Boiling nitric acid corrosion electrochemical test experimental device in high-temperature decompression environment

Abstract

The utility model discloses an electrochemical test experimental device for boiling nitric acid corrosion in a high-temperature reduced-pressure environment, which relates to the technical field of electrochemical test and consists of a reduced-pressure boiling corrosion reaction system, an electrochemical test system, a heating system, an acid gas absorbing and drying system, a vacuum degree control system and an automatic integrated control system. The decompression boiling corrosion reaction system is connected with the acid gas absorption and drying system, the vacuum degree control system and the heating system are respectively connected with the acid gas absorption and drying system and are in contact with the decompression boiling corrosion reaction system, and an automatic integrated control system is adopted to control the experimental device. The experimental device disclosed by the utility model can test and simulate the electrochemical corrosion behavior of high-temperature reduced-pressure boiling nitric acid in the environment of the evaporator for spent fuel post-treatment, and can realize weight loss and electrochemical test of various materials under the condition of reduced-pressure boiling strong corrosive solution at the same time.

Description

Technical Field

[0001] This utility model relates to the field of electrochemical testing technology, specifically to an experimental device for electrochemical testing of boiling nitric acid corrosion under high temperature and low pressure conditions. Background Technology

[0002] Currently, there are two main types of nitric acid corrosion experimental apparatus: nitric acid corrosion weight loss experimental apparatus and nitric acid corrosion electrochemical experimental apparatus. Nitric acid corrosion weight loss experiments characterize the corrosion rate by measuring the weight loss of the sample before and after corrosion, making them suitable for evaluating the corrosion resistance of different materials. However, they cannot accurately reflect the localized corrosion conditions of materials (such as pitting corrosion and intergranular corrosion), and also have the disadvantage of a long experimental cycle. Electrochemical experiments, on the other hand, provide a rapid, real-time, and accurate corrosion measurement method, and can obtain information on the thermodynamics and kinetics of chemical reactions, revealing the microscopic mechanisms of corrosion behavior.

[0003] In the chemical production field, boiling nitric acid corrosion under high-temperature and low-pressure environments is frequently encountered. For example, in the PUREX solvent extraction process, a mainstream process in the reprocessing and regeneration cycle of spent nuclear reactor fuel, nitric acid is used as a salting-out agent. The evaporator, a key processing unit, experiences boiling nitric acid corrosion under high-temperature and low-pressure conditions. Therefore, it is crucial to study the corrosion resistance and service life of the evaporator's structural materials under these conditions. This necessitates conducting electrochemical experiments simulating boiling nitric acid corrosion under high-temperature and low-pressure environments.

[0004] However, there are many challenges in safely, accurately, and reliably conducting electrochemical experiments on boiling nitric acid corrosion under high temperature and reduced pressure conditions:

[0005] ① The electrochemical experiment of boiling nitric acid corrosion under high temperature and reduced pressure is not a simple single device, but a complex device system because of the strong corrosiveness of high temperature nitric acid, the risk of nitric acid vapor leakage, and the problem of nitric acid tail gas emission during the vacuuming and depressurization process.

[0006] ② The problem of precise air pressure control in this experimental device system: Only by maintaining precise and stable air pressure control in this experimental device system can the actual working conditions be accurately simulated.

[0007] ③ Because the high-temperature environment in the boiling nitric acid corrosion reactor can damage the reference electrode used for the simultaneous electrochemical test, only the working electrode and auxiliary electrode are placed in the reactor, while the reference electrode is placed separately. However, the gas pressure will affect the solubility of KCl in the solution where the reference electrode is located, which in turn will affect the potential of the reference electrode and reduce the precision and accuracy of the electrochemical test. How to ensure that the reference electrode located outside the reactor is in the same pressure state as the working electrode and auxiliary electrode in the depressurized environment of the reactor in order to ensure the accuracy of the electrochemical test is an unavoidable challenge.

[0008] ④ The vibration generated by the vacuum pump during gas extraction can cause significant interference to the electrochemical testing system, which is also a challenge in the depressurized boiling nitric acid corrosion electrochemical experiment.

[0009] ⑤ The sealing of the device and the treatment of harmful exhaust gases are also challenges.

[0010] Due to the numerous challenges mentioned above, previous electrochemical tests have primarily focused on boiling nitric acid corrosion under normal pressure. Electrochemical experiments on boiling nitric acid corrosion under high-temperature and low-pressure conditions are rarely reported in professional literature, and no relevant patents have been found. Therefore, there is an urgent need to develop an experimental apparatus suitable for electrochemical testing of boiling nitric acid corrosion under high-temperature and low-pressure conditions. This apparatus would provide a scientific and effective solution to the aforementioned challenges, accurately simulate the relevant service environment of materials, and provide technical support for studying the corrosion resistance and service life of materials under boiling nitric acid corrosion under high-temperature and low-pressure conditions. Utility Model Content

[0011] The purpose of this invention is to provide an experimental apparatus for electrochemical testing of boiling nitric acid corrosion under high temperature and low pressure conditions, which solves the problem that existing nitric acid corrosion weight loss test apparatus and nitric acid corrosion electrochemical test apparatus cannot carry out weight loss experiments and electrochemical experiments under depressurized boiling conditions, so as to study the corrosion resistance and service life of materials under boiling nitric acid corrosion under high temperature and low pressure conditions.

[0012] This invention addresses numerous technical challenges in electrochemical experiments involving boiling nitric acid corrosion under high-temperature and low-pressure conditions, such as precise pressure control, maintaining equal pressure between the reference electrode, working electrode, and auxiliary electrode, vibration interference during the evacuation process, device sealing, and the treatment of harmful exhaust gases. It innovatively provides a systematic solution that enables highly realistic simulation and reproduction of high-temperature and low-pressure conditions, and allows for high-precision electrochemical testing of boiling nitric acid corrosion under these conditions, thus overcoming the shortcomings and limitations of existing technologies.

[0013] To achieve the above objectives, the technical solution adopted by this utility model is as follows: An electrochemical testing apparatus for boiling nitric acid corrosion under high temperature and reduced pressure is provided. This apparatus comprises a reduced pressure boiling corrosion reaction system, an electrochemical testing system, a heating system, an acid gas absorption and drying system, a vacuum control system, and an automated integrated control system. The reduced pressure boiling corrosion reaction system is connected to the acid gas absorption and drying system. The vacuum control system and the heating system are respectively connected to the acid gas absorption and drying system and contact the reduced pressure boiling corrosion reaction system. An automated integrated control system is used to control the experimental apparatus.

[0014] The reduced pressure boiling corrosion reaction system is used to hold the solutions and samples required for the reaction and to provide a reduced pressure reaction site for the experiment. The reduced pressure boiling corrosion reaction system includes a reactor, an expanded polytetrafluoroethylene gasket, a reactor cover, and a quick-release clamp. An expanded polytetrafluoroethylene gasket is placed between the reactor and the reactor cover, and the three are fixed by the quick-release clamp.

[0015] The electrochemical testing system is used for electrochemical testing and includes a working electrode, a special platinum electrode, a reference electrode, wire I, wire II, wire III, wire IV, a reference electrode placement box, a pin-shaped terminal block, a nitrate bridge, a salt bridge outer sleeve, a through-wall flange tube sealing sleeve I, a through-wall flange tube sealing sleeve II, and an electrochemical workstation.

[0016] The heating system includes a heating jacket and a temperature measuring sleeve. A reactor is placed inside the heating jacket. The temperature measuring sleeve is inserted through the frosted opening on the reactor cover and extends below the liquid surface in the reactor. The temperature measuring sleeve is filled with dimethyl silicone oil for heat transfer.

[0017] The acid gas absorption and drying system includes a condenser, pipe I, pipe II, a circulating water tank, gas guide pipe I, a safety box, gas guide pipe II, a gas washing bottle, gas guide pipe III, a double-tower solid tail gas absorber, gas guide pipe IV, and a drying tower. The condenser is connected to the reduced pressure boiling corrosion reaction system through the frosted port on the reactor cover. It is connected to the circulating water tank through pipe I and pipe II respectively. The upper opening of the condenser is connected to the safety box through gas guide pipe I. The safety box is connected to the gas washing bottle through gas guide pipe II. The gas washing bottle is connected to the double-tower solid tail gas absorber through gas guide pipe III. The double-tower solid tail gas absorber is connected to the drying tower through gas guide pipe IV.

[0018] The vacuum control system includes a high-precision vacuum gauge I, a high-precision vacuum gauge II, a diaphragm-type polytetrafluoroethylene vacuum pump, and a gas delivery pipe V. The high-precision vacuum gauge I is installed above the reference electrode placement box and is connected to the gas pressure control module of the automated integrated control system via wire V. The high-precision vacuum gauge II is installed above the safety box and is connected to the gas pressure control module of the automated integrated control system via wire VI. The diaphragm-type polytetrafluoroethylene vacuum pump is connected to the acid gas absorption and drying system via the gas delivery pipe V.

[0019] The automated integrated control system includes a control cabinet, a pneumatic control module, a temperature control module, wires V, VI, and VII, a temperature sensor, PTFE electrically controlled pipeline valves I, II, III, IV, and V, an online nitrogen oxide monitor, wires VIII, IX, X, XI, XII, XIII, XIV, and XV, a data cable, and a computer. The pressure control module and high-precision vacuum gauge I are connected via wire V. The pressure control module and high-precision vacuum gauge II are connected via wire VI. The pressure control module and diaphragm PTFE vacuum pump are connected via wire VII to control the operating power and start / stop of the diaphragm PTFE vacuum pump. The temperature control module and temperature sensor are connected via wire VIII. The temperature control module and heating mantle are connected via wire IX to control the temperature and start / stop of the heating mantle. Both the pressure control module and temperature control module are located in the control cabinet. PTFE electrically controlled pipeline valves I, II, and III are also included. I, IV, and V are electrically controlled PTFE pipeline valves installed on gas inlet pipes I, II, III, IV, and V, respectively. They are connected to the pipeline valve control module via wires X, XI, XII, XIII, and XIV to control the opening angle of the five PTFE electrically controlled pipeline valves. An online nitrogen oxide monitor is installed behind the diaphragm PTFE vacuum pump and connected to the control cabinet via wire XV to monitor the nitrogen oxide content of the gas discharged from the diaphragm PTFE vacuum pump in real time. The computer is connected to the electrochemical workstation via a data cable.

[0020] Preferably, the reactor cover of the reduced pressure boiling corrosion reaction system has four frosted glass openings and one circular hole, which are used to fix the condenser tube, working electrode, special platinum electrode, temperature measuring sleeve, and salt bridge outer sleeve, respectively. The salt bridge outer sleeve is fixed to the circular hole of the reactor cover by a through-wall flange tube sealing sleeve I.

[0021] Preferably, the through-wall flange sealing sleeve I and through-wall flange sealing sleeve II are composed of a PTFE through-wall flange tube with external threads, an expanded PTFE washer attached to the flange and an internal expanded PTFE soft liner, and a PTFE fixing nut with internal threads and an expanded PTFE washer attached to the top. In use, the PTFE through-wall flange tube is first passed through the reserved hole, the expanded PTFE washer is inserted into the container, and then the PTFE fixing nut is tightened.

[0022] Preferably, a porous gas guide plate made of polytetrafluoroethylene is installed at the gas inlet of the condenser tube of the acid gas absorption and drying system. The openings on the plate gradually become less dense from the center outward, so as to uniformly distribute the flow field and reduce the vibration caused by the gas flow during extraction.

[0023] Preferably, the gas washing bottle of the acid gas absorption and drying system is filled with saturated Na2CO3 solution to absorb HNO3 vapor in the tail gas generated by the reactor.

[0024] Preferably, the salt bridge outer sheath of the electrochemical testing system is composed of a PTFE half-circular tube with a tenon structure, a PTFE half-circular tube with a tenon-groove structure, and a circular PTFE rib. The circular PTFE rib has three circular vent holes and one circular salt bridge hole. The vent holes are used to connect the gas pressure between the reactor and the reference electrode box, and the salt bridge hole is used to fix and protect the salt bridge tube. The circular PTFE rib can be divided into two parts, which are respectively fused into the PTFE half-circular tube with the tenon structure and the PTFE half-circular tube with the tenon-groove structure.

[0025] Preferably, the dual-tower solid exhaust gas absorber of the acid gas absorption and drying system is U-shaped, with multiple layers of detachable mesh-like partitions installed in the two vertical sections. Filter bags made of GORE-TEX fabric and filled with NaOH solid are placed on the partitions to achieve water-proof and air-permeable purposes, thereby chemically absorbing NOx and CO2 in the exhaust gas. The semi-circular middle section is filled with activated carbon particles for physical adsorption.

[0026] Preferably, the vacuum control system uses a diaphragm-type polytetrafluoroethylene vacuum pump to reduce the pressure of the reactor, reference electrode placement box, acid gas absorption and drying system of the entire device. The high-precision vacuum gauge I and high-precision vacuum gauge II provide real-time feedback of the current vacuum level to the pressure control module. The pressure control module compares the real-time vacuum level with the set vacuum level to control the power and start / stop of the diaphragm-type polytetrafluoroethylene vacuum pump.

[0027] Preferably, both the working electrode and the specially made platinum electrode of the electrochemical testing system are rod-shaped structures with boss-like designs.

[0028] Preferably, the lower part of the drying tower of the acid gas absorption and drying system is filled with CaCl2 particles, the gas guide pipe IV is connected to the lower gas inlet of the drying tower, and the gas guide pipe V is connected to the upper gas outlet of the drying tower.

[0029] In this invention, all components and independent parts that serve as carriers, such as the polytetrafluoroethylene diaphragm pump, are fixed to the experimental frame by means of external pins and shock-absorbing bottom lining material.

[0030] This invention provides an electrochemical testing device for boiling nitric acid corrosion under high temperature and reduced pressure conditions. It can accurately conduct electrochemical experiments and weight loss tests on materials under reduced pressure boiling nitric acid corrosion conditions, acquiring real-time electrochemical information such as corrosion potential, corrosion current, and electrochemical impedance spectroscopy, as well as weight loss information such as corrosion rate. This enables the study of corrosion mechanisms and rapid evaluation of corrosion resistance under relevant environments. Furthermore, it can perform highly realistic simulations of relevant production and operating conditions in the chemical industry, such as simulating the reduced pressure boiling corrosion environment of nitric acid during the operation of spent fuel reprocessing evaporators, and simulating the corrosion behavior of mechanical parts or metal components in equipment used in processes such as reduced pressure evaporation and distillation. This allows for the evaluation of the corrosion resistance and service life of materials under relevant environments. In addition, it can also serve as an experimental device for fundamental research such as the study of saturated vapor pressure.

[0031] In addition, the device employs an automatic control system and a small-flow diaphragm pump, which enables precise control of the gas pressure inside the device and effectively reduces vibration during the pumping process, minimizing the impact on the reference electrode and improving the accuracy of electrochemical testing. The application of the through-wall flange tube sealing sleeve ensures the device's corrosion resistance and sealing performance to a great extent while guaranteeing quick and convenient assembly and disassembly. The design of the dual-tower solid tail gas absorber in the acid gas absorption and drying system not only provides gas purification for the entire device and protects the safety of the downstream vacuum pump operation, but also reduces pressure drop loss during pumping through the design of the sieve partition and the application of the waterproof and breathable membrane, providing favorable conditions for stabilizing the gas pressure inside the device.

[0032] This utility model has the following advantages and beneficial effects:

[0033] 1. This utility model adopts a modular design, and each part of the device can be easily disassembled, combined, and modified.

[0034] 2. This utility model adopts an automatic control system and a small-flow diaphragm pump, which can achieve precise control of the gas pressure inside the device, effectively reduce vibration during the gas extraction process, reduce the impact on the reference electrode, and improve the accuracy of electrochemical testing.

[0035] 3. This invention can simultaneously perform electrochemical testing and weight loss experiments on materials under reduced pressure boiling nitric acid corrosion, and can also simultaneously perform weight loss tests on multiple materials under reduced pressure boiling nitric acid corrosion, greatly improving experimental efficiency.

[0036] 4. Compared with existing nitric acid electrochemical experimental devices, this invention can achieve high-precision electrochemical testing of boiling nitric acid corrosion reaction under different temperatures, vacuum levels, and concentrations, and can monitor electrochemical parameters such as corrosion current and corrosion potential of materials in real time. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of an electrochemical testing device for corrosion of boiling nitric acid under high temperature and low pressure environment according to this utility model.

[0038] Figure 2 This is a schematic diagram of the decompression boiling corrosion reaction system and related devices of this utility model.

[0039] Figure 3 This is a schematic diagram of the salt bridge outer sleeve of this utility model.

[0040] Figure 4 This is a schematic diagram of the sealing sleeve for the through-wall flange tube of this utility model.

[0041] Figure 5 This is a partial schematic diagram of the dual-tower solid exhaust gas absorber of this utility model.

[0042] Figure 6 This is a schematic diagram of the specially made platinum electrode of this utility model.

[0043] In the diagram: 1. Reactor; 2. Reactor cover; 3. Expanded PTFE gasket; 4. Temperature measuring sleeve; 5. Heating jacket; 6. Through-wall flange tube sealing sleeve I; 7. Through-wall flange tube sealing sleeve II; 8. Nitrate bridge; 9. Salt bridge outer sleeve; 10. Working electrode; 11. Special platinum electrode; 12. Reference electrode placement box; 13. High-precision vacuum gauge I; 14. Reference electrode; 15. Pin terminal; 16. Saturated KCl beaker; 17. Electrochemical workstation; 18. Condenser; 19. Safety box; 20. High-precision vacuum gauge II; 21. Gas washing bottle; 22. Double-tower solid tail gas absorber; 23. Drying tower; 24. Gas pressure control module; 25. Temperature control module; 26. Control cabinet; 27. Diaphragm PTFE vacuum pump; 28. Wire I; 29. ​​Wire II; 30. Wire I II; 31. Wire IV; 32. Wire V; 33. Wire VI; 34. Wire VII; 35. Wire VIII; 36. Wire IX; 37. Temperature sensor; 39. Air duct I; 40. Air duct II; 41. Air duct III; 42. Air duct IV; 43. Air duct V; 44. PTFE electrically controlled pipeline valve I; 45. PTFE electrically controlled pipeline valve II; 46. PTFE electrically controlled pipeline valve III; 47. PTFE electrically controlled pipeline valve IV; 48. PTFE electrically controlled pipeline valve V; 49. Online nitrogen oxide monitor; 50. Wire X; 51. Wire XI; 52. Wire XII; 53. Wire XIII; 54. Wire XIV; 55. Wire XV; 56. Computer; 57. Data cable; 58. Pipeline valve control module. Detailed Implementation

[0044] The specific embodiments of this utility model will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate this utility model, but are not intended to limit its scope.

[0045] Example

[0046] In this embodiment, as Figure 1-6 As shown, an electrochemical testing apparatus for boiling nitric acid corrosion under high temperature and reduced pressure includes a reduced pressure boiling corrosion reaction system, an electrochemical testing system, a heating system, an acid gas absorption and drying system, a vacuum control system, an automated integrated control system, and a walk-in fume hood. The reduced pressure boiling corrosion reaction system, the electrochemical testing system, the heating system, the acid gas absorption and drying system, the vacuum control system, and the automated integrated control system are all placed inside the walk-in fume hood.

[0047] Reduced pressure boiling corrosion reaction system, such as Figure 2 As shown, the device consists of a reactor 1, an expanded polytetrafluoroethylene (ePTFE) gasket 3, a reactor cover 2, and quick-connect clamps. The ePTFE gasket 3 is placed between the reactor 1 and the reactor cover 2, and the three are fixed together by quick-connect clamps. The reactor 1 contains a simulated spent fuel reprocessing solution for electrochemical testing of the working electrode 10. The working electrode 10 for electrochemical testing is inserted into the reactor 1 through a pre-reserved opening in the reactor cover 2. Its special frustum-shaped protrusion will be stuck outside the pre-reserved opening in the reactor cover 2. As the gas pressure inside the device decreases, the working electrode 10 will be pressed tightly against the cover due to the pressure difference between the inside and outside of the device. The specially made platinum electrode 11 is fixed in the same way. The device described in this utility model can not only perform electrochemical testing on the specially made working electrode, but also perform depressurized boiling weight loss experiments on test pieces of various sizes and non-standard samples. When performing weight loss experiments, it is only necessary to close the two openings of the reactor cover 2 where the electrode is inserted and the opening of the outer sleeve for fixing the salt bridge.

[0048] The electrochemical testing system consists of a working electrode 10, a specially made platinum electrode 11, a reference electrode 14, wires I28, II29, III30, IV31, a reference electrode placement box 12, pin-shaped terminals 15, a nitrate bridge 8, a salt bridge outer sleeve 9, a through-wall flange tube sealing sleeve I6, a through-wall flange tube sealing sleeve II7, and an electrochemical workstation 17; among which, the specially made platinum electrode 11 is as follows... Figure 6As shown, the system consists of a copper connector, a PTFE boss, a PTFE outer rod, and a platinum sheet. The working electrode 10, a specially made platinum electrode 11, and a reference electrode 14 are respectively placed in the reduced-pressure boiling corrosion reaction system and the reference electrode placement box 12. The working electrode 10 and the specially made platinum electrode 11 are connected to the electrochemical workstation 17 via wires III30 and IV31, respectively. The reference electrode 14 is connected to the pin-shaped terminal 15 via wire I28, and then to the electrochemical workstation 17 via wire II29, thus forming the three-electrode system required for electrochemical testing. The electrochemical workstation 17 is connected to the computer 56 via data cable 57 for electrochemical testing of the sample corrosion reaction. The specially made platinum electrode of this invention is as follows... Figure 6 As shown, it consists of a copper connector, a PTFE boss, a PTFE outer rod, and a platinum sheet.

[0049] The heating system includes a heating jacket 5 and a temperature measuring sleeve 4. The reactor 1 is placed in the heating jacket 5. The temperature measuring sleeve 4 is inserted through the frosted port of the reactor cover 2 and extends below the liquid surface of the reactor 1. The temperature measuring sleeve 4 is filled with dimethyl silicone oil for heat transfer.

[0050] The heating system and the automated integrated control system are connected via wire VIII35 and wire IX36 to regulate and control the temperature of the corrosion reaction in the depressurized boiling corrosion reaction system.

[0051] The acid gas absorption and drying system consists of a condenser 18, pipe I, pipe II, a circulating water tank, a gas guide pipe I39, a safety box 19, a gas guide pipe II40, a gas washing bottle 21, a gas guide pipe III41, a double-tower solid tail gas absorber 22, a gas guide pipe IV42, and a drying tower 23. The condenser 18 is connected to the circulating water tank through pipes I and II. The condenser 18 is connected to the corresponding opening in the center of the reactor cover 2. The upper opening of the condenser 18 is connected to the safety box 19 through the gas guide pipe I39. The safety box 19 is connected to the gas washing bottle 21 through the gas guide pipe II40. The gas washing bottle 21 is connected to the double-tower solid tail gas absorber 22 through the gas guide pipe III41. The double-tower solid tail gas absorber 22 is connected to the drying tower 23 through the gas guide pipe IV42, thereby purifying the acid gas generated during the operation of the depressurized boiling corrosion reaction system.

[0052] The vacuum control system consists of a high-precision vacuum gauge I13, a high-precision vacuum gauge II20, a diaphragm-type polytetrafluoroethylene vacuum pump 27, and a gas guide tube V43. The vacuum control system is connected to the acid gas absorption and drying system via the gas guide tube V43. The high-precision vacuum gauge I13 and the high-precision vacuum gauge II20 are connected to the automated integrated control system via wires V32 and VI33, respectively. The gas pressure control module 24 in the automated integrated control system controls the operating power and start / stop of the diaphragm-type polytetrafluoroethylene vacuum pump 27 to control the vacuum level in the device.

[0053] The automated integrated control system includes a temperature control module 25, a pneumatic pressure control module 24, a pipeline valve control module 58, PTFE electrically controlled pipeline valves I44, II45, III46, IV47, and V48, an online nitrogen oxide monitor 49, wires V32, VI33, and VII34, a temperature sensor 37, VIII35, IX36, X50, XI51, XII52, XIII53, XIV54, and XV55, a data cable 57, and a computer 56.

[0054] In this embodiment, the reactor 1 of the reduced pressure boiling corrosion reaction system is placed in the heating jacket 5; an expanded polytetrafluoroethylene gasket 3 is placed on the reactor 1, and the reactor cover 2 is placed on the expanded polytetrafluoroethylene gasket 3, and the three are tightened by quick-release clamps. A through-wall flange sealing sleeve II7 is installed at the reserved hole of the reactor cover 2, and a condenser tube 18 is installed at the reserved opening in the center of the reactor cover 2. The other three reserved holes are respectively inserted into the working electrode 10, the special platinum electrode 11, and the temperature measuring sleeve 4. The temperature measuring sleeve 4 is filled with dimethyl silicone oil, and then the temperature sensor 37 is inserted into the temperature measuring sleeve 4.

[0055] In this embodiment, the nitrate bridge 8 of the electrochemical testing system is installed inside the outer sleeve 9 of the salt bridge, with one end inserted into the simulated feed liquid contained in the reactor 1, and the other end inserted into the saturated KCl beaker 16 in the reference electrode placement box 12 equipped with a high-precision vacuum gauge I13. The outer sleeve 9 of the salt bridge and the reference electrode placement box 12 are sealed by the through-wall flange tube sleeve I6. Similar to the nitrate bridge 8, the reference electrode 14 is also inserted into the saturated KCl beaker 16. The reference electrode 14 is connected to the pin terminal 15 through the wire I28. The pin terminal 15 is connected to the electrochemical workstation 17 through the wire II29. The working electrode 10 and the special platinum electrode 11 are connected to the electrochemical workstation 17 through the wire III30 and the wire IV31, respectively, thus forming a three-electrode system.

[0056] In this embodiment, the condenser 18 of the acid gas absorption and drying system is connected to the circulating water tank through pipe I and pipe II respectively. The condenser 18 is connected to the safety box 19, which is equipped with a high-precision vacuum gauge II20, through the gas guide pipe I39. The safety box 19 is connected to the gas washing bottle 21 containing saturated Na2CO3 through the gas guide pipe II40. The gas washing bottle 21 is connected to the double-tower solid tail gas absorber 22 through the gas guide pipe III41. Filter bags containing NaOH solid made of GORE-TEX fabric are placed on each partition of the vertical part connected to the double-tower solid tail gas absorber 22. The semi-circular part in the middle is filled with activated carbon particles. Then, it is connected to the drying tower 23, which is filled with CaCl2 particles at the bottom, through the gas guide pipe IV42.

[0057] In this embodiment, both the vacuum control system and the heating system are controlled by an automated integrated control system. The operating power and start / stop status of the diaphragm-type PTFE vacuum pump 27 in the vacuum control system are fed back to the pressure control module 24 in real time by high-precision vacuum gauges I13 and II20, and controlled by the built-in algorithm of the pressure control module 24. Similarly, the operating power and start / stop status of the heating jacket 5 in the heating system are fed back to the temperature control module 25 in real time by the temperature sensor 37 inserted in the temperature sensing sleeve 4, and controlled by the built-in algorithm of the temperature control module 25.

[0058] In this embodiment, the automated integrated control system includes a pressure control module 24, a temperature control module 25, and a pipeline valve control module 58. The pipeline valve control module 58 is connected to polytetrafluoroethylene (PTFE) electrically controlled pipeline valves I44, II45, III46, IV47, and V48 via wires X50, X151, XII52, XIII53, and XIV54. In actual operation, a specific target vacuum level will be set. At this time, the pipeline valve control module 58 will open all PTFE electrically controlled pipeline valves. When the high-precision vacuum gauge I13 displays that the target vacuum level has been reached, PTFE electrically controlled pipeline valves I44 and II45 will be closed. At this time, the high-precision vacuum gauge II20 will be lower than the target vacuum level. Then, the diaphragm-type PTFE vacuum pump 27 will be reversed with minimal power to make the gas pressure of the acid gas absorbent drying system (excluding the condenser 18 and safety box 19) slightly higher than the target vacuum level. At this time, PTFE electrically controlled valve V48 will be closed, and PTFE electrically controlled valve II45 will be opened until the high-precision vacuum gauge II20 displays that the target vacuum level has been reached, after which PTFE electrically controlled valve II45 will be closed. After opening the polytetrafluoroethylene (PTFE) electrically controlled valve I44 and starting the reduced pressure boiling corrosion test, gas will be generated in reactor 1. When the value of the high-precision vacuum gauge II20 is higher than the target vacuum level, open the PTFE electrically controlled valve V48 and operate the diaphragm PTFE vacuum pump 27 according to the value exceeding the target vacuum level. When the acid gas absorbent drying system (excluding the condenser 18 and safety box 19) forms a negative pressure relative to the safety box 19, open the PTFE electrically controlled valve II45. When the vacuum levels of the high-precision vacuum gauges I13 and II20 are both at the target vacuum level, open the PTFE electrically controlled valves III46, IV47, and V48 at 45° until the end of the experiment.

[0059] In this embodiment, a through-wall flange tube sealing sleeve structure is provided at both ends of the reactor cover 2, the reference electrode placement box 12, and the salt bridge outer sleeve 9 for sealing and facilitating the insertion and removal of the salt bridge outer sleeve 9, as shown in the example. Figure 4 As shown, the through-wall flange sealing sleeve specifically consists of a PTFE through-wall flange tube with external threads, an expanded PTFE gasket attached to the flange and an internal expanded PTFE soft liner, and a PTFE fixing nut with internal threads and an expanded PTFE gasket attached to the top. Taking the through-wall flange sealing sleeve I6 installed on the reactor cover 2 as an example, first, place the expanded PTFE gasket at the corresponding opening, then insert the PTFE through-wall flange tube into the opening, so that its external thread portion enters the inside of the reactor cover 2, insert another expanded PTFE gasket from its external thread and fit against the inner wall of the reactor cover 2, and then tighten the PTFE fixing nut along the external thread of the PTFE through-wall flange tube. Because the through-wall flange tube is lined with expanded polytetrafluoroethylene soft liner, the rigid part at one end of the salt bridge outer sleeve 9 can be directly inserted to achieve sealing and fixation. The installation process of the through-wall flange tube sealing sleeve II7 connected to the reference electrode placement box 12 is the same.

[0060] In this embodiment, before assembling the experimental apparatus, the through-wall flange tube sealing sleeve I6 and the through-wall flange tube sealing sleeve II7 are installed on the reactor cover 2 and the reference electrode placement box 12, respectively. Then, the saturated KCl beaker 16 is placed in the reference electrode placement box 12, and the pin-shaped terminal 15 and the high-precision vacuum gauge I13 are inserted into the reserved holes in the reference electrode placement box 12, respectively. Finally, the reference electrode 14 is inserted into the saturated KCl beaker 16 and connected to the pin-shaped terminal 15 with the wire I28.

[0061] After completing all the assembly of the reference electrode placement box 12, place the reactor 1 into the heating jacket 5, place the expanded polytetrafluoroethylene gasket 3 on the reactor 1, and fix the reactor cover 2 to the reactor 1 and the expanded polytetrafluoroethylene gasket 3 with quick-release clamps. Insert the temperature measuring sleeve 4 filled with dimethyl silicone oil and the condenser tube 18 into the corresponding holes of the reactor cover 2, respectively. Connect the condenser tube 18 to the circulating water tank via pipes I and II. Insert the high-precision vacuum gauge II20 into the corresponding hole of the safety box 19. Then connect the safety box 19 and the condenser tube 18 with the gas guide pipe I39 equipped with the polytetrafluoroethylene electrically controlled valve I44, and connect the gas guide pipe II4 with the gas guide pipe II4 equipped with the polytetrafluoroethylene electrically controlled valve II45. A gas washing bottle 21 containing saturated Na2CO3 solution is connected to a double-tower solid tail gas absorber 22 filled with medicine packs and activated carbon granules via a gas pipe III41 equipped with a polytetrafluoroethylene (PTFE) electrically controlled valve III46. A drying tower 23 filled with CaCl2 granules at the bottom is connected to a gas pipe IV42 equipped with a PTFE electrically controlled valve IV47. A diaphragm-type PTFE vacuum pump 27 is then connected via a gas pipe V43 equipped with a PTFE electrically controlled valve V48. An online nitrogen oxide monitor 49 is installed after the diaphragm-type PTFE vacuum pump 27 and connected to a pressure control module 24 built into the control cabinet 26 via a wire XV55.

[0062] After completing the main assembly of the device, insert the salt bridge outer sleeve 9 into the through-wall flange sealing sleeve II7, and insert the other end into the reactor 1 through the through-wall flange sealing sleeve I6 installed on the reactor top cover 2, so that the nitrate bridge 8 can be inserted below the liquid level of the saturated KCl beaker 16. Insert the temperature sensor 37 into the temperature measuring sleeve 4, and connect it to the temperature control module 25 with wire VIII35, and connect the temperature control module 25 and the heating jacket 5 with wire IX36. Connect the high-precision vacuum gauge I13 and high-precision vacuum gauge II20 to the pressure control module 24 with wires V32 and VI33 respectively, and connect the pressure control module 24 and the diaphragm PTFE vacuum pump 27 with wire VII34. The polytetrafluoroethylene (PTFE) electrically controlled pipeline valves I44, II45, III46, IV47, and V48, and the pipeline valve control module 58 are connected sequentially via wires X50, XI51, XII52, XIII53, and XIV54.

[0063] After adding an appropriate amount of simulated feed solution into reactor 1, insert the working electrode 10 and the special platinum electrode 11 into the corresponding holes on the reactor cover 2, and connect them to the electrochemical workstation 17 through wires III30 and IV31, respectively. The reference electrode 14 is connected to the pin terminal 15 through wire I28, and the pin terminal 15 is then connected to the electrochemical workstation 17 through wire II29. Connect the electrochemical workstation 17 to the computer 56 with a data cable 57 to complete the installation of the entire device.

[0064] After installation, set the target vacuum level required for the experiment in the air pressure control module 24 of the control cabinet 26, and set the temperature required for the experiment in the temperature control module 25. Once the simulated liquid in the reactor 1 reaches the depressurized boiling state, the electrochemical workstation 17 can be turned on, and the corresponding electrochemical test parameters can be set in the computer 56 to start the electrochemical test.

[0065] An electrochemical test experiment on the corrosion of boiling nitric acid under high temperature and reduced pressure was conducted using the above-mentioned apparatus, including the following steps:

[0066] S1: Set the target vacuum level required for the experiment in the air pressure control module 24 of the control cabinet 26, and set the temperature required for the experiment in the temperature control module 25.

[0067] S2: The simulated liquid in reactor 1 reaches a state of reduced pressure boiling;

[0068] S3: Turn on the electrochemical workstation 17, set the corresponding electrochemical test parameters in the computer 56, and start the electrochemical test;

[0069] S4: Set the specific target vacuum level, and the pipeline valve control module 58 opens all polytetrafluoroethylene electrically controlled pipeline valves;

[0070] S5: When the high-precision vacuum gauge I13 shows that the target vacuum level has been reached, close the polytetrafluoroethylene (PTFE) electrically controlled pipeline valve I44 and the PTFE electrically controlled pipeline valve II45.

[0071] S6: The vacuum level displayed by the high-precision vacuum gauge II20 will be lower than the target vacuum level. At this time, the diaphragm PTFE vacuum pump 27 will be reversed with extremely low power.

[0072] S7: Make the gas pressure of the acid gas absorption and drying system (excluding condenser 18 and safety box 19) slightly higher than the target vacuum level;

[0073] S8: Close the polytetrafluoroethylene (PTFE) solenoid valve V48 and open the PTFE solenoid valve II45;

[0074] S9: Once the high-precision vacuum gauge II20 displays that the target vacuum level has been reached, close the polytetrafluoroethylene (PTFE) electrically controlled valve II45 and open the PTFE electrically controlled pipeline valve I44.

[0075] S10: After the depressurized boiling corrosion test begins, gas will be generated in reactor 1;

[0076] S11: When the value of the high-precision vacuum gauge II20 is higher than the target vacuum level, open the polytetrafluoroethylene (PTFE) electronic valve V48 and operate the diaphragm-type PTFE vacuum pump 27 according to the value exceeding the target vacuum level.

[0077] S12: When the acid gas absorption and drying system (excluding condenser 18 and safety box 19) forms a negative pressure relative to safety box 19, open the polytetrafluoroethylene electric control valve II45;

[0078] S13: When the vacuum levels of high-precision vacuum gauge I13 and high-precision vacuum gauge II20 are both at the target vacuum level, open the polytetrafluoroethylene (PTFE) electrically controlled valves III46, IV47, and V48 at 45°.

[0079] S14: Open all valves until the experiment is over.

[0080] This experimental setup can simulate the high-temperature, depressurized boiling nitric acid corrosion environment with high fidelity, enabling precise electrochemical testing and weight loss experiments of materials under this environment. It can also acquire information such as corrosion potential and corrosion current in real time, allowing for rapid evaluation of materials. This provides data and technical support for the acid resistance performance, service life assessment, online corrosion monitoring, and corrosion mechanism research of related component materials.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model 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 or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope defined by this utility model.

Claims

1. An experimental apparatus for electrochemical testing of boiling nitric acid corrosion under high temperature and reduced pressure, characterized in that, The experimental setup consists of a reduced pressure boiling corrosion reaction system, an electrochemical testing system, a heating system, an acid gas absorption and drying system, a vacuum control system, and an automated integrated control system. The reduced pressure boiling corrosion reaction system includes a reactor, an expanded polytetrafluoroethylene gasket, a reactor cover, and quick-release clamps. An expanded polytetrafluoroethylene gasket is placed between the reactor and the reactor cover, and the three are fixed by quick-release clamps. The electrochemical testing system includes a working electrode, a specially made platinum electrode, a reference electrode, wire I, wire II, wire III, wire IV, a reference electrode placement box, pin-shaped terminals, a nitrate bridge, a salt bridge outer sleeve, a through-wall flange tube sealing sleeve I, a through-wall flange tube sealing sleeve II, and an electrochemical workstation. The heating system includes a heating jacket and a temperature measuring sleeve. The reactor is placed inside the heating jacket, and the temperature measuring sleeve is inserted through the frosted opening on the reactor cover and extends below the liquid surface in the reactor. The acid gas absorption and drying system includes a condenser, pipe I, pipe II, a circulating water tank, gas guide pipe I, a safety box, gas guide pipe II, a gas washing bottle, gas guide pipe III, a double-tower solid tail gas absorber, gas guide pipe IV, and a drying tower. The condenser is connected to the reduced pressure boiling corrosion reaction system through the frosted port on the reactor cover. It is connected to the circulating water tank through pipe I and pipe II respectively. The upper opening of the condenser is connected to the safety box through gas guide pipe I. The safety box is connected to the gas washing bottle through gas guide pipe II. The gas washing bottle is connected to the double-tower solid tail gas absorber through gas guide pipe III. The double-tower solid tail gas absorber is connected to the drying tower through gas guide pipe IV. The vacuum control system includes a high-precision vacuum gauge I, a high-precision vacuum gauge II, a diaphragm-type polytetrafluoroethylene vacuum pump, and a gas delivery pipe V. The high-precision vacuum gauge I is installed above the reference electrode placement box and is connected to the gas pressure control module of the automated integrated control system via wire V. The high-precision vacuum gauge II is installed above the safety box and is connected to the gas pressure control module of the automated integrated control system via wire VI. The diaphragm-type polytetrafluoroethylene vacuum pump is connected to the acid gas absorption and drying system via the gas delivery pipe V. The automated integrated control system includes a control cabinet, a pneumatic control module, a temperature control module, wires V, VI, and VII, a temperature sensor, PTFE electrically controlled pipeline valves I, II, III, IV, and V, an online nitrogen oxide monitor, wires VIII, IX, X, XI, XII, XIII, XIV, and XV, a data cable, and a computer. The pneumatic control module and the high-precision vacuum gauge I are connected via wire V, and the pneumatic control module and the high-precision vacuum gauge II are connected via wire VI. Wire VII connects the pneumatic control module to the diaphragm-type PTFE vacuum pump to control the operating power and start / stop of the diaphragm-type PTFE vacuum pump. The temperature control module and the temperature sensor are connected via wire VIII, and the temperature control module and the heating mantle are connected via wire IX to control the temperature and start / stop of the heating mantle.

2. The experimental apparatus for electrochemical testing of boiling nitric acid corrosion under high temperature and reduced pressure as described in claim 1, characterized in that, In the automated integrated control system, both the air pressure control module and the temperature control module are located in the control cabinet. PTFE electrically controlled pipeline valves I, II, III, IV, and V are respectively installed on gas guide pipes I, II, III, IV, and V. They are connected to the pipeline valve control module sequentially via wires X, XI, XII, XIII, and XIV to control the opening angle of the five PTFE electrically controlled pipeline valves. An online nitrogen oxide monitor is connected to the control cabinet via wire XV to monitor the nitrogen oxide content of the gas discharged from the diaphragm PTFE vacuum pump in real time. The computer is connected to the electrochemical workstation via a data cable.

3. The experimental apparatus for electrochemical testing of boiling nitric acid corrosion under high temperature and reduced pressure as described in claim 1, characterized in that, The reactor cover of the reduced pressure boiling corrosion reaction system has four frosted glass openings and one circular hole, which are used to fix the condenser tube, working electrode, special platinum electrode, temperature measuring sleeve, and salt bridge outer sleeve, respectively. The salt bridge outer sleeve is fixed to the circular hole of the reactor cover by a through-wall flange tube sealing sleeve I.

4. The experimental apparatus for electrochemical testing of boiling nitric acid corrosion under high temperature and reduced pressure as described in claim 1, characterized in that, The through-wall flange sealing sleeve I and through-wall flange sealing sleeve II consist of a PTFE through-wall flange tube with external threads, an expanded PTFE washer attached to the flange and an internal expanded PTFE soft liner, and a PTFE fixing nut with internal threads and an expanded PTFE washer attached to the top. In use, the PTFE through-wall flange tube is first passed through the reserved hole, the expanded PTFE washer is inserted into the container, and then the PTFE fixing nut is tightened.

5. The experimental apparatus for electrochemical testing of boiling nitric acid corrosion under high temperature and reduced pressure as described in claim 1, characterized in that, The gas inlet of the condenser tube of the acid gas absorption and drying system is equipped with a porous gas guide plate made of polytetrafluoroethylene. The openings on the plate gradually become less dense from the center to the outside, which is used to uniformly distribute the flow field and reduce the vibration caused by the gas flow during extraction. The gas washing bottle of the acid gas absorption and drying system is filled with saturated Na2CO3 solution to absorb HNO3 vapor in the tail gas generated by the reactor.

6. The experimental apparatus for electrochemical testing of boiling nitric acid corrosion under high temperature and reduced pressure as described in claim 1, characterized in that, The dual-tower solid exhaust gas absorber of the acid gas absorption and drying system is U-shaped. Multiple layers of detachable mesh-like baffles are installed in the two vertical sections. Filter bags made of GORE-TEX fabric and filled with NaOH solid are placed on the baffles to achieve water-proof and air-permeable purposes, chemically absorbing NOx and CO2 in the exhaust gas. The semi-circular part in the middle is filled with activated carbon particles for physical adsorption.

7. The experimental apparatus for electrochemical testing of boiling nitric acid corrosion under high temperature and reduced pressure as described in claim 1, characterized in that, The salt bridge outer sheath of the electrochemical testing system consists of a 1 / 2-circular PTFE tube with a tenon structure, a 1 / 2-circular PTFE tube with a mortise and tenon structure, and a circular PTFE rib. The circular PTFE rib has three circular vent holes and one circular salt bridge hole. The vent holes are used to connect the gas pressure between the reactor and the reference electrode box, and the salt bridge hole is used to fix and protect the salt bridge tube. The circular PTFE rib is divided into two parts, which are respectively fused into the 1 / 2-circular PTFE tube with the tenon structure and the 1 / 2-circular PTFE tube with the mortise and tenon structure.

8. The experimental apparatus for electrochemical testing of boiling nitric acid corrosion under high temperature and reduced pressure as described in claim 1, characterized in that, The vacuum control system uses a diaphragm-type polytetrafluoroethylene vacuum pump to reduce the pressure of the reactor, reference electrode placement box, acid gas absorption and drying system of the entire device. The high-precision vacuum gauge I and high-precision vacuum gauge II provide real-time feedback of the current vacuum level to the pressure control module. The pressure control module compares the real-time vacuum level with the set vacuum level to control the power and start / stop of the diaphragm-type polytetrafluoroethylene vacuum pump.

9. The experimental apparatus for electrochemical testing of boiling nitric acid corrosion under high temperature and reduced pressure as described in claim 1, characterized in that, The lower part of the drying tower is filled with CaCl2 particles. Gas pipe IV is connected to the air inlet at the lower end of the drying tower, and gas pipe V is connected to the air outlet at the upper end of the drying tower.

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