Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
THERMAL REDUCTION PROCESS FOR THE RECOVERY
OF REFRACTORY METAL OXIDES AND THE PRODUCTION OF
VANADIUM-RICH IRON ALLOYS FROM MINING RESIDUES OR
METALLURGICAL WASTES BY-PRODUCED DURING THE
BENEFICIATION AND UPGRADING OF TITANIA SLAGS.
FIELD
100011 The present disclosure relates to a thermal reduction process for the
recovery of refractory metal oxides and the production of vanadium-rich iron
alloys.
More specifically, but not exclusively, the present disclosure relates to a
thermal
reduction process for the recovery of refractory metal oxides and the
production of
vanadium-rich iron alloys from mining residues or metallurgical wastes by-
produced
during the beneficiation and upgrading of titania slags.
BACKGROUND
[0002] Titanium Feedstock for Ti02 Pigment Production
100031 Titanium is the ninth most abundant element in the Earth's crust.
Among the various titanium-based products, titanium dioxide (Ti02) holds, with
an
annual world production approaching 6 millions tons, the greatest industrial
and
commercial significance. Titanium dioxide is a high-volume chemical commodity
used
as a white pigment in paints, plastics, papers, inks, etc.
100041 Titanium, because of its strong chemical reactivity with oxygen,
occurs naturally as an oxide, titanate and/or silicate. Titanium dioxide
(Ti02) occurs
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usually as rutile and in a lesser extent as anatase and brookite. Among the
titanates,
those comprising iron such as ilmenite [FeTiO3], hemo-ilmenite [FeTiO3-Fe2O3],
or
titanomagnetite [(Ti,Fe)Fe204] are the most common.
100051 Ilmenite is the most important source of titanium dioxide by
tonnage, accounting for more than ninety percent of the Ti02 supplied to the
world
market. Ilmenite is mined either as hard-rock ilmenite (30-46 wt.% Ti02) or as
weathered and altered ilmenites (46-62 wt.% Ti02) in beach sands [1].
[0006J Ilmenites are commercially upgraded by an electrothermal smelting
or slagging process performed at high temperatures in an electric arc furnace
(EAF)
using anthracite coal as the reductant. This process yields a titaniferous
slag, also called
titanium slag or titania slag, along with pig iron as a co-product. Commercial
titanium
slags contain typically from 70-90 wt.% Ti02. Ilmenite ores are also upgraded
to
synthetic rutiles containing from 92-95 wt.% Ti02 by processes comprising the
reduction of iron oxides with sub-bituminous coal at moderately high
temperatures in
rotary kilns, followed by the removal of iron by leaching with strong mineral
acids.
Rutile, which exhibits a high Ti02 content (93-96% Ti02), is recovered along
with
zircon as a co-product during the beneficiation of ilmenite from beach sands.
[00071 The production of white titanium dioxide pigment is based on two
major commercial processes. The traditional "Sulphate Process" involves
digesting
hard rock ilmenite or titanium slag in concentrated sulfuric acid; pure Ti02
is obtained
by selective hydrolysis of the titanium-bearing liquors. The modern "Chloride
Process"
[2] comprises fluidizing a mixture of titanium-rich feedstocks such as beach
sand
ilmenite, titanium slag, synthetic rutile or natural rutile with petroleum
coke at high
temperatures ranging from 950 C to 1200 C in a stream of chlorine gas to
produce a
gaseous mixture of metal chlorides, including titanium tetrachloride (TiC14),
and other
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metal chlorides originating from impurities present in the feedstock. The
TiCl4 is further
separated and purified from the other metal chlorides by selective
condensation,
fractional distillation, or countercurrent extraction and subsequently
converted to pure
TiO2 by contacting it with oxygen at high temperatures. The chlorine gas is
recovered
during the oxidation step and recycled back to the chlorinator.
[0008] One of the main technical requirements for the sulphate process is
that the feedstock must be soluble in concentrated sulfuric acid. For the
chloride
process, the main technical requirements are a low content of alkaline-earth
metal
oxides and silica, as well as particle size distributions compatible with the
fluidization
procedure.
[0009] Although the smelting of hard rock ilmenites yields a titanium slag
suitable for the sulphate process, the smelting does not remove sufficient
amounts of
impurities, especially calcium and magnesium oxides, to render it suitable as
a
feedstock for the chloride process. A further upgrading of the titanium slag
by a process
including sizing, magnetic separation, oxidation, reduction, acid leaching and
finally
calcination is often required [3, 4]. Such a process has been commercialized
under the
trademark UGSTM. The upgraded titanium slag produced becomes a high-grade
feedstock suitable for the chloride process.
[0010] The UGSTM process also provides for the regeneration of
hydrochloric acid, by pyrohydrolysis of the spent hydrochloric acid solution
containing
the dissolved metal chlorides. The regenerated hydrochloric acid is recycled
back to the
leaching step. The pyrohydrolysis step is typically conducted at temperatures
of about
900 C, either in a fluidized bed or in circulating bed reactor. A significant
amount of
calcined metal oxides are also produced which are currently disposed off and
landfilled.
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[0011] The calcined metal oxides are typically in the form of dense solid
pellets having an essentially spherical shape and a particle size distribution
(PSD) such
as illustrated in Table 1. The average PSD comprises particles (about 65 wt.%)
having a
size ranging from about 425 m to about 850 m (20-35 mesh). Their apparent
density,
as determined by a helium pycnometer, is 4,000 kg.m"3 and their bulk density
1,700
kg.m 3. Each pellet is typically composed of concentric layers of metal oxides
that form
during the flash evaporation of the water and the subsequent hydrolysis of the
metal
chlorides.
[0012] Table 1: Particle size distribution of calcined metal oxides as
produced by the UGSTM process.
Particle Size (d/ m) Mass Fraction (wt. %)
-200 5
200-355 15
355-500 20
500-710 30
710-1000 25
+1000 5
Dp50 = 550 m
[0013] Typical chemical compositions and composition ranges for calcined
metal oxides as produced by the UGS rM process are illustrated in Table 2.
100141 Table 2: Chemical compositions and composition ranges for
calcined metal oxides as produced by the UGSTM process.
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Metal Oxide or Mass fraction Typical Mass Typical Mass
Element Range (wt. %) Fraction # 1 (wt. %) Fraction # 2 (wt. %)
Fe203 40.0 - 70.0 53.76 47.20
MgO 15.0 - 40.0 25.97 31.57
A1203 5.0 - 20.0 12.84 13.55
V205 0.1 - 3.0 1.83 1.86
CaO 0.1 - 3.0 1.35 1.99
Mn203 0.1 - 3.0 1.17 1.45
Cr203 0.1 - 2.0 0.78 0.84
Cl (chloride) 0.05 - 2.0 1.08 0.72
Si02 0.1 - 2.0 0.88 0.13
Ti02 0.05 - 0.9 0.58 0.66
Na (chloride) 0.01 - 0.2 0.09 0.07
K(chloride) 0.01 - 0.3 0.17 0.14
Co203 0.001 - 0.003 0.016 0.016
CuO 0.001 - 0.03 0.013 0.013
NiO 0.001 - 0.03 0.010 0.010
[0015] Because of the high iron, magnesium, and aluminum oxide content,
the synthetic mineral phases identified in the calcined metal oxides belong
mainly to the
spinel group of chemical formula AnBnI204 wherein A" = Mg2+, Fe2+, Mn2+, Ni2+
and
wherein Biii = A13+, Fe3+, Cr3+, V3+, Mn3+, Co +. The most common phases are
in order
of importance: magnesioferrite or pleonaste (MgFe2O4), donathite (MgFeA1O4),
spinel
senso-stricto (MgA12O4), and hercynite (FeA12O4). The remaining uncombined
free
magnesia is usually found as free periclase (MgO), also containing minute
amounts of
calcia (CaO) that is not combined with silica as calcium silicate (CaSiO3).
The chloride
residues are usually found as kalsiohalites (Na0,6K0.4C1). Because of
isomorphic
substitutions, the spinel-type phase also comprises in its crystal lattice
small amounts of
V, Mn, Cr, Ni and Co, sometimes even forming a single phase such as coulsonite
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(FeVZO4) or chromite (FeCrzO ). As a general rule, the calcined metal oxides
are
strongly ferromagnetic and exhibit a brownish color.
100161 Because of the particular chemistry of the calcined metal oxides, the
valuable content that can be recovered therefrom is considerably more than the
value of
its iron metal content. The reduction of one tonne of calcined metal oxides
"as
received", having the chemical composition as exemplified by "Mass Fraction
#1" in
Table 2, using a conventional reductant (e.g., coal, coke, hydrogen, natural
gas, smelter
gas or synthetic gas), yields 399.95 kilograms of a vanadium-rich iron alloy.
The
chemical composition of this vanadium-rich iron alloy was as follows: 94.02
wt.% Fe,
2.56 wt.% V, 2.04 wt.% Mn, 1.33 wt.% Cr as well as 300 ppm Co and 200 ppm Ni.
100171 Assuming a theoretical yield of 100%, there remains 416.20
kilograms of refractory metal oxides following the reduction having the
following
chemical composition: 62.40 wt.% magnesia (MgO), 30.85 wt.% alumina (A1203),
3.24
wt.% calcia (CaO), 2.11 wt.% silica (Si02), and finally 1.39 wt.% titania
(Ti02). If the
alumina and magnesia are chemically combined as spinel (MgAl2O4), the
refractory
mass contains about 44.44 wt.% of spinel (i.e. 184.96 kg; incorporating most
of the
titania as an impurity), and about 53.45 wt.% of fused magnesia (MgO) (i.e.
222.44 kg;
incorporating most of the calcia and finally 2.11 wt.% of free silica).
[0018] Based on the market price for pig iron (900 US$/tonne), vanadium
(80 US$/kg), chromium (11 US$/kg), and manganese (4.5 US$/kg) [Metal Bulletin
Monthly, June 9, 2008, Number 9050], the price of the vanadium-rich iron alloy
is
evaluated at 3,135 US$/tonne (i.e. 1,254 US$/tonne of calcined oxides "as
received").
Based on the price of spinel (500 US$/tonne) and dead burned magnesia (350
US$/tonne) [Industrial Minerals, January 2008], the refractory metal oxide
recovered
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can be evaluated at about 409 US$/tonne of magnesia spinel refractories (i.e.
170
US$/tonne of calcined metal oxides "as received").
[0019] Because of their elevated content in vanadium, manganese and
chromium, the vanadium-rich iron alloys are suitable as master alloys in the
steel
industry for the manufacture of high-strength low alloy steels (HSLA) and tool
steels as
well as powders in various powder metallurgical processes.
[0020] Another important and unique characteristic that pertains to both the
calcined metal oxides "as received" and the refractory metal oxides produced
following
thermal reduction, is their high refractoriness. Regarding the calcined metal
oxides "as
received", all the phases exhibit a high melting point: periclase (m.p. 2820
C),
magnesioferrite (m.p. 1800 C), hercynite (m.p. 1780 C), and chromite (m.p.
2075 C).
This refractory behavior distinguishes them from any type of iron ore
commercially
available and from most of the vanadium-rich slags (e.g., BF-slag, LD-slag,
and EAF-
slag) by-produced during the pre-treatment of vanadium-rich hot metal. This
refractoriness precludes the use of conventional smelting processes that
require the
addition of a fluxing agent (e.g. quartzite, silica sand, lime, and limestone)
to allow the
formation of a molten silicate slag having a low solidus temperature, and that
separates
easily from the liquid iron metal. Following thermal reduction, the remaining
non
reduced metal oxides are more refractory because they are essentially composed
of 50-
70 wt.% magnesia (m.p. 2820 C) and 30-50 wt.% spinel (m.p. 2135 C). Hence, at
the
temperatures used during the thermal reduction process, typically between 500
C to
1500 C, these refractory metal oxides remain in the solid state and, because
of their
high market value, no suitable fluxing agents or additives can be used to
lower the
melting temperature without jeopardizing their chemistry.
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[0021] There thus remains a need for a novel, simple and cost effective
process providing for the recovery of valuables from mining residues and
metallurgical
wastes such as calcined metal oxides produced as by-products in the UGSTM
process or
similar processes for the beneficiation and upgrading of titanium slags.
100221 The present description refers to a number of documents, the
contents of which are herein incorporated by reference in their entirety.
SUMMARY
[0023] The present disclosure broadly relates to a novel process for the
recovery of valuables from mining residues and metallurgical wastes. In an
embodiment, the present disclosure relates to a process for producing vanadium-
rich
iron alloys and refractory metal oxides from mining residues or metallurgical
wastes. In
a further embodiment, the present disclosure relates to a process for
producing
vanadium-rich iron alloys and refractory metal oxides from mining residues or
metallurgical wastes by-produced during the beneficiation and upgrading of
titania slags
from hard rock or beach sand ilmenites. In a further embodiment, the present
disclosure
relates to a process for producing vanadium-rich iron alloys and refractory
metal oxides
from calcined metal oxides. In a further embodiment, the present disclosure
relates to a
process for producing vanadium-rich iron alloys and refractory metal oxides
from
calcined metal oxides by-produced during the beneficiation and upgrading of
titania
slags from hard rock or beach sand ilmenites. In yet a further embodiment, the
present
disclosure relates to a process for producing vanadium-rich iron alloys and
refractory
metal oxides from calcined metal oxides produced as by-products in the UGSTM
process
or similar processes for the beneficiation and upgrading of titanium slags. In
yet a
further embodiment, the present disclosure relates to process for producing
vanadium-
rich iron alloys and refractory metal oxides from mining residues or
metallurgical
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wastes by-produced during the production of pig iron and steelmaking. In yet a
further
embodiment, the present disclosure relates to process for producing vanadium-
rich iron
alloys and refractory metal oxides from calcined metal oxides by-produced
during the
pyrohydrolysis or spray roasting of spent pickling acids.
[0024] In an embodiment, the present disclosure relates to a process for
producing vanadium-rich iron alloys and refractory ceramic materials from
mining
residues or metallurgical wastes. In a further embodiment, the present
disclosure relates
to a process for producing vanadium-rich iron alloys and refractory ceramic
materials
from mining residues or metallurgical wastes by-produced during the
beneficiation and
upgrading of titania slags from hard rock or beach sand ilmenites. In a
further
embodiment, the present disclosure relates to a process for producing vanadium-
rich
iron alloys and refractory ceramic materials from calcined metal oxides. In a
further
embodiment, the present disclosure relates to a process for producing vanadium-
rich
iron alloys and refractory ceramic materials from calcined metal oxides by-
produced
during the beneficiation and upgrading of titania slags from hard rock or
beach sand
ilmenites. In yet a further embodiment, the present disclosure relates to a
process for
producing vanadium-rich iron alloys and refractory ceramic materials from
calcined
metal oxides produced as by-products in the UGSTM process or similar processes
for the
beneficiation and upgrading of titanium slags.
[0025] In an embodiment, the present disclosure relates to a process
comprising submitting mining residues or metallurgical wastes to a reductive
thermal
treatment followed by magnetic separation. In a further embodiment, the
products
following magnetic separation are further upgraded into iron alloys and a
refractory
metal oxide feedstock.
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[0026] In an embodiment, the present disclosure relates to a process
comprising submitting calcined metal oxides to a reductive thermal treatment
followed
by magnetic separation. In a further embodiment, the products following
magnetic
separation are further upgraded into iron alloys and a refractory ceramic
feedstock.
[0027] In an embodiment, the present disclosure relates to a process for
producing vanadium-rich iron alloys and refractory metal oxides, the process
comprising:
[0028] submitting mining residues or metallurgical wastes to at least one
reductive thermal treatment to provide magnetic fractions of differing
magnetic
susceptibilities; and
[0029] recovering the magnetic fractions.
[0030] In an embodiment, the present disclosure relates to a process for
producing vanadium-rich iron alloys and refractory ceramic materials, the
process
comprising:
100311 submitting mining residues or metallurgical wastes to at least one
reductive thermal treatment to provide magnetic fractions of differing
magnetic
susceptibilities; and
[0032] recovering the magnetic fractions.
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[0033] In an embodiment, the present disclosure relates to a process for
producing vanadium-rich iron alloys and refractory metal oxides, the process
comprising:
[0034] submitting calcined metal oxides to at least one reductive thermal
treatment to provide magnetic fractions of differing magnetic
susceptibilities; and
[0035] recovering the magnetic fractions.
[0036] In an embodiment, the present disclosure relates to a process for
producing vanadium-rich iron alloys and refractory ceramic materials, the
process
comprising:
100371 submitting calcined metal oxides to at least one reductive thermal
treatment to provide magnetic fractions of differing magnetic
susceptibilities; and
100381 recovering the magnetic fractions.
[0039] In an embodiment, the present disclosure relates to a process for
producing vanadium-rich iron alloys and refractory metal oxides, the process
comprising:
[0040] submitting mining residues or metallurgical wastes to at least one
reductive thermal treatment to provide a reduced material;
100411 submitting the reduced material to at least one magnetic separation
step to provide magnetic fractions of differing magnetic susceptibilities; and
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100421 recovering the magnetic fractions.
[0043] In an embodiment, the present disclosure relates to a process for
producing vanadium-rich iron alloys and refractory ceramic materials, the
process
comprising:
[0044] submitting mining residues or metallurgical wastes to at least one
reductive thermal treatment to provide a reduced material;
[0045] submitting the reduced material to at least one magnetic separation
step to provide magnetic fractions of differing magnetic susceptibilities; and
[0046] recovering the magnetic fractions.
100471 In an embodiment, the present disclosure relates to a process for
producing vanadium-rich iron alloys and refractory metal oxides, the process
comprising:
100481 submitting calcined metal oxides to at least one reductive thermal
treatment to provide a reduced material;
100491 submitting the reduced material to at least one magnetic separation
step to provide magnetic fractions of differing magnetic susceptibilities; and
[0050] recovering the magnetic fractions.
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[0051] In an embodiment, the present disclosure relates to a process for
producing vanadium-rich iron alloys and refractory ceramic materials, the
process
comprising:
[0052] submitting calcined metal oxides to at least one reductive thermal
treatment to provide a reduced material;
100531 submitting the reduced material to at least one magnetic separation
step to provide magnetic fractions of differing magnetic susceptibilities; and
[0054] recovering the magnetic fractions.
[00551 In an embodiment of the present disclosure, the reductive thermal
treatment is performed at a temperature ranging from 500 C to 1,500 C.
[0056] In an embodiment, the reductive thermal treatment is performed on
mining residues or metallurgical wastes by-produced during the beneficiation
and
upgrading of titania slags from hard rock or beach sand ilmenites. In a
further
embodiment, the reductive thermal treatment is performed on calcined metal
oxides by-
produced during the beneficiation and upgrading of titania slags from hard
rock or
beach sand ilmenites. In yet a further embodiinent, the reductive thermal
treatment is
performed on calcined metal oxides produced as by-produced in the UGSTM
process or
similar processes for the beneficiation and upgrading of titanium slags.
[0057] In an embodiment of the present disclosure, the reductive thermal
treatment is performed at a temperature ranging from 500 C to 1,500 C or below
the
melting point or solidus temperature of the iron alloy.
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[0058] In an embodiment of the present disclosure, the magnetic separation
is performed using a magnetic flux ranging from about 0.01 Tesla to about 0.1
Tesla.
100591 In an embodiment of the present disclosure, the magnetic fractions
of differing magnetic susceptibilities comprise a fraction consisting of a
vanadium-rich
iron alloy and reductible elements and a fraction consisting of refractory
metal oxides
and non-reductible elements.
[0060] In an embodiment of the present disclosure, the fraction consisting
of a vanadium-rich iron alloy and reductible elements comprises a higher
magnetic
susceptibility relative to the fraction consisting of refractory metal oxides
and non-
reductible elements.
[0061] In an embodiment of the present disclosure, the fraction consisting
of a vanadium-rich iron alloy and reductible elements comprises vanadium,
chromium,
manganese, nickel and cobalt. In an embodiment of the present disclosure, the
fraction
consisting of refractory metal oxides and non-reductible elements comprises
magnesium, aluminum, calcium, titanium and silicon oxides.
[0062] The foregoing and other objects, advantages and features of the
present disclosure will become more apparent upon reading of the following non
restrictive description of illustrative embodiments thereof, given by way of
example
only with reference to the accompanying drawings, and which should not be
interpreted
as limiting the scope of the present disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0063] In the appended drawings:
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[0064] FIG. 1 shows a flowchart illustrating an exemplary process for
producing a vanadium-rich iron alloy and refractory metal oxides (e.g. spinel
magnesia)
from mining residues or metallurgical waste oxides according to an embodiment
of the
present disclosure; and
[0065] FIG. 2 shows a flowchart illustrating an exemplary process for
producing a vanadium-rich iron alloy and refractory metal oxides (e.g. spinel
magnesia)
from mining residues or metallurgical waste oxides according to a further
embodiment
of the present disclosure.
DETAILED DESCRIPTION
[0066] In order to provide a clear and consistent understanding of the terms
used in the present specification, a number of definitions are provided below.
Moreover, unless defined otherwise, all technical and scientific terms as used
herein
have the same meaning as commonly understood to one of ordinary skill in the
art to
which this invention pertains.
[0067] The use of the word "a" or "an" when used in conjunction with the
term "comprising" in the claims and/or the specification may mean "one", but
it is also
consistent with the meaning of "one or more", "at least one", and "one or more
than
one". Similarly, the word "another" may mean at least a second or more.
[0068] As used in this specification and claim(s), the words "comprising"
(and any form of comprising, such as "comprise" and "comprises"), "having"
(and any
fonn of having, such as "have" and "has"), "including" (and any form of
including,
such as "include" and "includes") or "containing" (and any form of containing,
such as
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"contain" and "contains"), are inclusive or open-ended and do not exclude
additional,
unrecited elements or process steps.
100691 The term "about" is used to indicate that a value includes an
inherent variation of error for the device or the method being employed to
determine the
value.
[0070] As used in this specification, the term "reductible oxides" refers to
metal oxides susceptible to reductive thermal treatment. Non limiting examples
of such
oxides include oxides of iron, chromium, vanadium, manganese, nickel and
cobalt.
100711 As used in this specification, the term "non-reductible oxides" refers
to metal oxides not susceptible to reductive thermal treatment. Non limiting
examples
of such oxides include oxides of magnesium, aluminum, titanium, silicon and
calcium.
[0072] As used in this specification, when referring to a titanium slag
obtained from a hard rock ilmenite, the term "impurity" essentially refers to
oxides of
magnesium, calcium, silicon, aluminum, vanadium, manganese, chromium, and
metallic iron. When referring to a titanium slag obtained from a beach sand
ilmenite, the
term "impurity" essentially refers to manganese and radioactive elements (e.g.
uranium
and thorium).
[0073] In an embodiment, the present disclosure relates to a process for
producing vanadium-rich iron alloys and refractory metal oxides from mining
residues
or metallurgical waste oxides such as calcined metal oxides. In an embodiment,
the
process comprises subjecting the mining residues or metallurgical waste oxides
to at
least one reductive thermal treatment step and at least one magnetic
separation step.
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[0074] In an embodiment, the present disclosure relates to a process for
producing vanadium-rich iron alloys and refractory metal oxides from mining
residues
and/or metallurgical waste metal oxides. In an embodiment, the process
comprises
subjecting the mining residues and/or metallurgical waste metal oxides to at
least one
reductive thermal treatment step. Following cooling, the reduced material is
subjected
to a comminution step including crushing and grinding. The comminuted material
is
then subjected to a magnetic separation procedure to provide magnetic
fractions of
differing magnetic susceptibilities. The magnetic fractions are subsequently
recovered
and analyzed. The products obtained (i.e. vanadium-rich iron alloys and
refractory
metal oxides) can be directly used or further upgraded depending on the
application.
[0075] In an embodiment, the present disclosure relates to a process for
producing vanadium-rich iron alloys and refractory metal oxides from calcined
metal
oxides produced as by-products in the UGSTM process. In an embodiment, the
process
comprises subjecting the calcined metal oxides to a pre-reduction step, either
during or
after being discharged from the pyrohydrolyser, by contacting the oxides with
either a
gaseous or solid reducing agent. This pre-reduction step provides for at least
a partial
reduction of the reducible oxides.
100761 It has been surprisingly discovered that the calcined metal oxides,
obtained from the pyrohydrolysis of the dissolved metal chlorides containing
spent acid
solution resulting from the UGSTM process, can be effectively reduced at
relatively low
temperatures to produce particles or platelets of an iron alloy containing
significant
amounts of vanadium, manganese and chromium, leaving a mixture of free
magnesium
oxide and spinel. In an embodiment of the present disclosure, the particles
and/or
platelets are subjected to a comminution step to provide a material that is
readily
subjected to magnetic separation. In an embodiment of the present disclosure,
the
magnetic separation is performed by means of a hand magnet.
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Ig
[0077] In an embodiment of the present disclosure, the reductive thermal
treatment step is performed using a gaseous reducing agent selected from the
group
consisting of hydrogen, natural gas, carbon monoxide, gaseous hydrocarbons,
synthesis
gas [i.e. syngas; mixture of carbon monoxide (CO) and hydrogen (H2)], producer
gas,
water gas and smelter gas. Other suitable gaseous reducing agents are known in
the art,
and are within the capacity of a skilled technician. In a further embodiment
of the
present disclosure, the reductive thermal treatment step is performed using a
solid
reducing agent including but not limited to carbon-based materials selected
from the
group consisting of charcoal, coal, carbon black, petroleum, metallurgical
cokes and
graphite. Other suitable solid reducing agents are known in the art, and are
within the
capacity of a skilled technician. In yet a further embodiment of the present
disclosure,
the reductive thermal treatment step is performed at temperatures ranging from
about
500 to about 700 C when using hydrogen gas as the reducing agent. In yet a
further
embodiment of the present disclosure, the reductive thermal treatment is
performed at
temperatures ranging from about 900 to about 1500 C when using carbon-based
materials as the reducing agent.
[0078] In an embodiment of the present disclosure, the reductive thermal
treatment step is performed using a vertical shaft furnace in which the
calcined metal
oxides are on a fluidized bed, a circulating bed or a moving bed. Further non-
limiting
examples of suitable apparatusses include a rotary hearth furnace, a multiple
heart
furnace, a rotary kiln, a reverberatory furnace and an induction furnace.
Other suitable
apparatusses are known in the art, and are within the capacity of a skilled
technician.
[0079] Comminution of the reduced material (following reductive thermal
treatment) provides for the substantial liberation of the iron alloy from the
refractory
metal oxides. Suitable comminution equipment is known in the art and is within
the
capacity of a skilled technician. Depending on the type of magnetic separator
used to
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sort the iron alloy from the refractory metal oxides, the comminution step can
be
performed in either dry or wet conditions by means of sand milling.
[0080] The magnetic separation can be performed in a single step or
multiple steps, in either dry or wet mode, using either a permanent magnet or
an
electromagnet. In an embodiment of the present disclosure, the median magnetic
fractions are recycled back for a further reductive thermal treatment step.
100811 In an embodiment of the present disclosure, the reductive thermal
treatment step is performed on calcined metal oxides obtained from the
pyrohydrolysis
of the spent acid solution resulting from the UGSTM process.
[0082] In an embodiment of the present disclosure, the reductive thermal
treatment step is performed on calcined metal oxides obtained from the
pyrohydrolysis
of a spent acid solution generated from the upgrading of chloride-type
titanium slags
having a titanium dioxide content ranging from about 76 to about 86 wt.% Ti02
using
the UGSTM process. In a further embodiment of the present disclosure, the
reductive
thermal treatment step is performed on calcined metal oxides obtained from the
pyrohydrolysis of a spent acid solution generated from the beneficiation and
upgrading
of titania slags from beach sand ilmenites using the Benelite or the Becher
process.
EXPERIMENTAL
[0083] A number of examples are provided hereinbelow, illustrating the
efficiency of the process of the present disclosure in the preparation of
vanadium-rich
iron alloys and refractory metal oxides from mining residues or metallurgical
waste
oxides.
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[0084] Example 1
[0085] A mass of calcined metal oxides (100 grams), by-produced during
the pyrohydrolysis of a spent aqueous acid solution containing metal chlorides
and
having the chemical composition reported in Table 2 (fraction #1) was
thoroughly
mixed with carbon black (20 grams) as reductant. The mixture was then
introduced into
a magnesia crucible (2" by 5") prepared by slip casting (Custom Ceramics Inc.)
and
covered by a lid. The loaded crucible was introduced into a box furnace (Blue
M,
Lindberg) and maintained at 1100 C over a period of 2 hours. Following
cooling, the
agglomerated mixture was ground in a pulverizer (Retsch) to produce a powder
having
a particle size < 200 mesh (<75 m). Any excess carbonaceous material (i.e.
carbon
black) was removed from the ground material by pouring it into a separatory
funnel
comprising carbon tetrachloride. Following decantation, the carbon-free
material was
dried in an oven kept at 80 C, cooled and subjected to magnetic separation
using a hand
magnet (Gilson). About 40 grams of an iron alloy powder was recovered along
with
about 40 grams of a white powder comprising refractory metal oxides. Chemical
analysis of the iron alloy powder revealed the following elemental
composition: 93
wt.% Fe, 2.5 wt.% V, 2.0 wt.% Mn, 1 wt.% Cr and 1.5 wt.% C. Chemical analysis
of
the white powder comprising refractory metal oxides revealed the following
composition: 62 wt.% MgO, 31 wt.% A1203, 3 wt.% CaO, 2 wt. % Si02 and 1 wt.%
Ti02. X-ray diffraction analysis revealed periclase and spinel as major
phases.
[0086] Example 2
[0087] A mass of calcined metal oxides (100 grams), by-produced during
the pyrohydrolysis of a spent aqueous acid solution containing metal chlorides
and
having the chemical composition reported in Table 2 (fraction #2) was
thoroughly
mixed with metallurgical coke (20 grams) as reductant. The mixture was then
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21
introduced into a magnesia crucible (2" by 5") prepared by slip casting
(Custom
Ceramics Inc.) and covered by a lid. The loaded crucible was introduced into a
box
furnace (Blue M, Lindberg) and maintained at 1000 C over a period of 2 hours.
Following cooling, the agglomerated mixture was ground in a pulverizer
(Retsch) to
produce a powder having a particle size < 200 mesh (<75 m). Any excess
carbonaceous material (i.e. carbon black) was removed from the ground material
by
pouring it into a separatory funnel comprising carbon tetrachloride. Following
decantation, the carbon-free material was dried in an oven kept at 80 C,
cooled and
subjected to magnetic separation using a hand magnet (Gilson). About 36 grams
of an
iron alloy powder was recovered along with about 48 grams of a slightly
yellowish
powder comprising refractory metal oxides. Chemical analysis of the iron alloy
powder
revealed the following elemental composition: 93 wt.% Fe, 3.0 wt.% V, 2.5 wt.%
Mn,
1.0 wt.% Cr and 0.5 wt.% C. Chemical analysis of the slightly yellowish powder
comprising refractory metal oxides revealed the following composition: 66 wt.%
MgO,
28 wt.% A1203, 4 wt.% CaO, 0.4 wt. % Si02 and 1.6 wt.% Ti02. X-ray diffraction
analysis revealed periclase and spinel as major phases.
100881 Example 3
100891 A mass of calcined metal oxides (100 grams), by-produced during
the pyrohydrolysis of a spent aqueous acid solution containing metal chlorides
and
having the chemical composition reported in Table 2 (fraction #1) was
introduced into
a vitreous silica tube (1" diameter) and fluidized by a stream of synthetic
smelter gas [a
mixture of 15 vol.% hydrogen and 85 vol.% carbon monoxide free of deleterious
sulfur-
bearing compounds (e.g., H2S, COS)]. The loaded tube was heated using a
vertical
furnace (Lindberg) and maintained at 1000 C over a period of 2 hours.
Following
cooling, the pellets were ground in a pulverizer (Retsch) to produce a powder
having a
particle size < 200 mesh (<75 m). The ground material was subjected to
magnetic
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22
separation using a hand magnet (Gilson). About 40 grams of an iron alloy
powder was
recovered along with about 40 grams of a white powder comprising refractory
metal
oxides. Chemical analysis of the iron alloy powder revealed the following
elemental
composition: 93.5 wt.% Fe, 2.5 wt.% V, 2.0 wt.% Mn, 1.5 wt.% Cr and 0.5 wt.%
C.
Chemical analysis of the white powder comprising refractory metal oxides
revealed the
following composition: 62 wt.% MgO, 31 wt.% A1203, 3 wt.% CaO, 2 wt. % Si02
and 1
wt.% Ti02. X-ray diffraction analysis revealed periclase and spinel as major
phases.
[0090] Example 4
[0091] A mass of calcined metal oxides (100 grams), by-produced during
the pyrohydrolysis of a spent aqueous acid solution containing metal chlorides
and
having the chemical composition reported in Table 2 (fraction #1) was
introduced into
a magnesia boat prepared by slip casting (Custom Ceramics Inc.). The loaded
magnesia
boat was introduced into a gas-tight tubular retort made of heat resistant
austenitic
stainless steel (AISI 310). The retort was heated using a horizontal tube
furnace
(Lindberg) and maintained at 900 C over a period of 2 hours while a stream of
pure
hydrogen gas was passing through it. Following cooling, the pellets were
ground in a
pulverizer (Retsch) to produce a powder having a particle size < 200 mesh (<75
gm).
The ground material was subjected to magnetic separation using a hand magnet
(Gilson). About 40 grams of an iron alloy powder was recovered along with
about 40
grams of a white powder comprising refractory metal oxides. Chemical analysis
of the
iron alloy powder revealed the following elemental composition: 94 wt.% Fe,
2.5 wt.%
V, 2.0 wt.% Mn, and 1.5 wt.% Cr. Chemical analysis of the white powder
comprising
refractory metal oxides revealed the following composition: 62 wt.% MgO, 31
wt.%
A1203, 3 wt.% CaO, 2 wt. % Si02 and 1 wt.% TiO2. X-ray diffraction analysis
revealed
periclase and spinel as major phases.
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23
[0092] Example 5
[0093] A mass of calcined metal oxides (100 grams), by-produced during
the pyrohydrolysis of a spent aqueous acid solution containing metal chlorides
and
having the chemical composition reported in Table 2 (fraction #2) was
thoroughly
mixed with bituminous coal (13 grams) as reductant and ground using a Braun
pulverizer to a particle size < 200 mesh (<75 m). The blend was then
introduced into a
magnesia crucible (2" by 5") prepared by slip casting (Custom Ceramics Inc.)
and
covered by a lid. The loaded crucible was introduced into a box furnace (Blue
M,
Lindberg) and maintained at 1000 C over a period of 2 hours. Following
cooling, the
agglomerated mixture was ground in a pulverizer (Retsch) to produce a powder
having
a particle size < 200 mesh (<75 m). Any excess carbonaceous material (i.e.
carbon
black) was removed from the ground material by pouring it into a separatory
funnel
comprising carbon tetrachloride. Following decantation, the carbon-free
material was
dried in an oven kept at 80 C, cooled and subjected to magnetic separation
using a hand
magnet (Gilson). About 36 grams of an iron alloy powder was recovered along
with
about 48 grams of a slightly yellowish powder comprising refractory metal
oxides.
Chemical analysis of the iron alloy powder revealed the following elemental
composition: 93 wt.% Fe, 3.0 wt.% V, 2.5 wt.% Mn, 1.0 wt.% Cr and 0.5 wt.% C.
Chemical analysis of the slightly yellowish powder comprising refractory metal
oxides
revealed the following composition: 66 wt.% MgO, 28 wt.% A1203, 4 wt.% CaO,
0.4
wt. % Si02 and 1.6 wt.% Ti02. X-ray diffraction analysis revealed periclase
and spinel
as major phases.
[0094] It is to be understood that the present disclosure is not limited in
its
application to the details of construction and parts as described hereinabove.
The
disclosure is capable of other embodiments and of being practiced in various
ways. It is
also understood that the phraseology or terminology used herein is for the
purpose of
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24
description and not limitation. Hence, although the present disclosure has
been
described hereinabove by way of illustrative embodiments thereof, it can be
modified,
without departing from the spirit, scope and nature of the subject disclosure
as defined
in the appended claims.
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REFERENCES
1. F. Cardarelli; Materials Handbook. A Concise Desktop Reference. Springer,
London, 2008, pp. 276-280.
2. U.S. Patent 4,078,039.
3. WO 04/104239.
4. U.S. Patent 5,830,420.
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