Effect of two-stage energy input on enhancing the flotation process of high-ash coal slime

To solve the mismatch problems of nonlinear changes of coal slurry properties and energy input during the continuous flotation process, we used a two-stage energy input method to promote the efficient recovery of clean coal and achieve maximized benefits. Results showed that the flotation rate constant increased with the increase in stirring speed and reached its maximum value of 0.0271 s-1 when the stirring speed increased to 1200 r/min under a single energy input, with a maximum combustible recovery of 74.35%. However, the short-term flotation results within 40 s showed that the combustible recovery increased with stirring speed and reached its maximum value of 50.19% at 1500 r/min. The stirring speed was set at 1800 r/min for a fast flotation period and 2400 r/min for an enhanced separation period, which could achieve a maximum combustible recovery of 89.21%. Furthermore, the adsorption density of the collector was optimized, exceeding that achieved under single-stage energy input. The flotation process could be optimized by two-stage energy input. Coarse coal particles were preferentially floated by low-speed stirring in the initial fast selection period. Fine coal particles were further separated during the enhanced separation period under the action of high-speed shear. Two-stage energy input could significantly improve the combustible recovery of the overall flotation of coal slime.