Wide-load multi-stage steam supply system and operation method thereof

Abstract

The embodiment of the invention provides a wide-load multi-stage steam supply system and an operation method thereof. The wide-load multi-stage steam supply system comprises a steam turbine power generation assembly and a heat supply assembly. The steam turbine power generation assembly comprises a main steam pipeline, a high-pressure cylinder, an intermediate-pressure cylinder, a low-pressure cylinder and a power generator. The heat supply assembly comprises a reheat steam pipeline, a steam supply mother pipeline, a steam supplementing pipeline, a medium-pressure cylinder steam exhaust pipeline and a heat supply network heater. The steam supply mother pipeline is connected with a reheat steam pipeline and an industrial steam supply device; a steam exhaust pipeline of the medium-pressure cylinder is respectively connected with a medium-low pressure communicating pipe and a heating network heater, and the heating network heater is connected with a resident heating device; the steam supplementing pipeline is respectively connected with the steam supply mother pipeline and the heat supply network heater; the steam supplementing pipeline conveys industrial supplied steam of the steam supplying main pipeline to the heat supply network heater for steam supplementing when the unit operates at low load. And meanwhile, the power grid peak regulation requirement and the heat consumer requirement are met, the resident heating and industrial steam supply requirements are considered while the unit peak regulation capacity is not affected in the heating season, and the thermal power unit peak regulation capacity can be released to the maximum extent.

Description

Technical Field

[0001] The embodiments of the present disclosure belong to the technical field of cogeneration, and specifically relate to a wide-load multi-stage steam supply system and an operation method thereof. Background Art

[0002] Power generation companies are implementing cogeneration (CHP) to combine the supply of heat and electricity, a highly efficient energy production method. Comparing coal-fired CHP with separate heat and power generation, CHP can save approximately 30% of coal to produce the same amount of heat and electricity, increasing overall efficiency from 50% to 75%.

[0003] In recent years, various regions have introduced policies encouraging local governments and organizations to further enhance the regulation capabilities of their power systems to meet the challenges posed by the rapid development of renewable energy. As a crucial component of the new power system, the regulation capabilities of thermal power units are particularly crucial, shouldering the responsibility of promoting the absorption of renewable energy. For cogeneration units that simultaneously supply industrial steam and residential heating, the minimum unit load can reach approximately 20% to 25% during the non-heating season. However, during the heating season, since heating is considered a civil service project, the minimum unit load is generally maintained at 30% to 35% to meet heating load requirements, significantly reducing the unit's peak-shaving capacity.

[0004] In view of the above problems, it is necessary to propose a wide-load multi-stage steam supply system and its operation method that are reasonably designed and effectively solve the above problems. Summary of the Invention

[0005] The embodiments of the present disclosure aim to solve at least one of the technical problems existing in the prior art and provide a wide-load multi-stage steam supply system and an operating method thereof.

[0006] One aspect of an embodiment of the present disclosure provides a wide-load multi-stage steam supply system for a cogeneration unit, comprising a steam turbine power generation component and a heat supply component;

[0007] The steam turbine power generation assembly includes a main steam pipe, a high-pressure cylinder, an intermediate-pressure cylinder, a low-pressure cylinder and a generator;

[0008] The heating components include a reheat steam pipeline, a steam supply main pipeline, a supplementary steam pipeline, an intermediate pressure cylinder exhaust pipeline and a heating network heater; wherein,

[0009] The inlet of the steam supply main pipeline is connected to the outlet of the reheat steam pipeline, and the outlet of the steam supply main pipeline is used to be connected to an industrial steam supply device;

[0010] The inlet of the medium-pressure cylinder exhaust pipe is connected to the medium- and low-pressure connecting pipes, the outlet of the medium-pressure cylinder exhaust pipe is connected to the inlet of the heat network heater, and the outlet of the heat network heater is used to be connected to the residential heating device;

[0011] The inlet of the supplementary steam pipeline is connected to the main steam supply pipeline, and the outlet of the supplementary steam pipeline is connected to the inlet of the heating network heater; wherein,

[0012] The supplementary steam pipeline is used to transport the industrial steam from the steam supply main pipeline to the heating network heater for supplementary steam when the unit is running at low load.

[0013] Optionally, the supplementary steam pipeline is provided with a first temperature and pressure reducing device, and the first temperature and pressure reducing device is used to reduce the industrial steam supply pressure to match the heating steam supply pressure.

[0014] Optionally, a first desuperheating water pipeline is further included, wherein the first desuperheating water pipeline is connected to the supplementary steam pipeline and is located at the outlet of the first desuperheating and pressure reducing device.

[0015] Optionally, the supplementary steam pipeline is further provided with a first electric valve.

[0016] Optionally, it further comprises a steam supply branch pipe, wherein the inlet of the steam supply branch pipe is respectively connected to the reheat steam pipe and the steam supply main pipe, the outlet of the steam supply branch pipe is connected to the intermediate pressure cylinder, and the steam supply branch pipe is provided with a central valve;

[0017] The intermediate valve is used to adjust the pressure of the steam supply main pipeline when the unit is running under load.

[0018] Optionally, it further includes a second desuperheating and pressure reducing device and a second desuperheating water pipeline;

[0019] The second temperature and pressure reducing device is arranged on the steam supply main pipeline;

[0020] The second desuperheating water pipeline is connected to the steam supply main pipeline and is located at the outlet of the second desuperheater and pressure reducer.

[0021] Optionally, the steam supply main pipeline is further provided with a first check valve, a second electric valve and a third electric valve;

[0022] The first check valve and the second electric valve are arranged near the inlet of the steam supply main pipeline;

[0023] The third electric valve is arranged close to the outlet of the steam supply main pipeline.

[0024] Optionally, the intermediate pressure cylinder exhaust pipe is provided with a second check valve, a regulating valve and a fourth electric valve in sequence.

[0025] Another aspect of the present disclosure provides an operating method for a wide-load multi-stage steam supply system, which is used in a cogeneration unit and the wide-load multi-stage steam supply system described above, wherein the operating method includes:

[0026] When the unit is running at medium or high load, the reheat steam pipe is connected to the steam supply main pipe to provide conventional industrial steam supply; and the intermediate pressure cylinder exhaust pipe is respectively connected to the intermediate and low pressure connecting pipes and the heating network heater to provide conventional steam supply for residential heating;

[0027] When the unit is running at low load, while carrying out conventional industrial steam supply and conventional residential heating steam supply, the supplementary steam pipeline is connected to the main steam supply pipeline and the heating network heater respectively, and the industrial steam supply from the main steam supply pipeline is transported to the heating network heater for supplementary steam.

[0028] Optionally, the method further includes:

[0029] When the unit is running at low load, the opening of the intermediate valve is closed to reduce the pressure of the steam supply main pipeline to the preset pressure value.

[0030] The wide-load multi-stage steam supply system and operation method of the disclosed embodiment are such that, when the unit is operating at low load, the system connects the supplementary steam pipeline to the main steam supply pipeline and the heating network heater respectively while performing conventional industrial steam supply and conventional residential heating steam supply, and transmits the industrial steam supply from the main steam supply pipeline to the heating network heater for supplementary steam, thereby meeting both the peak-shaving requirements of the power grid and the needs of heat users, and taking into account the needs of residential heating and industrial steam supply while not affecting the peak-shaving capacity of the unit during the heating season, thereby maximizing the peak-shaving capacity of the thermal power unit. The system has a small scope of modification, low investment, and a wide range of applicability, which is conducive to further promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a structural diagram of a wide-load multi-stage steam supply system according to one embodiment of the present disclosure;

[0032] Figure 2 This is a flow chart of an operating method of a wide-load multi-stage steam supply system according to another embodiment of the present disclosure. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the technical solutions of the embodiments of the present disclosure, the embodiments of the present disclosure are further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0034] like Figure 1 As shown, one aspect of an embodiment of the present disclosure provides a wide-load multi-stage steam supply system for a cogeneration unit, including a steam turbine power generation component and a heat supply component.

[0035] The steam turbine generator assembly consists of a main steam pipe 1, a high-pressure cylinder 2, an intermediate-pressure cylinder 3, a low-pressure cylinder 4, and a generator. The main steam pipe 1 is connected to the boiler. The main steam transported by the main steam pipe 1 passes through the high-pressure cylinder 2, the intermediate-pressure cylinder 3, and the low-pressure cylinder 4, driving the generator to generate electricity.

[0036] The heating components include a reheat steam pipe 5, a main steam supply pipe 6, a supplementary steam pipe 7, an intermediate pressure cylinder exhaust pipe 8 and a heating network heater 9.

[0037] The inlet of the steam supply main pipe 6 is connected to the outlet of the reheat steam pipe 5, and the outlet of the steam supply main pipe 6 is used to connect to the industrial steam supply device. Specifically, the reheated steam transported by the reheat steam pipe 5 is transported to the industrial steam supply device through the steam supply main pipe 6 to realize industrial steam supply.

[0038] The inlet of the intermediate-pressure cylinder exhaust pipe 8 is connected to the intermediate- and low-pressure connecting pipe 10. The outlet of the intermediate-pressure cylinder exhaust pipe 8 is connected to the inlet of the heating network heater 9. The outlet of the heating network heater 9 is connected to the residential heating system. The intermediate- and low-pressure connecting pipe 10 is installed between the intermediate-pressure cylinder 3 and the low-pressure cylinder 4.

[0039] Specifically, the medium- and low-pressure connecting pipe 10 is perforated to extract steam, which is then transported to the heating network heater 9 through the medium-pressure cylinder exhaust pipe 8 for heating, and then transported to the residential heating device to provide heating for the residents. The medium- and low-pressure connecting pipe 10 is equipped with a hydraulically controlled butterfly valve 24.

[0040] The inlet of the supplementary steam pipeline 7 is connected to the main steam supply pipeline 6 , and the outlet of the supplementary steam pipeline 7 is connected to the inlet of the heating network heater 9 .

[0041] Among them, the supplementary steam pipeline 7 is used to transport the industrial steam supply from the steam supply main pipeline 6 to the heating network heater 9 for supplementary steam when the unit is running at low load, so as to meet the heating needs of residents when the unit is running at low load.

[0042] That is to say, part of the steam supply from the steam supply main pipeline 6 is transported to the industrial steam supply device for industrial steam supply, and the other part enters the heat network heater 9 through the supplementary steam pipeline 7 and is heated before being transported to the residential heating device to realize residential heating steam supply.

[0043] The wide-load multi-stage steam supply system of the disclosed embodiment is provided with a steam supplement pipeline. When the unit is operating at low load, the steam supplement pipeline is connected to the steam main pipeline and the heating network heater respectively while performing conventional industrial steam supply and conventional residential heating steam supply. The industrial steam supply from the steam main pipeline is transported to the heating network heater for steam supplement. This not only meets the peak-shaving requirements of the power grid, but also meets the needs of heat users. While not affecting the peak-shaving capacity of the unit during the heating season, it takes into account the needs of residential heating and industrial steam supply, and can maximize the peak-shaving capacity of the thermal power unit. The system has a small modification scope, low investment amount, and a wide range of applications, which is conducive to further promotion.

[0044] For example, Figure 1 As shown, the supplementary steam pipeline 7 is provided with a first temperature and pressure reducing device 11, which is used to reduce the industrial steam supply pressure to match the heating steam supply pressure.

[0045] Specifically, after the industrial steam supply in the main gas supply pipeline 6 enters the supplementary steam pipeline 7, the industrial steam supply pressure is reduced to match the heating steam supply pressure through adjustment by the first temperature and pressure reducing device 11, so that the steam supply pressure entering the heating network heater 9 from the supplementary steam pipeline 7 reaches the preset value, thereby achieving more reliable steam supply to the heating network heater 9.

[0046] It should be noted that the cooling water of the first cooling and pressure reducing device 11 comes from the condensate system of the unit. In addition, the cooling water in the first cooling and pressure reducing device 11 is not used during normal operation and is only used for regulation and standby.

[0047] In the above embodiments, by providing the first temperature and pressure reducing device in the supplementary steam pipeline, the steam supply pressure and temperature in the supplementary steam pipeline can be adjusted, thereby achieving more reliable steam supply to the heating network heater.

[0048] For example, Figure 1 As shown, the system further includes a first desuperheating water pipeline 12 , which is connected to the supplementary steam pipeline 7 and is located at the outlet of the first desuperheating and pressure reducing device 11 .

[0049] Specifically, the industrial steam supply temperature is generally consistent with the heating extraction temperature. Under certain operating conditions, significant temperature deviations may require the addition of desuperheated water. If the steam supply temperature after adjustment by the first desuperheater / pressure reducer 11 does not drop to the preset value, desuperheated water in the first desuperheater / water pipe 12 can be used to further cool the steam supply in the supply steam pipe 7, bringing the steam supply temperature to the preset value and ensuring more reliable supply steam.

[0050] For example, Figure 1 As shown, the supplementary steam pipeline 7 is further provided with a first electric valve 13. The first electric valve 13 controls the opening and closing of the supplementary steam pipeline 7. When the unit is operating at medium to high loads, the first electric valve 13 is closed, and the supplementary steam pipeline 7 is closed, and no supplementary steam is supplied to the heating network heater 9. When the unit is operating at low loads, while providing conventional steam supply for industrial and residential heating, the first electric valve 13 is opened, connecting the supplementary steam pipeline 7 to the main steam supply pipeline 6 and the heating network heater 9, respectively, to supply steam to the heating network heater 9.

[0051] For example, Figure 1 As shown, the system also includes a steam supply branch pipe 14, the inlet of the steam supply branch pipe 14 is connected to the reheat steam pipe 5 and the steam supply main pipe 6 respectively, the outlet of the steam supply branch pipe 14 is connected to the intermediate pressure cylinder 3, and the steam supply branch pipe 14 is provided with a central valve 15.

[0052] The intermediate valve 15 is used to adjust the pressure of the steam supply main pipeline 6 when the unit is running under load.

[0053] It should be noted that when the unit is operating at medium to high loads, the reheated steam pressure can meet the needs of low-pressure users, and the intermediate valve 15 does not need to be involved in regulation. When the unit is operating at low loads, the reheated steam pressure cannot meet the needs of low-pressure users. In this case, the intermediate valve 15 is involved in regulation. By reducing the opening of the intermediate valve 15, the pressure in the steam supply main pipeline 6 is increased, so that the reheated steam pressure in the steam supply main pipeline 6 meets the needs of low-pressure users.

[0054] For example, Figure 1 As shown, the system also includes a second desuperheater 16 and a second desuperheating water pipe 17. The second desuperheater 16 is provided on the steam supply main pipe 6 and can desuperheat and reduce the pressure of the reheated steam entering the steam supply main pipe 6 to meet the temperature and pressure requirements of the industrial steam supply.

[0055] The second desuperheating water pipeline 17 is connected to the steam supply main pipeline 6 and is located at the outlet of the second desuperheater and pressure reducer 16 .

[0056] Specifically, after the reheated steam entering the steam supply main pipe 6 is cooled and reduced in pressure by the second cooling and pressure reducing device 16, if the temperature of the reheated steam in the steam supply main pipe 6 is still higher than the preset value, it is necessary to further adjust the steam supply temperature in the steam supply main pipe 6 through the cooling water in the second cooling water pipe 17 to meet the preset value, so as to provide industrial steam supply more reliably.

[0057] For example, Figure 1 As shown, the steam supply main pipeline 6 is further provided with a first check valve 18 , a second electric valve 19 and a third electric valve 20 .

[0058] The first check valve 18 and the second electric valve 19 are arranged near the inlet of the steam supply main pipeline 6. The third electric valve 20 is arranged near the outlet of the steam supply main pipeline 6.

[0059] Specifically, the second electric valve 19 and the third electric valve 20 control the opening and closing of the steam supply main pipeline 6. The first check valve 18 prevents steam backflow. When industrial steam supply is required, the first check valve 18, the second electric valve 19, and the third electric valve 20 are all opened to allow the steam in the steam supply main pipeline 6 to enter the industrial steam supply device for industrial steam supply.

[0060] For example, Figure 1As shown, the intermediate-pressure cylinder exhaust steam pipeline 8 is sequentially equipped with a second check valve 21, a regulating valve 22, and a fourth electric valve 23. The second check valve 21 prevents steam backflow. The regulating valve 22 adjusts the steam flow rate within the intermediate-pressure cylinder exhaust steam pipeline 8. The fourth electric valve 23 controls the opening and closing of the intermediate-pressure cylinder exhaust steam pipeline 8. When steam is needed for residential heating, the fourth electric valve 23 is opened, allowing steam from the intermediate- and low-pressure connecting pipes 10 to be delivered to the heating network heater 9 via the intermediate-pressure cylinder exhaust steam pipeline 8.

[0061] like Figure 2 As shown, another aspect of the embodiment of the present disclosure provides an operating method S100 for a wide-load multi-stage steam supply system, which is used for a cogeneration unit and for the wide-load multi-stage steam supply system mentioned above. The specific structural features of the wide-load multi-stage steam supply system have been described in detail above and will not be repeated here.

[0062] The operating method S100 of the wide-load multi-stage steam supply system may specifically include:

[0063] S110. When the unit is operating at medium or high load, the reheat steam pipeline is connected to the steam supply main pipeline for conventional industrial steam supply; and the medium-pressure cylinder exhaust pipeline is connected to the medium- and low-pressure connecting pipes and the heat network heater respectively for conventional steam supply for residential heating.

[0064] Specifically, when the unit is operating at medium or high load, the reheat steam pipe 5 is connected to the steam supply main pipe 6 for conventional industrial steam supply; and the intermediate pressure cylinder exhaust pipe 8 is respectively connected to the intermediate and low pressure connecting pipes 10 and the heat network heater 9, and the steam supply in the intermediate and low pressure connecting pipes 10 is transported to the heat network heater 9 through the intermediate pressure cylinder exhaust pipe 8 for heating to carry out conventional steam supply for residential heating.

[0065] S120: When the unit is running at low load, while carrying out conventional industrial steam supply and conventional residential heating steam supply, the supplementary steam pipeline is connected to the steam supply main pipeline and the heating network heater respectively, and the industrial steam supply from the steam supply main pipeline is transported to the heating network heater for supplementary steam.

[0066] Specifically, when the unit is operating at low load, while providing conventional industrial steam supply and conventional steam supply for residential heating, the supplementary steam pipeline 7 is connected to the steam supply main pipeline 6 and the heating network heater 9 respectively, and the industrial steam supply from the steam supply main pipeline 6 is transported to the heating network heater 9 for supplementary steam, thereby meeting the steam supply for residential heating when the unit is operating at low load.

[0067] Exemplarily, the method further includes:

[0068] When the unit is running at low load, the opening of the intermediate valve 15 is closed to increase the pressure of the steam supply main pipeline 6, and the pressure of the steam supply main pipeline 6 is adjusted to the preset pressure value to meet the needs of low-pressure industrial users.

[0069] like Figure 1 As shown, the specific process of the operation method S100 of the wide-load multi-stage steam supply system according to the embodiment of the present disclosure can be as follows:

[0070] 1. Conventional steam supply mode

[0071] The unit is running at medium to high load. At this time, the hot resteam pressure can meet the needs of low-pressure users. The central connecting valve 15 does not need to be adjusted. At this time, the industrial steam is supplied by the steam supply main pipeline 6, that is, the second electric valve 19 and the third electric valve 20 are opened, the second temperature and pressure reducer 16 is put into operation, and the first electric valve 13 is closed. The heating demand can be met through the conventional heating operation mode, that is, the regulating valve 22 and the fourth electric valve 23 are opened, and the medium-pressure cylinder exhaust pipe 8 transports the steam in the medium- and low-pressure connecting pipe 10 to the heating network heater 9 for heating and then provides heating to the users, realizing conventional steam supply for residential heating.

[0072] 2. Zhonglian valve parameter adjustment steam supply mode

[0073] The unit is running at low load. At this time, the hot resteam pressure cannot meet the needs of low-pressure industrial users. The central valve 15 is adjusted to reduce the opening of the central valve 15 and adjust the pressure of the steam supply main pipeline 6 to the preset pressure value. At this time, the industrial steam is supplied by the steam supply main pipeline 6, that is, the second electric valve 19 and the third electric valve 20 are opened, the second temperature and pressure reducer 16 is put into operation, and the first electric valve 13 is closed. The heating demand can be met through the conventional heating operation mode, that is, the regulating valve 22 and the fourth electric valve 23 are opened, and the medium-pressure cylinder exhaust pipe 8 transports the steam supply in the medium- and low-pressure connecting pipe 10 to the heating network heater 9 for heating and then provides heating to the user, realizing conventional steam supply for residential heating.

[0074] According to the conventional operation mode, in order to ensure that the heating load meets user demand during the heating season, the deep peak load is basically maintained at around 30% to 35%. After the system is transformed, as the load decreases, the steam extraction flow rate of the medium and low pressure connecting pipes 10 cannot meet the demand of heat users, and it is necessary to supply steam to the heating network heater 9 through the steam supply pipe 7. That is, open the first electric valve 13, and after the industrial steam supply pressure is reduced to match the heating steam extraction pressure through the first desuperheater and pressure reducer 11, supply steam to the heating network heater 9 through the steam supply pipe 7. This operation mode can make the unit's deep load regulation as low as about 20%.

[0075] In addition, for some units, the heating capacity of this system has already reached its maximum value, and in extremely cold weather, steam needs to be added through the system to further increase the heating capacity.

[0076] Take a 350MW unit as an example, the industrial steam supply pressure is 1.5MPa,

[0077] 350℃, the lowest operating load of the unit during the current deep peak-shaving operation is about 115MW. At this time, the steam consumption of high-pressure users is about 100t / h, and the steam extraction for residential heating is about 200t / h, which is equivalent to a heating load of about 151MW. In order to ensure the heating demand, the deep peak-shaving capacity of the unit has reached its limit. In order to further tap the deep peak-shaving potential of the unit while ensuring that the unit's heating capacity can meet the demand, the method of using the steam supply pipe 7 to supply steam to the heating network heater 9 is used to increase the heating supply.

[0078] The unit was modeled and calculated using Ebslion. The calculation results are shown in Table 1:

[0079] Table 1 Heating capacity of the unit under the operation method of the wide load multi-stage steam supply system according to the embodiment of the present disclosure

[0080]

[0081] As shown in Table 1, when the unit load is 70 MW and the wide-load multi-stage steam supply system is used, the heating load is 151.5 MW, which is consistent with the heating load when the unit load is 115 MW and no steam is supplied to the heating network heater 9. In other words, the wide-load multi-stage steam supply system operation method of the disclosed embodiment not only improves the peak-shaving capacity of the heating unit during winter heating operation to a certain extent, but also further increases the unit's heating capacity during extremely cold weather when the unit's heating capacity approaches its limit.

[0082] The operating method of the wide-load multi-stage steam supply system of the disclosed embodiment is that when the unit is operating at low load, while providing conventional steam supply for industrial and residential heating, the supplementary steam pipeline is connected to the main steam supply pipeline and the heating network heater, respectively, and the industrial steam supply from the main steam supply pipeline is transported to the heating network heater for supplementary steam. This meets both the peak-shaving requirements of the power grid and the needs of heat users. During the heating season, while not affecting the peak-shaving capacity of the unit, it also takes into account the needs of residential heating and industrial steam supply, thereby maximizing the peak-shaving capacity of the thermal power unit. This system requires minimal modification, requires low investment, and has a wide range of applicability, making it conducive to further promotion.

[0083] It is understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the embodiments of the present disclosure, but the embodiments of the present disclosure are not limited thereto. Those skilled in the art may make various modifications and improvements without departing from the spirit and essence of the embodiments of the present disclosure, and such modifications and improvements are also considered to be within the scope of protection of the embodiments of the present disclosure.

Claims

1. A wide load multi-stage steam supply system for a cogeneration unit, characterized in that: Including steam turbine power generation components and heating components; The steam turbine power generation assembly includes a main steam pipe, a high-pressure cylinder, an intermediate-pressure cylinder, a low-pressure cylinder and a generator; The heating components include a reheat steam pipeline, a steam supply main pipeline, a supplementary steam pipeline, an intermediate pressure cylinder exhaust pipeline and a heating network heater; wherein, The inlet of the steam supply main pipeline is connected to the outlet of the reheat steam pipeline, and the outlet of the steam supply main pipeline is used to be connected to an industrial steam supply device; The inlet of the medium-pressure cylinder exhaust pipe is connected to the medium- and low-pressure connecting pipes, the outlet of the medium-pressure cylinder exhaust pipe is connected to the inlet of the heat network heater, and the outlet of the heat network heater is used to be connected to the residential heating device; The inlet of the supplementary steam pipeline is connected to the main steam supply pipeline, and the outlet of the supplementary steam pipeline is connected to the inlet of the heating network heater; wherein, The supplementary steam pipeline is used to transport the industrial steam from the steam supply main pipeline to the heating network heater for supplementary steam when the unit is running at low load.

2. The system according to claim 1, wherein: The supplementary steam pipeline is provided with a first temperature and pressure reducing device, which is used to reduce the industrial steam supply pressure to match the heating steam supply pressure.

3. The system according to claim 2, characterized in that It also includes a first desuperheating water pipeline, which is connected to the supplementary steam pipeline and is located at the outlet of the first desuperheating and pressure reducing device.

4. The system according to any one of claims 1 to 3, characterized in that The supplementary steam pipeline is further provided with a first electric valve.

5. The system according to any one of claims 1 to 3, characterized in that It also includes a steam supply branch pipe, the inlet of the steam supply branch pipe is connected to the reheat steam pipe and the steam supply main pipe respectively, the outlet of the steam supply branch pipe is connected to the intermediate pressure cylinder, and the steam supply branch pipe is provided with a central valve; The intermediate valve is used to adjust the pressure of the steam supply main pipeline when the unit is running under load.

6. The system according to any one of claims 1 to 3, characterized in that It also includes a second desuperheating and pressure reducing device and a second desuperheating water pipeline; The second temperature and pressure reducing device is arranged on the steam supply main pipeline; The second desuperheating water pipeline is connected to the steam supply main pipeline and is located at the outlet of the second desuperheater and pressure reducer.

7. The system according to claim 6, characterized in that The steam supply main pipeline is also provided with a first check valve, a second electric valve and a third electric valve; The first check valve and the second electric valve are arranged near the inlet of the steam supply main pipeline; The third electric valve is arranged close to the outlet of the steam supply main pipeline.

8. The system according to any one of claims 1 to 3, characterized in that The medium-pressure cylinder exhaust pipe is sequentially provided with a second check valve, a regulating valve and a fourth electric valve.

9. A method for operating a wide-load multi-stage steam supply system for a combined heat and power unit, characterized in that: The wide-load multi-stage steam supply system according to any one of claims 1 to 8, wherein the operating method comprises: When the unit is running at medium or high load, the reheat steam pipe is connected to the steam supply main pipe to provide conventional industrial steam supply; and the intermediate pressure cylinder exhaust pipe is respectively connected to the intermediate and low pressure connecting pipes and the heating network heater to provide conventional steam supply for residential heating; When the unit is running at low load, while carrying out conventional industrial steam supply and conventional residential heating steam supply, the supplementary steam pipeline is connected to the main steam supply pipeline and the heating network heater respectively, and the industrial steam supply from the main steam supply pipeline is transported to the heating network heater for supplementary steam.

10. The operating method according to claim 9, characterized in that: The method further comprises: When the unit is running at low load, the opening of the intermediate valve is closed to reduce the pressure of the steam supply main pipeline to the preset pressure value.

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