A solar energy assisted carbon capture system based on hitec high temperature molten salt heat storage

Abstract

This invention discloses a solar-assisted carbon capture system based on Hitec high-temperature molten salt thermal energy storage, relating to the field of carbon capture technology. Its main objective is to reduce the impact of steam extraction from the thermal power plant's thermal unit on the plant's load. The main technical solution employed is as follows: a carbon capture unit; a thermal power plant unit; a flash heat exchanger; a trough solar thermal unit; and a Hitec high-temperature molten salt thermal energy storage unit. The fifth-stage steam extraction from the thermal power plant unit, after heat exchange in the flash heat exchanger, supplies heat to the carbon capture unit. The steam remaining after heat exchange in the carbon capture unit enters the trough solar thermal unit and / or the Hitec high-temperature molten salt thermal energy storage unit, where it is heated by the heat transfer medium and / or the Hitec molten salt thermal energy storage medium before returning to the low-pressure heater unit. This achieves simultaneous or separate heating of the carbon capture unit by the trough solar thermal unit and the Hitec high-temperature molten salt thermal energy storage unit, as well as power generation from the thermal power plant's thermal unit.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of carbon capture, in particular to a solar energy assisted carbon capture system based on Hitec high-temperature molten salt heat storage. BACKGROUND

[0002] Common heat storage forms mainly include sensible heat storage, phase change heat storage and chemical reaction heat storage. Sensible heat storage refers to that the amount of stored heat can be directly measured by the increase in temperature of solid or liquid. Phase change heat storage, also called latent heat storage, has a heat storage density at least one order of magnitude higher than that of sensible heat storage materials, and can absorb or release a large amount of heat energy under constant temperature conditions. Chemical reaction heat storage uses reversible chemical reactions to realize heat storage and heat release through conversion between heat energy and chemical energy.

[0003] Molten salt heat storage is a sensible heat storage technology that uses the temperature difference in the heating or cooling process of materials to realize heat energy storage and release. Throughout the working temperature range, the heat storage material always remains in a liquid state. Molten salt is a molten body formed after salt is melted, and is a molten body composed of metal cations and non-metal anions. Molten salt has the characteristics of high boiling point, low viscosity, high volumetric heat, high use temperature, high thermal stability, high specific heat capacity, high convective heat transfer coefficient, low saturated vapor pressure and the like, and is an excellent heat transfer and storage medium with good heat transfer and storage capacity, and has been widely used in the field of heat storage and photothermal.

[0004] Molten salt is a molten liquid of salt, and the commonly used molten salt refers to the molten body of inorganic salt. The solid state of inorganic salt forming a molten state is mostly ionic crystal, which melts to form an ionic melt at high temperature. Therefore, the most common molten salt is composed of alkali metals or alkaline earth metals and halides, silicates, carbonates, nitrates and phosphates. Compared with traditional working fluids, molten salt has a wide range of use temperature (from tens of degrees Celsius to more than 1,000 degrees Celsius), high heat transfer performance, low working pressure, low price and a series of advantages.

[0005] Molten salt heat storage includes two working processes of heat storage and heat release. When the sunlight is sufficient, solar energy is used as the energy to heat the molten salt, and the molten salt stores solar energy; when the sunlight is insufficient, the high-temperature molten salt exchanges heat with water in the heat exchange system to generate water vapor, and the water vapor is used as the heat source of the carbon capture system regenerator, and the absorbent in the regenerator is regenerated through heat exchange.

[0006] The principle of molten salt thermal storage technology is that when the power generation exceeds the load demand, the electricity is used to heat the molten salt, and then the high-temperature molten salt is stored in a container. When the load demand is greater than the power generation, the high-temperature molten salt is pumped out and exchanges heat with water through a heat exchanger to generate steam, thereby driving the steam turbine to generate electricity. The molten salt thermal storage technology combined with the solar thermal power generation system can make the solar thermal power generation system have the ability of energy storage and night power generation, and is an economical technology. It has been practically commercialized in developed countries such as Europe and parts of North America. The United States was the first to use molten salt as a heat transfer and heat storage medium for solar thermal power generation, and achieved good results in the Solar Two solar thermal power generation experimental power station. In July 2010, the Italian National Power Group built the world's first Archimedes solar thermal power station in Sicily, which completely uses molten salt for heat storage.

[0007] The high-temperature molten salt system for heat storage mainly includes:

[0008] 1. Carbonate: Carbonate is a salt compound containing carbonate ions, which is widely distributed in nature, has large reserves and low price. Carbonate phase change has the characteristics of large latent heat, large viscosity, small corrosion, large specific heat and density, etc., and can form a high-temperature, oxygen-free and water-free state to meet the high-temperature heat transfer and heat storage of solar thermal power generation. Carbonate has low price and large solubility, but some carbonates have high-temperature decomposition problems. Common carbonates include sodium carbonate, potassium carbonate, lithium carbonate, etc. Different carbonates can be mixed in different proportions to obtain eutectic mixtures with different properties. When potassium carbonate and sodium carbonate are mixed in a mass ratio of 3:2, the eutectic compound with the lowest melting point is obtained, with a melting point of 977 K, a melting heat of 364.25 kJ / kg, and a heat capacity of 0.921 kJ / (kg·K). The properties are stable below 1103 K and do not decompose. The ternary salt formed by mixing sodium carbonate, potassium carbonate and lithium carbonate in a molar ratio of 30.6:26.8:42.5 has a melting point of 666 K.

[0009] 2. Fluoride salts: Fluorides are mainly some alkali earth metals, alkali metals and some difficultly soluble fluorides of metals, which are anhydrous salts. They have high melting point, large latent heat of phase change, low vapor pressure in molten state, small viscosity and good compatibility with container materials, etc. They are good high temperature heat storage materials. Common fluorides include sodium fluoride, potassium fluoride, magnesium fluoride, etc. When used as high temperature heat storage materials, fluorides are generally mixed with some fluorides in certain proportions to form eutectic mixtures to reduce the melting point and adjust the heat storage capacity. For example, the melting point of the mixture of sodium fluoride, calcium fluoride and magnesium fluoride with a mass ratio of 65:23:12 is 1018 K. The solar power generation and heat storage system with a power of 25 kW designed by the National Aeronautics and Space Administration of the United States uses lithium fluoride-calcium fluoride as the heat storage material, which has good effect. However, fluorides also have great disadvantages in use, mainly in two aspects: 1) large volume change during phase change, which brings difficulties to the storage pipeline and container, for example, the volume of lithium fluoride increases by about 23% from solid to liquid; 2) poor thermal conductivity, which leads to hot spots and thermal release.

[0010] 3. Chloride salts: Chlorides are generally low in price and various in types, and have low viscosity, large specific heat, large thermal conductivity, large latent heat of phase change and good stability, but are highly corrosive. They can be mixed in different proportions to prepare low melting point mixed molten salts. Common chlorides include sodium chloride, potassium chloride, calcium chloride, magnesium chloride, lithium chloride, etc.

[0011] 4. Nitrate salts: Nitrate salts are the most widely used and mature molten salts in solar power generation. They have small corrosion, low price, excellent heat and mass transfer performance, etc. The melting point is about 573 K, and the thermal properties are stable below 773 K without decomposition. Nitrate molten salts include single salt, binary molten salt, ternary molten salt and multi-component molten salt. The melting point of single salt is high, which easily leads to "frozen pipe phenomenon" in use, which limits the application range of single salt; binary molten salt not only ensures the change of thermal conductivity and heat of fusion, but also reduces the melting point, has good heat storage performance and heat transfer characteristics, and is suitable for use as a molten salt heat storage material. It has very wide application in chemical and petrochemical industries, and can be used as a heat transfer and heat storage medium in solar thermal power generation and solar hydrogen production. The representative binary molten salt mainly includes Solar Salt molten salt system (KNO3-NaNO3 mass fraction 40%:60%); ternary molten salt can greatly reduce the melting point of the system, but the thermal conductivity and heat of fusion of the system will also decrease, mainly including Hitec molten salt system (NaNO3-KNO3-NaNO2 mass fraction ratio of 7%:53%:40%) and HitecXL molten salt system (CaNO3-KNO3-NaNO3 mass fraction ratio of 48%:45%:7%). The three kinds of nitrate molten salt systems are used as heat transfer and storage medium in foreign solar thermal power stations. SUMMARY

[0012] Therefore, the application provides a solar energy assisted carbon capture system based on Hitec high-temperature molten salt heat storage, which mainly aims to reduce the influence of steam extraction of a thermal unit of a thermal power plant on the load of the thermal power plant.

[0013] To achieve the above-mentioned purpose, the application mainly provides the following technical scheme:

[0014] The embodiment of the application provides a solar energy assisted carbon capture system based on Hitec high-temperature molten salt heat storage. The system comprises:

[0015] a carbon capture unit;

[0016] a thermal unit of a thermal power plant, which comprises a superheater, a reheater connected with the superheater, a steam turbine connected with an outlet of the superheater and an outlet of the reheater respectively, a condenser connected with the steam turbine, a shaft seal heater connected with the condenser, a low-pressure heater unit connected with the shaft seal heater and the condenser respectively, a deaerator connected with the low-pressure heater unit, and a high-pressure heater unit connected with the deaerator, wherein the high-pressure heater unit is connected with an inlet of the superheater, the steam turbine comprises eight stages of steam extraction, wherein the first stage of steam extraction to the fourth stage of steam extraction are connected with the high-pressure heater unit and the deaerator respectively, the fifth stage of steam extraction to the eighth stage of steam extraction are connected with the low-pressure heater unit respectively, and the second stage of steam extraction is connected with an inlet of the reheater;

[0017] a flash heat exchanger connected with the carbon capture unit and the fifth stage of steam extraction respectively, so that the fifth stage of steam extraction is heated through the flash heat exchanger and then supplies heat to the carbon capture unit;

[0018] a trough type solar thermal unit connected with the carbon capture unit and the low-pressure heater unit respectively, wherein the trough type solar thermal unit is used for collecting solar energy to heat a heat-conducting working medium, converting the heated heat-conducting working medium into electric energy for power supply, and storing the heated heat-conducting working medium which is not converted into electric energy;

[0019] a Hitec high-temperature molten salt heat storage unit connected with the carbon capture unit, the trough type solar thermal unit and the low-pressure heater unit respectively, and the trough type solar thermal unit is further used for delivering the stored heated heat-conducting working medium to the Hitec high-temperature molten salt heat storage unit to heat Hitec molten salt heat storage working medium in the Hitec high-temperature molten salt heat storage unit;

[0020] The steam after heat exchange of the carbon capture unit enters the trough solar thermal unit and / or the Hitec high-temperature molten salt heat storage unit, is heated by the heat-conducting working medium and / or the Hitec molten salt heat storage working medium, and then returns to the low-pressure heater unit, so as to realize simultaneous or separate heating of the carbon capture unit by the trough solar thermal unit and the Hitec high-temperature molten salt heat storage unit and power generation of the thermal unit of the thermal power plant.

[0021] As described above, the carbon capture unit comprises a water washing tower, an absorption tower connected to the water washing tower, a lean liquid pump connected to an inlet of the absorption tower, a rich liquid pump connected to an outlet of the absorption tower, a lean-rich liquid heat exchanger connected to the lean liquid pump and the rich liquid pump respectively, a regeneration tower connected to the lean-rich liquid heat exchanger, a condenser connected to a first outlet of the regeneration tower, a reboiler connected to a second outlet of the regeneration tower and the lean-rich liquid heat exchanger respectively, and a steam-water separator connected to the condenser and the regeneration tower respectively, wherein the first inlet of the reboiler and the first outlet of the reboiler are connected to the flash heat exchanger.

[0022] As described above, the steam turbine comprises a steam turbine high-pressure cylinder, a steam turbine intermediate-pressure cylinder, and a steam turbine low-pressure cylinder.

[0023] The low-pressure heater unit comprises a first low-pressure heater, a second low-pressure heater, a third low-pressure heater, and a fourth low-pressure heater connected in series, wherein the first low-pressure heater is connected to the deaerator, and the fourth low-pressure heater is connected to the shaft seal heater.

[0024] The high-pressure heater unit comprises a first high-pressure heater, a second high-pressure heater, and a third high-pressure heater connected in series, wherein the first high-pressure heater is connected to the superheater inlet, and the third high-pressure heater is connected to the deaerator.

[0025] The steam turbine high-pressure cylinder provides a first-stage extraction steam and a second-stage extraction steam, the steam turbine intermediate-pressure cylinder provides a third-stage extraction steam and a fourth-stage extraction steam, and the steam turbine low-pressure cylinder provides a fifth-stage extraction steam to an eighth-stage extraction steam, wherein the first-stage extraction steam is connected to the first high-pressure heater, the second-stage extraction steam is connected to the second high-pressure heater and the reheater inlet respectively, the third-stage extraction steam is connected to the third high-pressure heater, the fourth-stage extraction steam is connected to the deaerator, the fifth-stage extraction steam is connected to the first low-pressure heater, the sixth-stage extraction steam is connected to the second low-pressure heater, the seventh-stage extraction steam is connected to the third low-pressure heater, and the eighth-stage extraction steam is connected to the fourth low-pressure heater.

[0026] As described above, the trough solar thermal unit and the Hitec high-temperature molten salt heat storage unit are connected to a return water pipeline between the first low-pressure heater and the second low-pressure heater.

[0027] As described above, the trough type solar photo-thermal unit comprises a heat collecting unit, a first heat exchanging unit connected with the heat collecting unit, a heat storing unit connected with the first heat exchanging unit and the heat collecting unit respectively, and a power generating unit connected with the first heat exchanging unit;

[0028] The heat collecting unit is used for collecting solar energy to heat the heat conducting medium.

[0029] The first heat exchanging unit is used for exchanging heat with the heat collecting unit, then supplying the power generating unit to generate power and delivering the excess heat to the heat storing unit for heat storage.

[0030] The heat storing unit is used for storing the heated heat conducting medium.

[0031] The power generating unit is used for supplying power for the pump of the carbon capture system.

[0032] As described above, the heat conducting medium adopts heat conducting oil.

[0033] As described above, the Hitec high temperature molten salt heat storing unit comprises a hot salt tank connected with the heat storing unit, a cold salt tank connected with the heat storing unit, and a second heat exchanging unit connected with the hot salt tank and the cold salt tank respectively.

[0034] The cold salt tank is used for storing the Hitec molten salt heat storing medium, the Hitec molten salt heat storing medium is heated by the heat conducting medium delivered by the heat storing unit to obtain the Hitec high temperature molten salt, the Hitec high temperature molten salt is delivered to the hot salt tank for storage and to the second heat exchanging unit, the second heat exchanging unit is used for exchanging heat between the Hitec high temperature molten salt and water to generate steam, the steam enters the carbon capture unit to supply heat for the carbon capture unit, and the heat exchanged Hitec molten salt is delivered to the cold salt tank for storage.

[0035] As described above, the Hitec molten salt adopts a Hitec molten salt system, and the Hitec molten salt system is NaNO3-KNO3-NaNO2.

[0036] The mass fraction ratio of the NaNO3-KNO3-NaNO2 is 7%:53%:40%.

[0037] The heat capacity of the NaNO3-KNO3-NaNO2 is 1.56 (KJ·(kg·K -1 ).

[0038] By means of the above technical scheme, the solar energy assisted carbon capture system based on Hitec high temperature molten salt heat storage has at least the following advantages:

[0039] The solar-assisted carbon capture system based on Hitec high-temperature molten salt thermal energy storage of this invention addresses the issue of low load matching between the power plant's carbon capture unit and the solar thermal unit. To fully utilize the energy of the solar thermal unit and reduce the impact of steam extraction from the thermal power plant's thermal unit on the power plant's load, a Hitec high-temperature molten salt thermal energy storage unit is introduced into the system. Heat transfer oil is used as the heat transfer medium between the Hitec unit and the trough solar thermal unit. Based on the heat load of the carbon capture unit and the photothermal-electric conversion efficiency of the trough solar thermal unit, the Hitec high-temperature molten salt thermal energy storage unit is applied for heat storage and peak shaving.

[0040] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the structure of the solar-assisted carbon capture system based on Hitec high-temperature molten salt thermal storage according to the present invention;

[0042] Figure 2 This is a schematic diagram of the carbon capture unit structure of the present invention;

[0043] Figure 3 This is a schematic diagram of the trough-type solar thermal unit structure of the present invention;

[0044] Figure 4 This is a block diagram illustrating the working principle of the Hitec high-temperature molten salt thermal storage unit of the present invention. Detailed Implementation

[0045] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description of the specific implementation methods, structures, features and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0046] like Figure 1 As shown, an embodiment of the present invention proposes a solar-assisted carbon capture system based on Hitec high-temperature molten salt thermal storage, which includes: a carbon capture unit 1, a thermal power plant thermal unit 2, a flash heat exchanger 3, a trough solar thermal unit 4, and a Hitec high-temperature molten salt thermal storage unit 5.

[0047] like Figure 2As shown, the carbon capture unit 1, which includes a water washing tower 101, an absorption tower 102 connected with the water washing tower 101, a lean liquid pump 103 connected with an inlet of the absorption tower 102, a rich liquid pump 104 connected with an outlet of the absorption tower 102, a lean-rich liquid heat exchanger 105 connected with the lean liquid pump 103 and the rich liquid pump 104 respectively, a regeneration tower 106 connected with the lean-rich liquid heat exchanger 105, a condenser 107 connected with a first outlet of the regeneration tower 106, a reboiler 108 connected with a second outlet of the regeneration tower 106 and the lean-rich liquid heat exchanger 105 respectively, a steam-water separator 109 connected with the condenser 107 and the regeneration tower 106 respectively, and the first inlet of the reboiler 108 and the first outlet of the reboiler 108 are connected with the flash heat exchanger 3. The specific process flow is as follows: the flue gas treated by the power plant environmental protection equipment is countercurrently contacted with the lean liquid in the absorption tower and a chemical reaction occurs, and most of the CO2 is absorbed by the absorption liquid, the lean liquid becomes the rich liquid, the treated flue gas is recovered by the water washing tower, and the remaining flue gas is discharged to the atmosphere through the chimney. The rich liquid at the bottom of the absorption tower is sprayed into the tower from top to bottom after passing through the lean-rich liquid heat exchanger, and then enters the reboiler for desorption, and the rich liquid is regenerated into the lean liquid. The desorbed CO2 enters the condenser at the top of the regeneration tower and the steam-water separator for purification, and the lean liquid regenerated by the regeneration tower flows out from the bottom of the regeneration tower, exchanges heat with the lean-rich liquid heat exchanger and the condenser, and then mixes with the absorption liquid supplemented into the system and enters the absorption tower again; under the pushing of the lean liquid pump and the rich liquid pump, it reciprocates between the absorption tower and the regeneration tower, forming a process flow of continuous absorption and desorption of CO2. In order to prevent high-temperature corrosion and degradation of the absorption liquid, the temperature of the rich liquid in the reboiler is generally controlled at 395K, and assuming that the heat exchange temperature difference of the heat exchanger is 10K, the temperature of the steam side is 405K, and the corresponding saturated steam pressure is 0.28Mpa.

[0048] As Figure 1As shown, the thermal unit 2 of the power plant comprises a superheater 201, a reheater 202 connected with the superheater 201, a steam turbine 203 connected with the outlet of the superheater 201 and the outlet of the reheater 202 respectively, a condenser 204 connected with the steam turbine 203, a shaft seal heater 205 connected with the condenser 204, a low-pressure heater unit 206 connected with the shaft seal heater 205 and the condenser 204 respectively, a deaerator 207 connected with the low-pressure heater unit 206, and a high-pressure heater unit 208 connected with the deaerator 207, wherein the high-pressure heater unit 208 is connected with the inlet of the superheater 201, the steam turbine 203 comprises 8 levels of extraction, wherein the 1st to 4th levels of extraction are connected with the high-pressure heater unit 208 and the deaerator 207 respectively, the 5th to 8th levels of extraction are connected with the low-pressure heater unit 206 respectively, and the 2nd level of extraction is connected with the inlet of the reheater 202. Specifically, the steam turbine 203 comprises a high-pressure cylinder 2031, a medium-pressure cylinder 2032, and a low-pressure cylinder 2033; the low-pressure heater unit 206 comprises a first low-pressure heater 2061, a second low-pressure heater 2062, a third low-pressure heater 2063, and a fourth low-pressure heater 2064 connected in series, wherein the first low-pressure heater 2061 is connected with the deaerator 207, and the fourth low-pressure heater 2064 is connected with the shaft seal heater 205; the high-pressure heater unit 208 comprises a first high-pressure heater 2081, a second high-pressure heater 2082, and a third high-pressure heater 2083 connected in series, wherein the first high-pressure heater 2081 is connected with the inlet of the superheater 201, and the third high-pressure heater 2083 is connected with the deaerator 207; the high-pressure cylinder 2031 provides the 1st and 2nd levels of extraction 20311 and 20312, the medium-pressure cylinder 2032 provides the 3rd and 4th levels of extraction 20321 and 20322, and the low-pressure cylinder 2033 provides the 5th to 8th levels of extraction, wherein the 1st level of extraction 20311 is connected with the first high-pressure heater 2081, the 2nd level of extraction 20312 is connected with the second high-pressure heater 2082 and the inlet of the reheater 202 respectively, the 3rd level of extraction 20321 is connected with the third high-pressure heater 2083, the 4th level of extraction 20322 is connected with the deaerator 207, the 5th level of extraction 20331 is connected with the first low-pressure heater 2061, the 6th level of extraction 20332 is connected with the second low-pressure heater 2062, the 7th level of extraction 20333 is connected with the third low-pressure heater 2063, and the 8th level of extraction 20334 is connected with the fourth low-pressure heater 2064.In specific work, the steam generated by the superheater in the thermal unit of the thermal power plant enters the high-pressure cylinder of the steam turbine to do work, one way returns to the reheater to absorb heat, the reheated reheat steam enters the medium-pressure cylinder of the steam turbine and the low-pressure cylinder of the steam turbine in turn to do work, and then becomes condensed water through the condenser, enters the superheater again through the shaft seal heater, the low-pressure heater, the deaerator and the high-pressure heater, and becomes steam again.

[0049] As shown in Figure 1 The flash heat exchanger 3 is connected with the carbon capture unit 1, and the 8-stage steam extraction of the steam turbine, because the steam parameters of the 6th to 8th stage steam extraction are too low, only the parameters of the 1st to 5th stage steam extraction meet the energy requirement of the absorbent regeneration of the carbon capture unit, according to the energy level matching theory, low-parameter steam extraction should be used as much as possible, therefore, the 5th stage steam extraction is selected as the heat source to directly supply heat for the carbon capture system, because the temperature of the 5th stage steam extraction is too high, the flash heat exchanger is needed to flash heat exchange before supplying heat for the carbon capture unit, therefore, the flash heat exchanger 3 is connected with the 5th stage steam extraction, and the 5th stage steam extraction supplies heat for the carbon capture unit 1 after heat exchange through the flash heat exchanger 3.

[0050] As shown in Figure 3As shown, the trough solar thermal unit 4 is connected with the carbon capture unit 1 and the low-pressure heater unit 206 respectively, and the trough solar thermal unit heats the heat-conducting medium by collecting solar energy, converts the heated heat-conducting medium into electric energy, and stores the excess heated heat-conducting medium which is not converted into electric energy. During the day when the sunlight is sufficient, the steam after heat exchange in the carbon capture unit enters the trough solar thermal unit, is heated by the heat-conducting medium, and then returns to the backwater pipeline between the first low-pressure heater and the second low-pressure heater in the low-pressure heater unit, so as to realize the heating of the carbon capture unit by the trough solar thermal unit and the power generation of the thermal unit in the power plant. The trough solar thermal unit 4 comprises a heat collection unit 401, a first heat exchange unit 402 connected with the heat collection unit 401, a heat storage unit 403 connected with the first heat exchange unit 402 and the heat collection unit 401 respectively, and a power generation unit 404 connected with the first heat exchange unit 402. The heat collection unit 401 is used for collecting solar energy to heat the heat-conducting medium, and mainly comprises heat collection pipes, heat collection mirror surfaces, a support structure and a control system. The heat collection unit 401 uses the heat collection mirror surfaces and the heat collection pipes to absorb the solar thermal energy to heat the heat-conducting medium in the heat collection pipes. The first heat exchange unit 402 is used for heat exchange with the heat collection unit 401, supplies the power generation unit 404 for power generation, and delivers the excess heat to the heat storage unit 403 for heat storage. The heat storage unit 403 is used for storing the heated heat-conducting medium. The power generation unit 404 is used for supplying power for the pump of the carbon capture unit. The heat storage unit 403 mainly comprises a heat storage tank and a heat storage medium. The trough solar thermal power generation unit mainly uses the heat collection mirror surfaces and the heat collection pipes to focus and absorb the solar thermal energy, and then converts the solar thermal energy into electric energy. In the present application, the heat-conducting medium is heat-conducting oil. The trough solar thermal system belongs to a medium-temperature solar thermal system, and the operating temperature range can reach 563-823K, which meets the temperature range requirement of the heat source for the regeneration of the absorbing agent in the carbon capture unit, matches the heat storage temperature of the Hitec high-temperature molten salt heat storage unit, and is the only successful commercial operation scheme of the solar thermal power generation at present, and can be modularized or jointly operated, and is suitable for heating the carbon capture unit.

[0051] As Figure 4As shown, the Hitec high-temperature molten salt heat storage unit 5 is connected with the carbon capture unit 1, the trough solar thermal unit 4, and the low-pressure heater unit 206, respectively, and the trough solar thermal unit 4 is also used to deliver the stored heated heat-conducting medium to the Hitec high-temperature molten salt heat storage unit to heat the Hitec molten salt heat storage medium in the Hitec high-temperature molten salt heat storage unit. At night or on cloudy days, the steam after heat exchange in the carbon capture unit 1 enters the Hitec high-temperature molten salt heat storage unit to be heated by the Hitec molten salt heat storage medium, and then returns to the backwater pipeline between the first low-pressure heater and the second low-pressure heater in the low-pressure heater unit, so as to realize the heat supply of the Hitec high-temperature molten salt heat storage unit to the carbon capture unit and the power generation of the thermal unit of the power plant. On cloudy days, the trough solar thermal unit and the Hitec high-temperature molten salt heat storage unit can simultaneously supply heat to the carbon capture unit. The Hitec high-temperature molten salt heat storage unit 5 comprises a hot salt tank 501 connected with the heat storage unit 403, a cold salt tank 502 connected with the heat storage unit 403, and a second heat exchange unit 503 connected with the hot salt tank 501 and the cold salt tank 502, respectively. The cold salt tank 502 is used to store the Hitec molten salt heat storage medium, and during the day when the sunlight is sufficient, the heat-conducting medium in the heat storage unit 403 heats the Hitec molten salt heat storage medium in the cold salt tank 502 to obtain Hitec high-temperature molten salt, which is stored in the hot salt tank 501. At night or on cloudy days, the Hitec high-temperature molten salt stored in the hot salt tank 501 is delivered to the second heat exchange unit 503 to exchange heat with water to generate steam, which enters the carbon capture unit 1 to supply heat to the carbon capture unit, and the heat-exchanged Hitec molten salt is stored in the cold salt tank 502. The Hitec molten salt heat storage medium adopts the Hitec molten salt system, and the Hitec molten salt system adopts NaNO3-KNO3-NaNO2. The mass fraction ratio of NaNO3-KNO3-NaNO2 is 7%:53%:40%, and the heat capacity of NaNO3-KNO3-NaNO2 is 1.56 (KJ·(kg·K) -1 ). The melting point of NaNO3-KNO3-NaNO2 is significantly reduced to 415K compared with the currently widely used Solar Salt molten salt system, which makes the system run more safely and reduces the energy consumption and operation and maintenance cost of the start-up and shutdown process.

[0052] The solar energy auxiliary carbon capture system based on the Hitec high-temperature molten salt heat storage of the embodiment of the application is based on the low matching degree between the load of the power plant carbon capture unit and the load of the solar light and heat unit, in order to fully utilize the energy of the solar light and heat unit and reduce the influence of the steam extraction of the thermal unit of the thermal power plant on the load of the thermal power plant, the Hitec high-temperature molten salt heat storage unit is introduced into the system, heat conducting oil is used as the heat transfer medium between the Hitec high-temperature molten salt heat storage unit and the trough type solar light and heat unit, and the Hitec high-temperature molten salt heat storage unit is applied to heat storage and peak shaving according to the heat load of the carbon capture unit and the light and heat electric conversion efficiency of the trough type solar light and heat unit.

[0053] The above is only the preferred embodiment of the application, and does not limit the application in any form. Any simple modification, equivalent change and modification of the above embodiment according to the technical essence of the application still belongs to the scope of the technical solution of the application.

Claims

1. A solar-assisted carbon capture system based on Hitec high-temperature molten salt thermal storage, characterized in that: It includes: Carbon capture unit; A thermal power plant thermal unit includes a superheater, a reheater connected to the superheater, a steam turbine connected to the outlet of the superheater and the outlet of the reheater respectively, a condenser connected to the steam turbine, a shaft seal heater connected to the condenser, a low-pressure heater unit connected to the shaft seal heater and the condenser respectively, a deaerator connected to the low-pressure heater unit, and a high-pressure heater unit connected to the deaerator. The high-pressure heater unit is connected to the inlet of the superheater. The steam turbine includes eight stages of extraction steam, wherein the first to fourth stages of extraction steam are connected to the high-pressure heater unit and the deaerator respectively, the fifth to eighth stages of extraction steam are connected to the low-pressure heater unit respectively, and the second stage of extraction steam is connected to the inlet of the reheater. A flash heat exchanger is connected to the carbon capture unit and the fifth-stage extraction steam, respectively, so that the fifth-stage extraction steam can supply heat to the carbon capture unit after heat exchange through the flash heat exchanger. The parabolic trough solar thermal unit is connected to the carbon capture unit and the low-pressure heater unit respectively. The parabolic trough solar thermal unit collects solar energy to heat the heat transfer medium and converts the heated heat transfer medium into electrical energy to supply power, and stores the excess heated heat transfer medium that has not been converted into electrical energy. The Hitec high-temperature molten salt thermal storage unit is connected to the carbon capture unit, the trough solar thermal unit, and the low-pressure heater unit. The trough solar thermal unit is also used to transport the stored heated thermally conductive medium to the Hitec high-temperature molten salt thermal storage unit to heat the Hitec molten salt thermal storage medium in the Hitec high-temperature molten salt thermal storage unit. After the carbon capture unit completes its heat exchange, the steam enters the trough solar thermal unit and / or the Hitec high-temperature molten salt thermal storage unit. After being heated by the heat transfer medium and / or the Hitec molten salt thermal storage medium, the steam returns to the low-pressure heater unit, enabling the trough solar thermal unit and the Hitec high-temperature molten salt thermal storage unit to simultaneously or independently heat the carbon capture unit and generate electricity from the thermal power unit of the power plant.

2. The solar-assisted carbon capture system based on Hitec high-temperature molten salt thermal storage according to claim 1, characterized in that, The carbon capture unit includes a water washing tower, an absorption tower connected to the water washing tower, a lean liquid pump connected to the inlet of the absorption tower, a rich liquid pump connected to the outlet of the absorption tower, lean and rich liquid heat exchangers connected to the lean liquid pump and the rich liquid pump respectively, a regeneration tower connected to the lean and rich liquid heat exchangers, a condenser connected to the first outlet of the regeneration tower, a reboiler connected to the second outlet of the regeneration tower and the lean and rich liquid heat exchangers respectively, and a steam-water separator connected to the condenser and the regeneration tower respectively. The first inlet and the first outlet of the reboiler are both connected to the flash heat exchanger.

3. The solar-assisted carbon capture system based on Hitec high-temperature molten salt thermal storage according to claim 1, characterized in that, The steam turbine includes a high-pressure cylinder, an intermediate-pressure cylinder, and a low-pressure cylinder. The low-pressure heater unit includes a first low-pressure heater, a second low-pressure heater, a third low-pressure heater, and a fourth low-pressure heater connected in series. The first low-pressure heater is connected to the deaerator, and the fourth low-pressure heater is connected to the shaft seal heater. The high-pressure heater unit includes a first high-pressure heater, a second high-pressure heater, and a third high-pressure heater connected in series. The first high-pressure heater is connected to the superheater inlet, and the third high-pressure heater is connected to the deaerator. The turbine high-pressure cylinder provides first-stage and second-stage extraction steam, the turbine intermediate-pressure cylinder provides third-stage and fourth-stage extraction steam, and the turbine low-pressure cylinder provides fifth to eighth-stage extraction steam. The first-stage extraction steam is connected to the first high-pressure heater, the second-stage extraction steam is connected to the second high-pressure heater and the reheater inlet, the third-stage extraction steam is connected to the third high-pressure heater, the fourth-stage extraction steam is connected to the deaerator, the fifth-stage extraction steam is connected to the first low-pressure heater, the sixth-stage extraction steam is connected to the second low-pressure heater, the seventh-stage extraction steam is connected to the third low-pressure heater, and the eighth-stage extraction steam is connected to the fourth low-pressure heater.

4. The solar-assisted carbon capture system based on Hitec high-temperature molten salt thermal storage according to claim 3, characterized in that, Both the trough-type solar thermal unit and the Hitec high-temperature molten salt thermal storage unit are connected to the return water pipeline between the first low-pressure heater and the second low-pressure heater.

5. The solar-assisted carbon capture system based on Hitec high-temperature molten salt thermal storage according to claim 1, characterized in that, The parabolic trough solar thermal unit includes a heat collection unit, a first heat exchange unit connected to the heat collection unit, a heat storage unit connected to the first heat exchange unit and the heat collection unit respectively, and a power generation unit connected to the first heat exchange unit. The solar collector unit is used to collect solar-heated heat transfer fluid; The first heat exchange unit is used to exchange heat with the heat collection unit, and then supply the heat to the power generation unit to generate electricity and transfer the excess heat to the heat storage unit for heat storage. The heat storage unit is used to store the heated heat-conducting working fluid. The power generation unit is used to power the pumps of the carbon capture system.

6. The solar-assisted carbon capture system based on Hitec high-temperature molten salt thermal storage according to claim 1, characterized in that, The heat transfer medium used is heat transfer oil.

7. The solar-assisted carbon capture system based on Hitec high-temperature molten salt thermal storage according to claim 5, characterized in that, The Hitec high-temperature molten salt thermal storage unit includes a hot salt tank connected to the thermal storage unit, a cold salt tank connected to the thermal storage unit, and a second heat exchange unit connected to the hot salt tank and the cold salt tank respectively; The cold salt tank is used to store Hitec molten salt as a heat storage medium. The Hitec molten salt is heated by the heat transfer medium transported by the heat storage unit to obtain Hitec high-temperature molten salt. The Hitec high-temperature molten salt is transported to the hot salt tank for storage and to the second heat exchange unit. The second heat exchange unit is used to exchange heat between the Hitec high-temperature molten salt and water to generate steam. The steam enters the carbon capture unit to provide heat for the carbon capture unit. After heat exchange, the Hitec molten salt is transported to the cold salt tank for storage.

8. The solar-assisted carbon capture system based on Hitec high-temperature molten salt thermal storage according to claim 1, characterized in that, The Hitec molten salt adopts the Hitec molten salt system, which is NaNO3-KNO3-NaNO2; The mass fraction ratio of NaNO3-KNO3-NaNO2 is 7%∶53%∶40%; The heat capacity of NaNO3-KNO3-NaNO2 is 1.56 KJ·(kg·K). -1 .

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