Study On Slag-iron Bath Smelting Reduction Process For Alumina-rich Iron Ore Processing

Alumina-rich iron ore resources have abundant reserves in China.But due to the complexity of its composition and the difference in grade,they have not been fully utilized.In this paper,a novel slag-iron bath smelting reduction process for alumina-rich iron ore processing is presented,and its production process is as follows:a rotary hearth furnace(RHF)is equipped with carbon bearing pellets for pre-reduction;the melting,final reduction and slag-making are taken place in smelting reduction vessel(SRV)with metallized pellets and flux;the SRV gas is reformed in a gas reforming furnace(GRF)gas to produce high quality gas.The SRV is designed with a three-level lances arrangement,including the top oxygen lance for the post combustion of gas and efficient heat transfer;middle coal&oxygen lance for the melting of pellet and flux in upper slag and stirring;bottom coal&oxygen lance for the reduction of residual iron oxides and extra energy supply.Study of the process from the static model,physical model,laboratory experiment,pilot test is carried out in this paper to provide theoretical support and reference for industrial application.An overall static model of the slag-iron smelting reduction process is established in this paper,and the effects of pellet metallization rate(PMR),post combustion rate(PCR)and other operating parameters are studied to evaluate the mass and energy consumption of the process.Further establishment of a zoned static model is applied to investigate the effects of PCR in different reaction zones on the coal and oxygen distribution and coal consumption.The recommended PCR in SRV in the top free space is 55%,the upper slag 15%,the bottom slag 0%,and the PMR in SRV is 80%.The coal consumption,energy consumption,coal distribution and oxygen distribution can be flexibly controlled by three-level lance arrangement in SRV.In light of the present condition of the domestic gas shortage,the coal gasification routes in the current process mode are studied in this paper.The mass and energy consumption and operation parameters are calculated and optimized in RHF route and DRS(Direct Reduction Shaft)route with different PMR,and optimum conditions of the coal gasification process and applicable conditions are obtained.For example,if the process is mainly focused on iron making and slagging,the RHF route is recommended and with proper PMR,the PCR in SRV of 20%,and the oxygen preheat temperature of 700?.On the basis of mass and heat balance calculation,a physical model of the SRV is established.Orthogonal experimental method is used to study the effects of the lance angle and insertion depth of side blowing lances and the arrangement of bottom blowing tuyeres on the mixing time and significance of each operation parameters.The optimum blowing conditions with shortest mixing time is obtained as:double asymmetric bottom blowing arrangement,50°blowing angle and 180mm insertion depth of middle layer lances,50° blowing angle and 180mm insertion depth of bottom layer lances.The significance of insertion depth of middle layer lance and blowing angle of bottom later lance to the mixing time is relatively poorer,which can be adjusted according to actual production requirements without significant Effect on the mixing time of SRV.Numerical simulation of the melting phenomenon of alumina-rich pellet in molten slag is carried out using one-dimension non-steady heat transfer model,to investigate the effects of slag bath temperature,pellet diameter,pellet preheat temperature,PMR,and slag C/A on the pellets melting process,and the melting time,the temperature distribution of internal pellet and slag shell are obtained.Taking C/A for example,with the slag C/A reducing from 1.7 to 1.4,the melting time of pellet isdecreased by 25s.The differential scanning calorimetry(DSC)experiment is used in this paper to investigate the final slag phase composition of SRV,and scanning electron microscope(SEM),Energy Dispersive Spectrometer(EDS)are applied to analyze the experimental samples.The influences of different cooling rates,C/A,MgO addition on the final slag phase composition are obtained and so as the optimum solidification condition of SRV slag.Taking C/A1.4 as an example,with MgO addition of 0,1,2%,the optimum cooling rate is 10,10,15?/min,respectively.In order to realize the application of slag-iron bath smelting reduction process to actual production and verify the laboratory results,pilot tests of alumina-rich pellet smelting reduction are carried out in a It medium frequency induction furnace using industrial raw materials.The laboratory results is verified and some industrial problems in the practical application have been optimized.The pilot test has realized the total separation of iron and slag and obtained self-pluverized active high alumina slag.To achieve industry application,the recommended parameters from the pilot test are 1600? of the melting temperature,1.2?1.7 of C/A,less than 1%of MgO,and similar or better heat preservation measures as pilot test.