A CO catalytic purification device and a preparation method of a composite oxide catalytic layer

Abstract

A CO catalytic purification device and a preparation method of a composite oxide catalytic layer, the device comprising: an outer straight pipe, an inserted spiral catalytic core, the inserted spiral catalytic core being coaxially sleeved in the outer straight pipe and being a detachable module; the inserted spiral catalytic core taking foamed nickel as a base material and being shaped into a continuous spiral blade structure; a Co3O4 / Mn3O4 composite oxide catalytic layer being combined on the surface of the foamed nickel framework through chemical bonds; the Co3O4 / Mn3O4 composite oxide being obtained by pyrolysis of a CoMn-MOF-74 precursor in-situ grown on the surface of the foamed nickel, and the catalytic layer being free of a binder coating layer. The present application can significantly improve the catalytic conversion rate of harmful gases, the MOF thin film thickness can be precisely controlled by using the solvent thermal method for in-situ growth of the catalyst, the oxide coating is uniform after pyrolysis, and there is no defect of uneven thickness and local catalytic loss in traditional coating, thereby improving the CO purification effect.

Description

Technical Field

[0001] This invention belongs to the field of mine ventilation and air purification technology, specifically relating to a CO catalytic purification device and a method for preparing a composite oxide catalytic layer. Background Technology

[0002] The technology for controlling carbon monoxide (CO) in coal mines has mainly gone through three stages of development: physical adsorption, chemical absorption, and catalytic oxidation. Early methods used adsorbent materials such as activated carbon or molecular sieves to fill filter devices, capturing CO through physical adsorption. However, the adsorption capacity was limited, requiring frequent replacement or regeneration after saturation, making it only suitable for temporary emergency treatment. Chemical absorption, through a complexation reaction between liquid absorbent and CO, can achieve high absorption efficiency, but requires a liquid circulation system, resulting in bulky equipment. The absorbent is also prone to deactivation and poses a risk of secondary pollution, making it unsuitable for applications in confined underground spaces. Currently, the mainstream method is catalytic oxidation, which uses a catalyst to oxidize CO into harmless CO2 at room temperature or low temperature, with the reaction formula 2CO + O2 → 2CO2. This method has been widely studied due to its lack of secondary pollution and stable operation.

[0003] However, existing catalytic oxidation methods have the following problems: Defect 1: Low mass transfer efficiency and poor catalyst utilization. In a fixed particle packed bed, a channeling effect occurs when gas flows along the gaps between particles. Due to the random packing of particles and the varying pore sizes in different areas, the gas flow preferentially passes through channels with the least resistance, forming the mainstream path. Most CO molecules are carried away before they can even contact the catalyst. In actual operation, the catalyst that effectively participates in the reaction typically accounts for only 40%-60% of the total packing.

[0004] Defect 2: High pressure drop and high ventilation energy consumption. Particle beds are porous media, and airflow must overcome significant frictional resistance as it passes through them. Pressure drop increases quadratically with bed thickness and flow velocity. Mine ventilation volumes often range from thousands to tens of thousands of cubic meters per hour, resulting in pressure drops in particle beds that can reach hundreds or even thousands of Pascals, leading to high fan energy consumption. Increasing particle size to reduce resistance would sacrifice specific surface area and conversion efficiency, making it difficult to balance pressure drop and efficiency.

[0005] Defect 3: Prone to clogging, prone to deactivation, and short lifespan. The mine contains a large amount of coal dust and moisture. Dust accumulates on the surface of the bed, gradually blocking the airflow channels and causing the pressure drop to rise continuously. Simultaneously, water molecules compete with CO for adsorption at the catalyst's active sites. Under normal temperature and high humidity conditions, water vapor easily condenses into a liquid film on the catalyst surface, preventing CO from contacting the active sites and leading to rapid catalyst deactivation. Frequent catalyst replacement increases maintenance costs and also affects production continuity.

[0006] The fundamental reason lies in the separation of structure and function in traditional reactors. The particles are merely catalyst carriers and do not participate in the flow field organization. This separation renders the reactor incapable of actively controlling the airflow, making it unable to guide CO to fully contact the catalyst and difficult to cope with interference from dust and moisture. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a CO catalytic purification device and a method for preparing a composite oxide catalytic layer. This device ensures continuous, comprehensive, and efficient contact between mine exhaust gas and the catalytically active sites during its flow, significantly improving the catalytic conversion rate of harmful gases. It solves the technical problems of insufficient contact between airflow and catalyst and low catalyst utilization in existing technologies, thereby improving the efficiency of pollutant treatment in mine ventilation systems. Furthermore, the catalyst of this invention is grown in situ using a solvothermal method, allowing for precise control of the MOF film thickness. After pyrolysis, the oxide coating is uniform, avoiding the defects of uneven thickness and localized catalytic loss found in traditional coatings, thus improving the CO purification effect.

[0008] To achieve the above objectives, the present invention provides a CO catalytic purification device, comprising: The outer straight pipe is a standard round pipe structure with flanges or clamps at both ends. An internal spiral catalyst core is coaxially sleeved inside the outer straight tube and is a detachable module; The inserted spiral catalyst core uses nickel foam as the base material and is formed into a continuous spiral blade structure; the surface of the nickel foam skeleton is bonded with a Co3O4 / Mn3O4 composite oxide catalyst layer by chemical bonds; the Co3O4 / Mn3O4 composite oxide is obtained by pyrolysis of the CoMn-MOF-74 precursor grown in situ on the surface of the nickel foam, and the catalyst layer has no binder coating layer.

[0009] Preferably, the helical blades are fixed to the inner wall of the outer straight tube at their ends or edges, forming an open structure without a central rod; The inner wall of the outer straight pipe and the surface of the spiral blade together form a continuous, closed, spiral fluid channel.

[0010] Preferably, the catalytic purification device of the present invention further includes: The perforation consists of multiple through holes, regularly formed on both sides of the spiral blade wall.

[0011] Preferably, the perforations are distributed in a gradient aperture along the airflow direction, with a larger aperture at the inlet and a smaller aperture at the rear. The large aperture at the front reduces the risk of dust blockage, while the small aperture at the rear maintains the catalytic area, thus forming an axial functional partition with the spiral structure.

[0012] Preferably, the present invention removes accumulated dust by blowing from the inside of the outer straight pipe outward with pulsed airflow. The perforations serve as the blowing channels during dust removal, and the position distribution of the perforations is consistent with the structure of the spiral blades, so that the pulsed airflow can evenly brush the front and back surfaces of the spiral blades and the inner wall of the outer straight pipe along the spiral path.

[0013] Preferably, the device of the present invention includes multiple outer straight pipes, which are installed in an array in the CO purification system of the mine return air roadway. The multiple outer straight pipes are connected in series or in parallel in the ventilation pipeline through flange interfaces to form a spatial array layout, and form an installation matching relationship with the flange structure of the outer straight pipes.

[0014] This invention also provides a method for preparing a composite oxide catalyst layer, comprising the following steps: S1. Take the shaped spiral foam nickel and perform multi-media ultrasonic cleaning on the shaped spiral foam nickel to remove surface oil and oxide layer. S2. Immerse the pretreated spiral nickel foam from S1 into a Co-containing solution. 2+ Salt, Mn 2+ A DMF-water-ethanol mixed solution of salt and 2,5-dihydroxyterephthalic acid ligand was sealed and heated to carry out a solvothermal reaction to obtain CoMn-MOF-74 crystals; the metal framework surface of nickel foam provides nucleation sites, and CoMn-MOF-74 crystals are directly nucleated in situ on the surface of nickel foam and grow outward to form a uniform and dense MOF crystal film. S3. Calcine the CoMn-MOF-74-loaded nickel foam in an air atmosphere to decompose and remove the MOF organic ligands. The metal ions are converted into Co3O4 / Mn3O4 composite oxides, which grow on the surface of the nickel foam by relying on Ni-O-Co / Mn chemical bonds to form a mesoporous Co3O4 / Mn3O4 composite oxide catalytic layer.

[0015] Preferably, in step S1, the ultrasonic cleaning is performed sequentially using acetone, dilute hydrochloric acid, and deionized water.

[0016] Preferably, in step S2, the solvothermal reaction is carried out at 100~150℃ for 12~24h.

[0017] Preferably, in step S3, the CoMn-MOF-74-loaded nickel foam is calcined at 350~450℃ for 2~4 hours.

[0018] This invention combines an outer straight pipe with an internally inserted spiral catalyst core to form a central rod-less open spiral flow channel structure. This forces the mine ventilation airflow to flow along a continuous, closed spiral path formed by the inner wall of the outer straight pipe and the surface of the spiral blades, significantly extending the contact distance between the airflow and the catalyst interface. Simultaneously, the regularly spaced perforations on the spiral blades allow for localized radial penetration and turbulent disturbance within the spiral channel, enhancing mass transfer efficiency. The catalyst coating is uniformly applied to the entire surface of the spiral blades and the entire inner wall of the outer straight pipe, ensuring catalytic activity on every inner surface of the fluid channel and maximizing the utilization of the catalytic reaction area. This synergistic structural design completely overcomes the shortcomings of traditional straight-pipe or packed-bed catalytic converters, such as airflow short-circuiting, numerous dead zones, and low catalytic surface area utilization. It ensures continuous, comprehensive, and efficient contact between mine exhaust gas and the catalytically active sites during flow, significantly improving the catalytic conversion rate of harmful gases. This solves the technical problems of insufficient airflow-catalyst contact and low catalyst utilization in existing technologies, resulting in a significant improvement in pollutant treatment efficiency in mine ventilation systems.

[0019] The catalyst of this invention uses nickel foam as a framework substrate, and grows MOF-74 precursor in situ on its surface by solvothermal method. After pyrolysis conversion, a Co3O4 / Mn3O4 composite oxide monolithic catalyst is obtained. The catalyst is no longer coated later, but is grown in situ on the nickel foam framework by chemical bonding. Compared with the dense oxide prepared by traditional impregnation and coating methods, it exposes a large number of CO catalytic active sites, and has better low-temperature catalytic performance, which can achieve efficient CO purification under low-temperature conditions.

[0020] Compared with the prior art, the present invention has the following advantages: 1. High mass transfer efficiency and high catalyst utilization: In granular beds, airflow typically takes shortcuts, leaving most of the catalyst unused. This invention uses helical blades to create a rotating path for the airflow, and centrifugal force continuously throws CO towards the wall. The holes on the blades also create localized jets that repeatedly scour the wall. The airflow remains in contact with the catalyst throughout its path, resulting in a much larger effective reaction area compared to granular beds.

[0021] 2. Reduced pressure and energy consumption: Particle buildup inevitably increases air resistance, and the greater the airflow, the greater the resistance. This invention eliminates the need for a bulking bed; the airflow follows a spiral channel, and the perforations provide space for flow distribution, preventing pressure from continuously accumulating upwards. For the same airflow, the fan output is significantly lower.

[0022] 3. Anti-clogging, moisture-resistant, and durable: Downhole dust and moisture are the biggest killers of catalysts. The spiral blades of this invention throw large dust particles outward, making them less likely to accumulate on the catalyst surface. During dust removal, a simple blow from the inside out creates a ready-made purging channel through the perforations, resulting in thorough dust removal. The catalyst is embedded in the metal surface, not attached, and will not be dislodged by long-term airflow, resulting in a much longer lifespan than particle beds.

[0023] 4. Easy to replace without interrupting production. The outer straight pipe is just a straight pipe that is connected to the pipeline with a flange and does not move. The catalytic components are all on the inner spiral catalytic core. If it is deactivated, just pull out the old inner spiral catalytic core and insert the new inner spiral catalytic core. There is no need to disassemble the pipeline, and the downtime is very short.

[0024] 5. The space is fully utilized, the structure is compact, and only the outer surface of the particles is active in the particle bed. This invention utilizes the inner wall of the outer straight tube, both sides of the blades, and the inner wall of the perforation. For the same volume, the effective reaction surface is much larger, and the dimensions of this invention can be adjusted as needed. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the present invention.

[0026] In the diagram: 1. Outer straight tube, 2. Inner spiral catalyst core, 3. Spiral blade structure, 4. Perforation. Detailed Implementation

[0027] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0028] This invention no longer uses the catalyst as a loose particle filler, but rather it is firmly bonded to the metal foam substrate by chemical bonds, so that the catalytic function and structural support are integrated into one, no longer relying on the accumulation of loose particles, and fundamentally eliminating the structural root cause of bed blockage and the square-law increase in pressure drop.

[0029] like Figure 1 As shown, the present invention provides a CO catalytic purification device, comprising: Outer straight pipe 1, the outer straight pipe 1 is a standard round pipe structure, with flange or clamp interfaces at both ends, which can be directly connected in series in the mine ventilation pipeline for convenient connection and sealing with the mine ventilation pipeline; The inner spiral catalyst core 2 is coaxially sleeved inside the outer straight tube 1 and is a detachable module. When the catalyst is deactivated, the entire inner spiral catalyst core 2 can be extracted and replaced, which is convenient for replacement and maintenance. The inserted spiral catalyst core 2 uses nickel foam as the base material and is formed into a continuous spiral blade structure 3; the surface of the nickel foam skeleton is bonded with a Co3O4 / Mn3O4 composite oxide catalyst layer by chemical bonds; the Co3O4 / Mn3O4 composite oxide is obtained by pyrolysis of the CoMn-MOF-74 precursor grown in situ on the surface of the nickel foam, and the catalyst layer has no binder coating layer. The spiral blade structure 3 of the present invention is fixed to the inner wall of the outer straight tube by the end or edge, forming an open structure without a central rod. The present invention maintains its shape by the spiral blade itself, and the absence of a central rod occupying the internal space allows the inner ring area to participate in radial mixing when the airflow flows in the channel, avoiding the problem of the catalyst on the surface of the central rod being blocked by dust, while also reducing the weight of the inner core.

[0030] The inner wall of the outer straight pipe 1 and the surface of the spiral blade structure 3 together form a continuous, closed, spiral fluid channel.

[0031] The present invention also includes: perforations 4, which are multiple through holes regularly formed on both sides of the wall of the spiral blade structure 3; perforations 4 can promote local disturbance and cross-mixing of airflow in the spiral channel, thereby enhancing mass transfer efficiency; the perforations 4 of the present invention have a dual function: first, to provide a diversion path for airflow in addition to the main spiral channel, allowing some airflow to pass through the holes from the high-pressure zone into the adjacent low-pressure zone, forming a local microjet that directly impacts the other side of the spiral blade surface, thinning the concentration boundary layer on the catalyst surface and accelerating the transfer of CO to the active sites; second, to effectively balance the overall pressure drop and prevent the continuous accumulation of pressure in the spiral channel; Through the combined effect of the above-mentioned structures, this invention ensures that the airflow remains in full contact with the high specific surface area catalyst coating throughout the entire flow process. This completely overcomes the problems of airflow short-circuiting, local catalyst accumulation, or underutilization in traditional straight-through reactors. It extends the contact path between the airflow and the catalyst and achieves full coverage of the reaction interface, significantly improving the utilization rate of the catalyst and the overall catalytic efficiency. This effectively solves the technical problem of insufficient catalytic degradation of pollutants in mine ventilation systems.

[0032] Furthermore, the number of helical blade structures 3 in this invention is set to two, three, or four. The pitch and number of turns of the helix are matched with the aperture and opening ratio of the perforation. The number of helical blades determines the total flow channel density of the helical channel. The pitch and number of turns affect the airflow rotation intensity and residence time. The aperture and opening ratio of the perforation 4 regulate the microjet intensity and flow splitting ratio. The three factors work together to enhance the synergistic effect of Dean's vortex and local jet. The number of helical blade structures 3 is set to two, three, or four, and its number directly determines the total flow channel density of the helical channel, thereby regulating the uniformity of airflow distribution and velocity gradient within the channel. The pitch and number of turns of the helix synergistically affect the rotation intensity and residence time of the airflow along the axial direction. The smaller the pitch and the more turns the spiral blades rotate, the more intense the airflow rotation and the stronger the Dean vortex, promoting radial mixing. The aperture and opening ratio of the perforation 4 precisely control the intensity and splitting ratio of the microjets ejected from the front and back of the spiral blades, allowing local high-speed jets to impact the catalyst wall boundary layer, effectively thinning the concentration gradient and enhancing mass transfer efficiency. By matching the number of spiral blades, pitch and number of turns, perforation aperture and opening ratio, the radial transport effect of the Dean vortex and the microscopic boundary layer disturbance effect of the microjets are synergistically activated. Without significantly increasing the system pressure drop, the contact frequency and reaction efficiency between the airflow and the catalyst coating are greatly improved, especially under low flow velocity ventilation conditions in mines, significantly improving the stability and adjustability of CO conversion rate.

[0033] The perforations 4 of this invention feature a gradient aperture distribution along the airflow direction, with a larger aperture at the inlet and a smaller aperture at the rear. The large aperture at the front reduces the risk of dust blockage, while the small aperture at the rear maintains the catalytic area, forming an axial functional zone in conjunction with the spiral structure. This gradient aperture distribution along the airflow direction allows for low-resistance diversion of the airflow upon entering the spiral fluid channel, effectively reducing the accumulation and blockage risk of dust particles in the inlet area. As the airflow progresses along the spiral path towards the rear, the gradually narrowing rear aperture ensures sufficient contact between the airflow and the catalyst coating while maintaining a high catalytic surface area density in the rear region. This prevents a sharp reduction in catalytic area due to local blockage, thus forming an axial functional zone with the continuous closed spiral fluid channel enclosed by the inner wall of the outer straight pipe and the spiral blades. This achieves a synergistic effect of front-end anti-blockage and rear-end efficient catalysis, significantly improving the long-term operational stability and catalytic efficiency of the device in dusty mine ventilation environments. This invention addresses the gradient aperture distribution of the perforation 4 along the airflow direction. Those skilled in the art can select appropriate aperture sizes for the inlet and rear end sections based on common sense. This invention does not limit the specific aperture dimensions.

[0034] This invention removes accumulated dust by blowing a pulsed airflow from the inside of an outer straight pipe outwards. Perforations serve as the blowing channels during dust removal, and their location is consistent with the structure of the helical blades. This allows the pulsed airflow to uniformly clean both sides of the helical blades and the inner wall of the outer straight pipe along a helical path. The airflow is uniformly injected through the regularly spaced perforations on both sides of the helical blade wall, directly impacting the dust deposited on the catalyst coating surface. This achieves comprehensive and synchronous dust removal of the catalyst layer on both sides of the helical blades and the inner wall of the outer straight pipe. Because the perforations are consistent with the helical blade structure, and the airflow path perfectly matches the fluid channel shape, the dust removal airflow covers the entire catalytic reaction surface without any dead angles along the helical trajectory. This effectively restores the effective reaction area lost due to dust accumulation, significantly delays catalytic efficiency decay, and improves the stability and maintenance cycle of the device during long-term operation.

[0035] The device of the present invention includes multiple outer straight pipes 1, which are installed in an array in the CO purification system of the mine return air roadway. The multiple outer straight pipes are connected in series or in parallel in the ventilation pipeline through flange interfaces to form a spatial array layout, and form an installation matching relationship with the flange structure of the outer straight pipes. Multiple outer straight pipes 1 are connected in series or in parallel to the existing ventilation ducts of the mine return air roadway through flanges or clamps at both ends, forming a spatial array layout. This layout and the flange structure of the outer straight pipes 1 form an installation matching relationship, allowing each outer straight pipe 1 to be independently disassembled and flexibly arranged in different sections of the roadway. Combined with the detachable modular design of the internal spiral catalyst core 2, the catalytic purification unit can be evenly distributed and synergistically acted in a large air volume and large space range. The continuous spiral fluid channel formed by the spiral blades 3 and the inner wall of the outer straight pipe 1, together with the through holes regularly opened on both sides, causes the airflow to generate multi-level vortices and penetrating diffusion when passing through each outer straight pipe, significantly extending the gas-liquid contact path and improving the utilization rate of the catalyst coating. Through the array-like networking of multiple outer straight pipes 1, not only is the problem of purification coverage blind spots caused by insufficient single-pipe processing capacity solved, but also seamless connection with the mine ventilation duct network structure is achieved, forming a scalable, adjustable, and highly adaptable distributed catalytic purification system, effectively improving the overall system's removal efficiency and operational stability of pollutants in the mine return air.

[0036] A method for preparing a composite oxide catalyst layer includes the following steps: S1. Take the shaped spiral foam nickel and perform multi-media ultrasonic cleaning on the shaped spiral foam nickel to remove surface oil and oxide layer; the ultrasonic cleaning is carried out in sequence with acetone, dilute hydrochloric acid and deionized water to remove oil and oxide layer on the surface of the foam nickel and obtain a clean nickel substrate.

[0037] S2. Immerse the spiral nickel foam pretreated by S1 into a Co-containing solution. 2+ Salt, Mn 2+ A DMF-water-ethanol mixed solution containing salt and 2,5-dihydroxyterephthalic acid ligand, with a volume ratio of DMF, water, and ethanol of 8:3:2, containing Co. 2+ Salt, Mn 2+ The concentrations of salt and 2,5-dihydroxyterephthalic acid ligand in the DMF-water-ethanol mixed solution were 1.09 mmol, 2.19 mmol, and 1.09 mmol, respectively. The solution was sealed and heated to carry out a solvothermal reaction. The metal framework surface of the nickel foam provided nucleation sites, and CoMn-MOF-74 crystals were directly nucleated in situ on the surface of the nickel foam and grew outward to form a uniform and dense MOF crystal film. In step S2, the solvothermal reaction was carried out at 100~150℃ for 12~24 h.

[0038] S3. The CoMn-MOF-74-loaded nickel foam is calcined at high temperature in air to decompose and remove the MOF organic ligands. The metal ions are converted into Co3O4 / Mn3O4 composite oxides, which grow on the surface of the nickel foam by Ni-O-Co / Mn chemical bonds to form a high specific surface area Co3O4 / Mn3O4 mesoporous catalyst layer. The CoMn-MOF-74-loaded nickel foam is then calcined at 350~450℃ for 2~4h.

[0039] This invention involves immersing a porous metal foam substrate, shaped into a continuous helical blade, in a solvent system containing metal salts and organic ligands. A solvothermal reaction is then performed at 100-150°C for 12-24 hours, causing metal-organic framework crystals to uniformly nucleate and grow in situ on the foam surface, avoiding the poor adhesion and localized peeling problems associated with traditional coating processes. Subsequently, heat treatment at 350-450°C for 2-4 hours in an oxidizing atmosphere promotes the complete decomposition of the organic ligands, converting metal ions into Co3O4 / Mn3O4 composite oxide nanoparticles. These nanoparticles are firmly bonded to the nickel foam substrate through Ni-O-Co / Mn chemical bonds, significantly improving the structural stability of the catalyst layer under long-term gas flow scouring. The key to achieving uniform and dense growth of CoMn-MOF-74 crystals on the three-dimensional framework of nickel foam lies in the precise matching of pretreatment processes, solvothermal conditions, and precursor concentrations. Insufficient growth results in insufficient catalyst loading and low activity; excessive growth clogs the pores of the nickel foam and causes a surge in pressure drop.

[0040] The catalyst layer formed by this invention has both a high specific surface area and a rich mesoporous structure, which effectively enhances the contact probability between CO and active sites. At the same time, since no additional binder or post-treatment coating step is required, the risk of pore blockage is avoided, the original permeability of the substrate is maintained, and airflow resistance is reduced and the service life of the catalyst module is extended.

[0041] In this invention, the mine ventilation airflow enters the device through flanges or clamps at both ends of the outer straight pipe 1. The airflow is forced to flow continuously along the spiral path by the continuous, closed, spiral fluid channel formed by the inner wall of the outer straight pipe 1 and the surface of the spiral blades 3 of the inserted spiral catalyst core 2, thus extending the contact stroke between the airflow and the catalyst interface. The spiral blades 3 are one or more spiral strips continuously wound along the axis of the outer straight pipe, with an outer diameter smaller than the inner diameter of the outer straight pipe. They are fixed to the inner wall of the outer straight pipe through their ends or edges, forming an open structure without a central rod, thus preventing short circuits or vortex dead zones from forming in the central area when the airflow flows in the channel. During the flow of the airflow in the spiral channel, part of the airflow passes through the through holes regularly opened on both sides of the spiral blade 3 wall, forming local micro-jet streams that impact the catalyst coating surface in adjacent areas, thinning the concentration boundary layer and enhancing mass transfer efficiency. The through holes are distributed in a gradient aperture along the airflow direction, with a larger aperture at the inlet to reduce the risk of dust blockage and a smaller aperture at the rear to maintain the catalyst area, forming an axial functional partition with the spiral structure. The catalyst coating is a composite oxide doped with Co3O4 / Mn3O4, uniformly loaded on the entire surface of the spiral blades and the entire inner wall of the outer straight pipe, making the entire inner wall of the fluid channel an active catalytic reaction surface. CO reacts with oxygen on the catalyst surface at low temperature to generate CO2. When dust accumulates on the catalyst surface during operation, a pulsed airflow is applied from the inside of the outer straight pipe outward, using perforations as a purging channel, so that the pulsed airflow evenly washes the front and back surfaces of the spiral blades and the inner wall of the outer straight pipe along the spiral path, removing the accumulated dust and restoring the catalytic reaction area. When the catalyst of the inserted spiral catalyst core is deactivated, the fixing device can be loosened, and the entire inserted spiral catalyst core can be pulled out of the outer straight pipe for replacement. The outer straight pipe remains fixed in place without disassembling the ventilation pipeline. Multiple outer straight pipes are connected in series or parallel to the ventilation pipeline of the mine return air roadway through flange interfaces to form a spatial array layout. The outer straight pipes work together to achieve distributed catalytic purification of mine ventilation airflow with large volume and large space.

[0042] Example A method for preparing a composite oxide catalyst layer is provided. Table 1 below lists the process parameters (solvothermal reaction temperature, solvothermal reaction time, calcination temperature and calcination time) and CO conversion rates used in Examples 1-3, respectively.

[0043] Table 1. Process parameters and CO conversion rates used in Examples 1-3.

[0044] As shown in Table 1 above, Example 1 exhibits the highest CO conversion rate. This is further demonstrated by comparing the processing technology of Example 1 with that of Comparative Examples 1-3. Performance testing and analysis results are then presented. I. Test subjects and comparison examples: 1. Example 1: Inserted spiral nickel foam blades, Co3O4 / Mn3O4 grown in situ on the surface of the nickel foam, with 2 / 3 / 4 blades and different combinations of geometric parameters.

[0045] 2. Comparative Example 1 (Catalytic Straight Tube): A straight tube with the same diameter, the inner wall of which is loaded with the same chemical composition of Co3O4 / Mn3O4 catalyst by conventional slurry coating method, without helical internal insertion elements.

[0046] 3. Comparative Example 2 (Catalytic Straight Tube): A straight tube with the same diameter, the inner wall of which is grown in situ on the surface of nickel foam to form a Co3O4 / Mn3O4 catalyst, without any helical insert elements.

[0047] 4. Comparative Example 3: The inner spiral foam nickel blades were loaded with a Co3O4 / Mn3O4 catalyst of the same chemical composition by a conventional slurry coating method.

[0048] In Comparative Example 1, the preparation and coating processes of the Co3O4 / Mn3O4 catalyst with the same chemical composition are as follows: 1. Take Co(NO3)2·6H2O and Mn(NO3)2·4H2O according to Co 2+ :Mn 2+ The solution was prepared by dissolving the metal in deionized water at a molar ratio of 5:2 to obtain a mixed salt solution with a total metal ion concentration of 0.15 mol / L. The solution was then stirred in a water bath at 50°C, and 0.8 mol / L (NH4)2CO3 solution was added dropwise to the pH to 8.5 ± 0.2. After complete precipitation, the solution was aged at 50°C for 4 hours. After filtration and washing, the solution was dried at 110°C for 12 hours and then calcined in a muffle furnace at 420°C for 3.5 hours to obtain Co3O4 / Mn3O4 composite oxide powder.

[0049] 2. The above Co3O4 / Mn3O4 composite oxide powder was mixed with boehmite, nitric acid and deionized water in a mass ratio of 28:12:1.5:58.5 and ball-milled in a planetary ball mill at 350 r / min for 3.5 hours to obtain a catalytic slurry.

[0050] 3. The inner wall of the outer straight tube is ultrasonically cleaned sequentially with acetone, dilute hydrochloric acid, and deionized water to remove surface oil and oxide layers, exposing a clean metallic nickel surface. The tube is then immersed in the slurry using the dip-coat method, allowed to stand for 4 minutes, and then pulled out at a speed of 3 cm / min. It is then dried at 90℃ for 1.5 hours. This process is repeated three times, with a target coating amount of 6–9 mg / cm². 2 Finally, it is roasted at 400℃ for 3 hours.

[0051] In Comparative Example 3, the preparation and coating processes of the Co3O4 / Mn3O4 catalyst with the same chemical composition differ from those in Comparative Example 1 in step 3. The other steps 1 and 2 are consistent with those in Comparative Example 1. The specific process of step 3 is as follows: the shaped spiral nickel foam is completely immersed in the slurry, left to stand for 4 minutes, and then pulled out at a speed of 3 cm / min. After draining off the excess slurry, it is dried at 90℃ for 1.5 hours. This process is repeated 3 times, and finally calcined at 400℃ for 3 hours.

[0052] II. Test conditions: The inlet CO concentration is 500 × 10⁻⁶. -6 That is, 7.45 × 10 -3 mol / m 3 The temperature was 25℃; the flow state was steady-state laminar flow; the inlet velocities were 0.2m / s, 0.5m / s, and 1.0m / s; the test platform was COMSOL Multiphysics CFD simulation, which was verified by mesh independence.

[0053] III. Performance Test Results: 1. Comparison of CO conversion rates: Table 2 Comparison of CO conversion rates

[0054] As shown in Table 2, the conversion rate of the present invention is significantly improved. Under the same low flow rate of 0.2 m / s, the optimal conversion rate of the present invention is 51.07%~64.96%, which is 53%~95% higher than the conversion rate of 33.31% of the catalytic straight tube.

[0055] 2. Comparison of flow resistance: Table 3 Comparison of Flow Resistance

[0056] As shown in Table 3, the flow resistance is extremely low. The pressure drop of all the schemes of this invention is less than 2.1 Pa, and the lowest can reach 0.29 Pa. It can be passively operated by utilizing the natural negative pressure of the coal mine extraction pipeline without the need for external power.

[0057] In summary, the present invention has the following advantages: 1. High mass transfer efficiency and high catalyst utilization: In granular beds, the gas flow typically takes shortcuts, leaving most of the catalyst unused. This device uses helical blades to create a rotating path for the gas flow. Centrifugal force continuously throws CO against the wall, and the holes in the blades create localized jets that repeatedly scour the wall. The gas flow is in contact with the catalyst wherever it travels in the channel, resulting in a much larger effective reaction area compared to granular beds.

[0058] 2. Lower pressure and lower energy consumption: Particle accumulation inevitably leads to air resistance, and the greater the air volume, the greater the resistance. This device has no accumulating bed; the airflow follows the spiral channel, and the perforations provide space for flow distribution, preventing pressure from continuously accumulating upwards. For the same air volume, the fan output is much lower.

[0059] 3. Anti-clogging, moisture-resistant, and durable: Downhole dust and moisture are the biggest killers of catalysts. The helical blades themselves throw large dust particles outward, making them less likely to accumulate on the catalyst surface. During dust removal, a blow from the inside out creates ready-made purging channels in the pores, resulting in thorough dust removal. The catalyst is grown on the metal surface, not pasted on, and will not be dislodged by long-term airflow, giving it a much longer lifespan than particle beds.

[0060] 4. Easy to replace without interrupting production. The outer tube is just a straight pipe that is connected to the pipeline with a flange and remains stationary. The catalytic converter is located on the core. If it deactivates, simply remove the old core and insert the new one. There is no need to disassemble the pipeline, and the downtime is very short.

[0061] 5. The device makes full use of space and has a compact structure, with only the outer surface of the particles acting as the active surface. It utilizes the inner wall of the outer tube, both sides of the blades, and the inner wall of the pores, resulting in a much larger effective reaction surface for the same volume, allowing for a smaller device.

Claims

1. A CO catalytic purification device, characterized in that, include: The outer straight pipe is a standard round pipe structure with flanges or clamps at both ends. An internal spiral catalyst core is coaxially sleeved inside the outer straight tube and is a detachable module; The inserted spiral catalyst core uses nickel foam as the base material and is formed into a continuous spiral blade structure; the surface of the nickel foam skeleton is bonded with a Co3O4 / Mn3O4 composite oxide catalyst layer by chemical bonds; the Co3O4 / Mn3O4 composite oxide is obtained by pyrolysis of the CoMn-MOF-74 precursor grown in situ on the surface of the nickel foam, and the catalyst layer has no binder coating layer.

2. The CO catalytic purification device according to claim 1, characterized in that, The spiral blades are fixed to the inner wall of the outer straight tube through their ends or edges, forming an open structure without a central rod; The inner wall of the outer straight pipe and the surface of the spiral blade together form a continuous, closed, spiral fluid channel.

3. The CO catalytic purification device according to claim 2, characterized in that, Also includes: The perforation consists of multiple through holes, regularly formed on both sides of the spiral blade wall.

4. The CO catalytic purification device according to claim 3, characterized in that, The perforations are distributed in a gradient size along the airflow direction, with larger pores at the inlet and smaller pores at the rear. The large pores at the front reduce the risk of dust blockage, while the small pores at the rear maintain the catalytic area, forming an axial functional zone with the spiral structure.

5. The CO catalytic purification device according to claim 4, characterized in that, Dust is removed by blowing from the inside of the outer straight pipe outward with pulsed airflow. The perforations serve as the blowing channels during dust removal. The perforations are distributed in the same way as the spiral blade structure, so that the pulsed airflow can evenly brush the front and back surfaces of the spiral blade and the inner wall of the outer straight pipe along the spiral path.

6. The CO catalytic purification device according to claim 4, characterized in that, The device includes multiple outer straight pipes, which are installed in an array in the CO purification system of the mine return air roadway. The multiple outer straight pipes are connected in series or in parallel in the ventilation pipeline through flange interfaces to form a spatial array layout, and form an installation matching relationship with the flange structure of the outer straight pipes.

7. The method for preparing a composite oxide catalyst layer according to claims 1-6, characterized in that, Includes the following steps: S1. Take the shaped spiral foam nickel and perform multi-media ultrasonic cleaning on the shaped spiral foam nickel to remove surface oil and oxide layer. S2. Immerse the pretreated spiral nickel foam from S1 into a Co-containing solution. 2+ Salt, Mn 2+ A DMF-water-ethanol mixed solution of salt and 2,5-dihydroxyterephthalic acid ligand was sealed and heated to carry out a solvothermal reaction to obtain CoMn-MOF-74 crystals; the metal framework surface of nickel foam provides nucleation sites, and CoMn-MOF-74 crystals are directly nucleated in situ on the surface of nickel foam and grow outward to form a uniform and dense MOF crystal film. S3. Calcine the CoMn-MOF-74-loaded nickel foam in an air atmosphere to decompose and remove the MOF organic ligands. The metal ions are converted into Co3O4 / Mn3O4 composite oxides, which grow on the surface of the nickel foam by relying on Ni-O-Co / Mn chemical bonds to form a mesoporous Co3O4 / Mn3O4 composite oxide catalytic layer.

8. The method for preparing a composite oxide catalyst layer according to claim 7, characterized in that, In step S1, ultrasonic cleaning is performed sequentially using acetone, dilute hydrochloric acid, and deionized water.

9. The method for preparing a composite oxide catalyst layer according to claim 7, characterized in that, In step S2, a solvothermal reaction is carried out at 100~150℃ for 12~24h.

10. The method for preparing a composite oxide catalyst layer according to claim 7, characterized in that, In step S3, the CoMn-MOF-74-loaded nickel foam is calcined at 350-450℃ for 2-4 hours.

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