Behavior of Alkali‐Bearing Minerals in Coking and Blast Furnace Processes

Abstract

The distribution, structural, and textural features, and behavior of alkali‐bearing (K and Na) minerals are characterized from coking coals to feed coke and blast furnace (BF) coke. In coals, they are mostly represented by phyllosilicates (illite, montmorillonite, biotite, and muscovite) and feldspars. During the coking process, phyllosilicates retain a layered texture of their aggregates. Under coking conditions, feldspars keep the original outlines of mineral grains and bulk composition. There are no substantial changes in the volume of mineral grains and these alkali‐bearing minerals have no physical effect on the coke matrix at coking temperatures. Thermodynamic calculations have shown that there are two major alkali‐bearing mineral phases left in the system toward the end of the coking process – albite and leucite. Under BF conditions, Na is fully transferred to the molten phase above 1000 °C, while K partly occurs in leucite up to 1434 °C. The formation of intercalation compounds under BF conditions starts at 1127–1136 °C. Since K is referred to as a main intercalate phase in coke, then attention should primarily be focused on the presence of K‐bearing minerals in coking coals. The quality of coals is assessed by the amount of K‐bearing phyllosilicates and K‐feldspars.