Classifications

• • 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
  • H05H1/32—Plasma torches using an arc
  • H05H1/42—Plasma torches using an arc with provisions for introducing materials into the plasma, e.g. powder, liquid

Definitions

• Devices for obtaining high temperatures are known, in which a fluid at high temperatures is carried by passing it through an arc discharge between two electrodes. Such devices are used in particular in pro ection, welding and chemical reaction at high temperature, the material to be treated being introduced into the plasma in the form of powder, liquid or gas.
• the arc is established between two electrodes, at least one of which is hollow, and the material to be treated is generally introduced downstream of the area where the arc is maintained.
• the purpose of the following method of the invention is to remedy these drawbacks, while making it possible to operate such installations in one. power of several megawatts.
• the process for obtaining high temperatures is characterized in that it consists in establishing between several cathodes and one or more hollow anodes separate arcs, in maintaining a flow of inert gas between the cathodes and the or the anodes, to dispose the cathodes substantially along the generatrix of a cone matching the entry of the first anode, and to introduce the material to be treated by a tube located in the axis of the cone and the anode.
• the method according to the invention also consists in introducing the fluid for constricting and guiding the arcs along each cathode.
• Figure 1 a section of a device carrying out the process according to the invention and comprising for reasons of simplicity only two cathodes;
• FIG. 1 The electrical connection diagram for the device in Figure 1;
• Figure 3 a variant of Figure 1, In the case of materials to be treated likely to be highly aggressive vis-à-vis the anode;
• FIGS. 4A, 4B, 4C of the variants of the direction of the injection of fluid with respect to the arc in the case of FIG. 3;
• Figure 5 a variant of Figure 3, in the case of in ect materials particularly reactive vis-à-vis the anode;
• FIGS. 6A and 6B respectively a device with crossed arcs and a view of the configuration of crossed arcs, and Figure 7 a variant of Figures 6.
• the cathodes 1 and 2 are usually metal made up of a refractory tip 14 ′ and 14 ", welded and brazed on metal supports 15 * and 15", cooled by an injected fluid in 10 'by the 16' and 16 "tubes and evacuated by 10".
• the anode 3 is common and two arcs 5 and 6 are introduced.
• the material to be treated is introduced by the injector 4 using a fluid 8.
• the fluid for constricting and guiding the arcs 5 and 6 is introduced along each cathode at 9 ', 9 ", so as to lengthen the two arcs and to move the anodic spots 12 and 13 in the axial direction towards the outlet. of the anode 3.
• electrodes are cooled by a suitable fluid (10 ', 10 "for the cathodes; 11', 11" for the anode).
• Each cathode is connected to the negative pole of a direct current generator or rectifier 17,18, the positive pole of which is connected to the 'anode, which in the case shown is common.
• the example of this figure 2 can easily be extended to a larger number of cathodes and to the same number of rectifiers.
• a known means such as a high frequency pilot discharge between each cathode and the input of the anode.
• the problems are less acute on the side of the anode spot, which is distributed naturally over a larger area, which results in lower current densities.
• an inert or non-oxidizing gas such as Argon, Nitrogen, Helium or hydrogen, or a Liquid such as water.
• the subject to be treated is likely to be. Jtement aggressive vis-à-vis the anode, for example if it is to react at high temperature of atomic oxygen with TiCL4 in order to obtain Ti02, we will usefully use the variant shown in Figure 3.
• the hollow anode is divided into several parts 3a, 3b, 3c, 3d electrically isolated from each other.
• the arcs 6 and 7 are first struck between the cathodes 1 and 2 and the nearest anode-3a by the action of the switches 19a, 20a. These two arcs are then progressively lengthened by increasing the gas flow rates 9 ′ and 9 ", so as to move the anode spots 12 and 13 towards the second part of the anode 3b, at the same time the switches 19b are engaged, 20b and, as soon as the anode spots have reached the anode 3b, the connection of the first anode 3a is interrupted by opening the switches 19a, 20a. It is possible, if this is desirable, to introduce at this time an additional fluid 22a per 1 'intei— valle 21a separating the anode 3a from the anode 3b. In this way we ensure a better guidance of the a "- towards the exit of the Anode 3b.
• This injection of fluid can take various directions with respect to the arc, parallel, inclined or tangential as shown respectively in FIGS. 4A, 4B, 4C.
• This upe of cold fluid stabilizes the discharge, prevents parasitic discharges to the previous anode, maintaining the anode spots 12 and 13 towards the outlet of the anode 3b, and provides additional cooling of this anode.
• the switch 19c is closed, then 19b is opened, an additional fluid 22b by 21b is introduced and thus transferred gradually the anodic spots towards the exit of the torch on the 3d anode.
• anodic spots 12 and 13 on an anode 23 insulated from 3d and protected active elements of the plasma by an inert fluid 24.
• the stability of the discharge can usefully be improved by rotating the anode spots under the action of an auxiliary magnetic field 25 produced by the winding 26.
• anode 23 can be cooled by known means, not shown.
• FIG. 6A shows a device with two cathodes 1, 2 and an anode made up of four years rings 3'a, 3'b, 3'c, 3'd, these rings being composed of two cooled segments, electrically isolated and each connected to the positive pole of one of the two rectifiers.
• the inclination of the cathodes 1, 2 and the auxiliary jets 9 ',. 9 "allows, after arcing between the arcs and the anode 3'a, to pass the anodic spot of each arc to an anode segment offset angularly by 60 ° on Anode 3 'b, 120 ° on the anode 3'c and 180 ° on the anode 3' This gives the configuration of crossed arcs 6 and 7 shown in Figure 6B.
• each cathode is followed by an initiating and guiding nozzle and the plasma jet, which leaves this initiating nozzle, is directly oriented towards the anode segment arranged at 180 ° .
• the device is shown in FIG. 7.
• these nozzles are replaced by a single anode pierced with a number of passages as much as with cathodes and serving to channel and orient the plasmas at priming.
• the latter in the case of destruction of waste, the latter can be introduced after having been preheated by passage through a traditional burner.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Plasma & Fusion (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Physical Or Chemical Processes And Apparatus (AREA)
• Discharge Heating (AREA)

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• 1990
  • 1990-06-06 EP EP19900908438 patent/EP0428671A1/de not_active Withdrawn
  • 1990-06-06 WO PCT/BE1990/000026 patent/WO1990015516A1/fr not_active Application Discontinuation

Non-Patent Citations (1)

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