A method for extracting high-purity helium gas based on cryo-adsorption

Abstract

The present invention relates to the technical field of helium extraction, and particularly to a method for extracting high-purity helium based on cryo-adsorption. The content includes: in a low-temperature environment, using cryo-adsorption materials, through a dynamic adsorption scheduling optimization algorithm, performing adsorption treatment on the mixed gas to obtain unadsorbed helium and the cryo-adsorption material after adsorbing impurity gases; performing desorption treatment on the cryo-adsorption material after adsorbing impurity gases to obtain desorbed and enriched helium; performing cryogenic fractionation treatment on the desorbed and enriched helium and the unadsorbed helium to obtain high-purity helium. It solves the technical problems of low helium extraction efficiency, low purity, and low recovery rate in traditional helium extraction methods.

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 cryo-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, enabling different components of the gas to condense at different temperatures, thereby achieving the separation of helium. However, cryogenic fractionation has certain limitations. Especially when dealing with complex gas mixtures, it is often difficult to achieve efficient separation due to the small boiling point differences between helium and other gases (such as nitrogen, oxygen, argon, etc.). In addition, the cryogenic fractionation process requires high energy consumption, and the equipment is complex and the operating costs are high.

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

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

[0006] A method for extracting high-purity helium based on cryo-adsorption of the present invention specifically includes the following technical solutions:

[0007] A method for extracting high-purity helium based on cryo-adsorption includes the following steps:

[0008] S1. In a low-temperature environment, using low-temperature adsorption materials, through a dynamic adsorption scheduling optimization algorithm, conduct a preliminary component analysis of 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 low-temperature 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 helium that has not been adsorbed and the low-temperature adsorption materials after adsorbing the impurity gases.

[0009] S2. Conduct a desorption treatment on the low-temperature adsorption materials after adsorbing the impurity gases to obtain desorbed and enriched helium; conduct a low-temperature fractionation treatment on the desorbed and enriched helium and the helium that has not been adsorbed to obtain high-purity helium.

[0010] Preferably, S1 specifically includes:

[0011] The specific calculation formula for the adsorption effect is as follows:

[0012] ,

[0013] where, is the adsorption effect at time; is the specific surface area of the low-temperature adsorption materials; is the pore volume of the low-temperature adsorption materials; is the average pore diameter of the low-temperature adsorption materials; is the surface polarity coefficient; is the temperature of the adsorption bed at time; is at time the pressure of the adsorption bed; is an 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 at time the concentration of impurity gases in the mixed gas.

[0014] Preferably, S1 specifically includes:

[0015] The adjustments of the temperature, pressure, and gas flow rate are respectively achieved through the following formulas:

[0016] ,

[0017] ,

[0018] ,

[0019] Among them, and respectively represent the change amounts of temperature and pressure during the adsorption process at moment; is the temperature adjustment coefficient; is the maximum adsorption capacity of the cryogenic adsorption material; is at the concentration of impurity gas in the mixed gas at moment; is at the concentration of helium in the mixed gas at moment; is the pressure adjustment coefficient; is the concentration of impurity gas in the mixed gas at the previous moment; is at the gas flow rate at moment; is the initial gas flow rate, indicating the gas flow rate of the adsorption bed under standard conditions.

[0020] Preferably, the S1 specifically includes: the judgment conditions for stopping the adsorption process are as follows:

[0021] 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 indicates that the cryogenic adsorption material is saturated and the adsorption process needs to be stopped;

[0022] 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;

[0023] When the impurity gas concentration drops to the preset adsorption threshold, the adsorption process can be stopped;

[0024] When any of the above stopping conditions is met, stop the adsorption process and output the unadsorbed helium and the cryogenic adsorption material after adsorbing the impurity gas.

[0025] Preferably, the S2 specifically includes:

[0026] During the process of desorbing the cryogenic adsorption material after adsorbing the impurity gas, gradually increase the temperature and decrease the pressure to desorb the impurity gas adsorbed on the surface of the cryogenic adsorption material, and control the heating rate and pressure reduction rate during the desorption process.

[0027] Preferably, the S2 specifically includes:

[0028] Preferably, the S2 specifically includes:

[0029] During the desorption process of the cryo-adsorption material after adsorbing impurity gases, the impurity gases are guided into 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 gas.

[0030] Preferably, the S2 specifically includes:

[0031] Using the different boiling point differences between gas molecules, the unadsorbed helium gas and the desorbed and enriched helium gas are subjected to cryogenic fractionation to obtain high-purity helium gas.

[0032] The beneficial effects of the technical solution of the present invention are:

[0033] 1. By using cryo-adsorption materials 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 in real time, impurity gases (such as nitrogen, oxygen, argon, etc.) are gradually removed, enabling the efficient recovery of helium gas.

[0034] 2. Adopt a desorption process of gradually increasing temperature and decreasing pressure. By controlling the heating rate and pressure reduction rate, while ensuring the effective desorption of impurity gases, the helium gas is retained to the greatest extent. During the desorption process, as the temperature and pressure change, the impurity gases are rapidly desorbed, and the helium gas, due to its lower desorption temperature and weaker adsorption force, remains in the adsorption bed, improving the recovery rate of helium gas and ensuring the purity of helium gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a flowchart of a method for extracting high-purity helium gas based on cryo-adsorption according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0036] 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 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 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 shall fall within the protection scope of the present invention.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field of the present invention.

[0038] The following specifically describes the specific solution of a method for extracting high-purity helium gas based on cryo-adsorption provided by the present invention in conjunction with the drawings.

[0039] Refer to the attachedFigure 1 , which shows a flowchart of a method for extracting high-purity helium gas based on cryogenic adsorption provided by an embodiment of the present invention. The method includes the following steps:

[0040] S1. In a cryogenic environment, using cryogenic adsorption materials, through a dynamic adsorption scheduling optimization algorithm, the mixed gas is subjected to adsorption treatment to obtain unadsorbed helium gas and cryogenic adsorption materials after adsorbing impurity gases;

[0041] First, in an adsorption device at low temperature (such as liquid nitrogen temperature or lower temperature (for example, below 77K)), a cryogenic adsorption material (such as 5A molecular sieve, dehydrated activated carbon or modified silica gel) with low adsorption to helium gas and high selective adsorption ability to impurity gases (such as nitrogen, oxygen, argon, etc.) is used 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;

[0042] Through the dynamic adsorption scheduling optimization algorithm, the mixed gas is subjected to adsorption treatment using cryogenic adsorption materials; the dynamic adsorption scheduling optimization algorithm can adaptively adjust the adsorption conditions and gradually adsorb impurity gases to obtain unadsorbed helium gas and cryogenic adsorption materials after adsorbing impurity gases. The specific implementation process is as follows:

[0043] First, a gas analyzer is used to perform preliminary composition analysis on 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;

[0044] Furthermore, based on the existing adsorption kinetic model, combined with the concentration of impurity gases 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 measuring with sensors and undergoing normalization processing; the specific formula for the adsorption effect is as follows:

[0045] ,

[0046] where, is the adsorption effect at moment, reflecting the adsorption capacity of the adsorption bed for gas at the current moment, which will change 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 impurity gases, measured 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, and is determined according to the specific characteristics of the cryogenic adsorption material; is the surface polarity coefficient, which depends on the polarity degree of the surface functional groups of the cryogenic adsorption material. A positive value indicates a preference for impurity gases, and is determined according to the type of cryogenic adsorption material and can be measured by surface tension or contact angle; is at the temperature of the adsorption bed at the moment; is at the pressure of the adsorption bed at the moment; is an 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, and is determined according to 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 and 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 adsorption kinetic experimental data, and 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 is obtained through experiments, and the value range is ; is at the concentration of the impurity gas in the mixed gas at the 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;

[0047] 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:

[0048] ,

[0049] ,

[0050] ,

[0051] where, and respectively represent at The change amounts of temperature and pressure during the adsorption process at a moment, which are used to control the change ranges 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, and its value range is ; is the maximum adsorption capacity of the cryo-adsorption material, which represents the maximum amount of gas that the cryo-adsorption material can adsorb under ideal conditions and is specifically set according to the characteristics of the cryo-adsorption material and the adsorption conditions; is at the concentration of impurity gas in the mixed gas at a moment; is at the concentration of helium in the mixed gas at a moment; Item is used to adjust the change range of temperature so that helium can be preferentially retained while 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, and its value range is ; is the concentration of impurity gas in the mixed gas at the previous moment (i.e., at a moment); Item is used to determine the adjustment range of pressure; is at the gas flow rate at a moment, which represents 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 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;

[0052] Based on the adsorption effect calculated in real time, the concentrations of helium and impurity gas in the mixed gas monitored in real time, and the gas flow rate, a judgment condition for stopping the adsorption process is constructed to judge whether it is necessary to stop the adsorption process. The specific judgment conditions are as follows:

[0053] Saturation of the cryo-adsorption material: When the adsorption effect of the cryo-adsorption material infinitely reaches the maximum adsorption capacity , that is, when the difference between the maximum adsorption capacity of the cryo-adsorption material and the adsorption effect of the cryo-adsorption material is less than the adsorption effect difference threshold, it indicates that the cryo-adsorption material is saturated, and 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 ;

[0054] Stability of helium outflow: 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 gases. At this time, the adsorption process can be stopped;

[0055] Reduction of impurity gas concentration: When the concentration of impurity gases drops to the adsorption threshold set according to the expert experience method it means that most of the impurity gases have been removed and the adsorption effect has reached the expectation, and the adsorption process can be stopped;

[0056] 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 gases.

[0057] S2. Perform desorption treatment on the cryogenic adsorption material after adsorbing impurity gases to obtain desorbed and enriched helium; perform cryogenic fractionation treatment on the desorbed and enriched helium and the helium that has not been adsorbed to obtain high-purity helium.

[0058] After the adsorption is completed and the unadsorbed helium is discharged, the adsorption bed will enter the desorption stage. In order to efficiently release the adsorbed impurity gases and retain helium, first, by heating, the impurity gases in the adsorption bed are desorbed from the surface of the cryogenic adsorption material; specifically, the temperature of the adsorption bed is gradually increased from low temperature (about 77K) to the preset desorption temperature range, such as it can be set between 100K and 150K, to provide sufficient thermal energy to desorb the impurity gases adsorbed on the surface of the cryogenic 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, so as to avoid premature desorption of helium or damage to the structure of the cryogenic adsorption material;

[0059] At the same time, during the heating process, in order to further promote the desorption of impurity gases, 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 the preset desorption pressure range, such as between 10kPa and 30kPa, and the pressure reduction rate is controlled at, for example, between 2kPa / min and 5kPa / min, to avoid unstable gas flow or damage to the cryogenic adsorption material caused by too fast pressure change;

[0060] During the desorption process, the impurity gases are 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 concentration of the impurity gases drops to the desorption threshold set according to the expert experience method, immediately switch the gas channel to collect the helium-rich gas (i.e., desorbed and enriched helium) into a dedicated helium storage component. The concentration of helium in the desorbed and enriched helium is already higher than other impurity components, but due to the residual of some impurity components, further purification is still required;

[0061] 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 existing cooling system of the fractionation column. Since the boiling point of helium is extremely low (about -268.93 °C), the evaporation pressure of helium is lower than that of other impurity gases in the low-temperature environment. Therefore, helium can be separated from other gases in the cryogenic fractionation column through precise temperature control and the pressure gradient of the fractionation column, and finally high-purity helium is obtained.

[0062] In summary, a method for extracting high-purity helium based on cryogenic adsorption is completed.

[0063] The sequence 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 result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0064] Each embodiment in this specification is described in a progressive manner. For the same or similar parts between each embodiment, reference can be made to each other. The key point of each embodiment is to illustrate the differences from other embodiments.

[0065] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit 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 make the essence of the corresponding technical solutions 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 gas based on cryo-adsorption, characterized in that, It includes the following steps: S1. In a low-temperature environment, using a low-temperature adsorption material, through a dynamic adsorption scheduling optimization algorithm, conduct a preliminary component analysis of the mixed gas entering the adsorption bed to obtain the concentrations of helium and impurity gases in the mixed gas; Based on the adsorption kinetic model, combined with the concentration of impurity gases in the mixed gas, the characteristics of the low-temperature adsorption material, and the adsorption conditions, calculate the adsorption effect; the adsorption conditions include temperature, pressure, and gas flow rate; The calculation formula for the adsorption effect is as follows: ， Among them, is the adsorption effect at . 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 at the temperature of the adsorption bed; is at the pressure of the adsorption bed; 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 at the concentration of the impurity gas in the mixed gas at the moment. Based on the adsorption effect, dynamically adjust the temperature, pressure, and gas flow rate. The specific formula is: ， ， ， Among them, and respectively represent the change amounts of temperature and pressure during the adsorption process at moment; 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 moment; is the concentration of helium in the mixed gas at moment; is the pressure adjustment coefficient; is the concentration of impurity gas in the mixed gas at the previous moment; is the gas flow rate at moment; is the initial gas flow rate, indicating the gas flow rate of the adsorption bed under standard conditions; Construct a judgment condition for stopping the adsorption process: The difference between the maximum adsorption capacity of the low-temperature adsorption material and the adsorption effect of the low-temperature material is less than a preset adsorption effect difference threshold; The output helium concentration reaches a stable value, and the gas flow rate no longer increases; The concentration of impurity gases drops to a preset adsorption threshold; When any of the above stopping conditions is met, stop the adsorption process and output the helium gas that has not been adsorbed and the low-temperature adsorption material after adsorbing the impurity gases; S2. Perform a desorption treatment on the low-temperature adsorption material after adsorbing the impurity gases to obtain desorbed and enriched helium gas; perform a low-temperature fractionation treatment on the desorbed and enriched helium gas and the helium gas that has not been adsorbed to obtain high-purity helium gas.

2. The method for extracting high-purity helium gas based on cryo-adsorption according to claim 1, wherein The S2 specifically includes: During the process of performing a desorption treatment on the low-temperature adsorption material after adsorbing the impurity gases, desorb the impurity gases adsorbed on the surface of the low-temperature adsorption material by gradually increasing the temperature and reducing the pressure, and control the heating rate and pressure reduction rate during the desorption process.

3. The method for extracting high-purity helium gas based on cryo-adsorption according to claim 2, characterized in that, The S2 specifically includes: During the process of performing a desorption treatment on the low-temperature adsorption material after adsorbing the impurity gases, the impurity gases are 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 gases drops to the set desorption threshold, switch the gas channel to collect the desorbed and enriched helium gas.

4. A method for extracting high-purity helium gas based on cryo-adsorption according to claim 3, characterized in that, The S2 specifically includes: Utilize the different boiling point differences between gas molecules to perform a low-temperature fractionation treatment on the helium gas that has not been adsorbed and the desorbed and enriched helium gas to obtain high-purity helium gas.

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