Production of refining alumina-containing fluxes by sintering from technogenic raw materials

Abstract

Modern Russian steelmaking plants use predominantly alumina-containing materials for liquefying lime in a ladle-furnace unit, which replaced fluorspar. Alumina-containing materials currently available on the market cannot be used directly in steelmaking without preliminary preparation (refining, heat treatment or briquetting), or are simply unsuitable for ladle processing of steel. This work describes laboratory studies on the production of refining alumina-containing fluxes by sintering in units such as machines for pellets firing or producing agglomerate (in the temperature range of 1200 – 1500 °C) from clean metallurgical waste (fine dust from the production of alumina and burnt lime), meeting the requirements of steelmaking plants by chemical composition and mechanical properties. A comparison was made of sintering technological schemes with the introduction of hydra­ted lime and a mixture of hydrated lime and calcium carbonate in a 1:1 ratio as a source of CaO. We determined that the maximum permissible CaO content in sintered briquettes when using a mixture of hydrated lime and calcium carbonate in the charge, which does not lead to hydration destruction in air, is in the range of 2.3 - 3.6 %, depending on the holding temperature. The maximum permissible content of Al2O3 in sintered briquettes when using hydrated lime in the charge, which does not lead to hydration destruction in air, is in the range of 9.5 – 31.7 %, depending on the holding temperature. In existing fuel units it is possible to obtain fluxes by sintering only when using hydrated lime as a source of CaO, because adding calcium carbonate to the charge (9 – 22 %) requires an increase in holding temperature (above 1500 °C) or holding time (more than 25 min).