DE112006001974B4 - Method for operating a gas turbine and gas turbine for carrying out the method - Google Patents

Abstract

Method for operating a gas turbine (11), which is used in particular in a combined cycle power plant (30, 40), in which process air is drawn in and compressed by the gas turbine (11), the compressed air for combustion of a coal-derived syngas of a combustion chamber ( 18, 19), and the hot gases produced in the combustion are depressurized in a subsequent turbine (16, 17) by performing work, whereby a part of the compressed air is decomposed into oxygen and nitrogen, and the oxygen in one A coal gasification plant (34) is used to generate the syngas, and wherein a portion of the compressed air is used to cool the charged by the hot gases parts of the gas turbine (11), characterized in that a gas turbine (11) is used with reheat, which two combustion chambers (18, 19) and two turbines (16, 17), wherein in the first combustion chamber (18) syngas using the densified burned in the air and the resulting hot gases in the first turbine (16) are relaxed, and burned in the second combustion chamber syngas using the gases coming from the first turbine (16) and the resulting hot gases in the second turbine (17) are relaxed, and used in the air separation nitrogen for cooling the gas turbine (11) is used, that the gas turbine (11 a first compressor (13) for compressing sucked air to a first pressure stage and a second compressor (14) for further compression the air from the first pressure stage to a second, higher pressure stage comprises that part of the air coming from the first compressor (13) is decomposed into oxygen and nitrogen, and that the nitrogen resulting from this decomposition is used to cool the second combustion chamber (18). and a second turbine (17) is used, and that a part of the compressed air branched off for the separation from the first compressor (13) is used by the first compressor (13) or the decomposition is diverted and mixed with the nitrogen produced during the decomposition and intended for cooling.

Description

TECHNICAL AREA

The present invention relates to the field of power plant technology. It relates to a method for operating a (stationary) gas turbine according to the preamble of claim 1, as well as a gas turbine for carrying out the method.

STATE OF THE ART

It is a gas turbine with reheat reheat gas turbine known (see for example the US 5 577 378 A or "State-of-the-art gas turbines - a letter update", ABB Review 0211997, 15 Turbine type GT26), which combines flexible operation with very low exhaust emissions.

• - es beim Verdichter bereits eine bedeutsame Abzweigung von Verdichterluft bei mittleren Verdichterdrücken gibt,
• - das Konzept der sequentiellen Verbrennung eine erhöhte Stabilität der Verbrennung bei verringerten Werten des Sauerstoffüberschusses ermöglicht, und
• - ein Sekundärluftsystem vorhanden ist, welches es ermöglicht, Luft aus dem Verdichter abzuzweigen, herunterzukühlen und die heruntergekühlte Luft zur Kühlung der Brennkammer und der Turbine zu verwenden.

The machine architecture of the gas turbine type GT26 is unique and is ideally suited to the realization of a concept, which is the subject of the present invention, because:

• there is already a significant diversion of compressor air at medium compressor pressures,
• the concept of sequential combustion enables increased stability of combustion at reduced levels of excess oxygen, and
• - There is a secondary air system, which makes it possible to divert air from the compressor, to cool down and to use the cooled air for cooling the combustion chamber and the turbine.

The principle of the known gas turbine with reheat is in 1 shown. The gas turbine 11 , part of a combined cycle power plant 10 is, includes on a common wave 15 arranged two compressors in series, namely a low-pressure compressor 13 and a high pressure compressor 14 , as well as two combustion chambers, namely a high-pressure combustion chamber 18 and a reheat combustion chamber 19 , and associated turbines, namely a high pressure turbine 16 and a low-pressure turbine 17 , The wave 15 drives a generator 12 on.

The operation of the system is as follows: Air is supplied via an air inlet 20 from the low-pressure compressor 13 sucked and first compressed to an intermediate pressure level (about 20 bar). The high pressure compressor 14 then compresses the air further to a high pressure level (about 32 bar). Cooling air is diverted both at the intermediate pressure level and at the high pressure level and cooled in associated OTC coolers (OTC) 23 and 24 and over cooling lines 25 and 26 for cooling to the combustion chambers 18 . 19 and turbines 16 . 17 forwarded. The remaining air from the high pressure compressor 14 becomes the high-pressure combustion chamber 18 led and there by burning one over the fuel supply 21 The resulting exhaust gas is then in the subsequent high-pressure turbine 16 relaxed under work to a medium pressure level. After expansion, the exhaust gas becomes in the reheat combustion chamber 19 by burning one over the fuel supply 22 fuel is reheated before it is in the subsequent low-pressure turbine 17 is relaxed under further work.

The through the cooling lines 25 . 26 flowing cooling air is at suitable locations of the combustion chambers 18 . 19 and turbines 16 . 17 injected in order to limit the material temperatures to an acceptable level. That from the low-pressure turbine 17 Exhaust gas coming through a heat recovery steam generator 27 (HRSG = Heat-Recovery Steam Generator) sent; to generate steam within a water-steam cycle through a steam turbine 29 flows and does more work there. After flowing through the heat recovery steam generator 27 Finally, the exhaust gas is passed through an exhaust pipe 28 delivered to the outside. The OTC coolers 23 . 24 are part of the water-steam cycle; superheated steam is generated at their outputs.

By the two independent, consecutive burns in the combustion chambers 18 and 19 a great flexibility in the operation is achieved; the combustion chamber temperatures can be adjusted so that the maximum efficiency is achieved within the existing limits. The low emissions of the sequential combustion system are due to the inherently low levels of emissions that can be achieved during reheat (under certain conditions, the second combustion even results in NOx consumption).

On the other hand, combined-cycle power plants with single-stage combustion in gas turbines are known (see, for example, US Pat US 4,785,622 A , the US 5,406,786 A or US Pat. No. 6,513,317 B2 ), in which a coal gasification plant is integrated in order to provide the required for the gas turbine fuel in the form of coal-derived syngas.

Such combined cycle power plants are referred to as IGCC (Integrated Gasification Combined Cycle) systems.

The present invention is based on the recognition that through the use of gas turbines with reheating in an IGCC plant the advantages of this type of gas turbine for the system can be utilized in a special way.

PRESENTATION OF THE INVENTION

It is an object of the invention to provide a method for operating a cooperating with a coal gasification gas turbine, which. characterized by, improved efficiency and can be realized particularly low with existing components, and to provide a gas turbine for carrying out the method.

• Es wird kein OTC-Kühler benötigt, wodurch sich der Wirkungsgrad erhöht. Es wird weniger Kühlluft benötigt, was ebenfalls dem Wirkungsgrad zugute kommt. Der vergleichsweise kalte Stickstoff aus der Luftzerlegungsanlage kann zur Kühlung kritischer Komponenten verwendet werden, während die wärmere Luft aus dem Verdichter zur Kühlung weniger kritischer Komponenten herangezogen werden kann; auch dies verbessert den Wirkungsgrad der Anlage.
• Die beschrieben Kühlung kann bei Gasturbinen bekannter Baurat mit Zwischenüberhitzung wie z.B. der Gasturbine vom Typ GT26 aufgrund des spezifischen Sekundärluftsystems besonders einfach realisiert werden.

The object is solved by the entirety of the features of claims 1 and 4. It is essential that in a working with syngas from a coal gasification gas turbine plant, a gas turbine is used with reheat, comprising two combustion chambers and two turbines, burned in the first combustion chamber syngas using the compressed air and relaxes the resulting hot gases in the first turbine In the second combustion chamber, syngas is burned using the gases coming from the first turbine and the resulting hot gases in the second turbine are expanded, and the nitrogen resulting from the air separation is used to cool the gas turbine. The solution according to the invention has the following advantages:

• There is no OTC cooler needed, which increases the efficiency. Less cooling air is needed, which also benefits the efficiency. The comparatively cold nitrogen from the air separation plant can be used to cool critical components, while the warmer air from the compressor can be used to cool less critical components; This also improves the efficiency of the system.
• The described cooling can be realized particularly easily in gas turbines of known construction rate with reheating, such as, for example, the gas turbine of type GT26, due to the specific secondary air system.

The inventive method is inter alia characterized in that the gas turbine comprises a first compressor for compressing sucked air to a first pressure stage and a second compressor for further compression of the air from the first pressure stage to a second, higher pressure stage, that part of The first coming compressor air is decomposed into oxygen and nitrogen, and that the resulting nitrogen in this decomposition nitrogen is used for cooling the second combustion chamber and the second turbine.

In this case, a portion of the branched off for the decomposition compressed air is diverted from the first compressor before decomposition and mixed with the resulting during the decomposition and intended for cooling nitrogen. Particularly favorable conditions arise when about 50% of the branched off for the decomposition compressed air from the first compressor branched before the decomposition and mixed with the resulting during the decomposition and intended for cooling nitrogen. Preferably, the nitrogen produced during the decomposition is compacted prior to mixing with the compressed air branched off before the decomposition.

The gas turbine according to the invention is characterized in that a branch line is provided which branches off from the input side of the air separation plant and opens at a designated point in the nitrogen line, and that in the nitrogen line between the outlet of the air separation plant and the predetermined point of the mouth of the Branch line a compressor for the compression of the nitrogen is arranged.

Preferably, the gas turbine has two cascaded compressors, the air separation plant is connected on the input side to the output of the first compressor, and the nitrogen line is guided to the second combustion chamber and the second turbine.

In particular, the air separation plant has an oxygen line for discharging the oxygen produced during the decomposition, which is fed to a plant for producing syngas by means of coal gasification, and a syngas feed line transports the generated syngas from the plant for producing syngas to the combustion chambers.

list of figures

• 1 das vereinfachte Schema eines Kombikraftwerks mit einer Gasturbine mit Zwischenüberhitzung bzw. sequentieller Verbrennung nach dem Stand der Technik;
• 2 das vereinfachte Schema einer IGCC-Anlage mit einer Gasturbine mit Zwischenüberhitzung bzw. sequentieller Verbrennung, wie sie zur Verwirklichung der Erfindung geeignet ist; und
• 3 ein Ausführungsbeispiel für die Kühlung nach der Erfindung mit dem bei der Luftzerlegung gewonnenen Stickstoff in einer Anlage der in 2 gezeigten Art.

The invention will be explained in more detail with reference to embodiments in conjunction with the drawings. Show it

• 1 the simplified scheme of a combined cycle power plant with a gas turbine with reheat or sequential combustion according to the prior art;
• 2 the simplified scheme of an IGCC plant with a reheat gas turbine or sequential combustion, as is suitable for implementing the invention; and
• 3 an embodiment of the cooling according to the invention with the obtained in the air separation nitrogen in a plant of in 2 shown type.

WAYS FOR CARRYING OUT THE INVENTION

In the 2 In a highly simplified schematic, an IGCC system with a reheat gas turbine or sequential combustion combustor as is suitable for practicing the invention is shown. The combined cycle power plant 30 includes a gas turbine 11 with a low pressure compressor 13 , a subsequent high-pressure compressor 14 , a high-pressure combustion chamber 18 with a subsequent high-pressure turbine 16 and a reheat combustion chamber 19 with a subsequent low-pressure turbine 17 , The compressors 13 . 14 and the turbines 16 . 17 sit on a common wave 15 from which a generator 12 is driven. The combustion chambers 18 and 19 be via a Syngaszuleitung 31 supplied with syngas as fuel, which by gasification of coal (coal 33 ) in a coal gasification plant 34 is produced. The coal gasification plant 34 is a cooling device 35 for the Syngas, a cleaning system 36 and a CO ₂ separator 37 with a CO ₂ outlet 38 downstream of the discharge of the deposited CO 2.

For coal gasification in the coal gasification plant 34 is used oxygen (O ₂ ), which in an air separation plant 32 won and over an oxygen line 32a is supplied. The air separation plant 32 receives compressed air from the outlet of the low-pressure compressor 13 , The nitrogen which also forms during the decomposition ( N2 ) is, for example, via a nitrogen line 32b the low-pressure combustion chamber 19 fed.

For cooling the hot gas loaded components of the combustion chambers 18 . 19 and turbines 16 . 17 is compressed cooling air at the outputs of the two compressors 13 and 14 tapped, in a downstream OTC cooler 23 or. 24 cooled, and then over appropriate cooling lines 25 and 26 supplied to the bodies to be cooled. At the exit of the low-pressure turbine 17 is a heat recovery steam generator 27 arranged, together with a connected steam turbine 29 Part of a water-steam cycle is. That from the heat recovery steam generator 27 exiting exhaust gas is via an exhaust pipe 28 delivered to the outside.

In such a system configuration is now according to 3 changed the cooling. In the combined cycle power plant 40 the 3 Although the high pressure combustion chamber 18 and the high-pressure turbine 16 still cooled by compressed air at the outlet of the high pressure compressor 14 branched off and then in an OTC cooler 24 is cooled down. The cooling of the reheat combustion chamber 19 and the low-pressure turbine 17 However, now takes another way. This is done at the output of the low-pressure compressor 13 Discharged compressed air at 50% in the air separation plant 32 decomposed into oxygen and nitrogen. The other 50% will be in a branch line 39 at the air separation plant 32 past. The over the oxygen line 32a from the air separation plant 32 Dissipated oxygen becomes as in 2 shown used for coal gasification. The generated, relatively cool nitrogen is through the nitrogen line 32b a compressor 41 fed and after compression with the 50% air from the branch line 39 mixed. The gas temperature after mixing is then about 300-400 ° C, so that a cooling of the low-pressure compressor 13 extracted cooling air is not necessary. The. The resulting mixture is then used to cool the hot components of the reheat combustion chamber 19 and the low-pressure turbine 17 used.

• - Es wird kein OTC-Kühler benötigt, wodurch sich der Wirkungsgrad erhöht.
• - Es wird weniger Kühlluft benötigt, was ebenfalls dem Wirkungsgrad zugute kommt.
• - Der vergleichsweise kalte Stickstoff aus der Luftzerlegungsanlage kann zur Kühlung kritischer Komponenten verwendet werden, während die wärmere Luft aus dem Verdichter zur Kühlung weniger kritischer Komponenten herangezogen werden kann; auch dies verbessert den Wirkungsgrad der Anlage.
• - Die beschriebene Kühlung kann bei Gasturbinen bekannter Bauart mit Zwischenüberhitzung wie z.B. der Gasturbine vom Typ GT26 aufgrund des spezifischen Sekundärluftsystems besonders einfach realisiert werden.

The advantages of this type of cooling are:

• - There is no OTC cooler needed, which increases the efficiency.
• - Less cooling air is needed, which also benefits the efficiency.
• - The comparatively cold nitrogen from the air separation plant can be used to cool critical components, while the warmer air from the compressor can be used to cool less critical components; This also improves the efficiency of the system.
• - The described cooling can be particularly easily realized in gas turbines of known design with reheat, such as the gas turbine type GT26 due to the specific secondary air system.

The prerequisite for the realization of this concept is that undiluted coal gas can be used in the two combustion chambers of the gas turbine. The main technical challenges in burning such undiluted coal gas in the combustor of a gas turbine are: achieving low emissions,
a sufficient distance from the limits of flashbacks and pulsations, the maintenance of flexibility in operation in the event of changes in the quality of coal gas, as well as the possibility of support with other fuels (natural gas or oil), and
the bleeding and feeding of cooling air into the areas of the hot gas channel in the combustion chamber and in the turbine.

1. 1. Der bei der Zwischenüberhitzung inhärente Vorteil bezüglich NOx kann auch auf das Syngas übertragen werden, wenn die Verbrennungstemperaturen in den beiden Brennkammern optimal ausgewählt werden, insbesondere mit einer gemäßigten Temperaturerhöhung in der ersten Stufe (Hochdruckbrennkammer 18).
2. 2. Die Stabilität der Verbrennung und die Flexibilität beim Betrieb der Gasturbine mit Zwischenüberhitzung sind grösser als bei einer vergleichbaren Gasturbine mit einstufiger Verbrennung. Die Betriebsgrenzen werden typischerweise durch die Flammenauslöschung und den Flammenrückschlag und/oder Emissionsniveaus für eine vorgegebene Flammentemperatur gegeben, was zu einem erlaubten Bereich von Brennstoffqualitäten und Brennstoffreaktivitäten führt. In der Gasturbine mit Zwischenüberhitzung ist diese Betriebsgrenze deutlich erhöht, weil zwei Verbrennungssysteme den Betrieb bei zwei unabhängigen Flammentemperaturen ermöglichen, z.B. mit einer niedrigeren Temperatur .in der ersten Stufe und einer höheren Temperatur in der zweiten Stufe, mit geringen Nachteilen bezüglich des NOx.
3. 3. Die Anforderungen für den Gasdruck können minimiert werden, wenn das Brenngas unverdünnt (ohne Stickstoff) in das erste und zweite Verbrennungssystem injiziert wird, die typischerweise mit Drücken im Bereich> 30 bar bzw. zwischen 15 und 20 bar arbeiten.
4. 4. Das Konzept der Extraktion von Kühlluft, die anschließend heruntergekühlt und in die Maschine wieder eingespeist wird, eignet sich besonders gut für die Verwendung von Stickstoff als Kühlmedium.

For IGCC plants, these challenges can be overcome particularly well by a gas turbine with reheat for the following reasons:

1. 1. The inherent in the reheating advantage with respect to NOx can also be transferred to the syngas when the combustion temperatures are optimally selected in the two combustion chambers, in particular with a moderate temperature increase in the first stage (high-pressure combustion chamber 18 ).
2. 2. The stability of the combustion and the flexibility in the operation of the gas turbine with reheat are greater than in a comparable gas turbine with single-stage combustion. The operating limits are typically given by flame extinction and flashback and / or emission levels for a given flame temperature, resulting in an allowable range of fuel qualities and fuel reactivities. In the superheated gas turbine, this operating limit is significantly increased because two combustion systems allow operation at two independent flame temperatures, eg lower temperature in the first stage and higher temperature in the second stage, with minor disadvantages with respect to NOx.
3. 3. The requirements for gas pressure can be minimized if the fuel gas is injected undiluted (without nitrogen) into the first and second combustion systems, which typically operate at pressures in the range> 30 bar and between 15 and 20 bar.
4. 4. The concept of extraction of cooling air, which is then cooled down and fed back into the machine, is particularly well suited for the use of nitrogen as a cooling medium.

Claims (7)

Method for operating a gas turbine (11), which is used in particular in a combined cycle power plant (30, 40), in which process air is drawn in and compressed by the gas turbine (11), the compressed air for combustion of a coal-derived syngas of a combustion chamber ( 18, 19), and the hot gases produced in the combustion are depressurized in a subsequent turbine (16, 17) by performing work, whereby a part of the compressed air is decomposed into oxygen and nitrogen, and the oxygen in one A coal gasification plant (34) is used to generate the syngas, and wherein a portion of the compressed air is used to cool the charged by the hot gases parts of the gas turbine (11), characterized in that a gas turbine (11) is used with reheat, which two combustion chambers (18, 19) and two turbines (16, 17), wherein in the first combustion chamber (18) syngas using the compression combusted and the resulting hot gases in the first turbine (16) are relaxed, and burned in the second combustion chamber syngas using the gases coming from the first turbine (16) and the resulting hot gases in the second turbine (17) are relaxed, and used in the air separation nitrogen for cooling the gas turbine (11) is used, that the gas turbine (11 a first compressor (13) for compressing sucked air to a first pressure stage and a second compressor (14) for further compression the air from the first pressure stage to a second, higher pressure stage comprises that part of the air coming from the first compressor (13) is decomposed into oxygen and nitrogen, and that the nitrogen resulting from this decomposition is used to cool the second combustion chamber (18). and second turbine (17) is used, and that a part of the compressed for the decomposition compressed air from the first compressor (13) branched off before the decomposition and mixed with the nitrogen produced during the decomposition and intended for cooling. Method according to Claim 1 characterized in that about 50% of the compressed air branched off for disassembly from the first compressor (13) is diverted prior to disassembly and mixed with the nitrogen produced during disassembly and intended for cooling. Method according to Claim 1 or 2 , characterized in that the nitrogen produced during the decomposition is compacted before being mixed with the compressed air branched off before the decomposition. Gas turbine (11) for performing the method according to Claim 1 , which gas turbine (11) is designed as a reheat gas turbine and compressor (13, 14) for compressed intake air and two combustion chambers (18, 19) and two turbines (16, 17), wherein in the first combustion chamber (18) a fuel is burned using the compressed air and the resulting hot gases in the first turbine (16) are relaxed, and wherein burned in the second combustion chamber using the gases coming from the first turbine (16) and the resulting hot gases in the second turbine (17) are relaxed, characterized in that a Luftzerlegungsanalge (32) is provided, which on the input side to the compressor (13, 14) is connected and the output side, a nitrogen line (32b) for discharging the nitrogen produced during the decomposition, and that the nitrogen line (32b) is in communication with parts of the gas turbine (11) which are loaded by the hot gases, and in that a branch line (39) is provided, which from the input side of the air separation plant (32) branches off and at a designated point in the nitrogen line (32b) opens. Gas turbine after Claim 4 , characterized in that in the nitrogen line (32b) between the output of the air separation plant (32) and the predetermined point of the junction of the branch line (39) is arranged a compressor (41) for compressing the nitrogen. Gas turbine after one of the Claims 4 or 5 , characterized in that the gas turbine (11) comprises two compressors (13, 14) connected in series, the air separation plant (32) being connected on the input side to the output of the first compressor (13), and the nitrogen line (32b) being connected to the second combustion chamber (32). 18) and to the second turbine (17) is guided. Gas turbine after one of the Claims 4 to 6 , characterized in that the air separation plant (32) on the output side an oxygen line (32a) for discharging the oxygen resulting from the decomposition, which is led to a plant (33, .., 38) for generating syngas by means of coal gasification, and that Syngaszuleitung (31) the generated syngas from the plant (33, .., 38) transported to the production of syngas to the combustion chambers.

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