6
Perhaps one of the most interesting notes to highlight
in the performance of pellet binders is in the addition of
various modifier chemistries – particularly zeta potential
modifiers, and among those particularly dispersants. Halt
and Kawatra (2017) investigated the impact of various zeta
potential modifiers on the strength of pellets bound with
starch and found that under dispersing conditions the pel-
lets were formed to be smoother, stronger, and much more
abrasion resistant. The last point is particularly useful for
reducing the dustiness of the pellets involved (Halt and
Kawatra, 2017) during and after the pelletization step.
The addition of fluxes and other reagents is generally
a metallurgical requirement and have minimal impact on
the pelletization process itself. Insoluble calcium and mag-
nesium, as is presented in common fluxes, have minimal
interactions with the pelletization process, and are added
here as it is both convenient and low impact. The “other
reagents” would typically include adding fuels such as car-
bon for the induration step. In cold-bonded pellets, reduc-
ing agents can also be added in preparation for the smelting
step, as without an induration step they can survive to the
final reduction step.
Once the pellets are grown to the target size (usually
9–12mm), they typically proceed an induration furnace
(almost always rotary kiln or straight grate furnaces in the
U.S.) to be fired. The firing process hardens the pellets to
the strength required in typical blast furnace processing.
Opportunities in Pelletization
In general, the major opportunities in pelletization pro-
cesses involve using more readily available reagents in more
effective manners. Reagents which are readily available,
especially locally, especially at very low costs (as some prod-
ucts which could be seen as wastes have some potential as
pellet binders) are preferred, especially if they can be made
to work well. There is a very considerable variety of poten-
tial pellet binders which have been investigated over the
years (Eisele and Kawatra, 2003 Claremboux and Kawatra,
2022).
In addition, zeta potential interactions and potentially
other surface interactions have been shown to be able to
augment at least starch chemistries (Halt and Kawatra,
2017). This incidentally appears to have been used in other
pellet binder products already, as many carboxymethyl-cel-
luloses have dispersants added to them too, although this
may be more in response to the sensitivity of such reagents
to calcium and magnesium ions as opposed to an attempt
to take advantage of the dispersing effects.
Other major opportunities involve optimizing the
induration step. One branch of this approach (Sivrikaya
et al., 2012) investigated using boron-rich colemanite to
lower the recrystallization temperature of the silica in the
pellets, allowing the induration step to proceed at signifi-
cantly lower temperatures (roughly 900°C instead of around
1300°C) without lowering pellet strength. However, to this
author’s knowledge, it has not been determined yet whether
the quantity of boron added to the pellet via this process is
potentially detrimental to the steelmaking step. If it can be
shown not to be, then this can present a significant energy
savings to a pelletization plant. Otherwise, perhaps alterna-
tive reagents exist which could have a comparable impact on
stabilizing the silica recrystallization at lower temperatures.
Another interesting opportunity is in improving the
quality of the pellet feed for the needs of the pelletization
process itself. As mentioned prior, HPGR has recently
received significant attention as a methodology of reduc-
ing the size and increasing the surface area of the iron ore
concentrates before pelletization. Van der Meer (2015) and
Campos et al. (2019) are two studies exploring these pos-
sibilities, and which show that finer pelletization feeds can
be readily achieved with the technology. The main advan-
tage here is that HPGR is functional and effective at the
moisture contents targeted by pellet feed, and the finer size
distributions can assist in the formation of more uniformly
sized and stronger pellets (van der Meer, 2015).
It is also possible to use roller mills to better mix the
binders into the pellet feed. In an exploration of the bond-
ing mechanisms of sodium bentonite it was found that by
mixing the bentonite into a magnetite pellet feed using a
roller mill to spread the bentonite through the feed, the
bentonite dosage requirement could be approximately
halved (Kawatra and Ripke, 2003). It is important to note
however that the roller mill was not being used to grind
down the pellet feed material further – the roller spacing
was maintained greater than 1cm and no significant pres-
sure was evolved on the material as it passed between the
rolls. Instead the roller mill was solely used to spread and
effectively smear the bentonite within the pellet feed.
REDUCTION
The final step of taking iron ore and making it a suitable
feedstock for steelmaking is to reduce the iron oxides to
metallic iron. Most iron is processed in blast furnaces to
a pig iron metal, the process of which informs the major-
ity of the requirements for iron ore pellets (Claremboux
and Kawatra, 2022), with relatively limited alternative
operations such as direct reduction or direct smelting of
iron feeds. There are also some entirely different process-
ing routes, such as organic processing and bioleaching
technologies which remain a topic of interest especially in
Perhaps one of the most interesting notes to highlight
in the performance of pellet binders is in the addition of
various modifier chemistries – particularly zeta potential
modifiers, and among those particularly dispersants. Halt
and Kawatra (2017) investigated the impact of various zeta
potential modifiers on the strength of pellets bound with
starch and found that under dispersing conditions the pel-
lets were formed to be smoother, stronger, and much more
abrasion resistant. The last point is particularly useful for
reducing the dustiness of the pellets involved (Halt and
Kawatra, 2017) during and after the pelletization step.
The addition of fluxes and other reagents is generally
a metallurgical requirement and have minimal impact on
the pelletization process itself. Insoluble calcium and mag-
nesium, as is presented in common fluxes, have minimal
interactions with the pelletization process, and are added
here as it is both convenient and low impact. The “other
reagents” would typically include adding fuels such as car-
bon for the induration step. In cold-bonded pellets, reduc-
ing agents can also be added in preparation for the smelting
step, as without an induration step they can survive to the
final reduction step.
Once the pellets are grown to the target size (usually
9–12mm), they typically proceed an induration furnace
(almost always rotary kiln or straight grate furnaces in the
U.S.) to be fired. The firing process hardens the pellets to
the strength required in typical blast furnace processing.
Opportunities in Pelletization
In general, the major opportunities in pelletization pro-
cesses involve using more readily available reagents in more
effective manners. Reagents which are readily available,
especially locally, especially at very low costs (as some prod-
ucts which could be seen as wastes have some potential as
pellet binders) are preferred, especially if they can be made
to work well. There is a very considerable variety of poten-
tial pellet binders which have been investigated over the
years (Eisele and Kawatra, 2003 Claremboux and Kawatra,
2022).
In addition, zeta potential interactions and potentially
other surface interactions have been shown to be able to
augment at least starch chemistries (Halt and Kawatra,
2017). This incidentally appears to have been used in other
pellet binder products already, as many carboxymethyl-cel-
luloses have dispersants added to them too, although this
may be more in response to the sensitivity of such reagents
to calcium and magnesium ions as opposed to an attempt
to take advantage of the dispersing effects.
Other major opportunities involve optimizing the
induration step. One branch of this approach (Sivrikaya
et al., 2012) investigated using boron-rich colemanite to
lower the recrystallization temperature of the silica in the
pellets, allowing the induration step to proceed at signifi-
cantly lower temperatures (roughly 900°C instead of around
1300°C) without lowering pellet strength. However, to this
author’s knowledge, it has not been determined yet whether
the quantity of boron added to the pellet via this process is
potentially detrimental to the steelmaking step. If it can be
shown not to be, then this can present a significant energy
savings to a pelletization plant. Otherwise, perhaps alterna-
tive reagents exist which could have a comparable impact on
stabilizing the silica recrystallization at lower temperatures.
Another interesting opportunity is in improving the
quality of the pellet feed for the needs of the pelletization
process itself. As mentioned prior, HPGR has recently
received significant attention as a methodology of reduc-
ing the size and increasing the surface area of the iron ore
concentrates before pelletization. Van der Meer (2015) and
Campos et al. (2019) are two studies exploring these pos-
sibilities, and which show that finer pelletization feeds can
be readily achieved with the technology. The main advan-
tage here is that HPGR is functional and effective at the
moisture contents targeted by pellet feed, and the finer size
distributions can assist in the formation of more uniformly
sized and stronger pellets (van der Meer, 2015).
It is also possible to use roller mills to better mix the
binders into the pellet feed. In an exploration of the bond-
ing mechanisms of sodium bentonite it was found that by
mixing the bentonite into a magnetite pellet feed using a
roller mill to spread the bentonite through the feed, the
bentonite dosage requirement could be approximately
halved (Kawatra and Ripke, 2003). It is important to note
however that the roller mill was not being used to grind
down the pellet feed material further – the roller spacing
was maintained greater than 1cm and no significant pres-
sure was evolved on the material as it passed between the
rolls. Instead the roller mill was solely used to spread and
effectively smear the bentonite within the pellet feed.
REDUCTION
The final step of taking iron ore and making it a suitable
feedstock for steelmaking is to reduce the iron oxides to
metallic iron. Most iron is processed in blast furnaces to
a pig iron metal, the process of which informs the major-
ity of the requirements for iron ore pellets (Claremboux
and Kawatra, 2022), with relatively limited alternative
operations such as direct reduction or direct smelting of
iron feeds. There are also some entirely different process-
ing routes, such as organic processing and bioleaching
technologies which remain a topic of interest especially in