Gas purification device with wide temperature range selection

Abstract

The invention discloses a gas purification device with wide temperature range selection. Purification and regeneration processes are carried out in a vacuum cover. In the purification process, a refrigerating machine serves as a cold source, cold energy is transmitted to an adsorption unit through a cold conduction and heat insulation assembly, a first temperature sensor and a first heater are arranged at the secondary cold head, a second temperature sensor and a second heater are arranged at the adsorption unit, and the first heater is matched with a temperature controller to control the temperature of the secondary cold head; the second heater cooperates with the temperature controller to calibrate the temperature of the adsorption unit again in the low-temperature purification stage, the two temperature control points are the same, the temperature control precision is + / -0.1 K, and the feed gas enters the adsorption unit after being pre-cooled for four times to complete purification. In the regeneration process, the second heater serves as a heat source, and impurities in the adsorption unit are desorbed and discharged along the pipeline. According to the device, the temperature during adsorption is controllable in a range of 5-200K, the temperature uniformity is + / -0.3 K, the temperature during regeneration is controllable in a range of 200-500K, the process is simple, the structure is compact, crude helium with the purity of 98% or above can be purified, and ultra-pure helium with the purity of not less than 6N can be output.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of gas separation and purification technology by adsorption method, and particularly relates to a wide-temperature-range selected gas purification device. BACKGROUND

[0002] As a non-renewable rare gas, helium is widely used in military, medical, semiconductor and low-temperature superconducting fields, and the price of helium is very high, so recycling and reusing helium is a current hot topic, and the purification of recycled helium is a key work of helium reuse.

[0003] The traditional helium low-temperature purification method mainly uses liquid nitrogen as a cold source, removes impurity gases in helium by low-temperature adsorption, and generally uses two sets of purifiers to switch operation. During the purification process, liquid nitrogen needs to be continuously supplied to the purifier, and during desorption, the liquid nitrogen needs to be discharged and then heated and activated for regeneration. The purification work is quite cumbersome, the equipment occupies a large space, the adsorption effect is not ideal, and because the gas adsorption device mostly uses liquid nitrogen as a cold source, the temperature can only stay in the 77K liquid nitrogen temperature range, and adsorption in the temperature range below or above 77K cannot be achieved, which greatly restricts the selection of the adsorption temperature range. At the same time, the temperature is difficult to achieve precise control during adsorption. Some impurities mixed in helium, such as neon, need to be adsorbed and removed below 30K, which cannot be achieved by the existing purification device. Moreover, liquid nitrogen is a dangerous chemical, and it is easy to cause frostbite, suffocation and other dangers during operation. Furthermore, the traditional adsorption purification equipment mostly needs to be connected to a heat conduction device for heat transfer to complete the regeneration process, which occupies a large space and restricts the use range of the equipment, and the temperature is limited to below 373K, resulting in a long desorption time. Therefore, there is an urgent need for a purification device that can expand the adsorption temperature range, is simple in equipment, small in occupied space, short in desorption time and safe in operation. SUMMARY

[0004] The present application aims to provide a wide-temperature-range selected gas purification device with high temperature control precision, which realizes precise temperature control by using a step-by-step temperature control method.

[0005] The technical scheme of the present application is as follows: a wide-temperature-range selected gas purification device, comprising a vacuum cover, a refrigeration machine as a cold source, and a temperature control system for step-by-step control of the temperature of the adsorption unit. The raw gas is heated by the heat exchange system and then enters the adsorption unit after heat exchange with the product gas and the cold output end of the refrigeration machine. The secondary cold head of the refrigeration machine is connected to the adsorption unit through a cold-conduction and heat-insulation assembly. The temperature control system comprises a temperature controller, a first temperature sensor arranged on the secondary cold head and connected to the temperature controller, a second temperature sensor arranged on the adsorption unit and connected to the temperature controller, and an upper computer for transmitting the temperature control point signal to the temperature controller and realizing temperature closed-loop control.

[0006] Further, the refrigerating machine is a G-M refrigerating machine, a pulse tube refrigerating machine or a Stirling refrigerating machine, and the cold output end of the refrigerating machine comprises a first cold head and a second cold head.

[0007] Preferably, the temperature control system further comprises a first heater cooperating with the temperature controller to control the temperature of the second cold head and a second heater cooperating with the temperature controller to control the temperature of the adsorption unit again; the first heater and the second heater are connected to the temperature controller. The second heater provides a heat source in the regeneration process of restoring the performance of the adsorption unit.

[0008] Further, the heat exchange system comprises a first heat exchanger connected to the raw gas input end, a first cold head heat exchanger connected to the outlet of the first heat exchanger, a second heat exchanger connected to the outlet of the first cold head heat exchanger, and a second cold head heat exchanger connected to the second heat exchanger, and the outlet of the second cold head heat exchanger is connected to the adsorption unit. The first cold head heat exchanger and the second cold head heat exchanger are respectively arranged at the first cold head and the second cold head.

[0009] Further, the cold conducting and heat insulating assembly has the characteristics of high thermal resistance in the high temperature zone and low thermal resistance in the low temperature zone, and the material is preferably sapphire.

[0010] Further, the adsorption material filled in the adsorption unit can be activated carbon, molecular sieve or metal getter, and the outside of the adsorption unit is wrapped by a high thermal conductivity material, and the material is preferably oxygen-free copper.

[0011] Advantages: Compared with the prior art, the present application has the following advantages: (1) The refrigerating machine is used instead of liquid nitrogen as a cold source, which is safe to operate, and the purification process has a wide temperature range to choose from. The temperature control system controls the temperature of the adsorption process at 5-200K and the temperature of the regeneration process at 200-500K; (2) The temperature of the second cold head of the refrigerating machine is controlled first, and then the temperature of the adsorption unit is controlled again. The upper computer transmits signals to the temperature controller to control the temperature sensor and the heater in a PID closed loop, and the temperature control accuracy is ±0.1K and the temperature uniformity is ±0.3K, so that the raw gas and the adsorption material in the adsorption unit are in contact without temperature difference; (3) The purification and regeneration processes are completed in one device. Liquid nitrogen is replaced by a refrigerating machine as a cold source during purification, and a heater is used instead of an external heat conducting device as a heat source during regeneration, so that the structure is compact, the equipment is small and simple, and the process is simple. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 Figure 1 is a structural schematic diagram of the gas purification device of the present application. DETAILED DESCRIPTION

[0013] The technical solutions of the present application will be further described below with reference to the drawings.

[0014] The gas purification device with a wide temperature range selection according to the present application, as shown in Figure 1As shown, the gas purification and regeneration process is carried out in the vacuum cover 1, and a cold screen 7 is arranged in the vacuum cover, and the heat exchange system, the cold output end of the refrigerator, the adsorption unit and part of the components in the temperature control system are arranged in the cold screen 7, so that the cold loss can be reduced, the low-temperature components in the cold screen and the vacuum cover are prevented from radiating heat, the damage or performance decline of the equipment components caused by the too large temperature difference is avoided, and the service life of the equipment is prolonged. The refrigerator is used instead of the traditional liquid nitrogen as the cold source, so that the purification process has a wide temperature range to be selected, and the problems of frostbite and room breathing of liquid nitrogen are avoided. The refrigerator 2 can be a G-M refrigerator, a pulse tube refrigerator or a Stirling refrigerator, preferably, a two-stage refrigerator is selected, so that the refrigeration efficiency at deep low temperature can be ensured, and the refrigerator is especially suitable for helium purification which has high requirements for deep low temperature technology. The cold output end of the refrigerator includes a first-stage cold head 21 and a second-stage cold head 22, the temperature is reduced to 40-60K by the first-stage cold head, and the temperature is reduced to 5-15K by the second-stage cold head. Through the “step-by-step precooling” mode, the second-stage cold head does not need to be directly cooled from room temperature, but is “relay” cooled on the basis of the first-stage cold head, so that the refrigeration efficiency and stability at deep low temperature are greatly improved.

[0015] The heat exchange system 4 includes a first-stage heat exchanger 41, a first-stage cold head heat exchanger 42, a second-stage heat exchanger 43 and a second-stage cold head heat exchanger 44. The first-stage heat exchanger 41 is connected with the gas inlet 8, and the first-stage heat exchanger is sequentially connected with the first-stage cold head heat exchanger 42, the second-stage heat exchanger 43 and the second-stage cold head heat exchanger 44. After being cooled through the four-stage precooling, the gas enters the adsorption unit 3. The first-stage cold head heat exchanger and the second-stage cold head heat exchanger are arranged at the first-stage cold head and the second-stage cold head respectively, and are made of an interval wall heat exchanger. The inner wall material is preferably copper, and the outer wall material is preferably stainless steel. The first-stage heat exchanger and the second-stage heat exchanger are made of a double-pipe heat exchanger. The inner tube material is preferably copper, and the outer tube material is preferably stainless steel.

[0016] The adsorption effect of the adsorption material on different impurity gases is different at different temperatures, so the temperature control of the adsorption unit 3 is very important. In the traditional purification device, the temperature control precision of the adsorption unit is not high, so the purity of the helium gas is not high. The temperature of the adsorption unit is controlled by the temperature control system in stages. The first temperature sensor 62 is arranged at the two-stage cold head 22, and the first heater 65 is fastened on the two-stage cold head. The first temperature sensor and the first heater are both connected to the temperature controller 61, and the temperature controller is controlled by the upper computer 64. Similarly, the second temperature sensor 63 is arranged at the adsorption unit 3, and the second heater 66 is fastened on the adsorption unit. The second temperature sensor and the second heater are both connected to the temperature controller 61, and the temperature controller is controlled by the upper computer 64. The same temperature control temperature is set on the upper computer interface. When the cold quantity is transmitted to the two-stage cold head 22, the first temperature sensor 62 transmits the temperature signal to the temperature controller. The upper computer controls the first temperature sensor and the first heater through the temperature controller to realize the primary temperature control of the two-stage cold head. The cold quantity on the two-stage cold head is transmitted to the adsorption unit through the cold-conducting and heat-insulating assembly 5. The upper computer controls the second temperature sensor and the second heater through the temperature controller to realize the secondary temperature control of the adsorption unit, so that the raw gas and the adsorption material in the adsorption unit are in contact without temperature difference. Because the cold source is provided by the refrigerator, the temperature control range is very wide. The temperature in the adsorption process is controlled at 5-200K, and the temperature in the regeneration process is controlled at 200-500K. Through the step-by-step temperature control, the temperature control precision is ±0.1K, and the temperature uniformity is ±0.3K. The crude helium gas with a purity of more than 98% can be purified and output as ultra-pure helium gas with a purity of not less than 6N.

[0017] In order to transmit the cold quantity to the adsorption unit without loss, the material of the cold-conducting and heat-insulating assembly 5 is preferably sapphire, and other materials with the characteristics of high thermal resistance in the high temperature zone and low thermal resistance in the low temperature zone can also be used. The cold-conducting and heat-insulating assembly is fastened and connected between the two-stage cold head and the adsorption unit. The adsorption material filled in the adsorption unit 3 can be activated carbon, molecular sieve or metal getter. The outside of the adsorption unit is wrapped by a high thermal conductivity material, and the material is preferably oxygen-free copper. The adsorption unit is movably connected in the pipeline and can be replaced at any time.

[0018] The raw gas enters from the gas inlet 8, passes through the flow controller 12, enters the first heat exchanger 41, exchanges heat with the product gas treated by the device to complete the first cooling; then flows into the first cold head heat exchanger 42 to exchange heat with the first cold head 21 of the refrigerator to complete the second cooling; then flows into the second heat exchanger 43 to complete the third cooling with the product gas treated by the adsorption unit 3; then flows into the second cold head heat exchanger 44 to complete the fourth cooling with the second cold head 22, and then enters the adsorption unit. At this time, the adsorption unit has reached the set temperature through the temperature control system. In the adsorption unit 3, the impurity gas in the raw gas is adsorbed, and only helium gas flows out and flows into the second heat exchanger 43 to complete the first re-warming with the raw gas flowing through it. Then, the helium gas flows into the first heat exchanger 41 to complete the second re-warming with the raw gas just entering the device, and then flows out of the device from the product gas outlet 9. The arrangement of the first heat exchanger and the second heat exchanger in the device can exchange heat between the output low-temperature ultrapure helium gas and the input high-temperature raw helium gas, pre-cool the helium gas in the input pipeline, reduce the production cost, and improve the cooling efficiency.

[0019] The adsorption material in the adsorption unit 3 needs to be regenerated to realize recycling after a period of use due to being covered with impurities. In the high-temperature regeneration process, the second heater 66 tightly fixed on the adsorption unit 3 provides heat, replacing the external heat conduction device to perform heat transfer regeneration, so that the regeneration temperature has a wider and higher temperature range and temperature control, greatly reducing the equipment space and desorption time of the adsorption unit. The temperature control parameters are set on the upper computer 64 interface to control the temperature of the adsorption unit only. The temperature range is 200-500K, waiting for temperature rise, and after the temperature reaches the set value, it lasts for 2 hours. At this time, the impurity gas adsorbed in the adsorption unit is desorbed, causing the pressure in the pipeline to increase. The high-pressure gas after desorption is discharged from the system pressure relief port 10, and the remaining low-pressure residual gas is pumped out from the system evacuation port 11 by the vacuum pump. The vacuum degree is ≤10 -5 orders of magnitude and remains stable, and the regeneration process ends. The regeneration process and the purification process are carried out in the same set of purification equipment, which simplifies the work flow, reduces the equipment space and desorption time, and has high universality and promotion value.

[0020] The device can not only be used for gas purification in industry, but also be used as an experimental device. According to the experimental needs, the temperature of the adsorption unit, the type of raw gas, the inlet flow or the type of activated carbon can be changed to verify the influence of different parameters on the adsorption effect and achieve the experimental purpose.

Claims

1. A wide temperature range selected gas purification device comprising a vacuum housing (1), characterized in that, The cryogenic machine (2) is also included as a cold source, and a temperature control system is used to control the temperature of the raw material gas and the adsorption unit (3) step by step. The raw material gas exchanges heat with the product gas and the cold output end of the cryogenic machine through a heat exchange system, and then enters the adsorption unit (3). The secondary cold head (22) of the cryogenic machine is connected with the adsorption unit through a cold conduction and heat insulation assembly (5). The temperature control system includes a temperature controller (61), a first temperature sensor (62) arranged at the secondary cold head of the cryogenic machine and connected with the temperature controller, a second temperature sensor (63) arranged at the adsorption unit and connected with the temperature controller, and an upper computer (64) for transmitting the temperature control point signal to the temperature controller and realizing temperature closed-loop control.

2. The gas purification device according to claim 1, characterized in that, The temperature control system further includes a first heater (65) cooperating with the temperature controller (61) to control the temperature of the secondary cold head (22), and a second heater (66) cooperating with the temperature controller (61) to control the temperature of the adsorption unit (3) again. The first heater (65) and the second heater (66) are connected with the temperature controller (61).

3. The gas purification device of claim 2, wherein, The second heater (66) provides a heat source in the regeneration process of restoring the performance of the adsorption unit (3).

4. The gas purification device of claim 1, wherein, The cold output end of the cryogenic machine further includes a primary cold head (21).

5. The gas purification device of claim 1, wherein, The heat exchange system includes a primary heat exchanger (41) connected with the raw material gas input end, a primary cold head heat exchanger (42) connected with the outlet of the primary heat exchanger (41), a secondary heat exchanger (43) connected with the outlet of the primary cold head heat exchanger (42), and a secondary cold head heat exchanger (44) connected with the secondary heat exchanger. The outlet of the secondary cold head heat exchanger (42) is connected with the adsorption unit (3).

6. The gas purification device of claim 1, wherein, The primary cold head heat exchanger (42) and the secondary cold head heat exchanger (42) are arranged at the primary cold head (21) and the secondary cold head (22), respectively.

7. The gas purification device of claim 1, wherein, The cold conduction and heat insulation assembly (5) is preferably sapphire.

8. The gas purification device of claim 1, wherein, The adsorption unit (3) is wrapped by a high thermal conductivity material.

9. The gas purification device of claim 1, wherein, The adsorption material filled in the adsorption unit (3) can be activated carbon, molecular sieve or metal getter.

10. The gas purification device of claim 1, wherein, The cryogenic machine (2) adopts a G-M cryogenic machine, a pulse tube cryogenic machine or a Stirling cryogenic machine.

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