CARBON DIOXIDE RECOVERY SYSTEM

A carbon dioxide recovery system, which is configured to separate and recover carbon dioxide from a carbon dioxide containing gas, includes an adsorption unit that includes an adsorbent material that is configured to adsorb and desorb the carbon dioxide. The adsorbent material is configured to radiate heat in response to adsorption of the carbon dioxide and is configured to absorb the heat in response to desorption of the carbon dioxide. The adsorption unit is one of a plurality of adsorption units, and adjacent two adsorption units among the plurality of adsorption units contact with each other. When one of the adjacent two adsorption units adsorbs the carbon dioxide, another one of the adjacent two adsorption units desorbs the carbon dioxide.

TECHNICAL FIELD

The present disclosure relates to a carbon dioxide recovery system configured to recover carbon dioxide from a carbon dioxide containing gas.

BACKGROUND

There has been proposed a device that is configured to separate the carbon dioxide from the carbon dioxide containing gas through use of an adsorbent material which is installed in an adsorption unit and is configured to adsorb and desorb the carbon dioxide in response to a pressure change. At the time of adsorbing the carbon dioxide, the temperature of the adsorbent material is increased by heat radiation, and thereby the carbon dioxide adsorption amount of the adsorbent material is decreased. In contrast, at the time of desorbing the carbon dioxide, the temperature of the adsorbent material is decreased by heat absorption, and thereby the carbon dioxide desorption amount of the adsorbent material is decreased.

SUMMARY

According to the present disclosure, there is provided a carbon dioxide recovery system configured to separate and recover carbon dioxide from a carbon dioxide containing gas, which contains the carbon dioxide. The carbon dioxide recovery system includes an adsorption unit. The adsorption unit includes an adsorbent material which is configured to adsorb and desorb the carbon dioxide. The adsorbent material is configured to radiate heat in response to adsorption of the carbon dioxide and is configured to absorb the heat in response to desorption of the carbon dioxide.

According to one aspect of the present disclosure, the adsorption unit is one of a plurality of adsorption units, and adjacent two adsorption units among the plurality of adsorption units contact with each other. When one of the adjacent two adsorption units adsorbs the carbon dioxide, another one of the adjacent two adsorption units desorbs the carbon dioxide. Heat is exchanged between the one of the adjacent two adsorption units, which adsorbs the carbon dioxide, and the another one of the adjacent two adsorption units, which desorbs the carbon dioxide.

According to another aspect of the present disclosure, the adsorbent material is a porous metal organic framework in which organic ligands are coordinated to metallic elements, and the metallic elements contain a precious metal.

According to another aspect of the present disclosure, the adsorption unit includes a high heat capacity material that has a heat capacity which is higher than a heat capacity of the adsorbent material.

DETAILED DESCRIPTION

There has been proposed a device that is configured to separate carbon dioxide from a carbon dioxide containing gas through use of an adsorbent material which is installed in an adsorption unit and is configured to adsorb and desorb the carbon dioxide in response to a pressure change. At the time of adsorbing the carbon dioxide, the temperature of the adsorbent material is increased by heat radiation, and thereby the carbon dioxide adsorption amount of the adsorbent material is decreased. In contrast, at the time of desorbing the carbon dioxide, the temperature of the adsorbent material is decreased by heat absorption, and thereby the carbon dioxide desorption amount of the adsorbent material is decreased.

In view of the above point, the above-described device has a heat exchanger that is configured to exchange the heat between: a feed gas, the temperature of which becomes high due to pressurization of the feed gas before the time of feeding the feed gas to the adsorption unit; and a post-processing gas, which is discharged from the adsorption unit and has the low temperature, to reduce the temperature of the feed gas.

However, since the above-described device exchanges the heat between the feed gas and the post-processing gas, a heat exchange efficiency of the device is low. Furthermore, it is necessary to provide the heat exchanger, and thereby the device becomes large and more complicated.

Furthermore, although the above-described device limits the temperature increase of the adsorbent material at the time of carbon dioxide adsorption by feeding the feed gas, the temperature of which is decreased, to the adsorption unit, the above-described device cannot deal with the temperature decrease of the adsorbent material at the time of the carbon dioxide desorption.

According to the present disclosure, there is provided a carbon dioxide recovery system that includes an adsorption unit. The adsorption unit includes an adsorbent material which is configured to adsorb and desorb carbon dioxide. The adsorbent material is configured to radiate heat in response to adsorption of the carbon dioxide and is configured to absorb the heat in response to desorption of the carbon dioxide. The adsorption unit is one of a plurality of adsorption units, and adjacent two adsorption units among the plurality of adsorption units contact with each other. When one of the adjacent two adsorption units adsorbs the carbon dioxide, another one of the adjacent two adsorption units desorbs the carbon dioxide. Heat is exchanged between the one of the adjacent two adsorption units, which adsorbs the carbon dioxide, and the another one of the adjacent two adsorption units, which desorbs the carbon dioxide.

Therefore, the heat exchange is directly made between: the adsorption unit, the temperature of which is increased by the heat radiation in response to the carbon dioxide adsorption; and the adsorption unit, the temperature of which is decreased by the heat absorption in response to the carbon dioxide desorption. As a result, the temperature increase of the adsorbent material in response to the carbon dioxide adsorption and the temperature decrease of the adsorbent material in response to the carbon dioxide desorption can be effectively limited by the simple configuration in which the direct heat exchange is made between the adjacent adsorption units.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each of the following embodiments, the same reference signs may be assigned to portions that are the same as or equivalent to those described in the preceding embodiment(s), and the description thereof may be omitted. Further, when only a portion of a structure is described in each embodiment, the description of the rest of the structure described in the preceding embodiment may be applied to the rest of the structure. In addition to the combinations of portions that are specifically shown to be combinable in the respective embodiments, it is also possible to partially combine the embodiments even if they are not specifically shown, provided that the combinations are not impeded.

First Embodiment

Hereinafter, a first embodiment of the present disclosure will be described with reference to the drawings.

As shown inFIG.1, a carbon dioxide recovery system10of the present embodiment includes a plurality (two in this instance) of gas feeders11,19, a plurality (two in this instance) of adsorption units13,14, a plurality (two in this instance) of throttle valves15,16and a storage20. These devices are connected by a plurality of gas passages100-103. The gas feeders11,19and the throttle valves15,16serve as a pressure regulator that is configured to adjust a carbon dioxide partial pressure at insides of the adsorption units13,14.

The gas passages100-103are gas pipes which are configured to conduct a gas therethrough. The gas passages100-103include feed passages100, discharges passage101, an outlet passage102and a recovery passage103.

A carbon dioxide containing gas, which is fed to the adsorption units13,14, is conducted through the feed passages100. The carbon dioxide containing gas contains carbon dioxide and a non-carbon dioxide gas while the non-carbon dioxide gas is a gas that is other than the carbon dioxide. For example, an exhaust gas of an internal combustion engine or an atmospheric gas may be used as the carbon dioxide containing gas.

The feed passages100include a first feed passage100a, a second feed passage100band a third feed passage100c. The first feed passage100abranches into the second feed passage100band the third feed passage100con a downstream side of the first feed passage100ain a gas flow direction. The second feed passage100band the third feed passage100care arranged parallel to each other. The first feed passage100ais configured to communicate with only one of the second feed passage100band the third feed passage100cat once.

A first passage switching valve12is installed at a connection point at which the first feed passage100a, the second feed passage100band the third feed passage100care connected with each other. The first passage switching valve12is a three-way valve and is configured to switch between: one state, in which the first feed passage100aand the second feed passage100bare communicated with each other through the first passage switching valve12; and another state, in which the first feed passage100aand the third feed passage100care communicated with each other through the first passage switching valve12.

The first gas feeder11is installed in the first feed passage100a. The first gas feeder11is a compressor that is configured to compress the carbon dioxide containing gas and feed the compressed carbon dioxide containing gas to the adsorption units13,14. The carbon dioxide containing gas, which is fed from the first gas feeder11, flows toward the adsorption units13,14through the feed passages100a,100b,100c.

In the present embodiment, the plurality of adsorption units13,14include a primary adsorption unit13and a secondary adsorption unit14. The primary adsorption unit13and the secondary adsorption unit14have an identical structure.

The primary adsorption unit13and the secondary adsorption unit14are arranged parallel to each other and are installed to the second feed passage100band the third feed passage100c, respectively. The primary adsorption unit13and the secondary adsorption unit14are arranged adjacent to each other.

Each of the adsorption units13,14is a device that is configured to adsorb and desorb the carbon dioxide to separate the carbon dioxide from the carbon dioxide containing gas. The adsorption unit13,14introduces the carbon dioxide containing gas into an inside of the adsorption unit13,14and discharges: the non-carbon dioxide gas (carbon dioxide removed gas) that is a remaining gas from which the carbon dioxide is separated; or the carbon dioxide that is separated from the carbon dioxide containing gas.

The adsorption and the desorption of the carbon dioxide are alternately executed in the adsorption units13,14. That is, when one of the adjacent adsorption units13,14adsorbs the carbon dioxide, the other one of the adjacent adsorption units13,14desorbs the carbon dioxide. Specifically, in a case where the primary adsorption unit13adsorbs the carbon dioxide, the secondary adsorption unit14desorbs the carbon dioxide. Furthermore, in another case where the primary adsorption unit13desorbs the carbon dioxide, the secondary adsorption unit14adsorbs the carbon dioxide.

FIG.2shows an enlarged view of a portion of the adsorption unit13,14shown inFIG.1. As shown inFIG.2, each of the adsorption units13,14includes an adsorbent material13a,14a. The adsorbent material13a,14aof the present embodiment is in a form of particles. The adsorbent material13a,14ais used in a state where the adsorbent material13a,14ais filled in a housing13b,14b.

The adsorbent material13a,14ais a material that can adsorb and desorb the carbon dioxide. The adsorbent material13a,14ais configured to adsorb the carbon dioxide contained in the carbon dioxide containing gas under a predetermined adsorption condition and desorb the carbon dioxide under a predetermined desorption condition.

A material, which adsorbs and desorbs the carbon dioxide in response to a pressure change, is used as the adsorbent material13a,14aof the present embodiment, so that the adsorption condition and the desorption condition of the adsorbent material13a,14aare set to be different pressures, respectively. The amount of carbon dioxide adsorption (hereinafter referred to as the carbon dioxide adsorption amount) of the adsorbent material13a,14achanges according to the carbon dioxide partial pressure. Specifically, the carbon dioxide adsorption amount of the adsorbent material13a,14ais increased when the carbon dioxide partial pressure is increased. When the carbon dioxide partial pressure at the inside of the adsorption unit13,14is made relatively high, the carbon dioxide can be adsorbed onto the adsorbent material13a,14a. Furthermore, when the carbon dioxide partial pressure at the inside of the adsorption unit13,14is made relatively low, the carbon dioxide can be desorbed from the adsorbent material13a,14a. That is, in the case where the carbon dioxide is adsorbed at the adsorption unit13,14, the carbon dioxide partial pressure at the inside of the adsorption unit13,14may be set to a predetermined pressure. Furthermore, in the case where the carbon dioxide is desorbed at the adsorption unit13,14, the carbon dioxide partial pressure at the inside of the adsorption unit13,14may be set to a pressure that is lower than the predetermined pressure.

For example, zeolite or a porous metal organic framework (MOF) may be used as the adsorbent material13a,14a. For example, LTA-type zeolite, FER-type zeolite, MEW-type zeolite, MFI-type zeolite, MOR-type zeolite, LTL-type zeolite, FAU-type zeolite, or BEA-type zeolite may be used as the zeolite. For example, [Cu(4,4′-dihydroxybiphenyl-3-carboxyl)2(4,4′-bipyridyl)]n, [Cu(PF6−)2(1,2-bis(4-pyridyl)ethane)]n, [Cu(CF3SO3−)2(1,3-bis(4-pyridyl)propane)2]n, {[Cu(PF6−)(2,2-bis(4-pyridyl)]PF6−}n, and the like may be used as the porous metal organic framework.

As shown inFIG.1, each of the adsorption units13,14includes the housing13b,14bthat receives the adsorbent material13a,14a. The housing13b,14bhas: a gas inlet, through which the carbon dioxide containing gas is introduced into the inside of the housing13b,14b; and a gas outlet, through which the non-carbon dioxide gas (the carbon dioxide removed gas) or the carbon dioxide is discharged from the inside of the housing13b,14b.

The adsorption units13,14are arranged to contact with each other, and the housings13b,14bare thermally in contact with each other. Therefore, the adsorption units13,14are configured such that the housings13b,14bcan directly exchange the heat between the housings13b,14b. It is desirable that the housings13b,14bare made of a material, such as aluminum, copper, SUS (steel use stainless), which has an excellent heat transfer property.

The adsorbent material13a,14ais configured to radiate the heat in response to the adsorption of the carbon dioxide and is configured to absorb the heat in response to the desorption of the carbon dioxide. The carbon dioxide adsorption capacity of the adsorbent material13a,14ais decreased when the temperature of the adsorbent material13a,14ais increased by the heat radiated from the adsorbent material13a,14ain response to the adsorption of the carbon dioxide. The carbon dioxide desorption capacity of the adsorbent material13a,14ais decreased when the temperature of the adsorbent material13a,14ais decreased by the heat absorption in response to the desorption of the carbon dioxide.

In the case where the temperature of the adsorbent material13a,14ais increased, the temperature of the housing13b,14bis also increased. Furthermore, when the temperature of the adsorbent material13a,14ais decreased, the temperature of the housing13b,14bis also decreased. In the case where the temperature difference exists between the adsorbent materials13a,14aof the adjacent adsorption units13,14, the heat is transferred between the adsorbent materials13a,14athrough the housings13b,14b.

The discharge passages101are connected to the downstream sides of the adsorption units13,14. The discharge passages101include a first discharge passage101aand a second discharge passage101b. The first discharge passage101ais connected to the primary adsorption unit13, and the second discharge passage101bis connected to the secondary adsorption unit14. The non-carbon dioxide gas or the carbon dioxide, which is discharged from the primary adsorption unit13, flows through the first discharge passage101a. The non-carbon dioxide gas or the carbon dioxide, which is discharged from the secondary adsorption unit14, flows through the second discharge passage101b.

The first throttle valve15is installed to the first discharge passage101a, and the second throttle valve16is installed to the second discharge passage101b. Each of the throttle valves15,16includes a variable throttle mechanism which is configured to adjust a valve opening degree of the throttle valve15,16, so that the throttle valve15,16can change the gas pressure at the inside of the corresponding adsorption unit13,14by adjusting a passage cross-sectional area of the throttle valve15,16. In the case where the first gas feeder11pressurizes the carbon dioxide containing gas and feeds the pressurized carbon dioxide containing gas, the gas pressure at the inside of the adsorption unit13,14can be increased by decreasing the valve opening degree of the throttle valve15,16. In contrast, the gas pressure at the inside of the adsorption unit13,14can be decreased by increasing the valve opening degree of the throttle valve15,16.

The first discharge passage101aand the second discharge passage101bare connected to the outlet passage102and the recovery passage103, respectively, which are located on the downstream side of the first discharge passage101aand the second discharge passage101b. Each of the first discharge passage101aand the second discharge passage101bcan be communicated with a corresponding one of the outlet passage102and the recovery passage103. In a case where the first discharge passage101ais communicated with the outlet passage102, the second discharge passage101bis communicated with the recovery passage103. In another case where the first discharge passage101ais communicated with the recovery passage103, the second discharge passage101bis communicated with the outlet passage102.

A second passage switching valve17is installed at a connection point at which the first discharge passage101a, the outlet passage102and the recovery passage103are connected with each other. The second passage switching valve17is a three-way valve and is configured to switch between: one state, in which the first discharge passage101aand the outlet passage102are communicated with each other through the second passage switching valve17; and another state, in which the first discharge passage101aand the recovery passage103are communicated with each other through the second passage switching valve17.

A third passage switching valve18is installed at a connection point at which the second discharge passage101b, the outlet passage102and the recovery passage103are connected with each other. The third passage switching valve18is a three-way valve and is configured to switch between: one state, in which the second discharge passage101band the outlet passage102are communicated with each other through the third passage switching valve18; and another state, in which the second discharge passage101band the recovery passage103are communicated with each other through the third passage switching valve18.

The outlet passage102is communicated with the atmosphere. The non-carbon dioxide gas, which is discharged from the adsorption unit13,14, is released to the atmosphere through the outlet passage102.

The second gas feeder19is installed in the recovery passage103. The recovery passage103is connected to the storage20. The second gas feeder19suctions the carbon dioxide discharged from the adsorption unit13,14and feeds it to the storage20. The carbon dioxide, which is discharged from the adsorption unit13,14is fed to the storage20through the recovery passage103.

A blower or a compressor may be used as the second gas feeder19. The storage20is a device that stores the carbon dioxide which is separated from the carbon dioxide containing gas at the adsorption unit13,14. In the present embodiment, a high-pressure tank, which stores the high-pressure carbon dioxide, is used as the storage20, and the compressor, which pressurizes the carbon dioxide and feeds the pressurized carbon dioxide to the storage20, is used as the second gas feeder19.

As shown inFIG.3, the carbon dioxide recovery system10includes a controller unit21. The controller unit21includes a well-known microcomputer, which includes a CPU (at least one processor), a ROM, and a RAM, and peripheral circuits thereof. The controller unit21performs various calculations and processes based on a control program stored in the ROM and controls operations of various control subject devices. The controller unit21is configured to output a control signal to the gas feeders11,19, the passage switching valves12,17,18and the throttle valves15,16to execute the operation control of the gas feeders11,19, the passage switching control of the passage switching valves12,17,18, and the opening degree control of the throttle valves15,16.

Next, the operation of the carbon dioxide recovery system10of the present embodiment will be described with reference toFIG.4. The operation of the carbon dioxide recovery system10is controlled by the controller unit21.

The upper side ofFIG.4indicates a case where the primary adsorption unit13adsorbs the carbon dioxide, i.e., executes carbon dioxide adsorption, and the secondary adsorption unit14desorbs the carbon dioxide, i.e., executes carbon dioxide desorption. The lower side ofFIG.4indicates another case where the primary adsorption unit13desorbs the carbon dioxide, and the secondary adsorption unit14adsorbs the carbon dioxide. InFIG.4, the gas passages100-103, through which the gas is flowing, are indicated by a bold line.

Now, there will be described the case of the upper side ofFIG.4where the primary adsorption unit13executes the carbon dioxide adsorption, and the secondary adsorption unit14executes the carbon dioxide desorption. It is assumed that the secondary adsorption unit14is in the state where the carbon dioxide has been previously adsorbed on the adsorbent material14a.

The first passage switching valve12is switched to the state where the first feed passage100aand the second feed passage100bare communicated with each other through the first passage switching valve12, and the second passage switching valve17is switched to the state where the first discharge passage101aand the outlet passage102are communicated with each other through the second passage switching valve17. Furthermore, the third passage switching valve18is switched to the state where the second discharge passage101band the recovery passage103are communicated with each other through the third passage switching valve18. Also, the valve opening degree of the first throttle valve15is decreased, and the valve opening degree of the second throttle valve16is increased. Then, the operation of the first gas feeder11and the operation of the second gas feeder19are started.

The carbon dioxide containing gas, which is pressurized by the first gas feeder11, is fed to the primary adsorption unit13through the first feed passage100aand the second feed passage100b. At the primary adsorption unit13, the carbon dioxide, which is contained in the carbon dioxide containing gas, is adsorbed on the adsorbent material13a, and the non-carbon dioxide gas, which is not adsorbed at the primary adsorption unit13, is released to the atmosphere through the first discharge passage101aand the outlet passage102.

At the secondary adsorption unit14, the carbon dioxide is desorbed from the adsorbent material14a, on which the carbon dioxide has been previously adsorbed. The carbon dioxide, which is desorbed at the secondary adsorption unit14, is suctioned by the second gas feeder19and is fed to the storage20through the second discharge passage101band the recovery passage103. Then, the storage20stores the received carbon dioxide.

At the primary adsorption unit13, the adsorbent material13aradiates the heat in response to the adsorption of the carbon dioxide. At the secondary adsorption unit14, the adsorbent material14aabsorbs the heat in response to the desorption of the carbon dioxide. Therefore, a temperature difference is generated between the adsorbent material13aof the primary adsorption unit13and the adsorbent material14aof the secondary adsorption unit14, and the heat is exchanged between the primary adsorption unit13and the secondary adsorption unit14through the housings13b,14b. Thus, the temperature increase of the adsorbent material13ais limited at the primary adsorption unit13, and thereby the carbon dioxide adsorption capacity of the adsorbent material13acan be maintained longer as much as possible. Furthermore, the temperature decrease of the adsorbent material14ais limited at the secondary adsorption unit14, and thereby the carbon dioxide desorption capacity of the adsorbent material14acan be maintained longer as much as possible.

At the primary adsorption unit13, when the carbon dioxide is continuously adsorbed, the carbon dioxide adsorption amount of the adsorbent material13aapproaches a saturation amount, and thereby a carbon dioxide adsorption rate of the adsorbent material13ais gradually decreased. At the secondary adsorption unit14, when the carbon dioxide is continuously desorbed, the carbon dioxide adsorption amount of the adsorbent material14ais decreased, and thereby a carbon dioxide desorption rate of the adsorbent material14ais gradually decreased. Therefore, at a predetermined timing, the primary adsorption unit13switches its operation from the carbon dioxide adsorption to the carbon dioxide desorption, and the secondary adsorption unit14switches its operation from the carbon dioxide desorption to the carbon dioxide adsorption.

Next, there will be described the case of the lower side ofFIG.4where the primary adsorption unit13executes the carbon dioxide desorption, and the secondary adsorption unit14executes the carbon dioxide adsorption.

The first passage switching valve12is switched to the state where the first feed passage100aand the third feed passage100care communicated with each other through the first passage switching valve12, and the second passage switching valve17is switched to the state where the first discharge passage101aand the recovery passage103are communicated with each other through the second passage switching valve17. Furthermore, the third passage switching valve18is switched to the state where the second discharge passage101band the outlet passage102are communicated with each other through the third passage switching valve18. Also, the valve opening degree of the first throttle valve15is increased, and the valve opening degree of the second throttle valve16is decreased. The operation of the first gas feeder11and the operation of the second gas feeder19are maintained.

The carbon dioxide containing gas, which is pressurized by the first gas feeder11, is fed to the secondary adsorption unit14through the first feed passage100aand the third feed passage100c. At the secondary adsorption unit14, the carbon dioxide, which is contained in the carbon dioxide containing gas, is adsorbed on the adsorbent material14a, and the non-carbon dioxide gas, which is not adsorbed at the secondary adsorption unit14, is released to the atmosphere through the second discharge passage101band the outlet passage102.

At the primary adsorption unit13, the carbon dioxide is desorbed from the adsorbent material13a, on which the carbon dioxide has been previously adsorbed. The carbon dioxide, which is desorbed at the primary adsorption unit13, is suctioned by the second gas feeder19and is fed to the storage20through the first discharge passage101aand the recovery passage103. Then, the storage20stores the received carbon dioxide.

At the secondary adsorption unit14, the adsorbent material14aradiates the heat in response to the adsorption of the carbon dioxide. At the primary adsorption unit13, the adsorbent material13aabsorbs the heat in response to the desorption of the carbon dioxide. Therefore, a temperature difference is generated between the adsorbent material13aof the primary adsorption unit13and the adsorbent material14aof the secondary adsorption unit14, and the heat is exchanged between the primary adsorption unit13and the secondary adsorption unit14through the housings13b,14b. Therefore, the temperature decrease of the adsorbent material13ais limited at the primary adsorption unit13, and thereby the carbon dioxide desorption capacity of the adsorbent material13acan be maintained longer as much as possible. The temperature increase of the adsorbent material14ais limited at the secondary adsorption unit14, and thereby the carbon dioxide adsorption capacity of the adsorbent material14acan be maintained longer as much as possible.

According to the present embodiment described above, in the carbon dioxide recovery system10, in which the adsorption units13,14alternately execute the carbon dioxide adsorption and the carbon dioxide desorption, the heat can be directly exchanged between the adsorption unit13,14, which executes the carbon dioxide adsorption, and the adsorption unit13,14, which executes the carbon dioxide desorption.

Therefore, the heat exchange is efficiently made between: the adsorption unit13,14, in which the temperature of the adsorbent material13a,14ais increased by the heat radiation in response to the carbon dioxide adsorption; and the adsorption unit13,14, in which the temperature of the adsorbent material13a,14ais decreased by the heat absorption in response to the carbon dioxide desorption. As a result, the temperature increase of the adsorbing adsorbent material13a,14ain response to the carbon dioxide adsorption thereof and the temperature decrease of the desorbing adsorbent material13a,14ain response to the carbon dioxide desorption thereof can be limited by the simple configuration in which the direct heat exchange is made between the adsorption units13,14. In this way, the carbon dioxide adsorption performance and the carbon dioxide desorption performance of the carbon dioxide recovery system10can be improved, and the operating energy of the carbon dioxide recovery system10can be reduced.

Furthermore, the adsorption units13,14of the present embodiment are respectively configured to execute the corresponding one of the carbon dioxide adsorption and the carbon dioxide desorption by changing the carbon dioxide partial pressure. Therefore, the adsorption units13,14do not have the function for limiting the temperature change of the adsorbent materials13a,14a, and thereby the temperature change of the respective adsorption units13,14in response to the carbon dioxide adsorption or the carbon dioxide desorption is likely to occur. In the above-described configuration, in which the carbon dioxide adsorption or the carbon dioxide desorption is executed by changing the pressure, the temperature change of the respective adsorbent materials13a,14acan be advantageously limited by directly exchanging the heat between the adsorption unit13,14, which executes the carbon dioxide adsorption, and the adsorption unit13,14, which executes the carbon dioxide desorption.

Second Embodiment

Next, a second embodiment of the present disclosure will be described. In the present embodiment, there will be described only points, which are different from the first embodiment.

FIG.5schematically shows the arrangement of the adsorption units13,14of the second embodiment. As shown inFIG.5, in the second embodiment, a plurality of primary adsorption units13and a plurality of secondary adsorption units14are provided. That is, in the second embodiment, there are provided a plurality of adsorption units13,14, each of which executes the carbon dioxide adsorption, and a plurality of adsorption units13,14, each of which executes the carbon dioxide desorption. In the example shown inFIG.5, the number of the primary adsorption units13is two, and the number of the secondary adsorption units14is two.

As shown inFIG.5, the primary adsorption units13and the secondary adsorption units14are stacked in a predetermined stacking direction. Therefore, the adsorption units13,14are multilayered in the predetermined stacking direction. InFIG.5, an up-to-down direction is the stacking direction of the adsorption units13,14, and upper and lower surfaces of the adsorption units13,14, which are respectively located on the upper side and the lower side in the up-to-down direction, serve as contact surfaces of the adsorption units13,14, and the contact surfaces of each adjacent two of the adsorption units13,14contact with each other.

The primary adsorption units13and the secondary adsorption units14are alternatively arranged adjacent to each other. That is, the adsorption units13,14, which execute the carbon dioxide adsorption, and the adsorption units13,14, which execute the carbon dioxide desorption, are alternatively arranged adjacent to each other. Thus, it is possible to increase a contact surface area between the adsorption unit13,14, which executes the carbon dioxide adsorption, and the adsorption unit13,14, which executes the carbon dioxide desorption, to increase the heat exchange surface areas among the adsorption units13,14.

FIG.6shows the gas flow direction with a dotted line arrow in each of the adsorption units13,14and the gas passages100b,100c,101a,101b.FIG.7shows the gas flow direction with the dotted line arrow in each of the adsorption units13,14. InFIGS.6and7, the gas flow direction in the primary adsorption unit13is indicated by a reference sign A, and the gas flow direction in the secondary adsorption unit14is indicated by a reference sign B.

As shown inFIG.6, in the primary adsorption unit13, the gas is fed from the second feed passage100band flows in the gas flow direction A and is then discharged through the first discharge passage101a. In the secondary adsorption unit14, the gas is fed from the third feed passage100cand flows in the gas flow direction B and is then discharged through the second discharge passage101b.

As shown inFIGS.6and7, the gas flow direction A of each primary adsorption unit13and the gas flow direction B of each secondary adsorption unit14coincide with each other. Therefore, the heat is exchanged between an upstream portion of the primary adsorption unit13and an upstream portion of the secondary adsorption unit14, which are located on the upstream side in the gas flow direction, and the heat is exchanged between a downstream portion of the primary adsorption unit13and a downstream portion of the secondary adsorption unit14, which are located on the downstream side in the gas flow direction.

A temperature gradient is generated at the adsorption unit13,14in the gas flow direction due to the heat radiation in response to the carbon dioxide adsorption and the heat absorption in response to the carbon dioxide desorption. In the adsorption unit13,14, which executes the carbon dioxide adsorption, the temperature gradient is generated such that the temperature is increased toward the downstream side in the gas flow direction due to the heat radiation in response to the carbon dioxide adsorption. In the adsorption unit13,14, which executes the carbon dioxide desorption, the temperature gradient is generated such that the temperature is decreased toward the downstream side in the gas flow direction due to the heat absorption in response to the carbon dioxide desorption. Therefore, the temperature difference becomes large between the downstream portion of the adsorption unit13,14, which executes the carbon dioxide adsorption, and the downstream portion of the adsorption unit13,14, which executes the carbon dioxide desorption.

By coinciding the gas flow direction A of the primary adsorption unit13and the gas flow direction B of the secondary adsorption unit14, it is possible to exchange the heat between the high temperature portion of the adsorption unit13,14, which executes the carbon dioxide adsorption, and the low temperature portion of the adsorption unit13,14, which executes the carbon dioxide desorption, while the high temperature portion and the low temperature portion of the adsorption units13,14exhibit the large temperature difference therebetween. Therefore, in the case where the heat is exchanged between the primary adsorption unit13and the secondary adsorption unit14, the amount of transferred heat between the primary adsorption unit13and the secondary adsorption unit14can be increased to improve the heat exchange efficiency.

FIG.8shows a shape of a cross-section of a contact area, at which the primary adsorption unit13and the secondary adsorption unit14contact with each other. As shown inFIG.8, the contact surface of the primary adsorption unit13and the contact surface of secondary adsorption unit14, which are placed adjacent to each other, are respectively shaped to have a series of protrusions and recesses (i.e., a series of protrusions spaced from one another forming a series of recesses therebetween). The series of protrusions and recesses of the contact surface of the primary adsorption unit13and the series of protrusions and recesses of the contact surface of the secondary adsorption unit14correspond with each other such that each of the recesses of one of the primary adsorption unit13and the secondary adsorption unit14has a shape that corresponds to a shape of a corresponding one of the protrusions of the other one of the primary adsorption unit13and the secondary adsorption unit14.

In the example shown inFIG.8, the cross-section of the contact surface of each of the primary adsorption unit13and the secondary adsorption unit14has a corrugated shape with a series of ridges and furrows (serving as the series of protrusions and recesses). By providing the series of protrusions and recesses at each of the contact surfaces of each adjacent two of the adsorption units13,14, the heat exchange surface area of each of these adjacent adsorption units13,14can be increased to improve the heat exchange efficiency therebetween.

InFIG.8, a direction, which is perpendicular to the plane ofFIG.8, is the gas flow direction of each of the primary adsorption unit13and the secondary adsorption unit14. Each of the series of protrusions and recesses formed at each of the primary adsorption unit13and the secondary adsorption unit14is elongated in the gas flow direction of each of the primary adsorption unit13and the secondary adsorption unit14. That is, a longitudinal direction of each of the series of the protrusions and recesses at each of the primary adsorption unit13and the secondary adsorption unit14coincides with the gas flow direction. Therefore, the gas flow along the adsorption unit13,14is not interfered by the series of protrusions and recesses formed at each of the primary adsorption unit13and the secondary adsorption unit14.

The provision of the series of protrusions and recesses formed at the adsorption units13,14is not limited to the contact surfaces of the adjacent adsorption units13,14, which contact with each other, and the series of protrusions and recesses may be formed at a contact surface of the adsorption unit13,14, which contacts the outside air. With this configuration, the heat exchange surface area between the adsorption unit13,14and the outside air can be increased. In a case where the temperature of the adsorption unit13,14becomes higher than the outside air temperature due to the heat radiation in response to the carbon dioxide adsorption, it is possible to limit the increase of the temperature of the adsorption unit13,14through the heat exchange with the outside air. In another case where the temperature of the adsorption unit13,14becomes lower than the outside air temperature due to the carbon dioxide desorption, it is possible to limit the decrease of the temperature of the adsorption unit13,14through the heat exchange with the outside air.

In the second embodiment described above, the adsorption units13,14are multilayered by stacking the plurality of primary adsorption units13and the plurality of secondary adsorption units14. In this way, the heat exchange surface areas of each of the primary adsorption units13and the secondary adsorption units14can be increased to increase the heat transfer amount among the primary adsorption units13and the secondary adsorption units14, so that the heat exchange efficiency can be improved.

Furthermore, in the second embodiment, the gas flow direction of the primary adsorption unit13and the gas flow direction of the secondary adsorption unit14coincide with each other, i.e., are the same direction. Thereby, it is possible to exchange the heat between the high temperature portion of the adsorption unit13,14, which executes the carbon dioxide adsorption, and the low temperature portion of the adsorption unit13,14, which executes the carbon dioxide desorption, while the high temperature portion and the low temperature portion of the adsorption units13,14exhibit the large temperature difference therebetween. Therefore, the heat transfer amount between these adsorption units13,14can be increased, and thereby the heat exchange efficiency can be improved.

Furthermore, in the second embodiment, the series of protrusions and recesses are formed at each of the contact surface of the primary adsorption unit13and the contact surface of the secondary adsorption unit14which contact with each other. By providing the series of protrusions and recesses at each of the contact surfaces of each adjacent two of the adsorption units13,14, the heat exchange surface area of each of these adjacent adsorption units13,14can be increased to improve the heat exchange efficiency therebetween.

Third Embodiment

Next, a third embodiment of the present disclosure will be described. In the present embodiment, there will be described only points, which are different from the embodiments described above.

In the third embodiment, a porous metal organic framework (MOF) is used as the adsorbent material13a,14aof each of the adsorption units13,14. As shown inFIG.9, the porous metal organic framework is a porous three-dimensional framework in which organic ligands41are coordinately bonded to metallic elements40. The porous metal organic framework has a large number of small pores and has a high carbon dioxide adsorption capacity. In contrast, the porous metal organic framework tends to have a smaller heat capacity due to the smaller number of constituent atoms per unit volume.

In the adsorbent material13a,14aof the third embodiment, the metallic elements40, which form the porous metal organic framework, contain a precious metal. Examples of such a precious metal include Ag (silver), Au (gold), Pt (platinum), etc.

The precious metals are metals which respectively have a large atomic weight and a relatively large heat capacity. Therefore, by using the porous metal organic framework, which includes the precious metal as the metallic elements40and serves as the adsorbent material13a,14a, the heat capacity of the adsorbent material13a,14aitself can be effectively increased. The increased heat capacity of the adsorbent material13a,14acan limit the temperature increase of the adsorbent material13a,14acaused by the heat radiation in response to the carbon dioxide adsorption and can limit the temperature decrease of the adsorbent material13a,14acaused by the heat absorption in response to the carbon dioxide desorption.

Fourth Embodiment

Next, a fourth embodiment of the present disclosure will be described. In the present embodiment, there will be described only points, which are different from the embodiments described above.

For example, the porous metal organic framework (MOF) may be used as the adsorbent material13a,14aof each of the adsorption units13,14of the fourth embodiment. As shown inFIG.10, the adsorbent material13a,14aof the fourth embodiment includes a high heat capacity material22combined with the adsorbent material13a,14aserving as a carrier. That is, in the fourth embodiment, the adsorbent material13a,14aand the high heat capacity material22are integrally provided as a composite material.

The high heat capacity material22is a material that has a higher heat capacity than the adsorbent material13a,14a, and paraffin may be used as the high heat capacity material22. The paraffin is a material that can be easily composited with the porous metal organic framework, and the latent heat associated with the phase change of the paraffin can be used.

The composite material, which includes the adsorbent material13a,14aand the high heat capacity material22, can be obtained by, for example, mixing particles of the adsorbent material13a,14aand particles of the high heat capacity material22. The high heat capacity material22may be inserted into the small pores of the adsorbent material13a,14a.

According to the fourth embodiment, the high heat capacity material22is compounded with the adsorbent material13a,14a, so that the heat capacity of the adsorbent material13a,14acan be increased. Thereby, the temperature increase of the adsorbent material13a,14acaused by the heat radiation in response to the carbon dioxide adsorption can be limited, and the temperature decrease of the adsorbent material13a,14acaused by the heat absorption in response to the carbon dioxide desorption can be limited.

Fifth Embodiment

Next, a fifth embodiment of the present disclosure will be described. In the present embodiment, there will be described only points, which are different from the embodiments described above.

As shown inFIG.11, each of the adsorption units13,14of the fifth embodiment includes the high heat capacity material22besides the adsorbent material13a,14a. The high heat capacity material22is received along with the adsorbent material13a,14ain the housing13b,14bof the adsorption unit13,14. The high heat capacity material22of the fifth embodiment is in a form of particles and is formed separately from the adsorbent material13a,14a(more specifically, the particles of the adsorbent material13a,14a). For example, metal sphere particles made of aluminum may be used as the high heat capacity material22of the fifth embodiment. The high heat capacity material22is arranged in contact with the adsorbent material13a,14a, and thereby the heat can be transferred between the high heat capacity material22and the adsorbent material13a,14a.

According to the fifth embodiment, each of the adsorption units13,14includes the high heat capacity material22formed separately from the adsorbent material13a,14a, so that the heat capacity of the whole adsorption unit13,14can be increased. Thereby, the temperature increase of the adsorbent material13a,14acaused by the heat radiation in response to the carbon dioxide adsorption can be limited, and the temperature decrease of the adsorbent material13a,14acaused by the heat absorption in response to the carbon dioxide desorption can be limited.

Furthermore, according to the fifth embodiment, since the high heat capacity material22is formed separately from the adsorbent material13a,14a, the contact surface area of the adsorbent material13a,14a, which contacts with the gas, is increased in comparison to the fourth embodiment. Therefore, the carbon dioxide adsorption performance of the adsorbent material13a,14acan be ensured while limiting the temperature change of the adsorbent material13a,14acaused by the carbon dioxide adsorption and the carbon dioxide desorption.

Sixth Embodiment

Next, a sixth embodiment of the present disclosure will be described. In the present embodiment, there will be described only points, which are different from the embodiments described above.

As shown inFIG.12, according to the sixth embodiment, the high heat capacity material22is covered with the adsorbent material13a,14a. For example, metal sphere particles made of aluminum may be used as the high heat capacity material22of the sixth embodiment. This particulate high heat capacity material22is used as a core, and an outer peripheral surface of the particulate high heat capacity material22is coated with the adsorbent material13a,14a.

According to the sixth embodiment, the high heat capacity material22is covered with the adsorbent material13a,14a, so that the heat capacity of the whole adsorption unit13,14can be increased. Thereby, the temperature increase of the adsorbent material13a,14acaused by the heat radiation in response to the carbon dioxide adsorption can be limited, and the temperature decrease of the adsorbent material13a,14acaused by the heat absorption in response to the carbon dioxide desorption can be limited.

Furthermore, according to the sixth embodiment, since the high heat capacity material22is formed at the inside of the adsorbent material13a,14a, the contact surface area of the adsorbent material13a,14a, which contacts with the gas, is increased in comparison to the fourth embodiment. Therefore, the carbon dioxide adsorption performance of the adsorbent material13a,14acan be ensured while limiting the temperature change of the adsorbent material13a,14acaused by the carbon dioxide adsorption and the carbon dioxide desorption.

Seventh Embodiment

Next, a seventh embodiment of the present disclosure will be described. In the present embodiment, there will be described only points, which are different from the embodiments described above.

At the respective adsorption units13,14, the temperature of the adsorbent material13a,14achanges due to the heat radiation caused by the carbon dioxide adsorption or the heat absorption caused by the carbon dioxide desorption. At this time, the amount of radiated heat from the adsorbent material13a,14ain response to the carbon dioxide adsorption or the amount of absorbed heat at the adsorbent material13a,14ain response to the carbon dioxide desorption may vary depending on a location in the adsorption unit13,14. For example, in the adsorption unit13,14, at a high packing density area, at which a packing density of the adsorbent material13a,14ais higher than another area, the amount of radiated heat or the amount of absorbed heat of the adsorbent material13a,14acaused by the carbon dioxide adsorption or the carbon dioxide desorption is increased to cause a larger temperature change in this high packing density area in comparison to the other area.

When the variations in the amount of radiated heat or the amount of absorbed heat occur at the adsorbent material13a,14a, a heat distribution (also referred to as a temperature distribution) is generated in the adsorption unit13,14. The heat distribution of the adsorption unit13,14refers to a distribution of temperature change (also referred to as a distribution of temperature change amount) caused by the heat radiation or the heat absorption of the adsorbent material13a,14ain response to the carbon dioxide adsorption or the carbon dioxide desorption.

In the seventh embodiment, a volume ratio of the high heat capacity material22at the adsorption unit13,14is changed according to the heat distribution of the adsorption unit13,14. The volume ratio of the high heat capacity material22at the adsorption unit13,14can be adjusted by, for example, changing a mixing ratio of the high heat capacity material22relative to the adsorbent material13a,14ain any one of the configurations of the fourth to sixth embodiments described above.

In an example shown inFIG.13, at each of the adsorption units13,14, the amount of radiated heat or the amount of absorbed heat of the adsorbent material13a,14ain response to the carbon dioxide adsorption or the carbon dioxide desorption is increased from the right side to the left side ofFIG.13. As shown inFIG.13, at an area of the adsorption unit13,14where the heat distribution is large, the volume ratio of the high heat capacity material22is increased. In contrast, at another area of the adsorption unit13,14where the heat distribution is small, the volume ratio of the high heat capacity material22is decreased.

Specifically, in the adsorption unit13,14, at an area where the amount of radiated heat in response to the carbon dioxide adsorption is equal to or larger than a predetermined amount of radiated heat, or an area where the amount of absorbed heat in response to the carbon dioxide desorption is equal to or larger than a predetermined amount of absorbed heat, the volume ratio of the high heat capacity material22is increased in comparison to another area. At the adsorption unit13,14, the area where the amount of radiated heat in response to the carbon dioxide adsorption is equal to or larger than the predetermined amount of radiated heat, or the area where the amount of absorbed heat in response to the carbon dioxide desorption is equal to or larger than the predetermined amount of absorbed heat can be determined based on, for example, the packing density of the adsorbent material13a,14aat the respective areas of the adsorption unit13,14.

In the seventh embodiment described above, the volume ratio of the high heat capacity material22at the adsorption unit13,14is changed according to the heat distribution of the adsorption unit13,14. In this way, the temperature change of the adsorbent material13a,14ain response to the carbon dioxide adsorption or the carbon dioxide desorption can be effectively limited.

Furthermore, according to the seventh embodiment, by changing the volume ratio of the high heat capacity material22at the adsorption unit13,14according to the heat distribution at the adsorption unit13,14, the amount of unnecessary high heat capacity material22, which does not contribute to the carbon dioxide adsorption, can be limited as much as possible. Therefore, the carbon dioxide adsorption performance of the adsorbent material13a,14acan be ensured while limiting the temperature change of the adsorbent material13a,14acaused by the carbon dioxide adsorption and the carbon dioxide desorption.

The present disclosure is not limited to the above-described embodiments and may be modified in various ways as follows without departing from the spirit of the present disclosure. Furthermore, the components disclosed in the above embodiments may be suitably combined within a practical extent.

For example, in each of the embodiments described above, there is described the example where each of the adsorption units13,14executes the carbon dioxide adsorption and the carbon dioxide desorption according to the carbon dioxide partial pressure difference. Alternatively, a different type of adsorption unit13,14, which is different from this type, may be used. For example, an adsorption unit, which is configured to execute the carbon dioxide adsorption and the carbon dioxide desorption according to a temperature difference, may be used, or an adsorption unit, which includes an electrochemical cell that is configured to adsorb and desorb the carbon dioxide according to a difference in a voltage applied between electrodes, may be used.

Furthermore, in the third to seventh embodiments described above, there is described the example where the plurality of adsorption units13,14are provided. However, the present disclosure is not limited to this. The third to seventh embodiments may be applied to a carbon dioxide recovery system that includes a single adsorption unit.

Although the present disclosure has been described with reference to the embodiments and the modifications, it is understood that the present disclosure is not limited to the embodiments and the modifications and structures described therein. The present disclosure also includes various variations and variations within the equivalent range. In addition, the various combinations and forms are shown in this disclosure. However, other combinations and forms including only one element, more or less, are also within the scope and idea of the present disclosure.