NH3-SCR (Selective Catalytic Reduction) denitration system and method for synergistically purifying CO

Abstract

The invention belongs to the technical field of industrial flue gas purification, and particularly relates to an NH3-SCR denitration system and method for cooperatively purifying CO. According to the invention, the core-shell catalyst is designed based on the difference of NH3 and CO oxidation reaction mechanisms, the core-shell catalyst is used in a denitration system to realize NH3 and CO co-oxidation, and NH3 / CO co-oxidation heat release is utilized to improve the NH3-SCR inlet flue gas temperature and improve the denitration efficiency. According to the invention, by utilizing the difference of reaction mechanisms of NH3-SCR denitration, NH3 oxidation and CO oxidation, multi-component efficient collaborative purification of NOx, escape NH3 and CO in industrial flue gas is realized, and the energy consumption of the system is obviously reduced through function integration.

Description

Technical Field

[0001] The present invention belongs to the technical field of industrial flue gas purification, and more specifically relates to a NH 3 -SCR denitrification system and method. Background Art

[0002] Industrial industries that use fossil fuels usually produce large amounts of NO x The direct emission of these waste gases will pose a serious threat to the ecological environment and human health. 3 The selective catalytic reduction method with a reducing agent is currently the mainstream technology for industrial flue gas denitrification. x Ultra-low emission requirements, the amount of ammonia sprayed is usually greater than the theoretical reaction stoichiometric ratio (NH 3 / NO=1), leading to severe NH 3 Escape secondary pollution.

[0003] CN112892547A discloses a catalyst for simultaneously removing nitrogen oxides and carbon monoxide and a preparation method thereof. The catalyst is a supported catalyst with γ-Al 2 O 3 As a carrier, Mn, Cu, Ce oxides are used as active components. The metal salts of Mn, Cu, and Ce are prepared into a mixed salt solution according to a certain ratio. The metal precursor is uniformly loaded on the γ-Al under ultrasonic-assisted conditions. 2 O 3 The supported catalyst is obtained after drying and calcination. The catalyst has excellent NH 3 -SCR and CO oxidation performance, capable of achieving NO x and CO. This invention only achieves the removal of NO x The synergistic removal of CO and NH 3 Caused by secondary pollution.

[0004] CN117654543A discloses a method for preparing a catalyst for low-temperature selective catalytic oxidation of slipped ammonia, the catalyst comprising precious metal elements and transition metal oxides, wherein the precious metal elements include but are not limited to one or two or more of gold, silver, platinum, palladium, etc., and the loading amount thereof is 0.1%-10%, and the transition metals include copper and iron, and the mass ratio thereof is 1:5-5:1. This invention only solves the problem of NH 3 - Low concentration NH during SCR denitrification 3 The escape problem does not achieve the coordinated removal of CO.

[0005] In view of the shortcomings of the existing technology, it is urgent to provide a method that can synergistically purify industrial flue gas NO x NH 3 , CO and other pollutants. Summary of the invention

[0006] The purpose of the present invention is to provide a NH3 that synergistically purifies CO. 3 -SCR denitrification system and method, based on NH 3 Based on the differences in the reaction mechanisms of CO oxidation, core-shell catalysts were designed to achieve NH 3 Co-oxidation with CO to utilize NH 3 / CO co-oxidation exotherm increases NH 3 -SCR inlet flue gas temperature, improve denitrification efficiency. The present invention significantly reduces the energy consumption of the denitrification system through functional integration, and realizes industrial flue gas NO x NH 3 , CO and other pollutants to solve the problems existing in the above-mentioned prior arts.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] One of the technical solutions of the present invention is to provide a NH 3 / CO co-oxidation catalyst, the NH 3 / CO co-oxidation catalyst is a core-shell catalyst;

[0009] The core-shell catalyst is composed of NH 3 The oxidation catalyst is a core layer structure, and the CO oxidation catalyst is a shell layer structure.

[0010] Furthermore, the core layer structure includes redox sites and acidic sites; and the shell layer structure includes redox sites.

[0011] Optionally, the redox sites of the core layer structure include Pt δ+ Ions and / or Ag δ+ ions, acidic sites including W δ+ Ions, Mo δ+ Ions and Nb δ+ ions; the redox sites of the shell structure include Cu δ+ Ion, Co δ+ Ion, Mn δ+ Ions and Fe δ+ At least one of the ions.

[0012] Optionally, the core layer is Pt / WO 3 、Pt / MoO 3 、Pt / Nb 2 O 5 、Ag / WO3 、Ag / MoO 3 or Ag / Nb 2 O 5 , the shell is CuO x (x=1、1 / 2)、CoO x (x=1、3 / 2、4 / 3)、MnO x (x=3 / 2、4 / 3、2) or FeO x (x=1, 3 / 2, 4 / 3).

[0013] In some specific embodiments, the core-shell catalyst has a diameter of 10 to 30 nm and a specific surface area of ​​200 to 400 m 2 / g, and the shell structure thickness is 2 to 5 nm.

[0014] Technical solution 2 of the present invention: providing a NH3 that can synergistically purify CO 3 -SCR denitration system, the NH 3 -SCR denitration system includes: flue gas heat exchanger and denitration reactor;

[0015] The denitration reactor comprises an air inlet pipe arranged at the top, an air outlet pipe arranged at the bottom, and an ammonia injection grid, an NH 3 -SCR catalyst fixed bed and containing the above NH 3 A fixed bed of a / CO co-oxidation catalyst;

[0016] The flue gas heat exchanger is fixedly arranged around the air inlet pipe and the air outlet pipe of the denitration reactor to collect the NH 3 The heat released by the fixed bed reaction of the / CO co-oxidation catalyst is transferred to the air inlet duct of the denitration reactor to increase the flue gas temperature;

[0017] The NH 3 -The number of layers of the SCR catalyst fixed bed is two.

[0018] Technical solution 3 of the present invention: providing a NH3 for synergistic purification of CO 3 -SCR denitration method, using the above denitration system to perform denitration, the steps include:

[0019] Industrial flue gas flows in from the air intake duct and is supplied by the ammonia injection grid with NH 3 After mixing, flow through NH 3 -SCR catalyst fixed bed, in NH 3 - NO is generated under the action of SCR catalyst x Selective catalytic reduction reaction to obtain transition flue gas;

[0020] The transition flue gas flows through NH3 / CO co-oxidation catalyst fixed bed, in NH 3 CO oxidation reaction and NH 3 Oxidation reaction to obtain exhaust gas;

[0021] The exhaust gas is discharged through the exhaust duct, and the CO oxidation reaction and NH 3 The heat of the oxidation reaction is used to increase the temperature of the industrial flue gas flowing in from the air intake duct.

[0022] Furthermore, the industrial flue gas includes NO x and CO.

[0023] Preferably, the NO in the industrial flue gas x The concentration is 200mg / Nm 3 ~500mg / Nm 3 , the concentration of CO is 5000mg / Nm 3 ~15000mg / Nm 3 .

[0024] Furthermore, the temperature of the industrial flue gas is 120-200°C.

[0025] Furthermore, the industrial flue gas flows through NH 3 -The space velocity of the SCR catalyst fixed bed is 3000h -1 ~60000h -1 .

[0026] Furthermore, the NH 3 -SCR catalyst is VW / TiO 2 catalyst.

[0027] Preferably, the VW / TiO 2 The V content in the catalyst is 0.3wt.% to 0.5wt.%, W content is 1wt.% to 5wt.%, TiO 2 The specific surface area is 150~250m 2 / g.

[0028] Furthermore, the amount of ammonia sprayed by the ammonia injection grid is greater than NH 3 - The theoretical ammonia nitrogen ratio of SCR reaction, preferably the ammonia nitrogen ratio is 1 to 1.5.

[0029] Furthermore, the transition flue gas includes CO and NH 3 .

[0030] Preferably, the CO concentration in the transition flue gas is 5000 mg / Nm 3 ~15000mg / Nm3 , NH 3 The concentration is 2.5mg / Nm 3 ~50mg / Nm 3 .

[0031] Furthermore, the transition flue gas flows through NH 3 The space velocity of the fixed bed of the / CO co-oxidation catalyst is 50000h -1 ~150000h -1 .

[0032] In the present invention, the transition flue gas is subjected to CO oxidation reaction and NH 3 The temperature of the exhaust flue gas obtained after the oxidation reaction can be increased by 30 to 70°C compared to the temperature of the transition flue gas.

[0033] The fourth technical solution of the present invention is to provide a NH 3 / CO co-oxidation catalyst or the above denitration system or the above method for collaboratively purifying NH in industrial flue gas 3 and applications of CO pollutants.

[0034] Furthermore, the above NH 3 Co-oxidation of NH / CO in industrial flue gas 3 The application of pollutants and CO pollutants specifically includes the following: 3 -SCR catalyst treatment of NH 3 The transition of flue gas from pollutants to CO pollutants passes through the NH 3 / CO co-oxidation catalyst for CO oxidation and NH 3 Oxidation reaction to achieve NO reduction in industrial flue gas x , escape NH 3 , efficient collaborative purification of CO multi-components.

[0035] The present invention discloses the following technical effects:

[0036] The present invention is based on NH 3 Based on the difference in the CO oxidation reaction mechanism, core-shell catalysts were designed. The Gibbs free energy of CO oxidation reaction is lower than that of NH 3 The objective fact of Gibbs free energy of oxidation reaction is that NH 3 The oxidation catalyst is placed in the core layer of the core-shell material, and the CO oxidation catalyst is placed in the shell layer of the core-shell material. The high concentration CO oxidation releases heat, increases the flue gas temperature, and promotes NH 3 Oxidation reaction occurs. At the same time, acidic sites are added to the core layer to promote NH 3 Adsorbed on the catalyst surface. 3 The CO / CO co-oxidation reaction is exothermic and the heat is transferred to NH 3-SCR inlet flue gas, significantly reducing the energy consumption of the denitrification system (the denitrification system in the existing technology needs to be treated with supplementary heat, and the supplementary heat treatment will increase the emission of carbon dioxide) and the V content in the catalyst, while increasing NH 3 -SCR denitrification efficiency. It can achieve efficient removal of multiple pollutants and achieve significant economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0038] Figure 1 Schematic diagram of the denitration system of the present invention; wherein 1 is a flue gas heat exchanger, 2 is an ammonia injection grid, 3 is NH 3 -SCR catalyst fixed bed, 4 is NH 3 / CO co-oxidation catalyst fixed bed, 5 is CO oxidation catalyst, 6 is NH 3 Oxidation catalyst, 7 is an air intake pipe, and 8 is an air outlet pipe. DETAILED DESCRIPTION

[0039] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0040] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0041] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0042] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0043] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0044] Figure 1 The schematic diagram of the denitration system of the present invention is shown in FIG. 1 , wherein 1 is a flue gas heat exchanger, 2 is an ammonia injection grid, 3 is NH 3 -SCR catalyst fixed bed, 4 is NH 3 / CO co-oxidation catalyst fixed bed, 5 is CO oxidation catalyst, 6 is NH 3 Oxidation catalyst, 7 is an air intake pipe, and 8 is an air outlet pipe.

[0045] The NO in the industrial flue gas used in the specific embodiment of the present invention x The concentration is 400mg / Nm 3 , the concentration of CO is 10000mg / Nm 3 .

[0046] NH used in the specific embodiment of the present invention 3 / CO co-oxidation catalyst, with a diameter of 20nm and a specific surface area of ​​320m 2 / g, and the shell structure thickness is controlled at about 4nm.

[0047] Example 1

[0048] use Figure 1 The denitrification system shown in the figure synergistically purifies NH 3 and NH of CO 3 -SCR denitration method, comprising the steps of:

[0049] Industrial flue gas (180℃) flows through the NH 3 -SCR catalyst fixed bed (20000h -1 ), the NH supplied to the ammonia injection grid (ammonia nitrogen ratio is 1.5) 3 NO x Selective catalytic reduction reaction to obtain transition flue gas (180°C); the transition flue gas flows through NH 3 / CO co-oxidation catalyst fixed bed (60000h -1 ), in NH 3 The shell structure of the catalyst causes CO oxidation, while the core structure causes NH3 Oxidation reaction to obtain exhaust flue gas (230°C); the exhaust flue gas passes through a flue gas heat exchanger to transfer heat to NH 3 -SCR intake duct industrial flue gas.

[0050] Among them, NH 3 -The number of layers of the SCR catalyst fixed bed is two; 0.5wt.%V-1wt.%W / TiO 2 Catalyst (other existing NH 3 -SCR catalyst can also achieve the technical purpose of the present invention) as NH 3 -SCR catalyst, TiO 2 The specific surface area is between 150 and 250 m 2 / g; using Ag / WO 3 @CuO x (x = 1 and / or 1 / 2) catalyst as NH 3 / CO co-oxidation catalyst.

[0051] It should be noted that when x is 1 or 1 / 2 or the two forms coexist, the technical effect is basically the same (the same applies to the following x values).

[0052] In this embodiment, 0.5wt.%V-1wt.%W / TiO 2 The preparation method or commercial purchase channel of the catalyst is not limited and does not affect the realization of the technical effect. The following is one of the conventional preparation methods, and the steps are: preparing 0.5wt.%V-1wt.%W / TiO by impregnation 2 Catalyst: Stir in aqueous solution at room temperature for more than 1 hour, dry by rotary evaporation, and calcine in a muffle furnace at 400℃ for 4 hours to obtain 0.5wt.%V-1wt.%W / TiO 2 Catalyst, wherein TiO 2 P25, purchased from Sigma; WO 3 The precursor is ammonium metatungstate; V 2 O 5 The precursor is ammonium metavanadate; the raw material ratio is formulated according to the loading amount.

[0053] In this embodiment, Ag / WO 3 @CuO x (x=1 and / or 1 / 2) catalyst (wherein Ag is 1wt%, WO 3 The preparation steps of 3wt%) are:

[0054] S1, using carbon spheres (CSs) as templates, Ag / WO was impregnated 3 Loaded on the surface of nano-CSs, where the precursor of Ag is silver nitrate, WO 3The precursor of CSs is ammonium metatungstate. CSs was stirred in an aqueous solution of silver nitrate and ammonium metatungstate (the molar ratio of silver nitrate to ammonium metatungstate was 1:16.75) at room temperature for more than 1 hour. After rotary evaporation and drying, it was placed in a muffle furnace and calcined at 500°C for 4 hours to remove the CSs template and obtain Ag / WO 3 ;

[0055] CSs were obtained by a hydrothermal method: sucrose (0.06 mol, 20 g) was dissolved in distilled water (400 mL), stirred evenly, and then the sucrose solution was transferred to a 500 mL sealed polytetrafluoroethylene-lined autoclave (maintained at 200 °C for 5 h). After the reaction was completed, it was naturally cooled to room temperature, and the brown product was collected by centrifugation, washed several times with ethanol and distilled water, and dried at 60 °C for 12 h to obtain CSs;

[0056] S2, CuO by impregnation x (x=1 and / or 1 / 2) loaded on Ag / WO 3 Surface, where CuO x The precursor of (x=1 and / or 1 / 2) is copper nitrate. Ag / WO 3 Stir in a copper nitrate aqueous solution for more than 1 hour, dry by rotary evaporation, and place in a muffle furnace for 4 hours at 400 ° C to obtain Ag / WO 3 @CuO x (x=1 and / or 1 / 2) catalyst.

[0057] In the exhaust gas, NO x Emission concentration ≈40mg / Nm 3 , CO emission concentration ≈ 2500mg / Nm 3 , NH 3 Emission concentration ≈2mg / Nm 3 .

[0058] Example 2

[0059] Compared with Example 1, the only difference is that Ag / WO 3 @CuO x (x=1, 1 / 2) Catalyst adjusted to Pt / WO 3 @CuO x (x=1 and / or 1 / 2) catalyst.

[0060] In this example, Pt / WO 3 @CuO x The preparation steps of (x=1 and / or 1 / 2) are:

[0061] Compared with the Ag / WO in Example 1 3 @CuO xCompared with the preparation method of (x=1 and / or 1 / 2), the only difference is that silver nitrate is replaced by chloroplatinic acid.

[0062] In the exhaust gas, NO x Emission concentration ≈50mg / Nm 3 , CO emission concentration ≈ 2000mg / Nm 3 , NH 3 Emission concentration ≈1.5mg / Nm 3 .

[0063] Example 3

[0064] Compared with Example 1, the only difference is that Ag / WO 3 @CuO x (x = 1 and / or 1 / 2) The catalyst is adjusted to Ag / WO 3 @CoO x (x=1, and / or 3 / 2, and / or 4 / 3) catalyst (copper nitrate is replaced by cobalt nitrate in the preparation method).

[0065] In the exhaust gas, NO x Emission concentration ≈40mg / Nm 3 , CO emission concentration ≈ 3500mg / Nm 3 , NH 3 Emission concentration ≈2mg / Nm 3 .

[0066] Comparative Example 1

[0067] Compared with Example 1, the only difference is that NH 3 The fixed bed of the CO / CO co-oxidation catalyst was replaced with NH 3 -SCR catalyst fixed bed.

[0068] In the exhaust gas, NO x Emission concentration ≈50mg / Nm 3 , CO emission concentration ≈ 10000mg / Nm 3 , NH 3 Emission concentration ≈20mg / Nm 3 .

[0069] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0070] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one 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 present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An NH3 / CO co-oxidation catalyst, wherein the NH3 / CO co-oxidation catalyst is a core-shell catalyst; The core-shell catalyst has an NH3 oxidation catalyst as a core layer structure and a CO oxidation catalyst as a shell layer structure.

2. The NH3 / CO co-oxidation catalyst according to claim 1, characterized in that The core layer structure includes redox sites and acidic sites; and / or The shell structure includes redox sites.

3. The NH3 / CO co-oxidation catalyst according to claim 2, characterized in that The redox sites of the core layer structure include Pt δ+ Ions and / or Ag δ+ ions, acidic sites including W δ+ Ions, Mo δ+ Ions and Nb δ+ At least one of the ions; and / or The redox sites of the shell structure include Cu δ+ Ion, Co δ+ Ion, Mn δ+ Ions and Fe δ+ At least one of the ions.

4. The NH3 / CO co-oxidation catalyst according to claim 1, characterized in that The core-shell catalyst has a diameter of 10 to 30 nm and a specific surface area of ​​200 to 400 m 2 / g, and the shell structure thickness is 2 to 5 nm.

5. An NH3-SCR denitration system for collaborative purification of CO, characterized in that: The NH3-SCR denitration system comprises: a flue gas heat exchanger and a denitration reactor; The denitration reactor comprises an air inlet pipe arranged at the top, an air outlet pipe arranged at the bottom, and arranged in sequence from top to bottom: an ammonia injection grid, an NH3-SCR catalyst fixed bed layer, and a fixed bed layer comprising the NH3 / CO co-oxidation catalyst according to any one of claims 1 to 4; The flue gas heat exchanger is fixedly arranged around the air inlet pipe and the air outlet pipe of the denitration reactor, and is used to collect the heat released by the fixed bed reaction of the NH3 / CO co-oxidation catalyst and transfer it to the air inlet pipe of the denitration reactor to increase the flue gas temperature; The number of layers of the NH3-SCR catalyst fixed bed is two.

6. A NH3-SCR denitration method for collaborative purification of CO, characterized in that: Denitrification is carried out using the denitrification system according to claim 5, the steps comprising: Industrial flue gas flows in from the air intake pipe, mixes with NH3 supplied by the ammonia injection grid, and then flows through the NH3-SCR catalyst fixed bed. Under the action of the NH3-SCR catalyst, NO x Selective catalytic reduction reaction to obtain transition flue gas; The transition flue gas flows through the fixed bed of NH3 / CO co-oxidation catalyst, and CO oxidation reaction and NH3 oxidation reaction occur under the action of NH3 / CO co-oxidation catalyst to obtain exhaust flue gas; The exhaust flue gas is discharged through the exhaust duct, and the heat of the CO oxidation reaction and the NH3 oxidation reaction is collected by the flue gas heat exchanger and used to increase the temperature of the industrial flue gas flowing in from the intake duct.

7. The method according to claim 6, characterized in that The industrial flue gas includes NO x and CO at a temperature of 120 to 200°C; and / or The industrial flue gas flows through the fixed bed of NH3-SCR catalyst at a space velocity of 3000 h -1 ~60000h -1 ; and / or The ammonia injection amount of the ammonia injection grid is greater than the theoretical ammonia nitrogen ratio of the NH3-SCR reaction.

8. The method according to claim 6, characterized in that The transition flue gas includes CO and NH3; and / or The space velocity of the transition flue gas flowing through the fixed bed of NH3 / CO co-oxidation catalyst is 50000h -1 ~150000h -1 .

9. The method according to claim 6, characterized in that The NH3-SCR catalyst is a VW / TiO2 catalyst; and / or The VW / TiO2 catalyst has a V content of 0.3 wt.% to 0.5 wt.%, a W content of 1 wt.% to 5 wt.%, and a specific surface area of ​​TiO2 of 150 to 250 m 2 / g.

10. Use of the NH3 / CO co-oxidation catalyst according to any one of claims 1 to 4, the denitration system according to claim 5, or the method according to any one of claims 6 to 9 in the coordinated purification of NH3 pollutants and CO pollutants in industrial flue gas.

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