"In situ" studies on cokes drilled from tuyere to deadman in a large-scale working blast furnace

The properties and deterioration of coke have a significant impact on the thermal efficiency, fuel consumption, and CO2 emissions of blast furnace. Coke sample drilling is one of the effective ways to investigate coke behaviors in a working blast furnace. However, previous coke sample drilling process involved compressed coke, which cannot accurately reflect the actual condition of coke in blast furnace. Therefore, "in situ" coke samples were drilled for three times from tuyere to deadman in their original positions within a large-scale working blast furnace in the present work. The results show that the coke particle size degradation reaches 85.36 % in the 0-5 m zone at the tuyere level. The proportion of coke size less than 3 mm increases sharply along the tuyere di-rection, and a new method of calculating the depth of the tuyere raceway zone is proposed for the first time. The study based on the grey relational analysis shows that the depth of the raceway is closely related to the blast volume and the blast kinetic energy. Main factors causing the degradation of coke in the tuyere level are fully revealed in different regions. It is suggested to reduce CaO and alkali metals brought in blast furnace in order to protect coke.