Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~044~99
The present invention relates to a process for prod~lcing metallic
zirconium, more particularly relates to a process for producing metallic
zirconium wherein zirconium tetrachloride is reduced with metallic
magnesium and then the obtained metallic zirconium is distilled in
S vacuum to remove the byproduced magnesium chloride and unreacted
metallic magnesium which are present in said obtained metallic zirconium.
A prior industrial production of metallic zirconium has been
càrried out by reducing zirconium tetrachloride with metallic magnesium
at a high temperature and under an inert gas atmosphere. In this process,
metallic magnesium is charged in a reducing crucible which is provided
at a lower part of a retort and is heated to melt and then is reacted with
zirconium tetrachloride vapor which is generated by a sublimation of
solid zirconium tetrachloride in an upper part of the retort and which i9
introduced onto the surface of the molten metallic magnesium from the
top of the reducing crucible to thereby deposit and adhere the obtained
zirconium sponge on the inner wall of the reducing crucible; and then
the obtained zirconium sponge in the reducing crucible is subjected to a
vacuum distillation.
Furthermore, another process has been proposed for the produc-
tion of metallic zirconium in which zirconium tetrachloride vapor is fed
from outside the retort into the reducing crucible inside the retort to
reactwith molten metallic magnesium contained in the reducing crucible,
and by_produced magnesium chloride alone is taken out from the reduc-
ing crucible, and then the obtained zirconium sponge in the reducing
crucible is subjected to a vacuum distillation.
In both vacuum distilling operations, the crucible is entirely
placed in a vacuum distillation device for a removal of by-produced
magnesium chloride and unreacted metallic magnesium from the zirco-
nium sponge at a high temperature and under a reduced pressure.
According to the former process, in the reducing step there are
disadvantages that a velocity of the generation of zirconium tetrachloride
vapor is very low, the reaction time is considerably long, the reaction
velocity can not be controlled and the obtained zirconium sponge is dense,
and particularly in the vacuum distillation step there are disadvantages
that the zirconium sponge should be subjected to a vacuum distillation with
an entire amount of by-produced magnesium chloride and unreacted
metallic magnesium and as a result the amount of the zirconium sponge
to be distilled becomes comparatively small.
According to the latter process, in the reducing step the above
mentioned disadvantages can be overcome but there are disadvantages
that it is necessary to provide a valve at the comparatively upper part
of the reducing crucible in order to remove the impurity such as
magnesium chloride which is by-produced after the completion of the
reducing reaction and since the construction and provision of this valve
are very complicated and the sealing of the valve is very difficult and
thus this process is unpractical, and particularly in the vacuum distilla-
tion step there are still same disadvantages as described in the former
proces s .
The principal object of the present invention is to provide an
improved process for producing metallic zirconium which can completely
mitigate the aforesaid disadvantages in the vacuum distillation of these
conventional processes for producing metallic zirconium by reducing
zirconium tetrachloride with metallic magnesium.
The another object of the present invention is to provide a process
for producing metallic zirconium wherein the most part of the by-produced
magnesium chloride and unreacted metallic magnesium can be separated
from the obtained metallic zirconium without the complication of the device.
The present invention is a process for producing metallic zirconium
characterized in that a reducing crucible deposited with zirconium sponge
which is formed by reducing zirconium tetrachloride with metallic magnesium
in a reducing reaction device is put out from the reducing reaction device
and only the part which is deposited with zirconium sponge in the reducing
cruciblc is cut and the lower cut parts are piled up in a device for a
vacuum distillation and then the zirconium sponge which is deposited in
5 the cut parts is purified by a vacuum distillation.
The above objects and advantages of the present invention may be
appreciated by referring to the following description, taken in conjunction
with drawings, in which:
Fig. 1 is a schematic side view, the section, of a conventional
10 dev;ce for reducing zirconium tetrachloride;
Fig. 2 is a schematic side view9 in section, of another conventional
device for reducing zirconium tetrachloride;
Fig. 3 is a schematic side view, in section, of a device for reducing
zirconium tetrachloride which is suitable for the practice of the process
of the present invention; and
Fig. 4 is a schematic side view, in section, of a vacuum distilla-
tion device which is suitable for the practice of the process of the present
invention.
In a prior conventional process for producing metallic zirconium,
20 the device for reducing zirconium tetrachloride shown in Fig. 1 being used,
a pre-solidified zirconium tetrachloride 12 which is deposited on an outer
coil 1 and an inner coil 2 is heated by heating element 5 to vaporize, and
the obtained zirconium tetrachloride vapor is descended, and it is intro-
duced into a reducing crucible 8 through holes 7' which are provided on a
25 vapor phase can 7. The zirconium tetrachloride vapor is reacted with a
molten metallic magnesium 9 to form metallic zirconium 11 and magnesium
chloride 10. In Fig. 1, 3 is a gas valve, 4 is a heating elements, 6 is a
retort, 13 is a heating element and 14 is a baffle plate.
According to the another process, the device for reducing zirconium
30 tetrachloride shown in EFig. 2 being used, a reducing crucible 8 is provided
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10448~9
in a retort 15 which is heated by a heating element 16, zirconium tetra-
chloride vapor is introduced from the top of the reducing crucible 8 and
then is reacted with metallic magnesium 9 contained in the reducing
crucible 8 to form zirconium sponge 11 and magnesium chloride 10.
~ince a longer time than the time which is necessary for a removal of
impurity such as magnesium chloride is required at the following vacuum
distillation of the zirconium sponge in this condition, the impurity such
as magnesium chloride is discharged by providing a valve Vl for discharge~
ingtheimpurity at the upper part of the reducing crucible 8, In Fig, 2,
V2 is a valve for discharging magnesium chloride from the retort 15,
In the process of the present invention, the cutting of the reducing
crucible is carried out in the point of view that when metallic zirconium
is produced by the reduction of zirconium tetrachloride with metallic
magnesiùm, magnesium chloride and other impurities are formed as a
by-product and the separation of these by-products from the metallic
zirconium requires a remarkably long time even if a vacuu~n-distillation
is effected and therefore it is possible to reduce the distillation time if
a large portion of these magnesium chloride and other impurities has
been already removed from the metallic zirconium before the vacuum
distillation is effected.
Namely, the reducing crucible is cut off from the part of the
reducing crucible which contains a large portion of magnesium chloride
and other impurities and which is deposited with a minor amount of
metallic zirconium,
In this case, it is preferable to cut the reducing crucible at a
predetermined height. In short, it is an aim to remove a large portion
of magnesium chloride and other impurities so that it is preferable to
cut off the remaining portion of the reducing crucible which is deposited
with metallic zirconium containing a very small quantity of magnesium
chloride and other impurities.
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lV~89g
The process of the present invention will be illustrdtively explained
with reference to Figs. 3 and 4.
~eferring to l~ig. 3, a reducing crucible 8 is provided in a retort
17 which is heated in a gas furnace G and which is isolated from the air.
The reducing crucible 8 is provided with a guide pipe 19 for zirconium
tetrachloride vapor and is degassed to a vacuum and then an inert gas
such as argon gas is introduced thereinto. Then the reducing crucible 8
is heated to a temperature of 800 to 900C to melt metallic magnesium
contained therein. At that time, the pressure in the retort 17 is main~
tained at about 0. 1 kg/cm2 (gauge pressure).
Then zirconium tetrachloride vapor is introduced into the reducing
crucible 8 through a feeding tube 18 and a guide pipe 19. In the reducing
crucible 8, the zirconium tetrachloride is reacted with a molten metallic
magnesium to form zirconium sponge 11 and the formed zirconium sponge
11 is accumulated on the bottom of the reducing crucible 8. Due to the
difference between the specific gravity of the molten magnesium chloride
and that of the molten metallic magnesium, the latter overlies the former
and as a result the reduction of zirconium tetrachloride by metallic magnesium
proceeds continuously.
When the pressure inside the retort 17 is remarkably raised and
also zirconium tetrachloride vapor becomes to bleed through the bleeding
valve 21, the reduction is concluded and then the introduction of zirconium
tetrachloride vapor is stopped. When the reducing crucible 8 gets cold,
it is taken out of the retort 17 and is cut at the line A - A shown in Fig. 3 toseparate the large portion of magnesium chloride and metallic magnesium
from the zirconium sponge. The remaining magnesium chloride is dis-
charged by a suitable means. In Fig. 3, 10 is metallic magnesium, 20 is
a feeding pipe for zirconium tetrachloride vapor and 22 is an evacuation
pipe.
The lower cut part of the reducing crucible 8 in which the zirconium
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iO4~1~9~
~pon~Je is con~ined is transferrecl to a vacuum distil~ation
d4 vic~ after the ma~ncsium chlorid~ content has bccn removed.
On the other hand, the magnesium chloride is dis-
charged from the remaining upper part of the reducing crucible
8 which contains a lar~e portion of ma~nesium chloride and
therea~ter the magnesium chloride is separated from ~he zirconium
sponge which is adhered to the inner wall of the upper part of
the reducing crucible 8 and the adhered zirconcium sponge is
scraped out from the crucible wall by a suitable mechanical
means and the scraped zirconium sponge is distilled in vacuum
to remove co-existing magnesium chloride and unreacted metallic
magnesium, and then the zirconium sponge is chlorinated to form
zirconium tetrachloride which is re-used.
The vacuum distillation of the zirconium sponge
which is present in the lower cut part of the reducing crucible
is carried out in the vacuum distillation device as shown in
Fig. 4.
In a lower furnace 28, there is placed a distillate
reservoir 29 provided with an evacuation tube 24 at the lower
level, a baffle plate 26 along the wall of the reservoir 29 and
distillate discharging means 25 at the bottom. The distillate
reservoir 29 is also provided with astand 23 on the rack 30 at
the top for mounting in a stack plural lower cut part 8' of the
reducing crucible containing zirconium sponge 11 (in Fig. 4,
the vacuum distillation device contains three such parts). A
heated upper furnace 27 for the stack is placed on the lower
furnace 28 and over the retort encasing the stack of the crucible
portions in a sealed way. In Fig. 4, 31 is a retort and 32 is
a heating element.
The zirconium sponge is distilled in vacuum at a
temperature of about l,000C and under a reduced pressure of
10 2 Torr for several days, is cooled, and is taken out of the
lower cut part of the reducing crucible 8 in sequence.
As understood from the description set forth above,
according to
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.. . . ... . . . . . . .
lV4~9~3
the process of the present invention the space inside the retort 31 of the
vacuum distillation device is effectively occupied by a stack of lower cut
parts of the reducing crucible generally filled with the zirconium sponge,
with small amount of contaminants as compared with the sponge. ThereforeJ
5 the efficiency of the whole operations are considerably increased as com-
pared with that of the prior conventional processes.
The operation of the particular embodiment of the present invention
will now be described in an example for using at least two reducing devices
as shown in Fig. 3 and the vacuum distilling device as shown in Fig. 4.
The reducing crucible charged with 850 to 1, 000 kg of metallic
magnesium is placed inside the retort, and the space inside the retort is
degassed to vacuum and heated to a temperature of 250- to 300-C, and
thereafter the space is filled with argon gas at a pressure of about 0. 1 kg/cm2.
Then the retort is heated to the temperature of 800C to melt
metallic magnesium therein and kept at that temperature for 5 to 8 hours.
The pressure inside the retort is kept at about 0.1 kg/cm2 by an occasional
bleeding in case of remarkable pressure raise. Zirconium tetrachloride
vapor is fed at a rate of 65 kg/h through the feeding tube into the reducing
crucible with the initial pressure inside the storage tank (not shown) for
zirconium tetrachloride of 1. 2 to 1 5 kg/cm2 In the feedings, differential
pressure inside the storage tank and the retort is kept at 0 1 to 0. 2 kg/cm2.
The pressure inside the retort is kept at 0.1 to 0, 2 kg/cm2 by an occasional
bleeding in case of remarkable pressure raise. The reducing operation is
carried out at a temperature of about 850C for 30 to 40 hours with the
production of zirconium sponge at a rate of 25 kg/h on an average. By
bleeding of the zirconium tetrachloride vapor in a remarkable pressure
raise inside the retort, the conclusion of the reducing reaction is recognized.
After several hours of cooling following the conclusion of the reaction,
the reducing crucibles are taken out of the furnace, cut as shown in the line
A - A of Fig. 3, and discharged from magnesium chloride. Magnesium
104~
chloride remaining in the upper part of the reducing crucibles is pres~ed
out mechanically, and the zirconium sponge which is adhered to the reducing
crucible wall is mechanically scraped out therefrom and the scraped zirco-
nium sponge is separated from magnesium chloride and other impurities
and unreacted metallic magnesium by a vacuum distillation and crushed into
lumps for a chlorination of zirconium sponge. The lower parts of the
reducing crucibles which are cut are piled up together in the vacuum distilla-
tion device for removal of magnesium chloride, unreacted metallic magnesium
and other contaminants from zi~conium sponge, under the reduced pressure
of 10-2 mmHg and at a temperature of about 1, 000C for a week. The zir-
conium sponge is discharged from the lower parts of the reducing crucibles
which are withdrawn from the vacuum distillation device and is crushed to
give a product.
After three runs of vacuum distillation (for six batches ), the furnace
is heated to 800 C to melt metallic magnesium for recovery into a ladle
(not shown). The metallic magnesium thus recovered is used again for the
reduction of zirconium tetrachloride after the washing of the metallic
magnesium with an acid.
The lower part of the reducing crucible free from zirconium sponge
is welded to the upper cut part of the reducing crucible to re-use for the
reducing reaction.
As described above in detail, the operation time of the process of
the present invention is far shorter than that of conventional processes in
which the zirconium sponge is distilled to remove the most of the magnesium
chloride, because the most of the magnesium chloride by-produced during
the reducing operation is removed from zirconium sponge before the distilla-
tion in vacuum is carried out so that the volume to be distilled in vacuum
is small. Furthermore, the number of necessary vacuum distillation
d evice~
dovioc is less than that of reducing furnaces (at most as many vacuum
distillation device as reducing furnaces ). According to the present invention,
4~'3'3
reducing furnaces are free from a complicated means for discharging
by-products as required conventionally.
