WO2007017486A1

WO2007017486A1 - Method for operating a gas turbine, and gas turbine for carrying out the method

Info

Publication number: WO2007017486A1
Application number: PCT/EP2006/065103
Authority: WO
Inventors: Eribert Benz; Peter Flohr; Manfred Wirsum
Original assignee: Alstom Technology Ltd
Priority date: 2005-08-10
Filing date: 2006-08-07
Publication date: 2007-02-15
Also published as: DE112006001974B4; CA2618007C; CA2618007A1; JP2009504965A; DE112006001974A5

Abstract

The invention relates to a method for operating a gas turbine (11) in a combined-cycle power plant (40), in which method air is sucked in and compressed by the gas turbine (11), which air is fed to a combustion chamber (18, 19) for the combustion of a synthesis gas which is obtained from coal, wherein a part of the compressed air is decomposed into oxygen and nitrogen. An improved degree of efficiency is achieved by the use of a gas turbine (11) with reheating, which gas turbine (11) has two combustion chambers (18, 19) and two turbines (16, 17), wherein synthesis gas is burnt in the first combustion chamber (18) with use of the compressed air and the hot gases which are produced are expanded in the first turbine (16), and wherein synthesis gas is burnt in the second combustion chamber with use of the gases which come from the first turbine (16) and the hot gases which are produced are expanded in the second turbine (17), and wherein the nitrogen which is produced during the decomposition of the air is used to cool the gas turbine (11).

Description

DESCRIPTION

METHOD FOR OPERATING A GAS TURBINE AND GAS TURBINE FOR

IMPLEMENTATION OF THE PROCEDURE

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

A reheat gas turbine gas turbine is known (see eg US-A-5,577,378 or "State-of-the-art gas turbines - a letter update", ABB Review 02/1997, Fig. 15, turbine type GT26 ), which combines flexible operation with very low exhaust emissions.

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 with reduced oxygen excess values, and there is a secondary air system which allows air to escape from the air

Discharge 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 shown in Fig. 1. The gas turbine 11, which is part of a combined cycle power plant 10, comprises two compressors connected in series on a common shaft 15, namely a low-pressure compressor 13 and a high-pressure compressor 14, and two combustion chambers, namely a high-pressure combustion chamber 18 and a reheat combustion chamber 19, and associated turbines, namely one High pressure turbine 16 and a low pressure turbine 17. The shaft 15 drives a generator 12 at.

The operation of the system is the following: Air is sucked through a Luftein lass 20 from the low-pressure compressor 13 and first compressed to an intermediate pressure level (about 20 bar). The high pressure compressor 14 then further compresses the air 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 = Once Through Cooler) 23 and 24 and forwarded via cooling lines 25 and 26 for cooling to the combustion chambers 18, 19 and turbines 16, 17. The remaining air from the high-pressure compressor 14 is guided to the high-pressure combustion chamber 18 and fed there by combustion via the fuel supply 21 Fuel heated up. The resulting exhaust gas is then expanded in the subsequent high-pressure turbine 16 under work to an average pressure level. After expansion, the exhaust gas in the reheat combustor 19 is reheated by combustion of a fuel supplied via the fuel supply 22 before it is expanded in the subsequent low-pressure turbine 17 under further work.

The cooling air flowing through the cooling lines 25, 26 is injected at suitable locations of the combustion chambers 18, 19 and turbines 16, 17 to the

Limit material temperatures to a reasonable level. The exhaust gas coming from the low-pressure turbine 17 is passed through a heat recovery steam generator

27 (HRSG = JHeat Recovery Steam Generator) sent to generate steam that flows within a water-steam cycle through a steam turbine 29 and there performs more work. After flowing through the

Heat recovery steam generator 27, the exhaust gas finally 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 is achieved a great flexibility in operation; 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 one-stage combustion in the gas turbines are known (see eg US-A-4,785,622 or US-B2-6,513,317), in which a coal gasification plant is integrated in order to supply the gas required for the gas turbine in the form of syngas obtained from coal provide. Such combined cycle power plants are referred to as IGCC systems (IGCC = Integrated Gasification Combined Cycle).

The present invention is based on the recognition that the use of gas turbines with reheating in an IGCC plant, the advantages of this type of gas turbine for the system can be made useful 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 is characterized by improved efficiency and can be implemented particularly low with existing components, and to provide a gas turbine for performing the method.

The object is solved by the entirety of the features of claims 1 and 6. 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 used in gas turbines of known construction rate with reheating such. Due to the specific secondary air system, the type GT26 gas turbine can be realized particularly easily.

An embodiment of the inventive method is 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 particular, a portion of the branched off for the decomposition compressed air is diverted from the first compressor before the decomposition and with the at the

Disassembled resulting and intended for cooling nitrogen mixed.

Particularly favorable conditions arise when about 50% of the for

Disassembling branched compressed air from the first compressor before the

Diverting branched and mixed with the resulting during disassembly and intended for cooling nitrogen. The preferred in the

Decomposing resulting nitrogen prior to mixing with the compressed before the decomposition compressed compressed air.

An embodiment of 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 output the air separation plant and the predetermined point of the junction of the branch line a compressor for the compression of the nitrogen is arranged.

Preferably, the gas turbine on two compressors connected in series, the air separation plant is the input side to the output of the first

Compressor connected, and the nitrogen line is led to the second combustion chamber and the second turbine.

The air separation plant has in particular on the output side an oxygen line for discharging the oxygen produced during the separation, which is guided to a plant for the production of syngas by means of coal gasification, and that a Syngaszuleitung transported syngas generated by the plant for the production of syngas to the combustion chambers.

BRIEF EXPLANATION OF THE FIGURES

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

Fig. 1 shows the simplified diagram of a combined cycle power plant with a

Gas turbine with reheat or sequential

Combustion according to the prior art;

Figure 2 is a simplified schematic of an IGCC plant with a reheat gas turbine or sequential combustor suitable for practicing the invention; and

Fig. 3 shows an embodiment of the cooling according to the invention with the nitrogen obtained in the air separation in a plant of the type shown in Fig. 2. WAYS FOR CARRYING OUT THE INVENTION

FIG. 2 shows in a greatly simplified scheme an IGCC system with a reheat gas turbine or sequential combustion gas, as is suitable for realizing the invention. The combined cycle power plant 30 comprises 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 following

Low-pressure turbine 17. The compressor 13, 14 and the turbines 16, 17 sit on a common shaft 15, from which a generator 12 is driven. The combustion chambers 18 and 19 are supplied via a Syngaszuleitung 31 with syngas as fuel, which is produced by gasification of coal (coal feed 33) in a coal gasification plant 34. The coal gasification plant 34 is a cooling apparatus 35 for the syngas, a cleaning plant 36, and a CO ₂ - downstream separator 37 with a CO ₂ output 38 for discharging the separated CO _2.

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

For cooling the hot gas loaded components of the combustion chambers 18, 19 and turbines 16, 17 condensed cooling air is tapped at the outputs of the two compressors 13 and 14, cooled in a downstream OTC cooler 23 and 24, and then via corresponding cooling lines 25 and 26 fed to the bodies to be cooled. At the output of the low-pressure turbine 17, a heat recovery steam generator 27 is arranged, which is part of a water-steam cycle together with a connected steam turbine 29. The exiting from the heat recovery steam generator 27 exhaust gas is discharged via an exhaust pipe 28 to the outside.

In such a system configuration, the cooling is now switched according to FIG. 3. In the combined cycle power plant 40 of FIG. 3, the high-pressure combustion chamber 18 and the high-pressure turbine 16 are still cooled by compressed air, which is branched off at the outlet of the high-pressure compressor 14 and then cooled down in an OTC cooler 24. However, the cooling of the reheat combustion chamber 19 and the low-pressure turbine 17 now takes place in other ways. For this purpose, at the output of the low-pressure compressor 13 branched compressed air is decomposed to 50% in the air separation plant 32 in oxygen and nitrogen. The other 50% are passed in a branch line 39 to the air separation plant 32. The oxygen discharged via the oxygen line 32a from the air separation plant 32 is used - as shown in FIG. 2 - for coal gasification. The generated, relatively cool nitrogen is supplied through the nitrogen line 32 b to a compressor 41 and mixed after compression with the 50% air from the branch line 39. The gas temperature after mixing is then about 300-400 ⁰ C, so that a cooling of the extracted at the low-pressure compressor 13 cooling air is not necessary. The resulting mixture is then used to cool the hot components of reheat combustor 19 and low pressure turbine 17.

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

Cooling critical components are used while the warmer air from the compressor is used to cool less critical components can be used; This also improves the efficiency of the 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 the combustion of such undiluted coal gas in the combustion chamber of a gas turbine are:

- the achievement of low emission levels,

- a sufficient distance to the limits of flashbacks and pulsations,

- Maintaining 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 tapping and feeding of cooling air in the areas of the hot gas channel in the combustion chamber and in the turbine.

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

1. The inherent in the reheat advantage over 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. 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 determined by the Flame extinction and the flashback and / or emission levels given for a given flame temperature, resulting in a permitted 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 first stage temperature and second stage higher temperature, with minor disadvantages with respect to NOx. 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. 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.

LIST OF REFERENCE NUMBERS

10,30,40 combined cycle power plant

11 gas turbine

12 generator

13 low-pressure compressor

14 high pressure compressor

15 shaft (gas turbine)

16 high-pressure turbine

17 low-pressure turbine

18 high pressure combustion chamber

19 reheat combustion chamber

20 air intake

21, 22 Fuel supply

23.24 OTC cooler

25.26 cooling line

27 heat recovery steam generator

28 exhaust pipe

29 steam turbine (steam cycle)

31 Syngas supply line

32 air separation plant

32a oxygen line

32b nitrogen line

33 coal feed

34 coal gasification plant

35 cooling device

36 cleaning system

37 CO ₂ separator

38 CO ₂ exit

39 branch line

41 compressors

Claims

1. A method for operating a gas turbine (11), which in particular in a combined cycle power plant (30, 40) is used, in which process by the gas turbine (11) air is sucked and compressed, the compressed air for combustion of a syngas obtained from coal one Combustion chamber (18, 19) is supplied, and the hot gases resulting from the combustion in a subsequent turbine (16, 17) are relaxed by performing work, wherein a portion of the compressed air is decomposed into oxygen and nitrogen, and the oxygen in a coal gasification plant (34) is used to generate the syngas, and wherein a portion of the compressed air is used for cooling the hot gases loaded parts of the gas turbine (11), characterized in that

- A gas turbine (11) is used with reheat, which comprises two combustion chambers (18, 19) and two turbines (16, 17), wherein combusted in the first combustion chamber (18) syngas using the compressed air and the resulting hot gases in the first turbine (16) are relaxed, and wherein in the second combustion chamber under Syngas

Using the gases coming from the first turbine (16) burned and the resulting hot gases in the second turbine (17) are relaxed, and

- The resulting nitrogen in the air separation is used to cool the gas turbine (11).

2. The method according to claim 1, characterized in that the gas turbine (11) has a first compressor (13) for compressing sucked air to a first pressure stage and a second compressor (14) for further compression of the air from the first pressure stage to a second , Higher pressure level comprises part of the air coming out of the first compressor (13) being decomposed into oxygen and nitrogen, and the nitrogen resulting from this decomposition being used to cool the second combustion chamber (18) and second turbine (17).

3. The method according to claim 2, characterized in that a part of the branched off for the decomposition compressed air from the first compressor (13) branched off before the decomposition and mixed with the resulting during the decomposition and intended for cooling nitrogen.

4. The method according to claim, characterized in that about 50% of the branched for the decomposition compressed air from the first compressor (13) branched off before the decomposition and mixed with the resulting during the decomposition and intended for cooling nitrogen.

5. The method according to claim 3 or 4, characterized in that the nitrogen produced during the decomposition is compressed prior to mixing with the branched prior to the decomposition of compressed air.

6. Gas turbine (11) for carrying out the method according to claim 1, which gas turbine (11) is designed as a gas turbine with reheat and compressor (13, 14) for the compression of sucked 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 are expanded in the first turbine (16), and wherein in the second combustion chamber, the fuel using the first Turbine (16) combusted incoming gases and the resulting hot gases in the second turbine (17) are relaxed, characterized in that an air separation plant (32) is provided which is connected on the input side to the compressors (13, 14) and on the output side has a nitrogen line (32b) for discharging the nitrogen produced during the decomposition, and in that the nitrogen line (32b) is replaced by the hot gases loaded parts of the gas turbine (11) is in communication.

7. Gas turbine according to claim 6, characterized in that a branch line (39) is provided, which branches off from the input side of the air separation plant (32) and opens at a designated point in the nitrogen line (32b).

8. Gas turbine according to claim 7, 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.

9. Gas turbine according to one of claims 6 to 8, characterized in that the gas turbine (11) has two compressors (13, 14) connected in series, the air separation plant (32) on the input side to the output of the first compressor (13) is connected, and the nitrogen line (32b) is guided to the second combustion chamber (18) and to the second turbine (17).

10. Gas turbine according to one of claims 6 to 9, characterized in that the air separation plant (32) on the output side an oxygen line (32 a) for discharging the resulting in the decomposition

Oxygen, which is led to a plant (33, .., 38) for generating syngas by means of coal gasification, and that a Syngaszuleitung (31) the syngas generated by the plant (33, .., 38) for generating syngas to transported to the combustion chambers.