Breaking and Screening Process in Beneficiation

Generally, the crushing process consists of sieving work. The crushing work and sieving work compose the crushing stage. The crushing and sieving process includes total crushing stages (sometimes the ore washing work is included).

The basic crushing and sieving process in dressing plant is like the following picture:

Generally speaking, in gold dressing plants and medium and small dressing plants, the two stage or three stage crushing and sieving process are usually used. The large dressing plants often use the three stage crushing and sieving process. Even in some large plants, the four stage crushing and sieving process is used for the raw ores have large size. The power consumption in ore grinding work is too large. In order to reduce the energy consumption and reduce the size of the final crushing products as much as possible, the principle of more crushing and less grinding should be guaranteed and the workload of each stage crusher should be balanced distribution.

The two stage crushing process can be classified into two stage open-circuit crushing and the two stage closed-circuit crushing. The open-circuit crushing is the crushing products don't need to come back this stage crushing work for being crushed again; the closed-circuit crushing is that: after the crushing products are sieved, the products with unqualified particle size (the products on the screen) will come back this stage crushing work to be crushed again. For the two crushing process, most of the dressing plants will use two stage closed-circuit crushing process, which is the two stage crusher and the sieving machine form the closed-circuit producing. This process will guarantee the particle size requirements of crushing products and will not influence the ball mill grinding work. The two stage open-circuit crushing process will be used in some gravity dressing plants and the crushing products will be sent to rod mill. The two stage crushing process is only fit for the small scale mines underground and the production capacity is less than 500t per day, for in these plants the needed total reduction rate is not large and the process load of the crusher is not high.

The three stage crushing process is the most commonly used crushing and sieving process in dressing plants. This process can be classified into three stage open-circuit crushing (pic.c) and the three stage closed-circuit crushing. In two stage and three stage process, each crushing work is equipped with prescreening to enhance the production capacity of crusher and avoid the ore mud’s blocking. In some cases, the first and second crushing work does not need the prescreening. For the three stage open-circuit crushing process, the final stage is open-circuit so the particle size requirements of crushing products are hardly to be guaranteed. So the large dressing plants often process the ore stones with high water content. The three stage closed-circuit crushing process is usually used crushing and sieving process in large and medium dressing plants. In materials transporting, the crushing products in two stage crushing are mixed with the products in third stage and sent to closed-circuit vibrating screen work.