JP7324159B2 - Acid gas removal device and removal method - Google Patents

Description

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

Carbon dioxide capture and storage technology (CCS) has been attracting attention as one of the effective measures against global warming. In particular, the use of CCS equipment for facilities that generate a large amount of carbon dioxide gas (for example, thermal power plants, ironworks, and cement plants) is being studied all over the world.

One CCS facility is a chemical absorption method in which carbon dioxide-containing exhaust gas is brought into contact with an absorption solvent to separate and recover carbon dioxide. Although this is a common CCS process, silicone oil, amine-based solutions, ionic solutions, etc. are often employed as absorption solvents (Patent Document 1).

In general, the composition of exhaust gas varies greatly depending on the medium through which the exhaust gas is emitted and the raw material that produces the exhaust gas. Mercury contained in can be roughly divided into Hg (zero valence) and Hg (II valence).
In recent years, there has been a strong demand for the prevention of environmental pollution caused by mercury, and in 2017, the Minamata Convention on Mercury came into effect.

Japanese Patent No. 4274846

When trying to remove acid gas from flue gas containing mercury as described above, mercury may also be absorbed by the acid gas absorbing solvent, resulting in oxidation (decomposition) of the absorbing solvent and acid gas. In some cases, the performance of the absorbing solvent deteriorated, and it became impossible to effectively separate and recover the acid gas in the exhaust gas.

In the process of desorbing the acid gas from the solvent that has absorbed the acid gas, the mercury that was absorbed in the solvent is also desorbed, and the obtained acid gas (for example, product carbon dioxide gas) may contain mercury. As a result, there are problems such as the impact on the environment and the decrease in the purity of the acid gas, which lowers the value of the product.

The present inventors conducted a laboratory test to verify how much mercury contained in exhaust gas is separated into an amine absorbing solvent in the absorption tower and recovered in the regeneration tower. As a result, (1) Hg (0 valence) is difficult to be absorbed by the amine absorption liquid, (2) Hg (II valence) is absorbed by the amine absorption liquid, but is then reduced to 0 valence by the amine, At the same time, it was confirmed that the amine was oxidized.

In the present invention, attention is paid to Hg (II value) contained in the carbon dioxide-containing exhaust gas. First, the primary object is to reduce Hg (II valence) to zero valence before entering an acid gas such as a CCS facility, etc., to prevent Hg (II valence) from being absorbed in the absorption tower. The second purpose of this is to suppress the oxidation (deterioration) of the absorbing solvent circulating in the CCS facility. A third object is to reduce the amount of mercury contained in the carbon dioxide gas (product carbon dioxide gas) at the outlet of the regeneration tower.

Accordingly, an acid gas removal apparatus according to an embodiment of the present invention includes:
a mercury reducer that reduces divalent mercury contained in the exhaust gas by contacting the exhaust gas containing acid gas and mercury with the mercury reducing solution;
an absorber that causes an acidic gas absorption solvent to absorb the acidic gas contained in the gas derived from the mercury reducer;
a regenerator for desorbing the acidic gas from the acidic gas-absorbing solvent that has absorbed the acidic gas and regenerating the acidic gas-absorbing solvent;
It is characterized in that the acidic gas absorbing solvent regenerated in the regenerator is reused in the absorber.

Then, the method for removing acid gas according to an embodiment of the present invention comprises:
a reducing step of reducing divalent mercury contained in the exhaust gas by contacting the exhaust gas containing acid gas and mercury with a mercury reducing solution;
an absorption step of absorbing the acidic gas contained in the gas derived from the mercury reducer into an acidic gas absorbing solvent;
a regeneration step of desorbing the acidic gas from the acidic gas absorbing solvent that has absorbed the acidic gas to regenerate the acidic gas absorbing solvent;
It is characterized by comprising a step of reusing the acidic gas absorbing solvent regenerated in the regenerator in the absorber.

According to the acidic gas removing apparatus and the acidic gas removing method according to the embodiment of the present invention, since the mercury (II valence) contained in the exhaust gas is reduced in the mercury reducer, the absorber of the acidic gas removing apparatus The introduction or absorption of mercury, which is harmful and causes deterioration of the performance of the absorbing solvent, is effectively suppressed in other acid gas removing devices, acid gas absorbing solvents, and the like.

Therefore, when removing or recovering acid gas such as carbon dioxide capture and storage technology (CCS), deterioration suppression of acid gas absorption solvent, improvement of removal / recovery efficiency of acid gas, stabilization, improvement of durability, It is possible to reduce maintenance costs. In addition, it is possible to effectively prevent mercury from being diffused into the environment from the acid gas remover.

The mercury reducing solution used for the mercury reduction can be easily obtained from the acid gas removing apparatus in operation. In addition, since the acidic gas absorbing solvent that has been used and deteriorated in the acidic gas removing apparatus can also be used, it becomes possible to effectively utilize the solvent that has conventionally been disposed of as a mercury reducing solution.

BRIEF DESCRIPTION OF THE DRAWINGS The drawing which shows the outline|summary of the removal apparatus of the acidic gas by embodiment of this invention. Drawing which shows Hg (II value) content change in an acidic gas absorption solvent.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described based on embodiments with reference to the drawings.
It should be noted that the present invention is not limited to the following embodiments as they are, and can be embodied by modifying constituent elements without departing from the gist of the present invention at the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the following embodiments. For example, some components can be deleted from all components shown in the embodiments. Further, elements across different embodiments may be combined as appropriate.
BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as necessary.

<Equipment for removing acid gas>
FIG. 1 is a drawing showing an outline of an acid gas removing apparatus according to an embodiment of the present invention.
An acid gas removal apparatus according to an embodiment of the present invention, as shown in FIG.
a mercury reducer 101 that reduces divalent mercury contained in the exhaust gas by contacting the exhaust gas containing acid gas and mercury with the mercury reducing solution;
an absorber 1 for absorbing acidic gas contained in the gas derived from the mercury reducer 101 in an acidic gas absorbing solvent;
a regenerator 9 for desorbing the acidic gas from the acidic gas absorbing solvent that has absorbed the acidic gas and regenerating the acidic gas absorbing solvent;
It is characterized in that the acidic gas absorbing solvent regenerated in the regenerator 19 is reused in the absorber 1 .

More particularly, a preferred acid gas removal apparatus according to embodiments of the present invention, as shown in FIG.
a mercury reducer 101 that reduces mercury (II valence) contained in exhaust gas 102 containing acid gas and mercury;
An absorber that removes acid gas from the exhaust gas containing acid gas and mercury by causing the acid gas absorption solvent 2 to absorb the acid gas by contacting the exhaust gas 3 containing acid gas and mercury with the acid gas absorption solvent 4. 1 and
a regenerator 9 for desorbing the acid gas from the acid gas-containing absorption solvent 6 that has absorbed the acid gas and regenerating the acid gas-containing absorption solvent 6, wherein the acid gas regenerated by the regenerator 9. The absorption solvent 5 is configured to be reused in the absorber 1 .

An exhaust gas 102 containing acid gas and mercury is introduced into a mercury reducer 101, contacts a mercury reducing solution 103 in the mercury reducer 101, and mercury (II valent) in the exhaust gas 102 is reduced. The mercury reducing liquid 103 that has come into contact with the exhaust gas 102 in the mercury reducer 101 is taken out from the lower part of the mercury reducer 101 and then introduced into the mercury reducer 101 from the upper part of the mercury reducer 101 by the mercury reducing liquid transfer pump 104 . and circulated inside the mercury reducer 101 so as to come into contact with the exhaust gas containing acid gas and mercury again.

Between the mercury reducer 101 and the absorber 1, a mercury measuring instrument 107 for measuring the concentration of mercury (II value) on-line is arranged. is preferably provided with a mercury reducing solution inlet 106 for supplying the mercury reducing solution and/or a mercury reducing solution outlet 107 for discharging the mercury reducing solution in order to correct the concentration of the mercury reducing solution. In particular, using the measurement value of the mercury measuring instrument 107, the concentration of mercury (II value) contained in the exhaust gas containing acidic gas is measured online, and when the specified value is exceeded, the mercury reducing solution introduction port and / or the mercury It is preferable to correct the concentration of the mercury reducing solution by opening and closing the reducing solution outlet. As the mercury measuring instrument 107, it is preferable to use an atomic absorption spectrophotometer and an atomic fluorescence measuring instrument.

As the reducing liquid, one capable of reducing mercury (II valence) contained in the exhaust gas can be used, and preferably one containing, for example, an amine solvent, silicone oil, or an ionic liquid can be used. Among these, amine-based solvents are particularly preferred. Examples of the amine-based solvent include an acidic gas absorbing solvent.

In the embodiment of the present invention, when an amine-based solvent is used as the mercury reducing liquid, the amine-based solvent can be, for example, an acidic gas absorbing solvent employed in an acidic gas removal apparatus as shown in FIG. can. As such an acidic gas absorbing solvent, preferably, for example, (a) a condensate of the gas discharged from the absorber, (b) a condensate of the gas discharged from the regenerator, (c) the above ( Either one of (a) and (b) an acidic gas-absorbing solvent obtained from sources other than (b), or a mixed solvent of two or more of these can be used.

As the mercury reducing solution, a used acidic gas absorbing solvent whose performance or function as an acidic gas absorbing solvent has deteriorated as a result of being used in an acidic gas removing apparatus such as that shown in FIG. 1, for example, can be used. can be done.

As described above, in the acid gas removal device according to the embodiment of the present invention, the mercury reducing solution can be easily obtained from the acid gas removal device. In addition, in the embodiment of the present invention, it is possible to effectively utilize, as a mercury reducing solution, even an acidic gas absorbing solvent that has been discarded in the past due to its reduced performance or function as an acidic gas absorbing solvent.

In the acid gas removal apparatus according to the embodiment of the present invention shown in FIG. , is introduced into the absorber 1 from the bottom of the absorber 1 . This exhaust gas is introduced into the lower region of the absorber 1 and comes into contact with the absorption solvent 5 supplied from the upper part of the absorber 1 .

The pH value of the acidic gas-absorbing solvent may be adjusted to at least 9 or more, but it is preferable to appropriately select optimum conditions according to the type, concentration, flow rate, etc. of the harmful gas contained in the exhaust gas.

In addition to the above-mentioned amine compounds and solvents such as water, this absorption solvent contains other compounds such as nitrogen-containing compounds, antioxidants, pH adjusters, etc. that improve the absorption performance of carbon dioxide. can be contained in

In this manner, the exhaust gas containing the acidic gas contacts the acidic gas absorbing solvent inside the absorber 1, whereby the acidic gas in the exhaust gas is absorbed and removed by the absorbing solvent. The exhaust gas 4 from which the acid gas has been removed is cooled by the cooler 18 , separated into a liquid phase and a gas phase by the gas-liquid separator 19 , and the liquid phase portion is circulated to the absorber 1 . On the other hand, the gas phase portion is discharged to the outside of the acid gas remover.

The absorbing solvent 6 that has absorbed the acid gas in the absorber 1 is sent to the heat exchanger 8 by the transfer pump 7 , heated, and then sent to the regenerator 9 . The acidic gas-absorbing solvent introduced into the regenerator 9 moves from the top to the bottom in the regenerator 3, during which the acidic gas is desorbed from the acidic gas-absorbing solvent. The desorbed acid gas 10 is cooled by the cooler 15 and separated into a liquid phase and a gas phase by the gas-liquid separator 13 , and the liquid phase portion is circulated to the regenerator 9 using the transfer pump 12 . On the other hand, the gas phase portion is discharged to the outside of the acid gas remover.

The acidic gas-absorbing solvent regenerated in the regenerator 9 is sent to the heat exchanger 8 and the absorbent cooler 16 using the pump 17, circulated to the absorber 1, and is again converted to the acidic gas inside the absorber 1. used for the absorption of

A part of the acidic gas absorbing liquid led out from the regenerator 9 is heated in the reboiler 11 and then introduced into the regenerator 9 again. This allows the temperature inside the regenerator to be controlled.

FIG. 2 shows changes in Hg (II value) content in the acidic gas absorbing solvent. As shown in FIG. 2, when the mercury reducing solution was brought into contact with an acidic gas absorbing solvent containing Hg (II valence) for 30 minutes, the amount of mercury (II valence) in the acidic gas absorbing solvent was can be reduced to about 1/50 of that before contact.

<Method for removing acid gas>
A method for removing acid gases according to an embodiment of the present invention comprises:
a reduction step (step (a)) of reducing divalent mercury contained in the exhaust gas by contacting the exhaust gas containing acid gas and mercury with a mercury reducing solution;
an absorption step (step (b)) of absorbing the acidic gas contained in the gas discharged from the mercury reducer into an acidic gas absorbing solvent;
a regeneration step (step (c)) of regenerating the acidic gas absorbing solvent by desorbing the acidic gas from the acidic gas absorbing solvent that has absorbed the acidic gas;
It is characterized by comprising a step (step (d)) of reusing the acidic gas absorbing solvent regenerated in the regenerator in the absorber.

The acid gas removal method according to the embodiment of the present invention comprising the above steps (a) to (d) can preferably be carried out in the acid gas removal apparatus shown in FIG.

The contact between the exhaust gas containing acid gas and mercury and the mercury reducing solution is not particularly limited. A method of spraying mercury reducing solution into a stream of gas (atomization or spray method), or mixing acid gas and mercury-containing gas with mercury reducing solution in a reducer containing a porcelain or metal mesh filler. It can be carried out by a method of contacting the and in a countercurrent manner.

The temperature inside the mercury reducer 101 is preferably from room temperature to 60° C. or less. More preferably 50°C or less, particularly preferably 20 to 45°C. The lower the temperature, the less the absorption solvent is affected. The lower limit of the treatment temperature can be determined according to the gas temperature in the process, the heat recovery target, and the like. The pressure inside the mercury reducer 101 is generally approximately atmospheric pressure. Although it is possible to pressurize to a higher pressure in order to improve the reduction performance, it is preferable to carry out under atmospheric pressure in order to suppress the energy consumption required for compression.

In the absorber 1, the method of contacting the acid gas-containing gas with the acid gas absorbing solvent is not particularly limited. a method in which an acidic gas-absorbing solvent is atomized into a gas stream containing acidic gases (atomization or spray method), or a gas containing acidic gases in an absorber containing porcelain or metal mesh packing It can be carried out by, for example, a method of contacting the acidic gas absorbing solvent in counter current.

The temperature inside the absorber 1 is preferably from room temperature to 60° C. or less. More preferably 50°C or less, particularly preferably 20 to 45°C. The lower the temperature, the more acid gas is absorbed, but the lower limit of the treatment temperature can be determined according to the process gas temperature, heat recovery target, and the like. The pressure during acid gas absorption is usually about atmospheric pressure. Although it is possible to pressurize to a higher pressure in order to improve the absorption performance, it is preferable to carry out under atmospheric pressure in order to suppress the energy consumption required for compression.

In the regenerator 9, the temperature of the acidic gas absorbing solvent during the acidic gas separation is usually 70°C or higher, preferably 80°C or higher, more preferably 90 to 120°C. The higher the temperature, the greater the amount of desorbed acid gas, but the higher the temperature, the more energy required to heat the absorbent, so the temperature can be determined by the gas temperature in the process, the heat recovery target, and the like. The pressure at the time of desorbing the acid gas can usually be about 1 to 3 atmospheres. Although the pressure can be reduced to a lower pressure in order to improve the desorption performance, it is preferable to reduce the energy consumption required for the pressure reduction within this range.

The acidic gas-absorbing solvent after separating the acidic gas can be sent to the absorber 1 again and reused (recycled). Also, the heat generated during the absorption of acid gas is generally heat-exchanged and cooled by a heat exchanger for preheating the aqueous solution injected into the regenerator in the recycling process of the aqueous solution.

The purity of the acid gas recovered in this manner is usually as high as 99% by volume or more. This pure acidic gas or highly concentrated acidic gas can be used as a raw material for synthesizing chemicals or polymeric substances, a cooling agent for food freezing, and the like. In addition, it is also possible to isolate and store the recovered acid gas underground where technology is currently being developed.

Among the processes described above, the process of separating the acidic gas from the acidic gas absorbing solvent to regenerate the acidic gas absorbing solvent is the part that consumes the most energy, and this process accounts for about 50 to 80% of the total process. of energy may be consumed. Therefore, by reducing the energy consumption in the process of regenerating the acidic gas absorbing solvent, the cost of the process of absorbing and separating the acidic gas can be reduced, and the acidic gas can be economically removed from the exhaust gas.

The method for removing acid gas according to the embodiment of the present invention comprising the above steps (a) to (d) may further comprise other steps as required. Preferable specific examples of such other steps include, for example, a measuring step (step (e)) of measuring the mercury concentration in the gas derived from the mercury reducer 101; A control step (step (f)) of controlling the introduction of the mercury reducing solution into the reducer 101 can be mentioned.

The method for removing acid gas according to the embodiment of the present invention comprising such steps (a) to (f) includes, as shown in FIG. Using the installed mercury measuring instrument 107, the concentration of mercury (II value) contained in the exhaust gas containing acidic gas is measured online, and when the prescribed value is exceeded, the mercury reducing solution inlet and/or mercury reduction are automatically performed. It is preferable to correct the concentration of the mercury reducing solution by opening and closing the liquid outlet.

Mercury contained in exhaust gas discharged from coal-fired power generation is generally in the states of Hg (zero valence) and Hg (II valence). Of these, Hg (II valence) is reduced to Hg (0 valence) by the reducing power of the carbon dioxide absorbing solvent, but on the other hand, the carbon dioxide absorbing solvent oxidizes and decomposes, so it is an original function. Carbon dioxide absorption capacity decreases. However, if it is possible to reduce the Hg (II value) contained in the mercury-containing exhaust gas before it enters the absorber in which the carbon dioxide absorbing solvent circulates, it is convenient because the carbon dioxide absorbing solvent does not undergo oxidative decomposition. . For example, by circulating the carbon dioxide absorbing solvent that is no longer needed in the mercury reducer, the Hg (II valence) contained in the mercury-containing exhaust gas is reduced to Hg (0 valence). The carbon-absorbing solvent becomes less susceptible to oxidative decomposition. Then, since it changed to Hg (0 valence) before entering the absorber, it is difficult to be taken in by the carbon dioxide absorbing solvent circulating in the absorber, and the carbon dioxide-containing absorbing solvent after absorbing carbon dioxide is regenerated. There is no concern that mercury will accompany the carbon dioxide gas when the carbon dioxide gas is regenerated after being transferred to the regenerator, and the concentration of mercury contained in the carbon dioxide gas (product CO ₂ ) at the outlet of the regenerator is also reduced. Advantageously, the purity of the product _CO2 is also higher.

The mercury reducing liquid circulating in the mercury reducer provided in the front stage of the absorber is composed of the unnecessary carbon dioxide absorbing solvent, the unnecessary absorption tower outlet gas condensed water, and the unnecessary regeneration tower outlet. Gas condensate may be mentioned.

If the mercury reducing solution is continuously used, the mercury reducing solution itself is oxidized and deteriorated, resulting in a decrease in the mercury reducing ability. As a result, the oxidative influence on the carbon dioxide absorbing solvent circulating in the absorber increases over time. Therefore, it is desirable to control the concentration of Hg (II value) contained in the carbon dioxide-containing exhaust gas introduced into the absorber. Therefore, as shown in FIG. 1, a mercury measuring instrument 107 capable of online monitoring of the concentration of Hg (II value) is provided in the line through which the carbon dioxide-containing exhaust gas flows. When the arbitrarily set prescribed value of the mercury concentration is exceeded, it means that the reducing ability of the mercury reducing solution is lowered. For the replacement work, a sequence is set to control opening/closing of one or both of the mercury reducing solution introduction port 105 and the mercury reducing solution extraction port 106 that respond to opening/closing according to the output value of the mercury measuring instrument. As a result, since the mercury reducing solution is automatically replaced, the concentration of mercury contained in the carbon dioxide-containing exhaust gas can be controlled.

Examples of acid gases include carbon dioxide (CO ₂ ) contained in the exhaust gas, as well as acid gases such as hydrogen sulfide (H ₂ S) and carbonyl sulfide (COS). Typical examples of gases containing acid gases and mercury include gases containing carbon dioxide, such as flue gas emitted from thermal power plants and the like. As the acidic gas absorbing solvent, for example, when the acidic gas is carbon dioxide, it is preferable to use an amine compound, particularly preferably a solvent such as water, an amine-based solvent, silicone oil or an ionic liquid. can be used, and if necessary, a liquid absorbent containing auxiliary materials such as antioxidants and pH adjusters can be used.

In the reducer 101 for carrying out the step (a), the catalytic reduction method of the exhaust gas containing acid gas and mercury and the mercury reducing solution is preferably a packed bed method, a tray method, a wet scrubber method, or the like.

Although the acid gas removal apparatus and removal method according to several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, changes, or additions can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof. Further, the embodiments of the present invention are not limited to the mode in which only the mercury contained in the exhaust gas is removed or reduced, but other atoms or compounds, etc. are removed along with the mercury or modified to have less impact on the environment. It also includes the aspect to be done.

1: Absorber, 2: Absorber, 3: Carbon dioxide-containing exhaust gas, 4: Carbon dioxide-removing exhaust gas, 5: Lean solvent, 6: Rich solvent, 7: Rich liquid transfer pump, 8: Regenerative heat exchanger, 9: Regenerator 10: Regeneration unit 11: Reboiler 12: Regenerator condensed water transfer pump 13: Regenerator outlet separator 14: Carbon dioxide gas 15: Regenerator outlet gas cooler 16: Lean liquid cooler 17: lean liquid transfer pump, 18: absorber outlet gas cooler, 19: absorber outlet separator, 20: absorber outlet gas condensed water, 21: regenerator outlet gas condensed water, 101: mercury reducer, 102: mercury-containing exhaust gas, 103: Mercury reducing solution, 104: Mercury reducing solution transfer pump, 105: Mercury reducing solution inlet, 106: Mercury reducing solution outlet, 107: Mercury measuring instrument

Claims (6)

a mercury reducer that reduces divalent mercury contained in the exhaust gas by contacting the exhaust gas containing acid gas and mercury with the mercury reducing solution;
an absorber that causes an acidic gas absorption solvent to absorb the acidic gas contained in the gas derived from the mercury reducer;
a regenerator for desorbing the acidic gas from the acidic gas-absorbing solvent that has absorbed the acidic gas and regenerating the acidic gas-absorbing solvent;
An acidic gas removal apparatus for reusing the acidic gas absorbing solvent regenerated in the regenerator in the absorber,
The mercury reducing liquid is a condensate of the gas discharged from the absorber and/or a condensate of the gas discharged from the regenerator, an amine solvent, silicone oil and/or an ionic liquid. and an acid gas removal device. a mercury measuring instrument for measuring the mercury concentration in the gas derived from the mercury reducer; and referring to the mercury concentration measured by the mercury measuring instrument to control the introduction of the mercury reducing solution into the mercury reducer. 2. The acid gas removal apparatus of claim 1 , further comprising a controller. 3. The acid gas removing apparatus according to claim 2 , wherein said mercury meter is an atomic absorption spectrophotometer or an atomic fluorescence spectrometer. The acid gas remover according to any one of claims 1 to 3 , wherein the mercury reducer is of a packed bed type, tray type or wet scrubber type. a reducing step of reducing divalent mercury contained in the exhaust gas by contacting the exhaust gas containing acid gas and mercury with a mercury reducing solution;
an absorption step of absorbing the acidic gas contained in the gas derived from the mercury reducer into an acidic gas absorbing solvent;
a regeneration step of desorbing the acidic gas from the acidic gas absorbing solvent that has absorbed the acidic gas to regenerate the acidic gas absorbing solvent;
A method for removing acidic gases comprising a step of reusing the acidic gas absorbing solvent regenerated in the regenerator in the absorber,
The mercury reducing liquid is a condensate of gas derived from the absorption step and/or a condensate of gas derived from the regenerator, an amine solvent, silicone oil and/or an ionic liquid. and a method for removing acid gas. The method further comprises a measuring step of measuring the mercury concentration in the gas derived from the mercury reducer, and a control step of referring to the mercury concentration and controlling introduction of the mercury reducing liquid into the mercury reducer. Item 6. The method for removing acid gas according to item 5 .

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