Combined heat and power system based on high and low pressure cylinder zero output and extraction heat storage and operation method

Abstract

This invention discloses a combined heat and power (CHP) system and its operation method based on zero output of high and low pressure cylinders and extraction steam storage. The system includes a CHP system and a thermal storage system. New pipelines and valve groups are added to the CHP system to allow a small amount of cooling steam to maintain safe idling of the high-pressure and low-pressure cylinders. In the thermal storage system, the cold molten salt in the molten salt side thermal storage loop absorbs the sensible heat of the main steam and reheat steam in two streams. In the steam-water side thermal loop released by the thermal storage system, the hot molten salt heats the water working fluid to produce superheated steam. During periods of medium to high electricity demand, the exhaust steam from the intermediate-pressure cylinder supplies steam to heat users. During periods of low electricity demand, the low-pressure cylinder is in a zero-output state, and the exhaust steam from the intermediate-pressure cylinder supplies steam to heat users. During periods of extremely low electricity demand, the high-pressure and low-pressure cylinders are in a zero-output state, and the reheat steam after heat exchange is injected through an ejector group to supply steam to heat users via the exhaust steam from the intermediate-pressure cylinder. During the heat release phase of the thermal storage system, the thermal storage system replaces part or all of the steam supply from the CHP system. This system can broaden the operating range of CHP and achieve energy cascade utilization.

Description

Technical Field

[0001] This invention relates to the field of cogeneration technology, specifically to a cogeneration system and operation method based on zero output of high and low pressure cylinders and extraction steam storage. Background Technology

[0002] Combined heat and power (CHP) units significantly improve the primary energy utilization rate of coal by simultaneously supplying electricity and heat, and are widely used in industrial steam supply and residential heating. However, traditional CHP units are limited by the "heat-driven power generation" operating mode, with deep coupling of heat and electricity loads, and a limited range of unit power generation adjustment, making it difficult to meet the urgent needs of new power systems for flexible peak and frequency regulation. Based on this, technologies such as low-pressure cylinder zero-output, high and low-pressure bypass heating, heat pumps, electric boilers, and extraction steam storage have been gradually proposed and applied in engineering practice. While some progress has been made, under the background of high-proportion renewable energy integration in new power systems, it is still necessary to form a systematic solution with deep decoupling of heat and power through full-condition adaptive design optimization and multi-energy flow coordinated control. This will enable a synergistic improvement in the unit's ability to flexibly adjust power generation and maintain stable output of heating parameters, thereby enhancing the overall energy efficiency and economy of the system. Summary of the Invention

[0003] To address the problems existing in the prior art, the present invention aims to provide a combined heat and power (CHP) system and its operation method based on zero output of high and low pressure cylinders and extraction steam storage. This system includes a CHP system and a thermal storage system. New pipelines and valve groups are added to the CHP system to allow the introduction of a small amount of cooling steam to maintain safe idling of the high-pressure and low-pressure cylinders. In the thermal storage system, the cold molten salt in the molten salt side thermal storage circuit is divided into two streams to absorb the sensible heat of the main steam and reheat steam. In the steam-water side heat release circuit of the thermal storage system, the hot molten salt heats the water working fluid to produce superheated steam. During periods of medium to high electricity demand, the exhaust steam from the intermediate-pressure cylinder supplies steam to heat users. During periods of low electricity demand, the low-pressure cylinder is in a zero-output state, and the exhaust steam from the intermediate-pressure cylinder supplies steam to heat users. During periods of extremely low electricity demand, the high-pressure and low-pressure cylinders are in a zero-output state, and the reheat steam after heat exchange is injected through an ejector group to supply steam to heat users via the exhaust steam from the intermediate-pressure cylinder. During the heat release phase of the thermal storage system, the thermal storage system replaces part or all of the steam supply from the CHP system. This system can broaden the thermoelectric operating domain and realize the cascade utilization of energy.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A combined heat and power system based on zero output of high and low pressure cylinders and extraction steam storage includes a combined heat and power system and a thermal storage system; The cogeneration system includes a boiler 1, a high-pressure cylinder 2, an intermediate-pressure cylinder 3, a low-pressure cylinder 4, a generator 5, a condenser 6, a condensate pump 7, a low-pressure regenerative heater group 8, a deaerator 9, a feedwater pump 10, a high-pressure regenerative heater group 11, a main steam valve 12, a hot-section reheat steam regulating valve 13, a steam inlet valve 14 from the intermediate-pressure cylinder to the low-pressure cylinder, and a steam supply valve 15. The main steam outlet of boiler 1 is connected to the steam inlet of main steam valve 12, the steam outlet of main steam valve 12 is connected to the steam inlet of high-pressure cylinder 2, and the exhaust outlet of high-pressure cylinder 2 is connected to the cold-section reheat steam inlet of boiler 1. The reheat steam outlet of the hot section of furnace 1 is connected to the steam inlet of the hot section reheat steam regulating valve 13. The steam outlet of the hot section reheat steam regulating valve 13 is connected to the steam inlet of the intermediate-pressure cylinder 3. The exhaust outlet of the intermediate-pressure cylinder 3 is connected to the steam inlet of the intermediate-pressure cylinder to low-pressure cylinder inlet valve 14. The steam outlet of the intermediate-pressure cylinder to low-pressure cylinder inlet valve 14 is connected to the steam inlet of the low-pressure cylinder 4. The exhaust outlet of the low-pressure cylinder 4 is connected to the hot-side steam inlet of condenser 6. The hot-side condensate outlet of condenser 6 is connected to the inlet of condensate pump 7. The condensate outlet of condensate pump 7 is connected to the condensate inlet of the low-pressure regenerative heater group 8. The condensate outlet of the low-pressure regenerative heater group 8 is connected to the condensate inlet of the deaerator 9; the saturated water outlet of the deaerator 9 is connected to the inlet of the feedwater pump 10; the outlet of the feedwater pump 10 is connected to the feedwater inlet of the high-pressure regenerative heater group 11; and the feedwater outlet of the high-pressure regenerative heater group 11 is connected to the feedwater inlet of the boiler 1. The extraction steam outlet of the high-pressure cylinder 2 is connected to the steam inlet of the high-pressure regenerative heater group extraction steam control valve group 19; the steam outlet of the high-pressure regenerative heater group extraction steam control valve group 19 is connected to the steam inlet of the high-pressure regenerative heater group 11; and the extraction steam outlet of the intermediate-pressure cylinder 3 is connected to the deaerator extraction steam inlet. Steam control valve 20 is connected to the steam inlet; deaerator extraction steam control valve 20 is connected to the steam inlet of deaerator 9; low-pressure cylinder 4 extraction steam outlet is connected to the steam inlet of low-pressure regenerative heater group extraction steam control valve group 21; low-pressure regenerative heater group extraction steam control valve group 21 steam outlet is connected to the steam inlet of low-pressure regenerative heater group 8; high-pressure cylinder 2, intermediate-pressure cylinder 3, and low-pressure cylinder 4 drive generator 5 through a rotating shaft to output electrical power; part of the exhaust steam from intermediate-pressure cylinder 3 is connected to the steam inlet of steam supply valve 15; the steam from the outlet of steam supply valve 15 is connected to the steam pipeline network of heat user 29.

[0005] The zero-output technical modification of the high and low pressure cylinders in the cogeneration system includes: adding a steam pipeline to the reheat steam outlet of the hot section of boiler 1, which is connected to the steam inlet of high pressure cylinder 2 through the main reheat steam connecting valve 16; adding a high pressure cylinder exhaust to reheater isolation valve 17 at the connecting pipeline between the exhaust of high pressure cylinder 2 and the reheat steam inlet of the cold section of boiler 1; adding a steam pipeline to the exhaust of high pressure cylinder 2, which is connected to the hot side steam inlet of condenser 6 through the high pressure cylinder exhaust valve 18; and adding a steam pipeline to the exhaust of intermediate pressure cylinder 3, which is connected to the steam inlet of low pressure cylinder 4 through the intermediate and low pressure cylinder bypass valve 22. The molten salt side of the thermal storage system includes a cold salt tank 30, a cold tank molten salt pump 31, a cold salt valve 32, a molten salt flow regulating valve 33 for the main steam molten salt heat exchanger, a molten salt flow regulating valve 34 for the reheat steam molten salt heat exchanger, a main steam molten salt heat exchanger 35, a reheat steam molten salt heat exchanger 36, a hot salt tank 37, a hot tank molten salt pump 39, a hot salt valve 40, and a molten salt steam generator 41. In the thermal storage loop, the outlet of the cold salt tank 30 is connected to the inlet of the cold tank molten salt pump 31, and the outlet of the cold tank molten salt pump 31 is connected to the inlet of the cold salt valve 32. The molten salt working fluid passing through the outlet of the cold salt valve 32 is connected in two ways: one way to the inlet of the molten salt flow regulating valve 33 for the main steam molten salt heat exchanger, and the other way to the molten salt in the reheat steam molten salt heat exchanger. The inlet of flow regulating valve 34 is connected to the main steam molten salt heat exchanger. The outlet of molten salt flow regulating valve 33 of the main steam molten salt heat exchanger is connected to the molten salt inlet of the main steam molten salt heat exchanger 35. The molten salt outlet of the main steam molten salt heat exchanger 35 is connected to the inlet of the hot salt tank 37. The outlet of molten salt flow regulating valve 34 of the reheat steam molten salt heat exchanger is connected to the molten salt inlet of the reheat steam molten salt heat exchanger 36. The molten salt outlet of the reheat steam molten salt heat exchanger 36 is connected to the inlet of the hot salt tank 37. In the heat release circuit, the outlet of the hot salt tank 37 is connected to the inlet of the hot salt tank 37. The outlet of the hot salt tank 37 is connected to the molten salt inlet of the molten salt steam generator 41 through the hot salt pump 39 and the hot salt valve 40. The molten salt outlet of the molten salt steam generator 41 is connected to the cold salt tank 30. The connection relationship between the steam-water side of the thermal storage system and the cogeneration system is as follows: The steam inlet of the main steam molten salt heat exchanger 35 is connected to the main steam outlet of boiler 1 via the main steam bypass valve 23. The steam outlet of the main steam molten salt heat exchanger 35 is divided into three paths: the first path is connected to the cold section reheat steam inlet of boiler 1; the second path is connected to the steam inlet of the high-pressure regenerative heater group 11 via the high-pressure regenerative heater group steam control valve group 24; and the third path is connected to the deaerator 9 steam inlet via the deaerator steam control valve 25. The steam inlet of the reheat steam molten salt heat exchanger 36 is connected to the main steam outlet of boiler 1 via the hot section reheat steam bypass valve 26. The hot section reheat steam outlet is connected, and the reheat steam molten salt heat exchanger 36 steam outlet is connected to the primary inlet of steam ejector group 28; the secondary inlet of steam ejector group 28 is connected to the exhaust outlet of intermediate pressure cylinder 3 through secondary flow regulating valve 27 of steam ejector group, and the outlet of steam ejector group 28 is connected to the steam pipeline network of heat user 29; the water working fluid side inlet of molten salt steam generator 41 is connected to the outlet of deaerator 9 through feedwater flow regulating valve 38, and the water working fluid side outlet of molten salt steam generator 41 is connected to the steam pipeline network of heat user 29.

[0006] The structure of the turbine regenerative system and its auxiliary equipment in the cogeneration system, including condensate pump 7, low-pressure regenerative heater group 8, deaerator 9, feedwater pump 10, and high-pressure regenerative heater group 11, is determined based on the actual equipment configuration of the modified unit. The high-pressure regenerative heater group extraction steam control valve group 19, deaerator extraction steam control valve 20, and low-pressure regenerative heater group extraction steam control valve group 21 must have the ability to completely cut off the steam source. When the high-pressure cylinder 2 is in zero-output condition, the heating steam source of the deaerator 9 and high-pressure regenerative heater group 11 is switched to the main steam after heat exchange and pressure reduction treatment. The appropriate pressure range after throttling is determined according to the equipment characteristics and deoxygenation effect of the deaerator 9.

[0007] The outlet parameters of the steam ejector group 28 meet the requirements of the heat user parameters through the following means: First, the opening degree of the hot section reheat steam regulating valve 13, the hot section reheat steam bypass valve 26, the secondary flow regulating valve 27 of the steam ejector group, and the operating state of the feedwater pump 10 are changed to regulate the primary and secondary flow steam inlet flow and pressure; Second, the external flow and pressure applicable range of the steam ejector group 28 is expanded by the external series or parallel structure of the ejector, and its internal flow and pressure applicable range is expanded by the internal flow area adjustable mechanism.

[0008] The operating parameters of the cogeneration system based on zero output of high and low pressure cylinders and extraction steam storage must meet the following constraints: the boiler operates safely and meets environmental protection standards; the axial thrust of the steam turbine is controlled within the allowable range; the exhaust temperature of the steam turbine unit is controlled within the allowable range of the materials; and the inlet steam of the boiler reheat system and the inlet working fluid of the steam ejector group both have a superheat of more than 20°C.

[0009] The temperature difference between the main steam molten salt heat exchanger 35 and the reheat steam molten salt heat exchanger 36 is not less than 20°C, and the pinch temperature between the molten salt working medium and the steam-water working medium in the molten salt steam generator 41 is not less than 5°C.

[0010] In the zero-output condition of the high-pressure cylinder 2, the cooling steam flow rate is adjusted by adjusting the opening of the main resteam connecting valve 16, external water spraying is implemented for pre-cooling, and the vacuum degree of the condenser 6 is controlled to maintain the thermal stress of the high-pressure cylinder within the safe threshold. In the zero-output condition of the low-pressure cylinder 4, the cooling steam flow rate is adjusted by adjusting the opening of the intermediate and low-pressure cylinder bypass valve 22, internal water spraying is implemented for cooling, and the vacuum degree of the condenser 6 is controlled to maintain the thermal stress of the low-pressure cylinder within the safe threshold.

[0011] An operation method for a combined heat and power (CHP) system based on zero-output high and low pressure cylinders and extraction steam thermal storage, wherein the CHP system is based on the coupled connection of multiple sets of newly added pipelines and the coordinated control of multiple valve groups, combined with the thermal storage system and zero-output high and low pressure cylinder technology, and supports flexible switching of multiple operating modes to match different heat and power load demands, specifically including the following basic modes: 1) Normal steam supply mode: During periods of medium to high electricity load demand, the thermal storage system and its associated pipeline valves are in hot standby mode. Part of the steam discharged from the intermediate pressure cylinder 3 enters the low pressure cylinder 4 through the intermediate pressure cylinder to low pressure cylinder steam inlet valve 14, and the remaining steam discharged from the intermediate pressure cylinder 3 is connected to the steam network of the heat user 29 through the steam supply valve 15. 2) Low-pressure cylinder zero-output mode: During periods of low electricity demand, the heat storage system and its associated pipeline valves are in hot standby mode. The medium and low-pressure cylinder bypass valve 22 is opened, and the steam inlet valve 14 from the medium-pressure cylinder to the low-pressure cylinder is closed. A small amount of steam from the medium-pressure cylinder 3 is used as cooling steam and enters the low-pressure cylinder 4 before flowing into the condenser 6, keeping the low-pressure cylinder 4 in a zero-output state. The power output of the generator 5 is reduced, and the remaining steam from the medium-pressure cylinder 3 is supplied to the steam network of the heat user 29 through the steam supply valve 15. 3) Zero Output Mode for High and Low Pressure Cylinders: During periods of extremely low electrical load demand, the main reheat steam connecting valve 16, the high-pressure cylinder exhaust valve 18, and the intermediate and low-pressure cylinder bypass valve 22 are opened. The main steam valve 12, the high-pressure cylinder exhaust to reheater isolation valve 17, the high-pressure regenerator extraction control valve group 21, the deaerator extraction control valve 22, the low-pressure regenerator extraction control valve group 23, the intermediate-pressure cylinder to low-pressure cylinder inlet valve 14, and the steam supply valve 15 are closed. A small amount of cooling steam can enter the high-pressure cylinder 2 and the low-pressure cylinder 4 and then flow into the condenser 6. The high-pressure cylinder 2 and the low-pressure cylinder 4 are in a zero output state. The main steam bypass valve 23, the hot section reheat steam regulating valve 13, the hot section reheat steam bypass valve 26, the high-pressure regenerator group steam control valve group 24, the deaerator steam control valve 25, and the steam ejector group secondary flow regulating valve 27 are opened, and the opening degree of each valve is adjusted in a coordinated manner to match the system flow and pressure distribution. After releasing sensible heat in the main steam molten salt heat exchanger 35, all the main steam flows to the reheat steam inlet of the cold section of boiler 1, the steam inlet of the high-pressure regenerator group 11, and the steam inlet of the deaerator 9 in three separate streams. Part of the reheat steam releases sensible heat in the reheat steam molten salt heat exchanger 36 and flows as working steam to the primary inlet of the steam ejector group 28. After being pressurized by the exhaust steam from the intermediate pressure cylinder 3, it is supplied to the steam pipeline network of the heat user 29. Under the condition of meeting the steam quality requirements, the power output of the generator 5 is reduced. On the molten salt side, the cold salt valve 32, the molten salt flow regulating valve 33 of the main steam molten salt heat exchanger, and the molten salt flow regulating valve 34 of the reheat steam molten salt heat exchanger in the heat storage system are opened. The cold tank molten salt pump 31 drives the cold molten salt in the cold salt tank 30 to flow to the main steam molten salt heat exchanger 35 and the reheat steam molten salt heat exchanger 36 to absorb the heat of the sensible heat section of the steam. The molten salt after absorbing heat flows to the hot salt tank 37. 4) Steam generator supplementary steam mode: During the heat release stage of the thermal storage system, the feedwater flow regulating valve 38 and the hot salt valve 40 are opened. The hot tank molten salt pump 39 drives the hot molten salt into the molten salt steam generator 41 to heat the water working medium into superheated steam, which is then supplied to the steam network of the heat user 29. The thermal storage system replaces part or all of the steam supply of the cogeneration system, reducing the fuel consumption of boiler 1 and increasing the power output of generator 5.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention adopts the technology of high and low pressure bypass heating and low pressure cylinder zero output, adopts the method of full extraction of main steam and large-scale extraction of hot reheat steam, and integrates thermal storage technology to achieve high and low pressure cylinder zero output, greatly reducing the minimum technical output of the unit and expanding the thermal power operation range of the cogeneration system. (2) The system can be modularly arranged, and only the bypass pipeline and its matching valve group need to be modified for the original system.

[0013] (3) Under low load conditions, the unit still has a relatively strong throttling capability through the coordinated control of the thermal storage system and the turbine system. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the system of the present invention. Detailed Implementation

[0015] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0016] like Figure 1 As shown, the present invention provides a cogeneration system based on zero output of high and low pressure cylinders and extraction steam storage, comprising a cogeneration system and a thermal storage system. The cogeneration system includes a boiler 1, a high-pressure cylinder 2, an intermediate-pressure cylinder 3, a low-pressure cylinder 4, a generator 5, a condenser 6, a condensate pump 7, a low-pressure regenerative heater group 8, a deaerator 9, a feedwater pump 10, a high-pressure regenerative heater group 11, a main steam valve 12, a hot-section reheat steam regulating valve 13, a steam inlet valve 14 from the intermediate-pressure cylinder to the low-pressure cylinder, and a steam supply valve 15. The main steam outlet of boiler 1 is connected to the steam inlet of main steam valve 12, the steam outlet of main steam valve 12 is connected to the steam inlet of high-pressure cylinder 2, and the exhaust outlet of high-pressure cylinder 2 is connected to the cold-section reheat steam inlet of boiler 1. The reheat steam outlet of the hot section of furnace 1 is connected to the steam inlet of the hot section reheat steam regulating valve 13. The steam outlet of the hot section reheat steam regulating valve 13 is connected to the steam inlet of the intermediate-pressure cylinder 3. The exhaust outlet of the intermediate-pressure cylinder 3 is connected to the steam inlet of the intermediate-pressure cylinder to low-pressure cylinder inlet valve 14. The steam outlet of the intermediate-pressure cylinder to low-pressure cylinder inlet valve 14 is connected to the steam inlet of the low-pressure cylinder 4. The exhaust outlet of the low-pressure cylinder 4 is connected to the hot-side steam inlet of condenser 6. The hot-side condensate outlet of condenser 6 is connected to the inlet of condensate pump 7. The condensate outlet of condensate pump 7 is connected to the condensate inlet of the low-pressure regenerative heater group 8. The condensate outlet of the low-pressure regenerative heater group 8 is connected to the condensate inlet of the deaerator 9; the saturated water outlet of the deaerator 9 is connected to the inlet of the feedwater pump 10; the outlet of the feedwater pump 10 is connected to the feedwater inlet of the high-pressure regenerative heater group 11; and the feedwater outlet of the high-pressure regenerative heater group 11 is connected to the feedwater inlet of the boiler 1. The extraction steam outlet of the high-pressure cylinder 2 is connected to the steam inlet of the high-pressure regenerative heater group extraction steam control valve group 19; the steam outlet of the high-pressure regenerative heater group extraction steam control valve group 19 is connected to the steam inlet of the high-pressure regenerative heater group 11; and the extraction steam outlet of the intermediate-pressure cylinder 2 is connected to the deaerator extraction steam inlet. Steam control valve 20 is connected to the steam inlet; deaerator extraction steam control valve 20 is connected to the steam inlet of deaerator 9; low-pressure cylinder 4 extraction steam outlet is connected to the steam inlet of low-pressure regenerative heater group extraction steam control valve group 21; low-pressure regenerative heater group extraction steam control valve group 21 steam outlet is connected to the steam inlet of low-pressure regenerative heater group 8; high-pressure cylinder 2, intermediate-pressure cylinder 3, and low-pressure cylinder 4 drive generator 5 through a rotating shaft to output electrical power; part of the exhaust steam from intermediate-pressure cylinder 3 is connected to the steam inlet of steam supply valve 15; the steam from the outlet of steam supply valve 15 is connected to the steam pipeline network of heat user 29.

[0017] The zero-output technical modification of the high and low pressure cylinders in the cogeneration system includes: adding a steam pipeline to the reheat steam outlet of the hot section of boiler 1, which is connected to the steam inlet of high pressure cylinder 2 through the main reheat steam connecting valve 16; adding a high pressure cylinder exhaust to reheater isolation valve 17 at the connecting pipeline between the exhaust of high pressure cylinder 2 and the reheat steam inlet of the cold section of boiler 1; adding a steam pipeline to the exhaust of high pressure cylinder 2, which is connected to the hot side steam inlet of condenser 6 through the high pressure cylinder exhaust valve 18; adding a steam pipeline to the exhaust of intermediate pressure cylinder 3, which is connected to the steam inlet of low pressure cylinder 4 through the intermediate and low pressure cylinder bypass valve 22. The advantage is that by adding pipelines and valve groups, the steam flow rate entering high pressure cylinder 2 and low pressure cylinder 4 can be effectively reduced, thereby reducing the shaft power transmitted from high pressure cylinder 2 and low pressure cylinder 4 to generator 5 through the rotating shaft, achieving a significant reduction in the external power output of generator 5, and at the same time increasing the steam flow rate of intermediate pressure cylinder 3 exhaust to the steam network of heat user 29.

[0018] The molten salt side of the thermal storage system includes a cold salt tank 30, a cold tank molten salt pump 31, a cold salt valve 32, a molten salt flow regulating valve 33 for the main steam molten salt heat exchanger, a molten salt flow regulating valve 34 for the reheat steam molten salt heat exchanger, a main steam molten salt heat exchanger 35, a reheat steam molten salt heat exchanger 36, a hot salt tank 37, a hot tank molten salt pump 39, a hot salt valve 40, and a molten salt steam generator 41. In the thermal storage loop, the outlet of the cold salt tank 30 is connected to the inlet of the cold tank molten salt pump 31, and the outlet of the cold tank molten salt pump 31 is connected to the inlet of the cold salt valve 32. The molten salt working fluid passing through the outlet of the cold salt valve 32 is connected in two ways: one way to the inlet of the molten salt flow regulating valve 33 for the main steam molten salt heat exchanger, and the other way to the molten salt in the reheat steam molten salt heat exchanger. The inlet of flow regulating valve 34 is connected to the main steam molten salt heat exchanger. The outlet of molten salt flow regulating valve 33 of the main steam molten salt heat exchanger is connected to the molten salt inlet of the main steam molten salt heat exchanger 35. The molten salt outlet of the main steam molten salt heat exchanger 35 is connected to the inlet of the hot salt tank 37. The outlet of molten salt flow regulating valve 34 of the reheat steam molten salt heat exchanger is connected to the molten salt inlet of the reheat steam molten salt heat exchanger 36. The molten salt outlet of the reheat steam molten salt heat exchanger 36 is connected to the inlet of the hot salt tank 37. In the heat release circuit, the outlet of the hot salt tank 37 is connected to the inlet of the hot salt tank 37. The outlet of the hot salt tank 37 is connected to the molten salt inlet of the molten salt steam generator 41 through the hot salt pump 39 and the hot salt valve 40. The molten salt outlet of the molten salt steam generator 41 is connected to the cold salt tank 30. The connection relationship between the steam-water side of the thermal storage system and the cogeneration system is as follows: The steam inlet of the main steam molten salt heat exchanger 35 is connected to the main steam outlet of boiler 1 via the main steam bypass valve 23. The steam outlet of the main steam molten salt heat exchanger 35 is divided into three paths: the first path is connected to the cold section reheat steam inlet of boiler 1; the second path is connected to the steam inlet of the high-pressure regenerative heater group 11 via the high-pressure regenerative heater group steam control valve group 24; and the third path is connected to the deaerator 9 steam inlet via the deaerator steam control valve 25. The steam inlet of the reheat steam molten salt heat exchanger 36 is connected to the hot section reheat steam outlet of boiler 1 via the hot section reheat steam bypass valve 26. The steam outlet of the reheat steam molten salt heat exchanger 36 is connected to the steam ejector group. The primary inlet of steam ejector group 28 is connected; the secondary inlet of steam ejector group 28 is connected to the exhaust outlet of intermediate pressure cylinder 3 through secondary flow regulating valve 27, and the outlet of steam ejector group 28 is connected to the steam network of heat user 29. The advantage is that the thermal storage system can further reduce the output power of generator 5 under the minimum stable combustion load of boiler 1, while also meeting the steam supply parameter requirements of the steam network of heat user 29. The water-side inlet of molten salt steam generator 41 is connected to the outlet of deaerator 9 through feedwater flow regulating valve 38, and the water-side outlet of molten salt steam generator 41 is connected to the steam network of heat user 29. The advantage is that the steam generation method of the thermal storage system can broaden the thermal power operating range of the cogeneration system in the normal operating area, and also provides a new means of peak shaving and frequency regulation through the thermal storage system. The structure of the turbine regenerative system and its auxiliary equipment in the cogeneration system, including condensate pump 7, low-pressure regenerative heater group 8, deaerator 9, feedwater pump 10, and high-pressure regenerative heater group 11, is determined based on the actual equipment configuration of the modified unit. The high-pressure regenerative heater group extraction steam control valve group 19, deaerator extraction steam control valve 20, and low-pressure regenerative heater group extraction steam control valve group 21 must have the ability to completely cut off the steam source. When the high-pressure cylinder 2 is in zero-output condition, the heating steam source of the deaerator 9 and the high-pressure regenerative heater group 11 is switched to the main steam after heat exchange and pressure reduction treatment. The appropriate pressure range after throttling is determined according to the equipment characteristics and deoxygenation effect of the deaerator 9. The advantage is that it can ensure that the feedwater inlet temperature of the boiler 1 is within the original safe operating range when the high-pressure cylinder 2 is in zero-output condition, ensure the safe and stable operation of the boiler tail flue, avoid excessive pollutant emissions, and also ensure the normal operation of the deoxygenation process of the deaerator 9. The outlet parameters of the steam ejector group 28 meet the requirements of the heat user parameters through the following means: First, by changing the opening degree of the hot section reheat steam regulating valve 13, the hot section reheat steam bypass valve 26, the secondary flow regulating valve 27 of the steam ejector group, and the operating state of the feedwater pump 10, the flow rate and pressure of the primary and secondary flow inlets are adjusted; Second, the external flow rate and pressure applicable range of the steam ejector group 28 are expanded through the external series or parallel structure of the ejector, and its internal flow rate and pressure applicable range are expanded through the internal flow area adjustable mechanism. The advantage is that the outlet parameters of the steam ejector group 28 can meet the steam supply parameter requirements under wide load operating conditions. The operating parameters of the cogeneration system based on zero-output high and low-pressure cylinders and extraction steam storage must meet the following constraints: safe boiler operation and compliance with environmental standards; turbine axial thrust controlled within allowable range; turbine exhaust temperature controlled within material allowable range; and both the boiler reheat system inlet steam and the steam ejector group inlet working fluid having a superheat of over 20°C. The advantage is that it ensures the cogeneration system's operating parameters are within the design operating range, guaranteeing the safe operation of the cogeneration system under wide load conditions.

[0019] The temperature difference between the main steam molten salt heat exchanger 35 and the reheat steam molten salt heat exchanger 36 is not less than 20°C. This provides sufficient temperature margin for the control system of the thermal storage system, buffering the impact of external parameter fluctuations on the outlet parameters of the main steam molten salt heat exchanger 35 and the reheat steam molten salt heat exchanger 36. It also reduces the heat exchange area and equipment cost of the main steam molten salt heat exchanger 35 and the reheat steam molten salt heat exchanger 36. The pinch-point temperature between the molten salt working fluid and the steam-water working fluid in the molten salt steam generator 41 is not less than 5°C. This ensures the normal operation of the heat exchange process while avoiding excessive heat exchange area and equipment cost.

[0020] In the zero-output condition of the high-pressure cylinder 2, the cooling steam flow rate is adjusted by adjusting the opening of the main resteam connecting valve 16, external water spraying is implemented for pre-cooling, and the vacuum degree of the condenser 6 is controlled to maintain the thermal stress of the high-pressure cylinder within the safe threshold. In the zero-output condition of the low-pressure cylinder 4, the cooling steam flow rate is adjusted by adjusting the opening of the intermediate and low-pressure cylinder bypass valve 22, internal water spraying is implemented for cooling, and the vacuum degree of the condenser 6 is controlled to maintain the thermal stress of the low-pressure cylinder within the safe threshold.

[0021] An operation method for a combined heat and power (CHP) system based on zero-output high and low pressure cylinders and extraction steam thermal storage, wherein the CHP system is based on the coupled connection of multiple sets of newly added pipelines and the coordinated control of multiple valve groups, combined with the thermal storage system and zero-output high and low pressure cylinder technology, and supports flexible switching of multiple operating modes to match different heat and power load demands, specifically including the following basic modes: 1) Normal steam supply mode: During periods of medium to high electricity load demand, the thermal storage system and its associated pipeline valves are in hot standby mode. Part of the steam discharged from the intermediate pressure cylinder 3 enters the low pressure cylinder 4 through the intermediate pressure cylinder to low pressure cylinder steam inlet valve 14, and the remaining steam discharged from the intermediate pressure cylinder 3 is connected to the steam network of the heat user 29 through the steam supply valve 15. 2) Low-pressure cylinder zero-output mode: During periods of low electricity demand, the heat storage system and its associated pipeline valves are in hot standby mode. The medium and low-pressure cylinder bypass valve 22 is opened, and the steam inlet valve 14 from the medium-pressure cylinder to the low-pressure cylinder is closed. A small amount of steam from the medium-pressure cylinder 3 is used as cooling steam and enters the low-pressure cylinder 4 before flowing into the condenser 6, keeping the low-pressure cylinder 4 in a zero-output state. The power output of the generator 5 is reduced, and the remaining steam from the medium-pressure cylinder 3 is supplied to the steam network of the heat user 29 through the steam supply valve 15. 3) Zero Output Mode for High and Low Pressure Cylinders: During periods of extremely low electrical load demand, the main reheat steam connecting valve 16, the high-pressure cylinder exhaust valve 18, and the intermediate and low-pressure cylinder bypass valve 22 are opened. The main steam valve 12, the high-pressure cylinder exhaust to reheater isolation valve 17, the high-pressure regenerator extraction control valve group 21, the deaerator extraction control valve 22, the low-pressure regenerator extraction control valve group 23, the intermediate-pressure cylinder to low-pressure cylinder inlet valve 14, and the steam supply valve 15 are closed. A small amount of cooling steam can enter the high-pressure cylinder 2 and the low-pressure cylinder 4 and then flow into the condenser 6. The high-pressure cylinder 2 and the low-pressure cylinder 4 are in a zero output state. The main steam bypass valve 23, the hot section reheat steam regulating valve 13, the hot section reheat steam bypass valve 26, the high-pressure regenerator group steam control valve group 24, the deaerator steam control valve 25, and the steam ejector group secondary flow regulating valve 27 are opened, and the opening degree of each valve is adjusted in a coordinated manner to match the system flow and pressure distribution. After releasing sensible heat in the main steam molten salt heat exchanger 35, all the main steam flows to the reheat steam inlet of the cold section of boiler 1, the steam inlet of the high-pressure regenerator group 11, and the steam inlet of the deaerator 9 in three separate streams. Part of the reheat steam releases sensible heat in the reheat steam molten salt heat exchanger 36 and flows as working steam to the primary inlet of the steam ejector group 28. After being pressurized by the exhaust steam from the intermediate pressure cylinder 3, it is supplied to the steam pipeline network of the heat user 29. Under the condition of meeting the steam quality requirements, the power output of the generator 5 is reduced. On the molten salt side, the cold salt valve 32, the molten salt flow regulating valve 33 of the main steam molten salt heat exchanger, and the molten salt flow regulating valve 34 of the reheat steam molten salt heat exchanger in the heat storage system are opened. The cold tank molten salt pump 31 drives the cold molten salt in the cold salt tank 30 to flow to the main steam molten salt heat exchanger 35 and the reheat steam molten salt heat exchanger 36 to absorb the heat of the sensible heat section of the steam. The molten salt after absorbing heat flows to the hot salt tank 37. 4) Steam generator make-up steam mode: During the heat release phase of the thermal storage system, the feedwater flow regulating valve 38 and the hot salt valve 40 are opened. The molten salt pump 39 in the hot tank drives the hot molten salt into the molten salt steam generator 41 to heat the water working fluid into superheated steam, which is then supplied to the steam network of the heat user 29. The thermal storage system replaces part or all of the steam supply from the cogeneration system, reducing the fuel consumption of boiler 1 and increasing the power output of generator 5.

[0022] This invention regulates the external power output of a combined heat and power (CHP) unit's generator by switching between zero-output low-pressure cylinder, zero-output high-pressure cylinder, and the thermal storage system. This broadens the unit's CHP operating range, meets the demands of different electrical and thermal load periods, and achieves cascaded utilization of the thermal storage system's energy. While specific embodiments of the invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the invention. Those skilled in the art should understand that various modifications or variations that can be made without creative effort based on the disclosed technical solutions of this invention should be included within the scope of protection of this invention.

Claims

1. A combined heat and power system based on zero output of high and low pressure cylinders and extraction steam heat storage, characterized in that, This includes combined heat and power systems and thermal storage systems; The cogeneration system includes a boiler (1), a high-pressure cylinder (2), a medium-pressure cylinder (3), a low-pressure cylinder (4), a generator (5), a condenser (6), a condensate pump (7), a low-pressure regenerative heater group (8), a deaerator (9), a feedwater pump (10), a high-pressure regenerative heater group (11), a main steam valve (12), a hot section reheat steam regulating valve (13), a steam inlet valve (14) from the medium-pressure cylinder to the low-pressure cylinder, and a steam supply valve (15); the main steam outlet of the boiler (1) is connected to the steam inlet of the high-pressure cylinder (2) through the main steam valve (12). The outlet of the high-pressure cylinder (2) is connected to the cold section reheat steam inlet of the boiler (1). The hot section reheat steam outlet of the boiler (1) is connected to the steam inlet of the intermediate-pressure cylinder (3) through the hot section reheat steam regulating valve (13). The outlet of the intermediate-pressure cylinder (3) is connected to the steam inlet of the low-pressure cylinder (4) through the intermediate-pressure cylinder to low-pressure cylinder steam inlet valve (14). The outlet of the low-pressure cylinder (4) is connected to the hot side steam inlet of the condenser (6). The hot side condensate outlet of the condenser (6) is connected to the inlet of the condensate pump (7). The condensate pump (7) condensates... The condensate outlet is connected to the condensate inlet of the low-pressure regenerative heater group (8), the condensate outlet of the low-pressure regenerative heater group (8) is connected to the condensate inlet of the deaerator (9), the saturated water outlet of the deaerator (9) is connected to the inlet of the feed water pump (10), the outlet of the feed water pump (10) is connected to the feed water inlet of the high-pressure regenerative heater group (11), and the feed water outlet of the high-pressure regenerative heater group (11) is connected to the feed water inlet of the boiler (1); the extraction steam outlet of the high-pressure cylinder (2) is connected to the high-pressure regenerative heater group through the extraction steam control valve group (19). The steam inlet of the heater group (11) is connected, the steam outlet of the intermediate pressure cylinder (3) is connected to the steam inlet of the deaerator (9) through the deaerator steam extraction control valve (20), and the steam outlet of the low pressure cylinder (4) is connected to the steam inlet of the low pressure regenerative heater group (8) through the low pressure regenerative heater group steam extraction control valve group (21); the high pressure cylinder (2), intermediate pressure cylinder (3) and low pressure cylinder (4) drive the generator (5) through the rotating shaft to output electric power to the outside; part of the exhaust steam of the intermediate pressure cylinder (3) is connected to the steam network of the heat user (29) through the steam supply valve (15); The technical modifications to the high and low pressure cylinders in the cogeneration system include: adding a steam pipeline to the reheat steam outlet of the hot section of boiler (1), which is connected to the steam inlet of the high pressure cylinder (2) through the main reheat steam connecting valve (16); adding a high pressure cylinder exhaust to reheater isolation valve (17) at the connecting pipeline between the exhaust of the high pressure cylinder (2) and the reheat steam inlet of the cold section of boiler (1); adding a steam pipeline to the exhaust of the high pressure cylinder (2), which is connected to the hot side steam inlet of the condenser (6) through the high pressure cylinder exhaust valve (18); adding a steam pipeline to the exhaust of the medium pressure cylinder (3), which is connected to the steam inlet of the low pressure cylinder (4) through the medium and low pressure cylinder bypass valve (22); The molten salt side of the thermal storage system includes a cold salt tank (30), a cold tank molten salt pump (31), a cold salt valve (32), a molten salt flow regulating valve (33) for the main steam molten salt heat exchanger, a molten salt flow regulating valve (34) for the reheat steam molten salt heat exchanger, a main steam molten salt heat exchanger (35), a reheat steam molten salt heat exchanger (36), a hot salt tank (37), a hot tank molten salt pump (39), a hot salt valve (40), and a molten salt steam generator (41). In the thermal storage loop, the outlet of the cold salt tank (30) is connected to the inlet of the cold salt valve (32) through the cold tank molten salt pump (31). One path of the molten salt working medium through the outlet of the cold salt valve (32) is connected to the inlet of the molten salt flow regulating valve (33) for the main steam molten salt heat exchanger, and the other path is connected to the reheat steam molten salt heat exchanger. The inlet of the molten salt flow regulating valve (34) of the main steam molten salt heat exchanger is connected to the inlet of the molten salt of the main steam molten salt heat exchanger (35), the outlet of the molten salt of the main steam molten salt heat exchanger (35) is connected to the inlet of the hot salt tank (37), the outlet of the molten salt flow regulating valve (34) of the reheat steam molten salt heat exchanger is connected to the inlet of the reheat steam molten salt heat exchanger (36), and the outlet of the reheat steam molten salt heat exchanger (36) is connected to the inlet of the hot salt tank (37); in the heat release circuit, the outlet of the hot salt tank (37) is connected to the inlet of the molten salt steam generator (41) through the hot salt pump (39) and the hot salt valve (40), and the outlet of the molten salt steam generator (41) is connected to the cold salt tank (30); The connection relationship between the steam-water side of the thermal storage system and the cogeneration system is as follows: The steam inlet of the main steam molten salt heat exchanger (35) is connected to the main steam outlet of the boiler (1) via the main steam bypass valve (23). The steam outlet of the main steam molten salt heat exchanger (35) is divided into three paths: the first path is connected to the cold section reheat steam inlet of the boiler (1); the second path is connected to the high-pressure regenerative heater group (11) via the high-pressure regenerative heater group steam control valve group (24); and the third path is connected to the deaerator (9) steam inlet via the deaerator steam control valve (25). The steam inlet of the reheat steam molten salt heat exchanger (36) is connected to the boiler (1) via the hot section reheat steam bypass valve (26). The hot section reheat steam outlet is connected, and the reheat steam molten salt heat exchanger (36) steam outlet is connected to the primary inlet of the steam ejector group (28); the secondary inlet of the steam ejector group (28) is connected to the exhaust outlet of the intermediate pressure cylinder (3) through the secondary flow regulating valve (27) of the steam ejector group, and the outlet of the steam ejector group (28) is connected to the steam network of the heat user (29); the water working fluid side inlet of the molten salt steam generator (41) is connected to the outlet of the deaerator (9) through the feed water flow regulating valve (38), and the water working fluid side outlet of the molten salt steam generator (41) is connected to the steam network of the heat user (29).

2. A combined heat and power system based on zero output of high and low pressure cylinders and extraction steam heat storage according to claim 1, characterized in that, The structure of the turbine regenerative system and its auxiliary equipment, including the condensate pump (7), low-pressure regenerative heater group (8), deaerator (9), feedwater pump (10) and high-pressure regenerative heater group (11), is determined based on the equipment configuration of the actual modified unit; the extraction steam control valve group (19) of the high-pressure regenerative heater group, the extraction steam control valve (20) of the deaerator, and the extraction steam control valve group (21) of the low-pressure regenerative heater group must have the ability to completely cut off the steam source; when the high-pressure cylinder (2) is in zero-output condition, the heating steam source of the deaerator (9) and the high-pressure regenerative heater group (11) is switched to the main steam after heat exchange and pressure reduction treatment; the appropriate pressure range after throttling is determined according to the equipment characteristics and deoxygenation effect of the deaerator (9).

3. A combined heat and power system based on zero output of high and low pressure cylinders and extraction steam heat storage according to claim 1, characterized in that, The outlet parameters of the steam ejector group (28) meet the requirements of the heat user parameters by means of the following: First, the opening degree of the hot section reheat steam regulating valve (13), the hot section reheat steam bypass valve (26), the secondary flow regulating valve (27) of the steam ejector group and the operating state of the feed water pump (10) are changed to regulate the primary flow and secondary flow inlet steam flow and pressure; Second, the external flow and pressure applicable range of the steam ejector group (28) is expanded by the external series or parallel structure of the ejector, and its internal flow and pressure applicable range is expanded by the internal flow area adjustable mechanism.

4. A combined heat and power system based on zero output of high and low pressure cylinders and extraction steam heat storage according to claim 1, characterized in that, The operating parameters of the cogeneration system based on zero output of high and low pressure cylinders and extraction steam storage must meet the following constraints: the boiler operates safely and meets environmental protection standards; the axial thrust of the steam turbine is controlled within the allowable range; the exhaust temperature of the steam turbine unit is controlled within the allowable range of the materials; and the inlet steam of the boiler reheat system and the inlet working fluid of the steam ejector group both have a superheat of more than 20°C.

5. A combined heat and power system based on zero output of high and low pressure cylinders and extraction steam storage as described in claim 1, characterized in that, The temperature difference between the main steam molten salt heat exchanger (35) and the reheat steam molten salt heat exchanger (36) is not less than 20°C, and the temperature of the heat exchange pinch point between the molten salt working medium and the steam-water working medium in the molten salt steam generator (41) is not less than 5°C.

6. A combined heat and power system based on zero output of high and low pressure cylinders and extraction steam storage as described in claim 1, characterized in that, When the high-pressure cylinder (2) operates at zero output, the cooling steam flow rate is adjusted by adjusting the opening of the main resteam connecting valve (16), water spraying is implemented outside the cylinder for pre-cooling, and the vacuum degree of the condenser (6) is controlled to maintain the thermal stress of the high-pressure cylinder within the safe threshold. When the low-pressure cylinder (4) operates at zero output, the cooling steam flow rate is adjusted by adjusting the opening of the intermediate and low-pressure cylinder bypass valve (22), water spraying is implemented inside the cylinder for cooling, and the vacuum degree of the condenser (6) is controlled to maintain the thermal stress of the low-pressure cylinder within the safe threshold.

7. The operation method of a combined heat and power system based on zero output of high and low pressure cylinders and extraction steam heat storage as described in any one of claims 1 to 6, characterized in that, The cogeneration system, based on the coupled connection of multiple sets of newly added pipelines and the coordinated control of multiple valve groups, combined with the thermal storage system and the zero-output technology of high and low pressure cylinders, supports flexible switching of multiple operating modes to match different thermal and power load demands, specifically including the following basic modes: (1) Normal steam supply mode: During periods of medium to high electricity load demand, the heat storage system and its associated pipeline valves are in a hot standby state. Part of the steam discharged from the medium pressure cylinder (3) enters the low pressure cylinder (4) through the steam inlet valve (14) from the medium pressure cylinder to the low pressure cylinder, and the remaining steam discharged from the medium pressure cylinder (3) is connected to the steam network of the heat user (29) through the steam supply valve (15). (2) Low-pressure cylinder zero output mode: During periods of low electricity demand, the heat storage system and its associated pipeline valves are in hot standby mode. The bypass valve (22) of the medium and low pressure cylinders is opened, and the steam inlet valve (14) from the medium pressure cylinder to the low pressure cylinder is closed. A small amount of steam from the medium pressure cylinder (3) is discharged as cooling steam and enters the low pressure cylinder (4) and flows into the condenser (6), maintaining the low pressure cylinder (4) in a zero output state. The power output of the generator (5) is reduced, and the remaining steam from the medium pressure cylinder (3) is supplied to the steam network of the heat user (29) through the steam supply valve (15). (3) Zero output mode for high and low pressure cylinders: During periods of extremely low electrical load demand, open the main reheat steam connecting valve (16), the high-pressure cylinder exhaust valve (18), and the intermediate and low-pressure cylinder bypass valve (22), and close the main steam valve (12), the high-pressure cylinder exhaust to reheater isolation valve (17), the high-pressure regenerator extraction control valve group (21), the deaerator extraction control valve (22), the low-pressure regenerator extraction control valve group (23), the intermediate-pressure cylinder to low-pressure cylinder inlet valve (14), and the steam supply valve (15). After the cooling steam enters the high-pressure cylinder (2) and the low-pressure cylinder (4), it flows into the condenser (6). The high-pressure cylinder (2) and the low-pressure cylinder (4) are in a zero-output state. The main steam bypass valve (23), the hot section reheat steam regulating valve (13), the hot section reheat steam bypass valve (26), the high-pressure regenerator steam control valve group (24), the deaerator steam control valve (25), and the secondary flow regulating valve (27) of the steam ejector group are opened, and the opening degree of each valve is adjusted in coordination to match the system flow rate and pressure. Force distribution: After releasing sensible heat in the main steam molten salt heat exchanger (35), all the main steam flows to the boiler (1) cold section reheat steam inlet, the high-pressure regenerator group (11) steam inlet, and the deaerator (9) steam inlet in three separate paths. Part of the reheat steam releases sensible heat in the reheat steam molten salt heat exchanger (36) and flows as working steam to the steam ejector group (28) primary inlet. After being ejected from the intermediate pressure cylinder (3) and pressurized, it is supplied to the heat user (29) steam network. The steam supply quality requirements are met. Under the condition of demand, the power output of the generator (5) is reduced; on the molten salt side, the cold salt valve (32), the molten salt flow regulating valve (33) of the main steam molten salt heat exchanger and the molten salt flow regulating valve (34) of the reheat steam molten salt heat exchanger in the heat storage circuit of the heat storage system are opened, and the cold tank molten salt pump (31) drives the cold molten salt in the cold salt tank (30) to flow to the main steam molten salt heat exchanger (35) and the reheat steam molten salt heat exchanger (36) to absorb the heat of the steam sensible heat section, and the molten salt after absorbing heat flows to the hot salt tank (37). (4) Steam generator supplementation mode: During the heat release stage of the heat storage system, the feedwater flow regulating valve (38) and the hot salt valve (40) are opened, and the hot tank molten salt pump (39) drives the hot molten salt into the molten salt steam generator (41) to heat the working water into superheated steam, and supply it to the heat user (29) steam network; the heat storage system replaces part or all of the cogeneration system for steam supply, reducing the boiler (1) fuel consumption and increasing the generator (5) external power output.

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