Material moisture includes external moisture and internal moisture, which has little effect on the screening process. For example, sifting some bituminous coal, the sieve process is difficult to reach 10% moisture, but for lignite with inherent moisture up to 40%, the screening process can be carried out as usual. The external moisture of the material increases to some extent, the viscosity increases, easy to plug the mesh, will make the fine particles bonded into a group, and attached to large particles, the material can not be stratified layering, resulting in a marked decline in screening efficiency.
When sieving the same material with the same moisture content with different meshes, the effect of moisture on the screening efficiency is different. The larger the size of the mesh, the less likely it is to block the mesh and the less water is affected. In addition, the distribution of moisture in each particle size is uneven, the finer particle size of the material, due to the relatively high surface area of high moisture content, so that the water on the sieve greatly reduced, will not affect the smooth progress of the screening process, therefore, High material moisture seriously affect the screening process, consider ways to increase the sieve to improve the screening efficiency.
Sieve material containing clay material, even in the case of low moisture, screening may also be difficult. Because such materials not only easily clumps, and will plug the sieve, it is difficult to remove, reduce the screening efficiency, or even the screening process can not be carried out. When the material with high mud content is sieved, in order to prevent the plugging of the mesh, an efficient sieving device such as an electric heating screen or a string screen can be selected. If the process conditions permit, wet screening can be used, that is, to use water spray.