U.S. patent application number 10/575224 was filed with the patent office on 2007-06-14 for method for producing ti or ti alloy through reduction by ca.
This patent application is currently assigned to SUMITOMO TITANIUM CORPORATION. Invention is credited to Masahiko Hori, Tadashi Ogasawara, Kazuo Takemura, Toru Uenishi, Yuko Urasaki, Makoto Yamaguchi.
Application Number | 20070131057 10/575224 |
Document ID | / |
Family ID | 34437599 |
Filed Date | 2007-06-14 |
United States Patent
Application |
20070131057 |
Kind Code |
A1 |
Ogasawara; Tadashi ; et
al. |
June 14, 2007 |
Method for producing ti or ti alloy through reduction by ca
Abstract
A method for producing Ti or Ti alloys through reduction by Ca,
including: a reduction step of holding a molten salt, containing
CaCl.sub.2 and having Ca dissolved therein, in a reactor vessel 1,
and reacting a metallic chloride containing TiCl.sub.4 with Ca in
said salt to generate particles of Ti or Ti alloys in said salt;
and a separation step of separating particles of Ti or Ti alloys,
generated in said salt, from said salt. An electrolysis step 8, in
which CaCl.sub.2 discharged outside the reactor vessel 1 is
electrolyzed into Ca and Cl.sub.2, and the generated Ca is used for
the generation reaction of Ti or Ti alloys in the reactor vessel 1,
is preferably added. In the electrolysis step 8, an alloy electrode
made of a molten Ca alloy, if applied for a cathode, is effective
in enhancing the electricity efficiency, and also can be
effectively utilized as a carrier medium of Ca for raising a Ca
concentration of molten salt. By this method, high-purity Ti metals
can be efficiently and economically produced.
Inventors: |
Ogasawara; Tadashi; (Hyogo,
JP) ; Yamaguchi; Makoto; (Hyogo, JP) ; Hori;
Masahiko; (Hyogo, JP) ; Uenishi; Toru; (Hyogo,
JP) ; Urasaki; Yuko; (Hyogo, JP) ; Takemura;
Kazuo; (Amagasaki-shi, JP) |
Correspondence
Address: |
CLARK & BRODY
1090 VERMONT AVENUE, NW
SUITE 250
WASHINGTON
DC
20005
US
|
Assignee: |
SUMITOMO TITANIUM
CORPORATION
1, Higashihama-cho, Amagasaki-shi,
Hyogo
JP
660-8533
|
Family ID: |
34437599 |
Appl. No.: |
10/575224 |
Filed: |
October 6, 2004 |
PCT Filed: |
October 6, 2004 |
PCT NO: |
PCT/JP04/14734 |
371 Date: |
April 7, 2006 |
Current U.S.
Class: |
75/368 ;
75/372 |
Current CPC
Class: |
C25C 3/02 20130101; C22B
34/1272 20130101; C25C 3/28 20130101; C22B 34/1295 20130101 |
Class at
Publication: |
075/368 ;
075/372 |
International
Class: |
B22F 9/24 20060101
B22F009/24 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 10, 2003 |
JP |
2003-352661 |
Feb 20, 2004 |
JP |
2004-044552 |
Mar 16, 2004 |
JP |
2004-074445 |
Claims
1. A method for producing Ti or Ti alloys through reduction by Ca,
the method comprising: a reduction step in which a molten salt,
containing CaCl.sub.2 and having Ca dissolved therein, is held in a
reactor vessel, and a metallic chloride containing TiCl.sub.4
reacts with said Ca in the molten salt to generate Ti particles or
Ti alloy particles in said molten salt; and a separation step in
which the Ti particles or Ti alloy particles, generated in said
molten salt, is separated from said molten salt.
2. A method for producing Ti or Ti alloys through reduction by Ca
according to claim 1, wherein said molten salt containing
CaCl.sub.2 is a molten salt containing CaCl.sub.2 and NaCl.
3. A method for producing Ti or Ti alloys through reduction by Ca
according to claim 1, wherein said metallic chloride containing
TiCl.sub.4 is a mixed gas containing TiCl.sub.4 and other metallic
chloride.
4. A method for producing Ti or Ti alloys through reduction by Ca
according to claim 1, wherein, by holding a molten metal containing
Ca on a molten salt, Ca is supplied from the molten metal to the
molten salt located below.
5. A method for producing Ti or Ti alloys through reduction by Ca
according to claim 4, wherein said molten metal containing Ca is a
molten metal containing Ca and Mg.
6. A method for producing Ti or Ti alloys through reduction by Ca
according to claim 1, wherein CaCl.sub.2 being a by-product
associated with the generation of Ti or Ti alloys is discharged
outside the reactor vessel.
7. A method for producing Ti or Ti alloys through reduction by Ca
according to claim 6, including an electrolysis step of
electrolyzing CaCl.sub.2, being discharged outside the reactor
vessel, into Ca and Cl.sub.2, wherein Ca generated by the
electrolysis step is used for the generation reaction of Ti or Ti
alloys in the reactor vessel.
8. A method for producing Ti or Ti alloys through reduction by Ca,
the method comprising a combined system of a reduction step and a
circulation-type electrolysis step, wherein said reduction step
includes the steps of: holding a molten salt, containing CaCl.sub.2
and having Ca dissolved therein, in a reactor vessel; and reacting
a metallic chloride containing TiCl.sub.4 with Ca in the molten
salt to generate Ti particles or Ti alloy particles in the molten
salt, and wherein said circulation-type electrolysis is configured
that a molten salt, being used for producing said Ti or Ti alloys
and discharged from said reactor vessel, is electrolyzed to
generate and replenish Ca in said molten salt which is returned to
said reactor vessel, and wherein, in electrolyzing as above, an
alloy electrode made of a molten Ca alloy is employed for a
cathode.
9. A method for producing Ti or Ti alloys through reduction by Ca
according to claim 8, wherein, in said electrolysis step, a molten
salt within an electrolytic cell, together with the interface
between a molten Ca alloy, constituting said alloy electrode, and
said molten salt, is divided into an anode side and a counter-anode
side by installing a partition wall, and wherein a molten salt to
be supplied from said reactor vessel is introduced on said
counter-anode side.
10. A method for producing Ti or Ti alloys through reduction by Ca
according to claim 8, includes a Ti separation step in which the
generated Ti particles or Ti alloy particles are separated from a
molten salt within or outside said reactor vessel, wherein, in a
discharging step in which a molten salt being used for generating
Ti particles or Ti alloy particles is discharged outside said
reactor vessel, Ti particles or Ti alloy particles generated in a
molten salt are discharged, together with said molten salt, outside
the reactor vessel, and wherein, in said Ti separation step, said
Ti particles or Ti alloy particles are separated from a molten salt
discharged outside the reactor vessel, and wherein, in said
electrolysis step, the molten salt from which said Ti particles or
Ti alloy particles are separated and removed is electrolyzed.
11. A method for producing Ti or Ti alloys through reduction by Ca
according to claim 1, wherein, in said electrolysis step, a
metallic chloride containing TiCl.sub.4 is supplied in a molten
salt.
12. A method for producing Ti or Ti alloys through reduction by Ca,
the method comprising: a Ca generation step by electrolyzing,
wherein a molten salt containing CaCl.sub.2 is electrolyzed by
employing a molten Ca alloy as a cathode to increase a Ca content
ratio in said molten Ca alloy; a Ca replenishment step, wherein the
molten Ca alloy in which Ca has increased by the Ca generation step
gets contacted with the molten salt containing CaCl.sub.2 to have
Ca dissolved in said molten salt; and, a Ti generation step by a
reducing reaction, wherein a metallic chloride containing
TiCl.sub.4 is supplied into the molten salt in which Ca gets
dissolved in the Ca replenishment step to thereby generate Ti
particles or Ti alloy particles in the molten salt.
13. A method for producing Ti or Ti alloys through reduction by Ca
according to claim 12, further including a Ti separation step in
which Ti particles or Ti alloy particles generated in a molten salt
are separated from the molten salt.
14. A method for producing Ti or Ti alloys through reduction by Ca
according to claim 12, wherein a molten salt containing CaCl.sub.2
is held in an electrolytic cell as well as a reactor vessel, and
wherein a Ca generation step by electrolyzing proceeds within the
electrolytic cell, while transferring a molten Ca alloy from the
electrolytic cell to the reactor vessel, to undergo a Ca
replenishment step as well as a Ti generation step, and wherein the
molten Ca alloy in which Ca is consumed within the reactor vessel
returns to the electrolytic cell.
15. A method for producing Ti or Ti alloys through reduction by Ca
according to claim 14, wherein the temperature of molten salt in
said electrolytic cell is set to be lower than that of molten salt
in said reactor vessel.
16. A method for producing Ti or Ti alloys through reduction by Ca
according to claim 12, wherein, as holding a molten salt containing
CaCl.sub.2 within a reactor vessel doubling as an electrolytic
cell, an electrolysis by employing a molten Ca alloy as a cathode
is carried out, while a molten salt within the reactor vessel,
together with the interface between said molten salt and the molten
Ca alloy, is divided into an anode side and a counter-anode side by
installing a partition wall, in which a Ca generation step is
carried out on the anode side and a Ca replenishment step as well
as a Ti generation step are carried out on the counter-anode
side.
17. A method for producing Ti or Ti alloys through reduction by Ca
according to claim 7, further including a chlorination step in
which Cl.sub.2 generated in said electrolysis step is reacted with
TiO.sub.2 to thereby generate TiCl.sub.4, wherein TiCl.sub.4
generated in the chlorination step is utilized in the generation
reaction for Ti or Ti alloys within a reactor vessel.
18. A method for producing Ti or Ti alloys through reduction by Ca
according to claim 1, wherein generated Ti or Ti alloys, together
with a molten salt, is discharged outside said reactor vessel, and
wherein said Ti or Ti alloys are separated from the molten salt
outside the vessel.
19. A method for producing Ti or Ti alloys through reduction by Ca
according to claim 13, wherein a molten salt being separated from
Ti or Ti alloys in a Ti separation step is introduced to a Ca
generation step by electrolyzing and/or a Ti generation step by a
reducing reaction.
20. A method for producing Ti or Ti alloys through reduction by Ca
according to claim 13, wherein a molten salt being separated from
Ti or Ti alloys in a Ti separation step is utilized in a Ti
generation step to be reacted with a molten Ca alloy in which Ca is
consumed to increase Ca in the molten Ca alloy by unreacted Ca in
the molten salt, and then, the molten Ca alloy is used in a Ca
replenishment step.
21. A method for producing Ti or Ti alloys through reduction by Ca
according to claim 12, wherein said molten salt containing
CaCl.sub.2 is a multi-element-system molten salt which contains at
least one of NaCl, KCL, LiCl and CaF.sub.2 other than
CaCl.sub.2.
22. A method for producing Ti or Ti alloys through reduction by Ca
according to claim 12, wherein said metallic chloride containing
TiCl.sub.4 is a mixture of TiCl.sub.4 and other metallic
chloride.
23. A method for producing Ti or Ti alloys through reduction by Ca
according to claim 12, wherein Ti or Ti alloys to be generated are
particles with an average particle size of 0.5-50 .mu.m.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method for producing Ti
or Ti alloys through reduction by Ca (hereinafter, can be referred
to as "by a Ca reduction"), in which a metallic chloride containing
TiCl.sub.4 is reduced by Ca to produce Ti metals or Ti alloys.
BACKGROUND ART
[0002] The Kroll method for reducing TiCl.sub.4 by Mg is generally
used as an industrial production method of Ti metals. In the Kroll
method, Ti metal is produced through a reduction step--vacuum
separation step. In a reduction step, TiCl.sub.4 which is of a raw
material of Ti is reduced by Mg in a reactor vessel to produce the
sponge-like Ti metals. In a vacuum separation step, unreacted Mg
and MgCl.sub.2 formed as a by-product are removed from the
sponge-like Ti metals produced in the reactor vessel.
[0003] To explain the reduction step in detail, in the reduction
step, the reactor vessel is filled with the molten Mg, and
TiCl.sub.4 liquid is supplied from above the liquid surface of
molten Mg. This allows TiCl.sub.4 to be reduced by Mg in the
vicinity of the liquid surface of molten Mg to generate Ti metals
in a particulate form. The generated Ti metal sequentially moves
downward. At the same time, molten MgCl.sub.2 is generated as a
by-product in the vicinity of the liquid surface. A specific
gravity of molten MgCl.sub.2 is larger than that of molten Mg. The
molten MgCl.sub.2 which is of the by-product moves downward due to
the specific-gravity difference, and the molten Mg emerges in the
liquid surface instead. The molten Mg is continuously supplied to
the liquid surface by the specific-gravity difference substitution,
and the reaction is continued.
[0004] In the production of Ti metals by the Kroll method,
high-purity products can be produced. However, in the Kroll method,
because the products are produced in a batch manner, the production
costs are increased and the price of products becomes remarkably
expensive. One of factors of the increased production costs is the
difficulty of enhancing a feed rate of TiCl.sub.4. The following
three reasons are considered to restrict the feed rate of
TiCl.sub.4.
[0005] In order to improve the productivity in the Kroll method, it
is effective to increase the feed rate of TiCl.sub.4 which is of
the raw material of Ti, i.e., to enhance a supply amount of molten
Mg to the liquid surface per unit area and/or per unit time.
However, when the feed rate is excessively increased, the rate of
the specific-gravity difference substitution cannot keep up with
the reaction rate, so that MgCl.sub.2 remains in the liquid
surface, and TiCl.sub.4 is supplied to MgCl.sub.2, thus resulting
in decreasing the utilization efficiency of TiCl.sub.4. As a
result, the supplied raw material becomes an unreacted generated
gas (referred to as an unreacted gas) such as an unreacted
TiCl.sub.4 gas and an unreacted TiCl.sub.3 gas, and the unreacted
gas is discharged outside the reactor vessel. It is necessary to
avoid the generation of unreacted gas, because a rapid increase in
the inner pressure within the reactor vessel is associated with the
generation of unreacted gas. There is a limit of the feed rate of
TiCl.sub.4 which is of the raw material of Ti by reason of the
above.
[0006] When the feed rate of TiCl.sub.4 is enhanced, a
precipitation amount of Ti is increased in the inner surface of
reactor vessel above the liquid surface. As the reducing reaction
proceeds, the liquid surface of molten Mg rises intermittently.
Therefore, the precipitated Ti in the inner surface of the upper
portion of the reactor vessel is immersed in the molten Mg in the
later stage of the reducing reaction, which causes the effective
area of the Mg liquid surface to be decreased to thereby reduce the
reaction rate. In order to suppress the decrease of reaction rate,
it is necessary that the feed rate of TiCl.sub.4 be restricted to
prevent the Ti precipitation in the inner surface of the upper
portion of reactor vessel. Japanese Patent Application Publication
No. 8-295955 proposes a different countermeasure for suppressing
the Ti precipitation in the inner surface of the upper portion of
reactor vessel. However, the countermeasure proposed in Japanese
Patent Application Publication No. 8-295955 is not sufficient.
[0007] In the Kroll method, since the reaction is performed only in
the vicinity of the liquid surface of molten Mg liquid in the
reactor vessel, an exothermic area is narrowed. Therefore, when
TiCl.sub.4 is supplied at a high rate, cooling cannot keep up with
the supply of TiCl.sub.4 in the reaction area. This also causes the
feed rate of TiCl.sub.4 to be restricted.
[0008] Although the feed rate of TiCl.sub.4 is not directly
affected, in the Kroll method, Ti is generated in a particulate
form in the vicinity of the liquid surface of molten Mg liquid, and
Ti moves downward. However, because of wetting properties (adhesion
properties) of molten Mg, the generated Ti particles moves downward
and sinks to accumulate as sediment while aggregated, and the Ti
particles are sintered to grow in particulate size to be the
lump-like Ti at melting-temperature conditions during moving
downward, which makes it difficult to discharge the Ti particles
outside the reactor vessel. Therefore, in the Kroll method, the
continuous production is difficult to be performed, and the
improvement of productivity is blocked. This is why Ti is produced
in the batch manner as well as in the form of sponge titanium by
the Kroll method.
[0009] With reference to Ti production methods except the Kroll
method, for example, U.S. Pat. No. 2,205,854 describes that,
besides Mg, Ca can be used as the reducing agent of TiCl.sub.4.
U.S. Pat. No. 4,820,339 describes a method for producing Ti through
the reducing reaction by Ca, in which the molten salt of CaCl.sub.2
is held in the reactor vessel, the metallic Ca powder is supplied
into the molten salt from above, Ca is dissolved in the molten
salt, and a TiCl.sub.4 gas is supplied from below to react the
dissolved Ca with TiCl.sub.4 in the molten salt of CaCl.sub.2.
[0010] In the reduction by Ca, Ti metals are generated from
TiCl.sub.4 by the reaction of the following chemical formula (i),
and CaCl.sub.2 is also generated as the by-product at the same
time. Ca has a stronger affinity to Cl than Mg has, and Ca is
suitable for the reducing agent of TiCl.sub.4 in principle.
Particularly, in the method described in U.S. Pat. No. 4,820,339,
Ca is used while dissolved in the molten CaCl.sub.2. When the
reducing reaction by Ca is utilized in the molten CaCl.sub.2, like
the Kroll method, TiCl.sub.4 is supplied to the liquid surface of
reducing agent in the reactor vessel, which enlarges the reaction
area compared with the case that the reaction area is restricted in
the vicinity of liquid surface. Accordingly, since the exothermic
area is also enlarged to facilitate cooling, the feed rate of
TiCl.sub.4 which is of the raw material of Ti can be largely
enhanced, and the remarkable improvement of productivity can be
also expected. TiCl.sub.4+2Ca.fwdarw.Ti+2CaCl.sub.2 (i)
[0011] However, it is difficult for the method described in U.S.
Pat. No. 4,820,339 to be adopted as the industrial Ti production
method. It is because the metallic Ca powder is used as the
reducing agent. Namely, since the metallic Ca powder is highly
expensive, the purchase and use of metallic Ca powder leads to
increase the production costs to be higher than that of the Kroll
method in which the feed rate of TiCl.sub.4 is restricted. In
addition, highly reactive Ca is extremely difficult to handle,
which also becomes the factor of blocking the industrial
application of the method for producing Ti by the Ca reduction.
[0012] U.S. Pat. No. 2,845,386 describes the Olsen method as
another Ti production method. This method is a kind of oxide
direct-reduction method for directly reducing TiO.sub.2 by Ca.
Although the oxide direct-reduction method is highly efficient, it
is not suitable for producing high-purity Ti. The reason is that
this method entails to use expensive high-purity TiO.sub.2.
DISCLOSURE OF THE INVENTION
[0013] It is an object of the present invention to provide a method
for economically producing high-purity Ti metals or high-purity Ti
alloys with high efficiency without using an expensive reducing
agent.
[0014] In order to achieve the above object, the present inventors
consider that reducing TiCl.sub.4 by Ca is indispensable and made
an attempt to utilize Ca that dissolves in the molten salt of
CaCl.sub.2 as described in U.S. Pat. No. 4,820,339. Since Ca
dissolves in CaCl.sub.2 by about 1.5%, by utilizing the reducing
reaction that Ca reduces TiCl.sub.4 in this molten CaCl.sub.2,
there is a possibility that the feed rate of TiCl.sub.4 can be
increased to thereby enhance the production efficiency
dramatically, as afore-mentioned.
[0015] In the method for producing Ti by such a Ca reduction, Ca in
the molten salt is consumed as the reaction expressed by the above
equation (i) progresses. In replenishing the consumed amount, the
metallic Ca powder needs to be continuously supplied into the
reducing reaction vessel according to the method described in U.S.
Pat. No. 4,820,339.
[0016] The present inventors consider that Ca in the molten salt,
decreased by consumption during the reducing reaction, needs to be
economically replenished in order to industrially establish the
method for producing Ti by a Ca reduction, and came up with, as the
replenishing means, the method of utilizing Ca being produced by an
electrolysis of molten salt, as well as with the method of using
this Ca in circulation. Namely, although Ca in the molten salt
should be consumed in association with the reducing reaction, when
electrolyzing this molten salt, Ca is generated in the molten salt.
So by reusing Ca thus obtained for the reducing reaction, it
becomes unnecessary to replenish Ca by outside source. Moreover, in
this method, there is no need to strictly take out Ca only, which
should be one factor to enhance the economic efficiency. If Ca
should be independently extracted as a solid matter, a lot of
difficulties are accompanied, while merely generating Ca in the
molten salt is relatively easy to be done.
[0017] The present invention is completed based on such conception
and pertains to a method for producing Ti or Ti alloys by a Ca
reduction as described in the following (1), (2) or (3).
[0018] (1) A method for producing Ti or Ti alloys by a Ca
reduction, includes: a reduction step in which a molten salt,
containing CaCl.sub.2 and having Ca dissolved therein, is held in a
reactor vessel, and a metallic chloride containing TiCl.sub.4 is
reacted with Ca in the molten salt to generate Ti particles or Ti
alloy particles in the molten salt; and a separation step in which
Ti particles or Ti alloy particles, generated in the molten salt,
are separated from the molten salt (hereinafter, referred to as a
first production method).
[0019] (2) A method for producing Ti or Ti alloys by a Ca
reduction, the method comprising a combined process of a reduction
step and a circulation-type electrolysis step, wherein said
reduction step includes the steps of holding a molten salt,
containing CaCl.sub.2 and having Ca dissolved therein, in a reactor
vessel; and, reacting a metallic chloride containing TiCl.sub.4
with Ca in the molten salt to generate Ti particles or Ti alloy
particles in the molten salt, and wherein said circulation-type
electrolysis is configured such that the molten salt, being used
for producing said Ti or Ti alloys and discharged outside said
reactor vessel, is electrolyzed to generate and replenish Ca in
said molten salt which is returned to said reactor vessel, and
wherein, in electrolyzing as above, an alloy electrode made of
molten Ca alloy is employed for a cathode (hereinafter, referred to
as a second production method).
[0020] (3) A method for producing Ti or Ti alloys by a Ca
reduction, includes the steps of: generating Ca by an electrolysis
in which a molten salt containing CaCl.sub.2 is electrolyzed by
employing a molten Ca alloy as a cathode to increase a Ca content
ratio in said molten Ca alloy; replenishing Ca by dissolving Ca in
relevant molten salt in which the molten Ca alloy, having Ca
increased by the Ca generation step, get contacted with the molten
salt containing CaCl.sub.2; and, generating Ti by a reducing
reaction such that a metallic chloride containing TiCl.sub.4 is
supplied into the molten salt having the dissolved Ca by the Ca
replenishing step to thereby generate Ti or Ti alloys in the molten
salt (hereinafter, referred to as a third production method).
[0021] A first production method as above is the method including:
a reduction step in which Ti particles or Ti alloy particles are
generated in the molten salt; and, a separation step in which Ti
particles or Ti alloy particles thus generated are separated from
the molten salt, but can adopt the embodiment mode, as described
hereinbelow, such that CaCl.sub.2 generated as a by-product in
association with the generation of Ti or Ti alloys is discharged
outside the reactor vessel to be electrolyzed for generating Ca
that is to be utilized in the generation reaction (namely, the
reducing reaction of TiCl.sub.4) of Ti or Ti alloys. A second
production method has a feature in respect of using an alloy
electrode made of molten Ca alloy for a cathode. Besides, in these
methods i.e., a first and a second production method, in order to
use Ca in circulation, the molten CaCl.sub.2 salt with the enhanced
Ca concentration is circulated between the reducing step and the
electrolysis step.
[0022] Also, a third production method appears to be similar to a
second production method in respect of using an alloy Ca alloy
electrode in the electrolysis step, but has a feature of making use
of molten Ca alloy with the increased Ca content ratio as a carrier
medium for transferring Ca, in using Ca circularly.
[0023] The method for producing Ti or the Ti alloys by a Ca
reduction is named the "OYIK method" after initials of four persons
of Ogasawara, Yamaguchi, Ichihasi, and Kanazawa who deeply engages
in conception, development, and completion.
[0024] In a first through a third production method, as Ti
particles are generated by the Ca reduction in the molten salt
containing CaCl.sub.2, the region where the reducing reaction takes
place expands and simultaneously the exothermic region is also
enlarged. Further, the vapor pressure of Mg at 850.degree. C. is
6.7 kPa (50 mmHg), whereas the vapor pressure of Ca is as extremely
small as 0.3 kPa (2 mmHg). By this difference in the vapor
pressure, Ti precipitated on the inner surface at the upper portion
of reactor vessel, when Ca is used, is much less than that when Mg
is used. Consequently, in a first through a third production
method, it becomes possible to greatly increase the feed rate of
TiCl.sub.4.
[0025] Further, Ca is inferior in wetting properties (adhesion
properties) to Mg, and the Ca adhering to precipitated Ti particles
is dissolved in CaCl.sub.2, so that the aggregation of particles
becomes less in the generated titanium particles and sintering is
significantly lessened. Therefore, generated Ti can be discharged
outside the reactor vessel in a particle state, and the Ti
production can continuously be operated.
[0026] In a first through a third production method, a metallic
chloride containing TiCl.sub.4 (hereinafter, may referred to as
TiCl.sub.4 simply) reacts with Ca dissolved in the molten salt
containing CaCl.sub.2 (hereinafter, may be referred to as a molten
salt or molten CaCl.sub.2 simply). Further, in a first production
method, it is not prohibited to hold the molten Ca liquid on the
molten CaCl.sub.2 liquid surface within the reactor vessel. Rather,
by holding the molten Ca liquid on the molten CaCl.sub.2 liquid
surface, Ca can be supplied from the Ca liquid layer to the
CaCl.sub.2 liquid layer located below to thereby enable the
reaction efficiency to be raised. Also, the reducing reaction even
in the molten Ca liquid becomes possible, thus enabling the
reaction efficiency to be raised too.
[0027] In a first through a third production method, as a supply
mode of TiCl.sub.4 to the molten CaCl.sub.2 liquid, although it is
preferable for TiCl.sub.4 in a gas state to be directly supplied
into the molten CaCl.sub.2 liquid since the contact efficiency of
TiCl.sub.4 with Ca in the molten CaCl.sub.2 liquid is high, it is
also possible for TiCl.sub.4 in a liquid state or in a gas state to
be supplied on the liquid surface of molten CaCl.sub.2 liquid, or
it is also possible for TiCl.sub.4 in a liquid state or in a gas
state to be supplied on the liquid surface of molten Ca liquid or
deep into the liquid which is held on the liquid surface of molten
CaCl.sub.2 liquid.
[0028] And further, when the method for reducing TiCl.sub.4 by Ca
is applied to the supply of TiCl.sub.4, there are various
advantages compared with the Kroll method in which the reduction is
performed by Mg.
[0029] In the Kroll method in which the reduction is performed by
Mg, the TiCl.sub.4 liquid is supplied to the liquid surface of
molten Mg liquid. Conventionally it is tried that TiCl.sub.4 gas is
supplied into the molten Mg liquid in aiming the expansion of the
reaction region. However, as described above, since Mg has the
large vapor pressure, Mg vapor intrudes in a supply nozzle to react
with TiCl.sub.4, and a supply pipe is clogged. The problem of
nozzle clogging still remains even if TiCl.sub.4 gas is supplied
into the molten MgCl.sub.2 liquid. This is attributed to the fact
that the melt is agitated by bubbling of TiCl.sub.4 and sometimes
molten Mg reaches the supply nozzle, although a clogging frequency
of the supply pipe is decreased. As much as anything, even if
TiCl.sub.4 is supplied to the molten MgCl.sub.2 liquid, because Mg
is not dissolved in the melt, the Ti precipitation reaction is
unlikely to occur.
[0030] On the contrary, in the method of reducing TiCl.sub.4 by Ca,
the nozzle clogging is hardly generated when the TiCl.sub.4 gas is
supplied into the molten CaCl.sub.2 liquid. Therefore, TiCl.sub.4
gas can be supplied into the molten CaCl.sub.2 liquid, and
TiCl.sub.4 gas can also be supplied into the molten Ca liquid. That
the molten Ca has the small vapor pressure is cited as the reason
why the nozzle clogging is hardly generated.
[0031] Namely, in a first through a third production method in
which TiCl.sub.4 is reduced by Ca, it is particularly desirable
that TiCl.sub.4 be directly supplied in a gas state into the molten
salt, and this supply mode can be applied with no problem in the
actual operation. It is also possible that TiCl.sub.4 is supplied
on the liquid surface of molten salt, or it is also possible that
liquid or gaseous TiCl.sub.4 is supplied on the liquid surface or
into the liquid of the molten Ca liquid held on the molten
CaCl.sub.2 liquid. These supply modes can also be applied with no
problem in the actual operation.
[0032] In a first through a third production method, the reduction
step (Ti generation step by the reducing reaction in a third
production method as above corresponds to the reduction step) is
meant to undergo the reducing reaction by Ca dissolved in the
molten salt to generate Ti or Ti alloys in a particulate form
and/or powder form (hereinafter, may referred to as Ti particles or
Ti alloy particles) within the reactor vessel.
[0033] In handling Ti particles or Ti alloy particles generated in
the molten salt, it is also possible for these to be separated from
the molten salt in the reactor vessel. However, in this case, the
production mode becomes the batch manner. In order to improve the
productivity in the Ti production, Ti particles and the molten
CaCl.sub.2 liquid may be separated from each other outside the
reactor vessel by utilizing the Ti generated in a particulate form
to discharge the Ti particles outside the reactor vessel together
with the molten CaCl.sub.2 liquid. The Ti particles can simply be
separated from the molten CaCl.sub.2 liquid by a squeezing
operation such as a mechanical compression. In a first production
method as above, this separation step is included, and a second and
a third production method can also employ such an embodiment
mode.
[0034] CaCl.sub.2 is generated as the by-product at the same time
when Ti is generated in the molten salt. Namely, the dissolved Ca
concentration decreases, while CaCl.sub.2 increases. Therefore, it
is preferable for CaCl.sub.2 within the vessel to be discharged
toward the outside of the vessel according to the extent of the
generation of CaCl.sub.2, and particularly preferable to discharge
it at the later stage after Ca is used for generating Ti, i.e., at
the stage in which Ca dissolved in CaCl.sub.2 is consumed. In a
second production method, this discharging operation is included,
and a first production method can employ the embodiment mode to
apply this discharging operation. However, in a third production
method, the molten Ca alloy is utilized as a carrier medium for
transferring Ca as afore-mentioned, so the molten salt is not
discharged to the outside.
[0035] It is preferable that CaCl.sub.2 discharged as above is
electrolyzed into Ca and Cl.sub.2, and the Ca thus produced
replenishes the depleted Ca in the molten salt in which Ca
concentration is lowered in association with the reducing reaction.
Also, it is preferable that Ti particles or Ti alloy particles
generated in the molten salt is extracted together with the molten
salt outside the reactor vessel, and further, the remaining molten
salt after Ti particles or Ti alloy particles are separated is
similarly treated. A second production method as above comprises
this circulation-type electrolysis step, and a first production
method can be operated with the embodiment mode including this
step.
[0036] The molten salt in which the Ca concentration recovers like
this is returned to the reduction step, and by repeating this
operation over and over again, Ti or Ti alloys are produced. The
phenomenon that takes place here regarding Ca is basically an
increase or decrease only in the dissolved Ca concentration in the
molten salt in circulation process, and the operation such as
discharging Ca independently and replenishing Ca is not required.
Therefore, high-purity Ti metals or Ti alloys can be produced with
high efficiency plus economically without using an expensive
reducing agent.
[0037] Further, a third production method also comprises a Ca
generation step in which the molten salt containing CaCl.sub.2 is
electrolyzed, and a Ca replenishment step in which Ca in the molten
salt whose Ca concentration is lowered is replenished, but differs
from a first or a second production method in terms of utilizing
the molten Ca alloy as a carrier medium for Ca.
[0038] In a first through a third production method, an electric
current efficiency in an electrolysis step should affect the
economic efficiency, which influences on the success and failure of
establishing a commercially viable production technology. One of
grave causes that lower the electric current efficiency in this
electrolysis step is the presence of unreacted dissolved Ca in the
molten salt being transferred from the reduction step to the
electrolysis step.
[0039] Namely, in the reduction step, while the reducing reaction
proceeds in the molten salt within the reactor vessel, the
dissolved Ca, i.e., a reducing agent, in the molten salt is
consumed, but not necessarily consumed entirely, so that it cannot
be avoided for the unreacted dissolved Ca to be retained more or
less in the molten salt being transferred from the reduction step
to the electrolysis step.
[0040] In the electrolysis step, the reactions expressed by
chemical formulas (ii) and (iii) proceed, Ca is generated at a
cathode and Cl.sub.2 gas is generated at an anode. The prevention
of Ca generated at the cathode from moving to the anode can be
achieved by using a separating membrane etc., for instance.
However, when the dissolved Ca is retained in the molten salt
transferred to the electrolysis step, it is difficult to remove Ca
from the neighborhood of the anode, so that, due to the back
reaction in which the above Ca reacts with the released Cl.sub.2 to
turn back to CaCl.sub.2, the electric current efficiency during
electrolyzing is lowered. 2Cl.sup.-.fwdarw.2e.sup.-+Cl.sub.2
(anode) (ii) Ca.sup.2++2e.sup.-.fwdarw.Ca (cathode) (iii)
[0041] Although it is necessary in the reduction step that Ca
exists in the molten salt, on the contrary, in the electrolysis
step of replenishing Ca, the existence of Ca provides harm.
[0042] In a second production method, an alloy electrode made of
molten Ca alloy (hereinafter, referred to as the molten Ca alloy
electrode, or the alloy electrode simply) is employed for the
cathode in the electrolysis step. By this, it becomes possible to
rigorously preclude the adverse effect by the unreacted dissolved
Ca in the molten salt transferred to the electrolysis step. In this
case, it is preferable that the molten salt within the electrolytic
cell, together with the interface between the molten Ca alloy
constituting the above alloy electrode and the molten salt is
divided into an anode side and a counter-anode side by installing a
partition wall to thereby introduce the molten salt being supplied
from the reactor vessel into the above counter-anode side.
[0043] Like this, when the molten salt on the anode side is
electrolyzed while supposing that the dissolved Ca is essentially
not contained, not only Cl.sub.2 gas emerges on the surface of the
anode but also Ca is generated at the interface between the molten
Ca alloy constituting the cathode and the molten salt on the anode
side, and the generated Ca is absorbed by the above molten Ca alloy
electrode. The molten salt on the anode side usually does not
contain the dissolved Ca, and, if any, the amount is extremely
small, so that neither the back reaction nor its accompanying
effect like the drop of the electric current efficiency takes
place.
[0044] Meanwhile, the molten salt on the counter-anode side is the
one transferred from the reduction step, which contains the
unreacted dissolved Ca though the amount is not so much. At the
interface between the alloy electrode (cathode) and the molten salt
on the counter-anode side, Ca is released from the alloy electrode
(cathode) to the molten salt on the counter-anode side. Namely,
only the anode side within the electrolytic cell becomes an
electrolysis processing region, and, on this anode side, Ca is
efficiently generated by the electrolysis of molten salt in the
state where the dissolved Ca does not exist, so that, by the
generated Ca, Ca is replenished to the molten salt on the
counter-anode side (namely, the used molten salt which being
transferred from the reduction step) via the above alloy electrode
(cathode).
[0045] Thus, while the drop of the electric current efficiency in
the electrolysis step due to that the unreacted and dissolved Ca
remains is avoided, the dissolved Ca is replenished to the molten
salt. The reason why the absorption of Ca takes place on the anode
side of alloy electrode and Ca is released on the counter-anode
side thereof is considered as below.
[0046] Ca is generated at the alloy electrode and at the interface
on the anode side of the molten salt, but, as the anode side has an
electric potential (the electric potential difference is
generated), the generated Ca metals are taken into the alloy
electrode in the cathode. Consequently, the Ca concentration in the
alloy electrode rises. Meanwhile, as there is no electric potential
at the alloy electrode and at the interface on the counter-anode
side of the molten salt, Ca is driven to dissolve in the molten
salt from the alloy electrode owing to the difference of Ca
concentration between the alloy electrode and the molten salt.
Since the Ca concentration in the molten salt on the counter-anode
side becomes low due to the reducing reaction, Ca can readily
dissolve in the molten salt. The above reason is applicable to the
molten Ca alloy electrode to be employed in a third production
method as described hereinbelow.
[0047] On the anode side, the amount of molten salt decreases as
the electrolysis proceeds. To replenish it, it can be done by
either way: the molten salt that does not contain the dissolved Ca
is newly replenished; or part of the molten salt transferred from
the reduction step is circularly used. In the event that part of
the molten salt transferred from the reduction step is used only,
the amount of dissolved Ca to be brought in as the mixture is
limitedly small, so that the back reaction can be controlled so as
not to pose any harm.
[0048] As regards the Ca alloy constituting a molten Ca alloy
electrode, Mg--Ca alloy, Al--Ca alloy, Zn--Ca alloy and the like
are preferable. It is because the melting point of these Ca alloys
is relatively low such that it is 500.degree. C. or above in case
of Mg--Ca alloy, 600.degree. C. or above in case of Al--Ca alloy,
and 420.degree. C. or above in case of Zn--Ca alloy respectively.
In order to ensure such a low melting point, it is preferable for
the Ca concentration in Mg--Ca alloy to be 45% or less, more
preferably 15% or less. In case of Al --Ca alloy, it is preferable
to be 20% or less. Also, in case of Zn--Ca alloy, it is preferable
to be 40% or less, more preferably 20% or less. Meanwhile, the
lower limit of Ca concentration is preferably set to 0.5%. The
reason is that the more the difference between the Ca concentration
of molten salt on the counter-anode and the Ca concentration of
molten Ca alloy is, the faster the dissolving rate of Ca into the
molten salt becomes.
[0049] It is not impossible to use Pb--Ca alloy or Sn--Ca alloy,
but either one has a drawback that the melting point is too
low.
[0050] By the way, the usage of molten alloy electrode as a cathode
for the electrolysis of CaCl.sub.2, is described in the
specification of U.S. Pat. No. 4,992,096. However, the electrolysis
of CaCl.sub.2 in it is applied for producing Fe/Nd by a Ca
reduction, and moreover, the circulation of CaCl.sub.2 is not
applied, thus the above two aspects distinguish over the usage of
molten alloy electrode in a first through a third production
method.
[0051] In a first or a second production method as above, as the
means for the replenishment of Ca in the molten salt that is
consumed in the reducing reaction, the molten salt whose Ca
concentration is raised by the electrolysis of molten salt is
circularly used. However, this method entails circulating a large
amount of molten salt between the reactor vessel and the
electrolytic cell, thereby requiring a large scale of
equipment.
[0052] Eventually, in a third production method, the molten Ca
alloy electrode is used for a cathode in the electrolysis step, and
is utilized as a carrier medium for transferring Ca. Namely, in a
second production method, the generated Ca on the side of cathode
gets dissolved in the molten Ca alloy constituting the electrode
and this Ca elutes off from the above molten Ca alloy to the used
molten salt, that is introduced from the reactor vessel, to thereby
raise the Ca concentration of molten salt, which is circularly
operated to end up in using Ca in circulation. By contrast, in a
third production method, the molten Ca alloy with the increased Ca
content ratio is transferred to the reactor vessel to get contacted
with the molten salt containing CaCl.sub.2, and Ca gets dissolved
into this molten salt, thus enabling Ca to be used circularly.
[0053] In a third production method as above, the electrolytic cell
is necessary for proceeding the Ca generation step by the
electrolysis (namely, to carry out the operation of the Ca
generation step), and the reactor vessel is necessary for
proceeding the Ti generation step by the reducing reaction. But the
electrolytic cell and the reactor vessel can be one cell (or
vessel) to be used in share.
[0054] In case the electrolytic cell and the reactor vessel are
independently provided, for example, the molten salt containing
CaCl.sub.2 is held in the electrolytic cell and in the reactor
vessel, wherein the operation of Ca generation step by the
electrolysis in the electrolytic cell is proceeded and, in
parallel, the molten Ca alloy is transferred from the electrolytic
cell to the reactor vessel to thereby proceed the Ca replenishment
step along with the Ti generation step within the reactor vessel
and transfer the molten Ca alloy salt whose Ca is consumed within
the cell to the electrolytic cell reversely.
[0055] In this case, it is possible to give the temperature
difference of molten salt between in the electrolytic cell and in
the reactor vessel. In this regard, there is a merit as below. For
example, it is the case that the temperature of molten salt in the
electrolytic cell is set lower than that in the reactor vessel.
Namely, it comes as a combination of a high-temperature reduction
and a low-temperature electrolysis. In this respect, owing to the
high-temperature reduction, the Ca reactivity rises to enhance the
efficiency of generating Ti or Ti alloys, and, owing to the
low-temperature electrolysis, the Ca solubility in the molten salt
is reduced, thus resulting in promoting the transfer of Ca from the
molten salt to the molten Ca alloy.
[0056] In case the electrolytic cell and the reactor vessel becomes
one cell (or vessel) to be used in share, for example, the molten
salt containing CaCl.sub.2 is held in the reactor vessel that
serves as the electrolytic cell also, and the molten salt within
the reactor vessel, together with the interface between this molten
salt and the molten Ca alloy that constitutes the cathode is
divided into an anode side and a counter-anode side by
incorporating a partition wall, and thus, electrolyzing is
proceeded. In the vicinity of the anode, Cl.sub.2 gas is generated,
and Ca is generated at the cathode (the molten Ca alloy) or in the
neighboring region to the cathode, that is divided by the partition
wall and disposed toward the anode side (Ca generation step). The
generated Ca is taken in the molten Ca alloy. Meanwhile, on the
counter-anode side, the replenishment step that Ca elutes off from
the molten Ca alloy to the molten salt proceeds.
[0057] In this case, although the operation to incorporate the
temperature difference of molten salt between in the electrolytic
cell and in the reactor vessel becomes difficult, the structure of
the cell (or vessel) becomes simple, and neither the facility nor
the costs for transporting the molten salt are needed.
[0058] As regards handling of Ti particles or Ti alloy particles
generated in the molten salt, as afore-mentioned, a third
production method also can adopt an embodiment mode that includes
the Ti separation step in which the generated Ti or Ti alloys is
separated from the molten salt.
[0059] As regards handling of the molten salt that is separated
from Ti or Ti alloys, it is rational and economical to introduce it
to the Ca generation step by the electrolysis and/or to the Ti
generation step by the reducing reaction.
[0060] Also, it can be arranged such that the molten salt separated
from Ti or Ti alloys in the Ti separation step gets reacted with
the molten Ca alloy whose Ca is consumed in the Ti generation step
to increase Ca in the molten Ca alloy by the unreacted Ca in the
molten salt and then this molten Ca alloy can be used in the Ca
replenishment step. By doing so, Ca can be replenished into the
molten Ca alloy without relying on the electrolysis.
[0061] And, by subjecting it to react with the molten Ca alloy
whose Ca is consumed as above, the unreacted Ca can be removed from
the molten salt that is separated from Ti or Ti alloys. Owing to
this, when the molten salt separated from Ti or Ti alloys is
introduced into the Ca generation step by the electrolysis, the
back reaction can be prevented, which proves to be
advantageous.
[0062] It is better for this replenishment of Ca without relying on
the electrolysis to be proceeded at the low temperature. In case of
the low temperature operation, the Ca solubility in the molten salt
decreases, the removal efficiency of the unreacted is enhanced, and
also, the transfer of Ca into the molten Ca alloy is promoted, so
that Ca in the molten Ca alloy readily gets increased.
[0063] In a first through a third production method, although
CaCl.sub.2 with the melting point of 780.degree. C. as the molten
salt is used, a mixed molten salt with NaCl, KCl or CaF.sub.2 can
be used also. If the mixed molten salt should be used, the melting
point decreases to enable the temperature of molten salt to be
lowered, thus increasing the durability of the vessel material to
extend the service life thereof and suppressing the vaporization of
Ca and salt from the liquid surface. For example, if it were the
mixed salt with NaCl, the melting point of molten salt can be
lowered down to about 500.degree. C.
[0064] The merit for the vessel material by lowering the
temperature of molten salt can be appreciated in all steps
including the reduction step and the electrolysis step. In
addition, in the electrolysis step, by lowering the temperature of
molten salt, the Ca solubility decreases, and the convection and
the diffusion of molten salt are also suppressed, thereby resulting
in suppressing the back reaction of Ca as described above. If the
extent of reaction in the reduction step should be regarded as
important, only the temperature of molten salt in the reduction
step can be elevated.
[0065] Further, in a first production method as above, the
embodiment mode that the molten Ca liquid can be held on the molten
salt in the reactor vessel could be employed, but in this case, it
becomes impossible to lower the temperature of molten salt to the
melting point of Ca (838.degree. C.) or less. That said, by mixing
Ca with other alkaline-earth metal or alkali metal, the melting
point thereof can be lowered. For example, by mixing Ca with Mg,
the melting point can be lowered down to 516.degree. C. What is
more, since only Ca from the mixture of Ca and Mg dissolves in the
molten salt of CaCl.sub.2 and Mg hardly does, it is possible to
proceed the reducing reaction of TiCl.sub.4 by Ca dissolved in
CaCl.sub.2 even if the molten metal of Ca with addition of Mg
should be used.
[0066] In a first through a third production method, as for the raw
material of Ti, basically TiCl.sub.4 is adopted, but by using
TiCl.sub.4 as the mixture of other metallic chloride, Ti alloys can
be produced also. Since TiCl.sub.4 and other metallic chloride are
reduced by Ca simultaneously, Ti alloy particles can be produced by
this method. Meanwhile, the metallic chloride here in can be either
gaseous state or liquid state.
[0067] Now, as regards the size of the generated Ti or Ti alloys,
the average particle diameter thereof is preferably set to 0.5-50
.mu.m. The reason is as below. Namely, after these particles are
generated in the molten salt, these particles should be discharged
from the molten salt. But, if it were not small size enough so as
to flow together with the molten salt, it becomes difficult to
discharge it. Therefore, the proper size is preferably 50 .mu.m or
less. Here, why the minimum proper size is set to 0.5 .mu.m is
that, when being lower than this, although possible to discharge
it, it becomes difficult to separate from the molten salt.
[0068] With regard to handling of CaCl.sub.2 that is discharged
outside the reactor vessel, as afore-mentioned, this is
electrolyzed into Ca and Cl.sub.2 and the generated Ca by the
electrolysis is used for the generation reaction of Ti in the
reactor vessel. Meanwhile, it is preferable that the generated
Cl.sub.2 by the electrolysis gets reacted with TiO.sub.2 to yield
TiCl.sub.4 that is to be utilized for the generation reaction of Ti
in the reactor vessel.
[0069] By configuring such a cycle, Ca which is very expensive to
buy can be repeatedly used as the reducing agent, and the costs for
generating TiCl.sub.4 can be maintained lower, thus enabling the
production costs of Ti or Ti alloys to be decreased.
[0070] Here, what should be particularly noted is that the costs
for producing Ca is lowered by requiring no strict separation of
Ca, that is generated by the electrolysis step, from CaCl.sub.2.
One of the reasons why Ca has not been utilized thus far for the
commercial production of Ti metals, is that the separation of Ca
from CaCl.sub.2 is difficult. Namely, while Mg can be produced by
electrolyzing MgCl.sub.2, Mg hardly dissolve in MgCl.sub.2, thus
enabling the generated Mg to be recovered efficiently. Also, Na can
be efficiently produced by electrolyzing NaCl in similar manner
with Mg. On the other hand, Ca can be produced by electrolyzing
CaCl.sub.2, but the generated Ca dissolves in CaCl.sub.2, thus
making it difficult to efficiently produce Ca only, which is
additionally compounded by the phenomenon that the generated Ca
turns back to CaCl.sub.2 due to the back reaction. Such being the
case, the productivity is poor, although the technique to enhance
the recovery rate of Ca by the application of cooling the electrode
in producing Ca by the electrolysis should be attempted, still
leaving the production costs of Ca to be significantly high.
[0071] In a first through a third production method, the molten
salt with the dissolved Ca is proactively utilized, so that, even
if Ca is mixed with the molten salt in the electrolysis step, it is
not an issue at all by simply taking care of the back reaction, and
there is no need to strictly separate Ca only. Namely, it is
sufficient enough that the whole molten salt with Ca, or Ca that
gets contained in the molten Ca alloy is charged from the
electrolytic cell to the reactor vessel. Thus, the production costs
of Ca by the electrolysis can be dramatically cut.
BRIEF DESCRIPTION OF THE DRAWINGS
[0072] FIG. 1 is a view explaining a configuration of an apparatus
for producing Ti metals that represents a first embodiment mode in
a first production method;
[0073] FIG. 2 is a view explaining a configuration of an apparatus
for producing Ti metals that represents a second embodiment mode in
a first production method;
[0074] FIG. 3 is a view explaining a configuration of an apparatus
for producing Ti metals that represents a third embodiment mode in
a first production method;
[0075] FIG. 4 is a view explaining a configuration of an apparatus
for producing Ti metals that represents a first embodiment mode in
a second production method;
[0076] FIG. 5 is a view explaining a configuration of an apparatus
for producing Ti metals that represents a second embodiment mode in
a second production method;
[0077] FIG. 6 is a view explaining a configuration of an apparatus
for producing Ti metals that represents a third embodiment mode in
a second production method;
[0078] FIG. 7 is a view explaining a configuration of an apparatus
for producing Ti metals that represents a first embodiment mode in
a third production method;
[0079] FIG. 8 is a view explaining a configuration of an apparatus
for producing Ti metals that represents a second embodiment mode in
a third production method; and,
[0080] FIG. 9 is a view explaining a configuration of an apparatus
for producing Ti metals that represents a third embodiment mode in
a third production method.
BEST MODE FOR CARRYING OUT THE INVENTION
[0081] Hereinbelow, each embodiment mode for a first production
method through a third production method is recited with reference
to the drawings.
1. A First Production Method
[0082] FIG. 1 is a view explaining a configuration of an apparatus
for producing Ti metals that represents a first embodiment mode in
a first production method.
[0083] In a first embodiment mode for a first production method, a
cylindrical reactor vessel 1 is employed. The reactor vessel 1 is a
closed vessel made of iron. A reducing agent supply pipe 2 for
supplying Ca which is a reducing agent is disposed at the ceiling
portion of the reactor vessel 1. The bottom portion of reactor
vessel 1 is made to have a tapered figuration with the opening
diameter that gradually getting smaller downward so as to
facilitate the discharge of the generated Ti particles, and, at the
center part of the lower end part thereof, a Ti discharge pipe 3
for discharging the generated Ti is provided.
[0084] Meanwhile, at the inside of the reactor vessel 1, a
cylindrical separating wall 4 with the embedded heat exchanger is
disposed at the position with a predetermined space off from the
inside surface of straight cylindrical vessel body. At the upper
area of reactor vessel 1, a molten salt discharge pipe 5 for
discharging sideways CaCl.sub.2 in the reactor vessel is provided,
and, at the lower area thereof, a raw material supply pipe 6 for
supplying TiCl.sub.4 that is a raw material of Ti is provided to
penetrate the separating wall 4 to reach the central part of the
plenum in the vessel.
[0085] During the operation, the molten CaCl.sub.2 liquid, as the
molten salt, where Ca dissolves is held in the reactor vessel 1.
The liquid surface thereof is set to the height level that is lower
than the upper end of the separating wall 4 but higher than the
molten salt discharge pipe 5. At the inside of separating wall 4,
the molten Ca liquid as the molten metal containing Ca is held on
the molten CaCl.sub.2 liquid surface.
[0086] Then, as being set as above, TiCl.sub.4 gas as a metallic
chloride containing TiCl.sub.4 is supplied to the molten CaCl.sub.2
at the inner side from the separating wall 4 by means of the raw
material supply pipe 6. By this, at the inner side from the
separating wall 4, TiCl.sub.4 is reduced by Ca in the molten
CaCl.sub.2 liquid to thereby generate Ti metals in a particulate
form within the molten CaCl.sub.2 liquid.
[0087] TiCl.sub.4 gas that is supplied into the molten CaCl.sub.2
liquid turns to numerous bubbles which buoy and move upward in the
molten CaCl.sub.2 liquid and promote stirring the molten CaCl.sub.2
liquid, thus enhancing the reaction efficiency.
[0088] Thus generated Ti particles in the molten CaCl.sub.2 liquid
on the inner side from the separating wall 4 within the reactor
vessel 1 moves downward in the above liquid to accumulate as
sediment at the bottom area within the vessel. The accumulated Ti
particles are discharged downward together with the molten
CaCl.sub.2 liquid through the Ti discharge pipe 3 and transferred
to a separation step 7.
[0089] The molten CaCl.sub.2 liquid in which Ca is consumed by the
reducing reaction on the inner side from the separating wall 4
within the reactor vessel 1 moves, via the lower part of separating
wall 4, upward on the outer side of separating wall 4, and gets
discharged through the molten salt discharge pipe 5. The discharged
molten CaCl.sub.2 liquid is to be transferred to an electrolysis
step 8.
[0090] On the inner side from the separating wall 4, Ca elutes in
the molten CaCl.sub.2 liquid from the molten Ca liquid held on the
liquid surface of molten CaCl.sub.2 liquid to thereby get
replenished. Along with this, on the molten CaCl.sub.2 liquid at
the inner side from the separating wall 4, Ca is replenished
through the reducing agent supply pipe 2.
[0091] The way things are, the Ti metals can be continuously
produced within the reactor vessel 1. On the inner side from the
separating wall 4, by utilizing the molten CaCl.sub.2 liquid in
which Ca dissolves, as the reducing reaction is carried out by Ca
within said molten CaCl.sub.2 liquid, the reaction region expands
to the almost all area on the inner side from the separating wall
4, thus enabling the feed rate of TiCl.sub.4 to be increased. By
reason of various aspects including the above, high-purity Ti
particles are produced with the high efficiency, being exactly what
is afore-mentioned.
[0092] Here, the separating wall 4 blocks the molten CaCl.sub.2
liquid containing Ca abundantly prior to be used in reducing
TiCl.sub.4 to mix with the molten CaCl.sub.2 liquid with few Ca
after use to thereby enhance the reaction efficiency.
[0093] Meanwhile, in the separation step 7, the Ti particles
discharged together with the molten CaCl.sub.2 liquid from the
reactor vessel 1 are separated from the molten CaCl.sub.2 liquid.
To be concrete, said Ti particles are compressed to squeeze out the
molten CaCl.sub.2 liquid. Then, Ti particles are cleaned. The
molten CaCl.sub.2 liquid that is obtained in the separation step 7
is transferred together with the molten CaCl.sub.2 liquid
discharged from the reactor vessel 1 to the electrolysis step
8.
[0094] In the electrolysis step 8, the molten CaCl.sub.2 liquid
from the reactor vessel 1 as well as the separation step 7 is
electrolyzed into Ca and Cl.sub.2 gas. Ca returns to the inside of
reactor vessel 1. Here, Ca does not need to be separated strictly
from CaCl.sub.2, and can return to the inside of reactor vessel 1
together with CaCl.sub.2 without causing any problem. It is because
CaCl.sub.2 with the dissolved Ca is used in the reactor vessel 1.
Owing to this ease in the separation operation, the production
costs of Ca by the electrolysis is lowered.
[0095] Cl.sub.2 gas generated in the electrolysis step 8 is
transferred to a chlorination step 9. Here, TiO.sub.2 is subjected
to a chlorination process to yield TiCl.sub.4. Further, by using a
carbon powder, oxygen generated as a by-product is discharged in
the form of CO.sub.2. TiCl.sub.4 thus made is introduced into the
inside of reactor vessel 1 through the raw material supply pipe 6.
The way things are, by circulating CaCl.sub.2, Ca as the reducing
agent and Cl.sub.2 gas are cycled. That is, essentially by only
supplementing TiO.sub.2 and C, Ti metals are continuously
produced.
[0096] FIG. 2 is a view explaining a configuration of an apparatus
for producing the Ti metals that represents a second embodiment
mode in a first production method. A second embodiment mode in a
first production method here differs from a first embodiment mode
with respect to that the reducing agent supply pipe 2a is provided
at the lower part of reactor vessel 1 and from its lower part, Ca
is supplied on the inner side of separating wall 4.
[0097] In this second embodiment mode, the molten Ca liquid as the
reducing agent comes up from below to float on the inner side of
separating wall 4 due to the specific gravity difference from the
molten CaCl.sub.2 liquid. In this flotation process, Ca gets
dissolved in CaCl.sub.2 to enhance the efficiency of Ca
dissolution. The molten Ca thus floated remains to lie on the
surface of molten CaCl.sub.2 liquid to get Ca dissolved in the
molten CaCl.sub.2 located below.
[0098] FIG. 3 is a view explaining a configuration of an apparatus
for producing Ti metals that represents a third embodiment mode in
a first production method;
[0099] This third embodiment mode differs in terms of the location
of the raw material supply pipe 6a. Namely, in a first embodiment
mode or in a second embodiment mode, the raw material supply pipe
6a is configured to supply TiCl.sub.4 into the central part of the
inside of vessel, while in a third embodiment mode, it is
configured to supply TiCl.sub.4 into the off-set position from the
centerline, being located on the inner side from the separating
wall 4. By applying this configuration, the convection due to the
gas lift of TiCl.sub.4 gas takes place within the molten CaCl.sub.2
liquid on the inner side of separating wall 4. Owing to this
convection in CaCl.sub.2, the dissolution of Ca into CaCl.sub.2 is
promoted to thereby enhance the dissolution efficiency.
2. A Second Production Method
[0100] FIG. 4 is a view explaining a configuration of an apparatus
for producing Ti metals that represents a first embodiment mode in
a second production method.
[0101] In the first embodiment mode in a second production method,
the reactor vessel 1 in which the reduction step is carried out and
the electrolytic cell 10 in which the electrolysis step is carried
out are employed. The reactor vessel 1 holds the Ca-rich molten
CaCl.sub.2, as the molten salt, in which comparatively abundant Ca
dissolves. The melting point of CaCl.sub.2 is about 780.degree. C.,
and this molten salt is heated to the melting point or above.
[0102] As regards the reactor vessel 1, the gaseous TiCl.sub.4 is
injected into the molten salt within the reactor vessel 1 in a
randomly-dispersed manner, and is reduced by the dissolved Ca in
the molten salt to generate Ti metals in a particulate form. The
generated Ti particles incrementally accumulate at the bottom of
reactor vessel 1 due to the specific gravity difference.
[0103] Ti particles accumulated at the bottom of reactor vessel 1
are discharged, together with the molten salt lying at the said
bottom, from the reactor vessel 1 and transferred to the separation
step 7. In the separation step 7, Ti particles that are discharged
together with the molten salt from the reactor vessel 1 are
separated from the molten salt. To be concrete, said Ti particles
are compressed to squeeze out the molten salt. Ti particles
obtained in the Ti separation step 7 are to be melted to yield Ti
ingots.
[0104] Meanwhile, the molten salt separated from Ti particles in
the Ti separation step 7 is the used molten salt where Ca is
consumed and the Ca concentration is lowered. This molten salt is
transferred from the reactor vessel 1 to the electrolytic cell
10.
[0105] In the electrolytic cell 10, the molten CaCl.sub.2 as the
molten salt is electrolyzed between an anode 11 and a cathode 12 to
generate Cl.sub.2 gas on the side of anode 11 and to generate Ca on
the side of cathode 12. Here, the cathode 12 denotes a molten Ca
alloy electrode 14, comprising: a heat resistant vessel 13 with an
open bottom part to be inserted into the molten salt in the
electrolytic cell 10; a molten Ca alloy 14 contained within the
heat resistant vessel 13; an electrode rod 15 penetrating the
ceiling part of heat resistant vessel 13 to be inserted into said
molten Ca alloy 14; and a partition wall 16 dividing the molten
salt within the electrolytic cell 10 into an anode side and a
counter-anode side.
[0106] The molten Ca alloy 14 here is represented by, for example,
Mg --Ca liquid whose specific gravity is smaller than that of the
molten salt. The partition wall 16 which is heat resistant and has
an insulation capability is provided just beneath the cathode 12,
wherein the upper end part of said wall is inserted into the molten
Ca alloy 14 and the lower end part is closely attached to the
bottom plate part of electrolytic cell 10 so as to bisect the
molten salt within the electrolytic cell 10 together with the
interface between the molten Ca alloy 14 and the molten salt
located below into the anode side and the counter-anode side.
[0107] The molten salt transferred to the electrolytic cell 10
directly from the reactor vessel 1 or via the Ti separation step 7
is introduced on the counter-anode side within the electrolytic
cell 10. The molten salt on the anode side essentially consists of
the molten CaCl.sub.2 without containing the dissolved Ca. This
molten salt on the anode side is electrolyzed between the anode 11
and the cathode 12 to generate Cl.sub.2 gas on the side of anode 11
and Ca on the side of cathode 12. The generated Ca on the side of
cathode 12 elutes into the molten Ca alloy.
[0108] Meanwhile, the molten salt on the counter-anode side is the
used molten salt which is introduced from the reactor vessel 1, and
contains unreacted and dissolved Ca, while dissolved Ca therein is
consumed. Ca elutes into this molten salt from the molten Ca alloy
14. Thus, dissolved Ca is replenished to the used molten salt which
is introduced from the reactor vessel 1, and the molten salt that
became Ca-rich is introduced to the reactor vessel 1 through the
reducing agent supply pipe 2, thus being circularly used in
generating Ti particles by the Ca reduction.
[0109] On the other hand, the Cl.sub.2 gas generated in the
vicinity of the surface of anode 11 is transferred to a
chlorination step 9. In the chlorination step 9, TiO.sub.2 is
chlorinated to yield TiCl.sub.4 as a raw material of Ti. TiCl.sub.4
thus made is introduced into the reactor vessel 1 through the raw
material supply pipe 6 to be used circularly for producing Ti
particles by the Ca reduction.
[0110] As shown as above, in a first embodiment mode in a second
production method, the molten salt (the molten CaCl.sub.2 in which
Ca dissolved) circulates among the reduction step (reactor vessel
1), the separation step 7 and the electrolysis step (electrolytic
cell 10), and by repeating the operation that the Ca consumed in
the reduction step (reactor vessel 1) is replenished in the
electrolysis step (electrolytic cell 10), the production of Ti
continues in the reduction step (reactor vessel 1). Namely, without
replenishing nor discharging the solid Ca, by simply controlling
the Ca concentration in the molten salt, high-quality Ti particles
are continuously produced by the Ca reduction.
[0111] Moreover, in the process where, to replenish Ca, the used
molten salt that contains unreacted and dissolved Ca is introduced
to the electrolysis step, the unreacted dissolved Ca is introduced
to the counter-anode side that is a non-electrolyzing region within
the electrolytic cell 10 and is kept indifferent with the
electrolysis to thereby block the back reaction by said dissolved
Ca. Therefore, the electric current efficiency in the electrolysis
step is enhanced. On the anode side that is an electrolyzing region
within the electrolytic cell 10, as electrolyzing proceeds, the
molten CaCl.sub.2 is consumed. To replenish it, the molten
CaCl.sub.2 that does not contain the dissolved Ca essentially is
supplemented from the outside source. Or, a small amount of used
molten salt is introduced on the anode side, independently from or
in combination with the above supplementing (route shown by the
broken line in FIG. 4).
[0112] By the way, the temperature of molten salt in either step is
controlled to be higher than the melting point of CaCl.sub.2 (about
780.degree. C.).
[0113] FIG. 5 is a view explaining a configuration of an apparatus
for producing Ti metals that represents a second embodiment mode in
a second production method.
[0114] In this second embodiment mode, the structure of reactor
vessel 1 is concretely defined. The reactor vessel 1 that is
employed here is a closed vessel with a cylindrical form that is
made of iron. A reducing agent supply pipe 2 for supplying Ca which
is a reducing agent is disposed at the ceiling portion of the
reactor vessel 1. The bottom portion of reactor vessel 1 is made to
have a tapered figuration with the opening diameter that gradually
getting smaller downward so as to facilitate the discharge of the
generated Ti particles, and, at the center part of the lower end
part thereof, a Ti discharge pipe 3 for discharging the generated
Ti is provided.
[0115] Meanwhile, at the inside of the reactor vessel 1, a
cylindrical separating wall 4 with the embedded heat exchanger is
disposed at the position with a predetermined space off from the
inside surface of straight cylindrical vessel body. At the upper
area of reactor vessel 1, a molten salt discharge pipe 5 for
discharging sideways CaCl.sub.2 in the reactor vessel is provided,
and, at the lower area thereof, a raw material supply pipe 6 for
supplying TiCl.sub.4 that is a raw material of Ti is provided to
penetrate the separating wall 4 to reach the central part of the
plenum in the vessel.
[0116] During the operation, the molten CaCl.sub.2 liquid, for
example as the molten salt, where Ca dissolves is held in the
reactor vessel 1. The liquid surface thereof is set to the height
level that is lower than the upper end of the separating wall 4 but
higher than the molten salt discharge pipe 5. [0108] Then, as being
set as above, TiCl.sub.4 gas as a metallic chloride containing
TiCl.sub.4 is supplied to the molten CaCl.sub.2 at the inner side
from the separating wall 4 by means of the raw material supply pipe
6. By this, at the inner side from the separating wall 4,
TiCl.sub.4 is reduced by Ca in the molten CaCl.sub.2 liquid to
thereby generate Ti metals in a particulate form within the molten
CaCl.sub.2 liquid.
[0117] TiCl.sub.4 gas that is supplied into the molten CaCl.sub.2
liquid turns to numerous bubbles which buoy and move upward in the
molten CaCl.sub.2 liquid and promote stirring the molten CaCl.sub.2
liquid, thus enhancing the reaction efficiency.
[0118] The generated Ti particles in the molten CaCl.sub.2 liquid
on the inner side from the separating wall 4 within the reactor
vessel 1 move downward in this liquid to accumulate as sediment at
the bottom area within the vessel. The accumulated Ti particles are
discharged downward together with the molten CaCl.sub.2 liquid
through the Ti discharge pipe 3 and transferred to a separation
step 7.
[0119] The molten CaCl.sub.2 liquid in which Ca is consumed by the
reducing reaction on the inner side from the separating wall 4
within the reactor vessel 1 moves, via the lower part of separating
wall 4, upward on the outer side of separating wall 4, and gets
discharged through the molten salt discharge pipe 5. The discharged
molten CaCl.sub.2 liquid is to be transferred to an electrolysis
step 8.
[0120] The way things are, the Ti metals can be continuously
produced within the reactor vessel 1. On the inner side from the
separating wall 4, by utilizing the molten CaCl.sub.2 liquid in
which Ca dissolves, as the reducing reaction is carried out by Ca
within said molten CaCl.sub.2 liquid, the reaction region expands
to the almost all area on the inner side from the separating wall
4, thus enabling the feed rate of TiCl.sub.4 to be increased. By
reason of various aspects including the above, high-purity Ti
particles are produced with the high efficiency, being exactly what
is afore-mentioned.
[0121] Here, the separating wall 4 blocks the molten CaCl.sub.2
liquid containing Ca abundantly prior to be used in reducing
TiCl.sub.4 to mix with the molten CaCl.sub.2 liquid with few Ca
after use to thereby enhance the reaction efficiency.
[0122] Meanwhile, in the separation step 7, the Ti particles
discharged together with the molten CaCl.sub.2 liquid from the
reactor vessel 1 are separated from the molten CaCl.sub.2 liquid.
To be concrete, said Ti particles are compressed to squeeze out the
molten CaCl.sub.2. Then, Ti particles are cleaned. The molten
CaCl.sub.2 liquid that is obtained in the separation step 7 is
transferred together with the molten CaCl.sub.2 liquid discharged
from the reactor vessel 1 to the electrolysis step 8.
[0123] In the electrolysis step 8, the molten CaCl.sub.2 liquid
from the reactor vessel 1 as well as the separation step 7 is
electrolyzed into Ca and Cl.sub.2 gas. Ca returns to the inside of
reactor vessel 1. Here, Ca does not need to be separated strictly
from CaCl.sub.2, and can return to the inside of reactor vessel 1
together with CaCl.sub.2 without causing any problem. It is because
CaCl.sub.2 with the dissolved Ca is used in the reactor vessel 1.
Owing to this ease in the separation operation, the production
costs of Ca by the electrolysis is lowered.
[0124] Cl.sub.2 gas generated in the electrolysis step 8 is
transferred to a chlorination step 9. Here, TiO.sub.2 is subjected
to a chlorination process to yield TiCl.sub.4. Further, by using a
carbon powder, oxygen generated as a by-product is discharged in
the form of CO.sub.2. TiCl.sub.4 thus made is introduced into the
inside of reactor vessel 1 through the raw material supply pipe 6.
The way things are, by circulating CaCl.sub.2, Ca as the reducing
agent and Cl.sub.2 gas are cycled. That is, essentially by only
supplementing TiO.sub.2 and C, Ti metals are continuously
produced.
[0125] FIG. 6 is a view explaining a configuration of an apparatus
for producing Ti metals that represents a third embodiment mode in
a second production method.
[0126] In a third embodiment mode, the position of the raw material
supply pipe 6a is different in comparison with a second embodiment
mode. Namely, in a second embodiment mode, the raw material supply
pipe 6a is configured to supply TiCl.sub.4 into the central part of
the inside of vessel, while in a third embodiment mode, it is
configured to supply TiCl.sub.4 into the off-set position from the
centerline, being located on the inner side from the separating
wall 4.
[0127] By applying this configuration, the convection due to the
gas lift of TiCl.sub.4 gas takes place within the molten CaCl.sub.2
liquid on the inner side of separating wall 4. Owing to this
convection in CaCl.sub.2, the reduction efficiency is enhanced.
[0128] In either embodiment mode, that the temperature of molten
salt can be lowered by using the mixed molten salt is as
afore-mentioned.
3. A Third Production Method
[0129] FIG. 7 is a view explaining a configuration of an apparatus
for producing Ti metals that represents a first embodiment mode in
a third production method.
[0130] In a first embodiment mode in a third production method, the
reactor vessel 1 in which the Ti generation step by the reducing
reaction is carried out and the electrolytic cell 10 in which the
Ca replenishment step by electrolyzing is carried out are employed.
The reactor vessel 1 holds the Ca-rich molten CaCl.sub.2, as the
molten salt, in which comparatively abundant Ca dissolves. The
melting point of CaCl.sub.2 is about 780.degree. C., and this
molten salt is heated to the melting point or above.
[0131] The inside cavity except the bottom part in the reactor
vessel 1 is bisected by the heat resistant partition wall 17,
wherein one is a reduction compartment 18 and the other is a Ca
replenishment compartment 19 in which the molten Ca alloy gets in
contact with the molten salt so as to make Ca in the molten Ca
alloy to dissolve in the molten salt. Both compartments are in flow
communication at the under part of reactor vessel 1 where to allow
the molten salt to freely flow back and forth.
[0132] As regards the reduction compartment 18, the gaseous
TiCl.sub.4 is injected into the molten salt within the reactor
vessel 1 in a randomly-dispersed manner, and is reduced by the
dissolved Ca in the molten salt to generate Ti metals in a
particulate form. The generated Ti particles incrementally
accumulate at the bottom of reactor vessel 1 due to the specific
gravity difference.
[0133] Ti particles accumulated at the bottom of reduction
compartment 18 are discharged, together with the molten salt lying
at the said bottom, from the reduction compartment 18 and
transferred to the Ti separation step 7. In the Ti separation step
7, Ti particles that are discharged together with the molten salt
from the reduction compartment 18 are separated from the molten
salt. To be concrete, said Ti particles are compressed to squeeze
out the molten salt. Ti particles obtained in the Ti separation
step 7 are to be melted to yield Ti ingots.
[0134] Meanwhile, the molten salt separated from Ti particles in
the Ti separation step 7 is the used molten salt where Ca is
consumed and the Ca concentration is lowered. This molten salt is
transferred to said electrolytic cell 10.
[0135] In the electrolytic cell 10, molten CaCl.sub.2 as the molten
salt is held and the electrolysis of said molten CaCl.sub.2 is
carried out by means of an anode 11 and a cathode 12. By this,
Cl.sub.2 gas is generated on the side of anode 11 and Ca is
generated on the side of cathode 12.
[0136] Here, the cathode 12 denotes a molten Ca alloy electrode, to
be concrete, comprising: a heat resistant vessel 13 having
insulation capability and an open bottom part to be inserted into
the molten salt in the electrolytic cell 10; a molten Ca alloy 14
contained within the heat resistant vessel 13; and, an electrode
rod 15 penetrating the ceiling part of heat resistant vessel 13 to
be inserted into said molten Ca alloy 14. The generated Ca on the
side of cathode 12 is taken into the molten Ca alloy 14 within the
heat resistant vessel 13 as an alloy or in the liquid state. Thus,
the Ca concentration in the molten Ca alloy 14 within the heat
resistant vessel 13 rises.
[0137] When the Ca concentration in the molten Ca alloy 14 within
the heat resistant vessel 13 reaches the predetermined
concentration (for example, 15%), this molten Ca alloy 14 with the
high Ca concentration is charged to the Ca replenishment
compartment 19 within the reactor vessel 1 from above through a
first transport pipe 20.
[0138] At this occasion, on the molten salt within the Ca
replenishment compartment 19, the molten Ca alloy 14' that was
charged previously floats. This molten Ca alloy 14' has the high Ca
concentration when charged, but, by releasing Ca toward the molten
salt located below to have it dissolved, it becomes to have a low
Ca concentration (for example, a few %). In this regard, in
parallel with the transport of molten Ca alloy having the high Ca
concentration from the heat resistant vessel 13 to the Ca
replenishment compartment 19, the used molten Ca alloy 14' with the
low Ca content that floats above the molten salt in the Ca
replenishment compartment 19 is transported to the inside of heat
resistant vessel 13 through a second transport pipe 21.
[0139] Thus, the Ca replenishment by dissolving from the molten Ca
alloy 14 to the below molten salt can be continued in the Ca
replenishment compartment 19. As a result, Ca that is consumed in
association with the generation of Ti particles in the reduction
compartment 18 can be replenished to thereby sustain said
generation reaction.
[0140] On the other hand, the Cl.sub.2 gas generated in the
vicinity of the surface of anode 11 is transferred to a
chlorination step 9. In the chlorination step 9, TiO.sub.2 and C
are chlorinated to yield TiCl.sub.4 as a raw material of Ti and to
release CO.sub.2 gas also. TiCl.sub.4 thus made is introduced into
the reactor vessel 1 through the raw material supply pipe 6 to be
used circularly for producing Ti particles by the Ca reduction.
[0141] The way things are, in a first embodiment mode in a third
production method, Ca in the molten salt is consumed by the Ca
reducing reaction in the reactor vessel 1, an then, this Ca is
generated by the electrolysis of molten salt in the electrolytic
cell 10 to be used circularly for generating Ti particles by the
reducing reaction. Moreover, there is no need to circulate the
molten salt between the reactor vessel 1 and the electrolytic cell
10 for using Ca in circulation. The molten Ca alloy 14 is used for
the cathode in the electrolytic cell 10, and by utilizing it as a
carrier medium for transferring Ca to merely reciprocate between
the reactor vessel 1 and the electrolytic cell 10, it becomes
possible to keep supplying Ca to the molten salt in the reactor
vessel 1 to sustain the Ti production.
[0142] Hence, without replenishing nor discharging the solid Ca, as
well as without circulating a huge amount of molten salt, in quite
a simple manner, high-quality Ti particles can be continuously
produced by the Ca reduction. By the way, the temperature of molten
salt in either step is controlled to be higher (for example,
800-850.degree. C.) than the melting point of CaCl.sub.2 (about
780.degree. C.).
[0143] FIG. 8 is a view explaining a configuration of an apparatus
for producing Ti metals that represents a second embodiment mode in
a third production method.
[0144] As the molten salt, a multi-element system molten salt
having the low melting point where CaCl.sub.2 is mixed with other
chloride is employed. Before introducing the molten salt, being
separated from Ti particles in the Ti separation step 7, to the
electrolytic cell 10, said molten salt is introduced to the Ca
removal cell 22. Let the melting point of molten salt be set to,
for example, 650.degree. C., the high-temperature operation such
that the temperature of molten salt is heightened to 850.degree. C.
or so is applied in the reactor vessel 1. Meanwhile, the
low-temperature operation such that the temperature of molten salt
is lowered down to 700.degree. C. or so is applied in the
electrolytic cell 10 and in the Ca removal cell 22.
[0145] By carrying out the high-temperature operation
(high-temperature reduction) in the reactor vessel 1, the
reactivity of Ca rises, thus making it possible to offset the
decrease of reactivity due to the drop of Ca content ratio in the
relevant molten salt. Meanwhile, by carrying out the
low-temperature operation in the electrolytic cell 10 and in the Ca
removal cell 22, the unreacted Ca in the molten salt to be
introduced to the electrolytic cell 10 can be eliminated
beforehand, thus suppressing the back reaction and its resultant
effect on decreasing the electric current efficiency.
[0146] Namely, the molten salt transferred from the reactor vessel
1 to the electrolytic cell 10 via the Ti separation step 7 is the
used one which still retains the unreacted dissolved Ca, while the
majority of the dissolved Ca is consumed. When the unreacted Ca
happens to be brought in to the electrolytic cell 10, it reacts
with Cl.sub.2 gas generated on the side of anode 11 to turn back to
CaCl.sub.2, i.e., the so-called back reaction takes place, where
the electrolytic current is consumed, thus lowering the electric
current efficiency.
[0147] In the Ca removal cell 22, the molten salt introduced from
the Ti separation step 7 (retains the unreacted Ca) is mixed with
part of the used molten Ca alloy 14' (designated by Mg in FIG. 8)
having the low Ca concentration and being transferred from the Ca
replenishment compartment 19 to the heat resistant vessel 13 in the
electrolytic cell 10. Hence, the unreacted Ca in the molten salt is
taken into the molten Ca alloy 14' with the low Ca concentration,
so that the unreacted Ca is removed and the molten Ca alloy 14 with
the high Ca concentration is generated.
[0148] By introducing the molten salt without the unreacted Ca to
the electrolytic cell 10 in this way, the molten salt can be
circularly used without any waste, and the back reaction,
attributable to the unreacted Ca in the molten salt, as well as the
resultant drop of electric current efficiency can be suppressed.
The molten Ca alloy 14 (designated by Mg--Ca in FIG. 8) with the
high Ca concentration, being regenerated in the Ca removal cell 22,
is introduced to the Ca replenishment compartment 19 in the reactor
vessel 1.
[0149] By carrying out the low-temperature operation in the
electrolytic cell 10, the Ca solubility in the molten salt
decreases, and also, the convection and diffusion of molten salt
are suppressed. From this aspect also, the back reaction can be
suppressed. Besides, by carrying out the low-temperature operation
in the Ca removal cell 22, the Ca solubility decreases to
precipitate Ca, and then, the precipitated Ca is absorbed by the
alloy.
[0150] As above, in a second embodiment mode in a third production
method, by incorporating the temperature difference in molten salt
between the reactor vessel 1 and the electrolytic cell 10, the
electric current efficiency in the Ca generation step by the
electrolysis can be enhanced.
[0151] FIG. 9 is a view explaining a configuration of an apparatus
for producing Ti metals that represents a third embodiment mode in
a third production method. This third embodiment mode differs from
a first embodiment mode and a second embodiment mode over the
following aspects.
[0152] The reactor vessel 1 doubles as the electrolytic cell,
comprising a reduction compartment 24 with a deep bottom and an
electrolysis compartment 24 with a shallow bottom. An anode 11 is
disposed within the electrolysis compartment 24 but on the counter
side as opposed to the reduction compartment side, whereas the heat
resistant vessel 13 constituting a cathode 12 is disposed so as to
ride over the interface between the reduction compartment 23 and
the electrolysis compartment 24. And, the molten salt in the
reactor vessel 1, together with the interface between the molten Ca
alloy 14 and the molten salt within the heat resistant vessel 13,
is divided into an anode side and a counter-anode side by a
partition wall 16 that is disposed at the interface between the
reduction compartment 23 and the electrolysis compartment 24. In
other words, the anode side corresponds to the electrolysis
compartment 24 with the shallow bottom, while the counter-anode
side corresponds to the reduction compartment 23 with the deep
bottom.
[0153] As regards the operation, on the counter-anode side within
the reactor vessel 1, i.e., in the reduction compartment 23,
TiCl.sub.4 as a raw material of Ti is introduced in the molten salt
therein to be reduced by Ca in the molten salt to thereby generate
Ti particles. Meanwhile, on the anode side, i.e., in the
electrolysis compartment 24, the electrolysis of molten salt by
means of the anode 11 and cathode 12 proceeds to generate Ca. The
generated Ca is taken in the molten Ca alloy 14 within the heat
resistant vessel 13. The Ca taken in the molten Ca alloy 14 is
released and dissolves in the molten salt on the counter-anode
side, i.e., in the reduction compartment 23 within the reactor
vessel 1. Hence, the Ca consumed in association with the generation
of Ti particles is replenished.
[0154] With regard to a feature in a third embodiment mode,
firstly, it should be noted that, since the reactor vessel doubles
as the electrolytic cell, the structure of vessel is simple.
Secondly, since there is no transport of molten Ca alloy 14 between
the electrolytic cell and the reactor vessel, the operational
efficiency rises. Moreover, the equipment for the transport between
the electrolytic cell and the reactor vessel becomes unnecessary,
so that the equipment is simplified from this aspect. However, it
is difficult to incorporate the temperature difference in the
molten salt between the reducing region and the electrolyzing
region.
[0155] By the way, although not shown in the diagram, also in a
third embodiment mode in a third production method, Ca in the
molten salt to be introduced to the electrolysis compartment 24 can
be removed beforehand like the case in a second embodiment
mode.
INDUSTRIAL APPLICABILITY
[0156] Since either method for producing Ti or Ti alloys by the Ca
reduction shown in a first through a third production method as
above is the method of reducing TiCl.sub.4, high-purity Ti metals
or Ti alloys can be produced. Ca is used as the reducing agent for
it, particularly the molten salt containing CaCl.sub.2 and having
Ca dissolved therein is held in the reactor vessel, and the
metallic chloride containing TiCl.sub.4 is reacted with Ca in the
molten salt to generate Ti particles or Ti alloy particles in the
molten CaCl.sub.2 liquid, which allows the enhancement of the feed
rate of TiCl.sub.4 which is of the raw material of Ti, and also
allows the continuous operation. Further, there is neither the need
to replenish expensive Ca metals nor the need to apply the
operation for independently handling Ca which is highly reactive
and difficult to handle.
[0157] Also, according to a second production method, in addition
to the above, the drop of electric current efficiency due to the
mixture of unreacted Ca, being of an issue in the electrolysis
step, can be effectively suppressed by employing the molten Ca
alloy electrode. Further, according to a third production method,
the molten Ca alloy electrode employed in the electrolysis step is
utilized as a carrier medium for transferring Ca, so that the
circulation of molten salt in a large scale becomes
unnecessary.
[0158] Accordingly, the method for producing Ti or Ti alloys by the
present invention can be widely applied as means for producing
high-purity Ti metals with high efficiency and economically.
* * * * *