The Mechanism Of Carbothermic Reduction Of Alumina Catalyzed By Molten Iron

Al₂O₃-C refractories are widely used in continous casting process in steelmaking due to its high thermal conductivity,superior thermal shock resistance and wear resistance.With the development of clean steelmaking,interactions between Al₂O₃-C refractories and steel and its effects on the steel quality becomes an important issue,for example,the dissolution of carbon from refractories in steel is the main reason for carbon pickup of steel.On the other hand,papers about chemical interactions in Al₂O₃-C/Fe system have been reported in recent years and carbothermic reduction of alumina under steelmaking temperature is possible in Al₂O₃-C/Fe system.Therefore,it is of great significance to study the carbothermic reduction of alumina in order to reduce the damage and improve the quality of molten steel.The paper consists of three parts.Firstly,the effects of CO gas and CO₂ gas partial pressure,initial Al and C content in iron on the reaction of Al₂O₃-C/Fe system were calculated with the aid of thermodynamic software.Then,the reaction of Al₂O₃-C/Fe system in argon atmosphere and the influence on the composition of molten iron were studied by means of thermal analysis and high temperature thermogravimetric experiments.Finally,the reaction of Al₂O₃-C/Fe system and its influence on the composition of molten iron were studied with coke powder covered.The conclusions are as follows:?1?The thermodynamic calculation shows that the solid state reaction between Al₂O₃ and C is greatly affected by the CO partial pressure and temperature.When the CO partial pressure is 0.1Pa,Al₂O₃ and C can react to generate liquid aluminum at about 1171?,can react to generate Al gas at about 1135?,can react to generate Al₂O gas at about 1147?.Under the same temperature and CO partial pressure,the reaction in Al₂O₃-C/Fe system is more likely to occur than that in Al₂O₃-C system.When the partial pressure of CO is relatively low,with the increase of initial Al content and C content in iron,[Al]content and[C]content in liquid iron are increased.When the CO partial pressure is relatively high,with the increase of initial Al content and C content in iron,[Al]content and[C]content in liquid iron do not change.?2?Under the condition of flowing argon atmosphere,the carbon monoxide gas produced by the reaction was taken out of the system with argon,which made the carbon monoxide gas pressure in the system very low,and the Al in the Al₂O₃-C/Fe system was generated at high temperature.The contact state of Al₂O₃-C refractories and iron had an impact on the reaction in the Al₂O₃-C/Fe system.The reaction was intense when each component in Al₂O₃-C/Fe system was mixed by powder,and the Al content in the metal sample was high after experiment.When the pure iron powder was placed in the Al₂O₃-C crucible,the Al content in the metal sample was low.?3?When crucibles were heated with coke covered,there was enough oxygen to react with coke to produce CO as the experiment was carried out in the air,and the CO pressure of the system was very high.The Al content in the metal sample after experiment was very low,at about 0.02%.?4?Mechanism of carbothermal reduction of alumina catalyzed by iron.Alumina dissolved into liquid iron at high temperature in argon atmosphere,CO gas generated in the reaction by[C]and[O]in iron melt was removed out of Al₂O₃-C/Fe system very quickly when experiment was done in flowing argon atomphere and that accelerated the reaction between[C]and[O]in iron melt and result in the decrease of[O]content.The dissolution process of Al₂O₃ in iron melt was accelerated with the decrease of[O]content,resulting in the increase of[Al]content in iron melt.