EP1421832B1 - Plasma burner with microwave stimulation - Google Patents

Plasma burner with microwave stimulation Download PDF

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Publication number
EP1421832B1
EP1421832B1 EP02762243A EP02762243A EP1421832B1 EP 1421832 B1 EP1421832 B1 EP 1421832B1 EP 02762243 A EP02762243 A EP 02762243A EP 02762243 A EP02762243 A EP 02762243A EP 1421832 B1 EP1421832 B1 EP 1421832B1
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EP
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Prior art keywords
metallic tube
plasma
hollow
hollow metallic
waveguide
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EP02762243A
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German (de)
French (fr)
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EP1421832A1 (en
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Jeng-Ming Wu
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/26—Plasma torches
    • H05H1/30—Plasma torches using applied electromagnetic fields, e.g. high frequency or microwave energy
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/48—Generating plasma using an arc
    • H05H1/50—Generating plasma using an arc and using applied magnetic fields, e.g. for focusing or rotating the arc

Definitions

  • the invention relates to a plasma torch with microwave excitation, in which a plasma is generated by acting with a gas microwaves.
  • a plasma torch with a microwave generator which has a waveguide for guiding the microwaves generated by the microwave generator and a branched from the waveguide metallic hollow tube, wherein centrally within the metallic hollow tube from the waveguide in the metallic Hollow tube extending electrically conductive elongated nozzle, which has a nozzle tip at its projecting into the metallic hollow tube end, and the metallic hollow tube in height of the flame, preferably in the nozzle tip starting an increase in diameter, extending in the longitudinal direction of the plasma torch at least over the Area of the flame extends.
  • the increase in diameter is intended to ensure that the propagation conditions for microwaves are also met in the area of the flame, so that a stable plasma is generated.
  • the plasma gas serving process gas is guided through the nozzle in the range of high microwave power density at the nozzle tip.
  • the improvement in the stability of the plasma achieved by means of this solution by improving the propagation conditions of the microwaves in the area of the flame has not proved sufficient in practical operation, in particular in the case of large pressure fluctuations of the process gas.
  • Even in practical operation made constant adjustment of the microwave impedance of the waveguide and the metallic hollow tube has not led to a sufficient stabilization of the plasma at pressure fluctuations of the process gas, in particular to a stable ignition or re-ignition of the plasma.
  • the invention is therefore based on the problem of providing a plasma torch with microwave excitation, which is sufficiently good even with large pressure fluctuations of the process gas for a stable plasma Ensures propagation conditions for the microwaves and ensures a stable ignition or re-ignition of the plasma without a constant adjustment of the microwave impedance of the waveguide and the metallic hollow tube is required.
  • microwaves in this region of the metallic hollow tube can be well forwarded even in the event of pressure fluctuations of the process gas changing line conditions, without a constant adjustment of the microwave impedance of the waveguide or the metallic hollow tube is required.
  • the invention is based on the finding that the plasma as a coaxial inner conductor with respect to its electrical properties not behave as previously assumed because of the free electrons therein as a metallic conductor, but that these electrical properties of the plasma to a considerable extent by the pressure of the supplied process gas depend.
  • the inventive electrically conductive windings are designed in the form of a single-layer cylindrical coil or as a single conductor loops.
  • the inventive electrically conductive windings are arranged floating or are in electrical contact with the metallic hollow tube.
  • the number or spacing of the turns to each other can vary, without the effect significantly decreases.
  • the turns should fill in the cavity of the hollow tube formed by the increase in diameter in its longitudinal direction, wherein the individual turns should be sufficiently spaced apart, ie spaced at least by the thickness of the line material used.
  • it makes sense to cool the turns for example, by using tubular conduit material perform.
  • the hollow conductor branches off from the branch of the metallic hollow tube, a further metallic hollow tube section and extending in the region of the diameter enlargement inner conductor extends through the waveguide in this opposite further metallic hollow tube section.
  • the volumes of both hollow tube sections should be connected by a nonconducting hollow tube element which passes through the waveguide and is arranged sealingly therewith so that process gas introduced into this opposite hollow tube section does not flow into the waveguide but into the hollow tube having the diameter enlargement.
  • the inner conductor terminating in the region of the increase in diameter is then arranged inside this nonconducting tubular element, so that the plasma is formed inside the nonconducting tubular element.
  • the process gas is introduced in such a way that the process gas flows at the end of the inner conductor in the area of the diameter increase with low turbulence intensity. This is particularly important for a safe ignition or reignition of the plasma of particular importance. This is achieved, for example, by a previously described, as far as possible from the Duchmesserveriesrung and thus the end of the coaxial inner conductor was made introducing the process gas.
  • the plasma burner according to the invention has a rectangular waveguide 1, by means of which microwaves generated by a microwave generator (not shown) are conducted to the plasma torch.
  • the rectangular waveguide 1 is provided at the end with an adjustable short circuit 2 in order to adapt its impedance to different applications.
  • a metallic hollow tube 3 connects with a diameter D1, that has a stepped diameter increase 4 to a diameter D2, which extends at least over the region of the plasma 5.
  • a likewise metallic hollow pipe section 3 'with a diameter D1 which is completed by an adjustable short circuit 6 for changing the impedance of the hollow tube 3, 3'.
  • two gas supply ports 7 are arranged at the metallic hollow pipe section 3 '.
  • the volumes of the hollow tube 3 and the hollow tube section 3 ' are connected to each other by an electrically non-conductive tube section 8, preferably made of quartz glass and delimited from the volume of the rectangular waveguide 1, so that in the hollow tube section 3' initiated process gas is not in the rectangular waveguide 1 can penetrate.
  • sealing rings 9 are provided for sealing here sealing rings 9 .
  • an electrically conductive inner conductor 10 is arranged, which ends at the beginning of the stepped diameter increase 4 of the hollow tube 3.
  • the end of the inner conductor 10 is designed as a tip 11.
  • a plurality of turns with winding spacing a having single-layer cylindrical coil 12 is arranged.
  • the cylindrical coil 12 is electrically isolated from the metallic hollow tube 3. It is dimensioned with respect to its inner diameter D3 so that it encloses the resulting plasma 5 coaxial, without coming into contact with it.
  • the diameter D1 of the hollow tube 3 or of the hollow tube section 3 ' is approximately 50 mm
  • the diameter D2 of the stepped diameter increase 4 approximately 85 mm
  • the inner diameter D3. the single-layer cylindrical coil 12 about 55 mm.
  • the cross-sectional diameter of the conductor material used for the cylindrical coil 12 is about 6 mm, the winding spacing a about 20 mm.
  • Plasma 5 As a result of the increase in the electric field strength at the tip 11 of the inner conductor 10 ignites a plasma 5, which extends with the flowing process gas in the cavity formed by the diameter increase 4.
  • Plasma 5, enlarged diameter hollow tube 4 and inventively arranged Zylinderspuie 12 form an electrical Wellenieitungssystem, which is suitable in terms of its parameters impedance and transmission bandwidth in a special way for forwarding the microwaves in this region of the plasma torch.
  • the electrical interaction between the cylindrical coil 12 and the diameter-enlarged hollow tube 4 as a coaxial outer conductor of this waveguide system on the one hand and the plasma 5 as a coaxial inner conductor on the other hand causes a sufficiently good transmission of microwaves even with changing pressure conditions of the process gas, the is called changing electrical properties of the plasma 5.
  • FIG. 2 shows a modification of the described plasma burner to the effect that inside the hollow tube 3, 3 'a nonconductive tube 13, preferably of quartz glass, is arranged and the cylindrical coil 12 has been designed to be coolable and electrically connected to the enlarged diameter hollow tube 4.
  • the nonconductive tube 13 is arranged such that it guides the process gas introduced via the gas supply connections 7 within the plasma burner. Possibly. Of course, this gas routing can extend beyond the plasma torch. This is important for applications where the process gas contains substances or where the process produces substances that must not escape into the environment.
  • the coolability of the cylindrical coil 12 is advantageous when the plasma torch operates in continuous operation.

Description

Die Erfindung betrifft einen Plasmabrenner mit Mikrowellenanregung, bei dem ein Plasma durch mit einem Gas wirkende Mikrowellen erzeugt wird.The invention relates to a plasma torch with microwave excitation, in which a plasma is generated by acting with a gas microwaves.

Aus der DE 195 11 915 A1 ist bereits ein Plasmabrenner mit einem Mikrowellengenerator bekannt, der einen Hohlleiter zur Leitung der vom Mikrowellengenerator generierten Mikrowellen sowie ein von dem Hohlleiter abzweigendes metallisches Hohlrohr aufweist, wobei mittig innerhalb des metallischen Hohlrohres eine sich vom Hohlleiter aus in das metallische Hohlrohr erstreckende elektrisch leitende längliche Düse, die an ihrem in das metallischen Hohlrohr ragenden Ende eine Düsenspitze aufweist, angeordnet ist und das metallische Hohlrohr in Höhe der Flamme, bevorzugt im Bereich der Düsenspitze beginnend ein Durchmesservergrößerung aufweist, die sich in Längsrichtung des Plasmabrenners mindestens über den Bereich der Flamme erstreckt. Die Durchmesservergrößerung soll dabei sicherstellen, dass auch im Bereich der Flamme die Ausbreitungsbedingungen für Mikrowellen erfüllt sind, so dass ein stabiles Plasma erzeugt wird. Das der Plasmaerzeugung dienende Prozessgas wird dabei durch die Düse in den Bereich hoher Mikrowellenleistungsdichte an der Düsenspitze geführt. Die mittels dieser Lösung durch die Verbesserung der Ausbreitungsbedingungen der Mikrowellen im Bereich der Flamme erreichte Verbesserung der Stabilität des Plasmas hat sich aber im praktischen Betrieb, insbesondere bei großen Druckschwankungen des Prozessgases als nicht ausreichend erwiesen. Auch eine im praktischen Betrieb vorgenommene ständige Anpassung der Mikrowellenimpedanz des Hohlleiters sowie des metallischen Hohlrohres hat nicht zu einer ausreichenden Stabilisierung des Plasmas bei Druckschwankungen des Prozessgases, insbesondere zu einer stabilen Zündung bzw. Wiederzündung des Plasmas geführt.
Der Erfindung liegt deshalb die Problemstellung zugrunde, einen Plasmabrenner mit Mikrowellenanregung zu schaffen, der auch bei großen Druckschwankungen des Prozessgases für ein stabiles Plasma ausreichend gute Ausbreitungsbedingungen für die Mikrowellen sicherstellt und eine stabile Zündung bzw. Wiederzündung des Plasmas gewährleistet, ohne dass eine ständige Anpassung der Mikrowellenimpedanz des Hohlleiters sowie des metallischen Hohlrohres erforderlich ist.From DE 195 11 915 A1 a plasma torch with a microwave generator is already known, which has a waveguide for guiding the microwaves generated by the microwave generator and a branched from the waveguide metallic hollow tube, wherein centrally within the metallic hollow tube from the waveguide in the metallic Hollow tube extending electrically conductive elongated nozzle, which has a nozzle tip at its projecting into the metallic hollow tube end, and the metallic hollow tube in height of the flame, preferably in the nozzle tip starting an increase in diameter, extending in the longitudinal direction of the plasma torch at least over the Area of the flame extends. The increase in diameter is intended to ensure that the propagation conditions for microwaves are also met in the area of the flame, so that a stable plasma is generated. The plasma gas serving process gas is guided through the nozzle in the range of high microwave power density at the nozzle tip. However, the improvement in the stability of the plasma achieved by means of this solution by improving the propagation conditions of the microwaves in the area of the flame has not proved sufficient in practical operation, in particular in the case of large pressure fluctuations of the process gas. Even in practical operation made constant adjustment of the microwave impedance of the waveguide and the metallic hollow tube has not led to a sufficient stabilization of the plasma at pressure fluctuations of the process gas, in particular to a stable ignition or re-ignition of the plasma.
The invention is therefore based on the problem of providing a plasma torch with microwave excitation, which is sufficiently good even with large pressure fluctuations of the process gas for a stable plasma Ensures propagation conditions for the microwaves and ensures a stable ignition or re-ignition of the plasma without a constant adjustment of the microwave impedance of the waveguide and the metallic hollow tube is required.

Erfindungsgemäß wird dieses Problem durch einen Plasmabrenner den Merkmalen des ersten Patentanspruches gemäß gelöst. Die nachfolgenden Ansprüche 2 bis 5 betreffen zweckmäßige Ausgestaltungen der erfindungsgemäßen Lösung.
Es wurde gefunden, dass innerhalb des von der Durchmesservergrößerung gemäß DE 19 511 915 A1 gebildeten Hohlraumes das Plasma koaxial umschließend in Längsrichtung zueinander beabstandet angeordnete elektrisch leitfähige Windungen wesentlich die Ausbreitungsbedingungen der Mikrowellen verbessern, so dass die Stabilität des Plasmas auch bei erheblichen Druckschwankungen des eingeleiteten Prozessgases gewährleistet ist. Durch diese elektrisch leitfähigen Windungen wird die Übertragungsbandbreite des vom metallischen Hohlrohr als Außenleiter und dem Plasma als koaxialen Innenleiter gebildeten Systems zur Mikrowellenleitung deutlich erhöht. Damit können Mikrowellen in diesem Bereich des metallischen Hohlrohres auch bei infolge von Druckschwankungen des Prozessgases sich verändernden Leitungsbedingungen gut weitergeleitet werden, ohne dass eine ständige Anpassung der Mikrowellenimpedanz des Hohlleiters bzw. des metallischen Hohlrohres erforderlich ist. Die Erfindung basiert auf der Erkenntnis, dass sich das Plasma als koaxialer Innenleiter bezüglich seiner elektrischen Eigenschaften nicht wie bisher angenommen wegen der darin befindlichen freien Elektronen wie ein metallischer Leiter verhält, sondern, dass diese elektrischen Eigenschaften des Plasmas in erheblichem Maße vom Druck des zugeführten Prozessgases abhängen.
Für die angestrebte Wirkung der Vergrößerung der Übertragungsbandbreite des aus Hohlrohr und Plasma gebildeten Mikrowellenleitungssystems ist es, wie Untersuchungen ergeben haben, unerheblich, ob die erfindungsgemäßen elektrisch leitfähigen Windungen in Form einer einlagigen Zylinderspule oder als einzelne Leiterschleifen ausgeführt sind. Es hat sich gezeigt, dass es ebenso unerheblich ist, ob die erfindungsgemäßen elektrisch leitfähigen Windungen potenzialfrei angeordnet sind oder mit dem metallischen Hohlrohr in elektrischem Kontakt stehen. Auch Anzahl bzw. Abstand der Windungen zueinander können variieren, ohne dass die Wirkung deutlich nachlässt. Bevorzugt sollten die Windungen aber den durch die Durchmesservergrößerung gebildeten Hohlraum des Hohlrohres in dessen Längsrichtung ausfüllen, wobei die einzelnen Windungen ausreichend voneinander, d. h. mindestens um die Dicke des verwendeten Leitungsmateriales, beabstandet sein sollten. Für einen Dauerbetrieb des Plasmabrenners ist es sinnvoll, die Windungen kühlbar, beispielsweise durch Verwendung rohrförmigen Leitungsmateriales, auszuführen.
Als zweckmäßig hat es sich auch erwiesen, wenn vom Hohlleiter gegenüber der Abzweigung des metallischen Hohlrohres ein weiterer metallischer Hohlrohrabschnitt abzweigt und der im Bereich der Durchmesservergrößerung endende Innenleiter sich durch den Hohlleiter hindurch in diesen gegenüberliegenden weiteren metallischen Hohlrohrabschnitt erstreckt. Die Volumina beider Hohlrohrabschnitte sollten durch ein durch den Hohlleiter hindurchgehendes und gegenüber diesem dichtend angeordnetes nichtleitendes Hohlrohrelement verbunden sein, so dass in diesem gegenüberliegenden Hohlrohrabschnitt eingeleitetes Prozessgas nicht in den Hohlleiter strömt, sondern in das die Durchmesservergrößerung aufweisende Hohlrohr. Selbstverständlich ist es auch möglich, ein beide Hohlrohrabschnitte oder auch den gesamten Plasmabrenner durchspannendes nichtleitendes Rohrelement zur Leitung des Prozessgases vorzusehen. Der im Bereich der Durchmesservergrößerung endende Innenleiter ist dann innerhalb dieses nichtleitenden Rohrelementes angeordnet, so dass das Plasma innerhalb des nichtleitenden Rohrelementes entsteht. Wichtig für die Stabilität des Plasmas ist es, wie anhand von Untersuchungen ebenfalls gefunden wurde, dass die Prozessgaseinleitung so erfolgt, dass das Prozessgas am Ende des Innenleiters im Bereich der Durchmesservergrößerung mit geringer Turbulenzintensität strömt. Die ist insbesondere für ein sicheres Zünden bzw. Wiederzünden des Plasmas von besonderer Bedeutung. Erreicht wird dies beispielsweise durch eine vorstehend beschriebene, möglichst entfernt von der Duchmesservergrößerung und damit dem Ende des koaxialen Innenleiters erfolgte Einleitung des Prozessgases.According to the invention this problem is solved by a plasma torch the features of the first claim. The following claims 2 to 5 relate to appropriate embodiments of the solution according to the invention.
It has been found that, within the cavity formed by the increase in diameter according to DE 19 511 915 A1, the plasma coaxially surrounding electrically longitudinally spaced apart electrically conductive windings substantially improve the propagation conditions of the microwaves, so that the stability of the plasma is maintained even under considerable pressure fluctuations of the introduced process gas is guaranteed. These electrically conductive windings significantly increase the transmission bandwidth of the microwave waveguide system formed by the metallic hollow tube as outer conductor and the plasma as coaxial inner conductor. Thus, microwaves in this region of the metallic hollow tube can be well forwarded even in the event of pressure fluctuations of the process gas changing line conditions, without a constant adjustment of the microwave impedance of the waveguide or the metallic hollow tube is required. The invention is based on the finding that the plasma as a coaxial inner conductor with respect to its electrical properties not behave as previously assumed because of the free electrons therein as a metallic conductor, but that these electrical properties of the plasma to a considerable extent by the pressure of the supplied process gas depend.
For the desired effect of increasing the transmission bandwidth of the hollow pipe and plasma formed microwave line system, it has, as investigations have shown, irrelevant whether the inventive electrically conductive windings are designed in the form of a single-layer cylindrical coil or as a single conductor loops. It has been shown that it is also irrelevant whether the inventive electrically conductive windings are arranged floating or are in electrical contact with the metallic hollow tube. The number or spacing of the turns to each other can vary, without the effect significantly decreases. Preferably, however, the turns should fill in the cavity of the hollow tube formed by the increase in diameter in its longitudinal direction, wherein the individual turns should be sufficiently spaced apart, ie spaced at least by the thickness of the line material used. For a continuous operation of the plasma torch, it makes sense to cool the turns, for example, by using tubular conduit material perform.
It has also proven to be advantageous if the hollow conductor branches off from the branch of the metallic hollow tube, a further metallic hollow tube section and extending in the region of the diameter enlargement inner conductor extends through the waveguide in this opposite further metallic hollow tube section. The volumes of both hollow tube sections should be connected by a nonconducting hollow tube element which passes through the waveguide and is arranged sealingly therewith so that process gas introduced into this opposite hollow tube section does not flow into the waveguide but into the hollow tube having the diameter enlargement. Of course, it is also possible to provide a both hollow tube sections or the entire plasma torch spanning non-conductive tube element for guiding the process gas. The inner conductor terminating in the region of the increase in diameter is then arranged inside this nonconducting tubular element, so that the plasma is formed inside the nonconducting tubular element. It is also important for the stability of the plasma, as has also been found on the basis of investigations, that the process gas is introduced in such a way that the process gas flows at the end of the inner conductor in the area of the diameter increase with low turbulence intensity. This is particularly important for a safe ignition or reignition of the plasma of particular importance. This is achieved, for example, by a previously described, as far as possible from the Duchmesservergrößerung and thus the end of the coaxial inner conductor was made introducing the process gas.

Nachfolgend soll die Erfindung an einem Beispiel näher erläutert werden. Die zugehörigen Zeichnungen zeigen in

Figur 1
eine Prinzpdarstellung eines erfindungsgemäßen Plasmabrenners und in
Figur 2
eine Modifizierung des in Figur 1 dargestellten erfindungsgemäßen Plasmabrenners.
Below, the invention will be explained in more detail by way of example. The accompanying drawings show in
FIG. 1
a Prinzpdarstellung a plasma burner according to the invention and in
FIG. 2
a modification of the plasma burner according to the invention shown in Figure 1.

Wie Figur 1 zeigt, weist der erfindungsgemäße Plasmabrenner einen Rechteck-Hohlleiter 1 auf, mittels dessen von einem nicht dargestellten Mikrowellengenerator erzeugte Mikrowellen zum Plasmabrenner geleitet werden. Der Rechteck-Hohlleiter 1 ist am Ende mit einem verstellbaren Kurzschluss 2 versehen, um seine Impedanz an unterschiedliche Anwendungsfälle anzupassen. An einer Seite des Rechteck-Hohlleiters 1 schließt sich ein metallisches Hohlrohr 3 mit einem Durchmesser D1 an, dass eine stufenförmige Durchmesservergrößerung 4 auf einen Durchmesser D2 aufweist, die sich mindestens über den Bereich des Plasmas 5 erstreckt. Auf der gegenüberliegenden Seite des Rechteck-Hohlleiters 1 schließt sich axial fluchtend zum Hohlrohr 3 ein ebenfalls metallischer Hohlrohrabschnitt 3' mit einem Durchmesser D1 an, der durch einen verstellbaren Kurzschluss 6 zur Veränderung der Impedanz des Hohlrohres 3, 3' abgeschlossen ist. Am metallischen Hohlrohrabschnitt 3' sind zwei Gaszuführungsanschlüsse 7 angeordnet. Die Volumina des Hohlrohres 3 und des Hohlrohrabschnittes 3' sind durch einen elektrisch nichtleitenden Rohrabschnitt 8, vorzugsweise aus Quarzglas, miteinander verbunden und gegenüber dem Volumen des Rechteck-Hohlleiters 1 abgegrenzt, so dass in den Hohlrohrabschnitt 3' eingeleitetes Prozessgas nicht in den Rechteck-Hohlleiter 1 eindringen kann. Zur Abdichtung sind hier Dichtungsringe 9 vorgesehen. Koaxial innerhalb des Hohlrohres 3, 3' ist ein elektrisch leitfähiger Innenleiter 10 angeordnet, der am Beginn der stufenförmigen Durchmesservergrößerung 4 des Hohlrohres 3 endet. Bevorzugt ist das Ende des Innenleiters 10 als Spitze 11 ausgeführt. Im von der stufenförmigen Durchmesservergrößerung 4 des Hohlrohres 3 gebildeten Hohlraum ist erfindungsgemäß eine mehrere Windungen mit Windungsabstand a aufweisende einlagige Zylinderspule 12 angeordnet. Die Zylinderspule 12 ist gegenüber dem metallischen Hohlrohr 3 potentialgetrennt. Sie ist bezüglich ihres Innendurchmessers D3 so bemessen, dass sie das entstehende Plasma 5 koaxial umschließt, ohne mit ihm in Kontakt zu geraten.
Bei einer Ausführung des Plasmabrenners für eine Mikrowellenfrequenz von 2,45 GHz betragen der Durchmesser D1 des Hohlrohres 3 bzw. des Hohlrohrabschnittes 3' ca. 50 mm, der Durchmesser D2 der stufenförmigen Durchmesservergrößerung 4 ca. 85 mm und der Innendurchmesser D3. der einlagigen Zylinderspule 12 ca. 55 mm. Der Querschnittsdurchmesser des für die Zylinderspule 12 verwendeten Leitungsmaterials beträgt ca. 6 mm, der Windungsabstand a ca. 20 mm.
Zum Betrieb des Plasmabrenners werden über den Rechteck-Hohlleiter 1 Mikrowellen zum Hohlrohr 3 und weiter über das aus dem Hohlrohr 3 und dem Innenleiter 10 bestehende Koaxialleitersystem bis in den Bereich der stufenförmigen Durchmesservergrößerung 4 bzw. dem als Spitze 11 ausgeführten Ende des koaxialen Innenleiters 10 geleitet. Gleichzeitig wird über die Gaszuführungsanschlüsse 7 Prozessgas zugeführt, das durch das Hohlrohr 3, 3' zur Spitze 11 des Innenleiters 10 strömt. Beim Durchströmen des Hohlrohres 3, 3' wird seine Turbulenzintensität verringert. Infolge der Erhöhung der elektrischen Feldstärke an der Spitze 11 des Innenleiters 10 zündet ein Plasma 5, das sich mit dem strömenden Prozessgas in den von der Durchmesservergrößerung 4 gebildeten Hohlraum erstreckt. Plasma 5, durchmesservergrößertes Hohlrohr 4 und erfindungsgemäß angeordnete Zylinderspuie 12 bilden ein elektrisches Wellenieitungssystem, das bezüglich seiner Parameter Impedanz und Übertragungsbandbreite in besonderer Weise zur Weiterleitung der Mikrowellen in diesem Bereich des Plasmabrenners geeignet ist. Die elektrische Wechselwirkung zwischen Zylinderspule 12 und durchmesservergrößertem Hohlrohr 4 als koaxialem Außenleiter dieses Wellenleitungssystems einerseits und dem Plasma 5 als koaxialem Innenleiter andererseits bewirkt eine ausreichend gute Weiterleitung der Mikrowellen auch bei sich ändernden Druckverhältnissen des Prozessgases, das heißt sich verändernden elektrischen Eigenschaften des Plasmas 5. Damit wird ein stabiles Plasma 5 und ein sicheres Zünden bzw. Wiederzünden dieses Plasmas 5 erreicht. Dabei kann die Impedanz des Wellenleitungssystems bei Bedarf mittels des Kurzschlusses 6 unterschiedlichen Anwendungsfällen angepasst werden.
Figur 2 zeigt eine Modifizierung des beschriebenen Plasmabrenners dahingehend, dass innerhalb des Hohlrohres 3, 3' ein nichtleitendes Rohr 13, vorzugsweise aus Quarzglas, angeordnet ist und die Zylinderspule 12 kühlbar ausgeführt wurde und mit dem durchmesservergrößerten Hohlrohr 4 elektrisch in Verbindung steht. Das nichtleitende Rohr 13 ist, wie Figur 2 zeigt, so angeordnet, dass es das über die Gaszuführungsanschlüsse 7 eingeleitete Prozessgas innerhalb des Plasmabrenners führt. Ggf. kann sich diese Gasführung natürlich über den Plasmabrenner hinaus erstrecken. Dies ist für Anwendungsfälle wichtig, bei denen das Prozessgas Substanzen enthält oder bei denen im Prozess Substanzen entstehen, die nicht in die Umwelt entweichen dürfen. Die Kühlbarkeit der Zylinderspule 12 ist vorteilhaft, wenn der Plasmabrenner im Dauerbetrieb arbeitet.As FIG. 1 shows, the plasma burner according to the invention has a rectangular waveguide 1, by means of which microwaves generated by a microwave generator (not shown) are conducted to the plasma torch. The rectangular waveguide 1 is provided at the end with an adjustable short circuit 2 in order to adapt its impedance to different applications. On one side of the rectangular waveguide 1, a metallic hollow tube 3 connects with a diameter D1, that has a stepped diameter increase 4 to a diameter D2, which extends at least over the region of the plasma 5. On the opposite side of the rectangular waveguide 1 is axially aligned to the hollow tube 3, a likewise metallic hollow pipe section 3 'with a diameter D1, which is completed by an adjustable short circuit 6 for changing the impedance of the hollow tube 3, 3'. At the metallic hollow pipe section 3 ', two gas supply ports 7 are arranged. The volumes of the hollow tube 3 and the hollow tube section 3 'are connected to each other by an electrically non-conductive tube section 8, preferably made of quartz glass and delimited from the volume of the rectangular waveguide 1, so that in the hollow tube section 3' initiated process gas is not in the rectangular waveguide 1 can penetrate. For sealing here sealing rings 9 are provided. Coaxially within the hollow tube 3, 3 ', an electrically conductive inner conductor 10 is arranged, which ends at the beginning of the stepped diameter increase 4 of the hollow tube 3. Preferably, the end of the inner conductor 10 is designed as a tip 11. Im from the step-shaped increase in diameter 4 of the hollow tube 3 cavity formed according to the invention a plurality of turns with winding spacing a having single-layer cylindrical coil 12 is arranged. The cylindrical coil 12 is electrically isolated from the metallic hollow tube 3. It is dimensioned with respect to its inner diameter D3 so that it encloses the resulting plasma 5 coaxial, without coming into contact with it.
In an embodiment of the plasma torch for a microwave frequency of 2.45 GHz, the diameter D1 of the hollow tube 3 or of the hollow tube section 3 'is approximately 50 mm, the diameter D2 of the stepped diameter increase 4 approximately 85 mm and the inner diameter D3. the single-layer cylindrical coil 12 about 55 mm. The cross-sectional diameter of the conductor material used for the cylindrical coil 12 is about 6 mm, the winding spacing a about 20 mm.
To operate the plasma torch 1 microwaves to the hollow tube 3 and further over the consisting of the hollow tube 3 and the inner conductor 10 coaxial conductor system up to the region of the stepped diameter increase 4 and the tip 11 designed as the end of the coaxial inner conductor 10 is passed through the rectangular waveguide , At the same time process gas is supplied via the gas supply ports 7, which flows through the hollow tube 3, 3 'to the tip 11 of the inner conductor 10. As it flows through the hollow tube 3, 3 'its turbulence intensity is reduced. As a result of the increase in the electric field strength at the tip 11 of the inner conductor 10 ignites a plasma 5, which extends with the flowing process gas in the cavity formed by the diameter increase 4. Plasma 5, enlarged diameter hollow tube 4 and inventively arranged Zylinderspuie 12 form an electrical Wellenieitungssystem, which is suitable in terms of its parameters impedance and transmission bandwidth in a special way for forwarding the microwaves in this region of the plasma torch. The electrical interaction between the cylindrical coil 12 and the diameter-enlarged hollow tube 4 as a coaxial outer conductor of this waveguide system on the one hand and the plasma 5 as a coaxial inner conductor on the other hand causes a sufficiently good transmission of microwaves even with changing pressure conditions of the process gas, the is called changing electrical properties of the plasma 5. Thus, a stable plasma 5 and a safe ignition or reignition of this plasma 5 is achieved. In this case, the impedance of the waveguide system can be adjusted if necessary by means of the short circuit 6 different applications.
FIG. 2 shows a modification of the described plasma burner to the effect that inside the hollow tube 3, 3 'a nonconductive tube 13, preferably of quartz glass, is arranged and the cylindrical coil 12 has been designed to be coolable and electrically connected to the enlarged diameter hollow tube 4. As shown in FIG. 2, the nonconductive tube 13 is arranged such that it guides the process gas introduced via the gas supply connections 7 within the plasma burner. Possibly. Of course, this gas routing can extend beyond the plasma torch. This is important for applications where the process gas contains substances or where the process produces substances that must not escape into the environment. The coolability of the cylindrical coil 12 is advantageous when the plasma torch operates in continuous operation.

Claims (5)

  1. A plasma burner with microwave stimulation, having a waveguide (1) for guiding the microwaves generated by a microwave generator, a hollow metallic tube (3) branching off from the waveguide, a core (10) disposed centrally inside the hollow metallic tube (3) and coaxially with the hollow metallic tube and which is shorter than the hollow metallic tube (3), extending at least from the waveguide (1) into the hollow metallic tube (3), an increased diameter (4) of the hollow metallic tube (3) starting approximately at the end of the coaxially arranged core (10) and expanding at least over the length thereof towards the plasma (5) in the longitudinal direction of the plasma burner, a separation (8) of the hollow space in the hollow metallic tube (3) from the hollow space in the waveguide (1) by an insulator (8), and a device (7) for introducing a process gas into the hollow space formed by the hollow metallic tube (3) and the insulating separator (8) from the waveguide (1),
    characterised in that
    electrically conductive coils (12) are arranged at a distance from each other and in the longitudinal direction of the hollow space of the diameter expansion (4) in the area of the diameter expansion (4) of the hollow metallic tube (3) inside the hollow metallic tube (3), which coils surround but are not in contact with the plasma (5).
  2. The plasma burner as recited in claim 1,
    characterised in that
    the electrically conductive coils (12) take the form of a single-layer cylinder coil (12) with a separation of one winding, which fully occupy in the longitudinal direction the hollow space in the hollow metallic tube (3) formed by the diameter expansion (4).
  3. The plasma burner as recited in either of claims 1 or 2,
    characterised in that
    the electrically conductive coils (12) are arranged with so as to be electrically insulated from the hollow tube (3).
  4. The plasma burner as recited in any of claims 1 to 3,
    characterised in that
    the electrically conductive coils (12) have a channel along which a coolant is passed.
  5. The plasma burner as recited in any of claims 1 to 4,
    characterised in that
    gas inlet connectors (7) to introduce the process gas into the hollow metallic tube (3) are arranged at a distance from the diameter expansion (4), i.e. on the section (3') of the hollow metallic tube at the end of the coaxial core (10).
EP02762243A 2001-08-28 2002-08-20 Plasma burner with microwave stimulation Expired - Lifetime EP1421832B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE10143114 2001-08-28
DE10143114 2001-08-28
PCT/DE2002/003102 WO2003026365A1 (en) 2001-08-28 2002-08-20 Plasma burner with microwave stimulation

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EP1421832A1 EP1421832A1 (en) 2004-05-26
EP1421832B1 true EP1421832B1 (en) 2006-10-04

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US20060052883A1 (en) * 2004-09-08 2006-03-09 Lee Sang H System and method for optimizing data acquisition of plasma using a feedback control module
TW200742506A (en) * 2006-02-17 2007-11-01 Noritsu Koki Co Ltd Plasma generation apparatus and work process apparatus
DE102006019664B4 (en) * 2006-04-27 2017-01-05 Leibniz-Institut für Plasmaforschung und Technologie e.V. Cold plasma hand-held device for the plasma treatment of surfaces
US20100074810A1 (en) * 2008-09-23 2010-03-25 Sang Hun Lee Plasma generating system having tunable plasma nozzle
US7921804B2 (en) * 2008-12-08 2011-04-12 Amarante Technologies, Inc. Plasma generating nozzle having impedance control mechanism
US20100201272A1 (en) * 2009-02-09 2010-08-12 Sang Hun Lee Plasma generating system having nozzle with electrical biasing
US20100254853A1 (en) * 2009-04-06 2010-10-07 Sang Hun Lee Method of sterilization using plasma generated sterilant gas
US20150279626A1 (en) * 2014-03-27 2015-10-01 Mks Instruments, Inc. Microwave plasma applicator with improved power uniformity
US9653266B2 (en) * 2014-03-27 2017-05-16 Mks Instruments, Inc. Microwave plasma applicator with improved power uniformity
PL235377B1 (en) 2016-04-05 2020-07-13 Edward Reszke Adapter shaping the microwave electromagnetic field that heats toroidal plasma discharge
RU2650197C1 (en) * 2017-03-09 2018-04-11 Общество С Ограниченной Ответственностью "Твинн" Multi-stage plasmotron

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EP1421832A1 (en) 2004-05-26
DE50208353D1 (en) 2006-11-16
US20040262268A1 (en) 2004-12-30
WO2003026365A1 (en) 2003-03-27
TWI313147B (en) 2009-08-01

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