Method for extracting carbon dioxide from flue gas

Abstract

To provide a method for extracting carbon dioxide from a flue gas.SOLUTION: A method for extracting carbon dioxide from a flue gas includes a preparing process, an acid removing process, and a purifying and liquefying process. The preparing process is implemented by collecting the flue gas generated by oxygen-enriched combustion of a glass raw material with methane from a glass furnace. The flue gas includes the carbon dioxide, nitrogen, water vapor, oxygen, fluoric acid compounds, and boric acid compounds. The acid removing process is implemented by performing a first acid removing operation. The first acid removing operation is implemented by using a sodium hydroxide aqueous solution to remove the fluoric acid compounds and the boric acid compounds in the flue gas. The purifying and liquefying process is implemented by using a purifying and liquefying unit to extract the flue gas that already undergoes the acid removing process, so as to obtain liquid carbon dioxide having a purity greater than 99%.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for extracting carbon dioxide, and in particular to a method for extracting carbon dioxide from flue gas produced by a smelter. [Background technology]

[0002] Glass melting furnaces produce hot flue gases, and the conventional method of treating the flue gases is to add alkali to remove fluorine compounds, then cool the flue gases with a large amount of air to precipitate boron compounds, and vent the flue gases.

[0003] However, after carrying out the conventional flue gas treatment method, the volume ratio of carbon dioxide in the flue gas (about 2% to 3%) is too low, making it difficult to recycle carbon dioxide. Summary of the Invention [Problem to be solved by the invention]

[0004] The technical problem that the present invention aims to solve is to address the shortcomings of the prior art by providing a method for extracting carbon dioxide from flue gas, which solves the problem that after carrying out the conventional method for extracting carbon dioxide from flue gas, the volume ratio of carbon dioxide in the flue gas is too low, making it difficult to recycle carbon dioxide. [Means for solving the problem]

[0005] In order to solve the above technical problems, one technical means adopted by the present invention provides a method for extracting carbon dioxide from flue gas, which includes a preparation step of collecting flue gas from methane-oxygen enriched combustion of glass raw material in a glass melting furnace, an acid removal step of performing a first acid removal operation on the flue gas to remove hydrofluoric acid compounds and boric acid compounds in the flue gas with an aqueous sodium hydroxide solution, and a purification and liquefaction step of extracting liquid carbon dioxide having a purity of more than 99% from the flue gas that has been subjected to the acid removal step in a purification and liquefaction unit, where the flue gas contains carbon dioxide, nitrogen gas, water vapor, oxygen gas, hydrofluoric acid compounds, and boric acid compounds.

[0006] Preferably, in the preparation step, the temperature of the flue gas is 1,000°C to 1,500°C, and, assuming the volume of the flue gas to be 100%, the carbon dioxide content is 30% to 34%, the nitrogen gas content is 1% to 5%, the water vapor content is 58% to 62%, and the oxygen gas content is 2% to 6%.

[0007] Preferably, in the preparation step, the content of the hydrofluoric acid compound is greater than 0 milligrams / cubic meter and less than 500 milligrams / cubic meter, and the content of the boric acid compound is greater than 0 milligrams / cubic meter and less than 15 milligrams / cubic meter.

[0008] Preferably, the method for extracting carbon dioxide from flue gas further comprises a cooling step, after the preparing step and before the acid removing step, in which the flue gas is cooled with water so as to reduce the temperature of the flue gas to between 200°C and 400°C.

[0009] Preferably, in the acid removal step, the flue gas is further subjected to a second acid removal operation, in which hydrofluoric acid compounds and boric acid compounds in the flue gas are removed with sodium bicarbonate powder.

[0010] Preferably, in the acid removal step, in the first acid removal operation, the hydrofluoric acid compounds and boric acid compounds in the flue gas are removed with a sodium hydroxide aqueous solution by a semi-dry acid removal tower, and in the second acid removal operation, the hydrofluoric acid compounds and boric acid compounds in the flue gas are removed with sodium bicarbonate powder by a dry acid removal unit. After the first acid removal operation, the temperature of the flue gas is reduced to 170°C to 200°C, and after the second acid removal operation, the temperature of the flue gas is maintained at 170°C to 200°C.

[0011] Preferably, with the volume of the flue gas taken as 100%, the carbon dioxide content is 21% to 25%, the nitrogen gas content is 1% to 3%, the water vapor content is 70% to 74%, and the oxygen gas content is 1% to 3%.

[0012] Preferably, the method for extracting carbon dioxide from the flue gas further comprises a removal step, after the acid removal step and before the purification and liquefaction step, of filtering and removing solid waste with a bag filter, the solid waste being generated from hydrofluoric acid compounds and boric acid compounds in the flue gas after the acid removal step.

[0013] Preferably, the method for extracting carbon dioxide from flue gas further includes a cooling and dehydration step, prior to the purification and liquefaction step, of reducing the temperature of the flue gas to 20°C to 40°C and reducing the water vapor content in the flue gas, and after the cooling and dehydration step, the carbon dioxide content is 75% or more and the water vapor content is 10% or less, assuming that the volume of the flue gas is 100%.

[0014] Preferably, in the cooling and water removal process, the flue gas is first cooled by water having a temperature of 50°C to 80°C in a heat recovery unit, and after the water absorbs the thermal energy of the flue gas, it changes into hot water or steam having a temperature of about 95°C to 165°C. The hot water or steam is then cooled in an absorption chiller connected to the heat recovery unit and changes into low-temperature water, and the low-temperature water reduces the temperature of the flue gas in the cooling and water removal process.

[0015] Preferably, after the cooling and water removal process, the volume of the flue gas is 100%, and the carbon dioxide content is 78% to 82%, the nitrogen gas content is 5% to 9%, the water vapor content is 2% to 6%, and the oxygen gas content is 7% to 11%. Effect of the Invention

[0016] As an advantageous effect of the present invention, the method for extracting carbon dioxide from flue gas according to the present invention has the technical features of "collecting flue gas produced by methane-oxygen enriched combustion of glass raw material in a glass melting furnace" and "removing hydrofluoric acid compounds and boric acid compounds in the flue gas with an aqueous sodium hydroxide solution", which effectively solves the problem that the volume ratio of carbon dioxide in the flue gas is too low after carrying out the conventional flue gas treatment method, making it difficult to recycle carbon dioxide.

[0017] Furthermore, in the cooling and dewatering process, the hot water or steam obtained by absorbing the thermal energy of the flue gas is passed through the absorption chiller and cooled to become low-temperature water, and then the flue gas is further cooled with the low-temperature water, thereby recycling the thermal energy. [Brief description of the drawings]

[0018] [Figure 1] 1 is a flow chart of a method for extracting carbon dioxide from flue gas according to a first embodiment of the present invention. [Diagram 2] FIG. 1 is a block diagram of a flue gas extraction system according to a first embodiment of the present invention. [Diagram 3] 4 is a flow chart of a method for extracting carbon dioxide from flue gas according to a second embodiment of the present invention. [Figure 4] FIG. 4 is a block diagram of a flue gas extraction system according to a second embodiment of the present invention. [Diagram 5] 4 is a flow chart of a method for extracting carbon dioxide from flue gas according to a third embodiment of the present invention. [Figure 6] FIG. 4 is a block diagram of a flue gas extraction system according to a third embodiment of the present invention. [Figure 7] 1 is a flow chart of a method for extracting carbon dioxide from flue gas according to a fourth embodiment of the present invention. [Figure 8] FIG. 10 is a block diagram of a flue gas extraction system according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] In order to better understand the features and technical contents of the present invention, please refer to the following detailed description of the present invention and the accompanying drawings, which are provided for reference and explanation only and are not intended to limit the scope of the present invention.

[0020] Hereinafter, the "method for extracting carbon dioxide from flue gas" according to the embodiment of the present invention will be described in detail with reference to certain specific embodiments, and those skilled in the art will be able to understand the advantages and effects of the present invention based on the contents disclosed in this specification. The present invention can be implemented or applied in other different specific embodiments, and various modifications and changes can be made to each detail in this specification based on different perspectives and applications without departing from the concept of the present invention. In addition, as described in advance, the accompanying drawings of the present invention are simple schematic illustrations and are not drawn based on actual size. The technical contents of the present invention will be described in more detail based on the following embodiments, but the disclosed contents do not limit the protection scope of the present invention.

[0021] It should be understood that, although the present specification may use the terms "first", "second", "third" and the like to describe various elements or signals, these elements or signals are not limited by these terms. These terms are mainly used to distinguish one element from another element or one signal from another signal. In addition, the term "or" used in the present specification may include any one or more combinations of the associated listed items according to actual circumstances.

[0022] [First embodiment] As shown in Fig. 1, which is a flow chart of the method for extracting carbon dioxide from flue gas according to the first embodiment of the present invention, and Fig. 2, which is a block diagram of a flue gas extraction system according to the first embodiment of the present invention, the first embodiment of the present invention provides a method for extracting carbon dioxide from flue gas. The method for extracting carbon dioxide from flue gas includes at least a preparation step S110, an acid removal step S120, and a purification and liquefaction step S130.

[0023] In the preparation step S110, flue gas from the methane-oxygen enriched combustion of glass frit is collected in the glass melting furnace 10. The flue gas includes carbon dioxide, nitrogen gas, water vapor, oxygen gas, hydrofluoric acid compounds, and boric acid compounds. The hydrofluoric acid compounds may be acidic components such as HF, and the boric acid compounds may be acidic components such as H3BO3, HBO2, B2O3, or BF3, but the present invention is not limited to the specific components of the hydrofluoric acid compounds and the boric acid compounds. It is worth noting that the hydrofluoric acid compounds and the boric acid compounds are produced by burning glass frits, and therefore, methods of extracting carbon dioxide from flue gas in other technical fields that do not produce hydrofluoric acid compounds and boric acid compounds are not applicable to the method of extracting carbon dioxide from flue gas according to the present invention.

[0024] The oxygen enrichment is achieved by removing a portion of the nitrogen gas from the air, and the oxygen gas usually occupies 21% or more of the total gas volume. In the preparation step S110 of this embodiment, the oxygen gas occupies 92% to 96% of the total gas volume in the glass melting furnace, and preferably 94% or more.

[0025] Compared with the flue gas produced by introducing air into the glass melting furnace, the volume of carbon dioxide in the flue gas produced by methane-oxygen enriched combustion is relatively high, which improves the possibility of recycling carbon dioxide. To be more specific, the volume of carbon dioxide in the flue gas produced by methane-oxygen enriched combustion is more than 30%, while the volume of carbon dioxide in the flue gas produced by air combustion is about 12%.

[0026] In the flue gas S110 of this embodiment, the temperature of the flue gas is 1,000°C to 1,500°C, and, with the volume of the flue gas being 100%, the carbon dioxide content is 30% to 34%, the nitrogen gas content is 1% to 5%, the water vapor content is 58% to 62%, and the oxygen gas content is 2% to 6%.

[0027] Preferably, the flue gas has a temperature of 1,200°C to 1,400°C, and the flue gas has a carbon dioxide content of 31% to 33%, a nitrogen gas content of 2% to 4%, a water vapor content of 59% to 61%, and an oxygen gas content of 2% to 6%, relative to the volume of the flue gas being 100%. More preferably, the flue gas has a temperature of about 1,300°C, and the flue gas has a carbon dioxide content of about 32%, a nitrogen gas content of about 3%, a water vapor content of about 60%, and an oxygen gas content of about 4%, relative to the volume of the flue gas being 100%.

[0028] In the preparation step S110 of this embodiment, the content of hydrofluoric acid compound is more than 0 milligrams / cubic meter and less than 500 milligrams / cubic meter, and the content of boric acid compound is more than 0 milligrams / cubic meter and less than 15 milligrams / cubic meter.Preferably, the content of hydrofluoric acid compound is more than 0 milligrams / cubic meter and less than 400 milligrams / cubic meter, and the content of boric acid compound is more than 0 milligrams / cubic meter and less than 10 milligrams / cubic meter.

[0029] In the acid removal step S120, a first acid removal operation is performed on the flue gas. In the first acid removal operation, hydrofluoric acid compounds and boric acid compounds in the flue gas are removed with an aqueous sodium hydroxide solution. To be more specific, in the acid removal step S120 of this embodiment, in the first acid removal operation, hydrofluoric acid compounds and boric acid compounds in the flue gas are removed with an aqueous sodium hydroxide solution by a semi-dry acid removal tower 20. In this embodiment, the weight percent concentration of the aqueous sodium hydroxide solution is 2% to 4%, but the present invention is not limited thereto.

[0030] After the first acid removal operation, the temperature of the flue gas is reduced to 170°C to 200°C, and after the second acid removal operation, the temperature of the flue gas is maintained at 170°C to 200°C. The flue gas has a carbon dioxide content of 21% to 25%, a nitrogen gas content of 1% to 3%, a water vapor content of 70% to 74%, and an oxygen gas content of 1% to 3%, based on a volume of the flue gas of 100%. Preferably, after the acid removal step S120, the flue gas has a carbon dioxide content of about 23%, a nitrogen gas content of about 2%, a water vapor content of about 72%, and an oxygen gas content of about 2%, based on a volume of the flue gas of 100%.

[0031] In the purification and liquefaction step S130, liquid carbon dioxide having a purity of more than 99% is extracted from the flue gas that has been subjected to the acid removal step S120 in a purification and liquefaction unit 40.

[0032] After the acid removal step and before the purification and liquefaction step, the method may further include a removal step S121 of filtering and removing by-products generated from hydrofluoric acid compounds and boric acid compounds in the flue gas using a bag filter 30. The by-products may be, for example, alkaline solids containing fluorine or boron (e.g., sodium hydroxide or sodium bicarbonate), but the present invention is not limited thereto. The by-products may be recycled, but the present invention is not limited to the use of the by-products.

[0033] In addition, in this embodiment, the method for extracting carbon dioxide from the flue gas can be carried out by a carbon dioxide extraction system 100, and the carbon dioxide 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.

[0034] [Second embodiment] As shown in Fig. 3, which is a flow chart of a method for extracting carbon dioxide from flue gas according to a second embodiment of the present invention, and Fig. 4, which is a block diagram of a flue gas extraction system according to a second embodiment of the present invention, this embodiment is similar to the first embodiment, so the same parts of the two embodiments will not be described repeatedly. In addition, the differences between the two embodiments are as follows:

[0035] In this embodiment, after the preparing step S110 and before the acid removing step S120, the method further includes a cooling step S111 in which the flue gas is cooled with water to reduce the temperature of the flue gas to 200° C. to 400° C. Preferably, after the cooling step S111, the temperature of the flue gas is about 300° C. In another embodiment, in the cooling step S111, the flue gas may be cooled with air, or the flue gas may be cooled with air first and then cooled with water, but the present invention is not limited thereto.

[0036] In the cooling process of this embodiment, the flue gas is cooled by boiler water in the heat recovery cooling unit 11, and the boiler water is converted into steam after absorbing the thermal energy of the flue gas.

[0037] [Third embodiment] As shown in Fig. 5, which is a flow chart of a method for extracting carbon dioxide from flue gas according to a third embodiment of the present invention, and Fig. 6, which is a block diagram of a flue gas extraction system according to a third embodiment of the present invention, this embodiment is similar to the second embodiment, so the same parts of the two embodiments will not be described repeatedly. In addition, the differences between the two embodiments are as follows:

[0038] The acid removal step S120a further includes a second acid removal operation for removing hydrofluoric acid compounds and boric acid compounds in the flue gas with sodium bicarbonate powder. Preferably, in the acid removal step, the second acid removal operation is performed after the first acid removal operation.

[0039] In the second acid removal operation, hydrofluoric and boric acid compounds in the flue gas are removed with sodium bicarbonate powder by dry acid removal unit 21.

[0040] [Fourth embodiment] As shown in Fig. 7, which is a flow chart of a method for extracting carbon dioxide from flue gas according to a fourth embodiment of the present invention, and Fig. 8, which is a block diagram of a flue gas extraction system according to a fourth embodiment of the present invention, this embodiment is similar to the third embodiment, so the same parts of the two embodiments will not be described repeatedly. In addition, the differences between the two embodiments are as follows:

[0041] The method for extracting carbon dioxide from flue gas further includes a cooling and dewatering step S122 before the purification and liquefaction step S130 and after the removal step S121, in which the temperature of the flue gas is reduced to 20°C to 40°C and the water vapor content in the flue gas is reduced. Preferably, the temperature of the flue gas is reduced by about 30°C after the cooling and dewatering step S122.

[0042] In the cooling and water removal step S122 of this embodiment, the temperature of the flue gas and the water vapor content of the flue gas are reduced in a cooling and water removal unit 31. In addition, before the flue gas is introduced into the cooling and water removal unit 31, the flue gas may be cooled by passing through a heat recovery unit 32 in advance. The heat recovery unit 32 may be connected to an absorption chiller 33, and the heat recovery unit 32 may cool the flue gas by reflux water having a temperature of 50°C to 80°C.

[0043] After the reflux water absorbs the thermal energy of the flue gas, it changes into hot water or steam with a temperature of about 95°C to 165°C, and the hot water or the steam is cooled by the absorption refrigerator 33 to change into low-temperature water, and the low-temperature water is introduced into the cooling and water removal unit 31 in the cooling and water removal step S122 to reduce the temperature of the flue gas. The low-temperature water may be 4°C to 7°C, but the present invention is not limited thereto. It is also worth noting that the hot water or the steam formed after the reflux water absorbs the thermal energy of the flue gas is not limited to being applied to the cooling and water removal unit 31. The thermal energy of the hot water or the steam may be recycled to heat another unit (e.g., another unit not included in the flue gas extraction system 100) so as to realize the recycling of thermal energy.

[0044] After the cooling and water removal step S122, the carbon dioxide content is 75% or more and the water vapor content is 10% or less, assuming that the volume of the flue gas is 100%. Specifically, after the cooling and water removal step S122, the carbon dioxide content is 78% to 82%, the nitrogen gas content is 5% to 9%, the water vapor content is 2% to 6%, and the oxygen gas content is 7% to 11%, assuming that the volume of the flue gas is 100%.

[0045] Preferably, after the cooling and water removal step S122, the carbon dioxide content is 79% to 81%, the nitrogen gas content is 6% to 8%, the water vapor content is 3% to 5%, and the oxygen gas content is 8% to 10%, relative to the volume of the flue gas being 100%. More preferably, after the cooling and water removal step S122, the carbon dioxide content is about 80%, the nitrogen gas content is about 7%, the water vapor content is about 4%, and the oxygen gas content is about 9%, relative to the volume of the flue gas being 100%.

[0046] [Measurement of experimental data] Comparing the methods for extracting carbon dioxide from flue gas according to Examples 1 to 4 and a Comparative Example, the steps of Examples 1 to 4 and the Comparative Example are summarized in Table 1.

[0047] The flue gas before the acid removal step is referred to as the first flue gas, and the flue gas before the purification and liquefaction step is referred to as the second flue gas. The gases contained in the first flue gas and their volume ratios, as well as the temperature of the first flue gas, are as shown in Table 2 below. The gases contained in the second flue gas and their volume ratios, as well as the temperature of the second flue gas, are as shown in Table 3 below.

[0048] [Table 1]

[0049] [Table 2]

[0050] [Table 3]

[0051] [Consideration of measurement results] In the comparative example, since the glass raw material was burned by air combustion, the volume ratio of carbon dioxide in the first flue gas and the second flue gas was both lower than the volume ratio of carbon dioxide in the first flue gas and the second flue gas in Example 1.

[0052] Since the method for extracting carbon dioxide from flue gas according to Example 2 includes a cooling step, the temperature of the first flue gas was relatively low.

[0053] Since the method for extracting carbon dioxide from flue gas according to Example 3 includes the first acid removal operation and the second acid removal operation, the amount of hydrofluoric acid compounds contained in the second flue gas was relatively small.

[0054] Since the method for extracting carbon dioxide from flue gas in Example 4 includes a cooling and water removal process, the proportion of carbon dioxide contained in the second flue gas is relatively high, and the amount of hydrofluoric acid compounds contained in the second flue gas is relatively small.

[0055] [Advantageous Effects of the Embodiments] As an advantageous effect of the present invention, the method for extracting carbon dioxide from flue gas according to the present invention has the technical features of "collecting flue gas produced by methane-oxygen enriched combustion of glass raw material in a glass melting furnace" and "removing hydrofluoric acid compounds and boric acid compounds in the flue gas with an aqueous sodium hydroxide solution", which effectively solves the problem that the volume ratio of carbon dioxide in the flue gas is too low after carrying out the conventional flue gas treatment method, making it difficult to recycle carbon dioxide.

[0056] Furthermore, in the cooling and dewatering process, the hot water or steam obtained by absorbing the thermal energy of the flue gas is passed through the absorption chiller and cooled to become low-temperature water, and then further cooled with the low-temperature water, thereby recycling the thermal energy.

[0057] The above disclosure is merely a preferred embodiment of the present invention, and the scope of the claims of the present invention is not limited thereto. Therefore, all equivalent technical modifications made by utilizing the specification and drawings of the present invention are included in the scope of the claims of the present invention. [Explanation of symbols]

[0058] 100... Carbon Dioxide Extraction System 10...Glass melting furnace 11...Heat recovery cooling unit 20...Semi-dry acid removal tower 21...Dry acid removal unit 30...Bag filter 31...Cooling and water removal unit 32...Heat recovery unit 33...Absorption refrigeration machine 40...Purification and liquefaction unit S110...preparation process S111...Cooling process S120,S120a...Acid removal process S121...Removal process S122...Cooling / water removal process S130...purification / liquefaction process

Claims

1. a preparation step of collecting flue gas from methane-oxygen enriched combustion of glass raw material in a glass melting furnace; an acid removal step of performing a first acid removal operation on the flue gas to remove hydrofluoric acid compounds and boric acid compounds in the flue gas with an aqueous sodium hydroxide solution; and a purification and liquefaction step, extracting liquid carbon dioxide having a purity of more than 99% from the flue gas that has been subjected to the acid removal step in a purification and liquefaction unit, 1. A method for extracting carbon dioxide from flue gas, wherein the flue gas contains carbon dioxide, nitrogen gas, water vapor, oxygen gas, a hydrofluoric acid compound, and a boric acid compound.

2. 2. The method for extracting carbon dioxide from flue gas according to claim 1, wherein in the preparation step, the temperature of the flue gas is 1,000°C to 1,500°C, and the volume of the flue gas is taken as 100%, the carbon dioxide content is 30% to 34%, the nitrogen gas content is 1% to 5%, the water vapor content is 58% to 62%, and the oxygen gas content is 2% to 6%.

3. 2. The method for extracting carbon dioxide from flue gas according to claim 1, wherein in the preparation step, the content of hydrofluoric acid compounds is greater than 0 milligrams per cubic meter and less than 500 milligrams per cubic meter, and the content of boric acid compounds is greater than 0 milligrams per cubic meter and less than 15 milligrams per cubic meter.

4. 2. The method of claim 1 further comprising a cooling step in which, after the preparing step and before the acid removing step, the flue gas is cooled with water to reduce the temperature of the flue gas to between 200°C and 400°C.

5. 2. The method for extracting carbon dioxide from flue gas as claimed in claim 1, wherein the acid removal step further comprises subjecting the flue gas to a second acid removal operation in which hydrofluoric acid compounds and boric acid compounds in the flue gas are removed with sodium bicarbonate powder.

6. In the acid removal step, in the first acid removal operation, hydrofluoric acid compounds and boric acid compounds in the flue gas are removed with a sodium hydroxide aqueous solution by a semi-dry acid removal tower, and in the second acid removal operation, hydrofluoric acid compounds and boric acid compounds in the flue gas are removed with sodium bicarbonate powder by a dry acid removal unit; 6. The method of claim 5, 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 at between 170°C and 200°C.

7. 2. The method for extracting carbon dioxide from flue gas according to claim 1, wherein the volume of the flue gas is 100%, and the carbon dioxide content is 21% to 25%, the nitrogen gas content is 1% to 3%, the water vapor content is 70% to 74%, and the oxygen gas content is 1% to 3%.

8. The method further includes a removal step in which by-products are filtered and removed using a bag filter after the acid removal step and before the purification and liquefaction step; 2. The method of claim 1, wherein the by-products are produced from hydrofluoric and boric acid compounds in the flue gas after the acid removal step.

9. The method further includes a cooling and dehydration step, which reduces the temperature of the flue gas to 20°C to 40°C and reduces the water vapor content in the flue gas before the purification and liquefaction step; 2. The method for extracting carbon dioxide from flue gas as described in claim 1, wherein after the cooling and water removal process, the carbon dioxide content is 75% or more and the water vapor content is 10% or less, assuming that the volume of the flue gas is 100%.

10. 10. The method for extracting carbon dioxide from flue gas according to claim 9, wherein in the cooling and water removal process, the flue gas is first cooled by water having a temperature of 50°C to 80°C in a heat recovery unit, and after the water absorbs the thermal energy of the flue gas, it is changed into hot water or steam having a temperature of 95°C to 165°C, and the hot water or the steam is cooled by an absorption chiller connected to the heat recovery unit and changed into low-temperature water, and the low-temperature water reduces the temperature of the flue gas in the cooling and water removal process.

11. 10. The method for extracting carbon dioxide from flue gas according to claim 9, wherein after the cooling and water removal steps, the volume of the flue gas is taken as 100%, and the carbon dioxide content is 78% to 82%, the nitrogen gas content is 5% to 9%, the water vapor content is 2% to 6%, and the oxygen gas content is 7% to 11%.

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