Two-stage Sabatier carbon dioxide methanation reaction system and method using cold energy of Martian atmosphere

Abstract

The present invention discloses a dual-stage Sabatier carbon dioxide methanation reaction system and method using the cold energy of the Martian atmosphere. The present invention constructs a gradient temperature field along the flow direction of the reaction gas by setting a dual-stage Sabatier reactor, a high-temperature Sabatier reactor is set in the front stage to increase the reaction speed, and a low-temperature Sabatier reactor based on Martian atmospheric cooling is set in the rear stage to increase the conversion rate of carbon dioxide to methane, while making full use of the low-temperature environment of Mars, achieving the goal of efficient preparation of methane propellant.

Description

Technical Field

[0001] The present invention relates to the field of Mars exploration technology, and in particular to a double-stage Sabatier carbon dioxide methanation reaction system and method utilizing cold energy of the Martian atmosphere. Background Art

[0002] In-situ preparation of Mars propellant refers to the exploration, acquisition and use of Mars' natural resources to prepare launch vehicle propellant on Mars. It is a key technology for realizing extraterrestrial manned exploration and future space colonization and other extraterrestrial activities. The main component of the atmosphere on the surface of Mars is carbon dioxide, accounting for 95.32% of the total, and propellant can be obtained through reduction reactions. There are many technical paths for carbon dioxide reduction. Considering various factors such as maturity, operability, economy, and long-term stability, carbon dioxide hydrogenation and methanation (Sabatier reaction) has become the current mainstream technology and has been successfully applied on the International Space Station to treat carbon dioxide produced by astronauts' breathing.

[0003] The Sabatier reaction is a highly exothermic process limited by thermodynamic equilibrium. To increase the Sabatier reaction rate, the reactor must be maintained at a high temperature, while to increase the conversion rate, the reactor needs to be at a lower temperature. Since the reactors in the current Sabatier reaction system are all integrated structures, it is difficult to achieve the goals of high reaction speed and reaction rate at the same time. In addition, the average temperature on Mars is about 216K, and the temperature difference between day and night is as high as 80K. The temperature fluctuations in the application environment of the Sabatier reaction system of the space station are relatively small, making it difficult to adapt to the low temperature environment on the surface of Mars. Summary of the invention

[0004] The purpose of the present invention is to solve the technical problem that the Sabatier reaction system in the prior art is difficult to use reliably in the low temperature environment on the surface of Mars, and to provide a two-stage Sabatier carbon dioxide methanation reaction system and method that utilizes the cold energy of the Martian atmosphere. The present invention constructs a gradient temperature field along the flow direction of the reaction gas by setting a two-stage Sabatier reactor, a high-temperature Sabatier reactor is set in the front stage to increase the reaction speed, and a low-temperature Sabatier reactor based on Martian atmospheric cooling is set in the rear stage to increase the conversion rate of carbon dioxide to methane, while making full use of the low temperature environment of Mars, achieving the goal of efficient preparation of methane propellant.

[0005] The specific technical solutions adopted by the present invention are as follows:

[0006] In a first aspect, the present invention provides a two-stage carbon dioxide methanation Sabatier reaction system utilizing cold energy of the Martian atmosphere, which comprises a liquid carbon dioxide storage tank, a high-pressure hydrogen source, a vaporizer, a preheater, an intercooler, a high-temperature Sabatier reactor, and a low-temperature Sabatier reactor;

[0007] The vaporizer, preheater and intercooler are respectively provided with a first passage and a second passage constituting heat exchange contact;

[0008] The liquid carbon dioxide storage tank is connected to the first passage of the vaporizer, the first pressure regulating valve and the mixer in sequence through the carbon dioxide pipeline; the high-pressure hydrogen source is connected to the hydrogen pipeline and the mixer in sequence through the hydrogen pipeline; the mixer is connected to the first passage of the preheater, the first passage of the intercooler and the electric heater in sequence through the mixed gas preheating pipeline, the electric heater is connected to the high-temperature Sabatier reactor, the second passage of the intercooler, the second passage of the vaporizer, the low-temperature Sabatier reactor and the second passage of the preheater in sequence through the mixed gas reaction pipeline, and the outlet of the second passage of the preheater is vented;

[0009] The low-temperature Sabatier reactor is provided with an external heat exchange passage for introducing the Martian atmosphere. The external heat exchange passage and the reaction chamber of the low-temperature Sabatier reactor form heat exchange, and the reaction temperature of the low-temperature Sabatier reactor can be controlled by adjusting the flow of Martian atmosphere in the external heat exchange passage.

[0010] As a preferred embodiment of the first aspect, the evaporator adopts a fin-tube heat exchanger.

[0011] As a preferred embodiment of the first aspect, the preheater adopts an air-to-air plate heat exchanger.

[0012] As a preferred embodiment of the first aspect, the intercooler adopts an air-to-air plate heat exchanger.

[0013] As a preferred embodiment of the first aspect, the high-temperature Sabatier reactor and the low-temperature Sabatier reactor are both externally coated with insulation material.

[0014] As a preferred embodiment of the first aspect, both the high-temperature Sabatier reactor and the low-temperature Sabatier reactor are filled with a Sabatier reaction catalyst.

[0015] As a preferred embodiment of the first aspect, the inlet end of the carbon dioxide pipeline is located below the liquid level of the liquid carbon dioxide storage tank, and the liquid carbon dioxide in the liquid carbon dioxide storage tank is driven into the carbon dioxide pipeline by self-pressurization.

[0016] As a preferred embodiment of the above first aspect, the high-pressure hydrogen source adopts a high-pressure hydrogen cylinder group.

[0017] As a preferred embodiment of the first aspect, the external heat exchange passage in the low-temperature Sabatier reactor is provided with a variable frequency low-temperature fan to provide power for conveying the Martian atmosphere.

[0018] In a second aspect, the present invention provides a two-stage carbon dioxide methanation Sabatier reaction method using the cold energy of the Martian atmosphere using the system described in any one of the schemes of the first aspect, comprising:

[0019] S1, after the liquid carbon dioxide in the liquid carbon dioxide storage tank is pressurized, it enters the first passage of the vaporizer through the carbon dioxide pipeline, absorbs the heat of the reaction gas in the second passage of the vaporizer to complete vaporization, and then enters the mixer through the first pressure regulating valve; at the same time, the high-pressure hydrogen in the high-pressure hydrogen source enters the mixer through the hydrogen pipeline and the second pressure regulating valve; the pressurized hydrogen and carbon dioxide gas are mixed in the mixer according to the stoichiometric ratio of the Sabatier reaction to form a mixed gas whose pressure meets the reaction requirements;

[0020] S2, the mixed gas in the mixer first enters the first passage of the preheater through the mixed gas preheating pipeline, absorbs the heat of the reaction gas in the second passage of the preheater to complete the first temperature increase, then enters the first passage of the intercooler, absorbs the heat of the reaction gas in the second passage of the intercooler to complete the second temperature increase, and finally enters the electric heater to complete the third temperature increase and reach the set Sabatier reaction start temperature;

[0021] S3, the mixed gas at the outlet of the electric heater first enters the high-temperature Sabatier reactor through the mixed gas reaction pipeline, and under the action of the Sabatier reaction catalyst in the high-temperature Sabatier reactor, part of the carbon dioxide and hydrogen undergo a reduction reaction to generate methane and water and release reaction heat, so that the mixed gas is converted into a reaction gas containing carbon dioxide, hydrogen, methane and water;

[0022] S4. The reaction gas discharged from the high-temperature Sabatier reactor continues to enter the second passage of the intercooler, exchanges heat with the mixed gas in the first passage of the intercooler for cooling, and then enters the second passage of the vaporizer for cooling with the liquid carbon dioxide in the first passage of the vaporizer; the cooled reaction gas enters the low-temperature Sabatier reactor, and the remaining carbon dioxide and hydrogen continue to undergo reduction reaction under the action of the Sabatier reaction catalyst in the low-temperature Sabatier reactor to generate methane and water and release reaction heat, and during the reaction process, the Martian atmosphere is introduced into the external heat exchange passage of the low-temperature Sabatier reactor to cool the low-temperature Sabatier reactor, thereby improving the reaction conversion rate in the low-temperature Sabatier reactor;

[0023] S5. The reaction gas at the outlet of the low-temperature Sabatier reactor enters the second passage of the preheater, exchanges heat with the mixed gas in the first passage of the preheater and is cooled, and is finally discharged to an external reaction gas storage device or recovery device.

[0024] As a preferred embodiment of the second aspect, the reaction gas temperature in the high-temperature Sabatier reactor is 400-450°C, and the reaction gas temperature in the low-temperature Sabatier reactor is 250-350°C.

[0025] Compared with the prior art, the present invention has the following outstanding and beneficial technical effects: a high-temperature Sabatier reactor and a low-temperature Sabatier reactor are arranged in different temperature zones, and an intermediate heat exchange device is used to achieve a reasonable decrease in the temperature of the reaction gas, while achieving the goals of high reaction speed and high conversion efficiency; the low-temperature Sabatier reactor is cooled by the Martian atmosphere, making full use of the environmental characteristics of Mars to improve the in-situ preparation efficiency of methane propellant; liquid carbon dioxide is adjusted by vaporization pressure, without the need to configure specific boosting equipment, and vaporization cold energy is used to cool the high-temperature Sabatier reaction gas, thereby improving the conversion rate of subsequent Sabatier reactions; a preheater is arranged to preheat the mixed gas for the first time, fully recovering the heat from the reaction gas in the low-temperature Sabatier reactor, and an intermediate cooler is arranged to recover the heat from the reaction gas in the high-temperature Sabatier reactor and preheat the mixed gas for the second time, thereby greatly reducing the power consumption of the electric heater.

[0026] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of a two-stage carbon dioxide methanogenesis Sabatier reaction system utilizing cold energy of the Martian atmosphere according to the present invention.

[0028] In the figure: carbon dioxide pipeline 1, liquid carbon dioxide storage tank 2, vaporizer 3, first pressure regulating valve 4, hydrogen pipeline 5, high-pressure hydrogen source 6, second pressure regulating valve 7, mixed gas preheating pipeline 8, mixer 9, preheater 10, intercooler 11, electric heater 12, mixed gas reaction pipeline 13, high-temperature Sabatier reactor 14, low-temperature Sabatier reactor 15. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned purpose, features and advantages of the present invention more obvious and easy to understand, the specific implementation mode of the present invention is described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. The technical features in each embodiment of the present invention can be combined accordingly without conflicting with each other.

[0030] In the description of the present invention, it is to be understood that when an element is considered to be "connected" to another element, it may be directly connected to the other element or indirectly connected, that is, there are intermediate elements. On the contrary, when an element is said to be "directly" connected to another element, there are no intermediate elements.

[0031] In the description of the present invention, it should be understood that the terms "first" and "second" are only used for the purpose of distinguishing descriptions, and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features.

[0032] like Figure 1 As shown, in a preferred embodiment of the present invention, a two-stage carbon dioxide methanogenic Sabatier reaction system utilizing the cold energy of the Martian atmosphere is provided, and its components include a carbon dioxide pipeline 1, a liquid carbon dioxide storage tank 2, a vaporizer 3, a first pressure regulating valve 4, a hydrogen pipeline 5, a high-pressure hydrogen source 6, a second pressure regulating valve 7, a mixed gas preheating pipeline 8, a mixer 9, a preheater 10, an intercooler 11, an electric heater 12, a mixed gas reaction pipeline 13, a high-temperature Sabatier reactor 14, and a low-temperature Sabatier reactor 15. In the Sabatier reaction system, the core components are the high-temperature Sabatier reactor 14 and the low-temperature Sabatier reactor 15. The purpose of setting up two Sabatier reactors is to solve the contradiction between the reaction rate and the conversion rate of the Sabatier reaction, because to increase the Sabatier reaction rate, the reactor must be maintained at a higher temperature, while to increase the conversion rate, the reactor needs to be at a lower temperature. Therefore, in the present invention, the Sabatier reaction is divided into two stages as a whole. A gradient temperature field along the flow direction of the reaction gas is constructed by setting a double-stage Sabatier reactor. A high-temperature Sabatier reactor 14 is set in the front stage to increase the reaction speed so that most of the materials react in this stage. A low-temperature Sabatier reactor 15 is set in the rear stage to increase the conversion rate of carbon dioxide to methane and convert all materials as much as possible.

[0033] It should be noted that the high temperature Sabatier reactor 14 and the low temperature Sabatier reactor 15 in the present invention, wherein "high temperature" and "low temperature" are relative concepts, that is, the reaction temperature in the high temperature Sabatier reactor 14 is required to be higher than the reaction temperature in the low temperature Sabatier reactor 15. However, the specific reaction temperature values ​​of the high temperature Sabatier reactor 14 and the low temperature Sabatier reactor 15 can be set according to actual needs. Generally speaking, the high temperature section close to the upper limit can be selected in the reaction temperature range of the Sabatier reaction as the reaction temperature in the high temperature Sabatier reactor 14, and the low temperature section close to the lower limit can be selected in the reaction temperature range of the Sabatier reaction as the reaction temperature in the low temperature Sabatier reactor 15. As a preferred implementation of an embodiment of the present invention, the reaction gas temperature in the high temperature Sabatier reactor 14 can be set to 400-450°C, and the reaction gas temperature in the low temperature Sabatier reactor 15 can be set to 250-350°C.

[0034] In addition, in order to fully save the energy of running the reaction system on Mars, the present invention is provided with components such as a vaporizer 3, a preheater 10, and an intercooler 11 to reasonably utilize the heat energy and cold amount in the entire reaction process. Among them, the vaporizer 3, the preheater 10, and the intercooler 11 are respectively provided with a first passage and a second passage constituting heat exchange contact. As a preferred implementation method of the embodiment of the present invention, the vaporizer 3 can adopt a fin-tube heat exchanger, the preheater 10 can adopt an air-to-air plate heat exchanger, and the intercooler 11 can also adopt an air-to-air plate heat exchanger.

[0035] In the reaction system of the present invention, the raw materials of the Sabatier reaction include carbon dioxide and hydrogen, which are supplied through a liquid carbon dioxide storage tank 2 and a high-pressure hydrogen source 6, respectively. The liquid carbon dioxide storage tank 2 is connected to the first passage of the vaporizer 3, the first pressure regulating valve 4 and the mixer 9 in sequence through the carbon dioxide pipeline 1. The high-pressure hydrogen source 6 is connected to the hydrogen pipeline 5 and the mixer 9 in sequence through the hydrogen pipeline 5. The mixer 9 is connected to the first passage of the preheater 10, the first passage of the intercooler 11 and the electric heater 12 in sequence through the mixed gas preheating pipeline 8, and the electric heater 12 is connected to the high-temperature Sabatier reactor 14, the second passage of the intercooler 11, the second passage of the vaporizer 3, the low-temperature Sabatier reactor 15 and the second passage of the preheater 10 in sequence through the mixed gas reaction pipeline 13, and the outlet of the second passage of the preheater 10 is vented.

[0036] In the present invention, the high-pressure hydrogen source 6 can be realized by using a pressurizing device to pressurize the hydrogen, or can directly use a high-pressure gas cylinder group. In this embodiment, a high-pressure hydrogen gas cylinder group is used.

[0037] In addition, the liquid carbon dioxide in the liquid carbon dioxide storage tank 2 can of course also be pressurized and transported by cryogenic fluid transportation equipment. However, since liquid carbon dioxide itself is easy to vaporize, the inlet end of the carbon dioxide pipeline 1 can be set below the liquid level of the liquid carbon dioxide storage tank 2 in this embodiment, so that the liquid carbon dioxide in the liquid carbon dioxide storage tank 2 forms a high-pressure environment in the top space of the storage tank after vaporization, and then drives the liquid carbon dioxide into the carbon dioxide pipeline 1 in a self-pressurizing manner.

[0038] It should be noted that the purpose of setting the first pressure regulating valve 4 and the second pressure regulating valve 7 is to increase the gas pressure entering the mixer 9 so that it meets the requirements of the final Sabatier reaction for the reaction pressure. The outlet pressure of the first pressure regulating valve 4 and the second pressure regulating valve 7 is adjustable, and the specific outlet pressure value is set according to the actual reaction needs. In actual use, the outlet pressure of the first pressure regulating valve 4 can be set first, and the liquid carbon dioxide in the liquid carbon dioxide storage tank 2 enters the first passage of the vaporizer 3 through the carbon dioxide pipeline 1 under self-pressurization drive, absorbs the heat of the high-temperature reaction gas to complete vaporization, and then enters the mixer 9 through the first pressure regulating valve 4; the outlet pressure of the second pressure regulating valve 7 is set, and the high-pressure hydrogen in the high-pressure hydrogen bottle group enters the mixer 9 through the hydrogen pipeline 5 and the second pressure regulating valve 7. Hydrogen and carbon dioxide gas are mixed in a specific ratio, and the mixed gas pressure is about 3.0MP. It should be noted that the mixing ratio of hydrogen and carbon dioxide gas in the mixer 9 needs to be adjusted according to the material ratio required for the actual Sabatier reaction, preferably to meet the raw material stoichiometric ratio of the Sabatier reaction.

[0039] In addition, since the role of the vaporizer 3, preheater 10, intercooler 11, and electric heater 12 is to rationally utilize the cold and hot energy in various materials and reaction gases during the entire reaction process. The Sabatier reaction needs to be heated at the start so that the catalyst in the reactor reaches the required initial reaction temperature. After the reaction starts, it does not need to be heated again, and the reaction temperature can be maintained by its own heat release. Therefore, the mixed gas in the mixer 9 needs to be heated three times by the preheater 10, the intercooler 11, and the electric heater 12 to reach the set Sabatier reaction start-up temperature, such as 400-450°C. The reaction gas that reaches the Sabatier reaction start-up temperature will release a large amount of reaction heat after the high-temperature Sabatier reaction occurs in the high-temperature Sabatier reactor 14. The reaction heat causes the reaction gas to heat up rapidly to form a high-temperature reaction gas. The high-temperature reaction gas enters the intercooler 11 and the vaporizer 3 in turn for heat exchange cooling, and then enters the low-temperature Sabatier reactor 15 to continue the low-temperature Sabatier reaction.

[0040] However, although the high-temperature reaction gas has been pre-heat exchanged and cooled before entering the low-temperature Sabatier reactor 15, if the temperature of the reaction gas has not yet reached the temperature that can maximize the conversion rate, it is necessary to continue heat exchange cooling. Therefore, the present invention is provided with an external heat exchange passage for introducing the Martian atmosphere in the low-temperature Sabatier reactor 15, and the external heat exchange passage and the reaction chamber of the low-temperature Sabatier reactor 15 constitute heat exchange, and the reaction temperature of the low-temperature Sabatier reactor 15 can be controlled by adjusting the flow rate of the Martian atmosphere in the external heat exchange passage. As a preferred implementation method of the embodiment of the present invention, the external heat exchange passage in the low-temperature Sabatier reactor 15 can be connected to the outlet of the variable frequency low-temperature fan, and the variable frequency low-temperature fan provides the power for conveying the Martian atmosphere. The power of the variable frequency low-temperature fan can be adjusted to change the flow rate of the Martian atmosphere input. The larger the flow rate, the lower the reaction temperature in the low-temperature Sabatier reactor 15, and vice versa. The higher the reaction temperature in the low-temperature Sabatier reactor 15. Therefore, in actual operation, according to the required reaction temperature in the low-temperature Sabatier reactor 15, the power of the variable frequency low-temperature fan can be adjusted to keep it at the reaction temperature.

[0041] In addition, since the Sabatier reaction in the low-temperature Sabatier reactor 15 still releases a large amount of reaction heat, the temperature of the reaction gas at the outlet of the low-temperature Sabatier reactor 15 is still relatively high. This part of the reaction gas can enter the preheater 10 for heat exchange and then be discharged.

[0042] In addition, since the temperature of the Martian atmosphere is relatively low, in order to ensure the normal progress of the Sabatier reaction, the high-temperature Sabatier reactor 14 and the low-temperature Sabatier reactor 15 are both covered with insulating materials. The reactor structure of the high-temperature Sabatier reactor 14 and the low-temperature Sabatier reactor 15 is not limited, and any Sabatier reactor in the prior art can be used to achieve it, and the reaction chamber of the reactor is filled with a Sabatier reaction catalyst. The form of the Sabatier reaction catalyst is not limited, and Ru, Ni, Co, Fe, Mo, etc. have good catalytic activity for the Sabatier reaction, and can be selected according to actual conditions.

[0043] In another embodiment of the present invention, based on the above-mentioned two-stage carbon dioxide methanation Sabatier reaction system using the cold energy of the Martian atmosphere, a two-stage carbon dioxide methanation Sabatier reaction method using the cold energy of the Martian atmosphere is also provided, which comprises the following steps:

[0044] S1. After the liquid carbon dioxide in the liquid carbon dioxide storage tank 2 is pressurized, it enters the first passage of the vaporizer 3 through the carbon dioxide pipeline 1, absorbs the heat of the reaction gas in the second passage of the vaporizer 3 to complete vaporization, and then enters the mixer 9 through the first pressure regulating valve 4; at the same time, the high-pressure hydrogen in the high-pressure hydrogen source 6 enters the mixer 9 through the hydrogen pipeline 5 and the second pressure regulating valve 7; the pressurized hydrogen and the carbon dioxide gas are mixed in the mixer 9 according to the stoichiometric ratio of the Sabatier reaction to form a mixed gas whose pressure meets the reaction requirements.

[0045] In this embodiment, the mixed gas pressure in the mixer 9 is preferably adjusted to about 3.0 MPa, which can be adjusted by setting the outlet pressure of the first pressure regulating valve 4 and the outlet pressure of the second pressure regulating valve 7 .

[0046] S2, the mixed gas in the mixer 9 first enters the first passage of the preheater 10 through the mixed gas preheating pipeline 8, absorbs the heat of the reaction gas in the second passage of the preheater 10 to complete the first temperature increase, then enters the first passage of the intercooler 11, absorbs the heat of the reaction gas in the second passage of the intercooler 11 to complete the second temperature increase, and finally enters the electric heater 12 to complete the third temperature increase and reach the set Sabatier reaction start-up temperature.

[0047] S3, the mixed gas at the outlet of the electric heater 12 first passes through the mixed gas reaction pipeline 13 and enters the high-temperature Sabatier reactor 14. Since the temperature and pressure of the mixed gas have reached the set temperature at this time, part of the carbon dioxide and hydrogen undergo a reduction reaction to generate methane and water under the action of the Sabatier reaction catalyst in the high-temperature Sabatier reactor 14, and a large amount of reaction heat is released. Since the generation of reaction heat causes the reaction gas to heat up rapidly, although the high temperature will accelerate the reaction rate but will also inhibit the conversion rate, only part of the carbon dioxide and hydrogen in the high-temperature Sabatier reactor 14 are reduced to methane and water. Therefore, after passing through the high-temperature Sabatier reactor 14, the mixed gas is converted into a reaction gas containing carbon dioxide, hydrogen, methane and water vapor.

[0048] S4, the reaction gas discharged from the high-temperature Sabatier reactor 14, including carbon dioxide, hydrogen, methane and water vapor, continues to enter the second passage of the intercooler 11, heat-exchanges and cools with the mixed gas in the first passage of the intercooler 11, and then enters the second passage of the vaporizer 3, heat-exchanges and cools with the liquid carbon dioxide in the first passage of the vaporizer 3. The cooled reaction gas enters the low-temperature Sabatier reactor 15, and the remaining carbon dioxide and hydrogen continue to undergo reduction reaction under the action of the Sabatier reaction catalyst in the low-temperature Sabatier reactor 15, generating methane and water and releasing reaction heat. In the process of the Sabatier reaction in the low-temperature Sabatier reactor 15, the Martian atmosphere can be introduced into the external heat exchange passage of the low-temperature Sabatier reactor 15 under the action of equipment such as variable frequency low-temperature fans, thereby cooling the low-temperature Sabatier reactor 15 and improving the reaction conversion rate in the low-temperature Sabatier reactor 15. The reaction temperature in the low-temperature Sabatier reactor 15 can be controlled at 250-350°C by adjusting the power of the variable frequency low-temperature fan. Since the reaction gas has been cooled twice and is in a relatively low temperature range as a whole, and the reaction gas is further cooled by the cooling of the Martian atmosphere, the conversion rate in the low-temperature Sabatier reactor 15 will be greatly improved, allowing most of the carbon dioxide and hydrogen to be converted.

[0049] S5. Since the Sabatier reaction releases a large amount of reaction heat, the temperature of the reaction gas at the outlet of the low-temperature Sabatier reactor 15 is still relatively high. Therefore, the reaction gas at the outlet of the low-temperature Sabatier reactor 15 needs to urgently enter the second passage of the preheater 10, and after heat exchange and cooling with the mixed gas in the first passage of the preheater 10, it is finally discharged to an external reaction gas storage device or recovery device.

[0050] As a preferred implementation method of the embodiment of the present invention, the reaction gas discharged from the second passage of the preheater 10 can enter the reaction gas separation and liquefaction system, which is used to liquefy and separate the carbon dioxide, hydrogen, methane and water vapor in the reaction gas step by step according to their respective phase change points.

[0051] It should be noted that, since the Sabatier reaction needs to be heated at the start-up to make the catalyst in the reactor reach the required Sabatier reaction start-up temperature, no further heating is required after the reaction is started, and the reaction temperature can be maintained by its own heat release. Therefore, during the entire reaction process, the electric heater 12 in step S2 can be turned on only during the reactor start-up phase, and can be kept off after the high-temperature Sabatier reactor 14 is started, and can be restarted if the reaction temperature in the high-temperature Sabatier reactor 14 is insufficient.

[0052] The above-described embodiment is only a preferred solution of the present invention, but it is not intended to limit the present invention. A person skilled in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A two-stage carbon dioxide methanation Sabatier reaction system using cold energy from the Martian atmosphere, characterized in that: It includes a liquid carbon dioxide storage tank (2), a high-pressure hydrogen source (6), a vaporizer (3), a preheater (10), an intermediate cooler (11), a high-temperature Sabatier reactor (14) and a low-temperature Sabatier reactor (15); The vaporizer (3), the preheater (10), and the intercooler (11) are respectively provided with a first passage and a second passage constituting heat exchange contact; The liquid carbon dioxide storage tank (2) is connected to the first passage of the vaporizer (3), the first pressure regulating valve (4) and the mixer (9) in sequence through the carbon dioxide pipeline (1); the high-pressure hydrogen source (6) is connected to the hydrogen pipeline (5) and the mixer (9) in sequence through the hydrogen pipeline (5); the mixer (9) is connected to the first passage of the preheater (10), the first passage of the intermediate cooler (11) and the electric heater (12) in sequence through the mixed gas preheating pipeline (8); the electric heater (12) is connected to the high-temperature Sabatier reactor (14), the second passage of the intermediate cooler (11), the second passage of the vaporizer (3), the low-temperature Sabatier reactor (15) and the second passage of the preheater (10) in sequence through the mixed gas reaction pipeline (13); the outlet of the second passage of the preheater (10) is vented; The low-temperature Sabatier reactor (15) is provided with an external heat exchange passage for introducing the Martian atmosphere, the external heat exchange passage and the reaction chamber of the low-temperature Sabatier reactor (15) form a heat exchange, and the reaction temperature of the low-temperature Sabatier reactor (15) can be controlled by adjusting the flow rate of the Martian atmosphere in the external heat exchange passage.

2. The two-stage carbon dioxide methanation Sabatier reaction system using cold energy of the Martian atmosphere as claimed in claim 1, characterized in that: The vaporizer (3) adopts a fin-tube heat exchanger.

3. The two-stage carbon dioxide methanation Sabatier reaction system using cold energy of the Martian atmosphere as claimed in claim 1, characterized in that: The preheater (10) adopts an air-to-air plate heat exchanger.

4. The two-stage carbon dioxide methanation Sabatier reaction system using cold energy of the Martian atmosphere as claimed in claim 1, characterized in that: The intercooler (11) adopts an air-to-air plate heat exchanger.

5. The two-stage carbon dioxide methanation Sabatier reaction system using cold energy of the Martian atmosphere as claimed in claim 1, characterized in that: The high-temperature Sabatier reactor (14) and the low-temperature Sabatier reactor (15) are both coated with thermal insulation materials.

6. The two-stage carbon dioxide methanation Sabatier reaction system using cold energy of the Martian atmosphere as claimed in claim 1, characterized in that: The high-temperature Sabatier reactor (14) and the low-temperature Sabatier reactor (15) are both filled with a Sabatier reaction catalyst.

7. The two-stage carbon dioxide methanation Sabatier reaction system using cold energy of the Martian atmosphere as claimed in claim 1, characterized in that: The inlet end of the carbon dioxide pipeline (1) is located below the liquid level of the liquid carbon dioxide storage tank (2), and the liquid carbon dioxide in the liquid carbon dioxide storage tank (2) is driven into the carbon dioxide pipeline (1) by self-pressurization.

8. The two-stage carbon dioxide methanation Sabatier reaction system using cold energy of the Martian atmosphere as claimed in claim 1, characterized in that: The high-pressure hydrogen source (6) adopts a high-pressure hydrogen bottle group.

9. A two-stage carbon dioxide methanation Sabatier reaction method using the cold energy of the Martian atmosphere using the system as claimed in any one of claims 1 to 8, characterized in that: include: S1, pressurizing the liquid carbon dioxide in the liquid carbon dioxide storage tank (2), entering the first passage of the vaporizer (3) through the carbon dioxide pipeline (1), absorbing the heat of the reaction gas in the second passage of the vaporizer (3) to complete vaporization, and then entering the mixer (9) through the first pressure regulating valve (4); at the same time, the high-pressure hydrogen in the high-pressure hydrogen source (6) enters the mixer (9) through the hydrogen pipeline (5) and the second pressure regulating valve (7); the pressurized hydrogen and the carbon dioxide gas are mixed in the mixer (9) according to the stoichiometric ratio of the Sabatier reaction to form a mixed gas whose pressure meets the reaction requirements; S2, the mixed gas in the mixer (9) first enters the first passage of the preheater (10) through the mixed gas preheating pipeline (8), absorbs the heat of the reaction gas in the second passage of the preheater (10) to complete the first temperature increase, then enters the first passage of the intermediate cooler (11), absorbs the heat of the reaction gas in the second passage of the intermediate cooler (11) to complete the second temperature increase, and finally enters the electric heater (12) to complete the third temperature increase and reach the set Sabatier reaction start temperature; S3, the mixed gas at the outlet of the electric heater (12) first enters the high-temperature Sabatier reactor (14) through the mixed gas reaction pipeline (13), and under the action of the Sabatier reaction catalyst in the high-temperature Sabatier reactor (14), part of the carbon dioxide and hydrogen undergo a reduction reaction to generate methane and water and release reaction heat, so that the mixed gas is converted into a reaction gas containing carbon dioxide, hydrogen, methane and water; S4, the reaction gas discharged from the high-temperature Sabatier reactor (14) continues to enter the second passage of the intermediate cooler (11), exchanges heat with the mixed gas in the first passage of the intermediate cooler (11) for cooling, and then enters the second passage of the vaporizer (3), exchanges heat with the liquid carbon dioxide in the first passage of the vaporizer (3) for cooling; the cooled reaction gas enters the low-temperature Sabatier reactor (15), and the remaining carbon dioxide and hydrogen continue to undergo a reduction reaction under the action of the Sabatier reaction catalyst in the low-temperature Sabatier reactor (15), generating methane and water and releasing reaction heat, and during the reaction process, the Martian atmosphere is introduced into the external heat exchange passage of the low-temperature Sabatier reactor (15) to cool the low-temperature Sabatier reactor (15), thereby improving the reaction conversion rate in the low-temperature Sabatier reactor (15); S5. The reaction gas at the outlet of the low-temperature Sabatier reactor (15) enters the second passage of the preheater (10), exchanges heat with the mixed gas in the first passage of the preheater (10) and is cooled, and is finally discharged to an external reaction gas storage device or recovery device.

10. The two-stage Sabatier reaction method for methanation of carbon dioxide using cold energy of the Martian atmosphere as claimed in claim 9, characterized in that: The reaction gas temperature in the high-temperature Sabatier reactor (14) is 400-450°C, and the reaction gas temperature in the low-temperature Sabatier reactor (15) is 250-350°C.

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