THERMAL POWER STATION

Abstract

The invention relates to a thermal power station and a method for storing heat by means of a steam generator a water-steam cycle which is connected to the steam generator and to a thermal store. Said thermal store comprises a first container for a heat store medium when it is cold, a second container for the heat store medium when it is hot, and a heat exchanger which is connected to the two containers and which is connected to the heat-steam cycle via a water-steam feed line and a water-steam discharge line. The thermal store has an additional heat exchanger which is connected to the two containers, an air feed line and an air discharge line being provided, the air discharge line being connected to the combustion air feed line leading to the combustion chamber.

Claims

1. A thermal power station having a steam generator, which comprises a combustion chamber with a feed for combustion air, having a water-steam cycle, which is connected to the steam generator, and having a thermal store, which is connected to the water-steam cycle, wherein the thermal store comprises a first container for a heat store medium when it is cold, a second container for the heat store medium when it is hot, and a heat exchanger which is connected to the first container and to the second container, wherein the heat exchanger is connected to the water-steam cycle via a water-steam feed line and a water-steam discharge line, wherein the heat store medium can be conveyed from the first container via the heat exchanger to the second container in order to absorb heat from the water and steam, wherein the thermal store comprises an additional heat exchanger which is connected to the first container and to the second container, wherein an air feed line for feeding air into the additional heat exchanger and an air discharge line for discharging the air from the additional heat exchanger are provided, wherein the heat store medium can be conveyed from the second container via the additional heat exchanger to the first container in order to dissipate heat to the air, wherein the air discharge line is connected to the feed for combustion air into the combustion chamber.

2. The thermal power station according to claim 1, wherein a first shut-off device is provided between the first container and the heat exchanger and/or a second shut-off device is provided between the first container and the additional heat exchanger and/or a third shut-off device is provided between the second container and the heat exchanger and/or a fourth shut-off device is provided between the second container and the additional heat exchanger.

3. The thermal power station according to claim 1, wherein solid particles, including sand or corundum, are arranged as heat store medium in the first and/or second container.

4. The thermal power station according to claim 1, wherein a fluidised bed heat exchanger is provided each as the heat exchanger and/or as the additional heat exchanger.

5. The thermal power station according to claim 1, wherein air preheater for preheating the combustion air for the combustion chamber is provided.

6. The thermal power station according to claim 5, wherein the air feed line for the additional heat exchanger is branched from a connection line between the air preheater and the combustion chamber.

7. The thermal power station according to claim 5, wherein the air preheater is connected to a fresh air inlet, wherein the air feed line for the additional heat exchanger is connected to a fluidisation air inlet.

8. The thermal power station according to claim 7, wherein the fresh air inlet is connected to a fresh air fan and/or the fluidisation air inlet is connected to a fluidisation fan.

9. The thermal power station according to claim 6, wherein an output line for discharging waste combustion gases from the combustion chamber is provided, where the output line comprises a line portion leading into the air preheater and an additional line portion leading into a water preheater of the water-steam cycle.

10. The thermal power station according to claim 1, wherein an electrical heating element, including a resistance heater, is installed in the heat exchanger.

11. A method for storing heat in a thermal power station which comprises a steam generator with a combustion chamber and a feed for combustion air and a water-steam cycle, said method having the following steps: conveying a heat store medium when it is cold from a first container via a heat exchanger to a second container, conducting water and steam from the water-steam cycle (5) through the heat exchanger with heat being exchanged with the heat store medium, conveying the heat store medium when it is hot from the second container via an additional heat exchanger into the first container, conducting air through the additional heat exchanger with heat being exchanged with the heat store medium when it is hot, and feeding the air as combustion air into the combustion chamber.

Description

[0031] The invention will be explained in greater detail hereinafter with reference to preferred exemplary embodiments, but is not limited thereto. In the drawing:

[0032] FIG. 1 shows a block diagram of a thermal power station according to the invention, in which the thermal energy of a steam flow branched between a steam generator and a turbine is dissipated in a heat exchanger to a powdery heat store medium, wherein the stored thermal energy is fed back as required in an additional heat exchanger from the heat store medium into an airflow for a combustion chamber of the steam generator;

[0033] FIG. 2 shows a block diagram of the essential components of the thermal power station according to FIG. 1; and

[0034] FIG. 3 shows a block diagram of a further thermal power station according to the invention.

[0035] FIG. 1 schematically shows a thermal power station 1 in the form of a steam power station with a steam generator 2 which comprises a combustion chamber 3 (shown separately for the sake of clarity) with a feed 4 for combustion air and a feed 39 for fuel. A water-steam cycle 5 is connected to the steam generator 2. The steam generator 2 is connected via a first valve 6 to a turbine 7, to which there is connected a generator G. The water-steam cycle 5 additionally comprises further components provided as standard in the prior art, in particular a condenser 8, a feedwater pump 9 and a feed water preheater 10.

[0036] The thermal power station 1 additionally comprises a thermal store 11 shown in a simplified manner in FIG. 1 and visible in detail in FIG. 2 for buffering thermal energy of the steam guided in the water-steam cycle 5.

[0037] As can be seen in particular from FIG. 2, the thermal store device 11 comprises a first container 12 for a heat store medium when it is cold, a second container 13 for the heat store medium when it is hot and a heat exchanger 14 connected to the first container 12 and to the second container 13. A bed of solid particles, in particular sand, is provided as heat store medium. The heat exchanger 14 is connected to the water-steam cycle 5 via a water-steam feed line 15 and a water-steam discharge line 16. A pump 17 visible in FIG. 1 is arranged in the water-steam discharge line 16 in order to compensate for any pressure losses. A valve 40 is provided in the water-steam feed line 15. The heat store medium can be conveyed from the first container 12 via the heat exchanger 14 to the second container 13 in order to absorb heat from the water and steam.

[0038] In addition, the thermal store 11 comprises an additional heat exchanger 18, which is connected to the first container 12 and to the second container 13. An air feed 19 for feeding air into the additional heat exchanger 18 and an air discharge line 20 for discharging the air once it has passed through the additional heat exchanger 18 is also provided. In a discharging process the heat store medium is conveyed from the second container 13 via the additional heat exchanger 18 to the first container 12 in order to dissipate heat to the air. The air discharge line 20 is connected to the feed 4 into the combustion chamber 3, such that the air heated in the additional heat exchanger 18 in the heat exchange with the heat store medium can be introduced as combustion air into the combustion chamber 3.

[0039] As can be seen from FIG. 2, a first shut-off device 21 is provided between the first container 12 and the heat exchanger 14, a second shut-off device 22 is provided between the first container 12 and the additional heat exchanger 18, a third shut-off device 23 is provided between the second container 13 and the heat exchanger 14, and a fourth shut-off device 24 is provided between the second container 13 and the additional heat exchanger 18.

[0040] In the shown embodiment, fluidised bed heat exchangers are provided as heat exchanger 14 and as additional heat exchanger 18. In this case the heat exchanger 14 comprises a fluidisation air feed (not shown in FIG. 2), by means of which the bed of heat store medium can be fluidised. The fluidisation air, however, is not provided as a heat carrier medium for charging the heat store medium in the heat exchanger 14. The heat is dissipated to the heat store medium substantially completely by the steam fed via the water-steam feed line 15.

[0041] As can be seen from FIG. 1, the thermal power station 1 comprises an air preheater 25 for preheating the combustion air prior to entry into the combustion chamber 3. The air preheater 25 is connected via a fresh air fan 26 to a fresh air inlet 27. The waste combustion gases generated in the combustion chamber 3 are delivered into an output line 28, which is connected to the air preheater 25. A heat exchange between the waste combustion gases in the output line 28 and the fresh air coming from the fresh air inlet 27 occurs in the air preheater 25, such that the waste combustion gases are cooled and the fresh air is preheated accordingly. The cooled waste combustion gases can then be released into the surrounding environment.

[0042] In the variant of FIG. 1 a bypass line 29 leads away from a connection line 30 between the air preheater 25 and the combustion chamber 3 which bypass line 29 is connected to the air feed 19 into the additional heat exchanger 18. The air discharge line 20 from the additional heat exchanger 18 leads back into the connection line 30. A shut-off element 31 is arranged in the bypass line 29. An additional shut-off element 32 is arranged in the connection line 30. With the aid of the shut-off element 31 and the additional shut-off element 32, the volume flow in the bypass line 29 can be adjusted. In the discharging state a volume flow of air that is much higher as compared to a fluidisation volume flow is guided via the bypass line 29 into the additional heat exchanger 18, so that the airflow can function as a heat carrier medium for the thermal energy stored in the heat store medium.

[0043] An electrical heating element in the form of a resistance heater 40 is additionally visible in FIG. 2 schematically and is guided into the heat exchanger 14. The resistance heater 40 is connected to a power grid in order to be able to heat the heat store medium in the heat exchanger 14 as required by conversion of electrical energy into thermal energy. The resistance heater 40 can be activated alternatively or additionally to the water-steam cycle 5, for example so as to set an optimal operating temperature of the heat store medium.

[0044] FIG. 3 shows an alternative variant which differs from the embodiment of FIG. 1 in respect of the discharging process. Merely the differences between the embodiment according to FIG. 3 and that of FIG. 1 will be discussed hereinafter.

[0045] According to FIG. 3 the air feed 19 for the additional heat exchanger 18 is connected to a fluidisation air inlet 33 separate from the fresh air inlet 27. The key advantage of this embodiment lies in the possibility of being able to use fans or compressors especially adapted to the volume flows and pressures. In addition, the air preheater 25 can be decoupled from the higher pressure after the fluidisation air inlet 33, which leads to a more economical embodiment of the air preheater 25. The fluidisation air inlet 33 is connected in the shown embodiment to a fluidisation fan 34. In this embodiment the output line 28 comprises a line portion 35 leading into the air preheater 25 and a further line portion 37 leading into a water preheater 36 of the water-steam cycle 5. In the charging state the waste combustion gases are guided via the line portion 35 to the air preheater 25. Once the waste combustion gases have cooled in the air preheater 25, the waste combustion gases are discharged into the surrounding environment. In the discharging state the waste combustion gases are guided via the line portion 37 into the water preheater 36 of the water-steam cycle 5. The waste combustion gases can thus be effectively cooled during the discharge in the switched-off state of the fresh air fan 26. In order to be able to conduct the waste combustion gases to the air preheater 25 during the charging process and to the water preheater 36 during the discharging process, a shut-off valve 38 is arranged in each of the line portions 35 and 37.

[0046] A method having at least the following steps can therefore be carried out: conveying a heat store medium when it is cold from a first container 12 via a heat exchanger 14 to a second container 13, and in the meantime conducting water and steam of the water-steam cycle 5 of the thermal power station 1 through the heat exchanger 14 with dissipation of heat to the heat store medium, conveying the heat store medium when it is hot from the second container 13 via the additional heat exchanger 18 into the first container 12, and in the meantime conducting air through the additional heat exchanger with absorption of heat from the heat store medium when it is hot, and then feeding the air as combustion air into the combustion chamber 3.