JP2021194556A - Acidic gas removal device and acidic gas removal method - Google Patents

Abstract

To provide an acidic gas removal device and an acidic gas removal method which improve acidic gas removal efficiency in gas and plant operation stability.SOLUTION: An acidic gas removal device includes: an absorber 1 for bringing treated gas 101 containing acidic gas into contact with an acidic gas absorption liquid 110d containing amine, and making the acidic gas absorption liquid absorb the acidic gas in the treated gas; a regenerator 2 for removing the acidic gas from the acidic gas absorption liquid 111 after the absorption by the acidic gas, and regenerating the acidic gas absorption liquid; an acid component remover 4 for converting an acidic gas absorption liquid 104 containing an acid component derived from the absorber or the regenerator into a purified liquid 105 having a reduced amount of the acid component by electrodialysis, collecting the acid component from the acidic gas absorption liquid containing the acid component, and converting the acidic gas absorption liquid into a concentrated liquid 107 having high acid component concentration; and a gas-liquid separator 18 for separating the acidic gas from the concentrated liquid.SELECTED DRAWING: Figure 1

Description

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

In thermal power plants and steel mills that use a large amount of fossil fuel, combustion exhaust gas generated by burning fossil fuel in a boiler, coal gasified gas (gasified gas), natural gas, etc. for example, carbon dioxide _(CO 2), contains SOx, NOx, NOx, the acid gas components such as _{H 2} S.

Conventionally, in order to suppress the release of the acid gas component contained in such combustion exhaust gas into the atmosphere, an amino group-containing compound (amine-based compound) has been used in the absorption tower to absorb the gas containing the acid gas component. A method of removing an acid gas component from a treated gas and recovering the acid gas component by contacting the containing liquid with gas and liquid to absorb the acid gas component into the absorbing liquid is being energetically studied.

For example, an absorption tower in which an absorption liquid containing an amino group-containing compound is brought into contact with an exhaust _{gas to absorb an acid gas component such as CO 2 in} the exhaust gas into the absorption liquid, and an absorption liquid having absorbed the acid gas component are heated and absorbed. Equipped with a regeneration tower that releases acid gas components from the liquid, the regenerated absorption liquid is supplied to the absorption tower again for reuse, and the absorption liquid is circulated in the system between the absorption tower and the regeneration tower for use. CO ₂ recovery devices and the like are known.

_{However, when CO 2} in the gas is absorbed during operation, in addition to SOx and NOx, carbonyl sulfide, hydrogen cyanide, thiocyanic acid, thiosulfuric acid, and other inorganic acids react with the amino group-containing compound in the absorption liquid. As a result, a deteriorated product called Heat Stable Amine Salt (HSAS) is produced. Further, when the absorption liquid is heated and regenerated, the amino group-containing compound is decomposed by reacting with heat or oxygen in the gas to produce a heat-stable amine salt. Such a thermostable amine salt is not decomposed by heating when the absorption liquid is regenerated in the regeneration tower and is not separated from the absorption liquid, so that it is accumulated in the absorption liquid. Accumulation of such a heat-stable amine salt not only lowers the acid gas absorption efficiency of the absorption liquid but also causes corrosion of the apparatus. Therefore, it is desired to remove the heat-stability amine salt from the absorption liquid. ing.

As a method for removing such a thermostable amine salt from the absorption liquid, for example, electrodialysis using a bipolar membrane is known. In addition, since it permeates the ion exchange membrane and causes the loss of amine, a chamber having an amine purification function in order from the cathode side to the anode side between the facing electrodes by combining the bipolar membrane and the anion exchange membrane. Using an electrodialysis device having a three-chamber structure consisting of a chamber having an amine recovery function and a chamber having an acid recovery function, the heat-stable amine salt from the absorption liquid is suppressed by electrodialysis while suppressing the loss of amine. Is known to be removed by moving it to a concentrate.

International Publication No. 2014/073733 U.S. Patent Publication No. 2012/0235087

_{CO 2} (hydrogen carbonate ion, carbonate ion) loaded into the absorption liquid together with the anion acid was also removed into the concentrate, but the CO ₂ remained unused. The present invention has been made in consideration of such circumstances, and the removed CO _{2 is also utilized as the recovered CO 2} of the acid gas removing device to improve the acid gas removing efficiency and the plant operation stability. With the goal.

According to the present invention, the removed CO _{2 can also be utilized as the recovered CO 2} of the acid gas removing device, and the acid gas recovery efficiency can be improved and the plant operation stability can be improved.

The schematic diagram which shows the structure of the acid gas removing apparatus by the embodiment of this invention. The schematic diagram which shows the structure of the acid component remover in the embodiment of this invention. The schematic diagram which shows the structure of the acid gas removing apparatus by the embodiment of this invention. The schematic diagram which shows the structure of the acid gas removing apparatus by the embodiment of this invention. The schematic diagram which shows the structure of the acid gas removing apparatus by the embodiment of this invention.

The acid gas removing device according to the embodiment of the present invention is
An absorber having an absorption unit that brings the acid gas to be treated containing an acid gas into contact with an acid gas absorbing liquid containing an amine to absorb the acid gas in the acid gas to be absorbed by the acid gas absorbing liquid.
A regenerator having a regenerator that removes acid gas from the acid gas absorbing liquid after absorbing the acid gas and regenerates the acid gas absorbing liquid, and a regenerator.
The acid gas absorbing solution containing the acid component derived from the absorber or the regenerator is converted into a purified solution in which the amount of the acid component is reduced by electrodialysis, and the acid is acid from the acid gas absorbing solution containing the acid component. An acid component remover that recovers the components to make a concentrated solution with a high acid component concentration,
A gas-liquid separator that separates acid gas from the concentrate,
It is characterized by having.

The method for removing acid gas according to the embodiment of the present invention is as follows.
It is characterized by having the following steps (a) to (d).
Step (a): A step of bringing an acid gas-containing gas to be treated and an acid gas absorbing liquid containing an amine into contact with each other to allow the acid gas in the gas to be treated to be absorbed by the acid gas absorbing liquid.
Step (b): A step of removing the acid gas from the acid gas absorbing liquid after absorbing the acid gas and regenerating the acid gas absorbing liquid.
Step (c): The acid gas absorbing solution in which the acid component is accumulated in the step (a) or the step (b) is converted into a purified solution in which the amount of the acid component is reduced by electrodialysis, and the acid component is contained. Acid component removal step, which recovers the acid component from the acid gas absorbing solution to make a concentrated solution with a high acid component concentration.
Step (d): A gas-liquid separation step of separating an acid gas from the concentrated liquid.

Hereinafter, embodiments of the present invention will be described in more detail. Although the case where the acid gas is carbon dioxide (CO ₂ ) will be described in detail in the present specification, the present invention is not limited to the case where the _{acid gas is carbon dioxide (CO 2).}

[Acid gas remover]
FIG. 1 is a schematic view showing a basic configuration of an acid gas removing device according to a preferred embodiment of the present invention.
The acid gas removing device shown in FIG. 1 is
It has an absorption unit 1a in which the acid gas 101 to be treated containing an acid gas and the acid gas absorbing liquid 110d containing an amine are brought into contact with each other to absorb the acid gas in the acid gas 101 to be absorbed by the acid gas absorbing liquid 110d. Absorber 1 and
A regenerator 2 having a regenerating unit that removes the acid gas from the acid gas absorbing liquid 111 after absorbing the acid gas and regenerates the acid gas absorbing liquid, and the regenerator 2.
The acid gas absorbing 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, and the acid is acid from the acid gas absorbing liquid 104 containing the acid component. An acid component remover 4 and an acid component remover 4 for recovering the components to prepare a concentrated solution 107 having a high acid component concentration.
A gas-liquid separator 18 that separates acid gas from the concentrated liquid 107,
It is an acid gas removing device provided with.

In apparatus for removing acidic gases, absorbing liquid that absorbs CO ₂ of the gas to be treated (exhaust gas) in 101 containing CO ₂ is circulated between the absorber 1 and the regenerator 2 (hereinafter, referred to as the system) is doing. An absorbent liquid (rich absorbent liquid) 111 having absorbed _{CO 2} in the exhaust gas 101 is supplied from the absorber 1 to the regenerator 2. From the regenerator 2 to the absorber 1, an absorbent liquid (lean absorbent) 110a regenerated from the rich absorbent liquid 111 from which a part or almost all CO _{2 is removed by the regenerator 2 is supplied.}

The absorption liquid is preferably an amine-based aqueous solution containing an amine-based compound (amino group-containing compound) and water. Preferred amine-based compounds include, for example, monoethanolamine, primary amines such as 2-amino-2-methyl-1-propanol, diethanolamine, secondary amines such as 2-methylaminoethanol, and tri. Ethanolamines, tertiary amines such as N-methyldiethanolamine, polyethylenepolyamines such as ethylenediamine, triethylenediamine, diethylenetriamine, piperazins, piperidines, cyclic amines such as pyrrolidines, xylylene diamines and the like. Examples thereof 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 usually used as an aqueous solution containing 10 to 70% by weight of these amine compounds. In addition, the absorbent liquid includes a reaction accelerator, _{a nitrogen-containing compound that improves the absorption performance of acid gas such as CO 2} , an anticorrosive agent to prevent corrosion of plant equipment, and an extinguishing agent to prevent foaming, if necessary. Other compounds such as a foaming agent, an antioxidant for preventing deterioration of the absorbing liquid, and a PH adjusting agent can be appropriately contained in an arbitrary ratio as long as the effect of the absorbing liquid is not impaired.

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

The absorber 1 shown in FIG. 1 has _{a CO 2} absorbing unit (acid gas absorbing unit) 1a that absorbs _{CO 2} in the exhaust gas 101 into the lean absorbing liquid 110a, and a cover from which the acid gas has been removed by the _{CO 2 absorbing unit 1a.} It has a gas cleaning unit 3 that cleans the treated gas (CO ₂ removed exhaust gas) with the cleaning liquid 121a _{and recovers the amine accompanying the CO 2 removed exhaust gas.}

Here, the CO ₂ absorbing portion 1a is preferably formed of a filler to enhance gas-liquid contact efficiency. A _{liquid disperser can be provided above the CO 2} absorption unit 1a, and the lean absorbent liquid 110d supplied to the absorber 1 is dispersed and dropped toward the _{CO 2 absorption unit 1a by the liquid disperser.} The exhaust gas 101 supplied into the absorber 1 flows from the lower part of the absorber 1 toward the tower top (upper part) side. When _{the exhaust gas 101 rising in the absorber in the CO 2} absorbing unit 1a comes into contact with the lean absorbing liquid 110d in a countercurrent manner, for example, a reaction as shown in the following formulas (1) and (2) occurs, and the thermally decomposable salt occurs. (R ₃ NH ₂ CO ₂ ) and a heat-stable amine salt (R ₃ NHX) are formed, and 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 CO ₂ in the exhaust gas 101 to become a rich absorption liquid 111, which is stored in a lower portion, and the rich absorption liquid 111 contains a pyrolytic salt and a heat-stable amine salt.

The rich absorbent 111 absorbs organic acids generated by the 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 thermal stability amine salt accumulates. Here, R indicates a hydrogen, 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)
R ₃ N + HX → R ₃ NHX ・ ・ ・ (2)

CO ₂ flue gas passing through the CO ₂ absorbing section 1a is increased inside the absorber 1, is supplied to the gas cleaning section 3.
The gas cleaning unit 3 cleans the CO ₂ removed exhaust gas with the cleaning liquid 121a to recover the amine accompanying the _{CO 2 removed exhaust gas.} In the present 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 unit 3 is provided inside the absorber 1 and is provided above the CO ₂ absorption unit 1a, which is downstream of the CO ₂ absorption unit 1a in _{the gas flow direction of the CO 2 removed exhaust gas.} A liquid disperser is provided above the gas cleaning unit 3, and the cleaning liquid 121a supplied to the absorber 1 is dispersed and dropped toward the gas cleaning unit 3 by the liquid disperser. In the gas cleaning section 3, CO ₂ flue gas is washed with a washing solution 121a, amine accompanying the CO ₂ flue gas is removed from the CO ₂ flue gas. Although the gas cleaning unit 3 is housed in the absorber 1, it may be provided outside the absorber 1 and may be a gas cleaning unit independent of the absorber 1.

The cleaning liquid 121a after contacting with the CO ₂ removed exhaust gas is stored in a cleaning liquid storage unit (not shown) provided in the lower part of the gas cleaning unit 3, and a cleaning liquid circulation line L11 is connected to the cleaning liquid storage unit. The cleaning liquid circulation line L11 is provided with a circulation pump 12, and the cleaning liquid 121a is sent by the circulation pump 12 and is supplied again from the upper part of the gas cleaning unit 3.
The more acidic the cleaning liquid 121a is, the higher the cleaning efficiency is. For example, pure water or sulfuric acid water is used.

Since the cleaning liquid 121a _{contains amines in the CO 2} removed exhaust gas, if the cleaning liquid 121a continues to circulate between the gas cleaning unit 3 and the cleaning liquid circulation line L11, the amine concentration in the cleaning liquid 121a continues to increase, so that the amines in the cleaning liquid 121a continue to increase. Recovery performance may decrease. A part of the cleaning liquid 121a circulating between the gas cleaning unit 3 and the cleaning liquid circulation line L11 may be discharged to the outside or may be mixed with the absorbing liquid in the system. The cleaning liquid circulation line L11 can be replenished with new cleaning liquid.
The CO ₂ removed exhaust gas is purified by the gas cleaning unit 3 and then discharged to the outside from the upper part of the absorber 1 as the treated combustion exhaust gas 102.

On the other hand, the rich absorbent liquid 111 stored in the lower portion of the absorber 1 is discharged from the lower portion of the absorber 1, passes through the rich absorbent liquid supply line L3, and is provided in the rich absorbent liquid supply line L3 (shown). It is boosted by heat exchanger 9 and heat-exchanged with the lean absorbing liquid 110a regenerated in the regenerator 2 in the heat exchanger 9, and then supplied to the regenerator 2. In the heat exchanger 9, the rich absorbing liquid 111 is heat-exchanged with the lean absorbing liquid 110a, so that the lean absorbing liquid 110a becomes a heat source and the rich absorbing liquid 111 is heated. On the contrary, the rich absorbing liquid 111 serves as a cooling source, and the lean absorbing liquid 110a is cooled. As the heat exchanger 9, known heat exchangers such as a plate heat exchanger and a shell & tube heat exchanger can be used.

_{The regenerator 2 releases CO 2} from the rich absorbent 111 to regenerate the rich absorbent 111 as the lean absorbent 110a. The rich absorbent 111 is supplied into the regenerator 2 and heated by steam (steam) in the reboiler 8, so that CO ₂ contained in the rich absorbent 111 is desorbed and contained in the rich absorbent 111. It becomes a lean absorbent 110a from which some or almost all CO _{2 is removed.}

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

The CO ₂ gas is discharged from the upper part of the regenerator 2 together with the water vapor that evaporates from the lean absorbing liquid 110a at the same time. The _{regenerator outlet gas 118 containing CO 2} gas and water vapor is cooled by the cooling water in the cooler 6, and the water vapor is condensed into water. Then, the regenerator outlet gas 119 containing the condensed water and the CO ₂ gas is supplied to the gas-liquid separator 7, 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 absorbent liquid 110a stored in the lower part of the regenerator 2 is discharged from the lean absorbent liquid discharge line L4 from the lower part of the regenerator 2, and is cooled by exchanging heat with the rich absorbent liquid 111 in the heat exchanger 9. After that, the lean absorbent liquid 110a is cooled by the cooler 5 and then supplied to the absorber 1.

An absorption liquid extraction line L8 branched from the lean solution discharge line L4 and connected to the acid component remover 4 is provided, and a part of the lean solution 110a supplied to the absorber 1 is used as the acid as the lean absorption liquid 104 to be treated. It 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 connecting the acid component remover 4 and the lean solution discharge line L10 is provided, 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 FIG. 1, the position where the liquid extraction line L8 branches from the lean solution discharge line L4 is preferably between the cooler 5 and the absorber 1, but it is more upstream than the cooler 5 in the flow direction of the absorbed liquid. May be.

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

The concentrated liquid 107 discharged from the acid recovery chamber 11 is supplied to the gas-liquid separator 18. The gas-liquid separator 18 may also serve as a tank for storing the concentrated liquid.
The acid component of the heat-stability amine salt is removed from the lean absorption liquid 104 and moves to the concentrate 106, while the hydrogen carbonate ion or the carbonate ion in the lean absorption liquid 104 also moves to the concentrate 106 and moves to the concentrate 107. Hydrogen carbonate ion or carbonate ion accumulates. The concentrate 107 is circulated and supplied to the acid component remover 4 as the concentrate 106. However, the more acidic the concentrate, the smaller the amount of hydrogen carbonate ion or carbonate ion dissolved as ions in the concentrate, and the more the concentrate is. It will be present as CO _{2 gas in 107.}

The concentrate 107 containing the _{CO 2 gas is separated into the CO 2} gas 112 and the concentrate 106 by the gas-liquid separator 18.
The concentrated liquid 106 separated by the gas-liquid separator 18 is supplied to the acid component remover 4 again, while the CO ₂ gas 112 separated by the gas-liquid separator 18 is supplied from the regenerator 2 at the confluence 13. It merges with the derived CO _{2 gas 103.}

The pH of the concentrate 107 is preferably 8 or less. There is no lower limit of pH, but if the pH exceeds 8, CO ₂ is almost dissolved as hydrogen carbonate ion or carbonate ion in the concentrate 107 as described later, which is not preferable because the amount of _{CO 2 recovered is reduced.} As for the pH of the concentrated liquid 107, the acid component contained in the lean absorbing liquid 104 moves to the concentrated liquid 107, so that the pH of the concentrated liquid 107 is kept acidic. Further, the acidity can be easily adjusted by adding an acid such as sulfuric acid to the concentrate 107, for example.

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

Then, in the embodiment of the present invention, as shown in FIG. 3, an acid gas storage tank 19 and an acid gas flow rate adjusting valve are located between the acid gas outlet of the gas-liquid separator 18 and the confluence portion 13. It is preferable to arrange 20. By arranging the acid gas storage tank 19, it is possible to suppress pressure fluctuations inside the line L13, inside the gas-liquid separator 18, and inside the acid component removing 47, for example, removing the acid component in the acid component removing device 4. 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 facility or the CO ₂ utilization facility (not shown).

The pressure inside the gas-liquid separator 18 is preferably atmospheric pressure or higher. The recovered CO ₂ gas is used as it is, and is also used for storage in a storage tank and press-fitting into the ground, so the higher the pressure, the better. _{Therefore, it is preferable that the CO 2} gas 112 recovered from the acid component remover 4 also has a high pressure, and by keeping the gas-liquid separator 18 at least atmospheric pressure or higher, it is possible to obtain _{CO 2 gas above atmospheric pressure.} Become. The lean absorbing liquid 104 to be treated is pressurized and supplied to the acid component remover 4 as necessary in order to increase the atmospheric pressure to atmospheric pressure or higher.

As shown in FIG. 3, it is preferable to dispose the acid gas flow rate measuring instrument 21 on the discharge line L6 of _{the CO 2} gas 103 derived from the regenerator 2. In such a preferred embodiment of the present invention, the acid gas flow rate adjusting valve 20 can be controlled according to the acid gas flow rate obtained by the acid gas flow rate measuring device 21. By doing so, when _{the flow rate of the CO 2} gas 103 decreases, the supply amount from the acid gas storage tank 19 is increased so that the _{CO 2} gas in the _{CO 2} storage facility or the CO ₂ utilization facility (not shown) can be used. _{The amount of CO 2} gas supplied can be made constant according to the required flow rate. Further, _{when the flow rate of the CO 2 gas 103 increases, the amount of CO 2} gas supplied can be made constant by reducing the supply amount from the acid gas storage tank 19. Further, 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 the optimum range.

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

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

Further, 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 transferred from the lean absorbing liquid 104 to be treated, and the hydrogen carbonate dissolved in the condensed water 120b becomes more acidic. The ion or carbonate ion becomes a CO ₂ gas and is recovered by the gas-liquid separator 18, and the _{amount of CO 2} recovered can be further increased.

Further, as shown in FIG. 5, the regenerator 2 can be provided with a gas cleaning unit 22 provided with a packed bed. In the gas cleaning unit 22, by cleaning the acid gas generated when the acid gas absorbing solution is regenerated, the amine compound is dissolved and recovered in the cleaning solution, and the amine compound is discharged to the outside of the regenerator 2. Suppress. The cleaning solution can be circulated. For example, after introducing the cleaning liquid from the upper part of the gas cleaning unit 22 and bringing it into contact with the acid gas, it can be taken out from the lower part of the gas cleaning unit 22 and introduced again into the upper part of the gas cleaning unit 22. The more acidic the cleaning liquid is, the higher the cleaning efficiency is. For example, pure water, sulfuric acid water, or the like can be used in addition to condensed water obtained by cooling the gas 118 discharged from the regeneration unit 2 with a cooler 6 and condensing it. ..

Then, if necessary, as shown in FIG. 5, at least a part 122c of the cleaning liquid 122b obtained from this gas cleaning unit 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 transferred from the lean absorbing liquid 104 to be treated, and the cleaning liquid 122c becomes more acidic. The hydrogen carbonate ion or carbonate ion dissolved in 122c _{becomes CO 2} gas and is recovered by the gas-liquid separator 18, and the _{amount of CO 2} recovery can be further increased.

[Acid component remover]
The details of the acid component remover 4 in the acid gas remover according to the embodiment of the present invention will be further described with reference to FIGS. 1 to 5.
The preferred acid component remover 4 shown in FIG. 2 is
Anode 13, cathode 14,
Between the anode 13 and the cathode 14, the first anion exchange membrane 15A-1, the bipolar membrane 17BP and the second anion exchange membrane 15A-2 are formed from the anode 13 side to the cathode 14 side. It comprises an electrodialysis structure consisting of four chambers formed by being spaced apart from each other in this order.
The first chamber arranged on the anode 13 side of the first anion exchange membrane 15A-1 is an acid recovery chamber 11a for recovering the ^{acid component X − removed from the acid gas absorbing liquid 104 containing the acid component.} And
The second chamber arranged between the first anion exchange membrane 15A-1 and the bipolar film 17BP removes the ^{acid component X − from the acid gas absorbing liquid 104 containing the acid component.} Room 10a
A third chamber arranged between the bipolar membrane 17BP and the second anion exchange membrane 15A-2 recovers the ^{acid component X − removed from the acid gas absorbing solution 104 containing the acid component.} Acid recovery chamber 11b,
The fourth chamber arranged on the cathode 14 side of the second anion exchange film 15A-2 is an absorption liquid purification chamber 10b for removing the ^{acid component X − from the acid 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, 15A-2, and a bipolar membrane 17BP. The inside of the acid component remover 4 is divided into four regions, an absorption liquid purification chamber 10a and 10b, and an acid recovery chamber 11a and 11b, by an anion exchange membrane 15A and a bipolar membrane 17BP. An anion exchange membrane 15A-1, a bipolar membrane 17BP, and an anion exchange membrane 15A-2 are arranged in this order between the cathode 14 and the anode 13 from the anode 13 toward the cathode 14. The cathode 14 and the anode 13 may be immersed in the electrode liquid.

In the present embodiment, two acid recovery chambers 11a and 11b and two absorption liquid purification chambers 10a and 10b are formed, but it is sufficient that one or more sets of absorption liquid purification chambers and acid recovery chambers are formed. , Further may be formed in a plurality. Further, the number of combinations of the absorption liquid purification chamber and the acid recovery chamber does not have to 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 exist in a single chamber.

The bipolar membrane 17BP is a composite membrane in which an anion exchange membrane and a cation exchange membrane are laminated, and is arranged so that the anode side is an anion exchange membrane and the cathode side is a cation exchange membrane. When a voltage is applied in the presence of water at a voltage higher than the theoretical decomposition voltage of water, the water can be electrolyzed into hydrogen ions and hydroxide ions. Specifically, a known bipolar film such as Neosepta 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 an anion exchange group capable of allowing anions to pass through and blocking the passage of cations are used. The anion exchange film 15A is composed of, for example, a polymer having a weakly basic functional group such as a primary amino group, a secondary amino group, or a tertiary amino group in a strongly basic group of a quaternary ammonium group. A film or the like can be used. Specifically, known shades such as Neosepta AMX, Neosepta AHA (manufactured by Astom Co., Ltd., trade name); Ceremion AMV, Ceremion AMT, Ceremion DSV, Ceremion ASV, Ceremion AHO (manufactured by AGC Engineering Co., Ltd., trade name). An ion exchange membrane can be used.

The absorption liquid purification chamber 10a is a region 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 bipolar on the cathode side. The 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 via the anion exchange membrane 15A-1.
The acid recovery chamber 11b is a region between the bipolar membrane 17BP and the anion exchange membrane 15A-2, and the bipolar membrane 17BP is arranged on the anode side of the acid recovery chamber 11b and the anion exchange membrane 15A-2 on the cathode side. Is placed.

The absorption liquid 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.
The lean absorbent liquid 104 to be treated is supplied to the absorbent liquid purification chambers 10a and 10b. Further, the concentrate 106 is supplied to the acid recovery chambers 11a and 11b.

As the lean absorbent 104, the lean absorbent 110a used in the acid gas remover 4 shown in FIG. 1 may be used and may be continuously or completely withdrawn from the acid gas remover, or may be absorbed after the acid gas is removed. It can be a liquid.

When a voltage is applied to both electrodes, in the absorption liquid purification chambers 10a and 10b, the acid component (X ⁻ ) of the heat-stable amine salt contained in the lean absorbent liquid 104 to be treated is an anion, so that the anode 13 side Is drawn to. As a result, the acid component (X ⁻ ) of the heat-stable salt in the absorption liquid purification chamber 10a passes through the anion exchange membrane 15A-1 from the absorption liquid purification chamber 10a and moves to the acid recovery chamber 11a. ^{The acid component (X −} ) of the heat-stable amine salt is removed from the treated lean absorbent 104, and the acid component of the heat-stable amine salt is accumulated in the concentrate 106.

Then, the acid component (X ⁻ ) of the heat-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, so that it is to be treated. ^{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 concentrate 106.

Further, in the bipolar membrane 17BP, water electrolysis occurs inside the membrane, hydrogen ions are on the cation exchange membrane side (cathode 14 side) of the bipolar membrane 17BP, and hydroxide ions are on the anion exchange membrane side of the bipolar membrane 17BP. Move to (the anode 13 side). Therefore, the hydroxide ion moves from the bipolar film 17BP to the absorption liquid purification chamber 10a, and the hydrogen ion moves from the bipolar film 17BP to the acid recovery chamber 11b, so that the hydroxide ion is supplied to the absorption liquid purification chamber 10a. Hydrogen ions are supplied to the concentrate 106.

The lean absorption liquid 105 discharged from the absorption liquid purification chambers 10a and 10b may be supplied to the acid gas removing device, and may be circulated and supplied to the absorption liquid purification chambers 10a and 10b again to further supply the acid component of the heat-stability amine salt. May be removed. Further, the operation may be performed via a separately installed absorbent 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. Circulation operation may be performed via a separately installed concentrate tank.

In this way, the acid component of the heat-stable amine salt is removed from the lean absorption liquid 104, but on the other hand, the hydrogen carbonate ion or the carbonate ion in the lean absorption liquid 104 of the absorption liquid purification chambers 10a and 10b is also an anion exchange membrane. It passes through 15A-1 or the anion exchange membrane 15A-2 and moves to the concentrate 106, and hydrogen carbonate ion or carbonate ion is accumulated in the concentrate. The concentrate 107 is circulated and supplied to the acid component remover 4 as the concentrate 106. However, the more acidic the concentrate, the smaller the amount of hydrogen carbonate ion or carbonate ion dissolved as ions in the concentrate, and the more the concentrate is. It will be present as CO _{2 gas in 107.}

The concentrate 107 containing the _{CO 2 gas is separated into the CO 2} gas 112 and the concentrate 106 by the gas-liquid separator 18. The CO ₂ gas 112 merges 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).}

When the acid component of the thermostable amine salt reaches a predetermined concentration, the concentrate can be discarded and a new concentrate can be supplied. Further, only a part of the concentrated solution can be continuously extracted, a new concentrated solution can be continuously supplied, and the operation can be performed so that the acid component of the stable amine salt in the concentrated solution is maintained at a predetermined concentration.
Therefore, according to the present embodiment, the removed CO _{2 can also be utilized as the recovery CO 2} of the acid gas removing device, and the recovery efficiency of the acid gas can be improved.

[How to remove acid gas]
The method for removing acid gas according to the embodiment of the present invention is characterized by comprising the following steps (a) to (d).
Step (a): A step of bringing an acid gas-containing gas to be treated and an acid gas absorbing liquid containing an amine into contact with each other to allow the acid gas in the gas to be treated to be absorbed by the acid gas absorbing liquid.
Step (b): A step of removing the acid gas from the acid gas absorbing liquid after absorbing the acid gas and regenerating the acid gas absorbing liquid.
Step (c): The acid gas absorbing solution in which the acid component is accumulated in the step (a) or the step (b) is converted into a purified solution in which the amount of the acid component is reduced by electrodialysis, and the acid component is contained. Acid component removal step, which recovers the acid component from the acid gas absorbing solution to make a concentrated solution with a high acid component concentration.
Step (d): A gas-liquid separation step of separating an acid gas from the concentrated liquid.

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

The method for removing acid gas according to the embodiment of the present invention is a preferred embodiment of a method in which at least a part of the concentrated liquid is supplied to the acidic gas absorbing liquid and the amine in the concentrated liquid is returned to the acidic gas absorbing liquid. And include. A part of the amine in the acid gas absorbing liquid also moves to the concentrated liquid, resulting in an amine loss. However, when the amine in the concentrated liquid is returned, the acid gas absorbing liquid is recovered while recovering the acid gas in the concentrated liquid. It is 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.

Although the acid component removing apparatus and the acid component removing method according to some embodiments of the present invention have been described above, these embodiments are presented as examples and do not limit the scope of the invention. .. These embodiments can be implemented in various other embodiments, and various omissions, replacements, changes, additions, and the like can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

1: Absorber, 2: Regenerator, 4: Acid component remover, 18: Gas-liquid separator, 13: Auxiliary, 14: Cathode, 15A-1: First anion exchange film, 17BP: Bipolar film, 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, 19: Acid gas storage tank, 20 : Acid gas flow rate adjustment valve, 21: Acid gas flow rate measuring instrument, 22: Gas cleaning unit

Claims (11)

An absorber having an absorption unit that brings the acid gas to be treated containing an acid gas into contact with an acid gas absorbing liquid containing an amine to absorb the acid gas in the acid gas to be absorbed by the acid gas absorbing liquid.
A regenerator having a regenerator that removes acid gas from the acid gas absorbing liquid after absorbing the acid gas and regenerates the acid gas absorbing liquid, and a regenerator.
The acid gas absorbing solution containing the acid component derived from the absorber or the regenerator is converted into a purified solution in which the amount of the acid component is reduced by electrodialysis, and the acid is acid from the acid gas absorbing solution containing the acid component. An acid component remover that recovers the components to make a concentrated solution with a high acid component concentration,
A gas-liquid separator that separates acid gas from the concentrate,
A device for removing acid gas, which comprises. The acid component remover is
Anode, cathode,
From the three chambers formed by arranging at least one anion exchange membrane and a bipolar membrane apart from each other in this order from the anode side to the cathode side between these anodes and cathodes. Equipped with an electrodialysis structure
The 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 acid gas absorbing solution containing the acid component.
The second chamber arranged between the anion exchange membrane and the bipolar membrane is an absorption liquid purification chamber for removing the acid component from the acid gas absorbing liquid containing the acid component.
The acid gas removal according to claim 1, wherein the third chamber arranged on the cathode side of the bipolar film is an acid recovery chamber for recovering the acid component removed from the acid gas absorbing solution containing the acid component. Device. The acid gas removing device according to claim 1 or 2, further comprising a confluence of the acid gas derived from the gas-liquid separator and the acid gas derived from the regenerator. The acid gas removal according to any one of claims 1 to 3, further comprising an acid gas storage tank and an acid gas flow rate adjusting valve between the acid gas outlet of the gas-liquid separator and the confluence portion. Device. The acid gas removing device according to any one of claims 1 to 4, wherein the gas-liquid separator has an internal pressure of atmospheric pressure or higher. A gas cleaning unit that cleans the gas discharged from the absorption unit with a cleaning liquid,
The acid gas removing device according to any one of claims 1 to 5, further comprising a flow path for supplying at least a part of the cleaning liquid obtained from the gas cleaning unit to the acid component removing device. At least one of a gas cleaning unit that cleans the gas discharged from the regenerator with a cleaning liquid or a condensing unit that cools the gas discharged from the regenerator to obtain a condensed liquid.
Claims 1 to further include a flow path for supplying at least a part of the cleaning liquid obtained from the gas cleaning unit or at least a part of the condensed liquid obtained from the condensing unit to the acid component remover. Item 6. The acid gas removing device according to any one of 6. The acid gas removing device according to claim 6 or 7, wherein the cleaning liquid is water or acidic water. The acid gas removing device according to claim 1 to 8, wherein the concentrated solution has a pH of 8 or less. A method for removing acid gas, which comprises the following steps (a) to (d).
Step (a): A step of bringing an acid gas-containing gas to be treated and an acid gas absorbing liquid containing an amine into contact with each other to allow the acid gas in the gas to be treated to be absorbed by the acid gas absorbing liquid.
Step (b): A step of removing the acid gas from the acid gas absorbing liquid after absorbing the acid gas and regenerating the acid gas absorbing liquid.
Step (c): The acid gas absorbing solution in which the acid component is accumulated in the step (a) or the step (b) is converted into a purified solution in which the amount of the acid component is reduced by electrodialysis, and the acid component is contained. Acid component removal step, which recovers the acid component from the acid gas absorbing solution to make a concentrated solution with a high acid component concentration.
Step (d): A gas-liquid separation step of separating an acid gas from the concentrated liquid. The method for removing an acidic gas according to claim 10, wherein at least a part of the concentrated solution is supplied to the acidic gas absorbing solution, and the amine in the concentrated solution is returned to the acidic gas absorbing solution.

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