Analysis of the problems arising in washing of raw coal from different sources in an alternate manner and remedial measures

After the shifting of the raw coal cleaning pattern from a mixed to an alternate manner, the problems faced by the plant involve poor raw coal predesliming and medium draining effects and unsteadiness of coal washing operations. To cope with the situation, technical transformation work is made by the plant by taking the following targeted measures: replacing screenplates at fore-section of desliming screen with ones fitted with aprons and part of the plates with T-shaped ones, and adding a row of water sprayers, for attaining an intensified desliming effect; adding regulating valves on branch pipes of water spraying system of medium draining screen for enabling the screen to better adapt to variation of feed rate; and shifting heavy medium suspension split-flow adjustment from automatic to manual modes to make it possible to adjust separation density to the preset value in a short time, for thus ensuring the consistency of quality of separated products. The technical transformation work has yielded tangible results as evidenced by the rise of desliming efficiency from 77% to 83%, a drop of medium consumption from 0.88 kg/t to 0.79 kg/t, the possibility to vary heavy medium suspension density up or down 0.01 g/cm³ in a short time of about two minutes—a cut of three minutes compared with automatic adjustment mode, and an increase of combined clean coal yield from 68.67% to 70.86%.