In the practical production of mining industry, the widely used crushing methods at present are still predominated by mechanical force crushing, including crushing, cutting, breaking, grinding and impacting, and the non-mechanical force crushing such as ultrasonic crushing has not been in application in the industrial production yet.
The types of the crushing equipment that is used in the modern industry are various and the classifying methods vary as well. The crushing machines can be divided according to their working principle and structural features into jaw crusher, cone crusher, roller crusher and impact crusher.
(2) Screening work. The process of separating the mixed materials of different sizes according to their granularity level is called screening. Two products can be obtained by screening: one is above screen products whose granularity is smaller than the screen hole so that they are able to go through the screen surface, and the other is under screen products that are left on the screen surface. In order to make the screening process come true, the materials should do relative motion on the screen surface, the purpose of which is on one hand to keep the material layers on the screen surface in a loose state and to produce layers according to the granularity, and on the other hand, the motion of the materials and the screen promotes the materials that block the screen mesh to break away the screen surface which will help the materials go through the screen mesh.
(3) Grinding process. The main task of grinding process is to realize the monomer separation of useful minerals and provide suitable dressing granularity for the beneficiation work so that it is the crucial procedure of the ore dressing technology.
The ore grinding equipment that is widely used in the ore dressing plant is ball mill and rod mill and the autogenous mill also has wide application in some new established plants in recent years. At the same time, some special fine mills such as vertical mill and vibrating mill have also been used in the ore grinding operation.
(4) Grading work. The process of separating the materials into several granularity categories according to the different settling rate of the particles in the media is called grading. The media that are used in the grading include air and water and that using the air as the medium is called dry grading and that using water as the grading medium is called wet grading. In the wet grading, according to the difference of operational purpose and equipment used, it can be divided into water power grading and mechanical grading.