Purification method of electronic-grade ultra-pure natural gas

Abstract

The invention provides an electronic-grade ultrapure natural gas purification method. The electronic-grade ultrapure natural gas purification method comprises the following steps that S1, raw natural gas is subjected to dust removal; s2, dehydrating the natural gas subjected to dust removal in S1; s3, performing magnetic fine particle removal treatment on the natural gas dehydrated in the S2; s4, sequentially carrying out dealkylation and decarbonization treatment on the natural gas from which the magnetic fine particles are removed in the step S3; s5, the natural gas subjected to dealkylation and decarbonization in the step S4 enters a magnetic fluidized bed reactor to be subjected to demercuration treatment; and S6, purifying the mercury-removed natural gas obtained in the step S5 through a nano-scale precision filter to obtain the ultra-pure natural gas. According to the method, dust removal and dehydration treatment are performed in sequence, and then dealkylation and decarburization are performed by adopting a double-membrane method, so that efficient and synchronous removal of carbon dioxide and hydrocarbon impurities by the same process is realized; the magnetic fluidized bed reactor is used for carrying out rapid demercuration treatment on the natural gas, so that the demercuration efficiency is improved, the separation and recovery of the catalyst become simple, convenient and efficient, and the preparation of 5N-grade ultra-pure natural gas can be ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of natural gas purification, and particularly to a method for purifying electronic-grade ultra-pure natural gas. Background Art

[0002] As an important source of industrial gas, the raw natural gas usually contains various impurities (such as hydrocarbons, carbon, moisture, particulate matter, mercury, etc.). If it is directly used in semiconductor or electronic manufacturing without deep purification, these impurities may cause equipment damage, process failure, reduction of product yield, and even safety accidents.

[0003] The raw natural gas contains a large amount of dust particulate matter, iron impurities, etc. The particulate matter enters the reaction chamber with the gas flow, scratches the surface of the wafer or deposits on optical components (such as lasers), affecting the lithography accuracy. Especially in the deposition of nanoscale thin films, the particles may embed in the insulating layer (such as SiO2), causing an increase in local conductivity and leading to chip short circuits. Secondly, when the hydrocarbon concentration in the raw natural gas is relatively high, it is prone to explosion in high-temperature, high-pressure or open-fire environments, threatening the safety of the factory. In processes such as CVD and etching, unreacted hydrocarbons may deposit in the chamber, forming carbon films or residues, contaminating the semiconductor substrate. In addition, carbon impurities in the raw natural gas may form pinholes or particles in thin film deposition (such as ALD), affecting the electrical properties of semiconductor devices. Carbon particles are easily deposited in gas pipelines, valves and reaction chambers, resulting in poor gas flow or equipment failure. The moisture in the raw natural gas reacts with metal components (such as tungsten electrodes, stainless steel pipes) at high temperatures to generate oxides (such as Fe2O3), shortening the equipment life. Water vapor condenses on the surface of the photoresist, resulting in blurred patterns or edge defects after development. The moisture decomposes into OH- free radicals in the plasma and reacts with silane (SiH4) to generate SiO2, contaminating the chamber.

[0004] With the development of modern industry, especially in high-end fields such as semiconductors and electronics, the purity requirements for natural gas are becoming increasingly stringent, and the demand for 5N (99.999%) grade ultra-pure natural gas is growing continuously. However, the traditional natural gas purification process has many limitations. For example, conventional decarbonization and dehydrocarbonization methods are difficult to efficiently remove multiple impurities simultaneously, resulting in the difficulty of reaching the 5N grade for the purity of the purified gas; for the removal of iron impurities, ordinary filtration methods cannot meet the requirements of deep purification; in terms of mercury removal, existing technologies often have problems such as incomplete mercury removal, complex processes, and high costs.

[0005] Therefore, it is urgent to develop an efficient, comprehensive and economical ultra-pure natural gas purification process.

[0006] In view of this, it is necessary to improve the natural gas purification method in the prior art to solve the above problems. Summary of the Invention

[0007] The object of the present invention is to disclose a method for purifying electronic-grade ultra-pure natural gas. By removing hydrocarbons and carbon dioxide through a dual-membrane method and then subjecting it to mercury removal treatment in a magnetic fluidized bed reactor, most of the chemical components in natural gas are removed, and 5N-grade ultra-pure natural gas is obtained for use in the electronics industry.

[0008] To achieve the above object, the present invention provides a method for purifying electronic-grade ultra-pure natural gas, comprising the following steps:

[0009] S1: Dust-removing the raw natural gas.

[0010] S2: Dehydrating the natural gas after dust removal in S1.

[0011] S3: Removing magnetic fine particles from the dehydrated natural gas in S2.

[0012] S4: Sequentially removing hydrocarbons and carbon dioxide from the natural gas after removing magnetic fine particles in S3.

[0013] S5: Feeding the natural gas after removing hydrocarbons and carbon dioxide in S4 into a magnetic fluidized bed reactor for mercury removal treatment.

[0014] S6: After purifying the natural gas after mercury removal in S5 through a nano-precision filter, ultra-pure natural gas is obtained.

[0015] In some embodiments, a dust-removing filter is used in S1 to remove dust from the raw natural gas.

[0016] In some embodiments, a coalescing filter is used in S2 to dehydrate the natural gas.

[0017] In some embodiments, a hydrocarbon removal membrane unit and a carbon dioxide removal membrane unit are used in S4 for treatment.

[0018] In some embodiments, a magnetic fluidized bed reactor is used in S5 for mercury removal treatment. A magnetic mercury removal catalyst is provided in the magnetic fluidized bed reactor, and the magnetic mercury removal catalyst is a magnetic composite material with Fe3O4 as the magnetic core.

[0019] In some embodiments, the magnetic mercury removal catalyst is an Fe3O4-based TiS2 / ZnS double-layer loaded magnetic mercury removal catalyst.

[0020] In some embodiments, the operating pressure of the hydrocarbon removal membrane unit is 2 - 3 MPa, the temperature is 20 - 30 °C, the operating pressure of the carbon dioxide removal membrane unit is 2.5 - 3.5 MPa, and the temperature is 25 - 35 °C.

[0021] In some embodiments, the filling amount of the magnetic mercury removal catalyst in the magnetic fluidized bed reactor is 20-40% of the volume of the magnetic fluidized bed reactor, the inlet gas velocity of the magnetic fluidized bed reactor is 0.1-0.3 m / s, the temperature of the magnetic fluidized bed reactor is set at 130-170 °C, and the reaction time is set at 8-15 min.

[0022] In some embodiments, the filtration accuracy of the nanoscale precision filter is 2-10 nm.

[0023] In some embodiments, the filtration accuracy of the coalescing filter is 0.2-1 μm.

[0024] In some embodiments, in S3, a magnetic filter is used for treatment, the magnetic field strength of the magnetic filter is 0.4-0.8 T, and the velocity of the natural gas entering the magnetic filter is 0.4-0.6 m / s.

[0025] In some embodiments, the dehydrocarbonation membrane unit uses a polyvinylidene fluoride membrane and / or a polyethersulfone membrane, and the decarbonation membrane unit uses a membrane material containing an amino functional group.

[0026] In some embodiments, the Fe3O4-based TiS2 / ZnS double-layer supported magnetic mercury removal catalyst comprises an Fe3O4 magnetic core, an intermediate TiS2 layer, and an outer ZnS layer which are distributed in sequence; the particle size of the Fe3O4 magnetic core is 50–100 nm, and the saturation magnetization intensity is 100–110 emu / g; the thickness of the TiS2 layer is 1–3 nm; the thickness of the ZnS layer is 1–3 nm.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: This method first removes dust and water, and then uses a magnetic filter to remove magnetic particles in natural gas to avoid damaging the membrane materials in subsequent processes; the double-membrane method is used for dehydrocarbonation and decarbonation, realizing the efficient and synchronous removal of carbon dioxide and hydrocarbon impurities in the same process; the magnetic fluidized bed reactor and the Fe3O4-based TiS2 / ZnS double-layer supported magnetic mercury removal catalyst are used to quickly remove mercury from natural gas, which not only improves the mercury removal efficiency but also makes the separation and recovery of the catalyst simple and efficient. Finally, as the last process, a nanoscale precision filter provides a more reliable guarantee for the preparation of ultra-pure natural gas, ensuring the preparation of 5N-level ultra-pure natural gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the purification process of electronic-grade ultra-pure natural gas shown in the present invention;

[0029] Figure 2 It is a schematic diagram of the structure of the electronic-grade ultra-pure natural gas purification device shown in the present invention. Detailed Embodiments

[0030] The present invention will be described in detail below in conjunction with the embodiments shown in the accompanying drawings. However, it should be noted that these embodiments are not limitations on the present invention, and any equivalent transformation or substitution in function, method, or structure made by those of ordinary skill in the art according to these embodiments shall fall within the protection scope of the present invention.

[0031] Example 1

[0032] As Figure 1 shown, an electronic-grade ultra-pure natural gas purification device includes a dust removal filter 1, a coalescing filter 2, a magnetic filter 3, a dehydrocarbonation membrane unit 4, a decarbonation membrane unit 5, a magnetic fluidized bed reactor 6, and a nano-precision filter 7 connected in sequence.

[0033] The dust removal filter 1 is a bag filter or a ceramic filter tube filter. In this embodiment, a ceramic filter tube filter is preferably used. According to actual needs, the ceramic filter tube can also be loaded with a catalyst.

[0034] The filtration accuracy of the coalescing filter 2 is 0.2 - 1 μm, and the speed of the natural gas entering the coalescing filter 2 is 8 - 12 m3 / (h·m2).

[0035] The magnetic filter 3 is provided with a first magnetic pole 31, which uses a strong magnetic field to adsorb iron-containing impurities in the natural gas and remove the iron impurities. Removing iron from the natural gas first can prevent iron impurities from entering the subsequent dehydrocarbonation membrane unit 4 and decarbonation membrane unit 5 and scratching the membrane material, resulting in the failure of dehydrocarbonation and decarbonation. In addition, removing iron impurities first can also improve the mercury removal efficiency of the magnetic fluidized bed reactor 6, prevent iron impurities from entering the magnetic fluidized bed reactor 6, and affect the operation of the magnetic mercury removal catalyst, playing a role in iron removal and security.

[0036] The dehydrocarbonation membrane unit 4 uses a polyvinylidene fluoride (PVDF) membrane and / or a polyethersulfone (PES) membrane. In this embodiment, a polyvinylidene fluoride (PVDF) membrane and a polyethersulfone (PES) membrane are preferably used. The PVDF membrane is used as a pre-membrane to preferentially intercept most hydrocarbons, reducing the load of the subsequent decarbonation membrane unit 5, that is, reducing the occupation of CO2 adsorption sites by hydrocarbons. The PES membrane is used as a post-membrane to deeply intercept residual small-molecule hydrocarbons and improve the purity of methane (CH4).

[0037] The decarbonation membrane unit 5 uses a membrane material containing an amino functional group. This membrane material can be a polyamide (PA), polyethersulfone (PES), or polyvinylidene fluoride (PVDF) as a support membrane, and an amino functional group (such as trimethylamine, aniline) is introduced through interfacial polymerization or post-treatment to form a hydrophilic surface or chemical adsorption site.

[0038] The membrane pore size of the decarbonization membrane unit 5 is 0.1 - 1 nm, and selective separation can be achieved through molecular sieve effect and chemical adsorption. Due to the presence of amino groups (-NH2) on its surface, it has strong polarity. Therefore, CO2 molecules can be preferentially adsorbed through hydrogen bonding and electrostatic interaction.

[0039] Its working principle: CO2 molecules react with amino functional groups to form ammonium bicarbonate (NH4HCO3) or carbamate (NH2COO - ), achieving reversible chemical adsorption. For unreacted CO2 molecules, they are intercepted through the molecular size screening of the membrane material.

[0040] In this embodiment, for this electronic grade ultra-pure natural gas purification device, the hydrocarbon removal membrane unit 4 is located in front of the decarbonization membrane unit 5. First, hydrocarbon removal treatment is carried out, and then decarbonization treatment is carried out. The method of this embodiment can protect the membrane material of the decarbonization membrane unit 5 and improve the decarbonization efficiency. Specifically: C2 - C5 hydrocarbons in natural gas are easily adsorbed by the amine-based membrane, and long-term contact will cause poisoning of the amine functional groups and reduce the CO2 selectivity. Removing hydrocarbons first can avoid this problem and extend the life of the amine-based membrane, and the life can be increased by 30% - 50%.

[0041] A second magnetic pole 61 is provided in the magnetic fluidized bed reactor 6, and a magnetic field generator 62 is provided on the outer periphery of the magnetic fluidized bed reactor 6, which can form a directional or non-directional magnetic field in the magnetic fluidized bed reactor 6. The magnetic mercury removal catalyst can move along a set trajectory under the action of the magnetic field to complete mercury removal. When the reaction is completed, the magnetic mercury removal catalyst can be adsorbed on the second magnetic pole 61 through the action of the second magnetic pole 61 to achieve separation and recovery.

[0042] According to needs, a magnetic mercury removal catalyst replenishing device 8 can also be configured to regularly replenish the magnetic mercury removal catalyst into the magnetic fluidized bed reactor 6.

[0043] A number of precision filter elements 71 are installed in the nanoscale precision filter 7 to further purify the natural gas, and at the same time, it can be used as a security filter to prevent the magnetic mercury removal catalyst from the previous section from breaking away and reaching here.

[0044] Example 2

[0045] This embodiment provides an electronic grade ultra-pure natural gas purification method, including the following steps:

[0046] S1: Dust the raw natural gas.

[0047] S2: Dehydrate the natural gas after dust removal in S1.

[0048] S3: Treat the dehydrated natural gas in S2 to remove magnetic fine particles; this step is processed using a magnetic filter 3, the magnetic field strength of the magnetic filter 3 is 0.4 - 0.8 T, and the speed of the natural gas entering the magnetic filter 3 is 0.4 - 0.6 m / s;

[0049] S4: Sequentially subject the natural gas after removing magnetic fine particles in S3 to dehydrocarbonation and decarbonation treatments;

[0050] S5: Feed the natural gas after dehydrocarbonation and decarbonation in S4 into a magnetic fluidized bed reactor 6 for mercury removal treatment;

[0051] S6: After the mercury-removed natural gas in S5 is purified by a nanoscale precision filter 7, the filtration accuracy of the nanoscale precision filter 7 is 2 - 10 nm, and finally ultra-pure natural gas is obtained.

[0052] Among them, a dust removal filter 1 is used in S1 for dust removal of the raw natural gas, removing impurities such as dust and large particles in the raw natural gas.

[0053] A coalescing filter 2 is used in S2 for dehydration treatment of the natural gas, removing moisture in the natural gas, and the filtration accuracy of the coalescing filter is 0.2 - 1 μm.

[0054] In S4, a dehydrocarbonation membrane unit 4 and a decarbonation membrane unit 5 are used for treatment. The dehydrocarbonation membrane unit 4 uses a polyvinylidene fluoride membrane and / or a polyethersulfone membrane, and the operating pressure of the dehydrocarbonation membrane unit 4 is 2 - 3 MPa, and the temperature is 20 - 30 °C.

[0055] The decarbonation membrane unit 5 uses a membrane material containing an amino functional group. The operating pressure of the decarbonation membrane unit 5 is 2.5 - 3.5 MPa to enhance the solubility of CO2, the temperature is 25 - 35 °C, and deprotonation of the amino group is avoided.

[0056] In S5, a magnetic fluidized bed reactor 6 is used for mercury removal treatment. A magnetic mercury removal catalyst is provided in the magnetic fluidized bed reactor 6, and the magnetic mercury removal catalyst is a magnetic composite material with Fe3O4 as the magnetic core. In this embodiment, the magnetic mercury removal catalyst is an Fe3O4-based TiS2 / ZnS double-layer supported magnetic mercury removal catalyst.

[0057] The filling amount of the magnetic mercury removal catalyst in the magnetic fluidized bed reactor 6 is 20 - 40% of the volume of the magnetic fluidized bed reactor 6. The intake gas speed of the magnetic fluidized bed reactor 6 is 0.1 - 0.3 m / s, the temperature of the magnetic fluidized bed reactor 6 is set to 130 - 170 °C, and the reaction time is set to 8 - 15 min to ensure that the magnetic mercury removal catalyst can fully react and perform mercury removal treatment on the natural gas.

[0058] The Fe3O4-based TiS2 / ZnS double-layer supported magnetic mercury removal catalyst comprises a sequentially distributed Fe3O4 magnetic core, an intermediate TiS2 layer, and an outer ZnS layer; the Fe3O4 magnetic core has a particle size of 50–100 nm and a saturation magnetization intensity of 100–110 emu / g; the TiS2 layer has a thickness of 1–3 nm; the ZnS layer has a thickness of 1–3 nm.

[0059] The double-layer structure of the Fe3O4-based TiS2 / ZnS double-layer supported magnetic mercury removal catalyst has more advantages than the single-layer structure in the prior art. As the outermost layer, the ZnS layer can effectively prevent the TiS2 layer from being affected, and the sulfur resistance is significantly improved; the ZnS layer can assist Hg 0 adsorption under lightless conditions. Therefore, the double-layer structure has a higher mercury removal rate under ultraviolet light assistance. In addition, the ZnS layer can protect the magnetic core and reduce the loss of the Fe3O4 magnetic core in high-temperature or oxidation environments, and the saturation magnetization intensity is increased by 10–20%. The double-layer structure can be quickly recovered by a magnetic field, reducing the catalyst loss rate.

[0060] Through the purification method of this embodiment, 5N grade ultra-pure natural gas can be prepared to achieve the purification of methane.

[0061] Example 3

[0062] Select or simulate self-made natural gas containing a certain amount of slag, water, hydrocarbons (mainly ethane, propane, etc.), carbon dioxide, nitrogen, iron impurities, and mercury. The specific contents are as follows: the slag content is 50 mg / m 3 , the water content is 500 mg / m 3 , the total hydrocarbon content is 2% (volume fraction), the carbon dioxide content is 3% (volume fraction), the nitrogen content is 5% (volume fraction), the iron impurity content is 10 mg / m 3 , and the mercury content is 10 μg / m 3 .

[0063] Purification process:

[0064] S1: First, perform dust removal treatment on the raw natural gas.

[0065] S2: Coalescing filter 2 for dehydration treatment: The filtration accuracy of the coalescing filter element is 0.2 μm. The natural gas enters the coalescing device at a flow rate of 100 m 3 / h, stays in the device for 5 min, and then enters the filtration device, with a filtration speed of 10 m 3 / (h·m 2 ).

[0066] S3: Magnetic filter 3 for iron removal treatment: The magnetic field intensity of the magnetic filter 3 is 0.4 T, the flow rate of the natural gas in the magnetic filter 3 is 0.4 m / s, and the residence time is 3 min.

[0067] S4: Hydrocarbon and carbon dioxide removal by dual-membrane method: The operating pressure of the hydrocarbon removal membrane unit 4 is 2 MPa, the temperature is 20 °C, and the gas feed flow rate is 70 m 3 / h. The operating pressure of the carbon dioxide removal membrane unit 5 is 3 MPa, the temperature is 30 °C, and the gas feed flow rate is 80 m 3 / h.

[0068] S5: Mercury removal by magnetic fluidized bed reactor 6: The filling amount of the magnetic mercury removal catalyst in the magnetic fluidized bed reactor 6 is 30% of the volume of the magnetic fluidized bed reactor 6. The fluidization velocity of natural gas is 0.2 m / s, the reaction temperature is 150 °C, and the reaction time is 10 min. The magnetic mercury removal catalyst used is Fe3O4-based ZnS / TiS2 double-layer supported magnetic composite material.

[0069] S6: Purification by nano-precision filter 7: The pore size of the precision filter element 71 is 5 nm. Natural gas passes through the nano-precision filter 7 at a flow rate of 60 m 3 / h, and the filtration pressure is 1.5 MPa.

[0070] After purification, the slag content in natural gas is reduced to 1 mg / m 3 or less, the water content is reduced to 10 mg / m 3 or less, the total hydrocarbon content is reduced to 0.001% (volume fraction) or less, the carbon dioxide content is reduced to 0.001% (volume fraction) or less, the nitrogen content is reduced to 0.001% (volume fraction) or less, the iron impurity content is reduced to 1 mg / m 3 or less, and the mercury content is reduced to 0.1 μg / m 3 or less.

[0071] Example 4

[0072] Select or simulate self-made natural gas containing a certain amount of slag, water, hydrocarbons (mainly ethane, propane, etc.), carbon dioxide, nitrogen, iron impurities and mercury. The specific contents are: slag content 80 mg / m 3 , water content 800 mg / m 3 , total hydrocarbon content 3% (volume fraction), carbon dioxide content 4% (volume fraction), nitrogen content 6% (volume fraction), iron impurity content 15 mg / m 3 , mercury content 15 μg / m 3 .

[0073] Purification process:

[0074] S1: First, perform dust removal on the raw natural gas;

[0075] S2: Dewatering by coalescing filter 2: The filtration accuracy of the coalescing filter element is 0.6 μm. Natural gas passes through at 150 m3 The flow rate of / h enters the coalescing device, stays in the device for 5 minutes, and then enters the filtering device with a filtering speed of 15m 3 / (h·m 2 ).

[0076] S3: Iron removal treatment by magnetic filter 3: The magnetic field intensity of magnetic filter 3 is 0.5T, the flow rate of natural gas in magnetic filter 3 is 0.6m / s, and the residence time is 4 minutes.

[0077] S4: Hydrocarbon and carbon dioxide removal treatment by dual-membrane method: The operating pressure of the hydrocarbon removal membrane unit 4 is 2.8MPa, the temperature is 28°C, and the gas feed flow rate is 80m 3 / h. The operating pressure of the carbon dioxide removal membrane unit 5 is 3.5MPa, the temperature is 35°C, and the gas feed flow rate is 90m 3 / h.

[0078] S5: Mercury removal treatment by magnetic fluidized bed reactor 6: The filling amount of the magnetic mercury removal catalyst in the magnetic fluidized bed reactor 6 is 20% of the volume of the magnetic fluidized bed reactor 6. The fluidization speed of natural gas is 0.1m / s, the reaction temperature is 130°C, and the reaction time is 15 minutes. The magnetic mercury removal catalyst used is Fe3O4-based ZnS / TiS2 double-layer supported magnetic composite material.

[0079] S6: Purification treatment by nano-precision filter 7: The pore diameter of the precision filter element 71 is 10nm, and natural gas passes through the nano-precision filter 7 at a flow rate of 70m 3 / h, and the filtration pressure is 1.8MPa.

[0080] After purification, the slag content in natural gas is reduced to 2mg / m 3 or less, the water content is reduced to 15mg / m 3 or less, the total hydrocarbon content is reduced to 0.002% (volume fraction) or less, the carbon dioxide content is reduced to 0.002% (volume fraction) or less, the nitrogen content is reduced to 0.002% (volume fraction) or less, the iron impurity content is reduced to 2mg / m 3 or less, the mercury content is reduced to 0.2μg / m 3 or less, and 5N grade ultra-pure natural gas is prepared.

[0081] Example 5

[0082] Select or simulate self-made natural gas containing a certain amount of slag, water, hydrocarbons (mainly ethane, propane, etc.), carbon dioxide, nitrogen, iron impurities and mercury. The specific contents are: slag content 30mg / m 3 , water content 300mg / m 3, the total hydrocarbon content is 2% (volume fraction), the carbon dioxide content is 3% (volume fraction), the nitrogen content is 3% (volume fraction), and the iron impurity content is 8 mg / m 3 , the mercury content is 8 μg / m 3 .

[0083] Purification process:

[0084] S1: First, the raw natural gas is subjected to dust removal treatment;

[0085] S2: Coalescing filter 2 for dehydration treatment: The precision of the filter medium using the coalescing filter element is 1 μm. The natural gas enters the coalescing device at a flow rate of 80 m 3 / h, stays in the device for 5 minutes, and then enters the filtering device with a filtering speed of 10 m 3 / (h·m 2 ).

[0086] S3: Magnetic filter 3 for iron removal treatment: The magnetic field strength of magnetic filter 3 is 0.8 T, the flow rate of natural gas in magnetic filter 3 is 0.6 m / s, and the residence time is 2 minutes.

[0087] S4: Dual-membrane method for hydrocarbon and carbon dioxide removal treatment: The operating pressure of the hydrocarbon removal membrane unit 4 is 3 MPa, the temperature is 30 °C, and the gas feed flow rate is 60 m 3 / h. The operating pressure of the carbon dioxide removal membrane unit 5 is 2.5 MPa, the temperature is 25 °C, and the gas feed flow rate is 70 m 3 / h.

[0088] S5: Magnetic fluidized bed reactor 6 for mercury removal treatment: The filling amount of the magnetic mercury removal catalyst in the magnetic fluidized bed reactor 6 is 40% of the volume of the magnetic fluidized bed reactor 6. The fluidization velocity of natural gas is 0.3 m / s, the reaction temperature is 170 °C, and the reaction time is 8 minutes. The magnetic mercury removal catalyst used is Fe3O4-based ZnS / TiS2 double-layer supported magnetic composite material.

[0089] S6: Nanoscale precision filter 7 for purification treatment: The pore diameter of the precision filter element 71 is 2 nm. The natural gas passes through the nanoscale precision filter 7 at a flow rate of 50 m 3 / h, and the filtration pressure is 1.5 MPa.

[0090] After purification, the slag content in the natural gas is reduced to 0.5 mg / m 3 or less, the water content is reduced to 5 mg / m 3 or less, the total hydrocarbon content is reduced to 0.0005% (volume fraction) or less, the carbon dioxide content is reduced to 0.0005% (volume fraction) or less, the nitrogen content is reduced to 0.0005% (volume fraction) or less, and the iron impurity content is reduced to 0.5 mg / m 3Hereinafter, the mercury content is reduced to 0.05 μg / m 3 Hereinafter.

[0091] In summary, the present invention adopts a multi-stage purification process of dust removal - coalescence filtration dehydration - magnetic iron removal - hydrocarbon and carbon dioxide removal by dual membrane method - mercury removal by magnetic fluidized bed - nano-precision filtration, which can realize the purification of natural gas for 5N-level electronic industry.

[0092] The series of detailed descriptions listed above are only specific descriptions of the feasible implementation modes of the present invention, and they are not intended to limit the protection scope of the present invention. Any equivalent implementation modes or changes made without departing from the technical spirit of the present invention should be included within the protection scope of the present invention.

[0093] In addition, it should be understood that although this specification is described according to implementation modes, not every implementation mode only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other implementation modes understandable by those skilled in the art.

Claims

1. A method for purifying electronic grade ultrapure natural gas, characterized in that: The following steps are involved: S1: remove dust from the raw natural gas; S2: Dehydration of the natural gas after dust removal in S1; S3: remove magnetic fine particles from the dehydrated natural gas in S2; S4: dehydrogenation and decarbonization of the natural gas after the magnetic fine particles are removed in S3; S5: the natural gas after dehydrogenation and decarbonization in S4 enters into a magnetic fluidized bed reactor for mercury removal treatment; S6: The natural gas after mercury removal in S5 is purified by a nano-scale precision filter to obtain ultra-pure natural gas.

2. The method for purifying electronic grade ultrapure natural gas according to claim 1, characterized in that: In S1, a dust removal filter is used to remove dust from the raw natural gas.

3. The method for purifying electronic grade ultrapure natural gas according to claim 1, characterized in that: In S2, a coalescing filter is used to perform natural gas dehydration treatment.

4. The method for purifying electronic grade ultrapure natural gas according to claim 1, characterized in that: In the S4, a hydrocarbon removal membrane unit and a carbon removal membrane unit are used for treatment.

5. The method for purifying electronic grade ultrapure natural gas according to claim 4, characterized in that: In S5, a magnetic fluidized bed reactor is used for mercury removal treatment. A magnetic mercury removal catalyst is arranged in the magnetic fluidized bed reactor. The magnetic mercury removal catalyst is a magnetic composite material with Fe3O4 as a magnetic core.

6. The method for purifying electronic grade ultrapure natural gas according to claim 5, characterized in that: The magnetic mercury removal catalyst is a Fe3O4-based TiS2 / ZnS double-layer supported magnetic mercury removal catalyst.

7. The method for purifying electronic grade ultrapure natural gas according to claim 5, characterized in that: The operating pressure of the hydrocarbon removal membrane unit is 2-3 MPa and the temperature is 20-30°C, and the operating pressure of the carbon removal membrane unit is 2.5-3.5 MPa and the temperature is 25-35°C.

8. The method for purifying electronic grade ultrapure natural gas according to claim 7, characterized in that: The filling amount of the magnetic mercury removal catalyst in the magnetic fluidized bed reactor is 20-40% of the volume of the magnetic fluidized bed reactor, the air inlet speed of the magnetic fluidized bed reactor is 0.1-0.3 m / s, the temperature of the magnetic fluidized bed reactor is set to 130-170° C., and the reaction time is set to 8-15 min.

9. The method for purifying electronic grade ultrapure natural gas according to claim 1, characterized in that: The filtration accuracy of the nanometer-level precision filter is 2-10nm.

10. The method for purifying electronic grade ultrapure natural gas according to claim 3, characterized in that: The filtration accuracy of the coalescing filter is 0.2-1 μm.

11. The method for purifying electronic grade ultrapure natural gas according to claim 1, characterized in that: The S3 is processed by a magnetic filter, the magnetic field strength of the magnetic filter is 0.4-0.8T, and the speed at which the natural gas enters the magnetic filter is 0.4-0.6m / s.

12. The method for purifying electronic grade ultrapure natural gas according to claim 4, characterized in that: The hydrocarbon removal membrane unit uses a polyvinylidene fluoride membrane and / or a polyethersulfone membrane, and the carbon removal membrane unit uses a membrane material containing an amino functional group.

13. The method for purifying electronic grade ultrapure natural gas according to claim 6, characterized in that: The Fe3O4-based TiS2 / ZnS double-layer supported magnetic mercury removal catalyst comprises a Fe3O4 magnetic core, a middle TiS2 layer and an outer ZnS layer distributed in sequence; the Fe3O4 magnetic core has a particle size of 50-100nm and a saturation magnetization intensity of 100-110emu / g; the TiS2 layer has a thickness of 1-3nm; and the ZnS layer has a thickness of 1-3nm.

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