A method for preparing low-temperature ammonia-free denitrification catalyst using industrial solid waste

Abstract

This invention relates to a method for preparing a low-temperature denitrification catalyst using industrial by-products. The method involves mixing and grinding industrial solid waste vanadium-titanium smelting slag and coking plant dust, which is then used as a catalyst carrier. Metal ions from by-products such as electroplating sludge and electrolytic cation mud are precipitated and enriched using an acidic solution, and then used as catalytic particle elements. These particles are impregnated into the solid waste carrier, enriching the catalyst's catalytic performance and improving its efficiency. Under low-temperature conditions, CO in flue gas is directly used to reduce nitrogen oxides, achieving low manufacturing costs and low operating consumption. This method enables the reuse of industrial solid waste and by-products, reducing the environmental harm caused by the release of heavy metal pollutants. Compared to NH3-SCR denitrification technology, this technology eliminates the need to purchase liquid ammonia, ammonia water, or urea as reducing agents, reducing flue gas denitrification costs. It also solves problems associated with ammonia reducing agents, such as equipment corrosion, high storage and usage risks, inaccurate metering of reducing agents, and the potential formation of ammonium sulfate.

Description

Technical Field

[0001] This invention belongs to the field of flue gas denitrification treatment, and particularly relates to a method for preparing a low-temperature ammonia-free denitrification catalyst using industrial solid waste. Background Technology

[0002] Industrial flue gas contains large amounts of nitrogen oxides and sulfur dioxide, and my country has implemented ultra-low emission standards to address these issues. Currently, flue gas desulfurization and denitrification technologies are relatively mature and have good control effects on high concentrations of pollutants. However, there are still problems with poor treatment efficiency and high treatment costs for flue gas containing low-temperature, low-concentration pollutants. Traditional denitrification processes use SCR catalysts and add ammonia water or ammonia gas to participate in the redox reaction to remove nitrogen oxides from the flue gas. Although NH3-SCR technology has advantages such as high denitrification rate, relatively simple equipment and process flow, and no wastewater or waste generation, leading to its widespread application, it also has some fatal drawbacks in practical applications: First, the technology requires the purchase of liquid ammonia or ammonia water, which increases operating costs, and the easy leakage of liquid ammonia causes difficulties in operation and storage; second, it is difficult to accurately measure the amount of ammonia added during use, and the existence of ammonia escape will cause secondary pollution of flue gas; more importantly, although the catalyst used in this technology has good catalytic denitrification activity, it can also oxidize SO2 in the flue gas to SO3. SO3 reacts with NH3 to form ammonium sulfate, which not only corrodes and blocks pipelines, but can also deposit on the catalyst surface, causing catalyst deactivation. To prevent this phenomenon, the reaction temperature of SCR technology is required to be above 300℃. However, after electrostatic precipitator treatment, the flue gas temperature will drop to 150-160℃. Therefore, the SCR unit can only be placed before the electrostatic precipitator process, which will lead to a large amount of toxic dust depositing on the catalyst surface, affecting the catalyst's denitrification activity, stability, and lifespan. Therefore, developing catalysts with good low-temperature activity and strong resistance to SO2 poisoning, as well as seeking new, economical, and effective reducing agents to replace NH3, has become a research hotspot in flue gas denitrification. Furthermore, flue gas typically contains CO; therefore, utilizing CO in flue gas to simultaneously reduce NO to N2 can not only eliminate both pollutants simultaneously, but the process is also simple, producing no waste liquid or residue. Thus, developing and preparing novel ammonia-free denitrification catalysts, reducing catalyst production costs, eliminating the need for additional reagents, and reducing energy consumption are important future development directions for denitrification catalysts.

[0003] The key to current flue gas denitrification technology lies in the selection of catalyst materials and the catalytic environment: inexpensive and readily available materials and a mild catalytic reaction environment will lead to lower energy consumption and greater economic benefits. Patent 202111350784.7 describes the preparation of a denitrification catalyst from vanadium ore tailings after acid digestion and alkali precipitation. Patent 202110529976.8 describes the preparation of a flue gas desulfurization catalyst using a combination of vanadium-titanium blast furnace slag, steelmaking sintering ash, and coke impregnated with metal salts. Patent 202210041114.5 describes the preparation of a flue gas denitrification catalyst using electrolytic manganese anode mud after impregnation with a simple sodium chloride solution. Patent 202210586404.8 describes the preparation of a CO removal catalyst using copper anode mud. Patent 201710196286.9 describes the preparation of a flue gas denitrification catalyst using dry quenching coke dust as a carrier, loaded with various metal particles, and using ammonia as a reducing agent. Patents 200910188157.0 and 201310383956.X use CO in flue gas as a reducing agent to catalytically oxidize SO2 and NO in the flue gas. Some of these patents utilize industrial solid waste or byproducts as catalysts, loading metal salts onto their surfaces to synthesize composite materials, which can improve catalytic efficiency and thus increase the conversion rate of nitrogen oxides, effectively reducing the cost of catalyst raw materials. Some patents use CO as a reducing agent, avoiding the input of ammonia and reducing operating costs. However, in all of these patents, the catalytic reaction temperature needs to be greater than 200℃, which will result in significant energy consumption, hindering the application of the patented technology in industrial production.

[0004] Therefore, while selecting low-cost and easily synthesized catalytic materials, we must also prepare catalysts with high catalytic activity to reduce the reaction temperature of catalytic denitration, reduce energy consumption, improve economic efficiency, and promote the transformation of patented technologies into industrial production. Summary of the Invention

[0005] This invention aims to address the shortcomings of existing industrial denitrification technologies by providing a technical method for preparing a low-temperature denitrification catalyst using industrial by-products. It utilizes vanadium-titanium smelting slag and coking plant dust as catalyst carriers; and employs metal ions from by-products such as electroplating sludge and electrolytic cation mud as catalytic particle elements, enriching the catalyst's catalytic performance and improving its efficiency. Under low-temperature conditions, it directly utilizes CO in flue gas to reduce nitrogen oxides, achieving low manufacturing costs and low operating consumption. This enables the reuse of industrial solid waste and by-products, reducing the environmental harm caused by the release of heavy metal pollutants. Compared to NH3-SCR denitrification technology, this technology eliminates the need to purchase liquid ammonia, ammonia water, or urea as reducing agents, reducing flue gas denitrification costs. It also solves problems associated with ammonia reducing agents, such as equipment corrosion, high storage and usage risks, inaccurate metering of reducing agents, and the potential formation of ammonium sulfate.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A method for preparing a low-temperature ammonia-free denitrification catalyst using industrial solid waste includes the following steps:

[0008] 1) Electroplating sludge and electrolytic anode sludge are mechanically mixed at a mass ratio of 3:(1~5) to obtain mixture I.

[0009] 2) The mixture I is dried, ground and sieved to obtain the mixture II.

[0010] 3) Immerse mixture II in an acidic solution, heat and stir at 40-70°C for 2-5 hours, let stand, and then centrifuge at high speed to separate the filtrate and residue.

[0011] 4) The residue separated in step 3) is calcined at 1000-1500℃ in air atmosphere for 1-5 hours to obtain the remaining residue.

[0012] 5) The remaining residue from step 4), vanadium-titanium blast furnace slag, and coking plant dust were ball-milled and mixed in a mass ratio of (1-2):5:(1-3) to obtain active powder with a particle size of 50-200 mesh.

[0013] 6) The active powder from step 5) is immersed in the filtrate collected in step 3) at a solid-liquid volume ratio of 1:(5-20), for an immersion time of 24-48 hours and a temperature of 30-50°C.

[0014] 7) After impregnation, wash the solid until the pH of the washing solution is 6-7, then dry the solid and calcine it at 500-700℃ in air for 2-3 hours to obtain catalyst powder.

[0015] 8) The catalyst powder and polyaniline are ball-milled and mixed at a mass ratio of (5-10):1, and then extruded into strips or spheres under pressure to obtain an industrial denitrification catalyst.

[0016] The electroplating sludge mentioned in step 1) above is one or a mixture of several of the following: zinc plating, copper plating, nickel plating, cobalt plating, palladium plating, and platinum plating sludge.

[0017] The electrolytic anode mud mentioned in step 1) above is one or a mixture of several of the following: copper anode mud, lead anode mud, crude nickel anode mud, crude tin anode mud, antimony anode mud, and bismuth anode mud.

[0018] In step 2) above, the particle size of mixed substance II is 100-300 mesh.

[0019] The acidic solution mentioned in step 3) above is a mixed solution of nitric acid, sulfuric acid and hydrochloric acid, with a mixing volume ratio of nitric acid: sulfuric acid: hydrochloric acid = 5:(1~2):(3~4).

[0020] The coking plant dust mentioned in step 5) above is environmental dust.

[0021] The pressure condition in step 8) above is 0.5 to 1.5 MPa.

[0022] The catalyst is used at a temperature of ≤200℃.

[0023] Compared with existing technologies, the beneficial effects of this invention are:

[0024] The low-temperature denitrification catalyst provided by this invention utilizes the pores inherent in vanadium-titanium smelting slag and coking plant dust as a catalyst carrier; it utilizes the rich variety and large quantity of metal ions present in electroplating sludge and electrolytic cation mud as catalytic particle elements, thereby enriching the catalyst's catalytic performance and improving its catalytic efficiency. This allows it to directly utilize CO in flue gas to reduce nitrogen oxides under low-temperature conditions, achieving low manufacturing costs and low operating consumption. Detailed Implementation

[0025] The present invention is further illustrated below by way of embodiments, but these embodiments are not intended to limit the invention to the scope of the embodiments described. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0026] Example 1:

[0027] 1) Electroplating copper and cobalt sludge and electrolytic crude nickel and antimony anode sludge are mechanically mixed in a mass ratio of 1:2:2:2 to obtain mixture I.

[0028] 2) Dry the mixture I, grind it to 200 mesh, and sieve it to obtain the mixture II.

[0029] 3) Immerse mixture II in a mixed solution of nitric acid, sulfuric acid and hydrochloric acid in a volume ratio of 5:1:3, heat and stir at 50°C for 4 hours, let stand, and then centrifuge at high speed to separate the filtrate and residue.

[0030] 4) The residue separated in step 3) is calcined at 1100℃ in air for 3 hours to obtain the remaining residue.

[0031] 5) The remaining residue from step 4), vanadium-titanium blast furnace slag, and coking plant environmental dust were ball-milled and mixed in a mass ratio of 1.5:5:2.5 to obtain active powder with a particle size of 150 mesh.

[0032] 6) The active powder from step 5) is immersed in the filtrate collected in step 3) at a solid-liquid volume ratio of 1:8, for a duration of 30 hours and a temperature of 35°C.

[0033] 7) After impregnation, wash the solid until the pH of the washing solution is 6-7, then dry the solid and calcine it at 600℃ in air for 2.5 hours to obtain catalyst powder.

[0034] 8) The catalyst powder and polyaniline were ball-milled and mixed at a mass ratio of 6:1, and then extruded into spherical shapes under a pressure of 0.8 MPa to obtain an industrially viable denitrification catalyst.

[0035] The nitrogen oxide removal rate of the prepared denitrification catalyst was tested:

[0036] It is used for treating exhaust gas from an oxygen-enriched combustion furnace. The flue gas contains: 13% oxygen; 20% CO2; 55% H2O; 2% nitrogen; 80 ppm nitrogen oxides; and 500 ppm CO. The total flow rate is 15000 Nm³. 3 / h, flue gas temperature is 180℃. The denitrification rate of the catalyst is calculated by the formula: η=([NOx]in-[NOx]out) / [NOx]in×100%, where [NOx]in and [NOx]out represent the NOx concentration at the inlet and outlet, respectively, i.e., before and after the reaction. The NOx concentration is obtained by continuous monitoring of an online flue gas analyzer.

[0037] The test results showed that the NOx content in the gas after treatment with the denitrification catalyst was 10 ppm, and the denitrification removal rate was 87.5%.

[0038] Example 2:

[0039] 1) Electroplating zinc and nickel sludge and electrolytic crude tin and bismuth anode sludge are mechanically mixed in a mass ratio of 1:2:3:2 to obtain mixture I.

[0040] 2) Dry mixture I, grind it to 150 mesh, and sieve it to obtain mixture II.

[0041] 3) Immerse mixture II in an acidic solution, heat and stir at 60°C for 3 hours, let stand, and centrifuge at high speed to separate the filtrate and residue; the acidic solution is a mixture of nitric acid, sulfuric acid and hydrochloric acid, with a volume ratio of nitric acid:sulfuric acid:hydrochloric acid = 5:2:4.

[0042] 4) The residue separated in step 3) is calcined at 1300℃ in air for 4 hours to obtain the remaining residue.

[0043] 5) The remaining residue from step 4), vanadium-titanium blast furnace slag, and coking plant environmental dust are ball-milled and mixed at a mass ratio of 1:5:2 to obtain active powder with a particle size of 100 mesh.

[0044] 6) The active powder from step 5) is immersed in the filtrate collected in step 3) at a solid-liquid volume ratio of 1:15, for an immersion time of 28 hours and a temperature of 45°C.

[0045] 7) After impregnation, wash the solid until the pH of the washing solution is 6-7, then dry the solid and calcine it at 550°C in air for 3 hours to obtain catalyst powder.

[0046] 8) The catalyst powder and polyaniline were ball-milled and mixed at a mass ratio of 9:1, and then extruded into strips or spheres under a pressure of 1.2 MPa to obtain an industrial denitrification catalyst.

[0047] The above catalyst is used for sintering flue gas treatment. The flue gas contains: 12% oxygen; 36% H2O; 15% nitrogen; 20% carbon dioxide; 500 ppm sulfur dioxide; 162 ppm nitrogen oxides; and 100 ppm CO. The total flow rate is 20,000 Nm³. 3 / h, flue gas temperature is 150℃. The denitrification rate of the catalyst is calculated by the formula: η=([NOx]in-[NOx]out) / [NOx]in×100%, where [NOx]in and [NOx]out represent the NOx concentration at the inlet and outlet, respectively, i.e., before and after the reaction. The NOx concentration is obtained by continuous monitoring of an online flue gas analyzer.

[0048] The test results showed that the NO content in the gas after treatment with the denitrification catalyst was 25 ppm, and the denitrification removal rate was 84.6%.

[0049] Example 3:

[0050] 1) Electroplating palladium and platinum sludge and electrolytic copper and lead anode sludge are mechanically mixed in a mass ratio of 1.5:1.5:2:2 to obtain mixture I.

[0051] 2) Dry mixture I, grind it to 250 mesh, and sieve it to obtain mixture II.

[0052] 3) Immerse mixture II in an acidic solution, heat and stir at 65°C for 2 hours, let stand, and centrifuge at high speed to separate the filtrate and residue; the acidic solution is a mixture of nitric acid, sulfuric acid and hydrochloric acid, with a volume ratio of nitric acid:sulfuric acid:hydrochloric acid = 5:1.5:4.

[0053] 4) The residue separated in step 3) is calcined at 1400℃ in air for 2 hours to obtain the remaining residue.

[0054] 5) The remaining residue from step 4), vanadium-titanium blast furnace slag, and coking plant environmental dust were ball-milled and mixed in a mass ratio of 2:5:3 to obtain active powder with a particle size of 100 mesh.

[0055] 6) The active powder from step 5) is immersed in the filtrate collected in step 3) at a solid-liquid volume ratio of 1:10, an immersion time of 40 h, and a temperature of 30 °C.

[0056] 7) After impregnation, wash the solid until the pH of the washing solution is 6-7, then dry the solid and calcine it at 700°C in air for 2 hours to obtain catalyst powder.

[0057] 8) The catalyst powder and polyaniline were ball-milled and mixed at a mass ratio of 8:1, and then extruded into strips or spheres under a pressure of 1.4 MPa to obtain an industrial denitrification catalyst.

[0058] The above catalyst is used to treat coke oven flue gas, which contains: 8% oxygen; 20% H2O; 30% nitrogen; 14% carbon dioxide; 120 ppm sulfur dioxide; 90 ppm nitrogen oxides; and 50 ppm CO, with a total flow rate of 5 Nm³. 3 / h, flue gas temperature is 185℃. The denitrification rate of the catalyst is calculated by the formula: η=([NOx]in-[NOx]out) / [NOx]in×100%, where [NOx]in and [NOx]out represent the NOx concentration at the inlet and outlet, respectively, i.e., before and after the reaction. The NOx concentration is obtained by continuous monitoring of an online flue gas analyzer.

[0059] The test results showed that the NO content in the gas after treatment with the denitrification catalyst was 15 ppm, and the denitrification removal rate was 83.3%.

[0060] 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, shall still fall within the scope of protection of the present invention.

Claims

1. A method for preparing a low-temperature ammonia-free denitrification catalyst using industrial solid waste, characterized in that, The following steps are included: 1) Electroplating sludge and electrolytic anode sludge are mechanically mixed at a mass ratio of 3:(1~5) to obtain mixture I; 2) Mixture I is dried, ground, and sieved to obtain mixture II; 3) Immerse mixture II in an acidic solution, heat and stir at 40~70℃ for 2~5 hours, let stand, and then centrifuge at high speed to separate the filtrate and residue; 4) The residue separated in step 3) is calcined at 1000~1500℃ in air atmosphere for 1~5 hours to obtain the remaining residue; 5) The remaining residue from step 4), vanadium-titanium blast furnace slag, and coking plant dust were ball-milled and mixed in a mass ratio of (1~2):5:(1~3) to obtain active powder with a particle size of 50~200 mesh. 6) The active powder from step 5) is immersed in the filtrate collected in step 3) at a solid-liquid volume ratio of 1:(5~20), for an immersion time of 24~48h, and at a temperature of 30~50℃; 7) After impregnation, wash the solid until the pH of the washing solution is 6~7, then dry the solid and calcine it at 500~700℃ in air for 2~3 hours to obtain catalyst powder. 8) The catalyst powder and polyaniline are ball-milled and mixed at a mass ratio of (5~10):1, and then extruded into strips or spheres under pressure to obtain an industrial denitrification catalyst. The electroplating sludge mentioned in step 1) above is one or a mixture of several of the following: zinc plating, copper plating, nickel plating, cobalt plating, palladium plating, and platinum plating sludge. The electrolytic anode mud mentioned in step 1) above is one or a mixture of several of the following: copper anode mud, lead anode mud, crude nickel anode mud, crude tin anode mud, antimony anode mud, and bismuth anode mud.

2. The method for preparing a low-temperature ammonia-free denitrification catalyst using industrial solid waste according to claim 1, characterized in that, In step 2) above, the particle size of mixed substance II is 100~300 mesh.

3. The method for preparing a low-temperature ammonia-free denitrification catalyst using industrial solid waste according to claim 1, characterized in that, The acidic solution mentioned in step 3) above is a mixed solution of nitric acid, sulfuric acid and hydrochloric acid, with a mixing volume ratio of nitric acid: sulfuric acid: hydrochloric acid = 5: (1~2): (3~4).

4. The method for preparing a low-temperature ammonia-free denitrification catalyst using industrial solid waste according to claim 1, characterized in that, The coking plant dust mentioned in step 5) above is environmental dust.

5. The method for preparing a low-temperature ammonia-free denitrification catalyst using industrial solid waste according to claim 1, characterized in that, The pressure condition in step 8) above is 0.5~1.5 MPa.

6. The method for preparing a low-temperature ammonia-free denitrification catalyst using industrial solid waste according to claim 1, characterized in that, The catalyst is used at a temperature of ≤200℃.