A Study of Ring Formation of Sponge Iron in the Rotary Kiln

Ring formation and heavy build-up in an experimental rotary kiln for production of sponge iron using hematite pellets, bituminous coal and nut coke have been described. The build-up from different parts of the kiln was visually examined and its mineral composition was studies in detail by microscopial and X-ray methods. Besides some metallic iron, the minerals identified were magnetite, fayalite, wustite, iron cordierite, hercynite, anorthite and traces of haematite in different combinations. Relevant binary, ternary and quartenary phase diagrams concerning the obse-rved mineral assemblages were examined in detail. The occurrence of the observed minerals was explained in the light of known phase diagrams. The actual chemical anal-ysis of a sample from the zone of heavy build-up was composed of mainly of FeO. Fe20 A1203 and Si02 (besides some mtallic iron) and this composition was located in relevant phase diagram. The minimum temperature at which liquid would form was indicated from a study of these diagrams.The factors responsible for the build-up were examined