Method for recovering carbon dioxide from a gaseous carbon dioxide source

Abstract

To provide a method for recovering carbon dioxide which can recover the carbon dioxide by using the reduced number of reaction towers.SOLUTION: A method for recovering carbon dioxide comprises: an absorption step of supplying a gaseous carbon dioxide supply source 1 and a carbon dioxide-lean absorption liquid 4 to an absorption and regeneration tower 11 to bring the gaseous carbon dioxide supply source into contact with the carbon dioxide-lean absorption liquid in the absorption and regeneration tower, thereby allowing carbon dioxide 5 in the gaseous carbon dioxide supply source to be reactively absorbed by the carbon dioxide-lean absorption liquid to obtain a carbon dioxide-rich absorption liquid 3; and a regeneration step of supplying the carbon dioxide-rich absorption liquid to the absorption and regeneration tower to heat the carbon dioxide-rich absorption liquid in the absorption and regeneration tower, thereby desorbing the carbon dioxide from the carbon dioxide-rich absorption liquid to recover the carbon dioxide and obtain the carbon dioxide-lean absorption liquid comprising an amine compound. In the method, the absorption step and the regeneration step are alternately repeated.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, Reference 2 describes a gaseous carbon dioxide source as CO 2 A gaseous carbon dioxide supply source inlet for introducing into the absorption tower, and a gaseous carbon dioxide supply source 2 The gaseous carbon dioxide supply source outlet discharged from the absorption tower and the amine compound-containing absorption liquid are 2 The absorption liquid inlet is used to introduce the amine compound-containing absorption liquid into the absorption tower. 2 A CO2 absorbing apparatus having an absorption liquid outlet for discharging from an absorption tower and a static mixer having a spiral perforated vane as a packing. 2 In the absorption tower, CO 2 A gaseous carbon dioxide supply source containing the above-mentioned is contacted with an amine compound-containing absorption liquid in a countercurrent or parallel flow manner using a packing material to thereby obtain CO 2a first step of reacting and absorbing the amine compound-containing absorbing liquid, the first step being such that a 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; 2 A part of the amine compound-containing absorbing liquid is recovered from the absorption tower, the recovered amine compound-containing absorbing liquid is cooled, and the cooled amine compound-containing absorbing liquid is cooled at a position upstream of the packing in the flow direction of the amine compound-containing absorbing liquid to absorb CO 2 a second step of supplying the gaseous carbon dioxide source to the absorption tower, and a second step of supplying the gaseous carbon dioxide source to the absorption tower at a position downstream of the packing in a flow direction of the gaseous carbon dioxide source from the gaseous carbon dioxide source inlet toward the gaseous carbon dioxide source outlet. 2 a step of supplying a liquid to an absorption tower and contacting the liquid with a gaseous carbon dioxide source, a step of recovering the liquid that has come into contact with the gaseous carbon dioxide source, and a step of cooling the recovered liquid. 2 The absorption liquid inlet for introducing the amine compound-containing absorption liquid into the stripper tower is 2 The absorption liquid outlet from the stripper and the steam from the CO 2 The steam inlet for the stripping tower and the CO 2 CO 2 CO emitted from the stripper 2 A CO2 extractor having a discharge port and a packing that is a static mixer having a spiral perforated vane. 2 In the stripper tower, CO 2 The amine compound-containing absorbing solution is contacted with steam in a countercurrent manner in a packing to extract CO from the amine compound-containing absorbing solution. 2 This regenerates the amine compound-containing absorption liquid and releases CO 2 The first step of recovering CO comprises: an amine compound-containing absorbing solution flowing from an absorbing solution inlet to an absorbing solution outlet; and steam flowing from a steam inlet to a CO 2 The first step is to detect CO 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. 2A part of the amine compound-containing absorbing liquid is recovered from the stripper tower, the recovered amine compound-containing absorbing liquid is heated, and the heated amine compound-containing absorbing liquid is cooled to a position downstream of the packing in the flow direction of the amine compound-containing absorbing liquid to remove CO 2 A second step of supplying the amine compound-containing absorption liquid to a stripping column, and a second step of supplying the amine compound-containing absorption liquid to a stripping column at a position downstream of the packing in the flow direction of the amine compound-containing absorption liquid. 2 A part of the amine compound-containing absorbing solution is recovered from the stripping tower, the recovered amine compound-containing absorbing solution is heated to generate steam, and the steam is introduced into the steam inlet to CO 2 and a third step of supplying the amine compound-containing absorbing solution to a stripping tower. [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 carried out simultaneously and continuously 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) 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 to an absorption and regeneration tower, contacting the gaseous carbon dioxide supply source with the carbon dioxide lean absorbing liquid in the absorption and regeneration 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 storage therein; A regeneration step of supplying the carbon dioxide-rich absorbing liquid in the carbon dioxide-rich absorbing liquid storage tank to the absorption and regeneration tower, heating the carbon dioxide-rich absorbing liquid in the absorption and 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 storage; It consists of: The carbon dioxide lean absorbing liquid and the carbon dioxide rich absorbing liquid are used as absorbents. AlkanolaminesThe absorbing liquid contains Repeating the absorption step and the regeneration step alternately; 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 and regeneration 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 absorption and regeneration tower is heated to generate an upward flow of vapor of the absorbing liquid at a saturation temperature in the absorption and regeneration tower, thereby heating the inside of the absorption and regeneration tower, and the carbon dioxide rich absorbing liquid is heated by flowing the carbon dioxide rich absorbing liquid in a downward flow (1). 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 95% (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 and the regeneration step are repeated by an automatic 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 recovery apparatus for carrying out an embodiment of the method for recovering carbon dioxide in a gaseous carbon dioxide source of the present invention. [Diagram 2] FIG. 2 is a diagram showing an example of an absorption step performed using the carbon dioxide recovery device in FIG. [Diagram 3] FIG. 2 is a diagram showing an example of a mode of a temperature increasing operation of an absorption and regeneration tower before a regeneration step performed using the carbon dioxide recovery apparatus in FIG. [Figure 4] FIG. 2 is a diagram showing an example of a regeneration process performed using the carbon dioxide recovery device in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The method for recovering carbon dioxide from a gaseous carbon dioxide supply source of the present invention will be described with reference to Figs. 1 to 4. Fig. 1 is a schematic flow diagram of a carbon dioxide recovery apparatus for carrying out an embodiment of the method for recovering carbon dioxide from a gaseous carbon dioxide supply source of the present invention. Fig. 2 is a diagram showing an embodiment of an absorption step performed using the carbon dioxide recovery apparatus in Fig. 1. Fig. 3 is a diagram showing an embodiment of a temperature increase operation of an absorption and regeneration tower before a regeneration step performed using the carbon dioxide recovery apparatus in Fig. 1. Fig. 4 is a diagram showing an embodiment of a regeneration step performed using the carbon dioxide recovery apparatus in Fig. 1.

[0019] In FIG. 1, a carbon dioxide recovery device 10 includes: an absorption / regeneration tower 11 in which an absorption step and a regeneration step are alternately performed and in which a contact mechanism 12 is installed; A carbon dioxide-rich absorbing liquid storage tank 13 for storing the carbon dioxide-rich absorbing liquid 3 obtained by performing the absorption step; a carbon dioxide lean absorbing liquid storage tank 14 for storing the carbon dioxide lean absorbing liquid 4; a tower upper supply pipe 21 having one end connected to the carbon dioxide lean absorbent storage tank 14 and the other end connected to the upper part of the absorption and regeneration tower 11; An absorption liquid cooler 19 is attached to the upper part of the tower before the tower upper supply pipe 21; A tower bottom discharge pipe 22, one end of which is connected to the bottom of the absorption and regeneration tower 11 and the other end of which is connected to the carbon dioxide-rich absorption liquid storage tank 13; A branch pipe 23 for sending carbon dioxide lean absorbing liquid, which branches off from the tower bottom discharge pipe 22 and is connected to the carbon dioxide lean absorbing liquid storage tank 14; a carbon dioxide-rich absorbing liquid delivery pipe 24 having one end connected to the carbon dioxide-rich absorbing liquid storage tank 13 and the other end connected to the middle of the tower upper supply pipe 21; A tower bottom heating branch pipe 25 that branches off from the tower bottom discharge pipe 22 near the tower bottom and connects to the bottom of the tower; A reboiler 16 attached to the tower bottom heating branch pipe 25; a gaseous carbon dioxide supply source supply pipe 27 connected to the lower part of the absorption and regeneration tower 11 for supplying the gaseous carbon dioxide supply source 1 to the absorption and regeneration tower 11; a top gas discharge pipe 28 connected to the top of the absorption and regeneration tower 11 for discharging the treated flue gas 2 or carbon dioxide 5 from the absorption and regeneration tower 11; A carbon dioxide extraction pipe 29 branched off from the top gas discharge pipe 28 for recovering carbon dioxide 5; A carbon dioxide cooler 17 attached to the carbon dioxide extraction pipe 29; A gas-liquid separator 18 is provided downstream of the carbon dioxide cooler 17 of the carbon dioxide extraction 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; A connecting pipe 301 that branches off from the column bottom discharge pipe 22 and is connected to the middle of the column upper supply pipe 21; A bypass pipe 302 that branches off from the tower upper supply pipe 21 in a stage preceding the absorption liquid cooler 19 and is connected to the tower upper supply pipe 21 in a stage following the absorption liquid cooler 19; a heat exchanger 15 provided at an intersection of the tower bottom discharge pipe 22 and the tower upper supply pipe 21 for exchanging heat between the liquid in the tower bottom discharge pipe 22 and the liquid in the tower upper supply pipe 21; has.

[0020] In addition, the tower upper supply pipe 21 is located upstream of the position where the carbon dioxide-rich absorbing liquid delivery pipe 24 is connected, the tower upper supply pipe 21 is located downstream of the position where the carbon dioxide-rich absorbing liquid delivery pipe 24 is connected and upstream of the position where the connecting pipe 301 is connected, the tower upper supply pipe 21 is located downstream of the position where the connecting pipe 302 branches and upstream of the absorbing liquid cooler, the tower bottom discharge pipe 22 is located downstream of the position where the carbon dioxide-lean absorbing liquid delivery branch pipe 23 branches, The branch pipe 23 for sending the carbon dioxide-rich absorbing solution, the carbon dioxide-rich absorbing solution delivery pipe 24, the coolant return pipe 26, the gaseous carbon dioxide supply source supply pipe 27, and the column overhead gas discharge pipe 28 downstream of the position where the carbon dioxide discharge pipe 29 branches off, the carbon dioxide discharge pipe 29, the connecting pipe 301, and the bypass pipe 302 are respectively provided with valves 31, 41, 43, 32, 33, 34, 36, 37, 38, 39, 40, and 42.

[0021] Although not shown, liquid sending pumps for sending liquid are attached to the tower top supply pipe 21, the tower bottom discharge pipe 22, the carbon dioxide lean absorption liquid sending branch pipe 23, the carbon dioxide rich absorption liquid sending pipe 24, the tower bottom heating branch pipe 25, and the coolant return pipe 26. When the operation of the carbon dioxide recovery device 10 is controlled by an automatic control system, an electronic computer for automatic control is installed, and the electronic computer has an operation program and a control program for various devices, and is connected to valves, various sensors, pumps, etc. so as to be able to input signals from them and output signals to them.

[0022] 2 to 4, an embodiment of the method for recovering carbon dioxide in a gaseous carbon dioxide supply source according to the present invention, which is carried out by the carbon dioxide recovery device 10, will be described. As the carbon dioxide lean absorbing solution 4 and the carbon dioxide rich absorbing solution 3 used below, an aqueous solution of absorption containing an absorbent can be mentioned.

[0023] First, an example of the absorption step performed by the carbon dioxide recovery device 10 will be described with reference to FIG. With valve 31 open, valve 41 open, valve 32 open, valve 33 closed, valve 34 closed, valve 36 open, valve 37 open, valve 38 open, valve 39 closed, valve 40 closed, valve 42 closed, valve 43 open, and valve 44 closed, as shown by the bold lines in FIG. 2 , the gaseous carbon dioxide source 1 is supplied from the gaseous carbon dioxide source supply pipe 27 to the lower part of the absorption and regeneration tower 11, while the carbon dioxide lean absorbing liquid 4 in the carbon dioxide lean absorbing liquid storage tank 14 is supplied to the upper part of the absorption and regeneration tower 11 via the tower upper supply pipe 21, and the gaseous carbon dioxide source 1 is caused to flow upward in the absorption and regeneration tower 11 and the carbon dioxide lean absorbing liquid 4 is caused to flow downward, thereby causing the gaseous carbon dioxide source 1 and the carbon dioxide lean absorbing liquid 4 to come into contact with each other in a countercurrent manner in the absorption and regeneration 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, carbon dioxide is reactively absorbed into the carbon dioxide lean absorbing liquid 4 to produce a carbon dioxide rich absorbing liquid 3, and the carbon dioxide rich absorbing liquid 3 accumulates at the bottom of the absorption and regeneration tower 11. Next, the carbon dioxide rich absorbing liquid 3 accumulated at the bottom of the absorption and regeneration tower 11 is sent to the carbon dioxide rich absorbing liquid storage tank 13 via the tower bottom discharge pipe 22 and stored therein. In this manner, the absorption step is performed for a predetermined time using the carbon dioxide recovery device 10.

[0024] Next, the temperature raising operation of the absorption and regenerator before the regeneration step, which is performed by the carbon dioxide recovery device 10, will be described with reference to Fig. 3. In Fig. 3, first, valve 31 is opened, valve 41 is opened, valve 32 is opened, valve 33 is closed, valve 34 is closed, valve 36 is opened, valve 37 is closed, valve 38 is closed, valve 39 is opened, valve 40 is opened, valve 42 is opened, valve 43 is closed, and valve 44 is opened, and the carbon dioxide lean absorption liquid 4 in the carbon dioxide lean absorption liquid storage tank 14 is supplied to the upper part of the absorption and regenerator 11 through the upper part supply pipe 21, the bypass pipe 302, and the upper part supply pipe 21, as shown by the thick line in Fig. 3, while the carbon dioxide lean absorption liquid 4 is accumulated in the bottom of the tower through the tower bottom discharge pipe 22 and the tower bottom heating branch pipe 25, as shown by the thick line in Fig. 3. A part of the carbon dioxide lean absorbing liquid 4 that has accumulated in the bottom of the tower 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 absorption and regeneration tower 11. By repeating this process, the carbon dioxide lean absorbing liquid 4 that has accumulated in the bottom of the tower is heated, and at the same time, the heated carbon dioxide lean absorbing liquid 4 at the bottom of the tower is supplied to the upper part of the absorption and regeneration tower 11 via the tower bottom discharge pipe 22, the connecting pipe 301, the tower upper supply pipe 21, the bypass pipe 302, and the tower upper supply pipe 21. As a result, the carbon dioxide lean absorbing liquid 4 is heated, the absorbing liquid at the bottom of the tower becomes an absorbing liquid at a saturation temperature, an upward flow of the vapor of the absorbing liquid at the saturation temperature occurs, and heating inside the absorption and regeneration tower 11 is started.

[0025] Next, the replacement operation of the carbon dioxide-rich absorbing liquid 3 will be described. The valve 31 is closed, the valve 41 is opened, the valve 32 is closed, the valve 33 is opened, the valve 34 is opened, the valve 36 is opened, the valve 37 is closed, the valve 38 is closed, the valve 39 is opened, the valve 40 is closed, the valve 42 is opened, the valve 43 is closed, and the valve 44 is opened, and the carbon dioxide-rich absorbing liquid 3 in the carbon dioxide-rich absorbing liquid storage tank 13 is supplied to the upper part of the absorption and regeneration tower 11 through the carbon dioxide-rich absorbing liquid delivery pipe 24, the tower upper supply pipe 21, the bypass pipe 302, and the tower upper supply pipe 21. This completes the replacement of the carbon dioxide-lean absorbing liquid 4 with the carbon dioxide-rich absorbing liquid 3.

[0026] Next, the regeneration step performed by the carbon dioxide recovery apparatus 10 will be described with reference to Fig. 4. In Fig. 4, valve 31 is closed, valve 41 is opened, valve 32 is closed, valve 33 is opened, valve 34 is opened, valve 36 is opened, valve 37 is closed, valve 38 is closed, valve 39 is opened, valve 40 is closed, valve 42 is opened, valve 43 is closed, and valve 44 is opened, as shown by the bold lines in Fig. 4, the carbon dioxide lean absorption liquid 4 accumulated at the bottom of the absorption and regeneration tower 11 is partially extracted from the tower bottom heating branch pipe 25, heated by the reboiler 16, and the heated carbon dioxide lean absorption liquid 4 is returned to the tower bottom, and the carbon dioxide lean absorption liquid 4 accumulated at the bottom of the absorption and regeneration tower 11 is By heating the carbon-lean absorbing liquid 4, an upward flow of vapor of the absorbing liquid at the saturation temperature is generated, and while heating the inside of the absorption and regeneration tower 11, the carbon dioxide-rich absorbing liquid 3 in the carbon dioxide-rich absorbing liquid storage tank 13 is supplied to the upper part of the absorption and regeneration tower 11 via the carbon dioxide-rich absorbing liquid delivery pipe 34, the tower upper supply pipe 21, the bypass pipe 302, and the tower upper supply pipe 21, and the carbon dioxide-rich absorbing liquid 3 is caused to flow downward, thereby heating the carbon dioxide-rich absorbing liquid 3 in the absorption and regeneration tower 11. At this time, carbon dioxide is desorbed from the carbon dioxide-rich absorbing liquid 3, and the carbon dioxide-lean absorbing liquid 4 is generated, and the carbon dioxide-lean absorbing liquid 4 accumulates at the bottom of the absorption and regeneration tower 11. Next, the desorbed carbon dioxide 5 is recovered through the tower top gas discharge pipe 28 and the carbon dioxide extraction pipe 29, and a part of the carbon dioxide lean absorbing liquid 4 accumulated at the bottom of the absorption and regeneration tower 11 is sent to the carbon dioxide lean absorbing liquid storage tank 14 through the tower bottom discharge pipe 22 and the carbon dioxide lean absorbing liquid sending branch pipe 23, and stored. In addition, since the carbon dioxide 5 discharged from the absorption and regeneration tower 11 contains water vapor and a small amount of absorbent, the carbon dioxide 5, water vapor, and absorbent discharged from the absorption and regeneration tower 11 are cooled by the carbon dioxide cooler 17, and the condensed water and absorbent are separated by the gas-liquid separator 18, and the carbon dioxide 5 after gas-liquid separation is recovered. 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 for a predetermined time using the carbon dioxide recovery device 10.

[0027] Thereafter, the above absorption step and regeneration step are repeated to carry out the embodiment of the method for recovering carbon dioxide in a gaseous carbon dioxide supply source of the present invention.

[0028] 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 to an absorption and regeneration tower, contacting the gaseous carbon dioxide supply source with the carbon dioxide lean absorbing liquid in the absorption and regeneration 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 storage; A regeneration step of supplying the carbon dioxide-rich absorbing liquid in the carbon dioxide-rich absorbing liquid storage tank to the absorption and regeneration tower, heating the carbon dioxide-rich absorbing liquid in the absorption and 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 storage; It consists of: The carbon dioxide lean absorption liquid and the carbon dioxide rich absorption liquid are absorption liquids containing an absorbent; Repeating the absorption step and the regeneration step alternately; 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:

[0029] The method for recovering carbon dioxide from a gaseous carbon dioxide supply source of the present invention comprises an absorption step and a regeneration step. In the method for recovering carbon dioxide from a gaseous carbon dioxide supply source of the present invention, the absorption step for a predetermined time and the regeneration step for a predetermined time are alternately repeated. The respective implementation times of the absorption step and the regeneration step are appropriately selected.

[0030] 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 are alternately performed in the same tower, i.e., the absorption and regeneration tower, so that the method for recovering carbon dioxide in a gaseous carbon dioxide supply source of the present invention is a so-called batch processing method.

[0031] The absorption step in the method for recovering carbon dioxide in a gaseous carbon dioxide source of the present invention is a step of supplying a gaseous carbon dioxide source and a carbon dioxide-lean absorbing liquid to an absorption and regeneration tower, contacting the gaseous carbon dioxide source with the carbon dioxide-lean absorbing liquid in the absorption and regeneration tower to reactively absorb the carbon dioxide in the gaseous carbon dioxide 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 storage.

[0032] 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.

[0033] The carbon dioxide concentration in the gaseous carbon dioxide supply source supplied to the absorption / regeneration 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 / regeneration tower is 90 to 300 kPa, and preferably 90 to 130 kPa.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] The carbon dioxide cyclic loading amount of the absorbent contained in the absorption liquid is preferably 0.85 mol (CO 2 ) / L (solution) or more, particularly preferably 2.0 to 7.0 mol (CO 2 ) / L (solution). When the carbon dioxide cyclic loading amount of the absorbent is within the above range, the amount of circulating absorption liquid is reduced, and the 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 the absorbent (mol(CO 2 ) / L(solution) = carbon dioxide absorption at 40°C and 20 kPa (mol(CO 2 ) / L (solution) - Carbon dioxide absorption at 120°C and 100 kPa (mol (CO 2 ) / L(solution))

[0038] The absorption rate of carbon dioxide of the absorbent contained in the absorbing solution is preferably 0.09 mol (CO 2) / L (of solution) per minute or more, and particularly preferably 0.10 to 0.20 mol (CO 2 ) / L (of solution) per minute. When the carbon dioxide absorption rate of the absorbent is within the above range, reactive absorption of carbon dioxide in the absorption step is promoted, and the height of the absorption and regeneration tower can be reduced.

[0039] The carbon dioxide desorption energy of the absorbent contained in the absorption liquid is preferably 90 kJ / mol (CO 2 ) or less, particularly preferably 30 to 75 kJ / mol (CO 2 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.

[0040] 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.

[0041] The absorption and regeneration tower is a vessel in which the absorption step and the regeneration step are performed alternately. The absorption and regeneration tower is not particularly limited as long as it can perform the absorption step and the regeneration step alternately. The size of the absorption and regeneration 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, pressure, allowable pressure loss, and carbon dioxide recovery rate of the absorption step and the regeneration step, etc.

[0042] In the absorption and regeneration tower, a contact mechanism is preferably installed in order to increase the absorption rate of carbon dioxide from the gaseous carbon dioxide supply source and the regeneration efficiency of the carbon dioxide-rich absorption liquid. 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 amount.

[0043] In the absorption step, the method of contacting the gaseous carbon dioxide supply source with the carbon dioxide-lean absorbing liquid in the absorption and regeneration 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 upward, and supply the carbon dioxide-lean absorbing liquid from the upper part of the tower and flow it downward, thereby contacting the carbon dioxide-lean absorbing liquid with the gaseous carbon dioxide supply source in a countercurrent manner.

[0044] The reaction conditions in the absorption step are not particularly limited, but the temperature of the gaseous carbon dioxide supply source is preferably 10 to 65°C, and the temperature of the carbon dioxide lean absorption solution is preferably 30 to 50°C.

[0045] In the absorption step, the carbon dioxide absorption rate is usually set to 90 to 95% depending on the carbon dioxide utilization plan.

[0046] 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 the carbon dioxide absorption rate is set too high when using such a gaseous carbon dioxide supply source, in order to satisfy sufficient contact under a low carbon dioxide partial pressure, the height of the absorption and regeneration tower must be made very large, or in some cases, the pressure inside the absorption and regeneration tower must be increased to about 500 kPa or more by installing a compressor or the like.

[0047] On the other hand, when the absorption step of the method for recovering carbon dioxide in 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, the height of the absorption and regeneration tower can be significantly reduced, and the pressure in the absorption and regeneration tower does not need to be increased. Therefore, in the absorption step of the method for recovering carbon dioxide in a gaseous carbon dioxide source of the present invention, the absorption rate of carbon dioxide is preferably 25 to 95%, more preferably 25 to 90%, still more preferably 25 to 85%, and particularly preferably 30 to 75%, thereby reducing the cost of implementing the method for recovering carbon dioxide in a gaseous carbon dioxide source of the present invention and the construction cost of a carbon dioxide recovery device. The carbon dioxide absorption rate is a value calculated by the following formula. Carbon dioxide absorption rate (%) = ((carbon dioxide flow rate in gaseous carbon dioxide source (Nm 3 / 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

[0048] 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 / regeneration 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 / regeneration tower and pass the treated gas through the water washing facility.

[0049] 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 and regeneration 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 and regeneration tower and cools it to room temperature.

[0050] 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 an absorption and regeneration tower, heating the carbon dioxide-rich absorbing liquid in the absorption and 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 storage.

[0051] In the regeneration step, an example of a method for heating the carbon dioxide-rich absorbing liquid in the absorption and regeneration tower is to heat the carbon dioxide-lean absorbing liquid accumulated at the bottom of the absorption and regeneration tower, generate an upward flow of vapor of the absorbing liquid at the saturation temperature in the absorption and regeneration tower, heat the inside of the absorption and regeneration tower, and heat the carbon dioxide-rich absorbing liquid by flowing the carbon dioxide-rich absorbing liquid in a downward direction.

[0052] As a method for heating the carbon dioxide lean absorption liquid accumulated at the bottom of the absorption and regeneration tower, for example, a method can be mentioned in which a portion of the carbon dioxide lean absorption liquid accumulated at the bottom of the absorption and regeneration tower is extracted, the extracted carbon dioxide lean absorption liquid is heated, and then returned to the bottom of the tower.

[0053] In addition, other methods for heating the carbon dioxide-rich absorbing liquid in the absorption and regeneration tower in the regeneration step include a method in which the carbon dioxide-rich absorbing liquid in the absorption and 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.

[0054] In the regeneration step, it is preferable to heat the carbon dioxide-rich absorbing liquid in the absorption and regeneration tower, and recover the carbon dioxide desorbed from the carbon dioxide-rich absorbing liquid from the tower top. Since the carbon dioxide discharged from the absorption and 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 absorption and regeneration tower.

[0055] 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 tower bottom so that the outlet temperature of the tower top is 100 to 105° C. In the regeneration step, the temperature of the carbon dioxide-lean absorbing solution accumulated in the tower bottom is preferably the saturation temperature of the absorbing solution.

[0056] In addition, in the method for recovering carbon dioxide in a gaseous carbon dioxide supply source of the present invention, the repetition of the absorption step and the regeneration step can be controlled by an automatic control system. The automatic control system is constructed so as to enable control of switching between the absorption step and the regeneration step, control of the operating capacity, various responses in the event of a malfunction, etc., by operation control by a single or higher-level computer system or a communication function with an external system.

[0057] Thus, in the method for recovering carbon dioxide from a gaseous carbon dioxide supply source of the present invention, the absorption step and the regeneration step can be performed in the same absorption and regeneration tower, so that even if a single reaction tower is used, carbon dioxide from a gaseous carbon dioxide supply source can be recovered. In addition, in the method for recovering carbon dioxide from a gaseous carbon dioxide supply source of the present invention, the absorption rate of carbon dioxide in the absorption step is preferably 25 to 90%, more preferably 25 to 85%, and particularly preferably 30 to 75%, so that the height of the absorption and regeneration tower can be significantly reduced compared to when the absorption rate of carbon dioxide in the absorption step is 90 to 95%. Therefore, 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.

[0058] The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. EXAMPLES

[0059] (Examples 1 to 2) <Absorption process> Using the carbon dioxide recovery device shown in Fig. 1, in the flow shown in Fig. 2, a gaseous carbon dioxide supply source 1 having a carbon dioxide concentration shown in Table 1 was supplied from the lower part of the absorption and regeneration tower, and a carbon dioxide lean absorbing liquid (aqueous solution of 30 mass % monoethanolamine (MEA)) in a carbon dioxide lean absorbing liquid storage tank was supplied from the upper part 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 supplied / hour)) shown in Table 1, at the temperature and pressure shown in Table 1, and an absorption step was performed for 8 hours. The results are shown in Table 1. In Table 1, "4 moles of absorbent / CO 2 The "total molar ratio of source 1" refers to "(total moles of the absorption liquid (MEA solution) fed at the tower inlet per hour) / (total moles of the gas in gaseous carbon dioxide source 1 fed at the tower inlet per hour)."

[0060] <Regeneration process> Next, using the carbon dioxide recovery device shown in Figure 1, the carbon dioxide was heated to the saturation temperature according to the flow shown in Figure 3. Next, after replacing with a carbon dioxide-rich absorbing liquid, the carbon dioxide-rich absorbing liquid in the carbon dioxide-rich absorbing liquid storage tank was supplied from the top of the tower while the carbon dioxide-lean absorbing liquid at the bottom of the tower was heated to the saturation temperature according to the flow shown in Figure 4, and a regeneration step was performed for 8 hours at the temperature shown in Table 1. The results are shown in Table 1.

[0061] [Table 1] [Explanation of symbols]

[0062] 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 equipment 11 Absorption and regeneration tower 12 Contact mechanism 13 Carbon dioxide-rich absorbent storage tank 14 Carbon dioxide lean absorbent storage tank 15 Heat exchanger 16 Reboiler 17 Carbon dioxide cooler 18 Gas-liquid separator 19 Absorption liquid cooler 21 Tower upper supply pipe 22 Bottom discharge pipe 23 Branch pipe for carbon dioxide lean absorption liquid supply 24 Carbon dioxide rich absorbing liquid delivery 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 extraction pipe 31, 32, 33, 34, 37, 38, 39, 40, 41, 44 Valves 45 Water Vapor 301 Connecting Pipe 302 Bypass pipe

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 to an absorption and regeneration tower, contacting the gaseous carbon dioxide supply source with the carbon dioxide lean absorbing liquid in the absorption and regeneration 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 storage; A regeneration step of supplying the carbon dioxide-rich absorbing liquid in the carbon dioxide-rich absorbing liquid storage tank to the absorption and regeneration tower, heating the carbon dioxide-rich absorbing liquid in the absorption and 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 storage; It consists of: the carbon dioxide lean absorption liquid and the carbon dioxide rich absorption liquid are absorption liquids containing alkanolamine as an absorbent; Repeating the absorption step and the regeneration step alternately; 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 and regeneration 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 absorption liquid accumulated at the bottom of the absorption and regeneration tower is heated to generate an upward flow of vapor of the absorption liquid at a saturation temperature in the absorption and regeneration tower, thereby heating the inside of the absorption and regeneration tower, and the carbon dioxide-rich absorption liquid is heated by flowing the carbon dioxide-rich absorption 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 95%.

5. 5. The method for recovering carbon dioxide in a gaseous carbon dioxide supply source according to claim 1, wherein the absorption step and the regeneration step are repeated under an automatic control system.

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