HIGH THERMAL PERFORMANCE MICROWAVE PLASMA TORCH

Abstract

Scalable plasma torch with a thermal output of 500-1000 kW and a process for starting the plasma torch. The plasma torch comprises a microwave chamber (40) with a centrally located supply line (20) for the process gas or plasma gas. An arrangement of combined mode converters and microwave emitters (30) in the wall of the microwave chamber (40) couples circularly polarized microwaves with a wavelength of 915 MHz or 2.45 GHz into the plasma, enabling high thermal output for industrial applications. The microwaves are generated separately in dedicated magnetron microwave generators and fed to the combined mode converters / emitters via rectangular waveguides.

Claims

[1] Device for generating a plasma jet of high thermal power, comprising a microwave chamber with one or more port openings in the walls for coupling microwaves into the microwave chamber and a central tube for supplying process gas, characterized by , that the microwave emitter ports in the walls of the microwave chamber radiate circularly polarized microwaves into the process gas, whereby in a first plane, four emitter ports for microwaves are arranged offset by approximately a quarter circle angle, and in a second plane, four further emitter ports are arranged substantially opposite each other by approximately a quarter circle angle, wherein the emitter ports of the first level are offset from the emitter ports of the second level by approximately one eighth of a circle, so that the microwave power from eight microwave emitter ports can be coupled into the process gas at an angle. [2] Device according to claim 1, characterized by additional levels with microwave emitter ports at a distance of lambda / 4 of the incident wavelength, whereby the coupled microwave power can be increased in a scalable manner. [3] Apparatus according to claim 1 or claim 2, wherein the microwave emitter ports each couple a microwave power of 10 to 150 kW into the process gas. [4] Device according to one of claims 1 to 3, wherein the microwave emitter ports each receive their power with low loss via a rectangular waveguide from a magnetron. [5] Apparatus according to any one of claims 1 to 4, wherein the inner walls of the microwave emitter ports are shaped so that the microwaves arriving through the rectangular waveguides are converted into circularly polarized microwaves. [6] Apparatus according to any one of claims 1 to 5, wherein the microwave emitter ports perform mode conversion from a linearly polarized TE10 wave to a circularly polarized TE11 wave which is coupled into the process gas. [7] Apparatus according to any one of claims 1 to 6, wherein plate-shaped shields are arranged in the microwave chamber between the emitter ports to counteract crosstalk between adjacent microwave emitter ports. [8] Device according to any one of claims 1 to 7, wherein the microwave emitter ports radiate microwaves at preferably 915 megahertz or 2.45 GHz. [9] Apparatus according to any preceding claim, wherein the supply line for the process gas is a refractory quartz glass or ceramic tube. [10] Apparatus according to any preceding claim, wherein the supply line has a diameter of 300 mm, a wall thickness of 20 mm and a length of 800 mm and releases the process gas at the field maximum. [11] Apparatus according to any preceding claim, wherein the microwave chamber has a diameter of about 975 mm and a length of 700 mm. [12] Device according to one of the preceding claims, wherein the ignition of the plasma in the chamber is carried out by a microwave generator with 100 KW and 915 MHz and the microwave emitter ports of the other generators are connected in series. [13] Device according to one of the preceding claims, wherein the ignition of the plasma is carried out via a special microwave generator which can generate the necessary microwave power density. [14] A method for generating a plasma jet, comprising the steps of: Providing a device according to any one of claims 1-13, Ignition of the plasma remotely via a single microwave generator that generates the necessary power density, and sequentially connecting additional microwave generators that couple circularly polarized microwaves with a wavelength of 915 MHz or 2.45 GHz into the plasma.

Images