An air-cooled heating unit and its flexible deep peak shaving method

Abstract

The present application discloses an air-cooled heat supply unit and a flexible deep peak shaving method for the air-cooled heat supply unit, belonging to the field of thermoelectric technology. Through the coordination among the heat supply water pipeline, the centrifugal heat pump station, the buried pipe system, the air-cooled island, the exhaust device, the steam heater of the heat supply network first station, and the low-pressure cylinder, the present application conducts and divides different components according to different working conditions. Without modifying the flow path part of the steam turbine, the flexible deep peak shaving of the air-cooled heat supply unit can be achieved, which can cope with different working conditions and is applicable to a variety of application scenarios. It solves the problem in the prior art that "the flexible deep peak shaving method greatly reduces the energy utilization efficiency and cannot be applied to the peak shaving of the air-cooled heat supply unit in the summer pure condensing condition".

Description

Technical Field

[0001] This application relates to the field of thermoelectric technology, and particularly relates to an air-cooled heat supply unit and a method for flexible deep peak shaving thereof. Background Art

[0002] The statements herein only provide background art related to this application and do not necessarily constitute prior art.

[0003] Currently, with the rapid growth of the installed capacity of new energy power such as wind power and photovoltaic power in China, the phenomena of "wind abandonment" and "power abandonment" are serious in some regions. The coordination and cooperation problem between existing thermal power generation units and new energy generation units needs to be solved urgently, and higher requirements are put forward for the flexible deep peak shaving ability of thermal power units.

[0004] Currently, the actual peak shaving ability of pure condensing units in China is generally about 50% of the rated capacity, and the peak shaving ability of typical extraction condensing units during the heating period is only about 20% of the rated capacity. In order to fully tap the peak shaving potential of thermal power units and improve the renewable energy consumption capacity of the system, the National Energy Administration issued the "Notice on Pilot Projects for Thermal Power Flexibility Transformation", and provinces such as Shanxi and Shandong also issued relevant notices on the flexibility transformation of coal-fired power units. Through flexibility transformation, the peak shaving ability of thermal power units is increased by 20% of the rated capacity, and the minimum technical output reaches 40% - 50% of the rated capacity. The peak shaving ability of pure condensing units is increased by 15% - 20% of the rated capacity, and the minimum technical output reaches 30% - 35% of the rated capacity.

[0005] Regarding the flexibility transformation of thermal power units for flexible deep peak shaving, it is currently mainly concentrated on heat supply units. The mature technologies include low-pressure cylinder optical axis transformation, low-pressure cylinder zero-power transformation, high and low bypass heat supply, electric boiler energy storage, etc. The main idea of these technical solutions is to reduce the power of the steam turbine by throttling high-parameter steam and reducing the steam flow rate through the steam turbine, or to consume more generated electric energy through electric heating to achieve the purpose of power supply peak shaving. Due to the existence of huge losses, these flexible deep peak shaving methods greatly reduce the energy utilization efficiency. Moreover, for the peak shaving of the pure condensing condition in summer, these technologies have no effect. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the purpose of the embodiments of this application is to provide an air-cooled heat supply unit and a method for flexible deep peak shaving of the air-cooled heat supply unit, so as to solve the problems of low energy utilization efficiency of the existing peak shaving methods and inability to cope with the pure condensing condition in summer.

[0007] In order to achieve the above purpose, the embodiments of this application provide the following technical solutions:

[0008] An air-cooled unit, comprising a heat network return water pipeline, a heat network supply water pipeline, a centrifugal heat pump station, a buried pipe system, an external condenser, an air-cooled island, an exhaust steam device, a heat network first-stage steam heater, a low-pressure cylinder and a connecting pipe;

[0009] The heat network return water pipeline is connected to the centrifugal heat pump station, the centrifugal heat pump station is connected to the heat network first-stage steam heater, the heat network return water pipeline is connected to the external condenser, the external condenser is connected to the heat network first-stage steam heater, and the heat network first-stage steam heater is connected to the heat network supply water pipeline;

[0010] The external condenser is connected to the centrifugal heat pump station, the centrifugal heat pump station is connected to the buried pipe system, and the buried pipe system is connected to the external condenser;

[0011] The connecting pipe is connected to the heat network first-stage steam heater, and the heat network first-stage steam heater is connected to a drain cooler; the low-pressure cylinder is connected to the exhaust steam device, the exhaust steam device is respectively connected to the air-cooled island and the external condenser, and the exhaust steam device is connected to a regenerative heating system.

[0012] By adopting the above technical solution, it is possible to achieve the connection and separation between different systems without modifying the flow passage part of the steam turbine, and further achieve the peak shaving of the air-cooled heat supply unit.

[0013] Further, the heat network return water pipeline is connected to the heat network water inlet of the centrifugal heat pump station, and the heat network water outlet of the centrifugal heat pump station is connected to the heat network water inlet of the heat network first-stage steam heater through a pipeline; a first heat network return water function switching valve is provided on the heat network return water pipeline, and the first heat network return water function switching valve is located between the heat network return water pipeline and the heat network water inlet of the centrifugal heat pump station;

[0014] The heat network return water pipeline is connected to the internal circulation water inlet of the external condenser, the internal circulation water outlet of the external condenser is connected to the heat network water inlet of the heat network first-stage steam heater through a pipeline, the heat network water outlet of the heat network first-stage steam heater is connected to the heat network supply water pipeline, a second hot water return water function switching valve is provided on the heat network return water pipeline, and the second hot water return water function switching valve is located between the heat network return water pipeline and the internal circulation water inlet; an internal circulation water pump bypass valve and a first internal circulation water function switching valve are sequentially arranged on the pipeline between the internal circulation water outlet of the external condenser and the heat network water inlet of the heat network first-stage steam heater along the flow direction of the heat network water.

[0015] Further, the outlet of the internal circulating water of the external condenser is communicated with the inlet of the internal circulating water of the centrifugal heat pump station through a pipeline, the outlet of the internal circulating water of the centrifugal heat pump station is communicated with the inlet of the buried pipe system through a pipeline, and the outlet of the buried pipe system is communicated with the inlet of the internal circulating water of the external condenser through a pipeline;

[0016] A pipeline between the outlet of the internal circulating water of the external condenser and the inlet of the internal circulating water of the centrifugal heat pump station is successively provided with an internal circulating water pump and a second internal circulating water function switching valve along the flow direction of the internal circulating water, and a buried pipe switching valve is arranged on the pipeline between the outlet of the buried pipe system and the inlet of the internal circulating water of the external condenser.

[0017] Further, the pipeline between the outlet of the internal circulating water of the external condenser and the inlet of the internal circulating water of the centrifugal heat pump station is communicated with the pipeline between the outlet of the internal circulating water of the centrifugal heat pump station and the buried pipe system, and an internal circulating water pump bypass valve is arranged at the communication point, and the internal circulating water pump bypass valve is located between the internal circulating water pump and the second internal circulating water function switching valve.

[0018] Further, the connecting pipe is communicated with the steam inlet of the steam heater at the head station of the heat network, and the water flow outlet of the steam heater at the head station of the heat network is communicated with the drain cooler; the exhaust outlet of the low-pressure cylinder is communicated with the exhaust device through a pipeline, and the exhaust outlet of the exhaust device is communicated with the air-cooled island and the external condenser respectively through pipelines; the air-cooled island and the external condenser are respectively communicated with the condensate inlet of the exhaust device through pipelines; the condensate outlet of the exhaust device is communicated with the regenerative heating system through a pipeline;

[0019] A condensate pump is arranged on the pipeline between the condensate outlet of the exhaust device and the regenerative heating system, and an air-cooled island exhaust steam isolation valve is arranged on the pipeline between the exhaust outlet of the exhaust device and the air-cooled island.

[0020] The embodiment of the present application also provides a flexible deep peak shaving method for an air-cooled heating unit, including the following steps:

[0021] Judge the working condition of the air-cooled heating unit according to the time and the working condition of the air-cooled heating unit;

[0022] Execute the corresponding peak shaving strategy according to the working condition of the air-cooled heating unit; among them, the working conditions of the air-cooled heating unit include non-heating season pure condensing high load condition, non-heating season pure condensing low load condition, heating season extraction condensing high load condition and heating season extraction condensing low load condition.

[0023] Further, if it is the non-heating season pure condensing high load condition, the following steps are executed:

[0024] Close the first heat network return water function switching valve, the second heat network return water function switching valve, the first internal circulating water function switching valve, and the second internal circulating water function switching valve to disconnect the centrifugal heat pump station, the steam heater of the heat network head station, the heat network return water pipeline from the external condenser;

[0025] Open the internal circulating water bypass valve and the buried pipe switching valve to form a passage between the external condenser and the buried pipe system;

[0026] Close the internal circulating water pump bypass valve and start the internal circulating water pump.

[0027] By adopting the above technical solution, due to the high environmental temperature in the non-heating season, the cooling effect of the air cooling island is poor, resulting in a relatively high exhaust back pressure of the low-pressure cylinder, and the power generation capacity of the air-cooled unit is limited, and it may even not be able to generate electricity at full load; through the external condenser and the buried pipe system, the cooling capacity of the low-pressure cylinder exhaust is increased, the exhaust pressure is reduced, and the power generation capacity of the unit is improved, realizing high-load peak regulation in the non-heating season.

[0028] Further, if it is a non-heating season pure condensing low-load condition, the following steps are executed:

[0029] Close the first heat network return water function switching valve, the second heat network return water function switching valve, the first internal circulating water function switching valve, and the second internal circulating water function switching valve to disconnect the centrifugal heat pump station and the heat network return pipeline from the external condenser;

[0030] Open the internal circulating water bypass valve and the buried pipe switching valve to form a passage between the external condenser and the buried pipe system;

[0031] Close the internal circulating water pump bypass valve and start the internal circulating water pump.

[0032] By adopting the above technical solution, due to the high environmental temperature in the non-heating season, the cooling effect of the air cooling island is poor, resulting in a relatively high exhaust back pressure of the low-pressure cylinder; to protect the last-stage blades of the low-pressure cylinder, the steam flow rate through the low-pressure cylinder cannot be too low, generally around 30% THA condition, and in case of high-temperature weather, it can even reach up to 50% THA. The power generation of the steam turbine unit is proportional to the steam flow rate through the cylinder, so it is difficult for the air-cooled unit to reduce the power generation load below 30% in the non-heating season; through the external condenser and the buried pipe system, the cooling capacity of the low-pressure cylinder exhaust is increased, the exhaust pressure is reduced, thereby reducing the steam flow rate limit through the low-pressure cylinder, and realizing low-load peak regulation in the non-heating season.

[0033] Further, if it is a heating season extraction condensing high-load condition, the following steps are executed:

[0034] Shut down the centrifugal heat pump station and the internal circulating water pump;

[0035] Open the second heat network return water function switching valve and the first internal circulating water function switching valve, and close the first heat network return water function switching valve, the second internal circulating water function switching valve, the internal circulating water bypass valve and the buried pipe switching valve to connect the heat network return water pipeline and the steam heater at the heat network head station to the external condenser, and disconnect the centrifugal heat pump station and the buried pipe system from the heat network return water pipeline;<{} <{}

[0036] Open the internal circulating water bypass valve and the internal circulating water pump bypass valve;<{} <{}

[0037] Adjust the air-cooled island and raise the back pressure of the air-cooled heat supply unit to above 30 kPa.<{} <{}

[0038] By adopting the above technical solution, since the conventional heat network water heating usually uses extraction steam for heating, and the parameters (saturation temperature) of the extraction steam for heating are much higher than the heat network water temperature, there is a large energy efficiency loss in the steam heater at the heat network head station, and the power generation of the unit will also be affected; by connecting the external condenser to the heat network return water, part of the waste heat of the low-pressure cylinder exhaust is recovered, the extraction steam for heating is reduced, so as to increase the work done by the low-pressure cylinder and improve the power generation capacity on the premise of meeting the heating load.<{} <{}

[0039] Furthermore, if it is the extraction condensing low-load condition in the heating season, the following steps shall be executed:<{} <{}

[0040] Open the first heat network return water function switching valve, the second internal circulating water function switching valve and the buried pipe switching valve, and close the second heat network return water function switching valve and the first internal circulating water function switching valve to connect the centrifugal heat pump station and the buried pipe system to the external condenser, and disconnect the external condenser from the heat network return water pipeline and the steam heater at the heat network head station;<{} <{}

[0041] Close the internal circulating water bypass valve and the internal circulating water pump bypass valve, and start the internal circulating water pump;<{} <{}

[0042] Start the centrifugal heat pump station;<{} <{}

[0043] Turn off the air-cooled island.<{} <{}

[0044] By adopting the above technical solutions, during the heating season when the conventional extraction-condensing unit supplies heat, to prevent the air-cooled island from freezing, the exhaust steam pressure of the low-pressure cylinder should not be lower than 10 kPa under low power generation, which keeps the steam flow rate in the low-pressure cylinder at a relatively high level, generally around 20% of the THA condition. Additionally, to ensure stable heat supply, a relatively high extraction steam flow rate for heating must be maintained, which keeps the steam flow rate in the high-pressure and intermediate-pressure cylinders at a relatively high level and the power generation still relatively high. By extracting the heat of the internal circulating water through a centrifugal heat pump station to heat the return water of the heat network, the internal circulating water can be cooled to 5 - 10 °C, thereby recovering the heat stored in the buried pipes and the waste steam heat of the external condenser, enabling the low-pressure cylinder to obtain a back pressure of 4 - 5 kPa, further reducing the steam flow rate in the low-pressure cylinder, while reducing the extraction steam flow rate for heating, and then reducing the steam flow rate in the high-pressure and intermediate-pressure cylinders and the power generation load. In addition, the centrifugal heat pump station also consumes a large amount of electric energy, further reducing the external power supply rate of the steam turbine unit.

[0045] The technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0046] 1. The technical solutions provided in the present application can cope with the peak shaving of the pure condensing condition in both the heating season and the non-heating season, not limited to peak shaving at low power generation, but also can increase the power generation at high power generation; there are no steam bypass and throttling phenomena during the peak shaving process, and the thermal system of the steam turbine has less loss, and the energy utilization efficiency of the thermal power unit is not reduced;

[0047] 2. For the pure condensing high-load condition in the non-heating season, the technical solutions provided in the present application increase the power generation capacity through back pressure regulation, and at the same time store the waste steam waste heat in the formation through the buried pipes. There is no increase in fuel consumption during the peak shaving process, and there are significant energy-saving benefits; for the extraction-condensing low-load condition in the heating season, the centrifugal heat pump recovers the waste heat stored in the buried pipes in the non-heating season. There is no increase in fuel consumption during the peak shaving process, and there are significant energy-saving benefits.

[0048] 3. The technical solutions provided in the present application do not involve the transformation of the steam flow part of the steam turbine, and the safety of the steam turbine is guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The schematic diagrams in the specification forming a part of the present application are used to provide a further understanding of the present application. The schematic embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation of the present application.

[0050] Figure 1 is a connection schematic diagram of the air-cooled heat supply unit provided in the embodiment of the present application;

[0051] Figure 2 is a connection schematic diagram of the air-cooled heat supply unit under the peak shaving state of the pure condensing high-load condition in the non-heating season provided in the embodiment of the present application;

[0052] Figure 3 It is a schematic connection diagram of an air-cooled heat supply unit under the peak shaving state of pure condensing low load in the non-heating season provided by an embodiment of the present application;

[0053] Figure 4 It is a schematic connection diagram of an air-cooled heat supply unit under the peak shaving state of extraction condensing high load in the heating season provided by an embodiment of the present application;

[0054] Figure 5 It is a schematic connection diagram under the peak shaving state of extraction condensing low load in the heating season provided by an embodiment of the present application;

[0055] In the figure: 1. First heat network return water function switching valve, 2. Second heat network return water function switching valve, 3. Centrifugal heat pump station, 4. First internal circulating water function switching valve, 5. Second internal circulating water function switching valve, 6. Internal circulating water bypass valve, 7. Ground buried pipe switching valve, 8. Ground buried pipe system, 9. Internal circulating water pump bypass valve, 10. Internal circulating water pump, 11. External condenser, 12. Air-cooled island exhaust steam isolation valve, 13. Air-cooled island, 14. Exhaust steam device, 15. Condensate pump, 16. Heat network first station steam heater, 17. Extraction steam regulating valve, 18. Connecting pipe, 19. Connecting pipe regulating valve, 20. Low pressure cylinder.

[0056] The distances or sizes between each part are exaggerated for showing the positions of each part, and the schematic diagram is only for illustration. Detailed implementation manners

[0057] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present application. Unless otherwise specified, all technical and scientific terms used in the present application have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0058] It should be noted that the terms used herein are only for describing the specific implementation manners and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the present application clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should also be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or their combinations;

[0059] For the convenience of description, if the words "upper", "lower", "left" and "right" appear in the present application, they only indicate the same directions as the upper, lower, left and right of the attached drawings themselves, and do not limit the structure. They are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present application.

[0060] Glossary: Terms such as "installation", "connection", "linkage", "fixation" in this application should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated one; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium. It can be an internal connection between two components or an interaction relationship between two components. For those of ordinary skill in the art, the specific meaning of the terms in this application can be understood according to specific circumstances.

[0061] Embodiment 1

[0062] As introduced in the background art, the flexibility deep peak shaving method in the prior art significantly reduces the energy utilization efficiency and cannot be applied to the peak shaving of air-cooled heat supply units in the pure condensing condition during summer (non-heating season). To solve the above technical problems, this application proposes an air-cooled heat supply unit that can achieve the segmentation and conduction between systems and the switching of different working states without modifying the flow path part of the steam turbine, facilitating the flexibility deep peak shaving of the air-cooled heat supply unit.

[0063] As Figure 1 As shown, an embodiment of this application describes an air-cooled heat supply unit, which includes a heat network return water pipeline, a heat network supply water pipeline, a centrifugal heat pump station 3, a buried pipe system 8, an external condenser 11, an air-cooled island 13, an exhaust device 14, a heat network primary station steam heater 16, a low-pressure cylinder 20, and a connecting pipe 18.

[0064] The heat network return water pipeline is connected to the heat network water inlet of the centrifugal heat pump station 3, and the heat network water outlet of the centrifugal heat pump station 3 is connected to the heat network water inlet of the heat network primary station steam heater 16 through a pipeline; the heat network return water pipeline is connected to the internal circulating water inlet of the external condenser 11, and the internal circulating water outlet of the external condenser 11 is connected to the internal circulating water inlet of the centrifugal heat pump station 3 through a pipeline. The internal circulating water outlet of the centrifugal heat pump station 3 is connected to the inlet of the buried pipe system 8 through a pipeline, and the outlet of the buried pipe system 8 is connected to the internal circulating water inlet of the external condenser 11 through a pipeline.

[0065] A first heat network return water function switching valve 1 is installed on the heat network return water pipeline, and the first heat network return water function switching valve 1 is located between the heat network return water pipeline and the heat network water inlet of the centrifugal heat pump station 3; a second heat network return water function switching valve 2 is installed on the heat network return water pipeline, and the second heat network return water function switching valve 2 is located between the heat network return water pipeline and the internal circulating water inlet of the external condenser 11; a circulating water pump 10 and a second internal circulating water function switching valve 5 are installed in sequence along the flow direction of the internal circulating water on the pipeline between the internal circulating water outlet of the external condenser 11 and the internal circulating water inlet of the centrifugal heat pump station 3, and a buried pipe switching valve 7 is installed on the pipeline between the outlet of the buried pipe system 8 and the internal circulating water inlet of the external condenser 11.

[0066] The return water pipeline of the heat network is connected to the inner circulating water inlet of the external condenser 11. The inner circulating water outlet of the external condenser 11 is connected to the heat network water inlet of the steam heater 16 at the heat network first station through a pipeline. The heat network water outlet of the steam heater 16 at the heat network first station is connected to the heat network supply pipeline. A second hot water return function switching valve is installed on the return water pipeline of the heat network, and the second hot water return function switching valve is located between the return water pipeline of the heat network and the inner circulating water inlet of the external condenser 11. Along the flow direction of the heat network water, an inner circulating water pump 10 bypass valve and a first inner circulating water function switching valve 4 are installed in sequence on the pipeline between the inner circulating water outlet of the external condenser 11 and the heat network water inlet of the steam heater 16 at the heat network first station. The pipeline between the inner circulating water outlet of the external condenser 11 and the inner circulating water inlet of the centrifugal heat pump station 3 and the pipeline between the inner circulating water outlet of the centrifugal heat pump station 3 and the buried pipe system 8 are connected, and an inner circulating water pump bypass valve is installed at the connection, and the inner circulating water pump bypass valve is located between the inner circulating water pump 10 and the second inner circulating water function switching valve 5.

[0067] The connecting pipe 18 is connected to the steam inlet of the steam heater 16 at the heat network first station. The water flow outlet of the steam heater 16 at the heat network first station is connected to the drain cooler. The connecting pipe 18 is connected to the inlet of the low-pressure cylinder 20. The exhaust outlet of the low-pressure cylinder 20 is connected to the exhaust device 14 through a pipeline. The exhaust outlet of the exhaust device 14 is connected to the air-cooled island 13 and the external condenser 11 respectively through pipelines. The air-cooled island 13 and the external condenser 11 are respectively connected to the condensate inlet of the exhaust device 14 through pipelines. The condensate outlet of the exhaust device 14 is connected to the regenerative heating system through a pipeline. A connecting pipe regulating valve 19 is installed on the connecting pipe 18, and the connecting pipe regulating valve 19 is located between the connecting pipe 18 and the inlet of the low-pressure cylinder 20. A condensate pump 15 is installed on the pipeline between the condensate outlet of the exhaust device 14 and the regenerative heating system, and an air-cooled island exhaust steam isolation valve 12 is installed on the pipeline between the exhaust outlet of the exhaust device 14 and the air-cooled island 13.

[0068] The working mode of this embodiment is as follows:

[0069] The return water pipeline of the heat network is connected to the heat network water inlet of the centrifugal heat pump station 3 through the first heat network return water function switching valve 1. The heat network water outlet of the centrifugal heat pump station 3 is connected to the heat network water inlet of the steam heater 16 at the heat network first station through a pipeline. The return water pipeline of the heat network is connected to the inner circulating water inlet of the external condenser 11 through the second heat network return water function switching valve 2. The inner circulating water outlet of the external condenser 11 is connected to the heat network water inlet of the steam heater 16 at the heat network first station through the inner circulating water pump bypass valve 9 and the first inner circulating water function switching valve 4. The heat network water outlet of the steam heater 16 at the heat network first station is connected to the heat network supply pipeline to realize heat network water supply.

[0070] The outlet of the internal circulating water in the external condenser 11 is connected to the inlet of the internal circulating water of the centrifugal heat pump station 3 through the internal circulating water pump 10 and the second internal circulating water function switching valve 5. The outlet of the internal circulating water of the centrifugal heat pump station 3 is connected to the inlet of the buried pipe system 8. The outlet of the buried pipe system 8 is connected to the inlet of the internal circulating water of the external condenser 11 through the buried pipe switching valve 7. An internal circulating water bypass valve 6 is installed on the internal circulating water pipeline at the inlet and outlet of the centrifugal heat pump station 3 to realize the internal circulation of water.

[0071] Upstream of the connecting pipe regulating valve 19, a heating extraction steam regulating valve 17 is taken out and connected to the steam inlet of the steam heater 16 at the head station of the heat network. The condensate water of the steam heater 16 at the head station of the heat network flows to the drain cooler. The exhaust steam of the low-pressure cylinder 20 is connected to the exhaust steam device 14. The exhaust steam device 14 is connected to the air-cooled island 13 and the external condenser 11 through pipelines. The condensate water of the air-cooled island 13 and the external condenser 11 is collected in the exhaust steam device 14. The condensate water pump 15 is responsible for discharging the condensate water of the exhaust steam device 14 to the regenerative heating system to realize the steam flow.

[0072] Embodiment 2

[0073] Based on the above air-cooled heat supply unit, combined with Figures 2 - 5 , this embodiment of the application provides a method for flexible deep peak shaving of an air-cooled heat supply unit. The method for flexible deep peak shaving of the air-cooled heat supply unit includes the following steps:

[0074] S1. According to the time and the working state of the air-cooled heat supply unit, judge the working condition of the air-cooled heat supply unit;

[0075] S2. According to the working condition of the air-cooled heat supply unit, execute the corresponding peak shaving strategy; among them, the working conditions of the air-cooled heat supply unit include the pure condensing high load condition in the non-heating season, the pure condensing low load condition in the non-heating season, the extraction condensing high load condition in the heating season, and the extraction condensing low load condition in the heating season.

[0076] In the non-heating season, due to the relatively high ambient temperature, the back pressure of the air-cooled unit is generally between 30 and 45 kPa, and can reach up to 52 kPa at most. The increase in back pressure limits the power generation capacity of the unit. Taking a 350 MW supercritical air-cooled unit as an example, under the main steam TRL condition of the 350 MW supercritical air-cooled unit, the power is 391 MW when the choking back pressure is 7 kPa, the power is 385 MW when the designed back pressure is 12.3 kPa, the power is 352 MW when the back pressure is 32 kPa, and the power is 334 MW when the back pressure is 52 kPa. The formation within the depth range of -10 to -200 m is the constant temperature layer, and it is generally 10 to 18 °C in the northern region.

[0077] Therefore, if it is the pure condensing high load condition in the non-heating season, the following steps are executed:

[0078] Close the first heat network return water function switching valve 1, the second heat network return water function switching valve 2, the first internal circulating water function switching valve 4 and the second internal circulating water function switching valve 5 to disconnect the centrifugal heat pump station 3 and the heat network return pipeline from the external condenser 11;

[0079] Open the internal circulating water bypass valve 6 and the buried pipe switching valve 7 to form a passage between the external condenser 11 and the buried pipe system 8;

[0080] Close the internal circulating water pump bypass valve and start the internal circulating water pump 10.

[0081] At this time, the connection schematic diagram of the air-cooled heat supply unit is as Figure 2 shown. Through the buried pipe system 8, internal circulating water at 25 - 35 °C can be obtained. Through the external condenser 11, the back pressure of the steam turbine can be maintained at about 7 kPa. Thus, under the condition of the same main steam parameters, the steam turbine can do more work and improve the power generation capacity. Under the conditions of the main steam parameters and the flow rate TRL working condition, the power generation capacity of the unit can be increased to more than 391 MW, with an increase amplitude of more than 10% TAH, and up to 15% TAH for high temperature weather. Since no additional fuel consumption is incurred during the peak shaving process, the increased power generation is pure profit.

[0082] The low-load peak shaving of thermal power units is to enable the power grid to absorb more new energy power generation. Therefore, the lower the operating power generation load of thermal power units, the more new energy power the power grid can absorb. For thermal power units that achieve deep low-load peak shaving, the power grid will give peak shaving subsidies.

[0083] In the non-heating season, due to the high ambient temperature, the cooling effect of the air-cooled island 13 is poor, resulting in a relatively high exhaust back pressure of the low-pressure cylinder 20. To protect the last-stage blades of the low-pressure cylinder 20, the steam flow rate through the low-pressure cylinder 20 cannot be too low, generally around 30% THA working condition. In case of high temperature weather, it can even reach up to 50% THA. The power generation of the steam turbine unit is proportional to the steam flow rate. Therefore, it is difficult for the power generation load of air-cooled units in the non-heating season to drop below 30% TAH.

[0084] Therefore, if it is a pure condensing low-load working condition in the non-heating season, the following steps shall be executed:

[0085] Close the first heat network return water function switching valve 1, the second heat network return water function switching valve 2, the first internal circulating water function switching valve 4 and the second internal circulating water function switching valve 5 to disconnect the centrifugal heat pump station 3 and the heat network return pipeline from the external condenser 11;

[0086] Open the internal circulating water bypass valve 6 and the buried pipe switching valve 7 to form a passage between the external condenser 11 and the buried pipe system 8;

[0087] Close the internal circulating water pump bypass valve and start the internal circulating water pump 10.

[0088] At this time, the connection schematic diagram of the air-cooled heat supply unit is as follows Figure 3 As shown, by means of the external condenser 11 and the buried pipe system 8, the cooling capacity of the exhaust steam of the low-pressure cylinder 20 is increased, so that the back pressure of the steam turbine can be reduced from 33 - 52 kPa to 5 - 6 kPa. Without affecting the safety of the steam turbine, the steam flow rate through the low-pressure cylinder 20 can be reduced to 80 - 100 t / h at the lowest. The corresponding pure condensing power generation capacity is about 10% THA. For a 350 MW class supercritical air-cooled unit, the corresponding unit power generation load is 30 - 40 MW, and the depth of peak shaving with increased low-load flexibility is more than 65 MW. Since the fuel consumption is not increased during the peak shaving process, the peak shaving subsidy income is pure income.

[0089] When the extraction condensing unit supplies heat for heating, it is completed by extracting the exhaust steam of the middle-pressure cylinder. The maximum heating extraction steam volume of a 350 MW supercritical air-cooled unit is about 500 - 550 t / h, corresponding to a heating capacity of about 380 MW. Due to a large amount of steam being extracted, the steam inlet volume of the low-pressure cylinder 20 is greatly reduced, and the work done by the steam turbine is also greatly reduced. The power generation capacity is only up to 80% of the rated value at most.

[0090] Therefore, if it is the high-load condition of extraction condensing during the heating season, the following steps are carried out:

[0091] Close the centrifugal heat pump station 3 and the internal circulation water pump 10;

[0092] Open the second heat network return water function switching valve 2 and the first internal circulation water function switching valve 4, and close the first heat network return water function switching valve 1, the second internal circulation water function switching valve 5, the internal circulation water bypass valve 6 and the buried pipe switching valve 7 so that the heat network return water pipeline is connected to the external condenser 11 and the centrifugal heat pump station 3 and the buried pipe system 8 are separated from the heat network return water pipeline;

[0093] Open the internal circulation water pump bypass valve and close the internal circulation water pump 10;

[0094] Adjust the air-cooled island 13 to raise the back pressure of the air-cooled heat supply unit to more than 30 kPa.

[0095] At this time, the connection schematic diagram of the air-cooled heat supply unit is as follows Figure 4 As shown, through the above steps, the back pressure of the unit can be raised to 30 - 45 kPa, and the exhaust steam is used to heat the heat network return water, greatly reducing the heating extraction steam volume, thereby increasing the steam inlet volume of the low-pressure cylinder 20 and increasing the power generation capacity. Under the heating load of 380 MW and the main steam THA condition, the power generation capacity can be increased by 35 - 80 MW, and the increase amplitude is more than 10% THA. The exhaust steam is used to heat the heat network return water, and the power generation capacity is increased by reducing the heating extraction steam volume. Since the fuel consumption is not increased during the peak shaving process, the increased power generation is pure income.

[0096] During the heating season when the conventional extraction-condensing unit supplies heat, to prevent the air-cooled island 13 from freezing, the exhaust steam pressure of the low-pressure cylinder 20 should not be lower than 10 kPa under low power generation. This keeps the steam flow rate through the low-pressure cylinder 20 at a relatively high level, generally around 20% of the THA condition (corresponding to about 160 t / h for a 350 MW supercritical air-cooled unit); additionally, to ensure stable heat supply, a relatively high extraction steam volume for heating must be maintained, which keeps the steam flow rate through the high and medium-pressure cylinders at a relatively high level and the power generation still at a relatively high level. For example, for a 350 MW class supercritical air-cooled unit, the minimum power generation load under the extraction-condensing condition is 75% of THA when the heating load is 380 MW.

[0097] Therefore, if it is the low-load condition of extraction-condensing during the heating season, the following steps are executed:

[0098] Open the first heat network return water function switching valve 1, the second internal circulating water function switching valve 5, and the buried pipe switching valve 7, and close the second heat network return water function switching valve 2 and the first internal circulating water function switching valve 4 to connect the centrifugal heat pump station 3, the buried pipe system 8 with the external condenser 11, and disconnect the external condenser from the heat network return water pipeline;

[0099] Close the internal circulating water bypass valve 6 and the internal circulating water pump bypass valve, and start the internal circulating water pump 10;

[0100] Start the centrifugal heat pump station 3;

[0101] Close the air-cooled island 13.

[0102] At this time, the connection schematic diagram of the air-cooled heat supply unit is as Figure 5 shown. The centrifugal heat pump station 3 recovers the heat stored in the buried pipes and the waste heat of the exhaust steam of the external condenser to heat the heat network return water, reducing the extraction steam volume for heating. While meeting the heating load requirements, the back pressure of the low-pressure cylinder 20 is reduced to 4 - 5 kPa, and the steam flow rate through the low-pressure cylinder 20 of the 350 MW supercritical air-cooled unit is maintained at 60 - 80 t / h. Since the steam flow rate through the steam turbine is significantly reduced, the power generation load will also decrease. Under a heating load of 380 MW, the power generation load can be reduced to a minimum of 25% of THA. In addition, the centrifugal heat pump station 3 also consumes a large amount of electric energy, further reducing the external power supply rate of the steam turbine unit, and can meet the peak shaving requirements within the range of 0 - 75% of THA.

[0103] On the premise of not affecting the safety of the steam turbine and maintaining the stability of the heating load, the steam flow rate through the low-pressure cylinder 20 of the 350 MW class supercritical air-cooled unit can be reduced to a minimum of 60 - 80 t / h, and the power supply load can be adjusted within the range of 0 - 75% of THA. Since no additional fuel consumption occurs during the peak shaving process, the peak shaving subsidy income is pure income; during the deep adjustment process, the heating capacity increased to meet the stable heating load comes from the waste heat stored in the buried pipe system 8 and the waste heat of the exhaust steam of the external condenser, without additional fuel consumption, which belongs to pure energy-saving income.

[0104] In this embodiment, the valves, water pumps, centrifugal heat pumps, etc. are opened and closed through an electrical automatic control system (DCS).

[0105] Although the specific implementation manners of the present application are described above in conjunction with the accompanying drawings, they do not limit the protection scope of the present application. Those skilled in the art should understand that, based on the technical solutions of the present application, various modifications or deformations that can be made by those skilled in the art without creative efforts are still within the protection scope of the present application.

Claims

1. An air-cooled heating unit, characterized in that, It includes a heat network return water pipeline, a heat network supply water pipeline, a centrifugal heat pump station, a buried pipe system, an external condenser, an air-cooled island, an exhaust steam device, a heat network first-stage steam heater, a low-pressure cylinder, and a connecting pipe; The heat network return water pipeline is connected to the centrifugal heat pump station, the centrifugal heat pump station is connected to the heat network first-stage steam heater, the heat network return water pipeline is connected to the external condenser, the external condenser is connected to the heat network first-stage steam heater, and the heat network first-stage steam heater is connected to the heat network supply water pipeline; The external condenser is connected to the centrifugal heat pump station, the centrifugal heat pump station is connected to the buried pipe system, and the buried pipe system is connected to the external condenser; The connecting pipe is connected to the heat network first-stage steam heater, and the heat network first-stage steam heater is connected to a drain cooler; the low-pressure cylinder is connected to the exhaust steam device, the exhaust steam device is respectively connected to the air-cooled island and the external condenser, and the exhaust steam device is connected to a regenerative heating system; The heat network return water pipeline is connected to the heat network water inlet of the centrifugal heat pump station, and the heat network water outlet of the centrifugal heat pump station is connected to the heat network water inlet of the heat network first-stage steam heater through a pipeline; a first heat network return water function switching valve is provided on the heat network return water pipeline, and the first heat network return water function switching valve is located between the heat network return water pipeline and the heat network water inlet of the centrifugal heat pump station; The heat network return water pipeline is connected to the internal circulating water inlet of the external condenser, the internal circulating water outlet of the external condenser is connected to the heat network water inlet of the heat network first-stage steam heater through a pipeline, the heat network water outlet of the heat network first-stage steam heater is connected to the heat network supply water pipeline, and a second hot water return water function switching valve is provided on the heat network return water pipeline, and the second hot water return water function switching valve is located between the heat network return water pipeline and the internal circulating water inlet; an internal circulating water pump bypass valve and a first internal circulating water function switching valve are sequentially provided on the pipeline between the internal circulating water outlet of the external condenser and the heat network water inlet of the heat network first-stage steam heater along the flow direction of the heat network water; The connecting pipe is connected to the inlet of the low-pressure cylinder, the exhaust steam outlet of the low-pressure cylinder is connected to the exhaust steam device through a pipeline, and the exhaust steam outlet of the exhaust steam device is respectively connected to the air-cooled island and the external condenser through pipelines.

2. The air-cooled heat supply unit according to claim 1, characterized in that, The internal circulating water outlet of the external condenser is connected to the internal circulating water inlet of the centrifugal heat pump station through a pipeline, the internal circulating water outlet of the centrifugal heat pump station is connected to the inlet of the buried pipe system through a pipeline, and the outlet of the buried pipe system is connected to the internal circulating water inlet of the external condenser through a pipeline; An internal circulating water pump and a second internal circulating water function switching valve are sequentially provided on the pipeline between the internal circulating water outlet of the external condenser and the internal circulating water inlet of the centrifugal heat pump station along the flow direction of the internal circulating water, and a buried pipe switching valve is provided on the pipeline between the outlet of the buried pipe system and the internal circulating water inlet of the external condenser.

3. The air-cooled heat supply unit according to claim 2, wherein The pipeline between the outlet of the internal circulating water of the external condenser and the inlet of the internal circulating water of the centrifugal heat pump station is connected to the pipeline between the outlet of the internal circulating water of the centrifugal heat pump station and the buried pipe system. An internal circulating water pump bypass valve is provided at the connection, and the internal circulating water pump bypass valve is located between the internal circulating water pump and the second internal circulating water function switching valve.

4. The air-cooled heat supply unit according to claim 3, wherein The connecting pipe is connected to the steam inlet of the steam heater of the heat network primary station, and the water flow outlet of the steam heater of the heat network primary station is connected to the drain cooler; the exhaust outlet of the low-pressure cylinder is connected to the exhaust device through a pipeline, and the exhaust outlet of the exhaust device is connected to the air-cooled island and the external condenser respectively through pipelines; the air-cooled island and the external condenser are respectively connected to the condensate inlet of the exhaust device through pipelines; the condensate outlet of the exhaust device is connected to the regenerative heating system through a pipeline; A condensate pump is provided in the pipeline between the condensate outlet of the exhaust device and the regenerative heating system, and an air-cooled island exhaust steam isolation valve is provided in the pipeline between the exhaust outlet of the exhaust device and the air-cooled island.

5. The deep peak shaving method for the air-cooled heat supply unit based on the air-cooled heat supply unit described in claim 4, characterized in that, It includes the following steps: According to the time and the working state of the air-cooled heat supply unit, judge the working condition of the air-cooled heat supply unit; According to the working condition of the air-cooled heat supply unit, execute the corresponding peak shaving strategy; among them, the working conditions of the air-cooled heat supply unit include non-heating season pure condensing high load condition, non-heating season pure condensing low load condition, heating season extraction condensing high load condition and heating season extraction condensing low load condition.

6. The method for deep peak shaving of the flexibility of the air-cooled heat supply unit according to claim 5, characterized in that, If it is the non-heating season pure condensing high load condition, then execute the following steps: Close the first heat network return water function switching valve, the second heat network return water function switching valve, the first internal circulating water function switching valve and the second internal circulating water function switching valve to cut off the centrifugal heat pump station and the heat network return pipeline from the external condenser; Open the internal circulating water bypass valve and the buried pipe switching valve to form a path between the external condenser and the buried pipe system; Close the internal circulating water pump bypass valve and start the internal circulating water pump.

7. The method for deep peak shaving of the flexibility of the air-cooled heat supply unit according to claim 5, wherein, If it is the non-heating season pure condensing low load condition, then execute the following steps: Close the first heat network return water function switching valve, the second heat network return water function switching valve, the first internal circulating water function switching valve and the second internal circulating water function switching valve to cut off the centrifugal heat pump station and the heat network return pipeline from the external condenser; Open the internal circulating water bypass valve and the buried pipe switching valve to form a path between the external condenser and the buried pipe system; Close the internal circulating water pump bypass valve and start the internal circulating water pump.

8. The method for deep peak shaving of the flexibility of the air-cooled heat supply unit according to claim 5, characterized in that If it is the heating season extraction condensing high load condition, then execute the following steps: Stop the centrifugal heat pump station and the internal circulating water pump; Open the second heat network return water function switching valve and the first internal circulating water function switching valve, and close the first heat network return water function switching valve, the second internal circulating water function switching valve, the internal circulating water bypass valve and the buried pipe switching valve to connect the heat network return pipeline to the external condenser and cut off the centrifugal heat pump station and the buried pipe system from the heat network return pipeline; Open the internal circulating water pump bypass valve and stop the internal circulating water pump; Adjust the air-cooled island to raise the back pressure of the air-cooled heat supply unit to more than 30 kPa.

9. The method for deep peak shaving of the flexibility of the air-cooled heat supply unit according to claim 5, characterized in that, If it is the heating season extraction condensing low load condition, then execute the following steps: Open the first heat network return water function switching valve, the second internal circulating water function switching valve and the buried pipe switching valve, and close the second heat network return water function switching valve and the first internal circulating water function switching valve to connect the centrifugal heat pump station, the buried pipe system with the external condenser, and disconnect the external condenser from the heat network return water pipeline; Close the internal circulating water bypass valve and the internal circulating water pump bypass valve, and start the internal circulating water pump; Start the centrifugal heat pump station; Close the air-cooled island.

Images