Basic Research On HIsmelt Ironmaking Process

HIsmelt smelting reduction ironmaking process can use less than 6 mm particle size fine ore and pulverized coal as raw material to greatly reduce ironmaking cost,decrease environmental pollution without coking,sintering and pellet process,follow the increasingly strict environmental protection policy of China's steel industry,solve low-grade high-phosphorite iron ore based on strong oxidizability of smelting reduction vessel.The characteristics of hot metal produced by HIsmelt process are that silicon content is almost zero,phosphorus content is very low,and sulfur content is high.HIsmelt process is one of the most influential and valuable non-blast furnace ironmaking processes in the world.Enlightened by characters of HIsmelt process and thermodynamic theory of carbon reduction,the analysis result shows that the theoretical reduction of 1 ton iron requires 322 kg carbon(187 kg as reducing agent,135 kg as heating agent)and 175 Nm3 oxygen.According to increasing the slag-metal phosphorus distribution ratio,the higher oxygen ion activity aO2-3/2 and FeO activity(the ratio of PCO2/PCO),the better,the lower phosphate activity coefficient ?PO43-,the better.Inspired by the ore pre-reduction of HIsmelt process,the unreacted core model was studied to analyze the restrictive step on the reduction reaction.The physical and chemical properties,and roasting properties of limonite were studied by XRF,XRD and TG-DSC,the transformation process of reduction of limonite in hydrogen was also studied.The reaction mechanism of limonite under various experimental conditions were determined.It is concluded that the restrictive step of the reduction process is the inner diffusion of reducing gas in the reduction product layer.Reduction process of high phosphorus titanomagnetite in smelting reduction vessel of HIsmelt process was simulated.The effects of temperature,basicity,C/O ratio,reduction time and reduction rate on the reduction process of high phosphorus titanomagnetite pellets were studied by smelting reduction experiment,and the effects of C,P and S contents in molten iron on the reduction process were also studied.The result was that high temperature promotes dephosphorization within initial 10 minutes of the reaction.Under the experimental conditions,the best dephosphorization and desulfurization effect is at R=1.3,the best dephosphorization effect is at C/O=1.When C/O is between 1 and 1.4,the sulfur content in molten iron decreases with the increase of C/O ratio.Based on the slag ion-molecule coexistence theory(IMCT),the prediction models of phosphorus distribution ratio and silicon distribution ratio between slag and metal in multicomponent slag system were established respectively.Testified by actual production data of HIsmelt plant,the result was that theoretical phosphorus distribution ratio and silicon distribution ratio between slag and metal were same as industrial production,and the contribution rate of slag components on dephosphorization and desilication was concluded that the synergistic action of slag components has a significant effect on the phosphorus distribution ratio and the silicon distribution ratio,the contribution rate of 3CaO·P2O5 to dephosphorization was 99.7%,and that of 2CaO SiO2,CaO SiO2,CaO MgO·2SiO2,2CaO·Al2O3·SiO2,CaO·MgO SiO2 to desilication was 22.81%,19.92%,18.24%,16.22%and 12%,respectively.Chinese HIsmelt process was studied by IMCT theory analysis,for keeping highest phosphorus distribution ratio and silicon distribution ratio,the composition of the best slag system was successfully predicted by IMCT,the result was as follows,29?30%SiO2,12?13%Al2O3,40?42%CaO,6.5 or 9%MgO,5?6%FexO,[%P]=0.024,[%Si]=0.011,these calculated parameters were almost consistent with industrial production parameters.Phosphorus distribution ratio and silicon distribution ratio of high phosphorus titanomagnetite and limonite,and best slag system were successfully predicted,the results of[%P]and[%Si]for best slag system were received.For high phosphorus titanomagnetite,the components of best slag system was as follows,33?35%Si02,8?9%Al2O3,40?42%CaO,9%MgO,6?7%FexO,[%P]=0.034,[%Si]=0.0023.For limonite,the components of best slag system was as follows,33?35%Si02,10?13%A1203,40?42%CaO,9%MgO,6?7%FexO,[%P]=0.042,[%Si]=0.0028.The smelting reduction vessel that is the main reactor of the HIsmelt process was numerically simulated.The activity of hot metal and molten slag in SRV was studied.The influence of the incidence angle of the top lance on the gas-liquid and slag-metal movement in SRV was investigated.The theoretical SRV smelting analysis in the HIsmelt process was completed to provide strong process analysis and risk management guarantee for HIsmelt industrial production.