Denitration and decarbonization catalyst for sintering machine as well as preparation method and application of denitration and decarbonization catalyst

Abstract

The invention relates to a denitration and decarburization catalyst for a sintering machine as well as a preparation method and application thereof. The denitration and decarburization catalyst comprises a cordierite honeycomb ceramic carrier, two areas are formed on the cordierite honeycomb ceramic carrier, and the two areas are an SCR denitration catalyst coating area and a CO oxidation catalyst coating area respectively; the SCR denitration catalyst coating area is coated with an active component containing V2O5, MoO3, CeO2, WO3 and TiO2, and the active component containing the V2O5, the MoO3, the CeO2, the WO3 and the TiO2; the CO oxidation catalyst coating area is coated with an active component containing a noble metal Pd and / or Pt, CeO2 and a TiO2 and / or Al2O3 carrier. The catalyst disclosed by the invention has the advantages that by optimizing the selection and proportion of the active components and the carrier, the catalyst disclosed by the invention can keep higher denitration and decarbonization activity in a wider temperature range, and compared with a traditional catalyst, the catalyst disclosed by the invention effectively widens an active temperature window and improves the adaptability to different working conditions.

Description

Technical Field

[0001] This invention relates to a denitrification and decarbonization catalyst for sintering machines, its preparation method, and its application, belonging to the field of catalysts. Background Technology

[0002] Sintering machines are key pieces of equipment in the steel production process. During the sintering of ore, they generate a large amount of flue gas. This flue gas has a complex composition, containing not only high concentrations of nitrogen oxides (NOx) but also a certain amount of carbon monoxide (CO). If directly emitted, NOx will exacerbate environmental problems such as acid rain and photochemical smog, while CO will cause energy waste and harm human health. Therefore, it is necessary to treat the sintering machine flue gas for denitrification and decarbonization.

[0003] Currently, while some technologies exist for treating sintering machine exhaust gas, numerous problems remain. Existing denitrification technologies, such as selective catalytic reduction (SCR), can remove NOx to some extent, but often fail to effectively treat CO in the exhaust gas. Some catalysts attempting to simultaneously treat NOx and CO exhibit insufficient activity and poor sulfur and water resistance under the complex operating conditions of sintering machine exhaust gas. For example, the activity of some catalysts drops significantly at low temperatures (120℃-180℃), failing to meet the temperature requirements of the sintering machine exhaust gas. Simultaneously, the high concentration of SO2 and other components in the sintering machine exhaust gas easily leads to catalyst poisoning and deactivation, greatly shortening the catalyst's lifespan. Therefore, there is an urgent practical need to develop a catalyst specifically designed for the characteristics of sintering machine exhaust gas, capable of efficiently and stably removing both NOx and CO simultaneously. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a denitrification and decarburization catalyst for sintering machines, its preparation method, and its application. The technical solution of this invention is as follows: A denitrification and decarburization catalyst for a sintering machine, comprising: Cordierite honeycomb ceramic carrier; two regions are formed on the cordierite honeycomb ceramic carrier, namely an SCR denitrification catalyst coating region and a CO oxidation catalyst coating region; the SCR denitrification catalyst coating region is coated with an active component containing V2O5, MoO3, CeO2, WO3 and TiO2; the CO oxidation catalyst coating region is coated with an active component containing noble metal Pd and / or Pt, CeO2 and TiO2 and / or Al2O3 support.

[0005] In the SCR denitrification catalyst coating, the mass fraction of each component, based on the total mass of the coating, is as follows: V2O5: 1%-5%, MoO3: 3%-8%, CeO2: 2%-6%, WO3: 1%-4%, with the balance being TiO2.

[0006] In the CO oxidation catalyst coating, the mass fraction of each component, based on the total mass of the coating, is as follows: precious metals Pd and / or Pt: 0.1%-2%, CeO2: 5%-15%, and the balance is TiO2 and / or Al2O3.

[0007] The pore size of the cordierite honeycomb ceramic carrier is 1-10 mm.

[0008] A method for preparing a catalyst includes the following steps: S1. Cordierite matrix pretreatment: cleaning, drying and calcination; S2. Preparation of SCR denitrification coating slurry: TiO2, V2O5 precursor, MoO3 precursor, CeO2 precursor, WO3 precursor, binder and dispersant are mixed and ground in solvent; S3. Preparation of CO oxidation coating slurry: TiO2 and / or Al2O3, noble metal precursor, CeO2 precursor, binder and dispersant are mixed and ground in solvent; S4. The pretreated cordierite matrix is ​​divided into two parts, which are then immersed in SCR denitrification coating slurry and CO oxidation coating slurry respectively, and then purged and dried. S5. Calcination treatment: First, heat the catalyst in a muffle furnace to 300-400℃ at a heating rate of 1-2℃ / min and hold for 1-2 hours. Then, heat the catalyst to 500-600℃ at a heating rate of 2-3℃ / min and calcine for 3-5 hours to obtain the final denitrification and decarbonization catalyst for sintering machines.

[0009] In step S1, the cleaning is performed using deionized water or ethanol with ultrasonic cleaning at a power of 200-500W and a time of 10-30 minutes to remove oil and dust from the surface; the drying temperature is 100-150℃ and the drying time is 2-4 hours to remove residual moisture after cleaning; the calcination temperature is 500-700℃ and the calcination time is 1-3 hours to remove organic impurities from the surface and to roughen the substrate surface.

[0010] In step S2, the V2O5 precursor is ammonium metavanadate, the MoO3 precursor is ammonium molybdate, the CeO2 precursor is cerium nitrate or cerium sulfate, and the WO3 precursor is ammonium metatungstate; the solvent is deionized water, ethanol, or ethylene glycol, and the amount of solvent used is such that the solid content of the slurry is 30%-60%; the mass of the binder is 2%-8% of the total mass of the slurry; and the mass of the dispersant is 0.5%-3% of the total mass of the slurry.

[0011] In step S2, the portion immersed in the SCR denitrification coating slurry is immersed for 10-30 minutes, then removed, and excess coating liquid is blown off the surface and pores with compressed air, and dried in an oven at 80-100℃ for 2-4 hours; the portion immersed in the CO oxidation coating slurry is immersed for 10-30 minutes, then removed, and excess coating liquid is blown off with compressed air, and dried in an oven at 80-100℃ for 2-4 hours.

[0012] In the CO oxidation coating slurry, the noble metal precursor is palladium nitrate, palladium chloride, chloroplatinic acid or platinum nitrate, and the CeO2 precursor is cerium nitrate or cerium sulfate; the binder is silica sol, alumina sol or sodium carboxymethyl cellulose, and the dispersant is citric acid, polyethylene glycol or sodium dodecylbenzene sulfonate.

[0013] An application of the catalyst described above in the treatment of flue gas from a sintering machine, wherein the catalyst simultaneously achieves NOx removal and CO oxidation within a temperature range of 250-450°C.

[0014] The advantages of this invention are: (1) By optimizing the selection and ratio of active components and supports, the catalyst of the present invention can maintain high denitrification and decarbonization activity in a wide temperature range (250℃-450℃). Compared with traditional catalysts, it effectively broadens the active temperature window and improves the adaptability to different working conditions.

[0015] (2) The same carrier is coated with a partitioned coating method of “half coated with SCR denitrification catalyst and half coated with CO oxidation catalyst”. Through functional partition integration, the multi-pollutant synergistic treatment is achieved. There is no need to configure separate carriers for SCR denitrification and CO oxidation. A single cordierite carrier can simultaneously deal with two pollutants (nitrogen oxides and carbon monoxide). It is especially suitable for scenarios with limited flue gas treatment space, which can reduce equipment volume and installation cost.

[0016] (3) The combination of tungsten with TiO2 can improve the stability of TiO2 and inhibit the transformation of the support crystal form from anatase to rutile; tungsten itself has good thermal stability, which can reduce the sintering phenomenon of the catalyst.

[0017] (4) The addition of molybdenum oxide, cerium oxide and other components enhances the catalyst’s resistance to poisons such as alkali metals and arsenic, significantly improves the catalyst’s anti-poisoning performance and extends the catalyst’s service life.

[0018] (5) Using titanium dioxide as a carrier effectively inhibits the oxidation of SO2, reduces the generation of SO3, and reduces the generation of byproducts such as ammonium bisulfate, thus ensuring the stable operation of the system.

[0019] (6) Low-temperature and high-efficiency CO oxidation: The synergistic effect of precious metals palladium or platinum or palladium and platinum and cerium oxide enables CO to be oxidized efficiently at lower temperatures (200℃-300℃), reducing energy consumption and making it suitable for more temperature-sensitive process scenarios.

[0020] (7) Titanium dioxide support has good chemical stability and certain catalytic activity, which can improve the low-temperature CO oxidation activity and enhance the anti-sulfur poisoning performance. Alumina support has high specific surface area and pore structure, excellent thermal stability and good mechanical strength, which can provide good support and dispersion for active components. The mixed support of titanium dioxide and alumina can balance low-temperature activity and high-temperature stability, and optimize the anti-poisoning performance.

[0021] (8) The synergistic effect between the cordierite matrix and the active components enables the catalyst to maintain stable activity during long-term operation, reducing the frequency of catalyst replacement and lowering operating costs. Detailed Implementation

[0022] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer as a result. However, these embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention. Those skilled in the art should understand that modifications or substitutions can be made to the details and form of the technical solutions of the present invention without departing from the spirit and scope of the present invention, but all such modifications and substitutions fall within the protection scope of the present invention.

[0023] Example 1: 1. Cordierite matrix pretreatment: Select honeycomb cordierite matrix (pore size 5mm), ultrasonically clean it with deionized water at 300W power for 20min, then dry it at 120℃ for 3h, and finally calcine it at 600℃ for 2h, and cool it for later use.

[0024] 2. Preparation of SCR denitrification coating slurry: 86g of titanium dioxide powder, 4.8g of ammonium metavanadate, 7.8g of ammonium molybdate, 10.2g of cerium nitrate, and 3.1g of ammonium metatungstate were dispersed in 90g of deionized water. 5g of silica sol (binder, accounting for 5% of the total slurry mass) and 2g of citric acid (dispersant, accounting for 2% of the total slurry mass) were added. The mixture was first stirred at 700r / min for 1.5h, and then transferred to a planetary ball mill for grinding for 2.5h. The particle size of the slurry was controlled to be 2-3μm to obtain the SCR denitrification coating slurry.

[0025] 3. Preparation of CO oxidation coating slurry: 89.2g of titanium dioxide powder, 2g of palladium nitrate and 10g of cerium nitrate were dispersed in 80g of ethanol, 4g of aluminum sol (binder) and 1g of polyethylene glycol (dispersant) were added, and the mixture was stirred at 600r / min for 1h, and then ground in a ball mill for 2h. The particle size of the slurry was controlled to be 2-3μm to obtain CO oxidation coating slurry.

[0026] 4. Regional Coating: Divide the pretreated cordierite matrix into two parts, labeled A and B. Immerse part A in the coating solution for the SCR denitrification section for 20 minutes, shaking the matrix every 5 minutes to ensure wetting of the pores. After removal, blow off excess coating solution from the surface and pores with 0.3 MPa compressed air, and dry in an oven at 90°C for 3 hours. Immerse part B in the coating solution for the CO oxidation section for 20 minutes, shaking the matrix every 5 minutes to ensure wetting of the pores. After removal, blow off excess coating solution with 0.3 MPa compressed air, and dry in an oven at 90°C for 3 hours. 5. Calcination treatment: The coated and dried cordierite matrix is ​​first heated to 350°C in a muffle furnace at a heating rate of 1.5°C / min and held at that temperature for 1.5 hours. Then, it is heated to 550°C at a heating rate of 2.5°C / min and calcined for 4 hours to obtain the final denitrification and decarbonization catalyst for sintering machines.

[0027] Example 2: 1. Cordierite matrix pretreatment: Select honeycomb cordierite matrix (pore size 8mm), ultrasonically clean it with ethanol at 400W power for 15min, then dry it at 140℃ for 2.5h, and finally calcine it at 600℃ for 1.53h, and cool it for later use.

[0028] 2. Preparation of SCR denitrification coating slurry: 86g of titanium dioxide powder, 2.4g of ammonium metavanadate, 11g of ammonium molybdate, 5.1g of cerium nitrate, and 5.4g of ammonium metatungstate were dispersed in 100g of ethylene glycol. 6g of sodium carboxymethyl cellulose (binder) and 2g of citric acid (dispersant) were added. The mixture was stirred at 700r / min for 2h, and then transferred to a planetary ball mill for grinding for 3h. The particle size of the slurry was controlled to be 3-4μm to obtain the SCR denitrification coating slurry.

[0029] 3. Preparation of CO oxidation coating slurry: 87.7g alumina, 1.2g chloroplatinic acid, and 30.6g cerium nitrate were dispersed in 80g deionized water, and 3g silica sol (binder) and 1g polyethylene glycol (dispersant) were added. The mixture was stirred at 700r / min for 1.5h, and then transferred to a planetary ball mill for 2.5h. The particle size of the slurry was controlled to be 3-4μm to obtain the CO oxidation coating slurry.

[0030] 4. Regional Coating: The pretreated cordierite matrix is ​​divided into two parts, labeled A and B. Part A is immersed in the coating solution for the SCR denitrification section for 25 minutes, then removed and the excess coating solution in the surface and pores is blown away with 0.25 MPa compressed air. It is then dried in an oven at 85°C for 3.5 hours. Part B is immersed in the coating solution for the CO oxidation section for 25 minutes, then the excess coating solution is blown away with 0.25 MPa compressed air. It is then dried in an oven at 85°C for 3.5 hours. 5. Calcination treatment: The cordierite matrix after coating and drying is first heated to 380℃ in a muffle furnace at a heating rate of 1.2℃ / min and held for 1.2 hours. Then, it is heated to 580℃ at a heating rate of 2.8℃ / min and calcined for 3.5 hours to obtain the final denitrification and decarbonization catalyst for sintering machines.

[0031] Example 3: 1. Cordierite matrix pretreatment: Select a honeycomb cordierite matrix (pore size 2mm), ultrasonically clean it with deionized water at 25300W power for 28min, then dry it at 110℃ for 3.5h, and finally calcine it at 5500℃ for 2.5h, and cool it for later use.

[0032] 2. Preparation of SCR denitrification coating slurry: Disperse 85g titanium dioxide powder, 7.2g ammonium metavanadate, 5.5g ammonium molybdate, 14.1g cerium nitrate, and 2.3g ammonium metatungstate in 85g deionized water, add 4g silica sol (binder) and 2.5g polyethylene glycol (dispersant), stir at 700r / min for 1.2h, then transfer to a planetary ball mill for 2h to grind, controlling the slurry particle size to 1-2μm to obtain SCR denitrification coating slurry.

[0033] 3. Preparation of CO oxide coating slurry: 92.2g of titanium dioxide powder, 4.5g of palladium nitrate, and 15.3g of cerium sulfide were dispersed in 70g of ethanol. 7g of aluminum sol (binder) and 0.6g of citric acid (dispersant) were added. The mixture was stirred at 700r / min for 1.8h, and then transferred to a planetary ball mill for 2.2h. The particle size of the slurry was controlled to be 1-2μm to obtain the CO oxide coating slurry.

[0034] 4. Divide the pretreated cordierite matrix into two parts, labeled A and B. Immerse part A in the coating solution of the SCR denitrification section for 15 minutes, then remove it and blow off excess coating solution from the surface and pores with 0.35 MPa compressed air. Dry it in an oven at 95°C for 2.5 hours. Immerse part B in the coating solution of the CO oxidation section for 15 minutes, then blow off excess coating solution with 0.35 MPa compressed air. Dry it in an oven at 95°C for 2.5 hours. 5. Calcination treatment: The coated and dried cordierite matrix is ​​first heated to 320°C in a muffle furnace at a heating rate of 1.8°C / min and held at that temperature for 1.8 hours. Then, it is heated to 520°C at a heating rate of 2.2°C / min and calcined for 4.5 hours to obtain the final denitrification and decarbonization catalyst for sintering machines.

[0035] Performance test data: The equipment used for the test was: a catalyst performance evaluation reaction device; the designed flue gas conditions are shown in Table 1. Table 1 shows the design flue gas conditions: ; Table 2. Test results at 350℃: ; Table 3. Test results at different temperatures: ; At the optimal temperature of 350℃, all three embodiments achieved a denitrification efficiency exceeding 92% and a CO conversion rate exceeding 95%, meeting the requirements for industrial flue gas purification. At low temperatures (220℃), the denitrification efficiency was ≥78% and the CO conversion rate ≥82%. Performance remained stable at high temperatures (420℃), demonstrating wide temperature adaptability and suitability for various operating conditions. After 1200 hours of continuous operation, the degradation rate was less than 4%, proving the catalyst's excellent long-term stability and a service life of up to 3 years.

[0036] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A denitrification and decarburization catalyst for a sintering machine, characterized in that, include: Cordierite honeycomb ceramic carrier; Two regions are formed on the cordierite honeycomb ceramic carrier: an SCR denitrification catalyst coating region and a CO oxidation catalyst coating region. The SCR denitrification catalyst coating area is coated with an active component containing V2O5, MoO3, CeO2, WO3 and TiO2; The CO oxidation catalyst coating region is coated with an active component comprising noble metals Pd and / or Pt, CeO2, and TiO2 and / or Al2O3 supports.

2. The denitrification and decarburization catalyst for sintering machines according to claim 1, characterized in that, In the SCR denitrification catalyst coating, the mass fraction of each component, based on the total mass of the coating, is as follows: V2O5: 1%-5%, MoO3: 3%-8%, CeO2: 2%-6%, WO3: 1%-4%, balance TiO2.

3. The denitrification and decarburization catalyst for sintering machines according to claim 1, characterized in that, In the CO oxidation catalyst coating, the mass fraction of each component, based on the total mass of the coating, is as follows: Precious metals Pd and / or Pt: 0.1%-2%, CeO2: 5%-15%, balance TiO2 and / or Al2O3.

4. The denitrification and decarburization catalyst for sintering machines according to claim 1, characterized in that, The pore size of the cordierite honeycomb ceramic carrier is 1-10 mm.

5. A method for preparing the catalyst according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Cordierite matrix pretreatment: cleaning, drying and calcination; S2. Preparation of SCR denitrification coating slurry: TiO2, V2O5 precursor, MoO3 precursor, CeO2 precursor, WO3 precursor, binder and dispersant are mixed and ground in solvent; S3. Preparation of CO oxidation coating slurry: TiO2 and / or Al2O3, noble metal precursor, CeO2 precursor, binder and dispersant are mixed and ground in solvent; S4. The pretreated cordierite matrix is ​​divided into two parts, which are then immersed in SCR denitrification coating slurry and CO oxidation coating slurry respectively, and then purged and dried. S5. Calcination treatment: First, heat the catalyst in a muffle furnace to 300-400℃ at a heating rate of 1-2℃ / min and hold for 1-2 hours. Then, heat the catalyst to 500-600℃ at a heating rate of 2-3℃ / min and calcine for 3-5 hours to obtain the final denitrification and decarbonization catalyst for sintering machines.

6. The preparation method according to claim 5, characterized in that, In step S1, the cleaning is performed using deionized water or ethanol with ultrasonic cleaning at a power of 200-500W and a time of 10-30 minutes to remove oil and dust from the surface; the drying temperature is 100-150℃ and the drying time is 2-4 hours to remove residual moisture after cleaning; the calcination temperature is 500-700℃ and the calcination time is 1-3 hours to remove organic impurities from the surface and to roughen the substrate surface.

7. The preparation method according to claim 5, characterized in that, In step S2, the V2O5 precursor is ammonium metavanadate, the MoO3 precursor is ammonium molybdate, the CeO2 precursor is cerium nitrate or cerium sulfate, and the WO3 precursor is ammonium metatungstate; the solvent is deionized water, ethanol, or ethylene glycol, and the amount of solvent used is such that the solid content of the slurry is 30%-60%; the mass of the binder is 2%-8% of the total mass of the slurry; and the mass of the dispersant is 0.5%-3% of the total mass of the slurry.

8. The preparation method according to claim 5, characterized in that, In step S2, the part immersed in the SCR denitrification coating slurry is immersed for 10-30 minutes, then removed, and excess coating liquid on the surface and in the pores is blown away with compressed air, and then dried in an oven at 80-100℃ for 2-4 hours. For the portion immersed in the CO oxidation coating slurry, immerse for 10-30 minutes, remove and blow off excess coating liquid with compressed air, then dry in an oven at 80-100℃ for 2-4 hours.

9. The preparation method according to claim 6, characterized in that, In the CO oxidation coating slurry, the noble metal precursor is palladium nitrate, palladium chloride, chloroplatinic acid or platinum nitrate, and the CeO2 precursor is cerium nitrate or cerium sulfate; the binder is silica sol, alumina sol or sodium carboxymethyl cellulose, and the dispersant is citric acid, polyethylene glycol or sodium dodecylbenzene sulfonate.

10. The application of a catalyst as described in any one of claims 1-4 in the treatment of sintering machine flue gas, characterized in that, The catalyst simultaneously achieves NOx removal and CO oxidation within a temperature range of 250-450℃.