Carbon dioxide recovery method and carbon dioxide recovery system

Abstract

To provide a process that allows carbon dioxide to be separated and recovered from a large amount of combustion exhaust gas in a space-saving and energy-saving way.SOLUTION: A carbon dioxide recovery method includes: an absorption step for causing an absorber to absorb carbon dioxide by making combustion exhaust gas containing carbon dioxide pass a radial flow type separation apparatus comprising the absorber; and a discharge step for discharging carbon dioxide from the absorber by making steam pass the separation apparatus.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for separating and recovering carbon dioxide from a gas containing carbon dioxide and a carbon dioxide recovery system.

Background Art

[0002] The problem of global warming due to the increase in the concentration of carbon dioxide in the atmosphere has been pointed out for a long time. In order to solve this problem, reducing the amount of carbon dioxide emissions into the atmosphere has become an urgent issue. Among the sources of carbon dioxide emissions into the atmosphere, combustion exhaust gases from waste incineration plants and thermal power plants account for a large proportion together with the exhaust gases of automobiles. Among these, in thermal power plants, fossil fuels such as coal, oil, and natural gas are burned to heat water in a boiler to produce high-temperature and high-pressure steam (water vapor), and this is used to drive a steam turbine, and generally, a generator directly connected to its rotating shaft is rotated to generate electricity. However, in recent years, gas turbine power generation that drives a gas turbine using natural gas as fuel instead of a steam turbine, and combined cycle power generation that drives a steam turbine with steam generated by utilizing the waste heat of the combustion exhaust gas of the gas turbine have also been put into practical use, and it can be said that the improvement of thermal efficiency and the reduction of power generation cost in thermal power generation have reached a considerable level. Also, regarding the treatment of combustion exhaust gases from these power plants, air pollution prevention technologies such as dust removal, desulfurization, and denitration have already reached a considerable level. However, regarding the reduction of the amount of carbon dioxide emissions into the atmosphere described above, although the study from the aspect of conversion from fossil fuels to renewable energy has been actively carried out, the study from the aspect of post-combustion recovery (PCC) of carbon dioxide from combustion exhaust gases is still not sufficient at present.

[0003] In addition, recently, not only the recovery of carbon dioxide from combustion exhaust gas but also the utilization and storage (CCUS) of the recovered carbon dioxide have been demanded. Technologies for separating and recovering carbon dioxide from the combustion exhaust gas of a coal-fired boiler with a carbon dioxide concentration of 13 to 14% by volume using an amine absorption solution have already been put into practical use. However, the wet absorption process of carbon dioxide using an amine absorption solution has had difficulties in terms of the cost related to renewable energy. Therefore, as a carbon dioxide absorbent to replace the amine aqueous solution, a solid absorbent capable of reducing renewable energy has been developed, and a carbon dioxide separation and recovery process using this has been studied. Non-Patent Documents 1 and 2 disclose technologies for recovering carbon dioxide by a fixed-bed reactor using a solid absorbent.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Non-Patent Documents

[0005]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The carbon dioxide separation and recovery processes studied so far mainly aim at separating and recovering carbon dioxide (concentration 13 - 14 vol%) contained in the combustion exhaust gas of coal-fired boilers. In contrast, the combustion exhaust gas from boilers using oil as fuel has a carbon dioxide concentration of less than 10 vol%, and the combustion exhaust gas from boilers or gas turbines using natural gas as fuel has a carbon dioxide concentration of less than 6 vol% (usually 3 - 4 vol%). Compared with the combustion exhaust gas from coal-fired boilers, the carbon dioxide concentration is low, about one-half to one-fourth. This itself contributes to the reduction of carbon dioxide emissions. However, to recover carbon dioxide from such combustion exhaust gas with a low carbon dioxide concentration, it is necessary to process a large amount of combustion exhaust gas.

[0007] The carbon dioxide separation and recovery process using a fixed-bed reactor with a solid absorbent as disclosed in Non-Patent Documents 1 and 2 is an excellent method with low costs related to renewable energy itself. However, when attaching this to, for example, an existing thermal power generation (including gas turbine power generation and combined cycle power generation) plant using oil or natural gas as fuel, it is necessary to increase the space for installing the fixed-bed reactor to process a large amount of gas, or increase the flow rate of the combustion exhaust gas in the fixed-bed reactor. As a result, the operating cost per unit recovery amount of carbon dioxide increases. Furthermore, there may be cases where it is difficult to newly install a carbon dioxide separation and recovery plant of a scale necessary to process all the combustion exhaust gas due to lack of space. Also, there is a limit to increasing the flow rate of the combustion exhaust gas in the fixed-bed reactor. The present invention has been made in view of the above problems. That is, the present invention aims to solve the problem of providing a process capable of separating and recovering carbon dioxide from a large amount of combustion exhaust gas in a space-saving and energy-saving manner.

Means for Solving the Problems

[0008] A method for recovering carbon dioxide according to one aspect of the present invention includes an absorption step of passing combustion exhaust gas containing carbon dioxide through a radial flow type separation device provided with an absorbent to absorb carbon dioxide in the absorbent, and a release step of releasing carbon dioxide from the absorbent by passing steam through the separation device.

[0009] Further, a carbon dioxide recovery system according to another aspect of the present invention includes a radial flow type separation device provided with an absorbent, a first conduit for guiding combustion exhaust gas containing carbon dioxide to the separation device, and a second conduit for guiding steam to the separation device.

Advantages of the Invention

[0010] A process is provided that enables the separation and recovery of carbon dioxide from a large amount of combustion exhaust gas in a space-saving and energy-saving manner.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0012] The method according to the present invention is a method for separating and recovering carbon dioxide from a gas mixture containing carbon dioxide, particularly combustion exhaust gas under atmospheric pressure. The method according to the present invention is a space-saving and energy-saving method particularly suitable for separating and recovering carbon dioxide from combustion exhaust gas from a gas turbine in a gas turbine power generation plant or a combined cycle power generation plant using natural gas as fuel. With the method according to the present invention, for example, it has the feature that it is relatively easy to attach a plant for separating and recovering carbon dioxide from combustion exhaust gas to an existing power generation plant.

[0013] In the method according to the present invention, SA-VSA (steam-assisted vacuum swing adsorption) using an absorbent is utilized to separate and recover carbon dioxide from a gas mixture containing carbon dioxide, particularly combustion exhaust gas under atmospheric pressure. Conventionally, for recovering carbon dioxide from a gas mixture containing carbon dioxide (CO2 concentration is 10% by volume or more), an amine absorption method using, for example, an aqueous monoethanolamine solution as an absorption liquid is usually used. However, when recovering carbon dioxide from a gas mixture with a low carbon dioxide concentration (CO2 concentration is less than 10% by volume), for example, combustion exhaust gas from a gas turbine power plant or a combined cycle power plant using natural gas as fuel (CO2 concentration is less than 6% by volume), in particular, it is necessary to use an amine that binds carbon dioxide more strongly in the amine absorption method. For this reason, the cost required for heating during regeneration and the cost for replenishing and replacing the deteriorated amine increase. Therefore, as the absorbent, it is preferable to use a solid absorbent that has more excellent carbon dioxide absorption and desorption characteristics (particularly desorption characteristics) and has the advantage that it does not contain water, so it is not necessary to include the latent heat of vaporization of water in the heating energy during regeneration.

[0014] As such a solid absorbent, one prepared by supporting a polyamine compound on a granular inorganic porous carrier, for example, porous silica, can be preferably used. The granular porous silica can be obtained, for example, by adding a pore-expanding agent such as trimethylbenzene to an acetic acid acidic aqueous solution of a hydrophilic polymer (for example, P-123 of Sigma-Aldrich), mixing well, adding an aqueous sodium silicate solution, gently mixing at room temperature for 24 hours, further allowing to stand at 100 °C for 24 hours, filtering and washing the obtained solid matter, drying the obtained solid matter at 80 °C for 2 days, and granulating the obtained dried solid matter to a particle size of about 2 mm by calcining the powder obtained by calcining the dried solid matter in the atmosphere at 550 °C for 4 hours. The granular porous silica thus obtained is dispersed in, for example, methanol, and a suitable polyamine compound (for example, tetraethylenepentamine with protected functional groups) is added to this dispersion to impregnate the porous silica with the polyamine compound and then dried, whereby a granular porous silica supporting the polyamine compound can be obtained (see Non-Patent Document 1).

[0015] The separation and recovery of carbon dioxide by SA-VSA is carried out by alternately repeating an absorption step of absorbing and capturing carbon dioxide contained in the gas to be treated containing carbon dioxide by bringing the gas to be treated into contact with the absorbent under normal pressure, and a release step of releasing carbon dioxide by bringing the absorbent that has absorbed carbon dioxide into contact with low-temperature steam under reduced pressure. In SA-VSA, since the absorbent is placed under normal pressure in the absorption operation and under reduced pressure in the release operation, these operations are to be carried out in an airtight container. The gas-solid contact operation between the gas to be treated and the solid absorbent in the absorption step can be carried out in various forms such as a packed bed, a moving bed, and a fluidized bed. However, if it is desired that the concentration of carbon dioxide in the gas to be treated is low and the leakage of carbon dioxide into the treated gas is almost zero, a packed bed form with good contact efficiency and less channeling is preferred. On the other hand, in the gas-solid contact operation between the steam and the solid absorbent in the release step, since the flow rate of the steam is significantly smaller than the flow rate of the gas to be treated, the adoption of a moving bed or a fluidized bed is not possible, and the same packed bed form as in the absorption step is to be used.

[0016] The method according to the present invention is characterized in that it can treat a large amount of gas to be treated in the absorption step. When the space velocity GHSV of the gas to be treated in the absorption step is about 2,000 to 6,000 / h, in order to reduce the pressure loss related to the energy for boosting the pressure of the gas to be treated under atmospheric pressure with a blower or the like, the aspect ratio of the packed bed ([bed thickness] / [flow path cross-sectional area]) is suppressed to about 1,500 mm (the superficial velocity of the empty tower baseline is about 0.5 m / s on average) in order to suppress the layer thickness of the packed bed to about 1,500 mm (the superficial velocity of the empty tower baseline is about 0.5 m / s on average). 1 / 2) needs to be made quite small. However, if the flow channel cross-sectional area (= layer cross-sectional area) is increased to reduce the aspect ratio of the packed bed, the installation area (footprint) may become too large in a normal type of packed bed where the gas to be treated flows vertically. If there is enough space to install the carbon dioxide separation and recovery device from the beginning within a vast site, there is no problem. However, in the case of attaching a carbon dioxide separation and recovery device to an existing power plant later, there is often no room for the installation area. In such a case, if the packed bed is of a type where the gas passes horizontally (horizontal flow type), the flow channel cross-sectional area can be expanded vertically without expanding the installation area. Representative examples of such horizontal flow type packed bed forms are the leaf (flat plate) type (parallel flow type) and the tube type (radial flow type). The leaf (flat plate) type means that the packed bed is arranged in a hollow flat plate shape standing upright, and the fluid passes through the packed bed horizontally and in parallel. On the other hand, the radial flow type means that the packed bed is arranged in a standing circular tube shape, and the fluid passes through the packed bed horizontally and radially from the inside to the outside or from the outside to the inside of the circular tube. In either form, a plurality of packed beds can be arranged in one large airtight container, or one packed bed can be arranged in one airtight container. When one packed bed is arranged in one airtight container, it is most compact and takes up the least space to accommodate the radial flow type packed bed in a cylindrical airtight container. Also, the radial flow type has the advantage that since the packed bed is arranged in a tubular shape, it has a higher pressure resistance than the leaf (flat plate) type where the packed bed is arranged in a flat plate shape. In the present invention, from the viewpoint of strength when processing a large amount of gas to be treated at high speed by vacuum suction, the packed bed of the absorbent is preferably of the radial flow type. Note that the layer thickness of the packed bed is preferably as thin as possible. Specifically, from the viewpoint of suppressing pressure loss, it is preferably 3,000 mm or less.

[0017] On the other hand, in the release step according to the present invention, it is characterized in that the steam consumption can be suppressed to a low level. To release carbon dioxide from the absorbent that has absorbed carbon dioxide in the absorption step, the inside of the container housing the packed bed is evacuated to reduce the total pressure to less than 1 atm, and at the same time, steam is introduced and passed through the packed bed. By using a horizontal flow type packed bed, pressure loss can be suppressed and carbon dioxide can be absorbed. However, if uneven flow occurs in the airtight container, the pressure loss increases. Therefore, it is desirable to suppress uneven flow as much as possible. In the release process, from the viewpoint of reducing energy costs, it is preferable to minimize the steam consumption as much as possible. However, if the volumetric flow rate of steam is reduced for this purpose, uneven flow is likely to occur in the airtight container. Therefore, from the viewpoint of increasing the volumetric flow rate to suppress uneven flow, it is necessary to introduce steam under reduced pressure. In SA-VSA, originally, the main operation in the release process is depressurization by evacuation, and the introduction of steam is merely an auxiliary operation. The technical significance of introducing steam is that when carbon dioxide absorbed by the absorbent is released under reduced pressure, the latent heat of release is taken away from the absorbent, and this is compensated by the sensible heat and latent heat of condensation of the steam. That is, introducing steam in the release process is considered to have the effect of promoting release by preventing excessive cooling of the absorbent and maintaining a constant temperature when carbon dioxide is suddenly released from the absorbent under reduced pressure in VSA (Vacuum Swing Adsorption), and by maintaining continuous release. In particular, when using a horizontal flow type packed bed, due to the structure of the equipment, it is difficult to indirectly heat the packed bed in the airtight container, and direct heating using the sensible heat of steam is important. From the above viewpoints, it is preferable that at least a part of the introduced steam condenses in the packed bed and gives its latent heat of condensation to the packed bed. In the release process, the atmosphere in which the packed bed is placed is depressurized from atmospheric pressure. If the temperature of the introduced steam is 100°C or higher, the steam will not condense until the temperature in the packed bed drops below the dew point (less than 100°C) under the reduced pressure conditions. Therefore, it is preferable that the temperature of the introduced steam is less than 100°C. This "steam at less than 100°C" is referred to as "low-temperature steam". The total pressure in the release process is preferably reduced to 10 - 45 kPaA (the last "A" means absolute pressure) by a steam total pressure control mechanism in practical use, and it is more preferable that the temperature of the introduced steam is less than 80°C. The mass of carbon dioxide contained in the steam after passing through the separation device is tCO2 Let the mass of water contained in the steam after passing through the separation device be t H2O When this is the case, from the perspective of improving the efficiency of operating energy, the discharge process is such that t H2O / t CO2 For example, it is preferable to include controlling the amount of steam supplied to the separation device by a steam amount control mechanism so that it is within the range of 0.5 or more and 1.8 or less.

[0018] FIG. 1 is a schematic cross-sectional view showing an example of a radial flow type separation device preferably used in the method according to the present invention. FIG. 1(a) schematically shows a vertical cross-section of the device, and FIG. 1(b) schematically shows a horizontal cross-section of the device along the line A-A' in FIG. 1(a). The separation device 1 in FIG. 1 forms a cylindrical packed bed 13 filled with an absorbent between a cylindrical inner pipe 11 and a cylindrical outer basket 12 coaxially arranged inside a vertical cylindrical outer shell container 10, and the absorbent extends in the vertical direction (referred to as the first direction). Inside the packed bed 13 (inside the cylindrical inner pipe 11), there is a columnar central space 14 serving as a first flow path, and outside the packed bed 13 (outside the cylindrical outer basket 12), there is a tubular peripheral space 15 serving as a second flow path between the inner wall of the outer shell container 10. The central space (first flow path) 14 and the peripheral space (second flow path) 15 each have a first gas inlet / outlet 16 and a second gas inlet / outlet 17 at their lower ends, and the cylindrical inner pipe 11 and the cylindrical outer basket 12 are each configured to be gas-permeable. By configuring the cylindrical inner pipe 11 and the cylindrical outer basket 12 so that the columnar central space (first flow path) 14 and the tubular peripheral space (second flow path) 15 sandwich the packed bed 13, a gas flow path is formed from the first gas inlet / outlet 16 through the central space (first flow path) 14, the packed bed 13, and the peripheral space (second flow path) 15 to the second gas inlet / outlet 17, or from the second gas inlet / outlet 17 through the peripheral space (second flow path) 15, the packed bed 13, and the central space (first flow path) 14 to the first gas inlet / outlet 16. The gas to be treated may flow in from the first gas inlet / outlet 16 and flow out from the second gas inlet 17, or vice versa. Also, although details will be described later, when releasing carbon dioxide absorbed by the absorbent (i.e., regenerating the absorbent), a method of introducing steam in the same direction as the flow of the gas to be treated (cocurrent regeneration method) can be adopted, or a method of introducing steam in the opposite direction to the flow of the gas to be treated (countercurrent regeneration method) can be adopted. Then, depending on the direction of the gas to be treated in the absorption step and the direction of the steam in the release step, conduits (not shown) for guiding combustion exhaust gas for guiding carbon dioxide are switchably connected to the first gas inlet / outlet 16 and the second gas inlet / outlet 17.Further, the second conduit is connected to a steam amount control mechanism (not shown) that controls the amount of steam supplied to the separation device.

[0019] When introducing the gas to be treated from the first gas inlet / outlet 16, the gas to be treated introduced from the first conduit flows upward through the central space (first flow path) 14, and during this process, it gradually penetrates into the packing layer 13 while absorbing carbon dioxide and passes through to the peripheral space (second flow path) 15 side. After that, it flows downward through the peripheral space (second flow path) 15, and the treated gas is discharged from the second gas inlet 17. Here, in the first flow path (central space), as the gas to be treated gradually escapes, the upward velocity decreases, but the pressure is substantially constant from the bottom to the top (since there is no part causing pressure loss in the middle). Similarly, in the second flow path (peripheral space), as the treated gas gradually adds in, the downward velocity increases, but the pressure is substantially constant from the top to the bottom. Therefore, the pressure difference between the first flow path (central space) 14 and the second flow path (peripheral space) 15 is substantially uniform from the bottom to the top of the packing layer 13, and the flow rate passing through the packing layer 13 is substantially uniform from the bottom to the top. When introducing the gas to be treated from the second gas inlet / outlet 17, although the direction of gas flow is reversed, it can be said that the gas flow velocity and pressure are the same as when introducing the gas to be treated from the first gas inlet / outlet 16. However, when the difference in the cross-sectional area (flow path cross-sectional area) of the cross-section perpendicular to the first direction between the first flow path (central space) 14 and the second flow path (peripheral space) 15 becomes large, the flow velocity rising in the first flow path (central space) 14 and the flow velocity falling in the second flow path (peripheral space) 15 will be significantly different. Therefore, even if the pressure difference between both sides of the packing layer is uniform from the bottom to the top, it is considered that uneven flow is likely to occur. For this reason, it is preferable that the ratio of the horizontal cross-sectional area of the central space (first flow path) 14 to the cross-sectional area of the cross-section perpendicular to the first direction of the peripheral space (second flow path) 15 is approximately 1, specifically 0.8 or more and 1.25 or less.

[0020] In the apparatus of FIG. 1, both the first gas inlet / outlet 16 and the second gas inlet / outlet 17 are provided at the bottom of the first flow path 14 and the second flow path 15, respectively. However, both of them may be provided at the top, or one may be provided at the top and the other at the bottom. When both are provided at the top, it is only different in that the pipes for the gas to be treated and the pipes for the treated gas come to the top instead of the bottom. Regarding the gas flow in the apparatus, it can be said that it is the same as when both are provided at the bottom. However, when one is provided at the top and the other at the bottom, the direction of the flow in the first flow path and the direction of the flow in the second flow path become the same, and the way of the vertical change in the flow velocity of the first flow path rising or falling is opposite to the way of the vertical change in the flow velocity of the second flow path rising or falling (the flow velocity gradually decreases on the inflow side and gradually increases on the outflow side). Therefore, even if the horizontal cross-sectional area of the central space and the horizontal cross-sectional area of the peripheral space are made substantially equal, the flow velocities on both sides of the packed bed cannot be made substantially equal over the entire height from the bottom to the top. Thus, regardless of the ratio of the horizontal cross-sectional area of the central space to the horizontal cross-sectional area of the peripheral space, it is considered that uneven flow is likely to occur. From the above, it is preferable that the first gas inlet / outlet and the second gas inlet / outlet are provided at the ends on the same side of the first and second flow paths.

[0021] In the absorption process, the absorbent that has absorbed carbon dioxide is regenerated by releasing the absorbed carbon dioxide in the subsequent release process, and is further used for carbon dioxide absorption again in the next absorption process. In the release process, the entire space inside the outer shell container 1 including the packed bed and the first and second flow paths is depressurized by a vacuum pump as a steam total pressure control mechanism. The vacuum pump is connected to either the first or the second gas inlet / outlet for evacuation. On the other hand, steam is introduced from the gas inlet / outlet to which the vacuum pump is not connected and flows through the same flow path as the flow path of the gas to be treated. At this time, as described above, if the flow direction of the gas to be treated in the absorption process is the same as the flow direction of the steam in the release process, it is co-current release (co-current regeneration), and if it is the opposite, it is counter-current release (counter-current regeneration). Since counter-current regeneration is superior to co-current regeneration in terms of release efficiency and the purity of the released carbon dioxide, it is preferable to perform counter-current regeneration in the release process. Note that the mass flow rate of the steam in the release process is much smaller than the mass flow rate of the gas to be treated in the absorption process. However, in the release process, since the total pressure including the steam inside the outer shell container is preferably reduced to 10 to 45 kPaA (about 0.1 to 0.45 atm), the volume flow rate is not so small, and it is considered that the same flow velocity change as in the absorption process is shown in the first and second flow paths. However, in the release process, it is considered that uneven flow is more likely to occur than in the absorption process because the total pressure is low. Therefore, it can be said that, more so than in the absorption process, the first gas inlet / outlet and the second gas inlet / outlet are preferably provided at the ends on the same side of the first and second flow paths. That is, in the present invention, it is preferable that the separation device has a gas introduction part for introducing combustion exhaust gas or steam and a gas discharge part for discharging combustion exhaust gas or steam at the ends on the same side of the first flow path and the second flow path extending in the first direction.

[0022] FIG. 2 is a conceptual diagram showing an example of separating and recovering carbon dioxide from the combustion exhaust gas of a power plant by applying the method according to the present invention. The combustion exhaust gas from the power plant is discharged into the atmosphere from the chimney, but at least a part of it is extracted from the flue and induced into a carbon dioxide separation and recovery plant (PCC plant) 200 that implements the method according to the present invention by a flue gas blower (booster) 100. After the carbon dioxide contained in the combustion exhaust gas is separated and recovered, it is configured to be returned to the flue. The steam for regeneration used in the carbon dioxide separation and recovery plant (PCC plant) 200 may be supplied from the steam supply facility of the thermal power plant provided in the power plant in order to suppress construction costs and operating costs. The recovered carbon dioxide is 2 compressed by a compressor 300 and stored or used for useful purposes.

[0023] FIG. 3 is a diagram schematically explaining a configuration example of a carbon dioxide separation and recovery apparatus (PCC plant) 200 that implements the method according to the present invention, including a separation apparatus 1 (1A, 1B) at the center of the PCC plant 200 and facilities attached thereto. In FIG. 3, two separation apparatuses 1A and 1B are used, and they are programmed so that when one is in the absorption step, the other is in the release step, and the absorption step and the release step are alternately repeated to continuously perform the carbon dioxide separation and recovery operation. However, it can also be configured to use three or more separation apparatuses, program them so that some of the towers are in the release step and the other towers are in the absorption step, and rotate and use these towers to continuously perform the carbon dioxide separation and recovery operation. The combustion exhaust gas drawn from the flue is pressurized by a flue gas blower (booster) 100 and enters the scrubber unit 400. After being dust-removed with washing water there, it is introduced into the separation apparatus 1A in the absorption step, and the gas after carbon dioxide is recovered by passing through the packing layer of the absorbent is configured to be returned to the flue. In FIG. 3, the flow of the combustion exhaust gas in the separation tower 1A is omitted, and it does not specifically show that the combustion exhaust gas flows in from the top of the separation apparatus and out from the bottom. On the other hand, low-temperature and low-pressure steam is introduced into the separation apparatus 1B in the release step. When the inside of the separation apparatus 1B is depressurized, carbon dioxide is released. After the released carbon dioxide is withdrawn from the separation apparatus together with the steam, the steam accompanying the flow of carbon dioxide is separated as drain, and the remaining carbon dioxide is recovered. At least a part of the low-temperature and low-pressure steam introduced into the separation apparatus 1B may be supplied from a thermal power plant.

Explanation of Signs

[0024] 1 Separation apparatus 1A First separation apparatus 1B Second separation apparatus 10 Outer shell container 11 Inner cylindrical pipe 12 Outer cylindrical basket 13 Packing layer 14 Central space (first flow path) 15 Peripheral space (second flow path) 16 First gas inlet / outlet 17 Second gas inlet / outlet 100 Flue gas blower (booster) 200 Carbon dioxide separation and recovery plant 300 CO 2 Compressor 400 Scrubber unit

Claims

1. In a radial flow type separation device provided with an absorbent, an absorption step of passing combustion exhaust gas containing carbon dioxide through the absorbent to absorb carbon dioxide in the absorbent, and a release step of releasing carbon dioxide from the absorbent by passing steam through the separation device A method for recovering carbon dioxide, comprising:

2. The method for recovering carbon dioxide according to claim 1, wherein the concentration of carbon dioxide in the combustion exhaust gas is 10% by volume or less.

3. The separation device has a first flow path through which the combustion exhaust gas or the steam before passing through the absorbent flows, and a second flow path through which the combustion exhaust gas or the steam after passing through the absorbent flows, both the first flow path and the second flow path extend in a first direction, The separation device has a gas introduction part for introducing the combustion exhaust gas or the steam and a gas discharge part for discharging the combustion exhaust gas or the steam at the same side ends of the first flow path and the second flow path extending in the first direction. The method for recovering carbon dioxide according to claim 1.

4. The separation device has a first flow path through which the combustion exhaust gas or the steam before passing through the absorbent flows, and a second flow path through which the combustion exhaust gas or the steam after passing through the absorbent flows, both the first flow path and the second flow path extend in a first direction, The ratio of the cross-sectional area of the second flow path in the direction perpendicular to the first direction to the cross-sectional area of the first flow path in the direction perpendicular to the first direction is 0.8 or more and 1.25 or less. The method for recovering carbon dioxide according to claim 1.

5. Let the mass of carbon dioxide contained in the steam after passing through the separation device be \(t\). ＣＯ２ Let the mass of water contained in the steam after passing through the separation device be \(t\). Ｈ２Ｏ When this is done, The discharging step is controlled such that t Ｈ２Ｏ / t ＣＯ２ is in the range of 0.5 or more and 1.8 or less. The method for recovering carbon dioxide according to claim 1 includes this control.

6. The release step includes controlling so that the total pressure of the steam supplied to the separation device is 10 kPaA or more and 45 kPaA or less. The method for recovering carbon dioxide according to claim 1.

7. A carbon dioxide recovery system including a radial flow type separation device provided with an absorbent, a first conduit for guiding combustion exhaust gas containing carbon dioxide to the separation device, and a second conduit for guiding steam to the separation device.

8. The flow path through which the combustion exhaust gas guided from the first conduit or the steam guided from the second conduit flows in the separation device extends in a first direction. The carbon dioxide recovery system according to claim 7, wherein the separation device has a gas introduction part for introducing the combustion exhaust gas or the steam and a gas discharge part for discharging the combustion exhaust gas or the steam at ends on the same side with respect to the first direction.

9. The separation device has a first flow path through which the combustion exhaust gas or the steam flows before passing through the absorbent, and a second flow path through which the combustion exhaust gas or the steam flows after passing through the absorbent. Both the first flow path and the second flow path extend in the first direction. The ratio of the cross-sectional area of the second flow path in a direction perpendicular to the first direction to the cross-sectional area of the first flow path in a direction perpendicular to the first direction is 0.8 or more and 1.25 or less. The carbon dioxide recovery system according to claim 7.

10. The carbon dioxide recovery system according to claim 7, further comprising a steam amount control mechanism for controlling the amount of steam supplied to the separation device.

11. The carbon dioxide recovery system according to claim 7, further comprising a steam total pressure control mechanism for controlling the total pressure of the steam supplied to the separation device.

Images