Abstract
A three-dimensional CFD model of a straight grate furnace for indurating iron-oxide pellets was developed for exploring conditions of furnace operation for fluid flow, heat transfer and reactions. The model includes reactions for natural gas combustion in the gas phase and calcination and magnetite oxidation as well as drying in the pellet bed. The performance of the model was investigated with a series of pellet production rates that included adjustments to the fuel rates to achieve proper induration temperatures in the pellet bed. The model may be used to discover opportunities for process improvement.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
Abbreviations
- a:
-
specific area of heat or mass transfer, m2/m3
- d:
-
mean pellet diameter, m
- ds:
-
depth of solids in the pellet bed on the grate, m
- Dox:
-
diffusivity of oxygen in air, m2/s
- Dw:
-
diffusivity of water in air, m2/s
- f:
-
flux agent, Ca or Mg in molecular formulas for carbonates
- G:
-
mass flux, kg/m2 s
- h:
-
heat transfer coefficient, W/m2 K
- Hf:
-
enthalpy of flux reaction at the reaction temperature, J/kg
- HCO2:
-
enthalpy of formation of CO2 at the reaction temperature, J/kg
- HfCO3:
-
enthalpy of formation of carbonate compound at the reaction temperature, J/kg
- Hfo:
-
enthalpy of formation of flux oxide, J/kg
- Hh:
-
enthalpy of formation of hematite at the reaction temperature, J/kg
- Hm:
-
enthalpy of formation of magnetite at the reaction temperature, J/kg
- Ho:
-
enthalpy of formation of oxygen at the reaction temperature, J/kg
- Hox:
-
heat of magnetite reaction with oxygen at the reaction temperature, J/kg
- kd:
-
mass transfer coefficient, m/s
- kf:
-
rate constant for carbonate thermolysis, 1/s
- km:
-
rate constant for magnetite reaction, m/s
- kox:
-
mass transfer coefficient for O2, m/s
- ṁs:
-
rate of solids feed to the grate, kg/s
- Mf:
-
molecular weight of flux compound, kg/kmol
- Mm:
-
molecular weight of magnetite, kg/kmol
- Mox:
-
molecular weight of oxygen, kg/kmol
- Mw:
-
molecular weight of water, kg/kmol
- P:
-
total pressure, Pa
- Ps:
-
saturation vapor pressure, Pa
- Qc:
-
specific heat transfer rate by convection, J/m3·s
- Qf:
-
specific source of heat in the pellet bed from the flux reaction, J/m3·s
- Qox:
-
specific source of heat in the pellet bed from the magnetite reaction, J/m3·s
- Rg:
-
ideal gas constant
- Sf:
-
source of CO2 in the gas from the flux reactions, kg/m3·s
- Sox:
-
source of O2 in the gas from the magnetite reaction, kg/m3·s
- Sw:
-
source of water in the gas from drying evaporation, kg/m3·s
- T:
-
temperature, K
- Tb:
-
bed temperature, K
- Tg:
-
bulk gas temperature, K
- Ts:
-
bulk solids temperature, K
- ugr:
-
grate speed, m/s
- wgr:
-
grate width, m
- Xm:
-
degree of magnetite oxidation [see Eq. (12)]
- Xw:
-
degree of drying [see Eq. (2)]
- yox:
-
mole fraction of oxygen in the gas
- yw:
-
mole fraction of water in the gas
- εb:
-
porosity of pellet bed
- εp:
-
porosity of pellets
- κ:
-
thermal conductivity of gas, J/msK
- ρf:
-
mass concentration of carbonates in the pellet, kg/m3
- ρm:
-
mass concentration of magnetite in the unreacted pellet core, kg/m3
- ρs:
-
bulk bed solids mass concentration, kg/m3
- ρw:
-
mass concentration of water in the pellet, kg/m3
- τ:
-
tortuosity of pores in pellets
- μ:
-
gas viscosity, Pa·s
References
ANSYS. ANSYS CFX. April 29, 2013, https://doi.org/www.ansys.com/Products/Simulation+Technology/Fluid+Dynamics/Fluid+Dynamics+Products/ANSYS+CFX (accessed April 29, 2013).
Croft, T.N. et al., “CFD Analysis of an Induration Cooler of an Iron Ore Grate-Kiln Pelletising Process,” Minerals Engineering, 22, no. 9–10 (2009): 859–873.
Englund, D.J., Davis, R.A., and Murr, D.L., “Application of Computational Fluid Dynamics Modeling at National Steel Pellet Company,” Ironmaking Conference Proceedings 58th Duluth, 1999, pp. 545–557.
Englund, D.J., Davis, R.A., and Anderson, R.C., “Refinement of a CFD Model for Prediction of Gas Flow Distribution in the Drying Zone of a Pellet Induration Furnace,” Annual Meeting of the Minnesota Section, SME, Duluth, Society for Mining, Metallurgy and Exploration, 1995, pp. 87–110.
Fuerstenau, M.C. and Han, K.N., Principles of Mineral Processing, 3rd ed. Littleton, Society for Mining, Metallurgy and Exploration, 2003.
Gaskell, D.R., Introduction to Metallurgical Thermodynamics, 2nd ed., New York, Taylor & Francis, 1981.
Outokumpu, HSC Chemistry, n.d.
Papanastassiou, D. and Bitsianes, G., “Mechanisms and kinetics underlying the oxidation of magnetite in the induration of iron ore pellets,” Metallurgical Transactions 4, no. 2 (1973): 487–496.
Sjostrom, U., Lundqvist, M., and Eriksson, O., “Application of Computational Fluid Dynamics Modeling on the Grate-Kiln Process at LKAB,” Fifth International Conferenceon CFD in the Process Industries, Melbourne: CSIRO, 2006, pp. 1–6.
SolidWorks, n.d., https://doi.org/www.solidworks.com.
Thurlby, J.A., Batterham, R.J., and Turner, R.E., “Development and vailidation of a methematical model for the moving grate indurator of iron ore pellets,” International Journal of Mineral Processing, 6 (1979): 43–64.
Wakao, N. and Kaguei, S., Heat and Mass Transfer in Packed Beds, New York, Gordon and Breach, 1982.
Wynnyckyj, J.R. and Batterham, R.J., “Iron Ore Sintering and Pellet Induration Processes,” 4th International Symposium on Agglomeration Toronto, 1985, pp. 957–994.
Author information
Authors and Affiliations
Corresponding author
Additional information
Paper number MMP-13-086.
Discussion of this peer-reviewed and approved paper is invited and must be submitted to SME Publications Dept. prior to May 31, 2015.
Rights and permissions
About this article
Cite this article
Englund, D.J., Davis, R.A. CFD model of a straight-grate furnace for iron oxide pellet induration. Mining, Metallurgy & Exploration 31, 200–208 (2014). https://doi.org/10.1007/BF03402471
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/BF03402471