Formation of potassium slag in olivine fluxed blast furnace pellets

Abstract

Mineralogical evaluation of olivine pellets coated with kaolinite, taken from the LKAB experimental blast furnace, shows significant reactions with potassium. Sampling has revealed strong potassium deposition in pellets in the lower shaft close to the wall, but much less deposition towards the furnace centre. Iron reduction and the deformation of the pellets were enhanced in the zone of high alkali deposition. Thin sections of pellet samples were prepared to distinguish amorphous and crystalline slag phases for a better understanding of the formation of the potassium rich slag. Olivine breaks down to various extents to form a SiO₂–FeO–MgO–K₂O glass. The kaolinite coating shows strong reaction throughout the cross-section of the lower shaft to form kalsilite (KAlSiO₄) and K₂O rich glassy slag. Studies of thin sections of the slag products were shown to be very useful in separating amorphous phases such as the K₂O rich glass from the crystalline olivine rim.