Thermal power generating unit steam turbine heat supply system and heat supply method

Abstract

The invention discloses a thermal power generating unit steam turbine heat supply system and a heat supply method. A steam outlet of the boiler is communicated with a steam inlet of the steam turbine; a steam outlet of the steam turbine communicates with a steam inlet of the back pressure steam turbine through a first branch pipe, and the steam outlet of the back pressure steam turbine is configured to be suitable for being connected with a steam using device; an output shaft of the back pressure type steam turbine is in transmission connection with an input shaft of the motor generator, the output power of the motor generator is adjustable, so that the rotating speed of the back pressure type steam turbine is constant, and the motor generator is configured to be connected with a power utilization system. According to the steam turbine heat supply system of the thermal power generating unit, a gas source higher than the gas source required by a steam using device can be converted into electric energy, gradient utilization of energy is achieved, energy loss of high-quality steam is reduced, the energy conversion rate is increased, and energy conservation and efficiency improvement are achieved.

Description

Technical Field

[0001] This invention relates to the field of heating system technology, and in particular to a heating system and heating method for a steam turbine of a thermal power unit. Background Technology

[0002] Industrial steam consumption is characterized by fluctuating steam volume while maintaining relatively constant pressure and temperature parameters. However, the pressure and temperature of steam extracted from turbines in thermal power plants generally do not match those of industrial steam. Furthermore, variations in unit load cause the pressure and temperature of the steam source supplying industrial steam to change. To address these contradictions, thermal power plants typically use steam sources with parameters higher than those required for industrial steam, employing desuperheaters and pressure reducers to meet these requirements. However, during the process of reducing the pressure of high-quality steam to lower-quality steam through throttling, the desuperheater and pressure reducer cannot fully utilize the energy inherent in the high-quality steam, resulting in energy loss. Summary of the Invention

[0003] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a steam turbine heating system for thermal power units, which can convert a gas source exceeding the requirements of the steam-consuming device into electrical energy, achieving cascaded energy utilization, reducing energy loss from high-quality steam, improving energy conversion efficiency, and realizing energy saving and efficiency improvement.

[0004] The present invention also proposes a heating method.

[0005] According to a first aspect of the present invention, a steam turbine heating system for a thermal power unit includes: a boiler; a steam turbine, wherein the steam outlet of the boiler is connected to the steam inlet of the steam turbine; a back-pressure steam turbine, wherein the steam outlet of the steam turbine is connected to the steam inlet of the back-pressure steam turbine via a first branch pipe, the steam outlet of the back-pressure steam turbine being configured to be connected to a steam-consuming device; and an electric generator, wherein the output shaft of the back-pressure steam turbine is drively connected to the input shaft of the electric generator, the output power of the electric generator is adjustable to keep the rotational speed of the back-pressure steam turbine constant, and the electric generator being configured to be connected to an electrical system.

[0006] According to the thermal power unit steam turbine heating system of the present invention, by setting up a back-pressure steam turbine and an electric generator, the heating system can provide stable steam to the steam-consuming device, and when the gas source pressure is greater than the steam consumption pressure, it can convert the gas source pressure higher than that required by the steam-consuming device into electrical energy, thereby realizing the cascade utilization of energy, reducing the energy loss of high-quality steam, improving the energy conversion rate, and achieving energy saving and efficiency improvement.

[0007] According to some embodiments of the present invention, the heating system further includes a steam compressor, wherein the steam outlet of the steam turbine is connected to the steam inlet of the steam compressor via a second branch pipe, and the steam outlet of the steam compressor is configured to be connected to a steam-consuming device.

[0008] According to some embodiments of the present invention, the output shaft of the electric generator is connected to the input shaft of the steam compressor, and the electric generator is used to drive the steam compressor to rotate.

[0009] According to some embodiments of the present invention, the heating system further includes a variable speed clutch connected between the electric generator and the steam compressor.

[0010] According to some embodiments of the present invention, the heating system further includes: a first control valve, which is arranged on the first branch pipe and / or the second branch pipe, for controlling the steam outlet of the steam turbine to be switched to be connected to the steam inlet of the back-pressure steam turbine and / or connected to the air inlet of the steam compressor.

[0011] According to some embodiments of the present invention, the heating system further includes: a steam exhaust pipe, one end of which is connected to the steam outlet of the back-pressure steam turbine, and the other end of which is configured to be connected to the condenser and / or the steam exhaust device of the steam turbine.

[0012] According to some embodiments of the present invention, the heating system further includes: a second control valve connected in series on the exhaust pipe for controlling the on / off state of the exhaust pipe.

[0013] According to a second aspect of the present invention, a heating method is used in a steam turbine heating system for a thermal power unit according to a first aspect of the present invention. The heating method includes: step S1, confirming whether the gas source pressure of the steam turbine is greater than the steam consumption pressure of the steam-consuming device; if yes, proceeding to step S2; if no, proceeding to step S3; step S2, controlling the steam outlet of the steam turbine to connect with the steam inlet of the back-pressure steam turbine, so that the heating system supplies heat to the steam-consuming device through the back-pressure steam turbine; step S3, controlling the steam outlet of the steam turbine to connect with the steam inlet of the steam compressor, so that the heating system supplies heat to the steam-consuming device through the steam compressor.

[0014] According to the heating method of the present invention, the heating system can meet the gas supply requirements of the steam-using device under various operating loads.

[0015] According to some embodiments of the present invention, step S2 includes: step S21, controlling the output power of the electric generator to make the rotational speed of the back-pressure steam turbine reach a preset speed, the exhaust pressure parameter reach a preset pressure value, and the temperature parameter reach a preset temperature value; step S22, controlling the steam outlet of the steam turbine to connect with the steam inlet of the back-pressure steam turbine; step S23, controlling the steam outlet of the back-pressure steam turbine to connect with the steam-consuming device, so that the heating system supplies heat to the steam-consuming device through the back-pressure steam turbine.

[0016] According to some embodiments of the present invention, step S3 includes: step S31, controlling the steam outlet of the steam turbine to be connected to the steam inlet of the back-pressure steam turbine and the steam inlet of the steam compressor; step S32, controlling the steam outlet of the steam compressor to be connected to the steam-consuming device, and the steam outlet of the back-pressure steam turbine to be connected to the exhaust pipe; step S33, controlling the electric generator to drive the steam compressor and the back-pressure steam turbine to rotate, so that the rotational speed of the back-pressure steam turbine reaches a preset rotational speed, the outlet pressure of the steam compressor reaches a preset pressure value, and the outlet flow rate reaches a preset flow rate value.

[0017] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a steam turbine heating system for a thermal power unit according to an embodiment of the present invention; Figure 2 This is a schematic flowchart of a heating method according to an embodiment of the present invention; Figure 3 This is a schematic flowchart of step S2 of the heating method according to an embodiment of the present invention; Figure 4 This is a schematic flowchart of step S3 of the heating method according to an embodiment of the present invention.

[0019] Figure label: 100. Heating system; 10. Steam turbine; 20. Back-pressure steam turbine; 21. First branch pipe; 30. Electric generator; 40. Steam compressor; 41. Second branch pipe; 50. Gearbox clutch; 60. First control valve; 70. Exhaust pipe; 80. Second control valve; 91. Third control valve; 92. Fourth control valve. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0021] The following is for reference. Figure 1 A heating system 100 for a steam turbine 10 of a thermal power unit according to an embodiment of the first aspect of the present invention is described.

[0022] like Figure 1 As shown, a heating system 100 for a thermal power unit turbine 10 according to a first aspect embodiment of the present invention includes: a boiler, a turbine 10, a back-pressure turbine 20, and an electric generator 30. The steam outlet of the boiler is connected to the steam inlet of the turbine 10. The steam outlet of the turbine 10 is connected to the steam inlet of the back-pressure turbine 20 through a first branch pipe 21. The steam outlet of the back-pressure turbine 20 is configured to be connected to a steam-consuming device. The output shaft of the back-pressure turbine 20 is drivenly connected to the input shaft of the electric generator 30. The output power of the electric generator 30 is adjustable to keep the rotational speed of the back-pressure turbine 20 constant. The electric generator 30 is configured to be connected to an electrical system.

[0023] The boiler, as the system's steam generating device, is mainly used to convert the chemical energy of fuel into the thermal energy of steam. The steam turbine 10 is mainly used to receive the high-temperature and high-pressure steam output from the boiler and convert the thermal energy of the steam into mechanical energy, realizing primary heat energy recovery. The back-pressure steam turbine 20 is also mainly used to cool, depressurize, and regulate the parameters of the steam, so that the steam processed by it meets the pressure and temperature requirements of the steam-using device and ensures the stability of the gas supply. The electric generator 30 is connected to the back-pressure steam turbine 20 and is mainly used to recover and utilize the steam extracted by the steam turbine 10, converting the gas source higher than that required by the steam-using device into electrical energy, thereby realizing the cascade utilization of energy, reducing the energy loss of high-quality steam, improving the energy conversion rate, and achieving energy saving and efficiency improvement.

[0024] Specifically, when the steam parameters are greater than the steam parameters of industrial users, the speed of the back-pressure turbine 20 can be calculated according to the steam demand of the steam-consuming device, and then the output power of the electric generator 30 can be adjusted according to the required speed so that the speed of the back-pressure turbine 20 reaches the demand and remains constant.

[0025] It should be noted that the pressure and temperature of the steam-using device are generally fixed values, and only the steam flow rate will change. In this case, it is only necessary to adjust the load of the generator to keep the speed of the back-pressure steam turbine 20 constant and the exhaust pressure and temperature constant. Only by changing the inlet steam flow rate of the back-pressure small steam turbine 10, the changes in the steam flow rate of industrial users can be met.

[0026] According to the heating system 100 of the steam turbine 10 of the thermal power unit of the present invention, by setting a back-pressure steam turbine 20 and an electric generator 30, the heating system 100 can provide stable steam to the steam-consuming device, and when the gas source pressure is greater than the steam consumption pressure, it can convert the gas source pressure higher than that required by the steam-consuming device into electrical energy, thereby realizing the cascade utilization of energy, reducing the energy loss of high-quality steam, improving the energy conversion rate, and achieving energy saving and efficiency improvement.

[0027] According to some embodiments of the present invention, such as Figure 1 As shown, the heating system 100 also includes a steam compressor 40. The steam outlet of the steam turbine 10 is connected to the steam inlet of the steam compressor 40 via a second branch pipe 41. The steam outlet of the steam compressor 40 is configured to be connected to a steam-consuming device. Specifically, the steam compressor 40 is mainly used to compress the steam discharged from the steam turbine 10 to increase its pressure and temperature, so that it meets the temperature and pressure requirements of the steam-consuming device.

[0028] For example, refer to Figure 1 The steam compressor 40 is also equipped with a third control valve 91 at its steam outlet, which is used to control the connection and disconnection between the steam compressor 40's steam outlet and the steam-consuming device; the back-pressure steam turbine 20 is equipped with a fourth control valve 92 at its steam outlet, which is used to control the connection and disconnection between the back-pressure steam turbine 20's steam outlet and the steam-consuming device.

[0029] According to some embodiments of the present invention, such as Figure 1 As shown, the output shaft of the electric generator 30 is connected to the input shaft of the steam compressor 40, and the electric generator 30 is used to drive the steam compressor 40 to rotate. Specifically, the electric generator 30 can both act as a generator to recover energy and as an electric motor to drive the steam compressor 40. This facilitates bidirectional energy transfer and rapid switching, and helps to improve the overall energy utilization rate and operating condition adaptability of the system.

[0030] According to some embodiments of the present invention, such as Figure 1 As shown, the heating system 100 also includes a speed-changing clutch 50, which is connected between the electric generator 30 and the steam compressor 40. Specifically, the speed-changing clutch 50 can adjust the speed of the steam compressor 40, so that when steam is supplied to the steam-consuming device through the steam compressor 40, the outlet flow rate can meet the requirements for adjusting the industrial steam flow rate; at the same time, it can also disconnect the steam compressor 40 from the steam supply system when it is not in use, reducing useless mechanical losses and energy consumption in the steam supply system and improving the overall operating efficiency of the system.

[0031] According to some embodiments of the present invention, such as Figure 1As shown, the heating system 100 also includes a first control valve 60, which is arranged on the first branch pipe 21 and / or the second branch pipe 41, for controlling the steam outlet of the steam turbine 10 to be switched to be connected to the steam inlet of the back pressure steam turbine 20 and / or connected to the steam inlet of the steam compressor 40.

[0032] The phrase "the first control valve 60 is arranged on the first branch pipe 21 and / or the second branch pipe 41" can be understood as meaning that the first control valve 60 can be arranged only on the first branch pipe 21, or only on the second branch pipe 41, or the first control valve 60 can be arranged on both the first branch pipe 21 and the second branch pipe 41. For example, as shown in the figure, there are two first control valves 60, which are arranged on the first branch pipe 21 and the second branch pipe 41 respectively, and are used to control the on / off state of the first branch pipe 21 and the second branch pipe 41 as well as the flow rate.

[0033] The statement "The first control valve 60 is used to control the connection of the steam outlet of the steam turbine 10 to the steam inlet of the back-pressure steam turbine 20 and / or to the steam inlet of the steam compressor 40" means that by controlling the first control valve 60, the steam outlet of the steam turbine 10 can be connected only to the steam inlet of the back-pressure steam turbine 20, only to the steam inlet of the steam compressor 40, or both. It should be noted that the specific steam inlet to which the steam outlet of the steam turbine 10 is connected is selected based on the actual situation.

[0034] According to some embodiments of the present invention, such as Figure 1 As shown, the heating system 100 also includes an exhaust pipe 70. One end of the exhaust pipe 70 is connected to the steam outlet of the back-pressure turbine 20, and the other end is configured to connect to the exhaust device of the condenser and / or the turbine 10. The exhaust pipe 70 is primarily used when the back-pressure turbine 20 is not in operation, with the electric motor driving the back-pressure turbine 20 to maintain an no-load condition. Specifically, in this condition, the steam inlet of the back-pressure turbine 20 receives cooling steam through the first branch pipe 21. This cooling steam, after being processed by the back-pressure turbine 20, enters the condenser and / or the exhaust device of the turbine 10 through the exhaust pipe 70 to achieve heat energy reuse. Simultaneously, the exhaust pipe 70 also prevents the back-pressure turbine from experiencing forced draft and keeps the back-pressure turbine 20 in a hot standby state, thus enabling rapid switching.

[0035] According to some embodiments of the present invention, such as Figure 1As shown, the heating system 100 also includes a second control valve 80, which is connected in series with the exhaust pipe 70 to control the opening and closing of the exhaust pipe 70. This allows the exhaust pipe 70 to be closed when not in use, for example, when steam is supplied to the steam-consuming device through the outlet of the back-pressure turbine 20. This ensures that the pressure and temperature at the outlet of the back-pressure turbine 20 meet the requirements of the steam-consuming device.

[0036] According to the heating method of the second aspect of the present invention, it is used in the heating system 100 of the steam turbine 10 of the thermal power unit according to the first aspect of the present invention, such as Figure 2 As shown, the heating methods include: Step S1: Confirm whether the gas source pressure of the steam turbine 10 is greater than the steam consumption pressure of the steam consumption device. If yes, proceed to step S2; otherwise, proceed to step S3. Step S2: Connect the steam outlet of the steam turbine 10 to the steam inlet of the back-pressure steam turbine 20 so that the heating system 100 supplies steam to the steam-consuming device through the back-pressure steam turbine 20. Step S3: Connect the steam outlet of the steam turbine 10 to the steam inlet of the steam compressor 40 so that the heating system 100 supplies steam to the steam-consuming device through the steam compressor 40.

[0037] Specifically, when the gas source pressure of the steam turbine 10 is detected to be greater than the steam consumption pressure of the steam-consuming device, the first control valve 60 is controlled to connect the first branch pipe 21, so that the steam outlet of the steam turbine 10 is connected to the steam inlet of the back-pressure steam turbine 20, thereby allowing the heating system 100 to supply steam to the steam-consuming device after processing by the back-pressure steam turbine 20; when the gas source pressure of the steam turbine 10 is detected to be less than the steam consumption pressure of the steam-consuming device, the first control valve 60 is controlled to cut off the connection of the first branch pipe 21 and connect the second branch pipe 41, so that the steam outlet of the steam turbine 10 is connected to the steam inlet of the steam compressor 40, thereby allowing the heating system 100 to supply steam to the steam-consuming device through the steam compressor 40.

[0038] According to the heating method of the present invention, the heating system 100 can meet the gas supply requirements of the steam-using device under various operating loads.

[0039] According to some embodiments of the present invention, such as Figure 3 As shown, step S2 includes: Step S21: Connect the steam outlet of the steam turbine 10 to the steam inlet of the back-pressure steam turbine 20. Step S22: Control the output power of the electric generator 30 so that the speed of the back-pressure steam turbine 20 reaches the preset speed, the exhaust pressure parameter reaches the preset pressure value, and the temperature parameter reaches the preset temperature value. Step S23: Connect the steam outlet of the back-pressure steam turbine 20 to the steam-consuming device so that the heating system 100 supplies steam to the steam-consuming device through the back-pressure steam turbine 20.

[0040] Specifically, when the gas source pressure of the steam turbine 10 is detected to be greater than the steam consumption pressure of the steam-using device, the first control valve 60 is first controlled to connect the first branch pipe 21 and disconnect the connection of the second branch pipe 41. Then, based on the outlet pressure and temperature of the steam turbine 10, the output power of the electric generator 30 is set so that the speed of the back-pressure steam turbine 20 reaches the preset speed, the exhaust pressure parameter reaches the preset pressure value, and the temperature parameter reaches the preset temperature value, and these preset speed, preset pressure, and preset temperature are maintained at all times. Then, the steam outlet of the back-pressure steam turbine 20 is connected to the steam-using device to supply steam to the steam-using device. In this way, while ensuring a relatively stable pressure and temperature entering the steam-using device, the energy loss of high-quality steam during the throttling and pressure reduction process can be solved, realizing the cascade utilization of energy and achieving the purpose of energy saving and efficiency improvement.

[0041] It should be noted that when steam is supplied to the steam-consuming device through the back-pressure steam turbine 20, since the electric generator 30, the back-pressure steam turbine 20 and the steam compressor 40 are coaxial, the electric generator 30 will drive the steam compressor 40 to rotate. However, since a speed-changing clutch 50 is provided, the steam compressor 40 can be disengaged from the system, that is, its speed is reduced to zero. This can prevent the steam compressor 40 from running idle on the shaft when not in operation, reduce useless mechanical losses and energy consumption, and improve the overall operating efficiency of the system.

[0042] According to some embodiments of the present invention, such as Figure 4 As shown, step S3 includes: Step S31: Connect the steam outlet of the steam turbine 10 to the steam inlet of the back-pressure steam turbine 20 and the steam inlet of the steam compressor 40. Step S32: Connect the steam outlet of the steam compressor 40 to the steam-consuming device, and connect the steam outlet of the back-pressure steam turbine 20 to the exhaust pipe 70. Step S33: Control the electric generator 30 to drive the steam compressor 40 and the back-pressure steam turbine 20 to rotate, so that the speed of the back-pressure steam turbine 20 reaches the preset speed, the outlet pressure of the steam compressor 40 reaches the preset pressure value, and the outlet flow rate reaches the preset flow rate value.

[0043] Specifically, when the gas source pressure of the steam turbine 10 is detected to be less than the steam consumption pressure of the steam-consuming device, the first control valve 60 is controlled to connect the steam outlet of the steam turbine 10 with the steam inlet of the steam compressor 40, and the flow rate of the first branch pipe 21 is controlled to be reduced to a preset value. Then, the electric generator 30 is controlled to drive the back pressure steam turbine 20 to rotate, so that its speed is maintained at a preset speed. At the same time, the electric generator 30 drives the steam compressor 40 to rotate through the speed change clutch 50, so that the outlet pressure of the steam compressor 40 reaches the preset pressure value and the outlet flow rate reaches the preset flow rate value.

[0044] The electric generator 30 drives the back-pressure steam turbine 20 to rotate, maintaining its speed at a preset speed. This ensures that when the heating system 100 uses the steam compressor 40 to supply steam to the steam-consuming device, the back-pressure steam turbine 20 is always rotating. This keeps the back-pressure steam turbine 20 in a hot standby state. Therefore, when the steam source pressure of the steam turbine 10 is detected to be greater than the steam consumption pressure of the steam-consuming device, the steam supply mode can be quickly switched.

[0045] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0046] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0047] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0048] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0049] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A steam turbine heating system for a thermal power unit, characterized in that, include: boiler; Steam turbine (10), the steam outlet of the boiler is connected to the steam inlet of the steam turbine (10); A back-pressure steam turbine (20), wherein the steam outlet of the steam turbine (10) is connected to the steam inlet of the back-pressure steam turbine (20) via a first branch pipe (21), and the steam outlet of the back-pressure steam turbine (20) is configured to be connected to a steam-consuming device. An electric generator (30) is provided, wherein the output shaft of the back-pressure turbine (20) is connected to the input shaft of the electric generator (30), the output power of the electric generator (30) is adjustable so that the speed of the back-pressure turbine (20) is constant, and the electric generator (30) is configured to be connected to an electrical system.

2. The steam turbine heating system for thermal power units according to claim 1, characterized in that, Also includes: A steam compressor (40) is provided, wherein the steam outlet of the steam turbine (10) is connected to the steam inlet of the steam compressor (40) via a second branch pipe (41), and the steam outlet of the steam compressor (40) is configured to be connected to a steam-using device.

3. The steam turbine heating system for thermal power units according to claim 2, characterized in that, The output shaft of the electric generator (30) is connected to the input shaft of the steam compressor (40), and the electric generator (30) is used to drive the steam compressor (40) to rotate.

4. The steam turbine heating system for thermal power units according to claim 3, characterized in that, Also includes: A speed-changing clutch (50) is connected between the electric generator (30) and the steam compressor (40).

5. The steam turbine heating system for thermal power units according to claim 2, characterized in that, Also includes: A first control valve (60) is arranged on the first branch pipe (21) and / or the second branch pipe (41) for controlling the steam outlet of the steam turbine (10) to be switched to be connected to the steam inlet of the back pressure steam turbine (20) and / or to be connected to the steam inlet of the steam compressor (40).

6. The steam turbine heating system for thermal power units according to any one of claims 1-5, characterized in that, Also includes: The exhaust pipe (70) has one end connected to the steam outlet of the back-pressure steam turbine (20) and the other end configured to be connected to the condenser and / or the exhaust device of the steam turbine (10).

7. The steam turbine heating system for thermal power units according to claim 6, characterized in that, Also includes: A second control valve (80) is connected in series with the exhaust pipe (70) and is used to control the opening and closing of the exhaust pipe (70).

8. A heating method for use in a steam turbine heating system of a thermal power unit according to any one of claims 1-7, characterized in that, The heating method includes: Step S1: Confirm whether the gas source pressure of the steam turbine (10) is greater than the steam pressure of the steam-using device. If yes, proceed to step S2; otherwise, proceed to step S3. Step S2: Connect the steam outlet of the steam turbine (10) to the steam inlet of the back-pressure steam turbine (20) so that the heating system (100) supplies heat to the steam-consuming device through the back-pressure steam turbine (20); Step S3: Connect the steam outlet of the steam turbine (10) to the steam inlet of the steam compressor (40) so that the heating system (100) supplies heat to the steam-using device through the steam compressor (40).

9. The heating method according to claim 8, characterized in that, Step S2 includes: Step S21: Control the output power of the electric generator (30) so that the speed of the back pressure turbine (20) reaches the preset speed, the exhaust pressure parameter reaches the preset pressure value, and the temperature parameter reaches the preset temperature value. Step S22: Connect the steam outlet of the steam turbine (10) to the steam inlet of the back-pressure steam turbine (20); Step S23: Connect the steam outlet of the back-pressure steam turbine (20) to the steam-consuming device so that the heating system (100) supplies heat to the steam-consuming device through the back-pressure steam turbine (20).

10. The heating method according to claim 8, characterized in that, Step S3 includes: Step S31: Connect the steam outlet of the steam turbine (10) to the steam inlet of the back-pressure steam turbine (20) and the steam inlet of the steam compressor (40); Step S32: Connect the steam outlet of the steam compressor (40) to the steam-using device, and connect the steam outlet of the back-pressure steam turbine (20) to the exhaust pipe; Step S33: Control the electric generator (30) to drive the steam compressor (40) and the back pressure turbine (20) to rotate, so that the speed of the back pressure turbine (20) reaches the preset speed, the outlet pressure of the steam compressor (40) reaches the preset pressure value, and the outlet flow rate reaches the preset flow rate value.

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