A method for separating hydrogen during natural gas pipeline mixing

Abstract

This invention discloses a method for separating hydrogen during mixed natural gas pipeline transportation, comprising the following steps: Step 1, material selection; Step 2, pipeline surface treatment; Step 3, gas transportation; Step 4, physical gas separation; Step 5, gas membrane separation; Step 6, negative feedback reflux separation. This invention utilizes a volumetric separation method with expanded pipeline volume, resulting in low cost and good economic efficiency. Combined with a filter membrane for filtration separation, the two separation methods improve the gas separation effect. Through component surface treatment, pipeline material control, and control of hydrogen concentration and pressure, hydrogen embrittlement is avoided, improving the safety of gas transportation and preventing material breakage and leakage. The separated gas is tested using a concentration detection device; unqualified gas is recirculated for re-separation, facilitating effective separation of the mixed gas and improving the purity of the separated gas.

Description

Technical Field

[0001] This invention relates to the field of natural gas separation technology, specifically a method for separating hydrogen during natural gas pipeline mixing. Background Technology

[0002] Natural gas refers to all gases that exist naturally in the world, including gases formed by various natural processes in the atmosphere, hydrosphere, and lithosphere. However, the commonly used definition of "natural gas" is a narrower definition from an energy perspective, referring to a mixture of hydrocarbon and non-hydrocarbon gases naturally occurring in underground strata. In petroleum geology, it usually refers to oilfield gas and gas field gas. Its composition is mainly hydrocarbons, but it also contains non-hydrocarbon gases. During hydrogen transportation, it is frequently mixed with natural gas. After transportation, the natural gas needs to be separated. While existing methods for separating hydrogen during natural gas pipeline mixing are relatively comprehensive, they still have certain shortcomings.

[0003] 1. The existing hydrogen separation method for mixed transportation in natural gas pipelines has poor hydrogen separation effect during use. When hydrogen is separated using a single method, there are still many impurities in the separated gas, which greatly reduces the quality of the separated gas.

[0004] 2. In the existing process of mixing hydrogen with natural gas pipelines, hydrogen can corrode metal pipelines, causing hydrogen embrittlement. In severe cases, this can lead to pipeline leaks, greatly reducing the safety of the gas transmission process.

[0005] 3. In the existing natural gas pipeline mixed hydrogen transport separation method, non-target gases are still present in the separated gas during the separation process, and the gas cannot be separated by feedback, which reduces the purity of the separated gas. Summary of the Invention

[0006] The purpose of this invention is to provide a method for separating hydrogen during natural gas pipeline mixing, in order to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for separating hydrogen during mixed transportation in a natural gas pipeline, comprising the following steps: Step 1, material selection; Step 2, pipeline surface treatment; Step 3, gas transportation; Step 4, physical gas separation; Step 5, gas membrane separation; Step 6, negative feedback reflux separation;

[0008] In step one above, the material of the pipeline is selected before the mixed hydrogen is transported through the natural gas pipeline. A pipeline made of a specific material is selected as the carrier for transporting the mixed gas.

[0009] In step two above, after the pipe material in step one is selected, it is cast into sections of pipe. Then, a special material is used to coat the inner and outer walls of the pipe. After coating, the pipe is welded and fixed with screws to form a conveying pipe.

[0010] In step three above, when using the natural gas pipeline made in step two to transport the mixed gas, the pressure of the transported gas and the concentration of hydrogen are regulated to ensure that the gas pressure and hydrogen are within a suitable range, and the gas is transported under safe and suitable conditions.

[0011] In step four above, after the mixed gas from step three is transported, when the mixed gas is transported to the hydrogen receiving station, the volume of the pipeline is expanded and the flow rate of the mixed gas is reduced to 0.01 m / s to reduce turbulence and flow of hydrogen and natural gas. The two are separated by using the upper and lower connecting pipelines based on their different specific gravities. After separation, they are temporarily stored in hydrogen and natural gas temporary storage tanks respectively.

[0012] In step five above, after the natural gas and hydrogen from step four are temporarily stored, the stored hydrogen and natural gas are filtered and separated using a filter membrane. The hydrogen and natural gas that have been initially separated are then separated again and set aside for later use.

[0013] In step six above, after the gas membrane separation in step five, the separated gas is monitored in real time. If the content of non-target gas in the gas exceeds the standard, the gas is sent back to the membrane separator for secondary separation until the content of non-target gas in the gas reaches the standard. At this time, the qualified gas is sent to the storage tank for storage.

[0014] Furthermore, in step one, based on the fact that the liquefaction temperature of natural gas is -162°C and the liquefaction temperature of hydrogen is -259.2°C, the gas in the pipeline is lowered to -163°C to liquefy and separate the natural gas, thereby obtaining hydrogen.

[0015] Furthermore, in step one, the natural gas pipeline is welded from low-carbon steel plates with a P percentage content ≤0.015% and a S percentage content ≤0.004%. The low-carbon steel plates also contain a variety of trace alloying elements, with a hardness ≤200hb. The S percentage content in the weld is ≤0.010%, and the P percentage content is ≤0.020%. The hardness value of the weld joint is ≤200hb after Sr treatment.

[0016] Furthermore, in step one, the inner wall of the natural gas pipeline is coated with a ceramic film.

[0017] Furthermore, in step two, the special material is a nickel-cobalt alloy.

[0018] Furthermore, in step three, when the hydrogen content in the mixed gas is less than 10%, the pipeline pressure is below 7.7 MPa; when the hydrogen content in the mixed gas is greater than 10%, the pipeline pressure is below 5.38 MPa.

[0019] Furthermore, in step four, the volume of the pipe is increased by 100-1000 times.

[0020] Furthermore, in step five, the filter membrane in the filter is one or more of the following: ceramic membrane, polymer membrane, molecular sieve membrane, and metal membrane.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] 1. The present invention uses a volumetric separation method with expanded pipe volume for separation, which is low-cost and economical. Combined with a filter membrane for filtration separation, the two separation methods are combined to improve the gas separation effect.

[0023] 2. This invention avoids hydrogen embrittlement by controlling the surface treatment of components, the pipe materials, and the concentration and pressure of hydrogen, thereby improving the safety of gas transportation and preventing material breakage and leakage.

[0024] 3. This invention uses a concentration detection device to detect the separated gas, and unqualified gas is returned for re-separation, thereby improving the purity of the separated gas. Attached Figure Description

[0025] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Please see Figure 1 The present invention provides an embodiment of a method for separating hydrogen during natural gas pipeline mixing, comprising the following steps: Step 1, material selection; Step 2, pipeline surface treatment; Step 3, gas transportation; Step 4, physical gas separation; Step 5, gas membrane separation; and Step 6, negative feedback reflux separation.

[0028] In step one above, the material of the pipeline is selected before the mixed hydrogen is transported through the natural gas pipeline. A pipeline made of a specific material is selected as the carrier for transporting the mixed gas.

[0029] In step one above, based on the fact that the liquefaction temperature of natural gas is -162°C and the liquefaction temperature of hydrogen is -259.2°C, the temperature of the natural gas in the pipeline is lowered to -163°C to liquefy and separate the natural gas, thereby obtaining hydrogen.

[0030] In step one above, the natural gas pipeline is welded from low-carbon steel plates with a P percentage content ≤0.015% and a S percentage content ≤0.004%. The low-carbon steel plates also contain a variety of trace alloying elements, and their hardness is ≤200hb. The S percentage content in the weld is ≤0.010%, and the P percentage content is ≤0.020%. The hardness value of the weld joint is ≤200hb after Sr treatment.

[0031] In step one above, the inner wall of the natural gas pipeline is coated with a ceramic film.

[0032] In step two above, after the pipe material in step one is selected, it is cast into sections of pipe. Then, a special material is used to coat the inner and outer walls of the pipe. The special material is a nickel-cobalt alloy. After coating, the pipe is welded and fixed with screws to form a conveying pipe.

[0033] In step three above, when using the natural gas pipeline constructed in step two to transport the mixed gas, the pressure of the transported gas and the concentration of hydrogen are regulated to ensure that the gas pressure and hydrogen are within a suitable range. When the hydrogen content in the mixed gas is less than 10%, the pipeline pressure is below 7.7 MPa, and when the hydrogen content in the mixed gas is greater than 10%, the pipeline pressure is below 5.38 MPa, so that the gas is transported under safe and suitable conditions.

[0034] In step four above, after the mixed gas from step three is transported to the hydrogen receiving station, the volume of the pipeline is increased by 100-1000 times, and the flow velocity of the mixed gas is reduced to 0.01 m / s to reduce turbulence and flow of hydrogen and natural gas. The two are separated by their different specific gravities. After separation, they are temporarily stored in hydrogen and natural gas storage tanks respectively.

[0035] In step five above, after the natural gas and hydrogen from step four are temporarily stored, the stored hydrogen and natural gas are filtered and separated using a filter membrane. The filter membrane is one or more of ceramic membrane, polymer membrane, molecular sieve membrane and metal membrane. The hydrogen and natural gas after the initial separation are separated again and then set aside for later use.

[0036] In step six above, after the gas membrane separation in step five, the separated gas is monitored in real time. If the content of non-target gas in the gas exceeds the standard, the gas is sent back to the membrane separator for secondary separation until the content of non-target gas in the gas reaches the standard. At this time, the qualified gas is sent to the storage tank for storage.

[0037] Based on the above, the advantages of this invention are as follows: Firstly, material selection is performed before pipeline transportation, using corrosion-resistant X42 and X52 pipeline steel as raw materials to produce the transport pipeline. Simultaneously, the inner and outer walls of the pipeline are coated with a nickel-cobalt alloy metal coating, enhancing the pipeline's corrosion resistance and resistance to hydrogen embrittlement. Furthermore, during transportation, when the hydrogen content in the mixed gas is less than 10%, the pipeline pressure is below 7.7 MPa; when the hydrogen content in the mixed gas is greater than 10%, the pipeline pressure is below 5.38 MPa, maintaining the hydrogen concentration and pressure inside the pipeline at a controlled level. Within a suitable range, this effectively reduces hydrogen embrittlement and corrosion, extends pipeline lifespan, and improves operational safety. Simultaneously, the separation process expands the pipeline volume by 100-1000 times, utilizing the difference in specific gravity between hydrogen and natural gas for separation, resulting in good economic efficiency. Furthermore, after gravity separation, a filter membrane is used for further separation; the combined use of these two methods enhances the separation effect. Real-time monitoring of the separated gas is conducted; if the concentration of non-target gases exceeds the standard, gas is recirculated and subjected to further filter membrane separation, effectively removing impurities and improving the purity of the separated gas.

[0038] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for separating hydrogen during natural gas pipeline mixing, comprising the following steps: Step 1, material selection; Step 2, pipe surface treatment; Step 3, gas transportation; Step 4, physical gas separation; Step 5, gas membrane separation; Step 6, negative feedback reflux separation; characterized in that: In step one above, before transporting the mixed hydrogen through the natural gas pipeline, the material of the pipeline is selected, and a pipeline made of low carbon steel plate is selected as the carrier for transporting the mixed gas. In step two above, after the pipe material in step one is selected, it is cast into sections of pipe. Then, nickel-cobalt alloy is used to coat the inner and outer walls of the pipe. After coating, it is welded and fixed with screws to form a conveying pipe. In step three above, when using the natural gas pipeline made in step two to transport the mixed gas, the pressure of the transported gas and the concentration of hydrogen are controlled to ensure that the pipeline pressure is below 7.7 MPa when the hydrogen content is less than 10%, and the pipeline pressure is below 5.38 MPa when the hydrogen content in the mixed gas is greater than 10%. In step four above, after the mixed gas from step three is transported, when the mixed gas is transported to the hydrogen receiving station, the volume of the pipeline is expanded and the flow velocity of the mixed gas is reduced to 0.01 m / s to reduce turbulence and flow of hydrogen and natural gas. Taking advantage of the difference in specific gravity between the two, they are separated using upper and lower connecting pipelines. After separation, they are temporarily stored in hydrogen and natural gas temporary storage tanks respectively. In step five above, after the natural gas and hydrogen from step four are temporarily stored, the stored hydrogen and natural gas are filtered and separated using a filter membrane. The hydrogen and natural gas that have been initially separated are then separated again and set aside for later use. In step six above, after the gas membrane separation in step five, the separated gas is monitored in real time. If the content of non-target gas in the gas exceeds the standard, the gas is sent back to the membrane separator for secondary separation until the content of non-target gas in the gas reaches the standard. At this time, the qualified gas is sent to the storage tank for storage.

2. The method for separating hydrogen during natural gas pipeline mixing according to claim 1, characterized in that: Based on the fact that the liquefaction temperature of natural gas is -162°C and the liquefaction temperature of hydrogen is -259.2°C, the gas in the pipeline is lowered to -163°C to liquefy and separate the natural gas, thereby obtaining hydrogen. In step one, the natural gas pipeline is welded from low-carbon steel plates with a P percentage content ≤0.015 and a S percentage content s ≤0.

004. The low-carbon steel plates also contain a variety of trace alloying elements, and their hardness is ≤200hb. The S percentage content in the weld is ≤0.010%, and the P percentage content is ≤0.020%. The hardness value of the weld joint is ≤200hb after Sr treatment. In step one, the inner wall of the natural gas pipeline is coated with a ceramic film.

3. The method for separating hydrogen during natural gas pipeline mixing according to claim 1, characterized in that: In step four, the volume of the pipe is increased by 100-1000 times.

4. The method for separating hydrogen during natural gas pipeline mixing according to claim 1, characterized in that: In step five, the filter membrane in the filter is one or more of the following: ceramic membrane, polymer membrane, molecular sieve membrane, and metal membrane.

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