Co2 separation method

Abstract

To provide a CO2 separation method where CO2 contained in compressed-air is efficiently dissolved in drain and CO2 can be effectively recovered from the drain.SOLUTION: Compressed-air temperature is gradually fallen to preset temperature by passing each device in the formation process of compressed-air. CO2 is dissolved in drain generated in each device as the temperature is dropped and a CO2-containing drain is flown into a CO2 recovery device from each device via an outlet tube, a drain trap and a drain collecting pipe and CO2 is separated and recovered from a means to separate and recover the CO2-containing drain in the CO2 recovery device.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for separating CO2 in a compressed air pressure circuit. More specifically, it relates to a method of dissolving CO2 in the drain generated in each subsequent-stage device in a compressed air pressure circuit and separating CO2 from the drain when the drain is discharged.

Background Art

[0002] In a compressed air pressure circuit, a large amount of water vapor is contained in the compressed air compressed by a compressor. In each device (hereinafter, may be simply referred to as "each device") such as an air tank, a cyclone separator, and an air dryer disposed in the compressed air pressure circuit, it is cooled or collides with the inner wall to become drain, and is discharged together with the compressed exhaust through a drain trap from the discharge port provided in each device.

[0003] In the drain generated under the high-pressure environment in each device, due to Henry's law and the temperature drop due to the structure of each device, more CO2 in the compressed air dissolves than usual. However, in the previous compressed air pressure circuit, since there is no specification for the arrangement order or the number of arrangements of each device, the amount of CO2 dissolved in the drain is not stable. Depending on the arrangement mode, the CO2 in the compressed air becomes saturated, and the CO2 cannot be sufficiently dissolved in the drain and is sent to the utilization equipment as it is and released into the atmosphere as it is. There were such problems. Also, in a separation tank for separating foreign substances (hereinafter, simply referred to as "foreign substances") such as dust, microorganisms, and oil mist from the drain discharged from the compressed air pressure circuit, the CO2 dissolved in the drain cannot be adsorbed completely and is released into the atmosphere simultaneously with the drain discharge. There were such problems. Therefore, there has been a demand for means capable of efficiently dissolving CO2 in the drain in the compressed air pressure circuit and separating and recovering the CO2 dissolved in the drain before it is released into the atmosphere.

[0004] To solve the above problems, technical proposals described in Japanese Patent No. 6247788 (Patent Document 1) and Japanese Patent No. 6887099 (Patent Document 2) have been made. That is, Patent Document 1 describes a technique for measuring the pH value in the drain discharged from a boiler device and performing neutralization of carbon dioxide or reduction of oxygen concentration based on the measured value. Further, Patent Document 2 describes a technique for flowing a CO2-containing gas into a container equipped with a nozzle for mixing and spraying a CO2 absorbent and a gas to absorb CO2.

[0005] However, in the technical proposal described in Patent Document 1, since the amount of carbon dioxide neutralization is determined by the pH value of the drain, it is not a technique for the purpose of complete separation and recovery of carbon dioxide contained in the drain and does not solve the above problems. Also, in the technical proposal described in Patent Document 2, it is difficult to spray the CO2 absorbent over the entire CO2-containing gas only by spraying from the nozzle, and the CO2 that has not come into contact with the absorbent will be discharged as it is. Further, the technical target is only gas, and the recovery of CO2 in the drain, which is a liquid, is not considered, and thus it does not solve the above problems either.

[0006] The applicant of the present application focused on the amount of CO2 dissolved in the drain generated in each device, and under the idea of whether it is possible to efficiently dissolve the CO2 contained in the compressed air into the drain and effectively recover the CO2 from the drain, by gradually lowering the temperature of the compressed air for each device, the CO2 is efficiently dissolved in the drain generated in each device without saturating the CO2, and the CO2 is separated and recovered from the drain, and a method that can be discharged to the outside as clean drain has been developed, leading to the proposal of the "CO2 separation method" according to the present invention.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems 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 drain and effectively recovering CO2 from the drain.

Means for Solving the Problems

[0009] To solve the above problems, the present invention provides a compressed air pressure circuit in which compressed air generated by a compressor is sent to a utilization device via each device. At least a plurality of devices selected from an air tank, a moisture separator, and a refrigerated air dryer are arranged as each device. A drain pipe through which drain discharged from each arranged device flows, a drain trap provided at a predetermined location of the drain pipe, a collecting pipe that merges the drain discharged from one or more drain pipes and sends it to a subsequent CO2 recovery device, and a CO2 recovery device that separates and recovers CO2 from the drain flowing in from the collecting pipe. By causing the compressed air to pass through each device during the generation process of the compressed air, the temperature of the compressed air is gradually lowered to a preset temperature. As the temperature decreases, CO2 dissolves into the drain generated in each device. By allowing the CO2-containing drain to flow into the CO2 recovery device via the drain pipe, the drain trap, and the drain collecting pipe from each device, means for separating and recovering CO2 from the CO2-containing drain in the CO2 recovery device is adopted.

[0010] The present invention also adopts means in which each of the above devices is arranged in the order of an air tank, a moisture separator, and a refrigerated air dryer.

[0011] Furthermore, the present invention adopts means in which the temperature under pressure of the compressed air flowing into the air tank is 70°C or lower, the temperature under pressure of the compressed air flowing into the moisture separator is 40°C or lower, and the temperature under pressure of the compressed air flowing into the refrigerated air dryer is 10°C or lower.

Effects of the Invention

[0012] According to the CO2 separation method of the present invention, by passing through at least a plurality of devices among the air tank, the water separator, and the refrigerated air dryer, the temperature of the compressed air is gradually reduced to the set temperature, and due to the synergistic effect of pressure and temperature reduction, the amount of CO2 dissolved in the drain generated in each device can be increased. Therefore, it is possible to efficiently remove CO2 in the compressed air by dissolving it in the drain, and it is possible to supply clean compressed air without CO2 to the subsequent use equipment, achieving excellent effects such as this.

[0013] Moreover, according to the CO2 separation method of the present invention, by arranging an air tank, a water separator, and a refrigerated air dryer in this order as each device after the compressor, at least three stages of temperature reduction are possible in the compressed air pressure circuit. In particular, by arranging a refrigerated air dryer in the last stage, it is possible to suddenly reduce the temperature of the compressed air before supplying it to the use equipment and suddenly increase the amount of CO2 dissolved in the drain, achieving excellent effects such as this.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0015] The CO2 separation method 1 according to the present invention is characterized in that while gradually reducing the temperature of the compressed air in each device in the compressed air pressure circuit 2, the CO2 in the compressed air is dissolved in the drain generated in each device. Hereinafter, an embodiment of the CO2 separation method 1 according to the present invention will be described with reference to the drawings. Furthermore, the CO2 separation method 1 according to the present invention is not limited to the embodiments described below, and can be appropriately modified within the scope of the technical idea of the present invention, that is, within the scope of shapes, dimensions, materials, etc. that can exhibit the same operational 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 the drain depending on the pressure and temperature of the compressed air in the CO2 separation method. Specifically, the amount of CO2 dissolved in 1 cm of water 3 is represented in cm 3 The CO2 separation method 1 according to the present invention is adopted in the compressed air pressure circuit 2. The compressed air pressure circuit 2 is provided with a drain trap 10 for discharging drain, a discharge pipe 11, and a CO2 recovery device 13 for separating and recovering CO2 in the drain.

[0017] The compressed air pressure circuit 2 sends the compressed air generated by the compressor 3 to the utilization equipment connected to the subsequent stage. Depending on the usage mode of the utilization equipment, there are provided an air tank 4 for temporarily storing the compressed air, a moisture separator 5 for separating water vapor and the like contained in the compressed air, a refrigeration type air dryer 6 for dehumidifying by cooling the compressed air, and other devices. There are no particular limitations on the types and numbers of the devices arranged in the compressed air pressure circuit 2, which will be appropriately determined according to the purpose of using the compressed air and the utilization equipment. Naturally, an air pipe 7 capable of sending compressed air is provided between the compressor 3, each device, and the utilization equipment. In the compressed air pressure circuit 2, water vapor contained in the sent compressed air adheres to and combines with the inner walls of each device, pipes, etc., resulting in the generation of drain, which is moisture.

[0018] ​The compressor 3 is a device that compresses the atmosphere to generate compressed air and sends it to the subsequent stage. There are oil-free compressors and oil-injected compressors for the compressor 3, and either type of compressor 3 can be adopted. However, as the compressor 3 in the present invention, an oil-free type is more suitable. By adopting an oil-free type compressor 3, there is no oil contamination in the generated compressed air, and thus there is no oil contamination in the drain generated in the subsequent stage equipment. Therefore, in the entire compressed air pressure circuit, filter devices, adsorbents, etc. for removing oil become unnecessary, which is very beneficial. The compressor 3 inhales the atmosphere from the air inlet and boosts and compresses it to a predetermined pressure (for example, 0.7 Mpa). As shown in FIG. 2, the atmosphere contains CO2, which is a greenhouse gas, water vapor, and there are also foreign substances floating in the air. Therefore, the compressed air sent out from the compressor 3 naturally contains CO2, water vapor, and foreign substances. In the air compression process in the compressor 3, heat is generated, and although it varies depending on the type and method of the compressor 3, generally the compressed air becomes hot up to about 100 to 200 °C under pressure. Then, the compressed air generated by the compressor 3 is sent through the air pipe 7 to the devices and equipment arranged in the subsequent stage.

[0019] The air tank 4 is a device that temporarily stores compressed air in the tank and then sends it to the subsequent stage. The air tank 4 is a tank for temporarily storing the compressed air generated by the compressor 3, and is arranged at the subsequent stage of the compressor 3 via the air pipe 7. The high-temperature compressed air at about 100 to 200 °C under pressure that exits the compressor 3 is affected by the outside air and its temperature drops when passing through the air pipe 7, and when flowing into the air tank 4, it drops 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 to be sent is stabilized, which helps to suppress the water hammer action (water hammer phenomenon) of the fluid (compressed air) at the start and stop of the compressor 3, and helps to reduce the load on the equipment arranged at the subsequent stage of the air tank 4. The compressed air flowing into the air tank 4 is affected by the outside air outside the air tank 4, and its temperature will further decrease. Then, due to the decrease in the amount of saturated water vapor caused by the temperature drop of the compressed air, the water vapor that has become water droplets will further condense, resulting in the generation of drain in the air tank 4. The temperature of such drain will be the same as the temperature of the compressed air, that is, 70°C or lower (about 60 - 70°C).

[0020] The moisture separator 5 is a device that separates water droplets and foreign substances contained in the compressed air by centrifugal force and sends air to the subsequent stage. The moisture separator 5 is a cyclone separator that separates and removes water droplets and foreign substances contained in the compressed air by the centrifugal force generated inside the moisture separator 5, and sends the clean compressed air from which the water droplets and foreign substances have been removed to the subsequent stage. The compressed air at 70°C or lower under pressure that exits the air tank 4 is affected by the outside air when passing through the air pipe 7 and its temperature decreases. When it flows into the moisture separator 5, it drops to 50°C or lower (about 40 - 50°C) under pressure. The water droplets in the compressed air flowing into the moisture separator 5 are condensed and dropped onto the inner wall by centrifugal force to become drain, and only the compressed air from which the moisture has been removed is discharged to the subsequent stage. Also, in the separation and removal action by the moisture separator 5, the water droplets combined with foreign substances have an increased mass compared to the uncombined moisture, so the separation action by centrifugal force works more significantly and can be easily removed. The compressed air passing through the inside of the moisture separator 5 is affected by the outside air outside the moisture separator 5, and its temperature further decreases in the same way as the air tank 4. Due to the decrease in the amount of saturated water vapor, the water vapor in the compressed air becomes water droplets, is centrifugally separated, and forms drain. The temperature of such drain will be the same as the temperature of the compressed air, that is, 50°C or lower (about 40 - 50°C).

[0021] The refrigeration type air dryer 6 is a device that removes moisture by forcibly cooling the compressed air and sends it to the subsequent stage. The refrigerated air dryer 6 has a structure in which compressed air is cooled by utilizing the latent heat of vaporization of the refrigerant provided within the refrigerated air dryer 6, thereby reducing the amount of saturated water vapor and atomizing the water vapor into water droplets. By removing the drain generated thereby, dried compressed air is sent to the subsequent stage. The compressed air at a pressure of 50°C or lower after exiting the moisture separator 5 is affected by the outside air and its temperature drops when passing through the air pipe 7, and when flowing into the refrigerated air dryer 6, it drops to 30°C or lower under pressure (approximately 20 to 30°C). The compressed air flowing into the refrigerated air dryer 6 is cooled within the refrigerated air dryer 6, and its temperature drops to 10°C or lower under pressure (approximately 0 to 10°C). The temperature of the drain generated within the refrigerated air dryer 6 will drop along with the cooling effect on the compressed air, and will be at least the same temperature as the compressed air, that is, 10°C or lower (approximately 0 to 10°C). Therefore, a large amount of CO2 will dissolve into the drain, and it becomes possible to send clean compressed air with a reduced CO2 concentration to the subsequent utilization equipment. Normally, when using an air dryer as a device in a compressed air pressure circuit, in addition to the refrigerated air dryer 6, an adsorption type air dryer that dries compressed air using a desiccant or a membrane air dryer that purges the air containing moisture by passing compressed air through a polymer membrane are also conceivable adoption modes. However, since reducing the temperature of the generated drain is also one of the purposes, in the present invention, the adoption mode of the refrigerated air dryer 6 is preferable.

[0022] The drain generated in each device and the air piping 7 is under a high-pressure environment due to the surrounding compressed air. Therefore, according to Henry's law, more CO2 will dissolve than under atmospheric pressure. Also, as shown in Figure 3, the amount of CO2 dissolved in the drain increases with a decrease in temperature. However, there is a limit to the amount of CO2 that can be dissolved in the drain itself. When the temperature of the compressed air is rapidly decreased by a device such as the 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 the subsequent device or equipment while remaining in the compressed air. Therefore, it is preferable to arrange a plurality of devices downstream of the compressor 3, gradually lower the temperature of the compressed air step by step as it passes through each device, and gradually dissolve CO2 in the drain to reduce the CO2 concentration in the compressed air and adjust the amount of CO2 dissolved in the drain.

[0023] For example, when verifying the case of arranging an air tank 4, a moisture separator 5, and a refrigerated air dryer 6 in this order downstream of the compressor 3, the relationship between the temperature of the compressed air generated at a pressure of 0.7 MPa and the CO2 solubility (the amount of CO2 dissolved per 1 cm of water) is as shown in the table of Figure 3. First, when flowing into the air tank 4, by reducing the temperature to 70°C or less under pressure, specifically about 60 - 70°C, the CO2 solubility becomes 2.32 - 2.88 cm. 3 And when flowing into the moisture separator 5, by reducing the temperature to 50°C or less under pressure, specifically about 40 - 50°C, the CO2 solubility becomes 3.44 - 4.24 cm. 3 Finally, the compressed air, which was 30°C or less when flowing into the refrigerated air dryer 6, is forcibly reduced to about 0 - 10°C by the refrigerated air dryer 6, and the CO2 solubility becomes 9.6 - 13.68 cm. 3 3 In this way, due to the pressure of the compressed air itself and the gradual temperature drop in each device, the CO2 solubility gradually increases as it passes through each device. Therefore, even if the amount of CO2 dissolved in the drain reaches saturation in the air tank 4, CO2 can still be dissolved in the subsequent moisture separator 5 and refrigerated air dryer 6. Also, since the CO2 concentration in the compressed air has decreased due to the devices arranged in the front stage, in the refrigerated air dryer 6 arranged in the last stage, it is possible to dissolve CO2 without saturating the amount of CO2 dissolved in the drain, contributing to the supply of clean compressed air with a low CO2 concentration to the subsequent equipment for use.

[0024] Regarding the structure and arrangement mode of the air pipe 7 connecting between each device, there is no particular limitation. However, it is preferable to determine the structure and arrangement mode of the air pipe 7 in consideration of the set pressure temperature when the compressed air flows into each device and the influence of the external environment to reach the temperature. For example, when it is assumed that the inflow temperature is higher than the set temperature, a so-called air-cooling function can be achieved by increasing the passing distance by making the air pipe 7 meander, etc., so that it is more affected by the outside air and the temperature of the compressed air is reduced. Or, as the same air-cooling function, a mode of blowing air to the air pipe 7 with a fan or the like is also preferable. Furthermore, a structure that can achieve a so-called water-cooling function can be considered by making the air pipe 7 have a double-pipe structure, passing compressed air through the inner peripheral side, and passing cold water through the outer peripheral side to reduce the temperature of the compressed air due to the influence of the cold water. In addition, it is also preferable to arrange a temperature sensor for measuring the inflow temperature of the compressed air in each device and appropriately exert the above-described air-cooling function and water-cooling function according to the measured inflow temperature.

[0025] The discharge pipe 11 is a pipe for discharging the drain generated in each device, and is connected to the vicinity of the lower part of each device and a predetermined location of the collecting pipe 12, respectively. The pipe diameter of the discharge pipe 11 is not particularly limited, but will be determined by the amount of drain that can be generated in each device and the installation mode. Also, although there is no particular limitation on the connection point with the manifold pipe 12, in order to efficiently allow the drain flowing in the discharge pipe 11 to flow into the manifold pipe 12, a connection mode to the vicinity of the upper surface portion of the horizontally extending manifold pipe 12 is preferable.

[0026] At a predetermined intermediate position of the discharge pipe 11, a drain trap 10 for mechanically discharging the inflowing drain to the manifold pipe 12 is provided. The drain trap 10 is disposed at a predetermined position of the discharge pipe 11 connected to the lower end of each device, for example, at a substantially central position of the discharge pipe 11 as shown in FIG. 1, and is a device that mechanically sends the drain discharged from each device through the discharge pipe 11 to the manifold pipe 12. There are electromagnetic type, float type, etc. for the drain trap 10 depending on the discharge method, and any method may be used. In addition, a valve 14 as shown in the figure is provided in the middle of the discharge pipe 11 connecting each device and the drain trap 10 as necessary, and it is possible to adjust the drain discharge amount from each device.

[0027] The manifold pipe 12 is a pipe that combines the drains flowing in from the respective connected discharge pipes 11 and sends them to the subsequent CO2 recovery device 13. The collecting pipe 12 is a pipe extending horizontally. It combines the drain flowing in through the discharge pipe 11 connected to a predetermined location of the collecting pipe 12 and conveys it toward the CO2 recovery device 13 provided in the subsequent stage. The diameter (cross-sectional area) of the pipe used for the collecting pipe 12 is not particularly limited. For example, by making it equal to or less than the total cross-sectional area of the discharge pipes 11 connected to the collecting pipe 12, the pressure of the drain that converges in the collecting pipe 12 and is conveyed to the CO2 recovery device 13 can be automatically increased. Also, the connection mode with the CO2 recovery device 13 is not particularly limited, but as shown in FIG. 1, a mode of connecting to a predetermined location below the CO2 recovery device 13 is preferable. By adopting such a mode, the drain flowing into the lower part of the CO2 recovery device 13 rises in a substantially vertical direction while contacting the adsorbent filled in the CO2 recovery device 13. Therefore, compared with the mode in which the drain flows in and descends from above, the passing speed of the drain decreases, and excellent effects such as more reliable adsorption of CO2 by the adsorbent are achieved. Further, the connection part between the collecting pipe 12 and the CO2 recovery device 13 rises upward. However, since the drain in the collecting pipe 12 has a high pressure, the drain is smoothly pushed into the CO2 recovery device 13 without staying in the pipe.

[0028] Incidentally, when arranging the discharge pipe 11 connecting each device to the collecting pipe 12, as shown in FIG. 1, a mode of arranging a check valve 15 in the subsequent stage of the drain trap 10 is preferable. By arranging the check valve 15, it becomes possible to prevent the backflow of the drain from the collecting pipe 12 into the discharge pipe 11. Further, by adopting such a mode, the pressure applied to the collecting pipe 12 at the same time as the drain inflow is not dispersed to the plurality of discharge pipes 11, and pressurization of the drain in the collecting pipe 12, an increase in CO2 solubility, and further, efficient inflow of the drain into the CO2 recovery device 13 can be achieved. Regarding the specific configuration of the check valve 15, conventionally known equipment may be used and is not particularly limited. Further, although there are no particular limitations on the number of installations and the installation locations, a mode of installing each for each discharge pipe 11 connected to each device is preferable.

[0029] The CO2 recovery device 13 is a device that separates and recovers foreign substances from the drain discharged from the compressed air pressure circuit 2 and flowing in through the discharge pipe 11 and the manifold 12, and then discharges the clean drain to the outside. The CO2 recovery device 13 is a cylindrical body having a hollow portion and with its top surface and bottom surface closed. The hollow portion is filled with an adsorbent capable of adsorbing foreign substances, CO2, etc. An inlet through which the drain flows from the manifold 12 into the hollow portion and an outlet through which the drain flowing into the hollow portion can be discharged to the outside are respectively formed. Also, regarding the specific structure of the CO2 recovery device 13 and the CO2 recovery means from the CO2 recovery device 13, existing devices and means can be adopted and are not particularly limited. However, for the recovery means, for example, a chemical absorption method that separates CO2 by utilizing a chemical reaction generated by the contact of the atmosphere with an alkaline aqueous solution such as an amine, a physical absorption method that physically absorbs CO2 at high pressure and low temperature using an absorbent liquid such as activated carbon or polyethylene glycol, a solid absorption method that physically and chemically adsorbs CO2 by contacting an adsorbent such as an amine compound or lithium, a membrane separation method that separates and recovers CO2 using a polymer membrane or the like with a pressure difference as the driving force, and other existing means can be variously applied. Furthermore, there is no particular limitation on the adsorbent filled into the hollow portion, and an adsorbent necessary for performing the selected CO2 recovery means may be appropriately filled. For example, activated carbon subjected to a polarity imparting treatment can be considered. By performing a polarity imparting treatment on the activated carbon, an improvement in the CO2 retention ability by chemical adsorption of the activated carbon in water (in the drain) can be expected. There are several methods for the polarity imparting treatment to the activated carbon. For example, a method of imparting a charge using an inexpensive phosphoric acid solution and chemically adsorbing CO2 by electrostatic force can be considered. As other adsorbents, a non-woven fabric with amines attached can also be adopted.

[0030] Regarding the CO2 separation method 1 having the above configuration, its main operations and functions will be described. First, the compressed air generated by the compressor 3 flows into the air tank 4 through the air pipe 7 and is temporarily stored in the tank. Inside such an air tank 4, the pressure and temperature of the compressed air are reduced from 70°C at the time of inflow to 70°C or lower (for example, 60°C). Thereafter, the compressed air flowing from the air tank 4 into the water separator 5 has water droplets and foreign matters separated by centrifugal force. In such a water separator 5, the pressure and temperature of the compressed air are reduced from 50°C at the time of inflow to 50°C or lower (for example, 40°C). Then, the compressed air from which foreign matters have 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 the downstream equipment for use. In such a refrigerated air dryer 6, the pressure and temperature are reduced from 30°C at the time of inflow to 10°C or lower (for example, 0 to 10°C). Due to such operations and effects, the moisture in the compressed air is condensed in each device and the air pipe 7 and becomes drain, which is stored at the lower part of each device. Also, 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 lower part of each device. A drain trap 10 is provided at a substantially central position of the discharge pipe 11, and the drain is mechanically sent from the discharge pipe 11 to the collecting pipe 12. The drain flowing into the collecting pipe 12 is sent to the CO2 recovery device 13 while merging with the drain flowing in from other devices. Then, the drain flowing into the CO2 recovery device 13 has the CO2 and foreign matters in the drain separated and recovered by the filled adsorbent, and thereafter, the clean drain is discharged to the outside. In addition, the drain passing through the drain trap 10 is released from the high-pressure environment due to the compressed air. Along with the pressure drop, the solubility of CO2 in the drain also decreases (see Figure 3), and the CO2 exceeding the solubility becomes a bubble (gas) and is released from the drain in the discharge pipe 11 and the collecting pipe 12. The CO2 recovery device 13 can effectively recover such bubble (gas)-formed CO2.

[0032] As described above, the basic configuration and operation of the CO₂ separation method 1 according to the present invention have been explained. However, the present invention is not limited to the configuration shown in the above embodiments and drawings. For example, by disposing an oil filter before or after the refrigerated air dryer 6, a further temperature drop can be expected. At the same time, even when an oil-fed compressor is used as the compressor 3, it is possible to provide clean compressed air without oil and without CO₂ to the subsequent 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 by each device arranged as the compressed air pressure circuit 2, and contributes to providing clean compressed air with a low CO₂ content to the subsequent equipment. Further, by allowing the drain with a large amount of dissolved CO₂ to flow into the CO₂ recovery device 13 through the discharge pipe 11 and the collecting pipe 12, it is possible to pre-separate and recover the CO₂ released when discharging the drain to the outside.

Industrial Applicability

[0034] The present invention can be adopted in all fields that use compressed air, such as manufacturing and processing industries, cleaning industries, dentistry, etc. It also plays a part as a measure to reduce CO₂ in the atmosphere, which is also said to be a cause of global warming. Therefore, it is considered that the industrial applicability of the "CO₂ separation method" according to the present invention is great.

Explanation of Signs

[0035] 1 CO₂ separation method 2 Compressed air pressure circuit 3 Compressor 4 Air tank 5 Moisture separator 6 Refrigerated air dryer 7 Air pipe 10 Drain trap 11 Discharge pipe 12 Collecting pipe 13 CO₂ recovery device 14 valves 15 check valves

Claims

1. In a compressed air pressure circuit in which compressed air generated by a compressor is sent to a utilization device via each device, at least a plurality of devices selected from an air tank, a moisture separator, and a refrigerated air dryer are arranged as each device, a drain pipe through which drain discharged from each arranged device flows, a drain trap provided at a predetermined location of the drain pipe, a collecting pipe that merges the drain discharged from one or more drain pipes and sends it to a CO2 recovery device in the subsequent stage, and a CO2 recovery device that separates and recovers CO2 from the drain flowing in from the collecting pipe, The temperature of the compressed air is gradually lowered to a preset temperature by passing through each device during the generation process of the compressed air, and CO2 is dissolved in the drain generated in each device as the temperature decreases. The CO2-containing drain flows from each device into the CO2 recovery device via the drain pipe, the drain trap, and the drain collecting pipe, and the CO2 recovery device separates and recovers CO2 from the CO2-containing drain. A CO2 separation method characterized by this.

2. The CO2 separation method according to claim 1, characterized in that each of the devices is arranged in the order of an air tank, a moisture separator, and a refrigerated air dryer.

3. The CO2 separation method according to claim 2, characterized in that the temperature under pressure of the compressed air flowing into the air tank is 70°C or lower, the temperature under pressure of the compressed air flowing into the moisture separator is 50°C or lower, and the temperature under pressure of the compressed air flowing into the refrigerated air dryer is 30°C or lower.

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