Method for microfluidic enhancement of synchronous desulfurization and carbon sequestration of red mud slurry

Abstract

The application discloses a kind of microfluidic enhanced red mud slurry simultaneous desulfurization carbon sequestration methods, belong to industrial flue gas pollution control and bulk industrial solid waste resource utilization technical field.Simultaneous desulfurization carbon sequestration of red mud slurry method in prior art relies on complex high-temperature modification, mass transfer efficiency is low, particle is easy to block, reactor is difficult to enlarge technical problem, the application adopts wet ultrafine pretreatment combined with serpentine microchannel reactor technology, by red mud in-situ activation and flow field synergistic control realizes flue gas efficient simultaneous desulfurization carbon sequestration.The application process is simple, low in cost, stable in operation, provides a new technical approach for red mud bulk solid waste resource utilization and industrial flue gas pollution reduction and carbon sequestration collaborative management.

Description

Technical Field

[0001] This invention belongs to the technical field of industrial flue gas pollution control and resource utilization of bulk industrial solid waste red mud, specifically involving a microfluidic-enhanced method for simultaneous desulfurization and carbon fixation of red mud slurry. Background Technology

[0002] Red mud is a large-scale, highly alkaline solid waste generated during the alumina industry. In 2025, my country's annual red mud emissions exceeded 120 million tons, with a cumulative stockpile exceeding 2 billion tons, and a comprehensive utilization rate of less than 15%. The large-scale stockpiling of red mud not only occupies valuable land resources but also pollutes soil and groundwater due to alkaline leachate, posing serious environmental safety hazards. Red mud is rich in alkaline active components such as Fe2O3, CaO, and MgO, possessing natural potential for flue gas desulfurization and CO2 mineralization and carbon sequestration. Utilizing red mud to achieve simultaneous flue gas desulfurization and carbon sequestration can not only solve the environmental problems caused by red mud stockpiling but also achieve synergistic treatment of industrial flue gas pollution reduction and carbon reduction, resulting in significant environmental and economic benefits.

[0003] Existing red mud slurry desulfurization and carbon fixation technologies mostly employ traditional reactors such as stirred tanks and spray towers. These technologies suffer from problems such as low gas-liquid-solid three-phase mass transfer efficiency, easy particle deposition and clogging, and significant competitive adsorption of SO2 and CO2, resulting in low simultaneous desulfurization and carbon fixation efficiency and poor system stability. Microfluidic technology has advantages such as high mass transfer efficiency and rapid interface renewal, which can effectively enhance multiphase reaction processes. However, for the red mud slurry gas-liquid-solid three-phase system, problems still exist such as easy particle clogging of microchannels, poor continuous operation stability, and limited processing throughput. Currently, there is a lack of a red mud slurry microfluidic reaction technology that does not require complex red mud pretreatment, and simultaneously achieves high-efficiency mass transfer, anti-clogging operation, and simultaneous desulfurization and carbon fixation.

[0004] Therefore, developing a microfluidic enhancement method that is simple, low-cost, stable in operation, and applicable to the simultaneous desulfurization and carbon fixation of red mud slurry is of great significance for realizing the resource utilization of red mud and reducing pollution and carbon emissions from industrial flue gas. Summary of the Invention

[0005] To address the technical problems of low mass transfer efficiency and easy deposition and clogging of red mud particles in the existing red mud slurry method for simultaneous desulfurization and carbon fixation, the present invention aims to provide a microfluidic-enhanced method for simultaneous desulfurization and carbon fixation of red mud slurry. This method eliminates the need for complex pre-modification treatment of the red mud. Through a serpentine microchannel reactor, combined with red mud activation and synergistic flow field control technology, it overcomes the limitations of gas-liquid-solid three-phase mass transfer, achieving simultaneous and efficient removal of SO2 and CO2 from flue gas.

[0006] The objective of this invention is achieved by including the following steps: S1. Red mud pretreatment: After crushing, drying and removing impurities, and wet ultrafine ball milling, the red mud raw material is controlled to make the particle size distribution of red mud particles reach D90≤100μm, so as to obtain uniform red mud particles. S2. Red mud slurry preparation: The red mud pretreated by ultrafine processing in step S1 is mixed with water and stirred evenly to prepare a red mud slurry with a solid mass fraction of 10%~40%, which is used as a desulfurization and carbon fixation absorption liquid. S3. Simultaneous Desulfurization and Carbon Fixation Reaction: Gases containing SO2 and CO2 are simultaneously introduced into a serpentine microchannel microfluidic reactor at a gas-liquid volume ratio of 10-100:1 with the red mud slurry prepared in step S2. The simultaneous desulfurization and carbon fixation reaction is carried out under normal pressure and temperature conditions (20℃-40℃). The serpentine microchannel generates eddy currents, inhibiting the deposition of red mud particles on the bottom of the channel and further increasing the gas-liquid-solid three-phase contact area, thus enhancing the mass transfer process. During the reaction, the concentrations of SO2 and CO2 in the reactor outlet gas are detected using a flue gas analyzer. The synergistic adsorption capacity of the red mud for SO2 / CO2 in this invention is ≥60% higher than that of the original red mud, with a desulfurization efficiency ≥95% and a sulfur capacity ≥180mg / g; the carbon fixation efficiency is ≥80%, and the carbon fixation amount is ≥90mg / g.

[0007] In this invention, the multi-level serpentine microchannels are fabricated in an integrated manner using micro-nano fabrication technology and are arranged in a regular pattern. This array is specifically designed to address the issues of particle deposition and clogging in the three-phase reaction system of red mud slurry, which is characterized by high three-phase mass transfer resistance. Unlike conventional microchannel devices that are only used for fluid mixing, this array is a key functional unit for achieving long-term stable operation of the reactor and breaking through the limits of mass transfer efficiency.

[0008] Preferably, the red mud raw material is sintered red mud.

[0009] Preferably, the pretreatment in step S1 specifically involves: crushing the red mud raw material, drying it at 105°C for 24 hours to remove free moisture and volatile impurities, ball milling it, and then passing it through a 200-mesh sieve.

[0010] Preferably, the serpentine microchannel has a radius of curvature of 1mm to 5mm, a circular cross-section with a diameter of 0.1mm to 2mm, and a length of 5cm to 20cm.

[0011] Preferably, the serpentine microchannel microfluidic reactor includes a reactor body, which is cylindrical, and at least one serpentine microchannel is provided through the reactor body. Adjacent serpentine microchannels are spaced apart and do not communicate with each other, and are arranged in a parallel array.

[0012] Preferably, the serpentine microchannel microfluidic reactor is made of PDMS-COC composite material, resin, quartz glass, or alkali-resistant stainless steel. (PDMS-COC is a multilayer composite polymer material prepared by interfacial bonding of polydimethylsiloxane and cyclic olefin copolymer. It is a high-performance special substrate in the field of microchannel chips / reactors. In this invention, a composite structure of COC rigid substrate + PDMS functional layer is mainly adopted to meet the requirements of alkali resistance and mechanical stability in the simultaneous desulfurization and carbon fixation process of red mud slurry.)

[0013] Preferably, the SO2 concentration in the gas during step S3 is 100 mg / m³. 3 (Standard conditions) ~13000 mg / m³ 3 (Standard conditions), CO2 concentration is 1000 mg / m³ 3 ~18000mg / m 3 (Standard condition).

[0014] The principle of this invention: Through ultrafine ball milling, the particle size of red mud is controlled to D90≤100μm, with good dispersibility, preventing large particles and agglomerates from entering the microchannels and solving the microchannel blockage problem at its source. Utilizing the microscale confinement effect of the serpentine microchannels, the gas-liquid-solid three-phase contact area is increased by 1-2 orders of magnitude compared to traditional reactors. The secondary flow generated by the serpentine channels increases the mass transfer coefficient by more than 30% compared to straight channels. High shear force under microfluidic conditions continuously breaks down small red mud agglomerates, constantly exposing fresh Ca2+ and Mg2+ alkaline active sites, achieving in-situ activation of the red mud without the need for complex modification processes such as high-temperature calcination and metal loading, significantly reducing energy consumption and cost. The localized turbulence generated by the serpentine microchannels forms a high-speed scouring zone at the bottom of the channel, effectively inhibiting the deposition of red mud particles under gravity and ensuring long-term stable operation of the system.

[0015] The beneficial effects of this invention are: 1. Simplified process and reduced cost: There is no need for cumbersome pre-modification treatments such as microwave roasting and metal oxide loading of red mud. The process is simplified, energy consumption is reduced by more than 40%, and potential secondary pollution is avoided.

[0016] 2. High mass transfer efficiency and fast reaction rate: Through the mass transfer enhancement effect of the serpentine microchannel, desulfurization efficiency ≥95% and sulfur capacity ≥180mg / g can be achieved; carbon fixation efficiency ≥80% and carbon fixation amount ≥90mg / g;

[0017] 3. Excellent anti-clogging performance and stable operation: Through the synergistic effect of wet ultrafine pretreatment and eddy current disturbance within the serpentine microchannel, red mud particle deposition can be effectively suppressed. Experimental verification shows that the system exhibits no clogging after continuous operation for ≥24 hours, with outlet pollutant concentration fluctuations ≤3%, demonstrating good operational stability. Attached Figure Description

[0018] Figure 1 This is a schematic flowchart of the method of the present invention; Figure 2 A perspective view of the reactor with multiple serpentine microchannels. In the diagram: 1-Reactor body, 2-Serpentine microchannel. Detailed Implementation

[0019] The present invention will be further described below with reference to the embodiments and accompanying drawings, but this does not limit the present invention in any way. Any changes or substitutions made based on the teachings of the present invention shall fall within the protection scope of the present invention.

[0020] Unless otherwise specified, all chemical reagents used in the embodiments and comparative examples of this invention were commercially available analytical grade. The red mud raw material used in the embodiments and comparative examples of this invention was sintering red mud produced by an aluminum company in Shandong, China.

[0021] In this embodiment, the formula for calculating flue gas desulfurization efficiency is: η SO2 =(C SO2,in -C SO2,out ) / C SO2,in The formula for calculating 100% carbon sequestration efficiency is: η CO2 =(C CO2,in -C CO2,out ) / C CO2,in ×100% where, C in C represents the pollutant concentration in the flue gas at the reactor inlet. out The concentration of pollutants in the flue gas at the reactor outlet was detected using a flue gas analyzer. Example 1

[0022] As attached Figure 1 , Figure 2 As shown in this embodiment, the method for simultaneous desulfurization and carbon fixation of red mud slurry enhanced by microfluidics includes the following steps: S1. Red mud pretreatment: Red mud was dried at 105℃ for 24 hours to remove free water and volatile impurities. After crushing, it was subjected to wet ultrafine ball milling to obtain red mud particles with D90=85μm. The particles were then passed through a 200-mesh sieve for later use. The ball-to-material ratio was 10:1, the ball milling speed was 400 r / min, and the ball milling time was 60 min to obtain D90=85μm red mud particles. 90 Red mud particles with a diameter of 85μm; S2. Preparation of absorption slurry: Mix the red mud particles obtained in step S1 with water and stir at 300 r / min for 30 min to prepare a red mud slurry with a solid mass fraction of 10%, which will be used as the desulfurization and carbon fixation absorption liquid. S3. Simultaneous Desulfurization and Carbon Sequestration Reaction: Simulated flue gas containing SO2 and CO2 and red mud slurry prepared in step S2 are simultaneously introduced into a serpentine microchannel microfluidic reactor at a gas-liquid volume ratio of 50:1; the SO2 concentration in the simulated flue gas is 2000 mg / m³. 3 (Standard conditions), CO2 concentration is 3000 mg / m³ 3 (Standard conditions); reaction temperature is 25℃, reaction residence time is 2 min; The serpentine microchannel microfluidic reactor includes a reactor body 1, which is cylindrical with a diameter of 7cm. Twenty serpentine microchannels 2 are arranged through the reactor body 1. Adjacent serpentine microchannels 2 are spaced apart and do not communicate with each other, and are arranged in a parallel array. The radius of curvature of the serpentine microchannel is 3mm, the channel cross-section is circular with a diameter of 1mm and a length of 10cm. The reactor material is resin. In this embodiment, the SO2 concentration in the flue gas at the reactor outlet was 76 mg / m³, as detected online. 3 (Standard conditions), desulfurization efficiency is 96.2%; CO2 concentration is 552 mg / m³. 3 (Standard conditions) The carbon fixation efficiency is 81.6%; the sulfur capacity is 186 mg / g and the carbon fixation amount is 93 mg / g; the system runs continuously for 24 hours without any blockage in the microchannels, and the outlet pollutant concentration fluctuates by ≤3%, indicating good operational stability. Example 2

[0023] The microfluidic-enhanced method for simultaneous desulfurization and carbon fixation of red mud slurry in this embodiment is based on Example 1, but differs from Example 1 in that: Step S2 prepares a red mud slurry with a solid mass fraction of 15%; Step S3 simulates an SO2 concentration of 3000 mg / m³ in the flue gas. 3 (Standard conditions), CO2 concentration is 5000 mg / m³ 3 (Under standard conditions), the gas and liquid are simultaneously introduced into the reactor at a gas-liquid volume ratio of 30:1; In this embodiment, the SO2 concentration in the reactor outlet flue gas was measured to be 93 mg / m³ via online monitoring. 3 (Standard conditions), desulfurization efficiency is 96.9%; CO2 concentration is 960 mg / m³. 3 (Standard conditions) The carbon sequestration efficiency is 80.8%; the system shows no blockage after continuous operation for ≥24 hours, and the outlet pollutant concentration fluctuates by ≤3%, indicating good operational stability. Example 3

[0024] The microfluidic-enhanced method for simultaneous desulfurization and carbon fixation of red mud slurry in this embodiment is based on Example 1, but differs from Example 1 in that: Step S2 prepares a red mud slurry with a solid mass fraction of 25%; Step S3 simulates an SO2 concentration of 5000 mg / m³ in the flue gas. 3 (Standard conditions), CO2 concentration is 10000 mg / m³ 3 (Under standard conditions), the gas and liquid are simultaneously introduced into the reactor at a gas-liquid volume ratio of 70:1; The reaction temperature was 40℃ and the reaction residence time was 2 min.

[0025] In this embodiment, the SO2 concentration in the reactor outlet flue gas was measured to be 215 mg / m³ via online monitoring. 3 (Standard conditions), desulfurization efficiency is 95.7%; CO2 concentration is 1850 mg / m³. 3 (Standard conditions) The carbon sequestration efficiency is 81.5%; the system shows no blockage after continuous operation for ≥24 hours, and the outlet pollutant concentration fluctuates by ≤3%, indicating good operational stability. Example 4

[0026] The microfluidic-enhanced method for simultaneous desulfurization and carbon fixation of red mud slurry in this embodiment is based on Example 1, but differs from Example 1 in that: Step S2 prepares a red mud slurry with a solid mass fraction of 10%; The radius of curvature of the serpentine microchannel in step S3 is 1 mm, the channel diameter is 0.1 mm, and the length is 5 cm. The SO2 concentration in the simulated flue gas was 1000 mg / m³. 3 (Standard conditions), CO2 concentration is 2000 mg / m³ 3 (Under standard conditions), the gas and liquid are simultaneously introduced into the reactor at a gas-liquid volume ratio of 10:1.

[0027] In this embodiment, the SO2 concentration in the reactor outlet flue gas was measured to be 28 mg / m³ via online monitoring. 3 (Standard conditions), desulfurization efficiency is 97.2%; CO2 concentration is 376 mg / m³. 3 (Standard conditions), carbon sequestration efficiency is 81.2%. Example 5

[0028] The microfluidic-enhanced method for simultaneous desulfurization and carbon fixation of red mud slurry in this embodiment is based on Example 1, but differs from Example 1 in that: Step S2 prepares a red mud slurry with a solid mass fraction of 40%; The radius of curvature of the serpentine microchannel in step S3 is 5mm, the channel diameter is 2mm, and the length is 20cm. The SO2 concentration in the simulated flue gas was 13000 mg / m³. 3 (Standard conditions), CO2 concentration is 18000 mg / m³ 3 (Under standard conditions), the gas and liquid are simultaneously introduced into the reactor at a gas-liquid volume ratio of 100:1.

[0029] In this embodiment, the SO2 concentration in the reactor outlet flue gas was measured to be 585 mg / m³ via online monitoring. 3 (Standard conditions), desulfurization efficiency is 95.5%; CO2 concentration is 3420 mg / m³. 3 (Standard conditions) The carbon sequestration efficiency is 81.0%; the system shows no blockage after continuous operation for ≥24 hours, and the outlet pollutant concentration fluctuates by ≤3%, indicating good operational stability. Example 6

[0030] The microfluidic-enhanced method for simultaneous desulfurization and carbon fixation of red mud slurry in this embodiment is based on Example 1, but differs from Example 1 in that: Step S2 prepares a red mud slurry with a solid mass fraction of 20%; Step S3 simulates an SO2 concentration of 4000 mg / m³ in the flue gas. 3 (Standard conditions), CO2 concentration is 8000 mg / m³ 3 (Under standard conditions), the gas and liquid are simultaneously introduced into the reactor at a gas-liquid volume ratio of 40:1.

[0031] In this embodiment, the SO2 concentration in the flue gas at the reactor outlet was 156 mg / m³, as detected online. 3 (Standard conditions), desulfurization efficiency is 96.1%; CO2 concentration is 1480 mg / m³. 3 (Standard conditions), carbon sequestration efficiency is 81.5%. Example 7

[0032] The microfluidic-enhanced method for simultaneous desulfurization and carbon fixation of red mud slurry in this embodiment is based on Example 1, but differs from Example 1 in the following ways: In step S3, a serpentine microchannel 2 is provided through the reactor body 1 (cylindrical, 7cm in diameter) of the serpentine microchannel microfluidic reactor. The serpentine microchannel 2 is located at the central axis of the reactor body. The other reactor parameters (radius of curvature 3mm, circular channel cross-section, diameter 1mm, length 10cm, material is resin) are exactly the same as in Example 1.

[0033] In this embodiment, the SO2 concentration in the reactor outlet flue gas was 536 mg / m³, as detected online. 3 (Standard conditions), desulfurization efficiency is 73.2%; CO2 concentration is 1359 mg / m³. 3 (Standard conditions), the carbon fixation efficiency is 54.7%; the results of this embodiment show that a single serpentine microchannel cannot meet the core technical requirements of the present invention for simultaneous desulfurization and carbon fixation.

[0034] Comparative Example 1 This comparative method is based on Example 1, but differs from Example 1 in that the serpentine microchannel microfluidic reactor in step S3 is replaced with a traditional stirred tank reactor. The same flow rate is introduced into the bottom aeration head of the stirred tank reactor, the stirring speed is 300 r / min, and the reaction is carried out at room temperature and pressure.

[0035] In this comparative example, the average SO2 concentration in the reactor outlet flue gas was measured to be 392 mg / m³. 3 (Under standard conditions), the desulfurization efficiency was only 80.4%; the CO2 concentration was 2340 mg / m³. 3 (Under standard conditions), the carbon fixation efficiency was only 22.0%, far lower than the treatment effect of Example 1.

[0036] Comparative Example 2 This comparative method is based on Example 1, but differs from Example 1 in that: step S1 only involves dry grinding, without wet ultrafine ball milling, and the red mud particles D 90 =186μm, and the other parameters are exactly the same as in Example 1.

[0037] In this comparative example, after the system ran continuously for 4 hours, the microchannel became severely blocked, the outlet flow rate decreased by 60%, the desulfurization efficiency dropped to 65.2%, and the carbon fixation efficiency dropped to 50.1%; this proves that wet ultrafine pretreatment is one of the key steps of this invention.

Claims

1. A method for simultaneous desulfurization and carbon fixation of red mud slurry enhanced by microfluidics, characterized in that... Includes the following steps: S1. Red mud pretreatment: After crushing, drying and removing impurities, the red mud raw material is subjected to wet ultrafine ball milling. The ball milling process parameters are controlled so that the particle size distribution of the red mud particles reaches D90≤100μm, and uniform red mud particles are obtained. S2. Preparation of absorption slurry: Mix the red mud pretreated by ultrafine processing in step S1 with water and stir at a speed of 200 r / min to 500 r / min for 20 min to 60 min to prepare a red mud slurry with a solid mass fraction of 10% to 40%, which is used as the desulfurization and carbon fixation absorption liquid. S3. Simultaneous desulfurization and carbon fixation reaction: Gas containing SO2 and CO2 and red mud slurry prepared in step S2 are simultaneously introduced into a serpentine microchannel microfluidic reactor at a gas-liquid volume ratio of 10~100:1, and the simultaneous desulfurization and carbon fixation reaction is carried out under normal pressure conditions of 20℃~40℃.

2. The method for simultaneous desulfurization and carbon fixation of red mud slurry enhanced by microfluidics according to claim 1, characterized in that... The red mud raw material mentioned in step S1 is sintered red mud; the red mud pretreatment specifically involves drying the red mud at 105℃ for 24 hours to remove free water and volatile impurities, crushing it, and then wet ultrafine ball milling it, followed by passing it through a 200-mesh sieve.

3. The method for simultaneous desulfurization and carbon fixation of red mud slurry enhanced by microfluidics according to claim 1, characterized in that... The serpentine microchannel microfluidic reactor includes a reactor body (1), which is cylindrical. At least one serpentine microchannel (2) is provided through the reactor body (1). Adjacent serpentine microchannels (2) are spaced apart and do not communicate with each other, and are arranged in a parallel array.

4. The method for simultaneous desulfurization and carbon fixation of red mud slurry enhanced by microfluidics according to claim 3, characterized in that... The serpentine microchannel (2) has a radius of curvature of 1mm to 5mm, a circular cross-section with a diameter of 0.1mm to 2mm, and a length of 5cm to 20cm.

5. The method for simultaneous desulfurization and carbon fixation of red mud slurry enhanced by microfluidics according to claim 1, characterized in that... The serpentine microchannel microfluidic reactor is made of PDMS-COC composite material, resin, quartz glass, or alkali-resistant stainless steel.

6. The method for simultaneous desulfurization and carbon fixation of red mud slurry enhanced by microfluidics according to claim 1, characterized in that... In step S3, the SO2 concentration in the gas containing SO2 and CO2 is 100 mg / m³. 3 ~13000mg / m 3 CO2 concentration is 1000 mg / m³ 3 ~18000mg / m 3 .

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