Effect of Selective Pellet Loading on Burden Distribution and Blast Furnace Operations

Good permeability of the blast furnace bed is of paramount importance for stable operations of the same and to achieve it, controlled burden distribution is the key. While coke is primarily used to maintain permeability of the furnace bed (with the ferrous burden particles being considerably smaller), global calls for reducing CO2 emissions substantially are pushing blast furnaces to consume lower amounts of the same. Considering this, other burden distribution methods must be explored to maximize permeability of the burden layer. To do so, efforts are made to control pellet dumping in the burden layer in such a way that it occupies more volume in the mid-radial portions away from the walls. Pellets being spherical in shape and having narrower size distributions than sinter offer more inter particle porosity. Discrete element method (DEM) simulations are used to study the effect of the delay in pellet loading time in the ferrous burden (composed of pellets and sinter) on the positioning in the hopper. This positioning is found to subsequently affect the hopper output constitution, which then affects the radial constitution of the ferrous burden layer. Delaying the pellet loading on the ferrous burden is found to delay emptying of the same from the hopper, resulting in more pellets occupying the mid-radial region of ferrous burden layer in the blast furnace. Based on the observations from simulations, trials are taken in blast furnace and relevant parameters are monitored to capture the effect of such a charging practice on operations.

Automated summary

The permeability of the blast furnace bed is crucial for stable operations. Coke is traditionally used to maintain permeability, but due to the need to reduce CO2 emissions, blast furnaces are now consuming lower amounts of coke. This necessitates the exploration of alternative burden distribution methods to maximize permeability. Delaying the loading of pellets in the ferrous burden is found to result in more pellets occupying the mid-radial region of the burden layer, thus improving permeability.