Large-temperature-difference high-temperature fused salt and water heat exchange steam generation system

Abstract

The utility model discloses a large-temperature-difference high-temperature fused salt and water heat exchange steam production system. The system comprises a fused salt storage tank, a high-pressure hot water storage tank, a fused salt-water / steam heat exchanger and a steam pocket, the fused salt-water / steam heat exchanger is of a multi-shell-pass spiral coil pipe type heat exchanger structure. A plurality of limiting inner barrels are arranged in a shell barrel to form annular cavities of different levels, a plurality of heat transfer pipes are connected in parallel and wound around a central pipe or the wall of an upper-level fiber inner barrel to form spiral coil pipes, and a plurality of sets of spiral coil pipes are arranged in the annular cavities respectively. A shell side fused salt liquid inlet, a shell side fused salt liquid outlet, a pipe side water inlet and a pipe side steam outlet are formed in the shell cylinder body; the fused salt-water / steam heat exchanger is connected with an outlet and an inlet of the fused salt storage tank and further connected with a water outlet and an inlet of the high-pressure hot water storage tank. High-temperature thermal shock damage of the heat exchanger and pipeline blockage caused by fused salt solidification can be effectively eliminated, membrane boiling of water is inhibited, the heat transfer efficiency is high, and system operation is safe and reliable.

Description

Technical Field

[0001] This utility model relates to the field of molten salt thermal storage technology, and in particular to a high-temperature molten salt heat exchange steam generation system with water under the condition of a large temperature difference of 600-650℃ and an inlet and outlet temperature difference of more than 370℃. Background Technology

[0002] High-temperature molten salts are widely used in thermal power generation and peak shaving, combined heat and power (CHP), heat pump energy storage, deep peak shaving in thermal power plants, and concentrated solar power (CSP). Currently, molten salt thermal storage uses solar salt, which has drawbacks such as a high melting point of 220℃, susceptibility to freezing and clogging of pipelines, a maximum operating temperature below 570℃, small temperature difference in thermal storage, and low thermal storage density. In recent years, with the technological advancement of low-melting-point, high-decomposition-temperature molten salt composite thermal storage materials, composite materials of molten salts with melting points ≤180℃ and decomposition temperatures ≥600℃, such as sodium nitrate, potassium nitrate, sodium nitrite, potassium nitrite, sodium carbonate, calcium carbonate, and calcium chloride, have been successfully developed and are expected to be applied.

[0003] High-temperature molten salt heat exchange with water to generate high-pressure steam is an important application of molten salt thermal storage technology. To improve the thermal efficiency of molten salt, the inlet and outlet temperature difference of the molten salt in the heat exchanger must be maximized. However, the outlet temperature of the molten salt is limited by its melting point; too low a temperature causes the liquid molten salt to solidify and block the pipes. Furthermore, a large heat transfer temperature difference places high demands on the heat exchanger's resistance to stress damage. Traditional U-tube heat exchangers can no longer meet these requirements.

[0004] Chinese invention patent application CN115406283A discloses a single high-temperature molten salt energy storage device, including a heat exchanger, a pressure stabilizing device, and a molten salt circulation pipeline. The heat exchanger includes a shell, cooling medium pipelines, and heating medium pipelines; the cooling medium pipelines and heating medium pipelines are located inside the shell. The pressure stabilizing device includes a molten salt circulation pump and a pressure stabilizing tank, with the pressure stabilizing tank, molten salt circulation pump, and shell connected sequentially through the molten salt circulation pipeline. However, this technology mainly addresses the impact problem of water in the heat exchanger and cannot solve the thermal stress damage to the molten salt heat exchanger caused by large temperature differences.

[0005] Chinese invention patent application CN117739724A discloses a high-temperature molten salt exothermic system. The input end of a hot salt tank is connected to the outlet end of a heat storage system, and the output end is connected to a steam-molten salt heat exchanger and an adjacent hot salt tank. The heat inlet of the steam-molten salt heat exchanger is connected to the hot salt tank, and its heat outlet is connected to both the reheater outlet header and the thermal system. Its air inlet is connected to the gas supply system. The heat inlet of the feedwater-molten salt heat exchanger is connected to the steam-molten salt heat exchanger, its heat outlet is connected to the thermal system, and its cold outlet is connected to a cold salt tank. The inlet end is connected to the feedwater system. Although this technology solves the problem of the small molten salt utilization temperature range by setting the heat inlet end to be connected to the hot salt tank, the heat outlet end to be connected to the boiler low-temperature reheater outlet header and the thermal system respectively, and the air inlet end of the steam molten salt heat exchanger to be connected to the air supply system, it mainly uses the unit steam to heat the molten salt to store heat during the low steam consumption period, and uses the high temperature molten salt to heat the feedwater to supply steam during the peak steam consumption period. However, it cannot solve the thermal stress damage to the molten salt heat exchanger caused by the large temperature difference. Utility Model Content

[0006] This invention addresses the problem of thermal shock damage to heat exchangers caused by high-temperature molten salt above 600℃ and large temperature difference heat exchange conditions above 370℃. It provides a high-temperature, high-pressure molten salt-water / steam heat exchange system with large temperature difference that can effectively eliminate high-temperature thermal shock damage to heat exchangers and molten salt solidification clogging of pipes, suppress film boiling of water, has high heat transfer efficiency, and ensures safe and reliable system operation.

[0007] The large temperature difference in this application refers to a temperature difference of 370℃ or higher, high temperature refers to a temperature of 600℃ or higher, and high pressure refers to a pressure of 10-15 MPa.

[0008] This practical objective is achieved through the following technical solution:

[0009] A high-temperature, high-pressure molten salt-water / steam heat exchange system with large temperature difference includes a molten salt storage tank, a high-pressure hot water storage tank, a molten salt-water / steam heat exchanger, and a steam drum. The molten salt-water / steam heat exchanger is a multi-shell spiral coil heat exchanger structure. Inside the shell, multiple limiting inner cylinders are spaced apart around a central tube. The first limiting inner cylinder and the central tube, the two adjacent limiting inner cylinders, and the outermost limiting inner cylinder and the shell form annular cavities with open ends. Multiple heat transfer tubes are connected in parallel and wound around the central tube or the wall of the upper-level fiber inner cylinder to form spiral coils. Multiple sets of spiral coils... The tubes are respectively installed in the annular cavity; the shell body is provided with a shell-side molten salt liquid inlet, a shell-side molten salt liquid outlet, a tube-side water inlet, and a tube-side steam outlet; the molten salt-water / steam heat exchanger is connected to the outlet and inlet of the molten salt storage tank through the shell-side molten salt liquid inlet and the shell-side molten salt liquid outlet, respectively, and is connected to the outlet and inlet of the high-pressure hot water storage tank through the tube-side water inlet and the tube-side steam outlet, respectively; the tube-side steam outlet is also connected to the steam drum; both the molten salt storage tank and the high-pressure hot water storage tank are equipped with electric heaters; one end of each set of spiral coils is connected to the tube-side water inlet, and the other end is connected to the tube-side steam outlet.

[0010] To further achieve the objectives of this invention, preferably, the molten salt inlet pipe and molten salt outlet pipe of the molten salt-water / steam heat exchanger are respectively equipped with a first molten salt valve and a second molten salt valve; the inlet pipe and outlet pipe of the molten salt-water / steam heat exchanger, which are respectively connected to the outlet and inlet of the high-pressure hot water storage tank, are respectively equipped with a second hot water valve and a first hot water valve; the outlet pipe of the molten salt-water / steam heat exchanger is equipped with a first steam pipeline valve on the pipe connecting to the steam drum; and the pipe connecting the steam drum and the inlet of the high-pressure hot water storage tank is equipped with a second steam pipeline valve.

[0011] Preferably, the molten salt inlet pipe and the water inlet pipe of the molten salt-water / steam heat exchanger are respectively equipped with a molten salt pump and a hot water circulation pump.

[0012] Preferably, the inlet pipe of the high-pressure hot water storage tank is equipped with a water supply valve and a water supply pump.

[0013] Preferably, the molten salt inlet pipe and the molten salt outlet pipe are respectively equipped with a first temperature measuring point and a second temperature measuring point, and a molten salt mass flow meter is also installed in the molten salt inlet pipe of the molten salt-water / steam heat exchanger.

[0014] Preferably, the top of the shell is provided with an exhaust port, and the bottom is provided with a molten salt drain port.

[0015] Preferably, the pipes for the vent and the molten salt drain are respectively equipped with an air vent valve and a molten salt drain valve.

[0016] Preferably, a steam outlet valve is installed on the upper part of the steam drum; a water inlet pressure gauge and a steam outlet pressure gauge are respectively installed on the outlet and inlet pipes of the molten salt-water / steam heat exchanger; the number of limiting inner cylinders is 2-4; and the spiral coil can withstand a pressure of 10-15 MPa.

[0017] The control method of the large temperature difference, high temperature and high pressure molten salt-water / steam heat exchange system is as follows: First, the deoxygenated water in the high-pressure hot water storage tank is electrically heated and then sent to each group of spiral coils to preheat the molten salt-water / steam heat exchanger. When the pressure of the deoxygenated water is heated to 4-6 MPa, high-temperature molten salt at 600-650℃ is sent to the shell-side molten salt liquid inlet of the molten salt-water / steam heat exchanger. The high-temperature molten salt in the shell side exchanges heat with the deoxygenated water in the spiral coils. The outlet temperature of the molten salt is controlled at 200-230℃ to heat the water in the spiral coils to form steam at 10-15 MPa. The steam enters the steam drum.

[0018] Preferably, a portion of the steam is drawn from the steam drum into a high-pressure hot water storage tank to form high-pressure saturated water from the room-temperature deoxygenated water; when the system stops operating, the vent valve and the molten salt drain valve are opened to discharge and collect the high-temperature liquid molten salt from the molten salt-water / steam heat exchanger.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0020] 1) In the present technology, due to the low temperature of molten salt and the small temperature difference of heat transfer, the traditional U-tube heat exchanger structure is generally adopted. However, such heat exchangers are difficult to withstand the long-term normal operation of molten salt at a high inlet temperature of 600℃ and a large temperature difference of more than 370℃. This invention adopts multiple heat transfer tubes connected in parallel and wound around the central tube or the upper-level fiber inner cylinder wall to form a spiral coil. Multiple sets of spiral coils are respectively set in the annular cavity. The spiral coil structure has free contraction characteristics and can expand and contract autonomously with the temperature difference, which can effectively suppress the influence of large temperature difference thermal stress.

[0021] 2) This utility model adopts a multi-shell design. Inside the shell, multiple limiting inner cylinders are spaced apart around the central tube. The first limiting inner cylinder and the central tube, the two adjacent limiting inner cylinders, and the outermost limiting inner cylinder and the shell form annular cavities with both ends connected. Each annular cavity is equipped with a set of spiral coils, which ensures sufficient and rapid heat exchange between the molten salt in the shell side and the deoxygenated water in the tube side, and enhances the convective heat transfer of the molten salt.

[0022] 3) For molten salt with a temperature above 600℃, if it directly enters the heat exchanger to exchange heat with water, and the heat exchanger itself is at room temperature, it will cause a huge thermal shock to the heat exchanger, leading to stress damage. This invention uses an electric heater to heat and pressurize the deoxygenated water in the high-pressure hot water storage tank, and then introduces it into the molten salt-water / steam heat exchanger. When the pressure of the deoxygenated water is controlled to about 4MPa, the heated high-pressure deoxygenated water can preheat the molten salt-water / steam heat exchanger by about 170℃, which can effectively offset the thermal stress damage caused by the high-temperature molten salt to the molten salt-water / steam heat exchanger during system startup, ensuring the system can operate effectively for a longer period of time.

[0023] 4) The solidification temperature of molten salt is usually below 170℃. If the molten salt is below 170℃, it will solidify and block the pipe. This invention controls the outlet temperature of molten salt by countercurrent heat exchange between molten salt and water. Moreover, the molten salt at the outlet of the molten salt heat exchanger directly enters the molten salt heating tank and no longer exchanges heat with water, which greatly reduces the risk of molten salt solidifying and blocking the pipe.

[0024] 5) In operation, this utility model directly mixes the inlet deoxygenated water with steam to form high-temperature water with a pressure of over 4MPa, which then enters the molten salt-water / steam heat exchanger to exchange heat with the high-temperature molten salt. This greatly reduces the heat transfer temperature difference during the heat exchange process, thereby suppressing film boiling of the water and improving heat transfer efficiency.

[0025] 6) This invention effectively solves the problem of reliable operation of molten salt-water / steam heat exchangers with high inlet temperature of 600℃ and large temperature difference of over 370℃. It also solves the damage caused by thermal shock to heat exchangers by large temperature difference and high temperature, and improves heat transfer efficiency, system reliability and safety. It has good practicality. Attached Figure Description

[0026] Figure 1 This is a diagram of a high-temperature molten salt and water heat exchange system with a large temperature difference for steam generation.

[0027] Figure 2 for Figure 1 A schematic diagram of the molten salt-water / steam heat exchanger.

[0028] Figure 3 for Figure 2 Schematic diagram of the spiral coil structure.

[0029] The diagram shows: molten salt storage tank ST1, high-pressure hot water storage tank ST2, molten salt-water / steam heat exchanger H, steam drum BD, molten salt pump P1, hot water circulation pump P2, makeup water pump P3, first molten salt valve V1, second molten salt valve V2, first steam pipeline valve V3, second steam pipeline valve V4, first hot water valve V5, second hot water valve V6, makeup water valve V7, vent valve V8, molten salt drain valve V9, steam outlet valve V10, steam outlet pressure gauge PI1, inlet water pipe pressure gauge PI2, molten salt mass flow meter F, first temperature measuring point T1 and second temperature measuring point T2, shell body 1, central pipe 2, first limiting inner cylinder 3, second limiting inner cylinder 4, third limiting inner cylinder 5, molten salt drain port 6, exhaust port 7, shell-side molten salt liquid inlet 8, shell-side molten salt liquid outlet 9, pipe-side water inlet 10, and pipe-side steam outlet 11. Detailed Implementation

[0030] To better understand this utility model, the following description, in conjunction with the accompanying drawings and embodiments, will further illustrate the utility model, but the implementation of this utility model is not limited thereto.

[0031] For heat exchange conditions involving high-temperature molten salts above 600℃ and large temperature differences above 370℃, this practical application develops a molten salt-water / steam heat exchanger with high heat transfer efficiency and resistance to large temperature difference stress, as well as eliminates high-temperature thermal shock damage to the heat exchanger and molten salt solidification clogging of the pipes. This is a key technology for promoting the engineering application of low-melting-point, high-decomposition-temperature molten salt composite thermal storage materials.

[0032] The core feature of this invention lies in the development of a molten salt-water / steam heat exchanger structure, which is the first multi-shell spiral coil heat exchanger structure. Within the shell, multiple limiting inner cylinders are spaced apart around a central tube. Annular cavities with open ends are formed between the first limiting inner cylinder and the central tube, between adjacent limiting inner cylinders, and between the outermost limiting inner cylinder and the shell. Multiple heat transfer tubes are connected in parallel and wound around the central tube or the wall of the upper-level fiber inner cylinder to form spiral coils. Multiple sets of spiral coils are respectively arranged in the annular cavities. The shell has a shell-side molten salt liquid inlet, a shell-side molten salt liquid outlet, a tube-side water inlet, and a tube-side steam outlet. Furthermore, this invention's heat exchange system features a molten salt-water / steam heat exchanger structure where the tube-side inlet is water and the outlet is steam. This structure allows the molten salt-water / steam heat exchanger to be connected to the outlet and inlet of the molten salt storage tank via the shell-side molten salt liquid inlet and shell-side molten salt liquid outlet, respectively, and to the outlet and inlet of the high-pressure hot water storage tank via the pipe-side water inlet and pipe-side steam outlet, respectively.

[0033] This practical design involves multiple heat transfer tubes connected in parallel and wound around the central tube or the inner wall of the upper-level fiber cylinder to form a spiral coil. Multiple sets of spiral coils are respectively set in annular cavities. The spiral coil structure has free contraction characteristics and can expand and contract autonomously with changes in temperature difference, which can effectively suppress the influence of large temperature difference thermal stress.

[0034] This utility model proposes incorporating an electrically heated high-pressure hot water storage tank into a molten salt / steam heat exchange system. This preheats the heat exchanger during system startup, reducing thermal shock damage caused by the high-temperature molten salt. During operation, it minimizes the temperature difference between the molten salt and water / steam, suppresses film boiling heat transfer, and improves the heat exchanger's heat transfer efficiency and reliability.

[0035] As for the various pumps and valves, pressure gauges and temperature test points that are set up in conjunction with the molten salt storage tank, high-pressure hot water storage tank, molten salt-water / steam heat exchanger and steam drum, they can all be obtained by combining the above-mentioned structural features with the purpose of this invention through experimentation.

[0036] like Figure 1 As shown, a high-temperature, high-pressure molten salt-water / steam heat exchange system with a large temperature difference mainly consists of a molten salt storage tank ST1, a high-pressure hot water storage tank ST2, a molten salt-water / steam heat exchanger H, and a steam drum BD. The molten salt inlet pipe and molten salt outlet pipe of the molten salt-water / steam heat exchanger H are connected to the outlet and inlet of the molten salt storage tank ST1, respectively. The water inlet pipe and outlet pipe of the molten salt-water / steam heat exchanger H are connected to the outlet and inlet of the high-pressure hot water storage tank ST2, respectively. The outlet pipe of the molten salt-water / steam heat exchanger H is also connected to the steam drum BD. Electric heaters are installed in both the molten salt storage tank ST1 and the high-pressure hot water storage tank ST2.

[0037] The large temperature difference, high temperature and high pressure molten salt-water / steam heat exchange system also includes a molten salt pump P1, a hot water circulation pump P2, a makeup water pump P3, a first molten salt valve V1, a second molten salt valve V2, a first steam pipeline valve V3, a second steam pipeline valve V4, a first hot water valve V5, a second hot water valve V6, a makeup water valve V7, a drain valve V8, a molten salt drain valve V9, and a steam outlet valve V10, etc. The molten salt inlet pipe and the molten salt outlet pipe of the molten salt-water / steam heat exchanger H are respectively equipped with a first molten salt valve V1 and a second molten salt valve V2. The molten salt inlet pipe and the molten salt outlet pipe are also respectively equipped with a first temperature measuring point T1 and a second temperature measuring point T2. A molten salt mass flow meter F is also installed in the molten salt inlet pipe of the molten salt-water / steam heat exchanger H. The molten salt-water / steam heat exchanger H, connected to the outlet and inlet of the high-pressure hot water storage tank ST2, is equipped with a second hot water valve V6 and a first hot water valve V5 on its inlet and outlet pipes, respectively. The outlet pipe of the molten salt-water / steam heat exchanger H is also connected to the steam drum BD, with a first steam pipeline valve V3 on its connecting pipe. The steam drum BD is connected to the inlet of the high-pressure hot water storage tank ST2, with a second steam pipeline valve V4 on its connecting pipe. The molten salt inlet pipe and the water inlet pipe of the molten salt-water / steam heat exchanger H are equipped with a molten salt pump P1 and a hot water circulation pump P2, respectively. The water inlet pipe of the high-pressure hot water storage tank ST2 is equipped with a water supply valve V7 and a water supply pump P3. An evacuation valve V8 is installed at the top of the molten salt-water / steam heat exchanger H, and a molten salt drain valve V9 is installed at the bottom. A steam outlet valve V10 is installed on the upper part of the steam drum BD. A pressure gauge PI1 for the inlet water pipe and a pressure gauge PI2 for the steam outlet pipe are installed on the outlet and inlet water pipe of the molten salt-water / steam heat exchanger H, respectively. The molten salt pump P1 needs to withstand a high temperature of over 650℃; the hot water circulation pump P2 and the makeup water pump P3 need to withstand a pressure of over 15MPa; the first molten salt valve V1, the second molten salt valve V2, the vent valve V8, and the molten salt drain valve V9 need to withstand high temperatures; the first steam pipeline valve V3, the second steam pipeline valve V4, the first hot water valve V5, the second hot water valve V6, the makeup water valve V7, and the steam outlet valve V10 all need to withstand high pressure.

[0038] like Figure 2 As shown, the molten salt-water / steam heat exchanger H is a multi-shell spiral coil heat exchanger structure. Inside the shell body 1, multiple limiting inner cylinders are spaced apart around the central tube 2. The first limiting inner cylinder and the central tube, the two adjacent limiting inner cylinders, and the outermost limiting inner cylinder and the shell body 1 respectively form annular cavities with connected ends, as shown in the figure. Figure 3As shown, multiple heat transfer tubes are connected in parallel and wound around the central tube or the upper-level fiber inner cylinder wall to form a spiral coil. Multiple sets of spiral coils are respectively arranged in annular cavities. The shell body 1 is provided with a molten salt drain port 6, an exhaust port 7, a shell-side molten salt liquid inlet 8, and a shell-side molten salt liquid outlet 9. An exhaust port 7 is installed at the top of the molten salt-water / steam heat exchanger H. After operation, the exhaust port 7 is opened to connect to the outside, ensuring that the molten salt-water / steam heat exchanger H is connected to the atmosphere, allowing the remaining liquid molten salt to be discharged through the molten salt drain port 6 at the bottom of the molten salt-water / steam heat exchanger H. A vent valve V8 and a molten salt drain valve V9 are respectively installed on the pipes of the exhaust port 7 and the molten salt drain port 6. One end of the spiral coil is connected to the tube-side water inlet 10, and the other end is connected to the tube-side steam outlet 11. Preferably, the molten salt-water / steam heat exchanger H has a 2-4 stage shell-side structure, such as... Figure 2 The molten salt-water / steam heat exchanger H shown is a four-stage shell-side structure. A first-stage annular space is formed between the central tube and the first limiting inner cylinder 3; a second-stage annular space is formed between the first limiting inner cylinder 3 and the second limiting inner cylinder 4; a third-stage annular space is formed between the second limiting inner cylinder 4 and the third limiting inner cylinder 5; and a fourth-stage annular space is formed between the third limiting inner cylinder 5 and the shell body 1. Molten salt enters the molten salt-water / steam heat exchanger H from the molten salt liquid inlet 8 on the upper shell side of the shell body 1, flowing sequentially through the fourth-stage annular space, the third-stage annular space, the second-stage annular space, and the first-stage annular space, finally exiting from the molten salt liquid outlet 9 on the shell side. High-temperature liquid molten salt flows outside the spiral coil within the annular space, while deoxygenated water flows inside the coil, resulting in counter-current heat exchange between the molten salt and deoxygenated water. The deoxygenated water flows inside the tubes, and by selecting appropriate inner diameter and wall thickness, it can withstand pressures of 10-15 MPa. The spiral coil structure reduces the impact of large temperature difference stress. The spiral flow of deoxygenated water inside the tube enhances boiling heat transfer and suppresses the influence of film boiling heat transfer. Countercurrent heat exchange can improve the heat transfer efficiency of the heat exchanger.

[0039] When the system starts, the molten salt in the molten salt storage tank ST1 is energized and heated to 600-650℃. The first molten salt valve V1 and the second molten salt valve V2 are closed, as are the vent valve V8, the molten salt drain valve V9, the first steam pipeline valve V3, the second steam pipeline valve V4, and the steam outlet valve V10. The first hot water valve V5, the second hot water valve V6, and the water supply valve V7 are opened. The water supply pump P3 is started to send room temperature deoxygenated water into the high-pressure hot water storage tank ST2 and the tube side of the molten salt-water / steam heat exchanger H. After the deoxygenated water is full, the water supply valve V7 is closed and the water supply pump P3 is stopped. The electric heater of the high-pressure hot water storage tank ST2 is turned on to heat the deoxygenated water, and the hot water circulation pump P2 is started until the deoxygenated water is heated to saturated hot water at 4-6MPa. Then the electric heater of the high-pressure hot water storage tank ST2 is stopped. Preheating the molten salt-water / steam heat exchanger H with deoxygenated hot water can prevent thermal shock to the heat exchanger from the high-temperature molten salt, and increase the inlet water temperature to reduce the heat transfer temperature difference of the molten salt-water / steam heat exchanger H, thereby reducing the impact of thermal stress.

[0040] During system operation, close the first hot water valve V5, open the first steam pipeline valve V3 and the second steam pipeline valve V4, open the first molten salt valve V1, the second molten salt valve V2, and the makeup water valve V7, and start the makeup water pump P3. High-temperature molten salt from molten salt storage tank ST1 flows in the shell side of the molten salt-water / steam heat exchanger H, while deoxygenated water from high-pressure hot water storage tank ST2 flows in the tube side. After heat exchange with the high-temperature molten salt, it forms steam at 10-15 MPa and flows into the steam drum BD. If it is necessary to increase the superheat of the steam, the electric heater in the steam drum BD can be started to heat the steam. Open the steam outlet valve V10 to provide steam to the user. Part of the steam flows into the high-pressure hot water storage tank ST2 and mixes directly with the room-temperature deoxygenated water from the makeup water pump P3 to form saturated hot water at 4-6 MPa, which is then sent to the tube side of the molten salt-water / steam heat exchanger H via the hot water circulation pump P2.

[0041] When the system stops, shut down all electric heaters in the system, turn off molten salt pump P1, hot water circulation pump P2, and makeup water pump P3, and close the first molten salt valve V1, the second molten salt valve V2, the first steam pipeline valve V3, the second steam pipeline valve V4, the steam outlet valve V10, the second hot water valve V6, and the makeup water valve V7. Open the vent valve V8 and the molten salt drain valve V9 to discharge and collect the high-temperature liquid molten salt from the molten salt-water / steam heat exchanger H.

[0042] Example 1

[0043] When the system starts, the molten salt in the molten salt storage tank ST1 is energized and heated to 600℃. The first molten salt valve V1 and the second molten salt valve V2 are closed, as are the vent valve V8, the molten salt drain valve V9, the first steam pipeline valve V3, the second steam pipeline valve V4, and the steam outlet valve V10. The first hot water valve V5, the second hot water valve V6, and the water supply valve V7 are opened. The water supply pump P3 is started to send room temperature deoxygenated water into the tube side of the high-pressure hot water storage tank ST2 and the molten salt-water / steam heat exchanger H. After the deoxygenated water is full, the water supply valve V7 is closed and the water supply pump P3 is stopped. The electric heater of the high-pressure hot water storage tank ST2 is turned on to gradually heat the deoxygenated water, and the hot water circulation pump P2 is started to send hot water into the tube side of the heat exchanger H and circulate between the molten salt-water / steam heat exchanger H and the high-pressure hot water storage tank ST2 to preheat the molten salt-water / steam heat exchanger H. When the pressure of steam outlet pressure gauge PI2 is 4MPa, stop the electric heater of high-pressure hot water storage tank ST2.

[0044] During system operation, the first hot water valve V5 is closed, the first steam pipeline valve V3 and the second steam pipeline valve V4 are opened, the first molten salt valve V1, the second molten salt valve V2, and the makeup water valve V7 are opened, and the makeup water pump P3 is started. High-temperature molten salt at 600℃ from molten salt storage tank ST1 flows in the shell side of the molten salt-water / steam heat exchanger H, while 4MPa saturated deoxygenated water from high-pressure hot water storage tank ST2 flows in the tube side and exchanges heat with the 600℃ high-temperature molten salt. The mass flow rate of the molten salt is controlled by adjusting the first molten salt valve V1, so that the molten salt outlet temperature T2 of the molten salt-water / steam heat exchanger H is 230℃, at which point the temperature difference between the molten salt inlet and outlet is 370℃. Adjust the second hot water valve V6 to make the steam outlet pressure gauge PI1 of the molten salt-water / steam heat exchanger H read 10 MPa. Steam at 10 MPa enters the steam drum BD. If it is necessary to increase the superheat of the steam, the electric heater inside the steam drum BD can be activated to heat the steam. Open the steam outlet valve V10 to provide steam to the user. Adjust the second pipeline steam valve V4 to allow some steam to flow into the high-pressure hot water storage tank ST2, where it mixes directly with the room-temperature deoxygenated water supplied from the makeup water pump P3 to form saturated hot water at 4 MPa. This saturated hot water is then sent to the tube side of the molten salt-water / steam heat exchanger H via the hot water circulation pump P2.

[0045] When the system stops, shut down all electric heaters in the system, turn off molten salt pump P1, hot water circulation pump P2, and makeup water pump P3, and close the first molten salt valve V1, the second molten salt valve V2, the first steam pipeline valve V3, the second steam pipeline valve V4, the steam outlet valve V10, the second hot water valve V6, and the makeup water valve V7. Open the vent valve V8 and the molten salt drain valve V9 to discharge and collect the high-temperature liquid molten salt from the molten salt-water / steam heat exchanger H.

[0046] Example 2

[0047] When the system starts, the molten salt in the molten salt storage tank ST1 is energized and heated to 620℃. The first molten salt valve V1 and the second molten salt valve V2 are closed, as are the vent valve V8, the molten salt drain valve V9, the first steam pipeline valve V3, the second steam pipeline valve V4, and the steam outlet valve V10. The first hot water valve V5, the second hot water valve V6, and the water supply valve V7 are opened. The water supply pump P3 is started to send room temperature deoxygenated water into the high-pressure hot water storage tank ST2 and the tube side of the molten salt-water / steam heat exchanger H. After the deoxygenated water is full, the water supply valve V7 is closed and the water supply pump P3 is stopped. The electric heater of the high-pressure hot water storage tank ST2 is turned on to gradually heat the deoxygenated water, and the hot water circulation pump P2 is started to send hot water into the tube side of the molten salt-water / steam heat exchanger H and circulate it between the molten salt-water / steam heat exchanger H and the high-pressure hot water storage tank ST2 to preheat the molten salt-water / steam heat exchanger H. When the pressure of steam outlet pressure gauge PI2 is 5MPa, stop the electric heater of high-pressure hot water storage tank ST2.

[0048] During system operation, the first hot water valve V5 is closed, the first steam pipeline valve V3 and the second steam pipeline valve V4 are opened, the first molten salt valve V1, the second molten salt valve V2, and the makeup water valve V7 are opened, and the makeup water pump P3 is started. High-temperature molten salt at 620℃ from molten salt storage tank ST1 flows in the shell side of the molten salt-water / steam heat exchanger H, while 5MPa saturated deoxygenated water from high-pressure hot water storage tank ST2 flows in the tube side and exchanges heat with the 620℃ high-temperature molten salt. The mass flow rate of the molten salt is controlled by adjusting the first molten salt valve V1, so that the molten salt outlet temperature T2 of the molten salt-water / steam heat exchanger H is 210℃, at which point the temperature difference between the molten salt inlet and outlet is 410℃. Adjust the second hot water valve V6 to make the steam outlet pressure gauge PI1 of the molten salt-water / steam heat exchanger H read 12MPa. Steam at 12MPa enters the steam drum BD. If it is necessary to increase the superheat of the steam, the electric heater inside the steam drum BD can be activated to heat the steam. Open the steam outlet valve V10 to provide steam to the user. Adjust the second pipeline steam valve V4 to allow some steam to flow into the high-pressure hot water storage tank ST2, where it mixes directly with the room-temperature deoxygenated water supplied from the makeup water pump P3 to form saturated hot water at 5MPa. This hot water is then sent to the tube side of the molten salt-water / steam heat exchanger H via the hot water circulation pump P2.

[0049] When the system stops, shut down all electric heaters in the system, turn off molten salt pump P1, hot water circulation pump P2, and makeup water pump P3, and close the first molten salt valve V1, the second molten salt valve V2, the first steam pipeline valve V3, the second steam pipeline valve V4, the steam outlet valve V10, the second hot water valve V6, and the makeup water valve V7. Open the vent valve V8 and the molten salt drain valve V9 to discharge and collect the high-temperature liquid molten salt from the molten salt-water / steam heat exchanger H.

[0050] Example 3

[0051] During system startup, molten salt in molten salt storage tank ST1 is heated to 650℃ by energizing it. First molten salt valve V1 and second molten salt valve V2 are closed, as are vent valve V8, molten salt drain valve V9, first steam pipeline valve V3, second steam pipeline valve V4, and steam outlet valve V10. First hot water valve V5, second hot water valve V6, and water supply valve V7 are opened. Water supply pump P3 is started to deliver room temperature deoxygenated water into the tube side of high-pressure hot water storage tank ST2 and heat exchanger H. After the deoxygenated water is full, water supply valve V7 is closed and water supply pump P3 is stopped. The electric heater of high-pressure hot water storage tank ST2 is turned on to gradually heat the deoxygenated water, and hot water circulation pump P2 is started to deliver hot water into the tube side of heat exchanger H, circulating between heat exchanger H and high-pressure hot water storage tank ST2 to preheat heat exchanger H. When the pressure on steam outlet pressure gauge PI2 reaches 6MPa, the electric heater of high-pressure hot water storage tank ST2 is stopped.

[0052] During system operation, the first hot water valve V5 is closed, the first steam pipeline valve V3 and the second steam pipeline valve V4 are opened, the first molten salt valve V1, the second molten salt valve V2, and the makeup water valve V7 are opened, and the makeup water pump P3 is started. High-temperature molten salt at 620℃ from molten salt storage tank ST1 flows in the shell side of the molten salt-water / steam heat exchanger H, while 6MPa saturated deoxygenated water from high-pressure hot water storage tank ST2 flows in the tube side and exchanges heat with the high-temperature molten salt at 650℃. The mass flow rate of the molten salt is controlled by adjusting the first molten salt valve V1, so that the molten salt outlet temperature T2 of the molten salt-water / steam heat exchanger H is 200℃, at which point the temperature difference between the molten salt inlet and outlet is 450℃. Adjust the second hot water valve V6 to make the steam outlet pressure gauge PI1 of the molten salt-water / steam heat exchanger H read 15MPa. Steam at 15MPa enters the steam drum BD. If it is necessary to increase the superheat of the steam, the electric heater inside the steam drum BD can be activated to heat the steam. Open the steam outlet valve V10 to provide steam to the user. Adjust the second pipeline steam valve V4 to allow some steam to flow into the high-pressure hot water storage tank ST2, where it mixes directly with the room-temperature deoxygenated water supplied from the makeup water pump P3 to form saturated hot water at 6MPa. This saturated hot water is then sent to the tube side of the molten salt-water / steam heat exchanger H via the hot water circulation pump P2.

[0053] When the system stops, shut down all electric heaters in the system, turn off molten salt pump P1, hot water circulation pump P2, and makeup water pump P3, and close the first molten salt valve V1, the second molten salt valve V2, the first steam pipeline valve V3, the second steam pipeline valve V4, the steam outlet valve V10, the second hot water valve V6, and the makeup water valve V7. Open the vent valve V8 and the molten salt drain valve V9 to discharge and collect the high-temperature liquid molten salt from the molten salt-water / steam heat exchanger H.

[0054] From above Figure 1-3 As can be seen from Examples 1-3, the large temperature difference, high temperature and high pressure molten salt-water / steam heat exchange system of the present invention has the following characteristics:

[0055] 1) Traditional U-tube heat exchangers are difficult to withstand long-term normal operation of molten salt at an inlet temperature of 600℃ and a large temperature difference of over 370℃. This invention adopts multiple heat transfer tubes connected in parallel and wound around the central tube or the inner wall of the upper-level fiber cylinder to form a spiral coil. Multiple sets of spiral coils are respectively set in an annular cavity. The spiral coil structure has free contraction characteristics and can expand and contract autonomously with changes in temperature difference, which can effectively suppress the influence of large temperature difference thermal stress.

[0056] 2) This utility model adopts a multi-shell design. Inside the shell, multiple limiting inner cylinders are spaced apart around the central tube. The first limiting inner cylinder and the central tube, the two adjacent limiting inner cylinders, and the outermost limiting inner cylinder and the shell form annular cavities with both ends connected. Each annular cavity is equipped with a set of spiral coils, which ensures sufficient and rapid heat exchange between the molten salt in the shell side and the deoxygenated water in the tube side, and enhances the convective heat transfer of the molten salt.

[0057] 3) This utility model uses an electric heater to heat and pressurize the deoxygenated water in a high-pressure hot water storage tank, and then introduces it into a molten salt-water / steam heat exchanger. When the pressure of the deoxygenated water is controlled to about 4MPa, the heated high-pressure deoxygenated water can preheat the molten salt-water / steam heat exchanger to about 170℃, which can effectively offset the thermal stress damage caused by the high temperature molten salt to the molten salt-water / steam heat exchanger during system startup, and ensure the effective operation of the system for a longer period of time.

[0058] 4) This utility model controls the outlet temperature of molten salt by countercurrent heat exchange between molten salt and water. Moreover, the molten salt at the outlet of the molten salt heat exchanger directly enters the molten salt heating tank and no longer exchanges heat with water, which greatly reduces the risk of molten salt solidification and blockage of the pipeline.

[0059] 5) In operation, this utility model directly mixes the inlet deoxygenated water with steam to form high-temperature water with a pressure of over 4MPa, which then enters the molten salt-water / steam heat exchanger to exchange heat with the high-temperature molten salt. This greatly reduces the heat transfer temperature difference during the heat exchange process, thereby suppressing film boiling of the water and improving heat transfer efficiency.

[0060] 6) This invention effectively solves the problem of reliable operation of molten salt-water / steam heat exchangers with high inlet temperature of 600℃ and large temperature difference of over 370℃. It also solves the damage caused by thermal shock to heat exchangers by large temperature difference and high temperature, and improves heat transfer efficiency, system reliability and safety. It has good practicality.

Claims

1. A high-temperature molten salt and water heat exchange steam generation system with large temperature difference, characterized in that, The system includes a molten salt storage tank, a high-pressure hot water storage tank, a molten salt-water / steam heat exchanger, and a steam drum. The molten salt-water / steam heat exchanger is a multi-shell spiral coil heat exchanger structure. Inside the shell, multiple limiting inner cylinders are spaced apart around a central tube. The first limiting inner cylinder and the central tube, the two adjacent limiting inner cylinders, and the outermost limiting inner cylinder and the shell form annular cavities with open ends. Multiple heat transfer tubes are connected in parallel and wound around the central tube or the wall of the upper-level fiber inner cylinder to form spiral coils. Multiple sets of spiral coils are respectively arranged in the annular cavities. The shell body is equipped with a shell-side molten salt liquid inlet, a shell-side molten salt liquid outlet, a tube-side water inlet, and a tube-side steam outlet. The molten salt-water / steam heat exchanger is connected to the outlet and inlet of the molten salt storage tank through the shell-side molten salt liquid inlet and the shell-side molten salt liquid outlet, respectively, and is connected to the outlet and inlet of the high-pressure hot water storage tank through the tube-side water inlet and the tube-side steam outlet, respectively. The tube-side steam outlet is also connected to the steam drum. Both the molten salt storage tank and the high-pressure hot water storage tank are equipped with electric heaters. One end of each set of spiral coils is connected to the tube-side water inlet, and the other end is connected to the tube-side steam outlet.

2. The high-temperature molten salt and water heat exchange steam generation system with large temperature difference according to claim 1, characterized in that, The molten salt inlet pipe and molten salt outlet pipe of the molten salt-water / steam heat exchanger are respectively equipped with a first molten salt valve and a second molten salt valve; the inlet pipe and outlet pipe of the molten salt-water / steam heat exchanger, which are respectively connected to the outlet and inlet of the high-pressure hot water storage tank, are respectively equipped with a second hot water valve and a first hot water valve; the outlet pipe of the molten salt-water / steam heat exchanger is equipped with a first steam pipeline valve on the pipe connecting to the steam drum; and the pipe connecting the steam drum to the inlet of the high-pressure hot water storage tank is equipped with a second steam pipeline valve.

3. The high-temperature molten salt and water heat exchange steam generation system with large temperature difference according to claim 1, characterized in that, The molten salt inlet pipe and the water inlet pipe of the molten salt-water / steam heat exchanger are respectively equipped with a molten salt pump and a hot water circulation pump.

4. The high-temperature molten salt and water heat exchange steam generation system with large temperature difference according to claim 1, characterized in that, The high-pressure hot water storage tank is equipped with a water supply valve and a water supply pump on its inlet pipe.

5. The high-temperature molten salt and water heat exchange steam generation system with large temperature difference according to claim 2, characterized in that, The molten salt inlet pipe and the molten salt outlet pipe are respectively equipped with a first temperature measuring point and a second temperature measuring point. The molten salt inlet pipe of the molten salt-water / steam heat exchanger is also equipped with a molten salt mass flow meter.

6. The high-temperature molten salt and water heat exchange steam generation system with large temperature difference according to claim 1, characterized in that, The shell body is equipped with an exhaust port at the top and a molten salt drain port at the bottom.

7. The high-temperature molten salt and water heat exchange steam generation system with large temperature difference according to claim 6, characterized in that, The pipes for the exhaust port and the molten salt drain port are respectively equipped with an air vent valve and a molten salt drain valve.

8. The high-temperature molten salt and water heat exchange steam generation system with large temperature difference according to claim 1, characterized in that, A steam outlet valve is installed on the upper part of the steam drum.

9. The high-temperature molten salt and water heat exchange steam generation system with large temperature difference according to claim 1, characterized in that, A pressure gauge for the inlet water pipe and a pressure gauge for the steam outlet are installed on the outlet and inlet water pipes of the molten salt-water / steam heat exchanger, respectively.

10. The high-temperature molten salt and water heat exchange steam generation system with large temperature difference according to claim 1, characterized in that, The number of limiting inner cylinders is 2-4; the spiral coil can withstand a pressure of 10-15MPa.

Images