A method for purifying helium by pressure swing adsorption

Abstract

The present invention provides a method for purifying helium by pressure swing adsorption, the method comprising: at least two adsorption towers are alternately connected in parallel to perform a pressure swing adsorption process; the pressure swing adsorption process of any of the adsorption towers comprises in sequence: an equal pressure drop adsorption step, a flushing step and a flushing and final filling step; the adsorption tower performing the equal pressure drop adsorption step conveys adsorbed gas to the adsorption tower performing the flushing step to complete the flushing process; the adsorbed gas and product gas output by the adsorption tower performing the equal pressure drop adsorption step are passed into the adsorption tower performing the flushing and final filling step to complete flushing and final filling at the same time. The purification method based on adsorption pressure swing provided by the present invention optimizes the process steps of the adsorption pressure swing process, adopts flushing of adsorbed gas and flushing of mixed adsorbed gas and product gas to regenerate the adsorbent, thereby increasing the effective working capacity of the adsorbent and improving the purity of helium. At the same time, it reduces the consumption of product gas by adsorbent regeneration in the process and improves the recovery rate of helium.

Description

Technical Field

[0001] The invention belongs to the technical field of gas separation, and relates to a method for purifying helium, and in particular to a method for purifying helium by pressure swing adsorption. Background Art

[0002] Helium is a colorless, odorless, gaseous rare gas at room temperature. It is a very important strategic resource and is widely used in aerospace, medical, semiconductor, superconducting materials, nuclear reactor cooling, deep-sea diving, pipeline leak detection, high-end processing and other fields. For example, helium has an ultra-low boiling point (-268.95℃, 4.125K), and can be used as a coolant in superconducting fields such as medical imaging MRI equipment; helium has a low density and stable chemical properties, and can be used as a gas for filling spacecraft or advertising balloons, and can also serve as an inert gas shielding gas in semiconductor processing, optical fiber manufacturing, metal welding and other fields; helium has excellent thermal conductivity, and its thermal conductivity coefficient under standard conditions is as high as 0.1444W / m / K, and it serves as a heat transfer medium in nuclear power generation devices; helium has extremely low solubility in blood and can be used as a diving gas for deep diving operations.

[0003] The main methods for helium extraction include cryogenic method, pressure swing adsorption method, membrane separation method, etc. The most commonly used industrial method is cryogenic separation method, which uses the difference in boiling points of various components in the raw gas to separate helium, but it has high energy consumption, large equipment investment, and complex process, which greatly reduces its economic benefits.

[0004] Pressure swing adsorption is a method of separating helium by utilizing the difference in adsorption capacity of the adsorbent for each component of the mixed gas at different pressures. This method has simple process, small equipment footprint, low investment, low energy consumption, high degree of automation and no pollution to the environment. In recent years, the application of pressure swing adsorption has increased year by year.

[0005] The main indicators of the effectiveness of pressure swing adsorption method for separating gases include the purity of the product gas and the recovery rate of the product gas. For example, CN111282397A discloses a pressure swing adsorption gas high recovery rate separation system and a separation method thereof. The system and the separation method increase the recovery rate of the product gas by adding an intermediate tank and increasing multiple pressure equalization. The method decomposes a pressure equalization step into multiple pressure equalization steps to improve the gas recovery rate, but requires multiple intermediate tanks and multiple programmable valves, and the device system is relatively complex; CN116747667A discloses a pressure swing adsorption gas separation system and a separation method, the adsorption step is designed as a high-pressure main adsorption step and a low-pressure auxiliary adsorption step, thereby increasing the total feed adsorption time, and the gas recovery rate is significantly improved, but the purity of the product gas cannot be guaranteed; CN112206636A discloses a four-tower pressure swing adsorption method, the process steps are designed to be sequentially adsorbed, the first pressure equalization step down, forward discharge, the second pressure equalization step down, reverse discharge, flushing, the second pressure equalization step up, the first pressure equalization step up and the final filling step, so as to simplify the control system and process, but the purity and recovery rate of the product gas of this method cannot be guaranteed.

[0006] In the current prior art, there are still common problems such as numerous process steps, high operational difficulty, which is not conducive to actual production, and difficulty in simultaneously ensuring the purity and recovery rate of the separated gas. Therefore, it is necessary to provide a new method for purifying helium by pressure swing adsorption. Summary of the invention

[0007] The object of the present invention is to provide a method for purifying helium by pressure swing adsorption, which improves the purity of helium by optimizing the process steps of the adsorption pressure swing process, and at the same time reduces the consumption of product gas by adsorbent regeneration in the process, thereby improving the recovery rate of helium.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] The present invention provides a method for purifying helium by pressure swing adsorption, the method comprising:

[0010] At least two adsorption towers are alternately connected in parallel to perform a pressure swing adsorption process;

[0011] The pressure swing adsorption process of any of the adsorption towers comprises in sequence: an equal pressure drop adsorption step, a flushing step and a flushing final filling step;

[0012] The equalizing pressure drop adsorption step comprises: introducing the raw gas into the adsorption tower for adsorption, and simultaneously delivering the adsorbed gas to other adsorption towers connected to the adsorption tower for equalizing pressure drop adsorption;

[0013] When any of the adsorption towers is performing the flushing step, at least one other adsorption tower is performing the equal pressure drop adsorption step, and the adsorption tower performing the equal pressure drop adsorption step delivers the adsorbed gas to the adsorption tower performing the flushing step, and performs auxiliary desorption on the adsorption tower performing the flushing step, thereby completing the flushing process;

[0014] When any of the adsorption towers is performing the flushing and final filling steps, at least one other adsorption tower is performing the equalizing pressure drop adsorption step, and the product gas in the storage container and the adsorbed gas output by the adsorption tower performing the equalizing pressure drop adsorption step are introduced into the adsorption tower performing the flushing and final filling steps, thereby completing the flushing process and the final filling process at the same time.

[0015] The purification method based on pressure swing adsorption provided by the present invention completes a flushing process and / or a final filling process for an adsorption tower connected thereto while an adsorption process is being carried out in one adsorption tower, thereby simplifying the process steps; when the adsorbent of the adsorption tower is regenerated after the adsorption is completed, flushing with the adsorbed gas of another tower and flushing with a mixture of the adsorbed gas and the product gas are used for regeneration, so that the regeneration effect of the adsorbent is good and the effective working capacity of the adsorbent is improved; at the same time, when flushing with a mixture of the adsorbed gas and the product gas is used, the adsorption tower is not connected to the outside, so that the flushing and final filling processes are completed at the same time, a large amount of product gas is saved, and the recovery rate of helium is improved.

[0016] Compared with the prior art, the present application optimizes the pressure swing adsorption process steps, simplifies the process flow, and simultaneously achieves high purity (more than 99%) and high recovery rate (more than 80%) of helium.

[0017] When there are at least three adsorption towers, the pressure swing adsorption process of any of the adsorption towers further includes: an adsorption step, at least one equalizing pressure drop step, an inversion step, at least one equalizing pressure increase step and a waiting step.

[0018] In the same time period, at least one adsorption tower performs an adsorption step or an equal pressure drop adsorption step.

[0019] The adsorption step is arranged before the equalization pressure drop adsorption step.

[0020] The pressure drop equalization step is arranged between the pressure drop equalization adsorption step and the flushing step.

[0021] The inversion step is arranged between the equalization pressure drop adsorption step and the flushing step.

[0022] The pressure equalization step is arranged between the flushing step and the flushing and final filling step.

[0023] The waiting step is arranged after the flushing and final filling step.

[0024] The adsorption step is to introduce raw gas into the adsorption tower, and the adsorbent in the tower performs adsorption to obtain product gas. The impurity gas outlet and the pressure-equalizing gas outlet of the adsorption tower are closed, and the adsorbed gas is not transported to other adsorption towers.

[0025] The equalizing pressure drop step is a process in which a higher-pressure adsorption tower that has completed adsorption or equalizing pressure drop (referring to the equalizing pressure drop in the previous stage) is connected to a lower-pressure adsorption tower that has completed inversion or flushing to increase the pressure. At this time, the lower-pressure adsorption tower performs the equalizing pressure increase step, and the pressures of the two adsorption towers tend to be similar or equal, that is, the adsorption tower performing the equalizing pressure drop step is connected to the adsorption tower performing the equalizing pressure increase step.

[0026] The equal pressure drop operation can effectively preserve the compression energy of the gas in the high-pressure adsorption tower, reduce energy consumption, and improve the recovery rate of helium. The equal pressure increase operation can recover the gas components discharged from the high-pressure tower and reduce energy consumption.

[0027] When the number of adsorption towers is at least three, one or more pressure equalization operations are performed during the pressure swing adsorption process to avoid fluidization and wear of the adsorbent.

[0028] The number of pressure equalization operations (including pressure equalization drop and / or pressure equalization increase) is set according to the number of adsorption towers (N), and the number of pressure equalization operations is less than or equal to N-1.

[0029] The reverse step is to discharge the gas in the adsorption tower to the external environment in the direction opposite to the adsorption direction, and the raw gas port, the pressure equalizing gas port and the product gas port of the adsorption tower are all closed.

[0030] The flushing step is to introduce gas into the adsorption tower in the reverse adsorption direction to regenerate the adsorbent, and the generated gas is discharged to the external environment.

[0031] The flushing and final filling step is to introduce gas into the adsorption tower in the reverse direction of adsorption to regenerate the adsorbent. At the same time, the outlet end of the impurity gas of the adsorption tower is closed, so that the pressure of the adsorption tower reaches the pressure specified in the adsorption step, thereby completing the flushing and pressure final rise processes at the same time.

[0032] The final rise process can cause the adsorption front to move backward and improve the purity of the helium product gas.

[0033] The waiting step is that the adsorption tower cooperates with other adsorption towers to complete corresponding operations and then pauses.

[0034] Preferably, the pressure of the adsorption process is 2-100 bar, for example, it can be 2 bar, 10 bar, 20 bar, 30 bar, 40 bar, 50 bar, 60 bar, 70 bar, 80 bar, 90 bar or 100 bar, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0035] Preferably, the temperature of the adsorption process is -250 to 100°C, for example, it can be -250°C, -200°C, -150°C, -100°C, -50°C, 0°C, 50°C or 100°C, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably -196 to 50°C.

[0036] Preferably, the ratio of the product gas to the gas in the adsorption tower performing the equal pressure drop adsorption step is 0-99%, excluding 0, for example, it can be 1%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or 99%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] Preferably, when there are two adsorption towers, the pressure swing adsorption process of any of the adsorption towers is sequentially: an equal pressure drop adsorption step, a flushing step and a flushing final filling step.

[0038] The coordination process of the two adsorption towers is:

[0039] Table 1

[0040]

[0041] The pressure swing adsorption process and coordination relationship of the two adsorption towers are as follows:

[0042] (1) The first adsorption tower performs an equal pressure drop adsorption step, and the second adsorption tower performs a flushing step;

[0043] (2) the first adsorption tower performs an equal pressure drop adsorption step, and the second adsorption tower performs a flushing and final filling step;

[0044] (3) the first adsorption tower performs a flushing step, and the second adsorption tower performs an equal pressure drop adsorption step;

[0045] (4) The first adsorption tower performs a flushing and final filling step, and the second adsorption tower performs an equalizing pressure drop adsorption step.

[0046] The pressure drop adsorption step is divided into a first-stage pressure drop adsorption step and a second-stage pressure drop adsorption step, so that the working time of the same step between the adsorption towers is equal, and the pressure change of the two adsorption towers in the pressure swing adsorption process and the working time required for the corresponding steps are:

[0047] Table 2

[0048]

[0049] Preferably, when there are three adsorption towers, the pressure swing adsorption process of any of the adsorption towers is sequentially: adsorption step, equal pressure drop adsorption step, equal pressure drop step, inversion step, flushing step, equal pressure increase step, flushing and final filling step and waiting step.

[0050] The coordination process of the three adsorption towers is:

[0051] Table 3

[0052]

[0053] The pressure swing adsorption process and coordination relationship of the three adsorption towers are as follows:

[0054] (1) The first adsorption tower performs an equal pressure drop adsorption step, the second adsorption tower performs a waiting step, and the third adsorption tower performs a flushing step;

[0055] (2) the first adsorption tower performs an equal pressure drop step, the second adsorption tower performs an adsorption step, and the third adsorption tower performs an equal pressure increase step;

[0056] (3) the first adsorption tower performs a reverse placement step, the second adsorption tower performs an equal pressure drop adsorption step, and the third adsorption tower performs a flushing and final filling step;

[0057] (4) The first adsorption tower performs a flushing step, the second adsorption tower performs an equal pressure drop adsorption step, and the third adsorption tower performs a waiting step;

[0058] (5) the first adsorption tower performs an equal pressure increase step, the second adsorption tower performs an equal pressure drop step, and the third adsorption tower performs an adsorption step;

[0059] (6) The first adsorption tower performs a flushing and final filling step, the second adsorption tower performs a reverse placement step, and the third adsorption tower performs an equal pressure drop adsorption step;

[0060] (7) The first adsorption tower performs a waiting step, the second adsorption tower performs a flushing step, and the third adsorption tower performs an equal pressure drop adsorption step;

[0061] (8) The first adsorption tower performs an adsorption step, the second adsorption tower performs an equal pressure increase step, and the third adsorption tower performs an equal pressure drop step;

[0062] (9) The first adsorption tower performs an equal pressure drop adsorption step, the second adsorption tower performs a flushing and final filling step, and the third adsorption tower performs a reverse placement step.

[0063] The equal pressure drop adsorption step is divided into a first-stage equal pressure drop adsorption step and a second-stage equal pressure drop adsorption step, so that the working time of the same step between the adsorption towers is equal. The pressure change of the three adsorption towers in the pressure swing adsorption process and the working time required for the corresponding steps are:

[0064] Table 4

[0065]

[0066] Preferably, the raw gas for the pressure swing adsorption includes helium and impurity gas, and the impurity gas includes any one of CH4, N2, O2 or H2O or a combination of at least two of them. Typical but non-limiting combinations include a combination of CH4 and N2, a combination of N2 and O2, a combination of O2 and H2O, a combination of CH4, N2 and O2, a combination of N2, O2 and H2O, or a combination of CH4, N2, O2 and H2O.

[0067] Preferably, the helium content in the raw gas is 0-99%, excluding 0, for example, it can be 1%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or 99%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0068] Preferably, the raw gas is dehydrated before the pressure swing adsorption.

[0069] Preferably, any of the adsorption towers is connected to a raw gas pipeline, an impurity gas pipeline, a product gas pipeline and a pressure-equalizing gas pipeline.

[0070] Preferably, the raw gas pipeline, impurity gas pipeline, product gas pipeline and pressure-equalizing gas pipeline of any of the adsorption towers are independently provided with valves.

[0071] Preferably, the adsorbent in the adsorption tower includes any one of zeolite molecular sieve, alumina or silica gel, or a combination of at least two of them. Typical but non-limiting combinations include a combination of zeolite molecular sieve and alumina, a combination of alumina and silica gel, a combination of zeolite molecular sieve and silica gel, or a combination of zeolite molecular sieve, alumina and silica gel.

[0072] Compared with the prior art, the present invention has the following beneficial effects:

[0073] The purification method based on adsorption pressure swing provided by the present invention optimizes the process steps of the adsorption pressure swing process, adopts post-adsorption gas flushing and post-adsorption gas and product gas mixed flushing to regenerate the adsorbent, thereby increasing the effective working capacity of the adsorbent and improving the purity of helium, with the purity of helium reaching more than 99%. At the same time, the consumption of product gas by adsorbent regeneration in the process is reduced, and the recovery rate of helium is increased, with the recovery rate of helium reaching more than 80%. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Figure 1 1 is a schematic diagram of the structure of a two-tower pressure swing adsorption device system of the method provided in Example 1;

[0075] Figure 2It is a schematic structural diagram of a three-tower pressure swing adsorption device system of the method provided in Example 2;

[0076] Among them, 1, the first adsorption tower; 2, the second adsorption tower; 3, the third adsorption tower; 101, the raw gas buffer tank; 201, the impurity gas buffer tank; 301, the equalizing gas buffer tank; 401, the product gas buffer tank; 10-14, valves; 20-24, valves; 31-34, valves; 40, valve. DETAILED DESCRIPTION

[0077] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0078] Example 1

[0079] This embodiment provides a method for purifying helium by pressure swing adsorption, the method using a two-tower pressure swing adsorption device system;

[0080] The pressure swing adsorption process of any of the adsorption towers is sequentially: an equal pressure drop adsorption step, a flushing step, and a flushing and final filling step;

[0081] When one of the adsorption towers is performing the flushing step, the adsorption tower performing the equal pressure drop adsorption step performs auxiliary desorption of its transport gas to complete the flushing process;

[0082] When one of the adsorption towers is performing the flushing and final filling steps, the gas from the adsorption tower performing the equalizing pressure drop adsorption step and the product gas are introduced into the tower to complete the flushing process and the final filling process at the same time.

[0083] The raw gas composition in this embodiment is He 80%, CH4 9.6%, N2 9.56%, O2 0.84%, and the raw gas flow rate is 35 Nm 3 / h, the temperature is 298.15 K.

[0084] like Figure 1 As shown, the two-tower pressure swing adsorption device system includes:

[0085] A first adsorption tower 1 and a second adsorption tower 2;

[0086] The first adsorption tower 1 and the second adsorption tower 2 are respectively connected to a raw gas pipeline, an impurity gas pipeline, a pressure equalizing gas pipeline and a product gas pipeline;

[0087] The raw gas pipeline is provided with a raw gas buffer tank 101, a main valve 10, and adsorption tower branch valves 11 and 21;

[0088] The impurity gas pipeline is provided with an impurity gas buffer tank 201, a main valve 20, and adsorption tower branch valves 12 and 22;

[0089] The pressure equalizing gas pipeline is provided with a valve 13;

[0090] The product gas pipeline is provided with a product gas buffer tank 401, a main valve 40, and adsorption tower branch valves 14 and 24;

[0091] The adsorbent of the adsorption tower is zeolite molecular sieve.

[0092] In order to clearly illustrate the technical solution, in this embodiment, the equal pressure drop adsorption step is divided into a first equal pressure drop adsorption step and a second equal pressure drop adsorption step, so that the working time of the same step between the adsorption towers is equal.

[0093] When one of the adsorption towers is performing the first equal pressure drop adsorption step, the adsorption tower is performing the adsorption process, and at the same time, gas is transported through the pipeline to the adsorption tower performing the flushing step for auxiliary desorption to complete the flushing process;

[0094] When one of the adsorption towers is performing the second equal pressure drop adsorption step, the adsorption tower performs the adsorption process, and at the same time, gas is transported through a pipeline to the adsorption tower performing the flushing and final filling steps, and the gas of the adsorption tower performing the second equal pressure drop adsorption step and the product gas are introduced into the adsorption tower of the flushing and final filling steps in a certain proportion, and the flushing process and the final filling process are completed at the same time.

[0095] For ease of understanding, the coordination of the two adsorption towers during the pressure swing adsorption process is described in Table 5.

[0096] Table 5

[0097]

[0098] As shown in Table 5, the specific process of pressure swing adsorption is as follows:

[0099] (1) The first adsorption tower 1 performs the first pressure drop adsorption step, and the second adsorption tower 2 performs the flushing step:

[0100] Open valves 10, 11, 14 and 40, and the raw gas enters the first adsorption tower 1 through the raw gas buffer tank 101 for adsorption process, adsorbs impurity components, obtains product gas helium, and enters the product gas buffer tank 401;

[0101] At the same time, valves 13, 22 and 20 are opened, the impurity gas adsorbed in the second adsorption tower 2 is desorbed, the gas in the first adsorption tower 1 is transported to the second adsorption tower 2 through valve 13 for auxiliary desorption, and the desorbed impurity gas is transported to the outside through the impurity gas buffer tank 201, and the other valves are closed;

[0102] (2) The first adsorption tower 1 performs the second pressure drop adsorption step, and the second adsorption tower 2 performs the flushing and final filling step:

[0103] Valves 10 and 11 remain open, and the first adsorption tower 1 continues the adsorption process;

[0104] At the same time, valves 13, 14 and 40 remain open, and the gas in the first adsorption tower 1 and the product gas from the product gas buffer tank 401 are introduced into the second adsorption tower 2 through valve 13 at a ratio of 95:5, so as to flush the second adsorption tower 2 and regenerate the adsorbent. At the same time, the pressure in the tower is increased to complete the final charging, and the other valves are closed;

[0105] (3) The first adsorption tower 1 performs a flushing step, and the second adsorption tower 2 performs a first pressure drop adsorption step:

[0106] Valves 12 and 20 are opened, and the adsorbent in the first adsorption tower 1 is desorbed and transported to the outside through the impurity gas buffer tank 201;

[0107] At the same time, valves 10, 21, 24, 40 and 13 are opened, the raw gas enters the second adsorption tower 2 through the raw gas buffer tank 101 for adsorption, and the helium gas obtained enters the product gas buffer tank 401. Part of the gas in the tower is transported to the first adsorption tower 1 through valve 13 for auxiliary desorption, and the desorbed gas is transported to the outside, and the other valves are closed;

[0108] (4) The first adsorption tower 1 performs a flushing and final filling step, and the second adsorption tower 2 performs a second pressure drop adsorption step:

[0109] Valves 10 and 21 remain open, and the second adsorption tower 2 continues the adsorption process;

[0110] At the same time, valves 13, 24 and 40 remain open, and the gas and product gas of the second adsorption tower 2 are introduced into the first adsorption tower 1 in a ratio of 95:5 to flush the first adsorption tower 1. At the same time, the pressure in the tower is increased to complete the final charging, and the other valves are closed;

[0111] (5) Repeat steps (1) to (4) in a cycle.

[0112] During the adsorption pressure swing process, the starting pressure, ending pressure and working time corresponding to each step of any adsorption tower are summarized in Table 6.

[0113] Table 6

[0114]

[0115] In this embodiment, after the raw gas is purified to obtain helium, the purity of the obtained helium product gas is measured to be 99%, and the recovery rate of helium is 80%.

[0116] Example 2

[0117] This embodiment provides a method for purifying helium by pressure swing adsorption, the method using a three-tower pressure swing adsorption device system;

[0118] The pressure swing adsorption process of any of the adsorption towers is sequentially: an adsorption step, an equal pressure drop adsorption step, an equal pressure drop step, an inversion step, a flushing step, an equal pressure increase step, a flushing and final filling step, and a waiting step;

[0119] When one of the adsorption towers is performing the flushing step, the adsorption tower performing the equal pressure drop adsorption step performs auxiliary desorption of its transport gas to complete the flushing process;

[0120] When one of the adsorption towers is performing the flushing and final filling steps, the gas from the adsorption tower performing the equalizing pressure drop adsorption step and the product gas are introduced into the tower to complete the flushing process and the final filling process at the same time.

[0121] The raw gas composition in this embodiment is He 80%, CH4 9.6%, N2 9.56%, O2 0.84%, and the raw gas flow rate is 35 Nm 3 / h, the temperature is 298.15 K.

[0122] like Figure 2 As shown, the three-tower pressure swing adsorption device system includes:

[0123] A first adsorption tower 1, a second adsorption tower 2 and a third adsorption tower 3;

[0124] The first adsorption tower 1, the second adsorption tower 2 and the third adsorption tower 3 are respectively connected with a raw gas pipeline, an impurity gas pipeline, a pressure equalizing gas pipeline and a product gas pipeline;

[0125] The raw gas pipeline is provided with a raw gas buffer tank 101, a main valve 10, and adsorption tower branch valves 11, 21 and 31;

[0126] The impurity gas pipeline is provided with an impurity gas buffer tank 201, a main valve 20, and adsorption tower branch valves 12, 22 and 32;

[0127] The pressure-equalizing gas pipeline is provided with a pressure-equalizing gas buffer tank 301, and adsorption tower branch valves 13, 23 and 33;

[0128] The product gas pipeline is provided with a product gas buffer tank 401, a main valve 40, and adsorption tower branch valves 14, 24 and 34;

[0129] The adsorbent of the adsorption tower is zeolite molecular sieve.

[0130] In order to clearly illustrate the technical solution, in this embodiment, the equal pressure drop adsorption step is divided into a first equal pressure drop adsorption step and a second equal pressure drop adsorption step, so that the working time of the same step between the adsorption towers is equal.

[0131] It should be noted that the names "first" and "second" are used to distinguish and describe the corresponding relationship between the flushing step and the flushing and final filling step and the equalizing pressure drop adsorption step, and do not represent the absolute process order.

[0132] When one of the adsorption towers is performing the first equal pressure drop adsorption step, the adsorption tower is performing the adsorption process, and at the same time, gas is transported through the pipeline to the adsorption tower performing the flushing step for auxiliary desorption to complete the flushing process;

[0133] When one of the adsorption towers is performing the second equal pressure drop adsorption step, the adsorption tower performs the adsorption process, and at the same time, gas is transported through a pipeline to the adsorption tower performing the flushing and final filling steps, and the gas of the adsorption tower performing the second equal pressure drop adsorption step and the product gas are introduced into the adsorption tower of the flushing and final filling steps in a certain proportion, and the flushing process and the final filling process are completed at the same time.

[0134] For ease of understanding, the coordination of the three adsorption towers during the pressure swing adsorption process is illustrated in Table 7.

[0135] Table 7

[0136]

[0137] As shown in Table 7, the specific process of pressure swing adsorption is as follows:

[0138] (1) The first adsorption tower 1 performs the first pressure drop adsorption step, the second adsorption tower 2 performs the waiting step, and the third adsorption tower 3 performs the flushing step:

[0139] Open valves 10, 11, 14 and 40, and the raw gas enters the first adsorption tower 1 for adsorption process, adsorbs impurity components to obtain product gas helium, and enters the product gas buffer tank 401;

[0140] The second adsorption tower 2 is in the waiting process;

[0141] Open valves 13, 33, 32 and 20, and a certain amount of gas is charged from the first adsorption tower 1 into the third adsorption tower 3 through the pressure equalization gas buffer tank 301 to perform auxiliary desorption, complete the flushing process, and the desorbed impurity gas is transported to the outside, and the other valves are closed;

[0142] (2) The first adsorption tower 1 performs an equal pressure drop step, the second adsorption tower 2 performs an adsorption step, and the third adsorption tower 3 performs an equal pressure increase step:

[0143] Open valves 10, 21, 24, and 40, and the raw gas enters the second adsorption tower 2 for adsorption to obtain product gas;

[0144] Open valves 13 and 33, the gas in the first adsorption tower 1 is charged into the third adsorption tower 3, the first adsorption tower 1 completes the pressure drop process, the third adsorption tower 3 completes the pressure increase process, the remaining helium in the gap of the first adsorption tower 1 is recovered, and the pressure of the third adsorption tower 3 is increased, and the remaining valves are closed;

[0145] (3) The first adsorption tower 1 performs the inversion step, the second adsorption tower 2 performs the second pressure drop adsorption step, and the third adsorption tower 3 performs the flushing and final filling step:

[0146] Open valves 12 and 20, and the first adsorption tower 1 is put into reverse operation, the adsorbent in the first adsorption tower 1 is desorbed, and the desorbed impurity gas is transported to the outside;

[0147] Open valves 10 and 21, and the second adsorption tower 2 performs the adsorption process;

[0148] Open valves 23, 33, 40 and 24, and pass the gas in the second adsorption tower 2 and the product gas in the product gas buffer tank 401 into the third adsorption tower 3 in a ratio of 95:5, flush the tower to achieve adsorbent regeneration, and increase the pressure to achieve final charging, and the remaining valves are closed;

[0149] (4) The first adsorption tower 1 performs a flushing step, the second adsorption tower 2 performs a first pressure drop adsorption step, and the third adsorption tower 3 performs a waiting step:

[0150] Open valves 10, 21, 24 and 40, and the second adsorption tower 2 performs the adsorption process;

[0151] Open valves 13, 23, 12 and 20, and the gas from the second adsorption tower 2 enters the first adsorption tower 1 for auxiliary desorption, and the impurity gas is transported to the outside;

[0152] The third adsorption tower 3 is in the waiting process, and the other valves are closed;

[0153] (5) The first adsorption tower 1 performs a pressure-raising step, the second adsorption tower 2 performs a pressure-dropping step, and the third adsorption tower 3 performs an adsorption step:

[0154] Open valves 13 and 23, and the gas in the second adsorption tower 2 flows into the first adsorption tower 1, recovering the remaining helium in the gap of the second adsorption tower 2, and increasing the pressure of the first adsorption tower 1;

[0155] Open valves 10, 31, 34 and 40, adsorption tower 3 performs adsorption process, and the other valves are closed;

[0156] (6) The first adsorption tower 1 performs a flushing and final filling step, the second adsorption tower 2 performs a reversing step, and the third adsorption tower 3 performs a second equal pressure drop adsorption step:

[0157] Open valves 10 and 31, and the third adsorption tower 3 performs the adsorption process;

[0158] Open valves 13, 33, 34 and 40, and pass the gas from the third adsorption tower 3 and the product gas into the first adsorption tower 1 in a ratio of 95:5 to perform flushing to achieve adsorbent regeneration, and increase the pressure to achieve final charging;

[0159] Open valves 22 and 20, desorb the adsorbent in the second adsorption tower 2, and transport the impurity gas to the outside, and close the other valves;

[0160] (7) The first adsorption tower 1 performs a waiting step, the second adsorption tower 2 performs a flushing step, and the third adsorption tower 3 performs a first equal pressure drop adsorption step:

[0161] Open valves 10, 31, 34 and 40, and the third adsorption tower 3 performs an adsorption process to obtain product gas;

[0162] Open valves 23, 33, 22 and 20, a certain amount of gas from the third adsorption tower 3 flows into the second adsorption tower 2 for auxiliary desorption, and the impurity gas is discharged to the outside, and the other valves are closed;

[0163] (8) The first adsorption tower 1 performs an adsorption step, the second adsorption tower 2 performs an equal pressure increase step, and the third adsorption tower 3 performs an equal pressure drop step:

[0164] Open valves 10, 11, 14 and 40, and the first adsorption tower 1 performs an adsorption process to obtain product gas;

[0165] Open valves 23 and 33, and the gas from the third adsorption tower 3 flows into the second adsorption tower 2 to complete the pressure equalization, and the remaining valves are closed;

[0166] (9) The first adsorption tower 1 performs the second pressure drop adsorption step, the second adsorption tower 2 performs the flushing and final filling step, and the third adsorption tower 3 performs the inversion step:

[0167] Open valves 10 and 11, and the first adsorption tower 1 performs the adsorption process;

[0168] Open valves 13, 23, 14 and 40, and the gas in the first adsorption tower 1 and the product gas flow into the second adsorption tower 2 in a ratio of 95:5, so as to perform flushing to achieve adsorbent regeneration and increase the pressure to achieve final charging;

[0169] Open valves 32 and 20, desorb the adsorbent in the third adsorption tower 3, discharge the impurity gas, and close the remaining valves;

[0170] (10) Repeat the above steps to cycle.

[0171] During the adsorption pressure swing process, the starting pressure, ending pressure and corresponding working time of each step for any adsorption tower are summarized in Table 8.

[0172] Table 8

[0173]

[0174] In this embodiment, after the raw gas is purified to obtain helium, the purity of the obtained helium product gas is 99.9%, and the recovery rate of helium is 80%.

[0175] Comparative Example 1

[0176] This comparative example provides a method for purifying helium by pressure swing adsorption, wherein the method uses Figure 1 A two-tower pressure swing adsorption unit system is shown.

[0177] The raw gas composition in this comparative example is He 80%, CH4 9.6%, N2 9.56%, O2 0.84%, and the raw gas flow rate is 35 Nm 3 / h, the temperature is 298.15 K.

[0178] The method comprises the following steps:

[0179] (1) The first adsorption tower 1 performs the adsorption step, and the second adsorption tower 2 performs the inversion step:

[0180] Open valves 10, 11, 14 and 40, and the raw gas enters the first adsorption tower 1 through the raw gas buffer tank 101 for adsorption process, adsorbs impurity components, obtains product gas helium, and enters the product gas buffer tank 401;

[0181] At the same time, valves 22 and 20 are opened to desorb the impurity gas in the second adsorption tower 2, and the other valves are closed;

[0182] (2) The first adsorption tower 1 performs a pressure drop step, and the second adsorption tower 2 performs a pressure increase step:

[0183] Open valve 13, the first adsorption tower 1 and the second adsorption tower 2 are connected to complete the pressure equalization process;

[0184] (3) The first adsorption tower 1 performs the inversion step, and the second adsorption tower 2 performs the adsorption step:

[0185] Open valves 10, 21, 24 and 40, and the raw gas enters the second adsorption tower 2 for adsorption to obtain product gas;

[0186] Open valve 12, the first adsorption tower 1 desorbs the impurity gas, and the other valves are closed;

[0187] (4) The first adsorption tower 1 performs a pressure-raising step, and the second adsorption tower 2 performs a pressure-dropping step:

[0188] Open valve 13, the first adsorption tower 1 and the second adsorption tower 2 are connected to complete the pressure equalization process;

[0189] (5) Repeat steps (1) to (4) in a cycle, with each step lasting 60 seconds.

[0190] In this comparative example, the purity of the obtained helium product gas is 90%, and the recovery rate of helium is 40%.

[0191] Table 9

[0192]

[0193] Compared with Example 1, Comparative Example 1 is not suitable for actual production because there is no flushing of high-purity helium, resulting in insufficient regeneration of the adsorption tower, and the purity and recovery rate of helium are significantly reduced.

[0194] In summary, the purification method based on adsorption pressure swing provided by the present invention optimizes the process steps of the adsorption pressure swing process, adopts post-adsorption gas flushing and post-adsorption gas and product gas mixed flushing to regenerate the adsorbent, thereby improving the effective working capacity of the adsorbent and improving the purity of helium, the purity of helium reaching more than 99%, and at the same time, reducing the consumption of product gas during adsorbent regeneration in the process, improving the recovery rate of helium, and the recovery rate of helium reaching more than 80%.

[0195] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for purifying helium by pressure swing adsorption, characterized in that: The method comprises: At least two adsorption towers are alternately connected in parallel to perform a pressure swing adsorption process; The pressure swing adsorption process of any of the adsorption towers comprises in sequence: an equal pressure drop adsorption step, a flushing step and a flushing final filling step; The equalizing pressure drop adsorption step comprises: introducing the raw gas into the adsorption tower for adsorption, and simultaneously delivering the adsorbed gas to other adsorption towers connected to the adsorption tower for equalizing pressure drop adsorption; When any of the adsorption towers is performing the flushing step, at least one other adsorption tower is performing the equal pressure drop adsorption step, and the adsorption tower performing the equal pressure drop adsorption step delivers the adsorbed gas to the adsorption tower performing the flushing step, and performs auxiliary desorption on the adsorption tower performing the flushing step, thereby completing the flushing process; When any of the adsorption towers is performing the flushing and final filling step, at least one other adsorption tower is performing the equal pressure drop adsorption step, and the product gas in the storage container and the adsorbed gas output by the adsorption tower performing the equal pressure drop adsorption step are introduced into the adsorption tower performing the flushing and final filling step, and the flushing process and the final filling process are completed at the same time; When there are two adsorption towers, the pressure swing adsorption process of any of the adsorption towers is sequentially: an equal pressure drop adsorption step, a flushing step, and a flushing and final filling step; The pressure swing adsorption process and coordination relationship of the two adsorption towers are as follows: (1) The first adsorption tower performs an equal pressure drop adsorption step, and the second adsorption tower performs a flushing step; (2) the first adsorption tower performs an equal pressure drop adsorption step, and the second adsorption tower performs a flushing and final filling step; (3) the first adsorption tower performs a flushing step, and the second adsorption tower performs an equal pressure drop adsorption step; (4) The first adsorption tower performs a flushing and final filling step, and the second adsorption tower performs an equal pressure drop adsorption step; When there are at least three adsorption towers, the pressure swing adsorption process of any of the adsorption towers further comprises: an adsorption step, at least one pressure drop step, an inversion step, at least one pressure increase step, and a waiting step; In the same time period, at least one adsorption tower performs an adsorption step or an equal pressure drop adsorption step; The adsorption step is arranged before the equalization pressure drop adsorption step; The pressure drop equalization step is arranged between the pressure drop equalization adsorption step and the flushing step; The inversion step is arranged between the equalizing pressure drop adsorption step and the flushing step; The pressure equalization step is arranged between the flushing step and the flushing and final filling step; The waiting step is arranged after the flushing and final filling step.

2. The method according to claim 1, characterized in that The pressure of the adsorption process is 2-100 bar.

3. The method according to claim 1, characterized in that The temperature of the adsorption process is between -250 and 100°C.

4. The method according to claim 1, characterized in that: The product gas accounts for 0-99% of the adsorbed gas output from the adsorption tower performing the equal pressure drop adsorption step, and does not include 0.

5. The method according to claim 1, characterized in that When there are three adsorption towers, the pressure swing adsorption process of any of the adsorption towers is sequentially: adsorption step, equal pressure drop adsorption step, equal pressure drop step, inversion step, flushing step, equal pressure increase step, flushing and final filling step, and waiting step; The pressure swing adsorption process and coordination relationship of the three adsorption towers are as follows: (1) The first adsorption tower performs an equal pressure drop adsorption step, the second adsorption tower performs a waiting step, and the third adsorption tower performs a flushing step; (2) the first adsorption tower performs an equal pressure drop step, the second adsorption tower performs an adsorption step, and the third adsorption tower performs an equal pressure increase step; (3) the first adsorption tower performs a reverse placement step, the second adsorption tower performs an equal pressure drop adsorption step, and the third adsorption tower performs a flushing and final filling step; (4) The first adsorption tower performs a flushing step, the second adsorption tower performs an equal pressure drop adsorption step, and the third adsorption tower performs a waiting step; (5) the first adsorption tower performs an equal pressure increase step, the second adsorption tower performs an equal pressure drop step, and the third adsorption tower performs an adsorption step; (6) The first adsorption tower performs a flushing and final filling step, the second adsorption tower performs a reverse placement step, and the third adsorption tower performs an equal pressure drop adsorption step; (7) The first adsorption tower performs a waiting step, the second adsorption tower performs a flushing step, and the third adsorption tower performs an equal pressure drop adsorption step; (8) The first adsorption tower performs an adsorption step, the second adsorption tower performs an equal pressure increase step, and the third adsorption tower performs an equal pressure drop step; (9) The first adsorption tower performs an equal pressure drop adsorption step, the second adsorption tower performs a flushing and final filling step, and the third adsorption tower performs a reverse placement step.

6. The method according to claim 1, characterized in that The raw gas for the pressure swing adsorption includes helium and impurity gas, and the impurity gas includes any one of CH4, N2, O2 or H2O or a combination of at least two thereof; The helium content in the raw gas is 0-99%, excluding 0.

7. The method according to claim 6, characterized in that The raw gas is dehydrated before the pressure swing adsorption.

8. The method according to claim 1, characterized in that The adsorbent in the adsorption tower includes any one of zeolite molecular sieve, alumina or silica gel, or a combination of at least two of them.

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