Activation Grinding of Coal in Production of Low-Ash High-Purity Concentrates

The present investigation is focused on feasibility of activation grinding to expose mineral components and to improve reactivity of surface layers of a particle. Particular attention is given to grindability, demineralization, modification of reactive capacity of organic components, metamorphism of coal substance, type and level of energy effects. It is demonstrated that disintegrating grinding with a free destructive impact is the most efficient process to open intergrown aggregates and to higher the energy state of surface coal layers in combustion and ignition processes. The activating dispersion of long-flame coal at the particle collision velocity V = 100 m/s yields – 20 µm products showing the greatest dispersability. The most favorable for processing product of – 0.25 + 0.02 mm is produced from long-flame and lean coals at V = 40 m/s. Long-flame coal fraction of – 20 µm exhibits the highest ash-content, A c being as high as 30 % and the removal of this fraction can be considered as a coal enrichment operation. Significant differences established in the thermal-oxidative destruction kinetics of initial and activated coals and the reduction in activation energy permit to higher oxidation velocity by 20% and to intensify fuel combustion. It is found experimentally that high demineralization of coals with 1% and lower ash content is feasible by the chemical treatment of mechanically activated coals in an aqueous medium at a centrifugal-planetary mill, operating at shear-and-crushing mode. The process is accompanied with defect formation and amorphisation of mineral component structures: quartz, feldspars, sheet silicates, clays along with improving their activity.