Multi-stage filtering and purifying integrated device for low-melting-point ternary nitro molten salt

Abstract

The invention provides a multi-stage filtration and purification integrated device for low-melting-point ternary nitro fused salt, and particularly relates to the technical field of mechanical automation, the multi-stage filtration and purification integrated device comprises a pretreatment module, a multi-stage filtration module and a deep purification module which are sequentially communicated according to the flowing direction of fused salt, and each module is hermetically connected through a heat tracing pipeline and is matched with an auxiliary integrated system; a complete purification flow channel is formed. The pretreatment module realizes fused salt melting constant temperature, rough filtration and dehydration; the multi-stage filtering module is used for removing impurities stage by stage through a ceramic membrane, a metal fiber membrane and a composite adsorbent; and the deep purification module is used for removing volatile impurities, homogenizing and caching. According to the low-melting-point ternary nitro molten salt purification device, the purity and the use stability of the low-melting-point ternary nitro molten salt are effectively improved, and the purification requirements of related molten salt application scenes are met.

Description

TECHNICAL FIELD

[0001] The application provides a multi-stage filtering and purifying integrated device for low-melting ternary nitro-based molten salt, and particularly relates to the technical field of mechanical automation. BACKGROUND

[0002] The low-melting ternary nitro-based molten salt is widely used in large-scale photothermal energy storage, fine chemical reaction medium and high-end material synthesis due to its excellent characteristics such as wide temperature range stability, excellent heat conduction and heat storage performance. The purity level of the molten salt is directly related to the operation safety, medium recycling service life and core function stability of the downstream system. Therefore, the efficient purification process and supporting device of the molten salt become a key support link for the industrialization promotion in the field. SUMMARY

[0003] In view of the defects in the prior art, the application provides a multi-stage filtering and purifying integrated device for low-melting ternary nitro-based molten salt, which can effectively solve the technical problems in the background art.

[0004] To achieve the above purpose, the application is implemented by the following technical solutions: A multi-stage filtering and purifying integrated device for low-melting ternary nitro-based molten salt, comprising a pretreatment module, a multi-stage filtering module and a deep purification module connected in series according to the flow direction of the molten salt, each module being sealingly communicated through a heat tracing pipeline to form an integrated continuous purification flow channel; The pretreatment module comprises a jacketed preheating unit, a coarse filter device and a dehydration unit, the jacketed preheating unit being used to heat the raw material molten salt to a molten state and maintain a constant temperature, the coarse filter device being internally provided with a stainless steel sintered mesh filter element, and the dehydration unit being internally filled with molecular sieves; The multi-stage filtering module is composed of a first-stage precision filtering unit, a second-stage deep filtering unit and a third-stage adsorption filtering unit, the first-stage precision filtering unit being provided with a ceramic membrane filter assembly, the second-stage deep filtering unit being provided with a metal fiber membrane filter assembly, and the third-stage adsorption filtering unit being internally provided with a composite layered packed adsorbent; The deep purification module comprises a vacuum degassing unit and a constant-temperature homogenization buffer device, the vacuum degassing unit being used to remove volatile impurities in the molten salt, and the constant-temperature homogenization buffer device being used to temporarily store and homogenize the purified molten salt. Further, it further comprises: The auxiliary integrated system comprises a pressure regulating system, a safety protection system and a power delivery subsystem, the pressure regulating system comprising a vacuum valve and a vacuum gauge, the safety protection system being provided with a molten salt valve, and the power delivery subsystem comprising a molten salt delivery pump; Further, the first-stage precision filtering unit is composed of a first tank body, a first sealing ring, a bottom support plate, a perforated flower plate, a filter core, a filter core protection cover, a temperature sensor assembly, a jacket and a heat preservation layer. The first tank body includes a first tank body and a first tank lid, the first tank body and the first tank lid are fastened together by bolts, and the end faces of the two are provided with matching first annular grooves; The first sealing ring is embedded between the first can body and the first can lid; The bottom support plate is fixed to the upper surface of the annular support ring of the first tank body by screws; The perforated plate is oriented and assembled into the inner cavity of the first tank body along the guide groove on the inner wall of the first tank body; The filter element is a slender hollow cylindrical tubular component made of ceramic membrane; The two ends of the filter element protective cover are respectively fixed to the opposite sides of the bottom support plate and the perforated plate; The temperature sensor assembly is installed symmetrically at both ends, and is fixed to the two outer ends of the first tank body respectively; The jacket is fitted around the cylindrical section of the first tank body, and an electric heating wire is embedded inside it. The insulation layer is made of 50mm thick rock wool and is fully wrapped around the outside of the jacket of the first tank body.

[0005] Furthermore, a guide groove is provided on the inner wall of the first tank in the circumferential direction.

[0006] Furthermore, the cylindrical section of the first tank body is provided with a first molten salt inlet, a first molten salt outlet, and a first slag discharge port; The first molten salt inlet is sealed and connected to the outlet of the dehydration unit of the pretreatment module through a heat tracing pipeline, the first molten salt outlet is sealed and connected to the inlet of the secondary depth filtration unit through a heat tracing pipeline, and the first slag discharge port is located at the bottom of the first tank and equipped with a sealing valve.

[0007] Furthermore, the temperature sensor assembly consists of a sleeve, a temperature sensor, a cover fixing plate, and a cover.

[0008] The inner wall of the sleeve is provided with an internal thread, and the outer wall is provided with an external thread. The external thread on the outer wall engages with the internal thread of the first tank body wall to fix it in place inside the first tank body wall. The temperature sensor is assembled inside the sleeve by the external thread on its outer wall engaging with the internal thread on the inner wall of the sleeve, and its detection end penetrates the sleeve and extends into the inner cavity of the first tank body. The cover fixing plate is welded to the outside of the first tank body; The cover is fixed to the preset mounting position of the cover fixing plate by screws.

[0009] Furthermore, the three-stage adsorption filtration unit consists of a second tank, a second sealing ring, an elastic pressure ring, a partition, a porous support plate, an adsorbent, the temperature sensor assembly, a jacket, and an insulation layer. The second tank body is composed of a second tank body and a second tank cover. The second tank body and the second tank cover are fastened together by bolts, and their end faces are provided with matching annular grooves. The second sealing ring is embedded between the second can body and the second can lid; The elastic pressure ring is made of fluororubber, and an annular stainless steel skeleton is embedded inside it through in-mold vulcanization. It is fastened to the upper surface of the upper support ring of the second tank body by screws. The partition is a circular stainless steel mesh sheet, which is fastened to the upper surface of the support ring in the middle of the second tank body by screws; The porous support plate is a circular stainless steel mesh sheet, and its upper surface is covered with a quartz sand pad layer with a thickness of 20mm. The porous support plate is fastened to the upper surface of the lower support ring of the second tank body by bolts. The adsorbent comprises a chelating ion exchange resin and modified activated carbon, wherein the chelating ion exchange resin is packed above the partition plate and the modified activated carbon is packed below the partition plate. The temperature sensor assembly is installed symmetrically at both ends, and is fixed to the two outer ends of the second tank body respectively.

[0010] The jacket is fitted around the cylindrical section of the second tank body, and an electric heating wire is embedded inside it; The insulation layer is made of 50mm thick rock wool and is fully wrapped around the outside of the jacket of the second tank body.

[0011] Furthermore, the cylindrical section of the second tank body is provided with a second molten salt inlet, a second molten salt outlet, and a second slag discharge port; The second molten salt inlet is sealed and connected to the outlet of the secondary depth filtration unit through a heat tracing pipeline, and the second molten salt outlet is sealed and connected to the inlet of the vacuum degassing unit through a heat tracing pipeline. The second slag discharge port is located at the bottom of the second tank and is equipped with a sealing valve.

[0012] Furthermore, the device adopts a series-connected heat tracing pipe structure, including a pretreatment module, a multi-stage filtration module, a deep purification module, and an auxiliary integrated system arranged between the heat tracing pipes connected in sequence; wherein, the pretreatment module is located at the front of the device and consists of a jacketed preheating unit, a coarse filtration device, and a dehydration unit; the multi-stage filtration module is located in the middle of the device and consists of a first-stage precision filtration unit, a second-stage deep filtration unit, and a third-stage adsorption filtration unit; the deep purification module is located at the end of the device and consists of a vacuum degassing unit and the constant temperature homogenization buffer device.

[0013] Compared with the known prior art, the technical solution provided by this invention has the following beneficial effects: Firstly, it achieves integrated continuous purification, avoiding the risks of channel blockage and impurity introduction: The device adopts an integrated architecture in which pretreatment modules, multi-stage filtration modules, and deep purification modules are connected in series according to the molten salt flow direction. Each module is sealed and connected through heat-traced pipelines, forming a complete and continuous purification channel. The heat-traced pipelines, together with the jacket heating and rock wool insulation layer of each unit, can prevent channel blockage caused by cooling and solidification of molten salt during transportation and processing; at the same time, the sealed connection structure can isolate the intrusion of external air, dust and other impurities, ensuring the purification effect from the transmission stage and adapting to the needs of continuous industrial production.

[0014] Secondly, multi-stage layered purification significantly improves the purity and compatibility of molten salt: Through a layered treatment logic of pretreatment, multi-stage filtration, and deep purification, precise removal of different types of impurities in the molten salt is achieved: The pretreatment module uses stainless steel sintered mesh for coarse filtration and molecular sieve dehydration to first intercept coarse particulate impurities and remove moisture; the multi-stage filtration module uses ceramic membrane precision filtration and metal fiber membrane deep filtration to remove micron-sized fine suspended matter step by step, and then uses chelating ion exchange resin and modified activated carbon separated by partitions to adsorb ionic pollutants and organic impurities respectively; the vacuum degassing unit of the deep purification module further removes volatile impurities. This design can cover multiple types of impurities, including coarse, fine, ionic, and volatile impurities, ensuring that the purity of the molten salt meets the requirements of high-end applications such as solar thermal energy storage and fine chemicals, and reducing corrosion and heat transfer efficiency degradation in downstream equipment.

[0015] Third, it enhances system operational stability and reduces equipment maintenance risks: The device is equipped with symmetrically installed temperature sensor components, which can monitor the molten salt temperature in each unit in real time. Combined with jacket heating and rock wool insulation, it ensures that the molten salt is always in a stable molten state, avoiding uneven temperature that could damage the molten salt performance. The device also assists in the integrated system's pressure regulation, safety protection, and power transmission functions, which can accurately control the flow channel pressure, avoid medium leakage or equipment damage caused by sudden pressure changes, and facilitate operation and maintenance, thereby improving the long-term reliability and safety of the device. Attached Figure Description

[0016] Figure 1 This is a system diagram of a multi-stage filtration and purification integrated device for low-melting-point ternary nitro molten salts proposed in this invention; Figure 2 This is a structural diagram of the first-stage precision filtration unit of a multi-stage filtration and purification integrated device for low-melting-point ternary nitro molten salt proposed in this invention. Figure 3 This is a structural diagram of the guide tank of a multi-stage filtration and purification integrated device for low-melting-point ternary nitro molten salt proposed in this invention; Figure 4This is a schematic diagram of the inlet, outlet, and slag discharge port of the first tank of a multi-stage filtration and purification integrated device for low-melting-point ternary nitro molten salt proposed in this invention. Figure 5 This is a structural diagram of a temperature sensor component in a multi-stage filtration and purification integrated device for low-melting-point ternary nitro molten salts proposed in this invention. Figure 6 This is a structural diagram of a three-stage adsorption filtration unit for a multi-stage filtration and purification integrated device for low-melting-point ternary nitro molten salts proposed in this invention. Figure 7 This is a schematic diagram of the inlet, outlet, and slag discharge port of the second tank of a multi-stage filtration and purification integrated device for low-melting-point ternary nitro molten salt proposed in this invention.

[0017] The labels in the diagram represent: 1-Pretreatment module, 11-Jacketed preheating unit, 12-Coarse filtration device, 13-Dehydration unit, 2-Multi-stage filtration module, 21-First-stage precision filtration unit, 211-First tank body, 2111-First canister, 21111-First annular groove, 21112-Guide groove, 21113-First molten salt inlet, 21114-First molten salt outlet, 21115-First slag discharge port, 2112-First tank cover, 212-First sealing ring, 213-Bottom support plate, 214-Perforated plate, 215-Filter element, 216-Filter element protective cover, 217-Temperature sensor assembly, 2171-Sleeve, 2172-Temperature sensor, 2173-Cover fixing Fixed plate, 2174-Cover, 218-Jacket, 219-Insulation layer, 22-Secondary depth filtration unit, 23-Third-stage adsorption filtration unit, 231-Second tank body, 2311-Second tank body, 23111-Second annular groove, 23112-Second molten salt inlet, 23113-Second molten salt outlet, 23114-Second slag discharge port, 232-Second sealing ring, 233-Elastic pressure ring, 234-Baffle plate, 235-Porous support plate, 2351-Quartz sand pad, 236-Adsorbent, a-Molten salt valve, b-Molten salt transfer pump, c-Vacuum valve, d-Vacuum gauge, e-Nitrogen tank, f-Vacuum unit, g-Heat tracing pipe, h-Nitrogen pipe, i-Vacuum pipe. Detailed Implementation

[0018] The present invention will be further described below with reference to embodiments.

[0019] The current technology and equipment for purifying low-melting-point ternary nitro molten salts still face significant technical bottlenecks, making it difficult to adapt to the demands of industrial continuous production and high-precision purification. Specific drawbacks are as follows: Firstly, existing purification systems mostly adopt a decentralized modular splicing architecture, with pretreatment, filtration, and deep impurity removal functions being independent of each other. The units are connected by conventional pipelines, without forming an integrated sealing and heat tracing system. On the one hand, the molten salt is prone to local cooling and solidification due to heat dissipation from the pipelines, causing flow channel blockage. On the other hand, the sealing performance at the module connection is insufficient, which can easily introduce impurities such as external air and dust, directly weakening the purification effect. Secondly, there are defects in the design of the filtration layer. Traditional purification devices mostly rely on a single filter medium, which can only intercept coarse particulate impurities and cannot effectively remove micron-sized fine suspended matter and ionic pollutants. As a result, the purity of molten salt is difficult to meet the requirements of high-end application scenarios, and it is easy to cause problems such as corrosion of internal components and decrease in heat transfer efficiency during subsequent use. Third, the dehydration and degassing processes have poor coordination. Existing equipment often operates the dehydration and degassing processes separately. The dehydration unit often uses conventional desiccants, which are prone to incomplete dehydration due to adsorption saturation. The degassing process lacks targeted vacuum environment and temperature matching control, resulting in a high residual amount of volatile impurities in the molten salt, which seriously affects the chemical stability of the molten salt. Fourth, the system's operational stability is insufficient. Some purification units are not equipped with precise temperature control and safety protection mechanisms. The heating modules are mostly designed for local heating, which can easily lead to uneven temperature distribution of the molten salt, destroying its molten state stability. Furthermore, there is a lack of a unified pressure regulation system. During continuous operation, sudden changes in flow channel pressure can easily cause media leakage or equipment damage, restricting the efficiency of continuous industrial production.

[0020] To overcome the aforementioned drawbacks, the present invention employs the following embodiments to address the current situation.

[0021] Example 1: Reference Appendix Figure 1 This is a schematic diagram of a multi-stage filtration and purification integrated device for low-melting-point ternary nitro molten salt. It includes a pretreatment module 1, a multi-stage filtration module 2 and a deep purification module 3 connected in series according to the molten salt flow direction. Each module is sealed and connected through a heat tracing pipeline to form an integrated continuous purification flow channel. The pretreatment module 1 includes a jacketed preheating unit 11, a coarse filtration device 12, and a dewatering unit 13. The jacketed preheating unit 11 is used to heat the raw material molten salt to a molten state and maintain the temperature. The coarse filtration device 12 has a built-in stainless steel sintered mesh filter element. The dewatering unit 13 is filled with molecular sieves. The multi-stage filtration module 2 consists of a first-stage precision filtration unit 21, a second-stage depth filtration unit 22, and a third-stage adsorption filtration unit 23. The first-stage precision filtration unit 21 is equipped with a ceramic membrane filtration assembly, the second-stage depth filtration unit 22 is equipped with a metal fiber membrane filtration assembly, and the third-stage adsorption filtration unit 23 is equipped with a composite layered adsorbent. The deep purification module 3 includes a vacuum degassing unit 31 and a constant temperature homogenization buffer device 32. The vacuum degassing unit 31 is used to remove volatile impurities from the molten salt, and the constant temperature homogenization buffer device 32 is used to temporarily store and homogenize the purified molten salt.

[0022] In this embodiment, an integrated continuous processing framework for the purification of low-melting-point ternary nitro molten salts is constructed by defining the core module architecture, key connection methods, and basic processing logic.

[0023] In another embodiment, it also includes: The auxiliary integrated system 4 includes a pressure regulating system 41, a safety protection system 42, and a power transmission subsystem 43. The pressure regulating system includes a vacuum valve c and a vacuum gauge d. The safety protection system is equipped with a molten salt valve a. The power transmission subsystem includes a molten salt transmission pump b.

[0024] The pressure regulation system precisely controls the pressure environment within the flow channel, adapting to the purification process requirements of each module while ensuring stable system pressure. The safety protection system ensures operational safety and system stability during device operation, mitigating risks such as leakage and abnormal flow. The power delivery subsystem provides continuous power for the flow of molten salt within the integrated flow channel, which is a key guarantee for achieving continuous purification. like Figure 2 As shown, in one embodiment, the primary precision filtration unit 21 is composed of a first tank 211, a first sealing ring 212, a bottom support plate 213, a perforated plate 214, a filter element 215, a filter element protective cover 216, a temperature sensor assembly 217, a jacket 218, and a heat insulation layer 219. The first tank body 211 includes a first tank body 2111 and a first tank cover 2112. The first tank body 2111 and the first tank cover 2112 are fastened together by bolts, and the end faces of the two are provided with matching first annular grooves 21111. The first sealing ring 212 is embedded between the first can body 2111 and the first can lid 2112; The bottom support plate 213 is fixed to the upper surface of the annular support ring of the first tank body 2111 by screws; The perforated plate 214 is oriented and assembled into the inner cavity of the first tank body 2111 along the guide groove 21112 on the inner wall of the first tank body 2111; The filter element 215 is a slender hollow cylindrical tubular component made of ceramic membrane; The two ends of the filter element protective cover 216 are respectively fixed to the opposite sides of the bottom support plate 213 and the perforated plate 214; The temperature sensor assembly 217 is installed symmetrically at both ends, and is fixed to the outer ends of the first tank body 2111 respectively; The jacket 218 is fitted on the outside of the cylindrical section of the first tank body 2111, and an electric heating wire is embedded inside it; The insulation layer 219 is made of 50mm thick rock wool and is fully wrapped around the outside of the jacket 218 of the first tank body 2111.

[0025] The first tank body 2111 and the first tank cover 2112 are fastened together by bolts to form a sealed pressure vessel, which is adapted to the system pressure when the molten salt flows, and at the same time isolates external air, dust and other impurities to prevent secondary pollution. The first annular groove 21111 on the end face of the first tank body 2111 and the first tank cover 2112 provides installation space for the first sealing ring 212, further enhancing the sealing effect. The first sealing ring 212 is embedded between the tank body and the tank cover to seal and prevent leakage. It can fill the tiny gap at the joint between the two, completely block the leakage channel of molten salt, and prevent external impurities from entering the tank and contaminating the molten salt, thus ensuring the purity of the filtered molten salt. The bottom support plate 213 and the perforated plate 214 form an upper and lower clamping structure, which not only provides stable support for the filter element, but also guides the molten salt to flow evenly across the surface of the filter element through the perforated design of the support plate and the perforated plate, avoiding incomplete filtration caused by excessive local flow rate. The porous perforated plate 214 fixes the position of the filter element, ensuring that the filter element is vertical and evenly distributed, and avoids filter element displacement and leakage due to the impact of molten salt flow. The ceramic membrane filter element 215 removes micron-sized fine impurities. The slender hollow cylindrical tubular structure is based on the optimization of molten salt fluid characteristics and filtration efficiency, increasing the effective filtration area: within the limited tank space of the first-stage precision filtration unit 21, the slender structure can maximize the filtration area by arranging multiple parallel tubes in conjunction with the positioning of the perforated plate 214, increasing the molten salt throughput per unit time and adapting to the industrial requirements of the continuous purification flow channel of the device; the hollow cylindrical tubular internal and external cavity structure allows the molten salt to form a cross-flow path with the outer wall in and the inner wall out. When the molten salt flows along the outer wall of the filter element, part of it enters the inner cavity through the membrane pores to complete filtration, while the rest, carrying impurities that have not been intercepted, continues to flow, which can reduce the accumulation of impurities on the membrane surface, avoid rapid clogging caused by dead-end filtration, extend the filter element backwashing cycle, and reduce operation and maintenance costs; the "low flow resistance design" of the slender structure can reduce the pressure loss of molten salt flow, and with the stable pressure supply of the molten salt delivery pump b in the power delivery subsystem, ensure that the molten salt has a uniform flow rate throughout the multi-stage filtration module, avoiding sudden changes in local flow rate that could affect filtration accuracy; The protective cover 216 is fixed at both ends to the support plate and the tube sheet. It can buffer the flow rate impact when molten salt enters the unit and prevent high-speed molten salt from directly washing the surface of the filter element and causing damage to the ceramic membrane. At the same time, it prevents impurity particles from impacting the filter element due to sudden changes in flow rate, extends the service life of the filter element, and ensures the continuous and stable filtration function. The temperature sensor assembly 217 is installed symmetrically at both ends of the tank body for real-time monitoring. It can simultaneously monitor the molten salt temperature at the inlet and outlet of the tank and provide real-time temperature data. If the temperature difference between the two ends is too large, the jacket heating power can be adjusted in time to avoid local solidification. It provides data support for the temperature control system of the entire device, ensures temperature coordination between the primary filter unit and the front and rear modules, and ensures the stability of the molten salt state in the overall flow channel. The active heating function of the jacket 218 is installed on the outside of the cylindrical section of the tank body. The jacket 218 has a built-in electric heating wire, which can adjust the heating power in real time according to the feedback of the temperature sensor 217 to compensate for the heat loss of molten salt during the filtration process, ensure that the molten salt in the tank is always in a molten flow state, avoid clogging of the filter element or pipeline due to cooling and solidification, maintain a stable temperature environment, and avoid temperature fluctuations affecting the filtration performance of the ceramic membrane. The passive insulation function of the 50mm rock wool insulation layer 219 is fully covered by the rock wool insulation layer on the outside of the jacket. It has a low thermal conductivity and good insulation effect, which reduces heat loss after the jacket is heated, reduces energy consumption, avoids safety hazards caused by excessive temperature on the outer wall of the tank, and maintains the temperature uniformity inside the tank to prevent local temperature differences from causing instability in the molten salt state.

[0026] like Figure 3 As shown, in one embodiment, the inner wall of the first tank body 2111 is provided with a guide groove 21112 in the circumferential direction.

[0027] The guide groove 21112 is used to prevent the porous plate 213 from shifting, tilting or rotating during assembly: The core function of the porous plate 213 is to fix the ceramic membrane filter element 215. If it is misaligned during assembly, the filter element will be unevenly distributed in the tank, which will cause the molten salt to flow through the filter element at an uneven flow rate. Areas with a fast flow rate will not be filtered thoroughly, while areas with a slow flow rate will be easily clogged, directly affecting the micron-level precision filtration effect.

[0028] like Figure 4 As shown, in one embodiment, the cylindrical section of the first tank body 2111 is provided with a first molten salt inlet 21113, a first molten salt outlet 21114 and a first slag discharge port 21115; The first molten salt inlet 21113 is sealed and connected to the outlet of the dehydration unit 13 of the pretreatment module 1 through a heat tracing pipeline. The first molten salt outlet 21114 is sealed and connected to the inlet of the secondary depth filtration unit 22 through a heat tracing pipeline. The first slag discharge port 21115 is located at the bottom of the first tank body 2111 and is equipped with a sealing valve.

[0029] The core function of the first molten salt inlet 21113 is to supply the molten salt raw material to be filtered to the first-stage precision filtration unit. Its design and connection relationship directly determine the stability and purity protection of the raw material supply. It connects to the pretreatment module and receives the molten salt after coarse filtration and dehydration. It is sealed and connected to the discharge port of the dehydration unit 13 of the pretreatment module through a heated pipeline. The inlet is set at the bottom of the cylindrical section to adapt to the filter flow channel design. This allows the molten salt to enter the tank and diffuse evenly along the tank wall to the outer wall of the ceramic membrane filter element 215. This avoids the molten salt directly impacting the filter element and ensures that the molten salt can fully cover all filter element surfaces, maximizing the use of the filtration area and improving filtration efficiency. The core function of the first molten salt outlet 21114 is to transport the molten salt that has undergone micron-level fine filtration to the next stage module. It is a key connection point to ensure the continuity of the overall purification process. It connects to the secondary depth filtration unit and transmits molten salt with low impurity load through a heated pipeline to the inlet of the secondary depth filtration unit 22. Together with the inlet, it forms a reasonable filtration flow channel in the tank. Both the outlet and the inlet are located in the cylindrical section of the tank body, which can guide the molten salt to form a stable flow path along the outer wall and inner wall of the filter element in the tank, ensuring full contact between the molten salt and the filter element, avoiding short-circuit flow, and ensuring thorough filtration.

[0030] The core function of the first slag outlet 21115 is to periodically discharge the impurities trapped by the first-stage precision filtration unit. This is crucial to preventing filter element clogging and extending the unit's service life. The bottom is designed to utilize gravity sedimentation, which facilitates the collection of impurities. The slag outlet is located at the bottom of the first tank 2111, which conforms to the laws of physics: after impurities in the molten salt are trapped by the ceramic membrane filter element, they will gradually settle to the bottom of the tank due to gravity. The bottom slag outlet can directly discharge the deposited impurities without additional power, reducing energy consumption and ensuring more thorough cleaning.

[0031] like Figure 5 As shown, in one embodiment, the temperature sensor assembly 217 consists of a sleeve 2171, a temperature sensor 2172, a cover fixing plate 2173, and a cover 2174.

[0032] The inner wall of the sleeve 2171 is provided with an internal thread, and the outer wall is provided with an external thread. The external thread of the outer wall is threaded into the internal thread of the first tank body 2111, and the sleeve is fixedly assembled inside the wall of the first tank body 2111. The temperature sensor 2172 is assembled inside the sleeve 2171 by the external thread on its outer wall engaging with the internal thread on the inner wall of the sleeve 2171, and its detection end penetrates the sleeve 2171 and extends into the inner cavity of the first tank body 2111. The cover fixing plate 2173 is welded to the outside of the first tank body 2111; The cover 2174 is fixed to the preset mounting position of the cover fixing plate 2173 by screws.

[0033] The structure and installation logic of the temperature sensor assembly 217 enable it to accurately, stably, and safely monitor the temperature of the molten salt in the primary precision filter unit in real time, providing reliable data support for the temperature control system of the entire unit, and ultimately ensuring that the molten salt is always in a stable molten state and that the filtration performance is consistent. The cover fixing plate 2173 provides a structural fixing reference plate welded to the outside of the tank body, providing a stable installation carrier for the cover, preventing the cover from falling off due to vibration or external force, and ensuring the continuous effectiveness of the protective function; at the same time, the welding fixing method has high strength and is suitable for long-term high temperature and vibration operating environment; The 2174 cover is an external protective shell that isolates external interference, preventing damage to components caused by accidental contact with sensor terminals or tool collisions during operation and maintenance, and also preventing dust, oil, and other contaminants from adhering to the sensor terminals.

[0034] like Figure 6 As shown, in one embodiment, the three-stage adsorption filtration unit 23 is composed of a second tank 231, a second sealing ring 232, an elastic pressure ring 233, a partition 234, a porous support plate 235, an adsorbent 236, the temperature sensor assembly 217, a jacket 218, and a heat insulation layer 219. The second tank body 231 is composed of a second tank body 2311 and a second tank cover 2312. The second tank body 2311 and the second tank cover 2312 are fastened together by bolts, and the end faces of the two are provided with matching annular grooves 23111. The second sealing ring 232 is embedded between the second can body 2311 and the second can lid 2312; The elastic pressure ring 233 is made of fluororubber, and an annular stainless steel skeleton is embedded inside it through in-mold vulcanization. It is fastened to the upper surface of the upper support ring of the second tank body 2311 by screws. The partition 234 is a circular stainless steel mesh sheet, which is fastened to the upper surface of the support ring in the middle of the second tank body 2311 by screws; The porous support plate 235 is a circular stainless steel mesh sheet, and its upper surface is covered with a quartz sand pad 2351 with a thickness of 20mm. The porous support plate 235 is fastened to the upper surface of the lower support ring of the second tank body 2311 by bolts. The adsorbent 236 comprises a chelating ion exchange resin and modified activated carbon, wherein the chelating ion exchange resin is filled above the partition 234 and the modified activated carbon is filled below the partition 234. The temperature sensor assembly 217 is installed symmetrically at both ends, and is fixed to the outer ends of the second tank body 2311 respectively.

[0035] The jacket 218 is fitted on the outside of the cylindrical section of the second tank body 2311, and an electric heating wire is embedded inside it; The insulation layer 219 is made of 50mm thick rock wool and is fully wrapped around the outside of the jacket 218 of the second tank body 2311.

[0036] The main body of the second tank is the foundation for bearing and sealing. The tank body and the tank cover are fastened together by bolts. The end face is provided with an adapted annular groove to form a sealed pressure container to withstand the system pressure when the molten salt flows, avoid the tank body deformation causing misalignment of the adsorption layer, isolate the outside air and dust, and prevent molten salt leakage. The second sealing ring 232 is embedded between the tank body and the tank cover to seal and prevent leakage. It fills the tiny gap at the joint between the two, completely blocking the channels for molten salt leakage and the intrusion of external impurities, ensuring that the adsorption process is carried out in a pure environment and avoiding secondary contamination of the adsorbed molten salt. The elastic pressure ring 233 is fastened to the upper support ring of the tank body. The elastic pressure compacts the upper chelating ion exchange resin to prevent the resin particles from short-circuiting due to excessive gaps. At the same time, the fluororubber material is resistant to molten salt corrosion and high temperature, making it suitable for long-term operating environments. The stainless steel skeleton ensures the structural strength of the pressure ring. The baffle 234 is fixed to the support ring in the middle of the tank body. It serves as a physical separator between the upper and lower layers of adsorbent and can also guide the molten salt from the upper resin to flow smoothly into the lower activated carbon through the mesh, ensuring that the molten salt is in full contact with the two layers of adsorbent. The porous support plate 235 is a circular stainless steel mesh sheet with a 20mm quartz sand pad 2351 on the upper surface. The quartz sand particles are uniform and have high chemical stability, which can prevent the lower modified activated carbon particles from being lost with the flow of molten salt. At the same time, it plays a role in uniform liquid distribution, guiding the molten salt to slowly and evenly penetrate through the activated carbon layer, avoiding local flow rate too fast and resulting in incomplete adsorption. The support plate is fixed to the support ring at the bottom of the tank with bolts to provide stable support for the adsorbent, prevent the adsorbent from collapsing due to gravity or molten salt impact, ensure uniform adsorption layer thickness, and maintain a stable adsorption flow channel. The composite layered adsorbent 236 provides targeted purification. The adsorbent consists of a chelating ion exchange resin and modified activated carbon, layered and filled by separators 234 to form a targeted adsorption chain. The upper layer of chelating ion exchange resin utilizes its strong chelating ability for metal ions to precisely capture residual ionic pollutants in the molten salt, filling the gap in the removal of ionic impurities by the first two stages of filtration. The lower layer of modified activated carbon, with its large specific surface area and abundant pore structure, adsorbs organic impurities in the molten salt, preventing these impurities from affecting the chemical stability of the molten salt, while also improving the color and purity of the molten salt. This layered design avoids mutual interference in adsorption efficiency caused by mixing the two adsorbents, ensuring that each adsorbent focuses on the target impurities and improves purification precision.

[0037] likeFigure 6 As shown, in one embodiment, the cylindrical section of the second tank body 2311 is provided with a second molten salt inlet 23112, a second molten salt outlet 23113 and a second slag discharge port 23114; The molten salt inlet 23112 is sealed and connected to the outlet of the secondary depth filtration unit 22 via a heat tracing pipeline. The molten salt outlet 23113 is sealed and connected to the inlet of the vacuum degassing unit 31 via a heat tracing pipeline. The slag discharge port 23114 is located at the bottom of the second tank body 2311 and is equipped with a sealing valve.

[0038] The second molten salt inlet 23112 is the raw material input port of the tertiary adsorption filtration unit 23. Its core function is to stably deliver the molten salt after the secondary deep filtration to the adsorption system, laying the foundation for the subsequent removal of ions and organic impurities. Connecting to the secondary deep filtration unit 23, the low-solid-impurity molten salt is sealed to the outlet of the secondary deep filtration unit 22 via a heated pipeline. The secondary deep filtration unit 22 has already removed the submicron-sized solid particles remaining after the primary precision filtration. The molten salt received at the inlet only contains residual ionic pollutants and organic impurities, preventing solid particles from clogging the adsorbent pores, ensuring the adsorbent focuses on its core purification function, and extending the adsorbent's lifespan. The second molten salt outlet 23113 is the product output port of the three-stage adsorption filtration unit. Its core function is to stably transport the molten salt that has completed the removal of ions and organic impurities to the deep purification module. It is the key connection point between the multi-stage filtration module and the deep purification module. It connects to the vacuum degassing unit and transmits low-impurity load molten salt through a heat-traced pipeline to the inlet of the vacuum degassing unit 31 in a sealed connection. The second slag discharge port 23114 is the impurity discharge port of the three-stage adsorption filtration unit. Its core function is to periodically remove sedimented impurities generated during adsorption, preventing their accumulation from affecting adsorption efficiency or clogging the flow channels. Bottom positioning utilizes gravity settling to achieve centralized impurity removal. The slag discharge port is located at the bottom of the second tank 2311, conforming to the physical settling principle: a small amount of non-adsorbent impurities may be generated during adsorption; these impurities will settle to the bottom of the tank due to gravity, and the bottom slag discharge port can directly discharge them without additional power, resulting in more thorough cleaning and lower energy consumption. In one embodiment, the device employs a series-connected heat tracing pipe structure, comprising a pretreatment module 1, a multi-stage filtration module 2, a deep purification module 3, and an auxiliary integrated system 4 arranged between the heat tracing pipes, connected in sequence; wherein, the pretreatment module 1 is located at the front of the device and consists of a jacketed preheating unit 11, a coarse filtration device 12, and a dehydration unit 13; the multi-stage filtration module 2 is located in the middle of the device and consists of a primary precision filtration unit 21, a secondary deep filtration unit 22, and a tertiary adsorption filtration unit 23; the deep purification module 3 is located at the end of the device and consists of a vacuum degassing unit 31 and the constant temperature homogenization buffer device 32.

[0039] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the present invention.

Claims

1. A multi-stage filtration and purification integrated device for low-melting-point ternary nitro molten salts, characterized in that, It includes a pretreatment module (1), a multi-stage filtration module (2) and a deep purification module (3) connected in series according to the molten salt flow direction. Each module is sealed and connected through a heat tracing pipeline to form an integrated continuous purification channel. The pretreatment module (1) includes a jacketed preheating unit (11), a coarse filtration device (12), and a dewatering unit (13). The jacketed preheating unit (11) is used to heat the raw material molten salt to a molten state and keep it at a constant temperature. The coarse filtration device (12) has a built-in stainless steel sintered mesh filter element. The dewatering unit (13) is filled with molecular sieves. The multi-stage filtration module (2) consists of a first-stage precision filtration unit (21), a second-stage deep filtration unit (22), and a third-stage adsorption filtration unit (23). The first-stage precision filtration unit (21) is equipped with a ceramic membrane filtration assembly, the second-stage deep filtration unit (22) is equipped with a metal fiber membrane filtration assembly, and the third-stage adsorption filtration unit (23) is equipped with a composite layered adsorbent. The deep purification module (3) includes a vacuum degassing unit (31) and a constant temperature homogenization buffer device (32). The vacuum degassing unit (31) is used to remove volatile impurities from the molten salt, and the constant temperature homogenization buffer device (32) is used to temporarily store and homogenize the purified molten salt.

2. The integrated multi-stage filtration and purification device for low-melting-point ternary nitro molten salts according to claim 1, characterized in that, Also includes: The auxiliary integrated system (4) includes a pressure regulating system (41), a safety protection system (42) and a power transmission subsystem (43). The pressure regulating system includes a vacuum valve (c) and a vacuum gauge (d). The safety protection system is equipped with a molten salt valve (a). The power transmission subsystem includes a molten salt transmission pump (b).

3. The integrated multi-stage filtration and purification device for low-melting-point ternary nitro molten salts according to claim 1, characterized in that, The first-stage precision filtration unit (21) consists of a first tank (211), a first sealing ring (212), a bottom support plate (213), a perforated plate (214), a filter element (215), a filter element protective cover (216), a temperature sensor assembly (217), a jacket (218), and a heat insulation layer (219); The first tank body (211) includes a first tank body (2111) and a first tank cover (2112). The first tank body (2111) and the first tank cover (2112) are fastened together by bolts, and the end faces of the two are provided with a matching first annular groove (21111). The first sealing ring (212) is embedded between the first can body (2111) and the first can lid (2112); The bottom support plate (213) is fixed to the upper surface of the annular support ring of the first tank body (2111) by screws; The perforated plate (214) is oriented and assembled into the inner cavity of the first tank body (2111) along the guide groove (21112) on the inner wall of the first tank body (2111); The filter element (215) is a slender hollow cylindrical tubular component made of ceramic membrane; The two ends of the filter element protective cover (216) are respectively fixed to the opposite sides of the bottom support plate (213) and the perforated plate (214); The temperature sensor assembly (217) is installed symmetrically at both ends and is fixed to the outer ends of the first tank body (2111); The jacket (218) is fitted on the outside of the cylindrical section of the first tank body (2111), and an electric heating wire is embedded inside it; The insulation layer (219) is made of 50mm thick rock wool and is fully wrapped around the outside of the jacket (218) of the first tank body (2111).

4. The integrated multi-stage filtration and purification device for low-melting-point ternary nitro molten salts according to claim 3, characterized in that, The inner wall of the first tank body (2111) is provided with a guide groove (21112) in the circumferential direction.

5. The integrated multi-stage filtration and purification device for low-melting-point ternary nitro molten salts according to claim 3, characterized in that, The cylindrical section of the first tank body (2111) is provided with a first molten salt inlet (21113), a first molten salt outlet (21114) and a first slag discharge port (21115). The first molten salt inlet (21113) is sealed and connected to the outlet of the dehydration unit (13) of the pretreatment module (1) through a heat tracing pipeline. The first molten salt outlet (21114) is sealed and connected to the inlet of the secondary depth filtration unit (22) through a heat tracing pipeline. The first slag discharge port (21115) is located at the bottom of the first tank body (2111) and is equipped with a sealing valve.

6. The integrated multi-stage filtration and purification device for low-melting-point ternary nitro molten salts according to claim 3, characterized in that, The temperature sensor assembly (217) consists of a sleeve (2171), a temperature sensor (2172), a cover fixing plate (2173), and a cover (2174).

7. The inner wall of the sleeve (2171) is provided with an internal thread and the outer wall is provided with an external thread. The external thread of the outer wall is threaded into the internal thread of the first tank body (2111) and is fixedly assembled inside the wall of the first tank body (2111). The temperature sensor (2172) is assembled inside the sleeve (2171) by the external thread of its outer wall engaging with the internal thread of the inner wall of the sleeve (2171), and its detection end penetrates the sleeve (2171) and extends into the inner cavity of the first tank body (2111). The cover fixing plate (2173) is welded to the outside of the first tank body (2111); The cover (2174) is fixed to the preset mounting position of the cover fixing plate (2173) by screws.

8. The integrated multi-stage filtration and purification device for low-melting-point ternary nitro molten salts according to claim 1, characterized in that, The three-stage adsorption filtration unit (23) consists of a second tank (231), a second sealing ring (232), an elastic pressure ring (233), a partition (234), a porous support plate (235), an adsorbent (236), the temperature sensor assembly (217), a jacket (218), and a heat insulation layer (219); The second tank body (231) is composed of a second tank body (2311) and a second tank cover (2312). The second tank body (2311) and the second tank cover (2312) are fastened together by bolts, and the end faces of the two are provided with matching annular grooves (23111). The second sealing ring (232) is embedded between the second can body (2311) and the second can lid (2312); The elastic pressure ring (233) is made of fluororubber, and an annular stainless steel skeleton is embedded inside it by in-mold vulcanization. It is fastened to the upper surface of the upper support ring of the second tank body (2311) by screws. The partition (234) is a circular stainless steel mesh sheet, which is fastened to the upper surface of the support ring in the middle of the second tank body (2311) by screws; The porous support plate (235) is a circular stainless steel mesh sheet, and its upper surface is covered with a quartz sand pad (2351) with a thickness of 20mm. The porous support plate (235) is fastened to the upper surface of the lower support ring of the second tank body (2311) by bolts. The adsorbent (236) includes a chelating ion exchange resin and modified activated carbon, wherein the chelating ion exchange resin is filled above the partition (234); and the modified activated carbon is filled below the partition (234). The temperature sensor assembly (217) is installed symmetrically at both ends and is fixed to the outer ends of the second tank body (2311); The jacket (218) is fitted on the outside of the cylindrical section of the second tank body (2311), and an electric heating wire is embedded inside it; The insulation layer (219) is made of 50mm thick rock wool and is fully wrapped around the outside of the jacket (218) of the second tank body (2311).

9. The integrated multi-stage filtration and purification device for low-melting-point ternary nitro molten salts according to claim 7, characterized in that, The cylindrical section of the second tank body (2311) is provided with a second molten salt inlet (23112), a second molten salt outlet (23113) and a second slag discharge port (23114). The second molten salt inlet (23112) is sealed and connected to the outlet of the secondary depth filtration unit (22) through a heat tracing pipeline. The second molten salt outlet (23113) is sealed and connected to the inlet of the vacuum degassing unit (31) through a heat tracing pipeline. The second slag discharge port (23114) is located at the bottom of the second tank body (2311) and is equipped with a sealing valve.

10. The integrated multi-stage filtration and purification device for low-melting-point ternary nitro molten salts according to claim 1, characterized in that, The device adopts a series structure of heat tracing pipes, including a pretreatment module (1), a multi-stage filtration module (2), a deep purification module (3) connected in sequence, and an auxiliary integrated system (4) arranged between the heat tracing pipes; wherein, the pretreatment module (1) is located at the front of the device and consists of a jacketed preheating unit (11), a coarse filtration device (12) and a dehydration unit (13); the multi-stage filtration module (2) is located in the middle of the device and consists of a first-stage precision filtration unit (21), a second-stage deep filtration unit (22) and a third-stage adsorption filtration unit (23); the deep purification module (3) is located at the end of the device and consists of a vacuum degassing unit (31) and the constant temperature homogenization buffer device (32).

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