EP4065889B1 - Combustion of the co in secondary metallurgical exhaust gas, with calorific value control and volume flow control - Google Patents

Combustion of the co in secondary metallurgical exhaust gas, with calorific value control and volume flow control Download PDF

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Publication number
EP4065889B1
EP4065889B1 EP20812007.1A EP20812007A EP4065889B1 EP 4065889 B1 EP4065889 B1 EP 4065889B1 EP 20812007 A EP20812007 A EP 20812007A EP 4065889 B1 EP4065889 B1 EP 4065889B1
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EP
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Prior art keywords
gas
waste gas
afterburning
exhaust gas
volume flow
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EP20812007.1A
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German (de)
French (fr)
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EP4065889A1 (en
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Volker Wiegmann
Frank Dorstewitz
Andreas Kemminger
Helmut Biehl
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SMS Group GmbH
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SMS Group GmbH
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G7/00—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals
    • F23G7/06—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals of waste gases or noxious gases, e.g. exhaust gases
    • F23G7/08—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals of waste gases or noxious gases, e.g. exhaust gases using flares, e.g. in stacks
    • F23G7/085—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals of waste gases or noxious gases, e.g. exhaust gases using flares, e.g. in stacks in stacks
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G7/00—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals
    • F23G7/06—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals of waste gases or noxious gases, e.g. exhaust gases
    • F23G7/08—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals of waste gases or noxious gases, e.g. exhaust gases using flares, e.g. in stacks
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G2204/00—Supplementary heating arrangements
    • F23G2204/10—Supplementary heating arrangements using auxiliary fuel
    • F23G2204/103—Supplementary heating arrangements using auxiliary fuel gaseous or liquid fuel
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G2207/00—Control
    • F23G2207/20—Waste supply
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G2207/00—Control
    • F23G2207/40—Supplementary heat supply
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G2209/00—Specific waste
    • F23G2209/14—Gaseous waste or fumes
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G2209/00—Specific waste
    • F23G2209/14—Gaseous waste or fumes
    • F23G2209/141—Explosive gases
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G2900/00—Special features of, or arrangements for incinerators
    • F23G2900/55—Controlling; Monitoring or measuring
    • F23G2900/55003—Sensing for exhaust gas properties, e.g. O2 content
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G2900/00—Special features of, or arrangements for incinerators
    • F23G2900/55—Controlling; Monitoring or measuring
    • F23G2900/55011—Detecting the properties of waste to be incinerated, e.g. heating value, density
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23K—FEEDING FUEL TO COMBUSTION APPARATUS
    • F23K2900/00—Special features of, or arrangements for fuel supplies
    • F23K2900/05004—Mixing two or more fluid fuels
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2221/00—Pretreatment or prehandling
    • F23N2221/10—Analysing fuel properties, e.g. density, calorific

Definitions

  • the invention relates to a method for the afterburning of exhaust gases containing carbon monoxide from metallurgical processes with discontinuous exhaust gas volumes, the composition and / or quantity of which changes during a period within which exhaust gas is produced.
  • Such metallurgical processes can be, for example, secondary metallurgical processes in which a molten metal is degassed or decarburized.
  • Flare gases In petrochemical and metallurgical processes it is generally known to burn exhaust gases with so-called flares. Flare gases often have different qualities. To ensure that the torch burns steadily, the gas must have a minimum combustible content. If this is not the case, natural gas may be added as fuel gas. Calorimeters are usually used to determine the calorific value of the flare gas. These include a measuring cell in which a measuring gas is burned. If the sample gas is successfully ignited, the amount of energy released during combustion or the calorific value of the gas is determined and, if necessary, natural gas is mixed into the flare gas.
  • carbon-containing material is fed to a melt pool of metal and slag in a direct melting vessel, with hot gas from furnaces being fed into a gas space is supplied above the melt bath for the purpose of afterburning the reaction gases of the melt bath.
  • the resulting exhaust gas is used with fuel gas and oxygen-containing combustion air to heat the ovens, whereby the temperature of the gas space in the ovens is regulated by supplying the exhaust gas with fuel gas and combustion air depending on the oxygen content in the exhaust gas of the ovens, if the exhaust gas has a certain calorific value falls below.
  • a method according to the preamble of claim 1 is, for example, from US 5,980,606 A known. Further state of the art is from the documents US 2019/242575 A1 and US 6,042,633 A known.
  • the invention is therefore based on the object of providing a method for the afterburning of carbon monoxide-containing exhaust gases from metallurgical processes with discontinuous exhaust gas volumes and exhaust gas compositions, which enables safe afterburning of the exhaust gas with a lower environmental impact.
  • One aspect of the invention relates to a method for the afterburning of carbon monoxide-containing exhaust gases from metallurgical processes with discontinuously occurring exhaust gas volumes, the composition of which changes during a period within which exhaust gas is produced, the method comprising conditioning the exhaust gas before the afterburning, such that At least one fuel gas and / or another additional gas is added in a controlled manner to the exhaust gas upstream of the afterburning, the regulation taking place depending on the composition of the exhaust gas and / or depending on the exhaust gas volume flow.
  • the afterburning of the exhaust gas preferably takes place with an open flame in the area of the mouth of an exhaust gas duct into the atmosphere.
  • the afterburning of the exhaust gas can take place in a combustion chamber provided for this purpose.
  • the invention can be summarized in that, according to the invention, both the calorific value of the exhaust gas and the exhaust gas volume flow are regulated, so that on the one hand the most complete combustion possible is ensured and, on the other hand, it is ensured that the exhaust gas volume flow is adjusted in such a way that a flow velocity of the exhaust gas in the relevant Cross section sets that is smaller than a flame propagation speed of the exhaust gas, so that re-ignition of the exhaust gas into an exhaust gas duct is excluded.
  • the exhaust gas composition and the exhaust gas volume flow are interrelated, especially if an inert gas is added as additional gas.
  • Nitrogen is expediently added to the exhaust gas as additional gas in order to increase the exhaust gas volume flow. This reduces the calorific value of the exhaust gas, which means that the amount of fuel gas supplied, for example in the form of natural gas, may have to be increased.
  • a calorific value of the exhaust gas is determined indirectly via the carbon monoxide content of the exhaust gas using at least one device for gas analysis becomes. For this purpose, results from a gas analysis that is required anyway can be used in secondary metallurgical processes.
  • control takes place depending on the carbon monoxide content of the exhaust gas, with the control goal of the greatest possible conversion of carbon monoxide to carbon dioxide, so that essentially stoichiometric afterburning is guaranteed.
  • control is carried out in such a way that the calorific value of the exhaust gas does not fall below ⁇ 2kWh/Nm 3 ( ⁇ 200 BTU/scf). It has surprisingly been found that with such a calorific value, an afterburning of carbon monoxide of over 97% is possible.
  • the control can be carried out in such a way that the exhaust gas volume flow does not fall below a given minimum volume flow.
  • the minimum volume flow of the exhaust gas is expediently determined as a function of the flow velocity of the exhaust gas in a given flow cross section so that the flow velocity is smaller than a flame propagation velocity of the exhaust gas during combustion.
  • Typical flame propagation speeds are on the order of approximately 0.2 to 0.5 m/s.
  • the afterburning is preferably carried out using at least one supporting gas torch arranged in or on a chimney.
  • fuel gas and/or additional gas or inert gas is expediently carried out via separate feed lines with volume flow controllable valves, which are controlled, for example, by means of a software controller.
  • a software controller can be implemented, for example, using a programmable logic controller.
  • the invention further relates to a method for exhaust gas aftertreatment during vacuum treatment of liquid steel in a secondary metallurgy
  • Process comprising the afterburning of the exhaust gas from the vacuum treatment of a metal melt by means of at least one torch in or on an exhaust gas duct of a vacuum pump, the method comprising conditioning of the exhaust gas before the afterburning, such that the exhaust gas upstream of the afterburning at least one fuel gas and / or a Additional gas is added in a controlled manner, the regulation taking place depending on the composition of the exhaust gas and depending on the exhaust gas volume flow.
  • the vacuum treatment of liquid steel is usually a batch process in which the exhaust gas aftertreatment according to the invention is particularly useful and expedient.
  • the exhaust gas aftertreatment according to the invention preferably takes place in secondary metallurgical processes such as VD, VD-OB, RH, RH-TOP, RH-OB, VacAOD VODC or VOD processes.
  • the afterburning is carried out periodically only during the decarburization phase of the molten metal. If the CO proportion of the exhaust gas falls below a predetermined minimum value, which is significantly below the value that would justify an increase in the calorific value with fuel gas, afterburning preferably does not take place. This is due to the fact that during the degassing of a melt, which in itself already represents a discontinuous process, exhaust gas containing carbon monoxide is only produced for a certain period of time.
  • the invention further relates to an afterburning device for afterburning exhaust gas during a vacuum treatment of liquid steel in a secondary metallurgical process, comprising at least one torch on an exhaust of an exhaust duct of a vacuum pump of a secondary metallurgical system, means for supplying fuel gas to the torch, and means for feeding an inert gas in the exhaust duct of the vacuum pump upstream of the flare, means for determining the exhaust gas volume flow and/or for measuring the exhaust gas velocity within the exhaust duct, means for analyzing the exhaust gas composition, means for metering the fuel gas and the inert gas and means for Control of the dosage of the fuel gas and/or the inert gas depending on the exhaust gas composition.
  • Volume flow controllable valves can be provided as means for metering the fuel gas and the inert gas, which are each arranged in feed lines for fuel gas and for natural gas, which are connected to the exhaust gas duct.
  • At least one control device is provided as a means for metering fuel gas and/or inert gas, the input variables of which are the exhaust gas composition, the exhaust gas volume flow, the amount of fuel gas supplied and the amount of inert gas supplied.
  • control device comprises at least one programmable logic controller.
  • control device can control a support burner of the torch in such a way that the torch is only operated when exhaust gas containing CO is produced.
  • afterburning device 1 which comprises a torch 2 with a support burner 3, which is connected to the exhaust 4 of an exhaust duct 5 of a vacuum pump, not shown, of a metallurgical plant.
  • the metallurgical system can, for example, include a casting ladle and devices for degassing the molten metal contained in the casting ladle.
  • the degassing of the metal melt can be carried out, for example, using a partial degassing process, such as the Ruhrstahl-Heraeus process, in which a vacuum vessel is immersed in the melt for degassing, with vacuum pumps designed as steam jet pumps generating a negative pressure in the vacuum vessel for degassing the melt becomes.
  • Multi-stage vacuum pumps which are connected to an exhaust gas duct 5, are usually used for this purpose.
  • vacuum pump is predominantly used in the singular in the present application.
  • this also includes an arrangement of vacuum pumps or a pump with a large number of pump stages.
  • the support burner 3 of the torch 2 can be put into and out of operation or ignited and extinguished via a control device 6.
  • the exhaust gas duct 5 is connected upstream of the flare 2 to an extinguishing line 7, a feed line 8 for fuel gas and a feed line 9 for nitrogen.
  • Nitrogen can be supplied as an extinguishing agent from an extinguishing agent tank 10 to the exhaust gas duct 5 via the extinguishing line 7.
  • a flow measuring device 11 for determining the exhaust gas volume flow is arranged in the exhaust gas duct 5 upstream of the mouth of the feed line 8 for fuel gas into the exhaust gas duct 5 and downstream of the mouth of the feed line 9 for nitrogen. Upstream of the mouth of the feed lines 9 in the A gas analysis device 12 is also provided in the exhaust gas duct, with which the exhaust gas composition is preferably continuously determined.
  • the supply of fuel gas and nitrogen as inert gas into the exhaust gas duct 5 is controlled according to the invention by means of a control device 21, the control scheme of which is shown below based on the illustration in Figure 2 is explained.
  • the control device 21, which is in Figure 3 is shown in simplified form, controls valves 13, 14 provided in the feed lines 8, 9, each of which meter more or less fuel gas or inert gas or nitrogen into the exhaust gas duct 5.
  • the control scheme shown includes two interdependent control circuits 15, 16, with a first control circuit 15 as a reference variable that regulates the calorific value of the exhaust gas determined based on the gas composition, and the in Figure 2
  • the second control circuit 16 shown below regulates the exhaust gas volume flow as a reference variable.
  • the calorific value of the exhaust gas is determined based on the measured values from the gas analysis device 12 via the CO proportion.
  • the gas analysis device 12 supplies, among other things, the oxygen content and the carbon monoxide content of the exhaust gas.
  • the CO content or carbon monoxide content of the exhaust gas determines its calorific value.
  • the calorific value of the exhaust gas continues to depend on the nitrogen content of the exhaust gas.
  • the exhaust gas volume flow must not fall below a certain minimum value in order to ensure sufficient gas velocity and thus prevent possible re-ignition in the exhaust gas duct.
  • an appropriate amount of inert gas or nitrogen is supplied to the exhaust duct, which in turn has an impact on the calorific value of the exhaust gas.
  • the calorific value of the exhaust gas should not fall below a specified minimum value, for example in the order of ⁇ 2kWh/Nm 3 (200 BTU/scf). This value corresponds to a stoichiometrically complete combustion of the CO
  • the first control circuit 15 includes a first control device 17 for the fuel gas supply, which acts on the volume flow controllable valve 13 in the feed line 8 for fuel gas.
  • the reference variable for the calorific value is determined using a calorific value calculator 18 specified, which uses the actual calorific value, the exhaust gas volume flow, the exhaust gas composition and the actual nitrogen volume flow from the second control circuit 16 as input variables.
  • the second control circuit 16 includes a second control device 19 for nitrogen addition, which acts on the valve 14 that can control the volume flow.
  • the second control circuit 16 further includes a volume flow computer 20, which uses the actually supplied nitrogen volume flow and the fuel gas volume flow as input variables.
  • the volume flow calculator 20 specifies the reference variable for the minimum exhaust gas volume flow and, in parallel, supplies this value to the calorific value calculator 18.
  • Figure 4 illustrates the exhaust gas composition and the amount of exhaust gas during a typical degassing process of a secondary metallurgical treatment of a steel melt, with the pressure prevailing during decarburization, the amount of exhaust gas, the amount of inert gas, the amount of natural gas and the CO proportion of the exhaust gas being plotted over time.
  • the pressure drop (vacuum/thin solid line) at the beginning of the degassing process and the pressure increase at the end of the degassing process are easily recognizable. This is accompanied by an initially high and then decreasing CO formation.
  • the dotted line illustrates the calorific value of the exhaust gas supported by the addition of natural gas (CH 4 ), whereas the bold solid curve illustrates the addition of nitrogen.

Description

Die Erfindung betrifft ein Verfahren zur Nachverbrennung von kohlenmonoxidhaltigen Abgasen aus metallurgischen Prozessen mit diskontinuierlich anfallenden Abgasvolumina, deren Zusammensetzung und/oder Menge sich während einer Periode, innerhalb welcher Abgas anfällt, verändert.The invention relates to a method for the afterburning of exhaust gases containing carbon monoxide from metallurgical processes with discontinuous exhaust gas volumes, the composition and / or quantity of which changes during a period within which exhaust gas is produced.

Solche metallurgischen Prozesse können beispielsweise sekundärmetallurgische Prozesse sein, bei denen eine Metallschmelze entgast oder entkohlt wird.Such metallurgical processes can be, for example, secondary metallurgical processes in which a molten metal is degassed or decarburized.

Bei vielen metallurgischen Prozessen fallen Abgase mit niedrigem Heizwert und chemischen Bestandteilen wie z.B. Kohlenmonoxid an, die nicht ohne Nachverbrennung in die Atmosphäre abgegeben werden sollten.Many metallurgical processes produce exhaust gases with a low calorific value and chemical components such as carbon monoxide, which should not be released into the atmosphere without afterburning.

Bei petrochemischen und metallurgischen Prozessen ist es grundsätzlich bekannt, Abgase mit sogenannten Fackeln zu verbrennen. Fackelgase weisen häufig unterschiedliche Qualitäten auf. Um sicherzustellen, dass die Fackel stetig brennt, muss das Gas einen Mindestgehalt an brennbaren Anteilen aufweisen. Ist dies nicht der Fall, wird gegebenenfalls Erdgas als Brenngas zugemischt. Zur Bestimmung des Heizwerts des Fackelgases werden üblicherweise Kalorimeter verwendet. Diese umfassen eine Messzelle, in der ein Messgas verbrannt wird. Bei einer erfolgreichen Zündung des Messgases wird die bei der Verbrennung abgegebene Energiemenge bzw. der Heizwert des Gases bestimmt und gegebenenfalls wird dem Fackelgas Erdgas zugemischt.In petrochemical and metallurgical processes it is generally known to burn exhaust gases with so-called flares. Flare gases often have different qualities. To ensure that the torch burns steadily, the gas must have a minimum combustible content. If this is not the case, natural gas may be added as fuel gas. Calorimeters are usually used to determine the calorific value of the flare gas. These include a measuring cell in which a measuring gas is burned. If the sample gas is successfully ignited, the amount of energy released during combustion or the calorific value of the gas is determined and, if necessary, natural gas is mixed into the flare gas.

Bei einem in der WO 2016/123666 beschriebenen metallurgischen Schmelzverfahren wird kohlenstoffhaltiges Material einem Schmelzbad von Metall und Schlacke in einem Direktschmelzgefäß zugeführt, wobei heißes Gas aus Öfen einem Gasraum oberhalb des Schmelzebads zwecks Nachverbrennung der Reaktionsgase des Schmelzebads zugeführt wird. Das dabei entstehende Abgas wird mit Brenngas und sauerstoffhaltiger Verbrennungsluft zur Beheizung der Öfen verwendet, wobei die Temperatur des Gasraums in den Öfen durch die Zufuhr des Abgases mit Brenngas und Verbrennungsluft in Abhängigkeit des Sauerstoffgehalts im Abgas der Öfen geregelt wird, wenn das Abgas einen bestimmten Heizwert unterschreitet.At one in the WO 2016/123666 In the metallurgical melting process described, carbon-containing material is fed to a melt pool of metal and slag in a direct melting vessel, with hot gas from furnaces being fed into a gas space is supplied above the melt bath for the purpose of afterburning the reaction gases of the melt bath. The resulting exhaust gas is used with fuel gas and oxygen-containing combustion air to heat the ovens, whereby the temperature of the gas space in the ovens is regulated by supplying the exhaust gas with fuel gas and combustion air depending on the oxygen content in the exhaust gas of the ovens, if the exhaust gas has a certain calorific value falls below.

Insbesondere bei sekundärmetallurgischen Prozessen, bei denen die Entgasung einer Metallschmelze vorgesehen ist, fällt infolge der Verringerung des Kohlenstoffanteils der Schmelze ein kohlenmonoxidhaltiges Abgas an, dem zur Nachverbrennung Heizgas in konstanten Mengen zugesetzt wird, um eine sichere Nachverbrennung zu gewährleisten. Diese Vorgehensweise wird allerdings nicht dem Umstand gerecht, dass sich typischerweise bei der Entgasung von Metallschmelzen die Abgaszusammensetzung und der Abgasvolumenstrom im Laufe des Verfahrens ändern. Daher ist es für eine sichere Nachverbrennung des Abgases erforderlich, dem Abgas entsprechende Mengen an Heizgas, typischerweise Erdgas, zuzugeben. Abgesehen davon, dass der erhöhte Brenngasverbrauch erhöhte Kosten verursacht, geht eine solche Vorgehensweise auch mit einem erhöhten Ausstoß an Kohlendioxid einher, was aus Umweltschutzgründen nicht wünschenswert ist.Particularly in secondary metallurgical processes in which the degassing of a metal melt is provided, as a result of the reduction in the carbon content of the melt, an exhaust gas containing carbon monoxide is produced, to which heating gas is added in constant quantities for post-combustion in order to ensure safe post-combustion. However, this procedure does not take into account the fact that when degassing metal melts, the exhaust gas composition and the exhaust gas volume flow typically change over the course of the process. Therefore, for safe afterburning of the exhaust gas, it is necessary to add appropriate amounts of heating gas, typically natural gas, to the exhaust gas. Apart from the fact that the increased fuel gas consumption causes increased costs, such an approach is also accompanied by increased emissions of carbon dioxide, which is undesirable for environmental reasons.

Ein Verfahren gemäß Oberbegriff von Anspruch 1 ist beispielsweise aus der US 5 980 606 A bekannt. Weiterer Stand der Technik ist aus den Dokumenten US 2019/242575 A1 und US 6 042 633 A bekannt.A method according to the preamble of claim 1 is, for example, from US 5,980,606 A known. Further state of the art is from the documents US 2019/242575 A1 and US 6,042,633 A known.

Der Erfindung liegt daher die Aufgabe zugrunde, ein Verfahren zur Nachverbrennung von kohlenmonoxidhaltigen Abgasen aus metallurgischen Prozessen mit diskontinuierlich anfallenden Abgasvolumina und Abgaszusammensetzungen bereitzustellen, dass eine sichere Nachverbrennung des Abgases bei einer geringeren Umweltbelastung ermöglicht.The invention is therefore based on the object of providing a method for the afterburning of carbon monoxide-containing exhaust gases from metallurgical processes with discontinuous exhaust gas volumes and exhaust gas compositions, which enables safe afterburning of the exhaust gas with a lower environmental impact.

Die Aufgabe wird gelöst mit den Merkmalen der Ansprüche 1 und 9. Vorteilhafte Ausgestaltungen der Erfindung ergeben sich aus den Unteransprüchen.The task is solved with the features of claims 1 and 9. Advantageous embodiments of the invention result from the subclaims.

Ein Gesichtspunkt der Erfindung betrifft ein Verfahren zur Nachverbrennung von kohlenmonoxidhaltigen Abgasen aus metallurgischen Prozessen mit diskontinuierlich anfallenden Abgasvolumina, deren Zusammensetzung sich während einer Periode, innerhalb welcher Abgas anfällt, verändert, wobei das Verfahren eine Konditionierung des Abgases vor der Nachverbrennung umfasst, derart, dass dem Abgas stromaufwärts der Nachverbrennung wenigstens ein Brenngas und/oder ein weiteres Zusatzgas geregelt zugegeben wird, wobei die Regelung in Abhängigkeit der Zusammensetzung des Abgases und/oder in Abhängigkeit des Abgasvolumenstroms erfolgt.One aspect of the invention relates to a method for the afterburning of carbon monoxide-containing exhaust gases from metallurgical processes with discontinuously occurring exhaust gas volumes, the composition of which changes during a period within which exhaust gas is produced, the method comprising conditioning the exhaust gas before the afterburning, such that At least one fuel gas and / or another additional gas is added in a controlled manner to the exhaust gas upstream of the afterburning, the regulation taking place depending on the composition of the exhaust gas and / or depending on the exhaust gas volume flow.

Die Nachverbrennung des Abgases erfolgt bei dem Verfahren gemäß der Erfindung vorzugsweise mit einer offenen Flamme im Bereich der Mündung eines Abgaskanals in die Atmosphäre. Alternativ kann die Nachverbrennung des Abgases in einer hierfür vorgesehenen Brennkammer erfolgen.In the method according to the invention, the afterburning of the exhaust gas preferably takes place with an open flame in the area of the mouth of an exhaust gas duct into the atmosphere. Alternatively, the afterburning of the exhaust gas can take place in a combustion chamber provided for this purpose.

Die Erfindung kann dahingehend zusammengefasst werden, dass erfindungsgemäß sowohl der Heizwert des Abgases als auch der Abgasvolumenstrom geregelt werden, sodass einerseits eine möglichst vollständige Verbrennung gewährleistet ist und andererseits sichergestellt ist, dass der Abgasvolumenstrom so eingestellt ist, dass sich eine Strömungsgeschwindigkeit des Abgases in dem betreffenden Querschnitt einstellt, die kleiner ist als eine Flammenausbreitungsgeschwindigkeit des Abgases, sodass eine Rückzündung des Abgases in einen Abgaskanal ausgeschlossen ist.The invention can be summarized in that, according to the invention, both the calorific value of the exhaust gas and the exhaust gas volume flow are regulated, so that on the one hand the most complete combustion possible is ensured and, on the other hand, it is ensured that the exhaust gas volume flow is adjusted in such a way that a flow velocity of the exhaust gas in the relevant Cross section sets that is smaller than a flame propagation speed of the exhaust gas, so that re-ignition of the exhaust gas into an exhaust gas duct is excluded.

Die Abgaszusammensetzung und der Abgasvolumenstrom bedingen einander, insbesondere wenn als Zusatzgas ein Inertgas zugegeben wird. Zweckmäßigerweise wird dem Abgas als Zusatzgas Stickstoff zugeführt, um den Abgasvolumenstrom zu erhöhen. Dadurch verringert sich der Heizwert des Abgases, wodurch gegebenenfalls die Menge an zugeführtem Brenngas, beispielsweise in Form von Erdgas, erhöht werden muss.The exhaust gas composition and the exhaust gas volume flow are interrelated, especially if an inert gas is added as additional gas. Nitrogen is expediently added to the exhaust gas as additional gas in order to increase the exhaust gas volume flow. This reduces the calorific value of the exhaust gas, which means that the amount of fuel gas supplied, for example in the form of natural gas, may have to be increased.

Bei einer bevorzugten Variante des Verfahrens gemäß der Erfindung ist vorgesehen, dass ein Heizwert des Abgases mittelbar über den Kohlenmonoxid Gehalt des Abgases unter Verwendung wenigstens einer Einrichtung zur Gasanalyse bestimmt wird. Hierzu können bei sekundärmetallurgischen Prozessen Ergebnisse aus einer ohnehin erforderlichen Gasanalyse herangezogen werden.In a preferred variant of the method according to the invention, it is provided that a calorific value of the exhaust gas is determined indirectly via the carbon monoxide content of the exhaust gas using at least one device for gas analysis becomes. For this purpose, results from a gas analysis that is required anyway can be used in secondary metallurgical processes.

Entsprechend kann vorgesehen sein, dass die Regelung in Abhängigkeit des Kohlenmonoxid Gehalts des Abgases erfolgt, mit dem Regelungsziel eines größtmöglichen Umsatzes von Kohlenmonoxid zu Kohlendioxid, sodass im Wesentlichen eine stöchiometrische Nachverbrennung gewährleistet ist.Accordingly, it can be provided that the control takes place depending on the carbon monoxide content of the exhaust gas, with the control goal of the greatest possible conversion of carbon monoxide to carbon dioxide, so that essentially stoichiometric afterburning is guaranteed.

Bei einer besonders bevorzugten Variante des Verfahrens ist vorgesehen, dass die Regelung so geführt wird, dass ein Heizwert des Abgases von ≥ 2kWh/Nm3 ( ≥ 200 BTU/scf) nicht unterschritten wird. Es hat sich überraschend herausgestellt, dass bei einem solchen Heizwert eine Nachverbrennung des Kohlenmonoxids von über 97% möglich ist.In a particularly preferred variant of the method, it is provided that the control is carried out in such a way that the calorific value of the exhaust gas does not fall below ≥ 2kWh/Nm 3 (≥ 200 BTU/scf). It has surprisingly been found that with such a calorific value, an afterburning of carbon monoxide of over 97% is possible.

Weiterhin kann erfindungsgemäß die Regelung so geführt werden, dass der Abgasvolumenstrom einen gegebenen Mindestvolumenstrom nicht unterschreitet. Zweckmäßigerweise wird der Mindestvolumenstrom des Abgases in Abhängigkeit der Strömungsgeschwindigkeit des Abgases in einem gegebenen Strömungsquerschnitt so festgelegt, dass die Strömungsgeschwindigkeit kleiner ist als eine Flammenausbreitungsgeschwindigkeit des Abgases bei der Verbrennung. Typische Flammenausbreitungsgeschwindigkeiten besitzen eine Größenordnung von etwa 0,2 bis 0,5 m/s.Furthermore, according to the invention, the control can be carried out in such a way that the exhaust gas volume flow does not fall below a given minimum volume flow. The minimum volume flow of the exhaust gas is expediently determined as a function of the flow velocity of the exhaust gas in a given flow cross section so that the flow velocity is smaller than a flame propagation velocity of the exhaust gas during combustion. Typical flame propagation speeds are on the order of approximately 0.2 to 0.5 m/s.

Vorzugsweise wird die Nachverbrennung mittels wenigstens einer in oder an einem Kamin angeordneten Stützgas-Fackel durchgeführt.The afterburning is preferably carried out using at least one supporting gas torch arranged in or on a chimney.

Die Zugabe von Brenngas und/oder Zusatzgas bzw. Inertgas erfolgt zweckmäßigerweise über getrennte Speiseleitungen mit Volumenstrom regelbaren Ventilen, welche beispielsweise mittels eines Software-Reglers angesteuert werden. Ein solcher Regler kann beispielsweise mittels einer speicherprogrammierbaren Steuerung realisiert werden.The addition of fuel gas and/or additional gas or inert gas is expediently carried out via separate feed lines with volume flow controllable valves, which are controlled, for example, by means of a software controller. Such a controller can be implemented, for example, using a programmable logic controller.

Die Erfindung betrifft weiterhin ein Verfahren zur Abgasnachbehandlung während einer Vakuumbehandlung von flüssigem Stahl bei einem sekundärmetallurgischenThe invention further relates to a method for exhaust gas aftertreatment during vacuum treatment of liquid steel in a secondary metallurgy

Prozess umfassend die Nachverbrennung des Abgases aus der Vakuumbehandlung einer Metallschmelze mittels wenigstens einer Fackel in oder an einem Abgaskanal einer Vakuumpumpe, wobei das Verfahren eine Konditionierung des Abgases vor der Nachverbrennung umfasst, derart, dass dem Abgas stromaufwärts der Nachverbrennung wenigstens ein Brenngas und/oder ein Zusatzgas geregelt zugegeben wird, wobei die Regelung in Abhängigkeit der Zusammensetzung des Abgases und in Abhängigkeit des Abgasvolumenstroms erfolgt.Process comprising the afterburning of the exhaust gas from the vacuum treatment of a metal melt by means of at least one torch in or on an exhaust gas duct of a vacuum pump, the method comprising conditioning of the exhaust gas before the afterburning, such that the exhaust gas upstream of the afterburning at least one fuel gas and / or a Additional gas is added in a controlled manner, the regulation taking place depending on the composition of the exhaust gas and depending on the exhaust gas volume flow.

Die Vakuumbehandlung von flüssigem Stahl ist üblicherweise ein Batch Verfahren, bei dem die erfindungsgemäße Abgasnachbehandlung besonders sinnvoll und zweckmäßig ist. Die Abgasnachbehandlung gemäß der Erfindung findet vorzugsweise bei sekundärmetallurgischen Prozessen wie zum Beispiel VD, VD-OB, RH, RH-TOP, RH-OB, VacAOD VODC oder VOD Verfahren statt.The vacuum treatment of liquid steel is usually a batch process in which the exhaust gas aftertreatment according to the invention is particularly useful and expedient. The exhaust gas aftertreatment according to the invention preferably takes place in secondary metallurgical processes such as VD, VD-OB, RH, RH-TOP, RH-OB, VacAOD VODC or VOD processes.

Bei einer besonders bevorzugten Variante dieses Verfahrens ist vorgesehen, dass die Nachverbrennung periodisch nur während der Entkohlungsphase der Metallschmelze durchgeführt wird. Unterschreitet der CO Anteil des Abgases einen vorgegebenen Mindestwert, der deutlich unter dem Wert liegt, der eine Erhöhung des Heizwerts mit Brenngas rechtfertigen würde, erfolgt vorzugsweise keine Nachverbrennung. Dies ist dem Umstand geschuldet, dass während der Entgasung einer Schmelze, die an und für sich bereits einen diskontinuierlichen Vorgang darstellt, nur während einer bestimmten Zeitspanne kohlenmonoxidhaltiges Abgas anfällt.In a particularly preferred variant of this method, it is provided that the afterburning is carried out periodically only during the decarburization phase of the molten metal. If the CO proportion of the exhaust gas falls below a predetermined minimum value, which is significantly below the value that would justify an increase in the calorific value with fuel gas, afterburning preferably does not take place. This is due to the fact that during the degassing of a melt, which in itself already represents a discontinuous process, exhaust gas containing carbon monoxide is only produced for a certain period of time.

Eine Nachverbrennung ist nur während dieser Zeitspanne sinnvoll und notwendig.Afterburning only makes sense and is necessary during this period.

Die Erfindung betrifft weiterhin eine Nachverbrennungseinrichtung zur Nachverbrennung von Abgas während einer Vakuumbehandlung von flüssigem Stahl bei einem sekundärmetallurgischen Prozess, umfassend wenigstens eine Fackel an einem Auspuff eines Abgaskanals einer Vakuumpumpe einer sekundärmetallurgischen Anlage, Mittel zur Zuführung von Brenngas an die Fackel, Mittel zur Einspeisung eines Inertgases in den Abgaskanal der Vakuumpumpe stromaufwärts der Fackel, Mittel zur Ermittlung des Abgasvolumenstroms und/oder zur Messung der Abgasgeschwindigkeit innerhalb des Abgaskanals, Mittel zur Analyse der Abgaszusammensetzung, Mittel zur Dosierung des Brenngases und des Inertgases sowie Mittel zur Regelung der Dosierung des Brenngases und/oder des Inertgases in Abhängigkeit von der Abgaszusammensetzung.The invention further relates to an afterburning device for afterburning exhaust gas during a vacuum treatment of liquid steel in a secondary metallurgical process, comprising at least one torch on an exhaust of an exhaust duct of a vacuum pump of a secondary metallurgical system, means for supplying fuel gas to the torch, and means for feeding an inert gas in the exhaust duct of the vacuum pump upstream of the flare, means for determining the exhaust gas volume flow and/or for measuring the exhaust gas velocity within the exhaust duct, means for analyzing the exhaust gas composition, means for metering the fuel gas and the inert gas and means for Control of the dosage of the fuel gas and/or the inert gas depending on the exhaust gas composition.

Als Mittel zur Dosierung des Brenngases und des Inertgases können Volumenstrom regelbare Ventile vorgesehen sein, die jeweils in Speiseleitungen für Brenngas und für Erdgas angeordnet sind, welche an den Abgaskanal angeschlossen sind.Volume flow controllable valves can be provided as means for metering the fuel gas and the inert gas, which are each arranged in feed lines for fuel gas and for natural gas, which are connected to the exhaust gas duct.

Vorzugsweise ist als Mittel zur Dosierung von Brenngas und/oder Inertgas wenigstens eine Regeleinrichtung vorgesehen, deren Eingangsgrößen die Abgaszusammensetzung, der Abgasvolumenstrom, die Menge an zugeführtem Brenngas und die Menge an zugeführtem Inertgas sind.Preferably, at least one control device is provided as a means for metering fuel gas and/or inert gas, the input variables of which are the exhaust gas composition, the exhaust gas volume flow, the amount of fuel gas supplied and the amount of inert gas supplied.

Bei einer bevorzugten Variante der Nachverbrennungseinrichtung ist vorgesehen, dass die Regeleinrichtung wenigstens eine speicherprogrammierbare Steuerung umfasst.In a preferred variant of the afterburning device it is provided that the control device comprises at least one programmable logic controller.

Weiterhin kann die Regeleinrichtung einen Stützbrenner der Fackel steuern, derart, dass ein Betrieb der Fackel nur dann vorgesehen ist, wenn CO haltiges Abgas anfällt.Furthermore, the control device can control a support burner of the torch in such a way that the torch is only operated when exhaust gas containing CO is produced.

Die Erfindung wird nachstehend unter Bezugnahme auf die beigefügten Zeichnungen erläutert.The invention is explained below with reference to the accompanying drawings.

Es zeigen:

Figur 1
eine schematische Darstellung der Nachverbrennungseinrichtung gemäß der Erfindung an einer sekundärmetallurgischen Einrichtung,
Figur 2
ein Regelschema des Verfahrens gemäß der Erfindung,
Figur 3
eine schematische Darstellung des Reglers, welcher bei dem Regelverfahren gemäß der Erfindung Anwendung findet und
Figur 4
eine Darstellung die die Abgaszusammensetzung und die Abgasmenge während eines Entgasungsvorgangs zeigt, wobei der Regeleingriff vor der Nachverbrennung ebenfalls dargestellt ist.
Show it:
Figure 1
a schematic representation of the afterburning device according to the invention on a secondary metallurgical device,
Figure 2
a control scheme of the method according to the invention,
Figure 3
a schematic representation of the controller which is used in the control method according to the invention and
Figure 4
a representation showing the exhaust gas composition and the amount of exhaust gas during a degassing process, with the control intervention before afterburning also being shown.

Es wird zunächst Bezug genommen auf die in Figur 1 dargestellte Nachverbrennungseinrichtung 1, die eine Fackel 2 mit einem Stützbrenner 3 umfasst, welche an den Auspuff 4 eines Abgaskanals 5 einer nicht dargestellten Vakuumpumpe einer metallurgischen Anlage angeschlossen ist. Die metallurgische Anlage kann beispielsweise eine Gießpfanne und Einrichtungen zur Entgasung der in der Gießpfanne enthaltenen Metallschmelze umfassen. Die Entgasung der Metallschmelze kann beispielsweise nach einem Teilmengen-Entgasungs-Verfahren, wie dem Ruhrstahl-Heraeus Verfahren erfolgen, bei dem ein Vakuumgefäß zur Entgasung in die Schmelze eingetaucht wird, wobei in dem Vakuumgefäß über als Dampfstrahlpumpen ausgebildete Vakuumpumpen ein Unterdruck zur Entgasung der Schmelze erzeugt wird. Üblicherweise werden hierzu mehrstufige Vakuumpumpen verwendet, welche an einen Abgaskanal 5 angeschlossen sind. Aus Vereinfachungsgründen wird in der vorliegenden Anmeldung überwiegend der Begriff Vakuumpumpe in der Einzahl verwendet. Im Sinne der Erfindung ist hierunter allerdings auch eine Anordnung von Vakuumpumpen oder eine Pumpe mit einer Vielzahl von Pumpenstufen zu verstehen.First of all, reference is made to the in Figure 1 shown afterburning device 1, which comprises a torch 2 with a support burner 3, which is connected to the exhaust 4 of an exhaust duct 5 of a vacuum pump, not shown, of a metallurgical plant. The metallurgical system can, for example, include a casting ladle and devices for degassing the molten metal contained in the casting ladle. The degassing of the metal melt can be carried out, for example, using a partial degassing process, such as the Ruhrstahl-Heraeus process, in which a vacuum vessel is immersed in the melt for degassing, with vacuum pumps designed as steam jet pumps generating a negative pressure in the vacuum vessel for degassing the melt becomes. Multi-stage vacuum pumps, which are connected to an exhaust gas duct 5, are usually used for this purpose. For reasons of simplification, the term vacuum pump is predominantly used in the singular in the present application. For the purposes of the invention, however, this also includes an arrangement of vacuum pumps or a pump with a large number of pump stages.

Der Stützbrenner 3 der Fackel 2 kann über eine Steuereinrichtung 6 in und außer Betrieb genommen werden bzw. gezündet und gelöscht werden.The support burner 3 of the torch 2 can be put into and out of operation or ignited and extinguished via a control device 6.

Der Abgaskanal 5 ist stromaufwärts der Fackel 2 an eine Löschleitung 7, eine Speiseleitung 8 für Brenngas und eine Speiseleitung 9 für Stickstoff angeschlossen. Über die Löschleitung 7 ist Stickstoff als Löschmittel aus einem Löschmitteltank 10 dem Abgaskanal 5 zuführbar.The exhaust gas duct 5 is connected upstream of the flare 2 to an extinguishing line 7, a feed line 8 for fuel gas and a feed line 9 for nitrogen. Nitrogen can be supplied as an extinguishing agent from an extinguishing agent tank 10 to the exhaust gas duct 5 via the extinguishing line 7.

In dem Abgaskanal 5 ist stromaufwärts der Mündung der Speiseleitung 8 für Brenngas in den Abgaskanal 5 und stromabwärts der Mündung der Speiseleitung 9 für Stickstoff eine Durchfluss-Messeinrichtung 11 zur Bestimmung des Abgasvolumenstroms angeordnet. Stromaufwärts der Mündung der Speiseleitungen 9 in den Abgaskanal ist weiterhin eine Gasanalyse-Einrichtung 12 vorgesehen, mit welcher vorzugsweise fortlaufend die Abgaszusammensetzung ermittelt wird. In Abhängigkeit der Abgaszusammensetzung und des Durchflusses durch den Abgaskanal 5 erfolgt erfindungsgemäß eine Steuerung der Zufuhr von Brenngas und Stickstoff als Inertgas in den Abgaskanal 5 mittels einer Regeleinrichtung 21 deren Regelschema nachstehend anhand der Darstellung in Figur 2 erläutert wird. Die Regeleinrichtung 21, die in Figur 3 vereinfacht dargestellt ist, steuert in den Speiseleitungen 8, 9 vorgesehene Ventile 13, 14 an, die jeweils mehr oder weniger an Brenngas oder Inertgas bzw. Stickstoff in den Abgaskanal 5 dosieren.A flow measuring device 11 for determining the exhaust gas volume flow is arranged in the exhaust gas duct 5 upstream of the mouth of the feed line 8 for fuel gas into the exhaust gas duct 5 and downstream of the mouth of the feed line 9 for nitrogen. Upstream of the mouth of the feed lines 9 in the A gas analysis device 12 is also provided in the exhaust gas duct, with which the exhaust gas composition is preferably continuously determined. Depending on the exhaust gas composition and the flow through the exhaust gas duct 5, the supply of fuel gas and nitrogen as inert gas into the exhaust gas duct 5 is controlled according to the invention by means of a control device 21, the control scheme of which is shown below based on the illustration in Figure 2 is explained. The control device 21, which is in Figure 3 is shown in simplified form, controls valves 13, 14 provided in the feed lines 8, 9, each of which meter more or less fuel gas or inert gas or nitrogen into the exhaust gas duct 5.

Das in Figur 2 dargestellte Regelschema umfasst zwei voneinander abhängige Regelkreise 15,16, wobei ein erster Regelkreis 15 als Führungsgröße den aufgrund der Gaszusammensetzung ermittelten Heizwert des Abgases regelt, und der in Figur 2 darunter dargestellte zweite Regelkreis 16 als Führungsgröße den Abgasvolumenstrom regelt. Der Heizwert des Abgases wird anhand der Messwerte aus der Gasanalyse-Einrichtung 12 über den CO Anteil ermittelt. Die Gasanalyse-Einrichtung 12 liefert unter anderem den Sauerstoffanteil und den Kohlenmonoxid Anteil des Abgases. Der CO Anteil bzw. Kohlenmonoxid Anteil des Abgases bestimmt dessen Heizwert.This in Figure 2 The control scheme shown includes two interdependent control circuits 15, 16, with a first control circuit 15 as a reference variable that regulates the calorific value of the exhaust gas determined based on the gas composition, and the in Figure 2 The second control circuit 16 shown below regulates the exhaust gas volume flow as a reference variable. The calorific value of the exhaust gas is determined based on the measured values from the gas analysis device 12 via the CO proportion. The gas analysis device 12 supplies, among other things, the oxygen content and the carbon monoxide content of the exhaust gas. The CO content or carbon monoxide content of the exhaust gas determines its calorific value.

Der Heizwert des Abgases ist weiterhin abhängig vom Stickstoffgehalt des Abgases. Der Abgasvolumenstrom darf einen bestimmten Mindestwert nicht unterschreiten, um eine hinreichende Gasgeschwindigkeit sicherzustellen und damit eine mögliche Rückzündung in dem Abgaskanal zu verhindern. Um dies zu gewährleisten, wird dem Abgaskanal eine entsprechende Menge an Inertgas bzw. Stickstoff zugeführt, was wiederum eine Rückwirkung auf den Heizwert des Abgases hat. Der Heizwert des Abgases soll einen vorgegebenen Mindestwert, beispielsweise in der Größenordnung von ≥ 2kWh/ Nm3 (200 BTU/scf) nicht unterschreiten. Dieser Wert entspricht einer stöchiometrisch vollständigen Verbrennung des COThe calorific value of the exhaust gas continues to depend on the nitrogen content of the exhaust gas. The exhaust gas volume flow must not fall below a certain minimum value in order to ensure sufficient gas velocity and thus prevent possible re-ignition in the exhaust gas duct. To ensure this, an appropriate amount of inert gas or nitrogen is supplied to the exhaust duct, which in turn has an impact on the calorific value of the exhaust gas. The calorific value of the exhaust gas should not fall below a specified minimum value, for example in the order of ≥ 2kWh/Nm 3 (200 BTU/scf). This value corresponds to a stoichiometrically complete combustion of the CO

Der erste Regelkreis 15 umfasst eine erste Steuereinrichtung 17 für die Brenngaszufuhr, die das Volumenstrom regelbare Ventil 13 in der Speiseleitung 8 für Brenngas einwirkt. Die Führungsgröße für den Heizwert wird über einen Heizwertrechner 18 vorgegeben, der als Eingangsgrößen den tatsächlichen Heizwert, den Abgasvolumenstrom, die Abgaszusammensetzung und den tatsächlichen Stickstoffvolumenstrom aus dem zweiten Regelkreis 16 verwendet.The first control circuit 15 includes a first control device 17 for the fuel gas supply, which acts on the volume flow controllable valve 13 in the feed line 8 for fuel gas. The reference variable for the calorific value is determined using a calorific value calculator 18 specified, which uses the actual calorific value, the exhaust gas volume flow, the exhaust gas composition and the actual nitrogen volume flow from the second control circuit 16 as input variables.

Der zweite Regelkreis 16 umfasst eine zweite Steuereinrichtung 19 für Stickstoffzugabe, die auf das den Volumenstrom regelbare Ventil 14 einwirkt. Der zweite Regelkreis 16 umfasst weiterhin einen Volumenstrom Rechner 20, der als Eingangsgrößen den tatsächlich zugeführten Stickstoffvolumenstrom und den Brenngasvolumenstrom verwendet. Der Volumenstromrechner 20 gibt die Führungsgröße für den Mindest - Abgasvolumenstrom vor und liefert parallel dazu diesen Wert an den Heizwertrechner 18.The second control circuit 16 includes a second control device 19 for nitrogen addition, which acts on the valve 14 that can control the volume flow. The second control circuit 16 further includes a volume flow computer 20, which uses the actually supplied nitrogen volume flow and the fuel gas volume flow as input variables. The volume flow calculator 20 specifies the reference variable for the minimum exhaust gas volume flow and, in parallel, supplies this value to the calorific value calculator 18.

Figur 4 veranschaulicht die Abgaszusammensetzung und die Abgasmenge während eines typischen Entgasungsvorgangs einer sekundärmetallurgischen Behandlung einer Stahlschmelze, wobei der bei der Entkohlung vorherrschende Druck, die Abgasmenge, die Inertgasmenge, die Erdgasmenge und der CO Anteil des Abgases über die Zeit aufgetragen sind. Ohne weiteres erkennbar ist der Druckabfall (Vakuum/dünne durchgezogene Linie) zu Beginn des Entgasungsvorgangs und der Druckanstieg bei Beendung des Entgasungsvorgangs. Dies geht einher mit einer anfänglich hohen und dann nachlassenden CO Bildung. Die punktierte Linie veranschaulicht den durch die Zugabe von Erdgas (CH4) gestützten Heizwert des Abgases, wohingegen die fette durchgezogene Kurve die Stickstoffzugabe veranschaulicht. Figure 4 illustrates the exhaust gas composition and the amount of exhaust gas during a typical degassing process of a secondary metallurgical treatment of a steel melt, with the pressure prevailing during decarburization, the amount of exhaust gas, the amount of inert gas, the amount of natural gas and the CO proportion of the exhaust gas being plotted over time. The pressure drop (vacuum/thin solid line) at the beginning of the degassing process and the pressure increase at the end of the degassing process are easily recognizable. This is accompanied by an initially high and then decreasing CO formation. The dotted line illustrates the calorific value of the exhaust gas supported by the addition of natural gas (CH 4 ), whereas the bold solid curve illustrates the addition of nitrogen.

BezugszeichenlisteReference symbol list

11
Nachverbrennungseinrichtungafterburning device
22
Fackeltorch
33
StützbrennerSupport burner
44
AuspuffExhaust
55
Abgaskanalexhaust duct
66
SteuereinrichtungControl device
77
LöschleitungExtinguishing line
88th
Speiseleitung für BrenngasFeed line for fuel gas
99
Speiseleitung für StickstoffFeed line for nitrogen
1010
LöschmitteltankExtinguishing agent tank
1111
Durchfluss-MesseinrichtungFlow measuring device
1212
Gasanalyse-EinrichtungGas analysis facility
13, 1413, 14
VentileValves
1515
erster Regelkreisfirst control loop
1616
zweiter Regelkreissecond control circuit
1717
erste Steuereinrichtungfirst control device
1818
HeizwertrechnerCalorific value calculator
1919
zweite Steuereinrichtungsecond control device
2020
VolumenstromrechnerVolume flow calculator
2121
RegeleinrichtungControl device

Claims (15)

  1. Method for the afterburning of waste gases with carbon monoxide content from metallurgical processes with discontinuously arising waste gas volumes, the composition and/or quantity of which changes or change during a period within which waste gas arises, wherein the method comprises conditioning the waste gas prior to the afterburning, characterised in that at least one combustion gas and supplementary gas are added under regulation to the waste gas upstream of the afterburning, wherein the regulation is carried out in dependence on the composition of the waste gas and in dependence on the waste gas volume flow and wherein an inert gas, preferably nitrogen, is added as supplementary gas.
  2. Method according to claim 1, characterised in that a calorific value of the waste gas is determined indirectly by way of the carbon monoxide content of the waste gas with use of a gas analysis device (12).
  3. Method according to one of claims 1 and 2, characterised in that the regulation in dependence on the carbon monoxide content of the waste gas is carried out with the regulation objective of achieving a maximum conversion of carbon monoxide into carbon dioxide.
  4. Method according to any one of claims 1 to 3, characterised in that the regulation is conducted in such a way that the calorific value of the waste gas does not fall below ≥ 2 kWh/Nm3 (≥ 200 BTU/scf).
  5. Method according to any one of claims 1 to 4, characterised in that the regulation is conducted in such a way that the waste gas volume flow does not fall below a given minimum volume flow.
  6. Method according to claim 5, characterised in that the minimum volume flow of the waste gas is so determined in dependence on the flow speed of the waste gas in a given flow cross-section that the flow speed is greater than a flame propagation speed of the waste gas during combustion.
  7. Method according to any one of claims 1 to 6, characterised in that the afterburning is performed by means of at least one support gas torch (2) arranged in or at a chimney.
  8. Method according to claim 7, characterised in that the addition of combustion gas and/or inert gas is carried out by way of supply lines (8, 9) with valves (13, 14) able to regulate volume flow.
  9. Method for waste gas post-treatment during vacuum treatment of liquid steel in a metallurgical process comprising afterburning of the waste gas from the vacuum treatment of a metal melt by means of at least one torch (2) in or at a waste gas channel (5) of a vacuum pump, wherein the method comprises conditioning of the waste gas prior to the afterburning in such a way that at least one combustion gas and supplementary gas are added under regulation to the waste gas upstream of the afterburning, wherein the regulation is carried out in dependence on the composition of the waste gas and in dependence on the waste gas volume flow.
  10. Method according to claim 9, characterised in that the afterburning is performed periodically only during a decarburisation phase of the metal melt.
  11. Afterburning equipment for the afterburning of waste gas during a vacuum treatment of liquid steel in a secondary metallurgical process, comprising at least one torch (2) at an exhaust (4) of a waste gas channel (5) of a vacuum pump of a secondary metallurgical plant, means for conducting combustion gas to the torch, means for supply of an inert gas to the waste gas channel of the vacuum pump upstream of the torch (2), means for determining the waste gas volume flow and/or for measuring the waste gas velocity within the waste gas channel (5), means for analysis of the waste gas composition, means for metering the combustion gas and the inert gas as well as means for regulation of the metering of the combustion gas and/or the inert gas in dependence on the waste gas composition.
  12. Afterburning equipment according to claim 11, characterised in that provided as means for metering the combustion gas and the inert gas are valves (13, 14) which are able to regulate volume flow and which are each arranged in feed lines (8, 9), which are connected with the waste gas channel (5), for combustion gas and for inert gas.
  13. Afterburning equipment according to one of claims 11 and 12, characterised in that provided as means for metering of combustion gas and/or inert gas is at least one regulating device (21) the input variables of which are the waste gas composition, the waste gas volume flow, the quantity of fed combustion gas and the quantity of fed inert gas.
  14. Afterburning equipment according to claim 13, characterised in that the regulating device comprises at least one memory-programmable control.
  15. Afterburning equipment according to one of claims 13 and 14, characterised in that the regulating device controls a support burner (3) of the torch (2).
EP20812007.1A 2019-11-27 2020-11-23 Combustion of the co in secondary metallurgical exhaust gas, with calorific value control and volume flow control Active EP4065889B1 (en)

Applications Claiming Priority (2)

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