Diffusion behavior and distribution regulation of MgO in MgO-bearing pellets

Abstract

In this paper, the diffusion behavior between MgO and Fe₂O₃ (the main iron oxide in pellets) is investigated using a diffusion couple method. In addition, the distribution regulation of MgO in MgO-bearing pellets is analyzed via pelletizing experiments. The results illustrate that MgO is prone to diffuse into Fe₂O₃ in the form of solid solution; the diffusion rate considered here is 13.64 µm·min^-1. Most MgO content distributes in the iron phase instead of the slag phase. The MF phase {(Mg_1-x Fe_x)O·Fe₂O₃, x ≤ 1} is generated in the MgO-bearing pellets. However, the distribution of MgO in the radial direction of the pellets is inconsistent. The solid solution portion of MgO in the MF phase is larger in the outer layer of the pellets than in the inner layer. In this work, the approximate chemical composition of the MF phase in the outer layer of the pellets is {(Mg_0.35-0.77·Fe_0.65-0.23) O·Fe₂O₃} and in the inner layer is {(Mg_0.13-0.45·Fe_0.87-0.55) O·Fe₂O₃}.

Keywords

magnesia / iron oxide / ore pellets / diffusion / distribution

References

[1] Shen F.M., Gao Q.J., Wei G., Jiang X., Shen Y.S. Densification process of MgO bearing pellets. Steel Res. Int., 2015, 86(6): 644.

[2] Fu J.Y., Zhu D.Q. Basic Principles, Techniques and Equipment of the Iron Ore Oxidized Pellets, 2005 336.

[3] Gao Q.J., Shen F.M., Jiang X., Guo W., Zheng H.Y. Gas-solid reduction kinetic model of MgO-fluxed pellets. Int. J. Miner. Metall. Mater., 2014, 21(1): 12.

[4] Nishimura T., Higuchi K., Naito M., Kunitomo K. Evaluation of softening, shrinking and melting reduction behavior of raw materials for blast furnace. ISIJ Int., 2011, 51(8): 1316.

[5] Iljana M., Mattila O., Alatarvas T., Kurikkala J., Paananen T., Fabritius T. Effect of circulating elements on the dynamic reduction swelling behaviour of olivine and acid iron ore pellets under simulated blast furnace shaft conditions. ISIJ Int., 2013, 53(3): 419.

[6] Chun T.J., Zhu D.Q., Pan J. Influence of sulfur content in raw materials on oxidized pellets. J. Cent. South Univ. Technol., 2011, 18(6): 1924.

[7] Li S.H., Chen T.J., Zhang Y.M., Zhao J. Experimental study on application of Mg-bearing additives in iron ore pellet. Sintering Pelletizing, 2011, 36(1): 33.

[8] Gao Q.J., Wei G., Jiang X., Zheng H.Y., Shen F.M. Characteristics of calcined magnesite and its application in oxidized pellet production. J. Iron Steel Res. Int., 2014, 21(4): 408.

[9] Zhou G.F., Yang F. Effects of adding MgO on pelletizing ability and strength of pellet. Res. Iron Steel, 2009, 37(2): 10.

[10] Kemppainen A., Mattila O., Heikkinen E.P., Paananen T., Fabritius T. Effect of H₂-H₂O on the reduction of olivine pellets in CO-CO₂ gas. ISIJ Int., 2012, 52(11): 1973.

[11] Gao Q.J., Wei G., He Y.B., Shen F.M. Effect of MgO on compressive strength of pellet. J. Northeast. Univ. Nat. Sci., 2013, 34(1): 103.

[12] Pal J., Ghorai S., Goswami M.C., Ghosh D., Bandyopadhyay D., Ghosh S. Behavior of fluxed lime iron oxide pellets in hot metal bath during melting and refining. Int. J. Miner. Metall. Mater., 2013, 20(4): 329.

[13] Shen F.M., Jiang X., Wu G.S., Wei G., Li X.G., Shen Y.S. Proper MgO addition in blast furnace operation. ISIJ Int., 2006, 46(1): 65.

[14] Gao Q.J., Shen F.M., Wei G., Jiang X., Zheng H.Y. Effects of MgO containing additive on low-temperature metallurgical properties of oxidized pellet. J. Iron Steel Res. Int., 2013, 20(7): 25.

[15] Biswas A.K. Principles of Blast Furnace Ironmaking: Theory and Practice, 1981 38.

[16] Gao Q.J., Wen Q.L., Wei G., Jiang X., Shen F.M. Study on the effect of caustic calcined magnesite to quality of green-pellets, 2012 102.

[17] Khaki J.V., Kashiwaya Y., Ishii K. High temperature behaviour of self-fluxed pellets during heating up reduction. Ironmaking Steelmaking, 1994, 21(1): 56.

[18] Jiang X., Wu G.S., Li G.S., Shen F.M. Study on improving the softening-melting properties of MgO bearing iron ores. J. Northeast. Univ. Nat. Sci., 2007, 28(3): 365.

[19] Wang X. Ferrous Metallurgy, 2002 74.

[20] Semberg P., Andersson C., Björkman B. Interaction between iron oxides and olivine in magnetite pellets during reduction to wustite at temperatures of 1000–1300°C. ISIJ Int., 2013, 53(3): 391.

[21] Shen F.M., Gao Q.J., Jiang X., Wei G., Zheng H.Y. Effect of magnesia on the compressive strength of pellets. Int. J. Miner. Metall. Mater., 2014, 21(5): 431.

[22] Singh M., Björkman B. Effect of reduction conditions on the swelling behaviour of cement-bonded briquettes. ISIJ Int., 2004, 44(2): 294.

[23] Zhou C.D. Technical Manual of Blast Furnace Production, 2002 50.

[24] Eisenhüttenleute V.D. Slag Atlas, 1995 70.