CN113101786B - Flue gas carbon dioxide capture system and method based on organic solvent absorption-extraction regeneration cycle - Google Patents
Flue gas carbon dioxide capture system and method based on organic solvent absorption-extraction regeneration cycle Download PDFInfo
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- CN113101786B CN113101786B CN202110505341.4A CN202110505341A CN113101786B CN 113101786 B CN113101786 B CN 113101786B CN 202110505341 A CN202110505341 A CN 202110505341A CN 113101786 B CN113101786 B CN 113101786B
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Abstract
The invention relates to a flue gas carbon dioxide capture system based on organic solvent absorption-extraction regeneration circulation, which comprises a flue gas pretreatment tower, an absorption tower, an extraction regeneration tower, a desorption tower, a water balance tower and a solvent recovery tower, wherein the absorption tower is connected with the extraction regeneration tower through a pipeline; a flue gas outlet at the top of the flue gas pretreatment tower is connected to a flue gas inlet at the lower part of the absorption tower; a flue gas outlet at the top of the absorption tower is connected to a flue gas inlet at the bottom of the water balance tower; a flue gas outlet at the top of the water balance tower is connected to a flue gas inlet at the bottom of the solvent recovery tower through a flue gas pipeline; and a rich liquid outlet of the absorption tower is connected to a rich liquid inlet at the bottom of the extraction regeneration tower, and an organic phase outlet at the top of the extraction regeneration tower is connected to an organic solvent inlet at the upper part of the absorption tower through a cooler. The beneficial effects of the invention are: the system gives full play to the CO of the organic solvent in the absorption tower2High absorption rate, rich solution in regeneration tower CO2The advantage of large circulation capacity, thus reducing the size of the absorption tower, reducing the heat consumption of the desorption tower and reducing the carbon capture cost.
Description
Technical Field
The invention belongs to the technical field of flue gas carbon dioxide capture, and particularly relates to a flue gas carbon dioxide capture system and method based on organic solvent absorption-extraction regeneration cycle.
Background
Global warming due to human greenhouse gas emissions is a major challenge facing the world today. As the largest fixed emission source in China, coal-fired power plants and industrial flue gas CO2The trapping is an important choice for realizing the carbon neutralization target in China. The chemical absorption method is the only method capable of capturing the flue gas CO on a large scale at the present stage2The technical scheme of (1).
Diluted weak base aqueous solution is most commonly used as flue gas CO2Absorbents for chemical absorption technology, such as 20% -30% aqueous ethanolamine (MEA) solutions, have been used in megaton/year coal fired power plant flue gas CO2A trapping engineering device. MEA sorbent CO absorption2Then the obtained product is sent into a desorption tower to be heated and desorbed CO2Desorption of CO2After heat of the MEA absorbent is recovered by a lean-rich liquid heat exchanger, CO is sent back2An absorption tower. But CO of conventional MEA aqueous solution (20% -30%)2The absorption rate is slow and to achieve a 90% capture rate, CO2The equipment size of the absorption tower is large, so that the system investment cost is high, and the large-scale application of the technology is greatly limited. MEA aqueous solution (20% -30%) has high water content (70% -80%), and liquid phase CO 2Lower concentration, resulting in CO2A large amount of heat is consumed in the desorption process for evaporation and temperature rise of water, so that the running energy consumption of the system is high.
In recent years, researchers at home and abroad propose organic solvent systems based on little water or non-water as CO2The absorbent helps to increase CO2The rate of absorption. Experimental measurements of Yuan et al (DOI:10.1016/j. ces.2018.02.026) show that the 30% MEA/66% NMP organic solvent system is due to CO2The physical solubility is higher than that of the conventional 30 percent MEA/water system, and CO2The absorption rate can be increased by a factor of 4.
Organic solvent system absorbs CO due to polarity reduction2The post-extraction is easy to generate phase separation phenomenon, which causes the absorbent to absorb CO2The absorption rate and the absorption capacity of (b) are greatly changed. The Chinese invention patent (CN108079746B) discloses that the compound is used as CO on the premise of organic solvent based on high-concentration mixed amine2Absorbents, e.g. ethanolamine/diethylaminoethanol systems, having a total mass concentration of 70% to 80%, in absorbing CO2Then liquid-liquid phase separation is carried out to form an organic phase and an aqueous solution phase, and CO of the aqueous solution phase2The absorption capacity is improved by 30 to 60 percent. Furthermore, Liu et al (DOI:10.1016/j. cej.2020.126503) found, by experimental studies, CO2The physical solubility of the gas in the organic phase is 2-7 times higher than that of the aqueous phase, resulting in CO in the organic phase 2Absorption Rate ratio Water solubleLiquid phase is 3-5 times faster, and absorbed CO2Spontaneously transferred and concentrated in the aqueous phase, resulting in CO in the aqueous phase2The circulation capacity is 2-5 times higher, the amount of the required regeneration solution is greatly reduced, and the regeneration energy consumption can be effectively reduced.
Similarly, researchers have proposed a variety of CO absorption in recent years2Followed by a self-extracting organic solvent system. Chinese invention patent (CN106039936B) discloses an organic solvent system of diethylenetriamine/pentamethyldiethylenetriamine, the total mass concentration is about 70-86%. Chinese invention patent (CN106984152B) discloses an organic solvent system of N-ethylethanolamine/N, N-diethylethanolamine, the total mass concentration is 99.0-99.5%. Chinese invention patent (CN110052117A) discloses an organic solvent system (total mass concentration is 60-80%) of organic amine such as monoethanolamine and water, which is used as CO, and takes dimethyl sulfoxide, N-methyl pyrrolidone and the like as a synergist2Trapped liquid-liquid phase change absorbent.
For such absorption of CO2An organic solvent with post-phase separation, and Chinese patent (CN104958998A) discloses CO regenerated by rich liquid phase separation and tearing2Capture system, organic solvent absorption of CO2Post phase separation and enrichment of CO2The aqueous solution phase is sent to be regenerated, the organic phase and the regenerated aqueous solution phase are mixed again and then sent back to the absorption tower to absorb CO 2. The process system utilizes water solution phase CO2The advantage of large circulation capacity, thereby reducing the regeneration energy consumption, but the organic phase with faster CO can not be fully exerted2Advantage of absorption rate, therefore CO of the absorption column2The absorption rate is slower. On the other hand, since the organic solvent has a high volatility, it is highly volatile in CO2In the trapping process, the organic solvent is easy to be discharged along with the flue gas, so that the loss cost of the absorbent is increased, and pollutants such as aerosol and the like can be formed, so that the serious environmental pollution is caused. Meanwhile, as the organic solvent is volatilized, the water carried away with the flue gas will damage the water balance of the system. Therefore, the development of flue gas CO based on organic solvent is urgently needed2A capture system.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a novel organic solvent-based organic solventThe flue gas carbon dioxide capture system and method of absorbent absorption-extraction regeneration circulation realize the circulation of organic solvent in the absorption tower and the enrichment of CO by the three-tower circulation design2The aqueous solution of (A) is circulated in a desorption tower to fully exert the CO of the organic solvent2CO in aqueous solution with high absorption rate2The advantage of high circulation capacity is favorable for reducing the carbon capture cost; meanwhile, the process scheme of the water balance tower and the solvent recovery tower is provided for solving the problems of organic solvent volatilization and system water balance.
The flue gas carbon dioxide capture system based on organic solvent absorption-extraction regeneration circulation comprises a flue gas pretreatment tower, an absorption tower, an extraction regeneration tower, a desorption tower, a water balance tower and a solvent recovery tower; a flue gas outlet at the top of the flue gas pretreatment tower is connected to a flue gas inlet at the lower part of the absorption tower; a flue gas outlet at the top of the absorption tower is connected to a flue gas inlet at the bottom of the water balance tower; a flue gas outlet at the top of the water balance tower is connected to a flue gas inlet at the bottom of the solvent recovery tower through a flue gas pipeline; a rich liquid outlet of the absorption tower is connected to a rich liquid inlet at the bottom of the extraction regeneration tower, and an organic phase outlet at the top of the extraction regeneration tower is connected to an organic solvent inlet at the upper part of the absorption tower through a cooler; an extract inlet at the upper part of the extraction regeneration tower is connected with a water solution phase hot barren liquor outlet at the bottom of the desorption tower through a barren and rich liquor heat exchanger, and a water solution phase cold rich liquor outlet at the bottom of the extraction regeneration tower is connected with a water solution phase hot rich liquor inlet at the upper part of the desorption tower through a barren and rich liquor heat exchanger; the regenerated gas outlet at the top of the desorption tower is connected to the inlet of a condenser, and CO of the condenser2The outlet is connected to the compressor inlet.
Preferably, the method comprises the following steps: the flue gas pretreatment tower adopts a water washing tower or an alkali washing tower, and adopts an empty tower or a packed tower structurally; the lower part of the flue gas pretreatment tower is provided with a flue gas inlet; the upper part of the flue gas pretreatment tower is provided with an aqueous solution or alkali solution inlet, the bottom of the flue gas pretreatment tower is provided with an aqueous solution or alkali solution outlet and is connected to the aqueous solution or alkali solution inlet through a cooler to form a circulating pipeline; the bottom of the flue gas pretreatment tower is also connected to a sewage discharge pipe.
Preferably, the method comprises the following steps: the absorption tower is a packed tower; the extraction regeneration tower is a liquid-liquid extraction tower; the structure of the extraction regeneration tower adopts a plate tower or a packed tower; the bottom of the extraction regeneration tower is provided with a heater.
Preferably, the method comprises the following steps: the lower part of the desorption tower is provided with a reboiler, the inlet of the reboiler is connected with the water solution phase outlet at the bottom of the desorption tower, and the outlet of the reboiler is connected with the lower part of the desorption tower; the desorption tower is connected with the extraction regeneration tower through a lean-rich liquid heat exchanger, a cold side inlet of the lean-rich liquid heat exchanger is connected with the bottom of the extraction regeneration tower, a corresponding outlet is connected with the upper part of the desorption tower, a hot side inlet is connected with the bottom of the desorption tower, and a corresponding outlet is connected with the upper part of the extraction regeneration tower; the condensed water outlets of the condenser and the compressor are connected to a condensed water inlet at the upper part of the desorption tower.
Preferably, the method comprises the following steps: the water balance tower is a packed tower or a plate tower; the upper part of the water balance tower is provided with a washing liquid inlet, the lower part of the water balance tower is provided with a washing liquid outlet, the washing liquid outlet is connected to the washing liquid inlet through a cooler on the solution pipeline to form a circulating pipeline, and the washing liquid outlet is also connected to an extract liquid inlet on the upper part of the extraction regeneration tower; the upper part of the solvent recovery tower is provided with a solvent washing liquid inlet, the lower part of the solvent recovery tower is provided with a solvent washing liquid outlet, the solvent washing liquid outlet is connected to the solvent washing liquid inlet through a cooler to form a circulating pipeline, and the solvent washing liquid outlet is also connected to a sewage discharge pipe; the solvent recovery column structurally adopts a packed column, a plate column or a membrane contactor.
The working method of the flue gas carbon dioxide capture system based on the organic solvent absorption-extraction regeneration cycle comprises the following steps:
s1, enabling the flue gas to enter from the lower part of the flue gas pretreatment tower and flow from bottom to top, and enabling the aqueous solution or the alkali solution in the flue gas pretreatment tower to be in countercurrent contact with the flue gas from top to bottom;
s2, enabling the flue gas at the outlet of the pretreatment tower to enter from the lower part of the absorption tower, flow from bottom to top and be discharged from the top of the absorption tower; the organic solvent in the absorption tower is in countercurrent contact with the flue gas from top to bottom, and CO is discharged from the bottom of the absorption tower and absorbed2The organic solvent rich solution of (4);
s3, enabling the flue gas discharged from the top of the absorption tower to enter a water balance tower and flow from bottom to top, enabling a water washing liquid in the water balance tower to be in countercurrent contact with the flue gas from top to bottom and then discharged from the lower part of the water balance tower, and mixing part of the water washing liquid with a water solution entering the upper part of the extraction regeneration tower through a solution pipeline; flue gas discharged from the top of the water balance tower enters a solvent recovery tower and flows from bottom to top, a solvent washing liquid in the solvent recovery tower is in countercurrent contact with the flue gas from top to bottom, the solvent washing liquid is discharged from the lower part of the solvent recovery tower and is sent to waste liquid for recovery, and the flue gas is discharged from the top of the solvent recovery tower through a flue gas pipeline;
S4, pumping the rich organic solvent liquid from the bottom of the absorption tower into the inlet at the lower part of the extraction regeneration tower, flowing from bottom to top, discharging from the top of the extraction regeneration tower, and circularly absorbing CO in the upper part of the absorption tower2(ii) a The extraction liquid enters from the upper part of the extraction regeneration tower, is in countercurrent contact with the organic solvent rich solution from top to bottom, and is discharged from the bottom of the extraction regeneration tower;
s5, allowing the hot rich liquid of the aqueous solution phase to flow from top to bottom to desorb CO2Then, discharging from the bottom of the desorption tower; a reboiler at the lower part of the desorption tower heats up and heats the tower body of the desorption tower, and the aqueous solution phase hot barren solution discharged from the bottom of the desorption tower is sent back to the upper part of the extraction regeneration tower after passing through a barren and rich solution heat exchanger; CO desorbed from the top of the desorption tower2And sending the condensate water into a condensation and compression unit, and sending the condensate water of the condenser and the compressor back to the upper part of the desorption tower after recovering the condensate water.
Preferably, the method comprises the following steps: in step S1, the temperature of the flue gas after passing through the flue gas pretreatment tower is reduced to 40 ℃.
Preferably, the method comprises the following steps: in step S3, the water washing solution is a diluted aqueous solution corresponding to the organic solvent in the absorption column.
Preferably, the method comprises the following steps: in step S4, the temperature range for extraction regeneration is 50-90 ℃.
Preferably, the method comprises the following steps: in step S5, the operating temperature range of the desorption tower is 100-150 ℃; the heat source of the reboiler is from high-temperature steam, part of water solution phase discharged from the bottom of the desorption tower enters the reboiler, the water solution phase generates steam after passing through the reboiler, and CO is purged 2A desorption tower; the reboiler adopts a falling film reboiler or a thermosyphon reboiler; the lean-rich liquid heat exchanger recovers heat in an aqueous solution phase discharged from the bottom of the desorption tower and preheats the heat into the lean-rich liquid heat exchangerThe aqueous solution phase enters a desorption tower; the lean-rich liquid heat exchanger adopts a shell-and-tube or plate heat exchanger, and the heat exchange temperature difference range is 5-15 ℃.
The invention has the beneficial effects that:
(1) the system gives full play to the CO of the organic solvent in the absorption tower2High absorption rate, rich solution in regeneration tower CO2The advantage of large circulation capacity, thus reducing the size of the absorption tower, reducing the heat consumption of the desorption tower and reducing the carbon capture cost.
(2) The system adopts' CO2Absorption tower-extraction regeneration tower-CO2Desorption tower 'three-tower circulation scheme' pre-enriching CO in organic solvent by extraction regeneration tower2Regenerating organic solvent, and desorbing CO by heating organic solution in desorption tower2And the energy consumption of system operation is reduced.
(3) This system considers organic solvent to volatilize and leads to system water balance and solvent emission problem, sets up the water balance tower and is used for maintaining system water balance, sets up the organic solvent that solvent recovery tower retrieved the emission, guarantees system steady operation, reduces pollutant simultaneously and discharges.
Drawings
FIG. 1 is a schematic diagram of a flue gas carbon dioxide capture system based on an organic solvent absorption-extraction regeneration cycle;
FIG. 2 is a schematic diagram of a three-column process system "organic solvent (DEEA) absorption-extractive regeneration-aqueous solution (AEEA) desorption";
FIG. 3 is a schematic diagram of a water balance tower controlling the water balance of a carbon dioxide capture system;
FIG. 4 is a schematic diagram of a further control system for the amine emission from the solvent recovery column.
Description of the reference numerals: 1-flue gas inlet; 2-a flue gas pretreatment tower; 3-a cooler; 4, discharging sewage; 5, a flue gas inlet of the absorption tower; 6-an absorption tower; 7-flue gas outlet of absorption tower; 8-rich liquid outlet of the absorption tower; 9-extraction regeneration tower; 10-an organic phase outlet of the extraction regeneration tower; 11-aqueous solution phase cold rich liquid at the outlet of the extraction regeneration tower; 12-a water balance tower; 13-flue gas outlet of water balance tower; 14-outlet of water washing liquid of water balance tower; 15-solvent recoveryA tower; 16-discharging clean flue gas; 17-solvent wash outlet; 18-lean-rich liquor heat exchanger; 19-aqueous solution phase hot rich liquid; 20-a desorber; 21-aqueous solution phase hot lean solution; 22-a reboiler; 23-aqueous solution phase cold barren liquor; 24-regeneration gas; 25-a condenser; 26-condensed water; 27-pure CO 2(ii) a 28-a compressor; 29-pressurized pure CO2。
Detailed Description
The present invention will be further described with reference to the following examples. The following examples are set forth merely to aid in the understanding of the invention. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
Example one
The flue gas carbon dioxide capture system based on organic solvent absorption-extraction regeneration circulation comprises a flue gas pretreatment tower 2, an absorption tower 6, an extraction regeneration tower 9, a desorption tower 20, a water balance tower 12 and a solvent recovery tower 15; a flue gas outlet at the top of the flue gas pretreatment tower 2 is connected to a flue gas inlet at the lower part of the absorption tower 6; a flue gas outlet at the top of the absorption tower 6 is connected to a flue gas inlet at the bottom of the water balance tower 12; a flue gas outlet at the top of the water balance tower 12 is connected to a flue gas inlet at the bottom of the solvent recovery tower 15 through a flue gas pipeline; a rich liquid outlet of the absorption tower 6 is connected to a rich liquid inlet at the bottom of the extraction regeneration tower 9, and an organic phase outlet at the top of the extraction regeneration tower 9 is connected to an organic solvent inlet at the upper part of the absorption tower 6 through a cooler 3; an extract inlet at the upper part of the extraction regeneration tower 9 is connected with an aqueous solution phase hot barren liquor outlet at the bottom of the desorption tower 20 through a barren and rich liquor heat exchanger 18, and an aqueous solution phase cold rich liquor outlet at the bottom of the extraction regeneration tower 9 is connected with an aqueous solution phase hot rich liquor inlet at the upper part of the desorption tower 20 through the barren and rich liquor heat exchanger 18; the regeneration gas outlet at the top of the desorption tower 20 is connected to the inlet of a condenser 25, and the CO of the condenser 25 2The outlet is connected to the inlet of the compressor 28.
As a preferred embodiment, the flue gas pretreatment tower 2 can adopt a water washing tower or an alkali washing tower, and can structurally select an empty tower or a packed tower for cooling the flue gas and cooling the flue gasRemoving SO in flue gas2And the like, impurity acid gases. The lower part of the flue gas pretreatment tower 2 is provided with a flue gas inlet 1. The upper part of the flue gas pretreatment tower is provided with an aqueous solution or alkali solution inlet, and the bottom of the flue gas pretreatment tower is provided with an aqueous solution or alkali solution outlet and is connected to the aqueous solution or alkali solution inlet through a cooler 3 to form a circulating pipeline. The bottom of the flue gas pretreatment tower is also connected to a sewage discharge pipe.
As a preferred embodiment, the absorption tower 6 uses an organic solvent as CO2Absorbent, and the absorption tower is a packed tower.
As a preferred embodiment, the extractive regeneration column 9 is a liquid-liquid extraction column, and the organic solvent phase is countercurrently contacted with the aqueous phase. The structure of the extraction regeneration tower 9 can be a plate tower or a packed tower. The bottom of the extraction regeneration tower 9 is provided with a heater for controlling the temperature of extraction regeneration in the tower.
In a preferred embodiment, a reboiler 22 is provided at the lower part of the desorption tower 20, an inlet of the reboiler is connected to an outlet of the aqueous solution phase at the bottom of the desorption tower, and an outlet of the reboiler is connected to the lower part of the desorption tower. The desorption tower is connected with the extraction regeneration tower through the lean-rich liquid heat exchanger, a cold side inlet of the lean-rich liquid heat exchanger is connected with the bottom of the extraction regeneration tower, a corresponding outlet is connected with the upper part of the desorption tower, a hot side inlet is connected with the bottom of the desorption tower, and a corresponding outlet is connected with the upper part of the extraction regeneration tower.
In a preferred embodiment, the water balance tower 12 is a packed tower or a tray tower for controlling the water balance of the system. The upper part of the water balance tower is provided with a washing liquid inlet, the lower part of the water balance tower is provided with a washing liquid outlet, the washing liquid outlet is connected to the washing liquid inlet through a cooler 3 on the solution pipeline to form a circulating pipeline, and the washing liquid outlet is also connected to an extract liquid inlet on the upper part of the extraction regeneration tower.
As a preferred embodiment, the upper part of the solvent recovery tower 15 is provided with a solvent washing liquid inlet, the lower part of the solvent recovery tower 15 is provided with a solvent washing liquid outlet, the solvent washing liquid outlet is connected to the solvent washing liquid inlet through the cooler 3 to form a circulating pipeline, and the solvent washing liquid outlet is also connected to a sewage discharge pipe. The solvent recovery tower can be a packed tower, a plate tower or a membrane contactor (the membrane contactor is an independent device and can be independently used for solvent recovery, and the packed tower and the plate tower are collectively called as the solvent recovery tower).
As a preferred embodiment, the condensed water outlets of the condenser 25 and the compressor 28 are connected to a condensed water inlet at an upper portion of the desorption tower 20.
Example two
The working method of the flue gas carbon dioxide capture system based on the organic solvent absorption-extraction regeneration cycle comprises the following steps: the lower part of the flue gas pretreatment tower 2 is provided with a flue gas inlet 1, and flue gas is evacuated after sequentially passing through the flue gas pretreatment tower 2, an absorption tower 6, a water balance tower 12 and a solvent recovery tower 15; organic solvent absorbs CO in the absorption tower 6 2After entering the extraction regeneration tower 9, the mixture is sent back to the absorption tower 6 for circulating absorption of CO2(ii) a Enrichment of CO2Desorbs CO in the desorption column 202Then enters an extraction regeneration tower 9 and is sent back to a desorption tower 20 for circularly desorbing CO2. The method specifically comprises the following steps:
s1, enabling the flue gas to enter from the lower part of the flue gas pretreatment tower 2 and flow from bottom to top, and enabling the aqueous solution or the alkali solution in the flue gas pretreatment tower to be in countercurrent contact with the flue gas from top to bottom;
as a preferred embodiment, the temperature of the flue gas after passing through the flue gas pretreatment column is reduced to about 40 ℃.
S2, enabling the flue gas at the outlet of the pretreatment tower to enter from the lower part of the absorption tower 6, flow from bottom to top and be discharged from the top of the absorption tower; the organic solvent in the absorption tower is in countercurrent contact with the flue gas from top to bottom, and CO is discharged from the bottom of the absorption tower and absorbed2The organic solvent rich solution of (4);
s3, enabling the flue gas discharged from the top of the absorption tower to enter a water balance tower 12 and flow from bottom to top, enabling a water washing liquid in the water balance tower 12 to be in countercurrent contact with the flue gas from top to bottom and then discharged from the lower part of the water balance tower, and mixing part of the water washing liquid with a water solution entering the upper part of an extraction regeneration tower through a solution pipeline; flue gas discharged from the top of the water balance tower enters a solvent recovery tower 15 and flows from bottom to top, a solvent washing liquid in the solvent recovery tower is in countercurrent contact with the flue gas from top to bottom, the solvent washing liquid is discharged from the lower part of the solvent recovery tower and is sent to waste liquid for recovery, and the flue gas is discharged from the top of the solvent recovery tower through a flue gas pipeline;
As a preferred example, a dilute aqueous solution corresponding to the organic solvent in the absorption column is used as the water washing liquid, and the concentration thereof is determined by the volatility of the organic solvent.
S4, pumping the rich liquid of organic solvent discharged from the bottom of the absorption tower into the inlet at the lower part of the extraction regeneration tower 9, flowing from bottom to top, discharging from the top of the extraction regeneration tower, and then feeding into the upper part of the absorption tower for circularly absorbing CO2(ii) a The extraction liquid enters from the upper part of the extraction regeneration tower, is in countercurrent contact with the organic solvent rich solution from top to bottom, and is discharged from the bottom of the extraction regeneration tower;
as a preferred embodiment, the temperature range of the extraction regeneration is 50-90 ℃, and the increase of the temperature is beneficial to increase of the extraction regeneration rate, thereby reducing the volume of the extraction tower.
S5, allowing the hot rich liquid of the aqueous solution phase to flow from top to bottom in the desorption tower 20 to desorb CO2Then, discharging from the bottom of the desorption tower; a reboiler 22 at the lower part of the desorption tower heats the tower body of the desorption tower, and the aqueous solution phase hot barren liquor 21 discharged from the bottom of the desorption tower passes through the barren and rich liquor heat exchanger 18 and is sent back to the upper part of the extraction regeneration tower; CO desorbed from the top of the desorption tower2The condensed water 26 sent into the condensing and compressing unit, the condenser 25 and the compressor 28 is recycled and then sent back to the upper part of the desorption tower;
As a preferred embodiment, the operating temperature range of the desorption tower is 100-150 ℃; the heat source of the reboiler is high-temperature steam, part of the aqueous solution phase discharged from the bottom of the desorption tower enters the reboiler, the outlet of the reboiler is connected with the lower part of the desorption tower, the aqueous solution phase generates steam after passing through the reboiler, and CO is swept2A desorber; the reboiler can be a falling film reboiler or a thermosiphon reboiler; the lean-rich liquid heat exchanger is used for recovering heat in an aqueous solution phase discharged from the bottom of the desorption tower and preheating the aqueous solution phase entering the desorption tower; the lean-rich liquid heat exchanger can be a shell-and-tube or plate heat exchanger, and the heat exchange temperature difference range is 5-15 ℃.
EXAMPLE III
FIG. 2 shows three-tower CO capture2Technical scheme showsThe intention is that the absorption tower uses organic solvent to absorb CO2The components and mass concentration are as follows: 92% DEEA/2% AEEA/6% H2And O. The absorption tower operates at 40 ℃, and CO is absorbed completely2The organic solvent is sent to the lower part of the extraction regeneration tower, discharged from the top and returned to the absorption tower for circularly absorbing CO2。
CO2The desorption tower adopts an aqueous solution phase, and the components and mass concentration are as follows: 40% AEEA/40% H2O/10% DEEA. The desorption tower operates at 120 ℃ to desorb CO2The water solution phase is recovered with heat through the lean and rich liquor heat exchanger, sent to the extract liquid inlet at the upper part of the extraction regeneration tower, discharged from the bottom of the extraction tower from top to bottom, and returned to CO through the lean and rich liquor heat exchanger 2A desorption tower. The extraction regeneration tower was operated at 50 ℃.
Example four
The flue gas temperature is 60 ℃, the pretreatment tower adopts a water washing tower, the temperature of the flue gas is 40 ℃ after the temperature of the pretreatment tower is reduced, the flue gas is in a wet saturation state (the moisture content is about 7 percent, the water vapor partial pressure is about 7.4kPa), and CO in the flue gas2The concentration was 12.0%, as shown in FIG. 3. The organic solvent in the absorption tower is 30 percent of MEA/66 percent of NMP/4 percent of H2O, CO in the absorption column2The capture rate is 90 percent, because of CO2The absorption reaction was exothermic and the absorber outlet temperature was about 55 ℃. The water concentration in the flue gas at the outlet of the absorption tower was about 18% (water vapor partial pressure about 18.4kPa), and the emission of MEA due to volatilization was evaluated at 3452mg/m3。
The water balance tower adopts MEA diluted aqueous solution, the mass concentration is 3.6 percent of MEA, and the operation temperature is 40.9 ℃. The outlet gas had a moisture concentration of 7.6% (water vapor partial pressure of about 7.7kPa) under the assumption that the water balance column outlet was at thermodynamic conditions. Under this temperature, the moisture in the gas of absorption tower outlet can be retrieved to the water balance tower, guarantees that the moisture flow of outlet gas is equal with the moisture flow in the absorption tower flue gas import, keeps system water balance promptly. Meanwhile, the water balance tower can recover part of the organic solvent. Under the working condition, the MEA discharge at the outlet of the water balance tower is reduced to 17.8mg/m 3。
EXAMPLE five
The solvent recovery column may be a packed column, an empty column, a membrane contactor, etc., depending on the volatility of the absorbent and the technical economy.
Example four organic solvent MEA/NMP/H2The MEA discharge level at the outlet of the water balance tower is still higher. To further reduce MEA emissions, consider the solvent recovery column as a packed column, with the scrubbing liquid as water, and the operating temperature at 25 ℃, as shown in fig. 4.
At this temperature, the washed solvent recovery column recovers the moisture in the flue gas by reducing the temperature, e.g., at 25 ℃, the moisture concentration in the outlet gas of the solvent recovery column is reduced from 7.6% (water vapor partial pressure about 7.7kPa) to 3.5% (water vapor partial pressure about 3.6kPa), and the MEA emissions are reduced to 0.08mg/m3。
The system gives full play to the CO of the organic solvent in the absorption tower2High absorption rate, rich solution in regeneration tower CO2The advantage of large circulation capacity, thus reducing the size of the absorption tower, reducing the heat consumption of the desorption tower and reducing the carbon capture cost; meanwhile, the system considers the problems of water balance and solvent emission of the system caused by volatilization of the organic solvent, ensures stable operation of the system and reduces pollutant emission.
Claims (10)
1. A flue gas carbon dioxide capture system based on organic solvent absorption-extraction regeneration cycle is characterized in that: comprises a flue gas pretreatment tower (2), an absorption tower (6), an extraction regeneration tower (9), a desorption tower (20), a water balance tower (12) and a solvent recovery tower (15); a flue gas outlet at the top of the flue gas pretreatment tower (2) is connected to a flue gas inlet at the lower part of the absorption tower (6); a flue gas outlet at the top of the absorption tower (6) is connected to a flue gas inlet at the bottom of the water balance tower (12); a flue gas outlet at the top of the water balance tower (12) is connected to a flue gas inlet at the bottom of the solvent recovery tower (15) through a flue gas pipeline; a rich liquid outlet of the absorption tower (6) is connected to a rich liquid inlet at the bottom of the extraction regeneration tower (9), and an organic phase outlet at the top of the extraction regeneration tower (9) is connected to an organic solvent inlet at the upper part of the absorption tower (6) through a cooler (3); an extract liquid inlet at the upper part of the extraction regeneration tower (9) is connected with an aqueous solution phase hot barren solution outlet at the bottom of the desorption tower (20) through a barren and rich solution heat exchanger (18), an aqueous solution phase cold rich solution outlet at the bottom of the extraction regeneration tower (9) is connected with an aqueous solution phase hot barren solution outlet at the upper part of the desorption tower (20) through the barren and rich solution heat exchanger (18) The hot rich liquor inlet of the aqueous solution phase; the regenerated gas outlet at the top of the desorption tower (20) is connected to the inlet of a condenser (25), and CO of the condenser (25)2The outlet is connected to the inlet of a compressor (28).
2. The flue gas carbon dioxide capture system based on organic solvent absorption-extraction regeneration cycle of claim 1, characterized in that: the flue gas pretreatment tower (2) adopts a water washing tower or an alkali washing tower, and adopts an empty tower or a packed tower structurally; the lower part of the flue gas pretreatment tower (2) is provided with a flue gas inlet (1); the upper part of the flue gas pretreatment tower is provided with an aqueous solution or alkali solution inlet, the bottom of the flue gas pretreatment tower is provided with an aqueous solution or alkali solution outlet and is connected to the aqueous solution or alkali solution inlet through a cooler (3) to form a circulating pipeline; the bottom of the flue gas pretreatment tower is also connected to a sewage discharge pipe.
3. The flue gas carbon dioxide capture system based on organic solvent absorption-extraction regeneration cycle of claim 1, characterized in that: the absorption tower (6) is a packed tower; the extraction regeneration tower (9) is a liquid-liquid extraction tower; the structure of the extraction regeneration tower (9) adopts a plate tower or a packed tower; the bottom of the extraction regeneration tower (9) is provided with a heater.
4. The flue gas carbon dioxide capture system based on organic solvent absorption-extraction regeneration cycle of claim 1, characterized in that: a reboiler (22) is arranged at the lower part of the desorption tower (20), the inlet of the reboiler is connected with the water solution phase outlet at the bottom of the desorption tower, and the outlet of the reboiler is connected with the lower part of the desorption tower; the desorption tower is connected with the extraction regeneration tower through a lean-rich liquid heat exchanger, a cold side inlet of the lean-rich liquid heat exchanger is connected with the bottom of the extraction regeneration tower, a corresponding outlet is connected with the upper part of the desorption tower, a hot side inlet is connected with the bottom of the desorption tower, and a corresponding outlet is connected with the upper part of the extraction regeneration tower; the condensed water outlets of the condenser (25) and the compressor (28) are connected to the condensed water inlet at the upper part of the desorption tower (20).
5. The flue gas carbon dioxide capture system based on organic solvent absorption-extraction regeneration cycle of claim 1, characterized in that: the water balance tower (12) is a packed tower or a plate tower; the upper part of the water balance tower is provided with a washing liquid inlet, the lower part of the water balance tower is provided with a washing liquid outlet, the washing liquid outlet is connected to the washing liquid inlet through a cooler (3) on a solution pipeline to form a circulating pipeline, and the washing liquid outlet is also connected to an extract liquid inlet on the upper part of the extraction regeneration tower; the upper part of the solvent recovery tower (15) is provided with a solvent washing liquid inlet, the lower part of the solvent recovery tower (15) is provided with a solvent washing liquid outlet, the solvent washing liquid outlet is connected to the solvent washing liquid inlet through a cooler (3) to form a circulating pipeline, and the solvent washing liquid outlet is also connected to a sewage discharge pipe; the solvent recovery column structurally adopts a packed column, a plate column or a membrane contactor.
6. A method of operating a flue gas carbon dioxide capture system based on an organic solvent absorption-extraction regeneration cycle as claimed in claim 1, comprising the steps of:
s1, enabling the flue gas to enter from the lower part of the flue gas pretreatment tower (2) and flow from bottom to top, and enabling the aqueous solution or the alkali solution in the flue gas pretreatment tower to be in countercurrent contact with the flue gas from top to bottom;
S2, enabling flue gas at the outlet of the pretreatment tower to enter from the lower part of the absorption tower (6), flow from bottom to top and be discharged from the top of the absorption tower; the organic solvent in the absorption tower is in countercurrent contact with the flue gas from top to bottom, and CO is discharged from the bottom of the absorption tower and absorbed2The organic solvent rich solution of (4);
s3, enabling the flue gas discharged from the top of the absorption tower to enter a water balance tower (12) and flow from bottom to top, enabling water washing liquid in the water balance tower (12) to be in countercurrent contact with the flue gas from top to bottom and then discharged from the lower part of the water balance tower, and mixing part of the water washing liquid with the water washing liquid entering the upper part of the extraction regeneration tower through a solution pipeline; the flue gas discharged from the top of the water balance tower enters a solvent recovery tower (15) and flows from bottom to top, a solvent washing liquid in the solvent recovery tower is in countercurrent contact with the flue gas from top to bottom, the solvent washing liquid is discharged from the lower part of the solvent recovery tower and is sent to waste liquid for recovery, and the flue gas is discharged from the top of the solvent recovery tower through a flue gas pipeline;
s4, discharging organic solvent rich liquid from the bottom of the absorption towerPumping into the lower inlet of the extraction regeneration tower (9), flowing from bottom to top, discharging from the top of the extraction regeneration tower, and circularly absorbing CO in the upper part of the absorption tower2(ii) a The extraction liquid enters from the upper part of the extraction regeneration tower, is in countercurrent contact with the organic solvent rich liquid from top to bottom and is discharged from the bottom of the extraction regeneration tower;
S5, allowing the hot rich liquid of the aqueous solution phase to enter from the upper part of the desorption tower (20) and flow from top to bottom to desorb CO2Then, discharging from the bottom of the desorption tower; a reboiler (22) at the lower part of the desorption tower heats up and heats the tower body of the desorption tower, and the water solution phase hot barren liquor (21) discharged from the bottom of the desorption tower is sent back to the upper part of the extraction regeneration tower after passing through a barren and rich liquor heat exchanger (18); CO desorbed from the top of the desorption tower2Condensed water (26) sent to a condensing and compressing unit, a condenser (25) and a compressor (28) is recovered and then sent to the upper part of the desorption tower.
7. The working method of the flue gas carbon dioxide capture system based on the organic solvent absorption-extraction regeneration cycle as claimed in claim 6, wherein: in step S1, the temperature of the flue gas after passing through the flue gas pretreatment tower is reduced to 40 ℃.
8. The working method of the flue gas carbon dioxide capture system based on the organic solvent absorption-extraction regeneration cycle as claimed in claim 6, wherein: in step S3, the water washing solution is a diluted aqueous solution corresponding to the organic solvent in the absorption column.
9. The working method of the flue gas carbon dioxide capture system based on the organic solvent absorption-extraction regeneration cycle as claimed in claim 6, wherein: in step S4, the temperature range for extraction regeneration is 50-90 ℃.
10. The working method of the flue gas carbon dioxide capture system based on the organic solvent absorption-extraction regeneration cycle as claimed in claim 6, wherein: in step S5, the operating temperature range of the desorption tower is 100-150 ℃; the heat source of the reboiler is high-temperature steam, and part of water discharged from the bottom of the desorption towerThe solution phase enters a reboiler, the water solution phase generates steam after passing through the reboiler, and CO is purged2A desorption tower; the reboiler adopts a falling film reboiler or a thermosyphon reboiler; the lean-rich liquid heat exchanger recovers heat in an aqueous solution phase discharged from the bottom of the desorption tower and preheats the aqueous solution phase entering the desorption tower; the lean-rich liquid heat exchanger adopts a shell-and-tube or plate heat exchanger, and the heat exchange temperature difference range is 5-15 ℃.
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