A catalyst suitable for denitrification of high NOx concentration flue gas in nuclear industry

Abstract

The invention provides a catalyst suitable for denitrification of flue gas with high NOx concentration in nuclear industry, relates to the technical field of flue gas treatment, and comprises the following components by mass ratio: 65-85 parts of a composite carrier, 10-30 parts of an active ingredient and 1-3 parts of an inhibitor, wherein the active ingredient is loaded on the composite carrier, and the inhibitor is added into the active ingredient; the invention uses a mixture of vanadium oxide and cerium oxide, ammonium tungstate and ammonium molybdate as main active ingredients, and simultaneously adds a proper amount of lanthanum, cerium and neodymium oxidants as inhibitors; during the use of the catalyst, when radioactive nuclides enter the catalyst layer along with the flue gas, the inhibitor can quickly react with the nuclides to form insoluble or stable compounds, thereby preventing the radioactive nuclides from further diffusing into the catalyst or enriching on its surface, thereby not only reducing the influence of radioactive pollution on the catalyst performance, but also effectively extending the service life of the catalyst.

Description

Technical Field

[0001] The invention relates to the technical field of flue gas treatment, and in particular to a catalyst suitable for denitrification of flue gas with high NOx concentration in nuclear industry. Background Art

[0002] NOx in nuclear industry flue gas mainly comes from the fuel combustion process. Especially when nuclear facilities need auxiliary energy (such as electricity and heat), the flue gas produced by combustion may contain high concentrations of NOx. In addition, although the nuclear industry itself does not directly produce NOx, other industrial activities or transportation around nuclear facilities may also affect air quality and indirectly increase NOx emissions. NOx is a major air pollutant that has caused great harm to human health and the ecological environment. It can not only lead to the formation of photochemical smog and affect atmospheric visibility, but also generate nitric acid and nitrate aerosols through chemical reactions in the atmosphere, thereby forming acid rain and causing acidification pollution to water bodies and soil. In addition, NOx is also one of the greenhouse gases and has a certain impact on global climate change.

[0003] In the treatment of flue gas, a treatment method of using a catalyst in combination with a reducing agent is required, such as SCR denitrification, which is one of the most widely used flue gas denitrification technologies. Its principle is based on the selective catalytic reduction reaction of nitrogen oxides (NOx) and ammonia (NH3) under the action of a catalyst to generate harmless nitrogen (N2) and water (H2O). However, radionuclides may exist in the flue gas. Radionuclides have specific chemical and physical properties, such as high water solubility, strong radioactivity, and long half-life. These properties make them difficult to be completely removed. When the catalyst adsorbs these radionuclides, the adsorption efficiency may decrease due to the occupation of the adsorption site or the destruction of the catalyst structure. The stability of the catalyst directly affects its service life. The strong radioactivity of the radionuclides may destroy the active site or structure of the catalyst, resulting in the deactivation of the catalyst or the degradation of its performance. The existing catalyst lacks a means of inhibiting the adsorption of radionuclides, resulting in a short service life of the catalyst, a short replacement cycle, and an increase in the cost of use. Therefore, the present invention proposes a catalyst suitable for denitrification of flue gas with high NOx concentration in the nuclear industry to solve the problems existing in the prior art. Summary of the invention

[0004] In view of the above problems, the present invention proposes a catalyst suitable for denitrification of flue gas with high NOx concentration in the nuclear industry. The catalyst suitable for denitrification of flue gas with high NOx concentration in the nuclear industry can quickly react with nuclides through inhibitors to form insoluble or stable compounds, preventing them from further diffusing into the interior of the catalyst or enriching on its surface, thereby playing the role of a reverse element. This can not only reduce the impact of radioactive pollution on the performance of the catalyst, but also effectively extend the service life of the catalyst and reduce the cost of use.

[0005] To achieve the purpose of the present invention, the present invention is implemented by the following technical scheme: a catalyst suitable for denitrification of flue gas with high NOx concentration in nuclear industry, comprising the following components by mass ratio: 65-85 parts of a composite carrier, 10-30 parts of an active ingredient and 1-3 parts of an inhibitor, wherein the active ingredient is loaded on the composite carrier, and an inhibitor is added to the active ingredient;

[0006] The active ingredient comprises the following components in a mass ratio: a mixture of 70-96 parts of vanadium oxide and cerium oxide, 1-10 parts of ammonium tungstate, and 1-15 parts of ammonium molybdate;

[0007] The composite carrier comprises the following components in a mass ratio: 70-99.8 parts of a nano-anatase titanium dioxide mixture, 0.1-10 parts of cordierite and 0.1-20 parts of ceramic fiber;

[0008] The inhibitor is a mixture of one or more oxidants of lanthanum, cerium and neodymium.

[0009] A further improvement is that the vanadium oxide is a composite oxide of vanadium and one or more of iron, copper, lanthanum, bismuth, niobium and tantalum.

[0010] A further improvement is that the cerium oxide is a composite oxide of cerium and one or more of iron, copper, lanthanum, bismuth, niobium and tantalum.

[0011] A further improvement is that the nano-anatase titanium dioxide mixture is a mixture of nano-anatase titanium dioxide and one or more of aluminum oxide, zirconium dioxide and silicon dioxide.

[0012] A further improvement is that the cordierite and ceramic fiber are mixed to form cordierite honeycomb ceramics, and the cordierite honeycomb ceramics are mixed with the nano-anatase titanium dioxide mixture after acid pretreatment.

[0013] A further improvement is that the acid used for pretreatment is 5wt%-50wt% nitric acid, hydrochloric acid or sulfuric acid aqueous solution, and the acid treatment conditions are immersion at room temperature for 4 hours and then drying at 70°C.

[0014] A further improvement is that the inhibitor is one or a mixture of more than one of lanthanum oxide, cerium dioxide and neodymium trioxide.

[0015] A further improvement is that the preparation method comprises the following steps:

[0016] S1: dissolving a mixture of vanadium oxide and cerium oxide, ammonium tungstate and ammonium molybdate in oxalic acid solution or deionized water, and adjusting the pH value to obtain an active ingredient;

[0017] S2: mixing cordierite and ceramic fiber into cordierite honeycomb ceramics and performing acid treatment;

[0018] S3: mixing the nano-anatase titanium dioxide mixture with the cordierite honeycomb ceramic and calcining them to obtain a composite carrier;

[0019] S4: adding the inhibitor to the active ingredient and mixing, and then mixing with the composite carrier, deionized water, a binder, and a lubricant to obtain a comprehensive mixture;

[0020] S5: kneading, aging, high-pressure filtering, molding, drying and calcining the comprehensive mixture to obtain a finished catalyst product.

[0021] A further improvement is that in S1, the pH value is adjusted to 7-8.

[0022] A further improvement is that in S3, during calcination, the temperature is controlled at 500-600°C and calcined for 2-6 hours, then the temperature is raised to 600-750°C and calcined for 2-4 hours.

[0023] The beneficial effects of the present invention are:

[0024] 1. The present invention uses a mixture of vanadium oxide and cerium oxide, ammonium tungstate and ammonium molybdate as main active ingredients, and adds appropriate amounts of lanthanum, cerium and neodymium oxidants as inhibitors. During the use of the catalyst, when radioactive nuclides enter the catalyst layer with flue gas, the inhibitors can quickly react with these nuclides to form insoluble or stable compounds, preventing them from further diffusing into the interior of the catalyst or enriching on its surface, playing the role of reverse elements. This can not only reduce the impact of radioactive pollution on the performance of the catalyst, but also effectively extend the service life of the catalyst and reduce the cost of use.

[0025] 2. The present invention mixes cordierite and ceramic fiber into cordierite honeycomb ceramics, and after acid treatment, mixes and calcines with a nano-rutile titanium dioxide mixture. The obtained composite carrier has a porous and stable microporous structure, has good mechanical strength, and is adapted to the operation requirements of industrial flue gas treatment equipment. Through the synergistic effect of the composite carrier and the inhibitor, the catalyst's resistance to sulfur poisoning is improved, and the service life of the catalyst is further extended. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a preparation flow chart of the present invention. DETAILED DESCRIPTION

[0027] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with examples. The examples are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

[0028] Embodiment 1

[0029] according to Figure 1As shown, this embodiment proposes a catalyst suitable for denitrification of high NOx concentration flue gas in the nuclear industry, comprising the following components by mass ratio: 65 parts of a composite carrier, 10 parts of an active ingredient and 1 part of an inhibitor, wherein the active ingredient is loaded on the composite carrier, and an inhibitor is added to the active ingredient;

[0030] The active ingredient includes the following components in mass ratio: 70 parts of a mixture of vanadium oxide and cerium oxide, 1 part of ammonium tungstate, and 1 part of ammonium molybdate;

[0031] The composite carrier comprises the following components in a mass ratio: 70 parts of a nano-anatase titanium dioxide mixture, 0.1 parts of cordierite and 0.1 parts of ceramic fiber;

[0032] The vanadium oxide is a composite oxide of vanadium, iron and copper. The cerium oxide is a composite oxide of cerium, iron and copper. The nano-anatase titanium dioxide mixture is a mixture of nano-anatase titanium dioxide, aluminum oxide and zirconium dioxide. The inhibitor is a mixture of lanthanum oxide and cerium dioxide.

[0033] The cordierite and ceramic fiber are mixed into cordierite honeycomb ceramics, and the cordierite honeycomb ceramics are mixed with the nano-anatase titanium dioxide mixture after acid pretreatment. The acid used for pretreatment is: 5wt%-50wt% nitric acid, hydrochloric acid or sulfuric acid aqueous solution, and the acid treatment conditions are immersion at room temperature for 4 hours and drying at 70°C.

[0034] The catalyst comprises the following preparation steps:

[0035] S1: dissolving a mixture of vanadium oxide and cerium oxide, ammonium tungstate and ammonium molybdate in oxalic acid solution or deionized water, and adjusting the pH value to 7.5 to obtain an active ingredient;

[0036] S2: mixing cordierite and ceramic fiber into cordierite honeycomb ceramics and performing acid treatment;

[0037] S3: Mixing the nano-anatase titanium dioxide mixture with the cordierite honeycomb ceramic and calcining the mixture. During calcination, the temperature is controlled at 550° C. for 6 hours, and then the temperature is raised to 700° C. for 4 hours to obtain a composite carrier.

[0038] S4: adding the inhibitor to the active ingredient and mixing, and then mixing with the composite carrier, deionized water, a binder, and a lubricant to obtain a comprehensive mixture;

[0039] S5: kneading, aging, high-pressure filtering, molding, drying and calcining the comprehensive mixture to obtain a finished catalyst product.

[0040] Embodiment 2

[0041] according to Figure 1As shown, this embodiment proposes a catalyst suitable for denitrification of flue gas with high NOx concentration in the nuclear industry, comprising the following components by mass ratio: 70 parts of a composite carrier, 20 parts of an active ingredient and 2 parts of an inhibitor, wherein the active ingredient is loaded on the composite carrier, and an inhibitor is added to the active ingredient;

[0042] The active ingredient includes the following components in a mass ratio: 85 parts of a mixture of vanadium oxide and cerium oxide, 5 parts of ammonium tungstate, and 5 parts of ammonium molybdate;

[0043] The composite carrier comprises the following components in a mass ratio: 85 parts of a nano-anatase titanium dioxide mixture, 5 parts of cordierite and 10 parts of ceramic fiber;

[0044] The vanadium oxide is a composite oxide of vanadium, lanthanum and bismuth. The cerium oxide is a composite oxide of cerium, lanthanum and bismuth. The nano-anatase titanium dioxide mixture is a mixture of nano-anatase titanium dioxide, zirconium dioxide and silicon dioxide. The inhibitor is a mixture of lanthanum oxide and neodymium trioxide.

[0045] The cordierite and ceramic fiber are mixed into cordierite honeycomb ceramics, and the cordierite honeycomb ceramics are mixed with the nano-anatase titanium dioxide mixture after acid pretreatment. The acid used for pretreatment is: 5wt%-50wt% nitric acid, hydrochloric acid or sulfuric acid aqueous solution, and the acid treatment conditions are immersion at room temperature for 4 hours and drying at 70°C.

[0046] The catalyst comprises the following preparation steps:

[0047] S1: dissolving a mixture of vanadium oxide and cerium oxide, ammonium tungstate and ammonium molybdate in oxalic acid solution or deionized water, and adjusting the pH value to 7.5 to obtain an active ingredient;

[0048] S2: mixing cordierite and ceramic fiber into cordierite honeycomb ceramics and performing acid treatment;

[0049] S3: Mixing the nano-anatase titanium dioxide mixture with the cordierite honeycomb ceramic and calcining the mixture. During calcination, the temperature is controlled at 550° C. for 6 hours, and then the temperature is raised to 700° C. for 4 hours to obtain a composite carrier.

[0050] S4: adding the inhibitor to the active ingredient and mixing, and then mixing with the composite carrier, deionized water, a binder, and a lubricant to obtain a comprehensive mixture;

[0051] S5: kneading, aging, high-pressure filtering, molding, drying and calcining the comprehensive mixture to obtain a finished catalyst product.

[0052] Embodiment 3

[0053] according to Figure 1As shown, this embodiment proposes a catalyst suitable for denitrification of flue gas with high NOx concentration in the nuclear industry, comprising the following components by mass ratio: 85 parts of a composite carrier, 30 parts of an active ingredient, and 3 parts of an inhibitor, wherein the active ingredient is loaded on the composite carrier, and an inhibitor is added to the active ingredient;

[0054] The active ingredient includes the following components in a mass ratio: 96 parts of a mixture of vanadium oxide and cerium oxide, 10 parts of ammonium tungstate, and 15 parts of ammonium molybdate;

[0055] The composite carrier comprises the following components in a mass ratio: 99.8 parts of a nano-anatase titanium dioxide mixture, 10 parts of cordierite and 20 parts of ceramic fiber;

[0056] The vanadium oxide is a composite oxide of vanadium, niobium and tantalum. The cerium oxide is a composite oxide of cerium, niobium and tantalum. The nano-anatase titanium dioxide mixture is a mixture of nano-anatase titanium dioxide, aluminum oxide and silicon dioxide. The inhibitor is a mixture of lanthanum oxide, cerium dioxide and neodymium oxide.

[0057] The cordierite and ceramic fiber are mixed into cordierite honeycomb ceramics, and the cordierite honeycomb ceramics are mixed with the nano-anatase titanium dioxide mixture after acid pretreatment. The acid used for pretreatment is: 5wt%-50wt% nitric acid, hydrochloric acid or sulfuric acid aqueous solution, and the acid treatment conditions are immersion at room temperature for 4 hours and drying at 70°C.

[0058] The catalyst comprises the following preparation steps:

[0059] S1: dissolving a mixture of vanadium oxide and cerium oxide, ammonium tungstate and ammonium molybdate in oxalic acid solution or deionized water, and adjusting the pH value to 7.5 to obtain an active ingredient;

[0060] S2: mixing cordierite and ceramic fiber into cordierite honeycomb ceramics and performing acid treatment;

[0061] S3: Mixing the nano-anatase titanium dioxide mixture with the cordierite honeycomb ceramic and calcining the mixture. During calcination, the temperature is controlled at 550° C. for 6 hours, and then the temperature is raised to 700° C. for 4 hours to obtain a composite carrier.

[0062] S4: adding the inhibitor to the active ingredient and mixing, and then mixing with the composite carrier, deionized water, a binder, and a lubricant to obtain a comprehensive mixture;

[0063] S5: kneading, aging, high-pressure filtering, molding, drying and calcining the comprehensive mixture to obtain a finished catalyst product.

[0064] Verify data:

[0065] After screening, lanthanide elements (lanthanum oxide, cerium dioxide, neodymium trioxide) were selected as inhibitors. Due to their unique electronic structure and chemical properties, these elements can form stable compounds or complexes with radioactive nuclides (such as cesium Cs, strontium Sr, etc.), thereby inhibiting their enrichment in the catalyst. During the use of the catalyst, when radioactive nuclides enter the catalyst layer with the flue gas, the inhibitors can quickly react with these nuclides to form insoluble or stable compounds, preventing them from further diffusing into the catalyst or enriching on its surface. This can not only reduce the impact of radioactive contamination on catalyst performance, but also effectively extend the service life of the catalyst. Lanthanum oxide (La 2 O 3 ): Lanthanum oxide is a stable oxide that has the ability to bind to radioactive nuclides. It can reduce the adsorption and internal diffusion of radioactive nuclides on the catalyst surface by forming lanthanum compounds with radioactive nuclides. 2 ): Cerium dioxide is not only the main oxide form of cerium, the rare earth element with the largest reserves on earth, but also has a unique Ce 3+ / Ce 4+ The valence state conversion has excellent antioxidant properties. In the catalyst, cerium dioxide can not only act as a radionuclide inhibitor, but also participate in the catalytic reaction through its redox properties, further improving the denitrification performance of the catalyst. 2 O 3 ): Neodymium trioxide is a metal oxide with stable chemical properties. As a radionuclide inhibitor, it can combine with radionuclides to form insoluble neodymium compounds, thereby effectively inhibiting the enrichment of radionuclides in the catalyst. The amount of inhibitor added is adjusted according to the actual situation (1-3 parts of inhibitor) to ensure that while effectively inhibiting the enrichment of radionuclides, it will not have a negative impact on the denitrification performance of the catalyst.

[0066] The catalyst performance was tested by simulating the high NOx concentration flue gas environment of the nuclear industry to verify its denitrification efficiency, anti-poisoning ability, mechanical strength and the effect of inhibiting the enrichment of radioactive nuclides. The experimental results show that after adding inhibitors, the catalyst can maintain its efficient denitrification performance while significantly improving its ability to resist radioactive pollution and service life.

[0067]

[0068]

[0069] Resistance to radioactive contamination: "Low" means it is more sensitive to radioactive contamination and easily damaged; "Medium" means it has a certain resistance to contamination, but may still be damaged in a high-intensity radioactive environment; "Medium-high" means it has better resistance to contamination and can resist radioactive contamination to a certain extent; "High" means it has very good resistance to contamination and can adapt to resist most radioactive contamination.

[0070] Service life: The range given is an estimate based on typical operating conditions. Actual service life will vary depending on many factors including catalyst purity, operating temperature, pressure, reactant concentration, impurity content, and catalyst regeneration and maintenance.

[0071] The present invention uses a mixture of vanadium oxide and cerium oxide, ammonium tungstate and ammonium molybdate as the main active ingredients, and adds an appropriate amount of lanthanum, cerium and neodymium oxidants as inhibitors. During the use of the catalyst, when radioactive nuclides enter the catalyst layer with flue gas, the inhibitor can quickly react with these nuclides to form insoluble or stable compounds, preventing them from further diffusing into the catalyst or enriching on its surface, playing the role of reverse elements, which can not only reduce the impact of radioactive pollution on the performance of the catalyst, but also effectively extend the service life of the catalyst and reduce the cost of use. In the high-concentration NOx flue gas environment of the nuclear industry, the catalyst of the present invention can achieve a NOx conversion rate of ≥95%, significantly reducing the NOx content in the flue gas. The catalyst maintains high-efficiency catalytic activity in a wide temperature range (150°C-420°C), and is adapted to the complex and changeable flue gas temperature conditions of the nuclear industry. In the present invention, cordierite and ceramic fiber are mixed into cordierite honeycomb ceramics, which are then acid-treated and mixed with a nano-rutaceous titanium dioxide mixture and calcined. The obtained composite carrier has a porous and stable microporous structure, has good mechanical strength, and is adapted to the operating requirements of industrial flue gas treatment equipment. Through the synergistic effect of the composite carrier and the inhibitor, the catalyst's ability to resist sulfur poisoning is improved, further extending the catalyst's service life.

[0072] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A high NOx filter suitable for nuclear industry x Catalysts for denitrification of flue gas with high NO concentration in nuclear industry x The invention is applied in the denitrification of concentrated flue gas, characterized in that: The catalyst comprises the following components in a mass ratio: 65-85 parts of a composite carrier, 10-30 parts of an active ingredient and 1-3 parts of an inhibitor, wherein the active ingredient is loaded on the composite carrier, and the inhibitor is added to the active ingredient; The active ingredient comprises the following components in a mass ratio: a mixture of 70-96 parts of vanadium oxide and cerium oxide, 1-10 parts of ammonium tungstate, and 1-15 parts of ammonium molybdate; The composite carrier comprises the following components in a mass ratio: 70-99.8 parts of a nano-anatase titanium dioxide mixture, 0.1-10 parts of cordierite and 0.1-20 parts of ceramic fiber; The inhibitor is one or a mixture of more than one of lanthanum oxide, cerium dioxide and neodymium trioxide; The preparation method of the catalyst comprises the following preparation steps: S1: dissolving a mixture of vanadium oxide and cerium oxide, ammonium tungstate and ammonium molybdate in oxalic acid solution or deionized water, and adjusting the pH value to obtain an active ingredient; S2: mixing cordierite and ceramic fiber into cordierite honeycomb ceramics and performing acid treatment; S3: mixing the nano-anatase titanium dioxide mixture with the cordierite honeycomb ceramic and calcining them to obtain a composite carrier; S4: adding the inhibitor to the active ingredient and mixing, and then mixing with the composite carrier, deionized water, a binder, and a lubricant to obtain a comprehensive mixture; S5: kneading, aging, high-pressure filtering, molding, drying and calcining the comprehensive mixture to obtain a finished catalyst product.

2. The use according to claim 1, characterized in that: The vanadium oxide is a composite oxide of vanadium and one or more of iron, copper, lanthanum, bismuth, niobium and tantalum.

3. The use according to claim 2, characterized in that: The cerium oxide is a composite oxide of cerium and one or more of iron, copper, lanthanum, bismuth, niobium and tantalum.

4. The use according to claim 1, characterized in that: The nano-anatase titanium dioxide mixture is a mixture of nano-anatase titanium dioxide and one or more of aluminum oxide, zirconium dioxide and silicon dioxide.

5. The use according to claim 1, characterized in that: The acid used for the acid treatment is: 5wt%-50wt% nitric acid, hydrochloric acid or sulfuric acid aqueous solution, and the acid treatment conditions are: immersion at room temperature for 4 hours and then drying at 70°C.

6. The use according to claim 1, characterized in that: In S1, the pH value is adjusted to 7-8.

7. The use according to claim 1, characterized in that: In S3, during calcination, the temperature is controlled at 500-600°C and calcined for 2-6 hours, then the temperature is raised to 600-750°C and calcined for 2-4 hours.

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