Abstract: In order to study the selective dissociation characteristics of coking coal middlings in stirred mill,taking the coking coal middlings of Guobei Coal Preparation Plant as the object,the sample properties,grinding conditions optimization, dissociation characteristics of grinding products and particle shape characteristics were studied. The flotation effects of grinding products of stirred mill and rod mill under the same grinding fineness were compared. The results showed that under the optimal grinding conditions of stirred mill grinding time of 4 min,ceramic ball diameter of 6 mm,medium filling rate of 60% and grinding concentration of 55%,the grinding products with -0. 074 mm content of 79. 39% were floated,the concentrated coal (Ad = 11. 50%) products with yield of 61. 49% were obtained. At the same grinding fineness,the grinding time required by the stirred mill was shorter,and the yield of high-ash fine mud was lower. The yield of flotation concentrated coal (Ad =11. 50%) of the grinding products was 9. 82 percentage points higher than that of the rod mill,indicating that the stirred mill had a better dissociation effect. SEM analysis further confirmed that there were less micro-fine gangue minerals on the surface of the stirred mill grinding products,the particle sphericity (R0 ) was low,and the elongation (EW) was high,which was conducive to the adhesion of particles and bubbles. The research results can provide process ideas for selective dissociation of coking coal middlings.

Key words: coking coal middlings,optimization of grinding conditions,dissociation characteristics,particle shape coefficient, flotation