CH624650A5 - Process for the manufacture of fibres by means of gas streams with saving of energy - Google Patents

Description

The invention relates to a method and a device for manufacturing fibers from a stretchable material, in particular mineral materials such as glass or similar compositions which are brought to the molten state by heating. However, since the device is more particularly advantageous in the case of drawing glass and similar thermoplastic materials, the description refers, by way of example, to the case of glass.

Certain techniques using vortex currents to manufacture fibers by drawing molten glass are already known.

In particular, patent publication FR No. 2223318 describes the formation of pairs of counter-rotating vortices in an interaction zone created by directing and causing a secondary or carrier gas jet to penetrate into a larger main gas stream, a net of molten glass being brought into this area to be stretched there.

Different types of devices used for drawing a material in an interaction zone are already described in the patent cited above and in patent applications FR Nos 76.03416 or 76.37884. In all cases, a flow or a gaseous jet whose kinetic energy per unit of volume is greater than that of the main stream, is penetrated into a main stream, this jet having a section whose dimension, transverse to the main stream, lower than the latter. A net of stretchable material is introduced into the zone of interaction of the jet with the main stream, either directly by gravity, or by initially bringing the net into the gaseous jet to thus entrain it in the zone of interaction.

In the following analysis, it will be taken into account that the drawing of thermoplastic materials such as glass must necessarily take place at high temperature. The glass is therefore melted by heating, for example at a temperature above about 1250 ° C. and, to obtain high yields, the temperature of the drawing gases in contact with the thread of material and the fiber in formation.

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must also be high enough to keep the glass at the high temperature appropriate for drawing.

In patent publication FR No. 2223318, the secondary gas jet and the main stream both have relatively high temperatures, for example of the order of 800 ° C. for the jet and 1580 ° C. for the main stream.

Although patent application No. 76.03416 describes the possibility of using low temperatures for the jet, for example close to room temperature, it provides for relatively high temperatures for the main stream, such as those mentioned above.

But, given, on the one hand, that the main stream contains large volumes of gas and, on the other hand, that only a part of these is used for the drawing of the thermoplastic material in the area of interaction, heating all of the main stream gases to relatively high temperatures results in considerable energy or heat losses.

This loss of energy is avoided by the technique of the present invention which allows, unlike the known technique, not only to use a jet at low temperature, but also to use a main current whose temperature is relatively low. The method according to the invention is defined by claim 1.

The technique of the present method, called energy localization, leads to significant energy savings and has, in addition, other advantages. For example, it makes possible the rapid cooling of the fibers after drawing, which increases the mechanical resistance characteristics of the fibers for a large number of thermoplastic materials. This also makes it possible to obtain very long fibers, a result which is particularly sought after for certain applications.

The advantages of the invention will appear in the following description relating to the various embodiments of the device illustrated by way of example in the drawings:

fig. 1 shows a schematic view, in elevation, of the main elements of a device according to the invention, in which a pair of jets is used at each fiberizing center, and of which certain parts are shown in section;

fig. 2 is a schematic perspective view on a larger scale, showing the operation of the device of FIG. 1;

fig. 3 is a vertical section, on a large scale, of the elements forming a fiberizing center, in the plane of the emitting orifices of the jets;

fig. 4 shows a vertical section of the elements of a fiberizing center relating to another embodiment of the device;

fig. 5 is a perspective diagram illustrating the operation of the device of FIG. 4;

fig. 6 is a plan view of several adjacent jets and portions of the main stream which correspond to FIGS. 4 and 5,

but omitting the supply of glass and fibers during formation;

fig. 7 is a view similar to FIG. 4, but comprising an additional member;

fig. 8 is an elevational view, partially in vertical section, showing the adaptation of the characteristics of the present device to a fiberizing device such as that of FIG. 11 of patent FRNo 2223318;

fig. 9a and 9b are schematic sections of a fiberizing center, FIG. 9a illustrating the conditions and the fiberizing process in an interaction zone without localization of the energy, while FIG. 9b shows the same fiber center but using the energy localization technique, and FIG. 10 is a graph showing an advantage of the present invention when applied to fiberizing certain types of thermoplastic mineral materials.

In the detailed description which follows, reference will first be made to the device shown in the drawings and then the aspects relating to the location of the energy in the operation of this device will be analyzed.

We first refer to fig. 1, on which is schematically represented at 8 a main current generator such as a burner, provided with a nozzle 9 emitting in a roughly horizontal direction a main current 10. This can of course be directed in other directions .

A manifold 13 connected via a connection 12 to a jet manifold 11 supplies the latter with compressed gas, for example compressed air. We can also see, in fig. 2 and 3, that the jet manifold 11 comprises pairs of orifices 14 and 15 for the emission of jets, the successive pairs of orifices bearing the references 14a-15a; 14b-15b; 14c-15c; 14d-15d; 14th-15th; the jets emitted from these pairs of orifices are identified by the corresponding letters. Fig. 2 shows in perspective three pairs of jets while a single pair of jets a-a is shown in FIGS. 1 and 3. For each pair of jets there is a fiber center.

At each fiberizing center, the jets of a pair, for example the jets a-a, abut each other in their common plane and produce a combined flow, indicated at A in fig. 1, in which a net of stretchable material is subjected to a first stage of stretching or primary stretching. The combined flow or combined carrier jet progresses downwards and enters the main stream 10 creating with this latter an interaction zone which is used for a second stretching step.

In these figures, a glass supply source is shown diagrammatically at 16; it comprises a die 17 having a series of pins 18 for feeding glass spaced apart, which each have a feeding hole 18a, and, upstream, a metering hole 19. The glass is thus brought in the form of bulbs G from which glass filaments S flow downwards, each fiberizing center comprising a bulb and a net. The fibers formed from a series of fiber centers distributed transversely over the width of the main stream 10 are then deposited on a perforated conveyor or strip 20 in the form of a sheet of fibers B. The distribution of the fibers on this conveyor is produced inside a chamber delimited for example by a wall 21, thanks to the action of suction chambers 22 preferably arranged under the conveyor 20, and connected by conduits 23 to one or more suction fans , shown schematically at 24. The fiber drawing carried out with the preceding device is explained and analyzed more precisely with reference to FIGS. 2 and 3.

As already specified above, the process specific to each fiberizing center is preferably linked to the action of the jets of the neighboring centers. Fig. 2 shows the drawing process completely for the fiber center corresponding to the jets b-b, and only partially for the fiber centers relating to the jets a-a and c-c. Fig. 3 shows on a larger scale what occurs at the fiberizing center comprising the jets a-a; to analyze the process or the operation, it is recalled first of all that any gaseous jet induces a movement of ambient air as soon as it is emitted from an orifice. Consequently, each of the jets a comprises a central part j, or core, surrounded by a gas envelope containing induced air designated by the letter i. This envelope grows rapidly as the flow of the jet progresses,

while the heart of the jet remains the relatively short central part having the shape of a cone. The gases forming the heart of the jet have a speed equal to that of the jet when it leaves the orifice,

while the velocity of the envelope gases decreases as the flow progresses. The arrows shown in fig. 2 or 3 indicate the induction of air by the flow of the jets, but also by the flow of the main current.

When using a pair of jets having approximately the same kinetic energy per unit of volume and preferably also approximately the same dimension, these two jets having their axes located in the same plane and converging so as to abut against each other preferably at an acute angle, the combined flow spreads laterally, downstream of the impact region of the two jets,

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that is to say, it expands in directions transverse to the plane of the axes of the jets.

The pairs of jets or the planes containing their axes are close enough to each other so that at each fiberizing center the lateral development of the combined flow coming from a pair of jets is hampered or limited by impact on the flow of pairs of neighboring jets during blooming. This impact of neighboring combined flows develops two pairs of small vortices in each flow, the vertices of the vortices of the same pair being located at a distance from each other on either side of the plane of the axes of the jets. We have shown diagrammatically in FIGS. 2 and 3 of the upper and lower pairs of vortices. The vortices of the upper pair bearing the reference tu-tu are formed by currents rotating in the direction of each other in the upper part of the vortices, and in the opposite direction in their lower part. On the contrary, the vortices of the lower pair referenced by the letters tl-tl rotate in opposite direction to the vortices of the upper pair.

Between the two pairs of vortices, in the region of mutual impact of the jets, a zone L of laminar flow associated with these vortices forms, at the level of which the induced air call is very intense, and this is precisely in this laminar flow zone, on the side of the upper vortices, that the glass thread S is introduced. This thread is formed from the bulb or cone of glass G, the position of which is offset from the jet emitter. However, the glass bulb G being in the stretchable or fluid state at the outlet of the feeding nipple, the stretchable glass net S is delivered relative to the initial position of the bulb, in the direction of the flow zone laminar L, as a result of the intense call for induced air, and this effect ensures the supply of the stretchable material into the laminar zone. Therefore, even if there is a slight misalignment of the glass supply nipple 18 relative to the pair of jets, the induced air intake will automatically compensate for this defect and will lead the glass net into the appropriate position.

It will thus be understood that, by forming at each fiberizing center at least one pair of vortices bordering a laminar flow zone and by bringing the material, in the stretchable state, into a region close to said zone, the net of material is automatically entrained in this zone by the induced air currents which, as specified above, automatically compensate for any misalignments, which leads to stabilize the introduction of the stretchable material. This stability is obtained even when the glass supply nipples are significantly spaced from the jet emitters, a spacing which is desirable to facilitate the adjustment and maintenance of the appropriate temperature both for the supply nipples and for the jet emitters.

Downstream of the laminar zone L, the two vortices tu-tu, but also tl-tl, tend to merge and, when the flow progresses downstream, they tend to lose their identity, as shown in FIG. 2 in the section showing the two pairs of vortices which arise in the jets c-c. The combined flow of each pair of jets then progresses downward to enter the main stream 10, as illustrated for the flow from the pair of jets b-b; the combined jet then forms, with the main current and inside it, the interaction zone fully analyzed in the patent publication FR No. 2223318 mentioned above, zone which comprises an additional pair of T vortices.

It will be noted that each plane containing the axes of the jets of the same pair preferably cuts the main current along a line practically parallel to the direction of propagation of the latter.

Each glass thread S is thus subjected to a primary drawing in the flow of combined jets, between the laminar flow zone, or point of introduction of the glass, and the point of penetration of the jet in the main stream, the thread partially stretched then being subjected to an additional stretch in the zone of interaction of said flow with the main stream. It can be seen in the figures that these two drawing steps are carried out without breaking up the glass thread, so that each thread produces a single fiber.

To obtain the previously described process at each fiberizing center, in particular the formation of pairs of vortices each bordering a laminar flow zone, a pair of jets is used which preferably have the same kinetic energy per unit volume. The sections of these two jets also preferably have identical surfaces, but it is possible to admit a small difference between these surfaces, in particular if the kinetic energies per unit of volume of the two jets are practically the same. In addition, the sections of the two jets of a fiberizing center advantageously have the same shape.

Furthermore, it is not necessary for the cross section of a jet to have exactly the same dimensions in directions parallel and transverse to the plane containing their axes and, moreover, these dimensions are not necessarily equal to the corresponding dimensions of the second throw of the same pair. However, it is preferable and advantageous that these dimensions are identical or very close within a jet, but also for the two jets of a fiberizing center. In addition, it is desirable that the pairs of neighboring jets have substantially the same dimensions to allow uniform formation of the pairs of vortices bordering the laminar flow zones during the impact of each combined flow on the neighboring flow in progress. lateral development. This identity of the jets of successive fiber centers makes it possible to obtain uniform and homogeneous fiber conditions in the different interaction zones created by penetration of the jets into the main stream.

For penetration, the combined flow must have a kinetic energy per unit of volume greater than that of the main current when it reaches it.

It will also be noted that the jets grouped in pairs must have certain specific characteristics to form the laminar flow zone into which the glass net can be introduced without fragmentation. It is indeed important that the axes are located practically in the same plane and meet in this plane, preferably at an acute angle.

In the system described above with reference to figs. 1,2 and 3, the characteristics relating to the location of the energy can be used in several ways. It is first of all provided that the gas streams in the interaction zone formed by penetration of the jet into the main stream contain combustible and oxidizing components in proportions such that the mixture is combustible. Preferably, the fuel and the oxidizer are in approximately stoichiometric proportions in the immediate vicinity of the stretchable material. The manner of introducing these components into the interaction zone is explained in detail below, after the description of the other embodiments of the device shown in the drawings.

We therefore refer to the device of FIGS. 4, 5 and 6 which is also described in patent application FR No. 76.37884. In the latter, a series of secondary gas jets, or carrier jets, is generated, with which a deflector is associated; the jets are thus deflected and directed towards a main stream into which they penetrate, and the glass nets are introduced into the flow of the jets, then entrained by them in the corresponding interaction zones formed in the main stream. We first refer to fig. 4 schematically showing the main elements of a fiberizing center. On the left, a part of a burner or a generator 25 is represented which comprises a nozzle 26 emitting a main current 27.

A jet manifold 28 has a series of emission orifices 29 through which the jets indicated by the letters a, b, c and d are emitted in FIG. 5. The jet manifold 28 can be supplied with pressurized fluid via the connection 31 connected to the supply tube 30. On this nurse 28 is mounted a plate or deflector flap 40, which covers the series of jets and whose edge 41 has a position such that the jets abut against this deflector.

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A die 32, associated with a body or with a suitable means for supplying glass indicated at 33, comprises supply pins 34, and a glass net is directed towards each jet flow described below to be then brought downstream to the area of interaction of the main stream 27. As specified in the following description, fiberizing occurs in the jet, but also in the main stream, then the latter delivers the fibers to the right, as well as 'it is represented in fig. 4, to form a sheet which is deposited on a perforated conveyor belt or conveyor.

The nozzle 26 emitting the main stream has an outlet of large width. Preferably, the die 32 also has a large dimension in the direction perpendicular to the plane of FIG. 4 and makes it possible to supply all of the nipples 34 with glass.

The jets emitted by the emission orifices 29 are subjected to a deflection or to a guidance by means of a deflector which cooperates with these jets to generate pairs of counter-rotating vortices used at least for the primary drawing, but also for bringing the partially stretched nets in the interaction zones created by the penetration of the jets into the main stream. In order to generate the pairs of counter-rotating vortices of the jets, the deflector plate 40 is associated with a group of jets emitting orifices. As seen in particular in FIG. 5, the deflector plate preferably takes the form of a folded sheet, part of which covers the jet manifold on which it is fixed and the other part of which has a free edge 41 disposed on the path of the jets emitted from the orifices 29, and advantageously placed along a line which occupies the axes of these jet orifices.

This position of the deflecting plate 40 and its edge 41 causes the impact of each of the jets against the internal face of the plate 40, which causes said jets to flourish. Thus, there is shown in FIG. 5 the flow of four of the jets emitted from the orifices a, b, c and d and it will be noted that each of them opens out laterally as it approaches the edge 41 of the plate.

It is intended that the emission orifices 29 of the jets are sufficiently close to one another and that the deflector is arranged so that at the time of their lateral expansion, the neighboring jets abut against each other in the region of the edge 41 of the plate. Preferably, as shown in fig. 5, this mutual impact of the neighboring jets occurs as close as possible to the free edge 41 of the deflector plate 40. This results in the formation of pairs of counter-rotating vortices shown in FIG. 5 in association with each of the three jets emitted by the orifices a, b, c.

To analyze the formation of the vortices in each jet, we refer in particular to the vortices 42b and 43b, associated with the jet coming from the orifice b. Note that these vortices have their vertices located substantially at the edge of the deflector plate 40 on opposite sides of the jet in the vicinity of the zone in which the jet in the process of blooming abuts against the neighboring jets emitted from the orifices a and c , also in the process of flourishing. The vortices 42b and 43b are counter-rotating, and they increase as they progress until they meet at a distance and downstream from the edge 41 of the deflector plate. These vortices 42b and 43b also have a component directed downstream.

Due to the spacing between the vertices or points of formation of the vortices 42b and 43b and taking into account their progressive enlargement, an approximately triangular zone 44b is formed between the vortices and the edge of the deflecting plate; this triangular zone has a relatively low pressure and undergoes a large influx of induced air, but its flow remains however almost laminar. It is in this zone that the molten glass net or other stretchable material is introduced and, due to the laminar nature of the flow in this triangular zone, the glass net is not fragmented, but is led in the region between the two vortices.

The directions of rotation of the currents in the jet vortices 42b and 43b are opposite, the vortex 42b rotating clockwise in the representation of FIG. 5, while the vortex 43b rotates in the opposite direction. Thus, the currents in these two vortices approach each other towards their upper part and then flow downwards towards the central zone or laminar zone 44b.

For the pair of vortices 45a and 46a associated with the jet coming from the orifice a, the directions of rotation are indicated by arrows, which is mentioned above. It is understood that, for the flow of the jet from the orifice a, a section is shown at the downstream end of the laminar flow zone 44a, that is to say in the vicinity of the area in which the two vortices, after enlarging, begin to merge, this phenomenon continuing as the flow of the jet progresses downstream. It is also clearly seen that the flow of the jet coming from the orifice a comprises not only the pair of vortices 45a and 46a, but also another pair of vortices 47a and 48a having, relative to each other, reverse direction of rotation, as shown in fig. 5, but in this case the vortex 48a rotates clockwise, while the vortex 47a rotates in the opposite direction. Such double pairs of vortices are of course generated by each of the jets and associated with each of them.

As regards fig. 5, it will also be noted that, when the flow progresses from the plane in which the vortices associated with the orifice a are represented, the four vortices tend to merge and to reform a less characterized flow, as shown in section 49c to through the flow of the jet coming from the orifice c. The vortex movements decrease in intensity and the whole flow, including the laminar flow of the central zone of the jet, mixes in the region indicated in 49c, the jet then progressing downstream towards the main current 27.

In fig. 5, the representation of the various portions of the jet has been shown diagrammatically for clarity. For example, in the zone situated a little downstream from their origin, the pairs of vortices which originate in each of the jets appear slightly distant from the pair of vortices arising in each neighboring jet, when in reality these various vortices are practically contiguous.

Due to the shape of the jet flow in the laminar zone and in the pairs of vortices, in particular in the upper pair of each group, the introduction of the stretchable material net marked with the letter S for the fiber center comprising the jet orifice ba results in entraining the thread in the laminar flow of the central zone. This brings the net into the high speed zone located between two vortices and, therefore, it is stretched as shown in fig. 5. This stretching takes place substantially in an area corresponding to the plane P. The action of the pairs of jet vortices causes the fiber stretched to be whipped substantially in the area of the plane P so that the stretching does not result in projecting the fibers being formed to adjacent jets.

The jet then flows to the upper limit of the main stream 27 by entraining the fiber being drawn and it must have kinetic energy per unit of volume still sufficient to penetrate this main stream.

Then begins a second fiberizing step which takes place according to the principles explained in detail in the aforementioned French publication No. 2223318.

Of course, in the region of penetration of the secondary jets into the main stream, the flow and the speed of each jet are still sufficiently concentrated in the vicinity of the axis so that each of the jets individually develops a zone of interaction with the stream. . Thus, in fig. 5, a pair of counter-rotating vortices indicated in TT is generated in the interaction zone, which creates currents causing an additional stretching of the fiber being formed. This fiber is then carried by the combined flow of the jet and the main stream to a suitable receiving means, for example the conveyor 20 of FIG. 1.

There is shown in FIG. 5 the air induction by arrows oriented in the direction of flow of the jet, and it can be seen that the air is induced in the laminar zone near the edge of the plate

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deflector, but also as the jet flows downstream.

The operating conditions which can be used in the device described above are specified in the following description which also defines the areas within which these conditions may vary.

As with the first embodiment of the device described above, the combustible and oxidizing components can be introduced into the system of FIGS. 4,5 and 6 in different ways, which will be considered later.

We first refer to the device shown in FIG. 7 which has the same numerical references as that of FIG. 4 for their common parts.

An additional organ appears in FIG. 7 to introduce the combustible or oxidizing components into the interaction zone. A supply line 35 for the fuel and / or the oxidant is connected to a series of emission nozzles 36 which are spaced and directed towards the main stream so as to send the fluid to a region adjacent to the interaction zone Z, and located immediately upstream of it. In fig. 8, the main current generated by the generator 50 is emitted by the nozzle 51 in an area bounded above by the plate 52 and on the lower side by the plate 53 curved downward to deviate from the mean plane of the main current. Cooling tubes 53a can be mounted on this bottom plate if desired. The die 55 for the glass supply is provided with a series of orifices 56 distant from each other, arranged over the width of the main stream transverse to the direction of propagation, so as to bring stretches of stretchable material into this main stream. Just upstream of the glass supply orifices, the upper plate 52 has a series of jet emission orifices 29, each of them being associated and aligned with a corresponding glass supply orifice. The orifices 29 are supplied with compressed fluid by the manifold 54 connected to the conduits 54a and 54b.

The plate 52 further comprises another collector 57 connected to a series of successive orifices 57a arranged transversely to the main stream, associated and aligned each with a glass supply orifice 56 and the corresponding jet emission orifice 29. .

This collector 57 is supplied with gaseous fuel via the line 59 which can be connected to a main supply 60.

A downstream plate 58 disposed along a peripheral region of the main stream constitutes an upper limit thereto, and has a cooling tube 58a. Some elements of this device are similar to those of FIG. 11 in the prior patent publication FR No. 2223318.

In the embodiment of FIG. 8, the fuel is introduced for example through the orifices 57a, while the air used for the secondary jets arrives through the orifices 29, which makes it possible to obtain a mixture of fuel and oxidizer in the zone of interaction with the main stream.

In addition, an introduction of additional air can be made in the main stream upstream of the interaction zone by means of supply channels, upper and lower 61 and 62, located in the region of the connection of the main current generator. 50 with the nozzle 51. Each supply channel is terminated by a slot or a plurality of supply orifices shown diagrammatically at 63. This introduction of additional air into the main stream serves in particular to obtain certain advantageous conditions, for example an adequate temperature of the main current, conditions which are linked to the technique of energy localization. Indeed,

when the combustion of the fuel is carried out in the interaction zone, it is not necessary to use a main current whose temperature is as high as that required in the absence of this localized combustion. As a result, significant fuel savings can be made during the development of the main stream.

It is obvious that, in order to produce a main current at a relatively low temperature and at the desired speed, it is possible, instead of resorting to the introduction of additional air, to completely eliminate the use of a burner and to replace it with any other device comprising for example a heat exchanger in which the gases of the main stream are heated.

Before considering other means for supplying the fuel and the oxidizer, reference is made to FIGS. 9a and 9b which we will compare to analyze the energy localization process and the resulting saving of energy or fuel.

Fig. 9a shows the conditions under which stretching takes place in an interaction zone created between a jet and a main current, in the absence of the energy localization technique. The emission nozzle 64 generates a main stream preferably having a large width, that is to say a large dimension in a direction perpendicular to the plane of the figure, so that several pairs of glass supply members 65 and jet emitter 66 can be associated with the main stream to allow the manufacture of a large number of fibers. The glass net and the secondary jet have the references S and J respectively, the zone of interaction between the jet and the main stream being indicated at Z. With such a device and with a current glass composition, the temperature of the jet can be either of the order of 800 ° C (as described in patent publication FR No 2223318), or much lower and close to ambient (as in patent application FR No 76.03416). In these two cases, the temperature of the main stream varies between 1500 and 1750 ° C., depending on the temperature of the jet so as to obtain in the interaction zone the desired temperature for drawing the glass net. It has been indicated in fig. 9a, a temperature of 1700 ° C. in the vicinity of the lips of the main stream nozzle, the heart C of which extends to the zone of interaction with the jet, so that the zone in which the stretching actually takes place there is in fact an intermediate temperature between that of the main current and that of the jet. Downstream of the interaction zone, the successive isothermal lines represent the gradual decrease in temperatures, for example 1600, 1400 and 1200 ° C.

Fig. 9b shows diagrammatically exactly the same elements of the device as FIG. 9a, but it represents the conditions which prevail when the energy localization technique is applied. For this purpose, the jet transmitter 65 can be supplied with a pressurized mixture containing a combustible gas, while additional air or oxygen can be supplied by the nozzle 64 supplying the main current, the gases of the latter being, at the time of their emission, at a much lower temperature than when operating under the conditions of FIG. 9a. The temperature of the main stream can be, for example, of the order of 600 ° C. at its exit from the nozzle, as shown by the isothermal lines, and the temperature of a large part of the gases then decreases, for example reaching values of approximately 400,300 and 200 ° C in areas located downstream of the nozzle and corresponding to those of the isothermal lines 1600, 1400 and 1200 ° C in fig. 9a.

Although it is possible to supply the fuel by means of the main stream, it is preferred that this fuel constitutes in part the secondary jet, that is to say that it is introduced into the gases of the secondary jet as described above. Thus the jet J is used not only to create the interaction zone into which the glass net S is brought, but it also brings therein a combustible component which is intimately mixed with the oxidant, in particular with the excess air, brought into the interaction zone by the main current. Thanks to the presence of vortex currents in the interaction zone, it is possible to obtain the very intimate mixture that is sought.

With regard to the proportions of the fuel and of the oxidizer, it will first be noted that it is preferable to use stoichiometric proportions. However, a combustible mixture can be obtained even with proportions deviating from the stoichiometry. Thus, in the case of a mixture with natural gas, the quantity of air can vary within a range of between approximately

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0.8 and 1.7 times the amount of air corresponding to the stoichiometric proportions. These appropriate amounts of oxidizer and fuel form in the interaction zone a combustible mixture which has a flash point below the temperatures of the molten glass compositions ordinarily used for fiberizing, so that the glass stream fed to be introduced into the interaction zone can ignite or ignite the combustible mixture formed therein. Consequently the desired temperature, for example 1700 ° C., can be reached in the interaction zone Z and thus allow the drawing of the net of material î o and its transformation into fiber, although the temperature of the main stream at the same time downstream and upstream of said zone is much lower than this value. It will also be noted that the interaction zone created with each of the jets may comprise only a very small part of the total volume of the main current. However, since only this part must necessarily reach the higher temperatures required for drawing, a very great energy saving is thus obtained by the technique compared to systems in which the total volume of the main current is brought to the temperature d 'drawing. 20

It is important to also note that the stretching technique in an interaction zone is particularly well suited to the localization of thermal energy due to the presence of a region at low pressure and at low speed which is formed in the vicinity. immediate of each glass thread and generally surround it, without the need to interpose another material element.

The fuel or the oxidizer can thus be injected into the interaction zone to form the combustible mixture, while the presence of hot glass makes it possible to ignite this mixture. The high-speed vortex currents, or vortices, characteristic of the interaction zone, are useful in the energy localization technique for effecting an intimate mixture of the fuel and the oxidant, as already mentioned. On the other hand, these vortex currents sometimes moving in the direction of the current, sometimes against the current, there necessarily exist in the interaction zone regions with relatively low flow velocity compared to that of the main current. However, the existence of such regions with low flow speed constitutes one of the conditions for ignition of the fuel mixture to occur and for stable combustion to be maintained. The importance of this characteristic is emphasized 40 by recalling that with a mixture of natural gas and air, the flame propagation speed is of the order of 0.3 to a few meters per second at 20 ° C.

Although this flame propagation speed increases with a rise in temperature, it remains always very low 45 compared to the speed of the main current. However, the interaction zone being also characterized by the presence in certain regions of a flow at a speed lower than the speed of propagation of the flame, it is possible to ignite the combustible mixture and to maintain a stable combustion. The reasons sq mentioned previously seem to explain the phenomena of ignition and combustion stability in the interaction zone, but it is probably possible to find other explanations for this phenomenon.

In addition, in the device described with reference to FIG. 9b, the flame front ss has a tendency to adhere to the source of ignition, that is to say to the glass net itself or to the net of material which it is desired to raise or maintain at the temperature of proper stretching. It is indeed possible to obtain this attachment of the flame, on the one hand,

because the temperature of the glass is much higher than the ignition temperature of the mixture and can reach, for example, twice that temperature and, on the other hand, because in contact with the surface of the glass net develops a boundary layer of combustible mixture which is brought to the ignition conditions by the heat given off by the glass. It therefore follows that a layer of combustion is located around the glass and triggers in the adjacent layers and in the interaction zone a localized and stable combustion remaining attached to the glass net during drawing.

Since a large part of the heat exchange with the glass net takes place by contact of the hot gases with its surface, the process described efficiently ensures the heat transfer necessary to maintain the glass net in a stretchable state since the zone in which an intense heat is released is precisely that which immediately envelops said net.

Another advantage of the process described consists in that, with a large number of glass compositions, the mechanical resistance of the fibers produced is increased when the temperature of the fiber is rapidly reduced as soon as the drawing is completed. However, these favorable conditions are achieved here, as clearly shown by the isotherms of FIG. 9b.

In the device shown in figs. 1,2 and 3, the pair of gaseous jets aa can thus contain the combustible component necessary to achieve the desired result, and consequently serves not only to entrain the glass in the zone of interaction with the main current, but also to introduce the fuel therein, the air being able to be brought into the system by means of the main stream 10, as in FIG. 9b. In this way, and by choosing jet and main current temperatures such as those indicated above with reference to this figure, the location of the energy and the fuel economy sought can be obtained.

Likewise for the embodiment of FIGS. 4,5 and 6, it is possible to introduce, if desired, the entire combustible component with the gas jet, the air being able to be brought in at the same time as the main stream, preferably with a simultaneous lowering of the temperature of the latter at values such as those suggested above in relation to FIG. 9b in order to save maximum energy.

For the variants of fig. 7 and 8, the fuel can be introduced independently of the jet, that is to say separately, as already specified. With regard to the oxidizer, and in particular the air, it can be supplied either by means of the jet itself, or by the main current, or by both.

Fig. 8 shows an embodiment of the device used to introduce air with the main stream, in which air is added to this flow near the emission nozzle 51. By this means, the total volume of gas required and the desired temperature by burning, for example, only a small volume of the gases intended to form the main stream, the localized combustion process then taking place in the interaction zones which surround the threads of material, in order to locally produce the temperature rise required for stretching, as explained with reference to fig. 9b.

The energy localization process also has particular advantages for drawing certain categories of matter, such as certain types of rock and other natural or synthetic mineral materials for which the drawing temperature range is particularly narrow. . In the graph in fig. 10 have been reported the variations of the viscosity -q as a function of the temperature t for two different types of stretchable material, one, 10a, being a glass commonly used for fiberizing, while the other, 10b, corresponds to a natural rock for which the temperature range leading to adequate viscosities for drawing is very limited. It can be seen on this graph that the viscosity range located between points A and B, and allowing stretching, corresponds, for glass, to a temperature range ta-tb much more extensive than for rock (temperature range t 'a — t'b).

By introducing the fuel in an appropriate quantity into the main current interaction zone, the zone where the temperature suitable for drawing rock or any similar material prevails can be extended downstream, thus facilitating the maintenance of the viscosity desired for a longer period.

With regard to devices where the stretching processes such as those shown in FIGS. 1 to 3.4 to 6.7, in which the stretch of stretchable material is subjected to the action of the jet before penetration of i

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the latter in the main stream, it should be noted that, even if the fuel and the oxidizer are both present in the flow at the place where the stretchable matter is brought into it, the ignition will not occur not necessarily there. It may even, depending on the different operating conditions chosen, such as, for example, the temperature of the jet or its speed, not take place until the jet has reached the main current or has entered this latest.

The values of the various parameters contained in the following description correspond to operating conditions which can be used but are in no way limiting. In particular although the fuel given by way of example is natural gas, it may however consist of synthetic gas or of a mixture, certain liquid fuels also being usable in sprayed or vaporized form.

With a fiber center of the type shown in Figs. 1 to 3, the main stream 10 is generated from heated and compressed air and has a temperature of about 600 ° C; its speed is close to 300 m / s and its pressure is approximately 0.18 bar. The axes of the two secondary jets form an angle of 60 °. One of these jets comprises a mixture of 1 part by volume of natural gas and 5 3 parts of air, and the second jet consists of 4 parts by volume of air. The temperature of the jets is approximately 20 ° C, they also have a speed close to 330 m / s and a pressure of approximately 2.5 bars. The glass mesh is brought to a temperature of around 1300 ° C.

io With a fiber center such as that described in fig. 7, the same conditions as those mentioned above can be used for the main stream 27. The jet is formed of air at a temperature of 20 ° C., a speed of 330 m / s and a pressure of 2.5 bars . In this case, the supply of natural gas is carried out by the emitting member 36 at a pressure of approximately 0.5 bar and at a speed of 200 m / s. The glass is delivered by the supply nipple 34 at a temperature in the region of 1300 C.

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Claims (17)

624,650 2 1. Method for manufacturing fibers from an inorganic thermoplastic material in which a main gas stream and a secondary gas jet are generated, the cross section of which, transverse to the main stream, has a smaller dimension than that of the latter, kinetics per unit volume of the secondary jet being greater than that of the main stream, the jet being directed transverse to the main stream and penetrating therein to create an interaction zone which comprises eddy currents and according to which a stretchable material is brought into the zone, characterized in that the gas streams in the interaction zone contain combustible and oxidizing components in proportions leading to a combustible mixture and in that the stretch of stretchable material is brought into the zone at a temperature at least equal to the ignition temperature of the mixture. 2. Method according to claim 1, characterized in that the combustible and oxidizing components are in approximately stoichiometric proportion in the interaction zone. 3. Method according to one of claims 1 or 2, characterized in that one of the components introduced into the interaction zone constitutes at least part of the jet or of the main stream. 4. Method according to one of the preceding claims, characterized in that one of the components introduced into the interaction zone constitutes at least part of the jet, the other component introduced into this zone constituting at least part of the current main. 5. Method according to one of the preceding claims, characterized in that the fuel introduced into the interaction zone constitutes part of the jet and the oxidizing component at least part of the main stream. 6. Method according to one of claims 1 or 2, characterized in that the oxidant introduced into the interaction zone constitutes a part of the secondary jet or of the main stream and in that the combustible component is introduced into said zone while generating a jet of pressurized gaseous fuel directed towards the main stream and entering the region of the interaction zone. 7. Method according to claim 6, characterized in that the fuel jet directed towards the main stream enters it at a point located upstream of the secondary jet. 8. Method according to one of claims 1 or 2, characterized in that the combustible component is introduced into the interaction zone by generating a jet of gaseous fuel under pressure directed towards the main stream and entering it upstream of the secondary jet and in that the oxidant is introduced into the main stream in the form of air supplied under pressure therein upstream of the fuel jet. 9. Method according to one of the preceding claims, characterized in that the temperature of the main stream in a region located upstream of the interaction zone is lower than that of the stretch of stretchable material brought into said zone. 10. Method according to claim 1, characterized in that the oxidizing component is introduced into the interaction zone in the form of at least part of the main stream, the combustible component being introduced into said area independently of the jet and of the stream main. 11. Method according to claim 1, characterized in that a main gas stream is generated and a plurality of secondary gas flows each having a section whose dimension, in a direction transverse to the main stream, is less than that of this latter and each having a kinetic energy per unit volume greater than that of the main stream, each secondary flow being directed transverse to the main stream and entering therein thereby creating an interaction zone, which a thread of thermoplastic material is brought into each interaction zone and that a combustible mixture of an oxidizer and a fuel is formed in each of the interaction zones and that this mixture is ignited in each of said zones. 12. Method according to claim 11, characterized in that each interaction zone is supplied with fuel by the corresponding secondary flows. 13. Method according to claim 11, characterized in that each interaction zone is supplied with oxidant by the corresponding secondary flows. 14. Device for implementing the method according to claim 1, comprising a main current generator, a member emitting a secondary gas jet provided with an emission orifice whose size or width, transverse to the main current, is less than that of the outlet of the latter, the jet being directed to intersect the main stream and enter it by creating an interaction zone, and a power source bringing a stream of molten material into the interaction zone, characterized in that it comprises an independent member for introducing the fuel into the interaction zone. 15. Device according to claim 14, characterized in that the fuel introduction member is provided with an orifice placed at the limit of the main current. 16. Device according to claim 14, characterized in that the fuel introduction member comprises a transmitter whose orifice is located at a distance from the limit of the main current. 17. Device according to claim 14, characterized in that the member for introducing the fuel is arranged so that it brings the fuel into the main stream upstream of the zone of penetration of the secondary jet in the latter.