Decarburizing agent for removing carbon dioxide in natural gas at normal temperature as well as removing method and device

Abstract

The invention discloses a decarburizing agent for removing carbon dioxide in natural gas at normal temperature and a removal method and device, and relates to the technical field of removal of carbon dioxide in natural gas. The decarburizing agent comprises a physical solvent and an activating agent, the physical solvent comprises methoxy diglycol acetate, butoxy diglycol acetate and glyceryl triacetate, and the activating agent comprises 1-(1-aminopropyl)-3-methylimidazolium bromide, piperazine and polyvinyl caprolactam. Based on the development of the novel efficient decarburizing agent, the decarburizing process parameters are further optimized, the absorption temperature and pressure of the absorption tower are relatively low, and the energy consumption is remarkably reduced. The method solves the problem of high energy consumption of a decarburization method in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon dioxide removal from natural gas, and in particular to a decarbonizing agent, a method and a device for removing carbon dioxide from natural gas at room temperature. Background Art

[0002] Natural gas is a mixture of hydrocarbon gases, usually containing CO2 and other components. CO2 in natural gas brings many hazards to natural gas transportation and deep processing. CO2 in natural gas will cause serious corrosion to equipment and pipelines. At the same time, excessive CO2 content will reduce the calorific value of natural gas. In addition, during the deep processing of natural gas, CO2 will produce solid dry ice at extremely low temperatures, causing equipment blockage. Therefore, CO2 in natural gas needs to be purified, and the most widely used natural gas decarbonization technology is chemical absorption.

[0003] The chemical absorption method uses weak alkaline absorbents to react with CO2 to generate unstable salts, and then the salts reversely decompose under certain conditions (such as heating) to release CO2, thereby achieving the purpose of enriching CO2 in flue gas. Among them, the amine method is the most widely used. The chemical absorption method has a large absorption capacity, good absorption effect, and the absorbent is recycled, and high-purity CO2 can be obtained. However, the regeneration temperature of the amine method is high, generally reaching above 115°C, and it consumes a lot of energy. Therefore, the development of low-energy decarbonization methods is of great significance for saving energy and improving economic benefits. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a decarbonization agent, a removal method and a device for removing carbon dioxide from natural gas at room temperature, so as to solve the problem of high energy consumption of the decarbonization method in the prior art.

[0005] The technical solution of the present invention to solve the above technical problems is as follows: a decarbonization agent for removing carbon dioxide from natural gas at room temperature is provided, comprising: a physical solvent and an activator, the physical solvent comprises methoxydiglycol acetate, butoxydiglycol acetate and triacetin, and the activator comprises 1-(1-aminopropyl)-3-methylimidazolium bromide, piperazine and polyvinyl caprolactam.

[0006] On the basis of the above technical solution, the present invention can also be improved as follows:

[0007] Furthermore, the mass ratio of the physical solvent, 1-(1-aminopropyl)-3-methylimidazolium bromide, piperazine and polyvinyl caprolactam is 90-92:5-7:2-3:1-2.

[0008] Furthermore, the mass ratio of methoxydiglycol acetate, butoxydiglycol acetate and triacetin is 40:35:25.

[0009] The present invention also provides a method for removing carbon dioxide from natural gas at room temperature, comprising the following steps:

[0010] S1: The raw natural gas is pressurized and cooled in sequence, and then introduced into the bottom of the absorption tower. In the absorption tower, the raw natural gas is countercurrently contacted with the above-mentioned decarbonizing agent from top to bottom, and the purified gas is discharged from the absorption tower to obtain a decarbonized rich liquid that absorbs carbon dioxide and methane;

[0011] S2: passing the decarbonized rich liquid obtained in step S1 into a flash tower, and sequentially performing flash evaporation in the high-pressure section, the medium-pressure section and the low-pressure section to obtain flash gas and decarbonized rich liquid after flash evaporation;

[0012] S3: The decarbonized rich liquid after flash evaporation obtained in step S2 is introduced into a regeneration tower, and gas stripping desorption is performed in the atmospheric pressure section and the vacuum section in sequence to obtain desorbed gas and lean liquid.

[0013] On the basis of the above technical solution, the present invention can also be improved as follows:

[0014] Furthermore, in step S1, the carbon dioxide content in the natural gas raw gas is 5-45vt%.

[0015] Furthermore, in step S1, the raw natural gas is pressurized and cooled in sequence, and after the droplets are removed, it is passed into the bottom of the absorption tower.

[0016] Furthermore, in step S1, after the purified gas is discharged from the absorption tower, it is discharged after droplet separation, and the separated droplets are passed into the absorption tower.

[0017] Furthermore, in step S1, the reaction temperature of the absorption tower is 25-30°C, and the absorption pressure is 1.3-1.5 MPa.

[0018] Furthermore, in step S2, the flash gas obtained in the high-pressure section and the flash gas obtained in the medium-pressure section are pressurized and cooled in sequence, and then mixed with the raw natural gas and enter the absorption tower.

[0019] Furthermore, in step S2, the flash gas obtained in the low-pressure section enters the regeneration tower as stripping gas for gas stripping desorption.

[0020] Furthermore, in step S2, the high-pressure flash vapor pressure is 0.8-1 MPa, the medium-pressure flash vapor pressure is 0.5-0.6 MPa, and the low-pressure flash vapor pressure is 0.2-0.4 MPa.

[0021] Furthermore, in step S3, the reaction temperature of the regeneration tower is 25-30°C, the pressure of the atmospheric section is 0.1-0.2 MPa, and the pressure of the vacuum section is 0.01-0.02 MPa.

[0022] Furthermore, in step S3, the desorbed gas obtained in the normal pressure section and the desorbed gas obtained in the vacuum section are mixed, and the liquid droplets are separated and then discharged, and the separated liquid droplets enter the normal pressure section.

[0023] Furthermore, in step S3, the obtained lean liquid is passed into an absorption tower for recycling.

[0024] The present invention also provides a device for removing carbon dioxide from natural gas at room temperature, comprising an absorption tower, a flash tower and a regeneration tower; the absorption tower is provided with a raw natural gas inlet, a purified gas outlet and a decarbonized rich liquid outlet; the flash tower is provided with a high-pressure section, a medium-pressure section and a low-pressure section from bottom to top, the bottom of the high-pressure section and the top of the medium-pressure section are connected through a first pipeline, the bottom of the medium-pressure section and the top of the low-pressure section are connected through a second pipeline, a decarbonized rich liquid inlet is provided on the high-pressure section, flash steam outlets are provided on the high-pressure section, and a post-flash decarbonized rich liquid outlet is provided on the low-pressure section; the decarbonized rich liquid outlet is connected to the decarbonized rich liquid inlet; the regeneration tower is provided with a post-flash decarbonized rich liquid inlet, a gas stripping gas inlet, a desorption gas outlet and a lean liquid outlet; the post-flash decarbonized rich liquid outlet is connected to the post-flash decarbonized rich liquid inlet.

[0025] On the basis of the above technical solution, the present invention can also be improved as follows:

[0026] Furthermore, the raw natural gas inlet and the decarbonized rich liquid outlet are both arranged at the bottom of the absorption tower; and the purified gas outlet is arranged at the top of the absorption tower.

[0027] Furthermore, the regeneration tower is provided with a normal pressure section and a vacuum section from bottom to top, and the bottom of the normal pressure section and the top of the vacuum section are connected by a third pipeline; the inlet of the decarbonized rich liquid after flash evaporation is arranged at the top of the normal pressure section; the gas stripping gas inlet is arranged at the bottom of the normal pressure section; the desorption gas outlets are respectively arranged at the top of the normal pressure section and the top of the vacuum section; and the lean liquid outlet is arranged at the bottom of the vacuum section.

[0028] Furthermore, the lean liquid outlet and the top of the absorption tower are connected through a pipeline.

[0029] Furthermore, a lean liquid pump is provided on the pipeline between the lean liquid outlet and the top of the absorption tower.

[0030] Furthermore, the flash steam outlet of the low-pressure section is communicated with the stripping gas inlet at the bottom of the atmospheric pressure section.

[0031] Furthermore, the desorption gas outlet at the top of the atmospheric section and the desorption gas outlet at the top of the vacuum section are connected to the multi-cyclone separator through pipelines respectively, and a vacuum pump is arranged on the pipeline between the desorption gas outlet at the top of the vacuum section and the multi-cyclone separator; the multi-cyclone separator is provided with a desorption gas outlet and a first droplet outlet.

[0032] Furthermore, the first liquid droplet outlet is communicated with the normal pressure section.

[0033] Furthermore, the flash steam outlet of the high-pressure section and the flash steam outlet of the medium-pressure section are both connected to the flash steam compressor through pipelines, the flash steam compressor is connected to the flash steam heat exchanger through pipelines, and the flash steam heat exchanger is connected to the raw natural gas inlet through pipelines.

[0034] Furthermore, the purified gas outlet is connected to the purified gas separator through a pipeline, and the purified gas separator is provided with a gas outlet and a second liquid droplet outlet, and the second liquid droplet outlet is connected to the absorption tower.

[0035] Furthermore, the raw natural gas inlet is connected to the raw gas separator through a pipeline, the raw gas separator is connected to the raw gas heat exchanger through a pipeline, the raw gas heat exchanger is connected to the raw gas compressor, and a third liquid droplet outlet is provided on the raw gas separator.

[0036] Furthermore, the flash gas heat exchanger is connected to the raw gas separator tank through a pipeline.

[0037] The present invention has the following beneficial effects:

[0038] 1. The present invention adopts a new type of high-efficiency decarbonizing agent composed of a physical solvent and an activator, which has strong absorption and desorption capabilities and a decarbonization efficiency of up to 85.3%. In the activator, the introduction of an amine group in the structure of 1-(1-aminopropyl)-3-methylimidazolium bromide increases the absorption load of CO2, piperazine can promote the reaction of 1-(1-aminopropyl)-3-methylimidazolium bromide absorbing CO2, and polyvinyl caprolactam can reduce the collision probability of methane molecular clusters in the solution, thereby reducing / slowing down the dissolution of methane, and the methane loss rate is less than 0.5%.

[0039] 2. Based on the development of new high-efficiency decarbonizers, the decarbonization process parameters have been further optimized. The absorption temperature and pressure of the absorption tower are relatively low, with the absorption temperature being 25-30°C and the absorption pressure being 1.3-1.5MPa, which significantly reduces energy consumption.

[0040] 3. Use high-efficiency multi-cyclone separator to separate absorbent droplets carried by desorbed gas, so that absorbent recovery is more thorough and desorbed gas purity is higher.

[0041] 4. There is no secondary pollution, no dust on the site, no strong noise, and no new solid, gas and liquid emissions.

[0042] 5. Regeneration does not require steam heating. The method of the present invention is a process in which the decarbonized rich liquid is flashed to remove methane and then enters the desorption tower to desorb CO2. Therefore, no heat input is required and the energy consumption is low.

[0043] 6. The present invention is a CO2 removal technology that combines a new type of high-efficiency room-temperature decarbonization agent with a room-temperature decarbonization process. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a device diagram of the present invention.

[0045] Among them, 1. Absorption tower; 2. Flash tower; 3. Regeneration tower; 4. Purified gas separator; 5. Raw gas liquid separator; 6. Raw gas compressor; 7. Raw gas heat exchanger; 8. Flash gas compressor; 9. Flash gas heat exchanger; 10. Vacuum pump; 11. Multi-cyclone separator; 12. Lean liquid pump. DETAILED DESCRIPTION

[0046] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples are only used to explain the present invention and are not used to limit the scope of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0047] Please combine Figure 1 , a device for removing carbon dioxide from natural gas at room temperature, comprising an absorption tower 1, a flash tower 2 and a regeneration tower 3; the absorption tower 1 is provided with a raw natural gas inlet, a purified gas outlet and a decarbonized rich liquid outlet; the flash tower 2 is provided with a high-pressure section, a medium-pressure section and a low-pressure section from bottom to top, the bottom of the high-pressure section and the top of the medium-pressure section are connected through a first pipeline, the bottom of the medium-pressure section and the top of the low-pressure section are connected through a second pipeline, a decarbonized rich liquid inlet is provided on the high-pressure section, flash steam outlets are provided on the high-pressure section, the medium-pressure section and the low-pressure section are all provided with a flash steam outlet, and a post-flash decarbonized rich liquid outlet is provided on the low-pressure section; the decarbonized rich liquid outlet is connected to the decarbonized rich liquid inlet; the regeneration tower 3 is provided with a post-flash decarbonized rich liquid inlet, a gas stripping gas inlet, a desorption gas outlet and a lean liquid outlet; the post-flash decarbonized rich liquid outlet is connected to the post-flash decarbonized rich liquid inlet.

[0048] The raw natural gas inlet and the decarbonized rich liquid outlet are both arranged at the bottom of the absorption tower 1; and the purified gas outlet is arranged at the top of the absorption tower 1.

[0049] The regeneration tower 3 is provided with a normal pressure section and a vacuum section from bottom to top, and the bottom of the normal pressure section and the top of the vacuum section are connected through a third pipeline; the inlet of the decarbonized rich liquid after flash evaporation is arranged at the top of the normal pressure section; the gas stripping gas inlet is arranged at the bottom of the normal pressure section; the desorption gas outlets are arranged at the top of the normal pressure section and the top of the vacuum section respectively; the lean liquid outlet is arranged at the bottom of the vacuum section.

[0050] The lean liquid outlet is connected to the top of the absorption tower 1 through a pipeline; a lean liquid pump 12 is arranged on the pipeline between the lean liquid outlet and the top of the absorption tower.

[0051] The flash steam outlet of the low-pressure section is communicated with the stripping gas inlet at the bottom of the atmospheric pressure section.

[0052] The desorption gas outlet at the top of the atmospheric section and the desorption gas outlet at the top of the vacuum section are connected to the multi-cyclone separator 11 through pipelines respectively, and a vacuum pump 10 is arranged on the pipeline between the desorption gas outlet at the top of the vacuum section and the multi-cyclone separator 11; the multi-cyclone separator 11 is provided with a desorption gas outlet and a first droplet outlet.

[0053] The first liquid drop outlet is communicated with the normal pressure section.

[0054] The flash steam outlet of the high-pressure section and the flash steam outlet of the medium-pressure section are both connected to the flash steam compressor 8 through a pipeline, the flash steam compressor 8 is connected to the flash steam heat exchanger 9 through a pipeline, and the flash steam heat exchanger 9 is connected to the raw natural gas inlet through a pipeline.

[0055] The purified gas outlet is communicated with the purified gas separator 4 through a pipeline. The purified gas separator 4 is provided with a gas outlet and a second liquid droplet outlet. The second liquid droplet outlet is communicated with the absorption tower 1 .

[0056] The raw natural gas inlet is connected to the raw gas separator 5 through a pipeline, the raw gas separator 5 is connected to the raw gas heat exchanger 7 through a pipeline, the raw gas heat exchanger 7 is connected to the raw gas compressor 6, and a third liquid droplet outlet is provided on the raw gas separator 5.

[0057] The flash gas heat exchanger 9 is connected to the raw gas liquid separator 5 through a pipeline.

[0058] Embodiment 1:

[0059] A decarbonizing agent for removing carbon dioxide from natural gas at room temperature, comprising a physical solvent and an activator, wherein the physical solvent comprises methoxydiglycol acetate, butoxydiglycol acetate and triacetin (in a mass ratio of 40:35:25), and the activator comprises 1-(1-aminopropyl)-3-methylimidazolium bromide, piperazine and polyvinyl caprolactam; wherein the mass ratio of the physical solvent, 1-(1-aminopropyl)-3-methylimidazolium bromide, piperazine and polyvinyl caprolactam is 90:5:2:1.

[0060] A method for removing carbon dioxide from natural gas at room temperature, comprising the following steps:

[0061] (1) Raw natural gas (CO2 content of 15vt%, CH4 content of 85vt%) is passed through a raw gas compressor 6 and a raw gas heat exchanger 7 in sequence to be pressurized and cooled. After the liquid droplets are removed, the raw natural gas is passed into the bottom of an absorption tower 1. In the absorption tower 1, the raw natural gas is countercurrently contacted with a decarbonizing agent from top to bottom, and CO2 and a small amount of CH4 in the gas are absorbed. The purified gas is discharged from the absorption tower 1, and the raw gas is separated from the liquid droplets by a raw gas separator 5 and then discharged to the next stage. The separated liquid droplets are passed into the absorption tower 1 to obtain a decarbonized rich liquid that absorbs carbon dioxide and a small amount of CH4. The reaction temperature of the absorption tower 1 is 25° C., and the absorption pressure is 1.3 MPa.

[0062] (2) The decarbonized rich liquid obtained in step (1) is passed into a flash tower 2, and flash evaporation is performed in high-pressure, medium-pressure and low-pressure sections in sequence to obtain flash gas and decarbonized rich liquid after flash evaporation; wherein the flash gas obtained in the high-pressure section and the flash gas obtained in the medium-pressure section are mainly CH4 and a small amount of CO2, and are pressurized and cooled by a flash gas compressor 8 and a flash gas heat exchanger 9 in sequence, and then mixed with the raw natural gas and enter the absorption tower 1 for recycling, and the flash gas obtained in the low-pressure section (mainly CO2) enters the regeneration tower 3 as stripping gas for stripping desorption; the flash pressure of the high-pressure section is 0.8 MPa, the pressure of the medium-pressure flash gas is 0.5 MPa, and the pressure of the low-pressure flash gas is 0.2 MPa;

[0063] (3) The decarbonized rich liquid after flash evaporation obtained in step (2) is passed into a regeneration tower 3, and gas stripping desorption is performed in atmospheric pressure section and vacuum section in sequence to obtain desorbed gas and lean liquid; wherein, the reaction temperature of the regeneration tower 3 is 25°C, the pressure of the atmospheric pressure section is 0.1 MPa, and the pressure of the vacuum section is 0.01 MPa; during desorption in the atmospheric pressure section, CO2 is desorbed from the liquid phase and forms desorbed gas together with the gas stripping gas, the desorbed gas obtained in the atmospheric pressure section and the desorbed gas obtained in the vacuum section (passing through a vacuum pump 10) are mixed, and the liquid droplets are separated by a multi-cyclone separator 11 and then discharged to enter a subsequent section, the separated liquid droplets enter the atmospheric pressure section, and the obtained lean liquid is passed into the absorption tower 1 by a lean liquid pump 12 for recycling.

[0064] Embodiment 2:

[0065] A decarbonizing agent for removing carbon dioxide from natural gas at room temperature comprises a physical solvent and an activator, wherein the physical solvent comprises methoxydiglycol acetate, butoxydiglycol acetate and triacetin (in a mass ratio of 40:35:25), and the activator comprises 1-(1-aminopropyl)-3-methylimidazolium bromide, piperazine and polyvinyl caprolactam; wherein the mass ratio of the physical solvent, 1-(1-aminopropyl)-3-methylimidazolium bromide, piperazine and polyvinyl caprolactam is 91:6:2.5:1.5.

[0066] A method for removing carbon dioxide from natural gas at room temperature, comprising the following steps:

[0067] (1) Raw natural gas (CO2 content of 5vt%, CH4 content of 95vt%) is passed through a raw gas compressor 6 and a raw gas heat exchanger 7 in sequence to be pressurized and cooled. After the liquid droplets are removed, the raw natural gas is passed into the bottom of an absorption tower 1. In the absorption tower 1, the raw natural gas is countercurrently contacted with a decarbonizing agent from top to bottom, and CO2 and a small amount of CH4 in the gas are absorbed. The purified gas is discharged from the absorption tower 1, and the raw gas liquid separator 5 is used to separate the liquid droplets, and then the gas is discharged to the next stage. The separated liquid droplets are passed into the absorption tower 1 to obtain a decarbonized rich liquid that absorbs carbon dioxide and a small amount of CH4. The reaction temperature of the absorption tower 1 is 28°C, and the absorption pressure is 1.4MPa.

[0068] (2) The decarbonized rich liquid obtained in step (1) is passed into a flash tower 2, and flash evaporation is performed in a high-pressure section, a medium-pressure section, and a low-pressure section in sequence to obtain flash gas and a decarbonized rich liquid after flash evaporation; wherein the flash gas obtained in the high-pressure section and the flash gas obtained in the medium-pressure section are mainly CH4 and a small amount of CO2, and are pressurized and cooled by a flash gas compressor 8 and a flash gas heat exchanger 9 in sequence, and then mixed with the raw natural gas and enter the absorption tower 1 for recycling, and the flash gas obtained in the low-pressure section (mainly CO2) enters the regeneration tower 3 as a stripping gas for stripping desorption; the flash pressure of the high-pressure section is 0.9 MPa, the pressure of the medium-pressure flash gas is 0.55 MPa, and the pressure of the low-pressure flash gas is 0.3 MPa;

[0069] (3) The decarbonized rich liquid after flash evaporation obtained in step (2) is passed into a regeneration tower 3, and gas stripping desorption is performed in atmospheric pressure section and vacuum section in sequence to obtain desorbed gas and lean liquid; wherein, the reaction temperature of the regeneration tower 3 is 28°C, the pressure of the atmospheric pressure section is 0.15 MPa, and the pressure of the vacuum section is 0.015 MPa; during desorption in the atmospheric pressure section, CO2 is desorbed from the liquid phase and forms desorbed gas together with the gas stripping gas, the desorbed gas obtained in the atmospheric pressure section and the desorbed gas obtained in the vacuum section (passing through a vacuum pump 10) are mixed, and the liquid droplets are separated by a multi-cyclone separator 11 and then discharged to enter a subsequent section, the separated liquid droplets enter the atmospheric pressure section, and the obtained lean liquid is passed into the absorption tower 1 by a lean liquid pump 12 for recycling.

[0070] Embodiment 3:

[0071] A decarbonizing agent for removing carbon dioxide from natural gas at room temperature, comprising a physical solvent and an activator, wherein the physical solvent comprises methoxydiglycol acetate, butoxydiglycol acetate and triacetin (in a mass ratio of 40:35:25), and the activator comprises 1-(1-aminopropyl)-3-methylimidazolium bromide, piperazine and polyvinyl caprolactam; wherein the mass ratio of the physical solvent, 1-(1-aminopropyl)-3-methylimidazolium bromide, piperazine and polyvinyl caprolactam is 92:7:3:2.

[0072] A method for removing carbon dioxide from natural gas at room temperature, comprising the following steps:

[0073] (1) Raw natural gas (CO2 content of 45vt%, CH4 content of 55vt%) is passed through a raw gas compressor 6 and a raw gas heat exchanger 7 in sequence to be pressurized and cooled. After the liquid droplets are removed, the raw natural gas is passed into the bottom of an absorption tower 1. In the absorption tower 1, the raw natural gas is countercurrently contacted with a decarbonizing agent from top to bottom, and CO2 and a small amount of CH4 in the gas are absorbed. The purified gas is discharged from the absorption tower 1, and the raw gas is separated from the liquid droplets by a raw gas separator 5 and then discharged to the next stage. The separated liquid droplets are passed into the absorption tower 1 to obtain a decarbonized rich liquid that absorbs carbon dioxide and a small amount of CH4. The reaction temperature of the absorption tower 1 is 30° C., and the absorption pressure is 1.5 MPa.

[0074] (2) The decarbonized rich liquid obtained in step (1) is passed into a flash tower 2, and flash evaporation is performed in high-pressure, medium-pressure and low-pressure sections in sequence to obtain flash gas and decarbonized rich liquid after flash evaporation; wherein the flash gas obtained in the high-pressure section and the flash gas obtained in the medium-pressure section are mainly CH4 and a small amount of CO2, which are pressurized and cooled by a flash gas compressor 8 and a flash gas heat exchanger 9 in sequence, and then mixed with the raw natural gas and enter the absorption tower 1 for recycling, and the flash gas obtained in the low-pressure section (mainly CO2) enters the regeneration tower 3 as stripping gas for stripping desorption; the flash pressure of the high-pressure section is 1 MPa, the pressure of the medium-pressure flash gas is 0.6 MPa, and the pressure of the low-pressure flash gas is 0.4 MPa;

[0075] (3) The decarbonized rich liquid after flash evaporation obtained in step (2) is passed into a regeneration tower 3, and gas stripping desorption is performed in atmospheric pressure section and vacuum section in sequence to obtain desorbed gas and lean liquid; wherein, the reaction temperature of the regeneration tower 3 is 30°C, the pressure of the atmospheric pressure section is 0.2 MPa, and the pressure of the vacuum section is 0.02 MPa; during desorption in the atmospheric pressure section, CO2 is desorbed from the liquid phase and forms desorbed gas together with the gas stripping gas, the desorbed gas obtained in the atmospheric pressure section and the desorbed gas obtained in the vacuum section (passing through a vacuum pump 10) are mixed, and the liquid droplets are separated by a multi-cyclone separator 11 and then discharged to enter a subsequent section, the separated liquid droplets enter the atmospheric pressure section, and the obtained lean liquid is passed into the absorption tower 1 by a lean liquid pump 12 for recycling.

[0076] Embodiment 4:

[0077] A decarbonizing agent for removing carbon dioxide from natural gas at room temperature, same as Example 1.

[0078] A method for removing carbon dioxide from natural gas at room temperature, comprising the following steps:

[0079] In step (1), the reaction temperature of absorption tower 1 is 30° C., the absorption pressure is 1.5 MPa, and the rest is the same as in Example 1.

[0080] Test example

[0081] 1. The purified gas and desorbed gas obtained in Example 1 and Example 4 were tested. When the gas flow rate and solution circulation volume were constant, the results were shown in Table 1.

[0082] Table 1 Chemical composition of natural gas before and after decarbonization

[0083]

[0084] It can be seen from Table 1 that the method of the present invention has a good decarburization effect.

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A decarbonizing agent for removing carbon dioxide from natural gas at room temperature, characterized in that: The invention comprises a physical solvent and an activator. The physical solvent comprises methoxydiglycol acetate, butoxydiglycol acetate and triacetin. The activator comprises 1-(1-aminopropyl)-3-methylimidazolium bromide, piperazine and polyvinyl caprolactam.

2. The decarbonizing agent for removing carbon dioxide from natural gas at room temperature according to claim 1, characterized in that: The mass ratio of the physical solvent, 1-(1-aminopropyl)-3-methylimidazolium bromide, piperazine and polyvinyl caprolactam is 90-92:5-7:2-3:1-2.

3. A method for removing carbon dioxide from natural gas at room temperature, characterized in that: The following steps are involved: S1: The raw natural gas is pressurized and cooled in sequence, and then introduced into the bottom of an absorption tower (1), and in the absorption tower (1), it is countercurrently contacted with the decarbonizing agent according to claim 1 from top to bottom, and the purified gas is discharged from the absorption tower (1) to obtain a decarbonized rich liquid that absorbs carbon dioxide and methane; S2: passing the decarbonized rich liquid obtained in step S1 into a flash tower (2), and sequentially performing flash evaporation in the high-pressure section, the medium-pressure section and the low-pressure section to obtain flash gas and decarbonized rich liquid after flash evaporation; S3: The decarbonized rich liquid after flash evaporation obtained in step S2 is introduced into a regeneration tower (3), and gas stripping and desorption are performed in the atmospheric pressure section and the vacuum section in sequence to obtain desorbed gas and lean liquid.

4. The method for removing carbon dioxide from natural gas at room temperature according to claim 3, characterized in that: In step S1, the reaction temperature of the absorption tower (1) is 25-30°C, and the absorption pressure is 1.3-1.5 MPa.

5. The method for removing carbon dioxide from natural gas at room temperature according to claim 3, characterized in that: In step S2, the flash gas obtained in the low-pressure section enters the regeneration tower (3) as stripping gas for stripping desorption.

6. The method for removing carbon dioxide from natural gas at room temperature according to claim 3, characterized in that: In step S2, the high-pressure flash vapor pressure is 0.8-1 MPa, the medium-pressure flash vapor pressure is 0.5-0.6 MPa, and the low-pressure flash vapor pressure is 0.2-0.4 MPa.

7. A device for removing carbon dioxide from natural gas at room temperature, characterized in that: The invention comprises an absorption tower (1), a flash tower (2) and a regeneration tower (3); the absorption tower (1) is provided with a raw natural gas inlet, a purified gas outlet and a decarbonized rich liquid outlet; the flash tower (2) is provided with a high-pressure section, a medium-pressure section and a low-pressure section from bottom to top, the bottom of the high-pressure section and the top of the medium-pressure section are connected through a first pipeline, the bottom of the medium-pressure section and the top of the low-pressure section are connected through a second pipeline, the high-pressure section is provided with a decarbonized rich liquid inlet, the high-pressure section, the medium-pressure section and the low-pressure section are all provided with flash steam outlets, and the low-pressure section is provided with a post-flash decarbonized rich liquid outlet; the decarbonized rich liquid outlet is connected to the post-flash decarbonized rich liquid inlet; the regeneration tower (3) is provided with a post-flash decarbonized rich liquid inlet, a gas stripping gas inlet, a desorption gas outlet and a lean liquid outlet; the post-flash decarbonized rich liquid outlet is connected to the post-flash decarbonized rich liquid inlet.

8. The device for removing carbon dioxide from natural gas at room temperature according to claim 7, characterized in that: The regeneration tower (3) is provided with a normal pressure section and a vacuum section from bottom to top, and the bottom of the normal pressure section and the top of the vacuum section are connected through a third pipeline; the inlet of the decarbonized rich liquid after flash evaporation is arranged at the top of the normal pressure section; the stripping gas inlet is arranged at the bottom of the normal pressure section; the desorption gas outlets are respectively arranged at the top of the normal pressure section and the top of the vacuum section; and the lean liquid outlet is arranged at the bottom of the vacuum section.

9. The device for removing carbon dioxide from natural gas at room temperature according to claim 7, characterized in that: The flash steam outlet of the high-pressure section and the flash steam outlet of the medium-pressure section are both connected to a flash steam compressor (8) through a pipeline, the flash steam compressor (8) is connected to a flash steam heat exchanger (9) through a pipeline, and the flash steam heat exchanger (9) is connected to the raw natural gas inlet through a pipeline.

10. The device for removing carbon dioxide from natural gas at room temperature according to claim 7, characterized in that: The raw natural gas inlet is connected to the raw gas liquid separator (5) via a pipeline, the raw gas liquid separator (5) is connected to the raw gas heat exchanger (7) via a pipeline, the raw gas heat exchanger (7) is connected to the raw gas compressor (6), and a third liquid droplet outlet is provided on the raw gas liquid separator (5).

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