Carbon dioxide trapping and liquefying system

Abstract

The utility model relates to the technical field of carbon dioxide trapping and utilization, and particularly discloses a carbon dioxide trapping and liquefying system, which comprises a gas-liquid separation module, a gas storage tank, a gas compression module and a carbon dioxide liquefying and collecting module, the gas-liquid separator is used for carrying out gas-liquid separation on collected tail gas; the gas storage tank is arranged at the downstream of the gas-liquid separation module and is used for storing the dry gas subjected to gas-liquid separation; the gas compression module is arranged at the downstream of the gas storage tank and is used for pressurizing the dry gas; and the carbon dioxide liquefaction and collection module is arranged at the downstream of the gas compression module and is used for cooling and liquefying the pressurized dry gas to obtain liquid carbon dioxide. The system is simple in process, a refrigerant and expensive refrigeration equipment are not needed in the liquefaction process, the occupied area is small, and the operation cost is low; the carbon emission of the methanol reforming hydrogen production fuel cell system is reduced, and the economic benefit of the fuel cell system is increased.

Description

Technical Field

[0001] The utility model relates to the technical field of carbon dioxide capture and utilization, in particular to a carbon dioxide capture and liquefaction system. Background Art

[0002] At present, the application of clean energy such as natural gas and hydrogen energy has gradually become a new development direction for the energy industry. The fuel cell system uses methanol reforming hydrogen production technology to produce hydrogen-rich gas to meet power generation needs. In order to ensure the voltage and life of the fuel cell, there are strict requirements for the composition of the hydrogen-rich mixed gas entering the fuel cell. The methanol reforming hydrogen production fuel cell system is the main source of electricity supply for the park, and its exhaust gas contains water vapor, carbon dioxide, oxygen and nitrogen. In order to cope with global climate change and energy crises, and in order to truly achieve the goals of "carbon neutrality" and "carbon peak" in the energy field, how to reduce the amount of carbon dioxide produced and emitted by the methanol reforming hydrogen production fuel cell system is one of the important factors restricting the utilization and development of clean energy.

[0003] Compared with the huge cost of low-emission process research and development in clean energy applications, the technology of effectively recycling and utilizing carbon dioxide in the exhaust emissions of the corresponding system has a wider range of applications and is less difficult to convert. At the same time, carbon dioxide has a zero ODP value, a negligible GWP value, good stability, low price, abundant natural reserves, high density, large specific heat and volumetric cooling capacity, high latent heat and thermal conductivity, and is an ideal refrigerant. Liquid carbon dioxide products are widely used in industrial fields such as petrochemicals, food preservation, and metal welding.

[0004] Chemical absorption is the main method for capturing carbon dioxide from large fixed emission sources at this stage, but the recovered carbon dioxide raw materials are all in gaseous form. In order to facilitate transportation, the captured carbon dioxide gas needs to be liquefied and transported by tank trucks. The carbon dioxide purity in the raw gas usually obtained is low, only about 95%, and there is nearly 5% water and other trace impurities, such as nitrogen, methane, hydrogen sulfide, oxygen and other impurity gases. After absorbing carbon dioxide from fixed exhaust gas, liquid carbon dioxide products are obtained through the action of multi-stage compressors and coolers.

[0005] However, compared with the capture and utilization of high partial pressure carbon dioxide in the tail gas of fossil fuels such as coal, the enrichment of low partial pressure carbon dioxide produced in the process of utilizing clean energy such as natural gas and hydrogen is difficult and the purification cost is high. At present, there are many studies on the treatment methods of high partial pressure carbon dioxide tail gas, and the chemical absorption method has also been applied in demonstration projects such as coal-fired power plants. However, for clean energy utilization scenarios such as hydrogen production and gas-fired power generation, the tail gas treatment volume is large but the carbon dioxide partial pressure is low. The cost of the chemical absorption method is too high, and the equipment investment of the entire refrigeration system is large, the process is complex, and the technical cost is high. Utility Model Content

[0006] The technical problem to be solved by the utility model is: how to solve the problems of high cost and complicated process in the prior art.

[0007] In order to solve the above technical problems, the utility model provides a carbon dioxide capture and liquefaction system for capturing and liquefying carbon dioxide in the exhaust gas discharged from a methanol reforming hydrogen production fuel cell system, comprising:

[0008] A gas-liquid separation module, which is disposed at the tail gas discharge end of the methanol reforming hydrogen production fuel cell system and is used for gas-liquid separation of the collected tail gas;

[0009] A gas storage tank, which is arranged downstream of the gas-liquid separation module and is used to store dry gas after gas-liquid separation;

[0010] a gas compression module, the gas compression module being disposed downstream of the gas storage tank and being used to pressurize the dry gas; and

[0011] A carbon dioxide liquefaction collection module is provided downstream of the gas compression module and is used for cooling and liquefying the pressurized dry gas to obtain liquid carbon dioxide.

[0012] Further preferably, the gas-liquid separation module comprises:

[0013] A solenoid valve, the solenoid valve being connected to an exhaust gas discharge end of the methanol reforming hydrogen production fuel cell system;

[0014] a gas-liquid separator, which is disposed downstream of the solenoid valve and is used to separate the collected tail gas into gas and liquid; and

[0015] The dryer is arranged between the gas-liquid separator and the gas storage tank, and is used for further drying the gas after gas-liquid separation to obtain dry gas.

[0016] Further preferably, a stop valve is provided between the dryer and the gas storage tank.

[0017] Further preferably, the gas tank is provided with a pressure transmitter for obtaining the air pressure in the gas tank and a temperature transmitter for obtaining the air temperature in the gas tank.

[0018] Further preferably, the gas compression module comprises:

[0019] a gas compressor, which is disposed downstream of the gas storage tank and is used to pressurize the dry gas to obtain high-pressure gas; and

[0020] An air pump is provided between the gas storage tank and the gas compressor, and is used for conveying the dry gas in the gas storage tank to the gas compressor for pressurization.

[0021] Further preferably, a three-way valve is provided between the air pump and the gas compressor.

[0022] Further preferably, a gas flow meter is provided at the output end of the air pump.

[0023] Further preferably, the carbon dioxide liquefaction collection module comprises:

[0024] A condenser, the condenser is arranged downstream of the gas compressor, and the condenser is used to initially cool the high-pressure gas to obtain high-pressure and low-temperature gas;

[0025] a Laval tube, the Laval tube being disposed downstream of the condenser, and being used for expanding the high-pressure and low-temperature gas to a supersonic speed to reduce the mole fraction of carbon dioxide in the high-pressure and low-temperature gas, so as to liquefy the carbon dioxide; and

[0026] A liquid carbon dioxide recovery tank is disposed downstream of the Laval pipe and is used to store liquefied carbon dioxide.

[0027] Further preferably, the carbon dioxide liquefaction collection module further comprises an exhaust valve, and the exhaust valve is connected to the liquid carbon dioxide recovery tank for exhausting gas.

[0028] Further preferably, a heat exchanger is further included, wherein the heat exchanger is arranged downstream of the liquid carbon dioxide recovery tank, and the return air end of the heat exchanger is connected to the three-way valve to form a closed-loop structure.

[0029] Compared with the prior art, the carbon dioxide capture and liquefaction system provided by the utility model has the following beneficial effects:

[0030] The carbon dioxide capture and liquefaction system can capture and liquefy carbon dioxide in the tail gas emitted by the methanol reforming hydrogen production system, perform gas-liquid separation on the collected tail gas through the gas-liquid separation module to obtain dry gas, and the gas storage tank is used to store the dry gas after gas-liquid separation, and then the dry gas is pressurized by the gas compression module, and finally the pressurized dry gas is cooled and liquefied by the carbon dioxide liquefaction collection module to obtain liquid carbon dioxide; the system does not require the use of refrigerants and expensive refrigeration equipment in the liquefaction process, occupies a small area, and has low operating costs; and has a high energy recovery rate and high system safety, without the risk of secondary pollution and safety hazards caused by leakage of refrigeration solvents such as ammonia and Freon; the carbon emissions of the methanol reforming hydrogen production fuel cell system are reduced, and the economic benefits of the fuel cell system are increased; in addition, the obtained liquid carbon dioxide can also be used as a working fluid in the refrigeration system to reduce the ambient temperature in the corresponding industrial system, and can also be used as a source of raw materials for high-purity carbon dioxide products, thereby achieving energy conservation and emission reduction in industrial parks. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of a carbon dioxide capture and liquefaction system described in the utility model.

[0032] In the figure:

[0033] 1. Solenoid valve; 2. Gas-liquid separator; 3. Dryer; 4. Stop valve; 5. Gas storage tank; 6. Pressure transmitter; 7. Temperature transmitter; 8. Air pump; 9. Gas flow meter; 10. Three-way valve; 11. Gas compressor; 12. Condenser; 13. Laval tube; 14. Liquid carbon dioxide recovery tank; 15. Exhaust valve; 16. Methanol reforming hydrogen production fuel cell system; 17. Heat exchanger. DETAILED DESCRIPTION

[0034] The following is a further detailed description of the specific implementation of the present invention in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0035] In the description of the present invention, it should be understood that the terms "upstream", "downstream", "inside", "outside", "between", "inlet end", "outlet end" and the like used in the present invention to indicate orientations or positional relationships are 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 device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0036] In addition, 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 an indirect connection 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 utility model can be understood according to specific circumstances.

[0037] like Figure 1 As shown, the utility model provides a carbon dioxide capture and liquefaction system for capturing and liquefying carbon dioxide in the exhaust gas discharged from the methanol reforming hydrogen production fuel cell system 16. The carbon dioxide capture and liquefaction system includes a gas-liquid separation module, a gas storage tank 5, a gas compression module and a carbon dioxide liquefaction collection module from upstream to downstream. The system has a simple process, does not require the use of refrigerants and expensive refrigeration equipment during the liquefaction process, occupies a small area, and has low operating costs; and has a high energy recovery rate and high system safety. There is no secondary pollution risk and safety hazard caused by leakage of refrigeration solvents such as ammonia and Freon; it reduces the carbon emissions of the methanol reforming hydrogen production fuel cell system and increases the economic benefits of the fuel cell system.

[0038] In some embodiments, a gas-liquid separation module is provided at the exhaust gas discharge end of the methanol reforming hydrogen production fuel cell system 16, and is used to perform gas-liquid separation on the collected exhaust gas. The gas storage tank 5 is provided downstream of the gas-liquid separation module, and is used to store the dry gas after gas-liquid separation. The gas compression module is provided downstream of the gas storage tank 5, and is used to pressurize the dry gas. The carbon dioxide liquefaction collection module is provided downstream of the gas compression module, and is used to cool and liquefy the pressurized dry gas to obtain liquid carbon dioxide. The collected exhaust gas is subjected to gas-liquid separation by the gas-liquid separation module to obtain dry gas. The gas storage tank is used to store the dry gas after gas-liquid separation, and the dry gas is pressurized by the gas compression module. Finally, the pressurized dry gas is cooled and liquefied by the carbon dioxide liquefaction collection module to obtain liquid carbon dioxide. The obtained liquid carbon dioxide can also be used as a working fluid in a refrigeration system to reduce the ambient temperature in the corresponding industrial system, and can also be used as a source of raw materials for high-purity carbon dioxide products, thereby achieving energy conservation and emission reduction in industrial parks.

[0039] In some embodiments, the gas-liquid separation module includes a solenoid valve 1, a gas-liquid separator 2 and a dryer 3, wherein the solenoid valve 1 is connected to the exhaust gas emission end of the methanol reforming hydrogen production fuel cell system 16, and is used to transport the collected exhaust gas of the methanol reforming hydrogen production fuel cell system 16 to the gas-liquid separator 2, and the gas-liquid separator 2 is arranged downstream of the solenoid valve 1, and is used to perform gas-liquid separation on the collected exhaust gas and perform preliminary separation of water vapor in the exhaust gas. The dryer 3 is arranged between the gas-liquid separator 2 and the gas storage tank 5, and the dryer 3 is equipped with a dehumidifier. The gas after gas-liquid separation is further dried by the dryer 3 to obtain dry gas, so as to completely remove water vapor and avoid the presence of moisture in the subsequent condensation and liquefaction process to affect the purity of carbon dioxide.

[0040] In some embodiments, in order to ensure the gas pressure and temperature in the gas storage tank 5 , a stop valve 4 is further provided between the dryer 3 and the gas storage tank 5 to control the amount of gas entering the gas storage tank 5 .

[0041] In some embodiments, in order to monitor the air pressure and temperature in the gas storage tank 5, the gas storage tank 5 is provided with a pressure transmitter 6 for obtaining the air pressure in the gas storage tank 5 and a temperature transmitter 7 for obtaining the air temperature in the gas storage tank 5, which is beneficial to the control of subsequent processes and increases the subsequent liquefaction amount of carbon dioxide.

[0042] In some embodiments, the gas compression module includes a gas compressor 11 and an air pump 8. The air pump 8 is arranged between the gas storage tank 5 and the gas compressor 11. The air pump 8 is used to transport the dry gas in the gas storage tank 5 to the gas compressor 11 for pressurization. The gas compressor 11 is used to pressurize the dry gas to obtain high-pressure gas.

[0043] In some embodiments, a three-way valve 10 is provided between the air pump 8 and the gas compressor 11 . The provision of the three-way valve 10 is beneficial to the subsequent recycling of carbon dioxide.

[0044] In some embodiments, a gas flow meter 10 is provided at the output end of the air pump 8 to obtain the amount of gas entering the gas compressor 11 and ensure the normal and efficient operation of the gas compressor 11 .

[0045] In some embodiments, the carbon dioxide liquefaction and collection module includes a condenser 12, a Laval tube 13 and a liquid carbon dioxide recovery tank 14. The condenser 12 is arranged downstream of the gas compressor 11, and the condenser 12 is used to preliminarily cool the high-pressure gas to obtain high-pressure and low-temperature gas; the Laval tube 13 is arranged downstream of the condenser 12, and the Laval tube 13 is used to expand the high-pressure and low-temperature gas to supersonic speed to reduce the molar fraction of carbon dioxide in the high-pressure and low-temperature gas, so that the carbon dioxide is liquefied. The liquid carbon dioxide recovery tank 14 is arranged downstream of the Laval tube 13 for storing the liquefied carbon dioxide.

[0046] In the above embodiment, the front half of the Laval tube 13 shrinks from large to small and shrinks to a narrow throat in the middle, and then expands from small to large and expands outward to the base of the arrow. The gas in the arrow body flows into the front half of the nozzle under high pressure, and escapes from the rear half after passing through the narrow throat. This structure can change the speed of the airflow due to the change of the spray cross-sectional area, so that the airflow changes from subsonic to sonic, and finally accelerates to supersonic.

[0047] In the above embodiment, since the boiling point of carbon dioxide is -78.5°C, the boiling point of oxygen is -183°C, the boiling point of nitrogen is -196°C, and the boiling point of hydrogen is -252.8°C, when the high-pressure low-temperature gas expands to supersonic speed through the Laval tube 13, the temperature of the high-pressure low-temperature gas continues to decrease, and after the target temperature is reached in the nozzle expansion section, the carbon dioxide is the first to condense and liquefy, forming a gas-liquid two-phase flow.

[0048] In some embodiments, the carbon dioxide liquefaction collection module also includes an exhaust valve 15, which is connected to the liquid carbon dioxide recovery tank 14 for exhausting gas. When the carbon dioxide is liquefied, the remaining gas mainly contains nitrogen and oxygen, and the nitrogen and oxygen can be discharged from the liquid carbon dioxide recovery tank 14 through the exhaust valve 15, thereby realizing the recycling of liquid carbon dioxide.

[0049] In some embodiments, a heat exchanger 17 is also included. The heat exchanger 17 is arranged downstream of the liquid carbon dioxide recovery tank 14. The return air end of the heat exchanger 17 is connected to the three-way valve 10 to form a closed-loop structure. The liquid carbon dioxide is stored in the liquid carbon dioxide recovery tank 14 and can be used as a working fluid in the refrigeration system of the industrial park. After heat exchange with the park environment, it is remixed with the exhaust gas along the pipeline and condensed again through the gas compressor 11, the condenser 12, and the Laval tube 13 to obtain liquefied carbon dioxide, thereby realizing the circulation of carbon dioxide.

[0050] In other embodiments, the heat exchanger 17 can also exchange heat with other devices, or can be used as a raw material source for high-purity carbon dioxide products or used to synthesize green methanol, and then be re-entered into the methanol reforming hydrogen production battery system as fuel. This is not limited here.

[0051] The working process of the utility model is as follows: the methanol reforming hydrogen production fuel cell system is the main source of power supply for the industrial park, and the exhaust gas thereof contains water vapor, carbon dioxide, oxygen and nitrogen. After the exhaust gas passes through the solenoid valve 1, the gas-liquid separator 2 and the dryer 3 equipped with a dehydrating agent through the pipeline, the water vapor in the exhaust gas is removed, and the obtained dry gas is stored in the gas storage tank 5, and under the action of the air pump 8, it is transported to the gas compressor 11 and the condenser 12, pressurized and cooled, and the obtained high-pressure and low-temperature gas passes through the Laval tube 13, and after accelerating the cooling and reaching the target temperature, the carbon dioxide is liquefied, and the obtained gas-liquid mixture enters the liquid carbon dioxide recovery tank 14, and the unliquefied exhaust gas components are discharged into the atmosphere through the exhaust valve 15; the liquid carbon dioxide can be used as the working fluid of the refrigeration system of the industrial park, and after heat exchange with the industrial park environment through the heat exchanger 17, it is mixed with the exhaust gas again along the pipeline and the three-way valve 10, and then condensed through the gas compressor 11, the condenser 12 and the Laval tube 13 again to obtain liquefied carbon dioxide, thereby realizing the circulation of carbon dioxide.

[0052] In summary, the embodiment of the utility model provides a carbon dioxide capture and liquefaction system, which can capture and liquefy carbon dioxide in the tail gas emitted by the methanol reforming hydrogen production system, and perform gas-liquid separation on the collected tail gas through a gas-liquid separation module to obtain dry gas, and the gas storage tank is used to store the dry gas after gas-liquid separation, and then the dry gas is pressurized by the gas compression module, and finally the pressurized dry gas is cooled and liquefied by the carbon dioxide liquefaction collection module to obtain liquid carbon dioxide; the system does not require the use of refrigerants and expensive refrigeration equipment in the liquefaction process, occupies a small area, and has low operating costs; and has a high energy recovery rate and high system safety, without the risk of secondary pollution and safety hazards caused by leakage of refrigeration solvents such as ammonia and Freon; the carbon emissions of the methanol reforming hydrogen production fuel cell system are reduced, and the economic benefits of the fuel cell system are increased; in addition, the obtained liquid carbon dioxide can also be used as a working fluid in the refrigeration system to reduce the ambient temperature in the corresponding industrial system, and can also be used as a source of raw materials for high-purity carbon dioxide products, thereby achieving energy conservation and emission reduction in industrial parks.

[0053] The above is only a preferred embodiment of the utility model. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the utility model, and these improvements and substitutions should also be regarded as the protection scope of the utility model. The above shows and describes the basic principles, main features and advantages of the utility model. For those skilled in the art, it is obvious that the utility model is not limited to the details of the above preferred embodiments. The embodiments should be regarded as exemplary and non-restrictive. The scope of the utility model is defined by the attached claims rather than the above description, so it is intended to include all changes that fall within the meaning and scope of the equivalent elements of the claims in the utility model.

[0054] In addition, it should be understood that although this specification is described according to implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in the embodiments can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A carbon dioxide capture and liquefaction system, used to capture and liquefy carbon dioxide in the exhaust gas of a methanol reforming hydrogen production fuel cell system, characterized in that: include: A gas-liquid separation module, which is disposed at the tail gas discharge end of the methanol reforming hydrogen production fuel cell system and is used for gas-liquid separation of the collected tail gas; A gas storage tank, which is arranged downstream of the gas-liquid separation module and is used to store dry gas after gas-liquid separation; a gas compression module, the gas compression module being disposed downstream of the gas storage tank and being used to pressurize the dry gas; and A carbon dioxide liquefaction collection module is provided downstream of the gas compression module and is used for cooling and liquefying the pressurized dry gas to obtain liquid carbon dioxide.

2. A carbon dioxide capture and liquefaction system according to claim 1, characterized in that: The gas-liquid separation module comprises: A solenoid valve, the solenoid valve being connected to an exhaust gas discharge end of the methanol reforming hydrogen production fuel cell system; a gas-liquid separator, which is disposed downstream of the solenoid valve and is used to separate the collected tail gas into gas and liquid; and The dryer is arranged between the gas-liquid separator and the gas storage tank, and is used for further drying the gas after gas-liquid separation to obtain dry gas.

3. A carbon dioxide capture and liquefaction system according to claim 2, characterized in that: A stop valve is also provided between the dryer and the gas storage tank.

4. A carbon dioxide capture and liquefaction system according to claim 3, characterized in that: The gas storage tank is provided with a pressure transmitter for obtaining the air pressure in the gas storage tank and a temperature transmitter for obtaining the air temperature in the gas storage tank.

5. A carbon dioxide capture and liquefaction system according to claim 1, characterized in that: The gas compression module comprises: a gas compressor, which is disposed downstream of the gas storage tank and is used to pressurize the dry gas to obtain high-pressure gas; and An air pump is provided between the gas storage tank and the gas compressor, and is used for conveying the dry gas in the gas storage tank to the gas compressor for pressurization.

6. A carbon dioxide capture and liquefaction system according to claim 5, characterized in that: A three-way valve is arranged between the air pump and the gas compressor.

7. A carbon dioxide capture and liquefaction system according to claim 5, characterized in that: A gas flow meter is provided at the output end of the air pump.

8. A carbon dioxide capture and liquefaction system according to claim 6, characterized in that: The carbon dioxide liquefaction collection module comprises: A condenser, the condenser is arranged downstream of the gas compressor, and the condenser is used to initially cool the high-pressure gas to obtain high-pressure and low-temperature gas; a Laval tube, the Laval tube being disposed downstream of the condenser, and being used for expanding the high-pressure and low-temperature gas to a supersonic speed to reduce the mole fraction of carbon dioxide in the high-pressure and low-temperature gas, so as to liquefy the carbon dioxide; and A liquid carbon dioxide recovery tank is disposed downstream of the Laval pipe and is used to store liquefied carbon dioxide.

9. A carbon dioxide capture and liquefaction system according to claim 8, characterized in that: The carbon dioxide liquefaction collection module further includes an exhaust valve, which is connected to the liquid carbon dioxide recovery tank and is used to exhaust gas.

10. A carbon dioxide capture and liquefaction system according to claim 8, characterized in that: It also includes a heat exchanger, which is arranged downstream of the liquid carbon dioxide recovery tank, and the return air end of the heat exchanger is connected to the three-way valve to form a closed-loop structure.

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