DE10004187C5 - Method for operating a gas and steam turbine plant and thereafter operating plant - Google Patents

Abstract

Method for operating a gas and steam turbine plant (1), in which the flue gas (R) leaving a gas turbine (2) is passed through a heat recovery steam generator (20) whose heating surfaces into the water-steam cycle (16) are at least two In one operating state without steam introduction into the steam turbine (12), the steam (F) generated in a high-pressure stage (40) is fed into a condenser (18) connected downstream of the steam turbine (12). is diverted, and wherein from this outflowing condensate (K) is at least partially conveyed while bypassing a Kondensatvorwärmers (26) as feed water (S) directly into a first high-pressure economizer (64).

Description

The invention relates to a method for operating a gas and steam turbine plant, in which the flue gas emerging from a gas turbine is passed through a heat recovery steam generator whose heating surfaces are connected in the water-steam circuit of a steam turbine. It also refers to a gas and steam turbine plant operating according to this method.

From the DE 196 27 425 is a hybrid solar combination plant known and a method for their operation. The hybrid solar combined plant consists of a gas turbine group, a steam turbine group, a heat recovery steam generator and a solar steam generator and is designed for operation either in a hybrid solar combined cycle operation, or a solar operation or a combined operation. In hybrid solar combined cycle operation, preheated water from the heat recovery steam generator is introduced into the solar steam generator via a solar feedwater line, the steam generated by the steam is mixed with the steam generated in the heat recovery steam generator and the mixture produced is superheated and the steam thus generated is used to operate the steam turbine , In solar operation, steam is generated only by means of the solar steam generator by the feed water is preheated in at least one feedwater pre-heater with exhaust steam from the steam turbine and fed to the solar steam generator. The solar generated steam is then delivered to the steam turbine. In combined operation, steam is generated only by means of the heat recovery steam generator by the feed water is passed through the heat recovery steam generator and the steam generated is supplied to the steam turbine. In combined operation, the hybrid solar combined cycle plant is thus operated as a pure gas and steam turbine plant.

In a gas and steam turbine, the heat contained in the relaxed working fluid or flue gas from the gas turbine is used to generate steam for the steam turbine connected in a water-steam cycle. The heat transfer takes place in a gas turbine downstream heat recovery steam generator or boiler, are arranged in the heating surfaces in the form of tubes or tube bundles. These in turn are connected in the water-steam cycle of the steam turbine. The water-steam cycle usually comprises several, for example three, pressure stages, wherein in each pressure stage as a heating surfaces, a preheater and an evaporator and a superheater are provided. In order to implement the highest possible proportion of the amount of heat contained in the flue gas, a condensate preheater for warming up condensed water from the steam turbine is additionally provided in the heat recovery steam generator.

The temperature of the steam supplied to the steam turbine depends essentially on the temperature of the effluent from the gas turbine flue gas. At a temperature of the entering into the heat recovery steam generator flue gas of about 570 ° C is a live steam temperature of about 540 ° C at a live steam pressure of z. B. reaches 120 bar. The total amount of water conducted in the water-steam circuit is dimensioned such that the flue gas leaving the heat recovery steam generator is cooled as a result of heat transfer to a temperature of about 70 ° C. to 100 ° C. This means, in particular, that the heating surfaces exposed to the hot flue gas and water-steam drums intended for water-steam separation are designed for full-load or nominal operation in which a system efficiency of currently approximately 55% to 60% is achieved.

In order to enable the operation of the gas turbine and this flue gas side downstream heat recovery steam generator even if the turbine z. B. due to startup and shutdown or a steam turbine quick-closing is out of order, have the various pressure levels in the steam system such gas and steam turbine each have a diverter. The problem with a corresponding bypass operation is the low-pressure steam generated, which is expanded during normal or partial load operation of the steam turbine in this and condensed in the downstream condenser, even without steam turbine to cool and relax. In order to be able to introduce the steam into the existing condenser, therefore, its vapor pressure and steam temperature in the low-pressure diverter station is reduced to the required values by means of injection water from a condensate line. Also, in some cases, the steam produced is blown into the atmosphere via the roof. The same problem arises analogously in a three-pressure system with or without reheating with respect to the generated medium-pressure steam.

Disadvantages of this diversion concept are, in particular, the plant parts and control effort leading to an undesirable reduction in plant availability. Thus, both the low-pressure bypass and the medium-pressure diversion require water injection, piping, sensors for quantity measurement, additional fittings, control valves and the like.

The invention is therefore based on the object to provide a method for operating a gas and steam turbine plant, in which the aforementioned disadvantages are avoided during a Umleitbetriebs. Furthermore, a particularly suitable for carrying out the process gas and steam turbine plant should be specified.

With regard to the method, the object is achieved according to the invention by the features of claim 1. For this purpose, in the operating state without steam introduction into the steam turbine, in particular at their arrival or departure and at a steam turbine rapid closure, in addition to only a high-pressure bypass the condensate preheater flows at least partially. In a three-pressure system, moreover, the first of two high-pressure economizers connected in series is at least partially circulated around. As a result, the usually provided elaborate low and medium pressure bypass stations can be saved.

The invention is based on the consideration that a gas and steam turbine plant can also be operated without low-pressure diversion - and in the case of a three-pressure system even without medium-pressure diversion - when operating steam turbine, if in this operating condition no low pressure or medium pressure steam is produced or produced. The shutdown of low-pressure steam production can be achieved by increasing the pressure in the low-pressure stage, z. B. to about 10 bar to 15 bar, done, as this is the boiling point of the condensate above the available flue gas temperature and consequently no evaporation.

In addition, a temperature control of the condensate preheating be switched so that the condensate temperature at the outlet of the condensate preheater is about 120 ° C to 130 ° C. As a result, the high and medium pressure systems comparatively cold feed water is supplied with the result that the flue gas is taken in comparison to the operation with steam turbine more heat. This in turn leads due to a heat shift that the low-pressure system is less heat available.

The same applies in the medium-pressure range or system, although there, as a result of a corresponding heat shift, the steam production can be practically shut down. A shutdown of the steam production in the low-pressure region can be achieved in a simple manner that the condensate preheater is at least partially bypassed or circulated by means of a bypass. If in a three-pressure system, in addition, the first high-pressure economizer of usually two high-pressure economizers connected in series on the feed water side flows around by means of a bypass, the inlet temperature of the feed water into the second high-pressure economizer is additionally lowered. As a result, this again takes comparatively more heat from the flue gas, so that the medium-pressure system correspondingly less heat is available. In this way, not only the low-pressure steam production but also the medium-pressure steam production can effectively be reduced practically to zero.

By introducing the generated high-pressure steam into the condenser bypassing the steam turbine, the intermediate superheater usually provided in a multi-pressure system is no longer flowed through. When decommissioning of the steam turbine thus such a multi-pressure reheater system can be converted during operation of the gas turbine plant by targeted heat shifts within the heat recovery steam generator while avoiding the use of low pressure and medium pressure Umleitstationen in an indentation system.

With regard to the turbine system, the object is achieved according to the invention by the features of claim 3. Advantageous embodiments are the subject matter of the dependent claims.

The advantages achieved by the invention are, in particular, that the capacity of the usually provided condensate and feedwater pump and by the elimination of a low-pressure Umleitstation in a three-pressure system of the consequent reduced injection water demand at diversion the heat load of the capacitor is reduced by about 10%. Overall, this results in a significant reduction in investment and equipment costs as a result of saving the Umleitsysteme, even if the low-pressure or medium-pressure system, in particular their water-steam drums are to be interpreted for a higher pressure. As the number of active components decreases compared to a conventional system with diverter stations, the system availability and the maintenance costs as well as spare parts provisioning are reduced.

An embodiment of the invention will be explained in more detail with reference to a drawing. Therein, the single figure shows schematically a gas and steam turbine plant with only a high-pressure diverter.

The gas and steam turbine plant 1 according to 1 includes a gas turbine plant 1a and a steam turbine plant 1b , The gas turbine plant 1a includes a gas turbine 2 with coupled air compressor 4 and one of the gas turbine 2 upstream combustion chamber 6 , in the fuel B under supply of compressed air L from the air compressor 4 to the working fluid or fuel gas A for the gas turbine 2 is burned. The gas turbine 2 and the air compressor 4 as well as a generator 8th sit on a common turbine shaft 10 ,

The steam turbine plant 1b includes a steam turbine 12 with coupled generator 14 and in a water-steam cycle 16 one of the steam turbine 12 downstream capacitor 18 and a heat recovery steam generator 20 , The steam turbine 12 has a first pressure stage or a high pressure part 12a and a second printing stage or a medium-pressure part 12b and a third pressure stage or a low pressure part 12c up, over a common turbine shaft 22 the generator 14 drive.

For feeding in the gas turbine 2 relaxed working fluid or flue gas R in the heat recovery steam generator 20 is an exhaust pipe 24 to the heat recovery steam generator 20 connected on the input side. The relaxed flue gas R from the gas turbine 2 leaves the heat recovery steam generator 20 on the output side in the direction of a fireplace, not shown.

The heat recovery steam generator 20 includes a condensate preheater as heating surfaces 26 , the input side via a condensate line 28 into which a condensate pump 30 is switched, with condensate K from the condenser 18 is fed. The condensate preheater 26 is the output side to the suction side of a feedwater pump 34 guided. To bypass the condensate preheater as needed 26 this is with a bypass line 36 into which a motor-operated valve 38 switched, bypassed.

The feed water pump 34 is formed in the embodiment as a high-pressure feed pump with medium pressure extraction. It brings the condensate K on for a high pressure part 12a the steam turbine 12 assigned high pressure stage 40 the water-steam cycle 16 suitable pressure level. The over the feed water pump 34 guided condensate K, which is on the pressure side of the feedwater pump 34 is referred to as feedwater S, is medium pressure a feedwater pre-heater 42 fed. This is the output side to a medium-pressure drum 44 connected. Analogous is the condensate preheater 26 on the output side via a motor-operated valve 46 to a low-pressure drum 48 connected.

The medium-pressure drum 44 is with a in the heat recovery steam generator 20 arranged medium pressure evaporator 50 to form a water-steam cycle 52 connected. Steam side is to the medium-pressure drum 44 a medium pressure superheater 54 connected, the output side to a high pressure part 12a on the output side with a reheater 56 connecting exhaust steam line 58 connected. The reheater 56 again, the output side is via a steam line 60 into which a motor-operated valve 62 is switched to the medium-pressure part 12b the steam turbine 12 connected.

High pressure side is the feedwater pump 34 via a first high-pressure economizer 64 and a downstream of this feedwater and within the heat recovery steam generator 20 flue gas side upstream second high-pressure economizer 66 to a high-pressure drum 68 guided. The high-pressure drum 68 is in turn with a in the heat recovery steam generator 20 arranged high-pressure evaporator 70 to form a water-steam cycle 72 connected. For discharging live steam F is the high-pressure drum 68 to one in the heat recovery steam generator 20 arranged high-pressure superheater 74 connected, the output side with the high pressure part 12a the steam turbine 12 via a motor-operated valve 76 connected is. The first high-pressure economizer 64 is also with a bypass line 78 bridged, in turn, a motorized valve 80 is switched.

The feedwater heater 42 and the medium pressure evaporator 50 as well as the medium pressure superheater 54 forms together with the reheater 56 and the medium-pressure part 12b the medium pressure stage 82 the water-steam cycle 16 , Analog forms in the heat recovery steam generator 20 arranged and to form a water-steam circulation 84 with the low-pressure drum 48 connected low-pressure evaporator 86 together with one to the low-pressure drum 48 Low pressure superheater connected on the steam side 88 and the low pressure part 12c the steam turbine 12 the low pressure stage 90 the water-steam cycle 16 , This is the low pressure superheater 88 on the output side via a steam line 92 into which a motor-operated valve 94 is switched, with the entry of the low pressure part 12c the steam turbine 12 connected.

For bypassing or diverting the high-pressure part as required 12a the steam turbine 12 is one of the high pressure superheater 74 with the high pressure part 12a connecting live steam line 96 over a steam line 98 into which a motor-operated valve 100 is switched directly to the capacitor 18 connected. Here, the serving as high-pressure bypass steam line 98 in the flow direction of the live steam F in front of the valve 76 to the main steam line 96 connected.

Such a diverting operation, in particular when starting or stopping the steam turbine 12 and is provided at a steam turbine rapid closure, leads to a diversion of the generated live steam F, bypassing the steam turbine 12 directly into the condenser 18 , This will be the valve 76 closed and the valve 100 open. Parallel to this is the condensate preheater 26 at least partially bypassed by the in the bypass line 36 lying valve 38 is opened. This causes the condensate K on the suction side of the feedwater pump 34 a mixing temperature T _M , which is due to the at least partial flow around the condensate preheater 26 established. This mixing temperature T _M is smaller than the condensate temperature T _K with completely flowed through, ie not flow around condensate preheater 26 , Also when preheating a partial flow K 'of the condensate K in the condensate preheater 26 adjusts a mixing temperature T _M , which is smaller than the temperature of the operation of the steam turbine 12 the condensate preheater 26 leaving condensate K.

In this way, enters both the feedwater pre-heater 42 as well as in the first high-pressure economizer 64 comparatively cold feed water S, with the result that the flue gas R in the flow direction before the low pressure stage 90 is cooled comparatively strong. This gives the low-pressure stage 90 , ie in particular the low-pressure evaporator 86 comparatively little heat, so in the low-pressure stage 90 at least then no more low pressure steam is produced when the boiling temperature of the water within the low pressure drum 48 the exhaust or flue gas temperature in this area of the heat recovery steam generator 20 equivalent. Even in the event that the exhaust gas temperature is slightly above the boiling point of the water within the low-pressure drum 48 is located, there is a pressure, in which the boiling temperature within the low-pressure drum 48 greater than or equal to the flue gas temperature.

A corresponding heat shift within the heat recovery steam generator 20 in the field of low-pressure heating surfaces, ie the low-pressure evaporator 86 and the low pressure superheater 88 , takes place in that both the feedwater pre-heater 42 as well as the first high-pressure economizer 64 comparatively cool feed water S is supplied. This thus takes the flue gas R comparatively much heat, so that the low-pressure heating surfaces 86 . 88 comparatively little heat is available.

In that also the first high-pressure economizer 64 over the bypass line 78 is at least partially flows around or umführt, a corresponding heat shift also takes place in the area of the heating surfaces of the medium-pressure stage 82 ie in the area of the medium-pressure evaporator 50 and the medium pressure evaporator 54 , Reason for this, in turn, is that the second high-pressure economizer 66 comparatively cool feed water S is again supplied to a mixing temperature T _M '. The second high pressure economizer 66 removes that in this area of the heat recovery steam generator 20 flowing flue gas R opposite the operation with steam turbine turn in addition heat, which the medium-pressure heating surfaces 50 and 54 thus is no longer available. As with the reduction in low-pressure steam production, the medium-pressure steam production is thus virtually completely discontinued. Thus, only high-pressure steam or live steam F is generated, but on the steam turbine 12 leading steam line 98 directly into the condenser 18 is initiated.

By means of this method is thus at shutdown of the steam turbine 12 , z. B. as a result of start-up or shutdown or in the case of a steam turbine quick-closing, by targeted heat transfer within the heat recovery steam generator 20 transferred in simple manner the described multi-pressure system with reheat in an impression system. This method thus enables the operation of the gas turbine 2 and the heat recovery steam generator 20 without low and medium pressure diverter station, when the steam turbine 12 is out of order.

Claims (2)

Method for operating a gas and steam turbine plant ( 1 ), in which the gas turbine ( 2 ) flue gas (R) via a heat recovery steam generator ( 20 ) whose heating surfaces in the water-steam cycle ( 16 ) of at least two pressure stages ( 40 . 90 ) having steam turbine ( 12 ), wherein in an operating state without steam introduction into the steam turbine ( 12 ) in a high-pressure stage ( 40 ) generated steam (F) in one of the steam turbine ( 12 ) downstream capacitor ( 18 ), and wherein from this outflowing condensate (K) at least partially bypassing a condensate preheater ( 26 ) as feed water (S) directly into a first high-pressure economizer ( 64 ). Method according to claim 1, characterized in that in a three-pressure system ( 40 . 82 . 90 ) with a medium-pressure stage ( 82 ) additionally the first high-pressure economizer ( 64 ) flows at least partially and the feed water (S) directly into a second high-pressure economizer ( 66 ) leading to the first high-pressure economizer ( 64 ) downstream of the water side and upstream of the flue gas side.

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