A control method for electric field enhanced catalytic formaldehyde removal

Abstract

The application discloses a kind of electric field reinforced catalytic aldehyde removal control methods for formaldehyde efficient removal, it is related to formaldehyde removal technical field, in the purification reactor, pre-adsorption activated carbon block and deep oxidation activated carbon block are oppositely arranged, and opposite reaction cavity is formed between the two;First noble metal catalyst layer and second noble metal catalyst layer are respectively arranged on the surface of pre-adsorption activated carbon block and deep oxidation activated carbon block towards opposite reaction cavity, and activation catalytic reaction zone and mineralization catalytic reaction zone are formed along the flow direction of formaldehyde-containing gas;Through pulse DC power supply, electric field reinforced zone under pulse corona discharge state is formed in opposite reaction cavity, formaldehyde-containing gas is sequentially completed activation and deep oxidation in activation catalytic reaction zone and mineralization catalytic reaction zone after pre-enrichment, can improve formaldehyde removal rate and carbon dioxide selectivity, reduce intermediate product accumulation, and improve continuous operation stability.

Description

Technical Field

[0001] This invention relates to the field of formaldehyde removal technology, specifically to an electric field-enhanced catalytic formaldehyde removal control method for efficient formaldehyde removal. Background Technology

[0002] With the continuous development of environmental governance, formaldehyde, as a typical oxygen-containing volatile organic compound, has attracted increasing attention due to its long-term slow release, concentration fluctuations, and difficulty in complete mineralization under low temperature conditions. Regarding formaldehyde treatment, related technologies have generally evolved from single physical adsorption to catalytic synergy, and then to electric field or plasma-enhanced catalysis.

[0003] At present, single adsorption schemes can only capture formaldehyde, which is prone to secondary release due to adsorption saturation. Although the integrated catalytic oxidation scheme can improve the conversion rate, the catalytic sites are usually evenly distributed along the bed, which can easily lead to premature loading in the inlet area and insufficient utilization in the downstream area, resulting in the accumulation of intermediate products and low carbon dioxide selectivity. Electric field or plasma enhancement schemes often only enhance the discharge itself and fail to organize the enrichment of formaldehyde, interface activation and deep mineralization into a continuous process. Therefore, they generally have problems such as low energy utilization, increased by-products such as ozone and insufficient operational stability. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the technical solution of this invention is as follows: An electric field-enhanced catalytic formaldehyde removal control method for efficient formaldehyde removal includes the following steps: S1. Pre-adsorption activated carbon blocks and deep oxidation activated carbon blocks are arranged opposite each other in the purification reactor, and a reaction chamber with a width of 3mm to 12mm is formed between the pre-adsorption activated carbon blocks and the deep oxidation activated carbon blocks. S2. A first noble metal catalyst layer is provided on the side of the pre-adsorbed activated carbon block facing the opposite reaction chamber, and a second noble metal catalyst layer is provided on the side of the deep oxidation activated carbon block facing the opposite reaction chamber. The first and second noble metal catalyst layers sequentially form an activation catalytic reaction zone and a mineralization catalytic reaction zone along the flow direction of formaldehyde-containing gas. The length of the activation catalytic reaction zone along the flow direction accounts for 25% to 45% of the total effective length of the first and second noble metal catalyst layers along the flow direction. S3. Connect the pre-adsorbed activated carbon block and the deep oxidation activated carbon block to the positive and negative terminals of the pulsed DC power supply, respectively, and apply the corresponding pulsed DC voltage according to the width of the opposing reaction chamber, so as to form an electric field enhancement zone in the opposing reaction chamber under the pulsed corona discharge state. S4. Formaldehyde-containing gas first flows through the pre-adsorption activated carbon block for pre-enrichment, and then enters the opposing reaction chamber. Under the action of the electric field enhancement zone, formaldehyde molecules are converted into activated intermediate products in the activation catalytic reaction zone. The activated intermediate products enter the mineralization catalytic reaction zone with the gas flow and are further converted into carbon dioxide and water. The incompletely converted components enter the deep oxidation activated carbon block for further oxidation.

[0005] Furthermore, in S1, the opposing reaction chamber is a slit-type reaction chamber; The ratio of the length of the opposing reaction chamber along the direction of formaldehyde gas flow to the width of the opposing reaction chamber is 15:1 to 60:1.

[0006] Furthermore, in S1, the opposing reaction chamber is formed by the inner surface of the pre-adsorbed activated carbon block and the relative inner surface of the deep-oxidized activated carbon block. Insulating flow guiding components are provided at the inlet and outlet ends of the opposing reaction chamber to ensure that formaldehyde-containing gas enters the opposing reaction chamber uniformly and passes through the activation catalytic reaction zone and the mineralization catalytic reaction zone along the axial direction of the opposing reaction chamber.

[0007] Furthermore, in S1, the formaldehyde-containing gas does not come into direct contact with the deep-oxidation activated carbon block before entering the opposing reaction chamber; Once the formaldehyde-containing gas leaves the opposing reaction chamber, it does not return to the pre-adsorbed activated carbon block. The thickness of the pre-adsorption activated carbon block is greater than that of the deep oxidation activated carbon block, and the pre-adsorption activated carbon block has a pore size distribution dominated by micropores, while the deep oxidation activated carbon block has a pore size distribution dominated by mesopores.

[0008] Furthermore, in S2, a first noble metal catalyst layer and a second noble metal catalyst layer are respectively provided on the surfaces of the pre-adsorbed activated carbon block and the deep-oxidized activated carbon block facing the opposing reaction chamber. The first and second noble metal catalyst layers form an activation catalytic reaction zone and a mineralization catalytic reaction zone along the flow direction of formaldehyde-containing gas; Furthermore, the penetration depth into the continuous pores inside the corresponding activated carbon block is no greater than 50 μm.

[0009] Furthermore, in S2, the activation catalytic reaction zone and the mineralization catalytic reaction zone are continuously connected along the direction of formaldehyde-containing gas flow; No inactive transition zone is set between the activation catalytic reaction zone and the mineralization catalytic reaction zone; The activation catalytic reaction zone is located upstream, and the mineralization catalytic reaction zone is located downstream.

[0010] Furthermore, in S2, the catalyst loading per unit interface area in the mineralization catalytic reaction zone is 1.2 to 2.2 times that in the activation catalytic reaction zone. The catalyst supported on the activated catalytic reaction zone includes a first noble metal catalyst; The catalyst supported in the mineralization catalytic reaction zone includes a second noble metal catalyst; The first noble metal catalyst is platinum (Pt), with a platinum (Pt) loading of 0.01 wt% to 0.1 wt%. The second noble metal catalyst is iridium (Ir), with an iridium loading of 0.05 wt% to 0.2 wt%.

[0011] Furthermore, in S3, the average electric field strength within the opposing reaction chamber is 1.0 kV / mm to 2.2 kV / mm; The frequency of the pulsed DC power supply is 200Hz to 800Hz; The pulse rise time is 50ns to 200ns, and the duty cycle is 1% to 10%.

[0012] Furthermore, in S4, the pre-enriched formaldehyde-containing gas enters the deep oxidation activated carbon block only through the opposing reaction chamber; The residence time of formaldehyde gas in the opposing reaction chamber is 0.05s to 0.12s.

[0013] The beneficial effects of this invention are as follows: 1. By setting up a counter-reaction chamber between the pre-adsorption activated carbon block and the deep oxidation activated carbon block, and limiting the formaldehyde-containing gas to be pre-enriched by the pre-adsorption activated carbon block before entering the counter-reaction chamber, the formaldehyde can be locally concentrated before entering the electric field enhancement zone, thereby increasing the contact probability between formaldehyde and the catalytic interface. At the same time, the slit-type counter-reaction chamber is conducive to stabilizing the electric field distribution and gas flow path, reducing ineffective diffusion and bypass passage, and improving the initial activation efficiency of formaldehyde.

[0014] 2. By setting a first noble metal catalyst layer and a second noble metal catalyst layer on both sides of the opposing reaction chamber, and forming an activation catalytic reaction zone and a mineralization catalytic reaction zone along the gas flow direction, the initial activation process of formaldehyde and the deep oxidation process of the activated intermediate products can be completed in segments. In addition, the two zones are continuously connected, there is no catalytically active transition zone, and the mineralization catalytic reaction zone has a higher catalyst loading per unit interface area, which helps to reduce the accumulation of intermediate products and improve the selectivity of carbon dioxide and the overall degree of mineralization.

[0015] 3. When the opposing reaction chamber is used in conjunction with the partitioned precious metal catalytic structure, the pre-enrichment, interface activation and deep mineralization of formaldehyde can be organized into a continuous reaction path. Combined with the pulsed corona discharge state formed by the pulsed DC power supply, formaldehyde molecules can be activated and oxidized sequentially within a controlled residence time, thereby simultaneously improving the formaldehyde removal rate, mineralization efficiency and continuous operation stability, and reducing the adverse effects of byproducts such as ozone on the treatment effect. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the method steps of the present invention; Figure 2 This is a schematic diagram of the opposing reaction chamber structure of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1 Please see Figure 1 and Figure 2 This invention provides an electric field-enhanced catalytic formaldehyde removal control method for efficient formaldehyde removal, comprising the following steps: S1. Pre-adsorption activated carbon blocks and deep oxidation activated carbon blocks are arranged opposite each other in the purification reactor, and a reaction chamber with a width of 3mm to 12mm is formed between the pre-adsorption activated carbon blocks and the deep oxidation activated carbon blocks. S2. A first noble metal catalyst layer is provided on the side of the pre-adsorbed activated carbon block facing the opposite reaction chamber, and a second noble metal catalyst layer is provided on the side of the deep oxidation activated carbon block facing the opposite reaction chamber. The first and second noble metal catalyst layers sequentially form an activation catalytic reaction zone and a mineralization catalytic reaction zone along the flow direction of formaldehyde-containing gas. The length of the activation catalytic reaction zone along the flow direction accounts for 25% to 45% of the total effective length of the first and second noble metal catalyst layers along the flow direction. S3. Connect the pre-adsorbed activated carbon block and the deep oxidation activated carbon block to the positive and negative terminals of the pulsed DC power supply, respectively, and apply the corresponding pulsed DC voltage according to the width of the opposing reaction chamber, so as to form an electric field enhancement zone in the opposing reaction chamber under the pulsed corona discharge state. S4. Formaldehyde-containing gas first flows through the pre-adsorption activated carbon block for pre-enrichment, and then enters the opposing reaction chamber. Under the action of the electric field enhancement zone, formaldehyde molecules are converted into activated intermediate products in the activation catalytic reaction zone. The activated intermediate products enter the mineralization catalytic reaction zone with the gas flow and are further converted into carbon dioxide and water. The incompletely converted components enter the deep oxidation activated carbon block for further oxidation.

[0019] In this embodiment, a continuous formaldehyde purification test device is built using exhaust gas purification from a hot-pressing production line for engineered wood products as the application scenario.

[0020] The purification reactor adopts a corrosion-resistant rectangular shell, and pre-adsorption activated carbon blocks, opposing reaction chambers, and deep oxidation activated carbon blocks are arranged sequentially along the airflow direction inside the shell.

[0021] The pre-adsorption activated carbon blocks are made of coconut shell-based molded activated carbon, with a thickness of 18 mm and a specific surface area of ​​1020 m². 2 / g, pore size distribution is mainly micropores; deep oxidation activated carbon blocks are made of coal-based molded activated carbon, with a thickness of 12mm and a specific surface area of ​​710m². 2 / g, the pore size distribution is mainly mesoporous.

[0022] The pre-adsorption activated carbon block and the deep oxidation activated carbon block are arranged opposite each other, forming a 6mm wide opposing reaction chamber between them. The length of the opposing reaction chamber along the flow direction of formaldehyde-containing gas is 180mm.

[0023] A first noble metal catalyst layer was prepared by preparing a pre-adsorbed activated carbon block facing the opposite reaction chamber. The first noble metal catalyst layer used chloroplatinic acid as a precursor and was prepared by equal-volume impregnation, drying at 60°C, and reduction treatment at 250°C, wherein the platinum (Pt) loading was 0.015 wt%. A second noble metal catalyst layer is prepared by using a deep oxidation activated carbon block facing the opposite reaction chamber. The second noble metal catalyst layer uses chloroiridic acid as a precursor and is prepared by impregnation, drying at 80°C and calcination at 300°C. The iridium loading is 0.060 wt%.

[0024] The first and second noble metal catalyst layers form an activation catalytic reaction zone and a mineralization catalytic reaction zone sequentially along the formaldehyde-containing gas flow direction. The length of the activation catalytic reaction zone accounts for 35% of the total action length, and the length of the mineralization catalytic reaction zone accounts for 65% of the total action length.

[0025] The activation catalytic reaction zone is located upstream, and the mineralization catalytic reaction zone is located downstream. The two are continuously connected and there is no transitional zone without catalytic activity in between.

[0026] The pre-adsorption activated carbon block and the deep oxidation activated carbon block are connected to the positive and negative terminals of the pulsed DC power supply, respectively. The frequency of the pulsed DC power supply is set to 400Hz, the rise time is 100ns, and the duty cycle is 4%. The output voltage is adjusted to stabilize the average electric field strength in the opposing reaction chamber at 1.6kV / mm.

[0027] The formaldehyde-containing gas is prepared by mixing formaldehyde standard gas with air, and the inlet formaldehyde concentration is controlled at 3.0 mg / m³. 3 The gas temperature is controlled at 32℃, the relative humidity at 55%, and the processing air volume at 120m³. 3 / h.

[0028] Formaldehyde-containing gas first flows through a pre-adsorbed activated carbon block for pre-enrichment, and then enters the opposing reaction chamber; Formaldehyde molecules are transformed into activated intermediate products in the activated catalytic reaction zone under the action of the electric field enhancement zone. They then enter the mineralization catalytic reaction zone to continue being transformed into carbon dioxide and water. The incompletely transformed components then enter the deep oxidation activated carbon block for further oxidation.

[0029] The device operated continuously for 8 hours, continuously collecting data on formaldehyde concentration, carbon dioxide concentration, ozone concentration, pressure drop, and energy consumption at the outlet during the steady-state phase. Boundary comparison and structural comparison were set up for comparison to verify the rationality of the ratio of the width of the opposing reaction chamber to the length of the activated catalytic reaction zone.

[0030] Table 1: Effects of the width of the opposing reaction chamber and the proportion of the length of the activated catalytic reaction zone on formaldehyde purification performance Parameters / Test Subjects Example 1 of the present invention - within the window of the present invention Comparative Example 1 - Reaction Chamber Too Narrow Comparative Example 2 - Reaction Chamber Too Wide Comparative Example 3 - Activation Region Too Short Comparative Example 4 - Activation Region Too Long Comparative Example 5 - No opposing reaction chamber Comparative Example 6 - Partitionless Catalysis Width of the opposing reaction chamber (mm) 6 2 14 6 6 0 6 Percentage of activated catalytic reaction zone length (%) 35 35 35 20 50 0 100 Average electric field strength (kV / mm) 1.6 1.6 1.6 1.6 1.6 0 1.6 Pulse frequency (Hz) 400 400 400 400 400 0 400 Dwell time (s) 0.08 0.04 0.13 0.08 0.08 0.11 0.08 Formaldehyde concentration at the inlet (mg / m3) 3 3 3 3 3 3 3 Formaldehyde removal rate (%) 96.9 87.8 83.6 89.4 91.2 68.7 84.1 Carbon dioxide selectivity (%) 85.3 70.5 66.1 72.8 69.7 41.2 60.4 Ozone concentration at the outlet (mg / m3) 0.013 0.028 0.017 0.018 0.021 0 0.026 Pressure drop (Pa) 121 214 79 119 123 97 118 Removal rate retention rate after 8 hours (%) 95.4 84.2 86.5 88.1 87.4 74.3 82.7 As can be seen from the results in Table 1, Example 1 of the present invention is superior to the comparative examples in terms of formaldehyde removal rate, carbon dioxide selectivity and operational stability.

[0031] In Example 1 of this invention, the formaldehyde removal rate reached 96.9%, the carbon dioxide selectivity reached 85.3%, and the removal rate retention rate reached 95.4% after 8 hours. This indicates that by using a continuous combination of pre-adsorbed activated carbon blocks, opposing reaction chambers, a first noble metal catalyst layer, a second noble metal catalyst layer, and activation catalytic reaction zone and mineralization catalytic reaction zone, formaldehyde is not only adsorbed, but can also complete pre-enrichment, activation and deep mineralization along a fixed reaction path.

[0032] In Comparative Example 5, after the opposing reaction chamber was removed, the formaldehyde removal rate was only 68.7% and the carbon dioxide selectivity was only 41.2%. This indicates that the opposing reaction chamber is not a formal gap structure, but a key technical feature that determines whether the electric field enhancement zone can be effectively established and whether the gas-solid interface can be confined and coupled.

[0033] After the partitioning design of the activation catalytic reaction zone and the mineralization catalytic reaction zone was removed in Comparative Example 6, the formaldehyde removal rate dropped to 84.1% and the carbon dioxide selectivity dropped to 60.4%. This indicates that the partitioning of the first and second precious metal catalyst layers along the process is not a simple catalyst spreading, but is directly related to whether the formaldehyde activation stage and the mineralization stage of the activated intermediate product can each be in a more suitable reaction environment.

[0034] The table also provides direct support for the rationality of the process boundary range.

[0035] In Comparative Example 1, reducing the width of the opposing reaction chamber to 2 mm enhanced the electric field coupling, but significantly increased the voltage drop to 214 Pa, and the outlet ozone concentration to 0.028 mg / m³. 3This indicates that an excessively narrow reaction chamber restricts airflow and intensifies partial discharge side reactions. In Comparative Example 2, after increasing the width of the opposing reaction chamber to 14 mm, the formaldehyde removal rate dropped to 83.6% and the carbon dioxide selectivity dropped to 66.1%, indicating that an excessively wide reaction chamber would weaken the coupling between interfaces and reduce the effective utilization rate of the electric field.

[0036] Therefore, the 3mm to 12mm specified in claim 1 is not an arbitrary value, but an effective window obtained by comparing and screening the two ends of the operating conditions, which are "too narrow" and "too wide". The process boundary of the proportion of the length of the activated catalytic reaction zone also has a clear basis.

[0037] In Comparative Example 3, when the length of the activated catalytic reaction zone was reduced to 20%, the formaldehyde removal rate and carbon dioxide selectivity decreased to 89.4% and 72.8%, respectively, indicating that an excessively short activated catalytic reaction zone would lead to insufficient initial activation of formaldehyde. In Comparative Example 4, the length of the activated catalytic reaction zone was increased to 50%. Although the formaldehyde removal rate remained at 91.2%, the carbon dioxide selectivity decreased to 69.7%. This indicates that an excessively long activated catalytic reaction zone would compress the length of the mineralization catalytic reaction zone, making it difficult for the activated intermediate products to be fully and deeply oxidized.

[0038] Therefore, it can be seen that the activation catalytic reaction zone, which accounts for 25% to 45% of the total reaction length, can enable a better continuous division of labor between the front-end activation and the back-end mineralization.

[0039] It should be noted that: pre-adsorption activated carbon blocks refer to activated carbon functional units located upstream of the airflow that preferentially undertake the function of formaldehyde capture and concentration. The role of pre-adsorption activated carbon blocks is not simply adsorption, but to transform low-concentration, dispersed formaldehyde molecules into locally high-concentration reaction precursor streams, providing a stable feed for subsequent interfacial catalysis.

[0040] Deep oxidation activated carbon blocks refer to activated carbon functional units located downstream of the gas flow that preferentially undertake the deep oxidation of intermediate products. The purpose of deep oxidation activated carbon blocks is to receive residual components that have not been fully converted after the mineralization catalytic reaction zone and continue to propel them towards carbon dioxide and water. Together, they form a reaction system with a clear division of labor between the front and back ends.

[0041] The opposing reaction chamber is not an ordinary gap, but a confined reaction space formed by pre-adsorbed activated carbon blocks and deep-oxidized activated carbon blocks. On the one hand, the opposing reaction chamber shortens the diffusion distance between active species and formaldehyde molecules, and on the other hand, it confines the electric field enhancement zone inside the slit space, thus taking into account the discharge intensity, gas-solid mass transfer and catalyst utilization. The width of the opposing reaction chamber is set to 3mm to 12mm, which is conducive to forming a stable electric field window while maintaining continuous ventilation, and avoids insufficient field strength due to excessively large gaps or increased voltage drop and discharge instability due to excessively small gaps.

[0042] The first and second noble metal catalyst layers are the material basis of this embodiment. The first noble metal catalyst layer preferentially undertakes the adsorption activation and bond energy weakening of formaldehyde molecules; the second noble metal catalyst layer preferentially undertakes the deep oxidation of activated intermediate products.

[0043] The activation catalytic reaction zone and the mineralization catalytic reaction zone formed sequentially along the flow direction embody the concept of spatial partitioning catalysis. Traditional schemes often distribute the same catalyst evenly across the entire reaction surface, which can easily lead to premature saturation of the inlet zone and insufficient utilization of the downstream zone. By spatial partitioning, the two reaction requirements of "easy adsorption and easy activation" and "easy mineralization and easy termination" are separated in the flow direction, so that the formaldehyde conversion pathway changes from random parallel to directional series.

[0044] The pulsed corona discharge state is the energy input method of this invention. The pulsed DC power supply generates high-energy electrons, active oxygen species and locally excited state particles in the opposing reaction chamber, which can enhance the initial stage of formaldehyde activation and reduce the risk of local overheating caused by continuous DC.

[0045] In conjunction with the activation catalytic reaction zone and the mineralization catalytic reaction zone, the pulsed corona discharge state is no longer just a simple discharge, but becomes a coupled driving force for catalytic activation and deep oxidation.

[0046] As can be seen from Table 1, Example 1 of the present invention shows better results in terms of formaldehyde removal rate, carbon dioxide selectivity and continuous operation stability compared with conventional activated carbon beds, non-opposing reaction chamber structures and non-partitioned catalytic structures.

[0047] The opposing reaction chambers allow the gas to couple more fully with the catalytic interface within the confined space. The division of labor between the activation catalytic reaction zone and the mineralization catalytic reaction zone along the process allows the initial activation of formaldehyde molecules and the deep oxidation of activated intermediate products to be continuously connected. This not only improves the overall formaldehyde removal efficiency, but also increases the degree of conversion of the final products into carbon dioxide and water, and reduces the accumulation of intermediate products and the probability of side reactions.

[0048] Meanwhile, even with ozone byproducts kept at a low level, the invention can still maintain high processing capacity and good operational stability. This indicates that the invention does not rely solely on increasing discharge intensity or catalyst dosage to achieve performance improvement, but rather achieves effective matching of mass transfer, activation, and mineralization processes through the synergistic design of the opposing reaction chamber and the partitioned catalytic structure.

[0049] It should be noted that the width of the opposing reaction cavity and the pulsed DC voltage are selected in correspondence with the average electric field strength, which is determined by the ratio of the peak value of the pulsed DC voltage to the width of the opposing reaction cavity.

[0050] When the width of the opposing reaction cavity is in the range of 3mm to 12mm, the peak value of the pulsed DC voltage is selected according to the principle of making the average electric field strength in the opposing reaction cavity reach 1.0kV / mm to 2.2kV / mm, so as to form an electric field enhancement zone in the opposing reaction cavity under the pulsed corona discharge state.

[0051] During implementation, the width of the opposing reaction cavity is first determined, and then the corresponding peak value of the pulsed DC voltage is calculated according to the range of the average electric field strength, and the voltage is gradually increased from low to high. When a stable pulse discharge occurs in the opposing reaction cavity and no continuous arcing occurs, it is determined that an electric field enhancement zone in the pulsed corona discharge state is formed in the opposing reaction cavity, and the corresponding voltage is used as the working voltage.

[0052] Example 2 Please refer to Figure 1 and Figure 2 Specifically: In S1, the opposing reaction chamber is a slit-type reaction chamber; The ratio of the length of the opposing reaction chamber along the direction of formaldehyde gas flow to the width of the opposing reaction chamber is 15:1 to 60:1.

[0053] In S1, the opposing reaction chamber is formed by the inner surface of the pre-adsorbed activated carbon block and the relative inner surface of the deep-oxidized activated carbon block. Insulating flow guiding components are provided at the inlet and outlet ends of the opposing reaction chamber to ensure that formaldehyde-containing gas enters the opposing reaction chamber uniformly and passes through the activation catalytic reaction zone and the mineralization catalytic reaction zone along the axial direction of the opposing reaction chamber.

[0054] In S1, the formaldehyde-containing gas does not come into direct contact with the deep oxidation activated carbon block before entering the opposing reaction chamber; Once the formaldehyde-containing gas leaves the opposing reaction chamber, it does not return to the pre-adsorbed activated carbon block. The thickness of the pre-adsorption activated carbon block is greater than that of the deep oxidation activated carbon block, and the pre-adsorption activated carbon block has a pore size distribution dominated by micropores, while the deep oxidation activated carbon block has a pore size distribution dominated by mesopores.

[0055] In this embodiment, the exhaust gas purification of a hot-pressing production line for engineered wood products is used as the application scenario, and the same continuous formaldehyde purification device as in Embodiment 1 is built.

[0056] The purification reactor adopts a rectangular insulating shell, and the pre-adsorption activated carbon blocks, opposing reaction chambers and deep oxidation activated carbon blocks are arranged in sequence along the airflow direction inside.

[0057] The pre-adsorption activated carbon blocks are made of coconut shell-based molded activated carbon, with a thickness of 18 mm and a specific surface area of ​​1020 m². 2 / g; Deep oxidation activated carbon blocks are made of coal-based molded activated carbon, with a thickness of 12mm and a specific surface area of ​​710m². 2 / g.

[0058] Two pieces of activated carbon are arranged in parallel opposite directions. The first and second noble metal catalyst layers are still respectively set on the opposite inner surfaces, and continuously form the activation catalytic reaction zone and the mineralization catalytic reaction zone along the airflow direction.

[0059] The pulsed DC power supply frequency is set to 400Hz, the rise time is set to 100ns, and the duty cycle is set to 4%. The average electric field strength in the opposing reaction chamber is maintained at 1.6kV / mm by adjusting the output voltage.

[0060] The formaldehyde concentration at the entrance was controlled at 3.0 mg / m³. 3 The air volume was controlled at 120 m³ / h, the temperature at 32℃, and the relative humidity at 55%.

[0061] In this embodiment, only the length of the opposing reaction chamber along the flow direction of formaldehyde-containing gas is changed, thereby forming different length-to-width ratios.

[0062] In Example 2 of this invention, the width of the opposing reaction chamber is 6 mm and the length is 180 mm, corresponding to a length-to-width ratio of 30:1; the reference embodiments are 15:1 and 60:1 respectively; the comparative examples are 10:1 and 75:1 respectively.

[0063] To avoid interference from other variables, the activated carbon material, catalyst type, precious metal loading, gas composition, power supply parameters, and operating time of each group of devices were kept consistent, and only the performance differences caused by changes in aspect ratio were compared.

[0064] After 8 hours of continuous operation, the average value within 2 hours of steady-state operation was taken as the evaluation result. The test indicators included formaldehyde removal rate, carbon dioxide selectivity, outlet ozone concentration, pressure drop, and removal rate retention rate after 8 hours.

[0065] This embodiment can directly verify whether the technical range of "slit-type reaction chamber" and "length to width ratio of 15:1 to 60:1" in this embodiment has sufficient process basis, and reveal the influence of this range on the balance between axial residence path, interface mass transfer efficiency, discharge stability and by-product control.

[0066] Table 2: Comparison of formaldehyde purification performance under different aspect ratios of the opposing reaction chambers Parameters / Test Subjects Example 2 of the present invention Refer to Example 1 Refer to Example 2 Comparative Example 2-1 Comparative Example 2-2 Width of the opposing reaction chamber (mm) 6 6 6 6 6 Length of opposing reaction chamber (mm) 180 90 360 60 450 Length / Width Ratio 30:1 15：1 60:10 10:1 75:1 Formaldehyde concentration at the inlet (mg / m3) 3 3 3 3 3 Air volume handled (m³ / h) 120 120 120 120 120 Average electric field strength (kV / mm) 1.6 1.6 1.6 1.6 1.6 Pulse frequency (Hz) 400 400 400 400 400 Dwell time (s) 0.08 0.05 0.12 0.04 0.15 Formaldehyde removal rate (%) 96.4 93.8 94.1 88.2 85 Carbon dioxide selectivity (%) 84.6 79.2 80.1 71.6 68.4 Ozone concentration at the outlet (mg / m3) 0.014 0.016 0.017 0.021 0.019 Pressure drop (Pa) 122 101 168 92 184 Removal rate retention rate after 8 hours (%) 95.1 91.3 90.8 85.6 83.9 Table 2 shows that the "opposing reaction chamber is a slit-type reaction chamber, and the length-to-width ratio is 15:1 to 60:1" defined in this embodiment is not an arbitrary setting, but an effective boundary obtained through process effect screening.

[0067] First, let's look at Example 2, Reference Example 1, and Reference Example 2 of the present invention, which are within the scope of the invention.

[0068] The three groups of experiments achieved formaldehyde removal rates of 96.4%, 93.8%, and 94.1%, respectively, and carbon dioxide selectivity of 84.6%, 79.2%, and 80.1%, respectively. The removal rate retention rate was also higher than 90% after 8 hours.

[0069] This indicates that as long as the opposing reaction chambers maintain a slit-like structure and the length-to-width ratio is between 15:1 and 60:1, the gas can accommodate both a sufficient axial reaction path and acceptable flow resistance within the chambers, allowing the division of labor between the activation catalytic reaction zone and the mineralization catalytic reaction zone to be fully utilized.

[0070] In particular, Example 2 of the present invention has the best performance in all indicators at a ratio of 30:1, indicating that the intermediate value is more conducive to achieving a balance between residence time, pressure drop and field enhancement efficiency.

[0071] Comparative Examples 1-1 and 2-2 correspond to cases below the lower limit and above the upper limit, respectively.

[0072] The length-to-width ratio of Comparative Example 1-1 was only 10:1, resulting in a formaldehyde removal rate of 88.2% and a carbon dioxide selectivity of 71.6%.

[0073] This result indicates that when the opposing reaction chamber is too short, although the gas resistance is low, the axial residence path of formaldehyde molecules in the activation catalytic reaction zone and the mineralization catalytic reaction zone is insufficient. The activated intermediate product leaves the reaction chamber before it can fully advance to the final product, resulting in a decrease in the overall degree of mineralization.

[0074] When the length-to-width ratio of Comparative Example 2-2 reached 75:1, the formaldehyde removal rate further decreased to 85.0%, the carbon dioxide selectivity decreased to 68.4%, the pressure drop increased to 184 Pa, and the removal rate retention rate was only 83.9% after 8 hours.

[0075] This result indicates that while an excessively long opposing reaction chamber increases the theoretical residence path, it also leads to a higher pressure drop and more significant flow unevenness, which affects the uniformity of gas flow through the reaction chamber and the stability of the discharge zone, while also increasing the probability of local side reactions.

[0076] Compared with Example 2 of the present invention, both excessively short and excessively long directions lead to a significant decrease in performance, thus proving that the range of 15:1 to 60:1 has clear process rationality.

[0077] Furthermore, the changes in ozone concentration at the outlet also show that a moderate aspect ratio is beneficial for balancing purification efficiency and byproduct control.

[0078] Example 2 of this invention achieves the highest formaldehyde removal rate and carbon dioxide selectivity while maintaining an outlet ozone concentration of only 0.014 mg / m³. 3This indicates that at this aspect ratio, the active species generated by pulsed corona discharge can be used more effectively for formaldehyde activation and mineralization, rather than being converted into a large amount of byproducts.

[0079] As can be seen from Table 2, the limitation of the slit-type opposing reaction chamber and its length-to-width ratio in this embodiment is essentially a synergistic limitation of the reactor size and flow path.

[0080] This limitation is not a simple size optimization, but is directly related to whether the electric field enhancement zone can be stably formed in this embodiment, whether formaldehyde can be continuously converted along the activation catalytic reaction zone and the mineralization catalytic reaction zone, and whether the device can operate stably for a long time.

[0081] Example 3 Please refer to Figure 1 and Figure 2 Specifically: In S2, a first noble metal catalyst layer and a second noble metal catalyst layer are respectively provided on the surfaces of the pre-adsorbed activated carbon block and the deep oxidation activated carbon block facing the opposite reaction chamber. The first and second noble metal catalyst layers form an activation catalytic reaction zone and a mineralization catalytic reaction zone along the flow direction of formaldehyde-containing gas; Furthermore, the penetration depth into the continuous pores inside the corresponding activated carbon block is no greater than 50 μm.

[0082] In S2, the activation catalytic reaction zone and the mineralization catalytic reaction zone are continuously connected along the direction of formaldehyde-containing gas flow; No inactive transition zone is set between the activation catalytic reaction zone and the mineralization catalytic reaction zone; The activation catalytic reaction zone is located upstream, and the mineralization catalytic reaction zone is located downstream.

[0083] In S2, the catalyst loading per unit interface area in the mineralization catalytic reaction zone is 1.2 to 2.2 times that in the activation catalytic reaction zone. The catalyst supported on the activated catalytic reaction zone includes a first noble metal catalyst; The catalyst supported in the mineralization catalytic reaction zone includes a second noble metal catalyst; The first noble metal catalyst is platinum (Pt), with a platinum (Pt) loading of 0.01 wt% to 0.1 wt%. The second noble metal catalyst is iridium (Ir), with an iridium loading of 0.05 wt% to 0.2 wt%.

[0084] In this embodiment, the exhaust gas purification of a hot-pressing production line for engineered wood products is used as the application scenario, and a continuous purification device identical to that in Embodiments 1 and 2 is constructed.

[0085] The purification reactor adopts a rectangular insulating shell, inside which are arranged pre-adsorption activated carbon blocks, opposing reaction chambers and deep oxidation activated carbon blocks in sequence.

[0086] This embodiment focuses on verifying the limitations in claims 5-7 regarding the location of the interfacial catalytic layer, the penetration depth, the continuous connection between the activated catalytic reaction zone and the mineralization catalytic reaction zone, as well as the ratio of noble metal loading to catalyst loading per unit interfacial area.

[0087] A first noble metal catalyst layer was prepared on the surface of the pre-adsorbed activated carbon block facing the opposite reaction chamber using a mask spraying method. The precursor was chloroplatinic acid, and alumina sol was added to the spraying solution as a binder. After drying at 60℃ for 6 hours, the layer was heat-treated at 180℃ for 2 hours under a nitrogen atmosphere to form a surface-confined catalyst layer mainly composed of platinum (Pt), with the Pt loading controlled at 0.04 wt%. A second noble metal catalyst layer was prepared on the surface of the deeply oxidized activated carbon block facing the opposite reaction chamber using the same process. The precursor was chloroiridium acid, and the iridium (Ir) loading was controlled at 0.12 wt%.

[0088] During spraying, the two catalyst layers are distributed only on their respective surfaces facing the opposing reaction chambers by masking the boundaries.

[0089] It should be noted that the first and second noble metal catalyst layers can be prepared by impregnation or mask spraying.

[0090] When the precursor is loaded using the impregnation method, the precursor solution is preferably a mixed solvent of deionized water and anhydrous ethanol, the precursor concentration is preferably 0.2 g / L to 2.0 g / L, the liquid-to-solid ratio is preferably 0.6 mL / g to 1.5 mL / g (based on precious metal elements), and the impregnation time is preferably 10 min to 60 min. After impregnation, the precursor is dried at 50℃ to 90℃ for 2 h to 8 h, and then subjected to heat treatment.

[0091] When the precursor is loaded using a mask spraying method, the spraying liquid is preferably composed of a precursor, a mixed solvent, and a binder. The precursor concentration is preferably 0.5 g / L to 5.0 g / L. The spraying thickness is preferably 5 μm to 30 μm based on precious metal elements. After each spraying, the mixture is allowed to stand for 1 min to 5 min, and then the spraying is repeated 1 to 5 times. The mask opening length is determined according to the design length of the activation catalytic reaction zone and the mineralization catalytic reaction zone.

[0092] When the precursor is chloroplatinic acid, it is preferable to carry out the reduction treatment at 180°C to 300°C in a hydrogen / nitrogen mixed atmosphere with a volume fraction of 3% to 10%. When the precursor is chloroiridic acid, it is preferred to calcine it at 200℃~350℃ in an air atmosphere or an inert atmosphere; the heating rate is preferably 1℃ / min~5℃ / min, and the holding time is preferably 1h~4h.

[0093] By controlling the precursor concentration, liquid-solid ratio, spraying thickness, number of repetitions, and heat treatment conditions, the first and second noble metal catalyst layers can be mainly distributed on the surface area of ​​the corresponding activated carbon block facing the opposite reaction chamber, and the penetration depth into the continuous pores inside the corresponding activated carbon block can be no more than 50 μm.

[0094] According to cross-sectional scanning electron microscopy and elemental line scanning, the maximum penetration depth of the first noble metal catalyst layer along the continuous pores inside the pre-adsorbed activated carbon block is 26 μm, and the maximum penetration depth of the second noble metal catalyst layer along the continuous pores inside the deep oxidation activated carbon block is 33 μm, both not exceeding 50 μm.

[0095] Along the flow direction of formaldehyde-containing gas, the first 63mm is defined as the activation catalytic reaction zone, and the last 117mm is defined as the mineralization catalytic reaction zone. The two are continuously connected, and there is no transition zone without catalytic activity in between.

[0096] By weighing the mass difference before and after catalyst layer deposition and calculating the catalyst loading per unit interface area based on the projected interface area of ​​the opposing reaction chamber, the activated catalytic reaction zone was found to be 0.104 mg / cm². 2 The mineralization catalytic reaction zone has a concentration of 0.176 mg / cm³. 2 The load ratio is 1.69, which is within the range of 1.2 to 2.2 as defined in claim 7.

[0097] After 8 hours of steady-state operation, the formaldehyde concentration, carbon dioxide concentration, ozone concentration, pressure drop, and removal rate retention rate at the outlet were collected, and four comparative examples were set up: Comparative example 1 simultaneously adjusted the ratio of platinum (Pt), iridium (Ir), and loading to below the lower limit. Comparative Example 2 simultaneously adjusted the platinum (Pt), iridium (Ir), and loading ratio to above the upper limit; Comparative Example 3 was prepared using a vacuum impregnation method, which allowed the catalyst to penetrate to a depth of more than 50 μm; Comparative Example 4 includes a 10mm non-catalytically active transition zone between the activated catalytic reaction zone and the mineralization catalytic reaction zone. This set of experiments is used to illustrate the rationality of the process boundaries in claims 5-7 and their impact on purification performance.

[0098] Table 3: Influence of the critical process boundary of the activated catalytic reaction zone / mineralization catalytic reaction zone on formaldehyde purification performance Parameters / Test Subjects Example 3 of the present invention - within the scope Comparative Example 3-1 - Low Boundary Deviation Comparative Example 3-2 - High Boundary Deviation Comparative Example 3-3 - Penetration Depth Exceeds Limit Comparative Examples 3-4 - Existence of a non-catalytic transition region Platinum (Pt) loading (wt%) 0.04 0.005 0.15 0.04 0.04 Iridium (Ir) loading (wt%) 0.12 0.03 0.25 0.12 0.12 Maximum penetration depth (μm) 33 31 35 86 33 Catalyst loading ratio per unit interface area in the mineralized zone / activated zone 1.69 1.05 2.45 1.68 1.68 Length of the non-catalytic transition region (mm) 0 0 0 0 10 Formaldehyde concentration at the inlet (mg / m3) 3 3 3 3 3 Formaldehyde removal rate (%) 96.6 88.7 90.2 86.9 88.4 Carbon dioxide selectivity (%) 84.9 72.6 74.1 67.3 70.1 Ozone concentration at the outlet (mg / m3) 0.014 0.017 0.019 0.022 0.019 Pressure drop (Pa) 124 123 126 141 127 Removal rate retention rate after 8 hours (%) 95 87.5 88.1 82.6 85.4 Table 3, based on four types of comparative examples, provides a comprehensive verification of all key process boundaries in this embodiment.

[0099] In Example 3 of this invention, the platinum (Pt) loading, iridium (Ir) loading, catalyst penetration depth, catalyst loading ratio per unit interface area between the mineralization catalytic reaction zone and the activation catalytic reaction zone, and the length of the non-catalytic transition zone all fall within the scope defined in the claims. The formaldehyde removal rate reaches 96.6%, the carbon dioxide selectivity reaches 84.9%, and the removal rate retention rate reaches 95.0% after 8 hours. This indicates that under the synergistic effect of surface confined loading, continuous partitioning, and loading gradient, the pre-enrichment, activation, and deep mineralization of formaldehyde molecules can form a relatively complete continuous pathway.

[0100] Comparative Example 3-1 simultaneously reduced the platinum (Pt) loading, iridium (Ir) loading, and loading ratio below the lower limit, resulting in a formaldehyde removal rate of 88.7% and a carbon dioxide selectivity of 72.6%.

[0101] This result indicates that insufficient platinum (Pt) in the activation catalytic reaction zone weakens the initial adsorption and activation ability of formaldehyde molecules, while insufficient iridium (Ir) and a low loading ratio in the mineralization catalytic reaction zone weaken the subsequent deep oxidation ability of the activated intermediate products.

[0102] In Comparative Example 3-2, after simultaneously increasing the above three parameters to the upper limit, the formaldehyde removal rate and carbon dioxide selectivity were also lower than those in Example 3 of this invention, indicating that more precious metals are not necessarily better. Excessive load can lead to interface coverage, mass transfer obstruction, and increased side reactions. The load range and load ratio defined in this embodiment have clear process screening criteria.

[0103] Comparative Example 3-3 only changed the catalyst penetration depth to more than 50 μm, and the formaldehyde removal rate decreased to 86.9%, the carbon dioxide selectivity decreased to 67.3%, and the pressure drop increased to 141 Pa.

[0104] This result directly demonstrates that the "penetration depth not greater than 50μm" in this embodiment is of substantial significance.

[0105] If the catalyst penetrates too deeply into the continuous pores inside the activated carbon block, it will occupy the pore space that should be used for pre-enrichment and subsequent oxidation, while weakening the concentration of interfacial reactions and reducing the coupling between the electric field enhancement zone and the catalytically active interface. Comparative Example 4, with only a 10mm non-catalytically active transition zone, showed that the formaldehyde removal rate and carbon dioxide selectivity decreased to 88.4% and 70.1%, respectively. This demonstrates that the "continuous connection without a non-catalytically active transition zone" in this embodiment can reduce the residence of activated intermediate products in the ineffective zone, avoid the waste of short-lived active species, and thus improve continuous conversion efficiency.

[0106] As can be seen from Table 3, the technical features in this embodiment are not a simple repetition of embodiments 1-2, but rather a further refinement and limitation of the spatial position, partitioning connection method, and noble metal loading gradient of the interface catalytic layer.

[0107] Through these constraints, the pre-enrichment / deep oxidation function of the activated carbon block body and the catalytic function of the interfacial catalytic layer maintain their respective functions while forming a continuous coupling. Therefore, it can achieve results superior to existing conventional solutions in terms of formaldehyde removal rate, carbon dioxide selectivity and operational stability.

[0108] Example 4 Please refer to Figure 1 and Figure 2 Specifically: In S3, the average electric field strength in the opposing reaction chamber is 1.0 kV / mm to 2.2 kV / mm; The frequency of the pulsed DC power supply is 200Hz to 800Hz; The pulse rise time is 50ns to 200ns, and the duty cycle is 1% to 10%.

[0109] In this embodiment, the tail gas purification of the hot pressing production line of artificial board is taken as the object, and a continuous pulse corona enhanced catalytic purification device is built; at the same time, the aforementioned process content of Embodiments 1-3 is still used.

[0110] This embodiment only examines the electric field parameters, namely the average electric field strength, pulse frequency, pulse rise time, and duty cycle.

[0111] In this embodiment, the average electric field strength is set to 1.6 kV / mm, the pulse frequency is set to 400 Hz, the pulse rise time is set to 100 ns, and the duty cycle is set to 4%. All four parameters are within the range defined in claim 8.

[0112] To verify the rationality of the process boundary, four sets of comparative examples were set up.

[0113] Comparative Example 4-1 adjusts the average electric field strength to 0.8 kV / mm to examine the response effect below the lower limit; Comparative Example 4-2 adjusts the average electric field strength to 2.5 kV / mm to examine the effect when it exceeds the upper limit; Comparative Example 4-3 maintains an average electric field strength of 1.6 kV / mm, but adjusts the frequency to 100 Hz, the pulse rise time to 30 ns, and the duty cycle to 0.5% to examine the case where the three pulse parameters are all below the window value. Comparative Example 4-4 also maintains an average electric field strength of 1.6 kV / mm, but adjusts the frequency to 1000 Hz, the pulse rise time to 250 ns, and the duty cycle to 12% to examine the situation where the three pulse parameters are all higher than the window value.

[0114] Each group ran continuously for 8 hours, and during the steady-state phase, the outlet formaldehyde concentration, outlet carbon dioxide concentration, outlet ozone concentration, unit energy consumption, and removal rate retention rate after 8 hours were continuously collected.

[0115] This embodiment directly verifies the impact of the constant electric field process window on formaldehyde activation efficiency, deep mineralization capacity, by-product control, and energy consumption level, thus providing experimental support for the process boundaries of average electric field strength of 1.0kV / mm to 2.2kV / mm, pulse frequency of 200Hz to 800Hz, pulse rise time of 50ns to 200ns, and duty cycle of 1% to 10%.

[0116] Table 4: Influence of electric field process window on formaldehyde purification performance Parameters / Test Subjects Example 4 of the present invention - within the scope Comparative Example 4-1 - Electric Field Strength Below the Lower Limit Comparative Example 4-2 - Electric field strength exceeds the upper limit Comparative Example 4-3 - Pulse parameters below range Comparative Example 4-4 - Pulse parameters are above the range Average electric field strength (kV / mm) 1.6 0.8 2.5 1.6 1.6 Pulse frequency (Hz) 400 400 400 100 1000 Pulse rise time (ns) 100 100 100 30 250 Duty cycle (%) 4 4 4 0.5 12 Width of the opposing reaction chamber (mm) 6 6 6 6 6 Formaldehyde concentration at the inlet (mg / m3) 3 3 3 3 3 Formaldehyde removal rate (%) 96.5 88.4 91.3 89 90.1 Carbon dioxide selectivity (%) 84.4 70.6 72.9 71.8 69.7 Ozone concentration at the outlet (mg / m3) 0.014 0.01 0.036 0.012 0.043 Energy consumption per unit (Wh / m3) 0.044 0.031 0.068 0.033 0.071 Removal rate retention rate after 8 hours (%) 94.9 86.8 88.2 87.4 86.5 Table 4 shows that the combination of average electric field strength, pulse frequency, pulse rise time and duty cycle in this embodiment has clear process significance and is not an arbitrary combination of values.

[0117] In Example 4 of this invention, all four parameters fall within the defined ranges. At this point, the formaldehyde removal rate reaches 96.5%, the carbon dioxide selectivity reaches 84.4%, the outlet ozone concentration is only 0.014 mg / m³, and the unit energy consumption is 0.044 Wh / m³. 3 The removal rate remained at 94.9% after 8 hours.

[0118] This result indicates that, within the defined parameter window, a relatively stable pulsed corona discharge state can be formed in the opposing reaction chamber, and a good balance can be achieved between the active species generation rate, the interface activation efficiency, and the subsequent mineralization efficiency.

[0119] Comparative Example 4-1 reduced the average electric field strength to 0.8 kV / mm while keeping other parameters unchanged. The result was a decrease in formaldehyde removal rate to 88.4% and carbon dioxide selectivity to 70.6%. Although the outlet ozone concentration and unit energy consumption both decreased, this was achieved at the cost of insufficient activation capacity. This indicates that when the average electric field strength is below 1.0 kV / mm, pulse discharge cannot provide enough high-energy electrons and active particles, resulting in insufficient initial activation of formaldehyde in the catalytic reaction zone. Consequently, the effective intermediate products subsequently received by the mineralization catalytic reaction zone are reduced.

[0120] In Comparative Example 4-2, after increasing the average electric field strength to 2.5 kV / mm, the formaldehyde removal rate improved compared to Comparative Example 4-1, but the carbon dioxide selectivity remained at only 72.9%, and the outlet ozone concentration increased to 0.036 mg / m³. 3 The unit energy consumption increased to 0.068 Wh / m³. 3 This indicates that when the average electric field strength is higher than 2.2 kV / mm, more of the discharge energy is converted into byproducts such as ozone and ineffective energy consumption, and the overall purification path is not optimized accordingly.

[0121] Therefore, 1.0 kV / mm to 2.2 kV / mm can balance activation capacity and side reaction suppression, and is an effective boundary with experimental evidence.

[0122] Comparative Examples 4-3 and 4-4 focus on examining the window rationality of three pulse parameters: frequency, rise time, and duty cycle.

[0123] In Comparative Examples 4-3, the frequency of 100 Hz, rise time of 30 ns, and duty cycle of 0.5% are all lower than the lower limits in this embodiment. At this time, the formaldehyde removal rate is only 89.0%, and the carbon dioxide selectivity is only 71.8%.

[0124] The results indicate that when the frequency is too low, the number of pulse discharges per unit time is insufficient; when the duty cycle is too low, the average concentration of active species is too low; and although a short rise time can form a spike pulse, the overall energy input is insufficient, which leads to the inability of the activation reaction and mineralization reaction in the opposing reaction chamber to continue coupling.

[0125] In Comparative Examples 4-4, the frequency of 1000 Hz, rise time of 250 ns, and duty cycle of 12% were all higher than the upper limits of this embodiment. The formaldehyde removal rate was 90.1%, the carbon dioxide selectivity further decreased to 69.7%, and the outlet ozone concentration increased to 0.043 mg / m³. 3 The unit energy consumption reaches 0.071 Wh / m³. 3 This indicates that when the parameters are too high, the discharge tends to be more frequent and continuous, the heat accumulation is enhanced, the amount of by-products generated increases, and the excessively long rise time weakens the peak characteristics of high-energy electrons, ultimately leading to an increase in unit energy consumption without a corresponding increase in purification efficiency.

[0126] As can be seen from Table 4, this embodiment does not limit a single electrical parameter in isolation, but couples the average electric field strength, frequency, rise time and duty cycle into a complete process window.

[0127] This window ensures stable pulsed corona discharge within the opposing reaction chamber while allowing the activation and mineralization catalytic reaction zones to perform activation and deep oxidation functions respectively under the same electric field conditions. Simultaneously, it keeps ozone byproducts and unit energy consumption at low levels. Compared to the comparative example, this embodiment demonstrates superior performance in formaldehyde removal rate, carbon dioxide selectivity, operational stability, and byproduct control.

[0128] Example 5 Please refer to Figure 1 and Figure 2 Specifically: In S4, the pre-enriched formaldehyde-containing gas enters the deep oxidation activated carbon block only through the opposing reaction chamber; The residence time of formaldehyde gas in the opposing reaction chamber is 0.05s to 0.12s.

[0129] In this embodiment, the technical significance of the defined material path and residence time window is explained.

[0130] The application scenario of this embodiment is the same as that of embodiments 1 to 4, and it still focuses on the purification of exhaust gas from the hot pressing production line of artificial board.

[0131] The purification reactor, pre-adsorption activated carbon block, deep oxidation activated carbon block, opposing reaction chamber size, first precious metal catalyst layer, second precious metal catalyst layer, electric field parameters, inlet formaldehyde concentration, temperature, relative humidity and treatment air volume are all based on the conditions of Example 1.

[0132] The pre-adsorption activated carbon block is used for initial concentration of formaldehyde, while the deep oxidation activated carbon block is used to receive residual components that are not fully converted after the reaction chamber. Structurally, the formaldehyde-containing gas is first passed through the pre-adsorption activated carbon block, then enters the reaction chamber, and subsequently enters the deep oxidation activated carbon block only from the outlet of the reaction chamber. No bypass channels are provided to directly enter the deep oxidation activated carbon block, bypassing the reaction chamber. By adjusting the inlet flow rate, the residence time of the formaldehyde-containing gas in the reaction chamber is stabilized at 0.08 s, which falls within the range of 0.05 s to 0.12 s defined in this embodiment.

[0133] In this embodiment, "entering the deep oxidation activated carbon block only through the opposing reaction chamber" essentially defines a unique material path. This limitation ensures that formaldehyde molecules enriched by the pre-adsorption activated carbon block must first undergo electric field enhancement and interfacial catalysis within the opposing reaction chamber before entering the deep oxidation activated carbon block for subsequent oxidation. If a bypass channel exists, some gas will bypass the activation and mineralization reaction zones and directly enter the deep oxidation activated carbon block, thus weakening the opposing reaction chamber's role as the main reaction space and reducing the formaldehyde removal rate and carbon dioxide selectivity shown in Table 1. Therefore, this path limitation is not a simple flow path selection, but a necessary condition to ensure the complete establishment of the "pre-enrichment, activation, mineralization, and subsequent oxidation" reaction chain in Example 1.

[0134] In this embodiment, the "dwell time of 0.05 s to 0.12 s" is a process boundary limit for the mass transfer and reaction coupling time in the opposing reaction chamber.

[0135] Table 1 directly supports this: In Example 1, the residence time was 0.08 s, the formaldehyde removal rate reached 96.9%, and the carbon dioxide selectivity reached 85.3%; In Comparative Example 1, the residence time was 0.04 s, which was lower than the lower limit, and the formaldehyde removal rate dropped to 87.8%. This indicates that when the residence time is too short, although the formaldehyde molecules have entered the opposing reaction chamber, the reaction process in the activation catalytic reaction zone and the mineralization catalytic reaction zone is insufficient. In Comparative Example 2, the residence time was 0.13 s, which was higher than the upper limit. The formaldehyde removal rate dropped to 83.6%, and the carbon dioxide selectivity dropped to 66.1%. At the same time, the pressure drop changed more significantly, indicating that when the residence time is too long, the gas flow rate decreases, and the field enhancement efficiency and interface utilization are actually affected.

[0136] Therefore, the range of 0.05 s to 0.12 s is not an arbitrarily given numerical range, but rather an effective process window obtained by comparing and filtering values ​​below the lower limit, within the range, and above the upper limit in Table 1.

[0137] As further illustrated in Table 1, the 0.08 s residence time and the limitation of the formaldehyde molecules entering the deep oxidation activated carbon block solely through the opposing reaction chamber in this embodiment not only result in a high formaldehyde removal rate but also demonstrate that formaldehyde molecules form a well-defined and sequentially stable reaction pathway among the pre-adsorption activated carbon block, the opposing reaction chamber, and the deep oxidation activated carbon block. This pathway allows for the full utilization of the electric field enhancement zone, the activation catalytic reaction zone, and the mineralization catalytic reaction zone, thereby improving carbon dioxide selectivity and reducing intermediate product residues.

[0138] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for controlling formaldehyde removal through electric field-enhanced catalytic process, characterized in that, Includes the following steps: S1. Pre-adsorption activated carbon blocks and deep oxidation activated carbon blocks are arranged opposite each other in the purification reactor, and a reaction chamber with a width of 3mm to 12mm is formed between the pre-adsorption activated carbon blocks and the deep oxidation activated carbon blocks. S2. A first noble metal catalyst layer is provided on the side of the pre-adsorbed activated carbon block facing the opposite reaction chamber, and a second noble metal catalyst layer is provided on the side of the deep oxidation activated carbon block facing the opposite reaction chamber. The first and second noble metal catalyst layers sequentially form an activation catalytic reaction zone and a mineralization catalytic reaction zone along the flow direction of formaldehyde-containing gas. The length of the activation catalytic reaction zone along the flow direction accounts for 25% to 45% of the total effective length of the first and second noble metal catalyst layers along the flow direction. S3. Connect the pre-adsorbed activated carbon block and the deep oxidation activated carbon block to the positive and negative terminals of the pulsed DC power supply, respectively, and apply the corresponding pulsed DC voltage according to the width of the opposing reaction chamber, so as to form an electric field enhancement zone in the opposing reaction chamber under the pulsed corona discharge state. S4. Formaldehyde-containing gas first flows through the pre-adsorption activated carbon block for pre-enrichment, and then enters the opposing reaction chamber. Under the action of the electric field enhancement zone, formaldehyde molecules are converted into activated intermediate products in the activation catalytic reaction zone. The activated intermediate products enter the mineralization catalytic reaction zone with the gas flow and are converted into carbon dioxide and water. The incompletely converted components enter the deep oxidation activated carbon block for further oxidation.

2. The electric field-enhanced catalytic formaldehyde removal control method for efficient formaldehyde removal according to claim 1, characterized in that, In S1, the opposing reaction chamber is a slit-type reaction chamber; The ratio of the length of the opposing reaction chamber along the flow direction of formaldehyde-containing gas to the width of the opposing reaction chamber is 15:1 to 60:

1.

3. The electric field-enhanced catalytic formaldehyde removal control method for efficient formaldehyde removal according to claim 2, characterized in that, In S1, the opposing reaction chamber is formed by the inner surface of the pre-adsorbed activated carbon block and the opposing inner surface of the deep-oxidized activated carbon block. The inlet and outlet ends of the opposing reaction chamber are respectively provided with insulating flow guiding components so that formaldehyde-containing gas enters the opposing reaction chamber uniformly and passes through the activation catalytic reaction zone and the mineralization catalytic reaction zone along the axial direction of the opposing reaction chamber.

4. The electric field-enhanced catalytic formaldehyde removal control method for efficient formaldehyde removal according to claim 3, characterized in that, In S1, the formaldehyde-containing gas does not come into direct contact with the deep oxidation activated carbon block before entering the opposing reaction chamber; Once the formaldehyde-containing gas leaves the opposing reaction chamber, it does not return to the pre-adsorbed activated carbon block. The thickness of the pre-adsorption activated carbon block is greater than the thickness of the deep oxidation activated carbon block, and the pre-adsorption activated carbon block has a pore size distribution mainly composed of micropores, while the deep oxidation activated carbon block has a pore size distribution mainly composed of mesopores.

5. The electric field-enhanced catalytic formaldehyde removal control method for efficient formaldehyde removal according to claim 2, characterized in that, In S2, a first noble metal catalyst layer and a second noble metal catalyst layer are respectively provided on the surfaces of the pre-adsorbed activated carbon block and the deep oxidation activated carbon block facing the opposing reaction chamber. The first noble metal catalyst layer and the second noble metal catalyst layer form an activation catalytic reaction zone and a mineralization catalytic reaction zone along the flow direction of formaldehyde-containing gas; Furthermore, the penetration depth into the continuous pores inside the corresponding activated carbon block is no greater than 50 μm.

6. The electric field-enhanced catalytic formaldehyde removal control method for efficient formaldehyde removal according to claim 5, characterized in that, In S2, the activated catalytic reaction zone and the mineralization catalytic reaction zone are continuously connected along the formaldehyde-containing gas flow direction; No inactive transition region is provided between the activated catalytic reaction zone and the mineralization catalytic reaction zone; The activation catalytic reaction zone is located upstream, and the mineralization catalytic reaction zone is located downstream.

7. The electric field-enhanced catalytic formaldehyde removal control method for efficient formaldehyde removal according to claim 6, characterized in that, In S2, the catalyst loading per unit interface area in the mineralization catalytic reaction zone is 1.2 to 2.2 times that in the activation catalytic reaction zone. The catalyst supported on the activated catalytic reaction zone includes a first noble metal catalyst; The catalyst supported on the mineralization catalytic reaction zone includes a second noble metal catalyst; The first noble metal catalyst is platinum (Pt), and the loading of platinum (Pt) is 0.01 wt% to 0.1 wt%. The second noble metal catalyst is iridium (Ir), and the iridium loading is 0.05 wt% to 0.2 wt%.

8. The electric field-enhanced catalytic formaldehyde removal control method for efficient formaldehyde removal according to claim 7, characterized in that, In S3, the average electric field strength within the opposing reaction chamber is 1.0 kV / mm to 2.2 kV / mm; The frequency of the pulsed DC power supply is 200Hz to 800Hz; The pulse rise time is 50ns to 200ns, and the duty cycle is 1% to 10%.

9. The electric field-enhanced catalytic formaldehyde removal control method for efficient formaldehyde removal according to claim 8, characterized in that, In S4, the pre-enriched formaldehyde-containing gas enters the deep oxidation activated carbon block only through the opposing reaction chamber; The residence time of formaldehyde gas in the opposing reaction chamber is 0.05s to 0.12s.

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