Mineral Transition Of Fe,Al-Associated Ore During Carbothermic Reduction Process

In China,the iron-bearing resources reserve is huge.It is significant for the sustainable development of our bauxite resource and ore resource if we make a comprehensive utilization of them.Almandine Ore iron oxide and alumina content were lower,cannot reach the respective industrial grade requirements,the traditional method for producing alumina and iron is not economic,but high iron bauxite has a higher total content of useful components.Task Force proposed a "Reduction rotary hearth furnace-Furnace melting points-Extracting alumina from calcium aluminate slag" to deal with high iron bauxite,comprehensive utilization of high iron bauxite.In this paper,this technology-based,high iron bauxite,coal,AR calcium carbonate and lime as raw material,systematic research on the rotary hearth furnace pre-reduction stage,under different conditions almandine Ore during sintering iron metallization rate,calcium aluminate mineral phase formation rule,macro and microstructure of the charge.Effect of MgO impurities and cooling system on calcium aluminate slag mineral phase and the leaching rate.The main findings as follows:When the reduction time is 0?60 minutes,burden metallization rate increases with reduction time,if extended to 90 minutes,burden metallization rate declines;In pre-reduced ore,the main mineral phase for Fe??-2CaO·SiO2?CaO?12CaO·7Al2O3?2CaO·Al2O3·SiO2?3CaO·Al2O3,and with the increase of reduction time,the main phase is not change,but content is change.Pre-reduction increases with time,and the amount of liquid is increase,and enhance the strength of pre-reduced ore.When reduction temperature is 1200??1350?,with the increase of temperature,the change of material column apparent morphology is bigger,when 1350?,part of the burden generates autogenously pulverization effect.When the temperature is not same,the kinds of phase constant,mainly includes the ?-2CaO·SiO2?CaO?12CaO·7Al2O3?2CaO·Al2O3·SiO2?3CaO·Al2O3.when temperature is 1350?,?-C2S turned into ?-C2S.When C/A is 0.4?1.2,the burden metallization rate of pre-reduced ore increases at first and then reduce.When C/A is 0.8,metallization rate is highest,is 55.98%.The change of the phase composition is not big,the main phase includes Fe??-2CaO·SiO2?CaO?12CaO·7Al2O3?2CaO·Al2O3·SiO2?3CaO·Al2O3.With the C/O has little effect on burden metallization rate,the burden metallization rate as the C/O rise slightly elevated.The main phase of pre-reduced ore includes Fe??-2CaO·SiO2?CaO?12CaO·7Al2O3?2CaO·Al2O3·SiO2?3CaO·Al2O3.The optimum conditions for the process of pre-reduced is:pre-reduction temperature is 1250?,holding time for 30 min,C/A is 0.8,C/O is 1.2,at this time the metallization rate of pre-reduced ore was 63.10%.In process of pre-reduced,the content of MgO in lime greatly affected phase composition of calcium aluminate slag.When the lime content higher MgO,Al2O3 mainly exist in 20CaO·13Al2O3·3MgO·3SiO2.The leaching rate of alumina is low.When the lime content little MgO,the Al2O3 mainly exist in 12CaO·7Al2O3.The leaching rate of alumina is high.The amount of 20CaO·13Al2O3·3MgO·3SiO2 determine the leaching rate of alumina.In process of pre-reduced,the cooling rate greatly affected phase composition of calcium aluminate slag.Phase analysis show that with slowing cooling rate,there will be a growing number of Al2O3 and MgO style reaction to generate 20CaO·13Al2O3·3MgO·3SiO2,not benefit leaching of Al2O3 in calcium aluminate slag.But the cooling rate should not exceed 20 ?/min,otherwise,most of the Al2O3 will exist in 2CaO·Al2O3 ·SiO2 phase.