A system and method for generating CO2 hydrate from flue gas.

Abstract

This invention discloses a system and method for generating CO2 hydrate from flue gas, belonging to the field of flue gas recovery technology. The system includes a flue gas reaction device, a hydrate reaction promoter supply device, and a primary hydrate generation reaction device. Flue gas is introduced into the flue gas reaction device, where liquid water and condensed gas are formed under the action of heat exchange components. During the condensation of water vapor into liquid water, a hydrate reaction promoter is introduced through the hydrate reaction promoter supply device. The liquid water and hydrate reaction promoter are collected in the flue gas reactor, and the liquid water is atomized. The atomized water vapor and condensed gas are then introduced into the primary hydrate generation reaction device, where solid CO2 hydrate is formed on the surface of the first roller. This method uses the abundant water vapor inherent in the flue gas as a basic raw material. In the reaction device, the rolling of the roller continuously coats the surface with a liquid water film, which is then rapidly and efficiently converted into CO2 hydrate under high pressure.

Description

Technical Field

[0001] This invention relates to the field of flue gas recovery technology, and more specifically, to a system and method for generating CO2 hydrate from flue gas. Background Technology

[0002] The in-depth development of carbon dioxide capture and storage (CCVS) technology is of great significance for mitigating global warming. Traditional carbon capture methods include absorption, adsorption, cryogenic separation, metal oxide separation, and membrane separation. Among these, chemical absorption is relatively mature and suitable for low CO2 concentrations and atmospheric pressure conditions. However, it requires a large amount of absorbent, which needs to be replenished during the cycle, has high reagent requirements, and its regeneration process is energy-intensive. While membrane separation is simple in process and easy to operate, it has high requirements for the feed gas, requiring pretreatment, dehydration, and filtration, and the purity of the obtained product is not high.

[0003] The hydrate method for separating CO2 from flue gas offers a significant cost reduction while effectively improving separation efficiency compared to traditional methods. Gas hydrates are compounds formed by water and gas molecules under high pressure and low temperature conditions. Under appropriate low temperature and high pressure, water molecules form cage-like structures of different shapes and sizes through hydrogen bonding. Different types of gas molecules are trapped within these structures, thus forming gas hydrates. The principle behind the hydrate method for separating mixed gases is that the phase equilibrium differences during the formation of hydrates from binary and multi-component gases are relatively large. Therefore, gases that are more likely to form gas hydrates enter the hydrate phase, while gases that are less likely to form gas hydrates remain in the gas phase, thereby achieving the separation of mixed gases.

[0004] In carbon capture technology using hydrates, the conditions required for CO2 hydrate formation are milder than those for nitrogen hydrates. Therefore, the hydrate method can be applied to the capture of greenhouse gases such as carbon dioxide. Furthermore, gaseous hydrates have a high energy density; one volume of hydrate can release approximately 170 volumes of gas under standard conditions. However, the hydrate nucleation process is random and involves a long induction period before nucleation. The heat released during hydrate formation can inhibit further hydrate formation if this heat is not removed promptly, resulting in low hydrate formation efficiency. Additionally, once hydrates form, the hydrate layer at the water-gas interface significantly reduces gas permeability, leading to a gradual and significant decrease in gas mass transport capacity during the growth phase after nucleation.

[0005] Furthermore, the hydrates generated by existing technologies are mostly loose, snowflake-like or form hydrate slurries, which occupy most of the growth space and are not conducive to efficient and continuous reaction. Therefore, although gaseous hydrates have great potential for carbon dioxide capture and storage, the relatively low capture rate and low gas capture capacity in the general hydrate carbon capture process limit the commercial application scale of hydrate-based carbon capture technology.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The present invention aims to provide a system and method for generating CO2 hydrate from flue gas to solve or improve the above-mentioned technical problems.

[0008] This invention can be implemented as follows:

[0009] In a first aspect, the present invention provides a system for generating CO2 hydrate from flue gas, comprising a flue gas reaction device, a hydrate reaction promoter supply device, a primary hydrate generation reaction device, and a first CO2 hydrate collection device.

[0010] The flue gas reaction device includes a flue gas reactor and a water vapor separator. The water vapor separator has a flue gas inlet, a hydrate reaction promoter inlet, a liquid water outlet, and a condensate gas outlet, and is equipped with a heat exchanger. The hydrate reaction promoter inlet is connected to a hydrate reaction promoter supply device, and the liquid water outlet is connected to the flue gas reactor. The flue gas reactor is equipped with an ultrasonic oscillator for atomizing the liquid water, and is also equipped with an atomized water vapor outlet.

[0011] The primary hydrate generation reaction device includes a primary hydrate generation reactor; the primary hydrate generation reactor is provided with a condensate exhaust gas inlet, an atomized water vapor inlet, a first CO2 hydrate generation mechanism, and a first CO2 hydrate outlet; the condensate exhaust gas inlet is connected to the condensate exhaust gas outlet through a first connecting pipe, and the atomized water vapor inlet is connected to the atomized water vapor outlet of the flue gas reactor through a second connecting pipe, and the atomized water vapor and the CO2 component in the condensate exhaust gas generate solid CO2 hydrate in the first CO2 hydrate generation mechanism;

[0012] The first CO2 hydrate collection device is connected to the first CO2 hydrate outlet.

[0013] In an optional embodiment, the first CO2 hydrate generating mechanism includes a first roller, with both ends of the first roller connected to a first rotating shaft. Both the first rotating shaft and the first roller are hollow structures to allow the flow of refrigerant for heat exchange.

[0014] In an optional embodiment, the system further includes a secondary hydrate formation reaction device and a second CO2 hydrate collection device;

[0015] The primary hydrate generation reactor is also equipped with a CO2 exhaust gas outlet;

[0016] The secondary hydrate generation reaction device includes a secondary hydrate generation reactor; the secondary hydrate generation reactor is equipped with a CO2 waste gas inlet, an exhaust outlet, a second CO2 hydrate generation mechanism, and a second CO2 hydrate outlet; the CO2 waste gas inlet is connected to the CO2 waste gas outlet through a third connecting pipe, and the CO2 components in the CO2 waste gas generate solid CO2 hydrate in the second CO2 hydrate generation mechanism.

[0017] The second CO2 hydrate collection device is connected to the second CO2 hydrate outlet.

[0018] In an optional embodiment, the second CO2 hydrate generating mechanism includes a second roller, with both ends of the second roller connected to a second rotating shaft. Both the second rotating shaft and the second roller are hollow structures to allow the flow of refrigerant for heat exchange.

[0019] Secondly, the present invention provides a method for generating CO2 hydrate from flue gas, comprising the following steps: using the system of any of the foregoing embodiments, the flue gas is introduced into the water vapor separator of the flue gas reaction device, so that the water vapor in the flue gas is condensed into liquid water under the action of the heat exchanger in the water vapor separator; during the process of water vapor condensing into liquid water, a hydrate reaction promoter is introduced into the water vapor separator through a hydrate reaction promoter supply device, and then the liquid water and the hydrate reaction promoter are collected together in the flue gas reactor; the ultrasonic oscillator in the flue gas reactor is turned on to atomize the liquid water, and the atomized water vapor is introduced into the primary hydrate generation reaction device through a second connecting pipe;

[0020] The condensed exhaust gas generated after heat exchange in the water vapor separator is introduced into the primary hydrate generation reaction device through the first connecting pipe. The condensed exhaust gas and the CO2 component in the atomized water vapor form solid CO2 hydrate on the surface of the first roller in the primary hydrate generation reaction device, and then are collected in the first CO2 hydrate collection device.

[0021] In an optional embodiment, the CO2 waste gas in the primary hydrate generation reactor is connected to the second CO2 hydrate generation mechanism through a third connecting pipe, so that the CO2 components in the CO2 waste gas generate solid CO2 hydrate on the surface of the second roller of the second CO2 hydrate generation mechanism, and then collected in the second CO2 hydrate collection device.

[0022] In an optional embodiment, the flue gas is increased to a pressure of not less than 10 MPa before entering the water vapor separator.

[0023] In an optional embodiment, the condensate exhaust gas is pressurized to P1 before entering the primary hydrate formation reactor; the CO2 exhaust gas is pressurized to P2 before entering the secondary hydrate formation reactor.

[0024] Where P2 > P1, P1 ≥ 10 MPa.

[0025] In an optional embodiment, the surface temperature of the first roller and the second roller is <0°C, and the surface pressure of the first roller and the surface pressure of the second roller are both ≥10MPa.

[0026] In an optional embodiment, the temperature inside both the first CO2 hydrate collection device and the second CO2 hydrate collection device does not exceed -5°C.

[0027] The beneficial effects of this invention include:

[0028] This invention creatively proposes a system and method for generating CO2 hydrate from flue gas. The method involves passing flue gas into a water vapor separator of a flue gas reaction device, where water vapor in the flue gas condenses into liquid water under the action of a heat exchanger within the separator. During this condensation process, a hydrate reaction promoter is introduced into the water vapor separator via a hydrate reaction promoter supply device. The liquid water and the promoter are then collected together in a flue gas reactor. An ultrasonic oscillator within the reactor is activated to atomize the liquid water. The atomized water vapor is then introduced into a primary hydrate generation reaction device via a second connecting pipe. The condensed flue gas, generated after heat exchange in the water vapor separator, is then introduced into the primary hydrate generation reaction device via a first connecting pipe. The condensed flue gas and the CO2 component in the atomized water vapor form solid CO2 hydrate on the surface of a first roller in the primary hydrate generation reaction device, which is then collected in a first CO2 hydrate collection device. This method can quickly and efficiently separate CO2 gas from flue gas. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the system for generating CO2 hydrate from flue gas provided by the present invention.

[0031] Icons: 1-Flue gas reactor; 2-Water vapor separator; 3-Heat exchanger; 4-First observation window; 5-First exhaust gas pressure booster pump; 6-Primary hydrate formation reactor; 7-First connecting pipe; 8-Second connecting pipe; 9-First roller; 10-First rotating shaft; 11-First scraper; 12-First hydrate collection pipe; 13-First manual gate valve; 14-First electric gate valve; 15-First CO2 hydrate storage container; 16-Second observation window; 17-First container external temperature control coil; 18-The 19-Hydrate reaction promoter injection pump; 20-Hydrate reaction promoter storage cylinder; 21-Inlet valve; 22-Third connecting pipe; 23-Second waste gas pressure booster pump; 24-Second roller; 25-Second rotating shaft; 26-Second scraper; 27-Second hydrate collection pipe; 28-Second manual gate valve; 29-Second electric gate valve; 30-Second CO2 hydrate storage container; 31-Third observation window; 32-Second container external temperature control coil; 33-Second vent; 34-Exhaust port. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0033] The system and method for generating CO2 hydrate from flue gas provided by the present invention will be described in detail below.

[0034] like Figure 1 As shown, the present invention provides a system for generating CO2 hydrate from flue gas, which includes a flue gas reaction device, a hydrate reaction promoter supply device, a primary hydrate generation reaction device, and a first CO2 hydrate collection device.

[0035] The flue gas reaction device includes a flue gas reactor 1 and a water vapor separator 2. The water vapor separator 2 can be, for example, a high-pressure resistant cylindrical container. It has a flue gas inlet, a hydrate reaction promoter inlet, a liquid water outlet, and a condensate outlet. A heat exchanger 3 (such as heat exchange plates) is installed inside the water vapor separator 2. The hydrate reaction promoter inlet is connected to a hydrate reaction promoter supply device, and the liquid water outlet is connected to the flue gas reactor 1.

[0036] For example, the flue gas inlet can be located in the lower region of the water-vapor separator 2, and the flue gas inlet can be equipped with an inlet valve 21; the hydrate reaction promoter inlet can be located above the flue gas inlet, the heat exchanger 3 is located above the hydrate reaction promoter inlet, and the condensate gas outlet is located at the bottom of the water-vapor separator 2. In some optional embodiments, the water-vapor separator 2 may also be equipped with a first observation window 4.

[0037] The flue gas reactor 1 is equipped with an ultrasonic oscillator for atomizing liquid water, and the flue gas reactor 1 also has an atomized water vapor outlet. A high-pressure liquid water injector can be installed inside the flue gas reactor 1, and one or more high-pressure resistant high-frequency ultrasonic oscillators can be deployed therein. The flue gas reactor 1 can withstand a gas pressure ≥10MPa.

[0038] The hydrate reaction accelerator supply device includes a hydrate reaction accelerator injection pump 19 and a hydrate reaction accelerator storage cylinder 20, which is connected to the hydrate reaction accelerator inlet via a pipeline.

[0039] The primary hydrate formation reactor includes a primary hydrate formation reactor 6. The primary hydrate formation reactor 6 is equipped with a condensate exhaust gas inlet, an atomized water vapor inlet, a first CO2 hydrate formation mechanism, and a first CO2 hydrate outlet. The condensate exhaust gas inlet is connected to the condensate exhaust gas outlet via a first connecting pipe 7, and the atomized water vapor inlet is connected to the atomized water vapor outlet of the flue gas reactor 1 via a second connecting pipe 8. The atomized water vapor and the CO2 components in the condensate exhaust gas generate solid CO2 hydrate in the first CO2 hydrate formation mechanism. A first CO2 hydrate collection device is connected to the first CO2 hydrate outlet. The primary hydrate formation reactor 6 also has a CO2 exhaust gas outlet.

[0040] The condensate exhaust gas is first pressurized by the first exhaust gas pressure booster pump 5, which is connected to the first connecting pipe 7 (also known as the first high-pressure connecting pipe), before being introduced into the primary hydrate generation reaction device. The second connecting pipe can be referred to as the second high-pressure connecting pipe.

[0041] The aforementioned first CO2 hydrate generating mechanism includes a first roller 9 (such as a high-pressure resistant stainless steel roller), with the two ends of the first roller 9 connected to a first rotating shaft 10. Both the first rotating shaft 10 and the first roller 9 are hollow structures to allow the flow of refrigerant for heat exchange.

[0042] Preferably, the primary hydrate generation reactor 6 is further provided with a first scraper 11, which is used to scrape off the CO2 hydrate on the surface of the first roller 9 so that CO2 hydrate can be continuously generated on the surface of the first roller 9.

[0043] In some optional embodiments, the first CO2 hydrate collection device includes a first hydrate collection pipe 12, a first manual gate valve 13, a first electric gate valve 14, and a first CO2 hydrate storage container 15. The first CO2 hydrate storage container 15 is provided with a second observation window 16, and a first external temperature control coil 17 may be provided on the outside of the first CO2 hydrate storage container 15. A first vent 18 is also provided at the upper end of the first CO2 hydrate storage container 15.

[0044] Furthermore, the above system may also include a secondary hydrate formation reaction device and a second CO2 hydrate collection device. The secondary hydrate formation reaction device includes a secondary hydrate formation reactor; the secondary hydrate formation reactor is provided with a CO2 waste gas inlet, an exhaust port 34 (the exhaust port 34 can be controlled by an electric gate valve), a second CO2 hydrate formation mechanism, and a second CO2 hydrate outlet; the CO2 waste gas inlet is connected to the CO2 waste gas outlet through a third connecting pipe 22, and the CO2 components in the CO2 waste gas are converted into solid CO2 hydrates by the second CO2 hydrate formation mechanism;

[0045] The second CO2 hydrate collection device is connected to the second CO2 hydrate outlet.

[0046] The CO2 waste gas is first pressurized by a second waste gas pressure booster pump 23 connected to the third connecting pipe 22 (also known as the third high-pressure connecting pipe) before being introduced into the secondary hydrate generation reaction device. The aforementioned second CO2 hydrate generation mechanism includes a second roller 24 (such as a high-pressure resistant stainless steel roller), with two ends of the second roller 24 connected to a second rotating shaft 25. Both the second rotating shaft 25 and the second roller 24 are hollow structures to allow for the flow of refrigerant for heat exchange.

[0047] Preferably, the secondary hydrate generation reactor is further provided with a second scraper 26, which is used to scrape off the CO2 hydrate on the surface of the second roller 24 so that CO2 hydrate can be continuously generated on the surface of the second roller 24.

[0048] In some optional embodiments, the second CO2 hydrate collection device includes a second hydrate collection pipe 27, a second manual gate valve 28, a second electric gate valve 29, and a second CO2 hydrate storage container 30. The second CO2 hydrate storage container 30 is provided with a third observation window 31, and a second external temperature control coil 32 may be provided on the outside of the second CO2 hydrate storage container 30. A second vent 33 is also provided at the upper end of the second CO2 hydrate storage container 30.

[0049] Accordingly, the present invention also provides a method for generating CO2 hydrate from flue gas, comprising the following steps: using the above-mentioned system, the flue gas is introduced into the water vapor separator 2 of the flue gas reaction device, so that the water vapor in the flue gas is condensed into liquid water under the action of the heat exchanger 3 in the water vapor separator 2; during the process of water vapor condensing into liquid water, a hydrate reaction promoter is introduced into the water vapor separator 2 through a hydrate reaction promoter supply device, and then the liquid water and the hydrate reaction promoter are collected together in the flue gas reactor 1. The ultrasonic oscillator inside the flue gas reactor 1 is turned on to atomize the liquid water. The atomized water vapor is introduced into the primary hydrate generation reaction device through the second connecting pipe 8. The condensed waste gas generated after the flue gas is heated by the heat exchanger 3 in the water vapor separator 2 is introduced into the primary hydrate generation reaction device through the first connecting pipe 7. The condensed waste gas and the CO2 component in the atomized water vapor form solid CO2 hydrate on the surface of the first roller 9 in the primary hydrate generation reaction device, and then it is collected in the first CO2 hydrate collection device.

[0050] The surface temperature of the first roller 9 can be regulated by the internal circulating coolant, ensuring that the surface temperature of the first roller 9 reaches the suitable low-temperature, high-pressure reaction conditions for CO2 hydrate formation in a high-pressure environment. Combined with the continuous injection of high-pressure water vapor carrying reaction promoter particles into the primary hydrate formation reactor 6, the surface of the continuously rotating first roller 9 inside the primary hydrate formation reactor 6 will maintain a consistently low temperature. The temperature conditions inside the primary hydrate formation reactor 6 are higher in areas other than the surface of the first roller 9. The water vapor, atomized by the ultrasonic oscillator, will concentrate and migrate towards the first surface, condensing into an aqueous film layer. At this point, under the action of the reaction promoter particles in the solution, the water film layer will rapidly absorb CO2 gas under high-pressure conditions and simultaneously complete the transformation process into a solid hydrate structure.

[0051] Inside the primary hydrate formation reactor 6, the first roller 9 rotates continuously under ambient temperature and high pressure. The circulating refrigerant keeps the outer surface temperature of the first roller 9 below 0°C. The hydrate structure continuously absorbs CO2 components from the flue gas and rapidly generates them on the roller surface. Therefore, CO2 in the flue gas is efficiently captured and separated through the hydrate structure. As the hydrate structure continues to grow and thicken on the roller surface, the first scraper 11 scrapes off the hydrate and exposes new contact surfaces for further continuous generation of the hydrate structure, ultimately achieving continuous and sustained formation and growth of CO2 hydrates in the reactor.

[0052] Furthermore, the CO2 waste gas in the primary hydrate generation reactor 6 is connected to the second CO2 hydrate generation mechanism through the third connecting pipe 22, so that the CO2 components in the CO2 waste gas generate solid CO2 hydrate on the surface of the second roller 24 of the second CO2 hydrate generation mechanism, and then collected in the second CO2 hydrate collection device.

[0053] In some alternative embodiments, the flue gas is increased to a pressure of not less than 10 MPa before entering the water vapor separator 2.

[0054] In some optional embodiments, the condensate exhaust gas is pressurized to P1 before entering the primary hydrate formation reactor 6; the CO2 exhaust gas is pressurized to P2 before entering the secondary hydrate formation reactor; wherein, P2 > P1, and P1 ≥ 10 MPa.

[0055] In some alternative embodiments, the surface temperature of the first roller 9 and the second roller 24 is <0°C, and the surface pressure of the first roller 9 and the surface pressure of the second roller 24 are both ≥10MPa.

[0056] In some alternative embodiments, the temperature inside both the first CO2 hydrate collection device and the second CO2 hydrate collection device does not exceed -5°C.

[0057] Specifically, please refer to the following methods:

[0058] S1: Collect the exhaust gas emitted from the flue and initially pressurize it to ≥10MPa. Open the air inlet valve 21 of the water-vapor separator 2 and introduce the initially pressurized flue gas into the water-vapor separator 2.

[0059] S2: Flue gas is the exhaust gas produced after fuel combustion. It is usually at a high temperature (≥90°C) and contains abundant water vapor (by volume percentage, the flue gas itself can carry 10%~25% water vapor). Therefore, when the pressurized flue gas passes through the heat exchanger 3 in the water vapor separator 2, the water vapor in the flue gas will be pre-cooled and condensed into liquid water, and then flow downward into the flue gas reactor 1 under the action of gravity.

[0060] S3: During the process of water vapor condensing into liquid water, the accelerator powder or a certain concentration of accelerator solution in the hydrate reaction accelerator storage cylinder 20 is injected into the water vapor separator 2 under high pressure using the hydrate reaction accelerator injection pump 19.

[0061] S4: Start the high-pressure liquid water injector in the flue gas reactor 1 to inject the condensed liquid water into the high-pressure high-frequency ultrasonic oscillator. Then start the ultrasonic oscillator to atomize the injected liquid water and transport it to the primary hydrate generation reactor 6 through the second connecting pipe 8.

[0062] S5: Start the first exhaust gas pressure boosting pump 5 to boost the condensed flue gas to a suitable pressure value (≥10MPa), and then transport it to the primary hydrate generation reactor 6 through the first connecting pipe 7, so that the pressure in the primary hydrate generation reactor 6 reaches the pressure value required for hydrate generation.

[0063] S6: Start the first rotating shaft 10 of the first roller 9 in the primary hydrate generation reactor 6, so that the first rotating shaft 10 drives the first roller 9 to rotate at a constant speed. The central part of the first rotating shaft 10 and the first roller 9 is a hollow structure, through which the external circulating temperature-controlled liquid (coolant) can flow, thereby controlling the temperature of the outer surface of the first roller 9 and keeping it at a low temperature (e.g., -0.5°C). Therefore, the first CO2 hydrate can be formed on the outer surface of the first roller 9 at low temperature (-0.5°C) and high pressure (≥10MPa), thereby fixing the CO2 component in the flue gas in the form of solid CO2 hydrate on the outer surface of the first roller 9, realizing the efficient capture and separation of CO2 gas in flue gas by the hydrate method.

[0064] The reaction equation for the conversion of liquid water and CO2 gas into a solid CO2 hydrate structure under appropriate low temperature and high pressure conditions can be expressed as follows:

[0065] CO2 + 5.75H2O → CO2·5.75H2O.

[0066] S7: As the first roller 9 continues to rotate, solid hydrate begins to form on the surface of the first roller 9. As the hydrate layer gradually thickens, the first scraper 11 located below the first roller 9 will scrape off the hydrate that has accumulated to a certain thickness from the outer surface of the first roller 9 by means of the constant speed rolling process of the first roller 9.

[0067] The CO2 hydrate formation reaction mainly occurs at the gas / liquid interface; therefore, increasing the gas / liquid contact area is crucial for improving the reaction efficiency. Furthermore, once hydrates form at the gas / liquid interface, their solid structure hinders further gas dissolution in the liquid phase, thus impeding the continued reaction. Therefore, this invention addresses these two key factors limiting the hydrate formation rate by incorporating a certain amount of reaction promoter into an aqueous solution to prepare a promoter solution. The solution is then ultrasonically vibrated to form atomized water vapor with a specific promoter concentration. This water vapor is then condensed again at low temperature onto the outer surface of a stainless steel roller, ultimately forming a thin liquid water film containing a certain mass ratio of promoter. This liquid water film increases the gas / liquid contact area, thereby enhancing the CO2 hydrate formation rate. Combined with the effect of the chemical promoter dissolved in the water film, the synergistic effect of these two factors significantly improves the efficiency of CO2 treatment in flue gas using the hydrate method. In addition, the hydrate formation reaction process can quickly clear the already formed hydrate structure, comprehensively solve the key technical problems that limit the hydrate formation reaction rate, and improve the reaction efficiency and operation continuity of the hydrate method for treating CO2 in flue gas.

[0068] S8: The scraped-off hydrate structure is collected by gravity through the first hydrate collection pipe 12 into the first CO2 hydrate storage container 15. Since the temperature of the first CO2 hydrate storage container 15 is below zero degrees (e.g., -10°C) in a frozen state, the solid CO2 hydrate scraped off from the outer surface of the first roller 9 will be quickly frozen and enter a "self-protection" state once it enters the first CO2 hydrate storage container 15, that is, the hydrate prepared under normal pressure will remain stable for a long time without decomposition.

[0069] S9: When the CO2 hydrate contained in the first CO2 hydrate storage container 15 approaches the volume limit, close the first manual gate valve 13 and the first electric gate valve 14 to disconnect the high-pressure gas path between the first CO2 hydrate storage container 15 and the primary hydrate generation reactor 6.

[0070] S10: Open the first vent 18 at the top of the first CO2 hydrate storage container 15 to discharge the excess high-pressure waste gas in the first CO2 hydrate storage container 15. Then, the first CO2 hydrate storage container 15 can be disassembled from the primary hydrate generation reactor 6, and the hydrate sample in the first CO2 hydrate storage container 15 can be transferred, collected and stored in the next step.

[0071] S11: When the CO2 concentration in the residual gas after the reaction in the primary hydrate generation reactor 6 does not meet the emission requirements, the second exhaust gas pressure booster pump 23 needs to be started to further pressurize the residual gas in the primary hydrate generation reactor 6 to a higher pressure (≥20MPa), and then the high-pressure gas is injected into the secondary hydrate generation reactor.

[0072] S12: The second roller 24 in the secondary hydrate formation reactor is activated. The second rotating shaft 25 drives the second roller 24 to rotate at a constant speed. Similar to the rotating shaft and roller in the previous stage reactor, both have a hollow structure in the middle, and the temperature-controlled circulating liquid can flow through the middle of them, thereby controlling the temperature of the outer surface of the second roller 24 to a lower temperature (e.g., -0.5℃). Although the temperature of the second roller 24 is the same as that of the first roller 9 in the previous stage, the pressure conditions are significantly higher than those in the previous stage reactor (at least 10 MPa higher). Therefore, with the continuous formation of CO2 hydrate under higher pressure conditions, the CO2 gas concentration in the secondary hydrate formation reactor will be further reduced, thereby reaching or even exceeding the exhaust gas emission standards.

[0073] S13: Similar to the hydrate transfer and storage operation in the first CO2 hydrate storage container 15, close the second manual gate valve 28 and the second electric gate valve 29, open the second vent 33 to release the remaining high-pressure gas in the second CO2 hydrate storage container 30, disassemble the second CO2 hydrate storage container 30 from the secondary hydrate generation reactor, and proceed with the next step of transfer, collection and storage of the hydrate sample in the second CO2 hydrate storage container 30.

[0074] S14: When the exhaust gas in the secondary hydrate generation reactor reaches or falls below the designed CO2 gas concentration after being treated by the hydrate method, the valve at exhaust port 34 can be activated to directly discharge the reaction tail gas that meets the exhaust gas emission standards into the atmosphere.

[0075] S15: If the CO2 concentration in the exhaust gas from the secondary hydrate formation reactor does not meet the expected target, the number of stages in the high-pressure reactor can be increased. Each additional stage increases the reaction pressure. Therefore, by gradually increasing the pressure during the reaction process, the CO2 concentration in the reaction gas can be gradually reduced until the expected concentration is reached.

[0076] In other words, the reactor proposed in this invention can be used in multiple series without limitation. The pressure conditions for the hydrate formation reaction increase significantly with the increase of the number of series stages, thereby minimizing the CO2 gas concentration in the remaining gas after the hydrate formation reaction and giving full play to the reaction efficiency of the hydrate method in treating CO2 in flue gas.

[0077] Continuing from the above, the solution provided by this invention first condenses the flue gas into liquid water, then adds a CO2 hydrate formation reaction promoter to enhance the reactivity of the liquid water. Next, a high-frequency ultrasonic oscillator is used to rapidly atomize the solution, restoring the water in the flue gas to form a water mist carrying promoter microparticles. Then, under high-pressure gas conditions, the water mist is condensed onto a stainless steel roller with freely adjustable temperature. Because the ultrasonically atomized water mist contains abundant promoter microparticles, during the re-condensation process on the roller surface, the water mist reacts rapidly with the CO2 gas in the flue gas under the action of the promoter, forming a hydrate and covering the roller surface. This process rapidly and efficiently separates the CO2 gas from the flue gas, fixing it layer by layer as a solid hydrate on the stainless steel surface under high-pressure gas conditions. At this time, a scraper located below the stainless steel roller continuously scrapes off the solid hydrate with the continuous rotation of the roller, and the hydrate powder scraped off by the scraper is collected in the first CO2 hydrate storage container 15 by gravity. As the generated hydrates are continuously scraped off the rollers, the stainless steel surface of the rollers is exposed again, allowing new hydrate structures to continue to form on their surface. With the repeated formation and scraping off of hydrate structures on the roller surface, CO2 in the continuously fed exhaust gas is continuously captured and separated by these repeatedly generated hydrate structures. Ultimately, this method can achieve the goal of rapidly capturing and separating CO2 from flue gas.

[0078] In summary, the method proposed in this invention uses a condensation pipe before the hydrate formation reaction to initially condense the large amount of naturally occurring water vapor in the flue gas into liquid water. A high-pressure injection pump then injects a certain amount of reaction promoter solution into the condensed liquid water to enhance its reactivity. Subsequently, the aqueous solution is atomized into a water mist carrying catalyst particles by a high-pressure ultrasonic oscillator and injected into the high-pressure reactor. The atomized water vapor condenses on the outer surface of a stainless steel roller, forming a thin liquid water film. This water vapor condensation method increases the gas / liquid phase contact area, accelerates the dissolution of CO2 gas into the liquid phase, and thus increases the CO2 hydrate formation reaction rate. Furthermore, a scraper installed at the lower end of the roller scrapes away the hydrate accumulated on the outer surface after it reaches a certain thickness, exposing the outer surface of the roller again for the adhesion of the condensed liquid water film and its conversion into the hydrate phase. The process of the liquid water film adhering to the outer surface of the roller and the hydrate structure being scraped off is repeated continuously. Ultimately, the efficient capture and separation of CO2 in flue gas can be achieved through the rapid hydrate generation method.

[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for generating CO2 hydrate from flue gas, characterized in that, Includes the following steps: A system for generating CO2 hydrates from flue gas involves passing the flue gas into a water vapor separator of a flue gas reaction device. Under the action of a heat exchanger within the water vapor separator, the water vapor in the flue gas condenses into liquid water. During this condensation process, a hydrate reaction promoter is introduced into the water vapor separator via a hydrate reaction promoter supply device. The liquid water and the hydrate reaction promoter are then collected together in a flue gas reactor. An ultrasonic oscillator within the flue gas reactor is activated to atomize the liquid water. The atomized water vapor is then introduced into the primary hydrate generation reaction device through a second connecting pipe. The flue gas is condensed after being heated by the heat exchanger in the water vapor separator. The condensed gas is then introduced into the primary hydrate generation reaction device through the first connecting pipe. The condensed gas and the CO2 component in the atomized water vapor form solid CO2 hydrate on the surface of the first roller in the primary hydrate generation reaction device, and then the solid hydrate is collected in the first CO2 hydrate collection device. The system includes a flue gas reaction device, a hydrate reaction promoter supply device, a primary hydrate generation reaction device, and a first CO2 hydrate collection device. The flue gas reaction device includes a flue gas reactor and a water vapor separator; the water vapor separator is provided with a flue gas inlet, a hydrate reaction promoter inlet, a liquid water outlet, and a condensate gas outlet, and a heat exchanger is installed inside the water vapor separator; the hydrate reaction promoter inlet is connected to the hydrate reaction promoter supply device, and the liquid water outlet is connected to the flue gas reactor; the flue gas reactor is provided with an ultrasonic oscillator for atomizing liquid water, and the flue gas reactor is provided with an atomized water vapor outlet; The primary hydrate generation reaction device includes a primary hydrate generation reactor; the primary hydrate generation reactor is provided with a condensate exhaust gas inlet, an atomized water vapor inlet, a first CO2 hydrate generation mechanism, and a first CO2 hydrate outlet; the condensate exhaust gas inlet is connected to the condensate exhaust gas outlet through a first connecting pipe, and the atomized water vapor inlet is connected to the atomized water vapor outlet of the flue gas reactor through a second connecting pipe, wherein the atomized water vapor and the CO2 component in the condensate exhaust gas generate solid CO2 hydrate in the first CO2 hydrate generation mechanism; The first CO2 hydrate collection device is connected to the first CO2 hydrate outlet; The surface temperature of the first roller is <0℃, and the surface pressure of the first roller is ≥10MPa; The first CO2 hydrate generating mechanism includes a first roller, with both ends of the first roller connected to a first rotating shaft. Both the first rotating shaft and the first roller are hollow structures to allow the flow of refrigerant for heat exchange.

2. The method according to claim 1, characterized in that, The system also includes a secondary hydrate generation reaction device and a second CO2 hydrate collection device; The primary hydrate generation reactor is also equipped with a CO2 exhaust gas outlet; The secondary hydrate generation reaction device includes a secondary hydrate generation reactor; the secondary hydrate generation reactor is provided with a CO2 waste gas inlet, an exhaust outlet, a second CO2 hydrate generation mechanism, and a second CO2 hydrate outlet; the CO2 waste gas inlet is connected to the CO2 waste gas outlet through a third connecting pipe, and the CO2 component in the CO2 waste gas generates solid CO2 hydrate in the second CO2 hydrate generation mechanism; The second CO2 hydrate collection device is connected to the second CO2 hydrate outlet.

3. The method according to claim 2, characterized in that, The second CO2 hydrate generating mechanism includes a second roller, with two ends of the second roller connected to a second rotating shaft. Both the second rotating shaft and the second roller are hollow structures to allow the flow of refrigerant for heat exchange.

4. The method according to claim 3, characterized in that, The CO2 waste gas in the primary hydrate generation reactor is connected to the second CO2 hydrate generation mechanism through a third connecting pipe, so that the CO2 component in the CO2 waste gas generates solid CO2 hydrate on the surface of the second roller of the second CO2 hydrate generation mechanism, and is then collected in the second CO2 hydrate collection device.

5. The method according to claim 1, characterized in that, The flue gas is increased to a pressure of not less than 10 MPa before entering the water vapor separator.

6. The method according to claim 4, characterized in that, The condensate waste gas is pressurized to P1 before entering the primary hydrate formation reactor; the CO2 waste gas is pressurized to P2 before entering the secondary hydrate formation reactor. Where P2 > P1, P1 ≥ 10 MPa.

7. The method according to claim 4, characterized in that, The surface temperature of the second roller is <0℃, and the surface pressure of the second roller is ≥10MPa.

8. The method according to claim 4, characterized in that, The temperature inside both the first CO2 hydrate collection device and the second CO2 hydrate collection device does not exceed -5℃.

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