Device and method for enriching ultra-low concentration hydrocarbons in natural gas

Abstract

The present invention provides an apparatus and method for enriching ultra-low concentration hydrocarbons in natural gas, wherein the apparatus comprises: several independently arranged cold-trap controlled chambers and hot water storage tanks independently arranged from the cold-trap controlled chambers, at least one fraction collection chamber, and a vacuum pump; the hot water storage tanks and the cold-trap controlled chambers are used to hold low-temperature-resistant coils; the gas cylinder for holding natural gas is connected to the gas inlet of the low-temperature-resistant coil via a pipeline through a first valve; the gas outlet of the low-temperature-resistant coil is connected to the inlet of the fraction collection chamber via a pipeline through a second valve, a vacuum pump, and a third valve; the outlet of the fraction collection chamber is connected to an analysis system via a pipeline through a fourth valve; and the vacuum pump is used to remove air from the pipeline and other gas components to be removed during the purification process. The present invention can achieve non-fractionation enrichment of low-concentration hydrocarbon components in natural gas and can provide the necessary technical support for further analysis of individual hydrocarbon gas molecules.

Description

Technical Field

[0001] The present invention relates to a device and a method for enriching ultra-low concentration hydrocarbon substances in natural gas, belonging to the technical field of natural gas pre-processing. Background Art

[0002] As a clean and efficient energy source, natural gas is gaining increasing attention worldwide for its development and utilization. Globally, natural gas resources are far greater than those of oil, ensuring sufficient resources for its development. However, with increasing exploration and demand for natural gas resources, deep formations are becoming a key focus of natural gas research. Deep natural gas is primarily composed of methane, with ethane and propane, among others, often exceeding 1 mol%, and containing extremely trace amounts of light hydrocarbons. The geochemical characteristics of natural gas (composition, isotopes, and cluster isotopes) are crucial for revealing its genetic type, source, accumulation patterns, and the prediction of favorable areas. However, due to the changing nature of exploration targets, conventional analytical techniques have proven difficult to accurately analyze the characteristics of these ultra-low-concentration hydrocarbons (such as ethane and above) in natural gas. This, in particular, requires enrichment and separation of highly purified individual compounds for analysis.

[0003] Gas chromatographs and isotope mass spectrometers are commonly used to determine hydrocarbon composition and characteristics. Both instruments have specific detection limit requirements. Currently, high-resolution isotope mass spectrometry for cluster isotope analysis requires a pure component concentration of at least 1.5 mL. However, deep-seated natural gas contains relatively low levels of wet components and light hydrocarbons, making it essential to enrich and separate a sufficient amount of pure compounds for instrumental testing and analysis.

[0004] Currently, the most commonly used methods for enriching low-concentration components in natural gas are solid-phase microextraction (SPME) and modified gas chromatography. SPME is designed to detect low-concentration high-molecular-weight hydrocarbons. After enrichment, the relative concentrations of methane, ethane, and propane decrease significantly, while the concentrations of higher-carbon hydrocarbons increase significantly. Modifications to gas chromatography techniques can also enable analysis of low-concentration high-molecular-weight hydrocarbons to a certain extent. However, this does not substantially enrich and separate low-molecular-weight hydrocarbons such as ethane and propane, addressing the problem of enriching low-concentration components. The total injection volume is typically between 2mL and 10mL, which is measured in milliliters. Furthermore, moisture and light hydrocarbons have low boiling points and are easily lost. During these enrichment processes, isotopic fractionation easily occurs with the escape of methane, making it difficult to achieve complete, non-fractionation-free enrichment, limiting further research into deep-seated natural gas characteristics.

[0005] In summary, the content of wet gas components and light hydrocarbons in deep natural gas is relatively low, and cannot be directly tested and analyzed by instruments; previous enrichment technologies can analyze low-concentration high-molecular hydrocarbons to a certain extent, but have not substantially enriched and separated individual low-molecular hydrocarbons such as ethane and propane; in addition, wet gas and light hydrocarbon components have low boiling points and are easily lost, and methane overflow can easily cause isotopic fractionation.

[0006] Therefore, providing a new device and method for enriching ultra-low concentration hydrocarbon substances in natural gas has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] In order to solve the above-mentioned shortcomings and deficiencies, one object of the present invention is to provide a device for enriching ultra-low concentration hydrocarbon substances in natural gas.

[0008] Another object of the present invention is to provide a method for enriching ultra-low concentration hydrocarbon substances in natural gas.

[0009] To achieve the above objectives, the present invention provides, on the one hand, a device for enriching ultra-low concentration hydrocarbons in natural gas, wherein the device comprises: a plurality of cold-trap controlled chambers independently provided, a hot water storage tank independently provided from the cold-trap controlled chambers, at least one fraction collection chamber, and a vacuum pump;

[0010] The hot water storage tank and the cold trap controlled room are used to hold low temperature resistant coils;

[0011] A gas cylinder for containing natural gas is connected to the gas inlet of the low-temperature resistant coil via a pipeline through a first valve, the gas outlet of the low-temperature resistant coil is connected to the inlet of the fraction collection chamber via a pipeline through a second valve, a vacuum pump, and a third valve, and the outlet of the fraction collection chamber is connected to the analysis system via a pipeline through a fourth valve;

[0012] The vacuum pump is used to remove air from the pipeline and other gas components to be removed during the purification process.

[0013] In the present invention, those skilled in the art can choose to enrich and collect target hydrocarbon substances in natural gas according to actual operational requirements. Accordingly, the device for enriching ultra-low concentration hydrocarbon substances in natural gas includes at least one fraction collection chamber; for example, in a specific embodiment of the present invention, the target hydrocarbon substance is propane. At this time, if the device is provided with a fraction collection chamber, methane, ethane and propane need to be collected in sequence through the fraction collection chamber; the device can also be provided with two fraction collection chambers, one of which is used to collect methane and ethane, and the other is used to collect the target hydrocarbon substance propane; of course, the device can also be provided with three fraction collection chambers to collect methane, ethane and propane respectively. In either case, the purpose of the present invention can be achieved.

[0014] As a specific embodiment of the above-mentioned device of the present invention, the fraction collection chamber includes at least a first collection chamber and a second collection chamber, the second collection chamber is used to collect target hydrocarbon substances in natural gas, and the first collection chamber is used to collect other hydrocarbon substances in natural gas, wherein the other hydrocarbon substances are hydrocarbon substances with a carbon number smaller than the carbon number of the target hydrocarbon substances.

[0015] As a specific embodiment of the above-described device of the present invention, the fraction collection chamber includes a methane collection chamber, an ethane collection chamber, a propane collection chamber, and a butane and butane-containing hydrocarbon collection chamber arranged in parallel; the gas outlet of the low-temperature resistant coil is connected to the inlets of the methane collection chamber and the ethane collection chamber respectively through a pipeline via a second valve, a vacuum pump, a third valve, and a first bifurcated inlet valve; the outlets of the methane collection chamber and the ethane collection chamber are connected to the analysis system respectively through a pipeline via the first bifurcated outlet valve and a fourth valve;

[0016] The gas outlet of the low-temperature resistant coil is further connected to the inlets of the propane collection chamber and the butane and butane-containing hydrocarbons collection chamber respectively through a pipeline via a second valve, a vacuum pump, a third valve, and a second bifurcated inlet valve. The outlets of the propane collection chamber and the butane and butane-containing hydrocarbons collection chamber are respectively connected to the analysis system through a pipeline via the second bifurcated outlet valve and a fourth valve.

[0017] Among them, the inlets and outlets of the methane collection chamber, ethane collection chamber, propane collection chamber and butane and hydrocarbons above butane collection chamber are also respectively provided with inlet valves and outlet valves to respectively control the closing and opening of the methane collection chamber, ethane collection chamber, propane collection chamber and butane and hydrocarbons above butane collection chamber.

[0018] As a specific embodiment of the above-mentioned device of the present invention, a NaOH column and a CuSO4 column are sequentially arranged on the pipeline between the second bifurcated inlet valve and the inlet valve of the propane collection chamber.

[0019] As a specific embodiment of the above-mentioned device of the present invention, a low-temperature thermometer is respectively provided in the several cold-trap controlled chambers that are independently arranged from each other and the hot water storage tanks that are independently arranged from the cold-trap controlled chambers.

[0020] Among them, the cold trap controlled chamber and the hot water storage tank in the device provided by the present invention are set independently of each other. Those skilled in the art can reasonably set the number of cold trap controlled chambers according to the needs of on-site operations and can replace the cold trap controlled chambers according to the required temperature differences; in addition, those skilled in the art can also replace the cold trap controlled chamber with a hot water storage tank according to the actual required temperature conditions.

[0021] In the device provided by the present invention, the cold trap controlled chamber, vacuum pump, low temperature thermometer, NaOH column, CuSO4 column and analysis system are all conventional equipment.

[0022] For example, in a specific embodiment of the present invention, the cold trap controlled chamber is a stainless steel container, and the stainless steel container is coated with thermal insulation cotton; the NaOH column is a column filled with NaOH, and the CuSO4 column is a column filled with CuSO4.

[0023] On the other hand, the present invention also provides a method for enriching ultra-low concentration hydrocarbons in natural gas, wherein the method utilizes the above-mentioned device for enriching ultra-low concentration hydrocarbons in natural gas, and comprises:

[0024] (1) Open all valves in the device, remove air from the pipeline by using a vacuum pump, close the second valve, fill the low-temperature resistant coil with natural gas, and close the remaining valves in the device after the filling is completed; then place the low-temperature resistant coil in a first cold trap controlled chamber, wherein the first cold trap controlled chamber is filled with pure liquid nitrogen, and after all hydrocarbon gases including methane are solid, open the second valve and continue to vacuum to quickly remove H2 and N2 in the natural gas;

[0025] (2) closing the second valve and placing the low-temperature resistant coil in a second cold-trap controlled chamber to completely gasify only the methane, wherein the second cold-trap controlled chamber is filled with liquid nitrogen and ethanol;

[0026] (3) repeatedly placing the low-temperature resistant coil in the first cold trap controlled chamber and the second cold trap controlled chamber to purify the methane, opening the second valve and the third valve after purification to collect the methane in the fraction collection chamber, and closing all valves after the collection is completed;

[0027] (4) placing the low-temperature resistant coil in a third cold-trap controlled chamber to completely vaporize only the ethane, wherein the third cold-trap controlled chamber is filled with dry ice and acetone;

[0028] (5) The low-temperature resistant coil is repeatedly placed in the first cold trap controlled room and the third cold trap controlled room to purify the ethane. After purification, the second valve and the third valve are opened to collect the ethane using the fraction collection chamber. After the collection is completed, all valves are closed.

[0029] As a specific embodiment of the above method of the present invention, when it is desired to enrich and collect propane in natural gas, the method further comprises:

[0030] (6) placing the low-temperature resistant coil in step (5) in a fourth cold-trap controlled-temperature chamber to completely vaporize only the propane, wherein the fourth cold-trap controlled-temperature chamber contains ethylene glycol and dry ice;

[0031] (7) The low-temperature resistant coil is repeatedly placed in the first cold trap controlled room and the fourth cold trap controlled room to purify the propane. After purification, the second valve and the third valve are opened to collect the propane using the fraction collection chamber. After the collection is completed, all valves are closed.

[0032] As a specific embodiment of the above method of the present invention, the method further comprises, before step (6):

[0033] Place the low-temperature resistant coil in step (5) in the first cold-trap controlled-temperature chamber, wait until all hydrocarbon gases including propane are solid, open the second valve, and continue to evacuate; then place the low-temperature resistant coil in the fourth cold-trap controlled-temperature chamber.

[0034] In the present invention, considering that the propane content in natural gas is relatively low, in order to meet the requirement of the amount of propane after purification, it is generally necessary to re-add the natural gas sample to the low-temperature resistant coil in step (5); at this time, it is best to place the low-temperature resistant coil after the natural gas sample is added in the first cold trap temperature-controlled chamber again, so that all hydrocarbon gases including propane are in solid state.

[0035] As a specific embodiment of the above-described method of the present invention, in step (7), the low-temperature resistant coil is placed in the first cold-trap controlled temperature chamber, and the system is evacuated to remove impurity gases, and then the low-temperature resistant coil is placed in the fourth cold-trap controlled temperature chamber.

[0036] As a specific embodiment of the above method of the present invention, when it is desired to enrich and collect butane and hydrocarbons above butane in natural gas, the method further comprises:

[0037] (8) The low-temperature resistant coil in step (7) is placed in a hot water storage tank. After the butane and hydrocarbon components above butane in the natural gas are gasified, the second valve and the third valve are opened to collect the butane and hydrocarbon components above butane using the fraction collection chamber. After the collection is completed, all valves are closed.

[0038] As a specific embodiment of the above-described method of the present invention, in step (2), liquid nitrogen and ethanol are injected into the second cold-trap controlled chamber to make the temperature inside the second cold-trap controlled chamber higher than -161.5°C but lower than -88.6°C, so as to completely gasify only methane.

[0039] As a specific embodiment of the above method of the present invention, in step (2), liquid nitrogen and ethanol are injected into the second cold-trap controlled chamber to make the temperature inside the second cold-trap controlled chamber -150°C, so that the methane is completely gasified.

[0040] As a specific embodiment of the above method of the present invention, in step (3), the number of repetitions is 3-5 times.

[0041] As a specific embodiment of the above-described method of the present invention, in step (3), the first cold-trap controlled chamber and the second cold-trap controlled chamber are repeatedly used to purify methane so that the gas chromatograph cannot detect the presence of other impurity gases with lower boiling points than methane (such as H2 and He, etc.) in the natural gas.

[0042] As a specific embodiment of the above method of the present invention, in step (3), the methane collection chamber in the fraction collection chamber is frozen by using the first cold trap temperature-controlled chamber to assist in quickly and completely collecting methane.

[0043] As a specific embodiment of the above-described method of the present invention, in step (3), the low-temperature resistant coil is placed in a first cold-trap controlled temperature chamber, and the system is evacuated to remove impurity gases, and then the low-temperature resistant coil is placed in a second cold-trap controlled temperature chamber.

[0044] As a specific embodiment of the method described above, the following steps are further included between step (3) and step (4):

[0045] (4-1) Place the low-temperature resistant coil in step (3) in the first cold trap controlled room, wait until all hydrocarbon gases including ethane are solid, open the second valve, and continue to evacuate.

[0046] In the present invention, considering that the ethane content in natural gas is relatively low, in order to meet the requirement for the amount of ethane after purification, it is generally necessary to re-add the natural gas sample to the low-temperature resistant coil in step (3); at this time, it is best to place the low-temperature resistant coil after the natural gas sample is added in the first cold trap temperature-controlled chamber through step (4-1) so that all hydrocarbon gases including ethane are in solid state.

[0047] As a specific embodiment of the above-described method of the present invention, the steps between step (3) and step (4-1) further include: opening the second valve and the third valve, using a vacuum pump to evacuate the device to remove all gaseous methane, and then closing the second valve; repeatedly placing the low-temperature resistant coil in the first cold trap controlled chamber and the second cold trap controlled chamber to gasify all residual methane and evacuate the device.

[0048] As a specific embodiment of the above-described method of the present invention, in step (4), dry ice and acetone are injected into the third cold-trap controlled chamber to make the temperature inside the third cold-trap controlled chamber higher than -88.6°C but lower than -42.09°C, so as to completely vaporize only ethane.

[0049] As a specific embodiment of the above method of the present invention, in step (4), dry ice and acetone are injected into the third cold trap controlled chamber to make the temperature inside the cold trap controlled chamber -77°C to completely vaporize the ethane.

[0050] As a specific embodiment of the above method of the present invention, in step (5), the number of repetitions is 3-5 times.

[0051] As a specific embodiment of the above method of the present invention, in step (5), the ethane collection chamber in the fraction collection chamber is frozen by using the first cold trap temperature-controlled chamber to assist in quickly and completely collecting ethane.

[0052] As a specific embodiment of the above-described method of the present invention, in step (5), the low-temperature resistant coil is placed in the first cold-trap controlled temperature chamber, and the system is evacuated to remove impurity gases, and then the low-temperature resistant coil is placed in the third cold-trap controlled temperature chamber.

[0053] As a specific embodiment of the above-described method of the present invention, after step (5), the method further includes: opening the second valve and the third valve, using a vacuum pump to evacuate all gaseous ethane in the device, and then closing the second valve and the third valve.

[0054] As a specific embodiment of the above-described method of the present invention, in step (6), ethylene glycol and dry ice are injected into the fourth cold-trap controlled chamber to make the temperature inside the fourth cold-trap controlled chamber higher than -42.09°C but lower than -0.5°C, so that only propane is completely vaporized.

[0055] As a specific embodiment of the above method of the present invention, in step (6), ethylene glycol and dry ice are injected into the fourth cold-trap controlled chamber to make the temperature inside the cold-trap controlled chamber -10.5°C so that the propane is completely vaporized.

[0056] As a specific embodiment of the above method of the present invention, in step (7), the number of repetitions is 3-5 times.

[0057] As a specific embodiment of the above-described method of the present invention, in step (7), before collecting propane in the fraction collection chamber, the gas is first passed through a NaOH column and a CuSO4 column in sequence to remove CO2 and water from the gas, respectively.

[0058] As a specific embodiment of the above method of the present invention, in step (7), the propane collection chamber in the fraction collection chamber is frozen by using the first cold trap temperature-controlled chamber to assist in quickly and completely collecting the propane.

[0059] As a specific embodiment of the above method of the present invention, in step (8), the temperature of the hot water stored in the hot water storage tank is greater than -0.5°C.

[0060] As a specific embodiment of the above method of the present invention, in step (8), the temperature of the hot water stored in the hot water storage tank is 60°C.

[0061] As a specific embodiment of the above-described method of the present invention, in step (8), the butane and butane-containing hydrocarbons collection chamber in the fraction collection chamber is frozen using the first cold-trap controlled temperature chamber to assist in the rapid and complete collection of butane and butane-containing hydrocarbons.

[0062] Deep-seated natural gas is primarily composed of a mixture of hydrocarbons and non-hydrocarbon gases. Over 99 mol% of the hydrocarbons are methane, with less than 1 mol% of ethane and propane, and extremely trace amounts of light hydrocarbons. The method provided by this invention can enrich hydrocarbons above ultra-low concentrations of ethane in natural gas, enabling precise analysis of the carbon, hydrogen, and cluster isotopic signatures of each component.

[0063] In response to the problem that low-concentration hydrocarbons in natural gas are difficult to enrich and analyze, the present invention provides a device and method for enriching ultra-low concentration hydrocarbon substances in natural gas. According to the different boiling points of different components in natural gas, the device and method utilize cold traps with different media and hot water storage tanks to enrich low-concentration hydrocarbon substances in natural gas. The content of individual hydrocarbon molecules can be enriched to the milliliter level without fractionation (i.e., low-concentration hydrocarbon components in natural gas can be enriched without fractionation). This can provide the necessary technical support for further analysis of individual hydrocarbon gas molecules, and provide a basis for realizing isotope testing of natural gas components and each component, thereby providing strong technical support for natural gas, especially deep natural gas exploration. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0065] Figure 1 This is a schematic structural diagram of the device for enriching ultra-low concentration hydrocarbon substances in natural gas provided in Example 1 of the present invention.

[0066] Figure 2 This is a graph showing the freezing and boiling points of methane, ethane, propane, and butane in natural gas.

[0067] Description of main figures:

[0068] 1. Gas cylinder;

[0069] 2. The first cold trap controlled room;

[0070] 3. Fraction collection chamber;

[0071] 31. Methane collection chamber;

[0072] 311. Methane inlet valve;

[0073] 312. Methane outlet valve;

[0074] 32. Ethane collection chamber;

[0075] 321, ethane inlet valve;

[0076] 322. Ethane outlet valve;

[0077] 33. Propane collection chamber;

[0078] 331, propane inlet valve;

[0079] 332. Propane outlet valve;

[0080] 34. Collection chamber for butane and hydrocarbons above butane;

[0081] 341. Butane and hydrocarbon inlet valves above butane;

[0082] 342. Butane and hydrocarbon outlet valves above butane;

[0083] 4. Vacuum pump;

[0084] 5. First valve;

[0085] 6. Second valve;

[0086] 7. The third valve;

[0087] 71. First bifurcation inlet valve;

[0088] 72. Second bifurcated inlet valve;

[0089] 8. Fourth valve;

[0090] 81. First bifurcation outlet valve;

[0091] 82. Second bifurcated outlet valve;

[0092] 9. Analysis system;

[0093] 10. Low temperature thermometer;

[0094] 11. Low temperature resistant coil;

[0095] 12. NaOH column;

[0096] 13. CuSO4 column. DETAILED DESCRIPTION

[0097] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solutions of the present invention are described in detail below in conjunction with the following specific embodiments, but they should not be construed as limiting the scope of implementation of the present invention.

[0098] Example 1

[0099] This embodiment provides a device for enriching ultra-low concentration hydrocarbon substances in natural gas, wherein the structural schematic diagram of the device for enriching ultra-low concentration hydrocarbon substances in natural gas is as follows: Figure 1 As shown, from Figure 1 As can be seen, it includes: a first cold-trap controlled chamber 2, a second cold-trap controlled chamber, a third cold-trap controlled chamber, a fourth cold-trap controlled chamber, and a hot water storage tank independently provided with these cold-trap controlled chambers (only the first cold-trap controlled chamber is shown in the figure, and those skilled in the art can replace the first cold-trap controlled chamber with the second cold-trap controlled chamber, the third cold-trap controlled chamber, the fourth cold-trap controlled chamber and the hot water storage tank as needed), a fraction collection chamber 3 and a vacuum pump 4;

[0100] The hot water storage tank, the first cold trap controlled chamber 2, the second cold trap controlled chamber, the third cold trap controlled chamber and the fourth cold trap controlled chamber are used to hold the low temperature resistant coil 11;

[0101] A gas cylinder 1 for containing natural gas is connected to the gas inlet of the low-temperature resistant coil via a pipeline through a first valve 5. The gas outlet of the low-temperature resistant coil is connected to the inlet of the fraction collection chamber 3 via a pipeline through a second valve 6, a vacuum pump 4, and a third valve 7. The outlet of the fraction collection chamber 3 is connected to the analysis system 9 via a pipeline through a fourth valve 8.

[0102] The vacuum pump 4 is used to remove the air in the pipeline and other gas components to be removed during the purification process.

[0103] In this embodiment, the fraction collection chamber 3 includes a methane collection chamber 31, an ethane collection chamber 32, a propane collection chamber 33, and a butane and butane-containing hydrocarbon collection chamber 34 arranged in parallel; the gas outlet of the low-temperature resistant coil 11 is connected to the inlets of the methane collection chamber 31 and the ethane collection chamber 32 through a pipeline via a second valve 6, a vacuum pump 4, a third valve 7, and a first bifurcated inlet valve 71, respectively. The outlets of the methane collection chamber 31 and the ethane collection chamber 32 are connected to the analysis system 9 through pipelines via a first bifurcated outlet valve 81 and a fourth valve 8, respectively.

[0104] The gas outlet of the low-temperature resistant coil 11 is also connected to the inlets of the propane collection chamber 33 and the butane and butane-containing hydrocarbons collection chamber 34 through a pipeline via the second valve 6, the vacuum pump 4, the third valve 7, and the second bifurcated inlet valve 72, respectively. The outlets of the propane collection chamber 33 and the butane and butane-containing hydrocarbons collection chamber 34 are connected to the analysis system 9 through pipelines via the second bifurcated outlet valve 82 and the fourth valve 8, respectively.

[0105] The inlets and outlets of the methane collecting chamber 31, the ethane collecting chamber 32, the propane collecting chamber 33, and the butane and butane-related hydrocarbons collecting chamber 34 are further provided with inlet valves and outlet valves, respectively, to control the closing and opening of the methane collecting chamber 31, the ethane collecting chamber 32, the propane collecting chamber 33, and the butane and butane-related hydrocarbons collecting chamber 34, respectively. The inlet valve and outlet valve of the methane collecting chamber 31 are a methane inlet valve 311 and a methane outlet valve 312, the inlet valve and outlet valve of the ethane collecting chamber 32 are an ethane inlet valve 321 and an ethane outlet valve 322, the inlet valve and outlet valve of the propane collecting chamber 33 are a propane inlet valve 331 and a propane outlet valve 332, and the inlet valve and outlet valve of the butane and butane-related hydrocarbons collecting chamber 34 are a butane and butane-related hydrocarbons inlet valve 341 and a butane and butane-related hydrocarbons outlet valve 342.

[0106] In this embodiment, a NaOH column 12 and a CuSO 4 column 13 are sequentially provided on the pipeline between the second bifurcated inlet valve 72 and the propane inlet valve 331 .

[0107] In this embodiment, low-temperature thermometers 10 are respectively provided in the first cold-trap controlled chamber 2 , the second cold-trap controlled chamber, the third cold-trap controlled chamber, the fourth cold-trap controlled chamber and hot water storage tanks independently provided with the cold-trap controlled chambers.

[0108] Example 2

[0109] This embodiment provides a method for enriching ultra-low concentration hydrocarbons in natural gas, wherein the method utilizes the apparatus for enriching ultra-low concentration hydrocarbons in natural gas provided in Example 1 and includes the following specific steps:

[0110] 1) Connect the gas cylinder, open all valves in the device, remove air from the pipeline using a vacuum pump, close the second valve, open the gas cylinder valve, and fill the low-temperature resistant coil with natural gas. Wait for 2 minutes. After the filling is completed, close the gas cylinder valve and the remaining valves in the device. Then, place the low-temperature resistant coil in a first cold trap controlled chamber, wherein the first cold trap controlled chamber is filled with pure liquid nitrogen (temperature of -196°C). Wait for 30 minutes until all hydrocarbon gases including methane are solid. Then, open the second valve and continue to vacuum to quickly remove H2 and N2 in the natural gas.

[0111] 2) Close the second valve and quickly place the low-temperature resistant coil in a second cold trap chamber containing liquid nitrogen and ethanol (at -150°C) for 5 minutes to completely vaporize only the methane.

[0112] 3) repeatedly placing the low-temperature resistant coil in the first cold-trap controlled chamber and the second cold-trap controlled chamber (a total of three times), wherein after the low-temperature resistant coil is placed in the first cold-trap controlled chamber, the system is evacuated using a vacuum pump and the vacuum degree is controlled to be less than 50 mTorr to purify the methane, and the purification is completed when the gas chromatography detects no other hydrocarbon substances in the natural gas except methane. The content of the gaseous components after each purification is shown in Table 1; after purification, the second valve, the third valve, the first bifurcated inlet valve, and the methane inlet valve are opened to collect methane using the methane collection chamber in the fraction collection chamber, and the methane collection chamber in the fraction collection chamber is frozen using the first cold-trap controlled chamber to assist in quickly and completely collecting the methane. After the collection is completed, all valves are closed;

[0113] Table 1

[0114]

[0115] Open the second valve, the third valve, and the first bifurcated inlet valve, use a vacuum pump to evacuate all gaseous methane in the device, and then close the second valve; place the low-temperature resistant coil in the first cold trap controlled chamber and the second cold trap controlled chamber in sequence to vaporize all residual methane, and then evacuate and remove it;

[0116] 4) Considering the low ethane content, in order to meet the requirement for the amount of purified ethane, it is generally necessary to re-add natural gas sample to the low-temperature resistant coil. Then, the low-temperature resistant coil after the natural gas sample is added is placed in the first cold trap controlled chamber, where the first cold trap controlled chamber is filled with pure liquid nitrogen (temperature of -196°C). Wait for 10 minutes until all hydrocarbon gases, including ethane, are solid. Then, open the second valve and continue vacuuming.

[0117] 5) Place the low-temperature resistant coil in a third cold trap chamber containing dry ice and acetone (at -77°C) and wait for 5 minutes to allow only the ethane to completely vaporize.

[0118] 6) repeatedly placing the low-temperature resistant coil in the first cold-trap controlled chamber and the third cold-trap controlled chamber (a total of 4 times), wherein after the low-temperature resistant coil is placed in the first cold-trap controlled chamber, the system is evacuated by a vacuum pump and the vacuum degree is controlled to be <50 mTorr to purify the ethane, wherein the content of the gaseous components after each purification is shown in Table 2; after purification, the second valve, the third valve, the first bifurcated inlet valve, and the ethane inlet valve are opened, and the ethane collection chamber in the fraction collection chamber is used to collect ethane, and the ethane collection chamber in the fraction collection chamber is frozen by the first cold-trap controlled chamber for 5 minutes to assist in rapid and complete collection of ethane, and all valves are closed after collection is completed;

[0119] Table 2

[0120]

[0121] Open the second valve, the third valve, and the first bifurcated inlet valve, and use a vacuum pump to evacuate the device to remove all gaseous ethane. After the vacuum level is <50 mTorr, close the second valve, the third valve, and the first bifurcated inlet valve.

[0122] 7) Considering the low propane content, in order to meet the propane quantity requirement after purification, it is generally necessary to re-add natural gas sample to the low-temperature resistant coil. Then, the low-temperature resistant coil after adding natural gas sample is placed in the first cold trap controlled chamber, where the first cold trap controlled chamber is filled with pure liquid nitrogen (temperature is -196°C). Wait for 10 minutes until all hydrocarbon gases including propane are completely solid. Then, open the second and third valves and continue to vacuum to remove any possible ethane.

[0123] 8) Place the low-temperature resistant coil in a fourth cold-trap controlled chamber containing ethylene glycol and dry ice (at -10.5°C) for 5 minutes to completely vaporize the propane.

[0124] 9) The low-temperature resistant coil was repeatedly placed in the first cold-trap controlled chamber and the fourth cold-trap controlled chamber (a total of 4 times), wherein the low-temperature resistant coil was placed in the first cold-trap controlled chamber, and the system was evacuated by a vacuum pump and the vacuum degree was controlled to <50mTorr (in the embodiment of the present invention, the vacuum degree can be controlled to extract the components that do not need to be collected in the low-temperature resistant coil and prevent other components in the air from entering the coil) to purify the propane, wherein the content of hydrocarbon components in the gas after each purification is shown in Table 3, after purification, the second valve, the third valve and the second bifurcated inlet valve were opened, and the valves were closed after 5 minutes to allow the gas to fully react in the NaOH column and the CuSO4 column to remove CO2 and water in the gas. After 10 minutes, the propane inlet valve was opened, and the propane collection chamber in the fraction collection chamber was used to collect propane, and the propane collection chamber in the fraction collection chamber was frozen by the first cold-trap controlled chamber to assist in the rapid and complete collection of propane, the content of which is shown in Table 4, and all valves were closed after the collection was completed;

[0125] Table 3

[0126]

[0127] Table 4

[0128]

[0129] 10) The low-temperature resistant coil is placed in a hot water storage tank having a temperature of 60°C. The hot water is used to heat the low-temperature resistant coil for 10-20 minutes. After the residual butane and hydrocarbon components above butane in the low-temperature resistant coil are vaporized, the second valve, the third valve, the second bifurcated inlet valve, and the butane and hydrocarbon components above butane inlet valve are opened. The butane and hydrocarbon components above butane in the fraction collection chamber are collected using the butane and hydrocarbon components above butane collection chamber, and the butane and hydrocarbon components above butane in the fraction collection chamber are frozen using the first cold trap temperature control chamber to assist in the rapid and complete collection of butane and hydrocarbon components above butane. The collection is completed after 5 minutes, and the second valve is closed. The collected butane and hydrocarbon components above butane are reserved for isotope or component analysis.

[0130] The freezing point and boiling point data of methane, ethane, propane and butane in natural gas can be found in Figure 2 shown.

[0131] In summary, in order to address the problem of difficulty in enriching and analyzing low-concentration hydrocarbons in natural gas, an embodiment of the present invention provides a device and method for enriching ultra-low-concentration hydrocarbon substances in natural gas. The device and method provided by the embodiment of the present invention utilize cold traps with different media and hot water storage tanks based on the different boiling points of different components in natural gas to enrich low-concentration hydrocarbon substances in natural gas. The device and method can achieve the enrichment of the content of individual hydrocarbon molecules to the milliliter level without fractionation (that is, the non-fractionation enrichment of low-concentration hydrocarbon components in natural gas can be achieved). This can provide the necessary technical support for further analysis of individual hydrocarbon molecules, provide a basis for realizing isotope testing of natural gas components and each component, and provide strong technical support for deep natural gas exploration.

[0132] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, substitutions of equivalent components, or equivalent changes and modifications made within the scope of patent protection, should still fall within the scope of this patent. Furthermore, the technical features of this invention may be freely combined with one another, with other technical inventions, and with other technical inventions.

Claims

1. A method for enriching ultra-low concentration hydrocarbons in natural gas, characterized in that: The method utilizes a device for enriching ultra-low concentration hydrocarbon substances in natural gas, the device for enriching ultra-low concentration hydrocarbon substances in natural gas comprising: a plurality of cold trap controlled chambers independently provided, a hot water storage tank independently provided with the cold trap controlled chambers, at least one fraction collection chamber, and a vacuum pump; The hot water storage tank and the cold trap controlled room are used to hold low temperature resistant coils; A gas cylinder for containing natural gas is connected to the gas inlet of the low-temperature resistant coil via a pipeline through a first valve, the gas outlet of the low-temperature resistant coil is connected to the inlet of the fraction collection chamber via a pipeline through a second valve, a vacuum pump, and a third valve, and the outlet of the fraction collection chamber is connected to the analysis system via a pipeline through a fourth valve; The vacuum pump is used to remove air from the pipeline and other gas components to be removed during the purification process; The method comprises: (1) Open all valves in the device, remove air from the pipeline by using a vacuum pump, close the second valve, fill the low-temperature resistant coil with natural gas, and close the remaining valves in the device after the filling is completed; then place the low-temperature resistant coil in a first cold trap controlled chamber, wherein the first cold trap controlled chamber is filled with pure liquid nitrogen, and after all hydrocarbon gases including methane are solid, open the second valve and continue to vacuum to quickly remove H2 and N2 in the natural gas; (2) closing the second valve and placing the low-temperature resistant coil in a second cold-trap controlled chamber to completely gasify only the methane, wherein the second cold-trap controlled chamber is filled with liquid nitrogen and ethanol; (3) repeatedly placing the low-temperature resistant coil in the first cold trap controlled chamber and the second cold trap controlled chamber to purify the methane, opening the second valve and the third valve after purification to collect the methane in the fraction collection chamber, and closing all valves after the collection is completed; (4) placing the low-temperature resistant coil in a third cold-trap controlled chamber to completely vaporize only the ethane, wherein the third cold-trap controlled chamber is filled with dry ice and acetone; (5) The low-temperature resistant coil is repeatedly placed in the first cold trap controlled room and the third cold trap controlled room to purify the ethane. After purification, the second valve and the third valve are opened to collect the ethane using the fraction collection chamber. After the collection is completed, all valves are closed.

2. The method according to claim 1, characterized in that The fraction collecting chamber includes at least a first collecting chamber and a second collecting chamber, wherein the second collecting chamber is used to collect target hydrocarbon substances in natural gas, and the first collecting chamber is used to collect other hydrocarbon substances in natural gas, wherein the other hydrocarbon substances are hydrocarbon substances with a carbon number smaller than that of the target hydrocarbon substances.

3. The method according to claim 2, characterized in that The fraction collection chamber includes a methane collection chamber, an ethane collection chamber, a propane collection chamber, and a butane and butane-containing hydrocarbon collection chamber arranged in parallel; the gas outlet of the low-temperature resistant coil is connected to the inlets of the methane collection chamber and the ethane collection chamber respectively through a pipeline via a second valve, a vacuum pump, a third valve, and a first bifurcated inlet valve, and the outlets of the methane collection chamber and the ethane collection chamber are connected to the analysis system respectively through a pipeline via the first bifurcated outlet valve and a fourth valve; The gas outlet of the low-temperature resistant coil is further connected to the inlets of the propane collection chamber and the butane and butane-containing hydrocarbons collection chamber respectively through a pipeline via a second valve, a vacuum pump, a third valve, and a second bifurcated inlet valve. The outlets of the propane collection chamber and the butane and butane-containing hydrocarbons collection chamber are respectively connected to the analysis system through a pipeline via the second bifurcated outlet valve and a fourth valve. Among them, the inlets and outlets of the methane collection chamber, ethane collection chamber, propane collection chamber and butane and hydrocarbons above butane collection chamber are also respectively provided with inlet valves and outlet valves to respectively control the closing and opening of the methane collection chamber, ethane collection chamber, propane collection chamber and butane and hydrocarbons above butane collection chamber.

4. The method according to claim 3, characterized in that A NaOH column and a CuSO4 column are sequentially arranged on the pipeline between the second bifurcated inlet valve and the inlet valve of the propane collection chamber.

5. The method according to claim 1, wherein Low-temperature thermometers are respectively provided in a plurality of cold-trap controlled-temperature chambers that are independently arranged with each other and in hot water storage tanks that are independently arranged with the cold-trap controlled-temperature chambers.

6. The method according to any one of claims 1 to 5, characterized in that When it is desired to enrich and collect propane in natural gas, the method further comprises: (6) placing the low-temperature resistant coil in step (5) in a fourth cold-trap controlled-temperature chamber to completely vaporize only the propane, wherein the fourth cold-trap controlled-temperature chamber contains ethylene glycol and dry ice; (7) The low-temperature resistant coil is repeatedly placed in the first cold trap controlled room and the fourth cold trap controlled room to purify the propane. After purification, the second valve and the third valve are opened to collect the propane using the fraction collection chamber. After the collection is completed, all valves are closed.

7. The method according to claim 6, characterized in that The method further comprises, before step (6): Place the low-temperature resistant coil in step (5) in the first cold-trap controlled-temperature chamber, wait until all hydrocarbon gases including propane are solid, open the second valve, and continue to evacuate; then place the low-temperature resistant coil in the fourth cold-trap controlled-temperature chamber.

8. The method according to claim 6, characterized in that In step (7), the low-temperature resistant coil is placed in the first cold-trap controlled temperature chamber, and the system is evacuated to remove impurity gases, and then the low-temperature resistant coil is placed in the fourth cold-trap controlled temperature chamber.

9. The method according to claim 6, characterized in that When it is desired to enrich and collect butane and hydrocarbons above butane in natural gas, the method further comprises: (8) The low-temperature resistant coil in step (7) is placed in a hot water storage tank. After the butane and hydrocarbon components above butane in the natural gas are gasified, the second valve and the third valve are opened to collect the butane and hydrocarbon components above butane using the fraction collection chamber. After the collection is completed, all valves are closed.

10. The method according to any one of claims 1 to 5, characterized in that In step (2), liquid nitrogen and ethanol are injected into the second cold-trap controlled chamber to make the temperature inside the second cold-trap controlled chamber higher than -161.5°C but lower than -88.6°C, so as to completely gasify only methane.

11. The method according to claim 10, characterized in that In step (2), liquid nitrogen and ethanol are injected into the second cold-trap controlled chamber to make the temperature inside the second cold-trap controlled chamber -150° C., so that the methane is completely gasified.

12. The method according to any one of claims 1 to 5, characterized in that In step (3), the repetition frequency is 3-5 times.

13. The method according to any one of claims 1 to 5, characterized in that In step (3), the first cold-trap controlled chamber and the second cold-trap controlled chamber are repeatedly used to purify methane so that the gas chromatograph cannot detect the presence of other impurities with lower boiling points than methane in the natural gas.

14. The method according to any one of claims 1 to 5, characterized in that In step (3), the methane collection chamber in the fraction collection chamber is frozen using the first cold trap temperature-controlled chamber to assist in quickly and completely collecting methane.

15. The method according to any one of claims 1 to 5, characterized in that In step (3), the low-temperature resistant coil is placed in a first cold-trap controlled temperature chamber, and the system is evacuated to remove impurity gases, and then the low-temperature resistant coil is placed in a second cold-trap controlled temperature chamber.

16. The method according to any one of claims 1 to 5, characterized in that Also included between step (3) and step (4): (4-1) Place the low-temperature resistant coil in step (3) in the first cold trap controlled room, wait until all hydrocarbon gases including ethane are solid, open the second valve, and continue to evacuate.

17. The method according to claim 16, characterized in that Between step (3) and step (4-1), the following steps are also included: opening the second valve and the third valve, using a vacuum pump to evacuate the device to remove all gaseous methane, and then closing the second valve; repeatedly placing the low-temperature resistant coil in the first cold trap controlled chamber and the second cold trap controlled chamber to allow all residual methane to be gasified and vacuumed out.

18. The method according to any one of claims 1 to 5, characterized in that In step (4), dry ice and acetone are injected into the third cold trap controlled chamber to make the temperature inside the third cold trap controlled chamber higher than -88.6°C but lower than -42.09°C, so as to completely vaporize only ethane.

19. The method according to claim 18, characterized in that In step (4), dry ice and acetone are injected into the third cold trap controlled chamber to make the temperature inside the cold trap controlled chamber -77°C, so that the ethane is completely vaporized.

20. The method according to any one of claims 1 to 5, characterized in that In step (5), the number of repetitions is 3-5 times.

21. The method according to any one of claims 1 to 5, characterized in that In step (5), the ethane collection chamber in the fraction collection chamber is frozen using the first cold trap temperature-controlled chamber to assist in quickly and completely collecting ethane.

22. The method according to any one of claims 1 to 5, characterized in that In step (5), the low-temperature resistant coil is placed in the first cold-trap controlled temperature chamber, and the system is evacuated to remove impurity gases, and then the low-temperature resistant coil is placed in the third cold-trap controlled temperature chamber.

23. The method according to any one of claims 1 to 5, characterized in that After step (5), the method further includes: opening the second valve and the third valve, using a vacuum pump to create a vacuum to remove all gaseous ethane in the device, and then closing the second valve and the third valve.

24. The method according to claim 6, characterized in that In step (6), ethylene glycol and dry ice are injected into the fourth cold-trap controlled chamber to make the temperature inside the fourth cold-trap controlled chamber higher than -42.09°C but lower than -0.5°C, so as to completely vaporize only the propane.

25. The method according to claim 24, characterized in that In step (6), ethylene glycol and dry ice are injected into the fourth cold trap controlled chamber to make the temperature inside the cold trap controlled chamber -10.5°C, so that the propane is completely gasified.

26. The method according to claim 6, characterized in that In step (7), the number of repetitions is 3-5 times.

27. The method according to claim 6, characterized in that In step (7), before the propane is collected in the fraction collection chamber, the gas is first passed through a NaOH column and a CuSO4 column in sequence to remove CO2 and water from the gas, respectively.

28. The method according to claim 6, characterized in that In step (7), the propane collection chamber in the fraction collection chamber is frozen using the first cold trap temperature-controlled chamber to assist in quickly and completely collecting the propane.

29. The method according to claim 9, characterized in that In step (8), the temperature of the hot water stored in the hot water storage tank is greater than -0.5°C.

30. The method according to claim 9 or 29, characterized in that In step (8), the temperature of the hot water stored in the hot water storage tank is 60°C.

31. The method according to claim 9 or 29, characterized in that In step (8), the first cold trap temperature-controlled chamber is used to freeze the butane and hydrocarbon components above butane in the fraction collection chamber to assist in quickly and completely collecting the butane and hydrocarbon components above butane.

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