Patent Application
20140245888
The present invention relates to a CO2 recovery apparatus and a CO2 recovery method for reducing concentration of amine compounds remaining in and being emitted from a decarbonated exhaust gas from which CO2 has been removed by being contacted with an absorbing liquid.
As a cause of global warming, the greenhouse effect due to CO2 is pointed out, and countermeasures against the same most be quickly taken internationally in saving the global environment. Various fields of human activity burning fossil fuel as generation sources of CO2, the demand for suppression of CO2 emissions is further increasing. Accordingly, for power generation facilities such as thermal power plants and the like using a large amount of fossil fuel, a method that exhaust gas from a boiler is contacted with an amine-based absorbing liquid such as an aqueous solution of amine compound so as to remove CO2 in the exhaust gas and recover the same is energetically studied.
When recovering CO2 from exhaust gas using such an absorbing liquid, a decarbonated exhaust gas from which the CO2 is recovered is accompanied by the absorbing liquid and anime compounds derived from the absorbing liquid. Additionally, in order to prevent air pollution by the amine compounds, it is necessary to reduce the discharge amount of the amine compounds which are emitted together with the decarbonated exhaust gas.
Conventionally, Patent Literature 1 discloses that plural stages of water washing portions which recover an amine compound accompanied by a decarbonated exhaust gas by bringing a washing liquid into contact with the decarbonated exhaust gas from which CO2 is absorbed and removed by a gas-liquid contact with an absorbing liquid are provided, and a recovery process of an amine compound accompanying a decarbonated exhaust gas is sequentially performed in the plural stages of the water washing portions. For the washing liquid of Patent Literature 1, condensed water obtained by condensing and separating moisture contained in CO2 in a process where CO2 is diffused from an amine-based absorbing liquid which has absorbed the CO2 so as to regenerate the amine-based absorbing liquid is used.
Further, conventionally, Patent Literature 2 discloses that a cooling portion where a decarbonated exhaust gas from which CO2 is absorbed and removed by a gas-liquid contact with an absorbing liquid is cooled, and a contact portion where condensed water which has been condensed in the cooling portion and the decarbonated exhaust gas are in counterflow contact with each other. Furthermore Patent Literature 2 discloses that a water washing portion which recovers an amine compound accompanying a decarbonated exhaust gas by bringing a washing liquid into contact with the decarbonated exhaust gas from which CO2 is absorbed and removed by a gas-liquid contact with an absorbing liquid are provided, and for the washing liquid, condensed water which has been condensed in a cooling tower where exhaust gas before CO2 is recovered therefrom is used.
Patent Literature 1: Japanese Patent Application Laid-open No. 2002-126439
Patent Literature 2: Japanese Patent Application Laid-open No. 8-80421
However, in recent years, it is desired to further reduce concentration of components of an absorbing liquid regaining in and being emitted from a decarbonated exhaust gas in terms of environmental preservation. Especially, when installing CO2 recovery apparatuses for exhaust gas from thermal power plants and the like which have a large amount of flow of processing gas anticipated in the future, a large amount of exhaust gas is emitted, and thereby the emission amount of components of an absorbing liquid remaining in and being emitted from a decarbonated exhaust gas tends to increase. Therefore, it is necessary to further reduce the concentration of emitted components of an absorbing liquid.
The present invention is to solve the above-mentioned problem and to provide a CO2 recovery apparatus and a CO2 recovery method capable of further reducing concentration of amine compounds remaining in and being emitted from a decarbonated exhaust gas.
According to a first aspect of the present invention in order to solve the above-mentioned problem, there is provided a CO2 recovery apparatus including: a CO2 absorption tower for bringing a CO2-containing exhaust gas containing CO2 and a CO2 absorbing liquid into contact with each other so as to remove CO2 and make a purified exhaust gas; and an absorbing liquid regeneration tower for separating CO2 from the CO2 absorbing liquid which has absorbed CO2 so as to regenerate the CO2 absorbing liquid, wherein a lean solution from which CO2 has been removed in the absorbing liquid regeneration tower is reused in the CO2 absorption tower, wherein a cooling tower for cooling the CC2-containing exhaust gas containing CO2 is provided on a side of an upstream flow of the CO2 absorption tower and a temperature (T2 ) of the purified exhaust gas exhausted from the CO2 absorption tower is set to be lower than a temperature (T1) of the CO2-containing exhaust gas containing CO2 cooled in the cooling tower (T1>T2), and wherein an evaporation portion is configured to evaporate a condensed water made by condensing water vapor discharged from the absorbing liquid regeneration tower.
According to a second aspect of the present invention, there is provided the CO2 recovery apparatus according to the first aspect, wherein the CO2 absorption tower includes: a CO2 absorption portion for absorbing CO2 in the CO2-containing exhaust gas by the CO2 absorbing liquid, a water washing portion for cooling a CO2-removed exhaust gas by the washing liquid and for recovering the CO2 absorbing liquid which accompanies the same, the water washing portion being provided on a side of a downstream flow of a gas flow of the CO2 absorption portion; a washing liquid circulation line for supplying the washing liquid containing the CO2 absorbing liquid recovered in the water washing portion from a side of a top of the water washing portion so as to circulate and wash the washing liquid; an extraction line for extracting a part of the washing liquid containing the CO2 absorbing liquid as an extracted liquid from the washing liquid circulation line; and a concentration portion for concentrating the CO2 absorbing liquid while separating a gas component from the extracted liquid.
According to a third aspect of the present invention, there is provided the CO2 recovery apparatus according to the second aspect, wherein the concentration portion includes: a concentration tower for heating an extracted water; a concentrated liquid return line for returning a concentrated liquid separated from the concentration tower to the CO2 absorption tower; and an acid washing tower for treating a volatile component contained in a gas component separated in the concentration tower with an acid and recovering the volatile component.
According to a forth aspect of the present invention, there is provided a CO2 recovery method for using a CO2 absorption tower for removing CO2 by bringing a CO2-containing exhaust gas containing CO2 and a CO2 absorbing liquid into contact with each other so as to remove CO2 and an absorbing liquid regeneration tower for regenerating the CO2 absorbing liquid by separating CO2 from the CO2 absorbing liquid absorbing CO2 so as to reuse a lean solution from which CO2 has been removed in the absorbing liquid regeneration tower in the CO2 absorption tower, wherein a cooling tower for cooling the CO2-containing exhaust gas containing CO2 is provided on a side of an upstream flow of the CO2 absorption tower, the CO2 recovery method including: setting a temperature of a purified exhaust gas exhausted from the CO2 absorption tower (T2) to be lower than a temperature of the CO2-containing exhaust gas containing CO2 cooled in the cooling tower (T1) (T1>T2); and evaporating, in an evaporation portion, a condensed water made by condensing a water vapor discharged from the absorbing liquid regeneration tower.
According to the present invention, concentration of amine compounds of an absorbing liquid remaining in and being emitted from a decarbonated exhaust gas can be further reduced, and also recovered absorbing liquid can be concentrated to be reused.
Hereunder, the present invention will be specifically described referring to the figures. Note that the present invention is not limited by this example, and when there are plural examples, they include what are configured by combining each embodiment. Further, components in the examples below include what a person skilled in the art can easily conceive or what is substantially identical to the same.
The CO2 recovery apparatus according to the present invention will be described referring to the figures.
As illustrated in
Note that the washing liquid 20 is circulated in the first water washing portion 13B1 as well in combination with the washing liquid circulation line L1.
Also note that, although not illustrated, the extracted liquid 21 from the first water washing portion 13B1 is merged into the CO2 absorbing liquid 12.
In the CO2 recovery apparatus 10A of this example, a thermometer 81 and a thermometer 82 are provided to a CO2-containing exhaust gas supply line L11 where the CO2-containing exhaust gas 11A is introduced into the CO2 absorption tower 13 and a purified exhaust gas exhaust line L12 where the purified exhaust gas 11B exhausted from the CO2 absorption tower 13 is exhausted respectively to measure each gas temperature (T1, T2).
Then, as a result of a measurement, a control apparatus, not illustrated, controls a gas temperature of the purified exhaust gas 11B at the outlet of the water washing portion 13B (T2) so as to set the same lower than a gas temperature at the inlet of the CO2 absorption tower 13 (T1) (T1>T2).
As a result, lowering the gas temperature of the purified exhaust gas 11B at the outlet of the CO2 absorption tower 13 (T2) than a gas temperature of the CO2-containing exhaust gas 11A to be introduced (T1) makes it possible to increase the amount of condensed water, and consequently, amine concentration in liquid in the water washing portion 13B is reduced, amine vapor pressure becomes lower, and the amount of accompanying CO2 absorbing liquid (amine solution or the like) is reduced, thereby making it possible to reduce emissions thereof to the outside.
Note that, in the absorption tower 13, the CO2-containing exhaust gas 11A is brought into counterflow contact with the alkanolamine-based CO2 absorbing liquid 12 in the CO2 absorption portion 13A provided on the lower side of the CO2 absorption tower 13, and CO2 in the CO2-containing exhaust gas 11A is absorbed by the CO2 absorbing liquid 12 by a chemical reaction (R—NH2+H2O+CO2—R—NH3HCO3).
Then, the CO2-removed exhaust gas after CO2 is removed rises to the water washing portion 13B side via a chimney tray 16 and is brought into gas-liquid contact with the washing liquid 20 supplied from the top side of the water washing portion 13B so as to recover the CO2 absorbing liquid 12 accompanying the CO2-removed exhaust gas.
After that, the purified exhaust gas 11B from which the CO2 absorbing liquid 12 has been removed is exhausted outside from a tower top portion 13C of the CO2 absorption tower 13. Note that a sign 73 indicates a mist eliminator which captures mist in gas.
The rich solution 12A having absorbed CO2 is boosted by a rich solvent pomp 51 interposed in a rich solution supply tube 50, heated by the lean solution 12B regenerated in the absorbing liquid regeneration tower 14 in a rich/lean solution heat exchanger 52, and supplied to the top side of the absorbing liquid regeneration tower 14.
The rich solution 12A emitted from the top side of the regeneration tower 14 to the inside of the tower emits most of CO2 by heating by means of water vapor from the tower bottom. The CO2 absorbing liquid 12 emitting part or most of CO2 in the regeneration tower 14 is called “semi-lean solution”. The semi-lean solution, not illustrated, becomes the lean solution 12B from which almost all CO2 has been removed when it flows down to the bottom of the regeneration tower 14. The lean solution 12B is heated by saturated water vapor 62 in a regeneration heater 61 interposed in a circulation line L20. The saturated water vapor 62 after heating becomes water-vapor-condensed water 63.
On the other hand, a CO2 gas 41 accompanied by water vapor dissipated from the rich solution 12A and the semi-lean solution, not illustrated, in the tower is omitted from a tower top portion 14A of the regeneration tower 14.
Then, the CO2 gas 41 accompanied by water vapor is guided out by a gas exhaust line L21, the water vapor is concentrated by a condenser 42 interposed in the gas exhaust line L21, a condensed water 44 is separated in a separation drum 43, and a CO2 gas is emitted out of the system and separately subjected to post-processing such as compression recovery.
The condensed water 44 which has been separated in the separation drum 43 is supplied to the upper portion of the absorbing liquid regeneration tower 14 by a condensed water circulation pump 46 interposed in a condensed water line L22A.
Note that, although not illustrated, part of the condensed water 44 is supplied to the top side of the water washing portion 13B as the washing liquid 20 of the CO2 absorbing liquid 12 and used for absorbing the CO2 absorbing liquid 12 accompanying the CO2-removed exhaust gas.
The regenerated CO2 absorbing liquid (lean solution 12B) is sent to the CO2 absorption tower 13 side by a lean solution pump 54 via a lean solution supply tube 53, and circulatedly used as the CO2 absorbing liquid 12.
Accordingly, the CO2 absorbing liquid 12 forms a closed passage circulating through the CO2 absorption tower 13 and the absorbing liquid regeneration tower 14, and is reused in the CO2 absorption portion 13A of the CO2 absorption tower 13. Note that the CO2 absorbing liquid 12 is supplied by a replenishment line which is not illustrated as necessary, and a CO2 absorbing liquid is regenerated by a reclaimer which is not illustrated as necessary.
Additionally, the CO2-containing exhaust gas 11A supplied to the CO2 absorption tower 13 is cooled by cooling water 71 in a cooling tower 70 provided to its front stage side, and then introduced into the CO2 absorption tower 13. Note that a sign 72 indicates a circulation pump, a sign 74 indicates a cooling apparatus, L10 indicates a cooling water circulation line, L11indicates a CO2-containing exhaust gas supply line, and L12 indicates a purified exhaust gas exhaust line, respectively.
Thus, the CO2 absorbing liquid 12 which is circulatedly used through the CO2 absorption tower 13 and the absorbing liquid regeneration tower 14 brings a CO2-removed exhaust gas from which CO2 has been removed and the washing liquid 20 into counterflow contact with each other and the CO2 absorbing liquid 12 accompanying the CO2-removed exhaust gas is absorbed and removed by the washing liquid 20 in the water washing portion 13B so as to prevent diffusion to the outside of the absorption tower 13.
In order to reuse the CO2 absorbing liquid 12 absorbed and removed by the washing liquid 20, in this example, the concentration portion 22 is provided and the CO2 absorbing liquid 12 is returned to the water washing portion 13B side via a concentrated liquid feed line L3 which feeds the concentrated liquid 23 which is concentrated in the concentration portion 22 so as to concentrate and use the CO2 absorbing liquid 12.
In this example, the thermometer 81 and the thermometer 82 are provided to the CO2-containing exhaust gas supply line L11 and the purified exhaust gas exhaust line L12 respectively to measure each gas temperature (T1, T2).
Then, as a result of a measurement, a control apparatus, not illustrated, controls a gas temperature of the purified exhaust gas 11B at the outlet of the water washing portion 13B (T2) so as to set the same lower than a gas temperature at the outlet of the cooling tower 70 (T1) (T1>T2).
As a result, lowering the gas temperature of the purified exhaust gas 11B at the outlet of the CO2 absorption tower 13 (T2) makes it possible to increase the amount of condensed water, and consequently, amine concentration in liquid in the water washing portion 13B is reduced, amine vapor pressure becomes lower, and the amount of accompanying CO2 absorbing liquid (amine solution or the like) is reduced, thereby making it possible to reduce emissions thereof to the outside.
When the gas temperature of the purified exhaust gas 11B (T2) is lowered from 40° C. to 35° C. here, it is confirmed that amine compound concentration ratio in gas of the purified exhaust gas 11B is decreased to 0.5 at 35° C. with respect to 1 at 40° C.
In this manner, the amount of condensed water is increased by lowering the gas temperature at the outlet of the absorption tower 13 (T2). Therefore, in this example, the condensed water 44 which is condensed in the separation drum 43 separating moisture from the CO2 gas 41 accompanied by water vapor discharged from the tower top portion 14A in the absorbing liquid regeneration tower 14 is fed to an evaporation portion 90 via a condensed water line L22B so as to evaporate the same as a water vapor 91 here, thereby keeping a water balance in the system of the CO2 recovery facility. In this manner, the water discharge amount of the CO2 recovery facility can be reduced by the discharge to the outside of the system as the water vapor 91. L9 is a discharge line for the water vapor 91. L6 is a liquid return line for supplying the liquid in the evaporation portion 90 to the washing liquid circulation line L1.
Note that the condensed water 44 supplied to the evaporation portion 90 is heated by a heat exchanger 92. The CO2 gas 41 accompanied by water vapor discharged from the top of the regeneration tower 14, the lean solution 12B fed from the regeneration tower 14 to the absorption tower 13 and heat-exchanged in the rich/lean solution heat exchanger 52, or the water-vapor-condensed water 63 condensed by the regeneration heater 61 can be used as a heat source of the heat exchanger so as to heat the condensed water 44 to about 60 to 90 degrees, for example.
Additionally, as the condensed water 44 fed to the evaporation portion 90 is water vapor separated from the tower top portion 14A of the absorbing liquid regeneration tower 14, concentration of its basic component (amine) as an absorbing liquid component is extremely low. Therefore, it can be discharged to the outside of the system as the water vapor 91 as it is.
Further, in this example, part of the washing liquid 20 circulating the second water washing portion 13B2 on the top side of the water washing portion 13B is extracted and concentrated in the concentration portion 22 to be made to the concentrated liquid 23, and the concentrated liquid 23 is returned to a puddle portion of the first water washing portion 13B1. Therefore, a volatile component in the washing liquid 20 can be separated from the washing liquid 20, and thereby water washing capability of the water washing portion 13B can be improved.
Furthermore, as a mass balance of water is maintained in the CO2 absorption tower 13 by returning the concentrated liquid 23 concentrated in the concentration portion 22 to the first water washing portion 13B1 side, extra moisture does not enter the absorbing liquid regeneration tower 14, and thereby the amount of steam necessary for separating CO2 can be reduced.
Note that a collapse of water balance due to generation of condensed water is resolved by the concentration of the washing liquid 20 in the concentration portion 22, and also, in the concentration of the washing liquid, the volatile component in the washing liquid can be diffused from the washing liquid to be separated therefrom, and thereby the water washing capability of the water washing portion 13B can be improved.
Note that, for example, an evaporation apparatus, a vapor compression concentration apparatus, or the like can be used in the concentration portion 22. The evaporation apparatus in which the washing liquid 20 is heated to be evaporated while being stored in an evaporator, the concentrated liquid 23 is supplied to the next evaporator, and also the water vapor 24 is used as a heating source in the next evaporator, and the evaporators are provided plurally can be exemplified.
Also, the vapor compressing concentration apparatus pressurizes the water vapor 24 generated in the evaporator with a compressor so as to raise the temperature, thereby using the same as a heat source for heating, and can reduce power consumption upon concentration.
As illustrated in
An acid 29 is added to the acid washing tower 27 from an acid supply portion (not illustrated) and recovered in an acid treatment liquid as a sulfate, then treated in a waste liquid process portion 30 via a supply line L8.
Although sulphuric acid, for example, can be used as the acid 29 charged here, the present invention is not limited to the same.
Note that, as the acid 29, hydrochloric acid, phosphoric acid, boric acid, carbonic acid, oxalic acid, or the like other than sulfuric acid can be given.
Although any will do as the concentration portion 22 so long as it heats part of extracted water of the washing liquid 20, a concentration tower 22A as illustrated in
In the concentration tower 22A illustrated in
Additionally, in this example, a separation drum 22C is provided to a supply line L4A to which the gas component 24 is guided out from the top of the concentration tower 22A so as to separate moisture and an absorbing liquid from the gas component 24, thereby preventing accompaniment of the moisture and absorbing liquid to the outside and also preventing dissipation of the moisture and absorbing liquid to the outside of the system. The gas component 24 separated in the separation drum 22C is supplied to the acid washing tower 27 via a supply line L48, and treated with acid here. Note that liquid separated in the separation drum 22C is returned to the concentration tower 22A via a supply line L40.
In the concentration tower 22B illustrated in
A washing liquid containing an absorbing liquid which does not accompany the air 94 is supplied to the first water washing portion 13B1 as the concentrated liquid 23. In order to facilitate accompaniment of the volatile component, the air 94 may be heated by a heat exchanger, not illustrated.
The air containing the volatile component is sent to the acid washing tower 27 and washed with acid so as to remove the volatile component therefrom, and then sent to the evaporation portion 90. Note that the gas component 24 may be supplied to the concentration tower 22B so as to be used as the air 94 which generates water vapor.
As described above, according to the present invention, concentration of amine compounds remaining in and being emitted from a decarbonated exhaust gas can be further reduced, and also a concentrated absorbing liquid can be effectively reused.
10A, 10B CO2 Recovery Apparatus
11A CO2-Containing Exhaust Gas
12 Co2 Absorbing Liquid
12A Rich Solution
12B Lean Solution
13 CO2 Absorption Tower (Absorption Tower)
14 Absorbing Liquid Regeneration Tower (Regeneration Tower)
20 Washing Liquid
21 Extracted Liquid
22 Concentration Portion
23 Concentrated Liquid
24 Gas Component
90 Evaporation Portion
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-199882 | Sep 2011 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2012/073102 | 9/10/2012 | WO | 00 | 1/30/2014 |
