A synergistic purification method for NO in low-temperature flue gas x Systems and methods with CO

Abstract

This invention belongs to the field of industrial flue gas purification technology, and more specifically relates to a method for synergistically purifying NO in low-temperature flue gas. x A system and method for CO denitrification. This invention addresses the problem that the oxidation reaction of NO and CO is easily inhibited by SO2 and H2O in flue gas. It designs a core-shell catalyst for a denitrification system, achieving NO / CO co-oxidation under complex atmospheres. By partially oxidizing NO to NO2, a rapid SCR reaction is initiated, improving low-temperature denitrification efficiency. Simultaneously, the heat release from NO / CO co-oxidation increases the SCR inlet flue gas temperature, enhancing the energy self-sufficiency of the denitrification system. Overall, this invention, through flue gas composition conditioning and temperature regulation, achieves synergistic purification of NO in low-temperature flue gas, balancing high-efficiency low-temperature denitrification with CO pollution control. x With CO.

Description

Technical Field

[0001] This invention belongs to the field of industrial flue gas purification technology, and more specifically relates to a method for synergistically purifying NO in low-temperature flue gas. x Systems and methods related to CO. Background Technology

[0002] Industrial NO x Since the implementation of ultra-low emission retrofitting, emissions have decreased year by year, but the total amount remains large, indicating significant room for improvement. CO, as a typical product of incomplete combustion of fossil fuels, often combines with NO in industrial flue gas. x Coexistence, for example, in the flue gas from steel sintering. Therefore, NO x The need for synergistic treatment of NO and CO is urgent. NH3-SCR is the most widely used denitrification technology in industry, but it faces severe CO control challenges and carbon emission reduction pressures due to the need for blast furnace gas reheating. Oxidating NO and CO before the SCR denitrification reaction not only removes CO and fully utilizes its oxidation heat release, but also improves the low-temperature activity of the SCR catalyst through a rapid SCR reaction pathway. In summary, the industrial flue gas NO+CO co-oxidation-coupled SCR denitrification technology has promising application prospects.

[0003] CN114797463A discloses a device system and method for low-temperature SCR denitrification of sintering flue gas using CO catalytic heat exchange in series. This system replaces traditional heat exchangers with CO catalytic regenerative heat exchangers, reducing the number of heat exchange elements and eliminating the need for blast furnace gas during steady-state operation, while simultaneously storing and converting heat from sintering flue gas and the flue gas after denitrification. This method fully utilizes the heat release from CO oxidation to ensure the temperature of the inlet pipe of the SCR denitrification reactor reaches the set requirements. However, this invention only achieves CO oxidation-coupled SCR denitrification and does not consider adjusting NO. x The ingredients are designed to accelerate SCR denitrification efficiency.

[0004] CN108355656A discloses a flue gas NO pre-oxidation catalyst, its preparation method and application, and a low-temperature flue gas denitrification method. The catalyst includes a support and an active component loaded on the support. The active component contains γ-Fe₂O₃ with a particle size of 2–30 nm, and the support is a composite containing γ-Al₂O₃ and TiO₂ in a mass ratio of 1:(0.15–0.4). Under pre-oxidation conditions, this method oxidizes some NO to NO₂, significantly improving the subsequent denitrification efficiency. However, this invention only achieves NO oxidation coupled with SCR denitrification and does not achieve synergistic CO removal.

[0005] However, under actual operating conditions, the gas composition is complex, and catalysts are easily deactivated by toxic substances. Firstly, SO2 is a common toxic gas, widely present in various industrial flue gases. Even after desulfurization, trace amounts of SO2 can still easily poison and deactivate oxidation catalysts. Furthermore, the presence of H2O in industrial flue gas severely inhibits the redox capacity of oxidation catalysts.

[0006] CN114160161A discloses a Pt-Fe bimetallic catalyst for CO and NO oxidation, its preparation method, and its applications. The catalyst uses TiO2 as a support and is loaded with active components and promoters. The active components include elemental Pt and / or Pt oxides, with a mass percentage of 0.01–0.2 wt.%, and the promoters include Fe oxides, with a mass percentage of 0.2–1 wt.%. This catalyst synergistically oxidizes approximately 50% of NO and 100% of CO, satisfying flue gas composition conditioning and temperature control. This invention only achieves NO / CO co-oxidation in a water-containing atmosphere, does not consider the poisoning effect of trace SO2 on the catalyst, and does not achieve SCR coupled denitrification; it only presents a prospective application.

[0007] To address the shortcomings of existing technologies, there is an urgent need to provide a method that can efficiently and synergistically purify NO in industrial flue gas at low temperatures. x Systems and methods for CO. Summary of the Invention

[0008] The purpose of this invention is to provide a method for synergistically purifying NO in low-temperature flue gas. x A system and method for CO, to solve the problems existing in the prior art.

[0009] To achieve the above objectives, the present invention provides the following solution:

[0010] One of the technical solutions of the present invention is to provide a NO / CO co-oxidation catalyst for low-temperature flue gas, wherein the NO / CO co-oxidation catalyst is a core-shell catalyst;

[0011] The core-shell catalyst uses a NO / CO co-oxidation catalyst as the core layer and a sulfur-resistant hydrophobic catalyst as the shell layer.

[0012] Furthermore, the core layer is a spinel catalyst with redox sites.

[0013] Optionally, the redox sites of the spinel catalyst include Co. δ+ Ions, Mn δ+ Ions, Cu δ+ Ions, Cr δ+ Ions and Ni δ+ At least one of the ions.

[0014] Optionally, the spinel catalyst includes Co3O4, MnCo2O4, CuCo2O4, CrCo2O4 or NiCo2O4 with Co-based spinel as the substrate model.

[0015] Furthermore, the shell layer is a molecular sieve catalyst with acidic and hydrophobic sites.

[0016] Optionally, the acidic sites of the molecular sieve catalyst can be adjusted by changing the Si / Al ratio, which is 44, 46, 48 or 50, preferably 44.

[0017] Optionally, the hydrophobic sites include La δ+ Ions, Pr δ+ Ions and Sm δ+ At least one of the ions.

[0018] Optionally, the molecular sieve catalyst includes La / HZSM-5, Pr / HZSM-5, or Sm / HZSM-5, which are based on HZSM-5.

[0019] Furthermore, the core-shell catalyst has a diameter of 10-20 nm and a specific surface area of ​​200-400 m². 2 / g, with a shell thickness of 2-5nm.

[0020] The second technical solution of this invention: providing a method for synergistically purifying NO in low-temperature flue gas. x A system with CO, the system including a flue gas heat exchanger and a denitrification reactor;

[0021] The denitrification reactor includes an inlet pipe arranged sequentially along the flue gas flow direction, a fixed bed containing the aforementioned NO / CO co-oxidation catalyst for low-temperature flue gas, an ammonia injection grid, an NH3-SCR catalyst fixed bed, and an outlet pipe.

[0022] The flue gas heat exchanger is connected to the inlet and outlet pipes of the denitrification reactor via a flue, and is used to collect the heat released by the reaction and increase the temperature of the flue gas entering the inlet pipe of the denitrification reactor.

[0023] The present invention provides a synergistic purification method for NO in low-temperature flue gas. x In the CO system, the flue gas heat exchanger is closely connected to the inlet and outlet pipes of the denitrification reactor through the flue. It is used to collect the heat released by the fixed bed reaction of the NO / CO co-oxidation catalyst in the low-temperature flue gas, and then exchange heat with the raw industrial flue gas to transfer the heat to the inlet pipe of the denitrification reactor to increase the flue gas temperature.

[0024] The third technical solution of this invention: providing a method for synergistically purifying NO in low-temperature flue gas. xThe method for CO, wherein the above-described system is used to process NO. x Co-purification with CO, the steps include:

[0025] Industrial flue gas (complex component flue gas) flows into the denitrification reactor through the inlet pipe. It first passes through a fixed bed containing a NO / CO co-oxidation catalyst for low-temperature flue gas. Under the action of the catalyst, NO oxidation and CO oxidation reactions occur to obtain transition flue gas.

[0026] The transition flue gas and the NH3 supplied by the ammonia injection grid are mixed and then flow through the NH3-SCR catalyst fixed bed, where the SCR reaction occurs under the action of the NH3-SCR catalyst to obtain the emission flue gas.

[0027] The exhaust gas is discharged to a flue gas heat exchanger through an exhaust pipe, where the heat released by the reaction is collected and used to increase the temperature of the flue gas entering the inlet pipe of the denitrification reactor.

[0028] Furthermore, the industrial flue gas includes NO. x , CO, SO2 and H2O, of which NO x The NO content in the medium is not less than 90%.

[0029] Optionally, the NO in the industrial flue gas x The concentration is 200-600 mg / Nm 3 Preferably 400-500 mg / Nm 3 .

[0030] Optionally, the concentration of CO in the industrial flue gas is 5000-15000 mg / Nm³. 3 The preferred concentration is 7000-11000 mg / Nm³. 3 .

[0031] Optionally, the concentration of SO2 in the industrial flue gas is 30-55 mg / Nm³. 3 Preferably 45-50 mg / Nm 3 .

[0032] Optionally, the concentration of H2O in the industrial flue gas is 5-18 vol%, preferably 10-12 vol%.

[0033] Furthermore, the inflow temperature of the industrial flue gas is 120-200℃.

[0034] Furthermore, the space velocity of the industrial flue gas flowing through the fixed bed containing the NO / CO co-oxidation catalyst for low-temperature flue gas is 24,000-60,000 h⁻¹. -1 .

[0035] When the industrial flue gas flows through the fixed bed containing the NO / CO co-oxidation catalyst for low-temperature flue gas, the NO oxidation reaction and CO oxidation reaction occur under the action of the catalyst, and the temperature of the resulting transition flue gas can be increased by 50-80°C compared with the temperature of the original industrial flue gas.

[0036] Furthermore, the NH3-SCR catalyst is a V2O5-WO3 / TiO2 catalyst.

[0037] Optionally, the V active component in the V2O5-WO3 / TiO2 catalyst has a content of 0.5-1.5 wt.%, the W auxiliary component has a content of 6-10 wt.%, the TiO2 is anatase DT-51 type, and the specific surface area of ​​the TiO2 is 100-200 m². 2 / g.

[0038] The V2O5-WO3 / TiO2 catalyst is suitable for NH3-SCR within a temperature window of 200-280℃.

[0039] Furthermore, the transition flue gas includes NO. x SO2 and H2O, of which NO x The NO / NO2 molar ratio is 0.9-1.1, preferably 1.

[0040] In the transition flue gas, NO x The concentrations of SO2 and H2O are close to those of industrial flue gas, while the concentrations of NO... x The NO / NO2 molar ratio changes.

[0041] Furthermore, the ammonia injection amount of the ammonia injection grid is greater than the theoretical ammonia-nitrogen ratio of the NH3-SCR reaction, preferably an ammonia-nitrogen ratio of 1-1.5.

[0042] Furthermore, the space velocity of the transition flue gas flowing through the NH3-SCR catalyst fixed bed is 30,000-100,000 h⁻¹. -1 .

[0043] In this invention, the transition flue gas flows through the NH3-SCR catalyst fixed bed and undergoes a rapid SCR reaction. The reaction rate is nearly ten times higher than that of the standard SCR reaction that occurs when industrial flue gas flows through the NH3-SCR catalyst fixed bed, resulting in a significant improvement in denitrification efficiency.

[0044] This invention addresses the problem that the oxidation reaction of NO and CO is easily inhibited by SO2 and H2O in flue gas. It designs a core-shell catalyst for a denitrification system, achieving NO / CO co-oxidation under complex atmospheres. By partially oxidizing NO to NO2, a rapid SCR reaction is initiated, improving low-temperature denitrification efficiency. Simultaneously, the heat released from NO / CO co-oxidation increases the flue gas temperature at the SCR inlet, enhancing the energy self-sufficiency of the denitrification system. Overall, this invention achieves NO / CO co-oxidation in low-temperature flue gas by conditioning the flue gas composition and regulating the temperature, thus balancing high-efficiency low-temperature denitrification with CO pollution control.

[0045] Fourth technical solution of the present invention: providing the above-mentioned NO / CO co-oxidation catalyst, system, or method for the synergistic purification of NO in low-temperature flue gas. x The application of pollutants and CO pollutants.

[0046] In application, industrial flue gas passes through a NO / CO co-oxidation catalyst for low-temperature flue gas, undergoing NO and CO oxidation reactions to obtain transition flue gas. This process modifies the composition and increases the temperature of the original industrial flue gas. The transition flue gas is then mixed with NH3 supplied by an ammonia injection grid and passed through an NH3-SCR catalyst for a rapid SCR reaction, ultimately achieving NO reduction in the original industrial flue gas. x Low-temperature, high-efficiency, and synergistic purification of CO.

[0047] The present invention discloses the following technical effects:

[0048] This invention is based on NO in industrial flue gas x To address the technical problem that the oxidation reaction of CO is easily inhibited by SO2 and H2O in flue gas, a core-shell catalyst was designed. The acidic sites in the core-shell catalyst can inhibit SO2 adsorption, and the hydrophobic sites can inhibit H2O dissociation and adsorption. In addition, the present invention places the sulfur-resistant hydrophobic molecular sieve catalyst in the shell layer of the core-shell material to protect the spinel catalyst in the core layer for the NO / CO oxidation reaction. At the same time, since the Gibbs free energy of the NO oxidation reaction is higher than that of the CO oxidation reaction, and the adsorption sites of NO and CO on metal oxides are different, the present invention simultaneously achieves partial oxidation of NO and complete oxidation of CO to obtain transition flue gas. The transition flue gas flows through the NH3-SCR catalyst fixed bed, realizing CO treatment while significantly improving the denitrification reaction rate, which is more green and efficient than the traditional SCR denitrification scheme.

[0049] NO in the synergistic purification of low-temperature flue gas xIn the CO-based method, on the one hand, NO is partially oxidized to NO2, which triggers a rapid SCR reaction in the NH3-SCR catalyst fixed bed, improving the low-temperature denitrification efficiency while optimizing the ammonia injection rate and reducing ammonia escape pollution; on the other hand, the heat release from the NO / CO co-oxidation is fully utilized, and the heat is transferred to the NH3-SCR inlet flue gas through a flue gas heat exchanger, improving the energy self-sufficiency of the denitrification system (the denitrification system in the existing technology requires heat treatment, which results in a significant increase in energy consumption, poor technical and economic efficiency, and the carbon increment effect cannot be ignored).

[0050] The method provided by this invention is adapted to actual working conditions, taking into account both low-temperature and high-efficiency denitrification and CO pollution control, and has good economic benefits and application prospects. Attached Figure Description

[0051] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0052] Figure 1 This invention provides a synergistic method for purifying NO in low-temperature flue gas. x A schematic diagram of the CO system; where 1 is a flue gas heat exchanger, 2 is an inlet pipe, 3 is a fixed bed of NO / CO co-oxidation catalyst for low-temperature flue gas, 4 is a sulfur-resistant hydrophobic molecular sieve catalyst, 5 is a NO / CO co-oxidation catalyst, 6 is an ammonia injection grid, 7 is an NH3-SCR catalyst fixed bed, and 8 is an outlet pipe. Detailed Implementation

[0053] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0054] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0055] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0056] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0057] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0058] Unless otherwise specified, all raw materials and reagents involved in the specific embodiments of this invention are commercially available products.

[0059] Unless otherwise specified, room temperature and normal temperature in the specific embodiments of this invention refer to 20-30℃.

[0060] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0061] Figure 1 This invention provides a synergistic method for purifying NO in low-temperature flue gas. x A schematic diagram of the CO system; where 1 is a flue gas heat exchanger, 2 is an inlet pipe, 3 is a fixed bed of NO / CO co-oxidation catalyst for low-temperature flue gas, 4 is a sulfur-resistant hydrophobic molecular sieve catalyst, 5 is a NO / CO co-oxidation catalyst, 6 is an ammonia injection grid, 7 is an NH3-SCR catalyst fixed bed, and 8 is an outlet pipe.

[0062] NO in industrial flue gas used in the specific embodiments of the present invention x The concentration is 500 mg / Nm 3 The CO concentration was 9000 mg / Nm³. 3 The concentration of SO2 is 50 mg / Nm³. 3 The concentration of H2O is 10 vol%, of which NO x The concentration of NO in the medium was 450 mg / Nm³. 3 .

[0063] The NO / CO co-oxidation catalyst used in the specific embodiments of this invention for low-temperature flue gas has a diameter of 15 nm and a specific surface area of ​​275 m². 2 / g, with the shell thickness controlled at 3nm.

[0064] Example 1

[0065] In this embodiment, the fixed bed containing the NO / CO co-oxidation catalyst for low-temperature flue gas is one layer, and the NH3-SCR catalyst fixed bed is two layers; a 0.7wt.%V-7wt.%W / TiO2 catalyst is used as the NH3-SCR catalyst, and the specific surface area of ​​TiO2 in the catalyst is 100-200m². 2 Between / g; Co3O4@La / HZSM-5 catalyst was used as the NO / CO co-oxidation catalyst for low-temperature flue gas.

[0066] In this embodiment, the 0.7wt.%V-7wt.%W / TiO2 catalyst can be a commercially available product or a self-made catalyst. The preparation steps of the impregnation method are as follows:

[0067] A certain amount of ammonium metavanadate (NH4VO3) was dissolved in deionized water acidified with oxalic acid. Then, a certain amount of ammonium tungstate ((NH4)) was added to the aqueous solution sequentially. 10 H2(W2O7)6) and TiO2 (anatase DT-51 type) were mixed and stirred rapidly for 1 h. The water in the slurry was evaporated using a rotary vacuum evaporator at 60 °C. Then, the sample was continuously calcined in air at 500 °C for 3 h to obtain a 0.7 wt.% V-7 wt.% W / TiO2 catalyst. The raw material ratio was determined according to the loading.

[0068] In this embodiment, the Co3O4 loading of the Co3O4@La / HZSM-5 catalyst is 10 wt.%, and the La loading is 1.5 wt.%. The preparation steps are as follows:

[0069] S1. Co3O4 was loaded onto hollow mesoporous SiO2 by impregnation, wherein the precursor of Co was cobalt nitrate hexahydrate Co(NO3)2·6H2O; the hollow mesoporous SiO2 was added to an aqueous solution of Co(NO3)2·6H2O at room temperature and stirred for 2 h. After the water was evaporated by rotary evaporation, the sample was dried at 120℃ for 12 h and then calcined in a muffle furnace at 500℃ for 2 h to obtain Co3O4 / SiO2 with a Co3O4 loading of 10 wt.%;

[0070] S2. Weigh 20 g of cetyltrimethylammonium bromide (CATB) and dissolve it in 100 mL of deionized water. Stir magnetically at 600 r / min for 30 min until the solution is clear. Add 650 mL of anhydrous ethanol and continue stirring for 15 min. Add 150 mL of ammonia water (NH3·H2O) at room temperature and stir for 8 min to obtain a homogeneous solution. Add a silicon source mixture of methyltrimethoxysilane (MTMS) and tetraethyl orthosilicate (TEOS) in a 1:1 ratio. Stir for 1.5 h to form a milky white turbid silica suspension. After precipitation for 30 min, remove the supernatant. Centrifuge three times with anhydrous ethanol at 8000 r / min, then increase the speed to 10000 r / min and wash three times with anhydrous ethanol. Vacuum dry the precipitate at 90 °C for 12 h. Finally, calcine the dried semi-finished powder in a muffle furnace at 650 °C for 6 h to obtain hollow mesoporous SiO2.

[0071] S3. Aluminum nitrate nonahydrate Al(NO3)3·9H2O, used as the aluminum source, was dissolved in a mixed solution of water and ethanol (EtOH) in a stainless steel autoclave lined with polytetrafluoroethylene. Co3O4 / SiO2 powder was then added under continuous stirring. Tetrapropylammonium hydroxide (TPAOH) was then added dropwise, and the reaction mixture was stirred continuously at room temperature for 6 hours. Ammonia water (NH3·H2O) was then added to the mixed solution under stirring, and stirring continued for 0.5 hours (the molar ratio of reactants in the precursor solution was 10:1 TPAOH:1 Al(NO3)3:50 SiO2:400 EtOH:300 NH3:1500 H2O). The hydrothermal reaction was carried out at 180℃ for 72 hours. After the reaction, the product was separated by filtration, thoroughly washed with deionized water and ethanol, and dried at 120℃ for 12 hours. It was then calcined in a muffle furnace at 500℃ for 4 hours to obtain Co3O4@HZSM-5.

[0072] S4. The Co3O4@HZSM-5 powder was impregnated in a 2% aqueous solution of lanthanum nitrate hexahydrate La(NO3)3·6H2O at 70℃ (the volume of the aqueous solution of La(NO3)3·6H2O was 1.5 times that of Co3O4@HZSM-5); the impregnated powder was dried at 110℃ for 4h, and then calcined in a muffle furnace at 550℃ for 4h to obtain the Co3O4@La / HZSM-5 catalyst.

[0073] Synergistic purification of NO in low-temperature flue gas x The method of CO, using Figure 1 The system shown includes the following steps:

[0074] Step 1: Industrial raw flue gas (180℃) flows through the inlet pipe into a fixed bed (40000h) containing a NO / CO co-oxidation catalyst for low-temperature flue gas. -1The adsorption of SO2 and the dissociation and adsorption of H2O are suppressed under the shell layer of the NO / CO co-oxidation catalyst used for low-temperature flue gas, reducing or avoiding the poisoning effect of SO2 and H2O on the catalyst. Under the action of the core layer, NO oxidation reaction and CO oxidation reaction occur to obtain transition flue gas (240℃).

[0075] Step 2: The transition flue gas is mixed with NH3 (ammonia-nitrogen ratio of 1.25) supplied by the ammonia injection grid and then flows through the NH3-SCR catalyst fixed bed (60,000 h⁻¹). -1 A rapid SCR reaction occurs, resulting in exhaust gas (240℃).

[0076] Step 3: The exhaust gas passes through a flue gas heat exchanger, transferring heat to the denitrification reactor to increase the temperature of the industrial flue gas in the intake pipe.

[0077] Example 2

[0078] Compared with Example 1, the difference is that Co3O4@La / HZSM-5 is changed to MnCo2O4@La / HZSM-5 catalyst. Specifically, in the preparation process, the precursor Co(NO3)2·6H2O supported on hollow mesoporous SiO2 is replaced with equal amounts of Mn(NO3)2·4H2O and Co(NO3)2·6H2O in a molar ratio of 1:2.

[0079] Example 3

[0080] Compared with Example 1, the only difference is that the Co3O4@La / HZSM-5 catalyst is changed to CuCo2O4@La / HZSM-5 catalyst. Specifically, in the preparation process, the precursor Co(NO3)2·6H2O supported on hollow mesoporous SiO2 is replaced with equal amounts of Cu(NO3)2·3H2O and Co(NO3)2·6H2O in a molar ratio of 1:2.

[0081] Example 4

[0082] Compared with Example 1, the only difference is that the Co3O4@La / HZSM-5 catalyst is changed to CrCo2O4@La / HZSM-5 catalyst. Specifically, in the preparation process, the precursor Co(NO3)2·6H2O supported on hollow mesoporous SiO2 is replaced with an equal amount of Cr(NO3)3·6H2O and Co(NO3)2·6H2O in a molar ratio of 1:2.

[0083] Example 5

[0084] Compared with Example 1, the only difference is that the Co3O4@La / HZSM-5 catalyst is changed to NiCo2O4@La / HZSM-5 catalyst. Specifically, in the preparation process, the precursor Co(NO3)2·6H2O supported on hollow mesoporous SiO2 is replaced with equal amounts of Ni(NO3)2·6H2O and Co(NO3)2·6H2O in a molar ratio of 1:2.

[0085] Example 6

[0086] Compared with Example 1, the only difference is that the Co3O4@La / HZSM-5 catalyst is changed to Co3O4@Pr / HZSM-5 catalyst. Specifically, in the preparation process, La(NO3)3·6H2O is replaced with an equimolar amount of Pr(NO3)3·6H2O.

[0087] Example 7

[0088] Compared with Example 1, the only difference is that the Co3O4@La / HZSM-5 catalyst is changed to Co3O4@Sm / HZSM-5 catalyst. Specifically, in the preparation process, La(NO3)3·6H2O is replaced with an equimolar amount of Sm(NO3)3·6H2O.

[0089] Comparative Example 1

[0090] The only difference from Example 1 is that the fixed bed containing the NO / CO co-oxidation catalyst for low-temperature flue gas is replaced with an NH3-SCR catalyst fixed bed.

[0091] Comparative Example 2

[0092] The only difference from Example 1 is that Co3O4@La / HZSM-5 was changed to a Co3O4 catalyst.

[0093] Comparative Example 3

[0094] Compared with Example 1, the only difference is that Co3O4@La / HZSM-5 is changed to Co3O4@HZSM-5 catalyst, specifically the product obtained in step S3 of the Co3O4@La / HZSM-5 catalyst preparation.

[0095] Comparative Example 4

[0096] Compared with Example 1, the only difference is that Co3O4@La / HZSM-5 was modified into a La / Co3O4 catalyst. Specifically, Co3O4 powder was impregnated in a 2% aqueous solution of lanthanum nitrate hexahydrate La(NO3)3·6H2O at 70°C (the volume of the La(NO3)3·6H2O aqueous solution was 1.5 times that of Co3O4); the impregnated powder was dried at 110°C for 4 hours, and then calcined in a muffle furnace at 550°C for 4 hours to obtain the La / Co3O4 catalyst.

[0097] Test case

[0098] Industrial flue gas was treated using the methods of Examples 1-7 and Comparative Examples 1-4, and the catalytic performance of the catalyst was tested. NO x The conversion rate and CO oxidation rate results are shown in Table 1.

[0099] Table 1

[0100] <![CDATA[SO2 concentration / mg / Nm 3 > <![CDATA[H2O content / %]]> ammonia nitrogen ratio <![CDATA[NO x Conversion rate / % CO oxidation rate / % Example 1 50 10 1.25 95 97 Example 2 50 10 1.25 97 98 Example 3 50 10 1.25 93 95 Example 4 50 10 1.25 88 90 Example 5 50 10 1.25 98 98 Example 6 50 10 1.25 95 94 Example 7 50 10 1.25 92 90 Comparative Example 1 50 10 1.25 81 2 Comparative Example 2 50 10 1.25 83 6 Comparative Example 3 50 10 1.25 87 37 Comparative Example 4 50 10 1.25 82 6

[0101] Comparing the data from Examples 1-7 and Comparative Example 1 shown in Table 1, it can be seen that under the action of the co-oxidation catalyst fixed bed, i.e., by adjusting the NO2 / NO ratio in the raw industrial flue gas, the denitrification efficiency of the denitrification reaction occurring in the NH3-SCR catalyst fixed bed is improved. Meanwhile, the treatment results of Examples 1-7 demonstrate that the NO / CO co-oxidation catalyst and method of this invention for low-temperature flue gas can solve the CO treatment problem. A comparison of Examples 1-7 and Comparative Examples 2-4 shows that the NO / CO co-oxidation catalyst of this invention for low-temperature flue gas (low-temperature complex flue gas) has excellent anti-sulfur and hydrophobic properties, can cope with actual complex atmospheres, and has good application prospects.

[0102] Synergistic purification of NO in low-temperature flue gas using the methods in Examples 1-2 and Comparative Example 1 x In the adjustment method for CO, the ammonia-nitrogen ratio, NO x The conversion rate results are shown in Table 2.

[0103] Table 2

[0104] <![CDATA[SO2 concentration / mg / Nm 3 > <![CDATA[H2O content / %]]> ammonia nitrogen ratio <![CDATA[NO x Conversion rate / % Example 1 50 10 1.25 95 Example 1 50 10 1.1 94 Example 1 50 10 1 94 Example 2 50 10 1.25 97 Example 2 50 10 1.1 95 Example 2 50 10 1 94 Comparative Example 1 50 10 1.25 81 Comparative Example 1 50 10 1.1 70 Comparative Example 1 50 10 1 59

[0105] As can be seen from Table 2, NO in Comparative Examples 1-2 and Comparative Example 1 under different ammonia-nitrogen ratios... x As can be seen from the conversion rate, Examples 1 and 2 not only achieved a significant improvement in denitrification efficiency but also solved the CO treatment problem. Furthermore, they optimized the ammonia injection rate and reduced ammonia escape pollution. It can be seen that even with a reduction in the ammonia injection rate, Examples 1 and 2 still maintained a high NO content. x Conversion rate.

[0106] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0107] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A NO / CO co-oxidation catalyst for low-temperature flue gas, characterized in that, The NO / CO co-oxidation catalyst is a core-shell catalyst; The core-shell catalyst uses a NO / CO co-oxidation catalyst as the core layer and a sulfur-resistant hydrophobic catalyst as the shell layer. The core layer is a spinel catalyst with redox sites; The shell layer is a molecular sieve catalyst with acidic and hydrophobic sites; The redox sites of the spinel catalyst include Co. δ+ Ions, Mn δ+ Ions, Cu δ+ Ions, Cr δ+ Ions and Ni δ+ At least one of the ions; The spinel catalyst includes Co3O4, MnCo2O4, CuCo2O4, CrCo2O4 or NiCo2O4 with Co-based spinel as the substrate model; The molecular sieve catalysts include La / HZSM-5, Pr / HZSM-5, or Sm / HZSM-5, which are based on HZSM-5.

2. The NO / CO co-oxidation catalyst for low-temperature flue gas as described in claim 1, characterized in that, The core-shell catalyst has a diameter of 10-20 nm and a specific surface area of ​​200-400 m². 2 / g, with a shell thickness of 2-5nm.

3. A method for synergistically purifying NO in low-temperature flue gas x The system with CO is characterized by, The system includes a flue gas heat exchanger and a denitrification reactor; The denitrification reactor includes an inlet pipe arranged sequentially along the flue gas flow direction, a fixed bed containing the NO / CO co-oxidation catalyst for low-temperature flue gas as described in any one of claims 1-2, an ammonia injection grid, an NH3-SCR catalyst fixed bed, and an outlet pipe. The flue gas heat exchanger is connected to the inlet and outlet pipes of the denitrification reactor via a flue, and is used to collect the heat released by the reaction and increase the temperature of the flue gas entering the inlet pipe of the denitrification reactor.

4. A method for synergistically purifying NO in low-temperature flue gas x The method with CO is characterized by, The method uses the system described in claim 3 to perform NO removal. x Co-purification with CO, the steps include: Industrial flue gas flows into the denitrification reactor through the inlet pipe. It first passes through a fixed bed containing a NO / CO co-oxidation catalyst for low-temperature flue gas. Under the action of the catalyst, NO oxidation and CO oxidation reactions occur to obtain transition flue gas. The transition flue gas and the NH3 supplied by the ammonia injection grid are mixed and then flow through the NH3-SCR catalyst fixed bed, where the SCR reaction occurs under the action of the NH3-SCR catalyst to obtain the emission flue gas. The exhaust gas is discharged to a flue gas heat exchanger through an exhaust pipe, where the heat released by the reaction is collected and used to increase the temperature of the flue gas entering the inlet pipe of the denitrification reactor.

5. The method as described in claim 4, characterized in that, The industrial flue gas includes NO x , CO, SO2 and H2O, of which NO x The NO content in the medium is not less than 90%.

6. The method as described in claim 5, characterized in that, NO in industrial flue gas x The concentration is 200-600 mg / Nm 3 ; And / or, the concentration of CO in the industrial flue gas is 5000-15000 mg / Nm³. 3 ; And / or, the concentration of SO2 in the industrial flue gas is 30-55 mg / Nm³. 3 ; And / or, the concentration of H2O in the industrial flue gas is 5-18 vol.

7. The method as described in claim 4, characterized in that, The NH3-SCR catalyst is a V2O5-WO3 / TiO2 catalyst.

8. The method as described in claim 4, characterized in that, The inflow temperature of the industrial flue gas is 120-200℃; And / or, the space velocity of the industrial flue gas flowing through the fixed bed containing the NO / CO co-oxidation catalyst for low-temperature flue gas is 24,000-60,000 h⁻¹. -1 ; And / or, the amount of ammonia injected into the ammonia injection grid is greater than the theoretical ammonia-nitrogen ratio for the NH3-SCR reaction; And / or, the space velocity of the transition flue gas flowing through the NH3-SCR catalyst fixed bed is 30,000-100,000 h⁻¹. -1 .

9. A NO / CO co-oxidation catalyst according to any one of claims 1-2, or a system according to claim 3, or a method according to any one of claims 4-8, for the synergistic purification of NO in low-temperature flue gas. x Applications of pollutants and CO pollutants.

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