Condensing steam turbine plant and methods for operating such a steam turbine plant

Abstract

The invention relates to a condensing steam turbine plant (1) comprising at least one steam turbine (2), a water-cooled condenser (3) connectable to the exhaust steam of the steam turbine (2), and a further heating condenser (4) connectable to the exhaust steam of the steam turbine (2). The heating condenser (4) is arranged parallel to the water-cooled condenser (3) on the steam side, the water-cooled condenser (3) having a backwater control (5) for the condensate, by which the available heat exchanger surface area (6) of the water-cooled condenser (3) can be adjusted via the water level of the condensate in the water-cooled condenser (3). The invention further comprises methods for operating such a condensing steam turbine plant (1).

Description

[0001] The invention relates to a condensing steam turbine plant, hereinafter also referred to as steam turbine plant for the sake of simplicity, according to the preamble of independent patent claim 1, and to methods for operating such a steam turbine plant according to independent patent claims 3 and 4.

[0002] To increase the overall efficiency of a steam turbine plant, steam turbine plants often have, in addition to the water-cooled condenser for condensing the exhaust steam, one or more heating condensers, through which the waste heat from the steam can be used for heating purposes. A typical application is the feed-in of the heat into a district heating / heating network. The steam turbine plant should be able to meet the flexible demand of the district heating / heating network year-round and / or alternatively, transfer the exhaust steam to the water-cooled condenser.

[0003] In general, two variants for heat generation using a heating condenser have established themselves on the market: - If an existing plant is designed for pure condensation, the waste heat from the exhaust steam cannot be utilized and is released into the environment via the cooling water. Intermediate steam extraction at the turbine supplies the heating condensers with steam, and the energy is transferred to the district heating network. - If an existing system is designed as a backpressure system, the waste heat can only be utilized if the district heating network can absorb it. If no other heat consumers are connected, the system must be shut down, thus also ceasing electricity production.

[0004] To achieve greater flexibility, isolated solutions involving parallel operation of a condenser and a heating condenser were implemented in the past, albeit as an "either-or" solution. Many operators opted to switch from pure condensation operation to pure heating condensation operation once the heating network reached a certain demand. However, this requires that the heat-consuming system (e.g., district heating network) can also absorb the heat. Furthermore, the steam turbine must be shut down and restarted after the switchover process.

[0005] Another possible, partially flexible solution is to throttle the exhaust steam mass flow to the water-cooled condenser using a control device (control flap or valve). The disadvantages of this solution are the increased space requirement and the use of additional, cost-intensive fittings, which are often limited in flexibility by the controllable range (e.g., minimum opening angle for flaps, etc.). In pure condensation operation, the system efficiency is reduced due to the increased pressure drop in the exhaust steam section.

[0006] An object of the present invention is therefore to provide a steam turbine plant in which waste heat can be dissipated flexibly and continuously either to the water-cooled condenser (cooling medium: cooling water) or to the heating condenser (cooling medium: heating water).

[0007] A further object of the invention is to provide methods for operating such a steam turbine plant.

[0008] The problem is solved with regard to the steam turbine system by the features of independent patent claim 1 and with regard to the methods by the features of independent patent claims 3 and 4.

[0009] Further advantages and embodiments of the invention, which can be used individually or in combination with one another, are the subject of the dependent claims.

[0010] The condensing steam turbine system according to the invention comprising at least one steam turbine, a water-cooled condenser connectable to the exhaust steam of the steam turbine and a further heating condenser connectable to the exhaust steam of the steam turbine is characterized in that the heating condenser is arranged on the steam side parallel to the water-cooled condenser and the water-cooled condenser has a build-up control for the condensate, by means of which the available heat exchanger surface of the water-cooled condenser can be adjusted via the water level of the condensate in the water-cooled condenser.

[0011] The exhaust steam from the steam turbine is connected to both the water-cooled condenser and the heating condenser via an exhaust steam duct and / or piping into a common pressure chamber (without shutoff). By accumulating the condensate in the water-cooled condenser, the heating surface of the water-cooled condenser can be reduced, thus increasing the exhaust steam pressure. This allows the amount of exhaust steam flowing to the heating condenser to be flexibly and continuously controlled.

[0012] The heat exchangers must be designed / constructed for such a "backup control" or, in existing systems, possibly adapted. The variable weight (condenser + backup condensate) caused by backing up must also be taken into account in the installation concept and the static and dynamic calculations. A basic prerequisite for such a concept is that the turbine can cover the required exhaust steam pressure ranges. This may require a modification of the turbine end blading.

[0013] One embodiment of the invention provides for the heating condenser to interact with a district heating network and transfer heat from the exhaust steam to the district heating network. This allows the steam turbine plant to serve the flexible demand of a district heating network year-round, resulting in a particularly high overall utilization rate of the steam turbine plant.

[0014] A method according to the invention for operating a steam turbine system according to claim 1 or 2 is characterized in that the amount of heat supplied to the heating condenser is regulated via the accumulation control by raising the water level in the water-cooled condenser by accumulating the condensate, thereby reducing the heat exchanger surface of the water-cooled condenser, which leads to an increased exhaust steam pressure, thereby increasing the amount of exhaust steam to the heating condenser. This can, for example, accommodate an increased heat demand of a connected district heating network.

[0015] Another method according to the invention for operating a steam turbine system according to claim 1 or 2 is characterized in that the amount of heat supplied to the heating condenser is regulated via the accumulation control by reducing the water level in the water-cooled condenser, thereby increasing the heat exchanger surface of the water-cooled condenser, which leads to a reduced exhaust steam pressure, thereby reducing the amount of exhaust steam supplied to the heating condenser. This allows the amount of heat supplied to the district heating network to be reduced.

[0016] Both processes enable simple, flexible and yet stepless control of the amount of heat provided to the water-cooled condenser and / or the heating generator.

[0017] Further advantages of the invention are explained below using an embodiment.

[0018] Fig.1 shows only a schematic and not to scale representation of a steam turbine plant according to the invention, in which essentially only the components necessary for explaining the invention are shown.

[0019] The steam turbine system 1 comprises a steam turbine 2, as well as a water-cooled condenser 3 and a heating condenser 4. The water-cooled condenser 3 and the heating condenser 4 are connected to the steam outlet of the steam turbine 2 via a common exhaust steam line 9, with the exhaust steam line 9 forming a common pressure chamber (without shut-off devices). The water-cooled condenser 3 includes a back-up control 5 for the condensate accumulating in the water-cooled condenser 3. By backing up the condensate, the available heat exchanger surface 6 of the water-cooled condenser 3 can be continuously varied. The back-up control 5 includes a drain control valve 5' and a level measurement device 5'' operatively connected to the drain control valve 5'. The non-backed-up condensate is pumped out by a pump 10 and fed back into the water-steam circuit of the steam turbine system 1.

[0020] The amount of heat supplied to the heating condenser 4 is controlled by the accumulation control 5. For this purpose, the water level in the water-cooled condenser 3 is changed by accumulating the condensate, thereby changing the heat exchanger surface 6 of the water-cooled condenser 3, which leads to a changed exhaust steam pressure, allowing the exhaust steam quantity to the heating condenser to be continuously controlled.

[0021] In the exemplary embodiment, the heating condenser 4 interacts with a district heating network 7 and can transfer thermal energy from the exhaust steam to the district heating network 7. Depending on the amount of heat required, more or less exhaust steam is supplied to the heating condenser 4. If only a small amount of heat is required from the district heating network 7 during summer operation, the accumulation control 5 is operated so that the water level 8 in the water-cooled condenser 3 only reaches a low water level. In the event that there is no heat demand at all from the district heating network 7, the condensate can also be completely drained from the water-cooled condenser 3. In both cases, a large heat exchanger surface 6 is available within the water-cooled condenser 3, so that a large amount of exhaust steam condenses in the water-cooled condenser 3. This greatly reduces the exhaust steam pressure and no or only a very small amount of exhaust steam flows to the heating condenser.If, however, a larger amount of heat is required by the district heating network during winter operation, the water-cooled condenser 3 can be flooded with a larger amount of condensate using the overflow control, thereby reducing the effective heat exchanger surface 6. This increases the exhaust steam pressure, and a correspondingly larger amount of exhaust steam is directed to the heating condenser 4.

[0022] The accumulation control 5 enables, for the first time, continuous, demand-based control of the exhaust steam. Flexible parallel and / or individual operation of the water-cooled condenser 3 and the heating condenser 4 is possible without having to shut down the steam turbine system 1.

Claims

[1] Condensation steam turbine plant (1) comprising at least one steam turbine (2), a water-cooled condenser (3) connectable to the exhaust steam of the steam turbine (2) and a further heating condenser (4) connectable to the exhaust steam of the steam turbine (2), characterized by that the heating condenser (4) is arranged on the steam side parallel to the water-cooled condenser (3) and the water-cooled condenser (3) has a build-up control (5) for the condensate, by means of which the available heat exchanger surface (6) of the water-cooled condenser (3) can be adjusted via the water level of the condensate in the water-cooled condenser (3). [2] Condensation steam turbine plant according to claim 1, characterized by that the heating condenser (4) interacts with a district heating network (7) and can transfer heat from the exhaust steam to the district heating network (7). [3] Method for operating a condensing steam turbine plant (1) according to claim 1 or 2, characterized by that the amount of heat supplied to the heating condenser (4) is regulated by increasing the water level (8) in the water-cooled condenser (3) by accumulating the condensate, whereby the heat exchanger surface (6) of the water-cooled condenser (3) is reduced, which leads to an increased exhaust steam pressure, whereby the amount of exhaust steam to the heating condenser (4) is increased. [4] Method for operating a condensing steam turbine plant (1) according to claim 1 or 2, characterized by that the amount of heat supplied to the heating condenser (4) is regulated by reducing the water level (8) in the water-cooled condenser (3), whereby the heat exchanger surface (6) of the water-cooled condenser (3) is increased, which leads to a reduced exhaust steam pressure, whereby the amount of exhaust steam to the heating condenser (4) is reduced.

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