Method for absorbing carbon dioxide in industrial flue gas by adopting red mud

Abstract

The invention discloses a method for absorbing carbon dioxide in industrial flue gas by using red mud, and belongs to the technical field of carbon dioxide. The reaction rate is enhanced through microorganism in-situ enzyme production, the enzyme activity stability is improved through oxygen regulation and control, and meanwhile harmless and high-value utilization of the red mud is achieved.

Description

Technical Field

[0001] This invention belongs to the field of carbon dioxide technology, specifically relating to a method for absorbing carbon dioxide from industrial flue gas using red mud. Background Technology

[0002] Red mud is an industrial solid waste generated during the alumina production process. Due to its high alkali content (pH value of 11.0-12.0), its utilization has become a global problem. Currently, the amount of red mud discharged is approximately 100 million tons, while the resource utilization rate is less than 5%. The current disposal method is mainly damming and stockpiling, which not only occupies a large amount of land, but also the filtrate from red mud stockpiles is prone to seepage, polluting farmland soil, surface water, and groundwater. Therefore, the harmless treatment and comprehensive utilization of red mud is urgently needed.

[0003] Extensive research has been conducted both domestically and internationally on the direct use of red mud in cement, building materials, microcrystalline glass, geopolymers, and catalysts. Red mud also has some applications in environmental protection, such as adsorbing pollutants and neutralizing acidic waste. This application focuses on solving the problem of red mud adsorbing and neutralizing carbon dioxide in industrial flue gas. Early patent applications (such as CN110655342A) focused on carbon fixation efficiency, activating the inert mineral phases (such as calcium silicate) in red mud through high-temperature roasting (>800℃) to enhance its CO2 absorption activity. However, this method has drawbacks such as high energy consumption (requiring high temperature and ball milling), multiple steps (roasting-ball milling-hydrothermal-drying), and the product being ordinary carbonates. Subsequent patents have gradually shifted towards high-value products and resource recycling. For example, Chinese patent application CN113800792A employs a low-temperature, low-pressure reaction, utilizing mechanochemical activation or microbial catalysis to convert carbon fixation products into magnetic adsorbents or catalyst supports. This reduces the energy consumption required for red mud carbon fixation, avoids high-temperature steps, and focuses more on the added value of the products. However, this approach is limited by the reaction rate between red mud and carbon dioxide, resulting in low carbon fixation efficiency. Chinese patent CN115417409B utilizes organic amine regeneration coupling technology, reacting CO2-rich liquor with red mud to simultaneously achieve organic amine regeneration and red mud dealkalization. The carbonation reaction is completed at room temperature or medium temperature (30-100℃), avoiding high-temperature energy consumption, simplifying the process, and co-producing high-value chemicals such as sodium carbonate. However, it requires multi-industry collaboration and lacks broad applicability.

[0004] In summary, existing technologies suffer from drawbacks such as low carbon sequestration efficiency, low utilization rate of red mud resources, high equipment requirements, and low economic benefits. Therefore, developing a red mud carbon sequestration method that conforms to the concept of "treating waste with waste," has low energy consumption, and is widely applicable is of great practical significance. Summary of the Invention

[0005] The aforementioned red mud carbon fixation methods suffer from low carbon fixation efficiency, low red mud resource utilization rate, high equipment requirements, and low economic benefits. The purpose of this invention is to provide a method for absorbing carbon dioxide from industrial flue gas using red mud. This method enhances the reaction rate by producing enzymes in situ through microorganisms and couples oxygen regulation to improve enzyme activity stability, thereby achieving both the harmlessness and high-value utilization of red mud.

[0006] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0007] On one hand, the present invention provides a method for absorbing carbon dioxide from industrial flue gas using red mud, comprising the following steps:

[0008] (1) Red mud pretreatment: crush the red mud particles to a particle size ≤100μm and adjust the moisture content to 20-40%;

[0009] (2) Microbial inoculation and cultivation: Inoculate the pretreated red mud with a microbial agent that produces carbonic anhydrase and cultivate it at 25-37℃ and pH 7.5-8.5 to make the concentration of microbial enzyme production 50-200 U / g red mud;

[0010] (3) Carbon fixation reaction: The red mud-microorganism mixture obtained in step (2) is placed in a closed reactor, and industrial flue gas containing carbon dioxide is introduced. The reaction temperature is controlled at 30-45℃ to carry out the carbon fixation reaction.

[0011] (4) Product separation: After solid-liquid separation, the solid product is carbonate-stabilized red mud, and the liquid is reused in step (2) as a microbial culture medium.

[0012] Furthermore, in step (1), the red mud is crushed to a particle size ≤100μm and the moisture content is adjusted to 20-40% to increase the specific surface area and mass transfer efficiency.

[0013] Further, in step (2), the microorganism is selected from at least one of Microbacterium oxysporum, Bacillus spp. or engineered Escherichia coli.

[0014] Furthermore, in step (2), the concentration of the enzyme produced by the microorganism is 100-200 U / g red mud.

[0015] Furthermore, in step (2), the inoculum culture time is 12-48 hours.

[0016] Further, in step (2), the microbial agent is a mixed microbial community of Microbacillus oxidans and Bacillus spp., with a mass ratio of 1:2 to 2:1, and the inoculation amount of the agent is 1-5% of the dry weight of the red mud.

[0017] This invention utilizes a synergistic effect of microorganisms and enzyme catalysis, by screening highly active enzyme-producing strains to directly utilize metal ions (Fe) in red mud. 3+ Al 3+ As an enzyme-catalyzed reaction cofactor, it breaks through the limitations of traditional chemical methods that rely on high temperature / strong acid.

[0018] Further, in step (3), the volume fraction of oxygen in the industrial flue gas is 5-15%; or oxygen is added to the reactor until the dissolved oxygen concentration is ≥3 mg / L.

[0019] Furthermore, in step (3), the reactor is an airlift bioreactor, where carbon dioxide is dispersed through a microporous aeration device with a bubble diameter ≤0.5 mm and a gas-liquid contact area ≥200 m². 2 / m 3 .

[0020] Furthermore, the red mud is red mud produced by the Bayer process.

[0021] The method of this invention significantly enhances microbial activity by supplementing oxygen, thereby achieving long-term maintenance of enzyme activity and synergistic optimization of CO2 absorption rate.

[0022] Furthermore, in step (4), after solid-liquid separation, the carbonate-stabilized red mud can be directly used for building materials or safe landfill, and the liquid is recycled to the microbial culture step to form a closed loop.

[0023] Using the method of this invention, the liquid after the reaction can be reused as a culture medium, and the solid product can be safely landfilled or used as a building material raw material, which is in line with the concept of "treating waste with waste".

[0024] The beneficial effects of this invention are as follows: This invention enhances the reaction rate by producing enzymes in situ through microorganisms and improves the stability of enzyme activity by coupling oxygen regulation, breaking through the efficiency bottleneck of chemical methods, and realizing the harmless and high-value utilization of red mud. Specifically, it includes: (1) High carbon fixation efficiency: The method of this invention has a CO2 absorption rate of ≥90%, which is more than 30% higher than the traditional chemical method, and can directly treat high-concentration CO2 flue gas (10-20%), replacing the traditional amine absorption process. (2) Low temperature and energy saving: The reaction temperature of this invention is ≤45℃, no high-temperature activation is required, energy consumption is reduced, liquid is recycled, which meets the carbon neutrality target. (3) High-value products can be obtained, with carbonate purity >85%, which can be processed into industrial-grade calcium carbonate or magnetic adsorption materials, and can also be used in papermaking, plastics, medicine and other fields. (4) Environmental protection: all liquids are recycled, and the heavy metal leaching rate is <0.1 ppm. Detailed Implementation

[0025] For ease of understanding, this application will be described more fully below, and preferred embodiments are given. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this invention. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products available on the market.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0027] The culture medium used in this invention comprises a mixed liquid consisting of glucose, disodium hydrogen phosphate, magnesium sulfate, calcium carbonate, potassium chloride, and water, in a mass ratio of 7:2:0.5:1:0.1:85.

[0028] Example 1

[0029] Red mud pretreatment: Take red mud from an aluminum plant (composition: CaO 15%, Fe2O3 25%, Al2O3 18%), crush it to 80μm, and adjust the moisture content to 30%.

[0030] Microbial inoculation: Microbacterium oxysporum (CGMCC No. 1.123) and Bacillus subtilis (CCTCC AB 2012063) were mixed at a mass ratio of 1:1. The inoculation amount of the microbial agent was 3% of the dry weight of the red mud. The mixture was cultured at 30℃ and pH 8.0 for 24 hours. The carbonic anhydrase activity was measured to be 150 U / g red mud.

[0031] Carbon fixation reaction: The mixture is loaded into an airlift reactor, and industrial flue gas (containing 10% CO2 and 10% O2) is introduced. The temperature is controlled at 35°C, and the reaction is carried out for 5 hours.

[0032] Results: CO2 absorption rate was 92%, CaCO3 purity in solid product was 87%, dissolved oxygen in liquid was 4.2 mg / L, and enzyme activity retention rate was 95%.

[0033] Example 2

[0034] Red mud pretreatment: Take red mud from an aluminum plant (composition: CaO 15%, Fe2O3 25%, Al2O3 18%), crush it to 80μm, and adjust the moisture content to 20%.

[0035] Microbial inoculation: Microbacterium oxysporum (CGMCC No. 1.123) and Bacillus subtilis (CCTCC AB 2012063) were mixed at a mass ratio of 1:2. The inoculation amount was 1% of the dry weight of the red mud. The mixture was cultured at 30℃ and pH 8.0 for 24 hours, and the carbonic anhydrase activity was measured to be 150 U / g red mud.

[0036] Carbon fixation reaction: The mixture is loaded into an airlift reactor, and industrial flue gas (containing 10% CO2 and 10% O2) is introduced. The temperature is controlled at 35°C, and the reaction is carried out for 5 hours.

[0037] Results: CO2 absorption rate was 91%, CaCO3 purity in solid product was 86%, dissolved oxygen in liquid was 4.0 mg / L, and enzyme activity retention rate was 94%.

[0038] Example 3

[0039] Red mud pretreatment: Take red mud from an aluminum plant (composition: CaO 15%, Fe2O3 25%, Al2O3 18%), crush it to 100μm, and adjust the moisture content to 40%.

[0040] Microbial inoculation: Microbacterium oxysporum (CGMCC No. 1.123) and Bacillus subtilis (CCTCC AB 2012063) were mixed at a mass ratio of 2:1. The inoculation amount of the microbial agent was 5% of the dry weight of the red mud. The mixture was cultured at 30℃ and pH 8.0 for 48 hours. The carbonic anhydrase activity was measured to be 100 U / g red mud.

[0041] Carbon fixation reaction: The mixture is loaded into an airlift reactor, and industrial flue gas (containing 10% CO2 and 10% O2) is introduced. The temperature is controlled at 35°C, and the reaction is carried out for 5 hours.

[0042] Results: CO2 absorption rate was 92%, CaCO3 purity in solid product was 86%, dissolved oxygen in liquid was 4.3 mg / L, and enzyme activity retention rate was 96%.

[0043] Example 4

[0044] Red mud pretreatment: Take red mud from an aluminum plant (composition: CaO 15%, Fe2O3 25%, Al2O3 18%), crush it to 80μm, and adjust the moisture content to 20%.

[0045] Microbial inoculation: Engineered Escherichia coli was used for inoculation at a rate of 5% of the dry weight of the red mud. The mixture was incubated at 35°C and pH 7.5 for 24 hours, and the carbonic anhydrase activity was measured to be 200 U / g of red mud.

[0046] Carbon fixation reaction: The mixture is loaded into an airlift reactor, and industrial flue gas (containing 15% CO2 and 5% O2) is introduced. The temperature is controlled at 35°C, and the reaction is carried out for 5 hours.

[0047] Results: CO2 absorption rate was 78%, CaCO3 purity in solid product was 88%, dissolved oxygen in liquid was 4.4 mg / L, and enzyme activity retention rate was 97%.

[0048] Example 5

[0049] Red mud pretreatment: Take red mud from an aluminum plant (composition: CaO 15%, Fe2O3 25%, Al2O3 18%), crush it to 80μm, and adjust the moisture content to 20%.

[0050] Microbial inoculation: Engineered Escherichia coli was used for inoculation at a rate of 5% of the dry weight of the red mud. The mixture was incubated at 35°C and pH 7.5 for 24 hours, and the carbonic anhydrase activity was measured to be 200 U / g of red mud.

[0051] Carbon fixation reaction: The mixture is loaded into an airlift reactor, and industrial flue gas (containing 5% CO2 and 15% O2) is introduced. The temperature is controlled at 35°C, and the reaction is carried out for 5 hours.

[0052] Results: CO2 absorption rate was 91%, CaCO3 purity in solid product was 85%, dissolved oxygen in liquid was 4.0 mg / L, and enzyme activity retention rate was 94%.

[0053] Example 6

[0054] Red mud pretreatment: Take red mud from an aluminum plant (composition: CaO 15%, Fe2O3 25%, Al2O3 18%), crush it to 80μm, and adjust the moisture content to 20%.

[0055] Microbial inoculation: Microbacterium oxygenatum (CGMCC No. 1.123) was used for inoculation. The inoculation amount was 5% of the dry weight of red mud. The mixture was cultured at 35℃ and pH 7.5 for 24 hours. The carbonic anhydrase activity was measured to be 200 U / g red mud.

[0056] Carbon fixation reaction: The mixture is loaded into an airlift reactor, and industrial flue gas (containing 5% CO2 and 15% O2) is introduced. The temperature is controlled at 35°C, and the reaction is carried out for 5 hours.

[0057] Results: CO2 absorption rate was 81%, CaCO3 purity in solid product was 85%, dissolved oxygen in liquid was 4.0 mg / L, and enzyme activity retention rate was 94%.

[0058] Example 7

[0059] Red mud pretreatment: Take red mud from an aluminum plant (composition: CaO 15%, Fe2O3 25%, Al2O3 18%), crush it to 80μm, and adjust the moisture content to 20%.

[0060] Microbial inoculation: Bacillus subtilis (CCTCC AB 2012063) was used for inoculation. The inoculation amount was 2% of the dry weight of the red mud. The mixture was cultured at 35℃ and pH 7.5 for 24 hours. The carbonic anhydrase activity was measured to be 200 U / g red mud.

[0061] Carbon fixation reaction: The mixture is loaded into an airlift reactor, and industrial flue gas (containing 5% CO2 and 15% O2) is introduced. The temperature is controlled at 35°C, and the reaction is carried out for 5 hours.

[0062] Results: CO2 absorption rate was 81%, CaCO3 purity in solid product was 85%, dissolved oxygen in liquid was 4.0 mg / L, and enzyme activity retention rate was 94%.

[0063] Example 8

[0064] Red mud pretreatment: Take red mud from an aluminum plant (composition: CaO 15%, Fe2O3 25%, Al2O3 18%), crush it to 80μm, and adjust the moisture content to 30%.

[0065] Microbial inoculation: Microbacterium oxysporum (CGMCC No. 1.123) and Bacillus subtilis (CCTCC AB 2012063) were mixed at a mass ratio of 1:1. The inoculation amount of the microbial agent was 3% of the dry weight of the red mud. The mixture was cultured at 30℃ and pH 8.0 for 24 hours. The carbonic anhydrase activity was measured to be 150 U / g red mud.

[0066] Carbon fixation reaction: The mixture is loaded into an airlift reactor, and industrial flue gas (containing 15% CO2 and 10% O2) is introduced. The temperature is controlled at 35°C, and the reaction is carried out for 5 hours.

[0067] Product separation: After solid-liquid separation, the solid product is carbonate-stabilized red mud, and the liquid is reused in step (2) as a microbial culture medium.

[0068] Results: CO2 absorption rate 91%, CaCO3 purity in solid product 85%, dissolved oxygen in liquid 4.0 mg / L, enzyme activity retention rate 94%. Heavy metals (Fe 3+ Al 3+ The dissolution rate is <0.1 ppm.

[0069] Example 9

[0070] Red mud pretreatment: Take red mud from an aluminum plant (composition: CaO 15%, Fe2O3 25%, Al2O3 18%), crush it to 80μm, and adjust the moisture content to 30%.

[0071] Microbial inoculation: Microbacterium oxysporum (CGMCC No. 1.123) and Bacillus subtilis (CCTCC AB 2012063) were mixed at a mass ratio of 1:1.5. The inoculation amount of the microbial agent was 3% of the dry weight of the red mud. The mixture was cultured at 30℃ and pH 8.0 for 24 hours, and the carbonic anhydrase activity was measured to be 200 U / g red mud.

[0072] Carbon fixation reaction: The mixture is loaded into an airlift reactor, and industrial flue gas (containing 15% CO2 and 10% O2) is introduced. The temperature is controlled at 35°C, and the reaction is carried out for 5 hours.

[0073] Product separation: After solid-liquid separation, the solid product is carbonate-stabilized red mud, and the liquid is reused in step (2) as a microbial culture medium.

[0074] Results: CO2 absorption rate was 93%, CaCO3 purity in the solid product was 86%, dissolved oxygen in the liquid was 4.0 mg / L, and enzyme activity retention rate was 95%. Heavy metals (Fe...) 3+ Al 3+ The dissolution rate is <0.1 ppm.

[0075] Example 10

[0076] Red mud pretreatment: Take red mud from an aluminum plant (composition: CaO 15%, Fe2O3 25%, Al2O3 18%), crush it to 80μm, and adjust the moisture content to 20%.

[0077] Microbial inoculation: Microbacterium oxysporum (CGMCC No. 1.123) and Bacillus subtilis (CCTCC AB 2012063) were mixed at a mass ratio of 1.5:1. The inoculation amount of the microbial agent was 3% of the dry weight of the red mud. The mixture was cultured at 30℃ and pH 8.0 for 24 hours, and the carbonic anhydrase activity was measured to be 150 U / g red mud.

[0078] Carbon fixation reaction: The mixture is loaded into an airlift reactor, and industrial flue gas (containing 15% CO2 and 10% O2) is introduced. The temperature is controlled at 35°C, and the reaction is carried out for 5 hours.

[0079] Product separation: After solid-liquid separation, the solid product is carbonate-stabilized red mud, and the liquid is reused in step (2) as a microbial culture medium.

[0080] Results: CO2 absorption rate was 92%, CaCO3 purity in the solid product was 85%, dissolved oxygen in the liquid was 4.0 mg / L, and enzyme activity retention rate was 95%. Heavy metals (Fe...) 3+ Al 3+ The dissolution rate is <0.1 ppm.

[0081] Example 11

[0082] The effect of different oxygen volume fractions in industrial flue gas on CO2 absorption rate was investigated, with the rest of the process the same as in Example 1. The results are shown in the table below.

[0083]

[0084] Comparative Example 1

[0085] The microbial inoculation step is omitted, and the rest is the same as in Example 1.

[0086] Results: CO2 absorption rate was 61%, and the purity of CaCO3 in the solid product was 24%.

[0087] Comparative Example 2

[0088] The inoculum amount was 0.5% of the dry weight of the red mud, and the rest was the same as in Example 1.

[0089] Results: CO2 absorption rate was 66%, and the purity of CaCO3 in the solid product was 80%.

[0090] The embodiments described above merely illustrate the implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for absorbing carbon dioxide in industrial flue gas using red mud, characterized in that, The method comprises the following steps: (1) Red mud pretreatment: crushing red mud particles to a particle size of ≤100 μm and adjusting the moisture content to 20-40%; (2) Microbial inoculation and culture: inoculating carbonic anhydrase-producing microbial inoculum into the pretreated red mud and culturing at 25-37°C and pH 7.5-8.5 to obtain a microbial enzyme concentration of 50-200 U / g red mud; (3) Carbon fixation reaction: placing the red mud-microbial mixture obtained in step (2) in a sealed reactor, introducing industrial flue gas containing carbon dioxide, and controlling the reaction temperature to be 30-45°C to perform the carbon fixation reaction; (4) Product separation: after solid-liquid separation, the solid product is carbonate-stabilized red mud, and the liquid is reused as the microbial culture solution in step (2).

2. The method of claim 1, wherein: In step (2), the microorganism is at least one selected from the group consisting of Microbacterium oxydans, Bacillus, and engineered Escherichia coli.

3. The method of claim 1, wherein: In step (2), the microbial enzyme concentration is 100-200 U / g red mud.

4. The method of claim 1, wherein: In step (3), the oxygen volume fraction in the industrial flue gas is 5-15%; or oxygen is supplemented to the reactor to obtain a dissolved oxygen concentration of ≥3 mg / L.

5. The method of claim 1 or 2, wherein: In step (2), the microbial inoculum is a mixed microbial flora of Microbacterium oxydans and Bacillus, with a mass ratio of 1:2-2:1, and the inoculum inoculation amount is 1-5% of the dry weight of the red mud.

6. The method of claim 1, wherein: In step (3), the reactor is a gas-lift bioreactor, carbon dioxide is dispersed by a microporous aeration device with bubble diameter ≤0.5 mm, gas-liquid contact area ≥200 m 2 / m 3 .

7. The method of any one of claims 1-6, wherein, The red mud is red mud produced by the Bayer process.

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