Melt Down Behaviour of a Fused Layer in the Blast Furnace Cohesive Zone.

Abstract

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.

Modeling of Blast Furnace with Layered Cohesive Zone

“…The shape and position of the CZ can change significantly with operational conditions [1,6] and, because of its restricted permeability and role as a gas and liquid distributor, largely determines the BF performance and operational stability. To understand this zone, several numerical and physical experiments have been conducted to study the hightemperature properties of iron-bearing materials, [7][8][9][10][11][12][13][14] reaction mechanisms, [15] fluid flow behavior, and temperature distributions [6,[16][17][18][19][20] within the CZ. These studies highlight the complex softening-melting behavior, which include the variation of permeability and strong horizontal gas and liquid flows in the CZ.…”

Role of Al₂O₃ in Interfacial Morphology and Reactive Wetting Behaviour between Carbon-unsaturated Liquid Iron and Simulant Coke Substrate

“…This trend of varied carbon dissolution with the initial carbon concentration of the iron samples agrees well with previous studies. [2][3][4]8,11) From these results, Al 2 O 3 is concluded to impede carbon transport phenomena from the substrate to the molten iron sample; larger initial carbon contents in the iron sample also cause decreases in the carbon absorption capacity of the iron sample.…”

Review on Modeling and Simulation of Blast Furnace

“…Liquid slag and iron generated in CZ trickle down or drop in “icicle” through the coke bed to the hearth, and during this process, exhibit complicated behaviors, including for example: (i), an unsaturated liquid percolates through a packed bed in the form of rivulets or drops; (ii) localized upward liquid flow, saturation and flooding may occur in CZ: (iii), the effect of packing property on liquid flow is significant; and (iv), slag may exist in a BF as a non‐wetting or wetting liquid depending on its reaction with coke, and slag and iron flows may be closely coupled. To describe these features, a few models have been proposed, including the potential flow, probability model, probability‐continuous model, tube network dynamic model, and force balance model, as reviewed by Yagi and Dong et al Among them, the so called force balance model is probably the most promising in describing various liquid behaviors within CZ and coke zones. In such a model, the liquid as rivulets or droplets flows under the influence of gravity, gas drag, and bed resistance, which are in balance with each other.…”

“…Notably, the predicted droplets usually have different sizes or present a discrete characteristic within the computational domain, depending on operational conditions, packing structures, as well as liquid, and coke properties. This force balance model has been successfully implemented in different BF process models . Below is the representative the force balance model developed Wang et al, which includes a liquid flow sub‐model featured by the force balance that applies to the discrete liquid flow and a liquid dispersion sub‐model to consider the stochastic motion that relates to a complicated packing structure.…”

“…[66] www. REVIEW probability-continuous model, tube network dynamic model, and force balance model, as reviewed by Yagi [10] and Dong et al [11] Among them, the so called force balance model [46,[138][139][140][141][142][143][144][145][146] is probably the most promising in describing various liquid behaviors within CZ and coke zones. In such a model, the liquid as rivulets or droplets flows under the influence of gravity, gas drag, and bed resistance, which are in balance with each other.…”