A Multi-Stage Waste Incineration Flue Gas Purification System and Method

Abstract

This invention discloses a multi-stage waste incineration flue gas purification system and method, relating to the field of flue gas purification. The first layer, along the flue gas flow direction, sequentially comprises a first purification section and a second purification section. The first purification section contains several first channels, and the second purification section contains several second channels. The pore size of the first channels is smaller than that of the second channels, and both the first and second channels have several grooves on their inner walls. The second layer, along the flue gas flow direction, sequentially comprises an inlet zone, a transition zone, and an outlet zone. The inlet zone, transition zone, and outlet zone respectively contain a first wave channel, a second wave channel, and a third wave channel. The third layer, along the flue gas flow direction, comprises several catalytic reduction channels, and the inner walls of these catalytic reduction channels are provided with several V₂O₅@WO₃ core-shell nanoislands. This invention treats flue gas through a first-layer high-temperature pyrolysis, a second-layer gradient catalytic oxidation, and a third-layer selective catalytic reduction, achieving a progressively deeper removal of pollutants.

Description

Technical Field

[0001] This invention relates to the field of flue gas removal, and more specifically to a waste incineration flue gas purification system and method based on multi-stage treatment. Background Technology

[0002] Waste incineration is an important method for urban solid waste treatment, but the incineration process generates a large number of harmful pollutants, mainly including dioxins, nitrogen oxides (NOx), heavy metals (such as mercury, lead, and cadmium), and particulate matter. Traditional flue gas purification processes have the following problems: Firstly, current technologies for dioxin removal mainly rely on activated carbon adsorption. However, activated carbon adsorption suffers from saturation, requiring frequent replacement, resulting in high operating costs, and it cannot completely decompose dioxin molecules. Although high-temperature pyrolysis can effectively decompose dioxins, traditional pyrolysis devices are often simple in structure, have insufficient flue gas residence time, and limited pyrolysis efficiency.

[0003] Secondly, in terms of denitrification, existing selective catalytic reduction (SCR) technologies typically operate within a single temperature range, with fixed catalyst active components, making it difficult to adapt to the complex composition and concentration variations of pollutants in waste incineration flue gas. Especially when treating flue gas containing both NOx and heavy metals, traditional catalysts are prone to poisoning and deactivation, resulting in short service lives.

[0004] Furthermore, existing technologies for the removal of heavy metals mainly rely on adsorption or condensation, but these methods are not effective at removing gaseous heavy metals (especially zero-valent mercury) and are prone to causing secondary pollution.

[0005] Therefore, existing purification systems lack synergy among their various treatment units, often exhibiting a simple series connection. This fails to fully utilize the promoting effect of upstream treatment on downstream treatment, resulting in low overall purification efficiency and high energy consumption. Thus, there is an urgent need to develop a waste incineration flue gas purification system and method capable of efficiently and synergistically removing multiple pollutants. Summary of the Invention

[0006] One object of the present invention is to provide a multi-stage waste incineration flue gas purification system and method, comprising a first layer, a second layer, and a third layer connected in sequence. The temperature of the first layer is greater than 850°C, mainly used for dioxin pyrolysis and particulate matter capture; the temperature of the second layer is 300-500°C, mainly used for the catalytic oxidation of nitrogen oxides and heavy metals; the temperature of the third layer is 360-400°C, mainly used for the selective catalytic reduction of nitrogen oxides, thereby eliminating dioxins and nitrogen oxides (NOx) in the flue gas generated from waste incineration. x Effective removal of heavy metals (such as mercury, lead, cadmium, etc.) and particulate matter.

[0007] This objective is achieved using the following technical solution: The waste incineration flue gas purification system based on multi-stage treatment includes a first layer, a second layer, and a third layer connected in sequence. The temperature of the first layer is greater than 850℃, the temperature of the second layer is 300-500℃, and the temperature of the third layer is 360-400℃.

[0008] The first layer is provided with a first purification section and a second purification section in sequence along the flue gas flow direction. The first purification section is provided with a number of first channels and the second purification section is provided with a number of second channels. The aperture of the first channel is smaller than that of the second channel. The inner walls of the first channel and the second channel are provided with a number of grooves. The small-aperture first channel can generate higher airflow velocity and stronger turbulence, which is beneficial to improving heat transfer efficiency and the pyrolysis rate of dioxin molecules; while the large-aperture second channel reduces airflow resistance, prolongs flue gas residence time, and ensures complete pyrolysis of dioxins.

[0009] The first channel has an aperture of 0.5-1.0 mm, and the second channel has an aperture of 1.5-2.5 mm. The small aperture of the first channel generates a higher gas flow velocity, enhancing turbulent mixing and improving the heat and mass transfer coefficients. Although the residence time of high-temperature flue gas (>850℃) in the small-aperture channel is short (approximately 0.5-1 second), the strong turbulence ensures that dioxin molecules fully contact the high-temperature wall surface, achieving rapid pyrolysis. The small aperture also has a sieving effect on large particles, while the inertial collision effect generated by the high flow velocity enhances the particle capture efficiency.

[0010] The larger aperture of the second channel reduces the gas velocity (typically 1-3 m / s) and extends the flue gas residence time to 1-2 seconds, ensuring complete decomposition of dioxins. This design avoids excessively high system resistance caused by small apertures throughout the entire process, reduces fan energy consumption, and ensures long-term stable system operation as the larger aperture is less prone to blockage by particulate matter.

[0011] More importantly, both the first and second channels have several grooves on their inner walls. These grooves are not merely simple surface roughening treatments, but rather a hydrodynamic structure designed for this system. When high-temperature flue gas flows through the grooved channels, local eddies and recirculation zones are formed inside the grooves, significantly enhancing the contact time and contact area between the flue gas and the channel walls. This enhanced turbulent mixing effect allows dioxin molecules to be fully exposed to the high-temperature environment, thereby achieving efficient pyrolysis and decomposition.

[0012] Meanwhile, the groove structure also has a particulate matter capture function. When particulate matter in the flue gas passes through the groove, it is effectively captured inside the groove due to inertia and eddy current settling effect, achieving preliminary removal of particulate matter. This structure, which integrates pyrolysis and capture, avoids the problem of needing to set up separate dust removal equipment in traditional processes, simplifying the system structure.

[0013] The depth of the groove is 0.1-0.3 mm. When the flue gas flows through the groove, a stable vortex structure is formed inside the groove. These vortices significantly enhance the mixing of the mainstream and the wall boundary layer. The presence of the groove disrupts the original laminar boundary layer, allowing the high-temperature flue gas to directly contact the wall, improving the heat transfer coefficient and the actual residence time, thus providing sufficient time for dioxin pyrolysis.

[0014] Size effect analysis; If the depth of the groove is less than 0.1 mm, the eddy current intensity is insufficient, the turbulence enhancement effect is not obvious, and the capture effect on particulate matter is limited; if the depth of the groove is greater than 0.3 mm, a dead zone may be formed, leading to local dust accumulation and blockage. Excessively deep grooves will weaken the mechanical strength of the channel wall.

[0015] The grooves are 0.1-0.3mm deep, which can generate stable and effective eddies, enhancing heat and mass transfer while avoiding the risk of blockage.

[0016] Furthermore, the second layer is arranged sequentially along the flue gas flow direction as an inlet zone, a transition zone, and an outlet zone. Within each of these zones, several parallel first, second, and third corrugated plates are installed. Several first S-shaped baffles are positioned between adjacent first corrugated plates, forming several first corrugated channels. Similarly, several second S-shaped baffles are positioned between adjacent second corrugated plates, forming several second corrugated channels. Several third S-shaped baffles are positioned between adjacent third corrugated plates, forming several third corrugated channels. Within each of the first, second, and third corrugated channels, several MnO atoms are arranged in a direction perpendicular to the axis. X -CeO2 nanowire forest; The first, second, and third wave plates are all coated with a carrier coating, which is a composite coating of titanium oxide and aluminum oxide. The carrier coating on the first wave plate consists of the following parts by weight: 95-100 parts of titanium dioxide and 0-2 parts of aluminum oxide; the carrier coating on the second wave plate consists of the following parts by weight: 82-87 parts of titanium dioxide and 12-17 parts of aluminum oxide; and the carrier coating on the third wave plate consists of the following parts by weight: 60-65 parts of titanium dioxide and 35-40 parts of aluminum oxide.

[0017] The high titanium content in the inlet zone ensures excellent thermal stability and chemical inertness, enabling it to withstand the impact of high-temperature flue gas from the first layer; the moderate aluminum content in the transition zone balances thermal stability and specific surface area; and the high aluminum content in the outlet zone provides the largest specific surface area and adsorption capacity, which is beneficial for capturing residual pollutants.

[0018] Furthermore, in the first wave channel, MnO XThe Mn:Ce molar ratio in the CeO2 nanowire forest is 4-6:1. MnO in the second wave channel... X The molar ratio of Mn:Ce in the CeO2 nanowire forest is 2-3:1. MnO in the third wave channel... X The molar ratio of Mn:Ce in the -CeO2 nanowire forest is 1:1.

[0019] The high manganese content in the inlet zone provides extremely strong oxidizing power, enabling rapid oxidation of easily oxidizable pollutants in the flue gas, especially zero-valent mercury (Hg). 0 ) is oxidized to divalent mercury (Hg) 2+ The medium manganese content in the transition zone maintains good oxidation activity and improves catalyst stability. The molar ratio in the outlet zone fully utilizes the synergistic effect of cerium's oxygen storage capacity and manganese's oxidation capacity to ensure the complete removal of residual pollutants.

[0020] The thickness of the carrier coating is 50-100 μm. If it is too thin, the specific surface area will be insufficient, making it impossible to load enough MnO. X -CeO2 nanowire forests result in a limited number of active sites and low catalytic efficiency.

[0021] While an excessively thick coating increases the surface area, it introduces significant internal diffusion resistance. Reactant molecules must penetrate the thicker coating to reach the internal active sites, and product molecules must diffuse outwards, which substantially reduces the effective catalytic efficiency. The carrier coating thickness is 50-100 μm, which ensures sufficient specific surface area while controlling internal diffusion resistance within a reasonable range, ensuring that over 90% of the catalyst surface can effectively participate in the reaction. Waste incineration flue gas temperatures reach 300-500℃, requiring the coating to have good thermal conductivity to maintain the optimal temperature for the catalytic reaction. An excessively thick coating will create thermal resistance, leading to a large temperature difference between the coating surface and the substrate, affecting catalytic activity. A thickness of 50-100 μm ensures rapid heat transfer, maintaining a uniform reaction temperature across the entire coating.

[0022] The first, second, and third wave channels form a three-dimensional flow channel structure. The first wave plate has a wavelength of 1.4-1.6 mm and an amplitude of 0.25-0.35 mm; the second wave plate has a wavelength of 1.0-1.2 mm and an amplitude of 0.35-0.45 mm; and the third wave plate has a wavelength of 0.6-0.8 mm and an amplitude of 0.30-0.40 mm. The first wave plate guides the flue gas to initially change direction with a longer wavelength and a lower amplitude, avoiding inlet impact losses; the second wave plate, with its highest amplitude, creates the strongest turbulence in the central region where pollutant concentration is still high, maximizing mass transfer efficiency; the third wave plate maintains a smaller wavelength to sustain the disturbance, while moderately reducing the amplitude to balance pressure drop control and tail-end mixing uniformity.

[0023] The first, second, and third wave channels not only extend the flue gas residence time, but more importantly, they enable the flue gas to fully contact the active sites of the nanowire forest, significantly improving catalytic efficiency.

[0024] Compared with traditional particulate or film catalysts, this invention uses dry MnO X -CeO2 nanowire forests not only have a large specific surface area, providing more active sites per unit volume; the vertically arranged structure facilitates airflow and reduces pressure drop; the nanoscale size effect enhances catalytic activity.

[0025] On the other hand, the third layer employs a V2O5@WO3 core-shell nanoisland structure for selective catalytic reduction. V2O5 serves as the active component, while WO3 acts as the support and co-catalyst. The core-shell structure encapsulates the V2O5 within the WO3, protecting the active component and enhancing catalytic performance through interfacial effects. The size of the core-shell nanoislands is controlled at the nanoscale (50-200 nm), forming a high-density distribution on the inner wall of the catalytic reduction channel, ensuring a highly efficient SCR reaction.

[0026] The third layer operates at a temperature of 360-400℃, ensuring the optimal activity temperature window for the V2O5-WO3 catalyst while avoiding catalyst deactivation due to excessively high temperatures. After the second layer of catalytic oxidation, most of the NO in the flue gas is converted into NO2, which is beneficial for the subsequent rapid SCR reaction, i.e., NO + NO2 + 2NH3 → 2N2 + 3H2O, significantly improving the denitrification efficiency.

[0027] Compared with existing waste incineration flue gas purification processes, the high-temperature pyrolysis of the first layer of this invention not only removes dioxins but also provides suitable temperature conditions for the second layer; the catalytic oxidation of the second layer not only removes heavy metals but also oxidizes NO to NO2, creating favorable conditions for the rapid SCR reaction of the third layer; and the third layer completes the final deep denitrification.

[0028] Based on actual production, this invention sets gradients in the carrier coating, the ratio of active components, and the size of channels. This system can provide the most suitable purification conditions according to the composition and concentration characteristics of pollutants in different locations of flue gas, avoiding the one-size-fits-all problem of traditional uniform catalysts.

[0029] On the other hand, the present invention includes a method for purifying flue gas from waste incineration based on multi-stage treatment, the purification method comprising the following steps: Step S1: The flue gas generated by waste incineration is passed sequentially through the first purification section and the second purification section of the first layer. When the flue gas flows through the first and second channels at a temperature greater than 850°C, the turbulence generated by the grooves pyrolyzes dioxins and captures particulate matter. Step S2: After the flue gas from the first layer passes through the second purification section and is cooled to 300-500℃, it is sequentially introduced into the inlet area, transition area, and outlet area of ​​the second layer. As the flue gas flows through the first, second, and third wave channels, it passes through MnO... X -CeO2 nanowire forest catalytic oxidation of nitrogen oxides and heavy metals in flue gas; In step S3, the flue gas from the second layer through the outlet zone is adjusted to 360-400°C and then introduced into the third layer. When the flue gas flows through the catalytic reduction channel, nitrogen oxides are removed by the catalytic reduction of V2O5@WO3 core-shell nano islands.

[0030] The dioxin molecules in the first layer undergo CO and C-Cl bond breakage in high-temperature environments above 850°C, ultimately decomposing into harmless substances such as CO2, H2O, and HCl. This invention, through the synergistic effect of small-aperture channels and grooved structures, ensures that the residence time of flue gas in the high-temperature zone exceeds 2 seconds, meeting the kinetic requirements for complete dioxin decomposition.

[0031] The second layer of MnO X The -CeO2 system exhibits excellent redox properties. Mn 4+ / Mn 3+ and Ce 4+ / Ce 3+ The redox pairs can effectively activate oxygen molecules, generating reactive oxygen species. These reactive oxygen species can convert Hg... 0 Oxidized to Hg 2+ This process oxidizes NO to NO2. The gradient Mn:Ce ratio design enables strong oxidation in the inlet region and high stability in the outlet region, achieving an optimal balance between oxidation efficiency and catalyst lifetime.

[0032] The V2O5@WO3 catalyst in the third layer exhibits optimal SCR activity within a temperature window of 360-400℃. After the second layer of oxidation, the NO2 / NOx ratio in the flue gas approaches 0.5, which is conducive to rapid SCR reaction and improves denitrification efficiency.

[0033] Compared with the prior art, the present invention has the following advantages and beneficial effects: This invention relates to a multi-stage waste incineration flue gas purification system and method. The system treats flue gas through a three-stage process: a first-stage high-temperature pyrolysis, a second-stage gradient catalytic oxidation, and a third-stage selective catalytic reduction, achieving a progressively deeper removal of pollutants. Dioxins are pyrolyzed in the first stage, heavy metals and some nitrogen oxides are efficiently oxidized in the second stage, and residual nitrogen oxides are deeply reduced in the third stage. Compared to traditional flue gas treatment processes, this system offers higher purification efficiency and avoids the secondary pollution problems associated with activated carbon adsorption.

[0034] The inlet zone of this invention has strong oxidizing ability, which can quickly process high-concentration pollutants, and the outlet zone has high stability, which can ensure deep purification. This invention solves the problem of overtreatment in traditional purification systems. Attached Figure Description

[0035] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the connection structure between the first, second, and third layers; Figure 2 This is a schematic diagram of the first layer; Figure 3 This is a schematic diagram of the structure of the first and second channels; Figure 4 This is a schematic diagram of the second layer structure; Figure 5 A structural schematic diagram of several first wave plates, several second wave plates, and several third wave plates; Figure 6 This is a schematic diagram of the third layer; Figure 7 This is a schematic diagram of the structure of several catalytic reduction channels in the third layer.

[0036] The attached diagram shows the markings and corresponding component names: 1-First layer, 2-First purification section, 3-Second purification section, 4-First channel, 5-Second channel, 6-Groove, 7-Second layer, 8-Inlet area, 9-Transition area, 10-Outlet area, 11-MnO X -CeO2 nanowire forest, 12-first wave plate, 121-first S-shaped partition, 13-second wave plate, 131-second S-shaped partition, 14-third wave plate, 141-third S-shaped partition, 15-catalytic reduction channel, 16-V2O5@WO3 core-shell nanoisland, 17-third layer. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0038] In the description of this invention, it should be understood that the terms "front", "rear", "left", "right", "up", "down", "vertical", "horizontal", "high", "low", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this invention.

[0039] Example 1

[0040] A multi-stage waste incineration flue gas purification system, such as Figure 1 As shown, it includes a first layer 1, a second layer 7 and a third layer 17 connected in sequence. The temperature of the first layer 1 is greater than 850℃, the temperature of the second layer 7 is 300-500℃, and the temperature of the third layer 17 is 360-400℃.

[0041] First layer 1, as shown Figure 2 As shown, the first layer 1 is provided with a first purification section 2 and a second purification section 3 in sequence along the flue gas flow direction. The first purification section 2 is provided with a number of first channels 4 and the second purification section 3 is provided with a number of second channels 5. The aperture of the first channel 4 is smaller than the aperture of the second channel 5. The inner walls of the first channel 4 and the second channel 5 are provided with a number of grooves 6. In some embodiments, the depth of the groove 6 is 0.1-0.3 mm.

[0042] In some embodiments, the first channel 4 and the second channel 5 are both polygonal through holes, preferably regular hexagonal.

[0043] In some embodiments, the aperture of the first channel 4 is 0.5-1.0 mm, and the aperture of the second channel 5 is 1.5-2.5 mm. When the aperture of the first channel 4 is 0.5 mm and the aperture of the second channel 5 is 2.5 mm, the structures of the first channel 4 and the second channel 5 are as follows. Figure 3 As shown.

[0044] The structure of the second layer 7 is as follows: Figure 4As shown, the second layer 7 is arranged sequentially along the flue gas flow direction as follows: an inlet area 8, a transition area 9, and an outlet area 10. Within the inlet area 8, transition area 9, and outlet area 10, several parallel first wave plates 12, second wave plates 13, and third wave plates 14 are respectively arranged. Several first S-shaped baffles 121 are arranged between adjacent first wave plates 12, forming several first wave channels; several second S-shaped baffles 131 are arranged between adjacent second wave plates 13, forming several second wave channels; several third S-shaped baffles 141 are arranged between adjacent third wave plates 14, forming several third wave channels. The structure of the inlet area 8, transition area 9, and outlet area 10 with several parallel first wave plates 12, second wave plates 13, and third wave plates 14 is as follows: Figure 5 As shown, the first wave plate 12 has a wavelength of 1.4-1.6 mm and an amplitude of 0.25-0.35 mm; the second wave plate 13 has a wavelength of 1.0-1.2 mm and an amplitude of 0.35-0.45 mm; and the third wave plate 14 has a wavelength of 0.6-0.8 mm and an amplitude of 0.30-0.40 mm.

[0045] Furthermore, the first wave plate 12, the second wave plate 13 and the third wave plate 14 are all provided with a carrier coating, the thickness of which is 50-100μm.

[0046] The carrier coating is a composite coating of titanium oxide and aluminum oxide. The carrier coating on the first wave plate 12 includes the following parts by weight: 95-100 parts of titanium dioxide and 0-2 parts of aluminum oxide; the carrier coating on the second wave plate 13 includes the following parts by weight: 82-87 parts of titanium dioxide and 12-17 parts of aluminum oxide; the carrier coating on the third wave plate 14 includes the following parts by weight: 60-65 parts of titanium dioxide and 35-40 parts of aluminum oxide.

[0047] Secondly, several MnO atoms are arranged in the first, second, and third wave channels along a direction perpendicular to the axis. X -CeO2 nanowire forest 11; The MnO X -CeO2 nanowire forest 11 is composed of MnO X The vertically oriented nanowire array, formed by co-doping CeO2 with x=1.5–2.0, has a single nanowire diameter of 20-50 nm, a length of 1-5 μm, and a density of 100-500 nanowires per square micrometer. It is grown in situ on the carrier coating surface of the inner wall of the wave channel by hydrothermal method.

[0048] In some embodiments, MnO in the first wave channel X The molar ratio of Mn:Ce in the -CeO2 nanowire forest is 4-6:1.

[0049] In some embodiments, MnO in the second wave channel X The molar ratio of Mn:Ce in the -CeO2 nanowire forest is 2-3:1.

[0050] In some embodiments, MnO in the third wave channel X The molar ratio of Mn:Ce in the -CeO2 nanowire forest is 1:1.

[0051] The structure of the third layer 17 is as follows: Figure 6 As shown, the third layer 17 has several catalytic reduction channels 15 arranged along the flue gas flow direction, such as... Figure 7 As shown, several V2O5@WO3 core-shell nanoislands are arranged on the inner wall of the catalytic reduction channel 15.

[0052] A multi-stage treatment-based method for purifying flue gas from waste incineration includes the following steps: Step S1: The flue gas generated by waste incineration is passed sequentially through the first purification section 2 and the second purification section 3 of the first layer 1. When the flue gas flows through the first channel 4 and the second channel 5 at a temperature greater than 850°C, the turbulence effect generated by the groove 6 pyrolyzes dioxins and captures particulate matter. In step S2, the flue gas from the first layer 1, after being cooled to 300-500℃ in the second purification section 3, is sequentially introduced into the inlet zone 8, transition zone 9, and outlet zone 10 of the second layer 7. As the flue gas flows through the first, second, and third wave channels, it passes through MnO... X -CeO2 nanowire forest catalytic oxidation of nitrogen oxides and heavy metals in flue gas; In step S3, the flue gas from the second layer 7 through the outlet zone 10 is adjusted to 360-400℃ and then introduced into the third layer 17. When the flue gas flows through the catalytic reduction channel 15, nitrogen oxides are removed by the catalytic reduction of V2O5@WO3 core-shell nano islands 16.

[0053] The V2O5@WO3 core-shell nanoislands refer to composite nanostructures with V2O5 as the core and WO3 as the shell, which are dispersed in an island-like manner on the inner wall of the catalytic reduction channel 15. The average particle size is 20-100nm, the coverage density is 5-20 per square micrometer, and the shell thickness is 5-20nm.

[0054] Example 2 Based on the above embodiments, this system includes a first layer 1, a second layer 7, and a third layer 17 connected in sequence. The temperature of the first layer 1 is 880°C, the temperature of the second layer 7 is 420°C, and the temperature of the third layer 17 is 380°C.

[0055] The diameter of the first channel 4 in the first layer 1 is 0.7 mm; the diameter of the second channel 5 is 2.0 mm. Both the first channel 4 and the second channel 5 have grooves 6 on their inner walls, with a groove depth of 0.2 mm. Both the first channel 4 and the second channel 5 are regular hexagonal through holes.

[0056] The first wave plate 12 of the second layer 7 has a wavelength of 1.5 mm and an amplitude of 0.3 mm; the second wave plate 13 has a wavelength of 1.1 mm and an amplitude of 0.4 mm; and the third wave plate 14 has a wavelength of 0.7 mm and an amplitude of 0.35 mm.

[0057] The carrier coating is a composite coating of titanium oxide and aluminum oxide. The carrier coating on the first wave plate 12 includes the following parts by weight: 100 parts of titanium dioxide and 0 parts of aluminum oxide; the carrier coating on the second wave plate 13 includes the following parts by weight: 85 parts of titanium dioxide and 15 parts of aluminum oxide; the carrier coating on the third wave plate 14 includes the following parts by weight: 62 parts of titanium dioxide and 38 parts of aluminum oxide.

[0058] MnO grows vertically on the inner walls of the first, second, and third wave channels. X -CeO2 nanowire forest x=1.8, with individual nanowires having a diameter of 30-45nm, a length of 2-4μm, and a density of approximately 300 nanowires per square micrometer. The Mn:Ce molar ratio is 5:1, 2.5:1, and 1:1 in the inlet, transition, and outlet regions, respectively.

[0059] The third layer 17 contains several catalytic reduction channels 15, and V2O5@WO3 core-shell nano islands are distributed on their inner walls. These nano islands have V2O5 as the core and WO3 as the shell, with an average particle size of 60nm and a shell thickness of 15nm. They are dispersed in an island-like manner on the inner wall of the catalytic reduction channels 15, with a coverage density of 12 per square micrometer.

[0060] Example 3 Based on the above embodiments, the difference between this embodiment and embodiment 2 is that the aperture of the first channel 4 in the first layer 1 is 2.0 mm, and the aperture of the second channel 5 is 0.7 mm. Both the first channel 4 and the second channel 5 have grooves 6 on their inner walls, with a groove depth of 0.2 mm.

[0061] Example 4 Based on the above embodiments, the difference between this embodiment and embodiment 2 is that the wavelength of the first wave plate 12 of the second layer 7 is 0.7 mm and the amplitude is 0.35 mm; the wavelength of the second wave plate 13 is 1.1 mm and the amplitude is 0.4 mm; and the wavelength of the third wave plate 14 is 1.5 mm and the amplitude is 0.3 mm.

[0062] Example 5 Based on the above embodiments, the difference between this embodiment and embodiment 2 is that the first wave channel, the second wave channel and the third wave channel are regular hexagonal channels.

[0063] Example 6 Based on the above embodiments, the difference between this embodiment and Embodiment 2 is that the carrier coating is a composite coating of titanium oxide and aluminum oxide. The carrier coating on the first wave plate 12 includes the following parts by weight: 62 parts of titanium dioxide and 38 parts of aluminum oxide; the carrier coating on the second wave plate 13 includes the following parts by weight: 85 parts of titanium dioxide and 15 parts of aluminum oxide; and the carrier coating on the third wave plate 14 includes the following parts by weight: 100 parts of titanium dioxide and 0 parts of aluminum oxide.

[0064] Example 7 Based on the above embodiments, the difference between this embodiment and embodiment 2 is that the carrier coating is a composite coating of titanium oxide and aluminum oxide. The carrier coatings on the first wave plate 12, the second wave plate 13 and the third wave plate 14 all include the following parts by weight: 85 parts of titanium dioxide and 15 parts of aluminum oxide.

[0065] Example 8 Based on the above embodiments, the difference between this embodiment and embodiment 2 is that in the second layer 7, the Mn:Ce molar ratio is 1:1, 2.5:1 and 5:1 in the inlet region, transition region and outlet region, respectively.

[0066] Example 9 Based on the above embodiments, the difference between this embodiment and embodiment 2 is that in the second layer 7, the Mn:Ce molar ratio is 3:1 in the inlet region, transition region and outlet region.

[0067] Example 10 Based on the above embodiments, the difference between this embodiment and embodiment 2 is that the third layer 17 is provided with a plurality of catalytic reduction channels 15, and a V2O5@WO3 / TiO2 coating is provided on its inner wall. That is, 1.5wt%V2O5 and 8wt%WO3 are loaded on the third layer 17 by impregnation, without a core-shell structure.

[0068] Example 11 Based on the above embodiments, the difference between this embodiment and embodiment 2 is that the wavelengths of the first wave plate 12, the second wave plate 13 and the third wave plate 14 of the second layer 7 are all 0.7 mm and the amplitudes are all 0.35 mm.

[0069] Example 12 Based on the above embodiments, the difference between this embodiment and embodiment 2 is that, in this embodiment, several first wave channels are formed between two adjacent first wave plates 12, and there is no first S-shaped partition 121; several second wave channels are formed between two adjacent second wave plates 13, and there is no second S-shaped partition 131; several third wave channels are formed between two adjacent third wave plates 14, and there is no third S-shaped partition 141.

[0070] Example 13 For Examples 2-12, dioxin-like pollutants in the flue gas were detected at the first inlet and the first outlet, respectively; nitrogen oxides (NOx) in the flue gas were detected at the second inlet and the third outlet, respectively. x Heavy metals (Hg, Pb, Cd, etc.) in the flue gas are detected at the second inlet and the third outlet, respectively; particulate matter (PM) in the flue gas is detected at the first inlet and the third outlet, respectively.

[0071] Under the same intake conditions (flue gas flow rate: 10,000 Nm³), 3 / h; Inlet concentration: Dioxin 2.5ng TEQ / m 3 NO x 350mg / m 3 Hg 0.15mg / m 3 Pb 0.8 mg / m 3 Cd 0.05 mg / m 3 Particulate matter 80mg / m³ 3 The inlet and outlet concentrations of pollutants in Examples 2–12 were detected, and the results are shown in Table 1: Table 1 Example 2 99.92 96.5 98.3 97 Example 3 94.7 95.2 96.8 83.5 Example 4 99.85 82.6 76.4 91.3 Example 5 99.80 93.0 95.1 89.7 Example 6 99.88 80.3 72.9 90.8 Example 7 99.85 86.7 84.2 91.0 Example 8 99.82 78.5 69.8 90.5 Example 9 99.87 85.4 82.1 91.2 Example 10 99.90 83.2 97.9 91.8 Example 11 99.75 79.8 74.3 87.6 Example 12 99.60 68.4 61.2 84.3 As shown in Table 1, in the multi-stage waste incineration flue gas purification system provided by this invention, the efficient synergistic removal of pollutants depends on the precise matching and gradient synergy of the structure, materials, and flow field of the first, second, and third layers. Example 2 illustrates the corresponding solution of this invention. Only when the first, second, and third layers are configured in coordination can this system simultaneously achieve ultra-low emissions of dioxins, nitrogen oxides, heavy metals, and particulate matter. Compared to Example 2, Example 3 reversed the aperture of the first layer channels; the first channel had an aperture of 2.0 mm, and the second channel had an aperture of 0.7 mm. This adjustment resulted in a decrease in the dioxin removal rate to 94.7%, a decrease in the particulate matter removal rate to 83.5%, and a decrease in the NO removal rate. xThe removal rate of heavy metals was slightly reduced. This is because placing the large-aperture channel at the front end significantly reduced the flow velocity of the flue gas in the first layer, shortening the measured residence time from 1.8 seconds in Example 2 to 1.1 seconds in Example 3. Therefore, Example 3 was insufficient to achieve complete pyrolysis of dioxin molecules. At the same time, the low flow velocity weakened the inertial collision and interception efficiency of particulate matter at the groove. Therefore, the gradient design of the first channel with a small aperture to the second channel with a large aperture in the first layer of the present invention is not arbitrary, but is intended to gradually release flow resistance while ensuring sufficient reaction time, thereby improving the system purification efficiency and achieving system pressure drop.

[0072] Compared to Example 2, Example 4 differs in the arrangement of the first and third corrugated plates; specifically, the inlet region is 0.7 mm and the outlet region is 1.5 mm. The total pressure drop of the system in Example 2 is 850 Pa, while that in Example 4 is 1100 Pa. The NO in Example 4... x The removal rate decreased to 82.6%, and the heavy metal removal rate dropped to 76.4%. In the flue gas inlet area, dioxin pyrolysis products, NO, and Hg... 0 When pollutant concentrations are at their highest, strong turbulence is urgently needed to enhance mass transfer and activate catalyst surface reactions. However, Example 4 uses the shortest wavelength first corrugated plate, which, while causing intense local disturbances, results in rapid channel contraction and expansion due to the excessively short wavelength. This leads to the coexistence of local high-speed jets and recirculation zones, resulting in uneven airflow distribution and some catalyst surfaces being bypassed and not effectively utilized. Furthermore, due to the excessive pressure drop at the inlet section, a large amount of flue gas is forced to turn to a low-resistance path, further weakening the overall contact efficiency. Moreover, although the pollutant concentration has significantly decreased after the initial reaction, Example 4 uses the longest wavelength in the third corrugated plate 14, resulting in a smoother flow field that cannot maintain a sufficient gas-solid interface renewal rate, leaving the catalyst active sites in the later stages idle.

[0073] Compared to Example 2, Example 6 reverses the Ti / Al ratio of the second carrier coating, resulting in a high Al content (38% Al2O3) in the inlet region and a pure TiO2 content in the outlet region. x The removal rates of MnO and heavy metals decreased to 80.3% and 72.9%, respectively. While Al2O3 can improve thermal stability, it also covers the acidic sites on the TiO2 surface, inhibiting the removal of MnO. x Dispersion and oxidation activity; the inlet region acts as a dispersing and oxidizing agent for NO and Hg. 0 In the critical region of oxidation, if the support is mainly Al2O3, the initial oxidation rate is significantly reduced, and even the presence of highly active components later on cannot compensate for insufficient initial conversion. Therefore, a high TiO2 content must be introduced upfront to support the initiation of a strong oxidation reaction.

[0074] Compared to Example 2, Example 8 exhibits a reversed Mn:Ce molar ratio gradient, with a 1:1 ratio in the inlet region and a 5:1 ratio in the outlet region. Results: NO xThe removal rates of nitrogen and heavy metals were only 78.5% and 69.8%, respectively. Mn is a byproduct of low-temperature oxidation of NO and Hg. 0 The main active component, Ce, primarily functions as a co-catalyst and oxygen storage agent. When high levels of Mn are concentrated in the outlet region, while NO and Hg in the flue gas are at this point... 0 The concentration has decreased significantly, leaving no catalyst for highly active sites; conversely, due to insufficient Mn content in the inlet region, the key oxidation reaction failed to start in time. Therefore, the active component gradient must match the pollutant concentration gradient, i.e., high-activity components should be introduced first, and medium- and low-activity components should be introduced later, in order to achieve efficient utilization throughout the entire process.

[0075] Compared to Example 2, Example 10 uses a conventional V2O5-WO3 / TiO2 impregnation coating for its third layer, instead of V2O5@WO3 core-shell nanoislands. Although the removal rates of dioxins and heavy metals are close to the baseline, NO... x The removal rate dropped significantly to 83.2%. This is because V2O5 in traditional coatings tends to agglomerate, has poor dispersion of active sites, and lacks the protection of a WO3 shell, making it more prone to deactivation in sulfur-containing flue gas. In contrast, the core-shell structure not only improves the stability of V2O5 but also enhances the adsorption of NH3 and activation of NO through interfacial effects, which is particularly beneficial to the rapid SCR pathway, i.e., NO + NO2 + 2NH3 → 2N2 + 3H2O.

[0076] Example 12 differs from Example 2 only in that it retains the parallel wave plate. x The removal rates of heavy metals and other substances plummeted to 68.4% and 61.2%, respectively. Without the first, second, and third S-shaped baffles, the flue gas flowed along a straight channel, resulting in a thick boundary layer, a low catalyst surface renewal rate, and a relatively low actual active area participating in the reaction.

[0077] Compared to Example 2, in Example 5, the cross-section of the second wave channel is changed from a sinusoidal waveform as defined in this invention to a regular hexagon. x The removal rate decreased from 96.5% to 93.0%, the heavy metal removal rate decreased from 98.3% to 95.1%, and the particulate matter removal rate also decreased slightly. This is because the hexagonal channel weakens flue gas turbulence, while the sinusoidal channel generates a continuous and smooth secondary flow, allowing the gas flow to be evenly distributed along the catalyst surface and effectively suppressing boundary layer thickening. Experimental observations show that the catalyst surface utilization rate under the hexagonal structure is only 82%, while the sinusoidal channel can reach over 94%. Therefore, the geometry of the channel cross-section directly affects the mass transfer efficiency.

[0078] Compared to Example 2, Example 7 sets the ratio of TiO2 to Al2O3 in the second carrier coating to be the same throughout, without a gradient distribution. The result was NO. xThe removal rates of pollutants and heavy metals decreased to 86.7% and 84.2%, respectively. Example 7 could not match the spatial decay pattern of pollutant concentrations in the flue gas. In the inlet region, the excessively high proportion of Al2O3 covered some of the acidic sites of TiO2, inhibiting MnO2 removal. x The dispersion and oxidation activity of NO and Hg leads to their dispersibility and oxidation. 0 The initial conversion rate was insufficient; the low TiO2 ratio in the outlet region led to decreased thermal stability, making it prone to sintering during long-term operation. In contrast, Example 2, through gradient design, ensured both strong oxidation capability at the front end and improved structural stability at the back end.

[0079] Compared to Example 2, Example 9 used a Mn:Ce molar ratio of 3:1 in the second layer. Although the removal rates of dioxins and particulate matter remained essentially unchanged, NO... x The removal rates of nitrogen and heavy metals decreased to 85.4% and 82.1%, respectively. The NO oxidation rate in the inlet zone was limited; while the Mn content in the outlet zone was far higher than actual requirements, resulting in waste of active components. More importantly, a high Ce ratio helps improve the catalyst's oxygen storage capacity and poisoning resistance; therefore, the Ce content should be increased in the downstream section where pollutant concentrations are low to extend its lifespan.

[0080] Compared with Example 2, Example 11 uses the same wavelength for the first, second, and third wave plates. x The removal rate dropped to 79.8%, the heavy metal removal rate fell to 74.3%, and the particulate matter removal rate also decreased to 87.6%. Furthermore, the total pressure drop of the system in Example 2 was 850 Pa, while the pressure drop in Example 11 reached 1250 Pa. The smaller wavelength in the inlet region caused excessively high local flow velocities and a sharp increase in pressure drop, leading to airflow deviation and insufficient catalyst utilization in some areas. Maintaining a small wavelength in the outlet region failed to appropriately widen the flow channel according to the decreasing pollutant concentration, instead increasing unnecessary resistance and weakening the mixing uniformity of the tail gas. In contrast, the wavelength gradient setting in Example 2 ensured a reasonable distribution of turbulence intensity from front to back, i.e., strong inlet disturbance to promote rapid response and moderately gentle outlet disturbance to ensure controllable pressure drop and uniform flow field.

[0081] In summary, the first, second, and third layers defined in this invention—namely, the pre-positioned small holes and grooves in the first layer, the gradient arrangement in the second layer, and the core-shell nano-islands in the third layer—can complement each other around the physicochemical characteristics of multiple pollutants in waste incineration flue gas, achieving efficient, stable, and low-resistance synergistic purification of multiple pollutants.

[0082] Example 14 Accelerated aging experiments were conducted under simulated waste incineration flue gas conditions. The flue gas composition was as follows: NO: 300 mg / m³ 3 Hg 0 0.1 mg / m 3Dioxins: 2.0 ng-TEQ / m³ 3 SO2: 1000ppm, HCl: 300ppm, H2O: 10vol%. The pollutant removal efficiency of the device was tested before and after a 1000-hour aging test, and the results are shown in Table 2.

[0083] Table 2 <![CDATA[NO x ]]> 96.5 94.8 1.7 Heavy metals (Hg) 98.3 96.5 1.8 Dioxins 99.2 98.0 1.2 Particulate matter 97.0 96.8 0.2 As shown in Table 2, after 1000 hours of continuous operation in a harsh flue gas environment containing high concentrations of SO2 and HCl, the removal rate of various pollutants by the present invention decreased by less than 2%, demonstrating excellent long-term operational stability and resistance to sulfur / chlorine poisoning.

[0084] Example 15 Based on the above embodiments, MnO X The gradient preparation method for CeO2 nanowire forests is an existing technology, and MnO X The gradient preparation method for -CeO2 nanowire forests may include the following steps: Step 1, carrier coating pretreatment The first corrugated plate 12, the second corrugated plate 13 and the third corrugated plate 14 with TiO2-Al2O3 composite coating, i.e. carrier coating, were calcined in air at 400°C for 2 hours and then cooled to room temperature. Step 2, nanowire growth in the entry region; Preparation of precursor solution: 0.1 parts KMnO4, 0.02 parts Ce(NO3)3·6H2O, adjust pH to 2.5 with HNO3; The first corrugated plate 12 was immersed in the solution and hydrothermally reacted at 180°C for 6 hours. After being removed, it was washed with deionized water, dried at 100°C, and calcined in air at 350°C for 2 hours.

[0085] Step 3, nanowire growth in the transition region; Preparation of precursor solution: 0.06 parts KMnO4, 0.03 parts Ce(NO3)3·6H2O, pH=3.0; The second corrugated plate 13 was immersed in the solution and hydrothermally reacted at 160°C for 8 hours. After being removed, it was washed with deionized water, dried at 100°C, and calcined in air at 350°C for 2 hours.

[0086] Step 4, nanowire growth in the export region; Preparation of precursor solution: 0.03 parts KMnO4, 0.03 parts Ce(NO3)3·6H2O, pH=3.5; The third corrugated plate 14 was immersed in the solution and hydrothermally reacted at 140°C for 10 hours. After being removed, it was washed with deionized water, dried at 100°C, and calcined in air at 350°C for 2 hours.

[0087] Example 16 Based on the above embodiments, the preparation method of V2O5@WO3 core-shell nanoislands is an existing technology, and the preparation method of V2O5@WO3 core-shell nanoislands may include the following steps: Step 1, Preparation of V2O5 cores The third layer was calcined in air at 400°C for 2 hours to remove surface impurities, and then cooled to room temperature. The third layer is a metal or ceramic substrate. Ammonium metavanadate (NH4VO3) was dissolved in deionized water to prepare a 0.05-0.1M solution. The pH was then adjusted to 2-3 with dilute nitric acid to form a clear V2O5 precursor solution.

[0088] The pretreated third layer is completely immersed in the above V2O5 precursor solution and left to stand at room temperature for 2-4 hours to ensure that the solution fully penetrates the inner wall of the channel.

[0089] Remove the impregnated substrate and dry it in an oven at 80-100℃ for 4-6 hours to allow the moisture to evaporate slowly.

[0090] The dried matrix is ​​placed in a muffle furnace and calcined in air at 450-500℃ for 2-3 hours to decompose ammonium metavanadate into V2O5 nanoparticles, thus obtaining the V2O5 core structure.

[0091] Step 2, WO3 shell coating Sodium tungstate (Na2WO4) was dissolved in deionized water to prepare a 0.1-0.2M solution. The pH was then adjusted to 1-2 with dilute hydrochloric acid to form a clear WO3 precursor solution.

[0092] Immerse the third layer, which has formed V2O5 cores in step 1, in a WO3 precursor solution and let it stand at room temperature for 1-2 hours.

[0093] After removing from the oven, dry in an oven at 80-100℃ for 2-4 hours.

[0094] The dried third layer was calcined in air at 400-450℃ for 1-2 hours to decompose sodium tungstate and form a WO3 shell on the surface of V2O5 particles, finally obtaining a V2O5@WO3 core-shell nanoisland structure.

[0095] The terms "first," "second," and "third," etc., used are merely for clarity of description and are not intended to restrict any order or emphasize importance. Furthermore, the term "connection" used herein, unless otherwise specified, can refer to a direct connection or an indirect connection via other components.

[0096] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A waste incineration flue gas purification system based on multi-stage treatment, characterized in that, It includes a first layer (1), a second layer (7) and a third layer (17) connected in sequence, wherein the temperature of the first layer (1) is greater than 850℃, the temperature of the second layer (7) is 300-500℃, and the temperature of the third layer (17) is 360-400℃; The first layer (1) is provided with a first purification section (2) and a second purification section (3) in sequence along the flue gas flow direction. The first purification section (2) is provided with a number of first channels (4) and the second purification section (3) is provided with a number of second channels (5). The aperture of the first channel (4) is smaller than the aperture of the second channel (5). The inner walls of the first channel (4) and the second channel (5) are provided with a number of grooves (6). The second layer (7) is arranged in sequence with an inlet area (8), a transition area (9), and an outlet area (10) along the flue gas flow direction. Several parallel first wave plates (12), second wave plates (13), and third wave plates (14) are respectively arranged in the inlet area (8), the transition area (9), and the outlet area (10). Several first S-shaped baffles (121) are arranged between two adjacent first wave plates (12) to form several first wave channels. Several second S-shaped baffles (131) are arranged between two adjacent second wave plates (13) to form several second wave channels. Several third S-shaped baffles (141) are arranged between two adjacent third wave plates (14) to form several third wave channels. Several MnO are arranged in the first wave channel, the second wave channel, and the third wave channel in a direction perpendicular to the axis. X -CeO2 nanowire forest; The third layer (17) has several catalytic reduction channels (15) arranged along the flue gas flow direction, and several V2O5@WO3 core-shell nano islands (16) are arranged on the inner wall of the catalytic reduction channels (15).

2. The waste incineration flue gas purification system based on multi-stage treatment according to claim 1, characterized in that, The first wave plate (12) has a wavelength of 1.4-1.6 mm and an amplitude of 0.25-0.35 mm; the second wave plate (13) has a wavelength of 1.0-1.2 mm and an amplitude of 0.35-0.45 mm; the third wave plate (14) has a wavelength of 0.6-0.8 mm and an amplitude of 0.30-0.40 mm.

3. The waste incineration flue gas purification system based on multi-stage treatment according to claim 1, characterized in that, The first wave plate (12), the second wave plate (13) and the third wave plate (14) are all provided with a carrier coating. The carrier coating is a composite coating of titanium oxide and aluminum oxide. The carrier coating on the first wave plate (12) includes the following parts by weight: 95-100 parts of titanium dioxide and 0-2 parts of aluminum oxide; the carrier coating on the second wave plate (13) includes the following parts by weight: 82-87 parts of titanium dioxide and 12-17 parts of aluminum oxide; the carrier coating on the third wave plate (14) includes the following parts by weight: 60-65 parts of titanium dioxide and 35-40 parts of aluminum oxide.

4. The waste incineration flue gas purification system based on multi-stage treatment according to claim 1, characterized in that, MnO in the first wave channel X The molar ratio of Mn:Ce in the -CeO2 nanowire forest is 4-6:

1.

5. The waste incineration flue gas purification system based on multi-stage treatment according to claim 1, characterized in that, MnO in the second wave channel X The molar ratio of Mn:Ce in the -CeO2 nanowire forest is 2-3:

1.

6. The waste incineration flue gas purification system based on multi-stage treatment according to claim 1, characterized in that, MnO in the third wave channel X The molar ratio of Mn:Ce in the -CeO2 nanowire forest is 1:

1.

7. The waste incineration flue gas purification system based on multi-stage treatment according to claim 3, characterized in that, The thickness of the carrier coating is 50-100μm.

8. The waste incineration flue gas purification system based on multi-stage treatment according to claim 1, characterized in that, The aperture of the first channel (4) is 0.5-1.0 mm, and the aperture of the second channel (5) is 1.5-2.5 mm.

9. The waste incineration flue gas purification system based on multi-stage treatment according to claim 1, characterized in that, The depth of the groove (6) is 0.1-0.3mm.

10. A method for purifying flue gas from waste incineration based on multi-stage treatment, characterized in that, Based on the purification system according to any one of claims 1-9, the purification method includes the following steps: Step S1: The flue gas generated by the waste incineration is passed through the first purification section (2) and the second purification section (3) of the first layer (1) in sequence. When the flue gas is at a temperature greater than 850°C, it pyrolyzes dioxins through the turbulence effect generated by the groove (6) while flowing through the first channel (4) and the second channel (5), and captures particulate matter. In step S2, the flue gas from the first layer (1) is cooled to 300-500℃ through the second purification section (3) and then sequentially introduced into the inlet area (8), transition area (9) and outlet area (10) of the second layer (7). As the flue gas flows through the first wave channel, the second wave channel and the third wave channel, it passes through MnO X -CeO2 nanowire forest catalytic oxidation of nitrogen oxides and heavy metals in flue gas; In step S3, the flue gas from the second layer (7) is adjusted to 360-400°C through the outlet zone (10) and then introduced into the third layer (17). When the flue gas flows through the catalytic reduction channel (15), nitrogen oxides are removed by the catalytic reduction of the V2O5@WO3 core-shell nano islands (16).

Images