Note: Descriptions are shown in the official language in which they were submitted.
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USE OF H2 OBTAINED FROM THERMAL DECOMPOSITION OF
NATURAL GAS FOR IRON ORE REDUCTION
TECHNOLOGICAL FIELD
This disclosure relates to the use of by-products obtained from natural gas
thermal
decomposition in iron ore reduction.
BACKGROUND
Natural gas has been used in metallurgical process such as in reforming
processes for
generating CO and H2 as reductant gases. CO gas reduces ore more actively than
H2 gas
but generates green-house gas (GHG). The use of natural gas in metallurgical
processes
suffers from several setbacks: off-gas from a reducer contains CO2 which
requires rather
expensive systems for its separation. In addition, high oxygen potential (and
operating
temperature) is preferable in order to avoid mechanical problems due to carbon-
deposition,
which decreases the reduction efficiency of gas.
It would be highly desirable to be provided with an improved process for
reducing iron ores.
BRIEF DESCRIPTION OF THE DRAWINGS
Reference will now be made to the accompanying drawing, showing by way of
illustration, a
preferred embodiment thereof, and in which:
Figure 1 illustrates an embodiment of the process described herein. The
natural gas is
thermally decomposed into carbon black (solid carbon or C) and hydrogen gas
(H2) in a
decomposer. The hydrogen gas produced from the thermally decomposed natural
gas is
used (either alone or in combination with other gases) to reduce an iron ore
in a reducer. The
ore reduction by-products and target products (H2/H20, Fern or TiO2 for
example) can either
be submitted to a condensation step in a condenser to separate water (H2O)
from the
hydrogen gas (H2, which is recycled back in the reducer) or to a separation
step (in a smelter
or aerator) to generate target products (e.g., iron (Fe) and/or titanium
dioxide (TiO2, in an
embodiment in the form of a titania slag or a synthetic rutile)).
DETAILED DESCRIPTION
The process described herein concerns the reduction of an iron using H2 from
the thermal
decomposition of natural gas as well as from recycling H2 (from the condenser)
as the
reducing gas/reductant gas. The reducing/reductant gas is obtained from the
thermal
decomposition of natural gas (CH4) and from the condenser. In an embodiment,
the process
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is advantageous at least because no green-house gases are produced during the
ore
reduction since no carbon units (e.g. solid carbon or gaseous carbon such as
CO) participate
in the reduction process. Further, this process allows the production of
lucrative by-products
(carbon black/solid carbon) target products (titania slag, synthetic rutile
and iron) as well as
recyclable by-products (e.g., H2 gas). Further, the use of H2 from the thermal
decomposition
of natural gas as a reducing/reductant gas is associated with fast reduction
kinetics or a
higher global gas reduction efficiency (even at low temperature), easy
recycling of reducer
off-gas and easy off-gas cleaning (allowing recycling of the H2 gas) as well
as high global gas
reduction efficiency.
The present disclosure thus provides processes for reducing an iron ore.
Broadly, the said
process comprises: (i) thermally decomposing, in a decomposer, a natural gas
(CH4) into an
hydrogen gas (H2) and carbon black (C); (ii) reducing said iron ore with a
reducing gas
comprising the hydrogen gas of step (i) to provide: (a) a first gaseous
mixture comprising the
hydrogen gas and a water vapor; and (b) a second mixture comprising at least
one target
product of the iron ore; (iii) separating, in a separator (e.g., a smelter or
an aerator), the
second mixture to enrich the at least target product in the second mixture;
(iv) condensing, in
a condenser, the water vapor of the first gaseous mixture into liquid water to
separate the
hydrogen gas from the liquid water; and (v) recycling the hydrogen gas of step
(iv) in the
reducer of step (ii). In an embodiment, the process further comprises, after
step (iv),
recuperating the liquid water. In another embodiment, the process further
comprises, after
step (i), recuperating carbon black.
In an embodiment, the reducing gas can comprise additional gases such as
hydrogen gas
which was not generated from natural gas, one or more carrier gas, air, oxygen
and/or CO
gas, etc. In another embodiment, the reducing gas consists essentially of or
consists of the
hydrogen gas of step (i). In still a further embodiment, the reducing gas is
devoid or
substantially devoid of CO gas. In another embodiment, the hydrogen gas which
has been
used as a reducing gas can also be used to provide heat.
In an embodiment, the second mixture is a solid mixture, a liquid mixture or a
combination of
a solid mixture and a liquid mixture.
In an embodiment, the iron ore that can be submitted to this process is an
iron oxide ore.
Exemplary iron oxide ores include, but are not limited to hematite (Fe203-
containing ore),
wustite (FeO-containing ore), magnetic ore (Fe3SO4-containing ore) as well as
combinations
thereof. In such embodiments, the at least one target product comprises iron.
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In another embodiment, the iron ore that can be submitted to this process is
an iron titanium
oxide ore. Exemplary iron titanium oxide ores include, but are not limited to
ilmenite (FeTiO3-
containing ore). Ilmenite can be obtained in the form of an ilmenite-hematite
mixture, a
weathered ilmenite, a titano-vanadium-magnetite as well as combinations
thereof. In such
embodiment, the at least one target product comprises TiO2 and Fe. Further, in
some
embodiments, the second mixture is titania slag or synthetic rutile.
While the invention has been described in connection with specific embodiments
thereof, it
will be understood that the scope of the claims should not be limited by the
preferred
embodiments set forth in the examples, but should be given the broadest
interpretation
consistent with the description as a whole.
