Vol.:(0123456789) 1 3
Journal of Thermal Analysis and Calorimetry
https://doi.org/10.1007/s10973-020-10532-1
Mathematical modeling of thermal behavior of single iron ore pellet
during heat hardening oxidation
H. Amani
1
· E. K. Alamdari
1
· H. Ale Ebrahim
2
· A. Estupinan
3
· B. Peters
3
Received: 4 March 2020 / Accepted: 23 December 2020
© Akadémiai Kiadó, Budapest, Hungary 2021
Abstract
In this study, a one-dimensional generic model capable of being integrated with reactor scale models is proposed for a single
pellet through solving the transient diferential conservation equations. Predicted results comparison with the experimental
data showed close agreement. In addition, the model was used to investigate the relevance of physical characteristics of pellet,
reacting gas composition, difusion factors, and prevailing regime. It was found that the pure magnetite pellet could achieve
a temperature rise of about 245 K at oxygen concentration of 40 vol.%, whereas the maximum temperature diference inside
the pellet was approximately 24 K. Moreover, increasing pellet size, the maximum attainable temperature reached a peak and
then leveled out. Furthermore, by decreasing the pore diameter, the pellet size with peak temperature shifted to the smaller
pellet sizes. Analyzing the numerical results also showed that for the small pellet sizes, shortening the difusion path leads
to the spreading of the reaction interface. The modeling methodology herein can be applied to any particulate processes and
is not limited to the aforementioned case.
Keywords Non-catalytic gas–solid reactions · Heat and mass transfer · Iron ore pellets · Modeling · Magnetite oxidation
Introduction
Magnetite ( Fe
3
O
4
) had a great share in feedstock supplement
for steel industry through the last 50 years and will continue
to have from now on [1]. The oxidation of magnetite, which
follows Eq. 1, being highly exothermic, provides a notable
part of the energy required for heat hardening (induration)
of iron ore pellets during pelletizing process. It also leads to
strong bonding between the grains and reduces dust genera-
tion during the transport and loading. Furthermore, studies
indicated that iron-based metal oxides are promising materi-
als for chemical looping combustion (CLC) technology, as
they are environmentally safe and relatively inexpensive [2,
3]. Due to the aforementioned industrial importance, there
exists a sizeable volume of literature on the oxidation of
Fe
3
O
4
( FeO ⋅ Fe
2
O
3
) powder and pellets [3–9]:
The duration and temperature of the oxidation cycle play a
key role during the iron ore pellet induration. Variation in
oxidation degree of pellets gives rise to process instability,
since it causes the variation of recuperated air in induration
systems [10]. Microscopic examination of interface during
the oxidation of magnetite pellets has demonstrated that
although the interface of the reaction is a fairly sharp at
high temperatures, it shows very difusive character at the
low temperatures [5, 11].
Regarding heterogeneous reactions, various mathemat-
ical models on a particle level have been introduced to
describe the temporal evolution of involved solid and gas-
eous reactants [12–15]. Major developments in this field
have been reviewed lately by Ghadi et al. [16]. As pointed
out by Melchiori and Canu [ 17], the major difference
between these models arise from the dependency of the
reaction rate expression on the solid reactant concentra-
tion. Some of the basic assumptions for developing these
(1)
4Fe
3
O
4
+ O
2
= 6Fe
2
O
3
H =-119 kJ mol
-1
Fe
3
O
4
.
* E. K. Alamdari
alamdari@aut.ac.ir
1
Department of Materials and Metallurgical Engineering,
Amirkabir University of Technology (Tehran Polytechnic),
424 Hafez Ave, Tehran 15875-4413, Iran
2
Department of Chemical Engineering, Amirkabir University
of Technology (Tehran Polytechnic), Tehran, Iran
3
Faculty of Science, Technology and Medicine, University
of Luxembourg, 2 avenue de l’Université, Esch-sur-Alzette,
Luxembourg