Behaviour of Coal associated Minerals during Coking and Blast Furnace Processes - a Review

Metallurgical coke is made from a mix of several types of coal that contain various minerals, including quartz, carbonates, feldspars, sulphides and a number of phyllosilicates, represented by clay minerals and micas. During coking and coke consumption processes the minerals undergo various physical and chemical changes, which in the case of coke oven batteries include desulphurization, decarbonation, dehydration, dehydroxylation, polymorph transformations, melting with the formation of an alkali and silica-rich liquid, and transformation to another crystalline phase. The typical modifications of mineral phases in a blast furnace (BF) coke are polymorph transformations, melting, and the formation of another crystalline phase. These events are also preceded by notable changes in the shape of crystalline aggregates. All these changes affect the coke properties and the processes occurring in a BF. Mineralogical data can help us to better understand the processes taking place in coke batteries and in a BF, and to improve the quality of a coke by more careful selection of coal blends and setting optimal temperatures for its pre-heating. The degradation of a BF coke by alkalis can be reduced by the addition of certain minerals to the feed coke before charging into the BF.