JP2023140120A - Gas separator - Google Patents

Abstract

To recover highly-concentrated CO2 with less energy consumption.SOLUTION: A gas separator 10 comprises: a first separation module 1a and a second separation module 1b either of which has a separation membrane selectively permeating a specific gas component, the former recovering the specific gas component at a first recovery rate and the latter recovering the specific gas component at a second recovery rate lower than the first recovery rate; a first supply line that supplies raw material gas containing the specific gas component with a predetermined concentration or more to the first separation module 1a; a second supply line that recovers from the first separation module 1a permeation gas passing through the separation membrane to supply to the second separation module 1b; and a third supply line that recovers from the second separation module 1b the permeation gas passing through the separation membrane to supply to the first separation module 1a.SELECTED DRAWING: Figure 4

Description

The present invention relates to a gas separation device that separates specific components from a mixed gas.

As this type of device, a device is known that recovers high-concentration CO ₂ using a separation membrane that selectively permeates carbon dioxide (CO ₂ ) in the air (see, for example, Patent Document 1). . In the apparatus described in Patent Document 1, a plurality of membrane separation modules are connected in series and CO ₂ is separated and recovered in multiple stages, thereby recovering highly concentrated CO ₂ .

JP2020-195968A

However, when separation and recovery are performed in multiple stages as in the apparatus of Patent Document 1, the CO ₂ partial pressure in the supplied gas decreases in the later stages, and the CO ₂ partial pressure difference, which is the driving force for permeation, decreases. It becomes difficult to recover high-concentration CO ₂ due to the amount of energy used.

A gas separation device that is one aspect of the present invention includes a first separation module that has separation membranes that selectively transmit specific gas components, and that collects specific gas components at a first recovery rate; a second separation module that recovers a specific gas component at a lower second recovery rate; a first supply line that supplies a raw material gas containing a specific gas component at a predetermined concentration or higher to the first separation module; and a first separation module. a second supply line that collects the permeate gas that has permeated the separation membrane from the second separation module and supplies it to the second separation module; and a third supply line that collects the permeation gas that has permeated the separation membrane from the second separation module and supplies it to the first separation module. A supply line.

According to the present invention, highly concentrated CO ₂ can be recovered with a small amount of energy consumption.

1 is a diagram for explaining a separation membrane used in a gas separation device according to an embodiment of the present invention. A diagram for explaining the relationship between CO ₂ recovery rate and separation and recovery energy for each initial CO ₂ concentration. 1 is a block diagram schematically showing an example of the configuration of main parts of a gas separation device according to an embodiment of the present invention. FIG. 3 is a block diagram schematically showing another example of the configuration of main parts of the gas separation device according to the embodiment of the present invention.

Embodiments of the present invention will be described below with reference to FIGS. 1 to 4. A gas separation device according to an embodiment of the present invention separates and recovers a specific component from a mixed gas using a separation membrane that selectively permeates a specific component in the mixed gas. In particular, high concentration specific components are separated and recovered. In the following, an example will be described in which CO ₂ is separated and recovered from a raw material gas such as the atmosphere or factory exhaust gas containing a high concentration of CO ₂ (for example, about 1 to 10 vol %).

FIG. 1 is a diagram for explaining a separation membrane M used in a gas separation device according to an embodiment of the present invention. As shown in FIG. 1, the separation membrane M is configured as a thin film of polydimethylsiloxane (PDMS), for example, and selects CO ₂ from among air containing nitrogen (N ₂ ), oxygen (O ₂ ), CO _{2 ,} etc. transparently. The permeation of CO ₂ proceeds using the partial pressure difference between the CO ₂ partial pressure on the supply side and the CO ₂ partial pressure on the permeation side as a driving force, and continues until the partial pressure difference disappears.

FIG. 2 is a diagram for explaining the relationship between the CO ₂ recovery rate and the separation and recovery energy for each initial CO ₂ concentration (supply-side CO ₂ concentration). The CO ₂ recovery rate [%] is calculated as the amount of CO ₂ recovered [ton-CO ₂ /day] with respect to the amount of CO ₂ [ton-CO ₂ /day] in the source gas.

As shown in Figure 2, when CO 2 is separated and recovered from a raw material gas with a relatively high initial CO ₂ concentration (for example, 10% or more), the _{CO 2 partial} pressure on the supply side is relatively high, so the CO ₂ recovery rate is The separation and recovery energy [GJ/ton-CO ₂ ] used to increase the CO 2 is relatively small. On the other hand, when CO 2 is separated and recovered from a raw material gas with a relatively low initial CO ₂ concentration (for example, less than 10%), _{CO 2 partial} pressure on the supply side is relatively low, so CO ₂ is used to increase the CO 2 recovery rate. The amount of separation and recovery energy required becomes extremely large.

If such separation and recovery is performed in multiple stages, _the CO ₂ recovery rate of the entire device can be increased _. Increasing the rate increases energy usage, which increases the energy usage of the device as a whole. Therefore, in this embodiment, by performing separation and recovery in multiple stages and setting only the first stage to a high recovery rate, the gas separation device is configured as follows so that highly concentrated CO ₂ can be recovered with less energy consumption. do.

FIGS. 3 and 4 are block diagrams schematically showing an example of the configuration of main parts of the gas separation device 10 according to the embodiment of the present invention. As shown in FIGS. 3 and 4, the gas separation device 10 includes a plurality of separation modules 1 (three separation modules 1a to 1c in the figure) connected in series, a supply line L1 (L1a to L1c), and a recovery line. L2 (L2a to L2c) and an exhaust line L3 (L3a to L3c). The plurality of separation modules 1 may be configured by connecting in series a plurality of separation modules 1 provided in parallel with each other.

The separation module 1 is configured as a hollow fiber membrane module, a spiral type module, etc. using a separation membrane M (FIG. 1). The internal space of the separation module 1 is divided into a first space on the supply side and a second space on the permeation side using the separation membrane M as a partition wall.

The first-stage separation module 1a is configured so that the CO ₂ recovery rate is higher than a predetermined recovery rate (for example, 90% or higher) in order to reduce the concentration of CO ₂ in the exhaust gas after separation and recovery to a sufficiently low concentration. The second-stage and subsequent separation modules 1b and 1c are configured to have a low CO ₂ recovery rate (for example, about 10%) in order to sufficiently reduce the amount of energy used for separation and recovery. Adjust the membrane performance (gas permeability, CO ₂ selectivity), membrane area, supply side pressure, permeate side pressure, supply side flow rate (flow rate), permeate side flow rate, etc. of the separation membrane M adopted in each separation module 1. By doing so, the CO ₂ recovery rate of each separation module 1 can be set to an appropriate value.

The supply lines L1a to L1c supply the mixed gas to the first spaces of the separation modules 1a to 1c, respectively. The supply lines L1a to L1c may be provided with a compressor that pressure-feeds the supply gas, a regulating valve that adjusts the flow rate on the supply side, and the like.

The recovery lines L2a to L2c recover the permeated gas that has passed through the separation membrane M from the second spaces of the separation modules 1a to 1c, respectively. The recovery lines L2a to L2c may be provided with a vacuum pump that reduces the pressure in the second space of each separation module 1a to 1c, a regulating valve that adjusts the flow rate on the permeate side, and the like. The final recovered gas after separation and recovery by the gas separation device 10 is obtained from the recovery line L2c at the last stage.

The exhaust lines L3a to L3c exhaust air after CO ₂ has been separated from the first spaces of the separation modules 1a to 1c, respectively. The exhaust lines L3a to L3c may be provided with a vacuum pump, a regulating valve for adjusting the exhaust flow rate, or the like. The exhaust line L3a at the front stage is opened to the atmosphere, and exhaust gas containing CO ₂ at a sufficiently low concentration is discharged into the atmosphere from the separation module 1a at the front stage, which is set at a high recovery rate.

The supply line L1a constitutes a raw material supply line that supplies raw material gas to the foremost separation module 1a. The recovery line L2a and the supply line L1b constitute an intermediate supply line that recovers the permeated gas from the separation module 1a and supplies it to the subsequent separation module 1b. The recovery line L2b and the supply line L1c constitute an intermediate supply line that recovers the permeated gas from the separation module 1b and supplies it to the subsequent separation module 1c.

The exhaust line L3b and the supply line L1a constitute a reflux line that recovers the permeated gas from the separation module 1b and supplies it to the preceding separation module 1a. In the example of FIG. 3, the exhaust line L3c and the supply line L1b constitute a reflux line that recovers the permeate gas from the separation module 1c and supplies it to the preceding separation module 1b. In the example of FIG. 4, the exhaust line L3c and the supply line L1a constitute a reflux line that recovers the permeate gas from the separation module 1c and supplies it to the foremost separation module 1a.

In this way, by refluxing the recovered gas in the later stages set to a low recovery rate to the earlier stages, high-concentration CO ₂ can be recovered with less energy consumption in the gas separation device 10 as a whole ( Figure 3, Figure 4). In addition, when the recovered gas in the latter stage is recirculated to the first stage, the amount of energy used in the first stage is further reduced, and high-concentration CO ₂ can be recovered with even less energy used in the gas separation device 10 as a whole ( Figure 4).

According to this embodiment, the following effects can be achieved.
(1) The gas separation device 10 has a separation membrane M that selectively permeates CO ₂ , and has a first-stage separation module 1a that recovers CO ₂ with a high recovery rate and a separation module 1a that recovers CO ₂ with a low recovery rate. The permeate gas is recovered from the downstream separation module 1b, the raw material supply line (supply line L1a) that supplies the raw material gas containing CO ₂ with a predetermined concentration or higher to the forefront separation module 1a, and the forefront separation module 1a. An intermediate supply line (recovery line L2a and supply line L1b) that supplies the downstream separation module 1b, and a reflux line (exhaust line L3b and A supply line L1a) is provided (FIGS. 3 and 4). In this way, by setting the first-stage separation module 1a to a high recovery rate and setting the second-stage separation module 1b to a low recovery rate, and by refluxing the recovered gas in the second stage to the first stage with a high recovery rate, the entire gas separation device 10 can be improved. It is possible to recover high concentrations of CO ₂ with low energy consumption.

(2) The gas separation device 10 includes a separation module 1c that has a separation membrane M and recovers CO ₂ at a low recovery rate, and collects permeate gas from the preceding separation module 1b and supplies it to the subsequent separation module 1c. An intermediate supply line (recovery line L2b and supply line L1c) and a reflux line (exhaust line L3c and supply line L1a or exhaust line L3c and supply line L1b) (FIGS. 3 and 4). In this way, by setting the subsequent separation modules 1b to 1c at a low recovery rate and refluxing the recovered gas in the subsequent stages to the previous stages, the gas separation device 10 as a whole can achieve a higher concentration of CO with less energy consumption. ₂ can be collected.

(3) The reflux line (exhaust line L3c and supply line L1a) collects the permeate gas from the latter stage separation module 1c and supplies it to the first stage separation module 1a (FIG. 4). In this way, by setting the latter stage separation module 1c to a low recovery rate and circulating the recovered gas in the latter stage to the first stage, the energy consumption of the first stage is further reduced, and the gas separation device 10 as a whole consumes less energy. A high concentration of CO ₂ can be recovered based on the amount used.

(4) The raw material gas is the atmosphere or factory exhaust gas. In the first stage, which uses atmospheric air or factory exhaust gas containing high concentrations of CO ₂ as raw material gas, CO ₂ can be recovered with a high recovery rate even with relatively low energy consumption (Figure 2), so the entire gas separation device 10 It is possible to recover high concentrations of CO ₂ with low energy consumption.

In the embodiment described above, an example in which CO ₂ is separated is explained with reference to FIG. 1 and the like, but the specific components to be separated by the gas separation device are not limited to these. The gas separation device can be suitably applied when separating a high concentration specific component, such as when separating CO ₂ from factory exhaust gas.

The above description is merely an example, and the present invention is not limited to the above-described embodiments and modifications as long as the characteristics of the present invention are not impaired. It is also possible to arbitrarily combine the above embodiment and one or more of the modifications, and it is also possible to combine the modifications.

1, 1a to 1c separation module, 10 gas separation device, L1a to L1c supply line, L2a to L2c recovery line, L3a to L3c exhaust line

Claims (4)

A first separation module, each having a separation membrane that selectively permeates a specific gas component, recovers the specific gas component at a first recovery rate, and a second separation module that recovers the specific gas component at a second recovery rate lower than the first recovery rate. a second separation module for recovering gas components;
a first supply line that supplies a source gas containing the specific gas component at a predetermined concentration or higher to the first separation module;
a second supply line that collects permeated gas that has permeated the separation membrane from the first separation module and supplies it to the second separation module;
A gas separation device comprising: a third supply line that collects permeated gas that has permeated through the separation membrane from the second separation module and supplies it to the first separation module. The gas separation device according to claim 1,
a third separation module having the separation membrane and recovering the specific gas component at a third recovery rate lower than the first recovery rate;
a fourth supply line that collects the permeated gas that has permeated the separation membrane from the second separation module and supplies it to the third separation module;
A gas separation apparatus further comprising: a fifth supply line that collects permeated gas that has permeated through the separation membrane from the third separation module and supplies it to the first separation module or the second separation module. The gas separation device according to claim 2,
The gas separation device is characterized in that the fifth supply line collects the permeated gas that has permeated the separation membrane from the third separation module and supplies it to the first separation module. In the gas separation device according to any one of claims 1 to 3,
The specific gas component is carbon dioxide,
A gas separation device characterized in that the raw material gas is the atmosphere or factory exhaust gas.

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