Mineral Liberation Properties of Iron Ores with Different Grain Sizes by Particle-Bed Breakage and Traditional Grinding

More efficient liberation of valuable minerals from gangue would bring enormous benefits to the comminution process and the downstream beneficiation processes. However, whether particle-bed breakage can improve liberation compared with traditional grinding has been controversial. In this study, three types of iron ores with 3-0.425 mm were comminuted to -0.425 mm via the piston-die compression unit or the dry ball mill at essentially the same grinding degrees. Liberation analysis was performed using Mineral Liberation Analyzer (MLA) for each breakage method and the size fraction product. Statistical methods based on bootstrap resampling and standardized mean differences (SMD) were used to quantitatively analyze the significance of differences in the liberation distribution of iron oxide minerals with different breakage methods. MLA tests showed that the particle-bed breakage did not significantly improve the liberation degree compared to the ball mill grinding; the maximum difference of the proportion of 80-100% liberated iron oxide mineral in a certain size fraction with the two breakage methods was only 5%. The SMD was less than 1.2 in most size/composition classes, which indicated that the difference in the liberation distribution of iron oxide minerals between the two breakage methods was not statistically significant in most size/composition classes. The particle-bed breakage slightly improved the liberation of iron oxide minerals compared to ball mill grinding at the particle size of the products close to the grain size of the iron oxide minerals in the feeds.