Study On The Mechanism Of The Influence Of Primary Magnetite On The Reduction Process Of Hematite

iron ore resources are abundant in China,but most of them are complex and difficult to choose iron ore.The magnetization roasting-magnetic separation process is one of the most effective techniques for dealing with complex and difficult ore.In the semi-industrial test of suspension magnetization roasting of Anshan-type refractory hematite in China,it is found that when the calcined ore contains a certain amount of primary magnetite,it can effectively strengthen the magnetite roasting process of hematite and significantly improve the quality of roasting ore.And sorting indicators.Researchers at home and abroad on the magnetization roasting of hematite mainly focus on the control of calcination conditions,and lack of in-depth systematic research on the influence mechanism of magnetite in the process of magnetite roasting of hematite.The Qi Dashan iron ore was taken as the research object in this thesis,and the process mineralogy characteristics of Qi Dashan iron ore were analyzed.By comparing the magnetization roasting-magnetic separation test results of different magnetite content ore samples,the original magnetite pair was determined.The influence of the optimum process parameters of the hematite magnetization roasting was carried out.The vibrating sample magnetometer VSM was used to further examine the magnetic characteristics of each calcined product.The laser confocal scanning microscope and hot stage microscope were used to observe the hematite magnetization roasting process.The surface morphology changes,and the mechanism of the influence of primary magnetite in the ore on the magnetization roasting process of hematite is explored.The research on the mineralogy of Qidashan iron ore shows that the metal minerals in the ore are mainly magnetite,hematite and a small amount of limonite,and their contents are 19.70%,18.74%and 0.55%,respectively.The non-metallic minerals are mainly quartz with a content of 56.35%,and a small amount of carbonate minerals,amphibole,pyroxene and chlorite.The total iron grade of the ore is 30.65%,of which the magnetic iron content is 22.10%,the distribution rate is as high as 72.10%,and the distribution rate of red brown iron is only 16.32%.The ore was treated by weak magnetic separation and ore blending to prepare test ore samples with ratios of magnetite and hematite of 1:40,1:4,2:4,and 3:4,respectively.For the magnetite and hematite ratios of 1:40,1:4,2:4,3:4,the tube roaster was used for magnetization roasting-magnetic separation test to compare each roasted product.The difference in magnetic properties and sorting indexes of the four ore samples finally determined the appropriate magnetization roasting conditions for the four ore samples.Among them,theroasting temperature was 580℃,the roasting time was 5 minutes,the mixed gas(CO+CO2)flow rate was 550 ml/min,and the CO concentration was 30%.;Compared with the original ore,the increase in the saturation magnetic moment per unit mass of the roasted product(unit:Am2·kg-1)is 8.35,10.54,13.06,and 16.70 respectively;after the roasted product is sorted,the magnetic separation concentrate TFe is obtained The grades are 62.17%,64.32%,64.72%,65.22%,and the corresponding recovery rates are 84.02%,88.88%,90.99%,and 92.02%technical indicators.When the ratio of primary magnetite to hematite is 2:4,that is,the content of primary magnetite is 33%,the magnetic conversion rate of the roasted product is the highest,reaching 99.62%.A laser confocal scanning microscope was used to observe the surface morphology of the bulk sample.A hot-bed microscope was used to conduct a magnetization roasting test on the lump sample,and the surface of the sample was observed continuously and intermittently.The test results show that when a single hematite is magnetized and roasted,the sample surface reacts first.When the basic hematite reaction is complete,cracks occur on the surface of the sample and the internal hematite reacts.When the roasted raw ore contains a certain amount of magnetic In the case of iron ore,cracks first occurred at the interface between magnetite and hematite,and then hematite began to react.As the reduction reaction of hematite extends along the new inner surface of the lattice fracture to the inside of the hematite,the newly generated cracked inner surface is more active than the outer surface,and the primary magnetite is beneficial to hematite.The formation of ruptured inner surface of the ore,thereby promoting the reduction reaction of hematite.