Carbon dioxide separation apparatus and carbon dioxide separation method

Abstract

The present invention provides a carbon dioxide separation device that can improve the concentration of carbon dioxide contained in the permeate gas separated by a separation membrane module. [Solution] The carbon dioxide separation apparatus comprises: a first separation membrane module that selectively permeates carbon dioxide from a gas containing carbon dioxide; a second separation membrane module to which the permeate gas from the first separation membrane module is supplied and which selectively permeates carbon dioxide; a first passage for discharging the permeate gas from the second separation membrane module; a second passage for supplying the permeate gas from the second separation membrane module to the first separation membrane module or the second separation membrane module; a third passage for discharging the unpermeated gas from the second separation membrane module; and a fourth passage for supplying the unpermeated gas from the second separation membrane module to the first separation membrane module or the second separation membrane module.

Description

Technical Field

[0001] The present invention relates to a carbon dioxide separation device and a carbon dioxide separation method.

Background Art

[0002] One of the causes of global warming is an increase in the emissions of greenhouse gases such as carbon dioxide. In order to reduce the emissions of carbon dioxide, technologies for separating and recovering carbon dioxide from exhaust gases and the atmosphere are being developed.

[0003] As a technology related to the membrane separation method using a gas separation membrane, for example, Patent Document 1 discloses a methane concentration system in which a plurality of stages of carbon dioxide permeation membranes are combined. The system of Patent Document 1 guides the non-permeating gas of the previous stage permeation membrane to the subsequent stage permeation membrane, and further separates carbon dioxide to obtain high-concentration methane.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The technology described in Patent Document 1 increases the concentration of non-permeating gas and does not improve the concentration of permeating gas. <9000029>

[0006] The present disclosure aims to provide a carbon dioxide separation device and the like that can improve the concentration of carbon dioxide contained in the permeating gas separated by a separation membrane module.

Means for Solving the Problems

[0007] A carbon dioxide separation apparatus according to one aspect of the present disclosure comprises: a first separation membrane module that selectively permeates carbon dioxide from a gas containing carbon dioxide; a second separation membrane module to which the permeate gas of the first separation membrane module is supplied and which selectively permeates carbon dioxide; a first passage for discharging the permeate gas of the second separation membrane module; a second passage for supplying the permeate gas of the second separation membrane module to the first separation membrane module or the second separation membrane module; a third passage for discharging the unpermeated gas of the second separation membrane module; and a fourth passage for supplying the unpermeated gas of the second separation membrane module to the first separation membrane module or the second separation membrane module.

[0008] A carbon dioxide separation method relating to one aspect of the present disclosure is a carbon dioxide separation method using a carbon dioxide separation apparatus, the carbon dioxide separation apparatus comprising: a first separation membrane module that selectively permeates carbon dioxide from a gas containing carbon dioxide; a second separation membrane module to which the permeate gas of the first separation membrane module is supplied and which selectively permeates carbon dioxide; a first passage for discharging the permeate gas of the second separation membrane module; a second passage for supplying the permeate gas of the second separation membrane module to the first separation membrane module or the second separation membrane module; a third passage for discharging the unpermeated gas of the second separation membrane module; and a fourth passage for supplying the unpermeated gas of the second separation membrane module to the first separation membrane module or the second separation membrane module, wherein the flow path or flow rate of the permeate gas or unpermeated gas of the second separation membrane module is adjusted according to the carbon dioxide concentration of the permeate gas of the second separation membrane module. [Effects of the Invention]

[0009] According to this disclosure, the concentration of carbon dioxide contained in the permeate gas separated by the separation membrane module can be improved. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows an example configuration of the carbon dioxide separation system of this embodiment. [Modes for carrying out the invention]

[0011] (1) A carbon dioxide separation apparatus according to one aspect of the present disclosure comprises: a first separation membrane module that selectively permeates carbon dioxide from a gas containing carbon dioxide; a second separation membrane module to which the permeate gas from the first separation membrane module is supplied and which selectively permeates carbon dioxide; a first passage for discharging the permeate gas from the second separation membrane module; a second passage for supplying the permeate gas from the second separation membrane module to the first separation membrane module or the second separation membrane module; a third passage for discharging the unpermeated gas from the second separation membrane module; and a fourth passage for supplying the unpermeated gas from the second separation membrane module to the first separation membrane module or the second separation membrane module.

[0012] In this specification, "selective" means that the carbon dioxide concentration is higher after permeation than before permeation through the separation membrane module, and does not mean that only carbon dioxide permeates. "Permeated gas" means the gas that has permeated through the separation membrane module. "Unpermeated gas" means the gas that has not permeated through the separation membrane module.

[0013] When separating carbon dioxide using separation membrane modules, one possible method is to connect multiple separation membrane modules in series and supply the permeate gas from the preceding separation membrane module to the subsequent separation membrane module to improve the final concentration of carbon dioxide. The concentration of carbon dioxide in the permeate gas increases each time it passes through a separation membrane module that selectively permeates carbon dioxide. However, if the concentration of carbon dioxide in the raw material gas itself is low, it is difficult to obtain sufficiently concentrated carbon dioxide even when using multiple separation membrane modules.

[0014] According to the carbon dioxide separation apparatus described in (1) above, the permeate and unpermeated gas from the second separation membrane module can be resupplied to a specific separation membrane module through the second and fourth passages. By circulating the permeate gas containing concentrated carbon dioxide to the carbon dioxide separation apparatus, the carbon dioxide concentration of the final permeate gas can be improved. Since the carbon dioxide concentration can be increased by circulating the permeate gas, a stable supply of high-concentration carbon dioxide can be obtained regardless of the carbon dioxide concentration of the raw gas. By circulating the unpermeated gas containing carbon dioxide that was not separated by the separation membrane module to the carbon dioxide separation apparatus, the amount of carbon dioxide supplied to the carbon dioxide separation apparatus can be increased, improving the carbon dioxide concentration of the final permeate gas. The processing capacity of the separation membrane module can be fully utilized, and carbon dioxide can be separated efficiently.

[0015] (2) In the carbon dioxide separation apparatus described in (1) above, the second passage may supply the permeate gas from the second separation membrane module to the second separation membrane module, and the fourth passage may supply the unpermeated gas from the second separation membrane module to the first separation membrane module.

[0016] With the above configuration, the carbon dioxide concentration of the permeate gas from the second separation membrane module can be increased by resupplying the permeate gas from the second separation membrane module to the second separation membrane module. Furthermore, by resupplying the unpermeated gas from the second separation membrane module to the first separation membrane module, which is upstream of the second separation membrane module, the amount of carbon dioxide supplied to the first and second separation membrane modules can be increased, thereby improving the yield of the carbon dioxide separation apparatus.

[0017] (3) The carbon dioxide separation apparatus described in (1) or (2) above may include a first adjustment unit that adjusts the flow path or flow rate of the permeate gas of the second separation membrane module according to the carbon dioxide concentration of the permeate gas of the second separation membrane module.

[0018] According to the above configuration, the flow path or flow rate of the permeate gas in the second separation membrane module can be selectively switched according to the carbon dioxide concentration of the permeate gas in the second separation membrane module, thereby allowing adjustment of the balance between increasing the carbon dioxide concentration of the permeate gas in the second separation membrane module and the carbon dioxide recovery rate.

[0019] (4) In the carbon dioxide separation apparatus described in (3) above, if the carbon dioxide concentration of the permeate gas from the second separation membrane module is greater than or equal to a predetermined value, the first adjustment unit may increase the flow rate of the permeate gas from the second separation membrane module discharged through the first passage, and if the carbon dioxide concentration of the permeate gas from the second separation membrane module is less than a predetermined value, the first adjustment unit may decrease the flow rate of the permeate gas from the second separation membrane module discharged through the first passage.

[0020] According to the above configuration, if the carbon dioxide concentration of the permeate gas in the second separation membrane module is high, the carbon dioxide recovery rate can be improved by increasing the amount of permeate gas discharged from the second separation membrane module. If the carbon dioxide concentration of the permeate gas is low, the final carbon dioxide concentration of the permeate gas can be increased by reducing the amount of permeate gas discharged from the second separation membrane module and increasing the circulation rate.

[0021] (5) Any one of the carbon dioxide separation apparatuses described in (1) to (4) above may include a second adjustment unit that adjusts the flow path or flow rate of the unpermeated gas in the second separation membrane module according to the carbon dioxide concentration of the supply gas supplied to the first separation membrane module and the carbon dioxide concentration of the unpermeated gas in the second separation membrane module.

[0022] According to the above configuration, the flow path or flow rate of the unpermeated gas of the second separation membrane module can be selectively switched according to the carbon dioxide concentration of the supply gas supplied to the first separation membrane module and the unpermeated gas of the second separation membrane module. For example, when the carbon dioxide concentration of the unpermeated gas of the second separation membrane module is somewhat higher than that of the supply gas of the first separation membrane module, by circulating the unpermeated gas of the second separation membrane module, it is possible to suppress a decrease in the separation efficiency of the carbon dioxide concentration of the separation membrane module, reliably obtain the effect of increasing the carbon dioxide concentration commensurate with the recycling of the unpermeated gas, and improve the recovery rate.

[0023] (6) The carbon dioxide separation device according to any one of (1) to (5) above may include a second adjustment unit that adjusts the flow path or flow rate of the unpermeated gas of the second separation membrane module according to the flow rate of the supply gas supplied to the first separation membrane module and the amount of decrease in the carbon dioxide concentration of the supply gas due to mixing of the unpermeated gas of the second separation membrane module with the supply gas.

[0024] According to the above configuration, the flow path or flow rate of the unpermeated gas of the second separation membrane module can be selectively switched according to the flow rate of the supply gas supplied to the first separation membrane module and the amount of decrease in the carbon dioxide concentration due to mixing of the unpermeated gas of the second separation membrane module with the supply gas. Considering the processing capacity of the first separation membrane module, the unpermeated gas suitable for recycling can be appropriately re-supplied.

[0025] (7) In the carbon dioxide separation device according to (6) above, when the flow rate of the supply gas is less than a predetermined value and the amount of decrease in the carbon dioxide concentration of the supply gas is less than a predetermined value, the second adjustment unit increases the flow rate of the unpermeated gas of the second separation membrane module supplied through the fourth passage, and when the flow rate of the supply gas is less than a predetermined value and the amount of decrease in the carbon dioxide concentration of the supply gas is not less than a predetermined value, the second adjustment unit may increase the flow rate of the unpermeated gas of the second separation membrane module discharged through the third passage.

[0026] According to the above configuration, it is possible to reliably obtain the effect of increasing the carbon dioxide concentration to match the recycling of unpermeated gas. When the flow rate of the supplied gas is high and the decrease in carbon dioxide concentration is small, the carbon dioxide recovery rate can be improved by increasing the amount of unpermeated gas recycled in the second separation membrane module. If the above requirements are not met, the decrease in the separation efficiency of the separation membrane module in terms of carbon dioxide concentration can be suppressed by increasing the amount of unpermeated gas discharged in the second separation membrane module.

[0027] (8) In any one of the carbon dioxide separation apparatuses described in (1) to (7) above, the carbon dioxide concentration of the unpermeated gas of the second separation membrane module may be higher than the carbon dioxide concentration of the supply gas supplied to the first separation membrane module or the second separation membrane module, which is the destination of the unpermeated gas of the second separation membrane module via the fourth passage.

[0028] With the above configuration, it is possible to reliably obtain the effect of increasing the carbon dioxide concentration to a level that is commensurate with the recycling of the unpermeated gas from the second separation membrane module.

[0029] (9) Any one of the carbon dioxide separation devices described in (1) to (8) above may include at least one of the following: a first sensor for detecting the carbon dioxide concentration of the supply gas supplied to the first separation membrane module; a second sensor for detecting the carbon dioxide concentration of the unpermeated gas of the second separation membrane module; a third sensor for detecting the carbon dioxide concentration of the permeated gas of the second separation membrane module; a fourth sensor for detecting the flow rate of the supply gas supplied to the first separation membrane module; and a third sensor for detecting the flow rate of the unpermeated gas of the second separation membrane module.

[0030] With the above configuration, the operating status of the carbon dioxide separation device can be accurately monitored in real time. Based on the detected data, the operation of the carbon dioxide separation device can be appropriately controlled.

[0031] (10) A carbon dioxide separation method according to one aspect of the present disclosure is a carbon dioxide separation method using a carbon dioxide separation apparatus, the carbon dioxide separation apparatus comprising: a first separation membrane module that selectively permeates carbon dioxide of a gas containing carbon dioxide; a second separation membrane module to which the permeate gas of the first separation membrane module is supplied and which selectively permeates carbon dioxide; a first passage for discharging the permeate gas of the second separation membrane module; a second passage for supplying the permeate gas of the second separation membrane module to the first separation membrane module or the second separation membrane module; a third passage for discharging the unpermeated gas of the second separation membrane module; and a fourth passage for supplying the unpermeated gas of the second separation membrane module to the first separation membrane module or the second separation membrane module, wherein the flow path or flow rate of the permeate gas or unpermeated gas of the second separation membrane module is adjusted according to the carbon dioxide concentration of the permeate gas of the second separation membrane module.

[0032] This disclosure will be described in detail with reference to drawings illustrating embodiments thereof.

[0033] Figure 1 shows an example of the configuration of the carbon dioxide separation system S of this embodiment. The carbon dioxide separation system S of this embodiment is a system that concentrates, separates, and recovers carbon dioxide from a raw material gas containing carbon dioxide. The carbon dioxide separation system S comprises a carbon dioxide separation device 1 that separates carbon dioxide and a control device 9 that controls the carbon dioxide separation device 1.

[0034] The carbon dioxide separation apparatus 1 is a multi-stage carbon dioxide separation apparatus equipped with multiple separation membrane modules 2. In the carbon dioxide separation apparatus 1, the multiple separation membrane modules 2 are connected in series, and the permeate gas that has passed through the preceding separation membrane module 2 is supplied to the subsequent separation membrane module 2. Each stage may consist of two or more separation membrane modules 2 connected in parallel. The arrangement and number of separation membrane modules 2 provided in the carbon dioxide separation apparatus 1 can be selected according to the required processing volume, carbon dioxide concentration, recovery rate, etc.

[0035] In the example shown in Figure 1, the carbon dioxide separation device 1 is a two-stage device and comprises three separation membrane modules 2, including the first stage first separation membrane modules 21 and 22 connected in parallel, and the second stage second separation membrane module 23 connected in series with respect to the first stage.

[0036] The first separation membrane module 21 is equipped with a separation membrane that selectively permeates carbon dioxide (CO2). Examples of separation membranes that can be used include hollow fiber type, spiral type, tubular type, pleated type, and plate & frame type (stack type). Examples of membrane materials include polymer materials such as polyimide, cellulose acetate, polysulfone, and polycarbonate, and inorganic materials such as porous silica and porous carbon.

[0037] The first separation membrane module 22 and the second separation membrane module 23 have the same configuration as the first separation membrane module 21 and have a separation membrane that selectively permeates CO2. The separation membranes of the first separation membrane module 22 and the second separation membrane module 23 may be of the same type as the separation membrane of the first separation membrane module 21, or they may be of a different type.

[0038] In the first separation membrane modules 21, 22 and the second separation membrane module 23, a gas containing CO2 is brought into contact with the separation membrane, and the CO2 is separated by permeating the supply side (the side to which the gas is supplied) of the first separation membrane modules 21, 22 and the second separation membrane module 23 by increasing the pressure.

[0039] The separation method of the separation membrane module 2 is not limited to the example described above. It may also be a method of reducing the pressure on the permeate side (the side from which the permeate gas is discharged) of the separation membrane module 2, or a method of introducing sweep gas to the permeate side of the separation membrane module 2, etc.

[0040] The raw material gas supplied to the first separation membrane modules 21 and 22 is a gas containing carbon dioxide, such as air or exhaust gas. The concentration of carbon dioxide in the raw material gas is, for example, 0.01 vol% to 30 vol%. The raw material gas contains components other than carbon dioxide. Other components in the raw material gas include, for example, nitrogen, water vapor, oxygen, carbon monoxide, hydrogen sulfide, carbonyl sulfide, sulfur dioxide, nitrogen dioxide, methane, and hydrogen.

[0041] The first separation membrane modules 21 and 22 are connected to a raw material gas supply channel 71 for supplying raw material gas, an intermediate supply channel 72 for supplying permeate gas that has permeated through the first separation membrane modules 21 and 22 to the second separation membrane module 23, and an intermediate discharge channel 73 for discharging unpermeated gas that has not permeated through the first separation membrane modules 21 and 22.

[0042] The raw material gas supply channel 71 supplies raw material gas to the first separation membrane modules 21 and 22. Downstream of the raw material gas supply channel 71, it branches at a branching point and connects to each of the first separation membrane modules 21 and 22. The raw material gas is distributed and supplied to each of the first separation membrane modules 21 and 22.

[0043] The raw material gas may be pretreated by scrubbing, thermal decomposition, plasma decomposition, catalytic reaction, dehumidification, etc.

[0044] The intermediate supply channel 72 connects the first separation membrane modules 21 and 22 to the second separation membrane module 23. The intermediate supply channel 72 supplies the permeate gas discharged from the first separation membrane modules 21 and 22 to the second separation membrane module 23. Upstream of the intermediate supply channel 72, it branches out corresponding to each of the first separation membrane modules 21 and 22 and merges at the confluence point.

[0045] The intermediate discharge channel 73 discharges the unpermeated gas from the first separation membrane modules 21 and 22 to the outside of the system. Alternatively, the intermediate discharge channel 73 may be connected to an unpermeated gas recovery unit (not shown) that recovers the unpermeated gas, and the unpermeated gas from the first separation membrane modules 21 and 22 may be supplied to the unpermeated gas recovery unit. Upstream of the intermediate discharge channel 73, the channels branch out corresponding to each of the first separation membrane modules 21 and 22 and merge at the confluence point.

[0046] The second separation membrane module 23 is connected to a permeate gas discharge channel 74 for discharging permeate gas that has permeated through the second separation membrane module 23, and an unpermeate gas discharge channel 75 for discharging unpermeate gas that has not permeated through the second separation membrane module 23.

[0047] The permeate gas discharge passage 74 connects the second separation membrane module 23 to the permeate gas recovery unit 8, which recovers the permeate gas. The permeate gas discharge passage 74 allows the permeate gas discharged from the second separation membrane module 23 to flow to the permeate gas recovery unit 8. The permeate gas discharge passage 74 corresponds to the first passage.

[0048] The unpermeated gas discharge channel 75 discharges the unpermeated gas from the second separation membrane module 23 to the outside of the system. Alternatively, the unpermeated gas discharge channel 75 may be connected to an unpermeated gas recovery unit (not shown) that recovers the unpermeated gas, and the unpermeated gas from the second separation membrane module 23 may be supplied to the unpermeated gas recovery unit. The unpermeated gas discharge channel 75 corresponds to the third passage.

[0049] The carbon dioxide separation device 1 includes a permeate gas reduction path 76 for circulating the permeate gas from the second separation membrane module 23, and an unpermeate gas reduction path 77 for circulating the unpermeated gas from the second separation membrane module 23. The permeate gas reduction path 76 corresponds to the second passage, and the unpermeate gas reduction path 77 corresponds to the fourth passage.

[0050] The permeate gas reduction path 76 supplies the permeate gas from the second separation membrane module 23, which flows through the permeate gas discharge path 74, to the second separation membrane module 23. One end of the permeate gas reduction path 76 is connected to the middle of the permeate gas discharge path 74, and the other end is connected to a point downstream of the confluence point of the intermediate supply path 72.

[0051] The impermeable gas recirculation path 77 supplies the impermeable gas from the second separation membrane module 23, which flows through the impermeable gas discharge path 75, to the first separation membrane modules 21 and 22. One end of the impermeable gas recirculation path 77 is connected to the middle of the impermeable gas discharge path 75, and the other end is connected to a point upstream of the branching point of the raw material gas supply path 71.

[0052] The raw gas supply channel 71, intermediate supply channel 72, intermediate discharge channel 73, permeate gas discharge channel 74, unpermeated gas discharge channel 75, permeate gas return channel 76, and unpermeated gas return channel 77 are not particularly limited, and known piping or the like can be used as appropriate.

[0053] The carbon dioxide separation device 1 comprises a compressor 3, a flow rate adjustment unit 4, a flow rate sensor 5, and a concentration sensor 6.

[0054] The compressor 3 is installed on the supply side of each stage of the separation membrane module 2. The compressor 3 is a device for compressing and sending out gas. By increasing the pressure of the gas supplied to the separation membrane module 2 by the compressor 3, the partial pressure of the gas on the supply side can be made higher than the partial pressure of the gas on the permeate side.

[0055] The compressor 3 includes a first compressor 31 and a second compressor 32. The first compressor 31 is located downstream of the connection point between the raw gas supply line 71 and the unpermeated gas reduction line 77, and upstream of the branching point, and boosts the pressure on the supply side of the first separation membrane modules 21 and 22. The second compressor 32 is located downstream of the connection point between the intermediate supply line 72 and the permeated gas reduction line 76, and boosts the pressure on the supply side of the second separation membrane module 23.

[0056] The flow rate adjustment unit 4 is a device for adjusting the flow rate of permeate gas and impermeate gas. The flow rate adjustment unit 4 includes, for example, an electromagnetic valve capable of adjusting the flow rate of permeate gas or impermeate gas, an electromagnetic valve for switching whether or not permeate gas or impermeate gas can pass through, and an opening capable of adjusting the amount of permeate gas or impermeate gas that passes through. The flow rate adjustment unit 4 may also be a mass flow controller.

[0057] The flow rate adjustment unit 4 includes the first to fourth flow rate adjustment units 41 to 44. The first flow rate adjustment unit 41 is located downstream of the connection point between the permeate gas discharge path 74 and the permeate gas return path 76, and adjusts the flow rate of the permeate gas from the second separation membrane module 23 that is supplied to the permeate gas recovery unit 8 through the permeate gas discharge path 74. The second flow rate adjustment unit 42 is located in the permeate gas return path 76, and adjusts the flow rate of the permeate gas from the second separation membrane module 23 that is supplied to the second separation membrane module 23 through the permeate gas return path 76. The third flow rate adjustment unit 43 is located downstream of the connection point between the unpermeated gas discharge path 75 and the unpermeated gas return path 77, and adjusts the flow rate of the unpermeated gas from the second separation membrane module 23 that is discharged outside the system through the unpermeated gas discharge path 75. The fourth flow rate adjustment unit 44 is located in the unpermeated gas return path 77, and adjusts the flow rate of the unpermeated gas from the second separation membrane module 23 that is supplied to the first separation membrane modules 21 and 22 through the unpermeated gas return path 77.

[0058] The first flow rate adjustment section 41 and the second flow rate adjustment section 42 are examples of the first adjustment section, and the third flow rate adjustment section 43 and the fourth flow rate adjustment section 44 are examples of the second adjustment section. As the first and second adjustment sections, any suitable configuration can be used that can adjust at least one of the flow path and flow rate of the permeate gas and the unpermeated gas of the second separation membrane module 23. For example, the first adjustment section may be a switching valve provided at the connection between the permeate gas discharge passage 74 and the permeate gas return passage 76 to adjust the flow path of the permeate gas or the flow path and flow rate. The second adjustment section may be a switching valve provided at the connection between the unpermeated gas discharge passage 75 and the unpermeate gas return passage 77 to adjust the flow path and flow rate of the unpermeated gas.

[0059] The flow sensor 5 is a sensor device for detecting the flow rate of various gases (e.g., raw material gas, permeate gas, unpermeate gas, etc.) flowing into the carbon dioxide separation device 1. The flow sensor 5 outputs the detected flow rate data obtained from the detection to the control device 9.

[0060] The flow sensor 5 includes a first flow sensor 51 and a second flow sensor 52. The first flow sensor 51 is located upstream of the connection point between the raw material gas supply path 71 and the unpermeable gas reduction path 77, and detects the flow rate of the raw material gas supplied to the first separation membrane modules 21 and 22 through the raw material gas supply path 71. The flow rate of the raw material gas detected by the first flow sensor 51 is the total flow rate of the raw material gas supplied to each of the first separation membrane modules 21 and 22, and is the flow rate of the raw material gas in a state where it is not mixed with unpermeable gas circulated through the unpermeable gas reduction path 77.

[0061] The second flow sensor 52 is located upstream of the connection point between the unpermeable gas discharge path 75 and the unpermeable gas return path 77, and detects the flow rate of unpermeable gas discharged from the second separation membrane module 23.

[0062] The number and location of flow sensors 5 in the carbon dioxide separation device 1 can be selected according to the configuration and flow path design of the carbon dioxide separation device 1. The flow sensors 5 may be installed downstream of the connection between the permeate gas discharge path 74 and the permeate gas return path 76, downstream of the connection between the permeate gas return path 76 and the unpermeate gas discharge path 75 and the unpermeate gas return path 77, or in the unpermeate gas return path 77, etc. The flow sensors 5 may also be included in the flow rate adjustment unit 4.

[0063] The concentration sensor 6 is a sensor device for detecting the concentrations of various gases contained in the various gases flowing through the carbon dioxide separation device 1. For example, the concentration sensor 6 detects the CO2 concentration. The concentration sensor 6 outputs the detected CO2 concentration data obtained from the detection to the control device 9.

[0064] The concentration sensor 6 includes first concentration sensors 61 to third concentration sensors 63. The first concentration sensor 61 is located upstream of the connection point between the raw material gas supply path 71 and the unpermeable gas reduction path 77, and detects the CO2 concentration of the raw material gas supplied to the first separation membrane modules 21 and 22 through the raw material gas supply path 71. The CO2 concentration of the raw material gas detected by the first concentration sensor 61 is the CO2 concentration of the raw material gas in a state where it is not mixed with unpermeable gas circulated through the unpermeable gas reduction path 77.

[0065] The second concentration sensor 62 is located upstream of the connection point between the unpermeable gas discharge path 75 and the unpermeable gas return path 77, and detects the CO2 concentration of the unpermeable gas discharged from the second separation membrane module 23. The third concentration sensor 63 is located upstream of the connection point between the permeable gas discharge path 74 and the permeable gas return path 76, and detects the CO2 concentration of the permeable gas discharged from the second separation membrane module 23.

[0066] The concentration sensor 6 may include a fourth concentration sensor (not shown). The fourth concentration sensor is provided, for example, downstream of the connection point between the raw material gas supply line 71 and the unpermeable gas reduction line 77, and upstream of the branching point. The fourth concentration sensor can detect the CO2 concentration of the mixed gas of the unpermeable gas of the second separation membrane module 23 and the raw material gas circulated through the unpermeable gas reduction line 77.

[0067] The operation of the carbon dioxide separation device 1 is described below. The raw material gas containing CO2 is supplied to each of the first separation membrane modules 21 and 22 through the raw material gas supply line 71. The permeated gas from the first separation membrane modules 21 and 22 is supplied to the subsequent second separation membrane module 23 through the intermediate supply line 72. The unpermeated gas from the first separation membrane modules 21 and 22 is discharged out of the system through the intermediate discharge line 73.

[0068] The permeate gas from the second separation membrane module 23 is recovered in the permeate gas recovery unit 8 via the permeate gas discharge passage 74. The unpermeated gas from the second separation membrane module 23 is discharged outside the system via the unpermeate gas discharge passage 75.

[0069] The carbon dioxide in the raw gas is concentrated each time it passes through each separation membrane module 2. In the carbon dioxide separation device 1, the CO2 concentration of the raw gas < the CO2 concentration of the permeate gas from the first separation membrane modules 21 and 22 < the CO2 concentration of the permeate gas from the second separation membrane module 23.

[0070] In the carbon dioxide separation apparatus 1 of this embodiment, the permeate gas and unpermeated gas of the second separation membrane module 23 are recycled according to the state of the permeate gas and unpermeated gas of the second separation membrane module 23. The permeate gas of the second separation membrane module 23 is supplied back to the second separation membrane module 23 through the permeate gas reduction path 76 as needed. The permeate gas of the second separation membrane module 23 is supplied back to the second separation membrane module 23 through the permeate gas reduction path 76 as needed. By recycling the permeate gas and unpermeated gas of the second separation membrane module 23, the concentration of carbon dioxide contained in the permeate gas recovered in the permeate gas recovery unit 8 is improved.

[0071] The gas supplied to the first separation membrane modules 21 and 22 may be the raw material gas, the unpermeated gas from the second separation membrane module 23, or a mixed gas of the raw material gas and the unpermeated gas from the second separation membrane module 23. The gas supplied to the second separation membrane module 23 may be the permeated gas from the first separation membrane modules 21 and 22, and the permeated gas from the second separation membrane module 23.

[0072] The control device 9 is a computer that controls the operation of the carbon dioxide separation system S. The control device 9 includes a processor such as a CPU (Central Processing Unit) as a processing unit (not shown), memory, a communication unit, and an input / output interface. The memory stores various computer programs and data referenced by the processor. The control device 9 may further include a display unit for displaying images, an operation unit for receiving user input, and so on. The control device 9 is connected to the carbon dioxide separation device 1 by wire or wireless connection.

[0073] The control device 9 may be located away from the carbon dioxide separation device 1. The control device 9 may be connected to the carbon dioxide separation device 1 via a communication network such as the Internet or a LAN (Local Area Network), and may send and receive detection data and control signals to and from the carbon dioxide separation device 1 via the communication network. The control device 9 may also send and receive various information to and from the carbon dioxide separation device 1 via a computer located near the carbon dioxide separation device 1.

[0074] The control device 9 generates a control signal to control the operation of the flow rate adjustment unit 4 based on the detection data from the flow rate sensor 5 and the concentration sensor 6, according to a procedure described later. The control device 9 outputs the generated control signal to the carbon dioxide separation device 1 to control the operation of each part.

[0075] The operation control of the carbon dioxide separation device 1 will be described below. In this embodiment, the control device 9 is described as automatically performing the operation control of the carbon dioxide separation device 1, but this is not the only option, and some operations may be performed manually.

[0076] The control device 9 controls the flow of permeate gas through the second separation membrane module 23 based on the CO2 concentration of the permeate gas through the second separation membrane module 23.

[0077] The control device 9 acquires the detected value of the CO2 concentration of the permeate gas from the second separation membrane module 23 discharged from the second separation membrane module 23 via the third concentration sensor 63.

[0078] The control device 9 determines whether the detected CO2 concentration of the permeate gas from the second separation membrane module 23 is equal to or greater than a preset concentration threshold. The concentration threshold can be, for example, the required CO2 concentration in the specifications of the carbon dioxide separation device 1, or a value obtained by adding a predetermined margin to the required CO2 concentration.

[0079] If the detected CO2 concentration of the permeate gas is above the concentration threshold, the flow rate of permeate gas supplied to the permeate gas recovery unit 8 is increased, and the flow rate of permeate gas circulated to the second separation membrane module 23 is decreased, thereby controlling the flow of permeate gas in the second separation membrane module 23.

[0080] If the detected CO2 concentration of the permeate gas is below the concentration threshold, the flow rate of permeate gas supplied to the permeate gas recovery unit 8 is reduced compared to the current flow rate, and the flow rate of permeate gas circulated to the second separation membrane module 23 is increased, thereby controlling the flow rate of permeate gas in the second separation membrane module 23.

[0081] The flow rate of permeate gas supplied to the permeate gas recovery unit 8, and the flow rate of permeate gas circulated to the second separation membrane module 23, can be adjusted by adjusting at least one of the first flow rate adjustment unit 41 and the second flow rate adjustment unit 42. For example, the flow rate of the second flow rate adjustment unit 42 may be set to the maximum flow rate (always fully open), and the flow rate of the first flow rate adjustment unit 41 may be varied to adjust the flow rate of the permeate gas discharge path 74 and the permeate gas return path 76 of the permeate gas discharged from the second separation membrane module 23.

[0082] If the detected CO2 concentration of the permeate gas is above the concentration threshold, the control device 9 controls the first flow rate adjustment unit 41 to increase its flow rate from the current flow rate. If the detected CO2 concentration of the permeate gas is below the concentration threshold, the control device 9 controls the first flow rate adjustment unit 41 to decrease its flow rate from the current flow rate. The control device 9 calculates the set value or change value for the flow rate of the first flow rate adjustment unit 41 such that the larger the difference between the detected CO2 concentration and the concentration threshold, the greater the increase or decrease in flow rate.

[0083] The flow of permeate gas in the second separation membrane module 23 may be controlled by adjusting the flow rate of the second flow rate adjustment unit 42, or by adjusting the respective flow rates of the first flow rate adjustment unit 41 and the second flow rate adjustment unit 42. The flow of permeate gas in the second separation membrane module 23 may also be controlled by adjusting the flow path of the permeate gas discharged from the second separation membrane module 23. For example, the control device 9 switches the flow path of the permeate gas so that when the detected value of the CO2 concentration of the permeate gas is above a concentration threshold, the permeate gas flows to the downstream side of the permeate gas discharge path 74, and when the detected value of the CO2 concentration of the permeate gas is below the concentration threshold, the permeate gas flows to the permeate gas return path 76.

[0084] Furthermore, the control device 9 controls the flow of the unpermeable gas in the second separation membrane module 23 based on the CO2 concentration of the raw material gas supplied to the first separation membrane modules 21 and 22, the CO2 concentration of the unpermeable gas in the second separation membrane module 23, and the flow rate of the raw material gas supplied to the first separation membrane modules 21 and 22. More specifically, the control device 9 controls the flow of the unpermeable gas in the second separation membrane module 23 based on the amount of decrease in the CO2 concentration of the raw material gas due to the mixing of the unpermeable gas from the second separation membrane module 23 with the raw material gas supplied to the first separation membrane modules 21 and 22, and the flow rate of the raw material gas.

[0085] The control device 9 acquires the detected CO2 concentration and flow rate of the raw material gas supplied to the first separation membrane modules 21 and 22 through the first concentration sensor 61 and the first flow rate sensor 51. The control device 9 acquires the detected CO2 concentration and flow rate of the unpermeated gas discharged from the second separation membrane module 23 through the second concentration sensor 62 and the second flow rate sensor 52.

[0086] The control device 9 calculates the CO2 concentration of the mixed gas when the raw material gas and the unpermeated gas from the second separation membrane module 23 are mixed, based on the detected CO2 concentration and flow rate of the acquired raw material gas and the detected CO2 concentration and flow rate of the unpermeated gas from the second separation membrane module 23. The control device 9 determines the amount of decrease in CO2 concentration when the unpermeated gas from the second separation membrane module 23 is mixed with the raw material gas by subtracting the CO2 concentration of the mixed gas calculated from the detected CO2 concentration of the acquired raw material gas.

[0087] If a detection value for the CO2 concentration of the mixed gas of the raw gas and the unpermeated gas from the second separation membrane module 23 is obtained, the decrease in CO2 concentration may be determined by subtracting the detection value of the CO2 concentration of the mixed gas from the detection value of the CO2 concentration of the raw gas.

[0088] The control device 9 determines whether the detected flow rate of the acquired raw material gas is less than a preset flow rate threshold and whether the decrease in the specified CO2 concentration is less than a preset decrease threshold. The flow rate threshold and decrease threshold can be set by considering, for example, the permeability coefficient of the first separation membrane modules 21 and 22, the pressure difference between the supply side and the permeate side of the first separation membrane modules 21 and 22, etc. The flow rate threshold and decrease threshold can be set to values ​​such that the CO2 concentration of the permeate gas from the first separation membrane modules 21 and 22 can be increased to a certain extent or more when the unpermeated gas from the second separation membrane module 23 is mixed in.

[0089] If the detected flow rate of the raw material gas is below the flow rate threshold and the decrease in CO2 concentration is below the decrease threshold, the flow of impermeable gas in the second separation membrane module 23 is controlled to increase the flow rate of impermeable gas circulated to the first separation membrane modules 21 and 22. In the above control, the flow rate of impermeable gas discharged to the outside of the system via the impermeable gas discharge passage 75 may be decreased from the current level. In the above control, the flow rate of impermeable gas circulated to the first separation membrane modules 21 and 22 may be greater than the flow rate of impermeable gas discharged to the outside of the system.

[0090] If the detected flow rate of the raw material gas is below the flow rate threshold, and the decrease in CO2 concentration is not below the decrease threshold, the flow of impermeable gas in the second separation membrane module 23 is controlled to increase the flow rate of impermeable gas discharged to the outside of the system via the impermeable gas discharge passage 75 compared to the current flow rate. In the above control, the flow rate of impermeable gas circulated to the first separation membrane modules 21 and 22 may be reduced compared to the current flow rate. In the above control, the flow rate of impermeable gas discharged to the outside of the system may be increased compared to the flow rate of impermeable gas circulated to the first separation membrane modules 21 and 22.

[0091] The case in which the detected value of the raw material gas flow rate is less than the flow rate threshold and the decrease in CO2 concentration is not less than the decrease threshold includes the case in which the detected value of the raw material gas flow rate is equal to or greater than the flow rate threshold and the decrease in CO2 concentration is less than the decrease threshold, the case in which the detected value of the raw material gas flow rate is less than the flow rate threshold and the decrease in CO2 concentration is equal to or greater than the decrease threshold, and the case in which the detected value of the raw material gas flow rate is equal to or greater than the flow rate threshold and the decrease in CO2 concentration is equal to or greater than the decrease threshold.

[0092] In the determination process described above, the flow rate of the unpermeated gas circulated through the second separation membrane module 23 to the first separation membrane modules 21 and 22 may be specified such that the requirement that the amount of decrease in CO2 concentration is less than the decrease threshold is met. For example, the upper limit of the maximum flow rate or percentage of unpermeated gas circulated through the first separation membrane modules 21 and 22 is specified such that the amount of decrease in CO2 concentration, calculated based on the detected CO2 concentration and flow rate of the raw gas and the detected CO2 concentration and flow rate of the unpermeated gas in the second separation membrane module 23 multiplied by a specific percentage, is less than the decrease threshold. Once the upper limit of the maximum flow rate or percentage of unpermeated gas that can result in a decrease in CO2 concentration less than the decrease threshold is specified, the flow of unpermeated gas in the second separation membrane module 23 is controlled to vary the flow rate of the unpermeated gas according to the specified upper limit of the maximum flow rate or percentage.

[0093] The flow rate of impermeable gas discharged to the outside of the system via the impermeable gas discharge passage 75, and the flow rate of impermeable gas circulated to the first separation membrane modules 21 and 22, can be adjusted by adjusting at least one of the third flow rate adjustment unit 43 and the fourth flow rate adjustment unit 44.

[0094] If the detected flow rate of the raw material gas is less than the flow rate threshold and the decrease in CO2 concentration is less than the decrease threshold, the control device 9 increases the flow rate of the third flow rate adjustment unit 43 compared to the current flow rate. The control device 9 may further decrease the flow rate of the fourth flow rate adjustment unit 44 compared to the current flow rate. For example, the control device 9 fully opens the third flow rate adjustment unit 43 and fully closes the fourth flow rate adjustment unit 44. The control device 9 may calculate the set value or change value of the flow rate of the third flow rate adjustment unit 43 such that the larger the difference between the detected flow rate of the raw material gas and the flow rate threshold, and the larger the difference between the decrease in CO2 concentration and the decrease threshold, the greater the increase in flow rate. If the maximum flow rate or upper limit of the percentage of unpermeated gas that can result in a decrease in CO2 concentration below the decrease threshold is specified, the control device 9 may calculate the set value or change value of the flow rate of the third flow rate adjustment unit 43 according to the specified result.

[0095] If the detected flow rate of the raw material gas is less than the flow rate threshold, and the decrease in CO2 concentration is not less than the decrease threshold, the control device 9 increases the flow rate of the fourth flow rate adjustment unit 44 compared to the current flow rate. The control device 9 may further decrease the flow rate of the third flow rate adjustment unit 43 compared to the current flow rate. For example, the control device 9 fully opens the fourth flow rate adjustment unit 44 and fully closes the third flow rate adjustment unit 43. The control device 9 may calculate the set value or change value of the flow rate of the fourth flow rate adjustment unit 44 such that the amount of increase in flow rate increases as the difference between the detected flow rate of the raw material gas and the flow rate threshold increases, and as the difference between the decrease in CO2 concentration and the decrease threshold increases.

[0096] In the determination process described above, the control device 9 may separately perform a determination process to determine whether the detected value of the raw gas flow rate is less than the flow rate threshold, and a determination process to determine whether the decrease in CO2 concentration is less than the decrease threshold.

[0097] The above describes an example of controlling the flow of unpermeated gas in the second separation membrane module 23 based on the flow rate of the raw material gas and the decrease in CO2 concentration. Alternatively, the control of the flow of unpermeated gas in the second separation membrane module 23 may be performed based on the detected value of the flow rate of the raw material gas and the detected value of the CO2 concentration of the unpermeated gas in the second separation membrane module 23. For example, if the detected value of the flow rate of the raw material gas is less than a preset flow rate threshold, and the detected value of the CO2 concentration of the unpermeated gas in the second separation membrane module 23 is greater than or equal to a preset concentration threshold, the flow rate of unpermeated gas circulated to the first separation membrane modules 21 and 22 is increased from the current level. If the detected value of the flow rate of the raw material gas is less than a preset flow rate threshold, and the detected value of the CO2 concentration of the unpermeated gas in the second separation membrane module 23 is not greater than or equal to a preset concentration threshold, the flow rate of unpermeated gas discharged outside the system is increased from the current flow rate. By using the CO2 concentration of the unpermeated gas in the second separation membrane module 23 instead of the decrease in CO2 concentration, the computational load of the determination process is reduced.

[0098] From the viewpoint of further reducing the computational load, the flow of impermeable gas in the second separation membrane module 23 may be controlled based on the detected CO2 concentration of the impermeable gas in the second separation membrane module 23 and the detected CO2 concentration of the raw material gas. For example, if the detected CO2 concentration of the impermeable gas in the second separation membrane module 23 is greater than or equal to the detected CO2 concentration of the raw material gas, the flow rate of impermeable gas circulated to the first separation membrane modules 21 and 22 is increased from the current flow rate. If the detected CO2 concentration of the impermeable gas in the second separation membrane module 23 is less than the detected CO2 concentration of the raw material gas, the flow rate of impermeable gas discharged outside the system is increased from the current flow rate.

[0099] The control device 9 controls the flow of permeate and unpermeated gas in the second separation membrane module 23 by repeatedly executing the above-described process at predetermined or appropriate time intervals during the operation of the carbon dioxide separation device 1. This control allows the recovery amount to be maximized while maintaining the CO2 concentration of the permeate recovered by the carbon dioxide separation device 1 at or above the desired concentration.

[0100] The carbon dioxide separation device 1 may be configured to include three or more separation membrane modules 2. When it includes three or more separation membrane modules 2, other separation membrane modules may be connected before and after at least one of the first and second separation membrane modules which are continuously connected in series. Other separation membrane modules may be connected in series between the first and second separation membrane modules. When other separation membrane modules are connected between the first and second separation membrane modules, the unpermeated gas from the second separation membrane module can be supplied to the first separation membrane module, and the permeated gas from the second separation membrane module can be supplied to the second separation membrane module or other separation membrane modules.

[0101] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The technical features described in each embodiment can be combined with each other, and the scope of the present invention is intended to include all modifications within the claims and equivalents thereof. The sequences shown in each embodiment are not limiting, and within the bounds of consistency, the order of each processing step may be changed, and multiple processes may be executed in parallel. The processing entity for each process is not limiting, and within the bounds of consistency, the processing of each device may be executed by other devices.

[0102] The matters described in each embodiment can be combined with each other. Furthermore, the independent and dependent claims described in the claims can be combined with each other in any combination, regardless of the form of reference. In addition, the claims use a form in which claims referencing two or more other claims (multi-claim form), but are not limited to this. A form in which multi-claims referencing at least one multi-claim (multi-multi-claim) may also be used. [Explanation of symbols]

[0103] S Carbon Dioxide Separation System 1. Carbon dioxide separation device 2 Separation membrane module 21,22 First separation membrane module 23. Second Separation Membrane Module 3. Compressor 4 Flow rate adjustment section 41 1st flow rate adjustment section 42 2nd flow rate adjustment section 43 3rd flow rate adjustment section 44 4th flow rate adjustment section 5 Flow Sensor 51. First flow sensor 52 Second flow sensor 6. Concentration sensor 61. First concentration sensor 62 Second concentration sensor 63 Third concentration sensor 8 Permeate gas recovery unit 9 Control device 71. Raw material gas supply route 72 Intermediate supply route 73 Intermediate discharge channel 74 Permeable gas discharge channel 75 Impermeable gas discharge channel 76 Permeable gas reduction path 77 Unpermeable Gas Reduction Path

Claims

1. A first separation membrane module that selectively permeates carbon dioxide from a gas containing carbon dioxide, The permeate gas from the first separation membrane module is supplied to a second separation membrane module that selectively permeates carbon dioxide, A first passage for discharging the permeate gas from the second separation membrane module, A second passage for supplying the permeate gas from the second separation membrane module to the first separation membrane module or the second separation membrane module, A third passage for discharging unpermeated gas from the second separation membrane module, The system includes a fourth passage for supplying the unpermeated gas from the second separation membrane module to the first separation membrane module or the second separation membrane module. Carbon dioxide separation device.

2. The second passage supplies the permeate gas of the second separation membrane module to the second separation membrane module. The fourth passage supplies the unpermeated gas from the second separation membrane module to the first separation membrane module. The carbon dioxide separation apparatus according to claim 1.

3. The second separation membrane module is equipped with a first adjustment unit that adjusts the flow path or flow rate of the permeate gas in the second separation membrane module according to the carbon dioxide concentration of the permeate gas in the second separation membrane module. A carbon dioxide separation apparatus according to claim 1 or claim 2.

4. If the carbon dioxide concentration of the permeate gas from the second separation membrane module is above a predetermined value, the first adjustment unit increases the flow rate of the permeate gas from the second separation membrane module discharged through the first passage. If the carbon dioxide concentration of the permeate gas from the second separation membrane module is below a predetermined value, the first adjustment unit reduces the flow rate of the permeate gas from the second separation membrane module discharged through the first passage. The carbon dioxide separation apparatus according to claim 3.

5. The second adjustment unit adjusts the flow path or flow rate of the unpermeated gas in the second separation membrane module according to the carbon dioxide concentration of the supply gas supplied to the first separation membrane module and the carbon dioxide concentration of the unpermeated gas in the second separation membrane module. A carbon dioxide separation apparatus according to claim 1 or claim 2.

6. The second adjustment unit adjusts the flow path or flow rate of the unpermeated gas in the second separation membrane module in accordance with the flow rate of the supply gas supplied to the first separation membrane module and the amount by which the carbon dioxide concentration of the supply gas decreases due to the mixing of the unpermeated gas from the second separation membrane module with the supply gas. A carbon dioxide separation apparatus according to claim 1 or claim 2.

7. If the flow rate of the supply gas is less than a predetermined value and the decrease in the carbon dioxide concentration of the supply gas is less than a predetermined value, the second adjustment unit increases the flow rate of the unpermeated gas of the second separation membrane module supplied through the fourth passage. If the flow rate of the supply gas is less than a predetermined value and the decrease in the carbon dioxide concentration of the supply gas is not less than a predetermined value, the second adjustment unit increases the flow rate of the unpermeated gas from the second separation membrane module discharged through the third passage. The carbon dioxide separation apparatus according to claim 6.

8. The carbon dioxide concentration of the unpermeated gas in the second separation membrane module is higher than the carbon dioxide concentration of the supply gas supplied to the first or second separation membrane module, which is the destination of the unpermeated gas from the second separation membrane module via the fourth passage. A carbon dioxide separation apparatus according to claim 1 or claim 2.

9. The system comprises at least one of the following: a first sensor for detecting the carbon dioxide concentration of the supply gas supplied to the first separation membrane module; a second sensor for detecting the carbon dioxide concentration of the unpermeated gas in the second separation membrane module; a third sensor for detecting the carbon dioxide concentration of the permeated gas in the second separation membrane module; a fourth sensor for detecting the flow rate of the supply gas supplied to the first separation membrane module; and a third sensor for detecting the flow rate of the unpermeated gas in the second separation membrane module. A carbon dioxide separation apparatus according to claim 1 or claim 2.

10. A method for separating carbon dioxide using a carbon dioxide separation device, The carbon dioxide separation device is A first separation membrane module that selectively permeates carbon dioxide from a gas containing carbon dioxide, The permeate gas from the first separation membrane module is supplied to a second separation membrane module that selectively permeates carbon dioxide, A first passage for discharging the permeate gas from the second separation membrane module, A second passage for supplying the permeate gas from the second separation membrane module to the first separation membrane module or the second separation membrane module, A third passage for discharging unpermeated gas from the second separation membrane module, The system includes a fourth passage for supplying the unpermeated gas from the second separation membrane module to the first separation membrane module or the second separation membrane module, The flow path or flow rate of the permeated or unpermeated gas in the second separation membrane module is adjusted according to the carbon dioxide concentration of the permeated gas in the second separation membrane module. Carbon dioxide separation method.

Images