Method for preparing helium by combining oxidation method with membrane separation
阅读说明：本技术 氧化法结合膜分离制备氦气的方法 (Method for preparing helium by combining oxidation method with membrane separation ) 是由 魏昕 郦和生 张新妙 孟凡宁 于 2020-05-22 设计创作，主要内容包括：本发明涉及提氦领域,公开了一种氧化法结合膜分离制备氦气的方法,该方法包括：(1)将含有氦气的原料气进行氧化处理得到混合物I；(2)将所述混合物I依次进行脱水处理、除氧处理以得到混合物II；(3)将所述混合物II经过至少一级膜进行膜分离提纯以制得纯化氦气。该方法避免了深冷技术对设备和能耗的极高要求,可较大幅度的降低建设和运行成本,使得纯化氦气制备过程更加经济。(The invention relates to the field of helium extraction, and discloses a method for preparing helium by combining an oxidation method with membrane separation, which comprises the following steps: (1) carrying out oxidation treatment on a helium-containing feed gas to obtain a mixture I; (2) sequentially carrying out dehydration treatment and deoxidization treatment on the mixture I to obtain a mixture II; (3) and (3) performing membrane separation and purification on the mixture II through at least one stage of membrane to obtain purified helium. The method avoids the extremely high requirements of cryogenic technology on equipment and energy consumption, and can greatly reduce the construction and operation cost, so that the preparation process of the purified helium is more economic.)
1. A method for producing helium by oxidation coupled with membrane separation, the method comprising:
(1) carrying out oxidation treatment on a helium-containing feed gas to obtain a mixture I;
(2) sequentially carrying out dehydration treatment and deoxidization treatment on the mixture I to obtain a mixture II;
(3) and (3) performing membrane separation and purification on the mixture II through at least one stage of membrane to obtain purified helium.
2. The method according to claim 1, characterized in that the oxidation treatment is carried out by means of combustion and/or catalytic oxidation;
preferably, the combustion is selected from at least one of direct combustion and regenerative combustion;
preferably, the oxidation treatment is by pure oxygen assisted oxidation.
3. The method according to claim 1 or 2, wherein the dehydration treatment is performed by at least one of condensation, adsorption, and absorption;
preferably, the adsorption in the dehydration treatment is performed using at least one of a water-absorbent resin, plant ash, and activated carbon;
preferably, the absorption in the dehydration treatment is performed using at least one of alkali, concentrated sulfuric acid, soda lime, and anhydrous calcium chloride.
4. The method according to any one of claims 1 to 3, wherein the dehydration treatment is carried out by means of condensation, and the temperature of the mixture I after condensation is lower than 90 ℃;
preferably, the conditions of the dehydration treatment are controlled so that the content of water vapor of the mixture I after the dehydration treatment is less than 1.8 vol%.
5. The method according to any one of claims 1 to 4, wherein the oxygen removal treatment is performed by at least one of adsorption and absorption;
preferably, the adsorption in the oxygen removal treatment is performed by using at least one of activated carbon, carbon molecular sieves, silica gel and zeolite molecular sieves;
preferably, the absorption in the oxygen removal treatment is performed by using at least one of ferrous oxide, ferrous chloride, ferrous sulfate and nano-iron;
preferably, the oxygen removal treatment is performed in a molecular sieve absorber.
6. The method according to any one of claims 1 to 5, wherein the conditions of the oxygen removal treatment are controlled so that the oxygen content of the mixture I after the oxygen removal treatment is 2% by volume or less.
7. The method according to any one of claims 1 to 6, wherein the film is prepared from at least one of a synthetic resin and a metal organic framework material;
preferably, the synthetic resin is selected from at least one of polysulfone, polyethersulfone, polyimide, polypropylene, polyethylene, synthetic resin, polyvinylidene fluoride, polytetrafluoroethylene, polyetheretherketone, and polydimethylsiloxane;
preferably, the synthetic resin is selected from at least one of an alternating copolymer, a block copolymer and a graft copolymer;
preferably, the membrane is a homogeneous membrane and/or a non-homogeneous membrane;
preferably, the membrane is at least one of a flat sheet membrane, a hollow fiber and a tubular membrane.
8. The process according to any one of claims 1 to 6, wherein the membrane has a number of stages of 2 or more, preferably 2 to 20 stages, more preferably 2 to 3 stages.
9. A method according to any one of claims 1 to 7, wherein during the membrane separation process the pressure across each membrane stage is such that: the positive pressure side pressure is 0.01-50MPa, preferably 0.2-2.0 MPa;
preferably, the pressure on both sides of each stage of membrane satisfies: the pressure difference between the permeation side pressure and the positive pressure side pressure is 0.1-20 MPa, preferably 0.3-2.1 MPa.
10. The method according to any one of claims 1 to 9, wherein the membrane separation purification is performed by using a membrane having more than 2 stages, and after the mixed gas passes through one of the stages of the membrane, the method further comprises: pressurizing the mixed gas, and then feeding the pressurized mixed gas into a next-stage membrane for membrane separation and purification.
11. The method of any one of claims 1-10, wherein the feed gas is at least one of natural gas, oilfield associated gas, chemical waste gas, and flash gas obtained by processing natural gas;
preferably, the volume fraction in helium in the feed gas is between 5 and 20%.
Technical Field
The invention relates to the field of helium extraction, in particular to a method for preparing helium by combining an oxidation method with membrane separation.
Background
Helium is a very important industrial gas because of its extremely stable chemical properties, strong diffusibility, good thermal conductivity, low solubility and low latent heat of vaporization. Due to its unique properties, helium has wide application in the fields of low temperature, aerospace, electronic industry, biomedical and nuclear facilities, etc., and is one of the important basic materials for the development of national security and high technology industries. With the continuous development of economy, the demand of helium in China also rapidly increases. At present, helium in China mainly depends on imports; in order to meet the demand of national economic development on helium resources and the strategic demand of national defense safety, a method for preparing high-concentration helium with low energy consumption is urgently needed to be developed.
Helium extraction processes are classified into cryogenic processes and non-cryogenic processes. The cryogenic process is a common method for industrialization at present. The cryogenic process has the problems of strict design and manufacturing requirements on equipment, higher construction and operation cost, high energy consumption and the like in the process of extracting helium from natural gas, and meanwhile, the economic benefit is not competitive.
Disclosure of Invention
The invention aims to solve the problems of harsh equipment, higher cost and high energy consumption in the existing cryogenic process.
In order to achieve the above object, the present invention provides a method for producing helium by an oxidation process combined with membrane separation, the method comprising:
(1) carrying out oxidation treatment on a helium-containing feed gas to obtain a mixture I;
(2) sequentially carrying out dehydration treatment and deoxidization treatment on the mixture I to obtain a mixture II;
(3) and (3) performing membrane separation and purification on the mixture II through at least one stage of membrane to obtain purified helium.
In addition, when hydrogen exists in raw material gas, the separation effect is poor because the condensation temperature of the hydrogen and the helium is very low, and the high-purity helium is difficult to prepare.
However, in the invention, firstly, light hydrocarbons such as methane and the like and hydrogen in the raw material gas are converted into carbon dioxide and water vapor by an oxidation method (preferably a combustion method), and because the physical and chemical properties of the carbon dioxide, the water vapor and the helium have large differences with the helium, the water vapor, the oxygen and the helium can be separated by dehydration treatment, oxygen removal treatment and membrane separation; then separating nitrogen, carbon dioxide, water vapor, oxygen and the like in the raw materials from helium through membrane separation operation, and finally preparing a helium product; the purity of the helium product prepared by the method is over 90 volume percent, and the purity of the helium product in most embodiments can reach over 99 volume percent.
Furthermore, the membrane separation in the method provided by the invention has the advantages of low energy consumption, low investment cost, stable operation, mild conditions and the like, and can greatly reduce the energy consumption in the helium separation process; and the prepared helium concentration is not influenced by hydrogen, and can reach higher concentration. Particularly, the membrane separation can be directly operated under the conditions of normal temperature and low pressure to concentrate helium, so that the extremely high requirements of a cryogenic technology on equipment and energy consumption are avoided, the construction and operation cost can be greatly reduced, and the helium preparation process is more economical.
The invention solves the problem of helium purification, can realize high-efficiency utilization of helium resources such as natural gas, oilfield associated gas, chemical industry and other waste gases, and has very high value of the prepared purified helium and very wide application prospect.
Drawings
FIG. 1 is a process flow diagram of a preferred embodiment of the oxidation process coupled with membrane separation provided by the present invention for producing helium.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The invention provides a method for preparing helium by combining an oxidation method with membrane separation, which comprises the following steps:
(1) carrying out oxidation treatment on a helium-containing feed gas to obtain a mixture I;
(2) sequentially carrying out dehydration treatment and deoxidization treatment on the mixture I to obtain a mixture II;
(3) and (3) performing membrane separation and purification on the mixture II through at least one stage of membrane to obtain purified helium.
In the above method, the order of the dehydration treatment and the oxygen removal treatment is not critical, and the dehydration treatment may be performed first or the oxygen removal treatment may be performed first.
In the above method, it is preferable that the oxidation treatment is carried out by combustion and/or catalytic oxidation from the viewpoint of efficiency of oxidation; wherein, to further facilitate real-time combustion, more preferably, the combustion is selected from at least one of direct combustion and thermal combustion. In order to further accelerate the oxidation rate and at the same time avoid the introduction of impurity gases, it is further preferred that the oxidation process is assisted by pure oxygen (pure oxygen has the advantage of not increasing the excess nitrogen composition and reducing the load on the subsequent separation process).
Meanwhile, in the invention, in order to facilitate the implementation of the dehydration treatment, it is preferable that the dehydration treatment is performed by at least one of condensation, adsorption, and absorption.
Wherein, in order to further facilitate the implementation of the adsorption in the dehydration treatment, it is preferable that the adsorption in the dehydration treatment is performed using at least one of a water absorbent resin, plant ash, and activated carbon.
Wherein, in order to further facilitate the implementation of the absorption in the dehydration treatment, the absorption in the dehydration treatment is performed by using at least one of alkali, concentrated sulfuric acid, soda lime and anhydrous calcium chloride. In the present invention, the concentrated sulfuric acid is a sulfuric acid solution having a concentration of 70 wt% or more unless otherwise specified.
Wherein, in order to further facilitate the implementation of condensation in the dehydration treatment, preferably, the dehydration treatment is performed in a condensation manner, and the temperature of the mixture I after condensation is lower than 90 ℃.
In the above embodiment, the concentration of the water vapor after the dehydration treatment can be changed accordingly by controlling the conditions of the dehydration treatment, and in order to further reduce the content of the water vapor in the helium product produced, it is preferable to control the conditions of the dehydration treatment so that the content of the water vapor after the mixture I is dehydrated is less than 1.8 vol%.
In the present invention, in order to further facilitate the implementation of the oxygen removal treatment, it is preferable that the oxygen removal treatment is performed by at least one of adsorption and absorption.
Wherein, in order to further facilitate the adsorption in the oxygen removal treatment, preferably, the adsorption in the oxygen removal treatment is performed using at least one of activated carbon, carbon molecular sieve, silica gel, and zeolite molecular sieve.
Similarly, in order to further facilitate the absorption in the oxygen removal treatment, the absorption in the oxygen removal treatment is performed by using at least one of ferrous oxide, ferrous chloride, ferrous sulfate and nano-iron; more preferably, the oxygen removal treatment is performed in a molecular sieve absorber.
In the above embodiment, the concentration of water vapor after dehydration treatment can be changed accordingly by controlling the conditions of dehydration treatment, and in order to further reduce the oxygen content in the produced helium product, it is preferable to control the conditions of oxygen removal treatment so that the oxygen content of mixture I after oxygen removal treatment is 2 vol% or less.
In the present invention, in order to further improve the selectivity of the membrane to helium and impurity gases, it is preferable that the membrane is prepared from at least one material of a synthetic resin and a metal-organic framework material; more preferably, the synthetic resin is selected from at least one of polysulfone, polyethersulfone, polyimide, polypropylene, polyethylene, synthetic resin, polyvinylidene fluoride, polytetrafluoroethylene, polyetheretherketone, and polydimethylsiloxane; further preferably, the synthetic resin is at least one selected from the group consisting of an alternating copolymer, a block copolymer and a graft copolymer.
In addition, in order to further improve the selectivity of the membrane to helium, preferably, the membrane is a homogeneous membrane and/or a heterogeneous membrane;
in addition, in order to further improve the selectivity of the membrane to helium, it is preferable that the membrane is at least one of a flat sheet membrane, a hollow fiber and a tubular membrane.
In the present invention, in order to further increase the helium concentration in the helium product produced, it is preferred that the number of stages of the membrane be 2 or more, preferably 2 to 20 stages, more preferably 2 to 3 stages.
In the membrane separation process of the above embodiment, in order to further increase the helium concentration in the produced helium product while considering the tolerance range of the membrane module and the equipment, it is preferable that the pressure across each stage of membrane satisfies, during the membrane separation process: the pressure at the positive pressure is 0.01-50MPa, preferably 0.2-2.0 MPa in view of the requirement on equipment, and preferably 4.0-5.0 MPa in view of the purification effect; further preferably, the pressure on both sides of each stage of membrane satisfies: the pressure difference between the permeation side pressure and the positive pressure side pressure is 0.1-20 MPa, preferably 0.3-2.1 MPa in terms of equipment requirements, and preferably 10-20 MPa in terms of purification effect, wherein the permeation side pressure is either atmospheric pressure or negative pressure, and is negative pressure in most cases, for example, the permeation side pressure is-0.1 MPa when the positive pressure is 0.2 MPa.
In the above embodiment, in order to further increase the helium concentration in the produced helium product, preferably, the membrane separation purification is performed by using a membrane with more than 2 stages, and after the mixed gas passes through one of the stages of membranes, the method further comprises: pressurizing the mixed gas, and then feeding the pressurized mixed gas into a next-stage membrane for membrane separation and purification.
Finally, in order to improve the method and enable the method to be further popularized, preferably, the raw material gas is at least one of natural gas, oilfield associated gas, chemical waste gas and flash steam obtained by processing natural gas. More preferably, the volume fraction in helium in the feed gas is between 5 and 20%.
The present invention will be described in detail below by way of examples. In the following examples, helium, methane, nitrogen, CO2The concentrations of hydrogen, water and oxygen were determined by gas chromatography.
Example 1
In natural gas produced at a field, the volume fraction of helium is 8.5%, and the concentrations of other gases are 35% by volume methane, 37.3% by volume nitrogen, 2.1% by volume hydrogen, 7.6% by volume carbon dioxide, and 9.5% by volume oxygen, respectively.
The technology of the invention is adopted to carry out direct combustion and step-by-step treatment and concentration processes (the step-by-step treatment and concentration processes comprise dehydration treatment, oxygen removal treatment and membrane separation) on the gas produced by the gas field. The waste gas after combustion is directly sent into the subsequent processes of cooling, water removal, oxygen removal and membrane separation through pipelines.
Oxidation treatment: adopts a direct combustion mode and adopts pure oxygen as combustion-supporting gas in the combustion process.
And (3) dehydration treatment: and (3) cooling by using circulating water to remove water, wherein the temperature of the water-cooled gas is 89 ℃, the condensed water is taken out and then introduced into water-absorbent resin to remove gaseous water, and the content of water vapor after dehydration is 1.4 volume percent.
And (3) deoxidizing treatment: and (3) deoxidizing by adopting a molecular sieve adsorption tower, and if the deoxidizing does not reach the preset effect, repeatedly adsorbing by using the molecular sieve adsorption tower to reduce the oxygen concentration to 0.1 volume percent.
Membrane separation: the hollow fiber membrane component made of polyimide is adopted to carry out primary and secondary membrane separation operation on the deaerated gas. The pressure on two sides of each membrane satisfies the following conditions: the pressure of the primary membrane at the positive pressure is 0.2Mpa, the permeation side is operated at negative pressure, the pressure is-0.09 Mpa, and the pressure difference between the permeation side pressure and the pressure at the positive pressure is 0.29Mpa (the permeation side is added with vacuum of 0.09 Mpa). The secondary membrane adopts the gas at the permeation side of the primary membrane as raw material gas, the pressure of the positive pressure side of the secondary membrane is increased to 0.2Mpa by a compressor, the permeation side adopts negative pressure operation, the pressure is-0.09 Mpa, and the pressure difference between the permeation side pressure and the positive pressure side pressure is 0.29Mpa (the permeation side is added with vacuum of 0.09 Mpa). The gas composition of each step is detailed in table 1.
TABLE 1
Composition volume%
Helium gas
Methane
Nitrogen gas
CO2
Hydrogen gas
Water (W)
Oxygen gas
Raw material gas
8.5
35
37.3
7.6
2.1
0.1
9.5
After burning
5.1
0.1
22.4
25.4
1.3
42.0
3.7
Cooling to remove water
9.1
0.1
39.9
40.7
2.2
1.4
6.6
After deoxidization
9.7
0.1
42.6
43.6
2.4
1.5
0.1
Primary membrane
94.2
0
2.2
1.6
1.9
0.1
0
Second-order film
99.88
0
0.01
0.01
0.1
0
0
As can be clearly seen from the above table: the process technology can effectively convert hydrogen and methane two kinds of micromolecular combustible gases which are difficult to separate from helium in mixed gas into CO easy to separate from helium through a combustion section2And water vapor, the concentration of hydrogen can be reduced to 1.3% of volume fraction, the helium concentration in the feed gas is increased to 9.7% by volume through cooling water removal and oxygen removal operations, nitrogen and carbon dioxide are separated from helium after separation by a primary membrane, the helium concentration is increased to 94.2% by volume, the helium concentration is increased to 99.88% by volume after separation by a secondary membrane, the hydrogen concentration is 0.1% by volume, and the nitrogen and carbon dioxide are 0.01% by volume respectively.
Example 2
The flash gas (BOG) of a liquefied natural gas station has a gas composition of 15.7% by volume of helium, and concentrations of other gases of 19.9% by volume of methane, 57.7% by volume of nitrogen, 6.65% by volume of hydrogen, and 0.05% by volume of carbon dioxide, respectively.
The technology of the invention is adopted to carry out oxidation and step-by-step treatment concentration processes (the step-by-step treatment concentration process comprises dehydration treatment, oxygen removal treatment and membrane separation) on the flash steam (BOG) of the natural gas station.
Oxidation treatment: the method is carried out by adopting a heat accumulation combustion mode, and pure oxygen is adopted as combustion-supporting gas in the combustion process. The waste gas after combustion is directly sent into the subsequent processes of cooling, water removal, oxygen removal and membrane separation through pipelines.
And (3) dehydration treatment: circulating water cooling is adopted, the temperature of the gas after water cooling is 89 ℃, condensed water is taken out and then is introduced into water-absorbing resin to remove gaseous water, and the content of water vapor after dehydration is 0.07 volume percent.
And (3) deoxidizing treatment: and in the deoxidization stage, a molecular sieve adsorption tower is used for deoxidization, and if the deoxidization does not reach the preset effect, the molecular sieve adsorption tower is used for repeated adsorption, so that the oxygen concentration is reduced to 1.13 vol%.
Membrane separation: the hollow fiber membrane component made of polyimide is adopted to carry out primary and secondary membrane separation operation on the deaerated gas. The pressure on two sides of each membrane satisfies the following conditions: the pressure of the primary membrane positive pressure is 50.0Mpa, the pressure of the primary membrane permeation side is 40.0Mpa, and the primary membrane differential pressure is 10.0 Mpa; the air outlet at the permeation side of the primary membrane is used as a material at the positive pressure side of the secondary membrane, the air inlet pressure is 40.0Mpa, the pressure at the permeation side of the secondary membrane is 20.0Mpa, and the pressure difference of the secondary membrane is 20.0 Mpa; the material at the secondary membrane permeation side is used as the material at the tertiary membrane positive pressure side, the pressure is 20.0Mpa, the pressure at the tertiary membrane permeation side is 0.5Mpa, and the pressure difference between the two is 19.50 Mpa. The gas composition of each step is detailed in table 2.
TABLE 2
Composition volume%
Helium gas
Methane
Nitrogen gas
Hydrogen gas
CO2
Water (W)
Oxygen gas
Raw material gas
15.7
19.9
57.7
6.65
0.05
0
0
After burning
10.88
0.14
39.97
0.03
13.65
31.87
3.46
Cooling to remove water
15.76
0.20
57.91
0.05
18.77
0.07
7.24
After deoxidization
16.88
0.22
61.57
0.05
20.09
0.06
1.13
Primary membrane
98.53
0.02
1.23
0.01
0.2
0.008
0.002
Second-order film
99.97
0
0.024
0.002
0.002
0
0
Three-stage film
＞99.99
0
＜0.001
＜0.001
＜0.001
0
0
As can be clearly seen from the above table, the process technology of the invention can effectively convert hydrogen and methane two kinds of small molecule combustible gases which are difficult to separate from helium in the mixed gas into CO which is easy to separate from helium through the combustion section2And water vapor, the concentration of hydrogen can be reduced to 0.03% of volume fraction, the helium concentration in the feed gas is increased to 16.88% by volume through cooling water removal and oxygen removal operations, the residual hydrogen, nitrogen and carbon dioxide are greatly reduced through primary membrane separation operations, so that the helium concentration is increased to 98.53% by volume, the helium concentration is increased to 99.97% by volume after passing through a secondary membrane, the concentrations of methane, nitrogen, hydrogen, carbon dioxide and the like are all lower than 0.001% by volume after passing through three-stage membrane separation, and the helium concentration reaches high purity of 99.99% by volume.
Example 3
After pretreatment (two-stage flash) of the natural gas produced at a field, the volume fraction of helium was 19.7%, and the concentrations of other gases were 15.9% by volume methane, 53.7% by volume nitrogen, 0.05% by volume hydrogen, 10.65% by volume carbon dioxide, 0.05% by volume oxygen, water, and other light hydrocarbons were not detected.
The technology of the invention is adopted to carry out oxidation and step-by-step treatment and concentration processes (the step-by-step treatment and concentration processes comprise dehydration treatment, oxygen removal treatment and membrane separation) on the gas produced by the gas field.
Oxidation treatment: the method adopts a direct combustion mode, pure oxygen is adopted as combustion-supporting gas in the combustion process, and the combusted waste gas is directly sent into the gas storage cabinet through a pipeline.
And (3) dehydration treatment: precooling by a precooler, reducing the temperature of the gas to 120 ℃, and then entering into the processes of cooling water removal, deoxidization and membrane separation. Cooling and dewatering by adopting circulating water, reducing the temperature of the combusted gas to 80 ℃, and introducing water-absorbent resin to remove gaseous water after removing condensed water;
and (3) deoxidizing treatment: and (3) deoxidizing by adopting a molecular sieve adsorption tower, and if the deoxidizing does not reach the preset effect, repeatedly adsorbing by using the molecular sieve adsorption tower to reduce the oxygen concentration to 0.92 volume percent.
Membrane separation: and (3) performing secondary membrane separation operation on the deaerated gas by adopting a polysulfone hollow fiber homogeneous membrane component. The pressure on two sides of each membrane satisfies the following conditions: the positive pressure side pressure is 0.01Mpa, the permeation side pressure is-0.09 Mpa, and the pressure difference between the permeation side pressure and the positive pressure side pressure is 0.1 Mpa. After the pressure of the permeation side gas of the primary membrane is increased by a compressor, the gas enters the secondary membrane to be used as positive pressure gas inlet, the gas inlet pressure is 0.2Mpa, the pressure of the permeation side of the secondary membrane is-0.09 Mpa, the pressure difference of the secondary membrane is 0.29Mpa, and the gas components in each step are shown in Table 3 in detail.
TABLE 3
Composition volume%
Helium gas
Methane
Nitrogen gas
Hydrogen gas
CO2
Water (W)
Oxygen gas
Raw material gas
19.7
15.9
53.7
10.65
0.05
0
0
After burning
14.45
0.15
39.38
0.04
11.51
30.80
3.67
Cooling to remove water
20.68
0.21
56.36
0.05
15.47
0.07
7.16
After deoxidization
22.07
0.22
60.15
0.06
16.52
0.06
0.92
Primary membrane
92.87
0.27
4.22
0.11
2.5
0.01
0.02
Second-order film
99
0.1
0.4
0.2
0.3
0
0
As can be clearly seen from the above table, the process technology of the invention can effectively convert hydrogen and methane two kinds of small molecule combustible gases which are difficult to separate from helium in the mixed gas into CO which is easy to separate from helium through the combustion section2And water vapor, the concentration of hydrogen can be reduced to 0.04% of volume fraction, the helium concentration in the feed gas is increased to more than 22.07 volume percent through cooling, water removal and oxygen removal operations, nitrogen and carbon dioxide are separated from helium after the separation of the primary membrane, the helium concentration is increased to 92.87%, the helium concentration is increased to 99 volume percent after the separation of the secondary membrane, and the hydrogen concentration is 0.2 volume percent.
Example 4
After pretreatment (two-stage flash) of the natural gas produced at a field, the volume fraction of helium was 19.7%, and the concentrations of the other gases were 15.9% by volume methane, 53.7% by volume nitrogen, 10.65% by volume hydrogen, and 0.05% by volume carbon dioxide, respectively.
Oxidation treatment: the natural gas flash gas in two stages is first supplemented with air to a concentration sufficient for oxidation to occur, at which point the oxygen concentration in the gas is 15 vol%). The hydrogen and methane are removed by a direct combustion method.
And (3) dehydration treatment: and then the combusted gas enters a step-by-step treatment and concentration process, the combusted waste gas is directly sent into a gas storage cabinet through a pipeline, and then precooled by a precooler, the temperature is reduced to 120 ℃, and then the gas enters the processes of cooling water removal, deoxidization and secondary membrane separation. Wherein, the cooling and dewatering adopt circulating water cooling, the temperature of the gas after combustion is reduced to 78 ℃, and the condensed water is removed and then is introduced into water-absorbing resin to remove gaseous water.
And (3) deoxidizing treatment: and (3) deoxidizing by adopting a molecular sieve adsorption tower, and if the deoxidizing does not reach the preset effect, repeatedly adsorbing by using the molecular sieve adsorption tower to reduce the oxygen concentration to 0.01 volume percent.
Membrane separation: and (3) performing secondary membrane separation operation on the deaerated gas by adopting a polysulfone hollow fiber homogeneous membrane component. The pressure on two sides of each membrane satisfies the following conditions: the pressure of the primary membrane positive pressure is 1.0Mpa, the vacuum operation pressure of the permeation side is-0.1 Mpa, and the pressure difference between the permeation side pressure and the positive pressure is 1.1 Mpa. The permeation side of the primary membrane is used as a positive pressure side material of the secondary membrane, the positive pressure side pressure is 2.0Mpa, the permeation side pressure is 0Mpa, and the pressure difference is 2.0 Mpa. The gas composition of each step is detailed in table 4.
TABLE 4
Composition volume%
Helium gas
Methane
Nitrogen gas
Hydrogen gas
CO2
Water (W)
Oxygen gas
Raw material gas
19.7
15.9
53.7
10.65
0.05
0
0
After burning
3.91
0.02
83.18
0.17
3.14
8.21
1.37
Cooling to remove water
4.25
0.02
90.34
0.18
3.13
0.59
1.49
After deoxidization
4.31
0.02
91.70
0.18
3.18
0.60
0.01
Primary membrane
38.03
0.02
60.9
0.34
0.16
0.3
0.25
Second-order film
90
0.01
9.8
0.06
0.09
0.03
0.01
As can be clearly seen from the above table, the process technology of the invention can effectively convert hydrogen and methane two kinds of small molecule combustible gases which are difficult to separate from helium in the mixed gas into CO which is easy to separate from helium through the combustion section2And water vapor, the concentration of hydrogen can be reduced to 0.17% of volume fraction, water vapor and excessive oxygen are removed through cooling water removal and oxygen removal operations, the helium concentration is increased to 4.31% by volume, the concentrations of nitrogen and carbon dioxide are reduced after separation through a primary membrane, the helium concentration is increased by 38.03% by volume, and the helium concentration is increased to 90% by volume after passing through a secondary membrane. Finally, the hydrogen concentration was 0.06 vol%, the carbon dioxide concentration was 0.09 vol%, and the other off-gas concentrations were less than 0.1 vol%. This gas can be used as crude helium or as a raw material for further production of high purity helium.
Example 5
After pretreatment (two-stage flash) of the natural gas produced at a field, the volume fraction of helium was 19.7%, and the concentrations of other gases were 15.9% by volume methane, 53.7% by volume nitrogen, 0.05% by volume hydrogen, 10.65% by volume carbon dioxide, water, oxygen, and other light hydrocarbons were not detected.
The technology of the invention is adopted to carry out combustion and step-by-step treatment and concentration processes on the gas produced by the gas field.
Oxidation treatment: the method adopts a direct combustion mode, pure oxygen is adopted as combustion-supporting gas in the combustion process, and the combusted waste gas is directly sent into the gas storage cabinet through a pipeline.
And (3) dehydration treatment: the burned waste gas is precooled by a precooler, the temperature is reduced to 100 ℃, and then the waste gas enters the processes of cooling water removal, deoxidization and secondary membrane separation. Wherein, the cooling and dewatering adopt circulating water cooling, the temperature of the gas after burning is reduced to 60 ℃, and the condensed water is introduced into water-absorbing resin to remove gaseous water after being removed.
And (3) deoxidizing treatment: and (3) deoxidizing by adopting a molecular sieve adsorption tower, and if the deoxidizing does not reach the preset effect, repeatedly adsorbing by using the molecular sieve adsorption tower to reduce the oxygen concentration to 0.92 volume percent.
Membrane separation: and (3) performing secondary membrane separation operation on the deaerated gas by adopting a hollow fiber homogeneous membrane prepared from a polyimide material. The pressure on two sides of each membrane satisfies the following conditions: the positive pressure side pressure is 2.0Mpa, the permeation side pressure is 1.0Mpa lower than the positive pressure side pressure, the pressure difference is 1.0Mpa, the secondary membrane takes the gas at the permeation side of the primary membrane as the gas inlet, the positive pressure side pressure is 1.0Mpa, the permeation side pressure is-0.09 Mpa, and the pressure difference is 1.09 Mpa. The gas composition of each step is detailed in Table 5.
TABLE 5
Composition volume%
Helium gas
Methane
Nitrogen gas
Hydrogen gas
CO2
Water (W)
Oxygen gas
Raw material gas
19.7
15.9
53.7
0.05
10.65
0
0
After burning
14.45
0.15
39.38
0.04
11.51
30.8
3.67
Cooling to remove water
20.68
0.21
56.36
0.05
15.48
0.07
7.15
After deoxidization
22.07
0.22
60.15
0.06
16.52
0.06
0.92
Primary membrane
92.87
0.27
4.22
0.11
2.5
0.01
0.02
Second-order film
99.5
0.05
0.2
0.05
0.2
0
0
As can be clearly seen from the above table, the process technology of the invention can effectively convert hydrogen and methane two kinds of small molecule combustible gases which are difficult to separate from helium in the mixed gas into CO which is easy to separate from helium through the combustion section2And water vapor, the concentration of hydrogen can be reduced to 0.04% by volume; the helium concentration in the feed gas is increased to 22 volume percent through cooling water removal and oxygen removal operations; after the primary membrane separation, the nitrogen and carbon dioxide concentrations are continuously increased to 4.22 volume percent and 2.5 percent, and the helium concentration is increased to 92.87 volume percent; after passing through the secondary membrane, the helium concentration is increased to 99.5 volume percent, and the hydrogen concentration is 0.05 volume percent.
Example 6
The procedure was carried out in accordance with example 1, except that the polyimide hollow fiber membrane module was replaced with a polyvinylidene fluoride flat membrane module, and the gas components in each step are shown in Table 6.
TABLE 6
Composition volume%
Helium gas
Methane
Nitrogen gas
CO2
Hydrogen gas
Water (W)
Oxygen gas
Raw material gas
8.5
35
37.3
7.6
2.1
0.1
9.5
After oxidation
4.9
0.1
22.3
25.1
1.7
42.0
3.9
Cooling to remove water
9.5
0.1
39.5
40.7
2.2
1.8
6.2
After deoxidization
9.8
0.1
42.5
43.2
2.2
2.1
0.1
Primary membrane
91.2
0
2.2
3.6
2.9
0.1
0
Second-order film
98.6
0
0.1
0.1
1.2
0
0
Example 7
The procedure was carried out in accordance with example 1 except that the polyimide-based hollow fiber membrane module was replaced with a metal-organic framework tubular membrane module, and the gas components in each step are shown in Table 7.
TABLE 7
Composition volume%
Helium gas
Methane
Nitrogen gas
CO2
Hydrogen gas
Water (W)
Oxygen gas
Raw material gas
8.5
35
37.3
7.6
2.1
0.1
9.5
After oxidation
4.8
0.1
22.3
25.2
1.7
42
3.9
Cooling to remove water
9.1
0.1
39.7
40.6
1.6
1.8
7.1
After deoxidization
9.8
0.1
40.5
45.1
1.6
1.2
1.7
Primary membrane
90.2
0
4.2
3.9
1.6
0.1
0
Second-order film
99.2
0
0.3
0.3
0.2
0
0
Comparative example 1
The natural gas from example 1 was subjected to cryogenic process for helium extraction with the gas composition detailed in table 8. The process comprises compressing raw material gas to 10Mpa, and cooling to-96 deg.C.
TABLE 8
Composition volume%
Helium gas
Methane
Nitrogen gas
CO2
Hydrogen gas
Water (W)
Oxygen gas
Raw material gas
8.5
35
37.3
7.6
2.1
0.1
9.5
Helium gas product
99
0.1
0.1
0.1
1.0
0
0
Wherein the energy consumption for helium production in example 1 was 500 kw/ton, while the operation consumption in example 1 in comparative example 1 was 2500 kw/ton. By comparison, example 1 can reduce energy consumption by 80%.
Comparative example 2
The procedure was carried out as in example 1, except that the combustion treatment and the dehydration treatment were not carried out, and the gas composition in each step is specified in Table 9.
TABLE 9
Composition volume%
Helium gas
Methane
Nitrogen gas
CO2
Hydrogen gas
Water (W)
Oxygen gas
Raw material gas
8.5
35
37.3
7.6
2.1
0.1
9.5
After deoxidization
45.6
27.9
22.5
3.4
0.5
0
0.1
Primary membrane
82.5
10
6.2
1.2
0.1
0
0
Second-order film
9.2
34.3
36.2
8.9
2.6
0.1
8.7
Comparative example 3
The procedure is as in example 1, except that the pressure on both sides of the membranes of each stage satisfies the following conditions: the primary membrane positive pressure side pressure is 0.05Mpa, the permeation side pressure is 0Mpa, and the pressure difference between the primary membrane permeation side pressure and the positive pressure side pressure is 0.05 Mpa. The pressure of the secondary membrane positive pressure is 0.05Mpa, the pressure of the permeation side is 0Mpa, and the pressure difference between the secondary membrane permeation side pressure and the pressure of the positive pressure is 0.05 Mpa. The gas composition of each step is detailed in table 10.
Watch 10
Composition volume%
Helium gas
Methane
Nitrogen gas
CO2
Hydrogen gas
Water (W)
Oxygen gas
Raw material gas
8.5
35
37.3
7.6
2.1
0.1
9.5
After burning
5.1
0.1
22.4
25.4
1.3
42.0
3.7
Cooling to remove water
8.9
3.7
37.3
45.7
1.4
0
3.0
After deoxidization
10.1
3.1
39.6
44.5
2.6
0
0.1
Primary membrane
45.8
2.5
28.5
20.6
2.6
0
0
Second-order film
71.2
5.1
16.1
3.5
4.1
0
0
Compared with the cryogenic process, the method disclosed by the invention not only can extract high-purity helium from the feed gas, but also has very mild requirements on equipment and process conditions, and more importantly, the process disclosed by the invention greatly reduces the energy consumption.
As can be seen from a comparison of example 1 with comparative example 2, the combined combustion process and membrane separation process successfully extracts high purity helium gas from the feed gas.
As can be seen from comparison of example 1 with comparative example 3, the membrane separation effect is not good under the condition that the pressure difference between the membrane positive pressure side pressure, the permeate side pressure and the positive pressure side pressure is small. And under the condition that the pressure difference between the membrane positive pressure side pressure, the permeation side pressure and the positive pressure side pressure is overlarge, the requirement on equipment is overlarge, and the popularization of the invention is not facilitated.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.