Boiling nitric acid corrosion electrochemical test experimental device and method in high-temperature reduced-pressure environment

Abstract

The invention discloses an experimental device and method for electrochemical testing of boiling nitric acid corrosion in a high-temperature reduced-pressure environment, and relates to the technical field of electrochemical testing, the experimental device is composed of a reduced-pressure boiling corrosion reaction system, an electrochemical testing 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 and method can test and simulate the electrochemical corrosion behavior of the high-temperature reduced-pressure boiling nitric acid in the evaporator environment for spent fuel post-treatment, and can realize the 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] The invention relates to the technical field of electrochemical testing, and in particular to a boiling nitric acid corrosion electrochemical testing experimental device and method under a high-temperature and reduced-pressure environment. Background Art

[0002] At present, there are two main types of nitric acid corrosion test devices: nitric acid corrosion weight loss test device and nitric acid corrosion electrochemical test device. Among them, the nitric acid corrosion weight loss test characterizes the corrosion rate by the weight loss of the sample before and after corrosion, which is suitable for evaluating the corrosion resistance of different materials, but it cannot accurately reflect the local corrosion of the material (such as pitting, intergranular corrosion, etc.), and it also has the disadvantage of a long test cycle; while the electrochemical experiment provides a fast, real-time, and accurate corrosion measurement method, and can obtain chemical reaction thermodynamics and reaction kinetics information, revealing the microscopic mechanism of corrosion behavior.

[0003] In the field of chemical production, boiling nitric acid corrosion under high temperature and reduced pressure environment is often encountered. For example, in the PUREX solvent extraction process, the mainstream process of spent fuel reprocessing and regeneration cycle in nuclear reactors, nitric acid is used as a salting-out agent. Boiling nitric acid corrosion under high temperature and reduced pressure environment exists in the evaporator of the main processing equipment. It is urgent to study the corrosion resistance and service life of the structural materials of the evaporator under such conditions. This requires simulating a high temperature and reduced pressure environment to conduct electrochemical experiments on boiling nitric acid corrosion.

[0004] However, there are many difficulties in safely, accurately and reliably carrying out boiling nitric acid corrosion electrochemical experiments under high temperature and reduced pressure environment:

[0005] ① The electrochemical experiment of boiling nitric acid corrosion under high temperature and reduced pressure environment is determined by 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 vacuum decompression process. This experimental device is not a simple single device, but a complex device system;

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

[0007] ③ Since the high temperature environment in the boiling nitric acid corrosion experiment reactor will damage the reference electrode used in the electrochemical test carried out simultaneously, only the working electrode and the auxiliary electrode are placed in the reactor, and the reference electrode is placed alone. The air pressure will affect the solubility of KCl in the solution where the reference electrode is located, and then affect the potential of the reference electrode, reducing the precision and accuracy of the electrochemical test. How to ensure that the reference electrode outside the reactor is in an isobaric state with the working electrode and the auxiliary electrode in the reduced pressure environment of the reactor to ensure the accuracy of the electrochemical test is an unavoidable difficulty;

[0008] ④ The vibration generated by the vacuum pump during evacuation will cause great interference to the electrochemical test system, which is also a difficulty in the reduced pressure boiling nitric acid corrosion electrochemical experiment;

[0009] ⑤The sealing problem of the device and the treatment of harmful exhaust gas are also difficult points.

[0010] Because of the above difficulties, electrochemical tests were mainly carried out for boiling nitric acid corrosion under normal pressure in the past. Electrochemical experiments on boiling nitric acid corrosion under high temperature and reduced pressure environment were rarely reported in professional literature, and no relevant patents were found. In view of this, it is urgent to invent an electrochemical test experimental device and method for boiling nitric acid corrosion under high temperature and reduced pressure environment, which can provide scientific and effective solutions to the above difficulties, accurately simulate the relevant service environment of the material, and provide technical support for studying the corrosion resistance and service life of the material under boiling nitric acid corrosion under high temperature and reduced pressure environment. Summary of the invention

[0011] The purpose of the present invention is to provide a boiling nitric acid corrosion electrochemical test experimental device and method under a high-temperature and reduced-pressure environment, so as to solve the problem that the existing nitric acid corrosion weight loss experimental device and nitric acid corrosion electrochemical test device cannot carry out weight loss experiments and electrochemical experiments under reduced-pressure boiling conditions, so as to study the boiling nitric acid corrosion corrosion resistance and service life of materials under a high-temperature and reduced-pressure environment.

[0012] The present invention innovatively provides a systematic solution to the many technical difficulties faced in the electrochemical experiment of boiling nitric acid corrosion under a high-temperature and reduced-pressure environment, such as: the problem of precise control of gas pressure, the problem of maintaining equal pressure between the reference electrode, the working electrode and the auxiliary electrode, the problem of vibration interference in the air extraction process, the problem of device sealing, the problem of handling harmful exhaust gas, etc. The present invention can simulate and restore the high-temperature and reduced-pressure working conditions with high fidelity, and conduct high-precision electrochemical test experiments on boiling nitric acid corrosion under this environment, thereby making up for the shortcomings and limitations of the prior art.

[0013] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present invention is: firstly, a boiling nitric acid corrosion electrochemical test experimental device under high temperature and reduced pressure environment is provided, and the experimental device is composed of a reduced pressure boiling corrosion reaction system, an electrochemical test system, a heating system, an acid gas absorption and drying system, a vacuum control system and an automatic 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 with the reduced pressure boiling corrosion reaction system, and the automatic integrated control system is used to control the experimental device.

[0014] The reduced pressure boiling corrosion reaction system is used to hold the solution and sample required for the reaction, and provides a reduced pressure reaction place 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. The expanded polytetrafluoroethylene gasket is placed between the reactor and the reactor cover, and the three are fixed by a quick-release clamp.

[0015] The electrochemical test system is used for electrochemical testing, and comprises a working electrode, a special platinum electrode, a reference electrode, a wire I, a wire II, a wire III, a wire IV, a reference electrode placement box, a pin-shaped terminal, 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 comprises a heating jacket and a temperature measuring sleeve. The reactor is placed in the heating jacket. The temperature measuring sleeve is inserted through the frosted opening of the reactor cover and penetrates below the liquid level of the reactor. The temperature measuring sleeve is filled with dimethyl silicone oil for heat transfer.

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

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

[0019] The automated integrated control system comprises a control cabinet, an air pressure control module, a temperature control module, a wire V, a wire VI, a wire VII, a temperature sensor, a polytetrafluoroethylene electric-controlled pipeline valve I, a polytetrafluoroethylene electric-controlled pipeline valve II, a polytetrafluoroethylene electric-controlled pipeline valve III, a polytetrafluoroethylene electric-controlled pipeline valve IV, a polytetrafluoroethylene electric-controlled pipeline valve V, an online nitrogen oxide monitor, a wire VIII, a wire IX, a wire X, a wire XI, a wire XII, a wire XIII, a wire XIV, a wire XV, a data line, and a computer. The air pressure control module is connected to the high-precision vacuum gauge I via wire V, the air pressure control module is connected to the high-precision vacuum gauge II via wire VI, the air pressure control module is connected to the diaphragm polytetrafluoroethylene vacuum pump via wire VII to control the operating power and start and stop of the diaphragm polytetrafluoroethylene vacuum pump, the temperature control module is connected to the temperature sensor via wire VIII, the temperature control module is connected to the heating sleeve via wire IX to control the temperature and start and stop of the heating sleeve, the air pressure control module and the temperature control module are both placed in the control cabinet, polytetrafluoroethylene electric control pipeline valve I, polytetrafluoroethylene electric control pipeline valve II, polytetrafluoroethylene electric control pipeline valve II I. Polytetrafluoroethylene electric-controlled pipeline valve IV and polytetrafluoroethylene electric-controlled pipeline valve V are respectively installed on air duct I, air duct II, air duct III, air duct IV and air duct V, and are connected to pipeline valve control modules through wire X, wire XI, wire XII, wire XIII and wire XIV in sequence to control the opening angles of the five polytetrafluoroethylene electric-controlled pipeline valves. An online nitrogen oxide monitor is installed behind a diaphragm polytetrafluoroethylene vacuum pump and is connected to a control cabinet through a wire XV to monitor the nitrogen oxide content of exhaust gas from the diaphragm polytetrafluoroethylene vacuum pump in real time. The computer is connected to an electrochemical workstation via a data cable.

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

[0021] Preferably, the through-wall flange tube sealing sleeve I and the through-wall flange tube sealing sleeve II are composed of a polytetrafluoroethylene through-wall flange tube with an external thread, an expanded polytetrafluoroethylene gasket attached to the flange and an expanded polytetrafluoroethylene soft lining attached inside, and a polytetrafluoroethylene fixing nut with an internal thread and an expanded polytetrafluoroethylene gasket attached to the top. When in use, the polytetrafluoroethylene through-wall flange tube is first passed through the reserved hole, the expanded polytetrafluoroethylene gasket is inserted into the container, and then the polytetrafluoroethylene fixing nut is tightened.

[0022] Preferably, a polytetrafluoroethylene porous gas guide slow flow plate is installed at the gas inlet of the condenser tube of the acid gas absorption and drying system, and the holes on the plate are gradually sparse from the center to the outside to evenly distribute the flow field and slow down 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 a saturated Na2CO3 solution to absorb the HNO3 vapor in the tail gas generated by the reactor.

[0024] Preferably, the salt bridge outer sleeve of the electrochemical test system is composed of a polytetrafluoroethylene 1 / 2 round tube with a tenon structure, a polytetrafluoroethylene 1 / 2 round tube with a tongue and groove structure, and a circular polytetrafluoroethylene rib. The circular polytetrafluoroethylene rib has three circular vents and a circular salt bridge hole, the vent is used to connect the air pressure between the reactor and the reference electrode box, the salt bridge hole is used to fix and protect the salt bridge tube, and the circular polytetrafluoroethylene rib can be divided into two, respectively welded in the polytetrafluoroethylene 1 / 2 round tube with a tenon structure and the polytetrafluoroethylene 1 / 2 round tube with a tongue and groove structure.

[0025] Preferably, the double-tower solid exhaust gas absorber of the acid gas absorption and drying system is U-shaped, and a multi-layer detachable mesh partition is installed in the two vertical parts. A filter bag made of GORE-TEX fabric and filled with NaOH solid is placed on the partition to achieve the purpose of water-proof and breathable, thereby chemically absorbing NOx and CO2 in the exhaust gas. The middle semicircular part is filled with activated carbon particles for physical adsorption.

[0026] Preferably, the vacuum control system adopts a diaphragm polytetrafluoroethylene vacuum pump to reduce the pressure of the reactor, reference electrode placement box, acid gas absorption and drying system of the entire device, and the current vacuum degree is fed back to the air pressure control module in real time through high-precision vacuum gauge I and high-precision vacuum gauge II. The air pressure control module compares the real-time vacuum degree with the set vacuum degree to control the power and start and stop of the diaphragm polytetrafluoroethylene vacuum pump.

[0027] Preferably, the working electrode and the special platinum electrode of the electrochemical testing system are both rod-shaped structures with a boss-shaped design.

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

[0029] In the present invention, all the components and independent parts used as the carrier, such as the polytetrafluoroethylene diaphragm pump, etc., are fixed on the experimental frame by means of external pins and bottom lining shock-absorbing materials.

[0030] The present invention also provides a boiling nitric acid corrosion electrochemical test experimental method under high temperature and reduced pressure environment, which is implemented by using the above device:

[0031] S1: Set the target vacuum required for the experiment in the air pressure control module of the control cabinet, and set the temperature required for the experiment in the temperature control module;

[0032] S2: The simulated liquid in the reactor reaches the reduced pressure boiling state;

[0033] S3: Turn on the electrochemical workstation, set corresponding electrochemical test parameters in the computer, and start the electrochemical test;

[0034] S4: Setting a specific target vacuum degree, the pipeline valve control module opens all polytetrafluoroethylene electronically controlled pipeline valves;

[0035] S5: When the high-precision vacuum gauge I shows that the target vacuum degree has been reached, close the polytetrafluoroethylene electric control pipeline valve I and the polytetrafluoroethylene electric control pipeline valve II;

[0036] S6: The vacuum degree displayed by the high-precision vacuum gauge II will be lower than the target vacuum degree. At this time, the diaphragm polytetrafluoroethylene vacuum pump is reversed at very low power;

[0037] S7: Make the gas pressure of the acid gas absorption and drying system (excluding the condenser and the safety box) slightly higher than the target vacuum degree;

[0038] S8: close the polytetrafluoroethylene electric control valve V, and open the polytetrafluoroethylene electric control valve II;

[0039] S9: until the high-precision vacuum gauge II shows that the target vacuum degree has been reached, the polytetrafluoroethylene electric control valve II is closed and the polytetrafluoroethylene electric control pipeline valve I is opened;

[0040] S10: After the reduced pressure boiling corrosion test begins, gas will be generated in the reactor;

[0041] S11: When the value of the high-precision vacuum gauge II is higher than the target vacuum degree, the polytetrafluoroethylene electric control valve V is opened and the diaphragm polytetrafluoroethylene vacuum pump is operated according to the value exceeding the target vacuum degree;

[0042] S12: When the acid gas absorption and drying system (excluding the condenser and the safety box) forms a negative pressure relative to the safety box, open the polytetrafluoroethylene electric control valve II;

[0043] S13: When the vacuum degrees of the high-precision vacuum gauge I and the high-precision vacuum gauge II are both the target vacuum degrees, the polytetrafluoroethylene electric control valve III, the polytetrafluoroethylene electric control valve IV, and the polytetrafluoroethylene electric control valve V are opened at 45°;

[0044] S14: Open all valves until the end of the experiment.

[0045] The present invention provides an electrochemical test experimental device and method for boiling nitric acid corrosion under a high-temperature and reduced-pressure environment, which can accurately implement electrochemical experiments and weight loss tests of materials under a reduced-pressure boiling nitric acid corrosion environment, obtain electrochemical information such as corrosion potential, corrosion current, and electrochemical impedance spectrum of the materials in real time, and can obtain weight loss information such as corrosion rate, so as to realize the research on the corrosion mechanism of the materials under relevant environments and the rapid evaluation of corrosion resistance; it can also perform highly realistic simulation of relevant production and operation conditions in the chemical industry, such as simulating the reduced-pressure boiling nitric acid corrosion environment when a spent fuel reprocessing evaporator is in operation, simulating the corrosion behavior of mechanical parts or metal components of equipment used in processes such as reduced-pressure evaporation and reduced-pressure distillation, etc., and can evaluate the corrosion resistance and service life of materials under relevant environments; in addition, it can also be used as an experimental device for basic research such as studying the saturated vapor pressure of substances.

[0046] In addition, the device adopts an automatic control system and a small-flow diaphragm pump, which can achieve precise control of the air pressure inside the device, effectively reduce vibration during the vacuum process, reduce the impact on the reference electrode, and improve the accuracy of electrochemical testing; the application of through-wall flange tube sealing sleeves, while ensuring quick and convenient disassembly and assembly of the device, greatly ensures the corrosion resistance and sealing of the device; the design of the double-tower solid tail gas absorber in the acid gas absorption and drying system of the device, on the one hand, provides gas purification for the entire device and protects the safety of the operation of the rear vacuum pump; on the other hand, through the design of the sieve partition and the application of waterproof and breathable membrane, the pressure drop loss in the device during vacuuming is reduced, providing favorable conditions for stabilizing the air pressure in the device.

[0047] The present invention has the following advantages and beneficial effects:

[0048] 1. The present invention adopts modular design, and each part of the device can be easily disassembled, assembled and remodeled.

[0049] 2. The present invention adopts an automatic control system and a small-flow diaphragm pump, which can achieve precise control of the air pressure in the device, effectively reduce vibration during the air extraction process, reduce the impact on the reference electrode, and improve the accuracy of electrochemical testing.

[0050] 3. The present invention can simultaneously realize the electrochemical test and weight loss experiment of nitric acid corrosion of materials under reduced pressure boiling environment, and can also simultaneously realize the weight loss test of multiple materials under reduced pressure boiling nitric acid corrosion, thereby greatly improving the experimental efficiency.

[0051] 4. Compared with the existing nitric acid electrochemical experimental device, the present invention can realize high-precision electrochemical testing of boiling nitric acid corrosion reaction under conditions of different temperatures, different vacuum degrees, different concentrations, etc., and can monitor electrochemical parameters such as corrosion current and corrosion potential of the material in real time. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 It is a structural schematic diagram of a boiling nitric acid corrosion electrochemical test experimental device under a high-temperature and reduced-pressure environment of the present invention.

[0053] Figure 2 It is a schematic diagram of the reduced pressure boiling corrosion reaction system and its related devices of the present invention.

[0054] Figure 3 Schematic diagram of the salt bridge outer sleeve of the present invention.

[0055] Figure 4 It is a schematic diagram of the through-wall flange pipe sealing sleeve of the present invention.

[0056] Figure 5 It is a partial schematic diagram of the double-tower solid tail gas absorber of the present invention.

[0057] Figure 6 This is a schematic diagram of the specially made platinum electrode of the present invention.

[0058] Figure 7 This is the electrochemical curve measured by the present invention.

[0059] In the figure: 1. Reactor; 2. Reactor cover; 3. Expanded polytetrafluoroethylene gasket; 4. Temperature measuring sleeve; 5. Heating sleeve; 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-shaped terminal; 16. Saturated KCl beaker; 17. Electrochemical workstation; 18. Condenser; 19. Safety box; 20. High-precision vacuum gauge II; 21. Washing bottle; 22. Double-tower solid tail gas absorber; 23. Drying tower; 24. Air pressure control module; 25. Temperature control module; 26. Control cabinet; 27. Diaphragm polytetrafluoroethylene 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. Polytetrafluoroethylene electric-controlled pipeline valve I; 45. Polytetrafluoroethylene electric-controlled pipeline valve II; 46. Polytetrafluoroethylene electric-controlled pipeline valve III; 47. Polytetrafluoroethylene electric-controlled pipeline valve IV; 48. Polytetrafluoroethylene electric-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 DESCRIPTION

[0060] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0061] Example

[0062] In this embodiment, Figure 1-6 As shown, an electrochemical test experimental device for boiling nitric acid corrosion under a high-temperature and reduced-pressure environment includes a reduced-pressure boiling corrosion reaction system, an electrochemical test 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 test system, the heating system, the acid gas absorption and drying system, the vacuum control system, and the automated integrated control system are all placed in the walk-in fume hood.

[0063] The reduced pressure boiling corrosion reaction system is as follows Figure 2 As shown, the device is composed of a reactor 1, an expanded polytetrafluoroethylene gasket 3, a reactor cover 2, and a quick-install clamp. The expanded polytetrafluoroethylene gasket 3 is placed between the reactor 1 and the reactor cover 2, and the three are fixed by the quick-install clamp. The spent fuel post-processing simulated liquid is placed in the reactor 1 for electrochemical testing of the working electrode 10. The working electrode 10 for electrochemical testing is inserted into the reactor 1 through the reserved opening of the reactor cover 2, and its special truncated cone-shaped protrusion will be stuck outside the reserved opening of the reactor cover 2. As the air pressure in the device decreases, the working electrode 10 will be tightly attached to the cover due to the pressure difference between the inside and outside of the device, and the special platinum electrode 11 is also fixed in the same way. The device of the present invention can not only perform electrochemical testing on special working electrodes, but also perform reduced pressure boiling weight loss experiments on test pieces of various sizes and non-standard samples. When performing the weight loss test, it is only necessary to close the openings of the reactor cover 2 for inserting electrodes at two locations and the opening of the fixed salt bridge outer sleeve.

[0064] The electrochemical test system is composed of a working electrode 10, a special platinum electrode 11, a reference electrode 14, a wire I28, a wire II29, a wire III30, a wire IV31, a reference electrode placement box 12, a pin-shaped terminal 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; wherein the special platinum electrode 11 is as follows Figure 6As shown, it is composed of a copper terminal, a polytetrafluoroethylene boss, a polytetrafluoroethylene outer rod and a platinum sheet; the working electrode 10, the special platinum electrode 11, and the reference electrode 14 are respectively arranged in the reduced pressure boiling corrosion reaction system and the reference electrode placement box 12. 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. The reference electrode 14 is connected to the pin-shaped terminal 15 through the wire I28, and then connected to the electrochemical workstation 17 through the wire II29, thereby forming a three-electrode system required for electrochemical testing. The electrochemical workstation 17 is connected to the computer 56 via the data line 57 for electrochemical testing of sample corrosion reactions. The special platinum electrode of the present invention is as shown in FIG. Figure 6 As shown, it is composed of a copper terminal, a polytetrafluoroethylene boss, a polytetrafluoroethylene outer rod and a platinum sheet.

[0065] The heating system includes a heating sleeve 5 and a temperature measuring sleeve 4. The reactor 1 is placed in the heating sleeve 5. The temperature measuring sleeve 4 is inserted through the frosted opening of the reactor upper cover 2 and penetrates below the liquid level of the reactor 1. The temperature measuring sleeve 4 is filled with dimethyl silicone oil for heat transfer.

[0066] The heating system and the automatic integrated control system are connected via wire VIII35 and wire IX36, and are used to adjust and control the temperature of the corrosion reaction in the reduced pressure boiling corrosion reaction system.

[0067] The acid gas absorption and drying system consists of a condenser 18, a tube I, a tube II, a circulating water tank, an air guide pipe I39, a safety box 19, an air guide pipe II40, a gas washing bottle 21, an air guide pipe III41, a double-tower solid tail gas absorber 22, an air guide pipe IV42, and a drying tower 23; the condenser 18 is connected to the circulating water tank through tubes I and II, the condenser 18 is connected to the corresponding opening in the center of the reactor upper cover 2, the upper end opening of the condenser 18 is connected to the safety box 19 through the air guide pipe I39, the safety box 19 is connected to the gas washing bottle 21 through the air guide pipe II40, the gas washing bottle 21 is connected to the double-tower solid tail gas absorber 22 through the air guide pipe III41, and the double-tower solid tail gas absorber 22 is connected to the drying tower 23 through the air guide pipe IV42, so as to purify the acid gas generated during the operation of the reduced pressure boiling corrosion reaction system.

[0068] The vacuum control system consists of a high-precision vacuum gauge I13, a high-precision vacuum gauge II20, a diaphragm polytetrafluoroethylene vacuum pump 27, and an air duct V43; the vacuum control system is connected to the acid gas absorption and drying system via the air duct V43, and 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 air pressure control module 24 in the automated integrated control system controls the operating power and start and stop of the diaphragm polytetrafluoroethylene vacuum pump 27, thereby achieving control of the vacuum degree in the device.

[0069] The automated integrated control system includes a temperature control module 25, an air pressure control module 24, a pipeline valve control module 58, a polytetrafluoroethylene electric-controlled pipeline valve I44, a polytetrafluoroethylene electric-controlled pipeline valve II45, a polytetrafluoroethylene electric-controlled pipeline valve III46, a polytetrafluoroethylene electric-controlled pipeline valve IV47, a polytetrafluoroethylene electric-controlled pipeline valve V48, an online nitrogen oxide monitor 49, a wire V32, a wire VI33, a wire VII34, a temperature sensor 37, a wire VIII35, a wire IX36, a wire X50, a wire XI51, a wire XII52, a wire XIII53, a wire XIV54, a wire XV55, a data cable 57, and a computer 56.

[0070] In this embodiment, the reactor 1 of the reduced pressure boiling corrosion reaction system is placed in the heating sleeve 5; an expanded polytetrafluoroethylene gasket 3 is placed on the reactor 1, the reactor cover 2 is placed on the expanded polytetrafluoroethylene gasket 3, and the three are clamped together by a quick-release clamp, a through-wall flange tube sealing sleeve II7 is installed at the reserved hole in the reactor cover 2, a condenser 18 is installed at the reserved opening in the center of the reactor cover 2, and 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.

[0071] In this embodiment, the nitrate bridge 8 of the electrochemical test system is installed in the salt bridge outer sleeve 9, so that one end of it is inserted into the simulated liquid contained in the reactor 1, and the other end is inserted into the saturated KCl beaker 16 in the reference electrode placement box 12 equipped with a high-precision vacuum gauge I13. The salt bridge outer sleeve 9 and the reference electrode placement box 12 are sealed by a through-wall flange tube sleeve I6. Like 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-shaped terminal 15 through a wire I28, and the pin-shaped terminal 15 is connected to the electrochemical workstation 17 through a wire II29. The working electrode 10 and the special platinum electrode 11 are connected to the electrochemical workstation 17 through a wire III30 and a wire IV31, respectively, thereby forming a three-electrode system.

[0072] In this embodiment, the condenser 18 of the acid gas absorption and drying system is connected to the circulating water tank through tube I and tube II respectively. The condenser 18 is connected to the safety box 19 with a high-precision vacuum gauge II20 installed on the top through the air duct I39. The safety box 19 is connected to the washing bottle 21 filled with saturated Na2CO3 through the air duct II40. The washing bottle 21 is connected to the double-tower solid exhaust gas absorber 22 through the air duct III41. Filter bags made of GORE-TEX fabric filled with NaOH solid are placed on each partition of the vertical part connected to the double-tower solid exhaust gas absorber 22. The semicircular part in the middle is filled with activated carbon particles, and then connected to the drying tower 23 filled with CaCl2 particles at the bottom through the air duct IV42.

[0073] In this embodiment, the vacuum control system and the heating system are both controlled by an automated integrated control system. The operating power and start / stop of the diaphragm polytetrafluoroethylene vacuum pump 27 of the vacuum control system are fed back to the air pressure control module 24 by the real-time data of the high-precision vacuum gauge I13 and the high-precision vacuum gauge II20, and are controlled by the built-in algorithm of the air pressure control module 24. The operating power and start / stop of the heating sleeve 5 of the heating system are fed back to the temperature control module 25 by the real-time data of the temperature sensor 37 inserted in the temperature measuring sleeve 4, and are controlled by the built-in algorithm of the temperature control module 25.

[0074] In this embodiment, the automated integrated control system includes an air pressure control module 24, a temperature control module 25 and a pipeline valve control module 58, wherein the pipeline valve control module 58 is connected to polytetrafluoroethylene electric-controlled pipeline valve I44, polytetrafluoroethylene electric-controlled pipeline valve II45, polytetrafluoroethylene electric-controlled pipeline valve III46, polytetrafluoroethylene electric-controlled pipeline valve IV47, and polytetrafluoroethylene electric-controlled pipeline valve V48 through wire X50, wire XI51, wire XII52, wire XIII53, and wire XIV54. In actual operation, a specific target vacuum degree will be set. At this time, the pipeline valve control module 58 will open all polytetrafluoroethylene electric-controlled pipeline valves. When the high-precision vacuum gauge I13 shows that the target vacuum degree has been reached, the polytetrafluoroethylene electric-controlled pipeline valve I44 and the polytetrafluoroethylene electric-controlled pipeline valve II45 will be closed. At this time, the high-precision vacuum gauge II20 will be lower than the target vacuum degree. At this time, the diaphragm polytetrafluoroethylene vacuum pump 27 will be reversed with extremely small power to make the air pressure of the acid gas absorbent drying system (excluding the condenser 18 and the safety box 19) slightly higher than the target vacuum degree. At this time, the polytetrafluoroethylene electric-controlled valve V48 will be closed, and the polytetrafluoroethylene electric-controlled valve II45 will be opened until the high-precision vacuum gauge II20 shows that the target vacuum degree has been reached, then the polytetrafluoroethylene electric-controlled valve II45 will be closed and Open the polytetrafluoroethylene electric control valve I44. After the reduced pressure boiling corrosion test begins, gas will be generated in the reactor 1. When the value of the high-precision vacuum gauge II20 is higher than the target vacuum degree, open the polytetrafluoroethylene electric control valve V48 and operate the diaphragm polytetrafluoroethylene vacuum pump 27 according to the value exceeding the target vacuum degree. When the acid gas absorbent drying system (excluding the condenser 18 and the safety box 19) forms a negative pressure relative to the safety box 19, open the polytetrafluoroethylene electric control valve II45. When the vacuum degrees of the high-precision vacuum gauge I13 and the high-precision vacuum gauge II20 are both the target vacuum degrees, open the polytetrafluoroethylene electric control valve III46, the polytetrafluoroethylene electric control valve IV47, and the polytetrafluoroethylene electric control valve V48 at 45° until all valves are opened at the end of the experiment.

[0075] In this embodiment, the through-wall flange pipe sealing sleeve structure for sealing and facilitating the insertion and removal of the salt bridge outer sleeve 9 is provided at the reactor upper cover 2, the reference electrode placement box 12 and both ends of the salt bridge outer sleeve 9. Figure 4 As shown, the through-wall flange pipe sealing sleeve specifically consists of a polytetrafluoroethylene through-wall flange pipe with external threads, an expanded polytetrafluoroethylene gasket attached to the flange and an expanded polytetrafluoroethylene soft lining attached therein, and a polytetrafluoroethylene fixing nut with internal threads and an expanded polytetrafluoroethylene gasket attached to the top. Taking the through-wall flange pipe sealing sleeve 16 installed on the reactor cover 2 as an example, the expanded polytetrafluoroethylene gasket is first placed at the corresponding hole, and then the polytetrafluoroethylene through-wall flange pipe is inserted into the hole so that its external thread part enters the inner side of the reactor cover 2, and another expanded polytetrafluoroethylene gasket is inserted from the external thread and fits the inner wall of the reactor cover 2, and then the polytetrafluoroethylene fixing nut is tightened along the external thread of the polytetrafluoroethylene through-wall flange pipe. Since the through-the-wall flange tube is equipped with an expanded polytetrafluoroethylene soft lining, the hard part of one end of the salt bridge outer sleeve 9 can be directly inserted to achieve sealing and fixation. The installation process of the through-the-wall flange tube sealing sleeve II7 connected to the reference electrode placement box 12 is the same.

[0076] In this embodiment, before assembling the experimental device, the through-wall flange tube sealing sleeve I6 and the through-wall flange tube sealing sleeve II7 are respectively installed on the reactor cover 2 and the reference electrode placement box 12, and 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 respectively inserted into the reserved holes in the reference electrode placement box 12, and finally the reference electrode 14 is inserted into the saturated KCl beaker 16 and connected to the pin-shaped terminal 15 with a wire I28.

[0077] After completing all the assembly of the reference electrode placement box 12, put 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 a quick-release clamp, insert the temperature measuring sleeve 4 filled with dimethyl silicone oil and the condenser 18 into the corresponding holes of the reactor cover 2, connect the condenser 18 to the circulating water tank through the connecting pipe I and the pipe II, insert the high-precision vacuum gauge II20 into the corresponding hole of the safety box 19, and then connect the safety box 19 and the condenser 18 with the air guide pipe I39 equipped with the polytetrafluoroethylene electric control valve I44, and connect the air guide pipe II4 equipped with the polytetrafluoroethylene electric control valve II45. 0 is connected to the washing bottle 21 filled with saturated Na2CO3 solution, and the double-tower solid tail gas absorber 22 filled with medicine packages and activated carbon particles is connected with the air guide pipe III41 equipped with a polytetrafluoroethylene electric control valve III46, and the drying tower 23 with the bottom filled with CaCl2 particles is connected with the air guide pipe IV42 equipped with a polytetrafluoroethylene electric control valve IV47, and then the diaphragm polytetrafluoroethylene vacuum pump 27 is connected with the air guide pipe V43 equipped with a polytetrafluoroethylene electric control valve V48, and the online nitrogen oxide monitor 49 is installed behind the diaphragm polytetrafluoroethylene vacuum pump 27, and it is connected to the air pressure control module 24 built into the control cabinet 26 through the wire XV55.

[0078] After the installation of the main body of the device is completed, the outer sleeve 9 of the salt bridge is inserted into the through-wall flange tube sealing sleeve II7, and the other end is inserted into the reactor 1 from the through-wall flange tube sealing sleeve I6 installed from the reactor upper cover 2, so that the nitrate bridge 8 can be inserted below the liquid level of the saturated KCl beaker 16. The temperature sensor 37 is inserted into the temperature measuring sleeve 4, and the temperature control module 25 is connected with the wire VIII35, and the temperature control module 25 and the heating sleeve 5 are connected with the wire IX36. The high-precision vacuum gauge I13 and the high-precision vacuum gauge II20 are connected to the air pressure control module 24 with the wire V32 and the wire VI33 respectively, and the air pressure control module 24 and the diaphragm polytetrafluoroethylene vacuum pump 27 are connected through the wire VII34. The polytetrafluoroethylene electric-controlled pipeline valve I44, the polytetrafluoroethylene electric-controlled pipeline valve II45, the polytetrafluoroethylene electric-controlled pipeline valve III46, the polytetrafluoroethylene electric-controlled pipeline valve IV47, the polytetrafluoroethylene electric-controlled pipeline valve V48 and the pipeline valve control module 58 are connected in sequence through the wire X50, the wire XI51, the wire XII52, the wire XIII53 and the wire XIV54.

[0079] After adding an appropriate amount of simulated liquid into the reactor 1, the working electrode 10 and the special platinum electrode 11 are respectively inserted into the corresponding holes of the reactor cover 2, and connected to the electrochemical workstation 17 through the wire III30 and the wire IV31 respectively. The reference electrode 14 is connected to the pin-shaped terminal 15 through the wire I28, and the pin-shaped terminal 15 is connected to the electrochemical workstation 17 through the wire II29. The electrochemical workstation 17 is connected to the computer 56 with the data cable 57, and the entire device is installed.

[0080] After the installation is completed, the target vacuum degree required for the experiment is set in the air pressure control module 24 of the control cabinet 26, and the temperature required for the experiment is set in the temperature control module 25. After the simulated liquid in the reactor 1 reaches the reduced pressure 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.

[0081] The above device is used to carry out an electrochemical test method for boiling nitric acid corrosion under a high temperature and reduced pressure environment, comprising the following steps:

[0082] S1: Set the target vacuum degree required for the experiment in the air pressure control module 24 of the control cabinet 26, and set the temperature required for the experiment (90° C.) in the temperature control module 25;

[0083] S2: The simulated liquid in the reactor 1 reaches a reduced pressure boiling state;

[0084] S3: Turn on the electrochemical workstation 17, set corresponding electrochemical test parameters in the computer 56, and start the electrochemical test;

[0085] S4: Setting a specific target vacuum degree of -70 kPa, the pipeline valve control module 58 opens all polytetrafluoroethylene electric-controlled pipeline valves;

[0086] S5: When the high-precision vacuum gauge I13 shows that the target vacuum degree has been reached, the polytetrafluoroethylene electric control pipeline valve I44 and the polytetrafluoroethylene electric control pipeline valve II45 are closed;

[0087] S6: The vacuum degree displayed by the high-precision vacuum gauge II20 will be lower than the target vacuum degree, and at this time, the diaphragm polytetrafluoroethylene vacuum pump 27 is reversed at a very low power;

[0088] S7: Make the gas pressure of the acid gas absorption and drying system (excluding the condenser 18 and the safety box 19) slightly higher than the target vacuum degree;

[0089] S8: close the polytetrafluoroethylene electric control valve V48, and open the polytetrafluoroethylene electric control valve II45;

[0090] S9: until the high-precision vacuum gauge II20 shows that the target vacuum degree has been reached, the polytetrafluoroethylene electric control valve II45 is closed and the polytetrafluoroethylene electric control pipeline valve I44 is opened;

[0091] S10: After the reduced pressure boiling corrosion test begins, gas will be generated in the reactor 1;

[0092] S11: When the value of the high-precision vacuum gauge II20 is higher than the target vacuum degree, the polytetrafluoroethylene electric control valve V48 is opened and the diaphragm polytetrafluoroethylene vacuum pump 27 is operated according to the value exceeding the target vacuum degree;

[0093] S12: When the acid gas absorption and drying system (excluding the condenser 18 and the safety box 19) forms a negative pressure relative to the safety box 19, the polytetrafluoroethylene electric control valve II45 is opened;

[0094] S13: When the vacuum degrees of the high-precision vacuum gauge I13 and the high-precision vacuum gauge II20 are both the target vacuum degrees, the polytetrafluoroethylene electric control valve III46, the polytetrafluoroethylene electric control valve IV47, and the polytetrafluoroethylene electric control valve V48 are opened at 45°;

[0095] S14: Open all valves until the end of the experiment.

[0096] The electrochemical test results are as follows Figure 7 As shown in the figure, the corrosion current density of the reduced pressure boiling sample is much smaller than that of the normal pressure boiling sample, but slightly larger than that of the normal pressure sample at the same temperature. The cathode process of the polarization curve of the reduced pressure boiling sample is significantly promoted, resulting in an increase in the corrosion current density, but the increased corrosion current density is still much smaller than that of the normal pressure boiling sample.

[0097] This experimental device can simulate the high-temperature, reduced-pressure, boiling nitric acid corrosion environment with high fidelity, realize accurate electrochemical testing and weightlessness experiments of materials in this environment, obtain real-time information such as the corrosion potential and corrosion current of the materials, and realize rapid evaluation of materials. It can provide data and technical support for the acid resistance of related component materials, service life assessment, online corrosion monitoring, and corrosion mechanism research.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope defined by the present invention.

Claims

1. A boiling nitric acid corrosion electrochemical test experimental device under high temperature and reduced pressure environment, characterized in that: The experimental device consists of a reduced pressure boiling corrosion reaction system, an electrochemical test 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 comprises a reactor, an expanded polytetrafluoroethylene gasket, a reactor cover, and a quick-install clamp, wherein the expanded polytetrafluoroethylene gasket is placed between the reactor and the reactor cover, and the three are fixed by the quick-install clamp; The electrochemical test system comprises a working electrode, a special platinum electrode, a reference electrode, a wire I, a wire II, a wire III, a wire IV, a reference electrode placement box, a pin-shaped terminal, 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 comprises a heating jacket and a temperature measuring sleeve, the reactor is placed in the heating jacket, and the temperature measuring sleeve is inserted through the frosted opening of the reactor cover and penetrates below the liquid level of the reactor; The acid gas absorption and drying system comprises a condenser, a tube I, a tube II, a circulating water tank, an air pipe I, a safety box, an air pipe II, an air washing bottle, an air pipe III, a double-tower solid tail gas absorber, an air pipe IV, and a drying tower. The condenser is connected to the reduced pressure boiling corrosion reaction system through the frosted port of the reactor cover, and is connected to the circulating water tank through tubes I and II respectively, and the upper end opening of the condenser is connected to the safety box through the air pipe I, the safety box is connected to the air washing bottle through the air pipe II, the air washing bottle is connected to the double-tower solid tail gas absorber through the air pipe III, and the double-tower solid tail gas absorber is connected to the drying tower through the air pipe IV; The vacuum control system comprises a high-precision vacuum gauge I, a high-precision vacuum gauge II, a diaphragm polytetrafluoroethylene vacuum pump, and an air guide tube V. The high-precision vacuum gauge I is installed above the reference electrode placement box and is connected to the air pressure control module of the automated integrated control system via a wire V. The high-precision vacuum gauge II is installed above the safety box and is connected to the air pressure control module of the automated integrated control system via a wire VI. The diaphragm polytetrafluoroethylene vacuum pump is connected to the acid gas absorption and drying system via the air guide tube V. The automated integrated control system comprises a control cabinet, an air pressure control module, a temperature control module, a wire V, a wire VI, a wire VII, a temperature sensor, a polytetrafluoroethylene electric-controlled pipeline valve I, a polytetrafluoroethylene electric-controlled pipeline valve II, a polytetrafluoroethylene electric-controlled pipeline valve III, a polytetrafluoroethylene electric-controlled pipeline valve IV, a polytetrafluoroethylene electric-controlled pipeline valve V, an online nitrogen oxide monitor, a wire VIII, a wire IX, a wire X, a wire XI, a wire XII, a wire XIII, a wire XIV, a wire XV, a data line, and a computer; the air pressure control module is connected to a high-precision vacuum gauge I via a wire V, the air pressure control module is connected to a high-precision vacuum gauge II via a wire VI, the air pressure control module is connected to a diaphragm polytetrafluoroethylene vacuum pump via a wire VII to control the operating power and start and stop of the diaphragm polytetrafluoroethylene vacuum pump, the temperature control module is connected to a temperature sensor via a wire VIII, and the temperature control module is connected to a heating sleeve via a wire IX to control the temperature and start and stop of the heating sleeve.

2. The electrochemical test device for boiling nitric acid corrosion under high temperature and reduced pressure environment according to claim 1 is characterized in that: The air pressure control module and the temperature control module in the automated integrated control system are both placed in a control cabinet; polytetrafluoroethylene electrically controlled pipeline valve I, polytetrafluoroethylene electrically controlled pipeline valve II, polytetrafluoroethylene electrically controlled pipeline valve III, polytetrafluoroethylene electrically controlled pipeline valve IV, and polytetrafluoroethylene electrically controlled pipeline valve V are respectively installed on air pipe I, air pipe II, air pipe III, air pipe IV, and air pipe V; the pipeline valve control modules are connected in sequence through wire X, wire XI, wire XII, wire XIII, and wire XIV to control the opening angles of the five polytetrafluoroethylene electrically controlled pipeline valves; an online nitrogen oxide monitor is connected to the control cabinet through wire XV to monitor the nitrogen oxide content of the exhaust gas of a diaphragm polytetrafluoroethylene vacuum pump in real time; and a computer is connected to an electrochemical workstation via a data cable.

3. The electrochemical test device for boiling nitric acid corrosion under high temperature and reduced pressure environment according to claim 1 is characterized in that: The reactor cover used in the reduced pressure boiling corrosion reaction system is provided with four frosted glass openings and a circular hole, which are respectively used to fix the condenser, the working electrode, the special platinum electrode, the temperature measuring sleeve, and the salt bridge outer sleeve. The salt bridge outer sleeve is fixed to the circular hole of the reactor cover through a through-wall flange tube sealing sleeve I.

4. The electrochemical test device for boiling nitric acid corrosion under high temperature and reduced pressure environment according to claim 1 is characterized in that: The through-wall flange pipe sealing sleeve I and the through-wall flange pipe sealing sleeve II are composed of a polytetrafluoroethylene through-wall flange pipe with an external thread, an expanded polytetrafluoroethylene gasket attached to the flange and an expanded polytetrafluoroethylene soft liner attached inside, and a polytetrafluoroethylene fixing nut with an internal thread and an expanded polytetrafluoroethylene gasket attached to the top. When in use, first pass the polytetrafluoroethylene through-wall flange pipe through the reserved hole, insert the expanded polytetrafluoroethylene gasket into the container, and then tighten the polytetrafluoroethylene fixing nut.

5. The electrochemical test device for boiling nitric acid corrosion under high temperature and reduced pressure environment according to claim 1 is characterized in that: A polytetrafluoroethylene porous gas-guiding slow-flow plate is installed at the gas inlet of the condenser tube of the acid gas absorption and drying system. The holes on the plate are gradually sparse from the center to the outside, which is used to evenly distribute the flow field and slow down the vibration caused by the gas flow during gas extraction; the gas washing bottle of the acid gas absorption and drying system is filled with a saturated Na2CO3 solution to absorb the HNO3 vapor in the tail gas produced by the reactor.

6. The electrochemical test device for boiling nitric acid corrosion under high temperature and reduced pressure environment according to claim 1 is characterized in that: The double-tower solid exhaust absorber of the acid gas absorption and drying system is U-shaped, with multiple layers of detachable mesh partitions installed in the two vertical parts. Filter bags made of GORE-TEX fabric filled with NaOH solids are placed on the partitions to achieve the purpose of waterproofing and breathability, chemically absorbing NOx and CO2 in the exhaust gas. The semicircular part in the middle is filled with activated carbon particles for physical adsorption.

7. The electrochemical test device for boiling nitric acid corrosion under high temperature and reduced pressure environment according to claim 1 is characterized in that: The salt bridge outer sleeve of the electrochemical test system consists of a polytetrafluoroethylene 1 / 2 round tube with a tenon structure, a polytetrafluoroethylene 1 / 2 round tube with a tongue and groove structure, and a circular polytetrafluoroethylene rib; wherein the circular polytetrafluoroethylene rib is provided with three circular vents and a circular salt bridge hole, the vent is used to connect the air pressure between the reactor and the reference electrode box, the salt bridge hole is used to fix and protect the salt bridge tube, and the circular polytetrafluoroethylene rib is divided into two, which are respectively welded in the polytetrafluoroethylene 1 / 2 round tube with a tenon structure and the polytetrafluoroethylene 1 / 2 round tube with a tongue and groove structure.

8. The electrochemical test device for boiling nitric acid corrosion under high temperature and reduced pressure environment according to claim 1 is characterized in that: The vacuum control system adopts a diaphragm polytetrafluoroethylene vacuum pump to reduce the pressure of the reactor, reference electrode placement box, acid gas absorption and drying system of the whole device. The current vacuum degree is fed back to the air pressure control module in real time through high-precision vacuum gauge I and high-precision vacuum gauge II. The air pressure control module will compare the real-time vacuum degree with the set vacuum degree to control the power and start and stop of the diaphragm polytetrafluoroethylene vacuum pump.

9. The electrochemical test device for boiling nitric acid corrosion under high temperature and reduced pressure environment according to claim 1, characterized in that: The lower part of the drying tower is equipped with CaCl2 particles, the air guide pipe IV is connected to the air inlet at the lower end of the drying tower, and the air guide pipe V is connected to the air outlet at the upper end of the drying tower.

10. An electrochemical test method for boiling nitric acid corrosion under high temperature and reduced pressure environment, characterized in that: The experimental device according to any one of claims 1 to 9 is used to implement the method, which specifically comprises the following steps: S1: Set the target vacuum required for the experiment in the air pressure control module of the control cabinet, and set the temperature required for the experiment in the temperature control module; S2: The simulated liquid in the reactor reaches the reduced pressure boiling state; S3: Turn on the electrochemical workstation, set corresponding electrochemical test parameters in the computer, and start the electrochemical test; S4: Setting a specific target vacuum degree, the pipeline valve control module opens all polytetrafluoroethylene electronically controlled pipeline valves; S5: When the high-precision vacuum gauge I shows that the target vacuum degree has been reached, close the polytetrafluoroethylene electric control pipeline valve I and the polytetrafluoroethylene electric control pipeline valve II; S6: The vacuum degree displayed by the high-precision vacuum gauge II will be lower than the target vacuum degree. At this time, the diaphragm polytetrafluoroethylene vacuum pump is reversed at low power; S7: does not include condenser and safety box, so that the gas pressure of acid gas absorption and drying system is higher than the target vacuum degree; S8: close the polytetrafluoroethylene electric control valve V, and open the polytetrafluoroethylene electric control valve II; S9: until the high-precision vacuum gauge II shows that the target vacuum degree has been reached, the polytetrafluoroethylene electric control valve II is closed and the polytetrafluoroethylene electric control pipeline valve I is opened; S10: After the reduced pressure boiling corrosion test begins, gas will be generated in the reactor; S11: When the value of the high-precision vacuum gauge II is higher than the target vacuum degree, the polytetrafluoroethylene electric control valve V is opened and the diaphragm polytetrafluoroethylene vacuum pump is operated according to the value exceeding the target vacuum degree; S12: does not include condenser and safety box. When the acid gas absorption and drying system forms negative pressure relative to the safety box, open the polytetrafluoroethylene electric control valve II; S13: When the vacuum degrees of the high-precision vacuum gauge I and the high-precision vacuum gauge II are both the target vacuum degrees, the polytetrafluoroethylene electric control valve III, the polytetrafluoroethylene electric control valve IV, and the polytetrafluoroethylene electric control valve V are opened at 45°; S14: Open all valves until the end of the experiment.

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