Rate-enhancement effect of CO in magnetite concentrate particle reduction by H₂+CO mixtures

ABSTRACT

The kinetics of the reduction of magnetite concentrate particles by H₂+CO mixtures have been investigated in drop-tube reactors (DTRs) to obtain rate expressions for the design of novel flash ironmaking reactors. The experimental temperature varied from 1423 K (1150°C) to 1873 K (1600°C). The H₂/CO ratio was varied from 0.5 to 2, which is the typical composition range of the product gas from the partial oxidation of natural gas. The experimental data were analysed separately in two temperature ranges 1423 K (1150°C)–1623 K (1350°C) and 1623 K (1350°C)–1873 K (1600°C), as the magnetite concentrate particles tend to fuse and melt at temperatures above 1623 K (1350°C) changing the reduction mechanism. CFD (Computational Fluid Dynamics) simulations were used to more accurately account for temperature and concentration variations. Synergistic effects were observed in the reduction by H₂+CO mixtures compared with the simple summation of contributions of the individual component gases.

KEYWORDS:

• Flash ironmaking
• drop-tube reactor
• reduction kinetics
• CO+H₂ mixture
• CFD
• Rate expression
• High temperaure
• magnetite particles

Acknowledgements

The support and resources from the Center for High Performance Computing at the University of Utah are gratefully acknowledged.

Disclosure statement

No potential conflict of interest was reported by the author(s). This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favouring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

Nomenclature

Ap:	=	surface area of particle (m2)
dp:	=	geometric mean particle diameter (m)
Ki:	=	equilibrium constant
mp:	=	particle mass (kg)
pi:	=	partial pressure of species i (atm)
T:	=	gas phase temperature (K)
Tp:	=	particle temperature (K)
ui:	=	gas phase velocity components (m s−1)
up:	=	particle velocity (m s−1)
X:	=	reduction degree
ϵp:	=	particle emissivity
${\rho }_P$:	=	particle density (kg m−3)
σ:	=	Stefan–Boltzmann constant (W m−2 K−4)

Additional information

Funding

The authors acknowledge the financial support from the US DOE under Award Number DE-EE0005751 with cost share by the American Iron and Steel Institute (AISI) and the University of Utah.