Application of manganous limestone as a fluxing addition at pellets production

Abstract

Usage of non-fluxed pellets in blast furnaces results in blocking of hearth coke filling, decreasing of blast furnaces productivity and increasing of coke rate. The wide range of plastic-viscous state and non-sufficient filterability of pellets slag portion through the coke filling are the main reasons of the consequences. Fluxed pellets have narrower interval of plastic-viscous state and better filterability of pellets slag portion through the coke filling. Their utilization enables to decrease the gas-dynamic resistance of blast furnace cohesion zone, to eliminate progressive hearth blocking, to intensify the hot metal production process and to increase its economic efficiency. In 70–80thof the previous century attempts were made to substitute the bentonite in burden at pellets production by hydrated lime and burnt lime, by marl, by nontronite clay, by red sludge and other additives, combining properties of the raw pellets strengthening and fluxing. But the methods listed were not implemented practically, in particular, because of difficulties in those two properties effective combining. Last years a new raw material appeared at the fluxes market – the manganous limestone. Manganese oxide, contained in it, decreases the sinter smelting temperature, calcium carbonate acts as a flux, while water and physical properties of the limestone improve the increase of the burden lump-forming capacity and sinter strength. The aim of the study was to check the manganous limestone influence on the production process and raw pellets strength, change of roasting parameters and strength of roasted pellets, as well as change of high-temperature properties of fluxed pellets made of Stojlensky GOK concentrates. The study were carried out in laboratory conditions by usage of Dash-Salakhlin bentonite and manganous limestone. The results of laboratory study of both raw and roasted pellets, obtained at utilization of manganous limestone as a fluxing additive to burden, showed, that their physical and mechanical properties are higher and metallurgical properties are higher, compared with non-fluxed pellets.