Carbon dioxide separation device, carbon dioxide separation method, fuel synthesis device, and fuel synthesis method

Abstract

Provided are a carbon dioxide separation device, etc., capable of effectively separating carbon dioxide from air, such as the atmosphere.　A carbon dioxide separation device 10 is a device that separates carbon dioxide from air containing nitrogen, oxygen, and carbon dioxide. Specifically, the carbon dioxide separation device 10 mainly includes a temperature adjusting unit 11, a pressurizing unit 12, and a separating unit 13. The temperature adjusting unit 11 is configured to adjust the temperature of air. The pressurizing unit 12 is configured to pressurize the air. The separating unit 13 is configured to separate carbon dioxide from the air. The temperature adjusting unit 11 and the pressurizing unit 12 bring the temperature of the air into a temperature band in which oxygen and nitrogen are in a gaseous state and carbon dioxide is in a liquid state. The separating unit 13 separates the carbon dioxide in a liquid state from the air. The separating unit 13 separates the carbon dioxide from the air by gravitational settling or centrifugal separation.

Description

Carbon dioxide separation device, carbon dioxide separation method, fuel synthesis device and fuel synthesis method

[0001] The present invention relates to a carbon dioxide separator that separates carbon dioxide from the atmosphere.

[0002] The concentration of carbon dioxide in the atmosphere is on the rise. Specifically, according to a report by the Japan Meteorological Agency, the global average concentration of carbon dioxide in the atmosphere rose from 340 ppm in 1985 to 410 ppm in 2020.

[0003] Factors contributing to the long-term increase in atmospheric carbon dioxide concentration include human activities such as the consumption of fossil fuels, cement production, and changes in land use such as deforestation. Some of the emitted carbon dioxide is absorbed by plants and the oceans, but the rest accumulates in the atmosphere. Therefore, if human activities continue at their current rate, the concentration of carbon dioxide in the atmosphere is expected to rise further.

[0004] Meanwhile, the Earth is currently warmer than it has been in the past 1,400 years. Global warming not only causes an increase in average temperatures, but also brings about various climate changes, such as abnormally high temperatures (heat waves) and an increase in heavy rainfall and droughts. The effects are already being seen in natural ecosystems and human society, such as changes in biological activity due to the earlier arrival of spring, and impacts on water resources and agricultural crops. Global temperatures are expected to rise further in the future, which is likely to have more serious impacts on water, ecosystems, food, coastal areas, and more.

[0005] Although the causal relationship between the rise in atmospheric carbon dioxide concentration and global warming has not yet been clearly clarified, there is a clear correlation between the two. Therefore, it is expected that global warming can be curbed by suppressing the rise in atmospheric carbon dioxide concentration.

[0006] The following patent documents describe inventions for separating carbon dioxide from gas.

[0007] Japanese Patent No. 6086998 Japanese Patent Application Laid-Open No. 2010-266154 Japanese Patent Application Laid-Open No. 2009-262016 Japanese Patent No. 3778674

[0008] However, various problems are expected to arise when attempting to reduce the concentration of carbon dioxide in the atmosphere on a global scale.

[0009] It is generally believed that the atmosphere is composed mostly of nitrogen (78.08%), oxygen (20.95%), argon (0.93%), and carbon dioxide (0.03%). However, a method for effectively separating carbon dioxide from air with this composition has not yet been established.

[0010] The present invention has been made in view of the above problems, and an object of the present invention is to provide a carbon dioxide separation device and the like that can effectively separate carbon dioxide from air such as the atmosphere.

[0011] The present invention is a carbon dioxide separation device that separates carbon dioxide from atmospheric air containing nitrogen, oxygen, and carbon dioxide, and is equipped with a temperature adjustment unit that adjusts the temperature of the air, a pressurization unit that pressurizes the air, and a separation unit that separates the carbon dioxide from the air, wherein the temperature adjustment unit and the pressurization unit set the temperature and pressure of the air to a zone where the oxygen and nitrogen are in a gaseous or supercritical state and the carbon dioxide is in a liquid state, and the separation unit separates the carbon dioxide in a liquid state from the air.

[0012] The carbon dioxide separation method of the present invention is a method for separating carbon dioxide from air, which is the atmosphere containing nitrogen, oxygen, and carbon dioxide, and is characterized in that the temperature and pressure of the air are set to a range in which the oxygen and nitrogen are in a gaseous or supercritical state and the carbon dioxide is in a liquid state, and the carbon dioxide in a liquid state is separated from the air.

[0013] According to the carbon dioxide separator of the present invention, it is possible to provide a carbon dioxide separator that can effectively separate carbon dioxide from air such as the atmosphere.

[0014] FIG. 1 is a block diagram showing a carbon dioxide separation apparatus and a fuel synthesis apparatus according to an embodiment of the present invention. FIG. 2 is a temperature-pressure diagram of nitrogen. FIG. 3 is a temperature-pressure diagram of oxygen. FIG. 4 is a temperature-pressure diagram of carbon dioxide. FIG. 5 is a temperature-pressure diagram of nitrogen, oxygen, and carbon dioxide. FIG. 6 is a flow chart showing a carbon dioxide separation method and a fuel synthesis method according to an embodiment of the present invention.

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, the same components are generally designated by the same reference numerals, and repeated description will be omitted.

[0016] FIG. 1 is a block diagram showing a carbon dioxide separator 10 and a fuel synthesizer 16 according to this embodiment.

[0017] The carbon dioxide separation device 10 is a device that separates carbon dioxide from air containing nitrogen, oxygen, and carbon dioxide. Specifically, the carbon dioxide separation device 10 mainly comprises a temperature adjustment unit 11, a pressurization unit 12, a separation unit 13, and an arithmetic control unit 17. The carbon dioxide separation device 10 also has an air storage unit 14. The carbon dioxide separation device 10 may further comprise a carbon dioxide storage unit (not shown) for storing the liquid carbon dioxide separated by the separation unit 13.

[0018] The air storage unit 14 is a tank for storing air, such as atmospheric air. The air storage unit 14 has a configuration that allows the air stored therein to be sealed. Furthermore, the air storage unit 14 may have a heat-insulating structure to effectively liquefy the air inside the air storage unit 14. The air storage unit 14 may also be provided with a temperature sensor stored inside the air storage unit 14. Furthermore, the air storage unit 14 may also be provided with a pressure sensor that detects the pressure of the air stored inside the air storage unit 14. The temperature sensor and the pressure sensor transmit electrical signals indicating the measured values ​​to the calculation control unit 17.

[0019] The temperature adjustment unit 11 is configured to adjust the temperature of the air. Specifically, the temperature adjustment unit 11 is configured to cool or heat the air stored inside the air storage unit 14. When the temperature adjustment unit 11 functions as a heating device, the temperature adjustment unit 11 is composed of an electric heating wire, a heat pump, or the like, configured to heat the air storage unit 14 from the surroundings. On the other hand, when the temperature adjustment unit 11 functions as a cooling device, the temperature adjustment unit 11 is composed of a refrigeration cycle, for example, a vapor compression refrigeration cycle or an air compression refrigeration cycle, configured to cool the air storage unit 14 from the surroundings.

[0020] The pressurizing unit 12 is configured to pressurize the air. Specifically, the pressurizing unit 12 is, for example, a compressor that compresses the air stored inside the air storage unit 14.

[0021] The separation unit 13 is configured to separate carbon dioxide from air. Specifically, the separation unit 13 separates carbon dioxide in a liquid state from air. The separation unit 13 separates carbon dioxide from air by gravitational settling or centrifugation.

[0022] When liquid carbon dioxide is separated from air by gravitational settling, the separation unit 13 is, for example, an outlet formed at the bottom end of the air storage unit 14. Liquid carbon dioxide has a higher specific gravity than gaseous oxygen and nitrogen. Therefore, the liquid carbon dioxide is discharged to the outside from the separation unit 13, which is an outlet formed at the bottom end of the air storage unit 14. This allows the liquid carbon dioxide to be separated from the air.

[0023] When separating liquid carbon dioxide from air by centrifugation, air containing liquid carbon dioxide is rotated by a centrifugal separator, the separation unit 13. As a result, the liquid carbon dioxide, which has a high specific gravity, collects on the radially outer side and can then be separated from the air.

[0024] The temperature adjusting unit 11 and the pressurizing unit 12 adjust the temperature of the air to a temperature range where oxygen and nitrogen are in a gaseous or supercritical state and carbon dioxide is in a liquid state. This will be described later with reference to FIG. 4 etc.

[0025] The arithmetic control unit 17 is composed of a semiconductor element such as a CPU (Central Processing Unit). The arithmetic control unit 17 may include a semiconductor storage device such as a RAM (Random Access Memory) or a ROM (Read Only Memory) as a storage unit. Such a storage unit stores programs, parameters, etc. The arithmetic control unit 17 executes the functions and methods described below based on the programs, parameters, etc. read from the storage unit.

[0026] The fuel synthesizer 16 has a fuel synthesis unit 15 in addition to the carbon dioxide separation device 10. Specifically, the fuel synthesizer 16 produces synthetic fuel from the liquid carbon dioxide obtained by the separation unit 13 of the carbon dioxide separation device 10. Such a synthesis method will be described later with reference to Fig. 4 etc.

[0027] Here, the physical properties of each component of air will be described with reference to Figures 2A, 2B, and 2C. In Figures 2A, 2B, and 2C, the horizontal axis represents temperature, and the vertical axis represents pressure.

[0028] 2A is a temperature-pressure diagram of nitrogen. Referring to FIG. 2A, nitrogen can be in a solid, liquid, gas, or supercritical state depending on the temperature and pressure. In this embodiment, as will be described later, the temperature and pressure of air are controlled so that nitrogen is in a gas or supercritical state.

[0029] 2B is a temperature-pressure diagram of oxygen. Like the nitrogen described above, oxygen also changes its phase state depending on the temperature and pressure. In this embodiment, as will be described later, the temperature and pressure of the air are controlled so that the oxygen is in a gaseous or supercritical state.

[0030] 2C is a temperature-pressure diagram of carbon dioxide. Similar to the nitrogen and oxygen described above, carbon dioxide also changes its phase state depending on the temperature and pressure. In this embodiment, as will be described later, the temperature and pressure of the air are controlled so that carbon dioxide becomes liquid.

[0031] 3 and 4 are temperature-pressure diagrams of nitrogen, oxygen, and carbon dioxide. In FIGS. 3 and 4, the phase changes of nitrogen are indicated by solid lines, the phase changes of oxygen by dotted lines, and the phase changes of carbon dioxide by dashed lines. Furthermore, in FIGS. 3 and 4, the temperature and pressure ranges that make it possible to separate carbon dioxide from air are indicated by hatching. In FIG. 3, the hatching indicates the region where carbon dioxide is in a liquid phase and nitrogen and oxygen are in a gas phase or supercritical state. In FIG. 4, the hatching indicates the region where carbon dioxide is in a liquid phase and nitrogen and oxygen are in a gas phase.

[0032] The temperature and pressure at which phase changes occur differ for nitrogen, oxygen, and carbon dioxide, and in this embodiment, as will be described later, this difference is used to separate carbon dioxide from air.

[0033] 5 is a flowchart showing a carbon dioxide separation method and a fuel synthesis method according to an embodiment of the present invention. The carbon dioxide separation method and the fuel synthesis method according to this embodiment will be described with reference to FIG. 5 and the above-mentioned figures.

[0034] The carbon dioxide separation method according to this embodiment is a method for separating carbon dioxide from air containing nitrogen, oxygen, and carbon dioxide. In the carbon dioxide separation method according to this embodiment, the temperature and pressure of the air are set to a range in which oxygen and nitrogen are in a gas phase or a supercritical state and carbon dioxide is in a liquid state, and the liquid carbon dioxide is separated from the air. In addition to the carbon dioxide separation method, the fuel synthesis method according to this embodiment includes a step of synthesizing fuel from the carbon dioxide separated from the air.

[0035] In the following description, steps S10 to S12 constitute a carbon dioxide separation method, and these steps plus step S13 constitute a fuel synthesis method.

[0036] In step S10, the calculation control unit 17 adjusts the temperature of the air. Specifically, first, atmospheric air is introduced into the air storage unit 14 shown in Fig. 1 and the air storage unit 14 is sealed. Next, the calculation control unit 17 controls the temperature adjustment unit 11 to adjust the temperature of the air stored in the air storage unit 14 to a predetermined temperature range.

[0037] Furthermore, in step S11, the calculation control unit 17 adjusts the pressure of the air. Specifically, the pressure of the air stored in the air storage unit 14 is adjusted to a predetermined pressure-temperature range by the pressurizing unit 12, which is, for example, a compressor.

[0038] Here, steps S10 and S11 may be executed simultaneously, step S11 may be executed after step S10, or step S11 may be executed after step S10.

[0039] The temperature and pressure of the air in steps S10 and S11 vary depending on the state of nitrogen and oxygen.

[0040] 3, hatched regions in the temperature-pressure diagram indicate that carbon dioxide is in the liquid phase, nitrogen is in the gas phase or supercritical state, and oxygen is in the gas phase or supercritical state. The temperature range in this region is equal to or higher than the solubility line of carbon dioxide and equal to or lower than 31.1°C, which is the critical point of carbon dioxide. The pressure range in this region is higher than the boiling line of carbon dioxide.

[0041] For example, when the pressure of the air stored in the air storage section 14 is 2 MPa and the temperature is −40° C. (P1), carbon dioxide is in a liquid phase, and nitrogen and oxygen are in a gas phase. In this case, the density of nitrogen is 29.6 kg / m ３ and oxygen is 34.2 kg / m ３ and carbon dioxide is 1119 kg / m ３ In this case, the density of the liquid carbon dioxide is much greater than that of the gaseous nitrogen and oxygen, so in a later step this density difference can be used to separate the carbon dioxide from the air.

[0042] When the pressure of the air stored in the air storage section 14 is 10 MPa and the temperature is 20°C (P2), carbon dioxide is in a liquid phase, and nitrogen and oxygen are in a supercritical state. In this case, the density of nitrogen is 115.0 kg / m ３ and oxygen is 138.7 kg / m ３ and carbon dioxide is 856.3 kg / m ３In this case, the density of carbon dioxide in the liquid phase is greater than that of nitrogen and oxygen in the supercritical state, so this density difference can be used to separate the carbon dioxide in a later step.

[0043] In Figure 4, the temperature-pressure diagram shows hatched regions where carbon dioxide is in the liquid phase and nitrogen and oxygen are in the gas phase. The temperature range of this region is above the dissolution line of carbon dioxide and below -1°C. Here, -1°C, which is the upper limit of the temperature range, is the temperature of point P3 where the line indicating the critical pressure of nitrogen and the boiling line of carbon dioxide intersect. Furthermore, the pressure range of this region is above the boiling line of carbon dioxide and below 3.4 MPa. Here, 3.4 MPa, which is the upper limit of the pressure range, is the critical pressure of nitrogen.

[0044] As mentioned above, in such a region (for example, P1 mentioned above), the density of carbon dioxide in liquid phase is much greater than that of nitrogen and oxygen in gas phase, and therefore, in a later step, this density difference can be used to separate carbon dioxide.

[0045] In step S12, the calculation and control unit 17 separates the liquid carbon dioxide from the air. Specifically, the temperature and pressure of the air stored in the air storage unit 14 through steps S10 and S11 are in the hatched region in FIG. 3.

[0046] In the hatched areas of Figure 3, nitrogen and oxygen are in the gas phase or supercritical state, and carbon dioxide is in the liquid phase. As mentioned above, when the pressure of the air stored in the air storage section 14 is 2 MPa and the temperature is -40°C, the density of nitrogen is 29.6 kg / m ３ and oxygen is 34.2 kg / m ３ and carbon dioxide is 1119 kg / m ３ Therefore, the density of carbon dioxide is much greater than that of nitrogen and oxygen.

[0047] Therefore, in this step, carbon dioxide can be easily separated from nitrogen and oxygen by utilizing this density difference. Gravitational settling or centrifugation can be used as the separation method. When gravitational settling is used, a discharge section is provided at the bottom of the air storage section 14, liquid phase carbon dioxide is extracted from the discharge section, and the extracted carbon dioxide is stored in a separate container. When centrifugation is used, the air is rotated by a centrifuge, and carbon dioxide that has moved radially outward is extracted from the air storage section 14, and the extracted carbon dioxide is stored in a separate container.

[0048] In step S13, the calculation and control unit 17 synthesizes fuel from the separated carbon dioxide. Specifically, synthetic fuel is produced from the carbon dioxide separated from the air in step S12. In this step, first, activated water is produced from carbon dioxide and water using a specific photocatalyst. Next, carbon dioxide and seed oil are reacted with the activated water to continuously produce synthetic fuel having the same composition as the seed oil. Here, for example, light oil, heavy oil, kerosene, gasoline, kerosene, etc. can be used as the seed oil.

[0049] Specifically, activated water is produced from carbon dioxide and water using a photocatalyst, as shown in the reaction shown in the following formula: CO2 + H2O ⇒ CO + H2 + O2 Next, carbon dioxide and seed oil are reacted with the activated water to produce hydrocarbons (fuel), as shown in the reaction shown in the following formula: This reaction is generally called the Fischer-Tropsch reaction: nCO + (2n + 1)H2 ⇒ CnH2n + 2 + nH2O Summarizing the above, the reaction shown in the following formula occurs: nCO2 + (n + 1)H2 ⇒ CnH2n + 2 + nO2 By carrying out the above reaction, fuel is produced from H2 obtained by the photocatalytic reaction of carbon dioxide fixed from the atmosphere and water. This fuel is also called e-fuel because it is a synthetic fuel produced from CO2 and H2 obtained without using fossil fuels.

[0050] The separation of carbon dioxide and fuel synthesis according to this embodiment requires energy. It is desirable to use natural energy (clean energy) obtained from wind power generation, solar power generation, etc. as this energy. In this way, carbon dioxide separation and fuel synthesis can be performed while reducing the burden on the global environment.

[0051] Although the embodiments of the present invention have been described above, the present invention is not limited to these and can be modified within the scope of the present invention. In addition, the above-described embodiments can be combined with each other.

[0052] REFERENCE SIGNS LIST 10 Carbon dioxide separation device 11 Temperature control section 12 Pressurization section 13 Separation section 14 Air storage section 15 Fuel synthesis section 16 Fuel synthesis device 17 Calculation control section

Claims

1. A carbon dioxide separation device that separates carbon dioxide from atmospheric air containing nitrogen, oxygen, and carbon dioxide, comprising: a temperature control unit that controls the temperature of the air; a pressurizing unit that pressurizes the air; and a separation unit that separates the carbon dioxide from the air, wherein the temperature control unit and the pressurizing unit set the temperature and pressure of the air to a range in which the oxygen and nitrogen are in a gaseous or supercritical state and the carbon dioxide is in a liquid state, and the separation unit separates the carbon dioxide in a liquid state from the air.

2. The carbon dioxide separation device described in claim 1, characterized in that the temperature control unit and the pressurization unit set the temperature and pressure of the air to a range in which the oxygen and nitrogen are in a gaseous state and the carbon dioxide is in a liquid state.

3. The carbon dioxide separator according to claim 1, wherein the separation section separates the carbon dioxide from the air by gravitational settling or centrifugation.

4. A method for separating carbon dioxide from atmospheric air containing nitrogen, oxygen, and carbon dioxide, comprising: setting the temperature and pressure of the air to a range in which the oxygen and nitrogen are in a gaseous or supercritical state and the carbon dioxide is in a liquid state; and separating the carbon dioxide in a liquid state from the air.

5. A fuel synthesis device comprising the carbon dioxide separation device according to claim 1 and a fuel synthesis section, wherein the fuel synthesis section synthesizes fuel from the carbon dioxide separated from the air by the carbon dioxide separation device.

6. A fuel synthesis method comprising the carbon dioxide separation method according to claim 4, and synthesizing fuel from the carbon dioxide separated from the air.

Images