DE102011107536B4 - Burner, in particular inductively coupled plasma torch, preferably for the production of semi-finished products for bending-insensitive glass fibers - Google Patents

Abstract

Inductively coupled plasma torch for producing semi-finished products for bending-insensitive glass fibers, comprising a tubular burner channel (1), an induction coil (2) surrounding the burner channel and an outer sheath (3), the sheath having a closed or porous structure (4) porous structure or the clearance space between the outer wall of the burner channel and the sheath of a fluid (5) is flowed through, characterized in that the space between the outer sheath and the burner channel for a Screengasstrom is formed with a volume flow rate of up to 200 l / min wherein the sheath (3) is formed of a porous ceramic, a porous glass, a porous polymer plastic and / or a double-walled tube with a porous filling body whose porous structure is in the form of channels (6) oriented parallel to the longitudinal axis of the induction coil, in which the fluid (5) the porous Struk flows parallel to the burner channel (1), wherein a turbulent gas flow is avoided and its uniform distribution is effected, the induction coil is located close to the burner channel, with a very tight winding of the induction coil is provided around the tubular burner channel and the envelope in the longitudinal axis direction of the overall arrangement starting from a burner foot (15) along the burner channel (1) and reaching to a predetermined distance to the induction coil and ends, but the induction coil does not surround.

Description

The invention relates to a burner, in particular inductively coupled plasma torch preferably for the production of semi-finished products for bending-insensitive glass fibers according to the preamble of claim 1 and 4 and a method for coating with such a burner.

Inductively coupled plasma torches form a known state of the art. In such devices, a plasma is generated, which then flows through a burner channel. The burner channel is surrounded by a coil winding which can be acted upon by an electrical voltage and generates a magnetic field in the burner channel via the electric current generated thereby. Thus, the plasma flowing in the burner channel can be influenced in its flow behavior and thus the operation of the plasma torch can be controlled.

The US Pat. No. 3,694,618 teaches a high-pressure thermal plasma system. The document discloses a coil winding, which is located completely within a gap in the direction of the burner longitudinal axis and is closed by a sheath to the outside.

The GB 1 091 498 A teaches a gas heating apparatus. This has a wound around a burner tube induction coil in the form of a copper tube. The induction coil is located in the direction of the burner longitudinal axis completely within a cavity. This is enclosed from the outside by a covering.

The US Pat. No. 3,620,008 discloses an exhaust gas purification system for combustion processes. The apparatus shown there is not a burner apparatus for carrying out manufacturing processes for glass fibers. In the device shown there, an induction coil is located in the direction of the burner longitudinal axis completely within a space traversed by a fluid.

The WO 95/33362 A1 relates to a liquid-stabilized plasma flame. According to the teaching disclosed therein, there is a coil winding in an outer shell, wherein a porous tube forms an inner burner tube. A fluid flows inwardly through the outer shell to the porous tube where it at least partially enters the combustion chamber. Also there, the induction coil is completely covered in the direction of the burner longitudinal axis.

This basic geometric structure can be realized constructively in various ways. For example, the burner channel may be formed as a tube of a dielectric material. This tube is usually concentrically enclosed by an outer tube. The gap between the inner and the outer tube is flowed through by a coolant. The coil winding is either embedded in a massive gap, which in turn is flowed through by a coolant, or outside the outermost tube. This design makes it possible to protect the coil winding from the direct action of the hot plasma and to cool sufficiently. As a result, operation of the plasma torch with high power is possible.

However, such a pipe construction is associated with some serious disadvantages. These affect on the one hand the adjustment of the two tubes. On the other hand, the heat transfer between the coolant and the coil winding very often proves to be unsatisfactory. Another disadvantage of such tubular structures is that the coil winding is relatively far away from the plasma stream to be influenced. As a result, the magnetic field B and the magnetic flux Phiinhalb the burner interior decreases.

To address these problems, it has been proposed to embed the coil winding in a dielectric material. In the DE 2 112 888 A a high-frequency induction plasma torch is described, in which the coil windings are either inserted into recesses of a wall of the tube or are located directly in the wall of the tube. For the coil winding in the document, a helical structure of a tubular conductive material, such as copper, proposed, which is flowed through by the coolant. The embedding of the winding in the pipe wall by means of a thermosetting, heat-resistant material, preferably a ceramic material.

In the DE 692 16 970 T2 An induction plasma torch with a water-cooled ceramic termination tube will be described. In the arrangement mentioned there, the induction coil is also embedded in the burner tube. For the tube, cast ceramic materials or composite polymers are proposed.

The US 5,877,471 A. proposes a structure in which the tubular coil winding is sandwiched between tubular bodies, at least one of the bodies being made of a dielectric material. The space occupied by the winding is traversed by a coolant.

The DE 10 2010 014 056 A1 discloses embodiments in which the induction coil is completely enveloped and in which the enclosure over the entire longitudinal axis direction of the burner extends or is placed around an inner burner glass.

The DE 10 2010 050 082 A1 teaches a multi-shell burner tube, which is inten- tively traversed by a fluid and is surrounded on the outside by a coil. The coil is not covered and is not completely or partially washed by the fluid.

The US 5,743,961 A discloses a thermal spray coating apparatus with induction coil and envelope in the form of a cavity. The coil is housed in its entire length and is located within the enclosure.

With such embedded coil windings, it is possible to improve the coupling between the induction coil and the plasma. However, it turns out that this advantage has to be paid for by a complex cooling of the induction coil. Since the embedding makes it impossible or difficult to circulate the windings with a coolant, the windings must thus be flowed through by a coolant itself. Due to the relatively poor heat conduction in such an embedding, a correspondingly higher cooling effect must be achieved by the coolant. Although the basic structure of the plasma torch can be relatively easily accomplished with a double-walled construction of the burner tube, a single-walled construction of the burner tube with embedded coil winding, however, requires additional supply lines, holes or channels and therefore is additionally complicated. As a result, the structure of the burner is correspondingly complex, in particular in the event of replacement or other maintenance work.

It is therefore the object underlying the invention to provide a burner assembly which allows optimal flame distribution and easy interchangeability and in which a sustainable cooling of the coil winding is given in conjunction with a simple construction of the winding. Furthermore, a trouble-free introduction of process media into the plasma stream should be made possible, wherein the burner tube should have the simplest possible structure. The entire device should therefore be easy to assemble, low maintenance and thus cost-effective. The supply of the precursors should be carried out by a nozzle design in such a way that a high material efficiency is achieved with the lowest possible energy input.

The object is achieved with a burner, in particular an inductively coupled plasma torch with the features of the independent claims 1 and 4 and a method according to claim 22.

The inductively coupled plasma torch contains a burner channel through which flows a plasma and an induction coil surrounding the burner channel, as well as an enclosure. The envelope has a porous structure, which can be traversed by a fluid.

The plasma torch is characterized according to the main claim 1 characterized in that the space between the outer casing and the burner channel is formed for a Screengasstrom with a volume flow rate of up to 200 l / min, wherein the sheath of a porous ceramic, a porous glass, a porous Polymer plastic and / or a double wall pipe is formed with a porous filler, the porous structure is formed in the form of parallel to the longitudinal axis of the induction coil oriented channels. In these channels, the fluid flows through the porous structure parallel to the burner channel, avoiding turbulent gas flow and causing it to be evenly distributed. The induction coil is located close to the burner channel, with a very tight winding of the induction coil is provided around the tubular burner channel. The envelope in the longitudinal axis direction of the overall arrangement runs starting from a burner foot along the burner channel and reaches up to a predetermined distance to the induction coil and ends there. However, it does not surround the induction coil.

According to the features of independent claim 4, an inductively coupled plasma torch is provided for producing semifinished products for bending-insensitive glass fibers, comprising a tubular burner channel, an induction coil surrounding the burner channel and an outer casing, wherein the casing has dielectric properties and a porous structure, wherein the porous Structure is traversed by a fluid, further based on the fluid flow on the burner upper side of the distance space or the porous structure is closed and the burner upper side radially arranged fluid outlet openings are present in the enclosure, wherein the fluid enters through the burner underside open distance space. This is characterized by the fact that the tubular burner channel has bulges oriented radially to the middle of the channel for shaping the plasma gas flow.

The construction according to the invention is based on the one hand on the idea of making the envelope itself permeable. For this purpose, the envelope has a porous, for example a spongy, structure. This porous structure can be at least partially flooded with a fluid, soaked and / or flowed through. The entire porous structure stands both with the optionally embedded induction coil and with it flowing fluid in thermal contact, thus allowing intensive cooling of the coil turns. In addition, the porous structure makes it possible to introduce and guide a process medium in a simple manner. Another advantage is that a preheating of the medium occurs and can be used to advantage.

The latter is particularly advantageous with regard to use of the plasma torch in coating processes according to the invention. In many high temperature coating processes, the precursor containing medium is introduced into the coating process at temperatures significantly less than 150 ° C. As a result, there is a strong temperature gradient to the several thousand degrees Celsius hot plasma flame. The coating speed, which is composed proportionally of the reaction rate of the precursor and the surface processes (such as melting steps), but is highly sensitive to temperature. Too rapid inflow of a relatively cold precursor medium reduces the coating speed and thus leads to an increased use of energy. However, efficient use of energy is indispensable both economically and ecologically in the face of rising energy prices. Increasing the temperature of the Precursorgases thus not only reduces the "cold blowing" of the hot coating zone, but also increases the coating efficiency while reducing the necessary energy.

The porous structure can be flowed through in various ways. In a first embodiment, the porous structure can be flowed through in the direction of the longitudinal axis of the induction coil. Such an embodiment allows above all a cooling of the induction coil. At the same time, a medium can be moved within the envelope parallel to the plasma stream and fed into the plasma stream at a corresponding point.

In another embodiment, the porous structure can be traversed in the direction of the longitudinal axis of the induction coil and in the direction of the burner channel. As a result, the fluid flowing in the sheath can both cool the induction coil and also pass laterally into the burner channel, where it is added to the plasma as the process medium.

In a further embodiment, the porous structure has at least one opening leading into the burner channel. This can be introduced independently of the particular porous structure present.

In a first embodiment, the fluid is exclusively a coolant for the embedded induction coil. It preferably consists of a gas and / or gas mixture. Also conceivable are electrically non-suffering liquids (such as N _{2, l} ).

In a further embodiment, the fluid is a process medium which can be heated in the porous structure, preferably a gas mixture which is provided for introduction into the burner channel. In an advantageous embodiment, the process medium contains precursor components for a reactive conversion taking place in the burner channel.

The porous sheath can be made of different materials. It is a porous ceramic, porous composites, a porous glass and / or a porous polymer polymer used.

In one embodiment, a double-walled tube is used, the cavity between the inner and outer boundary containing a suitable amount of packing that produce the porosity. The coil may be located within this cavity should its cooling be in the foreground or else be mounted outside the double wall tube.

In an expedient embodiment, the porous envelope is at least partially transparent in an ultraviolet to infrared electromagnetic wavelength range, in particular in a range between 100 to 2000 nm. This embodiment enables a spectral detection of the processes within the burner channel.

In addition, the porous sheath is formed at least partially optically intransparent. This is particularly advantageous because the optical shielding of the radiation, the UV exposure of the environment is reduced. When the burner is used in a coating process, the screen also appropriately reduces the UV load on the substrate, which has a positive effect on its quality with regard to its optical and / or mechanical properties, depending on the substrate.

The outer shape and contour of the porous sheath may be formed in various ways. In one embodiment, the porous sheath and / or the induction coil has a cylinder and / or elliptical symmetry. This deviation may refer to both the inner and outer geometry of the envelope.

The outer and / or inner boundary of the porous envelope has in one embodiment at least one outer corner or a polygonal, in particular a four- or six-fold, symmetry. Thus, it is possible in the case of an angular embodiment of the outer boundary, the Enclosure with a suitable tool to capture and replace. By a deviation from the circular geometry in the inner boundary, it is advantageously possible to adapt the coating image to the substrate geometry.

In addition, the use of the burner based on the possibility of preheating the precursor is not limited to the heat source of the inductive plasma. Also possible is the use of flame burners with suitable fuels, such as hydrogen, natural gas, acetylene and / or propane burners for the coating processes.

In one embodiment, the enclosure is made in two parts. In this case, an inner casing immediately adjacent to the burner channel and an outer casing enveloping the induction coil are provided. The outer envelope may be porous.

On the other hand, the construction according to the invention is based on the idea that the envelope has a closed structure, wherein the distance space between the outer wall of the burner channel and the envelope can be traversed by a fluid, wherein the induction coil is located close to the burner channel and the envelope in the longitudinal axis direction of the overall arrangement reaches to a predetermined distance between 0 to about 30 cm to the induction coil, but this does not surround. In order to influence the fluid flow between the casing and the burner channel, a porous structure, preferably consisting of a metal and / or ceramic foam, may be present in sections, at least in the longitudinal direction. This ensures through the proper distribution of the fluid for a particularly uniform cooling of the components of the burner.

In this solution aspect of the invention, the outer burner boundary, d. H. the envelope only up to the induction coil zoom. In this case, a very narrow winding of the induction coil around the tubular burner channel, designed as a quasi inner burner glass is possible, which leads not only to an energy saving but also to an improved plasma flame distribution. With this solution, particularly high deposition rates or separation efficiencies can be achieved.

Embodiment 1

• Screen gas (gas between envelope and burner channel): up to 200 l / min N2
• Plasma gas 30 l / min O ₂ , 90 l / min N ₂
• Feed SiCl ₄ via nozzles above the burner channel: 1500 g / h of SiCl ₄
• Outer diameter burner channel 75 cm, wall thickness 2 mm
• Outer diameter wrapping 85 cm, wall thickness 2 mm
• Spacing Induction Coil / Sheath: 25-40 mm

Embodiment 2:

• Screen gas (gas between envelope and burner channel): up to 200 l / min N2
• Plasma gas 30 l / min O ₂ , 90 l / min N ₂ , 0.5 l / min SF ₆
• Feed SiCl ₄ via nozzles above the burner channel: 1000 g / h of SiCl ₄
• Outer diameter burner channel 65 cm, wall thickness 2 mm
• Outer diameter cover 75 cm, wall thickness 2 mm
• Spacing Induction Coil / Sheath: 25-40 mm

In a third basic idea according to the invention, in turn, an inductively coupled plasma material containing a tubular burner channel is assumed, with an induction coil surrounding the burner channel being present. In this case, the envelope is provided with a closed or a porous structure, wherein the porous structure or the distance space between the outer wall of the combustion channel and the envelope can be traversed by a fluid. Furthermore, based on the fluid flow on the burner upper side of the distance space or the porous structure executed closed. In addition, the upper side radially arranged fluid outlet openings are present in the enclosure, wherein the fluid enters through the burner underside open distance space. So here it is only closed at a double pipe arrangement, the upper edge. The lower side of the double tube assembly is open and can be clamped in a known Brennerfuß. The connection of the burner foot is used in this solution, in particular for the feeding of a SiCl ₄ / N ₂ mixture with optional SF ₆ portion, wherein the outlet openings lead the heated process gas to additional, located above the coil or above the burner nozzles.

In this embodiment, it is possible without disassembly or replacement of the coil to replace damaged burner tubes or burner glasses, since here the induction coil is not clamped between gas inlet and gas outlet openings quasi. Due to the upper side of the burner existing closed training, the predetermined orientation between the burner channel and enclosure can not change.

To form the plasma gas flow, there is the additional possibility that the tubular burner channel oriented radially to the channel center Bulges. These can be created using per se known glass processing techniques.

According to the basic concept of the invention presented here, preferably on the burner side, the envelope has a bulge for the introduction of an electrical ignition means, which is formed in contact with the tubular burner channel, preferably in contact with it. An otherwise required ignition tube can be omitted according to this inventive idea.

The burner according to the invention is particularly suitable for the production of coatings on substrates. Thus, it finds particular application in the production of semi-finished products for the optical industry from doped or undoped quartz glass. In this regard, reference is made to the method claims. In particular, burners of this type are used in coatings of semifinished products for producing bend-insensitive fibers, in which the optical losses relative to the radius of curvature of the fibers are particularly low.

In a preferred embodiment of the invention, at least one shielding gas curtain may be created around the burner assembly.

To generate the gas curtain at least one surrounding the burner rim is provided with a plurality of gas outlets. The flushing rim can be formed as a round, oval or polygonal closed tube with at least one gas supply. Through openings directly on the top or there used or molded tubular nozzles, which are arranged perpendicular or in a Winkelverkippung on the closed tube, there is a blowing of the screen gas or a Screengasgemisches or even the blowing of compressed air. Especially in the deposition of glass with low hydrogen content such a curtain is advantageous. The fluid flowing through it then ideally has a dew point of less than -40 ° C. In combination with pre-dried working and precursor gases, glass with a total hydrogen content (as OH groups and / or as hydrogen dissolved in the glass matrix) can be produced of significantly less than 1 ppm.

The burner channel and / or the aforementioned enclosure may have a surface optimized with respect to the mixed gas flow. Such a structure may approximate a helical course.

In a further embodiment, a housing surrounding the burner assembly may be provided, wherein the housing may also be designed as a burner unit for receiving a plurality of burners.

In a further embodiment of the invention, flow-calming means are formed in the burner base in the region of the plasma or precursor gas supply.

These means may comprise an insert for receiving a baffle, a grid and / or a metal, ceramic or glass wool structure. They may also be formed as composites of several previously mentioned components.

The aforesaid insert may comprise one or more concentrically arranged chambers.

The burner arrangement according to the invention is used in particular for coating one-dimensional or multidimensional surfaces or bodies, these surfaces or bodies consisting of or containing dielectric materials.

In this regard, deposition of thin layers of doped or undoped quartz glass, metal or semimetal materials, transition metals or alloys occurs. The coating can also be made in combination with additional flame burners, ovens or the like. In particular, coatings of substrates for the semiconductor and / or solar industry can preferably be performed based on silicon.

The coating direction can also be chosen to be different from 90 ° with respect to the angle between the longitudinal axis of the plasma torch arrangement and the surface to be coated. So it is here a tilt of the burner and the use of multiple burners possible. By oppositely arranged burner and introduced into the burner gap space to be coated surfaces or body, a double-sided coating can be made in one operation.

The feeding of the precursor gas can be carried out variably via one or more provided nozzles of the burner arrangement.

The following description of the nozzles is used in both flame burners and plasma torches. A particularly suitable embodiment of such nozzles is in 13a and b. In this case, a gas mixture 1 ( 25 ) through the innermost opening of a multiple tube in the coating process. Another gas mixture 2 ( 27 ) is added to the coating process by the tube of the multiple tubes, which is closest to the radius. The Separation of the two gas mixtures is carried out by a separation barrier ( 26 ), which in the simplest case has a smooth surface. In addition, this separation barrier may also have a lamellar and / or a helical structure with respect to the nozzle length, whereby the flows of the exiting gas streams are stabilized.

shows an embodiment in which the outlet opening of the inner gas mixture 1 protrudes relative to the other gas outlet openings. This allows a broader distribution of the components contained in the gas mixture 1. In the reverse case, the exit of the gas mixture 1, as in shown, locally before that of the gas mixture 2, so that the gas mixture 1 is advantageously enclosed by the gas mixture 2 and thus allows a directed material flow control of the gas mixture 1 in a suitable manner.

The principle of the double-pipe nozzle can be suitably transferred to a multi-pipe system, it being possible for several gas mixtures to have the same and / or different compositions.

In one embodiment, the gas mixture 1 consists of silicon tetrachloride and nitrogen, the gas mixture 2 of oxygen and a dopant preferably SF ₆ in variable volume fraction. At least one nozzle of this type is arranged movably above the burner. This design makes it possible to ideally produce doped quartz glass in the form of ingots with a low OH content.

In order to improve the mixing of the gas streams, it is provided to introduce flow-influencing elements in and / or on the nozzle head. On the one hand, this can be the already mentioned structuring of the separation barrier (FIG. 26 ) or at least one extending over at least one gas outlet opening web ( 28 ; 29 ), as in the 14 and 15 is shown.

In one embodiment, multiple lands become a grid 30 combined ( 16 ), which is attached to the nozzle end. This nozzle grid acts as a diffuser, which ensures a good mixing of the gas streams. If this web or grid contains at least one catalytically active component such as palladium, iridium and / or platinum, for example, the efficiency of the reaction can be increased and the properties of the glass matrix can be influenced in a targeted manner.

The materials used for the grid are not limited to the aforementioned elements or alloys, but depend on the intended use and application. Thus, the web or the lattice of dielectric materials such as ceramic and glass can be just as composed as metals or semi-metals or their alloys.

For coating optimization, existing nozzles can also be moved controlled in dependence on the coating direction.

The tube forming the burner channel can also be designed as a nozzle arrangement of concentric tubes for flow optimization.

In a further example for the production of quartz glass with the highest possible total hydrogen content, the nozzle is formed from a tenfold tube with a gas stream 1 consisting of SiCl ₄ and N ₂ . In other gas streams 2 and 3, hydrogen and oxygen are added and distributed alternately to the different openings of the multi-tubes. In this case, the structure of the nozzle corresponds to that of the burner already described several times. When using hydrogen can be dispensed with the energy input using the induction coil. In the 1 - 6 is in this case the structure without the induction coil ( 2 ) to accomplish.

The device according to the invention will be explained in more detail below with reference to exemplary embodiments. To clarify serve the 1 to 6b , The same reference numbers are used for identical and identically acting parts.

Show it:

1 an exemplary burner channel with an induction coil in a porous envelope,

2a a porous casing with a porous structure which can be flowed through in the direction of the longitudinal axis of the coil,

2 B a porous casing with a porous structure which can also be flowed through in the direction of the burner channel,

3a an induction coil with a partial cladding,

3b an induction coil with a complete transparent cladding,

4a an envelope having an outer contour in a six-fold symmetry, divided into an inner and outer envelope,

4b an envelope and a burner channel in an elliptical basic shape,

5a a porous envelope, with lateral inlet and outlet openings,

5b a porous enclosure with outlet openings in the burner longitudinal direction with the direction of the medium flow towards the burner center,

6a / 6b a porous enclosure with lateral inlet openings and a nozzle ring on the inside of the enclosure in the direction of the burner channel,

7 an embodiment of a burner with closed top and gas supply via a burner base and by means of open space or open porous structure, which is burner bottom side, and a channel-centered bulge in the tubular burner channel for forming the plasma gas flow,

8th a representation similar to that after 7 but with rectilinear burner channel and bulge in the enclosure for bringing an electrical ignition means, in particular an ignition wire,

9 a schematic diagram of a flushing bowl with Spülkranzdüsen,

10 and 11 Top views and side views of a burner base assembly with flow-calming means,

12 a side view of a burner with located in the burner foot insert for flow calming,

13a / b a nozzle consisting of a double tube,

14 / 15 a nozzle consisting of double tube with separation barrier and

16 a nozzle with a grid as a diffuser.

1 shows an exemplary basic structure of the inductance-coupled plasma burner according to the invention. The plasma burner contains a burner channel through which a plasma flows 1 , This one is from an induction coil 2 surround. The induction coil is of a cladding 3 locked in. The dielectric sheath thus forms at the same time the wall of the burner channel 1 , The cladding is of a porous structure 4 crossed, which is indicated in the example shown here by a pattern. The porous structure allows the envelope to flow through a fluid 5 , In the example shown here, the fluid enters the porous enclosure from below, impregnates its pore structure and leaves the enclosure via the upper end, the outer sides and optionally also in the direction of the burner channel 1 , In this case, the coil turns of the induction coil 2 lapped by the fluid. The inner surface of the porous structure of the envelope thereby causes a considerably enlarged surface of the coil turns and thus promotes the cooling effect of the fluid for the induction coil on the one hand and a heating of the fluid on the other.

The porous structure can be designed in various ways. In 2a is the porous structure in the form of parallel to the longitudinal axis of the induction coil oriented channels 6 educated. The fluid 5 thus flows through the porous structure parallel to the burner channel 1 , If the energy is not inductively introduced into the system but, for example, by the release of chemical heat of reaction, according to the invention, the induction coil 2 unnecessary. In this case, the burner is substantially similar to the previously described construction of the nozzle in the 13 - 16 , The fluid thus passes into the reaction zone only at the end of the coating. Such a shape of the porous structure is preferred if, in the case of the inductively coupled plasma torch, it is not intended to introduce the fluid into the plasma and the primary purpose of the induction coil is to be cooled.

The porosity depends to a large extent on the viscosity of the fluid. The choice of the smallest possible pores allows a long residence time and thus a better heating of the fluid for lowering the temperature gradient of the precursor gas. Packing or large pores allow good cooling of the coil.

In particular, a turbulent gas flow is avoided by the porous structure and ensures a uniform distribution. This is particularly advantageous if the precursor medium is to pass through the inner boundary in the burner channel, as can be evenly distributed to all outlet openings by a suitable choice of porosity of the material flow. In this case, in a preferred embodiment for the inductively coupled plasma torch, it is also possible to mount the coil outside the porous layer, ie outside the outer envelope.

The fluid itself preferably consists of a gas. The composition of the gas depends essentially on the function of the fluid. For cooling, preference is given to using compressed air, nitrogen or a noble gas, which was previously predried depending on the application. Alternatively, fluids and fluid mixtures with precursor additives are possible, which are suitable for introduction into the reaction zone of the burner z. B. the plasma stream are determined and react there in a predetermined manner.

In the embodiment in 2 B is the porous structure as a sponge or with the help of packing 7 trained and can be flowed through in principle in any direction. In the example shown here, the fluid enters 5 from below into the casing, soaks the sponge-like structure and occurs both at the top and in the area of the burner channel 1 out again. An outer seal 8th can be provided, which prevents leakage of the fluid on the outside of the enclosure.

In the 2a Of course, the pore arrangement shown may of course be modified so that at selected locations a passage of the fluid into the burner channel is possible. For this purpose, on the inside of the envelope, ie in the region of the burner channel, holes or scratches be attached, in which some parts of the channels 6 are open to the burner channel and therefore conduct the flowing fluid in them in the burner channel. Likewise, in 2 B individual sections of the inner surface of the enclosure to be covered in the burner channel and therefore allow passage of the fluid in this area only at individual selected locations. An example of such a configuration is in 6a / b shown.

The wrapping can be made of different materials. For example, heat-resistant ceramics, glass, composites or polymeric plastics can be used. It is also the use of metal-containing materials possible, especially if a flame burner is used as the heat source. The porous structure results either by foaming, co-sintering of a granulate, two-component mixtures with subsequent leaching of a soluble component, wherein in the base material corresponding cavities remain, and such, known manufacturing processes more. Also, a filling with suitable packing to produce the porosity executable. For the in 2a shown pore structure in the longitudinal direction is also a layered application of unfired ceramic lamellae or a wrapping of the induction coil with such lamellae and a subsequent burning this arrangement possible.

Corresponding production steps can also be carried out with polymer materials. In particular, wrapping and laminating the induction coil with a tissue and subsequent sintering together of the tissue are possible. In this case, the individual layers of fabric combine, but allow between the contact points porous spaces to flow through the fluid.

The enclosure does not necessarily include the induction coil. 3a shows an embodiment with a cladding only partially arranged. The fluid 5 Comes from below coming through the porous structure of the enclosure or the existing space there and laps the induction coil 2 from the outside. For this purpose, the envelope may have a distance of, for example, 0 cm to 30 cm to the nearest coil turn. The induction coil is placed very tightly around an inner burner glass and is exposed on the outside.

The envelope may also be made transparent at least in sections. 3b shows an example for this. The enclosure consists in this case of a transparent glass or a polymeric plastic. The material is preferably transparent in the infrared to ultraviolet spectral region, generally in the spectral region typical of the plasma. It makes it possible to detect the plasma state by means of optical analysis methods, in particular spectroscopic methods.

The shapes of the envelope and the inductors enclosed therein may differ from the cylindrical basic shape. 4a shows an embodiment with a sixfold symmetry for the outer contour. This can be very easily with a suitable tool, such as a wrench, grab and assemble. The burner channel 1 and the induction coil 2 keep their basic cylindrical shape in this example. At the in 4a The example shown is the wrapper in an inner wrapper 9 and an outer cladding 10 divided. The inner cover connects directly to the burner channel and is thermally particularly resistant. The outer envelope encloses above all the induction coil and forms the outer contour. Different materials can be used for the inner and outer sheaths. For example, the inner sheath may consist of a ceramic or a glass, while the outer sheath may be formed of a plastic.

4b shows an exemplary enclosure 3 with induction coil 2 and burner channel 1 with an elliptical cross section. The other properties of the envelope correspond to the aforementioned embodiments.

Furthermore, according to the embodiment of 5a provided in a further embodiment, an outlet opening 11 in the direction of the burner outside. By means of these, the heated precursor medium can be supplied to further injections (nozzls) which can be positioned separately in a separate manner, which in turn supply the material flow at a suitable point into the Blow in the reaction zone. The injections may in one embodiment consist of a single tube through which the preheated gas stream is passed. In this single tube may still contain flow-forming elements such as slot openings or multiple bores. Another embodiment is the already mentioned multiple tube, as in 13 is shown. The nozzles may have a deviating from the circular geometry in the plan view to the gas outlet. In this case, a rectangle is preferred, since it has proven to be particularly suitable for the coating of elongate substrates. But these outlet openings can also in a preferred embodiment according to 5b be attached directly to the top of the burner so that their flow direction are aligned substantially to the burner inside.

Furthermore, it is according to one in the 6a and 6b embodiment shown also possible, a number of access openings 13 on the inside of the burner in a suitable position. These openings are designed in their number, position and opening form suitable and can include, round, oval, angular elements in the form of individual nozzles or nozzle chains. In a suitable, in 6b embodiment shown form the access openings 13 at least one nozzle ring.

As shown 7 will turn from a burner channel 1 assumed that z. B. is formed by a burner glass made of high temperature resistant material.

The serving 3 has a closed structure in this embodiment. This results in a distance space between the wall of the burner channel forming tube and the enclosure 3 , which by a fluid (indicated direction of flow through arrows) can be flowed through.

Furthermore, based on the fluid flow shown burner top side of the distance space is closed and there are radially oriented fluid outlet openings 14 present, the removal of a heated, the burner foot 15 supply gas or fluids serve.

The tubular burner channel may bulges radially oriented toward the center of the channel 16 include, which serve the shaping of the plasma gas stream.

The envelope has, preferably burner underside, a tubular burner channel 1 prefers this touching, formed bulge 17 for bringing an electric ignition means, z. B. an ignition wire.

Because the quasi double tube arrangement according to the 7 and 8th closed only on the upper side, can be supplied via the lower side, which is open, process gas. The lower side is clamped in a known Brennerfuß. One in the 7 and 8th Not shown, the envelope surrounding the outside induction coil does not interfere with the replacement of the arrangement. This can be pulled upwards and removed from the burner base without having to disassemble the induction coil.

In the embodiment according to 8th is from a straight, cylindrical inner burner tube to form the tubular burner channel 1 with regard to the other features, to the explanations given for 7 referenced.

The 9 shows a schematic diagram of a purging ring with Spülkranzdüsen.

For particularly dry coatings or to better shape the gas outlet above the burner more gas curtains are beneficial. These gas curtains can with the help of in the 9 Purging ring shown can be generated, which surrounds either the burner itself and / or the nozzles or Nozzeln.

The sink is a round, oval or polygonal closed tube with at least one gas supply (not shown). Through the openings of the flushing bowl nozzles 19 on the top of the sink 18 the purge gas mixture or a similar gas suitable for purge exits. The scavenging nozzles 19 may be formed as pieces of pipe of a few centimeters in length, which have a longitudinal axis orientation, which runs parallel to the longitudinal axis of the corresponding burner assembly. Alternatively, it is also possible to set the Spülkranzdüsen at a predetermined angle, as shown in the 9 , on the left side, is symbolized.

The 10 and 11 serve to illustrate an embodiment in which a burner base assembly is provided with flow-calming means. On the left side is a plan view and on the right side a side view of the corresponding burner foot 15 shown. The flow-calming means can be an insert 20 include, which z. B. is annular and receives a structural body. The supply of the plasma and / or Precursorgases (indicated by the arrow 21 ) then takes place from below through the use for the purpose of gas calming. The burner foot 15 can use 20 surrounding still an inner burner glass 22 include.

In the presentation after 11 Again, it is a further development of a burner foot with flow-calming means, the use there includes two different structures on the one hand to calm the precursors and on the other hand to calm the plasma gas. An inner commitment 23 it serves to calm the precursors and a surrounding, external use 24 the calming of the plasma gases to be passed. The height of the gas leaks of the respective calming structures is as in the descriptions of the 13 explained, depending on the purpose.

A burner assembly based on the embodiment according to 3a but comprising the above-mentioned gas flow pacification insert 12 , Above the burner foot 15 is the already mentioned serving 10 present, up to a predetermined distance to the induction coil 2 zoom ranges. Inside the burner channel 1 is the insert 20 to calm the plasma or precursor gas or the gas mixture.

The usable as a chamber insert 20 can be used in particular in connection with the design of the burner channel and / or the envelope with respect to flow-optimizing surface.

LIST OF REFERENCE NUMBERS

1

Brenner channel

2

induction coil

3

wrapping

4

porous structure

5

fluid

6

longitudinal channels

7

sponge structure

8th

outer seal

9

inner cladding

10

outer cladding

11

Outlet opening of the heated medium z. B. for connection to Nozzle

12

Inlet opening with coolant

13

inner access openings

14

Fluid outlet opening

15

burner stand

16

bulge

17

bulge

18

Spülkranz

19

Spülkranzdüsen

20

commitment

21

gas flow

22

inner burner glass

23

Use for precursors

24

Use for plasma gas

25

Gas mixture 1

26

separation barrier

27

Gas mixture 2

28

web

29

web

30

grid

Claims (26)

Inductively coupled plasma torch for producing semi-finished products for bending-insensitive glass fibers, comprising a tubular burner channel ( 1 ), an induction coil surrounding the burner channel ( 2 ) and an outer envelope ( 3 ), wherein the envelope has a closed or porous structure ( 4 ), wherein the porous structure or the distance space between the outer wall of the burner channel and the envelope of a fluid ( 5 ), characterized in that the space between the outer envelope and the burner channel is designed for a Screengasstrom with a volume flow rate of up to 200 l / min, wherein the envelope ( 3 ) is formed of a porous ceramic, a porous glass, a porous polymer plastic and / or a double-walled tube with a porous filler whose porous structure in the form of parallel to the longitudinal axis of the induction coil oriented channels ( 6 ) is formed, in which the fluid ( 5 ) the porous structure parallel to the burner channel ( 1 ), wherein a turbulent gas flow is avoided and its uniform distribution is effected, the induction coil is located close to the burner channel, wherein a very tight winding of the induction coil is provided around the tubular burner channel and the envelope in the longitudinal axis direction of the overall arrangement starting from a burner foot ( 15 ) along the burner channel ( 1 ) and reaches up to a predetermined distance to the induction coil and ends, but the induction coil does not surround. Burner according to claim 1, characterized in that the predetermined distance is in the range of 0 cm to 30 cm. Burner according to Claim 1, characterized in that, in the case of very cold plasmas, the envelope ( 3 ) is shortened or deleted. Inductively coupled plasma torch for producing semi-finished products for bending-insensitive glass fibers, comprising a tubular burner channel ( 1 ), an induction coil surrounding the burner channel ( 2 ) and an outer envelope ( 3 ), the envelope ( 3 ) Dielectric properties and a porous structure, wherein the porous structure is flowed through by a fluid, further based on the fluid flow on the burner upper side of the distance space or the porous structure is closed and the upper side radially arranged fluid outlet openings are present in the enclosure, wherein the fluid inlet takes place through the burner underside open space space, characterized in that the tubular burner channel radially to the channel center oriented bulges ( 16 ) for shaping the plasma gas stream. Burner according to claim 4, characterized in that the dielectric sheath ( 3 ), preferably burner bottom side, one to the tubular burner channel ( 1 ) prefers this touching, formed bulge ( 17 ) for bringing an electric ignition means. Burner according to one of the preceding claims, characterized in that the fluid ( 5 ) is a coolant for the induction coil. Burner according to one of claims 1 to 5, characterized in that the fluid in the porous structure ( 4 ) or the distance space heatable process medium for introduction into the burner channel ( 1 ). Burner according to claim 7, characterized in that the process medium Precursoranteile for a reactive reacting in the burner channel. Burner according to one of the preceding claims, characterized in that the envelope ( 3 ) is at least partially transparent in an ultraviolet to infrared electromagnetic wavelength range, preferably in a range between 100 to 2000 nm, more preferably in a range between 190 nm and 1500 nm. Burner according to one of the preceding claims, characterized in that the envelope ( 3 ) and / or the induction coil ( 2 ) has a cylinder and / or elliptical symmetry. Burner according to one of claims 1 to 9, characterized in that the envelope ( 3 ) has at least one outer corner or a polygonal, in particular a four- or sechzählige, symmetry. Burner according to one of claims 1 to 9 or 11, characterized in that the envelope ( 3 ) has at least one inner corner or a polygonal, in particular a four- or sechzählige, symmetry. Burner according to one of the preceding claims, characterized in that the sheath is designed in two parts, wherein an immediately adjacent to the burner channel inner sheath ( 9 ) and an induction coil enveloping the outer envelope ( 10 ) is provided and at least the outer sheath is formed porous. Burner according to one of the preceding claims, characterized in that at least one gas curtain is generated around the burner assembly. Burner according to claim 14, characterized in that for generating the gas curtain at least one surrounding the burner rim ( 18 ) with a plurality of gas outlets ( 19 ) is provided. Burner according to one of the preceding claims, characterized in that the burner channel ( 1 ) and / or the envelope ( 3 ) have a flow-optimized surface in the form of a Helixverlaufs. Burner according to claim 16, characterized in that the coming into contact with the respective gas or fluid streams surfaces structuring in the form of flow-influencing elements in and / or on the burner head, in particular in the form of a separation barrier ( 26 ), at least one extending over at least one gas outlet opening web ( 28 ; 29 ), a combination of a plurality of webs to a arranged at the nozzle end and serving as a diffuser grid ( 30 ) exhibit. Burner according to one of the preceding claims, characterized in that an enclosure surrounding the burner assembly is provided. Burner according to one of the preceding claims, characterized in that in the burner base ( 15 ) in the region of a plasma or Precursorgaszuführung flow-calming means are formed. Burner according to Claim 19, characterized in that the means comprise an insert ( 20 ) for receiving a baffle, a grid and / or a metal or glass wool structure. Burner according to claim 20, characterized in that the insert ( 20 ) comprises one or more concentrically arranged chambers and / or pipe arrangements. Use of a burner according to any one of the preceding claims for coating single or multi-dimensional surfaces or bodies consisting of or containing dielectric materials. Use of a burner according to one of the preceding claims for a deposition thin layers of doped or undoped quartz glass, metal or semimetal materials, transition metals or alloys. Use of a burner according to one of claims 22 or 23 for carrying out a coating in combination with additional flame burners, ovens or the like means. Use of a burner according to one of claims 22 to 24, characterized in that the coating direction with respect to the angle between the longitudinal axis of the burner and the surface to be coated of 90 ° is selected differently, wherein a tilting of the burner takes place. Burner according to one of claims 22 to 25, characterized in that the supply of Precursorgase takes place variably via one or more provided nozzles of the burner assembly.

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