Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
  • C23C16/4412—Details relating to the exhausts, e.g. pumps, filters, scrubbers, particle traps
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/46—Removing components of defined structure
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S261/00—Gas and liquid contact apparatus
  • Y10S261/54—Venturi scrubbers

Definitions

• the present invention relates to industrial installations for manufacturing parts made of composite material comprising infiltration furnaces or chemical vapor deposition. More particularly, the invention relates to a gas extraction device for such installations.
• a known technique for manufacturing parts made of composite materials in particular parts made of thermostructural composite materials, such as carbon-carbon composites or composites with a ceramic matrix, consists of making preforms of the parts and densifying the preforms in kilns. 'chemical vapor infiltration or deposition.
• the preforms of the parts generally consist of fibrous textures.
• the preforms, optionally kept in shape by tools, are introduced into an oven in which a gas phase is admitted, the composition of which is chosen according to the nature of the matrix of the composite material.
• the gaseous phase diffuses within the porosity of the preforms and, by decomposition of one of its constituents or reaction between several constituents, leaves a solid deposit which gradually densifies the preforms by filling in their porosity, in order to form the matrix.
• the precursors used in the gas phase then usually comprises gaseous halides, in particular gaseous chlorides, which, in addition to their corrosive nature and their toxicity, can form significant solid deposits at the outlet of the oven. This is so, in particular with boron trichloride BCI3, precursor of the element boron.
• the object of the present invention is to provide a gas extraction device which avoids the aforementioned drawbacks, in particular which prevents the formation of parasitic deposits which can cause blockages.
• the present invention also aims to provide an extraction device comprising means for treating corrosive and toxic gases from the oven, before discharge to the atmosphere.
• a gas extraction device comprising a dry pump having an inlet connected to the oven to allow the establishment, inside the oven, of desired low pressure conditions, and the extraction of residual gases. ; and an atmospheric pressure hydrolysis reactor connected to an outlet of the dry pump and intended to receive residual gases coming from the furnace, the hydrolysis reactor comprising a first outlet for solid deposits or acid solutions originating from the hydrolysis of gases received and a second gas outlet connected to the atmosphere.
• means are provided for injecting a gas, preferably a neutral gas, such as nitrogen, between the inlet of the dry pump and the inlet of the hydrolysis reactor.
• a gas preferably a neutral gas, such as nitrogen
• the gas injection can be carried out both at the inlet of the dry pump and in a pipe connecting the dry pump to the hydrolysis reactor.
• this injection of gas contributes to oppose a counter current between the hydrolysis reactor and the pump and thus to prevent the products of the hydrolysis reaction from going back to the pump.
• Water supply means are advantageously provided for establishing a continuous liquid circulation between at least one access to the hydrolysis reactor and the first outlet thereof.
• the water supply means are connected to the hydrolysis reactor at least through the second outlet thereof, in order to be able to dissolve acid vapors from the reactor and avoid their rejection into the atmosphere.
• the water supply means can be connected to a water injection inlet in a column connected to the second outlet of the reactor.
• the first outlet from the hydrolysis reactor is connected to a neutralization tank in order to neutralize acid solutions produced by hydrolysis.
• the furnace 10 comprises a reaction chamber 11 delimited by a graphite armature 12.
• the armature is surrounded by a metal inductor 13 with interposition of a thermal insulator 14.
• the assembly is housed inside of a sealed metal enclosure 15.
• the armature 12 has the shape of a cylinder with a vertical axis closed at its lower part by a bottom 12a and at its upper part by a removable cover 12b.
• the preforms to be densified are placed on a perforated plate 16.
• the preforms are, for example, fibrous structures having a shape close to that of parts to be produced from composite material, possibly maintained in a tool.
• the plate 16 can rotate around a vertical axis coincident with that of the chamber 11. The rotation is controlled by a motor (not shown) coupled to the plate by a shaft 17 passing through the bottom 12a.
• a reaction gas phase containing the precursor (s) of the matrix of the composite material coming from reserves (not shown) is introduced into the chamber 11 by a supply pipe 18 which passes through the enclosure 15 and ends at the upper part of the chamber through the cover 12b.
• An additional flow of neutral gas for example nitrogen, can be added to the reaction gas phase to regulate the pressure in the chamber.
• the reaction gas phase entering the chamber 12 is forced to circulate in contact with preheating plates. These, formed of superimposed perforated plates 19, allow the reaction gas phase to be brought quickly to the temperature prevailing in the chamber.
• the extraction of the residual gas phase is carried out through one or more pipes 20 which are connected to the lower part of the chamber 11 by an annular passage 21 surrounding the shaft 17.
• the volume located around the armature 12 inside the enclosure 11 is continuously swept by a neutral gas, such as nitrogen. This is brought by a pipe 22. It is extracted from the enclosure 15 by a pipe 24. A neutral gas buffer is thus formed around the chamber 11.
• a neutral gas such as nitrogen
• a control unit receives signals produced by sensors and representative of the temperature and the pressure in the chamber 11 and controls a generator 28 which supplies the supply current to the inductor so maintaining the temperature in the chamber at the predetermined optimum value for the chemical vapor infiltration operation.
• the densification of the preforms contained in the infiltration furnace by ⁇ * a ceramic matrix, in particular a matrix formed at least partially from the ternary system Si-BC, including SiC, B4C and SiB uses precursors in the gas phase consisting of toxic, corrosive gases and capable of forming parasitic deposits at the outlet of the furnace 10.
• precursor gases are in particular gaseous chlorides such as Si x H y Cl z or BtH u ⁇ v (x , y, z, t, u and v being whole numbers).
• the extraction of gases from the oven is carried out by means of a dry pump 32 connected to the oven 10 by the pipe 30 and controlled by the installation control unit.
• dry pump is meant here a pump which, for its operation, does not use any liquid, such as oil or water, capable of reacting with the gases coming from the oven to form parasitic deposits.
• the pump could for example use the pump marketed by Edwards under the name Pompe Séche DP 180.
• This pump also offers the advantage of having an adjustable operating temperature up to 160 * C, which allows you to choose an operating temperature avoiding any phenomenon of recondensation in the pump body.
• a filter 34 can be mounted in the pipe 30 to retain solid particles having a size greater than a limit preferably between 10 and 15 microns.
• the filter 34 is for example constituted by a fine mesh of stainless steel, wound on itself, such as the ITF cyclonic effect filter sold by the company Edwards.
• Means for treating the gases extracted by the pump are provided downstream of the latter in order to avoid the rejection of toxic and corrosive gases to the atmosphere and the formation of parasitic deposits at the outlet of the pump.
• the treatment means comprise a hydrolysis reactor 50 operating at atmospheric pressure and connected to the outlet of the pump 32 by a pipe 40.
• the gases coming from the pump reach the reactor in an upward path, through a first part 42 of the pipe 40, then, along a downward path, firstly through a gas jet venturi 43, then through a tube 44 into which is inserted a helical part and which forms the terminal vertical part of the pipe 40.
• the tube 44 ends at the upper part of the hydrolysis tank 50, through a cover 50a.
• the acid solutions and solid deposits produced by the hydrolysis of the residual gases extracted by the pump are evacuated through an outlet 52, opening in the bottom 50b of the hydrolysis reactor.
• the outlet 52 is connected to a neutralization tank 60 by means of a pipe 62.
• the tank 60 contains a bath 64 suitable for neutralizing the acid solutions which are brought there by the pipe 62.
• a neutral gas for example nitrogen
• nitrogen is injected into the circuit of gases extracted from the furnace, on the one hand, at the inlet of the pump 32, through a line 46 and, on the other hand, in the part 42 of the connection between the pump and the hydrolysis reactor, upstream of the venturi 43, by a pipe 48.
• the injection of nitrogen has the effect of diluting the gases at the inlet of the pump 32 and of opposing an ascent to the pump of acid vapors or solid particles from the hydrolysis reactor 50, thus avoiding clogging of the pump vent.
• the venturi 43 and the tube 44 of the pipe part 42 leading to the hydrolysis reactor and the downward direction of the gases in the tube 44 reinforce the interface function between the pump 32 and the hydrolysis reactor 50 which is ensured by nitrogen injection.
• the hydrolysis reactor 50 has a gas outlet 54 communicating with the atmosphere through a tray column 70.
• a filter 72 for example constituted by "Rashig" rings is inserted in the column 70.
• An inlet for water injection 74 is provided in the column 70, at the top of the latter, and communicates with a water reserve (not shown) via a pipe 76.
• the water thus injected forms a mist in the column and enters the hydrolysis reactor 50 through the outlet 54 by forming a curtain of water 56.
• the infiltration furnace 10 is supplied with a gaseous phase containing gases which are precursors of SiC or of a ternary system Si-BC or of B4C
• the gaseous chlorides Si x H v Cl z or BH u Cl v are transformed in the hydrolysis reactor into a hydrochloric acid solution and into solid oxides Si ⁇ 2 and B2O3 with release of hydrogen.
• the gaseous species discharged into the atmosphere at the top of the column 70 are then constituted practically by hydrogen gas and the nitrogen injected into the extraction device.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Health & Medical Sciences (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Materials Engineering (AREA)
• Biomedical Technology (AREA)
• Environmental & Geological Engineering (AREA)
• Analytical Chemistry (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Chemical Vapour Deposition (AREA)
• Physical Or Chemical Processes And Apparatus (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Feeding, Discharge, Calcimining, Fusing, And Gas-Generation Devices (AREA)

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• 1994
  • 1994-12-05 FR FR9414584A patent/FR2727692A1/fr active Granted
• 1995
  • 1995-09-22 GB GB9519431A patent/GB2295831B/en not_active Expired - Fee Related
  • 1995-12-01 JP JP51735696A patent/JP3979663B2/ja not_active Expired - Lifetime
  • 1995-12-01 WO PCT/FR1995/001587 patent/WO1996017972A1/fr not_active Ceased
  • 1995-12-01 US US08/849,623 patent/US6051071A/en not_active Expired - Lifetime
  • 1995-12-01 EP EP95941752A patent/EP0797689B1/fr not_active Expired - Lifetime
  • 1995-12-01 DE DE69504868T patent/DE69504868T2/de not_active Expired - Lifetime
  • 1995-12-01 CA CA002206464A patent/CA2206464C/en not_active Expired - Fee Related
  • 1995-12-01 ES ES95941752T patent/ES2124033T3/es not_active Expired - Lifetime

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