The evolution of structural order, microstructure and mineral matter of metallurgical coke in a blast furnace: A review

The implementation of pulverized coal injection technology has resulted in the reduction in the amounts of coke being used in the blast furnace, which has led to increased demands for high quality cokes to provide enhanced performance. Under the twin pressures of resource shortage of coking coals and continuous requirements for improved coke quality, an in-depth understanding of coke behavior in blast furnace has become very important and pertinent. This review article is focused on a comprehensive investigation on the evolution of structural order, microstructure and mineral matter of metallurgical coke in a blast furnace and presents various mechanisms of coke degradation during its descent in a blast furnace toward establishing reference standards for coke quality and performance. Coke structure, microstructure and reactivity were investigated as a function of temperature, its location in the blast furnace and under the influence of alkalis above the tuyere level. The transformation of coke in the blast furnace hearth and its dissolution into hot metal were also reviewed. The current indices for evaluating coke quality were examined based on the modifications of coke structure, and several unresolved issues in the field requiring further research were identified. This literature survey has shown that while crystalline order and microstructure had a strong influence on carburization, gasification reactions and the strength of coke, factors such as mineral matter, alkalis, temperature were among some of the important factors that affected the degradation of coke in a blast furnace.