磁铁石英岩落锤冲击破碎效果与能量关系

为研究磁铁矿石机械冲击破碎效果与能量的关系,开展了落锤冲击破碎试验、数码显微镜观察试验和原子吸收光谱检测试验,分析了磁铁石英岩冲击破碎特征与矿物分离特征,得到了能量密度与矿石碎块的粒度分维数、平均粒度和矿物颗粒分离效率的理论关系. 研究发现,碎块粒度分布具有分形特征,粒度分形维数和平均粒度较全面的描述磁铁矿石英岩冲击破碎程度；磁铁石英岩经落锤冲击后,发生矿物颗粒分离的碎块粒度与矿物嵌布粒度一致,碎块粒度越小矿物颗粒分离越显著；与二段磨矿产物相比,冲击破碎分离的矿物颗粒形态与光学特征更接近原矿矿物学特征；冲击破碎分离的磁铁矿颗粒全铁品位高于二段磨矿产出的磁铁矿颗粒,可以满足选矿的需要. 结果表明:随能量密度的增大,碎块粒度分维数呈负指数增长的变化特征,碎块平均粒度呈三次多项式降低的变化特征,矿物颗粒分离效率呈三次多项式增长的变化特征; 磁铁矿石冲击破碎过程中通过增大破碎能量密度,提高矿石破碎程度,增大矿物颗粒质量分数,将矿物颗粒筛分后直接进入磁选,可降低单位磁铁矿石加工总能耗.

Relation of crushing effect of magnetite-quartzite to energy under drop weight impact

To investigate the relation of crushing effect of magnetite and energy under mechanical impact, the drop weight impact experiments, electron microscope observation test, and atomic absorption spectrometric analysis tests were carried out. The fragmentation characteristics and the separate mechanism of mineral particles of banded magnetite-quartzite under impact were analyzed, and the theoretical relations between energy density and size fractal dimension of fragments, average fragment size, and mineral particle separation efficiency were obtained. The study found that there were fractal characteristics in size distribution fragments, and the breakage extent of magnetite-quartzite under impact could be described more comprehensively with size fractal dimension and average fragment size. The fragment size under the separation of mineral particles was consistent with size of minerals, and the smaller the fragment size, the more remarkable the mineral separation is. The morphology and optical characteristics of separated particles after the impact crushing were closer to the mineralogical characteristics of the ore in comparison with the products of the second stage grinding, and the total iron grade of separated magnetite particles produced from impact crushing met the requirement of beneficiation for it was higher than that produced from the second stage grinding. The results showed that the average particle size decreased by cubic polynomial with the increase in energy density. The fractal dimension increased exponentially, and the separation efficiency of mineral particles increased by cubic polynomial. The specific energy consumed in magnetite ore processing could be reduced by increasing the breakage extent of magnetite-quartzite, the mass ratio of mineral particles, and energy density during crushing, and directly conducting magnetic separation after sieving mineral particles.