Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACK~OUND OF TnE INVENTION
The present invention relates to a vacuum-suction
degassing apparatus, in which gas-forming solute
ingredients are removed or recovered from a melt, such
as a molten metal, matte, or slag, through a porous
member.
Conventionally, the RH method, DH method, and other
degassing methods are used to remove gas-forming solute
ingredients from a molten metal. According to the RH or
Dl-l method, a large quantity of argon gas is blown into
the melt, the surface of which is kept at a vacuum or at
reduced pressure so that the partial pressure of the
gas-forming ingredients is lowered, thereby removing
these ingredients.
Requiring the use of argon gas in large quantity,
however, the conventional RH or DH degassing method
entails high running cost. Slnce much argon gas is
blown into the melt, moreover, the melt is liable to
splash so that many metal drops adhere to the wall
surface or some other parts of the apparatus, which
requires troublesome removal work. To cope with this
splashing of the melt, furthermore, the apparatUs is
inevitably increased in size, resulting in higher
equlpment cost.
SUMMARY OF ~ INVENTION
The obJect of the present invention is to provide a
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vacuum-suction degassing apparatus, in which gas-forming
ingredients can be easily removed from a melt without
using a large quantity of argon gas, so that the melt
can be degassed at low cost by means of a simple
apparatus.
A vacuum-suction degassing apparatus according to
' the first invention, a vessel containing a melt; a
porous member made of a porous material permeable to gas
and impermeable to melts, a portion thereof being
immersed in said melt in the vessel; and sucking means
for sucking gas from said melt or gas produced by a
reaction between said melt and said porous material
through said partitioning member, in a manner such that
the portion of said porous member which protrude over
the surL'ace oL' said melt is kept at a vacuum or at a
reduced pressure.
A vacuwll-suction degassing apparatus according to
the second invention, a vessel'containging a melt; a
cylindrical non-porous member; a porous member made o-L~ a
porous material permeable to gas and impermeable to
melts, being fitted into the lower portion of said non-
porous member and immersed in said melt in said vessel;
and sucking means for sucking gas from said melt or gas
produced by a reaction between said melt and sald porous
material through said partitioning member, in a manner
SUCtl that the inside o~' said non-porous member is kept
at a vacuum or at a reduced pressure. The partitioning
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member is sucked by said sucking means, thereby the
inside of the partitioning member being kept at a vacuum
or at reduced pressure. Also, the melt is stirred by
moving said partitioning member in said melt by said
stirring means so that gas in the melt or gas produced
by the reaction between the melt and the porous member
can be moved to vacuum or reduced pressure space inside
the partitioning member through said partitioning member
made of a porous material with high efficiency. Also,
the vacuum suction degassing apparatus according to the
present lnvention does not have to use argon gas, so
that its running cost is low and also it is possible to
suppress generation of splashes and reduce deposition of
base metal onto a wall surface of the apparatus. Thus,
according to the present invention, it is possible to '
reduce the equipment cost as well as its running cost.
Accordlng to the first invention, a portion of a
porous member made o~ a porous material which allows
permeation of gases but does not allow permeation of
molten materials is immersed in a melt, and another
portion of said porous member which protrudes above the
surface o~ melt is put in vacuum or under reduced
pressure. Gases o~ said melt or gases produced by
reactions between said melt and said porous material are
sucked through said porous member by sucking means.
According to the second invention, a porous member
is fitted into the lower portion o~ a cylindrical non-
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porous member and the porous member is immersed in saidmelt. Inside of said non-porous member is evacuated or
depressurized, and gases in said melt or gases produced
by reactions between said melt and said porous material
are sucked through said porous member by sucking means.
Thus, solute components in the melt, which produce
a gas phase, can easily be moved to the vacuum or
reduced pressure atmosphere.
Different from the conventional degassing method
where a large volume of argon gas is blown lnto, in this
invention, argon gas is not blown into, or a small
i volume of argon gas only enough to stir the melt is
b]own, so that an amount of argon gas used can
remarkably be reduced. Also, as the amount of argon gas
is extremely low, generation o~ splashes is suppressed,
and deposition of base metal on a wall surface of a
device can be reduced. For this reason, according to
the present invention, equipment cost can be reduced by
minimizing size of the apparatus, and also runnlng cost
can remarkbly be reduced.
BRIEF DESCRIPTION OF T~E DRAWINGS
Fig. 1 is a diagram ~or illustrating the principle
of the present invention,
Fig. 2 is a schematic cross-sectional view showing
a ~irst embodiment of the invention,
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Fig. 3 is a schematic cross-sectional view showing
second embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
First, description is made for a principle of this
invention with reference to Fig. 1. Partitioning member
1 is made of a porous material which is permeable to
gas, but impermeable to melts, such as molten metal,
molten matte, or molten slag. If melt 2 is brought Into
contact with one side of porous member 1, and if the
other side of member 1 is kept at a vacuum or at a
reduced pressure 3, the pressure on the wall surface in
contact with the melt drops without regard to the static
pressure o~ melt 2.
Accordingly, those impuritles or valuables in melt
2 which produce gaseous substances easily nucleate on
the wall surface of porous member 1 to form gas 4, and
resulting gas 4 permeates through member 1 and sucked
into space 3 at vacuum or reduced pressure atmosphere so
that the impurities or valuables are removed from the
melt and recovered lnto space 3 at vacuum or reduced
pressure atmosphere.
The inventor hereof realized that gas-~orming
ingredients can be removed from the melt on the basis o~
the principle described above, and brought the present
invention to completion.
The gas-~orming ingredients dissolved in the melt
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are sucked and removed ln the form of gases as follows:
N + N = N2 --- (1)
_ + H = H2 --- (2)
C + O = CO --- (3)
S + 20 = S02 --- (4)
The impurities in the melt may react with the
ingredients of the porous member, to form gases, and
then they may be removed through the porous member.
If the porous member is an oxide (MxOy), carbon in
the melt is removed in the form of a gas as follows:
yC + MxOy (solid) = xM + yCO --- (5)
If the porous member contains carbon, moreover,
oxygen in the melt is sucked and removed according to
the following reaction formula.
0 + C (solid) = CO --- (6)
The separative recovery of a valuable component (M)
which has high vapor pressure is achieved by gasifying
the valuable component according to the following
reaction ~ormulas.
xM = MX (gas) --- (7)
MOy = MOy (gas) --- (8)
MSy = MSy (gas) --- (g)
In this manner, the impurities, such as N, ~1, C, O,
and S, and the valuable components are sucked and
removed or recovered from the melt.
According to the present invention, by ad~usting
content of components of the partitioning member which
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react with the impurities or valuable components in a
melt, it is possible to control a reaction rate between
the impurities or valuable components in the melt and
components of the partitioning member.
~- 5 Note that a heating means may be added to heat a
porous member or a melt by energizing the porous member ;~
or burying a resistance wire previously in the porous
member and energizing the resistance wire, or by heating
the melt ~rom outside ( by means of, ~or instance,
plasma heating), for the purpose to prevent the
decrease o~ temperature of the melt due to heat emission
to atmosphere or the vessel or the decrease o~
temperature of the melt which occurs when the porous
member is immersed into the melt, or decrease of
temperature o~ the melt due to an endothermic reaction
between components o~ the porous member and the melt.
Various materials may be used ~or porous member,
includlng metal oxides or other metallic compounds (non-
oxides), carbon and mixtures thereo~ and metal, such as
Al2O3, MgO, CaO, SiO2, Fe2O3, Fe3O4~ Cr23~ BN~ Si3N4,
SlC, C, etc.. Preferably, the material used should not
react with the principal ingredient o~ melt 2 so that
porous member in contact with melt 2 can be prevented
~rom erosion loss and melt 2 can be kept clean.
Also, a material which hardly gets wet with melts
must be used ~or the partitloning member so that only gases
can pass through the partitioning member but any melt
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can not pass through the partitioning member.
Furthermore, it is preferable that a porosity of the
partitioning member is not more than 40%.
Furthermore, in order to prevent a melt from
entering the vacuum system even if a melt goes into the
immersed porous tube, it is preferable to allocate a
filter with small pressure loss in an upper section-of
the immersed porous tube to solidify the invading melt
-for trapping it.
The following is a description of a case in which
the present invention is applied to the removal or
recovery of gas-forming ingredients from a melt.
(1) First, the present invention can be applied to
decarburization, denitrogenation, and dehydrogenation
processes for removing carbon, nitrogen, or hydrogen
from molten iron.
When this method is applied to remove carbon from
molten iron, the main component of said partitioning
member should be Al2O3 or MgO, and such a material as
Fe2O3, Fe3O4, MnO, and SiO2 etc. should be mixed in as
main oxidizing agents for carbon in the molten iron.
But i-f a compounding ratio of the main oxidizing agent
is too high, a melting point of the partitionirlg member
goes down, or the mechanical strength thereof becomes
lower, and lr carbon content in the molten iron is too
low, oxygen content, in the molten iron goes up, so that a
compounding ratio of the main oxidizing agent must be
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declded according to the purpose and by re-ferring to the
phase diagram already established.
On the other hand, if this method is applied to
removal of nitrogen in molten iron, a stable oxide such
as CaO, Al2O3, or MgO should be used as said
partitioning member.
Also, i-f this invention is applied to simultaneous
removal of carbon and nitrogen in molten iron, the
compounding ratio o-f the oxidizing agent should be
changed according to target contents of carbon and
nitrogen in the molten iron.
(2) The invention can be also applied to a
deoxygenatlon process ~or removing oxygen from molten
copper.
(3) Further, the invention can be applied to a
dehydrogenatlon process for removing hydrogen -~rom molten
alumlnum.
(4) Furthermore, the invention can be applied to
decarburization, and dehydrogenation o~ molten silicon.
(5) According to the present invention, zinc can be
recovered ~rom molten lead.
(6) The invention can be also applied to a
desulfurization/deoxygenation process ~or removing
sulfur and oxygen ~rom molten copper matte.
' z5 (7) Further, the invention can be applied to the
" recovery o~ valuable metals (As, Sb, Bi, Se, Te, Pb, Cd,
etc.) ~rom molten copper matte or nickel matte.
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; (8) Furt}lerlllore, the invention can be applied to
the recovery of valuable metals (As, Sb, Bi, Se, Te, Pb,
Cd, Zn, etc.) from slag.
Detailed description is made below ~or embodiments
o-f this invention.
Fig.2 is a schematic cross-sectional view showing a
vacuum-suction degassing apparatus according to an
embodiment of the present invention. Melt 2 is stored
in vessel 5, and a lower half portion of porous member 6
is immersed in this molten material 2. Porous member 6
has a form of rod, and is made of a porous material
having pores which is permeable to gases and impermeable
to melts, such as molten metal, molten slag, and molten
matte. Therefore, melt 2 do not pass through.
Vessel 5 is placed in a decompression container (not
shown), and inside of the decompression container is
evacuated by the vacuum pump to maintain the inslde in
vacuum or under reduced pressure.
In the vacuum-suction degassing apparatus thus
constructed, although melt 2 does not permeate through
porous member 6, but as gases contained in pores of
porous member 6 are released to inside of the
decompression container, inside o~ pores o-f porous
member 6 are evacuated or depressurized. There-fore,
gases in melt 2 or gases produced by reactions between
components o~ the porous member 6 and the melt a pass
through the pores of porous member 6, and are released
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into vacuum or reduced pressure atmosphere in the
I decompression container. And, the gases are sucked by
i the vacuum pump and removed from inside o~ the
decompression container.
Fig.3 is a schematic cross-sectional view showing a
vacuum suction degassing apparatus according to an
embodiment of the second invention in this application.
Melt 2 is stored in vessel 5. Porous member 6a has
a form of rod, and is fitted into the lower portion of
cylindrical non-porous member 8 in a liquid-sealing
manner. Porous member 6a is made of a porous material
having pores which gases can permeate through but melt
2, such as molten metal, molten slag, or molten matte
can not enter and permeate through. Also, non-porous
member 8 is made of a non-porous material which gases
can not permeate through, and is linked to a vacuum pump
(not shown).
In the vacuwn suctlon degassing apparatus having
the con~iguratlon as described above, when inside of
norl-porous member 8 is evacuated or depressurized,
inside of pores of porous member 6 is evacuated or
depressurized. Therefore, gas-forming components in
molten 2 are exhausted through the pores of porous
member 6a into inside of non-porous member 8. And, the
gas-forming components are sucked by the vacuum pump and
recovered or exhausted.
Also in this embodiment, porous member 6a has only
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to be immersed in molten material 2, and even i~ depth
of a melt bath is small, degasification of molten
materials can be performed.
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