EP0928834B1 - Verfahren und Vorrichtung zum Kontrollieren des Taupunktes einer Ofenatmosphäre - Google Patents

Verfahren und Vorrichtung zum Kontrollieren des Taupunktes einer Ofenatmosphäre Download PDF

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Publication number
EP0928834B1
EP0928834B1 EP99300009A EP99300009A EP0928834B1 EP 0928834 B1 EP0928834 B1 EP 0928834B1 EP 99300009 A EP99300009 A EP 99300009A EP 99300009 A EP99300009 A EP 99300009A EP 0928834 B1 EP0928834 B1 EP 0928834B1
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EP
European Patent Office
Prior art keywords
furnace
hydrogen
oxygen
atmosphere
gas
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.)
Expired - Lifetime
Application number
EP99300009A
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English (en)
French (fr)
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EP0928834A1 (de
Inventor
Paul Francis Stratton
John Morris
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BOC Group Ltd
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BOC Group Ltd
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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
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • C21D1/76—Adjusting the composition of the atmosphere
    • 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
    • C21D11/00—Process control or regulation for heat treatments
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/002—Heat treatment of ferrous alloys containing Cr

Definitions

  • This invention relates to the control of the dew point in a protective atmosphere within a furnace, and in particular a furnace atmosphere containing hydrogen.
  • furnaces it is common for furnaces to be provided with a protective atmosphere, for example to prevent oxidation adversely affecting the processes within the furnace.
  • a vertical Bright Annealer (VBA) furnace used to anneal stainless steel sheet or strip, operates with a protective atmosphere having a composition of about 75% hydrogen and 25% nitrogen.
  • Such an atmosphere is highly reducing and very dry.
  • the furnace dew point can attain minus 70°C or even drier.
  • At such dryness levels there is a strong tendency toward the formation of a white powder deposit, particularly in the cooler regions of the furnace (for example the jet coolers), and these deposits inhibit the operating efficiency of the furnace, In order to remove the powder build-up it is usually necessary to shut down the furnace, which is time consuming and inefficient.
  • an improved method of controlling a furnace atmosphere dew point comprises withdrawing at least part of the flow of hydrogen being supplied to the furnace, reacting the withdrawn hydrogen with an oxygen-containing gas so as to produce a gas mixture consisting of an oxygen-free product gas, residual hydrogen and water, and directing the gas mixture into the atmosphere supplied to the furnace so as to maintain the water vapour content of the furnace atmosphere within a predetermined range.
  • Such an arrangement enables the provision of a controllable, automatic method of dew point adjustment of the furnace atmosphere, and enables the dew point to be accurately controlled and maintained within a given range.
  • the water vapour-containing gas mixture may be directed in to the flow of hydrogen prior to its introduction in to the furnace or, more preferably, may be directed in to the hot zone(s) of the furnace. In either case, the water vapour content can be accurately controlled, however the latter arrangement advantageously humidifies only a proportion of the total atmosphere flow in to the furnace and hence is inherently more efficient than the prior art methods in which the total atmosphere flow in to the furnace is humidified.
  • deoxo catalytic gas deoxygenation
  • Such deoxo units can profitably be used in the present invention to humidify a furnace atmosphere, being employed primarily as "water generators".
  • These deoxo units are highly efficient, and therefore water output can be precisely controlled; accordingly, the installation of a catalytic deoxo unit in the hydrogen pipeline serving the furnace enables the provision of a highly controllable method of dew point adjustment of the furnace atmosphere.
  • dew point sensing means and a suitable control device, such as a suitably programmed microprocessor, will produce a simple, inexpensive yet effective automatic dew point control system.
  • a suitable control device such as a suitably programmed microprocessor
  • Commercial deoxo units are also advantageous as they are completely self-contained, and do not require any external services or attention for their operation.
  • the invention further relates to an apparatus, as defined in claim 7, for controlling a furnace atmosphere dew point.
  • Figure 1 is a schematic diagram of an apparatus for humidifying the atmosphere supplied to a VBA furnace, and thus for controlling the dew point thereof.
  • a proportion of the hydrogen feed passing along supply line 2 to the VBA furnace is diverted along line 4 leading to a catalytic gas deoxygenation unit 6 thereto react with the oxygen in a supply of air passing along line 8 (the air typically being provided by a compressed air system, as cylinder gas or from a small compressor).
  • Flow meters 10 measure the flows of hydrogen and air into the deoxo unit 6, these flows being controlled by regulator valves 12.
  • Check valves 14 prevent back flows.
  • a valved off-take 16 is provided for sampling the gas supplied by the deoxo unit 6 for measuring the dew point.
  • hydrogen is supplied to the furnace atmosphere control system at high pressure (about 8bar) and the hydrogen withdrawn along line 4 is regulated to a lower pressure before passage through the deoxo unit 6. Passage through the deoxo unit results in a chemical combination of a proportion of the hydrogen and all of the oxygen in the air supply to the deoxo unit 6 in the ratio 2 to 1 by volume to form water vapour.
  • the outlet gases (hydrogen, water vapour and a small amount of nitrogen) is reintroduced back into the furnace atmosphere at a suitable low pressure (less than 8bar) location, such as into the main hydrogen feed immediately prior to its ingress into the furnace, or into the furnace itself.
  • dew point "shift" necessary to obtain dew point temperature levels within the range minus 40°C to minus 55°C is relatively minor.
  • a water vapour content within the above-mentioned VBA furnace atmosphere of 128ppm is equivalent to the higher dew point condition while 22ppm represents the dryer condition.
  • As the required water vapour levels are so low it is possible to accomplish the necessary humidification of the furnace atmosphere by treating only a small sidestream of the feed hydrogen supply to the furnace. Accordingly, up to about 3m 3 /hr of hydrogen (about 2.0% of the total hydrogen flow) is withdrawn for humidification.
  • the amount of water vapour produced can be controlled with great accuracy because the input flow rates of both hydrogen and air to the deoxo unit can be very accurately measured and controlled.
  • deoxo units are highly efficient in operation, and the size and hence expense of deoxo unit necessary could be reduced if it were desired to humidify the atmosphere in the furnace hot zone(s) only.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Furnace Details (AREA)

Claims (8)

  1. Verfahren zur Steuerung eines Ofenatmosphärentaupunkts, bei welchem im Gebrauch der Ofen mit einer Atmosphäre beschickt wird, die mindestens teilweise aus Wasserstoff besteht, wobei das Verfahren das Abziehen mindestens eines Teils der zum Ofen zugeführten Wasserstoffströmung, das Reagieren des abgezogenen Wasserstoffs mit einem sauerstoffhaltigen Gas, so daß ein aus einem sauerstofffreien Produktgas, restlichem Wasserstoff und Wasser bestehendes Gasgemisch erzeugt wird, und das Leiten des Gasgemischs in die zum Ofen zugeführte Atmosphäre umfasst, um den Wasserdampfgehalt der Ofenatmosphäre innerhalb eines vorgegebenen Bereichs zu halten.
  2. Verfahren nach Anspruch 1, welches das Steuern der Menge von abgezogenem Wasserstoff und/oder der Menge von damit reagiertem sauerstoffhaltigem Gas umfasst, um den vorgegebenen Wasserdampfgehaltsbereich zwischen etwa 10 ppm und etwa 200 ppm, vorzugsweise zwischen etwa 22 ppm und etwa 128 ppm, zu halten.
  3. Verfahren nach Anspruch 2, welches das Überwachen der Temperatur und/oder des Taupunkts der Ofenatmosphäre und die Steuerung der Menge(n) des abgezogenen Wasserstoffs und/oder des für die Reaktion zugeführten sauerstoffreichen Gases umfasst.
  4. Verfahren nach Anspruch 1, 2 oder 3, wobei das Gasgemisch in die Wasserstoffströmung vor deren Einleitung in den Ofen geleitet wird.
  5. Verfahren nach Anspruch 1, 2 oder 3, wobei das Gasgemisch in die heiße Zone(n) des Ofens eingeleitet wird.
  6. Verfahren nach einem der Ansprüche der vorhergehenden Ansprüche, wobei das sauerstoffhaltige Gas Luft ist.
  7. Einrichtung zur Steuerung eines Ofenatmosphärentaupunkts, bei welcher im Gebrauch der Ofen mit einer Atmosphäre beschickt wird, die mindestens teilweise aus Wasserstoff besteht, wobei die Einrichtung Mittel zum Abziehen mindestens eines Teils der zum Ofen zugeführten Wasserstoffströmung, Mittel zum Zuführen eines sauerstoffhaltigen Gases, Mittel zum Reagieren des abgezogenen Wasserstoffs mit dem sauerstoffhaltigen Gas zur Erzeugung eines Gasgemischs, das sauerstofffreies Produktgas, restlichen Wasserstoff und Wasser enthält, und Mittel zum Leiten des Gasgemischs in den Ofen umfasst, und wobei Mittel zur Steuerung der Menge(n) des abgezogenen Wasserstoffs und/oder des sauerstoffhaltigen Gases vorgesehen sind, um die Menge des erzeugten Wasserdampfs und folglich den Wasserdampfgehalt der Ofenatmosphäre innerhalb eines vorgegebenen Bereichs zu halten.
  8. Einrichtung nach Anspruch 7, wobei die Reaktionsmittel eine katalytische Gasdesoxiginierungseinheit umfassen.
EP99300009A 1998-01-12 1999-01-04 Verfahren und Vorrichtung zum Kontrollieren des Taupunktes einer Ofenatmosphäre Expired - Lifetime EP0928834B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB9800528.3A GB9800528D0 (en) 1998-01-12 1998-01-12 Furnace atmosphere dew point control
GB9800528 1998-01-12

Publications (2)

Publication Number Publication Date
EP0928834A1 EP0928834A1 (de) 1999-07-14
EP0928834B1 true EP0928834B1 (de) 2003-07-16

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EP99300009A Expired - Lifetime EP0928834B1 (de) 1998-01-12 1999-01-04 Verfahren und Vorrichtung zum Kontrollieren des Taupunktes einer Ofenatmosphäre

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EP (1) EP0928834B1 (de)
DE (1) DE69909535D1 (de)
GB (1) GB9800528D0 (de)
ZA (1) ZA989957B (de)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10255590A1 (de) * 2002-11-28 2004-06-17 Messer Griesheim Gmbh Verfahren zum kleberfreien Glühen von Metallteilen
JP2005120448A (ja) * 2003-10-17 2005-05-12 Chugai Ro Co Ltd 光輝焼鈍炉の制御方法
DE102010032919B4 (de) * 2010-07-30 2023-10-05 Air Liquide Deutschland Gmbh Verfahren und Vorrichtung zum Befeuchten eines brennbaren Gases

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4334938A (en) * 1980-08-22 1982-06-15 Air Products And Chemicals, Inc. Inhibited annealing of ferrous metals containing chromium
JPS58126930A (ja) * 1982-01-22 1983-07-28 Kawasaki Steel Corp ステンレス鋼帯の光輝焼鈍における表面光沢度調整方法
DE3526055C1 (de) * 1985-07-20 1986-03-27 Krupp Stahl Ag, 4630 Bochum Verfahren zur Herstellung von Wasserstoff/Stickstoff-Schutzgas-Gemischen zum Glühen kaltgewalzter Stahlbänder
US4744837A (en) * 1987-01-13 1988-05-17 Air Products And Chemicals, Inc. Bright annealing of stainless steels

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DE69909535D1 (de) 2003-08-21
GB9800528D0 (en) 1998-03-11
ZA989957B (en) 1999-05-06
EP0928834A1 (de) 1999-07-14

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