Method for recovering helium in tail gas of natural gas refinery plant

Abstract

The invention relates to the field of petroleum refining, and discloses a method for recovering helium in tail gas of a natural gas refinery, which comprises the following steps: (1) carrying out first membrane separation on the tail gas of the natural gas refinery; (2) combusting the permeation side gas separated by the first membrane, decarbonizing, and drying the decarbonized gas; (3) carrying out second membrane separation on the dried gas; (4) performing pressure swing adsorption on the permeation side gas separated by the second membrane to obtain high-purity helium; according to the method, helium in the residual tail gas in the natural gas refinery plant is recycled, energy waste is greatly reduced, and the problem of waste of the residual tail gas in the natural gas refinery plant is solved.

Description

Technical Field

[0001] The present invention relates to the field of petroleum refining, and particularly to a method for recovering helium from the tail gas of a natural gas refinery. By combining multi-step membrane separation, combustion dehydrogenation, acid removal, drying and pressure swing adsorption technologies, helium is recovered from the tail gas in the natural gas refinery. Background Art

[0002] Helium is a strategic special gas with low density, low boiling point and inert characteristics. It often occurs along with natural gas. Helium has a wide range of applications in many fields such as aerospace, deep diving, medical imaging, superconducting materials, semiconductors, hard disks, and cooling nuclear reactors, playing an important role that cannot be ignored. With the development of the economy, the demand for helium in China has increased rapidly. However, at present, China's helium supply almost completely depends on imports, and the upstream supply chain is severely restricted. To meet the demand for helium resources in China's economic development, it is urgent to develop a method for preparing high-purity helium with low energy consumption. China has relatively rich natural gas resources, but the helium content in natural gas is low and the purification is difficult. A large number of natural gas plants directly discharge helium, causing serious waste of resources. Therefore, it is particularly important to develop a technology for purifying low-concentration helium in natural gas.

[0003] The helium recovery technology from natural gas includes non-cryogenic methods and cryogenic methods. The non-cryogenic methods include physical adsorption method, solvent absorption method, membrane separation method and pressure swing adsorption method, and the cryogenic method is the cryogenic distillation method. The cryogenic process is the commonly used helium recovery method in industry at present, and about 90% of helium is extracted by the cryogenic method. The cryogenic process uses the difference in the critical temperatures of the components in natural gas to separate helium, but there are problems such as low operating flexibility, high equipment investment and high energy consumption, and it is not competitive in terms of economic benefits. The membrane separation method is to use the difference in the permeation performance of the components in natural gas during the processes of dissolution, diffusion and desorption under the driving force of the pressure difference on both sides of the membrane to separate helium. The membrane separation method has the advantages of simple operation, low energy consumption, low device construction and operation costs.

[0004] In modern natural gas refineries, the methanol synthesis unit is an important part. After methanol synthesis, the residual tail gas is separated by a membrane, and the hydrogen-rich gas on the permeate side is refluxed, and the methane-rich gas on the retentate side directly enters the combustion and is discharged. In this methane-rich gas, the helium concentration can generally reach between 0.5% and 2%. This is a great waste of helium resources.

[0005] Therefore, energy recovery and helium purification of this methane-rich gas can greatly reduce resource waste. Summary of the Invention

[0006] The object of the present invention is to overcome the problems of helium and energy waste in the residual tail gas in a natural gas refinery existing in the prior art, and to provide a method for recovering helium from the tail gas of a natural gas refinery. This method has the advantages of simple operation, low energy consumption, and low device construction and operation costs.

[0007] To achieve the above object, on the one hand, the present invention provides a method for recovering helium from the tail gas of a natural gas refinery, wherein the method comprises:

[0008] (1) performing a first membrane separation on the tail gas of the natural gas refinery;

[0009] (2) burning the permeate-side gas obtained from the first membrane separation and then performing decarbonization, and drying the decarbonized gas;

[0010] (3) performing a second membrane separation on the dried gas;

[0011] (4) obtaining high-purity helium from the permeate-side gas obtained from the second membrane separation through pressure swing adsorption.

[0012] Through the above technical solution, the present invention ingeniously couples membrane separation technology, combustion decarbonization technology, and pressure swing adsorption technology, and has the following advantages:

[0013] (1) Through the coupling process, the recovery of helium from the tail gas of the natural gas refinery is successfully achieved, and at the same time, combustion decarbonization can efficiently provide energy for the refinery, having high economic benefits;

[0014] (2) The whole process does not require cryogenic operation, significantly reducing the cost of helium purification, and at the same time ensuring the stability of the device operation;

[0015] (4) By gradually increasing the helium concentration through the second membrane separation, and removing hydrogen through decarbonization combustion and pressure swing adsorption, the traditional problem of difficult helium extraction from the tail gas of the refinery with low helium concentration and high hydrogen concentration is solved.

[0016] (3) In the preferred embodiment of the present invention, hydrogen is first enriched through a specific first membrane separation to increase the hydrogen concentration, so that combustion decarbonization can be efficiently performed. Detailed Embodiment

[0017] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0018] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only for illustrating and explaining the present invention, and are not used to limit the present invention.

[0019] The present invention provides a method for recovering helium from the tail gas of a natural gas refinery. Among them, the method includes:

[0020] (1) Perform a first membrane separation on the tail gas of the natural gas refinery;

[0021] (2) Burn the permeate-side gas from the first membrane separation and then perform decarbonization. The decarbonized gas is dried;

[0022] (3) Perform a second membrane separation on the dried gas;

[0023] (4) Obtain high-purity helium from the permeate-side gas of the second membrane separation through pressure swing adsorption.

[0024] In the present invention, the helium content in the tail gas of the natural gas refinery in step (1) is 0.1-2 wt%, preferably 0.5-2 wt%; the hydrogen content is 15-60 wt%.

[0025] In the present invention, the first membrane separation in step (1) selectively permeates helium and hydrogen; the separation membrane used in the first membrane separation can be selected from at least one of flat membranes, hollow fiber membranes, and tubular membranes; preferably, the material of the separation membrane can be selected from at least one of polysulfone, polyethersulfone, polyimide, polypropylene, polyethylene, synthetic resin, polyvinylidene fluoride, polytetrafluoroethylene, polyetheretherketone, polybenzimidazole, polydimethylsiloxane, cellulose acetate, polycarbonate, polymethyl methacrylate, silica, zeolite molecular sieve, carbon molecular sieve, and metal-organic framework material; in order to further improve the flux and selectivity of the separation membrane for helium and hydrogen, preferably, the separation membrane includes a hollow fiber membrane made of polyimide material or a flat membrane made of polybenzimidazole material.

[0026] In the present invention, the helium flux of the separation membrane used in the first membrane separation in step (1) is 200-500 GPU, the helium / methane separation coefficient is 100-200; the hydrogen / methane separation coefficient is 40-80; preferably, the helium / methane separation coefficient can be 110-170; the hydrogen / methane separation coefficient is 50-70.

[0027] In the present invention, in the first membrane separation in step (1), the pressure on the positive pressure side of the membrane separation can be 200-3000 kPa; preferably 500-2000 kPa; the pressure on the permeate side of the membrane separation is lower than the positive pressure side, and the pressure on the permeate side can also be negative pressure.

[0028] In the present invention, the positive pressure is the intake pressure on the upstream side of the separation membrane.

[0029] In the present invention, the first membrane separation may employ single-stage or multi-stage membrane separation technology; preferably single-stage membrane separation.

[0030] In the present invention, the equipment selected for the combustion in step (2) may be various boilers commonly used in the art; preferably a hydrogen-rich boiler; in the present invention, the first membrane separation enables the hydrogen concentration in the permeate-side gas to be greater than 80%, thus being more suitable for a hydrogen-rich boiler.

[0031] In the present invention, the equipment selected for the decarbonization in step (2) may be selected from various absorption towers commonly used in the art, preferably an alkaline absorption tower; preferably, the alkaline absorption tower may be selected from one of a packed tower, a plate tower, a spray tower, a bubble column or a liquid column tower; more preferably a packed tower; the packing in the packed tower may be at least one of a Raschig ring, a Pall ring, a cascade ring or a corrugated packing; preferably, the absorbent in the absorption tower may be various absorbents commonly used in the art. For example, the absorbent may be at least one of a sodium hydroxide solution, a sodium carbonate solution or a sodium bicarbonate solution.

[0032] In the present invention, the equipment selected for the drying in step (2) may be various drying towers commonly used in the art; preferably, the drying tower may be selected from one of a packed tower, a plate tower, a spray tower, a bubble column or a liquid column tower; the packing in the packed tower may be at least one of a Raschig ring, a Pall ring, a cascade ring or a corrugated packing; preferably, the desiccant in the drying tower may be various absorbents commonly used in the art. For example, the desiccant may be at least one of activated alumina, molecular sieve, calcium oxide or gypsum powder.

[0033] In the present invention, the type selection of the second membrane separation in step (3) is as described above and will not be elaborated here.

[0034] In the present invention, the membrane performance of the second membrane separation in step (3) is as described above and will not be elaborated here.

[0035] In the present invention, in the second membrane separation of step (3), the pressure on the positive-pressure side of the membrane separation is 500 - 5000 kPa; preferably 1000 - 3000 kPa; the pressure on the permeate side of the membrane separation is lower than that on the positive-pressure side, and the pressure on the permeate side may also be negative pressure.

[0036] In the present invention, the second membrane separation may employ single-stage or multi-stage membrane separation technology; preferably 1 - 3 stages. When performing multi-stage membrane separation, the positive-pressure of the separation membrane may be the same or different.

[0037] In the present invention, the adsorbent in the pressure swing adsorption of step (4) is selected from at least one of activated carbon, molecular sieve, metal-organic framework materials; the adsorption pressure is 0.5 - 10 MPa; preferably 2 - 10 MPa.

[0038] In the present invention, the method is applicable to the recovery of helium from natural gas tail gas with a low helium concentration and a high hydrogen concentration. The composition of the natural gas refinery tail gas is preferably: helium 0.5 - 2 vol%, hydrogen 15 - 60 vol%, nitrogen 28 - 31 vol%, oxygen 2.5 - 3.5 vol%, carbon monoxide 5 - 7 vol%, methane 26 - 28 vol%, and carbon dioxide 3 - 4 vol%.

[0039] In a preferred embodiment of the present invention, the separation membranes used in the first and second membrane separations can be selected from hollow fiber membranes made of polyimide material or flat membranes made of polybenzimidazole material; the helium / methane separation coefficient of the first and second separation membranes is 110 - 170, and the hydrogen / methane separation coefficient is 50 - 70; the first membrane separation adopts a single-stage membrane separation technology; the second membrane separation adopts a 1 - 3 stage membrane separation technology; in the first membrane separation, the positive pressure side pressure of the membrane separation is 500 - 2000 kPa; in the second membrane separation, the positive pressure side pressure of the membrane separation is 1000 - 3000 kPa; the adsorption pressure in the pressure swing adsorption is 2 - 10 MPa; by adopting the above preferred embodiment, the purity of the helium separated from the natural gas refinery tail gas is as high as over 99.9%.

[0040] The present invention will be described in detail below through examples. For those not specifying specific conditions in the following examples and comparative examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not indicating the manufacturer, they are all conventional products that can be obtained through commercial channels.

[0041] The gas composition analysis method uses a gas analyzer to test the gas concentration.

[0042] Example 1

[0043] The purification operation is carried out on the tail gas of a certain natural gas refinery by using the technology of the present invention. The composition of the raw gas (S1) includes: helium 0.7 vol%, hydrogen 28.4 vol%, nitrogen 30.19 vol%, oxygen 3.17 vol%, carbon monoxide 7.7 vol%, methane 26.34 vol%, and carbon dioxide 3.5 vol%.

[0044] First, the raw gas is subjected to the first membrane separation. The separation membrane used is a hollow fiber membrane made of polyimide material. The helium / methane separation coefficient of the membrane is 131, and the hydrogen / methane separation coefficient is 68. The positive pressure of the membrane separation is 2000 kPa. The gas (S2) on the permeate side of the membrane enters the hydrogen-rich boiler unit and is burned in a pure oxygen environment.

[0045] The boiler tail gas enters an alkali scrubbing tower for decarbonization operation. The alkali scrubbing tower adopts the structure of an absorption tower, and the absorbent is 10 wt% sodium hydroxide solution. Then it enters a drying tower for dehydration operation. The drying tower also adopts the structure of an absorption tower, and the desiccant is activated alumina.

[0046] The dried gas (S3) enters the second membrane separation unit for treatment. The separation membrane used is a hollow fiber membrane made of polyimide. The helium / methane separation coefficient of the membrane is 131, and the hydrogen / methane separation coefficient is 68. The separation process selects a two-stage membrane separation process, and the positive pressure is 1500 kPa and 1500 kPa respectively.

[0047] The gas (S4) after membrane separation enters the pressure swing adsorption unit for purification. 5A zeolite molecular sieve is selected as the adsorbent, and the adsorption pressure is 2 MPa. After adsorption, a high-purity helium product (S5) is obtained.

[0048] The main gas compositions of each step of helium purification are shown in Table 1.

[0049] Table 1 Gas composition table at each stage (gas composition %)

[0050]

[0051]

[0052] As can be seen from the above table, through the process technology of the present invention, a high-purity helium product with a purity of 99.93% can be obtained by combining membrane separation, hydrogen-rich boiler, alkali washing and drying, and pressure swing adsorption processes. At the same time, the boiler can provide 2100 kW of energy for the natural gas refinery.

[0053] Example 2

[0054] Recover helium according to the method of Example 1, the difference is that: the separation membrane used in the first membrane separation is a flat membrane made of polybenzimidazole, the helium / methane separation coefficient of the membrane is 114, and the hydrogen / methane separation coefficient is 52. The positive pressure of membrane separation is 1500 kPa; the separation membrane used in the second membrane separation is a flat membrane made of polybenzimidazole, the helium / methane separation coefficient of the membrane is 114, and the hydrogen / methane separation coefficient is 52. The separation process selects a three-stage membrane separation process, and the positive pressure is 1000 kPa, 1000 kPa, and 1000 kPa respectively.

[0055] Metal-organic framework material MOFs is selected as the adsorbent for pressure swing adsorption, and the adsorption pressure is 5 MPa.

[0056] The main gas compositions of each step of helium purification are shown in Table 2.

[0057] Table 2 Gas composition table at each stage (gas composition %)

[0058] Number He <![CDATA[H 2 > <![CDATA[N 2 > <![CDATA[O 2 > CO <![CDATA[CH 4 > <![CDATA[CO 2 > <![CDATA[H 2 O]]> S1 0.7 28.4 30.19 3.17 7.7 26.34 3.5 0 S2 2.57 87.14 3.37 0.35 0.86 2.95 2.76 0 S3 33.77 11.47 44.43 7.16 0.45 0.78 1.7 0.24 S4 75.85 23.43 0.13 0.02 <0.01 <0.01 0.57 <0.01 S5 99.94 0.06 0 0 0 0 <0.01 0

[0059] As can be seen from the above table, through the process technology of the present invention, high-purity helium gas products with a purity of 99.94% can be obtained by combining membrane separation, hydrogen-rich boiler, alkali washing and drying, and pressure swing adsorption processes. At the same time, the boiler can provide 2300 kW of energy for the natural gas refinery.

[0060] Example 3

[0061] Helium was recovered according to the method of Example 1, except that: the separation membrane used in the first membrane separation was a flat membrane of polyimide, the helium / methane separation coefficient of the membrane was 120, the hydrogen / methane separation coefficient was 55, and the positive pressure of the membrane separation was 1500 kPa.

[0062] The separation membrane used in the second membrane separation was a flat membrane of polyimide, the helium / methane separation coefficient of the membrane was 120, the hydrogen / methane separation coefficient was 55, the separation process selected a two-stage membrane separation process, and the positive pressures were 3000 kPa and 3000 kPa respectively.

[0063] Metal-organic framework material MOFs was selected as the adsorbent for pressure swing adsorption, and the adsorption pressure was 10 MPa.

[0064] The main gas compositions of each step of helium purification are shown in Table 3.

[0065] Table 3 Gas composition table at each stage (gas composition%)

[0066] Number He <![CDATA[H 2 > <![CDATA[N 2 > <![CDATA[O 2 > CO <![CDATA[CH 4 > <![CDATA[CO 2 > <![CDATA[H 2 O]]> S1 0.7 28.4 30.19 3.17 7.7 26.34 3.5 0 S2 2.67 87.94 3.06 0.32 0.78 2.67 2.56 0 S3 33.1 10.91 38 15.24 0.39 0.66 1.47 0.23 S4 76.4 22.67 0.32 0.13 <0.01 <0.01 0.48 <0.01 S5 99.94 0.06 0 0 0 0 <0.01 0

[0067] As can be seen from the above table, through the process technology of the present invention, high-purity helium gas products with a purity of 99.94% can be obtained by combining membrane separation, hydrogen-rich boiler, alkali washing and drying, and pressure swing adsorption processes. At the same time, the boiler can provide 2000 kW of energy for the natural gas refinery.

[0068] Example 4

[0069] Helium was recovered according to the method of Example 1, except that: the separation membrane used in the first membrane separation was a flat membrane made of polybenzimidazole, the helium / methane separation coefficient of the membrane was 114, the hydrogen / methane separation coefficient was 52, and the positive pressure of the membrane separation was 300 kPa.

[0070] The separation membrane used in the second membrane separation was a hollow fiber membrane made of polyimide, the helium / methane separation coefficient of the membrane was 131, the hydrogen / methane separation coefficient was 68, the separation process selected a two-stage membrane separation process, and the positive pressures were 500 kPa and 500 kPa respectively.

[0071] The main gas compositions of each step of helium purification are shown in Table 4.

[0072] Table 4 Gas composition table at each stage (gas composition%)

[0073] Number He <![CDATA[H 2 > <![CDATA[N 2 > <![CDATA[O 2 > CO <![CDATA[CH 4 > <![CDATA[CO 2 > <![CDATA[H 2 O]]> S1 0.7 28.4 30.19 3.17 7.7 26.34 3.5 0 S2 2.25 81.93 5.39 0.57 1.37 4.7 3.79 0 S3 24.47 8.93 58.74 3.92 0.6 1.02 2.12 0.2 S4 56.81 17.19 20.07 1.34 0.2 0.35 3.97 0.07 S5 99.89 0.06 <0.01 <0.01 0 0 <0.01 0

[0074] As can be seen from the above table, through the process technology of the present invention, high-purity helium gas products with a purity of 99.89% can be obtained by combining membrane separation, hydrogen-rich boiler, alkali washing and drying, and pressure swing adsorption processes. At the same time, the boiler can provide 2100 kW of energy for the natural gas refinery. When the positive pressure is within the preferred range, the product purity is higher.

[0075] Example 5

[0076] Helium was recovered according to the method of Example 1, except that the composition of the raw material gas (S1) was as follows: helium 1.8 vol%, hydrogen 30.5 vol%, nitrogen 28.5 vol%, oxygen 2.68 vol%, carbon monoxide 5.62 vol%, methane 27.4 vol%, and carbon dioxide 3.5 vol%.

[0077] The separation membrane used in the first membrane separation was a hollow fiber membrane made of polyimide material. The helium / methane separation coefficient of the membrane was 131, and the hydrogen / methane separation coefficient was 68. The positive pressure of the membrane separation was 2000 kPa.

[0078] The separation membrane used in the second membrane separation was a hollow fiber membrane made of polyimide material. The helium / methane separation coefficient of the membrane was 131, and the hydrogen / methane separation coefficient was 68. The separation process selected a single-stage membrane separation process, and the positive pressure was 1500 kPa.

[0079] The main gas compositions of each step of helium purification are shown in Table 5.

[0080] Table 5 Gas composition table at each stage (gas composition%)

[0081] Number He <![CDATA[H 2 > <![CDATA[N 2 > <![CDATA[O 2 > CO <![CDATA[CH 4 > <![CDATA[CO 2 > <![CDATA[H 2 O]]> S1 1.8 30.5 28.5 2.68 5.62 27.4 3.5 0 S2 5.67 84.18 3.27 0.31 0.64 3.15 2.78 0 S3 53.99 8.02 31.19 4.55 0.25 0.6 1.23 0.17 S4 80.99 11.79 5.24 0.77 0.04 0.1 1.04 0.03 S5 99.96 0.03 <0.01 <0.01 0 0 <0.01 0

[0082] As can be seen from the above table, through the process technology of the present invention, high-purity helium gas products with a purity of 99.96% can be obtained by combining membrane separation, hydrogen-rich boiler, alkali washing and drying, and pressure swing adsorption processes. At the same time, the boiler can provide 2800 kW of energy for the natural gas refinery.

[0083] Example 6

[0084] Helium was recovered according to the method of Example 1, except that both the first membrane separation and the second membrane separation selected polycarbonate flat membranes. The helium / methane separation coefficient of the membrane was 18, and the hydrogen / methane separation coefficient was 11.

[0085] The main gas compositions of each step of helium purification are shown in Table 6.

[0086] Table 6 Gas composition table at each stage (gas composition%)

[0087]

[0088]

[0089] As can be seen from the above table, through the process technology of the present invention, high-purity helium gas products with a purity of 99.83% can be obtained by combining a boiler, caustic washing and drying, and pressure swing adsorption processes. At the same time, the boiler can provide 2200 kW of energy for a natural gas refinery. By comparing with the data of Example 1, it can be seen that when using a preferred separation membrane for helium purification, the helium concentration and the quality of the product are higher than those of the helium gas and products separated by a non-preferred separation membrane.

[0090] Comparative Example 1

[0091] Recover helium according to the method of Example 1, the difference is that: the raw material gas is not subjected to the first membrane separation and is directly burned by the boiler. Since the hydrogen content does not meet the standard of a hydrogen-rich boiler, this boiler adopts a traditional boiler structure.

[0092] The main gas compositions of each step of helium purification are shown in Table 7.

[0093] Table 7 Gas Composition Table at Each Stage (Gas Composition %)

[0094] Number He <![CDATA[H 2 > <![CDATA[N 2 > <![CDATA[O 2 > CO <![CDATA[CH 4 > <![CDATA[CO 2 > <![CDATA[H 2 O]]> S1 0.7 28.4 30.19 3.17 7.7 26.34 3.5 0 S3 2.11 0.85 90.92 1.35 0.93 1.58 2.21 0.05 S4 30.41 11.96 40.38 0.6 0.41 0.71 15.51 0.02 S5 99.73 0.08 0.13 <0.01 <0.01 <0.01 0.05 0

[0095] As can be seen from the above table, through the process technology of the present invention, high-purity helium gas products with a purity of 99.73% can be obtained by combining a boiler, caustic washing and drying, and pressure swing adsorption processes. At the same time, the boiler can provide 1700 kW of energy for a natural gas refinery. Under the condition of no first membrane separation, the energy generated by the boiler combustion decreases, and the effect of helium purification also decreases accordingly. At the same time, the demand for the separation membrane area in this process increases several times, and the cost increases significantly.

[0096] Comparative Example 2

[0097] Recover helium according to the method of Example 1, the difference is that: after the raw material gas is subjected to the first membrane separation, it does not undergo boiler combustion and directly enters the caustic washing and drying and the subsequent second membrane separation unit.

[0098] The main gas compositions of each step of helium purification are shown in Table 8.

[0099] Table 8 Gas Composition Table at Each Stage (Gas Composition %)

[0100] Number He <![CDATA[H 2 > <![CDATA[N 2 > <![CDATA[O 2 > CO <![CDATA[CH 4 > <![CDATA[CO 2 > <![CDATA[H 2 O]]> S1 0.7 28.4 30.19 3.17 7.7 26.34 3.5 0 S2 2.7 88.29 2.93 0.31 0.75 2.55 2.47 0 S3 2.77 90.49 3 0.31 0.76 2.62 0.05 0 S4 4.85 95.15 <0.01 0 <0.01 <0.01 <0.01 0 S5 96.22 3.78 0 0 0 0 0 0

[0101] As can be seen from the above table, by using the recovery method of Comparative Example 2, a helium product with a purity of 96.22% is obtained, which cannot meet the high-purity standard and cannot provide boiler combustion energy for the refinery at the same time. The lack of a hydrogen-rich boiler will make it difficult to remove hydrogen, resulting in a significant decline in the quality of the product helium.

[0102] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including the combination of each technical feature in any other suitable manner. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for recovering helium from natural gas refinery tail gas, wherein: The method comprises: (1) The tail gas from a natural gas refinery is separated by the first membrane; (2) decarbonizing the permeate side gas separated by the first membrane after combustion, and drying the decarbonized gas; (3) the dried gas is subjected to a second membrane separation; (4) The permeate side gas separated by the second membrane is subjected to pressure swing adsorption to obtain high-purity helium.

2. The recycling method according to claim 1, wherein: In step (1), the helium content in the natural gas refinery tail gas is 0.1-2 vol%, preferably 0.5-2 vol%; And / or, the hydrogen content in the natural gas refinery tail gas is 15-60 vol%.

3. The recycling method according to claim 1, wherein: In step (1), the first membrane separation selectively permeates helium and hydrogen; the separation membrane used in the first membrane separation is selected from at least one of a flat membrane, a hollow fiber membrane and a tubular membrane; Preferably, the material of the separation membrane used for the first membrane separation is selected from at least one of polysulfone, polyethersulfone, polyimide, polypropylene, polyethylene, synthetic resin, polyvinylidene fluoride, polytetrafluoroethylene, polyetheretherketone, polybenzimidazole, polydimethylsiloxane, cellulose acetate, polycarbonate, polymethyl methacrylate, silicon dioxide, zeolite molecular sieve, carbon molecular sieve, and metal organic framework materials; Preferably, the separation membrane used in the first membrane separation is a hollow fiber membrane made of polyimide or a flat membrane made of polybenzimidazole.

4. The recycling method according to claim 1, wherein: In step (1), in the first membrane separation, the pressure on the positive pressure side of the membrane separation is 200-3000 kPa; preferably 500-2000 kPa; And / or, the pressure on the permeate separation side of the first membrane is lower than the pressure on the positive pressure side.

5. The recycling method according to claim 1, wherein: In step (2), the combustion equipment is selected from one of ordinary boilers, flue combustion and hydrogen-rich boilers; preferably a hydrogen-rich boiler; Preferably, the first membrane separation makes the hydrogen concentration in the permeate-side gas greater than 80%.

6. The recycling method according to claim 1, wherein: In step (2), the decarbonization is carried out in an alkaline absorption tower; Preferably, the alkaline absorption tower is selected from a packed tower, a plate tower, a spray tower, a bubbling tower or a liquid column tower; more preferably, it is a packed tower.

7. The recycling method according to claim 1, wherein: In step (3), the second membrane separation selectively permeates helium and hydrogen, and the separation membrane used in the second membrane separation is selected from at least one of a flat membrane, a hollow fiber membrane and a tubular membrane; Preferably, the material of the separation membrane used for the second membrane separation is selected from at least one of polysulfone, polyethersulfone, polyimide, polypropylene, polyethylene, synthetic resin, polyvinylidene fluoride, polytetrafluoroethylene, polyetheretherketone, polybenzimidazole, polydimethylsiloxane, cellulose acetate, polycarbonate, polymethyl methacrylate, silicon dioxide, zeolite molecular sieve, carbon molecular sieve, and metal organic framework materials; Preferably, the separation membrane used in the second membrane separation is a hollow fiber membrane made of polyimide or a flat membrane made of polybenzimidazole.

8. The recycling method according to claim 1, wherein: In step (3), in the second membrane separation, the pressure on the positive pressure side of the membrane separation is 500-5000 kPa; preferably 1000-3000 kPa; And / or, the pressure on the permeate separation side of the second membrane is lower than the pressure on the positive pressure side.

9. The recovery method according to claim 1, 3 or 7, wherein: The separation membranes used in the first membrane separation and the second membrane separation are the same or different, and the separation membranes used in the first membrane separation and the second membrane separation each independently meet the following requirements: helium flux is 200-500 GPU, helium / methane separation coefficient is 100-200; hydrogen / methane separation coefficient is 40-80.

10. The recycling method according to claim 1, wherein: In step (4), the adsorbent in the pressure swing adsorption is selected from at least one of activated carbon, molecular sieve, and metal organic framework material; And / or, the pressure of the pressure swing adsorption is 0.5-10 MPa.

Images