Method for enriching carbon dioxide, comprehensively utilizing carbon dioxide and co-producing chemical aluminum oxide

Abstract

The invention relates to the technical field of resource recovery, in particular to a method for enriching carbon dioxide and comprehensively utilizing and co-producing chemical aluminum oxide, which is used for solving the problems of high cost and large energy consumption in the traditional red mud treatment method, and more impurities, low purity and low economic value in the recovered chemical aluminum oxide. According to the method, carbon dioxide waste gas discharged from lime kilns, chemical plants, power plants and various kilns is enriched to serve as reaction gas, comprehensive resource utilization of the carbon dioxide waste gas is achieved, meanwhile, comprehensive resource utilization of red mud solid waste is achieved, environmental pollution is reduced, and under the effect of the recycled synergist, the carbon dioxide waste gas is recycled. The recycled chemical aluminum oxide is few in impurity, high in purity and high in economic value, green transformation and sustainable development of the aluminum oxide production industry are promoted, and the method has important significance in promoting circular economy and ecological civilization construction.

Description

Technical Field

[0001] The invention relates to the technical field of resource recovery, and in particular to a method for enriching carbon dioxide, comprehensively utilizing it and co-producing the chemical alumina. Background Art

[0002] With the development of modern aluminum industry, the scale of alumina industrial production is expanding day by day, and the industrial solid waste (red mud) generated in the process of preparing alumina is also increasing. Red mud contains a large amount of unextracted alumina. Direct open-air storage of red mud not only causes serious environmental pollution, but also is a huge waste of precious resources. The traditional method of treating red mud has high cost and high energy consumption, and the chemical alumina recovered contains many impurities, low purity, and low economic value. At the same time, industrial carbon dioxide waste gas is also one of the important problems of current environmental governance. Therefore, it is of great environmental and economic value to develop a method that can effectively recover chemical alumina in red mud and utilize the enriched carbon dioxide of carbon dioxide waste gas to comprehensively utilize and co-produce chemical alumina. Summary of the invention

[0003] In order to overcome the above-mentioned technical problems, the purpose of the present invention is to provide a method for enriching carbon dioxide for comprehensive utilization and co-production of chemical alumina: by uniformly mixing red mud, calcium oxide, a recovery enhancer and clean water, then adding them into a ball mill for ball milling to obtain a mixed slurry, then introducing a carbon dioxide-containing gas while stirring for a stirring reaction, cooling the reaction product after the reaction is completed, then vacuum filtering, drying the filter cake to obtain an aluminum hydroxide precipitate, and then calcining the aluminum hydroxide precipitate to obtain chemical alumina, thereby solving the problems of high cost and high energy consumption in traditional methods for treating red mud, and the recovered chemical alumina having many impurities, low purity and low economic value.

[0004] The purpose of the present invention can be achieved by the following technical solutions:

[0005] A method for enriching carbon dioxide and comprehensively utilizing it to co-produce chemical alumina comprises the following steps:

[0006] Step 1: Weigh 100-110 parts of red mud, 30-50 parts of calcium oxide, 1.8-5.6 parts of recovery synergist and 400-500 parts of clean water according to weight and set aside;

[0007] Step 2: Mix red mud, calcium oxide, recovery synergist and clean water evenly, then add them into a ball mill, and mill for 3-5 hours at a ball-to-material ratio of 3-4:1 and a rotation speed of 300-400r / min to obtain a mixed slurry;

[0008] Step 3: stirring and introducing carbon dioxide-containing gas for a stirring reaction for 1-5 hours at a temperature of 35-55° C. and a stirring rate of 300-400 r / min. After the reaction is completed, the reaction product is cooled to room temperature, and then vacuum filtered. The filter cake is placed in a vacuum drying oven and dried at a temperature of 110-120° C. for 3-5 hours to obtain an aluminum hydroxide precipitate;

[0009] Step 4: Place the aluminum hydroxide precipitate in a muffle furnace, and then calcine it at a temperature of 960-1000°C for 1-2 hours to obtain chemical aluminum oxide.

[0010] As a further solution of the present invention: the main components of the red mud in step 1 are as follows:

[0011] Al2O3 24.18wt%, SiO2 19.06wt%, CaO 12.92wt%, Na2O 8.49wt%, K2O 0.51wt%, MgO 0.66wt%, Fe2O3 17.05wt%, LOI 11.36wt%, others 5.77wt%.

[0012] As a further solution of the present invention: the introduction rate of the carbon dioxide-containing gas in step three is 0.6-1 L / min.

[0013] As a further solution of the present invention: the volume fraction of carbon dioxide in the carbon dioxide-containing gas in step three is 20-50%.

[0014] As a further solution of the present invention: the recovery synergist is prepared by the following steps:

[0015] Step s1: pentaerythritol, sodium hydroxide and anhydrous tetrahydrofuran are added to a four-necked flask equipped with a stirrer, a thermometer, an air guide tube, a reflux condenser and a constant pressure dropping funnel, and nitrogen is introduced for protection. The mixture is stirred for reaction at a temperature of 25-30° C. and a stirring rate of 300-400 r / min for 25-35 min. Then, the temperature is raised to reflux and allyl bromide is added dropwise while stirring. The dropping rate is controlled to 1-2 drops / s. After the dropwise addition is completed, the stirring reaction is continued for 10-15 h. After the reaction is completed, the reaction product is cooled to room temperature, and then the solvent is removed by rotary evaporation to obtain intermediate 1;

[0016] Step s2: 1,3-propanedithiol, maleic acid and toluene are added to a three-necked flask equipped with a stirrer and a thermometer, and stirred for reaction at a temperature of 25-30° C. and a stirring rate of 300-400 r / min for 25-35 min, and then the temperature is raised to 70-75° C. and the stirring reaction is continued for 4-5 h. After the reaction is completed, the reaction product is cooled to room temperature, and then added to anhydrous ether to precipitate, and vacuum filtered. The filter cake is placed in a vacuum drying oven and dried at a temperature of 50-55° C. for 2-3 h to obtain intermediate 2;

[0017] Step s3: Add intermediate 1, intermediate 2 and toluene to a three-necked flask equipped with a stirrer, a thermometer, an air duct and a reflux condenser, stir the reaction at a temperature of 25-30°C and a stirring rate of 300-400r / min for 10-20min, then raise the temperature to reflux and continue stirring the reaction for 8-10h. After the reaction is completed, cool the reaction product to room temperature, then add it to anhydrous ether, precipitate, vacuum filter, place the filter cake in a vacuum drying oven, and dry it at a temperature of 50-55°C for 3-5h to obtain a recovered synergist.

[0018] As a further solution of the present invention: the usage ratio of the pentaerythritol, sodium hydroxide, anhydrous tetrahydrofuran and allyl bromide in step s1 is 10 mmol:45-50 mmol:60-70 mL:41-45 mmol.

[0019] As a further solution of the present invention: the usage ratio of the 1,3-propanedithiol, maleic acid and toluene in step s2 is 10 mmol:10 mmol:30-40 mL.

[0020] As a further solution of the present invention: the usage ratio of the intermediate 1, intermediate 2 and toluene in step s3 is 10 mmol:44-48 mmol:80-100 mL.

[0021] Beneficial effects of the present invention:

[0022] The present invention discloses a method for enriching carbon dioxide for comprehensive utilization and co-producing chemical alumina, which comprises the following steps: uniformly mixing red mud, calcium oxide, a recovery enhancer and clean water, adding the mixture into a ball mill for ball milling to obtain a mixed slurry, introducing a carbon dioxide-containing gas while stirring for a stirring reaction, cooling the reaction product after the reaction is completed, vacuum filtering, drying the filter cake to obtain an aluminum hydroxide precipitate, and then roasting the aluminum hydroxide precipitate to obtain a chemical alumina. The present invention utilizes the enriched carbon dioxide waste gas discharged from lime kilns, chemical plants, power plants and various furnaces as a reaction gas, thereby realizing the comprehensive resource utilization of the carbon dioxide waste gas, and at the same time realizing the comprehensive resource utilization of red mud solid waste, reducing environmental pollution, and the recovered chemical alumina has high economic value, which is helpful to promote the green transformation and sustainable development of the alumina production industry, and is of great significance to promoting the construction of a circular economy and ecological civilization.

[0023] In the process of co-producing chemical alumina, a recovery enhancer is first prepared. First, pentaerythritol and allyl bromide react, and the alcoholic hydroxyl group on pentaerythritol reacts with the bromine atom on allyl bromide to introduce an olefinic group to obtain intermediate 1. Then, 1,3-propanedithiol and maleic acid react, and 1,3-propanedithiol and maleic acid react, and a thiol group on 1,3-propanedithiol reacts with an olefinic group on maleic acid to form an intermediate 2 containing a thiol group and two carboxyl groups. Finally, intermediate 1 and intermediate 2 react, and the olefinic group on intermediate 1 reacts with the thiol group on intermediate 2. A click chemical reaction is carried out to obtain a recovery enhancer; the molecular structure of the recovery enhancer contains a large number of carboxyl groups, which can exist in the form of electric charge in the solution, adsorb on the particle surface of red mud, calcium oxide and the generated precipitate through electrostatic effect, and disperse the particles through steric effect, effectively preventing aggregation between particles, thereby improving the fineness of the two reactions of red mud and calcium oxide, allowing them to fully react with carbon dioxide gas, and allowing impurities to be fully dispersed in water, so that the generated precipitate has high purity and few impurities, and the recovery efficiency and effect of the chemical aluminum oxide are high, and it has a high market value. DETAILED DESCRIPTION

[0024] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Embodiment 1:

[0026] This embodiment is a method for enriching carbon dioxide and comprehensively utilizing it to produce chemical alumina, comprising the following steps:

[0027] Step A1: 10 mmol pentaerythritol, 45 mmol sodium hydroxide and 60 mL anhydrous tetrahydrofuran were added to a four-necked flask equipped with a stirrer, a thermometer, a gas guide tube, a reflux condenser and a constant pressure dropping funnel, and nitrogen was introduced for protection. The mixture was stirred for reaction at a temperature of 25° C. and a stirring rate of 300 r / min for 25 min. Then, 41 mmol allyl bromide was added dropwise while stirring under reflux conditions, and the dropping rate was controlled to be 1 drop / s. After the addition was completed, the stirring reaction was continued for 10 h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation to obtain intermediate 1;

[0028] Step A2: 10 mmol of 1,3-propanedithiol, 10 mmol of maleic acid and 30 mL of toluene were added to a three-necked flask equipped with a stirrer and a thermometer, and the mixture was stirred at 25°C and a stirring rate of 300 r / min for 25 min, and then the mixture was heated to 70°C and stirred for 4 h. After the reaction, the reaction product was cooled to room temperature and then added to anhydrous ether to precipitate the precipitate, and vacuum filtered. The filter cake was placed in a vacuum drying oven and dried at 50°C for 2 h to obtain intermediate 2;

[0029] Step A3: 10 mmol of intermediate 1, 44 mmol of intermediate 2 and 80 mL of toluene were added to a three-necked flask equipped with a stirrer, a thermometer, a gas duct and a reflux condenser, and stirred for 10 min at a temperature of 25 ° C and a stirring rate of 300 r / min, and then the temperature was raised to reflux and the stirring reaction was continued for 8 h. After the reaction was completed, the reaction product was cooled to room temperature, and then added to anhydrous ether to precipitate, vacuum filtered, and the filter cake was placed in a vacuum drying oven and dried at a temperature of 50 ° C for 3 h to obtain a recovered synergist;

[0030] Step A4: 100 parts of red mud, 30 parts of calcium oxide, 1.8 parts of recovery synergist and 400 parts of clean water are weighed according to weight for standby use; the main components of the red mud are as follows: Al2O3 24.18wt%, SiO2 19.06wt%, CaO 12.92wt%, Na2O 8.49wt%, K2O 0.51wt%, MgO 0.66wt%, Fe2O3 17.05wt%, LOI 11.36wt%, and others 5.77wt%;

[0031] Step A5: red mud, calcium oxide, recovery synergist and clean water are mixed evenly, and then added into a ball mill, and ball milled for 3 hours at a ball-to-material ratio of 3:1 and a rotation speed of 300 r / min to obtain a mixed slurry;

[0032] Step A6: introducing a carbon dioxide-containing gas having a carbon dioxide volume fraction of 20% under stirring at a temperature of 35° C. and a stirring rate of 300 r / min for stirring reaction for 1 h, controlling the introduction rate of the carbon dioxide-containing gas to be 0.6 L / min. After the reaction is completed, the reaction product is cooled to room temperature, and then vacuum filtered. The filter cake is placed in a vacuum drying oven and dried at a temperature of 110° C. for 3 h to obtain an aluminum hydroxide precipitate;

[0033] Step A7: The aluminum hydroxide precipitate is placed in a muffle furnace, and then calcined at 960° C. for 1 hour to obtain chemical aluminum oxide.

[0034] Embodiment 2:

[0035] This embodiment is a method for enriching carbon dioxide and comprehensively utilizing it to produce chemical alumina, comprising the following steps:

[0036] Step A1: 10 mmol pentaerythritol, 48 mmol sodium hydroxide and 65 mL anhydrous tetrahydrofuran were added to a four-necked flask equipped with a stirrer, a thermometer, a gas guide tube, a reflux condenser and a constant pressure dropping funnel, and nitrogen was introduced for protection. The mixture was stirred for reaction at 28° C. and a stirring rate of 350 r / min for 30 min. Then, 43 mmol allyl bromide was added dropwise while stirring under reflux conditions, and the dropping rate was controlled to be 1 drop / s. After the addition was completed, the stirring reaction was continued for 12 h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation to obtain intermediate 1;

[0037] Step A2: 10 mmol of 1,3-propanedithiol, 10 mmol of maleic acid and 35 mL of toluene were added to a three-necked flask equipped with a stirrer and a thermometer, and stirred for reaction at 28°C and a stirring rate of 350 r / min for 30 min, then heated to 72°C and continued to stir for 4.5 h. After the reaction was completed, the reaction product was cooled to room temperature, then added to anhydrous ether, precipitated, vacuum filtered, and the filter cake was placed in a vacuum drying oven and dried at 52°C for 2.5 h to obtain intermediate 2;

[0038] Step A3: 10 mmol of intermediate 1, 46 mmol of intermediate 2 and 90 mL of toluene were added to a three-necked flask equipped with a stirrer, a thermometer, a gas duct and a reflux condenser, and stirred for reaction at a temperature of 28 ° C. and a stirring rate of 350 r / min for 15 min, then heated to reflux and continued to stir for 9 h. After the reaction, the reaction product was cooled to room temperature, then added to anhydrous ether, precipitated, vacuum filtered, and the filter cake was placed in a vacuum drying oven and dried at a temperature of 52 ° C. for 4 h to obtain a recovered synergist;

[0039] Step A4: 105 parts of red mud, 40 parts of calcium oxide, 3.7 parts of recovery synergist and 450 parts of clean water were weighed according to weight and set aside; the main components of the red mud are as follows: Al2O3 24.18wt%, SiO2 19.06wt%, CaO 12.92wt%, Na2O 8.49wt%, K2O 0.51wt%, MgO 0.66wt%, Fe2O3 17.05wt%, LOI 11.36wt%, and others 5.77wt%;

[0040] Step A5: red mud, calcium oxide, recovery synergist and clean water are mixed evenly, and then added into a ball mill, and ball milled for 4 hours at a ball-to-material ratio of 3.5:1 and a rotation speed of 350 r / min to obtain a mixed slurry;

[0041] Step A6: introducing a carbon dioxide-containing gas having a carbon dioxide volume fraction of 35% under stirring at a temperature of 45° C. and a stirring rate of 350 r / min for stirring reaction for 3 h, controlling the introduction rate of the carbon dioxide-containing gas to be 0.8 L / min. After the reaction is completed, the reaction product is cooled to room temperature, and then vacuum filtered. The filter cake is placed in a vacuum drying oven and dried at a temperature of 115° C. for 4 h to obtain an aluminum hydroxide precipitate;

[0042] Step A7: The aluminum hydroxide precipitate is placed in a muffle furnace, and then calcined at 980° C. for 1.5 h to obtain chemical aluminum oxide.

[0043] Embodiment 3:

[0044] This embodiment is a method for enriching carbon dioxide and comprehensively utilizing it to produce chemical alumina, comprising the following steps:

[0045] Step A1: 10 mmol pentaerythritol, 50 mmol sodium hydroxide and 70 mL anhydrous tetrahydrofuran were added to a four-necked flask equipped with a stirrer, a thermometer, a gas guide tube, a reflux condenser and a constant pressure dropping funnel, and nitrogen was introduced for protection. The mixture was stirred for reaction at a temperature of 30° C. and a stirring rate of 400 r / min for 35 min. Then, 45 mmol allyl bromide was added dropwise while stirring under reflux conditions, and the dropping rate was controlled to be 2 drops / s. After the addition was completed, the stirring reaction was continued for 15 h. After the reaction was completed, the reaction product was cooled to room temperature, and then the solvent was removed by rotary evaporation to obtain intermediate 1;

[0046] Step A2: 10 mmol of 1,3-propanedithiol, 10 mmol of maleic acid and 40 mL of toluene were added to a three-necked flask equipped with a stirrer and a thermometer, and the mixture was stirred at 30°C and 400 r / min for 35 min, then the mixture was heated to 75°C and stirred for 5 h. After the reaction, the reaction product was cooled to room temperature, then added to anhydrous ether, precipitated, and vacuum filtered. The filter cake was placed in a vacuum drying oven and dried at 55°C for 3 h to obtain intermediate 2;

[0047] Step A3: 10 mmol of intermediate 1, 48 mmol of intermediate 2 and 100 mL of toluene were added to a three-necked flask equipped with a stirrer, a thermometer, a gas guide tube and a reflux condenser, and stirred for reaction at a temperature of 30° C. and a stirring rate of 400 r / min for 20 min, then heated to reflux and continued to stir for 10 h. After the reaction was completed, the reaction product was cooled to room temperature, then added to anhydrous ether, precipitated, vacuum filtered, and the filter cake was placed in a vacuum drying oven and dried at a temperature of 55° C. for 5 h to obtain a recovered synergist;

[0048] Step A4: 110 parts of red mud, 50 parts of calcium oxide, 5.6 parts of recovery synergist and 500 parts of clean water were weighed according to weight and set aside; the main components of the red mud are as follows: Al2O3 24.18wt%, SiO2 19.06wt%, CaO 12.92wt%, Na2O 8.49wt%, K2O 0.51wt%, MgO 0.66wt%, Fe2O3 17.05wt%, LOI 11.36wt%, and others 5.77wt%;

[0049] Step A5: red mud, calcium oxide, recovery synergist and clean water are mixed evenly, and then added into a ball mill, and ball milled for 5 hours at a ball-to-material ratio of 4:1 and a rotation speed of 400 r / min to obtain a mixed slurry;

[0050] Step A6: introducing a carbon dioxide-containing gas having a carbon dioxide volume fraction of 50% under stirring at a temperature of 55° C. and a stirring rate of 400 r / min for stirring reaction for 5 h, controlling the introduction rate of the carbon dioxide-containing gas to be 1 L / min. After the reaction is completed, the reaction product is cooled to room temperature, and then vacuum filtered, and the filter cake is placed in a vacuum drying oven and dried at a temperature of 120° C. for 5 h to obtain an aluminum hydroxide precipitate;

[0051] Step A7: The aluminum hydroxide precipitate is placed in a muffle furnace, and then calcined at 1000° C. for 2 hours to obtain chemical aluminum oxide.

[0052] Comparative Example 1:

[0053] This comparative example is a method for enriching carbon dioxide and comprehensively utilizing it to produce chemical alumina, comprising the following steps:

[0054] Step A1: 110 parts of red mud, 50 parts of calcium oxide and 500 parts of clean water are weighed according to weight parts for use; the main components of the red mud are as follows: Al2O3 24.18wt%, SiO2 19.06wt%, CaO 12.92wt%, Na2O 8.49wt%, K2O 0.51wt%, MgO 0.66wt%, Fe2O3 17.05wt%, LOI 11.36wt%, and others 5.77wt%;

[0055] Step A2: red mud, calcium oxide and clean water are mixed evenly, and then added into a ball mill, and ball milled for 5 hours at a ball-to-material ratio of 4:1 and a rotation speed of 400 r / min to obtain a mixed slurry;

[0056] Step A3: introducing a carbon dioxide-containing gas having a carbon dioxide volume fraction of 50% under stirring at a temperature of 55° C. and a stirring rate of 400 r / min for stirring reaction for 5 h, controlling the introduction rate of the carbon dioxide-containing gas to be 1 L / min, cooling the reaction product to room temperature after the reaction is completed, and then vacuum filtering, placing the filter cake in a vacuum drying oven, and drying it at a temperature of 120° C. for 5 h to obtain an aluminum hydroxide precipitate;

[0057] Step A4: The aluminum hydroxide precipitate is placed in a muffle furnace, and then calcined at 1000° C. for 2 hours to obtain chemical aluminum oxide.

[0058] Comparative Example 2:

[0059] This comparative example is a method for enriching carbon dioxide and comprehensively utilizing it to produce chemical alumina, comprising the following steps:

[0060] Step A1: 110 parts of red mud, 50 parts of calcium oxide, 5.6 parts of sodium dodecyl sulfate and 500 parts of clean water are weighed according to weight and set aside; the main components of the red mud are as follows: Al2O3 24.18wt%, SiO2 19.06wt%, CaO 12.92wt%, Na2O 8.49wt%, K2O 0.51wt%, MgO 0.66wt%, Fe2O3 17.05wt%, LOI 11.36wt%, and others 5.77wt%;

[0061] Step A2: red mud, calcium oxide, sodium dodecyl sulfate and clean water are mixed evenly, and then added into a ball mill, and ball milled for 5 hours at a ball-to-material ratio of 4:1 and a rotation speed of 400 r / min to obtain a mixed slurry;

[0062] Step A3: introducing a carbon dioxide-containing gas having a carbon dioxide volume fraction of 50% under stirring at a temperature of 55° C. and a stirring rate of 400 r / min for stirring reaction for 5 h, controlling the introduction rate of the carbon dioxide-containing gas to be 1 L / min, cooling the reaction product to room temperature after the reaction is completed, and then vacuum filtering, placing the filter cake in a vacuum drying oven, and drying it at a temperature of 120° C. for 5 h to obtain an aluminum hydroxide precipitate;

[0063] Step A4: The aluminum hydroxide precipitate is placed in a muffle furnace, and then calcined at 1000° C. for 2 hours to obtain chemical aluminum oxide.

[0064] The chemical aluminum oxide of Examples 1-3 and Comparative Examples 1-2 was tested for composition, and the test results are as follows:

[0065] sample <![CDATA[Al2O3,wt%]]> <![CDATA[SiO2,wt%]]> <![CDATA[Na2O,wt%]]> <![CDATA[Fe2O3,wt%]]> CaO, wt% Example 1 98.97 0.061 0.58 0.014 0.14 Example 2 99.09 0.053 0.52 0.017 0.089 Example 3 99.18 0.046 0.51 0.021 0.056 Comparative Example 1 86.52 2.78 2.92 1.09 1.56 Comparative Example 2 94.18 0.75 0.91 1.16 0.88

[0066] Referring to the data in the above table, based on the comparison between Examples 1-3 and Comparative Examples 1-2, it can be seen that adding recovery enhancers and sodium dodecyl sulfate can effectively improve the purity of chemical alumina, and when the recovery enhancer is added, the impurities in the chemical alumina are removed more fully.

[0067] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0068] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A method for enriching carbon dioxide and comprehensively utilizing it to produce chemical alumina, characterized in that: The following steps are involved: Step 1: Weigh 100-110 parts of red mud, 30-50 parts of calcium oxide, 1.8-5.6 parts of recovery synergist and 400-500 parts of clean water according to weight and set aside; Step 2: Mix red mud, calcium oxide, recovery synergist and clean water evenly, then add them into a ball mill, and mill for 3-5 hours at a ball-to-material ratio of 3-4:1 and a rotation speed of 300-400r / min to obtain a mixed slurry; Step 3: stirring and introducing carbon dioxide-containing gas for a stirring reaction for 1-5 hours at a temperature of 35-55° C. and a stirring rate of 300-400 r / min. After the reaction is completed, the reaction product is cooled to room temperature, and then vacuum filtered. The filter cake is placed in a vacuum drying oven and dried at a temperature of 110-120° C. for 3-5 hours to obtain an aluminum hydroxide precipitate; Step 4: Place the aluminum hydroxide precipitate in a muffle furnace, and then calcine it at a temperature of 960-1000°C for 1-2 hours to obtain chemical aluminum oxide.

2. The method for enriching carbon dioxide and comprehensively utilizing it to produce chemical alumina according to claim 1, characterized in that: The main components of the red mud in step 1 are as follows: Al2O3 24.18wt%, SiO2 19.06wt%, CaO 12.92wt%, Na2O 8.49wt%, K2O 0.51wt%, MgO 0.66wt%, Fe2O3 17.05wt%, LOI 11.36wt%, others 5.77wt%.

3. The method for enriching carbon dioxide and comprehensively utilizing it to produce chemical alumina according to claim 1, characterized in that: The carbon dioxide-containing gas introduction rate in step 3 is 0.6-1 L / min.

4. The method for enriching carbon dioxide and comprehensively utilizing it to co-produce chemical alumina according to claim 1, characterized in that: The volume fraction of carbon dioxide in the carbon dioxide-containing gas in step three is 20-50%.

5. The method for enriching carbon dioxide and comprehensively utilizing it to co-produce chemical alumina according to claim 1, characterized in that: The recovery synergist is prepared by the following steps: Step s1: pentaerythritol, sodium hydroxide and anhydrous tetrahydrofuran are added to a four-necked flask equipped with a stirrer, a thermometer, an air guide tube, a reflux condenser and a constant pressure dropping funnel, and nitrogen is introduced for protection. The mixture is stirred for reaction at a temperature of 25-30° C. and a stirring rate of 300-400 r / min for 25-35 min. Then, the temperature is raised to reflux and allyl bromide is added dropwise while stirring. The dropping rate is controlled to 1-2 drops / s. After the dropwise addition is completed, the stirring reaction is continued for 10-15 h. After the reaction is completed, the reaction product is cooled to room temperature, and then the solvent is removed by rotary evaporation to obtain intermediate 1; Step s2: 1,3-propanedithiol, maleic acid and toluene are added to a three-necked flask equipped with a stirrer and a thermometer, and stirred for reaction at a temperature of 25-30° C. and a stirring rate of 300-400 r / min for 25-35 min, and then the temperature is raised to 70-75° C. and the stirring reaction is continued for 4-5 h. After the reaction is completed, the reaction product is cooled to room temperature, and then added to anhydrous ether to precipitate, and vacuum filtered. The filter cake is placed in a vacuum drying oven and dried at a temperature of 50-55° C. for 2-3 h to obtain intermediate 2; Step s3: Add intermediate 1, intermediate 2 and toluene to a three-necked flask equipped with a stirrer, a thermometer, an air duct and a reflux condenser, stir the reaction at a temperature of 25-30°C and a stirring rate of 300-400r / min for 10-20min, then raise the temperature to reflux and continue stirring the reaction for 8-10h. After the reaction is completed, cool the reaction product to room temperature, then add it to anhydrous ether, precipitate, vacuum filter, place the filter cake in a vacuum drying oven, and dry it at a temperature of 50-55°C for 3-5h to obtain a recovered synergist.

6. The method for enriching carbon dioxide and comprehensively utilizing it to co-produce chemical alumina according to claim 5, characterized in that: The usage ratio of the pentaerythritol, sodium hydroxide, anhydrous tetrahydrofuran and allyl bromide in step s1 is 10 mmol: 45-50 mmol: 60-70 mL: 41-45 mmol.

7. The method for enriching carbon dioxide and comprehensively utilizing it to co-produce chemical alumina according to claim 5, characterized in that: The usage ratio of the 1,3-propanedithiol, maleic acid and toluene in step s2 is 10 mmol:10 mmol:30-40 mL.

8. The method for enriching carbon dioxide and comprehensively utilizing it to co-produce chemical alumina according to claim 5, characterized in that: The usage ratio of the intermediate 1, intermediate 2 and toluene in step s3 is 10mmol:44-48mmol:80-100mL.