Mathematical model of the direct reduction of dust composite pellets containing zinc and iron

Abstract

Direct reduction of dust composite pellets containing zinc and iron was examined by simulating the conditions of actual production process of a rotary hearth furnace (RHF) in laboratory. A mathematical model was constructed to study the reduction kinetics of iron oxides and ZnO in the dust composite pellets. It was validated by comparing the calculated values with experimental results. The effects of furnace temperature, pellet radius, and pellet porosity on the reduction were investigated by the model. It is shown that furnace temperature has obvious influence on both of the reduction of iron oxides and ZnO, but the influence of pellet radius and porosity is much smaller. Model calculations suggest that both of the reduction of iron oxides and ZnO are under mixed control with interface reactions and Boudouard reaction in the early stage, but only with interface reactions in the later stage.

Keywords

rotary hearth furnaces / dust / zinc / ore pellets / direct reduction process / mathematical models / kinetics

References

[1] Yang X F, Chu MS, Shen FM, Zhang ZM. Mechanism of zinc damaging to blast furnace tuyere refractory. Acta Metall. Sin. Eng. Lett., 2009, 22(6): 454.

[2] Oda H, Takahashi M, Ibaraki T. Dust recycling technology by the rotary hearth furnace. Nippon Steel Tech. Rep., 2002 30.

[3] Oda H, Ibaraki T, Abe Y. Dust recycling system by the rotary hearth furnace. Nippon Steel Tech. Rep., 2006 147.

[4] Bandyopadhyay D, Chakraborti N, Ghosh A. A study on the kinetics of iron oxide reduction by solid carbon. Steel. Res., 1993, 64(7): 340.

[5] Abraham MC, Ghosh A. Kinetics of reduction of iron oxide by carbon. Ironmaking Steelmaking, 1979, 6(1): 14.

[6] Sun S, Lu WK. A theoretical investigation of kinetics and mechanisms of iron ore reduction in an ore/coal composite. ISIJ Int., 1999, 39(2): 123.

[7] Seaton CE, Foster JS, Valesco J. Reduction kinetics of hematite and magnetite pellets containing coal char. Trans. Iron Steel Inst. Jpn., 1983, 23(6): 490.

[8] Coetsee T, Pistorius PC, Villiers EE d. Ratedetermining steps for reduction in magnetite-coal pellets. Miner. Eng., 2002, 15(11): 919.

[9] Halder S, Fruehan RJ. Reduction of iron-oxidecarbon composites: Part II. Rates of reduction of composite pellets in a rotary hearth furnace simulator. Metall. Mater. Trans. B, 2008, 39(6): 796.

[10] Haque R, Ray HS, Mukherjee A. Reduction of iron ore fines by coal char fines-development of a mathematical model. Scand. J. Metall., 1992, 21(2): 78.

[11] Peng B, Zhang CF, Peng J. Research on the rate of zinc oxide reduction with CO. J. Cent. South. Univ. Technol., 2001, 32(2): 189.

[12] Rao YK. The kinetics of reduction of hematite by carbon. Metall. Trans., 1971, 2(5): 1439.

[13] Rao YK, El-Rahaiby SK. Direct reduction of lead sulfide with carbon and lime; Effect of catalysts: Part ii. analytical model. Metall. Trans. B, 1985, 16(3): 477.

[14] Han QY. Kinetics of Metallurgical Process, 1983 2nd ed. Beijing, Metallurgical Industry Press, 91.

[15] Shi JY, Donskoi E, McElwain DLS, Wibberley LJ. Modelling the reduction of an iron ore-coal composite pellet with conduction and convection in an axisymmetric temperature field. Math. Comput. Modell., 2005, 42(1–2): 45.

[16] Akiyama T, Ohta H, Takahashi R, Waseda Y, Yagi JI. Measurement and modeling of thermal conductivity for dense iron oxide and porous iron ore agglomerates in stepwise reduction. ISIJ Int., 1992, 32(7): 829.

[17] McAdam GD, O’Brien DJ, Marshall T. Rapid reduction of new zealand ironsands. Ironmaking Steelmaking, 1977, 4(1): 1.