Fused salt storage and release heat coupling thermal power generation system and use method thereof

Abstract

The invention relates to the technical field of thermal power generation, and discloses a fused salt storage and release heat coupling thermal power generation system and a use method thereof. The fused salt heat storage and release coupling thermal power generation system comprises a thermal power generation subsystem and a fused salt heat storage and release subsystem used for extracting a working medium in the thermal power generation subsystem for heat exchange so as to achieve heat storage or heat release. The component proportion of a heat storage material in the fused salt heat release subsystem is adjusted along with the change of the working condition, so that the melting point of the heat storage material under the heat storage working condition is smaller than that under the heat release working condition, and the working temperature range under the heat release working condition is larger than that under the heat storage working condition; therefore, the temperature needed by the molten salt heat release subsystem for heating the heat storage material under the heat storage working condition is lower, the heat release efficiency and quality are higher under the heat release working condition, the heat requirements of the heat storage working condition and the heat release working condition are better matched, the overall operation flexibility of the system is improved, and the operation cost of the system is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal power generation, and particularly relates to a molten salt heat storage and release coupled thermal power generation system and a method for using the same. Background Art

[0002] When new energy (such as wind energy, solar energy, and light energy) power generation is restricted by weather and climate conditions, in order to balance the instability after integrating these energies into the power grid, traditional thermal power generating units need to frequently adjust the power output to adapt to load changes, which puts higher requirements on the operation flexibility and energy utilization efficiency of the units. On the one hand, the frequent start-stop or large-scale power adjustment of thermal power generating units will cause damage to the equipment. For example, the boilers in thermal power generating units may suffer thermal stress damage due to rapid temperature changes, which may further lead to pipeline rupture; the turbine blades may develop cracks due to the continuously changing pressure; these problems will not only affect the stability of the power grid, increase the risk of power grid frequency and voltage fluctuations, but also shorten the service life of thermal power generating unit equipment; on the other hand, during the low power demand period, the inefficient operation of the units will result in energy waste and reduce the overall energy utilization efficiency of thermal power generating units.

[0003] As an efficient energy storage means, molten salt heat storage / release technology has had certain development in the fields of solar thermal utilization and the like by virtue of its long-time heat storage capacity, high heat storage density, and fast response regulation characteristics. However, when applying molten salt heat storage / release technology to thermal power units, although the design of existing molten salt heat storage and release coupled thermal power generation systems can recover part of the heat of thermal power generating units and improve the overall operation flexibility and energy utilization efficiency of the system to a certain extent, due to the mismatch between the heat requirements during the heat storage condition and the heat release condition, the operation flexibility of existing molten salt heat storage and release coupled thermal power generation systems is not sufficient to simultaneously meet the requirements of low heating cost and high heat release efficiency, resulting in a relatively high system operation cost. Summary of the Invention

[0004] The present invention provides a molten salt heat storage and release coupled thermal power generation system and a method for using the same, which solves the technical problem that the insufficient operation flexibility of the existing molten salt heat storage and release coupled thermal power generation system leads to a relatively high system operation cost.

[0005] In the first aspect of the present invention, a molten salt heat storage and release coupled thermal power generation system is provided, including: a thermal power generation subsystem and a molten salt heat storage and release subsystem;

[0006] The molten salt heat release subsystem is used to extract part of the working medium from the thermal power generation subsystem to exchange heat with the heat storage material, and its working state includes a heat storage condition or a heat release condition;

[0007] When the molten salt heat release subsystem enters the heat storage working condition, the first component ratio of the heat storage material in the molten salt heat release subsystem is the first preset ratio;

[0008] When the molten salt heat release subsystem enters the heat release working condition, the second component ratio of the heat storage material in the molten salt heat release subsystem is the second preset ratio;

[0009] The melting point of the heat storage material in the molten salt heat release subsystem when the first component ratio is the first preset ratio is less than the melting point of the heat storage material in the molten salt heat release subsystem when the second component ratio is the second preset ratio, and the working temperature range of the heat storage material in the molten salt heat release subsystem when the second component ratio is the second preset ratio is greater than the working temperature range of the heat storage material in the molten salt heat release subsystem when the first component ratio is the first preset ratio.

[0010] Optionally, the first component ratio is the mass ratio of sodium nitrate, potassium nitrate and sodium nitrite;

[0011] The first preset ratio is 7:53:40.

[0012] Optionally, the second component ratio is the mass ratio of sodium nitrate and potassium nitrate;

[0013] The second preset ratio is 3:2.

[0014] Optionally, the thermodynamic cycle form of the thermal power generation subsystem is a Rankine cycle.

[0015] Optionally, the molten salt heat release subsystem is specifically configured to extract part of the steam from the main steam pipeline and / or the reheater steam pipeline of the thermal power generation subsystem during the heat storage working condition, exchange heat with the heat storage material to reduce the temperature, and then transport it back to the thermal power generation subsystem.

[0016] Optionally, the flow rate of the high-temperature steam extracted by the molten salt heat release subsystem from the main steam pipeline of the thermal power generation subsystem during the heat storage working condition is less than or equal to 20% of the flow rate of the main steam pipeline;

[0017] The flow rate of the high-temperature steam extracted by the molten salt heat release subsystem from the reheater steam pipeline of the thermal power generation subsystem during the heat storage working condition is less than or equal to 30% of the flow rate of the reheater steam pipeline.

[0018] Optionally, the thermodynamic cycle form of the thermal power generation subsystem is a supercritical carbon dioxide Brayton cycle.

[0019] The second aspect of the present invention provides a method for using a molten salt heat storage and release coupled thermal power generation system, including:

[0020] Before the molten salt heat release subsystem of the molten salt energy storage and release coupled thermal power generation system enters the heat storage condition for the first time, add a first molten salt to the molten salt heat release subsystem as the heat storage material; the first component ratio of the first molten salt is a first preset ratio;

[0021] Before the molten salt heat release subsystem enters the heat release condition, adjust the second component ratio of the heat storage material in the molten salt heat release subsystem to a second preset ratio;

[0022] Before the molten salt heat release subsystem enters the heat storage condition for the nth time, adjust the first component ratio of the heat storage material in the molten salt heat release subsystem to the first preset ratio; n>1;

[0023] The melting point of the heat storage material in the molten salt heat release subsystem when the first component ratio is the first preset ratio is lower than the melting point of the heat storage material in the molten salt heat release subsystem when the second component ratio is the second preset ratio, and the working temperature range of the heat storage material in the molten salt heat release subsystem when the second component ratio is the second preset ratio is greater than the working temperature range of the heat storage material in the molten salt heat release subsystem when the first component ratio is the first preset ratio.

[0024] Optionally, the first molten salt is Hitec molten salt;

[0025] The first component ratio is the mass ratio of sodium nitrate, potassium nitrate and sodium nitrite;

[0026] The first preset ratio is 7:53:40.

[0027] Optionally, the second component ratio is the mass ratio of sodium nitrate and potassium nitrate;

[0028] The second preset ratio is 3:2.

[0029] It can be seen from the above technical solutions that the present invention has the following advantages:

[0030] The present invention provides a molten salt heat storage and release coupled thermal power generation system and its usage method. The molten salt heat storage and release coupled thermal power generation system includes a thermal power generation subsystem and a molten salt heat storage and release subsystem for extracting the working medium in the thermal power generation subsystem for heat exchange to achieve heat storage or heat release. In the heat storage condition of the molten salt heat release subsystem, the first component ratio of the heat storage material in the molten salt heat release subsystem is the first preset ratio, and in the heat release condition, the second component ratio of the heat storage material in the molten salt heat release subsystem is the second preset ratio; the melting point of the heat storage material when the first component ratio is the first preset ratio is lower than the melting point when the second component ratio is the second preset ratio, so that the molten salt heat release subsystem requires a lower temperature to heat the heat storage material in the heat storage condition; the working temperature range of the heat storage material when the second component ratio is the second preset ratio is greater than the working temperature range when the first component ratio is the first preset ratio, so that the efficiency and quality of heat release are higher in the heat release condition; the adjustment of the component ratio of the heat storage material in the molten salt heat release subsystem under different conditions enables the system to better match the heat requirements of the heat storage condition and the heat release condition, improves the overall operation flexibility of the system, and reduces the system operation cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0032] Figure 1 FIG. is a schematic diagram of the heat storage process of a molten salt heat storage and release coupled thermal power generation system provided by an embodiment of the present invention, wherein the thermal cycle form of the thermal power generation subsystem is a Rankine cycle;

[0033] Figure 2 FIG. is a schematic diagram of the heat release process of a molten salt heat storage and release coupled thermal power generation system provided by an embodiment of the present invention, wherein the thermal cycle form of the thermal power generation subsystem is a Rankine cycle;

[0034] Figure 3 FIG. is a schematic diagram of the heat release process of a molten salt heat storage and release coupled thermal power generation system provided by an embodiment of the present invention, wherein the thermal cycle form of the thermal power generation subsystem is a Rankine cycle;

[0035] Figure 4 FIG. is a schematic diagram of the heat release process of a molten salt heat storage and release coupled thermal power generation system provided by an embodiment of the present invention, wherein the thermal cycle form of the thermal power generation subsystem is a Rankine cycle;

[0036] Figure 5Schematic diagram of the heat release process of a molten salt energy storage and release coupled thermal power generation system provided by an embodiment of the present invention, wherein the thermal cycle form of the thermal power generation subsystem is a Rankine cycle;

[0037] Figure 6 Schematic diagram of the heat storage process of a molten salt energy storage and release coupled thermal power generation system provided by an embodiment of the present invention, wherein the thermal cycle form of the thermal power generation subsystem is a supercritical carbon dioxide Brayton cycle;

[0038] Figure 7 Schematic diagram of the heat release process of a molten salt energy storage and release coupled thermal power generation system provided by an embodiment of the present invention, wherein the thermal cycle form of the thermal power generation subsystem is a supercritical carbon dioxide Brayton cycle;

[0039] Figure 8 Flow chart of the steps of a method for using a molten salt energy storage and release coupled thermal power generation system provided by an embodiment of the present invention.

[0040] Reference numerals: 1 - low-temperature molten salt tank, 2 - high-temperature molten salt tank, 3 - heat exchanger, a - first inlet and outlet, b - second inlet and outlet, c - third inlet and outlet, d - fourth inlet and outlet, 4 - boiler, 5 - high-pressure cylinder, 6 - intermediate-pressure cylinder, 7 - low-pressure cylinder, 8 - generator, 9 - first condenser, 10 - second condenser, 11 - condensate pump, 12 - first low-pressure heater, 13 - second low-pressure heater, 14 - third low-pressure heater, 15 - fourth low-pressure heater, 16 - deaerator, 17 - feed water pump, 18 - first high-pressure heater, 19 - second high-pressure heater, 20 - third high-pressure heater, 21 - boiler, 22 - high-pressure cylinder, 23 - low-pressure cylinder, 24 - generator, 25 - cooler, 26 - main compressor, 27 - recompressor, 28 - low-temperature recuperator, 29 - high-temperature recuperator. Detailed implementation manners

[0041] An embodiment of the present invention provides a molten salt energy storage and release coupled thermal power generation system and a method for using the same, which are used to solve the technical problem that the operation flexibility of the existing molten salt energy storage and release coupled thermal power generation system is insufficient, resulting in a relatively high system operation cost.

[0042] In order to make the invention purpose, features, and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments described below are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0043] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0044] Unless otherwise clearly specified and defined, the terms "installed", "connected", "connected to" shall 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 directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0045] Embodiment 1 of the present invention provides a molten salt energy storage and release coupled thermal power generation system, including: a thermal power generation subsystem and a molten salt energy storage and release subsystem;

[0046] The molten salt heat release subsystem is used to extract part of the working medium from the thermal power generation subsystem for heat exchange with the heat storage material, and its working state includes a heat storage condition or a heat release condition;

[0047] When the molten salt heat release subsystem enters the heat storage condition, the first component ratio of the heat storage material in the molten salt heat release subsystem is the first preset ratio;

[0048] When the molten salt heat release subsystem enters the heat release condition, the second component ratio of the heat storage material in the molten salt heat release subsystem is the second preset ratio;

[0049] The melting point of the heat storage material in the molten salt heat release subsystem when the first component ratio is the first preset ratio is less than the melting point of the heat storage material in the molten salt heat release subsystem when the second component ratio is the second preset ratio, and the working temperature range of the heat storage material in the molten salt heat release subsystem when the second component ratio is the second preset ratio is greater than the working temperature range of the heat storage material in the molten salt heat release subsystem when the first component ratio is the first preset ratio.

[0050] It is understandable that the molten salt heat release subsystem includes a low-temperature molten salt tank, a high-temperature molten salt tank, and a heat exchanger; the molten salt heat release subsystem is used to extract a part of the high-temperature working medium from the thermal power generation subsystem during the heat storage condition, exchange heat with the low-temperature molten salt to cool it down to the low-temperature working medium, and then transport it back to the thermal power generation subsystem. The low-temperature molten salt is heated to the high-temperature molten salt and stored in the high-temperature molten salt tank; the molten salt heat release subsystem is also used to extract a part of the low-temperature working medium from the thermal power generation subsystem during the heat release condition, exchange heat with the high-temperature molten salt to heat it up to the high-temperature working medium, and then transport it back to the thermal power generation subsystem. The high-temperature molten salt is cooled to the low-temperature molten salt and stored in the low-temperature molten salt tank; flow valves and two-way pumps can be installed on the pipelines connected to the inlets and outlets of the heat exchanger, so that the flow direction and flow rate in the pipeline can be changed during different conditions, and the connection position between the heat exchanger and the thermal power generation subsystem can be changed; a temperature regulating device, such as a thermostat, a heating device, etc., can be installed on the pipeline connecting the high-temperature molten salt tank and the heat exchanger. The heat storage load can be calculated by combining the environmental condition parameters, the preset target temperature, and the actual temperature. The heat storage load is the heat required to maintain the target temperature, and the temperature of the heat storage material in the pipeline can be adjusted according to the heat storage load and using the temperature regulating device; the "high temperature" and "low temperature" mentioned in the present invention do not refer to specific temperature ranges. "High temperature" is a state with a higher temperature relative to "low temperature", and "low temperature" is a state with a lower temperature relative to "high temperature".

[0051] Both the first component ratio and the second component ratio refer to the ratio between some components in the heat storage material. Changing the ratio of each component in the heat storage material can change the physical properties of the heat storage material; the component ratio of the heat storage material in the molten salt heat release subsystem is adjusted according to the working condition change, so that the melting point of the heat storage material during the heat storage condition is less than the melting point during the heat release condition, and the working temperature range during the heat release condition is greater than the working temperature range during the heat storage condition. This can make the temperature required to heat the heat storage material by the molten salt heat release subsystem lower during the heat storage condition, and the heat release efficiency and quality higher during the heat release condition, better matching the heat requirements of the heat storage condition and the heat release condition, improving the overall operation flexibility of the system and reducing the system operation cost; in the present invention, the component ratio of the heat storage material in the molten salt heat release subsystem is adjusted by supplementing raw materials into the molten salt heat release subsystem. It should be noted that before supplementing raw materials into the molten salt heat release subsystem, it is necessary to first detect the components and their amounts of the heat storage material in the molten salt heat release subsystem to determine the amount of raw materials to be supplemented.

[0052] Specifically, the first component ratio is the mass ratio of sodium nitrate, potassium nitrate, and sodium nitrite, and the first preset ratio is 7:53:40;

[0053] The second component ratio is the mass ratio of sodium nitrate and potassium nitrate, and the second preset ratio is 3:2.

[0054] It should be noted that Hitec molten salt is a kind of molten salt composed of potassium nitrate ( ), sodium nitrite ( ), and sodium nitrate ( ), and the mass ratio of sodium nitrate, potassium nitrate, and sodium nitrite is 7:53:40; Hitec molten salt has the advantage of a low melting point, making it easier to reach the liquid state when heating and storing heat, reducing energy consumption and equipment burden, and reducing the risk of pipeline blockage due to freezing.

[0055] Solar salt is a binary mixture composed of sodium nitrate and potassium nitrate with a mass ratio of 3:2. It has a wide operating temperature range, good thermal stability, and also has advantages such as a low saturated vapor pressure and low viscosity. It can utilize its good thermal stability and high operating temperature range to release the stored heat more efficiently when releasing heat.

[0056] Before the molten salt heat release subsystem enters the heat storage condition for the first time after being emptied, Hitec molten salt can be added to the molten salt heat release subsystem as a heat storage material; due to the high reactivity of sodium nitrite in Hitec molten salt, the system has a fast response speed, and the heat storage material can quickly absorb and store heat during the heat storage stage; most of the sodium nitrite in the high-temperature heat storage material after the heat storage stage is consumed. Therefore, before the molten salt heat release subsystem enters the heat release condition, by replenishing sodium nitrate to the heat storage material, the mass ratio of sodium nitrate and potassium nitrate in the heat storage material can be made the same as that of solar salt, enabling the heat storage material to have a wider operating temperature range and improving the heat released by the heat storage material; then, before the molten salt heat release subsystem enters the heat storage process again, by replenishing sodium nitrite and potassium nitrate to the heat storage material, the mass ratio of sodium nitrate, potassium nitrate, and sodium nitrite in the heat storage material can be made the same as that of Hitec molten salt, enabling the heat storage material to have a lower melting point.

[0057] In the present invention, the thermoelectric power generation subsystem at least includes a heat source, a turbine unit, a cooling module, and a heating module; the thermoelectric cycle form of the thermoelectric power generation subsystem can be a Rankine cycle, a supercritical carbon dioxide Brayton cycle, etc.; when the user's electricity consumption is lower than the first preset electricity consumption value and the turbine unit reduces its load, at a working condition of 50% THA load, part of the high-temperature working medium in the thermoelectric power generation subsystem is extracted by using the excess power of the turbine unit to heat the heat storage material, and the heat-exchanged heat storage material enters the high-temperature molten salt tank of the molten salt heat release subsystem for storage and standby. The heat-exchanged low-temperature working medium can be discharged into the cooling module to reduce the output and load of the turbine unit and the power generation power of the thermoelectric power generation subsystem; when the user's electricity consumption is higher than the second preset electricity consumption value and the turbine unit increases its load, at a 100% THA load working condition, the heat released by the high-temperature heat storage material is used to heat part of the low-temperature working medium in the thermoelectric power generation subsystem. After heating the low-temperature working medium into a high-temperature working medium, it is transported to the steam turbine of the turbine unit to do work, improve the load and output of the turbine unit and save energy, and the heat-exchanged heat storage material enters the low-temperature tank for storage and standby. The present invention analyzes and selects the optimal peak shaving capacity among different coupled molten salt heat storage configurations, guides the selection of the optimal coupling scheme, and promotes the upgrading of thermal power flexibility. The first preset electricity consumption value and the second preset electricity consumption value can be set according to the specific parameters of the thermoelectric power generation subsystem and the power output adjustment requirements.

[0058] On the one hand, when the thermoelectric cycle form of the thermoelectric power generation subsystem is a Rankine cycle, the working medium in the thermoelectric power generation subsystem is water-steam or other working fluids with boiling points matching the temperature of the heat source; the molten salt heat release subsystem is specifically used to extract part of the steam from the main steam pipeline and / or the reheater steam pipeline of the thermoelectric power generation subsystem during the heat storage working condition, exchange heat with the heat storage material to cool it into low-temperature steam, and then transport it back to the thermoelectric power generation subsystem; both the main steam pipeline and the reheater steam pipeline are connected to the outlet of the heat source.

[0059] In order to improve the peak shaving capacity of the unit, avoid overheating of the reheater in the heat source (installed in the horizontal flue and the tail vertical flue of the boiler), and protect the steam turbine of the turbine unit from the influence of increased axial thrust and excessive stress on the last-stage blades, it is necessary to extract high-temperature steam from the main steam pipeline and / or the reheater steam pipeline as much as possible without affecting the operation of the turbine unit; further, the flow rate of the high-temperature steam extracted by the molten salt heat release subsystem from the main steam pipeline of the thermoelectric power generation subsystem during the heat storage working condition is less than or equal to 20% of the flow rate of the main steam pipeline or less than or equal to 72.6 kg / s, and the flow rate of the high-temperature steam extracted by the molten salt heat release subsystem from the reheater steam pipeline of the thermoelectric power generation subsystem during the heat storage working condition is less than or equal to 30% of the flow rate of the reheater steam pipeline or less than or equal to 95.7 kg / s.

[0060] The molten salt heat release subsystem is specifically further configured to extract a part of the feed water from the thermal power generation subsystem during the heat release condition, heat it up to high-temperature steam through heat exchange with the high-temperature molten salt, and then transport it back to the thermal power generation subsystem.

[0061] In a specific embodiment, reference can be made to Figure 1 , the heat source of the thermal power generation subsystem is the boiler 4. The boiler 4 is the core device that converts the chemical energy of the fuel into heat energy. The liquid water introduced into it absorbs heat and becomes high-temperature and high-pressure steam; the turbine unit includes a steam turbine and a generator 8. The steam turbine includes a high-pressure cylinder 5, an intermediate-pressure cylinder 6, and a low-pressure cylinder 7. The high-temperature and high-pressure steam continuously expands and does work in the high-pressure cylinder 5, intermediate-pressure cylinder 6, and low-pressure cylinder 7, driving the generator 8 to generate electricity; the cooling module is used to condense the steam discharged from the steam turbine back into water, including a first condenser 9 and a second condenser 10; the heating module includes a first heating sub-module, a deaerator 16, and a second heating sub-module; the deaerator 16 is used to remove the dissolved oxygen in the water to prevent the equipment from being oxidized and corroded; the first heating sub-module and the second heating sub-module are used to heat the condensed water to different temperatures; the first heating sub-module includes a first low-pressure heater 12, a second low-pressure heater 13, a third low-pressure heater 14, and a fourth low-pressure heater 15, and the second heating sub-module includes a first high-pressure heater 18, a second high-pressure heater 19, and a third high-pressure heater 20;

[0062] The boiler 4 is provided with a first gas outlet communicated with the inlet of the high-pressure cylinder 5 through a main steam pipeline, a second gas outlet communicated with the inlet of the intermediate-pressure cylinder 6 through a reheater steam pipeline, a first gas inlet communicated with the outlet of the high-pressure cylinder 5, and a first liquid inlet communicated with the feed water outlet of the third high-pressure heater 20. Among them, the first liquid inlet is communicated with the first gas outlet inside the boiler 4, and the first gas inlet is communicated with the second gas outlet inside the boiler 4;

[0063] The outlet of the high-pressure cylinder 5 is also respectively communicated with the steam inlet of the second high-pressure heater 19 and the steam inlet of the third high-pressure heater 20; the outlet of the intermediate-pressure cylinder 6 is respectively communicated with the steam inlet of the first high-pressure heater 18, the steam inlet of the deaerator 16, the steam inlet of the fourth low-pressure heater 15, and the inlet of the low-pressure cylinder 7; the outlet of the low-pressure cylinder 7 is communicated with the inlet of the first condenser 9, the inlet of the second condenser 10, the steam inlet of the first low-pressure heater 12, the steam inlet of the second low-pressure heater 13, and the steam inlet of the third low-temperature heater 14; the steam turbine is drivingly connected to the generator 8;

[0064] The outlet of the water collecting area of the first condenser 9 is communicated with the feed water inlet of the first low-pressure heater 12, and a condensate pump 11 can be provided on the communicating pipeline; the outlet of the water collecting area of the second condenser 10 and the circulation outlet of the first low-pressure heater 12 are respectively communicated with the inlet of the water collecting area of the first condenser 9;

[0065] The feed water outlet of the first low-pressure heater 12 is connected to the feed water inlet of the second low-pressure heater 13, and the circulation outlet of the second low-pressure heater 13 is connected to the circulation inlet of the first low-pressure heater 12; the feed water outlet of the second low-pressure heater 13 is connected to the feed water inlet of the third low-pressure heater 14, and the circulation outlet of the third low-pressure heater 14 is connected to the circulation inlet of the second low-pressure heater 13; the feed water outlet of the third low-pressure heater 14 is connected to the feed water inlet of the fourth low-pressure heater 15, and the circulation outlet of the fourth low-pressure heater 15 is connected to the circulation inlet of the third heater 14; the feed water outlet of the fourth low-pressure heater 15 is connected to the feed water inlet of the deaerator 16;

[0066] The feed water outlet of the deaerator 16 is connected to the feed water inlet of the first high-pressure heater 18, and a feed water pump 17 may be provided on the connecting pipeline; the feed water outlet of the first high-pressure heater 18 is connected to the feed water inlet of the second high-pressure heater 19, and the circulation outlet of the second high-pressure heater 19 is connected to the circulation inlet of the first high-pressure heater 18; the feed water outlet of the second high-pressure heater 19 is connected to the feed water inlet of the third high-pressure heater 20, and the circulation outlet of the third high-pressure heater 20 is connected to the circulation inlet of the second high-pressure heater 19;

[0067] The molten salt heat release subsystem includes a low-temperature molten salt tank 1, a high-temperature molten salt tank 2, and a heat exchanger 3;

[0068] The heat exchanger 3 is provided with a first inlet / outlet a, a second inlet / outlet b, a third inlet / outlet c, and a fourth inlet / outlet d, wherein the first inlet / outlet and the second inlet / outlet are connected inside the heat exchanger, and the third inlet / outlet and the fourth inlet / outlet are connected inside the heat exchanger;

[0069] The high-temperature molten salt tank 2 is connected to the first inlet / outlet a, and the low-temperature molten salt tank 1 is connected to the second inlet / outlet b;

[0070] When the molten salt heat release subsystem is in the heat storage condition, as Figure 1 shown, the third inlet / outlet c of the heat exchanger 3 is respectively connected to the main steam pipeline and the reheater steam pipeline, and the fourth inlet / outlet d is connected to the pipeline connecting the outlet of the low-pressure cylinder 7 and the first condenser 9;

[0071] When the molten salt heat release subsystem is in the heat release condition, there are various forms of connection between the third inlet / outlet c and the fourth inlet / outlet d of the heat exchanger 3 and the thermal power generation subsystem: The third inlet / outlet can be connected to the pipeline connecting the feed water outlet of the third high-pressure heater 20 and the first liquid inlet, the pipeline connecting the feed water outlet of the second high-pressure heater 19 and the feed water inlet of the third high-pressure heater 20, the pipeline connecting the feed water outlet of the first high-pressure heater 18 and the feed water inlet of the second high-pressure heater 19, the pipeline connecting the feed water outlet of the fourth low-pressure heater 15 and the feed water inlet of the deaerator 16, the pipeline connecting the feed water outlet of the third low-pressure heater 14 and the feed water inlet of the fourth low-pressure heater 15, the pipeline connecting the feed water outlet of the second low-pressure heater 13 and the feed water inlet of the third low-pressure heater 14, the pipeline connecting the feed water outlet of the first low-pressure heater 12 and the feed water inlet of the second low-pressure heater 13, or the pipeline connecting the outlet of the intermediate-pressure cylinder 6 and the inlet of the low-pressure cylinder 7;

[0072] The fourth inlet / outlet is connected to the pipeline connecting the feed water outlet of the second high-pressure heater 19 and the feed water inlet of the third high-pressure heater 20, the pipeline connecting the feed water outlet of the first high-pressure heater 18 and the feed water inlet of the second high-pressure heater 19, the pipeline connecting the feed water outlet of the deaerator 16 and the feed water inlet of the first high-pressure heater 18, the pipeline connecting the feed water outlet of the third low-pressure heater 14 and the feed water inlet of the fourth low-pressure heater 15, the pipeline connecting the feed water outlet of the second low-pressure heater 13 and the feed water inlet of the third low-pressure heater 14, the pipeline connecting the feed water outlet of the first low-pressure heater 12 and the feed water inlet of the second low-pressure heater 13, or the pipeline connecting the outlet of the first condenser 9 catchment area and the feed water inlet of the first low-pressure heater 12;

[0073] The third inlet / outlet and the fourth inlet / outlet are not connected to the same pipeline. Preferably, the pipeline connected by the fourth inlet / outlet is used to extract the feed water of the thermal power generation subsystem;

[0074] For more details, refer to Figures 2 to 5 , Figures 2 to 5 which gives four different connection schemes between the third inlet / outlet c and the fourth inlet / outlet d of the heat exchanger 3 and the thermal power generation subsystem under the heat release condition.

[0075] On the other hand, refer to Figures 6 to 7 When the thermal cycle form of the thermal power generation subsystem is a supercritical carbon dioxide Brayton cycle, the working medium in the thermal power generation subsystem is carbon dioxide;

[0076] The thermal power generation subsystem includes a heat source, a turbine unit, a cooling module, a heating module, and a compression module;

[0077] The heat source is the boiler 21; the compression module includes a main compressor 26 and a recompressor 27; the heating module includes a low-temperature recuperator 28 and a high-temperature recuperator 29; the turbine unit includes a high-pressure cylinder 22, a low-pressure cylinder 23 and a generator 24; the cooling module includes a cooler 25;

[0078] The boiler 21 is provided with a first outlet communicating with the inlet of the high-pressure cylinder 22, a second outlet communicating with the inlet of the low-pressure cylinder 23, a first inlet communicating with the outlet of the high-pressure cylinder 22, and a second inlet communicating with the working medium outlet of the high-temperature recuperator 29. Among them, the second inlet communicates with the first outlet inside the boiler 21, and the first inlet communicates with the second outlet inside the boiler 21;

[0079] The high-pressure cylinder 22 and the low-pressure cylinder 23 are drivingly connected to the generator 24, the recompressor 27 and the main compressor 26; the outlet of the low-pressure cylinder 23 communicates with the heat medium inlet of the high-temperature recuperator 29;

[0080] The heat medium outlet of the high-temperature recuperator 29 communicates with the heat medium inlet of the low-temperature recuperator 28, and the heat medium outlet of the low-temperature recuperator 28 communicates with the inlet of the cooler 25 and the inlet of the recompressor 27 respectively;

[0081] The outlet of the cooler 25 communicates with the inlet of the main compressor 26;

[0082] The outlet of the main compressor 26 communicates with the working medium inlet of the low-temperature recuperator 28, and the outlets of the recompressor 27 and the working medium outlet of the low-temperature recuperator 28 communicate with the working medium inlet of the high-temperature recuperator 29 respectively;

[0083] The molten salt heat release subsystem includes a low-temperature molten salt tank 1, a high-temperature molten salt tank 2 and a heat exchanger 3;

[0084] The heat exchanger 3 is provided with a first inlet / outlet a, a second inlet / outlet b, a third inlet / outlet c and a fourth inlet / outlet d. Among them, the first inlet / outlet communicates with the second inlet / outlet inside the heat exchanger, and the third inlet / outlet communicates with the fourth inlet / outlet inside the heat exchanger;

[0085] The high-temperature molten salt tank 2 communicates with the first inlet / outlet a, and the low-temperature molten salt tank 1 communicates with the second inlet / outlet b;

[0086] When the molten salt heat release subsystem is in the heat storage condition, as Figure 6 shown, the third inlet / outlet c of the heat exchanger 3 communicates with the pipeline connected between the outlet of the boiler 21 and the inlet of the high-pressure cylinder 22, and the fourth inlet / outlet d communicates with the pipeline connected between the outlet of the low-pressure cylinder 23 and the heat medium inlet of the high-temperature recuperator 29;

[0087] When the molten salt heat release subsystem is in the heat release condition, as Figure 7As shown, both the third inlet / outlet c and the fourth inlet / outlet d of the heat exchanger 3 are in communication with the pipeline connecting the outlet of the low-pressure cylinder 23 and the heat medium inlet of the high-temperature recuperator 29, wherein the fourth inlet / outlet is for air extraction.

[0088] In a preferred embodiment, the molten salt storage / discharge heat-coupled thermal power generation system provided by the present invention may further include a controller; during the heat release process, when the heat release load is consistent with the demand, in order to make the pressure and temperature at the third inlet / outlet of the heat exchanger 3 match the thermal power generation subsystem, the controller is used to control the output flow of the high-temperature molten salt by adjusting the opening degree of the flow valve on the pipeline connecting the first inlet / outlet and the high-temperature molten salt tank according to the temperature at the third inlet / outlet; the controller may also be used to adjust the opening degree of other flow valves in the system according to the load increase or decrease of the unit, and control the flow of the working medium extracted from the thermal power generation subsystem.

[0089] As Figure 8 shown, Embodiment 2 of the present invention provides a method for using a molten salt storage / discharge heat-coupled thermal power generation system, including:

[0090] Step 801, before the molten salt heat release subsystem of the molten salt storage / discharge heat-coupled thermal power generation system first enters the heat storage condition, adding the first molten salt to the molten salt heat release subsystem as the heat storage material; the first component ratio of the first molten salt is the first preset ratio;

[0091] Step 802, before the molten salt heat release subsystem enters the heat release condition, adjusting the second component ratio of the heat storage material in the molten salt heat release subsystem to the second preset ratio;

[0092] Step 803, before the molten salt heat release subsystem enters the nth heat storage condition, adjusting the first component ratio of the heat storage material in the molten salt heat release subsystem to the first preset ratio; n > 1;

[0093] The melting point of the heat storage material in the molten salt heat release subsystem when the first component ratio is the first preset ratio is less than the melting point of the heat storage material in the molten salt heat release subsystem when the second component ratio is the second preset ratio, and the working temperature range of the heat storage material in the molten salt heat release subsystem when the second component ratio is the second preset ratio is greater than the working temperature range of the heat storage material in the molten salt heat release subsystem when the first component ratio is the first preset ratio.

[0094] Further, the first molten salt is Hitec molten salt;

[0095] The first component ratio is the ratio of sodium nitrate, potassium nitrate and sodium nitrite;

[0096] The first preset ratio is 7:53:40.

[0097] Further, the second component ratio is the ratio of sodium nitrate and potassium nitrate;

[0098] The second preset ratio is 3:2.

[0099] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A molten salt heat storage and release coupled thermal power generation system, characterized in that: include: Thermal power generation subsystem and molten salt heat storage and release subsystem; The molten salt heat release subsystem is used to extract part of the working medium from the thermal power generation subsystem to exchange heat with the heat storage material, and its working state includes heat storage condition or heat release condition; When the molten salt heat release subsystem enters the heat storage state, the first component ratio of the heat storage material in the molten salt heat release subsystem is a first preset ratio; When the molten salt heat release subsystem enters the heat release working condition, the second component ratio of the heat storage material in the molten salt heat release subsystem is a second preset ratio; The melting point of the heat storage material in the molten salt heat release subsystem when the first component ratio is the first preset ratio is lower than the melting point of the heat storage material in the molten salt heat release subsystem when the second component ratio is the second preset ratio, and the operating temperature range of the heat storage material in the molten salt heat release subsystem when the second component ratio is the second preset ratio is higher than the operating temperature range of the heat storage material in the molten salt heat release subsystem when the first component ratio is the first preset ratio.

2. The method of use according to claim 1, characterized in that: The first component ratio is the mass ratio of sodium nitrate, potassium nitrate and sodium nitrite; The first preset ratio is 7:53:

40.

3. The method of use according to claim 2, characterized in that: The second component ratio is the mass ratio of sodium nitrate to potassium nitrate; The second preset ratio is 3:

2.

4. The molten salt heat storage and release coupled thermal power generation system according to any one of claims 1 to 3, characterized in that: The thermodynamic cycle of the thermodynamic generating subsystem is a Rankine cycle.

5. The molten salt heat storage and release coupled thermal power generation system according to claim 4, characterized in that: The molten salt heat release subsystem is specifically used to extract part of the steam from the main steam pipe and / or reheat steam pipe of the thermal power generation subsystem in the heat storage condition, and then transport it back to the thermal power generation subsystem after heat exchange and cooling with the heat storage material.

6. The molten salt heat storage and release coupled thermal power generation system according to claim 5, characterized in that: The flow rate of high-temperature steam extracted from the main steam pipeline of the thermal power generation subsystem by the molten salt heat release subsystem in the heat storage condition is less than or equal to 20% of the flow rate of the main steam pipeline; The flow rate of high-temperature steam extracted from the reheat steam pipeline of the thermal power generation subsystem by the molten salt heat release subsystem in the heat storage condition is less than or equal to 30% of the flow rate of the reheat steam pipeline.

7. The molten salt heat storage and release coupled thermal power generation system according to any one of claims 1 to 3, characterized in that: The thermodynamic cycle of the thermal power generation subsystem is a supercritical carbon dioxide Brayton cycle.

8. A method for using a molten salt heat storage and release coupled thermal power generation system, characterized in that: include: Before the molten salt heat release subsystem of the molten salt heat storage and release coupled thermal power generation system enters the heat storage condition for the first time, a first molten salt is added into the molten salt heat release subsystem as a heat storage material; the first component ratio of the first molten salt is a first preset ratio; Before the molten salt heat release subsystem enters the heat release working state, adjusting the second component ratio of the heat storage material in the molten salt heat release subsystem to a second preset ratio; Before the molten salt heat release subsystem enters the heat storage state for the nth time, adjusting the first component ratio of the heat storage material in the molten salt heat release subsystem to a first preset ratio; n＞1； The melting point of the heat storage material in the molten salt heat release subsystem when the first component ratio is the first preset ratio is lower than the melting point of the heat storage material in the molten salt heat release subsystem when the second component ratio is the second preset ratio, and the operating temperature range of the heat storage material in the molten salt heat release subsystem when the second component ratio is the second preset ratio is higher than the operating temperature range of the heat storage material in the molten salt heat release subsystem when the first component ratio is the first preset ratio.

9. The method of use according to claim 8, characterized in that: The first molten salt is Hitec molten salt; The first component ratio is the mass ratio of sodium nitrate, potassium nitrate and sodium nitrite; The first preset ratio is 7:53:

40.

10. The method of use according to claim 8, characterized in that: The second component ratio is the mass ratio of sodium nitrate to potassium nitrate; The second preset ratio is 3:2.

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