JP2012236170A - Method and apparatus for regeneration of deteriorated absorbing liquid, and carbon dioxide recovery system using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small deteriorated absorbing liquid regeneration method and apparatus capable of performing regeneration treatment of a deteriorated absorbing liquid, while a carbon dioxide recovery apparatus is operated.SOLUTION: The carbon dioxide recovery apparatus has an absorption tower 5 for recovering a carbon dioxide contained in a combustion exhaust gas 1 by bringing it into contact with a weak alkaline absorbing liquid 102, and a regeneration tower 8 for recovering the carbon dioxide from the absorbing liquid, wherein a portion of the deterioration absorbing liquid that absorbs a sulfur oxide is extracted, an alkali agent whose hydrogen ion concentration is higher than the absorbing liquid is mixed with the deteriorated absorbing liquid, and a salt of the generated sulfur oxide is separated from the deteriorated absorbing liquid.

Description

  The present invention relates to an absorbing liquid regeneration method, a deteriorated absorbing liquid regeneration apparatus, and a carbon dioxide recovery system using the same.

  From the viewpoint of preventing or suppressing global warming, there is an increasing demand for separating and recovering carbon dioxide in combustion exhaust gas.

As a means for separating and recovering carbon dioxide in combustion exhaust gas, as disclosed in Patent Document 1, carbon dioxide is absorbed in the absorbing liquid, and carbon dioxide from the absorbing liquid (hereinafter, carbon dioxide is expressed as CO _2). There is a CO ₂ recovery device and a CO ₂ recovery method. Examples of the absorbing liquid include an aqueous amine solution.

Absorbing liquid apparatus for separating and recovering carbon dioxide using is configured to include an absorption tower for absorbing CO _2, and a regenerator for the CO ₂ desorbed.

  The carbon dioxide separation / recovery process using this apparatus is as follows.

First, the combustion exhaust gas is guided to the absorption tower, and CO ₂ is absorbed by the absorption liquid. Next, the absorbing solution is sent to the regeneration tower to desorb CO ₂ . Then, the CO ₂ desorbed in the regeneration tower is compressed and liquefied and stored on the ground or sea floor.

  Sulfur oxide (hereinafter referred to as SOx) is contained in the exhaust gas combusted with fossil fuel. SOx is absorbed in an absorbing solution such as an aqueous amine solution and reacts with a weak alkaline substance such as an amine contained in the absorbing solution to generate a stable salt (Heat Stable Salt: HSS).

The generation of HSS is a deterioration of the absorbing solution, which reduces the CO ₂ absorption performance.

In order to regenerate the absorbing solution, as a first step, an alkaline agent (for example, sodium carbonate (Na ₂ CO ₃ )) having a higher hydrogen ion concentration (pH) than the above weakly alkaline substance is added, and the SOx is dissolved into SOx. Separate the minutes. Then, as the second stage, amine (R-NH ₂ ) is separated from 2Na ⁺ and SO ₄ ^2-, and weak alkaline substances are recovered and reused.

  As the separation method, for example, Patent Document 2 and Patent Document 3 show a distillation method. Non-Patent Document 1 discloses an electrodialysis method. Furthermore, Patent Document 4 discloses an ion exchange resin method.

JP 2007-61777 A JP 2008-221166 A JP-T-2001-521018 JP 59-169920 A

Masaki Iijima: CO2 recovery technology from fuel exhaust gas by chemical absorption method and effective use of CO2, disposal technology: Petrotech: 26, 11, 922-927 (2003)

In general, regeneration of the deteriorated absorbent (degraded absorbent) is performed during a period of periodic inspection after the CO ₂ recovery device (carbon dioxide recovery device) is stopped. However, since it is necessary to perform the regeneration process within a limited period, the operating rate is low, but there is a problem that the constituent devices become large.

  An object of the present invention is to reduce the size of constituent devices of a deteriorated absorbent regenerating apparatus by enabling continuous operation of a deteriorated absorbent regenerating apparatus that performs a regeneration process of the deteriorated absorbent while the carbon dioxide recovery apparatus is in operation. is there.

  The present invention absorbs sulfur oxides contained in combustion exhaust gas when the carbon dioxide contained in the combustion exhaust gas is recovered using an absorbing solution that includes a weak alkaline substance and its solvent and exhibits weak alkalinity. The resulting deterioration absorbing liquid is regenerated. At that time, the concentration of sulfur oxide contained in the deteriorated absorption liquid is detected, a part of the deteriorated absorption liquid is extracted, and an alkali agent having a higher hydrogen ion concentration than the absorption liquid is calculated from the concentration of sulfur oxide, It mixes with the extracted deterioration absorption liquid, the absorption liquid produced | generated by this and the salt of sulfur oxide are isolate | separated, It is characterized by reusing the separated absorption liquid.

  ADVANTAGE OF THE INVENTION According to this invention, the carbon dioxide recovery apparatus using absorption liquid and the reproduction | regeneration processing apparatus of deteriorated absorption liquid can be operate | moved stably simultaneously, and size reduction of the component apparatus of deterioration absorption liquid reproduction | regeneration apparatus can be achieved. Can do.

It is a schematic block diagram which shows the carbon dioxide collection system of an Example. It is a schematic block diagram which shows the deterioration absorption liquid reproduction | regeneration apparatus which attached the control part which controls the addition amount of an alkaline agent. 1 is a schematic configuration diagram showing a CO ₂ recovery device and a deteriorated absorbent regenerating device of an example that enables continuous operation. It is a flow diagram illustrating the continuous operation process of the CO ₂ recovery apparatus and deterioration absorbing solution regeneration apparatus of the embodiment. It is a flowchart which shows the analysis procedure of the sulfate ion concentration of an Example. It is a graph which shows the measurement result of a sulfate ion concentration.

  TECHNICAL FIELD The present invention relates to a method and apparatus for regenerating an absorbent (hereinafter also referred to as “degraded absorbent”) that has deteriorated due to SOx mixing in a carbon dioxide recovery device that uses an absorbent such as an aqueous amine solution. This invention relates to a technique for simultaneously and stably operating both a device for recovering carbon dioxide contained in an absorbent using an absorbing solution and a regenerating device for a deteriorated absorbing solution installed in association therewith.

  In the present invention, a tank for storing the deteriorated absorption liquid extracted from the carbon dioxide recovery apparatus is provided, and an alkali agent or an aqueous alkali solution is supplied to the tank so that the liquid is guided from the tank to the separation apparatus. Furthermore, a sulfur oxide concentration detection unit for detecting the concentration of sulfur oxide in the absorbing liquid in the tank, and an alkali agent or an alkaline aqueous solution that takes in the detected sulfur oxide concentration as a signal and is added in the deteriorated absorbing liquid regeneration processing apparatus. And a control unit for calculating the amount of the alkali agent or an alkali agent mixing unit for adding the amount of the alkali agent or the alkaline aqueous solution to the deterioration absorbing liquid.

  The sulfur oxide concentration detector may be provided in the absorption tower or the regeneration tower.

  The alkaline agent mixing part may be a static mixer.

  Further, the sulfur oxide concentration detection unit collects the deterioration absorbing solution, sequentially adds a small amount of an alkali agent or an aqueous alkali solution, sequentially measures sulfate compound ions in the deterioration absorbing solution, and determines the deterioration absorbing solution from the amount of change. You may make it determine the sulfur oxide density | concentration in it.

  The reaction in which SOx contained in the exhaust gas combusting fossil fuel reacts with the amine in the amine aqueous solution to produce a stable salt (Heat Stable Salt: HSS) is represented by the following reaction formula (1).

2R-NH ₂ + SOx → (R-NH ₂ ) ₂ SOx ... Reaction formula (1)
In the above reaction formula (1), the amine is described as R—NH _{2 for} convenience. The chemical formula of sulfur oxide is described as SOx. Using this, HSS is expressed as (R-NH ₂ ) ₂ SOx. Here, SOx is a general term for sulfur oxides such as SO ₃ , SO ₂ , SO, S ₂ O ₃ , S ₂ O _4, etc. SO ₂ (sulfurous acid gas) is the main component.

As an example of actual measurement values in a pulverized coal fired boiler incorporating a denitration apparatus and a desulfurization apparatus, the SOx concentration at the outlet of the denitration apparatus was about 1000 ppm, and the SOx concentration at the outlet of the desulfurization apparatus was about 30 ppm. Of the 30 ppm, SO ₂ was 98%, SO ₃ was 2%, and other SOx was 0%. Therefore, the concentration of SOx in contact with the absorbing solution can be assumed to be about 30 ppm. Even when pulverized coal containing a large amount of sulfur is used, it is considered to be about 100 ppm. Here, the SOx concentration is measured by gas analysis such as a gas chromatograph.

The generation of HSS is amine degradation, which reduces the CO ₂ absorption performance.

  The first stage for regenerating the amine is a reaction in which an alkali agent is added to separate SOx from HSS, and is represented by the following reaction formula (2).

(R-NH ₂ ) ₂ SO ₄ + Na ₂ CO ₃ → 2R-NH ₂ + 2Na ⁺ + SO ₄ ^2- + CO ₂ ... Reaction formula (2)
In the reaction formula (2), sodium carbonate (Na ₂ CO ₃ ) is used as the alkali agent. Further, it is described as a reaction for decomposing (R—NH ₂ ) ₂ SO ₄ , which is a kind of HSS produced by combining SO ₄ ^2- , which is the main component of SOx, and R—NH ₂ .

In the second step, amine (R-NH ₂ ) is separated from 2Na ⁺ and SO ₄ ^2-, and amine (R-NH ₂ ) is recovered and reused.

  Hereinafter, a deteriorated absorbent regenerating method, a deteriorated absorbent regenerating apparatus, and a carbon dioxide recovery system using the same according to an embodiment of the present invention will be described.

  The method for regenerating a deteriorated absorbent is a sulfur oxide contained in combustion exhaust gas when the carbon dioxide contained in the combustion exhaust gas is recovered using an absorption liquid that includes a weak alkaline substance and its solvent and exhibits weak alkalinity. This is a method for regenerating a deteriorated absorbent that has been absorbed by detecting the concentration of sulfur oxides contained in the deteriorated absorbent, extracting a portion of the deteriorated absorbent, and an alkali having a higher hydrogen ion concentration than the absorbent. The agent is mixed with the extracted deteriorated absorption liquid in an amount calculated from the concentration of sulfur oxide, the generated absorption liquid and the sulfur oxide salt are separated, and the separated absorption liquid is reused. And

  In the degraded absorbent regenerating method, it is desirable to add a weak alkaline substance or a solvent such as water to the separated absorbent to adjust the concentration of the weak alkaline substance contained in the reused absorbent.

  In the method for regenerating a deteriorated absorbent, the concentration of sulfur oxides is preferably detected by analyzing the deteriorated absorbent by liquid chromatography.

  In the deteriorated absorbent regenerating method, it is desirable to detect the concentration of sulfur oxide by analyzing the gas before contact with the absorbent and the gas after contact.

  In the deteriorated absorbent regenerating method, the sulfur oxide salt is preferably separated by a distillation method.

  In the degraded absorbent regenerating method, it is desirable that regeneration of the degraded absorbent is continuously performed simultaneously with the recovery of carbon dioxide.

  In the deterioration absorbing liquid regeneration method, the concentration of the sulfur oxide is changed by measuring the concentration of the sulfur oxide after the addition of each alkali agent when the alkali agent is added in a plurality of times. It is desirable to detect from.

  The deteriorated absorbent regenerating apparatus absorbs carbon dioxide contained in combustion exhaust gas by bringing it into contact with an absorbent having weak alkalinity and its solvent and exhibiting weak alkalinity, and recovers carbon dioxide from the absorbent. A carbon dioxide recovery device with a regeneration tower that regenerates the deteriorated absorbent produced by absorbing the sulfur oxide contained in the combustion exhaust gas, and detects the concentration of sulfur oxide contained in the deteriorated absorbent. A sulfur oxide concentration detecting unit, a first liquid feeding unit for extracting a part of the deteriorated absorbent from the absorption tower or the regeneration tower, and an alkali agent having a higher hydrogen ion concentration than the absorbing liquid. The alkali agent mixing part to be mixed with the deteriorated absorption liquid sent from, the separation part for separating the absorption liquid produced in the alkali agent mixing part and the salt of sulfur oxide, and the absorption liquid separated in this separation part Sent to absorption tower or regeneration tower A second liquid supply portion, characterized in that the amount of alkaline agent to be mixed with an alkaline agent mixing section and a control section for calculating the concentration of sulfur oxides.

  The degraded absorbent regenerating apparatus preferably further includes a concentration adjusting unit that adds a weak alkaline substance or a solvent to the absorbent separated by the separation unit.

  In the deteriorated absorbent regenerating apparatus, the sulfur oxide concentration detector is preferably a liquid chromatograph for analyzing the deteriorated absorbent.

  In the deteriorated absorbent regenerating apparatus, the sulfur oxide concentration detector is preferably a gas chromatograph for analyzing the gas at the inlet and outlet of the absorption tower.

  In the deteriorated absorbent regenerating apparatus, the separation unit is preferably an evaporator that distills the deteriorated absorbent mixed with an alkaline agent.

  In the deteriorated absorbent regenerating apparatus, it is desirable that the control unit adjusts the flow rates of the first liquid feeding unit and the second liquid feeding unit to be equal.

  In the deteriorated absorbent regenerator, the alkaline agent mixing section is preferably a static mixer.

  The carbon dioxide recovery system includes a carbon dioxide recovery device and a deteriorated absorbent regenerating device.

  Hereinafter, a combination of a carbon dioxide recovery device using an aqueous amine solution and an aqueous amine solution regeneration device will be described. In the following embodiment, an example in which carbon dioxide is recovered from exhaust gas from a pulverized coal-fired boiler is shown, but the type of exhaust gas is not limited to that from a boiler, and may be a gas containing carbon dioxide. That's fine.

  FIG. 1 shows a schematic configuration of a carbon dioxide separation / recovery system.

In this figure, a carbon dioxide separation / recovery system (also referred to as a carbon dioxide recovery system) includes a CO ₂ recovery device 20 and an absorbent regenerator 30 (also referred to as a deteriorated absorbent regenerator). CO ₂ recovery unit 20, compression to liquefy the absorption liquid 102 absorption tower 5 that absorbs CO ₂ using a regeneration column 8 CO ₂ from the absorbing solution 104 having absorbed elimination of CO _2, CO ₂ desorbed Including machine 4 etc. The absorbent regenerator 30 also includes a mixing tank 15 (alkaline agent mixing unit), an alkaline agent preparation tank 11, an evaporator 17 (separation unit), a condensate tank 12 and the like for extracting and storing the deteriorated absorbent 102. Including.

The flue gas 1 generated in the pulverized coal fired boiler enters a desulfurizer 3 for removing sulfur oxide (SOx) through a denitration device for removing nitrogen oxides (NOx) and a dust collector for removing soot dust. The flue gas 101 that has passed through the desulfurization device 3 is introduced into the CO ₂ recovery device 20.

In the CO ₂ recovery device 20, the combustion exhaust gas 101 that has passed through the desulfurization device 3 is guided to the absorption tower 5. The combustion exhaust gas 101 is in gas-liquid contact with the CO ₂ absorption liquid 102, and CO ₂ contained in the combustion exhaust gas 101 is absorbed. As the absorbing liquid 102, for example, an aqueous amine solution is suitable.

The exhaust gas 103 from which CO ₂ has been removed by the absorption tower 5 is discharged from the chimney 7. On the other hand, the absorption liquid 102 that has absorbed CO ₂ is heated to a temperature that releases CO ₂ in a liquid-liquid heat exchanger 6, is led to the regenerator 8, and desorbs CO _2. The absorption liquid 104 from which CO ₂ has been desorbed by the regeneration tower 8 is cooled by the liquid-liquid heat exchanger 6 and guided to the absorption tower 5.

In this way, by configuring the absorption liquids 102 and 104 to circulate between the absorption tower 5 and the regeneration tower 8, absorption and desorption of CO ₂ can be repeated.

The absorbing liquids 102 and 104 need to be at a low temperature when absorbing CO ₂ and at a high temperature when desorbing CO ₂ . The liquid-liquid heat exchanger 6 makes effective use of thermal energy for this temperature difference. Further, the absorption temperature and desorption temperature of CO ₂ have optimum temperatures depending on the types of the absorbing liquids 102 and 104. Although not shown, a heater or a cooler is additionally provided to efficiently absorb CO ₂ . -Detach.

Since the gas 105 containing CO ₂ desorbed in the regeneration tower 8 also contains water vapor, the gas 105 is dehumidified by the cooler 9 and then compressed by the compressor 4 to be contained in the gas 106. liquefying CO _2.

  When a gas containing SOx comes into contact with the absorbing liquid 102, SOx is absorbed by the absorbing liquid 102, and the amine and SOx contained in the absorbing liquid 102 react to generate a stable salt. This salt is called HSS (Heat Stable Salt). Since SOx contained in the combustion exhaust gas 1 removes most of the SOx by the desulfurization apparatus 3, the SOx mixed in the absorbing liquids 102 and 104 is a relatively small amount, but the absorbing liquids 102 and 104 are used for carbon dioxide recovery. Because of being repeatedly used, it gradually accumulates as HSS.

When CO ₂ is absorbed by the absorbing liquid 102, it reacts with the amine. CO ₂ is desorbed by heating the absorbing liquid 102, but SOx is not desorbed at the CO ₂ desorption temperature. Since the absorption liquids 102 and 104 are used after being circulated, the HSS generated in the absorption liquid 102 is accumulated in the absorption liquids 102 and 104. As the amount of HSS increases, the CO ₂ absorption performance decreases.

Hereinafter, the absorbing liquids 102 and 104 in which the CO ₂ absorbing performance is lowered are referred to as deteriorated absorbing liquids. In the present embodiment, the deterioration absorbing liquid is described as being a deteriorated amine aqueous solution, but the deterioration absorbing liquid is not limited to this.

In order to regenerate the degraded absorbent, first, an alkaline agent is added to the degraded absorbent and the SOx content is separated from the HSS. Examples of the alkaline agent include sodium carbonate (Na ₂ CO ₃ ).

When an alkaline agent is added to the deterioration absorbing solution, the amine contained in the deterioration absorbing solution is regenerated, but Na ions (Na ⁺ ) and SO ₄ ions (SO ₄ ²⁻ ) remain as impurities in the deterioration absorbing solution. Therefore, it is necessary to remove these impurities. Examples of the removing method include a distillation method, an electrodialysis method, and an ion exchange resin method.

The distillation method is a method in which water and amine are evaporated, Na ions and SO ₄ ions are reacted, and Na ₂ SO _{4 and the} like are precipitated and removed.

The electrodialysis method collects Na ions and SO ₄ ions in a region partitioned by an ion exchange membrane by applying a voltage to the solution and selectively allowing Na ions and SO ₄ ions to pass through the ion exchange membrane. It is a method to remove.

The ion exchange membrane method is a method in which Na ions and SO ₄ ions are adsorbed and removed from the ion exchange membrane.

  In the present embodiment, description will be made using a distillation method, but an electrodialysis method or an ion exchange membrane method may be applied.

In the absorbent regenerator 30, the absorbent 102 (deteriorated absorbent) is extracted from the absorption tower 5 of the CO ₂ recovery device 20 by the liquid feed pump 32 (first liquid feed section) and stored in the mixing tank 15. An alkaline aqueous solution is added to the mixing tank 15 from the alkaline agent preparation tank 11, and SOx is separated from HSS to produce an amine. The amount of the alkaline aqueous solution added is controlled by adjusting the opening of the valve 36. Depending on the type of the alkaline aqueous solution, the reaction for separating SOx from HSS is slow, so that by providing the mixing tank 15, the reaction can be made uniform by stirring or the like, and the residence time can be increased. Thereby, the usage-amount of the alkaline agent to add can be suppressed.

  The liquid obtained by separating the SOx component from the HSS in the mixing tank 15 is guided to the evaporator 17 by the liquid feed pump 33 and heated using the heat of the steam 16. The residue (concentrated liquid) precipitated by evaporation of water and amine is discharged from the extraction pipe 18. On the other hand, the evaporated water and amine are condensed in the gas cooler 19 and stored in the condensate tank 12.

In the condensate tank 12, amine concentration is adjusted by supplying amine 13 and water 14. That is, the condensate tank 12 is a concentration adjusting unit. The liquid in the condensate tank 12 is reused by returning it to the regeneration tower 8 of the CO ₂ recovery device 20 via the liquid feed pump 34 (second liquid feed section).

In the step of adding an alkaline aqueous solution to HSS and separating SOx in HSS, if the amount of alkali agent added is excessive, the amount of precipitates increases. For example, the use of Na ₂ CO _3, other Na ₂ SO ₄ as a precipitate, Na ₂ CO ₃ is also precipitated. Therefore, the alkali agent may be added in a necessary amount, and if it is too much, it becomes excessive and wastes the alkali agent. In order to solve this problem, it is important to control the amount of alkali agent added.

  FIG. 2 shows a deteriorated absorbent regenerating part (absorbing liquid regenerating apparatus 30 in FIG. 1) provided with a controller for adjusting the amount of alkali agent added.

  As shown in this figure, the deteriorated absorbent regenerating part is composed of a mixing tank 15, an evaporator 17, a condensate tank 12, and the like. The liquid feed pump 32 feeds the deteriorated absorbent (the absorbent 102 in FIG. 1) from the absorption tower 5 in FIG. 1 to the mixing tank 15. The liquid feed pump 33 feeds the deteriorated absorbent mixed with the alkaline agent in the alkaline agent preparation tank 11 from the mixing tank 15 to the evaporator 17. The water and amine evaporated by heating in the evaporator 17 are condensed in the gas cooler 19 and stored in the condensate tank 12.

  In the drawing, a liquid collection unit 35 and a liquid level sensor 37 are provided inside the mixing tank 15. The liquid collection unit 35 collects the liquid (deterioration absorption liquid) in the mixing tank 15 and sends it to the HSS concentration measurement unit 151. The HSS concentration measurement unit 151 measures the concentration of HSS contained in the liquid. The concentration is converted into an electric signal and sent to the control unit 40. In this embodiment, the HSS concentration measurement unit 151 is a liquid chromatograph. The HSS concentration measuring unit 151 may measure SOx components such as sulfate ions and sulfite ions as a total amount. Here, the liquid collection unit 35 and the HSS concentration measurement unit 151 are collectively referred to as a sulfur oxide concentration detection unit.

  The control unit 40 calculates the required amount of alkali agent added from the electrical signal relating to this concentration, the liquid level of the mixing tank 15 measured by the liquid level sensor 37, etc., sends an opening / closing command to the valve 36, and determines the required amount. Added. These series of operations can be automated. Thereby, a required amount of an alkaline agent can be added.

  Hereinafter, matters related to the control unit 40 will be further described.

  The liquid level sensor 37 also sends a signal to the control unit 40 even when the deteriorated absorption liquid led to the mixing tank 15 by operating the liquid feed pump 32 reaches a predetermined liquid level. In this case, the control unit 40 stops the liquid feed pump 32. This can also be automated.

When the liquid feed pump 32 is operated, the absorbing liquids 102 and 104 (amine aqueous solution) used in the CO ₂ recovery device 20 of FIG. 1 are reduced, and thus the reduced absorbing liquids 102 and 104 need to be replenished from the condensate tank 12. There is. Since the amount of the deteriorated absorbing liquid extracted and the amount of the regenerating absorbing liquid to be supplemented can be calculated from the outputs of the liquid feeding pumps 32 and 34, the output signals of the liquid feeding pumps 32 and 34 are sent to the control unit 40. Thus, the number of revolutions of the liquid feed pumps 32 and 34 can be automatically controlled.

The condensate tank 12 stores water and amine evaporated by the evaporator 17 and condensed by the gas cooler 19, and the composition of amine and water in the condensate is a composition required for the CO ₂ recovery device. Is not necessarily the same. For this reason, the amine 13 and the water 14 can be supplied to the condensate tank 12, and the composition of the condensate can be adjusted.

  A necessary amount of an alkaline agent is added to the deterioration absorbing liquid in the mixing tank 15 and the SOx component is desorbed from the HSS, and then the liquid feed pump 33 is operated to guide the liquid in the mixing tank 15 to the evaporator 17. When the liquid in the mixing tank 15 falls below a predetermined liquid level, the liquid feed pump 33 is stopped, and the liquid feed pump 32 is operated again to introduce the deteriorated absorption liquid to the mixing tank 15. Regenerate the degraded absorbent by operation.

  It is desirable that the liquid discharge flow rates of the liquid feed pumps 32, 33, and 34 are the same. Thereby, the amount of the absorbing liquid in the mixing tank 15, the evaporator 17 and the condensate tank 12 is kept constant, and a stable operation can be realized.

By realizing stable operation as described above, it becomes possible to operate simultaneously with the CO ₂ recovery device 20 of FIG. The capacities of the mixing tank 15, the evaporator 17 and the condensate tank 12 may be designed according to the regeneration speed required for the deteriorated absorbent, and are not limited to the operation during the stop period of the CO ₂ recovery device 20. For this reason, the capacities of the mixing tank 15, the evaporator 17 and the condensate tank 12 can be reduced as compared with the case where the capacity is operated only during the stop period.

In the case of Example 1, the CO ₂ recovery device 20 in FIG. 1 is a continuous operation. On the other hand, the absorbent regenerator 30 is basically a batch operation. This is because the amount of the SOx component accumulated in the absorbing liquids 102 and 104 in FIG. 1 is much smaller than the CO ₂ treatment amount. Therefore, in this embodiment, a configuration in which the absorbent regenerator 30 is also operated continuously is shown.

FIG. 3 shows a configuration in which the CO ₂ recovery device 20 and the absorbent regenerator 30 of FIG. 1 are continuously operated.

In order to continuously operate the CO ₂ recovery device 20 and the absorbent regenerator 30 of FIG. 1 simultaneously, it is necessary to continuously measure the HSS concentration in the CO ₂ recovery device 20.

  Therefore, in this figure, the liquid sampling part 35 is installed in the lower part of the regeneration tower 8, the stored absorption liquid 104 is sampled, and the HSS concentration is measured by the HSS concentration measuring part 151. In addition, the liquid collection | recovery part 35 may be installed in the lower part of the absorption tower 5, and may sample the absorbed liquid 102 stored. The HSS concentration measuring unit 151 of this embodiment is also a liquid chromatograph.

  In addition, a gas collection unit 301 that collects a part of the combustion exhaust gas 1 (gas at the inlet of the absorption tower 5) sent to the absorption tower 5 and a gas (outlet part of the absorption tower 5) that is sent from the absorption tower 5 to the chimney 7 The concentration of SOx is measured by a gas analysis unit 302 such as a gas chromatograph using a gas sampling unit 303 that collects a part of the gas), and the HSS concentration (sulfur oxide concentration) of the absorbing liquid 102 is determined from the concentration difference. ) May be calculated.

  In this figure, the absorption liquid 104 of the regeneration tower 8 is guided to the static mixer 38 (alkaline agent mixing section) by the liquid feed pump 32 and mixed with the alkaline agent sent from the alkaline agent preparation tank 11 by the liquid feed pump 33. It has become. The liquid exiting the static mixer 38 is guided to the evaporator 17. In addition, the structure of the evaporator 17 and the condensate tank 12 in this figure is the same as that of Example 1. FIG.

Here, the flow rate of the absorbing liquid 104 extracted from the regeneration tower 8 by the liquid feeding pump 32 is referred to as a deteriorated absorbing liquid extraction flow rate F _HSS . The flow rate of the alkaline agent sent from the alkaline agent preparation tank 11 by the liquid feed pump 33 is referred to as an alkaline aqueous solution flow rate _FOH .

  The concentration signal obtained by the HSS concentration measuring unit 35 is taken into the control unit 40, the required amount of alkali agent added is calculated, and the control unit 40 feeds the deterioration absorbing liquid (absorbing liquid 104) and the alkaline aqueous solution 32. The power of the liquid feed pump 33 is controlled. The continuous supply flow rates of the deterioration absorbing liquid and the alkaline aqueous solution are controlled by power control of the liquid feed pumps 32 and 33.

By extracting the deteriorated absorption liquid, the absorption liquid in the CO ₂ recovery device 20 is reduced, and the reduced amount is replenished from the condensate tank 12 via the liquid feed pump 34. Control of the amount of the deteriorated absorbent extracted and the amount of absorbent to be replenished is automated by the control unit 40.

Here, the regenerated absorbent replenishing flow rate F _A sent from the condensate tank 12 by the liquid feed pump 34 is referred to.

  The deterioration absorbing liquid and the alkaline aqueous solution were introduced into the static mixer 38 and mixed. In Example 2, the mixing tank was used. However, in the case of using an alkaline agent that rapidly removes SOx from HSS, a static mixer can be used, and the volume of the mixing unit can be reduced.

Next, the procedure for continuous operation of the CO ₂ recovery device 20 and the absorbent regenerator 30 of FIG. 1 will be described.

FIG. 4 is a flowchart showing the steps of continuous operation of the CO ₂ recovery device and the absorbent regenerator. The description of this figure is mainly based on the configuration of FIG.

In FIG. 4, the HSS concentration C _HSS of the absorbent 104 in the regeneration tower 8 constituting the CO ₂ recovery apparatus 20 of FIG. 1 is measured at regular time intervals (S401). When the concentration C _HSS becomes _equal to or higher than the prescribed C _HSS ^{* 1} , the absorbent regenerator 30 of FIG. 1 is operated (S402).

The three liquid feed pumps 32, 33, and 34 are activated (S403) so that the deteriorated absorbent extraction flow rate F _HSS and the regenerated absorbent replenishment flow rate F _A are the same (S404). Further, the alkaline aqueous solution flow rate F _OH is calculated from F _HSS and C _HSS and supplied (S405).

The evaporator 17 is heated after it reaches a prescribed liquid level so as not to be scooped (S406). Further, although not shown, it is desirable to have a function of controlling F _HSS and F _OH supplied in accordance with F _HSS so that the liquid level does not become too high.

While the absorbent regenerator is in operation, the regenerated absorbent is replenished in the CO ₂ recovery device, so the HSS concentration in the absorbent decreases. In order to regenerate the absorbing solution, energy for evaporating is required, and the regeneration processing when the HSS concentration is low uses useless energy.

Therefore, the HSS concentration C _HSS is measured at regular intervals while the absorbent regenerator is in operation (S407), and the absorption is performed when the concentration C _HSS falls below the specified C _HSS ^{* 2} (S408). It is desirable to perform an operation (S409) for stopping the heating of the evaporator 17 of the liquid regenerating apparatus and a stop operation for the liquid feed pumps 32, 33, and 34.

  Hereinafter, a method for measuring the HSS concentration will be described.

The reaction in which HSS, that is, (R—NH ₂ ) ₂ SOx, is generated from amine (R—NH ₂ ) and sulfur oxide (SOx) contained in the absorbing solution is represented by the above reaction formula (1).

  Since S is included in HSS, it is only necessary to measure S part of HSS.

The reaction of adding an alkaline agent such as Na ₂ CO ₃ to HSS is represented by the above reaction formula (2).

In the reaction formula (2), SO ₄ ^2- is a sulfate ion, and this sulfate ion may be measured.

  The sulfate ion can be measured by ion chromatography or a method of passing through an adsorbent for exchanging anions and then washing and titrating with an acid.

  Any method may be used, but in this example, a method of measuring sulfate ions was adopted.

  FIG. 5 is a flowchart showing the analysis procedure of the sulfate ion concentration.

A fixed amount of absorbing liquid 104 (amine aqueous solution W _a ) is collected from the regeneration tower 8 of FIG. 3 (S501), and a certain amount of ΔW _{OH is} added to Na ₂ CO ₃ (S502). The amount of sulfate ion W _{SO4, t} generated at that time is measured (S503). If W _{SO4, t} is larger than the sulfate ion amount W _{SO4, t-1} in the measurement before this measurement, Na ₂ CO ₃ is added again by a certain amount ΔW _OH (S502), and W _{SO4, t} is measured (S503). . If W _{SO4, t} is equal to or lower than W _{SO4, t−1,} it is determined that the supply amount (addition amount) of the alkaline agent Na ₂ CO ₃ has reached the supply amount required for the absorbent 104 ( S505). Here, the cumulative amount of Na ₂ CO ₃ added repeatedly is defined as W _OH .

FIG. 6 is a graph showing the measurement result of the sulfate ion concentration. The horizontal axis represents the amount of Na ₂ CO ₃ supplied, and the vertical axis represents the amount of sulfate ions.

In this figure, as the amount of Na ₂ CO ₃ supplied to the collected absorbent 104 increases, the amount of sulfate ions increases. However, after reaching the stoichiometric ratio of Na ₂ CO ₃ supply, even if additional Na ₂ CO ₃ is supplied, the amount of sulfate ions hardly increases.

As can be seen from the reaction formula (2), the SOx content is separated from the HSS as the amount of Na ₂ CO ₃ added increases. Typically, the amount of sulfate ions increases.

In this figure, there is shown a Na ₂ CO ₃ amount of sulfate ion amount, and required in the aqueous amine solution W _a. The interval between the plotted Na ₂ CO ₃ amounts is equal to ΔW _OH in FIG. This interval is reduced, it is desirable to increase the accuracy of the amount of sulfate ions in the aqueous amine solution W _a.

Sulfate ion amount in the resulting aqueous amine solution W _a, and Na from the total amount W _OH of ₂ CO _3, the Na ₂ CO ₃ amount required per unit amine solution can be obtained by W _a / W _OH.

In the actual process, it is desirable to add supplying a large amount of Na ₂ CO ₃ than Na ₂ CO ₃ supply amount that is stoichiometric. This is because the reaction when Na ₂ CO ₃ is added to the absorbing liquid 104 does not always proceed uniformly in a short time, and the deterioration of the absorbing liquid 104 proceeds due to the remaining unreacted sulfur oxide. This is to suppress as much as possible.

  In the above embodiment, the SOx concentration is measured by a liquid chromatograph, but the present invention is not limited to this, and the gas at the inlet and outlet of the absorption tower is sampled and measured by gas analysis such as a gas chromatograph. It may be used for controlling a liquid feed pump or the like.

Further, in the above examples, an aqueous amine solution was used as the absorbing solution, but the present invention is not limited to this, and a CO ₂ absorbing solution that exhibits weak alkalinity including a weakly alkaline substance and its solvent. Applicable if available. The weak alkaline substance preferably has a lower pH than an alkaline agent such as Na ₂ CO ₃ . Moreover, it is desirable that this weakly alkaline substance has a lower boiling point than the alkaline agent.

  An anion containing sulfur generated when a sulfur oxide is dissolved in a solvent such as water and a cation generated when an alkaline agent is dissolved in a solvent such as water are combined to form when the solvent is evaporated. The salt will be referred to as a sulfur oxide salt.

1: combustion exhaust gas, 3: desulfurizer, 4: compressor, 5: absorption tower, 6: liquid-liquid heat exchanger, 7: chimney, 8: regeneration tower, 9: cooler, 11: alkaline agent preparation tank, 12 : condensate tank 13: amine, 14: water, 15: mixing tank, 16: steam, 17: evaporator, 18: extraction tube, 19: gas cooler, 20: CO ₂ recovery apparatus, 30: absorbing liquid Regenerating apparatus, 32, 33, 34: liquid feed pump, 35: liquid sampling part, 36: valve, 37: liquid level sensor, 38: static mixer, 40: control part, 102, 104: absorbing liquid, 151: HSS Concentration measuring unit, 301, 303: gas sampling unit, 302: gas analyzing unit.

Claims (15)

  Deterioration caused by absorption of sulfur oxides contained in the combustion exhaust gas when the carbon dioxide contained in the combustion exhaust gas is recovered using an absorption liquid that includes a weak alkaline substance and its solvent and exhibits weak alkalinity. A method of regenerating an absorbing solution, wherein the concentration of the sulfur oxide contained in the deteriorated absorbing solution is detected, a part of the deteriorated absorbing solution is extracted, and an alkaline agent having a higher hydrogen ion concentration than the absorbing solution is extracted. An amount calculated from the concentration is mixed with the extracted deteriorated absorbent, and the produced absorbent and the salt of the sulfur oxide are separated, and the separated absorbent is reused. A method for regenerating a deteriorated absorbent.   2. The deteriorated absorbing liquid regeneration according to claim 1, wherein the weakly alkaline substance or the solvent is added to the separated absorbing liquid to adjust the concentration of the weakly alkaline substance contained in the absorbing liquid to be reused. Method.   The method for regenerating a deteriorated absorbent according to claim 1 or 2, wherein the concentration of the sulfur oxide is detected by analyzing the deteriorated absorbent by liquid chromatography.   The method for regenerating a deteriorated absorbent according to claim 1 or 2, wherein the concentration of the sulfur oxide is detected by analyzing a gas before contact with the absorbent and a gas after contact with the absorbent.   The deterioration absorbing liquid regeneration method according to any one of claims 1 to 4, wherein the salt is separated by a distillation method.   The method for regenerating a deteriorated absorbent according to any one of claims 1 to 5, wherein the regeneration of the deteriorated absorbent is continuously performed simultaneously with the recovery of the carbon dioxide.   The concentration is detected from the amount of change by measuring the concentration after the addition of each alkaline agent when the alkaline agent is added in a plurality of times. The method for regenerating a deteriorated absorbent according to any one of claims 6 to 7.   Carbon dioxide contained in the combustion exhaust gas is absorbed in contact with an absorbing liquid that exhibits weak alkalinity including a weak alkaline substance and its solvent, and a carbon dioxide having a regeneration tower that recovers the carbon dioxide from the absorbing liquid. A device that regenerates a deteriorated absorbent produced by absorbing the sulfur oxide contained in the combustion exhaust gas in the carbon recovery device, and detects the concentration of the sulfur oxide contained in the deteriorated absorbent. An oxide concentration detector, a first liquid delivery unit for extracting a part of the deteriorated absorbent from the absorption tower or the regeneration tower, and an alkaline agent having a higher hydrogen ion concentration than the absorbent. An alkaline agent mixing part to be mixed with the deteriorated absorption liquid sent from the liquid feeding part, a separation part for separating the absorption liquid produced in the alkaline agent mixing part and the salt of the sulfur oxide, and Separated A second liquid feeding section for sending the absorption liquid to the absorption tower or the regeneration tower; and a control section for calculating the amount of the alkali agent mixed in the alkali agent mixing section from the concentration. A deteriorated absorbent regenerator.   9. The deteriorated absorbent regenerating apparatus according to claim 8, further comprising a concentration adjusting unit for adding the weakly alkaline substance or the solvent to the absorbent separated by the separation unit.   The deteriorated absorbent regenerating apparatus according to claim 8 or 9, wherein the sulfur oxide concentration detector is a liquid chromatograph for analyzing the deteriorated absorbent.   The deteriorated absorbent regenerating apparatus according to claim 8 or 9, wherein the sulfur oxide concentration detector is a gas chromatograph for analyzing a gas at an inlet and an outlet of the absorption tower.   The deteriorated absorbent regenerating apparatus according to any one of claims 8 to 11, wherein the separation unit is an evaporator that performs distillation of the deteriorated absorbent mixed with the alkaline agent.   The deterioration absorbing liquid according to any one of claims 8 to 12, wherein the control unit adjusts the flow rates of the first liquid feeding unit and the second liquid feeding unit to be equal. Playback device.   The deteriorated absorbent regenerating apparatus according to any one of claims 8 to 13, wherein the alkaline agent mixing section is a static mixer.   A carbon dioxide recovery system comprising the carbon dioxide recovery device and the deteriorated absorbent regenerating device according to any one of claims 8 to 14.

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