A method for converting flue gas to calcium carbonate

Abstract

This invention provides a method for converting flue gas into calcium carbonate. [Solution] The method for converting flue gas to calcium carbonate includes a carbon dioxide capture step and a calcium carbonate formation step. In the carbon dioxide capture step, the injection flue gas is introduced into an alkaline aqueous solution to form a first solution. Taking the volume of the injection flue gas as 100%, the injection flue gas contains 10% to 80% carbon dioxide, 6.1% to 88% nitrogen, and 0.7% to 13.9% oxygen. The first solution contains a carbonate, and the carbonate is at least one of sodium carbonate and sodium bicarbonate. In the calcium carbonate formation step, calcium hydroxide powder is added to the first solution to form a second solution, and the second solution contains calcium carbonate powder formed by the reaction of the carbonate and the calcium hydroxide powder.

Description

Technical Field

[0003]

[0001] The present invention relates to a method for converting into calcium carbonate, and particularly to a method for converting flue gas into calcium carbonate.

Background Art

[0002] In existing flue gas treatment methods, flue gas cannot be effectively treated, and it has been difficult to recycle and reuse carbon dioxide in flue gas.

Summary of the Invention

Problems to be Solved by the Invention

[0003] The present invention mainly improves the problem that existing flue gas treatment methods cannot effectively treat flue gas and it is difficult to recycle and reuse carbon dioxide in flue gas, and provides a method for converting flue gas into calcium carbonate.

Means for Solving the Problems

[0004] In an embodiment of the present invention, a method for converting flue gas into calcium carbonate is provided. The method for converting the flue gas into calcium carbonate includes a carbon dioxide capture step of introducing the flue gas for injection into an alkaline aqueous solution which is an aqueous sodium hydroxide solution to form a first solution. Taking the volume of the flue gas for injection as 100%, the flue gas for injection contains 10% - 80% of carbon dioxide, 6.1% - 88% of nitrogen, and 0.7% - 13.9% of oxygen, and the first solution contains a carbonate which is at least one of sodium carbonate and sodium bicarbonate; and a calcium carbonate formation step of adding calcium hydroxide powder to the first solution to form a second solution, wherein the second solution contains calcium carbonate powder formed by the reaction of the carbonate and the calcium hydroxide powder.

[0005] Preferably, in the carbon dioxide capture step, with the volume of the injection flue gas set to 100%, the injection flue gas contains 60% to 80% carbon dioxide, 6.1% to 26.1% nitrogen, and 4.7% to 13.9% oxygen.

[0006] Preferably, the method for converting the flue gas to calcium carbonate further includes a pH value measurement step, which measures the pH value of the first solution after the carbon dioxide capture step and before the calcium carbonate formation step, and starts the calcium carbonate formation step when the pH value of the first solution becomes 11 to 12.

[0007] Preferably, in the calcium carbonate formation step, the second solution further contains sodium hydroxide formed by the reaction of the carbonate and the calcium hydroxide powder, wherein the sodium hydroxide is recyclable and used as the alkaline aqueous solution in the carbon dioxide capture step.

[0008] Preferably, in the calcium carbonate formation step, the pH of the second solution is controlled to 12-14.

[0009] Preferably, in the calcium carbonate formation step, exhaust gas is further generated, and with the volume of the exhaust gas being 100%, the exhaust gas contains 5% to 8% carbon dioxide, 88% to 93% nitrogen, and 2% to 4% oxygen.

[0010] Preferably, the method for converting the flue gas to calcium carbonate provides a carbon dioxide recovery rate of 80% or more, and the carbon dioxide recovery rate is defined as the difference between the carbon dioxide content in the injection flue gas and the carbon dioxide content in the exhaust gas divided by the carbon dioxide content in the injection flue gas.

[0011] Preferably, the method for converting the flue gas to calcium carbonate includes, before the carbon dioxide capture step, a preparation step of collecting flue gas from methane-oxygen enriched combustion of glass raw materials in a glass melting furnace, wherein the flue gas contains carbon dioxide, nitrogen, water vapor, oxygen, hydrofluoric acid compounds, and boric acid compounds; an acid removal step of performing a first acid removal operation on the flue gas, wherein the first acid removal operation removes hydrofluoric acid compounds and boric acid compounds in the flue gas with an aqueous sodium hydroxide solution; and a cooling and dewatering 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, wherein the flue gas after the cooling and dewatering step is used as the injection flue gas in the carbon dioxide capture step.

[0012] Preferably, in the acid removal step, a second acid removal operation is further performed on the flue gas, in which hydrofluoric acid compounds and boric acid compounds in the flue gas are removed with sodium bicarbonate powder.

[0013] Preferably, in the preparation step, with the volume of the flue gas being 100%, the carbon dioxide content is 30% to 34%, the nitrogen content is 1% to 5%, the water vapor content is 58% to 62%, and the oxygen content is 2% to 6%. [Effects of the Invention]

[0014] As described above, the method for converting flue gas to calcium carbonate according to the present invention has technical features such as "a carbon dioxide capture step of introducing the injection flue gas into the alkaline aqueous solution to form the first solution" and "a calcium carbonate formation step of adding calcium hydroxide powder to the first solution to form the second solution, the second solution containing calcium carbonate powder formed by the reaction of the carbonate and the calcium hydroxide powder," which effectively improves upon the fact that existing flue gas treatment methods cannot effectively treat flue gas and make it difficult to recycle and reuse carbon dioxide in flue gas. [Brief explanation of the drawing]

[0015] [Figure 1] This is a flowchart of a method for converting flue gas to calcium carbonate according to the first embodiment of the present invention. [Figure 2] This is a flowchart of a method for converting flue gas to calcium carbonate according to a second embodiment of the present invention. [Figure 3] This is a flowchart illustrating a method for converting flue gas to calcium carbonate according to a third embodiment of the present invention. [Modes for carrying out the invention]

[0016] To better understand the features and technical content of the present invention, the following detailed description and drawings of the present invention will be used with reference only; however, the provided description and drawings are for reference and illustrative purposes only and do not limit the present invention.

[0017] The following describes the implementation of the "method for converting flue gas to calcium carbonate" according to the present invention by 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 herein. The present invention can be implemented or applied by other different specific embodiments, and various modifications and changes can be made to each detail herein, based on different viewpoints and applications, as long as they do not deviate from the concept of the present invention. It should be noted in advance that the accompanying drawings of the present invention are for simple schematic explanation and are not drawn to actual size. The technical content of the present invention will be described in more detail below based on embodiments, but the scope of protection of the present invention is not limited by the contents disclosed.

[0018] It should be understood that while this specification may use terms such as “first,” “second,” and “third” to describe various elements or signals, these elements or signals are not limited by these terms. These terms are primarily used to distinguish one element from another, or one signal from another. Furthermore, the term “or” as used herein may, depending on the context, include any one or more of the items listed in relation to the subject.

[0019] [First Embodiment] Referring to Figure 1, Figure 1 is a flowchart of a method for converting flue gas to calcium carbonate according to a first embodiment of the present invention. Embodiments of the present invention provide a method for converting flue gas to calcium carbonate. The method for converting flue gas to calcium carbonate includes a carbon dioxide capture step S110 and a calcium carbonate formation step S120. Naturally, the method for converting flue gas to calcium carbonate may include other steps as needed, but the present invention is not limited thereto.

[0020] In the carbon dioxide capture step S110, the injection flue gas is introduced into an alkaline aqueous solution, which is an aqueous solution of sodium hydroxide, to form a first solution. The first solution contains a carbonate, which is at least one of sodium carbonate and sodium bicarbonate. The carbonate is produced by the reaction of the alkaline aqueous solution with carbon dioxide in the injection flue gas. The weight percentage concentration of the alkaline aqueous solution may be, for example, 3% to 10%, but the present invention is not limited thereto.

[0021] In the carbon dioxide capture step S110, taking the volume of the flue gas for injection as 100%, the flue gas for injection contains 10% - 80% carbon dioxide, 6.1% - 88% nitrogen, and 0.7% - 13.9% oxygen. It should be noted that the flue gas generated by burning glass raw materials in a glass melting furnace can be introduced into a first reaction device (not shown) for performing the carbon dioxide capture step S110 to be the flue gas for injection, but the present invention is not limited thereto. Further, the first reaction device may be, for example, a supergravity device, but the present invention is not limited thereto.

[0022] More specifically, the method of burning glass raw materials in a glass melting furnace can be classified into an air combustion method and a methane-oxygen enriched combustion method. When burning glass raw materials in a glass melting furnace by air combustion, taking the volume of the flue gas for injection as 100%, the flue gas for injection contains 10% - 18% carbon dioxide, 80% - 88% nitrogen, and 0.7% - 2% oxygen.

[0023] Preferably, in the carbon dioxide capture step S110, the flue gas for injection is obtained by burning glass raw materials in a glass melting furnace by adopting a methane-oxygen enriched combustion method. Taking the volume of the flue gas for injection as 100%, the flue gas for injection contains 60% - 80% carbon dioxide, 6.1% - 26.1% nitrogen, and 4.7% - 13.9% oxygen, but the present invention is not limited thereto.

[0024] It should be noted that compared with the flue gas generated by burning glass raw materials by the air combustion method, the flue gas generated by burning glass raw materials by the methane-oxygen enriched combustion method has a relatively high volume ratio of carbon dioxide, so it is more suitable as the flue gas for injection in the carbon dioxide capture step S110.

[0025] In the calcium carbonate formation step S120, calcium hydroxide powder is added to the first solution to form a second solution, and the second solution contains calcium carbonate powder formed by the reaction between the carbonate and the calcium hydroxide powder. After the calcium carbonate formation step S120, the calcium carbonate powder can be filtered and separated.

[0026] Furthermore, in the calcium carbonate formation step S120 of this embodiment, the second solution further contains sodium hydroxide formed by the reaction of the carbonate and the calcium hydroxide powder, and the sodium hydroxide is recycled and used as the alkaline aqueous solution in the carbon dioxide capture step S110.

[0027] Furthermore, exhaust gas is generated in the calcium carbonate formation step S120. Specifically, the calcium carbonate formation step S120 may be carried out in a second reactor (not shown), and the exhaust gas may be the gas discharged from the second reactor after the calcium carbonate formation step S120. The second reactor may be, for example, another supergravity device, but the present invention is not limited thereto. Taking the volume of the exhaust gas as 100%, the exhaust gas contains 5% to 8% carbon dioxide, 88% to 93% nitrogen, and 2% to 4% oxygen.

[0028] In the calcium carbonate formation step S120 of this embodiment, the pH of the second solution is controlled to 12-14, but the present invention is not limited thereto.

[0029] The method for converting flue gas to calcium carbonate provides a carbon dioxide recovery rate of 80% or more, and the carbon dioxide recovery rate is defined as the difference between the carbon dioxide content in the injected flue gas and the carbon dioxide content in the exhaust gas divided by the carbon dioxide content in the injected flue gas. Preferably, the carbon dioxide recovery rate provided by the method for converting flue gas to calcium carbonate is 86.66% to 93.75%.

[0030] [Second Embodiment] Referring to Figure 2, which is a flowchart of a method for converting flue gas to calcium carbonate according to the second embodiment of the present invention. Since the second embodiment of the present invention is similar to the first embodiment, the common points between the two embodiments will not be described redundantly here, and the differences between the two embodiments will be described below.

[0031] In this embodiment, the method for converting the flue gas to calcium carbonate after the carbon dioxide capture step S110 and before the calcium carbonate formation step S120 further includes a pH value measurement step S111 for measuring the pH value of the first solution, and when the pH value of the first solution becomes 11 to 12, the calcium carbonate formation step S120 is started.

[0032] The pH value measurement step S111 allows the carbon dioxide in the injection flue gas to react completely with the alkaline aqueous solution. After the pH value measurement step S111, the first solution is transported from the first reactor to the second reactor to perform the calcium carbonate formation step S120.

[0033] [Third Embodiment] Referring to Figure 3, Figure 3 is a flowchart of a method for converting flue gas to calcium carbonate according to the third embodiment of the present invention. Since the third embodiment of the present invention is similar to the first embodiment, the commonalities between the two embodiments will not be described redundantly here, and the differences between the two embodiments will be described below. The method for converting flue gas to calcium carbonate further includes a preparation step S101, an acid removal step S102, and a cooling / water removal step S103 prior to the carbon dioxide capture step S110.

[0034] In the preparation step S101, flue gas is collected from the methane-oxygen enriched combustion of glass raw materials in a glass melting furnace. The flue gas contains carbon dioxide, nitrogen, water vapor, oxygen, hydrofluoric acid compounds, and boric acid compounds. Preferably, in the preparation step S101, with the volume of the flue gas being 100%, the carbon dioxide content is 30% to 34%, the nitrogen content is 1% to 5%, the water vapor content is 58% to 62%, and the oxygen content is 2% to 6%.

[0035] The hydrofluoric acid compound may be an acidic component such as HF, and the boric acid compound may be an acidic component such as H3BO3, HBO2, B2O3, or BF3, but the present invention is not limited to the specific components of the hydrofluoric acid compound and the boric acid compound. It should be noted that the hydrofluoric acid compound and the boric acid compound are produced by burning glass raw materials.

[0036] In the preparation step S101 according to this embodiment, 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; however, the present invention is not limited thereto.

[0037] In the acid removal step S102, 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. In this embodiment, the weight percentage concentration of the aqueous sodium hydroxide solution is 2% to 4%, but the present invention is not limited thereto. Furthermore, the aqueous sodium hydroxide solution in the acid removal step S102 may be the same as or different from the alkaline aqueous solution in the carbon dioxide capture step S110, but the present invention is not limited thereto.

[0038] Preferably, in the acid removal step S102, a second acid removal operation is further performed on the flue gas, in which hydrofluoric acid compounds and boric acid compounds in the flue gas are removed with sodium bicarbonate powder. The first and second acid removal operations are carried out in a semi-dry acid removal tower (not shown) and a dry acid removal unit (not shown), respectively, but the present invention is not limited thereto.

[0039] In the cooling and dewatering step S103, 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. The cooling and dewatering step S103 may be performed by a cooling and dewatering unit (not shown), but the present invention is not limited thereto. After the cooling and dewatering step S103, the flue gas is used as the injection flue gas in the carbon dioxide capture step S110.

[0040] Specifically, after the flue gas is cooled, the water vapor in the flue gas can be removed by condensation into water, thereby reducing the water vapor content in the flue gas. After the cooling and water removal process S103, with the volume of the injected flue gas set to 100%, the injected flue gas contains 60% to 80% carbon dioxide, 6.1% to 26.1% nitrogen, and 4.7% to 13.9% oxygen.

[0041] [Advantageous effects of the embodiment] One advantageous effect of the present invention is that the method for converting flue gas to calcium carbonate according to the present invention has technical features such as "a carbon dioxide capture step of introducing the injection flue gas into an alkaline aqueous solution to form the first solution" and "a calcium carbonate formation step of adding calcium hydroxide powder to the first solution to form the second solution, the second solution containing calcium carbonate powder formed by the reaction of the carbonate and the calcium hydroxide powder," which effectively improves upon the fact that existing flue gas treatment methods cannot effectively treat flue gas and make it difficult to recycle and reuse carbon dioxide in flue gas.

[0042] The information disclosed herein represents only preferred and feasible embodiments of the present invention, and the claims of the present invention are not limited thereto. Therefore, all equivalent technical modifications made using the information in the specification and drawings of the present invention are included within the scope of the claims of the present invention. [Explanation of symbols]

[0043] S101 Preparation process S102 Acid removal process S103 Cooling / water removal process S110 Carbon Dioxide Capture Process S111 pH value measurement process S120 Calcium carbonate formation process

Claims

1. A carbon dioxide capture step comprising introducing an injection flue gas into an alkaline aqueous solution, which is an aqueous solution of sodium hydroxide, to form a first solution, wherein the injection flue gas, with a volume of 100%, contains 10% to 80% carbon dioxide, 6.1% to 88% nitrogen, and 0.7% to 13.9% oxygen, and the first solution contains a carbonate, which is at least one of sodium carbonate and sodium bicarbonate. A method for converting flue gas to calcium carbonate, comprising a calcium carbonate formation step of adding calcium hydroxide powder to the first solution to form a second solution, wherein the second solution contains calcium carbonate powder formed by the reaction of the carbonate and the calcium hydroxide powder.

2. The method for converting flue gas to calcium carbonate according to claim 1, wherein in the carbon dioxide capture step, the volume of the injected flue gas is set to 100%, and the injected flue gas contains 60% to 80% carbon dioxide, 6.1% to 26.1% nitrogen, and 4.7% to 13.9% oxygen.

3. The method for converting flue gas to calcium carbonate further includes a pH value measurement step of measuring the pH value of the first solution after the carbon dioxide capture step and before the calcium carbonate formation step, and the calcium carbonate formation step is started when the pH value of the first solution becomes 11 to 12, as described in claim 1.

4. The method for converting flue gas to calcium carbonate according to claim 1, wherein in the calcium carbonate formation step, the second solution further comprises sodium hydroxide formed by the reaction of the carbonate and the calcium hydroxide powder, the sodium hydroxide being recyclable and used as the alkaline aqueous solution in the carbon dioxide capture step.

5. The method for converting flue gas to calcium carbonate according to claim 1, wherein in the calcium carbonate formation step, the pH of the second solution is controlled to 12 to 14.

6. The method for converting flue gas to calcium carbonate according to claim 1, wherein in the calcium carbonate formation step, exhaust gas is further generated, and with the volume of the exhaust gas as 100%, the exhaust gas contains 5% to 8% carbon dioxide, 88% to 93% nitrogen, and 2% to 4% oxygen.

7. The method for converting flue gas to calcium carbonate according to claim 6, wherein the method provides a carbon dioxide recovery rate of 80% or more, and the carbon dioxide recovery rate is defined as the difference between the carbon dioxide content in the injected flue gas and the carbon dioxide content in the exhaust gas divided by the carbon dioxide content in the injected flue gas.

8. The method for converting the flue gas to calcium carbonate is, before the carbon dioxide capture step, A preparatory step for collecting flue gas from methane-oxygen enriched combustion of glass raw materials in a glass melting furnace, wherein the flue gas contains carbon dioxide, nitrogen, water vapor, oxygen, hydrofluoric acid compounds, and boric acid compounds. An acid removal step comprising performing a first acid removal operation on the flue gas, wherein the first acid removal operation involves removing hydrofluoric acid compounds and boric acid compounds in the flue gas with an aqueous sodium hydroxide solution, The method further includes a cooling and dewatering step that reduces the temperature of the flue gas to 20°C to 40°C and reduces the water vapor content in the flue gas. The method for converting flue gas to calcium carbonate according to claim 1, wherein the flue gas after the cooling and water removal step is used as the injection flue gas in the carbon dioxide capture step.

9. The method for converting flue gas to calcium carbonate according to claim 8, wherein the acid removal step further involves performing a second acid removal operation in which hydrofluoric acid compounds and boric acid compounds in the flue gas are removed with sodium bicarbonate powder.

10. The method for converting flue gas to calcium carbonate according to claim 8, wherein in the preparation step, with the volume of the flue gas being 100%, the carbon dioxide content is 30% to 34%, the nitrogen content is 1% to 5%, the water vapor content is 58% to 62%, and the oxygen content is 2% to 6%.

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