Magnetite’s role in the preparation of Coal
The mining of coal, whether by underground or open pit methods, usually contains a degree of incombustible materials e.g rocks mud etc. Customers require their product, in particular metallurgical coal, to be of the highest calorific value so these non-burning impurities (ash) need to be removed.
The process of separating magnetite from copper tailings involves magnetic separation, grinding and quality control to ensure that client specifications are achieved.
Coal preparation technology has developed around the differences in specific gravities of coal and the ash. Typically a coal preparation plant consists of breaking the coal into smaller pieces and then screening the larger solid ash particles. The remaining coal and ash is mixed into a heavier than water fluid. In simple terms the lighter coal floats to the top of the “heavy media” fluid and the ash sink. Both coal and ash are then screened to maxamize the recovery of the heavy media for reuse. The “washed” product is now ready for market. The more of this waste material that can be removed from coal, the greater its market value and the lower its transportation costs. Clean coal means higher profits for coal mining companies.
The most economical material that is used to create this heavy media is finely ground magnetite slurried in water. The required density of the medium depends on the coal’s properties and is simply adjusted by the amount of high density magnetite used. In the washing process not all the magnetite is recovered, hence, there is a steady demand for good quality magnetite.
Magnetite is a form of iron and is mined and sold for that purpose. In many parts of the world, including here in BC, magnetite is a by product of copper ore.
