EP0628358A1 - Verfahren und Vorrichtung zur Schichtabtragung von hitzebeständigen Feststoffen - Google Patents

Verfahren und Vorrichtung zur Schichtabtragung von hitzebeständigen Feststoffen Download PDF

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Publication number
EP0628358A1
EP0628358A1 EP94401203A EP94401203A EP0628358A1 EP 0628358 A1 EP0628358 A1 EP 0628358A1 EP 94401203 A EP94401203 A EP 94401203A EP 94401203 A EP94401203 A EP 94401203A EP 0628358 A1 EP0628358 A1 EP 0628358A1
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EP
European Patent Office
Prior art keywords
pyrolysis
materials
solid
heat
temperature
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP94401203A
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English (en)
French (fr)
Inventor
Daniel Szurminski
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Entreprise Gagneraud Pere et Fils
Original Assignee
Entreprise Gagneraud Pere et Fils
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Entreprise Gagneraud Pere et Fils filed Critical Entreprise Gagneraud Pere et Fils
Publication of EP0628358A1 publication Critical patent/EP0628358A1/de
Withdrawn legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/82—Descaling by thermal stresses
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B08—CLEANING
    • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B7/00—Cleaning by methods not provided for in a single other subclass or a single group in this subclass
    • B08B7/0064—Cleaning by methods not provided for in a single other subclass or a single group in this subclass by temperature changes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24C—ABRASIVE OR RELATED BLASTING WITH PARTICULATE MATERIAL
    • B24C1/00—Methods for use of abrasive blasting for producing particular effects; Use of auxiliary equipment in connection with such methods
    • B24C1/003—Methods for use of abrasive blasting for producing particular effects; Use of auxiliary equipment in connection with such methods using material which dissolves or changes phase after the treatment, e.g. ice, CO2

Definitions

  • the invention relates firstly, to a process for pickling solid heat-resistant materials coated with a layer which can be altered under the effect of heat and, secondly, to a device for carrying out this process.
  • the invention relates to the field of surface treatment.
  • the common technique used in this field is to use a two-step pickling process.
  • a first step is to introduce the materials to be stripped in a pyrolysis oven.
  • the heat given off by this oven generally of the order of 400 degrees Celsius (° C)
  • Part of the coatings will thus be gasified, while a residual part, mainly made up of mineral matter, will remain fixed to its support, although it is weathered.
  • a second step consists in cleaning the residues fixed on the materials to be stripped.
  • Two possibilities are proposed by the prior art.
  • a first possibility consists in using the sanding technique according to which a siliceous compound or a compound of the same type, is sprayed under the action of compressed air against the materials pretreated by pyrolysis. This possibility is rarely put into practice because of the particularly abrasive nature of the sprayed compounds.
  • a second possibility, widely used in industrial environments, consists in spraying water under high pressure on the materials pretreated by pyrolysis. The residues are then detached from their support and then entrained by the flow of water. The abrasion is negligible.
  • a first major drawback of this technique is due to the formation of sludge resulting from the dissolution of the residues in water. This sludge very often contains toxic compounds which must imperatively be treated. This therefore generates significant costs.
  • a second drawback lies in the oxidation of the generally metallic surfaces of the materials treated with water.
  • the subject of the invention is a process for pickling solid heat-resistant materials coated with a layer which can be altered under the effect of heat, which remedies the drawbacks exposed above at lower cost.
  • the method according to the invention is characterized in that it comprises a pyrolysis step followed by a cleaning step by spraying solid particles at low temperature which sublimates on contact with heat-resistant solid materials previously treated by pyrolysis.
  • the cleaning step according to the invention is advantageously carried out while the materials subjected to the action of pyrolysis are at a temperature above ambient temperature.
  • the cleaning step is preferably supplemented by a drying step.
  • the subject of the invention is a device for implementing this method.
  • the pickling device according to the invention shown in FIG. 1 comprises a pyrolysis oven 1, and a cleaning cabin 2.
  • the pyrolysis oven 1 and the cleaning cabin 2 are crossed by parallel conveyors, respectively referenced 3 and 4.
  • a relay conveyor 5 is arranged at one end of the pickling device, between the conveyors 3 and 4.
  • a inlet conveyor 6 is located at the other end of the pickling device, near the conveyor 3 of the pyrolysis oven 1.
  • modular insulating panels are advantageously arranged all around the pickling assembly.
  • FIGS. 1 and 2 relate to the treatment of sleds 7 which transport parts produced and treated in the production lines of various industries.
  • FIG. 1 represents the stacks obtained by the superposition of two sleds referenced 8.
  • Two brackets not shown in FIG. 1 are advantageously placed, one at the end of the inlet conveyor 6 of the sleds, between the latter and the conveyor 3 passing through the oven 1, and the other, between the relay conveyor 5 and the end of the conveyor 4.
  • the pyrolysis oven 1 is in particular made up of a cubic enclosure comprising on the one hand, an opening for charging stacks 8 of sleds on the side of the inlet conveyor 6 and, on the other hand, an opening for discharging said stacks, on the side opposite the conveyor. These two openings are provided with doors: the charging door referenced by the number 9, and the charging door referenced by the number 10. These doors are preferably sliding. Furthermore, a pipe 11 is connected within the pyrolysis oven 1.
  • the access to the cleaning cabin 2 is constituted for example by an entrance tunnel 12 of the sleds 7 while the exit of said sleds is effected by an exit tunnel 13.
  • this cabin has an entrance door 14.
  • the cleaning cabin 2 is advantageously equipped with a suction device such as an extractor hood and preferably comprises a device for blowing hot air.
  • this cabin comprises in part or in whole, the device shown diagrammatically in FIG. 2.
  • This device allows the projection of solid particles represented by all of the lines referenced 25.
  • These solid particles 25 are advantageously composed of carbon dioxide. However, they can be made up of other chemical compounds having at least partially the property of being in gaseous form at room temperature.
  • the projection assembly of FIG. 2 advantageously comprises a storage tank 15 for the liquid carbon dioxide 16, a device for producing 17,18,32 of the particles of carbon dioxide 25, a compressor dryer 19,20, and a projection apparatus 21.
  • the device for producing the particles 17, 18, 32 is connected, on the one hand, to the storage tank 15 for the liquid carbon dioxide 16 via a line 22 possibly fitted with a valve 23 and, on the other hand to the projection equipment 21, by means of a transport pipe 24 for the particles 25. Furthermore, the compressor-dryer 19,20 is connected both to the transport pipe 24 for the particles and to the projection equipment 21, via pipes 26 and 27.
  • a transport air flow control valve 28 can be arranged on the line 26 and a propulsion air flow control valve 29 can be arranged on the line 27.
  • the storage tank 15 for liquid carbon dioxide 16 consists in particular of external walls comprising carbon dioxide in the liquid state maintained at a pressure of the order of 20 bars and at a temperature of approximately -20 ° C.
  • the device for producing the particles comprises at least one expansion enclosure 17, a reservoir 18 for recovering the particles formed, and one or more calibrated panels 28 disposed between said expansion enclosure and said reservoir 18.
  • the compressor dryer consists of a compression enclosure 19 connected to a dryer 20.
  • the projection equipment comprises for example a gun 21 provided with a projection nozzle 31 and, behind this nozzle, a mixing chamber.
  • the materials to be stripped are referenced by the number 33 while the pyrolysis residues are referenced by the number 34.
  • the sleds 7 selected for pickling according to the invention are moved towards the entrance of the device, along the arrow referenced 32.
  • a bracket then allows the stacking of the sleds 7 on the conveyor 3
  • the first step in the process is a pyrolysis step.
  • the stack 8 of sleds 7 is placed in the pyrolysis oven 1 through the charging opening.
  • the charging door 9 and the charging door 10 are then closed.
  • the heat of the oven is then brought to a sufficient temperature so that the pyrolysis can take place without the materials to be stripped being altered.
  • the temperature reached is between 250 and 600 ° C.
  • the coating is then degraded into two parts. A first part is gasified and escapes through the pipe 11 to be subsequently treated by an afterburner.
  • a second part generally made up of altered mineral matter, remains fixed on the surfaces of the heat-resistant solid materials to be stripped.
  • the pyrolysis time varies according to the materials to be treated, however, this time can be estimated on average at fifteen minutes.
  • the charging door 10 is opened and the stacks 8 of sleds 7 are then discharged.
  • the pyrolysis step can take place by means different from the aforementioned pyrolysis oven.
  • this step can take place in an oven with a fluidized bed, that is to say an oven in which sand is suspended.
  • a second bracket then passes the sleds one by one from the conveyor 3 to the relay conveyor 5, which transports the sleds 7 to the conveyor 4. Another passage is finally made to the conveyor 4 before the sleds 7 are introduced into the cabin cleaning 2 through tunnel 12.
  • the sleds are cleaned and advantageously dried before exiting through the outlet tunnel 13 and joining the production line in the direction indicated by the arrow 33.
  • the liquid carbon dioxide stored in the tank 15 is conveyed by the pipe 23, to the expansion enclosure 17.
  • the liquid carbon dioxide then undergoes an expansion which is accompanied by a reduction in the pressure up to atmospheric pressure, and a parallel decrease in the temperature then reaching the temperature of -78 ° C. At such a temperature and at such a pressure, carbon dioxide is in the form of carbon dioxide snow.
  • the particles are then stored in the recovery tank 18 until the particle distribution valve 30 is opened.
  • the transport air flow control valve 28 and the propulsion air flow control valve 29 are open, and if the particle projection device is triggered, the particles previously accelerated by the air passing through the transport pipe 24 will then be projected by the nozzle 31 of the gun 21 under the effect of the parallel introduction of air under high pressure, distributed by the propellant air pipe 27 coming from the air compressor 19 and dried by the dryer 20, in the mixing chamber of the spray gun 21. The temperature of the particles is then close to -78 ° C.
  • the effectiveness of cleaning is an increasing function of three parameters: the kinetic energy acquired by the particles at the time of impact, the flow rate of these particles and the thermal shock undergone by the materials encountered.
  • the thermal shock comes from the difference in temperature between the particles of solid carbon dioxide and the materials encountered by these particles.
  • the greater the impact the easier it is to detach the residues fixed on the surface of the materials to be stripped. It is therefore not only advantageous to have carbon dioxide particles at low temperature, but it is also particularly advantageous to have very hot target materials. Consequently, the shorter the time between the pyrolysis step and the cleaning step, the hotter the materials to be cleaned, the greater the thermal shock, and the better the quality of the cleaning.
  • This delay is such that the materials subjected to the action of pyrolysis are at a temperature above ambient temperature. It is advantageously fifteen minutes after the end of the pyrolysis step. Indeed, if the cleaning step is carried out in the interval of fifteen minutes following the end of the pyrolysis step, the materials to be treated will in fact have a temperature much higher than room temperature often exceeding 80 ° C.
  • the solid carbon dioxide particles sublimate on contact with heat-resistant solid materials previously treated by pyrolysis.
  • the carbon dioxide gas then escapes into the atmosphere and the residues fall dry for recovery. They can then be collected by simple aspiration.
  • the cleaning cabin for implementing the method according to the invention, it is possible that a slight condensation of water is produced on the walls of the pickled materials. This is particularly the case when the atmosphere contained in the cleaning cabin is too humid. Drying carried out for example by blowing hot air on the walls of the pickled materials is then useful in order to prevent any oxidation of said materials. Such drying can be carried out directly in the cleaning cabin 2, or after the materials have passed through said cabin.
  • the sleds 7 return to the production line.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Cleaning In General (AREA)
EP94401203A 1993-06-08 1994-05-31 Verfahren und Vorrichtung zur Schichtabtragung von hitzebeständigen Feststoffen Withdrawn EP0628358A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9306857 1993-06-08
FR9306857A FR2706138B1 (fr) 1993-06-08 1993-06-08 Procédé et dispositif de décapage de matériaux solides thermorésistants.

Publications (1)

Publication Number Publication Date
EP0628358A1 true EP0628358A1 (de) 1994-12-14

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EP94401203A Withdrawn EP0628358A1 (de) 1993-06-08 1994-05-31 Verfahren und Vorrichtung zur Schichtabtragung von hitzebeständigen Feststoffen

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EP (1) EP0628358A1 (de)
FR (1) FR2706138B1 (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2837122A1 (fr) * 2002-03-15 2003-09-19 Aero Strip Procede de decapage de pieces en materiau metallique ou composite, recouvertes d'un revetement et dispositif pour la mise en oeuvre du procede
EP1445040A1 (de) * 2003-01-13 2004-08-11 Siemens Aktiengesellschaft Verfahren zur Entfernung mindestens einer spröden Schicht von einem Substrat

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
LU52459A1 (de) * 1966-11-28 1968-06-25
FR2377017A1 (fr) * 1977-01-07 1978-08-04 Murre Jean Pierre Procedes de nettoyage des faces externes des parois d'echange thermique
EP0535680A1 (de) * 1991-10-01 1993-04-07 Hughes Aircraft Company Anordnung und Verfahren für Feinreinigung durch Sprühstahl
DE4134731A1 (de) * 1991-10-21 1993-04-22 Michael Laumen Verfahren und vorrichtung zur emissionsfreien entfettung, entlackung und reinigung
JPH05177542A (ja) * 1991-12-24 1993-07-20 Nippon Steel Corp 金属材のスケール除去方法

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
LU52459A1 (de) * 1966-11-28 1968-06-25
FR2377017A1 (fr) * 1977-01-07 1978-08-04 Murre Jean Pierre Procedes de nettoyage des faces externes des parois d'echange thermique
EP0535680A1 (de) * 1991-10-01 1993-04-07 Hughes Aircraft Company Anordnung und Verfahren für Feinreinigung durch Sprühstahl
DE4134731A1 (de) * 1991-10-21 1993-04-22 Michael Laumen Verfahren und vorrichtung zur emissionsfreien entfettung, entlackung und reinigung
JPH05177542A (ja) * 1991-12-24 1993-07-20 Nippon Steel Corp 金属材のスケール除去方法

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 17, no. 595 (M - 1503) 29 October 1993 (1993-10-29) *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2837122A1 (fr) * 2002-03-15 2003-09-19 Aero Strip Procede de decapage de pieces en materiau metallique ou composite, recouvertes d'un revetement et dispositif pour la mise en oeuvre du procede
EP1445040A1 (de) * 2003-01-13 2004-08-11 Siemens Aktiengesellschaft Verfahren zur Entfernung mindestens einer spröden Schicht von einem Substrat

Also Published As

Publication number Publication date
FR2706138A1 (fr) 1994-12-16
FR2706138B1 (fr) 1995-08-11

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