Analysis of impact of mechanical degradation of iron ore pellets on gas flow in a direct reduction furnace using simulation

Abstract

Iron ore pellets are increasingly important in the production of sponge iron using reduction furnaces. The utilization of pellets present advantages over lump ores, increasing productivity, process stability and throughput. Compared to lump ores, pellets present higher resistance to mechanical degradation. Nevertheless, generation of fragments is still regarded as a challenge in operation. Fragments from pellets generated inside the furnace are known to have a strong influence on the properties of the reduction gas, creating operational problems such as increase in pressure drop, clustering and loss of efficiency. This work studies the influence of the mechanical degradation of iron ore pellets on the properties of the gas inside a reduction furnace. A numerical simulation methodology is proposed for the prediction of the relationship between the mechanical stressing of the pellet, the creation of fragments due to degradation and the influence of the fragments generated on the velocity and pressure fields of the reduction gas inside the furnace. The simulation methodology is applied to predict operation of an industrial MINIMOD MIDREX furnace. Results show that the proposed methodology presents great potential for the simulation of the reduction process giving useful insights about the behaviour of key variables and how they relate to the presence of fragments created due to degradation.