Absorbents for co-capture of sulfur dioxide and carbon dioxide, method for capture of sulfur dioxide and carbon dioxide from flue gas

Abstract

The application provides an absorbent for simultaneous capture of sulfur dioxide and carbon dioxide, and a method for capturing sulfur dioxide and carbon dioxide in flue gas. The absorbent comprises deionized water, an alcohol amine compound and an activator, wherein the alcohol amine compound is one or more of N-methyldiethanolamine, monoethanolamine, diethanolamine and triethanolamine, and the activator is at least two of diethylenetriamine, triethylenetetramine, dihydroxyethylpiperazine and piperazine. The special type of alcohol amine compound and the special type of activator are used to enable the absorbent to simultaneously absorb sulfur dioxide and carbon dioxide in the process of treating flue gas, both of which have high absorption efficiency, and the enriched carbon dioxide and sulfur dioxide can be desorbed to obtain carbon dioxide gas and sulfur dioxide gas, respectively. Based on the absorbent, the production efficiency is improved, the equipment investment is saved, and the absorbent has good industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of gas desulfurization and decarbonization technology, and more specifically, to an absorbent for the synergistic capture of sulfur dioxide and carbon dioxide, and a method for capturing sulfur dioxide and carbon dioxide in flue gas. Background Technology

[0002] In industries such as non-ferrous metallurgy, chemicals, and power, fossil fuels remain the primary energy source. The use of fossil fuels generates large amounts of flue gas containing sulfur dioxide and carbon dioxide. Flue gas purification processes are broadly categorized into non-resource-based and resource-based treatments. Non-resource-based treatment primarily involves converting acidic gases like sulfur dioxide in the flue gas into waste salts, such as gypsum and sodium sulfate, which are then treated as bulk solid waste. Carbon dioxide in the flue gas is generally left untreated until other components are treated to meet standards before being released together. Resource-based treatment typically uses an absorbent liquid employing a combined approach of "cooling and pressurizing absorption + heating and depressurizing desorption" to absorb and desorb sulfur dioxide or carbon dioxide, enriching the gas and then using it as an industrial raw material in other fields.

[0003] There are many types of ionic liquids used for absorbing sulfur dioxide in existing technologies, mainly including imidazole, guanidine, alkanolamine, quaternary ammonium, and quaternary phosphorus liquids. Ionic liquids used for absorbing carbon dioxide are primarily alkanolamines. Currently, commercially available alkanolamine carbon dioxide absorbents readily react with sulfur dioxide to form thermally stable salts, significantly reducing the carbon dioxide absorption efficiency. Furthermore, using two separate absorbents for the stepwise absorption and desorption of flue gas containing sulfur dioxide and carbon dioxide increases the investment in processes and equipment.

[0004] For the reasons mentioned above, it is necessary to develop an absorbent that can synergistically capture sulfur dioxide and carbon dioxide in flue gas to simplify equipment investment.

[0005] In view of the above, this application is hereby submitted. Summary of the Invention

[0006] The main objective of this invention is to provide an absorbent for the synergistic capture of sulfur dioxide and carbon dioxide, and a method for capturing sulfur dioxide and carbon dioxide in flue gas, so as to enable the synergistic capture of sulfur dioxide and carbon dioxide gas in flue gas.

[0007] To achieve the above objectives, according to one aspect of the present invention, an absorbent for the synergistic capture of sulfur dioxide and carbon dioxide is provided. The absorbent comprises deionized water, an alkanolamine compound, and an activator, wherein the alkanolamine compound is one or more selected from N-methyldiethanolamine, monoethanolamine, diethanolamine, and triethanolamine, and the activator is at least two selected from diethylenetriamine, triethylenetetramine, dihydroxyethylpiperazine, and piperazine.

[0008] Further, the amine compound is N-methyldiethanolamine, and the activator is a mixture of diethylenetriamine and dihydroxyethylpiperazine; preferably, the weight ratio between diethylenetriamine and dihydroxyethylpiperazine is 1 to 4:1.

[0009] Furthermore, the mass concentration of the alkanolamine compound in the absorbent is 1-20%, preferably 1-10%; the mass concentration of the activator in the absorbent is 1-20%, preferably 1-10%.

[0010] According to another aspect of the present invention, a method for capturing sulfur dioxide and carbon dioxide in flue gas is also provided, comprising: mixing deionized water, an alkanolamine compound, and an activator in a reaction vessel to prepare the absorbent; feeding the absorbent into an absorption tower from the top of the tower while simultaneously feeding flue gas into the absorption tower from the bottom of the tower, wherein the absorbent and flue gas undergo gas-liquid contact mass transfer in the absorption tower, resulting in a carbon dioxide-enriched absorbent liquid at the upper part of the tower and a sulfur dioxide-enriched absorbent liquid at the lower part of the tower; collecting the carbon dioxide-enriched absorbent liquid through a side outlet of the absorption tower and feeding it into a carbon dioxide desorption tower for carbon dioxide desorption, resulting in carbon dioxide gas and a first regenerated absorbent; returning the first regenerated absorbent liquid to the absorption tower from a position below the side outlet; collecting the sulfur dioxide-enriched absorbent liquid from the bottom of the absorption tower and feeding it into a sulfur dioxide desorption tower for sulfur dioxide desorption, resulting in sulfur dioxide gas and a second regenerated absorbent; and returning the second regenerated absorbent liquid from the top of the tower to the absorption tower.

[0011] Furthermore, the absorption tower is a packed tower or a plate tower, preferably a packed tower; preferably, the absorption tower has 20 to 40 theoretical plates, the side stream outlet is located at the 10th to 30th theoretical plate from top to bottom of the absorption tower, and the position where the first regenerated absorbent returns to the absorption tower is 1 to 5 theoretical plates lower than the side stream outlet.

[0012] Furthermore, the operating pressure of the absorption tower is 0–1.0 MPa, and the operating temperature is 0–100 °C; preferably, the operating pressure of the absorption tower is 0.1–0.5 MPa, and the operating temperature is 20–40 °C.

[0013] Furthermore, the absorbent is fed into the absorption tower from the top of the tower by the absorber feed pump, the carbon dioxide enriched absorbent is fed into the carbon dioxide desorption tower by the carbon dioxide desorption tower feed pump, and the sulfur dioxide enriched absorbent is fed into the sulfur dioxide desorption tower by the sulfur dioxide desorption tower feed pump.

[0014] Further, the carbon dioxide desorption tower is a packed tower or a plate tower, preferably a packed tower; preferably, the operating pressure of the carbon dioxide desorption tower is 0-1.0 MPa and the operating temperature is 0-100℃; more preferably, the operating pressure of the carbon dioxide desorption tower is 0-0.1 MPa and the operating temperature is 50-100℃; the sulfur dioxide desorption tower is a packed tower or a plate tower, preferably a packed tower; preferably, the operating pressure of the sulfur dioxide desorption tower is 0-1.0 MPa and the operating temperature is 0-150℃; more preferably, the operating pressure of the carbon dioxide desorption tower is 0-0.5 MPa and the operating temperature is 50-150℃.

[0015] Furthermore, the carbon dioxide desorption tower has a first top steam outlet and a first bottom outlet, and its bottom is also equipped with a carbon dioxide desorption tower bottom reboiler. The first top steam outlet is used to discharge carbon dioxide desorption steam, the first bottom outlet is used to discharge the first regenerated absorbent, and the carbon dioxide desorption tower bottom reboiler is used to provide heat to the carbon dioxide desorption tower so that a gas-liquid two-phase structure is formed inside. The capture method also includes: discharging the carbon dioxide desorption steam from the first top steam outlet and sending it to the top condenser of the carbon dioxide desorption tower for condensation treatment to obtain a first condensate and carbon dioxide gas; returning the first condensate to the carbon dioxide desorption tower; and cooling the first regenerated absorbent by the bottom discharge cooler of the carbon dioxide desorption tower and then returning it to the absorption tower by the bottom discharge pump of the carbon dioxide desorption tower.

[0016] Furthermore, the sulfur dioxide desorption tower has a second top steam outlet and a second bottom outlet, and its bottom is also equipped with a sulfur dioxide desorption tower bottom reboiler. The second top steam outlet is used to discharge sulfur dioxide desorption steam, and the second bottom outlet is used to discharge the second regenerated absorbent. The sulfur dioxide desorption tower bottom reboiler is used to provide heat to the sulfur dioxide desorption tower so that a gas-liquid two-phase structure is formed inside. The collection method also includes: discharging the sulfur dioxide desorption steam from the second top steam outlet and sending it to the sulfur dioxide desorption tower top condenser for condensation treatment to obtain a second condensate and sulfur dioxide gas; returning the second condensate to the sulfur dioxide desorption tower; and cooling the second regenerated absorbent through the sulfur dioxide desorption tower bottom discharge cooler and then returning it to the absorption tower via the sulfur dioxide desorption tower bottom discharge pump.

[0017] The present invention provides an absorbent for the synergistic capture of sulfur dioxide and carbon dioxide, comprising deionized water, an alkanolamine compound, and an activator. The alkanolamine compound is one or more selected from N-methyldiethanolamine, monoethanolamine, diethanolamine, and triethanolamine, and the activator is at least two selected from diethylenetriamine, triethylenetetramine, dihydroxyethylpiperazine, and piperazine. By employing the aforementioned specific types of alkanolamine compounds, especially in combination with the aforementioned specific types of activators, the absorbent can synergistically absorb sulfur dioxide and carbon dioxide during flue gas treatment, both exhibiting high absorption efficiency. Furthermore, the carbon dioxide and sulfur dioxide enriched within can be desorbed to yield carbon dioxide gas and sulfur dioxide gas, respectively. Based on this absorbent, the capture of both gases can be carried out in a single absorption tower, improving production efficiency and saving equipment investment, thus demonstrating promising prospects for industrial application. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0019] Figure 1 A schematic flowchart of a method for capturing sulfur dioxide and carbon dioxide in flue gas according to one embodiment of the present invention is shown.

[0020] The above figures include the following reference numerals:

[0021] 1. Reactor; 2. Absorber feed pump; 3. Absorber; 4. Carbon dioxide desorption tower feed pump; 5. Carbon dioxide desorption tower; 6. Carbon dioxide desorption tower top condenser; 7. Carbon dioxide desorption tower bottom reboiler; 8. Carbon dioxide desorption tower bottom discharge cooler; 9. Carbon dioxide desorption tower bottom discharge pump; 10. Sulfur dioxide desorption tower feed pump; 11. Sulfur dioxide desorption tower; 12. Sulfur dioxide desorption tower top condenser; 13. Sulfur dioxide desorption tower bottom reboiler; 14. Sulfur dioxide desorption tower bottom discharge cooler; 15. Sulfur dioxide desorption tower bottom discharge pump. Detailed Implementation

[0022] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0024] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0025] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0026] The terms "comprising," "including," "having," and "containing," etc., used in this document are open-ended, meaning they include but are not limited to. As described in the background section of this invention, using two absorbents to separately absorb and desorb flue gas containing sulfur dioxide and carbon dioxide in stages increases the investment in processes and equipment. To address this problem, this invention provides an absorbent for the synergistic capture of sulfur dioxide and carbon dioxide. This absorbent comprises deionized water, an alkanolamine compound, and an activator, wherein the alkanolamine compound is one or more selected from N-methyldiethanolamine, monoethanolamine, diethanolamine, and triethanolamine, and the activator is at least two selected from diethylenetriamine, triethylenetetramine, dihydroxyethylpiperazine, and piperazine.

[0027] The present invention provides an absorbent for the synergistic capture of sulfur dioxide and carbon dioxide, comprising deionized water, an alkanolamine compound, and an activator. The alkanolamine compound is one or more selected from N-methyldiethanolamine, monoethanolamine, diethanolamine, and triethanolamine, and the activator is at least two selected from diethylenetriamine, triethylenetetramine, dihydroxyethylpiperazine, and piperazine. By employing the aforementioned specific types of alkanolamine compounds, especially in combination with the aforementioned specific types of activators, the absorbent can synergistically absorb sulfur dioxide and carbon dioxide during flue gas treatment, both exhibiting high absorption efficiency. Furthermore, the carbon dioxide and sulfur dioxide enriched within can be desorbed to yield carbon dioxide gas and sulfur dioxide gas, respectively. Based on this absorbent, the capture of both gases can be carried out in a single absorption tower, improving production efficiency and saving equipment investment, thus demonstrating promising prospects for industrial application.

[0028] It should be noted that the use of specific alkanolamine compounds in this invention, with at least two of diethylenetriamine, triethylenetetramine, dihydroxyethylpiperazine, and piperazine as activators, is key to controlling the order of carbon dioxide and sulfur dioxide absorption. This ensures that during the flue gas absorption process in the absorption tower, carbon dioxide-rich liquid and sulfur dioxide-rich liquid are distributed in the upper and lower regions of the tower, facilitating the separate desorption of carbon dioxide and sulfur dioxide gases and achieving the simultaneous capture and recovery of these two independent gases. Conversely, if only one of diethylenetriamine, triethylenetetramine, dihydroxyethylpiperazine, and piperazine is used as an activator, or if other types of alkanolamine compounds are used, the above-mentioned effect cannot be achieved.

[0029] To further improve the synergistic capture effect of sulfur dioxide and carbon dioxide, in a preferred embodiment, the aforementioned alkanolamine compound is N-methyldiethanolamine, and the activator is a mixture of diethylenetriamine and dihydroxyethylpiperazine. Using a combination of N-methyldiethanolamine and the above activator for the synergistic capture of carbon dioxide and sulfur dioxide results in higher capture efficiency; treatment in the same absorption tower can capture carbon dioxide and sulfur dioxide gases with higher purity and yield. More preferably, the weight ratio between diethylenetriamine and dihydroxyethylpiperazine is 1 to 4:1. Controlling the ratio within this range is more conducive to improving the absorption rate difference between carbon dioxide and sulfur dioxide, and further improves the capture effect of carbon dioxide and sulfur dioxide. More preferably, the weight ratio between diethylenetriamine and dihydroxyethylpiperazine is 2 to 4:1.

[0030] In a preferred embodiment, the mass concentration of the alkanolamine compound in the absorbent is 1-20%, preferably 1-10%; the mass concentration of the activator in the absorbent is 1-20%, preferably 1-10%. Controlling the concentrations of each component within the above ranges allows for better matching of the concentrations of sulfur dioxide and carbon dioxide in the flue gas with the absorption rate in the absorption tower, thereby improving the overall performance.

[0031] The absorbent of this invention can be used to treat flue gas containing both sulfur dioxide and carbon dioxide, synergistically capturing both gases. It can also treat flue gas containing either sulfur dioxide or carbon dioxide. More preferably, the flue gas contains 0-30% carbon dioxide and 0-30% sulfur dioxide, with the remainder being gases such as oxygen and nitrogen, and the concentrations of carbon dioxide and sulfur dioxide are not simultaneously zero. Even more preferably, the flue gas contains 10-20% sulfur dioxide and 10-20% carbon dioxide by volume.

[0032] According to another aspect of the present invention, a method for capturing sulfur dioxide and carbon dioxide in flue gas is also provided, such as... Figure 1As shown, it includes: mixing deionized water, an alkanolamine compound, and an activator in a reactor 1 to prepare the absorbent; feeding the absorbent into the absorption tower 3 from the top of the tower, while simultaneously feeding flue gas into the absorption tower 3 from the bottom of the tower; the absorbent and flue gas undergo gas-liquid contact mass transfer in the absorption tower 3, resulting in a carbon dioxide-enriched absorbent liquid at the top of the tower and a sulfur dioxide-enriched absorbent liquid at the bottom of the tower; collecting the carbon dioxide-enriched absorbent liquid through the side outlet of the absorption tower 3 and feeding it into the carbon dioxide desorption tower 5 for carbon dioxide desorption, obtaining carbon dioxide gas and a first regenerated absorbent; returning the first regenerated absorbent to the absorption tower 3 from a position below the side outlet; collecting the sulfur dioxide-enriched absorbent liquid from the bottom of the absorption tower 3 and feeding it into the sulfur dioxide desorption tower 11 for sulfur dioxide desorption, obtaining sulfur dioxide gas and a second regenerated absorbent; and returning the second regenerated absorbent from the top of the tower to the absorption tower 3.

[0033] As described above, the absorbent for the synergistic capture of sulfur dioxide and carbon dioxide provided by this invention comprises deionized water, an alkanolamine compound, and an activator. The alkanolamine compound is one or more of N-methyldiethanolamine, monoethanolamine, diethanolamine, and triethanolamine, and the activator is at least two of diethylenetriamine, triethylenetetramine, dihydroxyethylpiperazine, and piperazine. By using the aforementioned specific types of alkanolamine compounds, especially when combined with the aforementioned specific types of activators, the absorbent can synergistically absorb sulfur dioxide and carbon dioxide during flue gas treatment, both exhibiting high absorption efficiency. Furthermore, the carbon dioxide and sulfur dioxide enriched within can be desorbed to yield carbon dioxide gas and sulfur dioxide gas, respectively. Based on this absorbent, the capture of both gases can be carried out in a single absorption tower, improving production efficiency and saving equipment investment, thus demonstrating promising prospects for industrial application.

[0034] In the specific production process using the above method, the absorbent prepared in reactor 1 is fed from the top of absorption tower 3, while the flue gas is fed from the bottom of absorption tower 3. Gas-liquid mass transfer occurs between the two in the absorption tower, and the purified flue gas is discharged from the top. Due to the rate difference between carbon dioxide and sulfur dioxide during mass transfer, carbon dioxide gas in the flue gas is absorbed and enriched in the upper part of absorption tower 3, serving as a carbon dioxide enriched absorbent, while sulfur dioxide gas is absorbed and enriched in the lower part of absorption tower 3, serving as a sulfur dioxide enriched absorbent. In particular, this invention, through side-stream extraction, can promptly discharge the carbon dioxide enriched absorbent concentrated in the upper part of absorption tower 3 from the system, thereby achieving timely separation from the sulfur dioxide enriched absorbent. The carbon dioxide desorption tower 5 can desorb carbon dioxide from the carbon dioxide enriched absorbent, and this invention returns the obtained first regenerated absorbent from a position below the side-stream outlet to absorption tower 3, which not only serves the purpose of recycling but also facilitates the capture of sulfur dioxide below. The sulfur dioxide desorption tower 11 desorbs sulfur dioxide from the sulfur dioxide enrichment absorbent to obtain sulfur dioxide gas, while the second regenerated absorbent is returned from the top of the absorption tower 3 for recycling. In actual operation, after the operation is stable, fresh absorbent can be selectively added to the absorption tower 3.

[0035] In a preferred embodiment, the absorber tower 3 is a packed tower or a plate tower, preferably a packed tower; preferably, the absorber tower 3 has 20 to 40 theoretical plates, the side stream outlet is located at the 10th to 30th theoretical plate from top to bottom of the absorber tower 3, and the position where the first regenerated absorbent returns to the absorber tower 3 is 1 to 5 theoretical plates lower than the side stream outlet. Using the above-mentioned absorber tower 3 and setting the side stream outlet and the return position of the first regenerated absorbent within the above-mentioned ranges are beneficial to further improving the synergistic capture effect of carbon dioxide and sulfur dioxide in the flue gas, and also have a better promoting effect on improving the separation effect of carbon dioxide and sulfur dioxide.

[0036] Typically, but not limitingly, the operating pressure of the absorption tower 3 is 0–1.0 MPa, and the operating temperature is 0–100 °C; preferably, the operating pressure of the absorption tower 3 is 0.1–0.5 MPa, and the operating temperature is 20–40 °C. Under the above pressure and temperature conditions, the absorption effect of carbon dioxide and sulfur dioxide is better.

[0037] The aforementioned towers are preferably connected via pipelines and the pumps connected to those pipelines to ensure the continuity of the production process. For example, ... Figure 1 As shown, the absorbent can be fed from the top of the absorption tower into the absorption tower 3 through the absorption tower feed pump 2, the carbon dioxide enriched absorbent can be fed into the carbon dioxide desorption tower 5 through the carbon dioxide desorption tower feed pump 4, and the sulfur dioxide enriched absorbent can be fed into the sulfur dioxide desorption tower 11 through the sulfur dioxide desorption tower feed pump 10.

[0038] To improve the desorption efficiency of carbon dioxide and sulfur dioxide and further improve the recovery rate, in a preferred embodiment, the carbon dioxide desorption tower 5 is a packed tower or a plate tower, preferably a packed tower; preferably, the operating pressure of the carbon dioxide desorption tower 5 is 0-1.0 MPa and the operating temperature is 0-100°C; more preferably, the operating pressure of the carbon dioxide desorption tower 5 is 0-0.1 MPa and the operating temperature is 50-100°C; the sulfur dioxide desorption tower 11 is a packed tower or a plate tower, preferably a packed tower; preferably, the operating pressure of the sulfur dioxide desorption tower 11 is 0-1.0 MPa and the operating temperature is 0-150°C; more preferably, the operating pressure of the carbon dioxide desorption tower 5 is 0-0.5 MPa and the operating temperature is 50-150°C.

[0039] In a preferred embodiment, such as Figure 1 As shown, the carbon dioxide desorption tower 5 has a first top steam outlet and a first bottom outlet, and its bottom is also equipped with a carbon dioxide desorption tower bottom reboiler 7. The first top steam outlet is used to discharge carbon dioxide desorption steam, and the first bottom outlet is used to discharge the first regenerated absorbent. The carbon dioxide desorption tower bottom reboiler 7 is used to provide heat to the carbon dioxide desorption tower 5 so that a gas-liquid two-phase structure is formed inside. The capture method also includes: discharging the carbon dioxide desorption steam from the first top steam outlet and sending it to the carbon dioxide desorption tower top condenser 6 for condensation treatment to obtain a first condensate and carbon dioxide gas; returning the first condensate to the carbon dioxide desorption tower 5; and cooling the first regenerated absorbent through the carbon dioxide desorption tower bottom discharge cooler 8 and then returning it to the absorption tower 3 via the carbon dioxide desorption tower bottom discharge pump 9.

[0040] Similarly, the sulfur dioxide desorption tower 11 has a second top steam outlet and a second bottom outlet, and its bottom is also equipped with a sulfur dioxide desorption tower bottom reboiler 13. The second top steam outlet is used to discharge sulfur dioxide desorption steam, the second bottom outlet is used to discharge the second regenerated absorbent, and the sulfur dioxide desorption tower bottom reboiler 13 is used to provide heat to the sulfur dioxide desorption tower 11 so that a gas-liquid two-phase structure is formed inside. The collection method also includes: discharging the sulfur dioxide desorption steam from the second top steam outlet and sending it to the sulfur dioxide desorption tower top condenser 12 for condensation treatment to obtain a second condensate and sulfur dioxide gas; returning the second condensate to the sulfur dioxide desorption tower 11; and cooling the second regenerated absorbent through the sulfur dioxide desorption tower bottom discharge cooler 14 and then returning it to the absorption tower 3 via the sulfur dioxide desorption tower bottom discharge pump 15.

[0041] With the above configuration, the steam at the top of the carbon dioxide desorption tower 5 is condensed by the condenser 6 at the top of the carbon dioxide desorption tower, and the condensate returns to the top of the carbon dioxide desorption tower 5, while the non-condensable carbon dioxide gas is drawn out of the boundary area; the bottom discharge of the carbon dioxide desorption tower is the first regenerated absorbent, which is cooled by the bottom discharge cooler 8 and then returned to the absorption tower 3 from below the side outlet; the steam at the top of the sulfur dioxide desorption tower 11 is condensed by the condenser 12 at the top of the sulfur dioxide desorption tower, and the condensate returns to the top of the sulfur dioxide desorption tower 11, while the non-condensable sulfur dioxide gas is drawn out of the boundary area; the bottom discharge of the sulfur dioxide desorption tower is the second regenerated absorbent, which is cooled by the bottom discharge cooler 14 and then returned to the absorption tower 3 from the top (preferably returned from the inlet of the absorption tower feed pump 2 for recycling).

[0042] During the preparation of the absorbent in the above-mentioned reactor 1, the following order of feeding is preferred: a. adding deionized water to the reactor; b. adding an alkanolamine compound to the reactor; c. adding an activator to the reactor; d. continuing to stir the mixture until it is homogeneous.

[0043] The present invention employs the above-mentioned capture method, which uses a tower gas "absorption-desorption" process to extract and separate sulfur dioxide and carbon dioxide by taking advantage of their different absorption positions in the absorption tower, thereby effectively improving production efficiency and saving equipment investment.

[0044] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0045] Example 1

[0046] This embodiment describes a method for the synergistic capture of sulfur dioxide and carbon dioxide, which employs the following techniques: Figure 1 The system shown:

[0047] The flue gas is from non-ferrous metal smelting, containing 10-20% sulfur dioxide and 10-20% carbon dioxide by volume. In reactor 1, a mixture of deionized water, N-methyldiethanolamine, activator diethylenetriamine, and dihydroxyethylpiperazine is added sequentially, and the mixture is stirred until homogeneous. The resulting absorbent contains 90% water, 2.5% N-methyldiethanolamine, 5% diethylenetriamine, and 2.5% dihydroxyethylpiperazine by mass.

[0048] The prepared absorbent is fed from the top of absorber 3 via absorber feed pump 2, while the flue gas is fed from the bottom of absorber 3. Gas-liquid mass transfer occurs between the two in absorber 3. Absorber 3 is a packed tower with 30 theoretical trays, operating at atmospheric pressure and 30°C. A side-stream outlet is located at the 15th theoretical tray from the top. Carbon dioxide in the flue gas is enriched in the absorbent at the top of absorber 3 and is extracted via the side-stream outlet. It is then fed from the top of carbon dioxide desorption tower 5 via carbon dioxide desorption tower feed pump 4. The vapor at the top of carbon dioxide desorption tower 5 is condensed by the carbon dioxide desorption tower condenser 6, and the condensate returns to the top of carbon dioxide desorption tower 5. Non-condensable carbon dioxide is extracted outside the boundary area. The bottom of carbon dioxide desorption tower 5 is regenerated absorbent, which is cooled by the carbon dioxide desorption tower bottom outlet cooler 8 and then returned to the tray below the side-stream outlet tray of absorber 3 via carbon dioxide desorption tower bottom outlet pump 9. Carbon dioxide desorption tower 5 is a packed tower, operating at a pressure of 0.05 MPa and a temperature of 80°C. Sulfur dioxide gas in the flue gas is enriched in the absorbent at the bottom of absorption tower 3 and directly extracted. It is fed into the top of sulfur dioxide desorption tower 11 via feed pump 10. The vapor at the top of sulfur dioxide desorption tower 11 is condensed by the top condenser 12, and the condensate returns to the top of tower 11. Non-condensable sulfur dioxide gas is extracted outside the boundary area. The bottom output of sulfur dioxide desorption tower 11 is regenerated absorbent, which is cooled by the bottom output cooler 14 and then returned to the inlet of feed pump 2 via bottom output pump 15 for recycling. Sulfur dioxide desorption tower 11 is a packed tower, operating at a pressure of 0.05 MPa and a temperature of 90°C. After the system stabilizes, fresh absorbent is replenished to the system from the reactor according to actual conditions.

[0049] The test results showed that the yield of carbon dioxide gas was 90% and the purity was 65%, while the yield of sulfur dioxide gas was 90% and the purity was 75%.

[0050] Example 2

[0051] The difference from Example 1 is as follows:

[0052] The absorption tower 3 has 40 theoretical trays, an operating pressure of 0.5 MPa, and an operating temperature of 40°C. A side feed outlet is provided at the 20th theoretical tray from the bottom.

[0053] The test results showed that the yield of carbon dioxide gas was 95% and the purity was 70%, while the yield of sulfur dioxide gas was 95% and the purity was 80%.

[0054] Example 3

[0055] The difference from Example 1 is as follows:

[0056] The absorption tower 3 has 20 theoretical trays, an operating pressure of 0.1 MPa, and an operating temperature of 30°C. A side feed outlet is provided at the 10th theoretical tray from the bottom.

[0057] The test results showed that the yield of carbon dioxide gas was 80% and the purity was 60%, while the yield of sulfur dioxide gas was 80% and the purity was 70%.

[0058] Example 4

[0059] The difference from Example 1 is as follows:

[0060] The absorption tower 3 has 15 theoretical trays, an operating pressure of 0.1 MPa, and an operating temperature of 30°C. A side feed outlet is provided at the 6th theoretical tray from the bottom.

[0061] The test results showed that the yield of carbon dioxide gas was 70% and the purity was 60%, while the yield of sulfur dioxide gas was 70% and the purity was 65%.

[0062] Example 5

[0063] The difference from Example 1 is as follows:

[0064] The absorbent contains 87% water, 10% N-methyldiethanolamine, 2% diethylenetriamine, and 1% dihydroxyethylpiperazine.

[0065] The test results showed that the yield of carbon dioxide gas was 90% and the purity was 65%, while the yield of sulfur dioxide gas was 90% and the purity was 75%.

[0066] Example 6

[0067] The difference from Example 1 is as follows:

[0068] The absorbent contains 87% water, 3% N-methyldiethanolamine, 8% diethylenetriamine, and 2% dihydroxyethylpiperazine.

[0069] The test results showed that the yield of carbon dioxide gas was 88% and the purity was 65%, while the yield of sulfur dioxide gas was 88% and the purity was 75%.

[0070] Example 7

[0071] The difference from Example 1 is as follows:

[0072] The absorbent contains 90% water, 2.5% N-methyldiethanolamine, 3.75% diethylenetriamine, and 3.75% dihydroxyethylpiperazine.

[0073] The test results showed that the yield of carbon dioxide gas was 85% and the purity was 64%, while the yield of sulfur dioxide gas was 86% and the purity was 75%.

[0074] Example 8

[0075] The difference from Example 1 is as follows:

[0076] In the absorbent, the alcohol amine compound is triethanolamine, and the activators are triethylenetetramine and piperazine, with the concentrations remaining constant.

[0077] The test results showed that the yield of carbon dioxide gas was 88% and the purity was 61%, while the yield of sulfur dioxide gas was 87% and the purity was 72%.

[0078] Example 9

[0079] The difference from Example 1 is as follows:

[0080] In the absorbent, the alcohol amine compound is monoethanolamine, and the activators are triethylenetetramine and piperazine, with the concentrations remaining constant.

[0081] The test results showed that the yield of carbon dioxide gas was 88% and the purity was 62%, while the yield of sulfur dioxide gas was 85% and the purity was 70%.

[0082] Comparative Example 1

[0083] The difference from Example 1 is as follows:

[0084] In the absorbent, the activator is only piperazine.

[0085] The test results showed that the yield of carbon dioxide gas was 55% and the purity was 48%, while the yield of sulfur dioxide gas was 60% and the purity was 59%.

[0086] Comparative Example 2

[0087] The difference from Example 1 is as follows:

[0088] The alcohol amine compound is methanolamine.

[0089] The test results showed that the yield of carbon dioxide gas was 40% and the purity was 45%, and the yield of sulfur dioxide gas was 40% and the purity was 45%.

[0090] Comparative Example 3

[0091] The difference from Example 1 is as follows:

[0092] Without side-stream extraction, the entire absorption and enrichment liquid is discharged through the bottom of absorption tower 3. Due to the competitive adsorption phenomenon between sulfur dioxide and carbon dioxide in the absorbent, the absorbent's absorption capacity for sulfur dioxide is greater than its absorption capacity for carbon dioxide. As a result, carbon dioxide cannot be fully absorbed by the absorbent, and absorption tower 3 cannot effectively remove carbon dioxide from the flue gas entering the tower. 60% of the carbon dioxide in the flue gas is extracted from the top of absorption tower 3, while the remaining carbon dioxide and all of the sulfur dioxide are enriched in the bottom enrichment liquid of absorption tower 3. After single-tower desorption, sulfur dioxide and carbon dioxide are mixed together and extracted from the top of the desorption tower. The recovery rate of carbon dioxide gas is 35%, and the recovery rate of sulfur dioxide gas is 50%. The carbon dioxide accounts for about 30% and the sulfur dioxide accounts for about 70% of the mixed gas.

[0093] 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. An absorbent for the synergistic capture of sulfur dioxide and carbon dioxide, characterized in that, The absorbent is composed of the following components: deionized water, an alkanolamine compound, and an activator, wherein the alkanolamine compound is N-methyldiethanolamine, and the activator is a mixture of diethylenetriamine and dihydroxyethylpiperazine.

2. The absorbent for the synergistic capture of sulfur dioxide and carbon dioxide according to claim 1, characterized in that, The weight ratio between the diethylenetriamine and the dihydroxyethylpiperazine is 1 to 4:

1.

3. The absorbent for the synergistic capture of sulfur dioxide and carbon dioxide according to claim 1 or 2, characterized in that, The mass concentration of the alkanolamine compound in the absorbent is 1-20%; the mass concentration of the activator in the absorbent is 1-20%.

4. The absorbent for the synergistic capture of sulfur dioxide and carbon dioxide according to claim 3, characterized in that, The mass concentration of the alkanolamine compound in the absorbent is 1-10%.

5. The absorbent for the synergistic capture of sulfur dioxide and carbon dioxide according to claim 3, characterized in that, The activator has a mass concentration of 1-10% in the absorbent.

6. A method for capturing sulfur dioxide and carbon dioxide in flue gas, characterized in that, include: Deionized water, an alcohol amine compound, and an activator are mixed in a reaction vessel (1) to prepare the absorbent according to any one of claims 1 to 5; The absorbent is fed into the absorption tower (3) from the top of the tower, and the flue gas is fed into the absorption tower (3) from the bottom of the tower. The absorbent and the flue gas undergo gas-liquid contact mass transfer in the absorption tower (3). Carbon dioxide enriched absorbent is obtained in the upper part of the tower, and sulfur dioxide enriched absorbent is obtained in the lower part of the tower. The carbon dioxide enriched absorbent is extracted through the side outlet of the absorber (3) and sent to the carbon dioxide desorption tower (5) for carbon dioxide desorption to obtain carbon dioxide gas and a first regenerated absorbent; the first regenerated absorbent is returned to the absorber (3) from a position below the side outlet. The sulfur dioxide enriched absorbent is taken from the bottom of the absorber (3) and sent to the sulfur dioxide desorption tower (11) for sulfur dioxide desorption to obtain sulfur dioxide gas and a second regenerated absorbent; the second regenerated absorbent is returned from the top of the tower to the absorber (3).

7. The collection method according to claim 6, characterized in that, The absorption tower (3) is a packed tower or a plate tower.

8. The collection method according to claim 7, characterized in that, The absorption tower (3) is a packed tower.

9. The collection method according to claim 7, characterized in that, The absorption tower (3) has 20 to 40 theoretical plates. The side-stream outlet is located at the 10th to 30th theoretical plate from top to bottom of the absorption tower (3). The position where the first regenerated absorbent returns to the absorption tower (3) is 1 to 5 theoretical plates lower than the side-stream outlet.

10. The collection method according to claim 7, characterized in that, The operating pressure of the absorption tower (3) is 0~1.0MPa and the operating temperature is 0~100℃.

11. The collection method according to claim 7, characterized in that, The operating pressure of the absorption tower (3) is 0.1~0.5MPa, and the operating temperature is 20~40℃.

12. The capture method according to any one of claims 6 to 11, characterized in that, The absorbent is fed from the top of the absorber into the absorber (3) via the absorber feed pump (2), the carbon dioxide enriched absorbent is fed into the carbon dioxide desorption tower (5) via the carbon dioxide desorption tower feed pump (4), and the sulfur dioxide enriched absorbent is fed into the sulfur dioxide desorption tower (11) via the sulfur dioxide desorption tower feed pump (10).

13. The collection method according to claim 12, characterized in that, The carbon dioxide desorption tower (5) is a packed tower or a plate tower; The sulfur dioxide desorption tower (11) is a packed tower or a plate tower.

14. The collection method according to claim 13, characterized in that, The carbon dioxide desorption tower (5) is a packed tower.

15. The collection method according to claim 13, characterized in that, The operating pressure of the carbon dioxide desorption tower (5) is 0~1.0MPa and the operating temperature is 0~100℃.

16. The capture method according to claim 13, characterized in that, The operating pressure of the carbon dioxide desorption tower (5) is 0~0.1MPa and the operating temperature is 50~100℃.

17. The collection method according to claim 13, characterized in that, The sulfur dioxide desorption tower (11) is a packed tower.

18. The collection method according to claim 13, characterized in that, The operating pressure of the sulfur dioxide desorption tower (11) is 0~1.0MPa and the operating temperature is 0~150℃.

19. The collection method according to claim 13, characterized in that, The operating pressure of the carbon dioxide desorption tower (5) is 0~0.5MPa and the operating temperature is 50~150℃.

20. The collection method according to claim 12, characterized in that, The carbon dioxide desorption tower (5) has a first top steam outlet and a first bottom outlet, and its bottom is also equipped with a carbon dioxide desorption tower bottom reboiler (7). The first top steam outlet is used to discharge carbon dioxide desorption steam, and the first bottom outlet is used to discharge the first regenerated absorbent. The carbon dioxide desorption tower bottom reboiler (7) is used to provide heat to the carbon dioxide desorption tower (5) so that a gas-liquid two-phase structure is formed inside it. The capture method further includes: The carbon dioxide desorption vapor is discharged from the steam outlet at the top of the first tower and sent to the condenser (6) at the top of the carbon dioxide desorption tower for condensation treatment to obtain the first condensate and the carbon dioxide gas; the first condensate is returned to the carbon dioxide desorption tower (5). After the first regenerated absorbent is cooled by the bottom discharge cooler (8) of the carbon dioxide desorption tower, it is returned to the absorption tower (3) via the bottom discharge pump (9) of the carbon dioxide desorption tower.

21. The collection method according to claim 12, characterized in that, The sulfur dioxide desorption tower (11) has a second top steam outlet and a second bottom outlet, and its bottom is also equipped with a sulfur dioxide desorption tower bottom reboiler (13). The second top steam outlet is used to discharge sulfur dioxide desorption steam, and the second bottom outlet is used to discharge the second regenerated absorbent. The sulfur dioxide desorption tower bottom reboiler (13) is used to provide heat to the sulfur dioxide desorption tower (11) to form a gas-liquid two-phase structure inside it. The collection method further includes: The sulfur dioxide desorption vapor is discharged from the steam outlet at the top of the second tower and sent to the condenser (12) at the top of the sulfur dioxide desorption tower for condensation treatment to obtain the second condensate and the sulfur dioxide gas; the second condensate is returned to the sulfur dioxide desorption tower (11). After the second regenerated absorbent is cooled by the bottom discharge cooler (14) of the sulfur dioxide desorption tower, it is returned to the absorption tower (3) via the bottom discharge pump (15) of the sulfur dioxide desorption tower.

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