EP2449228A2

EP2449228A2 - Method for operating a power plant using a gas turbine system

Info

Publication number: EP2449228A2
Application number: EP10739498A
Authority: EP
Inventors: Horst Meyrahn
Original assignee: RWE Power AG
Current assignee: RWE Power AG
Priority date: 2009-07-03
Filing date: 2010-07-02
Publication date: 2012-05-09
Also published as: WO2011000548A3; WO2011000548A2; DE102009031843A1

Abstract

The invention relates to a method for operating a power plant using a gas turbine system (1), comprising at least one compressor section (2), a combustion chamber (3), and at least one turbine (4), wherein the gas fed to the combustion chamber is drawn from a gas network, and the gas drawn from the gas network is decompressed to the pressure level required for the gas turbine and is pre-heated, wherein the pre-heating is accomplished by means of a cold shift from the combustion gas to the combustion air.

Description

Method for operating a power plant with a gas turbine plant

The invention relates to a method for operating a power plant with a gas turbine plant, comprising at least one compressor part, a combustion chamber and at least one turbine, wherein the gas supplied to the combustion chamber is taken from a gas network.

Such a method is known for example from DE 100 33 052 A1. In the method known from DE 100 33 052 A1, the most flexible way of driving the gas turbine in a wide load range above and below the nominal load is sought with high efficiency. this will

in particular achieved in that the intake air of the gas turbine passes through a heat transfer stage, while the intake air is either supplied heat or withdrawn heat in dependence on the power output of the gas turbine plant heat. With increasing power output cooling of the intake air, with decreasing power output, their heating.

The energy required for the heating, for example in the form of

Provided low pressure steam from a coupled steam turbine cycle. For cooling, a cooling medium is used, for example cold water or a refrigerant which extracts heat by evaporation of its environment.

The method described in DE 100 33 052 A1 is based on the finding that the output of a gas turbine plant directly from

Mass flow of the supplied working fluid and indirectly depends on the temperature of the intake air. With the method, a regulation of the power output of the gas turbine should be possible within certain limits.

In particular, the proposed in DE 100 33 052 A1 cooling the

Although intake air leads to an increase in performance of the gas turbine. However, this is not particularly advantageous if there are insufficient cooling potentials and temperature sinks must be generated by evaporation of a cooling medium. The invention is therefore based on the object to improve a method of the type mentioned in terms of a performance increase of the gas turbine. The object is first achieved by a method for operating a

Power plant with a gas turbine plant comprising at least one compressor part, a combustion chamber and at least one turbine, wherein the gas supplied to the combustion chamber is taken from a gas network, wherein the method is characterized in that the withdrawn gas from the gas first relaxes to the pressure required for the gas turbine pressure level and then preheated, the preheating at least partially by means of a

Cold shift is accomplished by the fuel gas to the combustion air. In a preferred variant of the method according to the invention, the temperature sink arising during the expansion of the fuel gas is at least partially used for conditioning the combustion air for the gas turbine.

That the efficiency of the gas turbine depends among other things on the

Temperature of the combustion air is, as far as well known,

for example, from DE 100 33 052 A1 and from numerous other publications. The colder the combustion air, the higher the

Efficiency, because cold air is known to have a higher density than warm air.

From an existing gas network, the fuel gas is usually referred to with a much higher pressure and a lower temperature than is required for the operation of the gas turbine. The operating pressure of a conventional gas pipeline can be up to 80 bar, whereas the pressure required for the gas turbine pressure level is about 25 bar. The temperature of the fuel gas supplied to the gas turbine should be about 25 ⁰ C, the temperature level of the natural gas provided in the natural gas pipeline is usually less than 25 ° C. The extracted from the pipeline natural gas / fuel gas is therefore usually first subjected to a gas preheating and then relaxed. The temperature level in the gas preheating is usually chosen so that the fuel gas after relaxation has the temperature level required for the gas turbine. The energy generated during gas expansion is converted into mechanical work and used, for example, for driving a generator.

When gas expansion via a throttle valve, the gas contained in the

Compression energy not used. Is the gas expansion in one

Gasentspannungsmaschine, for example, in a turboexpander or a gas expansion engine, the compression energy of the gas is converted into mechanical work and used for example for driving a generator. However, the cold created by the relaxation of the gas (Joule-Thomson-Effect) is not used in both cases, on the contrary, the natural gas is heated by preheating the gas by heating fossil fuels

reheated so that the gas after cooling by the relaxation reached the temperature required for entry into the gas turbine temperature level.

The invention uses the resulting in the relaxation of the gas

Temperature sink in two ways, on the one hand the thermodynamic effect is used as such energetically, i. the generated cold is used, on the other hand, the cold is used to increase the performance of the gas turbine.

According to the invention, therefore, preferably first a relaxation of the natural gas, then an increase in the temperature level, for example by means of a suitable heat exchanger and then the usual

Gas preheating.

Alternatively, initially only a partial gas preheating be carried out, wherein after the cooling of the gas during the relaxation, for example, in a

Gas relaxation machine, however, a temperature level is reached is lower than the temperature required for entry into the gas turbine. The further increase in the temperature level then takes place, for example, by means of a suitable heat exchanger. This resulting cold is also transferred from the fuel gas to the combustion air.

This approach is particularly advantageous when an existing power plant (with existing throttle valve for gas relaxation) with gas relaxation machines for the purpose of gas relaxation and use of the compression energy contained in the gas is retrofitted. The often existing in practice problem is solved that the warm-up capacity of the existing gas preheating is not sufficient to ensure the required for the entry of the fuel gas into the gas turbine high temperature level.

In an advantageous variant of the invention it is provided that the

Combustion air is cooled directly in at least one heat exchanger by means of the expanded fuel gas.

Alternatively, the combustion air, the heat by means of a heat transfer medium can be withdrawn, which in turn gives up the combustion air extracted heat the fuel gas.

Suitable heat transfer media are, for example, thermal oil or water or glycol or water-glycol mixtures or methanol. The combustion air of the gas turbine can be sucked in, for example, by a heat exchanger through which a heat transfer medium or cold fuel gas flows.

As a heat exchanger, for example, a fin heat exchanger can be provided, which is connected upstream of the intake manifold of the compressor.

Alternatively, the already compacted and at least partially heated

Combustion air over at least one with cooled fuel gas

be acted upon heat exchanger. A cold shift from the fuel gas to the combustion air can take place by means of a plurality of heat exchangers connected in series, in which heat exchangers an immediate heat transfer from the cold fuel gas to the combustion air can take place. Of course, there is one too

Parallel connection or combinations of series and parallel circuits of heat exchangers in the invention.

Alternatively, such a heat transfer can take place by means of a heat transfer medium, for which purpose possibly twice the number of heat exchangers is required.

The resulting in the relaxation of the fuel gas cold can be used in an advantageous manner in addition to the removal of heat of condensation from a coupled steam turbine process.

Preferably, the expansion of the fuel gas by means of at least one Gasentspannungsmaschine under additional use of mechanical energy. Advantageous variants of the method according to the invention will be explained with reference to three embodiments with reference to the accompanying drawings.

Show it:

Figures 1 and 2 first variants of the method according to the invention, in which a direct cooling of the already compressed and partially heated combustion air of the gas turbine takes place in several heat exchangers,

Figure 3 shows an alternative embodiment of the method according to the

Invention in which a cooling of the already compressed and partially heated combustion air of the gas turbine by means of a heat transfer medium takes place, and

Figure 4 shows a variant of the method according to the invention, in

which a cooling of sucked by the gas turbine

Combustion air by means of a heat transfer medium acted upon heat exchanger takes place.

The gas turbine 1 shown in the figures comprises in a known manner a compressor part 2, a combustion chamber 3 and a turbine 4. In the compressor part 2, ambient air is sucked in as combustion air 11, compressed and partially heated. The compressed heated combustion air 11 is mixed in the combustion chamber 3 with natural gas from a natural gas line 5 and burned; in the downstream turbine 4, the gas mixture is expanded, releasing mechanical work, which is used to generate electricity. The natural gas is provided for example from a natural gas pipeline, not shown, with a pressure of about 80 bar and a temperature of between 10 and 14 ° C. In an expansion stage 6, the natural gas is first expanded to a pressure of 25 bar, wherein at an inlet temperature of 14 ° C and an inlet pressure of about 80 bar behind the expansion stage at a pressure of 25 bar, a temperature of about -31 ^C C is established ,

In the variant of the method shown in FIG. 1, the fuel gas removed from the natural gas line 5 is first preheated by means of series-connected heat exchangers 7, for example to a temperature of approximately 200.degree. The heat required for this purpose is partially or completely decoupled from the combustion air behind the compressor 2. In the heat exchangers 7, the heat load of the combustion air in countercurrent to

Fuel gas / natural gas abandoned. Downstream of the gas preheating is an expansion stage 6.

In the expansion stage 6, one or more gas relaxation machines, for example in the form of turboexpanders, can be provided for expansion of the natural gas. In Gasentspannungsmaschinen the relaxation of the Gas usually performing mechanical work that can be absorbed by a compressor, a generator or a liquid brake. When the heat of the combustion air is transferred to the fuel gas before entering the expansion stage 6, the heating efficiency of the fuel gas, the current yield is approximately in the expansion stage provided

Gas expansion engine still increased. After cooling of the fuel gas in the expansion stage, the fuel gas is still significantly heated (> 25 ° C), so that one of the expansion stage downstream gas preheating can be dispensed with.

In the variant of the method shown in FIG. 1, the expansion stage 6 is followed by three heat exchangers 7 connected in series. In the

Heat exchangers 7, the fuel gas / natural gas with heat from the

Combustion air of the gas turbine 1 is gradually charged in countercurrent, as will be explained below. By means of the heat exchanger 7, the

Temperature of the fuel gas to be raised to about 10 ⁰ C. In the

Downstream gas preheating 8, the temperature of the fuel gas is then raised to 35 ° C.

The gas preheating can, for example, in a GUD process, if necessary, be operated with condensation heat from the feedwater circuit of the steam generator.

In the embodiment shown in Figure 2, a Teii the already compressed and preheated combustion air is branched off behind the compressor 2 via a bypass line 9 and passed through the heat exchanger 7, their

Heat load in countercurrent give the fuel gas / natural gas. The temperature of the branched off via the bypass line combustion air flow can be up to 400 ⁰ C. The heat transfer in the heat exchangers 7 takes place in the example shown in Figure 1 directly over the pipe walls. For example, the heat exchanger 7 may be formed as a tube bundle heat exchanger. The illustrated in Figure 3 embodiment of the method according to the invention differs only in so far from the embodiment shown in Figure 1, as the total of six heat exchangers 7 are provided, of which three are connected in series. Here, the heat transfer via a heat transfer medium, which takes place in between the

Expansion stage 6 and the gas preheating 8 provided first

Heat exchangers 7 a is cooled and in three second heat exchangers 7 b, which are connected to the gas turbine 1, is loaded via the branched off from the combustion chamber 3 combustion air with heat.

In the exemplary embodiment illustrated in FIG. 4, a first heat exchanger 7a is arranged between the expansion stage 6 and the gas preheating 8, a second heat exchanger 7b coupled thereto is connected upstream of the combustion air inlet 10 of the compressor 2. The first heat exchanger 7a and the second heat exchanger 7b communicate with each other via a heat exchange medium, for example via a methanol cycle. The second heat exchanger 7b may be formed, for example, as air-flowed finned heat exchanger. With an appropriate design of the heat exchanger 7b, for example, combustion air can be cooled at about 20 ⁰ C to a temperature of 15.4 ° C, which corresponds to a ΔT of 4.6 K. The achieved performance increase of the gas turbine is about 1, 2% of the full load to a temperature difference of 1 Kelvin.

LIST OF REFERENCE NUMBERS

1 gas turbine

2 compressors

3 combustion chamber

4 turbine

5 natural gas pipeline

6 expansion level

7a, b heat exchanger

8 gas preheating

9 bypass line

10 combustion air intake

11 combustion air

Claims

claims

1. A method for operating a power plant with a gas turbine plant, comprising at least one compressor part, a combustion chamber and at least one turbine, wherein the combustion chamber supplied gas is taken from a gas network, characterized in that the gas taken from the gas network to the gas required for the gas turbine Pressure level is relaxed and preheated, wherein the preheating is accomplished at least partially by means of cold shift of the fuel gas to the combustion air.

2. The method according to claim 1, characterized in that the resulting during the expansion of the fuel gas temperature sink is at least partially used to condition the combustion air for the gas turbine.

3. The method of claim 1 or 2, characterized in that the gas taken from the gas network is first expanded to the pressure required for the gas turbine pressure level and then preheated.

4. The method according to any one of claims 1 to 3, characterized in that the combustion air directly in at least one

Heat exchanger is cooled by means of the expanded fuel gas.

5. The method according to claim 1 to 4, characterized in that the

Combustion air, the heat is removed by means of a heat transfer medium, which in turn gives up the combustion air extracted heat the fuel gas.

6. The method according to claim 5, characterized in that as

Heat transfer medium thermal oil or water or glycol or water-glycol mixtures or methanol application find.

7. The method according to any one of claims 1 to 6, characterized in that the combustion air is sucked in by a heat transfer medium flowed through by a heat transfer medium or by cold combustion gas.

8. The method according to claim 7, characterized in that as

Heat exchanger at least one fin heat exchanger application is.

9. The method according to any one of claims 1 to 6, characterized in that already compressed and at least partially heated

Combustion air is passed through at least one acted upon with cooled or cold fuel gas heat exchanger.

10. The method according to any one of claims 1 to 9, characterized in that a cold shift from the fuel gas to the combustion air by means of several series-connected heat exchanger.

11. The method according to any one of claims 1 to 10, characterized in that in the expansion of the fuel gas resulting cold in addition to the removal of heat of condensation from a coupled

Steam turbine process is used.

12. The method according to any one of claims 1 to 11, characterized in that the relaxation of the fuel gas by means of at least one

Gas relaxation machine with additional use of mechanical

Energy takes place.