Method for extracting carbon dioxide from flue gas

Abstract

The invention discloses a method for extracting carbon dioxide from flue gas. The method for extracting carbon dioxide from flue gas comprises a pre-treatment step, a deacidification step and a purification and liquefaction step. In the pre-treatment step, flue gas generated by oxygen-enriched combustion of a glass raw material through methane in a glass furnace is collected. The flue gas contains carbon dioxide, nitrogen, water vapor, oxygen, a fluorine acid compound and a boric acid compound. In the acid removal step, first acid removal operation is carried out on the flue gas. The first deacidification operation is to remove a fluorine acid compound and a boric acid compound in the flue gas by using a sodium hydroxide aqueous solution. In the purification and liquefaction step, the flue gas subjected to the acid removal step is extracted by a purification and liquefaction unit, so that liquid carbon dioxide with the purity of more than 99% is obtained.

Description

Technical Field

[0001] The invention relates to a method for extracting carbon dioxide, in particular to a method for extracting carbon dioxide from flue gas generated by a glass melting furnace. Background Art

[0002] Glass melting furnaces produce high-temperature flue gas. The existing flue gas treatment method is to remove fluorine compounds by adding alkali, cool the flue gas with a large amount of air to precipitate boron compounds, and then discharge the flue gas.

[0003] However, after the existing flue gas treatment method is implemented, the volume ratio of carbon dioxide in the flue gas (about 2% to 3%) is too low, making it difficult to recycle the carbon dioxide. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for extracting carbon dioxide from flue gas in view of the shortcomings of the prior art, so as to effectively improve the problem that after the existing flue gas treatment method is implemented, the volume ratio of carbon dioxide in the flue gas is too low, making it difficult to recycle and reuse carbon dioxide.

[0005] In order to solve the above-mentioned technical problems, one of the technical solutions adopted by the present invention is to provide a method for extracting carbon dioxide from flue gas, which includes: a pre-step, collecting flue gas generated by burning glass raw materials with methane oxygen-enriched combustion in a glass melting furnace; wherein the flue gas contains carbon dioxide, nitrogen, water vapor, oxygen, fluoric acid compounds and boric acid compounds; a deacidification step, performing a first deacidification operation on the flue gas; wherein the first deacidification operation is to remove the fluoric acid compounds and boric acid compounds in the flue gas with a sodium hydroxide aqueous solution; and a purification and liquefaction step, extracting the flue gas that has passed the deacidification step with a purification and liquefaction unit to obtain liquid carbon dioxide with a purity greater than 99%.

[0006] Preferably, in the pre-step, the temperature of the flue gas is between 1,000°C and 1,500°C, based on the volume of the flue gas being 100%, the content of carbon dioxide is between 30% and 34%, the content of nitrogen is between 1% and 5%, the content of water vapor is between 58% and 62%, and the content of oxygen is between 2% and 6%.

[0007] Preferably, in the preceding step, the content of the fluoric acid compound is greater than 0 mg / m3 and less than 500 mg / m3, and the content of the boric acid compound is greater than 0 mg / m3 and less than 15 mg / m3.

[0008] Preferably, after the pre-step and before the acid removal step, the method for extracting carbon dioxide from flue gas further comprises a cooling step, wherein the flue gas is cooled by water to reduce the temperature of the flue gas to between 200°C and 400°C.

[0009] Preferably, in the acid removal step, a second acid removal operation is further performed on the flue gas, and the second acid removal operation is to remove fluoric acid compounds and boric acid compounds in the flue gas with sodium bicarbonate powder.

[0010] Preferably, in the deacidification step, the first deacidification operation is to remove the fluoric acid compounds and boric acid compounds in the flue gas by using a sodium hydroxide aqueous solution through a semi-dry deacidification tower, and the second deacidification operation is to remove the fluoric acid compounds and boric acid compounds in the flue gas by using sodium bicarbonate powder through a dry deacidification unit. After the first deacidification operation, the temperature of the flue gas is reduced to between 170°C and 200°C, and after the second deacidification operation, the temperature of the flue gas is maintained between 170°C and 200°C.

[0011] Preferably, based on the volume of the flue gas being 100%, the content of carbon dioxide is between 21% and 25%, the content of nitrogen is between 1% and 3%, the content of water vapor is between 70% and 74%, and the content of oxygen is between 1% and 3%.

[0012] Preferably, after the deacidification step and before the purification and liquefaction step, the method for extracting carbon dioxide from flue gas further comprises a removal step of filtering and removing waste solids formed by the deacidification step from the fluoric acid compounds and boric acid compounds in the flue gas using a bag filter.

[0013] Preferably, before the purification and liquefaction steps, the method for extracting carbon dioxide from flue gas further includes a cooling and dehydration step, reducing the temperature of the flue gas to between 20°C and 40°C and reducing the content of water vapor in the flue gas; wherein, after the cooling and dehydration step, based on the volume of the flue gas being 100%, the content of carbon dioxide is not less than 75%, and the content of water vapor is not more than 10%.

[0014] Preferably, in the cooling and dehydration operation, the flue gas is first cooled by water with a temperature between 50°C and 80°C in a heat recovery unit. After absorbing the heat of the flue gas, the water forms hot water or water vapor with a temperature between 95°C and 165°C and can be cooled by an absorption refrigerator connected to the heat recovery unit to form low-temperature water. Moreover, the low-temperature water can reduce the temperature of the flue gas in the cooling and dehydration step.

[0015] Preferably, after the cooling and dehydration step, based on the volume of the flue gas being 100%, the carbon dioxide content is between 78% and 82%, the nitrogen content is between 5% and 9%, the water vapor content is between 2% and 6%, and the oxygen content is between 7% and 11%.

[0016] One of the beneficial effects of the present invention is that the method for extracting carbon dioxide from flue gas provided by the present invention can effectively improve the problem that after the existing flue gas treatment method is implemented, the volume ratio of carbon dioxide in the flue gas is too low, making it difficult to recycle and reuse carbon dioxide, through the technical scheme of "collecting the flue gas generated by the methane-oxygen-enriched combustion of glass raw materials in a glass melting furnace" and "removing fluoric acid compounds and boric acid compounds in the flue gas with sodium hydroxide aqueous solution".

[0017] Furthermore, in the cooling and water removal operation, hot water or water vapor formed after absorbing the heat of the flue gas can be introduced into the absorption refrigerator to form low-temperature water, and then the flue gas is further cooled by the low-temperature water, thereby achieving the effect of heat energy recovery and reuse.

[0018] To further understand the features and technical contents of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are only for reference and description and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 FIG. 4 is a flow chart of a method for extracting carbon dioxide from flue gas according to a first embodiment of the present invention.

[0020] Figure 2 FIG. 1 is a block diagram of a smoke extraction system according to a first embodiment of the present invention.

[0021] Figure 3 FIG. 4 is a flow chart of a method for extracting carbon dioxide from flue gas according to a second embodiment of the present invention.

[0022] Figure 4 FIG. 4 is a block diagram of a fume extraction system according to a second embodiment of the present invention.

[0023] Figure 5 FIG. 4 is a flow chart of a method for extracting carbon dioxide from flue gas according to a third embodiment of the present invention.

[0024] Figure 6 FIG. 4 is a block diagram of a fume extraction system according to a third embodiment of the present invention.

[0025] Figure 7 FIG. 4 is a flow chart of a method for extracting carbon dioxide from flue gas according to a fourth embodiment of the present invention.

[0026] Figure 8 FIG. 4 is a block diagram of a fume extraction system according to a fourth embodiment of the present invention. DETAILED DESCRIPTION

[0027] The following is an explanation of the implementation method of the "method for extracting carbon dioxide from flue gas" disclosed in the present invention through specific embodiments. Those skilled in the art can understand the advantages and effects of the present invention from the contents disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and the details in this specification can also be modified and changed in various ways based on different viewpoints and applications without departing from the concept of the present invention. In addition, the drawings of the present invention are only simple schematic illustrations and are not depicted in actual size. It is stated in advance. The following embodiments will further explain the relevant technical contents of the present invention in detail, but the disclosed contents are not intended to limit the scope of protection of the present invention.

[0028] It should be understood that, although the terms "first", "second", "third", etc. may be used herein to describe various components or signals, these components or signals should not be limited by these terms. These terms are mainly used to distinguish one component from another component, or one signal from another signal. In addition, the term "or" used herein may include any one or more combinations of the associated listed items depending on the actual situation.

[0029] [First embodiment]

[0030] See also Figure 1 and Figure 2 As shown, Figure 1 is a schematic flow chart of a method for extracting carbon dioxide from flue gas according to a first embodiment of the present invention, and Figure 2 Schematic diagram of a smoke extraction system according to a first embodiment of the present invention. The first embodiment of the present invention provides a method for extracting carbon dioxide from smoke. The method for extracting carbon dioxide from smoke at least comprises a pre-processing step S110, an acid removal step S120, and a purification and liquefaction step S130.

[0031] In the pre-step S110, the flue gas generated by the combustion of glass raw materials with methane and oxygen-enriched combustion in the glass melting furnace 10 is collected. The flue gas contains carbon dioxide, nitrogen, water vapor, oxygen, fluoric acid compounds and boric acid compounds. The fluoric acid compound can be, for example, an acidic component such as HF, and the boric acid compound can be, for example, H 3 BO 3 , HBO 2 , B 2 O 3 or BF 3The present invention does not limit the specific components of the fluoric acid compound and the boric acid compound. It is worth mentioning that the fluoric acid compound and the boric acid compound are produced by burning glass raw materials. Therefore, the method for extracting carbon dioxide in other technical fields that does not produce fluoric acid compounds and boric acid compounds is not suitable for comparison with the method for extracting carbon dioxide from flue gas in the present invention.

[0032] The oxygen enrichment is obtained by removing part of the nitrogen in the air, and usually oxygen accounts for more than 21% of the total gas volume. In the pre-step S110 of this embodiment, oxygen accounts for 92% to 96% of the total gas volume introduced into the glass melting furnace, preferably more than 94%.

[0033] Compared to the flue gas generated by introducing air into the glass melting furnace, the flue gas generated by the oxygen-enriched combustion of methane has a higher volume of carbon dioxide, thereby increasing the possibility of recycling and reusing carbon dioxide. Specifically, the volume ratio of carbon dioxide in the flue gas generated by the oxygen-enriched combustion of methane is at least 30%, while the volume ratio of carbon dioxide in the flue gas generated by the combustion of air is about 12%.

[0034] In the pre-step S110 of the present embodiment, the temperature of the flue gas is between 1,000°C and 1,500°C, based on the volume of the flue gas being 100%, the content of carbon dioxide is between 30% and 34%, the content of nitrogen is between 1% and 5%, the content of water vapor is between 58% and 62%, and the content of oxygen is between 2% and 6%.

[0035] Preferably, the temperature of the flue gas is between 1,200° C. and 1,400° C., based on 100% by volume of the flue gas, the content of carbon dioxide is between 31% and 33%, the content of nitrogen is between 2% and 4%, the content of water vapor is between 59% and 61%, and the content of oxygen is between 2% and 6%. More preferably, the temperature of the flue gas is about 1,300° C., based on 100% by volume of the flue gas, the content of carbon dioxide is about 32%, the content of nitrogen is about 3%, the content of water vapor is about 60%, and the content of oxygen is about 4%.

[0036] In the pre-step S110 of the present embodiment, the content of the fluoric acid compound is greater than 0 mg / m3 and less than 500 mg / m3, and the content of the boric acid compound is greater than 0 mg / m3 and less than 15 mg / m3. Preferably, the content of the fluoric acid compound is greater than 0 mg / m3 and less than 400 mg / m3, and the content of the boric acid compound is greater than 0 mg / m3 and less than 10 mg / m3.

[0037] In the acid removal step S120, a first acid removal operation is performed on the flue gas. The first acid removal operation removes fluoric acid compounds and boric acid compounds in the flue gas with a sodium hydroxide aqueous solution. Specifically, in the acid removal step S120 of the present embodiment, the first acid removal operation removes fluoric acid compounds and boric acid compounds in the flue gas with a sodium hydroxide aqueous solution through a semi-dry acid removal tower 20. In addition, in the present embodiment, the weight percentage concentration of the sodium hydroxide aqueous solution is between 2% and 4%, but the present invention is not limited thereto.

[0038] After the first acid removal operation, the temperature of the flue gas is reduced to between 170°C and 200°C, and after the second acid removal operation, the temperature of the flue gas is maintained between 170°C and 200°C. Based on the volume of the flue gas being 100%, the content of carbon dioxide is between 21% and 25%, the content of nitrogen is between 1% and 3%, the content of water vapor is between 70% and 74%, and the content of oxygen is between 1% and 3%. Preferably, after the acid removal step S120, based on the volume of the flue gas being 100%, the content of carbon dioxide is about 23%, the content of nitrogen is about 2%, the content of water vapor is about 72%, and the content of oxygen is about 2%.

[0039] In the purification and liquefaction step S130, the flue gas that has passed the acid removal step S120 is extracted by the purification and liquefaction unit 40 to obtain liquid carbon dioxide with a purity greater than 99%.

[0040] After the deacidification step and before the purification and liquefaction step, the method for extracting carbon dioxide from flue gas may further include a removal step S121, in which the fluoric acid compound and the boric acid compound in the flue gas are filtered and removed by the byproducts formed by the deacidification step by a bag filter 30. The byproduct is, for example, an alkaline solid containing fluorine or boron (such as sodium hydroxide or sodium bicarbonate), but the present invention is not limited thereto. The byproduct can be recycled, but the present invention does not limit the use of the byproduct.

[0041] In addition, in this embodiment, the method of extracting carbon dioxide from flue gas can be performed by a flue gas extraction system 100, and the flue gas extraction system 100 includes the glass melting furnace 10, the semi-dry acid removal tower 20, the bag filter 30 and the purification and liquefaction unit 40.

[0042] [Second embodiment]

[0043] See also Figure 3 and Figure 4 As shown, Figure 3 is a schematic flow chart of a method for extracting carbon dioxide from flue gas according to a second embodiment of the present invention, and Figure 4Schematic diagram of a smoke extraction system according to a second embodiment of the present invention. This embodiment is similar to the first embodiment, so the similarities between the two embodiments are not described in detail, and the differences between the two embodiments are roughly described as follows.

[0044] In this embodiment, after the pre-step S110 and before the acid removal step S120, the method for extracting carbon dioxide from flue gas further comprises a cooling step S111, wherein the flue gas is cooled by water to reduce the temperature of the flue gas to between 200° C. and 400° C. Preferably, after the cooling step S111, the temperature of the flue gas is about 300° C. In the cooling step S111 of other embodiments, the flue gas may be cooled by air, or the flue gas may be cooled by air first and then by water, but the present invention is not limited thereto.

[0045] In the cooling step of this embodiment, the flue gas may be cooled by boiler water in the heat recovery cooling unit 11, and the boiler water changes into water vapor after absorbing the heat of the flue gas.

[0046] [Third embodiment]

[0047] See also Figure 5 and Figure 6 As shown, Figure 5 is a schematic flow chart of a method for extracting carbon dioxide from flue gas according to a third embodiment of the present invention, and Figure 6 Schematic diagram of a smoke extraction system according to a third embodiment of the present invention. This embodiment is similar to the second embodiment, so the similarities between the two embodiments are not described in detail, and the differences between the two embodiments are roughly described as follows.

[0048] In the deacidification step S120a, a second deacidification operation is also performed on the flue gas, and the second deacidification operation is to remove fluoric acid compounds and boric acid compounds in the flue gas with sodium bicarbonate powder. Preferably, in the deacidification step, the first deacidification operation is performed first and then the second deacidification operation is performed.

[0049] The second acid removal operation is to remove fluoric acid compounds and boric acid compounds in the flue gas by using sodium bicarbonate powder through the dry acid removal unit 21.

[0050] [Fourth embodiment]

[0051] See also Figure 7 and Figure 8 As shown, Figure 7 is a schematic flow chart of a method for extracting carbon dioxide from flue gas according to a fourth embodiment of the present invention, and Figure 8Schematic diagram of a smoke extraction system according to a fourth embodiment of the present invention. This embodiment is similar to the third embodiment, so the similarities between the two embodiments are not described in detail, and the differences between the two embodiments are roughly described as follows.

[0052] Before the purification and liquefaction step S130 and after the removal step S121, the method for extracting carbon dioxide from flue gas further comprises a cooling and dehydration step S122, which reduces the temperature of the flue gas to between 20°C and 40°C and reduces the content of water vapor in the flue gas. Preferably, after the cooling and dehydration step S122, the temperature of the flue gas is reduced to about 30°C.

[0053] In the cooling and dehumidifying step S122 of the present embodiment, the temperature of the flue gas and the content of water vapor in the flue gas may be reduced by the cooling and dehumidifying unit 31. In addition, before the flue gas enters the cooling and dehumidifying unit 31, the flue gas may be cooled by the heat recovery unit 32. The heat recovery unit 32 may be connected to an absorption chiller 33, and the heat recovery unit 32 may cool the flue gas with reflux water having a temperature of about 50°C to 80°C.

[0054] After the reflux water absorbs the heat of the flue gas, it forms hot water or water vapor with a temperature of about 95°C to 165°C. The absorption refrigerator 33 can reduce the temperature of the aforementioned hot water or water vapor to form low-temperature water, and the low-temperature water can be introduced into the cooling and water removal unit 31 in the cooling and water storage step S122 to cool the flue gas. The temperature of the low-temperature water can be between 4°C and 7°C, but the present invention is not limited to this. In addition, it is worth mentioning that the hot water or water vapor formed after the reflux water absorbs the heat of the flue gas is not limited to the cooling and water storage unit 31. The thermal energy of the hot water or water vapor can be reused to heat other units (such as other units not included in the flue gas extraction system 100) to achieve the effect of heat energy recovery and reuse.

[0055] After the cooling and dehydrating step S122, based on the volume of the flue gas being 100%, the content of carbon dioxide is not less than 75%, and the content of water vapor is not more than 10%. Specifically, after the cooling and dehydrating step S122, based on the volume of the flue gas being 100%, the content of carbon dioxide is between 78% and 82%, the content of nitrogen is between 5% and 9%, the content of water vapor is between 2% and 6%, and the content of oxygen is between 7% and 11%.

[0056] Preferably, after the cooling and dehydrating step S122, based on the volume of the flue gas being 100%, the content of carbon dioxide is between 79% and 81%, the content of nitrogen is between 6% and 8%, the content of water vapor is between 3% and 5%, and the content of oxygen is between 8% and 10%. More preferably, after the cooling and dehydrating step S122, based on the volume of the flue gas being 100%, the content of carbon dioxide is about 80%, the content of nitrogen is about 7%, the content of water vapor is about 4%, and the content of oxygen is about 9%.

[0057] [Experimental data test]

[0058] The methods for extracting carbon dioxide from flue gas in the first to fourth embodiments and the comparative example are compared. The steps in the first to fourth embodiments and the comparative example are summarized in Table 1 below.

[0059] In addition, the flue gas before performing the acid removal step is defined as the first flue gas, and the flue gas before performing the purification and liquefaction steps is defined as the second flue gas. The gases contained in the first flue gas and the volume ratio and the temperature of the first flue gas are summarized in Table 2, and the gases contained in the second flue gas and the volume ratio and the temperature of the second flue gas are summarized in Table 3.

[0060] [Table 1 Steps in the first to fourth embodiments and comparative examples]

[0061]

[0062] [Table 2 Gases and volume ratios contained in the first flue gas and the temperature of the first flue gas in the first to fourth embodiments]

[0063]

[0064] [Table 3 Gases included in the second flue gas and their volume ratios and the temperature of the second flue gas in the first to fourth embodiments]

[0065]

[0066]

[0067] [Test results discussion]

[0068] Since the glass raw material is burned in the comparative example by air combustion, the volume ratio of carbon dioxide in the first flue gas and the second flue gas is lower than that in the first flue gas and the second flue gas of the embodiment 1.

[0069] The method for extracting carbon dioxide from flue gas in Example 2 includes a cooling step, so the temperature of the first flue gas is relatively low.

[0070] The method for extracting carbon dioxide from flue gas in Example 3 includes a first acid removal operation and a second acid removal operation, so the second flue gas contains less fluoric acid compounds.

[0071] The method for extracting carbon dioxide from flue gas in Example 4 includes a cooling and water removal step, so the proportion of carbon dioxide in the second flue gas is higher and the fluoric acid compounds contained in the second flue gas are less.

[0072] [Beneficial effects of the embodiments of the present invention]

[0073] One of the beneficial effects of the present invention is that the method for extracting carbon dioxide from flue gas provided by the present invention can effectively improve the problem that after the existing flue gas treatment method is implemented, the volume ratio of carbon dioxide in the flue gas is too low, making it difficult to recycle and reuse carbon dioxide, through the technical scheme of "collecting the flue gas generated by the methane-oxygen-enriched combustion of glass raw materials in a glass melting furnace" and "removing fluoric acid compounds and boric acid compounds in the flue gas with sodium hydroxide aqueous solution".

[0074] Furthermore, in the cooling and water removal operation, hot water or water vapor formed after absorbing the heat of the flue gas can be introduced into the absorption refrigerator to form low-temperature water, and then the flue gas is further cooled by the low-temperature water, thereby achieving the effect of heat energy recovery and reuse.

[0075] The contents disclosed above are only preferred feasible embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Therefore, all equivalent technical changes made using the contents of the present invention description and drawings are included in the patent scope of the present invention.

Claims

1. A method for extracting carbon dioxide from flue gas, characterized in that: The method for extracting carbon dioxide from flue gas comprises: A pre-step of collecting flue gas generated by burning glass raw materials with methane-enriched oxygen in a glass melting furnace; wherein the flue gas contains carbon dioxide, nitrogen, water vapor, oxygen, fluoric acid compounds and boric acid compounds; an acid removal step, performing a first acid removal operation on the flue gas; wherein the first acid removal operation uses a sodium hydroxide aqueous solution to remove fluoric acid compounds and boric acid compounds in the flue gas; and The purification and liquefaction step uses a purification and liquefaction unit to extract the flue gas that has passed the acid removal step to obtain liquid carbon dioxide with a purity greater than 99%.

2. The method for extracting carbon dioxide from flue gas according to claim 1, characterized in that: In the pre-step, the temperature of the flue gas is between 1,000°C and 1,500°C, based on the volume of the flue gas being 100%, the content of carbon dioxide is between 30% and 34%, the content of nitrogen is between 1% and 5%, the content of water vapor is between 58% and 62%, and the content of oxygen is between 2% and 6%.

3. The method for extracting carbon dioxide from flue gas according to claim 1, characterized in that: In the preceding step, the content of the fluoric acid compound is greater than 0 mg / m3 and less than 500 mg / m3, and the content of the boric acid compound is greater than 0 mg / m3 and less than 15 mg / m3.

4. The method for extracting carbon dioxide from flue gas according to claim 1, characterized in that: After the pre-step and before the acid removal step, the method for extracting carbon dioxide from flue gas further comprises a cooling step, wherein the flue gas is cooled by water to reduce the temperature of the flue gas to between 200°C and 400°C.

5. The method for extracting carbon dioxide from flue gas according to claim 1, characterized in that: In the acid removal step, a second acid removal operation is also performed on the flue gas, and the second acid removal operation is to remove fluoric acid compounds and boric acid compounds in the flue gas with sodium bicarbonate powder.

6. The method for extracting carbon dioxide from flue gas according to claim 5, characterized in that: In the acid removal step, the first acid removal operation is to remove the fluoric acid compounds and boric acid compounds in the flue gas with an aqueous sodium hydroxide solution through a semi-dry acid removal tower, and the second acid removal operation is to remove the fluoric acid compounds and boric acid compounds in the flue gas with sodium bicarbonate powder through a dry acid removal unit; wherein, after the first acid removal operation, the temperature of the flue gas is reduced to between 170°C and 200°C, and after the second acid removal operation, the temperature of the flue gas is maintained between 170°C and 200°C.

7. The method for extracting carbon dioxide from flue gas according to claim 1, characterized in that: Based on the volume of the flue gas being 100%, the content of carbon dioxide is between 21% and 25%, the content of nitrogen is between 1% and 3%, the content of water vapor is between 70% and 74%, and the content of oxygen is between 1% and 3%.

8. The method for extracting carbon dioxide from flue gas according to claim 1, characterized in that: After the acid removal step and before the purification and liquefaction step, the method for extracting carbon dioxide from flue gas further comprises a removal step of filtering and removing byproducts of fluoric acid compounds and boric acid compounds in the flue gas through the acid removal step by using a bag filter.

9. The method for extracting carbon dioxide from flue gas according to claim 1, characterized in that: Before the purification and liquefaction steps, the method for extracting carbon dioxide from flue gas further includes a cooling and dehydration step, reducing the temperature of the flue gas to between 20°C and 40°C and reducing the content of water vapor in the flue gas; wherein, after the cooling and dehydration step, based on the volume of the flue gas being 100%, the content of carbon dioxide is not less than 75%, and the content of water vapor is not more than 10%.

10. The method for extracting carbon dioxide from flue gas according to claim 9, characterized in that: In the cooling and dehydration step, the flue gas is first cooled by water with a temperature between 50°C and 80°C in a heat recovery unit. After absorbing the heat of the flue gas, the water forms hot water or water vapor with a temperature between 95°C and 165°C and can be cooled by an absorption refrigerator connected to the heat recovery unit to form low-temperature water. The low-temperature water can reduce the temperature of the flue gas in the cooling and dehydration step.

11. The method for extracting carbon dioxide from flue gas according to claim 9, characterized in that: After the cooling and dehydration step, based on the volume of the flue gas being 100%, the carbon dioxide content is between 78% and 82%, the nitrogen content is between 5% and 9%, the water vapor content is between 2% and 6%, and the oxygen content is between 7% and 11%.

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