Note: Descriptions are shown in the official language in which they were submitted.
~Z~5S43
The instant invention relates to a process for the preparation of
titanium metal from ore comprising titanium oxides which process comprises the
steps of fluorinating the ore to convert the titanium oxides to ti~anium
fluorides and then reducing the titanium fluorides to titanium metal. Such
reduction-may be carried out by contacting the titanium fluorides as a molten
salt mixture with a molten alloy of zinc and aluminum at conditions whereby
titanium is converted into a titanium-~inc alloy and the aluminum is converted
into a fluoride of aluminum. The ore may be an ilmenite ore and the
fluorination may be carried out by contacting said ilmenite ore with a
fluosilicate salt as sodium fluosilicate.
Titanium metal has been essential to the aerospace industry since
the early fifties because it combines a high strength to weight ratio with
the ability to perform at much higher temperatures than aluminum or magnesium.
It also has growing usage in the chemical processing industries because of its
excellent resistance to chloride corrosion. Recently the world demand for
titanium has outstripped the limited production facilities causing it to be put
on allocation in the United States.
Most of the United States primary titanium is imported from Japan and
Europe. A majority of titanium is made by the "Kroll Process" which involves
magnesium reduction of titanium tetrachloride, which is in turn made from
rutile ~TiO2). Titanium metal is also made by Na reduction and electrowinning.
The product of the "Kroll Process" is a metallic sponge which is later
consolidated by a hlgh temperature arc melting process. The most important
consideration for any process making titanium is to prevent contamination with
either metallic or non-metallic impurities, because even small amounts of
oxygen or nitrogen can make the product brittle and unworkable, although
carefully controlled amounts of oxygen, nitrogen, and carbon may be added to
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strengthen titanium alloys.
United States Patent 2,550,447 teaches a process for preparing
titanium metal from titanium oxide ores such as rutile, anatase and ilmenite
which comprises reduction of the ore by aluminum followed by iodination of
the product obtained from such reduction. The iodinated product is then
reacted with potassium iodide. Finally, titanium tetraiodide is removed
from the potassium iodide and converted to titanium metal by either heat
decomposition or reduction. This process is a very expensive method for
making titanium metal.
United States Patent 2,781,261 discloses a process for converting
titanium dioxide to titanium by fluorinating titanium oxideJ neutralizing
the fluotitanic acid obtained, and reducing the neutralized fluotitanic acid
with aluminum.
Unlted States Patent 2,837,426 teaches`a process for converting ilme-
nite to an alkali metal fluotitanate by reacting ilmenite with sulfuric acid
to form the titanium sulfate, removing a portion of the iron included with
said titanium sulfate by reduction and precipitation of a reduced iron compound,
and finally converting the titanic sulfate filtrate to an insoluble fluotita-
nate by means of an ammonium and/or alkali metal fluoride solution.
United States Patent 3,857,264 teaches a process for preparing an
alkali metal chlorotitanate by digesting ilmenite in a mixture of sulfuric
and hydrochloric acid. Again, the iron present is precipitated out as ferrous
sulfate and then further recovered by the addition of HCl to precipitate a
ferrous chloride. Finally, potassium chloride is added to salt out potassium
chlorotitanate which may be reduced with a Group I metal to titanium.
United States Patent 3,012,878 teaches a process for reducing titanium
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S~3
halides to titanium me~al by use of sodium metal.
United States Patent 3,825,415 teaches a process, similar to the
process disclosed in United States Patent No.3,012,878, except that the
process is carried out in the vapor phase.
United States Patent 4,127,409 and 4,073,056 are related to the
recovery of zirconium and hafnium, respectively, by the reduction of the
corresponding potassium chlorozirconates or hafniates by means of an alloy
of aluminum and zinc.
According to the present invention, there is provided a process for
the preparation of titanium metal from an ilmenite ore comprising titanium
oxides and from about 14 to about 36%, by weight iron which comprises the
steps of:
~ a) fluorinating said ore by contacting said ore with an alkali
metal fluosilicate at a temperature of from about 600 to about 1000C to
form a fluorinated ore and thereby convert the titanium oxide to titanium
fluorides, and
(b) reducing said tltanium fluorides to titanium metal.
Thus, titanium metal is prepared from ores containing oxides of
titanium by fluorinating said ore to convert the oxides of titanium to fluorides
of titanium and then reducing said fluorides of titanium to titanium metal.In
a preferred embodiment of the-instant invention the ore is ilmenite which is a
ferric titanate, i.e.~ ilmenite contains both iron and titanium in the oxide
fo~m. The fluorination is preferably carried out by contacting the ore with a
fluosilicate salt such as an alkali metal fluosilicate, for example,
K2SiF6, Na2SiF6, etc. at a temperature from about 600C to 100~C preferably
750C to 950C. The iron and titanium are converted to fluorides which
may be leached from the fluorinated ore by an aqueous solution.
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~215543
The aqueous solution may contain a strong acid (a mineral acid) to enhance the
recovery of soluble titanium. The leaching solution may be treated to oxidize
the iron dissolved therein to the ferric state and precipitate out the
hydrolysis product thereof as ferric hydroxide. The ferric hydroxide may be
separated from the solution by filtration and filtrate utilized to recover
soluble titanium. If an aqueous acid leaching solution is used, the iron may
remain in the leaching solution after the fluorides of titanium are removed
as shown below.
If the preferred fluosilicate is utilized as the fluorinating agent
for the ore, the corresponding fluotitanate is the soluble titanium moiety.
For example when potassium fluosilicate is utilized as the fluorinating agent
a potassium fluotitanate salt will be dissolved in the leaching solution.
The leaching solution will also contain various other soluble fluorides such
as for example potassium fluoride. The solution may be evaporated and cooled
to precipitate out the fluotitanate, for example, the potassium fluotitanate.
The fluotitanate precipitate may then be filtered and dried at a
temperature of from about 110C to 150C and subsequently reduced to titanium
metal. The most preferred method of reduction comprises contacting the
fluotitanate as a molten salt with a molten zinc-aluminum alloy at a
temperature of from 650 to 1000C in an inert atmosphere. The titanium
present in the fluotitanate salt will be converted into a titanium-zinc alloy
by contacting with the aluminum-zinc alloy under such conditions and the
aluminum will be converted into corresponding aluminum halide, for example,
aluminum fluoride. The aluminum halide will dissolve in the molten salt phase
and may form a salt similar to cryolite i.e. a pseudocryolite such as mixtures
of Na3AlF6, Na5~13F~and AlF3. The molten z m c-titanium alloy is separated
from the molten salt mixture and passed through a distillation zone wherein
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the zinc is sublimed from the titanium under an inert atmosphere. The
titanium may be recovered in the form of a sponge.
The fluotitanate may alternatively be converted to titanium oxide
by contacting the recrystallized salt with an aqueous basic solution to
hydrolyze the titanium to the titanium tetrahydroxide. The titanium
tetrahydroxide may then be precipitated from the solution in the form of
titanium oxide including two waters of crystallization. The hydrolysis of
said fluotitanate salt may be effected in a solution having a pH of at least
about 5.0, and preferably from at least about 5.5, at a temperature of at
least about 20C.
llmenite which is an ore comprising titanium and iron oxides in
admlxture is available from various locations such as southern Georgia,
northern Florida, and California. The ore will typically comprise from 25 to
50% by weight, titanium and from 8 to 36% by weight, iron. A suitable ilmenite
ore may be ground to a finely divided physical state to make it more
susceptible to fluorination. For example, the ore may be ground to a particle
size of from 30 to 400 mesh and preferably from 100 to 400 mesh. The ore may
be fluorinated by fluorination agents known in the art such as F2, HF, SiF4,
-NH4F, NH2HF2, etc. However, in a most preferred embodiment of the instant
invention, the fluorinating agent will be a Eluosilicate salt. This material
is especially suitable because the more active fluorinating agents tend to
attack the various equipment suitable for carrying out the fluorinatihg process.
The fluosilicate salt is a solid at the suitable fluorinating
temperatures and therefore such fluorination may occur as a solid state
reaction between the ore and the fluosilicate. Typical fluosilicates include
potassium and sodium salts. Sodium fluosilicates, for examplel may be blended
with the ore at a weight ratio of from 0.5 to 5.0 and preferably from 1.0 to
- 5 -
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2.5 to effect adequate fluorination. Other titanium-containing ores such
as rutile and anatase, i.e., titanium oxides may also be utilized in this
process, however, ilmenite is preferred and therefore utilized herein for
description of the invention.
The fluorination will be carried out at conditions which are sufficient
to convert both the titanium and the iron in the ore into the respective
fluorlde derivatives; that~isj fluorides-of titanium and iron, respectively.
Por example, if sodium fluosilicate is utilized as a fluorinating agent, the
mixture of the fluosilicate and the ore will be heated to a temperature of
at least 600C preferably from 750 to 950C for a time sufficient to change
the iron and titanium from oxides to the fluorides. At higher te~peratures
the reactant mass may fuse and become difficult to remove from the reaction
chamber; at lower ternperatures the reaction does not progress at a suitable
rate.
It has been unexpectedly found that the presence of iron acts to
enhance the fluorination reaction of the fluosilicates noted above, and
as will be further elucidated below an increased recovery of soluble titanium
is thus obtained. The ilmenite ores which are low in iron content may
benefit from the addition of additional iron, for example, in the form of
ferric oxide. Other titanium ores such as rutile and anatase, which are
subsequently iron-free, have been found to be benefited greatly by the
addition of iron. Furthermore, it is found that the ilmenite ores having at
least from 14 to 36% iron are very easily flL~orinated by the above
fluosilicates and may not require additional ferric oxide. For the purpose
of this specification, the term "substantially iron free" shall mean less
than about 14~, by weight, iron.
It has been found that the addition of carbon in conjunction with
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either the iron present in the ilmenite ore or iron, e.g. ferric oxide,
which is added to the lower iron-containing ilmenites, or rutile or anatase
has a synergistic effect on the subsequent recovery of titanium. For example
from 1 to 10, and preferably from 1.2 to 4 weight % carbon may be admixed
with the above iron-con-taining-titanium ore to enhance the recovery of titanium.
It has been found that when using the preferred alkali fluosilicates
as fluorinating agents the fluorination reaction is benefited by being carried
out under an atmosphere of a gaseous fluorinating agent such as silicon
tetrafluoride. It is believed that the silicon tetrafluoride may be the
active fluorinating agent obtained from the fluosilicate and thus acts to
initiate and enhance the fluorination reaction of the ilmenite ore. Typically,
the fluorination reaction may be carried out under a partial pressure of from
.1 to 5 psig, preferably at least about 1 to about 70 psig, e.g. 30 psig of
silicon tetrafluoride. The upper pressure limit will be dictated by the
economics of carrying out high pressure reactions.
The fluorinated ore may be cooled and then ground prior to the
recovery of the soluble titanium by leaching the ground mixture of the
fluorinated ore and the residue of the fluorinating agent by contacting under
agitation with the leaching solution. The iron which is present in the ore in
the form of ferrous fluoride may be removed from the fluorinated ore by
oxidation and hydrolysis of the oxidation product. For example, during
leaching, the ground fluorinated ore may be heated in the presence o~ air to
a temperature of from 50 to 95C in order to oxidize the ferrous fluoride to
the ferric state. However, oxidation may take place during leaching as
noted or can be carried out prior to leaching. Preferably, oxidation and
leaching are carried out simultaneously so that the leaching solution assists
by hydrolyzing the oxidized iron to an insolùble ferric hydroxide.
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Leaching of the fluorinated ore may be carried out in an aqueous
solution which may beneficially contain a strong acid such as hydrochloric
or sulfuric acid. The pH of said leaching solution is preferably at least
about 0.1, preferably from about 2.0 to about 5Ø When an aqueous acid
leaching solution is utilized, the above described removal of iron may be
eliminated and the iron can remain in soiution after the separation of the
fluorides of titanium as described below.
The leaching may take place at a temperature of at least 25C,
preferably from 60 to 95C. The leaching is carried out for a time sufficient
to recover as much of the soluble fluorides of titanium as economically
possible. ~Typically, leaching is carried out for about 1 to 3 hours with the
ratio of leaching solution to the fluorinated ore varying from 15:1 to 5:1,
e.g., 10:1 on a volume to weight basis.
It has baen found that the recovery of the fluorides of titanium is
enhanced by leaching with an aqueous hydrogen fluoride solution. While there
is no theoretical reason for this improvement, it has been found that the
solutions of from 1 to 10%, by weight, HF, extract the soluble fluorides
of titanium, at a faster rate than the other leaching solutions including hydro-
chloric and sulfuric acid solutions. For example, the hydrogen fluoride
solutions may extract up to 100% of the titanium originally present in the ore
while corresponding solutions of HCl and sulfuric acid may obtain only 70% of
such titanium over the same ~ime period. Higher concentrations of HF are
operable, but are more corrosive and require difficult handling procedures.
The leaching solution may be filtered to remove oxidized iron as the
ferric hydroxide. The filtrate will comprise soluble fluorides of titanium,
for example in the preferred embodiment K2TiF6 or Na2TiF6. In addition, various
other soluble fluorides may be present in the filtrate such as fluoride salt of
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~2~5S43
the corresponding alkaline fluosilicate, such as sodium fluoride or potassium
fluoride. It has been surprisingly found that it is easy to separate the
fluorides of titanium from certain other soluble fluorides since solubility
characteristics are such that the fluorides of titanium precipitate as the
temperature of the solution is lowered while other fluorides such as sodium
fluoride are more soluble in lower temperature solutions. Thus, the solution
may be evaporated to concentrate soluble fluorides and then the temperature
decreased until the fluorides of titanium crystallize. The crystals of the
fluorides of titanium may be separated and dried at a temperature of from 50
to 150C to remove excess water.
If desirable, the fluorides of titanium may be crystallized from an
acidic iron containing solution substantially without contamination thereof.
The dried crystals of the fluorides of titanium may be reduced in a
reducing zone wherein they are preferably contacted, in a molten state, with
a molten zinc-aluminum alloy. The alloy may comprise from 1:99 to 20:80 parts
of Al to Zn. The molten salt and the alloy are mutually immiscible, and
therefore agitation must be provided in such reducing zone to assure intimate
contact. The reduciion will take place at a temperature of at least 650C to
1000C preferably from 700C to 900C. The time of contacting of said molten
alloy and molten salt will be varied to assure that the titanium present in
~he salt is converted into a titanium-zinc alloy. The aluminum prasent in the
aluminum-zinc alloy during the course of the reduction is converted into the
corresponding fluoride and may be isolated, when sodium fluosilicate is used
as the fluorinating agent, as the pseudo cryolite described above. After the
agitation is ceased~ the reduced mixture separates with the molten salt rising
to the top wherein it may be decanted from such mixture. Alternatively, the
molten titanium zinc alloy may be separated from the bottom of the vessel and
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passed to the reducing zone. Reduction must take place under inert conditions
because of titanium metal's propensity to pick up oxygen and nitrogen. Suitably,
an argon atmosphere is present during the reduction step. A suitable vessel
for carrying out the aforementioned reduction, as well as any of the various
high temperature operations described herein may be graphite.
It has been found that, during the reduction step, it is necessary
that both the salt and alloy phase be maintained above the liquidous temperature
to avoid solids formation which would be abrasive to both the agitator and the
reactor.
It is desirable to have as much titanium reduced into the molten zinc
alloy as possible to minimize the amount of zinc to be distilled in the
subsequent distillation step. At atmospheric pressure, the titanium-zinc alloy
boils at approximately 915C. At that temperature only 15% titanium can be
dissolved into the zinc before solids begin forming. However, if the reactor
is placed under elevated pressure ~about 1.5 atmospheres), then the molten
zinc-alloy boils at 950C and approximately 2-5% titanium can be dissolved in
zinc before the onset of solids formation.
To allow margin of safety, the reactor may be operated at 2 atmosph-
eres which will allow a temperature of slightly over 1000C before the mixture
boils and 25% by weight of titanium can be dissolved in tha solution without
solids formation. This results in a significant reduction in the amount of
zinc to be distilled from the titanium in the subsequent step. It should be
noted that if the pressure is increased still more in the hope of further
increasing the titanium solubility two problems occur.
The first problem is the solubility does not increase rapidly with
temperatures beyond 950C and secondly, there is a substantial increase in
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contamination by carbon from the reactor wall. The degree of carbon
contamination is severe above 1100C.
Other methods of reducing the fluorides of titanium to the
metal are known in the art and although, less preferred, may be
utilized in place of the zinc-aluminum alloy. Examples of other
prior art methods of reducing the fluorides of titanium to titanium
metal ore are described above.
The argon atmosphere or other inert atmosphere may be also
utilized during the subsequent separation of the titanium from the
titanium-zinc alloy. The molten titanium-zinc alloy will be passed
to a distillation zone wherein the zinc may be distilled off at a
temperature of from about 800C to 1000C to leave behind a titanium
sponge. Alternatively the zinc may be distilled from the zinc-
titanium alloy under a vacuum and at somewhat lower temperatures.
The titanium sponge may be sintered to reduce its surface
area. After sintering and cooling the sponge is passified by
exposure to dilute 2 to give a thin (monomolecular) protective coat-
ing of titanium oxide thereon before the sponge is exposed to a non-
inert atmosphere. The zinc will be recovered and recycled for use in
subsequent reducing steps.
The invention will now be further described, by way of
example only, with reference to the accompanying drawing which is
a flow diagram illustrating a preferred process of the present
invention.
38,000 lbs. of ilmenite having a composition of 31.6%
titanium and 35% iron is ground to a particle size of 100 mesh in
grinding zone 10. The ground ilmenite is then blended with 70,735
lbs. of sodium fluosilicate in blending zone 11. The blended
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mixture is passed into calcining zone 12 wherein it is heated to
a temperature of from 750 to 850C, in the presence of one
atmosphere of SiF4, for a time of about 6 hours whereby the titanium
oxides present in the ilmenite are converted to fluorides of
titanium and the silicon fluorides present in the fluosilicate are
converted to sillcon dioxide. The titanium is converted to a pro-
duct having the general formula
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5543
Na2TiF6 in accordance with the following reaction.
Na2SiF6 + 2/3 FeO-TiO2 --~ 2/3 Na2TiF6 + 2/3FeF2 + 2/3 NaF + SiO2
This reaction also shows that the iron present in the ilmenite is
converted to ferrous fluoride. The fluorinated mixture is then ground in
grinding zone 13 and leached with an aqueous hydrofluoric acid solution
containing 2.5% by weight hydrofluoric acid at a ratio of 10 lbs. of solution/
lb reactant. The leaching is carried out under oxidizing conditions, for
example, air may be contacted with the mixture during leaching to assist in
oxidizing the ferrous ions present in the leaching solution to ferric ions
which precipitate from the leaching solution to a pH of about 7. The solution
may be ~djusted to that pH if necessary by addition of a suitable base, e.g.
NaOH etc. During the leaching the silicon dioxide reaction product of the
fluorination will also be precipitated. The separation of the iron and silicon
dioxide are evident from the following equations which describ~ the leaching
step.
FeF2 + H20 + 1/2 02----~1/2 Fe203 ~ + 2HF
Na2TiF6 + 2/3 NaF + SiO ~ Na2TiF6 (solution) + 2/3 Naf + SiO2 ~
The ferric oxide and insoluble SiO2 is removed from said grinding and
leaching zone and may be dried and recovered as a mixture of silicon dioxide
and ferric oxide in zone 14. The solution after filtration of the ferric oxide
is ~assed to a crystallizing and drying zone 15 wherein about 740,000 lbs. of
water i5 removed by heat and/or vacuum and the dewatered solution is~ cool~ed to
a temperature of about 4C to crystallize sodium fluotitanate. The crystallized
fluotitanate is filtered and may then be passed into a reducing zone 16 wherein
46,906 lbs. of fluotitanate is contacted under an inert atmosphere at a
temperature of about 805C with 45,688 lbs. of a 10/90, by weight, molten alloy
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of aluminum and zinc. The fluotitanate is added, with agitation to the molten
alloy over a 2 hour time period, whereby the molten salt and molten alloy
solution are intimately contacted, i.e. by forming a dispersion of the molten
salt and the molten alloy. The reaction is instantaneous, thereore7 after
such 2 hour period of addition the titanium has been converted to a zinc
titanium alloy and the aluminum has been converted to an aluminum fluoride.
The titanium-zinc alloy is removed from the bottom of reducing zone 16 and
passed into distillation zone 17 wherein zinc is distilled off at a temperature
of at least 800C and at a vacuum of about 10-5 torr. The distilled zinc is
recycled back to reduction zone 16 for subsequent reuse. Titanium metal is
recovered from distillation zone 17 as a sponge 18. The molten salt mixture
which is a mixture of sodium and aluminum fluoride, i.e. a pseudo cryolite,
is recovered from the top of reduction zone 16 and sent to recovery zone ~19).
Alternatively, the recrystallized sodium fluotitanate from zone 15
may be passed into a precipitation-filtration zone 20 wherein the solution is
contacted with an aqueous sodium hydroxide solution to convert the soluble
titanium to the titanium oxide form. The titanium oxide precipitates from the
solution and is recovered in zone 21. Approximately 334 lbs. of NaOH per pound
of soluble titanium is required to precipitate the titanium dioxide. The
filtrate from zone 20 containing soluble fluorides is contacted with calcium
oxide in precipitation-filtration zone 22 to precipitate calcium fluoride~
which may be recovered at zone 23. The sodium fluoride-containing solution
from zone 22 may be passed into zone 24 wherein it may be contacted with a
23% solution of ~l2SiF6 to precipitate sodium fluosilicate which after drying
in zone 25, may be recycled to zone 11 for further fluorination use.
The following are working examples illustrating the instant
invention. There is no intention that the claims of this invention be bound
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to such working examples.
General Procedure for Fluorinating Ore ComRrising Titanium
Oxide and Recovering the Rësulting Fluorides o~ Titanium
Ilmenite ore concentrates of about 100 mesh particle size are blended
with sodium fluosilicate salt ~and in certain examples powdered iron oxide and/
or carbon3 to form a homogeneous mixture. The proportions of the ingredients
consist of 102 parts of ore, 244 parts of sodium fluosilicate, l54 parts of
ferric oxide and 12 parts carbon). The mixture is compacted into pellets or
briquets one inch in diameter by about one inch thick, and then heated in a
furnace to temperatures ranging from 650C to 850C. The specific temperature
is maintained for an extended time interval usually from one to six hours.
The material after cooling is removed from the furnace and ground to about 60
mesh particle size. The ground material is leached with water ~hich may
contain approximately 0.6 to 1.3 moles of a mineral acid preferably hydrochloric
or hydrofluoric acid at 96C for two hours. The volume of the leaching
solution employed is approximately ten times the weight of the ground material.
After separation of solids the solution is heated until two-thirds of its
volume is evaporated. When cooled to room temperature a crop of white crystals
of sodium fluotitanate is obtained, separated and then dried at 110-120C in a
conventional oven.
The following examples lists the specific parameters for reaction of
ilmenite ore and sodium fluosilicate and improvements derived by use of iron
oxide and carbon for recovery of titanium from the ore.
EXAMPLE 1
102 parts of ilmenite ore concentrates with a nominal particle size
of -100 mesh + 200 mesh and containing 46.9 weight percent titanium and
14.5 wt. % Fe were mixed with 244.5 parts of sodium fluosllicate salt and
formed into briquets or pellets. The briquets were heated in a furnace to
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750C for six hours. After cooling the briquets were removed from the furnace
and ground to about 60 mesh particle size. The ground mass is leached with
a 5 volume percent mineral acid solution, preferably hydrochloric or
hydrofluoric acid at 96C for ~wo hours. The volume of acid solution was
approximately ten times the weight of solid material employed. After
separation of the ore gangue the solution contains the soluble titanium
salts. 47.5 wt. % of the titanium contained in the ore concentrates was
extracted.
EXAMPLE 2
102 parts of ilmenite ore concentrates with a nominal particle
size of -100 + 200 mesh containing 46.9 wt. % titaniwn and 14.5 wt.% iron
were mixed with 244.5 parts of sodium fluosilicate salt and 12 parts of
carbon powder. The admixture formed into briquets or pellets were heated
(calcined) in a furnace to 750C for six hours. After cooling the briquets
were crushed and ground to pass a 60 mesh sieve. The ground material was
leached with a 5 volume percent mineral acid at 95C for two hours. After
separation of the insoluble gangue material the~solution containing the soluble
titanium salts indicated that 85.9% of the titanium in the ore had been
extracted. This represented an increase of 38.4% of extractable titanium due
to use of carbon in the calcining step.
EXAMPLE 3
102 parts of ore concentrates with a nominal particle size of -100
200 mech containing 46.9 wt.% titanium and 14.5 wt.% iron were mixed with
244.5 parts of sodium fluosilicate, 12 parts of carbon powder, and 54 parts of
ferric oxide powder. The admixture formed into briquets or pellets and heated
(calcined) in a furnace to 750C for 6 hours. After cooling the briquets were
crushed and ground to pass a 60 mesh sieve and then leached at 96C with 5
volume percent mineral acid ~HF) solution for two hours. The solution after
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separation of the insoluble gan~ue materials contained soluble fluotitanate
salts indicative of 89.2% of the titanium present in the ore. Hence the
addition of iron oxide prior to calcining the admixture resulted in an
additional improvement of extractable titanium of 3.3 wt. % over calcining
the admixture which contained carbon.
EXAMPLE 4
Comparable improvements of extractable titanium were obtained by
calcining the ore utilized above at temperatures of 850C as opposed to
calcining at 650C and 750C. These results are shown in the following Table 1:
Table 1
Calcine Admixture
Parts Calcine
Percent
--- Temp Time Extractable
Test No Ore Na SiF Carbon Fe O C` Hrs. Ti
- 2 - 6 -2-3
TOC-13 102 214.5 -- -- 650 6.0 17.1
TOC-14 102 244.5 12.0 -- 650 6.0 42.7
TOC-20 102 244.5 12.0 54 650 6.0 58.9
TOC-5 102 244.5 -- -- 750 6.0 47.5
TOC-10 102 244.5 12.0 -- 750 6.0 85.9
TOC-18 102 244.5 12.0 54 750 6.0 89.2
TOC-7 102 244.5 -- -- 850 6.0 68.4
TOC-ll 102 244.5 12.0 -- 850 6.0 89.6
TOC-l9 102 244.5 12.0 54 850 6.0 98.4
These results clearly show that the addition of carbon and/or iron to
ilmenite prior to fluorination results in a greater recovery of titanium. Note
the ore utilized above has b~en defined as a substantially "iron free" ilmenite
(less than about 14% by weight iron~ for the purposes of this specification.
However, in ilmenites comprising greater than 14%, by weight iron, carbon
without the addition of additional iron, should provide adequate recovery of
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L5543
titanium after fluorination.
EXAMPLE 5
One hundred parts of ilmenite ore containing 26.4 wt.% titanium and
36 wt.% iron were mixed with 244.5 parts of sodium fluosilicate and the
admixture formed into briquets or pellets. The briquets were heated to 750C
for six hours in a furnace. After cooling the briquets were crushed and
ground to pass a 60 mesh sieve and then leached with an aqueous solution of 5
volume percent mineral acid (HCl) at 96C for two hours. The volume of acid
solution employed was ten times the weight of ground calcine. After separation
of the insoluble ore gangue the amount of soluble titanium salts in the
solution was indicative of 92.3 wt.% of the titanium in the ore. This compares
to extractable titanium of 47.5% when ore containing only 14.5 wt.% iron had
been employed, thus demonstrating the unexpected improvement found in adding
iron to substantially iron-free ilmenite ores prior to fluorinating.
- EXAMPLE 6
One hundred parts of ilmenite ore containing 26.4 wt.% titanium and
36.4 wt.% iron were admixed with 244.5 parts of sodium fluosilicate salt and
12 parts of carbon powder and formed into briquets. The briquets were
calcined in a furnace at 750C for six hours. After cooling the briquets were
cooled, pulverized and leached with a ten fold volume of 5 volume percent
mineral acid at 96C for two hours. A~ter separation of the insoluble gangue
material the quantity of soluble titanium in solution represented 98.7% of the
titanium in the ore. The use of carbon in the calcine admixture resulted in
improving the extractable titanium by about 6.4% over 92.3 wt. % when no
carbon was used. The following Table 2 of test results shbw that carbon
improved recovery of titanium from ores containing high iron contents, i.e.,
the ore described in Example 6.
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TABLE 2
Calcine
Temp. Time
Test No. Ore Na SiF Carbon -C hrs. Ti~ Recovery %
~ 2---6
TOC-21 100 244.5 -- 750 6.0 92.3
TOC-44 100 244.5 12.0 750 6.0 98,7
TOC-24 100 244.5 12.0 650 6.0 42.7
TOC-23 100 244.5 -- 850 6.0 98.5
EXAMPLE 7
Reduction of the Recovered Sodiumfluotitanates and
- Recovery of Titanium
188 parts of sodium fluotitanate salts as obtained as previously
indicated is placed in a graphite crucible along with a zinc~aluminum alloy
consisting of 29 parts aluminum and 995 parts of zinc metal. [This represents
a molar ratio of 4 to 3 aluminum to titanium in accordance with the reaction
~see below)].
3 Na2TiF6 + 4 Al--~3 Ti ~ 3(Na24/AlF6)
pseudo cryolite
The crucible and contents are placed in an appropriate furnace
and the furnace sealed. A purge of argon gas is used to remove air from
furnace and provide an inert~gas at atmosphere. The mixture is heated to
about 500G then a graphite stirrer is inserted~into the molten mixture.
Heating is continued along with stirring of the mixture until the temperature
reaches about 620C. The temperature is ma m tained at 620C for about one
hour to ensure complete reaction of the sodium fluotitanate and aluminum metal.
The furnace is turned off and allowed to cool to room temperature and the
fused reaction mass removed. The salt portion at the top and the bottom melt
portion containing elemental titanium are separated. The titanium metal
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containing alloy is then placed in a zinc distillation unit and the zinc
distilled off at 910C, in the presence of argon, to leave a residue of
titanium metal.
The following Table 3 shows the conversion of titanium from the
salt, Na2TiF6, to the zinc-titanium metal.
TABLE 3
Parts Temp. Time
Test No. Na TiF Al Zinc C Hrs. Conversion %
-2 - 6 - - -
TRX-l 188 29 995 620 1.O 100
EXAMPLE 8
Reduction of Fluotitanate under Pressure
A 78 lb.charge,of zinc, 16.5 lbs.aluminum, and 100 lbs.of sodium
fluotitanate are placed in a graphite reactor maintained under 2 atmospheres
of argon pressure. The reactor is then heated to 960C and all ingredients
are allowed to melt. A graphite agitator is then lowered into the melt
rotated sufficiently rapidly to disperse the salt phase into-the molten alloy
phase for 30 minutes. After stirring the metal, the agitator is raised and
salt and alloy are poured separately into the cast iron molds still under 2
atmospheres argon pressure. The yield is a metal casting of 78 lbs.of zinc,
21 lbs.titanium and 0.005 lb. aluminum. The salt phase contains 2 lbs. titanium,
16.5 lbs. aluminum, 22 lbs. sodium and 55 lbs. fluorine.
The salt product from the reaction can be further processed with
additional aluminum zinc alloy to remove the residual titanium and yield a
salt suitable as an ingredient in aluminum electrowinning cells.
The alloy is processed by either vacuum distillation or distilled
with a carrier gas to remove zinc and to sinter the titanium into a titanium
sponge product.
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EXAMPLE 9
`COMPOSITION OF VARIOUS-ILMENITES
_
GeorgiaCalifornia Canadian
Element wt.% ~t.% wt.%
Ti 46.9 41.8 26.4
Fe 14.5 18.6 36
Si 4.7 6.0 1.7
Zr 2.9 1.4 Nil
Al 1.2 1.3 1.2
Mg 0.29 0.48 3.8
~u 1.3 2.5 0.19
V 0.13 0.13 0.036
Fe/Ti 0.31 0.44 1.36
The results obtained from the various ores, when fluorinated in
accordance with the above General Procedures, a~ter leaching wi~h dilute HF
~5 volume percent), are given in Table 5 below:
TABLE 5
Titanium % Recovery
Ore 650C 750C 800C 850C 950C
Georgia -- 50 -- 83 95
California 41 82 90 90 --
Canada 33 100 -- -- --
The results again demonstrate the importance of iron for the
fluorination reaction. The high iron-containing ore (Canada) shows substantially
100% recovery of titanium at 750C, whlle the lower iron-containing ores only
approach 100% recovery at a temperature of at least 900C.
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EXAMPLE 10
Improving the Purity of Sodium Fluotitanate
To make an acceptably pure titanium metal, the starting materials
must be correspondingly free of impurities, particularly phosphorus, iron and
silicon. Of these three elements, the most difficult one to control when
separating the preferred sodium fluotitanate is the silicon. The reason for
this is that one of the products of the reaction is SiO2 which can redissolve
in acid solution containing fluoride ion as follows:
SiO2 + 2NaF + 4HF -~ Na2SiF6 + 2H20
Since the Na2SiF6 has limited solubility it will drop out with the
titanium salt Na2TiF6 during crystallization. This is shown in Table 6
below, which gives the silicon and iron content of 5 crystallization
experiments.
TABLE 6
COMPOSITION OP SALTS OF lST CRYSTALLIZATION
ACID LEACHATE
wt.% XRD
Sample No. Ti Fe Si ~ Ti Salt wt.%
TOC-5-2AX 4.72 0.01 31.0Na2TiF6 20.5
TOC-7 22.1 0.02 2.32 6 95.9
TOC-21-2AX22.3 1.76 1.82Na2TiF6 96.8
TOC-23-2AX 23.3 4.22 1.91 Na2TiF6 - 87.4
Na2TiF14
TOC-34-2AX 21.1 1.44 8.08 Na2TiF6 91.6
To determine whether or not it is possible to separate the
silicofluorides from the titanofluorides a composite was made of the above
.
crystals and redissolved in water. Crystallizations made from these solutions
give the results shown in Table 7 below. Obviously, there has been
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considerable improvement in purity especially relative to silicon.
TABLE 7
COMPOSITION OF RECRYSTALLIZED SODIU~I FLUOTITANATE
Ti Fe Si Na2TiF6
Starting Composition 18.7 1.44 8.90 78.44
2nd Crystallization 21.2 0.04 2.4 92.0
3rd Crystallization 22.2 0.04 5.4 94.4
Recrystallization from
Mother Liquor 22.1 0.2 0.6 95.9
22.9 0.6 0.3 99.4
EXAMPLE 11
Effect of SiF4 Gas Pressure on Recovery by Water Leach
_ from llmenite Ores __
100 parts of ilmenite ore containing 26.4 percent titanium and 36
percent iron ground to pass a 100 mesh sieve were mixed with 244.5 parts of
sodium fluosilicate salts and then formed into compact briquets or pellets.
The pellets were heated in a closed evacuated furnace to a temperature of
750C for six hours. The pEessure of the furnace increased to a maximum of
28 inches of mercury total pressure durlng calcination. After cooling the
briquets were removedJ crushed and ground to pass a 60 mesh sieve and then
leached three successive times at 95C for several hours with 10 fold weight of
water. The quantity of titanium extracted by the water leaches represented
52.2% of the titanium present in the ore.
100 parts of ilmenite ore approximately 100 mesh particle size
containing 26.4 percent titanium and 36 percent iron were mixed with 244.5
parts of sodium ~luosilicate salts and formed into compacts of briquets or
pellets. The briquets were heated`in a closed, evacuated furnace to a
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temperature of 750C. Silicon tetrafluoride gas was then admitted to the
furnace wltil a pressure of 90 min. of Hg ~approximately 30 psig) was attained.
The briquets were maintained at 750C and under 30 psig SiF4 pressure for
six hours. After cooling and removal of the residual silicon tetrafluoride
gas the briquets were crushed and ground to pass a 60 mesh sieve. The
ground material was leached 3 successive times with 10 fold weights of water
at 95C for two hour periods each. The amount of titanium extracted by the
water leaches, representing 61.2 percent of the titanium present in the ore.
The increase in silicon tetrafluoride gas pressure was responsible for a
nine percent increase in titanium recovery.
TABLE 8
Parts SiF4 %
- --- Temp. TimePressure Titanium
Test No. Ore _ 2siF6 C hrs.mm Hg. Extracted
TOC-21 100 24405 750 6.0 28 52.2
TOC-34 100 244.5 750 6.0 90 61.2
EXAMPLE 12
Preparation of Rutile TiO by Hydrolysis of
Sodium Fluotitanate ~2olution
. . .
104 parts sodium fluotitanate salts dissolved in 2 liters of water
were added slowly to a one liter solution of sodium hydroxide containing 160
gallons NaOH to 95C over a period of one hour. The resulting solids were
separated from the solution and washed with additional water to remove
residual sodium fluoride salts. The solids after drying in a conventional
oven at 110 to 120C were repulped in one liter of a 5 volume percent
hydrochloric acid solution at 90C. for one-half hour. The solids were
separated by filtration, washed with 200 ml. of water, then dried in an oven
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at llQC for several hours.
Analysis of the solids showed the solids to be titanium dioxide
of the rutile crystal modification and containing less than 0.2 percent
sodium or fluorine.
TABLE 8
Parts Temp.Time C
Test No. Na2 ~ NaOH H20 C hrs.Dried
THX-l 104 160 4000 95 1.0100 - 120
Repulped with:
Parts 5 HCl Solution: 1000 for 1/2 hour.
Dried at 110 - 120C for 2 hours.
TABLE 9
Composition of Solids
Weight %
Ti Na F X-ray Diffraction
53.0 0.12 <0.1 Rutile modification TiO2
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