Investigation of coke collapse in the blast furnace using mathematical modeling and small scale experiments

Burden distribution plays a key role in controlling the gas flow conditions inside a blast furnace. The distribution of ore and coke influences the gas permeability distribution in the lumpy zone and also in the cohesive zone, where the gas flows mainly through the coke slits. Charging an ore dump on coke can sometimes cause the coke layer to collapse under the force of the heavier ore particles. This is known as ‘coke collapse’ or ‘coke push’, which results in a higher coke fraction near the center of the furnace than expected. In this work coke collapse phenomena are evaluated on model charging programs using small scale experiments and Discrete Element Modeling (DEM). DEM simulations were used to study the extent of collapse for different charging programs, and experiments were undertaken to verify the results of the simulations. The slope stability method was used to classify the collapse conditions into no collapse, impact failure or gravity failure, depending on the stability of the coke layer. The findings were also compared with results from an in-house mathematical model, which was modified to consider the effect of the collapse on the underlying layer. The corrected mathematical model was found to show results in general agreement with results from the DEM simulation.