Coupling heat storage thermal power plant rapid load tracking system and operation method

Abstract

The invention discloses a coupling heat storage thermal power plant rapid load tracking system and an operation method. The system comprises a coal-fired boiler, a steam extraction backpressure steam turbine unit, a pure condensing steam turbine unit, a deoxidization heat regeneration unit, a heat storage unit and a heat storage steam generator. The steam extraction backpressure steam turbine unit and the pure condensing steam turbine unit share the heat regeneration deoxidizing system and are both connected with the coal-fired boiler, and the heat storage unit stores off-peak electricity for generating low-pressure steam. In the low-carbon mode of system operation, steam generated by the heat storage steam generator is used for replacing low-pressure exhaust steam of the back extraction unit to reduce the boiler load, and in the peak mode, part of low-pressure exhaust steam of the back extraction unit is rapidly replaced by means of the rapid response characteristic of the heat storage unit, surplus main steam is fed into the pure condensing steam turbine unit to improve the generating capacity, and rapid load tracking is achieved. Carbon emission of a traditional thermal power plant can be reduced, thermoelectric decoupling of the traditional thermal power plant is achieved, and the rapid load tracking capacity of the traditional coal-fired thermal power plant is enhanced.

Description

Technical Field

[0001] The present invention belongs to the field of energy and power, and in particular relates to a fast load tracking system and an operation method of a thermal power plant coupled with heat storage. Background Art

[0002] Accelerating the construction of a new power system and improving the power grid's ability to absorb clean energy are the current trends in the power industry. In order to solve the problem of a large number of renewable energy grid-connected and its volatility and intermittency affecting the stability of power grid operation, traditional coal-fired power plants need to gradually transform from the original power supply pillar to comprehensive energy supply and power grid auxiliary power stations. However, in the actual production and life process, a large amount of thermal energy of different grades is still required, resulting in a large number of existing coal-fired thermal power plants being limited in their ability to adjust power generation loads under the premise of meeting the necessary heating demand due to the limitation of "heat-based electricity", and the peak-shaving service capacity of the power grid is reduced; at the same time, due to the thermal inertia of the heat exchange surface and the hysteresis of the pulverizing system, the load response rate of coal-fired boilers is much lower than that of steam turbines. However, when responding to power grid dispatch, it is limited by the strong coupling between coal-fired boilers and steam turbines, making it difficult for coal-fired thermal power plants to achieve rapid response dispatch. Summary of the invention

[0003] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a thermal power plant fast load tracking system and operation method coupled with heat storage, so as to provide technical support for coal-fired thermal power plants to increase energy storage, participate in grid peak regulation and grid dispatch rapid response functions.

[0004] To achieve the above purpose, the present invention adopts the following technical scheme.

[0005] A thermal power plant fast load following system coupled with heat storage, comprising a coal-fired boiler, an extraction back-pressure steam turbine unit, a pure condensing steam turbine unit, a deoxidation heat recovery unit, a heat storage unit and a heat storage steam generator; the coal-fired boiler generates main steam, and its steam outlet is connected to the extraction back-pressure steam turbine unit and the pure condensing steam turbine unit through a main steam header;

[0006] The extraction back-pressure steam turbine unit includes an extraction back-pressure steam turbine and an extraction back-pressure steam turbine generator set. The extraction back-pressure steam turbine is provided with a medium-pressure extraction to supply medium-pressure steam to medium-pressure steam heat users. The low-pressure exhaust port of the extraction back-pressure steam turbine is connected to the low-pressure steam heat user and the deoxidation and heat recovery unit to supply low-pressure steam one thereto; the pure condensing steam turbine unit is connected to the deoxidation and heat recovery unit to provide condensate thereto; the water supply inlet of the deoxidation and heat recovery unit is connected to a make-up water tank, and the water supply outlet is connected to the water supply inlet of the coal-fired boiler and the heat storage steam generator; the heat storage unit is connected in series to the heat storage medium pipeline of the heat storage steam generator, and the steam outlet of the heat storage steam generator is connected to the low-pressure steam heat user to supply low-pressure steam two thereto, and the low-pressure steam two is used to partially or completely replace the low-pressure steam one.

[0007] The present invention stores off-peak electricity through the heat storage unit, and uses the heat storage steam generator to generate low-pressure steam to replace part or all of the low-pressure steam for external heat supply, thereby reducing the coal consumption of coal-fired boilers and realizing the thermal power plant's participation in the negative peak regulation function of the power grid, the thermal and electric decoupling function, and the low-carbon operation function.

[0008] The present invention stores off-peak electricity through the heat storage unit and uses a heat storage steam generator to generate low-pressure steam 2 to replace part or all of the low-pressure steam 1, thereby reducing the steam consumption of the extraction back-pressure steam turbine generator set. The surplus steam from the coal-fired boiler is used to generate electricity in the pure condensing steam turbine unit, thereby realizing the thermal power plant's participation in the forward peak-shaving function of the power grid and the thermal-electric decoupling function.

[0009] The present invention can compensate for the slow rate of load change of coal-fired boilers through the rapid response characteristics of the heat storage unit and the heat storage steam generator, realize boiler turbine decoupling, and improve the rapid load tracking capability and operational flexibility of the thermal power plant.

[0010] In one embodiment, the extraction back-pressure steam turbine is provided with medium-pressure extraction, and an extraction port is provided between stages of corresponding pressure of the extraction back-pressure steam turbine according to the heat demand of medium-pressure steam heat users.

[0011] In one embodiment, the pure condensing steam turbine unit includes a pure condensing steam turbine and a pure condensing steam turbine generator set. The coal-fired boiler sends the main steam into the extraction back pressure steam turbine and / or the pure condensing steam turbine through the main steam distribution valve. The pure condensing steam turbine is connected to the condenser, the condenser is connected to the condensate pump, and the condensate pump is connected to the deoxidation heat recovery unit.

[0012] In one embodiment, the deaerator and heat recovery unit include a deaerator, a feed water pump, a low-pressure heater and a high-pressure heater which are connected in sequence through a feed water pipeline; the feed water inlet of the deaerator is the feed water inlet of the deaerator and heat recovery unit, which is connected to the condensate pump and the make-up water tank; the feed water outlet of the high-pressure heater is the feed water outlet of the deaerator and heat recovery unit, and hot water is sent to the feed water inlet of the coal-fired boiler and / or the feed water inlet of the heat storage steam generator through a feed water distribution valve.

[0013] In one embodiment, the heat storage unit comprises a low-temperature medium storage tank, a heat storage medium pump, a heat storage medium electric heater and a high-temperature medium storage tank, the outlet of the low-temperature medium storage tank is connected to the heat storage medium electric heater through the heat storage medium pump, the outlet of the heat storage medium electric heater is connected to the high-temperature medium storage tank, the outlet of the high-temperature medium storage tank is connected to the heat storage medium inlet of the heat storage steam generator, the heat storage medium outlet of the heat storage steam generator is connected to the inlet of the low-temperature medium storage tank, and the heat storage medium electric heater is used to use valley electricity to heat the heat storage medium.

[0014] In one embodiment, the heat storage medium used in the heat storage unit is a liquid heat storage medium or a liquid-solid phase change heat storage medium, and the operating temperature range of the heat storage medium is 150 to 550°C.

[0015] In one embodiment, the heat storage medium is nitrate molten salt, and the operating temperature range is 180-380°C.

[0016] In one embodiment, the temperature range of the medium-pressure steam is 400-500°C, preferably 480°C, and the temperature range of the low-pressure steam 1 and the low-pressure steam 2 is 250-350°C, preferably 300°C.

[0017] The operation method of the thermal power plant fast load following system coupled with heat storage of the present invention includes three operation modes: conventional operation, low-carbon operation and peak operation, which are respectively introduced as follows:

[0018] In the conventional operation, the extraction back-pressure steam turbine supplies medium-pressure steam to medium-pressure steam heat users and supplies low-pressure steam to low-pressure steam heat users. During the off-peak electricity period, the low-temperature heat storage medium from the heat storage steam generator is heated and stored in the heat storage unit;

[0019] The low-carbon operation reduces the load of the coal-fired boiler and the amount of coal used. The steam extraction back-pressure steam turbine supplies medium-pressure steam to medium-pressure steam heat users, and part of the feed water enters the heat storage steam generator. The heat storage steam generator uses the stored heat to generate low-pressure steam 2 and replaces part or all of the low-pressure steam 1, which is supplied to the low-pressure steam heat users, maintaining the heating load and achieving low-load operation of the coal-fired boiler.

[0020] During the peak operation, the extraction back-pressure steam turbine gradually reduces the low-pressure exhaust steam, and part of the feed water enters the heat storage steam generator. The heat storage steam generator uses the stored heat to generate low-pressure steam 2 and replaces part or all of the low-pressure steam 1, filling the reduction in low-pressure exhaust steam, thereby achieving a rapid decrease in the steam consumption of the extraction back-pressure steam turbine generator set. At the same time, the excess main steam of the coal-fired boiler is supplied to the pure condensing steam turbine unit for power generation. The coal-fired boiler simultaneously increases its load, thereby achieving a rapid increase in power generation while maintaining the same heat supply.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The thermal storage unit is coupled with the traditional coal-fired thermal power unit to achieve thermal and electrical decoupling of the coal-fired thermal power unit, adding two operating modes to the coal-fired thermal power unit, so that the coal-fired thermal power unit can meet the peak load regulation and energy storage requirements of the future new power system for coal-fired thermal power units.

[0023] (2) Relying on the rapid heat release characteristics of the heat storage unit, the coal-fired boiler can respond quickly to load changes. While ensuring the heating capacity of the coal-fired thermal power unit remains unchanged, it can make up for the shortcoming of the low load change rate of the coal-fired boiler and enhance the flexibility of the coal-fired unit in participating in the peak load regulation of the power grid.

[0024] (3) Through the use of heat storage units, traditional coal-fired thermal power plants can be transformed into comprehensive energy storage power stations, increasing their storage and absorption capacity for new energy electricity, achieving carbon savings and emission reductions in the operation of coal-fired thermal power plants, and improving the economic efficiency of coal-fired thermal power plants.

[0025] (4) Compared with the operating system that replaces the medium-pressure steam extraction, the low-pressure exhaust steam replacement can achieve a lower negative peak regulation depth of the thermal power plant. At the same time, due to the lower temperature and pressure levels, the cost of the heat storage steam generator is lower, reducing the overall cost of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic flow chart of the rapid load following system of a thermal power plant coupled with heat storage according to the present invention.

[0027] Among them, 1 coal-fired boiler; 2 extraction back-pressure steam turbine; 3 low-pressure steam heat user; 4 medium-pressure steam heat user; 5 deaerator; 6 feed water pump; 7 low-pressure heater; 8 high-pressure heater; 9 heat storage steam generator; 10 high-temperature medium storage tank; 11 heat storage medium electric heater; 12 low-temperature medium storage tank; 13 make-up water tank; 14 pure condensing steam turbine; 15 condenser; 16 main steam distribution valve; 17 feed water distribution valve; 18 heat storage medium pump; 19 condensate pump; 20 pure condensing steam turbine generator set; 21 extraction back-pressure steam turbine generator set. DETAILED DESCRIPTION

[0028] Specifically, the connection methods of the components of the thermal power plant fast load following system coupled with heat storage are as follows:

[0029] In order to make traditional coal-fired thermal power plants adapt to the requirements of future new power systems, it is necessary to carry out research on thermal-electric decoupling and flexibility transformation of coal-fired thermal power plants, add energy storage to traditional coal-fired thermal power plants, participate in grid peak regulation and rapid response functions, and give full play to the effect of existing coal-fired power.

[0030] Among various types of energy storage technologies, off-peak electric thermal storage has the characteristics of high technical reliability, good safety and excellent economic performance, and can achieve efficient heat storage in a wide range of temperature ranges in combination with different heat storage media. The sensible heat release process matches the steam generation process and can be organically combined with thermal power plants. At the same time, the rapid heat release characteristics of the heat storage system, especially the molten salt heat storage system, can quickly release heat and generate steam with corresponding parameters during the load change process of the thermal power plant, thereby improving the response speed of the thermal power plant, making up for the shortcomings of the slow response of coal-fired boilers to load, and thus improving the overall flexibility of the system.

[0031] To this end, the present invention provides a fast load following system for a thermal power plant coupled with heat storage, such as Figure 1 As shown, it mainly includes a coal-fired boiler 1, an extraction back-pressure steam turbine unit, a pure condensing steam turbine unit, a deoxidation heat recovery unit, a heat storage unit and a heat storage steam generator 9.

[0032] The coal-fired boiler 1 is a conventional device of a thermal power plant. The steam outlet of the coal-fired boiler 1 is connected to the extraction back-pressure steam turbine unit and the pure condensing steam turbine unit through the main steam header, and the main steam generated by the coal-fired boiler 1 is distributed to these two units.

[0033] The extraction back-pressure steam turbine unit generates electricity using the allocated main steam, and mainly includes an extraction back-pressure steam turbine 2 and an extraction back-pressure steam turbine generator set 21, and the main shaft of the extraction back-pressure steam turbine 2 is connected to the extraction back-pressure steam turbine generator set 21. The present invention sets medium-pressure extraction steam in the extraction back-pressure steam turbine 2, and the medium-pressure extraction steam is used to supply medium-pressure steam to the medium-pressure steam heat user 4; at the same time, the low-pressure exhaust steam of the extraction back-pressure steam turbine 2 supplies low-pressure steam to the low-pressure steam heat user 3 and the deoxidation heat recovery unit as needed.

[0034] The pure condensing steam turbine unit is connected to the water inlet of the deaeration and heat recovery unit to provide condensed water thereto. The water inlet of the deaeration and heat recovery unit is also connected to the water replenishment tank 13 so that water can be replenished through the water replenishment tank 13 when the condensed water is insufficient. The water outlet of the deaeration and heat recovery unit is connected to the water inlet of the coal-fired boiler 1 and the heat storage steam generator 9, which heats the condensed water and / or replenished water and then distributes it to the coal-fired boiler 1 and / or the heat storage steam generator 9.

[0035] The thermal storage steam generator 9 has a heat storage medium pipeline and a steam pipeline, which is used to generate steam by heating the hot water distributed by the deoxygenation and heat recovery unit through the heat storage medium. The generated steam is low-pressure steam and can be distributed to the low-pressure steam heat user 3 as needed. The heat storage unit is connected in series to the heat storage medium pipeline of the thermal storage steam generator 9, which is used to provide the heat storage medium with sufficient heat to the heat storage medium pipeline.

[0036] According to the above structure, the present invention stores off-peak electricity through a heat storage unit, and then utilizes the stored electricity to generate low-pressure steam through a heat storage steam generator 9 to replace part or all of the low-pressure exhaust steam for external heat supply, thereby reducing the coal consumption of the coal-fired boiler 1 and realizing the thermal power plant's participation in the negative peak regulation function of the power grid, the thermal-electric decoupling function and the low-carbon operation function.

[0037] Furthermore, this substitution can also reduce the steam consumption of the extraction back-pressure steam turbine generator set 21, so that the surplus steam of the coal-fired boiler 1 can generate electricity in the pure condensing steam turbine unit, thereby realizing the thermal power plant's participation in the grid's forward peak-shaving function and thermal-electric decoupling function.

[0038] At the same time, through the rapid response characteristics of the heat storage unit and the heat storage steam generator 9, the slow load rate problem of the coal-fired boiler 1 to change load can be compensated, the boiler turbine decoupling can be achieved, and the rapid load tracking capability and operation flexibility of the thermal power plant can be improved.

[0039] In an embodiment of the present invention, the pure condensing steam turbine unit includes a pure condensing steam turbine 14 and a pure condensing steam turbine generator set 20, and its power generation capacity can reach 50.0MW. The coal-fired boiler 1 generates main steam, which is connected to the main steam distribution valve 16 through the main steam main pipe. The outlet of the main steam distribution valve 16 is respectively connected to the steam inlet of the extraction back pressure steam turbine 2 and the steam inlet of the pure condensing steam turbine 14. The flow rate of steam entering the steam back pressure steam turbine 2 and the pure condensing steam turbine 14 is controlled by the opening degree of the main steam distribution valve 16, and the main steam is sent to the extraction back pressure steam turbine 2 and / or the pure condensing steam turbine 14. Further, a condenser 15 and a condensate pump 19 are arranged at the low-pressure exhaust port of the pure condensing steam turbine 14, the outlet of the pure condensing steam turbine 14 is connected to the inlet of the condenser 15, and the outlet of the condenser 15 is connected to the inlet of the condensate pump 19. The exhausted steam is condensed into water through the condenser 15, and the condensate pump 19 is connected to the deaeration and heat recovery unit to deliver the condensate to the deaeration and heat recovery unit.

[0040] In the embodiment of the present invention, the extraction back-pressure steam turbine 2 is provided with a medium-pressure extraction port, and the medium-pressure extraction port is connected to the medium-pressure steam heat user 4 through a pipeline to supply medium-pressure steam to the medium-pressure steam heat user 4. The low-pressure exhaust port of the extraction back-pressure steam turbine 2 is connected to the low-pressure steam heat user 3 through a pipeline to supply low-pressure steam to the low-pressure steam heat user 3. It is worth noting that the turbine unit of the present invention is not limited to the extraction back-pressure unit, and is also applicable to other types of cogeneration turbines such as back-pressure units.

[0041] In the embodiment of the present invention, the deaerator and heat recovery unit shall remove oxygen from the return water and heat the return water. It mainly includes a deaerator 5, a feed water pump 6, a low-pressure heater 7 and a high-pressure heater 8 which are connected in sequence through a feed water pipeline. Specifically, the deaerator 5 is connected to the water inlet of the feed water pump 6, the water outlet of the condensate pump 19 and the outlet of the water supply tank 13 through a pipeline; the outlet of the feed water pump 6 is connected to the water supply inlet of the low-pressure heater 7, and the water supply outlet of the low-pressure heater 7 is connected to the water supply inlet of the high-pressure heater 8. The water supply inlet of the deaerator 5 is the water supply inlet of the deaerator and heat recovery unit, and is connected to the condensate pump 19 and the water supply tank 13 at the same time to remove oxygen from the water. The heating steam inlet of the deaerator 5 is connected to the low-pressure exhaust port of the extraction back pressure steam turbine 2, and the low-pressure steam is used as the deoxygenation heat source. The feed water pump 6 is used to deliver water to the low pressure heater 7 and the high pressure heater 8 in sequence. The low pressure heater 7 and the high pressure heater 8 are used to heat the water. The steam extraction port between the turbine stages of the extraction back pressure steam turbine 2 is connected to the heating steam inlet of the high pressure heater 8 and the low pressure heater 7 through a pipeline, respectively, to provide a heat source for the high pressure heater 8 and the low pressure heater 7. The high pressure heater 8 and the low pressure heater 7 use a booster pump to drain and merge into the feed water. The feed water outlet of the high pressure heater 8 is the feed water outlet of the deaeration and heat recovery unit, which is connected to the feed water distribution valve 17. The hot water is sent to the feed water inlet of the coal-fired boiler 1 and / or the feed water inlet of the heat storage steam generator 9 through the feed water distribution valve 17 to control the feed water flow entering the heat storage steam generator 9.

[0042] In an embodiment of the present invention, the heat storage unit is used to store heat in the valley electric heating heating medium, which can use a liquid heat storage medium or a liquid-solid phase change heat storage medium. The use temperature range of the heat storage medium is 150-550°C, and it is further preferably a nitric acid molten salt, and the use temperature range is 180-380°C. The heat storage unit of this embodiment mainly includes a low-temperature medium storage tank 12, a heat storage medium pump 18, a heat storage medium electric heater 11 and a high-temperature medium storage tank 10. The steam outlet of the heat storage steam generator 9 is connected to the low-pressure steam user 3 through a pipeline, the heat storage medium inlet of the heat storage steam generator 9 is connected to the outlet of the high-temperature medium storage tank 10, and the heat storage medium outlet of the heat storage steam generator 9 is connected to the inlet of the low-temperature medium storage tank 12. The heat storage medium outlet of the low-temperature medium storage tank 12 is connected to the inlet of the heat storage medium pump 18, the outlet of the heat storage medium pump 18 is connected to the inlet of the heat storage medium electric heater 11, and the outlet of the heat storage medium electric heater 11 is connected to the inlet of the high-temperature medium storage tank 10.

[0043] The medium-pressure steam extraction of the present invention has a steam temperature range of 400-500°C, preferably 480°C, and the low-pressure steam exhaust of the present invention has a steam temperature range of 250-350°C, preferably 300°C.

[0044] The operation method of the thermal power plant fast load following system coupled with heat storage of the present invention is divided into three operation modes, namely, conventional operation mode, low-carbon operation mode and peak operation mode. Among them:

[0045] In the normal operation mode, the main steam generated by the coal-fired boiler 1 all enters the extraction back-pressure steam turbine 2, and the extraction back-pressure steam turbine 2 normally supplies medium-pressure steam to the medium-pressure steam heat user 4 and low-pressure steam to the low-pressure steam heat user 3, so as to meet the heat demand of the medium-pressure steam heat user 4 and the low-pressure steam heat user 3. At the same time, the extraction back-pressure steam turbine generator set 21 generates electric energy, and the rated parameter feed water is generated through the water supply tank 13 and the deoxidation and heat recovery unit and returned to the coal-fired boiler 1. At the same time, during the daily low electricity consumption period, the low-temperature medium from the heat storage steam generator 9 is heated and stored in the heat storage unit. For example, the heat storage medium in the low-temperature medium storage tank 12 is heated by the heat storage medium electric heater 11 and stored in the high-temperature medium storage tank 10. In this mode, the heat demand of the heat users is met, and the function of the thermal power plant participating in the negative peak regulation of the power grid is realized through the heat storage unit.

[0046] In the low-carbon operation mode, the extraction back-pressure steam turbine 2 reduces back-pressure exhaust, the coal-fired boiler 1 reduces the load, reduces the amount of coal used, and the extraction back-pressure steam turbine 2 supplies medium-pressure steam to the medium-pressure steam heat user 4. The feed water distribution valve 17 adjusts the amount of feed water entering the thermal storage steam generator 9, and the high-temperature heat storage medium stored in the high-temperature medium storage tank 10 enters the thermal storage steam generator 9. The thermal storage steam generator 9 generates low-pressure steam to supply the low-pressure steam heat user 3. The back-pressure exhaust volume reduced by the extraction back-pressure steam turbine 2 is consistent with the steam volume generated by the thermal storage steam generator 9, that is, the steam generated by the thermal storage steam generator 9 is used to replace the low-pressure exhaust of the extraction back-pressure steam turbine 2, and the heat demand of the low-pressure steam heat user 3 is met together, the heating load is maintained, and the coal-fired boiler 1 is operated at a low load. In this mode, the heat demand of heat users is met, and the coal consumption of the thermal power plant is reduced through the heat storage steam generator 9 and the heat storage unit, thereby improving the operating economy of the thermal power plant. At the same time, the amount of steam entering the extraction back-pressure steam turbine 2 is reduced, so the power generation of the generator set is reduced, realizing the thermal power plant's participation in the negative peak regulation of the power grid and the thermal and electric decoupling function of the thermal power unit.

[0047] In the peak operation mode, when the power plant receives the peak power generation dispatching instruction from the power grid, the extraction back-pressure steam turbine 2 gradually reduces the back-pressure exhaust steam and quickly reduces its low-pressure exhaust steam volume. Part of the feed water enters the heat storage steam generator 9. With the help of the rapid steam generation characteristics of the heat storage system, the heat storage steam generator 9 quickly generates low-pressure steam to supply the low-pressure steam heat user 3, converts the stored heat into low-pressure steam and fills the back-pressure exhaust steam reduction. For example, the back-pressure exhaust steam reduction of the extraction back-pressure steam turbine 2 is consistent with the steam generation of the heat storage steam generator 9, and the low-pressure steam volume supplied to the low-pressure steam heat user 3 is maintained unchanged, so as to achieve a rapid decrease in the steam consumption of the extraction back-pressure steam turbine generator set 21. At the same time, the main steam distribution valve 16 controls the main steam to transport the surplus main steam of the coal-fired boiler 1 to the pure condensing steam turbine 14 for power generation, so as to achieve rapid load tracking, and the coal-fired boiler 1 increases the load synchronously, so as to achieve a rapid increase in power generation while maintaining the heat supply unchanged. In this mode, the heat demand of heat users is met, and the characteristic of the heat storage steam generator 9 that it can quickly generate steam can be used to quickly reduce the amount of main steam entering the pure condensing steam turbine 14, making up for the shortcoming of the coal-fired boiler 2 in slow load adjustment, and strengthening the rapid load tracking capability of the thermal power plant. The pure condensing steam turbine 14 and the extraction back-pressure steam turbine 2 are used to jointly drive the generator set to increase the total power generation of the thermal power plant. The thermal decoupling of the thermal power plant is achieved by coupling the thermal power unit with the heat storage unit, adding the function of participating in the positive peak regulation of the power grid to the traditional coal-fired thermal power plant, and improving the operating flexibility of the coal-fired thermal power plant.

[0048] In combination with specific operating parameters, one of the possible embodiments of the system shown in the accompanying drawings is illustrated below:

[0049] The system is equipped with three coal-fired boilers 1, two of which are in operation at the same time and one is in standby. The rated evaporation capacity of a single coal-fired boiler is 210 t h -1 , the main steam temperature is 566℃ and the main steam pressure is 9.3MPa.

[0050] The heat storage medium used in the heat storage unit is ternary low-temperature molten salt HITEC XL [Ca(NO3)2-NaNO3-KNO3 42-15-43 by wt%], with an operating temperature range of 180-380°C and an operating pressure of 0.2MPa. The amount of molten salt used to generate the steam cycle is 4624t. In one cycle, the heat storage unit stores more than 400MWh of heat.

[0051] The power generation capacity of the pure condensing steam power generation unit ranges from 20.0 to 50.0 MW, the outlet temperature of the pure condensing steam turbine 14 is 45.8° C., and the outlet pressure is 0.7 MPa.

[0052] The system is equipped with two extraction back pressure steam turbines 2, which work simultaneously. The medium pressure extraction steam temperature of the two extraction back pressure steam turbines 2 is 480℃, the pressure is 4.8MPa, and the flow rate is 103t h -1 , low pressure exhaust temperature is 300℃, pressure is 1.0MPa, flow rate is 133t h -1 The medium-pressure steam supply and low-pressure steam supply are both 24 hours on the operating day. The power generation range of a single extraction back-pressure steam turbine 2 in the system is 10 to 17.2MW.

[0053] The maximum water inlet flow rate of the thermal storage steam generator 9 is 93~133 t h -1 , the inlet pressure is 10.2 bar and the inlet temperature is 158.1℃.

[0054] The present invention organically couples a heat storage system with a coal-fired thermal power plant, uses the heat storage system to absorb off-peak electricity from the power grid and stores it as thermal energy and replaces the low-pressure exhaust of an extraction back-pressure steam turbine unit, thereby enabling the thermal power plant to participate in the negative peak-shaving function of the power grid and the thermoelectric decoupling function, and improving the operating economy of the thermal power plant; by coupling a heat storage unit, an extraction back-pressure steam turbine unit and a pure condensing turbine unit, the overall power generation capacity of the thermal power plant is improved, and the thermal power plant can participate in the positive peak-shaving function of the power grid; based on the fast response and fast heat release and steam production characteristics of the heat storage system, the defect of slow load response of traditional coal-fired boilers is compensated, the strong connection between the decoupled boiler and the steam turbine is achieved, the coal-fired thermal power unit can quickly track the power grid load, and the operating flexibility of the thermal power unit is improved.

[0055] The present invention enables traditional thermal power plants to have the function of grid auxiliary services, reduces carbon emissions from traditional thermal power plants, improves operating economy, realizes thermal-electric decoupling of traditional thermal power plants, and enhances the rapid load tracking capability of traditional coal-fired thermal power plants.

Claims

1. A thermal power plant fast load following system coupled with heat storage, characterized in that: It comprises a coal-fired boiler (1), an extraction back-pressure steam turbine unit, a pure condensing steam turbine unit, a deoxidation heat recovery unit, a heat storage unit and a heat storage steam generator (9); the coal-fired boiler (1) generates main steam, and its steam outlet is connected to the extraction back-pressure steam turbine unit and the pure condensing steam turbine unit through a main steam main pipe; The extraction back-pressure steam turbine unit comprises an extraction back-pressure steam turbine (2) and an extraction back-pressure steam turbine generator set (21); the extraction back-pressure steam turbine (2) is provided with medium-pressure extraction to supply medium-pressure steam to a medium-pressure steam heat user (4); the low-pressure exhaust port of the extraction back-pressure steam turbine (2) is connected to a low-pressure steam heat user (3) and a deoxidation and heat recovery unit to supply low-pressure steam one to the user; the pure condensing steam turbine unit is connected to the deoxidation and heat recovery unit to supply condensate thereto; the water supply inlet of the deoxidation and heat recovery unit is connected to a water supply tank (13), and the water supply outlet is connected to the water supply inlet of the coal-fired boiler (1) and a heat storage steam generator (9); the heat storage unit is connected in series to the heat storage medium pipeline of the heat storage steam generator (9), and the steam outlet of the heat storage steam generator (9) is connected to the low-pressure steam heat user (3) to supply low-pressure steam two to the user, and the low-pressure steam two is used to partially or completely replace the low-pressure steam one.

2. The thermal power plant fast load following system coupled with heat storage according to claim 1 is characterized in that: The off-peak electricity is stored in the heat storage unit, and the heat storage steam generator (9) is used to generate low-pressure steam to replace part or all of the low-pressure steam for external heat supply, thereby reducing the coal consumption of the coal-fired boiler (1), and realizing the negative peak regulation function of the thermal power plant participating in the power grid, the thermal power decoupling function and the low-carbon operation function; The off-peak electricity is stored in the heat storage unit, and the heat storage steam generator (9) is used to generate low-pressure steam 2 to replace part or all of the low-pressure steam 1, thereby reducing the steam consumption of the extraction back-pressure steam turbine generator set (21), and the surplus steam of the coal-fired boiler (1) is used to generate electricity in the pure condensing steam turbine unit, thereby realizing the thermal power plant's participation in the forward peak regulation function of the power grid and the thermal power decoupling function; By using the rapid response characteristics of the heat storage unit and the heat storage steam generator (9), the problem of the slow rate of change of load of the coal-fired boiler (1) is compensated, the boiler and steam turbine are decoupled, and the rapid load tracking capability and operational flexibility of the thermal power plant are improved.

3. The thermal power plant fast load following system coupled with heat storage according to claim 1 is characterized in that: The extraction back-pressure steam turbine (2) is provided with a medium-pressure extraction, and an extraction port is provided at the interstage of the corresponding pressure of the extraction back-pressure steam turbine (2) according to the heat demand of the medium-pressure steam heat user (4).

4. The thermal power plant fast load following system coupled with heat storage according to claim 1 is characterized in that: The pure condensing steam turbine unit comprises a pure condensing steam turbine (14) and a pure condensing steam turbine generator set (20); the coal-fired boiler (1) delivers main steam to the extraction back pressure steam turbine (2) and / or the pure condensing steam turbine (14) through a main steam distribution valve (16); the pure condensing steam turbine (14) is connected to a condenser (15); the condenser (15) is connected to a condensate pump (19); and the condensate pump (19) is connected to a deoxidation heat recovery unit.

5. The thermal power plant fast load following system coupled with heat storage according to claim 1 is characterized in that: The deaerator and heat recovery unit comprises a deaerator (5), a water supply pump (6), a low-pressure heater (7) and a high-pressure heater (8) which are connected in sequence through a water supply pipeline; the water supply inlet of the deaerator (5) is the water supply inlet of the deaerator and heat recovery unit, which is connected to the condensate pump (19) and the water supply tank (13); the water supply outlet of the high-pressure heater (8) is the water supply outlet of the deaerator and heat recovery unit, and hot water is sent to the water supply inlet of the coal-fired boiler (1) and / or the water supply inlet of the heat storage steam generator (9) through a water supply distribution valve (17).

6. The thermal power plant fast load following system coupled with heat storage according to claim 1, characterized in that: The heat storage unit comprises a low-temperature medium storage tank (12), a heat storage medium pump (18), a heat storage medium electric heater (11) and a high-temperature medium storage tank (10); the outlet of the low-temperature medium storage tank (12) is connected to the heat storage medium electric heater (11) via the heat storage medium pump (18); the outlet of the heat storage medium electric heater (11) is connected to the high-temperature medium storage tank (10); the outlet of the high-temperature medium storage tank (10) is connected to the heat storage medium inlet of a heat storage steam generator (9); the heat storage medium outlet of the heat storage steam generator (9) is connected to the inlet of the low-temperature medium storage tank (12); and the heat storage medium electric heater (11) is used to heat the heat storage medium using valley electricity.

7. The thermal power plant fast load following system coupled with heat storage according to claim 1 is characterized in that: The heat storage medium used in the heat storage unit is a liquid heat storage medium or a liquid-solid phase change heat storage medium, and the operating temperature range of the heat storage medium is 150-550°C.

8. The thermal power plant fast load following system coupled with heat storage according to claim 1, characterized in that: The heat storage medium is nitrate molten salt, and the operating temperature range is 180-380°C.

9. The thermal power plant fast load following system coupled with heat storage according to claim 1, characterized in that: The temperature range of the medium-pressure steam is 400-500°C, preferably 480°C, and the temperature range of the low-pressure steam 1 and the low-pressure steam 2 is 250-350°C, preferably 300°C.

10. The method for operating the thermal power plant fast load following system coupled with heat storage according to claim 1 comprises three operating modes: conventional operation, low-carbon operation and peak operation, and is characterized in that: In the conventional operation, the extraction back-pressure steam turbine (2) supplies medium-pressure steam to the medium-pressure steam heat user (4), and supplies low-pressure steam to the low-pressure steam heat user (3). During the off-peak period, the low-temperature heat storage medium exiting the heat storage steam generator (9) is heated and stored in the heat storage unit; The low-carbon operation reduces the load of the coal-fired boiler (1), reduces the amount of coal used, and the extraction back-pressure steam turbine (2) supplies medium-pressure steam to the medium-pressure steam heat user (4). Part of the feed water enters the heat storage steam generator (9). The heat storage steam generator (9) uses the stored heat to generate low-pressure steam 2 and replaces part or all of the low-pressure steam 1, and supplies it to the low-pressure steam heat user (3), thereby maintaining the heating load and achieving low-load operation of the coal-fired boiler (1); During the peak operation, the extraction back-pressure steam turbine (2) gradually reduces the low-pressure exhaust steam, and part of the feed water enters the heat storage steam generator (9). The heat storage steam generator (9) uses the stored heat to generate low-pressure steam 2 and replace part or all of the low-pressure steam 1 to make up for the reduction in low-pressure exhaust steam, thereby achieving a rapid decrease in the steam consumption of the extraction back-pressure steam turbine generator set (21). At the same time, the excess main steam of the coal-fired boiler (1) is supplied to the pure condensing steam turbine unit for power generation. The coal-fired boiler (1) simultaneously increases its load, thereby achieving a rapid increase in power generation while maintaining the heat supply unchanged.

Images