Study On Microwave Deep Reduction And Reduction Kinetics Of Oolitic Hematite

China’s iron ore resources are abundant,but the iron ore resources are in short supply due to factors such as poor ore,difficulty in mining and utilization,and large demand.At the same time,the international iron ore prices soared,and the import of iron ore would subject China’s economic development to people.Based on these factors,China is eager to improve the current unfavorable situation.In this paper,the high-phosphorus-like hematite produced in western Hubei is the research object.It was found that the ore-mineral composition of high-phosphorus-like hematite was very complicated,the mineral phases were mutually adhesive,and the mineral grain size was extremely fine.The special braided structure was difficult to be treated by the general beneficiation process and was a complex and difficult to beneficiated.Deep reduction-magnetic separation was currently considered to be an effective method for treating the helium-like hematite.In this paper,we intend to use the deep reduction method to study the condition optimization experiment of microwave heating deep reduction of stellite hematite,and explore the mechanism of the reduction kinetic reaction process of the stellite hematite,which provides a way for the development and utilization of the stellite hematite and process optimization.Theoretical support.Taking coke as a reducing agent and using microwave heating reduction method,the ore can obtain a metallization rate of 92%or more when the carbon content was C/O of 1.5,the alkalinity is 0.8,and the reduction temperature is 1250℃for 10 min.The reduced material was finely ground to90%of the-0.074 mm particle size,and then the reduced magnetic powder with the iron grade and iron recovery rate higher than 90%could be obtained by the magnetic field strength 60 mT weak magnetic separation.This iron powder met the requirements of blast furnace raw materials.On the basis of the above,it was found that the heating temperature can achieve a good iron lifting effect in an appropriate interval.When the temperature is greater than 1150℃,the metallization rate could reach more than 80%.Although the metallization rate could reach 90%at 1250℃,in this case,due to the high efficiency of microwave heating,the ore had partially melted.At the same time,it was difficult to remove phosphorus at high temperature,but it was easy to react with metallic iron to form a compound,which reduced the mechanical properties of subsequent products.When the holding time was too long,the reduced iron easily combines with the silicate in the gangue mineral to form iron silicate,which was contrary to the purpose of the experiment.When the amount of CaO added was too large and the alkalinity was too large,the amount of reaction slag generated during the reduction reaction was excessive,which hinders the direct reaction between the iron oxide and the reducing agent.Adding a reducing agent to the ratio of C and iron oxide,if the reducing agent was added,the chemical equilibrium of the reaction could be effectively affected,the reaction was moved forward,and the reduction reaction was promoted.However,when the amount of the reducing agent was increased excessively,the excess carbon powder hindered the direct reaction of the iron oxide with the reducing agent,and the metallization rate was rather lowered.The carbothermic reduction kinetics of oolitic hematite was investigated at temperature of 1173K¹473 K by using thermogravimetric method.The effects of temperature on reduction degree and reaction rate were studied.The reduction reactions were fitted to several solid-state reaction mechanisms.The reaction restrictive mechanisms at different stage were analyzed.The phase composition,morphology and elementary composition of reduced samples were characterized by using XRD,SEM and EDX techniques.The research results show that the reduction degree and reaction rate are increase with the increased temperature,and the reaction rates are first increase and then decrease with the increase of reduction degree.Among them,when graphite was used as reducing agent at 1173 K¹373 K and 1373 K¹473 K,the carbothermic reductions are well fit to the interface chemical reaction model of 1-（1-α）^1/3and the Jander model of[1-（1-α）^1/3]²,respectively.The corresponding activation energies are 60.66 kJ/mol and 301.66 kJ/mol respectively.When charcoal was used as reducing agent at 1173¹373 K and 1373¹473 K,the carbothermic reductions are well fit to the interface chemical reaction model of 1-（1-α）¹/3/3 and the Jander model of[（1-α）^1/3-1]²,respectively.The corresponding activation energies are 70.02 kJ/mol and 215.36kJ/mol respectively.The analysis results of phase composition and microstructure for reduced samples are found to be consistent with those of reaction kinetic mechanism analysis.