Device for purifying liquefied carbon dioxide gas, and method for purifying liquefied carbon dioxide gas

Abstract

This purification device purifies liquefied carbon dioxide gas from raw-material carbon dioxide gas produced by a carbon dioxide gas production device. The raw-material carbon dioxide gas includes carbon dioxide gas and other gas having a boiling point lower than that of the carbon dioxide gas. The purification device comprises: a compressor for compressing the raw-material carbon dioxide gas; a dehumidifier for dehumidifying the raw-material carbon dioxide gas compressed by the compressor; a cooler for cooling the raw-material carbon dioxide gas that has passed through the dehumidifier, thereby liquefying the raw-material carbon dioxide gas to generate liquefied carbon dioxide gas from the raw-material carbon dioxide gas; a first storage tank that is configured to store the liquefied carbon dioxide gas and is configured to discharge the liquefied carbon dioxide gas separately into a first liquid component and a first gas component; and first piping for returning the first gas component to the production device.

Description

Liquefied carbon dioxide gas purification device and liquefied carbon dioxide gas purification method

[0001] The present disclosure relates to a liquefied carbon dioxide gas purification apparatus and a liquefied carbon dioxide gas purification method.

[0002] As one of the measures to combat global warming, carbon dioxide (CO ) emitted from factories and other places is being ２ In this regard, Japanese Patent Laid-Open Publication No. 2008-214190 (Patent Document 1) discloses a dry ice manufacturing device that uses carbon dioxide gas recovered from factory waste heat such as a chemical factory to manufacture dry ice.

[0003] JP 2008-214190 A

[0004] The purity of liquefied carbon dioxide gas is sometimes regulated by standards. For example, the Food Sanitation Act stipulates that a carbon dioxide concentration of 99.5 mol% or more is required for use as a food additive. As another example, the JIS standard stipulates that a carbon dioxide concentration of 99.8 mol% or more is required for use as a welding shielding gas. Therefore, there is a demand for technology to further purify high-purity carbon dioxide gas.

[0005] In one example of the present disclosure, there is provided a purification apparatus for purifying liquefied carbon dioxide gas from a raw carbon dioxide gas produced by a carbon dioxide gas production apparatus. The raw carbon dioxide gas includes carbon dioxide gas and another gas having a boiling point lower than that of the carbon dioxide gas. The purification apparatus includes a compressor for compressing the raw carbon dioxide gas, a dehumidifier for dehumidifying the raw carbon dioxide gas compressed by the compressor, a cooler for liquefying the raw carbon dioxide gas by cooling the raw carbon dioxide gas that has passed through the dehumidifier and producing liquefied carbon dioxide gas from the raw carbon dioxide gas, a first storage tank configured to store the liquefied carbon dioxide gas and configured to separate the liquefied carbon dioxide gas into a first liquid component and a first gas component and discharge them, and a first pipe for returning the first gas component to the production apparatus.

[0006] In one example of the present disclosure, the purification apparatus further includes a first heat exchanger for performing heat exchange between the raw carbon dioxide gas after passing through the dehumidifier and before passing through the cooler and the first gas component.

[0007] In one example of the present disclosure, the piping state of the first piping is configured to be switchable at least between a state in which the first gas component that has passed through the first heat exchanger is returned to the manufacturing apparatus and a state in which the first gas component is returned to the compressor. The purification apparatus includes a concentration sensor for detecting the concentration of carbon dioxide contained in the raw carbon dioxide gas as a reference concentration before the raw carbon dioxide gas is sent to the compressor, and a concentration sensor for detecting the concentration of carbon dioxide contained in the first gas component as a comparison concentration. The piping state of the first piping is switched depending on a comparison result between the reference concentration and the comparison concentration.

[0008] In one example of the present disclosure, the piping state of the first piping is switched to return the first gas component to the manufacturing apparatus when the comparison concentration is lower than the reference concentration, and is switched to return the first gas component to the compressor when the comparison concentration is higher than the reference concentration.

[0009] In one example of the present disclosure, the purification device further includes a second storage tank configured to store the first liquid component separated in the first storage tank and to separate the first liquid component into a second liquid component and a second gas component and discharge the separated first liquid component, wherein the pressure in the second storage tank is lower than the pressure in the first storage tank.

[0010] In one example of the present disclosure, the purification apparatus further includes a second storage tank configured to store the first liquid component separated in the first storage tank and to separate the first liquid component into a second liquid component and a second gas component and discharge them. The pressure in the second storage tank is lower than the pressure in the first storage tank. The purification apparatus further includes a second heat exchanger for exchanging heat between the raw carbon dioxide gas that has passed through the first heat exchanger and the second gas component.

[0011] In one example of the present disclosure, the purification device further includes a second pipe for returning the second gas component that has passed through the second heat exchanger to the compressor or the production device.

[0012] In one example of the present disclosure, the piping state of the second piping is configured to be switchable at least between a state in which the second gas component that has passed through the second heat exchanger is returned to the manufacturing apparatus and a state in which the second gas component is returned to the compressor. The purification apparatus further includes a concentration sensor for detecting the concentration of carbon dioxide contained in the raw carbon dioxide gas as a reference concentration before the raw carbon dioxide gas is sent to the compressor, and a concentration sensor for detecting the concentration of carbon dioxide contained in the second gas component as a comparison concentration. The piping state of the second piping is switched depending on a comparison result between the reference concentration and the comparison concentration.

[0013] In one example of the present disclosure, the piping state of the second piping is switched to return the second gas component to the manufacturing apparatus when the comparison concentration is lower than the reference concentration, and is switched to return the second gas component to the compressor when the comparison concentration is higher than the reference concentration.

[0014] Another example of the present disclosure provides a method for purifying liquefied carbon dioxide gas from raw carbon dioxide gas produced by a carbon dioxide gas production apparatus. The raw carbon dioxide gas includes carbon dioxide gas and another gas having a boiling point lower than that of the carbon dioxide gas. The purification method includes a step of compressing the raw carbon dioxide gas, a step of dehumidifying the raw carbon dioxide gas compressed in the compression step, a step of liquefying the raw carbon dioxide gas by cooling the raw carbon dioxide gas dehumidified in the dehumidification step to produce liquefied carbon dioxide gas from the raw carbon dioxide gas, a step of separating the liquefied carbon dioxide gas produced in the production step into a first liquid component and a first gas component and discharging them, and a step of returning the first gas component to the production apparatus.

[0015] The above and other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description of the invention taken in conjunction with the accompanying drawings.

[0016] FIG. 1 is a diagram showing an example of the configuration of a refining system according to a first embodiment. FIG. 2 is a diagram showing the configuration of a refining system according to a modified example. FIG. 3 is a diagram showing the configuration of a refining system according to a modified example. FIG. 4 is a schematic diagram showing an example of the hardware configuration of a control device. FIG. 5 is a flowchart showing the flow of control processing of a switching mechanism. FIG. 6 is a diagram showing an example of the configuration of a refining system according to a second embodiment. FIG. 7 is a diagram showing the configuration of a refining system according to a modified example. FIG. 8 is a diagram showing the flow of control processing of a switching mechanism. FIG. 9 is a diagram showing the results of numerical calculations when raw material carbon dioxide is purified under first numerical calculation conditions. FIG. 10 is a diagram showing the results of numerical calculations when raw material carbon dioxide is purified under second numerical calculation conditions.

[0017] Hereinafter, each embodiment according to the present invention will be described with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated. Note that each embodiment and each modified example described below may be selectively combined as appropriate.

[0018] [First embodiment] <A. Refining system 10> First, a refining system 10 according to a first embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing an example of the configuration of refining system 10 according to the first embodiment.

[0019] As shown in FIG. 1 , the refining system 10 includes a production apparatus 20 and a refining apparatus 100 .

[0020] The production apparatus 20 is an apparatus for producing purified carbon dioxide gas from exhaust gas from a boiler, industrial furnace, etc. The concentration of carbon dioxide gas contained in the exhaust gas is, for example, about 10 mol %. The production apparatus 20 produces high-purity carbon dioxide gas, for example, by an adsorption separation method.

[0021] The purified carbon dioxide gas produced by the production apparatus 20 contains not only carbon dioxide gas but also a small amount of other gases (e.g., nitrogen gas) whose boiling points are lower than that of the carbon dioxide gas. As an example, the concentration of carbon dioxide gas in the purified carbon dioxide gas is about 95 mol %, and the concentrations of other gases in the purified carbon dioxide gas are about 5 mol %. In addition, the purified carbon dioxide gas may contain moisture.

[0022] The production apparatus 20 is connected to a refining apparatus 100 via piping or the like. The purified carbon dioxide gas produced by the production apparatus 20 is sent to the refining apparatus 100 as raw carbon dioxide gas G0.

[0023] The refining device 100 is a device for purifying the raw carbon dioxide gas G0 sent from the manufacturing device 20 into high-purity carbon dioxide gas. The high-purity carbon dioxide gas is a product gas in which the carbon dioxide gas concentration in the raw carbon dioxide gas G0 has been further increased. The product gas may be a gas or a liquid. The carbon dioxide gas concentration in the high-purity carbon dioxide gas is higher than the carbon dioxide gas concentration in the raw carbon dioxide gas G0. As an example, the carbon dioxide gas concentration in the high-purity carbon dioxide gas is 99.5 mol% or more. As another example, the carbon dioxide gas concentration in the high-purity carbon dioxide gas is 99.9 mol% or more.

[0024] High-purity carbon dioxide gas as a product gas can be used in a variety of applications. For example, high-purity carbon dioxide gas is used as a food additive for carbonated drinks, etc. For another example, high-purity carbon dioxide gas is used as a shielding gas for welding.

[0025] More specifically, the refining device 100 includes a compressor 132, a dehumidifier 134, a cooler 138, and a first storage tank 150A.

[0026] An inlet of the compressor 132 is connected to the manufacturing apparatus 20 via a pipe. The compressor 132 is configured to compress the raw carbon dioxide gas G0 fed from the manufacturing apparatus 20. As an example, the compressor 132 increases the pressure of the raw carbon dioxide gas G0 to 2.0 MPaG or more.

[0027] An inlet of the dehumidifier 134 is connected via a pipe to an outlet of the compressor 132. The dehumidifier 134 is configured to dehumidify the raw material carbon dioxide gas G0 compressed by the compressor 132. In other words, the dehumidifier 134 is configured to remove moisture from the raw material carbon dioxide gas G0.

[0028] There are no particular limitations on the dehumidification method used by the dehumidifier 134. For example, the dehumidifier 134 may remove moisture using a dehumidifying agent or a dehumidifying membrane.

[0029] An inlet of the cooler 138 is connected via a pipe to an outlet of the dehumidifier 134. The cooler 138 is configured to liquefy the raw carbon dioxide gas G0 by cooling the raw carbon dioxide gas G0 that has passed through the dehumidifier 134, and to generate liquefied carbon dioxide gas from the raw carbon dioxide gas G0. As an example, the cooler 138 cools the raw carbon dioxide gas G0 to −20° C. or lower.

[0030] The cooling method by the cooler 138 is not particularly limited. As an example, the cooler 138 is a heat exchanger that exchanges heat between the raw material carbon dioxide G0 that has passed through the dehumidifier 134 and a refrigerant. More specifically, the flow path of the raw material carbon dioxide G0 inside the cooler 138 is configured to be adjacent to the flow path of the refrigerant inside the cooler 138. In this way, the refrigerant cools the raw material carbon dioxide G0. Examples of the refrigerant include a chlorofluorocarbon refrigerant and an ammonia refrigerant.

[0031] An inlet of the first storage tank 150A is connected via a pipe to an outlet of the cooler 138. The first storage tank 150A is configured to store the liquefied carbon dioxide gas produced in the cooler 138, and is configured to separate the liquefied carbon dioxide gas into a liquid component L1 (first liquid component) and a gas component G1 (first gas component) and discharge the separated gas.

[0032] As described above, the raw carbon dioxide gas G0 contains not only carbon dioxide gas but also a small amount of other gases (e.g., nitrogen gas) whose boiling points are lower than that of the carbon dioxide gas. Because the other gases vaporize more easily than the carbon dioxide gas, the concentration of carbon dioxide gas contained in the liquid component L1 is higher than the concentration of carbon dioxide gas contained in the gas component G1. In this way, by separating the gas component G1, the concentration of carbon dioxide gas contained in the liquid component L1 is further increased.

[0033] More specifically, the first storage tank 150A has an outlet for discharging the liquid component L1 and an outlet for discharging the gas component G1. The outlet for the gas component G1 is located above the outlet for the liquid component L1.

[0034] The first storage tank 150A is provided with a pipe F1 (first pipe) for returning the gas component G1 to the production apparatus 20. The pipe F1 connects the outlet for the gas component G1 in the first storage tank 150A with the inlet of the production apparatus 20. As a result, the gas component G1 is returned to the production apparatus 20 and used to produce new raw material carbon dioxide gas G0. As a result, the refining apparatus 100 can reduce the amount of raw material consumed by the production apparatus 20.

[0035] Furthermore, if the gas component G1 is returned to the compressor 132 instead of the manufacturing apparatus 20, there is a possibility that the nitrogen gas contained in the gas component G1 will accumulate in the refining apparatus 100. If the concentration of nitrogen gas accumulates in the refining apparatus 100, the raw carbon dioxide gas G0 will be difficult to liquefy in the cooler 138. In contrast, in the present embodiment, the gas component G1 is returned to the manufacturing apparatus 20, so that the carbon dioxide gas concentration of the raw carbon dioxide gas G0 can always be kept constant. This prevents nitrogen gas from accumulating in the refining apparatus 100, and makes it possible to avoid a situation in which the cooler 138 is unable to liquefy the raw carbon dioxide gas G0.

[0036] <B. Pre-cooling Mechanism> Next, a modified example of the refining device 100 shown in Fig. 1 will be described with reference to Fig. 2. Fig. 2 is a diagram showing the configuration of a refining system 10 according to the modified example.

[0037] The purification apparatus 100 shown in Figure 2 differs from the purification apparatus 100 shown in Figure 1 in that it includes a heat exchanger 136A. The other points are as described above, and therefore, the description thereof will not be repeated below.

[0038] The heat exchanger 136A is configured to exchange heat between the raw carbon dioxide gas G0 after passing through the dehumidifier 134 but before passing through the cooler 138, and the gas component G1 returned from the first storage tank 150A to the manufacturing apparatus 20. Because the gas component G1 has been cooled by the cooler 138, the temperature of the gas component G1 is lower than the temperature of the raw carbon dioxide gas G0. Therefore, the heat exchanger 136A can cool the raw carbon dioxide gas G0 by using the gas component G1. By pre-cooling the raw carbon dioxide gas G0 before it is sent to the cooler 138, energy consumption in the cooler 138 is reduced.

[0039] More specifically, a flow path A1 and a flow path A2 are provided inside the heat exchanger 136A. The flow path A1 constitutes a part of the pipe F10 that connects the dehumidifier 134 and the cooler 138. As an example, the flow path A1 is provided downstream of the dehumidifier 134 and upstream of the cooler 138 in the direction of the flow of the raw carbon dioxide gas G0.

[0040] Flow path A2 constitutes a part of the pipe F1 that connects first storage tank 150A and manufacturing apparatus 20. In other words, flow path A2 is provided downstream of first storage tank 150A and upstream of manufacturing apparatus 20 in the direction of the gas flow of gas component G1.

[0041] The flow paths A1 and A2 are spatially separated inside the heat exchanger 136 A. The flow paths A1 and A2 are positioned adjacent to each other inside the heat exchanger 136 A. This allows heat exchange to occur between the raw carbon dioxide gas G0 and the gas component G1, and the raw carbon dioxide gas G0 is cooled by the gas component G1.

[0042] <C. Pipe Switching Mechanism> Next, a modified example of the refining device 100 shown in Fig. 2 will be described with reference to Fig. 3. Fig. 3 is a diagram showing the configuration of a refining system 10 according to the modified example.

[0043] 3 differs from the refining device 100 shown in Fig. 2 in that it includes concentration sensors C0 and C1, a switching mechanism SW1, and a control device 50. The other points are as described above, and therefore, description thereof will not be repeated below.

[0044] In this modified example, the piping state of the piping F1 is configured to be at least switchable between a state in which the gas component G1 is returned to the manufacturing apparatus 20 and a state in which the gas component G1 is returned to the compressor 132. The switching of the piping state of the piping F1 is achieved, for example, by a switching mechanism SW1. The configuration of the switching mechanism SW1 is not particularly limited. In the example of FIG. 3, the switching mechanism SW1 is configured by a valve V1A and a valve V1B. The types of the valves V1A and V1B are not particularly limited. As an example, the valves V1A and V1B are ball valves.

[0045] More specifically, the pipe F1 branches so as to guide the gas component G1 that has passed through the heat exchanger 136A to the pipe F1A or the pipe F1B. The pipe F1A is configured to return the gas component G1 that has passed through the heat exchanger 136A to the inlet of the production apparatus 20. The pipe F1B is configured to return the gas component G1 that has passed through the heat exchanger 136A to the inlet of the compressor 132.

[0046] The valve V1A is provided on the pipe F1A and is configured to be switchable at least between an open state and a closed state. When the valve V1A is in the open state, the flow path from the first storage tank 150A to the manufacturing apparatus 20 is connected, and the gas component G1 is returned to the manufacturing apparatus 20. On the other hand, when the valve V1A is in the closed state, the gas component G1 does not flow to the manufacturing apparatus 20.

[0047] The valve V1B is provided on the pipe F1B and is configured to be switchable at least between an open state and a closed state. When the valve V1B is in the open state, the flow path from the first storage tank 150A to the inlet of the compressor 132 is connected, and the gas component G1 is returned to the compressor 132. On the other hand, when the valve V1B is in the closed state, the gas component G1 does not flow to the compressor 132.

[0048] The opening and closing of each of the valves V1A and V1B is controlled by the control device 50. Typically, the control device 50 controls the opening and closing states of the valves V1A and V1B to be opposite to each other. That is, when the control device 50 opens the valve V1A, it closes the valve V1B. On the other hand, when the control device 50 closes the valve V1A, it opens the valve V1B.

[0049] The concentration sensor C0 is a sensor for detecting the concentration of carbon dioxide contained in the raw carbon dioxide G0 (hereinafter also referred to as the "reference concentration D0"). The concentration sensor C0 can be installed at any position where the carbon dioxide concentration in the raw carbon dioxide G0 can be detected. In the example of FIG. 3, the concentration sensor C0 is installed downstream of the inlet for the raw carbon dioxide G0 and upstream of the compressor 132 in the direction of the gas flow of the raw carbon dioxide G0. As a result, the concentration sensor C0 detects the carbon dioxide concentration of the raw carbon dioxide G0 before it is sent to the compressor 132 as the reference concentration D0. The detected reference concentration D0 is output to the control device 50.

[0050] The type of the concentration sensor C0 is not particularly limited. For example, the concentration sensor C0 may be a non-dispersive infrared (NDIR) sensor or a photoacoustic sensor.

[0051] The concentration sensor C1 is a sensor for detecting the concentration of carbon dioxide contained in the gas component G1 (hereinafter also referred to as the "comparison concentration D1"). The concentration sensor C1 can be installed at any position where the concentration of carbon dioxide in the gas component G1 can be detected. In the example of FIG. 3, the concentration sensor C1 is installed downstream of the heat exchanger 136A and upstream of the switching mechanism SW1 in the direction of the gas flow of the gas component G1. As a result, the concentration sensor C1 detects the carbon dioxide concentration of the gas component G1 after passing through the heat exchanger 136A but before passing through the switching mechanism SW1 as the comparison concentration D1. The comparison concentration D1 detected by the concentration sensor C1 is output to the control device 50.

[0052] The type of the concentration sensor C1 is not particularly limited. The concentration sensor C1 may be an NDIR sensor or a photoacoustic sensor. The type of the concentration sensor C1 may be the same as or different from that of the concentration sensor C0.

[0053] The control device 50 switches the piping state of the pipe F1 depending on the result of the comparison between the reference concentration D0 and the comparison concentration D1. More specifically, when the comparison concentration D1 is lower than the reference concentration D0, the control device 50 switches the piping state of the pipe F1 so as to return the gas component G1 to the production apparatus 20. That is, in this case, the control device 50 controls the switching mechanism SW1 to open the valve V1A and close the valve V1B.

[0054] As a result, the gas component G1 is reused in the production of the raw carbon dioxide gas G0 in the production apparatus 20, and the refining apparatus 100 can reduce the amount of raw material consumed by the production apparatus 20. Furthermore, the refining apparatus 100 does not need to return the gas component G1 with a low carbon dioxide gas concentration to the compressor 132. This makes it possible to avoid the accumulation of nitrogen gas in the raw carbon dioxide gas G0, and as a result, to avoid a decrease in the carbon dioxide gas concentration.

[0055] On the other hand, when the comparative concentration D1 is higher than the reference concentration D0, the control device 50 switches the piping state of the piping F1 so as to return the gas component G1 to the compressor 132. That is, in this case, the control device 50 controls the switching mechanism SW1 so as to close the valve V1A and open the valve V1B.

[0056] In this way, when the comparative concentration D1 is higher than the reference concentration D0, the refining apparatus 100 does not need to return the gas component G1 to the production apparatus 20. This not only enables the refining apparatus 100 to reduce the required amount of raw carbon dioxide gas, but also enables the refining apparatus 100 to suppress energy consumption in the production apparatus 20.

[0057] Although the above description has been given of an example in which the piping state of the piping F1 is switched depending on the magnitude relationship between the reference concentration D0 and the comparison concentration D1, the conditions for switching the piping state of the piping F1 are not limited to this. As another example, the control device 50 may compare the comparison concentration D1 with a value obtained by adding a predetermined value to the reference concentration D0 or a value obtained by subtracting a predetermined value from the reference concentration D0.

[0058] Although the above description has been given of an example in which the switching mechanism SW1 is configured with the valves V1A and V1B, the configuration of the switching mechanism SW1 is not limited to this. As another example, the switching mechanism SW1 may be configured with a three-way valve.

[0059] <D. Hardware Configuration> Next, the hardware configuration of the above-mentioned control device 50 will be described in order with reference to Fig. 4. Fig. 4 is a schematic diagram showing an example of the hardware configuration of the control device 50.

[0060] The control device 50 includes a control circuit 101, a read only memory (ROM) 102, a random access memory (RAM) 103, a communication interface 104, and an auxiliary storage device 120. These components are connected to a bus 110.

[0061] The control circuit 101 is configured, for example, by at least one integrated circuit, which may be configured, for example, by at least one central processing unit (CPU), at least one graphics processing unit (GPU), at least one application specific integrated circuit (ASIC), at least one field programmable gate array (FPGA), or a combination thereof.

[0062] The control circuit 101 controls the operation of the control device 50 by executing various programs such as a control program 122. The control program 122 is a program for realizing various processes described in this specification. Upon receiving an execution command for the control program 122, the control circuit 101 reads the control program 122 from the auxiliary storage device 120 or the ROM 102 to the RAM 103. The RAM 103 functions as a working memory and temporarily stores various data required for executing the control program 122.

[0063] The communication interface 104 is an interface for periodic communication with external devices using a field network. The external devices include, for example, the above-mentioned concentration sensors C0 and C1, a concentration sensor C2 (see FIG. 8) (described later), the above-mentioned switching mechanism SW1, and a switching mechanism SW2 (see FIG. 8) (described later). The field network may be, for example, EtherCAT (registered trademark), EtherNet / IP (registered trademark), CC-Link (registered trademark), or CompoNet (registered trademark).

[0064] The auxiliary storage device 120 is, for example, a hard disk, a flash memory, an SSD (Solid State Drive), or other storage medium. The auxiliary storage device 120 stores the control program 122 and the like. Note that the storage location of the control program 122 is not limited to the auxiliary storage device 120, and it may be stored in a storage area of ​​the control circuit 101 (for example, a cache memory), the ROM 102, the RAM 103, an external device (for example, a server), or the like.

[0065] The control program 122 may be provided not as a standalone program but as part of an arbitrary program. In this case, various processes according to this embodiment are realized in cooperation with the arbitrary program. Even a program that does not include some of these modules does not deviate from the spirit of the control program 122 according to this embodiment. Furthermore, some or all of the functions provided by the control program 122 may be realized by dedicated hardware. Furthermore, the control device 50 may be configured in the form of a so-called cloud service in which at least one server executes part of the processes of the control program 122.

[0066] <E. Control Flow> Next, the control flow of the above-mentioned switching mechanism SW1 (see FIG. 3) will be described with reference to Fig. 5. Fig. 5 is a flowchart showing the flow of control processing of the switching mechanism SW1.

[0067] 5 is realized by the control device 50 of the refining device 100 executing the above-described control program 122 (see FIG. 4). In another aspect, part or all of the process may be performed by circuit elements or other hardware.

[0068] In step S110, the control device 50 determines whether the refining process has started in the refining device 100. Whether the refining process has started can be determined by various methods. As one example, the control device 50 determines that the refining process has started in the refining device 100 when it receives a refining start operation. If the control device 50 determines that the refining process has started in the refining device 100 (YES in step S110), it switches control to step S112. If not (NO in step S110), the control device 50 executes the process of step S110 again.

[0069] In step S112, the control device 50 acquires, as a reference concentration D0, the carbon dioxide concentration of the raw carbon dioxide G0 sent from the production device 20 to the refining device 100. The reference concentration D0 is acquired from the concentration sensor C0 (see FIG. 3) described above.

[0070] In step S114, the control device 50 acquires the carbon dioxide concentration of the gas component G1 discharged from the first storage tank 150A as a comparative concentration D1. The comparative concentration D1 is acquired from the concentration sensor C1 (see FIG. 3).

[0071] In step S120, the control device 50 determines whether the comparison concentration D1 obtained in step S114 is lower than the reference concentration D0 obtained in step S112. If the control device 50 determines that the comparison concentration D1 is lower than the reference concentration D0 (YES in step S120), the control device 50 switches control to step S122. If not (NO in step S120), the control device 50 switches control to step S124.

[0072] In step S122, the control device 50 switches the piping state of the refining device 100 so as to return the gas component G1 to the production device 20. More specifically, the control device 50 controls the switching mechanism SW1 so as to open the valve V1A and close the valve V1B.

[0073] In step S124, the control device 50 switches the piping state of the purification device 100 so as to return the gas component G1 to the compressor 132. More specifically, the control device 50 controls the switching mechanism SW1 so as to close the valve V1A and open the valve V1B.

[0074] In step S150, the control device 50 determines whether the refining process in the refining device 100 has ended. Whether the refining process has ended can be determined by various methods. As an example, the control device 50 determines that the refining process in the refining device 100 has ended when it receives a refining end operation. If the control device 50 determines that the refining process in the refining device 100 has ended (YES in step S150), it ends the processing shown in FIG. 5. If not (NO in step S150), the control device 50 returns control to step S112.

[0075] [Second embodiment] <F. Refining system 10> Next, a refining system 10 according to a second embodiment will be described with reference to Fig. 6. Fig. 6 is a diagram showing an example of the configuration of the refining system 10 according to the second embodiment.

[0076] The refining apparatus 100 shown in Figure 6 differs from the refining apparatus 100 shown in Figure 1 in that it includes a second storage tank 150B. The other points are as described above, and therefore, description thereof will not be repeated below.

[0077] The inlet of the second storage tank 150B is connected to the outlet of the first storage tank 150A via a pipe. The second storage tank 150B is configured to store the liquid component L1 separated in the first storage tank 150A, and to separate the liquid component L1 into a liquid component L2 (second liquid component) and a gas component G2 (second gas component) and discharge them.

[0078] More specifically, the second storage tank 150B has an outlet for discharging the liquid component L2 and an outlet for discharging the gas component G2. The outlet for the gas component G2 is located above the outlet for the liquid component L2.

[0079] The pressure in second storage tank 150B is lower than the pressure in first storage tank 150A. The pressure reduction is achieved, for example, by a pressure reducing valve V. Pressure reducing valve V is provided on a pipe connecting the outlet of first storage tank 150A and the inlet of second storage tank 150B. As a result, carbon dioxide, which is a high-boiling point component, is concentrated in second storage tank 150B due to gas-liquid equilibrium, and the carbon dioxide concentration in liquid component L2 becomes higher than the carbon dioxide concentration in liquid component L1.

[0080] The pressure in the second storage tank 150B can be set arbitrarily depending on the carbon dioxide concentration required for the product gas. Preferably, the pressure in the second storage tank 150B is adjusted to a level that does not solidify the liquid component L2. For example, the pressure in the second storage tank 150B is adjusted to 0.7 MPaG or higher.

[0081] The second storage tank 150B is provided with a pipe F2 (second pipe) for returning the separated gas component G2 to the production apparatus 20. The pipe F2 connects the outlet for the gas component G2 in the second storage tank 150B with the inlet of the production apparatus 20. As a result, the gas component G2 is returned to the production apparatus 20 and used to produce new raw material carbon dioxide gas G0. As a result, the refining apparatus 100 can reduce the amount of raw material consumed by the production apparatus 20.

[0082] 6 has been described as an example in which the pipe F2 is connected to the manufacturing apparatus 20, the pipe F2 may be connected to the compressor 132. In this case, the gas component G2 having a higher carbon dioxide concentration is returned to the compressor 132 through the pipe F2, and the gas component G1 having a lower carbon dioxide concentration is returned to the manufacturing apparatus 20 through the pipe F1.

[0083] <G. Pre-cooling Mechanism> Next, a modified example of the refining device 100 shown in Fig. 6 will be described with reference to Fig. 7. Fig. 7 is a diagram showing the configuration of the refining system 10 according to the modified example.

[0084] The refining apparatus 100 shown in Figure 7 differs from the refining apparatus 100 shown in Figure 6 in that it includes heat exchangers 136A and 136B. Other features are as described above, and therefore, description thereof will not be repeated below. Furthermore, since the heat exchanger 136A is as described above in Figure 2, description of the heat exchanger 136A will not be repeated below.

[0085] The heat exchanger 136B is configured to exchange heat between the raw carbon dioxide gas G0 after passing through the heat exchanger 136A but before passing through the cooler 138, and the gas component G2 returned from the second storage tank 150B to the manufacturing apparatus 20. Because the gas component G2 has been cooled by the cooler 138, the temperature of the gas component G2 is lower than the temperature of the raw carbon dioxide gas G0. Therefore, the heat exchanger 136B can cool the raw carbon dioxide gas G0 by using the gas component G2. By pre-cooling the raw carbon dioxide gas G0 before it is sent to the cooler 138, energy consumption in the cooler 138 is reduced.

[0086] Furthermore, since the pressure in second storage tank 150B is lower than the pressure in first storage tank 150A, the temperature of gas component G2 is lower than the temperature of gas component G1. Therefore, pre-cooling of raw carbon dioxide G0 by heat exchanger 136B is performed after pre-cooling of raw carbon dioxide G0 by heat exchanger 136A. As a result, raw carbon dioxide G0 is cooled sequentially by heat exchanger 136A and heat exchanger 136B, and energy consumption in cooler 138 is effectively reduced.

[0087] More specifically, a flow path B1 and a flow path B2 are provided inside the heat exchanger 136B. The flow path B1 constitutes a part of the pipe F10 that connects the dehumidifier 134 and the cooler 138. As an example, the flow path B1 is provided downstream of the heat exchanger 136A and upstream of the cooler 138 in the direction of the flow of the raw carbon dioxide gas G0.

[0088] Flow path B2 constitutes a part of piping F2 connecting second storage tank 150B and manufacturing apparatus 20. In other words, flow path B2 is provided downstream of second storage tank 150B and upstream of manufacturing apparatus 20 in the direction of the gas flow of gas component G2.

[0089] The flow paths B1 and B2 are spatially separated inside the heat exchanger 136 B. The flow paths B1 and B2 are positioned adjacent to each other inside the heat exchanger 136 B. This allows heat exchange to occur between the raw carbon dioxide gas G0 and the gas component G2, and the raw carbon dioxide gas G0 is cooled by the gas component G2.

[0090] <H. Pipe Switching Mechanism> Next, a modified example of the refining device 100 shown in Fig. 7 will be described with reference to Fig. 8. Fig. 8 is a diagram showing the configuration of a refining system 10 according to the modified example.

[0091] The refining device 100 shown in Figure 8 differs from the refining device 100 shown in Figure 7 in that it includes concentration sensors C0 to C2, switching mechanisms SW1 and SW2, and a control device 50. The other features are as described above, and therefore their description will not be repeated below. Furthermore, the concentration sensors C0 and C1 and the switching mechanism SW1 are as described above in Figure 3, and therefore their description will not be repeated below.

[0092] In this modified example, the piping state of the piping F2 is configured to be at least switchable between a state in which the gas component G2 is returned to the manufacturing apparatus 20 and a state in which the gas component G2 is returned to the compressor 132. The switching of the piping state of the piping F2 is achieved, for example, by a switching mechanism SW2. The configuration of the switching mechanism SW2 is not particularly limited. In the example of FIG. 8, the switching mechanism SW2 is configured by a valve V2A and a valve V2B. The types of the valves V2A and V2B are not particularly limited. As an example, the valves V2A and V2B are ball valves.

[0093] More specifically, the pipe F2 branches so as to guide the gas component G2 that has passed through the heat exchanger 136B to the pipe F2A or the pipe F2B. The pipe F2A is configured to return the gas component G2 that has passed through the heat exchanger 136B to the manufacturing apparatus 20. The pipe F2B is configured to return the gas component G2 that has passed through the heat exchanger 136B to the inlet of the compressor 132.

[0094] Valve V2A is provided on pipe F2A and is configured to be switchable at least between an open state and a closed state. When valve V2A is in the open state, the flow path from second storage tank 150B to manufacturing apparatus 20 is connected, and gas component G2 is returned to manufacturing apparatus 20. On the other hand, when valve V2A is in the closed state, gas component G2 does not flow to manufacturing apparatus 20.

[0095] The valve V2B is provided on the pipe F2B and is configured to be switchable at least between an open state and a closed state. When the valve V2B is in the open state, the flow path from the second storage tank 150B to the inlet of the compressor 132 is connected, and the gas component G2 is returned to the compressor 132. On the other hand, when the valve V2B is in the closed state, the gas component G2 does not flow to the compressor 132.

[0096] The opening and closing of each of the valves V2A and V2B is controlled by the control device 50. Typically, the control device 50 controls the opening and closing states of the valves V2A and V2B to be opposite to each other. That is, when the control device 50 opens the valve V2A, it closes the valve V2B. On the other hand, when the control device 50 closes the valve V2A, it opens the valve V2B.

[0097] The concentration sensor C2 is a sensor for detecting the concentration of carbon dioxide contained in the gas component G2 (hereinafter also referred to as the "comparison concentration D2"). The concentration sensor C2 can be installed at any position where it can detect the carbon dioxide concentration in the gas component G2. In the example of FIG. 8, the concentration sensor C2 is installed downstream of the heat exchanger 136B and upstream of the switching mechanism SW2 in the direction of the gas flow of the gas component G2. As a result, the concentration sensor C2 detects the carbon dioxide concentration of the gas component G2 after passing through the heat exchanger 136B but before passing through the switching mechanism SW2 as the comparison concentration D2. The comparison concentration D2 detected by the concentration sensor C2 is output to the control device 50.

[0098] The type of the concentration sensor C2 is not particularly limited. The concentration sensor C2 may be an NDIR sensor or a photoacoustic sensor. The type of the concentration sensor C2 may be the same as or different from the concentration sensors C0 and C1.

[0099] The control device 50 switches the piping state of the pipe F2 depending on the comparison result between the reference concentration D0 and the comparison concentration D2. More specifically, when the comparison concentration D2 is lower than the reference concentration D0, the control device 50 switches the piping state of the pipe F2 so as to return the gas component G2 to the production apparatus 20. That is, in this case, the control device 50 controls the switching mechanism SW2 to open the valve V2A and close the valve V2B.

[0100] As a result, the gas component G2 is reused in the production of the raw carbon dioxide gas G0 in the production apparatus 20, and the refining apparatus 100 can reduce the amount of raw material consumed by the production apparatus 20. Furthermore, the refining apparatus 100 does not need to return the gas component G2 with a low carbon dioxide gas concentration to the compressor 132. This makes it possible to avoid the accumulation of nitrogen gas in the raw carbon dioxide gas G0, and as a result, to avoid a decrease in the carbon dioxide gas concentration.

[0101] On the other hand, when the comparative concentration D2 is higher than the reference concentration D0, the control device 50 switches the piping state of the pipe F2 so as to return the gas component G2 to the compressor 132. That is, in this case, the control device 50 controls the switching mechanism SW2 so as to close the valve V2A and open the valve V2B.

[0102] In this way, when the comparative concentration D2 is higher than the reference concentration D0, the refining apparatus 100 does not need to return the gas component G2 to the production apparatus 20. This not only enables the refining apparatus 100 to reduce the required amount of raw carbon dioxide gas, but also enables the refining apparatus 100 to suppress energy consumption in the production apparatus 20.

[0103] Although the above description has been given of an example in which the piping state of the piping F2 is switched depending on the magnitude relationship between the reference concentration D0 and the comparison concentration D2, the conditions for switching the piping state of the piping F2 are not limited to this. As another example, the control device 50 may compare the comparison concentration D2 with a value obtained by adding a predetermined value to the reference concentration D0 or a value obtained by subtracting a predetermined value from the reference concentration D0.

[0104] Although the above description has been given of an example in which the switching mechanism SW2 is configured with the valves V2A and V2B, the configuration of the switching mechanism SW2 is not limited to this. As another example, the switching mechanism SW2 may be configured with a three-way valve.

[0105] <I. Control Flow> Next, the control flow of the above-mentioned switching mechanisms SW1 and SW2 (see FIG. 8) will be described with reference to Fig. 9. Fig. 9 is a flowchart showing the flow of control processing of the switching mechanisms SW1 and SW2.

[0106] 9 is realized by the control device 50 of the refining device 100 executing the above-described control program 122 (see FIG. 4). In another aspect, part or all of the process may be performed by circuit elements or other hardware.

[0107] In step S110, the control device 50 determines whether the refining process has started in the refining device 100. Whether the refining process has started can be determined by various methods. As one example, the control device 50 determines that the refining process has started in the refining device 100 when it receives a refining start operation. If the control device 50 determines that the refining process has started in the refining device 100 (YES in step S110), it switches control to step S112. If not (NO in step S110), the control device 50 executes the process of step S110 again.

[0108] In step S112, the control device 50 acquires, as a reference concentration D0, the carbon dioxide concentration of the raw carbon dioxide G0 sent from the production device 20 to the refining device 100. The reference concentration D0 is acquired from the concentration sensor C0 (see FIG. 8) described above.

[0109] In step S114, the control device 50 acquires the carbon dioxide concentration of the gas component G1 discharged from the first storage tank 150A as a comparative concentration D1. The comparative concentration D1 is acquired from the concentration sensor C1 (see FIG. 8).

[0110] In step S120, the control device 50 determines whether the comparison concentration D1 obtained in step S114 is lower than the reference concentration D0 obtained in step S112. If the control device 50 determines that the comparison concentration D1 is lower than the reference concentration D0 (YES in step S120), the control device 50 switches control to step S122. If not (NO in step S120), the control device 50 switches control to step S124.

[0111] In step S122, the control device 50 switches the piping state of the refining device 100 so as to return the gas component G1 to the production device 20. More specifically, the control device 50 controls the switching mechanism SW1 so as to open the valve V1A and close the valve V1B.

[0112] In step S124, the control device 50 switches the piping state of the purification device 100 so as to return the gas component G1 to the compressor 132. More specifically, the control device 50 controls the switching mechanism SW1 so as to close the valve V1A and open the valve V1B.

[0113] In step S134, the control device 50 acquires the carbon dioxide concentration of the gas component G2 discharged from the second storage tank 150B as a comparative concentration D2. The comparative concentration D2 is acquired from the concentration sensor C2 (see FIG. 8).

[0114] In step S140, the control device 50 determines whether the comparison concentration D2 acquired in step S134 is lower than the reference concentration D0 acquired in step S112. If the control device 50 determines that the comparison concentration D2 is lower than the reference concentration D0 (YES in step S140), the control device 50 switches control to step S142. If not (NO in step S140), the control device 50 switches control to step S144.

[0115] In step S142, the control device 50 switches the piping state of the refining device 100 so as to return the gas component G2 to the production device 20. More specifically, the control device 50 controls the switching mechanism SW2 so as to open the valve V2A and close the valve V2B.

[0116] In step S144, the control device 50 switches the piping state of the purification device 100 so as to return the gas component G2 to the compressor 132. More specifically, the control device 50 controls the switching mechanism SW2 so as to close the valve V2A and open the valve V2B.

[0117] In step S150, the control device 50 determines whether the refining process in the refining device 100 has ended. Whether the refining process has ended can be determined by various methods. As one example, the control device 50 determines that the refining process in the refining device 100 has ended when it receives a refining end operation. If the control device 50 determines that the refining process in the refining device 100 has ended (YES in step S150), it ends the processing shown in FIG. 9 . If not (NO in step S150), the control device 50 returns control to step S112.

[0118] <J. Numerical Calculation Results> The inventors confirmed the carbon dioxide concentrations of the raw carbon dioxide gas G0, the gas component G1, the liquid component L1, the gas component G2, and the liquid component L2 by numerical calculation. The numerical calculation was performed by constructing the refining apparatus 100 shown in Fig. 8 in the process simulator Pro / 2 manufactured by AVEVA. The results of the numerical calculation will be described below with reference to Figs. 10 and 11.

[0119] (J1. Numerical Calculation Result 1) FIG. 10 is a diagram showing a numerical calculation result SM1 when raw carbon dioxide gas G0 is refined under the first numerical calculation condition.

[0120] As a first numerical calculation condition, the inventors set the flow rate of the raw material carbon dioxide gas G0 from the manufacturing apparatus 20 to "10.0 Nm ３ / hr". The inventors also set the pressure of the raw carbon dioxide gas G0 in the compressor 132 to "2.3 MPaG". The inventors also set the temperature of the raw carbon dioxide gas G0 sent from the production apparatus 20 to the purification apparatus 100 to "40.0°C". The inventors also set the carbon dioxide gas concentration of the raw carbon dioxide gas G0 sent from the production apparatus 20 to the purification apparatus 100 to "95.0 mol%". The inventors also set the nitrogen gas concentration of the raw carbon dioxide gas G0 sent from the production apparatus 20 to the purification apparatus 100 to "5.0 mol%".

[0121] As a result, the following numerical calculation results were obtained for the liquid component L1 separated in the first storage tank 150A. That is, the flow rate of the liquid component L1 was 7.0 Nm ３ / hr". Furthermore, the pressure inside the first storage tank 150A became "2.3 MPaG". Furthermore, the temperature of the liquid component L1 became "-20.0°C". Furthermore, the carbon dioxide gas concentration in the liquid component L1 became "99.2 mol%". Furthermore, the nitrogen gas concentration in the liquid component L1 became "0.8 mol%".

[0122] Furthermore, the following numerical calculation results were obtained for the gas component G1 separated in the first storage tank 150A. That is, the flow rate of the gas component G1 was 3.0 Nm ３ / hr". Furthermore, the pressure inside the first storage tank 150A became "2.3 MPaG". Furthermore, the temperature of the gas component G1 became "-20.0°C". Furthermore, the carbon dioxide gas concentration in the gas component G1 became "85.1 mol%". Furthermore, the nitrogen gas concentration in the gas component G1 became "14.9 mol%".

[0123] Furthermore, the following numerical calculation results were obtained for the liquid component L2 separated in the second storage tank 150B. That is, the flow rate of the liquid component L2 was 5.8 Nm ３ / hr". Furthermore, the pressure inside the second storage tank 150B became "0.7 MPaG". Furthermore, the temperature of the liquid component L2 became "-47.0°C". Furthermore, the carbon dioxide gas concentration in the liquid component L2 became "99.93 mol%". Furthermore, the nitrogen gas concentration in the liquid component L2 became "0.07 mol%".

[0124] Furthermore, the following numerical calculation results were obtained for the gas component G2 separated in the second storage tank 150B. That is, the flow rate of the gas component G2 was 1.2 Nm ３ / hr". Furthermore, the pressure inside the second storage tank 150B became "0.7 MPaG". Furthermore, the temperature of the gas component G2 became "-47.0°C". Furthermore, the carbon dioxide gas concentration in the gas component G2 became "95.6 mol%". Furthermore, the nitrogen gas concentration in the gas component G2 became "4.4 mol%".

[0125] The carbon dioxide concentration of the liquid component L1 is "99.2 mol %", and if the carbon dioxide concentration required for the product is "99.2 mol %" or less, the second storage tank 150B does not necessarily need to be provided in the refining device 100.

[0126] The carbon dioxide concentration of the liquid component L2 is 99.93 mol %, which is higher than the carbon dioxide concentration of the liquid component L1, 99.2 mol %. Therefore, the liquid component L2 separated in the second storage tank 150B can be used for various purposes.

[0127] For example, the Food Sanitation Act stipulates that the concentration of liquefied carbon dioxide gas used as a food additive must be at least 99.5 mol%, and liquid component L2 satisfies this requirement. Therefore, liquid component L2 can also be used as a food additive.

[0128] As another example, the JIS standard stipulates that the concentration of liquefied carbon dioxide gas must be at least 99.8 mol% when used as a welding shielding gas, and liquid component L2 satisfies this requirement. Therefore, liquid component L2 can also be used as a welding shielding gas.

[0129] Furthermore, conventionally, distillation equipment was required to purify carbon dioxide gas with a concentration of 99 mol% or more. Distillation equipment is large, but the above-described purification device 100 is smaller than such distillation equipment. Furthermore, the cost of introducing the purification device 100 is lower than the cost of introducing a distillation device.

[0130] In addition, in the first storage tank 150A, "10.0 Nm ３ / hr" of raw material carbon dioxide gas G0 is "7.0 Nm ３ / hr" liquid component L1 and "3.0 Nm ３ / hr”, but as described above, the gas component G1 is returned to the production device 20 or the compressor 132. ３ / hr (=3.0×0.851) of carbon dioxide gas can be reused.

[0131] In addition, in the second storage tank 150B, "7.0 Nm ３ / hr" liquid component L1 is "5.8 Nm ３ / hr" liquid component L2 and "1.2 Nm ３ / hr”, but as described above, the gas component G2 is returned to the production device 20 or the compressor 132. ３ / hr (=1.2×0.956) of carbon dioxide gas can be reused.

[0132] (J2. Numerical Calculation Result 2) FIG. 11 is a diagram showing a numerical calculation result SM2 when raw carbon dioxide gas G0 is refined under the second numerical calculation conditions.

[0133] The second numerical calculation conditions are the same as the first numerical calculation conditions described above, except for the carbon dioxide gas concentration of the raw carbon dioxide gas G0 and the nitrogen gas concentration of the raw carbon dioxide gas G0. More specifically, as the second numerical calculation conditions, the inventors set the carbon dioxide gas concentration of the raw carbon dioxide gas G0 sent from the production apparatus 20 to the purification apparatus 100 to "90.0 mol%." Furthermore, the inventors set the nitrogen gas concentration of the raw carbon dioxide gas G0 sent from the production apparatus 20 to the purification apparatus 100 to "10.0 mol%."

[0134] As a result, the following numerical calculation results were obtained for the liquid component L1 separated in the first storage tank 150A. That is, the flow rate of the liquid component L1 was 3.5 Nm ３ / hr". Furthermore, the pressure inside the first storage tank 150A became "2.3 MPaG". Furthermore, the temperature of the liquid component L1 became "-20.0°C". Furthermore, the carbon dioxide gas concentration in the liquid component L1 became "99.2 mol%". Furthermore, the nitrogen gas concentration in the liquid component L1 became "0.8 mol%".

[0135] Furthermore, the following numerical calculation results were obtained for the gas component G1 separated in the first storage tank 150A. That is, the flow rate of the gas component G1 was 6.5 Nm ３ / hr". Furthermore, the pressure inside the first storage tank 150A became "2.3 MPaG". Furthermore, the temperature of the gas component G1 became "-20.0°C". Furthermore, the carbon dioxide gas concentration in the gas component G1 became "85.1 mol%". Furthermore, the nitrogen gas concentration in the gas component G1 became "14.9 mol%".

[0136] Furthermore, the following numerical calculation results were obtained for the liquid component L2 separated in the second storage tank 150B. That is, the flow rate of the liquid component L2 was 2.9 Nm ３ / hr". Furthermore, the pressure inside the second storage tank 150B became "0.7 MPaG". Furthermore, the temperature of the liquid component L2 became "-47.0°C". Furthermore, the carbon dioxide gas concentration in the liquid component L2 became "99.93 mol%". Furthermore, the nitrogen gas concentration in the liquid component L2 became "0.07 mol%".

[0137] Furthermore, the following numerical calculation results were obtained for the gas component G2 separated in the second storage tank 150B. That is, the flow rate of the gas component G2 was 0.6 Nm ３ / hr". Furthermore, the pressure inside the second storage tank 150B became "0.7 MPaG". Furthermore, the temperature of the gas component G2 became "-47.0°C". Furthermore, the carbon dioxide gas concentration in the gas component G2 became "95.6 mol%". Furthermore, the nitrogen gas concentration in the gas component G2 became "4.4 mol%".

[0138] As described above, it has been confirmed that even if the carbon dioxide concentration of the raw carbon dioxide gas G0 sent from the manufacturing apparatus 20 to the refining apparatus 100 is about "90.0 mol%", the carbon dioxide concentration of the liquid component L1 increases to "99.93 mol%", and the carbon dioxide concentration of the liquid component L2 increases to "99.93 mol%". Therefore, it has been confirmed that the carbon dioxide concentration of the raw carbon dioxide gas G0 sent to the refining apparatus 100 should be at least "90.0 mol%" or higher.

[0139] <K. Others> As described above, the refining device 100 refines high-purity raw carbon dioxide gas G0 into even higher-purity liquid components L1 and L2. This expands the applications of liquefied carbon dioxide gas and enables the effective use of exhaust gas. As a result, it is possible to contribute to activities for the Sustainable Development Goals (SDGs).

[0140] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0141] 10 Purification system, 20 Manufacturing apparatus, 50 Control device, 100 Purification apparatus, 101 Control circuit, 102 ROM, 103 RAM, 104 Communication interface, 110 Bus, 120 Auxiliary storage device, 122 Control program, 132 Compressor, 134 Dehumidifier, 136A Heat exchanger, 136B Heat exchanger, 138 Cooler, 150A First storage tank, 150B Second storage tank, A1 Flow path, A2 Flow path, B1 Flow path, B2 Flow path, C0 Concentration sensor, C1 Concentration sensor, C2 Concentration sensor, D0 Reference concentration, D1 Comparison concentration, D2 Comparison concentration, F1 Pipe, F10 Pipe, F1A Pipe, F1B Pipe, F2 Pipe, F2A Pipe, F2B Pipe, G0 Raw carbon dioxide, G1 Gas component, G2 Gas component, L1 liquid component, L2 liquid component, SM1 numerical calculation result, SM2 numerical calculation result, SW1 switching mechanism, SW2 switching mechanism, V pressure reducing valve, V1A valve, V1B valve, V2A valve, V2B valve.

Claims

1. A purification device for purifying liquefied carbon dioxide gas from raw carbon dioxide gas produced by a carbon dioxide gas production device, wherein the raw carbon dioxide gas contains carbon dioxide gas and another gas having a boiling point lower than that of the carbon dioxide gas, the purification device comprising: a compressor for compressing the raw carbon dioxide gas; a dehumidifier for dehumidifying the raw carbon dioxide gas compressed by the compressor; a cooler for liquefying the raw carbon dioxide gas by cooling the raw carbon dioxide gas that has passed through the dehumidifier, and producing liquefied carbon dioxide gas from the raw carbon dioxide gas; a first storage tank configured to store the liquefied carbon dioxide gas and configured to separate the liquefied carbon dioxide gas into a first liquid component and a first gas component and discharge them; and a first pipe for returning the first gas component to the production device.

2. The purification apparatus of claim 1, further comprising a first heat exchanger for exchanging heat between the raw carbon dioxide gas after passing through the dehumidifier and before passing through the cooler and the first gas component.

3. The refining apparatus according to claim 2, wherein the piping state of the first piping is configured to be switchable at least between a state in which the first gas component that has passed through the first heat exchanger is returned to the manufacturing apparatus and a state in which the first gas component is returned to the compressor, and the refining apparatus is equipped with: a concentration sensor for detecting the concentration of carbon dioxide contained in the raw carbon dioxide as a reference concentration before the raw carbon dioxide is sent to the compressor; and a concentration sensor for detecting the concentration of carbon dioxide contained in the first gas component as a comparison concentration, and the piping state of the first piping is switched depending on the comparison result between the reference concentration and the comparison concentration.

4. The purification device described in claim 3, wherein the piping state of the first piping is switched so as to return the first gas component to the manufacturing device when the comparison concentration is lower than the reference concentration, and is switched so as to return the first gas component to the compressor when the comparison concentration is higher than the reference concentration.

5. The purification device according to any one of claims 1 to 4, further comprising a second storage tank configured to store the first liquid component separated in the first storage tank and to separate the first liquid component into a second liquid component and a second gas component and discharge them, and the pressure in the second storage tank is lower than the pressure in the first storage tank.

6. The purification apparatus according to claim 2, further comprising a second storage tank configured to store the first liquid component separated in the first storage tank and configured to separate the first liquid component into a second liquid component and a second gas component and discharge them, the pressure in the second storage tank being lower than the pressure in the first storage tank, and the purification apparatus further comprising a second heat exchanger for exchanging heat between the raw carbon dioxide gas that has passed through the first heat exchanger and the second gas component.

7. The purification apparatus according to claim 6, further comprising a second pipe for returning the second gas component that has passed through the second heat exchanger to the compressor or the production apparatus.

8. The purification apparatus according to claim 7, wherein the piping state of the second piping is configured to be switchable at least between a state in which the second gas component that has passed through the second heat exchanger is returned to the manufacturing apparatus and a state in which the second gas component is returned to the compressor, and the purification apparatus further comprises: a concentration sensor for detecting the concentration of carbon dioxide contained in the raw carbon dioxide as a reference concentration before the raw carbon dioxide is sent to the compressor; and a concentration sensor for detecting the concentration of carbon dioxide contained in the second gas component as a comparison concentration, and the piping state of the second piping is switched depending on the comparison result between the reference concentration and the comparison concentration.

9. The purification device described in claim 8, wherein the piping state of the second piping is switched so as to return the second gas component to the manufacturing device when the comparison concentration is lower than the reference concentration, and is switched so as to return the second gas component to the compressor when the comparison concentration is higher than the reference concentration.

10. A method for purifying liquefied carbon dioxide gas from raw carbon dioxide gas produced by a carbon dioxide gas production apparatus, wherein the raw carbon dioxide gas contains carbon dioxide gas and another gas having a boiling point lower than that of the carbon dioxide gas, the method comprising: a step of compressing the raw carbon dioxide gas; a step of dehumidifying the raw carbon dioxide gas compressed in the compression step; a step of liquefying the raw carbon dioxide gas by cooling the raw carbon dioxide gas dehumidified in the dehumidification step, and producing liquefied carbon dioxide gas from the raw carbon dioxide gas; a step of separating the liquefied carbon dioxide gas produced in the production step into a first liquid component and a first gas component and discharging them; and a step of returning the first gas component to the production apparatus.

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