Melt down behaviour of a fused layer in the blast furnace cohesive zone

The cohesive, or softening-melting zone plays a critical role in determining blast furnace performance and stability. The effect of changes in the permeability of softening-melting ore and the subsequent distribution of gases and liquids around the anisotropic packing structure of coke and ore layers in this region must be understood before the blast furnace can be adequately modelled. This study aimed to address issues related to cohesive zone formation through low-temperature experimentation. Two investigations of meltdown behaviour were performed, classified according to geometrical characteristics. The first 'flat layer meltdown' investigation examined the softening-melting of flat cohesive layers extending across the furnace diameter. This configuration matched that used in high-temperature softening-melting tests. The second 'single layer meltdown' investigation concentrated on a single cohesive layer embedded in a permeable packing. This configuration can be likened to a single cohesive layer in a permeable cohesive zone, where gas is able to bypass ore through intermediate coke slits as permeability is lost. The meltdown of flat cohesive zones was characterised by variability and gas channelling, promoting furnace instability and preventing accurate modelling. The meltdown of single layers demonstrated the possibility of structural variation between the surface and core, and the change in contribution of convection and conduction to heating.