A catalyst for denitration of low-temperature flue gas of waste incineration and a preparation method thereof

Abstract

This invention relates to a catalyst for low-temperature flue gas denitrification in waste incineration and its preparation method, belonging to the field of catalyst preparation technology. The catalyst uses honeycomb cordierite as a matrix, and through an impregnation coating method, Fe2O3-CaO-ZSM-5 composite support, active component V2O5, and active additive MoO3 are sequentially coated on the matrix surface. The catalyst prepared by this invention exhibits excellent low-temperature denitrification activity and resistance to sulfur poisoning. Under sulfur-containing flue gas conditions at 150℃, NO... x The removal rate consistently remains above 92%. The addition of hydrophobic components to the catalyst gives it extremely strong resistance to water and alkali metal poisoning, meeting the denitrification requirements of flue gas generated from waste incineration.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation technology, specifically relating to a catalyst for low-temperature flue gas denitrification in waste incineration and its preparation method. Background Technology

[0002] Waste has a complex composition, and the flue gas produced during incineration contains large amounts of pollutants such as NOx, SOx, HCl, and dioxins. If these are discharged indiscriminately without treatment, they will inevitably cause serious environmental pollution problems. Incineration is currently one of the main methods of waste treatment. The flue gas produced by waste incineration units typically passes through a deacidification tower, dust removal equipment, and an SCR denitrification reactor for pollutant removal. After passing through the deacidification tower and dust removal equipment, most of the SOx, HCl, and dioxins can be effectively removed. However, a significant amount of SOx, water vapor, and alkali metal salts still enter the denitrification reaction zone. Simultaneously, the temperature of the flue gas after deacidification and dust removal will be reduced to 150℃, far below the applicable temperature of low-temperature denitrification catalysts on the market. Therefore, SCR denitrification catalysts with lower activation temperatures, as well as resistance to sulfur, water, and alkali metal poisoning, will become another demand in the denitrification market. Summary of the Invention

[0003] The present invention addresses the problem that the flue gas from waste incineration contains a high water vapor content and has a temperature below 150°C, making it unsuitable for treatment with existing denitrification catalysts. It provides a catalyst for low-temperature flue gas denitrification from waste incineration and its preparation method.

[0004] The present invention adopts the following technical solution: a catalyst for low-temperature flue gas denitrification in waste incineration, wherein the catalyst uses cordierite honeycomb as a substrate, and Fe2O3-CaO-ZSM-5 is coated on the substrate as a carrier. The carrier is coated with active ingredient V2O5 and active auxiliary agent MoO3. In the carrier Fe2O3-CaO-ZSM-5, the proportion of Fe2O3 is 8% to 13%, the proportion of CaO is 5% to 10%, the silicon-aluminum ratio of ZSM-5 is 65 to 85, the amount of carrier coating is 10% to 15% of the mass of the honeycomb substrate, the mass of V2O5 and MoO3 is 12% to 16% of the mass of the carrier, and the mass ratio of V2O5 to MoO3 is 1:3 to 1.3:3.

[0005] Preferably, the cordierite honeycomb matrix has dimensions of 120mm×120mm×150mm, an inner wall thickness of 0.75mm, an outer wall thickness of 0.9mm~1.1mm, and 30×30 holes.

[0006] The preparation method of the catalyst for low-temperature flue gas denitrification in waste incineration includes the following steps:

[0007] Step 1. Preparation of composite support

[0008] According to the design ratio, ferric nitrate nonahydrate, calcium oxide and ZSM-5 were weighed out. Ferric nitrate was loaded onto calcium oxide and ZSM-5 by equal volume impregnation method. The mixture was dried at 80℃ and calcined at 450℃ to obtain Fe2O3-CaO-ZSM-5 composite carrier.

[0009] Step 2. Carrier Coating

[0010] Add appropriate amounts of hydroxypropyl methylcellulose, polyethylene oxide and water to the composite carrier prepared in step 1, stir at high speed to obtain a viscous liquid, then completely immerse the cordierite honeycomb matrix in the viscous liquid, leave it for 5s to 10s and then take it out and place it in the room temperature environment to air dry naturally. Repeat this process until the loading meets the requirements, and calcine at 550℃ to complete the coating of the carrier.

[0011] Step 3. Application of active ingredients

[0012] Ammonium metavanadate and ammonium heptamolybdate were calcined at 500℃ to obtain V2O5 and MoO3 powders. Then, sodium methylsiloxane, hydroxypropyl methylcellulose, polyethylene oxide and water were added to the powders. After high-speed stirring, a viscous liquid was obtained. The active ingredients were further loaded onto the honeycomb structure after the support was loaded in the same way as in step 2. After drying at 80℃, the catalyst preparation was completed.

[0013] Preferably, in step 2, the mass ratio of hydroxypropyl methylcellulose to polyethylene oxide is 4:1 to 6:1.

[0014] Preferably, the viscosity of the viscous liquid in step 2 is 170 mm. 2 / s~200mm 2 / s.

[0015] Preferably, in step 3, the mass of sodium methylsilanolate is 20% to 30% of the total mass of V2O5 and MoO3 powders.

[0016] Preferably, in step 3, the mass ratio of hydroxypropyl methylcellulose to polyethylene oxide is 2:1 to 3.5:1.

[0017] Preferably, the viscosity of the viscous liquid in step 3 is 130 mm. 2 / s~160mm 2 / s.

[0018] The advantages of this invention are as follows:

[0019] (1) Excellent denitrification activity at low temperatures: Using molecular sieves as a support significantly increases the specific surface area of ​​the catalyst, providing more reaction sites for the denitrification reaction and enhancing the catalyst's denitrification activity; Fe2O3 forms lattice defects in the support, thereby forming impurity energy levels, significantly improving electron mobility and promoting the SCR denitrification reaction. Combined with the high content of V2O5 and MoO3 in the catalyst, the catalyst exhibits excellent denitrification activity at low temperatures.

[0020] (2) Strong comprehensive resistance to poisoning: In this invention, sodium methylsilanolate is added simultaneously when coating the active component of the catalyst, and the catalyst is prepared by low-temperature drying, so that sodium methylsilanolate is retained in the catalyst. During the use of the catalyst, sodium methylsilanolate can react with water, carbon dioxide, and calcium oxide to form a network of hydrophobic polymeric compounds, which isolates the poisoning effect of water vapor on the catalyst; at the same time, the addition of sodium methylsilanolate can form a uniform and stable Na+ layer on the catalyst surface, which repels alkali metal ions in flue gas and hinders the adsorption of alkali metals, thus playing a role in resisting alkali metal poisoning; in addition, molecular sieves are used as catalyst carriers to provide the catalyst with a richer pore structure, which greatly increases the adsorption capacity of ammonium sulfate and keeps the catalyst with high denitrification activity.

[0021] (3) Simple production process: Conventional honeycomb catalyst production process is often quite complex and the production cycle generally takes more than 10 days. The preparation process provided by this invention does not require complex production equipment. Coating and calcination can significantly shorten the catalyst production cycle and greatly reduce the catalyst production cost, making the catalyst highly competitive in the market. Attached Figure Description

[0022] Figure 1 The graph shows the denitrification activity test results of fresh catalyst and catalyst loaded with KCl in the embodiments and comparative examples of the present invention. Detailed Implementation

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0024] Example 1:

[0025] Step 1. Preparation of composite support

[0026] A Fe2O3-CaO-ZSM-5 composite carrier with a Fe2O3 content of 8% and a CaO content of 10% was prepared. Ferric nitrate nonahydrate, calcium oxide and ZSM-5 were weighed in proportion. Ferric nitrate was loaded onto calcium oxide and ZSM-5 by equal volume impregnation method. Then, the composite carrier was obtained by drying at 70℃ and calcining at 400℃.

[0027] Step 2. Carrier Coating

[0028] Take 750g of the composite carrier prepared in step 1, and slowly add hydroxypropyl methylcellulose, polyethylene oxide, and deionized water in batches. The mass ratio of hydroxypropyl methylcellulose to polyethylene oxide added each time is 4:1, resulting in a viscosity of 197 mm. 2 / s viscous liquid.

[0029] Take a cordierite honeycomb substrate with dimensions of 120mm×120mm×150mm, immerse the substrate completely in the viscous liquid, remove it after 5 seconds, and place it in the air to air dry naturally at room temperature. After multiple coatings, calculate that the carrier load mass is 10.07% of the substrate mass. Finally, calcine at 500℃ to complete the coating of the carrier.

[0030] Step 3. Application of active ingredients

[0031] Ammonium metavanadate and ammonium heptamolybdate were calcined at 450℃ to prepare the required V2O5 and MoO3 powders. V2O5 and MoO3 powders were weighed at a vanadium-molybdenum mass ratio of 1:3. At the same time, sodium methylsilanolate, which accounts for 20% of the total mass of vanadium and molybdenum, was weighed and the three were initially mixed.

[0032] Hydroxypropyl methylcellulose, polyethylene oxide, and deionized water were slowly added to the mixed powder in batches, with the mass ratio of hydroxypropyl methylcellulose to polyethylene oxide being 2:1 each time, resulting in a viscosity of 131 mm. 2 / s viscous liquid.

[0033] Finally, the active ingredients were further loaded onto the honeycomb structure after the support was loaded in the same manner as in step 2. After multiple coatings, the loading mass of the active ingredients was calculated to be 12.13% of the support mass. Finally, the catalyst was dried at 75°C to complete the preparation of the catalyst.

[0034] Example 2:

[0035] Step 1. Preparation of composite support

[0036] A Fe2O3-CaO-ZSM-5 composite carrier with a Fe2O3 content of 13% and a CaO content of 5% was prepared. Ferric nitrate nonahydrate, calcium oxide and ZSM-5 were weighed in proportion. Ferric nitrate was loaded onto calcium oxide and ZSM-5 by equal volume impregnation method. Then, the composite carrier was obtained by drying at 75℃ and calcining at 450℃.

[0037] Step 2. Carrier Coating

[0038] Take 800g of the composite carrier prepared in step 1, and slowly add hydroxypropyl methylcellulose, polyethylene oxide, and deionized water in batches. The mass ratio of hydroxypropyl methylcellulose to polyethylene oxide added each time is 6:1, resulting in a viscosity of 173 mm. 2 / s viscous liquid.

[0039] Take a cordierite honeycomb substrate with dimensions of 120mm×120mm×150mm, immerse the substrate completely in the viscous liquid, leave it for 8 seconds, remove it, and place it in the air to air dry naturally at room temperature. Through multiple coatings, the carrier load mass is calculated to be 14.95% of the substrate mass. Finally, the carrier coating is completed by calcination at 520℃.

[0040] Step 3. Application of active ingredients

[0041] Ammonium metavanadate and ammonium heptamolybdate were calcined at 480℃ to prepare the required V2O5 and MoO3 powders. V2O5 and MoO3 powders were weighed at a vanadium-molybdenum mass ratio of 1.3:3. Sodium methylsilanol, which accounts for 30% of the total mass of vanadium and molybdenum, was weighed at the same time. The three were then initially mixed.

[0042] Hydroxypropyl methylcellulose, polyethylene oxide, and deionized water were slowly added to the mixed powder in batches, with the mass ratio of hydroxypropyl methylcellulose to polyethylene oxide being 3.5:1 each time, resulting in a viscosity of 157 mm. 2 / s viscous liquid.

[0043] Finally, the active ingredients were further loaded onto the honeycomb structure after the support was loaded in the same manner as in step 2. After multiple coatings, the loading mass of the active ingredients was calculated to be 13.85% of the support mass. Finally, the catalyst was dried at 80°C to complete the preparation of the catalyst.

[0044] Example 3:

[0045] Step 1. Preparation of composite support

[0046] A Fe2O3-CaO-ZSM-5 composite carrier with Fe2O3 content of 11% and CaO content of 6% was prepared. Ferric nitrate nonahydrate, calcium oxide and ZSM-5 were weighed in proportion. Ferric nitrate was loaded onto calcium oxide and ZSM-5 by equal volume impregnation method. Then, the composite carrier was obtained by drying at 80℃ and calcining at 400℃.

[0047] Step 2. Carrier Coating

[0048] Take 1 kg of the composite carrier prepared in step 1, and slowly add hydroxypropyl methylcellulose, polyethylene oxide, and deionized water in batches. The mass ratio of hydroxypropyl methylcellulose to polyethylene oxide added each time is 5:1, resulting in a viscosity of 182 mm. 2 / s viscous liquid.

[0049] Take a cordierite honeycomb substrate with dimensions of 120mm×120mm×150mm, immerse the substrate completely in the viscous liquid, leave it for 10 seconds, remove it, and place it in the air to air dry naturally at room temperature. After multiple coatings, the carrier load mass is calculated to be 11.37% of the substrate mass. Finally, the carrier coating is completed by calcination at 550℃.

[0050] Step 3. Application of active ingredients

[0051] To prepare the required V2O5 and MoO3 powders, calcine ammonium metavanadate and ammonium heptamolybdate at 500℃. Weigh V2O5 and MoO3 powders at a vanadium-molybdenum mass ratio of 1.1:3, and simultaneously weigh sodium methylsilanol, which accounts for 22% of the total mass of vanadium and molybdenum. Mix the three powders in a preliminary manner.

[0052] Hydroxypropyl methylcellulose, polyethylene oxide, and deionized water were slowly added to the mixed powder in batches, with the mass ratio of hydroxypropyl methylcellulose to polyethylene oxide being 3:1 each time, resulting in a viscosity of 151 mm. 2 / s viscous liquid.

[0053] Finally, the active ingredients were further loaded onto the honeycomb structure after the support was loaded in the same manner as in step 2. After multiple coatings, the loading mass of the active ingredients was calculated to be 13.31% of the support mass. Finally, the catalyst was dried at 80°C to complete the preparation of the catalyst.

[0054] Example 4:

[0055] Step 1. Preparation of composite support

[0056] A Fe2O3-CaO-ZSM-5 composite carrier with a Fe2O3 content of 9.5% and a CaO content of 7.5% was prepared. Ferric nitrate nonahydrate, calcium oxide and ZSM-5 were weighed in proportion. Ferric nitrate was loaded onto calcium oxide and ZSM-5 by equal volume impregnation method. Then, the composite carrier was obtained by drying at 80℃ and calcining at 450℃.

[0057] Step 2. Carrier Coating

[0058] Take 900g of the composite carrier prepared in step 1, and slowly add hydroxypropyl methylcellulose, polyethylene oxide, and deionized water in batches. The mass ratio of hydroxypropyl methylcellulose to polyethylene oxide added each time is 4.5:1, resulting in a viscosity of 179 mm. 2 / s viscous liquid.

[0059] Take a cordierite honeycomb substrate with dimensions of 120mm×120mm×150mm, immerse the substrate completely in the viscous liquid, leave it for 5s to 10s, then remove it and let it air dry naturally at room temperature. After multiple coatings, the carrier load mass is calculated to be 13.27% of the substrate mass. Finally, the carrier coating is completed by calcination at 550℃.

[0060] Step 3. Application of active ingredients

[0061] To prepare the required V2O5 and MoO3 powders, calcine ammonium metavanadate and ammonium heptamolybdate at 500℃. Weigh V2O5 and MoO3 powders at a vanadium-molybdenum mass ratio of 1.2:3, and simultaneously weigh sodium methylsilanol, which accounts for 25% of the total mass of vanadium and molybdenum. Mix the three powders in a preliminary manner.

[0062] Hydroxypropyl methylcellulose, polyethylene oxide, and deionized water were slowly added to the mixed powder in batches, with the mass ratio of hydroxypropyl methylcellulose to polyethylene oxide being 2.5:1 each time, resulting in a viscosity of 139 mm. 2 / s viscous liquid.

[0063] Finally, the active ingredients were further loaded onto the honeycomb structure after the support was loaded in the same manner as in step 2. After multiple coatings, the loading mass of the active ingredients was calculated to be 15.27% of the support mass. Finally, the catalyst was dried at 80°C to complete the preparation of the catalyst.

[0064] Comparative example:

[0065] A commercially available low-temperature SCR denitration catalyst was purchased as a comparative example and compared with the honeycomb catalysts in Examples 1 to 4 in terms of low-temperature activity and resistance to poisoning. For the comparison of resistance to alkali metal poisoning, 0.75 wt% KCl was loaded onto fresh catalyst using an impregnation method, and then the denitration activity of the catalysts was compared. The activity test conditions were: NO... x Concentration of 280 mg / m 3 SO2 concentration is 1000 mg / m³ 3 The O2 concentration was 5%, the H2O concentration was 12%, and the space velocity was 10,000 h⁻¹. -1 The temperature is 150℃.

[0066] Depend on Figure 1 It can be seen that under the low-temperature flue gas conditions of 150℃ containing sulfur and water, the denitrification activity of the catalysts in Examples 1 to 4 is all above 90%, significantly higher than that of the comparative catalyst; while for the catalyst simulating alkali metal poisoning, the NO of the comparative catalyst is... x The removal rate decreased to approximately 20%, while the catalyst activity in Examples 1 to 4 only showed a slight decrease. Therefore, the low-temperature denitrification catalyst developed in this invention can meet the requirements for low-temperature flue gas denitrification at 150°C containing sulfur, water, and alkali metal components, and is fully applicable to flue gas denitrification in the waste incineration industry, exhibiting significant advantages compared to commercially available low-temperature denitrification catalysts.

Claims

1. A catalyst for low-temperature flue gas denitrification in waste incineration, characterized in that: The catalyst uses cordierite honeycomb as a matrix, coated with Fe2O3-CaO-ZSM-5 as a support, and then coated with the active ingredient V2O5 and the active additive MoO2. 3， In the Fe2O3-CaO-ZSM-5 carrier, Fe2O3 accounts for 8% to 13%, CaO accounts for 5% to 10%, the silicon-aluminum ratio in ZSM-5 is 65 to 85, the carrier coating amount is 10% to 15% of the mass of the honeycomb substrate, the mass of V2O5 and MoO3 is 12% to 16% of the mass of the carrier, and the mass ratio of V2O5 to MoO3 is 1:3 to 1.3:

3.

2. The catalyst for low-temperature flue gas denitrification in waste incineration according to claim 1, characterized in that: The cordierite honeycomb matrix has dimensions of 120 mm × 120 mm × 150 mm, an inner wall thickness of 0.75 mm, an outer wall thickness of 0.9 mm to 1.1 mm, and 30 × 30 holes.

3. The method for preparing the catalyst for low-temperature flue gas denitrification in waste incineration as described in claim 1, characterized in that: Includes the following steps: Step 1. Preparation of composite support According to the design ratio, ferric nitrate nonahydrate, calcium oxide and ZSM-5 were weighed out. Ferric nitrate was loaded onto calcium oxide and ZSM-5 by equal volume impregnation method. The mixture was dried at 70-80℃ and calcined at 400-450℃ to obtain Fe2O3-CaO-ZSM-5 composite carrier. Step 2. Carrier Coating Add appropriate amounts of hydroxypropyl methylcellulose, polyethylene oxide and water to the composite carrier prepared in step 1, stir at high speed to obtain a viscous liquid, then completely immerse the cordierite honeycomb matrix in the viscous liquid, leave it for 5 s to 10 s and then take it out and place it in the room temperature environment to air dry naturally. Repeat this process until the loading meets the requirements, and calcine at 500 to 550℃ to complete the coating of the carrier. Step 3. Application of active ingredients Ammonium metavanadate and ammonium heptamolybdate were calcined at 450-500℃ to obtain V2O5 and MoO3 powders. Then, sodium methylsiloxane, hydroxypropyl methylcellulose, polyethylene oxide and water were added to the powders. The mass ratio of hydroxypropyl methylcellulose to polyethylene oxide was 2:1 to 3.5:

1. After high-speed stirring, a viscous liquid was obtained. The active ingredients were further loaded onto the honeycomb structure after the support was loaded in the same way as in step 2. After drying at 75-80℃, the catalyst preparation was completed.

4. The method for preparing the catalyst for low-temperature flue gas denitrification in waste incineration according to claim 3, characterized in that: In step 2, the mass ratio of hydroxypropyl methylcellulose to polyethylene oxide is 4:1 to 6:

1.

5. The method for preparing the catalyst for low-temperature flue gas denitrification in waste incineration according to claim 3, characterized in that: The viscosity of the viscous liquid in step 2 is 170 mm. 2 / s~200 mm 2 / s.

6. The method for preparing the catalyst for low-temperature flue gas denitrification in waste incineration according to claim 3, characterized in that: In step 3, the mass of sodium methylsilanolate is 20% to 30% of the total mass of V2O5 and MoO3 powders.

7. The method for preparing the catalyst for low-temperature flue gas denitrification in waste incineration according to claim 3, characterized in that: The viscosity of the viscous liquid in step 3 is 130 mm. 2 / s~160 mm 2 / s.

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