CO2 Separation Method

Abstract

Provided is a CO2 separation method capable of efficiently dissolving CO2 contained in compressed air into a drain and effectively recovering CO2 from the drain. [Solution] The temperature of the compressed air is gradually lowered to a preset temperature by passing it through various devices during the compressed air generation process, and as the temperature drops, CO2 is dissolved into the drain generated in each device. The CO2-containing drain from each device flows into a CO2 capture device via an exhaust pipe, drain trap and drain manifold, and CO2 is separated and captured from the CO2-containing drain in the CO2 capture device.

Description

[Technical field]

[0001] This invention relates to a method for separating CO2 in a compressed air circuit, and more particularly to a method for dissolving CO2 in drain generated in each downstream device in the compressed air circuit, and separating CO2 from the drain when the drain is discharged. [Background technology]

[0002] In a compressed air circuit, the compressed air compressed by the compressor contains a large amount of water vapor. This water vapor becomes drain when it is cooled in each device such as an air tank, cyclone separator, and air dryer (hereinafter simply referred to as "each device") arranged in the compressed air circuit or collides with the inner walls, and is discharged together with the compressed exhaust air through a drain trap from an exhaust port provided in each device.

[0003] Due to Henry's law and the temperature drop caused by the structure of each device, more CO2 than usual will dissolve into the drain generated in the high-pressure environment inside each device. However, in previous compressed air circuits, there was no specification for the order or number of devices installed, so the amount of CO2 dissolved in the drain was not stable. Depending on the arrangement, the CO2 in the compressed air could become saturated, and the drain would be sent to the equipment being used without the CO2 being fully dissolved, and would be released directly into the atmosphere. In addition, separation tanks that separate foreign matter such as dust, microorganisms, and oil mist (hereinafter simply referred to as "foreign matter") from the drain discharged from the compressed air circuit also have the problem of being unable to adsorb all of the CO2 dissolved in the drain, which ends up being released into the atmosphere at the same time as the drain is discharged. Therefore, there was a need for a means to efficiently dissolve CO2 into the drain within the compressed air circuit, as well as to separate and capture the CO2 dissolved in the drain before it is released into the atmosphere.

[0004] In order to solve the above problems, technical proposals have been made in Japanese Patent No. 6247788 (Patent Document 1) and Japanese Patent No. 6887099 (Patent Document 2). That is, Patent Document 1 describes a technology for measuring the pH value in drain discharged from a boiler device and neutralizing carbon dioxide or reducing the oxygen concentration based on the measured value. In addition, Patent Document 2 describes a technology for absorbing CO2 by flowing a CO2-containing gas into a container equipped with a nozzle that mixes and sprays a CO2 absorbent and gas.

[0005] However, in the technical proposal described in Patent Document 1, the amount of carbon dioxide neutralized is determined by the pH value of the drain, so it is not a technology aimed at completely separating and recovering the carbon dioxide contained in the drain, and does not solve the above-mentioned problems. Furthermore, in the technical proposal described in Patent Document 2, it is difficult to spray the CO2 absorbent over the entire CO2-containing gas by spraying only from a nozzle, and any CO2 that does not come into contact with the absorbent is discharged as is. Furthermore, the technology targets only gases, and does not take into consideration the recovery of CO2 in drains, which are liquids, and therefore does not solve the above problems.

[0006] The applicant focused on the amount of CO2 dissolved in the drain produced in each device, and came up with the idea of ​​efficiently dissolving the CO2 contained in the compressed air into the drain and effectively recovering the CO2 from the drain. He developed a method in which the temperature of the compressed air is gradually lowered for each device, thereby efficiently dissolving the CO2 in the drain generated by each device without saturating it, and also separating and recovering the CO2 from the drain, which can be discharged to the outside as clean drain, leading to the proposal of the "CO2 separation method" of the present invention. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 6686591 [Patent Document 2] Patent No. 6887099 Summary of the Invention [Problem to be solved by the invention]

[0008] In view of the above problems, an object of the present invention is to provide a CO2 separation method capable of efficiently dissolving CO2 contained in compressed air into a drain and effectively recovering CO2 from the drain. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention provides a compressed air circuit in which compressed air generated by a compressor is sent to a utilization device through each device, the each device being an air tank, Cyclone type Water separator and refrigerated air dryer Ya The system is configured to include a discharge pipe through which drain discharged from each of the devices arranged in the system flows, a drain trap provided at a specified location of the discharge pipe, a collecting pipe that joins the drains discharged from one or more discharge pipes and sends them to a CO2 recovery device in a subsequent stage, and a CO2 recovery device that separates and recovers CO2 from the drain that flows in from the collecting pipe.The temperature of the compressed air is gradually lowered to a preset temperature by passing it through each device during the compressed air generation process, and as the temperature decreases, CO2 is dissolved in the drain generated in each device, and the CO2-containing drain is caused to flow from each device through the discharge pipe, the drain trap, and the collecting drain pipe into the CO2 recovery device, thereby separating and recovering CO2 from the CO2-containing drain in the CO2 recovery device.

[0010] The present invention also employs a means in which the above-mentioned devices are arranged in the following order: air tank, water separator, and refrigerated air dryer.

[0011] Furthermore, the present invention employs a means in which the temperature under pressure of the compressed air flowing into the air tank is 70°C or less, the temperature under pressure of the compressed air flowing into the water separator is 40°C or less, and the temperature under pressure of the compressed air flowing into the refrigerated air dryer is 10°C or less. Effect of the Invention

[0012] According to the CO2 separation method of the present invention, an air tank, a water separator, and a refrigerated air dryer are Complex of By passing the compressed air through several devices, the temperature of the compressed air can be gradually lowered to the set temperature, and the synergistic effect of the pressure and temperature reduction can increase the amount of CO2 dissolved in the drain generated in each device.This makes it possible to efficiently remove the CO2 in the compressed air by dissolving it in the drain, resulting in the excellent effect of supplying clean compressed air that does not contain CO2 to downstream equipment.

[0013] In addition, according to the CO2 separation method of the present invention, by arranging the air tank, water separator, and refrigerated air dryer as the respective devices downstream of the compressor in that order, it is possible to reduce the temperature in at least three stages within the compressed air pressure circuit. In particular, by arranging the refrigerated air dryer in the final stage, it is possible to rapidly reduce the temperature of the compressed air before it is sent to the utilization device, thereby rapidly increasing the amount of CO2 dissolved in the drain, which is an excellent effect. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is an explanatory diagram showing an embodiment of a CO2 separation method according to the present invention. [Diagram 2] FIG. 2 is an explanatory diagram showing the composition ratio of compressed air in the CO2 separation method according to the present invention. [Diagram 3] FIG. 2 is an explanatory diagram showing the CO2 solubility in drain in the CO2 separation method according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The greatest feature of the CO2 separation method 1 of the present invention is that the temperature of the compressed air is gradually lowered in each device in the compressed air pressure circuit 2, and at the same time, the CO2 in the compressed air is dissolved in the drain generated in each device. Hereinafter, an embodiment of a CO2 separation method 1 according to the present invention will be described with reference to the drawings. The CO2 separation method 1 according to the present invention is not limited to the embodiments described below, and can be modified as appropriate within the scope of the technical concept of the present invention, i.e., within the scope of shapes, dimensions, materials, etc. that can achieve the same functional effects.

[0016] FIG. 1 is an explanatory diagram showing a basic embodiment of the CO2 separation method according to the present invention. FIG. 2 is an explanatory diagram showing the composition ratio of compressed air in the CO2 separation method. FIG. 3 is an explanatory diagram showing the amount of CO2 dissolved in drain depending on the pressure and temperature of compressed air in the CO2 separation method. 3 The amount of CO2 dissolved in cm 3 This is expressed as: The CO2 separation method 1 of the present invention is adopted in a compressed air pressure circuit 2, which is equipped with a drain trap 10 and a discharge pipe 11 for discharging drain, and a CO2 recovery device 13 for separating and recovering CO2 in the drain.

[0017] The compressed air pressure circuit 2 sends compressed air generated by a compressor 3 to a utilization device connected downstream, and depending on the usage mode of the utilization device, various devices such as an air tank 4 for temporarily storing the compressed air, a water separator 5 for separating water vapor and the like contained in the compressed air, and a refrigerated air dryer 6 for dehumidifying by cooling the compressed air are provided. There is no particular limitation on the type and number of each device arranged in the compressed air pressure circuit 2, and these are determined appropriately according to the purpose of using the compressed air and the equipment to be used. Furthermore, air piping 7 capable of supplying compressed air is provided between the compressor 3 and each device and the equipment to be used. In the compressed air pressure circuit 2, water vapor contained in the compressed air being fed adheres to and binds with the inner walls and piping of each device, resulting in the generation of drainage water.

[0018] The compressor 3 is a device that compresses the atmosphere to generate compressed air and sends it to the downstream. There are oil-free and oil-lubricated compressors 3, and either type of compressor 3 can be used, but the oil-free type is more suitable as the compressor 3 in the present invention. By using the oil-free compressor 3, no oil gets mixed into the generated compressed air, and therefore no oil gets mixed into the drain generated by the downstream equipment, which is very beneficial as it eliminates the need for filter devices, adsorbents, etc. for removing oil in the compressed air pressure circuit in general. The compressor 3 draws in the air from an air intake port, and compresses it by increasing the pressure to a predetermined pressure (for example, 0.7 MPa). As shown in FIG. 2, the air contains greenhouse gases CO2 and water vapor, and also contains foreign matter suspended in the air. Therefore, the compressed air sent out from the compressor 3 naturally contains CO2, water vapor, and foreign matter. In the process of compressing the air in the compressor 3, heat is generated, and the compressed air becomes hot, generally to about 100 to 200°C under pressure, although this varies depending on the type and method of the compressor 3. The compressed air generated by the compressor 3 is then sent through the air piping 7 to the device or utilization device disposed downstream.

[0019] The air tank 4 is a device that temporarily stores compressed air in a tank and then sends the air to a subsequent stage. The air tank 4 is a tank for temporarily storing the compressed air generated by the compressor 3, and is disposed downstream of the compressor 3 via an air pipe 7. The compressed air having a high temperature of about 100 to 200°C under pressure that leaves the compressor 3 is affected by the outside air as it passes through the air pipe 7, causing its temperature to drop, and by the time it flows into the air tank 4, its temperature has dropped to 70°C or lower under pressure (generally about 60 to 70°C). By providing such an air tank 4, the pressure of the compressed air being supplied is stabilized, which helps to suppress the water hammer effect of the fluid (compressed air) when the compressor 3 is started or stopped, and helps to reduce the load on the equipment installed downstream of the air tank 4. The compressed air that flows into the air tank 4 is affected by the outside air outside the air tank 4, and the temperature further drops. Then, the amount of saturated water vapor decreases due to the drop in temperature of the compressed air, and the water vapor that has turned into droplets further condenses, resulting in the generation of drainage in the air tank 4. The temperature of such drainage becomes the same as that of the compressed air, that is, 70°C or lower (generally about 60 to 70°C).

[0020] The water separator 5 is a device that separates water droplets and foreign matter contained in the compressed air by centrifugal force and sends the air to the subsequent stage. The water separator 5 is a cyclone type separation device that separates and removes water droplets and foreign matter contained in the compressed air by centrifugal force generated within the water separator 5, and sends clean compressed air from which water droplets and foreign matter have been removed to a subsequent stage. The compressed air that leaves the air tank 4 at a temperature of 70°C or less under pressure is affected by the outside air as it passes through the air piping 7, causing its temperature to drop to 50°C or less under pressure (generally about 40 to 50°C) when it flows into the water separator 5. Water droplets in the compressed air that flows into the water separator 5 are struck against the inner wall by centrifugal force, condense, and fall to become drain, and only the compressed air from which the water has been removed is discharged to the subsequent stage. In addition, in the separation and removal action of the water separator 5, the water droplets that are bound to foreign matter have a larger mass than unbound water, so the separation action by centrifugal force works more prominently, and they can be easily removed. The compressed air passing through the water separator 5 is affected by the outside air outside the water separator 5, and the temperature further drops in the same way as in the air tank 4, and the water vapor in the compressed air turns into water droplets due to the decrease in the amount of saturated water vapor, and is centrifuged to become drain. The temperature of such drain becomes the same as that of the compressed air, that is, 50°C or less (generally about 40 to 50°C).

[0021] The refrigerated air dryer 6 is a device that removes moisture by forcibly cooling compressed air and sends the air to the subsequent stage. The refrigerated air dryer 6 has a structure in which the amount of saturated water vapor is reduced by cooling the compressed air using the latent heat of evaporation of a refrigerant provided in the refrigerated air dryer 6, turning the water vapor into water droplets, and the resulting drain is removed, thereby sending the dried compressed air to a subsequent stage. The compressed air that leaves the water separator 5 and has a pressure of 50°C or less is affected by the outside air as it passes through the air piping 7, causing its temperature to drop to 30°C or less under pressure (generally about 20 to 30°C) when it flows into the refrigerated air dryer 6. The compressed air that has flowed into the refrigerated air dryer 6 is cooled within the refrigerated air dryer 6, and its temperature drops to 10° C. or lower (generally about 0 to 10° C.) under pressure. The temperature of the drain generated in the refrigerated air dryer 6 drops as the compressed air cools, and becomes at least the same temperature as the compressed air, that is, 10°C or less (approximately 0 to 10°C). As a result, a large amount of CO2 dissolves in the drain, making it possible to send clean compressed air with a reduced CO2 concentration to downstream equipment. Normally, when an air dryer is used as a device in a compressed air pressure circuit, other than the refrigerated air dryer 6, it is possible to consider an adsorption air dryer that uses a desiccant to dry the compressed air, or a membrane air dryer that passes the compressed air through a polymer membrane to purge the air together with moisture. However, since one of the objectives is to lower the temperature of the generated drain, in the present invention, the embodiment that employs the refrigerated air dryer 6 is preferred.

[0022] The drain generated in each device and air piping 7 is in a high-pressure environment due to the surrounding compressed air, so that according to Henry's law, more CO2 dissolves in the drain than under atmospheric pressure. In addition, as shown in FIG. 3, the amount of CO2 dissolved in the drain also increases with a decrease in temperature. However, there is a limit to the amount of CO2 that can be dissolved in the drain itself, and if the temperature of the compressed air is suddenly lowered by a device such as a refrigerated air dryer 6, the amount of CO2 that can be dissolved in the drain becomes saturated, and the undissolved CO2 may be sent to a downstream device or utilization device while remaining in the compressed air. For this reason, it is preferable to provide multiple devices downstream of the compressor 3, gradually lower the temperature of the compressed air each time it passes through each device, gradually dissolve CO2 in the drain, and thereby reduce the CO2 concentration in the compressed air and adjust the amount of CO2 dissolved in the drain.

[0023] For example, when an air tank 4, a water separator 5, and a refrigerated air dryer 6 are arranged in this order behind the compressor 3, the temperature of the compressed air generated at a pressure of 0.7 MPa and the CO2 solubility (per cm3 of water) are 3 As shown in the table in Figure 3, the CO2 solubility is increased to 2.32-2.88 cm3 by first lowering the temperature to 70°C or less under pressure, specifically to about 60-70°C, when the air flows into the air tank 4. 3 When the water flows into the water separator 5, the temperature is lowered to 50°C or less under pressure, specifically to about 40 to 50°C, so that the CO2 solubility is 3.44 to 4.24 cm 3 Finally, the compressed air, which was below 30°C when it entered the refrigerated air dryer 6, is forcibly cooled to about 0 to 10°C by the refrigerated air dryer 6, so that the CO2 solubility becomes 9.6 to 13.68 cm 3 It becomes. In this way, because the pressure of the compressed air itself and the stepwise temperature drop in each device cause the CO2 solubility to gradually increase as the air passes through each device, even if the amount of dissolved CO2 in the drain in the air tank 4 becomes saturated, CO2 can be dissolved in the downstream water separator 5 and refrigerated air dryer 6. Also, because the CO2 concentration in the compressed air is reduced by the devices disposed in the preceding stages, the refrigerated air dryer 6 disposed in the final stage can dissolve CO2 without saturating the amount of dissolved CO2 in the drain, which contributes to supplying clean compressed air with a low CO2 concentration to downstream equipment.

[0024] The structure and arrangement of the air pipes 7 connecting the devices are not particularly limited, but it is preferable to determine the structure and arrangement of the air pipes 7 taking into consideration the set pressure temperature when the compressed air flows into each device and the external influences on reaching that temperature. For example, when it is expected that the inflow temperature will be higher than the set temperature, it is possible to consider an arrangement that can provide a so-called air-cooling function by making the air piping 7 meander to increase the passing distance and thereby increase the influence of outside air to lower the temperature of the compressed air. Alternatively, it is also preferable to provide the same air-cooling function by blowing air into the air piping 7 with a fan or the like. Furthermore, it is also possible to consider a structure in which the air piping 7 has a double pipe structure, in which compressed air passes through the inner periphery and cold water passes through the outer periphery, thereby achieving a decrease in the temperature of the compressed air by the effect of the cold water, thereby exhibiting a so-called water-cooling function. It is also preferable that each device is provided with a temperature sensor for measuring the inflow temperature of compressed air, and that the above-mentioned air-cooling function or water-cooling function is appropriately performed according to the measured inflow temperature.

[0025] The drain pipes 11 are pipes for discharging drainage generated in each device, and are connected to the vicinity of the lower part of each device and to a predetermined location of the collecting pipe 12, respectively. The diameter of the pipe used in the discharge pipe 11 is not particularly limited, but is determined by the amount of drainage that may be generated in each device and the installation mode. In addition, the connection point with the collector pipe 12 is not particularly limited, but in order to allow the drainage sent in the discharge pipe 11 to flow efficiently into the collector pipe 12, it is preferable to connect it to the vicinity of the upper surface part of the collector pipe 12 extending laterally.

[0026] A drain trap 10 is provided at a predetermined intermediate position of the drain pipe 11 to mechanically discharge the drainage flowing thereinto into a collecting pipe 12 . Drain trap 10 is disposed at a predetermined location of discharge pipe 11 connected to the bottom end of each device, for example, approximately at the center of discharge pipe 11 as shown in Figure 1, and is a device that mechanically sends the drain discharged from each device through discharge pipe 11 to a collecting pipe 12. Drain trap 10 comes in various types, such as an electromagnetic type and a float type, depending on the discharge method, and either type may be used. In addition, a valve 14 as shown in the figure may be provided in the middle of the drain pipe 11 connecting each device to the drain trap 10, if necessary, to adjust the amount of drain discharged from each device.

[0027] The collecting pipe 12 is a pipe that combines the drains flowing in from the respective connected exhaust pipes 11 and sends the combined drains to the CO2 recovery device 13 in the downstream stage. The collecting pipe 12 is a pipe extending horizontally, and combines the drain flowing in through the exhaust pipe 11 connected to a predetermined portion of the collecting pipe 12, and sends it toward the CO2 capture device 13 provided in the downstream. The diameter (cross-sectional area) of the pipe used in the collecting pipe 12 is not particularly limited, but for example, by making it equal to or less than the total cross-sectional area of ​​the exhaust pipe 11 connected to the collecting pipe 12, it is possible to automatically increase the pressure of the drain that is combined in the collecting pipe 12 and sent to the CO2 capture device 13. In addition, the connection mode with the CO2 capture device 13 is not particularly limited, but as shown in FIG. 1, it is preferable to connect to a predetermined portion below the CO2 capture device 13. By adopting such a mode, the drain that flows in below the CO2 capture device 13 rises in a substantially vertical direction while coming into contact with the adsorbent filled in the CO2 capture device 13, and therefore the passing speed of the drain is reduced compared to a mode in which the drain flows in and falls from above, and the adsorption of CO2 by the adsorbent is more reliably performed. This provides an excellent effect. In addition, the connection between the collecting pipe 12 and the CO2 recovery device 13 rises upward, but because high pressure is applied to the drain in the collecting pipe 12, the drain does not stagnate within the pipe and is pushed smoothly into the CO2 recovery device 13.

[0028] Incidentally, when disposing the discharge pipe 11 connecting each device to the collecting pipe 12, it is preferable to dispose a check valve 15 after the drain trap 10 as shown in Fig. 1. By disposing the check valve 15, it becomes possible to prevent the backflow of drain from inside the collecting pipe 12 to the discharge pipe 11. Furthermore, by adopting such an embodiment, the pressure applied to the collecting pipe 12 at the same time as the drain flows in is not dispersed to multiple discharge pipes 11, so that the pressure of the drain in the collecting pipe 12 and the increase in CO2 solubility can be efficiently applied, and the drain can efficiently flow into the CO2 recovery device 13. The specific configuration of the check valve 15 is not particularly limited and may be a conventionally known device. Furthermore, there is no particular limit to the number of check valves to be installed or the locations where they are installed, but it is preferable to install one check valve for each discharge pipe 11 connected to each device.

[0029] The CO2 recovery device 13 is a device that separates and recovers foreign matter from the drain discharged from the compressed air pressure circuit 2 and flowing in through the discharge pipe 11 and the collecting pipe 12, and then discharges the resultant as clean drain to the outside. The CO2 capture device 13 is a cylindrical body having a hollow portion and a closed top and bottom portions, and the hollow portion is filled with an adsorbent capable of adsorbing foreign matter and CO2, and has an inlet through which drain flows from the collecting pipe 12 into the hollow portion and an outlet through which the drain that has flowed into the hollow portion can be discharged to the outside. The specific structure of the CO2 capture device 13 and the means for capturing CO2 from the CO2 capture device 13 can be any existing device or means, and are not particularly limited. However, the capture means can be various existing means, such as a chemical absorption method that uses a chemical reaction that occurs when air comes into contact with an alkaline aqueous solution such as an amine to separate CO2, a physical absorption method that uses an absorbing solution such as activated carbon or polyethylene glycol to physically absorb CO2 under high pressure and low temperature, a solid absorption method that brings CO2 into contact with an adsorbent such as an amine compound or lithium to physicochemically adsorb it, and a membrane separation method that uses a polymer membrane or the like to separate and capture CO2 using a pressure difference as a driving force. Furthermore, there is no particular limitation on the adsorbent material filled into the hollow portion, and it is sufficient to fill it with an appropriate adsorbent material required for the selected CO2 capture means, and one possible example is activated carbon that has been treated to give it a polarity. By performing a polarity treatment on activated carbon, it is expected that the CO2 retention capacity of the activated carbon will be improved by chemical adsorption in water (in drainage). There are several methods for polarizing activated carbon, and one possible method is to use an inexpensive phosphoric acid solution to give an electric charge and chemically adsorb CO2 using electrostatic force. Other possible adsorbents include nonwoven fabric with amines attached.

[0030] The main operation and effects of the CO2 separation method 1 having the above configuration will be described. First, the compressed air generated by the compressor 3 flows into the air tank 4 through the air piping 7 and is temporarily stored in the tank. In the air tank 4, the temperature of the compressed air under pressure is lowered from 70°C at the time of inflow to below that (for example, 60°C). After that, the compressed air flows from the air tank 4 into the water separator 5, where water droplets and foreign matter are separated from the compressed air by centrifugal force. In the water separator 5, the temperature of the compressed air under pressure is lowered from 50°C at the time of inflow to below that (for example, 40°C). Then, the compressed air from which foreign matter has been removed by the water separator 5 flows into the refrigerated air dryer 6, where moisture is removed, and the compressed air with reduced temperature and humidity is sent to downstream use equipment. In the refrigerated air dryer 6, the temperature under pressure is lowered from 30°C at the time of inflow to below 10°C (for example, 0 to 10°C). By these operations and actions, the moisture in the compressed air is condensed in each device and in the air pipe 7, and becomes drain and is stored in the lower part of each device. In addition, since each device and the air pipe 7 are in a high-pressure environment due to the compressed air, more CO2 in the compressed air is dissolved in the stored drain than under atmospheric pressure.

[0031] Next, the drain stored in each device is discharged from the discharge pipe 11 connected to the bottom of each device. A drain trap 10 is provided at approximately the center of the discharge pipe 11, which mechanically sends the drain from the discharge pipe 11 to a collecting pipe 12. The drain that flows into the collecting pipe 12 is sent to a CO2 recovery device 13 while merging with the drain that flows in from each of the other devices. Then, the CO2 and foreign matter in the drain that flows into the CO2 recovery device 13 are separated and recovered by the adsorbent filled in the drain, and the drain is then discharged to the outside as clean drain. The drain that has passed through the drain trap 10 is released from the high pressure environment caused by the compressed air. As the pressure drops, the CO2 solubility in the drain also decreases (see FIG. 3), and CO2 that exceeds the solubility becomes foamy (gas) and is released from the drain through the exhaust pipe 11 and the collecting pipe 12. The CO2 recovery device 13 can effectively recover the CO2 that has become foamy (gas).

[0032] Although the basic configuration and operation / effects of the CO2 separation method 1 according to the present invention have been described above, the present invention is not limited to the configuration shown in the above embodiment or drawings. For example, by providing an oil filter before or after the refrigerated air dryer 6, a further temperature drop can be expected, and even if an oil-lubricated compressor is used as the compressor 3, it is possible to provide clean, oil-free, CO2-free compressed air to downstream equipment.

[0033] As described above, the CO2 separation method 1 according to the present invention can efficiently dissolve CO2 in the drain generated in each device by gradually lowering the temperature of the compressed air using each device arranged as the compressed air pressure circuit 2, which contributes to providing clean compressed air with a low CO2 content to downstream utilization equipment. Furthermore, by flowing the drain with a large amount of dissolved CO2 into the CO2 capture device 13 via the discharge pipe 11 and the collecting pipe 12, it becomes possible to separate and capture in advance the CO2 that is released when the drain is discharged to the outside. [Industrial Applicability]

[0034] The present invention can be used in any field that uses compressed air, such as manufacturing and processing, cleaning, dentistry, etc., and also plays a part in reducing atmospheric CO2, which is said to be a cause of global warming. Therefore, it is believed that the "CO2 separation method" of the present invention has great industrial applicability. [Explanation of symbols]

[0035] 1 CO2 separation method 2 Compressed air circuit 3. Compressor 4. Air Tank 5 Water separator 6 Refrigerated air dryer 7 Air piping 10 Drain Trap 11 Discharge pipe 12 Collecting pipe 13 CO2 capture unit 14 Valve 15 Check valve

Claims

1. In a compressed air circuit in which compressed air generated by a compressor is sent to a utilization device through each device, The equipment consists of an air tank, a cyclone-type water separator, and a refrigerated air dryer, arranged in that order. The system comprises an exhaust pipe through which drain discharged from each of the installed devices flows, a drain trap provided at a predetermined position of the exhaust pipe, a collecting pipe that combines the drains discharged from one or more exhaust pipes and sends them to a CO2 capture device in a downstream stage, and a CO2 capture device that separates and captures CO2 from the drain that flows in from the collecting pipe, A CO2 separation method characterized by gradually lowering the temperature of compressed air to a preset temperature by passing the compressed air through various devices during the compressed air generation process, dissolving CO2 into the drain generated in each device as the temperature drops, causing the CO2-containing drain from each device to flow into a CO2 capture device via an exhaust pipe, a drain trap and a drain manifold, and separating and capturing CO2 from the CO2-containing drain in the CO2 capture device.

2. The method for separating CO2 according to claim 1, characterized in that the compressed air flowing into the air tank has a temperature under pressure of 70°C or less, the compressed air flowing into the water separator has a temperature under pressure of 50°C or less, and the compressed air flowing into the refrigerated air dryer has a temperature under pressure of 30°C or less.

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