A system and method for treating a co2-containing flue gas

Abstract

The application discloses a system and method for treating CO2-containing flue gas, and the system comprises: a cyclone reactor, which is internally used for receiving CO2-containing flue gas and liquid absorbent, and is used for providing a place for the liquid absorbent to absorb CO2 in the flue gas, wherein the liquid absorbent comprises a dispersed phase and a continuous phase which are not mutually soluble; and an ultrasonic device, which is used for emitting ultrasonic waves to the liquid absorbent in the interior of the cyclone reactor. The application makes up the defect that the CO2 absorption effect is poor when a traditional CO2 capture technology is used to treat CO2-containing flue gas, and can effectively reduce carbon emission and has good absorption performance when treating low partial pressure tail gas.

Description

Technical Field

[0001] This application relates to the field of gas separation technology, specifically to a system and method for treating CO2-containing flue gas. Background Technology

[0002] Currently, post-combustion CO2 capture technology is the most commonly used CO2 emission reduction technology. Post-combustion CO2 capture technology refers to the separation and recovery of CO2 from flue gas using various technical means after fuel combustion. According to different separation methods, post-combustion CO2 capture technology can be divided into: chemical absorption, solid adsorption, membrane separation, and temperature-based phase separation, etc. Chemical absorption is a technology that selectively separates CO2 gas from flue gas using a chemical reaction between CO2 and a chemical absorbent. This technology is a continuous cyclical process, including two steps: CO2 absorption and desorption. In this process, the absorbent selectively absorbs CO2 from the flue gas at a lower temperature in the absorption tower to form a CO2-rich solution. Subsequently, the CO2-rich solution releases the absorbed CO2 at a higher temperature in the desorption tower, regenerating the absorbent. This process can efficiently remove CO2 from flue gas and produce high-purity CO2, with a CO2 removal efficiency of up to 99%. Despite this, the process still faces significant challenges due to high energy consumption and high investment and operating costs. Membrane separation technology is used for CO2 separation, but it has drawbacks such as high separation cost and low CO2 capture rate when treating low partial pressure flue gas. In addition, carbon emissions from waste gas produced by membrane separation still do not meet environmental requirements.

[0003] CN115253608A proposes a method for capturing CO2 from the flue gas of coal-fired power generating units. The CO2 capture method mentioned in this method is the traditional CO2 chemical absorption technology, which uses the alkanolamine method to capture CO2. However, the high regeneration energy consumption limits the application of this method in large-scale CO2 capture.

[0004] CN113491929A proposes an enhanced process for capturing carbon dioxide from flue gas using membrane separation. However, this method results in a low CO2 concentration in the product gas during CO2 capture, potentially leading to a higher residual CO2 concentration in the exhaust gas, thus limiting its application in large-scale CO2 capture. Summary of the Invention

[0005] In view of this, the main objective of this application is to provide a system and method for treating CO2-containing flue gas, which overcomes the shortcomings of traditional CO2 capture technology in treating CO2-containing flue gas with poor CO2 absorption effect, can effectively reduce carbon emissions, and has good absorption performance when treating low partial pressure tail gas (CO2 concentration of 1-10 vol%).

[0006] To achieve the above-mentioned objectives, the first aspect of this application provides a system for treating CO2-containing flue gas, comprising:

[0007] A cyclone reactor, the interior of which is used to receive CO2-containing flue gas and a liquid absorbent, and to provide a site for the liquid absorbent to absorb CO2 from the flue gas, the liquid absorbent comprising an immiscible dispersed phase and a continuous phase;

[0008] An ultrasonic device is used to emit ultrasonic waves into the liquid absorbent inside a cyclone reactor.

[0009] Furthermore, the ultrasonic device includes an ultrasonic generator and an ultrasonic probe connected to the ultrasonic generator, the ultrasonic probe being mounted on the side wall of the cyclone reactor.

[0010] Furthermore, the ultrasonic power of the ultrasonic generator is 500-2000W.

[0011] Furthermore, the outer shell of the cyclone reactor is equipped with a jacket containing circulating cooling water to stabilize the reaction temperature inside the cyclone reactor.

[0012] Furthermore, the dispersed phase of the liquid absorbent is 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6) or silicone oil, and the continuous phase is water or methanol.

[0013] Furthermore, when 1-butyl-3-methylimidazolium hexafluorophosphate is used as the dispersed phase, the volume fraction of 1-butyl-3-methylimidazolium hexafluorophosphate is ≤10%; when silicone oil is used as the dispersed phase, the volume fraction of silicone oil is ≤1%.

[0014] Furthermore, when 1-butyl-3-methylimidazolium hexafluorophosphate is used as the dispersed phase, the volume fraction of 1-butyl-3-methylimidazolium hexafluorophosphate is 1-5%; when silicone oil is used as the dispersed phase, the volume fraction of silicone oil is ≤0.1%.

[0015] Furthermore, the liquid absorbent also includes a hydrophilic surfactant.

[0016] Furthermore, the hydrophilic surfactant is Tween 80, and its concentration is ≤1 wt%.

[0017] Furthermore, the temperature of the absorbent input into the cyclone reactor is 20-60℃.

[0018] Furthermore, the gas-liquid flow rate volume ratio input to the cyclone reactor is 1 to 200:1, preferably 1 to 100:1.

[0019] Furthermore, the concentration of CO2 in the flue gas is 1-10%.

[0020] A second aspect of the present invention provides a method for treating CO2-containing flue gas, comprising the following steps:

[0021] CO2-containing flue gas and liquid absorbent enter the cyclone reactor to obtain a mixture; ultrasound inside the cyclone reactor enhances the mass transfer of the mixture.

[0022] CO2 in the flue gas is absorbed by a liquid absorbent to obtain decarbonized gas; the liquid absorbent comprises an immiscible dispersed phase and a continuous phase.

[0023] Furthermore, the liquid absorbent is in emulsion form, and the preparation method of the liquid absorbent includes: slowly adding a dispersed phase to a continuous phase under stirring, stirring, and obtaining an emulsion.

[0024] Compared with the prior art, this application has the following advantages:

[0025] In this invention, CO2-containing flue gas and a liquid absorbent enter a cyclone reactor to obtain a mixture. Ultrasonic waves inside the cyclone reactor enhance mass transfer in the mixture. The CO2 in the flue gas is absorbed by the liquid absorbent, resulting in decarbonized gas. The liquid absorbent comprises an immiscible dispersed phase and a continuous phase; that is, the absorbent is always a heterogeneous liquid phase. This characteristic persists throughout the entire CO2 absorption process. The dispersed phase exists independently and dispersed within the bulk liquid phase, while the continuous phase exists continuously and occupies the bulk. After adsorbing CO2 at the gas-liquid interface, the dispersed phase returns to the bulk continuous phase, transferring CO2 to it, thus completing CO2 absorption. Simultaneously, the dispersed phase increases the contact opportunities between the continuous phase and the gas, enhancing the turbulence of the continuous phase and further strengthening mass transfer. Furthermore, in this invention, when using a swirling reactor for gas-liquid reaction, the reactants are tangentially injected into the reactor, generating a swirling flow field within. The intense collision and high-speed rotation of the gas and liquid phases cause the liquid to break into droplets and liquid films, significantly improving the mass transfer performance between phases and resulting in excellent decarbonization efficiency with low energy consumption, meeting industrial decarbonization requirements. Ultrasonic waves can also accelerate fluid turbulence and the renewal rate of the phase surface, further enhancing the liquid phase mass transfer efficiency.

[0026] In summary, this invention employs a coupled process of swirling flow field technology, ultrasonic technology, and a gas-liquid-liquid three-phase system to continuously process low-concentration CO2 flue gas. This overcomes the shortcomings of traditional CO2 capture technology in treating CO2-containing flue gas, effectively reducing carbon emissions and exhibiting good absorption performance when treating low-partial-pressure tail gas.

[0027] Other features and advantages of this application will be described in detail in the following specific embodiments. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a system structure for treating CO2-containing flue gas, provided as an embodiment of the present invention.

[0029] The attached diagram is labeled as follows: 1 is a CO2 cylinder, 2 is an N2 cylinder, 3 is a gas buffer tank, 4 is a gas flow meter, 5 is an ultrasonic generator, 6 is a cyclone reactor, 7 is an ultrasonic probe, 8 is a booster pump, and 9 is a stirred tank. Detailed Implementation

[0030] The following will clearly and completely describe the concept and technical effects of this application in conjunction with embodiments, so as to fully understand the purpose, features and effects of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are all within the scope of protection of this application.

[0031] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The terms "first position" and "second position" refer to two different positions.

[0032] Unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, they can refer to fixed connections or detachable connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and connections within two components or interactions between two components. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0033] Experimental methods not specified in the examples are generally performed under conventional conditions and as described in the manual, or as recommended by the manufacturer. Unless otherwise specified, the general equipment, materials, reagents, etc. used are commercially available.

[0034] refer to Figure 1 The first aspect of the present invention provides a system for treating CO2-containing flue gas, comprising:

[0035] A cyclone reactor, the interior of which is used to receive CO2-containing flue gas and a liquid absorbent, and to provide a site for the liquid absorbent to absorb CO2 from the flue gas, the liquid absorbent comprising an immiscible dispersed phase and a continuous phase;

[0036] An ultrasonic device is used to emit ultrasonic waves into the liquid absorbent inside a cyclone reactor.

[0037] In this invention, during the gas-liquid reaction, the reaction components are tangentially injected into the swirling reactor, generating a swirling field within the reactor. In a specific example, the swirling reactor can be selected from a tubular gas-liquid swirling reactor or a spiral-bladed gas-liquid swirling reactor.

[0038] Understandably, a cyclone reactor is equipped with a gas inlet for CO2-containing flue gas, a liquid inlet for absorbent, a gas outlet for the decarbonized gas obtained after CO2 in the flue gas is absorbed by the liquid absorbent, and a liquid absorbent outlet after CO2 absorption. For example Figure 1 The diagram shows the gas inlet and liquid inlet located on both sides of the cyclone reactor, as well as the gas outlet located at the top of the cyclone reactor and the liquid inlet located at the bottom of the cyclone reactor.

[0039] In this invention, CO2-containing flue gas can be mixed before entering the cyclone reactor. In some examples, the CO2 and N2 generated by CO2 cylinder 1 and N2 cylinder 2 can be mixed evenly in gas buffer tank 3 before entering the cyclone reactor 6. Preferably, a gas flow meter 4 is installed on the mixed gas pipeline before entering the cyclone reactor 6 to control the gas flow rate entering the cyclone reactor.

[0040] In a specific example, the ultrasonic device includes an ultrasonic generator and an ultrasonic probe connected to the ultrasonic generator, such as... Figure 1 As shown, the ultrasonic probe 7, which is connected to the ultrasonic generator 5, is installed on the outer walls of both sides of the cyclone reactor 6. The ultrasonic generator has a conventional structure.

[0041] Preferably, the ultrasonic power of the ultrasonic generator is 500-2000W, and more preferably 800-1200W.

[0042] Preferably, the outer shell of the cyclone reactor is equipped with a jacket containing circulating cooling water to stabilize the reaction temperature inside the cyclone reactor.

[0043] Preferably, the dispersed phase of the liquid absorbent is 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6) or silicone oil, and the continuous phase is water or methanol.

[0044] Preferably, when the dispersed phase is 1-butyl-3-methylimidazolium hexafluorophosphate, the volume fraction of 1-butyl-3-methylimidazolium hexafluorophosphate is ≤10%; when the dispersed phase is silicone oil, the volume fraction of silicone oil is ≤1%.

[0045] Preferably, when the dispersed phase is 1-butyl-3-methylimidazolium hexafluorophosphate, the volume fraction of 1-butyl-3-methylimidazolium hexafluorophosphate is 1-5%, exemplarily 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, and 5%; when the dispersed phase is silicone oil, the volume fraction of silicone oil is ≤0.1%, exemplarily 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, and 0.1%.

[0046] Preferably, the absorbent further includes a hydrophilic surfactant.

[0047] Preferably, the hydrophilic surfactant is Tween 80, and its concentration is ≤1 wt%.

[0048] Preferably, the temperature of the absorbent input to the cyclone reactor is 20-60°C, exemplarily 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, and 60°C.

[0049] Preferably, the gas-liquid flow rate volume ratio input to the cyclone reactor is 1 to 200:1, more preferably 1 to 100:1, and exemplary values ​​are 1:1, 10:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, and 100:1.

[0050] Preferably, the CO2 concentration in the flue gas is 1-10%, and the flue gas temperature and pressure range is preferably 30-50°C and atmospheric pressure.

[0051] In this invention, the concentration ranges of each component of the absorbent are set based on physical properties such as viscosity and volatility, thereby reducing absorbent costs while significantly improving CO2 capture efficiency. The absorbent temperature and gas-liquid flow rate / volume ratio are primarily determined based on the CO2 capture effect. The coordination of the aforementioned parameters, including absorbent concentration, absorbent temperature, gas-liquid flow rate / volume ratio, and ultrasonic power, can enhance the CO2 capture effect.

[0052] A second aspect of the present invention provides a method for treating CO2-containing flue gas, comprising the following steps:

[0053] CO2-containing flue gas and liquid absorbent enter the cyclone reactor to obtain a mixture; ultrasound inside the cyclone reactor enhances the mass transfer of the mixture.

[0054] CO2 in the flue gas is absorbed by a liquid absorbent to obtain decarbonized gas; the liquid absorbent comprises an immiscible dispersed phase and a continuous phase.

[0055] Preferably, the absorbent is in emulsion form, and the method for preparing the absorbent includes: slowly adding a dispersed phase to a continuous phase while stirring, and stirring to obtain an emulsion. Exemplarily, it can be... Figure 1 The absorbent is placed in the stirred tank 9 shown and enters the cyclone reactor 7 through the booster pump 8.

[0056] Reference Figure 1 The process flow for treating CO2-containing flue gas according to this invention is as follows: CO2 and N2 generated by CO2 cylinder 1 and N2 cylinder 2 are mixed evenly in gas buffer tank 3, and then enter cyclone reactor 6 after passing through gas flow meter 4. The dispersed phase and continuous phase form an absorbent emulsion in stirred tank 9, which is then introduced into the cyclone reactor 6 by booster pump 8. Ultrasonic waves generated by ultrasonic generator 5 are transmitted into the cyclone reactor 6 through ultrasonic probe 7. Inside the cyclone reactor 6, CO2 in the flue gas is absorbed by the absorbent, completing the decarbonization treatment of the waste gas. The absorbent after absorbing CO2 leaves the cyclone reactor 6 from the bottom, and the flue gas after carbon capture treatment is directly discharged into the air.

[0057] The following examples are used to illustrate the system and method for treating CO2-containing flue gas of this application.

[0058] Example 1

[0059] The CO2-containing flue gas (CO2 concentration of 6%) was captured using the swirling flow field-ultrasonic technology-enhanced liquid-liquid two-phase system CO2 absorption process of this invention. The flue gas temperature and pressure were 40℃ and 0.1MPa, respectively. The CO2-containing flue gas and a 1-butyl-3-methylimidazolium hexafluorophosphate aqueous solution were fed into the swirling reactor at a gas-liquid flow rate-to-volume ratio of 90:1. The absorbent temperature was 25℃, and the absorbent contained 2% 1-butyl-3-methylimidazolium hexafluorophosphate by volume and 0.25 wt% Tween 80 by mass. The ultrasonic generator power was 900W. After treatment by this process, the CO2 capture rate was 72%.

[0060] Example 2

[0061] A process for capturing CO2-containing flue gas (CO2 concentration of 4%) using a swirling flow field-ultrasonic enhancement liquid-liquid two-phase system was employed. The flue gas temperature and pressure were 40℃ and 0.1MPa, respectively. The CO2-containing flue gas and an aqueous solution of 1-butyl-3-methylimidazolium hexafluorophosphate were fed into the swirling reactor at a gas-liquid flow rate-to-volume ratio of 40:1. The absorbent temperature was 30℃, and the absorbent contained 1.5% 1-butyl-3-methylimidazolium hexafluorophosphate (volume fraction) and 0.25 wt% Tween 80 (mass fraction). The ultrasonic generator power was 900W. After treatment with this process, the CO2 capture rate was 81%.

[0062] Example 3

[0063] A process for capturing CO2-containing flue gas (CO2 concentration of 3%) using a swirling flow field-ultrasonic enhancement liquid-liquid two-phase system was employed. The flue gas temperature and pressure were 40℃ and 0.1MPa, respectively. The CO2-containing flue gas and an aqueous solution of 1-butyl-3-methylimidazolium hexafluorophosphate were fed into a swirling reactor at a gas-liquid flow rate-to-volume ratio of 25:1. The absorbent temperature was 25℃, and the absorbent contained 3% 1-butyl-3-methylimidazolium hexafluorophosphate (volume fraction) and 0.25 wt% Tween 80 (mass fraction). The ultrasonic generator power was 1200W. After treatment with this process, the CO2 capture rate was 88%.

[0064] Example 4

[0065] A process for capturing CO2-containing flue gas (CO2 concentration of 4%) using a swirling flow field-ultrasonic enhancement liquid-liquid two-phase system was employed. The flue gas temperature and pressure were 40℃ and 0.1MPa, respectively. The CO2-containing flue gas and a silicone oil-methanol mixed solution were fed into the swirling reactor at a gas-liquid flow rate-to-volume ratio of 55:1. The absorbent temperature was 30℃, and the absorbent contained 0.01% silicone oil by volume and 0.1wt% Tween 80 by mass. The ultrasonic generator power was 800W. After treatment with this process, the CO2 capture rate was 79%.

[0066] Example 5

[0067] The difference from Example 1 is that Tween 80 is not added, and the volume fraction of 1-butyl-3-methylimidazolium hexafluorophosphate is 2%. After the flue gas is treated by this process, the CO2 capture rate is 64%. The absence of a surfactant leads to uneven distribution of the dispersed phase within the absorbent, resulting in a decrease in CO2 absorption efficiency.

[0068] Comparative Example 1

[0069] The difference from Example 1 is that ultrasonic methods are not used, but other experimental conditions remain the same. After the flue gas is treated by this process, the CO2 capture rate is 58%.

[0070] Comparative Example 2

[0071] The difference from Example 1 is that pure water was used as the absorbent, and other experimental conditions remained unchanged. After the flue gas was treated by this process, the CO2 capture rate was 6%.

[0072] As can be seen from the above embodiments, the method provided by the present invention can meet the capture requirements of CO2-containing gases. Utilizing swirling flow field-ultrasonic technology to enhance the treatment of flue gas in a liquid-liquid two-phase system can achieve a good CO2 capture rate, making it a novel and effective method for capturing CO2. This method can significantly reduce the CO2 concentration in the CO2 capture process, truly achieving net-zero CO2 emissions. Example 3 showed the best effect among Examples 1-5. Example 3 improved the CO2 absorption effect by reducing the gas-liquid volume ratio and increasing the power of the ultrasonic generator. Comparative Example 1, which did not use ultrasonic-enhanced mass transfer, and Comparative Example 2, which used a conventional non-liquid-liquid two-phase absorbent, showed a significant decrease in the CO2 capture rate.

[0073] Obviously, the above embodiments of this application are merely examples for clearly illustrating this application, and are not intended to limit the implementation of this application. Those skilled in the art can make other variations or modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All obvious variations or modifications derived from the technical solutions of this application are within the scope of the spirit and scope of this application.

Claims

1. A system for treating CO2-containing flue gas, characterized in that, include: A cyclone reactor, the interior of which is used to receive CO2-containing flue gas and a liquid absorbent, and to provide a site for the liquid absorbent to absorb CO2 from the flue gas, the liquid absorbent comprising an immiscible dispersed phase and a continuous phase; An ultrasonic device is used to emit ultrasonic waves into the liquid absorbent inside a cyclone reactor; The dispersed phase of the liquid absorbent is 1-butyl-3-methylimidazolium hexafluorophosphate or silicone oil, and the continuous phase is water or methanol.

2. The system for treating CO2-containing flue gas according to claim 1, characterized in that, The ultrasonic device includes an ultrasonic generator and an ultrasonic probe connected to the ultrasonic generator. The ultrasonic probe is installed on the side wall of the cyclone reactor. The ultrasonic power of the ultrasonic generator is 500-2000 W.

3. The system for treating CO2-containing flue gas according to claim 1, characterized in that, When the dispersed phase is 1-butyl-3-methylimidazolium hexafluorophosphate, the volume fraction of 1-butyl-3-methylimidazolium hexafluorophosphate is ≤10%; when the dispersed phase is silicone oil, the volume fraction of silicone oil is ≤1%.

4. The system for treating CO2-containing flue gas according to claim 3, characterized in that, When the dispersed phase is 1-butyl-3-methylimidazolium hexafluorophosphate, the volume fraction of 1-butyl-3-methylimidazolium hexafluorophosphate is 1-5%; when the dispersed phase is silicone oil, the volume fraction of silicone oil is ≤0.1%.

5. The system for treating CO2-containing flue gas according to claim 1, characterized in that, The liquid absorbent also includes a hydrophilic surfactant.

6. The system for treating CO2-containing flue gas according to claim 5, characterized in that, The hydrophilic surfactant is Tween 80, with a concentration ≤1 wt%.

7. The system for treating CO2-containing flue gas according to any one of claims 1-6, characterized in that, The temperature of the liquid absorbent input to the cyclone reactor is 20-60℃; the gas-liquid flow rate volume ratio input to the cyclone reactor is 1~200:

1.

8. The system for treating CO2-containing flue gas according to claim 7, characterized in that, The gas-liquid flow rate volume ratio input to the cyclone reactor is 1~100:

1.

9. The system for treating CO2-containing flue gas according to claim 1, characterized in that, The CO2 concentration in the flue gas is 1-10%.

10. A method for treating CO2-containing flue gas using the system according to any one of claims 1-9, characterized in that, Includes the following steps: CO2-containing flue gas and liquid absorbent enter the cyclone reactor to obtain a mixture; ultrasound inside the cyclone reactor enhances the mass transfer of the mixture. CO2 in the flue gas is absorbed by a liquid absorbent to obtain decarbonized gas; the liquid absorbent comprises an immiscible dispersed phase and a continuous phase.

11. The method for processing CO2-containing flue gas according to claim 10, characterized in that, The liquid absorbent is in emulsion state, and the preparation method of the liquid absorbent includes: slowly adding a dispersed phase to a continuous phase under stirring, stirring, and obtaining an emulsion.

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