According to different mining sieving purposes, sieving operations can be divided into the following categories:

1. Preparation sieving: its purpose is to prepare for the next operation. For example, before jigging, gravity concentration plant should sieve and classify the materials, and classify the products of different sizes.                              

2. Selective sieving: if the distribution of useful components in each particle size is very different, different quality particle size can be obtained by sieving equipment, and the low quality particle size can be sieved out, so as to improve the grade of the material.

3. Independent sieving: its purpose is to get the final product suitable for the user's requirements. For example, in the ferrous metallurgy industry, the iron rich ores with high iron content are often sieved into different sizes. The qualified large iron ores are put into the blast furnace for smelting, and the fine ores are put into the furnace through pellet or sintering.

4. Auxiliary sieving: this kind of sieving is mainly used in crushing operation of concentrator, which plays an auxiliary role in crushing operation. Generally there are two kinds of sieving and pre sieving.

   4.1 inspection and sieving refers to the sieving of ore after crushing. Its purpose is to ensure that the final crushing products meet the particle size requirements of grinding operation, and make unqualified crushing products return to crushing operation, such as sieving in front of medium and fine crushing machine, which not only plays the role of pre sieving, but also plays the role of inspection and sieving. Therefore, inspection and sieving can improve the utilization of crushing equipment, which is similar to the closed-circuit circulation of classifier and grinder, and can improve the grinding efficiency.

   4.2 pre sieving refers to the sieving before the ore enters the crusher, and the part that is qualified for the crusher is separated from the ore by the sieve, such as the grid sieve and sieving installed in front of the coarse crusher, and the products under the sieve. In this way, the amount of ore entering the crusher can be reduced, and the output of the crusher can be increased.

5. Dewatering sieving: the main purpose of this kind of sieving is to remove the moisture of materials, which is generally used in coal preparation plant and tailings dry discharge.

Here are some factors that affects the mining sieving process.

First: physical properties of materials, including particle size composition, humidity, mud content and particle shape.

Second: motion characteristics and structural parameters of sieve surface, including motion characteristics of it, length and width of it, size and shape of its hole, etc.

Finally: Operating conditions, including the size of productivity and uniformity of ore feeding.

Among the three factors mentioned above, the first one can not be changed at will except humidity. The second kind of factors must be considered carefully when designing the sieve. Only the third kind of factors can be adjusted in the actual production process.