New variants for making vanandium pig iron

Abstract

The Chusovoi Metallurgical Plant has had a great deal of experience in using vanadium-bearing wastes in metallurgical production. For example, the plant has developed a technology that produces vanadium pig irons with high concentrations of manganese and chromium and that is based on the use of discarded sludge from the production of vanadium pentoxide.As a rule, vanadium-bearing wastes are used in the production of sinter and in the charge of oxygen converters or blast furnaces. However, their use in blast-fumace smelting has an adverse effect on the technology currently employed to convert the given elements (Mn and Cr) and increases the amount of vanadium lost with the furnace slag.Researchers have developed and tested a new method of using wastes and semifinished products (chemical wastes, sludge, top dust, and highly basic vanadium-bearing converter slags) -sintering of these materials, followed by their melting in blast furnaces in a mixture with iron-ore-based materials that do not contain titanium. This method makes it possible to alter the structure of the slag melt and stabilize its properties in the blast-furnace hearth during the smelting of vanadium pig iron. The silicon content of the pig in the trial heats reached 1%, but there were no problems with the running of the furnace or hearth operations. The coefficient characterizing the distribution of vanadium between the pig and the slag increased from 2.3 to 9.5 and the amount of vanadium recovered increased by 5.4%. The content of vanadium pentoxide in the slag decreased from 0.331 to 0.088%, i.e., the irrecoverable losses of vanadium declined by a factor of 3.8.One heat was conducted on a charge consisting of 75% pellets from the Lebedinsk Mining-Concentration Combine and 25% local sinter (sintered from a charge that included 60% vanadium pentoxide). As the control variant, we smelted vanadium pig iron on a charge containing 75% pellets and 25% sinter from the Kachkanar Mining-Concentration Combine. There was no deterioration in the technical-economic indices characterizing the operation of the furnace.The expected change in the structure of the slag melt was realized by comparing the phase composition of the slags in the control period and the trial period. Whereas the slag in the trial period consisted of mellite and the associated phases -mervenite, rankinite, oldhamite, dicalcium silicate, and glass -the mellite-based slag in the control period was fundamentally different -it contained the following related titanium-bearing minerals, % (by vol.): -baikovite Ca2(Mg 3, Ti4+A12 , Ti3+)2(SiO4)2012 -up to 35; -titanavtite m[(CaO MgO 2SiO2)]n(CaO(A1, Ti)203 SiO2] -15-20; -spinel MgA1204 -3-15; -perovskite (CaTiO3) and titanium carbides (TIC) -in small amounts.The use of mathematical models to study heat-and mass-transfer processes in the blast fumace made it possible to establish that there were no significant changes in the heating and reducing potential of the gas from in the different periods ( Fig. 1). However, the change that occurred in the com...