Study On The Migration Behavior Of V&Cr In The Smelting Process Of V&Cr-Containing Hot Metal In Converter

China is the largest producer of vanadium products in the world because of its abundant vanadium resources and advanced vanadium development technology.However,chromium resources are extremely scarce and rely on imports for a long time.In Panxi area of China,the Hongge high chromium vanadium-titanium magnetite ore is a refractory ore associated with vanadium,chromium,titanium,iron and other metals,and it is a valuable chromium resource in China.It has important economic and social benefits to achieve the comprehensive utilization of this mineral resource,especially the effectively synchronous separation of vanadium and chromium from the resources.The representative utilization techniques of high chromium vanadium-titanium magnetite are the blast furnace and rotary hearth furnace techniques to direct reduction of V and Cr.In these techniques,vanadium and chromium are enriched from hot metal to the slag phase in the converter in the follow-up processes.The technique of oxidation and separation of vanadium from molten iron has been very mature,as most of the physical and chemical properties in vanadium extraction process using converters have been studied.However,the co-existence of vanadium and chromium in the hot metal significantly changes the physical properties,chemical heat and the solute activity of molten iron.New requirements have been put forward to investigate the synchronous oxidation process of vanadium and chromium.The migration behavior of vanadium and chromium between slag and hot metal,which could directly affect the synchronous oxidation and separation,is not well studied.Therefore,it is of great significance to study the migration behavior of vanadium and chromium in the converting process.In this thesis,the reaction temperatures of carbon-chromium oxide reaction and carbon-vanadium oxide reaction in the converter were analyzed by the combined MIVM and IMCT models.It was found that under[C]4.5%,[V]0.30%,[Cr]0.40%condition,the starting temperature of carbon-chromium oxide reaction was 1639.40 K,which was less affected by the chromium content in the hot metal but increased with the increase of vanadium content in molten iron.Under the same condition,the starting temperature of carbon-vanadium oxide reaction was 1767.37 K,and less affected by the vanadium content in the hot metal but increased with the increase of chromium content in the hot metal.The distribution of V and Cr between slag and hot metal was verified by the Thermodynamic model calculation and indirect experiments.The V and Cr distribution ratio between slag and hot metal increased with the increase of oxygen potentials and decreased with the increase of temperature.The results from the indirect determination of V-Cr distribution ratio between slag and hot metal shown that when the Cr₂O₃content in the slag increases from 2.5%to 8.0%,lg L_Crand lg L_Vincreased first and then decreased,and reached the maximum when the content of Cr₂O₃was about5.8%.lg L_Crand lg L_Vincreased if the V₂O₃content in the slag increased gradually.When Si O₂content in the slag increased,lg L_Crand lg L_Vslightly decreased.In the laboratory,all component hot metal was used to react with strong oxidizing slag,in the absence of oxygen,the oxidation rate of each element increased as the hot metal temperature increased.Vanadium and chromium oxides also reacted with carbon with the strong oxidizing slag.The reaction temperature of carbon and vanadium oxide was higher than that of carbon and chromium oxide.The critical temperature for the migration of chromium from the slag phase to the hot metal was lower(1573K),and the changing temperature had a greater influence on the migration of chromium.In the process of direct oxidation of vanadium and chromium with O₂,the higher the oxygen partial pressure and the temperature were benifical to the migration of vanadium and chromium from hot metal to slag.Through the experiments of oxidizing the V-Cr hot metal,single factor and orthogonal tests of the blowing process at the limit temperature were conducted in the induction furnace.The results further verified that low temperature was favorable for V-Cr migration from hot metal to slag.The effects of various factors on the vanadium oxidation in hot metal were as follows,oxygen pressure>pellet usage>oxygen blowing time>lance position,the best factors were,lace position 6cm?oxygen blowing time 10min?pellet 12kg?oxygen pressure 0.40MPa.The effects of various factors on chromium oxidation in hot metal were as follows:oxygen pressure>lance position>pellet usage>oxygen blowing time,the best factors were,lace position 5cm?oxygen blowing time 6min?pellet 10kg?oxygen pressure 0.35MPa.Increasing the usage of pellets increased the oxidation of slag and also controled a lower temperature in the converter.At the same time,with suitable oxygen pressure and lance position,the efficient migration of vanadium and chromium from the hot metal to slag can be realized.Based on the theoretical analysis and experimental results,the control requirements of V-Cr hot metal smelting process in converter were determined.Through industrial exploration tests,the best positions were gotten,the oxygen supply should separated in two-stage method(0.68MPa in the early stage and 0.72MPa in the last stage),1653k as the semi-steel control temperature,and 5.96kg/t Fe usage of pellet for every 0.10%increase of[Cr]in molten iron.Through the production of extracting vanadium and chromium from molten iron of 40000 tons,the developed technology of extracting vanadium and chromium from molten iron of converter has been successfully applied in industrial production.The oxidation rates of vanadium and chromium reached 90%and82%respectively,and the recovery rates were 85.61%and 76.66%respectively.The industrial and efficient extraction of vanadium and chromium from hot metal was realized.Under industrial production conditions,lg Lv was between 2.08?2.67,lg Lcr was between 1.59?2.31,lg Lv and lg Lcr increased with the increase of(Fe O),(V₂O3),(Cr₂O₃)content in slag,decreased with(Si O₂)content,and decreased with the increase of temperature.