Method for recovering carbon dioxide from a gaseous carbon dioxide source

Abstract

To provide a method for recovering carbon dioxide in a gaseous carbon dioxide supply source which is a method for recovering the carbon dioxide from a low-pressure gaseous carbon dioxide supply source, and which can reduce a site area for facilities.SOLUTION: A method for recovering carbon dioxide in a gaseous carbon dioxide supply source comprises: an absorption step of absorbing carbon dioxide 5 from a gaseous carbon dioxide supply source 1 to obtain a carbon dioxide-rich absorption liquid 3; a regeneration step of heating the carbon dioxide-rich absorption liquid to desorb the carbon dioxide and obtain a carbon dioxide-lean absorption liquid 4, and recovering the desorbed carbon dioxide; a carbon dioxide-lean absorption liquid transfer step of transferring the carbon dioxide-lean absorption liquid in a carbon dioxide-lean absorption liquid storage tank 14b for a regeneration tower to a carbon dioxide-lean absorption liquid storage tank 14a for an absorption tower; and a carbon dioxide-rich absorption liquid transfer step of transferring the carbon dioxide-rich absorption liquid in a carbon dioxide-rich absorption liquid storage tank 13a for the absorption tower to a carbon dioxide-rich absorption liquid storage tank 13b for the regeneration tower.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a capture process for capturing carbon dioxide from a low pressure gaseous carbon dioxide source. [Background technology]

[0002] In response to the recent demand for reducing carbon dioxide emissions in response to global warming, there are methods for separating and recovering carbon dioxide from gaseous carbon dioxide supply sources emitted from equipment such as blast furnaces, lime kilns, heating furnaces, reactors, and boilers at power plants, steel mills, cement plants, refineries, and chemical plants, or from carbon dioxide in the atmosphere.

[0003] A representative method for recovering carbon dioxide in a gaseous carbon dioxide supply source includes an absorption step in which the gaseous carbon dioxide supply source is brought into contact with an absorbent consisting of an aqueous solution of an alkanol (amine compound) to cause absorption and reaction, thereby obtaining a carbon dioxide-rich absorption liquid in which carbon dioxide has reacted with the absorbent, and a regeneration step in which carbon dioxide is obtained by desorbing carbon dioxide from the carbon dioxide-rich absorption liquid obtained by carrying out the absorption step, and at the same time, the absorbent is regenerated.

[0004] As a method for recovering carbon dioxide in such a gaseous carbon dioxide supply source, Cited Document 1 describes a carbon dioxide recovery apparatus equipped with a cooling tower, an absorption tower, and a regenerator, which includes a step of supplying the gaseous carbon dioxide supply source to the cooling tower to cool it, a step of supplying the cooled gaseous carbon dioxide supply source to the absorption tower and bringing it into contact with a regenerated absorbing liquid supplied from the regenerator to absorb the carbon dioxide in the gaseous carbon dioxide supply source into the regenerated absorbing liquid, and a step of heating the carbon dioxide absorbing solution stored in the bottom of the absorption tower by heat exchange with the regenerated absorbing liquid supplied from the regenerator, and then supplying it to the regenerator, The present invention discloses a method for utilizing exhaust heat in a carbon dioxide recovery process, which is a continuous absorption method, characterized in that in a carbon dioxide recovery process in a gaseous carbon dioxide source, which includes a step of heating the bottom of the regeneration tower with saturated steam to separate the carbon dioxide absorption solution into carbon dioxide and regenerated absorption liquid, and discharging and recovering the carbon dioxide from the regeneration tower, hot water return water is heated by either one or a combination of two or more of the following: heat exchange with the regenerated absorption liquid after the heat exchange, heat exchange with carbon dioxide exhausted from the regeneration tower, and heat exchange with saturated water after heating the bottom of the regeneration tower, to obtain hot water.

[0005] In addition, Cited Document 2 describes a method for producing a CO2-containing gaseous carbon dioxide supply source in a CO2 absorption tower, the method comprising: providing a gaseous carbon dioxide supply source inlet for introducing a gaseous carbon dioxide supply source into the CO2 absorption tower; a gaseous carbon dioxide supply source outlet for discharging the gaseous carbon dioxide supply source from the CO2 absorption tower; an absorbing liquid inlet for introducing an amine compound-containing absorbing liquid into the CO2 absorption tower; an absorbing liquid outlet for discharging the amine compound-containing absorbing liquid from the CO2 absorption tower; and a packing that is a static mixer having a spiral porous blade. a first step of reacting and absorbing CO2 contained in a gaseous carbon dioxide supply source into an amine compound-containing absorbing liquid, the first step being such that the gaseous carbon dioxide supply source flows from a gaseous carbon dioxide supply source inlet to a gaseous carbon dioxide supply source outlet and the amine compound-containing absorbing liquid flows from an absorbing liquid inlet to an absorbing liquid outlet; and a second step of recovering a part of the amine compound-containing absorbing liquid from the CO2 absorption tower at a position downstream of the packing in the flow direction of the amine compound-containing absorbing liquid from the absorbing liquid inlet toward the absorbing liquid outlet, cooling the recovered amine compound-containing absorbing liquid, and a second step of supplying an amine compound-containing absorption liquid to a CO2 absorption tower at a position upstream of the packing in a flow direction of the amine compound-containing absorption liquid, and a third step of supplying a liquid to the CO2 absorption tower at a position downstream of the packing in a flow direction of the gaseous carbon dioxide source from a gaseous carbon dioxide source inlet toward a gaseous carbon dioxide source outlet to bring the liquid into contact with the gaseous carbon dioxide source, recovering the liquid that has come into contact with the gaseous carbon dioxide source, and cooling the recovered liquid; A first step of contacting the amine compound-containing absorbing liquid containing CO2 with steam in a countercurrent manner at the packing to strip CO2 from the amine compound-containing absorbing liquid, thereby regenerating the amine compound-containing absorbing liquid and recovering CO2, in a CO2 stripping tower provided with an absorbing liquid inlet for introducing an amine compound-containing absorbing liquid into the CO2 stripping tower, an absorbing liquid outlet for discharging the amine compound-containing absorbing liquid from the CO2 stripping tower, a steam inlet for introducing steam into the CO2 stripping tower, a CO2 outlet for discharging CO2 from the CO2 stripping tower, and a packing which is a static mixer having a spiral porous blade,The present invention discloses a carbon dioxide recovery process which is a continuous absorption method and which simultaneously performs an amine compound-containing absorbing liquid regeneration method and a carbon dioxide recovery process which is a continuous absorption method, the process comprising at least one step selected from the group consisting of a first step in which an amine compound-containing absorbing liquid flows from an absorbing liquid inlet to an absorbing liquid outlet and steam flows from a steam inlet to a CO2 outlet, a second step in which a part of the amine compound-containing absorbing liquid is recovered from the CO2 stripper tower at a position downstream of the packing in the flow direction of the amine compound-containing absorbing liquid from the absorbing liquid inlet toward the absorbing liquid outlet, heating the recovered amine compound-containing absorbing liquid, and supplying the heated amine compound-containing absorbing liquid to the CO2 stripper tower at a position downstream of the packing in the flow direction of the amine compound-containing absorbing liquid, and a third step in which a part of the amine compound-containing absorbing liquid is recovered from the CO2 stripper tower at a position downstream of the packing in the flow direction of the amine compound-containing absorbing liquid, heating the recovered amine compound-containing absorbing liquid to generate steam, and supplying the steam to the CO2 stripper tower from the steam inlet. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2003-225537 A [Patent Document 2] International Publication No. 2018 / 190104 DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0007] In the above Patent Documents 1 and 2, a carbon dioxide absorption step and a carbon dioxide desorption step are simultaneously and continuously carried out to recover carbon dioxide from a gaseous carbon dioxide supply source.

[0008] However, depending on the operation of the factory, for example, in the case of a facility that operates only during the day and is shut down at night, the gaseous carbon dioxide supply source is not discharged at night, so the carbon dioxide recovery device must be shut down, resulting in low operation rates. Alternatively, there are cases where it is desired to gradually proceed with the recovery of carbon dioxide from the gaseous carbon dioxide supply source of the factory and increase the amount of processing depending on the situation. In addition, since the gaseous carbon dioxide supply source is low pressure, large equipment will be lined up as the recovery equipment, and it is expected that the factory site will already be filled and there will be no room to install all of the equipment for the recovery equipment.

[0009] Therefore, an object of the present invention is to provide a method for recovering carbon dioxide from a low-pressure gaseous carbon dioxide supply source, which can reduce the site area of ​​the equipment. [Means for solving the problem]

[0010] The above problems are solved by the present invention described below. That is, the present invention (1) provides an absorption tower with a gaseous carbon dioxide supply source containing carbon dioxide and a carbon dioxide lean absorbing liquid in a carbon dioxide lean absorbing liquid storage tank for the absorption tower, and in the absorption tower, the gaseous carbon dioxide supply source is brought into contact with the carbon dioxide lean absorbing liquid to absorb the carbon dioxide in the gaseous carbon dioxide supply source into the carbon dioxide lean absorbing liquid to obtain a carbon dioxide rich absorbing liquid, and then the carbon dioxide rich absorbing liquid is sent to the carbon dioxide rich absorbing liquid storage tank for the absorption tower and stored therein; A regeneration step of supplying the carbon dioxide-rich absorbing liquid in the carbon dioxide-rich absorbing liquid storage tank for the regeneration tower to the regeneration tower, heating the carbon dioxide-rich absorbing liquid in the regeneration tower to desorb carbon dioxide from the carbon dioxide-rich absorbing liquid to obtain the carbon dioxide-lean absorbing liquid, and then recovering the desorbed carbon dioxide and sending the carbon dioxide-lean absorbing liquid to the carbon dioxide-lean absorbing liquid storage tank for the regeneration tower to store it; a carbon dioxide lean absorbing liquid transfer step of transferring the carbon dioxide lean absorbing liquid in the carbon dioxide lean absorbing liquid storage tank for the regeneration tower to the carbon dioxide lean absorbing liquid storage tank for the absorption tower; A carbon dioxide-rich absorbing liquid transfer step of transferring the carbon dioxide-rich absorbing liquid in the carbon dioxide-rich absorbing liquid storage tank for the absorption tower to the carbon dioxide-rich absorbing liquid storage tank for the regeneration tower; having The carbon dioxide lean absorbing liquid and the carbon dioxide rich absorbing liquid are used as absorbents. Alkanolamines The absorbing liquid contains The carbon dioxide concentration in the gaseous carbon dioxide supply source is 2.0 to 25.0% by volume, and the pressure of the gaseous carbon dioxide supply source is 115 ~130kPa, The present invention provides a method for recovering carbon dioxide in a gaseous carbon dioxide source, comprising:

[0012] In addition, the present invention ( 2 In the absorption step, the gaseous carbon dioxide supply source is caused to flow in an upward direction and the carbon dioxide lean absorbing liquid is caused to flow in a downward direction in the absorption tower, thereby contacting the carbon dioxide lean absorbing liquid with the gaseous carbon dioxide supply source in a countercurrent manner (1 )of A method for recovering carbon dioxide in a gaseous carbon dioxide source is provided.

[0013] In addition, the present invention ( 3 ) is characterized in that, in the regeneration step, the carbon dioxide lean absorbing liquid accumulated at the bottom of the regeneration tower is heated to generate an upward flow of vapor of the absorbing liquid at a saturation temperature in the regeneration tower, thereby heating the inside of the regeneration tower, and the carbon dioxide rich absorbing liquid is heated by flowing the carbon dioxide rich absorbing liquid in a downward flow. Or (2) The present invention provides a method for recovering carbon dioxide in a gaseous carbon dioxide source.

[0014] In addition, the present invention ( 4 ) is characterized in that the absorption rate of carbon dioxide in the absorption step is 25 to 75% (1) to ( 3) A method for recovering carbon dioxide from a gaseous carbon dioxide source.

[0015] In addition, the present invention ( 5 ) is characterized in that the absorption step, the regeneration step, the carbon dioxide lean absorbing solution transfer step, and the carbon dioxide rich absorbing solution transfer step are carried out by an incoming / outgoing management control system (1) to ( 4 ) A method for recovering carbon dioxide from a gaseous carbon dioxide source. Effect of the Invention

[0016] According to the present invention, there can be provided a method for recovering carbon dioxide from a low-pressure gaseous carbon dioxide supply source, which can reduce the site area of ​​the equipment. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic flow diagram of a carbon dioxide capture system for carrying out an embodiment of the method for capturing carbon dioxide in a gaseous carbon dioxide source of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The method for recovering carbon dioxide in a gaseous carbon dioxide supply source of the present invention will be described with reference to Fig. 1. Fig. 1 is a schematic flow diagram of a carbon dioxide recovery system for carrying out an embodiment of the method for recovering carbon dioxide in a gaseous carbon dioxide supply source of the present invention.

[0019] 1, the carbon dioxide recovery system 10 comprises an absorption tower site 31, a regeneration tower site 32, a carbon dioxide-lean absorbing solution transfer means 33, and a carbon dioxide-rich absorbing solution transfer means 34. At the absorption tower site 31, an absorption step is carried out to absorb carbon dioxide in the gaseous carbon dioxide supply source 1, and at the regeneration tower site 32, a regeneration step is carried out to desorb and recover carbon dioxide from the carbon dioxide-rich absorbing solution.

[0020] The absorption tower site 31 includes an absorption tower 11 in which an absorption process is performed and in which a contact mechanism 19a is installed; A carbon dioxide-rich absorbing liquid storage tank 13a for an absorption tower for storing the carbon dioxide-rich absorbing liquid 3 obtained by performing the absorption step; In the absorption step, a carbon dioxide lean absorption liquid storage tank 14a for the absorption tower for storing the carbon dioxide lean absorption liquid 4 to be supplied to the absorption tower 11; a gaseous carbon dioxide supply source supply pipe 27 connected to a lower portion of the absorption tower 11 for supplying the gaseous carbon dioxide supply source 1 to the absorption tower 11; a top gas discharge pipe 28 connected to the top of the absorption tower 11 for discharging the treated exhaust gas 2 from the absorption tower 11; A carbon dioxide lean absorbing liquid supply pipe 21 having one end connected to the carbon dioxide lean absorbing liquid storage tank 14a for the absorber and the other end connected to the upper part of the absorber 11; a carbon dioxide-rich absorbing liquid discharge pipe 22 having one end connected to the bottom of the absorption tower 11 and the other end connected to the carbon dioxide-rich absorbing liquid storage tank 13a for the absorption tower; It consists of:

[0021] The regeneration tower site 32 includes a regeneration tower 12 in which a regeneration process is performed and in which a contact mechanism 19b is installed; A carbon dioxide lean absorbent storage tank 14b for a regeneration tower for storing the carbon dioxide lean absorbent 4 obtained by performing the regeneration step; In the regeneration step, a carbon dioxide-rich absorbing liquid storage tank 13b for the regeneration tower for storing the carbon dioxide-rich absorbing liquid 3 to be supplied to the regeneration tower 12; A carbon dioxide-rich absorbing liquid supply pipe 23, one end of which is connected to the carbon dioxide-rich absorbing liquid storage tank 13b for the regeneration tower and the other end of which is connected to the upper part of the regeneration tower 12; A carbon dioxide lean absorbent discharge pipe 24, one end of which is connected to the bottom of the regeneration tower 12 and the other end of which is connected to the carbon dioxide lean absorbent storage tank 14b for the regeneration tower; a heat exchanger 15 provided at an intersection of the carbon dioxide-rich absorbing liquid supply pipe 23 and the carbon dioxide-lean absorbing liquid discharge pipe 24 for performing heat exchange between the liquid in the carbon dioxide-rich absorbing liquid supply pipe 23 and the liquid in the carbon dioxide-lean absorbing liquid discharge pipe 24; A cooler 20 attached to the carbon dioxide lean absorption liquid discharge pipe 24; A tower bottom heating branch pipe 25 that branches off from the vicinity of the tower bottom of the carbon dioxide lean absorption liquid discharge pipe 24 and connects to the bottom of the tower; A reboiler 16 attached to the tower bottom heating branch pipe 25; a carbon dioxide exhaust pipe 29 connected to the top of the regeneration tower 12 for exhausting the carbon dioxide 5 from the regeneration tower 12; A carbon dioxide cooler 17 attached to the carbon dioxide exhaust pipe 29; A gas-liquid separator 18 is provided downstream of the carbon dioxide cooler 17 in the carbon dioxide exhaust pipe 29; A cooling liquid return pipe 26, one end of which is connected to the liquid recovery section of the gas-liquid separator 18 and the other end of which is connected to the top of the tower; It consists of:

[0022] The carbon dioxide lean absorbing liquid transfer means 33 is a means for transferring the carbon dioxide lean absorbing liquid 4 in the carbon dioxide lean absorbing liquid storage tank 14b for the regeneration tower at the regeneration tower site 32 to the carbon dioxide lean absorbing liquid storage tank 14a for the absorption tower at the absorption tower site 31. In addition, the carbon dioxide rich absorbing liquid transfer means 34 is a means for transferring the carbon dioxide rich absorbing liquid 3 in the carbon dioxide rich absorbing liquid storage tank 13a for the absorption tower at the absorption tower site 31 to the carbon dioxide rich absorbing liquid storage tank 13b for the regeneration tower at the regeneration tower site 32.

[0023] Although not shown, a liquid pump for sending the liquid is attached to the carbon dioxide lean absorbing liquid supply pipe 21, the carbon dioxide rich absorbing liquid discharge pipe 22, the carbon dioxide rich absorbing liquid supply pipe 23, the carbon dioxide lean absorbing liquid discharge pipe 24, the tower bottom heating branch pipe 25, and the cooling liquid return pipe 26. In addition, when the process is managed by the incoming / outgoing management control system, an electronic computer for incoming / outgoing management control is installed, and the electronic computer has an operation program, a process management program, and a control program for various devices. The incoming / outgoing management control system is constructed so that the electronic computer is connected to one or more absorption tower sites 31 and one or more regeneration tower sites 32 by a communication line such as optical fiber, wireless, or dedicated communication line, and the absorption process, the regeneration process, the carbon dioxide lean absorbing liquid transfer process, and the carbon dioxide rich absorbing liquid transfer process can be managed by the electronic computer.

[0024] Next, an embodiment of the method for recovering carbon dioxide in a gaseous carbon dioxide supply source of the present invention, which is carried out by a carbon dioxide recovery system 10, will be described with reference to Fig. 1. Note that the carbon dioxide lean absorbing solution 4 and the carbon dioxide rich absorbing solution 3 used below include aqueous solutions of an absorbent containing an absorbent.

[0025] First, an example of the absorption step performed at the absorption tower site 31 will be described. While the gaseous carbon dioxide supply source 1 is supplied to the lower part of the absorption tower 11 from the gaseous carbon dioxide supply source supply pipe 27, the carbon dioxide lean absorbing liquid 4 in the carbon dioxide lean absorbing liquid storage tank 14a for the absorption tower is supplied to the upper part of the absorption tower 11 through the carbon dioxide lean absorbing liquid supply pipe 21, and the gaseous carbon dioxide supply source 1 flows upward in the absorption tower 11 and the carbon dioxide lean absorbing liquid 4 flows downward in the absorption tower 11, so that the gaseous carbon dioxide supply source 1 and the carbon dioxide lean absorbing liquid 4 are brought into contact with each other in a countercurrent manner in the absorption tower 11. At this time, the carbon dioxide in the gaseous carbon dioxide supply source 1 reacts with the absorbent in the carbon dioxide lean absorbing liquid 4, and carbon dioxide is reactively absorbed in the carbon dioxide lean absorbing liquid 4, producing a carbon dioxide rich absorbing liquid 3, and the carbon dioxide rich absorbing liquid 3 accumulates at the bottom of the absorption tower 11. Next, the carbon dioxide-rich absorbing liquid 3 accumulated at the bottom of the absorption tower 11 is sent to the carbon dioxide-rich absorbing liquid storage tank 13a for the absorption tower through the carbon dioxide-rich absorbing liquid discharge pipe 22 and stored therein. In this manner, the absorption step is carried out at the absorption tower site 31.

[0026] Next, an example of the regeneration step performed at the regeneration tower site 32 will be described. In the regeneration tower 12, a part of the carbon dioxide lean absorbing liquid 4 accumulated at the tower bottom of the regeneration tower 12 is extracted, the steam 45 is sent to the reboiler 16, the carbon dioxide lean absorbing liquid 4 is heated in the reboiler 16, and the heated carbon dioxide lean absorbing liquid 4 is returned to the lower part of the regeneration tower 12, thereby heating the carbon dioxide lean absorbing liquid 4 accumulated at the tower bottom, making the absorbing liquid at the tower bottom an absorbing liquid at a saturation temperature, and an upward flow of steam of the absorbing liquid at the saturation temperature is generated in the regeneration tower 12, thereby heating the inside of the regeneration tower 12. Then, a part of the carbon dioxide lean absorbing liquid 4 accumulated at the bottom of the regeneration tower 12 is extracted, the carbon dioxide lean absorbing liquid 4 is heated by the reboiler 16, and the heated carbon dioxide lean absorbing liquid 4 is returned to the lower part of the regeneration tower 12. By repeating this process, an upward flow of the vapor of the absorbing liquid at the saturation temperature is generated in the regeneration tower 12, while the carbon dioxide rich absorbing liquid 3 in the carbon dioxide rich absorbing liquid storage tank 13b for the regeneration tower is supplied to the upper part of the regeneration tower 12 via the carbon dioxide rich absorbing liquid supply pipe 23, and the carbon dioxide rich absorbing liquid 3 is caused to flow downward, thereby heating the carbon dioxide rich absorbing liquid 3 in the regeneration tower 12. At this time, carbon dioxide is desorbed from the carbon dioxide rich absorbing liquid 3, the carbon dioxide lean absorbing liquid 4 is generated, and the carbon dioxide lean absorbing liquid 4 accumulates at the bottom of the regeneration tower 11. Next, the desorbed carbon dioxide 5 is recovered through the carbon dioxide discharge pipe 29, and a part of the carbon dioxide lean absorbing solution 4 accumulated at the bottom of the regenerator 12 is sent to the carbon dioxide lean absorbing solution storage tank 14b for the regenerator through the carbon dioxide lean absorbing solution 24 and stored therein. Since the carbon dioxide 5 discharged from the regenerator 12 contains water vapor and a small amount of absorbent, the carbon dioxide 5, water vapor and absorbent discharged from the regenerator 12 are cooled by the carbon dioxide cooler 17, and the condensed water and absorbent are separated by the gas-liquid separator 18 to recover the carbon dioxide 5 after gas-liquid separation. The water and absorbent separated by the gas-liquid separator 18 are returned to the top of the tower through the cooling liquid return pipe 26. In this way, the regeneration process is performed at the regenerator site 32.

[0027] Then, when the absorption step is performed at the absorption tower site 31, the carbon dioxide lean absorbing liquid 4 in the carbon dioxide lean absorbing liquid storage tank 14a for the absorption tower decreases, so the carbon dioxide lean absorbing liquid transfer means 33 transfers the carbon dioxide lean absorbing liquid 4 in the carbon dioxide lean absorbing liquid storage tank 14b for the regeneration tower at the regeneration tower site 32 to the carbon dioxide lean absorbing liquid storage tank 14a for the absorption tower to replenish it. Also, when the regeneration step is performed at the regeneration tower site 32, the carbon dioxide rich absorbing liquid 3 in the carbon dioxide rich absorbing liquid storage tank 13b for the regeneration tower decreases, so the carbon dioxide rich absorbing liquid transfer means 34 transfers the carbon dioxide rich absorbing liquid 3 in the carbon dioxide rich absorbing liquid storage tank 13a for the absorption tower at the absorption tower site 31 to the carbon dioxide rich absorbing liquid storage tank 13b for the regeneration tower to replenish it.

[0028] In the present invention, the absorption step at the absorption tower site 31 and the regeneration step at the regeneration tower site 32 can be carried out independently. In other words, the absorption step and the regeneration step may be carried out in parallel, or there may be a time period during which only the absorption step or only the regeneration step is carried out.

[0029] In this manner, the carbon dioxide recovery system 10 performs an absorption process, a regeneration process, a carbon dioxide lean absorption liquid transfer process, and a carbon dioxide rich absorption liquid transfer process, thereby carrying out an example of the method for recovering carbon dioxide in a gaseous carbon dioxide supply source of the present invention.

[0030] The method for recovering carbon dioxide in a gaseous carbon dioxide supply source of the present invention includes an absorption step of supplying a gaseous carbon dioxide supply source containing carbon dioxide and a carbon dioxide lean absorbing liquid in a carbon dioxide lean absorbing liquid storage tank for an absorption tower to an absorption tower, contacting the gaseous carbon dioxide supply source with the carbon dioxide lean absorbing liquid in the absorption tower to absorb the carbon dioxide in the gaseous carbon dioxide supply source into the carbon dioxide lean absorbing liquid to obtain a carbon dioxide rich absorbing liquid, and then transporting the carbon dioxide rich absorbing liquid to the carbon dioxide rich absorbing liquid storage tank for the absorption tower and storing it therein; A regeneration step of supplying the carbon dioxide-rich absorbing liquid in the carbon dioxide-rich absorbing liquid storage tank for the regeneration tower to the regeneration tower, heating the carbon dioxide-rich absorbing liquid in the regeneration tower to desorb carbon dioxide from the carbon dioxide-rich absorbing liquid to obtain the carbon dioxide-lean absorbing liquid, and then recovering the desorbed carbon dioxide and sending the carbon dioxide-lean absorbing liquid to the carbon dioxide-lean absorbing liquid storage tank for the regeneration tower to store it; a carbon dioxide lean absorbing liquid transfer step of transferring the carbon dioxide lean absorbing liquid in the carbon dioxide lean absorbing liquid storage tank for the regeneration tower to the carbon dioxide lean absorbing liquid storage tank for the absorption tower; A carbon dioxide-rich absorbing liquid transfer step of transferring the carbon dioxide-rich absorbing liquid in the carbon dioxide-rich absorbing liquid storage tank for the absorption tower to the carbon dioxide-rich absorbing liquid storage tank for the regeneration tower; having The carbon dioxide lean absorption liquid and the carbon dioxide rich absorption liquid are absorption liquids containing an absorbent; the carbon dioxide concentration in the gaseous carbon dioxide supply source is 50.0% by volume or less, and the pressure of the gaseous carbon dioxide supply source is 90 to 300 kPa; The present invention relates to a method for recovering carbon dioxide in a gaseous carbon dioxide source, the method comprising the steps of:

[0031] The method for recovering carbon dioxide in a gaseous carbon dioxide supply source of the present invention includes an absorption step, a regeneration step, a carbon dioxide-lean absorbing solution transfer step, and a carbon dioxide-rich absorbing solution transfer step. In the method for recovering carbon dioxide in a gaseous carbon dioxide supply source of the present invention, the absorption step and the regeneration step may be performed in the same time period, or there may be a time period in which only the absorption step is performed or a time period in which only the regeneration step is performed.

[0032] The absorption step in the method for recovering carbon dioxide in a gaseous carbon dioxide supply source of the present invention is a step of supplying a gaseous carbon dioxide supply source and a carbon dioxide-lean absorbing liquid to an absorption tower, contacting the gaseous carbon dioxide supply source with the carbon dioxide-lean absorbing liquid in the absorption tower to reactively absorb the carbon dioxide in the gaseous carbon dioxide supply source into the carbon dioxide-lean absorbing liquid to obtain a carbon dioxide-rich absorbing liquid, and then sending the obtained carbon dioxide-rich absorbing liquid to a carbon dioxide-rich absorbing liquid storage tank for the absorption tower for storage.

[0033] The gaseous carbon dioxide supply source for the absorption step is a gas containing carbon dioxide. Examples of the gaseous carbon dioxide supply source include exhaust gases discharged from equipment such as blast furnaces, lime kilns, heating furnaces, reactors, and boilers in power plants, steel mills, cement plants, oil refineries, and chemical plants. Another example of the gaseous carbon dioxide supply source is the atmosphere.

[0034] The carbon dioxide concentration in the gaseous carbon dioxide supply source supplied to the absorption tower is 50.0% by volume or less, preferably 2.0 to 25.0% by volume, and particularly preferably 2.0 to 20.0% by volume. The pressure of the gaseous carbon dioxide supply source supplied to the absorption tower is 90 to 300 kPa, and preferably 90 to 130 kPa.

[0035] In the method for recovering carbon dioxide from a gaseous carbon dioxide supply source of the present invention, the carbon dioxide lean absorption liquid and the carbon dioxide rich absorption liquid are both absorption liquids containing an absorbent. The carbon dioxide lean absorption liquid is an absorption liquid from which carbon dioxide has been desorbed in the regeneration process and from which the amount of carbon dioxide absorbed is small. On the other hand, the carbon dioxide rich absorption liquid is an absorption liquid from which carbon dioxide has been absorbed in the absorption process and from which the amount of carbon dioxide absorbed is large.

[0036] The absorbing liquid is not particularly limited as long as it can absorb carbon dioxide from a gaseous carbon dioxide supply source at 90 to 300 kPa, preferably 90 to 130 kPa.

[0037] The absorbent contained in the absorbing liquid includes all amine compounds, such as alkanolamines such as monoethanolamine, diethanolamine, diisopropanolamine, dimethyldiethanolamine, and triethanolamine, amino alcohols such as aminodiethylene glycol, hindered amine compounds, piperazine compounds, piperidine compounds, polyalkylpolyamine compounds, amino acid compounds, amino acid salt compounds, and derivatives thereof, and organic amine compounds. The absorbent may be one type or a combination of two or more types of the above in any mixing ratio. The absorbent is preferably one that has a high absorption rate, a large amount of carbon dioxide absorption, is thermally stable, and requires little energy during regeneration.

[0038] The carbon dioxide cyclic loading amount of the absorbent contained in the absorbing liquid is preferably 0.85 moles (CO2) / L (solution) or more, and particularly preferably 2.0 to 7.0 moles (CO2) / L (solution). When the carbon dioxide cyclic loading amount of the absorbent is within the above range, the amount of circulation of the absorbing liquid is reduced, and the required area required for installing the equipment can be reduced. In the present invention, the carbon dioxide cyclic loading amount of the absorbent is calculated by the following formula. Carbon dioxide cyclic loading of absorbent (moles (CO2) / L (solution)) = carbon dioxide absorption amount at 40°C and 20 kPa (moles (CO2) / L (solution)) - carbon dioxide absorption amount at 120°C and 100 kPa (moles (CO2) / L (solution))

[0039] The carbon dioxide absorption rate of the absorbent contained in the absorbing solution is preferably 0.09 mole (CO2) / L (solution) per minute or more, and particularly preferably 0.10 to 0.20 mole (CO2) / L (solution) per minute. When the carbon dioxide absorption rate of the absorbent is within the above range, the reactive absorption of carbon dioxide in the absorption step is promoted, and the height of the absorption tower can be reduced.

[0040] The carbon dioxide desorption energy of the absorbent contained in the absorbing solution is preferably 90 kJ / mol (CO2) or less, particularly preferably 30 to 75 kJ / mol (CO2). When the carbon dioxide desorption energy of the absorbent is within the above range, carbon dioxide desorption in the regeneration step occurs easily, and the required energy can be kept low.

[0041] The absorbing liquid may be, for example, an aqueous solution of an absorbent. The absorbing liquid is preferably an aqueous solution of an alkanolamine, and more preferably an aqueous solution of an alkanolamine having a concentration of 15 to 45% by mass.

[0042] The absorption tower is a vessel in which the absorption step is carried out. The absorption tower is not particularly limited as long as it can carry out the absorption step. The size of the absorption tower is appropriately selected depending on the discharge amount of the gaseous carbon dioxide supply source, the pressure of the gaseous carbon dioxide supply source, the temperature of the absorption step, the allowable pressure loss, the recovery rate of carbon dioxide, etc.

[0043] In the absorption tower, a contact mechanism is preferably installed to increase the absorption rate of carbon dioxide from the gaseous carbon dioxide supply source. Examples of the contact mechanism include packing, trays, sprays, fluidized packing, liquid film cross-flow contactor, high-speed swirling flow packing, mechanical force packing, etc., or combinations thereof, and are not particularly limited as long as they have an effective contact area and mass transfer rate.

[0044] In the absorption step, the method of contacting the gaseous carbon dioxide supply source with the carbon dioxide-lean absorbing liquid in the absorption tower is not particularly limited. In the absorption step, it is preferable to supply the gaseous carbon dioxide supply source from the lower part of the tower and flow it in an upward flow, and supply the carbon dioxide-lean absorbing liquid from the upper part of the tower and flow it in a downward flow, thereby contacting the gaseous carbon dioxide supply source with the carbon dioxide-lean absorbing liquid in a countercurrent manner.

[0045] The reaction conditions in the absorption step are not particularly limited, but the temperature of the gaseous carbon dioxide supply source is preferably 30 to 65°C, and the temperature of the carbon dioxide lean absorption solution is preferably 30 to 50°C.

[0046] In the absorption step, the carbon dioxide absorption rate is usually set to 80 to 90% depending on the carbon dioxide utilization plan.

[0047] When the carbon dioxide concentration in the gaseous carbon dioxide supply source is 50.0% by volume or less, preferably 2.0 to 25.0% by volume, and particularly preferably 2.0 to 20.0% by volume, and the pressure of the gaseous carbon dioxide supply source is 90 to 300 kPa, preferably 90 to 130 kPa, if such a gaseous carbon dioxide supply source is used and the carbon dioxide absorption rate is set too high, in order to satisfy sufficient contact under a low carbon dioxide partial pressure, the height of the absorption tower must be made very large, or in some cases, a compression device or the like must be installed to increase the pressure inside the absorption tower to a carbon dioxide partial pressure of about 500 kPa or more.

[0048] On the other hand, when the absorption step of the method for recovering carbon dioxide from a gaseous carbon dioxide source of the present invention is performed using a gaseous carbon dioxide source having a carbon dioxide concentration of 50.0% by volume or less, preferably 2.0 to 25.0% by volume, and particularly preferably 2.0 to 20.0% by volume, and a pressure of the gaseous carbon dioxide source of 90 to 300 kPa, preferably 90 to 130 kPa, if the absorption rate of carbon dioxide is preferably 25 to 95%, and particularly preferably 30 to 75%, the height of the absorption tower can be significantly reduced, and the pressure in the absorption tower does not need to be increased. Therefore, in the absorption step of the method for recovering carbon dioxide from a gaseous carbon dioxide source of the present invention, by setting the absorption rate of carbon dioxide to preferably 25 to 95%, and particularly preferably 30 to 75%, the cost for implementing the method for recovering carbon dioxide from a gaseous carbon dioxide source of the present invention and the construction cost of a carbon dioxide recovery device can be reduced. The absorption rate of carbon dioxide is a value calculated by the following formula. Carbon dioxide absorption rate (%) = ((carbon dioxide flow rate in gaseous carbon dioxide source (Nm3 / hour)-Carbon dioxide flow rate in treated exhaust gas (Nm 3 / hour) / carbon dioxide flow rate in gaseous carbon dioxide source (Nm 3 / hour))×100

[0049] In the absorption step, the gaseous carbon dioxide supply source after contact with the carbon dioxide lean absorption liquid, i.e., the treated gas, is discharged from the absorption tower and released into the atmosphere. In the absorption step, in order to remove the absorbent mixed in the treated gas and to prevent odor, it is preferable to provide a water washing facility on the upper part of the absorption tower and pass the treated gas through the water washing facility.

[0050] In the absorption step, when the carbon dioxide in the gaseous carbon dioxide supply source comes into contact with the carbon dioxide-lean absorption liquid in the absorption tower, causing the liquid temperature to rise due to reaction heat or the like and decreasing the absorption efficiency, it is preferable to install a cooler that extracts the carbon dioxide-lean absorption liquid from the middle of the absorption tower and cools it to room temperature.

[0051] The regeneration step in the method for recovering carbon dioxide in a gaseous carbon dioxide supply source of the present invention is a step of supplying a carbon dioxide-rich absorbing liquid to a regeneration tower, heating the carbon dioxide-rich absorbing liquid in the regeneration tower to desorb carbon dioxide from the carbon dioxide-rich absorbing liquid to obtain a carbon dioxide-lean absorbing liquid, and then recovering the desorbed carbon dioxide and sending the carbon dioxide-lean absorbing liquid to a carbon dioxide-lean absorbing liquid storage tank for the regeneration tower for storage.

[0052] The regeneration tower is a vessel in which the regeneration step is carried out. There are no particular limitations on the regeneration tower as long as it can carry out the regeneration step. The size of the regeneration tower is appropriately selected depending on the temperature, pressure, and flow rate of the carbon dioxide-rich absorbing liquid in the regeneration step.

[0053] In order to increase the regeneration efficiency of the carbon dioxide-rich absorbing liquid, it is preferable that a contact mechanism is installed in the regeneration tower. Examples of the contact mechanism include packing, trays, sprays, fluidized packing, liquid film cross-flow contact, high-speed swirling flow packing, mechanical force packing, etc., or combinations thereof, and are not particularly limited as long as they have an effective contact area and mass transfer amount.

[0054] In the regeneration step, an example of a method for heating the carbon dioxide-rich absorbing liquid in the regeneration tower is to heat the carbon dioxide-lean absorbing liquid accumulated at the bottom of the regeneration tower, generate an upward flow of vapor of the absorbing liquid at the saturation temperature in the regeneration tower, heat the inside of the regeneration tower, and heat the carbon dioxide-rich absorbing liquid by flowing the carbon dioxide-rich absorbing liquid in a downward direction.

[0055] As a method for heating the carbon dioxide lean absorption liquid accumulated at the bottom of the regeneration tower, for example, a method can be given in which a portion of the carbon dioxide lean absorption liquid accumulated at the bottom of the regeneration tower is extracted, the extracted carbon dioxide lean absorption liquid is heated, and then returned to the bottom of the tower.

[0056] In addition, other methods for heating the carbon dioxide-rich absorbing liquid in the regeneration tower in the regeneration step include a method in which the carbon dioxide-rich absorbing liquid in the regeneration tower is heated using heat from a gaseous carbon dioxide supply source, heat generated when compressing the recovered carbon dioxide, low-pressure steam using high-temperature condensed water after use of a turbine in a factory, or the like as a heat source.

[0057] In the regeneration step, it is preferable to heat the carbon dioxide-rich absorbing solution in the regeneration tower, and recover the carbon dioxide desorbed from the carbon dioxide-rich absorbing solution from the tower top. Since the carbon dioxide discharged from the regeneration tower contains a small amount of absorbent and / or water vapor, the absorbent and / or water vapor are condensed by cooling, and the condensed absorbent and / or water vapor are separated in a gas-liquid separator to obtain high-purity carbon dioxide. In addition, the condensed absorbent and / or water vapor are returned to the regeneration tower.

[0058] In the regeneration step, the temperature in the tower is not particularly limited as long as it is a temperature at which carbon dioxide is desorbed from the carbon dioxide-rich absorbing solution. For example, when the absorbing solution contains 30% by mass of monoethanolamine as an absorbent, in the regeneration step, it is preferable to control the heating temperature of the bottom of the tower so that the outlet temperature of the top of the tower is 100 to 105° C. In the regeneration step, the temperature of the carbon dioxide-lean absorbing solution accumulated in the bottom of the tower is preferably the saturation temperature of the absorbing solution.

[0059] In the method for recovering carbon dioxide in a gaseous carbon dioxide supply source of the present invention, the absorption step may be performed in one absorption tower, or in two or more absorption towers. In addition, in the method for recovering carbon dioxide in a gaseous carbon dioxide supply source of the present invention, when the absorption step is performed using two or more absorption towers, the absorption step may be performed in two or more absorption towers installed in the same factory, or the absorption step may be performed in each absorption tower installed in two or more different factories. For example, (i) two or more absorption towers can be installed in the same factory, carbon dioxide lean absorption liquid can be supplied to each absorption tower from the same carbon dioxide lean absorption liquid storage tank for the absorption tower, the absorption step can be performed, and the carbon dioxide rich absorption liquid can be stored in the same carbon dioxide rich absorption liquid storage tank for the absorption tower. In addition, (ii) absorption towers can be installed in two or more different factories, and in each factory, carbon dioxide lean absorption liquid can be supplied to each absorption tower from the carbon dioxide lean absorption liquid storage tank for the absorption tower of each factory, the absorption step can be performed, and the carbon dioxide rich absorption liquid can be stored in the carbon dioxide rich absorption liquid storage tank for the absorption tower of each factory.

[0060] In the method for recovering carbon dioxide in a gaseous carbon dioxide supply source of the present invention, the regeneration step may be performed in one regeneration tower, or in two or more regeneration towers. In addition, in the method for recovering carbon dioxide in a gaseous carbon dioxide supply source of the present invention, when the regeneration step is performed using two or more regeneration towers, the regeneration step may be performed in two or more regeneration towers installed in the same factory, or the regeneration step may be performed in each regeneration tower installed in two or more different factories. For example, (i) two or more regeneration towers can be installed in the same factory, a carbon dioxide-rich absorbing liquid can be supplied to each regeneration tower from the same carbon dioxide-rich absorbing liquid storage tank for the regeneration tower, a regeneration step can be performed, and the carbon dioxide-lean absorbing liquid can be stored in the same carbon dioxide-lean absorbing liquid storage tank for the regeneration tower. In addition, (ii) a regeneration tower can be installed in each of two or more different factories, and in each factory, a carbon dioxide-rich absorbing liquid can be supplied to each regeneration tower from the carbon dioxide-rich absorbing liquid storage tank for the regeneration tower of each factory, a regeneration step can be performed, and the carbon dioxide-lean absorbing liquid can be stored in the carbon dioxide-lean absorbing liquid storage tank for the regeneration tower of each factory.

[0061] The carbon dioxide lean absorbing liquid transfer step is a step of transferring the carbon dioxide lean absorbing liquid in the carbon dioxide lean absorbing liquid storage tank for the regeneration tower to the carbon dioxide lean absorbing liquid storage tank for the absorption tower. In the method for recovering carbon dioxide in a gaseous carbon dioxide supply source of the present invention, when the absorption step is performed in a factory where the absorption tower is installed, the carbon dioxide lean absorbing liquid in the carbon dioxide lean absorbing liquid storage tank for the absorption tower decreases, so it is necessary to replenish the carbon dioxide lean absorbing liquid. Therefore, in the carbon dioxide lean absorbing liquid transfer step, the carbon dioxide lean absorbing liquid generated and stored in the regeneration tower is transferred from the carbon dioxide lean absorbing liquid storage tank for the regeneration tower to the carbon dioxide lean absorbing liquid storage tank for the absorption tower in the factory where the absorption tower is installed.

[0062] In the carbon dioxide lean absorption liquid transfer step, the method for transferring the carbon dioxide lean absorption liquid in the carbon dioxide lean absorption liquid storage tank for the regeneration tower to the carbon dioxide lean absorption liquid storage tank for the absorption tower is not particularly limited, and examples thereof include a method of transporting by tank truck, a method of transporting by pipeline, a method of transporting by ship, and the like.

[0063] The carbon dioxide-rich absorbing liquid transfer step is a step of transferring the carbon dioxide-rich absorbing liquid in the carbon dioxide-rich absorbing liquid storage tank for the absorption tower to the carbon dioxide-rich absorbing liquid storage tank for the regeneration tower. In the method for recovering carbon dioxide in a gaseous carbon dioxide supply source of the present invention, when the regeneration step is performed in a factory where the regeneration tower is installed, the carbon dioxide-rich absorbing liquid in the carbon dioxide-rich absorbing liquid storage tank for the regeneration tower decreases, so it is necessary to replenish the carbon dioxide-rich absorbing liquid. Therefore, in the carbon dioxide-rich absorbing liquid transfer step, the carbon dioxide-rich absorbing liquid generated and stored in the absorption tower is transferred from the carbon dioxide-rich absorbing liquid storage tank for the absorption tower to the carbon dioxide-rich absorbing liquid storage tank for the regeneration tower in the factory where the regeneration tower is installed.

[0064] In the carbon dioxide-rich absorbing liquid transfer step, the method for transferring the carbon dioxide-rich absorbing liquid in the carbon dioxide-rich absorbing liquid storage tank for the absorption tower to the carbon dioxide-rich absorbing liquid storage tank for the regeneration tower is not particularly limited, and examples thereof include a method of transporting by tank truck, a method of transporting by pipeline, and a method of transporting by ship.

[0065] When the absorption process, the regeneration process, the carbon dioxide-lean absorption solution transfer process, and the carbon dioxide-rich absorption solution transfer process are controlled by the receipt-and-shipment management control system, an electronic computer for receipt-and-shipment management control is installed, and the electronic computer has an operation program, a process management program, and control programs for various devices. The electronic computer is connected to one or more absorption tower sites and one or more regeneration tower sites by communication lines such as optical fiber, wireless, and dedicated communication lines, and the receipt-and-shipment management control system is constructed so that the absorption process, the regeneration process, the carbon dioxide-lean absorption solution transfer process, and the carbon dioxide-rich absorption solution transfer process can be controlled by the electronic computer.

[0066] In the method for recovering carbon dioxide in a gaseous carbon dioxide supply source of the present invention, when the absorption step is performed in two or more different factories and the regeneration step is performed in two or more different factories, there are two or more carbon dioxide lean absorbing liquid storage tanks for the regeneration tower, two or more carbon dioxide lean absorbing liquid storage tanks for the absorption tower, two or more carbon dioxide rich absorbing liquid storage tanks for the absorption tower, and two or more carbon dioxide rich absorbing liquid storage tanks for the regeneration tower. However, which carbon dioxide lean absorbing liquid storage tank for the regeneration tower to which carbon dioxide lean absorbing liquid storage tank for the absorption tower, and which carbon dioxide rich absorbing liquid storage tank for the absorption tower to which carbon dioxide rich absorbing liquid storage tank for the regeneration tower to transfer are appropriately selected according to the production and consumption amounts of the carbon dioxide lean absorbing liquid or the carbon dioxide rich absorbing liquid at each factory.

[0067] Thus, in the method for recovering carbon dioxide from a gaseous carbon dioxide supply source of the present invention, since the factory where the absorption step is performed performs only the absorption step, the site area of ​​the equipment can be reduced. Also, in the method for recovering carbon dioxide from a gaseous carbon dioxide supply source of the present invention, the absorption step is performed in multiple factories, and the carbon dioxide-rich absorption liquid obtained therein can be concentrated in one or more factories performing the regeneration step, where the regeneration step is performed, so that economies of scale in the regeneration step can be easily obtained. For this reason, the method for recovering carbon dioxide from a gaseous carbon dioxide supply source of the present invention can reduce the cost of recovering carbon dioxide.

[0068] The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. EXAMPLES

[0069] Example 1 <Absorption process> At the absorption tower site of the carbon dioxide recovery system shown in Fig. 1, gaseous carbon dioxide supply source 1 having the carbon dioxide concentration shown in Table 1 was supplied from the bottom of the absorption tower, and carbon dioxide lean absorbing liquid (aqueous solution of 30 mass% monoethanolamine (MEA)) in a carbon dioxide lean absorbing liquid storage tank for the absorption tower was supplied from the top at the molar ratio ((total moles of the amount of absorbent (MEA solution) supplied / hour) / (total moles of the amount of gas supplied from gaseous carbon dioxide supply source 1 / hour)) shown in Table 1, at the temperature and pressure shown in Table 1, and an absorption process was performed for 8 hours. The results are shown in Table 1. In Table 1, the "total moles of absorbing solution 4 / total moles of CO2 supply source 1" refers to "(total moles of absorbing solution (MEA solution) supplied at the tower inlet per hour) / (total moles of gas in gaseous carbon dioxide supply source 1 supplied at the tower inlet per hour)."

[0070] <Regeneration process> At the regeneration tower site of the carbon dioxide recovery system shown in Figure 1, the carbon dioxide-rich absorbing liquid in the carbon dioxide-rich absorbing liquid storage tank for the regeneration tower was supplied to the top of the regeneration tower and heated to the saturation temperature. Next, while the carbon dioxide-lean absorbing liquid at the bottom of the tower was heated to the saturation temperature, the carbon dioxide-rich absorbing liquid in the carbon dioxide-rich absorbing liquid storage tank for the regeneration tower was supplied from the top of the tower, and the regeneration process was carried out for 8 hours at the temperature shown in Table 1. The results are shown in Table 1.

[0071] [Table 1] [Explanation of symbols]

[0072] 1. Gaseous carbon dioxide source 2. Process gas 3 Carbon dioxide rich absorbent 4. Carbon dioxide lean absorbent 5. Carbon Dioxide 10 Carbon dioxide capture system 11 Absorption tower 12 Regeneration Tower 13a Carbon dioxide-rich absorbent storage tank for absorption tower 13b Carbon dioxide-rich absorbent storage tank for regeneration tower 14a Carbon dioxide lean absorbent storage tank for absorption tower 14b Carbon dioxide lean absorbent storage tank for regeneration tower 15 Heat exchanger 16 Reboiler 17 Carbon dioxide cooler 18 Gas-liquid separator 19a, 19b Contact mechanism 20 Cooler 21 Carbon dioxide lean absorbent supply pipe 22 Carbon dioxide rich absorbent discharge pipe 23 Carbon dioxide lean absorbent supply pipe 24 Carbon dioxide rich absorbent discharge pipe 25 Tower bottom heating branch pipe 26 Coolant return pipe 27 Gaseous carbon dioxide supply pipe 28 Top gas discharge pipe 29 Carbon Dioxide Exhaust Pipe 31 Absorption Tower Site 32 Regeneration Tower Site 33 Carbon dioxide lean absorbing liquid transport means 34 Carbon dioxide rich absorbing liquid transport means 45 Water Vapor

Claims

1. an absorption step of supplying a gaseous carbon dioxide supply source containing carbon dioxide and a carbon dioxide lean absorbing liquid in a carbon dioxide lean absorbing liquid storage tank for the absorption tower to the absorption tower, contacting the gaseous carbon dioxide supply source with the carbon dioxide lean absorbing liquid in the absorption tower to absorb the carbon dioxide in the gaseous carbon dioxide supply source into the carbon dioxide lean absorbing liquid to obtain a carbon dioxide rich absorbing liquid, and then sending the carbon dioxide rich absorbing liquid to the carbon dioxide rich absorbing liquid storage tank for the absorption tower to store it; A regeneration step of supplying the carbon dioxide-rich absorbing liquid in the carbon dioxide-rich absorbing liquid storage tank for the regeneration tower to the regeneration tower, heating the carbon dioxide-rich absorbing liquid in the regeneration tower to desorb carbon dioxide from the carbon dioxide-rich absorbing liquid to obtain the carbon dioxide-lean absorbing liquid, and then recovering the desorbed carbon dioxide and sending the carbon dioxide-lean absorbing liquid to the carbon dioxide-lean absorbing liquid storage tank for the regeneration tower to store it; a carbon dioxide lean absorbing liquid transfer step of transferring the carbon dioxide lean absorbing liquid in the carbon dioxide lean absorbing liquid storage tank for the regeneration tower to the carbon dioxide lean absorbing liquid storage tank for the absorption tower; A carbon dioxide-rich absorbing liquid transfer step of transferring the carbon dioxide-rich absorbing liquid in the carbon dioxide-rich absorbing liquid storage tank for the absorption tower to the carbon dioxide-rich absorbing liquid storage tank for the regeneration tower; having the carbon dioxide lean absorption liquid and the carbon dioxide rich absorption liquid are absorption liquids containing alkanolamine as an absorbent; The carbon dioxide concentration in the gaseous carbon dioxide supply source is 2.0 to 25.0 volume %, and the pressure of the gaseous carbon dioxide supply source is 115 to 130 kPa; A method for recovering carbon dioxide in a gaseous carbon dioxide source, comprising:

2. 2. The method for recovering carbon dioxide in a gaseous carbon dioxide supply source according to claim 1, characterized in that, in the absorption step, the gaseous carbon dioxide supply source is caused to flow in an upward direction and the carbon dioxide-lean absorption liquid is caused to flow in a downward direction in the absorption tower, thereby contacting the carbon dioxide-lean absorption liquid with the gaseous carbon dioxide supply source in a countercurrent manner.

3. 3. The method for recovering carbon dioxide in a gaseous carbon dioxide supply source according to claim 1 or 2, characterized in that, in the regeneration step, the carbon dioxide-lean absorbing liquid accumulated at the bottom of the regeneration tower is heated to generate an upward flow of vapor of the absorbing liquid at a saturation temperature in the regeneration tower, thereby heating the inside of the regeneration tower, and the carbon dioxide-rich absorbing liquid is heated by flowing the carbon dioxide-rich absorbing liquid in a downward flow.

4. 4. The method for recovering carbon dioxide in a gaseous carbon dioxide supply source according to claim 1, wherein the absorption rate of carbon dioxide in the absorption step is 25 to 75%.

5. The method for recovering carbon dioxide in a gaseous carbon dioxide supply source according to any one of claims 1 to 4, characterized in that the absorption step, the regeneration step, the carbon dioxide lean absorption solution transfer step, and the carbon dioxide rich absorption solution transfer step are performed by an input / output management control system.

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