Analysis and discussion of molten iron pre-dephosphorization temperature on structure and behavior of dephosphorization slag
In order to explore the influence of dephosphorization slag structure evolution on dephosphorization effect and phosphorus migration and enrichment behavior at different molten iron temperatures,laboratory experiments were carried out at molten iron temperatures of 1 340℃to 1 420℃.The effect of different conditions on the dephos-phorization efficiency,and the structural characterization of the dephosphorization final slag after the experiment was carried out by using XRD,SEM-EDS,FTIR and Raman spectroscopy.Thermodynamic theoretical analysis shows that with the increase of temperature,the phosphorus distribution ration decreases gradually.The experiment of hot metal dephosphorization shows that when the temperature of hot metal is 1 380℃,the dephosphorization efficiency of hot metal is the highest,too high or too low temperature is not conducive to dephosphorization,and the silicon content of hot metal decreases gradually with the increase of temperature.And with the increase of temperature,the silicon content of molten iron gradually decreases.The results of XRD and SEM-EDS analysis show that phospho-rus is mainly enriched in the 2CaO·SiO2 crystallization region,and the phosphorus-rich phase is composed of 2CaO·SiO2-3CaO·P2O5 solid solution.The increase in temperature will reduce the proportion of phosphorus-rich phase.Raman and infrared analysis results show that the Si—O—Si bond is less affected by the temperature increase.When the temperature is low,the contents of Q1(Si),Q2(Si)and Q3(Si)in slag increase.When the tem-perature rises to 1 380℃,the Si—O—Si bond is broken and Q0(Si)increases.The silicate structure with low polymerization degree promotes the migration and aggregation of phosphorus,and the phosphorus in the form of Q1(P)gradually increases.When the temperature is between 1 380℃and 1 420℃,the higher molten iron tempera-ture inhibits the migration of phosphorus,and the silicon entering the slag tends to exist in the form of high polymer-ization degree,and the polymerization degree of slag gradually increases with the desilication reaction.In addition,due to the remarkable increase of FeO6 octahedron and the improvement of silicate polymerization degree,the migra-tion of phosphorus into the silicon-oxygen network structure was inhibited,and the phosphorus in the form of Q0(P)gradually increased and the diffusion degree of phosphorus in slag increased.It can provide theoretical guidance and reference for iron and steel enterprises to solve the problem of excessive phosphorus content in molten iron and con-trol a reasonable pre-dephosphorization temperature.
predephosphorizationhot metal temperatureiron oxide scaleinfrared spectrumRaman spectrumslag structure