U.S. patent application number 10/589949 was filed with the patent office on 2007-08-09 for method for producing ti or ti alloy through reduction by ca (as amended).
Invention is credited to Katsunori Dakeshita, Masahiko Hori, Tadashi Ogasawara, Toru Uenishi, Makoto Yamaguchi.
Application Number | 20070181435 10/589949 |
Document ID | / |
Family ID | 34889347 |
Filed Date | 2007-08-09 |
United States Patent
Application |
20070181435 |
Kind Code |
A1 |
Ogasawara; Tadashi ; et
al. |
August 9, 2007 |
Method for producing ti or ti alloy through reduction by ca (as
amended)
Abstract
The method by the invention in which a molten salt is held in a
reactor cell 1 to perform electrolysis in the molten salt of the
reactor cell, the molten salt containing CaCl.sub.2 while Ca being
dissolved in the molten salt, and Ti or Ti alloys are generated in
the molten salt by supplying a metallic chloride containing
TiCl.sub.4 into the molten salt such that the metallic chloride
containing TiCl.sub.4 is caused to react with Ca generated on a
cathode electrode side by the electrolysis, makes it possible to
produce the high-purity Ti metals or Ti alloy. Furthermore, the
reactor cell 1 includes a membrane 4 which partitions an inside of
the reactor cell into a side of an anode electrode 2 and a side of
a cathode electrode 3, and the membrane 4 blocks the movement of Ca
generated on the cathode electrode side in the reactor cell toward
the anode electrode side while permitting the molten salt to flow
in the reactor cell, which allows a back reaction by Ca to be
effectively suppressed. When an electroconductive porous material
is used as a cathode electrode, productivity can further be
improved.
Inventors: |
Ogasawara; Tadashi; (Hyogo,
JP) ; Yamaguchi; Makoto; (Hyogo, JP) ; Hori;
Masahiko; (Hyogo, JP) ; Uenishi; Toru; (Hyogo,
JP) ; Dakeshita; Katsunori; (Hyogo, JP) |
Correspondence
Address: |
CLARK & BRODY
1090 VERMONT AVENUE, NW
SUITE 250
WASHINGTON
DC
20005
US
|
Family ID: |
34889347 |
Appl. No.: |
10/589949 |
Filed: |
February 1, 2005 |
PCT Filed: |
February 1, 2005 |
PCT NO: |
PCT/JP05/01379 |
371 Date: |
August 18, 2006 |
Current U.S.
Class: |
205/366 ;
205/398 |
Current CPC
Class: |
C22B 34/1268 20130101;
C25C 3/28 20130101; C22B 34/129 20130101; C22B 5/04 20130101 |
Class at
Publication: |
205/366 ;
205/398 |
International
Class: |
C25C 3/28 20060101
C25C003/28 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 20, 2004 |
JP |
2004-044827 |
Nov 1, 2004 |
JP |
2004-318075 |
Claims
1. A method for producing Ti or Ti alloys through reduction by Ca,
comprising: a reduction electrolysis step in which a molten salt is
held in a reactor cell to perform electrolysis in the molten salt
of the reactor cell, the molten salt containing CaCl.sub.2 while Ca
being dissolved in the molten salt, and Ti or Ti alloys are
generated in said molten salt by supplying a metallic chloride
containing TiCl.sub.4 into said molten salt in order to cause the
metallic chloride containing TiCl.sub.4 to react with Ca generated
on a cathode electrode side by the electrolysis; and a Ti
separation step of separating said Ti or Ti alloys from the molten
salt inside the reactor cell or outside the reactor cell, wherein
said reactor cell is provided with a membrane which partitions an
inside of the reactor cell into an anode electrode side and the
cathode electrode side, said membrane blocking the movement of Ca
generated on the cathode electrode side in the reactor cell toward
the anode electrode side while permitting the molten salt to flow
in the reactor cell.
2. A method for producing Ti or Ti alloys through reduction by Ca,
comprising: a reduction electrolysis step in which a molten salt is
held in a reactor cell to perform electrolysis using an
electroconductive porous material as an cathode electrode in the
molten salt of the reactor cell, the molten salt containing
CaCl.sub.2 while Ca being dissolved in the molten salt, and Ti or
Ti alloys are generated in said molten salt by supplying a metallic
chloride containing TiCl.sub.4 into said molten salt through said
cathode electrode in order to cause the metallic chloride
containing TiCl.sub.4 to react with Ca generated on a cathode
electrode side by the electrolysis; and a Ti separation step of
separating said Ti or Ti alloys from the molten salt inside the
reactor cell or outside the reactor cell.
3. A method for producing Ti or Ti alloys through reduction by Ca,
comprising: a reduction electrolysis step in which a molten salt is
held in a reactor cell to perform electrolysis in the molten salt
of the reactor cell, the molten salt containing CaCl.sub.2 while Ca
being dissolved in the molten salt, and Ti or Ti alloys are
generated in said molten salt by supplying a metallic chloride
containing TiCl.sub.4 into said molten salt in order to cause the
metallic chloride containing TiCl.sub.4 to react with Ca generated
on a cathode electrode side by the electrolysis; a Ti separation
step of separating said Ti or Ti alloys from the molten salt inside
the reactor cell or outside the reactor cell; and a chlorination
step of causing Cl.sub.2 to react with TiO.sub.2 to generate
TiCl.sub.4, Cl.sub.2 being generated on an anode electrode side in
association with said electrolysis, wherein TiCl.sub.4 generated in
the chlorination step is used for the Ti or Ti alloy generation
reaction in said reactor cell.
4. A method for producing Ti or Ti alloys through reduction by Ca,
comprising: a reduction electrolysis step in which a molten salt is
held in a reactor cell to perform electrolysis in the molten salt
of the reactor cell, the molten salt containing CaCl.sub.2 while Ca
being dissolved in the molten salt, and Ti or Ti alloys are
generated in said molten salt by supplying a metallic chloride
containing TiCl.sub.4 into said molten salt in order to cause the
metallic chloride containing TiCl.sub.4 to react with Ca generated
on a cathode electrode side by the electrolysis; and a Ti
separation step of extracting Ti or Ti alloys generated in said
reactor cell to an outside of said reactor cell along with the
molten salt, and said Ti separation step of separating said Ti or
Ti alloys from the molten salt outside the reactor cell.
5. The method for producing Ti or Ti alloys through reduction by Ca
according to claim 4, wherein the molten salt separated from Ti or
Ti alloys outside said reactor cell is returned to said reactor
cell.
6. A method for producing Ti or Ti alloys through reduction by Ca,
comprising: a reduction electrolysis step in which a multi-system
molten salt is held in a reactor cell to perform electrolysis in
the molten salt of the reactor cell, the multi-system molten salt
containing at least one of NaCl, KCl, LiCl, and CaF.sub.2 in
addition to CaCl.sub.2, Ca being dissolved in the molten salt, and
Ti or Ti alloys are generated in said molten salt by supplying a
metallic chloride containing TiCl.sub.4 into said molten salt in
order to cause the metallic chloride containing TiCl.sub.4 to react
with Ca generated on a cathode electrode side by the electrolysis;
and a Ti separation step of separating said Ti or Ti alloys from
the molten salt inside the reactor cell or outside the reactor
cell.
7. The method for producing Ti or a Ti alloys through reduction by
Ca according to claim 6, wherein said multi-system molten salt
contains at least CaCl.sub.2 and NaCl at a ratio in which a melting
point of said multi-system molten salt becomes not more than
600.degree. C., and the mixed molten salt is held at temperatures
of not more than 600.degree. C. in said reduction electrolysis
step.
8. The method for producing Ti or a Ti alloys through reduction by
Ca according to claim 7, further comprising a Na separation step in
which the molten salt is temporarily extracted to the outside of
the reactor cell, the molten salt being used to generate Ti or Ti
alloys in said reactor cell, and the molten salt is heated to
temperatures of more than 600.degree. C. to generate Na; and then
said molten salt is returned to the inside of the reactor cell
after the generated Na is separated and removed.
9. The method for producing Ti or Ti alloys through reduction by Ca
according to claim 8, wherein said Na separation step is also used
as said Ti separation step.
10. The method for producing Ti or Ti alloys through reduction by
Ca according to claim 8, wherein Na separated from the molten salt
in said Na separation step is supplied to the reduction
electrolysis step.
11. A method for producing Ti or Ti alloys through reduction by Ca,
comprising: a reduction electrolysis step in which a molten salt is
held in a reactor cell to perform electrolysis in the molten salt
in the reactor cell, the molten salt containing CaCl.sub.2 while Ca
being dissolved in the molten salt, and generating Ti or Ti alloys
are generated in said molten salt by supplying a mixed gas
containing TiCl.sub.4 and other metallic chloride into said molten
salt in order to cause the mixed gas to react with Ca generated on
a cathode electrode side by the electrolysis; and a Ti separation
step of separating said Ti or Ti alloys from the molten salt inside
the reactor cell or outside the reactor cell.
12. A method for producing Ti or Ti alloys through reduction by Ca,
comprising: a reduction electrolysis step in which a molten salt is
held in a reactor cell to perform electrolysis in the molten salt
of the reactor cell, the molten salt containing CaCl.sub.2 while Ca
being dissolved in the molten salt, and Ti or Ti alloys are
generated in said molten salt by supplying a metallic chloride
containing TiCl.sub.4 into said molten salt in order to cause the
metallic chloride containing TiCl.sub.4 to react with Ca generated
on a cathode electrode side by the electrolysis, Ti or Ti alloys
being formed in powder whose average particle size ranging from 0.5
to 50 .mu.m; and a Ti separation step of separating said Ti or Ti
alloys from the molten salt inside the reactor cell or outside the
reactor cell.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method for producing Ti
or Ti alloys through reduction by Ca, in which a metallic chloride
containing titanium tetrachloride (TiCl.sub.4) is reduced by Ca to
produce Ti metals or Ti alloys.
BACKGROUND ART
[0002] A Kroll method for reducing TiCl.sub.4 by Mg is generally
used as an industrial production method of the titanium metals. In
the Kroll method, the Ti metals are produced through a reduction
step and a vacuum separation step. In the reduction step,
TiCl.sub.4 which is of a raw material of Ti is reduced in a reactor
vessel to produce the sponge metallic Ti. In the vacuum separation
step, unreacted Mg and magnesium chloride (MgCl.sub.2) formed as
by-products are removed from the sponge metallic Ti produced in the
reactor vessel.
[0003] The reduction step will be described in detail. In this
step, the reactor vessel is filled with the molten Mg, and the
TiCl.sub.4 liquid is supplied from above on 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 particulate
metallic Ti. The generated Ti metals move sequentially downward. At
the same time, the molten MgCl.sub.2 which is of the by-product is
generated near the liquid surface. A specific gravity of molten
MgCl.sub.2 is larger than that of the 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 reducing reaction of TiCl.sub.4 proceeds continuously.
[0004] In the Ti metal production by the Kroll method, a
high-purity product is produced. However, a production cost is
increased and the product becomes remarkably expensive. One of
factors of increased production cost is the difficulty in enhancing
a feed rate of TiCl.sub.4. The following three items are cited as
the reason why the feed rate of TiCl.sub.4 is restricted.
[0005] In order to improve 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 increase a supply amount of molten Mg
to the liquid surface per unit area or unit time. However, when the
feed rate of TiCl.sub.4 is excessively increased, the
specific-gravity difference substitution cannot keep up with the
reaction rate, so that while MgCl.sub.2 remains in the liquid
surface, TiCl.sub.4 is supplied to the MgCl.sub.2. As a result, the
supplied TiCl.sub.4 becomes lower grade chloride gases (referred to
as "unreacted gas") such as an unreacted TiCl.sub.4 gas and a
TiCl.sub.3 gas, and the unreacted gas is discharged outside the
reactor vessel, which reduces utilization efficiency of TiCl.sub.4.
It is necessary to avoid the generation of the unreacted gas,
because a rapid increase in inner pressure of the reactor vessel is
associated with the generation of the unreacted gas. Thus, there is
a limit of the feed rate of TiCl.sub.4 because of the above
reasons.
[0006] When the feed rate of TiCl.sub.4 is enhanced, Mg vapor
generated from the liquid surface of the molten Mg reacts with
TiCl.sub.4 vapor to increase a precipitation amount of 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 reducing reaction proceeds. Therefore, the
precipitated Ti in the inner surface of the upper portion of the
reactor vessel is immersed in the molten Mg at a late stage of the
reducing reaction, which causes the effective area of the Mg liquid
surface to be decreased to 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 the
reactor vessel.
[0007] Therefore, Japanese Patent Application Publication No.
8-295955 proposes a method in which the reaction efficiency is
enhanced by supplying liquid TiCl.sub.4 in a dispersive manner to
the liquid surface in which the molten Mg exists, and thereby the
Ti precipitation is suppressed in the inner surface of the upper
portion of the reactor vessel. However, the method proposed in
Japanese Patent Application Publication No. 8-295955 is not enough
to suppress the Ti precipitation. 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 the
temperature is locally elevated. Therefore, cooling becomes
difficult, so that the feed rate of TiCl.sub.4 is restricted.
[0008] Although the feed rate of TiCl.sub.4 is not directly
affected, in the Kroll method, Ti is generated in the particulate
form near the liquid surface of the molten Mg liquid, and moves
downward. However, because of wetting properties (adhesion
properties) of the molten Mg, the generated Ti powder moves
downward while aggregated, and the Ti particles are sintered to
grow the Ti particles in size by the temperature condition of the
molten liquid during moving downward, which makes it difficult to
discharge the Ti particles outside the reactor vessel. Therefore,
the continuous production is difficult to perform, and the
improvement of the productivity is blocked. This is the reason why
the Ti is produced in the batch manner in the form of the sponge
titanium by the Kroll method.
[0009] 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, for example, 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 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, the Ti metals are generated from
TiCl.sub.4 by the reaction of the following chemical formula (a),
and CaCl.sub.2 as the by-product is also generated at the same
time. Ca has a stronger affinity for Cl stronger than Mg has, and
Ca is suitable for the reducing agent of TiCl.sub.4 in principle.
TiCl.sub.4+2Ca.fwdarw.Ti+2CaCl.sub.2 (a)
[0011] 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, a reaction field is enlarged compared with the Kroll
method in which TiCl.sub.4 is supplied to the liquid surface of the
reducing agent in the reactor vessel and the reaction field is
limited to near the liquid surface. Therefore, because the
exothermic area is also enlarged to facilitate the cooling, the
feed rate of TiCl.sub.4 which is of the raw material of Ti can be
largely increased, and the remarkable improvement of the
productivity can be also expected.
[0012] However, it is difficult that the method described in U.S.
Pat. No. 4,820,339 is adopted as the industrial Ti production
method. When using the metallic Ca powder as the reducing agent,
since the metallic Ca powder is extremely expensive, the production
cost is higher than that of the Kroll method in which the feed rate
of TiCl.sub.4 is restricted. In addition, the highly reactive Ca is
extremely difficult to handle, which can also be the factor of
blocking the industrial application of the method for producing Ti
through the reduction by Ca.
[0013] An example of other Ti production methods includes an Olsen
method described in U.S. Pat. No. 2,845,386. The Olsen method is a
kind of oxide direct-reduction method for directly reducing
TiO.sub.2 by Ca, in which TiO.sub.2 is directly reduced by Ca, not
through TiCl.sub.4. Although the oxide direct-reduction method is
highly efficient, the oxide direct-reduction method is not suitable
for the production of the high-purity Ti because it is necessary to
use high-purity TiO.sub.2.
DISCLOSURE OF THE INVENTION
[0014] 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.
[0015] In order to achieve the above object, the present inventors
consider that TiCl.sub.4 be reduced by Ca, and the present
inventors look into the method for utilizing Ca dissolved in the
molten salt of CaCl.sub.2 described in U.S. Pat. No. 4,820,339.
[0016] In the method described in U.S. Pat. No. 4,820,339, Ca in
the molten salt is consumed in the reducing reactor vessel as the
reaction expressed by the chemical formula (a) proceeds, and it is
necessary to continuously supply the metallic Ca powder to the
reducing reactor vessel. However, in order to industrially
establish the method for producing Ti through reduction by Ca, the
present inventors focus on a method for controlling a dissolved Ca
concentration in the molten salt by electrolysis in consideration
of the fact that it is necessary that the Ca consumed in the
reducing reaction is economically replenished into the molten
salt.
[0017] That is, when the molten CaCl.sub.2 is electrolyzed in a
reactor cell, electrode reactions expressed by the following
chemical formulas (b) and (c) proceed to generate a Cl.sub.2 gas
near the surface of an anode electrode while generating Ca near the
surface of a cathode electrode, which allows the Ca concentration
to be increased in the molten salt. Therefore, when TiCl.sub.4 is
supplied to CaCl.sub.2 so as to react with Ca generated on the
anode electrode side, because Ca consumed in the Ti generation is
replenished as needed, the replenishment of metallic Ca from the
outside or extraction of metallic Ca becomes unnecessary, which
allows the Ti metals to be economically produced. Anode electrode:
2Cl.sup.-.fwdarw.2e.sup.-+Cl.sub.2 (b) Cathode electrode:
Ca.sup.2++2e.sup.-.fwdarw.Ca (c)
[0018] The method for replenishing Ca consumed by the reduction of
TiCl.sub.4 with Ca generated by the electrolysis can also be
achieved by respectively performing the reduction and the
electrolysis in a reducing cell and an electrolytic cell to
circulate the molten CaCl.sub.2 between the cells. However, when
TiCl.sub.4 is supplied to the molten CaCl.sub.2 in the reactor cell
so as to react with Ca generated on the cathode electrode side by
the electrolysis, the reactor cell can commonly be used as the
reducing cell and the electrolytic cell. Therefore, because it is
not necessary to separately provide the reducing cell and the
electrolytic cell, there is a great advantage from a viewpoint of
installation cost compared with the case in which the molten
CaCl.sub.2 is circulated between the reducing cell and the
electrolytic cell.
[0019] The present invention is made based on the above
consideration, and the summary of the present invention is a method
for producing Ti or Ti alloys through reduction by Ca according to
the following (1) to (7).
[0020] (1) A method for producing Ti or Ti alloys through reduction
by Ca, including: a reduction electrolysis step in which a molten
salt is held in a reactor cell to perform electrolysis in the
molten salt of the reactor cell, the molten salt containing
CaCl.sub.2 while Ca being dissolved in the molten salt and Ti or Ti
alloys are generated in the molten salt by supplying a metallic
chloride containing TiCl.sub.4 into the molten salt in order to
cause the metallic chloride containing TiCl.sub.4 to react with Ca
generated on a cathode electrode side by the electrolysis; and a Ti
separation step of separating the Ti or Ti alloys from the molten
salt inside the reactor cell or outside the reactor cell, in which
the reactor cell is provided with a membrane which partitions an
inside of the reactor cell into an anode electrode side and the
cathode electrode side, the membrane blocking the movement of Ca
generated on the cathode electrode side in the reactor cell to the
anode electrode side while permitting the molten salt to flow in
the reactor cell (hereinafter referred to as "production method
described in (1)").
[0021] (2) A method for producing Ti or Ti alloys through reduction
by Ca, including: a reduction electrolysis step in which a molten
salt is held in a reactor cell to perform electrolysis using an
electroconductive porous material as an cathode electrode in the
molten salt of the reactor cell, the molten salt containing
CaCl.sub.2 while Ca being dissolved in the molten salt, and Ti or
Ti alloys are generated in the molten salt by supplying a metallic
chloride containing TiCl.sub.4 into the molten salt through the
cathode electrode in order to cause the metallic chloride
containing TiCl.sub.4 to react with Ca generated on a cathode
electrode side by the electrolysis; and a Ti separation step of
separating the Ti or Ti alloys from the molten salt inside the
reactor cell or outside the reactor cell (hereinafter referred to
as "production method described in (2)").
[0022] (3) A method for producing Ti or Ti alloys through reduction
by Ca, including: a reduction electrolysis step in which a molten
salt is held in a reactor cell to perform electrolysis in the
molten salt of the reactor cell, the molten salt containing
CaCl.sub.2 while Ca being dissolved in the molten salt, and Ti or
Ti alloys are generated in the molten salt by supplying a metallic
chloride containing TiCl.sub.4 into the molten salt in order to
cause the metallic chloride containing TiCl.sub.4 to react with Ca
generated on a cathode electrode side by the electrolysis; a Ti
separation step of separating the Ti or Ti alloys from the molten
salt inside the reactor cell or outside the reactor cell; and a
chlorination step of causing Cl.sub.2 to react with TiO.sub.2 to
generate TiCl.sub.4, Cl.sub.2 being generated on an anode electrode
side in association with the electrolysis, in which TiCl.sub.4
generated in the chlorination step is used for the Ti or Ti alloy
generation reaction in the reactor cell (hereinafter referred to as
"production method described in (3)").
[0023] (4) A method for producing Ti or Ti alloys through reduction
by Ca, including: a reduction electrolysis step in which a molten
salt is held in a reactor cell to perform electrolysis in the
molten salt of the reactor cell, the molten salt containing
CaCl.sub.2 while Ca being dissolved in the molten salt, and Ti or
Ti alloys are generated in the molten salt by supplying a metallic
chloride containing TiCl.sub.4 into the molten salt in order to
cause the metallic chloride containing TiCl.sub.4 to react with Ca
generated on a cathode electrode side by the electrolysis; and a Ti
separation step in which Ti or Ti alloys generated in the reactor
cell are extracted to an outside of the reactor cell along with the
molten salt and the Ti or Ti alloys are separated from the molten
salt outside the reactor cell (hereinafter referred to as
"production method described in (4)").
[0024] (5) A method for producing Ti or Ti alloys through reduction
by Ca, including: a reduction electrolysis step in which a
multi-system molten salt is held in a reactor cell to perform
electrolysis in the molten salt of the reactor cell, the
multi-system molten salt containing at least one of NaCl, KCl,
LiCl, and CaF.sub.2 in addition to CaCl.sub.2, Ca being dissolved
in the molten salt, and Ti or Ti alloys are generated in the molten
salt by supplying a metallic chloride containing TiCl.sub.4 into
the molten salt in order to cause the metallic chloride containing
TiCl.sub.4 to react with Ca generated on a cathode electrode side
by the electrolysis; and a Ti separation step of separating the Ti
or Ti alloys from the molten salt inside the reactor cell or
outside the reactor cell (hereinafter referred to as "production
method described in (5)").
[0025] (6) A method for producing Ti or Ti alloys through reduction
by Ca, including: a reduction electrolysis step in which a molten
salt is held in a reactor cell to perform electrolysis in the
molten salt in the reactor cell, the molten salt containing
CaCl.sub.2 while Ca being dissolved in the molten salt, and Ti or
Ti alloys are generated in the molten salt by supplying a mixed gas
containing TiCl.sub.4 and another metallic chloride into the molten
salt in order to cause the mixed gas to react with Ca generated on
a cathode electrode side by the electrolysis; and a Ti separation
step of separating the Ti or Ti alloys from the molten salt inside
the reactor cell or outside the reactor cell (hereinafter referred
to as "production method described in (6)").
[0026] (7) A method for producing Ti or Ti alloys through reduction
by Ca, including: a reduction electrolysis step in which a molten
salt is held in a reactor cell to perform electrolysis in the
molten salt of the reactor cell, the molten salt containing
CaCl.sub.2 while Ca being dissolved in the molten salt, and Ti or
Ti alloys are generated in the molten salt by supplying a metallic
chloride containing TiCl.sub.4 into the molten salt in order to
cause the metallic chloride containing TiCl.sub.4 to react with Ca
generated on a cathode electrode side by the electrolysis, said Ti
or Ti alloys being formed in powder whose average particle size
ranging from 0.5 to 50 .mu.m; and a Ti separation step of
separating the Ti or Ti alloys from the molten salt inside the
reactor cell or outside the reactor cell (hereinafter referred to
as "production method described in (7)").
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is a view showing a relationship between a mixture
ratio and a melting point in a binary-system mixed molten salt of
CaCl.sub.2 and NaCl;
[0028] FIG. 2 is a block diagram showing a Ti metal production
apparatus to which a first embodiment mode according to the present
invention can be applied;
[0029] FIG. 3 is a block diagram showing a Ti metal production
apparatus to which a second embodiment mode according to the
present invention can be applied; and
[0030] FIG. 4 is a block diagram showing a Ti metal production
apparatus to which a third embodiment mode according to the present
invention can be applied.
BEST MODE FOR CARRYING OUT THE INVENTION
[0031] 1. Contents of the Method According to the Invention
(Production Methods Described in (1) to (7))
[0032] In each of the methods according to the present invention
for producing Ti or Ti alloys through the reduction by Ca, for
example, the molten CaCl.sub.2 which is of the molten salt is held
in the reactor cell. When TiCl.sub.4 is supplied to the molten salt
in the reactor cell, TiCl.sub.4 is reduced by Ca dissolved in the
molten salt, and the particulate and/or powdery metallic Ti
(hereinafter referred to as "Ti particles") is generated. Although
Ca dissolved in the molten salt is consumed in association with the
generation of the Ti particles, because the electrolysis of the
molten CaCl.sub.2 progresses in conjunction with the reducing
reaction in the reactor cell, Ca is generated on the cathode
electrode side and the dissolved Ca which is consumed in the
reducing reaction is replenished with Ca generated by the
electrolysis. Therefore, the metallic Ca replenishment operation
and the metallic Ca extraction operation are not required while the
Ti particles are continuously produced.
[0033] Conventionally one of the main reasons why Ca is not used in
the industrial production of the Ti metals is the difficulty in
separating Ca and CaCl.sub.2. Mg is produced by electrolyzing
MgCl.sub.2, and the generated Mg can efficiently be recovered
because Mg is hardly dissolved in MgCl.sub.2. Similarly to Mg, Na
can efficiently be produced by electrolyzing NaCl. On the other
hand, Ca is produced by electrolyzing CaCl.sub.2, and the generated
Ca is dissolved in CaCl.sub.2 by about 1.5%.
[0034] Therefore, it is difficult to efficiently produce only Ca.
In addition, there is also a phenomenon in which the dissolved Ca
generates CaCl.sub.2 by a back reaction (reaction in which Ca
generated on the cathode electrode side is bonded to Cl.sub.2
generated on the anode electrode side to return to CaCl.sub.2), so
that the production efficiency of Ca becomes worsened. For example,
the improvement of a recovery factor of Ca is performed by cooling
an electrode. However, the production cost of Ca is still high.
[0035] However, in the method for producing Ti or Ti alloys through
the reduction by Ca according to the present invention, Ca
dissolved in the molten CaCl.sub.2 is used and the Ca separation is
not required, so that the Ca electrolytic production cost can be
decreased.
[0036] When the Ca reduction in the molten salt is utilized, the
reducing reaction field is expanded and the heat generation area is
simultaneously enlarged. Mg has vapor pressure of 6.7 kPa (50 mmHg)
at 850.degree. C. while Ca has extremely small vapor pressure of
0.3 kPa (2 mmHg). Therefore, in the case where Ca is used for the
reduction process, the Ti precipitation amount becomes dramatically
lessened in the inner surface of the upper portion of the reactor
cell when compared with the use of Mg. Accordingly, in the method
for producing Ti or Ti alloys through the reduction by Ca according
to the present invention, the TiCl.sub.4 feed rate can be largely
increased.
[0037] In addition, Ca is inferior in wetting properties (adhesion
properties) to Mg, and Ca adhering to the precipitated Ti particles
is dissolved in CaCl.sub.2, so that the particle growth caused by
the aggregation and the sintering in the generated titanium
particles are significantly lessened. Therefore, the generated Ti
can be discharged in the form of particles from the reactor cell,
and the Ti production can continuously be operated.
[0038] For a supply mode of TiCl.sub.4 to the molten CaCl.sub.2
liquid, it is particularly desirable that TiCl.sub.4 be directly
supplied in the gas state into the molten CaCl.sub.2 liquid because
of higher contact efficiency of TiCl.sub.4 with Ca in the molten
CaCl.sub.2 liquid. However, the TiCl.sub.4 supply mode is not
limited to the one in which TiCl.sub.4 in the gas state is
supplied. For example, it is also possible that either the liquid
or gaseous TiCl.sub.4 is supplies to the liquid surface of the
molten CaCl.sub.2 liquid, or it is also possible that either the
liquid or gaseous TiCl.sub.4 is supplied to either the liquid
surface or the inside of the molten Ca liquid held on the molten
CaCl.sub.2 liquid.
[0039] In the case where the reducing reaction is generated by
supplying the TiCl.sub.4 liquid to the surface of the molten Ca
liquid held on the molten CaCl.sub.2 liquid, it is desirable that
the molten Ca liquid be held in a thin state to an extent in which
Ca in the molten CaCl.sub.2 liquid can be utilized. When the Ca
layer is thin, because Ca in the molten CaCl.sub.2 liquid is
involved in the reaction, the reaction can range from the molten Ca
layer to the molten CaCl.sub.2 layer to continue the Ti generation
even if the specific-gravity difference substitution becomes unable
to keep up with it due to the increase in the TiCl.sub.4 feed
rate.
[0040] For the supply of TiCl.sub.4 gas, the method for producing
Ti or Ti alloys through the reduction by Ca according to the
present invention has various advantages compared with the Kroll
method.
[0041] That is, in the Kroll method, the TiCl.sub.4 liquid is
supplied to the liquid surface of the molten Mg liquid, and it has
been tried that the TiCl.sub.4 gas is supplied into the molten Mg
liquid in order to enlarge the reaction field. However, as
described above, since the Mg has the large vapor pressure, the Mg
vapor intrudes in a supply nozzle to react with TiCl.sub.4, and the
supply nozzle is choked.
[0042] Meanwhile. it has been tried that the TiCl.sub.4 gas is
supplied into the molten MgCl.sub.2 liquid. However, the nozzle
choking problem still remains although a choking frequency of the
supply nozzle is decreased. This is because sometimes the melt is
stirred by the bubbling of the TiCl.sub.4 gas to cause the molten
Mg to reach the supply nozzle. Even if TiCl.sub.4 is supplied to
the molten MgCl.sub.2 liquid, the reducing reaction is difficult to
occur because Mg is hardly dissolved in the melt.
[0043] On the contrary, in the method of utilizing the Ca
reduction, the nozzle choking is hardly generated, and the
TiCl.sub.4 gas can be supplied into the molten CaCl.sub.2 liquid.
The reason why the nozzle choking is hardly generated is attributed
to the fact that the molten Ca has the small vapor pressure.
[0044] That is, the method for producing Ti or Ti alloys through
the reduction by Ca according to the present invention, it is
particularly desirable that TiCl.sub.4 be directly supplied in the
gas state to the molten CaCl.sub.2 liquid, and this supply mode can
be applied without any problem in the actual operation. It is also
possible to adopt the supply mode in which either the liquid or
gaseous TiCl.sub.4 is supplied to the liquid surface of the molten
CaCl.sub.2 liquid or to the liquid surface or the inside of the
molten Ca liquid held on the molten CaCl.sub.2 liquid.
[0045] In the method for producing Ti or Ti alloys through the
reduction by Ca according to the present invention, the Ti
particles generated in the molten CaCl.sub.2 liquid can be
separated from the molten CaCl.sub.2 liquid either in the reactor
cell or outside the reactor cell.
[0046] However, when the separation is performed in the reactor
cell, the production mode becomes the batch manner. In order to
improve the productivity, the Ti particles and the molten
CaCl.sub.2 liquid can be separated from each other outside the
reactor cell by utilizing the Ti generated in the particulate form
to discharge the Ti particles outside the reactor cell along with
the molten CaCl.sub.2 liquid. This step is included as the Ti
separation step in the production method described in (4).
According to the production method described in (4), the Ti
particles can simply be separated from the molten salt by a
squeezing operation by means of mechanical compression.
[0047] For handling Cl.sub.2 generated by the electrolysis, as
stipulated by the production method described in (3), desirably
Cl.sub.2 is caused to react with TiO.sub.2 to generate TiCl.sub.4,
and the TiCl.sub.4 is used for the Ti or Ti alloy generation
reaction in the reactor cell.
[0048] In the case where Ti is produced by the method according to
the present invention, TiCl.sub.4 is used as the raw material.
However, the Ti alloy can also be produced by mixing TiCl.sub.4 and
other metallic chloride. Because TiCl.sub.4 and other metallic
chloride are simultaneously reduced by Ca, the Ti alloy particles
can be produced by this method.
[0049] TiCl.sub.4 and other metallic chloride may be used in either
the gas state or the liquid state. However, as stipulated by the
production method described in (6), because of higher contact
efficiency of TiCl.sub.4 with Ca in the molten CaCl.sub.2 liquid,
desirably TiCl.sub.4 and other metallic chloride are used in the
mixed gas containing TiCl.sub.4 and other metallic chloride is
used.
[0050] In the method according to the present invention for
producing Ti or Ti alloys through the reduction by Ca, there are
problems such as the back reaction and the reactor material
wastage. In the back reaction, Ca (Ca generated on the cathode
electrode side or the unreacted Ca) in the molten CaCl.sub.2 are
bonded to Cl.sub.2 generated on the anode electrode side, and Ca
returns to CaCl.sub.2. The reactor material wastage is caused by
the high reactivity of Ca. When the back reaction is generated, the
current efficiency is decreased because the electrolytic current is
consumed for the back reaction.
[0051] As stipulated by the production method described in (1), the
back reaction problem, particularly the back reaction in which Ca
generated on the cathode electrode side is bonded to Cl.sub.2
generated on the anode electrode side can effectively be suppressed
by using a reactor cell including a membrane which partitions the
electrolytic cell into the anode electrode side and the cathode
electrode side. The reactor cell holds the molten salt, and the
membrane permits the molten salt to be circulated in the
electrolytic cell while blocking the movement of Ca generated on
the cathode electrode side to the anode electrode side in the
reactor cell.
[0052] On the other hand, to address the problem of the reactor
material wastage, it is effective that the molten salt is not
formed by the single CaCl.sub.2 but formed by a mixed salt so that
a melting point of the molten salt is decreased to lower the molten
salt temperature (namely bath temperature). That is, as stipulated
by the production method described in (5), usually CaCl.sub.2
having the melting point of 780.degree. C. is used as the molten
salt. However, like binary molten salts such as CaCl.sub.2--NaCl
and CaCl.sub.2--KCl and ternary molten salts such as
CaCl.sub.2--NaCl--KCl, at least one of other salts (for example,
NaCl, KCl, LiCl, and CaF.sub.2) can be mixed into CaCl.sub.2 to
form a multi-system molten salt.
[0053] This enables the melting point of the salt to be decreased
to lower the molten salt temperature. As a result, a life of the
reactor material can be lengthened, the reactor material cost can
be reduced, and the Ca or salt vaporization from the liquid surface
can also be suppressed.
[0054] The mixed molten salt in which NaCl is added to CaCl.sub.2
particularly needs care among the multi-system molten salts.
[0055] FIG. 1 shows a relationship between a mixture ratio and a
melting point in the binary molten salt of CaCl.sub.2 and NaCl. The
melting point of CaCl.sub.2 is singly about 780.degree. C., while
the melting point of NaCl is singly about 800.degree. C. However,
when CaCl.sub.2 and NaCl are mixed together, the melting point is
decreased to about 500.degree. C. at the minimum. The melting point
of the mixed salt becomes not more than 600.degree. C. when the
mixture ratio of NaCl ranges from about 20% to about 45%.
[0056] In the multi-system mixed molten salt such as
CaCl.sub.2--NaCl and CaCl.sub.2--NaCl--KCl containing CaCl.sub.2
and NaCl, as shown in the following chemical formulas (d) and (e),
there is a critical phenomenon in which Ca is generated at
temperatures not more than 600.degree. C. while Na is generated at
temperatures more than 600.degree. C. That is, even if CaCl.sub.2
is mixed in NaCl to lower the molten salt temperature to be at
temperatures more than 600.degree. C., Ca is not generated but Na
is generated in the molten salt, and the reducing reaction by Ca
does not proceed.
[0057] Therefore, in the case where the molten salt temperature is
decreased by mixing the NaCl with CaCl.sub.2, NaCl is mixed such
that the molten salt temperature becomes not more than 600.degree.
C., and it is necessary to manage the molten salt at the
temperatures not more than 600.degree. C.
2Na+CaCl.sub.2.fwdarw.Ca+2NaCl (T.ltoreq.600.degree. C.) (d)
Ca+2NaCl.fwdarw.2Na+CaCl.sub.2 (T>600.degree. C.) (e)
[0058] As described above, it should be careful that the
restriction in use exists in the multi-system molten salt
containing CaCl.sub.2 and NaCl. In the meantime, the critical
phenomenon is desirable from the viewpoint of reactor material
protection because the large decrease in molten salt temperature
can be realized. In addition, the critical phenomenon effectively
suppresses the back reaction, particularly the back reaction in
which the unreacted Ca is bonded to Cl.sub.2 generated on the anode
electrode side and Ca returns to CaCl.sub.2.
[0059] Specifically, in the case where the Ti particles generated
on the cathode electrode side in the reactor cell is separated from
the molten salt, as described above, form the view point of
operation, it is rational that the Ti particles are extracted to
the outside of the cell along with the molten salt after use and
the Ti particles are separated from the molten salt outside the
cell. In this case, usually the molten salt separated from the Ti
particles is returned onto the anode electrode side in the reactor
cell, the molten salt contains the unreacted Ca although the molten
salt is already used, which results in the back reaction.
[0060] However, the unreacted Ca in the molten salt is replaced by
Na through the reaction of the chemical formula (e), when the
molten salt having the temperature not more than 600.degree. C.
extracted from the cathode electrode side in the reactor cell is
temporarily heated more than 600.degree. C. outside the reactor
cell before the molten salt is returned to the anode electrode side
in the reactor cell. Unlike Ca, Na is not dissolved in the molten
salt but Na is separated from the molten salt, so that Na can be
separated and removed from the molten salt.
[0061] Therefore, when the molten salt is returned to the cathode
electrode side in the reactor cell after Na is separated and
removed, even if the molten salt temperature is lowered to
600.degree. C. or less on the anode electrode side in the reactor
cell, the reaction of the chemical formula (d) does not progress to
block the Ca regeneration because Na is removed.
[0062] That is, in the multi-system molten salt containing
CaCl.sub.2 and NaCl, Ca is dissolved in the molten salt while Na is
not dissolved in the molten salt. When the molten salt temperature
exceeds 600.degree. C., Na is generated instead of Ca. When the two
phenomena are combined, the unreacted Ca contained in the molten
salt after use can be decreased to effectively suppress the back
reaction caused by the unreacted Ca and the decrease in current
efficiency.
[0063] As stipulated by the production method described in (7),
desirably the average size of the generated Ti particles of Ti
alloy particles ranges from 0.5 to 50 .mu.m. After the Ti or Ti
alloy particles are generated in the molten salt, the Ti or Ti
alloy particles are extracted from the reactor cell along with the
molten salt, and the Ti or Ti alloy particles are separated from
the molten salt. The Ti or Ti alloy particles having the sizes not
more than 50 .mu.m can be fluidized along with the molten salt.
When the particle size is more than 50 .mu.m, it is difficult that
the Ti or Ti alloy particles are extracted from the reactor cell
along with the molten salt. Unless the Ti or Ti alloy particles are
not less than 0.5 .mu.m, it is difficult that the Ti or Ti alloy
particles are separated from the molten salt after the
extraction.
[0064] 2. Embodiment Modes of Method According to the Invention
[0065] Embodiment modes of the present invention will be described
below with reference to the drawing.
[0066] FIG. 2 is a block diagram showing a Ti metal production
apparatus to which a first embodiment mode of the present invention
can be applied.
[0067] A reactor cell 1 in which the reducing reaction and the
electrolytic reaction concurrently occur is used in the first
embodiment mode. The reactor cell 1 holds the Ca-rich molten
CaCl.sub.2 in which the relatively large amount of Ca is dissolved
as the molten salt. CaCl.sub.2 has the melting point of about
780.degree. C., and the molten salt of CaCl.sub.2 is heated to at
least the melting point thereof.
[0068] In the reactor cell 1, the molten CaCl.sub.2 which is of the
molten salt is electrolyzed by passing the current between an anode
electrode 2 and a cathode electrode 3, the Cl.sub.2 gas is
generated on the side of anode electrode 2, and Ca is generated on
the side of cathode electrode 3. The inside of the reactor cell 1
is divided into the anode electrode side and the cathode electrode
side by a membrane 4. The membrane 4 is formed by a porous ceramic
thin plate, and the membrane 4 blocks the movement of Ca generated
on the side of the cathode electrode 3 toward the side of the anode
electrode 2 while permitting the molten salt to be moved.
[0069] In the reactor cell 1, the gaseous TiCl.sub.4 is injected in
the dispersive manner into the molten salt on the cathode electrode
side in the cell in parallel with the electrolysis of the molten
salt. Therefore, the injected TiCl.sub.4 is reduced to generate the
particulate metallic Ti by the Ca dissolved in the molten salt. The
generated Ti particles move downward by the specific gravity
difference and accumulate at the bottom on the cathode electrode
side in the reactor cell 1.
[0070] The Ti particles accumulating at the bottom on the cathode
electrode side of the reactor cell 1 are extracted from the reactor
cell 1 along with the molten salt existing at the bottom of the
reactor cell 1, and the Ti particles and the molten salt are sent
to a Ti separation step. In the Ti separation step, the Ti
particles and molten salt discharged from the reactor cell 1 are
separated from the molten salt. Specifically the Ti particles are
compressed to squeeze the molten salt. The Ti particles obtained in
the Ti separation step is melted and formed in a Ti ingot.
[0071] On the other hand, the molten salt separated from the Ti
particles in the Ti separation step is designated as the molten
salt after use in which Ca is consumed to decrease the Ca
concentration. The molten salt separated in the Ti separation step,
along with other molten salt after use separately extracted from
the reactor cell 1, is introduced to the anode electrode side in
the reactor cell 1.
[0072] Ca in the molten salt is consumed on the cathode electrode
side in the reactor cell 1 as the Ti particles are generated by the
reducing reaction. However, Ca is generated near the surface of the
cathode electrode 3 in the cell by the electrolysis which proceeds
concurrently in the cell, and the consumed amount of Ca is
replenished by Ca generated though the electrolysis. That is,
TiCl.sub.4 supplied into the molten salt is sequentially reduced in
a direct manner by Ca generated near the surface of the cathode
electrode 3.
[0073] On the other hand, the molten salt after use is sequentially
introduced from the Ti separation step on the anode electrode side
in the reactor cell 1. Therefore, a unidirectional flow of the
molten salt is formed from the anode electrode side toward the
cathode electrode side in the reactor cell 1 to avoid the flow of
Ca generated on the cathode electrode side into the anode electrode
side. In the first embodiment mode shown in FIG. 2, the membrane 4
is provided to divide the inside of the reactor cell 1 into the
anode electrode side and the cathode electrode side. The
combination of the provision of the membrane and the operation
creating the unidirectional flow further effectively suppresses the
back reaction and the decrease in the current efficiency caused
thereby.
[0074] The Cl.sub.2 gas generated on the side of the anode
electrode 2 in the reactor cell 1 is sent to a chlorination step.
In the chlorination step, the Cl.sub.2 gas is caused to react with
TiO.sub.2 and carbon (C) (chlorination) to generate TiCl.sub.4
which is of the Ti raw material. The generated TiCl.sub.4 is
introduced to the reactor cell 1, and TiCl.sub.4 is used in a
circulating manner to generate the Ti particles by the Ca
reduction.
[0075] Thus, in the first embodiment mode, the Ti particle
generation by the Ca reduction, i.e., the Ca consumption and the Ca
replenishment by the electrolysis are concurrently performed in the
reactor cell 1. Therefore, it is not necessary to perform the Ca
replenishment and Ca retrieval in the solid state, and the
high-quality Ti particles can be produced continuously and
economically through the Ca reduction. The reactor cell 1 is used
as both the reducing cell and the electrolytic cell, so that there
is an economical advantage in the facilities. The flow of Ca
generated on the cathode electrode side into the anode electrode
side is avoided in the reactor cell 1, so that the back reaction in
which Ca reacts with the Cl.sub.2 gas generated on the anode
electrode side can be prevented.
[0076] The molten salt temperature is managed to be more than the
melting point (about 780.degree. C.) of CaCl.sub.2 in each
step.
[0077] FIG. 3 is a block diagram showing a Ti metal production
apparatus to which a second embodiment mode of the present
invention can be applied.
[0078] The second embodiment mode differs from the first embodiment
mode in the following points. That is, a mixture of CaCl.sub.2 and
NaCl is used as the molten salt. In the mixture, CaCl.sub.2 and
NaCl are mixed together at a mixture ratio in which the melting
point of the mixture becomes not more than 600.degree. C. The mixed
molten salt is held at temperatures of not more than 600.degree. C.
in the reactor cell 1, and the mixed molten salt is held at
temperatures of more than 600.degree. C. in a separation cell 5
used in the Ti separation step.
[0079] Because the molten salt is held at temperatures of not more
than 600.degree. C. the reactor cell 1 in which the reducing
reaction and the electrolytic reaction concurrently occur (namely,
low-temperature reduction and low-temperature electrolysis are
performed), Ca which is of the reducing agent exists in the molten
salt (see chemical formula (d)), even if the molten salt is the
mixed molten salt of CaCl.sub.2 and NaCl. Therefore, the reducing
reaction by Ca and the Ca generation and replenishment by the
electrolysis are concurrently performed. The low-temperature
reduction and the low-temperature electrolysis are performed in the
reactor cell 1, so that the reactor material life can be lengthened
to decrease the reactor material cost.
[0080] Because Ca has the higher reactivity than that of Mg, the
development of the reactor material which can withstand Ca for a
long period is the important technological problem in the mass
production of Ti or Ti alloys. The molten salt temperature is
decreased to reduce the impact on the reactor material during the
operation by the low-temperature reduction and the low-temperature
electrolysis, so that the present invention largely contributes to
solve the problem of the reactor material life.
[0081] On the other hand, in the Ti separation step, the molten
salt and the Ti particles are extracted from the reactor cell 1
into the separation cell 5, or the molten salt is independently
extracted from the reactor cell 1 into the separation cell 5. The
molten salt extracted from the reactor cell 1 is already used, and
the molten salt contains the slight amount of unreacted Ca although
Ca is consumed. When the molten salt containing the unreacted Ca is
returned to the side of the anode electrode 2 in the reactor cell
1, the unreacted Ca reacts with the Cl.sub.2 gas generated on the
side of the anode electrode 2 to generate the back reaction.
[0082] However, in the second embodiment mode, unlike the reactor
cell 1, the molten salt is held at temperatures of more than
600.degree. C. in the separation cell 5, so that the unreacted Ca
slightly contained in the molten salt is replaced by Na (see
chemical formula (e)). Unlike Na, Ca is not dissolved in the molten
salt, Ca is separated to float on the molten salt, and Ca is
removed from the molten salt. The molten salt in which the
unreacted Ca (namely, reducing agent metal) is removed is sent to
the side of the anode electrode 2 in the reactor cell 1, and the
molten salt temperature is managed to br not more than 600.degree.
C. Because Na is removed as described above, the reaction of the
chemical formula (d) does not occur, and Ca is not regenerated.
Therefore, the back reaction caused by the mixture of the unreacted
Ca and the decrease in current efficiency caused by the back
reaction are blocked.
[0083] That is, the Ti separation step in the second embodiment
mode also functions as the Na separation step (reducing agent
separation step), and the unreacted Ca in the molten salt returned
to the reactor cell 1 is removed by previously replacing the
unreacted Ca with Na, which enables the rational and economical
operation to be realized. Na separated from the molten salt in the
separation cell 5 is sent back to the side of the cathode electrode
3 in the reactor cell 1, Na returns to Ca (see chemical formula
(d)) by managing the melt at temperatures of not more than
600.degree. C., and Na is reused for the reducing reaction.
[0084] The molten salt temperature in the separation cell 5 can
obviously be set at the same temperature as the reactor cell 1
whose temperature is not more than 600.degree. C. In this case,
there is an advantage from the viewpoint of reactor material
durability while the unreacted Ca cannot be removed.
[0085] FIG. 4 is a block diagram showing a Ti metal production
apparatus to which a third embodiment mode of the present invention
can be applied.
[0086] The third embodiment mode differs from the first embodiment
mode in a structure of the cathode electrode 3. That is, the third
embodiment mode is a configuration example of the Ti metal
production apparatus in which the production method described in
(2) can be performed. The cathode electrode 3 is made of an
electroconductive porous material in the third embodiment mode
while the cathode electrode 3 is made of the solid metals such as
Fe and Ti in the first embodiment mode. Specifically, the cathode
electrode 3 is made of the electroconductive porous material such
as a Ti sintered porous material and a Fe sintered porous material.
In the third embodiment mode, the TiCl.sub.4 gas which is of the Ti
raw material is supplied into the molten salt on the side of the
cathode electrode 3 in the reactor cell 1 through the porous
cathode electrode 3 (namely, flows through the inside of the porous
material).
[0087] In the case where TiCl.sub.4 is supplied into the molten
salt on the cathode electrode side in the reactor cell 1, it is
necessary that TiCl.sub.4 is supplied to a portion near the surface
of the cathode electrode 3 as much as possible. Because the Ca
generation by the electrolysis is performed near the surface of the
cathode electrode 3, the reaction efficiency is increased when
TiCl.sub.4 is supplied to the portion near the surface of the
cathode electrode 3. The productivity of the Ti particles is
further improved by adopting the third embodiment mode.
[0088] In the third embodiment mode, similarly to the second
embodiment mode, the mixed molten salt of CaCl.sub.2 and NaCl can
be used, the low-temperature reduction and low-temperature
electrolysis can be performed with the mixed molten salt of
CaCl.sub.2 and NaCl, and the unreacted Ca (reducing agent) can be
separated at high temperatures.
[0089] In the first to third embodiment modes, carbon or graphite
is used as the anode electrode 2 to generate the Cl.sub.2 gas.
INDUSTRIAL APPILCABILITY
[0090] According to the method for producing Ti or Ti alloys
through the reduction by Ca according to the present invention, the
feed rate of TiCl.sub.4 which is of the raw material can be
enhanced, and the high-purity Ti or Ti alloys can continuously be
produced. In the reactor cell, the reducing reaction and the
electrolytic reaction can concurrently be caused to proceed, and Ca
consumed in the reducing reaction can be replenished by the
electrolytic reaction, so that it is not necessary to singly handle
Ca. The back reaction caused by Ca can also effectively be
suppressed.
[0091] Accordingly, the method according to the present invention
can effectively be utilized as means for efficiently and
economically producing the high-purity Ti metals or Ti alloys, and
the method according to the present invention can widely applied to
the industrial Ti or Ti alloy production method.
* * * * *