Thermal power unit cascade heat supply system and method

Abstract

The embodiment of the present application provides a kind of thermal power unit cascade heat supply system and method, belong to heating field.The thermal power unit cascade heat supply system, including thermal power unit and back extraction machine, the steam inlet pipeline of the back extraction machine is connected with the main steam pipeline of thermal power unit, for receiving the main steam of thermal power unit;The steam extraction pipeline of the back extraction machine is connected with the high-pressure heat supply header of thermal power unit, for exporting high-pressure heat supply for high-pressure heat supply header;The exhaust pipe of the back extraction machine is connected with the medium-pressure heat supply header of thermal power unit, for exporting medium-pressure heat supply for medium-pressure heat supply header.The present application recycles the work capacity of main steam by back extraction machine, compared with main steam extraction heat supply scheme, reduces water injection temperature reduction, and part of the steam extraction of back extraction machine after work and the exhaust of back extraction machine after complete work are used as high-pressure and medium-pressure heat supply steam source respectively, meet the demand of high and medium pressure combined heat supply, realize energy level matching heat supply, improve energy utilization.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of heat supply, in particular to a thermal power unit cascade heat supply system and a thermal power unit cascade heat supply method. BACKGROUND

[0002] Combined heat and power generation has significant advantages in energy saving and emission reduction due to its characteristics of "temperature matching and cascade utilization". The heat supply of combined heat and power generation units is divided into residential heating and industrial heating. The residential heating has a relatively perfect heat supply system such as extraction heating, low-grade heat cascade heating and heat pump waste heat recovery heating. The industrial heating, especially the high-parameter heating (2.3-6.0 MPa, 320-420℃) required by the chemical industry, generally adopts the extraction heating scheme of temperature reduction and pressure reduction.

[0003] For the higher energy level extraction heating scheme of temperature reduction and pressure reduction commonly used in industrial heating, the extraction of the extraction point with higher pressure or temperature level is used, and then the heat users use the extraction after temperature reduction and pressure reduction, which causes a waste of energy level matching to a certain extent, and the "temperature matching and cascade utilization" is not truly realized.

[0004] In view of the above reasons, the present application aims to provide a thermal power unit cascade heat supply system and a thermal power unit cascade heat supply method, which recycle the work capacity of the main steam by setting an extraction backpressure turbine, and the extraction and exhaust of the extraction backpressure turbine are used for high-pressure and medium-pressure heat supply respectively, thereby recycling the work capacity of the main steam, meeting the demand of high and medium pressure combined heat supply, and realizing energy level matching heat supply. SUMMARY

[0005] The present application aims to provide a thermal power unit cascade heat supply system and a thermal power unit cascade heat supply method, which recycle the work capacity of the main steam by setting an extraction backpressure turbine, and the extraction and exhaust of the extraction backpressure turbine are used for high-pressure and medium-pressure heat supply respectively, thereby recycling the work capacity of the main steam, meeting the demand of high and medium pressure combined heat supply, and realizing energy level matching heat supply.

[0006] To achieve the above-mentioned purpose, the first aspect of the present application provides a thermal power unit cascade heat supply system, comprising a thermal power unit and an extraction backpressure turbine,

[0007] The extraction backpressure turbine is connected to the main steam pipeline of the thermal power unit through a steam inlet pipeline, and is used to receive the main steam of the thermal power unit.

[0008] The extraction pipeline of the extraction backpressure turbine is connected to the high-pressure heat supply header of the thermal power unit, and is used to output high-pressure heat supply for the high-pressure heat supply header.

[0009] The exhaust steam pipeline of the extraction backpressure turbine is connected with the medium-pressure heating header of the thermal power unit, and is used for outputting medium-pressure heating for the medium-pressure heating header.

[0010] Preferably, the system further comprises a steam-steam heat exchanger, a high-pressure steam inlet end of the steam-steam heat exchanger is connected with an output end of the extraction steam pipeline, a high-pressure steam outlet end of the steam-steam heat exchanger is connected with an input end of the high-pressure heating header, a medium-pressure steam inlet end of the steam-steam heat exchanger is connected with an output end of the exhaust steam pipeline, and a medium-pressure steam outlet end of the steam-steam heat exchanger is connected with an input end of the medium-pressure heating header.

[0011] Preferably, the system further comprises a high-pressure heating auxiliary module and a medium-pressure heating auxiliary module,

[0012] an input end of the high-pressure heating auxiliary module is connected with the main steam pipeline, and an output end of the high-pressure heating auxiliary module is connected with the high-pressure heating header.

[0013] an input end of the medium-pressure heating auxiliary module is connected with a steam inlet end of the medium-pressure cylinder of the thermal power unit, and an output end of the medium-pressure heating auxiliary module is connected with the medium-pressure heating header.

[0014] Preferably, the system further comprises a heating reheater,

[0015] a first input end of the heating reheater is connected with an output end of the exhaust steam pipeline, and a first output end of the heating reheater is connected with the medium-pressure steam inlet end of the steam-steam heat exchanger.

[0016] a second input end of the heating reheater is connected with an exhaust end of the high-pressure cylinder, and a second output end of the heating reheater is connected with the medium-pressure heating header.

[0017] The heating reheater is used for heating exhaust steam output by the exhaust steam pipeline or heating exhaust steam output by the high-pressure cylinder.

[0018] Preferably, the system further comprises a reheating heater, an input end of the reheating heater is connected with the second output end of the heating reheater, an output end of the reheating heater is connected with the medium-pressure heating header, and the reheating heater is connected in series with the heating reheater, so as to protect the heating reheater.

[0019] Preferably, a heating reheater inlet bypass valve is arranged between the exhaust end of the high-pressure cylinder and the heating reheater, a heating reheater outlet bypass valve is arranged between the heating reheater and the reheating heater, and the exhaust end of the high-pressure cylinder is further provided with a high-pressure cylinder exhaust cutoff valve, so that when the high-pressure cylinder exhaust cutoff valve is closed, the heating reheater inlet bypass valve is opened, and the heating reheater outlet bypass valve is opened, the reheating heater is connected in series with the heating reheater.

[0020] Preferably, the system further comprises a temperature and pressure reducing module, the temperature and pressure reducing module comprising a first high-pressure heat supply temperature and pressure reducing valve, a second high-pressure heat supply temperature and pressure reducing valve, a first medium-pressure heat supply temperature and pressure reducing valve, and a second medium-pressure heat supply temperature and pressure reducing valve;

[0021] The input end of the first high-pressure heat supply temperature and pressure reducing valve is connected to the high-pressure steam outlet end of the steam-steam heat exchanger, and the output end of the first high-pressure heat supply temperature and pressure reducing valve is connected to the input end of the high-pressure heat supply header;

[0022] The input end of the second high-pressure heat supply temperature and pressure reducing valve is connected to the output end of the main steam pipeline, and the output end of the second high-pressure heat supply temperature and pressure reducing valve is connected to the input end of the high-pressure heat supply header;

[0023] The input end of the first medium-pressure heat supply temperature and pressure reducing valve is connected to the medium-pressure steam outlet end of the steam-steam heat exchanger, and the output end of the first medium-pressure heat supply temperature and pressure reducing valve is connected to the input end of the medium-pressure heat supply header;

[0024] The input end of the second medium-pressure heat supply temperature and pressure reducing valve is connected to the exhaust steam end of the high-pressure cylinder, and the output end of the second medium-pressure heat supply temperature and pressure reducing valve is connected to the input end of the medium-pressure heat supply header.

[0025] Preferably, the system further comprises a switching and adjusting module, the switching and adjusting module comprising a backpressure turbine admission adjusting valve, a high-pressure auxiliary heat supply adjusting valve, and a medium-pressure auxiliary heat supply adjusting valve;

[0026] The backpressure turbine admission adjusting valve is arranged on the admission pipeline and is used for controlling switching of the backpressure turbine into or out of operation;

[0027] The high-pressure auxiliary heat supply adjusting valve is arranged between the input end of the high-pressure heat supply auxiliary module and the main steam pipeline and is used for controlling switching of the high-pressure heat supply auxiliary module into or out of operation;

[0028] The medium-pressure auxiliary heat supply adjusting valve is arranged between the input end of the medium-pressure heat supply auxiliary module and the admission end of the medium-pressure cylinder and is used for controlling switching of the medium-pressure heat supply auxiliary module into or out of operation.

[0029] In a second aspect, an embodiment of the present application provides a method for cascade heat supply of a thermal power generating unit, which is implemented based on the cascade heat supply system of the thermal power generating unit as described above, and the method comprises the following steps:

[0030] The backpressure turbine extracts the main steam of the thermal power generating unit and uses the work capacity of the main steam to assist the thermal power generating unit to generate power;

[0031] The exhaust steam generated by the work of the backpressure turbine is used for high-pressure heat supply of the thermal power generating unit;

[0032] The exhaust steam generated by the work of the backpressure turbine is used for medium-pressure heat supply of the thermal power generating unit.

[0033] In a third aspect, the embodiment of the present application provides a cascade heat supply method of a thermal power unit, which is implemented based on the cascade heat supply system of the thermal power unit as described above, and the method comprises the following steps:

[0034] When the back pressure turbine module is put into operation, the high-pressure heat supply auxiliary module and the medium-pressure heat supply auxiliary module are taken out of operation, and the extraction steam generated by the work of the back pressure turbine is used for high-pressure heat supply of the thermal power unit, and the exhaust steam generated by the work of the back pressure turbine is used for medium-pressure heat supply of the thermal power unit.

[0035] When the back pressure turbine module is taken out of operation, the high-pressure heat supply auxiliary module and the medium-pressure heat supply auxiliary module are put into operation, the high-pressure heat supply auxiliary module is used for inputting the main steam of the thermal power unit into a high-pressure heat supply header after being de-pressurized and de-temperature-reduced, so as to realize stable high-pressure heat supply, and the medium-pressure heat supply auxiliary module is used for inputting the medium-pressure cylinder steam of the thermal power unit into a medium-pressure heat supply header after being de-pressurized and de-temperature-reduced, so as to realize stable medium-pressure heat supply.

[0036] The present application recycles the work capacity of the main steam by the back pressure turbine, reduces water injection and temperature reduction compared with the main steam extraction heat supply scheme, uses part of the extraction steam of the back pressure turbine after work and the exhaust steam of the back pressure turbine after complete work as high-pressure and medium-pressure heat supply steam sources respectively, meets the high and medium pressure combined heat supply demand, realizes energy level matching heat supply, and improves the energy utilization rate.

[0037] Other features and advantages of the embodiment of the present application will be described in detail in the following specific implementation part. DETAILED DESCRIPTION

[0038] The accompanying drawings are included to provide a further understanding of the embodiment of the present application, and constitute a part of the specification, and are used together with the following specific implementation to explain the embodiment of the present application, but do not constitute a limitation on the embodiment of the present application. In the drawings:

[0039] Figure 1 is a cascade heat supply flow chart of the thermal power unit when the back pressure turbine is running, provided by the embodiment 1 of the present application;

[0040] Figure 2 is a cascade heat supply flow chart of the thermal power unit when the back pressure turbine is taken out of operation, provided by the embodiment 1 of the present application.

[0041] Explanation of reference signs

[0042] 1 - extraction backpressure turbine, 2 - main steam line, 3 - high pressure heating header, 4 - medium pressure heating header, 5 - steam-steam heat exchanger, 6 - high pressure cylinder, 7 - heating reheater, 8 - reheating heater, 9 - heating reheater inlet bypass valve, 10 - heating reheater outlet bypass valve, 11 - high pressure cylinder exhaust stop valve, 12 - first high pressure heating desuperheating pressure reducing valve, 13 - second high pressure heating desuperheating pressure reducing valve, 14 - first medium pressure heating desuperheating pressure reducing valve, 15 - second medium pressure heating desuperheating pressure reducing valve, 16 - extraction backpressure turbine inlet regulating valve, 17 - high pressure auxiliary heating regulating valve, 18 - medium pressure auxiliary heating regulating valve, 19 - extraction backpressure turbine extraction regulating valve, 20 - steam-steam heat exchanger high pressure steam inlet valve, 21 - steam-steam heat exchanger medium pressure steam inlet valve, 22 - steam-steam heat exchanger high pressure steam outlet valve, 23 - steam-steam heat exchanger medium pressure steam outlet valve, 24 - high pressure heating auxiliary stop valve, 25 - first high pressure heating desuperheating water regulating valve, 26 - second high pressure heating desuperheating water regulating valve, 27 - first medium pressure heating desuperheating water regulating valve, 28 - second medium pressure heating desuperheating water regulating valve, 29 - medium pressure heating auxiliary stop valve, 30 - extraction backpressure turbine exhaust check valve, 31 - extraction backpressure turbine exhaust stop valve, 32 - medium pressure cylinder, 33 - heating reheater inlet steam header, 34 - heating reheater outlet steam header, 35 - reheating heater inlet steam header, 36 - reheating heater outlet steam header. DETAILED DESCRIPTION

[0043] The specific embodiments of the present application will be described in detail hereinafter with reference to the drawings. It should be understood that the specific embodiments described herein are merely illustrative and explanatory and are not intended to limit the present application.

[0044] In the embodiments of the present application, the orientation words such as "upper", "lower", "left", "right" used herein generally refer to the orientation or position relationship shown in the drawings or the orientation or position relationship when the product of the present application is used, unless otherwise specified. The terms "first", "second", "third" and the like are only used for distinguishing description, and cannot be understood as indicating or implying relative importance.

[0045] The terms "parallel", "vertical" and the like do not mean that the components must be absolutely parallel or vertical, but can be slightly inclined. For example, "parallel" only means that its direction is more parallel relative to "vertical", and does not mean that the structure must be completely parallel, but can be slightly inclined.

[0046] The terms "horizontal", "vertical", "suspension" and the like do not mean that the components must be absolutely horizontal, vertical or suspended, but can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0047] In addition, the terms "substantially", "approximately", and the like are used herein to describe applicable embodiments that exhibit "approximately" or "substantially" the qualitative property, where slight errors and / or deviations are accounted for as being acceptable and / or tolerable. For example, "substantially equal" means that the quantities are equal, plus or minus an acceptable range of tolerance / variation, and / or an acceptable range of tolerance / variation is included in a "substantially equal" relationship. As another example, "substantially perpendicular" means that the two lines are perpendicular, plus or minus an acceptable range of tolerance / variation, and / or an acceptable range of tolerance / variation is included in a "substantially perpendicular" relationship. Other instances and / or embodiments relating to the terms "substantially", "approximately", and the like will be apparent to those of ordinary skill in the art in view of the teachings provided herein.

[0048] In the description of the present application, it is necessary to point out that, unless otherwise explicitly specified and limited, the terms "arrange", "mount", "connect", "connect" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be directly connected, or indirectly connected through an intermediate medium, or the communication inside two elements. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0049] The "connection" described herein is used to express the electrical power connection or signal connection between two components; "connection" can be the direct connection of two elements, or the connection through an intermediate medium (such as a wire), or indirect connection through a third element.

[0050] The "signal connection" described herein is used to express the signal connection between two components, such as control signal and feedback signal; the "electrical connection" described herein is used to express the electrical power connection between two components; "connection" can be the direct connection between two parts, or indirect connection through a third part.

[0051] Embodiment 1

[0052] Please refer to Figure 1 , the first aspect of the present embodiment provides a thermal power unit cascade heat supply system, comprising a thermal power unit and an extraction back machine 1,

[0053] The extraction back machine 1 is connected with the main steam pipeline 2 of the thermal power unit, which is used to receive the main steam of the thermal power unit;

[0054] The extraction back machine 1 is connected with the high-pressure heat supply header 3 of the thermal power unit, which is used to output high-pressure heat supply for the high-pressure heat supply header 3;

[0055] The extraction back machine 1 is connected with the medium-pressure heat supply header 4 of the thermal power unit, which is used to output medium-pressure heat supply for the medium-pressure heat supply header 4.

[0056] In the present embodiment, the functions of the high-pressure heat supply header 3 and the medium-pressure heat supply header 4 include:

[0057] One: the steam of different pressure and temperature levels can be mixed evenly in the heat supply header;

[0058] Two: the heat supply header can buffer the pressure and temperature changes of the heat supply pipeline system caused by the heat load changes.

[0059] In the embodiment, the system further comprises a steam-steam heat exchanger 5, a high-pressure steam inlet end of the steam-steam heat exchanger 5 is connected to an output end of the extraction steam pipeline, a high-pressure steam outlet end of the steam-steam heat exchanger 5 is connected to an input end of the high-pressure heat supply header 3, a medium-pressure steam inlet end of the steam-steam heat exchanger 5 is connected to an output end of the exhaust steam pipeline, and a medium-pressure steam outlet end of the steam-steam heat exchanger 5 is connected to an input end of the medium-pressure heat supply header 4.

[0060] Specifically, the extraction steam of the extraction and exhaust machine 1 is used to provide high-pressure heat supply for the thermal power generating unit, and the exhaust steam of the extraction and exhaust machine 1 is used to provide medium-pressure heat supply for the thermal power generating unit.

[0061] The steam-steam heat exchanger 5 has the characteristics that the heat exchange fluids on both sides of the steam-steam heat exchanger 5 are steam, the pressure of the cold-side fluid is high, the pressure of the hot-side fluid is low, and the heat exchange between the two is completed in the heat exchanger.

[0062] The steam-steam heat exchanger 5 is selected to exchange heat between the extraction steam of the extraction and exhaust machine 1 and the exhaust steam of the extraction and exhaust machine 1, which is used to raise the temperature of the high-pressure extraction steam generated by the extraction and exhaust machine 1 to the heat supply requirement temperature to provide heat for the heat user, and is also used to lower the temperature of the medium-pressure exhaust steam generated by the extraction and exhaust machine 1 to the heat supply requirement temperature to provide heat for the heat user.

[0063] The high-pressure extraction steam and the medium-pressure exhaust steam after the heat exchange of the steam-steam heat exchanger 5 enter the high-pressure heat supply header 3 and the medium-pressure heat supply header 4 respectively to provide heat sources for the high-pressure heat supply header 3 and the medium-pressure heat supply header 4.

[0064] Further, the steam-steam heat exchanger 5 provided in the embodiment is a surface heat exchanger, the medium-pressure heat supply steam is arranged in the shell side of the steam-steam heat exchanger 5, and the high-pressure heat supply steam is arranged in the tube side of the steam-steam heat exchanger 5.

[0065] In the embodiment, the system further comprises a high-pressure heat supply auxiliary module and a medium-pressure heat supply auxiliary module,

[0066] an input end of the high-pressure heat supply auxiliary module is connected to the main steam pipeline 2, and an output end of the high-pressure heat supply auxiliary module is connected to the high-pressure heat supply header 3.

[0067] an input end of the medium-pressure heat supply auxiliary module is connected to a steam inlet end of the medium-pressure cylinder 32 of the thermal power generating unit, and an output end of the medium-pressure heat supply auxiliary module is connected to the medium-pressure heat supply header 4.

[0068] Specifically, the high-pressure heat supply auxiliary module is used to provide a heat source for the high-pressure heat header 3, and the medium-pressure heat supply auxiliary module is used to provide a heat source for the medium-pressure heat header 4.

[0069] The heat source of the high-pressure heat supply auxiliary module is derived from the main steam, and the heat source of the medium-pressure heat supply auxiliary module is derived from the medium-pressure cylinder 32.

[0070] When the extraction backpressure turbine 1 is faulted to exit operation, the high-pressure heat supply auxiliary module is used to supply heat for the high-pressure heat header 3, and the medium-pressure heat supply auxiliary module is used to supply heat for the medium-pressure heat header 4.

[0071] In the embodiment, the system further comprises a heat supply reheater 7,

[0072] The first input end of the heat supply reheater 7 is connected to the output end of the exhaust steam pipeline, and the first output end of the heat supply reheater 7 is connected to the medium-pressure steam inlet end of the steam-steam heat exchanger 5.

[0073] The second input end of the heat supply reheater 7 is connected to the exhaust steam end of the high-pressure cylinder 6, and the second output end of the heat supply reheater 7 is connected to the medium-pressure heat header 4.

[0074] The heat supply reheater 7 is used to heat the exhaust steam output by the exhaust steam pipeline or the exhaust steam output by the high-pressure cylinder 6.

[0075] Specifically, the heat supply reheater 7 is located in the high-temperature flue of the boiler.

[0076] In the embodiment, when the extraction backpressure turbine 1 is put into operation, the high-pressure heat supply auxiliary module and the medium-pressure heat supply auxiliary module exit operation, and the heat supply reheater 7 is used to heat the exhaust steam of the extraction backpressure turbine 1, so that the exhaust steam is better heat-exchanged with the extraction steam of the extraction backpressure turbine 1 in the steam-steam heat exchanger 5, the extraction steam output by the extraction backpressure turbine 1 is heated, the temperature of the extraction steam is improved, and the high-pressure heat supply is realized. In this way, the phenomenon that the temperature of the exhaust steam output by the extraction backpressure turbine 1 is not high enough, so that the extraction steam of the extraction backpressure turbine 1 cannot be well heat-exchanged in the steam-steam heat exchanger 5 is avoided.

[0077] In the embodiment, when the extraction backpressure turbine 1 exits operation, the high-pressure heat supply auxiliary module and the medium-pressure heat supply auxiliary module are put into operation, and the heat supply reheater 7 and the reheating heater 8 are used in series to heat the exhaust steam of the high-pressure cylinder 6, so that the temperature of the exhaust steam of the high-pressure cylinder 6 is increased to the rated temperature of the heat resteam, and the heat supply for the medium-pressure heat header 4 is realized.

[0078] In other embodiments of the present application, the heat supply reheater 7 adopts part of the heating surface of the original reheater of the boiler, so as to reduce the range of the reconstruction.

[0079] In the embodiment, the system further comprises a reheating heater 8, an input end of the reheating heater 8 is connected to a second output end of the heat supply reheater 7, and an output end of the reheating heater 8 is connected to the intermediate-pressure heat supply header 4, thereby forming a series connection of the reheating heater 8 and the heat supply reheater 7 to protect the heat supply reheater 7.

[0080] Specifically, the reheating heater 8 is used to protect the heat supply reheater 7. When the extraction backpressure turbine 1 is out of operation, no exhaust steam is generated, and the heat supply reheater 7 cannot be cooled, which easily causes the risk of dry burning of the heat supply reheater 7. By connecting the reheating heater 8 in series with the heat supply reheater 7, the exhaust steam of the high-pressure cylinder 6 is sequentially passed through the heat supply reheater 7 and the reheating heater 8, thereby forming protection for the heat supply reheater 7.

[0081] In the embodiment, the heat supply reheater 7 is further provided with a heat supply reheater inlet steam header 33 and a heat supply reheater outlet steam header 34.

[0082] In the embodiment, the reheating heater 8 is further provided with a reheater heater inlet steam header 35 and a reheater heater outlet steam header 36.

[0083] In the embodiment, a heat supply reheater inlet bypass valve 9 is arranged between the exhaust steam end of the high-pressure cylinder 6 and the heat supply reheater 7, a heat supply reheater outlet bypass valve 10 is arranged between the heat supply reheater 7 and the reheating heater 8, and a high-pressure cylinder exhaust steam stop valve 11 is further arranged at the exhaust steam end of the high-pressure cylinder 6. When the high-pressure cylinder exhaust steam stop valve 11 is closed, the heat supply reheater inlet bypass valve 9 is opened, and the heat supply reheater outlet bypass valve 10 is opened, the series connection of the reheating heater 8 and the heat supply reheater 7 is realized.

[0084] When the extraction backpressure turbine 1 is out of operation, the high-pressure cylinder exhaust steam stop valve 11 is closed, the heat supply reheater inlet bypass valve 9 is opened, and the heat supply reheater outlet bypass valve 10 is opened, thereby realizing the series connection of the reheating heater 8 and the heat supply reheater 7. The exhaust steam of the high-pressure cylinder 6 is sequentially passed through the heat supply reheater 7 and the reheating heater 8 for heating, and then enters the intermediate-pressure heat supply header 4 to provide a heat source for the intermediate-pressure heat supply header 4.

[0085] In the embodiment, the system further comprises a desuperheating and pressure reducing module, the desuperheating and pressure reducing module comprises a first high-pressure heat supply desuperheating and pressure reducing valve 12, a second high-pressure heat supply desuperheating and pressure reducing valve 13, a first intermediate-pressure heat supply desuperheating and pressure reducing valve 14, and a second intermediate-pressure heat supply desuperheating and pressure reducing valve 15.

[0086] An input end of the first high-pressure heat supply desuperheating and pressure reducing valve 12 is connected to a high-pressure exhaust end of the steam-steam heat exchanger 5, and an output end of the first high-pressure heat supply desuperheating and pressure reducing valve 12 is connected to an input end of the high-pressure heat supply header 3.

[0087] The input end of the second high-pressure heat supply pressure reducing valve 13 is connected with the output end of the main steam pipeline 2, and the output end of the second high-pressure heat supply pressure reducing valve 13 is connected with the input end of the high-pressure heat supply header 3.

[0088] The input end of the first medium-pressure heat supply pressure reducing valve 14 is connected with the medium-pressure steam outlet end of the steam-steam heat exchanger 5, and the output end of the first medium-pressure heat supply pressure reducing valve 14 is connected with the input end of the medium-pressure heat supply header 4.

[0089] The input end of the second medium-pressure heat supply pressure reducing valve 15 is connected with the exhaust end of the high-pressure cylinder 6, and the output end of the second medium-pressure heat supply pressure reducing valve 15 is connected with the input end of the medium-pressure heat supply header 4.

[0090] Specifically, the first high-pressure heat supply pressure reducing valve 12 is used to adjust the high-pressure heat supply steam parameter when the high-pressure heat supply steam parameter of the steam-steam heat exchanger 5 outlet is too high, so as to meet the high-pressure heat supply requirement.

[0091] The second high-pressure heat supply pressure reducing valve 13 is used to reduce the temperature and pressure of the main steam when the extraction backpressure turbine 1 exits the operation and the high-pressure heat supply is realized through the high-pressure heat supply auxiliary module, so as to make the high-pressure heat supply steam parameter meet the heat user requirement.

[0092] The first medium-pressure heat supply pressure reducing valve 14 is used to adjust the medium-pressure heat supply steam parameter when the medium-pressure heat supply steam parameter of the steam-steam heat exchanger 5 outlet is too high, so as to meet the medium-pressure heat supply requirement.

[0093] The second medium-pressure heat supply pressure reducing valve 15 is used to reduce the temperature and pressure of the medium-pressure cylinder 32 when the extraction backpressure turbine 1 exits the operation and the medium-pressure heat supply is realized through the medium-pressure heat supply auxiliary module, so as to make the medium-pressure heat supply steam parameter meet the heat user requirement.

[0094] In the embodiment, the system further comprises a switching and adjusting module, and the switching and adjusting module comprises an extraction backpressure turbine inlet adjusting valve 19, a high-pressure auxiliary heat supply adjusting valve 17 and a medium-pressure auxiliary heat supply adjusting valve 18.

[0095] The extraction backpressure turbine inlet adjusting valve 19 is arranged on the inlet pipeline and is used to control the switching of the extraction backpressure turbine 1 to be put into or exited.

[0096] The high-pressure auxiliary heat supply adjusting valve 17 is arranged between the input end of the high-pressure heat supply auxiliary module and the main steam pipeline 2 and is used to control the switching of the high-pressure heat supply auxiliary module to be put into or exited.

[0097] The medium-pressure auxiliary heat supply adjusting valve 18 is arranged between the input end of the medium-pressure heat supply auxiliary module and the inlet end of the medium-pressure cylinder 32 and is used to control the switching of the medium-pressure heat supply auxiliary module to be put into or exited.

[0098] In the embodiment, the switching and adjusting module further comprises: a back pressure turbine inlet steam adjusting valve 19, a high pressure steam inlet valve 20 of a steam-steam heat exchanger, a medium pressure steam inlet valve 21 of the steam-steam heat exchanger, a high pressure steam outlet valve 23 of the steam-steam heat exchanger, a medium pressure steam outlet valve 22 of the steam-steam heat exchanger, a high pressure heating auxiliary stop valve 24, a first high pressure heating desuperheating water adjusting valve 25, a second high pressure heating desuperheating water adjusting valve 26, a first medium pressure heating desuperheating water adjusting valve 27, a second medium pressure heating desuperheating water adjusting valve 28, a medium pressure heating auxiliary stop valve 29, a back pressure turbine exhaust valve 30, and a back pressure turbine exhaust stop valve 31.

[0099] The back pressure turbine exhaust adjusting valve 19 is used to adjust the flow and pressure of the exhaust steam of the back pressure turbine 1.

[0100] The back pressure turbine exhaust adjusting valve 19 and the back pressure turbine inlet adjusting valve 19 jointly adjust the flow and pressure of the exhaust steam of the back pressure turbine 1.

[0101] In a second aspect, the present application provides a method for cascade heating of a thermal power generating unit, which is implemented based on the cascade heating system of the thermal power generating unit as described above, and the method comprises the following steps:

[0102] The back pressure turbine 1 receives the main steam of the thermal power generating unit, and uses the power of the main steam to assist the thermal power generating unit to generate electricity.

[0103] The exhaust steam generated by the work of the back pressure turbine 1 is used for high pressure heating of the thermal power generating unit.

[0104] The exhaust steam generated by the work of the back pressure turbine 1 is used for medium pressure heating of the thermal power generating unit.

[0105] In the embodiment, the steam source of the back pressure turbine 1 is taken from the main steam, the main steam flows through the back pressure turbine 1 to generate electricity for power plant auxiliary machines, and the exhaust steam and the exhaust steam of the back pressure turbine 1 are used as the high pressure heating and medium pressure heating steam sources, respectively. Within the normal efficiency range (70%-85%) of the back pressure turbine 1, the exhaust steam and the exhaust steam of the back pressure turbine 1 are relatively low in temperature, and cannot meet the temperature requirements of high pressure heating and medium pressure heating. Therefore, a heating reheater 7 is arranged in the boiler to heat the exhaust steam of the back pressure turbine 1. The medium pressure heating steam after recovering the heat of the boiler is heated by a steam-steam heat exchanger to heat the high pressure heating steam, so as to increase the temperature of the high pressure heating steam to the temperature required by the high pressure heating, and at the same time, the temperature of the medium pressure heating steam is reduced to the temperature required by the medium pressure heating, without the need of water injection for desuperheating.

[0106] The application recovers the work capacity of the main steam by using the back pressure turbine 1, reduces the water injection for temperature reduction compared with the main steam extraction heating scheme, uses the extracted steam of the back pressure turbine 1 after partial work and the exhaust steam of the back pressure turbine 1 after complete work as high-pressure and medium-pressure heating steam sources respectively, meets the high and medium pressure combined heating demand, realizes the energy level matching heating, and improves the energy utilization rate; secondly, the application designs a heating reheater 7 and a steam heat exchanger 5 coupled heating system, recovers the boiler flue gas heat, can simultaneously increase the high and medium pressure heating steam temperature to the rated value, and realizes accurate heating; thirdly, the application designs a heating reheater 7 line switching system, which is used for connecting the heating reheater 7 and the reheating heater 8 in series when the back pressure turbine 1 is out of operation, avoids dry burning of the heating reheater 7, and improves the safety of the system.

[0107] In a third aspect, the application provides a thermal power unit cascade heating method, which is realized based on the thermal power unit cascade heating system as described above, and the method comprises the following steps:

[0108] When the back pressure turbine 1 is put into operation, the high-pressure heating auxiliary module and the medium-pressure heating auxiliary module are out of operation, the extracted steam generated by the work of the back pressure turbine 1 is used for high-pressure heating of the thermal power unit, and the exhaust steam generated by the work of the back pressure turbine 1 is used for medium-pressure heating of the thermal power unit.

[0109] When the back pressure turbine 1 is out of operation, the high-pressure heating auxiliary module and the medium-pressure heating auxiliary module are put into operation, the high-pressure heating auxiliary module is used for inputting the main steam of the thermal power unit into the high-pressure heating header 3 after temperature reduction and pressure reduction, so as to realize stable high-pressure heating, and the medium-pressure heating auxiliary module is used for inputting the medium-pressure cylinder 32 steam of the thermal power unit into the medium-pressure heating header 4 after temperature reduction and pressure reduction, so as to realize medium-pressure heating of the thermal power unit.

[0110] Specifically, as shown in Figure 1 The back pressure turbine 1 is put into operation, and the high-pressure heating auxiliary module and the medium-pressure heating auxiliary module are out of operation.

[0111] The extracted steam of the back pressure turbine 1 flows through the steam heat exchanger 5 and is supplied, the exhaust steam of the back pressure turbine 1 flows through the heating reheater 7 and the steam heat exchanger 5 and is supplied, the heating reheater outlet bypass valve 10 and the heating reheater inlet bypass valve 9 are closed, the high-pressure cylinder exhaust steam stop valve 11 is normally opened, the heating reheater 7 and the reheating heater 8 are independently operated,

[0112] The working condition is as follows:

[0113] The high-pressure heating steam flow is as follows: main steam→back pressure turbine inlet steam regulating valve 16→back pressure turbine 1→back pressure turbine extracted steam regulating valve 19→steam heat exchanger high-pressure steam inlet valve 20→steam heat exchanger 5→steam heat exchanger high-pressure steam outlet valve 21→first high-pressure heating temperature reduction and pressure reduction valve 12→high-pressure heating header 3;

[0114] The medium-pressure heat supply steam flow is: main steam→extraction turbine admission regulating valve 16→extraction turbine 1→extraction turbine exhaust valve 30→extraction turbine exhaust stop valve 31→heat supply reheater inlet steam header 33→heat supply reheater 7→heat supply reheater outlet steam header 34→steam-steam heat exchanger medium-pressure steam inlet valve 21→steam-steam heat exchanger 5→steam-steam heat exchanger medium-pressure steam outlet valve 22→first medium-pressure heat supply desuperheating and pressure reducing valve 14→medium-pressure heat supply header 4.

[0115] Specifically, as shown in FIG. 1, the embodiment further provides a thermal power unit cascade heat supply method. Figure 2 When the extraction turbine 1 is out of operation, the high-pressure heat supply auxiliary module and the medium-pressure heat supply auxiliary module are put into operation, the heat supply reheater outlet bypass valve 10 and the heat supply reheater inlet bypass valve 9 are opened, and the high-pressure cylinder exhaust stop valve 11 is closed, the heat supply reheater 7 and the reheating heater 8 are connected in series,

[0116] The working condition is as follows:

[0117] The high-pressure heat supply steam flow is: main steam→high-pressure heat supply auxiliary regulating valve 17→second high-pressure heat supply desuperheating and pressure reducing valve 13→high-pressure heat supply auxiliary stop valve 24→high-pressure heat supply header 3.

[0118] The medium-pressure heat supply steam flow is: reheating heater outlet steam header 36→medium-pressure heat supply auxiliary regulating valve 18→second medium-pressure heat supply desuperheating and pressure reducing valve 15→medium-pressure heat supply auxiliary stop valve 29→medium-pressure heat supply header 4.

[0119] The heat supply reheater 7 and the reheating heater 8 are connected in series, and the flow is: high-pressure cylinder 6→heat supply reheater inlet bypass valve 9→heat supply reheater inlet steam header 33→heat supply reheater 7→heat supply reheater outlet steam header 34→heat supply reheater outlet bypass valve 10→reheating heater inlet steam header 35→reheating heater 8→reheating heater outlet steam header 36→medium-pressure cylinder 32.

[0120] The above describes the optional implementation manners of the embodiment of the present application in detail in combination with the drawings, but the embodiment of the present application is not limited to the specific details in the above implementation manners, and various simple modifications can be made to the technical solutions of the embodiment of the present application within the technical concept range of the embodiment of the present application, and these simple modifications all belong to the protection range of the embodiment of the present application.

[0121] In addition, it should be noted that each specific technical feature described in the above specific implementation manners can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the embodiment of the present application will not further describe various possible combination manners.

[0122] Besides, the various different embodiments of the embodiments of the present application can also be combined arbitrarily, as long as the idea of the embodiments of the present application is not violated, which should be considered as the disclosed content of the embodiments of the present application.

Claims

1. A cascade heat supply system of a thermal power unit, characterized in that, The system comprises a thermal power unit, an extraction back pressure turbine (1), a steam-steam heat exchanger (5), and a heat supply reheater (7); The extraction back pressure turbine (1) is connected with a main steam pipeline (2) of the thermal power unit, and is used for receiving the main steam of the thermal power unit. The extraction steam pipeline of the extraction back pressure turbine (1) is connected with a high-pressure heat supply header (3) of the thermal power unit, and is used for outputting high-pressure heat supply for the high-pressure heat supply header (3). The exhaust steam pipeline of the extraction back pressure turbine (1) is connected with a medium-pressure heat supply header (4) of the thermal power unit, and is used for outputting medium-pressure heat supply for the medium-pressure heat supply header (4). The high-pressure steam inlet end of the steam-steam heat exchanger (5) is connected with the output end of the extraction steam pipeline, and the high-pressure steam outlet end of the steam-steam heat exchanger (5) is connected with the input end of the high-pressure heat supply header (3). The medium-pressure steam inlet end of the steam-steam heat exchanger (5) is connected with the output end of the exhaust steam pipeline, and the medium-pressure steam outlet end of the steam-steam heat exchanger (5) is connected with the input end of the medium-pressure heat supply header (4).

2. The cascade heat supply system of a thermal power generating unit according to claim 1, characterized in that, The first input end of the heat supply reheater (7) is connected with the output end of the exhaust steam pipeline, and the first output end of the heat supply reheater (7) is connected with the medium-pressure steam inlet end of the steam-steam heat exchanger (5). The second input end of the heat supply reheater (7) is connected with the exhaust end of the high-pressure cylinder (6), and the second output end of the heat supply reheater (7) is connected with the medium-pressure heat supply header (4). The system further comprises a high-pressure heat supply auxiliary module and a medium-pressure heat supply auxiliary module.

3. The cascade heat supply system of a thermal power generating unit according to claim 2, characterized in that, The input end of the high-pressure heat supply auxiliary module is connected with the main steam pipeline (2), and the output end of the high-pressure heat supply auxiliary module is connected with the high-pressure heat supply header (3).

4. The cascade heat supply system of a thermal power generating unit according to claim 3, characterized in that, The input end of the medium-pressure heat supply auxiliary module is connected with the steam inlet end of a medium-pressure cylinder (32) of the thermal power unit, and the output end of the medium-pressure heat supply auxiliary module is connected with the medium-pressure heat supply header (4).

5. The thermal power unit cascade heat supply system according to claim 2, characterised in that, The system further comprises a reheating heater (8), the input end of the reheating heater (8) is connected with the second output end of the heat supply reheater (7), the output end of the reheating heater (8) is connected with the medium-pressure heat supply header (4), and the reheating heater (8) is connected in series with the heat supply reheater (7) to protect the heat supply reheater (7). The exhaust end of the high-pressure cylinder (6) is provided with a heat supply reheater inlet bypass valve (9) between the heat supply reheater (7), the heat supply reheater (7) is provided with a heat supply reheater outlet bypass valve (10) between the reheating heater (8), and the exhaust end of the high-pressure cylinder (6) is further provided with a high-pressure cylinder exhaust stop valve (11). When the high-pressure cylinder exhaust stop valve (11) is closed, the heat supply reheater inlet bypass valve (9) is opened, and the heat supply reheater outlet bypass valve (10) is opened, the reheating heater (8) is connected in series with the heat supply reheater (7). The system further comprises a temperature and pressure reducing module, the temperature and pressure reducing module comprises a first high-pressure heat supply temperature and pressure reducing valve (12), a second high-pressure heat supply temperature and pressure reducing valve (13), a first medium-pressure heat supply temperature and pressure reducing valve (14), and a second medium-pressure heat supply temperature and pressure reducing valve (15). The input end of the first high-pressure heat supply temperature and pressure reducing valve (12) is connected with the high-pressure steam outlet end of the steam-steam heat exchanger (5), and the output end of the first high-pressure heat supply temperature and pressure reducing valve (12) is connected with the input end of the high-pressure heat supply header (3); The input end of the second high-pressure heat supply temperature and pressure reducing valve (13) is connected with the output end of the main steam pipeline (2), and the output end of the second high-pressure heat supply temperature and pressure reducing valve (13) is connected with the input end of the high-pressure heat supply header (3); The input end of the first medium-pressure heat supply temperature and pressure reducing valve (14) is connected with the medium-pressure steam outlet end of the steam-steam heat exchanger (5), and the output end of the first medium-pressure heat supply temperature and pressure reducing valve (14) is connected with the input end of the medium-pressure heat supply header (4); The input end of the second medium-pressure heat supply temperature and pressure reducing valve (15) is connected with the steam inlet end of the medium-pressure cylinder (32), and the output end of the second medium-pressure heat supply temperature and pressure reducing valve (15) is connected with the input end of the medium-pressure heat supply header (4).

6. The thermal power unit cascade heat supply system according to claim 2, characterised in that, The system further comprises a switching and adjusting module, which comprises a backpressure engine steam inlet adjusting valve (16), a high-pressure auxiliary heat supply adjusting valve (17) and a medium-pressure auxiliary heat supply adjusting valve (18); The backpressure engine steam inlet adjusting valve (16) is arranged on the steam inlet pipeline and is used for controlling switching of the backpressure engine (1) into or out of operation; The high-pressure auxiliary heat supply adjusting valve (17) is arranged between the input end of the high-pressure auxiliary heat supply module and the main steam pipeline (2) and is used for controlling switching of the high-pressure auxiliary heat supply module into or out of operation; The medium-pressure auxiliary heat supply adjusting valve (18) is arranged between the input end of the medium-pressure auxiliary heat supply module and the steam inlet end of the medium-pressure cylinder (32) and is used for controlling switching of the medium-pressure auxiliary heat supply module into or out of operation.

7. A method for cascade heat supply of a thermal power unit, characterized in that The method comprises the following steps: The backpressure engine (1) extracts the main steam of the thermal power generating unit, and the work capacity of the extracted steam is used to assist the thermal power generating unit to generate power; The extracted steam generated by the work of the backpressure engine (1) is used for high-pressure heat supply of the thermal power generating unit; The exhaust steam generated by the work of the backpressure engine (1) is used for medium-pressure heat supply of the thermal power generating unit.

8. A method for cascade heat supply of a thermal power unit, characterized in that The method comprises the following steps: When the backpressure engine (1) is in operation, the high-pressure auxiliary heat supply module and the medium-pressure auxiliary heat supply module are out of operation, the extracted steam generated by the work of the backpressure engine (1) is used for high-pressure heat supply of the thermal power generating unit, and the exhaust steam generated by the work of the backpressure engine (1) is used for medium-pressure heat supply of the thermal power generating unit; When the backpressure engine (1) is out of operation, the high-pressure auxiliary heat supply module and the medium-pressure auxiliary heat supply module are in operation, the high-pressure auxiliary heat supply module is used to input the main steam of the thermal power generating unit into the high-pressure heat supply header (3) after temperature and pressure reduction, so as to realize stable high-pressure heat supply, and the medium-pressure auxiliary heat supply module is used to input the steam inlet of the medium-pressure cylinder (32) of the thermal power generating unit into the medium-pressure heat supply header (4) after temperature and pressure reduction, so as to realize stable medium-pressure heat supply.

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