MXPA97004844A

MXPA97004844A - Device of excitation of

Info

Publication number: MXPA97004844A
Application number: MXPA/A/1997/004844A
Authority: MX
Inventors: Sindzingre Thierry; Rabia Stephane
Original assignee: L'air Liquide Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude
Priority date: 1996-07-02
Filing date: 1997-06-26
Publication date: 1998-01-01

Abstract

The present invention relates to a gas excitation device, comprising a gas excitation chamber (20; 56) provided with a gas inlet passage (28; 64) in communication with a primary source (36; 58) of gas. gas supply and an excited gas outlet passage (30; 70), characterized in that it comprises a throttle (34; 63) of Venturi effect, arranged in the gas path between the primary supply source (36; 58) and said entrance passage (28; 64) and because it also comprises a secondary source (32; 68; 69) of gas supply in communication with an area located after said throttling (34; 63), the gas being released by said secondary source (32; 68; 69) driven by Venturi effect towards said excitation chamber (20; 56) under the action of the gas released by the primary source

Description

GAS EXCITATION DEVICE The present invention relates to a gas excitation device for the formation of excited or unstable gaseous molecules, adapted in particular to the excitation of gases used in the field of surface treatment, or even in the treatment ( decontamination) of gaseous effluents. Gas excitation devices are known in the art, of the type comprising a gas excitation chamber provided with a gas inlet passage in communication with a primary gas supply source and an outlet passage of the gas. excited gas. This type of excitation device allows to transfer the chemical and thermal energy to a gas from the chemical and thermal energy from an electrical energy, operating at a temperature close to the ambient temperature. When it is in operation, this device needs an important gas consumption to guarantee a fast transport of chemically activated substances to an area of use (to minimize the "flight" time between (to gas input in the device and the arrival of excited substances to the surface to be treated when considering the example of a surface treatment.) This consumption of gas considerably affects the economic interest of such a device, for example, the difficulties in adapting these processes to the process are conceived. treatment of parts on a large scale, as is the case in the automotive industry or even glass, where the cost overrun of gas consumption is not always tolerable.

The purpose of the invention is to alleviate this drawback and provide a gas excitation device that has a low gas consumption? which also allows the aspiration of a gaseous addition mixture before the gas excitation chamber. The object of the invention is therefore a gas excitation device of the aforementioned type, characterized in that it comprises a venturi throttling disposed in the gas path between the primary supply source and the inlet passage and because it also comprises at least less a secondary source of gas supply in communication with an area located before said throttling, the gas released by said secondary source being driven by Venturl effect towards said excitation chamber under the action of the gas emitted by the primary source. It is understood that said device makes it possible in particular to understand the following situations: the surface treatment of objects under gas consumption economy conditions: for this purpose it can be envisaged to use, as a secondary gas source, the excited treatment gas used to make the surface treatment (the secondary gas resulting from the transformation of the primary gas into the interior of the excitation device that can be recycled at the level of the entrance passage); - the treatment (decontamination) of gaseous effluents: the secondary gas source can be constituted by the effluent, driven by the primary gas to the excitation chamber for its new treatment, and then evacuated from the device by the gas outlet passage in order to be reused or even evacuated to the outside. The gaseous effluents treated again, according to the invention, may come from very varied operations, which produce these effluents. By way of illustration, but in no way limiting, one can cite the case of metal welding furnaces, or even furnaces that perform heat treatment operations on metals or ceramics, or even continuous furnaces that carry out so-called "welding by" operations. remelting "which are welding operations of components in electronic circuits that use a solder paste whose formula also includes the metallic alloy that makes the solder joint, solvents and other more or less resinous chemical fluids that facilitate wetting. The rise in temperature causes, then in the atmosphere inside the furnace, important emanations, especially of solvents and other organic components that it is advantageous to be able to eliminate, either before rejecting the atmosphere towards the outside or to recycle it in order to reuse it. The invention can also comprise one or more of the following characteristics: the excitation device comprises a gas recirculation channel connecting a closed space located after the excitation chamber and said area arranged after the throttling with Venturi effect, said secondary source of gas supply constituted by said closed space; - said secondary source of gas supply is constituted by a supply source of addition gas connected, by means of a gas suction channel, with said zone arranged after the throttling of Venturi effect, said addition gas being, intended for to be mixed, after the excitation chamber, with the gas emitted by said primary source, for example, to form after the excitation, a surface treatment gas, or even, for example to be decontaminated (effluent) in the interior Of the device; - the primary supply source with gas is constituted by a power supply with Inert gas, said secondary source being constituted by an active gas supply source; - the excitation device comprises, already connected to a source of alternative high-frequency high voltage, a first internal exciter electrode of cylindrical shape and a second internal exciter electrode of cylindrical shape and provided with substantially opposite longitudinal grooves constituting said input passages and gas outlet, said first and second excitation electrodes being arranged coaxially and delimiting the so-called gas excitation chamber, a layer of a material being arranged on the surface of at least one of the electrodes with respect to the other electrode; - the excitation device comprises at least one homogenization chamber arranged at the outlet of at least one of said primary and secondary sources for the uniform distribution of the gas supplied to said excitation chamber; - the excitation device comprises a gas conduit comprising a first internal cylinder provided with a first end connected to the primary source of gas supply and a closed opposite end comprising a longitudinal groove, and a second external coaxial cylinder with respect to said first cylinder, provided with areas of opposite ends closed and comprising a longitudinal gas distributing slot in communication with said gas inlet passage? which extends in the opposite part of the groove disposed in said first cylinder, for the uniform distribution of the gas supplied to said excitation chamber. From the following description given solely by way of example and with reference to the accompanying drawings, other characteristics and advantages of the invention will arise, namely: FIG. 1 is a schematic cross-sectional view of an exciting device according to the invention; Figure 2 is a curve of the gas flow measured at the outlet of the excitation chamber as a function of the gas flow released by the primary supply source; and - Figure 3 is a schematic cross-sectional view of an exciting device according to another embodiment. In FIG. 1, an excitation device according to the invention, designated by the general reference numeral 10, has been shown. The embodiment exemplified here, for example, can be used for the excitation of a gas supplied by a primary supply source with gas in order to carry out a one-piece surface treatment 12. In this figure 1 it is seen that the excitation device comprises a first internal exciter electrode 14 of cylindrical shape externally coated with a layer 16 of dielectric material and disposed inside the a second external exciter electrode, also of cylindrical shape 18. The two exciter electrodes 14 and 18 are arranged coaxially and delimit a gas excitation chamber 20 between them. The second external electrode 18 is formed by the internal face of a longitudinal metal block 22 constituted by the association of two complementary parts 24 and 26 arranged facing each other and separated from one another. The two parts 24 and 26 are separated from each other by two passages 28 and 30, which respectively constitute a gas inlet passage 28 in the excitation chamber 20 and a gas exit passage 30 in communication with a closed space 32. in which the piece 12 to be treated is located.

It is also observed in FIG. 1 that the metal block 22 is arranged in a housing 33 provided with a longitudinal slot 34 disposed opposite the entrance passage 28 of the excitation chamber 20 and in communication with a gas conduit 36 connected to the the primary gas power source. The width of the throttle 34 (here represented in the form of a groove) is advantageously substantially lower than the inlet passage 28. Preferably a ratio between the two widths between 1 and 3 will be used. The gas conduit 36 It comprises a first internal cylinder 38 coaxial with the rest of the device and arranged inside a second cylinder 40 constituted by the cylindrical internal wall of a casing 42. The casing 42 is provided with a longitudinal slot 44 extending parallel to the axis of the casing. first cylinder 38 and in communication with the longitudinal slot 34 of the case 33. On the other hand, the first cylinder is provided with an opening 46 parallel to the opening 44 and arranged opposite thereto. The first cylinder 38 comprises a first end, located behind the plane of Figure 1, in communication with the gas supply source and an opposite end, located in front of the plane of Figure 1, closed.

On the other hand, the two opposite ends of the cylinder 40 are closed. Furthermore, the throttle 34 of the housing 33 here has a substantially V-shaped profile shape which causes in a known manner an increase in the velocity of the gas released by the gas supply source in the excitation chamber 20 as well as a corresponding decrease in the pressure of this gas (essentially in the vicinity of step 28). The box 33 and the metal block 22 are separated and delimit a gas suction channel 48 extending between the gas inlet passage 28, after the venturi throttling, 34 and the closed space 32. It is finally seen in the Figure 1, that the device is completed by an alternative high-voltage source 49 with high frequency connected to the internal excitation electrode 14 and to the external excitation electrode 18, for its polarization. It is understood that if the invention so far has been particularly illustrated by means of throttles with Venturi effect that appear in the form of grooves, other configurations can be attempted without departing from the framework of the invention, such as, for example, a row of holes at regular spaces. or not, or even with a determined and controlled spacing. The operation of the device of figure 1 is as follows.

The gas released by the power supply is provided at a pressure of the order of a few bars. It flows in the first cylinder 38 of the gas conduit 36. It then passes through the orifice 46, then between the space delimited by the first cylinder 38 and the second cylinder 40, then in the slot 34. In the course of this addressing , the gas suffers during the passage, a relatively important loss of load adapted to confer to this gas a homogeneous distribution of velocity and pressure along the gas transport conduit 36, and therefore along the groove 34 The gas then flows through the slot 34 and the passage 28 into the excitation chamber 20, in which it undergoes an excitation in a known manner, under the action of the electrodes 16 and 18 fed by the alternative voltage source. high frequency 49. The gas thus excited is then escaped, through the outlet passage 30, for example, for the treatment of a piece 12. As already mentioned above, the gas suffers, under the action of the choke 34 with Venturi effect, a pressure drop, after this throttling. This pressure drop causes an aspiration by Venturi effect, of the gas present in the suction channel 48 and therefore the gas present in the closed space 32.

It is understood that the gas, after the treatment of the piece 12, undergoes a recirculation and is reinjected in the excitation chamber 20 in order to re-excite it. The device just described then allows a considerable saving of treatment gas, since the de-excised gas present in the enclosed space 32 constitutes a secondary supply source? the supplied gas is mixed with the gas supplied by the primary gas supply source. In figure 2, in which a curve of the flow released at the exit of the gas outlet passage 30 as a function of the flow rate injected by the gas conduction conduit 36 is shown, it is seen that the device just described it allows a considerable saving of gas since, to obtain, for example, a gas flow close to 30 Nm3 / h of output, it is only necessary to inject 3 to 5 Nm3 / h of inlet gas. 3 shows a gas excitation device according to another embodiment. As in the example of the previous embodiment, described with reference to Figure 1, this excitation device comprises a primary excitation electrode 50 coaxial with a secondary excitation electrode 52 formed by the inner wall of a metallic block 54 in two parts and which delimits an excitation chamber 56 in communication with a primary source of gas supply by means of a gas transport conduit 58.

As before, the primary 50 and secondary electrodes 52 are connected to a high frequency alternative high voltage source 55 for excitation. It is seen in this figure 3, that the device further comprises a plate 60 superimposed on the metal block 54? spaced from it as well as the two excitation electrodes 50 and 52. The plate 60 is constituted by the association of two plates side by side delimiting a groove 63 forming a V-shaped throttle with Venturi effect in communication with a gas inlet passage 64 to the excitation chamber 56. The space delimited by the plate 60 and the metal block 54 constitutes a gas suction duct 66 in communication with two secondary gas supply sources 68 and 69 arranged on one side and the other metal block 54 and supplying gas or a gaseous addition mixture for a mixture with gas supplied by the primary source, for excitation for the purpose of a subsequent surface treatment. As in the embodiment described with reference to FIG. 1, the gas supplied by the secondary supply sources 68 and 69 is sucked, by Venturi effect, into the zone located after the throttling 63 and driven towards the excitation chamber 56 and escapes through an excited gas outlet passage 70 to a workpiece 71.

It is then understood that according to this embodiment, for example, it is possible to mix several treatment gases to create different gas-excited chemical substances for the purpose of effecting a surface treatment of the part 71. It can then be foreseen for both primary source as for the source of addition, a gas comprising at least one element of the groups formed by the inert gases, the oxidizing gases and the reducing gases. Of course, it is possible to provide the device just described with reference to Figure 3, a gas recirculation channel, as in the example of the embodiment of Figure 1. It should be noted, that preferably, each secondary source of Gas feed 68 and 69 is associated with a homogenization chamber 72 in order to allow, in a conventional manner, a uniform distribution of the gas, in speed and in pressure, in the duct 66 to propel it into the excitation chamber 56. therefore, if the exemplified embodiment of Figure 3 comprises two secondary sources of addition 68 and 69, it is perfectly understandable that only one is available, without thereby departing from the scope of the present invention. Also, if in connection with this figure 3 the application "surface treatment of objects" has been particularly evoked, it is understood that the installation of figure 3 or a very close installation (to one or several secondary sources) can be used for the treatment / decontamination of gaseous effluents, for example in the following framework: - the secondary source consists of effluents to be treated (that come from an operation of any kind); - the effluents are driven into the discharge for their new treatment, under the action of the primary gas, which can be, for example, an inert gas or even a more active gas such as a reducing gas; - the effluents once treated by the discharge, obtained at the outlet of gas 70, are then reused for an operation of the type from which they were later emitted, or even disposed of to the surrounding atmosphere.

Claims

CLAIMS 1. Gas excitation device, comprising a gas excitation chamber (20; 56) provided with a gas inlet passage (28; 64) in communication with a primary source (36; 58) of gas supply and an excited gas outlet passage (30; 70), CHARACTERIZED BECAUSE comprises a throttle (34; 63) of Venturi effect, arranged in the gas path between the primary supply source (36; 58) and said inlet passage (28; 64) and in that it also comprises a secondary source (32; 68; 69) for gas supply in communication with a zone located after said throttling (34; 63), the gas being released by said secondary source (32; 68.69) driven by Venturi effect towards said excitation chamber (20,56) under the action of the gas released by the primary source. Device according to claim 1, characterized in that it comprises a gas recirculation channel (48) connecting a closed space (32) located after the excitation chamber (20) and said zone arranged after the throttling (34) with effect Venturi, said secondary gas supply source being constituted by said closed space (32). Device according to claim 2, characterized in that said closed space is constituted by an interior space delimited by a contour, in communication with said excited gas outlet passage, within which a surface treatment of objects is practiced with help of said excited gas. Device according to claim 1, characterized in that said secondary source of gas supply is constituted by a source (68,69) of supply of connected addition gas, by means of a gas suction channel (66), with said zone disposed after the throttling (34; 63) of Venturi effect, intended to be mixed, before the excitation chamber (20; 56), with the gas supplied by said primary source. Device according to claim 4, characterized in that said source of secondary gas of addition is constituted by a gaseous effluent that must undergo a decontamination treatment inside the chamber. 6. Excitation device according to any of claims 1 to 5, CHARACTERIZED BECAUSE the primary source (36; 58) of gas supply is constituted by an inert gas supply source, said secondary source (32; 68,69) being constituted by an active gas supply source. 7. Excitation device according to any of claims 1 to 6, CHARACTERIZED BECAUSE it comprises, already connected to a high frequency alternative high voltage source (49; 55), a first internal exciter electrode (14; 50) of cylindrical shape and a second external exciter electrode (18; 52) of form cylindrical and provided with substantially opposite longitudinal grooves (28, 30, 64, 70) constituting said gas inlet and outlet passages, said first and second exciter electrodes being arranged coaxially and delimiting said chamber (20; 56) of gas excitation, a layer of a dielectric material being arranged on the surface of at least one of the two electrodes facing the other electrode. The excitation device according to one of the preceding claims, CHARACTERIZED BECAUSE it comprises at least one homogenization chamber (72) arranged as an outlet of at least one of said primary (58) and secondary (68,69) sources, for the uniform distribution of the gas supplied to said excitation chamber (56). Device according to any of claims 1 to 7, characterized in that it comprises a gas conduit comprising a first internal cylinder (38) provided with a first end connected to the primary source of gas supply and an opposite end closed and comprising a longitudinal slot (46), and a second external cylinder (40) coaxial to said first cylinder, provided with areas of opposite ends closed and comprising a longitudinal slot (44) gas distributor in communication with said passage (28) gas inlet and extending in opposite manner to the slot (46) disposed in said first cylinder (38) for uniform distribution of the gas supplied to said excitation chamber (20)). 10. Device according to one of the preceding claims, CHARACTERIZED BECAUSE said constriction has the shape of a substantially longitudinal groove whose width is substantially lower than that of said inlet passage (28). Device according to one of the preceding claims, CHARACTERIZED BECAUSE the primary source of gas is at a pressure greater than or equal to 3 bar. Device according to any of claims 1 to 11, characterized in that the gas supplied by said primary (36; 58) and secondary (32; 68,69) gas supply sources comprises at least one gas selected from the gases inert, oxidizing gases and reducing gases.