Natural gas desulfurization method and device

Abstract

The invention relates to a natural gas desulfurization method and device, and the method comprises the following steps: step S101, carrying out preliminary desulfurization on natural gas containing hydrogen sulfide to obtain desulfurized pregnant solution and preliminarily treated natural gas; step S102, carrying out flash evaporation on the desulfurized pregnant solution to obtain the pregnant solution and flash evaporation gas after flash evaporation; step S103, washing the flash steam through a washing solution so as to remove residual sulfur in the flash steam; step S104, washing the primarily treated natural gas by using a washing solution for washing flash steam to obtain final desulfurized natural gas; and S105, washing the primarily treated natural gas by using a washing solution for washing the flash steam to obtain the target natural gas. The content of organic sulfur in the natural gas can be reduced, and the regeneration energy consumption of an original desulfurization device is not increased.

Description

Technical Field

[0001] The present invention relates to the technical field of gas separation, and in particular to a natural gas desulfurization method and device. Background Art

[0002] Natural gas is a clean, low-carbon fossil energy source, and plays an important role in the global energy green and low-carbon transformation. However, natural gas extracted from underground usually contains a certain amount of H2S, CO2, COS, mercaptan and other organic sulfur, which needs to be processed before use. According to different sulfur contents, different natural gas treatment methods such as alcohol amine method, sulfone amine method, and wet oxidation method have been developed. Among them: alcohol amine method is the most widely used.

[0003] The patent with publication number CN116262190A uses an aqueous solution of a mixture of methyldiethanolamine and N-acetylmorpholine and adds an auxiliary agent that promotes the absorption of methyl mercaptan and carbonyl sulfide to remove organic sulfur.

[0004] CN116103067A uses an alkoxypropylamine compound to add to an organic amine solution to improve the organic sulfur removal rate. The patent with publication number CN101507891B uses thiazoles or fatty amines, phenols or a mixture thereof and a silicone defoamer to add to a solution of sterically hindered amines and alkanolamines to improve the organic sulfur removal effect. Publication number CN114699882A uses an etheramine compound such as 1-(2-(diethylamino)ethoxy)-2-butylamine alone or mixed with an alcohol amine aqueous solution to improve the organic sulfur removal effect.

[0005] However, the above methods all focus on improving the formula of the desulfurization liquid. The above methods do not take into account that after the desulfurization liquid absorbs a large amount of H2S and CO2, the solubility of organic sulfur in the amine liquid (the washing liquid described in the present invention) will be reduced, thereby affecting the removal of organic sulfur. If the amine liquid is replaced, the cost will increase. In addition, the above methods do not take into account the fact that the small amount of sulfur present in the regenerated gas during the regeneration process of the amine liquid will cause pollution to the environment. Summary of the invention

[0006] The main purpose of the present invention is to overcome the defects of the existing natural gas desulfurization method and device and to provide a new natural gas desulfurization method and device. The technical problem to be solved is to reduce the organic sulfur content in natural gas without increasing the regeneration energy consumption of the original desulfurization device, thereby making it more suitable for practical use and having industrial utilization value.

[0007] The main technical contents of the present invention are as follows:

[0008] In one aspect, a method for desulfurizing natural gas is provided, the method comprising:

[0009] Step S101, preliminarily desulfurizing natural gas containing hydrogen sulfide to obtain desulfurized rich liquid and preliminarily treated natural gas;

[0010] Step S102, flashing the desulfurized rich liquid to obtain flashed rich liquid and flash gas;

[0011] Step S103, washing the flash gas with a washing liquid to remove the residual sulfur in the flash gas;

[0012] Step S104, washing the preliminarily treated natural gas with a washing liquid for washing the flash gas to obtain a final desulfurized natural gas;

[0013] Step S105 , washing the preliminarily treated natural gas with a washing liquid for washing the flash gas to obtain target natural gas.

[0014] In an optional embodiment, in the step S101, a desulfurization tower is used to perform preliminary desulfurization on the natural gas containing hydrogen sulfide, wherein the desulfurizer in the desulfurization tower is an organic amine solution.

[0015] In an optional embodiment, the organic amine solution is a diethanolamine solution.

[0016] In an optional embodiment, in the step S103, a washing tower is used to wash the flash gas, wherein the washing tower is a washing tower with at least two layers.

[0017] In an optional embodiment, the washing liquid in step S103 includes a first branch amine liquid and a second branch amine liquid;

[0018] The first branch amine liquid is used to wash the flash gas, and the second branch amine liquid is used to wash the preliminarily treated natural gas.

[0019] In an optional embodiment, it also includes:

[0020] The sulfur content in the washed and preliminarily treated natural gas is detected. When the sulfur content is greater than a preset content, the preliminarily treated natural gas is washed again with the second branch amine liquid until the sulfur content is less than the preset content.

[0021] In an optional embodiment, the washing liquid in step S103 includes a first branch amine liquid and a second branch amine liquid;

[0022] The first branch amine liquid washes the flash gas, and the second branch amine liquid after washing the flash gas washes the preliminarily treated natural gas.

[0023] In an optional embodiment, in step S101, the desulfurization pressure is 5.5MPa-6.5MPa.

[0024] On the other hand, a natural gas desulfurization device is provided, the natural gas desulfurization device comprising: a desulfurization tower, a flash tower and a washing tower;

[0025] The desulfurization tower is provided with an air inlet and a liquid outlet at the bottom, and is connected to a washing tower at the top. The washing tower is used to process the hydrogen sulfide gas in the preliminarily treated natural gas at the top of the desulfurization tower;

[0026] The air inlet at the bottom of the desulfurization tower is used for the entry of natural gas containing hydrogen sulfide, and the liquid outlet is connected to the top of the flash tower through a pipeline;

[0027] The gas outlet of the flash tower is connected to the washing tower.

[0028] In an optional embodiment, a control valve is further included, and the control valve is arranged on the pipeline between the desulfurization tower, the flash tower and the washing tower.

[0029] By means of the above technical solution, the natural gas desulfurization method and device of the present invention have at least the following advantages:

[0030] The method provided in the embodiment of the present invention washes the flash gas with a washing liquid. Since a small amount of sulfur will still exist in the flash gas after flash evaporation, it will pollute the environment if it is directly discharged. The embodiment of the present invention washes the flash gas with a washing liquid to remove the remaining sulfur in the flash gas. Moreover, since the sulfur content in the flash gas is not high, the sulfur content in the washing liquid after washing the flash gas is also not high. Therefore, the washing liquid can continue to be used to wash the preliminarily treated natural gas to remove the sulfur in the preliminarily treated natural gas. The present invention can reduce the organic sulfur content in the natural gas without increasing the regeneration energy consumption of the original desulfurization device.

[0031] In summary, the special natural gas desulfurization method and device of the present invention washes the flash gas with a washing liquid. Since there is still a small amount of sulfur in the flash gas after flash evaporation, if it is directly discharged, it will pollute the environment. The embodiment of the present invention washes the flash gas with a washing liquid to remove the residual sulfur in the flash gas; and based on the low sulfur content in the flash gas, the sulfur content in the washing liquid after washing the flash gas is also low, so the washing liquid can continue to be used to wash the preliminarily treated natural gas to remove the sulfur in the preliminarily treated natural gas. The present invention can reduce the organic sulfur content in the natural gas without increasing the regeneration energy consumption of the original desulfurization device. It has the above-mentioned advantages and practical value, and no similar design has been published or used in similar natural gas desulfurization methods and devices, so it is indeed innovative. It has great improvements in both the natural gas desulfurization method and device and the function, and has great progress in technology, and has produced good and practical effects. It has multiple functions that are enhanced compared with the existing natural gas desulfurization method and device, so it is more suitable for practical use and has a wide range of industrial utilization value. It is truly a novel, progressive and practical new design.

[0032] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings.

[0033] The specific natural gas desulfurization method and device of the present invention are described in detail by the following examples and their accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic flow chart of a natural gas desulfurization method provided in an embodiment of the present invention.

[0035] Figure 2 A schematic diagram of the structure of a natural gas desulfurization device provided by the prior art.

[0036] Figure 3 A schematic diagram of the structure of a natural gas desulfurization device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0037] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the natural gas desulfurization method and device proposed by the present invention are described in detail below in combination with the accompanying drawings and preferred embodiments.

[0038] See also Figure 1 As shown, the natural gas desulfurization method and device of the preferred embodiment of the present invention mainly include the following steps:

[0039] Step S101, preliminarily desulfurize natural gas containing hydrogen sulfide to obtain desulfurized rich liquid and preliminarily treated natural gas.

[0040] Step S102, flashing the desulfurized rich liquid to obtain flashed rich liquid and flash gas.

[0041] Step S103, washing the flash gas with a washing liquid to remove the residual sulfur in the flash gas.

[0042] Step S104: washing the preliminarily treated natural gas with a washing liquid for washing the flash gas to obtain a final desulfurized natural gas.

[0043] Step S105: washing the preliminarily treated natural gas with a washing liquid for washing the flash gas to obtain target natural gas.

[0044] The method provided by the embodiment of the present invention has at least the following beneficial effects:

[0045] The method provided in the embodiment of the present invention washes the flash gas with a washing liquid. Since a small amount of sulfur will still exist in the flash gas after flash evaporation, it will pollute the environment if it is directly discharged. The embodiment of the present invention washes the flash gas with a washing liquid to remove the remaining sulfur in the flash gas. Moreover, since the sulfur content in the flash gas is not high, the sulfur content in the washing liquid after washing the flash gas is also not high. Therefore, the washing liquid can continue to be used to wash the preliminarily treated natural gas to remove the sulfur in the preliminarily treated natural gas. The present invention can reduce the organic sulfur content in the natural gas without increasing the regeneration energy consumption of the original desulfurization device.

[0046] The method and device provided by the embodiments of the present invention will be further explained and described below through optional embodiments.

[0047] It should be noted that in the embodiment of the present invention, the natural gas containing hydrogen sulfide is preliminarily desulfurized to obtain the desulfurized rich liquid and preliminarily treated natural gas, which can be prepared by the pure amine method in the related technology.

[0048] In an optional embodiment, in step S101, a desulfurization tower is used to perform preliminary desulfurization on the natural gas containing hydrogen sulfide, wherein the desulfurizer in the desulfurization tower is an organic amine solution.

[0049] In an optional embodiment, the organic amine solution is a diethanolamine solution.

[0050] In an optional embodiment, in step S103, a washing tower is used to wash the flash gas, wherein the washing tower has at least two layers of washing towers.

[0051] Two layers of washing towers are connected in series. Furthermore, the number of plates between the two layers of washing towers in series increases along the gas flow direction, thereby improving the washing effect of hydrogen sulfide in the gas, or when the hydrogen sulfide gas in the upper layer of washing tower is not washed cleanly, it can be further washed by the next layer of washing tower.

[0052] In an optional embodiment, the washing liquid in step S103 includes a first branch amine liquid and a second branch amine liquid.

[0053] The first branch amine liquid is used to wash the flash gas, and the second branch amine liquid is used to wash the preliminarily treated natural gas.

[0054] In an optional embodiment, the method further includes: detecting the sulfur content in the washed initially treated natural gas, and when the sulfur content is greater than a preset content, using a second branch amine liquid to wash the initially treated natural gas again until the sulfur content is less than a preset content.

[0055] In this embodiment, the first branch amine liquid and the second branch amine liquid are two independent amine liquids, that is, the first branch amine liquid and the second branch amine liquid are both amine liquids that have not absorbed hydrogen sulfide. The flash gas can be washed by the amine liquids of the two lean liquid branches to remove hydrogen sulfide in the flash gas, and the preliminarily treated natural gas can be washed to remove hydrogen sulfide in the preliminarily treated natural gas. This embodiment improves the treatment effect of hydrogen sulfide contained in natural gas and reduces the pollution of hydrogen sulfide in the flash gas to the environment.

[0056] In an optional embodiment, the washing liquid in step S103 includes a first branch amine liquid and a second branch amine liquid.

[0057] The first branch amine liquid washes the flash gas, and the second branch amine liquid after washing the flash gas washes the preliminarily treated natural gas.

[0058] In this embodiment, the second branch amine liquid is a branch of the first branch amine liquid, that is, the second branch amine liquid comes from the first branch amine liquid. In other words, the second branch amine liquid is formed by washing the flash gas with the first branch amine liquid. In this embodiment, the above method can achieve the treatment of a small amount of hydrogen sulfide in natural gas on the one hand, and on the other hand, there is no need to replace new amine liquid, thereby reducing the treatment cost of hydrogen sulfide.

[0059] In an optional embodiment, in step S101, the desulfurization pressure is 5.5MPa-6.5MPa.

[0060] See also Figure 1 , Figure 1 For the desulfurization device schematic diagram provided for related technologies, please refer to Figure 2On the other hand, a natural gas desulfurization device is also provided. Figure 2 A schematic diagram of a desulfurization device provided in an embodiment of the present invention, wherein the natural gas desulfurization device comprises: a desulfurization tower 1, a flash tower 2 and a washing tower 3.

[0061] The desulfurization tower 1 is provided with an air inlet and a liquid outlet at the bottom, and is connected to a washing tower 3 at the top. The washing tower 3 is used to process the hydrogen sulfide gas in the preliminarily treated natural gas at the top of the desulfurization tower 1 .

[0062] The air inlet at the bottom of the desulfurization tower 1 is used for the entry of natural gas containing hydrogen sulfide, and the liquid outlet is connected to the top of the flash tower 2 through a pipeline.

[0063] The gas outlet of the flash tower 2 is connected to the scrubbing tower.

[0064] In an optional embodiment, a control valve is further included, and the control valve is arranged on the pipeline between the desulfurization tower, the flash tower and the washing tower.

[0065] The method provided by the present invention will be explained and illustrated by means of specific examples below.

[0066] The acidic impurities in natural gas are: H2S 5.4%, CO2 8.3%, methyl mercaptan 250mg / Nm 3 ,Ethyl mercaptan 89mg / Nm 3 .

[0067] Example 1

[0068] The desulfurization pressure is 5.5 MPa, and 45% wt amine solution is used for desulfurization. The amount of amine liquid used for washing flash gas is 6.5% of the total amine liquid. Figure 2 ) after desulfurization by the method provided by 3 .

[0069] Example 2

[0070] The desulfurization pressure is 6.0 MPa, and 45% wt amine solution is used for desulfurization. The amount of amine liquid used for washing flash gas is 6.6% of the total amine liquid. Figure 2 ) After desulfurization by the method provided by 3 .

[0071] Example 3

[0072] The desulfurization pressure is 5.5 MPa, and 45% wt amine solution is used for desulfurization. The amount of amine liquid used for washing flash gas is 6.5% of the total amine liquid. Figure 2) After desulfurization by the method provided by 3 .

[0073] Example 4

[0074] The desulfurization pressure is 6.5 MPa, and 45% wt amine solution is used for desulfurization. The amount of amine liquid used for washing flash gas is 6.5% of the total amine liquid. Figure 2 After desulfurization by the method provided by ), the mercaptan content in the purified natural gas (target natural gas) is 13.5 mg / Nm 3 .

[0075] Comparative Example 1

[0076] The desulfurization pressure is 5.5MPa, 45%wt methyldiethanolamine is used for desulfurization, and the amount of amine liquid used for washing flash gas is 6.5% of the total amine liquid. Figure 2 After desulfurization by the method shown in the reference document 1, the mercaptan content in the purified natural gas (target natural gas) was measured to be 110 mg / Nm 3 .

[0077] Comparative Example 2

[0078] The desulfurization pressure is 5.5MPa, 45%wt methyldiethanolamine is used for desulfurization, and the amount of amine liquid used for washing flash gas is 6.5% of the total amine liquid. Figure 2 After desulfurization by the method shown in (reference document 1), the mercaptan content in the purified natural gas (target natural gas) is 62 mg / Nm 3 .

[0079] Comparative Example 3

[0080] The desulfurization pressure is 5.5MPa, 30%wt diethanolamine is used for desulfurization, the amount of amine liquid used for washing flash gas is 7% of the total amine liquid, and the attached Figure 2 After desulfurization by the method shown in (reference document 1), the mercaptan content in the purified natural gas (target natural gas) is 87 mg / Nm 3 .

[0081] Comparative Example 4

[0082] The desulfurization pressure is 5.5MPa, 30%wt diethanolamine is used for desulfurization, the amount of amine liquid used for washing flash gas is 7% of the total amine liquid, and the attached Figure 2 After desulfurization by the method shown in (reference document 1), the mercaptan content in the purified natural gas (target natural gas) is 45 mg / Nm 3 .

[0083] Comparative Example 5

[0084] The desulfurization pressure is 5.5MPa, and a 45%wt hindered amine solution of a certain formula is used for desulfurization. The amount of amine liquid used to wash the flash gas is 6.5% of the total amine liquid. Figure 2 After desulfurization by the method shown in (reference document 1), the mercaptan content in the purified natural gas (target natural gas) is 38 mg / Nm 3 .

[0085] It can be seen from Examples 1 to 4 and Comparative Examples 1 to 5 that after desulfurization by the method provided in the embodiments of the present invention, the mercaptan content in the purified natural gas (target natural gas) is less than 15 mg / Nm 3 Below, while the mercaptan content in Comparative Examples 1 to 5 is all below 35 mg / Nm 3 It can be seen from the above that the method provided by the embodiment of the present invention has a high desulfurization effect.

[0086] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes by using the methods and technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A natural gas desulfurization method, characterized in that: The method comprises Step S101, preliminarily desulfurizing natural gas containing hydrogen sulfide to obtain desulfurized rich liquid and preliminarily treated natural gas; Step S102, flashing the desulfurized rich liquid to obtain flashed rich liquid and flash gas; Step S103, washing the flash gas with a washing liquid to remove the residual sulfur in the flash gas; Step S104, washing the preliminarily treated natural gas with a washing liquid for washing the flash gas to obtain a final desulfurized natural gas; Step S105 , washing the preliminarily treated natural gas with a washing liquid for washing the flash gas to obtain target natural gas.

2. The natural gas desulfurization method according to claim 1, characterized in that: In the step S101, a desulfurization tower is used to perform preliminary desulfurization on the natural gas containing hydrogen sulfide, wherein the desulfurizer in the desulfurization tower is an organic amine solution.

3. The natural gas desulfurization method according to claim 2, characterized in that: The organic amine solution is a diethanolamine solution.

4. The natural gas desulfurization method according to claim 1, characterized in that: In the step S103, a washing tower is used to wash the flash gas, wherein the washing tower is a washing tower with at least two layers.

5. The natural gas desulfurization method according to claim 1, characterized in that: The washing liquid in step S103 includes a first branch amine liquid and a second branch amine liquid; The first branch amine liquid is used to wash the flash gas, and the second branch amine liquid is used to wash the preliminarily treated natural gas.

6. The natural gas desulfurization method according to claim 5, characterized in that: Also includes: The sulfur content in the washed and preliminarily treated natural gas is detected. When the sulfur content is greater than a preset content, the preliminarily treated natural gas is washed again with the second branch amine liquid until the sulfur content is less than the preset content.

7. The natural gas desulfurization method according to claim 1, characterized in that: The washing liquid in step S103 includes a first branch amine liquid and a second branch amine liquid; The first branch amine liquid washes the flash gas, and the second branch amine liquid after washing the flash gas washes the preliminarily treated natural gas.

8. The natural gas desulfurization method according to claim 7, characterized in that: In the step S101, the desulfurization pressure is 5.5MPa-6.5MPa.

9. A natural gas desulfurization device, characterized in that: The natural gas desulfurization device comprises: a desulfurization tower, a flash tower and a washing tower; The desulfurization tower is provided with an air inlet and a liquid outlet at the bottom, and is connected to a washing tower at the top. The washing tower is used to process the hydrogen sulfide gas in the preliminarily treated natural gas at the top of the desulfurization tower; The air inlet at the bottom of the desulfurization tower is used for the entry of natural gas containing hydrogen sulfide, and the liquid outlet is connected to the top of the flash tower through a pipeline; The gas outlet of the flash tower is connected to the washing tower.

10. The natural gas desulfurization device according to claim 9, characterized in that: It also includes a control valve, which is arranged on the pipeline between the desulfurization tower, the flash tower and the washing tower.

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