Liquid membrane absorption biogas purification system

Abstract

The invention discloses a liquid membrane absorption biogas purification system, and relates to the technical field of biogas purification, the liquid membrane absorption biogas purification system comprises a biogas filter, an absorption membrane assembly, a deacidified gas separator and an amine-rich liquid desorption system, the absorption membrane assembly comprises a tube pass formed by a hollow porous membrane with hydrophobic property, the tube pass input end of the absorption membrane assembly is connected with the output end of the biogas filter, the tube pass output end of the absorption membrane assembly is connected with the input end of the deacidified gas separator, the shell pass input end of the absorption membrane assembly is connected with the lean amine liquid output end of the rich amine liquid desorption system, and the shell pass output end of the absorption membrane assembly is connected with the rich amine liquid input end of the rich amine liquid desorption system. The method provided by the invention not only solves the problem of low purification precision of a pressure swing adsorption, membrane separation and high-pressure water washing method biogas purification technology, but also solves the problems of complex flow, more equipment, high investment and the like of a pressure swing adsorption series MDEA refined decarburization technology, and has the advantages of simple flow, simple equipment, easy prying, low energy consumption, high biogas purification efficiency and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of biogas purification, and in particular relates to a liquid membrane absorption biogas purification system. Background Art

[0002] As a clean energy, natural gas has the advantages of high calorific value, less pollution, safety, reliability and low cost. It is the most widely used green and low-carbon energy in the world today. Biogas is one of the most important development directions and is expected to be a supplement to natural gas in the future. my country has rich agricultural biomass resources, and the amount of resources that can be converted into energy is about 350 million tons of standard coal. Vigorously developing and recycling biogas is a powerful measure to increase my country's natural gas resources and help achieve carbon peak and carbon neutrality.

[0003] The main components of renewable biogas are methane (CH4) and carbon dioxide (CO2). At present, a large amount of biogas is still mainly used for low-grade heat, such as biogas power generation. With the continuous development of biogas projects, biogas production continues to increase, and the utilization of biogas continues to expand, such as using pressure swing adsorption, membrane separation and high-pressure water washing to purify biogas to obtain CNG that meets the quality standards of GB18047-2017 "Compressed Natural Gas for Vehicles" or GB17820-2018 "Natural Gas" or incorporate it into the natural gas pipeline network; such as deep purification and liquefaction to produce liquefied biomethane. However, the CO2 content in biomethane obtained by purifying biogas using pressure swing adsorption, membrane separation and high-pressure water washing cannot meet the requirements for producing liquefied natural gas.

[0004] Publication No. CN210438693U discloses a biogas purification device for removing and recovering carbon dioxide, and proposes a technical route of pressure swing adsorption and MDEA fine decarbonization (traditional amine decarbonization) in series, which solves the problem that the CO2 content in the biomethane obtained by biogas purification exceeds the liquefaction requirement. However, the process of pressure swing adsorption in series with MDEA fine decarbonization is relatively complicated, with more equipment and higher investment, and there are absorption towers and regeneration towers with a height of more than 15m. Summary of the invention

[0005] In view of the problems mentioned in the background technology, the purpose of the present invention is to provide a liquid membrane absorption biogas purification system to solve the problems mentioned in the background technology.

[0006] The above technical objectives of the present invention are achieved through the following technical solutions:

[0007] A liquid membrane absorption biogas purification system comprises a biogas filter, an absorption membrane assembly, a deacidification gas separator and a rich amine liquid desorption system, wherein the absorption membrane assembly comprises a tube side composed of a hollow porous membrane with hydrophobic properties, the tube side input end of the absorption membrane assembly is connected to the output end of the biogas filter, the tube side output end is connected to the input end of the deacidification gas separator, the shell side input end of the absorption membrane assembly is connected to the lean amine liquid output end of the rich amine liquid desorption system, and the shell side output end is connected to the rich amine liquid input end of the rich amine liquid desorption system.

[0008] As a preferred technical solution, the rich amine liquid desorption system includes a flash evaporation system, a desorption core system, a recycling system, an acid gas system and a lean amine liquid treatment system; the two sets of input ends of the flash evaporation system are respectively connected to the shell side output end of the absorption membrane assembly and the liquid output end of the acid gas system, the two sets of input ends of the desorption core system are respectively connected to the liquid output end of the flash evaporation system and the gas output end of the recycling system, the output end of the desorption core system is respectively connected to the input end of the recycling system and the acid gas system, and the liquid output end of the recycling system is connected to the shell side input end of the absorption membrane assembly through the lean amine liquid treatment system.

[0009] As a preferred technical solution, the flash system includes an amine liquid flash tank, the liquid output end of the absorption membrane assembly is connected to the rich amine liquid input end of the amine liquid flash tank, the liquid output end of the acid gas system is connected to the water replenishment input end of the amine liquid flash tank, and the liquid output end of the amine liquid flash tank is connected to the liquid input end of the desorption core system.

[0010] As a preferred technical solution, the desorption core system includes a desorption membrane assembly, the desorption membrane assembly includes a tube pass composed of a desorption porous membrane, the tube pass input end is connected to the liquid output end of the flash evaporation system, the tube pass output end is connected to the liquid input end of the recycling system, the shell input end is connected to the gas output end of the recycling system, and the shell output end is connected to the acid gas system input end.

[0011] As an optimal technical solution, the recycling system includes a reboiler, a gas-liquid separator and a heating device. The liquid output end of the desorption core system is connected to the reboiler input end, the reboiler output end is connected to the gas-liquid separator input end, the liquid output end of the gas-liquid separator is connected to the lean amine liquid treatment system input end, the gas output end of the gas-liquid separator is connected to the gas input end of the desorption core system, and the heating device heats the reboiler.

[0012] As a preferred technical solution, the acid gas system includes an acid gas cooler and an acid gas separator. The input end of the acid gas cooler is connected to the gas output end of the desorption core system, the output end of the acid gas cooler is connected to the input end of the acid gas separator, and the liquid output end of the acid gas separator is connected to the water replenishment input end of the flash evaporation system.

[0013] As a preferred technical solution, the lean amine liquid treatment system includes a lean liquid cooler, the input end of the lean liquid cooler is connected to the liquid output end of the recycling system, and the output end of the lean liquid cooler is connected to the pipe input end of the absorption membrane assembly.

[0014] As a preferred technical solution, it also includes a heat exchange system, which includes a lean-rich liquid heat exchanger, and the lean-rich liquid heat exchanger includes two groups of unconnected flow channels, the input end of one group of flow channels is connected to the liquid output end of the flash evaporation system, and the output end is connected to the liquid input end of the desorption core system, and the input end of the other group of flow channels is connected to the liquid output end of the recycling system, and the output end is connected to the input end of the lean amine liquid treatment system.

[0015] As a preferred technical solution, the rich amine liquid desorption system also includes an amine liquid circulation pump for circulating the amine liquid in the pipe path.

[0016] As a preferred technical solution, the amine liquid circulation pump is installed between the lean amine liquid treatment system and the absorption membrane assembly.

[0017] Beneficial Effects

[0018] The present invention solves the problem of low purification accuracy of biogas purification technologies such as pressure swing adsorption, membrane separation and high-pressure water washing, and solves the problems of complex process, multiple equipment and high investment of pressure swing adsorption series MDEA fine decarbonization technology. It has the advantages of simple process, simple equipment, easy assembly, low energy consumption and high biogas purification efficiency.

[0019] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A technical flow chart of a liquid membrane absorption biogas purification system proposed by the present invention;

[0021] Figure 2 This is the absorption principle diagram of the absorption membrane assembly;

[0022] Figure 3 This is the absorption principle diagram of the desorption membrane assembly.

[0023] Figure numerals: 11-biogas filter, 12-absorption membrane assembly, 121-hollow porous membrane, 13-deacidification gas separator, 21-amine liquid flash tank, 22-lean and rich liquid heat exchanger, 23-desorption membrane assembly, 231-desorption porous membrane, 24-reboiler, 25-gas-liquid separator, 26-acid gas cooler, 27-acid gas separator, 28-lean liquid cooler, 29-amine liquid circulation pump, 31-heating device. DETAILED DESCRIPTION

[0024] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar symbols throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0025] Example 1

[0026] refer to Figures 1 to 3 The liquid membrane absorption biogas purification system described in this embodiment includes a biogas filter 11, an absorption membrane assembly 12, a deacidification gas separator 13 and a rich amine liquid desorption system. The output end of the biogas filter 11 is connected to the tube side input end of the absorption membrane assembly 12, the lean amine liquid output end of the rich amine liquid desorption system is connected to the shell side input end of the absorption membrane assembly 12, the tube side output end of the absorption membrane assembly 12 is connected to the deacidification gas separator 13 input end, and the shell side output end of the absorption membrane assembly 12 is connected to the rich amine liquid input end of the rich amine liquid desorption system.

[0027] The absorption membrane assembly 12 includes a tube path composed of a hollow porous membrane 121. The hollow porous membrane 121 has hydrophobic properties and can separate biogas and amine liquid. The hollow porous membrane 121 provides a contactable mass transfer absorption interface. The CO2 in the biogas diffuses through the membrane pores to the membrane pore interface and contacts with the lean amine liquid for chemical absorption, thereby removing the CO2 in the biogas.

[0028] After the biogas is filtered by the biogas filter 11 to remove the impurities such as solid particles and dust carried by it, it enters the tube side of the absorption membrane assembly 12. The rich amine liquid desorption system outputs the lean amine liquid into the shell side of the absorption membrane assembly 12. The CO2 in the biogas diffuses to the membrane pore interface through the membrane pores. The lean amine liquid absorbs CO2 to become rich amine liquid and re-enters the rich amine liquid desorption system. The clean biomethane after CO2 is removed enters the deacidification gas separator 13 for deacidification and can be used. The lean amine liquid is used to take away the CO2 near the tube side to prevent excessive concentration from affecting the continuous CO2 removal.

[0029] The rich amine liquid desorption system includes a flash evaporation system, a heat exchange system, a desorption core system, a recycling system, an acid gas system and a lean amine liquid treatment system; the rich amine liquid output from the absorption membrane assembly 12 enters the flash evaporation system, and at the same time, the liquid output end of the acid gas system is connected to an input end of the flash evaporation system, the two input ends of the heat exchange system are respectively connected to the output ends of the flash evaporation system and the recycling system, the two output ends of the heat exchange system are respectively connected to the lean amine liquid treatment system and the desorption core system, the gas input end of the desorption core system is connected to the output end of the recycling system, the two output ends of the desorption core system are respectively connected to the input ends of the recycling system and the acid gas system, and the output end of the lean amine liquid treatment system is connected to the input end of the absorption membrane assembly 12.

[0030] The flash system includes an amine liquid flash tank 21. The rich amine liquid output from the absorption membrane assembly 12 enters the amine liquid flash tank 21. At the same time, the acid gas system outputs condensate to replenish the amine liquid flash tank 21. The amine liquid flash tank 21 flashes the high-concentration rich amine liquid, and the obtained natural gas is discharged for use. The obtained low-concentration rich amine liquid enters the heat exchange system.

[0031] The heat exchange system includes a lean-rich liquid heat exchanger 22, which includes two sets of unconnected tube passes, the input ends of the two sets of tube passes are respectively connected to the output end of the amine liquid flash tank 21 and the output end of the recycling system, the recycling system outputs high-temperature lean amine liquid to heat the low-temperature rich amine liquid in the other set of tube passes, the rich amine liquid after heat exchange is input into the desorption core system, and the lean amine liquid enters the lean amine liquid treatment system;

[0032] The desorption core system includes a desorption membrane assembly 23, which includes a desorption porous membrane 231 similar to the hollow porous membrane 121. The tube side input end composed of the desorption porous membrane 231 is connected to the output end of the lean-rich liquid heat exchanger 22, the tube side output end is connected to the input end of the recycling system, the shell side input end of the desorption membrane assembly 23 is connected to the output end of the recycling system, and the shell side output end is connected to the acid gas system; the rich amine liquid input from the desorption core system enters the tube side, and the CO2 in the rich amine liquid passes through the desorption porous membrane 231 and enters the shell side of the desorption membrane assembly 23, and the high-temperature steam output by the recycling system takes away the CO2 accumulated near the tube side, and outputs the high-temperature acid gas with CO2 to the acid gas system;

[0033] The acid gas system includes an acid gas cooler 26 and an acid gas separator 27. The input end of the acid gas cooler 26 is connected to the shell side output end of the desorption membrane assembly 23, the output end of the acid gas cooler 26 is connected to the input end of the acid gas separator 27, the acid gas output end of the acid gas separator 27 is connected to the external system, and the liquid output end of the acid gas separator 27 is connected to the input end of the amine liquid flash tank 21; high-temperature acid gas with CO2 is input into the acid gas cooler 26, the cooled acid gas enters the acid gas separator 27 for separation, the separated acid gas is output to the system, and the separated condensate replenishes the amine liquid flash tank 21;

[0034] The recycling system includes a reboiler 24, a gas-liquid separator 25 and a heating device 31. The tube side output end of the desorption membrane assembly 23 is connected to the input end of the reboiler 24, the output end of the reboiler 24 is connected to the input end of the gas-liquid separator 25, the liquid output end of the gas-liquid separator 25 is connected to the lean-rich liquid heat exchanger 22, and the gas output end is connected to the shell side input end of the desorption membrane assembly 23. The heating device 31 heats the reboiler 24; the lean amine liquid output from the tube side of the desorption membrane assembly 23 enters the reboiler 24 and is heated again by the heating device 31, the heated amine liquid enters the gas-liquid separator 25 for gas-liquid separation, the high-temperature steam after separation re-enters the shell side of the desorption membrane assembly 23 to remove CO2, and the high-temperature lean amine liquid after separation enters one group of tube sides of the lean-rich liquid heat exchanger 22 to heat the low-temperature rich amine liquid in another group of tube sides;

[0035] The lean amine liquid treatment system includes a lean liquid cooler 28, the input end of the lean liquid cooler 28 is connected to the lean amine liquid output end of the lean-rich liquid heat exchanger 22, and the output end of the lean liquid cooler 28 is connected to the shell side input end of the absorption membrane assembly 12; the lean liquid cooler 28 cools the lean amine liquid output from the lean-rich liquid heat exchanger 22, and inputs the cooled lean amine liquid into the shell side of the absorption membrane assembly 12 to take away the CO2 outside the hollow porous membrane 121;

[0036] It also includes an amine liquid circulation pump 29 for circulating the amine liquid in the pipe. Preferably, the amine liquid circulation pump 29 is installed between the lean liquid cooler 28 and the absorption membrane assembly 12.

[0037] Working process of rich amine liquid desorption system:

[0038] The rich amine liquid that absorbs CO2 in the shell side of the absorption membrane component 12 enters the amine liquid flash tank 21, and the rich amine liquid with reduced concentration output from the amine liquid flash tank 21 enters the lean-rich liquid heat exchanger 22. The high-temperature lean amine liquid output from the gas-liquid separator 25 heats the rich amine liquid, and the heat of the lean amine liquid is used to avoid energy waste. The lean amine liquid after cooling is cooled by the lean liquid cooler 28 and then enters the shell side of the absorption membrane component 12 through the amine liquid circulation pump 29 to absorb CO2. The rich amine liquid after heating enters the desorption membrane component 23 pipe side, and the CO2 therein passes through the desorption porous membrane 231 and enters the shell side. The gas-liquid separator 25 outputs the high-temperature lean amine liquid to heat the rich amine liquid. The heat of the lean amine liquid is used to avoid energy waste. The high-temperature steam discharged enters the shell side of the desorption membrane component 23 to take away the CO2 and turn it into high-temperature acid gas, which enters the acid gas cooler 26 for cooling. Then the acid gas separator 27 separates the cooled acid gas into acid gas and condensate. The condensate enters the amine liquid flash tank 21 for reuse, reducing the number of times the external desalted water is replenished to ensure the concentration of the amine liquid in the system. The rich amine liquid in the tube side of the desorption membrane component 23 is converted into lean amine liquid and enters the reboiler 24 for heating. The heated high-temperature lean amine liquid enters the gas-liquid separator 25 and is separated into high-temperature steam that enters the shell side of the desorption membrane component 23 and high-temperature lean amine liquid that enters the lean-rich liquid heat exchanger 22.

[0039] The device has the advantages of simple process, simple equipment, easy assembly, low energy consumption and high biogas purification efficiency.

[0040] It should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0041] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0042] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0043] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0044] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A liquid membrane absorption biogas purification system, comprising a biogas filter (11), an absorption membrane assembly (12), a deacidification gas separator (13) and a rich amine liquid desorption system, characterized in that: The absorption membrane assembly (12) comprises a tube side composed of a hollow porous membrane (121) having hydrophobic properties; the tube side input end of the absorption membrane assembly (12) is connected to the output end of the biogas filter (11); the tube side output end is connected to the input end of the deacidified gas separator (13); the shell side input end of the absorption membrane assembly (12) is connected to the lean amine liquid output end of the rich amine liquid desorption system; and the shell side output end is connected to the rich amine liquid input end of the rich amine liquid desorption system.

2. The liquid membrane absorption biogas purification system according to claim 1 is characterized in that: The rich amine liquid desorption system comprises a flash evaporation system, a desorption core system, a recycling system, an acid gas system and a lean amine liquid treatment system; two groups of input ends of the flash evaporation system are respectively connected to the shell side output end of the absorption membrane component (12) and the liquid output end of the acid gas system, two groups of input ends of the desorption core system are respectively connected to the liquid output end of the flash evaporation system and the gas output end of the recycling system, the output end of the desorption core system is respectively connected to the recycling system and the acid gas system input end, and the liquid output end of the recycling system is connected to the shell side input end of the absorption membrane component (12) through the lean amine liquid treatment system.

3. The liquid membrane absorption biogas purification system according to claim 2 is characterized in that: The flash system comprises an amine liquid flash tank (21), wherein the liquid output end of the absorption membrane assembly (12) is connected to the rich amine liquid input end of the amine liquid flash tank (21), the liquid output end of the acid gas system is connected to the water replenishment input end of the amine liquid flash tank (21), and the liquid output end of the amine liquid flash tank (21) is connected to the liquid input end of the desorption core system.

4. The liquid membrane absorption biogas purification system according to claim 2 is characterized in that: The desorption core system comprises a desorption membrane assembly (23), the desorption membrane assembly (23) comprises a tube pass composed of a desorption porous membrane (231), the tube pass input end is connected to the liquid output end of the flash evaporation system, the tube pass output end is connected to the liquid input end of the recycling system, the shell input end is connected to the gas output end of the recycling system, and the shell output end is connected to the acid gas system input end.

5. The liquid membrane absorption biogas purification system according to claim 2, characterized in that: The recycling system comprises a reboiler (24), a gas-liquid separator (25) and a heating device (31); the liquid output end of the desorption core system is connected to the input end of the reboiler (24); the output end of the reboiler (24) is connected to the input end of the gas-liquid separator (25); the liquid output end of the gas-liquid separator (25) is connected to the input end of the lean amine liquid treatment system; the gas output end of the gas-liquid separator (25) is connected to the gas input end of the desorption core system; and the heating device (31) heats the reboiler (24).

6. The liquid membrane absorption biogas purification system according to claim 2, characterized in that: The acid gas system comprises an acid gas cooler (26) and an acid gas separator (27), wherein the input end of the acid gas cooler (26) is connected to the gas output end of the desorption core system, the output end of the acid gas cooler (26) is connected to the input end of the acid gas separator (27), and the liquid output end of the acid gas separator (27) is connected to the water replenishment input end of the flash evaporation system.

7. The liquid membrane absorption biogas purification system according to claim 2, characterized in that: The lean amine liquid treatment system comprises a lean liquid cooler (28), the input end of the lean liquid cooler (28) is connected to the liquid output end of the recycling system, and the output end of the lean liquid cooler (28) is connected to the pipe side input end of the absorption membrane assembly (12).

8. The liquid membrane absorption biogas purification system according to claim 2, characterized in that: The invention also includes a heat exchange system, which includes a lean-rich liquid heat exchanger (22). The lean-rich liquid heat exchanger (22) includes two groups of non-connected flow channels, the input end of one group of flow channels is connected to the liquid output end of the flash evaporation system, and the output end is connected to the liquid input end of the desorption core system, and the input end of the other group of flow channels is connected to the liquid output end of the recycling system, and the output end is connected to the input end of the lean amine liquid treatment system.

9. The liquid membrane absorption biogas purification system according to claim 2, characterized in that: The rich amine liquid desorption system also includes an amine liquid circulation pump (29) for circulating the amine liquid in the pipe.

10. The liquid membrane absorption biogas purification system according to claim 9, characterized in that: The amine liquid circulation pump (29) is installed between the lean amine liquid treatment system and the absorption membrane assembly (12).

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