EP1320665B1 - Method for operating a gas and steam turbine system and a corresponding system - Google Patents

Abstract

The invention relates to a method for operating a gas and steam turbine system (1), comprising a gas turbine (2) that can be operated using both gas and oil. According to said method, during an operational changeover from gas to oil, in order to preheat the condensate, a partial stream (tS) of heated feed water (S') is injected into the cold condensate (K). To this end, the system (1) comprises a mixing device (44,46), in which at least one spray head (105) that is connected to a hot water conduit (101) for supplying the partial stream (tS) is located.

Description

The invention relates to a method of operation a gas and steam turbine plant, in which the one from both with gas as well as oil operable gas turbine exiting Flue gas is passed through a heat recovery steam generator, its heating surfaces in the water-steam cycle of a Number of pressure stages having steam turbine connected are, wherein in the heat recovery steam generator preheated condensate as compared to this under high pressure feed water heated and fed as steam to the steam turbine becomes.

In a gas and steam turbine plant is in the relaxed Working fluid or flue gas contained in the gas turbine Heat for generating steam for in a water-steam cycle switched steam turbine used. The heat transfer takes place in one of the gas turbine downstream Heat recovery steam generator or boiler, in which heating surfaces in Form of pipes or tube bundles are arranged. These in turn are connected in the water-steam cycle of the steam turbine. The water-steam cycle usually includes several, for example two or three, pressure stages, in each pressure stage as heating surfaces, a preheater and an evaporator and a superheater are provided. A Such gas and steam turbine plant is, for example EP 0 523 467 B1.

The total amount of water carried in the water-steam cycle is thereby dimensioned such that the leaving the heat recovery steam generator Flue gas due to heat transfer to a temperature is cooled from about 70 ° C to 100 ° C. this means in particular, that the hot flue gas exposed heating surfaces and provided for a water-steam separation pressure drums are designed for full load or nominal operation, at which achieves plant efficiency of currently around 55% to 60% becomes. For thermodynamic reasons, it will also sought that the temperatures of the individual heating surfaces guided and under different pressure Feed water as close as possible to the temperature profile of the along the heat recovery steam generator due to the heat exchange cooling flue gas. The goal here is the temperature difference between the guided over the individual heating surfaces Feedwater and the flue gas in each area of the To keep heat recovery steam generator as low as possible. To go with it the highest possible proportion of the amount of heat contained in the flue gas implement is in addition in the heat recovery steam generator a condensate preheater for heating condensed water provided from the steam turbine.

The gas turbine of such a gas and steam turbine plant can be designed for operation with different fuels be. Is the gas turbine designed for heating oil and natural gas, so is fuel oil as fuel for the gas turbine only for one short operating time, for example, for 100 to 500h / a, as so-called backup provided for natural gas. The gas and Steam turbine plant usually urgent for natural gas operation the gas turbine designed and optimized. In order to in fuel oil operation, especially when changing from gas operation on the oil operation, a sufficiently high inlet temperature of the condensate flowing into the heat recovery steam generator can ensure the necessary heat to different Be removed from the heat recovery steam generator itself.

One possibility is to completely remove the condensate preheater or partially to circulate and the condensate in one in the Water-steam cycle switched feed water tank by heating with low-pressure steam. Such However, method requires a large volume at low vapor pressures and possibly multi-stage heating steam system in Feed water tank, which is a common at large Aufheizspannen Degassing taking place in the feed water tank can endanger.

In particular, an effective degassing of the condensate to ensure the condensate temperature in the feedwater tank usually in a temperature range between 130 ° C and 160 ° C held. This is usually a preheat condensate over one with low pressure steam or Provided hot water from an economizer-fed preheater, so that the warm-up period of the condensate in the feedwater tank kept as small as possible. It is in particular in two- or three-pressure systems a hot water extraction from the high-pressure economizer required to heat enough to provide. However, this is especially true Three-pressure systems or circuits have the considerable disadvantage that an external, additional condensate preheater needed which is responsible for the high pressures and high temperatures or high temperature differences must be designed. These Method is therefore already due to the considerable costs and the additional space required for the condensate preheater extremely undesirable.

There is also the possibility of oil operation of the gas turbine condensate heating in the feed water tank or in the degasser supplied with a partial flow from a reheater Make or support steam. However, that is also this method, especially in modern plant circuits without feed water tank or without degasser not applicable, especially corresponding devices or apparatus for Mixing preheating missing.

Although from DE 197 36 889 C1 a compared to those described Methods with low equipment and operational Expenditure feasible method known on a Displacement of exhaust heat in the direction of condensate preheating as a result of degradation in the low pressure range and on a Installation of water-side economizer bypasses based. However, this method also meets certain requirements at the limits of realization.

The invention has for its object to provide a method for Operating a gas and steam turbine of the above-mentioned Specify type, the same at low equipment and operating expenses in more effective and in terms of plant efficiency favorable way a change of Gas operation on oil operation of the gas turbine under cover of a wide temperature range of the inlet temperature of in Ensures the heat recovery steam generator inflowing condensate. Furthermore, one for carrying out the method particularly suitable gas and steam turbine plant indicated become.

With respect to the method, the object is achieved according to the invention by the features of claim 1. For this purpose, it is provided that in comparison to the condensate under high pressure and a high temperature compared to the condensate Feed water via a pipeline to the cold condensate heat exchangerless and thus mixed directly by at a change of operation from gas to oil a partial flow of heated feed water is injected into the cold condensate and thus it is mixed.

The invention is based on the consideration that on a additional heat exchanger, which is the water-steam cycle withdrawn heated feed water or hot water before its pressure reduction to the temperature level of the condensate system should cool down, can be waived, if by injecting the hot water into the cold condensate one targeted evaporation of hot water and a subsequent Kondensaticn the forming water-steam mixture takes place. As a result, the formation of steam, d. H. a Steam formation can be allowed by the use of the additional Prevented heat exchanger after the pressure reduction shall be.

It can, especially in a three-pressure system, heated Feedwater from the medium pressure system, from the High-pressure system or be taken from both systems. The removal depends essentially on the required Heating heat for the condensate as well as on which plant efficiency when serving only as a backup oil operation of Gas turbine should be maintained at least.

The heated feed water or hot water is expediently in a two-printing system, i. H. in a two-pressure system from a high-pressure drum and a three-pressure system or in a three-pressure system from the high-pressure drum and / or from a medium pressure drum as Feedwater partial flow taken. Alternatively, the removal the partial flow also at the outlet of the high-pressure Econo-mizers or the medium-pressure economizer done.

If necessary, in addition, the pressure of the low-pressure system be raised to heat contained in the flue gas the low-pressure system downstream of this flue gas side Move condensate preheater out. Essential here is that the water-steam cycle at a suitable place removed heated feed water in the form of a feedwater partial stream without prior warm-up, i. without heat exchange in an additional heat exchanger the cold condensate is mixed.

With regard to the system, the object is achieved according to the invention by the features of claim 5. Advantageous embodiments are the subject of this dependent claims.

In case of a change of operation from gas to oil that from the partial flow of heated feed water the cold condensate heat exchangerless mix, the plant comprises a mixing device, over the cold condensate one as heating surface in the Heat recovery steam generator arranged arranged condensate preheater is. In the interior of the mixing device over which the Condensate flows, at least one spray head is arranged, via a hot water pipe from the water-steam cycle withdrawn heated feed water or hot water can be fed.

To when injecting the heated feed water or hot water Inadmissible or unwanted condensation impacts - so-called water hamer - to avoid, first in the the hot water line is pressurized hot water, i. the partial flow of heated feedwater by opening a the or each spray head upstream fitting for flowing brought. The thereby on a preferably spring-loaded Poppet of a valve provided in the spray head pending Differential pressure between the partial flow and the over the Mixer guided condensate lifts the valve cone from Valve seat down, allowing water through different holes or valve channels to a number of spray nozzles flows. The Flow through the narrow valve channels and spray nozzles leads to an increasing pressure reduction.

When the boiling conditions in the area of the spray nozzles are exceeded Part of the hot water is evaporated and thus the resulting mixture finely divided and the remaining Hot water cooled by evaporation. Through the injection and the very intimate mixing with the surrounding cold Condensate will be the upcoming small steam bubbles again condenses and together with the hot water to a mixing temperature brought under the pressure prevailing at this pressure Boiling temperature is. Depending on the necessary amount of hot water and the temperature are a corresponding number provided by spray heads, which then in a corresponding extended pipe section of a piping executed Hot water mixer of the mixing device are arranged.

In such an embodiment of the or each spray head is the by discharging the hot water as a result of its evaporation formed steam on especially many small openings of the respective spray head distributed within the mixing device lie below the condensate level. Thereby Only small steam bubbles enter through the condensate formed water bath.

The advantages achieved by the invention are in particular in that one required in oil operation of the gas turbine and increased compared to gas operation of the gas turbine Water inlet temperature in the heat recovery steam generator, too without additional heat exchanger or external condensate preheater by heat-exchanger-free spraying of high Pressurized feed water into the cold condensate with extra simple means is adjustable. It can by suitable embodiment of within a designated Mixing device arranged spray heads one below the Boiling temperature of the preheated or preheated condensate lying mixed temperature of the cold condensate In oil operation mixed partial flow on particularly simple and effective way. In addition, because of the recycled feed water throughput in the condensate preheater increases accordingly, can on previously required Kondensatumwälzpumpen be waived. In particular, is without Circuit modification covering a wide temperature range the steam generator or boiler inlet temperature possible.

As can be seen, in this way, the spare capacity the high-pressure feed water pump to be exploited because usually in oil operation compared to gas operation due lower gas turbine power even lower Flow rates are required. In addition, there is no admixture Of cold feed water necessary, whereby only a small one Flow rate of feed water to produce the corresponding Inlet temperature is required. As a result of circuit technology in a particularly effective way extended operating range is also a standardization possible. Further are the investment costs are particularly low.

Due to the comparatively less complex regulations and Switching is on the one hand a comparatively simple Operation and also a relatively high reliability achieved, as a total of less active components necessary. Because of the comparatively smaller component size are advantageously also the maintenance and reduced spare parts inventory.

FIG 1

schematisch eine für einen Betriebswechsel von Gas auf Öl ausgelegte Gas- und Dampfturbinenanlage mit einer Heißwasser-Mischeinrichtung,

FIG 2

die Mischeinrichtung gemäß FIG 1 in größerem Maßstab mit einer Anzahl von Sprühköpfen, und

FIG 3

einen Ausschnitt III aus FIG 2 in größerem Maßstab mit einem ein Ventil aufweisenden Sprühkopf.

Einander entsprechende Teile sind in allen Figuren mit den gleichen Bezugszeichen versehen.An embodiment of the invention will be explained in more detail with reference to a drawing. Show:

FIG. 1

schematically a gas and steam turbine plant designed for a change of operation from gas to oil with a hot water mixing device,

FIG. 2

the mixing device according to FIG 1 on a larger scale with a number of spray heads, and

FIG. 3

a section III of FIG 2 on a larger scale with a valve having a spray head.

Corresponding parts are provided in all figures with the same reference numerals.

The gas and steam turbine plant 1 according to the figure comprises a gas turbine plant 1a and a steam turbine plant 1b. The gas turbine plant 1a comprises a gas turbine 2 with coupled Air compressor 4 and one of the gas turbine 2 upstream Combustion chamber 6, to a fresh air line 8 of the Air compressor 4 is connected. In the combustion chamber. 6 opens a fuel line 10, via the combustion chamber. 6 optionally gas or oil as fuel B can be fed. This is under supply of compressed air L to the working medium or Fuel gas burned for the gas turbine 2. The gas turbine 2 and the air compressor 4 and a generator 12 sit on one common turbine shaft 14.

The steam turbine installation 1 b comprises a steam turbine 20 coupled generator 22 and in a water-steam cycle 24 a steam turbine 20 downstream capacitor 26 and a heat recovery steam generator 30. The steam turbine 20 has a first pressure stage or a high pressure part 20a and a second compression stage or a medium-pressure member 20b as well a third pressure stage or a low pressure part 20c on, via a common turbine shaft 32, the generator 22 drive.

For supplying relaxed in the gas turbine 2 working fluid or flue gas AM in the heat recovery steam generator 30 is a Exhaust pipe 34 to an input 30 a of the heat recovery steam generator 30 connected. That is along the heat recovery steam generator 30 due to indirect heat exchange with the water-steam cycle 24 guided condensate K and feed water S cooling flue gas AM from the gas turbine 2 leaves the heat recovery steam generator 30 via its output 30b in the direction of a fireplace, not shown.

The heat recovery steam generator 30 comprises as heating surfaces Condensate preheater 36, the input side via a condensate line 38, in which a condensate pump 40 is connected, is fed with condensate K from the condenser 26. Of the Condensate preheater 36 is the output side to the suction side of a Feedwater pump 42 out. In the condensate line 38th is a mixing device 44 with a tubular hot water mixer 46 switched.

The feedwater pump 42 is a high-pressure feed pump with Medium pressure taken trained. It brings the condensate K to one for a high-pressure part 20 a of the steam turbine 20 associated high-pressure stage 50 of the water-steam cycle 24th suitable pressure level of about 120 bar to 150 bar. About the Medium pressure is the condensate K by means of the feedwater pump 42 on a for a the medium-pressure part 20 b of Steam turbine 20 associated medium-pressure stage 70 suitable Pressure level from about 40 bar to 60 bar.

The guided via the feedwater pump 42 condensate K, the on the pressure side of the feedwater pump 42 as feed water S is partially high pressure a first High pressure economizer 51 or feedwater heater and fed via this a second high-pressure economizer 52. This is the output side via a valve 57 to a high-pressure drum 54 connected.

The feed water S is also partially under medium pressure via a check valve 71 and one of these downstream Valve 72 a feedwater or medium pressure economizer 73 supplied. This is the output side via a valve 74 connected to a medium-pressure drum 75. Analogous is as part of the low pressure part 20c of the steam turbine 20 associated low pressure stage 90 of the water-steam cycle 24 of the condensate preheater 36 on the output side via a Valve 91 is connected to a low-pressure drum 92.

The medium-pressure drum 75 is connected to a heat recovery steam generator 30 arranged medium-pressure evaporator 76 for the formation a water-steam circulation 77 connected. Steam side is on the intermediate-pressure drum 75 is connected to a reheater 78, the output side (hot ZÜ) to an input 79th the medium-pressure part 20b is guided and in the input side (cold ZÜ) one with an outlet 80 of the high-pressure part 20a of the steam turbine 20 connected exhaust steam line 81 out is.

High pressure side, the feedwater pump 42 via two valves 55, 56 and via the first high-pressure economizer 51 and downstream of this feed water side and within the waste heat steam generator 30 upstream flue gas side second high pressure economizer 52 as well as on demand provided additional valve 57 to the high-pressure drum 54th guided. This is in turn with a in the heat recovery steam generator 30 arranged high-pressure evaporator 58 to form a Water-steam circulation 59 connected. For removing live steam F is the high-pressure drum 54 to a in the heat recovery steam generator 30 arranged high pressure superheater 60 connected the output side with an input 61 of the high pressure part 20a of the steam turbine 20 is connected.

The high pressure economizers 51, 52 and the high pressure evaporator 58 and the high pressure superheater 59 together with the High-pressure part 20a, the high-pressure stage 50 of the water-steam cycle 24. The medium-pressure evaporator 76 and the reheater 78 forms together with the medium-pressure part 20b, the medium-pressure stage 70 of the water-steam cycle 24th Analog forms a arranged in the heat recovery steam generator 30 and to form a water-steam circulation 93 with the low-pressure drum 94 connected low-pressure evaporator 94 together with the low pressure part 20c of the steam turbine 20, the low pressure stage 90 of the water-steam cycle 24. This is the Low-pressure drum 92 on the steam side via a steam line 95th connected to an input 96 of the low-pressure part 20c. In the steam line 95 opens one with an outlet 97 of the medium-pressure part 20b connected overflow line 98. An output 99 of the low-pressure part 20c is via a steam line 100 connected to the capacitor 26.

The gas turbine 2 of the combined cycle power plant 1 is both operable with natural gas as well as fuel oil as fuel B When gas operation of the gas turbine 2, this has the heat recovery steam generator 30 supplied working fluids or flue gas AM a comparatively high purity, wherein the water-steam cycle 24 and the system components to this operating state designed and in terms of efficiency is optimized.

When changing from gas operation to oil operation of the gas turbine 2, a partial flow t S heated by means of a valve 102 with upstream check valve 103 is supplied to the mixing device 44, 46 via a partial flow or hot water line 101 and into the interior 104 via a spray head arrangement 105 Condensate K mixed. The partial flow ts of heated feed water S 'is taken off via a valve 106, preferably the high-pressure drum 54 on the water side. Alternatively, the heated feed water S 'as an adjustable partial flow tS can also be removed via a valve 107 to the first high-pressure economizer 51 or via a valve 108 to the second high-pressure economizer 52 on the output side.

In the illustrated three-pressure system may alternatively or additionally as an adjustable partial flow tS also the medium-pressure economizer 73 on the output side via a valve 109 or the medium-pressure drum 75 water side via a valve 110th heated feed water S 'are removed.

The admixture of the partial flow TS to the condensate K by injection of the guided over the hot water line 101 heated Feedwater S 'into the cold condensate K leads to a targeted evaporation and subsequent condensation the thereby forming water-steam mixture in the mixing device 44.46. The temperature is TS of the partial flow tS when it is removed as heated food water S 'from the high-pressure drum 54, for example, 320 ° C. By the injection of the partial flow tS and its intimate mixing with the cold condensate K can within the mixing device 44,46 - with appropriate adjustment of the amount of Partial flow TS by means of the valve 103 - a mixing temperature be set below that at this pressure in the Mixing device 44.46 prevailing boiling temperature is.

2 shows a preferred embodiment of the mixing device 44 and the hot water mixer 46. This has a the condensate line 38 connected to the inlet opening 111th for feeding the cold condensate K into the mixing device 44 and an outlet opening 112 through which the mixing device 44 connected to the condensate preheater 36 on the input side is. The tubular heating water mixer 46 of the mixing device 44 is thus turned on in the condensate line 38. In the interior 104 of the mixing device 44 are in Embodiment three spray heads 105 arranged. Depending on necessary amount of heating water and the temperature can more or fewer such spray heads 105 within the hot water mixer 46 may be provided.

As is comparatively clear from FIG. 3, is the respective spray head 105 via a mounting flange 113 with Vorschweißende 114 through a flange 115 into the interior 104 of the hot water mixer 46 out and in the respective desired position held. The spray head 105 is self-opening and points to a through a valve seat 116 and a valve plug 117 formed valve. In this case, the valve cone 117 is due to the spring force of a Spring pack 118 sealing in the closed position of the valve guided against the valve seat 116.

When switching from gas operation to oil operation of the gas turbine 2 becomes the in the hot water line 101 under pressure Hot water or heated feed water S ', i. the set Partial flow TS by opening one or each spray head 105 upstream shut-off valve 119 (FIG 2) for flowing brought. The thereby spring-loaded valve cone 117th pending differential pressure automatically lifts it from the valve seat 116 off. As a result, hereinafter referred to as hot water HW designated heated feed water S 'over one in the area the valve seat 117 provided annular space 120 and thus connected bores or valve channels 121 to a number of spray nozzles 122. In this case, preferably four to six spray nozzles 122 distributed on the circumference of the spray head 105 arranged.

The flow of hot water HW through the narrow holes or valve channels 121 and spray nozzles 122 leads to an increasing Pressure reduction. When the boiling conditions are exceeded in the area of the spray nozzles 122 becomes a part of the hot water HW evaporates and thus finely distributes the resulting mixture. In addition, the remaining hot water HW by evaporation cooled. Due to the injection of the partial flow ts heated Feedwater S 'or hot water HW and the effective Mixing with the spray heads 105 in the interior 104 Be the measuring device 44 surrounding cold condensate K resulting, small steam bubbles again condensed and together brought to a mixing temperature with the hot water HW, the below the prevailing at this pressure boiling temperature lies.

The spray heads 105 are each via a supply or intermediate line 123 with the hot water line 101 on the downstream side the shut-off valve 119 connected. Thus, depending on Number of spray heads 105 provided or required a corresponding number of intermediate lines 123 to the Hot water line 101 are connected. This is both the constructive as well as the production or assembly technology Effort for the respective interpretation of the mixing device 44.46 particularly low.

Due to the injection of the feedwater partial flow tS in the hot water mixer 46 caused admixture of hot water S 'to the cold condensate K can with particularly simple Means and in particular without the interposition of an additional Heat exchanger one in the oil operation of the gas turbine. 2 required and increased compared to gas operation Wasseroder Boiler inlet temperature TK 'of e.g. 120 to 130 ° C be set.

Claims (10)

1. Method of operating a gas turbine and steam turbine installation (1), in which the exhaust gas (AM) emerging from a gas turbine (2), which can be operated with both gas and oil, is routed via a waste-heat steam generator (30) whose heating surfaces are connected into the water/steam cycle (24) of a steam turbine (20) having a number of pressure stages (20a, 20b, 20c), condensate preheated in the waste-heat steam generator (30) being heated as feed water (S) at a pressure which is high relative to the condensate and being supplied as steam (F) to the steam turbine (20), characterized in that, in the case of a change from gas operation to oil operation, a partial flow (tS) of heated feed water (S') is injected into the cold condensate (K).
2. Method according to Claim 1, characterized in that the partial flow (tS) is extracted from a high-pressure stage (50) and/or a medium-pressure stage (70) of the water/steam cycle (24).
3. Method according to Claim 1 or 2, characterized in that the partial flow (tS) is extracted from the outlet end of a high-pressure economizer (51, 52) or medium-pressure economizer (73) provided as a heating surface in the waste-heat steam generator (30).
4. Method according to one of Claims 1 to 3, characterized in that the partial flow (tS) is extracted from a high-pressure drum (54) or medium-pressure drum (75) connected into the water/steam cycle (24).
5. Gas turbine and steam turbine installation (1) having a gas turbine (2), which can be operated with both gas and oil, and having a waste-heat steam generator (30) connected downstream of the exhaust-gas end of the gas turbine (2), the heating surfaces of which waste-heat steam generator (30) being connected into the water/steam cycle (24) of a steam turbine (20) comprising at least one low-pressure stage (20c) and one high-pressure stage (20b), characterized by a mixing device (44, 46) having an internal space (104), having an inlet opening (111) connected to the condensate main (38) for supplying cold condensate (K), having an outlet opening (112) connected at the inlet end to a condensate preheater (36) arranged as a heating surface in the waste-heat steam generator (30) and having at least one spray head (105) arranged within the internal space (104), to which spray head (105) it is possible to supply an adjustable partial flow (tS) of heated feed water (S') extracted from the pressure drum (54, 75) or from the economizer (51, 52, 73) by means of a hot water main (101) which is connected at the outlet end to the spray head (105) and which is routed at the supply end to a pressure drum (54, 75) connected at the water end into the water/steam cycle (24), and/or at the outlet end to an economizer (51, 52, 73), arranged as a heating surface in the waste-heat steam generator (30).
6. Gas turbine and steam turbine installation according to Claim 5, characterized in that a valve (103) for adjusting the partial flow (tS) is connected into the hot water main (101) upstream of the mixing device (44, 46) in the flow direction of the partial flow (tS).
7. Gas turbine and steam turbine installation according to Claim 5 or 6, characterized by a number of spray heads (122), which are each connected by an intermediate main (123) to the hot water main (101).
8. Gas turbine and steam turbine installation according to Claim 7, characterized in that a shut-off valve (119) is connected into the hot water main (101) upstream of the intermediate main (123), or each intermediate main (123), in the flow direction of the partial flow (tS).
9. Gas turbine and steam turbine installation according to one of Claims 5 to 8, characterized in that each spray head (105) has a valve (116, 117) which is self-opening as a function of the pressure difference between the partial flow (tS) and the cold condensate (K).
10. Gas turbine and steam turbine installation according to Claim 9, characterized in that the valve (116, 117) is connected to at least one spray nozzle (122) of the spray head (115) via at least one valve duct (121).

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