Review of dry screening theory and cross screening technology for wet cohesive fine coal

The theory and technology of dry depth screening of wet-cohesive fine-grained coal is the current research hotspot and difficulty in the international screening field. The easy blocking of the screen aperture and the short life of the screen deck are the two core basic problems in dry screening of wet cohesive fine coal. In order to grasp the current development status of dry screening theory and technology of wet cohesive fine coal, the problems in application and research of two types of widely used screening equipment of fine coal are analysed: equal thickness screen based on equal thickness screening theory and flip-flow screen based on flip-flow screening theory. Then, the research status of particle separation mechanism in the basic theory of the screening process is discussed. And, the shortcomings of DEM (Discrete Element Method) based numerical simulation of particle flow characteristics in the screening process are summarised. The results show that the basic theory of the screening process is the key to developing new screening technology and improving the design level of screening equipment. The separation behaviour of non-spherical wet-cohesive particles system, the flow characteristics of high wet-cohesive particles on the screen deck and the mechanism of penetration are the key issues of the basic theory of the screening process. The DEM-based numerical method can be used to further study the motion behaviour of non-spherical wet-cohesive particles in the screening process from the particle scale. Moreover, the structure characteristics and screening process mechanism of cross-screen are described. The application and research status of cross-screen technology both at home and abroad are summarised. The shortcomings of the basic theoretical research on the screening process of the cross-screen are analysed. And the main problems of the lack of optimisation design theory and method of key structure and process parameters of the cross-screen are pointed out. The research prospects of the cross-screening process mechanism based on screen surface-particle coupling simulation, the lightweight design of the cross-screen structure and the energy-saving optimisation control are proposed.