The kinetics of carbon monoxide reduction of magnetite concentrate particles through CFD modelling

ABSTRACT

The kinetics of CO reduction of magnetite concentrate particles was investigated in drop-tube reactors (DTR) to obtain a rate equation for the design and analysis of a flash ironmaking reactor. The effect of CO partial pressure was determined and temperature was varied from 1473 K to 1873 K in few seconds of residence time similar to that in a typical flash reactor. The experimental data were divided into two temperature ranges, below 1623 K and above where the magnetite concentrate melts. The reduction degrees achieved at temperatures below 1623 K were under 50%, while significant reduction degrees (higher than 85%) were achieved at higher temperatures. Computational fluid dynamics (CFD) analysis was employed to improve the accuracy of the rate expressions. It was determined that the nucleation and growth kinetics best describes the investigated reaction. The activation energy was 451 and 88 kJ mol⁻¹, respectively, below and above 1623 K.

KEYWORDS:

• Flash reduction
• drop-tube reactor
• CFD
• kinetics
• ironmaking
• magnetite
• Carbon Monoxide
• Rate Equation

Acknowledgements

The support and resources from the Center for High Performance Computing at the University of Utah are gratefully acknowledged. The authors acknowledge the financial support from the U.S. Department of Energy under Award Number DE-EE0005751 with cost share by the American Iron and Steel Institute (AISI) and the University of Utah.

Disclaimer

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 of a screen fraction (m)
k	=	rate constant for reduction of magnetite concentrate particles by CO (atm−1·s−1 or µm·atm−1·s−1)
K	=	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 (fraction)
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 U.S. Department of Energy under Award Number DE-EE0005751 with cost share by the American Iron and Steel Institute (AISI) and the University of Utah.