Pull-out force characteristics of wet pulverized coal on metal surfaces: Experiments and discrete element simulations

Wet pulverized coal produced during dust-suppression operations readily adheres to equipment surfaces, leading to blockage, wear, and increased operational resistance. To clarify the adhesion behavior of wet pulverized coal on metal surfaces, pull-out experiments were performed using pulverized coal samples with varying moisture contents and stainless steel sheets. The Discrete Element Model was then developed based on the Hertz–Mindlin model with Johnson–Kendall–Roberts (JKR) cohesion. The results show that the peak pull-out force first increases and then decreases with increasing moisture content, reaching its maximum at 15% among the tested moisture contents, while the effect of lifting velocity reverses at 25% and 30% moisture content. The JKR equivalent surface energies calibrated using experimental peak pull-out forces at 5 mm/s were applied at 1 mm/s without recalibration, showing reasonable agreement with experiments within the 0–20% moisture content range. Particle-scale analysis further shows that the modeled cohesive interactions restrict rapid particle rearrangement, stabilize local agglomerated structures, and delay the closure of voids behind the moving metal sheet. These results provide a theoretical basis and parameter reference for predicting wet pulverized coal adhesion and for designing anti-adhesion and anti-blockage strategies for coal storage and conveying equipment.