| At present,supply of iron ore of domestic production as raw material of domestic iron and steel industry is no more than 46%.For heavy shortage of iron ore reserves in our country,we need to develop new iron reserves timely.Magnetizing roasting followed by magnetic separation is a effective technique for beneficiation of refractory iron ore such as siderite,limonite and oolitic hematite which reserves be about 10 billion tons in China and can not be utilized effectively.To avoiding defect such as Complicated process and high cost of traditional magnetizing roasting technology and to take the advantage of fast heat and mass transferring of fluidization of gas-solid,a kind of new technology named circulating and fluidizing Magnetizing roasting was developed to convert oxidized iron ore to magnetite which can be recovery easily.The problem of oxidized iron ore can not be recovered by traditional roasting and high intensity magnetic separation was settled low costly.Basic fluidizing magnetizing roasting experimental equipment used in laboratory was researched and developed creatively.Design and selection of gas grid adapting to tailing from Daye iron mine was finished.By calculating theoretically and testing, Topgallant void ratio of gas grid was determined.At high temperature,the charge material was suspending in gas bed,experiments of different magnetizing roasting temperature and roasting duration have been run by leading to reductive atmosphere containing CO.It is proven that at temperature of 650℃-750℃,keeping roasting duration about to 10s-60s,iron siderite(FeCO3)and hematite(Fe2O3)can be converted into magnetite(Fe3O4).The equipment has the function of measure or adjust the temperature,the volume content of O2 and CO and duration of reaction quickly. The oxidized iron ore including high siderite from Daye iron mine(WISCO.)tailing was roasted there,magnetic separation of the output was carried out in tube magnetic tester,iron content in concentration is about to 60～61%,recovery of iron get to 85～90%,iron content in tailing reduced to 10～12%.The scientific hypothesis of flash magnetizing roasting of oxidized iron ore was proved true.It provided us with technology and theory basement on industry furnace research and design.The study on magnetizing reduction thermodymatics of high intensity magnetic separation concentrates of Daye Mine proved:because of there are high siderite in this type iron ore,CO and CO2 emitting out after siderite decomposing influenced on magnetic reaction heavily.The reaction of magnetizing roasting will be performed well when the CO volume percent is above 1%.By thermodymatics calculation,formula of phase change in step was proved and condition of the magnetization of siderite were also uncovered in the research first.In this dissertation,principal properties of the technology of magnetic Roasting in Multi-Grade Circulation and Fluidizing has been studied by development of equipment and optimization of technology flow.By calculation,in this reactor, touching area between gas and solid state is 10,000 times of it is in kiln when material is in heap state.For the fines which the size is under 0.2mm,Heat transfer coefficients between gas and solid get to 1000kW/(m2·k),600 times of it is the kiln, heat transferring efficiency is times up.It is proved that The fine iron ore(mean diameter is 0.0693mm)from Daye mine can be separated effectively in cyclone through design of its structure and calculation of gas velocity of transferring pipe and the cyclone.the ratio solid and gas is about 0.964Kg/Nm3,it is about 0.239 Kg/m3 in furnace at working.The separating efficiency is above 95%in the system.Article of the fine can not be short circuit and get the effect of multi-grade preheating.It was found that exhausting of heat energy be about to 1196KJ/kg,70%of kiln technology based on coal,82%of fluidizing roaster,75%of shaft furnace by the calculation of heat balance.Manufacture cost is highly decreased.Calculating of article suspending velocity and settling velocity in the cyclone indicated that it is coincident between the practice and the theory.So high gas-solid separating efficiency and full circulating preheating could be ensured. Calculating and testing of the pressure loss indicated that the main pressure loss produced by gas flowing,taking about 80%of the total,it is about 3000Pa,it is equal to four-grade whirling preheater of traditional cement manufacturing technology.A combination of Sprayed reaction furnace and cyclone is applied in the Multi-Grade Circulation and Fluidizing magnetic roasting system.So the charge can move along with the gas flow in turn,the default of distempered movement of gas flowing and super reduction of iron ore in the reactor bed smooth away.When oxidized iron ore from Daye mine(WISCO.)tailing are used as magnetizing reduction roasting material in continuous test.It is found that in the pilot test,the optimum process parameters list as:temperature of reactor in Fluidizing system should be 900～950℃,CO content of the reactor entry be about 1.5%～2.5%,the ratio solid and gas is about 0.8-1.0Kg/Nm3,which is very approach to calculated value.The iron grade of the concentration of low intensity magnetic separation is about 60%-61%,Fe recovery is about 92%～93%when grinding fineness is -0.074mm about 88%. Study on mineralogy of roasting product and concentration proved that magnetite is above 90%in iron mineralogy.The processing of pilot test indicates that operating parameters of the Multi-Grade Circulation and Fluidizing magnetic roasting technology can work in wide scale.The operation is so convenient that it can run stable and be controlled freely.Advantages such as high production ability fast reaction velocity and low exhaustion are also proved in research.So it is one of the most advanced technology of hematite,siderite and limonite magnetizing roasting.The success of Multi-Grade Circulation and Fluidizing magnetic roasting technology will widely develop the utilization of oxidized iron ore in our country, increase domestic effective iron ore reserves and produce large economic benefit and social benefit.
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