A method for CO2 absorption and heat recovery based on centrifugal force field

Abstract

The present application belongs to the technical field of CO2 capture and gas-liquid reaction, and solves the problems of low efficiency, large equipment volume and ineffective heat recovery of the existing absorption technology. A CO2 absorption and heat recovery method based on centrifugal force field is disclosed. The flue gas containing CO2 is introduced into the tower in a rotating manner about the absorption tower axis to form an upward rotating gas flow. The absorption liquid is sprayed downward from the top of the absorption tower. During the downward process of the absorption liquid, it passes through the alternating arrangement of dynamic and static rotational flow layers. In the dynamic rotational flow layer, the absorption liquid collides with the rotating part and is torn into droplets or liquid membranes by centrifugal force. In the static rotational flow layer, the absorption liquid containing CO2 and the flue gas pass through the fixed guide vanes for deflection and separation. The purified flue gas is discharged from the top of the absorption tower, and the absorption liquid enriched with CO2 is discharged from the bottom of the absorption tower. The mass transfer efficiency is greatly improved, the equipment volume is significantly reduced, and the reaction heat and flue gas waste heat are absorbed in time.

Description

Technical Field

[0001] This invention belongs to the field of CO2 capture and gas-liquid reaction technology, specifically relating to a method for CO2 absorption and heat recovery based on a centrifugal force field. Background Technology

[0002] Chemical absorption, represented by the amine method, is the mainstream technology for treating medium- and low-concentration flue gas (with a CO2 volume fraction of 3%–25%). The core equipment currently used is a packed tower, in which the CO2-containing flue gas and the absorbent liquid come into countercurrent or cross-current contact on the surface of the packing material. This technology has the following inherent drawbacks: 1. Mass transfer efficiency is limited by gravity and wetting: The liquid film (the amine solution is used as the absorbent and flows on the packing) flows slowly, with obvious local channeling (the amine solution only flows in some gaps of the packing) and dead zones (some gaps of the packing have no amine solution), resulting in a low mass transfer coefficient and requiring a relatively high tower height (usually 10-30 meters) (increasing the height can extend the absorption time, and widening the tower can increase the flue gas treatment capacity). 2. Large temperature difference loss: There is a large temperature difference between the flue gas (usually 50-80℃) and the absorbent (30-50℃). The tower does not effectively recover heat, which not only wastes energy but also increases the cooling load of the solution in the later stage. 3. Large equipment size: When processing the same amount of gas, the diameter and height of the packed tower are relatively large, which is not conducive to skid-mounted, mobile or space-constrained applications. 4. Prone to foaming (foaming, which can block the gaps in the packing and hinder the upward movement of flue gas) and flooding (when the flue gas velocity is too fast, the downward movement of the amine solution is obstructed): especially for amine solutions with low surface tension, the operation is inflexible. Summary of the Invention

[0003] In view of the problems of low absorption efficiency, large equipment size and failure to effectively recover heat in existing technologies, the purpose of this invention is to provide a CO2 absorption and heat recovery method based on centrifugal force field, so as to improve CO2 absorption efficiency, reduce tower height and tower diameter, and recover waste heat and reaction heat from flue gas.

[0004] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: A method for CO2 absorption and heat recovery based on centrifugal force field includes the following: (1) Flue gas containing CO2 is introduced into the tower in a manner that rotates about the axis of the absorption tower to form an upward rotating airflow; (2) The absorbent liquid is sprayed downwards from above the absorption tower; (3) During the downward flow of the absorbent liquid, it passes through alternating dynamic and static swirling layers. In the swirling layer, the absorbent collides with the rotating component and is torn into droplets or liquid film by centrifugal force, absorbing CO2 from the flue gas. The centrifugal acceleration generated by the rotating component is above 50g. In the static swirl layer, the CO2-containing absorbent liquid and flue gas pass through fixed guide vanes for deflection and separation; (4) The purified flue gas is discharged from the top of the absorption tower, and the CO2-enriched absorbent is discharged from the bottom of the absorption tower.

[0005] In this invention, CO2-containing flue gas enters the absorption tower, where it generates tangential velocity and rotates at high speed under the action of rotating components in the swirling layer. The absorbent liquid is sprayed from the top of the tower and, under the action of strong centrifugal force (centrifugal acceleration exceeding 50 times the acceleration due to gravity), is torn into tiny droplets or liquid films, which are strongly mixed with the flue gas. The mass transfer process occurs in the centrifugal force field of the swirling layer, where the droplet surface is constantly renewed, resulting in a high relative velocity between gas and liquid and a significantly improved CO2 absorption rate. In the centrifugal force field, the droplet diameter can be as small as 10–50 μm, and the gas-liquid interface area is increased by 1–2 orders of magnitude compared to packed towers. The CO2 absorption rate is increased by 30–50% at the same gas velocity. Furthermore, due to the presence of the centrifugal force field, it continuously shears the liquid film and destroys foam. This invention is also suitable for flue gas containing dust or impurities. By dynamically adjusting the rotation speed of the rotating components and the flue gas flow rate, it can also adapt to a wide range of load changes, broadening the operational flexibility. After passing through the dynamic swirl layer, the absorbent has a high velocity and is mainly in tangential motion. After entering the static swirl layer, the guide vanes will forcibly change the flow path of the absorbent. At the same time, the inertia will cause the droplets to collide with the guide vanes or the tower wall. The guide vanes extend the flow path by deflecting the flow, thereby extending the absorption time and further absorbing CO2. In addition, in the static swirl layer, the deflection caused by the guide vanes can also prevent the absorbent from being carried back to the dynamic swirl layer by the rising gas, thus achieving the separation of the rising flue gas and the falling absorbent. This invention treats flue gas and absorbent liquid using a centrifugal force field, which can effectively reduce the size of the absorption tower, increase the amount of flue gas treated per unit tower volume, and facilitate skid mounting and transportation.

[0006] In some alternative examples, the rotating component is an impeller or a turntable, powered by a motor.

[0007] As a preferred technical solution of the present invention, the internal channels of the absorption tower wall and the guide vanes are filled with heat exchange medium to absorb the waste heat and reaction heat of the flue gas; during the CO2 absorption process, the temperature inside the absorption tower is regulated by the heat exchange medium and controlled at 40-60℃, for example, 40℃, 41℃, 42℃, 43℃, 44℃, 45℃, 46℃, 47℃, 48℃, 49℃, 50℃, 51℃, 52℃, 53℃, 54℃, 55℃, 56℃, 57℃, 58℃, 59℃, and 60℃; Meanwhile, the working pressure of the heat exchange medium is 0.3 to 1.0 MPa, for example, it can be 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, or 0.9 MPa. The heat exchange medium (such as cooling water or heat transfer oil) flows through the channels in the tower wall or guide vanes to remove the heat of reaction or recover the waste heat of flue gas in a timely manner, so that the temperature distribution in the tower is more uniform and conducive to chemical absorption equilibrium.

[0008] In this invention, since the absorption of CO2 by the absorbent is an exothermic reaction, in order to improve the energy utilization rate and prevent the absorbent from overheating locally, which would lead to amine degradation and deterioration of the balance, a circulating heat exchange medium is introduced into the channel in the tower wall or the guide vanes. This heat exchange medium transfers the waste heat of the flue gas and the heat of the reaction to the outside, thus avoiding the temperature inside the absorption tower from exceeding the standard.

[0009] The beneficial effects of this invention are: 1. Mass transfer efficiency is significantly improved. In a centrifugal force field, the droplet diameter can be as small as 10-50 μm, the gas-liquid interface area is increased by 1-2 orders of magnitude compared with packed towers, and the CO2 absorption rate is increased by 30-50% at the same gas velocity; 2. The equipment volume is significantly reduced. Under the same processing capacity, the tower height can be reduced from 15-20 meters to 3-5 meters, and the diameter is reduced by more than 30%. The amount of flue gas processed per unit tower volume is increased, which facilitates skid-mounting and transportation. 3. Absorb the heat of reaction and waste heat of flue gas in a timely manner to prevent local overheating of the absorbent liquid from causing amine degradation and deterioration of the balance; 4. It has strong anti-foaming and anti-clogging capabilities. The centrifugal force field continuously shears the liquid film and destroys the foam, making it suitable for flue gas containing dust or impurities. Attached Figure Description

[0010] The present invention can be further illustrated by the non-limiting embodiments given in the accompanying drawings; Figure 1 This is a schematic diagram illustrating the principle of an embodiment of the present invention. Detailed Implementation The technical solutions of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings. The embodiments described herein are specific implementations of the present invention, used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary, and should not be construed as limiting the implementation methods or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein. Example

[0011] like Figure 1As shown, this embodiment provides a method for CO2 absorption and heat recovery based on a centrifugal force field. The flue gas containing CO2 is introduced into the absorption tower in a manner that rotates about the axis of the absorption tower to form an upward rotating airflow; The absorbent liquid is sprayed downwards from above the absorption tower through nozzles. As the absorbent flows downward, it passes through alternating dynamic and static swirling layers. In the swirling layer, the motor drives the impeller to rotate, and the absorbent liquid collides with the impeller and is torn into droplets or liquid film by centrifugal force, absorbing CO2 in the flue gas. The centrifugal acceleration generated by the impeller is 60 times the acceleration due to gravity. The reaction heat and waste heat of the flue gas during the CO2 absorption process are recovered by the cooling water in the absorption tower wall channel. In the static swirl layer, the CO2-containing absorbent liquid and flue gas pass through fixed guide vanes for deflection and separation. The cooling water in the internal channels of the guide vanes also plays a role in heat recovery. The purified flue gas is discharged from the top of the absorption tower after being demisted, while the CO2-enriched absorbent is discharged from the bottom of the absorption tower.

[0012] In this embodiment, CO2-containing flue gas enters the absorption tower, generates tangential velocity, and rotates at high speed under the action of the impeller in the dynamic swirling layer. The absorbent liquid is sprayed from the top of the tower and is torn into fine droplets or liquid films under the action of strong centrifugal force, which mixes strongly with the flue gas. After passing through the dynamic swirl layer, the absorbent has a high velocity and is mainly in tangential motion. After entering the static swirl layer, the guide vanes will forcibly change the flow path of the absorbent. At the same time, the inertia will cause the droplets to collide with the guide vanes or the tower wall. The guide vanes extend the flow path by deflecting the flow, thereby extending the absorption time and further absorbing CO2. In addition, in the static swirl layer, the deflection caused by the guide vanes can also prevent the absorbent from being carried back to the dynamic swirl layer by the rising gas, thus achieving the separation of the rising flue gas and the falling absorbent. In terms of heat recovery, the internal heat exchange medium flows through the channels in the tower wall or guide vanes to remove the heat of reaction or recover the waste heat of flue gas in a timely manner, making the temperature distribution inside the tower more uniform and conducive to chemical absorption equilibrium.

[0013] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for CO2 absorption and heat recovery based on a centrifugal force field, characterized in that: Includes the following: (1) Flue gas containing CO2 is introduced into the tower in a manner that rotates about the axis of the absorption tower to form an upward rotating airflow; (2) The absorbent liquid is sprayed downwards from above the absorption tower; (3) During the downward flow of the absorbent liquid, it passes through alternating dynamic and static swirling layers. In the swirling layer, the absorbent collides with the rotating components, is torn into droplets or liquid films by centrifugal force, and absorbs CO2 from the flue gas. In the static swirling layer, the CO2-containing absorbent liquid and flue gas pass through fixed guide vanes for deflection and separation; (4) The purified flue gas is discharged from the top of the absorption tower, and the CO2-enriched absorbent is discharged from the bottom of the absorption tower.

2. The method for CO2 absorption and heat recovery based on centrifugal force field according to claim 1, characterized in that: The internal channels of the absorption tower wall and guide vanes are filled with heat exchange medium to absorb the waste heat of flue gas and the heat of reaction.

3. The method for CO2 absorption and heat recovery based on centrifugal force field according to claim 2, characterized in that: During CO2 absorption, the temperature inside the absorption tower is regulated by the heat exchange medium and controlled at 40–60℃.

4. The method for CO2 absorption and heat recovery based on centrifugal force field according to claim 2, characterized in that: The heat exchange medium options include cooling water and heat transfer oil, and the working pressure of the heat exchange medium is 0.3 to 1.0 MPa.

5. The method for CO2 absorption and heat recovery based on centrifugal force field according to claim 1, characterized in that: In the dynamic vortex layer, the centrifugal acceleration generated by the rotating component is above 50g.

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