Low radon radioactivity, high temperature and high purity inert gas purifier

Abstract

A low radon radioactivity high temperature high purity inert gas purifier comprises a heat exchanger, a branch pipe, and an outlet pipe, a main pipe and an inlet pipe connected in sequence; the branch pipe connects the outlet pipe and the inlet pipe of the heat exchanger on the cold side, so that after the gas to be purified passes through the main pipe, the outlet pipe outputs the purified gas to the inlet pipe on the hot side of the heat exchanger; the heat exchanger allows the gas to be purified to fully absorb the heat of the purified gas and cool the purified gas to a safe temperature; the main pipe is filled with high purity metal fillers. The present invention utilizes low radioactive high purity metals such as zirconium, hafnium, iron, vanadium, titanium, copper, etc., which are smelted by electron beam or electrolytically refined, to react with nitrogen, hydrogen, oxygen and other elements in high purity inert gas at above 600°C to generate solid compounds, thereby achieving the purification of high purity inert gas, and the purification effect of high purity inert gas is good, and less radon gas is released, which can meet the high speed and high purity purification requirements of target materials such as argon and xenon in rare case experiments, and can also solve the availability of knife edge flanges under high temperature conditions. And the packing can be easily replaced after the packing service life ends.

Description

Technical Field

[0001] The present invention relates to the technical field of purification of high-purity inert gas, and in particular to a high-temperature high-purity inert gas purifier with low radon radioactivity, which can remove extremely trace amounts of N, O, H and other elements in high-purity inert gas at high speed and simultaneously does not emit obvious radioactive impurities such as radon and other chemical impurities that are harmful to particle detectors. Background Art

[0002] The signals expected by rare event high energy physics experiments such as dark matter detection and neutrinoless double beta decay detection are very rare and weak. The materials used to build the detectors and the detection media need to strictly control the radioactive background. The selection and source of low radioactive background metal materials is a core issue that needs to be urgently solved in the field of rare event high energy physics experiments. Inert gases such as xenon and argon are often used as target materials for such detectors. After the target particles collide with the target material, free electrons are released. Impurity elements such as N, O, and H in the target material will absorb free electrons and thus deteriorate the performance of the detector. Therefore, the content of N, O, and H in the target material needs to be strictly controlled.

[0003] At present, the high-purity xenon and argon used in general particle detectors use purifiers in the semiconductor industry to remove N, O, and H. The filler materials that play a purifying role are mainly zirconium-aluminum alloys, zirconium-vanadium-iron alloys, etc. The working temperature is generally below 400°C. The N, O, and H impurities in the inert gas react with the filler to produce solid compounds that are solidified, thereby purifying the gas. However, a disadvantage of this type of purifier is that the filler used has a high radon emission rate. Some purifiers have extremely high radon emission rates. These radons enter the particle detector with the circulating gas, causing the background to increase and deteriorating the detector performance. In addition, the existing purifiers are relatively expensive and have a low purification rate. For future detectors of tens of tons and hundreds of tons, the purification rates of these purifiers are still relatively low.

[0004] With the advancement of high-energy physics experimental research, the purity requirements for target materials are getting higher and higher, and the background level requirements for particle detectors are becoming more and more stringent, which puts higher requirements on purifiers, requiring better purification speed, purification effect, and low radon release rate. And as the scale of experiments expands, the experimental space becomes increasingly tight, so it is hoped that the purifier will not increase the volume while improving the purification performance. Summary of the invention

[0005] In order to solve the above problems, we need to start from two aspects. On the one hand, high-purity fillers are used. The optional fillers include zirconium, hafnium, titanium, vanadium, iron, copper, etc. These materials need to be smelted by vacuum electron beam or electrolytically refined and radioactively measured. 238 U. 232The Th content should not exceed 10mBq / kg to control the radon release rate of the purifier. On the other hand, the working temperature of the filler should be increased, such as to 800°C, so that the impurity elements and the filler have higher reaction activity and speed, and better purification effect can be obtained. However, at such a high temperature, it is difficult for existing flanges to simultaneously meet the requirements of high sealing, high cleanliness, and convenience of replacement, so flange sealing also needs to consider high temperature working conditions.

[0006] The technical solution of the present invention is as follows:

[0007] A low radon radioactivity, high temperature and high purity inert gas purifier is characterized in that it includes a main pipeline and connected inlet pipelines and outlet pipelines. The gas to be purified first exchanges heat with the purified gas in a heat exchanger, and then enters the main pipeline after being heated by a branch pipeline to react with the high purity metal filler inside. The N, H and O impurities in the gas react with the high purity metal filler to produce solid compounds and are purified. After being heated, the gas enters the outlet pipeline and the heat exchanger to exchange heat with the gas to be purified.

[0008] An upper end cap is sleeved outside the outlet pipe, a main heating and insulation layer is sleeved outside the main pipe, and a lower end cap is sleeved outside the inlet pipe; a sealing connection structure is provided between the upper end cap and the top of the main insulation layer, and between the lower end cap and the bottom of the main insulation layer;

[0009] The end cap blade flange and the upper end cap or the lower end cap are welded or integrally formed, the main pipeline blade flange and the main pipeline are welded or integrally formed, and the end cap blade flange and the main pipeline blade flange are sealed and fixedly connected by fasteners and sealing rings;

[0010] The upper and lower end caps are hollow inside for the outlet pipe or the inlet pipe to pass through, forming an inner pipe. One end of the inner pipe close to the end cap blade flange is sleeved with a plurality of flow-blocking fins to constrain the flow path of the high-temperature gas.

[0011] Furthermore, the high-purity metal filler is subjected to vacuum electron beam smelting or electrolytic refining and radioactivity measurement. 238 U. 232 The Th content does not exceed 10mBq / kg.

[0012] Preferably, the high purity metal filler is zirconium, hafnium, titanium, vanadium, copper or iron.

[0013] Furthermore, the surface temperature of the middle section of the main pipeline is not less than 600° C. in the working state.

[0014] Furthermore, the branch pipeline jacket is provided with a branch heating and insulation layer.

[0015] Furthermore, a heat dissipation mechanism is provided between the end cap blade flange and the main pipe blade flange and on the main pipe, so that the temperature of the end cap blade flange and the main pipe blade flange does not exceed 200°C.

[0016] Furthermore, the heat dissipation structure is a plurality of air-cooled heat sinks and / or water-cooled jackets.

[0017] Preferably, the air-cooled heat sink closest to the midpoint of the main pipe is close to the fixed ring on the inner wall of the main pipe, or if a water-cooled jacket is used, the water-cooled jacket on the outside of the main pipe is close to the fixed ring.

[0018] Furthermore, the outer diameter of the choke fin is 3 to 5 mm smaller than the inner diameter of the jacket tube, serving as a vacuum discharge channel, or the choke fin is arranged inside the jacket tube, and the choke fin is provided with a through hole, and the diameter of the through hole is 3 to 5 mm larger than the inner pipe.

[0019] Furthermore, the pipe section of the jacket pipe has no contact with the main pipe and the knife-edge flange and is at least 2 mm away from each other.

[0020] A filter screen or a porous plate is arranged inside the jacket pipe and at the lower fixing ring.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1) To ensure the working temperature of the knife-edge flange, a jacket pipe structure is designed inside the main pipeline and the knife-edge flange. The outer wall of the jacket pipe section is 5 to 10 mm away from the knife-edge flange. The high-temperature medium can only flow through the inside of the jacket pipe, and there is no forced convection between the knife-edge flange and the jacket. Because the thermal conductivity of the gas is poor, the heat transfer capacity between the high-purity medium gas of natural convection and the knife-edge flange is also small. The high-purity medium between the outer wall of the jacket pipe and the knife-edge flange has a substantial insulation effect, so the heating power of the high-temperature and high-purity medium on the knife-edge flange is small. Considering the heat dissipation of the knife-edge flange, the knife-edge flange and the gasket can be operated at a lower temperature, thereby ensuring the reliability and sealing of the knife-edge flange.

[0023] 2) High-purity fillers are placed in high-temperature alloy pipes, and outside the pipes are heating devices and insulation materials to ensure that the fillers work at a suitable temperature.

[0024] 3) The temperature of the purified medium is extremely high. After leaving the purification packing, it first exchanges heat with the low-temperature and room-temperature medium to be purified. On the one hand, it recovers energy and reduces the demand for intake heating power. On the other hand, it cools down the purified gas to ensure safe use.

[0025] 4) The materials used must be tested and controlled for radioactivity and radon release rate in advance to ensure that the purified gas will not be contaminated by radon. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the structure of an embodiment of a low radon radioactivity, high temperature and high purity inert gas purifier according to the present invention.

[0027] Figure 2 Structural design diagram of knife-edge flange embodiment 1 of the present invention suitable for high temperature working conditions

[0028] Figure 3 Structural design diagram of knife-edge flange embodiment 2 of the present invention suitable for high temperature working conditions

[0029] Figure 4 This is the structure diagram of the jacket pipe of the present invention

[0030] In the figure: 1-heat exchanger outlet pipe; 2-heat exchanger; 2A-heat exchanger hot side outlet pipe; 2B-heat exchanger hot side inlet pipe; 2C-heat exchanger cold side inlet pipe; 2D-heat exchanger cold side outlet pipe; 3-upper end cap; 4-main pipe; 5-main heating and insulation layer; 7-lower end cap; 8-inlet pipe; 10-branch pipe; 11-branch heating and insulation layer; 13-outlet pipe; 12-high purity metal filler; 21-end blade flange; 22-fastener; 23 copper sealing ring; 24-main pipe blade flange; 25-inner pipe; 26-choke fin; 27-upper jacket pipe; 28-screw; 29-upper side fixing ring; 30-air-cooled heat sink 31-lower side fixing ring; 32-filter or porous plate; 33-lower jacket pipe; 41-pipe section; 42-jacket pipe flange. DETAILED DESCRIPTION

[0031] The embodiments of the present invention are described in detail below with reference to the accompanying drawings, but the protection scope of the present invention shall not be limited thereto.

[0032] Raw material selection, use high-purity germanium spectrometer, ICP-MS and other trace detection equipment to select metal raw materials and cleaning agents with low radioactivity. The inner wall of the relevant pipeline and metal filler need to be measured for room temperature radon release rate and high temperature radon release rate, converted to radon release area, and can only be used if the radon release rate does not exceed 1mBq / square meter; metal filler 238 U. 232The Th radioactive background level does not exceed 10mBq / kg; during normal operation, the high-temperature pipe containing the metal filler has an outer wall at the insulation layer, and the operating temperature is not less than 600℃. The air inlet pipe or exhaust pipe of the high-temperature pipe extends into the jacket pipe, and there are one or more choke fins between the jacket pipe and the air inlet pipe and the exhaust pipe. The choke fin can be welded on the inside of the jacket pipe, and the cross-sectional area of ​​the choke fin through hole is 1 to 10 square centimeters larger than the cross-sectional area of ​​the air inlet pipe or the exhaust pipe. The choke fin can also be welded on the outside of the air inlet pipe and the exhaust pipe. The size of the choke fin is slightly smaller than the internal size of the jacket pipe, and the cross-sectional area of ​​the gap between them is 1 to 10 square centimeters.

[0033] Example 1

[0034] like Figure 1 As shown, the outlet pipe 1 is the outlet of the purified gas, connected to the hot side inlet pipe 2B of the heat exchanger 2. The heat exchanger 2 is a shell and tube heat exchanger or a plate heat exchanger or a shell and tube heat exchanger. The gas inlet 2C is the inlet of the gas to be purified, that is, the cold side inlet pipe of the heat exchanger 2. The branch pipe 10 is the high-temperature gas of the gas to be purified after passing through the heat exchanger 2. When the purified gas leaves the hot side outlet pipe of the heat exchanger 2, it has been cooled after sufficient heat exchange with the gas to be purified, which not only improves the safety of the equipment, but also effectively utilizes the heat energy. The branch pipe 10 is designed with a branch heating and insulation layer 11. When the temperature of the branch pipe 10 is lower than the rated temperature, the electric heating function is turned on until it reaches the rated temperature of 800°C. The gas to be purified passes through the branch pipe 10 to reach the inlet pipe 8 of the main pipe 4 and enters the main pipe 4. The main pipeline 4 is equipped with one or more high-purity metal fillers 12, which include high-purity zirconium, hafnium, vanadium, titanium, iron, copper, etc. The main pipeline 4 is provided with a main heating and insulation layer 5 on the outside. The main pipeline 4 is ensured to work at a rated temperature of 800°C by switching the electric heating function, and the heat is transferred to the internal metal filler 12 to obtain the desired reaction temperature. The gas to be purified passes through the gaps between the high-purity metal fillers 12, and the high-purity metal adsorbs the N, O, and H impurities in the gas to be purified and reacts to form solid compounds, thereby purifying the gas. The purified gas enters the particle detector after being cooled by the pipeline and the heat exchanger. The upper end cap 3 closes the upper end space of the main pipeline 4, and the pipeline 1 discharges the purified gas. The lower end cap 7 closes the lower end space of the main pipeline 4, and the heated gas to be purified is transported into the inlet pipeline 8. After removing the bolts connecting the upper end cap 3 and the lower end cap 7 to the main pipeline 4, the high-purity metal filler 12 in the high-temperature pipeline can be easily loaded and unloaded and replaced.

[0035] Figure 2 The structural design diagram of the knife-edge flange embodiment 1 of the present invention suitable for high temperature working conditions is as follows: Figure 2As shown, the connection structure and details of the main pipeline 4 and the upper end cap 3 are shown. The upper end cap 3 has a head blade flange 21, the model used in the present invention is CF160, with an inner diameter of 150mm, and a main pipeline blade flange 24 is provided at the upper end of the main pipeline 4. A copper sealing ring 23 is provided between the head blade flange 21 and the main pipeline blade flange 24, and the two blade flanges are connected by fasteners 22 to achieve sealing. There is an inner pipeline 25 inside the upper end cap, which is the discharge pipe of the purified gas. There are several circular flow-blocking fins 26 at the end of the inner pipeline 25, and the inner pipeline 25, the flow-blocking fins 26, and the head blade flange 21 are concentric. On the outside of the main pipeline 4, near the main pipeline near the knife-edge flange 24, that is, within a distance of 150 mm from the main pipeline knife-edge flange 24, there are several air-cooled heat sinks 30. The air-cooled heat sinks can also reserve threaded holes, through holes, etc. to facilitate the fixing of the heat pipe structure or other good thermal conductors to achieve the expansion design of the air cooling capacity. Here, it can also be designed as a water-cooled jacket to ensure that the main pipeline knife-edge flange 24 is not affected by the high temperature in the middle of the main pipeline 4. The air-cooled heat sink 30 is welded to the main pipeline 4 to obtain a good heat transfer effect. An upper side fixing ring 29 is welded inside the main pipeline 4, and a threaded through hole is provided on the upper side fixing ring 29. The flange 42 of the jacket pipe 27 is fixed to the upper side fixing ring 29 with screws 28. The upper side fixing ring 29 is at about the same height as the air-cooled heat sink 30 on the outside. After installation, the jacket pipe 27 is concentric with the main pipeline 4, the knife-edge flange 24, the pipe section of the upper end cap 3, the knife-edge flange 22, the pipeline 25, and the flow-blocking fin 26. The outer diameter of the flow-blocking fin 26 is 3 to 5 mm smaller than the inner diameter of the jacket tube 27, and serves as a discharge channel during the vacuum stage. The pipe section 41 of the jacket tube 27 has no direct contact with the main pipeline 4, the knife-edge flange 22, and the knife-edge flange 24, and is 2 mm to 10 mm or more away to avoid heat conduction between solids. Such a design can prevent the high-temperature, flowing purified gas from directly heating the knife-edge flange 22, the knife-edge flange 24 and the nearby pipe sections, so that the knife-edge flange 22 and the main pipeline knife-edge flange 24 are always within the rated operating temperature range of 200°C, ensuring the sealing of the flange.

[0036] The structure of the lower end cap 7 and its vicinity is the same as that of the upper end cap 3, which can also prevent the high-temperature gas to be purified from heating the knife-edge flange, and ensure that the knife-edge flange works within the rated temperature range and ensures the sealing performance. Figure 3 As shown, between the lower fixing ring 31 and the jacket pipe 33, there is a filter screen or porous plate 32 with the same outer diameter as the flange of the jacket pipe 33 or slightly smaller than the inner diameter of the main pipe 4, and the aperture is not greater than 2mm, so as to support the high-purity metal filler 12 within the specified range to ensure the purification process. The filter screen or porous plate 32 can also be welded to the lower fixing ring 31 of the main pipe 4.

[0037] The main pipeline 4 has a total length of 1 meter, a length of about 700 mm, a diameter of 150 mm, and an effective space of about 12 L for loading high-purity filler, and can be loaded with about 40 kg of 3 mm high-purity zirconium, or 80 kg of 3 mm high-purity hafnium, or a mixture of zirconium, hafnium, vanadium, titanium, and iron particles.

[0038] Tests have shown that the present invention utilizes low-radioactive high-purity metals such as zirconium, hafnium, iron, vanadium, titanium, etc., which have been smelted by electron beams, to react with nitrogen, hydrogen, oxygen, and other elements in high-purity inert gas at above 600°C to generate solid compounds, thereby achieving the purification of high-purity inert gas. The purification effect of high-purity inert gas is good, and less radon gas is released, which can meet the high-speed and high-purity purification requirements of target materials such as argon and xenon in rare case experiments. And the packing can be easily replaced after the service life of the packing ends. It can meet the convenience of replacing packing and ensuring sealing. The connection flange of the high-temperature pipeline is designed with jacketed pipes, flow-blocking fins and other structures to ensure that the connection blade flange works at a lower temperature. It can solve the needs of high-energy physics experiments in rare cases for high-speed purification of a large number of high-purity inert gases, and also solve the needs of high-temperature working conditions for high-sealing and high-cleanliness flange connections.

[0039] 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 preferred embodiments, those skilled in the art should understand that the technical solutions of the invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A low radon radioactivity, high temperature and high purity inert gas purifier, It is characterized in that It comprises a heat exchanger (2), a branch pipe (10), and an outlet pipe (1), a main pipe (4) and an inlet pipe (8) which are connected in sequence; The hot side inlet end (2B) of the heat exchanger (2) is connected to the outlet pipe (1), and the cold side inlet end (2C) of the heat exchanger (2) is used for inputting the gas to be purified; the cold side outlet end (2D) of the heat exchanger (2) is connected to one end of the branch pipe (10), and the other end of the branch pipe (10) is connected to the inlet pipe (8); a high-purity metal filler (12) is filled inside the main pipe (4); the high-purity metal filler is subjected to vacuum electron beam smelting or electrolytic refining, 238 U. 232 Th content does not exceed 10mBq / kg A main heating and heat-insulating layer (5) is provided on the outer jacket of the main pipeline (4), a lower end cover (7) is provided on the outer jacket of the inlet pipeline (8), and an upper end cover (3) is provided on the outer jacket of the outlet pipeline (1); When the gas to be purified enters the heat exchanger (2) through the cold side inlet end (2C) of the heat exchanger (2) and exchanges heat with the purified gas in the heat exchanger (2), it enters the main pipe (4) through the cold side outlet end (2D) of the heat exchanger (2) and then passes through the branch pipe (10) and the inlet pipe (8) in sequence. When the middle section of the main pipe (4) in the longitudinal direction accounts for 60% of the total length and is in a partial working state, the surface working temperature is not less than 600° C. The high-purity metal zirconium, hafnium, iron, vanadium, titanium and other metals with low radioactivity smelted by electron beam react with nitrogen, hydrogen, oxygen and other elements in the high-purity inert gas at above 600° C. to generate solid compounds, thereby purifying the high-purity inert gas. After purification, the gas is output through the outlet pipe (1) and enters the heat exchanger (2) through the hot side inlet end (2B) of the heat exchanger (2).

2. The low radon radioactivity, high temperature and high purity inert gas purifier according to claim 1, It is characterized in that The outlet pipe (1) is inserted into the internal hollow space of the upper end cover (3), and the inlet pipe (8) is inserted into the internal hollow space of the lower end cover (7), thereby forming an inner pipe connected from top to bottom by the outlet pipe (1), the main pipe (4) and the inlet pipe (8), and one end of the inner pipe is sleeved with a plurality of flow-blocking fins.

3. The low radon radioactivity, high temperature and high purity inert gas purifier according to claim 1, It is characterized in that A head blade flange and a main pipeline blade flange are provided between the upper end head (3) and the top of the main heating and thermal insulation layer (5), and between the bottom of the main heating and thermal insulation layer (5) and the lower end head (7).

4. The low radon radioactivity, high temperature and high purity inert gas purifier according to claim 3, It is characterized in that The end cap blade flange is welded to the upper end cap or the lower end cap as a whole or is directly processed and formed from a single piece of material, the main pipeline blade flange is welded to the main pipeline (4) as a whole or is directly processed and formed from a single piece of material, and the end cap blade flange is sealed and fixedly connected to the main pipeline blade flange via fasteners and sealing rings.

5. The low radon radioactivity, high temperature and high purity inert gas purifier according to claim 1, It is characterized in that The radon emission rate of the inner surface of the high-temperature pipeline does not exceed 1mBq / ㎡ at 25℃.

6. The low radon radioactivity, high temperature and high purity inert gas purifier according to claim 5, It is characterized in that The high-purity metal filler is zirconium, hafnium, titanium, vanadium, copper or iron.

7. The low radon radioactivity, high temperature and high purity inert gas purifier according to claim 1, It is characterized in that The branch pipeline (10) is provided with a branch heating and heat insulation layer (11) on its outer shell.

8. The low radon radioactivity, high temperature and high purity inert gas purifier according to claim 3 or 4, It is characterized in that A heat dissipation structure is also provided between the end cap blade flange and the main pipeline blade flange, at both ends of the main pipeline (4) close to the blade flange (24), and on the outside of the blade flange (34), so that the temperature of the end cap blade flange and the main pipeline blade flange does not exceed 200°C.

9. The low radon radioactivity, high temperature and high purity inert gas purifier according to claim 8, It is characterized in that The heat dissipation structure is a plurality of air-cooled heat sinks and / or water-cooled jackets.

10. The low radon radioactivity, high temperature and high purity inert gas purifier according to claim 9, It is characterized in that The air-cooled heat sink closest to the midpoint of the main pipeline is within 10 cm from the fixed ring of the inner wall.

11. The low radon radioactivity, high temperature and high purity inert gas purifier according to claim 9, It is characterized in that The water cooling jacket is located between the main pipeline heating and insulation layer (5) and the upper blade flange (24) and between the heating and insulation layer (5) and the lower blade flange (34).

12. The low radon radioactivity, high temperature and high purity inert gas purifier according to claim 2, It is characterized in that The outer diameter of the baffle fin (26) is 3 to 5 mm smaller than the inner diameter of the jacket tube; or the baffle fin (26) is welded to the inner side of the jacket tube (27), and the inner hole diameter of the baffle fin (26) is 3 to 5 mm larger than the diameter of the inner tube (25); serving as a vacuum discharge channel.

13. The low radon radioactivity, high temperature and high purity inert gas purifier according to claim 1, It is characterized in that It also includes a jacket pipe, an upper fixing ring and / or a lower fixing ring arranged in the main pipeline; the upper fixing ring and the lower fixing ring are respectively welded and fixed above and below the inner wall of the main pipeline, and threaded through holes are provided inside, so that the flange (42) of the jacket pipe (27) can be fixed to the upper fixing ring and / or the lower fixing ring by screws, and ensure that the pipe section (41) of the jacket pipe (27) is at least 2 mm away from the main pipeline and the knife-edge flange.

14. The low radon radioactivity, high temperature and high purity inert gas purifier according to claim 13, It is characterized in that The lower fixing ring is provided with a filter screen or a porous plate.

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