| The oolitic hematite is abundant in our country,accounting for 1/9 of the total iron ore resources.However,this type iron resource has not been widely exploited for its fine particle distribution,complex mineral composition and ore texture and be considered as one of the most refractory iron ore type in the world.The research of utilization of oolitic hematite not only can improve the available iron ore resources and also has great significance to healthy development of steel industry in China.In this paper,the experimental studies of suspension roasting of oolitic hematite have been done on the basis on the systematic study of technological mineralogy and determined the appropriate process system.The thermodynamics analysis,kinetics analysis,X-ray diffraction analysis,magnetic analysis,Mossbauer spectrum analysis were used to reveal thetransformation mechanism of iron minerals in the process of suspension roasting.The separation process of roasted material were carried out and formation the technology of suspension roasting and magnetic separation and flotation of oolitic hematite.Finally,the flow characteristics of oolitic hematite in suspension roasting furnace were simulated.The following conclusions were obtained by research:Process mineralogy research of oolitic hematite ore showed the total iron grade was 46.31%,mainly distributed in hematite and a small amount of iron distributed in ferrosilicate and siderite.The gangue minerals were mainly distributed in quartz,calcite,clay minerals and chamosite.The content of phosphorus is high in ore with the content of 1.25%,which mainly distributed in apatite.The ore is mainly composed of ooid structure which is consists of many concentric layers of hematite,quartz,chamosite,calcite and apatite.Thermodynamic analysis showed that hematite can be reduced to magnetite under the low concentration of H2 in the process of suspension roasting.The gangue minerals can reaction with each other and generated complex compounds.The experiments of oolitic hematite suspension roasting shows the appropriate conditions is particle size of 80%passing 0.074mm,gas velocity of 1.4m/s,H2 concentration of 40%,the reduction temperature of 650?,reduction time of 10s.Mossbauer spectrum analysis indicates that weakly magnetic iron minerals in ore were transformed to magnetite via suspension roasting and the magnetic susceptibility of roasted material can reached to 4.69×10-4 m3/kg.The magnetite closely disseminated with gangue minerals,the structure of ore was not changed,but the specific area,pore volume and pore size of particle were increased.Mineral processing index obtained by use of magnetization roasting and suspension roasting is comparative similar and roasting time was significantly reduced by use of suspension roasting.The type of cooling roasted material was studied.The research showed that an amount of magnetite can oxidized to strongly magnetic ?-Fe2O3 when roasted material cooled in an oxygen free atmosphere to 350? and then cooled in the air.As the oxidation reaction is exothermic reaction can release a large amount of heat and utilized of this energy can decrease the energy consumption.The isothermal kinetic research of oolitic hematite under H2 atmosphere showed this reaction can be divided into two stage of initial stage and final stage.The initial stage was controlled by chemical reaction with the activation energy of 44.52kJ·mol-1 and the final stage was controlled by 2-D diffusion with the activation energy of 50.64kJ·mol-1.The non-isothermal kinetic research of oolitic hematite under H2 atmosphere showed the reaction was controlled by 3-D diffusion with the activation energy of 89.51?103.80 kJ·mol-1.The isothermal kinetic research of oolitic hematite under CO atmosphere showed the reaction can be divided into two stage of initial stage and final stage.The initial stage was controlled by chemical reaction with the activation energy of 34.50kJ·mol-1,and the final stage was controlled by 3-D diffusion with activation energy of 42.69kJ·mol-1.The non-isothermal kinetic research of oolitic hematite under CO atmosphere showed the reaction was controlled by 3-D diffusion with the activation energy of 50.13?54.00 kJ·mol-1.The non-isothermal kinetic research of magnetite showed the oxidation reaction was controlled by 3-D diffusion with the activation energy of 40.32 kJ·mol-1.The magnetic separation of roasted material was carried out under the condition of one stage grinding fineness of 95%passing 0.074mm,the firsr stage magnetic field of 101kA/m,the second stage grinding fineness of 90%passing 0.035mm,two stage magnetic field of 68.6kA/m and the iron grade of 55.81%and iron recovery of 84.80%can obtained.The reverse flotation of magnetic concentrate was carried out under the optimal process conditions and agent usages can obtained the concentrate of iron grade of 60.13%,recovery of 74.58%and phosphorus content of 0.24%.The numerical simulation results found that particle concentration distribution presented obvious inhomogeneity in suspension roasting furnace.The particle concentration in furnace bottom is higher than in the top and the wall areas is higher than in central areas and formed a significant gas channel in the central areas of furnace.The particle velocity increased with the increase of gas velocity and decrease of particle size.The particle concentration decreased with the increase of gas velocity and decrease of particle size.The results have provided guidance for the exploitation and utilization of oolitic hematite and referenced to efficient use of other types of refractory iron ore. |
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