Optimization of Operating Conditions and Design Parameters on Coal Ultra-Fine Grinding Through Kinetic Stirred Mill Tests and Numerical Modeling

Abstract

This study investigated the ultra-fine coal grinding performance of four low- to moderate-cost grinding media: ceramic balls, granular sand, alumina beads, and silica beads. The kinetic grinding tests were conducted using a stirred mill, while different operating conditions, including the media size, solids concentration, and the addition of viscosity modifiers, were examined. Characterization studies in terms of particle size, shape, and surface morphology were further performed to support the experimental findings. Moreover, using population balance modeling, grinding simulation was performed in Matlab to forecast the particle size distribution based on the specific energy input and experimental size-related data. The results showed that silica beads generated the finest product size with a P80 of 5.9 µm from a feed size of 24.4 µm while having a specific energy (SE) input of 309 kWh/ton, compared to ceramic balls and alumina beads. Nonetheless, the least energy consumption of 109 kWh/ton was achieved by alumina beads; however, yielding a coarser product size of 15.5 µm. In addition, test results indicate that choosing suitable media sizes, reducing the solids concentration, and using viscosity modifiers enhance coal ultra-fine grinding performance. Under the optimized testing conditions, a P80 of 2.7 µm was produced with a corresponding SE input of 270 kWh/ton using silica beads ranging from 420 to 850 µm and a dispersant dosage of 14 kg/ton. Moreover, the mathematical models, generated based on the breakage function, selection function, and particle swarm optimization, provided an accurate forecast of the particle-size distribution at the end of the study.