The coal preparation process for production silicon coal at Xingmei Coal Mine from Xinjiang Uygur Autonomous Reign: process design and practice

Called silicon coal for short, the industrial silicon coal is a product which places a high requirement on quality indicators and high in sale price. Through analysis of the coal samples collected from Xingmei Mine, the feasibility of producing silicon coal with the raw coal, as well as the product structure and the production process are affirmed and defined, and the design of the coal preparation process is finalized. As shown by analysis of the coal property, the raw coal is low in contents of inherent ash, volatile matters and Fe₂O₃, making it feasible to produce silicon coal; considering that coking coal has currently a more mature market, the produce mix of the mine′s coal preparation plant should be made by predominately coking coal while making silicon coal subsidiary; as the raw coal contains a high percentage of coarse particles which is high in content of dirts, intelligent gangue removal separator can be used to enhance adaptability of coal preparation process and reduce labor intensity; considering the size requirement of both coking and silicon coal products, the upper size limit of separation should preferably be set at 25 mm or 50 mm and the lower size limit of separation is reduced to zero by taking account of the volume of size reduction and degree of liberation of raw coal; the raw coal is comparatively high in hardness, and when crushing is made according to the required upper size limit, the crushed coal contains a high percentage of coarser particles, which is conductive to the production of silicon coal; for producing silicon coal, the raw coal belongs to an extremely difficult-to-wash coal while for producing coking coal, the raw coal is a kind of moderately difficult-to-wash coal; and for producing either coking coal or silicon coal product using heavy-medium separation process, a very high theoretical yield can be gained. The designed coal washing process possesses the following special features: the pressure-fed 3-product heavy medium cyclone for treating dislimed coal is used as the primary washing equipment for higher adaptability to washability of feed coal, elimination of the problem of entrainment of fine dirts in clean coal product otherwise encountered with the use of gravity-fed H. M. cyclone, and higher adaptability to variation of raw coal property; the coal washing process of producing first coking coal and then silicon coal can help maintain stability of ash of product and facilitate medium draining operation; the primary H.M. cyclone′s first stage is in a cylindrical-conical form and is arranged at a negative inclination angle, which is conducive to increase of difference of separation densities between the cyclone′s first and second stages, and can meet the needs for producing coking coal through the first stage at a lower separating density, and for producing pure reject product through the second stage, as well as adapt to the raw coal property featuring a high yield of lighter materials; for medium draining, the sieve bend + linear vibrating screen draining process is applied, and the screens are arranged in a hall form and fitted with three rows of waters praying units and corresponding water-retaining dams for facilitating medium draining and maintenance of screen; several coal flow lines are reserved; and the entire washing system can be flexibly adjusted. The product structure and the coal preparation process designed based on analysis of raw coal property prove to be up to the requirements for the production of silicon coal and can bring about favorable economic benefits for Xingmei Mine. The work made in the paper may serve as a reference for other enterprises which are intending to produce silicon coal product.