The minerals exploitted from the mines mainly are the lean ore containning a lot of gangue ore, except a small number of rich ore with valuable minerals. For the metallurgical industry, if directly use the lean ore for smelting metal extraction, it will have a great energy consumption, a high production cost, due to the low content of useful components, complex mineral composition. For more economic exploitation and utilization of low grade of the lean ore, expanding of the mineral raw materials source, ore must be slected and enriched firstly before smelting to abandon the most gangues and make sure the contents of useful mineral reach the smelting requirements.
In the beneficiation process, there are two basic processes: one is dissociation, which refers to crush and grind the minerals firstly and then dissociate various kinds of the valuable particles from the minerals; second is sorting, which is the dissociation of mineral particles sorting by the physical and chemical properties. Due to the majority of useful minerals are closely associated with gangue and often in a micro-grained dissemination, it can not make seperation even there are big differences in their properties, if do not to make various minerals or components separated. Therefore, seperating the useful minerals and gangue firstly is the prerequisite for adopting any beneficiation methods, while the purpose for breaking and grinding is to make the useful minerals closing to the ore seperate with the gangue fully.
The grinding process is the process of decreasing the ore granularity. The dissociation of various useful mineral particles are generated in the process of particle size decreasing. If crushed product granularity is not too fine, the useful minerals and gangue have not fully dissociation and the separation effect is not good; If the granularity of grinding product is too fine, it will produce too much over- crushed particles. although a various useful mineral dissociation is complete, but the sorting index also is not very good. The reason is there is a certain lower limit for any selection method to handle the granularity of material. If lower than the limit, it will be difficult to separate the particles effectively (that is the over-crushed particles). For example, it is still not very good recovery the mineral particles under 5~10 m on flotation and lower than 19 m on gravity. So, the basic task of the secondary crushing and grinding in concentrator is to prepare the complete dissociation and slight degree of over-crushed materials, and the granularity of the material need to fit in the sorting methods. If the selection of process and equipment for the crushing operation is improper, the production operation management is not good, the final product or the dissociation of the crushing is not sufficient, or the over grinding is serious, it will lead to the decline of the technical and economic indicators of the mineral processing plant.
In the dressing plant, the equipment investment, production cost, electric energy consumption and the steel consumption of the crushing and grinding operations are often in the largest proportion, so the calculation and selection of crushing and grinding equipment, operation of management will determine the economic benefit of the concentrator in a large extent.
In general, the technical indicators and economic indicators of the mineral processing plant usually depend on the crushing and grinding, therefore every dressing workers must take the crushing and grinding process and the equipment seriously, to reduce the cost of ore crushing and grinding as much as possible.
