U.S. patent application number 11/665976 was filed with the patent office on 2008-09-11 for method and apparatus for producing ti through reduction by ca.
This patent application is currently assigned to SUMITOMO TITANIUM CORPORATION. Invention is credited to Masahiko Hori, Susumu Kosemura, Eiji Nishimura, Tadashi Ogasawara, Yuichi Ono, Toru Uenishi, Makoto Yamaguchi, Masanori Yamaguchi.
Application Number | 20080217184 11/665976 |
Document ID | / |
Family ID | 36319062 |
Filed Date | 2008-09-11 |
United States Patent
Application |
20080217184 |
Kind Code |
A1 |
Hori; Masahiko ; et
al. |
September 11, 2008 |
Method and Apparatus for Producing Ti Through Reduction by Ca
Abstract
An apparatus for producing Ti by Ca reduction by the invention
includes a reaction tank retaining a molten salt in which a molten
salt CaCl.sub.2 is contained and Ca is dissolved, an electrolytic
cell retaining a molten salt containing CaCl.sub.2, and a continuum
body which is movably constructed while part of the continuum body
is immersed in the molten salt either within the reaction tank or
electrolytic cell. In the inventive method for producing Ti by Ca
reduction, the molten salt in the electrolytic cell is electrolyzed
to generate Ca on the cathode side which is transported to the
reaction tank while deposited on and adheres to the continuum body,
and TiCl.sub.4 is supplied to the reaction tank to generate Ti. The
invention enables a feed rate of TiC1.sub.4 as a raw material to be
enhanced, and continuous production to be performed, while allowing
Ca consumed in the TiCl.sub.4 reduction reaction to be replenished
by electrolysis of CaCl.sub.2, which proves to have an economical
advantage, thus becoming means for efficiently and economically
producing high-purity metallic Ti to widely be applied.
Inventors: |
Hori; Masahiko; (Hyogo,
JP) ; Ogasawara; Tadashi; (Hyogo, JP) ;
Yamaguchi; Makoto; (Hyogo, JP) ; Uenishi; Toru;
(Hyogo, JP) ; Yamaguchi; Masanori; (Kanagawa,
JP) ; Ono; Yuichi; (Kanagawa, JP) ; Kosemura;
Susumu; (Kanagawa, JP) ; Nishimura; Eiji;
(Kanagawa, JP) |
Correspondence
Address: |
CLARK & BRODY
1090 VERMONT AVENUE, NW, SUITE 250
WASHINGTON
DC
20005
US
|
Assignee: |
SUMITOMO TITANIUM
CORPORATION
Hyogo
JP
TOHOTITANIUM CO., LTD.
Kanagawa
JP
|
Family ID: |
36319062 |
Appl. No.: |
11/665976 |
Filed: |
October 26, 2005 |
PCT Filed: |
October 26, 2005 |
PCT NO: |
PCT/JP05/19655 |
371 Date: |
March 28, 2008 |
Current U.S.
Class: |
205/398 ;
204/245 |
Current CPC
Class: |
C22B 34/1268 20130101;
C22B 34/129 20130101; C25C 7/007 20130101; C25C 3/28 20130101; C22B
34/1272 20130101; C25C 3/02 20130101 |
Class at
Publication: |
205/398 ;
204/245 |
International
Class: |
C25C 3/28 20060101
C25C003/28 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 1, 2004 |
JP |
2004-317842 |
Claims
1. A method for producing Ti through reduction by Ca, said method
comprising: a Ti generation step wherein TiCl.sub.4 is supplied to
a reaction tank to generate Ti in a molten salt while said molten
salt is retained in said reaction tank, the molten salt containing
CaCl.sub.2 and having Ca dissolved therein; an electrolytic step
wherein a molten salt is electrolyzed in an electrolytic cell to
generate Ca on a cathode side while said molten salt is retained in
said electrolytic cell, the molten salt containing CaCl.sub.2; and
a Ca transportation step wherein the Ca generated in said
electrolytic step is transported to said reaction tank while the Ca
is deposited on and adheres to a continuum body in said
electrolytic cell, said continuum body being movably constructed
while part of said continuum body is immersed in said molten salt
either within said reaction tank or electrolytic cell, and said
transported Ca is caused to dissolve in said molten salt retained
in said reaction tank.
2. The method for producing Ti through reduction by Ca according to
claim 1, wherein said continuum body is caused to function as a
cathode.
3. The method for producing Ti through reduction by Ca according to
claim 1, wherein a cathode is provided near part of said continuum
body, the part of said continuum body being immersed in said molten
salt.
4. The method for producing Ti through reduction by Ca as in claim
1, wherein said molten salt or said cathode in said electrolytic
cell is kept at a temperature of a melting point of Ca or less.
5. The method for producing Ti through reduction by Ca as in claim
1, wherein Ti generated in said Ti generation step is extracted to
the outside of said reaction tank along with said molten salt, Ti
is separated, and said molten salt is transported to said
electrolytic cell.
6. An apparatus for producing Ti through reduction by Ca, said
apparatus comprising: a reaction tank in which TiCI.sub.4 supplied
to a molten salt is caused to react with Ca to generate Ti while
said molten salt is retained, the molten salt containing CaCl.sub.2
and having Ca dissolved therein; an electrolytic cell which retains
a molten salt containing CaCl.sub.2, said electrolytic cell
including an anode and a cathode, said electrolytic cell performing
electrolysis in said molten salt to generate Ca on said cathode
side; and a continuum body which is movably constructed while part
of said continuum body is immersed in said molten salt either
within said reaction tank or electrolytic cell, the continuum body
transporting said generated Ca to said reaction tank while Ca is
deposited on and adheres to the part immersed in said electrolytic
cell, the continuum body causing said transported Ca to be
dissolved in said molten salt retained in said reaction tank.
7. The apparatus for producing Ti through reduction by Ca according
to claim 6, wherein said continuum body constitutes a cathode.
8. The apparatus for producing Ti through reduction by Ca according
to claim 6, wherein a cathode is provided near part of said
continuum body, the part of said continuum body being immersed in
said molten salt.
9. The apparatus for producing Ti through reduction by Ca as in
claim 6, wherein said molten salt or said cathode in said
electrolytic cell is kept at a temperature of a melting point of Ca
or less.
10. The apparatus for producing Ti through reduction by Ca as in
claim 6, comprising means for separating Ti from said molten salt
to transport said molten salt to said electrolytic cell after said
Ti separation, the Ti being generated in said reaction tank and
extracted to the outside of said reaction tank along with said
molten salt.
11. The method for producing Ti through reduction by Ca as in claim
2, wherein said molten salt or said cathode in said electrolytic
cell is kept at a temperature of a melting point of Ca or less.
12. The method for producing Ti through reduction by Ca as in claim
3, wherein said molten salt or said cathode in said electrolytic
cell is kept at a temperature of a melting point of Ca or less.
13. The method for producing Ti through reduction by Ca as in claim
2, wherein Ti generated in said Ti generation step is extracted to
the outside of said reaction tank along with said molten salt, Ti
is separated, and said molten salt is transported to said
electrolytic cell.
14. The method for producing Ti through reduction by Ca as in claim
3, wherein Ti generated in said Ti generation step is extracted to
the outside of said reaction tank along with said molten salt, Ti
is separated, and said molten salt is transported to said
electrolytic cell.
15. The method for producing Ti through reduction by Ca as in claim
4, wherein Ti generated in said Ti generation step is extracted to
the outside of said reaction tank along with said molten salt, Ti
is separated, and said molten salt is transported to said
electrolytic cell.
16. The apparatus for producing Ti through reduction by Ca as in
claim 7, wherein said molten salt or said cathode in said
electrolytic cell is kept at a temperature of a melting point of Ca
or less.
17. The apparatus for producing Ti through reduction by Ca as in
claim 8, wherein said molten salt or said cathode in said
electrolytic cell is kept at a temperature of a melting point of Ca
or less.
18. The apparatus for producing Ti through reduction by Ca as in
claim 7, comprising means for separating Ti from said molten salt
to transport said molten salt to said electrolytic cell after said
Ti separation, the Ti being generated in said reaction tank and
extracted to the outside of said reaction tank along with said
molten salt.
19. The apparatus for producing Ti through reduction by Ca as in
claim 8, comprising means for separating Ti from said molten salt
to transport said molten salt to said electrolytic cell after said
Ti separation, the Ti being generated in said reaction tank and
extracted to the outside of said reaction tank along with said
molten salt.
20. The apparatus for producing Ti through reduction by Ca as in
claim 9, comprising means for separating Ti from said molten salt
to transport said molten salt to said electrolytic cell after said
Ti separation, the Ti being generated in said reaction tank and
extracted to the outside of said reaction tank along with said
molten salt.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method and an apparatus
for producing metallic Ti through reduction by Ca, in which
titanium tetrachloride (TiCl.sub.4) is reduced by Ca to produce the
metallic Ti.
BACKGROUND ART
[0002] The Kroll method for reducing TiCl.sub.4 by Mg is generally
used as a method for industrially producing the metallic Ti.
TiCl.sub.4 is obtained by chlorinating titanium oxide (TiO.sub.2).
In the Kroll method, the metallic Ti is produced through a
reduction step and a vacuum separation step. In the reduction step,
TiCl.sub.4 is reduced by Mg in a reactor vessel. In the vacuum
separation step, unreacted Mg and magnesium chloride (MgCl.sub.2)
formed as a by-product are removed from the sponge metallic Ti
produced in the reactor vessel.
[0003] In the reduction step, the reactor vessel is filled with
molten Mg, and the TiCl.sub.4 liquid is supplied from above to a
liquid surface of the molten Mg. This allows TiCl.sub.4 to be
reduced by Mg near the liquid surface of the molten Mg to generate
the granular metallic Ti. At the same time, molten MgCl.sub.2 which
is of the by-product is generated near the liquid surface. The
generated metallic Ti sequentially moves downward. Because a
specific gravity of the molten MgCl.sub.2 is larger than that of
the molten Mg, the molten MgCl.sub.2 also moves downward, and the
molten Mg comes up to the liquid surface instead. The molten Mg is
continuously supplied to the liquid surface by the specific-gravity
difference substitution, and the reduction reaction of TiCl.sub.4
proceeds continuously.
[0004] In the metallic Ti production by the Kroll method, although
a high-purity product is produced, production costs increase and
products become remarkably expensive. One of factors of the
increased production costs is some difficulty in enhancing a feed
rate of TiCl.sub.4. The following items (a) to (c) can be cited as
the reason why the feed rate of TiCl.sub.4is restricted.
[0005] (a) In order to improve productivity in the Kroll method, it
is effective to enhance the feed rate of TiCl.sub.4, i.e., to
enhance an amount of molten Mg supplied to the liquid surface per
unit area or unit time. However, when the feed rate of TiCl.sub.4
is excessively enhanced, the rate of the specific-gravity
difference substitution cannot respond to the reaction rate,
MgCl.sub.2 remains on the liquid surface, and TiCl.sub.4 is
supplied to the MgCl.sub.2, which reduces utilization efficiency of
TiCl.sub.4. That is, the supplied TiCl.sub.4 becomes unreacted
lower chloride gases (referred to as "unreacted gases") such as an
unreacted TiCl.sub.4 gas and an unreacted TiCl.sub.3 gas, and the
unreacted gases are discharged outside the reactor vessel, which
reduces utilization efficiency of TiCl.sub.4. It is necessary to
avoid the generation of such unreacted gases, because a rapid
increase in inner pressure of the reactor vessel is associated with
the generation of the unreacted gases. Accordingly, there is a
limit of the feed rate of TiCl.sub.4.
[0006] (b) When the feed rate of TiC.sub.4 is enhanced, Mg vapor
generated from the liquid surface of the molten Mg reacts with
TiCl.sub.4 vapor to increase the amount of deposited Ti in the
inner surface of the reactor vessel above the liquid surface of the
molten Mg. On the other hand, the liquid surface of the molten Mg
rises as the reduction of TiCl.sub.4 proceeds. Therefore, the Ti
deposited on the inner surface of the upper portion of the reactor
vessel is immersed in the molten Mg at a later stage of the
reduction step, which causes the effective area of the liquid
surface to be reduced to decrease the reaction rate. In order to
suppress the decrease in reaction rate, it is necessary that the
feed rate of TiCl.sub.4 be restricted to prevent the Ti deposition
on the inner surface of the upper portion of the reactor vessel as
much as possible.
[0007] Japanese Patent Application Publication No. 0H8-295955
proposes a method in which the reaction efficiency is enhanced by
supplying the liquid TiCl.sub.4 in a dispersive manner to the
liquid surface where the molten Mg exists, and thereby the Ti
deposition is suppressed on the inner surface of the upper portion
of the reactor vessel. However, the method proposed in Japanese
Patent Application Publication No. 08-295955 is not enough to
suppress the Ti deposition.
[0008] (c) In the Kroll method, because the reaction is performed
only near the liquid surface of the molten Mg in the reactor
vessel, an exothermic area is narrowed and a temperature rises
locally. Therefore, cooling is hardly performed, which causes the
feed rate of TiCl.sub.4 to be restricted.
[0009] Although the feed rate of TiCl.sub.4 is not directly
affected, in the Kroll method, Ti generated in the granular form
near the liquid surface of the molten Mg is aggregated because of
wetting properties (adhesion properties) of the molten Mg, the Ti
granules moves downward while aggregated, and the Ti granules are
sintered to generate grain growth of the Ti granules by the heat
generated from the molten melt during the downward movement.
Therefore, it makes difficult to take out the generated Ti as fine
particles to the outside of the reactor vessel to recover the
generated Ti. In the Kroll method, the continuous production is
difficult to perform, and the improvement of the productivity is
blocked. This is because that Ti is produced as a sponge titanium
in a batch manner in the reactor vessel.
[0010] With reference to the Ti production methods except for the
Kroll method, for example, U.S. Pat. No. 2,205,854 describes that,
in addition to 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 reduction reaction by Ca, wherein the
molten salt of calcium chloride (CaCl.sub.2) is held in a reactor
vessel, metallic Ca powders are supplied into the molten salt from
above, Ca is dissolved in the molten salt, and 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.
[0011] In the reduction by Ca, the metallic Ti is generated from
TiCl.sub.4 by the reaction of the following chemical formula (i),
and CaCl.sub.2 which is of the by-product is also generated at the
same time:
TiCl.sub.4+2CaTi+2CaCl.sub.2 (i)
[0012] Ca has an affinity for Cl stronger than Mg has, and Ca is
suitable for a 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 molten CaCl.sub.2. When the reduction
reaction by Ca is utilized in the molten CaCl.sub.2, compared with
the Kroll method in which TiCl.sub.4 is supplied to the liquid
surface of the reducing agent in the reactor vessel, an area
(reaction field) where the reaction is created is enlarged, and the
exothermic area is also enlarged, which facilitates the cooling.
Accordingly, the feed rate of TiCl.sub.4 can be largely enhanced,
and the improvement of the productivity can be also expected.
[0013] However, the method described in U.S. Pat. No. 4,820,339 is
hardly adopted as the industrial Ti production method. In the
method, because highly expensive metallic Ca powders are used as
the reducing agent, the production cost becomes higher than that of
the Kroll method.
[0014] U.S. Pat. No. 2,845,386 describes another Ti production
method (Olsen method) in which TiO.sub.2 is directly reduced by Ca
not through TiCl.sub.4. The method is a kind of oxide
direct-reduction method. Although the method is highly efficient,
the oxide direct-reduction method is not suitable to produce a
high-purity Ti because it is necessary to use expensive high-purity
TiO.sub.2.
DISCLOSURE OF THE INVENTION
[0015] An object of the present invention is to provide a method
and an apparatus for economically producing a high-purity metallic
Ti with high efficiency without using an expensive reducing
agent.
[0016] In order to achieve the above object, the inventors consider
that the reduction of TiCl.sub.4 by Ca is indispensably required,
and the inventors study the method for utilizing Ca dissolved in
the molten salt of CaCl.sub.2 as described in U.S. Pat. No.
4,820,339.
[0017] In the method described in U.S. Pat. No. 4,820,339, Ca in
the molten salt is consumed in the reduction reactor vessel as the
reaction expressed by the chemical formula (i) proceeds, and it is
necessary to continuously supply the metallic Ca powders to the
reduction reactor vessel to replenish the consumed Ca.
[0018] However, in order to industrially establish the method for
producing Ti through reduction by Ca, the inventors proposes a
method for generating Ca by electrolysis of the molten CaCl.sub.2
liquid in an electrolytic cell to supply the CaCl.sub.2 liquid
containing Ca to the reaction tank in consideration of the fact
that it is necessary that Ca consumed by the reduction reaction is
economically replenished into the molten salt, i.e., it is
necessary that Ca is replenished at low costs.
[0019] That is, when the molten CaCl.sub.2 liquid is electrolyzed
in the electrolytic cell, electrode reactions expressed by the
following chemical formulas (ii) and (iii) proceed to generate a
Cl.sub.2 gas near the surface of an anode while Ca is generated
near the surface of a cathode, which allows the Ca concentration to
be increased in the electrolytic bath salt (molten CaCl.sub.2
liquid) near the cathode. Therefore, the molten CaCl.sub.2 liquid
containing the high-concentration Ca near the cathode is deposited
on and adheres to a metal plate, net, or wire having a temperature
lower than a bath temperature, and the molten CaCl.sub.2 liquid is
transported into the reaction tank, which allows Ca consumed for
the reduction of TiCl.sub.4 to be replenished as needed. Therefore,
the replenishment of the metallic Ca from the outside or the
extraction of the metallic Ca is not required, which allows the
metallic Ti to be economically produced.
Anode: 2Cl.sup.-2e+Cl.sub.2 (ii)
Cathode: Ca.sup.2++2eCa (iii)
[0020] The present invention is made based on the above
consideration, and the summary of the present invention resides in
(1) a Ti production method and (2) a production apparatus in which
the Ti production method is implemented.
[0021] (1) A first aspect of the present invention provides a
method for producing Ti through reduction by Ca, the method
including: a Ti generation step wherein TiCl.sub.4 is supplied to a
reaction tank to generate Ti in a molten salt while the molten salt
is retained in the reaction tank, the molten salt containing
CaCl.sub.2, the Ca being dissolved in the molten salt; an
electrolytic step wherein a molten salt is electrolyzed in an
electrolytic cell to generate Ca on an cathode side while the
molten salt is retained in the electrolytic cell, the molten salt
containing CaCl.sub.2; and a Ca transportation step wherein the Ca
generated in the electrolytic step is transported to the reaction
tank while the Ca is deposited on and adheres to a continuum body
in the electrolytic cell, the continuum body being movably
constructed while part of the continuum body is immersed in the
molten salt either within the reaction tank or electrolytic cell,
and the transported Ca is caused to dissolve in the molten salt
retained in the reaction tank.
[0022] In the Ti production method of (1), preferably the continuum
body is caused to function as a cathode. Therefore, Ca can
directly, electrolytically be deposited on the surface of the
continuum body.
[0023] In the Ti production method of (1), preferably a cathode is
provided near part of the continuum body, the part of the continuum
body being immersed in the molten salt.
[0024] In the Ti production method of (1), preferably the molten
salt or the cathode in the electrolytic cell is kept at a
temperature of a melting point of Ca or less. Therefore, Ca can
surely electrolytically be deposited on the surface of the
cathode.
[0025] In the Ti production method of (1), preferably Ti generated
in the Ti generation step is extracted to the outside of the
reaction tank along with the molten salt, Ti is separated, and the
molten salt is transported to the electrolytic cell. Therefore, Ti
can continuously be produced.
[0026] (2) A second aspect of the present invention provides an
apparatus for producing Ti through reduction by Ca, the apparatus
comprising: a reaction tank in which TiCl.sub.4 supplied to a
molten salt is caused to react with Ca to generate Ti while the
molten salt is retained, the molten salt containing CaCl.sub.2, the
Ca being dissolved in the molten salt; an electrolytic cell which
retains a molten salt containing CaCl.sub.2, the electrolytic cell
including an anode and a cathode, the electrolytic cell performing
electrolysis in the molten salt to generate Ca on the cathode side;
and a continuum body which is movably constructed while part of the
continuum body is immersed in the molten salt either in the
reaction tank or electrolytic cell, the continuum body transporting
the generated Ca to the reaction tank while Ca is deposited on and
adheres to the part immersed in the electrolytic cell, the
continuums body causing the transported Ca to dissolve in the
molten salt retained in the reaction tank.
[0027] In the Ti production apparatus of (2), preferably the
continuum body constitutes a cathode. Therefore, Ca can directly
electrolytically be deposited on the surface of the continuum
body.
[0028] In the Ti production apparatus of (2), preferably a cathode
is provided near part of the continuum body, the part of the
continuum body being immersed in the molten salt.
[0029] In the Ti production apparatus of (2), preferably the molten
salt or the cathode in the electrolytic cell is kept at a
temperature of a melting point of Ca or less. Therefore, Ca can
surely electrolytically be deposited on the surface of the
cathode.
[0030] In the Ti production apparatus of (2), preferably the Ti
production apparatus includes means for separating Ti from the
molten salt to transport the molten salt to the electrolytic cell
after the Ti separation, the Ti being generated in the reaction
tank and extracted to the outside of the reaction tank along with
the molten salt. Therefore, Ti can continuously be produced.
[0031] The method for producing Ti through reduction by Ca
according to the present invention is directed to a method for
reducing TiCl.sub.4 in which the high purity material is easily
obtained, so that the high-purity metallic Ti can be produced. Ca
is used as a reducing agent, and TiCl.sub.4 is caused to react with
Ca in the molten salt containing CaCl.sub.2, so that the feed rate
of TiCl.sub.4 can be enhanced. Ca to be consumed in the reduction
reaction can be replenished by the electrolysis of the molten
CaCl.sub.2 liquid, so that the present invention has the economical
advantage.
[0032] In addition, Ca is inferior to Mg in wetting properties
(adhesion properties), and the Ti granules are generated in the
molten CaCl.sub.2 liquid, so that the aggregation in the generated
Ti granules and the grain growth by the sintering are significantly
lessened. Therefore, the Ti granules can be taken out to the
outside of the reactor vessel, and the Ti production can
continuously be operated. The Ti production method of the present
invention can preferably implemented with the Ti production
apparatus of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1 is a view showing a configuration example of an
apparatus in which a Ti production method of the present invention
can be implemented; and
[0034] FIG. 2 is a view showing another configuration example of
the apparatus in which the Ti production method of the present
invention can be implemented
BEST MODE FOR CARRYING OUT THE INVENTION
[0035] A method and an apparatus according to the present invention
for producing Ti through reduction by Ca will be described below
with reference to the drawings.
[0036] FIG. 1 is a view showing a configuration example of an
apparatus (Ti production apparatus of the present invention) in
which a Ti production method of the present invention can be
implemented. As shown in FIG. 1, the apparatus comprises a reaction
tank 1, an electrolytic cell 2, and a continuum body 5. In the
reaction tank 1, TiCl.sub.4 supplied into a molten salt 3a is
caused to react with Ca to generate Ti. The electrolytic cell 2
retains a molten salt 3b containing CaCl.sub.2, and the
electrolytic cell 2 includes an anode 4 and a cathode (in the
example, the continuum body 5 constitutes the cathode). In the
electrolytic cell 2, the electrolysis is performed in the molten
salt 3b to generate Ca on the cathode side. The continuum body 5 is
movably constructed while part of the continuum body 5 is immersed
in the molten salt 3a, 3b either within the reaction tank 1 and
electrolytic cell 2. The continuum body 5 serves to transport the
generated Ca into the reaction tank 1 while Ca is deposited on and
adheres to the immersed part of the continuum body 5 in the
electrolytic cell 2, and the transported Ca is dissolved in the
molten salt 3a retained in the reaction tank 1.
[0037] The continuum body 5 is a so-called endless belt, and the
continuum body 5 is moved in an arrow direction of FIG. 1 while
part of the continuum body 5 is immersed in the molten salt 3a in
the reaction tank 1 as well as another part thereof being immersed
in the molten salt 3b in the electrolytic cell 2. The continuum
body 5 is rotatably constructed. However, when attention is focused
on the movement of a particular portion in the surface of the
continuum body 5, the portion can be deemed to be moved (i.e., the
portion is moved in the rotating direction of the continuum body),
so that the expression of "the continuum body 5 is movably
constructed" is adopted here according to the function in which Ca
is transported into the reaction tank 1 while Ca generated in the
electrolytic cell 2 is deposited and adheres to the continuum body
5 in the electrolytic cell 2.
[0038] In the example of FIG. 1, a barrier membrane 6b is provided
in the electrolytic cell 2, and a partition wall 6a is attached in
the reaction tank 1. The barrier membrane 6b blocks the movement of
Ca generated on the cathode side to the anode side. A lower portion
of the partition wall 6a is opened. The apparatus also includes
means for transporting only the molten salt 3a into the
electrolytic cell 2 after recovering Ti by the extraction of Ti
generated in the reaction tank 1 to the outside of the reaction
tank 1 along with the molten salt 3a. The apparatus is configured
so as to perform an operation in which chlorine (Cl.sub.2)
generated by the anode 4 in the electrolytic cell 2 is recovered
and caused to react with titanium oxide (TiO.sub.2) to generate
TiCl.sub.4 supplied into the reaction tank 1.
[0039] In order to implement the Ti production method of the
present invention using the apparatus having the above
configuration, at first the molten salt 3a in which CaCl.sub.2 is
includes while Ca is dissolved is retained in the reaction tank 1,
and TiCl.sub.4 is supplied into the reaction tank 1 to generate Ti
in the molten salt 3a. That is, a "Ti generation step" is
performed.
[0040] Usually the molten CaCl.sub.2 having a melting point of
780.degree. C. is used as the molten salt 3a. However, preferably
the temperature of the molten salt 3a is lowered because a lifetime
of the reaction tank 1 is extended while the vaporization of Ca or
the molten salt from the liquid surface is suppressed, when the
temperature of the molten salt 3a is lowered. Therefore, desirably
a mixed salt of CaCl.sub.2 and another salt is used as the molten
salt 3a. For example, when the mixed salt of CaCl.sub.2 and NaCl is
used as the molten salt 3a, the melting point of the molten salt 3a
can be lowered to about 500.degree. C. at the lowest
temperature.
[0041] Desirably TiCl.sub.4 is supplied in a gas state to the
molten salt 3a in the reaction tank 1 in consideration of contact
efficiency between TiCl.sub.4 and Ca in the molten salt. However,
the present invention is not limited to the gaseous TiCl.sub.4, but
the liquid TiCl.sub.4 can be supplied on the liquid surface of the
molten salt 3a or into the molten salt 3a. In the example of FIGS.
1 or 2, the liquid TiCl.sub.4 is supplied to the neighborhood of a
bottom portion of the reaction tank 1 through a supply pipe 7.
[0042] The supply of TiCl.sub.4 into the reaction tank 1 causes the
reaction of the chemical formula (i) to proceed to generate the
metallic Ti. Although Ca in the molten salt 3a is consumed in
association with the generation of Ti, Ca transported from the
electrolytic cell 2 to the continuum body 5 is dissolved, and the
molten salt whose Ca concentration is increased is supplied to the
neighborhood of a front end of the TiCl.sub.4 supply pipe 7 through
the opening in the lower portion of the partition wall 6a.
Therefore, the reaction of the chemical formula (i) proceeds
effectively.
[0043] Ti is generated in the form of granule or powder. The Ca is
much inferior to Mg in wetting properties (adhesion properties),
and Ca adhering to the deposited Ti granule is dissolved in
CaCl.sub.2. Therefore, the aggregation of the generated Ti granules
or the grain growth by sintering is hardly generated compared with
the case of Mg.
[0044] Ti generated in the molten salt 3a can be separated from the
molten salt 3a either inside the reaction tank 1 or outside the
reaction tank 1. However, when Ti is separated from the molten salt
3a inside the reaction tank 1, the operation becomes a batch
manner. In order to enhance the productivity, preferably Ti is
extracted to the outside of the reaction tank 1 along with the
molten salt 3a, and Ti is separated from the molten salt 3a outside
the reaction tank 1. Although only the generated Ti can be
extracted to the outside of the reaction tank 1, the operation
becomes a batch manner because CaCl.sub.2 is continuously increased
in the reaction tank 1.
[0045] The apparatus of FIG. 1 includes means for extracting the
generated Ti to the outside of the reaction tank along with the
molten salt 3a. Because the generated Ti takes the granular or
powder form, the generated Ti can easily separated from the molten
salt by a squeezing operation such as mechanical compression, and
the operation can continuously be performed. The separated Ti is
conveyed to a melting step.
[0046] On the other hand, the molten salt 3b containing CaCl.sub.2
is also retained in the electrolytic cell 2, and the molten salt 3b
is electrolyzed to generate Ca on the cathode side. That is, an
"electrolytic step" is performed.
[0047] As described above, when the molten CaCl.sub.2 liquid is
electrolyzed, Ca is generated near the surface of the cathode by
the electrode reactions of the chemical formulas (ii) and (iii).
The molten salt in which Ca is consumed by the reaction of the
chemical formula (i) in the reaction tank 1 to lower the Ca
concentration can also be used as the molten CaCl.sub.2 liquid.
[0048] The apparatus of FIG. 1 includes the means for transporting
only the molten salt into the electrolytic cell 2 after recovering
Ti by the extraction of Ti generated in the reaction tank 1 to the
outside of the reaction tank 1 along with the molten salt 3a, which
allows the formation of the cycle, in which the molten salt is
delivered to the electrolytic cell 2 after Ti is recovered and Ca
generated by the electrolysis is deposited on and adheres to the
continuum body 5 is returned to the reaction tank 1. Therefore, Ti
can continuously be produced.
[0049] During the electrolysis of the molten CaCl.sub.2 liquid,
there is a risk of generating a back reaction. In the back
reaction, Ca generated on the cathode side is returned to
CaCl.sub.2 by combining Ca and Cl.sub.2 generated on the side of
the anode 4. However, in the apparatus of FIG. 1, the continuum
body 5 constitutes the cathode, and the generated Ca is immediately
deposited on and adheres to the surface of the cathode (i.e.,
continuum body 5) while Cl.sub.2 generated on the side of the anode
4 is recovered as described later. Therefore, the back reaction is
hardly generated. Furthermore, in the example of FIG. 1, because
the barrier membrane 6b is provided to block the movement of Ca
generated on the cathode side to the side of the anode 4 (however,
the barrier membrane 6b cannot block the movements of Ca.sup.2+ and
Cl.sup.-), there is no risk of generating the back reaction. Like
the partition wall 6a, a partition wall whose lower portion is
opened can be used in place of the barrier membrane 6b.
[0050] As shown in FIG. 1, in order to supply Ca generated in the
electrolytic cell 2 to the reaction tank 1, the continuum body 5 is
used in the Ti production method of the present invention. The
continuum body 5 is movably constructed while part of the continuum
body 5 is immersed in the molten salt either in the reaction tank 1
or electrolytic cell 2. The generated Ca is deposited on and
adheres to the continuum body 5 in the electrolytic cell 2, Ca is
transported into the reaction tank 1, and Ca is dissolved in the
molten salt 3a retained in the reaction tank 1. That is, a "Ca
transportation step" is performed. In FIG. 1, a broken line shown
in part of the continuum body 5 indicates the deposited and adhered
Ca.
[0051] The continuum body 5 is slowly moved in the arrow direction
by drive rollers 8a and 8b. Focusing attention on a portion of the
continuum body 5 (or example, the portion designated by the letter
A in FIG. 1 where the continuum body 5 is pulled up in air from the
molten salt 3a), the temperature of the portion A in motion is
lowered while moving from the position, where the portion A is
currently shown in FIG. 1 (at this point, Ca is completely
dissolved without adhering to the continuum body 5), through the
drive roller 8a until the portion A is immersed in the molten salt
3b in the electrolytic cell 2. Therefore, the dissolved Ca near the
portion A is deposited on and adheres to the portion A (i.e., the
surface of the continuum body 5) along with CaCl.sub.2 soon after
the portion A is immersed in the molten salt 3b in the electrolytic
cell 2. In the apparatus of FIG. 1, the continuum body 5
constitutes the cathode, and Ca is directly deposited on the
surface of the continuum body 5, so that the deposition and
adhesion of Ca are generated more rapidly.
[0052] At this point, for example, when the mixed salt of
CaCl.sub.2 and NaCl is used as the molten salt, the temperature of
the molten salt is lowered to about 500.degree. C. which is much
lower than the melting point (839.degree. C.) of Ca. As the result,
Ca can be deposited efficiently and securely on the cathode.
[0053] Because the continuum body 5 (portion A) reaches the
reaction tank 1 through the drive roller 8b while Ca and CaCl.sub.2
are deposited and adhere to the surface of the continuum body 5
(portion A), Ca is transported from the electrolytic cell 2 to the
reaction tank 1 in association with the movement of the continuum
body 5. When the deposited and adhered Ca comes into contact with
the molten salt 3a in the reaction tank 1, Ca is gradually
dissolved to increase the Ca concentration of the molten salt 3a in
the reaction tank 1.
[0054] The metal plate, and the metal net or wire can be used as
the continuum body 5. Molybdenum, tantalum, and titanium are
suitable for the continuum body 5 because of excellent durability
in the molten salts 3a and 3b. When the continuum body is made of
metal, as shown in FIG. 1, the continuum body can function as the
cathode to directly electrolytically deposit Ca on the surface of
the continuum body. Therefore, desirably the continuum body is made
of metal.
[0055] The moving speed of the continuum body 5 can appropriately
be adjusted as long as Ca generated in the electrolytic cell 2 is
deposited on and adheres to the continuum body 5 without troubles,
as long as Ca is transported into the reaction tank 1 without
troubles, and as long as the transported Ca is dissolved in the
molten salt 3a in the reaction tank 1 without trouble.
[0056] Desirably the molten salt 3a in the reaction tank 1 is kept
at the temperature equal to or higher than the temperature of the
molten salt 3b in the electrolytic cell 2. Therefore, solubility of
Ca is enhanced to increase the Ca concentration of the molten salt
3a, and the TiCl.sub.4 reduction reaction of the chemical formula
(i) can efficiently be performed. Additionally, Ca which is
deposited on and adheres to the continuum body 5 can be dissolved
in the molten salt 3a at a higher rate.
[0057] The apparatus of FIG. 1 is configured to perform the
operation in which Cl.sub.2 generated by the anode 4 in the
electrolytic cell 2 is recovered to cause Cl.sub.2 to react with
TiO.sub.2 and carbon (C) and thereby TiCl.sub.4 supplied to the
reaction tank 1 is generated. That is, the Cl.sub.2 gas generated
in the electrolytic step is recovered, the Cl.sub.2 gas is caused
to react with TiO.sub.2 at a high temperature to generate
TiCl.sub.4, and TiCl.sub.4 is used as TiCl.sub.4 supplied to the
reaction tank 1.
[0058] When the operation (step) is incorporated into the Ti
production method, CaCl.sub.2 which is of the by-product through
the reduction of TiCl.sub.4 is introduced into the electrolytic
cell 2 and electrolyzed in the electrolytic cell 2, Ca generated by
the cathode is cyclically used as the reducing agent, and Cl.sub.2
generated by the anode is utilized in producing TiCl.sub.4. This
enables the metallic Ti to be continuously produced only by
replenishing TiO.sub.2 and C.
[0059] FIG. 2 is a view showing another configuration example of
the apparatus (Ti production apparatus of the present invention) in
which the Ti production method of the present invention can be
implemented. In the apparatus of FIG. 2, a cathode 9 is provided
near a portion where the continuum body 5 is immersed in the molten
salt 3b, while all other configurations of the apparatus of FIG. 2
are similar to those of FIG. 1.
[0060] The temperature of the continuum body 5 immersed in the
molten salt 3b in the electrolytic cell 2 is considerably lowered
compared with the temperature of the molten salt 3b. Therefore, in
the apparatus of FIG. 2, Ca generated near the surface of the
cathode 9 can be transported from the electrolytic cell 2 to the
reaction tank 1 while deposited on and adheres to the surface of
the continuum body 5.
[0061] An electrode being made of a material and in a shape, which
are commonly applied in the molten salt electrolysis such as
CaCl.sub.2, can be used as the cathode 9. For example, an electrode
made of a metal such as Fe and Ti can be used, and particularly a
porous electrode is desirably used. Because a surface area per unit
mass is increased, the electrolytic current can be enhanced to
increase the amount of generated Ca.
[0062] Desirably the porous electrode is made of the metal such as
Fe and Ti. The titanium oxide sintered material can also be used
because the titanium oxide sintered material exhibits good
conductivity at high temperatures.
[0063] When the cathode 9 is arranged near the continuum body 5
(i.e., near the portion where the continuum body 5 is immersed in
the molten salt 3b), Ca generated near the surface of the cathode 9
is easily deposited on and adheres to the surface of the continuum
body 5, which allows Ca to be transported from the electrolytic
cell 2 to the reaction tank 1.
INDUSTRIAL APPLICABILITY
[0064] According to the method for producing Ti through reduction
by Ca of the present invention, the feed rate of TiCl.sub.4 which
is of the raw material can be enhanced, and the continuous
production can be performed. Furthermore, the method of the present
invention has an economical advantage because Ca consumed in a
reduction reaction of TiCl.sub.4 can be replenished by the
electrolysis of CaCl.sub.2. Therefore, the Ti production method of
the present invention can efficiently be utilized as means for
economically producing the high-purity metallic Ti, and the Ti
production apparatus of the present invention can suitably be used
for the Ti production method of the present invention.
* * * * *