Low-temperature methanol washing decarburization device and method

Abstract

The invention discloses a low-temperature methanol washing decarburization device, which relates to the field of low-temperature methanol washing, and comprises the following steps: carrying out decarburization treatment on rich methanol in a low-temperature methanol washing process by adopting a built-in filler device, and reducing the internal pressure of methanol, reducing the solubility of carbon dioxide and enhancing the removal effect of carbon dioxide under the action of a filler capillary tube; the retention time of carbon dioxide in the system is prolonged through filling of filler micropores, the heat exchange effect of a gas-liquid system is enhanced through the large specific surface area of the filler, and cold energy is fully recycled; and the filler has water absorption and can be used for removing water in methanol. The device is reasonable in structure, and the molecular sieve funnel is arranged, so that the carbon dioxide separation efficiency can be effectively improved, the cold energy recovery is improved, and the methanol water content is controlled. The molecular sieve funnel is arranged at the lowermost part of the tank body, so that the cold transfer can be effectively increased, the device investment is reduced, the energy is saved, and the low-temperature methanol washing process is stably carried out.

Description

Technical Field

[0001] The invention belongs to the field of low-temperature methanol washing in chemical technology and relates to a method for removing hydrogen sulfide, carbon dioxide and organic sulfide from a mixed liquid. Background Art

[0002] The initial gases in the coal chemical, petroleum, natural gas and other industries are rich in carbon dioxide, hydrogen sulfide and sulfur-containing organic matter, which not only cause corrosion to equipment and pipelines, but also endanger the safety of downstream processes and operators. Therefore, they need to be purified, decarbonized and desulfurized before use.

[0003] Low-temperature methanol washing is widely used due to its low power consumption and high selectivity. In actual operation, the water content in the methanol solution needs to be strictly controlled. The common method is distillation and adding fresh methanol. The commonly used method is series flash evaporation to analyze carbon dioxide and recover the cold energy in low-temperature methanol. Traditional process equipment requires large investment, high steam consumption, and low cold energy recovery rate. How to improve the decarbonization effect of low-temperature methanol and reduce the water content of methanol is one of the problems that need to be solved today.

[0004] After searching, CN210521811U discloses a CO2 supergravity analysis device for the low-temperature methanol washing section. In the above-mentioned prior art, a filler made of foam nickel is disclosed. Under the action of gas pressure, the gas enters the filler made of foam nickel from the outer edge of the rotating filler bed; the motor drives the rotating filler bed to rotate, and the centrifugal force generated pushes the methanol to the outer edge of the rotating filler bed; in this process, the methanol is crushed and broken into microelements by the filler, and contacts with the gas at a very high relative speed for countercurrent heat transfer, so that the CO2 solubility inside the methanol is reduced to achieve the purpose of analyzing CO2. However, the above-mentioned prior art analyzes CO2 by enhancing heat exchange and increasing the temperature, which will cause the temperature of the lean methanol solution to rise. When the methanol is recycled, it is necessary to increase the external cooling supply, which increases energy consumption. Based on this, the present invention designs a low-temperature methanol decarbonization device and method. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems in the prior art and to propose a low-temperature methanol elution carbon device.

[0006] A low-temperature methanol washing and decarbonization device, comprising: a flash tank provided with a built-in filler device, wherein the built-in filler device is used to decarbonize the rich methanol in the low-temperature methanol washing process; a rich methanol inlet pipe and a lean methanol outlet pipe are respectively connected to the bottom of both sides of the flash tank, the rich methanol inlet pipe being connected to the bottom side of the built-in filler device; and a desorption gas outlet pipe is connected to the top of the flash tank;

[0007] The built-in filler device is a composite of one or more of a funnel, a coil, and a hollow ball, and is made of stainless steel, ceramic, etc. When in use, a built-in filler is a regular or irregular material rich in micropores, with a pore size of ≤1mm and a bulk density of 0.5-0.7g / mL. The filler forms microtubes with the methanol solution, forming a capillary effect of the filler, reducing the internal pressure of the liquid, reducing the solubility of CO2, and realizing CO2 analysis.

[0008] In the above-mentioned low-temperature methanol elution carbon device, the filler can be a composite of one or more porous materials such as molecular sieve, diatomaceous earth, metal foam, etc.

[0009] In the method for using the above device, when the device is used to perform the decarburization step, the flow rate of the rich methanol in the packing device is 30 to 800 of the volume of the packing.

[0010] In the method for using the above device, when the device is used to perform the decarburization step, the temperature of the rich methanol is -30 to -50°C.

[0011] In the method for using the above device, when the device is used to perform the decarburization step, the pressure difference between the inside and outside of the device is 0.05 to 2 MPa.

[0012] In the method of using the above device, after the water absorption of the filler is close to saturation, the internal methanol is discharged, and high-temperature nitrogen is introduced at normal pressure to dry and regenerate it. After the regeneration is completed, low-temperature methanol solution is introduced to achieve the reuse of the filler.

[0013] Compared with the existing technology, the advantages of the present invention are:

[0014] 1. It removes carbon dioxide from rich methanol quickly and efficiently, with minimal temperature fluctuations and low methanol moisture content. It offers advantages such as stable process, low equipment investment, and high cold recovery. It can be used to remove acid gases and organic sulfides from natural gas, refinery gas, synthesis gas, liquefied petroleum gas, and other gases, demonstrating excellent marketability.

[0015] 2. The packing regeneration process summarized in the present invention uses dry hot inert gas to purge the packing, which has the advantages of being simple, efficient, low-cost and extending the service life of the device.

[0016] 3. Compared with the existing technology, the present invention does not consume any extra kinetic energy or cooling capacity during use. No additional cooling capacity is required when methanol is recycled, which has the advantages of energy saving and efficiency improvement. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a diagram of a low-temperature methanol carbon elution device proposed by the present invention;

[0018] In the figure: 1 flash tank, 2 built-in filler device, 3 rich methanol inlet pipe, 4 lean methanol discharge pipe, 5 desorption gas discharge pipe. DETAILED DESCRIPTION

[0019] Reference Figure 1 , a low-temperature methanol washing and decarbonization device, comprising: a flash tank 1, wherein the flash tank 1 is provided with a built-in filling device 2, and the built-in filling device 2 is used to decarbonize the rich methanol in the low-temperature methanol washing process, the bottom of the two sides of the flash tank 1 are respectively connected to a rich methanol input pipe 3 and a lean methanol discharge pipe 4, the rich methanol input pipe 3 is connected to the bottom side of the built-in filling device 2, and the top of the flash tank 1 is connected to a decomposition gas discharge pipe 5. According to the low-temperature methanol decarbonization device of the above scheme, the methanol solution enters the bottom of the built-in filling device 2 through the rich methanol input pipe 3, and forms microtubes with the methanol solution through the filler to constitute a filler capillary. Due to the capillary action, the internal pressure of the liquid decreases, resulting in a decrease in the solubility of CO2, and CO2 escapes and decomposes. The CO2 gas escapes from the liquid and is led out from the decomposition gas discharge pipe 5 at the top, and the lean methanol is led out from the lean methanol discharge pipe 4 at the bottom. At the same time, the escape of CO2 from the methanol will take away a part of the heat, which is converted into kinetic energy of CO2 gas, so that the temperature of the methanol solution is reduced;

[0020] The built-in filler device 2 is a composite of one or more of a funnel, a coil, and a hollow ball, and is made of stainless steel, ceramic, etc. When in use, a built-in filler is a regular or irregular material rich in micropores, with a pore size of ≤1mm and a bulk density of 0.5-0.7g / mL. The filler forms microtubes with the methanol solution, forming a filler capillary effect, reducing the internal pressure of the liquid, reducing the solubility of CO2, and realizing CO2 analysis.

[0021] The principle of the present invention is as follows: the capillary effect between the filler and the methanol solution reduces the internal pressure of the methanol, reduces the solubility of carbon dioxide, and enhances the carbon dioxide removal effect; the micropores in the filler increase the residence time of carbon dioxide in the system, and the large specific surface area of ​​the filler enhances the heat exchange effect of the gas-liquid system and fully recovers the cold; the filler is also water-absorbent and removes moisture from the methanol, and no additional kinetic energy or cold consumption occurs during use. No additional cold supply is required when the methanol is recycled, which has the advantages of energy saving and efficiency improvement.

[0022] Example 1:

[0023] The packing material is 5A molecular sieve, and a side stream is introduced into the unit at a pressure of 4.2 MPa and a temperature of -50°C, resulting in a bed pressure drop of 2.0 MPa. After stable operation, the exhaust temperature of lean methanol is maintained at -52°C. The output gas composition is H2: 0.017 mol%; N2: 16.92%; CO: 0.85%; CH4: 0.02%; CO2: 80.6%; NH3: <0.1 vppm; CH3OH: 0.01%; H2O: 1.59%; and the methanol-water content is 0.1%.

[0024] Example 2:

[0025] The filler used was 5A molecular sieve, and the on-site side line was used. A 4.2MPa, -50°C carbon dioxide-rich methanol solution was introduced into the device, and the bed pressure drop was 2.0MPa. After 8000h of stable operation, the water content of the discharged methanol increased from the initial 0.05% to 0.8%.

[0026] Example 3:

[0027] The packing material is 5A molecular sieve, and a side stream is introduced into the unit at a pressure of 4.2 MPa and a temperature of -50°C, resulting in a bed pressure drop of 1.0 MPa. After stable operation, the exhaust temperature of lean methanol is maintained at -51°C. The output gas composition is H2: 0.015 mol%; N2: 21.9%; CO: 0.89%; CH4: 0.02%; CO2: 75.6%; NH3: <0.1 vppm; CH3OH: 0.01%; H2O: 1.59%; and the methanol-water content is 0.1%.

[0028] Example 4:

[0029] The packing material is 4A molecular sieve, and a side stream is introduced into the unit at a pressure of 4.2 MPa and a temperature of -50°C, resulting in a bed pressure drop of 2.0 MPa. After stable operation, the exhaust temperature of lean methanol is maintained at -52°C. The output gas composition is H2: 0.017 mol%; N2: 16.92%; CO: 0.85%; CH4: 0.02%; CO2: 80.6%; NH3: <0.1 vppm; CH3OH: 0.01%; H2O: 1.59%; and the methanol-water content is 0.09%.

[0030] Example 5:

[0031] The packing material is 13X molecular sieve. A side stream is introduced into the unit at 4.2 MPa, at a temperature of -50°C, into a carbon dioxide-rich methanol solution. The bed pressure drop reaches 2.0 MPa. After stable operation, the exhaust temperature of lean methanol is maintained at -52°C. The output gas composition is H2: 0.017 mol%; N2: 16.92%; CO: 0.85%; CH4: 0.02%; CO2: 80.6%; NH3: <0.1 vppm; CH3OH: 0.01%; H2O: 1.59%; and the methanol-water content is 0.11%.

[0032] Example 6:

[0033] The packing material is 13X molecular sieve. A side stream is introduced into the unit at 4.2 MPa, at a temperature of -50°C, and a CO2-rich methanol solution is introduced. The bed pressure drop is 1.0 MPa. After stable operation, the exhaust temperature of lean methanol is maintained at -51°C. The output gas composition is H2: 0.015 mol%; N2: 21.9%; CO: 0.89%; CH4: 0.02%; CO2: 75.6%; NH3: <0.1 vppm; CH3OH: 0.01%; H2O: 1.59%; and the methanol-water content is 0.1%.

[0034] Example 7:

[0035] The packing material is 13X molecular sieve. A side stream is introduced into the unit at 4.2 MPa, at a temperature of -30°C, and a CO2-rich methanol solution is introduced. The bed pressure drop is 1.0 MPa. After stable operation, the exhaust temperature of lean methanol is maintained at -30°C. The output gas composition is H2: 0.015 mol%; N2: 17.3%; CO: 0.89%; CH4: 0.02%; CO2: 80.0%; NH3: <0.1 vppm; CH3OH: 0.01%; H2O: 1.59%; and the methanol-water content is 0.08%.

[0036] Example 8:

[0037] The filler used was 13X molecular sieve, and a 4.2MPa, -30°C carbon dioxide-rich methanol solution was introduced into the device through the on-site side line. The bed pressure drop was 1.0MPa. After 8000 hours of stable operation, the water content of the discharged methanol increased from the initial 0.05% to 0.9%.

[0038] Example 9:

[0039] A coil-type built-in device was used, with 13X molecular sieve as the filler and a side line on site. A 4.2MPa, -30°C carbon dioxide-rich methanol solution was introduced into the device, with a bed pressure drop of 1.0MPa. After 6000 hours of stable operation, the water content of the discharged methanol increased from the initial 0.05% to 0.9%.

[0040] Example 10:

[0041] The coil-type internal device uses 13X molecular sieve as the packing material. A side stream is introduced into the device at a pressure of 4.2 MPa and a temperature of -30°C, resulting in a bed pressure drop of 1.0 MPa. After stable operation, the exhaust temperature of lean methanol is maintained at -30°C. The output gas composition is H2: 0.015 mol%; N2: 37.3%; CO: 0.89%; CH4: 0.02%; CO2: 60.0%; NH3: <0.1 vppm; CH3OH: 0.01%; H2O: 1.59%; and the methanol-water content is 0.08%.

[0042] Example 11:

[0043] The packing material was 13X molecular sieve, and a side stream was introduced into the unit at a pressure of 4.2 MPa and a temperature of -30°C, with a bed pressure drop of 1.0 MPa. The exhaust temperature of the lean methanol was maintained at -30°C. After 8000 hours of operation, the water content of the exhaust methanol increased from an initial 0.05% to 0.9%. After shutdown, the unit was completely drained of methanol, purged with dry nitrogen at 200-300°C for 48 hours, and then returned to service. The exhaust temperature of the lean methanol was maintained at -30°C. The output gas composition was H2: 0.015 mol%; N2: 17.3%; CO: 0.88%; CH4: 0.02%; CO2: 80.0%; NH3: <0.1 vppm; CH3OH: 0.02%; H2O: 1.59%; and the methanol water content was 0.08%.

[0044] Table 1 Results of methanol carbon dioxide and water content

[0045]

[0046] In summary, the low-temperature methanol decarbonization method provided by the present invention has the advantages of large load, stable methanol quality, renewable recycling, and low investment. The present invention can be used for the purification of natural gas, oil refinery gas, synthesis gas, liquefied petroleum gas and other gases, and has a good promotion effect.

[0047] It is understood from common technical knowledge that the present invention may be implemented by other embodiments that do not depart from its spirit or essential features. Therefore, the embodiments disclosed above are, in all respects, merely illustrative and not exclusive. All modifications within the scope of the present invention or equivalent to the scope of the present invention are intended to be encompassed by the present invention.

Claims

1. A low-temperature methanol elution carbon device, characterized in that: include: A flash tank (1), wherein a built-in filling device (2) is provided in the flash tank (1), and the built-in filling device (2) is used to decarbonize the rich methanol in the low-temperature methanol washing process, the bottoms of both sides of the flash tank (1) are respectively connected to a rich methanol input pipe (3) and a lean methanol discharge pipe (4), the rich methanol input pipe (3) is connected to the bottom side of the built-in filling device (2), and the top of the flash tank (1) is connected to a desorption gas discharge pipe (5); The built-in filler device (2) is a composite of one or more of a funnel, a coil, and a hollow ball, and is made of stainless steel, ceramic, etc. When in use, a built-in filler is a regular or irregular material rich in micropores, with a pore size of ≤1 mm and a bulk density of 0.5 to 0.7 g / mL. The filler forms microtubes with the methanol solution to form filler capillaries, thereby reducing the internal pressure of the liquid, reducing the solubility of CO2, and achieving CO2 analysis.

2. A low-temperature methanol elution carbon device according to claim 1, characterized in that: The filler can be a composite of one or more porous materials such as molecular sieve, diatomaceous earth, metal foam, etc.

3. A method for using the device according to claim 1, characterized in that: When the device is used to carry out the decarbonization step, the flow rate of the rich methanol in the packing device is 30 to 800 of the volume of the packing.

4. The method for using the device according to claim 3, characterized in that: When the decarbonization step is carried out using the device, the temperature of the rich methanol is -30 to -50°C.

5. The method for using the device according to claim 3, characterized in that: When the device is used to perform the decarburization step, the pressure difference between the inside and outside of the device is 0.05-2 MPa.

6. The method for using the device according to claim 3, characterized in that: When the packing is close to saturation in water absorption, the internal methanol is drained, and high-temperature nitrogen is introduced at normal pressure to dry and regenerate it. After the regeneration is completed, low-temperature methanol solution is introduced to realize the reuse of the packing.

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