Lightweight adsorption-desorption-resistant adsorption tower, coating process, helium purification system and helium purification method

Abstract

The invention discloses a light adsorption-desorption-resistant adsorption tower, a coating process, a helium purification system and a helium purification method, and mainly aims to solve the problem that in the prior art of natural gas helium purification, adsorption tower equipment is aged and corroded, and the purity stability of a helium product is influenced by adsorption and desorption formed by the adsorption tower. The light adsorption tower resistant to adsorption and desorption is provided, the service life of adsorption equipment is prolonged while the purity stability of a helium product is improved, and meanwhile the cost of helium purification through adsorption is reduced through the structural design of a helium purification system.

Description

Technical Field

[0001] The present invention relates to, in particular, a lightweight adsorption tower resistant to adsorption and desorption and a corresponding helium purification system and method. Background Art

[0002] The refining and purification of helium is an essential and important link in the process of natural gas helium extraction. The process mainly includes catalytic oxidation dehydrogenation, compression, drying, condensation, adsorption, etc. Adsorption is mainly based on pressure swing adsorption (PSA) process, and also includes temperature swing adsorption, vacuum pressure swing adsorption and other processes; the principle of pressure swing adsorption process and temperature swing adsorption process is to use the different adsorption capacity of solid adsorbents for different gases to achieve gas purification. When the gas passes through the adsorption bed, most of one (or several) gases in the mixed gas are adsorbed on the bed, and a small part flows out; most of another (or several) gases in the mixed gas are allowed to flow out, and a small part is adsorbed on the bed; thereby achieving the purpose of improving gas purity. Both processes belong to batch processing processes, and the solid adsorbent needs to be regenerated. The pressure swing adsorption process mainly regenerates the solid adsorbent by reducing pressure and analyzing, while the temperature swing adsorption process mainly regenerates the solid adsorbent by heating and heating. The adsorption process uses different adsorbents to adsorb components other than helium in natural gas to separate helium products. Generally, the adsorption tower is filled with separation beds of different adsorbent materials to deal with different components in natural gas, such as silica gel or alumina beds for removing moisture, activated carbon beds for removing carbon dioxide, zeolite beds for removing methane and nitrogen, etc.

[0003] The adsorbent is set in the adsorption tower to purify the natural gas passing through. For pressure swing adsorption, it specifically includes adsorption, decompression, desorption, cleaning, and pressurization. For example, the common system and method for separating hydrogen sulfide (H2S) or carbon dioxide (CO2) from the gas flow involves using a series of adsorption towers to absorb the target gaseous components into the solvent / reactant and then remove the solvent. This separation scheme requires a lot of equipment, and some gases in the natural gas will corrode the adsorption tower, affecting the service life of the equipment; in addition, the adsorption tower itself will also form adsorption and desorption phenomena, which will have a certain impact on the stability of the purity of the final helium product.

[0004] In view of this, this application is hereby filed. Summary of the invention

[0005] The present invention mainly aims at the problem that the aging corrosion of the adsorption tower equipment in the prior art of natural gas helium purification and the adsorption and desorption formed by the adsorption tower itself affect the purity stability of the helium product, and provides a lightweight adsorption tower resistant to adsorption and desorption, which improves the purity stability of the helium product and the service life of the adsorption equipment. At the same time, the cost of helium purification by adsorption is reduced through the structural design of the helium purification system.

[0006] In response to the above technical problems, the present application is implemented through the following technical solution: The present application provides a lightweight adsorption tower that is resistant to adsorption and desorption, and the inner wall of the adsorption tower is provided with a coating, which consists of: 50-90% polytetrafluoroethylene, 1-10% titanium dioxide, 0.5-2% dispersant, 1-20% n-butyl acetate and 0-5% additives.

[0007] Preferably, the coating is composed of: 75% polytetrafluoroethylene, 5% titanium dioxide, 1% dispersant, 15% n-butyl acetate and 4% additives.

[0008] Furthermore, the dispersant is BYK161 or a similar solvent dispersant; the auxiliary agent is a leveling agent and a defoaming agent, and the ratio of the leveling agent to the defoaming agent is 1:0.9-1.2.

[0009] Preferably, the lightweight adsorption tower is made of aluminum alloy.

[0010] Furthermore, the coating process of the lightweight adsorption-desorption resistant adsorption tower coating provided in the present application comprises the following steps:

[0011] A cold coating operation is adopted, that is, the above coating components are mixed and evenly coated on the inner wall of the adsorption tower at room temperature;

[0012] Then, cure under natural ventilation conditions for 48-240 hours;

[0013] Then, nitrogen is flushed in and the mixture is dried under vacuum at 100-140 degrees Celsius to obtain an adsorption tower with a stable coating.

[0014] Furthermore, the present application also provides a helium purification system, which is composed of a filtration and metering separation system, a three-stage membrane separation system, a three-stage compression system, a catalytic dehydrogenation system and a three-stage pressure swing adsorption system connected in sequence, wherein the membrane separation system includes a primary membrane separation unit, a secondary membrane separation unit and a tertiary membrane separation unit; the three-stage compression system includes a primary compression unit, a secondary compression unit and a tertiary compression unit;

[0015] The three-stage pressure swing adsorption system is based on the above-mentioned adsorption tower with a coating, and includes a primary pressure swing adsorption unit, a secondary pressure swing adsorption unit and a tertiary pressure swing adsorption unit which are sequentially connected to a buffer tank. The helium-containing raw gas is treated by the above-mentioned catalytic dehydrogenation system and then enters the primary pressure swing adsorption unit for treatment to obtain a primary helium-containing purified gas and a desorbed gas 1; the primary helium-containing purified gas enters the secondary pressure swing adsorption unit to obtain a secondary helium-containing purified gas and a desorbed gas 2, and the desorbed gas 2 returns to the feed port or the buffer tank of the first-stage compression unit, a part of the secondary helium-containing purified gas flows back to the primary pressure swing adsorption unit as regeneration gas, and a part of the secondary helium-containing purified gas enters the tertiary pressure swing adsorption unit; the secondary helium-containing purified gas is further treated in the tertiary pressure swing adsorption unit to obtain a high-purity helium product and a desorbed gas 3, and the desorbed gas 3 returns to the second-stage compression unit;

[0016] The pressure swing adsorption system comprises a plurality of adsorption towers, each of which has an air inlet and an air outlet, and is provided with a mixed adsorption bed inside, wherein an adsorbent for adsorbing impurities is arranged in the adsorption bed.

[0017] Preferably, the first-stage pressure swing adsorption unit is composed of adsorption towers A and B connected in series, which mainly undertakes the function of removing CO2 and H2O. When the raw gas passes through adsorption tower A, the CO2 and H2O therein are adsorbed, and after saturation, it is transferred to adsorption tower B for adsorption. Adsorption tower A is regenerated by heated purified gas that does not contain water and carbon dioxide and / or heated nitrogen; the second and third-stage pressure swing adsorption units adopt a six-tower vacuum process, and its adsorption and regeneration process consists of adsorption, multiple equalizing pressure reduction, inversion, vacuuming, multiple equalizing pressure increase and product pressure increase. The six adsorption towers alternately perform the above adsorption and regeneration operations to achieve continuous purification of the raw gas.

[0018] Preferably, the adsorption tower comprises at least one adsorption bed comprising at least three adsorption layers.

[0019] Preferably, when an adsorption layer containing five adsorption beds is provided in the adsorption tower, the first adsorption bed is an argon-neon desorption adsorbent, the second adsorption bed is a nitrogen-oxygen desorption adsorbent, the third adsorption bed is a nitrogen-oxygen desorption adsorbent, the fourth adsorption bed is a hydrocarbon desorption adsorbent, and the fifth adsorption bed is a dehydrated carbon dioxide adsorbent.

[0020] Furthermore, the helium purification system also includes a product gas valve and a control device arranged at the top of the adsorption tower. The control device includes a flow controller arranged between the adsorption towers and a temperature and pressure detection device arranged on the adsorption towers. The temperature and pressure detection device uses a temperature and pressure sensor.

[0021] The control device detects and controls the flow rate of the regeneration gas of the first-stage pressure swing adsorption unit through a flow controller, and starts an external nitrogen tank for replenishment when the regeneration gas flow rate does not reach the intake standard; at the same time, the temperature of the regeneration gas of the first-stage pressure swing adsorption unit is detected and regulated through the temperature detection device of the control device.

[0022] Furthermore, based on the above-mentioned adsorption tower and helium purification system, the present application also provides a helium purification method. Specifically, after the raw gas passes through the filtering and metering separation system, the three-stage membrane separation system, the three-stage compression system and the catalytic dehydrogenation system, it enters the primary pressure swing adsorption unit through the buffer tank, and first passes through the three interconnected adsorption beds of the A tower in the primary pressure swing unit, and enters the B tower for adsorption after saturation, and obtains the primary helium-containing purified gas and the desorbed gas 1 through the primary pressure swing adsorption; the primary helium-containing purified gas enters the secondary pressure swing adsorption unit through the buffer tank, and obtains the secondary through the six-tower vacuum adsorption. Helium-containing purified gas and desorbed gas 2, part of the secondary helium-containing purified gas is regulated by flow, temperature and pressure controllers, flows to tower A or tower B of the primary pressure swing adsorption unit for regeneration, and part enters the tertiary adsorption unit, and the desorbed gas 2 flows back to the feed inlet or buffer tank of the first-stage compression unit; the secondary helium-containing purified gas enters the tertiary pressure swing adsorption unit through the buffer tank, and obtains high-purity helium product and desorbed gas 3 through six-tower vacuum adsorption, and the desorbed gas 3 returns to the second-stage compression unit and merges with the secondary crude helium obtained by the secondary membrane separation unit before entering the tertiary membrane separation unit.

[0023] Compared with the prior art, the present application purifies helium by using a helium purification system using a lightweight adsorption tower made of aluminum alloy, and by coating the inside of the adsorption tower with a specified component, thereby increasing the service life of the adsorption tower equipment for extracting helium from natural gas by an adsorption method, reducing the helium purification cost through the structural design of the helium purification system, and further improving the purity of the helium product and ensuring the stability of the product purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 ; A schematic diagram of the structure of an adsorption tower provided in an embodiment of the present invention;

[0026] Figure 2 ; A photo of the uncoated aluminum alloy sheet sample provided in an embodiment of the present invention after a 60-day hydrogen sulfide corrosion test;

[0027] Figure 3 ; A photo of a coated aluminum alloy sheet sample provided in an embodiment of the present invention after a 60-day hydrogen sulfide corrosion test;

[0028] Figure 4; A schematic diagram of the flow structure of a helium purification system provided in an embodiment of the present invention;

[0029] Figure 5 ; A schematic diagram of the six-tower vacuum adsorption process structure provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0031] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is apparent to one of ordinary skill in the art that these specific details are not necessarily employed to practice the present invention. In other embodiments, in order to avoid obscuring the present invention, well-known structures, circuits, materials, or methods are not specifically described.

[0032] Throughout the specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment," "an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily all refer to the same embodiment or example. In addition, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. In addition, it will be appreciated by those of ordinary skill in the art that the figures provided herein are for illustrative purposes and that the figures are not necessarily drawn to scale. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0033] In the description of the present invention, the directions or positional relationships indicated by terms such as “front”, “rear”, “left”, “right”, “up”, “down”, “vertical”, “horizontal”, “high”, “low”, “inside” and “outside” are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limiting the scope of protection of the present invention.

[0034] Example

[0035] In addition to hydrocarbons such as CH4 (methane), C2H6 (ethane), C3H8 (propane), C4H 10 (n-butane, isobutane) and heavier C X H Y(X>4), etc., and also contains H2O (water), H2 (hydrogen), N2 (nitrogen), He (helium) and acidic gases such as CO2 (carbon dioxide), H2S (hydrogen sulfide) and C2H5SH (thiol). The acquisition of pure helium products through natural gas usually includes crude extraction of helium and refining (purification) of helium. The crude extraction of helium can be carried out by cryogenic condensation or membrane separation. The main impurities in crude helium include neon, hydrogen, oxygen, argon, nitrogen, methane, carbon monoxide, carbon dioxide, sulfur dioxide, etc. The helium refining (purification) process mainly includes dehydrogenation, compression, drying, condensation, adsorption and other processes. The refining of helium usually adopts adsorption technology. In simple terms, adsorption technology is a common system and method for separating crude helium impurities from gas streams, involving the use of a series of adsorption towers to absorb the target gaseous components into the solvent / reactant, and then removing the solvent. However, when a single-stage adsorption system is used for helium purification, the effect is not very ideal, so a multi-stage adsorption system is usually used in a cycle for helium purification, which involves multiple adsorption towers and adsorption beds. During operation, the adsorption tower will be affected by impurities in the helium and its desorption of impurities will also have a certain impact on the purity and stability of the pure helium product, increasing the cost of helium refining.

[0036] Therefore, if Figure 1 As shown, the embodiment of the present application provides a lightweight adsorption tower resistant to adsorption and desorption, and the aluminum adsorption tower is used in a multi-stage pressure swing adsorption system for natural gas helium purification. The adsorption tower of the helium purification system used in the present application is a lightweight aluminum adsorption tower resistant to adsorption and desorption with a coating, and the components of the coating are: polytetrafluoroethylene, titanium dioxide, dispersant, n-butyl acetate and additives.

[0037] Experimental evaluation of adsorption tower coating: test temperature: 40℃, relative humidity: 95%; gas concentration: 100ppmv, pressure 4MPa. Implementation standard GB12335-90. Hydrogen sulfide corrosion test of coated adsorption tower sample, inflation and pressure holding time: 60 days; neutral gas test of coated sample, nitrogen is used. Implementation standards GB / T10125-97 and GB12335-90.

[0038] Sample preparation method: Coat an aluminum alloy adsorption tower and several aluminum alloy sheets of the same size, and cure them for 120 hours under natural ventilation conditions; then flush with nitrogen and vacuum dry them at 120-150 degrees Celsius.

[0039] like Figure 1 As shown, an adsorption layer including five adsorption beds is provided in the adsorption tower in the embodiment.

[0040] Example 1

[0041] 75 parts of polytetrafluoroethylene, 5 parts of titanium dioxide, 1 part of BYK dispersant, 15 parts of n-butyl acetate and 4 parts of additives (2 parts of leveling agent, 2 parts of defoaming agent) are mixed to obtain a coating mixture; the coating mixture is uniformly cold-coated (at room temperature) on an aluminum alloy adsorption tower and a sample sheet; it is cured for 120 hours under natural ventilation conditions; then nitrogen is flushed in, and vacuum dried at 140 degrees Celsius to obtain an adsorption tower with a coating and 5 aluminum alloy sheet samples 1 of the same size.

[0042] Implementation 2

[0043] 70 parts of polytetrafluoroethylene, 8 parts of titanium dioxide, 2 parts of BYK dispersant, 12 parts of n-butyl acetate and 8 parts of additives (4 parts of leveling agent, 4 parts of defoaming agent) are mixed to obtain a coating mixture; the coating mixture is uniformly cold-coated (at room temperature) on an aluminum alloy adsorption tower and a sample sheet; it is cured for 120 hours under natural ventilation conditions; then nitrogen is flushed in, and vacuum dried at 140 degrees Celsius to obtain an adsorption tower with a coating and 5 aluminum alloy sheet samples 2 of the same size.

[0044] Example 3

[0045] 65 parts of polytetrafluoroethylene, 12 parts of titanium dioxide, 5 parts of dispersant, 10 parts of n-butyl acetate and 8 parts of additives (4 parts of leveling agent, 4 parts of defoaming agent) are mixed to obtain a coating mixture; the coating mixture is uniformly cold-coated (at room temperature) on an aluminum alloy adsorption tower and a sample sheet; it is cured for 120 hours under natural ventilation conditions; then nitrogen is flushed in, and vacuum dried at 140 degrees Celsius to obtain an adsorption tower with a coating and 5 aluminum alloy sheet samples 3 of the same size.

[0046] Comparative Example 1

[0047] Aluminum alloy adsorption tower without any coating.

[0048] Table 1 shows the results of the neutral gas test, neutral salt spray test and hydrogen sulfide corrosion test. It can be seen from Table 1 that the neutral gas resistance and hydrogen sulfide gas corrosion resistance of the coating samples of Examples 1 to 3 are significantly better than those of the uncoated sample of Comparative Example 1.

[0049] By comparing Example 1 with Example 2 and Example 3, it can be seen that the neutral gas corrosion resistance and hydrogen sulfide gas corrosion resistance of the coated adsorption tower sample with a slightly higher polytetrafluoroethylene content are better than those of the adsorption tower and sample piece with a lower polytetrafluoroethylene content.

[0050] Table 1 Test results

[0051] Neutral gas / salt spray test Hydrogen sulfide corrosion test Example 1 120 days / 1200 hours without rust 60 days without rust Example 2 112 days / 700 hours without rust 58 days without rust Example 3 110 days / 680 hours without rust 55 days without rust Comparative Example 1 Rust spots appear after 60 days / 400 hours Rust spots appear after 30 days

[0052] From the comparison of the actual experimental results, Figure 2 This is a photo of the inside of the adsorption tower cut after the uncoated adsorption tower of Comparative Example 1 was subjected to a 60-day hydrogen sulfide corrosion test, showing severe rust spots; Figure 3 This is a photo of the inside of the adsorption tower cut after the coated adsorption tower was subjected to a 60-day hydrogen sulfide corrosion test. There are no rust spots. Comparing the two, it is obvious that the coated adsorption tower was basically not affected by the hydrogen sulfide corrosion gas after 60 days.

[0053] Therefore, in practical applications, applying the coated adsorption tower to the natural gas helium purification system containing hydrogen sulfide will further improve the purity of helium and the stability of product purity.

[0054] Example 4

[0055] like Figure 4 , 5 shown.

[0056] The raw gas from the natural gas official website with a helium content of 100-5000ppm is introduced into the helium purification system. The pressure entering the boundary area of ​​this system is 2.1MPa. After pretreatment to meet the requirements of membrane separation for specific impurities, it enters the first-level membrane separation unit to increase the helium concentration to 0.19% to obtain primary crude helium; the primary crude helium on the permeate side is pressurized to about 2MPa by a first-stage compression unit and enters the second-level membrane separation unit to increase the helium concentration to 0.89% to obtain secondary crude helium; the secondary crude helium is pressurized to about 2MPa by a second-stage compression unit and enters the third-level membrane separation unit to obtain tertiary crude helium, at which time the helium concentration is 6.8%. The third-level membrane separation unit completes the preliminary concentration of helium in natural gas.

[0057] The three crude helium is pressurized to 1.8MPa by the three-stage compression unit and then enters the dehydrogenation system. Under the action of the palladium catalytic dehydrogenation agent, hydrogen and oxygen react to generate water, and the hydrogen impurities are removed to less than 1ppm, and then enter the primary PSA unit to mainly remove CO2 and H2O. The gas removed from CO2 and H2O enters the secondary and tertiary PSA systems to remove the remaining impurities such as N2, O2, CH4, CO2, H2 to less than 10ppm, and obtain the requirements of high-purity helium (99.9996%) product gas. The desorbed gas 2 of the secondary PSA unit and the desorbed gas 3 of the tertiary PSA unit enter the desorbed gas recovery to make the comprehensive helium yield greater than 90%, the desorbed gas 2 returns to the first compression unit before merging with the primary crude helium, and the desorbed gas 3 returns to the three-stage compression unit before merging with the tertiary crude helium; part of the primary helium-containing purified gas is refluxed to the primary PSA unit as regeneration gas to reduce the system operation cost while improving the product purity; the specific material balance table of Example 4 is shown in Table 2.

[0058] The primary PSA unit is composed of coated adsorption towers A and B connected in series, which are mainly responsible for removing CO2, H2O and H2S. When the crude helium passes through adsorption tower A, CO2 and H2O in it are adsorbed and transferred to adsorption tower B for adsorption after saturation. Adsorption tower A is regenerated by partially heated primary helium-containing purified gas that does not contain water and carbon dioxide. The temperature is 40 degrees Celsius and the molar flow rate is 1.02kgmol / h.

[0059] Each of the A and B adsorption towers is provided with an adsorption layer containing three adsorption beds, the first adsorption bed is a dehydrated carbon dioxide adsorbent molecular sieve, the second adsorption bed is a desulfurized sulfur dioxide adsorbent activated carbon, and the third adsorption bed is a dehydrated carbon dioxide adsorbent molecular sieve.

[0060] The secondary and tertiary PSA units adopt a six-tower vacuum process, and coating technology is used in the towers. The adsorption and regeneration process consists of adsorption, multiple equalization and pressure reduction, inversion, vacuuming, multiple equalization and pressure increase, and product pressure increase. The six adsorption towers alternately perform the above adsorption and regeneration operations to achieve continuous purification of the raw gas.

[0061] The first stage helium-containing purified gas enters the second stage PSA unit, such as Figure 5 As shown, the secondary PSA unit includes adsorption towers AF, and the specific working process is: six adsorption columns filled with five adsorption beds are connected in parallel, solenoid valves 101A-101F respectively control the raw gas feed of the adsorption columns, and solenoid valves 107A-107F and 108A-108F respectively control the reverse venting and vacuum desorption gas 2 from the above-mentioned corresponding adsorption columns to enter the buffer tank or the primary PSA unit; the unadsorbed component, i.e., the secondary helium-containing purified gas, is discharged through the product gas main pipe and enters the tertiary PSA unit and the primary PSA unit through the buffer tank respectively, and the solenoid valves 102A-102F control the gas discharged from the outlet end of the corresponding adsorption column, and then enter the buffer tank after being reduced in pressure by the pressure reducing valve to complete the cycle; solenoid valves 103A-103F and 104A-104F are used for pressure balance between the columns.

[0062] After the secondary helium-containing purified gas enters the tertiary PSA unit, it also goes through the six-tower vacuum process. The difference from the secondary PSA unit is that before the reverse venting and vacuum desorption gas 3 returns to the three-stage compression unit, the unadsorbed component, i.e., the tertiary helium-containing purified gas, is discharged through the product gas main pipe.

[0063] Each adsorption tower of the two-stage and three-stage PSA system is equipped with an adsorption layer containing five adsorption beds, as shown in the following figure: Figure 1 As shown, the first adsorption bed is an argon removal adsorbent using a low silicon ratio molecular sieve; the second adsorption bed is a nitrogen removal adsorbent using alumina; the third adsorption bed is a nitrogen removal adsorbent using alumina; the fourth adsorption bed is a hydrocarbon removal adsorbent using activated carbon; the fifth adsorption bed is a water removal adsorbent using a molecular sieve.

[0064] Table 1 is the physical balance table after Example 4

[0065]

[0066] Table 3 shows the change in purity of the product helium gas when the system of Example 4 is continuously operated for one week under the same experimental conditions.

[0067]

[0068] Comparative Example 2

[0069] The crude helium is introduced into a helium purification system, which differs from Example 4 mainly in that the adsorption towers used in the secondary and tertiary pressure swing adsorption units are both made of aluminum alloy without coating.

[0070] Table 4 is the physical balance table after comparative example 2

[0071]

[0072] Table 5 shows the change in purity of the product helium gas after continuous operation of the system of Comparative Example 2 for one week under the same experimental conditions.

[0073]

[0074]

[0075] Comparing the results in Tables 2 and 3 with Tables 4 and 5, the helium product without coating technology can only reach the pure helium standard of 99.995%, and many impurity indicators are slightly exceeded. From the experimental results for one week, the purity of the product of the adsorption tower with coating technology is also relatively stable.

[0076] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A light adsorption tower resistant to adsorption and desorption, wherein a mixed adsorption bed is arranged in the adsorption tower, and an adsorbent for adsorbing impurities is arranged in the adsorption bed, characterized in that: The inner wall of the adsorption tower is provided with a coating, which comprises: 50-90% of polytetrafluoroethylene, 1-10% of titanium dioxide, 0.5-2% of a dispersant, 1-20% of n-butyl acetate and 0-5% of an auxiliary agent.

2. A lightweight adsorption-resistant desorption adsorption tower according to claim 1, characterized in that: The coating consists of: 75% polytetrafluoroethylene, 5% titanium dioxide, 1% dispersant, 15% n-butyl acetate and 4% additives; the dispersant is BYK161; the additives include a leveling agent and a defoaming agent, and the ratio of the leveling agent to the defoaming agent is 1:0.9-1.

2.

3. A lightweight adsorption-resistant desorption adsorption tower according to claim 1, characterized in that: The adsorption tower is made of aluminum alloy.

4. A coating process for an adsorption tower coating, applied to a lightweight adsorption and desorption resistant adsorption tower as claimed in claims 1-3, characterized in that: The steps include: 1) Cold coating: evenly coating the prepared coating composition on the inner wall of the adsorption tower at room temperature; 2) Curing under natural ventilation conditions for 48-240h; 3) Pour in nitrogen and dry under vacuum at 100-140 degrees Celsius.

5. A helium purification system, using a light adsorption and desorption resistant adsorption tower as described in claims 1-3, consisting of a filtration and metering separation system, a three-stage membrane separation system, a three-stage compression system, a catalytic dehydrogenation system and a three-stage pressure swing adsorption system connected in sequence, wherein the membrane separation system includes a primary membrane separation unit, a secondary membrane separation unit and a tertiary membrane separation unit; the three-stage compression system includes a primary compression unit, a secondary compression unit and a tertiary compression unit; characterized in that: The three-stage pressure swing system comprises a primary pressure swing adsorption unit, a secondary pressure swing adsorption unit and a tertiary pressure swing adsorption unit which are sequentially connected to a buffer tank. The helium-containing raw gas enters the primary pressure swing adsorption unit for treatment after passing through a filtering and metering separation system, a three-stage membrane separation system, a three-stage compression system and a catalytic dehydrogenation system to obtain a primary helium-containing purified gas and a desorbed gas 1; the primary helium-containing purified gas is treated in the secondary pressure swing adsorption unit to obtain a secondary helium-containing purified gas and a desorbed gas 2, and the desorbed gas 2 is returned to the feed port or the buffer tank of the first compression unit, a part of the secondary helium-containing purified gas enters the primary pressure swing adsorption unit, and a part of the secondary helium-containing purified gas enters the tertiary pressure swing adsorption unit; the secondary helium-containing purified gas is treated in the tertiary pressure swing adsorption unit to obtain a high-purity helium product and a desorbed gas 3, and the desorbed gas 3 is returned to the second-stage compression unit; The pressure swing adsorption system comprises the adsorption tower as described in claims 1 to 4 above, as well as an air inlet and an air outlet, and there are multiple adsorption towers.

6. The helium purification system according to claim 5, characterized in that: The first-stage pressure swing adsorption unit is composed of adsorption towers A and B connected in series, and is regenerated by heated purified gas free of water and carbon dioxide / or heated nitrogen; the second-stage and third-stage pressure swing adsorption units adopt a six-tower vacuum process, and the adsorption and regeneration process consists of adsorption, multiple equalization and pressure reduction, inversion, vacuuming, multiple equalization and pressure increase, and product pressure increase.

7. The helium purification system according to claim 6, characterized in that: At least one adsorption layer containing at least three adsorption beds is arranged in the adsorption tower.

8. The helium purification system according to claim 5, characterized in that: The system also includes product gas valves and control devices arranged at the upper and lower ends of the adsorption tower; the control device detects and controls the flow rate of the regeneration gas of the first-stage pressure swing adsorption unit through a flow controller, and starts an external nitrogen tank for replenishment when the regeneration gas flow rate does not reach the intake standard; at the same time, the temperature of the regeneration gas of the first-stage pressure swing adsorption unit is detected and regulated through the temperature detection device of the control device.

9. A helium purification method, using a helium purification system as claimed in claims 5-8, characterized in that: The helium-containing raw gas is introduced into the helium purification system described in claims 5-8. After the raw gas passes through the filtering and metering separation system, the three-stage membrane separation system, the three-stage compression system and the catalytic dehydrogenation system, it enters the primary pressure swing adsorption unit through the buffer tank, and first passes through the A tower in the primary pressure swing adsorption unit, and switches to the B tower for adsorption after saturation. The A tower is regenerated with purified gas and / or nitrogen. The raw gas passes through the primary pressure swing adsorption unit to obtain a primary helium-containing purified gas and a desorbed gas 1; the primary helium-containing purified gas passes through the buffer tank into the secondary pressure swing adsorption unit, and undergoes six-tower vacuum adsorption to obtain a secondary helium-containing purified gas and a desorbed gas 2. The desorbed gas 2 is regulated by the flow control valve of the control device, and partially refluxes to the A tower or the B tower of the primary pressure swing adsorption unit for regeneration; the secondary helium-containing purified gas passes through the buffer tank into the three-stage pressure swing adsorption, and undergoes six-tower vacuum adsorption to obtain a high-purity helium product and a desorbed gas 3. The desorbed gas 3 is buffered in the buffer tank and enters the secondary compression unit.

10. The helium purification method according to claim 9, characterized in that: Each adsorption tower in the secondary and tertiary pressure swing adsorption units is provided with an adsorption layer containing five adsorption beds, wherein: the first adsorption bed is a dehydrated carbon dioxide adsorbent, the second adsorption bed is a deargon oxygen adsorbent, the third adsorption bed is a denitrogenated methane adsorbent, the fourth adsorption bed is a denitrogenated oxygen adsorbent, and the fifth adsorption bed is a dehydrogenated hydrocarbon adsorbent.

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