Title of Invention

GAS-AND STEAM-TURBINE PLANT AND METHOD OF OPERATING SUCH A PLANT

Abstract

A gas- and steam-turbine plant (1, 1') having a heat-recovery steam generator (30) which is connected downstream of a gas turbine (2) on the flue-gas side and the heating areas of which are connected in the water/steam circuit (24) of a steam turbine (20) is to be designed for an especially high plant efficiency. To this end, according to the invention, a condenser (80) connected downstream of the the steam turbine (20) on the steam side can be cooled via intake air (A) to be fed to the gas turbine (2).

Full Text

-1A- Description The invention relates to a gas- and steam-turbine plant having a heat-recovery steam generator which is connected downstream of a gas turbine on the flue-gas side and the heating areas of which are connected in the water/steam circuit of a steam turbine. It also relates to a method of operating such a gas- and steam-turbine plant. In a gas- and steam-turbine plant, the heat contained in the expanded working medium (flue gas) from the gas turbine is utilized to generate steam for the steam turbine. The heat transfer is effected in a heat-recovery steam generator, which is connected downstream of the gas turbine on the flue-gas side and in which heating areas are arranged in the form of tubes or banks of tubes. The latter in turn are connected in the water/steam circuit of the steam turbine. The water/steam circuit normally comprises a plurality of pressure stages, for example two pressure stages, each pressure stage having a preheating and an evaporator heating area. The steam generated in the heat-recovery steam generator is fed to the steam turbine, where it expands to perform work. In this case, the steam turbine may comprise a number, of pressure stages, which- are adapted , in their number and design to the design of the heat-recovery steam generator. The steam expanded in the steam turbine is normally fed to a condenser and condenses there. The condensate resulting during the condensation of the steam is fed again as feedwater to the heat-recovery steam generator, so that a closed water/steam circuit is obtained. The condenser of such a gas- and steam-turbine plant, like a heat exchanger, can normally be acted upon by a cooling medium, which extracts heat from the steam - 2 - for the condensation. In this case, water is normally provided as cooling medium; as an alternative, however, the condenser may also be designed as an air condenser, to which air is admitted as cooling medium. The object of the invention is to specify a gas- and steam-turbine plant of the abovementioned type which also has an especially high plant efficiency during various operating states. In addition, a method of operating such a gas- and steam-turbine plant with which an especially high plant efficiency can be achieved is to be specified. For a gas- and steam-turbine plant of the abovementioned type, this object is achieved according to the invention by virtue of the fact that a further condenser which can be cooled via intake air to be fed to the gas turbine is connected in parallel on the water/steam side with a main condenser assigned to the steam turbine. The invention is based on the idea that, for an especially high plant efficiency, heat which develops in the plant process should be utilized to the greatest possible extent. At the same time, the heat extracted from the steam during its condensation should also be returned, at least partly, into the plant process. On account of the temperature level of the steam of about 60°C during its condensation, the transfer of the heat extracted in the process into the intake air to be fed to the gas turbine is especially favourable. The total mass flow of fuel/air mixture which can be fed overall to the gas turbine per unit of time is reduced by the preheating of the intake air of the gas turbine, so that the maximum power output attainable by the gas turbine is lower than if the preheating of the intake air is dispensed with. It has been found, however, that the - fuel consumption drops to a greater extent than the maximum attainable power output during the preheating of the intake air by feeding of condensation heat, so that the overall efficiency increases. - 3 - In this case, the condenser, like an auxiliary condenser, may be acted upon by bleed steam from the steam turbine. In such an arrangement, the condenser can be utilized in an especially favourable manner for providing a rapid power reserve, which, for example, may also be required within a shorter reaction time to back up the line frequency of the electric network fed by the gas- and steam-turbine plant. To activate the power reserve, the steam feed to the condenser is interrupted in this case, so that the entire steam flow is directed via the main condenser. Therefore the preheating of the intake air for the gas turbine does not occur, which leads to a rapid increase in the maximum output delivered by the gas turbine. A compressor to which the intake air for the gas turbine can be fed via an intake-air line is normally assigned to the gas turbine. In an advantageous development, the condenser is connected directly in this intake-air line on the cooling-medium side. In such a refinement, the condenser is expediently designed as an air condenser, losses as a result of conversion processes being kept especially low on account of the single-stage heat transfer from the condensing steam to the intake air. In an alternative advantageous development, the condenser is connected to a heat exchanger on the cooling-medium side via an intermediate cooling circuit, which heat exchanger is in turn connected on the secondary side in the intake-air line connected upstream of the gas turbine. In such an arrangement, the transport of the heat transferred during the condensation to a medium directed in the intermediate cooling circuit is also possible over large distances in a comparatively simple manner. The steam-quantity ratio between the steam flows to be directed to the condenser and the main condenser is expediently adjustable, preferably as a function of the load state of the gas- and steam-turbine plant. During operation of such a plant, the steam flow - 4 - directed via the main condenser is condensed in a conventional manner with the use of an external cooling medium. At the same time, due to the adjustability of the steam-quantity ratio between the steam flows, the operating parameters of the steam flow directed via the condenser can be kept approximately constant in an especially simple manner, so that such a plant can be operated in an especially reliable manner. In addition, for every operating state of the plant, the intake air can thereby also be preheated to the maximum attainable temperature for the respective operating state. In this case, the main condenser has a condensate preheater connected downstream of it, in which arrangement condensate flowing off from the condenser, as viewed in the direction of flow of the condensate, can be fed downstream of the condensate preheater into the water/steam circuit of the steam turbine. Therefore the residual heat remaining in the condensate after the condensation of the steam can be introduced into the water/steam circuit in an especially favourable manner. With regard to the method of operating the gas- and steam-turbine plant, the stated object is achieved by intake air to be fed to the gas turbine being preheated via heat extracted during the condensation from steam flowing, off from the steam turbine. In the process, condensate obtained, during the condensation is advantageously admixed to preheated condensate directed in the water/steam circuit of the steam turbine. The advantages achieved with the invention consist in particular in the fact that, by the transfer of the heat extracted during the condensation of the steam to the intake air for the gas turbine, this heat can be utilized for the plant process. Such a gas- and steam-turbine plant therefore has an especially high plant efficiency. In this case, due to the fact that the maximum power output of the gas turbine is reduced - 5 - comparatively slightly, a favourable efficiency of the gas and steam turbine can be achieved in particular in the part-load range. It has also emerged that such a gas- and steam-turbine plant also exhibits comparatively lower pollutant emissions. In addition to other variables, the so-called changeover point, which indicates th'e output at which the gas turbine is to be changed over from diffusion operation to premix operation, is relevant to the pollutant emissions of a gas- and steam-turbine plant. The gas- and steam-turbine plant with preheated intake air for the gas turbine has a comparatively lower changeover point, so that it can also be run during comparatively low load states in premix operation, which is more favourable for low pollutant emissions. Exemplary embodiments of the invention are explained in more detail with reference to a accompanying drawing, in which: Figure 1 schematically shows a gas and steam-turbine plant, and Figure 2 schematically shows an alternative embodiment of a gas- and steam-turbine plant. The same parts are provided with the same reference numerals in both figures. The gas- and steam-turbine plant 1 or 1' respectively, schematically shown in each case in Figures 1, 2, comprises a gas-turbine plant la and a steam-turbine plant lb. The gas-turbine plant la comprises a gas turbine 2 with coupled air compressor 4. The air compressor 4 is connected on the inlet side to an intake-air line 5. Arranged upstream of the gas "turbine 2 is a combustion chamber 6, which is connected to a fresh-air line 8 of the air compressor 4. A fuel line 10 leads into the combustion chamber 6 of the gas turbine 2. The gas-turbine 2 and the air compressor 4 as well as a generator 12 sit on a common shaft 14. The steam-turbine plant lb comprises a steam turbine 20 with coupled generator 22 and, in a water/steam circuit 24, a main condenser 26, arranged - 6 - downstream of the steam turbine 20, as well as a heat-recovery steam generator 30. The steam turbine 20 consists of a first pressure stage or a high-pressure part 20a and a second pressure stage or an intermediate-pressure part 20b as well as a third pressure stage or a low-pressure part 20c, which drive the generator 22 via a common shaft 32. To feed working medium AM' or flue gas expanded in the gas turbine 2 into the heat-recovery steam generator 30, an exhaust-gas line 34 is connected to an inlet; 30a of the heat-recovery steam generator 30.' The expanded working medium AM' from the gas turbine 2 leaves the heat-recovery steam generator 30 via the outlet 30b of the latter in the direction of a stack (not shown in any more detail). In a first pressure stage or high-pressure stage of the water/steam circuit 24, the heat-recovery steam generator 30 comprises a high-pressure preheater or economizer 36, which is connected to a high-pressure drum 42 via a line 40 which can be shut off by a valve 38. The high-pressure drum 42 is connected to a high-pressure evaporator 44, arranged in the heat-recovery steam generator 30, for forming a water/steam circulation 46. To discharge live steam F, the high-pressure drum 42 is connected to a high-pressure superheater 48, which is arranged in the heat-recovery steam generator 30 and is connected on the outlet side to the steam inlet 49 of the high-pressure part 20a of the steam turbine 20. The steam outlet 50 of the high-pressure part 20a of the steam turbine 20 is connected via a steam line 52 ("cold REHEAT") to a reheater 54, the outlet 56 of which is connected via a steam line 58 to the steam inlet 60 of the intermediate-pressure part 20b of the steam turbine 20. The steam outlet 62 of the intermediate-pressure part 20b is connected via an overflow line 64 to the steam inlet 66 of the low-pressure part 20c of the steam turbine 20. The steam outlet 68 of the low-pressure, part 20c of the steam - 7 - turbine 20 is connected via a steam line 70 to the main condenser 26. The latter is connected to the economizer 36 via a feedwater line 72, in which a feedwater pump 74 and a condensate preheater 76 are connected, so that a closed water/steam circuit 24 results. In the exemplary embodiments according to Figures 1, 2, therefore, only the first pressure stage of the water/steam circuit 24 is shown in detail. However, further heating areas (not shown in any more detail) which are assigned in each case to an intermediate- or a low-pressure stage of the water/steam circuit 24 are arranged in the heat-recovery steam generator 30. These heating areas are connected in a suitable manner to the steam inlet 60 of the intermediate-pressure part 20b of the steam turbine 20 or to the steam inlet 66 of the low-pressure part 20c of the steam turbine 20. The gas- and steam-turbine plant 1, 1' is designed for achieving an especially high efficiency. To this end, a condenser 80 arranged downstream of the steam turbine 20 on the steam side and designed as an auxiliary condenser can be cooled via intake air A to be fed to the gas-turbine plant la. The condenser 80 is arranged downstream of the steam turbine 20 via a bleed-steam line 84, which can be shut off by a valve 82. On the outlet side, the condenser 80 is connected to the feedwater line 72 via a condenser line 86, so that the condenser™ 80, on the water/steam side, is connected in parallel with the main condenser 2 6 assigned to the steam turbine 20. In this case, the condensate line 86 is connected to the feedwater line 72 at a feeding point 88. The feeding point 88, as viewed in the direction of flow of the condensate K flowing off from the main condenser 26, is arranged downstream of the condensate preheater 76. The steam-quantity ratio between the partial steam flow directed to the main condenser 26 and the partial steam flow directed to the condenser 80 can be adjusted via the valve 82. For each relevant power output of the gas- and steam-turbine plant 1, 1', the - 8 - intake air A can be preheated up to the maximum attainable temperature by varying this steam-quantity ratio. The gas- and steam-turbine plant 1 according to Figure 1 is designed for a single-stage heat exchange between the partial steam flow to be condensed in the condenser 80 and the intake air A to be fed to the gas-turbine plant la. To this end, an air condenser, to which cooling air can be admitted as cooling medium, is provided as condenser 80. In this case, the condenser 80 is connected directly in the intake-air line 5 on the cooling-medium side. In the case of the gas- and steam- turbine plant 1, the losses occurring as a result of conversion processes during the heat transfer from the steam condensing in the condenser 80 to the intake air A are; kept especially low. In the exemplary embodiment according to Figure 2, however, a two-stage heat transfer from the steam to be condensed in the condenser 80 to the intake air A is provided. To this end, in the case of the gas- and steam-turbine plant 1' according to Figure 2, a separate heat exchanger 90 is connected in the intake-air line 5. The separate heat exchanger 90 is connected on the primary side to an intermediate circuit 92, to which the condenser 80 is connected on the cooling-medium side. In this case, heat-transfer medium W directed in the intermediate circuit .92 can be circulated by means of a circulation pump 94 connected in the intermediate circuit 92. During operation of the gas- and steam-turbine plant 1 or of the gas- and steam-turbine plant 1' , a partial steam flow extracted from the low-pressure part 20c of the steam turbine 20 is directed as bleed steam via the condenser 80. This partial steam flow is condensed in the condenser 80, the heat extracted from the steam during its condensation being transferred to the intake air A for the gas-turbine plant la. The condensate obtained during the condensation of the steam - 9 - in the condenser 80 is admixed to the preheated condensate K flowing off from the main condenser 26. By the transfer of the heat extracted from the partial steam flow during its condensation in the condenser 80 to the intake air A for the gas-turbine plant la, this heat is returned into the energy-conversion process of the gas- and steam-turbine plant 1 or respectively the gas- and steam-turbine plant 1'. The gas- and steam-turbine plant 1, 1' therefore has an especially high plant efficiency. On the other hand, however, the preheating of the intake air A for the gas-turbine plant la also results in the total mass flow' of the working medium AM which can be fed to the gas turbine 2 being smaller than if the preheating of the intake air A is dispensed with. The maximum power output attainable during operation of the gas turbine 2 is therefore comparatively smaller. The operation of the gas- and steam-turbine plant 1, 1' with preheating of the intake air A by condensation of bleed steam in the condenser 80 is therefore especially suitable for the part-load range. In addition, in this mode of operation, a rapid power reserve of the gas- and steam-turbine plant 1, 1' is ensured in an especially simple form, because, if the preheating of the intake air A is rapidly shut off, a rapid increase in the power output of the gas turbine 2 is made possible on account of the available total mass flow, which is then comparatively increased, of working medium AM for the gas turbine 2. - 10 - WE CLAIM 1. Gas- and steam-turbine plant (1, 1') having a heat-recovery steam generator (30) which is connected downstream of a gas turbine (2) on the flue-gas side and the heating areas of which are connected in the water/steam circuit (24) of a steam turbine (20), a further condenser (80) which can be cooled via intake air (A) to be fed to the gas turbine (2) being connected in parallel on the water/steam side with a main condenser (26) assigned to the steam turbine (20). 2. Gas- and steam-turbine plant (1, 1') according to Claim 1, in which an intake-air line (5) , in which the further condenser (80) is directly connected on the cooling-medium side, is connected upstream of a compressor assigned to the gas turbine (2). 3. Gas- and steam-turbine plant (1, 1') according to Claim 1, in which the further condenser (80) is connected to a heat exchanger (90) on the cooling-medium side via an intermediate cooling circuit (54), which heat exchanger (90) is connected on the secondary side in an intake-air line (5) , which is connected upstream of a compressor assigned to the gas turbine (2). 4. Gas- and steam-turbine plant (1, 1') according to one of Claims 1 to 3, in which the steam-quantity ratio of the steam flows to be directed to the further condenser (80) and the main condenser (26) is adjustable. 5. Gas- and steam-turbine plant (1, 1' ) according to one of Claims 1 to 4, whose main condenser (26) has a condensate preheater (76) connected downstream of it, in which arrangement condensate flowing off from the further condenser (80), as viewed in the direction of flow of the condensate, can be fed downstream of the condensate preheater (7 6) into the water/steam circuit (24) of the steam turbine (20). 6. Method of operating a gas- and steam-turbine plant {1, 1') according to one of Claims 1 to 5, in which intake air (A) to be fed to the gas turbine is - 11 - preheated via heat extracted during the condensation from steam flowing off from the steam turbine (20). 7. Method according to Claim 6, in which the condensate obtained during the condensation is admixed to preheated condensate which is directed in the water/steam circuit (24) of the steam turbine (20). A gas- and steam-turbine plant (1, 1') having a heat-recovery steam generator (30) which is connected downstream of a gas turbine (2) on the flue-gas side and the heating areas of which are connected in the water/steam circuit (24) of a steam turbine (20) is to be designed for an especially high plant efficiency. To this end, according to the invention, a condenser (80) connected downstream of the the steam turbine (20) on the steam side can be cooled via intake air (A) to be fed to the gas turbine (2).

Documents:

01622-cal-1998 abstract.pdf

01622-cal-1998 claims.pdf

01622-cal-1998 correspondence.pdf

01622-cal-1998 description(complete).pdf

01622-cal-1998 drawings.pdf

01622-cal-1998 form-1.pdf

01622-cal-1998 form-2.pdf

01622-cal-1998 form-3.pdf

01622-cal-1998 form-5.pdf

01622-cal-1998 gpa.pdf

01622-cal-1998 priority document.pdf

1622-CAL-1998-(12-10-2012)-FORM-27.pdf

1622-CAL-1998-CORRESPONDENCE 1.1.pdf

1622-CAL-1998-CORRESPONDENCE.pdf

1622-CAL-1998-FORM-27.pdf

1622-cal-1998-granted-abstract.pdf

1622-cal-1998-granted-acceptance publication.pdf

1622-cal-1998-granted-claims.pdf

1622-cal-1998-granted-correspondence.pdf

1622-cal-1998-granted-description (complete).pdf

1622-cal-1998-granted-drawings.pdf

1622-cal-1998-granted-examination report.pdf

1622-cal-1998-granted-form 1.pdf

1622-cal-1998-granted-form 2.pdf

1622-cal-1998-granted-form 3.pdf

1622-cal-1998-granted-form 5.pdf

1622-cal-1998-granted-gpa.pdf

1622-cal-1998-granted-letter patent.pdf

1622-cal-1998-granted-priority document.pdf

1622-cal-1998-granted-reply to examination report.pdf

1622-cal-1998-granted-specification.pdf

1622-cal-1998-granted-translated copy of priority document.pdf

1622-CAL-1998-PA 1.1.pdf

1622-CAL-1998-PA.pdf