Abstract: During the beneficiation process of coking coal,over 30% of middlings are generated. The fine and dispersed distribution of these middlings makes their separation and recovery challenging. In order to address this issue,the research team proposed a reprocessing technique for coking coal middlings based on deep liberation and ultrafine particle flotation. This method involves grinding with an energy-saving ceramic stirred mill,separation using a self-developed cyclone-static micro-bubble flotation column,and optimization of flotation parameters via the " Box-Behnken" response surface methodology. The results showed that high-ash coking coal middlings from a coal preparation plant in Henan could effectively release clean coal when ground to D90 = 12. 87 μm using a JM-1L stirred mill. Based on single-factor conditional tests and " Box-Behnken" model optimization,a fitting model for clean coal yield and flotation efficiency index was established. The optimal flotation performance was achieved with a diesel dosage of 4 601. 62 g / t,2-octanol dosage of 3 955. 56 g / t,and an impeller speed of 1 487. 4 r/ min, which was confirmed by actual flotation tests. The findings provide a theoretical basis for the industrial utilization of high-ash coking coal middlings. 

Key words: coking coal middlings reprocessing,deep dissociation,grinding with stirred mill,ultrafine flotation,response surface method