Effect of Ore Filling Ratio on Pulverization Performance and Energy Utilization During High-Pressure Gas Rapid Unloading

High-pressure gas rapid unloading (GRU) is an emerging ore pulverization technology capable of inducing cross-scale pulverization and generating micron-sized particles within milliseconds through rapid gas decompression. However, the influence of ore filling ratio on GRU pulverization performance remains unclear. Using BG iron ore as the experimental material and high-pressure air as the gas medium, this study investigates the effects of filling ratios of 1/3, 2/3, and 100% on GRU pulverization performance and energy utilization. The results show that as the filling ratio decreases from 100% to 1/3, the cumulative particle-size distribution curves of the pulverization products shift systematically leftward, with D50 and D80 decreasing from 2.3 mm and 18 mm to 0.15 mm and 6 mm, respectively. Rosin–Rammler fitting further indicates that the characteristic particle size decreases approximately linearly with decreasing filling ratio. Theoretical analysis reveals that a lower filling ratio reduces the ore mass accelerated by the propulsion gas, resulting in a higher ore ejection velocity, increased impact stress, and enhanced secondary pore gas pressure amplification, thereby promoting more thorough pulverization. However, specific surface energy consumption analysis shows that although lower filling ratios improve pulverization fineness, they also reduce energy utilization efficiency. Therefore, excessively low filling ratios may not represent the most economical operating condition for continuous GRU production, but may remain advantageous for applications requiring enhanced ultrafine pulverization or the processing of high-value minerals. These findings provide experimental and theoretical support for filling ratio optimization and process design in practical GRU applications.