A two-dimensional mathematical model is developed to describe iron oxides reduction in the shaft furnace of COREX ® smelting reduction process. Combined with mass, momentum and heat transfers between gas and solid phases in steady state, the model calculates and demonstrates the basic characteristics of the shaft furnace, such as velocity, pressure, temperature fields of relevant phases and species' mass fraction distributions. The reduction from magnetite to wustite occupies most part of the furnace, and the reduction degree of burden located near wall is comparatively higher than that close to centre. The model also considers the influence of down pipe gas, driven by the pressure drop between the shaft furnace and melter gasifier, on the reduction behaviors inside furnace. Compared with the base case, the down pipe gas featuring higher temperature prefers to flow toward the symmetry axis, where both gas temperature and solid metallization are promoted remarkably.KEY WORDS: shaft furnace; mathematical model; iron oxides reduction; down pipe gas.The assumptions in the two-dimensional, axisymmetric mathematical model are given as below:(1) The volume fraction of gas in the packed column is set as constant 18) ; (2) Ignoring the wall effect as the gas flows near the wall; (3) The solid flow velocity is uniformly distributed in both radial and axial directions; (4) The solid particle diameter and shape factor always keep constant; (5) The flux decomposition reactions, non-iron oxides reduction reactions and other reactions are not considered in the basic model. Conservation EquationsThe fundamental conservation equations of continuity, momentum, energy and species transport for steady state could be described by Eq. (3). 19) .......... (3) The variable f, dependant diffusive term G f and source term S f all varies with different kinds of conservation equations as summarized in Table 1. Phase PropertiesAccording to the ideal gas equation, the density of gas phase is a function of local temperature and pressure. The viscosities and thermal conductivities of species in gas phase are obtained by Sutherland's law 20,21) and the modified Eucken equation 22,23) respectively with the relevant data from Eckert and Drake's work.24) Based on each specie's viscosity or thermal conductivity and mole fraction, both the gas mixture viscosity or thermal conductivity could be derived from Eq. (4), which is in accordance with Wilke's work. where, V represents viscosity or thermal conductivity;As for solid phase including lump ore and pellet, the average apparent density and particle diameter are measured by experiment with the results as 4 190 kg/m 3 and 0.154 m respectively. The solid viscosity is 6 kg/m · s and its thermal conductivity is 0.8 W/m · K. 10)All species' thermodynamics data, such as heat capacity, enthalpy and entropy, are all from Perry's book, 26) and the gas or solid phase thermodynamic data are computed based on a simple mass fraction average of the species' if needed. Mass TransferDue to iron oxides multi-stage s...

The basic sintering characteristics of Yandi ore from Australia, including assimilation ability, liquid phase fluidity, self-strength of bonding phase, forming ability of silico ferrite of calcium and aluminum (SFCA), and so on, were investigated in detail. Besides, the high temperature behavior and function of sintering were obtained. As a result, the techniques for ore-proportioning in sintering were obtained. The results show that Yandi ore possessing higher assimilation ability, better liquid phase fluidity, lower self-strength of bonding phase, and better forming ability of SFCA, should be mixed with iron ores whose properties are opposite to those of Yandi ore. In the optimization of sintering ore-proportioning, Yandi ore, whose price is relatively low, can be mixed as high as 40wt%.

The effects of natural and forced convection on mass transfer were investigated, especially the composition-dependent material properties were used. Under natural convection, the stationary specimen became a cone. The mass transfer coefficient increased from 3.14 × 10 −5 to 5.31 × 10 −5 m s −1 at the temperatures of 1300-1450°C. The empirical formulas Sh = 0.144(GrSc) 0.325 and k = M(Δρ) 0.325 (L) −0.025 were found within the ranges of 1 × 10 8 < GrSc < 5 × 10 8 . Under forced convection, the rotating scrap cylinder became an irregular spiral. When the rotational speed changed from 141 to 423 r min −1 , the mass transfer coefficients were 7.50 × 10 −5 -1.72 × 10 −4 m s −1 at the temperatures of 1300-1400°C. The empirical formulas J D = 0.133(Re) −0.356 and k = M (n) 0.644 (L) 0.288 were obtained within the ranges of 1000 < Re < 4000.