Co2 separation system

Abstract

The present invention comprises: first CO2 separation equipment; second CO2 separation equipment; to-be-treated gas supply piping; first piping; high concentration CO2 gas discharge equipment; second piping; gas circulation equipment comprising a circulation gas discharge device including a flash tower and low concentration CO2; liquefied CO2 discharge piping; and CO2 treated gas discharge piping. The first CO2 separation equipment includes an absorption separation device using rubber as a CO2 absorber. The second CO2 separation equipment is composed of a deep cooling separation device. The first piping supplies the gas discharged from the first CO2 separation equipment to the second CO2 separation equipment. The circulation gas discharge device including the low concentration CO2 discharges the low concentration CO2 gas from the second CO2 separation equipment and the circulation gas from the flash tower. The CO2 treated gas discharge piping is connected to the absorption separation device.

Description

CO2 Separation System

[0001] The present invention is ２ Regarding separation systems.

[0002] From the perspective of reducing greenhouse gas emissions, taking into account desorption energy efficiency, ２ Low-energy CO2-containing combustion gas, natural gas, and biogas ２ There is a strong demand for the separation and recovery of CO, which is found in combustion gases and natural gas. ２ CO from medium concentration gases with concentrations between 5 and 50% ２ There is a high demand for separation and recovery.

[0003] Generally, the separation process of combustion gas or natural gas is carried out by CO ２ Various methods have been proposed depending on the concentration. ２ CO from medium concentration gases with concentrations between 5 and 20% ２ For separation and recovery, molten potassium carbonate was used in older facilities, but it is now being replaced by the AGR process using amine solvents. This is because corrosion of steel materials caused by molten potassium carbonate was a frequent problem. Amine solvents allow the absorbent to be regenerated by heat, and equipment maintenance is easy.

[0004] Unexamined Utility Model Publication No. 61-15489

[0005] Jun Matsumoto et al., Journal of Petroleum Technology, Vol. 76, No. 6, pp. 512-516 (November 2011); Izumi Ichinose et al., JACI GSC Symposium (June 15-16, 2022); Zenji Fujiyasu, Cryogenic Engineering, Vol. 5, No. 4, pp. 181-185 (1970); Shigeru Kimura, Hitachi Review, Vol. 48, No. 8, pp. 69-74 (August 1966)

[0006] CO2 absorber using amine solvent ２The above-mentioned method for recovering CO requires that the mixed gas be converted into high-pressure microbubbles and then dissolved in an amine solvent. In addition, the amine solvent must be sprayed from the top of an absorption tower several tens of meters high, which results in a large energy loss and requires a huge facility. Furthermore, there is a problem that a part of the absorbent volatilizes, which requires additional recovery costs. In view of the above-mentioned problems, the object of the present invention is to ２ Medium concentration CO of 5-50% ２ CO2 can be efficiently produced using low-energy combustion gases and natural gas containing CO2. ２ and provide a desired gas such as methane or a gas with reduced greenhouse gases; ２ The object is to provide a separation system.

[0007] The constitution of the present invention is as follows: (Constitution 1) First CO ２ Separation equipment and a second CO ２ a separation facility; a treated gas supply pipe; a first pipe; and a high-concentration CO ２ Gas exhaust equipment, second piping, flash tower and low concentration CO ２ a gas reflux facility including a reflux gas discharge device including a liquefied CO ２ Exhaust piping and CO ２ and a treated gas discharge pipe, ２ The separation facility separates the rubber into CO ２ an absorption / separation device that is provided as an absorbent, ２ The separation equipment separates CO from the gas to be treated by cryogenic separation. ２ and a cryogenic separation device for separating the first CO ２ The first pipe is connected to a separation facility via a valve to supply the gas to be treated to the absorption separation device, and the first pipe is connected to the first CO ２ The gas discharged from the separation equipment is ２ The flash tower supplies the cryogenic separation device, the liquefied CO ２ The low-concentration CO ２ The reflux gas discharge device includes the second CO２ CO having a concentration lower than the concentration in the first pipe from the separation equipment ２ and discharging a gas containing CO from the flash tower. ２ In the gas reflux facility, the low concentration CO ２ The gas discharged from the reflux gas discharge device containing ２ The CO is returned to the separation facility. ２ The treated gas discharge pipe is connected to the absorption / separation device via a valve. ２ Separation system. (Configuration 2) The absorption / separation device includes a first absorption tower group consisting of one or more absorption towers and a second absorption tower group consisting of one or more absorption towers, and the absorption towers each have a flow path for allowing a gas to flow while retaining the gas therein, and a CO ２ It has rubber as an absorbent material, ２ The separation system includes the flow path and the CO ２ 2. The CO2 separator of claim 1, further comprising a cooling means capable of cooling the absorbent, the cryogenic separation device, and the flash tower. ２ (Configuration 3) The CO separation system according to Configuration 2, wherein the first absorption tower group and the second absorption tower group are paired absorption tower groups having the same configuration. ２ (Configuration 4) A separation system for CO 2 in a gas introduced into the first group of absorbers and the second group of absorbers through the treated gas supply pipe. ２ 4. The CO concentration of the present invention is 5 mol % or more and 50 mol % or less. ２ Separation system. (Configuration 5) The high-concentration CO ２ CO emitted from gas exhaust equipment ２ The CO concentration is adjusted to 40 mol% or more and 80 mol% or less. ２ (Configuration 6) The CO separation system according to any one of Configurations 2 to 5, wherein the absorption pressure of the absorption tower is adjusted to 2 MPa or more and 10 MPa or less. ２ (Configuration 7) The CO separation system according to Configuration 2, wherein the cooling temperature is −60° C. or higher and 0° C. or lower. ２ Separation system. (Configuration 8) The low-concentration CO ２CO in reflux gas containing ２ 2. The method according to claim 1, wherein the concentration of CO is 10 mol % or more and 50 mol % or less. ２ (Configuration 9) The CO separation system according to any one of Configurations 1 to 8, wherein a compressor is connected to the treated gas supply pipe. ２ (Configuration 10) The CO separation system according to any one of Configurations 1 to 9, wherein a compressor is connected to the second pipe. ２ (Configuration 11) The CO separation system according to any one of Configurations 2 to 7, wherein the gas to be treated is introduced into the absorption tower via a dehydration facility that performs dehydration. ２ Separation system (Configuration 12) A gas to be treated introduction equipment, a first CO ２ Separation equipment and a second CO ２ Separation equipment and liquefied CO ２ Refining facilities and liquefied CO ２ the gas to be treated is introduced through an inlet for the gas to be treated and the gas to be treated is introduced through the inlet into the first CO ２ an inlet pipe leading to a separation facility; ２ The separation facility separates the rubber into CO ２ The second CO ２ The separation equipment separates CO from the gas to be treated by cryogenic separation. ２ a cryogenic separation device for separating CO ２ The purification equipment consists of pumps and liquefied CO ２ a purification device, ２ The purifier can extract CO2 in either a liquid, gas, or liquid and gas mixture. ２ From snowy CO ２ Liquefied CO ２ The liquefied CO is a CO purifying apparatus. ２ The refinery contains purified liquefied CO ２ The liquefied CO is introduced through a valve. ２ Liquefied CO supplied to the tank ２ supply piping and CO ２a first return gas pipe for supplying waste gas resulting from the liquefaction treatment to the absorption / separation device for retreatment, a purified gas supply pipe for supplying treated purified gas is connected to the absorption / separation device via a valve, and the CO 2 once absorbed by the rubber in the absorption / separation device is ２ an exhaust gas pipe for discharging a gas containing ２ a second return gas pipe for returning the gas treated in the cryogenic separation treatment, the concentration of which has been reduced, to the absorption / separation device; ２ The concentrated treated liquid is then liquefied CO ２ A CO purifier is connected to a supply pipe for the liquid to be treated, which supplies the liquid to the purification device via a pump. ２ (Configuration 13) The liquefied CO separation system. ２ The refinery is ２ a gas outlet; and a liquefied CO ２ A liquefied CO2 refrigerant having a heat insulating structure and an outlet ２ The treatment liquid supply facility includes a treatment liquid supply pipe, a treatment liquid supply opening / closing valve, a cooling device, and a CO ２ The treated liquid supply facility is provided with a jet nozzle, and the treated liquid supplied through the treated liquid supply pipe is cooled by the cooling device, and the treated liquid supply opening / closing valve is opened to cool the treated liquid. ２ The CO disposed in a purification vessel. ２ The liquefied CO ２ Snow-like CO in the refining vessel ２ The gas outlet is connected to an exhaust gas pipe via an on-off valve, and gaseous CO is sprayed from the exhaust gas pipe. ２ a gas containing the liquefied CO ２ At the outlet, liquefied CO ２ Liquefied CO2 is extracted through the valve. ２ An extraction pipe is connected to the liquefied CO ２A temperature adjustment device for heating is disposed adjacent to the outlet, and the liquefied CO ２ Snow-like CO generated and accumulated in the purification vessel ２ is liquid CO ２ The liquefied CO ２ 13. The CO according to claim 12, which can be taken out through a take-out pipe. ２ (Configuration 14) A CO separation system according to Configuration 12 or 13, wherein the introduction equipment comprises an introduction pipe that passes through an inlet for the gas to be treated, a first valve, a first buffer tank, a compressor, a dehydrator, and a second buffer tank, and reaches a switching valve provided in the at least one pair of absorption / separation apparatus, the first buffer tank being connected to the first reflux gas pipe, and the second buffer tank being connected to the second reflux gas pipe. ２ (Configuration 15) The CO separation system according to any one of Configurations 12 to 14, wherein the purified gas supply pipe is connected to a methane gas recovery tank. ２ (Configuration 16) The CO separation system of any one of configurations 1 to 15, wherein the rubber is provided in a state where pellets of different sizes are mixed. ２ (Configuration 17) The CO separation system of any one of configurations 1 to 15, wherein the rubber is provided in a rod shape. ２ 18. The CO separation system of claim 17, wherein the rubber is in the form of a hollow tube. ２ 19. The CO separation system of any one of claims 1 to 18, wherein the rubber is silicone rubber. ２ (Configuration 20) The cryogenic separation system includes a dehydration device that dehydrates a supplied gas, a cooling device that cools the gas introduced through the dehydration device, and a CO liquefied by the cooling. ２ and a device for discharging CO according to configuration 1 or 12. ２ Separation system.

[0008] According to the present invention, a medium concentration of CO 2 of 5 to 50% ２ Efficient CO2 emission reduction using low energy from combustion gases containing CO2, natural gas, etc. ２and CO to provide desired gases such as methane or reduced greenhouse gases. ２ A separation system is provided.

[0009] The CO of the present invention ２ FIG. 1 is a system configuration diagram showing the overall configuration of a separation system. ２ and CO ２ The first CO ２ FIG. 1 is a diagram showing the configuration of a separation facility. FIG. 2 is a diagram showing the configuration of an absorption tower. FIG. 3 is an explanatory diagram showing the connection structure of the absorption tower. ２ 1 is an explanatory diagram showing the shape of an absorbent material. ２ 1 is an explanatory diagram showing the arrangement of the absorbent material. ２ FIG. 1 is a diagram showing the configuration of a separation facility. ２ 1 is a characteristic diagram showing the absorption characteristics of CO using rubber. ２ 10 is a characteristic diagram showing the absorption characteristics of CO ２ FIG. 1 is a system configuration diagram showing the overall configuration of a separation system. ２ 1 is an explanatory diagram showing the configuration of a purification device. ２ 1 is a system configuration diagram showing the overall configuration of a separation system. ２ Liquefied CO in the treatment liquid by snow generation method ２ and N ２ The content of CO2 in the liquefied CO2 gas mixture was measured by gas chromatography. ２ FIG. 2 is an explanatory diagram showing the configuration of a refining device.

[0010] (Embodiment 1) In embodiment 1, the CO ２ The separation system 101 will be described with reference to FIG.

[0011] <Configuration> The CO of the present invention ２ The separation system 101 includes a first CO 2 separator having rubber as an absorbent material, as shown in FIG. ２ Separation equipment 1 and a second CO ２ Separation equipment 2, a treated gas supply pipe 3, a first pipe 4, and a high-concentration CO ２ Gas discharge equipment 42, gas reflux equipment 5, and liquefied CO ２ Discharge pipe 6 and CO２ and a treated gas discharge pipe 7.

[0012] CO ２ The separation system 101 may further include a pressure reducing facility 33 and / or a dehydration facility 34 as necessary for pre-treatment of the gas to be treated (gas to be treated). ２ Separation equipment 1 and second CO ２ The separation equipment 2 is connected to a temperature adjustment means 11 (an example of a "cooling means") and a temperature adjustment means 21 (an example of a "cooling means"), respectively, and is capable of efficiently and precisely adjusting the temperature, mainly by cooling. There are no particular restrictions on the temperature adjustment means 11 and 21, but examples thereof include vapor compression refrigerators, and there are no particular restrictions on the refrigerants, but examples thereof include fluorocarbons and CO ２ can be used.

[0013] The gas to be treated is methane, which is assumed to be biogas, with 30 to 50 mol% CO ２ and methane, which is assumed to be natural gas, containing 10 to 50 mol% CO. ２ and nitrogen gas (N ２ ) with 5 to 15 mol% CO ２ In this case, XX to △△ indicates a range from XX to △△. Considering the environment in which these gases are placed, methane in particular contains CO, which is easily liquefied in the gas to be treated. ２ In this state, CO can be efficiently separated by cryogenic separation methods. ２ To separate CO, low-temperature treatment below -60°C is required. ２ The energy efficiency of separation and recovery is significantly reduced. ２ and N ２ The phase diagram for a substance consisting of these is shown below. The lower left shows the gas state, the upper right shows the liquid state, and the center shows the liquid + gas state. The solid line shows the measured value, and the dashed line shows the predicted value by the calculation formula. Therefore, the inventors first tried to make a CO ２ Separation and recovery of methane, nitrogen, and CO ２The present invention has been developed to avoid the compatibility problem between nitrogen gas (N ２ ) with 5 to 50 mol% CO ２ If gas is mixed with CO, ２ Although the amount of CO2 varies, the same concept as when CO2 is mixed into methane gas can be applied.

[0014] The gas to be treated, such as natural gas, is supplied to the first CO ２ At this time, when the pressure of the gas to be treated is sufficiently high and / or when the gas contains a liquid material, the gas to be treated is decompressed through the pressure reducing equipment 33 to separate the first CO ２ When the gas to be treated contains a large amount of moisture, the gas to be treated is supplied to the separation equipment 1 through the dehydration equipment 34 as necessary. ２ It is supplied to a separation facility 1.

[0015] The pressure reducing facility 33 is a facility that is installed for the purpose of treating gas under high pressure of 60 MPa or more, such as when the gas is high-pressure gas that springs up from deep underground, and is composed of, for example, a choke and a temperature adjusting device. The temperature adjusting device is necessary to prevent the formation of methane hydrate when the gas contains water, for example, when the initial pressure is close to 120 MPa and rapid cooling by pressure reduction occurs. Furthermore, in the pressure reducing facility 33, water or condensate (liquid hydrocarbons) may be produced by cooling, and CO ２ Water and condensate can also be discharged from the pipes that discharge the gas. If the gas to be treated is natural gas, it is preferable to discharge the condensate, which is a valuable product.

[0016] The dehydration equipment 34 is a facility for removing moisture from the gas to be treated. Molecular sieves (zeolite, registered trademark), silica gel, activated carbon, activated alumina, ethylene glycol derivatives, and the like can be used as moisture removers. Dehydration equipment using silica gel or activated alumina, which can achieve a dew point of approximately -40°C, is particularly suitable. Water in the gas to be treated becomes almost liquid when the temperature is lowered, but the dehydration equipment 34 is used to remove moisture from the gas phase, which does not condense even at temperatures near room temperature. Although not shown, the dehydration equipment 34 may be equipped with, for example, a heater and a desorption steam cooler, which are connected by piping, to regenerate the moisture remover. For continuous operation, the dehydration equipment may include multiple absorption towers. For example, the dehydration equipment 34 is equipped when the gas to be treated is natural gas.

[0017] First CO ２ The separation facility 1 includes an absorption separation device (absorption tower) that uses rubber as an absorbent. As disclosed in Non-Patent Document 2, rubber is a CO ２ This material is expected to be a CO absorbent. ２ As shown in Fig. 3, the separation facility 1 includes, for example, at least a pair of absorption towers 12a and 12b. Each of the absorption towers 12a and 12b is controlled by a temperature control unit 11 to adjust the temperature of the CO ２ The temperatures are controlled to correspond to the absorption and separation steps.

[0018] As shown in FIG. 4 , the absorber 12 has, for example, pipes 17a and 17b at the top and bottom of its longitudinal direction. Optionally, a maintenance pipe 17c may be disposed on the side of the absorber 12 to improve maintainability. A plurality of rubber members 16 are housed inside the absorber 12. Here, the rubber members 16 are preferably rod-shaped, for example, as shown in FIG. 6 . The plurality of rubber members 16 are preferably arranged with their longitudinal direction aligned with the longitudinal direction of the absorber 12. Each rubber member 16 is preferably a columnar rubber member 16a, as illustrated in FIG. 6( a). FIG. 6( a) illustrates a case in which the columnar rubber member 16a is cylindrical. Alternatively, each rubber member 16 is preferably a hollow, tubular rubber member 16b, as illustrated in FIG. 6( b). The tubular rubber member 16b can also be said to have a through-hole along the x-direction. Gas can pass through the interior of the tubular rubber member 16b. 6B illustrates an example in which the tubular rubber 16b is cylindrical. In particular, the tubular rubber 16b is in frequent contact with the gas flowing around it, resulting in a large amount of CO ２ Since it can efficiently absorb gas, it is particularly preferred. On the other hand, columnar rubber 16a has the characteristics of being easy to reduce costs and maintain. Furthermore, as illustrated in FIG. 7 , two adjacent rubber pieces 16 among a plurality of rubber pieces 16 are preferably arranged with a gap 19 between them so that they do not come into contact with each other and a flow path through which gas flows in a laminar flow is secured. The gap 19 is provided over the entire length of the two adjacent rubber pieces 16. In other words, the gap 19 is a space through which gas flows along the longitudinal direction of the two rubber pieces 16. The distance of the gap 19 is expected to be, for example, 0.01 to 0.5 cm. Note that the distance of the gap 19 is the shortest distance between the outer peripheral surface of one rubber piece 16 and the outer peripheral surface of the other rubber piece 16 among the two adjacent rubber pieces 16. Note that the gap 19 may be secured using a jig 18 such as a spacer. A flow path is formed in the absorption tower to allow gas to flow while retaining it inside. This flow path is all the connected internal spaces of the absorption tower, and may be the gaps in the rubber 16a, the space inside the tube of the rubber 16b, or a connected space intentionally formed inside the absorption tower.

[0019] The effects of forming the rubber 16 in a rod shape include the following: First, it becomes easier to ensure a laminar gas flow path. Therefore, the filling rate of the absorbent material can be increased, and highly efficient CO ２ The advantages of this method are that it achieves gas absorption and desorption. Because it is a stable laminar flow, there is little instability associated with swelling of the rubber 16, and stable separation efficiency is always achieved. Secondly, the rod-shaped rubber 16 changes little over time, and high absorption and desorption efficiency can be achieved over a long period of time. On the other hand, when the absorbent material, which is commonly used in conventional methods, is in powder or pellet form, the initial absorption and desorption efficiency is high, but changes greatly over time, and the absorption and desorption efficiency decreases relatively quickly. Thirdly, the rod-shaped rubber 16 is easy to maintain, and the absorbent material can be replaced easily and quickly, and the replacement frequency is low. Furthermore, there is little contamination inside the device due to rubber replacement or deterioration over time, and there is little downtime for the device due to cleaning, etc.

[0020] The cross-sectional shape of the rubber 16 is not particularly limited, and examples include a circle, an ellipse, and a polygon. The cross-sectional shape of the rubber 16 is the shape formed by the periphery of the cross section in a plane perpendicular to the x-direction. However, rubber 16 having a circular cross-sectional shape (16a, 16b in FIG. 2) has the advantage of being easier to arrange and easier to maintain uniformity in the flow path through which gas flows, compared to rubber 16 having a cross-sectional shape other than a circle.

[0021] The thickness of the rubber 16 is 0.5 mm or more and 10 mm or less. When the thickness of the rubber 16 is within the above range, CO 2 is absorbed into the rubber from the gas flowing along the rubber 16 with sufficient efficiency. ２ If the thickness of the rubber 16 exceeds 10 mm, CO ２ Diffuse CO ２ If the thickness of the rubber is less than 0.5 mm, the rubber will not be able to stand upright due to insufficient rigidity, and maintenance will be impaired. From these viewpoints, the thickness of the rubber is more preferably 1 mm or more and 5 mm or less.

[0022] In the case of columnar rubber 16a, the thickness of rubber 16 refers to the width of the cross-sectional shape in a plane perpendicular to the longitudinal direction (x direction) of rubber 16. Here, the width of the cross-sectional shape refers to the length of the shortest line segment that passes through the center of the cross-sectional shape and connects two points on the periphery of the cross-sectional shape. Therefore, for example, in the case of cylindrical rubber 16a, the thickness of rubber 16 is the diameter, and in the case of elliptical cylindrical rubber 16a, the thickness of rubber 16 is the length of the minor axis.

[0023] On the other hand, in the case of the tubular rubber 16b, the thickness of the rubber 16 is the wall thickness (the length between the outer peripheral surface and the inner peripheral surface). Therefore, for example, in the case of the cylindrical rubber 16b, the thickness of the rubber 16 is the wall thickness ((outer diameter - inner diameter) / 2). The length of the rubber 16 is not particularly limited, but is assumed to be, for example, 40 to 2000 cm. In the tubular rubber 16b, from the viewpoint of ensuring a sufficient gas flow path, the cross-sectional area of ​​the through-hole (hollow portion) is, for example, 0.005 to 0.5 cm. ２ It is preferable that:

[0024] The spacing between adjacent rubber members 16 is preferably adjusted so that the packing rate of the rubber members 16 is 40% by volume or more and 90% by volume or less in the absorption tower 12. When the packing rate is within the above range, the gas flow flowing along the rubber members 16 becomes a laminar flow, and a sufficient amount of absorbent material is secured. As a result, the following rubber members can absorb CO with high efficiency. ２ From the above viewpoint, the filling rate of the rubber 16 in the absorber 12 is more preferably 60% by volume or more and 85% by volume or less.

[0025] CO ２ The rubber used as the absorbent material is one or more rubbers selected from the group consisting of silicone rubber, acrylonitrile butadiene rubber, styrene butadiene rubber, and urethane rubber, and silicone rubber is particularly preferred. Silicone rubber has a large market, is inexpensive, and many tubular and cylindrical products are sold. It is easy to process, and it is a CO ２ It has the characteristics of absorbing a large amount of water, having a high absorption / desorption rate, and being highly durable.

[0026] A crosslinked product of PDMS (PolyDiMethylSiloxane), a type of silicone rubber, is particularly preferred. The crosslinking method preferably uses a radical crosslinking agent or a method of crosslinking multiple vinyl groups in the PDMS molecule by hydrosilation. The latter method usually uses a platinum catalyst. Furthermore, considering the cost and resource recycling, CO ２ It is also preferable to use recycled rubber such as waste tires as the rubber for the absorbent material. The glass transition temperature of the rubber is preferably -150°C or higher and -10°C or lower. The SP value of the rubber at room temperature is 7.0 (cal / cm ３ ) ０．５ More than 10.0 (cal / cm ３ ) ０．５ The elastic modulus of the rubber at 25°C is preferably 0.03 MPa or more and 8 MPa or less. Rubbers meeting these conditions have high CO ２ It has an absorption capacity and an absorption / desorption efficiency. The glass transition temperature can be determined by dynamic viscoelasticity measurement. The SP value at room temperature (25°C) can be determined from various databases. The elastic modulus at 25°C can be determined by a tensile test.

[0027] The SP value at room temperature is 10.5 (cal / cm ３ ) ０．５ The following rubbers are generally hydrophobic, but some of them are prone to absorbing water. In such cases, making the rubber hydrophobic allows CO ２ At temperatures below freezing, water is easily absorbed into the rubber's interface and voids, and even a small amount of water can easily reduce the absorption capacity. In such cases, it is a good idea to have the rubber absorb hydrophobic molecules such as decane. This will suppress water absorption and reduce CO ２ The contact angle of water on the surface of the rubber absorbent material is sufficient if it is 80° or more and 150° or less. The SP value of the rubber at room temperature is ２ It is important that the SP value is close to that of CO ２ It is known that the SP value of rubber increases with decreasing temperature. The SP value of rubber also increases with decreasing temperature, but the increase in the SP value of PDMS rubber is due to the CO ２Therefore, in the range of -20°C to -40°C, a rubber with a slightly larger SP value than PDMS rubber is desirable. Such a rubber can be one in which the methyl groups in the PDMS rubber molecule are replaced with phenyl groups or the like. Here, the CO ２ The desorption of CO can be achieved by reducing the pressure, and since there is no need for heating, it is characterized by low energy consumption. In addition to or instead of the rubber rods, rubber pellets can also be used. It is also effective to mix aluminum pellets as a specific heat adjuster in addition to the rubber rods. In the case of rubber pellets, CO ２ If the absorption amount becomes too large, the gas flow paths between the pellets may be blocked due to swelling. In such cases, it is advisable to use a metal twisted wire or a metal mesh together to secure the flow paths. ２ To increase the absorption rate, a mixture of pellets of different sizes may be used.

[0028] As shown in FIG. ２ In order to improve the absorption amount and separation efficiency, it is also preferable to use, for example, a plurality of (three in FIG. 5) absorption towers 12_1, 12_2, and 12_3 connected in series.

[0029] The absorption towers 12a and 12b are connected to switching valves 13, 14 and 15. ２ The switching valve 13 is connected to the treated gas supply pipe 3 via a valve 31. The switching valve 14 is connected to the first pipe 4 via a valve 41. The switching valve 15 is connected to the CO ２ The treated gas supply pipe 3 is a pipe for supplying the treated gas to the absorption tower 12. The first pipe 4 is a pipe for supplying the CO ２ High concentration CO absorbed in the recovery absorbent ２ This is a pipe for recovering CO ２ The treated gas discharge pipe 7 discharges CO ２ This is a pipe for discharging gas after it has been absorbed.

[0030] The gas to be treated supplied from the gas to be treated supply pipe 3 is switched to be introduced into either the absorption tower 12a or 12b via the valve 31 and the switching valve 13. On the other hand, the gas supplied through the second pipe 51 described later is switched to be introduced into either the absorption tower 12a or 12b by switching the switching valves 13, 14, and 15. ２ Absorption operation, the other CO ２ As can be understood from the above explanation, the treated gas supply pipe 3 is operated in the first CO ２ It is connected to the separation equipment 1 via a valve 31 and functions as an element for supplying the gas to be treated to the absorption tower 12 (absorption separation device).

[0031] CO ２ A specific example of the absorption / desorption method is as follows: The switching valve 13 is opened to the absorber 12a side and closed to the absorber 12b side, the switching valve 14 is closed to the absorber 12a side and opened to the absorber 12b side, and the switching valve 15 is opened to the absorber 12a side and closed to the absorber 12b side, so that the absorber 12a is supplied with CO ２ Absorption operation, absorption tower 12b is CO ２ Thereafter, the switching valve 13 is closed to the absorber 12a side and opened to the absorber 12b side, the switching valve 14 is opened to the absorber 12a side and closed to the absorber 12b side, and the switching valve 15 is closed to the absorber 12a side and opened to the absorber 12b side, so that the absorber 12a is in CO ２ Desorption operation, absorption tower 12b is CO ２ This process is then repeated to ２ Here, the absorption and desorption are controlled by pressure. The absorption tower 12a or 12b is insulated, but it is preferable to use a temperature control means 11 for pre-cooling and maintaining a low temperature. Here, the temperature inside the absorption tower 12 during absorption is preferably −60° C. or higher and 0° C. or lower, and more preferably −40° C. or higher and −20° C. or lower. By controlling the temperature inside the absorption tower 12 within this range, it is possible to reduce the CO 2 during desorption. ２ When the temperature inside the absorption tower 12 is −50° C. or lower, some of the CO 2 is solidified during desorption. ２In such cases, the desorption pressure is set to CO ２ It is necessary to set the pressure below the sublimation pressure.

[0032] The switching of the absorption and desorption of the absorber 12a and 12b (switching of the valves 13, 14, and 15) is performed to ２ It is preferable to do this based on the gas breakthrough time characteristics. ２ Concentration (C / C ０ It is preferable to switch the valves at the timing when the temperature of the absorber 12a rises, and switch between absorption and desorption in the absorption towers 12a and 12b. By switching between absorption and desorption at this timing, the absorption and desorption efficiency can be maximized. ０ is CO ２ The initial concentrations are shown.

[0033] CO in the absorption towers 12a and 12b ２ The pressure during absorption is preferably adjusted to 2 MPa or more and 10 MPa or less. ２ The amount of absorption depends on the pressure, and the higher the pressure, the greater the amount of absorption. Below 2 MPa, the amount of absorption is small, and CO ２ This is not very preferable from the viewpoint of absorption treatment efficiency. On the other hand, if the pressure exceeds 10 MPa, it becomes difficult to maintain the pressure resistance of the absorption tower.

[0034] The gas desorbed from the absorption tower 12a or 12b is a low CO ２ The treated gas (CO ２ Treated gas) and higher CO ２ High concentration of CO ２ CO ２ The treated gas is passed through valve 71 and CO ２ Treated gas exhaust pipe 7 ２ The treated gas is discharged from the treated gas discharge facility. ２ The treated gas discharge pipe 7 is connected to the absorption separation device (absorption tower 12) via a valve 71. ２It is preferable to provide a check valve 72 for preventing backflow and adjusting the flow rate in the treated gas exhaust pipe 7. The check valve 72 can prevent gas from flowing in from the outside and also can prevent CO ２ The pressure of the gas in the treated gas discharge pipe 7 is ２ The flow rate can be adjusted so that it is slightly lower than the pressure during absorption, ensuring the gas residence time in the absorption tower. ２ Treated gas (CO ２ The removed gas) is CO ２ Since the concentration of CO is low, the gas will not freeze and clog even in polar regions, and it can be delivered to the consumer through a pipeline. Although not shown in Figure 1, a buffer tank is provided between the valve 71 and the check valve 72 to prevent CO ２ A part of the treated gas is returned to the absorption tower 12a or 12b, and the remaining CO ２ The concentration may be decreased or the pressure in the absorber 12a or 12b may be increased to a predetermined value. ２ CO in the treated gas ２ This makes it possible to further reduce the concentration.

[0035] Here, the CO in the gas introduced into the absorption towers 12a and 12b ２ The concentration of CO in the gas to be treated ２ The concentration is 5 mol% or more and 50 mol% or less, but CO ２ CO emitted from treated gas discharge facility ２ CO in the treated gas ２ The concentration is preferably adjusted to 2 mol % or more and 10 mol % or less. ２ If the concentration of the treated gas is adjusted to this range, corrosion prevention effects can be obtained when transporting it through a pipeline. ２ CO emitted from treated gas discharge facility ２It is more preferable that the concentration is adjusted to 0.5 mol % or more and 2 mol % or less. When the concentration is adjusted to this range, a large greenhouse gas reduction effect can be obtained in the case of nitrogen gas, and the range of industrial use can be expanded in the case of methane gas.

[0036] The absorption / separation apparatus includes a first absorption tower group consisting of one or more absorption towers 12a and a second absorption tower group consisting of one or more absorption towers 12b. The absorption towers 12a and 12b have a flow path for allowing the gas to flow while retaining it therein, and a CO ２ A configuration including rubber as an absorbent is also preferred. The first and second absorber groups are preferably paired absorber groups having the same configuration. ２ When desorption operation is performed, the other ２ It will be absorbed and put into operation.

[0037] High concentration CO ２ The gas is supplied through valve 41, high concentration CO ２ The second CO 2 is discharged through the gas discharge equipment (compressor) 42 and the first pipe 4. ２ The CO2 is then sent to the separation facility 2 for processing. ２ The gas discharged from the separation equipment 1 is ２ It serves as a component for supplying the separation facility 2. ２ sent to separation facility 2 (i.e., high-concentration CO ２ High concentration CO2 discharged from gas discharge equipment 42 ２ Gas CO ２ The concentration of high concentration CO is preferably 40 mol % or more and 80 mol % or less. ２ When the gas is adjusted to a concentration in this range, CO ２ This adjustment of the concentration is achieved by reducing the CO 2 concentration in the absorber towers 12a and 12b. ２ It can be adjusted by the temperature and pressure during absorption.

[0038] Here, high concentration CO ２ The gas is then mixed with the second CO ２The treatment in the separation facility 2 is extremely important for increasing the recovery rate of desired gases such as methane. ２ These CO ２ The absorbent is surrounded by a desired gas, such as gaseous methane at high pressure. ２ When gas is discharged, the desired gas is also discharged, and if this gas is discarded, it will result in a loss of the desired gas.

[0039] Second CO ２ The separation equipment 2 may be a cryogenic separation device that is commonly used, as disclosed in Patent Document 1 and Non-Patent Documents 3 and 4. ２ As shown in FIG. 8, the separation equipment 2 includes a temperature adjusting means 21, a dehydration device 23, a cooling device 24, and a liquefied CO ２ The apparatus is provided with a discharge device 25. Note that the dewatering device 23 may be unnecessary if sufficient dewatering is performed by the dewatering equipment 34.

[0040] First CO ２ High-concentration CO2 treated and generated in separation facility 1 ２ The gas is transported to the dehydration device 23 via the first pipe 4. The pressure here is, for example, 2 MPa or more and 10 MPa or less. The dehydration device 23 performs a dry gasification process to remove moisture from the compressed gas. As a dehydration method, a method using silica gel or zeolite is excellent. Here, it is preferable that the amount of water contained in the dehydrated dry gas is controlled to 10 ppm or less. Note that dehydration using silica gel is preferably carried out at 30°C or less, since the absorption capacity decreases at high temperatures. The dehydrated gas is supplied to the cooling device 24 via the pipe 27. Here, the cooling device 24 is not particularly limited, but it may be, for example, a CO ２ The cooling device 24 cools the supplied gas to a temperature between -60°C and 0°C. ２ is supplied with liquefied CO via a pipe 28. ２ The liquefied CO is transported to the discharge device 25 and discharged through the discharge pipe 51b. ２ The discharge device 25 discharges liquid CO ２It is necessary to cool it by the temperature adjusting means 21 in the same manner as the cooling device 24. ２ The gas containing CO is supplied to the first CO ２ It is fed to a separation facility.

[0041] The gas reflux facility 5 is a second CO ２ The gas treated in the separation equipment 2 is separated into a first CO ２ The gas reflux facility 5 is a facility for increasing the recovery rate of desired gases such as methane by refluxing the gas to the separation facility 1. As shown in FIG. ２ Gas exhaust route and high concentration CO ２ The gas exhaust path, the reflux gas exhaust device 58, and the second piping 51 for reflux are provided.

[0042] low concentration CO ２ The gas exhaust path includes, for example, a valve 56 and a pipe 51a. ２ The gas containing the above is led through a pipe 51 a via a valve 56 to a reflux gas discharge device 58 consisting of a compressor.

[0043] High concentration CO ２ The gas exhaust route is liquid CO ２ High concentration CO ２ This is equipment for guiding the gas to the reflux gas discharge device 58, and includes, for example, a pipe 51b, a valve 52, a flash tower 53, a valve 54, and a pipe 51c. ２ and other condensable gases in liquid form are separated in a flash tower 53, the processing temperature of which is controlled by a temperature adjustment means 59 (an example of a "cooling means"), and liquefied CO2 is separated via a valve 61. ２ The low-concentration CO ２ In the gas exhaust path, a check valve 57 equipped with a flow rate adjusting mechanism is provided in the middle of the pipe 51a. ２ In the gas exhaust path, it is preferable to provide a check valve 55 equipped with a flow rate adjusting mechanism in the middle of the pipe 51c. In the gas recirculation facility 5, the gas discharged from the recirculation gas exhaust device 58 is returned to the first CO ２ It is returned to the separation facility 1.

[0044] As can be understood from the above description, the reflux gas exhaust device 58 ２ CO having a lower concentration than the concentration in the first pipe 4 is discharged from the separation equipment 2. ２ The gas containing CO is discharged from the flash tower 53. ２ In this embodiment, the second pipe 51, the flash tower 53, and the low-concentration CO ２ The flash tower 53 and the reflux gas discharge device 58 constitute the gas reflux facility 5. ２ Separation equipment 2), liquefied CO ２ It is connected to the exhaust pipe 6 and the reflux gas exhaust device 58 via valves (52, 61, 54), respectively.

[0045] After conducting various experiments, it was found that the breakthrough time per absorber 12 is between 5 minutes and 120 minutes. ２ In this case, the gap between the rubber particles is large, and the pressure during absorption is high, between 2 MPa and 10 MPa, so that desired gases such as methane are easily trapped there. ２ The separation equipment 1 alone can cause a problem that the recovery rate of the desired gas is likely to decrease. To solve this problem, the present invention provides a first CO ２ The separation equipment 1 and the gas reflux device having the reflux gas discharge device (compressor) 58 and the second pipe 51 are provided, and a mixed gas containing a desired gas such as methane is recycled to the first CO ２ The recovery rate of the desired gas is increased by reprocessing using an absorption separation device, which is the separation facility 1. This process increases the recovery rate of the desired gas to, for example, 90% or more.

[0046] CO2 absorber using rubber ２ The separation system is ２ This method is characterized by the fact that it can separate the desired gases and requires less energy than the chemical absorption method using an amine solvent. Furthermore, the gas reflux device allows for a high recovery rate of the desired gas.

[0047] In addition, the first CO２ The temperature of the absorption tower 12 of the separation equipment 1 is ２ There is no problem even if the temperature is lower than that of the cryogenic separation device of the separation equipment 2. ２ In the separation facility, the second CO ２ Compared to separation equipment, CO in the gas ２ The concentration is low, and CO ２ This is because the solidification of CO in the absorption tower is difficult to occur at low temperatures. ２ The separation efficiency is higher.

[0048] Using the equipment of this embodiment, CO ２ When a mixed gas containing nitrogen at a concentration of approximately 30 mol% was treated, CO was efficiently produced with low energy consumption. ２ and CO ２ It was confirmed that nitrogen gas with a CO content of 2% or less could be efficiently obtained. ２ The separation system is a methane / CO ２ Since it can also be applied to mixed gases, it can be said that it will make it possible to transport natural gas extracted in polar regions by pipeline. Biogas also generally contains high concentrations of CO ２ Since it contains ２ Separation systems are also useful for treating biogas.

[0049] (Embodiment 2) In embodiment 2, similar to embodiment 1, ２ Medium concentration CO of 5-50% ２ Efficiently extract CO from the gas to be treated using low energy ２ It is possible to separate the recovered CO to supply a desired gas such as methane or a gas with reduced greenhouse gases. ２ However, liquefied CO with a purity of 99.99% or more ２ It is also possible to set the CO ２ The separation system 102 will now be described.

[0050] Liquefied CO with a purity of 99.99% or higher ２ is liquefied CO ２ It can be transported by a tank truck (the transport standard is liquefied CO2 with a purity of 99.9% or more).２ Therefore, recovered liquefied CO with a purity of 99.99% or more ２ The range of applications is extremely wide and the cost-effectiveness is also high. For example, the recovery and liquefaction of CO ２ It is expected to be used in industrial applications such as shielding gas for welding, agricultural applications such as greenhouse cultivation in high carbon dioxide gas environments and plant factories, drinking purposes, food preservation, dry ice production, medical applications, etc. In addition, it is expected to be used in high purity CO of 99.99% or more. ２ The production of hydrogen is carried out not only in the biogas purification process but also in the shift reaction product gas (usually 1-5 MPa, CO ２ It can also be applied to the refining process from CO2 (concentration of about 25% and hydrogen concentration of about 75%) and the exhaust gas from thermal power plants. ２ The recovery of this material will have an extremely large industrial impact.

[0051] CO ２ As shown in FIG. 11, the separation system 102 is a CO ２ In the separation system 101, the flash tower 53 liquefies CO ２ Replacing the purification facility 251, ２ Liquefied CO is discharged from the discharge pipe 6. ２ The tank 254 is equipped with the liquefied CO ２ The purification equipment 251 includes a pump 252 and a liquefied CO ２ A facility consisting of a purification unit 253 that extracts CO2 in either a liquid, gas, or liquid and gas mixture. ２ From snowy CO ２ Liquefied CO ２ Here, the snow-state CO ２ is microcrystalline CO ２ It refers to a form in which particles gather together like snow.

[0052] liquefied CO ２ As shown in FIG. 12, the purification device 253 is, for example, a CO ２ a gas outlet 232; and a liquefied CO ２ A liquefied CO2 evaporator having a heat insulating structure and an outlet 233 ２The apparatus includes one or more pairs of purification vessels (hereinafter referred to as thermally insulated vessels) 201. The treated liquid supply equipment 231 is located, for example, at the upper part of the thermally insulated vessel 201. Specifically, the treated liquid supply equipment 231 includes, for example, treated liquid supply pipes 207 and 205, a treated liquid supply opening / closing valve 203, a cooling device (pre-cooling device) 204, and a CO ２ Specifically, the treated liquid supply facility 231 cools the treated liquid supplied through the treated liquid supply pipe 207 by the preliminary cooling device 204 as needed, and opens the treated liquid supply opening / closing valve 203 to circulate the CO 2 contained in the heat-insulating container 201. ２ Snow-like CO 2 is ejected from the ejection nozzle 202 into the heat-insulating container 201. ２ The gas outlet 232 is located, for example, at the upper side of the heat-insulating container 201. An exhaust gas pipe 214 is connected to the gas outlet 232 via a pressure-reducing pressure adjustment valve 212 and an open / close valve 211. Gaseous CO is sprayed from the exhaust gas pipe 214. ２ The gas containing liquefied CO is discharged and the pressure is adjusted. Here, the exhaust gas pipe 214 is connected to a pipe 51c that is connected to the gas recirculation equipment 5. ２ The outlet 233 is located, for example, on the lower side of the heat-insulating container 201. ２ The outlet 233 is for liquefied CO ２ Liquefied CO via the withdrawal valve 222 ２ The extraction pipe 223 is connected. ２ A temperature adjustment device (heating device) 221 for heating is disposed adjacent to the outlet 233. The heating device 221 heats the CO2 in a snow state that is generated and accumulated in the insulated container 201. ２ is liquid CO ２ Liquefied CO ２ Extraction pipe 223 and liquefied CO ２ The liquefied CO flows through the discharge pipe 225. ２ It is configured so that it can be removed from the tank 254 and recovered.

[0053] The operation involves first liquefying CO containing about 35% methane in a cryogenic separator (5 MPa, around -60°C).２ liquefied CO ２ The liquefied CO ２ In the purification equipment 251, pre-cooling is performed using the cooling device 204 as needed. ２ / CH ４ In the case of methane (CH ４ ) containing CO ２ The treatment can be carried out to a degree that does not solidify. ２ / N ２ In the case of CO ２ However, since it tends to solidify, it is best to liquefy it at a temperature of -55°C or higher.

[0054] Liquid CO containing 35% methane at 5 MPa ２ The solidification temperature of liquid CO is around -70°C. ２ This is effective in reducing the enthalpy of pre-cooled liquid CO. ２ is sprayed forcefully from the nozzle 202 through the on-off valve 203 for supplying the liquid to be treated in a spray form. ２ The temperature of the mixed gas drops due to the heat of vaporization. ２ solidifies and becomes snow-like CO ２ Snow CO ２ Snow CO ２ Liquefied CO during production ２ The pressure in the refining device 253 is adjusted to a range of 2 MPa or less and 0.1 MPa or more. This pressure adjustment is performed by controlling the amount of gas discharged from the gas outlet.

[0055] CO ２ The heat of vaporization of CO is 347.9 kJ / kg at -55°C. ２ The enthalpy of the liquid is only 83.1 kJ / kg. At -70°C, CO ２ The enthalpy of the liquid is about 5.5 times the heat of vaporization. ２ The heat is absorbed by the large heat of vaporization, and the cold energy is converted into CO ２ The heat of vaporization of methane is also used for solidification. ２It is used as cold energy for solidification. Physicochemical estimations show that liquid CO at -70°C contains 35% methane. ２ Then, due to adiabatic expansion, 90% of CO ２ It becomes possible to solidify.

[0056] CO ２ The solidification efficiency is ２ In the second embodiment, the pressure of the cryogenic separation device is high at around 5 MPa, and the temperature is cooled to around -60°C. ２ CO in the purification facility 251 ２ The solidification efficiency is very good.

[0057] Snow CO ２ After the formation of the snow CO , the pressure-reducing valve 212 is closed to stop the discharge of gas from the gas outlet 232. At the same time, the heater 221 disposed at the bottom of the heat-insulating container 201 is operated to heat the snow CO . ２ Liquefied CO ２ The solid phase (snow CO ２ ) is CO ２ The purity of liquefied CO can be considered to be 100%. ２ The gas phase of the purification unit 253 contains methane and CO ２ and liquefied CO ２ A small amount of methane is also present in the liquid phase. The gas is discharged from the gas discharge port 232 until the methane in the liquid phase reaches a desired concentration. ２ CO inside ２ The concentration becomes 99.9%, and at that time, 9 times the weight of snow CO ２ If any remains, dissolving it will produce 99.99% liquid CO ２ is obtained.

[0058] Highly purified liquid CO ２ is liquefied CO ２ The liquefied CO is taken out from the outlet 233. ２ Extraction pipe 223 and liquefied CO ２ Liquefied CO is discharged through the discharge pipe 225. ２The CO is stored and recovered in a tank 254. Through the above process, a highly pure liquid CO of 99.99% or more can be produced with extremely high energy efficiency. ２ It is possible to extract the

[0059] Here, liquefied CO ２ 12, the purification device 253 is preferably provided with a pair of identical heat-insulating containers 201. In this way, by switching between the switching valves 206 and 224, snow CO 2 is generated in one of the heat-insulating containers 201. ２ The other insulated container 201 is used to generate snow CO ２ Liquefied CO ２ In the configuration having a pair of heat-insulating containers 201, the liquefied CO 2 having one of the heat-insulating containers 201 can be efficiently generated and extracted. ２ High purity liquefied CO2 is produced using the purification device 253a and the other 253b having the insulated vessel 201. ２ When manufacturing Snow CO ２ The time required to generate snow CO ２ and liquefied CO ２ It is desirable to make the time required for the discharge of the

[0060] liquefied CO ２ The purification device 253 can be continuously operated using one insulated container 201 instead of a pair of insulated containers 201. In this case, snow CO ２ Generation and Snow CO ２ Liquefied CO ２ and liquefied CO ２ The snow CO is removed at the same time. ２ Liquefied CO ２ In the production of snow CO ２ Since a part of the CO in the gas phase in the heat insulating container 201 is vaporized, ２ The partial pressure becomes high and the liquefied CO ２ On the other hand, continuous operation reduces the purification efficiency of liquefied CO ２ The production rate of liquefied CO can be increased. ２ The refining device 253 can be made compact.

[0061] Liquefied CO for continuous operation ２ The purification device 501 may be, for example, the device shown in Figure 15. ２ The purification device 501 includes a housing 511, a supply pipe 512 for the liquid to be treated, a valve 513, a cooling device 514, an adiabatic expansion treatment unit 515, a heater-integrated mesh 519, and a liquefied CO ２ It includes a discharge pipe 6, a valve 61, a pipe 541, a flow control mechanism 542, a pipe 543, and a flow control mechanism 544.

[0062] CO introduced from the treated liquid supply pipe 512 ２ The liquid to be treated containing CO is treated in the housing 511 and then liquefied CO ２ Liquefied CO purified to a desired purity is discharged from the discharge pipe 6. ２ The exhaust gas is taken out as reflux gas 552 through a pipe 51c and treated via a reflux gas discharge device 58 (not shown in FIG. 15). ２ A feature of the purification device 501 is that it is divided into an upper chamber 531 and a lower chamber 532 by a heater-embedded mesh 519. The upper chamber 531 is equipped with an exhaust gas discharge pipe 541 and a flow control mechanism (flow control valve or pump) 542 for adjusting the flow rate. The lower chamber 532 is equipped with an exhaust gas discharge pipe 543 and a flow control mechanism (flow control valve or pump) 544 for adjusting the differential pressure. Reflux gas 552 is discharged via the exhaust gas discharge pipe 541 and the flow control mechanism 542.

[0063] The gas is adjusted to an appropriate temperature by the cooling device 514, and is adiabatically expanded and sprayed by the treated liquid supply pipe 512 equipped with a nozzle. ２ 517 falls and accumulates on the heater-integrated mesh 519. As a result, snow-like CO 2 falls on the heater-integrated mesh 519. ２ A reservoir 520 is formed. In the upper chamber 531, sublimed CO ２ Gas 521 and blown-back gas 518 are generated. Meanwhile, snow-like CO 2 is generated on the mesh (heater-embedded mesh 519) heated by the heater. ２ It dissolves and CO ２The liquid CO falls as droplets 522 and deposits on the bottom of the housing 511. ２ The pressure in the pipe 543 is lowered below the pressure in the pipe 541, and the CO ２ The dripping of the droplets 522 is promoted, and the CO ２ Gases other than CH ４ This reduces the amount of liquefied CO2 produced. ２ This can contribute to improving the production efficiency and purity of the product.

[0064] CO according to the second embodiment ２ As with the first embodiment, the separation system is capable of obtaining desired gases such as methane with extremely high energy efficiency, and also produces liquid CO with a purity of 99.99% or more, which can be transported by tanker truck. ２ Furthermore, this method has the advantage of being able to recover the energy required for recovery.

[0065] In addition, Snow CO ２ High-purity liquefied CO ２ The advantages of this method for obtaining high-purity liquefied CO ２ It is known that solidification generally results in a high purity state. ２ However, the production of dry ice is one example of the solidification of CO. ２ If the exhaust gas contains methane, repeating the process of pressurizing and liquefying it in the recompression step will increase the partial pressure of the methane, resulting in the formation of solid CO ２ Leakage occurs when CO is extracted. ２ High purity CO is obtained by separating methane, which is highly compatible with ２ When extracting CO₂, it is necessary to separate the gas from the gas and liquid phases, but in general, this separation efficiency is not high. On the other hand, in the second embodiment, the methane concentration in the gas phase is reduced by using a rubber absorbent, and the liquid CO₂ is extracted at a temperature close to the solidification temperature. ２ Efficiently converts CO ２ By forming snow, high-purity liquefied CO is produced while reducing energy consumption. ２ is obtained.

[0066] Third Embodiment In a third embodiment, based on the second embodiment, a method for further improving the manufacturing stability and the tolerance of manufacturing conditions will be described.

[0067] CO of the third embodiment ２ The configuration of the separation system is as follows: ２ As shown in FIG. 13, the separation system 103 separates a desired gas, such as methane gas, from CO ２ a gas introduction facility for the gas to be treated, and a first CO ２ Separation equipment 301 and second CO ２ Separation equipment 302, pump 325 and liquefied CO ２ Liquefied CO2 with purification device 304 ２ Refining facilities and liquefied CO ２ 13, hydrogen gas (H 2 O 3 ) produced by the shift reaction is used as the desired gas such as methane gas. ２ ) is explained.

[0068] Here, the introduction equipment for the gas to be treated includes, for example, an inlet for the gas to be treated, and a first CO ２ and an inlet pipe (e.g., inlet pipes 316 and 318) leading to the separation equipment 301. ２ Separation equipment 301 separates rubber into CO ２ The system is equipped with at least one pair of absorption / separation devices (absorption towers) as absorbents. ２ The separation equipment 302 separates CO from the gas to be treated by cryogenic separation. ２ It is equipped with a cryogenic separation device (cryogenic separation tower) that separates

[0069] liquefied CO ２ The purification facility includes, as previously mentioned, pump 325 and liquefied CO ２ The purification unit 304 is provided. ２ The refining device 304 includes, for example, a liquefied CO ２ The same configuration as the purification device 253 (FIG. 12) is adopted. ２ The purifier 304 can be used to purify CO2 in either a liquid, gas, or liquid and gas mixture. ２From snowy CO ２ Purified liquefied CO ２ This is a device that produces liquefied CO ２ The purification unit 304 is a unit for purifying purified liquefied CO ２ liquefied CO through a valve (not shown) ２ Liquefied CO supplied to tank 305 ２ supply pipe 327 and CO ２ Waste gas from the liquefaction process is treated as a first CO ２ The first reflux gas pipe 331 is connected to the separation facility 301 to supply the gas for reprocessing to the absorption separation unit in the separation facility 301. The first reflux gas pipe 331 is equipped with pressure regulating valves 328 and 329 and a compressor 330.

[0070] First CO ２ A purified gas supply pipe 320 for supplying treated purified gas is connected to the absorption separation device (absorption tower) in the separation facility 301 via a switching valve 319. The purified gas supply pipe 320 supplies methane gas or the like (H ２ The purified gas after treatment is stored in the recovery tank 303 via a purified gas supply pipe 320. In addition, the CO ２ The exhaust gas pipe 322 for discharging the gas containing the second CO is supplied to the exhaust gas pipe 322 via the switching valve 321 and the compressor 323. ２ It is connected to the inlet of the cryogenic separation device in the separation facility 302 .

[0071] Second CO ２ The cryogenic separation device in the separation facility 302 contains CO 2 ２ The gas treated by the cryogenic separation treatment, whose concentration has been reduced, is treated with a first CO ２ a second return gas pipe 324 for returning the CO ２ The concentrated treated liquid is then liquefied CO ２ A supply pipe 326 for supplying the liquid to be treated to the purification device 304 via a pump 325 is connected to the purification device 304 .

[0072] The treated gas introduction equipment comprises a treated gas introduction pipe 316 that passes through a treated gas inlet, a first valve 311, a first buffer tank 312, a compressor 313, a dehydrator 314, and a second buffer tank 315, and reaches a switching valve 317 provided in one or more of the absorption / separation units. The treated gas inlet is, for example, the inlet of the pipe connected to the first valve 311 (the pipe connected on the opposite side of the first buffer tank 312). A first reflux gas pipe 331 is connected to the first buffer tank 312, and a second reflux gas pipe 324 is connected to the second buffer tank 315. The first buffer tank 312 and the second buffer tank 315 serve to stabilize the amount of gas introduced into the compressor and the absorption tower. The compressor 313 increases the pressure of the treated gas to about 5 MPa. This increases the first CO ２ The absorption separation device in the separation facility 301 uses rubber as an absorbent, and high CO ２ The dehydration device 314 plays a role in preventing ice accumulation inside the absorption tower and the cryogenic separation tower. The first reflux gas pipe 331 and the second reflux gas pipe 324 return the treated gas such as methane and the unrecovered CO ２ is reprocessed, thereby improving the recovery rate. It is also preferable that the facility for introducing the gas to be treated also be equipped with a desulfurization device (not shown) and a pre-cooling device using a heat exchanger (not shown) as needed. As for the locations where they are installed, the desulfurization device is preferably installed between the inlet for the gas to be treated and the first valve 311, and the pre-cooling device is preferably installed between the compressor 313 and the dehydration device 314, the former being preferable for maintenance reasons and the latter for dehydration efficiency reasons.

[0073] The absorbent material housed in the absorption tower is preferably provided in a rod shape, as described in embodiment 1. Furthermore, the rod shape is preferably a hollow tube shape, as described in embodiment 1.

[0074] It is also preferable that the rubber is provided in a state where pellets of different sizes are mixed. Pellets have the advantage of being easy to handle and easy to maintain. Pellets do not increase the filling rate of rubber, and CO ２ The dead volume in the absorber increases, ２ Although purification efficiency tends to decrease, by mixing pellets of various sizes, the dead volume can be reduced and sufficient CO ２ The size of each pellet is, for example, 0.125 mm. ３ Over 0.125cm ３ The following is assumed: Here, it is also preferable to change the mixing ratio of different pellets so that the rubber filling rate increases from the inlet to the outlet of the absorption tower. ２ Near the entrance of the absorption tower, ２ The contact time with gas containing CO is long, ２ On the other hand, the amount of CO ２ Near the outlet of the absorption tower, CO ２ The contact time with gas containing CO is short. ２ Because it comes into contact with gases with low CO concentration, ２ The amount of absorption will decrease. For this reason, it is also preferable to change the mixing ratio of different pellets so that the rubber filling rate increases from the inlet to the outlet. For the same reasons as explained in the first embodiment, silicone rubber is preferable as the rubber, and it is preferable to use a metal strand or a metal mesh together to ensure a flow path within the absorption tower.

[0075] Example 1 In Example 1, a CO2 film was formed using silicone made of PDMS. ２ Contamination N ２ The gas absorption characteristics were investigated. 105 g of silicone rods made of PDMS with a diameter of 2 mm and a length of 400 mm were bundled and placed in an absorption tower with a packing ratio of 66%. Then, a 70% molar ratio N ２ and 30% CO ２The gas consisting of was flowed at a flow rate of 192 sccm to examine the breakthrough characteristics. The results are shown in Figure 9. The temperature was -30°C. The results of monitoring the pressure on the in-side and out-side are shown in Figure 10. The data on the in-side and out-side are almost identical, and no significant difference in pressure was observed. The pressure decreases linearly until the breakthrough characteristics begin to saturate, and it can be seen that this is the characteristic. Table 1 shows the results of CO2 absorption of a 2 mm powder-like absorbent material made of PDMS and a 2 mm rod-like absorbent material, respectively. ２ Fill the absorber with CO ２ The results of the absorption and separation of the former and the latter were summarized. The loading rate of the former was 43% and that of the latter was 66%.

[0076]

[0077] (Example 2) In Example 2, CO ２ Contamination N ２ The liquid phase composition and purity were investigated when liquefaction and snow formation processes were carried out using mixed gases. First, a cryogenic separation tower was used to separate a 30% molar CO mixture at 5 MPa. ２ and 70% N ２ The mixed gas consisting of CO was cooled to -60°C and a part of it was liquefied. ２ N in ２ The concentration was estimated to be 6% by gas chromatography, and this value corresponds to the CO concentration at 5 MPa and -60°C. ２ / N ２ It was confirmed that the liquid phase composition was consistent with that in the phase diagram of the mixed system.

[0078] Next, N ２ Liquefied CO at 5 MPa and -60°C ２ CO ２ CO in the purification tower ２ The snow was purified by snow formation, where a stainless steel tube with an inner diameter of 5 mm was used to condense liquefied CO ２ at -60°C CO ２ The liquefied CO was transported to a purification tower and forcefully ejected from a circular nozzle with a diameter of 1 mm into a 500 cc cloth bag at atmospheric pressure. ２ is vaporized in one go, but is cooled rapidly by the heat of vaporization, so CO ２ Forms snow. ２The snow was dissolved and the purity was measured by gas chromatography. As shown in Figure 14, this liquefied CO ２ The purity of CO was found to be 99.995%. The measurement results are shown in Table 2. ２ Liquefied CO in snow production ２ Flow rate (N ２ Liquefied CO containing ２ The speed at which the air passes through the nozzle is approximately 25 cc / sec (approximately 35 Nm ３ / h).

[0079]

[0080] According to the present invention, CO ２ CO2 can be efficiently produced from combustion gas, natural gas, biogas, etc. that contain 5 to 50% of CO ２ This makes it possible to remove CO ２ It will be possible to process natural gas containing uranium at low cost and supply it through pipelines. In this way, the present invention makes it possible to effectively utilize gas that has been difficult to utilize until now, and is believed to greatly contribute to the development of industry and society.

[0081] 1: First CO ２ Separation equipment (absorption separation device) 2: Second CO ２ Separation equipment (cryogenic separation device) 3: Treated gas supply pipe 4: First pipe 5: Gas reflux equipment 6: Liquefied CO ２ Discharge pipe 7: CO ２ Treated gas discharge pipe 11: Temperature adjustment means 12: Absorption separation apparatus (absorption tower) 12a: Absorption separation apparatus (absorption tower) 12b: Absorption separation apparatus (absorption tower) 12_1: Absorption separation apparatus (absorption tower) 12_2: Absorption separation apparatus (absorption tower) 12_3: Absorption separation apparatus (absorption tower) 13: Switching valve 14: Switching valve 15: Switching valve 16: Rubber 16a: Rod-shaped rubber (cylindrical) 16b: Rod-shaped rubber (tube-shaped) 17a: Pipe 17b: Pipe 17c: Pipe 18: Spacer (jig) 19: Space 21: Temperature adjustment means 23: Dehydration apparatus 24: Cooling apparatus 25: Liquefied CO ２Emission device 27: Piping 28: Piping 31: Valve 32: Compressor 33: Pressure reducing equipment 34: Dehydration equipment 41: Valve 42: High concentration CO ２ Gas discharge equipment (compressor) 51: Second pipe 51a: Pipe 51b: Pipe 51c: Pipe 52: Valve 53: Flash tower 54: Valve 55: Check valve 56: Valve 57: Check valve 58: Reflux gas discharge device (compressor) 59: Temperature adjustment means 61: Valve 71: Valve 72: Check valve 101: CO ２ Separation System 102: CO ２ Separation System 103:CO ２ Separation system 201: liquefied CO ２ Purification vessel (insulated vessel) 202: Nozzle 203: Valve 204: Cooling device (backup cooling device) 205: Supply pipe for liquid to be treated 206: Switching valve 207: Supply pipe for liquid to be treated 211: Valve 212: Pressure adjustment valve 214: Exhaust gas pipe 221: Temperature adjustment equipment (heating device) 222: Valve 223: Liquefied CO ２ Extraction pipe 224: Switching valve 225: Liquefied CO ２ Discharge pipe 231: Treated liquid supply equipment 232: Gas discharge port 233: Liquefied CO ２ Outlet 251: liquefied CO ２ Purification equipment 252: Pump 253: Liquefied CO ２ Purification unit 253a: First liquefied CO ２ Purification unit 253b: Second liquefied CO ２ Purification device 254: Liquefied CO ２ Tank 301: First CO ２ Separation equipment (absorption separation device) 302: Second CO ２ Separation equipment (cryogenic separation device) 303: Recovery tank 304: Liquefied CO ２ Purification equipment (liquefied CO ２ Purifier) ​​305: Liquefied CO ２Tank 311: First valve (pressure control valve) 312: Buffer tank 313: Compressor 314: Dehydration device 315: Buffer tank 316: Inlet pipe 317: Switching valve 318: Inlet pipe 319: Switching valve 320: Purified gas supply pipe 321: Switching valve 322: Exhaust gas pipe 323: Compressor 324: Second reflux gas pipe 325: Pump 326: Treated liquid supply pipe 327: Liquefied CO ２ Supply pipe 328: Pressure regulating valve 329: Pressure regulating valve 330: Compressor 331: First reflux gas pipe 501: Liquefied CO for continuous operation ２ Purification device 511: Housing 512: Supply pipe for treated liquid 513: Valve 514: Cooling device 515: Adiabatic expansion treatment unit 516: CO ２ Spray 517: Granular Snow CO ２ 518: Blowback gas 519: Heater built-in mesh 520: Snow CO ２ Pool 521: Sublimation CO ２ Gas 522: CO ２ Droplet 523: Liquefied CO ２ 531: Upper chamber 532: Lower chamber 541: Piping 542: Flow rate control mechanism 543: Piping 544: Flow rate control mechanism 551: Liquefied CO ２ 552: Reflux gas

Claims

1. First CO ２ Separation equipment and a second CO ２ a separation facility; a treated gas supply pipe; a first pipe; and a high-concentration CO ２ Gas exhaust equipment, second piping, flash tower and low concentration CO ２ a gas reflux facility including a reflux gas discharge device including a liquefied CO ２ Exhaust piping and CO ２ and a treated gas discharge pipe, ２ The separation facility separates the rubber into CO ２ an absorption / separation device that is provided as an absorbent, ２ The separation equipment separates CO from the gas to be treated by cryogenic separation. ２ and a cryogenic separation device for separating the first CO ２ The first pipe is connected to a separation facility via a valve to supply the gas to be treated to the absorption separation device, and the first pipe is connected to the first CO ２ The gas discharged from the separation equipment is ２ The flash tower supplies the cryogenic separation device, the liquefied CO ２ The low-concentration CO ２ The reflux gas discharge device includes the second CO ２ CO having a concentration lower than the concentration in the first pipe from the separation equipment ２ and discharging a gas containing CO from the flash tower. ２ In the gas reflux facility, the low concentration CO ２ The gas discharged from the reflux gas discharge device containing ２ The CO is returned to the separation facility. ２ The treated gas discharge pipe is connected to the absorption / separation device via a valve. ２ Separation system.

2. The absorption separation device includes a first absorption tower group composed of one or more absorption towers and a second absorption tower group composed of one or more absorption towers. The absorption tower has a flow path for allowing a gas to flow while staying inside and rubber serving as a CO ２ absorbent. The CO ２ separation system further includes a cooling means capable of cooling the flow path, the CO ２ absorbent, the cryogenic separation device, and the flash tower. The CO ２ separation system according to claim 1.

3. The CO separation system according to claim 2, wherein the first absorption tower group and the second absorption tower group are absorption tower groups that form a pair with the same configuration. ２ Separation system.

4. The CO in the gas introduced into the first absorption tower group and the second absorption tower group through the gas supply pipe to be treated ２ concentration is 5 mol% or more and 50 mol% or less. The CO separation system according to claim 2 or 3 ２ separation system.

5. The high-concentration CO ２ CO discharged from the gas discharge facility ２ The concentration of which is adjusted to 40 mol% or more and 80 mol% or less, the CO separation system according to claim 4 ２ separation system.

6. The CO separation system according to any one of claims 2 to 5, wherein the absorption pressure of the absorption tower is adjusted to 2 MPa or more and 10 MPa or less. ２ separation system.

7. The temperature of the cooling is -60°C or higher and 0°C or lower. The CO separation system according to claim 2. ２ separation system.

8. The low-concentration CO ２ in the reflux gas containing CO ２ has a concentration of 10 mol% or more and 50 mol% or less. The CO ２ separation system according to claim 1.

9. The CO separation system according to any one of claims 1 to 8, wherein a compressor is connected to the gas to be treated supply pipe. ２ separation system.

10. The CO separation system according to any one of claims 1 to 9, wherein a compressor is connected to the second pipe. ２ separation system.

11. The CO separation system according to any one of claims 2 to 7, wherein the gas to be treated is introduced into the absorption tower via a dehydration facility for dehydration. ２ system.

12. An introduction facility for the gas to be treated, a first CO ２ separation facility, a second CO ２ separation facility, a liquefied CO ２ purification facility, and a liquefied CO ２ tank, wherein the introduction facility for the gas to be treated includes an inlet for the gas to be treated and an introduction pipe for guiding the gas to be treated from the inlet to the first CO ２ separation facility; the first CO ２ separation facility includes at least one pair or more of absorption separation devices provided with rubber as a CO ２ absorbent; the second CO ２ separation facility includes a cryogenic separation device for separating CO ２ from the gas to be treated by cryogenic separation treatment; the liquefied CO ２ purification facility includes a pump and a liquefied CO ２ purification device; the liquefied CO ２ purification device is a device for purifying CO ２ from any state of liquid, gas, or a mixture of liquid and gas to liquefied CO ２ via a snow state; the liquefied CO ２ purification device is connected with a liquefied CO ２ supply pipe for supplying the purified liquefied CO ２ to the liquefied CO ２ tank through a valve, and a first reflux gas pipe for supplying waste gas associated with the liquefaction process to the absorption separation device for reprocessing; a purified gas supply pipe for supplying the treated purified gas is connected to the absorption separation device through a valve; an exhaust gas pipe for discharging the gas containing CO ２ once absorbed by the rubber in the absorption separation device is connected to the inlet of the cryogenic separation device through a valve and a compressor; the cryogenic separation device is connected with a second reflux gas pipe for refluxing the treated gas associated with the cryogenic separation treatment, the CO ２ concentration of which is lower than when it is supplied to the cryogenic separation device, to the absorption separation device, and a treated liquid with a high CO ２ concentration is sent to the liquefied CO ２ purification facility, and a treated gas with a high CO ２ concentration is sent to the liquefied CO ２ A CO separation system connected to a liquid to be treated supply pipe that supplies to a refining device via a pump. ２ separation system.

13. The liquefied CO ２ The refinery is ２ a gas outlet; and a liquefied CO ２ A liquefied CO2 refrigerant having a heat insulating structure and an outlet ２ The treatment liquid supply facility includes a treatment liquid supply pipe, a treatment liquid supply opening / closing valve, a cooling device, and a CO ２ The treated liquid supply facility is provided with a jet nozzle, and the treated liquid supplied through the treated liquid supply pipe is cooled by the cooling device, and the treated liquid supply opening / closing valve is opened to cool the treated liquid. ２ The CO disposed in a purification vessel. ２ The liquefied CO ２ Snow-like CO in the refining vessel ２ The gas outlet has a function of spraying CO 2 , and an exhaust gas pipe is connected to the gas outlet through an on-off valve, and gaseous CO 2 is sprayed from the exhaust gas pipe. ２ a gas containing the liquefied CO ２ At the outlet, liquefied CO ２ Liquefied CO2 is extracted through the valve. ２ An extraction pipe is connected to the liquefied CO ２ A temperature adjustment device for heating is disposed adjacent to the outlet, and the liquefied CO ２ Snow-like CO generated and accumulated in the purification vessel ２ is liquid CO ２ The liquefied CO ２ The CO according to claim 12, which can be taken out through a take-out pipe. ２ Separation system.

14. The introduction device consists of an introduction pipe that reaches a switching valve provided in the one or more absorption separation devices through an inlet for the gas to be processed, a first valve, a first buffer tank, a compressor, a dehydration device, and a second buffer tank. The first reflux gas pipe is connected to the first buffer tank, and the second reflux gas pipe is connected to the second buffer tank. The CO separation system according to claim 12 or 13 ２ system.

15. The refined gas supply pipe is connected to the methane gas recovery tank. The CO separation system according to any one of claims 12 to 14. ２ Separation system.

16. The rubber is provided in a state where pellets of different sizes are mixed, and the CO separation system according to any one of claims 1 to 15. ２ Separation system.

17. The rubber is provided in a rod shape, and the CO separation system according to any one of claims 1 to 15. ２ Separation system.

18. The rubber according to claim 17 is in the form of a hollow tube, and the CO ２ separation system.

19. The rubber is silicone rubber, and the CO separation system according to any one of claims 1 to 18. ２ Separation system.

20. The cryogenic separation device includes a dehydration device for dehydrating the supplied gas, a cooling device for cooling the gas introduced through the dehydration device, and a device for discharging CO that has been liquefied by receiving the cooling. ２ The CO ２ separation system according to claim 1 or 12.

Images