Thermal power generating unit heat supply network drainage waste heat driven heat and power cogeneration peak regulation system and method

Abstract

The invention relates to the technical field of combined heat and power generation, in particular to a combined heat and power supply peak shaving system and method driven by drainage waste heat of a heat supply network of a thermal power generating unit. By efficiently coupling water supply of a conventional thermal power generating unit and a heat supply network with low-temperature waste heat power circulation and absorption heat pump waste heat supply circulation, low-temperature waste heat recovery heat supply which can be driven by a single waste heat source is achieved, secondary waste in the energy conversion process is avoided, and the energy conversion efficiency is improved; heat supply network drain water drives low-temperature waste heat power circulation, circulating water waste heat serves as a low-temperature heat source of absorption heat pump waste heat supply circulation, synchronous recovery of heat supply network drain water waste heat and steam turbine cold end waste heat is achieved, and gradient utilization of energy and flexible peak regulation of a unit are achieved. The problems that in the prior art, a cogeneration unit is poor in peak regulation capacity, and the heat supply network drainage waste heat utilization rate is low are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of cogeneration, and in particular to a cogeneration peak-shaving system and method driven by waste heat from a thermal network of a thermal power unit. Background Art

[0002] In order to reduce carbon emissions, new energy units such as wind power generation, hydropower generation, and photovoltaic power generation have begun to be applied to the power grid, and are gradually becoming an indispensable and important part, changing the energy structure of the power system. At present, the capacity of new energy units in the power system has accounted for more than half, and the amount of wind power and photovoltaic power connected to the grid has gradually increased. Due to the intermittent and unstable nature of new energy, the power grid needs to withstand scenarios with greater impact and fluctuations. As the amount of new energy connected to the grid increases, the requirements for peak and frequency regulation of thermal power units are becoming more severe. For example, solar power generation cannot be carried out at night, and wind power generation is limited by wind speed. This instability will lead to insufficient power supply or power supply fluctuations in the power grid, which will in turn affect the normal power consumption of users. When the output of new energy power generation is insufficient, thermal power units need to undertake more peak-shaving tasks to ensure the stable operation of the power grid. However, with the continuous increase in the installed capacity of new energy, the peak-shaving pressure of thermal power units is also gradually increasing. With the gradual implementation of the policies of the electricity spot trading market, the on-grid electricity price of thermal power fluctuates sharply within a scheduling day. In provinces with large photovoltaic installed capacity, the photovoltaic online power volume increases sharply at noon, and the on-grid electricity price of thermal power has been inverted. The on-grid electricity price of thermal power has also been inverted at night in provinces with large wind turbine installed capacity. For cogeneration units that carry residential heating heat loads, due to their operation mode of determining electricity by heat, they lack peak-shaving and frequency-regulating capabilities, suffer substantial losses in the spot trading market, and have poor economic performance throughout the year.

[0003] In view of the requirements for the steam-water circulation quality of the cogeneration unit, the existing heat network drain is no longer allowed to be directly sent back to the deaerator. The condensate must be sent back and purified by the fine treatment device. During the process, the temperature of the heat network drain is relatively high. Sending it directly into the condenser will cause vacuum destruction. There is a large amount of waste heat in the drain that can be used. If it is directly cooled by adding an intermediate heat exchanger and then sent to the condenser, it will cause heat waste.

[0004] Therefore, how to simultaneously solve the problems of waste heat from heat network drainage and high peak load regulation pressure of thermal power units has become the key to increasing the ability to profit in the spot trading market while ensuring the supply of heating heat load for users. Summary of the invention

[0005] In view of the problems in the prior art of poor peak-shaving capability of cogeneration units and low utilization rate of waste heat from heat network drainage, the present invention provides a cogeneration peak-shaving system and method driven by waste heat from heat network drainage of thermal power units.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides a combined heat and power peak regulation system driven by waste heat from the heat network of a thermal power unit, which at least comprises a heat network heater connected to the exhaust port of a medium pressure cylinder of a conventional thermal power unit and an absorber connected to the return water output end of the heat network circulating water; The heat network drain output end of the heat network heater is connected to a waste heat evaporator and a generator; The water output end of the waste heat evaporator and the water output end of the generator are both connected to the condenser in the conventional thermal power unit; The working fluid output end of the waste heat evaporator is connected to the turbine and the working fluid condenser in sequence, and the working fluid output end of the working fluid condenser is connected to the working fluid input end of the waste heat evaporator; the water output end of the working fluid condenser is divided into two paths, one of which is connected to the evaporator and the other is connected to the cooling tower; the water output ends of the evaporator and the cooling tower are combined and divided into two paths, one of which is connected to the condenser and the other is connected to the water input end of the working fluid condenser; The working medium concentrated solution output end of the generator is connected to a solution heat exchanger, and the solution heat exchanger is sequentially connected to the absorber, the solution heat exchanger cold end and the generator; The water vapor output end of the generator is connected to a condenser, and the condensed water output end of the condenser is connected to an evaporator; the evaporator is sequentially connected to an absorber, a solution heat exchanger and a generator; The circulating water return of the absorber is connected to the condenser, the heating network heater and the circulating water supply input end of the heating network in sequence.

[0007] Optionally, a steam electric regulating valve is provided between the heating network heater and the medium-pressure cylinder.

[0008] Optionally, a working fluid booster pump is provided between the working fluid condenser and the waste heat evaporator.

[0009] Optionally, a first drain electric regulating valve is provided between the waste heat evaporator and the condenser.

[0010] Optionally, a second drain electric regulating valve is provided between the generator and the condenser.

[0011] Optionally, a solution pump is provided between the cold end of the solution heat exchanger and the generator; a first expansion valve is provided between the generator and the hot end of the solution heat exchanger; and a second expansion valve is provided between the condenser and the evaporator.

[0012] Optionally, the solution pump is arranged coaxially with the turbine.

[0013] Optionally, a first circulating water electric regulating valve is provided between the cooling tower and the working medium condenser; a second circulating water electric regulating valve is provided between the cooling tower and the evaporator; and a third second circulating water electric regulating valve is provided between the condenser and the cooling tower output end.

[0014] Optionally, a heat network circulating water pump is provided between the heat network circulating water return output end and the absorber; and a circulating water pump is provided on the bus bar formed by merging the water output ends of the evaporator and the cooling tower.

[0015] The present invention provides a peak-shaving method for a combined heat and power peak-shaving system driven by the waste heat of water drainage from the thermal power unit, comprising: When conventional thermal power units need deep peak regulation or top load, the exhaust steam volume entering the heat network heater at the outlet of the heat network heater is adjusted to make the heat network drain water into two paths, one of which enters the waste heat evaporator, and then enters the condenser for cooling after heat exchange with the working fluid in the waste heat evaporator; the other enters the generator; The working fluid after heat exchange in the waste heat evaporator enters the turbine to do work; The exhaust steam of the organic working medium after the turbine has done work enters the working medium condenser, exchanges heat with the circulating water in the working medium condenser, and then releases heat and condenses; The organic working medium after heat release and condensation in the working medium condenser is returned to the waste heat evaporator; After the circulating water after heat exchange in the working medium condenser is combined with the circulating water produced by the condenser, it is divided into two paths, one of which enters the evaporator for cooling, and the other enters the cooling tower for cooling; After the circulating water cooled by the evaporator and cooling tower is combined, it is divided into two paths, one of which enters the condenser again, and the other enters the working medium condenser for working medium heat exchange; The concentrated working fluid solution in the generator enters the solution heat exchanger to transfer heat to the dilute solution on the other side of the solution heat exchanger, and then falls into the absorber to mix with the water vapor from the evaporator to release heat to heat the circulating water return water of the heat network, and then turns into a dilute working fluid solution and sends it to the generator; The water vapor generated by the generator enters the condenser to condense and release heat to perform secondary heating on the return water of the heat network circulating water to form condensed water; the condensed water enters the evaporator to absorb the residual heat of the circulating water and evaporate, and the evaporated water vapor enters the absorber and returns to the generator; The circulating water return water of the heating network enters the absorber and condenser in turn and is heated step by step. After the heat is exchanged with the heating extraction steam in the heating network heater to the water supply temperature, the circulating water supply of the heating network is completed to complete the peak load regulation.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a combined heat and power peak-shaving system driven by waste heat from the heat network of a thermal power unit, which at least includes a low-temperature waste heat power cycle connected to a conventional thermal power unit, and forms a low-temperature waste heat power cycle by arranging a waste heat evaporator, a turbine and a working medium condenser, thereby realizing heat exchange and work in the low-temperature waste heat power cycle; forms an absorption heat pump waste heat heating cycle by arranging a generator, a solution heat exchanger, an absorber, an evaporator and a condenser, and creatively couples the absorption heat pump waste heat heating cycle and the low-temperature waste heat power cycle with conventional thermal power units and heat network heating, and utilizes the waste heat from the outlet of the heat network heater to evaporate the organic working medium, so as to drive the low-temperature The organic working fluid in the waste heat power cycle circulates to do work; the internal working fluid of the absorption heat pump waste heat heating cycle uses the drain waste heat as the driving heat source, driving the internal working fluid circulation of the absorption heat pump waste heat heating cycle to complete the extraction and utilization of the low-temperature waste heat of the circulating water. The circulating water recovers the cold-end waste heat of the conventional thermal power unit and the cold-end waste heat of the low-temperature waste heat power cycle, so that a large amount of low-grade thermal energy contained in the circulating water can be recovered and heated up for heating the circulating water of the heat network. The driving heat source for all this comes from the drain waste heat of the heat network, which realizes that the drain waste heat simultaneously drives the low-temperature waste heat power cycle to generate mechanical energy to drive the absorption heat pump waste heat heating cycle to extract the cold-end waste heat. During periods when thermal power units require deep peak regulation or top load, the absorption heat pump waste heat heating cycle driven by the heat network drainage provides a large amount of heating capacity for the thermal power units, thereby reducing the amount of steam extraction for heating. During peak regulation periods, the amount of main steam in the steam-water cycle can be reduced, thereby reducing power generation to achieve peak regulation and frequency regulation. During top load periods, the amount of steam used for power generation in the steam-water cycle can be increased, thereby increasing the unit's online power generation to achieve peak top load, and achieving flexible peak regulation of thermal power units while making full use of the waste heat from the heat network drainage. When the spot trading electricity price is low, peak regulation can be used to reduce spot losses, and when the spot trading electricity price is high, top load can be used to increase spot profits. The flexibility of unit operation regulation is greatly improved while ensuring the thermal load at the residential heating end.

[0017] A steam electric regulating valve is arranged between the heating network heater and the medium pressure cylinder. The setting of the steam electric regulating valve can control the steam extraction amount of the medium pressure cylinder according to the peak regulation demand of the thermal power unit, flexibly adjust the heat extraction steam flow rate, and ensure that the heat supply load matches the heat supply demand.

[0018] A working medium booster pump is provided between the working medium condenser and the waste heat evaporator. The provision of the working medium booster pump can ensure that the working medium forms a stable circulation between the waste heat evaporator and the working medium condenser, thereby improving the stability and flexibility of the system.

[0019] A first drain electric regulating valve is provided between the waste heat evaporator and the condenser; a second drain electric regulating valve is provided between the generator and the condenser. The first drain electric regulating valve and the second drain electric regulating valve can accurately control the flow of circulating water from the waste heat evaporator and the generator into the condenser, ensuring safe and stable operation of the entire system.

[0020] A solution pump is provided between the cold end of the solution heat exchanger and the generator; a first expansion valve is provided between the generator and the hot end of the solution heat exchanger; and a second expansion valve is provided between the condenser and the evaporator. The solution pump provides power for the dilute working fluid solution to smoothly return to the generator and maintain the stable circulation of the working fluid; the first expansion valve can adjust the pressure of the solution flowing out of the generator and entering the hot end of the solution heat exchanger. By reducing the pressure of the solution, it can be more easily evaporated and heat-absorbed, thereby improving the refrigeration or heating efficiency of the system; the second expansion valve can adjust the flow of the working fluid flowing out of the condenser and entering the evaporator, ensuring that the cooling effect in the evaporator reaches the best state.

[0021] The solution pump is coaxially arranged with the turbine. By coaxially arranging the solution pump with the turbine, the power generated by the turbine can be used for the work of the solution pump, thereby realizing the hierarchical utilization of energy and reducing the energy loss of the entire peak-shaving system to a minimum.

[0022] A first circulating water electric regulating valve is provided between the cooling tower and the working medium condenser; a second circulating water electric regulating valve is provided between the cooling tower and the evaporator; and a third second circulating water electric regulating valve is provided between the condenser and the output end of the cooling tower. The setting of the first circulating water electric regulating valve can accurately control the cooling water flow rate delivered from the cooling tower to the working medium condenser, thereby adjusting the cooling effect according to the actual needs of the condenser; the second circulating water electric regulating valve is responsible for adjusting the circulating water delivered from the evaporator to the condensing tower, and the circulation of the system is stable. The third circulating water electric regulating valve is used to adjust the water circulation between the condensing tower and the condenser, which helps to maintain the stable working state of the condenser.

[0023] A heat network circulating water pump is arranged between the heat network circulating water return output end and the absorber; a circulating water pump is arranged on the busbar after the water output ends of the evaporator and the cooling tower are combined. The arrangement of the heat network circulating water pump and the circulating water pump can effectively ensure the stability and flexibility of the heat network water circulation and circulating water heat exchange, thereby ensuring the stability and flexibility of the peak load regulation system.

[0024] The present invention also provides a peak-shaving method for a combined heat and power peak-shaving system driven by the waste heat of water drainage from the thermal power unit. The method achieves low-temperature waste heat recovery and heating driven by a single waste heat source by efficiently coupling conventional thermal power units and water supply from the thermal power unit with a low-temperature waste heat power cycle and a waste heat heating cycle of an absorption heat pump, thereby avoiding secondary waste in the energy conversion process and improving energy conversion efficiency. The waste heat of water drainage from the thermal power unit is used to drive the low-temperature waste heat power cycle, and the waste heat of circulating water is used as the low-temperature heat source of the waste heat heating cycle of the absorption heat pump, thereby achieving the recovery of the waste heat of water drainage from the thermal power unit and the steam turbine. The synchronous recovery of waste heat at the cold end realizes the cascade utilization of energy, improves energy utilization efficiency and heating capacity, greatly improves the heating capacity of the cogeneration unit, and can reduce the amount of heating steam extraction while ensuring the heat load, realize thermal and electrical decoupling, improve the unit's peak load regulation and top peak load capabilities, and increase the unit's profits in the spot trading market; this method sends the heat network drain water into the condenser after waste heat utilization to avoid high-temperature drain water destroying the vacuum, while meeting actual requirements, achieving deep energy-saving potential, improving the thermal efficiency of the entire plant cycle, and achieving multiple optimizations of high efficiency, flexibility, energy saving, and carbon reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a schematic diagram of a combined heat and power peak-shaving system driven by waste heat from a thermal power unit heat network.

[0026] Figure 2 This is a diagram of a combined heat and power peak regulation method driven by waste heat from a thermal network of a thermal power unit according to the present invention.

[0027] Among them, 1- boiler; 2- high-pressure cylinder; 3- medium-pressure cylinder; 4- low-pressure cylinder; 5- condenser; 6- condensate pump; 7- low-pressure heater group; 8- deaerator; 9- feed water pump; 10- high-pressure heater group; 11- steam electric regulating valve; 12- heat network heater; 13- second drain electric regulating valve; 14- first drain electric regulating valve; 15- waste heat evaporator; 16- turbine; 17- working fluid condenser; 18- working fluid booster pump; 19- generator; 20- first expansion valve; 21- solution heat exchanger; 22- absorber; 23- solution pump; 24- condenser; 25- second expansion valve; 26- evaporator; 27- heat network circulating water pump; 28- cooling tower; 29- circulating water pump; 30- third circulating water electric regulating valve; 31- first circulating water electric regulating valve; 32- second circulating water electric regulating valve. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0029] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0031] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply 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 on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0032] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0033] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0035] See also Figure 1 , the present invention discloses a combined heat and power peak regulation system driven by waste heat from the heat network of a thermal power unit, comprising a conventional combined heat and power steam-water cycle, i.e., a conventional thermal power unit, a low-temperature waste heat power cycle, and an absorption heat pump waste heat heating cycle; The conventional cogeneration steam-water cycle includes a boiler 1, a high-pressure cylinder 2, a medium-pressure cylinder 3, a low-pressure cylinder 4, a condenser 5, a condensate pump 6, a low-pressure heater group 7, a deaerator 8, a feed water pump 9 and a high-pressure heater group 10; the low-temperature waste heat power cycle includes a waste heat evaporator 15, a turbine 16, a working fluid condenser 17 and a working fluid booster pump 18; the absorption heat pump waste heat heating cycle includes a generator 19, a first expansion valve 20, a solution heat exchanger 21, an absorber 22, a solution pump 23, a condenser 24, a second expansion valve 25 and an evaporator 26; The high-pressure feed water of the unit absorbs the heat of flue gas in the boiler 1 and evaporates into superheated steam, which enters the high-pressure cylinder 2 to do work. The exhaust gas is reheated by the boiler 1 and enters the medium-pressure cylinder 3 to do work. A part of the exhaust steam of the medium-pressure cylinder 3 enters the low-pressure cylinder 4 to continue to do work, and the other part enters the heating network heater 12 to heat the heating network circulating water. The high-pressure cylinder, the medium-pressure cylinder 3 and the low-pressure cylinder 4 drive the generator through the shaft to generate electricity and realize external power supply; the exhaust steam of the low-pressure cylinder 4 releases heat and condenses through the condenser 5, and the waste heat at the cold end is absorbed by the circulating water. The condensate is sent to the low-pressure heater 7 through the condensate pump 6 to be heated by the extraction steam, and then enters the deaerator 8 for deoxygenation, and then sent to the high-pressure heater 10 through the feed water pump 9 for heating and then sent back to the boiler to complete the steam-water cycle; The hot network drain at the outlet of the hot network heater 12 enters the waste heat evaporator 15 to drive the low-temperature waste heat power cycle. The electric control valve 11 is used to adjust the heating steam extraction amount entering the hot network heater 12. The valve opening is adjusted according to the waste heat recovery amount of the waste heat recovery system of the user's real-time heat load to control the heating steam extraction amount. When the waste heat recovery system increases the temperature rise of the hot network circulating water by a large amount, the heating steam extraction amount can be reduced; the organic working fluid in the low-temperature waste heat power cycle is heated and evaporated by the hot network drain in the waste heat evaporator 15, and then enters the turbine 16 to do work. The turbine 16 drives the coaxial solution pump 23 to provide power for it; the organic working fluid exhaust steam discharged from the turbine 16 enters the working fluid condenser 17 to release heat and condense, and The circulating water at the outlet of the working medium condenser 17 is combined with the circulating water at the outlet of the condenser 5 to enter the circulating water mother pipe. The third circulating water electric regulating valve 30 and the first circulating water electric regulating valve 31 are used to control the distribution of the circulating water flow entering the condenser 5 and the working medium condenser 17. After the circulating water at the outlet of the working medium condenser 17 is combined with the circulating water at the outlet of the condenser 5, it is divided into two paths in the mother pipe, one of which enters the evaporator 26 of the heat pump to extract the waste heat, and the other enters the cooling tower 28 for spraying and cooling; the circulating water after the two cooling paths is combined and pressurized by the circulating water pump 29 on the mother pipe, and is respectively sent to the condenser 5 and the working medium condenser 17; the second circulation The circulating water electric regulating valve 32 is used to control the distribution of the circulating water flow entering the cooling tower 28 and the evaporator 26; the internal circulating working fluid of the absorption heat pump waste heat heating cycle is lithium bromide, and the lithium bromide solution is heated by the heat network hydrophobicity in the generator 19 to evaporate water vapor and produce a lithium bromide concentrated solution. The concentrated solution is depressurized by the expansion valve 20 and then passes through the solution heat exchanger 21 to transfer heat to the dilute solution on the other side of the solution heat exchanger 21, and then falls into the absorber 22 to mix with the water vapor from the evaporator 26 to release heat and perform primary heating on the circulating water return water of the heat network; the dilute solution in the solution heat exchanger 21 is pumped to the generator 19 through the solution pump 23, and the water vapor generated by the generator 19 enters the condenser 24 to condense The heat release is used to perform secondary heating on the return water of the heat network circulation water. The condensed water is depressurized by the second expansion valve 25 and then enters the evaporator 26 to absorb the waste heat of the circulating water and evaporate. The evaporated water vapor enters the absorber 22. The first drain electric regulating valve 13 and the second drain electric valve 14 are used to control the amount of heat network water entering the waste heat evaporator 15 and the generator 19 respectively, so as to control the power of the low-temperature waste heat power circulation driving solution pump 23 to match the driving power of the absorption heat pump waste heat heating cycle, thereby improving work efficiency. The return water of the heat network circulation water is pressurized by the heat network circulation water pump 27, and then is step-heated by the absorber 22 and the condenser 24 in turn, and then heated to the water supply temperature by the heat network heater 12 and supplied to the heat users.

[0036] When the unit is peak-shaving, the absorption heat pump waste heat heating cycle driven by the heat network drainage provides a large amount of heating capacity for the thermal power unit, thereby reducing the amount of steam extraction for heating of the unit. During the peak-shaving period, the main steam volume of the steam-water cycle can be reduced, thereby reducing the power generation to achieve peak-shaving and frequency regulation. During the top load period, the amount of steam used for power generation in the steam-water cycle can be increased, thereby increasing the unit's online power generation to achieve peak top load, and realizing flexible peak-shaving of the thermal power unit while making full use of the waste heat from the heat network drainage. When the spot trading electricity price is low, peak-shaving can reduce spot losses, and when the spot trading electricity price is high, top load can increase spot profits, greatly improving the flexibility of unit operation regulation while ensuring the thermal load at the heating end of residents.

[0037] See also Figure 2 The present invention provides a peak-shaving method for a combined heat and power peak-shaving system driven by the waste heat of water drainage from the thermal power unit, comprising: S1: When the conventional thermal power unit needs deep peak regulation or top load, the exhaust steam volume entering the heat network heater 12 of the medium pressure cylinder 3 is adjusted, so that the heat network drainage water at the outlet of the heat network heater 12 is divided into two paths, one of which enters the waste heat evaporator 15, and enters the condenser 5 for cooling after heat exchange with the working medium in the waste heat evaporator 15; the other enters the generator 19; S2: The working fluid after heat exchange in the waste heat evaporator 15 enters the turbine 16 to perform work; S3: the exhaust steam of the organic working medium after the turbine 16 has done work enters the working medium condenser 17, and exchanges heat with the circulating water in the working medium condenser 17 and releases heat to condense; S4: returning the organic working medium condensed by the working medium condenser 17 to the waste heat evaporator 15; S5: After the circulating water after heat exchange in the working medium condenser 17 is combined with the circulating water generated by the condenser 5, it is divided into two paths, one of which enters the evaporator 26 for cooling, and the other enters the cooling tower 28 for cooling; S7: After the circulating water cooled by the evaporator 26 and the cooling tower 28 is combined, it is divided into two paths, one of which enters the condenser 5 again, and the other enters the working medium condenser 17 for working medium heat exchange; S8: The concentrated working fluid solution in the generator 19 enters the solution heat exchanger 21 to transfer heat to the dilute solution on the other side of the solution heat exchanger 21, and then falls into the absorber 22 to mix with the water vapor from the evaporator 26 to release heat to perform primary heating on the return water of the heat network circulation water, and is converted into a dilute working fluid solution, which is then sent to the generator 19; S9: The water vapor generated by the generator 19 enters the condenser 24 to condense and release heat to perform secondary heating on the return water of the heat network circulation water, and enters the evaporator 26 to absorb the residual heat of the circulation water and evaporate, and the evaporated water vapor enters the absorber 22 and returns to the generator 19; S10: The circulating water return from the heating network enters the absorber 22 and the condenser 24 in turn for step-by-step heating, and then exchanges heat with the heating extraction steam in the heating network heater 12 to the water supply temperature before supplying the circulating water to the heating network to complete the peak load regulation.

[0038] In summary, the present invention provides a combined heat and power peak-shaving system and method driven by waste heat from a thermal network of a thermal power unit. The method achieves low-temperature waste heat recovery and heating driven by a single waste heat source by efficiently coupling conventional thermal power units and thermal network water supply with a low-temperature waste heat power cycle and an absorption heat pump waste heat heating cycle, thereby avoiding secondary waste in the energy conversion process and improving energy conversion efficiency. The low-temperature waste heat power cycle is driven by thermal network drainage, and the circulating water waste heat is used as the low-temperature heat source for the absorption heat pump waste heat heating cycle, thereby achieving synchronous recovery of the thermal network drainage waste heat and the steam turbine cold end waste heat, realizing energy cascade utilization, improving energy utilization efficiency and heating capacity, and greatly improving the heating capacity of the cogeneration unit. The amount of steam extraction for heating can be reduced while ensuring the thermal load, achieving thermal and electrical decoupling, and improving the peak-shaving and top peak load capabilities of the unit, thereby increasing the unit's revenue in the spot trading market, achieving deep energy-saving potential, improving the thermal efficiency of the entire plant cycle, and achieving multiple optimizations of high efficiency, flexibility, energy saving, and carbon reduction.

[0039] The above description is only a preferred embodiment of the present invention and is not intended to impose any limitation on the technical solution of the present invention. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can also be subjected to several simple modifications and substitutions, and these modifications and substitutions are also within the scope of protection covered by the claims.

Claims

1. A combined heat and power peak-shaving system driven by waste heat from thermal network drainage of thermal power units, characterized in that: It at least comprises a heat network heater (12) connected to the steam exhaust port of the medium pressure cylinder (3) of a conventional thermal power unit and an absorber (22) connected to the return water output end of the heat network circulating water; The heat network drain output end of the heat network heater (12) is connected to a waste heat evaporator (15) and a generator (19); The water output end of the waste heat evaporator (15) and the water output end of the generator (19) are both connected to the condenser (5) in a conventional thermal power unit; The working fluid output end of the waste heat evaporator (15) is connected to the turbine (16) and the working fluid condenser (17) in sequence, and the working fluid output end of the working fluid condenser (17) is connected to the working fluid input end of the waste heat evaporator (15); the water output end of the working fluid condenser (17) is divided into two paths, one of which is connected to the evaporator (26) and the other is connected to the cooling tower (28); the water output ends of the evaporator (26) and the cooling tower (28) are combined and divided into two paths, one of which is connected to the condenser (5) and the other is connected to the water input end of the working fluid condenser (17); The working medium concentrated solution output end of the generator (19) is connected to a solution heat exchanger (21), and the solution heat exchanger (21) is sequentially connected to an absorber (22), a cold end of the solution heat exchanger (21), and the generator (19); The water vapor output end of the generator (19) is connected to a condenser (24), and the condensed water output end of the condenser (24) is connected to an evaporator (26); the evaporator (26) is sequentially connected to an absorber (22), a solution heat exchanger (21), and a generator (19); The circulating water return of the absorber (22) is connected in sequence to the condenser (24), the heating network heater (12) and the heating network circulating water supply input end.

2. The combined heat and power peak-shaving system driven by waste heat from the thermal network of a thermal power unit according to claim 1 is characterized in that: A steam electric regulating valve (11) is provided between the heating network heater (12) and the medium-pressure cylinder (3).

3. The combined heat and power peak-shaving system driven by waste heat from the thermal network of a thermal power unit according to claim 1 is characterized in that: A working medium booster pump (18) is provided between the working medium condenser (17) and the waste heat evaporator (15).

4. The combined heat and power peak-shaving system driven by waste heat from the thermal network of a thermal power unit according to claim 1 is characterized in that: A first drain electric regulating valve (14) is provided between the waste heat evaporator (15) and the condenser (5).

5. The combined heat and power peak-shaving system driven by waste heat from the thermal network of a thermal power unit according to claim 1, characterized in that: A second drain electric regulating valve (13) is provided between the generator (19) and the condenser (5).

6. The combined heat and power peak-shaving system driven by waste heat from the thermal network of a thermal power unit according to claim 1, characterized in that: A solution pump (23) is provided between the cold end of the solution heat exchanger (21) and the generator (19); a first expansion valve (20) is provided between the generator (19) and the hot end of the solution heat exchanger (21); and a second expansion valve (25) is provided between the condenser (24) and the evaporator (26).

7. The combined heat and power peak-shaving system driven by waste heat from thermal network drainage of thermal power units according to claim 6, characterized in that: The solution pump (23) is coaxially arranged with the turbine (16).

8. The combined heat and power peak-shaving system driven by waste heat from the thermal network of a thermal power unit according to claim 1, characterized in that: A first circulating water electric regulating valve (31) is provided between the cooling tower (28) and the working medium condenser (17); a second circulating water electric regulating valve (32) is provided between the cooling tower (28) and the evaporator (26); and a third second circulating water electric regulating valve (30) is provided between the condenser (5) and the output end of the cooling tower (28).

9. The combined heat and power peak-shaving system driven by waste heat from thermal network drainage of thermal power units according to claim 1, characterized in that: A heat network circulating water pump (27) is provided between the heat network circulating water return output end and the absorber (22); and a circulating water pump (29) is provided on the busbar formed by merging the water output ends of the evaporator (26) and the cooling tower (28).

10. A peak-shaving method for a combined heat and power peak-shaving system driven by waste heat from a thermal power unit heat network as claimed in any one of claims 1 to 9, characterized in that: include: When a conventional thermal power unit needs deep peak regulation or top load, the exhaust steam volume of the intermediate pressure cylinder (3) entering the heat network heater (12) is adjusted, so that the heat network drainage at the outlet of the heat network heater (12) is divided into two paths, one of which enters the waste heat evaporator (15) and enters the condenser (5) for cooling after heat exchange with the working fluid in the waste heat evaporator (15); and the other enters the generator (19); The working fluid after heat exchange in the waste heat evaporator (15) enters the turbine (16) to perform work; The exhaust steam of the organic working medium after the turbine (16) has done work enters the working medium condenser (17), exchanges heat with the circulating water in the working medium condenser (17), and then releases heat and condenses; The organic working medium after heat release and condensation in the working medium condenser (17) is returned to the waste heat evaporator (15); The circulating water after heat exchange in the working medium condenser (17) is combined with the circulating water generated by the condenser (5) and then divided into two paths, one of which enters the evaporator (26) for cooling, and the other enters the cooling tower (28) for cooling; After the circulating water has been cooled by the evaporator (26) and the cooling tower (28), it is combined and divided into two paths, one of which enters the condenser (5) again, and the other enters the working medium condenser (17) for working medium heat exchange; The concentrated working fluid solution in the generator (19) enters the solution heat exchanger (21) and transfers heat to the dilute solution on the other side of the solution heat exchanger (21). The concentrated working fluid solution then falls into the absorber (22) and mixes with the water vapor from the evaporator (26) to release heat and perform primary heating on the return water of the heat network circulation water, thereby converting the concentrated working fluid solution into the dilute working fluid solution and sending the solution to the generator (19). The water vapor generated by the generator (19) enters the condenser (24) to condense and release heat to perform secondary heating on the return water of the heat network circulating water, thereby forming condensed water; the condensed water enters the evaporator (26) to absorb the waste heat of the circulating water and evaporate, and the evaporated water vapor enters the absorber (22) and returns to the generator (19); The circulating water return water of the heating network enters the absorber (22) and the condenser (24) in sequence and is heated step by step. After the return water is heated to the water supply temperature through heat exchange with the heating extraction steam in the heating network heater (12), the circulating water supply of the heating network is carried out to complete the peak load regulation.

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