WO2014095237A1

WO2014095237A1 - Method for operating a gas turbine

Info

Publication number: WO2014095237A1
Application number: PCT/EP2013/074583
Authority: WO
Inventors: Tjark Eisfeld; Rafael Reckert; Marc Schäfer
Original assignee: Siemens Aktiengesellschaft
Priority date: 2012-12-20
Filing date: 2013-11-25
Publication date: 2014-06-26
Also published as: DE102012224009A1

Abstract

The invention relates to a method for operating a gas turbine (10) which, upstream of the inlet of the compressor (12), has a device for cooling the air that can be drawn in by the compressor (12). To prevent step changes in the output gas turbine power (P) in frequency backup operation and in load following mode, in order thereby to be able to adjust to any power point of the gas turbine (10), it is provided that the gas turbine (10) is operated at part load and the drawn-in air is simultaneously cooled. In this way, the output gas turbine power (P) is increased again, but the gas turbine is then operated with a fuel mass flow rate (m_B) lower than the fuel mass flow rate (m_B) that would be required to impart the power (P) in operation without cooling. The particular advantage of the invention lies in the fact that, accordingly, the output power (P) of the gas turbine (10) can be adapted in continuously variable fashion by virtue of either the temperature of the drawn-in air being lowered in continuously variable fashion and/or the flow rate of fuel supplied to the combustion chamber being increased or decreased in continuously variable fashion.

Description

description

Method for operating a gas turbine

The invention relates to a method for operating a gas turbine, which upstream of the inlet of the compressor has a Vor ^¬ direction for cooling the air sucked by the compressor, comprising the steps of: intake of ambient air, compaction of the intake air in the compressor, supplying

Fuel to the compressed air and combustion of the fuel-air mixture in at least one combustion chamber to a hot gas and expanding hot gas in a turbine, wherein the output power of the gas turbine is smaller than their rated power.

It is commonly known that stationary gas turbines and steam turbines are used for generating electrical energy. During operation, the gas turbine drives an electric generator, which converts the mechanical energy into electrical energy. The electrical energy thus generated is fed into a power distribution network, which usually has a nominal mains frequency of 50Hz or 60Hz. In accordance with national requirements, which are also widely known as grid codes, the network operators of such networks are obliged to keep the grid frequency as stable as possible. However, the actual network frequency depends on the load currently being polled. For example, an excessive electrical load in the power distribution network can cause its power frequency to drop. In this case, increase the power to be supplied by the power plants to compensate for the grid frequency drop.

In order to support the mains frequency, a distinction is made between different operating modes. In a primary frequency backup operation, power plants operating thereafter must be able to rapidly change their power output to limit the change in grid frequency. For this purpose, a control system monitors the Mains frequency and reacts too large deviations from the nominal frequency directly with an adjustment of the delivered

Power plant performance, which is referred to as primary control. If too much frequency drop the output power of the power station is quickly increased and decreased at too great Fri ^¬ quenzanstieg. Here is the slope

APsoii = f (An) with

ΔΡ _3ο ιι = required change in capacity and

Δη = frequency deviation

usually set in the national grid code.

A second operation mode for frequency support is the secondary frequency support operation. The task of the power plant is then to return the current frequency to its setpoint. Once the secondary control is activated and with the adjusted power the frequency error is reduced, the primary control will decrease the power. This will free them again for the next use. If it is foreseeable that the secondary control power would have to be active for a longer period of time, a minute reserve (also tertiary frequency control or tertiary frequency support) can be activated manually, whereby the power from the secondary control automatically decreases.

Power plant operators who operate their power plant in a frequency support mode will receive additional compensation, as the operator will in principle have to accept some disadvantages. On the one hand, the power plant has to be operated at partial load, so that it is capable of infinitely increasing its output power in the event of a drop in frequency - thus providing a reserve of energy. The power reserve may be 10% of the nominal load of the power plant, so that the operator must operate his power plant in the frequency support mode at a partial load of 90% and less. On the other hand, the power plant produ ^¬ decorates the lower output even at a lower efficiency, since the partial-load efficiency is always lower than the efficiency at rated load. In order to be able to retrieve such power reserves quickly, it is known from EP 1 507 078 A1 to use the wet compression for frequency support. The water injection is then activated only when the frequency support event occurs, which, however, can lead to a jump in rated load operation or to drop sizes that are above a maximum permissible value. Both effects are undesirable. The object of the present invention is therefore to provide a method for operating a gas turbine, in which the aforementioned disadvantages are avoided.

The problem underlying the invention is achieved by a method according to the features of claim 1. Advantageous developments of the method are specified in the dependent claims, whose features can be combined with each other in any desired manner. According to the invention it is provided that although the gas turbine outputs a power that is smaller than their rated power, the cooling of the intake air is activated and maintained ^¬ th. Preferably, the cooling of the intake air is effected by the addition of a liquid in the angesaug ^¬ th compressor from the air stream, whereby its temperature cools. The supplied amount of liquid - mostly deionized - is so large that its drops are not larger than a maximum allowable size. This ensures that all the droplets evaporate be ^¬ mood mutandis. If all droplets evaporate before entering the compressor, this is usually referred to as EVAP cooling. However, if drops also evaporate within the compressor, this is called a wet compression, which is also known in English as "wet compression". The addition of the liquid takes place via nozzles, which are arranged in the intake channel of the gas turbine ^¬ on a liquid-conducting pipe ^¬ grid. In order for the injection of the liquid If the maximum permissible droplet size is always exceeded, each nozzle must eject a minimum mass flow. Since most of these nozzles are not individually controllable, but only all at the same time or in a few groups, accordingly a total of a larger amount of liquid in the activation of the system is suddenly injected. In nominal ^¬ load operation, this leads to a jump in the output power at the start of water injection. However, such power jumps are inadmissible in the frequency support mode, and in particular in the secondary frequency support and in the load following operation, which is why the invention proposes, before the activation of the frequency support mode or

Lastfolge operation to first lower the output power of the gas turbine to a value below the

Nominal load and on the other then to start with the cooling of the intake air as explained and at least temporarily maintain. In principle, the

Gas turbine again more power than after

Initial lowering can provide, however, this can

Capacity increase can be compensated by the closing of the inlet guide vanes. In this operating state is the

Fuel mass flow then lower than during operation without cooling the intake compressor air or during operation without Flüssigkeitsseindüsung. Only then the corresponding operating mode - frequency support or load following operation - is activated. Starting from this starting operating point, the gas turbine is then able to steplessly each other

Achieve power above and below the starting operating point, without any performance leaps occur, by switching on the cooling of the intake air

be caused. At the same time it is achieved that when using EVAP cooling and "wet compression" to cool the intake air always such a large amount of liquid is supplied to the individual nozzles that generate drops that are smaller than the maximum allowable droplet size Reliable cooling of the intake air can be ensured without due to large drops adverse effects such as drop erosion occur in the compressor.

When the gas turbine is operated in the state according to the invention, the fuel mass flow can be lowered to reduce the power. Preferably, the fuel mass flow is first increased to increase performance until the maximum allowable value is reached. For any Leis ^¬ processing requirements preferably it is possible to increase the amount of liquid up to 100%. If, when lowering the power output, the adjustable inlet guide vanes have reduced the opening area of the compressor inlet to the lowest value, the fluid injection is switched off and the opening degree of the inlet guide vanes is increased again to avoid jumps in performance. As long as the gas turbine is then in the intake air-cooled partial load operation, the intake air cooling can be reactivated without a jump in performance.

Thus, a method is provided ^¬ propose to operate a gas turbine, which makes it possible to operate simultaneously with small droplet diameters in spite of an activation of the cooling of the inducted compressor air, the gas turbine with stepless adjustment of the output power. Another advantage is that the rapidly available power range of the gas turbine can be extended so.

The invention is of particular advantage when a liquid is added for cooling the sucked air, wherein the device for adding the liquid preferably comprises only one stage. In this case, one stage means that all nozzles arranged in the intake duct for supplying the liquid can be activated via a single control valve. Thus, there is only one group of nozzles that are simultaneously be ^¬ exaggerated. If there are two or more groups of nozzles that can be operated independently of one another, the injection unit has a corresponding number of stages. Further advantages and features of the invention are given in an exemplary embodiment which describes the invention in a purely schematic and not restrictive way. Show it :

Figure 1 shows the schematic structure of a gas turbine and

Figure 2 is a diagram in which the position of the inlet guide vanes of the compressor, the output Gasturbi ^¬ nenleistung and the amount of the compressor air to ^¬ led liquid is carried over the time each ^¬ . Figure 1 shows schematically a stationary gas turbine 10 with a compressor 12 and a turbine unit 14, the rotors are rigidly coupled together. Between the compressor outlet and the inlet section of the turbine unit 14, a combustion chamber 16 is provided. This can be designed as a silo separation chamber, tube combustion chamber or as an annular combustion chamber. In the case of tube combustion chambers usually ten, twelve or more tube combustion chambers are provided. At the compressor rotor also a generator 11 is coupled to generate electricity. At the air inlet of the compressor 12 are at their

Longitudinal axis pivotable inlet guide vanes 13 are provided, with which the compressor mass flow m _{v is} adjustable. The pivotable inlet guide vanes 13 are shown only schematically. The turbine unit 14 includes according to the embodiment, four consecutive turbine stages 14 _a , 14 _b , 14 _c and 14 _d , which are also only schematically Darge ^¬ represents.

In the flow path of the sucked in by the compressor 12 ambient air also equipped with a nozzle 15 pipe grille 17 is provided as a device 9 for cooling the air, which is mounted behind not shown air filters of the gas turbine 10. The pipe grid 17 is via a supply line, a liquid M, usually water or deionized, with high Pressure supplied, the amount of which is adjustable via a control valve 19. The nozzles 15 atomize the liquid, which is entrained by the sucked air. Meanwhile, the drops evaporate at least partially and thus cool the intake air. With the aid of the device 9, on the one hand, the temperature of the gas turbine intake air can be reduced if necessary and, on the other hand, the compressor mass flow m _{v can be} increased.

In operation, the compressor 12 draws in ambient air, compresses it and supplies it to the combustion chamber 16. There, the compressed air is mixed with a fuel B and burned in a flame to a hot gas HG. The hot gas HG flows into the inlet of the turbine unit 14 and relaxes work on the turbine blades of the turbine unit 14, not shown further. The resulting exhaust gas RG flows at the outlet of the turbine unit 14 via an exhaust gas diffuser, not shown. Thereafter, the exhaust gas RG is discharged either via a chimney into the environment or the exhaust gas RG is used in a so-called boiler, which is known as a heat recovery steam generator, for generating steam. The steam generated in the heat recovery steam generator is then used to drive steam turbines, not shown, or as process steam. With the aid of the fuel mass flow m _B and the compressor mass flow m _v , the power to be provided by the gas turbine 10 can be adjusted.

Provided that the dispensed from the gas turbine 10 output is to be gestei ^¬ Gert, the device 9 is activated. For this purpose, a liquid M is ejected via the nozzles 15. So that when injecting the liquid M drops arise whose diameter does not exceed a maximum diameter, each nozzle 15, if they are to inject the liquid M, fed a minimum amount. In this respect, the amount of liquid M that can be supplied to each nozzle 15 is infinitely variable only between the minimum quantity and the maximum quantity. By injecting the liquid M on the one hand, the sucked air is cooled before it enters the compressor 12, whereby the Compressor mass flow m _v increases. On the other hand, the mass flow increases. Both have a performance-enhancing effect on the gas turbine 10. The diagram of Figure 2 shows the from the gas turbine 10 from ^¬ given power P or to be provided by the gas turbine 10 power Psoii in%, the opening degree of IGV of the pivot ^¬ cash inlet guide vanes 13 of the compressor 10 in% and the relative mass flow of a liquid M each over time t.

Until the time to the gas turbine is operated in the usual manner in the prior art driving. The output gas turbine power P is meanwhile dependent on the ambient conditions, the amount of air flowing into the compressor 12 and the fuel quantity m _B supplied to the combustion chamber 16.

A first (black) dotted illustrated characteristic curve 20 indicates the power required by the grid code Psoii in percent. A second (red) dashed line characteristic 24 indicates the opening degree IGV of the variable inlet ^{guide ¬} blades 13, wherein the value of 100% represents the maximum opening degree. A third in full line ^{dargestell ¬} te characteristic curve 22 (blue) indicates that amount of liquid m _M , which is added to the intake passage of the compressor 12 for cooling the sucked compressor air.

Starting from a ansaugluftungekühlten operation proceeds in the inventive concept, the gas turbine 10 includes an operating point below the nominal load on, whereby the energy given Leis ^¬ tung P is regulated by a power regulator and the exhaust temperature by a temperature controller. The power controller regulates the fuel mass flow m _B and the temperature controller the compressor mass flow m _v via the adjustable inlet guide vanes 13. Then, at the time to a minimum mass flow m ^ in liquid M to the nozzles 15 led to ^¬ , after which at least the minimum liquid amount m ^ in the sucked air is added. A release to activate the frequency support mode takes place when despite the injection of the liquid M, the adjustable inlet guide vanes 13 can still be operated in the allowable adjustment. This check is expedient because the injection of the liquid M decreases the compressor inlet temperature, which is why the adjustable inlet guide vanes 13 should still be closed further.

Under certain circumstances, the adjustable inlet guide vanes 13 have to be closed in a pilot-operated manner. Subsequently, the output power P of the gas turbine 10 can be controlled via the fuel mass flow m _B for frequency support or in the load following operation, the amount of liquid m _M initially remains constant. The position of the adjustable blades 13 is then ^¬ Einlassleit gas temperature adapted for setting a predetermined exhaust. This type of power increase occurs until the variable inlet guide vanes 13 have reached their maximum position IGV (100%). Only then is the injected amount of liquid increased to further increase the output gas turbine power P. When reducing the power, first of all the liquid quantity m _{M is} reduced until the minimum liquid quantity m 1 is reached. Subsequently, the _B m abge ^¬ added gas turbine power P reduced over the amount of fuel and the liquid amount ^¬ m _M kept at a minimum liquid amount in m ^. By controlling to a constant temperature, the exhaust gas A ^¬ let shovel shut down according to 13. Upon reaching the minimum opening degree IGV for the liquid injection operation, the liquid injection is switched off and at the same time the degree of opening IGV the

Inlet guide vanes 13 enlarged again to

To avoid performance leaps.

The invention has been explained in more detail by means of an EVAP or by means of a wet-compression device. However, these embodiments are merely exemplary. The invention can also be used in devices for cooling the mass flow drawn by the compressor, which work according to other principles of action. Overall, the invention is for each Applicable cooling device in which a temperature jump occurs with activation of the cooling system.

The invention relates to a method for operating a gas turbine 10, the upstream of the inlet of the compressor 12, a device for cooling the air sucked from the compressor 12, comprising. In order to avoid cracks in the dispensed gas turbine Leis ^¬ tung P in frequency stabilization operation and the load-following operation, so as each power point of the gas turbine to be able to approach 10, it is provided that the gas ^¬ turbine 10 is operated at ansaugluftungekühlter partial load, and then - still before the gas turbine reaches an intake air-cooled nominal load - the sucked air is cooled down. This raises the output gas turbine power P though again, but the gas turbine is then with a

Fuel mass flow m _B operated, which is smaller than the fuel mass flow m _B , which would be required in non-cooled mode to provide the same power P. The particular advantage of the invention is that then the output power P of the gas turbine 10 can be adjusted stu ^¬ fenlos by either the temperature of the intake air is continuously lowered and / or the combustion chamber supplied amount of fuel continuously he ^¬ increases or decreases becomes.

Claims

claims

A method of operating a gas turbine (10), the

upstream of the inlet of the compressor (12) has a Vor ^¬ direction (9) for cooling the air sucked from the compressor (12),

with the steps:

Intake of ambient air, compression of the intake air in the compressor (12), supply of fuel

(B) compressed air, combusting the fuel-air mixture in at least one combustion chamber (16) into a hot gas and expanding the hot gas in a turbine (14),

wherein the output power (P) of the gas turbine (10) is smaller than the rated load,

characterized by the step

that the sucked air is cooled.

2. The method according to claim 1,

in which the gas turbine (10) is operated in the frequency support mode.

3. The method according to claim 2,

in which the frequency support mode includes the secondary Fre ^¬ quenzstützung.

4. The method according to claim 1, 2 or 3,

in which for the cooling of the sucked air of these a liquid (M) is added.

5. The method according to claim 4,

in which a minimum amount (mMMin) of liquid (M) is added without a frequency-sustaining power output. Method according to claim 5,

wherein the minimum amount (mMMin) 50% of the maximum amount of liquid cash zugeb ^¬ an addition device, or the minimum amount (mMMin) is 50% of the maximum zugebbaren flues ^¬ sigkeitsmenge a portion of an addition device.

Method according to claim 3, 4, 5 or 6,

wherein a ge during the frequency support operation ^¬ demanded increase in emitted gas turbine power (P) by further lowering the temperature of the compressor inflow (12) air and / or by increasing the sucked air amount is achieved.