EP0511479B1 - Process for the ignition of a gasification reactor - Google Patents

Description

The present invention relates to a method for igniting a gasification reactor operated under increased pressure and producing a partial oxidation gas consisting essentially of carbon monoxide and hydrogen following an interruption in operation by means of a pilot burner provided with a high-voltage ignition device and a flame monitor.

A burner of the type mentioned above is described for example in EP-A 0 363 787. This burner can be used both as a support burner and as a normal gasification or service burner for the production of CO and H₂-rich gases by partial oxidation in a pressurized reactor.

According to the prior art, gasification reactors operating at elevated pressure, in particular those which operate on the entrained flow principle, are first relaxed after a failure or an operational shutdown by reducing the pressure and then flushed and evacuated several times with intergas. This is to remove partial oxidation gas residues, prevent the formation of an explosive residual gas atmosphere and form a sufficiently inert atmosphere in the gasification reactor, to enable a safe re-ignition after each flame extinguishes. However, this process takes a long time and the inert purge gas must be kept available on the system at all times.

If the dedusting of the partial oxidation gas generated is wet, there is generally a further time delay in that the gas scrubbing, which is likewise under increased pressure, cannot be relaxed as quickly as desired. In operation, the temperature of the wash water is around 120 ° C, which corresponds to a saturated steam pressure of approx. 2 bar. When relaxing, this pressure can only be fallen below if the wash water has been cooled accordingly beforehand.

The method of operation described above enables the gasification reactor to be ignited again safely if necessary. However, since this is associated with the serious disadvantage that each extinguishing of the gasifier flame and each new ignition process cause the gasification system to be interrupted for a considerable period of time, the resulting loss of production naturally affects the economic result of the system accordingly. Another economic loss results from the fact that part of the partial oxidation gas still in the gasification plant can no longer be used in the downstream plants, such as the gas turbine of a gas and steam turbine power plant, because the pressure falls below the required minimum pressure. This residual gas must therefore be destroyed by flaring.

The invention is therefore based on the object To provide a method for igniting a gasification reactor which avoids the disadvantages described above.

The method of the type mentioned at the outset which is used to achieve this object is characterized in that the ignition process takes place in the gasification reactor which is not inertized and is under gasification pressure, the pilot burner having a defined ignition process from an upstream container for an ignition process which takes place without damage to the gasification reactor by means of explosions sufficient quantity of oxidizing agent is supplied, the quantity ratio of which to the fuel is adjusted so that the flame in the pilot burner is operated with a deficit of oxidizing agent, the ignition process being monitored by the flame monitor and, after the successful expiration thereof, the supply of further oxidizing agent for the normal operation of the gasification reactor is released.

The characteristic of the process according to the invention is that it does not relieve the gasification reactor or purge it with inert gas. The gasification reactor is thus still under an increased pressure during the ignition process, which corresponds to or slightly below the gasification pressure. Via the upstream container, only an amount of oxidizing agent is supplied to the gasification reactor during the ignition process in such a way that the ignition process can take place without damage to the gasification reactor due to explosions. Here, the gasification reactor is initially switched off from further supply of oxidizing agent. Only when the ignition process, which is monitored with the help of a flame monitor, has been successful the supply of further oxidizing agent is released to the extent required for the normal operation of the pilot burners of the gasification reactor. From this point on, the conditions for resuming production of the gasification reactor are met.

In the pilot burner required to carry out the method according to the invention, the ignition device, pilot burner and flame monitor can be attached to the gasification reactor in a spatially separated manner. According to another arrangement, it is also possible to combine the ignition device and the flame monitor with the pilot burner to form one structural unit. According to a preferred embodiment, the ignition device, pilot burner and flame monitor can finally be integrated in one or more gasification burners of the gasification reactor.

Further details of the method according to the invention are to be explained in more detail below with the aid of the flow diagram shown in the figure, which shows a plant for carrying out the method. In the flow diagram, only the system parts necessary for the description of the ignition process according to the invention are shown, while the other system parts, which relate to the actual gasification process, in particular the gasification burner and the downstream gas treatment, which are not the subject of the present invention, are not shown and described.

Here, the ignition device 1 is arranged in the gasification reactor 6. If necessary, it can be withdrawn into the lock 7 to protect it during normal gasification operation. As a result, it is also possible, if necessary, to repair or replace the ignition device 1 without having to relax the gasification reactor 6. The flame monitor 2 and the pilot burner 8 are also arranged in the gasification reactor 61. In deviation from the schematic representation in the figure, these system parts can of course be integrated into structural units in the manner described above. In the ignition device 1, ignition sparks are generated in a manner known per se by high-voltage discharge. The line 13 is used to supply current to the ignition device 1. The lock 7 is covered by the line 14 in which the valve 15 is provided, and the relaxation takes place via the line 27 in which the valve 28 is provided. The oxidizing agent required for the ignition process, preferably air or air enriched with oxygen, is located in the container 3 upstream of the pilot burner 8. The amount of oxidizing agent located there is dimensioned according to the invention so that it is sufficient for an ignition process taking place without damage to the gasification reactor 6 due to explosions.

Hierbei bedeuten:

π

Druckverhältnis nach/vor Explosion, bekannt aus Explosionsversuchen mit stöchiometrischen Gemischen bei Normaldruck

max

Maximalwert

p

Druck im Behälter vor der Explosion

Δ p

zulässige Druckerhöhung

Setzt man ideales Gasverhalten voraus, so gilt ferner

${\text{a = y}}_{\text{B}}{\text{+ y}}_{\text{L}}\text{ (2)}$

Hierbei bedeuten:

y_B

Molanteil Brenngas

y_L

Molanteil Oxidationsmittel (z.B. Luft)

Es ist bekannt, daß der maximale Explosionsdruck auftritt, wenn das Gemisch stöchiometrische Zusammensetzung aufweist. In diesem Fall liegen Brenngas und Oxidationsmittel in einem festen Verhältnis µ_S vor, das sich mit den gebräuchlichen Methoden der Verbrennungsrechnung ermitteln läßt. Hiermit geht G1.(2) über in

${\text{a = (µ}}_{\text{S}}{\text{+ 1) . y}}_{\text{L}}$

oder

Die zulässige Menge an Oxidationsmittel ist mit den Behälterdaten folgendermaßen verknüpft:

Hierbei bedeuten:

V

Behältervolumen

p

Druck im Behälter (vor dem Zündversuch)

T

Temperatur im Behälter

V_NL

Volumen des Oxidationsmittels im Normzustand

N

Normzustand

Die Gleichungen (1) bis (4) stellen somit eine Vorschrift dar, mit der die höchstzulässige Menge an Oxidationsmittel aus Explosions- und Behälterdaten ermittelt werden kann.The following relationships apply to the determination of this amount of oxidizing agent:
If the pressure increase Δ p in a container should not exceed a certain value specified by the explosion pressure, the permissible volume fraction of the reactants a is as follows:

${\text{a ≦ (Δ p / p) / (π}}_{\text{Max}}\text{- 1) (1)}$

Here mean:

π

Pressure ratio after / before explosion, known from explosion tests with stoichiometric mixtures at normal pressure

Max

Maximum value

p

Pressure in the container before the explosion

Δ p

permissible pressure increase

If one assumes ideal gas behavior, then the following also applies

${\text{a = y}}_{\text{B}}{\text{+ y}}_{\text{L}}\text{(2)}$

Here mean:

y _B

Molar fraction of fuel gas

y _L

Mole fraction of oxidizing agent (e.g. air)

It is known that the maximum explosion pressure occurs when the mixture has a stoichiometric composition. In this case, the fuel gas and oxidizing agent are in a fixed ratio µ _S , which can be determined using the usual methods of combustion calculation. Hereby, G1. (2) merges into

${\text{a = (µ}}_{\text{S}}{\text{+ 1). y}}_{\text{L}}$

or

The permissible amount of oxidizing agent is linked to the container data as follows:

Here mean:

V

Container volume

p

Pressure in the tank (before the ignition attempt)

T

Temperature in the tank

V _NL

Volume of oxidant in normal condition

N

Normal state

Equations (1) to (4) therefore represent a regulation with which the maximum permissible amount of oxidizing agent can be determined from explosion and container data.

Hierbei bedeuten:

V₃

Volumen Behälter 3

T_N

Temperatur i.Normzustand

T₃

Temperatur Behälter 3

Δ P₁₀

Differenzdruck Behälter-Vergaser

Aus dieser Gleichung ergibt sich durch Auflösung nach Δ P₁₀ die Gleichung

Die Temperatur T₃ wird durch das am Behälter 3 angeordnete Temperaturmeßgerät 17 ermittelt. Während des Zündvorganges ist der Behälter 3 nur über die Leitung 4 mit dem Zündbrenner 8 verbunden, von der weiteren Oxidationsmittelzufuhr über die Leitung 5 jedoch abgeschottet. Hierdurch ist selbst bei einem Versagen der Armaturen die Sicherheit der Anlage gewährleistet. Erst nachdem mit Hilfe des Flammenwächters 2 der Erfolg des Zündvorganges festgestellt worden ist, wird die Zufuhr von weiterem Oxidationsmittel über die Leitung 5 freigegeben. Hiermit sind die Voraussetzungen erfüllt, um nach Ablauf einer Stabilisierungsperiode im Zündbrennerbetrieb die in der Abbildung nicht dargestellten Vergasungsbrenner zu zünden und so den Betrieb der Vergasungsanlage fortzusetzen.This defined quantity of oxidizing agent is held in the container 3 by setting a defined differential pressure from the container 3 to the gasification reactor 6 via the differential pressure regulator 10. The maximum permissible setpoint for the differential pressure is derived from the equation known as the ideal gas law:

Here mean:

V₃

Volume of container 3

T _N

Temperature in normal condition

T₃

Temperature container 3

Δ P₁₀

Differential pressure tank carburetor

From this equation, the equation is obtained by resolution according to Δ P₁₀

The temperature T₃ is determined by the temperature measuring device 17 arranged on the container 3. During the ignition process, the container 3 is only connected to the pilot burner 8 via the line 4, but is sealed off from the further supply of oxidant via the line 5. This ensures the safety of the system even if the fittings fail. Only after the success of the ignition process has been determined with the aid of the flame monitor 2 is the supply of further oxidizing agent released via line 5. This fulfills the prerequisites for igniting the gasification burners not shown in the illustration after a stabilization period in the pilot burner operation and thus continuing the operation of the gasification system.

• 1. Überprüfung der Zündvorrichtung
  Hierzu wird die Zündvorrichtung 1 aus der Schleuse 7 in die Zündposition gefahren und in der Gasatmosphäre ohne Zufuhr von Oxidationsmittel getestet. Bei einer Hochspannungszündung wird beispielsweise der zeitliche Verlauf von Spannung und Strom mit gespeicherten Normalwerten verglichen.
  Besteht der Verdacht auf Fehlfunktion, so wird die Zündvorrichtung in die Schleuse 7 zurückgezogen. Nachdem diese inertisiert und entspannt ist, kann die Zündvorrichtung 1 repariert bzw. ausgetauscht und danach wieder in den Vergasungsreakton eingefahren werden.
• 2. Bespannen des Behälters 3
  Der durch die Gleichungen (1) bis (5) definierte Algorithmus gestattet, den Grenzwert des Differenzdrukkes zwischen dem Behälter 3 und dem Vergasungsreaktor 6 zu ermitteln. Es ist dies der höchstzulässige Wert, bei dem - selbst unter der Bedingung maximalen Zündzeitverzuges - keinerlei Beschädigung der Ausrüstungen auftreten kann. Der Sollwert des Differenzdruckes wird demgegenüber um einen Sicherheitsabstand verringert. Während des Bespannens des Behälters 3 sind die Ventile 18 und 19 geschlossen sowie das Ventil 21 geöffnet. Die Zufuhr von Oxidationsmittel zum Zündbrenner 8 und zum Mengenregler 12 ist demnach unterbrochen. Nach Öffnen des Ventils 26 wird der erforderliche Differenzdruck mit Hilfe des Differenzdruckreglers 10 über die Ventile 23 (Bespannen) und 25 (Entspannen) eingestellt. Die erforderliche Menge an Oxidationsmittel steht nunmehr bereit.
• 3. Einschalten der Zündvorrichtung 1
  Nach dem Einschalten der Zündvorrichtung 1 wird deren ordnungsgemäße Funktion erneut durch Beobachten der Strom/Spannungs-Charakteristik überprüft.
• 4. Freigabe der Brennstoffzufuhr
  Die Brennstoffzufuhr über die Leitung 9 zum Zündbrenner 8 wird mengengeregelt freigegeben. Die Mengenregelung erfolgt dabei durch den Mengenregler 11, der das Ventil 22 in der Leitung 9 steuert.
• 5. Freigabe des Oxidationsmittels
  Nachdem der erforderliche Differenzdruck zwischen dem Behälter 3 und dem Vergasungsreaktor 6 eingestellt worden und somit die gewünschte Oxidationsmittelmenge im Behälter 3 vorhanden ist, wird die Oxidationsmittelzufuhr über die Leitung 5 unterbrochen. Hierzu werden die Ventile 23 und 26 in der Leitung 5 geschlossen. Durch Öffnung des Ventils 25 in der Leitung 24 wird die erforderliche Zwischenentspannung und damit die vollständige Trennung des Behälters 3 von der Oxidationsmittel zufuhr erreicht. Nunmehr wird die Oxidationsmittelzufuhr zum Zündbrenner 8 in folgenden Schritten freigegeben:
  • Schließen des Ventils 21
  • Öffnen des Ventils 19
  • Inbetriebnahme der aus dem Mengenregler 12 und dem Ventil 18 gebildeten Mengenregelung.
  
  Gleichzeitig beginnt die Zeitmessung der Zündzeitüberwachung.
• 6. Zündzeitüberwachung
  Falls der Flammenwächter 2 binnen einer bestimmten Zeitspanne A nach Beginn der Oxidationsmittelzufuhr den Gutzustand erreicht und diesen Zustand für eine Zeitspanne B beibehält, wird das Ventil 25 geschlossen und die Ventile 23 und 26 geöffnet, so daß weiteres Oxidationsmittel über die Leitung 5 und den Behälter 3 zum Zündbrenner 8 nachströmen kann. Der Zündvorgang ist damit erfolgreich abgeschlossen.
  Erreicht der Flammenwächter 2 dagegen nicht den Gutzustand innerhalb der genannten Zeitspanne, wird die Zufuhr von Oxidationsmittel und Brennstoff unterbrochen und der Zündvorgang abgebrochen. Der Vergasungsreaktor 6 bleibt dabei unter seinem Druck. Nachdem die Bildung einer explosiven Gasatmosphäre innerhalb des Vergasungsreaktors durch hinreichende Spülung mit Inertgas verhindert worden ist, kann der Zündvorgang wiederholt werden.
• 7. Zündbrennerbetrieb
  Durch Regelung des Verhältnisses von Oxidationsmittel zu Brennstoff wird sichergestellt, daß die Flamme mit Unterschuß an Oxidationsmittel betrieben wird. Es wird ein CO-Gehalt von mehr als 2 Vol.% angestrebt. Freies Oxidationsmittel tritt daher nicht auf.
  Die Stabilität des Verbrennungsvorganges wird über den Flammenwächter 2 kontrolliert. Er nimmt in diesem Betriebszustand die übliche Sicherheits- bzw. Abschaltfunktion wahr.

The ignition process takes place as follows:

• 1. Check the ignition device
  For this purpose, the ignition device 1 is moved out of the lock 7 into the ignition position and tested in the gas atmosphere without the addition of oxidizing agent. In the case of a high-voltage ignition, for example, the time course of voltage and current is compared with stored normal values.
  If there is a suspicion of malfunction, the ignition device is withdrawn into the lock 7. After this has been rendered inert and relaxed, the ignition device 1 can be repaired or exchanged and then returned to the gasification reactor.
• 2. Cover the container 3
  The algorithm defined by equations (1) to (5) makes it possible to determine the limit value of the differential pressure between the tank 3 and the gasification reactor 6. This is the highest permissible value at which - even under the condition of maximum ignition delay - no damage to the equipment can occur. In contrast, the setpoint of the differential pressure is reduced by a safety margin. During the covering of the container 3, the valves 18 and 19 are closed and the valve 21 is open. The supply of oxidizing agent to the pilot burner 8 and to the quantity regulator 12 is accordingly interrupted. After opening the valve 26, the required differential pressure is set by means of the differential pressure regulator 10 via the valves 23 (covering) and 25 (relaxing). The required amount of oxidizing agent is now ready.
• 3. Switch on the ignition device 1
  After switching on the ignition device 1, its proper function is checked again by observing the current / voltage characteristic.
• 4. Release of the fuel supply
  The fuel supply via line 9 to pilot burner 8 is released in a quantity-controlled manner. The volume control is carried out by the volume controller 11, which controls the valve 22 in line 9.
• 5. Release of the oxidizing agent
  After the required differential pressure between the container 3 and the gasification reactor 6 has been set and thus the desired amount of oxidant is present in the container 3, the supply of oxidant via the line 5 is interrupted. For this purpose, valves 23 and 26 in line 5 are closed. By opening the valve 25 in the line 24, the required intermediate relaxation and thus the complete separation of the container 3 from the oxidant supply is achieved. Now the oxidant supply to the pilot burner 8 is released in the following steps:
  • Closing valve 21
  • Open valve 19
  • Commissioning of the quantity control formed from the quantity regulator 12 and the valve 18.
  
  At the same time, the timing of the ignition timing monitoring begins.
• 6. Ignition time monitoring
  If the flame monitor 2 reaches the good state within a certain period A after the start of the oxidant supply and maintains this state for a period B, the valve 25 is closed and the valves 23 and 26 opened, so that further oxidant via the line 5 and the container 3 can flow to pilot burner 8. The ignition process is now successfully completed.
  If, on the other hand, the flame monitor 2 does not reach the good state within the stated time period, the supply of oxidizing agent and fuel is interrupted and the ignition process is stopped. The gasification reactor 6 remains under its pressure. After the formation of an explosive gas atmosphere within the gasification reactor has been prevented by sufficient purging with inert gas, the ignition process can be repeated.
• 7. Pilot burner operation
  By regulating the ratio of oxidizing agent to fuel it is ensured that the flame is operated with a deficit of oxidizing agent. A CO content of more than 2% by volume is aimed for. Free oxidant therefore does not occur.
  The stability of the combustion process is controlled by the flame monitor 2. In this operating state, it performs the usual safety or shutdown function.

• Radikal verkürzte Stillstandszeiten des Vergasungsreaktors durch Vermeidung von Druckabbau und Inertisierung.
• Verringerung der Produktgasverluste durch Abfackeln und Vermischen mit Inertgas, daraus resulierend eine höhere Verfügbarkeit und Wirtschaflichkeit der gesamten Anlage.
• Entlastung der Umwelt, da das Verbrennen von nur teilweise entschwefeltem Rohgas mit Hilfe einer Fackel entfällt.

The invention offers the following advantages:

• Radically reduced downtimes of the gasification reactor by avoiding pressure reduction and inerting.
• Reduction of product gas losses through flaring and mixing with inert gas, resulting in higher availability and economy of the entire system.
• Relief for the environment, since the burning of partially desulphurized raw gas with the help of a torch is no longer necessary.

Claims (2)

1. Method for igniting a gasification reactor which is operated under elevated pressure and serves to generate a partial oxidation gas essentially comprising carbon monoxide and hydrogen following an interruption to operation by means of a pilot burner furnished with a high-voltage ignition apparatus and a flame failure safeguard, characterized in that the ignition operation proceeds in the gasification reactor which has not been flushed with inert gas and is under gasification pressure, a defined amount of oxidant sufficient for an ignition operation proceeding without damage to the gasification reactor as a result of explosions being fed from an upstream vessel to the pilot burner, the flow ratio of which oxidant to fuel being adjusted in such a way that the flame in the pilot burner is operated with a deficit of oxidant, the ignition operation being monitored by the flame failure safeguard and after successful completion of the same the feed of further oxidant being released for the routine operation of the gasification reactor.
2. Method according to Claim 1, characterized in that the feed of oxidant to the pilot burner is set so that in the gas arising in the combustion a CO content of more than 2 % by volume is present.

Images