JP2014205102A - Method and apparatus for recovering carbon dioxide in gas to be treated - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus capable of recovering carbon dioxide in a gas to be treated with high efficiency.SOLUTION: Carbon dioxide in a gas to be treated is recovered by a method comprising: a step (I) of obtaining a COrich absorption liquid by absorbing carbon dioxide in a COlean absorption liquid due to the contacting of the gas to be treated containing carbon dioxide to the COlean absorption liquid containing amines; a step (II) of reproducing the COrich absorption liquid obtained in the step (I) to the COlean absorption liquid by releasing carbon dioxide due to heating with steam of the COlean absorption liquid; a step (III) of obtaining steam by the flash evaporation of a part of the COlean absorption liquid reproduced in the step (II); and a step (IV) of supplying the steam of the COlean absorption liquid after increasing pressure while controlling to a proper temperature.

Description

  The present invention relates to a method and apparatus for recovering carbon dioxide in a gas to be processed with high efficiency by effectively utilizing heat generated by steam pressurizing means such as a blower.

Since the thermal power plant or the like to burn fossil fuels, carbon dioxide (CO ₂₎ a large amount occurs. Carbon dioxide is one of the causes of global warming, and the suppression of its emission is being promoted in each country. As a method for recovering carbon dioxide, a method using absorption of carbon dioxide by a liquid containing an amine such as alkanolamine (hereinafter sometimes referred to as an absorption liquid) is known (see, for example, Patent Document 1). ).

Absorption of carbon dioxide by the absorbing liquid is, as shown in FIG. 6, and a CO ₂ lean absorbing fluid which is showered from a gas to be treated 211 and nozzle 6 containing carbon dioxide is contacted countercurrently carbon dioxide CO ₂ lean Absorption tower 201 for obtaining CO ₂ rich absorption liquid (about 50-60 ° C) by absorbing it in the absorption liquid, and for regenerating CO ₂ lean absorption liquid by desorbing carbon dioxide from the CO ₂ rich absorption liquid An apparatus having at least a regeneration tower 213 and a heat exchanger 222 for heating the CO ₂ rich absorbent extracted from the absorption tower 201 with the CO ₂ lean absorbent (110 to 120 ° C.) extracted from the regeneration tower 213 Done in Since carbon dioxide is desorbed when the CO ₂ -rich absorbent is brought to a temperature range of 100 to 125 ° C., the regeneration tower 213 is heated by the steam supplied from the bottom of the regeneration tower (the steam of the absorbent evaporated by the reboiler 223). The The amount of heat supplied from the reboiler 223 is supplied by using a part of the power generation steam generated by the boiler (not shown). When the amount of water vapor used in the reboiler increases, the amount of water vapor used for power generation decreases. Therefore, various attempts have been made to reduce the amount of water vapor used in the reboiler from the viewpoint of power generation efficiency.

One method is to evaporate the high-temperature and high-pressure CO ₂ lean absorbent extracted from the lower part of the regeneration tower with a flash evaporator 216 to obtain steam, pressurize the steam with a blower 217, and supply the steam to the regeneration tower 213. Are known. Due to the pressurization by the blower 217, the steam temperature at the outlet of the blower may rise to nearly 200 ° C. In order to prevent overheating of the blower, measures are taken to suppress the steam temperature at the blower outlet to 140 ° C. or less by supplying cooling water to the cooling water line of the blower casing through the pipe 205 (see FIG. 6). Since the temperature of the cooling water that has passed through the cooling water line of the blower casing rises by about 30 ° C., it is cooled by a cooler or the like (not shown) and used again for cooling the blower.

Japanese Patent No. 3529855

In the conventional carbon dioxide recovery device, the blower casing is cooled with water to prevent overheating of the blower, but the heat generated in the blower is not used at all, and the thermal efficiency of the entire system is lowered.
An object of the present invention is to provide a method and apparatus for recovering carbon dioxide in a gas to be treated with high efficiency by effectively using heat generated by steam pressurizing means such as a blower. .

  As a result of studies to achieve the above object, the present inventors have completed the present invention including the following modes.

[1] Absorption tower for obtaining a CO ₂ rich absorption liquid by causing a CO ₂ lean absorption liquid to absorb CO ₂ into the CO ₂ lean absorption liquid by bringing the treated gas containing carbon dioxide into contact with the CO ₂ lean absorption liquid containing amines. ,
CO ₂ rich absorbent solution and a CO ₂ and steam of the lean absorption liquid is brought into contact countercurrently CO ₂ carbon dioxide from the rich absorbing liquid desorbed CO ₂ lean absorbent regenerator for regeneration,
A flash evaporator for evaporating a part of the CO ₂ lean absorption liquid regenerated in the regeneration tower to obtain steam, and the steam obtained in the flash evaporator by pressurizing while controlling the steam at an appropriate temperature The apparatus for collect | recovering the carbon dioxide in the to-be-processed gas which has a means to supply to.

[2] A means for pressurizing and supplying the steam obtained by the flash evaporator to the regeneration tower while controlling the steam at an appropriate temperature.
Recovering carbon dioxide in the gas to be treated according to [1], comprising means for adding water to the steam obtained by the flash evaporator, and means for pressurizing the steam added with water and supplying the steam to the regeneration tower Equipment for.
[3] The means for pressurizing and supplying the steam to the regeneration tower is provided with means for water cooling, and the water added to the steam is the water used in the water cooling means. [2] The apparatus for collect | recovering the carbon dioxide in the to-be-processed gas as described in any one of.
[4] There is a water washing tower for washing the treated gas from which carbon dioxide has been removed with water at the upper part of the absorption tower, and the water added to the steam is a part of the water used in the water washing tower [2] or [3] An apparatus for recovering carbon dioxide in the gas to be treated.
[5] A cooler for condensing water accompanying carbon dioxide desorbed at the top of the regeneration tower is attached, and the water added to the steam is part of the water condensed by the cooler [2] or [3] An apparatus for recovering carbon dioxide in the gas to be treated.

[6] A process of obtaining a CO ₂ rich absorbent by bringing a gas to be treated containing carbon dioxide into contact with a CO ₂ lean absorbent containing amines to absorb carbon dioxide in the CO ₂ lean absorbent (I) ,
A step (II) of regenerating the CO ₂ lean absorbing liquid by heating the CO ₂ rich absorbing liquid obtained in step (I) with the vapor of the CO ₂ lean absorbing liquid to desorb carbon dioxide;
A step (III) of obtaining a vapor by flash evaporation of a part of the CO ₂ lean absorbent regenerated in the step (II);
A process (IV) in which the vapor of the CO ₂ lean absorbent obtained in the process (III) is pressurized and supplied to the process (II) while being controlled at an appropriate temperature.
A method for recovering carbon dioxide in a gas to be treated.

[7] Step (IV)
Step (IV-1) of adding water to the steam of the CO ₂ lean absorbent obtained in step (III), and step of supplying pressurized steam to the step (II) (IV-2)
The method for recovering carbon dioxide in the gas to be treated according to [6].
[8] The method further includes a step (V) of washing the gas to be treated from which carbon dioxide has been removed in step (I) with water, and the water added in step (IV-1) is used in step (V). The method for recovering carbon dioxide in the gas to be treated according to [7], which is a part of water.
[9] The method further comprises a step (VI) of condensing water accompanying the carbon dioxide desorbed in the step (II), and the water added in the step (IV-1) is agglomerated in the step (VI). The method for recovering carbon dioxide in the gas to be treated according to [7], which is a part of the process.

  According to the apparatus and method of the present invention, the outlet steam temperature of the steam pressurizing means can be controlled efficiently, and heat can be supplied to the regeneration tower with high efficiency. In one embodiment of the present invention, water circulating in the carbon dioxide recovery device such as flush water of the gas to be treated from which carbon dioxide has been removed by the absorption tower and condensed water accompanying the carbon dioxide desorbed by the regeneration tower is used. Since it is used to control the steam temperature at the outlet of the steam pressurization means, the heat generated by the steam pressurization means can be recovered without disrupting the material balance in the carbon dioxide recovery device, and can be supplied to the regeneration tower. .

It is a figure showing the outline of the carbon dioxide recovery device concerning a first embodiment of the present invention. It is a figure which shows the outline | summary of the carbon dioxide recovery apparatus which concerns on 2nd embodiment of this invention. It is a figure which shows the outline | summary of the carbon dioxide collection apparatus which concerns on 3rd embodiment of this invention. It is a figure which shows the outline | summary of the carbon dioxide recovery apparatus which concerns on 4th embodiment of this invention. It is a figure which shows the outline | summary of the carbon dioxide recovery apparatus which concerns on 5th embodiment of this invention. It is a figure which shows the outline | summary of the carbon dioxide recovery apparatus of a prior art.

A method for recovering carbon dioxide in a gas to be treated according to an embodiment of the present invention comprises contacting a gas to be treated containing carbon dioxide with a CO ₂ lean absorbing solution containing amines to convert the carbon dioxide into CO ₂ lean. It is absorbed in the absorbing liquid, to obtain a CO ₂ rich absorbent solution (I), so step the CO ₂ rich absorbent solution obtained in (I) was heated on a steam of CO ₂ lean absorbing liquid carbon dioxide desorbed by obtained in the step of reproducing the CO ₂ lean absorbing solution Te (II), step a portion of the CO ₂ lean absorbing solution regenerated in (II) was flash evaporated to obtain a vapor step (III), the step (III) In addition, there is a step (IV) in which the vapor of the CO ₂ lean absorbent is pressurized and supplied to the step (II) while being controlled at an appropriate temperature.

  Here, examples of amines include alcoholic hydroxyl group-containing primary amines such as monoethanolamine and 2-amino-2-methyl-1-propanol, alcoholic hydroxyl group-containing groups such as diethanolamine and 2-methylaminoethanol. Tertiary amines, alcoholic hydroxyl group-containing tertiary amines such as triethanolamine, N-methyldiethanolamine, polyethylene polyamines such as ethylenediamine, triethylenediamine and diethylenetriamine, cyclic amines such as piperazines, piperidines and pyrrolidines , Polyamines such as xylylenediamine, amino acids such as methylaminocarboxylic acid, and the like, and mixtures thereof. Further, the absorption liquid may contain a carbon dioxide absorption accelerator or a corrosion inhibitor, and further methanol, polyethylene glycol, sulfolane and the like as other media.

  The method for recovering carbon dioxide in the gas to be treated according to an embodiment of the present invention can be performed by an apparatus as shown in FIGS. In the present invention, step (I), step (II), step (III) and step (IV) are usually carried out continuously and simultaneously.

Step (I): The gas 11 to be treated is supplied to the bottom of the absorption tower 1 by a blower 12, ascends the packed bed 2, and is discharged as a treated gas 8 from the top. The gas to be treated 11 may have a pressure equal to or higher than normal pressure, or may be normal pressure. The temperature of the gas to be treated 11 is preferably 100 ° C. or lower. A CO ₂ lean absorbent containing amines is poured onto the upper part of the packed bed 2 from the nozzle 6 and makes countercurrent contact with the gas to be treated in the packed bed 2 to absorb and absorb carbon dioxide in the gas to be treated. Accumulate at the bottom 10 of the tower. The liquid accumulated in the bottom 10 is rich in carbon dioxide and is called a CO ₂ rich absorption liquid. The temperature of the absorbing liquid in the packed bed 2 becomes higher than the temperature of the absorbing liquid in the nozzle 6 due to heat generated by absorption of carbon dioxide. Although it depends on the amount of carbon dioxide absorbed, the temperature rises up to about 40 ° C. Since the absorption liquid with a high liquid temperature has a low carbon dioxide absorption ability, it is cooled by the gas to be treated 11 supplied from the bottom of the absorption tower, and the temperature is lowered by about 10 to 30 ° C. compared to the maximum liquid temperature. The temperature of the CO ₂ rich absorbent at the bottom 10 of the absorption tower is about 50-60 ° C. Since the gas to be treated from which carbon dioxide has been removed is accompanied by an absorption liquid as mist, the gas to be treated from which carbon dioxide has been removed is washed with water in the water washing tower 7 before being discharged from the top ( Step (V)).

Step (II): The CO ₂ rich absorbent extracted from the bottom 10 is heated by the heat exchanger 22 and poured from the nozzle 14 above the packed bed 15 of the regeneration tower (desorption tower) 13. The poured liquid descends through the packed bed 15 and accumulates at the bottom of the regeneration tower. As will be described later, the liquid stored at the bottom of the regeneration tower has a low carbon dioxide content, and is called a CO ₂ lean absorbent. A reboiler 23 is attached to the bottom of the regeneration tower. The vapor obtained by heating and vaporizing the CO ₂ lean absorbent in the reboiler rises through the pipe 26 to the packed bed 15 and heats the CO ₂ rich absorbent that descends the packed bed 15 to a temperature of about 100 to 120 ° C. Desorb carbon. The desorbed carbon dioxide is discharged from the top of the regeneration tower, and the accompanying water is condensed in the cooler 9 (step (VI)). The condensed water obtained is returned to the regeneration tower. In the packed bed 15 of the regeneration tower 13, the lowest temperature (about 115 ° C.) is usually higher than the highest temperature.

The high-temperature and high-pressure CO ₂ lean absorbent stored at the bottom of the regeneration tower is withdrawn therefrom, cooled by the heat exchanger 22 and the cooler 24, and returned to the absorption tower 1. In the heat exchanger 22, the CO ₂ lean absorption liquid (about 110 to 120 ° C.) extracted from the bottom of the regeneration tower and the CO ₂ rich absorption liquid (about 50 to 60 ° C.) extracted from the bottom of the absorption tower. Heat exchange takes place between them. As the heat exchanger, existing heat exchangers such as a spiral heat exchanger, a plate heat exchanger, and a multi-tubular heat exchanger can be used.

Steps (III) and (IV): A part of the high-temperature and high-pressure CO ₂ lean absorbing liquid accumulated at the bottom of the regeneration tower is supplied to the flash evaporator 16 to generate steam. Water is then added to the steam obtained by flash evaporation. The added water immediately becomes steam. Steam generated from the flash evaporator and steam generated from the added water are pressurized by the blower 17 and supplied to the regeneration tower 13. Thus, when water is supplied to the upstream side of the blower, the steam temperature at the inlet of the blower 17 decreases, and even if heat is generated in the blower 17, the steam temperature at the outlet of the blower 17 can be suppressed to about 140 ° C. or lower. In the apparatus shown in FIG. 1 or 3, a part of the water used in the water washing tower 7 at the upper part of the absorption tower 1 is supplied upstream of the blower 17. In the apparatus shown in FIG. 2, a part of the water condensed by the cooler at the top of the regeneration tower is supplied upstream of the blower 17. In the apparatus shown in FIG. 4, a part of the water used in the water washing tower 7 at the upper part of the absorption tower 1 is passed through the cooling water line of the casing of the blower 17 and then supplied upstream of the blower 17. . In the apparatus shown in FIG. 5, a part of the water condensed by the cooler at the upper part of the regeneration tower is passed through the cooling water line of the casing of the blower 17 and then supplied upstream of the blower 17. In the apparatus shown in FIGS. 4 and 5, the blower 17 can be cooled from the outside, and the heat generated in the blower 17 can be supplied to the steam upstream of the blower 17.

  The amount of water supplied upstream of the blower 17 is not particularly limited as long as the steam temperature at the outlet of the blower 17 can be controlled within a predetermined range. For example, the amount of water supplied to the upstream side of the blower 17 can be set to 20% or less with respect to the amount of steam generated by the flash evaporator (steam generator) 16.

  The present invention will be described more specifically with reference to the following examples. In addition, this invention is not limited by these Examples.

Example 1
It implemented using the apparatus shown in FIG. Combustion exhaust gas 500Nm ³ / h containing 13% CO ₂ is supplied to the carbon dioxide absorption part of absorption tower 1 filled with regular packing of 6000mm in height, and 40 ° C aqueous solution containing 30% by weight of monoethanolamine (absorbing liquid ) Counter-current contact with 1500L / h and absorbed carbon dioxide. The remaining decarbonation exhaust gas was discharged from the upper part of the absorption tower. In order to make up for the steam to be supplied to the regeneration tower, 25 kg / h of steam was generated in the steam generation section 16, pressurized by the blower 17, and supplied to the regeneration tower.
When the blower 17 was operated without supplying cooling water to the blower casing, the steam temperature at the blower outlet rose to 190 ° C. Next, part of the water used in the water washing tower at the top of the absorption tower was supplied to the steam pipe upstream of the blower. The supply amount of water was set to 15% with respect to the amount of steam generated by the steam generating section 16. The steam temperature at the blower outlet was controlled at 160 ° C. All of the supplied water became steam and was supplied to the regeneration tower, where it was used to regenerate the absorbent.

Example 2
It implemented using the apparatus shown in FIG. Combustion exhaust gas 500Nm ³ / h containing 13% CO ₂ is supplied to the carbon dioxide absorption part of absorption tower 1 filled with regular packing of 6000mm in height, and 40 ° C aqueous solution containing 30% by weight of monoethanolamine (absorbing liquid ) Counter-current contact with 1500L / h and absorbed carbon dioxide. The remaining decarbonation exhaust gas was discharged from the upper part of the absorption tower. In order to make up for the steam to be supplied to the regeneration tower, 25 kg / h of steam was generated in the steam generation section 16, pressurized by the blower 17, and supplied to the regeneration tower.
When the blower 17 was operated without supplying cooling water to the blower casing, the steam temperature at the blower outlet rose to 190 ° C. Next, part of the water condensed by the cooler at the top of the regeneration tower was supplied to the steam pipe upstream of the blower. The supply amount of water was set to 15% with respect to the amount of steam generated by the steam generating section 16. The steam temperature at the blower outlet was controlled at 160 ° C. All of the supplied water became steam and was supplied to the regeneration tower, where it was used to regenerate the absorbent.

Example 3
It implemented using the apparatus shown in FIG. Combustion exhaust gas 500Nm ³ / h containing 13% CO ₂ is supplied to the carbon dioxide absorption part of absorption tower 1 filled with regular packing of 6000mm in height, and 40 ° C aqueous solution containing 30% by weight of monoethanolamine (absorbing liquid ) Counter-current contact with 1500L / h and absorbed carbon dioxide. The remaining decarbonation exhaust gas was discharged from the upper part of the absorption tower. In order to make up for the steam to be supplied to the regeneration tower, 25 kg / h of steam was generated in the steam generation section 16, pressurized by the blower 17, and supplied to the regeneration tower.
When the blower 17 was operated without supplying cooling water to the blower casing, the steam temperature at the blower outlet rose to 190 ° C. Next, part of the water used in the uppermost stage of the multistage water washing tower at the upper part of the absorption tower was supplied to the steam pipe upstream of the blower. The water used in the uppermost stage of the multistage water washing tower contains almost no amines. The supply amount of water was set to 15% with respect to the amount of steam generated by the steam generating section 16. The steam temperature at the blower outlet was controlled at 160 ° C. All of the supplied water became steam and was supplied to the regeneration tower, where it was used to regenerate the absorbent.

Example 4
It implemented using the apparatus shown in FIG. Combustion exhaust gas 500Nm ³ / h containing 13% CO ₂ is supplied to the carbon dioxide absorption part of absorption tower 1 filled with regular packing of 6000mm in height, and 40 ° C aqueous solution containing 30% by weight of monoethanolamine (absorbing liquid ) Counter-current contact with 1500L / h and absorbed carbon dioxide. The remaining decarbonation exhaust gas was discharged from the upper part of the absorption tower. In order to make up for the steam to be supplied to the regeneration tower, 25 kg / h of steam was generated in the steam generation section 16, pressurized by the blower 17, and supplied to the regeneration tower.
A portion of the water condensed by the cooler at the top of the regeneration tower was passed through the cooling water line of the blower casing and then supplied to the steam pipe upstream of the blower. The supply amount of water was set to 15% with respect to the amount of steam generated by the steam generating section 16. Since the condensed water is heated when passing through the cooling water line of the blower casing, it becomes difficult to become a drain when supplied to the steam pipe upstream of the blower. The steam temperature at the blower outlet was controlled at 150 ° C. All of the supplied water became steam and was supplied to the regeneration tower, where it was used to regenerate the absorbent.

Claims (9)

An absorption tower for obtaining a CO ₂ rich absorption liquid by causing a CO ₂ lean absorption liquid to absorb CO ₂ into the CO ₂ lean absorption liquid by bringing a treated gas containing carbon dioxide into contact with a CO ₂ lean absorption liquid containing amines.
CO ₂ rich absorbent solution and a CO ₂ and steam of the lean absorption liquid is brought into contact countercurrently CO ₂ carbon dioxide from the rich absorbing liquid desorbed CO ₂ lean absorbent regenerator for regeneration,
A flash evaporator for evaporating a part of the CO ₂ lean absorption liquid regenerated in the regeneration tower to obtain steam, and the steam obtained in the flash evaporator by pressurizing while controlling the steam at an appropriate temperature The apparatus for collect | recovering the carbon dioxide in the to-be-processed gas which has a means to supply to. Means for supplying steam to the regeneration tower by pressurizing the vapor obtained by the flash evaporator while controlling to an appropriate temperature,
The method for recovering carbon dioxide in the gas to be treated according to claim 1, comprising means for adding water to the steam obtained by the flash evaporator, and means for pressurizing the steam to which water has been added and supplying the steam to the regeneration tower. Equipment.   The means for pressurizing and supplying steam to the regeneration tower is provided with means for water-cooling the steam, and the water added to the steam is water used in the water-cooling means. An apparatus for recovering carbon dioxide in the gas to be treated.   A water washing tower for washing the treated gas from which carbon dioxide has been removed with water in the upper part of the absorption tower, and the water added to the steam is a part of the water used in the water washing tower. The apparatus for collect | recovering the carbon dioxide in the to-be-processed gas of 2 or 3.   A cooler for condensing water accompanying the carbon dioxide desorbed at the top of the regeneration tower is attached, and the water added to the steam is part of the water condensed by the cooler. The apparatus for collect | recovering the carbon dioxide in the to-be-processed gas of 2 or 3. A step (I) of obtaining a CO ₂ rich absorbent by contacting a gas to be treated containing carbon dioxide with a CO ₂ lean absorbent containing amines to absorb carbon dioxide in the CO ₂ lean absorbent;
A step (II) of regenerating the CO ₂ lean absorbing liquid by heating the CO ₂ rich absorbing liquid obtained in step (I) with the vapor of the CO ₂ lean absorbing liquid to desorb carbon dioxide;
A step (III) of obtaining a vapor by flash evaporation of a part of the CO ₂ lean absorbent regenerated in the step (II);
A process (IV) in which the vapor of the CO ₂ lean absorbent obtained in the process (III) is pressurized and supplied to the process (II) while being controlled at an appropriate temperature.
A method for recovering carbon dioxide in a gas to be treated. Step (IV)
Step (IV-1) of adding water to the steam of the CO ₂ lean absorbent obtained in step (III), and step of supplying pressurized steam to the step (II) (IV-2)
The method for recovering carbon dioxide in the gas to be treated according to claim 6.   The step (V) further includes a step (V) of washing the gas to be treated from which carbon dioxide has been removed in the step (I), and the water added in the step (IV-1) is the water used in the step (V). The method for recovering carbon dioxide in the gas to be treated according to claim 7, which is a part. Further comprising the step (VI) of condensing water accompanying the carbon dioxide desorbed in the step (II),
The method for recovering carbon dioxide in the gas to be treated according to claim 7, wherein the water added in the step (IV-1) is a part of the water aggregated in the step (VI).

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