electrical conductivity.
In addition, water has better electrical conductivity than ores, therefores, when the presence of water film on the ore surface, the conductivity will be greatly enhanced. Finally, the larger the porosity of the ore, the greater the specific surface area is and it has a strong moisture absorption. So, when the air humidity increases, the surface conductivity also increases significantly.
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