Biogas purification device based on natural gas pipeline pressure energy utilization

Abstract

The utility model relates to the technical field of biogas treatment, in particular to a biogas purification device based on natural gas pipeline pressure energy utilization, which is arranged between a high-pressure natural gas conveying pipeline and an urban pipe network and comprises a heat exchange component and a gas-liquid separation component. The heat exchange assembly comprises an expansion refrigerator used for depressurizing and refrigerating high-pressure natural gas, an outlet of the expansion refrigerator is connected with a heat exchanger, a first heat exchange pipe and a second heat exchange pipe are arranged in the heat exchanger, one end of the first heat exchange pipe communicates with the outlet of the expansion refrigerator, and the other end of the first heat exchange pipe is connected with an urban pipe network. One end of the second heat exchange pipe is connected with the biogas conveying unit, and the other end is connected with the low-temperature biogas output pipeline. Carbon dioxide in biogas is condensed through the heat exchange assembly, carbon dioxide gas in the biogas is removed through cold energy generated in the pressure reduction process of high-pressure natural gas, the condensed carbon dioxide is separated out through the gas-liquid separation assembly, and purification of the biogas is achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of biogas processing, in particular to a biogas purification device based on the utilization of natural gas pipeline pressure energy. Background Art

[0002] As global fossil raw materials are facing depletion, the development and application of biomass fuels has become a hot topic in various countries. The rapid development of large-scale biogas projects has also made the demand for biogas desulfurization and decarbonization purification as high-value-added biogas increasingly urgent. Biogas purification and refining technologies have been applied and developed to varying degrees. For example, some purification technologies such as pressure swing adsorption, physical absorption, chemical absorption, and membrane separation have been widely used. Through the purification and refining of biogas, impurities such as carbon dioxide in biogas can be removed.

[0003] On the other hand, long-distance natural gas pipelines are all transported at high pressure, and there is huge pressure energy in high-pressure natural gas pipelines. When transporting to urban pipelines, the pressure needs to be reduced. At present, pressure regulators are usually used to reduce the pressure. During the pressure reduction process, the temperature of natural gas decreases, generating cold energy.

[0004] In the process of transporting high-pressure natural gas to the urban pipeline network, when the pressure drop is large, in order to compensate for the temperature drop caused by the Joule-Thomson effect, it is necessary to heat the high-pressure natural gas before reducing the pressure. Not only can the pressure energy and cold energy of the high-pressure natural gas pipeline not be fully utilized, but additional energy is also required to heat the high-pressure natural gas, resulting in energy waste. Utility Model Content

[0005] In view of the above-mentioned deficiencies in the prior art, the utility model provides a biogas purification device based on the utilization of natural gas pipeline pressure energy, which realizes the utilization of high-pressure natural gas pipeline pressure energy and cold energy, and does not require additional energy consumption to heat the high-pressure natural gas, thereby improving energy utilization.

[0006] The utility model provides a biogas purification device based on the utilization of natural gas pipeline pressure energy, which is arranged between the high-pressure natural gas transmission pipeline and the urban pipeline network, and comprises:

[0007] The heat exchange component comprises an expansion refrigerator, the inlet of the expansion refrigerator is connected to the high-pressure natural gas transmission pipeline, and is used to reduce the pressure of the high-pressure natural gas for refrigeration. The outlet of the expansion refrigerator is connected to a heat exchanger, and a first heat exchange tube and a second heat exchange tube are arranged in the heat exchanger. One end of the first heat exchange tube is connected to the outlet of the expansion refrigerator, and the other end is connected to the city pipe network. One end of the second heat exchange tube is connected to the biogas transmission unit, and the other end is connected to the low-temperature biogas output pipeline.

[0008] The gas-liquid separation component has a gas-liquid inlet, a gas outlet and a liquid outlet. The gas-liquid inlet is connected to the low-temperature biogas output pipeline, the liquid outlet is connected to a carbon dioxide collection unit, and the gas outlet is connected to a biogas collection unit.

[0009] Preferably, the gas-liquid separation component comprises a first gas-liquid separator, and the gas-liquid inlet and the gas outlet and the liquid outlet are all arranged on the first gas-liquid separator.

[0010] Preferably, two groups of the heat exchange components are provided, and the two groups of the heat exchange components are arranged in series between the high-pressure natural gas transmission pipeline and the urban pipeline network.

[0011] Preferably, the first gas-liquid separator is disposed between the heat exchangers of the two groups of the heat exchange components, and the second heat exchange pipe outlet of the heat exchanger close to the high-pressure natural gas transmission pipeline is connected to the second gas-liquid separator.

[0012] Preferably, the carbon dioxide collection unit comprises a liquid carbon dioxide storage tank, and the liquid outlet of the first gas-liquid separator and the liquid outlet of the second gas-liquid separator are both connected to the liquid carbon dioxide storage tank.

[0013] Preferably, a refrigerant pipeline is provided inside the heat exchanger close to the urban pipeline network, and a refrigerant pump is provided outside the heat exchanger. The outlet of the refrigerant pump is connected to the inlet of the refrigerant pipeline. The inlet of the refrigerant pump is connected to a compressor. The inlet of the compressor is connected to the outlet of the refrigerant pipeline, and the outlet of the compressor is connected to the inlet of the refrigerant pump.

[0014] Preferably, a reboiler is provided between the compressor and the liquid carbon dioxide storage tank, the reboiler comprises a shell, a pipeline is provided inside the shell, a carbon dioxide outlet is provided at the bottom of the liquid carbon dioxide storage tank, the bottom of the shell is connected to the carbon dioxide outlet, the top of the shell is connected to the liquid carbon dioxide storage tank, the inlet of the pipeline is connected to the outlet of the compressor, and the outlet of the pipeline is connected to the inlet of the compressor.

[0015] Preferably, the inlet of the compressor is connected to a first flow divider, the outlet of the compressor is connected to a second flow divider, the inlet of the pipeline is communicated with the second flow divider, and the outlet of the pipeline is communicated with the first flow divider.

[0016] Compared with the prior art, the utility model provides a biogas purification device based on the utilization of natural gas pipeline pressure energy, which has the following beneficial effects:

[0017] The utility model condenses carbon dioxide in biogas through a heat exchange component, utilizes the cold energy generated in the process of reducing the pressure of high-pressure natural gas to remove carbon dioxide gas in the biogas, and separates the condensed carbon dioxide through a gas-liquid separation component, thereby purifying the biogas and making full use of the cold energy in the process of high-pressure natural gas pipeline transportation, while reducing the energy consumed in the process of developing a biogas project and improving the utilization rate of energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the overall structure of Embodiment 1 of the present utility model;

[0019] Figure 2 This is a schematic diagram of the overall structure of Embodiment 2 of the present utility model;

[0020] Figure 3 This is a schematic diagram of the overall structure of Example 3 of the utility model.

[0021] Description of reference numerals:

[0022] 1. Expansion refrigerator; 2. Heat exchanger; 6. First gas-liquid separator; 7. Second gas-liquid separator; 8. First stop valve; 9. Second stop valve; 10. Liquid carbon dioxide storage tank; 11. Reboiler; 12. Compressor; 13. Refrigerant pump; 14. First diverter; 15. Second diverter. DETAILED DESCRIPTION

[0023] The following is combined with Figures 1 to 3 , the specific implementation methods of the utility model are described in detail, but it should be understood that the protection scope of the utility model is not limited by the specific implementation methods.

[0024] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0025] In addition, in the description of this application, "plurality" means two or more than two. The terms "first" and "second" are used for descriptive purposes only and should not be understood as suggesting or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the feature.

[0026] Example 1

[0027] This embodiment provides a biogas purification device based on the utilization of natural gas pipeline pressure energy, such as Figure 1 As shown, the device is arranged between the high-pressure natural gas transmission pipeline and the urban pipeline network, and the biogas purification device includes a heat exchange component and a gas-liquid separation component.

[0028] Among them, the heat exchange component includes an expansion refrigerator 1, the inlet of the expansion refrigerator 1 is connected to the high-pressure natural gas transmission pipeline, and is used to reduce the pressure of the high-pressure natural gas for cooling. The outlet of the expansion refrigerator 1 is connected to the heat exchanger 2, and the heat exchanger is provided with a first heat exchange tube and a second heat exchange tube. One end of the first heat exchange tube is connected to the outlet of the expansion refrigerator 1, and the other end is connected to the urban pipeline network. One end of the second heat exchange tube is connected to the biogas transmission unit, and the other end is connected to the low-temperature biogas output pipeline.

[0029] The gas-liquid separation component has a gas-liquid inlet, a gas outlet, and a liquid outlet. The gas-liquid inlet is connected to the low-temperature biogas output pipeline, the liquid outlet is connected to a carbon dioxide collection unit, and the gas outlet is connected to a biogas collection unit. The gas-liquid separation component includes a first gas-liquid separator 6, on which the gas-liquid inlet, the gas outlet, and the liquid outlet are all arranged.

[0030] Figure 1 Among them, A is high-pressure natural gas, B is low-pressure natural gas, C is biogas, D is high-purity biogas, and E is carbon dioxide.

[0031] Working principle of this embodiment

[0032] The high-pressure natural gas (7-12MPa) is reduced to low-pressure natural gas (0.5-3MPa) through the expansion refrigerator 1. The temperature of the low-pressure natural gas after heat exchange with the biogas is increased to above 0°C and transported to the urban pipeline network; the temperature of the biogas is reduced after passing through the heat exchanger 2. During the cooling process, the carbon dioxide component in the biogas is condensed into liquid carbon dioxide. The liquid carbon dioxide is separated from the biogas through the first gas-liquid separator 6. The separated biogas is output from the gas outlet of the first gas-liquid separator 6 to achieve the purification of the biogas.

[0033] Example 2

[0034] Based on Example 1, this example provides a biogas purification device based on the utilization of natural gas pipeline pressure energy, such as Figure 2 As shown, two groups of heat exchange components are provided, and the two groups of heat exchange components are arranged in series between the high-pressure natural gas transmission pipeline and the urban pipeline network.

[0035] By providing two sets of heat exchange components, the biogas can be cooled step by step, thereby further improving the utilization rate of the high-pressure natural gas and the purification effect of the biogas.

[0036] In order to improve the purification rate of carbon dioxide in biogas, a gas-liquid separation is performed after each heat exchange to separate the liquid carbon dioxide. The first gas-liquid separator 6 is arranged between the heat exchangers 2 of the two groups of heat exchange components, and the second heat exchange pipe outlet of the heat exchanger close to the high-pressure natural gas transmission pipeline is connected to the second gas-liquid separator 7.

[0037] The carbon dioxide collection unit comprises a liquid carbon dioxide storage tank 10 , and the liquid outlet of the first gas-liquid separator 6 and the liquid outlet of the second gas-liquid separator 7 are both connected to the liquid carbon dioxide storage tank 10 .

[0038] Working principle of this embodiment

[0039] The biogas exchanges heat with the low-pressure natural gas, and the temperature drops to -30 to 0°C after the heat exchange. Part of the carbon dioxide in the biogas is liquefied and transported to the first gas-liquid separator 6 for gas-liquid separation. The separated biogas enters the heat exchanger 2 on one side of the high-pressure natural gas transmission pipeline to exchange heat with the high-pressure natural gas, and the temperature drops to -120 to -140°C. The carbon dioxide in the biogas C is basically liquefied and enters the second gas-liquid separator 7 for carbon dioxide separation. The high-purity biogas flows out from the D port, and the liquid carbon dioxide is finally stored in the liquid carbon dioxide storage tank 10.

[0040] Example 3

[0041] Based on Example 2, this example provides a biogas purification device based on the utilization of natural gas pipeline pressure energy, such as Figure 3 As shown, in order to further improve the heat exchange efficiency, a refrigerant pipeline is arranged inside the heat exchanger 2 close to the urban pipeline network, and a refrigerant pump 13 is arranged outside the heat exchanger 2. The outlet of the refrigerant pump 13 is connected to the inlet of the refrigerant pipeline, and the inlet of the refrigerant pump 13 is connected to a compressor 12. The inlet of the compressor 12 is connected to the outlet of the refrigerant pipeline, and the outlet of the compressor 12 is connected to the inlet of the refrigerant pump 13.

[0042] The biogas is cooled simultaneously by using the cold energy generated by the high-pressure natural gas and the refrigerant pipeline, thereby further increasing the cooling speed of the biogas.

[0043] Since part of the liquid carbon dioxide inside the liquid carbon dioxide storage tank 10 will be vaporized, in order to utilize the cold energy generated during the gasification of the liquid carbon dioxide, a reboiler 11 is arranged between the compressor 12 and the liquid carbon dioxide storage tank 10. The reboiler 11 includes a shell, a pipeline is arranged inside the shell, a carbon dioxide outlet is arranged at the bottom of the liquid carbon dioxide storage tank 10, the bottom of the shell is connected to the carbon dioxide outlet, the top of the shell is connected to the liquid carbon dioxide storage tank 10, the inlet of the pipeline is connected to the outlet of the compressor 12, and the outlet of the pipeline is connected to the inlet of the compressor 12.

[0044] Furthermore, the inlet of the compressor 12 is connected to a first splitter 14 , the outlet of the compressor 12 is connected to a second splitter 15 , the inlet of the pipeline is in communication with the second splitter 15 , and the outlet of the pipeline is in communication with the first splitter 14 .

[0045] Working principle of this embodiment

[0046] In order to further reduce the temperature of the biogas, the present embodiment sets a precooling circulation system at the heat exchanger 2 near the city pipe network, including a compressor 12, a second flow divider 15, a heat exchanger 2, and a first flow divider 14. The biogas is precooled to -60 to -30°C by low-pressure natural gas and refrigerant, and part of the carbon dioxide in the biogas is liquefied and enters the first gas-liquid separator 6. In addition, part of the liquid carbon dioxide in the liquid carbon dioxide storage tank 10 is gasified, and this part of the cold energy can also be used to cool the refrigerant in the biogas precooling circulation system.

[0047] The above disclosure is only a preferred specific embodiment of the present invention, but the embodiments of the present invention are not limited thereto, and any changes that can be conceived by technicians in this field should fall within the protection scope of the present invention.

Claims

1. A biogas purification device based on the utilization of natural gas pipeline pressure energy, the device is arranged between the high-pressure natural gas transmission pipeline and the urban pipeline network, characterized in that: The device includes: A heat exchange component, comprising an expansion refrigerator (1), wherein the inlet of the expansion refrigerator (1) is connected to the high-pressure natural gas transmission pipeline and is used to reduce the pressure of the high-pressure natural gas for refrigeration; the outlet of the expansion refrigerator (1) is connected to a heat exchanger (2); a first heat exchange tube and a second heat exchange tube are arranged in the heat exchanger; one end of the first heat exchange tube is connected to the outlet of the expansion refrigerator (1) and the other end is connected to a city pipe network; one end of the second heat exchange tube is connected to a biogas transmission unit and the other end is connected to a low-temperature biogas output pipeline; The gas-liquid separation component has a gas-liquid inlet, a gas outlet and a liquid outlet. The gas-liquid inlet is connected to the low-temperature biogas output pipeline, the liquid outlet is connected to a carbon dioxide collection unit, and the gas outlet is connected to a biogas collection unit.

2. The biogas purification device based on the utilization of natural gas pipeline pressure energy as claimed in claim 1, characterized in that: The gas-liquid separation component comprises a first gas-liquid separator (6), and the gas-liquid inlet and the gas outlet and the liquid outlet are all arranged on the first gas-liquid separator (6).

3. The biogas purification device based on utilizing the pressure energy of the natural gas pipeline according to claim 2, characterized in that: The heat exchange components are provided in two groups, and the two groups of heat exchange components are arranged in series between the high-pressure natural gas transmission pipeline and the urban pipeline network.

4. The biogas purification device based on utilizing the pressure energy of the natural gas pipeline according to claim 3, characterized in that: The first gas-liquid separator (6) is arranged between the heat exchangers (2) of the two groups of the heat exchange components, and the second heat exchange pipe outlet of the heat exchanger close to the high-pressure natural gas transmission pipeline is connected to the second gas-liquid separator (7).

5. The biogas purification device based on utilizing the natural gas pipeline pressure energy as claimed in claim 4, characterized in that: The carbon dioxide collection unit comprises a liquid carbon dioxide storage tank (10), and the liquid outlet of the first gas-liquid separator (6) and the liquid outlet of the second gas-liquid separator (7) are both connected to the liquid carbon dioxide storage tank (10).

6. The biogas purification device based on utilizing the pressure energy of the natural gas pipeline according to claim 5, characterized in that: A refrigerant pipeline is arranged inside the heat exchanger (2) on the side close to the urban pipeline network, and a refrigerant pump (13) is arranged outside the heat exchanger (2). The outlet of the refrigerant pump (13) is connected to the inlet of the refrigerant pipeline. The inlet of the refrigerant pump (13) is connected to a compressor (12). The inlet of the compressor (12) is connected to the outlet of the refrigerant pipeline, and the outlet of the compressor (12) is connected to the inlet of the refrigerant pump (13).

7. The biogas purification device based on utilizing the pressure energy of the natural gas pipeline according to claim 6, characterized in that: A reboiler (11) is arranged between the compressor (12) and the liquid carbon dioxide storage tank (10), and the reboiler (11) comprises a shell, a pipeline is arranged inside the shell, a carbon dioxide outlet is arranged at the bottom of the liquid carbon dioxide storage tank (10), the bottom of the shell is connected to the carbon dioxide outlet, the top of the shell is connected to the liquid carbon dioxide storage tank (10), the inlet of the pipeline is connected to the outlet of the compressor (12), and the outlet of the pipeline is connected to the inlet of the compressor (12).

8. The biogas purification device based on utilizing the natural gas pipeline pressure energy as claimed in claim 6, characterized in that: The inlet of the compressor (12) is connected to a first flow divider (14), the outlet of the compressor (12) is connected to a second flow divider (15), the inlet of the pipeline is in communication with the second flow divider (15), and the outlet of the pipeline is in communication with the first flow divider (14).

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