Low-side steam supply gradient utilization system and operation method

Abstract

The embodiment of the invention provides a low-bypass steam supply gradient utilization system and an operation method, the system comprises a steam subsystem, the steam subsystem comprises a low-bypass steam supply pipeline led out from a unit reheat steam pipeline, and the low-bypass steam supply pipeline is provided with a main path and a gradient utilization bypass; wherein a pressure-reducing and temperature-reducing device is arranged on the main path and is used for directly supplying steam to the outside after reheat steam is treated; a pressure reducing valve and a heat exchanger are sequentially arranged on the gradient utilization bypass and used for reducing the pressure of the reheated steam and then introducing the reheated steam into the heat exchanger for heat release, and the cooled steam is supplied to the outside; the heat supply network water subsystem comprises a heat supply network water return pipeline, a heat supply network heater and a heat supply network water supply pipeline; a heat supply network circulating pump is arranged on the heat supply network water return pipeline; wherein a first bypass is communicated with a pipeline between an outlet of the heat supply network circulating pump and an inlet of the heat supply network heater, the first bypass is connected to a water side inlet of the heat exchanger, and a water side outlet of the heat exchanger is connected to a heat supply network water supply pipeline through a pipeline.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure belong to the technical field of cogeneration, and particularly relate to a low-side steam supply cascade utilization system, an operation method and a cogeneration unit. BACKGROUND

[0002] In recent years, in order to adapt to the rapid increase of new energy power generation capacity, local policies have been introduced to comprehensively enhance the regulation capacity of the power system. As a key link in the construction of new power systems, the regulation role of thermal power units (especially cogeneration units) is increasingly prominent, and they bear the important task of supporting efficient consumption of new energy.

[0003] With the continuous tightening of grid peak shaving demand, during the heating period, the minimum load rate of the cogeneration unit is reduced to about 25%, causing the contradiction between power supply and heat supply to become increasingly prominent. For units that simultaneously undertake industrial steam supply and heating tasks, in the deep peak shaving condition, the balance of multiple loads of electricity, heat and steam must be coordinated, and the operation complexity significantly increases.

[0004] Therefore, how to solve the above problems has become a technical problem to be solved by those skilled in the art. SUMMARY

[0005] Embodiments of the present disclosure aim to at least solve one of the technical problems existing in the prior art, and provide a low-side steam supply cascade utilization system, an operation method and a cogeneration unit.

[0006] In a first aspect, the present disclosure provides a low-side steam supply cascade utilization system, characterized in that it comprises: a steam subsystem, the steam subsystem comprising a low-side steam supply pipeline drawn from a reheated steam pipeline of a unit, and a main pipeline and a cascade utilization bypass pipeline are arranged on the low-side steam supply pipeline; wherein a pressure and temperature reducer is arranged on the main pipeline, for directly supplying steam to the outside after processing the reheated steam; a pressure reducing valve and a heat exchanger are arranged in sequence on the cascade utilization bypass pipeline, for reducing the pressure of the reheated steam and then passing it into the heat exchanger to release heat, and the cooled steam is then supplied to the outside; a heat network water subsystem, the heat network water subsystem comprising a heat network return water pipeline, a heat network heater and a heat network water supply pipeline; a heat network circulating pump is arranged on the heat network return water pipeline; wherein a first bypass pipeline is connected between the outlet of the heat network circulating pump and the inlet of the heat network heater, the first bypass pipeline is connected to the water inlet of the heat exchanger, and the water outlet of the heat exchanger is connected to the heat network water supply pipeline through a pipeline.

[0007] Optionally, the step utilizes a bypass to communicate with the main path at the front end of the inlet of the pressure reducing valve, and merges with the main path at the rear end of the steam side outlet of the heat exchanger to form a parallel path.

[0008] Optionally, the steam subsystem further comprises: a first electric valve arranged on the main path pipe section before the point where the step utilization bypass communicates with the main path; a third electric valve arranged on the step utilization bypass for controlling the opening and closing of the step utilization bypass; a fourth electric valve arranged on the main path, and a second electric valve arranged on the main path after the point where the main path communicates with the step utilization bypass.

[0009] Optionally, a second regulating valve is arranged on the first bypass of the heat network water subsystem for regulating the flow of heat network return water into the heat exchanger; and a third regulating valve is arranged on the water supply pipeline of the heat network heater for regulating the flow of heat network return water through the heat network heater.

[0010] Optionally, the system further comprises a heating pipeline connected to the medium-pressure cylinder exhaust steam, and the heating pipeline is connected to the steam side of the heat network heater for heating the heat network water using the medium-pressure cylinder exhaust steam.

[0011] In a second aspect of the embodiments of the present disclosure, a low-bypass-steam step utilization operation method is provided, which is implemented according to the low-bypass-steam step utilization system described above, and the operation method comprises a summer operation mode and a winter step operation mode. When the summer operation mode is adopted, the step utilization bypass is closed, and the main path is opened, so that the reheated steam is directly supplied to the outside after being treated by the pressure reducing and temperature reducing device, and the heat network water subsystem stops operating. When the winter step operation mode is adopted, the main path and the step utilization bypass are simultaneously opened, so that part of the reheated steam is supplied to the outside after releasing heat in the heat exchanger through the step utilization bypass, and the heat network water subsystem is opened, so that part of the heat network return water flows through the heat exchanger to be heated.

[0012] Optionally, the winter step operation mode comprises: When the medium-pressure cylinder exhaust steam heating is started, the medium-pressure cylinder exhaust steam enters the heat network heater to perform primary heating on the heat network return water; The step utilization bypass is opened, so that the reheated steam enters the heat exchanger after being pressure-reduced by the pressure reducing valve; The first bypass of the heat network water subsystem is opened, so that part of the heat network return water flows through the heat exchanger to absorb the heat released by the reheated steam for secondary heating; The heat network water heated by the heat exchanger is collected into the heat network water supply pipeline. The steam that has been cooled and de-heated by the heat exchanger flows into the main pipeline and is supplied to the outside together with the steam that has been de-heated and de-pressurized by the main pipeline.

[0013] Optionally, the flow rate of the heat network return water entering the heat exchanger can be controlled by adjusting the opening of the second regulating valve, so as to control the secondary heating amount provided by the bypass in the stage; the flow rate of the heat network return water flowing through the heat network heater can be controlled by adjusting the opening of the third regulating valve, so as to control the primary heating amount provided by the exhaust steam from the intermediate pressure cylinder.

[0014] Optionally, when the unit is in deep peak shaving mode and needs to increase heating capacity, the opening of the second regulating valve is increased to increase the heat recovered from the cascade using the bypass.

[0015] A third aspect of the embodiments of this disclosure is to provide a combined heat and power (CHP) unit, wherein the CHP unit is configured with the aforementioned low bypass steam cascade utilization system.

[0016] The beneficial effects of the embodiments of this disclosure include: This application achieves a significant improvement in energy efficiency and flexible guarantee of heating and steam supply capacity for combined heat and power (CHP) units under deep peak-shaving conditions through the synergistic integration of steam cascade utilization and heating via the bypass of the heating network. Specifically, the system first depressurizes high-grade reheat steam via a cascade bypass, then heats part of the heating network return water in a heat exchanger (enhancing heating capacity). The steam is then cooled before being used for industrial steam supply, thus effectively recovering the high-grade heat energy that would otherwise be lost through direct depressurization and cooling. This modification resolves the contradiction between power supply and heating under low load conditions with relatively small investment, enhances the operational flexibility of the unit, and reduces throttling losses, achieving a win-win situation of energy saving and peak shaving. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a low-level bypass steam supply cascade utilization system according to an embodiment of the present disclosure.

[0018] In the diagram, 1. Reheat steam pipeline; 2. Main steam pipeline; 3. High-pressure cylinder; 4. Intermediate-pressure cylinder; 5. Low-pressure cylinder; 6. Heat exchanger; 7. Heat network heater; 8. First heat network circulation pump; 9. Second heat network circulation pump; 01. First electric valve; 02. First check valve; 03. Pressure reducing valve; 04. Pressure reducing and desuperheating device; 05. Second electric valve; 06. Second check valve; 07. Third electric valve; 08. Fourth electric valve; 21. Fifth electric valve; 22. Third check valve; 23. First regulating valve; 24. Sixth electric valve; 41. Fourth check valve; 42. Seventh electric valve; 43. Second regulating valve; 51. Eighth electric valve; 52. Ninth electric valve; 53. Tenth electric valve; 54. Eleventh electric valve; 55. Third regulating valve; 56. Twelfth electric valve. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] The embodiments of this application will be further described in detail below with reference to the accompanying drawings and examples. The detailed descriptions and accompanying drawings of the following embodiments are used to exemplarily illustrate the principles of this application, but should not be used to limit the scope of this application; that is, this application is not limited to the described embodiments. In the description of this application, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," etc., indicating orientation or positional relationships are only for the convenience of describing this application 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, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. "Vertical" is not strictly vertical, but within the allowable error range. "Parallel" is not strictly parallel, but within the allowable error range.

[0021] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this application depending on the specific circumstances.

[0022] like Figure 1 As shown, a low-voltage bypass steam supply cascade utilization system is characterized by comprising: The steam subsystem includes a low-level bypass steam supply line drawn from the unit's reheat steam pipeline 1, and the low-level bypass steam supply line is provided with a main line and a cascade utilization bypass line.

[0023] The main line is equipped with a pressure reducing and desuperheating device 04, which is used to process reheat steam and supply it directly to the outside.

[0024] The bypass of the cascade is equipped with a pressure reducing valve 03 and a heat exchanger 6, which are used to reduce the pressure of reheat steam and then pass it into the heat exchanger 6 to release heat. The cooled steam is then supplied to the outside.

[0025] The heating network water subsystem includes a heating network return water pipeline, a heating network heater 7, and a heating network supply water pipeline. A heating network circulation pump (including a first heating network circulation pump 8 and a second heating network circulation pump 9) is installed on the heating network return water pipeline.

[0026] A first bypass is connected to the pipeline between the outlet of the heat network circulation pump and the inlet of the heat network heater 7. The first bypass is connected to the water-side inlet of the heat exchanger 6, and the water-side outlet of the heat exchanger 6 is connected to the heat network water supply pipeline through a pipeline.

[0027] In some embodiments, the cascade utilizes a bypass to connect with the main path at the inlet front end of the pressure reducing valve 03, and merges with the main path at the steam side outlet rear end of the heat exchanger 6 to form a parallel path.

[0028] In some embodiments, the steam subsystem further includes: The first electric valve 01 is installed on the main pipeline section before the connection point between the bypass and the main pipeline of the cascade.

[0029] The third electric valve 07, which is installed on the bypass of the cascade utilization, is used to control the opening and closing of the bypass.

[0030] The fourth electric valve 08 is installed on the main road, and the second electric valve 05 is installed on the main road after the connection point between the main road and the ladder via the bypass.

[0031] In some embodiments, a second regulating valve 43 is provided on the first bypass of the heating network water subsystem to regulate the flow rate of the heating network return water flowing into the heat exchanger 6; a third regulating valve 55 is provided on the water supply pipeline of the heating network heater 7 to regulate the flow rate of the heating network return water flowing through the heating network heater 7.

[0032] In some embodiments, the system further includes a heating pipe connected to the exhaust steam of the intermediate pressure cylinder 4, the heating pipe being connected to the steam side of the heating network heater 7 for heating the heating network water using the exhaust steam from the intermediate pressure cylinder.

[0033] This application provides an operation method for low-level bypass steam supply cascade utilization, which is implemented according to the low-level bypass steam supply cascade utilization system described above. The operation method includes a summer operation mode and a winter cascade operation mode.

[0034] When operating in the summer mode, the cascade utilization bypass is closed and the main line is opened, so that the reheat steam is directly supplied to the outside after being processed by the pressure reducing and desuperheating device 04, and the heating network water subsystem stops operating.

[0035] When operating in the winter cascade operation mode, the main circuit and the cascade utilization bypass are opened simultaneously, so that some reheat steam is released in the heat exchanger 6 through the cascade utilization bypass and then supplied to the outside. At the same time, the heating network water subsystem is opened, so that some heating network return water flows through the heat exchanger 6 and is heated.

[0036] In some embodiments, the winter tiered operation mode includes: When the intermediate pressure cylinder 4 is started to exhaust steam for heating, the exhaust steam from the intermediate pressure cylinder enters the heating network heater 7 to perform primary heating of the heating network return water.

[0037] The bypass of the cascade is opened, allowing reheat steam to enter the heat exchanger 6 after being depressurized by the pressure reducing valve 03.

[0038] The first bypass of the heating network water subsystem is opened, allowing part of the heating network return water to flow through the heat exchanger 6, absorbing the heat released by the reheat steam for secondary heating.

[0039] The heated water from the heat exchanger 6 flows into the heat network water supply pipeline.

[0040] The steam that has been cooled and de-heated by the heat exchanger 6 flows into the main pipeline and is supplied to the outside together with the steam that has been de-heated and de-pressurized by the main pipeline.

[0041] In some embodiments, the flow rate of the heat network return water entering the heat exchanger 6 is controlled by adjusting the opening of the second regulating valve 43, thereby controlling the secondary heating amount provided by the bypass in the cascade. The flow rate of the heat network return water flowing through the heat network heater 7 is controlled by adjusting the opening of the third regulating valve 55, thereby controlling the primary heating amount provided by the exhaust steam from the intermediate pressure cylinder.

[0042] In some embodiments, when the unit is in deep peak shaving mode and needs to increase its heating capacity, the opening of the second regulating valve 43 is increased to increase the heat recovered from the cascade using the bypass.

[0043] This application achieves a significant improvement in energy efficiency and flexible guarantee of heating and steam supply capacity for combined heat and power (CHP) units under deep peak-shaving conditions through the synergistic integration of steam cascade utilization and heating via the bypass of the heating network. Specifically, the system first depressurizes high-grade reheat steam via a cascade bypass, then heats part of the heating network return water in a heat exchanger (enhancing heating capacity). The steam is then cooled before being used for industrial steam supply, thus effectively recovering the high-grade heat energy that would otherwise be lost through direct depressurization and cooling. This modification resolves the contradiction between power supply and heating under low load conditions with relatively small investment, enhances the operational flexibility of the unit, and reduces throttling losses, achieving a win-win situation of energy saving and peak shaving.

[0044] This application provides a combined heat and power (CHP) unit, which is equipped with the aforementioned low-level bypass steam cascade utilization system.

[0045] The system includes a steam pipeline connecting the intermediate-pressure cylinder 4 and the low-pressure cylinder 5. A fifth electric valve 21, a third check valve 22, and a first regulating valve 23 are sequentially installed on this steam pipeline. Steam flowing through this pipeline enters the heat exchanger 7 and the resulting condensate returns to the original unit's condensate system via a sixth electric valve 24. The main steam pipeline 2 is connected to the exhaust inlet of the high-pressure cylinder 3.

[0046] The low-pressure bypass steam supply pipeline is equipped with a main line and a cascade utilization bypass line; the main line of the low-pressure bypass steam supply pipeline is connected to the reheat steam pipeline 1 through a tee, and a first electric valve and a first check valve are installed on the main line. The steam flowing through the main line is supplied to the user after passing through the first electric valve 01, the first check valve 02, the pressure reducing and desuperheating device 04, the fourth electric valve 08, the second check valve 06, and the second electric valve 05.

[0047] The low-temperature bypass uses reheat extraction steam + desuperheating and pressure reducing device to supply industrial steam to meet the heating load of the unit under deep peak shaving conditions. However, since the high-grade steam is used for steam supply without fully performing work, there is a large thermal economic loss. Therefore, this solution proposes to add a cascade utilization bypass to the low-temperature bypass pipeline. The cascade utilization bypass is connected to heat exchanger 6 after being equipped with pressure reducing valve 03. After the net heat exchanger 6 heats the circulating water of the heating network and desuperheats it, steam is supplied to the outside through the third electric valve 07, the second check valve 06 and the second electric valve 05.

[0048] After being pressurized by the first heating network circulation pump 8 and the second heating network circulation pump 9, the return water from the heating network is connected to the first bypass through the outlet header of the first heating network circulation pump 8 and the second heating network circulation pump 9. The first bypass is connected to the water-side inlet of the heat exchanger 6. A second regulating valve is installed on the first bypass. After the return water from the heating network enters the heat exchanger 6 through the second regulating valve 43 and is heated, it enters the heating network supply water header after passing through the fourth check valve 41 and the seventh electric valve 42.

[0049] An operation mode of a low-level bypass steam supply cascade utilization system includes the following steps: 1. Summer working conditions When the unit is running in summer, the heating system is shut down and the unit only supplies industrial steam. At this time, after opening the first electric valve 01, the first check valve 02, the regulating valve 10 and the pressure reducing and desuperheating device 04, steam is supplied to the outside through the fourth electric valve 08, the second check valve 06 and the second electric valve 05.

[0050] 2. Low-level bypass cascade heating mode During winter operation, the intermediate exhaust heating system and industrial steam supply are simultaneously activated. To minimize throttling losses caused by desuperheating and pressure reduction, the intermediate exhaust steam supply system remains operational, i.e., the fifth electric valve 21, the third check valve 22, the first regulating valve 23, and the sixth electric valve 24 are opened. The heating network circulation pumps (including the first heating network circulation pump 8 and the second heating network circulation pump 9) are started. The eighth electric valve 51, the ninth electric valve 52, the tenth electric valve 53, the eleventh electric valve 54, and the third regulating valve 55 are all opened. The heating network circulating water is heated by the heating network heater 7 and then supplied to heat users. At the same time, the first electric valve 01, the first check valve 02, and the pressure reducing valve 03 are opened. The hot reheat steam bypasses the heat exchanger 6, exchanges heat, and then passes through the third electric valve 07, the second check valve 06, and the second electric valve 05 before being supplied to the outside.

[0051] When the bypass of the heating network circulating water system is put into operation, the fourth check valve 41 and the seventh electric valve 42 are opened, and the second regulating valve 43 and the third regulating valve 55 are controlled to adjust the water flow into the heat exchanger 6. After absorbing heat, the heating network circulating water enters the heating network water supply header.

[0052] In addition, when the unit needs deep peak shaving during winter heating, the system can be used to further increase the heating capacity while meeting the industrial steam supply demand.

[0053] Understandably, in this operating mode, low-level bypass heating is only a measure to meet heating demand to a certain extent. If it is necessary to further improve the heating capacity, the unit can also be modified to use high-level bypass and intermediate valve for heating according to the actual situation. The system operation mode is basically consistent with this system.

[0054] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A low-voltage bypass steam supply cascade utilization system, characterized in that, include: The steam subsystem includes a low-level bypass steam supply line drawn from the unit's reheat steam pipeline, and the low-level bypass steam supply line is provided with a main line and a cascade utilization bypass line. The main line is equipped with a pressure reducing and desuperheating device, which is used to process the reheat steam and then supply it directly to the outside. The cascade utilizes a bypass line with a pressure reducing valve and a heat exchanger, which are used to reduce the pressure of reheat steam and then pass it into the heat exchanger to release heat. The cooled steam is then supplied to the outside. A heating network water subsystem, comprising a heating network return water pipeline, a heating network heater, and a heating network supply water pipeline; a heating network circulation pump is installed on the heating network return water pipeline. A first bypass is connected to the pipeline between the outlet of the heating network circulation pump and the inlet of the heating network heater. The first bypass is connected to the water-side inlet of the heat exchanger, and the water-side outlet of the heat exchanger is connected to the heating network water supply pipeline via a pipeline.

2. The low-voltage bypass steam supply cascade utilization system according to claim 1, characterized in that, The cascade utilizes a bypass to connect with the main line at the inlet of the pressure reducing valve and merges with the main line at the outlet of the steam side of the heat exchanger to form a parallel path.

3. A low-voltage bypass steam supply cascade utilization system according to claim 2, characterized in that, The steam subsystem also includes: The first electric valve is installed on the main pipeline section before the connection point between the bypass and the main pipeline of the cascade. The third electric valve installed on the bypass of the cascade is used to control the opening and closing of the bypass of the cascade. The fourth electric valve is installed on the main road, and the second electric valve is installed on the main road after the connection point between the main road and the ladder via the bypass.

4. A low-voltage bypass steam supply cascade utilization system according to claim 3, characterized in that, A second regulating valve is installed on the first bypass of the heating network water subsystem to regulate the flow rate of the heating network return water flowing into the heat exchanger; a third regulating valve is installed on the water supply pipeline of the heating network heater to regulate the flow rate of the heating network return water flowing through the heating network heater.

5. A low-voltage bypass steam supply cascade utilization system according to claim 1, characterized in that, The system also includes a heating pipeline connected to the exhaust steam of the intermediate pressure cylinder. The heating pipeline is connected to the steam side of the heating network heater and is used to heat the heating network water using the exhaust steam of the intermediate pressure cylinder.

6. An operating method for low-level bypass steam supply cascade utilization, the method being implemented according to any one of claims 1-5 of a low-level bypass steam supply cascade utilization system, characterized in that, The operating methods include summer operating mode and winter tiered operating mode; When operating in the summer mode, the cascade utilization bypass is closed and the main line is opened, so that the reheat steam is directly supplied to the outside after being processed by the pressure reducing and desuperheating device, and the heating network water subsystem stops operating. When operating in the winter cascade operation mode, the main circuit and the cascade utilization bypass are opened simultaneously, so that some reheat steam is released in the heat exchanger through the cascade utilization bypass and then supplied to the outside. At the same time, the heating network water subsystem is opened, so that some heating network return water is heated by flowing through the heat exchanger.

7. The operating method according to claim 6, characterized in that, The winter tiered operation mode includes: When starting the intermediate pressure cylinder exhaust steam for heating, the exhaust steam from the intermediate pressure cylinder enters the heating network heater to perform primary heating of the heating network return water; The bypass of the aforementioned stage is opened, allowing reheat steam to enter the heat exchanger after being depressurized by the pressure reducing valve; The first bypass of the heating network water subsystem is opened, allowing a portion of the heating network return water to flow through the heat exchanger, absorbing the heat released by the reheat steam for secondary heating; The heated water from the heat exchanger flows into the heat network water supply pipeline. The steam that has been cooled and de-heated by the heat exchanger flows into the main pipeline and is supplied to the outside together with the steam that has been de-heated and de-pressurized by the main pipeline.

8. The operating method according to claim 7, characterized in that, The flow rate of the heat network return water entering the heat exchanger is controlled by adjusting the opening of the second regulating valve, thereby controlling the secondary heating amount provided by the bypass in the stage; the flow rate of the heat network return water flowing through the heat network heater is controlled by adjusting the opening of the third regulating valve, thereby controlling the primary heating amount provided by the exhaust steam from the intermediate pressure cylinder.

9. The operating method according to claim 8, characterized in that, When the unit is in deep peak shaving operation and needs to increase heating capacity, the opening of the second regulating valve is increased to increase the heat recovered from the cascade using the bypass.

10. A combined heat and power (CHP) unit, characterized in that, The cogeneration unit is equipped with a low-level bypass steam cascade utilization system as described in any one of claims 1-5.

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