System and method for synergistically purifying NOx and CO in low-temperature flue gas

Abstract

The invention belongs to the technical field of industrial flue gas purification, and particularly relates to a system and a method for synergistically purifying NOx and CO in low-temperature flue gas. On the basis of the problem that the oxidation reaction of NO and CO is easily and remarkably inhibited by SO2 and H2O in flue gas, the core-shell catalyst is designed for a denitration system, NO / CO co-oxidation in a complex atmosphere is achieved, and the low-temperature denitration efficiency is improved by partially oxidizing NO into NO2 and initiating a rapid SCR reaction; meanwhile, NO / CO co-oxidation heat release is used for increasing the temperature of flue gas at an SCR inlet, and energy self-supply of a denitration system is improved. On the whole, low-temperature efficient denitration and CO pollution control are both considered through flue gas component conditioning and temperature adjustment, and collaborative purification of NOx and CO in low-temperature flue gas is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of industrial flue gas purification, and more particularly relates to a system and method for synergistically purifying NO x and CO in low-temperature flue gas. BACKGROUND

[0002] Industrial source NO x The emission amount has been decreasing year by year since the ultra-low emission transformation, but the total amount is still very large, and there is still a huge treatment space. CO, as a typical product of incomplete combustion of fossil fuels, often coexists with NO x in industrial flue gas, for example, sintering flue gas. Therefore, the synergistic treatment of NO x and CO is urgent. NH3-SCR is the most widely used denitration technology in industry, but it faces the severe CO treatment and the carbon emission reduction pressure due to the need for combustion of blast furnace gas for heat supply. Oxidizing NO and CO before the SCR denitration reaction not only removes CO and fully utilizes its oxidation heat release, but also improves the low-temperature activity of the SCR catalyst through the rapid SCR reaction pathway. In summary, the industrial flue gas NO+CO co-oxidation-coupled SCR denitration technology has good application prospects.

[0003] CN114797463A discloses a device system and method for sintering flue gas CO catalytic heat exchange series low-temperature SCR denitration. The device system uses a CO catalytic heat storage and heat exchange device to replace the traditional heat exchanger, reduces the amount of heat exchange elements, and eliminates the need for blast furnace gas for system steady-state operation, while realizing the storage and conversion of sintering flue gas and denitration flue gas heat. This method makes full use of CO oxidation heat release to ensure that the SCR denitration reactor inlet pipeline temperature meets the set requirements. The invention only realizes CO oxidation-coupled SCR denitration, and does not consider adjusting the NO x composition to accelerate the SCR denitration efficiency.

[0004] CN108355656A discloses a flue gas NO pre-oxidation catalyst, its preparation method and application, and a low-temperature flue gas denitration method. The catalyst includes a carrier and an active component loaded on the carrier, wherein the active component contains γ-Fe2O3 with a particle size of 2-30 nm, and the carrier is a composite containing γ-Al2O3 and TiO2 with a mass ratio of 1: (0.15-0.4). This method oxidizes part of NO to NO2 under pre-oxidation conditions, greatly improving the subsequent denitration efficiency. The invention only realizes NO oxidation-coupled SCR denitration, and does not realize the synergistic removal of CO.

[0005] However, in actual working conditions, the gas composition is complex, and the catalyst is easily poisoned by toxic substances and seriously deactivated. First, SO2 is a common toxic gas, which widely exists in various industrial flue gas. Even after desulfurization, trace SO2 still easily leads to the poisoning and deactivation of the oxidation catalyst. In addition, the presence of H2O in the industrial flue gas seriously inhibits the redox ability of the oxidation catalyst.

[0006] CN114160161A discloses a Pt-Fe bimetallic catalyst for CO and NO oxidation, and a preparation method and application thereof. The catalyst takes TiO2 as a carrier, and is loaded with an active component and an auxiliary agent. The active component includes Pt element and / or oxide of Pt, with a mass percentage of 0.01-0.2wt.%, and the auxiliary agent includes oxide of Fe, with a mass percentage of 0.2-1wt.%. The catalyst cooperatively oxidizes about 50% of NO and 100% of CO, and meets the requirements of flue gas composition conditioning and temperature adjustment. The invention only realizes NO / CO co-oxidation in a water-containing atmosphere, and does not consider the poisoning effect of trace SO2 on the catalyst, and does not realize SCR coupled denitration, but only proposes a prospect.

[0007] In view of the deficiencies of the prior art, it is urgent to provide a system and method for efficiently and cooperatively purifying NO x and CO in industrial flue gas at low temperature. SUMMARY

[0008] The purpose of the present application is to provide a system and method for cooperatively purifying NO x and CO in low-temperature flue gas, so as to solve the problems existing in the prior art.

[0009] To achieve the above purpose, the present application provides the following solutions:

[0010] One of the technical solutions of the present application 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 takes the NO / CO co-oxidation catalyst as a core layer, and takes a sulfur-resistant hydrophobic catalyst as a shell layer.

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

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

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

[0015] Further, the shell layer is a molecular sieve catalyst having acid sites and hydrophobic sites.

[0016] Optionally, the acid sites of the molecular sieve catalyst are adjusted by changing the Si / Al ratio, and the Si / Al ratio is 44, 46, 48 or 50, preferably 44.

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

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

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

[0020] The second technical solution of the present application provides a system for synergistically purifying NO x and CO in low-temperature flue gas, which comprises a flue gas heat exchanger and a denitration reactor.

[0021] The denitration reactor comprises, in sequence along the flue gas flow direction, an inlet pipe, a fixed bed layer containing the above-mentioned NO / CO co-oxidation catalyst for low-temperature flue gas, an ammonia injection grid, a NH3-SCR catalyst fixed bed layer and an outlet pipe.

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

[0023] The system for synergistically purifying NO x and CO in low-temperature flue gas provided by the present application is characterized in that the flue gas heat exchanger is closely connected to the inlet pipe and the outlet pipe of the denitration reactor through a flue, and is used to collect the heat released by the reaction of the fixed bed layer of the NO / CO co-oxidation catalyst for low-temperature flue gas, and then exchanges heat with the industrial raw flue gas to transfer the heat to the inlet pipe of the denitration reactor to increase the flue gas temperature.

[0024] The third technical solution of the present application provides a system for synergistically purifying NO xThe method of removing NO from the flue gas of industry x The method of removing NO from the flue gas of industry

[0025] The flue gas of industry (complex component flue gas) flows into the denitration reactor through the inlet pipeline, and first passes through the fixed bed layer containing the NO / CO co-oxidation catalyst for low-temperature flue gas, and the NO oxidation reaction and the CO oxidation reaction occur under the action of the catalyst to obtain the transition flue gas;

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

[0027] The emission flue gas is discharged through the exhaust pipeline to the flue gas heat exchanger, and the heat released in the reaction is collected and used to raise the temperature of the flue gas entering the inlet pipeline of the denitration reactor.

[0028] Further, the flue gas of industry includes NO x , CO, SO2 and H2O, wherein the content of NO x is not less than 90%.

[0029] Optionally, the concentration of NO x in the flue gas of industry is 200-600 mg / Nm 3 , preferably 400-500 mg / Nm 3 .

[0030] Optionally, the concentration of CO in the flue gas of industry is 5000-15000 mg / Nm 3 , preferably 7000-11000 mg / Nm 3 .

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

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

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

[0034] Further, the space velocity of the flue gas of industry flowing through the fixed bed layer containing the NO / CO co-oxidation catalyst for low-temperature flue gas is 24000-60000 h -1 .

[0035] The industrial flue gas flowing through the fixed bed containing the NO / CO co-oxidation catalyst for low-temperature flue gas is subjected to NO oxidation reaction and CO oxidation reaction under the action of the catalyst, and the obtained transition flue gas temperature can be increased by 50-80℃ compared with the industrial original flue gas temperature.

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

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

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

[0039] Further, the transition flue gas comprises NO x , SO2 and H2O, wherein the molar ratio of NO x / NO2 in NO x is 0.9-1.1, and preferably 1.

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

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

[0042] Further, the space velocity of the transition flue gas flowing through the fixed bed of the NH3-SCR catalyst is 30000-100000h -1 .

[0043] In the present application, the transition flue gas flowing through the fixed bed of the NH3-SCR catalyst is subjected to rapid SCR reaction, and the reaction rate is nearly ten times higher than that of the standard SCR reaction of the industrial flue gas flowing through the fixed bed of the NH3-SCR catalyst, and the denitration efficiency is greatly improved.

[0044] The application is based on the problem that the oxidation reaction of NO and CO is easily inhibited by SO2 and H2O in flue gas, a core-shell catalyst is designed for a denitration system to realize NO / CO co-oxidation under complex atmosphere, the NO is partially oxidized to NO2 to trigger a rapid SCR reaction and improve the low-temperature denitration efficiency, and the NO / CO co-oxidation releases heat to improve the SCR inlet flue gas temperature and improve the energy self-sufficiency of the denitration system.

[0045] The fourth technical scheme of the application provides an application of the above NO / CO co-oxidation catalyst, the above system or the above method in co-purifying NO x Pollutants and CO pollutants.

[0046] In application, the industrial flue gas passes through the NO / CO co-oxidation catalyst for low-temperature flue gas to perform NO oxidation reaction and CO oxidation reaction to obtain transition flue gas, the composition of the industrial original flue gas is adjusted and the temperature is improved, the transition flue gas is mixed with NH3 supplied by the ammonia injection grid and then passes through the NH3-SCR catalyst to perform a rapid SCR reaction, and finally the industrial original flue gas is co-purified by NO x and CO at low temperature and high efficiency.

[0047] The application has the following technical effects:

[0048] The application is based on the technical problem that the oxidation reaction of NO x and CO in industrial flue gas is easily inhibited by SO2 and H2O in flue gas, a core-shell catalyst is designed, the acid sites in the core-shell catalyst can inhibit SO2 adsorption and the hydrophobic sites can inhibit H2O dissociation adsorption, the anti-sulfur hydrophobic molecular sieve catalyst is arranged in the shell layer of the core-shell material to protect the core layer spinel catalyst to perform NO / CO oxidation reaction, and the application simultaneously realizes NO partial oxidation and CO complete oxidation to obtain transition flue gas, the transition flue gas flows through the NH3-SCR catalyst fixed bed to realize CO treatment while the denitration reaction rate is greatly improved, and the traditional SCR denitration scheme is more green and efficient.

[0049] The application is based on the technical problem that the oxidation reaction of NO xIn the method with CO, on one hand, NO is partially oxidized into NO2 to initiate rapid SCR reaction in the NH3-SCR catalyst fixed bed, improve the low-temperature denitration efficiency, optimize the ammonia injection amount, and reduce the ammonia escape pollution; on the other hand, the heat released by 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 to improve the energy self-sufficiency of the denitration system (the denitration system in the prior art needs to be supplemented with heat, which causes a substantial increase in energy medium consumption, poor technical and economic performance, and cannot ignore the carbon increment effect).

[0050] The method provided by the application is suitable for actual working conditions, takes into account low-temperature high-efficiency denitration and CO pollution control, and has good economic benefits and application prospects. BRIEF DESCRIPTION OF DRAWINGS

[0051] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the present application, and serve as an aid in explaining the exemplary embodiments of the present application and their descriptions, and are not intended as an improper limitation of the present application. In the drawings:

[0052] Figure 1 The method provided by the application is suitable for actual working conditions, takes into account low-temperature high-efficiency denitration and CO pollution control, and has good economic benefits and application prospects. x The device schematic diagram of the system with CO; wherein, 1 is a flue gas heat exchanger, 2 is an inlet pipeline, 3 is a fixed bed layer of a NO / CO co-oxidation catalyst of 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 a fixed bed layer of an NH3-SCR catalyst, and 8 is an outlet pipeline. DETAILED DESCRIPTION

[0053] The detailed description of the various exemplary embodiments of the present application should not be considered as limiting the present application, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present application.

[0054] It should be understood that the terms described in the present application are only used to describe the particular embodiments, and are not used to limit the present application. In addition, for the numerical range in the present application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between any stated value or intermediate value in the stated range, and any other stated value or intermediate value in the stated range, is also included in the present application. The upper limit and the lower limit of these smaller ranges can 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 for low-temperature flue gas used in the specific embodiment of the present application has a diameter of 15 nm, a specific surface area of 275 m 2 / g, and a shell thickness controlled at 3 nm.

[0064] Example 1

[0065] In this example, the fixed bed layer containing the NO / CO co-oxidation catalyst for low-temperature flue gas is one layer, and the fixed bed of NH3-SCR catalyst is two layers; the 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 between 100-200 m 2 / g; the Co3O4@La / HZSM-5 catalyst is used as the NO / CO co-oxidation catalyst for low-temperature flue gas.

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

[0067] A certain amount of ammonium metavanadate NH4VO3 is dissolved in deionized water acidified by oxalic acid, and then a certain amount of ammonium tungstate ((NH4) 10 H2(W2O7)6) and TiO2 (anatase DT-51 type) are added into the aqueous solution in sequence and stirred rapidly for 1 h, the water in the slurry is evaporated using a rotary vacuum evaporator at 60℃, and then the sample is continuously calcined in air at 500℃ for 3 h to obtain the 0.7wt.%V-7wt.%W / TiO2 catalyst; the raw material usage ratio is matched according to the loading amount.

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

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

[0070] S2, 20 g of cetyltrimethylammonium bromide (CATB) was weighed into 100 mL of deionized water, and stirred at 600 r / min for 30 min until the solution was clear; 650 mL of anhydrous ethanol was added, and stirring was continued for 15 min, and then 150 mL of aqueous ammonia NH3·H2O was added at room temperature, and stirring was continued for 8 min to obtain a uniform solution; then a mixed solution of methyltrimethoxysilane (MTMS) and tetraethyl orthosilicate (TEOS) in a ratio of 1:1 was added, and stirring was continued for 1.5 h to form a milky white silica suspension, and then the supernatant was removed after the precipitate was allowed to settle for 30 min, and the precipitate was washed with anhydrous ethanol at 8000 r / min for 3 times, and then the speed was increased to 10000 r / min, and the precipitate was washed with anhydrous ethanol for 3 times; the precipitate was dried at 90°C under vacuum for 12 h, and finally the dried semi-finished product powder was calcined in a muffle furnace at 650°C for 6 h to obtain hollow mesoporous SiO2;

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

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

[0073] Simultaneous purification of NO x and CO in low-temperature flue gas using Figure 1 The system shown in FIG. 1, the steps include:

[0074] Step 1, the industrial raw flue gas (180°C) flows through a fixed bed layer (40000 h -1), under the shell effect of the NO / CO co-oxidation catalyst for low-temperature flue gas, the adsorption of SO2 and the dissociative adsorption of H2O are inhibited, and the poisoning effect of SO2 and H2O on the catalyst is reduced or avoided, the NO oxidation reaction and the CO oxidation reaction occur under the effect of the core layer, and the transition flue gas (240°C) is obtained;

[0075] Step 2, after the transition flue gas is mixed with NH3 (ammonia nitrogen ratio is 1.25) supplied by the ammonia injection grid, it flows through the NH3-SCR catalyst fixed bed layer (60000h -1 ), a rapid SCR reaction occurs, and the emission flue gas (240°C) is obtained;

[0076] Step 3, the emission flue gas passes through the flue gas heat exchanger to transfer heat to the denitration reactor for increasing the temperature of the industrial flue gas in the inlet pipeline.

[0077] Example 2

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

[0079] Example 3

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

[0081] Example 4

[0082] Compared with Example 1, the difference is only that Co3O4@La / HZSM-5 is adjusted to CrCo2O4@La / HZSM-5 catalyst, specifically, the precursor Co(NO3)2·6H2O loaded on the 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 during the preparation process.

[0083] Example 5

[0084] The difference compared with Example 1 is only that Co3O4@La / HZSM-5 is adjusted to NiCo2O4@La / HZSM-5 catalyst, specifically, the precursor Co(NO3)2·6H2O loaded on hollow mesoporous SiO2 is replaced by equal amount of Ni(NO3)2·6H2O and Co(NO3)2·6H2O in a molar ratio of 1:2 during preparation.

[0085] Example 6

[0086] The difference compared with Example 1 is only that Co3O4@La / HZSM-5 is adjusted to Co3O4@Pr / HZSM-5 catalyst, specifically, La(NO3)3·6H2O is replaced by equal molar Pr(NO3)3·6H2O during preparation.

[0087] Example 7

[0088] The difference compared with Example 1 is only that Co3O4@La / HZSM-5 is adjusted to Co3O4@Sm / HZSM-5 catalyst, specifically, La(NO3)3·6H2O is replaced by equal molar Sm(NO3)3·6H2O during preparation.

[0089] Comparative Example 1

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

[0091] Comparative Example 2

[0092] The difference compared with Example 1 is only that Co3O4@La / HZSM-5 is adjusted to Co3O4 catalyst.

[0093] Comparative Example 3

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

[0095] Comparative Example 4

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

[0097] Test Example

[0098] The industrial flue gas is treated by the method of Examples 1-7 and Comparative Examples 1-4, and the catalytic performance of the catalyst is tested. x The conversion rate and CO oxidation rate are shown in Table 1.

[0099] Table 1

[0100] SO2 concentration / mg / Nm 3 ]] H2O content / % Ammonia nitrogen ratio NO x Conversion / % 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] By comparing the data of Examples 1-7 and Comparative Example 1 shown in Table 1, it can be seen that the adjustment of the ratio of NO2 / NO in the industrial raw flue gas under the action of the co-oxidation catalyst fixed bed layer can improve the denitration efficiency of the denitration reaction occurring in the NH3-SCR catalyst fixed bed layer. Meanwhile, the treatment results of Examples 1-7 show that the NO / CO co-oxidation catalyst and method for low-temperature flue gas of the present application can solve the CO treatment problem; the comparison of Examples 1-7 and Comparative Examples 2-4 shows that the NO / CO co-oxidation catalyst for low-temperature flue gas (low-temperature complex flue gas) of the present application has excellent sulfur resistance and hydrophobicity, can cope with actual complex atmosphere, and has good application prospect.

[0102] The method of Examples 1-2 and Comparative Example 1 is used to co-purify NO x and CO in low-temperature flue gas, and the ammonia nitrogen ratio in the method is adjusted. x The conversion rate is shown in Table 2.

[0103] Table 2

[0104] SO2 concentration / mg / Nm 3 ]] H2O content / % Ammonia nitrogen ratio NO x Conversion / % 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, the NO x conversion rates of Comparative Examples 1-2 and Comparative Example 1 under different ammonia nitrogen ratios show that Examples 1 and 2 not only achieve a substantial increase in denitration efficiency, but also solve the CO treatment problem, and can optimize the ammonia injection amount and reduce ammonia escape pollution. It can be seen that even if the ammonia injection amount is reduced, Examples 1 and 2 still maintain a high NO x conversion rate.

[0106] The various embodiments described in this specification are intended to be illustrative only and in no way limit the scope of the application. Changes and modifications can be made by those skilled in the art, which employ the principles of the application, without departing from the scope thereof. Accordingly, the application is not limited to the embodiments described herein, but instead has scope to encompass any changes and modifications that serve the same, equivalent, or similar purposes.

[0107] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to those skilled in the art and are within the scope of the application as defined by the appended claims. The particular implementations shown and described are shown as being representative alternatives only. As such, the application is not limited to the described implementations and alterations and modifications can be made to the described implementations without departing from the spirit or scope of the application in its broadest form.

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.

2. The NO / CO co-oxidation catalyst for low-temperature flue gas as described in claim 1, characterized in that, 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; And / or, the spinel catalyst comprises Co3O4, MnCo2O4, CuCo2O4, CrCo2O4 or NiCo2O4 with Co-based spinel as the substrate model; And / or, the molecular sieve catalyst includes La / HZSM-5, Pr / HZSM-5 or Sm / HZSM-5 based on HZSM-5.

3. 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.

4. 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 1-3, 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.

5. 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 4 to perform NO removal. x The synergistic purification with CO involves the following steps: 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.

6. The method as described in claim 5, 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%.

7. The method as described in claim 6, 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.

8. The method as described in claim 5, characterized in that, The NH3-SCR catalyst is a V2O5-WO3 / TiO2 catalyst.

9. The method as described in claim 5, 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 .

10. A NO / CO co-oxidation catalyst according to any one of claims 1-3, or a system according to claim 4, or a method according to any one of claims 5-9, for the synergistic purification of NO in low-temperature flue gas. x Applications of pollutants and CO pollutants.

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