Boiling nitric acid three-phase corrosion weight loss experiment device under high temperature and reduced pressure environment

Abstract

The utility model provides a kind of boiling nitric acid three-phase corrosion weight loss experimental device under high-temperature pressure reduction environment, including pressure reduction boiling corrosion reaction system, heating system, nitric acid vapor absorption drying system, gas pressure regulating system and central control system;Pressure reduction boiling corrosion reaction system is arranged in heating system;Nitric acid vapor absorption drying system is connected with the pipeline of pressure reduction boiling corrosion reaction system;Gas pressure regulating system is connected with the pipeline of nitric acid vapor absorption drying system;Central control system is electrically connected with heating system and gas pressure regulating system.The utility model can realize high-fidelity simulation and reduction of high-temperature pressure reduction environment in boiling nitric acid corrosion weight loss experiment, solve the problem of simultaneous generation of nitric acid condensation phase and nitric acid vapor, the sealing problem in experimental process, gas pressure precision control problem, nitric acid tail gas emission treatment problem, realize material sample service environment accurate simulation, provide technical support for studying the boiling nitric acid corrosion corrosion resistance and service life of material sample under high-temperature pressure reduction environment.

Description

Technical Field

[0001] This utility model belongs to the field of material corrosion testing technology, and in particular relates to a three-phase corrosion weight loss experimental device for boiling nitric acid under high temperature and low pressure. Background Technology

[0002] In the field of chemical production, boiling nitric acid corrosion under high temperature and low pressure environments is often encountered. For example, in the PUREX solvent extraction 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 low pressure environments exists in the evaporator of the main processing equipment. If we want to study the corrosion resistance and service life of the evaporator structural materials under boiling nitric acid conditions in high temperature and low pressure environments, we need to conduct three-phase corrosion experiments of boiling nitric acid under simulated high temperature and low pressure environments.

[0003] However, conducting three-phase corrosion experiments of boiling nitric acid under high-temperature and low-pressure conditions safely, accurately, and reliably still faces many challenges:

[0004] ① Due to the strong corrosiveness of high-temperature nitric acid, the risk of leakage of nitric acid vapor, and the problem of nitric acid tail gas emission treatment, the experimental device is not a simple single device, but a complex comprehensive system.

[0005] ② The problem of precise air pressure control needs to be solved during the experiment, because only by maintaining precise and stable air pressure control during the experiment can the actual working conditions be accurately simulated.

[0006] ③ Because nitric acid vapor can be reliquefied at the cold end of the evaporator to form a condensate phase, the experimental setup must solve the problem of how to control the synchronous generation of nitric acid condensate phase and nitric acid vapor. If the secondary corrosion effect of nitric acid condensate phase on the surface of evaporator structural materials is ignored, it will be impossible to reproduce pitting corrosion initiation at the weld of the evaporator head, which will lead to insufficient working condition reproduction and distortion of corrosion mechanism.

[0007] ④ Since it is necessary to simulate a high-temperature and low-pressure environment, how to solve the sealing problem under such conditions is only a current challenge. Only when the experimental pressure is precisely controlled can a high-fidelity simulation and reproduction of the actual high-temperature and low-pressure working conditions be achieved.

[0008] Therefore, due to the numerous difficulties mentioned above, the current research mainly focuses on the weight loss experiments of boiling nitric acid under normal pressure, while there are few reports on the three-phase corrosion experiments of boiling nitric acid under high temperature and reduced pressure. Utility Model Content

[0009] To address the problems existing in the prior art, this utility model provides a three-phase corrosion weight loss experimental device for boiling nitric acid under high temperature and low pressure. It can achieve a high-fidelity simulation and reproduction of the high temperature and low pressure environment in the boiling nitric acid corrosion weight loss experiment, and solves the problems of synchronous generation of nitric acid condensate phase and nitric acid vapor, sealing during the experiment, precise control of gas pressure during the experiment, and emission treatment of nitric acid tail gas. It realizes the accurate simulation of the service environment of material samples, and provides technical support for studying the corrosion resistance and service life of material samples under boiling nitric acid corrosion under high temperature and low pressure.

[0010] To achieve the above objectives, this utility model adopts the following technical solution: a three-phase corrosion weight loss experimental device for boiling nitric acid under high temperature and reduced pressure, comprising a reduced pressure boiling corrosion reaction system, a heating system, a nitric acid vapor absorption and drying system, a pressure regulating system, and a central control system; the reduced pressure boiling corrosion reaction system is located within the heating system; the nitric acid vapor absorption and drying system is connected to the reduced pressure boiling corrosion reaction system via pipeline; the pressure regulating system is connected to the nitric acid vapor absorption and drying system via pipeline; and the central control system is electrically connected to both the heating system and the pressure regulating system.

[0011] The reduced pressure boiling corrosion reaction system includes a reactor body, a reactor cap, a polytetrafluoroethylene (PTFE) sample holder, and a condensate collection dish. The reactor body is used to hold nitric acid solution. The reactor cap is fastened to the top of the reactor body, and a PTFE sealing gasket is provided between the circumferential contact surfaces of the reactor cap and the reactor body. The reactor cap and the circumferential mounting edge of the reactor body are pressed and fixed together by quick-release clamps. The PTFE sample holder is horizontally fastened to the upper part of the reactor body. The condensate collection dish is vertically inserted above the PTFE sample holder.

[0012] Sample mounting blocks are fixedly installed on the inner surface of the reactor body, and the sample mounting blocks are evenly distributed along the circumference. Sample mounting grooves are evenly distributed along the circumference on the edge of the polytetrafluoroethylene (PTFE) sample mounting plate, and the number of sample mounting grooves is equal to the number of sample mounting blocks, with each groove corresponding to a specific position. A sample mounting matrix hole is provided in the middle of the PTFE sample mounting plate, and a collection dish positioning hole is provided between the sample mounting matrix hole and the sample mounting groove, with each collection dish positioning hole being evenly distributed along the circumference. Collection dish positioning pins are evenly distributed along the circumference at the bottom of the condensate collection dish, and the number of collection dish positioning pins is equal to the number of collection dish positioning holes, with each pin corresponding to a specific position.

[0013] A ring of teardrop-shaped condensate guiding beads is fixed on the inner surface of the reactor cap, and the diameter of the inscribed circle of the condensate guiding bead ring is smaller than the diameter of the collection port of the condensate collecting dish.

[0014] The heating system includes an electric heating mantle, a mercury thermometer, and a laser reflective thermometric cursor. The reactor body is placed inside the electric heating mantle. A thermometer hanging hole is provided on the polytetrafluoroethylene (PTFE) sample hanging plate between the sample hanging matrix hole and the collection dish positioning hole. The mercury thermometer is connected to the PTFE sample hanging plate through the thermometer hanging hole. The laser reflective thermometric cursor is fixedly mounted above the electric heating mantle on an iron frame.

[0015] The nitric acid vapor absorption and drying system includes a condenser, a circulating water tank, a safety bottle, a tail gas absorption bottle, and a tail gas absorber. The lower end of the inner tube of the condenser is vertically inserted into the center hole of the reactor cap, and an elbow is installed at the upper end of the inner tube. The inlet of the outer tube of the condenser is connected to the outlet of the circulating water tank, and the return outlet of the circulating water tank is connected to the outlet of the outer tube of the condenser. A three-hole stopper is installed at the mouth of the safety bottle, and a first gas guide tube connects the safety bottle and the elbow. The outlet end of the first gas guide tube passes through… A three-hole stopper extends into the safety bottle; the exhaust gas absorption bottle is filled with alkaline liquid, and a two-hole stopper is provided at the bottle opening. A second air guide tube is connected between the exhaust gas absorption bottle and the safety bottle. The inlet end of the second air guide tube passes through the three-hole stopper and extends into the safety bottle, while the outlet end of the second air guide tube passes through the two-hole stopper and extends into the exhaust gas absorption bottle. A third air guide tube is connected between the air inlet of the exhaust gas absorber and the exhaust gas absorption bottle, and the inlet end of the third air guide tube passes through the two-hole stopper and extends into the exhaust gas absorption bottle.

[0016] The exhaust gas absorber adopts a solid-state four-stage filtration structure, consisting of a first-stage filtration unit, a second-stage filtration unit, a third-stage filtration unit, and a fourth-stage filtration unit arranged vertically. Each adjacent filtration unit is separated by a waterproof and breathable membrane. The first-stage filtration unit uses a CaCl2 particle-filled structure; the second-stage filtration unit uses a modified zeolite molecular sieve-filled structure; the third-stage filtration unit uses a mixed CaCl2 particle and NaOH particle-filled structure; and the fourth-stage filtration unit uses a PTFE membrane.

[0017] The pressure regulation system includes a diaphragm-type polytetrafluoroethylene vacuum pump and a high-precision vacuum gauge; the suction port of the diaphragm-type polytetrafluoroethylene vacuum pump is connected to the outlet of the exhaust gas absorber through a fourth gas guide tube; the high-precision vacuum gauge extends into the safety bottle through a three-hole stopper.

[0018] The central control system includes a control cabinet, a temperature control module, a pressure control module, a first PTFE electrically controlled valve, a second PTFE electrically controlled valve, a third PTFE electrically controlled valve, a fourth PTFE electrically controlled valve, and an online nitrogen oxide detector. The temperature control module and the pressure control module are both located inside the control cabinet. The heating mantle and the laser reflective temperature measuring cursor are electrically connected to the temperature control module via cables. The first, second, third, and fourth PTFE electrically controlled valves are respectively installed on the first, second, third, and fourth gas guide pipes, and all four valves are electrically connected to the pressure control module via cables. The high-precision vacuum gauge is electrically connected to the pressure control module via a cable. The online nitrogen oxide detector is electrically connected to the control cabinet via a cable and is located behind the exhaust port of the diaphragm PTFE vacuum pump, used to monitor the nitrogen oxide content in the gas discharged from the diaphragm PTFE vacuum pump.

[0019] A method for testing the three-phase corrosion weight loss of boiling nitric acid under high temperature and low pressure conditions, using the aforementioned experimental apparatus for testing the three-phase corrosion weight loss of boiling nitric acid under high temperature and low pressure conditions, includes the following steps:

[0020] Step 1: Hang the material sample and mercury thermometer on the PTFE sample plate respectively, and insert the condensate collection dish into the PTFE sample plate to form a sample plate assembly;

[0021] Step 2: Transfer the sample assembly into the reactor body containing nitric acid solution, and fix the PTFE sample plate to the reactor body.

[0022] Step 3: Attach the reactor cap to the upper part of the reactor body and use quick-release clamps to press and fix the reactor cap to the reactor body;

[0023] Step 4: Securely insert the condenser tube into the reactor cover to complete the connection between the condenser tube and the circulating water tank;

[0024] Step 5: Set the target experimental temperature using the temperature control module and the target experimental air pressure using the air pressure control module;

[0025] Step 6: Start the heating mantle and the diaphragm PTFE vacuum pump. Heat the nitric acid solution in the reactor body through the heating mantle and depressurize the reactor body through the diaphragm PTFE vacuum pump until the experimental temperature and experimental pressure reach the target set values. At this time, the nitric acid solution in the reactor body is in a high temperature depressurization boiling state.

[0026] Step 7: During the three-phase corrosion weight loss experiment of boiling nitric acid under high temperature and reduced pressure on the material sample, the temperature control module dynamically adjusts the operating power of the heating mantle based on the data feedback from the laser reflective thermometer to maintain a stable experimental temperature; the pressure control module dynamically adjusts the operating power of the diaphragm PTFE vacuum pump and the valve core opening of each PTFE electrically controlled valve based on the data feedback from the high-precision vacuum gauge to maintain a stable experimental pressure; the online nitrogen oxide detector monitors the nitrogen oxide content of the gas emitted by the diaphragm PTFE vacuum pump in real time to monitor the cleanliness of the exhaust gas.

[0027] Step 8: After the corrosion weight loss experiment is completed, turn off the heating mantle, start the diaphragm PTFE vacuum pump in reverse, and at the same time adjust the valve core opening of each PTFE electrically controlled valve to the maximum until the gas pressure in the reactor body returns to normal pressure.

[0028] Step 9: Remove the quick-release clamps to release the pressure between the reactor cover and the reactor body. Then remove the reactor cover from the reactor body, remove the sample assembly from the reactor body, and finally remove the material sample from the PTFE sample plate.

[0029] The beneficial effects of this utility model are:

[0030] This invention relates to a high-temperature, reduced-pressure environment three-phase corrosion weight loss experimental apparatus for boiling nitric acid. The apparatus adopts a modular design, facilitating disassembly, assembly, and modification. A diaphragm-type polytetrafluoroethylene (PTFE) vacuum pump is used as the pressure-regulating device, enabling precise pressure control and reducing vibration during the pumping and depressurization process, thus improving operational safety. A specially designed PTFE sample holder allows for corrosion experiments on material samples in any single phase of nitric acid, or under arbitrary coupling of three phases of nitric acid, by adjusting the sample's suspension height, effectively improving experimental efficiency.

[0031] This invention relates to a high-temperature, reduced-pressure environment three-phase corrosion weight loss experimental apparatus for boiling nitric acid. The tail gas absorber in the apparatus adopts a solid-type four-stage filtration structure. On the one hand, it provides gas purification for the entire apparatus, protecting the operational safety of the downstream diaphragm-type PTFE vacuum pump. On the other hand, through the design of the sieve-hole partition and the application of the waterproof and breathable diaphragm, it effectively reduces the pressure drop loss within the apparatus during evacuation, providing favorable conditions for stabilizing the gas pressure within the apparatus. By using a combination of a mercury thermometer and a laser reflective temperature measuring cursor for temperature measurement, it avoids the problems of indirect and inaccurate temperature measurement associated with the traditional temperature measuring sleeve and temperature sensor combination method.

[0032] This invention relates to a high-temperature, reduced-pressure environment boiling nitric acid three-phase corrosion weight loss experimental apparatus, which can accurately implement the three-phase corrosion behavior of materials under reduced-pressure boiling nitric acid corrosion environment. For example, it can simulate the reduced-pressure boiling corrosion environment of nitric acid during the operation of a spent fuel reprocessing evaporator, or simulate the corrosion behavior of mechanical parts or metal components of equipment used in processes such as reduced-pressure evaporation and reduced-pressure distillation. It can not only evaluate the corrosion resistance and service life of materials under relevant environments, but also serve as an experimental apparatus for basic research such as the study of saturated vapor pressure of substances. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the experimental apparatus for three-phase corrosion weight loss of boiling nitric acid under high temperature and low pressure environment according to this invention.

[0034] Figure 2 This is a schematic diagram of the combined structure of the reactor body, reactor cover, polytetrafluoroethylene hanging plate, mercury thermometer, condenser tube and elbow of this utility model;

[0035] Figure 3 This is a schematic diagram of the structure of the polytetrafluoroethylene hanging sample plate of this utility model;

[0036] In the diagram, 1—reactor body, 2—reactor cover, 3—PTFE sample holder, 4—condenser collection dish, 5—sample holder mounting groove, 6—sample matrix hole, 7—collection dish positioning hole, 8—heating mantle, 9—mercury thermometer, 10—laser reflective temperature measuring indicator, 11—thermometer hanging hole, 12—condenser tube, 13—circulating water tank, 14—safety bottle, 15—tail gas absorption bottle, 16—tail gas absorber, 17—elbow, 18—first gas guide. Pipe, 19—Second gas guide pipe, 20—Third gas guide pipe, 21—Diaphragm-type PTFE vacuum pump, 22—High-precision vacuum gauge, 23—Fourth gas guide pipe, 24—Control cabinet, 25—Temperature control module, 26—Gas pressure control module, 27—First PTFE electrically controlled valve, 28—Second PTFE electrically controlled valve, 29—Third PTFE electrically controlled valve, 30—Fourth PTFE electrically controlled valve, 31—Online nitrogen oxide detector. Detailed Implementation

[0037] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0038] like Figures 1-3As shown, a three-phase corrosion weight loss experimental apparatus for boiling nitric acid under high temperature and reduced pressure includes a reduced pressure boiling corrosion reaction system, a heating system, a nitric acid vapor absorption and drying system, a pressure regulating system, and a central control system. The reduced pressure boiling corrosion reaction system is located within the heating system. The nitric acid vapor absorption and drying system is connected to the reduced pressure boiling corrosion reaction system via pipeline. The pressure regulating system is connected to the nitric acid vapor absorption and drying system via pipeline. The central control system is electrically connected to both the heating system and the pressure regulating system.

[0039] In this embodiment, the experimental apparatus for the three-phase corrosion weight loss of boiling nitric acid under high temperature and low pressure is set up inside a walk-in fume hood.

[0040] The reduced pressure boiling corrosion reaction system includes a reactor body 1, a reactor cap 2, a polytetrafluoroethylene (PTFE) sample holder 3, and a condensate collection dish 4. The reactor body 1 is used to hold nitric acid solution. The reactor cap 2 is fastened to the top of the reactor body 1, and a PTFE sealing gasket is provided between the circumferential contact surfaces of the reactor cap 2 and the reactor body 1. The reactor cap 2 and the circumferential mounting edge of the reactor body 1 are pressed and fixed by quick-release clamps. The PTFE sample holder 3 is horizontally fastened to the upper part of the reactor body 1. The condensate collection dish 4 is vertically inserted above the PTFE sample holder 3.

[0041] Sample mounting blocks are fixedly installed on the inner surface of the reactor body 1, and the sample mounting blocks are evenly distributed along the circumference. Sample mounting grooves 5 are evenly distributed along the circumference on the edge of the polytetrafluoroethylene sample mounting plate 3, and the number of sample mounting grooves 5 and sample mounting blocks are equal and their positions correspond one-to-one. A sample mounting matrix hole 6 is provided in the middle of the polytetrafluoroethylene sample mounting plate 3, and a collection dish positioning hole 7 is provided between the sample mounting matrix hole 6 and the sample mounting groove 5, and the collection dish positioning hole 7 is evenly distributed along the circumference. Collection dish positioning pins are evenly distributed along the circumference at the bottom of the condensate collection dish 4, and the number of collection dish positioning pins and collection dish positioning holes 7 are equal and their positions correspond one-to-one.

[0042] A ring of teardrop-shaped condensate guiding beads is fixed on the inner surface of the reactor cap 2, and the diameter of the inscribed circle of the condensate guiding bead ring is smaller than the diameter of the collection port of the condensate collecting dish 4.

[0043] In this embodiment, the reactor body 1, reactor cover 2, and sample mounting blocks are all made of high-strength borosilicate glass. There are four sample mounting blocks, which are fixed to the inner surface of the reactor body 1 by thermal bonding. There are four positioning holes 7 for the collection dish. There are ten condensate phase guiding beads, which are fixed to the inner surface of the reactor cover 2 by thermal bonding. The sample mounting matrix holes 6 have a matrix size of 15×16, which means a total of 240 sample mounting holes. Every four sample mounting holes form a group. The vertical groups of sample mounting holes are marked with letters, and the horizontal groups of sample mounting holes are marked with Arabic numerals. When mounting samples, each group of sample mounting holes can suspend one sample or a string of samples. By adjusting the suspension height of the samples, the samples can be completely immersed in the nitric acid solution, partially immersed in the nitric acid solution, or not immersed in the nitric acid solution, thereby achieving liquid phase corrosion, simultaneous gas-liquid two-phase corrosion, or gas phase corrosion of the samples.

[0044] The heating system includes an electric heating mantle 8, a mercury thermometer 9, and a laser reflective thermometer 10; the reactor body 1 is placed inside the electric heating mantle 8; a thermometer hanging hole 11 is provided on the polytetrafluoroethylene (PTFE) sample hanging plate 3 between the sample hanging matrix hole 6 and the collection dish positioning hole 7, and the mercury thermometer 9 is hung and connected to the PTFE sample hanging plate 3 through the thermometer hanging hole 11; the laser reflective thermometer 10 is fixedly mounted above the electric heating mantle 8 by an iron frame.

[0045] In this embodiment, the laser reflective temperature measuring cursor 10 operates at a wavelength of 1550nm, and its reflector group is made of sapphire material with a diamond coating. The temperature measuring range is 0~150℃, the temperature measuring accuracy is ±0.3℃, and the response time is ≤50ms. During temperature measurement, the laser reflective temperature measuring cursor 10 collects the mercury column height of the mercury column thermometer 9, and the temperature control module 25 of the central control system automatically converts the mercury column height data into temperature data. Based on the measured temperature data, the temperature control module 25 precisely controls the heating temperature of the electric heating mantle 8.

[0046] The nitric acid vapor absorption and drying system includes a condenser 12, a circulating water tank 13, a safety bottle 14, a tail gas absorption bottle 15, and a tail gas absorber 16. The lower end of the inner tube of the condenser 12 is vertically inserted into the center hole of the reactor cap 2, and an elbow 17 is installed at the upper end of the inner tube. The inlet of the outer tube of the condenser 12 is connected to the outlet of the circulating water tank 13, and the return outlet of the circulating water tank 13 is connected to the outlet of the outer tube of the condenser 12. A three-hole stopper is provided at the mouth of the safety bottle 14, and a first gas guide pipe 18 is connected between the safety bottle 14 and the elbow 17. The gas outlet of the first gas guide pipe 18... An inlet end of the exhaust gas absorber 16 passes through a three-hole stopper and extends into the safety bottle 14. The exhaust gas absorber 15 is filled with alkaline liquid. A two-hole stopper is provided at the mouth of the exhaust gas absorber 15. A second air guide tube 19 connects the exhaust gas absorber 15 and the safety bottle 14. The inlet end of the second air guide tube 19 passes through the three-hole stopper and extends into the safety bottle 14, while the outlet end of the second air guide tube 19 passes through the two-hole stopper and extends into the exhaust gas absorber 15. A third air guide tube 20 connects the inlet of the exhaust gas absorber 16 and the exhaust gas absorber 15. The inlet end of the third air guide tube 20 passes through the two-hole stopper and extends into the exhaust gas absorber 15.

[0047] In this embodiment, the central hole of the reactor cap 2 has a frosted structure; the alkaline liquid inside the tail gas absorption bottle 15 is a saturated Na2CO3 solution, which can perform metathesis of HNO3 in the tail gas and generate CO2 at the same time.

[0048] The exhaust gas absorber 16 adopts a solid-state four-stage filtration structure, which consists of a first-stage filtration unit, a second-stage filtration unit, a third-stage filtration unit, and a fourth-stage filtration unit arranged vertically. Each adjacent filtration unit is separated by a waterproof and breathable membrane. The first-stage filtration unit is filled with CaCl2 particles. The second-stage filtration unit is filled with modified zeolite molecular sieves. The third-stage filtration unit is filled with a mixture of CaCl2 particles and NaOH particles. The fourth-stage filtration unit uses a PTFE membrane.

[0049] In this embodiment, the waterproof and breathable diaphragm is made of GORE-TEX fabric, and the PTFE membrane has a porosity of 85%. The first-stage filtration unit uses CaCl2 particles to dry the exhaust gas, and the second-stage filtration unit uses modified zeolite molecular sieves to filter NO. X The physical adsorption of the exhaust gas is used in the first stage. The third stage filtration unit uses a mixture of CaCl2 particles and NaOH particles for the chemical adsorption of HNO3 and CO2 and further dries the exhaust gas. The PTFE membrane in the fourth stage filtration unit is used to filter solid particles in the exhaust gas.

[0050] The pressure regulation system includes a diaphragm-type polytetrafluoroethylene vacuum pump 21 and a high-precision vacuum gauge 22; the suction port of the diaphragm-type polytetrafluoroethylene vacuum pump 21 is connected to the outlet of the tail gas absorber 16 through the fourth gas guide pipe 23; the high-precision vacuum gauge 22 extends into the safety bottle 14 through the three-hole stopper.

[0051] In this embodiment, the port on the three-hole stopper through which the high-precision vacuum gauge 22 is inserted is covered with a PTFE membrane at its upper end and a filter tube at its lower end, which is filled with activated carbon particles and CaCl2 particles. The high-precision vacuum gauge 22 is connected to the port of the three-hole stopper by a thread, and a polytetrafluoroethylene gasket is installed at the connection for sealing. The high-precision vacuum gauge 22 must undergo three-proof treatment before the experiment. The diaphragm-type polytetrafluoroethylene vacuum pump 21 is fixed to the experimental frame by an external pin and a shock-absorbing base.

[0052] The central control system includes a control cabinet 24, a temperature control module 25, a pressure control module 26, a first polytetrafluoroethylene (PTFE) electrically controlled valve 27, a second PTFE electrically controlled valve 28, a third PTFE electrically controlled valve 29, a fourth PTFE electrically controlled valve 30, and an online nitrogen oxide detector 31. The temperature control module 25 and the pressure control module 26 are both housed inside the control cabinet 24. The electric heating mantle 8 and the laser reflective temperature measuring cursor 10 are both electrically connected to the temperature control module 25 via cables. The first PTFE electrically controlled valve 27, the second PTFE electrically controlled valve 28, the third PTFE electrically controlled valve 29, the fourth PTFE electrically controlled valve 30, and an online nitrogen oxide detector 31 are also included. The PTFE electrically controlled valve 29 and the fourth PTFE electrically controlled valve 30 are respectively installed on the first gas guide pipe 18, the second gas guide pipe 19, the third gas guide pipe 20, and the fourth gas guide pipe 23, and all four valves are electrically connected to the pressure control module 26 via cables; the high-precision vacuum gauge 22 is electrically connected to the pressure control module 26 via cables; the online nitrogen oxide detector 31 is electrically connected to the control cabinet 24 via cables, and the online nitrogen oxide detector 31 is located behind the exhaust port of the diaphragm PTFE vacuum pump 21, and is used to monitor the nitrogen oxide content in the gas discharged from the diaphragm PTFE vacuum pump 21.

[0053] In this embodiment, the temperature control module 25 has a photoelectric encoding reading function, which can convert the mercury column height of the mercury column thermometer 9 into a standard signal of 4mA to 20mA for output. It also has a vibration compensation function; when the diaphragm-type PTFE vacuum pump 21 operates, causing the overall vibration frequency of the experimental apparatus to be >30Hz, it can automatically perform digital filtering. The laser reflective temperature measuring cursor 10 is used to feed back the measured data to the temperature control module 25 in real time. The temperature control module 25 can adjust the operating power and start / stop status of the heating mantle 8 according to the real-time measured nitric acid solution temperature to ensure stability at high temperatures. High precision... Vacuum gauge 22 is used to feed back the vacuum level data in the pipeline chamber system to the pressure control module 26 in real time. The pressure control module 26 can adjust the operating power and start / stop status of the diaphragm PTFE vacuum pump 21 and the valve core opening of the four valves according to the real-time vacuum level data to ensure the stability of the pressure reduction state. The first PTFE electric control valve 27, the second PTFE electric control valve 28, the third PTFE electric control valve 29 and the fourth PTFE electric control valve 30 are all valves of the same model. The valve core opening control resolution is 0.1° and the inner wall of the valve flow channel is provided with a spiral guide groove.

[0054] A method for testing the three-phase corrosion weight loss of boiling nitric acid under high temperature and low pressure conditions, using the aforementioned experimental apparatus for testing the three-phase corrosion weight loss of boiling nitric acid under high temperature and low pressure conditions, includes the following steps:

[0055] Step 1: Hang the material sample and mercury thermometer 9 on the polytetrafluoroethylene (PTFE) sample plate 3 respectively, and insert the condensate collection dish 4 onto the PTFE sample plate 3 to form a sample assembly.

[0056] Step 2: Transfer the sample assembly into the reactor body 1 containing nitric acid solution, and fix the polytetrafluoroethylene sample plate 3 to the reactor body 1.

[0057] Step 3: Attach the reactor cover 2 to the upper part of the reactor body 1, and use quick-release clamps to press and fix the reactor cover 2 to the reactor body 1.

[0058] Step 4: Securely insert the condenser tube 12 into the reactor cover 2 to complete the connection between the condenser tube 12 and the circulating water tank 13;

[0059] Step 5: Set the target experimental temperature through the temperature control module 25 and the target experimental air pressure through the air pressure control module 26;

[0060] Step 6: Start the heating mantle 8 and the diaphragm PTFE vacuum pump 21. The heating mantle 8 heats the nitric acid solution in the reactor body 1, and the diaphragm PTFE vacuum pump 21 depressurizes the reactor body 1 until the experimental temperature and experimental pressure reach the target set value. At this time, the nitric acid solution in the reactor body 1 is in a high temperature depressurization boiling state.

[0061] Step 7: During the three-phase corrosion weight loss experiment of boiling nitric acid under high temperature and reduced pressure on the material sample, the temperature control module 25 dynamically adjusts the operating power of the heating mantle 8 based on the data fed back by the laser reflective temperature measuring cursor 10 to maintain the stability of the experimental temperature; the pressure control module 26 dynamically adjusts the operating power of the diaphragm PTFE vacuum pump 21 and the valve core opening of each PTFE electrically controlled valve based on the data fed back by the high-precision vacuum gauge 22 to maintain the stability of the experimental pressure; the online nitrogen oxide detector 31 monitors the nitrogen oxide content of the gas emitted by the diaphragm PTFE vacuum pump 21 in real time to monitor the cleanliness of the exhaust gas;

[0062] Step 8: After the corrosion weight loss experiment is completed, turn off the electric heating mantle 8, start the diaphragm PTFE vacuum pump 21 in reverse, and at the same time adjust the valve core opening of each PTFE electric control valve to the maximum until the gas pressure in the reactor body 1 returns to normal pressure.

[0063] Step 9: Remove the quick-release clamps, release the pressure and fixation between the reactor cover 2 and the reactor body 1, then remove the reactor cover 2 from the reactor body 1, then remove the sample hanging assembly from the reactor body 1, and finally remove the material sample from the polytetrafluoroethylene sample hanging plate 3.

[0064] The solutions in the embodiments are not intended to limit the scope of protection of this utility model. All equivalent implementations or modifications that do not depart from the scope of protection of this utility model are included in the scope of protection of this utility model.

Claims

1. A three-phase corrosion weight loss experimental apparatus for boiling nitric acid under high temperature and reduced pressure, characterized in that: It includes a vacuum boiling corrosion reaction system, a heating system, a nitric acid vapor absorption and drying system, a pressure regulating system, and a central control system; the vacuum boiling corrosion reaction system is located within the heating system; the nitric acid vapor absorption and drying system is connected to the vacuum boiling corrosion reaction system via pipeline; the pressure regulating system is connected to the nitric acid vapor absorption and drying system via pipeline; and the central control system is electrically connected to both the heating system and the pressure regulating system.

2. The experimental apparatus for three-phase corrosion weight loss of boiling nitric acid under high temperature and reduced pressure as described in claim 1, characterized in that: The reduced pressure boiling corrosion reaction system includes a reactor body, a reactor cap, a polytetrafluoroethylene (PTFE) sample holder, and a condensate collection dish. The reactor body is used to hold nitric acid solution. The reactor cap is fastened to the top of the reactor body, and a PTFE sealing gasket is provided between the circumferential contact surfaces of the reactor cap and the reactor body. The reactor cap and the circumferential mounting edge of the reactor body are pressed and fixed together by quick-release clamps. The PTFE sample holder is horizontally fastened to the upper part of the reactor body. The condensate collection dish is vertically inserted above the PTFE sample holder.

3. The experimental apparatus for three-phase corrosion weight loss of boiling nitric acid under high temperature and reduced pressure as described in claim 2, characterized in that: Sample mounting blocks are fixedly installed on the inner surface of the reactor body, and the sample mounting blocks are evenly distributed along the circumference. Sample mounting grooves are evenly distributed along the circumference on the edge of the polytetrafluoroethylene (PTFE) sample mounting plate, and the number of sample mounting grooves is equal to the number of sample mounting blocks, with each groove corresponding to a specific position. A sample mounting matrix hole is provided in the middle of the PTFE sample mounting plate, and a collection dish positioning hole is provided between the sample mounting matrix hole and the sample mounting groove, with each collection dish positioning hole being evenly distributed along the circumference. Collection dish positioning pins are evenly distributed along the circumference at the bottom of the condensate collection dish, and the number of collection dish positioning pins is equal to the number of collection dish positioning holes, with each pin corresponding to a specific position.

4. The experimental apparatus for three-phase corrosion weight loss of boiling nitric acid under high temperature and reduced pressure as described in claim 2, characterized in that: A ring of teardrop-shaped condensate guiding beads is fixed on the inner surface of the reactor cap, and the diameter of the inscribed circle of the condensate guiding bead ring is smaller than the diameter of the collection port of the condensate collecting dish.

5. The experimental apparatus for three-phase corrosion weight loss of boiling nitric acid under high temperature and reduced pressure as described in claim 2, characterized in that: The heating system includes an electric heating mantle, a mercury thermometer, and a laser reflective thermometric cursor. The reactor body is placed inside the electric heating mantle. A thermometer hanging hole is provided on the polytetrafluoroethylene (PTFE) sample hanging plate between the sample hanging matrix hole and the collection dish positioning hole. The mercury thermometer is connected to the PTFE sample hanging plate through the thermometer hanging hole. The laser reflective thermometric cursor is fixedly mounted above the electric heating mantle on an iron frame.

6. The experimental apparatus for three-phase corrosion weight loss of boiling nitric acid under high temperature and reduced pressure as described in claim 2, characterized in that: The nitric acid vapor absorption and drying system includes a condenser, a circulating water tank, a safety bottle, a tail gas absorption bottle, and a tail gas absorber. The lower end of the inner tube of the condenser is vertically inserted into the center hole of the reactor cap, and an elbow is installed at the upper end of the inner tube. The inlet of the outer tube of the condenser is connected to the outlet of the circulating water tank, and the return outlet of the circulating water tank is connected to the outlet of the outer tube of the condenser. A three-hole stopper is installed at the mouth of the safety bottle, and a first gas guide tube connects the safety bottle and the elbow. The outlet end of the first gas guide tube passes through… A three-hole stopper extends into the safety bottle; the exhaust gas absorption bottle is filled with alkaline liquid, and a two-hole stopper is provided at the bottle opening. A second air guide tube is connected between the exhaust gas absorption bottle and the safety bottle. The inlet end of the second air guide tube passes through the three-hole stopper and extends into the safety bottle, while the outlet end of the second air guide tube passes through the two-hole stopper and extends into the exhaust gas absorption bottle. A third air guide tube is connected between the air inlet of the exhaust gas absorber and the exhaust gas absorption bottle, and the inlet end of the third air guide tube passes through the two-hole stopper and extends into the exhaust gas absorption bottle.

7. The experimental apparatus for three-phase corrosion weight loss of boiling nitric acid under high temperature and reduced pressure as described in claim 6, characterized in that: The exhaust gas absorber adopts a solid-state four-stage filtration structure, consisting of a first-stage filtration unit, a second-stage filtration unit, a third-stage filtration unit, and a fourth-stage filtration unit arranged vertically. Each adjacent filtration unit is separated by a waterproof and breathable membrane. The first-stage filtration unit uses a CaCl2 particle-filled structure; the second-stage filtration unit uses a modified zeolite molecular sieve-filled structure; the third-stage filtration unit uses a mixed CaCl2 particle and NaOH particle-filled structure; and the fourth-stage filtration unit uses a PTFE membrane.

8. The experimental apparatus for three-phase corrosion weight loss of boiling nitric acid under high temperature and reduced pressure as described in claim 6, characterized in that: The pressure regulation system includes a diaphragm-type polytetrafluoroethylene vacuum pump and a high-precision vacuum gauge; the suction port of the diaphragm-type polytetrafluoroethylene vacuum pump is connected to the outlet of the exhaust gas absorber through a fourth gas guide tube; the high-precision vacuum gauge extends into the safety bottle through a three-hole stopper.

9. The experimental apparatus for three-phase corrosion weight loss of boiling nitric acid under high temperature and reduced pressure as described in claim 8, characterized in that: The central control system includes a control cabinet, a temperature control module, a pressure control module, a first PTFE electrically controlled valve, a second PTFE electrically controlled valve, a third PTFE electrically controlled valve, a fourth PTFE electrically controlled valve, and an online nitrogen oxide detector. The temperature control module and the pressure control module are both located inside the control cabinet. The heating mantle and the laser reflective temperature measuring cursor are electrically connected to the temperature control module via cables. The first, second, third, and fourth PTFE electrically controlled valves are respectively installed on the first, second, third, and fourth gas guide pipes, and all four valves are electrically connected to the pressure control module via cables. The high-precision vacuum gauge is electrically connected to the pressure control module via a cable. The online nitrogen oxide detector is electrically connected to the control cabinet via a cable and is located behind the exhaust port of the diaphragm PTFE vacuum pump, used to monitor the nitrogen oxide content in the gas discharged from the diaphragm PTFE vacuum pump.

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