CO/CO_2气氛下赤铁矿向磁铁矿的流化床还原转变
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摘要
采用纯矿物试验、等温还原法和微观结构分析法研究了赤铁矿向磁铁矿流化床还原转变行为及动力学.动力学研究表明,以20%CO和80%CO_2(质量分数)混合气体为还原流化剂、微型流化床为反应器,在还原温度为773～873 K时,赤铁矿向磁铁矿的选择性还原转化受磁铁矿晶核的形成和一维生长A3/2模型控制,反应的表观活化能ΔEa为49.64 k J/mol,指前因子A为6.55 s-1.BET比表面分析及扫描电镜测试结果表明,新生磁铁矿晶核呈致密针状结构,且长度不一;随着反应的进行,针状结构晶核增多并聚集形成多孔状的磁铁矿颗粒.
The reductive transformation behavior and kinetics of hematite to magnetite under fluidized bed conditions were studied by single mineral roasting test,isothermal reduction method and microstructure analysis.The results of reaction kinetics show that the selective reduction of hematite to magnetite with reductive fluidizing agent of 20 wt% CO-80 wt% CO2 in a microfluidized bed reactor at 773-873 K is controlled by formation of magnetite crystal nucleus and one-dimensional growth(A3/2 model),the apparent activation energy ΔEa of the reaction is49.64 kJ/mol and the pre-exponential factor A is 6.55 s-1.The results of BET specific surface analysis and scanning electron microscopy measurement show that the fresh magnetite nucleus are dense needle-like structure with different lengths,and that as the reaction proceeds,the magnetite nucleus with the needle-like structure increases and aggregates to form porous magnetite particles.
The reductive transformation behavior and kinetics of hematite to magnetite under fluidized bed conditions were studied by single mineral roasting test,isothermal reduction method and microstructure analysis.The results of reaction kinetics show that the selective reduction of hematite to magnetite with reductive fluidizing agent of 20 wt% CO-80 wt% CO2 in a microfluidized bed reactor at 773-873 K is controlled by formation of magnetite crystal nucleus and one-dimensional growth(A3/2 model),the apparent activation energy ΔEa of the reaction is49.64 kJ/mol and the pre-exponential factor A is 6.55 s-1.The results of BET specific surface analysis and scanning electron microscopy measurement show that the fresh magnetite nucleus are dense needle-like structure with different lengths,and that as the reaction proceeds,the magnetite nucleus with the needle-like structure increases and aggregates to form porous magnetite particles.
引文
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[15]Hayes P C,Grieveson P.Microstructural changes on the reduction of hematite to magnetite[J].Metallurgical and Materials Transactions:B,1981,12(3):579-587.
[16]Et-Tabirou M,DupréB,Gleitzer C.Hematite single crystal reduction into magnetite with CO-CO2[J].Metallurgical Transactions:B,1988,19(2):311-317.
[2]Yang H,Jing L,Zhang B.Recovery of iron from vanadium tailings with coal-based direct reduction followed by magnetic separation[J].Journal of Hazardous Materials,2011,185(2/3):1405-1411.
[3]Peng N,Peng B,Chai L Y,et al.Recovery of iron from zinc calcines by reduction roasting and magnetic separation[J].Minerals Engineering,2012,35:57-60.
[4]Yu J,Han Y,Li Y,et al.Separation and recovery of iron from a low-grade carbonate-bearing iron ore using magnetizing roasting followed by magnetic separation[J].Separation Science and Technology,2017,52(10):1768-1774.
[5]Liu X,Yu Y,Chen W.Phase change of chlorite in reducing atmosphere[J].Physicochemical Problems of Mineral Processing,2014,50(2):607-614.
[6]朱庆山,李洪钟.难选铁矿流态化磁化焙烧研究进展与发展前景[J].化工学报,2014,65(7):2437-2442.(Zhu Qing-shan,Li Hong-zhong.Status quo and development prospect of magnetizing roasting via fluidized bed for low grade iron ore[J].Journal of Chemical Industry and Engineering(China),2014,65(7):2437-2442.)
[7]Feng Z,Yu Y,Liu G,et al.Kinetics of the thermal decomposition of Wangjiatan siderite[J].Journal of Wuhan University of Technology(Materials Science Edition),2011,26(3):523-526.
[8]王儒,韩跃新,李艳军,等.鲕状赤铁矿悬浮焙烧的磁性研究[J].东北大学学报(自然科学版),2015,36(7):1024-1028.(Wang Ru,Han Yue-xin,Li Yan-jun,et al.Research on magnetic properties of oolitic hematite roasted by suspension roasting furnace[J].Journal of Northeastern University(Natural Science),2015,36(7):1024-1028.)
[9]Yu Y F,Qi C Y.Magnetizing roasting mechanism and effective ore dressing process for oolitic hematite ore[J].Journal of Wuhan University of Technology(Materials Science Edition),2011,26(2):176-181.
[10]Feilmayr C,Thurnhofer A,Winter F,et al.Reduction behavior of hematite to magnetite under fluidized bed conditions[J].ISIJ International,2004,44(7):1125-1133.
[11]Li Y,Zhu T.Recovery of low grade hematite via fluidized bed magnetizing roasting:investigation of magnetic properties and liberation characteristics[J].Ironmaking&Steelmaking,2012,39(2):112-120.
[12]Li Y,Wang R,Han Y,et al.Phase transformation in suspension roasting of oolitic hematite ore[J].Journal of Central South University,2015,22(12):4560-4565.
[13]Vyazovkin S,Burnham A K,Criado J M,et al.ICTAC Kinetics Committee recommendations for performing kinetic computations on thermal analysis data[J].Thermochimica Acta,2011,520(1/2):1-19.
[14]Hayes P C,Grieveson P.The effects of nucleation and growth on the reduction of Fe2O3 to Fe3O4[J].Metallurgical Transactions:B,1981,12(2):319-326.
[15]Hayes P C,Grieveson P.Microstructural changes on the reduction of hematite to magnetite[J].Metallurgical and Materials Transactions:B,1981,12(3):579-587.
[16]Et-Tabirou M,DupréB,Gleitzer C.Hematite single crystal reduction into magnetite with CO-CO2[J].Metallurgical Transactions:B,1988,19(2):311-317.
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