A method for capturing carbon dioxide from flue gas

Abstract

The present application aims at providing a method for capturing carbon dioxide in flue gas, belonging to the technical field of carbon dioxide capture, and specifically using microalgae as raw material to synthesize carbon dioxide absorbent and perform carbon dioxide capture. In the desorption process, ultrasonic intensification technology is adopted to make the solid catalyst fully contact with the carbon dioxide absorbent, so as to desorb carbon dioxide efficiently and obtain amino acid salt at the same time. The present application has the characteristics of efficiently capturing carbon dioxide in flue gas while co-producing amino acid salt, simple process flow, environmental friendliness and resourceful carbon dioxide capture.

Description

Technical Field

[0001] This invention belongs to the field of carbon dioxide capture technology, specifically relating to a method for capturing carbon dioxide from flue gas. Background Technology

[0002] Greenhouse gases emitted by human activities are the main cause of global climate change. Among the many greenhouse gases, carbon dioxide has the greatest impact on the greenhouse effect. For major energy-consuming countries, carbon dioxide mainly comes from the coal-fired power industry, making carbon dioxide emission reduction from coal-fired power plants a key focus of carbon dioxide emission control. Chemical absorption is currently the most widely used carbon dioxide capture method in practice, but its high regeneration energy consumption and high capture cost are key obstacles to its large-scale application. Monoethanolamine aqueous solution (MEA), as a primary amine solution, is the most commonly used absorbent in carbon dioxide capture due to its fast absorption rate and low material cost. However, traditional absorption schemes have some limitations, such as high absorbent regeneration energy consumption; significant losses during absorbent operation (evaporation, degradation); the risk of secondary pollution from amines; low carbon dioxide absorption efficiency and low carbon dioxide loading capacity during the recycling process; and the toxicity and corrosiveness of the absorbent to equipment. These problems lead to high investment and operating costs, hindering its large-scale industrial application. Therefore, developing novel absorbents with better performance than traditional alcoholamines and low-energy capture methods is crucial for reducing carbon dioxide capture costs.

[0003] In summary, current technologies for capturing carbon dioxide from flue gas in coal-fired power plants suffer from high regeneration energy consumption, high capture costs, and low efficiency, necessitating technological innovation and improvement. Microalgae are inexpensive to obtain and non-corrosive; therefore, it is worth considering using microalgae to synthesize bio-absorbents for capturing carbon dioxide from flue gas and co-producing amino acid salts. Ultrasonic enhancement technology could then be used in the desorption process to simplify the process, improve efficiency, and reduce energy consumption. Summary of the Invention

[0004] The purpose of this invention is to provide a method for capturing carbon dioxide from flue gas, which can utilize microalgae to synthesize carbon dioxide bioabsorbents to efficiently capture carbon dioxide from flue gas of coal-fired power plants.

[0005] The present invention adopts the following technical solution:

[0006] A method for capturing carbon dioxide from flue gas includes the following steps:

[0007] a) Add a strong alkaline solution to the microalgae and mix until completely dissolved to obtain a carbon dioxide absorbent;

[0008] b) Collect the flue gas after desulfurization, denitrification and dust removal, and control the temperature of the carbon dioxide absorbent to 30 to 60°C;

[0009] c) The carbon dioxide absorbent is in full contact with the introduced flue gas to absorb carbon dioxide. The pH value of the slurry is monitored. When the pH reaches 8 to 9, the carbon dioxide absorbent is desorbed and the excess solids are discharged. If the pH does not reach 8 to 9, the carbon dioxide absorbent is refluxed to react with the flue gas after desulfurization, denitrification and dust removal.

[0010] d) Detect the carbon dioxide concentration in the flue gas. When the carbon dioxide concentration is less than 5%, the flue gas is discharged through the gas outlet.

[0011] e) Add the solid catalyst to the carbon dioxide absorbent with a pH of 8 to 9, and use ultrasound to enhance the contact between the absorbent and the solid catalyst to desorb the carbon dioxide absorbent. Collect and store the desorbed carbon dioxide.

[0012] f) After the desorption reaction is complete, the desorbed carbon dioxide absorbent is discharged, and after cooling and crystallization, amino acid salts are obtained.

[0013] Furthermore, the microalgae mentioned in step a include one or more of Chlorella, Scenedesmus, Spirulina, Synechococcus, and Dussaea.

[0014] Furthermore, the strong alkaline solution mentioned in step a includes one or both of potassium hydroxide and sodium hydroxide, with a concentration of 0.5 mol / L to 2 mol / L.

[0015] Furthermore, the molar ratio of the microalgae to the strong alkaline solution in step a is 1-2.

[0016] Furthermore, the amount of flue gas in step b is 100t-300t, and the carbon dioxide concentration in the flue gas is 10-15%.

[0017] Furthermore, the solid in step c includes three or more of carbohydrates, lipids, ash, bicarbonates, and carbonates.

[0018] Furthermore, the flow rate ratio of the refluxing carbon dioxide absorbent in step c to the desorbed carbon dioxide absorbent in step e is 4-8:1.

[0019] Furthermore, the intensity of the ultrasonic enhancement in step e is 0.10 W / cm². 2 -0.30 W / cm 2 .

[0020] Further, the solid catalyst in step e includes one or more of TiO(OH)2, SiO2-Al2O3, and HZSM-5.

[0021] Further, the amino acid salt mentioned in step f includes one or more of glycine salt, alanine salt, proline salt, lysine salt, aspartic acid salt, glutamate salt, and leucine salt.

[0022] The beneficial effects of this invention are as follows:

[0023] The purpose of this invention is to provide a method for capturing carbon dioxide from flue gas. This method utilizes microalgae to synthesize a carbon dioxide bioabsorbent for efficient capture of carbon dioxide from coal-fired power plant flue gas and co-produce amino acid salts. The advantages of this invention are that it uses microalgae to synthesize the carbon dioxide absorbent and perform carbon dioxide capture; ultrasonic enhancement technology allows the carbon dioxide absorbent to be fully mixed with the solid catalyst, resulting in efficient desorption to obtain amino acid salts and carbon dioxide. During the capture process, there is no risk of secondary environmental pollution from amine volatilization and degradation, nor is there a decrease in capture efficiency due to absorbent loss. This effectively avoids material waste, saves costs, and achieves resource-efficient carbon dioxide capture.

[0024] In summary, the present invention has a simple process, can efficiently capture carbon dioxide from flue gas of coal-fired power plants, and produce amino acid salts and carbon dioxide. It also has significant energy-saving advantages and strong practicality. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the technical route for a method of capturing carbon dioxide in flue gas according to the present invention. Detailed Implementation

[0026] The present invention will be further illustrated below through specific embodiments.

[0027] Example 1

[0028] This embodiment provides a method for capturing carbon dioxide from flue gas, including the following steps:

[0029] a) Add a strong alkaline solution to the microalgae and mix until completely dissolved to obtain a carbon dioxide absorbent;

[0030] b) Collect the flue gas after desulfurization, denitrification, and dust removal, and control the temperature of the carbon dioxide absorbent to 50℃;

[0031] c) The carbon dioxide absorbent comes into full contact with the introduced flue gas to absorb carbon dioxide. The pH value of the slurry is monitored. When the pH reaches 8.6, the carbon dioxide absorbent is desorbed and the excess solids are discharged. The carbon dioxide absorbent with a pH below 8.6 is refluxed to react with the flue gas after desulfurization, denitrification and dust removal.

[0032] d) Detect the carbon dioxide concentration in the flue gas. When the carbon dioxide concentration is less than 5%, the flue gas is discharged through the gas outlet.

[0033] e) Add the solid catalyst to the carbon dioxide absorbent with a pH of 8.6, and use ultrasound to enhance the contact between the absorbent and the solid catalyst to desorb the carbon dioxide absorbent. Collect and store the desorbed carbon dioxide.

[0034] f) After the desorption reaction is complete, the desorbed carbon dioxide absorbent is discharged, and after cooling and crystallization, amino acid salts are obtained.

[0035] The microalgae in step a) above is Chlorella.

[0036] The strong alkaline solution in step a) above is potassium hydroxide.

[0037] In step a) above, the molar ratio of microalgae to strong alkaline solution is 1.5.

[0038] The concentration of the carbon dioxide absorbent in step a) above is 2.8 g / L.

[0039] The amount of flue gas after desulfurization, denitrification, and dust removal in step b) above is 100t.

[0040] The carbon dioxide concentration in the flue gas after desulfurization, denitrification, and dust removal in step b) above is 12.5%.

[0041] The flow rate ratio of the refluxing carbon dioxide absorbent in step c) to the desorbed carbon dioxide absorbent in step e) is 4:1.

[0042] The intensity of the ultrasonic enhancement in step e) above is 0.25 W / cm. 2 .

[0043] In this embodiment, the amino acid salt recovery rate was 10%, and the carbon dioxide capture rate was 60%.

[0044] Example 2

[0045] The method and workflow are the same as in Example 1, except that in step a), the microalgae used is *Scenedesmus*, the strong alkali solution is potassium hydroxide, the molar ratio of microalgae to strong alkali solution is 1, and the concentration of carbon dioxide absorbent is 1.8 g / L; in step b), the amount of flue gas after desulfurization, denitrification, and dust removal is 180 t, the carbon dioxide concentration is 10%, and the temperature of carbon dioxide absorbent is 40°C; in step c), the flow ratio of the recirculated carbon dioxide absorbent to the desorbed carbon dioxide absorbent in step e) is 7:1; and the intensity of ultrasonic enhancement in step e) is 0.13 W / cm². 2 .

[0046] In this embodiment, the amino acid salt recovery rate was 6.5%, and the carbon dioxide capture rate was 50%.

[0047] Example 3

[0048] The method and workflow are the same as in Example 1, except that in step a), the microalgae used is Spirulina, the strong alkaline solution is sodium hydroxide, the molar ratio of microalgae to strong alkaline solution is 2, and the concentration of carbon dioxide absorbent is 2.1 g / L; in step b), the amount of flue gas after desulfurization, denitrification, and dust removal is 150 t, the carbon dioxide concentration is 10.4%, and the temperature of carbon dioxide absorbent is 60℃; in step c), the flow ratio of the recirculated carbon dioxide absorbent to the desorbed carbon dioxide absorbent in step e) is 6:1; and in step e), the intensity of ultrasonic enhancement is 0.15 W / cm². 2 .

[0049] In this embodiment, the amino acid salt recovery rate was 7.3%, and the carbon dioxide capture rate was 52%.

[0050] Example 4

[0051] The method and workflow are the same as in Example 1, except that in step a), the microalgae used is Spirulina, the strong alkali solution is potassium hydroxide, the molar ratio of microalgae to strong alkali solution is 1.5, and the concentration of carbon dioxide absorbent is 2.6 g / L; in step b), the amount of flue gas after desulfurization, denitrification, and dust removal is 130 t, the carbon dioxide concentration is 11.1%, and the temperature of carbon dioxide absorbent is 40℃; in step c), the flow ratio of the recirculated carbon dioxide absorbent to the desorbed carbon dioxide absorbent in step e) is 5:1; and the intensity of ultrasonic enhancement in step e) is 0.17 W / cm². 2 .

[0052] In this embodiment, the amino acid salt recovery rate was 8.7%, and the carbon dioxide capture rate was 55%.

Claims

1. A method for capturing carbon dioxide from flue gas, characterized in that: Includes the following steps: a) Add a strong alkaline solution to the microalgae and mix until completely dissolved to obtain a carbon dioxide absorbent; b) Collect the flue gas after desulfurization, denitrification and dust removal, and control the temperature of the carbon dioxide absorbent to 30 to 60°C; c) The carbon dioxide absorbent is in full contact with the introduced flue gas to absorb carbon dioxide. The pH value of the slurry is monitored. When the pH reaches 8 to 9, the carbon dioxide absorbent is desorbed and the excess solids are discharged. If the pH does not reach 8 to 9, the carbon dioxide absorbent is refluxed to react with the flue gas after desulfurization, denitrification and dust removal. d) Detect the carbon dioxide concentration in the flue gas. When the carbon dioxide concentration is less than 5%, the flue gas is discharged through the gas outlet. e) Add the solid catalyst to the carbon dioxide absorbent with a pH of 8 to 9, and use ultrasound to enhance the contact between the absorbent and the solid catalyst to desorb the carbon dioxide absorbent. Collect and store the desorbed carbon dioxide. f) After the desorption reaction is complete, the desorbed carbon dioxide absorbent is discharged, and after cooling and crystallization, amino acid salts are obtained.

2. The method for capturing carbon dioxide from flue gas according to claim 1, characterized in that: The microalgae mentioned in step a include one or more of Chlorella, Scenedesmus, Spirulina, Synechococcus, and Dussaea.

3. The method for capturing carbon dioxide in flue gas according to claim 1, characterized in that: The strong alkaline solution mentioned in step a includes one or both of potassium hydroxide and sodium hydroxide, with a concentration of 0.5 mol / L to 2 mol / L.

4. The method for capturing carbon dioxide in flue gas according to claim 1, characterized in that: The molar ratio of microalgae to strong alkaline solution in step a is 1:1 to 2:

1.

5. The method for capturing carbon dioxide from flue gas according to claim 1, characterized in that: The amount of flue gas mentioned in step b is 100t-300t, and the carbon dioxide concentration in the flue gas is 10-15%.

6. The method for capturing carbon dioxide in flue gas according to claim 1, characterized in that: The solids mentioned in step c include three or more of the following: carbohydrates, lipids, ash, bicarbonates, and carbonates.

7. The method for capturing carbon dioxide in flue gas according to claim 1, characterized in that: The flow rate ratio of the refluxing carbon dioxide absorbent in step c to the desorbed carbon dioxide absorbent in step e is 4-8:

1.

8. The method for capturing carbon dioxide in flue gas according to claim 1, characterized in that: The intensity of the ultrasonic enhancement in step e is 0.10 W / cm. 2 -0.30 W / cm 2 .

9. The method for capturing carbon dioxide from flue gas according to claim 1, characterized in that: The solid catalyst mentioned in step e includes one or more of TiO(OH)2, SiO2-Al2O3, and HZSM-5.

10. A method for capturing carbon dioxide from flue gas according to claim 1, characterized in that: The amino acid salt mentioned in step f includes one or more of glycine salt, alanine salt, proline salt, lysine salt, aspartic acid salt, glutamate salt, and leucine salt.

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