Experiment And Energy Consumption Analysis Of Direct Reduction&Melting Separation Process For Low-grade Composite Iron Ore

Low grade and associated ores occupiy main role in China's metal mineral resources,in which the metal is difficult to be separated,resulting in poor utilization efficiency and short resource supply.The blast furnace smelting process using coke as energy source is a mature technology with low energy consumption,but it can only deal with high-grade iron ore.And the low-grade composite ore should be proceesed by ore-smelting electric furnace with much higher temperature.However,traditional one-step ore-smelting electric furnace consumes a lot of high-grade secondary energy.Considering low conversion efficiency of the secondary energy,the one-step ore-smelting electric furnace is not an economic method to process low-grade composite ore.In order to reduce the comprehensive energy consumption of smelting and achieve efficient use of low-grade polymetallic compound mineral resources,a two-step process of Direct Reduction-Melting Separation Process(DRMSP)was proposed in this paper,to realize the hierarchical reduction of iron oxides in different ore phases and the enrichment of other valuable elements.In the direct reduction process,the coal(primary energy)is used for material heating and iron oxide reduction;in the melting process,the high-quality electric power(secondary energy)is used to deeply reduce the FeO with high lattice energy,as well as to melt and separate the molten iron/valuable elements.To that end,the extraction of iron can be maximized and the enrichment of other valuable elements can be improved.The hot metal can be used for high-quality alloy smelting,and the enriched valuable elements can be extracted by the existing mature non-ferrous metal smelting process.Three typical low-grade composite iron ores,which are vanadium titanium magnetite from sea sand(VT),iron bearing copper tailings(IC)and laterite nickel iron ore(LN)are selected as the object of direct reduction process to conduct the experiment study and reaction kinetics analysis.The effects of molar ratio of carbon to oxygen,reduction temperature and reduction time on the metallization rate of iron oxide in composite ore were studied.And the experiments provided operation parameters for direct reduction of VT,IC and LN,where the molar ratio of carbon to oxygen is around 1.8,1.2,and 0.85,the reduction temperature is around 1300?,1200? and 1250?,and the reduction time is around 30 min,40 min and 20 min,respectively.Chemical dynamic analysis indicated that the reduction of VT and IC are firstly governed by chemical reaction,then controlled by chemical reaction and diffusion,finally dorminanted by diffusion.While the reduction of LN is firstly governed by chemical reaction,and then controlled by chemical reaction and diffusion.That results provide theoretical basis for industrial utilization of low-grade composite ore.With the purpose of industrial application,this paper proposed a novel DRMSP based on the RHF.The VT which is the most difficult to be smelt is selected as raw material.In the rotary hearth furnace,the carbothermal method is used to heat the materials and complete most of the reduction reactions at the same time.The huge power consumption of heating materials in the traditional one-step mine thermal power furnace is replaced by primary energy coal.After reduction,the hot material is sent to the molten pool of the submerged arc furnace.The material will melt rapidly in the high temperature liquid molten pool and be deeply reduced,which greatly shortens the reduction time of the submerged arc furnrnace and has significant energy saving effect.In this paper,experimental research was carried out on the pilot production line of the DRMSP based on the RHF,and the carbon supplement reduction technology by injecting coal into the liquid slag layer of the molten pool was developed innovatively,which realized the deep reduction of FeO in the solid solution of ferrous metatitanate(FeTiO3)lattice.The pilot study shows that,qualified high titanium slag products and vanadium pig iron with TiO2 at 82.5 wt.%can be obtained when using the VT sands with 22.4%?24.5%weight of TFe,and 55.3%?57.0 weight of TiO2 as raw materials.The high titanium slag product enriched with TiO2 can be used to produce titanium dioxide by the existing mature process route.The vanadium bearing hot metal can be used for high-quality alloy smelting or converter steelmaking to extract vanadium.To that end,the high value utilization of vanadium titanomagnetite from marine placer can be realized.The energy consumption per unit product of high titanium slag produced by the pilot line is 1462.4(kW·h)/t,which is 36.42%lower than that produced by the existing one-step submerged arc furnace process.