JPH04347485A - Method and device for recovering carbonic acid gas in air separating device - Google Patents

Abstract

PURPOSE:To recover carbonic gas in an air separating device, provided with a reversing type heat exchanger or an adsorption type moisture and carbonic gas remover, and contrive energy saving as well as the prevension of environmental contamination. CONSTITUTION:Ice, solidified and separated by reversing type heat exchangers 2a, 2b, and dry ice are evaporated by nitrogen gas for reverse washing while the evaporated gas is mixed with low-temperature and high-purity nitrogen gas in two stages through gas diffusers 14a, 14b, 24a, 24b. In the first stage, moisture is separated and removed as ice through gravity sedimenting separators 12a, 12b and separating filters 21a, 21b while carbonic acid gas is separated and removed in the second stage as dry ice through gravity sedimenting separators 29a, 29b and separating filters 39a, 39b whereby the nitrogen gas for reverse washing is recovered as nitrogen gas having comparatively high purity while carbonic gas is recovered by washing the dry ice with low- temperature carbonic acid gas reversely.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for recovering carbon dioxide gas in an air separation device.

0002

[Prior Art] Generally, oxygen (hereinafter abbreviated as O2)
and a method for removing moisture and carbon dioxide gas (hereinafter referred to as CO2 gas) contained in air, which is a raw material, in equipment whose purpose is to produce nitrogen (hereinafter referred to as N2) on an industrial scale. For example, JP-A-60
- Reversing using a reversing heat exchanger as disclosed in Publication No. 68104 to remove the contained moisture and CO2 gas by cooling and depositing them in the heat exchanger in the form of ice and dry ice. There is a type air separation device. The ice and dry ice accumulated inside this heat exchanger
The N2 gas separated at the same time by the air separation device is used for backwashing and discharged into the atmosphere from the heat exchanger.

[0003] Generally, more than half of the N2 gas generated from an air separation device is used for backwashing, and therefore is not recovered and used. In terms of equipment, two heat exchangers are installed in parallel, and backwashing and removal of moisture and CO2 gas from the feed air are performed alternately by switching the switching valve. Generally, they are installed side by side and used by switching.

FIG. 2 is a block diagram of an example of a conventional air separation apparatus using a reversing heat exchanger. In the figure, 1 is a raw air compressor, 2a and 2b are reversing heat exchangers, 3a to 3d are raw air switching valves, 4a to 4d are N2 gas switching valves for backwashing, and 5 is low temperature air after heat exchange. Pipe, 6 is an air separator, 7 is a high-purity N2 gas extraction pipe, 8 is a high-purity O2 gas extraction pipe, 9 is a backwashing N2 gas supply pipe, 10a, 10b
1 is a backwashing N2 gas extraction pipe, and 11 is a backwashing N2 gas discharge pipe.

[0005] The air compressed by the raw air compressor 1 is
The raw air is sent to one of the reversing type heat exchangers 2a and 2b, for example 2a, via the switching valves 3a to 3d, and is connected to the backwashing N2 gas supply pipe 9 and the backwashing N2 gas switching valve 4c. Approximately -8
Water is cooled to 0℃, CO2 gas becomes dry ice (water turns into ice at 0℃, CO2 gas becomes -7
(transforms into dry ice at 8.5℃) and is solidified, removed, and purified. The compressed air after heat exchange in the heat exchanger 2a is sent to the air separator 6 through the raw air switching valve 3c and the low-temperature air pipe 5, where it is separated and rectified into pure oxygen and pure nitrogen using a cryogenic separation method. The products are sent to customers via a high-purity N2 gas extraction pipe 7 and a high-purity O2 gas extraction pipe 8, respectively.

At this time, in the other reversing type heat exchanger 2b, the air separator 6 supplies N2 for backwashing to the ice and dry ice that solidified and separated the moisture and CO2 gas in the air in the previous cycle. By feeding N2 gas for backwashing through the gas supply pipe 9 and the N2 gas switching valve 4d for backwashing, the ice and dry ice accumulated in the heat exchanger 2b are vaporized and the N2 gas for backwashing is It is contained in the gas and is released into the atmosphere from the backwashing N2 gas discharge pipe 11 via the backwashing N2 gas switching valve 4b and the backwashing N2 gas extraction pipe 10b.

[0007]

[Problem to be solved by the invention] However, CO2
Although gas can be used for industrial purposes, such as as a raw material for extinguishing agents or as a chemical raw material, as mentioned above, it is used as a backwashing N2 gas along with water-containing N2 gas.
2 It is very uneconomical to dissipate the gas into the atmosphere from the gas discharge pipe. Furthermore, due to environmental problems such as global warming caused by the increase in the concentration of CO2 gas in the atmosphere, it is better to avoid recycling CO2 gas into the atmosphere as much as possible. The present invention has been made in order to solve the problems of the prior art as described above, and provides a method and device that can recover carbon dioxide gas in an air separation device using a reversing heat exchanger. The purpose is to

[0008]

[Means for Solving the Problems] A first aspect of the present invention is
A method for recovering carbon dioxide gas in an air separation device consisting of a reversing type heat exchanger and an air separator, wherein water and carbon dioxide gas in raw air are cooled and solidified in the heat exchanger to form ice and dry ice. a step of blowing nitrogen gas for backwashing into the ice and dry ice accumulated in the heat exchanger to vaporize it into moisture and carbon dioxide; and a step of vaporizing the mixed nitrogen gas containing moisture and carbon dioxide with the air. A process in which low-temperature, high-purity nitrogen gas generated in a separator is blown in and cooled to below 0°C to solidify only the water in the gas, separating and removing it as ice, and an even lower temperature of high-purity nitrogen gas. A step of cooling the mixed nitrogen gas to about -80°C by blowing in the nitrogen gas to solidify the carbon dioxide in the gas and separating and removing it as dry ice to recover recovered nitrogen gas, and adding carbon dioxide for backwashing to this dry ice A method for recovering carbon dioxide gas in an air separation device, comprising the steps of blowing gas, vaporizing it into carbon dioxide gas, and recovering it. In addition,
A step of recovering cooling heat by exchanging heat with the recovered nitrogen gas with raw material air can be added, and a step of recovering cooling heat by exchanging heat with the recovered carbon dioxide gas with raw material air can be added. .

[0009] A second aspect of the present invention is to use one raw material air compressor, and cool the air compressed by this raw material air compressor while being switched alternately to remove moisture and carbon dioxide contained therein. There are two reversing heat exchangers that solidify gas and deposit it as ice and dry ice, and one unit that deep-cools and separates the clean air from these heat exchangers to produce high-purity oxygen and nitrogen. an air separator, a backwashing nitrogen gas supply pipe that sends a portion of the nitrogen gas generated by the air separator to the heat exchanger for backwashing, and a backwashing nitrogen gas supply pipe from the heat exchanger. A backwashing nitrogen gas takeoff pipe for recovering gas and a first high-purity nitrogen A first diffuser blows in through a gas branch pipe, and a temperature signal of backwashing nitrogen gas from a temperature sensor installed downstream of the first diffuser is inputted to the first nitrogen gas branch pipe. a first temperature controller that controls the temperature of the backwashing nitrogen gas within a range of 0 to -10°C by adjusting the opening degree of the attached control valve; and a first temperature controller that is connected to the backwashing nitrogen gas extraction pipe. a first gravity sedimentation separator and/or a first separation filter for filtering and separating ice, and backwashing to vaporize the ice accumulated in the first gravity sedimentation separator and/or the first separation filter; An air fan that blows air,
A part of the low-temperature high-purity nitrogen gas produced in the air separator is installed downstream of the first gravity settling separator and/or the first separation filter and passes through a second high-purity nitrogen gas branch pipe. A second diffuser for blowing in nitrogen gas, and a second diffuser for blowing through the second high-purity nitrogen gas branch pipe by inputting a temperature signal of backwashing nitrogen gas from a temperature sensor installed downstream of the second diffuser. 2 diffuser and a control valve attached to the second high-purity nitrogen gas branch pipe by inputting the temperature signal of the backwashing nitrogen gas from the temperature detector attached downstream of the second diffuser. A second temperature controller that controls the temperature of the backwashing nitrogen gas to -80°C or less by adjusting the opening degree, and a second temperature controller that is connected downstream of the second diffuser to filter and separate dry ice in the gas. a second gravity sedimentation separator and/or a second separation filter, and a backwashing method in which low-temperature backwash carbon dioxide stored in a recovered carbon dioxide gas holder is blown into the second gravity sedimentation separator and/or second separation filter. It consists of a washing carbon dioxide gas supply pipe, a recovered carbon dioxide gas take-out pipe that recovers carbon dioxide gas vaporized from dry ice, and a recovered carbon dioxide gas compressor that boosts the pressure of the recovered carbon dioxide gas and sends it to the recovered carbon dioxide gas holder. This is a carbon dioxide recovery device in an air separation device characterized by the following. Note that a recovered nitrogen gas/feedstock air heat exchanger may be installed between the feedstock air compressor and the reversing type heat exchanger for recovering cooling heat by exchanging heat with recovered nitrogen gas with feedstock air. In addition, a recovered carbon dioxide/raw material air heat exchanger may be attached to the recovered carbon dioxide gas take-out pipe for recovering cooling heat by exchanging heat between the recovered carbon dioxide gas and the raw material air.

Furthermore, the method and apparatus of the present invention can also be applied to an air separation apparatus using an adsorption type moisture/carbon dioxide remover instead of a reversing type heat exchanger.

[0011]

[Function] According to the present invention, the N2 gas for backwashing containing moisture and CO2 gas used for backwashing in the reversing type heat exchanger (or adsorption type moisture/carbon dioxide remover) is heated in two stages. The initial objective was achieved by separating and removing moisture by mixing high-purity nitrogen gas and recovering CO2 gas. That is, in the first stage, low-temperature N2 gas obtained in an air separator is mixed and controlled to be within 0 to -10°C to solidify water into ice, and this ice is sent together with dust to a gravity sedimentation separator. Separate and remove using a separation filter. Furthermore, as a second stage, low-temperature N2 is added to the backwashing N2 gas from which moisture has been removed.
CO by mixing gases and controlling the temperature to below -80°C.
2. Solidify the gas as dry ice and separate and remove it using a gravity sedimentation separator and separation filter. This makes it possible to collect CO2 gas independently.

[0012] Note that the N2 gas for backwashing from which moisture and CO2 gas have been removed has a cooling heat of -80°C, and after heat exchange with raw air, this is used as an N2 gas source in a normal factory, for example. It can be effectively used as a purge gas. Here, to explain the thermal energy balance, first of all, for the first stage balance when solidifying water, the effective energy possessed by high-purity N2 from -180℃ to -10℃ is Q0N', and the required amount is V0N. ', the thermal energy balance can be expressed by the following equation (Equation 1).

Q0N'V0N'=QN'VN'+QH VH +
QC ′VC ′+Δ′…(Equation 1) Here, QN ′: Energy required to cool backwashing N2 gas from room temperature to -10°C VN ′; Amount required to secure QN ′ QH
; Moisture contained in N2 gas for backwashing -1 from room temperature
Amount of heat required to cool down to 0℃ VH; Amount QC required to ensure QH
'; Amount Δ required to ensure the amount of heat VC '; QC ' required to cool the CO2 gas contained in the N2 gas for backwashing from room temperature to -10°C
’: Due to the heat radiated by the equipment, the line temperature down to -10℃ and CO2
Regarding the balance of the second stage when solidifying gas, assuming that the effective energy possessed by high-purity N2 from -180℃ to -80℃ is Q0N'' and the required amount is V0N'', the thermal energy balance is as follows. It can be expressed by the formula (Math. 2).

Q0N″V0N″=QN″VN″+QC″VC
``+Δ'' ......(Math. 2) Here, QN '': Energy required to cool backwashing N2 gas to -10 to -80°C VN ''; Amount required to secure QN '' QC
″; -10 of CO2 gas contained in N2 gas for backwashing
Amount Δ required to secure the amount of heat VC ″;QC ″ required for cooling to ~-80°C
″: -10 to -80℃ line due to heat dissipation from equipment

[
0015

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing an embodiment of the present invention, and in the figure, the same members as those in the conventional example shown in FIG. In the figure, 12a, 12b
are the first gravity settling separators, and the switching valve 1 is the first gravity settling separator, respectively.
It is connected to the backwashing N2 gas extraction pipes 10a, 10b on the outlet side of the heat exchangers 2a, 2b via 3a, 13b. In addition,
First diffusers 14a, 14b are provided in the middle of these backwashing N2 gas extraction pipes 10a, 10b, and the control valve 1
First branch pipes 7a and 7b of the high-purity N2 gas extraction pipe 7 are connected via 5a and 15b. These control valves 15a and 15b are connected to the backwashing N2 gas extraction pipe 1.
a first temperature controller 17a that inputs temperature signals detected by temperature detectors 16a and 16b installed downstream of the first diffusers 14a and 14b of 0a and 10b, respectively;
17b controls its opening degree. Further, the first gravity settling separators 12a, 12b are connected to the switching valves 18a, 18.
One end thereof is connected to a drain pipe 20 facing the drain tank 19 via b.

[0016] Reference numerals 21a and 21b are first separation filters, which are connected downstream of the first gravity sedimentation separators 12a and 12b. Note that this first separation filter 21a, 2
1b is the first gravity sedimentation separator 12a, 1.
2b, or only the first gravity sedimentation separators 12a, 12b can be used.
The separation filters 21a and 21b may be omitted in some cases. An air fan 22 supplies backwash air to the first separation filters 21a and 21b via switching valves 23a and 23b, respectively.

24a and 24b are first separation filters 21
A, 21b is a second diffuser installed on the outlet side via switching valves 25a, 25b, and control valves 26a, 26
A second branch pipe 7c of the high-purity N2 gas extraction pipe 7 is connected via b. The opening degrees of the control valves 26a, 26b are controlled by second temperature controllers 28a, 28b which input temperature signals detected by temperature detectors 27a, 27b installed downstream of the second diffusers 24a, 24b, respectively. controlled. 29a, 29b are second gravity settling separators, which are connected to second diffusers 24a, 24b via switching valves 30a, 30b, respectively. 31a,
31b is a second separation filter connected downstream of the second gravity sedimentation separators 29a, 29b via switching valves 32a, 32b. This second separation filter 31a, 3
The outlet side of 1b is connected to a recovered N2 gas extraction pipe 34 via switching valves 33a and 33b. Note that the second separation filters 31a and 31b may be installed independently, or
Only the gravity sedimentation separators 29a and 29b may be used.

Reference numeral 35 denotes a recovered CO2 gas holder, and the recovered CO2 gas stored therein is sent to the consumer via a product CO2 gas supply pipe 36, and a part of it is sent to the CO2 gas pipe for backwashing. 37, the switching valves 38a, 38
b and 39a, 39b to second gravity settling separators 29a, 29b and second separation filters 31a, 31b, respectively. Reference numeral 40 denotes a recovered CO2 gas compressor, which supplies the recovered CO2 gas to the second gas via switching valves 42a, 42b and 43a, 43b.
gravity sedimentation separators 29a, 29b and second separation filters 31a, 31b, respectively.

Reference numeral 44 denotes a recovered N2 gas/raw material air heat exchanger, which exchanges heat between the recovered N2 gas sent through the recovered N2 gas extraction pipe 34 and the raw material air. 45 is collection N
2 gas compressor, and 46 is a recovered N2 gas feed pipe. Therefore, the ice or dry ice solidified in the heat exchanger 2b, for example, is removed from moisture by the backwashing N2 gas sent from the air separator 6 through the backwashing N2 gas supply pipe 9 and the switching valve 4d. It is vaporized into CO2 gas. and,
Switching valve 4b, backwashing N2 gas extraction pipe 10b, switching valve 13
When being sent to the first gravity sedimentation separator 12b via the high-purity N2 gas extraction pipe 7, the low-temperature high-purity N2 gas and the first It is mixed in the diffuser 14b,
At this time, the first temperature controller 17b controls the control valve 15b so that the temperature of the backwashing N2 gas is within 0 to -10°C.
The opening degree of the backwashing N2 gas is controlled, and only the water contained in the backwashing N2 gas is cooled and solidified again to become ice. This ice is filtered and removed by the first gravity sedimentation separator 12b and the first separation filter 21b. The ice deposited on the first gravity sedimentation separator 12b and the first separation filter 21b is
In the next cycle, the backwashing air sent from the air fan 22 through the switching valve 23b vaporizes it into moisture.
Switching valve 1 provided in the first gravity settling separator 12b
8b and the drain pipe 20, the water is temporarily stored in the drain tank 19, and then discharged to the outside of the system.

[0020] Next, the backwashing N2 gas from which moisture has been removed is sent to the second diffuser 24b from the second branch pipe 7c of the high-purity N2 gas extraction pipe 7 to the low-temperature high-purity N2 gas that is sent through the control valve 26b. At this time, the opening degree of the control valve 26b is controlled by the second temperature controller 28b so that the temperature of the backwashing N2 gas becomes -80°C or less, and the backwashing N2 gas is mixed with the backwashing N2 gas. The CO2 gas contained in the gas is cooled and solidified again to become dry ice, which is filtered and removed by the second gravity sedimentation separator 29b and the second separation filter 31b. The recovered N2 gas, which has reached a fairly high purity without containing moisture or CO2 gas, is sent to the recovered N2 gas/feed air heat exchanger 44 via the recovered N2 gas take-off pipe 34, where it is heat exchanged with the feed air. The pressure of the recovered N2 gas is increased by the compressor 45, and the recovered N2 gas is supplied to customers via the recovered N2 gas supply pipe 46.

[0021] Then, the second gravity sedimentation separator 29b
The dry ice removed and deposited by the second separation filter 31b is recovered in the next cycle.
b, low-temperature backwashing CO2 sent through 39b
Gas vaporized and recovered CO2 Recovered as gas C
O2 gas compressor 40 collects CO2 via switching valves 42b, 43b and recovered CO2 gas extraction pipe 41
It is fed into the gas holder 35 and stored.

[0022] If a recovered CO2 gas/raw material air heat exchanger (not shown) is provided in the middle of the recovered CO2 gas extraction pipe 41 and the raw material air is cooled by the cooling heat of the recovered CO2 gas, further improvement can be achieved. This is desirable from the perspective of energy conservation. In addition, although moisture, CO2 gas, and dust have been removed from the recovered N2 gas, trace amounts of H2 and CO cannot be removed, so a normal air separator 6
The purity is somewhat lower than that of the high-purity N2 gas obtained in the above-mentioned method, and it cannot be used in places where severe quality is required and where such problems are a problem. However, it can be used without any problems as a purge gas in ordinary factories.

[0023]Furthermore, although the above embodiment describes an air separation apparatus that uses two reversing heat exchangers to remove moisture and carbon dioxide from compressed air, the present invention is not limited to this. However, it can be applied when two adsorption type moisture/carbon dioxide removers are used instead of a reversing type heat exchanger.

[0024]

Effects of the Invention As explained above, according to the present invention, the N2 gas for backwashing can be recovered and the CO2 contained therein can be recovered.
Since gas can also be recovered with high efficiency, inexpensive CO2 gas can be supplied, which has great economic effects, and also contributes to the prevention of environmental pollution. Furthermore, the cooling heat of recovered N2 gas and recovered CO2 gas can be used to cool the feed air, and the energy saving effect within the air separation device system is significant.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram of an example of a conventional air separation device using a reversing heat exchanger.

[Explanation of symbols]

1 Raw material air compressors 2a, 2b Reversing type heat exchangers 3a to 3d
Raw air switching valves 4a to 4d N2 gas switching valve for backwashing 5 Low temperature air pipe 6 Air separator 7 High purity N2 gas extraction pipe 8 High purity O2 gas extraction pipe 9 N2 gas supply pipes for backwashing 10a, 10b Backwashing N2 gas extraction pipe 12a, 12
b First gravity sedimentation separator 13a, 13b, 18
a, 18b, 23a, 23b, 25a, 25b, 30a
, 30b switching valves 14a, 14b first diffuser 15a, 15b, 26a, 26b control valves 16a, 1
6b, 27a, 27b Temperature detector 17a, 17b
First temperature controller 20 Drain pipes 21a, 21b First separation filter 22 Air fans 24a, 24b Second diffuser 28a, 28b Second temperature controller 29a, 29b Second gravity settling separator 31a,
31b Second separation filter 32a, 32b, 33a
, 33b, 38a, 38b, 39a, 39b, 42a,
42b Switching valve 34 Recovered N2 gas take-off pipe 35 Recovered CO2 Gas holder 36 Product CO2 Gas feed pipe 37 Backwash CO2 Gas pipe 40 Recovered CO2 Gas compressor 41 Recovered CO2 Gas take-off pipes 43a, 43b Switching valve 44 Recovered N2 gas/raw material Air heat exchanger 45 Recovery N2 gas compressor 46 Recovery N2 gas supply pipe

Claims (8)

[Claims] 1. A method for recovering carbon dioxide gas in an air separation device comprising a reversing type heat exchanger and an air separator, the method comprising: cooling and solidifying moisture and carbon dioxide gas in raw air in the heat exchanger; a step of blowing nitrogen gas for backwashing into the ice and dry ice deposited in the heat exchanger to vaporize it into moisture and carbon dioxide gas, and a step of vaporizing the ice and dry ice containing the moisture and carbon dioxide gas. A step of blowing low-temperature high-purity nitrogen gas generated by the air separator into the nitrogen gas and lowering the temperature to 0° C. or lower to solidify only the moisture in the gas and separate and remove it as ice;
Further, a step of blowing low-temperature high-purity nitrogen gas to cool the mixed nitrogen gas to about -80°C to solidify carbon dioxide gas in the gas and separate and remove it as dry ice to recover recovered nitrogen gas; A method for recovering carbon dioxide gas in an air separation device, comprising the steps of blowing carbon dioxide gas for backwashing into dry ice, vaporizing it into carbon dioxide gas, and recovering it. 2. The method for recovering carbon dioxide gas in an air separation apparatus according to claim 1, further comprising the step of recovering cooling heat by exchanging heat between the recovered nitrogen gas and raw air. 3. The method for recovering carbon dioxide gas in an air separation apparatus according to claim 1 or 2, further comprising the step of recovering cooling heat by exchanging heat between the recovered carbon dioxide gas and raw air. 4. The air separation device according to claim 1, wherein the air separation device is applied to an air separation device using an adsorption type moisture/carbon dioxide remover instead of the reversing type heat exchanger. Method of recovering carbon dioxide gas. 5. One raw material air compressor, and the air compressed by this raw material air compressor is alternately cooled and the moisture and carbon dioxide contained therein are solidified to form ice and dry ice. two reversing type heat exchangers that deposit the air as oxygen, one air separator that deep-cools and separates the clean air from these heat exchangers to produce high-purity oxygen and nitrogen, and this air separator. a backwashing nitrogen gas feed pipe that sends a portion of the nitrogen gas generated in the step to the heat exchanger for backwashing;
A backwashing nitrogen gas extraction pipe for recovering backwashing nitrogen gas from the heat exchanger, and a low-temperature, high-purity nitrogen gas produced by the air separator that is installed in the middle of this backwashing nitrogen gas extraction pipe. A first diffuser blows a portion of the nitrogen gas through a first high-purity nitrogen gas branch pipe, and a temperature signal of backwashing nitrogen gas is input from a temperature sensor installed downstream of this first diffuser. The opening degree of the control valve attached to the first nitrogen gas branch pipe is adjusted to keep the temperature of the backwashing nitrogen gas from 0 to -1.
a first temperature controller that controls the temperature within a range of 0°C; and a first temperature controller that is connected to the backwashing nitrogen gas extraction pipe and filters and separates ice.
a gravity settling separator and/or a first separation filter; an air fan for delivering backwashing air to vaporize ice accumulated in the first gravity settling separator and/or the first separation filter; A second gravity sedimentation separator and/or a second separation filter installed downstream of the first gravity settling separator and/or the first separation filter and blowing a part of the low-temperature high-purity nitrogen gas produced in the air separator through a second high-purity nitrogen gas branch pipe. 2 diffuser and a control valve attached to the second high-purity nitrogen gas branch pipe by inputting the temperature signal of the backwashing nitrogen gas from the temperature detector attached downstream of the second diffuser. Adjust the opening degree to lower the temperature of the nitrogen gas for backwashing to -8
a second temperature controller that controls the temperature to below 0° C., and a second gravity sedimentation separator and/or second separation filter that is connected downstream of the second diffuser and filters and separates dry ice in the gas. , a backwashing carbon dioxide gas supply pipe that blows low-temperature backwashing carbon dioxide stored in the recovered carbon dioxide gas holder into the second gravity settling separator and/or the second separation filter, and carbon dioxide vaporized from dry ice. A carbon dioxide recovery device for an air separation device, comprising a recovered carbon dioxide gas take-out pipe for recovering gas, and a recovered carbon dioxide gas compressor for pressurizing the recovered carbon dioxide gas and sending it to the recovered carbon dioxide holder. 6. A recovered nitrogen gas/feed air heat exchanger is attached between the feed air compressor and the reversing type heat exchanger, which exchanges heat with recovered nitrogen gas with feed air to recover cooling heat. The carbon dioxide recovery device in an air separation device according to claim 5. 7. The recovered carbon dioxide gas/raw material air heat exchanger is attached to the recovered carbon dioxide gas extraction pipe for recovering cooling heat by exchanging heat between the recovered carbon dioxide gas and the raw material air. A carbon dioxide recovery device in the air separation device described above. 8. The air separation apparatus according to claim 5, wherein the air separation apparatus is applied to an air separation apparatus using an adsorption type moisture/carbon dioxide remover instead of the reversing type heat exchanger. Carbon dioxide recovery device.