U.S. patent application number 12/838899 was filed with the patent office on 2010-11-11 for ore reduction process and titanium oxide and iron metallization product.
This patent application is currently assigned to E. I. DU PONT DE NEMOURS AND COMPANY. Invention is credited to JOHN JAMES BARNES, Thomas Peter Battle, Mitsutaka Hino, Isao Kobayashi, Stephen Erwin Lyke, Dat Nguyen, Joseph M. Shekiro, JR., Akira Uragami.
Application Number | 20100285326 12/838899 |
Document ID | / |
Family ID | 37809563 |
Filed Date | 2010-11-11 |
United States Patent
Application |
20100285326 |
Kind Code |
A1 |
BARNES; JOHN JAMES ; et
al. |
November 11, 2010 |
ORE REDUCTION PROCESS AND TITANIUM OXIDE AND IRON METALLIZATION
PRODUCT
Abstract
The disclosure is directed to a process for producing separable
iron and titanium oxides from an ore containing titanium oxide and
ferric oxide, comprising: (a) forming agglomerates comprising
carbon-based materials and the ore, the quantity of carbon of the
agglomerates being sufficient for, at an elevated temperature,
reducing ferric oxide to ferrous oxide and forming a ferrous
oxide-rich molten slag, (b) introducing the agglomerates onto a
carbon bed of a moving hearth furnace; (c) heating the agglomerates
in the moving hearth furnace to a temperature sufficient for
reducing and melting the agglomerates to produce a ferrous
oxide-rich molten slag; (d) metallizing the ferrous oxide of the
molten slag by reaction of the ferrous oxide and the carbon of the
carbon bed at a furnace temperature sufficient for maintaining the
slag in a molten state; and (e) solidifying the slag after
metallization of the ferrous oxide to form a matrix of titanium
oxide-rich slag having a plurality of metallic iron granules
distributed there through; and (f) separating the metallic iron
granules from the slag, the slag comprising greater than 85%
titanium dioxide based on the entire weight of the matrix after
separation of the metallic iron. The disclosure is also directed to
a metallization product of a ferrous oxide-rich molten slag.
Inventors: |
BARNES; JOHN JAMES;
(Hockessin, DE) ; Lyke; Stephen Erwin;
(Wilmington, DE) ; Nguyen; Dat; (Chadds Ford,
PA) ; Hino; Mitsutaka; (Miyagi, JP) ; Uragami;
Akira; (Hyogo, JP) ; Kobayashi; Isao; (Hyogo,
JP) ; Battle; Thomas Peter; (West Chester, PA)
; Shekiro, JR.; Joseph M.; (Newark, DE) |
Correspondence
Address: |
E I DU PONT DE NEMOURS AND COMPANY;LEGAL PATENT RECORDS CENTER
BARLEY MILL PLAZA 25/1122B, 4417 LANCASTER PIKE
WILMINGTON
DE
19805
US
|
Assignee: |
E. I. DU PONT DE NEMOURS AND
COMPANY
Wilmington
DE
|
Family ID: |
37809563 |
Appl. No.: |
12/838899 |
Filed: |
July 19, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12430261 |
Apr 27, 2009 |
7780756 |
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12838899 |
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11512993 |
Aug 30, 2006 |
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12430261 |
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60712556 |
Aug 30, 2005 |
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60788173 |
Mar 31, 2006 |
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Current U.S.
Class: |
428/552 ;
75/369 |
Current CPC
Class: |
C21B 13/105 20130101;
Y02W 30/542 20150501; Y02W 30/50 20150501; Y10T 428/12056 20150115;
C21B 13/006 20130101; C21B 3/04 20130101; C21B 13/0046
20130101 |
Class at
Publication: |
428/552 ;
75/369 |
International
Class: |
B32B 15/04 20060101
B32B015/04; B22F 9/20 20060101 B22F009/20 |
Claims
1-19. (canceled)
20. A metallization product of a ferrous oxide-rich molten slag,
comprising: a matrix of a titanium oxide-rich slag having a
plurality of metallic iron granules distributed there through, the
metallic iron granules being mechanically separable from the matrix
of titanium oxide, the matrix comprising greater than 85% titanium
oxides based on the entire weight of the matrix after mechanical
separation of the mechanically separable portion of the metallic
iron.
21. The metallization product of claim 20 wherein the metallization
product is made by a process comprising: (a) providing an ore
comprising ferric oxide, ferrous oxide, and titanium oxide at
ambient temperatures; (b) mixing the ore with one or more carbon
source to form one or more agglomerates so that the ferric and the
ferrous oxides are not substantially reduced by the one or more
carbon source during this step; (c) introducing the one or more
agglomerates onto a carbon bed of a heating element; (d) heating
the one or more agglomerates on the carbon bed in the range of
about 130.degree. C. to about 180.degree. C. to reduce the ferric
oxide to ferrous oxide and to melt the one or more agglomerates to
form a ferrous oxide-rich molten slag to begin metallizing the
ferrous oxide, wherein the amount of the one or more carbon source
used in step (b) is such so that without the participation of
carbon present in the carbon bed, the carbon amount would be
insufficient for metallizing more than 50% of the ferrous and
ferric oxides in steps (d) and (e); (e) heating the one or more
agglomerates on the carbon bed to a maximum temperature of greater
than 1500 C to reach the desired extent of metallization by
reaction with the carbon bed, so that the ferrous oxide-rich molten
slag becomes a titanium oxide-rich slag that comprises large iron
droplets; (f) cooling the titanium oxide-rich slag until the
titanium oxide-rich slag solidifies to form the metallization
product.
22. The metallization product of claim 21 wherein the ore is a low
grade ore rich in titanium oxides and iron oxides.
23. The metallization product of claim 21 wherein the agglomerates
have a quantity of carbon that is less than a stoichiometric
quantity.
24. The metallization product of claim 21 wherein the ore contains
about 30 to about 50% iron oxides.
25. The metallization product of claim 21 wherein the amount of
carbon of the agglomerates ranges from about 0.5 to about 10 weight
percent, based on the entire weight of the agglomerates.
26. The metallization product of claim 21 wherein the ore is
ilmenite.
27. The metallization product of claim 21 wherein the ore is
ilmenite sand and the amount of carbon of the agglomerates ranges
from about 1.0 to about 8.0 weight percent, based on the entire
weight of the agglomerates.
28. The metallization product of claim 21 wherein the ore is
ilmenite rock.
29. The metallization product of claim 21 wherein the one or more
agglomerates formed from the mixing in step b comprise a plurality
of ore particles ranging in average particle size diameter from
about 0.1 to about 1.0 mm.
30-38. (canceled)
39. The metallization product of claim 21 wherein the furnace is a
tunnel furnace, a tube furnace or a rotary hearth furnace.
40. The metallization product of claim 21 wherein the amount of the
one or more carbon source is insufficient to reduce and metallize
more than about 20% of the ferric and ferrous oxides in step
(d).
41. The metallization product of claim 21 wherein the one or more
agglomerates of step (b) are heated to drying temperatures of about
100 to 200 C.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/712,556, filed Aug. 30, 2005 and U.S.
Provisional Application No. 60/788,173 filed Mar. 31, 2006, which
are each incorporated by reference in their entireties.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The disclosure relates to a process for the beneficiation of
titanium oxide-containing ores. More particularly the disclosure
relates to a process for reducing the ore in a moving hearth
furnace to form separable iron metal and titanium oxides. The
disclosure additionally relates to a titanium and iron
metallization product and the product of a process for the
beneficiation of titanium oxide-containing ores. More particularly
the disclosure relates to a titanium oxides and iron metallization
product made by a process for reducing the ore in a moving hearth
furnace to form separable iron metal and titanium oxides.
[0004] 2. Description of the Related Art
[0005] Moving hearth furnaces have been described for use in the
reduction of iron oxide. Iron oxide to be reduced is charged to the
rotary hearth furnace together with a source of carbon wherein the
charge is exposed to reducing conditions to form reduction products
comprising iron and slag.
[0006] In using a relatively pure iron oxide charge, reactivity of
molten iron oxide slag with the interior surfaces of the furnace
can be a concern. Consequently, that technology tends to use
amounts of carbon sufficient for solid state reduction where there
is rapid and substantially complete metallization of the iron oxide
before the formation, if any, of a molten phase. Consequently, if
and when the product of the solid state reduction is melted, there
may only be a relatively small metal oxide fraction available to
form the slag component. Additionally, since the iron metal
represents the majority of the reduction product, large and easily
recoverable iron granules form.
[0007] A carbon bed may be provided to protect the hearth from
contact with the reacting charge. Since the carbon content of the
charge is sufficient to provide rapid metallization, any minor
proportion of ferrous oxides that might remain to react with the
carbon bed would be an incidental and insignificant part of the
process.
[0008] Instead of using a rotary hearth process to reduce
substantially pure iron oxide, a rotary hearth process to reduce
low grade ores such as ilmenite which contain iron oxide, high
levels of titanium dioxide and metal oxide impurities has been
proposed for making reduction products containing metallic iron and
high grade titanium oxides such as synthetic rutile. However,
reducing a low grade ore such as ilmenite which contains high
levels of titanium dioxide and metal oxide impurities in a rotary
hearth process poses processing challenges that are not encountered
when reducing relatively pure iron oxide.
[0009] When conventional rotary hearth reduction technology is used
to recover metallic iron and titanium oxides from low grade ores
such as ilmenite, separating the small bits of iron metal which are
distributed throughout the relatively high slag content is a
problem. To solve this separation problem, a first pre-reduction
step to metallize the majority of the iron oxide followed by a
melting step, usually in an electric melter or intermediate hearth
furnace, has been described for forming more readily separable
molten iron that is relatively free of gangue and a slag that
contains a high titanium oxides content. However, this multi-step
process is a costly and energy intensive solution.
[0010] Mechanical separation of the numerous small bits of iron
metal distributed throughout the slag is impractical because the
bits of iron metal tend to be well below 50 microns in diameter.
Since 50 microns is the lowest practical size limit for separation
by sieving, most fine sieves having 400 wire per inch sieve which
is the limit for sieving 50 micron diameter particles, sieving such
numerous and small bits of iron metal is not a practical separation
process. Small bits of iron can be chemically separated but
chemical separation adds significantly to costs.
[0011] There is a need for an energy efficient rotary hearth
process for recovering easily separable metallic iron and titanium
oxides from low grade ore reduction products.
SUMMARY OF THE INVENTION
[0012] The disclosure is directed to a process for producing
separable iron and titanium oxides from an ore containing titanium
oxide and ferric oxide, typically a low grade ore rich in titanium
oxides and ferric oxide, even more typically ilmenite, comprising:
[0013] (a) forming agglomerates comprising carbon-based materials
and the ore, the quantity of carbon of the agglomerates being
sufficient for, at an elevated temperature, reducing ferric oxide
to ferrous oxide and forming a ferrous oxide-rich molten slag,
[0014] (b) introducing the agglomerates onto a carbon bed of a
moving hearth furnace; [0015] (c) heating the agglomerates in the
moving hearth furnace to a temperature sufficient for reducing and
melting the agglomerates to produce a ferrous oxide-rich molten
slag; [0016] (d) metallizing the ferrous oxide of the molten slag
by reaction of the ferrous oxide and the carbon of the carbon bed
at a furnace temperature sufficient for maintaining the slag in a
molten state; [0017] (e) solidifying the slag after metallization
of the ferrous oxide to form a matrix of titanium oxide-rich slag
having a plurality of metallic iron granules distributed there
through; and [0018] (f) separating the metallic iron granules from
the slag, the slag comprising greater than 85% titanium dioxide
based on the entire weight of the matrix after separation of the
metallic iron.
[0019] In one embodiment, the reducing and melting of the
agglomerates occurs simultaneously. Additionally, the metallizing
can be carried out under conditions sufficient for small molten
iron metal droplets formed in the molten slag to coalesce into
large molten iron metal droplets.
[0020] The disclosure is additionally directed to a metallization
product of a ferrous oxide-rich molten slag, comprising: a matrix
of a titanium oxide-rich slag having a plurality of metallic iron
granules distributed there through, the metallic iron granules
being mechanically separable from the matrix of titanium oxide, the
matrix comprising greater than 85% titanium oxides based on the
entire weight of the matrix after mechanical separation of the
mechanically separable portion of the metallic iron.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a top view of a rotary hearth furnace for the
reduction of titanium-rich ores and production of iron metal and
high grade titanium oxides.
[0022] FIG. 2 is a simplified schematic diagram of the process of
this disclosure.
[0023] FIG. 3 is an electron micrograph of 75 micron size slag
product of Example 1. Full field width is 115 microns.
[0024] FIG. 4 is a photographic image of the separated iron
granules of the product of Example 3.
[0025] FIG. 5 is an electron micrograph of less than 75 micron size
slag product after separation of iron granules of Example 3. Full
field width is 115 microns.
[0026] FIG. 6 is an optical micrograph of a metallization product
of a process similar to Example 3 before grinding.
DETAILED DESCRIPTION OF THE INVENTION
[0027] The disclosure uses a low grade ore rich in titanium oxides
and iron oxides. Titanium present in low grade ore occurs in
complex oxides, usually in combination with iron, and also
containing oxides of other metals and alkaline earth elements.
Titanium is commonly found as ilmenites, either as a sand or a hard
rock deposit. Low-grade titanium-rich ores, such as ilmenite sand
can contain from about 45 to about 65% titanium dioxide, about 30
to about 50% iron oxides and about 5 to about 10% gangue. Rock
deposits of ilmenite are reported to contain from about 45 to about
50% titanium dioxide, about 45 to about 50% iron oxides, and about
5 to about 10% gangue. The process of this disclosure can employ
such titanium-rich ores.
[0028] Agglomerates, useful as the charge to the rotary hearth
process, comprise the ore and a quantity of carbon sufficient for a
first stage melting wherein ferric oxide reduction to ferrous oxide
occurs under reducing conditions. The exact amount of carbon will
vary depending upon the iron oxide content of the ore, and
particularly upon the ferric oxide content. But, less than
stoichiometric quantities of carbon (i.e., quantities of carbon
sufficient to reduce all the iron oxides in the ore to metallic
iron) are used so that the agglomerates will melt before a second
stage metallizing wherein the majority of the ferrous oxide
reduction to iron metal occurs. A minor degree of such metallizing
may occur in the first stage and is not detrimental to the process
of this disclosure.
[0029] When the amount of carbon is referred to it means the fixed
carbon content of the material which provides a source of carbon.
Fixed carbon content is determined in the proximate analysis of
solid fuels, such as coal, by heating a sample, in the absence of
air, to 950.degree. C. to remove volatile matter (which typically
includes some carbon). The carbon that remains in the ash at
950.degree. C. is the fixed carbon content.
[0030] For a typical ore that can be used in the process of this
disclosure and containing about 30 to about 50% iron oxides, the
amount of carbon can range from about 0.5 to about 8.0 wt. %, more
typically about 1.0 to about 6.0 wt. % based on the entire weight
of the agglomerate. For ilmenite and/or sand containing ilmenite,
the amount of carbon can range from about 1.0 to about 8.0 wt. %,
more typically about 2.0 to about 6.0 wt. % based on the entire
weight of the agglomerate. For rock deposits of ilmenite, the
amount of carbon can range from about 0.5 to about 5.0 wt. %, more
typically about 1.0 to about 3.0 wt. % based on the entire weight
of the agglomerate.
[0031] Typically the amount of carbon in the agglomerates is
sufficient for reducing the ferric oxide but insufficient to
metallize more than about 50% of the ferrous oxide, more typically
insufficient to metallize more than about 20% of the ferrous oxide
based on the agglomerate.
[0032] The carbon source useful in the agglomerates can be any
carbonaceous material such as, without being limited thereto, coal,
coke, charcoal and petroleoum coke.
[0033] Agglomerates are formed by mixing the ore and the carbon
source, optionally together with a binder material, and shaping the
mixture into pellets, briquettes, extrudates or compacts which are
usually dried at temperatures ranging from about 100 to about
200.degree. C. Equipment capable of mixing and shaping the feed
components are well known to those skilled in the art. Typically
the agglomerates range in average diameter from about 2 to about 4
cm for ease of handling.
[0034] The optional binder material can be, without limitation
thereto, organic binders or inorganic binders such as bentonite or
hydrated lime. Suitable amounts of binder range from about 0.5 to
about 5 wt. %, typically about 1 to about 3 wt. % based on the
entire weight of the agglomerates. Unlike typical ore reduction
processes, the ore of the agglomerates can be used without being
ground into a fine powder. The ore may, however, be crushed and/or
screened, before being formed into agglomerates, to an average
particle size ranging from about 0.1 to about 1 mm to separate out
any large chunks which might pose handling problems. For example,
when rock deposits are used, they are usually crushed and screened
to obtain ore particles ranging in average size of about 0.1 to
about 1 mm.
[0035] The agglomerates are charged to a rotary hearth furnace
wherein they are heated to a temperature sufficient for the first
stage melting to produce a ferrous oxide-rich molten slag. In a
typical process, the agglomerates are charged through a feed chute
which deposits them onto a bed of carbonaceous material, typically
a bed of coal or coke particles. The thickness of the bed can range
from about 1 to about 5 cm.
[0036] The temperatures inside the moving hearth furnace sufficient
for the first stage melting can range from about 1300.degree. C. to
about 1800.degree. C., typically from about 1400.degree. C. to
about 1750.degree. C., and more typically from about 1500.degree.
C. to about 1700.degree. C. The particular temperature will depend
on ore composition. The period of time for this melting stage can
range from about 1 minute to about 5 minutes.
[0037] In the first stage melting, the carbon content of the
agglomerates is sufficient to reduce the ferric oxide to ferrous
oxide, but insufficient to complete any substantial metallization
and, additionally, not sufficient for the complete reduction of
ferrous oxide to iron metal.
[0038] The ferrous oxide-rich molten slag which results from the
first stage melting, contacts the carbon bed under reducing
conditions. Through this contact, the ferrous oxide is further
reduced in the second stage metallizing to produce the iron metal
product.
[0039] The temperature inside the moving hearth furnace in the
second stage metallizing is sufficiently high to keep the slag in a
molten state as the ferrous oxide metallization occurs. Suitable
temperatures inside the hearth furnace for this purpose can range
from about 1500.degree. C. to about 1800.degree. C., typically from
about 1600.degree. C. to about 1750.degree. C., and more typically
from about 1600.degree. C. to about 1700.degree. C. The particular
temperature required will vary depending upon ore composition.
[0040] On a large scale furnace, the temperature inside the furnace
in the first stage can be at least about 100.degree. C. lower than
the temperature in the second stage.
[0041] The period of time for this second stage metallizing can be
longer than that for the first stage melting and can range from
about 5 minutes to about 20 minutes. During the first stage,
reduction of ferric oxide in the presence of the carbon contained
in the agglomerates and melting occur rapidly. In contrast in the
second stage, allowing sufficient time for the ferrous oxide-rich
molten slag to flow over the carbon bed during the metallization
can enhance production of large metal particles since the iron
droplets of the molten slag will coalesce into larger droplets
which maintain their size during cooling to form solid metal
particles.
[0042] As the second stage metallization proceeds, the slag becomes
less fluid and the titanium concentration of the slag increases.
The conditions sufficient for maintaining slag fluidity can help
the iron droplets in the molten slag to coalesce which facilitates
the formation of the easily separable large particles of iron.
[0043] The slag solidifies as the metallization approaches
completion. Preferably, the metallization is carried out until at
least about 90% completion, based on the agglomerates, even more
preferably until at least about 95% completion. The iron metal
which can be in the form of large granules is readily separable
from the solid slag by cost effective processes. Mechanical
processes are ideally used for separating the iron metal. Chemical
processes such as chemical leaching are not needed. Additionally
extensive mechanical separation processes such as intensive
grinding are not needed.
[0044] Typical methods for separating the metal include crushing,
grinding, screening and magnetic separation.
[0045] Typically the iron granules of the process range in average
diameter from about 0.05 to about 10 mm, and more typically from
about 0.1 to about 5 mm. The term "granules" is used to distinguish
the large chunks of metallic iron produced by the process of this
disclosure as compared to the small particles of metallic iron
resulting from conventional processes.
[0046] Typically, the solid slag product of the process comprises
greater than about 85% titanium oxides, and more typically greater
than about 87% titanium oxides, based on the entire weight of the
solid slag product, after separation of the mechanically separable
metallic iron. The term "titanium oxides" means TiO.sub.2,
Ti.sub.3O.sub.5, and Ti.sub.2O.sub.3. The solid slag product may
also contain smaller amounts of titanium in the form of TiO, TiC
and TiN. The solid slag product may contain a minor amount of
residual metallic iron. The residual metallic iron is usually the
portion of metallic iron particles below about 50 microns in
diameter. Usually the amount of residual metallic iron is less than
about 6%, more typically less than about 4% based on the entire
weight of the solid slag product, after mechanical separation of
the mechanically separable metallic iron granules. There may be
other small amounts of impurities such as FeO, and other oxides.
The amount of these other impurities is usually less than 8% and
more typically less than 6% of the entire weight of the solid slag
product.
[0047] The moving hearth furnace can be any furnace which is
capable of exposing the agglomerates to at least two high
temperature zones on a bed of carbon. A suitable furnace can be a
tunnel furnace, a tube furnace or a rotary hearth furnace. The
process can employ a single furnace structure.
[0048] Referring to the drawings and more particularly to FIG. 1, a
rotary hearth furnace is used for reducing the charge. A furnace 10
is used having dimensions of a typical hearth furnace used in the
iron production industry. The rotary hearth furnace has a surface
30 that is rotatable from a feed material zone 12. The surface 30
can be a refractory layer surface or a vitreous hearth layer, both
of which are well known in the art of hearth furnace processing of
iron ores. The surface rotates from the feed material zone through
a plurality of burner zones 14, 16, 17, a reaction zone spanning at
least a portion of the burner zones and a discharger zone 18 that
comprises a cooling plate 48 and discharge device 28. The maximum
temperature of the furnace is typically reached in zone 17. The
first and second stages of the process of this disclosure occur in
the reaction zone. The surface 30 is rotatable in a repetitive
manner from the discharge zone 18 to the feed material zone 12 and
through the reaction zone for continuous operation. The burner
zones can each be fired by a plurality of air/fuel, oil fired, coal
fired or oxygen enriched burners 20 and 22.
[0049] The feed material zone 12 includes an opening 24 and a feed
mechanism 26 by which the agglomerates are charged to the furnace.
A layer comprising carbon is located on at least a major proportion
of the surface 30, typically the entire surface comprises a layer
comprising carbon and upon which the agglomerates are placed. The
layer comprising carbon may be placed on the surface by any
convenient means, typically by a solid material conveyor 34. The
agglomerates can be leveled to a useful height above the surface by
a leveler 29 that spans the width of the surface 30. The
agglomerates are continuously fed to the furnace by the feed
mechanism as the surface is rotated around the furnace and through
each zone. The speed of rotation is controlled by adjusting a
variable speed drive.
[0050] Referring to FIG. 2, the process is shown whereby the ore is
introduced to the mixing zone 51. The carbon can be introduced to a
size reduction zone 50 prior to introduction to the mixing zone 51
wherein the ore and the carbon together with any optional
additives, such as binders, are mixed together and formed into
agglomerates. The agglomerates are introduced to rotary hearth
furnace zone 52 wherein the ferric oxide of the agglomerates is
reduced and metallized as described herein. The hot product 42 as
shown in FIG. 1 is cooled by any convenient means such as quenching
with water. The cooled product is then screened in the screening
zone 53, then ground in grinding zone 54 to separate the iron metal
from the high grade titanium oxides product. Recycle material can
also be separated and introduced to the mixing zone 51. The iron
metal product may be formed into briquettes in briquetting zone 55
from which the iron metal product is withdrawn.
[0051] Alternately, on a smaller scale, tube furnaces of
conventional design using a high purity alumina tube as a retort
may be used. These furnaces may be heated to temperatures of about
1500.degree. C. to about 1700.degree. C., and operated under a
nitrogen or argon atmosphere.
[0052] In another embodiment of the disclosure, coal or coke
particles are added to the charge during the second phase
metallization in order to provide more reductant contact thereby
enhancing the metallization process
[0053] In yet another embodiment of the invention the undersized
slag (synthetic rutile) and iron-synthetic rutile composites are
separated from the titanium oxides product and recycled to the
process.
[0054] In one embodiment, the invention herein can be construed as
excluding any element or process step that does not materially
affect the basic and novel characteristics of the composition or
process. Additionally, the invention can be construed as excluding
any element or process step not specified herein.
[0055] Applicants specifically incorporate the entire content of
all cited references in this disclosure. Further, when an amount,
concentration, or other value or parameter is given as either a
range, preferred range, or a list of upper preferable values and
lower preferable values, this is to be understood as specifically
disclosing all ranges formed from any pair of any upper range limit
or preferred value and any lower range limit or preferred value,
regardless of whether ranges are separately disclosed. Where a
range of numerical values is recited herein, unless otherwise
stated, the range is intended to include the endpoints thereof, and
all integers and fractions within the range. It is not intended
that the scope of the invention be limited to the specific values
recited when defining a range.
EXAMPLES
[0056] The following Examples illustrate the present invention. All
parts, percentages and proportions are by weight unless otherwise
indicated. Particles sizes of less than 75 microns were determined
by analysis of electron micrograph images while larger sizes were
determined by sieving.
Example 1
[0057] In this Example the agglomerates contained too much
carbon.
[0058] Tablets were prepared by mixing and compacting together, at
ambient temperature, 79.7 percent by weight ilmenite ore (61%
TiO.sub.2, based on the total weight of the ore), and 20.3 percent
coal (71% fixed carbon, based on proximate analysis) into cylinders
20 mm in diameter and 7 mm thick. Residual water was removed from
the tablets by drying. The dried tablets were placed on a bed of
coke breeze in an alumina crucible and moved into a tube furnace
which had been heated to 1600.degree. C. under a nitrogen
atmosphere. The tube furnace is of conventional design using a high
purity alumina tube as a retort. The furnace temperature dropped on
the order of about 50.degree. C. when the tablets were initially
added. The temperature increased back to the starting temperature.
25 minutes after the tablets were added, the tablets were removed
from the furnace and allowed to cool. The tablets retained their
original shape which indicated that the tablets did not melt. Iron
metallization was found to be essentially 100%. The average
metallic iron particle size was about 15 microns. This iron could
not be readily separated from the titanium oxide-rich phase. The
size distribution of the resulting product indicated that the
separation would be difficult. Attempts to separate iron particles
of this size by grinding followed by magnetic separation were
unsuccessful because of small particle sizes. The titanium oxide
component of the resulting ground and separated product contained
too much iron while the iron component contained too much titanium
oxide.
[0059] An electron micrograph of full field width 115 microns of
the product of this Example after grinding is shown in FIG. 3
(ground product particles were mounted in resin, cut, polished and
imaged in the electron microscope such that residual iron particles
appear bright and titanium oxide-rich material appears grey). As
shown in FIG. 3, the slag matrix contained many small (less than 10
micron) particles of metallic iron which could not be effectively
removed by typical grinding and sieving separation processes.
Example 2
[0060] In this Example the temperature inside the furnace was too
low. Tablets were prepared by mixing and compacting together, at
ambient temperature, 95.5 percent by weight ilmenite ore (61%
TiO.sub.2, based on the total weight of the ore), 3 percent coal
(71% fixed carbon), and 1.5 percent wheat flour binder into
cylinders 20 mm in diameter and 7 mm thick. A small amount of
binder was needed because of the lower carbon content of the
tablets. Residual water was removed from the tablets by drying. The
dried tablets were placed on a bed of coke breeze in an alumina
crucible and moved into a tube furnace which had been heated to
1600.degree. C. under a nitrogen atmosphere. The furnace
temperature dropped on the order of about 50.degree. C. when the
tablets were initially added. The temperature gradually increased
back to the starting temperature. 25 minutes after the tablets were
added, the tablets were removed the tablets were removed from the
furnace and allowed to cool. Distortion and glassy appearance
indicated that the tablets had melted and re-solidified. Iron
metallization was found to be less than 60%. The average metallic
iron granule size was about 75 microns. While the metallized iron
could be separated, a substantial amount of un-metallized iron
remained intimately mixed with the titanium oxides.
Example 3
[0061] Tablets were prepared by mixing and compacting together, at
ambient temperature, 93.5 percent by weight ilmenite ore (61%
TiO.sub.2), 5.5 percent coal (71% fixed carbon), and 1 percent
wheat flour binder into cylinders 20 mm in diameter and 7 mm thick.
Residual water was removed from the tablets by drying. The dried
tablets were placed on a bed of coke breeze in an alumina crucible
and moved into a furnace which had been heated to 1675.degree. C.
under an argon atmosphere. The furnace temperature dropped on the
order of about 50.degree. C. when the tablets were initially added.
The temperature gradually increased back to the starting
temperature. 25 minutes after the tablets were added, the tablets
were removed and allowed to cool. Distortion and glassy appearance
indicated that the tablets had melted and re-solidified. Iron
metallization was found to be greater than 95% based on
quantitative x-ray diffraction analysis. The average metallic iron
granule size was more than 500 microns with 95% of the entire
amount of separated granules greater than 75 microns. Nearly all of
the iron could be removed from the finer, titanium oxide-rich phase
by crushing and sieving with a 200 mesh sieve. Elemental analysis
by ion-coupled plasma atomic emission spectroscopy determined that
the titanium oxide-rich phase contained 87% titanium oxide
(titanium content reported as TiO.sub.2 with sum of metal oxide
concentrations normalized to 100%). X-ray diffraction analysis
indicated that the titanium was mostly present as Ti.sub.3O.sub.5
with some Ti.sub.2O.sub.3.
[0062] FIG. 4 is a photographic image (full field width 12.5 mm) of
the iron granules which were mechanically separated from the
product made according to Example 3.
[0063] FIG. 5 is an electron micrograph (full field width 115
microns) of the less than 75 micron slag product after grinding and
removal of the iron granules by sieving (separated slag product
particles were mounted in resin, cut, polished and imaged in the
electron microscope such that residual iron particles appear bright
and titanium oxide-rich material appears grey). Comparing FIG. 5
with FIG. 3, the ground product of FIG. 3 contained a significant
content of iron metal and the iron metal particles were small,
making them difficult to separate by mechanical means. However, the
slag product shown in FIG. 5 shows few particles of iron metal
remaining within the solid slag product after separation of the
larger iron metal granules (FIG. 4) by grinding and sieving.
[0064] FIG. 6. is a polished cross section of a product of a
process similar to Example 3 before grinding. Even at the
relatively large scale of the figure, some of the iron granules are
visible.
[0065] The description of illustrative and preferred embodiments of
the present invention is not intended to limit the scope of the
invention. Various modifications, alternative constructions and
equivalents may be employed without departing from the true spirit
and scope of the appended claims.
* * * * *