Third, the type of screening operations
In coal preparation plants and screening plants, screening operations are widely used in raw coal preparation and product handling. According to their different tasks, can be divided into the following screening operations.
1. Prepare the screening
Also known as pre-screening. In the coal preparation plant, according to the requirements of crushing operations and sorting operations, raw coal is divided into different particle size, in order to prepare for further processing of coal.
For crushing operations, preparation of screening is to be broken before the already qualified size and the need to break the large pieces of separation, so that large pieces of material broken, to avoid excessive material crushing.
For sorting operations, due to a variety of coal preparation methods, require a certain selection of grain size, otherwise it will seriously affect the sorting effect, it should be required to separate the raw coal into different size.
2. Check sieving
After the material is crushed, the unqualified bulk material in the crushed product is separated and crushed to ensure the particle size requirement of the product.
3. Final screening
For screening plants, the screening of the grain size products are directly available to the user of commercial coal.
4. Dehydration screening
For the purpose of dehydration screening, in the coal preparation plant for the dehydration of selected products, used for dehydration sieve is called dehydration sieve.
5. Desliming screening
To remove the slime for the purpose of screening. In the coal preparation plant in order to reduce the high ash fine mud on the clean coal pollution, in the sieve on the dehydration process, strengthen the power of water spray to remove some fine mud, this operation is called desliming screening. In the heavy medium coal preparation plant, in order to reduce the pollution of the slime media system, before the coal into the heavy medium sorter should also be used mud screening.
6 to remove heavy media for the purpose of screening
In the heavy-medium coal preparation plant, heavy-medium coal products on the screen with a strong spray of water on the way to make products with the quality of separation. This kind of operation is called a mediation operation.
7. Selective screening
Selective screening refers to the process of screening, the coal not only by the size of grading, but also by quality classification of screening. For example, in high-sulfur coal containing pyrite-based sulfur, most of the sulfur content is concentrated in large lumps of coal that can be removed by sieving. In another example, for some mines, the ash content of the lower coal is higher and the ash content of the large coal is higher, and the large coal is separated by the screening machine, which can improve the quality of the tail coal by 1 ~ 2. On the contrary, some of the coal mine than the end of coal ash is also high, screening can improve the quality of lump coal. Again, because the coal and waste rock hardness difference is large, with the drum sieving machine crushing and screening, but also to achieve the separation by quality.
8. Slime recovery
For the purpose of recycling slime for coal preparation plant slime, tailings dehydration and other operations. For example: for simple jigging coal preparation plant (without flotation system) clean coal sieve dehydration sieve water or clean coal pit overflow slime recovery, in order to reduce the sedimentation tank area; for flotation system with jigging coal washing The coarse coal slurry can be directly mixed into the fine coal, the screen water into the flotation system, can reduce the flotation system, the amount of slime; for dense coal preparation plant clean coal Magnetic slag tailings slime recovery, sieve can be directly mixed with coal, simplify the process system; for thickener bottom flow coarse slime recovery, can reduce the burden of filter press.