阅读说明：本技术 用于将粉末状材料玻璃化的方法和装置 (Method and device for vitrifying a powdery material ) 是由 弗兰克·布吕诺 金-保尔·罗伯特-阿尔瑙伊尔 于 2018-07-20 设计创作，主要内容包括：本发明涉及一种用于将粉末状材料玻璃化的方法和装置,其中所述粉末状材料被引入到由第一腔室(11)界定的熔化区域中,借助被保护气体环绕的至少一个等离子体炬(15)在熔池(14)中熔化以供应所述池,所述熔池(14)的一部分从所述熔化区域递送到至少一个浇铸区域,每个浇铸区域由与所述第一腔室(11)流体连通的对应第二腔室(16)界定,并且其中熔池的所述部分在每个对应浇铸区域的溢流区域中被抽出。根据本发明,实施以下步骤：-抽出所述熔化区域内所述粉末状材料熔化所产生的气体和烟雾,所述气体和烟雾被至少一个屏障石(17)堵在所述第一腔室(11)中,每个屏障石(17)位于所述熔化区域和对应浇铸区域之间,每个屏障石(17)布置成使得至少它的自由端部同样能够决定从所述熔化区域流向所述对应浇铸区域的所述熔池(14)的所述部分,以及-在每个第二腔室(16)中至少抽出在所述抽出步骤期间产生的所述气体和烟雾。(The invention relates to a method and a device for vitrifying a powdery material, wherein the powdery material is introduced into a melting zone delimited by a first chamber (11), melted in a melt pool (14) by means of at least one plasma torch (15) surrounded by a protective gas to supply the pool, a portion of the melt pool (14) being delivered from the melting zone to at least one casting zone, each casting zone being delimited by a corresponding second chamber (16) in fluid communication with the first chamber (11), and wherein the portion of the melt pool is extracted in an overflow zone of each corresponding casting zone. According to the invention, the following steps are carried out: -extracting gases and fumes produced by the melting of the powdery material in the melting zone, said gases and fumes being trapped in the first chamber (11) by at least one barrier stone (17), each barrier stone (17) being located between the melting zone and the corresponding casting zone, each barrier stone (17) being arranged so that at least its free end is also able to determine the portion of the molten bath (14) that flows from the melting zone to the corresponding casting zone, and-extracting at least the gases and fumes produced during the extraction step in each second chamber (16).)

1. A method for vitrifying a powdered material, wherein the powdered material is introduced into a melting zone delimited by a first chamber (11), is melted in a melting bath (14) by means of at least one plasma torch (15) to feed the bath, the melting bath (14) being located in the melting zone, a portion of the melting bath (14) being delivered from the melting zone to at least one casting zone, each of the casting zones being delimited by a corresponding second chamber (16) in fluid communication with the first chamber (11), and wherein the portion of the melting bath is extracted in an overflow zone of each corresponding casting zone, characterized in that the following steps are carried out:

-extracting gases and fumes produced by the melting of the powdery material in the melting zone, said gases and fumes being trapped in the first chamber (11) by at least one barrier stone (17), each barrier stone (17) being located between the melting zone and the corresponding casting zone, each barrier stone (17) being arranged so that at least its free end is also able to determine the portion of the bath (14) flowing from the melting zone to the corresponding casting zone, and

extracting in each second chamber (16) at least said gases and fumes generated during said extraction step.

2. A method as claimed in claim 1, characterized by regulating the level of the molten bath (14), the extraction of the gases and fumes produced by the melting of the powdery material in the melting zone and the extraction of the gases and fumes in each second chamber (16) so as to promote the flow of molten material from the molten bath (14) to each casting zone.

3. The method according to claim 1 or 2, wherein each overflow zone comprises an outlet port having a side wall delimiting a passage through which the portion of the withdrawn molten bath (14) passes, at least part of said side wall extending outside the corresponding second chamber (16) comprising at least one orifice through which at least part of the gases and fumes are captured, so as to dilute the gases and fumes thus captured with external air.

4. A method according to any one of claims 1 to 3, wherein each overflow zone comprises an outlet port through which said portion of the extracted molten bath (14) passes, at least part of said gases and fumes produced during said extraction step being captured by one or more apertures located in the vicinity of said outlet port.

5. A method according to any one of claims 1 to 4, characterized in that, for at least one plasma torch (15), at least the portion of the plasma torch (15) located inside the first chamber (11) is surrounded by a protective gas curtain to protect at least said portion, at least one means for introducing a gaseous fluid being shaped for introducing and generating said gas curtain around said at least one portion.

6. The method according to any one of claims 1 to 5, characterized in that the overflow area of each casting area comprises a casting nozzle delimiting the level of the molten bath (14); for each casting zone, adjusting the height of the corresponding casting nozzle to adjust the level of the molten bath (14) such that, in operation, at least the free end of the corresponding barrier stone (17) is permanently submerged, thereby maintaining a seal between the molten bath and the corresponding casting zone for the gases and fumes generated in each of the molten bath and the corresponding casting zone.

7. An apparatus for vitrifying a powdered material, the apparatus for carrying out the method according to any one of claims 1 to 6, the apparatus comprising: a first chamber (11) delimiting a melting zone of the powdery material, the first chamber (11) comprising at least one plasma torch (15) for generating a melt pool (14) from the powdery material; at least one second chamber (16) delimiting a casting zone of molten material, said first and second chambers being in fluid communication so that a portion of the molten bath (14) flows from the melting zone to each corresponding casting zone, each casting zone comprising an overflow zone having an outlet port for withdrawing said portion of the molten bath (14), characterized in that

A barrier stone (17) is located between the melting zone and each casting zone and is arranged so that at least its free end defines the portion of the melt pool (14) that flows from the melting zone to the corresponding casting zone, the barrier stone (17) thus being intended to come into contact with the melt pool (14) in order to block gases and fumes produced in the melting zone and non-molten gases and fumes, the first chamber (11) comprising means for extracting the gases and fumes present in the melting zone, and

each second chamber (16) is configured to capture at least the gases and fumes generated during the extraction of the molten material.

8. The device according to claim 7, characterized in that each second chamber (16) comprises one or more holes for extracting the gas and fumes connected to a circuit for extracting the gas and fumes, said holes being located near or in the extraction port.

9. The apparatus according to claim 7 or 8, wherein the outlet port of each second chamber (16) comprises a side wall defining a passage for extracting said portion of the molten bath, said side wall extending outside the corresponding second chamber (16) and comprising at least one hole for extracting said gases and fumes, so that during the extraction of said portion external air is mixed with the gases and fumes collected thereby so as to dilute said gases and fumes.

10. The device according to any one of claims 7 to 9, characterized in that it comprises at least two second chambers, each defining a casting zone in fluid communication with the melting zone of the first chamber (11).

11. The device according to any one of claims 7 to 10, wherein the first chamber (11) has a circular, rectangular, square or oblong cross-section.

12. The device according to any one of claims 7 to 11, characterized in that it comprises at least one injection means for injecting a protective fluid at least a portion of at least one plasma torch (15) located inside the first chamber (11), said injection means being configured to generate a gas curtain around said portion so as to protect it from the extreme conditions prevalent in the first chamber (11).

13. The apparatus of claim 12, wherein the shielding gas is air or an inert gas.

Technical Field

The invention relates to a method for the continuous vitrification of powdery materials and to a device for carrying out said method.

The method and apparatus of the present invention are primarily intended to render inert, by vitrification, powdery or small-particle materials containing toxic substances such as asbestos or heavy metals such as mercury or lead, and their salts.

Background

It is well known that processing or producing materials in powder form may cause some of these materials to disperse into the surrounding atmosphere.

Such dispersions may be a source of risk for poisoning and may also act as a carrier for toxic gases or liquids.

Therefore, the handling and disposal of these powdered materials is a significant challenge from both a health and environmental standpoint.

For example, incineration of household, industrial or medical waste is considered a source of powdered material.

Specifically, incineration of household waste produces solid and gaseous emissions or incineration fumes.

The solid emissions form the mineral part of the waste, in particular, contain so-called "under boiler" ash, which are highly toxic powdered materials. In fact, these ashes contain heavy metals and their salts.

The gaseous effluents are more or less acidic in character, due to the presence of acidic gases such as HCl and HF, and SO₂And CO₂And the like gaseous acid anhydrides. These gaseous emissions also contain toxic compounds, such as heavy metals and their salts, and solid residues known as fly ash.

These gaseous emissions or fumes must be filtered and treated to neutralize their acidity, concentrate metals and their salts and hold the fly ash before being released into the atmosphere.

Currently, vitrification is considered to be the primary method of inerting these materials or hazardous incineration waste for storage or even recovery.

In fact, these silica and alumina containing materials liquefy and form a melt when subjected to temperatures above 1300 ℃.

This melt, when cooled, forms a crystalline material or a solid amorphous glass, a true heavy metal holding matrix, which can then be disposed of.

For example, document FR 2764877 in the name of the applicant discloses an apparatus for vitrifying a powdered material to be treated by melting it using a non-transferred arc plasma torch.

Although effective, this vitrification system causes some inconvenience.

Firstly, the device for vitrifying a powdered material comprises a furnace comprising a zone for melting the powdered material and a zone for casting a bath, these two zones being separated by a barrier stone. The suction fan draws out the gases and fumes produced by the melting of the powdery material in the melting zone through a duct.

It can therefore be observed that only a portion of the gases and fumes generated during the vitrification of the powdered material can be extracted for treatment. Thus, a significant portion of these gases and fumes are released into the surrounding environment, with deleterious effects on organisms that come into direct contact with them.

Furthermore, an inappropriate pressure difference applied between the melting zone and the casting zone can lead to losses when flowing from the melt bath to the corresponding casting zone, and even to losses when unmelted powdery material (also referred to as "unmelted") passes through.

In addition, wear of the barrier stones was also observed due to their prolonged contact with the molten material flowing from the bath to the casting area.

The wear of this block of barrier stone can cause the loss of watertightness between the two chambers it separates. Thus, fumes and gases generated by the melting of the powdered material in the melting zone may pass from the melting zone into the casting zone and be released into the surrounding atmosphere.

In addition, it can be seen that a barrier stone worn in this way would most likely result in a free access to the casting area.

Objects of the invention

The present invention is intended to overcome the drawbacks of the prior art and to address the above drawbacks by proposing a method for continuous vitrification of a powdered material that is simple, reliable and inexpensive in design and mode of operation.

In particular, one object of the present invention is a vitrification process for capturing all the gases and fumes generated during vitrification, preventing their release into the surrounding atmosphere, and thus controlling the health and environmental impact of such vitrification processes.

Another object of the invention is a method for significantly mitigating the deterioration of the extraction circuit of the gases and fumes produced by the vitrification of the powdered material, so as to eliminate maintenance operations over time.

Another object of the invention is a method of maintaining a seal between the melt zone and the casting zone during production.

The invention further aims to provide a device for implementing such a method, intended to render inert, by vitrification, a powdered material comprising toxic compounds, in particular heavy metals and their salts.

In particular, the method and the device of the invention allow an effective control of the melting process of the powdered material and of the obtainment of amorphous glass or crystalline material, which meet all the criteria applicable to the storage of inert waste even its recovery (for example, as building material).

Disclosure of Invention

To this end, the invention relates to a method for vitrifying a powdered material, wherein the powdered material is introduced into a melting zone delimited by a first chamber, is melted by means of at least one plasma torch in a melt pool for feeding the pool, the melt pool being located in the melting zone, a portion of the melt pool being delivered from the melting zone to at least one casting zone, each of the casting zones being delimited by a corresponding second chamber in fluid communication with the first chamber, and during which said portion of the melt pool is extracted in an overflow zone of each corresponding casting zone. According to the invention, the following steps are carried out:

-extracting gases and fumes produced by the melting of the powdery material in the melting zone, said gases and fumes being trapped in the first chamber by at least one barrier stone, each barrier stone being located between the melting zone and the corresponding casting zone, each barrier stone being arranged so that at least its free end is also able to determine the portion of the bath flowing from the melting zone to the corresponding casting zone, and

-extracting in each second chamber at least the gases and fumes generated during said extraction step.

This powdered material is introduced through at least one inlet port into a melting zone defined by the first chamber.

Each barrier stone determines or limits the amount of molten material flowing from the molten bath in the first or main chamber to the casting zone in the second chamber, this barrier stone preferably being arranged at the inlet of the casting zone.

During operation of the vitrification device, at least the end of this barrier stone is immersed in the molten material of the molten bath to provide a seal that prevents gases and fumes produced by the melting of the powdered material in the melting zone from propagating to the casting zone. The at least submerged end of this barrier stone also prevents unmelted or unmelted material from entering the casting area.

Advantageously, the overflow area of each casting area is located at one end of the corresponding casting area. By way of illustration only, this overflow region has a slope that slopes toward the outlet port, along which the molten material flows.

Advantageously, by means of the method of the invention, all gases and fumes produced in the vitrification device can be captured and evacuated therefrom for disposal. Any dispersion behaviour of the fumes and/or harmful gases into the atmosphere surrounding the vitrification device, in particular during the extraction phase, is thus avoided, which necessitates the addition of means for capturing their fumes.

According to one aspect of the method of the invention, the level of the bath, the extraction of gases and fumes produced by the melting of the powdered material in said melting zone and the extraction of gases and fumes in each second chamber are regulated so as to promote the flow of the molten material from the bath to each casting zone.

Such an embodiment is advantageously made possible by immersing at least the end of the at least one barrier stone separating the melting zone from the corresponding casting zone in the molten material, thereby ensuring the seal between these two zones.

Thus, the pressure of each zone is independently controlled, which makes it possible to regulate the bath level and the flow of the withdrawn molten material.

A pressure balance may be sought at least between a first chamber defining the melting zone and a second chamber defining the corresponding casting zone.

It is also possible to generate a negative pressure in the at least one second chamber which is greater than the negative pressure established in the first chamber containing the melt bath, in order to generate a suction effect on the at least one second chamber.

Such adjustment is effected, for example, by controlling the suction fan.

According to another aspect of the method of the invention, each overflow zone comprises an outlet port having a side wall delimiting a passage through which said portion of the withdrawn molten bath passes, at least part of said side wall extending outside said corresponding second chamber comprising at least one orifice through which at least part of said gases and fumes are captured, so as to dilute said gases and fumes thus captured with external air.

In fact, it was observed that the captured gases and fumes were acidic and caused rapid deterioration of the metal pipes of the collecting device that collected and discharged them.

Maintenance operations are then required to maintain the tightness of the extraction circuit, which requires the shut down of the vitrification system.

This makes the operation very costly.

Such external air extraction facilitates dilution of the gases and fumes thus captured, protecting the elements of the gas and fume extraction circuit located downstream.

Such embodiments also attempt to avoid cooling the vitrified tongue or molten material flowing through the outlet port, ensuring its extraction.

Alternatively or additionally, each overflow zone comprises an outlet port through which the portion of the withdrawn molten bath passes, at least a portion of the gases and fumes produced during the withdrawal step being captured by one or more apertures located in the vicinity of the outlet port.

Thus, these ports are located on the body of the corresponding second chamber, close to the outlet port.

According to another aspect of the process of the present invention, for at least one plasma torch, at least a portion of said plasma torch located inside said first chamber is surrounded by a protective gas curtain to protect at least said portion, at least one means for introducing a gaseous fluid is shaped for introducing and generating said gas curtain around said at least one portion.

According to yet another aspect of the method of the invention, the overflow zone of each casting zone has a casting nozzle defining the bath level; for each casting zone, adjusting the height of the corresponding casting nozzle to adjust the bath level such that at least the free end of said corresponding barrier stone is permanently submerged when the apparatus is in operation or production, thereby maintaining a seal between the bath and the corresponding casting zone for gases and fumes generated in each of the bath and the corresponding casting zone.

The invention also relates to a device for implementing the method for vitrifying a powdered material as described above, such device comprising: a first chamber defining a melting zone for the powdered material, the first chamber comprising at least one plasma torch for producing a melt pool from the powdered material; at least one second chamber defining a casting zone for molten material, the first and second chambers being in fluid communication such that a portion of the molten bath flows from the casting zone to each corresponding casting zone, each casting zone including an overflow zone having an outlet port for withdrawing the portion of the molten bath.

According to the present invention, there is provided,

-a barrier stone is located between the melting zone and each casting zone and is arranged so that at least its free end defines said portion of the melt pool flowing from the melting zone to the corresponding casting zone, whereby said barrier stone is intended to come into contact with the melt in order to block gases and fumes produced in the melting zone and unmelted material, said first chamber comprises means for extracting the gases and fumes present in the melting zone, and

-each second chamber is configured to capture at least gases and fumes generated during the extraction of said molten material.

Advantageously, the at least one plasma torch is a non-transferred arc plasma torch.

In various specific embodiments of such vitrification systems, each specific embodiment has its own specific advantages and utilizes a variety of possible technical combinations:

this first chamber comprises at least one means for injecting a powdered material into said chamber.

Preferably, each injection device is configured to ensure that the powdered material introduced thereby has a downward component from the first chamber and a horizontal component towards the casting area.

Advantageously, each introduction device is located on said first chamber, opposite the corresponding casting zone, with respect to the bath.

The overflow zone of each casting zone comprises a casting nozzle delimiting the bath level, at least the height of said casting nozzle being variable in order to adjust its position and thus vary the bath level, so that at least the free end of said barrier stone is submerged, ensuring the sealing of the corresponding casting zone and the melting zone,

-each second chamber comprises one or more holes for extracting said gas and fumes connected to a circuit for extracting gas and fumes, said holes being located near or in said extraction port.

Such embodiments have the advantage of maintaining heat in the extraction port and thus improve the flowability of the material to be extracted.

This extraction circuit advantageously comprises an interconnection duct, the inside of which is under vacuum, ensuring that the gases and fumes are extracted and conveyed to the gas and fume treatment unit.

By way of example, at least one first extraction hole may be located in a lower portion of the corresponding second chamber, close or proximate to the outlet port, in order to collect gases and fumes generated during the extraction of the molten material from the vitrification device.

-the outlet port of each second chamber comprises a side wall defining a passage for extracting said portion of the molten bath, said side wall extending outside said corresponding second chamber and comprising at least one hole for extracting said gases and fumes, so that during the extraction of said portion external air is mixed with said gases and fumes collected thereby so as to dilute said gases and fumes.

Such embodiments allow air to be sucked in through the free end of the outlet port, so that the gases and fumes captured thereby are diluted before being conveyed through the extraction circuit. Thus, the elements, for example the pipes of the extraction circuit, are advantageously protected.

Advantageously, at least one of these extraction holes is located below or below the overflow area.

By way of illustration only, this overflow member comprises a casting nozzle extending through a ramp that slopes towards the outlet port. For example, this outlet port may have a hollow tubular shape.

For example, the ports are evenly distributed on the periphery of the side wall delimiting the outlet port,

each second chamber is connected to at least one extraction circuit comprising at least one fan for sucking the gases and fumes generated in the corresponding chamber, the vitrification device comprising control means for controlling the fan and adjusting the bath level in the melting zone in order to promote the flow of a portion of the bath from the melting zone to the casting zone,

the device comprises at least two second chambers, each defining a casting zone in fluid communication with the melting zone of the first chamber,

the device comprises at least one device for extracting said molten material downstream of at least one outlet port,

-the first chamber has a circular, rectangular, square or oblong right cross section,

this device comprises at least one injection means for injecting a protective fluid at least at a portion of at least one plasma torch located inside said first chamber, said injection means being configured to generate a gas curtain around said portion so as to protect said portion from the extreme conditions prevalent in said first chamber.

Preferably, this protective gas is air or any other gas, such as an inert gas. By way of example, in the latter case it may be nitrogen (N)₂)。

Drawings

Other advantages, objects and specific features of the invention will become apparent from the following description provided by way of non-limiting explanation with respect to the accompanying drawings, in which:

figure 1 is a schematic cross-sectional view of a vitrification device according to a first particular embodiment of the present invention;

FIG. 2 is a partial top cross-sectional view of the overflow region of the vitrification device of FIG. 1;

figure 3 is a schematic cross-section of a vitrification device according to a second particular embodiment of the present invention.

Detailed Description

First, it should be noted that the drawings are not to scale.

Fig. 1 and 2 schematically illustrate an apparatus 10 for vitrifying a powdered material according to a particular embodiment of the present invention.

This device 10 comprises a cylindrical main melting chamber or furnace 11, which is constantly fed upwards with a flow of powdered material by means of an injection device 12. An inlet port 13, formed by an opening with a circular cross section provided in an orifice positioned in the side wall of the melting chamber 11, allows the injection of electric charges into this chamber 11. This injection device 12 is chosen because it is capable of delivering a controlled flow at pressures and temperatures imposed by the pressure and temperature conditions prevailing in the melting chamber 11. By way of example, this is a cooling screw. It is also possible to select an injection member by means of a plunger or pneumatic delivery under pressure.

The charge of the powdery material to be processed is injected into the melting chamber 11 in such a way that it has a horizontal injection component and a vertical injection component towards the bottom of the melting chamber 11. This charge thus falls by gravity into the molten pool 14 contained in the crucible.

The impact region of this charge to be treated with the melt pool 14 is the mixing region. The latter is therefore a mixing region: wherein the charge of the powdered material to be treated is mixed with the charge that has been melted into the liquid bath 14 into the liquid state by the energy input from the non-transferred arc plasma torch 15.

A non-transferred arc plasma torch 15 is mounted in an opening in the top of the melting chamber 11. It is mounted on the melting chamber 11 in a manner such that the plasma dart it emits is delivered directly into the molten bath 14. Such plasma darts may advantageously be directed at the molten bath 14 at an angle and stir the molten bath 14 at an angle.

The non-transferred arc plasma torch 15 preferably operates with pressurized and treated air as the plasma gas using atmospheric air compression and treatment means. It is also possible to use another plasma gas, for example by varying the percentages of oxygen and nitrogen relative to atmospheric air.

Advantageously, the end of the non-transferred arc torch 15 inside the main chamber 11 is surrounded by a film of gas, for example air or any other gas, forming a shield that protects the end of the torch 15 from the aggressive environment in the main chamber 11. This gas film is produced by means of a device (not shown) located on the melting chamber 11 for introducing gas, for example at room temperature.

The measuring and control means (not shown) enable the pressure and temperature in the melting chamber 11 to be recorded by pressure and temperature probes, the bath temperature to be recorded by an optical pyrometer, and the melting of the charge of the powdery material to be processed to be monitored by an endoscope (not shown). These measurements are used, for example, under the control of a processing unit, for example a microprocessor programmed for this purpose, to determine the power of the plasma torch 15 and/or the rate at which the charge of the powdered material to be processed is introduced into the bath, so as to control and optimize the melting process, in particular the plasma power required and sufficient for melting said charge to be processed.

The side walls, crucible and roof of the melting chamber 11 are all internally lined with a high temperature resistant refractory material, for example a chromium/corundum based material. The same is true of the inner wall of the second chamber 16.

Of course, in order to increase the processing capacity of the vitrification device 10, it is possible to equip the melting chamber 11 with at least two injection devices 12 having an electric charge of the powdery material and at least two non-transferred arc plasma torches 15 for heating the melt bath. The size of the crucible will then be increased to accommodate the larger volume of the melt pool 14. By way of example, the melting chamber 11 may also be elongated or oval. In order to ensure satisfactory discharge of the molten material forming the molten bath 14, this vitrification device may comprise at least two separate casting zones, each preferably connected to the melting chamber 11 opposite to the respective injection device 12.

The apparatus also includes a second chamber 16 defining a casting area for the molten material. This casting zone is in fluid communication with the melting zone through an opening, the upper part of which is delimited by the end of a barrier stone 17 located here between the main chamber 11 and the second chamber 16. Part of the molten material from the melt pool 14 can thus flow through this opening to the casting area.

The barrier stone 17 is arranged so that its free end, which together with the surrounding wall of the chamber delimits this opening, is immersed in the molten material. This barrier stone 17, which contacts the liquid bath 14, thus blocks the gases and fumes produced by the melting of the powdered material in the melting zone.

These fumes and gases are therefore still confined in the internal volume of the melting chamber 11 and are extracted by means of a chimney 18 located in the top of the melting chamber 11, said chimney 18 being connected to a fume extraction and treatment circuit. These fumes and gases contain in particular the charge-evaporated part of the powdered material, which is generated by the thermochemical reaction that takes place in the high-temperature melting zone of the melting chamber 11, generally between 1300 ℃ and 1600 ℃.

The second chamber 16 comprises burners 19 mounted on the side walls of this second chamber for maintaining the temperature of the molten material so that it can flow through the melting zone towards the outlet port. Of course, more generally, this may be any means of heating the molten material to maintain the temperature of the molten material flowing into the portion of the molten pool of the melting zone above its melting point, such as a non-transferred arc torch.

The second chamber 16 also has several openings 20 for extracting the gases and fumes generated in the casting area, these openings being connected to a gas and fume extraction circuit.

These extraction holes 20 are located at an overflow area comprising an outlet port for extracting the molten material in order to capture the gases and fumes generated during this extraction phase of the molten material. This overflow area is placed at the end of the casting area opposite to the end where the barrier stones 17 are arranged.

The overflow zone comprises overflow means including a casting nozzle 21, the casting nozzle 21 preferably being movable to adjust its position, and the height of the casting nozzle 21 being adjustable if necessary, making it possible to control the overflow level of the molten material and therefore the bath level in said casting zone. This casting nozzle 21 is extended by an inclined ramp 22, the inclined ramp 22 preferably being movable together with said casting nozzle 21 so that the overflowing molten material is directed towards an outlet port 23 for molten material from the melt pool 14.

As shown in fig. 2, this outlet port 23 for the molten material comprises a hollow duct, external to the body of the second chamber 16, connected to this latter through a casting hole and defining an internal passage 24 for the extraction of the molten material, which falls by gravity through the casting hole from the inclined ramp 22.

Here, the extraction holes 20 are distributed on the side wall of the hollow duct of the outlet port 23 so that the external air is sucked in simultaneously with the gas and the smoke.

These gases and fumes are therefore diluted mechanically, so that their deposition and corrosion effects on the pipes of the gas and fume extraction circuit 25 are greatly reduced. This extraction circuit 25 advantageously defines an envelope around the outlet port 23 so as to capture all the gases and fumes produced.

The molten material thus drawn out is subsequently cooled in the atmosphere, converting it into a non-toxic vitrified material. It should be noted that the extraction hole 20 is located outside and below the second chamber so as not to cool the molten material flowing into the melting zone.

It can be pulled by means of a cooled rotary rolling mill 26. This rolling mill 26 is used to draw overflow molten material from the overflow member out of the second chamber 16 from the casting area. Passing through the rolling mill 26 ensures that the solidified vitrified glass is amorphous.

Fig. 3 is a schematic cross-sectional view of a vitrification device 30 according to a second embodiment of the present invention.

Elements in fig. 3 having the same reference numerals as those in fig. 1 and 2 denote the same objects and will not be described below.

The vitrification device 30 shown in fig. 3 differs from the vitrification devices shown in fig. 1 and 2 in that it has at least one extraction hole 31 which is not located in the outlet port 23 but on the side wall of the second chamber delimiting the casting area. However, it is placed in the vicinity of this outlet port 23, ensuring the extraction of the gases and fumes generated during the extraction of the vitrified material.