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EP0778354B1 - Process for supplying controlled atmosphere gases into a heat treatment furnace and heat treatment plant - Google Patents

Process for supplying controlled atmosphere gases into a heat treatment furnace and heat treatment plant Download PDF

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Publication number
EP0778354B1
EP0778354B1 EP96119651A EP96119651A EP0778354B1 EP 0778354 B1 EP0778354 B1 EP 0778354B1 EP 96119651 A EP96119651 A EP 96119651A EP 96119651 A EP96119651 A EP 96119651A EP 0778354 B1 EP0778354 B1 EP 0778354B1
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EP
European Patent Office
Prior art keywords
gas
zone
oxygen
furnace
protective
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EP96119651A
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German (de)
French (fr)
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EP0778354A1 (en
Inventor
Reinhard Dipl.-Ing. Strigl
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Linde Gas AG
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Linde Gas AG
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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
    • 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
    • C21D1/763—Adjusting the composition of the atmosphere using a catalyst
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04521—Coupling of the air fractionation unit to an air gas-consuming unit, so-called integrated processes
    • F25J3/04527—Integration with an oxygen consuming unit, e.g. glass facility, waste incineration or oxygen based processes in general
    • F25J3/04539—Integration with an oxygen consuming unit, e.g. glass facility, waste incineration or oxygen based processes in general for the H2/CO synthesis by partial oxidation or oxygen consuming reforming processes of fuels
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04521—Coupling of the air fractionation unit to an air gas-consuming unit, so-called integrated processes
    • F25J3/04563—Integration with a nitrogen consuming unit, e.g. for purging, inerting, cooling or heating

Definitions

  • the invention relates to a method for supplying protective gas to a heat treatment furnace with several zones, in particular an entry and exit zone and a heating zone in which the protective gas is obtained using source gas is generated with an air separation plant working on site.
  • the invention relates to a corresponding heat treatment plant.
  • This reaction is usually carried out with one next to the one or more heat treatment furnaces arranged, in the core of a gas generator consisting of a catalyst accomplished, and the so-called endogas formed in the generator is in Usually supplied to the associated heat treatment system without further treatment. It is also known to use the same starting gas mixture in an oven arranged and in this way already set to a higher temperature level Implement catalyst retort and the product gas either directly into the furnace allow to flow in or also to subtract and distribute (see e.g. DE 39 42 810 A1.
  • EP-A-0 261 461 discloses a method for the heat treatment of metallic workpieces by means of a continuous furnace.
  • the treatment atmosphere in the area of the heating zone is supplied in the form of a gas mixture which is generated by a catalytic reaction of a hydrocarbon and air-containing gas.
  • the areas at the oven inlet and outlet are supplied with nitrogen.
  • the oxygen-contaminated nitrogen obtained from the dismantling plant directly that is to say without post-purification, as a protective gas, specifically in furnace zones in which the oxygen content of the protective gas is less critical.
  • these are generally the colder supply and removal tunnels in front of the heating chamber (prechamber) or, in the case of continuous systems, the inlet area in front of the heating zone or treatment chamber (inlet chamber with subsequent zone) and the cooling zone or cooling chamber of the system on the outlet side.
  • the nitrogen shielding gas not warmed up according to the invention also acts as a particularly effective cooling gas.
  • the proportion of oxygen to be converted in this gas fraction is very high - namely at least about 25% - so that an effective conversion reaction between the oxygen of the said product gas and a correspondingly admixed KW gas is appropriate 1.5 O 2 + 3.5 N 2 + 3 CH 4 ⁇ 3 CO + 6 H 2 + 3.5 N 2 can take place. Since the starting gas used here has a relatively low nitrogen content, the unnecessarily heated gas content is relatively low compared to the above-mentioned post-purification of impure nitrogen, and the formation of protective gas is therefore comparatively energy-efficient.
  • the predominantly Nitrogen-containing fraction with a purity of at least 98.5% and the oxygen-rich starting gas fraction is produced with 25 to 35% oxygen.
  • a particularly favorable embodiment of the procedure according to the invention is thereby characterized in that the oxygen-rich starting gas with one in the heat treatment furnace arranged catalyst retort is implemented, the retort and the reactants to a temperature above 500 ° C, preferably above 800 ° C, are heated, for which purpose the retort may be additionally heated.
  • the figure shows an elongated continuous furnace D with an inlet zone 3, a central heating and treatment zone 5 and a cooling zone 7.
  • a catalyst retort 2 inside the furnace, that is to say an aggregate containing a catalyst material and having gas outlet openings at its head end , arranged, which is connected via gas lines 6 and 8 on the one hand to a membrane-based, ie permeate air separation plant 1 and its oxygen outlet O 2+ and on the other hand is connected via lines 6 and 10 to a hydrocarbon source CnHm, eg natural gas.
  • a hydrocarbon source CnHm eg natural gas.
  • the second product gas outlet N 2 of the air separator 1 i.e.
  • the one which supplies a nitrogen-rich gas is finally connected directly to the heat treatment furnace via lines 11, 12 and 14, the gas supply line, however, specifically into the furnace inlet zone 3 - line 12 - and into the furnace outlet zone 7 - Line 14 - done.
  • the middle part of the heat treatment plant is not supplied with any gas which does not come from the nitrogen outlet of the air separation plant and is not further treated.
  • the shielding gas requirement of the continuous furnace shown can be, for example, 150 m 3 / h.
  • the permeation air separation plant 1 shown is now set so that approximately 110 m 3 of nitrogen gas with 99% purity are made available per hour.
  • This nitrogen gas, the so-called retentate is fed to the inlet zone 3 and the outlet zone 7 of the furnace shown in a quantity of 55 m 3 / h in each case, without removing further oxygen therefrom.
  • the still necessary for the heating zone 5, 40 m 3 / h of very low-oxygen protective gas are obtained according to the invention from the oxygen-rich gas, the so-called permeate, which also occurs in larger quantities in the operation of the air separation plant 1 described.
  • this is done by mixing 15.6 m 3 of this permeate, which contains about 31% oxygen and 69% nitrogen, in mixer 9 with 7 m 3 / h of natural gas (methane) and catalytically gas mixture obtained in catalyst retort 2 is converted to a protective gas containing about 24% CO, 48% H 2 and 28% N 2 and is released as such into the heating zone 5 of the furnace.
  • the catalyst 2 which is preferably a nickel catalyst, must be set to temperatures above 800 ° C., preferably 900 to 1050 ° C.
  • a large part of the heat supply for maintaining this temperature level is already guaranteed by the heating in the heating zone 5 of the continuous furnace D, which is heated to, for example, 800 to 900 ° C.
  • the protective gas quantity of 40 m 3 / h required for the heating zone is obtained.
  • Excess oxygen-rich permeate is released to the environment via an outlet A installed in the gas line 8 or advantageously supplied as O 2 -enriched air to the other jet pipes instead of air as an oxygen carrier for heating the jet pipes.
  • the shielding gas supplied in the middle part of the furnace represents a shielding gas consisting essentially of CO, H 2 and N 2 , while the shielding gas supplied on the inlet and outlet sides consists of almost pure nitrogen, the nitrogen purity for the complete avoidance of metallurgically disadvantageous effects at least about 99 % should be.
  • the supply of differently composed protective gases according to the invention also results in a protective gas composition that varies somewhat over the length of the furnace, which leads to an equally locally varying gas reactivity, which has its peak in particular in the heating zone of the furnace and which decreases towards the furnace ends.
  • an atmosphere with about 12% CO, 24% H 2 and 64% N 2 is usually established in the heating zone at the described conditions, which gives an atmosphere which is particularly advantageous for many annealing treatments, which is somewhat reducing and in terms of the carburizing effect has almost neutral properties for many materials.
  • the supply of the cold nitrogen shielding gas in the outlet area of the continuous furnace achieves an improved cooling performance compared to other annealing processes.
  • the method according to the invention thus has advantages such as the improved economy and the increased cooling capacity compared to methods in which only the nitrogen product of an on-site air separator is used for protective gas production, and thus represents an advantageous alternative to these methods.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Materials Engineering (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Furnace Details (AREA)
  • Control Of Heat Treatment Processes (AREA)
  • Feeding, Discharge, Calcimining, Fusing, And Gas-Generation Devices (AREA)
  • Carbon And Carbon Compounds (AREA)

Abstract

A protective gas for a heat treatment furnace with several zones is generated from the exit gas from an air separation unit. The gas fraction containing mainly nitrogen is passed into the intake zone and if necessary the exit zone of the furnace without further removal of oxygen. The protective gas used in the heating or treatment zone is obtained from at least a part of the oxygen rich gas fraction from the air separation unit mixed with natural gas or propane by heating and catalytic conversion to mainly carbon monoxide and hydrogen. Also claimed is a heat treatment furnace with a protective gas generating plant that includes an air separation unit (1) and a unit (2) for reacting O2 with a hydrocarbon gas as described above.

Description

Die Erfindung betrifft ein Verfahren zur Schutzgasversorgung eines Wärmebehandlungsofens mit mehreren Zonen, insbesondere einer Einlauf- und Auslaufzone sowie einer Heizzone, bei dem das Schutzgas unter Verwendung von Ausgangsgas gewonnen wird, das mit einer vor Ort arbeitenden Luftzerlegungsanlage erzeugt wird. Ebenso bezieht sich die Erfindung auf eine entsprechende Wärmebehandlungsanlage.The invention relates to a method for supplying protective gas to a heat treatment furnace with several zones, in particular an entry and exit zone and a heating zone in which the protective gas is obtained using source gas is generated with an air separation plant working on site. As well The invention relates to a corresponding heat treatment plant.

Grundsätzlich ist es bekannt, CO- und H2-haltige Schutz- oder Reaktionsgase für Wärmebehandlungen aus Luft und einem Kohlenwasserstoffgas (KW-Gas), insbesondere Erdgas, und mittels katalytischer Umsetzung der reaktiven Bestandteile, nämlich Sauerstoff und beispielsweise Methan, zu bilden. Die typische Bildungsreaktion, die eine unvollständige Verbrennung des KW-Gases darstellt, lautet hierbei wie folgt: (O2 + 4 N2) + 2 CH4 → 2 CO + 4 H2 + 4 N2
= Luft Basically, it is known to form CO and H 2 -containing protective or reaction gases for heat treatments from air and a hydrocarbon gas (KW gas), in particular natural gas, and by means of catalytic conversion of the reactive components, namely oxygen and, for example, methane. The typical formation reaction, which represents incomplete combustion of the KW gas, is as follows: (O 2 + 4 N 2 ) + 2 CH 4 → 2 CO + 4 H 2 + 4 N 2
= Air

Diese Reaktion wird üblicherweise mit einem neben dem oder den Wärmebehandlungsöfen angeordneten, im Kernstück aus einem Katalysator bestehenden Gasgenerator bewerkstelligt, und das im Generator gebildete, sogenannte Endogas wird im Regelfall ohne weitere Behandlung der zughörigen Wärmebehandlungsanlage zugeführt. Ebenso ist es bekannt, das gleiche Ausgangsgasgemisch in einer in einem Ofen angeordneten und auf diese Weise bereits auf ein höheres Temperaturniveau versetzten Katalysatorretorte umzusetzen und das Produktgas entweder direkt in den Ofen einfließen zu lassen oder auch abzuziehen und zu verteilen (siehe z.B. DE 39 42 810 A1.This reaction is usually carried out with one next to the one or more heat treatment furnaces arranged, in the core of a gas generator consisting of a catalyst accomplished, and the so-called endogas formed in the generator is in Usually supplied to the associated heat treatment system without further treatment. It is also known to use the same starting gas mixture in an oven arranged and in this way already set to a higher temperature level Implement catalyst retort and the product gas either directly into the furnace allow to flow in or also to subtract and distribute (see e.g. DE 39 42 810 A1.

Außerdem ist es auch bekannt, sogenannten kommerziellen Stickstoff, also Stickstoff der noch mit erheblichen Anteilen Sauerstoff (1% und mehr) verunreinigt ist auf diese Weise zu einer sauerstofffreien und somit brauchbaren Wärmebehandlungsatmophäre für metallisches Gut umzuwandeln (Fachartikel " Commercial Nitrogen - The Basis For A Universal Controlled Atmophere" aus Metal Science and Heat Treatment 1978, Heft 5/6, Seiten 377-381). It is also known as so-called commercial nitrogen which is still contaminated with considerable amounts of oxygen (1% and more) Way to an oxygen-free and therefore usable heat treatment atmosphere for metallic goods (technical article "Commercial Nitrogen - The Basis For A Universal Controlled Atmophere "from Metal Science and Heat Treatment 1978, booklet 5/6, pages 377-381).

In jüngerer Zeit ist mehrfach vorgeschlagen worden, einen kommerziellen Stickstoff mit etwa 0,5 bis 5 % Sauerstoff vor Ort bei Wärmebehandlungen mit Hilfe von nunmehr entsprechend weit entwickelten adsorptiven oder permeativen Luftzerlegungseinheiten bereitzustellen und daraus wiederum - wie beschrieben - ein nahezu sauerstofffreies Schutzgas herzustellen (siehe z.B. US-PS 5 242 509 = EP 0 482 992 (von 1990) oder DE-PS 42 12 307 (1992)). Mit den geschilderten Verfahren wird jeweils ein nahezu sauerstofffreies, CO, H2 und N2 enthaltendes Behandlungsgas erhalten, das für verschiedenste Wärmebehandlungen geeignet ist.In recent times, it has been proposed several times to provide a commercial nitrogen with about 0.5 to 5% oxygen on site during heat treatments with the aid of now appropriately developed adsorptive or permeative air separation units and, in turn, to produce an almost oxygen-free protective gas as described (see e.g. US Pat. No. 5,242,509 = EP 0 482 992 (from 1990) or DE-PS 42 12 307 (1992)). With the described processes, an almost oxygen-free treatment gas containing CO, H 2 and N 2 is obtained, which is suitable for a wide variety of heat treatments.

Nachteilig bei den letztgenannten Verfahren unter Einsatz einer Luftzerlegung vor Ort ist jedoch, daß zur Nachreinigung des Unrein-Stickstoffs beträchtliche Mengen an Energie erforderlich sind, da ja die Gesamtmenge an Unreinstickstoff auf die zur katalytischen Umsetzung des Restsauerstoffs erforderliche Temperatur zu erwärmen ist, um die sauerstoffentfernende Reaktion auszulösen. Im Ergebnis wird zwar ein ausgezeichnetes Behandlungsgas erhalten, jedoch stellt sich die Frage, ob nicht beispielsweise mit angeliefertem Reinstickstoff in Kombination mit einer der bekannten Endogaserzeugungsmethoden identische Schutzgase ähnlich ökonomisch hergestellt werden können, wobei hierbei auf die Luftzerlegung vor Ort vollständig verzichtet werden kann.A disadvantage of the latter methods using on-site air separation is, however, that considerable amounts of are used to purify the impure nitrogen Energy is required, since the total amount of impure nitrogen on the catalytic Reaction of the residual oxygen required temperature to be heated, to trigger the oxygen-removing reaction. The result is an excellent one Received treatment gas, but the question arises whether, for example with pure nitrogen supplied in combination with one of the known endogas production methods identical shielding gases produced in a similar economical manner can be completely omitted on site can be.

EP-A-0 261 461 offenbart ein Verfahren zur Wärmebehandlung metallischer Werkstücke mittels eines Durchlaufofens. Die Behandlungsatmosphäre im Bereich der Heizzone wird in Form einer Gasmischung zugeführt, die durch eine katalytische Umsetzung eines Kohlenwasserstoffe und Luftenthaltenden Gases erzeugt wird. Die Bereiche bei dem Ofeneinlauf und dem Ofenauslauf werden mit Stickstoff versorgt.EP-A-0 261 461 discloses a method for the heat treatment of metallic workpieces by means of a continuous furnace. The treatment atmosphere in the area of the heating zone is supplied in the form of a gas mixture which is generated by a catalytic reaction of a hydrocarbon and air-containing gas. The areas at the oven inlet and outlet are supplied with nitrogen.

Die Anmelderin hat sich vor diesem Hintergrund nunmehr speziell die Aufgabe gestellt, insbesondere die Ökonomie der Verfahren, die auf Basis der Luftzerlegung vor Ort arbeiten, zu verbessern.Against this background, the applicant has now set itself the task of improving , in particular, the economy of the processes which work on the basis of air separation on site.

Die Aufgabe wird erfindungsgemäß durch die Merkmale von Anspruch 1 gelöst. The object is achieved by the features of claim 1.

Es wird also vorgeschlagen, den von der Zerlegungsanlage erhaltenen, sauerstoffverunreinigten Stickstoff unmittelbar, d.h. ohne Nachreinigung, als Schutzgas anzuwenden, und zwar in Ofenzonen, in denen der Sauerstoffgehalt des Schutzgases weniger kritisch ist. Dies sind im allgemeinen bei nicht kontinuierlichen Öfen der kältere, vor der Heizkammer liegende Zufuhr- und Entnahmetunnel (Vorkammer) oder bei Durchlaufanlagen der vor der Heizzone oder Behandlungskammer liegende Einlaufbereich (Eintrittkammer mit nachfolgender Zone) sowie die ausgangsseitig liegende Kühlzone oder Abkühlkammer der Anlage. In der Kühlzone wirkt das erfindungsgemäß nicht angewärmte Stickstoffschutzgas außerdem auch als besonders effektives Kühlgas. In der auf Behandlungstemperatur zu haltenden Zone oder Kammer eines Ofens ist jedoch die Anwendung des Unrein-Stickstoffs als Schutz- oder Behandlungsgas nicht möglich. Daher ist hier ein anderes Schutzgas anzuwenden, das erfindungsgemäß aus dem zweiten, insbesondere bei permeativen und adsorptiven Luftzerlegern anfallenden, sauerstoffreichen Produktgas wiederum durch katalytische Umsetzung mit einem Kohlenwasserstoffgas erzeugt wird. Hierbei ist als erstes anzumerken, daß - da lediglich noch die Heizzone mit Schutzgas zu versorgen ist - zunächst nur noch eine geringere Gasmenge erforderlich ist, die etwa die Hälfte bis 1/4 des Gesamtbedarfs eines Ofens umfaßt. Zudem ist in dieser Gasfraktion der umzusetzende Sauerstoffanteil sehr hoch - nämlich wenigstens etwa 25 % - so daß eine effektive Umsetzungsreaktion zwischen dem Sauerstoff des besagten Produktgases und einem entsprechend zuzumischenden KW-Gas gemäß 1,5 O2 + 3,5 N2 + 3 CH4 → 3 CO + 6 H2 + 3,5 N2 stattfinden kann. Da bei dem hier angewandten Ausgangsgas ein relativ niedriger Stickstoffanteil vorliegt, ist der unnötig erhitzte Gasanteil im Vergleich zur oben angesprochenen Nachreinigung von Unrein-Stickstoff relativ niedrig und somit die Schutzgasbildung vergleichsweise energieökonomisch.It is therefore proposed to use the oxygen-contaminated nitrogen obtained from the dismantling plant directly, that is to say without post-purification, as a protective gas, specifically in furnace zones in which the oxygen content of the protective gas is less critical. In the case of non-continuous furnaces, these are generally the colder supply and removal tunnels in front of the heating chamber (prechamber) or, in the case of continuous systems, the inlet area in front of the heating zone or treatment chamber (inlet chamber with subsequent zone) and the cooling zone or cooling chamber of the system on the outlet side. In the cooling zone, the nitrogen shielding gas not warmed up according to the invention also acts as a particularly effective cooling gas. In the zone or chamber of a furnace to be kept at the treatment temperature, however, the use of the impure nitrogen as a protective or treatment gas is not possible. Therefore, another protective gas is to be used here, which, according to the invention, is in turn generated from the second, oxygen-rich product gas, which occurs in particular in the case of permeative and adsorptive air separators, by catalytic reaction with a hydrocarbon gas. First of all, it should be noted that - since only the heating zone is to be supplied with protective gas - initially only a smaller amount of gas is required, which comprises about half to 1/4 of the total requirement of a furnace. In addition, the proportion of oxygen to be converted in this gas fraction is very high - namely at least about 25% - so that an effective conversion reaction between the oxygen of the said product gas and a correspondingly admixed KW gas is appropriate 1.5 O 2 + 3.5 N 2 + 3 CH 4 → 3 CO + 6 H 2 + 3.5 N 2 can take place. Since the starting gas used here has a relatively low nitrogen content, the unnecessarily heated gas content is relatively low compared to the above-mentioned post-purification of impure nitrogen, and the formation of protective gas is therefore comparatively energy-efficient.

Hinsichtlich des zu erbringenden Aufwands ergibt sich ein Vorteil, wenn die Luftzerlegung vor Ort nicht kryogen, d.h. nicht nach der Tieftemperaturmethode, sondern permeativ oder adsorptiv ausgeführt wird. With regard to the effort to be achieved, there is an advantage if the air separation not cryogenic on site, i.e. not according to the low temperature method, but is carried out permeatively or adsorptively.

Für ein vorteilhaftes Funktionieren der Erfindung ist es ferner vorteilhaft, wenn die überwiegend Stickstoff enthaltende Fraktion mit einer Reinheit von wenigstens 98,5% und die sauerstoffreiche Ausgangsgas-Fraktion mit 25 bis 35 % Sauerstoff hergestellt wird.For an advantageous functioning of the invention, it is also advantageous if the predominantly Nitrogen-containing fraction with a purity of at least 98.5% and the oxygen-rich starting gas fraction is produced with 25 to 35% oxygen.

Eine besonders günstige Ausgestaltung des erfindungsgemäßen Vorgehens ist dadurch gekennzeichnet, daß das sauerstoffreiche Ausgangsgas mit einer im Wärmebehandlungsofen angeordneten Katalysatorretorte umgesetzt wird, wobei die Retorte und die Reaktionspartner auf eine Temperatur von über 500 °C, vorzugsweise über 800 °C, aufgeheizt werden, wozu die Retorte gegebenenfalls zusätzlich beheizt wird .A particularly favorable embodiment of the procedure according to the invention is thereby characterized in that the oxygen-rich starting gas with one in the heat treatment furnace arranged catalyst retort is implemented, the retort and the reactants to a temperature above 500 ° C, preferably above 800 ° C, are heated, for which purpose the retort may be additionally heated.

Ein erfindungsgemäßer Wärmebehandlungsofen wird in dem Anspruch 6 angegeben (die Gasleitungen enthalten selbstverständlich auch die notwendigen Ventile und Stellglieder).An inventive heat treatment furnace is specified in claim 6 (The gas pipes naturally contain also the necessary valves and actuators).

Anhand der anliegenden Figur wird im folgenden ein Ausführungsbeispiel der Erfindung näher beschrieben.An exemplary embodiment of the invention is described below with reference to the attached figure described in more detail.

Die Figur zeigt einen länglich ausgebildeten Durchlaufofen D mit einer Eintrittszone 3, einer mittig liegenden Heiz- und Behandlungszone 5 und einer Kühlzone 7. In der Heizzone 5 ist im Ofeninneren eine Katalysatorretorte 2, also ein ein Katalysatormaterial enthaltendes Aggregat, das an seinem Kopfende Gasauslaßöffnungen aufweist, angeordnet, das über Gasleitungen 6 und 8 einerseits mit einer auf Membranbasis, also permeativ arbeitenden Luftzerlegungsanlage 1 und dessen Sauerstoffausgang O 2+ in Verbindung steht und andererseits über Leitungen 6 und 10 mit einer Kohlenwasserstoffquelle CnHm, z.B. Erdgas, verbunden ist. An der Schnittstelle der Leitungen 8 und 10 ist ferner eine Misch- und Einstelleinheit 9 für die zufließenden Gase vorhanden. Der zweite Produktgasausgang N2 des Luftzerlegers 1, also derjenige der ein stickstoffreiches Gas liefert, ist schließlich über Leitungen 11, 12 und 14 direkt mit dem Wärmebehandlungsofen verbunden, wobei die Gaszuleitung jedoch spezifisch in die Ofeneinlaufzone 3 - Leitung 12 - und in die Ofenauslaufzone 7 - Leitung 14 - erfolgt. Dem Mittelteil der Wärmebehandlungsanlage wird kein, unmittelbar vom Stickstoffausgang der Luftzerlegungsanlage stammendes, nicht weiterbehandeltes Gas zugeführt.The figure shows an elongated continuous furnace D with an inlet zone 3, a central heating and treatment zone 5 and a cooling zone 7. In the heating zone 5 there is a catalyst retort 2 inside the furnace, that is to say an aggregate containing a catalyst material and having gas outlet openings at its head end , arranged, which is connected via gas lines 6 and 8 on the one hand to a membrane-based, ie permeate air separation plant 1 and its oxygen outlet O 2+ and on the other hand is connected via lines 6 and 10 to a hydrocarbon source CnHm, eg natural gas. At the interface of lines 8 and 10 there is also a mixing and setting unit 9 for the inflowing gases. The second product gas outlet N 2 of the air separator 1, i.e. the one which supplies a nitrogen-rich gas, is finally connected directly to the heat treatment furnace via lines 11, 12 and 14, the gas supply line, however, specifically into the furnace inlet zone 3 - line 12 - and into the furnace outlet zone 7 - Line 14 - done. The middle part of the heat treatment plant is not supplied with any gas which does not come from the nitrogen outlet of the air separation plant and is not further treated.

Ein erfindungsgemäßer Betrieb der gezeigten Anlage verläuft nunmehr wie folgt:Operation of the system shown according to the invention now proceeds as follows:

Der Schutzgasbedarf des gezeigten Durchlaufofens kann beispielsweise 150 m3/h betragen. Erfindungsgemäß wird nun die gezeigte, permeativ arbeitende Luftzerlegungsanlage 1 so eingestellt, daß etwa 110 m3 Stickstoffgas mit 99 %-iger Reinheit in der Stunde zur Verfügung gestellt werden. Dieses Stickstoffgas, das sogenannte Retentat, wird, ohne daraus weiteren Sauerstoff zu entfernen, in einer Quantität von jeweils 55 m3/h der Einlaufzone 3 und der Auslaufzone 7 des gezeigten Ofens zugeleitet. Die für die Heizzone 5 noch notwendigen, 40 m3/h an sehr sauerstoffarmem Schutzgas werden gemäß der Erfindung aus dem sauerstoffreichen Gas, dem sogenannten Permeat, gewonnen, das ebenfalls bei dem geschilderten Betrieb der Luftzerlegungsanlage 1 in größerer Menge anfällt. Im einzelnen erfolgt dies dadurch, daß 15,6 m3 dieses Permeats, das etwa 31 % Sauerstoff und 69 % Stickstoff enthält, im Mischer 9 mit 7 m3/h Erdgas (Methan) gemischt werden und das erhaltene Gasgemisch in der Katalysatorretorte 2 katalytisch zu einem etwa 24 % CO, 48 % H2 und 28 % N2 enthaltenden Schutzgas umgesetzt wird und als solches in die Heizzone 5 des Ofens entlassen wird. Hierbei ist - um die saubere Umsetzung der Ausgangsgase zu gewährleisten - der Katalysator 2, der vorzugsweise ein Nickelkatalysator ist, auf Temperaturen von oberhalb 800 C, vorzugsweise 900 bis 1050° C einzustellen.The shielding gas requirement of the continuous furnace shown can be, for example, 150 m 3 / h. According to the invention, the permeation air separation plant 1 shown is now set so that approximately 110 m 3 of nitrogen gas with 99% purity are made available per hour. This nitrogen gas, the so-called retentate, is fed to the inlet zone 3 and the outlet zone 7 of the furnace shown in a quantity of 55 m 3 / h in each case, without removing further oxygen therefrom. The still necessary for the heating zone 5, 40 m 3 / h of very low-oxygen protective gas are obtained according to the invention from the oxygen-rich gas, the so-called permeate, which also occurs in larger quantities in the operation of the air separation plant 1 described. In particular, this is done by mixing 15.6 m 3 of this permeate, which contains about 31% oxygen and 69% nitrogen, in mixer 9 with 7 m 3 / h of natural gas (methane) and catalytically gas mixture obtained in catalyst retort 2 is converted to a protective gas containing about 24% CO, 48% H 2 and 28% N 2 and is released as such into the heating zone 5 of the furnace. In order to ensure the clean conversion of the starting gases, the catalyst 2, which is preferably a nickel catalyst, must be set to temperatures above 800 ° C., preferably 900 to 1050 ° C.

Durch die durch nicht gezeigte Heizeinrichtungen auf beispielsweise 800 bis 900 C aufgeheizte Atmosphäre in der Heizzone 5 des Durchlaufofens D wird bereits ein Großteil der Wärmezufuhr zur Aufrechterhaltung dieses Temperaturniveaus gewährleistet. Eine zusätzlich Wärmemenge Qzu kann gegebenenfalls durch eine in die Katalysatorretorte 2 integrierte Heizung aufgebracht werden. Durch thermokatalytische Umsetzung der obengenannten Ausgangsmengen an Erdgas und sauerstoffreichem Gas wird also die für die Heizzone erforderliche Schutzgasmenge von 40 m3/h erhalten. Überschüsse an sauerstoffreichem Permeat werden dabei über einen in der Gasleitung 8 installierten Auslaß A an die Umgebung abgegeben oder als O2-angereicherte Luft den übrigen Strahlrohren statt Luft als Sauerstoffträger zur Beheizung der Strahlrohre vorteilhaft zugeleitet.A large part of the heat supply for maintaining this temperature level is already guaranteed by the heating in the heating zone 5 of the continuous furnace D, which is heated to, for example, 800 to 900 ° C. An additional quantity of heat Q to be optionally applied by an integrated in the catalyst retort 2 heating. By thermocatalytic conversion of the above-mentioned initial quantities of natural gas and oxygen-rich gas, the protective gas quantity of 40 m 3 / h required for the heating zone is obtained. Excess oxygen-rich permeate is released to the environment via an outlet A installed in the gas line 8 or advantageously supplied as O 2 -enriched air to the other jet pipes instead of air as an oxygen carrier for heating the jet pipes.

Insgesamt werden auf diese Weise dem Durchlaufofen D also 150 m3 Schutzgas/h zugeführt, wobei jeweils 55 m3 auf die Einlauf- bzw. Auslaufzone entfallen und der mittig im Ofen liegenden Heizzone die verbleibenden 40 m3 zugeführt werden. Das im Mittelteil des Ofens zugeführte Schutzgas stellt dabei ein im wesentlichen aus CO, H2 und N2 bestehendes Schutzgas dar, während das eingangs- und ausgangsseitig zugeführte Schutzgas aus nahezu reinem Stickstoff besteht, wobei die Stickstoffreinheit zur gänzlichen Vermeidung metallurgisch nachteiliger Effekte wenigstens etwa 99 % betragen sollte.In this way, a total of 150 m 3 of protective gas / h are fed to the continuous furnace D, 55 m 3 each being in the inlet and outlet zones and the remaining 40 m 3 being supplied to the central heating zone in the furnace. The shielding gas supplied in the middle part of the furnace represents a shielding gas consisting essentially of CO, H 2 and N 2 , while the shielding gas supplied on the inlet and outlet sides consists of almost pure nitrogen, the nitrogen purity for the complete avoidance of metallurgically disadvantageous effects at least about 99 % should be.

Durch die erfindungsgemäße Zuleitung unterschiedlich zusammengesetzter Schutzgase ergibt sich im übrigen eine über die Ofenlänge hinweg etwas variierende Schutzgaszusammensetzung, die zu einer ebenso örtlich variierenden Gasreaktivität führt, welche insbesondere in der Heizzone des Ofens ihre Spitze besitzt und die zu den Ofenenden hin abnimmt. Bei den beschriebenen Verhältnissen stellt sich nach Erfahrungen der Anmelderin in der Heizzone im Regelfall eine Atmosphäre mit etwa 12 % CO, 24 % H2 und 64 % N2 ein, womit eine für viele Glühbehandlungen besonders vorteilhafte Atmosphäre gegeben ist, die etwas reduzierende und hinsichtlich der Kohlungswirkung für viele Werkstoffe nahezu neutrale Eigenschaften aufweist. Im übrigen wird durch die Zufuhr des kalten Stickstoffschutzgases im Auslaufbereich des Durchlaufofens eine im Vergleich zu anderen Glühverfahren verbesserte Kühlleistung erzielt. Das erfindungsgemäße Verfahren weist also im Vergleich zu Verfahren, bei denen lediglich das Stickstoffprodukt eines vor Ort betriebenen Luftzerlegers zur Schutzgaserzeugung eingesetzt wird, Vorteile wie die verbesserte Ökonomie und die erhöhte Kühlleistung auf und stellt somit eine vorteilhafte Alternative zu diesen Verfahren dar.The supply of differently composed protective gases according to the invention also results in a protective gas composition that varies somewhat over the length of the furnace, which leads to an equally locally varying gas reactivity, which has its peak in particular in the heating zone of the furnace and which decreases towards the furnace ends. According to the experience of the applicant, an atmosphere with about 12% CO, 24% H 2 and 64% N 2 is usually established in the heating zone at the described conditions, which gives an atmosphere which is particularly advantageous for many annealing treatments, which is somewhat reducing and in terms of the carburizing effect has almost neutral properties for many materials. Incidentally, the supply of the cold nitrogen shielding gas in the outlet area of the continuous furnace achieves an improved cooling performance compared to other annealing processes. The method according to the invention thus has advantages such as the improved economy and the increased cooling capacity compared to methods in which only the nitrogen product of an on-site air separator is used for protective gas production, and thus represents an advantageous alternative to these methods.

Claims (6)

  1. Method for the protective gas supply of a heat-treatment furnace having a plurality of zones, in particular an intake zone and a heat zone, and if appropriate an exit zone, in which different protective gases are fed to the various zones, characterized in that the respective protective gas is produced using starting gas which is generated by an air fractionation plant operating on site,
    with the starting gas fraction which is obtained by the fractionation plant and predominantly contains nitrogen being produced at a purity of at least 98.5% and being introduced as protective gas without further oxygen removal into the intake zone and if appropriate the exit zone of the furnace
    and with a protective gas which is suitable for the heating zone or treatment zone being produced by mixing at least part of the oxygen-rich fraction, which is also produced by the fractionation plant, and is produced having an oxygen content of at least 25%, with a hydrocarbon gas,
    catalytically converting this mixture, with supply of heat, to a gas mixture which, in addition to nitrogen, chiefly comprises carbon monoxide and hydrogen, and feeding this gas mixture, as protective gas, to the heating zone (heat zone) of the furnace.
  2. Method according to Claim 1, characterized in that the air fractionation is carried out on site by permeation or adsorption.
  3. Method according to Claim 1 or 2, characterized in that an oxygen-rich starting gas fraction comprising 25 to 35% oxygen is produced.
  4. Method according to one of Claims 1 to 3, characterized in that the oxygen-rich starting gas is reacted with a hydrocarbon gas and with a catalyst retort disposed in a heat-treatment furnace, the retort and the reaction partner being heated to a temperature above 500°C, preferably above 800°C, for which purpose the retort is if appropriate additionally heated.
  5. Method according to Claim 1, characterized in that the hydrocarbon gas is natural gas or propane.
  6. Heat-treatment furnace having a protective gas supply, in which the intake zone and if appropriate the outlet zone (3,7) of the furnace are fitted with gas supply lines (12,14) and
    in which a reaction unit (2) for reaction of oxygen with a hydrocarbon gas is present, which unit releases or passes its product gas to the heating zone (5) of the furnace and is also connected to appropriate gas sources (CnHm), characterized in that
    the protective gas supply additionally comprises an air fractionation plant (1) with firstly the product gas outlet (N2) of the air fractionation plant (1) which delivers the gas fraction which predominantly comprises nitrogen (N2), being connected to the gas supply lines (12,14) for the intake zone and if appropriate the exit zone (3,7) of the furnace, and
    with, secondly, the product gas outlet (O2+) of the air-fractionation plant (1) which delivers the oxygen-rich fraction being connected to the reaction unit (2) via lines (8,6).
EP96119651A 1995-12-07 1996-12-06 Process for supplying controlled atmosphere gases into a heat treatment furnace and heat treatment plant Expired - Lifetime EP0778354B1 (en)

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DE19545764 1995-12-07
DE19545764A DE19545764C2 (en) 1995-12-07 1995-12-07 Process for producing protective gas for a heat treatment furnace and heat treatment plant

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IT1291479B1 (en) * 1997-01-29 1999-01-11 Rivoira Spa PROCESS OF HEAT TREATMENT OF METALLIC PIECES WITH A FERROUS BASE IN AN ACTIVE ATMOSPHERE WITH A HIGH CARBON POTENTIAL.
DE10051203A1 (en) * 2000-10-16 2002-04-25 Linde Ag Production of a treatment gas containing carbon monoxide and hydrogen used for heat treating metallic material comprises heating a gas mixture containing oxygen and nitrogen
DE10300141A1 (en) 2003-01-07 2004-07-15 Blue Membranes Gmbh Method and device for oxygen enrichment of air with simultaneous depletion of carbon dioxide
DE10347312B3 (en) * 2003-10-08 2005-04-14 Air Liquide Deutschland Gmbh Process for the heat treatment of iron materials
DK1718171T4 (en) 2004-01-28 2020-01-06 Curation Foods Inc container System
US9034405B2 (en) 2004-01-28 2015-05-19 Apio, Inc. Combinations of atmosphere control members
DE102005041817A1 (en) * 2005-09-02 2007-03-08 Behr Gmbh & Co. Kg Plant for the production of soldered components
DE102006013428B4 (en) * 2006-03-23 2012-09-13 Behr Gmbh & Co. Kg Plant and method for producing soldered components in a protective gas atmosphere
EP2558803B1 (en) 2010-04-13 2017-12-13 Carrier Corporation Controlled atmosphere systems and methods
JP2019189942A (en) * 2018-04-24 2019-10-31 エア・ウォーター株式会社 Annealing method of metal

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BR8504616A (en) * 1985-09-20 1987-04-28 Aichelin Ind E Comercio De For PROCESS FOR THE ENRICHMENT OF THE ATMOSPHERE OF OVENS IN THERMO-CHEMICAL TREATMENTS FOR METAL PIECES
DE3630833A1 (en) * 1986-09-10 1988-03-17 Linde Ag METHOD AND DEVICE FOR HEAT TREATING METAL WORKPIECES
DE3942810A1 (en) * 1989-12-23 1991-06-27 Linde Ag METHOD FOR PROVIDING AND DISTRIBUTING TREATMENT GAS IN HEAT TREATMENTS
FR2668584B1 (en) 1990-10-26 1994-03-18 Lair Liquide PROCESS FOR DEVELOPING A HEAT TREATMENT ATMOSPHERE AND HEAT TREATMENT PLANT.
DE4212307C2 (en) * 1992-04-13 1994-07-28 Messer Griesheim Gmbh Process for the production of a protective or reaction gas for the heat treatment of metals
US5364476A (en) * 1993-11-08 1994-11-15 Surface Combustion, Inc. Industrial variable carbon potential gas generator

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ATE200307T1 (en) 2001-04-15
DE59606708D1 (en) 2001-05-10
DE19545764A1 (en) 1997-06-12
DE19545764C2 (en) 2000-02-17

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