FR2589228A1 - Device for continuous production of materials obtained from substances in the molten state - Google Patents

Abstract

Device for continuous production of materials obtained from substances in the molten state. It preferably comprises a nonpolluting crucible 2 for receiving substances allowing the formation of the material, leaktight means 14 for introducing the substances into the crucible, means 6 for heating by induction the contents of the crucible and nonpolluting and leaktight means 48 for continuous discharge of the material once it has been formed. For a material of the ceramic type, these discharge means may comprise a nonpolluting and leaktight container, linked to the crucible. Application to the production of glasses or of corrosive metals.

Description

DEVICE FOR CONTINUOUSLY MAKING MATERIALS
OBTAINED FROM MELTED SUBSTANCES
The present invention relates to a device for the continuous production of materials obtained from substances in the molten state. IT applies in particular to the development of a first category of materials called in the following non-metallic materials ", this first category comprising glasses, ceramics, oxides and highly corrosive molten salts, and a second category of materials including very reactive metallic materials.

 Devices for the preparation of materials, in particular corrosive materials, are already known from a mixture of substances in the molten state, but these devices cannot operate continuously and are unsatisfactory, in particular because that they are polluting vis-à-vis corrosive materials that one may want to obtain with a degree of purity as high as possible.

 It is known that many pure materials used in industry are, in the molten state, so aggressive against refractory materials, that they cannot be produced in a hot crucible. Their aggressiveness results in an attack on the crucible, which leads first of all to a pollution of the materials to be produced then to a piercing of the crucible. The development of such materials is therefore preferably carried out in a cold crucible and under a controlled atmosphere in an attempt to avoid any pollution.

These pure materials to be developed are divided into the two categories mentioned above:
- The first category including
glasses, ceramics, oxides and molten salts
very corrosive that we want to get to a high degree
purity, these materials being used for example
in the glass industry (phosphated glasses, glasses
textiles, enamels ...) or in the electronics industry,
and
- The second category including Metals
very reactive such as lanthanides, actinides,
Titanium, zirconium, hafnium and their alLiag
es, ... as well as other more classic metals
that silicon (similar to a metal because sufficient
electrically conductive due to dopants
it contains), tantalum ..., which we want to develop
from their oxides, fluorides or chlorides, to a
high degree of purity, according to reactions of the type:
MF + xR at xRF + MX
MO + xR ~ + ~ xRO + M
x
MCLX + xR + xRCl + M
reactions in which M represents a metal and R
a reducer.

Currently the materials of the first
category can be worked out in crucibles
cold copper, cooled by a refrigerated liquid
rant. The material produced freezes in contact with the
cold copper and therefore forms its own crucible, copper, which is no longer in contact with the molten material,
no longer under attack. The cold copper crucible is
for example formed of juxtaposed copper tubes, re
cooled independently of each other and transparent
rents to the magnetic field of a solenoid inductor
which surrounds The crucible. The material to be developed and
melting is thus heated by direct induction, its conductivity at high temperature allowing the circulation of induced currents which give it heat by the Joule effect.

 During the preparation of these materials, the emptying of the crucible is sequential and can be done either by tilting and overflowing this crucible, or by emptying from below through a pouring nozzle, but, on the one hand, the emptying must not be total in order to be able to continue heating (the presence of a little molten material is always necessary to allow the circulation of the induced currents), and on the other hand the sealing of the installation comprising the crucible does not must not be broken.

 In the case of emptying by tilting and overflowing, the tightness of this installation can practically not be maintained, which causes pollution of the material to be produced and in the case of emptying from the bottom, the pouring nozzle s' use by polluting the product to be produced and it is very difficult to stop the pouring before total emptying and therefore to start heating the contents of the crucible after each emptying.

 The materials of the second category can also be produced by induction heating in cold crucibles of the same type as the crucible described above. In this case, the metal to be produced is isolated from cold copper by a thin layer of slag originating either from the production reaction or from voluntary addition. The quantity of metal produced at each operation is limited by the formation of a large quantity of secondary products of the reaction (oxides, fluorides, chlorides, etc.).

 These secondary products float above the metal, fill the upper part of the crucible and freeze when their level exceeds that of the inductor, which stops the development of the metal.

 The object of the present invention is to remedy the drawbacks mentioned above, by proposing a device making it possible to continuously develop materials obtained from a mixture of substances in the molten state, such as Materials of the two categories considered. previously, and also allowing, in an advantageous embodiment, to develop these materials without pollution.

Specifically, the present invention relates to a device for preparing a material obtained 'from a mixture of substances in the molten state, characterized in that it comprises: - a crucible intended to receive the substances, - means for introducing the substances into the
crucible, from above, - induction heating means, intended for
heat and keep the contents of the
crucible, - means for continuously discharging the material formed
in the crucible, and, when the material is metal
lique, - means of continuous evacuation of products
condaries resulting from mixing.

 When the material is non-metallic, it is also possible to provide means for continuously discharging the secondary (gaseous) products resulting from the mixing.

 According to a particular embodiment of the device which is the subject of the invention, the material being non-metallic, the crucible is filled with said substances up to a given level and the means for discharging the material comprise a container communicating, at this level, with inside the crucible and able to capture the material formed.

 According to another particular embodiment of the device which is the subject of the invention, the material being metallic, the means for discharging the material comprise a hearth constituting the bottom of the crucible, this hearth being movable relative to the rest of the crucible and separable from that -this.

 In a particular embodiment of the invention, the material being metallic, the crucible is filled with said substances to a given level and the means for discharging the secondary products comprise a container communicating, at this level, with the interior of the crucible and able to capture the secondary products, which are kept in the molten state and are located at the top of said content.

 Preferably (for a metallic or non-metallic material), the device which is the subject of the invention furthermore comprises prevention means, intended to prevent the penetration of the substances into the container, before they have interacted to form the material.

 The container can be connected to the crucible by an inclined pipe from the crucible to the container.

 In a particular embodiment, the material being metallic, the device comprises means for induction heating of the secondary products, capable of maintaining these secondary products in the molten state during the preparation of the material.

 According to a preferred embodiment of the device which is the subject of the invention, in order to prepare materials without pollution, in particular Materials of the two categories mentioned above, the crucible and the means for discharging the material are non-polluting vis-å -vis the material, the introduction means are sealed and tightly connected inside the crucible and the material and secondary product discharge means are sealed and tightly connected inside the crucible .

According to various specific achievements, in order to achieve this pollution-free development
when the material is non-metallic and the device comprises the container mentioned above, this container is sealed, non-polluting vis-à-vis the material and communicates in leaktight manner with the interior of the crucible,
when the material is metallic and the device comprises the sole mentioned above, this sole can be sealed in the interior of the crucible,
- when the material is metallic and
The device comprises the container mentioned above, this container is sealed and communicates in a sealed manner with the interior of the crucible,
- when the device includes the prevention means mentioned above, these are non-polluting vis-à-vis the material,
when the device comprises the pipe mentioned above, this pipe is leaktight and non-polluting vis-à-vis the material when the latter is non-metallic,
- the crucible is electrically conductive, grounded, provided with cooling means and transparent to induction,
- the container used with a metallic or non-metallic material, is electrically conductive, provided with cooling means and grounded.

 Finally, preferably, the introduction means comprise an airlock provided for receiving the substances, and a watertight cover which communicates with this airlock and which sealingly closes the upper part of the crucible and includes means for entering and leaving the gas.

The present invention will be better understood on reading the description which follows, of embodiments given purely by way of indication and in no way limiting, with reference to the appended drawings in which
FIG. 1 is a schematic view of a particular embodiment of the device which is the subject of the invention, usable for developing continuously and in its pure state very corrosive non-metallic materials, and
- Figure 2 is a schematic view of another particular embodiment of the device object of the invention, usable for developing continuously and in the pure state of highly reactive metallic materials.

 FIG. 1 schematically shows a particular embodiment of the device which is the subject of the invention, intended for the preparation of non-metallic materials such as glasses, ceramics, oxides and molten salts. The device shown in FIG. 1 comprises a cold crucible 2, for example made of copper. This crucible can be made up of a plurality of tubes or sectors of square section, made of copper, closed at each end, arranged side by side along the generators of a cylinder of revolution and separated from each other by an electrical insulator such as 'a thin layer of alumina, the tubes being made integral with each other by a fiberglass bandage surrounding the crucible thus formed.

 The crucible is provided with cooling means: in the example given, the crucible is cooled by a fluid such as water, which is sent into the lower part of each sector from an input manifold 3 communicating with each sector, and recovered by an outlet collector 4 communicating with the upper part of each sector.

 The device also comprises a solenoidal inductor 6 which is placed around the crucible without touching it and which is supplied by a high frequency current source not shown, the frequency of which is chosen according to the material to be produced, so that the substances intended for the preparation of this material can be melted in the crucible.

 The latter is earthed in order to be maintained at zero potential, which makes it possible to connect the crucible, in a sealed manner and without any electrical insulation constraint, to other elements of the device such as the head of supply or container (mentioned later), thus ensuring user safety in a simple manner.

 In addition, the crucible 2 is closed at its lower part by a hollow hearth 8 made of copper, which is provided with cooling means 10 intended to circulate a cooling fluid such as water in the hearth 8, and which is connected tightly to the crucible by means of a seal 12.

 The device shown in FIG. 1 also comprises a supply head 14 surmounting the crucible 2 and connected to the latter in a leaktight manner by means of a seal 16. The connection between the supply head and the crucible does not poses no safety problem for users given the grounding of crucible 2.

 The feed head 14 comprises, from top to bottom, an airlock 18 for introducing the substances (products to be melted or raw materials for the reaction to be carried out for the preparation of the material) as well as a cover 20 which closes the top. of the crucible 2 via the seal 16 and which is connected to the airlock 18 by means of a pipe provided with a valve 22. The airlock 18 is provided at its upper part with a funnel 24 which is intended for the reception of the products to be melted or of the raw materials of the reaction and which communicates with the interior of the airlock 18 by means of a pipe provided with a valve 26. The airlock 18 makes it possible to preserve the purity of the atmosphere located above the molten bath that one wishes to form in the crucible 2.

 The airlock 18 also comprises a line 28 provided with a valve 30 and provided for the introduction into the airlock 18 of an inert gas such as nitrogen or a rare gas as well as a line 32 provided with a valve 34 and provided for the evacuation of said gas from the airlock 18.

The cover 20 is provided with - a pipe 36 comprising a valve 38 and
planned for the supply of sweeping gas (inert gas
or any other type), - of a pipe 40 provided with a valve 42 and provided
for the evacuation of sweeping gases and products
secondary gas resulting from the interaction of the substances introduced and melted in the crucible, a means for treating said secondary gaseous products which can be connected to the pipe 40 if it is desired to use these gaseous secondary products subsequently or if the latter are too toxic or polluting to be discharged directly outside the device, and finally - from a pipe 44 fitted with a valve 46 and rac
strung to pumping means not shown,
this pipe being intended to evacuate the atmosphere located above the molten bath in the crucible when the preparation of the material must be carried out under vacuum.

 The device shown in FIG. 1 also includes a container or ingot mold 48 the interior of which communicates with the interior of the crucible 2 by means of a pipe or chute 50 opening on one side into the upper part of the crucible 2, at a given level 52 thereof, and on the other side, in the upper part of the container 48. Thus, by forming in the crucible a molten bath up to level 52, the non-metallic material formed which is found the upper part of this bath, can it be continuously discharged Ia-cond5ti crn -d1alimentent the crucible sufficiently over time in substances intended for the formation of the material) in the container 48 through the pipe 50.

 The latter and the container are airtight vis-à-vis the atmosphere outside the crucible and the pipe 50 is tightly connected to the crucible 48 by means of a suitable waterproof and removable connection 56. The container 48 is for example made of a metal such as copper and grounded. In addition, this container is cooled by cooling means 51 (a circulation of water around the container 48 for example) in order to avoid any pollution of the pure material 58 filling it after having been produced in the crucible. In addition, the container 48 is provided with a pipe 60 itself provided with a valve 62 and intended for the evacuation of gas or the evacuation of the container 48 by means of pumping means not shown.

 As indicated above, the crucible 2 can be produced by juxtaposition of copper sectors. In this case, the pipe 50 can pass between two adjacent sectors or through one of the sectors. This pipe 50 can also pass over the inductor 6 or between two turns of this inductor without touching these turns. Finally, the pipe 50 can be made of a refractory material if the latter does not pollute the material produced in the crucible or of a metal if no refractory material resists corrosion of the material produced in the crucible, by providing in this case of the cooling means not shown of the pipe 50. In this case. also, the connection 56 may consist of a bolted flange, provided with a metal seal.

 The device of FIG. 1 also comprises a deflector 64 plunging into the molten bath 54 and intended to prevent the starting substances from being evacuated by the pipe 50 before having interacted to form the material. The deflector 64 is for example made up of a plate fixed inside the crucible to the upper part thereof, opposite the end of the pipe 50 opening into the crucible, this deflector being inclined from the inner wall from the crucible to the center of it. This deflector 64 can be metallic and cooled for example by a circulation of water not shown, or made of a refractory material that the produced material cannot corrode, if such a refractory material exists.

 The device shown in FIG. 1 operates as follows: the valve 26 being open and the valve 22 closed, the substances necessary for the preparation of the material are introduced into the airlock 18 via the funnel 24 .

The valve 26 is closed. The airlock 18 is swept by an inert gas which is introduced through the line 28 and evacuated through the line 32. The valve 22 is open. The substances then fall into the cold crucible 2 and are melted using the heating means 6. The quantity of substances introduced is chosen so that the molten bath then obtained reaches level 52. The material formed present in the upper part of the molten bath, can then flow through the pipe 50 to fill the container 48. The substances are periodically introduced into the crucible 2 through the supply head 14 so that the molten bath permanently reaches level 52.

 It is thus possible to continuously develop, at a very high degree of purity, very corrosive materials of the first category, under a controlled atmosphere and without any contact with a hot material which risks being corroded by the material produced.

 In Figure 2, there is schematically shown another particular embodiment of the device object of the invention, intended for the development of metallic materials and in particular very reactive metals such as lanthanides, actinides, titanium, hafnium and zirconium. The device represented in FIG. 2 comprises a cold crucible 2 identical to the crucible described with reference to FIG. 1. This crucible is surmounted by a supply head 14 connected in leaktight manner to said crucible by means of a seal 16 and identical to the feed head described with reference to FIG. 1. The crucible 2 is further provided with cooling means as explained with reference to FIG. 1.

The device of FIG. 2 also comprises a container 49 (provided with a pipe 60 itself provided with a valve 62 as indicated with reference to the container 48 in FIG. 1), a pipe 50, a connection 56 between this line 50 and
The container 49 and a deflector 64, all of these elements being identical to their counterparts described with reference to FIG. 1 and having a relative arrangement identical to the arrangement of these counterparts.

 The crucible 2 shown in Figure 2 has, at its lower part, a hearth 9 made of copper, provided with cooling means 10 as explained with reference to Figure 1 in connection with the hearth 8. But in the case in FIG. 2, the base 9 is movable and connected in a leaktight manner to the crucible 2 by suitable means such as a bellows 66 one side of which is fixed in a sealed manner around the periphery of the lower part of the crucible 2 and the other of which side is tightly fixed around the periphery of the floor 9 by suitable removable fixing means, such as a flange 68 to which the bellows 66 is fixed and which is screwed onto the floor 9, a seal being interposed between the latter and the flange.

 The device shown in Figure 2 also includes a solenoidal conductor 70 which surrounds the crucible 2 without touching it and which extends below the pipe 50 over a certain length of said crucible. This inductor 70 is connected to a source of alternating current of high frequency not shown, this frequency being chosen so as to be able to melt the substances introduced into the crucible and intended for obtaining the metallic material. Another solenoidal inductor 72 surrounds, without touching it, the crucible 2 at the level of the latter, into which the pipe 50 opens.

This passes between two adjacent turns of this other inductor or above it. This other inductor is connected to an alternating current source, not shown, the frequency of which is higher than
The frequency of the inductor supply current 6.

We can distinguish three regions in the
molten bath formed in the crucible: a first region
74 which extends between the inductor 70 and the sole 9 and
in which we find, in the solid state, the metal or
metallic material formed from the molten bath, a
second region or metallic phase 76, which is located
at the level of the inductor 70 and in which there is a wet tat Liwuide, this same metal, stall. and a third
supernatant region or phase 78, which extends from
from the second region to level 52 and in
which are the secondary reaction products
tion.

The frequency of the supply current of
the other inductor 72 is chosen so as to be able
maintain these secondary products in the molten state.

When the melting temperature of the metal
wishes to elaborate in the device of figure 2
is much higher than the melting temperature
of these reaction side products, the other in
ductor 72 is not necessary.

The device of Figure 2 is used from
the following way to elaborate a metal: the subs
tances necessary for the development of this metal are
introduced into crucible 2 up to level 52, by
via the supply head 14, used
for this purpose as explained with reference to the
figure 1. The contents of the crucible are melted and then maintained
naked in the molten state thanks to the inductor 70, and the other
inductor 72 when the melting temperature of the mate
metallic thread is less than or close to tem
reaction temperature of secondary reaction products
tion.

The elaboration reaction takes place in
the supernatant phase 78 and the metal drops elabo
re descend into the metallic phase 76 and then from there to the bottom of the crucible, where a metal ingot is formed. A small proportion of the secondary products of the reaction slips between the molten metal and the cold crucible so as to form a thin thin insulating layer 80 which protects the cold copper of the crucible from corrosion by the molten metal. The movable sole 9 descends as the metal is produced.

Thus is kept constant "the upper level" 82 (substantially curvilinear) of the liquid metal in the crucible. The metal solidifies when it leaves the zone heated by the inductor 70 and an ingot 74 of pure metal is therefore obtained by continuous drawing surrounded by a thin layer of slag formed by the secondary products of the reaction.

 The ingot can be cut during drawing, to the desired length. To do this, this length being reached (which can be known by timing for example), the sole, which then occupies a position 84 shown in phantom in Figure 2, is held in place by non-support means shown, the fixing means 68 are disassembled and the bellows 66 is reassembled and held in the high position, thus showing the ingot whose cutting can be carried out by a sawing machine 86 for example.

 Most of the by-products of the elaboration reaction float above the liquid and are evacuated through the sealed pipe 50 to the sealed container 49. The deflector 64 prevents the substances introduced into the crucible from being evacuated towards the container 49 before having reacted.

 The device of FIG. 2 thus makes it possible to develop continuously and at a very high degree of purity, in the form of ingots of desired length, very reactive metals, the development being carried out under a controlled atmosphere and without any contact of the metal. with a hot material which may corrode on contact.

Claims (16)

 1. Device for preparing a material obtained from a mixture of substances in the molten state, characterized in that it comprises: - a crucible (2) intended to receive the substances, - means (14 ) the introduction of substances into  the crucible, from above, - means (6; 70, 72) of induction heating,  intended to heat and maintain the molten state  contents of the crucible, - means (48, 50; 9) for continuously discharging the  material formed in the crucible, and when the mate  riau is metallic, - means (49, 50) for continuous discharge of pro  secondary products resulting from the mixture.  2. Device according to claim 1, characterized in that, the material being non-metallic, the crucible (2) is filled with said substances up to a given level (52) and in that the means for removing the material comprise a container (48) communicating, at this level, with the interior of the crucible and capable of capturing the material formed.  3. Device according to claim 1, characterized in that, the material being metallic, the material discharge means comprise a hearth (9) constituting the bottom of the crucible, this soLe being movable relative to the rest of the crucible and separable from this one.  4. Device according to any one of claims 1 and 3, characterized in that the material being metallic, the crucible is filled with said substances up to a given level (52) and in that the means for discharging the secondary products comprise a container (49) communicating, at this level, with the interior of the crucible and able to capture the secondary products, which are kept in the molten state and are located at the top of said content.  5. Device according to any one of claims 2 and 4, characterized in that it further comprises prevention means (64), provided to prevent the penetration of substances into the container (2), before they did not interact to form the material.  6. Device according to any one of claims 2, 4 and 5, characterized in that the container (48, 49) is connected to the crucible (2) by a pipe (50) inclined from the crucible to the container.  7. Device according to any one of claims 1 and 3 to 6, characterized in that, the material being metallic, this device comprises means (72) of heating by induction of the secondary products, capable of maintaining these secondary products at the melt during the development of the material.  8. Device according to claim 1, ca acterized in that the crucible (2) and the means (48, 50; 9) for discharging the material are non-polluting vis-à-vis the material, in that the means d introduction (14) are sealed and tightly connected inside the crucible and in that the means (9, 48, 49, 50) for evacuating the material and the secondary products are sealed and tightly connected to inside the crucible.  9. Device according to claim 8, characterized in that, the material being non-metallic, the device conforms to claim 2 and in that the container (48) is sealed, non-polluting vis-à-vis the material and communicates tightly with the interior of the crucible (2).  10. Device according to claim 8, characterized in that, the material being metallic, the device conforms to claim 3 and in that the sole (9) is reliably sealable inside the crucible (2).  11. Device according to any one of claims 8 and 10, characterized in that, the material being metallic, the device conforms to claim 4 and in that the container (49) is leaktight and communicates leaktightly with the 'inside the crucible (2).  12. Device according to any one of claims 9 and 11, characterized in that the device conforms to claim 5 and in that said prevention means (64) are non-polluting vis-3-vis the material.  13. Device according to any one of claims 9, 11 and 12, characterized in that the device conforms to claim 6 and in that the pipe (50) is sealed and non-polluting vis-à-vis the material when this one is non-metallic lique.  14. Device according to any one of claims 8 to 13, characterized in that the crucible (2) is electrically conductive, grounded, provided with cooling means (4) and transparent to induction.  15. Device according to any one of claims 9 and II to 14, characterized in that the container (48, 49) is electrically conductive, provided with cooling means (51) and grounded.  16. Device according to any one of claims 8 to 15, characterized in that the introduction means (14) comprise an airlock (18) provided for receiving the substances, and a sealed cover (20) which communicates with this airlock and which tightly closes the upper part of the crucible (2) and comprises gas inlet and outlet means (36, 40, 44).