Abstract: To protect rare coal and promote the beneficial efficiency of the enterprise, the approach of coking middlings re-preparation by crushing and dissociation was explored. Coal quality of middlings from one coal preparation plant of Fenxi mining group was analyzed, and then crushing and flotation experiments were carried on. According to the requirement of 10.50% ash content，the theory concentrate yield was only 13.01% of middlings re-preparation with no crushing. While middlings were crushed to 13mm, 6mm and 3mm, the theory concentrate yield reached to 5.90%, 6.80% and 13.01% at the same ash content 10.50%. When ﹣0.5mm coal slime from middlings was separated through flotation consistent with the present experimental conditions on local, the yield of flotation clean coal 28.40% was too high as clean coal. The process improvement was put forward combined with the existing conditions: middlings crushed to -3mm, 3～0.5mm materiel separated in small diameter hydrocyclone, ﹣0.5mm coal slime mixed as middlings after dewatering in filter press.

Key words: coking coal, middling, re-preparation, crushing