Inter-particle percolation segregation during burden descent in the blast furnace

Abstract

Inter-particle percolation at the interfaces between burden layers directly influences the permeability of the burden in the shaft of the blast furnace. This paper studies inter-particle percolation of small particles (pellets) into large particles (coke) during the burden descent through small-scale experiments and simulations. A special device was designed for making it possible to consider the effect of the increase in cross-sectional area along with the burden descent. The simulations, which are based on the discrete element method, were first validated using one experimental case. An overall agreement was found between the experiments and the simulations. The velocity distribution of coke and pellet particles in the small bed, the trajectories along the height of the bed and the quantity of percolating particles at different heights of bed were investigated. The results show a considerable inter-particle percolation of pellets into the underlying coke layer at the wall area, but also a percolation over the whole radius of the system. These findings stress the importance of taking measures to prevent percolation by proper design of the charging programs in the operation of the blast furnace. © 2011 ISIJ.