Impact of high-temperature non-uniform degradation on fines clogging and gas flow in a coke bed

One of the major hindrances in mitigating CO2 emission from the steel industries is the insufficient efficiency improvement of the ironmaking blast furnaces due to the mixed use of the coke fuels having different properties as the reducing agent. This study investigated the gas flow and the clogging in the coke packed bed by the fine coke particles as a cause of the operational instability of the blast furnace. We analyzed the changes in the permeability of the packed bed due to the mechanical destruction of the cokes, which resulted in the generation of fine particles. The changes in the shapes of cokes due to the mechanical stress were tracked via 3D scanning, and this measurement was applied to several cokes having different values of coke strength after reaction (CSR). Using the measured information about particle shape and its variation, the effects of coke degradation on the gas flow distribution in the coke bed were analyzed by the Eulerian-Lagrangian coupling technique. Despite the strong correlation between the amount of coke destruction and the CSR values, the packed beds containing the same amount of fine particles showed a relatively large difference in the pressure drop. Such difference was attributed by the difference in the bed structure that were caused by the rotation and the slippage among the cokes due to the presence of fines between the coke particles. The the slippage between the coke fuels promote the constriction of the voids, thereby increasing the pressure drop. Thus, this study proves that the formation of the bridging among the cokes can maintain the permeability of the packed coke structure, thereby increasing the possibility of performing low-coke operations.

Automated summary

This study investigated the impact of fine coke particles on gas flow and clogging in the coke packed bed, revealing the potential for improving blast furnace efficiency. Mechanical destruction of cokes was found to change bed permeability, affecting gas flow distribution and pressure drop. The study demonstrates that forming bridges among cokes can maintain permeability and increase the possibility of low-coke operations.