Method for recovering component gas in exhaust gas and recovery apparatus therefor

Abstract

To provide a method for recovering component gas in exhaust gas which can continuously industrially treat a large amount of exhaust gas, and is excellent in energy efficiency, and its recovery device.SOLUTION: A recovery method of component gas in exhaust gas cools exhaust gas to a melting point or a sublimation point or lower of component gas in the exhaust gas, and recovers the component gas as a solid substance, wherein the component gas is one or more selected from carbon dioxide, dinitrogen monoxide, nitrogen dioxide, sulfur dioxide and sulfur trioxide, a cooling temperature for cooling the exhaust gas is -80°C or lower, and the recovery method uses a stirling cooler to cool the exhaust gas, separates the exhaust gas and the solid substance of the component gas, and accumulates and recovers the solid substance of the component gas. There is also provided a recovery method for the recovery method.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for recovering component gases in exhaust gas and a recovery apparatus therefor.

Background Art

[0002] In recent years, in order to prevent global warming, emission regulations on greenhouse gases including carbon dioxide have become even stricter. Specifically, as greenhouse gases, there are six types: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFC S ), perfluorocarbons (PFC S ), and sulfur hexafluoride (SF6). Considering the global warming potential and the concentration in the atmosphere, among these greenhouse gases, carbon dioxide, methane, and nitrous oxide are considered to particularly contribute significantly to global warming.

[0003] As the main emission sources of carbon dioxide, methane, and nitrous oxide, in addition to the exhaust gas of automobiles, there is exhaust gas discharged from thermal power plants, steel mills, chemical factories, etc. Therefore, in order to reduce the emission amount of carbon dioxide discharged from these industrial exhaust gases, many carbon dioxide recovery technologies have been studied and actually put into practical use.

[0004] As carbon dioxide separation and recovery technologies, chemical absorption method, physical recovery method, membrane separation method, physical adsorption method, cryogenic separation method, etc. are known. Among these, the chemical absorption method has been studied the most, adopted by large domestic companies, and multiple large-scale commercial plants are operating at home and abroad.

[0005] Here, the separation and recovery technology of carbon dioxide by cryogenic separation method, which has been less noticed in the past, was examined. When carbon dioxide is cooled under atmospheric pressure, it does not become a liquid, and when it is cooled to -78.5 °C, it changes from a gas to a solid (dry ice). There is no liquid carbon dioxide under atmospheric pressure. Therefore, by cooling the atmosphere to -78.5 °C or lower, carbon dioxide becomes a solid, and it becomes possible to capture carbon dioxide as a solid. From such a perspective, there are Patent Documents 1 to 3 as carbon dioxide recovery technologies that have already been published.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0007] In Patent Documents 1 and 2, methods of using liquefied natural gas or liquid nitrogen as a cooling source or using a compressor-type refrigerator are disclosed in order to cool the exhaust gas. The method of using liquefied natural gas or liquid nitrogen as a cooling source requires a storage tank and piping for handling an extremely low-temperature cooling source, and requires a huge investment. Also, neither method was necessarily an effective method as a method for continuously and efficiently treating a large amount of exhaust gas. The method described in Patent Document 3 is a method of introducing exhaust gas into a gas turbine and expanding it to a temperature below the liquefaction temperature of carbon dioxide, but it is necessary to rotate the turbine at high speed under high pressure, and it was not necessarily an effective method as a method for continuously and efficiently treating a large amount of exhaust gas.

[0008] As compact refrigerators with a proven track record, the Stirling cycle, Gifford-MacMahon cycle (GM cycle), and pulse tube refrigeration cycle are known. Among these, in principle, the Stirling cycle is the most energy-efficient. A cooling device using the Stirling cycle will be referred to as a Stirling cooler. As a means of cooling exhaust gas, a method using a Stirling cooler can be considered.

[0009] Patent Document 4 discloses a method of cooling biogas to -80°C using a Stirling cooler to solidify and separate carbon dioxide. However, the method described in Patent Document 4 relates to a system for stabilizing the methane concentration in biogas and is not aimed at cooling and recovering carbon dioxide, and there is still room for further improvement as a method for efficiently treating a large amount of exhaust gas continuously.

[0010] The present invention has been made in view of the above circumstances. That is, an object of the present invention is to provide a method for recovering component gases in exhaust gas that can industrially treat a large amount of exhaust gas continuously and is excellent in energy efficiency, and a recovery device therefor.

Means for Solving the Problems

[0011] As a result of intensive studies, the present inventor has adopted a Stirling cooler as a cooling means and developed a method for efficiently recovering solid substances of component gases in the cooled exhaust gas, and has been able to arrive at the present invention. That is, the present invention has the following configuration.

[0012] The first method for recovering component gas in the exhaust gas of the present invention is a method for recovering component gas in the exhaust gas, which cools the exhaust gas to a temperature equal to or lower than the melting point or sublimation point of the component gas in the exhaust gas to form the component gas into a solid and then recovers it. The component gas is any one or more selected from carbon dioxide, nitrous oxide, nitrogen dioxide, sulfur dioxide, and sulfur trioxide. The cooling temperature for cooling the exhaust gas is -80°C or lower. To cool the exhaust gas, a Stirling cooler is used, and the cooled exhaust gas is sprayed onto an endless jig that continuously drives, separating the exhaust gas from the solid of the component gas, and accumulating and recovering the solid of the component gas.

[0013] The second method for recovering component gas in the exhaust gas of the present invention is a method for recovering component gas in the exhaust gas, which cools the exhaust gas to a temperature equal to or lower than the melting point or sublimation point of the component gas in the exhaust gas to form the component gas into a solid and then recovers it. The component gas is any one or more selected from carbon dioxide, nitrous oxide, nitrogen dioxide, sulfur dioxide, and sulfur trioxide. The cooling temperature for cooling the exhaust gas is -80°C or lower. To cool the exhaust gas, a Stirling cooler is used, and the cooled exhaust gas is introduced into a cyclone, separating the exhaust gas from the solid of the component gas, and accumulating and recovering the solid of the component gas.

[0014] In addition, the first recovery device for component gases in the exhaust gas of the present invention is a recovery device for component gases in exhaust gas, which cools the exhaust gas to a temperature equal to or lower than the melting point or sublimation point of the component gases in the exhaust gas to form the component gases into solid substances for recovery. The component gas is any one or more selected from carbon dioxide, nitrous oxide, nitrogen dioxide, sulfur dioxide, and sulfur trioxide. It includes a dehumidifying device for removing water vapor in the exhaust gas, a preliminary cooling device for preliminarily cooling the exhaust gas, an exhaust gas cooling device for cooling the exhaust gas to -80°C or lower, a Stirling cooler for cooling the inside of the exhaust gas cooling device, an endless jig that is continuously driven, which sprays the exhaust gas onto the endless jig to separate the exhaust gas from the solid substance of the component gas and accumulate and recover the solid substance of the component gas, and a storage device for storing the recovered solid substance of the component gas.

[0015] In addition, the second recovery device for component gases in the exhaust gas of the present invention is a recovery device for component gases in exhaust gas, which cools the exhaust gas to a temperature equal to or lower than the melting point or sublimation point of the component gases in the exhaust gas to form the component gases into solid substances for recovery. The component gas is any one or more selected from carbon dioxide, nitrous oxide, nitrogen dioxide, sulfur dioxide, and sulfur trioxide. It includes a dehumidifying device for removing water vapor in the exhaust gas, a preliminary cooling device for preliminarily cooling the exhaust gas, an exhaust gas cooling device for cooling the exhaust gas to -80°C or lower, a Stirling cooler for cooling the inside of the exhaust gas cooling device, a cyclone for separating the exhaust gas from the solid substance of the component gas and accumulating and recovering the solid substance of the component gas, and a storage device for storing the recovered solid substance of the component gas.

Advantages of the Invention

[0016] The method and device for recovering component gases in the exhaust gas of the present invention can continuously treat a large amount of exhaust gas industrially and are excellent in energy efficiency.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described in detail, but the embodiments of the present invention are not limited to the specific embodiments described below.

[0019] (Greenhouse gas) In order to prevent global warming, among greenhouse gases, it is important to suppress the emissions of three gases, carbon dioxide, methane, and nitrous oxide, which have a large contribution to global warming.

[0020] On the other hand, typical components of exhaust gas discharged from thermal power plants, steel mills, chemical factories, etc. include carbon dioxide, carbon monoxide, methane, nitrogen oxides, sulfur oxides, hydrogen, etc. Nitrogen oxides include nitrogen dioxide, nitrous oxide, nitric oxide, etc. Sulfur oxides include sulfur dioxide, sulfur trioxide, sulfur monoxide, etc.

[0021] Looking at the temperatures at which these component gases solidify under atmospheric pressure, the sublimation point of carbon dioxide is -78.5°C, the melting point of nitrous oxide is -90.9°C, the melting point of nitrogen dioxide is -11.2°C, the melting point of sulfur dioxide is -72.4°C, and the melting point of sulfur trioxide is 16.9°C. Therefore, by cooling the exhaust gas to a temperature of -100°C or lower under atmospheric pressure, it becomes possible to simultaneously capture the five component gases of carbon dioxide, nitrous oxide, nitrogen dioxide, sulfur dioxide, and sulfur trioxide as solid substances. That is, it is possible to simultaneously capture carbon dioxide and nitrous oxide, which contribute significantly to global warming. Also, if we focus only on carbon dioxide, it is possible to capture carbon dioxide as a solid substance (dry ice) by cooling the exhaust gas to a temperature of -80°C or lower under atmospheric pressure.

[0022] (Stirling cooler) The inventor focused on a Stirling cooler as a cooling means for cooling the exhaust gas to -80°C or lower or -100°C or lower. A Stirling engine is a type of heat engine, which is a closed external combustion engine that converts thermal energy into mechanical energy. By running the cycle of this Stirling engine in reverse, it functions as a refrigerator (heat pump).

[0023] Among Stirling coolers, an external power source drives a motor to drive the reciprocating piston and displacer in cooperation to expand and compress the helium inside the engine, and based on the principle of a heat siphon, it cools the inside of the cabinet. β type A Stirling cooler is preferable. Furthermore, a free piston type Stirling cooler that uses gas bearings and operates without physical contact (friction) and without wear of moving parts is more preferable because it has a long lifespan and higher energy efficiency. Specifically, compared with conventional compressor type refrigerators, a free piston type Stirling cooler can reduce the energy required for cooling by 70 - 80%.

[0024] The free-piston Stirling cooler is a closed system that can rapidly cool the cooling section (head section) to below -100°C in a short time by simply supplying external power. Also, since it can be made lightweight and compact, multiple units can be installed side by side in various layouts outside the path for cooling exhaust gas, providing a high degree of freedom in equipment design.

[0025] In this embodiment, it is preferable to use a free-piston Stirling cooler. Incidentally, the thermal energy absorbed by the cooling section (head section) is discharged to the outside from the rear of the device.

[0026] (Method for recovering component gases in exhaust gas) Hereinafter, carbon dioxide will be mainly described as the component gas in the exhaust gas to be recovered. Therefore, it is assumed that the exhaust gas is cooled to -80°C or lower. However, when recovering other types of component gases such as nitrous oxide in addition to carbon dioxide, cooling to -80°C or lower is insufficient, and it is necessary to cool to -100°C or lower. Thus, it is necessary to appropriately change the cooling temperature according to the temperature at which the component gas to be recovered solidifies under atmospheric pressure. In the method for recovering component gases described below, even when targeting component gases other than carbon dioxide, the recovery can be performed basically in the same manner as in the case of carbon dioxide, except for the difference in cooling temperature.

[0027] Also, in each step of the method for recovering component gases in the exhaust gas, the operation of cooling the exhaust gas and recovering the component gas as a solid is basically performed near atmospheric pressure. Near atmospheric pressure means about 0.08 MPa to 0.15 MPa. If it is possible to cool the exhaust gas and recover the component gas near atmospheric pressure, a pressure vessel is not required, so the equipment cost can be significantly reduced, and operation work, maintenance work, etc. can be simplified.

[0028] (First embodiment of the first recovery device for component gases in exhaust gas) Figure 1 shows the configuration of a first embodiment of a first recovery device for component gases in exhaust gas. The first embodiment of the first recovery device includes a dehumidifying device 2 for removing water vapor in the exhaust gas, a pre-cooling device 3 for pre-cooling the exhaust gas, a cooling means 4 for cooling the inside of the pre-cooling device, an exhaust gas cooling device 5 for cooling the exhaust gas to -80°C or lower, a Stirling cooler 6 for cooling the inside of the exhaust gas cooling device, a recovery device 7 having an endless jig that is continuously driven, blowing the exhaust gas onto the endless jig to separate the exhaust gas from the solid matter of the component gas, accumulating and recovering the solid matter of the component gas, a cooling means 8 for cooling the endless jig, a storage device 9 for storing the recovered solid matter of the component gas, a liquefaction device 10 for the solid matter of the component gas, and a liquid storage device 11 for storing the liquefied component gas.

[0029] The exhaust gas is introduced from an exhaust gas discharge source 1 into the first recovery device for component gases in the exhaust gas. The exhaust gas may contain a large amount of water vapor. If a large amount of water vapor is contained, when cooling and solidifying carbon dioxide, there is a concern that the inside of the cooling device will be covered with an ice film, resulting in a decrease in cooling efficiency. Therefore, it is preferable to perform a dehumidification process of removing the water vapor in the exhaust gas in advance using the dehumidifying device 2. When the content of water vapor in the exhaust gas is low, the dehumidification process of removing the water vapor in the exhaust gas using the dehumidifying device 2 can be omitted.

[0030] As a method for removing the water vapor in the exhaust gas, a method of permeating through a layer of various known moisture absorbents may be used, or a method of cooling the exhaust gas to about 0°C to freeze and remove the water vapor may also be used. As the cooling means for cooling the exhaust gas to about 0°C, a Stirling cooler may be used, or other known cooling means may be used.

[0031] Next, in the pre-cooling device 3, a process of pre-cooling the exhaust gas is performed. In the dehumidification process, when the exhaust gas is cooled to about 0°C, the process of pre-cooling the exhaust gas using the pre-cooling device 3 can be omitted. Also, the dehumidification process of removing the water vapor in the exhaust gas using the dehumidifying device 2 and the process of pre-cooling the exhaust gas using the pre-cooling device 3 may be combined and performed as one process.

[0032] Inside the preliminary cooling device 3, in order to cool the exhaust gas, a number of barrier plates, louvers, etc. are installed to increase the surface area inside the device, resulting in a structure that makes it easy for the exhaust gas to come into contact. As the cooling means 4 for cooling the inside of the preliminary cooling device 3, a scooping cooler may be used, or other known cooling means may be used. Also, as described in FIG. 1, a part of the exhaust gas cooled to an extremely low temperature after the component gas is recovered as a solid matter is distributed by the distributor 12 and returned to the cooling means 4 for cooling the inside of the preliminary cooling device 3, and heat exchange is performed with the exhaust gas, and a method of preliminarily cooling the exhaust gas may be used.

[0033] Next, this cooling process of cooling the preliminarily cooled exhaust gas to -80°C or lower is performed. In this cooling process, the exhaust gas is cooled to -80°C or lower by the exhaust gas cooling device 5. Inside the exhaust gas cooling device 5, in order to cool the exhaust gas, a number of barrier plates, louvers, etc. are installed to increase the surface area inside the device, resulting in a structure that makes it easy for the exhaust gas to come into contact. As the cooling means for cooling the inside of the exhaust gas cooling device 5, the Stirling cooler 6 is used.

[0034] Since the Stirling cooler 6 is lightweight and compact, a plurality of them can be arranged in an appropriate layout on the outer wall of the exhaust gas cooling device 5 to effectively cool the inside of the exhaust gas cooling device 5. When cooling the exhaust gas cooling device 5 by the Stirling cooler, the exhaust gas cooling device 5 and the cooling part (head part) of the Stirling cooler may be directly connected, or a heat transfer pipe may be used, or a method of circulating a refrigerant may be used.

[0035] When the exhaust gas is cooled to -80°C or lower, carbon dioxide, which is a component gas in the exhaust gas, becomes a solid matter and floats in the exhaust gas. At this time, if there are a large number of solid fine particles such as dust in the exhaust gas, it is preferable because they act as nuclei during the sublimation and condensation of carbon dioxide.

[0036] Subsequent to this cooling step by the exhaust gas cooling device 5, the exhaust gas cooled to an extremely low temperature is introduced into a recovery device 7 that accumulates and recovers the solid matter of the component gas. The recovery device 7 includes an endless jig that is continuously driven, a spraying device that sprays the exhaust gas onto the endless jig, and an accumulation / recovery device that accumulates and recovers the solid matter of the component gas sprayed onto the endless jig. The process performed by the recovery device 7 is referred to as the accumulation / recovery process of the solid matter of the component gas.

[0037] FIG. 5 shows a schematic diagram of a first embodiment of a recovery device that accumulates and recovers the solid matter of the component gas. In FIG. 5, an example of a conveyor-shaped endless jig 23 is shown as the continuously driven endless jig 23. The spraying device that sprays the cooled exhaust gas onto the endless jig 23 has an exhaust gas introduction pipe 21 and a slit-shaped discharge port 22 with a narrow tip. The exhaust gas is slightly compressed when passing through the discharge port 22 with a narrow tip from the introduction pipe 21 at high speed. Then, since it is released into a wide space from the discharge port 22 and expands, there is an effect of further lowering the temperature of the exhaust gas.

[0038] The exhaust gas discharged from the discharge port 22 is sprayed onto the conveyor-shaped endless jig 23. A part of the solid matter 26 of carbon dioxide in the exhaust gas adheres to the endless jig 23 and moves to the back side as the conveyor moves. On the other hand, the remaining part of the solid matter 26 of carbon dioxide in the exhaust gas that did not adhere to the endless jig 23 falls below the conveyor after colliding with the conveyor. A part of the solid matter 26 of carbon dioxide that has moved to the back side as the conveyor moves is peeled off from the conveyor surface by a scraping jig 24 in contact with the conveyor surface and falls below the conveyor. The scraping jig 24 may be in the illustrated blade shape or may be in the shape of a rotating brush.

[0039] In this way, the solid matter 26 of carbon dioxide sprayed onto the conveyor-shaped endless jig 23, whether it adhered to the conveyor or not, all falls below the conveyor. Since there is an accumulation container 25 for the solid matter 26 of carbon dioxide below the conveyor, the solid matter 26 of carbon dioxide is accumulated and recovered by the accumulation container 25.

[0040] FIG. 6 shows a schematic diagram of a second embodiment of a recovery device that accumulates and recovers solid substances of component gas. In FIG. 6, an example of a cylindrical endless jig 23 is shown as the endless jig 23 that is continuously driven. The mechanism for accumulating and recovering the solid carbon dioxide 26 by the cylindrical endless jig 23 in FIG. 6 is the same as the mechanism for accumulating and recovering the solid carbon dioxide 26 by the conveyor-shaped endless jig 23 in FIG. 5, so the description thereof is omitted.

[0041] As the shape of the continuously driven endless jig 23, in addition to the conveyor shape and the cylindrical shape, it is also possible to have a shape such as a frustum of a cone. The endless jig 23 may be cooled by the cooling means 8 or may not be actively cooled, and is appropriately selected according to the recovery situation. As the cooling means 8 for cooling the endless jig 23, it is preferable to use a Stirling cooler.

[0042] The solid carbon dioxide 26 accumulated and recovered by the accumulation container 25 is then stored in a solid substance storage device 9 for storing the recovered solid substances of the component gas and stored in a state cooled to -80°C or lower.

[0043] When the solid substances of the component gas stored in the solid substance storage device 9 are to be transferred to the outside, it may be preferable to convert them into a liquid state for easy handling. In that case, the solid substances of the component gas stored in the solid substance storage device 9 are transferred to a liquefaction device 10 for the solid substances of the component gas. The component gas liquefied by the liquefaction device 10 is transferred to a liquid storage device 11 and carried out to the outside.

[0044] The liquefaction device 10 for the solid matter of the component gas and the liquid storage device 11 are both pressure vessels because they are controlled to a pressure exceeding atmospheric pressure (5 atmospheres or more). As a heating means for the liquefaction device 10 of the solid matter of the component gas, the thermal energy discharged from the back of the Stirling cooler can be utilized. In FIG. 1, a part of the thermal energy is introduced into the liquefaction device 10 as heating gas from the Stirling cooler 6 and utilized for heating the solid matter of the component gas.

[0045] The exhaust gas from which the component gas has been recovered in the recovery device 7 is then distributed by the distributor 12, and a part of it is used as the cooling means 4 for cooling the inside of the pre-cooling device 3, while the remaining part is discharged into the atmosphere from the chimney 13. Also, the exhaust gas used as the cooling means 4 for cooling the inside of the pre-cooling device 3 and the heating gas discharged from the Stirling cooler 6 used in the liquefaction device 10 for the solid matter of the component gas are similarly discharged into the atmosphere from the chimney 13.

[0046] As described above, the recovery of the component gas in the exhaust gas is carried out through the dehumidification process, the process of pre-cooling the exhaust gas, the main cooling process, the process of accumulating and recovering the solid matter of the component gas, and the process of storing the solid matter of the component gas. If necessary, the liquefaction process of the solid matter of the component gas and the storage process of the liquid of the component gas can be carried out. Through these processes, the component gas in the exhaust gas is recovered as solid matter, and the remaining exhaust gas is discharged into the atmosphere through the chimney 13.

[0047] (Second Embodiment of the First Recovery Device for the Component Gas in the Exhaust Gas) Figure 2 shows the configuration of the second embodiment of the first recovery device for component gases in exhaust gas. The second embodiment of the first recovery device includes a dehumidifying device 2 for removing water vapor in the exhaust gas, a pre-cooling device 3 for pre-cooling the exhaust gas, an exhaust gas cooling device 5 for cooling the exhaust gas to -80°C or lower, a Stirling cooler 6 for cooling the inside of the exhaust gas cooling device, an endless jig that is continuously driven, a recovery device 7 that blows the exhaust gas onto the endless jig to separate the exhaust gas from the solid matter of the component gas and accumulates and recovers the solid matter of the component gas, a cooling means 8 for cooling the endless jig, a storage device 9 for storing the recovered solid matter of the component gas, a liquefaction device 10 for the solid matter of the component gas, and a liquid storage device 11 for storing the liquefied component gas.

[0048] In the second embodiment of the first recovery device, a part of the exhaust gas after recovering the component gas as a solid matter is mixed with the exhaust gas to pre-cool the exhaust gas. That is, as shown in Figure 2, a part of the exhaust gas cooled to an extremely low temperature after recovering the component gas as a solid matter is distributed by a distributor 12 and introduced into the pre-cooling device 3 to be mixed with the exhaust gas transferred from the dehumidifying device 2. As a result, the exhaust gas is cooled and pre-cooled within the pre-cooling device 3. The mixing ratio of the exhaust gas transferred from the dehumidifying device 2 and the cooled exhaust gas transferred from the distributor 12 is appropriately set according to the temperature of the exhaust gas transferred from the dehumidifying device 2, the temperature of the exhaust gas transferred from the distributor 12, and the like.

[0049] Regarding other contents in the second embodiment of the first recovery device, they are the same as those in the first embodiment of the first recovery device, so the description thereof is omitted.

[0050] (First Embodiment of the Second Recovery Device for Component Gases in Exhaust Gas) Figure 3 shows the configuration of the first embodiment of the second recovery device for component gases in exhaust gas. The first embodiment of the second recovery device includes a dehumidifying device 2 for removing water vapor in the exhaust gas, a pre-cooling device 3 for pre-cooling the exhaust gas, a cooling means 4 for cooling inside the pre-cooling device, an exhaust gas cooling device 5 for cooling the exhaust gas to -80°C or lower, a Stirling cooler 6 for cooling inside the exhaust gas cooling device, a cyclone 14 for separating the exhaust gas from the solid matter of the component gas and accumulating and recovering the solid matter of the component gas, a storage device 9 for storing the recovered solid matter of the component gas, a liquefaction device 10 for liquefying the solid matter of the component gas, and a liquid storage device 11 for storing the liquefied component gas.

[0051] In the second recovery device for component gases in the exhaust gas, instead of the recovery device 7 which has an endless jig driven continuously in the first recovery device, blows the exhaust gas against the endless jig, separates the exhaust gas from the solid matter of the component gas, and accumulates and recovers the solid matter of the component gas, it has a cyclone 14 as a device for separating the exhaust gas from the solid matter of the component gas and accumulating and recovering the solid matter of the component gas.

[0052] Subsequent to this cooling step by the exhaust gas cooling device 5, the exhaust gas cooled to an extremely low temperature is introduced into a cyclone 14 that accumulates and recovers the solid matter of the component gas. The cyclone 14 is a device that separates the solid matter of the component gas from the flow of the exhaust gas by means of a vortex. Inside the cyclone 14, the solid matter of the component gas rotates as a vortex and collides with the inner wall etc. due to centrifugal force, and then falls downward in the cyclone 14. On the other hand, the gaseous exhaust gas is discharged from above the cyclone 14.

[0053] The solid matter of the component gas is accumulated and recovered by the cyclone 14 and discharged from below. The solid matter of the component gas accumulated and recovered by the cyclone 14 is then stored in a storage device 9 for the solid matter of the recovered component gas and stored in a cooled state at -80°C or lower.

[0054] Regarding other details in the first embodiment of the second recovery device, since they are the same as those in the first embodiment of the first recovery device, the description thereof will be omitted.

[0055] (Second Embodiment of the Second Recovery Device for Component Gases in Exhaust Gas) Fig. 4 shows the configuration of the second embodiment of the second recovery device for component gases in exhaust gas. The second embodiment of the second recovery device includes a dehumidifying device 2 for removing water vapor in the exhaust gas, a pre-cooling device 3 for pre-cooling the exhaust gas, an exhaust gas cooling device 5 for cooling the exhaust gas to -80°C or lower, a Stirling cooler 6 for cooling inside the exhaust gas cooling device, a cyclone 14 for separating the exhaust gas and the solid matter of the component gas and collecting the solid matter of the component gas, a storage device 9 for storing the recovered solid matter of the component gas, a liquefying device 10 for liquefying the solid matter of the component gas, and a liquid storage device 11 for storing the liquefied component gas.

[0056] The description of the cyclone 14 for collecting and recovering the solid matter of the component gas is the same as that in the first embodiment of the second recovery device for component gases in exhaust gas. Regarding other details in the second embodiment of the second recovery device, since they are the same as those in the second embodiment of the first recovery device, the description thereof will be omitted.

[0057] The boiling point of methane under atmospheric pressure is -161.6°C, and the melting point is -182.5°C. It is possible to cool and recover methane in the exhaust gas using a Stirling cooler. However, cooling and recovering it together with other component gases is considered to result in a large amount of energy loss. Therefore, it is preferable to first recover the component gas whose solidification temperature under atmospheric pressure is higher than -100°C, and then cool it to a lower temperature and recover methane by the same method as above. Also, instead of recovering methane in the exhaust gas, a method of decomposing and removing methane may be employed. As methods of decomposing and removing methane, there are a method of thermally decomposing by bringing methane into contact with an oxidation catalyst, a method of decomposing by plasma, and the like. That is, after cooling and recovering any one or more selected from carbon dioxide, nitrous oxide, nitrogen dioxide, sulfur dioxide, and sulfur trioxide in the exhaust gas into a solid substance, the methane in the exhaust gas can be cooled and recovered into a solid substance, or the methane in the exhaust gas can be decomposed and removed.

[0058] As can be seen from the content of the recovery device for component gases in the exhaust gas of the present embodiment described above, the method for recovering component gases in the exhaust gas of the present embodiment has the following characteristics. (1) Since the component gases in the exhaust gas are separated and recovered in a condensed solid or liquid state, the volume can be made very small, and subsequent storage and handling are easy. (2) Since the component gases in the exhaust gas can be separated and recovered in a relatively high-purity state without the intervention of other substances, it is easy to utilize the component gases thereafter. (3) Since the component gases in the exhaust gas can be recovered near atmospheric pressure, there is no need for pressure vessels or equipment for compressing to high pressure, etc., and the equipment cost can be reduced. (4) Since the component gases in the exhaust gas can be separated and recovered without using other chemicals, the recovery cost can be reduced compared to other recovery methods that use other chemicals, and equipment for recycling other chemicals is also unnecessary. (5) By using a Stirling cooler, the component gases in the exhaust gas can be recovered with better energy efficiency compared to the case of using a conventional cooling device such as a compressor. (6) Since relatively compact equipment can be used, it can be installed for various exhaust gas discharge facilities regardless of the scale.

[0059] Also, the method for recovering component gases in the exhaust gas of the present embodiment has the following characteristics. (1) As described above, the recovery device for component gases in the exhaust gas of this embodiment can improve energy efficiency by using a part of the exhaust gas after recovering the component gases as solids for pre-cooling the exhaust gas or by using the waste heat of the Stirling cooler for melting the solids of the component gases. (2) Since the recovery device for component gases in the exhaust gas of this embodiment can also recover nitrogen oxides and sulfur oxides, there is a possibility that it is not necessary to install desulfurization devices and denitration devices required for removing nitrogen oxides and sulfur oxides from the exhaust gas.

Explanation of Signs

[0060] 1 Exhaust gas emission source 2 Dehumidifying device 3 Pre-cooling device 4 Cooling means 5 Exhaust gas cooling device 6 Stirling cooler 7 Recovery device 8 Cooling means 9 Storage device for solids of component gases 10 Liquefaction device for solids of component gases 11 Liquid storage device 12 Distributor 13 Chimney 14 Cyclone 21 Introduction pipe for exhaust gas 22 Exhaust port 23 24 Scraping jig 25 Aggregation container 26 Solid matter of carbon dioxide

Claims

1. A method for recovering a component gas in exhaust gas, which cools the exhaust gas to a temperature equal to or lower than the melting point or sublimation point of the component gas in the exhaust gas to convert the component gas into a solid and then recovers the solid, wherein the component gas is any one or more selected from carbon dioxide, nitrous oxide, nitrogen dioxide, sulfur dioxide, and sulfur trioxide, the cooling temperature for cooling the exhaust gas is -80°C or lower, a Stirling cooler is used to cool the exhaust gas, the cooled exhaust gas is sprayed onto an endless jig that is continuously driven to separate the exhaust gas from the solid of the component gas, and the solid of the component gas is accumulated and recovered. A method for recovering a component gas in exhaust gas, characterized by the above.

2. The method for recovering a component gas in exhaust gas according to Claim 1, wherein the endless jig has a conveyor shape, a cylindrical shape, or a frustum shape.

3. The method for recovering a component gas in exhaust gas according to Claim 1 or Claim 2, wherein when the exhaust gas is sprayed onto the endless jig, the exhaust gas is ejected from an outlet with a narrow tip.

4. A method for recovering a component gas in exhaust gas, which cools the exhaust gas to a temperature equal to or lower than the melting point or sublimation point of the component gas in the exhaust gas to convert the component gas into a solid and then recovers the solid, wherein the component gas is carbon dioxide and nitrous oxide, the cooling temperature for cooling the exhaust gas is -100°C or lower, a free-piston Stirling cooler is used to cool the exhaust gas, the cooled exhaust gas is introduced into a cyclone to separate the exhaust gas from the solid of the component gas, and the solid of the component gas is accumulated and recovered. A method for recovering a component gas in exhaust gas, characterized by the above.

5. The method for recovering a component gas in exhaust gas according to Claim 4, wherein the operation of cooling the exhaust gas to convert the component gas into a solid and then recovering the solid is performed near atmospheric pressure.

6. The method for recovering a component gas in exhaust gas according to Claim 4 or Claim 5, wherein water vapor in the exhaust gas is removed before the exhaust gas is cooled to convert the component gas into a solid and then recovered.

7. The method for recovering a component gas in exhaust gas according to any one of Claims 4 to 6, wherein heat exchange is performed between a part of the exhaust gas after the component gas is recovered as a solid and the exhaust gas before cooling to pre-cool the exhaust gas before cooling.

8. A method for recovering a component gas in exhaust gas according to any one of claims 4 to 6, characterized in that a part of the exhaust gas after collecting the component gas in a solid state is mixed with the exhaust gas before cooling to pre-cool the exhaust gas before cooling.

9. A method for recovering a component gas in exhaust gas according to any one of claims 4 to 8, characterized in that the exhaust gas is cooled, the component gas is collected in a solid state, and then methane in the exhaust gas is recovered or removed.

10. An apparatus for recovering a component gas in exhaust gas, which cools the exhaust gas to a temperature equal to or lower than the melting point or sublimation point of the component gas in the exhaust gas to collect the component gas in a solid state, comprising: wherein the component gas is any one or more selected from carbon dioxide, nitrous oxide, nitrogen dioxide, sulfur dioxide, and sulfur trioxide; a dehumidifying device for removing water vapor in the exhaust gas; a pre-cooling device for pre-cooling the exhaust gas; an exhaust gas cooling device for cooling the exhaust gas to -80°C or lower; a Stirling cooler for cooling the inside of the exhaust gas cooling device; a recovery device having an endless jig that is continuously driven, blowing the exhaust gas against the endless jig to separate the exhaust gas from the solid matter of the component gas, and accumulating and collecting the solid matter of the component gas; a storage device for storing the recovered solid matter of the component gas and characterized by having the above.

11. An apparatus for recovering a component gas in exhaust gas, which cools the exhaust gas to a temperature equal to or lower than the melting point or sublimation point of the component gas in the exhaust gas to collect the component gas in a solid state, comprising: wherein the component gas is carbon dioxide and nitrous oxide; a dehumidifying device for removing water vapor in the exhaust gas; a pre-cooling device for pre-cooling the exhaust gas; an exhaust gas cooling device for cooling the exhaust gas to -100°C or lower; a free piston type Stirling cooler for cooling the inside of the exhaust gas cooling device; a cyclone for separating the exhaust gas from the solid matter of the component gas and accumulating and collecting the solid matter of the component gas; a storage device for storing the recovered solid matter of the component gas and characterized by having the above.

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