CN113578025B - Method and system for capturing carbon dioxide in flue gas - Google Patents

Method and system for capturing carbon dioxide in flue gas Download PDF

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CN113578025B
CN113578025B CN202110964926.2A CN202110964926A CN113578025B CN 113578025 B CN113578025 B CN 113578025B CN 202110964926 A CN202110964926 A CN 202110964926A CN 113578025 B CN113578025 B CN 113578025B
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carbon dioxide
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CN113578025A (en
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王长红
蒋凯琦
柴立元
李帅
向开松
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Hunan Tongfeng Qingcarbon Technology Co.,Ltd.
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Central South University
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    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
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Abstract

The invention provides a method for capturing carbon dioxide in flue gas, which comprises the following steps: conveying the flue gas containing carbon dioxide to an absorption device for absorbing the carbon dioxide to obtain absorption liquid and purified gas; conveying the absorption liquid to an anode chamber of an electrolytic absorption device for desorption to obtain a gas-liquid mixture containing a metal/ammonia coordination compound and carbon dioxide; carrying out gas-liquid separation treatment on the gas-liquid mixture to obtain carbon dioxide gas and separation liquid; conveying the separated liquid into a cathode chamber of the electro-desorption device, and performing electrodeposition on the separated liquid in the cathode chamber to obtain deposited metal and ammonia-containing solution; and sending the ammoniated solution to the absorption device for absorption of the carbon dioxide again. The invention provides a novel system for capturing carbon dioxide in flue gas, which can obviously reduce energy consumption and input cost, reduce ammonia volatilization and avoid degradation of an absorbent on the premise of efficiently purifying and separating the carbon dioxide in the flue gas.

Description

Method and system for capturing carbon dioxide in flue gas
Technical Field
The invention relates to the field of gas purification and separation, in particular to a method and a system for capturing carbon dioxide in flue gas.
Background
In recent years, global warming caused by greenhouse gases, particularly carbon dioxide, has become a problem of great concern worldwide. However, the environmental problems caused by carbon dioxide still stand out so far, and therefore how to effectively capture the carbon dioxide in the flue gas is an urgent problem to be solved at present.
Nowadays, the only post-combustion carbon dioxide capture process in the world that achieves commercial operation is a thermal regeneration amine capture process, which employs a thermal carbon capture technology and employs organic amine as an absorbent. Although it can effectively capture carbon dioxide, due to the economic constraints of high energy consumption and high reconstruction cost and the technical constraints of absorbent degradation, the large-scale commercial application of the process can not be realized in a short time, and the specific explanation is as follows:
the energy consumption is high: by adopting the heat regeneration amine method trapping process, the heat energy consumption reduces the power generation efficiency of a power plant by 18-30 percent, the energy consumption of the heat method amine trapping technology is mainly attributed to the high-temperature heat energy consumption (120-150 ℃) required by the regeneration of the amine solvent, and the energy consumption accounts for more than 60 percent of the total energy consumption; the reconstruction cost is high: to provide the steam heat energy required for the carbon capture process, the steam cycle system of a thermal power plant needs to be modified, for example, the amine capture project of "boundary dams" takes 14 billion dollars to process flue gas from a 160MW power plant, wherein the modification of the plant steam turbine and steam cycle system to extract steam suitable for amine regeneration takes 5 billion dollars; degradation of the absorbent: almost all organic amines, including monoethanolamine, diisopropanolamine, diethanolamine, methyldiethanolamine, and the like, undergo degradation of the amine (thermal degradation and oxidative degradation) and produce various degradation products, resulting in loss of the absorbent and reduction of the absorption capacity, thereby greatly increasing the operation and maintenance costs.
To address the problems associated with the thermal regeneration amine capture process, inorganic ammonia-based carbon capture technologies have emerged in the corresponding exemplary engineering and published patent literature. For example, chinese patent with publication number CN104107629B discloses a flue gas carbon dioxide capture system and capture method, wherein the capture method is based on thermal carbon capture, and comprises: 1. a carbon dioxide capture stage; 2. ammonia gas detection and recovery stage; 3. a carbon dioxide regeneration stage; 4. concentrating and heat-extracting phase of regenerated carbon dioxide; wherein the carbon dioxide regeneration stage in step 3 comprises: and heating the pregnant solution after capturing the carbon dioxide, introducing the pregnant solution into a regeneration tower, carrying out pyrolysis reaction in the regeneration tower to release the carbon dioxide, and simultaneously regenerating the ammonia water absorbent for capturing the carbon dioxide.
Compared with the trapping process by the thermal regeneration amine method, although the patent can reduce energy consumption and cost to a certain extent, the method of replacing inorganic ammonia with organic ammonia can avoid the problem of absorbent degradation as much as possible. However, this patent still belongs to a typical thermal carbon capture method, which mainly comprises an absorption tower for capturing carbon dioxide in flue gas and a desorption tower for releasing carbon dioxide by using thermal energy, the supply of which usually comes from plant or power station steam. The overall process property of the patent determines that the absorbent still has the characteristics of high energy consumption and high investment, and in addition, because the absorbent is regenerated by adopting a thermal method, a large amount of ammonia volatilization can be caused, and the later-stage ammonia recycling cost is increased.
In view of the above, a method and a system for capturing carbon dioxide in flue gas are needed to solve or at least alleviate the above technical defects of high energy consumption, high reconstruction cost, large ammonia volatilization, degradation of absorbent, and the like.
Disclosure of Invention
The invention mainly aims to provide a method and a system for trapping carbon dioxide in flue gas, and aims to solve the problems of high energy consumption, high reconstruction cost, high ammonia volatilization and absorbent degradation in the prior art.
In order to achieve the above object, the present invention provides a method for capturing carbon dioxide in flue gas, comprising the steps of:
s1, conveying the flue gas containing carbon dioxide to an absorption device for absorbing the carbon dioxide to obtain absorption liquid and purified gas, wherein the absorption device adopts ammonia-containing solution to absorb the carbon dioxide;
s2, conveying the absorption liquid to an anode chamber of an electrowinning device, wherein an electrode of the anode chamber adopts a metal electrode, and the metal electrode contains a transition metal element which is coordinated and combined with ammonia, so that the absorption liquid is desorbed under the action of the metal electrode in the anode chamber to obtain a gas-liquid mixture containing a metal/ammonia coordination compound and carbon dioxide;
s3, carrying out gas-liquid separation treatment on the gas-liquid mixture to obtain carbon dioxide gas and separation liquid; conveying the separated liquid into a cathode chamber of the electro-desorption device, and performing electrodeposition on the separated liquid in the cathode chamber to obtain deposited metal and ammonia-containing solution, wherein the cathode chamber and the anode chamber in the electro-desorption device are separated;
s4, conveying the ammonia-containing solution in the cathode chamber to the absorption device for absorbing the carbon dioxide.
Further, the ammonia-containing solution in the absorption tower is provided with a supporting electrolyte.
Further, the operating temperature of the absorption device in the absorption process is 10-40 ℃.
Further, the operating temperature in the electrolytic absorption device is 40-80 ℃; (ii) a The current density of the electric desorption device is 50-500A/m2。
Further, the transition metal element comprises one or more of zinc element, copper element, nickel element and silver element.
Further, the anode chamber and the cathode chamber are separated from each other by an anion exchange membrane.
Further, the gas-liquid separation process includes: sequentially carrying out flash evaporation and condensation on the gas-liquid mixture; obtaining initial separation liquid and gas to be condensed after flash evaporation, and obtaining carbon dioxide gas and condensate after condensation;
after the condensation, the condensate is mixed with the initial separation liquid to obtain the separation liquid.
Further, the electrode of the cathode chamber and the electrode of the anode chamber have the same transition metal element; and the electrode of the cathode chamber and the electrode of the anode chamber or the current direction are interchanged according to a preset period.
Further, the step S1 further includes: and leaching the purified gas to obtain separated ammonia and the gas to be discharged, wherein the separated ammonia exists in the form of ammonia-containing leacheate.
Further, conveying the ammonia-containing leacheate obtained through separation to a pretreatment device, and performing desulfurization treatment on the flue gas to be conveyed to the absorption device to obtain desulfurization liquid.
Further, heat exchange is carried out between the desulfurizing liquid which is not saturated and the ammonia-containing leacheate to be conveyed to the pretreatment device, after the heat exchange, the desulfurizing liquid which is not saturated is conveyed to a position where the purified gas is washed, and then the ammonia-containing leacheate with the desulfurizing liquid is conveyed to the desulfurization device.
The invention also provides a capturing system for obtaining the carbon dioxide in the flue gas, which comprises an absorption device, an electric desorption device and a gas-liquid separation device;
the absorption device is internally provided with ammonia-containing solution; the electrolytic absorption device comprises an anode chamber and a cathode chamber which are separated from each other, wherein the electrode of the anode chamber is a metal electrode, and the metal electrode contains a transition metal element which is coordinated and combined with ammonia;
the absorption device absorbs carbon dioxide after receiving the flue gas containing carbon dioxide to obtain absorption liquid and purified gas;
the anode chamber is communicated with an absorption liquid outlet of the absorption device, so that the absorption liquid is conveyed into the anode chamber from the inside of the absorption tower, and the absorption liquid is desorbed under the action of the metal electrode in the anode chamber to obtain a gas-liquid mixture containing a metal/ammonia coordination compound and carbon dioxide;
the gas-liquid separation device is communicated with a gas-liquid mixture outlet of the anode chamber, so that the gas-liquid mixture is conveyed into the gas-liquid separation device from the anode chamber, and then the gas-liquid mixture is separated to obtain carbon dioxide gas and separation liquid;
the cathode chamber is communicated with a separated liquid outlet of the gas-liquid separation device, so that the separated liquid is conveyed into the cathode chamber, and the separated liquid is subjected to electrodeposition in the cathode chamber to obtain deposited metal and ammonia-containing solution;
the absorption device is communicated with an ammonia-containing solution outlet of the cathode chamber, so that the ammonia-containing solution in the cathode chamber is conveyed to the inside of the absorption device, and the carbon dioxide is absorbed in the absorption device by the ammonia-containing solution.
Further, the capture system also comprises an ammonia separation and leaching device and a desulfurization device for flue gas pretreatment;
the purified gas inlet of the ammonia separation and leaching device is communicated with the purified gas outlet of the absorption device, so that the purified gas is conveyed from the absorption device to the ammonia separation and leaching device, and ammonia gas remaining in the purified gas is separated through the ammonia separation and leaching device to obtain ammonia-containing leaching liquid and gas to be discharged;
an ammonia-containing eluent inlet of the desulfurization device is communicated with an ammonia-containing eluent outlet of the ammonia separation and leaching device, and a return inlet of the ammonia separation and leaching device is communicated with a return outlet of the desulfurization device, so that the separated ammonia-containing eluent is conveyed from the ammonia separation and leaching device to the desulfurization device, the separated ammonia-containing eluent exists in the form of a desulfurization liquid after being combined with sulfur dioxide in the flue gas, the desulfurization liquid which is not in a saturated state flows back from the desulfurization device to the ammonia separation and leaching device to elute purified gas, and the separated ammonia-containing eluent is conveyed from the ammonia separation device to the desulfurization device;
and the exhaust port of the desulfurization device is communicated with the absorption device so as to convey the desulfurized flue gas containing carbon dioxide to the absorption device.
Furthermore, the absorption device is provided with an absorption area and a condensation area, the condensation area and the absorption area are arranged up and down and are isolated from each other through a partition plate, and the partition plate allows gas to pass through to block liquid substances;
wherein the absorption area is provided with a flue gas inlet for the flue gas to enter and an ammonia-containing solution inlet for the ammonia-containing solution to enter; the condensation zone is provided with a purified gas outlet for discharging the purified gas and an absorption liquid outlet for discharging the absorption liquid;
the absorption district with the condensation zone passes through the conveying line intercommunication, conveying line's one end with the bottom intercommunication in absorption district, conveying line's the other end with the upper portion intercommunication in condensation zone, the last cooling subassembly that installs of conveying line.
Further, the gas-liquid separation device comprises a flash tank and a condenser;
the gas-liquid mixture entry of flash tank with the gas-liquid mixture export intercommunication setting of anode chamber, the condenser treat the condensing gas entry with the condensing gas export intercommunication of waiting of flash tank, the condensate entry of flash tank with the condensate export intercommunication of condenser, the separator entry of cathode chamber with the separator export intercommunication of flash tank.
The trapping system further comprises a first heat exchange device, wherein a cold end inlet of the first heat exchange device is communicated with an absorption liquid outlet of the absorption device, a hot end outlet of the first heat exchange device is communicated with an absorption liquid inlet of the anode chamber, a hot end inlet of the first heat exchange device is communicated with an ammonia-containing solution outlet of the cathode chamber, and a cold end outlet of the first heat exchange device is communicated with an ammonia-containing solution inlet of the absorption device; the ammonia-containing solution to be conveyed into the absorption device and the absorption liquid to be conveyed into the anode chamber are subjected to heat exchange in the first heat exchange device;
absorbing liquid discharged from the absorbing device enters the first heat exchange device from the cold end inlet and is discharged from the first heat exchange device from the hot end outlet;
the ammoniated solution discharged from the cathode chamber enters the first heat exchange means from the warm end inlet and exits the first heat exchange means from the cold end outlet.
Compared with the prior art, the invention has the following advantages:
the invention provides a new system for capturing carbon dioxide in flue gas, and the traditional thermal cycle carbon capture is innovated to be the electrical cycle carbon capture with higher energy utilization rate, so that the energy efficiency is higher and the energy consumption is lower; the electrochemical system can avoid using low-pressure steam, and the flexibility of 'plug and play' enables the system to reduce the reconstruction cost of power plants and factories to the maximum extent, thereby reducing the investment cost; the inorganic ammonia has good chemical stability, is extremely difficult to degrade by combining the characteristic of the electrochemical system which operates at lower temperature, and in the process of ammonia regeneration, the characteristic of the electrochemical system which operates at lower temperature and the chemical characteristic of metal coordination are matched with each other, so that the volatilization of ammonia is obviously reduced, and the difficulty and the cost of ammonia recovery and use are reduced; in the whole system of the invention, carbon dioxide is absorbed in an absorption device by using an ammonia-containing solution; by adopting the transition metal element which is in coordination combination with ammonia as the electrode of the anode chamber, corresponding metal ions can be released into the carbon dioxide loaded absorption liquid in the anode chamber in an electrochemical dissolution mode, carbon dioxide is desorbed in a coordination combination mode with ammonia, and then the metal ions are electrodeposited in the cathode chamber to realize ammonia regeneration, so that the supply of the absorbent in the continuous carbon dioxide capturing process in a subsequent absorption device is ensured. In addition to the above advantages, the present invention is also useful for improving the cycle efficiency of the whole system, and in addition, the carbon dioxide capturing/decarbonizing rate in the present invention can reach 85% or more, and the purity of the finally discharged carbon dioxide product can reach 99% or more.
Drawings
In order to more clearly illustrate the embodiments or technical solutions of the present invention, the drawings used in the embodiments or technical solutions of the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
FIG. 1 is a schematic diagram of a trapping system according to an embodiment of the present invention;
FIG. 2 is a schematic view of an absorbent device according to an embodiment of the present invention;
the reference numbers indicate: the absorption device 110, the absorption zone 111, the condensation zone 112, the first heat exchange device 120, the cold end 121 of the first heat exchange device, the hot end 122 of the first heat exchange device, the anode chamber 131, the cathode chamber 132, the anion exchange membrane 133, the flash tank 141, the condenser 142, the desulfurizer 210, the second heat exchange device 220, the ammonia separation and leaching device 230, and the sulfur dioxide recovery device 240.
The implementation, functional features and advantages of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive efforts based on the embodiments of the present invention, are within the scope of protection of the present invention.
It should be noted that all the directional indicators (such as the upper and lower … …) in the embodiment of the present invention are only used to explain the relative position relationship, movement, etc. of the components in a specific posture (as shown in the drawings), and if the specific posture is changed, the directional indicator is changed accordingly.
In addition, descriptions such as "first", "second", etc. in the present invention are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature.
Moreover, the technical solutions in the embodiments of the present invention may be combined with each other, but it is necessary to be based on the realization of the technical solutions by those skilled in the art, and when the technical solutions are contradictory to each other or cannot be realized, such a combination of the technical solutions should not be considered to exist, and is not within the protection scope claimed by the present invention.
It will be appreciated by those skilled in the art that during the transportation, transportation or movement of the present invention, a pumping manner or a height difference manner may be selected, and the pumping manner may be specifically a manner of transporting the substance through a pipeline provided with a pump.
In order to capture carbon dioxide in flue gas and reduce energy consumption, reconstruction cost and absorbent degradation, referring to fig. 1-2, the invention provides a method for capturing carbon dioxide in flue gas, comprising the following steps:
s1, conveying the flue gas containing carbon dioxide to an absorption device 110 for absorbing the carbon dioxide to obtain absorption liquid and purified gas, wherein the absorption device 110 adopts ammonia-containing solution to absorb the carbon dioxide. The ammonia-containing solution in the absorption device 110 may contain a supporting electrolyte, and the supporting electrolyte may be potassium chloride, sodium sulfate, or the like; in addition, some additives may be added to the ammonia-containing solution in the absorption device 110, and the additives may be quaternary ammonium salts such as tetraethylammonium chloride and tetrapropylammonium chloride, synthetic polymers such as polyethylene glycol and polyacrylamide, and surfactants such as sodium dodecyl sulfate and dodecyltrimethylammonium bromide. Also, as a preference in the art, the operating temperature of the absorption device 110 during the absorption process may be 10 to 40 ℃.
It is required to know that the carbon content of the flue gas is 5% or more; the absorption liquid is a high carbon dioxide-loaded liquid obtained after carbon dioxide is absorbed by the ammoniated solution in the absorption apparatus 110, and the purified gas is a gas obtained after carbon dioxide is removed from the flue gas. In addition, the absorption device 110 may be a carbon dioxide absorption tower, and the absorption device 110 absorbs carbon dioxide by ammonia solution as a conventional technical means in the field.
The process of combining ammonia with carbon dioxide is as follows:
Figure GDA0003269555160000081
Figure GDA0003269555160000082
wherein CO in (R1) and (R2)2(l)Represents carbon dioxideAfter being conveyed to the absorption device, the ammonia-containing solution is introduced for reaction.
S2, conveying the absorption liquid to an anode chamber 131 of an electrolytic absorption device, wherein an electrode of the anode chamber 131 adopts a metal electrode containing a transition metal element which is coordinated and combined with ammonia, so that the absorption liquid is desorbed under the action of the metal electrode in the anode chamber 131 to obtain a gas-liquid mixture containing a metal/ammonia coordination compound and carbon dioxide; wherein the liquid component in the gas-liquid mixture is low carbon dioxide loading, high metal loading, primarily because carbon dioxide is mostly present in gaseous form. It is also to be understood that the operating temperature in the electroabsorption device is 40-80 ℃ and the current density of the electrodesorption device can be 50-500A/m2。
Note that, as an example of the transition metal element which is coordinately bound to ammonia, the transition metal element which is coordinately bound to ammonia includes one or more of a zinc element, a copper element, a nickel element, and a silver element; further, in a specific application process, only zinc element may be used as the transition metal element coordinately bound to ammonia in the present invention.
The electrolytic desorption device utilizes an electrochemical principle, adopts electrochemical circulation with high energy utilization rate, and can realize desorption of carbon dioxide and regeneration of ammonia by supplying power to the electric desorption device. The desorption of the carbon dioxide is specifically as follows: since the electrode of the anode chamber 131 contains the transition metal element (Me) capable of being coordinately bound with ammonia, the electrode of the anode chamber 131 can generate the corresponding metal ion (Me)2+) Through the coordination combination of the metal ions and ammonia, the carbon dioxide in the absorption liquid can be desorbed, so that the energy consumption is reduced on the premise of ensuring the desorption of the carbon dioxide.
The desorption process of carbon dioxide is as follows:
Figure GDA0003269555160000091
wherein Me in (R3)(s)Represents a transition metal element which is in a solid state and can be coordinately bound to ammonia.
It should be noted that although the metal ion is coordinately bound to ammonia to form a metal/ammonia complex, the metal/ammonia complex may be converted into a deposition metal and ammonia in the cathode chamber 132 by electrodeposition in the subsequent step S3, and the deposition metal may be attached to the electrode of the cathode chamber 132, and the ammonia may be dispersed in the solution in the cathode chamber 132 and may exist in the form of an ammonia-containing solution.
S3, carrying out gas-liquid separation treatment on the gas-liquid mixture to obtain carbon dioxide gas and separation liquid; the separated liquid is conveyed to a cathode chamber 132 of the electro-desorption device, so that the separated liquid is subjected to electro-deposition in the cathode chamber 132 to obtain deposited metal and ammonia-containing solution, and in addition, the cathode chamber 132 and the anode chamber 131 are separately arranged to prevent the cathode chamber 132 and the anode chamber 131 from influencing each other. Further, the anode chamber 131 and the cathode chamber 132 may be separated from each other by an anion exchange membrane 133 to prevent cations from moving between the anode chamber 131 and the cathode chamber 132.
It should be noted that the gas-liquid mixture containing the metal/ammonia complex and carbon dioxide needs to be subjected to the gas-liquid separation treatment in time to re-separate carbon dioxide from the solution, and during the separation of carbon dioxide from the solution, ammonia is already associated with the corresponding metal ion (Me)2+) The carbon dioxide in the gaseous state can therefore be separated from the solution relatively easily.
As an alternative, the gas-liquid separation treatment includes: sequentially carrying out flash evaporation and condensation on the gas-liquid mixture; and obtaining initial separation liquid and gas to be condensed after flash evaporation, and obtaining carbon dioxide gas and condensate after condensation. It is noted that the flash evaporation can be carried out in a conventional sealed container, and during the flash evaporation, the gas-liquid mixture is only required to be conveyed into the sealed container, and then gaseous substances (gas to be condensed) in the gas-liquid mixture are discharged from the upper opening of the sealed container and conveyed into a condenser for condensation; in addition, in the flash evaporation process, the temperature is not required to be increased, and only carbon dioxide is separated and discharged; in the condensation process, because part of volatile ammonia and water vapor exist in the gas to be condensed, the volatile ammonia and the water vapor can be separated from the gas to be condensed cooperatively through the condensation.
In addition, after the condensation, the condensate and the initial separation liquid are mixed to obtain the separation liquid, and the separation liquid can be obtained by conveying the condensate to a storage place of the initial separation liquid.
The carbon dioxide is separated to produce the separation liquid, and after the separation liquid is transported to the cathode chamber 132, ammonia regeneration and metal ion recovery are performed by the cathode chamber 132 of the electric desorption apparatus.
The process of electrodeposition can be understood with reference to the following formula:
Figure GDA0003269555160000101
wherein Me in (R4)(s) Represents a transition metal element which is solid, separated and can be coordinately bound with ammonia.
S4, sending the ammoniated solution in the cathode chamber 132 to the absorption device 110 for absorption of carbon dioxide, so as to realize complete sequence.
In order to recycle ammonia, ammonia produced in the cathode chamber 132 is transported to the absorption device 110 along with the solution for absorption of carbon dioxide, so that the whole system constitutes a complete cycle. Furthermore, the ammoniated solution in the cathode compartment 132 is low carbon dioxide loading and low metal loading, as the deposited metal will adhere to the electrodes in the cathode compartment 132.
The carbon dioxide capture rate/decarburization rate in the above embodiment can be 85% or more, and the purity of the finally discharged carbon dioxide product can be 99% or more.
The core thought of the above embodiment is as follows: ammonia is used as a carbon dioxide absorbent, then a transition metal element capable of being in coordination combination with the ammonia is used as an electrochemical medium for carbon dioxide desorption, and ammonia regeneration and metal deposition are realized through electrochemistry. Specifically, in the overall system, ammonia absorbs carbon dioxide in the absorption unit 110; the transition metal elements coordinated with ammonia are electrochemically dissolved in the carbon dioxide-loaded absorption solution in the anode chamber 131, and carbon dioxide is desorbed by means of coordination bonding with ammonia, and then ammonia regeneration is achieved by electrodeposition of metal ions through the cathode chamber 132, ensuring absorbent supply in the subsequent carbon dioxide capture process in the absorption apparatus 110. Because the embodiment adopts the electrochemical cycle with high energy utilization rate and the proper coordination effect, the method can not only ensure the desorption effect on carbon dioxide, but also ensure the breakage of the coordination bond of the metal/ammonia coordination compound, realize the cycle use of ammonia and the recovery of deposited metal, and ensure that the method has low energy consumption requirement and low operation cost.
As a preferable embodiment of the present invention, in order to improve the operability in the practical application process, on the basis of the above embodiments, the electrode of the cathode chamber 132 and the electrode of the anode chamber 131 may have the same transition metal element, for example, both the electrode of the cathode chamber 132 and the electrode of the anode chamber 131 contain zinc element. And, the electrode of the cathode chamber 132 and the electrode of the anode chamber 131 or the direction of current are interchanged at a preset period, thereby ensuring the continuous use of the electric desorption apparatus.
In addition to the above embodiments, in order to recover the ammonia carried in the purge gas, the step S1 further includes: and leaching the purified gas to obtain separated ammonia and the gas to be discharged, wherein the separated ammonia exists in the form of ammonia-containing leacheate. Further, after the purge gas is subjected to leaching, the ammonia-containing leaching solution obtained by the separation may be conveyed to a pretreatment device, so as to perform desulfurization treatment on the flue gas to be conveyed to the absorption device 110, thereby obtaining a desulfurization solution; wherein the pretreatment device may be a desulfurization device 210.
In addition, the desulfurization solution that is not saturated may be subjected to heat exchange with the ammonia-containing elution solution to be sent to the pretreatment apparatus, and after the heat exchange, the desulfurization solution that is not saturated may be sent to the elution place of the purge gas to elute the purge gas, and then the ammonia-containing elution solution with the desulfurization solution may be sent to the desulfurization apparatus 210. It should be understood that the purge gas may be purged with a circulating desulfurization solution, with an externally supplied water, or with both desulfurization and an externally supplied water.
Referring to fig. 1-2, in order to facilitate the development of the capturing method in the above embodiments, the present invention further provides a capturing system for obtaining carbon dioxide in flue gas, which includes an absorption device 110, an electric desorption device, and a gas-liquid separation device; it should be noted that the absorption device 110 is used for absorbing carbon dioxide in the flue gas; the electric desorption device is used for desorbing carbon dioxide and realizing the recovery of corresponding metal and the regeneration of ammonia; the gas-liquid separation device is used for separating carbon dioxide from liquid.
The absorption device 110 contains an ammonia-containing solution capable of absorbing carbon dioxide; the electrolytic absorption device comprises an anode chamber 131 and a cathode chamber 132 which are separated from each other, the electrolytic absorption device is generally provided with a power supply mechanism, the anode chamber 131 and the cathode chamber 132 can be separated by an anion exchange membrane 133, the electrode of the anode chamber 131 is a metal electrode, the metal electrode contains a transition metal element which is combined with ammonia in a coordination manner, and further, the transition metal element combined with ammonia in a coordination manner comprises one or more of zinc element, copper element, nickel element and silver element; in a specific application process, only zinc element can be used as the transition metal element coordinately bound with ammonia in the present invention.
Wherein, the absorption device 110 absorbs carbon dioxide after receiving the flue gas containing carbon dioxide to obtain absorption liquid and purified gas; the flue gas containing carbon dioxide enters through a flue gas inlet of the absorption device 110, and after the absorption device 110 absorbs the carbon dioxide, the absorption liquid is discharged from an absorption liquid outlet of the absorption device 110, and the purge gas is discharged from a purge gas outlet of the absorption device 110, which may be opened at the top of the absorption device 110 in a normal case.
The anode chamber 131 is communicated with an absorption liquid outlet of the absorption device 110, so that the absorption liquid is conveyed into the anode chamber 131 from the inside of the absorption tower, and the absorption liquid is desorbed under the action of the metal electrode in the anode chamber 131 to obtain a gas-liquid mixture containing a metal/ammonia coordination compound and carbon dioxide; specifically, the anode chamber 131 is provided with an absorption liquid inlet, and the absorption liquid inlet of the anode chamber 131 is communicated with the outlet of the absorption device 110, so as to complete the transportation of the absorption liquid.
The gas-liquid separation device is communicated with a gas-liquid mixture outlet of the anode chamber 131, so that the gas-liquid mixture is conveyed from the anode chamber 131 to the gas-liquid separation device, and then the gas-liquid mixture is separated to obtain pure carbon dioxide gas and separation liquid; specifically, the gas-liquid separation device is provided with a gas-liquid mixture inlet and a carbon dioxide outlet, the gas-liquid mixture inlet of the gas-liquid separation device is communicated with the gas-liquid mixture outlet of the anode chamber 131 to complete the transportation of the gas-liquid mixture, and the carbon dioxide is discharged from the carbon dioxide outlet of the gas-liquid separation device.
The cathode chamber 132 is communicated with a separated liquid outlet of the gas-liquid separation device, so that the separated liquid is conveyed into the cathode chamber 132, and the separated liquid is subjected to electrodeposition in the cathode chamber 132 to obtain deposited metal and ammonia-containing solution; specifically, the cathode chamber 132 is opened with a separated liquid inlet, and the separated liquid inlet of the cathode chamber 132 is communicated with a separated liquid outlet of the gas-liquid separation device, so as to complete the transportation of the separated liquid.
The absorption device 110 is disposed in communication with an outlet of the ammonia containing solution of the cathode chamber 132, so that the ammonia containing solution in the cathode chamber 132 is transported to the inside of the absorption device 110, and the ammonia containing solution is absorbed in the absorption device 110. Specifically, the absorption device 110 is further provided with an ammonia-containing solution inlet, and the ammonia-containing solution inlet of the absorption device 110 is communicated with the ammonia-containing solution outlet of the cathode chamber 132 to complete the transportation of the ammonia-containing solution; in addition, it should be noted that the absorption device 110 may be further provided with a fluid infusion port to implement a fluid infusion operation on the absorption device 110 periodically.
As a preferable scheme of each of the above embodiments, the capture system further comprises an ammonia separation and leaching device 230 and a desulfurization device 210 for flue gas pretreatment, wherein the desulfurization device 210 is usually provided with an ammonia-containing solution; in addition, through practical operation, the ammonia recovery rate of the desulfurization device 210 can reach more than 99%, and SO2The recovery rate can reach more than 95 percent.
The ammonia separation and leaching device 230 is communicated with a purified gas outlet of the absorption device 110, so that the purified gas is conveyed from the absorption device 110 to the ammonia separation and leaching device 230, and ammonia gas remaining in the purified gas is separated by the ammonia separation and leaching device 230, so as to obtain ammonia-containing leaching liquid and gas to be discharged; specifically, the top of the ammonia separation and leaching device 230 is provided with an outlet for gas to be discharged, the upper part of the ammonia separation and leaching device 230 is provided with a water inlet, and the lower part of the ammonia separation and leaching device 230 is provided with a purified gas inlet, so that the separation and recovery of the residual ammonia gas are realized in a water leaching manner.
The bottom of the ammonia separation and leaching device 230 is further provided with an ammonia-containing solution outlet, the upper part of the ammonia separation and leaching device 230 is further provided with a backflow inlet, the height of the backflow inlet is lower than that of the water inlet, and the desulfurization device 210 is provided with an ammonia-containing solution inlet and a backflow outlet. An ammonia-containing eluent inlet of the desulfurization device 210 is communicated with an ammonia-containing eluent outlet of the ammonia separation and elution device 230, a return inlet of the ammonia separation and elution device 230 is communicated with a return outlet of the desulfurization device 210, so that the separated ammonia is conveyed from the ammonia separation and elution device 230 to the desulfurization device 210 in the form of ammonia-containing eluent, the separated ammonia exists in the form of desulfurization liquid after being combined with sulfur dioxide in the flue gas, the desulfurization liquid which does not reach a saturated state flows back from the desulfurization device 210 to the ammonia separation and elution device 230 to elute the purified gas, and the separated ammonia-containing eluent is conveyed from the ammonia separation and elution device 230 to the desulfurization device 210 to form a circulation loop.
It should be noted that when the desulfurization solution is saturated, the liquid substance in the desulfurization device may be sent to the sulfur dioxide recovery device 240 for treatment, so as to obtain the sulfur dioxide utilizates, such as: the sulfur dioxide utilization product can be a sulfuric acid ammoniated fertilizer product.
In addition, the exhaust port of the desulfurization device 210 is communicated with the absorption device 110, specifically, the exhaust port of the desulfurization device 210 may be communicated with the flue gas inlet of the absorption device 110 to convey the carbon dioxide-containing flue gas after desulfurization treatment to the absorption device 110, and it should be understood that the desulfurization device 210 may pretreat the carbon dioxide-containing flue gas and convey the flue gas after pretreatment desulfurization to the absorption device 110 by the desulfurization device 210 to absorb the carbon dioxide.
As another preferred embodiment of the above embodiments, referring to fig. 2, the absorption device 110 is provided with an absorption region 111 and a condensation region 112, the condensation region 112 and the absorption region 111 are arranged above and below and isolated from each other by a partition which allows gas to pass through and blocks liquid substances, the partition may be a membrane partition, the membrane partition may be made of PTFE membrane, and preferably, the membrane partition may be made of Teflon PTFE membrane.
Wherein the absorption zone 111 is provided with a flue gas inlet for the flue gas to enter and an ammoniated solution inlet for the ammoniated solution to enter; the condensing area 112 is provided with a purified gas outlet for discharging the purified gas and an absorption liquid outlet for discharging the absorption liquid. Specifically, in the absorption apparatus 110, the flue gas inlet may be opened at a lower portion of the absorption zone 111, the ammonia-containing solution inlet may be opened at an upper portion of the absorption zone 111, the purge gas outlet may be opened at a top portion of the condensation zone 112, and the absorption liquid outlet may be opened at a lower portion of the condensation zone 112.
The absorption region 111 and the condensation region 112 are communicated with each other through a conveying pipeline, one end of the conveying pipeline is communicated with the bottom of the absorption region 111, the other end of the conveying pipeline is communicated with the upper portion of the condensation region 112, a cooling component is installed on the conveying pipeline, specifically, the communication position between the absorption region 111 and the pipeline can be located at the bottom of the absorption region 111, and the communication position between the condensation region 112 and the pipeline can be located at the upper portion of the condensation region 112 and is lower than the height position of the purified gas.
Specifically, the flue gas containing carbon dioxide enters the absorption zone 111 through the flue gas inlet, and the ammoniated solution enters the absorption zone 111 through the ammoniated solution inlet, and absorbs carbon dioxide in the absorption zone 111. After the ammonia-containing solution absorbs the carbon dioxide, the carbon dioxide is conveyed to the condensation area 112 along with the pipeline, and the purified gas obtained after absorption is discharged from the purified gas outlet, and the absorption liquid obtained after absorption of the carbon dioxide is discharged from the absorption liquid outlet. It should be noted that, because the cooling assembly is installed on the pipeline, ammonia can be present in the solution, thereby avoiding the volatilization of ammonia and ensuring the recycling of ammonia.
In order to separate the gas-liquid mixture and reduce the loss of ammonia, the gas-liquid separation device comprises a flash tank 141 and a condenser 142, wherein a gas-liquid mixture inlet of the flash tank 141 is communicated with a gas-liquid mixture outlet of the anode chamber 131, a gas inlet to be condensed of the condenser 142 is communicated with a gas outlet to be condensed of the flash tank 141, a condensate inlet of the flash tank 141 is communicated with a condensate outlet of the condenser 142, a separated liquid inlet of the cathode chamber 132 is communicated with a separated liquid outlet of the flash tank 141, the separated liquid is a mixture of an initial separated liquid and the condensate, the initial separated liquid is a liquid substance obtained by flashing in the flash tank 141, and the condensate is a liquid substance obtained by condensing in the condenser 142; in addition, the condenser 142 is further provided with a carbon dioxide outlet, and the carbon dioxide outlet may be located at the top of the condenser 142.
In order to improve the heat utilization rate, the capture system further comprises a first heat exchanging device 120, the first heat exchanging device 120 has a cold end and a hot end, which may be respectively referred to as a first heat exchanging device hot end 122 and a first heat exchanging device cold end 121 in fig. 1, a cold end inlet of the first heat exchanging device 120 is arranged to communicate with the absorbing liquid outlet of the absorbing device 110, a hot end outlet of the first heat exchanging device 120 is arranged to communicate with the absorbing liquid inlet of the anode chamber 131, a hot end inlet of the first heat exchanging device 120 is arranged to communicate with the ammonia-containing solution outlet of the cathode chamber 132, and a cold end outlet of the first heat exchanging device 120 is arranged to communicate with the ammonia-containing solution inlet of the absorbing device 110; the ammonia containing solution to be transferred to the absorption apparatus 110 and the absorption liquid to be transferred to the anode chamber 131 are heat exchanged in the first heat exchanging apparatus 120.
The absorption liquid discharged from the absorption device 110 enters the first heat exchange device 120 from the cold end inlet, and exits the first heat exchange device 120 from the hot end outlet; the ammoniated solution discharged from the cathode compartment 132 enters the first heat exchange means 120 from the warm end inlet and exits the first heat exchange means 120 from the cold end outlet.
It will be appreciated by those skilled in the art that the ammoniated solution is only heat exchanged with the absorbing liquid, transferring heat from the ammoniated solution to the absorbing liquid, the ammoniated solution and the absorbing liquid being isolated from each other in the first heat exchanging arrangement 120. A conveying channel between the cold-end outlet of the first heat exchanging device 120 and the ammoniated solution inlet of the absorption device 110 is used for conveying the ammoniated solution to the absorption device 110, and a cooling assembly can be installed on the conveying channel; a conveying channel between the hot end outlet of the first exchange device and the absorption liquid inlet of the anode chamber 131 is used for conveying the absorption liquid to the anode chamber 131, and a temperature rise assembly can be mounted on the conveying channel.
It will be appreciated by those skilled in the art that when the capture system comprises an ammonia separation and leaching device 230 and a desulfurization device 210, the ammonia-containing leacheate and the desulfurization solution can also be heat exchanged, and the heat exchange of the ammonia-containing leacheate and the desulfurization solution is performed by a second heat exchange device 220 for transferring the heat of the desulfurization solution to the ammonia-containing leacheate. In addition, after the heat exchange, the ammonia-containing leacheate can be continuously heated by the temperature-raising component in the process of being conveyed to the desulfurization device 210 so as to promote the desulfurization treatment in the desulfurization device 210; the desorbed liquid may be cooled by the cooling module after heat exchange during the process of being delivered to the ammonia separation and leaching device 230.
In the above technical solutions, the above are only preferred embodiments of the present invention, and the technical scope of the present invention is not limited thereby, and all the technical concepts of the present invention include the claims of the present invention, which are directly or indirectly applied to other related technical fields by using the equivalent structural changes made in the content of the description and the drawings of the present invention.

Claims (16)

1. A method for capturing carbon dioxide in flue gas is characterized by comprising the following steps:
s1, conveying the flue gas containing carbon dioxide to an absorption device for absorbing the carbon dioxide to obtain absorption liquid and purified gas, wherein the absorption device adopts ammonia-containing solution to absorb the carbon dioxide, and the ammonia-containing solution in the absorption device comprises NH3；
S2, conveying the absorption liquid to an anode chamber of an electrowinning device, wherein an electrode of the anode chamber adopts a metal electrode, and the metal electrode contains a transition metal element which is coordinated and combined with ammonia, so that the absorption liquid is desorbed under the action of the metal electrode in the anode chamber to obtain a gas-liquid mixture containing a metal/ammonia coordination compound and carbon dioxide;
s3, carrying out gas-liquid separation treatment on the gas-liquid mixture to obtain carbon dioxide gas and separation liquid; conveying the separated liquid into a cathode chamber of the electro-desorption device, and performing electrodeposition on the separated liquid in the cathode chamber to obtain deposited metal and ammonia-containing solution, wherein the cathode chamber and the anode chamber in the electro-desorption device are separated;
s4, sending the ammoniated solution in the cathode chamber to the absorption device for absorbing the carbon dioxide.
2. The method for capturing carbon dioxide from flue gas according to claim 1, wherein the ammonia-containing solution in the absorption tower contains a supporting electrolyte.
3. The method for capturing carbon dioxide from flue gas according to claim 1, wherein the operating temperature of the absorption device during the absorption process is 10-40 ℃.
4. The method of capturing carbon dioxide from flue gas according to claim 1,
the operating temperature in the electrolytic absorption device is 40-80 ℃; the current density of the electric desorption device is 50-500A/m2。
5. The method for capturing carbon dioxide from flue gas of claim 1, wherein the transition metal element comprises one or more of zinc element, copper element, nickel element and silver element.
6. The method for capturing carbon dioxide from flue gases according to claim 1, wherein the anode compartment and the cathode compartment are separated from each other by an anion exchange membrane.
7. The method of capturing carbon dioxide from a flue gas according to claim 1, wherein the gas-liquid separation process comprises: sequentially carrying out flash evaporation and condensation on the gas-liquid mixture; obtaining initial separation liquid and gas to be condensed after flash evaporation, and obtaining carbon dioxide gas and condensate after condensation;
after the condensation, the condensate is mixed with the initial separation liquid to obtain the separation liquid.
8. The method for capturing carbon dioxide from flue gas of claim 1, wherein the electrode of the cathode chamber and the electrode of the anode chamber have the same transition metal element; and the electrode of the cathode chamber and the electrode of the anode chamber or the current direction are interchanged according to a preset period.
9. The method for capturing carbon dioxide from flue gas according to any one of claims 1 to 8, wherein the step S1 further comprises: and leaching the purified gas to obtain separated ammonia and the gas to be discharged, wherein the separated ammonia exists in the form of ammonia-containing leaching liquid.
10. The method for capturing carbon dioxide from flue gas according to claim 9, wherein the ammonia-containing leacheate obtained by the separation is conveyed to a pretreatment device, so that the flue gas to be conveyed to the absorption device is subjected to desulfurization treatment to obtain desulfurization liquid.
11. The method for capturing carbon dioxide from flue gas according to claim 10, wherein the desulfurizing liquid which is not saturated and the ammonia-containing leacheate to be conveyed to the pretreatment device are subjected to heat exchange, and after the heat exchange, the desulfurizing liquid which is not saturated is conveyed to the position where the purifying gas is washed, and then the ammonia-containing leacheate with the desulfurizing liquid is conveyed to the desulfurization device.
12. A capture system for obtaining carbon dioxide in flue gas is characterized by comprising an absorption device, an electric desorption device and a gas-liquid separation device;
the absorption device is internally provided with ammonia-containing solution, and the ammonia-containing solution in the absorption device comprises NH3(ii) a The electrolytic absorption device comprises an anode chamber and a cathode chamber which are separated from each other, wherein the electrode of the anode chamber is a metal electrode, and the metal electrode contains a transition metal element which is coordinated and combined with ammonia;
the absorption device absorbs carbon dioxide after receiving the flue gas containing carbon dioxide to obtain absorption liquid and purified gas;
the anode chamber is communicated with an absorption liquid outlet of the absorption device, so that the absorption liquid is conveyed into the anode chamber from the inside of the absorption tower, and the absorption liquid is desorbed under the action of the metal electrode in the anode chamber to obtain a gas-liquid mixture containing a metal/ammonia coordination compound and carbon dioxide;
the gas-liquid separation device is communicated with a gas-liquid mixture outlet of the anode chamber, so that the gas-liquid mixture is conveyed into the gas-liquid separation device from the anode chamber, and then the gas-liquid mixture is separated to obtain carbon dioxide gas and separation liquid;
the cathode chamber is communicated with a separated liquid outlet of the gas-liquid separation device, so that the separated liquid is conveyed into the cathode chamber, and the separated liquid is subjected to electrodeposition in the cathode chamber to obtain deposited metal and ammonia-containing solution;
the absorption device is communicated with an ammonia-containing solution outlet of the cathode chamber, so that the ammonia-containing solution in the cathode chamber is conveyed to the inside of the absorption device, and the carbon dioxide is absorbed in the absorption device by the ammonia-containing solution.
13. The capture system for acquiring the carbon dioxide in the flue gas as claimed in claim 12, wherein the capture system further comprises an ammonia separation and leaching device and a desulfurization device for flue gas pretreatment;
the purified gas inlet of the ammonia separation and leaching device is communicated with the purified gas outlet of the absorption device, so that the purified gas is conveyed from the absorption device to the ammonia separation and leaching device, and ammonia gas remaining in the purified gas is separated through the ammonia separation and leaching device to obtain ammonia-containing leaching liquid and gas to be discharged;
an ammonia-containing eluent inlet of the desulfurization device is communicated with an ammonia-containing eluent outlet of the ammonia separation leaching device, a return inlet of the ammonia separation leaching device is communicated with a return outlet of the desulfurization device, so that the separated ammonia-containing eluent is conveyed from the ammonia separation leaching device to the desulfurization device, the separated ammonia-containing eluent exists in the form of a desulfurization solution after being combined with sulfur dioxide in the flue gas, the desulfurization solution which is not saturated flows back from the desulfurization device to the ammonia separation leaching device to leach the purified gas, and the purified gas is conveyed from the ammonia separation leaching device to the desulfurization device along with the separated ammonia-containing eluent;
and the exhaust port of the desulfurization device is communicated with the absorption device so as to convey the desulfurized flue gas containing carbon dioxide to the absorption device.
14. The capture system for acquiring carbon dioxide in flue gas according to claim 12, wherein the absorption device is provided with an absorption area and a condensation area, the condensation area and the absorption area are arranged above and below each other and are isolated from each other through a partition, and the partition allows gas to pass through and blocks liquid substances;
wherein the absorption area is provided with a flue gas inlet for the flue gas to enter and an ammonia-containing solution inlet for the ammonia-containing solution to enter; the condensation zone is provided with a purified gas outlet for discharging the purified gas and an absorption liquid outlet for discharging the absorption liquid;
the absorption district with the condensation zone passes through the conveying line intercommunication, conveying line's one end with the bottom intercommunication in absorption district, conveying line's the other end with the upper portion intercommunication in condensation zone, the last cooling assembly that installs of conveying line.
15. The capture system for obtaining carbon dioxide in flue gas according to claim 12, wherein the gas-liquid separation device comprises a flash tank and a condenser;
the gas-liquid mixture entry of flash tank with the gas-liquid mixture export intercommunication setting of anode chamber, the condenser treat the condensing gas entry with the condensing gas export intercommunication of waiting of flash tank, the condensate entry of flash tank with the condensate export intercommunication of condenser, the separator entry of cathode chamber with the separator export intercommunication of flash tank.
16. The system for capturing carbon dioxide in flue gas according to any one of claims 12 to 15, wherein the system further comprises a first heat exchange device, a cold end inlet of the first heat exchange device is arranged to communicate with an absorption liquid outlet of the absorption device, a hot end outlet of the first heat exchange device is arranged to communicate with an absorption liquid inlet of the anode chamber, a hot end inlet of the first heat exchange device is arranged to communicate with an ammonia-containing solution outlet of the cathode chamber, and a cold end outlet of the first heat exchange device is arranged to communicate with an ammonia-containing solution inlet of the absorption device; the ammonia-containing solution to be conveyed into the absorption device and the absorption liquid to be conveyed into the anode chamber are subjected to heat exchange in the first heat exchange device;
absorbing liquid discharged from the absorbing device enters the first heat exchange device from the cold end inlet and is discharged from the first heat exchange device from the hot end outlet;
ammoniated solution discharged from the cathode chamber enters the first heat exchange means from the hot side inlet and exits the first heat exchange means from the cold side outlet.
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