A study of rock ladder structure used in buffer storage of iron ore pellets: DEM simulation and analytical model

Abstract

Purpose This paper aims to analyze the abrasive damage of iron ore pellets (IOP) during charge inside day-bins in iron making plants. The rock-ladder structure of day-bin is the spotlight of this study. A numerical-analytical method is used to investigate the main geometrical features of the mentioned structure. Practical results of this study are expected to result in optimization of rock-ladder structure to reduce fine generation and lump formation during pellets downfall on the floors of rock-ladder. Design/methodology/approach One effective stage of pellets downfall on the floor of rock-ladder was simulated using discrete element method. A special post-process code is used to calculate parameters of pellets collisions for an analytical model which estimates fine generation during collisions. The main damaging mechanism during pellets storage inside day-bin is determined based on the comparison of the numerical-analytical results and industrial reports. Different rock-ladder designs are simulated to find optimal geometry of the rock-ladder structure. Findings According to the results, 85.4% of fines generation takes place during downfall of IOPs on the floors of rock ladder, and the rest of the fine debris is expected to be generated due to flow down under compressive load and vibratory discharge. The present study suggests an increase in the rock ladder floors distance from 1.63 to 2 m, but this suggestion should be confirmed by another study focusing on the breakage damage of IOPs. The idea of chamfering the floors corners not only removes lump-formation zones but also results in an approximately 5.7% reduction in the fines generation rate. Originality/value According to the results, introduced modification ideas for rock-ladder structure can result in lower fine generation, lower lump removal cost and lower manufacturing cost of rock-ladder structure.