Photovoltaic fused salt energy storage coupled lignite drying power generation system

Abstract

The utility model discloses a photovoltaic fused salt energy storage coupling lignite drying power generation system which comprises a photovoltaic fused salt heat storage and exchange module, a lignite drying module and a coal-fired power generation module. The photovoltaic fused salt heat storage and exchange module comprises a photovoltaic power generation assembly, a high-temperature fused salt heat storage tank, a high-temperature fused salt pump, a low-temperature fused salt heat storage tank, a low-temperature fused salt pump, a preheater, an evaporator, a fused salt superheater and a fused salt electric heater. The lignite drying module comprises a steam tubular dryer, a raw coal surge bin, a dust remover, a coal feeder, a dry coal surge bin, a dry coal conveyor, a condensate storage tank, a coal mill and a steam temperature and pressure reduction device; the coal-fired power generation module comprises a pulverized coal boiler, a steam turbine high-pressure cylinder, a steam turbine intermediate-pressure cylinder, a steam turbine low-pressure cylinder, a power generator, a condenser, a condensate pump, a low-pressure heater set, a deaerator, a water feeding pump and a high-pressure heater. The system not only can realize flexible switching of each sub-module, but also can realize large-scale lignite drying power generation, and meanwhile, has the functions of energy storage and thermal power peak regulation.

Description

Technical Field

[0001] This invention relates to the field of coal-fired power generation technology, specifically to a large-scale photovoltaic molten salt energy storage coupled lignite drying power generation system. Background Technology

[0002] Lignite has a high moisture content, is highly flammable and explosive, and is difficult to transport and store, which limits its utilization. Drying, dehydrating, and upgrading lignite can increase its energy density, reduce transportation costs, and decrease the size of downstream equipment. Molten salt energy storage technology is a novel physical energy storage technology with advantages such as high heat storage density, high efficiency, rapid regulation, high safety, long service life, and year-round peak shaving capability, making it suitable for flexible retrofitting of thermal power units and large-scale energy storage.

[0003] Existing technical document 1 (CN104179537B) discloses a lignite drying power generation system with coal water recovery and its implementation method. The lignite drying power generation system includes a boiler, steam turbine, feedwater pump, condenser, coal mill, as well as a lignite drying device, a coal water recovery device, a raw coal bunker, a low-pressure heater, a deaerator, a high-pressure heater, a condensate pump, and a steam-water mixer. The lignite drying device is connected to the coal water recovery device, raw coal bunker, low-pressure heater, deaerator, high-pressure heater, condensate pump, and steam-water mixer, and is also connected to the boiler, steam turbine, feedwater pump, condenser, and coal mill to form the lignite drying power generation system. However, the shortcoming of this existing document is that the system only simply meets the lignite drying needs of coal-fired power plants and cannot meet the frequent peak-shaving needs of current power plants. Currently, coal-fired power plants need to meet deep peak-shaving requirements to adapt to the grid connection of new energy power generation such as photovoltaic power generation. However, new energy power generation exhibits randomness and volatility, which poses certain difficulties for the stable operation of the power grid.

[0004] Existing technical document 2 (CN208418894U) discloses a molten salt energy storage and heating system for deep peak shaving and flexibility retrofitting of power plants, including a power plant boiler, a turbine intermediate pressure cylinder, a condensate tank, a low-temperature molten salt tank, and a high-temperature molten salt tank. It can store energy that cannot be connected to the grid and the heat loss due to desuperheating and depressurization in the form of high-temperature molten salt thermal energy, and release it when needed. However, the shortcomings of this existing document are that the extraction ratio of main steam and reheat steam from the boiler needs to be strictly controlled. Excessive extraction of main steam will cause the boiler reheater to overheat and be damaged. Extracting reheat steam to heat molten salt for thermal storage is limited because the steam saturation temperature corresponding to the extraction steam pressure is lower than the freezing point of molten salt. Only the sensible heat of the steam can be stored, and the latent heat of the steam cannot be utilized. The energy loss is relatively large, resulting in a small amount of heat storage and limited peak shaving depth.

[0005] Based on this, it is necessary to further improve and enhance the existing lignite drying and power plant generation technologies. The improved power generation system and its implementation methods can not only achieve effective recovery of moisture in lignite, but also ensure the safety of pulverized coal transportation. At the same time, the system can also absorb new energy sources and take into account the deep peak-shaving function of thermal power plants, effectively reducing the occurrence of curtailment of solar power. Utility Model Content

[0006] To address the shortcomings of existing technologies, this invention provides a photovoltaic molten salt energy storage coupled with lignite drying power generation system, which can effectively recover moisture from lignite and ensure the safety of pulverized coal transportation. At the same time, the system can also absorb new energy sources and perform deep peak shaving functions for thermal power plants, effectively reducing the occurrence of curtailment of solar power.

[0007] The present invention adopts the following technical solution.

[0008] This invention discloses a photovoltaic molten salt energy storage coupled lignite drying and power generation system, including a photovoltaic molten salt heat exchange module, a lignite drying module, and a coal-fired power generation module. The photovoltaic molten salt heat exchange module is equipped with a molten salt superheater, and the lignite drying module is equipped with a condensate storage tank, a coal mill, and a steam desuperheating and depressurization device. The photovoltaic molten salt heat exchange module is connected to the steam desuperheating and depressurization device in the lignite drying module through the molten salt superheater.

[0009] The coal-fired power generation module is equipped with a pulverized coal boiler, and the lignite drying module is connected to the pulverized coal boiler in the coal-fired power generation module through a condensate storage tank and a coal mill.

[0010] The photovoltaic molten salt heat storage and exchange module, the lignite drying module, and the coal-fired power generation module constitute a photovoltaic molten salt energy storage coupled lignite drying and power generation system.

[0011] Preferably, the photovoltaic molten salt heat exchange module further includes: a photovoltaic power generation module, a cryogenic molten salt storage tank, a cryogenic molten salt pump, and a molten salt electric heater;

[0012] The photovoltaic power generation module is connected to the molten salt electric heater, the high-temperature molten salt storage tank is connected to the high-temperature molten salt pump, and the outlet of the high-temperature molten salt pump is connected to the inlet of the molten salt electric heater.

[0013] Preferably, the photovoltaic molten salt storage and heat exchange module further includes: a cryogenic molten salt storage tank, a cryogenic molten salt pump, and a molten salt superheater;

[0014] The cryogenic molten salt storage tank is connected to the molten salt electric heating outlet, the cryogenic molten salt pump is connected to the cryogenic molten salt storage tank, and the cryogenic molten salt pump outlet is connected to the superheater shell-side inlet.

[0015] Preferably, the photovoltaic molten salt heat storage and exchange module further includes: a molten salt-feedwater evaporator and a molten salt-feedwater preheater;

[0016] The superheater shell-side outlet is connected to the evaporator tube-side inlet, the evaporator tube-side outlet is connected to the preheater shell-side inlet, and the preheater shell-side outlet is connected to the inlet of the cryogenic molten salt pump.

[0017] Preferably, the lignite drying module includes: a steam tube dryer, a raw coal buffer silo, a dust collector, a coal feeder, a dry coal buffer silo, a dry coal conveyor, a condensate storage tank, a coal mill, and a steam desuperheating and pressure reducing device;

[0018] The steam tube dryer includes: a first steam tube dryer and a second steam tube dryer; the raw coal buffer silo includes: a first raw coal buffer silo and a second raw coal buffer silo; and the coal feeder includes a first coal feeder and a second coal feeder.

[0019] The inlet of the first steam tube dryer is connected to the outlet of the first coal feeder, the inlet of the first coal feeder is connected to the outlet of the first raw coal buffer silo, and the dry coal outlet of the first steam tube dryer is connected to the inlet of the dry coal buffer silo.

[0020] Preferably, the inlet of the second steam tube dryer is connected to the outlet of the second coal feeder, the inlet of the second coal feeder is connected to the outlet of the second raw coal buffer silo, the dry coal outlet of the second steam tube dryer is connected to the inlet of the dry coal buffer silo, the outlet of the dry coal buffer silo is connected to the dry coal conveyor, and the dry coal conveying device is connected to the coal mill.

[0021] Preferably, the condensate storage tank includes: a first condensate storage tank and a second condensate storage tank;

[0022] The first steam tube dryer is connected to the first condensate storage tank, and the condensate is pumped to the deaerator via the first condensate pump. The second steam tube dryer is connected to the second condensate storage tank, and the condensate is pumped to the deaerator via the second condensate pump.

[0023] Preferably, the dust collector is located between the first raw coal buffer silo and the second raw coal buffer silo.

[0024] Preferably, the coal-fired power generation module includes: a pulverized coal boiler, a high-pressure cylinder of a steam turbine, a medium-pressure cylinder of a steam turbine, a low-pressure cylinder of a steam turbine, and a generator;

[0025] The pulverized coal boiler is connected to the high-pressure cylinder of the steam turbine, and the high-pressure cylinder, intermediate-pressure cylinder, and low-pressure cylinder of the steam turbine are connected in sequence. The low-pressure cylinder of the steam turbine is connected to the generator.

[0026] Preferably, the coal-fired power generation module further includes: a condenser, a condensate pump, a low-pressure heater, a deaerator, a feedwater pump, and a high-pressure heater;

[0027] The intermediate pressure cylinder of the steam turbine is connected to the deaerator, the low pressure cylinder is connected to the low pressure heater, and the exhaust steam enters the condenser and is connected to the condensate pump. The low pressure heater, deaerator, feedwater pump and high pressure heater are connected in sequence on the same horizontal line.

[0028] The beneficial effect of this utility model is that, compared with the prior art,

[0029] For large-scale wind, solar, and thermal power bases, the addition of an energy storage system significantly improves the grid's regulation capabilities, smooths the fluctuations in new energy power generation such as wind and solar, can absorb unstable new energy power generation, shift peaks and fill valleys, and the system has a simple composition that does not require much modification to the original power plant system, allowing for flexible switching.

[0030] (1) In the lignite drying water recovery module, a steam tube dryer is used to realize indirect heat exchange between steam and lignite. This not only solves the safety problems caused by direct drying, but also recovers the condensate after steam condensation, avoiding the waste of water resources. The raw coal is evenly distributed in the drying tube, resulting in good drying effect and fast drying speed. The heat of the waste gas after drying is exchanged with the condensate of the power plant, reducing heat loss and providing high efficiency, energy saving and environmental protection benefits.

[0031] (2) Compared with existing technologies, the system proposed in this application can improve boiler thermal efficiency by about 2%, reduce standard coal consumption for power generation by about 8 g / kWh, and recover about 120 t / h of water per 1000MW unit. The photovoltaic molten salt energy storage system can significantly absorb renewable energy generation. Calculations show that a 135MW unit is equivalent to saving 260,600 tons of standard coal and reducing carbon emissions by 649,600 tons, demonstrating significant social benefits. Furthermore, this system helps reduce the curtailment rate of solar power and has a positive impact on promoting the development of new energy sources.

[0032] (3) Coupling the photovoltaic molten salt energy storage module with the lignite drying power generation module can solve the load response problem caused by frequent peak shaving of the unit. When the unit is reducing the load, the energy storage module is turned on. When the unit is increasing the peak, the heat energy is released to realize the unit's rapid load increase. When the unit has a stable heating load, the energy storage module can be used to supply heat to the outside during the deep peak shaving stage, ensuring the stable output of the heat load and realizing thermoelectric decoupling. The system is simple, highly operable, and can be flexibly switched. Attached Figure Description

[0033] Figure 1 This is a system diagram of this application;

[0034] In the diagram: 1. Boiler; 2. High-pressure cylinder of steam turbine; 3. Intermediate-pressure cylinder of steam turbine; 4. Low-pressure cylinder of steam turbine; 5. Generator; 6. Condenser; 7. Condensate pump; 8. Low-pressure heater; 9. Deaerator; 10. Feedwater pump; 11. High-pressure heater; 12.1. First raw coal bunker; 12.2. Second raw coal bunker; 13.1. First coal feeder; 13.2. Second coal feeder; 14.1. First steam tube dryer; 14.2. Second steam tube dryer; 15. Dry coal buffer silo; 16. Dry coal conveyor; 17. Coal mill; 18.1. First condenser. 18.1 Liquid storage tank; 19.2 Second condensate storage tank; 19.1 First condensate pump; 19.2 Second condensate pump; 20 Waste gas / water heat exchanger; 21 Photovoltaic power generation module; 22 Molten salt electric heater; 23 High-temperature molten salt storage tank; 24 Low-temperature molten salt storage tank; 25 High-temperature molten salt pump; 26 Low-temperature molten salt pump; 27 Superheater; 28 Evaporator; 29 Preheater; 30 Desuperheater and pressure reducer; 31.1 First three-way valve; 31.2 Second three-way valve; 31.3 Water supply three-way valve; 31.4 Main water supply three-way valve; 32 Dust collector. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this utility model, other embodiments obtained by those skilled in the art without creative effort are all within the protection scope of this utility model.

[0036] Embodiment 1 of this utility model provides a large-scale photovoltaic molten salt energy storage coupled lignite drying power generation system, including a photovoltaic molten salt energy storage heat exchange module, a lignite drying module, and a coal-fired power generation module.

[0037] The photovoltaic molten salt heat exchange module includes: a photovoltaic power generation module 21, a high-temperature molten salt storage tank 23, a high-temperature molten salt pump 25, a low-temperature molten salt storage tank 24, a low-temperature molten salt pump 26, a molten salt-feedwater preheater 29, a molten salt-feedwater evaporator 28, a molten salt superheater 27, and a molten salt electric heater 22.

[0038] The photovoltaic power generation module 21 is connected to the molten salt electric heater 22. The low-temperature molten salt storage tank 24 is connected to the low-temperature molten salt pump 26, and the outlet of the low-temperature molten salt pump 26 is connected to the inlet of the molten salt electric heater 22. The high-temperature molten salt storage tank 23 is connected to the outlet of the molten salt electric heater 22. The high-temperature molten salt pump 25 is connected to the high-temperature molten salt storage tank 23, and the outlet of the high-temperature molten salt pump 25 is connected to the shell-side inlet of the superheater 27. The shell-side outlet of the superheater 27 is connected to the tube-side inlet of the evaporator 28, and the tube-side outlet of the evaporator 28 is connected to the shell-side inlet of the preheater 29. The preheater 29 shell-side outlet is connected to the inlet of the low-temperature molten salt storage tank 24. Feedwater enters the preheater 29 tube-side inlet through the first three-way valve 31.1. The preheater 29 tube-side outlet is connected to the evaporator 28 shell-side inlet. The evaporator 28 shell-side outlet is connected to the superheater 27 tube-side inlet. The superheater 27 tube-side outlet is split into two by the second three-way valve 31.2. One path enters the water spray desuperheating and pressure reducing device 30, and the other path enters the turbine high-pressure cylinder 2. Thus, the molten salt completes one thermodynamic cycle.

[0039] The lignite drying module includes: a steam tube dryer, a raw coal bunker, a dust collector 32, a coal feeder, a dry coal conveyor 16, a condensate storage tank, a coal mill 17, and a steam desuperheating and pressure reducing device 30.

[0040] Low-pressure superheated steam from the water spray desuperheating and pressure reducing device 30 is divided into two paths via the first three-way valve 31.1. One path enters the first steam tube dryer 14.1, with its inlet connected to the outlet of the first coal feeder 13.1, its inlet connected to the outlet of the first raw coal buffer silo 12.1, and its dry coal outlet connected to the inlet of the dry coal buffer silo 15. The other path enters the second steam tube dryer 14.2, with its inlet connected to the outlet of the second coal feeder 13.2. The inlet is connected to the outlet of the second raw coal buffer silo 12.2. The dry coal outlet of the second steam tube dryer 14.2 is connected to the inlet of the dry coal buffer silo 15. The outlet of the dry coal buffer silo 15 is connected to the dry coal conveyor 16. Then it enters the coal mill 17. After being ground by the coal mill 17, the dry coal enters the boiler 1 for combustion. The condensate from the first steam tube dryer 14.1 is discharged to the first condensate storage tank 18.1 and pumped to the deaerator 9 by the first condensate pump 19.1. Similarly, the condensate from the second steam tube dryer 14.2 is discharged to the second condensate storage tank 18.2 and pumped to the deaerator 9 by the second condensate pump 19.2.

[0041] Dust collector 32 filters and removes dust from the humid gas generated by the steam tube dryer. The filtered dust enters the dry coal buffer silo 15 for storage. The filtered exhaust gas enters the exhaust gas / water heat exchanger 20 to heat the condensate and recover the heat from the exhaust gas. The heated hot water is circulated to the deaerator inlet and merges with the condensate heated by the low-pressure heater to the deaerator 9.

[0042] The coal-fired power generation module includes a pulverized coal boiler 1, a high-pressure cylinder of a steam turbine 2, a medium-pressure cylinder of a steam turbine 3, a low-pressure cylinder of a steam turbine 4, a generator 5, a condenser 6, a condensate pump 7, a low-pressure heater group 8, a deaerator 9, a feedwater pump 10, and a high-pressure heater 11.

[0043] Steam generated from the combustion of feedwater in pulverized coal boiler 1 first enters the high-pressure cylinder 2 of the turbine. Part of the extracted steam enters the high-pressure heater 11. The exhaust steam from the high-pressure cylinder 2 is connected to the reheater of boiler 1. The reheated steam enters the intermediate-pressure cylinder 3 of the turbine. Part of the exhaust steam from the intermediate-pressure cylinder 3 heats the deaerator 9, and the rest enters the low-pressure cylinder 4. Part of the steam from the low-pressure cylinder 4 is extracted and enters the low-pressure heater 8. The exhaust steam enters the condenser 6, condenses, and then enters the condensate pump 7. Through the feedwater three-way valve 31.3, it enters the low-pressure heater 8 and the deaerator 9 in sequence. It is then sent to the high-pressure heater 11 by the feedwater pump 10. The feedwater enters the main feedwater three-way valve 31.4 and finally enters the boiler 1 to absorb heat.

[0044] Embodiment 2 of the present invention provides a working process of a large-scale photovoltaic molten salt energy storage coupled lignite drying power generation system.

[0045] The lignite drying and water recovery process is as follows:

[0046] Step A1: Two steam tube dryers are connected to two coal feeders respectively. Lignite with a particle size of ≤20mm and a moisture content of 35-50% is fed into the coal feeder after entering the raw coal buffer bin and then transported into the drying tube of the steam tube dryer.

[0047] It is worth noting that the parameters of the lignite drying module are crucial for the stable operation of the entire drying system. These parameters include steam flow rate, pressure, and temperature; dryer bearing lubricating oil temperature and pressure; raw coal quantity; dryer speed and main motor current; fan speed, nitrogen flow rate and pressure; dust collector oxygen content; carbon monoxide content; and dew point temperature.

[0048] When the steam tube dryer reaches the predetermined preheating time, start the coal feeder to feed coal evenly. Control the steam flow rate and temperature to match the dryer speed and coal feed rate. Observe the current fluctuation of the dryer's main motor. The current fluctuation value needs to be controlled within 8A under no-load conditions and within 15A during even feeding. At the same time as feeding the dryer, start the induced draft fan. The dust collector is equipped with a temperature and humidity transmitter, a gas content analyzer, and an online dew point temperature monitor to monitor the oxygen content, carbon monoxide content, and dew point temperature in the dust collector. When the oxygen content and carbon monoxide content in the dust collector exceed the system set value, activate the inert gas protection device and inject nitrogen into the dust collector to gradually reduce the oxygen content and carbon monoxide content to the safe set value. The oxygen content is generally controlled below 12% and the carbon monoxide content is controlled below 12ppm. The dew point temperature of the dust collector is generally controlled between 70 and 80℃. When the dew point temperature is too high, appropriately increase the dust collector's exhaust volume to ensure the stable operation of the entire drying module.

[0049] In step A2, the steam generated by the photovoltaic molten salt heat exchange module is cooled and depressurized by water spraying to reach the inlet steam state parameters of the steam tube dryer (pressure of 0.4-0.65MPa and temperature of 150-170℃). It enters the dryer through the main steam pipe and indirectly exchanges heat with the lignite in the drying tube. The dry coal after heat exchange enters the dry coal buffer silo through the dryer outlet for storage.

[0050] In a preferred but non-limiting embodiment of the present invention, the volume of the dry coal buffer bin should match the amount of dry coal required for the coal mill to maintain stable output for 4 hours.

[0051] In step A3, the humid gas (waste gas and coal dust evaporated from the raw coal) enters the dust collector under the action of the fan. After dust removal and filtration, the coal dust enters the dry coal buffer bin, and the water vapor enters the waste gas / water heat exchanger to recover water and heat.

[0052] In step A4, the superheated steam is condensed after heat exchange and enters the condensate recovery system. After being recovered by the condensate recovery device, it is pumped to the turbine regenerative system by the condensate pump.

[0053] The lignite drying and power generation process is as follows:

[0054] In step B1, the lignite dried by the drying module is sent from the dry coal buffer silo to the coal mill via the dry coal conveying device for grinding. After reaching a certain fineness, it is sent into the boiler furnace for combustion to generate high-temperature flue gas and release a large amount of heat.

[0055] Step B2: After being heated step by step by the regenerative system, the boiler feedwater first enters the boiler economizer to absorb the heat of the flue gas and is further preheated to the saturated water state. Then, the saturated water flows through the downcomer into the water-cooled wall to absorb heat and evaporate. It then precipitates saturated steam through the steam drum. The saturated steam is further heated to the superheated steam state by the boiler roof superheater.

[0056] Step B3: The steam is sent to the high-pressure cylinder of the turbine through the main steam pipeline of the boiler to do work. After expansion, the steam pressure and temperature decrease. It enters the boiler reheater through the reheat cold section pipeline to further absorb heat to a high temperature state. It enters the intermediate-pressure cylinder of the turbine through the reheat hot section pipeline to do work. The steam discharged from the intermediate-pressure cylinder enters the low-pressure cylinder of the turbine to continue to expand and do work.

[0057] In step B4, the steam turbine drives the generator to output electrical energy. The exhaust steam from the low-pressure cylinder of the steam turbine is condensed into water by the condenser and then pumped into the regenerative system to absorb heat step by step until it reaches the feedwater temperature.

[0058] The photovoltaic molten salt energy storage process for peak shaving and renewable energy absorption is as follows:

[0059] Step C1: When photovoltaic power generation is in excess, fluctuates greatly, or thermal power plants need to reduce load, turn on the molten salt electric heater to heat the low-temperature molten salt to a high-temperature state and store it in a high-temperature storage tank.

[0060] Step C2: When the unit needs to increase load, the high-temperature molten salt pump is turned on to extract the high-temperature molten salt into the steam generator, which heats the feedwater to generate superheated steam. Part of the steam is sent to the lignite drying system as a source of drying steam through the water spray desuperheater and pressure reducer, while the other part of the steam enters the high-pressure cylinder of the steam turbine to increase the steam intake of the steam turbine. This increases the unit's power generation and enables peak grid dispatch, achieving the purpose of deep peak regulation of the unit.

[0061] It is worth noting that when the unit has a stable heating load and deep peak shaving, due to the limitation of thermoelectric coupling, the use of energy storage modules can ensure a stable heat load supply for the unit under low load, which significantly improves the load regulation stability of the unit.

[0062] When photovoltaic power generation is excessive or unstable, the molten salt thermal energy storage system is activated. The photovoltaic power generated is stored in molten salt through a molten salt electric heater. High-temperature and high-pressure steam is generated through a molten salt feedwater heat exchanger. Part of the steam passes through a water spray desuperheating device and enters the lignite drying system, while the remaining steam enters the turbine to do work, increasing the unit's power generation load and achieving large-scale power generation while reducing curtailment. When photovoltaic power generation is stably connected to the grid, the last-stage extraction steam of the unit enters the lignite drying system through desuperheating and pressure reduction, realizing the recycling of drying steam. In addition, during grid dispatch, the excess electricity generated by the unit can still be stored in molten salt, enabling flexible adjustment of coal-fired power units.

[0063] The beneficial effect of this utility model is that, compared with the prior art,

[0064] For large-scale wind, solar, and thermal power bases, the addition of an energy storage system significantly improves the grid's regulation capabilities, smooths the fluctuations in new energy power generation such as wind and solar, can absorb unstable new energy power generation, shift peaks and fill valleys, and the system has a simple composition that does not require much modification to the original power plant system, allowing for flexible switching.

[0065] (1) In the lignite drying water recovery module, a steam tube dryer is used to realize indirect heat exchange between steam and lignite. This not only solves the safety problems caused by direct drying, but also recovers the condensate after steam condensation, avoiding the waste of water resources. The raw coal is evenly distributed in the drying tube, resulting in good drying effect and fast drying speed. The heat of the waste gas after drying is exchanged with the condensate of the power plant, reducing heat loss and providing high efficiency, energy saving and environmental protection benefits.

[0066] (2) Compared with existing technologies, the system using this patent application can increase boiler thermal efficiency by about 2%, reduce standard coal consumption for power generation by about 8g / kWh, and recover approximately 120t / h of water per 1000MW unit. The photovoltaic molten salt energy storage system can significantly absorb renewable energy generation. Calculations show that a 135MW unit is equivalent to saving 260,600 tons of standard coal and reducing carbon emissions by 649,600 tons, demonstrating significant social benefits. Furthermore, this system helps reduce the curtailment rate of solar power, which is of positive significance for promoting the development of new energy sources.

[0067] (3) Coupling the photovoltaic molten salt energy storage module with the lignite drying power generation module can solve the load response problem caused by frequent peak shaving of the unit. When the unit is reducing the load, the energy storage module is turned on. When the unit is increasing the peak, the heat energy is released to realize the unit's rapid load increase. When the unit has a stable heating load, the energy storage module can be used to supply heat to the outside during the deep peak shaving stage, ensuring the stable output of the heat load and realizing thermoelectric decoupling. The system is simple, highly operable, and can be flexibly switched.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of this utility model and not to limit it. Although the utility model has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of this utility model. Any modifications or equivalent substitutions that do not depart from the spirit and scope of this utility model should be covered within the protection scope of the claims of this utility model.

Claims

1. A photovoltaic molten salt energy storage coupled lignite drying and power generation system, comprising a photovoltaic molten salt energy storage heat exchange module, a lignite drying module, and a coal-fired power generation module, characterized in that: The photovoltaic molten salt heat exchange module is equipped with a superheater (27), and the lignite drying module is equipped with a condensate storage tank, a coal mill (17) and a steam desuperheating and depressurization device (30). The photovoltaic molten salt heat exchange module is connected to the steam desuperheating and depressurization device (30) in the lignite drying module through the superheater (27). The coal-fired power generation module is equipped with a pulverized coal boiler (1), and the lignite drying module is connected to the pulverized coal boiler (1) in the coal-fired power generation module through a condensate storage tank and a coal mill (17). The photovoltaic molten salt heat storage and exchange module, the lignite drying module, and the coal-fired power generation module constitute a photovoltaic molten salt energy storage coupled lignite drying and power generation system.

2. The photovoltaic molten salt energy storage coupled lignite drying power generation system according to claim 1, characterized in that: The photovoltaic molten salt heat exchange module also includes: a photovoltaic power generation module (21), a high-temperature molten salt storage tank (23), a high-temperature molten salt pump (25), and a molten salt electric heater (22); Among them, the photovoltaic power generation module (21) is connected to the molten salt electric heater (22), the high temperature molten salt storage tank (23) is connected to the high temperature molten salt pump (25), and the outlet of the high temperature molten salt pump (25) is connected to the inlet of the molten salt electric heater (22).

3. The photovoltaic molten salt energy storage coupled lignite drying power generation system according to claim 2, characterized in that: The photovoltaic molten salt heat exchange module also includes: a low-temperature molten salt storage tank (24), a low-temperature molten salt pump (26), and a superheater (27); Among them, the low-temperature molten salt storage tank (24) is connected to the outlet of the molten salt electric heater (22), the low-temperature molten salt pump (26) is connected to the low-temperature molten salt storage tank (24), and the outlet of the low-temperature molten salt pump (26) is connected to the shell-side inlet of the superheater (27).

4. A photovoltaic molten salt energy storage coupled lignite drying power generation system according to claim 2, characterized in that: The photovoltaic molten salt heat storage module also includes: a molten salt-feedwater evaporator (28) and a molten salt-feedwater preheater (29); The superheater (27) shell-side outlet is connected to the evaporator (28) tube-side inlet, the evaporator (28) tube-side outlet is connected to the preheater (29) shell-side inlet, and the preheater (29) shell-side outlet is connected to the inlet of the low-temperature molten salt pump (26).

5. A photovoltaic molten salt energy storage coupled lignite drying power generation system according to claim 1, characterized in that: The lignite drying module includes: a steam tube dryer, a raw coal buffer silo, a dust collector (32), a coal feeder, a dry coal buffer silo (15), a dry coal conveyor (16), a condensate storage tank, a coal mill (17), and a steam desuperheating and pressure reducing device (30). The steam tube dryer includes: a first steam tube dryer (14.1) and a second steam tube dryer (14.2); the raw coal buffer silo includes: a first raw coal buffer silo (12.1) and a second raw coal buffer silo (12.2); and the coal feeder includes a first coal feeder (13.1) and a second coal feeder (13.2). The inlet of the first steam tube dryer (14.1) is connected to the outlet of the first coal feeder (13.1), the inlet of the first coal feeder (13.1) is connected to the outlet of the first raw coal buffer silo (12.1), and the dry coal outlet of the first steam tube dryer (14.1) is connected to the inlet of the dry coal buffer silo (15).

6. A photovoltaic molten salt energy storage coupled lignite drying power generation system according to claim 5, characterized in that: The inlet of the second steam tube dryer (14.2) is connected to the outlet of the second coal feeder (13.2), the inlet of the second coal feeder (13.2) is connected to the outlet of the second raw coal buffer silo (12.2), the dry coal outlet of the second steam tube dryer (14.2) is connected to the inlet of the dry coal buffer silo (15), the outlet of the dry coal buffer silo (15) is connected to the dry coal conveyor (16), and the dry coal conveyor (16) is connected to the coal mill (17).

7. A photovoltaic molten salt energy storage coupled lignite drying power generation system according to claim 5, characterized in that: The condensate storage tank includes: a first condensate storage tank (18.1) and a second condensate storage tank (18.2); The first steam tube dryer (14.1) is connected to the first condensate storage tank (18.1), and the condensate is pumped to the deaerator (9) via the first condensate pump (19.1). The second steam tube dryer (14.2) is connected to the second condensate storage tank (18.2), and the condensate is pumped to the deaerator (9) via the second condensate pump (19.2).

8. A photovoltaic molten salt energy storage coupled lignite drying power generation system according to claim 5, characterized in that: The dust collector (32) is located between the first raw coal buffer silo (12.1) and the second raw coal buffer silo (12.2).

9. A photovoltaic molten salt energy storage coupled lignite drying power generation system according to claim 1, characterized in that: The coal-fired power generation module includes: a pulverized coal boiler (1), a high-pressure cylinder of a steam turbine (2), a medium-pressure cylinder of a steam turbine (3), a low-pressure cylinder of a steam turbine (4), and a generator (5); Among them, the pulverized coal boiler (1) is connected to the high-pressure cylinder (2) of the steam turbine, the high-pressure cylinder (2), the intermediate-pressure cylinder (3) and the low-pressure cylinder (4) of the steam turbine are connected in sequence, and the low-pressure cylinder (4) of the steam turbine is connected to the generator (5).

10. A photovoltaic molten salt energy storage coupled lignite drying power generation system according to claim 9, characterized in that: The coal-fired power generation module also includes: a condenser (6), a condensate pump (7), a low-pressure heater (8), a deaerator (9), a feedwater pump (10), and a high-pressure heater (11); The intermediate pressure cylinder (3) of the steam turbine is connected to the deaerator (9), the low pressure cylinder (4) of the steam turbine is connected to the low pressure heater (8), the exhaust steam enters the condenser (6) and is connected to the condensate pump (7), and the low pressure heater (8), deaerator (9), feed water pump (10) and high pressure heater (11) are connected in sequence on the same horizontal line.

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