JP7441123B2 - Acid gas removal device and acid gas removal method - Google Patents

Description

Embodiments of the present invention relate to an acid gas removal device and an acid gas removal method.

In thermal power plants and steel mills that use large amounts of fossil fuels, combustion exhaust gas generated by burning fossil fuels in boilers, coal gasification gas (gasification gas) that gasifies coal, natural gas, etc. For example, it contains acidic gas components such as carbon dioxide (CO ₂ ), SOx, NOx, NOx, and H ₂ S.

Conventionally, in order to suppress acidic gas components contained in such combustion exhaust gas from being released into the atmosphere, gases containing acidic gas components are treated with amino group-containing compounds (amine compounds) in absorption towers. A method of removing the acid gas component from the treated gas and recovering the acid gas component by bringing the acid gas component into gas-liquid contact with the absorbing liquid and absorbing the acid gas component into the absorbing liquid is being actively researched.

For example, an absorption tower that brings exhaust gas into contact with an absorption liquid containing an amino group-containing compound to absorb acidic gas components such as _CO2 in the exhaust gas, and an absorption tower that heats the absorption liquid that has absorbed acidic gas components to absorb Equipped with a regeneration tower that releases acidic gas components from the liquid, the regenerated absorption liquid is supplied to the absorption tower again for reuse, and the absorption liquid is circulated within the system between the absorption tower and the regeneration tower for use. CO ₂ recovery equipment and the like are known.

However, when absorbing _CO2 from gas during operation, in addition to SOx and NOx, carbonyl sulfide, hydrogen cyanide, thiocyanic acid, thiosulfuric acid, and other inorganic acids react with amino group-containing compounds in the absorption liquid. As a result, a degraded product called Heat Stable Amine Salt (HSAS) is produced. A thermally stable amine salt is also generated when the amino group-containing compound is decomposed by reacting with heat or oxygen in gas when the absorption liquid is heated and regenerated. Such thermally stable amine salts are not decomposed by heating during regeneration of the absorption liquid in the regeneration tower and are not separated from the absorption liquid, so they are accumulated in the absorption liquid. Accumulation of such heat-stable amine salts not only reduces the acid gas absorption efficiency of the absorption liquid but also causes corrosion of the equipment, so it is desirable to remove heat-stable amine salts from the absorption liquid. ing.

For example, electrodialysis using a bipolar membrane is known as a method for removing such heat-stable amine salts from the absorption liquid. In addition, since loss of amine occurs due to permeation through an ion exchange membrane, a bipolar membrane and an anion exchange membrane are combined, and a chamber with an amine purification function is installed between opposing electrodes in order from the cathode side to the anode side. Using an electrodialysis device consisting of a three-chamber structure consisting of a chamber with an amine recovery function and a chamber with an acid recovery function, thermally stable amine salts are extracted from the absorption liquid while suppressing amine loss through electrodialysis. There is a known method for removing it by transferring it to a concentrated solution.

International Publication No. 2014/077373 US Patent Publication No. 2012/0235087

CO ₂ (hydrogen carbonate ion, carbonate ion) loaded into the absorption liquid together with the acid as an anion was also removed to the concentrated liquid, but the CO ₂ remained unused. The present invention has been made in consideration of these circumstances, and aims to improve acid gas removal efficiency and plant operation stability by utilizing the removed CO ₂ as recovered CO ₂ of the acid gas removal device. With the goal.

According to the present invention, the removed CO ₂ can also be utilized as recovered CO ₂ of the acid gas removal device, thereby improving acid gas recovery efficiency and plant operation stability.

1 is a schematic diagram showing the configuration of an acid gas removal device according to an embodiment of the present invention. 1 is a schematic diagram showing the configuration of an acid component remover according to an embodiment of the present invention. 1 is a schematic diagram showing the configuration of an acid gas removal device according to an embodiment of the present invention. 1 is a schematic diagram showing the configuration of an acid gas removal device according to an embodiment of the present invention. 1 is a schematic diagram showing the configuration of an acid gas removal device according to an embodiment of the present invention.

The acid gas removal device according to the embodiment of the present invention includes:
an absorber having an absorption section that brings a gas to be treated containing an acidic gas into contact with an acidic gas absorption liquid containing an amine to absorb the acidic gas in the gas to be treated into the acidic gas absorption liquid;
a regenerator having a regeneration unit that removes acidic gas from the acidic gas absorption liquid after absorbing acidic gas and regenerates the acidic gas absorption liquid;
The acidic gas absorption liquid containing the acid component derived from the absorber or the regenerator is purified by electrodialysis, and the amount of the acid component is reduced, and the acidic gas absorption liquid containing the acid component is purified. an acid component remover that recovers the components and makes a concentrated liquid with a high acid component concentration;
a gas-liquid separator that separates acidic gas from the concentrated liquid;
It is characterized by comprising the following.

And, the acid gas removal method according to the embodiment of the present invention is as follows:
It is characterized by comprising the following steps (a) to (d).
Step (a): a step of bringing a gas to be treated containing an acidic gas into contact with an acidic gas absorption liquid containing an amine to absorb the acidic gas in the gas to be treated into the acidic gas absorption liquid;
Step (b): a step of removing acid gas from the acidic gas absorption liquid after absorbing acidic gas and regenerating the acidic gas absorption liquid;
Step (c): The acidic gas absorption liquid in which acid components have accumulated in the step (a) or step (b) is converted into a purified liquid with a reduced amount of the acid components by electrodialysis, and also contains the acid components. An acid component removal step in which the acid component is recovered from the acidic gas absorption liquid to create a concentrated liquid with a high acid component concentration;
Step (d): A gas-liquid separation step of separating acidic gas from the concentrated liquid.

Embodiments of the present invention will be described in further detail below. In this specification, the case where the acidic gas is carbon dioxide (CO ₂ ) will be described in detail, but the present invention is not limited to the case where the acidic gas is carbon dioxide (CO ₂ ).

[Acid gas removal equipment]
FIG. 1 is a schematic diagram showing the basic configuration of an acid gas removal apparatus according to a preferred embodiment of the present invention.
The acid gas removal device shown in FIG.
It has an absorption part 1a that brings the gas to be treated 101 containing an acidic gas into contact with the acidic gas absorption liquid 110d containing an amine and absorbs the acidic gas in the gas to be treated 101 into the acidic gas absorption liquid 110d. absorber 1,
a regenerator 2 having a regeneration unit that removes acidic gas from the acidic gas absorption liquid 111 after absorbing acidic gas and regenerates the acidic gas absorption liquid;
The acidic gas absorption liquid 104 containing the acid component derived from the regenerator 2 is converted into a purified liquid 105 in which the amount of the acid component is reduced by electrodialysis. an acid component remover 4 that collects the components and makes a concentrated liquid 107 with a high acid component concentration;
a gas-liquid separator 18 that separates acidic gas from the concentrated liquid 107;
This is an acid gas removal device comprising:

In this acid gas removal device, an absorption liquid that absorbs CO ₂ in a gas to be treated (exhaust gas) 101 containing CO ₂ is circulated between an absorber 1 and a regenerator 2 (hereinafter referred to as inside the system). are doing. An absorption liquid (rich absorption liquid) 111 that has absorbed CO ₂ in the exhaust gas 101 is fed from the absorber 1 to the regenerator 2 . From the regenerator 2 to the absorber 1, an absorption liquid (lean absorption liquid) 110a is supplied from the rich absorption liquid 111 in which part or almost all of the CO ₂ is removed in the regenerator 2 and regenerated.

Note that the absorption liquid is preferably an amine aqueous solution containing an amine compound (amino group-containing compound) and water. Preferred amine compounds include, for example, monoethanolamine, primary amines such as 2-amino-2-methyl-1-propanol, secondary amines such as diethanolamine and 2-methylaminoethanol, and triethanolamine. Tertiary amines such as ethanolamine and N-methyldiethanolamine, polyethylene polyamines such as ethylenediamine, triethylenediamine and diethylenetriamine, cyclic amines such as piperazine, piperidine and pyrrolidine, and xylylenediamine. Examples include polyamines and amino acids such as methylaminocarboxylic acid, and these can be used alone or in combination of two or more. The absorption liquid is used as an aqueous solution containing usually 10 to 70% by weight of these amine compounds. In addition, the absorption liquid may contain reaction accelerators, nitrogen-containing compounds to improve the absorption performance of acidic gases such as _CO2 , anticorrosives to prevent corrosion of plant equipment, and extinguishers to prevent foaming. Other compounds such as a foaming agent, an antioxidant for preventing deterioration of the absorption liquid, and a pH adjuster may be appropriately contained in any proportion within a range that does not impair the effects of the absorption liquid.

A typical example of the gas to be treated 101 is an exhaust gas containing CO ₂ , such as combustion exhaust gas discharged from a boiler or gas turbine in a thermal power plant, process exhaust gas generated in a steel mill, and the like. The gas to be treated 101 can preferably be pressurized by a blower or the like, cooled by a cooler, and then supplied into the absorber 1 from the lower part of the absorber 1 through a flue.

The absorber 1 shown in FIG. 1 includes a CO ₂ absorption part (acid gas absorption part) 1a that absorbs CO ₂ in exhaust gas 101 into a lean absorption liquid 110a, and a CO 2 absorption part (acid gas absorption part) 1a that absorbs CO ₂ in exhaust gas 101 into a lean absorption liquid 110a. It has a gas cleaning section 3 that cleans the process gas (CO ₂ removed exhaust gas) with a cleaning liquid 121a and recovers amine accompanying the CO ₂ removed exhaust gas.

Here, the CO ₂ absorption part 1a is preferably formed of a filler to improve gas-liquid contact efficiency. A liquid disperser can be provided above the CO ₂ absorption part 1a, and the lean absorption liquid 110d supplied to the absorber 1 is dispersed and dropped toward the CO ₂ absorption part 1a by the liquid disperser. The exhaust gas 101 fed into the absorber 1 flows from the lower part of the absorber 1 toward the top (upper part) side. In the CO ₂ absorption part 1a, when the exhaust gas 101 rising in the absorber comes into contact with the lean absorption liquid 110d in a counterflow, reactions such as those shown in the following formulas (1) and (2) occur, and thermally decomposable salts (R ₃ NH ₂ CO ₂ ) and a thermally stable amine salt (R ₃ NHX) are formed, and the CO ₂ in the exhaust gas 101 is absorbed by the lean absorption liquid 110d and removed from the exhaust gas 101.

The lean absorption liquid 110d absorbs _CO2 in the exhaust gas 101 to become a rich absorption liquid 111, which is stored in the lower part, and this rich absorption liquid 111 contains a thermally decomposable salt and a thermally stable amine salt.

The rich absorption liquid 111 absorbs organic acids generated by reaction with oxygen contained in the exhaust gas 101, SOx, NOx, carbonyl sulfide, hydrogen cyanide, thiocyanic acid, thiosulfuric acid, and other inorganic acids contained in the exhaust gas 101. The resulting thermostable amine salt accumulates. Here, R represents hydrogen or a substituted or unsubstituted alkyl group (which may form a heterocycle).

R ₃ N + CO ₂ + H ₂ O → R ₃ NH ₂ CO ₃ ...(1)
_R3N +HX → _R3NHX ...(2)

The CO ₂ removed exhaust gas that has passed through the CO ₂ absorption section 1 a rises inside the absorber 1 and is supplied to the gas cleaning section 3 .
In the gas cleaning section 3, the CO ₂ removed exhaust gas is cleaned with the cleaning liquid 121a to recover the amine accompanying the CO ₂ removed exhaust gas. In this embodiment, the CO ₂ removed exhaust gas is cleaned by the cleaning liquid cleaning liquid 121a in the gas cleaning unit 3. The gas cleaning section 3 is provided inside the absorber 1, and is provided above the CO ₂ absorption section 1a, which is downstream of the CO ₂ absorption section 1a in the gas flow direction of the CO ₂ removed exhaust gas. A liquid distributor is provided above the gas cleaning section 3, and the cleaning liquid 121a supplied to the absorber 1 is dispersed and dropped toward the gas cleaning section 3 by the liquid distributor. In the gas cleaning section 3, the CO ₂ removed exhaust gas is cleaned with the cleaning liquid 121a, and the amine accompanying the CO ₂ removed exhaust gas is removed from the CO ₂ removed exhaust gas. Note that although the gas cleaning section 3 is housed within the absorber 1, it may be provided outside the absorber 1 and serve as a gas cleaning device independent of the absorber 1.

The cleaning liquid 121a after coming into contact with the CO2 _- removed exhaust gas is stored in a cleaning liquid storage section (not shown) provided at the lower part of the gas cleaning section 3, and a cleaning liquid circulation line L11 is connected to the cleaning liquid storage section. A circulation pump 12 is provided in the cleaning liquid circulation line L11, and the cleaning liquid 121a is sent by the circulation pump 12 and is again supplied from the upper part of the gas cleaning section 3.
The more acidic the cleaning liquid 121a is, the higher the cleaning efficiency, and for example, pure water, sulfuric acid water, or the like is used.

Since the cleaning liquid 121a contains amines in the CO ₂ removed exhaust gas, as the cleaning liquid 121a continues to circulate through the gas cleaning section 3 and the cleaning liquid circulation line L11, the amine concentration in the cleaning liquid 121a continues to increase. Collection performance may deteriorate. A part of the cleaning liquid 121a circulating between the gas cleaning section 3 and the cleaning liquid circulation line L11 may be discharged to the outside, or may be mixed with the absorption liquid within the system. The cleaning liquid circulation line L11 can be replenished with new cleaning liquid.
After the CO2 _- removed exhaust gas is purified in the gas cleaning section 3, it is discharged from the upper part of the absorber 1 to the outside as a treated combustion exhaust gas 102.

On the other hand, the rich absorption liquid 111 stored in the lower part of the absorber 1 is discharged from the lower part of the absorber 1, passes through the rich absorption liquid supply line L3, and is connected to a pump (not shown) provided in the rich absorption liquid supply line L3. After being pressurized in the heat exchanger 9 and exchanging heat with the lean absorption liquid 110a regenerated in the regenerator 2, it is supplied to the regenerator 2. In the heat exchanger 9, the rich absorption liquid 111 is heated by exchanging heat with the lean absorption liquid 110a, so that the lean absorption liquid 110a serves as a heat source and the rich absorption liquid 111 is heated. Conversely, the rich absorption liquid 111 serves as a cooling source to cool the lean absorption liquid 110a. Note that as the heat exchanger 9, a known heat exchanger such as a plate heat exchanger or a shell & tube heat exchanger can be used.

The regenerator 2 releases CO ₂ from the rich absorption liquid 111 and regenerates the rich absorption liquid 111 as a lean absorption liquid 110a. The rich absorption liquid 111 is supplied into the regenerator 2 and heated by steam in the reboiler 8, whereby _CO2 contained in the rich absorption liquid 111 is desorbed and contained in the rich absorption liquid 111. A lean absorption liquid 110a is obtained from which part or almost all of the CO ₂ has been removed.

At this time, the lean absorption liquid 110a generates water vapor and the remaining CO ₂ is released as CO ₂ gas. The generated water vapor and _CO2 gas are released from the regenerator 2 as regenerator outlet gas 118. The lean absorption liquid 110a discharged from the regenerator 2 is supplied to the absorber 1 as a lean absorption liquid 110a via the heat exchanger 9 by a lean absorption liquid 110a pump (not shown).

The CO ₂ gas is discharged from the top of the regenerator 2 along with water vapor that evaporates at the same time from the lean absorption liquid 110a. Regenerator outlet gas 118 containing _CO2 gas and water vapor is cooled by cooling water in cooler 6, and the water vapor condenses into water. Then, the regenerator outlet gas 119 containing this condensed water and CO ₂ gas is supplied to the gas-liquid separator 7, where the CO ₂ gas 103 is separated from the condensed water 120a, and the CO ₂ gas 103 is discharged to the outside. Further, the condensed water 120a is extracted from the lower part of the gas-liquid separator 7 and supplied to the upper part of the regenerator 2.

The lean absorption liquid 110a stored in the lower part of the regenerator 2 is discharged from the lower part of the regenerator 2 through the lean absorption liquid discharge line L4, and is cooled by exchanging heat with the rich absorption liquid 111 in the heat exchanger 9. Thereafter, the lean absorption liquid 110a is cooled by the cooler 5 and then supplied to the absorber 1.

An absorption liquid extraction line L8 is provided which branches from the lean solution discharge line L4 and is connected to the acid component remover 4. A part of the lean solution 110a supplied to the absorber 1 is converted into an acid as the lean absorption liquid 104 to be processed. The absorbent liquid is supplied to the absorption liquid purification chamber 10 (details will be described later) of the component remover 4. Further, a purified absorption liquid supply line L9 is provided that connects the acid component remover 4 and the lean solution discharge line L10, and the purified lean solution 105 discharged from the absorption liquid purification chamber of the acid component remover 4 is purified. It is supplied to the lean solution discharge line L10 through the absorption liquid supply line L9. In addition, in FIG. 1, the position where the liquid extraction line L8 branches from the lean solution discharge line L4 is between the cooler 5 and the absorber 1, which is preferable, but it is preferably located on the upstream side of the cooler 5 in the flow direction of the absorption liquid. You can also use it as

Then, the concentrated liquid 106 is supplied to the acid recovery chamber 11 of the acid component remover 4 from the line L12.

Concentrated liquid 107 discharged from acid recovery chamber 11 is supplied to gas-liquid separator 18 . The gas-liquid separator 18 may also serve as a tank for storing concentrated liquid.
The acid component of the thermally stable amine salt is removed from the lean absorption liquid 104 and transferred to the concentrated liquid 106, while the bicarbonate ions or carbonate ions in the lean absorption liquid 104 are also transferred to the concentrated liquid 106 and transferred to the concentrated liquid 107. Bicarbonate or carbonate ions accumulate. The concentrated liquid 107 is circulated and supplied to the acid component remover 4 as the concentrated liquid 106, but the more acidic the concentrated liquid is, the smaller the amount of bicarbonate ions or carbonate ions dissolved in the concentrated liquid as ions, and the more acidic the concentrated liquid 107 as _CO2 gas.

Concentrated liquid 107 containing CO ₂ gas is separated into CO ₂ gas 112 and concentrated liquid 106 in gas-liquid separator 18 .
The concentrated liquid 106 separated by the gas-liquid separator 18 is again supplied to the acid component remover 4, while the CO ₂ gas 112 separated by the gas-liquid separator 18 is sent from the regenerator 2 to the confluence section 13. It merges with the CO ₂ gas 103 that has been led out.

It is preferable that the concentrated liquid 107 has a pH of 8 or less. Although there is no lower limit for the pH, if the pH exceeds 8, it is not preferable because most of the CO ₂ will be dissolved in the concentrated liquid 107 as bicarbonate ions or carbonate ions, resulting in a decrease in the amount of CO ₂ recovered, as will be described later. The pH of the concentrated liquid 107 is maintained at an acidic level because the acid component contained in the lean absorption liquid 104 moves to the concentrated liquid 107. Further adjustment to acidity can be easily achieved by, for example, adding an acid such as sulfuric acid to the concentrated liquid 107.

As described above, according to the acid gas removal apparatus according to the embodiment of the present invention, CO ₂ present in the concentrated liquids 106 and 107 of the acid component remover 4 is separated by the gas-liquid separator 18. As a result, this separated CO ₂ can also be utilized as CO ₂ recovered by the acid gas removal device, so that acid gas recovery efficiency and plant operation stability can be improved.

In the embodiment of the present invention, as shown in FIG. It is preferable to arrange 20. By arranging this acidic gas storage tank 19, it is possible to suppress pressure fluctuations inside the line L13, the gas-liquid separator 18, and the acid component removal 47. For example, the acid component removal in the acid component removal device 4 can be suppressed. can be performed stably and efficiently. Further, it is possible to adjust the supply amount from the acid gas storage tank 19 according to the required flow rate of CO ₂ gas in the CO ₂ storage equipment or CO ₂ utilization equipment (not shown).

The pressure inside the gas-liquid separator 18 is preferably at least atmospheric pressure. The recovered CO ₂ gas is used as is, and is also used for storage in storage tanks and injection into the ground, so the higher the pressure, the better. Therefore, it is preferable that the pressure of the CO ₂ gas 112 recovered from the acid component remover 4 is high, and by keeping the gas-liquid separator 18 at least at atmospheric pressure or higher, it is possible to obtain CO ₂ gas at a pressure higher than atmospheric pressure. Become. If necessary, the lean absorption liquid 104 to be treated is pressurized and supplied to the acid component remover 4 so as to have a pressure equal to or higher than atmospheric pressure.

As shown in FIG. 3, it is preferable to arrange an acidic gas flow meter 21 in the discharge line L6 of the CO ₂ gas 103 led out from the regenerator 2. In such a preferred embodiment of the present invention, the acidic gas flow rate adjustment valve 20 can be controlled according to the acidic gas flow rate determined by the acidic gas flow rate meter 21. By doing this, when the flow rate of CO ₂ gas 103 decreases, by increasing the supply amount from acid gas storage tank 19, CO ₂ gas in CO ₂ storage equipment or CO ₂ utilization equipment (not shown) is reduced. The amount of CO ₂ gas to be supplied can be made constant depending on the required flow rate. Further, when the flow rate of the CO ₂ gas 103 increases, the amount of CO ₂ gas to be supplied can be kept constant by decreasing the amount of supply from the acidic gas storage tank 19. Moreover, it becomes easy to control the pressure inside the line L13, the inside of the gas-liquid separator 18, and the inside of the gas-liquid separator 4 within an optimal range.

As shown in FIG. 3, at least a portion 121b of the cleaning liquid 121a obtained from the gas cleaning section 3 can be supplied to the acid component remover 4. When the cleaning liquid 121b (this cleaning liquid contains an amine) is supplied to the acid component remover 4, the amount of the concentrated liquid 106 used in the acid component remover 4 can be reduced.

Further, as shown in FIG. 4, at least a portion 120b of the condensed water 120a obtained from the gas-liquid separator 7 can be supplied to the acid component remover 4. When the condensed water 120b (this condensed water contains amine and CO ₂ ) is supplied to the acid component remover 4, the amount of concentrated liquid 106 used in the acid component remover 4 can be reduced.

Furthermore, when the condensed water 120b is supplied to the acid component remover 4, the condensed water 120b becomes more acidic due to the acid component that has moved from the lean absorption liquid 104 to be treated, and the hydrogen carbonate dissolved in the condensed water 120b becomes more acidic. The ions or carbonate ions become CO ₂ gas and are recovered by the gas-liquid separator 18, thereby making it possible to further increase the amount of CO ₂ recovered.

Further, the regenerator 2 can be provided with a gas cleaning section 22 including a packed bed, as shown in FIG. In this gas cleaning section 22, by cleaning the acidic gas generated when regenerating the acidic gas absorption liquid, the amine compound is dissolved and recovered in the cleaning liquid, and the amine compound is prevented from being discharged to the outside of the regenerator 2. suppress. The cleaning liquid can be circulated. For example, after the cleaning liquid is introduced from the upper part of the gas cleaning part 22 and brought into contact with the acidic gas, it can be taken out from the lower part of the gas cleaning part 22 and introduced into the upper part of the gas cleaning part 22 again. The more acidic the cleaning liquid is, the higher the cleaning efficiency; for example, in addition to condensed water obtained by cooling the gas 118 discharged from the regeneration unit 2 with the cooler 6, pure water, sulfuric acid water, etc. can be used. .

Then, if necessary, as shown in FIG. 5, at least a portion 122c of the cleaning liquid 122b obtained from the gas cleaning section can be supplied to the acid component remover 4. When the cleaning liquid 122c (this cleaning liquid contains dissolved CO ₂ and amine) is supplied to the acid component remover 4, the cleaning liquid 122c becomes more acidic due to the acid component that has moved from the lean absorption liquid 104 to be treated, and the cleaning liquid 122c becomes more acidic. The bicarbonate ions or carbonate ions dissolved in the gas 122c turn into CO ₂ gas and are recovered by the gas-liquid separator 18, thereby making it possible to further increase the amount of CO ₂ recovered.

[Acid component remover]
Details of the acid component remover 4 in the acid gas removal apparatus according to the embodiment of the present invention will be further explained with reference to FIGS. 1 to 5.
The preferred acid component remover 4 shown in FIG.
An anode 13, a cathode 14,
Between these anode 13 and cathode 14, from the anode 13 side to the cathode 14 side, a first anion exchange membrane 15A-1, a bipolar membrane 17BP, and a second anion exchange membrane 15A-2 are arranged. Equipped with an electrodialysis structure consisting of four chambers formed by separately arranging them in this order,
A first chamber disposed on the anode 13 side of the first anion exchange membrane 15A-1 is an acid recovery chamber 11a that recovers the acid component X ⁻ removed from the acidic gas absorption liquid 104 containing the acid component. and
A second chamber disposed between the first anion exchange membrane 15A-1 and the bipolar membrane 17BP performs absorption liquid purification for removing the acid component X ⁻ from the acidic gas absorption liquid 104 containing the acid component. Room 10a,
A third chamber disposed between the bipolar membrane 17BP and the second anion exchange membrane 15A-2 recovers the acid component X ⁻ removed from the acidic gas absorption liquid 104 containing the acid component. An acid recovery chamber 11b,
A fourth chamber disposed on the cathode 14 side of the second anion exchange membrane 15A-2 is an absorption liquid purification chamber 10b that removes the acid component X ⁻ from the acidic gas absorption liquid containing the acid component. It is an acid gas remover.

As shown in FIG. 2, the acid component remover 4 includes an anode 13, a cathode 14, anion exchange membranes 15A-1 and 15A-2, and a bipolar membrane 17BP. The inside of this acid component remover 4 is divided into four regions, ie, absorption liquid purification chambers 10a and 10b, and acid recovery chambers 11a and 11b, by an anion exchange membrane 15A and a bipolar membrane 17BP. Between the cathode 14 and the anode 13, an anion exchange membrane 15A-1, a bipolar membrane 17BP, and an anion exchange membrane 15A-2 are arranged in order from the anode 13 toward the cathode 14. The cathode 14 and anode 13 may be immersed in the electrode solution.

In this embodiment, two acid recovery chambers 11a, 11b and two absorption liquid purification chambers 10a, 10b are formed, but it is sufficient that one or more sets of absorption liquid purification chambers and acid recovery chambers are formed. , a plurality of them may be formed. Furthermore, the number of combinations of absorption liquid purification chambers and acid recovery chambers may not be the same. As long as one or more sets of the absorption liquid purification chamber and the acid recovery chamber are formed, the acid recovery chamber and the absorption liquid purification chamber may also exist as a single chamber.

The bipolar membrane 17BP is a composite membrane in which an anion exchange membrane and a cation exchange membrane are stacked, and are arranged so that the anion exchange membrane is on the anode side and the cation exchange membrane is on the cathode side. When a voltage higher than the theoretical decomposition voltage of water is applied in the presence of water, water can be electrolyzed into hydrogen ions and hydroxide ions. Specifically, a known bipolar membrane such as Neocepta BP-1E (manufactured by Astom Co., Ltd., trade name) can be used.

As the anion exchange membranes 15A-1 and 15A-2, polymer membranes having anion exchange groups that can pass anions and block the passage of cations are used. The anion exchange membrane 15A is made of a polymer having, for example, a strong basic group such as a quaternary ammonium group and a weakly basic functional group such as a primary amino group, a secondary amino group, or a tertiary amino group. A film such as the following can be used. Specifically, well-known shadows such as NeoSepta AMX, NeoSepta AHA (manufactured by Astom Co., Ltd., product name); Selemion AMV, Selemion AMT, Selemion DSV, Selemion ASV, Selemion AHO (manufactured by AGC Engineering Co., Ltd., Asahi Glass Co., Ltd., product name) Ion exchange membranes can be used.

The absorption liquid purification chamber 10a is an area between the anion exchange membrane 15A-1 and the bipolar membrane 17BP, and the anion exchange membrane 15A-1 is arranged on the anode side of the absorption liquid purification chamber 10a, and the bipolar membrane A membrane 17BP is arranged.

The acid recovery chamber 11a is located on the anode side of the absorption liquid purification chamber 10a, and is installed through the anion exchange membrane 15A-1.
The acid recovery chamber 11b is an area between the bipolar membrane 17BP and the anion exchange membrane 15A-2, and the bipolar membrane 17BP is disposed on the anode side of the acid recovery chamber 11b, and the anion exchange membrane 15A-2 is disposed on the cathode side. is located.

The absorbent purification chamber 10b is located on the cathode side of the acid recovery chamber 11b, and is installed via the anion exchange membrane 15A-2.
A lean absorption liquid 104 to be processed is supplied to the absorption liquid purification chambers 10a and 10b. Further, a concentrated liquid 106 is supplied to the acid recovery chambers 11a and 11b.

As the lean absorption liquid 104, the lean absorption liquid 110a used in the acidic gas remover 4 shown in FIG. Liquid is also fine.

When voltage is applied to both electrodes, in the absorption liquid purification chambers 10a and 10b, since the acid component (X ⁻ ) of the thermally stable amine salt contained in the lean absorption liquid 104 to be treated is an anion, the anode 13 side I'm drawn to it. As a result, the acid component (X ⁻ ) of the thermally stable salt in the absorption liquid purification chamber 10a moves from the absorption liquid purification chamber 10a to the acid recovery chamber 11a through the anion exchange membrane 15A-1. The acid component (X ⁻ ) of the heat-stable amine salt is removed from the treated lean absorption liquid 104, and the acid component of the heat-stable amine salt is accumulated in the concentrated liquid 106.

Then, the acid component (X ⁻ ) of the thermally stable salt in the absorption liquid purification chamber 10b passes through the anion exchange membrane 15A-2 from the absorption liquid purification chamber 10b and moves to the acid recovery chamber 11b. The acid component (X ⁻ ) of the heat-stable amine salt is removed from the lean absorption liquid 104, and the acid component of the heat-stable amine salt is accumulated in the concentrated liquid 106.

In addition, in the bipolar membrane 17BP, water electrolysis occurs inside the membrane, hydrogen ions are generated on the cation exchange membrane side (cathode 14 side) of the bipolar membrane 17BP, and hydroxide ions are generated on the anion exchange membrane side of the bipolar membrane 17BP. (to the anode 13 side). Therefore, hydroxide ions move from the bipolar membrane 17BP to the absorption liquid purification chamber 10a, and hydrogen ions move from the bipolar membrane 17BP to the acid recovery chamber 11b, so hydroxide ions are supplied to the absorption liquid purification chamber 10a. Hydrogen ions are supplied to the concentrated liquid 106.

The lean absorption liquid 105 discharged from the absorption liquid purification chambers 10a and 10b may be supplied to an acid gas removal device, and may be circulated and supplied again to the absorption liquid purification chambers 10a and 10b to further remove the acid component of the thermally stable amine salt. You may remove it. Alternatively, the system may be operated via a separately installed absorption liquid tank.
The concentrated liquid 107 discharged from the acid recovery chambers 11a and 11b is circulated and supplied to the acid recovery chambers 11a and 11b again. Circulating operation may be performed via a separately installed concentrate tank.

In this way, the acid component of the thermally stable amine salt is removed from the lean absorption liquid 104, but on the other hand, bicarbonate ions or carbonate ions in the lean absorption liquid 104 in the absorption liquid purification chambers 10a and 10b are also removed by the anion exchange membrane. It passes through the anion exchange membrane 15A-1 or the anion exchange membrane 15A-2 and moves to the concentrate 106, where hydrogen carbonate ions or carbonate ions are accumulated. The concentrated liquid 107 is circulated and supplied to the acid component remover 4 as the concentrated liquid 106, but the more acidic the concentrated liquid is, the smaller the amount of bicarbonate ions or carbonate ions dissolved in the concentrated liquid as ions, and the more acidic the concentrated liquid 107 as _CO2 gas.

Concentrated liquid 107 containing CO ₂ gas is separated into CO ₂ gas 112 and concentrated liquid 106 in gas-liquid separator 18 . The CO ₂ gas 112 joins with the CO ₂ gas 103 discharged from the gas-liquid separator 7, and is supplied to a CO ₂ storage facility or a CO ₂ utilization facility (not shown).
Further, the CO ₂ gas 112 may be directly supplied to a CO ₂ storage facility or a CO ₂ utilization facility (not shown).

The concentrate can be discarded and a new concentrate provided once the acid component of the heat-stable amine salt reaches a predetermined concentration. Further, it is possible to operate the apparatus so that only a portion of the concentrated liquid is continuously withdrawn and a new concentrated liquid is continuously supplied to maintain the acid component of the stable amine salt in the concentrated liquid at a predetermined concentration.
Therefore, according to the present embodiment, the removed CO ₂ can also be utilized as recovered CO ₂ of the acid gas removal device, and the acid gas recovery efficiency can be improved.

[How to remove acidic gas]
A method for removing acidic gas according to an embodiment of the present invention is characterized by comprising the following steps (a) to (d).
Step (a): a step of bringing a gas to be treated containing an acidic gas into contact with an acidic gas absorption liquid containing an amine to absorb the acidic gas in the gas to be treated into the acidic gas absorption liquid;
Step (b): a step of removing acid gas from the acidic gas absorption liquid after absorbing acidic gas and regenerating the acidic gas absorption liquid;
Step (c): The acidic gas absorption liquid in which acid components have accumulated in the step (a) or step (b) is converted into a purified liquid with a reduced amount of the acid components by electrodialysis, and also contains the acid components. An acid component removal step in which the acid component is recovered from the acidic gas absorption liquid to create a concentrated liquid with a high acid component concentration;
Step (d): A gas-liquid separation step of separating acidic gas from the concentrated liquid.

The acid gas removal method according to the embodiment of the present invention can preferably be easily carried out in the acid gas removal apparatus shown in FIGS. 1 to 5. For example, step (a) can be performed in the absorber 1, step (b) in the regenerator 2, step (c) in the acid gas remover 4, and step (d) in the gas-liquid separator 18. can.
Note that the acid gas removal method of the present invention also includes, as an embodiment, an acid gas removal method in which various operations or steps realized in the various devices shown in FIGS. 1 to 5 are performed. .

A method for removing acidic gas according to an embodiment of the present invention includes a method of supplying at least a portion of the concentrated liquid to the acidic gas absorption liquid and returning amines in the concentrated liquid to the acidic gas absorption liquid. and include. A part of the amine in the acidic gas absorption liquid also moves to the concentrated liquid, resulting in amine loss, but if the amine in the concentrated liquid is returned, the acidic gas absorption liquid is recovered while the acidic gas in the concentrated liquid is recovered. It becomes possible to suppress a decrease in the amine concentration of In this case, it is more preferable that the amount of acid component accumulated in the absorption liquid is small.

The acid component removal apparatus and acid component removal method according to several embodiments of the present invention have been described above, but these embodiments are presented as examples and do not limit the scope of the invention. . These embodiments can be implemented in various other forms, and various omissions, substitutions, changes, additions, etc. can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention, as well as within the scope of the invention described in the claims and its equivalents.

1: Absorber, 2: Regenerator, 4: Acid component remover, 18: Gas-liquid separator, 13: Anode, 14: Cathode, 15A-1: First anion exchange membrane, 17BP: Bipolar membrane, 15A -2: second anion exchange membrane, 11a: acid recovery chamber, 10a: absorption liquid purification chamber, 11b: acid recovery chamber, 10b: absorption liquid purification chamber, 13: confluence section, 19: acidic gas storage tank, 20 : Acidic gas flow rate adjustment valve, 21: Acidic gas flow rate measuring device, 22: Gas cleaning section

Claims (10)

an absorber having an absorption section that brings a gas to be treated containing an acidic gas into contact with an acidic gas absorption liquid containing an amine to absorb the acidic gas in the gas to be treated into the acidic gas absorption liquid;
a regenerator having a regeneration unit that removes acidic gas from the acidic gas absorption liquid after absorbing acidic gas and regenerates the acidic gas absorption liquid;
The acidic gas absorption liquid containing the acid component derived from the absorber or the regenerator is purified by electrodialysis, and the amount of the acid component is reduced, and the acidic gas absorption liquid containing the acid component is purified. an acid component remover that recovers the components and makes a concentrated liquid with a high acid component concentration;
a gas-liquid separator that separates acidic gas from the concentrated liquid;
Equipped with
An acidic gas removal device further comprising a confluence section for the acidic gas derived from the gas-liquid separator and the acidic gas derived from the regenerator. The acid component remover is
an anode, a cathode,
Between the anode and the cathode, at least one anion exchange membrane and a bipolar membrane are arranged in this order from the anode side to the cathode side, respectively. It is equipped with an electrodialysis structure,
A first chamber arranged on the anode side of the anion exchange membrane is an acid recovery chamber for recovering the acid component removed from the acidic gas absorption liquid containing the acid component,
A second chamber disposed between the anion exchange membrane and the bipolar membrane is an absorption liquid purification chamber that removes acid components from the acidic gas absorption liquid containing the acid components,
The removal of acidic gas according to claim 1, wherein the third chamber arranged on the cathode side of the bipolar membrane is an acid recovery chamber for recovering the acid component removed from the acidic gas absorption liquid containing the acid component. Device. The acidic gas removal device according to claim 1 or 2, further comprising an acidic gas storage tank and an acidic gas flow rate adjustment valve between the acidic gas outlet of the gas-liquid separator and the confluence section. The acidic gas removal device according to any one of claims 1 to 3, wherein the gas-liquid separator has an internal pressure equal to or higher than atmospheric pressure. a gas cleaning section that cleans the gas discharged from the absorption section with a cleaning liquid;
The acidic gas removal device according to any one of claims 1 to 4, further comprising a flow path for supplying at least a portion of the cleaning liquid obtained from the gas cleaning section to the acid component remover. at least one of a gas cleaning section that cleans the gas discharged from the regenerator with a cleaning liquid or a condensation section that cools the gas discharged from the regenerator to obtain a condensate;
Claims 1 to 3, further comprising a flow path for supplying at least a portion of the cleaning liquid obtained from the gas cleaning section or at least a portion of the condensate obtained from the condensation section to the acid component remover. 5. The acid gas removal device according to any one of 5. The acid gas removal device according to claim 5 or 6, wherein the cleaning liquid is water or acidic water. The acidic gas removal device according to claim 1, wherein the concentrated liquid has a pH of 8 or less. The following steps (a) to (d):
Step (a): a step of bringing a gas to be treated containing an acidic gas into contact with an acidic gas absorption liquid containing an amine to absorb the acidic gas in the gas to be treated into the acidic gas absorption liquid;
Step (b): a step of removing acid gas from the acidic gas absorption liquid after absorbing acidic gas and regenerating the acidic gas absorption liquid;
Step (c): The acidic gas absorption liquid in which the acid component has accumulated in the step (a) or step (b) is purified by electrodialysis, and the amount of the acid component is reduced, and the acidic gas absorption liquid is made to contain the acid component. An acid component removal step in which the acid component is recovered from the acidic gas absorption liquid to create a concentrated liquid with a high acid component concentration;
Step (d): a gas-liquid separation step of separating acidic gas from the concentrated liquid;
It is equipped with
A method for removing acidic gas, further comprising the step of combining the acidic gas removed in step (b) with the acidic gas separated in step (d). The method for removing acidic gas according to claim 9, wherein at least a portion of the concentrated liquid is supplied to the acidic gas absorption liquid, and the amine in the concentrated liquid is returned to the acidic gas absorption liquid.

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