Mineralogy and reactivity of cokes in a working blast furnace

Abstract

Coke samples from tuyere level of a blast furnace were obtained through tuyere drilling. Mineral matter of tuyere level cokes was quantified using SIROQUANT and examined using scanning electron microscope. The apparent CO2 reaction rates were measured using a fixed bed reactor. About 50% of the total inorganic matter of tuyere cokes was found to occur as amorphous or glassy phase. At most of the tuyere level locations, Quartz and mullite contents of the feed coke decreased significantly or disappeared. Silicon carbide and gupeiite were found to be the most notable and common silicon and iron bearing minerals of cokes particularly in the raceway region while gehlenite and spinel were the typical calcium and magnesium bearing minerals respectively. Tuyere level cokes also indicated the presence of significantly high potassium levels as well as the graphite formation. The apparent reaction rate of tuyere level cokes is shown to increase up to ten times of the feed coke reaction rate, and is strongly related to the total amount of potassium species. The study highlights the strong influence of the raceway temperature, the alkali loading and the hot metal presence on the modification of the mineralogy and reactivity of tuyere level cokes with implications on coke selection criterion.