A study on stagewise upgrading of coal slime for reducing its untreated volume at power coal preparation plant

In order to meet the requirement for reducing as much as possible the output of untreated coal slime, a study is made with the power coal treated by Huaibei Taoyuan Coal Preparation Plant as the object. Based on analysis of size and density and mineral composition of the coal, a three-stage technical route to attainment of the objective through the use of the following stagewise processes is proposed: reduction of ash of coarse slime and tailing through gravitational separation system and in-depth flotation process, respectively, and dewatering of tailing using new-type hydropress. Study results shows that for treatment of coarse slime, compared with teetered-bed separator, the use of spiral separator can lead to a much higher yield and a lower ash of clean slime, which are 88.82% and 23.05%, respectively; and the tailing is treated only through a single flotation process, and with the dosage of agents and feed density at 0.45 kg/t and 90 g/L, respectively, the concentrate yield and ash are 41.31% and 15.74%, respectively, raising the calorific value of concentrate to a level of 20.97 MJ/kg. Through separation of coarse slime, flotation of tailing, and dewatering of fine slime, the clean coarse slime and flotation concentrate both see a rise of calorific value by 23.50% and 65.30%, respectively. After dewatering all the slime products can be blended with clean coal, allowing calorific value of commercial coal to go up to 21.32 MJ/kg, and hence making it possible to realize in-plant full recovery of coal slime.