Thermal power generation transformation system based on small villiaumite cooling high-temperature reactor

Abstract

The invention relates to the technical field of high-temperature nuclear reactor power generation, and discloses a thermal power generation transformation system based on a small villiaumite cooling high-temperature reactor, which comprises a steam power cycle subsystem and a nuclear heat transfer subsystem, the in-reactor working medium FLiBe circulation loop is formed by the small villiaumite cooling high-temperature reactor core and the in-reactor heat exchanger; the steam power circulation subsystem comprises a main heat exchanger, a high-pressure cylinder, a primary reheating heat exchanger, an intermediate-pressure cylinder, a low-pressure cylinder, an intermediate-temperature preheating heat exchanger and a high-temperature preheating heat exchanger which sequentially form circulation through pipelines, circulation is formed among the in-pile heat exchanger, the main heat exchanger and the primary reheating heat exchanger through a secondary loop, and the secondary loop is filled with a flowing working medium FLiNaK; the thermal power generation transformation system based on the small villiaumite cooling high-temperature reactor can be matched with a supercritical / ultra-supercritical unit thermodynamic system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-temperature nuclear reactor power generation, in particular to a thermal power generation modification system based on a small fluorine salt-cooled high-temperature reactor. BACKGROUND

[0002] With the gradual transformation or elimination of traditional coal-fired thermal power units due to their high carbon emissions, there are still a large number of supercritical (SC) and ultra-supercritical (USC) grade thermal power units in service in China. The steam turbine equipment is efficient and mature in technology, and direct retirement will not only cause great waste of resources, but also affect the peak regulation and stability of the power system. Therefore, how to replace the low-carbon or zero-carbon heat source of the unit without replacing the steam turbine and main equipment has become one of the key problems in the green transformation of the current power system.

[0003] In the prior art, some studies have proposed the idea of using nuclear energy, solar energy or molten salt energy storage to replace coal as a heat source. Among them, nuclear energy is considered to be the most promising scheme due to its high stability and high energy density. Small fluorine salt-cooled high-temperature reactor technology has the advantages of modularity, high inherent safety, and high outlet temperature (>700°C), and is suitable as a high-temperature clean heat source.

[0004] However, the coupling of the high-temperature nuclear reactor system and the supercritical / ultra-supercritical unit thermal system has a mismatch problem, especially in the following key aspects: Precise adaptation of the supercritical main steam (≥28MPa, ≥600°C) and reheated steam system (6MPa, ≥600°C) to the temperature level of the heat source; Multi-exchanger heat supply structure design required for multiple heat sources; Therefore, there is an urgent need for a thermal power generation modification system based on a small fluorine salt-cooled high-temperature reactor that is adapted to the supercritical / ultra-supercritical unit thermal system. SUMMARY

[0005] To solve the above technical problems, the present application provides a thermal power generation modification system based on a small fluorine salt-cooled high-temperature reactor, which can adapt to the supercritical / ultra-supercritical unit thermal system.

[0006] The application provides a thermal power generation transformation system based on a small fluorine salt cooled high temperature reactor, which comprises a steam power cycle subsystem and a nuclear heat transfer subsystem; the nuclear heat transfer subsystem comprises a primary loop of a FLiBe circulating loop formed by a small fluorine salt cooled high temperature reactor core and an in-core heat exchanger; the steam power cycle subsystem comprises a main heat exchanger, a high pressure cylinder, a primary reheating heat exchanger, a medium pressure cylinder, a low pressure cylinder, a medium temperature preheating heat exchanger and a high temperature preheating heat exchanger which are sequentially connected by pipelines to form a cycle, a circulating loop is formed between the in-core heat exchanger, the main heat exchanger and the primary reheating heat exchanger, the circulating loop is filled with a flowing working medium FLiNaK, and the high pressure cylinder and the medium temperature preheating heat exchanger are connected by a pipeline.

[0007] Optionally, the exhaust outlet of the high pressure cylinder and the exhaust outlet of the medium pressure cylinder are respectively provided with a pressure compensation valve.

[0008] Optionally, a low temperature preheating heat exchanger is further connected between the low pressure cylinder and the medium temperature preheating heat exchanger, and the medium pressure cylinder, the low temperature preheating heat exchanger and the high temperature preheating heat exchanger are sequentially connected by pipelines.

[0009] Optionally, a condenser and a condenser water pump are further sequentially connected between the low pressure cylinder and the low temperature preheating heat exchanger.

[0010] Optionally, an oxygen remover is further connected between the low temperature preheating heat exchanger and the medium temperature preheating heat exchanger.

[0011] Optionally, the low temperature preheating heat exchanger, the medium temperature preheating heat exchanger, the high temperature preheating heat exchanger and the main heat exchanger are in countercurrent multi-stage series connection.

[0012] Optionally, the in-core heat exchanger is a PCHE heat exchanger, and the main heat exchanger is a PCHE micro-channel tube bundle heat exchanger.

[0013] Optionally, the steam power cycle subsystem further comprises a two-three loop heat exchanger, the two-three loop heat exchanger is connected in series between the primary reheating heat exchanger and the in-core heat exchanger through the two loop, and the two-three loop heat exchanger and the high temperature preheating heat exchanger form a cycle through the three loop, and the three loop is filled with a flowing working medium CO3LiNaK.

[0014] Optionally, the outlet temperature of the in-core heat exchanger is 650-670 DEG C, the outlet temperature of the main heat exchanger is 630-650 DEG C, the outlet temperature of the primary reheating heat exchanger is 600-650 DEG C, and the outlet temperature of the two-three loop heat exchanger is 450-480 DEG C.

[0015] Optionally, a primary loop pump is connected in series on the primary loop, a two loop pump is connected in series on the two loop, and a three loop pump is connected in series on the three loop.

[0016] Compared with the prior art, the technical scheme provided by the embodiment of the application has the following advantages: The embodiment of the present application provides a small fluorine salt cooling high temperature reactor based thermal power generation transformation system, a working medium FLiBe in a small fluorine salt cooling high temperature reactor, after being heated in a small fluorine salt cooling high temperature reactor core, the working medium FLiBe is discharged into a in-core heat exchanger to release heat, and then is transported back to the small fluorine salt cooling high temperature reactor core, the outlet temperature of the small fluorine salt cooling high temperature reactor core is 700 DEG C, FLiBe is used as a main coolant, and the small fluorine salt cooling high temperature reactor is operated in a high temperature interval of 500-700 DEG C, the high heat capacity characteristic of the small fluorine salt cooling high temperature reactor ensures that the small fluorine salt cooling high temperature reactor core has a high heat flow density output, the working medium FLiNaK in a secondary loop is used for heat exchange with the FLiBe in the in-core heat exchanger, and then the working medium FLiNaK is used for heating high-temperature preheated supercritical water in a main heat exchanger to obtain main steam, so that the main steam temperature reaches 650 DEG C / 30 MPa (a supercritical state), the temperature difference between the primary loop and the secondary loop is only 50 DEG C, the molten salt heat transfer temperature difference is small (≤100 DEG C), and the heat loss is lower than that of a coal-fired boiler (the traditional boiler flue gas loss is greater than or equal to 10 %), the working medium FLiNaK is selected as an intermediate working medium in the secondary loop, the operation temperature is 450 DEG C-600 DEG C, and the working medium FLiNaK is highly compatible with the FLiBe through the in-core heat exchanger, even if a break accident occurs, the two molten salts are mixed and still remain in a liquid state, the risk of melting the small fluorine salt cooling high temperature reactor core is avoided, then the working medium FLiNaK is discharged into a primary reheating heat exchanger to release heat, a steam system starts from a main steam pipeline, is generated by FLiNaK molten salt main heating, the main steam with a temperature of 650 DEG C and a pressure of 30 MPa enters a high-pressure cylinder, after work, the temperature is reduced to 450 DEG C, and the pressure is reduced to 8 MPa-10 MPa, part of the extracted gas enters a medium-temperature preheating heat exchanger to release heat, and the other part is heated to 600 DEG C by FLiNaK in the primary reheating heat exchanger, and then enters a medium-pressure cylinder, after entering the medium-pressure cylinder, part of the extracted gas enters the high-temperature preheating heat exchanger to release heat, and the other part enters a low-pressure cylinder to continue to work, the steam temperature is reduced to 50 DEG C, and the pressure is reduced to 5 kPa, and one cycle is completed. The FLiBe / FLiNaK is operated at normal pressure (0.3-0.5 MPa), and is quickly solidified when leaking, so that there is no explosion risk, the original unit equipment such as the high-pressure cylinder, the medium-pressure cylinder, the low-pressure cylinder and the regenerative heater is retained, the original power station grid connection interface is directly used, only the boiler is replaced by a nuclear island + molten salt heat exchanger group and supplementary heat exchange equipment, the original power plant is slightly changed, 60 % of the transformation cost is saved, through precise coupling of the nuclear heat source and the steam cycle, the high efficiency of the original high-parameter steam cycle is retained, and the high-temperature safety characteristic of the fluorine salt cooling reactor is also used, so that a feasible path is provided for the power application of the small modular high temperature reactor; the transformation cycle is shortened to 12 months (only 1 / 3 of a newly built nuclear power station), nuclear energy completely replaces the traditional coal-fired power station, and CO2 / SO2 / NOx emissions are eliminated. The annual CO2 emission reduction is about 300,000 tons / 100 MW unit, the fuel cost is reduced by 80 %, the thermal efficiency reaches 53 % (8 % higher than 45 % of the coal-fired power station), and the equivalent amount of standard coal saved is about 30,000 tons / 100 MW unit. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 A structure schematic diagram of a small fluorine salt cooling high temperature reactor based thermal power generation reconstruction system provided by the embodiment of the present application.

[0018] REFERENCE SIGNS: 1, in-vessel heat exchanger; 2, small fluorine salt cooling high temperature reactor core; 3, primary loop pump; 4, main heat exchanger; 5, primary reheating heat exchanger; 6, secondary and tertiary loop heat exchanger; 7, high pressure cylinder; 8, medium pressure cylinder; 9, low pressure cylinder; 10, condenser; 11, condensate pump; 12, medium temperature preheating heat exchanger; 13, deaerator; 14, low temperature preheating heat exchanger; 15, high temperature preheating heat exchanger; 16, tertiary loop pump; 17, secondary loop pump; 18, in-vessel working medium FLiBe; 19, working medium FLiNaK; 20, main steam; 21, high pressure cylinder extraction; 22, high pressure cylinder exhaust; 23, primary reheating supercritical water; 24, medium pressure cylinder exhaust; 25, low pressure cylinder exhaust; 26, condensate water; 27, pump outlet sub-cooled water; 28, low temperature preheating supercritical water; 29, deaerated water; 30, medium temperature preheating supercritical water; 31, high temperature preheating supercritical water; 32, high pressure extraction after heat exchange; 33, medium pressure cylinder extraction; 34, medium pressure extraction after heat exchange; 35, working medium CO3LiNaK. DETAILED DESCRIPTION

[0019] One specific embodiment of the present application will be described in detail below with reference to the accompanying drawings, but it should be understood that the protection scope of the present application is not limited by the specific embodiment.

[0020] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential" and the like are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the technical solutions of the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0021] The present application will be described below through several specific embodiments. In order to keep the following description of the embodiments of the present application clear and concise, the detailed description of known functions and known components can be omitted. When any component of the embodiments of the present application appears in more than one figure, the component can be indicated by the same reference numeral in each figure.

[0022] As Figure 1As shown, the embodiment of the present application provides a power generation transformation system of thermal power based on a small fluorine salt cooled high temperature reactor, which comprises a steam power cycle subsystem and a nuclear heat transfer subsystem; the nuclear heat transfer subsystem comprises a primary loop of a loop circuit of a nuclear working medium FLiBe 18 formed by a small fluorine salt cooled high temperature reactor core 2 and an in-core heat exchanger 1; the steam power cycle subsystem comprises a main heat exchanger 4, a high pressure cylinder 7, a primary reheating heat exchanger 5, a medium pressure cylinder 8, a low pressure cylinder 9, a medium temperature preheating heat exchanger 12 and a high temperature preheating heat exchanger 15 which are sequentially connected by pipelines to form a circulation, a circulation is formed between the in-core heat exchanger 1, the main heat exchanger 4 and the primary reheating heat exchanger 5 by a secondary loop, the secondary loop is filled with a flowing working medium FLiNaK 19, and the high pressure cylinder 7 and the medium temperature preheating heat exchanger 12 are connected by a pipeline.

[0023] The working process is as follows: The small fluorine salt cooled high temperature reactor core 2 is heated to heat the nuclear working medium FLiBe 18, the nuclear working medium FLiBe 18 is discharged into the in-core heat exchanger 1 to release heat, and then is transported back to the small fluorine salt cooled high temperature reactor core 2; the secondary loop working medium FLiNaK (fluorine lithium sodium potassium) 19 exchanges heat with the FLiBe 18 in the in-core heat exchanger 1, and then enters the main heat exchanger 4 to heat the main steam 20, enters the primary reheating heat exchanger 5 to release heat, the high temperature preheating supercritical water 31 is heated in the main heat exchanger 4 to obtain the main steam 20, enters the high pressure cylinder 7 to do work, the high pressure cylinder 7 is extracted in the middle part to obtain the high pressure cylinder extraction 21, the high pressure cylinder extraction 21 enters the medium temperature preheating heat exchanger 12 to release heat, the high pressure extraction 32 after heat exchange is mixed with the supercritical water heated in the medium temperature preheating heat exchanger 12, and then flows into the high temperature preheating heat exchanger 15, after being heated, flows back to the main heat exchanger 4, the high pressure cylinder exhaust 22 after the high pressure cylinder 7 does work enters the primary reheating heat exchanger 5 to be reheated, and then enters the medium pressure cylinder 8 to do work, the medium pressure cylinder 8 is extracted in the middle part, the medium pressure cylinder extraction 33 is mixed with the medium temperature preheating supercritical water 30 flowing out of the medium temperature preheating heat exchanger 12, and then flows into the high temperature preheating heat exchanger 15 to absorb heat. The medium pressure cylinder exhaust 24 after the medium pressure cylinder 8 does work enters the low pressure cylinder 9 to continue to do work, the low pressure cylinder exhaust 25 after the low pressure cylinder 9 does work enters the high temperature preheating heat exchanger 15 again to circulate. The primary loop fluorine salt (FLiBe) and the secondary loop fluorine salt (FLiNaK) are operated at normal pressure (0.3-0.5 MPa), and are quickly solidified when leaking, have high chemical stability, very low steam pressure, and no explosion risk even if leaking, which is superior to the high temperature and high pressure flue gas system of a coal-fired boiler. The primary reheating and secondary extraction heat exchange make the system thermal efficiency reach more than 45% (about 42% for a supercritical coal-fired unit), the extraction mixed flow process reduces the reheating end loss by about 3%-5%, completely replaces the coal-fired boiler, eliminates SO2, NOx and CO2 emissions, and meets the clean energy development demand.

[0024] The embodiment of the application provides a small fluorine salt cooling high temperature reactor based thermal power generation transformation system, a working medium FLiBe in a small fluorine salt cooling high temperature reactor, after being heated in a small fluorine salt cooling high temperature reactor core, the working medium FLiBe is discharged into a in-core heat exchanger to release heat, and then is transported back to the small fluorine salt cooling high temperature reactor core, the outlet temperature of the small fluorine salt cooling high temperature reactor core is 700 DEG C, FLiBe is used as a main coolant, and the small fluorine salt cooling high temperature reactor is operated in a high temperature interval of 500-700 DEG C, the high heat capacity characteristic of the small fluorine salt cooling high temperature reactor ensures that the small fluorine salt cooling high temperature reactor core has a high heat flow density output, the working medium FLiNaK in a secondary circuit is used for heat exchange with the FLiBe in the in-core heat exchanger, and then the working medium FLiNaK is used for heating high-temperature preheated supercritical water in a main heat exchanger to obtain main steam, so that the main steam temperature reaches 650 DEG C / 30 MPa (a supercritical state), the temperature difference is only 50 DEG C, the molten salt heat transfer temperature difference is small (≤100 DEG C), and the heat loss is lower than that of a coal-fired boiler (the traditional boiler flue gas loss is ≥10 %), the working medium FLiNaK is selected as an intermediate working medium in the secondary circuit, the operation temperature is 450 DEG C-600 DEG C, and the working medium FLiNaK is heat-exchanged with the primary circuit through the in-core heat exchanger, the physical properties of the working medium FLiNaK are highly compatible with the FLiBe, even if a break accident occurs, the two molten salts are mixed and still remain in a liquid state, the risk of the small fluorine salt cooling high temperature reactor core melting is avoided, then the working medium FLiNaK is discharged into a primary reheating heat exchanger to release heat, a steam system starts from a main steam pipeline, is generated by FLiNaK molten salt main heating, the main steam of 650 DEG C and 30 MPa enters a high-pressure cylinder, after work, the temperature is reduced to 450 DEG C, and the pressure is reduced to 8 MPa-10 MPa, part of the extracted gas enters a medium-temperature preheating heat exchanger to release heat, and the other part is heated to 600 DEG C by FLiNaK in the primary reheating heat exchanger, and the pressure is 6 MPa, and then enters a medium-pressure cylinder, after entering the medium-pressure cylinder, part of the extracted gas enters the high-temperature preheating heat exchanger to release heat, and the other part enters a low-pressure cylinder to continue work, the steam temperature is reduced to 50 DEG C, and the pressure is reduced to 5 kPa, and one cycle is completed. The FLiBe / FLiNaK is operated at normal pressure (0.3-0.5 MPa), and is quickly solidified when leaking, so that the explosion risk is avoided, the original unit equipment such as the high-pressure cylinder, the medium-pressure cylinder, the low-pressure cylinder and the regenerative heater is retained, the original power station grid connection interface is directly used, only the boiler is replaced by a nuclear island and a molten salt heat exchanger group and supplementary heat exchange equipment, the original power plant is slightly changed, 60 % of the transformation cost is saved, through precise coupling of the nuclear heat source and the steam cycle, the high efficiency of the original high-parameter steam cycle is retained, and the high-temperature safety characteristic of the fluorine salt cooling reactor is also used, so that a feasible path is provided for the power application of the small modular high temperature reactor; the transformation period is shortened to 12 months (only 1 / 3 of a newly built nuclear power station), nuclear energy completely replaces the traditional coal, and CO2 / SO2 / NOx emissions are eliminated. The annual CO2 emission reduction is about 300,000 tons / 100 MW unit, the fuel cost is reduced by 80 %, the thermal efficiency reaches 53 % (8 % higher than 45 % of the coal-fired power plant), and the equivalent amount of standard coal saved is about 30,000 tons / 100 MW unit.

[0025] Optionally, the high-pressure cylinder 7 and the medium-pressure cylinder 8 are respectively provided with a pressure compensation valve, and the heat exchange temperature difference is dynamically adjusted to ensure that the main steam 20 is stable at 28-31 MPa / 600-620℃.

[0026] Optionally, the low-pressure cylinder 9 is further connected with a low-temperature preheating heat exchanger 14, and the medium-pressure cylinder 8, the low-temperature preheating heat exchanger 14 and the high-temperature preheating heat exchanger 15 are sequentially connected by pipelines.

[0027] The high-pressure cylinder exhaust 22 of the high-pressure cylinder 7 after work enters the once-reheating heat exchanger 5 for reheating, and then enters the medium-pressure cylinder 8 for work. The medium-pressure cylinder 8 is extracted in the middle part, and the medium-pressure cylinder extraction 33 enters the low-temperature preheating heat exchanger 14 to heat the low-temperature water entering the system.

[0028] Optionally, the low-pressure cylinder 9 is further sequentially connected with the condenser 10 and the condensate pump 11.

[0029] The high-pressure cylinder exhaust 22 of the high-pressure cylinder 7 after work enters the once-reheating heat exchanger 5 for reheating, and then enters the medium-pressure cylinder 8 for work. The medium-pressure cylinder 8 is extracted in the middle part, and the medium-pressure cylinder extraction 33 enters the low-temperature preheating heat exchanger 14 to heat the water of the supercritical feedwater pump 11. After heat exchange, the medium-pressure extraction 34 after heat release is mixed with the medium-temperature preheating supercritical water 30 flowing out of the medium-temperature preheating heat exchanger 12, and then flows into the high-temperature preheating heat exchanger 15 for heat absorption. The medium-pressure cylinder exhaust 24 of the medium-pressure cylinder 8 after work enters the low-pressure cylinder 9 for further work. The low-pressure cylinder exhaust 25 after work of the low-pressure cylinder 9 enters the condenser 10 for condensation. After condensation, the condensate 26 enters the condensate pump 11 for pressurization. The pump outlet sub-cooled water 27 after pressurization flows into the low-temperature preheating heat exchanger 14 for heating. The low-temperature preheating supercritical water 28 enters the medium-temperature preheating heat exchanger 12 for heating, and then is mixed with the gas after heat release of the two extractions, and then flows into the high-temperature preheating heat exchanger 15 for further heating, and finally flows into the main heat exchanger 4 for heating, forming a closed loop.

[0030] Optionally, the low-temperature preheating heat exchanger 14 and the medium-temperature preheating heat exchanger 12 are further connected with a deaerator 13. The low-temperature preheating supercritical water 28 flows into the deaerator 13 for deaeration, and the deaerated water 29 after deaeration enters the medium-temperature preheating heat exchanger 12 for heating.

[0031] Optionally, the low-temperature preheating heat exchanger 14, the medium-temperature preheating heat exchanger 12, the high-temperature preheating heat exchanger 15 and the main heat exchanger 4 are in countercurrent multi-stage series, and the cold and hot fluids flow in opposite directions. Compared with parallel flow, a larger average temperature difference (ΔT) can be formed to improve the heat transfer efficiency. The multiple heat exchange units are sequentially connected, and the outlet fluid of the previous stage is used as the inlet of the next stage to realize the step-by-step utilization of heat.

[0032] Optionally, the in-pile heat exchanger 1 is a PCHE heat exchanger, and the main heat exchanger 4 is a PCHE micro-channel tube bundle heat exchanger, which exchanges heat with supercritical water through a partitioned micro-channel tube bundle.

[0033] Optionally, the steam power cycle subsystem further comprises a two-three loop heat exchanger 6, and the two-three loop heat exchanger 6 is connected in series between the once-reheated heat exchanger 5 and the in-pile heat exchanger 1 through the two loop, and the two-three loop heat exchanger 6 and the high-temperature preheating heat exchanger 15 form a circulation through the three loop, and the three loop is filled with a flowing working medium CO3LiNaK35.

[0034] The three loop (low-temperature section heat supply-frost prevention loop): the three loop adopts a working medium CO3LiNaK35 (Li2CO3-Na2CO3-K2CO3) low-melting-point molten salt (solidification point < 400 ℃), and operates at 400-550 ℃, extracts waste heat from the two loop through a countercurrent multi-stage series heat exchanger, and is used for heating and supplementing, completely avoiding the solidification risk of FLiNaK at the low-temperature section. The two loop working medium FLiNaK19 exchanges heat with the in-pile working medium FLiBe in the in-pile heat exchanger 1, then enters the main heat exchanger 4 to heat the main steam 20, enters the once-reheated heat exchanger 5 to release heat, and then enters the two-three loop heat exchanger 6 to exchange heat with CO3LiNaK. The working medium CO3LiNaK35 exchanges heat with FLiNaK in the one-two loop heat exchanger 6, and then enters the high-temperature preheating heat exchanger 15 to release heat. After releasing heat, it enters the two-three loop heat exchanger 6, and the high-temperature preheating heat exchanger 15 preheats water from 300 ℃ to 400 ℃, improving the heat recovery efficiency. The three loop is arranged in the two-three loop heat exchanger 6 before entering the 4 main heat exchanger, which makes up for the problem of insufficient water temperature after heat recovery, and avoids the solidification caused by direct heating of FLiNaK.

[0035] Optionally, the outlet temperature of the in-pile heat exchanger 1 is 650-670 ℃, the outlet temperature of the main heat exchanger 4 is 630-650 ℃, the outlet temperature of the once-reheated heat exchanger 5 is 600-650 ℃, and the outlet temperature of the two-three loop heat exchanger 6 is 450-480 ℃.

[0036] Optionally, a one loop pump 3 is connected in series on the one loop, a two loop pump 17 is connected in series on the two loop, and a three loop pump 16 is connected in series on the three loop.

[0037] The high-pressure cylinder exhaust 21 preheats the deoxygenated water 29 in the medium-temperature preheating heat exchanger 12, and the medium-pressure cylinder exhaust 33 preheats the pump outlet sub-cooled water 27 in the low-temperature preheating heat exchanger 14, which gradually supplies heat according to the temperature gradient through the molten salt-water heat exchanger network.

[0038] System architecture design The embodiment of the application takes a small fluorine salt cooled high temperature reactor (outlet temperature 700°C) as a core heat source, replaces a traditional supercritical coal-fired boiler, connects a nuclear reactor and a steam power cycle system through fluorine salt (FLiNaK, FLiBe) as a heat transfer medium, and realizes efficient conversion of "nuclear heat-steam-mechanical energy". The system retains the original steam cycle architecture of twice reheat + multi-stage preheating, replaces fossil fuel combustion with a nuclear reactor heat source, and realizes high temperature energy transmission through a molten salt heat exchange network.

[0039] Energy path: High temperature heat generated by the nuclear energy reactor is first absorbed by the primary loop FLiBe (lithium beryllium fluoride salt, working temperature 500°C-700°C), and heat is transferred to the secondary loop FLiNaK (lithium sodium potassium fluoride salt, working temperature 450-650°C) through the in-core heat exchanger 1. The secondary loop FLiNaK uses heat energy to heat water to a main steam state of 650°C, 28MPa-30MPa, and provides heat for a reheater after the high pressure cylinder exhaust, reheating the intermediate pressure steam from 450°C to 600°C, 6MPa. The tertiary loop CO3LiNaK (carbonate mixed salt, working temperature 400-550°C) is supplemented and heated to 500°C through the two-tertiary loop heat exchanger 6 after the high temperature preheating heat exchanger 15.

[0040] The three-stage heat exchange system realizes optimal design of thermal efficiency through energy grading, wherein FLiBe is used for the main steam section, FLiNaK serves both the reheating and high pressure regenerative sections, and CO3LiNaK serves the low temperature regenerative section, ensuring thermal matching of heat sources and demands at each stage.

[0041] Material path: The water vapor-condensed water circulation system constitutes the main circulation of the entire thermal power conversion device. In the initial state of the system, the condensate pump 11 pressurizes the condensed water 26 at 30°C, 5kPa to 50°C, 0.5MPa, and the water flow enters the low temperature preheating heat exchanger 14, which is heated to 150°C, 1.5MPa low temperature preheating supercritical water 28, and then enters the deaerator 13, which is deoxygenated to form deoxygenated water 29, which further enters the medium temperature preheating heat exchanger 12, which is heated to 400°C, 15MPa, and then the water flow enters the high temperature preheating heat exchanger 15, which is heated to 500°C, 20MPa by the high temperature heat of CO3LiNaK, and finally the water flow enters the main heat exchanger 4 and is heated to 650°C, 30MPa.

[0042] The steam system starts from the main steam pipeline, is heated by the main heat exchanger 4 to generate 650°C, 30MPa main steam 20 into the high-pressure cylinder 7, and after work, the temperature is reduced to 450°C, and the pressure is reduced to 8MPa-10MPa. Part of the high-pressure cylinder extraction 21 enters the medium-temperature preheating heat exchanger 12 to release heat, and the other part of the high-pressure cylinder exhaust 22 is heated again to 600°C by FLiNaK through the first reheat heat exchanger 5, and the supercritical water 23 after the first reheat at a pressure of 6MPa enters the medium-pressure cylinder 8. After entering the medium-pressure cylinder 8, part of the medium-pressure cylinder extraction 33 enters the low-temperature preheating heat exchanger 14 to release heat, and the other part of the medium-pressure cylinder exhaust 24 enters the low-pressure cylinder 9 to continue to work, and the steam temperature is reduced to 50°C, and the pressure is reduced to 5kPa to form the low-pressure cylinder exhaust 25, and finally condensed into liquid water in the condenser 11, completing a cycle period.

[0043] The three molten salt circuits exchange heat with the water vapor system through their respective dedicated heat exchangers without material exchange. Each molten salt circuit circulates within its own closed system, maintaining flow through pumps or natural circulation. The system design takes into account the freezing points and temperature adaptability of different molten salts, with FLiNaK suitable for high-temperature areas in the main steam section and CO3LiNaK suitable for medium and low-temperature areas. This separation of the reactor and power generation prevents large-scale accidents and prevents salt solidification and blockage during operation. Small fluorine salt-cooled high-temperature reactor (outlet temperature 700°C): Through the three-circuit molten salt system (FLiBe→FLiNaK→CO3LiNaK), heat is transferred in stages, which can increase the main steam parameters to 650°C / 30MPa (supercritical state) while maximizing heat utilization.

[0044] Molten salt heat exchange design: The CO3LiNaK three-circuit is dedicated to preheating in the 300-400°C low-temperature section to avoid the risk of high-temperature molten salt solidification.

[0045] CO3LiNaK has a melting point of <400°C, completely avoiding low-temperature solidification and blockage. Radioactivity is 100% enclosed in the primary circuit; molten salt has no risk of combustion and explosion; the system operates at normal pressure, with safety exceeding that of coal-fired boilers and traditional nuclear power plants.

[0046] The energy density of uranium fuel is 2,800,000 times that of coal. The annual fuel cost of a 100MW unit decreases from 120 million yuan for coal to 20 million yuan (uranium fuel + molten salt replenishment).

[0047] The freezing point of the secondary circuit working medium FLiNaK is relatively high, and direct heating of the condensate water can easily solidify or become viscous, reducing flowability and blocking the pipeline. The freezing point of the three-circuit working medium CO3LiNaK is relatively low, which can ensure good flowability when exchanging heat with water at a lower temperature. The three-circuit can preheat the low-temperature pump outlet sub-cooled water.

[0048] The FLiNaK chemistry of the secondary loop is more reactive, such as pipe rupture can react with water to cause serious accidents, and CO3LiNaK is carbonate, even if the heat exchanger pipe ruptures, it will be directly cooled and then dissolved in water, which is safer.

[0049] The above merely illustrates the specific embodiments of the present application, but the embodiments of the present application are not limited thereto, and any variations that can be thought of by those skilled in the art shall fall within the protection scope of the present application.

Claims

1. A thermal power generation retrofit system based on a small-sized fluorosalt-cooled high-temperature reactor, characterized by, It includes a steam power cycle subsystem and a nuclear heat transfer subsystem; The nuclear heat transfer subsystem includes: a loop of the in-core working fluid FLiBe (18) circulation loop formed by a small fluorine salt cooled high-temperature reactor core (2) and an in-core heat exchanger (1); The steam power cycle subsystem includes: a main heat exchanger (4), a high-pressure cylinder (7), a reheat heat exchanger (5), a medium-pressure cylinder (8), a low-pressure cylinder (9), a medium-temperature preheating heat exchanger (12), and a high-temperature preheating heat exchanger (15) that are connected in sequence by pipelines. The in-pile heat exchanger (1), the main heat exchanger (4), and the reheat heat exchanger (5) are connected by a second loop, which is filled with a flowing working fluid FLiNaK (19). The high-pressure cylinder (7) and the medium-temperature preheating heat exchanger (12) are connected by pipelines.

2. A fossil power plant retrofit system based on small fluorosalt cooled high temperature reactor according to claim 1, characterized in that, Each of the high-pressure cylinder (7) and the medium-pressure cylinder (8) is equipped with a pressure compensation valve at its exhaust outlet.

3. A fossil power plant retrofit system based on small fluorosalt cooled high temperature reactor according to claim 1, characterized in that, A low-temperature preheating heat exchanger (14) is also connected between the low-pressure cylinder (9) and the medium-temperature preheating heat exchanger (12). The medium-pressure cylinder (8), the low-temperature preheating heat exchanger (14), and the high-temperature preheating heat exchanger (15) are connected in sequence through pipelines.

4. A fossil power plant retrofit system based on small fluosalt cooled high temperature reactor according to claim 3, characterized in that, A condenser (10) and a condensate pump (11) are connected in sequence between the low-pressure cylinder (9) and the low-temperature preheating heat exchanger (14).

5. A fossil power plant retrofit system based on small fluosalt cooled high temperature reactor according to claim 3, characterized in that, A deaerator (13) is also connected between the low-temperature preheating heat exchanger (14) and the medium-temperature preheating heat exchanger (12).

6. A fossil power plant retrofit system based on small fluorosalt cooled high temperature reactor as claimed in claim 3 wherein, The low-temperature preheating heat exchanger (14), the medium-temperature preheating heat exchanger (12), the high-temperature preheating heat exchanger (15) and the main heat exchanger (4) are connected in a counter-current multi-stage series.

7. A fossil power plant retrofit system based on small fluosalt cooled high temperature reactor according to claim 1, characterized in that, The in-pile heat exchanger (1) is a PCHE heat exchanger, and the main heat exchanger (4) is a PCHE microchannel tube bundle heat exchanger.

8. A fossil power plant retrofit system based on small fluosalt cooled high temperature reactor according to claim 1, characterized in that, The steam power cycle subsystem also includes a second and third loop heat exchanger (6). The first reheat heat exchanger (5) and the in-pile heat exchanger (1) are connected in series via a second loop. The second and third loop heat exchangers (6) and the high-temperature preheating heat exchanger (15) form a cycle through a third loop. The third loop is filled with a flowing working fluid CO3LiNaK (35).

9. A small-sized fluorosalt-cooled fast reactor-based thermal power generation retrofit system according to claim 8, characterized by The outlet temperature of the in-core heat exchanger (1) is 650℃-670℃, the outlet temperature of the main heat exchanger (4) is 630℃-650℃, the outlet temperature of the primary reheat heat exchanger (5) is 600℃-650℃, and the outlet temperature of the secondary and tertiary loop heat exchangers (6) is 450℃-480℃.

10. A thermal power generation retrofit system based on a small fluorine salt-cooled high-temperature reactor as described in claim 8, characterized in that, A first-loop pump (3) is connected in series in the first loop, a second-loop pump (17) is connected in series in the second loop, and a third-loop pump (16) is connected in series in the third loop.

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