Marine natural gas processing method and system

Abstract

The present invention discloses a method for processing marine natural gas, comprising the following steps: S1, the marine raw natural gas is purified by a natural gas purification device to obtain purified raw gas, wherein the purified raw gas satisfies: oxygen volume percentage content ≤ 0.5%, sulfur content ≤ 0.1 mg / Nm 3 , free water content ≤10μM; S2, the purified raw gas is subjected to carbon separation by a carbon dioxide separation device to obtain purified gas and crude carbon dioxide gas, and the purified gas satisfies: carbon dioxide volume percentage content ≤0.5%; S3, the purified gas is subjected to cracking reaction in a molten medium cracking furnace to obtain a cracking mixed product; S4, the cracking mixed product is separated by a carbon collection device to obtain a solid carbon product and crude hydrogen; S5, the crude carbon dioxide gas and the crude hydrogen are passed into a methanol reactor to react to obtain an industrial-grade methanol product. The advantages are: the present invention can significantly improve the economic benefits of the marine natural gas processing method.

Description

Technical Field

[0001] The invention relates to a natural gas purification method, in particular to a comprehensive treatment method for marine natural gas. Background Art

[0002] my country has abundant oil and gas resources, among which the reserves of marine natural gas resources are large, which is an important guarantee for the development of my country's natural gas industry. The composition of marine natural gas is quite different from that of natural gas from other gas sources such as onshore coalbed methane and onshore shale gas. At present, similar treatment methods are usually used in this field. For example, typical treatment methods usually include pretreatment, dehydration, desulfurization, and decarbonization. Although the above method can also be used to process marine natural gas, the economic benefits are relatively low. Therefore, it is urgent to develop new technologies for the utilization of marine natural gas to support the high-quality development of my country's marine oil and gas industry. Summary of the invention

[0003] In order to solve the problem of low economic benefits of the marine natural gas processing methods in the prior art, the present invention provides a marine natural gas processing method and system.

[0004] The technical solution adopted by the present invention is: a method for processing marine natural gas, characterized in that it comprises the following steps:

[0005] S1. The marine raw natural gas is purified by a natural gas purification device to obtain a purified raw gas, wherein the purified raw gas meets the following requirements: oxygen content ≤ 0.5% by volume, sulfur content ≤ 0.1 mg / Nm 3 , free water content ≤10μM;

[0006] S2, the purified raw gas is subjected to carbon separation in a carbon dioxide separation device to obtain purified gas and crude carbon dioxide gas, wherein the purified gas satisfies: the volume percentage of carbon dioxide is ≤0.5%;

[0007] S3, the purified gas is subjected to a cracking reaction in a molten medium cracking furnace to obtain a cracking mixed product;

[0008] S4, the cracking mixed product is separated by a carbon collection device to obtain a solid carbon product and crude hydrogen;

[0009] S5. Passing the crude carbon dioxide gas and the crude hydrogen gas into a methanol reactor to react to obtain an industrial-grade methanol product.

[0010] As a further improvement of the present invention, the carbon dioxide volume fraction of the marine raw natural gas is ≥20%.

[0011] It is easy for those skilled in the art to understand that the "natural gas purification device" described in the present invention is a prior art in the art, and refers to a natural gas comprehensive purification device including a particulate filter, a free water separator, a desulfurizer, and a deoxygenator. For example, a specific scheme is given in the present invention: the natural gas purification device includes a filter for removing particulate matter from marine raw natural gas, a condensation separator for removing free water, a desulfurization tower for desulfurization, and a deoxygenation tower for deoxygenation. It is easy to understand that the above-mentioned condensation separator can also be replaced by a common adsorption dehydrator, and the desulfurization tower can also use a chemical desulfurizer, etc., as long as the corresponding purified raw gas index recorded in step S1 can be achieved.

[0012] As a further improvement of the present invention, the carbon dioxide separation device is an adsorption separation device or a membrane separation device.

[0013] The molten medium used in the molten medium cracking furnace is liquid metal, which may include copper, tin, bismuth, nickel, gallium, indium, and the like.

[0014] As a further improvement of the present invention, the solid carbon product includes graphite and graphene.

[0015] The present invention also discloses a marine natural gas processing system, comprising a natural gas purification device, a carbon dioxide separation device, a molten medium cracking furnace, a carbon collection device, a crude hydrogen storage tank, a methanol reactor and a methanol cooler which are sequentially connected through process pipelines; the gas outlet of the carbon dioxide separation device is connected to the crude carbon dioxide storage tank, and the gas outlet of the carbon dioxide storage tank is connected to the gas inlet of the methanol reactor.

[0016] The beneficial effects of the present invention are as follows: the unit cost of treating marine natural gas by the original treatment process is 10,140 yuan (main process treatment cost 6,850 yuan + waste gas emission treatment cost 3,290 yuan), and the unit economic benefit is 7,360 yuan (output value - cost); while the unit treatment cost after adopting this process is 11,500 yuan (main process treatment cost 9,500 yuan + methanol production cost 2,000 yuan), and the unit economic benefit is 9,910 yuan (output value - cost); compared with the original treatment process, the unit economic benefit is increased by 2,250 yuan. It can be seen that the present invention significantly improves the economic benefits of the marine natural gas treatment method. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is an equipment flow chart of the marine natural gas processing system of the present invention.

[0018] Figure 2 Schematic diagram of the structure of the molten medium cracking furnace of the embodiment. DETAILED DESCRIPTION

[0019] The present invention is further described below in conjunction with embodiments.

[0020] Embodiment 1:

[0021] The following steps are used to process marine natural gas:

[0022] S1. Marine raw natural gas (mined in the South China Sea of ​​my country, with a carbon dioxide volume fraction of 31.2%) is purified by a natural gas purification device to obtain a purified raw gas, wherein the oxygen volume percentage content of the purified raw gas is 0.37%, and the sulfur content is 0.064 mg / Nm 3 , the free water content is 8.6μM; the natural gas purification device includes a filter for removing particulate matter in marine raw natural gas, a condensation separator for removing free water, a desulfurization tower for removing sulfur, and a deoxygenation tower for removing oxygen.

[0023] S2. The purified raw gas is subjected to carbon separation in a carbon dioxide separation device to obtain purified gas and crude carbon dioxide gas, wherein the volume percentage of carbon dioxide in the purified gas is 0.42%; the carbon dioxide separation device is an adsorption separation device.

[0024] S3. The purified gas is subjected to a cracking reaction in a molten medium cracking furnace to obtain a cracking mixed product; the molten medium used in the molten medium cracking furnace is liquid metal, and the liquid metal is composed of copper, tin, bismuth, nickel, gallium and indium.

[0025] S4, the cracking mixed product is separated by a carbon collection device to obtain a solid carbon product and crude hydrogen;

[0026] S5. Passing the crude carbon dioxide gas and the crude hydrogen gas into a methanol reactor to react and obtain a methanol product. The obtained methanol product was tested for components according to the method of GB338-2011, and the results are shown in Table 1.

[0027] Embodiment 2:

[0028] The following steps are used to process marine natural gas:

[0029] S1. Marine raw natural gas (mined in the South my country Sea, with a carbon dioxide volume fraction of 23.0%) is purified by a natural gas purification device to obtain a purified raw gas, wherein the oxygen volume percentage content of the purified raw gas is 0.42% and the sulfur content is 0.075 mg / Nm 3 , the free water content is 8.9μM; the natural gas purification device includes a filter for removing particulate matter in marine raw natural gas, a condensation separator for removing free water, a desulfurization tower for removing sulfur, and a deoxygenation tower for removing oxygen.

[0030] S2. The purified raw gas is subjected to carbon separation in a carbon dioxide separation device to obtain purified gas and crude carbon dioxide gas, wherein the volume percentage of carbon dioxide in the purified gas is 0.38%; the carbon dioxide separation device is an adsorption separation device.

[0031] S3. The purified gas is subjected to a cracking reaction in a molten medium cracking furnace to obtain a cracking mixed product; the molten medium used in the molten medium cracking furnace is liquid metal, and the liquid metal is composed of copper, tin, bismuth, nickel, gallium and indium.

[0032] S4, the cracking mixed product is separated by a carbon collection device to obtain a solid carbon product and crude hydrogen;

[0033] S5. Passing the crude carbon dioxide gas and the crude hydrogen gas into a methanol reactor to react and obtain a methanol product. The obtained methanol product was tested for components according to the method of GB338-2011, and the results are shown in Table 1.

[0034] Embodiment three:

[0035] The following steps are used to process marine natural gas:

[0036] S1. Marine raw natural gas (mined in the South China Sea of ​​my country, with a carbon dioxide volume fraction of 35.1%) is purified by a natural gas purification device to obtain a purified raw gas, wherein the oxygen volume percentage content of the purified raw gas is 0.43%, and the sulfur content is 0.091 mg / Nm 3 , the free water content is 9.2μM; the natural gas purification device includes a filter for removing particulate matter in marine raw natural gas, a condensation separator for removing free water, a desulfurization tower for removing sulfur, and a deoxygenation tower for removing oxygen.

[0037] S2. The purified raw gas is subjected to carbon separation in a carbon dioxide separation device to obtain purified gas and crude carbon dioxide gas, wherein the volume percentage of carbon dioxide in the purified gas is 0.47%; the carbon dioxide separation device is an adsorption separation device.

[0038] S3. The purified gas is subjected to a cracking reaction in a molten medium cracking furnace to obtain a cracking mixed product; the molten medium used in the molten medium cracking furnace is liquid metal, and the liquid metal is composed of copper, tin, bismuth, nickel, gallium and indium.

[0039] S4, the cracking mixed product is separated by a carbon collection device to obtain a solid carbon product and crude hydrogen;

[0040] S5. Passing the crude carbon dioxide gas and the crude hydrogen gas into a methanol reactor to react and obtain a methanol product. The obtained methanol product was tested for components according to the method of GB338-2011, and the results are shown in Table 1.

[0041] Comparative Example 1:

[0042] This comparative example is a control experiment of Example 1, and is implemented according to the same steps and conditions as Example 1, except that the marine natural gas to be processed in Example 1 is replaced by onshore coalbed methane, and the other steps remain unchanged, and the quality of the purified natural gas is adjusted by controlling the natural gas purification device and the carbon dioxide separation device to ensure that it is basically consistent with Example 1 for comparison. The specific method is as follows:

[0043] S1. Onshore coalbed methane (with a carbon dioxide volume fraction of 5.7%) is purified by a natural gas purification device to obtain a purified raw gas, wherein the oxygen volume percentage content of the purified raw gas is 0.36% and the sulfur content is 0.062 mg / Nm 3 , the free water content is 8.4μM; the natural gas purification device includes a filter for removing particulate matter in marine raw natural gas, a condensation separator for removing free water, a desulfurization tower for removing sulfur, and a deoxygenation tower for removing oxygen.

[0044] S2. The purified raw gas is subjected to carbon separation in a carbon dioxide separation device to obtain purified gas and crude carbon dioxide gas, wherein the volume percentage of carbon dioxide in the purified gas is 0.42%; the carbon dioxide separation device is an adsorption separation device.

[0045] S3. The purified gas is subjected to a cracking reaction in a molten medium cracking furnace to obtain a cracking mixed product; the molten medium used in the molten medium cracking furnace is liquid metal, and the liquid metal is composed of copper, tin, bismuth, nickel, gallium and indium.

[0046] S4, the cracking mixed product is separated by a carbon collection device to obtain a solid carbon product and crude hydrogen;

[0047] S5. Passing the crude carbon dioxide gas and the crude hydrogen gas into a methanol reactor to react and obtain a methanol product. The obtained methanol product was tested for components according to the method of GB338-2011, and the results are shown in Table 1.

[0048] Comparative Example 2:

[0049] This comparative example is a control experiment of Example 1, and is implemented according to the same steps and conditions as Example 1, except that the marine natural gas to be processed in Example 1 is replaced with onshore shale gas, and the other steps remain unchanged, and the quality of the purified natural gas is adjusted by controlling the natural gas purification device and the carbon dioxide separation device to ensure that it is basically consistent with Example 1 for comparison. The specific method is as follows:

[0050] S1. Onshore shale gas (with a carbon dioxide volume fraction of 9.3%) is purified by a natural gas purification device to obtain a purified raw gas, wherein the purified raw gas has an oxygen volume percentage content of 0.36% and a sulfur content of 0.060 mg / Nm 3 , the free water content is 8.5μM; the natural gas purification device includes a filter for removing particulate matter in marine raw natural gas, a condensation separator for removing free water, a desulfurization tower for removing sulfur, and a deoxygenation tower for removing oxygen.

[0051] S2. The purified raw gas is subjected to carbon separation in a carbon dioxide separation device to obtain purified gas and crude carbon dioxide gas, wherein the volume percentage of carbon dioxide in the purified gas is 0.40%; the carbon dioxide separation device is an adsorption separation device.

[0052] S3. The purified gas is subjected to a cracking reaction in a molten medium cracking furnace to obtain a cracking mixed product; the molten medium used in the molten medium cracking furnace is liquid metal, and the liquid metal is composed of copper, tin, bismuth, nickel, gallium and indium.

[0053] S4, the cracking mixed product is separated by a carbon collection device to obtain a solid carbon product and crude hydrogen;

[0054] S5. Passing the crude carbon dioxide gas and the crude hydrogen gas into a methanol reactor to react and obtain a methanol product. The obtained methanol product was tested for components according to the method of GB338-2011, and the results are shown in Table 1.

[0055] Table 1 Methanol product composition test results

[0056]

[0057] As can be seen from Table 1, the quality index of the methanol product obtained by treating marine natural gas using the method of the present invention can fully meet the product index requirements of industrial-grade methanol. After the treatment object is replaced with onshore coalbed methane and onshore shale gas, the quality of the obtained methanol product is significantly reduced, and it cannot be sold and can only be discharged as wastewater; it is necessary to add an additional purification system to the original treatment plan, such as a deep purification device or system for crude hydrogen and crude carbon dioxide, as well as methanol extraction, distillation, ion membrane, biofilm system, etc. This will result in the economic benefits of methanol recovery using this method being far lower than the additional purification treatment cost, resulting in the entire treatment plan becoming meaningless. This is due to the difference in the composition of marine gas and onshore gas. Therefore, the marine natural gas treatment method of the present invention is only applicable to the comprehensive treatment of marine gas.

Claims

1. A method for processing marine natural gas, characterized in that: The steps include: S1. The marine raw natural gas is purified by a natural gas purification device to obtain a purified raw gas, wherein the purified raw gas meets the following requirements: oxygen content ≤ 0.5% by volume, sulfur content ≤ 0.1 mg / Nm 3 , free water content ≤10μM; S2, the purified raw gas is subjected to carbon separation in a carbon dioxide separation device to obtain purified gas and crude carbon dioxide gas, wherein the purified gas satisfies: the volume percentage of carbon dioxide is ≤0.5%; S3, the purified gas is subjected to a cracking reaction in a molten medium cracking furnace to obtain a cracking mixed product; S4, the cracking mixed product is separated by a carbon collection device to obtain a solid carbon product and crude hydrogen; S5. Passing the crude carbon dioxide gas and the crude hydrogen gas into a methanol reactor to react to obtain an industrial-grade methanol product.

2. The method for processing marine natural gas according to claim 1, characterized in that: The carbon dioxide volume fraction of the marine raw natural gas is ≥20%.

3. The method for processing marine natural gas according to claim 1, characterized in that: The natural gas purification device comprises a filter for removing particulate matter in marine raw natural gas, a condensation separator for removing free water, a desulfurization tower for removing sulfur and a deoxygenation tower for removing oxygen.

4. The method for processing marine natural gas according to claim 1, characterized in that: The carbon dioxide separation device is an adsorption separation device or a membrane separation device.

5. The method for processing marine natural gas according to claim 1, characterized in that: The molten medium used in the molten medium cracking furnace is liquid metal.

6. The method for processing marine natural gas according to claim 5, characterized in that: The liquid metals include copper, tin, bismuth, nickel, gallium and indium.

7. The method for processing marine natural gas according to any one of claims 1 to 6, characterized in that: The solid carbon products include graphite and graphene.

8. A marine natural gas processing system, comprising a natural gas purification device, a carbon dioxide separation device, a molten medium cracking furnace, a carbon collection device, a crude hydrogen storage tank, a methanol reactor and a methanol cooler, which are sequentially connected through process pipelines; the gas outlet of the carbon dioxide separation device is connected to the crude carbon dioxide storage tank, and the gas outlet of the crude carbon dioxide storage tank is connected to the gas inlet of the methanol reactor.

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