High-purity helium extraction method based on low-temperature adsorption

Abstract

The invention relates to the technical field of helium extraction, in particular to a high-purity helium extraction method based on low-temperature adsorption. The method comprises the following steps: in a low-temperature environment, carrying out adsorption treatment on mixed gas by utilizing a low-temperature adsorption material through a dynamic adsorption scheduling optimization algorithm to obtain unadsorbed helium and the low-temperature adsorption material after adsorbing impurity gas; carrying out desorption treatment on the low-temperature adsorption material after adsorbing the impurity gas to obtain desorbed enriched helium; and carrying out low-temperature fractionation treatment on desorbed and enriched helium and unadsorbed helium to obtain high-purity helium. The technical problems that a traditional helium extraction method is low in helium extraction efficiency, purity and recovery rate are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of helium extraction, and particularly to a method for extracting high-purity helium based on cryogenic adsorption. Background Art

[0002] Helium, as an important industrial gas, is widely used in superconducting magnetic resonance imaging (MRI), particle accelerators, aerospace, balloons, and other scientific research and industrial manufacturing. Due to its unique chemical properties (such as low boiling point, inert gas, etc.), helium plays an irreplaceable role in many high-tech fields. However, helium resources are relatively scarce and expensive, so how to efficiently extract and purify helium has become an important research topic.

[0003] Traditional helium extraction methods usually rely on cryogenic fractionation technology. This method cools the gas mixture so that gases of different components condense at different temperatures, thereby achieving the separation of helium. However, cryogenic fractionation has certain limitations. Especially when dealing with complex gas mixtures, due to the small boiling point difference between helium and other gases (such as nitrogen, oxygen, argon, etc.), it is often difficult to achieve efficient separation. In addition, the cryogenic fractionation process requires high energy consumption, and the equipment is complex and the operating cost is high.

[0004] In summary, traditional helium extraction methods have technical problems of low helium extraction efficiency, low purity, and low recovery rate. Summary of the Invention

[0005] The present invention provides a method for extracting high-purity helium based on cryogenic adsorption to solve the technical problems of low helium extraction efficiency, low purity, and low recovery rate of traditional helium extraction methods.

[0006] A method for extracting high-purity helium based on cryogenic adsorption of the present invention specifically includes the following technical solutions: A method for extracting high-purity helium based on cryogenic adsorption includes the following steps: S1. In a low-temperature environment, using cryogenic adsorption materials, through a dynamic adsorption scheduling optimization algorithm, perform a preliminary component analysis on the mixed gas entering the adsorption bed to obtain the concentrations of helium and impurity gases in the mixed gas; based on the adsorption kinetics model, combined with the concentration of impurity gases in the mixed gas, the characteristics of the cryogenic adsorption materials, and the adsorption conditions, calculate the adsorption effect; the adsorption conditions include temperature, pressure, and gas flow rate; based on the adsorption effect, combined with the concentrations of helium and impurity gases in the mixed gas, dynamically adjust the temperature, pressure, and gas flow rate; based on the adsorption effect, the concentrations of helium and impurity gases in the mixed gas, and the gas flow rate, construct a judgment condition for stopping the adsorption process; when the adsorption process stops, output the unadsorbed helium and the cryogenic adsorption materials after adsorbing the impurity gases; S2. Desorb the cryogenic adsorption material after adsorbing impurity gases to obtain desorbed and enriched helium gas; perform cryogenic fractionation on the desorbed and enriched helium gas and the unadsorbed helium gas to obtain high-purity helium gas.

[0007] Preferably, the S1 specifically includes: The specific calculation formula for the adsorption effect is as follows: , where, is the adsorption effect at time; is the specific surface area of the cryogenic adsorption material; is the pore volume of the cryogenic adsorption material; is the average pore diameter of the cryogenic adsorption material; is the surface polarity coefficient; is the temperature of the adsorption bed at time; is the pressure of the adsorption bed at time; is the exponent used to control the influence of temperature on the adsorption effect during the adsorption process; is the adsorption constant; is the decay constant of the impurity gas concentration; is the concentration of impurity gas in the mixed gas at time.

[0008] Preferably, the S1 specifically includes: The adjustment of the temperature, pressure, and gas flow rate is respectively achieved through the following formulas: , , , where, and respectively represent the change amounts of temperature and pressure during the adsorption process at time; is the temperature adjustment coefficient; is the maximum adsorption capacity of the cryogenic adsorption material; is the concentration of impurity gas in the mixed gas at time; is the concentration of helium gas in the mixed gas at time; is the pressure adjustment coefficient; is the concentration of impurity gas in the mixed gas at the previous time; is the gas flow rate at time; is the initial gas flow rate, representing the gas flow rate of the adsorption bed under standard conditions.

[0009] Preferably, the S1 specifically includes: The judgment conditions for stopping the adsorption process are as follows: When the difference between the maximum adsorption capacity of the cryo-adsorbent material and the adsorption effect of the cryo-material is less than the preset adsorption effect difference threshold, it indicates that the cryo-adsorbent material is saturated and the adsorption process needs to be stopped; When the output helium concentration reaches a stable value and the gas flow rate no longer increases, it indicates that the helium recovery rate has reached the maximum and the adsorption process can be stopped; When the impurity gas concentration drops to the preset adsorption threshold, the adsorption process can be stopped; When any of the above stopping conditions is met, stop the adsorption process and output the unadsorbed helium and the cryo-adsorbent material after adsorbing the impurity gas.

[0010] Preferably, the S2 specifically includes: During the desorption process of the cryo-adsorbent material after adsorbing the impurity gas, the impurity gas adsorbed on the surface of the cryo-adsorbent material is desorbed by gradually increasing the temperature and reducing the pressure, and the heating rate and pressure reduction rate are controlled during the desorption process.

[0011] Preferably, the S2 specifically includes: During the desorption process of the cryo-adsorbent material after adsorbing the impurity gas, the impurity gas is guided to the impurity gas collection pipeline through the exhaust system, and the composition of the discharged gas is monitored in real time by a gas analyzer. When the concentration of the impurity gas drops to the set desorption threshold, the gas channel is switched to collect the desorbed and enriched helium.

[0012] Preferably, the S2 specifically includes: Utilizing the different boiling point differences between gas molecules, the unadsorbed helium and the desorbed and enriched helium are subjected to cryogenic fractionation treatment to obtain high-purity helium.

[0013] The beneficial effects of the technical solution of the present invention are: 1. By using a cryo-adsorbent material and introducing a dynamic adsorption scheduling optimization algorithm to calculate the adsorption effect and adjust the adsorption conditions such as temperature, pressure, and gas flow rate in real time, impurity gases (such as nitrogen, oxygen, argon, etc.) are gradually removed, enabling efficient recovery of helium.

[0014] 2. Adopt a desorption process of gradually increasing temperature and decreasing pressure. By controlling the heating rate and pressure reduction rate, ensure that while effectively desorbing impurity gases, helium is retained to the greatest extent. During the desorption process, as the temperature and pressure change, the impurity gases are rapidly desorbed, while helium, due to its lower desorption temperature and weaker adsorption force, remains in the adsorption bed, improving the recovery rate of helium and ensuring the purity of helium. Description of the Drawings

[0015] Figure 1 It is a flow chart of a high-purity helium extraction method based on cryogenic adsorption according to the present invention. Detailed Embodiments

[0016] In order to further elaborate on the technical means and effects adopted by the present invention to achieve the intended invention purpose, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0018] The following specifically describes the specific solution of a high-purity helium extraction method based on cryogenic adsorption provided by the present invention in conjunction with the accompanying drawings.

[0019] Refer to the attached Figure 1 , which shows a flow chart of a high-purity helium extraction method based on cryogenic adsorption provided by an embodiment of the present invention. The method includes the following steps: S1. In a low-temperature environment, use a cryogenic adsorption material to perform adsorption treatment on the mixed gas through a dynamic adsorption scheduling optimization algorithm to obtain unadsorbed helium and the cryogenic adsorption material after adsorbing impurity gases; First, in an adsorption device at low temperature (such as liquid nitrogen temperature or lower temperature (for example, below 77K)), use a cryogenic adsorption material (such as 5A molecular sieve, dehydrated activated carbon or modified silica gel) that has low adsorption to helium and high selective adsorption ability to impurity gases (such as nitrogen, oxygen, argon, etc.) to perform adsorption treatment on the mixed gas. The cryogenic adsorption material can provide a large specific surface area at low temperature and can effectively adsorb impurity gases in its microporous structure; Through the dynamic adsorption scheduling optimization algorithm, the mixed gas is adsorbed by the cryogenic adsorption material; the dynamic adsorption scheduling optimization algorithm can adaptively adjust the adsorption conditions and gradually adsorb the impurity gas to obtain the unadsorbed helium gas and the cryogenic adsorption material after adsorbing the impurity gas. The specific implementation process is as follows: First, the gas analyzer conducts a preliminary composition analysis of the mixed gas entering the adsorption bed (i.e., the component for carrying the cryogenic adsorption material) to obtain the concentrations of helium gas and impurity gases (such as nitrogen, oxygen, argon, etc.) in the mixed gas; Furthermore, based on the existing adsorption kinetic model, combined with the concentration of the impurity gas monitored in real time, the characteristics of the cryogenic adsorption material, and the adsorption conditions, the adsorption effect is calculated; the adsorption conditions (temperature, pressure, and gas flow rate) are obtained by sensor measurement and normalized processing; the specific formula for the adsorption effect is as follows: , where, is the adsorption effect at time, reflecting the gas adsorption capacity of the adsorption bed at the current moment, which changes with time and is affected by factors such as temperature, pressure, and impurity gas concentration; is the specific surface area of the cryogenic adsorption material, representing the total surface area per unit mass of the cryogenic adsorption material, obtained according to the specific characteristics of the cryogenic adsorption material; is the pore volume of the cryogenic adsorption material. The larger the pore volume, the easier it is for the cryogenic adsorption material to capture the impurity gas, determined by mercury intrusion or nitrogen adsorption; is the average pore diameter of the cryogenic adsorption material, which determines whether the gas can enter the pore channels and is used to regulate selectivity, determined according to the specific characteristics of the cryogenic adsorption material; is the surface polarity coefficient, depending on the polarity degree of the surface functional groups of the cryogenic adsorption material. A positive value indicates a preference for the impurity gas, determined according to the type of cryogenic adsorption material, and can be measured by surface tension or contact angle; is the temperature of the adsorption bed at time; is the pressure of the adsorption bed at time; is the exponent used to control the influence of temperature on the adsorption effect during the adsorption process, indicating the degree of influence of temperature change on the adsorption effect. If has a large value, it means that the adsorption effect is more sensitive to temperature change, determined by the expert experience method in the specific application scenario, and the value range is ; is the adsorption constant, which represents the response sensitivity of temperature and pressure to the adsorption process, determines the adsorption capacity of the adsorption bed under specific conditions. The value of the adsorption constant is closely related to the characteristics of the cryogenic adsorption material, the type of gas, and the adsorption conditions, and is obtained by fitting the experimental data of adsorption kinetics. The value range is ; is the decay constant of the impurity gas concentration, which represents the decay constant describing the influence of the impurity gas concentration on the adsorption effect. As the impurity gas concentration increases, the adsorption effect of the adsorption bed will gradually weaken, and it is obtained through experiments. The value range is ; is the concentration of the impurity gas in the mixed gas at moment, which is obtained by real-time monitoring with a gas analyzer; In particular, the parameters in the above formula are all dimensionless form parameters obtained after normalization to avoid the problem of inconsistent data dimensions; Next, based on the real-time calculated adsorption effect , the temperature, pressure, and gas flow rate are adjusted in real time to achieve the optimal adsorption effect. By adjusting the adsorption conditions (temperature, pressure, and gas flow rate), the impurity gas can be effectively adsorbed while retaining helium as much as possible to avoid the loss of helium. The adjustment of temperature, pressure, and gas flow rate is achieved through the following formulas respectively: , , , where, and respectively represent the change amounts of temperature and pressure during the adsorption process at moment, which are used to control the change amplitudes of temperature and pressure; is the temperature adjustment coefficient, which represents the sensitivity of temperature adjustment to the adsorption process and is determined by the expert experience method. The value range is ; is the maximum adsorption capacity of the cryogenic adsorption material, which represents the maximum gas amount that the cryogenic adsorption material can adsorb under ideal conditions and is specifically set according to the characteristics of the cryogenic adsorption material and the adsorption conditions; is the concentration of the impurity gas in the mixed gas at moment; is the concentration of helium in the mixed gas at moment; The term is used to adjust the change amplitude of temperature so that helium can be preferentially retained while the impurity gas is effectively removed; is the pressure adjustment coefficient, which represents the sensitivity of pressure adjustment to the adsorption process and is determined by the expert experience method. The value range is ; is the concentration at the previous moment (i.e., The concentration of impurity gas in the mixed gas at a certain moment; Items used to determine the adjustment range of pressure; is at The gas flow rate at a certain moment, indicating the gas flow rate that needs to pass through the adsorption bed at a specific moment; is the initial gas flow rate, which is the gas flow rate of the adsorption bed under standard conditions; The change of the item directly affects the adjustment range of the gas flow rate; the parameters in the above formula are all dimensionless form parameters obtained after normalization to avoid the problem of inconsistent data dimensions; Based on the adsorption effect calculated in real time, the concentration of helium and impurity gas in the mixed gas monitored in real time, and the gas flow rate, construct the judgment conditions for stopping the adsorption process to judge whether it is necessary to stop the adsorption process. The specific judgment conditions are as follows: Saturation of cryogenic adsorption material: When the adsorption effect of the cryogenic adsorption material infinitely reaches the maximum adsorption capacity , that is, the maximum adsorption capacity of the cryogenic adsorption material and the adsorption effect of the cryogenic adsorption material The difference is less than the adsorption effect difference threshold, indicating that the cryogenic adsorption material is saturated. At this time, the adsorption process needs to be stopped; the adsorption effect difference threshold is set according to the expert experience method and can take a value of ; Helium outflow stability: When the helium concentration reaches a stable value and the gas flow rate no longer increases, it indicates that the recovery rate of helium has reached the maximum, and it is no longer effective to continue adsorbing impurity gas. At this time, the adsorption process can be stopped; Reduction of impurity gas concentration: When the impurity gas concentration drops to the adsorption threshold set according to the expert experience method, it means that most of the impurity gas has been removed and the adsorption effect has reached the expectation. The adsorption process can be stopped; When any of the above stopping conditions is met, stop the adsorption process and output the helium that has not been adsorbed and the cryogenic adsorption material after adsorbing impurity gas.

[0020] S2. Desorb the cryogenic adsorption material after adsorbing impurity gas to obtain desorbed and enriched helium; perform cryogenic fractionation on the desorbed and enriched helium and the helium that has not been adsorbed to obtain high-purity helium.

[0021] After the adsorption is completed and the unadsorbed helium gas is discharged, the adsorption bed will enter the desorption stage. In order to efficiently release the adsorbed impurity gas and retain helium gas, first, by heating, the impurity gas in the adsorption bed is desorbed from the surface of the low-temperature adsorption material; specifically, the temperature of the adsorption bed is gradually increased from a low temperature (about 77K) to a preset desorption temperature range, such as it can be set between 100K and 150K, to provide sufficient thermal energy for the desorption of the impurity gas adsorbed on the surface of the low-temperature adsorption material. The heating rate needs to be strictly controlled between 0.5K / min and 2K / min to ensure that the temperature change is not too fast, thereby avoiding premature desorption of helium gas or damage to the structure of the low-temperature adsorption material; At the same time, while heating, in order to further promote the desorption of the impurity gas, a pressure reduction operation can be combined to enhance the desorption effect. The gas pressure in the adsorption bed is gradually reduced from atmospheric pressure to a preset desorption pressure range, such as between 10kPa and 30kPa, and the pressure reduction rate is controlled at, for example, 2kPa / min to 5kPa / min, to avoid unstable gas flow or damage to the low-temperature adsorption material caused by too fast pressure change; During the desorption process, the impurity gas is guided to the impurity gas collection pipeline through the existing exhaust system, and the composition of the discharged gas is monitored in real time by a gas analyzer. When the impurity gas concentration drops to the desorption threshold set according to the expert experience method, the gas channel is immediately switched, and the helium-rich gas (i.e., desorbed and enriched helium gas) is collected into a dedicated helium gas storage component. The concentration of helium gas in the desorbed and enriched helium gas is already higher than that of other impurity components, but due to the residual of some impurity components, further purification is still required; Finally, the unadsorbed helium gas and the desorbed and enriched helium gas are subjected to cryogenic fractionation for further purification. The core technology of cryogenic fractionation is to separate by using the different boiling point differences between gas molecules. During this process, the gas temperature is controlled in a low-temperature environment set according to the expert experience method through the cooling system of the existing fractionation tower. Since the boiling point of helium gas is extremely low (about -268.93°C), the evaporation pressure of helium gas is lower than that of other impurity gases in the low-temperature environment. Therefore, helium gas can be separated from other gases in the cryogenic fractionation tower through precise temperature control and the pressure gradient of the fractionation tower, and finally high-purity helium gas is obtained.

[0022] In summary, a method for extracting high-purity helium gas based on low-temperature adsorption is completed.

[0023] The order of the invention embodiments is only for description and does not represent the superiority or inferiority of the embodiments. The processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0024] Each embodiment in this specification is described in a progressive manner. For the same or similar parts among the embodiments, reference can be made to each other, and the differences between each embodiment and other embodiments are emphasized.

[0025] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of each embodiment of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A method for extracting high-purity helium based on low-temperature adsorption, characterized in that: The following steps are involved: S1. In a low-temperature environment, using low-temperature adsorption materials and a dynamic adsorption scheduling optimization algorithm, a preliminary component analysis of the mixed gas entering the adsorption bed is performed to obtain the concentration of helium and impurity gases in the mixed gas; Based on the adsorption kinetics model, the adsorption effect is calculated in combination with the concentration of impurity gas in the mixed gas, the characteristics of the low-temperature adsorption material and the adsorption conditions; the adsorption conditions include temperature, pressure and gas flow rate; Based on the adsorption effect, combined with the concentration of helium and the concentration of impurity gas in the mixed gas, the temperature, pressure and gas flow rate are dynamically adjusted; based on the adsorption effect, the concentration of helium and the concentration of impurity gas in the mixed gas, and the gas flow rate, the judgment conditions for stopping the adsorption process are constructed; when the adsorption process stops, the unadsorbed helium and the low-temperature adsorption material after adsorbing the impurity gas are output; S2. Desorbing the low-temperature adsorption material after adsorbing the impurity gas to obtain desorbed enriched helium; performing low-temperature fractionation on the desorbed enriched helium and the unadsorbed helium to obtain high-purity helium.

2. A method for extracting high-purity helium based on low-temperature adsorption according to claim 1, characterized in that: The S1 specifically includes: The specific calculation formula of the adsorption effect is as follows: ， in, is Momentary adsorption effect; is the specific surface area of ​​the cryogenic adsorption material; is the pore volume of the cryogenic adsorption material; is the average pore size of the cryogenic adsorption material; is the surface polarity coefficient; is The temperature of the adsorption bed at any moment; is The pressure of the adsorption bed at all times; It is an index used to control the effect of temperature on adsorption during the adsorption process; is the adsorption constant; is the decay constant of the impurity gas concentration; is The concentration of impurity gases in the mixed gas at any moment.

3. A method for extracting high-purity helium based on low-temperature adsorption according to claim 2, characterized in that: The S1 specifically includes: The adjustment of the temperature, pressure and gas flow rate is achieved by the following formulas respectively: ， ， ， in, and Respectively expressed in The change of temperature and pressure during the adsorption process at each moment; is the temperature regulation coefficient; is the maximum adsorption capacity of the cryogenic adsorption material; is The concentration of impurity gas in the mixed gas at all times; is The concentration of helium in the mixed gas at all times; is the pressure regulation factor; is the concentration of impurity gas in the mixed gas at the previous moment; is Gas flow rate at the moment; is the initial gas flow rate, which represents the gas flow rate of the adsorption bed under standard conditions.

4. The method for extracting high-purity helium based on low-temperature adsorption according to claim 3, characterized in that: The S1 specifically includes: The judgment conditions for stopping the adsorption process are as follows: When the difference between the maximum adsorption capacity of the cryogenic adsorption material and the adsorption effect of the cryogenic material is less than the preset adsorption effect difference threshold, it means that the cryogenic adsorption material is saturated and the adsorption process needs to be stopped; When the output helium concentration reaches a stable value and the gas flow rate no longer increases, it means that the helium recovery rate has reached the maximum and the adsorption process can be stopped; When the impurity gas concentration drops to a preset adsorption threshold, the adsorption process can be stopped; When any of the above stop conditions is met, the adsorption process is stopped, and the unadsorbed helium and the low-temperature adsorption material after adsorbing the impurity gas are output.

5. The method for extracting high-purity helium based on low-temperature adsorption according to claim 1, characterized in that: The S2 specifically includes: In the process of desorbing the low-temperature adsorption material after adsorbing the impurity gas, the impurity gas adsorbed on the surface of the low-temperature adsorption material is desorbed by gradually increasing the temperature and reducing the pressure, and the heating rate and the pressure reduction rate are controlled during the desorption process.

6. The method for extracting high-purity helium based on low-temperature adsorption according to claim 5, characterized in that: The S2 specifically includes: During the desorption process of the low-temperature adsorption material after adsorbing the impurity gas, the impurity gas is guided to the impurity gas collection pipeline through the exhaust system, and the composition of the exhaust gas is monitored in real time by the gas analyzer. When the concentration of the impurity gas drops to the set desorption threshold, the gas channel is switched to collect the desorbed enriched helium.

7. The method for extracting high-purity helium based on low-temperature adsorption according to claim 6, characterized in that: The S2 specifically includes: By utilizing the different boiling points between gas molecules, the unadsorbed helium and the desorbed and enriched helium are subjected to low-temperature fractionation to obtain high-purity helium.

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