Abstract: At present,there is a lack of systematic and scientific characterization of the overall particle size distribution of pulverized products from ores under high pressure gas unloading at high-speed. Using an ultra-poor magnetite ore as raw material and liquid CO2 as working medium,Rosin-Rammler distribution function and fractal dimension are introduced to systematically analyze the particle size distribution characteristics of the products obtained under different osmotic pressures of liquid CO 2. The results showed that the particle size distribution of pulverized products is not uniform,and increasing the CO2 pressure can increase yield of fine particles. Rosin-Rammler distribution function can be used to fit the particle size distribution of the pulverized products. The fitting results demonstrated that the particle size distribution uniformity index decreases with the increase of CO 2 pressure,and the particle size becomes more uneven. In view of the shortage caused by large proportion of coarse particles,fractal dimension is introduced for further analysis. The results showed that the fractal dimension of the powders increases with the increase of CO 2 pressure,and the overall powder tends to be refined. The results of this study can provide reference for the subsequent scientific and systematic evaluation of the overall effect of CO2 high-speed unloading to pulverize various types of ores.

Key words: iron ore,liquid carbon dioxide,high-speed unloading,partical size distribution,Rosin-Rammler distribution function,fractal dimension