JP2015123379A - Device for recovering carbon dioxide in process target gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for recovering carbon dioxide with high efficiency effectively using waste heat generated in steam pressurization means.SOLUTION: Provided is a device for recovering carbon dioxide in process target gas, comprising: an absorption unit causing countercurrent contact between the process target gas containing carbon dioxide and COlean absorption liquid, and obtaining COrich absorption liquid by absorbing the carbon dioxide by the COlean absorption liquid; a regeneration unit causing countercurrent contact between the COrich absorption liquid from upward and the COlean absorption liquid from downward, desorbing the carbon dioxide from the COrich absorption liquid, and regenerating the COlean absorption liquid; a reboiler heating part of the COlean absorption liquid regenerated by the regeneration unit and generating steam; a pipe (a) supplying the steam generated by the reboiler downward of a lower portion of the regeneration unit; a flash evaporator evaporating part of the COlean absorption liquid regenerated by the regeneration unit and obtaining steam; and a pipe (b) pressurizing the steam obtained by the flash evaporator and supplying the pressurized steam to the regeneration unit.

Description

  The present invention relates to an apparatus capable of recovering carbon dioxide in a gas to be processed with high efficiency by effectively using 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 CO ₂ absorbing liquid) is known (for example, Patent Document 1). Etc.)

As shown in FIG. 3, the absorption of carbon dioxide by the CO ₂ absorption liquid counter-currents the gas to be treated 11 containing carbon dioxide introduced from the bottom of the absorption tower and the CO ₂ lean absorption liquid poured from the nozzle 6. The carbon dioxide is absorbed into the CO ₂ lean absorption liquid to obtain CO ₂ rich absorption liquid (about 50-60 ° C), and the carbon dioxide is desorbed from the CO ₂ rich absorption liquid. ₂ Regeneration unit 15 for regenerating to a lean absorption liquid, and CO ₂ rich absorption liquid extracted from the absorption tower 1 for heating with a CO ₂ lean absorption liquid (110 to 120 ° C.) extracted from the regeneration tower 13 It is carried out in an apparatus having at least a heat exchanger 22. Since carbon dioxide is desorbed when the CO ₂ -rich absorbing solution is brought to a temperature range of 100 to 125 ° C., the regeneration unit 15 is heated by steam supplied from the bottom of the regeneration tower (the absorbing solution vapor evaporated by the reboiler 23). The In the reboiler 23, the absorbing liquid is evaporated 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, so that it is desired to reduce the amount of water vapor used in the reboiler from the viewpoint of power generation efficiency.
As one method of reducing the amount of water vapor used in the reboiler, the CO ₂ lean absorption liquid extracted from the lower part of the regeneration tower is evaporated by the flash evaporator 16 to obtain steam, and this steam is pressurized by the blower 17 There is known a method of supplying below the lower part of the reproducing unit 15.

Japanese Patent No. 3529855

The vapor obtained with a flash evaporator may contain carbon dioxide. If steam containing carbon dioxide is supplied downward from the lower part of the regeneration unit, regeneration to the CO ₂ lean absorbent is hindered, and there is a concern that the efficiency of the entire system may be reduced.
An object of the present invention is to provide an apparatus capable of 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] and the processed gas and the CO ₂ lean absorbent solution containing carbon dioxide is contacted countercurrent absorber for carbon dioxide is absorbed into CO ₂ lean absorbing liquid to obtain a CO ₂ rich absorbent solution, from above reproducing unit for reproducing the vapor of CO ₂ rich absorbent solution and a CO ₂ lean absorbent liquid from the lower contacting countercurrent, carbon dioxide was desorbed from the CO ₂ rich absorbent liquid CO ₂ lean absorbing solution, reproduction A reboiler for heating a part of the CO ₂ lean absorption liquid regenerated in the unit to generate steam, a pipe (a) for supplying the steam generated in the reboiler downward from the lower part of the regenerator, A flash evaporator for evaporating a part of the CO ₂ lean absorbent regenerated in step 1 to obtain vapor, and a pipe for pressurizing the vapor obtained in the flash evaporator and supplying the vapor to the regeneration unit ( An apparatus for recovering carbon dioxide in a gas to be treated having b).
[2] The apparatus according to [1], further comprising a pipe (c) for supplying the CO ₂ lean absorbent stored in the bottom of the flash evaporator upward from the upper part of the absorber.
[3] and the processed gas and the CO ₂ lean absorbent solution containing carbon dioxide is contacted countercurrent absorber for carbon dioxide is absorbed into CO ₂ lean absorbing liquid to obtain a CO ₂ rich absorbent solution, from above reproducing unit for reproducing the vapor of CO ₂ rich absorbent solution and a CO ₂ lean absorbent liquid from the lower contacting countercurrent, carbon dioxide was desorbed from the CO ₂ rich absorbent liquid CO ₂ lean absorbing solution, reproduction A reboiler for heating a part of the CO ₂ lean absorption liquid regenerated in the regenerator to generate steam, a pipe for supplying the steam generated in the reboiler downward from the bottom of the regenerator (a), in the reboiler A flash evaporator for evaporating a part of the heated CO ₂ lean absorption liquid to obtain steam, and a pipe for pressurizing the steam obtained by the flash evaporator and supplying the steam to the regeneration unit (b For recovering carbon dioxide in the gas to be treated
[4] The apparatus according to [3], further comprising a pipe (d) for supplying the CO ₂ lean absorbing liquid stored in the bottom of the flash evaporator downward from the lower part of the regeneration unit.

  According to the present invention, when the apparatus that supplies the vapor which has been flash-evaporated and then pressurized is supplied to the regeneration unit at a position above the supply position of the steam generated by the reboiler, the regeneration of the absorbing liquid is not hindered. The steam used in the regeneration tower can be reduced.

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 a prior art. It shows the distribution of the CO ₂ loading of the absorbent solution in the regenerator.

An apparatus for recovering carbon dioxide in a gas to be treated according to an embodiment of the present invention makes a gas to be treated containing carbon dioxide and a CO ₂ lean absorbing solution come in countercurrent contact, and absorbs carbon dioxide through CO ₂ lean. absorber to obtain a CO ₂ rich absorbent solution to absorb the liquid, and a vapor of CO ₂ lean absorbent liquid from the CO ₂ rich absorbent solution and a lower from above is contacted countercurrent dioxide from CO ₂ rich absorbent solution reproducing unit for reproducing the carbon desorbed to CO ₂ lean absorbing liquid, the reboiler for generating steam by heating a portion of the CO ₂ lean absorbent that has been reproduced in the reproducing unit, was produced in the reboiler A pipe (a) for supplying steam below the regenerator, a flash evaporator for evaporating a part of the CO ₂ lean absorption liquid regenerated in the regenerator, and a flash evaporator Pressurize the obtained steam and supply the steam to the regeneration unit Having a tube (b) for.

An apparatus for recovering carbon dioxide in a gas to be treated according to another embodiment of the present invention makes a gas to be treated containing carbon dioxide and a CO ₂ lean absorbent come in countercurrent contact, and converts the carbon dioxide into CO _2. absorbing portion for obtaining a CO ₂ rich absorbent liquid is absorbed into the lean absorbent solution and a vapor of CO ₂ lean absorbent liquid from the CO ₂ rich absorbent solution and a lower from above is contacted countercurrent, CO ₂ rich absorbent solution reproducing unit for carbon dioxide desorbed to play CO ₂ lean absorbing fluid from the reboiler to generate steam by heating a portion of the CO ₂ lean absorbent that has been reproduced in the reproducing unit, generated in the reboiler A pipe (a) for supplying the generated steam downward from the lower part of the regeneration unit, a flash evaporator for evaporating a part of the CO ₂ lean absorption liquid heated by the reboiler to obtain steam, and a flash evaporator The steam obtained in step 1 is pressurized and the steam is recycled to the regeneration unit. Having a tube (b) for feeding.

The CO ₂ absorbing solution used in the present invention is usually a solution containing amines. Examples of the amines include alcoholic hydroxyl group-containing primary amines such as monoethanolamine and 2-amino-2-methyl-1-propanol, and alcoholic hydroxyl group-containing secondary amines such as diethanolamine and 2-methylaminoethanol. , Tertiary amines containing alcoholic hydroxyl groups such as triethanolamine and N-methyldiethanolamine, polyethylenepolyamines such as ethylenediamine, triethylenediamine and diethylenetriamine, cyclic amines such as piperazines, piperidines and pyrrolidines, Examples include polyamines such as xylylenediamine, amino acids such as methylaminocarboxylic acid, and the like, and mixtures thereof. The absorption liquid may contain a carbon dioxide absorption accelerator or a corrosion inhibitor. As the solvent, water is usually used, but an organic solvent such as methanol, polyethylene glycol, sulfolane and the like may be added to water.

As an apparatus according to an embodiment of the present invention, for example, an apparatus as shown in FIG. In the apparatus shown in FIG. 1, the gas 11 to be treated is supplied to the bottom of the absorption tower 1 by the blower 12, rises in the packed bed (absorption part) 2, and is discharged as the 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 from the nozzle 6 on the upper side of the packed bed 2 and comes into 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 or vapor, before being discharged from the top, in the washing unit 7, the gas to be treated from which carbon dioxide has been removed can be washed, Remove mist with a demister.

The CO ₂ rich absorbent extracted from the bottom 10 of the absorption tower is heated by the heat exchanger 22 and poured from the nozzle 14 above the packed bed (regeneration section) 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. The liquid collected 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. A part of the CO ₂ lean absorbent that has descended the packed bed 15 is heated by a reboiler to generate steam. Steam generated in the reboiler is supplied to the lower side of the filling layer 15 through a pipe 26, it rises in the filling layer 15 therefrom, about 100 to 120 ° C. by heating the CO ₂ rich absorbent solution to lower the filling layer 15 The carbon dioxide is desorbed from the CO ₂ rich absorbent at a temperature of The desorbed carbon dioxide is discharged from the top of the regeneration tower, and the accompanying water is condensed in the cooler 9. 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.

A part of the CO ₂ lean absorbing liquid accumulated at the bottom of the regeneration tower is supplied to the flash evaporator 16 to generate steam. The obtained steam is pressurized by the blower 17 and supplied to the regeneration unit 15 via the pipe 28.

In the conventional apparatus (FIG. 3), the steam pressurized by the blower 17 is supplied to the lower side of the regeneration unit, similar to the steam generated by the reboiler. In the flash evaporator, carbon dioxide desorption occurs simultaneously with the evaporation of the absorbing solution. For this reason, the steam pressurized by the blower 17 contains a little carbon dioxide. When the steam pressurized by the blower 17 is supplied to the lower side of the regeneration unit, CO ₂ loading as shown in FIG. That is, the partial pressure of carbon dioxide at the lower side of the regeneration section is increased, the desorption of carbon dioxide in the regeneration section is inhibited, and the carbon dioxide content in the CO ₂ lean absorbing liquid that accumulates at the bottom of the regeneration tower increases. The vertical axis of the graph in FIG. 4 corresponds to the height of the leftmost regeneration tower. Since the CO ₂ lean absorbent having a high carbon dioxide content has a low carbon dioxide absorption capacity, the efficiency of the entire apparatus may be reduced.

On the other hand, in the apparatus according to the present invention shown in FIG. 1, the steam pressurized by the blower 17 is above the supply position of the steam generated by the reboiler, that is, the regeneration unit 15, more specifically, the blower. 17 is supplied to the intermediate stage of the regeneration unit having a carbon dioxide partial pressure higher than the carbon dioxide partial pressure in the pressurized steam. In the apparatus shown in FIG. 1, CO ₂ loading as shown in FIG. That is, it can be seen that the carbon dioxide partial pressure on the lower side of the regeneration section is kept low, and the regeneration of the absorbent is almost completed.

In the apparatus shown in FIG. 1, the CO ₂ lean absorbing liquid accumulated at the bottom of the flash evaporator is transferred to the heat exchanger 22 and the cooler 24 together with the CO ₂ lean absorbing liquid accumulated at the bottom of the regeneration tower for cooling. And returned to the absorption tower 1. In the heat exchanger 22, heat exchange is performed between the CO ₂ lean absorption liquid (about 110 to 120 ° C.) and the CO ₂ rich absorption liquid (about 50 to 60 ° C.) extracted from the bottom of the absorption tower. 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.

An apparatus according to another embodiment of the present invention includes an apparatus as shown in FIG. The apparatus shown in FIG. 2 transfers a part of the CO ₂ lean absorption liquid accumulated at the bottom of the reboiler to the flash evaporator 16, and the CO ₂ lean absorption liquid accumulated at the bottom of the flash evaporator 16 is transferred to the bottom of the regeneration tower. The apparatus is the same as that shown in FIG. In the apparatus shown in FIG. 2, CO ₂ loading as shown in FIG.

  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% carbon dioxide is supplied to the absorption tower 1, and the absorption part 2 filled with regular packing materials with a total height of 6000mm is flowed upward, and contains 30% by weight monoethanolamine. A countercurrent contact was made with 1500 L / h of an aqueous solution (CO ₂ absorbent) at ℃, and carbon dioxide in the exhaust gas was absorbed and removed by the absorbent. The gas from which carbon dioxide was removed (treated gas) was discharged from the upper part of the absorption tower. The CO ₂ absorbent that absorbed carbon dioxide poured from the nozzle 14 of the regeneration tower.
The CO ₂ lean absorption liquid accumulated at the bottom of the regeneration tower was supplied to the flash evaporator 16 and vaporized to generate 25 kg / h of steam. The obtained steam was pressurized by the blower 17 and supplied to the intermediate stage of the regeneration unit 13. The steam pressurized by the blower 17 contained 10% carbon dioxide. Further, the intermediate stage of the regeneration unit 13 to which the steam is supplied had a carbon dioxide emission amount of 10% or more. The distribution of CO ₂ loading of the absorption liquid in the regeneration tower was as shown in FIG. 4 (b). It can be seen that the regeneration of the CO ₂ absorbent is performed efficiently.

Example 2
It implemented using the apparatus shown in FIG. The CO ₂ lean absorption liquid accumulated at the bottom of the reboiler was supplied to the flash evaporator 16 and vaporized to generate steam. Since the CO ₂ lean absorbing liquid accumulated at the bottom of the reboiler has a higher temperature than the CO ₂ lean absorbing liquid accumulated at the bottom of the regeneration tower, the amount of generated steam increased from that in Example 1. The obtained steam was pressurized by the blower 17 and supplied to the intermediate stage of the regeneration unit 13. The steam pressurized by the blower 17 contained about 10% carbon dioxide. Further, the intermediate stage of the regeneration unit 13 to which the steam is supplied had a carbon dioxide emission amount of 10% or more. The distribution of CO ₂ loading of the absorbent in the regeneration tower was the same as shown in FIG. 4 (b). It can be seen that the regeneration of the CO ₂ absorbent is performed efficiently.

Comparative Example 3
It implemented using the apparatus shown in FIG. The CO ₂ lean absorption liquid accumulated at the bottom of the regeneration tower was supplied to the flash evaporator 16 and vaporized to generate 25 kg / h of steam. The obtained steam was pressurized by the blower 17 and supplied to the lower side of the regeneration unit 13. The steam pressurized by the blower 17 contained 10% carbon dioxide. The distribution of CO ₂ loading of the absorption liquid in the regeneration tower was as shown in FIG. 4 (a). It can be seen that the regeneration of the CO ₂ absorbing solution is hindered by the supply of steam from the flash evaporator.

1: Absorption tower, 2: Absorption section, 6: Nozzle, 7: Cleaning section, 8: Treated gas,
10: Absorption tower bottom, 11: Gas to be treated, 12: Blower, 13: Regeneration tower,
14: Nozzle, 15: Regeneration unit, 16: Flash steamer, 17: Blower,
22: Heat exchanger, 23: Reboiler, 24: Cooler

Claims (4)

An absorption part for obtaining a CO ₂ rich absorbent by causing the gas to be treated containing carbon dioxide and the CO ₂ lean absorbent to counter-current contact and absorbing the carbon dioxide into the CO ₂ lean absorbent,
Reproduction for reproducing the vapor CO ₂ lean absorbent liquid from the CO ₂ rich absorbent solution and a lower from the upper countercurrent contacting, with carbon dioxide was desorbed from the CO ₂ rich absorbent liquid CO ₂ lean absorbing solution Part,
A reboiler for generating steam by heating a part of the CO ₂ lean absorbent regenerated in the regenerator,
A pipe (a) for supplying steam generated by the reboiler downward from the lower part of the regeneration unit,
A flash evaporator for evaporating a part of the CO ₂ lean absorbent regenerated in the regeneration unit to obtain steam, and for supplying the steam to the regeneration unit by pressurizing the steam obtained in the flash evaporator Tube (b)
An apparatus for recovering carbon dioxide in a gas to be treated. The apparatus according to claim 1, further comprising a pipe (c) for supplying the CO ₂ lean absorbing liquid accumulated at the bottom of the flash evaporator upward from the upper part of the absorbing part. An absorption part for obtaining a CO ₂ rich absorbent by causing the gas to be treated containing carbon dioxide and the CO ₂ lean absorbent to counter-current contact and absorbing the carbon dioxide into the CO ₂ lean absorbent,
Reproduction for reproducing the vapor CO ₂ lean absorbent liquid from the CO ₂ rich absorbent solution and a lower from the upper countercurrent contacting, with carbon dioxide was desorbed from the CO ₂ rich absorbent liquid CO ₂ lean absorbing solution Part,
A reboiler for generating steam by heating a part of the CO ₂ lean absorbent regenerated in the regenerator,
A pipe (a) for supplying steam generated by the reboiler downward from the lower part of the regeneration unit,
A flash evaporator for evaporating a part of the CO ₂ lean absorption liquid heated by the reboiler to obtain steam, and a tube for pressurizing the steam obtained by the flash evaporator and supplying the steam to the regeneration unit The apparatus for collect | recovering the carbon dioxide in the to-be-processed gas which has (b). The apparatus according to claim 3, further comprising a pipe (d) for supplying the CO ₂ lean absorbing liquid stored in the bottom of the flash evaporator downward from the lower part of the regeneration unit.

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