Denitration material and denitration method using co in cement kiln flue gas as reducing agent

Abstract

This invention discloses a denitrification material and method utilizing CO in cement kiln flue gas as a reducing agent. The method includes individually packaged denitrification agents A, B, and C. Denitrification agent A is formed by uniformly mixing crushed waste vanadium-based denitrification catalyst, cerium-zirconium solid solution, carbide slag, and spinel-type composite metal oxide, followed by grinding. Denitrification agent B is formed by crushing raw coal blocks and gangue, and then uniformly mixing them with limestone powder. Denitrification agent C is formed by uniformly mixing copper oxide with one or more of the following: cerium oxide, zirconium oxide, lanthanum oxide, manganese dioxide, cobalt oxide, and iron tetroxide, followed by adding electrolytic manganese slag and red mud, mixing thoroughly, and then grinding. These agents are added to the cement production process through different methods to synergistically achieve denitrification in the cement kiln. Utilizing CO in the cement production flue gas as a reducing agent, the entire process produces no secondary pollution and has no adverse effects on the performance of cement clinker.

Description

Technical Field

[0001] This invention belongs to the field of environmental engineering technology, and in particular relates to a denitrification material and denitrification method that utilizes CO in cement kiln flue gas as a reducing agent. Background Technology

[0002] The cement industry is one of the major sources of nitrogen oxide emissions, polluting the environment and harming human health. In recent years, the Ministry of Ecology and Environment has issued a series of policies and documents limiting the concentration and total amount of nitrogen oxide emissions. The "Comprehensive Work Plan for Energy Conservation and Emission Reduction" proposes that, by 2035, total nitrogen oxide emissions should decrease by more than 10% compared to 2020. The "Technical Guidelines for Formulating Emergency Emission Reduction Measures for Key Industries During Heavily Polluted Weather" classifies cement enterprises by performance, requiring cement enterprises with a performance level of A to have a nitrogen oxide emission limit of 50 mg / Nm³. 3 Ammonia escape <5mg / Nm 3 .

[0003] To achieve the aforementioned emission targets, SCR technology is one of the most mature and reliable denitrification technologies. Currently, in the cement industry, the main technologies used include high-temperature, high-dust SCR technology and medium-temperature, medium-dust SCR technology. Because the SNCR system uses escaped ammonia as a reducing agent, it produces a certain amount of ammonium sulfate, causing equipment corrosion and pipeline blockage, and also posing a secondary pollution problem.

[0004] Patent CN 113275008 discloses a CO-SCR catalyst, its preparation method, and its applications. It mentions its potential use in flue gas denitrification in the cement industry. The catalyst employs SiO2 balls loaded with Ir and K for the CO-SCR denitrification reaction, using precious metals as the main active components. However, the cement industry generates large volumes of flue gas and requires significant amounts of catalyst, making expensive precious metal catalysts unsuitable. Furthermore, this invention utilizes a fixed-bed catalyst. Combined with existing cement production processes, this requires placing the reactor at the preheater outlet. Within the temperature range of 225–350°C, the catalyst is affected by sulfides in the flue gas. In particular, the additive K reacts with SO2 and O2 to form potassium sulfate, and this reaction is irreversible at this temperature, leading to catalyst deactivation.

[0005] Patent CN 112138665A discloses a low-temperature, high-efficiency non-noble metal oxide catalyst for CO-SCR and its preparation method, using transition metal oxides CuCoAlO4. x As a catalyst; CN 113908842 A discloses a denitrification catalyst for CO-SCR flue gas denitrification and its preparation method, which prepares a Cu-Ce-Al / mullite catalyst. In the performance test process of these two invention patents, O2 was not introduced, but the CO-SCR reaction is extremely sensitive to the O2 concentration. After introducing O2, the denitrification efficiency will decrease significantly.

[0006] CN 112371126 A discloses a low-temperature CO-SCR denitration Cu-Fe / AC catalyst, its preparation method, and its application; CN 114682294 A discloses a CO-SCR denitration catalyst, its preparation method, and its application, using Y-type molecular sieves, TiO2, and magnesium oxide as supports, and oxides of La, Ce, and Sr as promoters; CN 112316946 discloses a low-temperature CO-SCR denitration Cu-Ni / AC catalyst and its preparation method; CN Patent 111229212 discloses a CO-SCR denitrification catalyst, its preparation method, and its application. It uses one or more of Cu, Fe, Ce, Co, and Ni oxides as active components. All of the above inventions use transition metals or rare earth metal oxides as active components and employ a fixed bed for CO-SCR denitrification. If applied to the cement industry, it needs to be placed at the preheater outlet. Since SO2 is easily oxidized by the catalyst to SO3, and then reacts with oxides to generate metal sulfates, sulfur poisoning may occur in the actual application of cement flue gas denitrification, affecting the service life of the catalyst. At the same time, the above invention patents do not address the issue of supplementing the source of CO.

[0007] In summary, the existing denitrification technologies in the cement industry have the following problems:

[0008] (1) When using ammonia as a reducing agent for SCR denitrification reaction, a certain amount of ammonium sulfate or ammonium nitrate will be generated at the back end, which will be deposited on the catalyst surface or inside the equipment and pipeline, causing catalyst deactivation, equipment corrosion or pipeline blockage.

[0009] (2) CO is used as a reducing agent in the application of fixed bed reactor for denitrification. Because the reaction is extremely sensitive to O2, the oxygen concentration will increase due to air leakage. The denitrification efficiency of cement kiln at the back end of the preheater will be greatly affected.

[0010] (3) When transition metal or rare earth metal oxides are used as active components of CO-SCR denitration catalysts, they will be affected by SO2 at lower temperatures, causing catalyst deactivation.

[0011] (4) When using fixed-bed CO-SCR denitrification, the catalyst deactivates quickly, resulting in waste denitrification catalyst. If identified as hazardous waste, this will greatly increase environmental protection costs. Summary of the Invention

[0012] To address the problems existing in the prior art, one of the objectives of this invention is to provide a denitrification material and method that utilizes CO in cement kiln flue gas as a reducing agent. This method uses denitrification agents A, B, and C as active components, which are added to the cement production process through different addition methods to synergistically exert a denitrification effect, achieving the desired denitrification effect in the cement kiln. Through this invention, CO in cement production flue gas can be used as a reducing agent, eliminating the need for external reducing agents to achieve NO reduction. x The process achieves removal and ultra-low emissions, with no secondary pollution and no adverse effects on the performance of cement clinker.

[0013] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a denitrification material that uses CO in cement kiln flue gas as a reducing agent, including individually packaged denitrification agent A, denitrification agent B and denitrification agent C;

[0014] The denitrification agent A is prepared by mixing crushed waste vanadium-based denitrification catalyst, cerium-zirconium solid solution, carbide slag, and spinel-type composite metal oxide evenly according to a certain mass ratio, and then grinding them to form denitrification agent A;

[0015] The denitrification agent B is prepared by crushing raw coal blocks and coal gangue into small particles of a certain size and mixing them evenly with limestone powder to form denitrification agent B.

[0016] The denitrification agent C is prepared by uniformly mixing a certain mass of copper oxide with one or more of cerium oxide, zirconium oxide, lanthanum oxide, manganese dioxide, cobalt oxide, and iron tetroxide, then adding electrolytic manganese slag and red mud, mixing evenly, and grinding to a certain particle size to form denitrification agent C.

[0017] The particle size of the denitrification agent A mixture after grinding is ≤80μm, and the residue on the sieve is less than 14%.

[0018] According to the mass fractions, the waste vanadium-based denitrification catalyst accounts for 2 to 5 parts; spinel-type composite metal oxide accounts for 10 to 13 parts; cerium-zirconium solid solution accounts for 2 to 8 parts; and calcium carbide slag accounts for 1 to 3 parts.

[0019] The A-site of the spinel-type composite metal oxide is Co. 2+ With Mg 2+ Cu 2+ Ni 2+ Mn 2+ Zn 2+ Cd 2+ One or more combinations thereof; B position is Fe 3+ With Al 3+ Co 3+ One or more combinations of Co 2+ Fe accounts for more than 20% of site A. 3+ It accounts for more than 30% of position B.

[0020] According to the mass fractions, the particle size of crushed coal lumps and coal gangue is 0.01-1 mm, the particle size of limestone powder is ≤80 μm, the sieve residue is less than 14%, the coal lumps account for 3-5 parts, the coal gangue particles account for 5-8 parts, and the limestone powder accounts for 1-2 parts.

[0021] According to the mass fraction, the denitrification agent C powder has a size of ≤40μm and a sieve residue of less than 8%, of which copper oxide accounts for 1-2 parts, cerium oxide accounts for 0-1 parts, zirconium oxide accounts for 0-1 parts, lanthanum oxide accounts for 0-1 parts, manganese dioxide accounts for 0-1 parts, cobalt oxide accounts for 0-1 parts, iron oxide accounts for 0-1 parts, electrolytic manganese slag accounts for 1-2 parts, and red mud accounts for 1-2 parts.

[0022] A denitrification method utilizing CO in cement kiln flue gas as a reducing agent, employing the aforementioned denitrification materials in combination to achieve denitrification using CO in the flue gas as a reducing agent, includes the following steps:

[0023] (1) Mix the denitrification agent C with pulverized coal evenly and spray it into the cement production system from the decomposition furnace;

[0024] (2) Add denitrification agent B to the rear end of the decomposition furnace outlet;

[0025] (3) After mixing the denitrification agent A with the raw material, the raw material is ground. The mixed raw material is added from the connecting duct of the C1 and C2 cyclones at the kiln tail.

[0026] The total denitrification material accounts for 0.1‰ to 1% of the raw material mass. Among them, according to the mass fraction, denitrification agent A accounts for 1 to 2 parts, denitrification agent B accounts for 3 to 8 parts, and denitrification agent C accounts for 1 to 3 parts.

[0027] The beneficial effects of this invention are:

[0028] 1) This invention can reduce NO in cement kiln flue gas. x The removal process utilizes CO from the cement production process as a reducing agent, without the addition of NH3, thus avoiding subsequent pipeline blockage and equipment corrosion.

[0029] 2) The temperature inside the decomposition furnace is high, reaching over 900℃. At this temperature, the solid waste components in denitrification agent C can be effectively decomposed into active catalytic components, which, together with other components in denitrification agent C, synergistically form a three-functional catalyst. On the one hand, it can catalyze the complete combustion of coal powder, reduce the ignition point and improve the burnout. At the same time, the active components move with the flue gas to the location where denitrification agent B is added.

[0030] 3) The principle of adding denitrification agent B at the rear end of the decomposition furnace is that the coal lumps and coal gangue in denitrification agent B are selected to be crushed into granules, which can prevent them from being carried away too quickly by the high-speed flue gas. At this point, the catalytic effect of denitrification agent C is used to promote the formation of some CO, thereby increasing the CO concentration at the outlet of the decomposition furnace. At the same time, under the catalytic effect of denitrification agent C, the CO-SCR reaction occurs, reducing NOx to N2 to achieve denitrification. The amount of denitrification agent B added can determine the amount of CO produced.

[0031] 4) Select to add denitrification agent B at the rear end of the decomposition furnace. The temperature here is higher, reaching over 800℃, which is conducive to the CO-SCR denitrification effect of the active components and is less affected by SO2.

[0032] 5) The addition of denitrification agent A can further oxidize the excessive CO into CO2, ensuring that CO emissions meet the standards. The cerium-zirconium solid solution and carbide slag play a synergistic denitrification role, further improving the denitrification efficiency while eliminating the impact of SO2.

[0033] 6) Through this invention, solid waste can be disposed of simultaneously with catalytic denitrification and recycled to create environmental value.

[0034] 7) The denitrification process using this invention does not generate additional dust or waste liquid, the process is simple to operate, and does not require additional equipment or land. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0036] This invention relates to a denitrification material that utilizes CO in cement kiln flue gas as a reducing agent, comprising individually packaged denitrification agent A, denitrification agent B, and denitrification agent C;

[0037] The denitrification agent A is prepared by mixing crushed waste vanadium-based denitrification catalyst, cerium-zirconium solid solution, carbide slag, and spinel-type composite metal oxide evenly according to a certain mass ratio, and then grinding them to form denitrification agent A;

[0038] The denitrification agent B is prepared by crushing raw coal blocks and coal gangue into small particles of a certain size and mixing them evenly with limestone powder to form denitrification agent B.

[0039] The denitrification agent C is prepared by uniformly mixing a certain mass of copper oxide with one or more of cerium oxide, zirconium oxide, lanthanum oxide, manganese dioxide, cobalt oxide, and iron tetroxide, then adding electrolytic manganese slag and red mud, mixing evenly, and grinding to a certain particle size to form denitrification agent C.

[0040] The particle size of the denitrification agent A mixture after grinding is ≤80μm, and the residue on the sieve is less than 14%.

[0041] According to the mass fractions, the waste vanadium-based denitrification catalyst accounts for 2 to 5 parts; spinel-type composite metal oxide accounts for 10 to 13 parts; cerium-zirconium solid solution accounts for 2 to 8 parts; and calcium carbide slag accounts for 1 to 3 parts.

[0042] The A-site of the spinel-type composite metal oxide is Co. 2+ With Mg 2+ Cu 2+ Ni 2+ Mn 2+ Zn 2+ Cd 2+ One or more combinations thereof; B position is Fe 3+ With Al 3+ Co 3+ One or more combinations of Co 2+ Fe accounts for more than 20% of site A. 3+ It accounts for more than 30% of position B.

[0043] According to the mass fractions, the particle size of crushed coal lumps and coal gangue is 0.01-1 mm, the particle size of limestone powder is ≤80 μm, the sieve residue is less than 14%, the coal lumps account for 3-5 parts, the coal gangue particles account for 5-8 parts, and the limestone powder accounts for 1-2 parts.

[0044] According to the mass fraction, the denitrification agent C powder has a size of ≤40μm and a sieve residue of less than 8%, of which copper oxide accounts for 1-2 parts, cerium oxide accounts for 0-1 parts, zirconium oxide accounts for 0-1 parts, lanthanum oxide accounts for 0-1 parts, manganese dioxide accounts for 0-1 parts, cobalt oxide accounts for 0-1 parts, iron oxide accounts for 0-1 parts, electrolytic manganese slag accounts for 1-2 parts, and red mud accounts for 1-2 parts.

[0045] A denitrification method utilizing CO in cement kiln flue gas as a reducing agent, employing the aforementioned denitrification materials in combination to achieve denitrification using CO in the flue gas as a reducing agent, includes the following steps:

[0046] (1) Mix the denitrification agent C with pulverized coal evenly and add it to the cement production system from the decomposition furnace;

[0047] (2) Add denitrification agent B to the rear end of the decomposition furnace outlet;

[0048] (3) After mixing the denitrification agent A with the raw material, the raw material is ground. The mixed raw material is added from the connecting duct of the C1 and C2 cyclones at the kiln tail.

[0049] The total denitrification material accounts for 0.1‰ to 1% of the raw material mass. Among them, according to the mass fraction, denitrification agent A accounts for 1 to 2 parts, denitrification agent B accounts for 3 to 8 parts, and denitrification agent C accounts for 1 to 3 parts.

[0050] Denitrification agents A, B, and C are used in combination to achieve the effect of denitrification of CO in flue gas;

[0051] The denitrification agent C is mixed evenly with pulverized coal and added to the cement production system from the decomposition furnace. Due to the small particle size of the denitrification agent C powder, it decomposes and reacts with each other in the decomposition furnace and moves with the flue gas towards the kiln tail preheater. The temperature at the point where the denitrification agent C is added is high, and solid waste components such as electrolytic manganese slag and red mud decompose and react to generate active substances, which move with other active components to the point where the denitrification agent B is added, and work together to exert the CO-SCR denitrification effect.

[0052] Adding denitrifying agent B to the rear end of the decomposition furnace outlet, a location within the preheater where O2 concentration is low (as low as 1%), is more conducive to the CO-SCR reaction. After the decomposition of denitrifying agent C, the powder moves to the location where denitrifying agent B was added. The small coal particles and C from the coal gangue in denitrifying agent B react with O2 under the catalysis of denitrifying agent C, further reducing the O2 concentration and simultaneously generating a certain amount of CO. Furthermore, the active components in denitrifying agent C catalyze the reduction reaction of CO and NOx to produce CO2 and N2. Since the active components are transition metals coupled with rare earth metals, they may react with SO2 and cause poisoning; higher temperatures can delay this reaction. Simultaneously, the limestone powder in denitrifying agent B can fix some sulfur dioxide, protecting the active components. The coal particles in denitrifying agent B are slightly larger than other particles, preventing them from flowing upwards with the flue gas.

[0053] Denitrification agent A is mixed with raw materials and then ground. The mixed raw materials are added through the connecting duct between the C1 and C2 cyclones at the kiln tail. The spinel active component in material A has variable valence and strong redox properties, which can realize the oxidation of CO and ensure that the CO emission meets the standards. At the same time, the waste vanadium-based denitrification catalyst has a low sulfur resistance temperature and can realize the generation of active components and catalytic NO at 550℃. x Further deep reduction and removal, cerium-zirconium solid solution and carbide slag play a synergistic role in denitrification, improving denitrification efficiency while eliminating the impact of SO2.

[0054] In the following examples, all quantities are parts by weight.

[0055] Example 1

[0056] (1) Preparation of denitrification agent A: 2 parts of waste vanadium-based denitrification catalyst, 2 parts of cerium-zirconium solid solution, 10 parts of spinel-type composite metal oxide, and 1 part of carbide slag were mixed evenly and ground until the particle size was ≤80μm (sieve residue below 14%), thus forming denitrification agent A; wherein the spinel composition is Co. 0.5 Zn 0.5 Fe 0.3 Al 0.7 O4;

[0057] (2) Preparation of denitrification agent B: Crush 3 parts of raw coal lumps and 5 parts of coal gangue into small particles of a certain size, and mix them evenly with 1 part of limestone powder to form denitrification agent B; the particle size of the crushed coal lumps and coal gangue is 0.01-0.1 mm, and the particle size of the limestone powder is ≤80 μm (less than 14% sieve residue);

[0058] (3) Preparation of denitrification agent C: Mix 1 part copper oxide and 1 part cerium oxide evenly, then add 1 part electrolytic manganese slag and 1 part red mud and mix evenly. Grind the mixture to a size of ≤40μm (screen residue less than 8%) to form denitrification agent C;

[0059] The mass fractions of denitrification agents A, B, and C are as follows: denitrification agent A is 1 part, denitrification agent B is 3 parts, and denitrification agent C is 1 part. The total mass fraction of denitrification agents A, B, and C is 0.5% of the raw meal mass.

[0060] The background emission concentration of nitrogen oxides at C1 outlet is 300 mg / Nm³. 3 After adding denitrification agents A, B, and C according to the above method, the nitrogen oxides in the exhaust gas decreased to 50 mg / Nm³. 3 .

[0061] Example 2

[0062] (1) Preparation of denitrification agent A: 5 parts of waste vanadium-based denitrification catalyst, 8 parts of cerium-zirconium solid solution, 13 parts of spinel-type composite metal oxide, and 2 parts of carbide slag are mixed evenly, and the mixture is then ground to form denitrification agent A; preferably, the particle size of the ground mixture of denitrification agent A is ≤80μm (with a sieve residue of less than 14%), wherein the spinel composition is Co. 0.5 Co 0.5 Fe 0.6 Al 0.4 O4;

[0063] (2) Preparation of denitrification agent B: 5 parts of raw coal lumps and 8 parts of coal gangue are crushed into small particles of a certain size and mixed evenly with 2 parts of limestone powder to form denitrification agent B; after crushing, the particle size of coal lumps and coal gangue is 0.1-0.2 mm, and the particle size of limestone powder is ≤80 μm (screen residue less than 14%).

[0064] (3) Preparation of denitrification agent C: Mix 2 parts copper oxide with 1 part cerium oxide, 1 part lanthanum oxide and 1 part manganese dioxide evenly, then add 2 parts electrolytic manganese slag and 2 parts red mud and mix evenly, then grind to a certain particle size to form denitrification agent C; the powder size of denitrification agent C is ≤40μm (less than 8% sieve residue).

[0065] The mass fractions of denitrification agents A, B, and C are as follows: denitrification agent A is 2 parts, denitrification agent B is 3 parts, and denitrification agent C is 3 parts. The total mass fraction of denitrification agents A, B, and C is 0.5% of the raw meal mass.

[0066] The background emission concentration of nitrogen oxides at C1 outlet is 400 mg / Nm³. 3 After adding denitrification agents A, B, and C according to the above method, the nitrogen oxides in the exhaust gas decreased to 35 mg / Nm³. 3 .

[0067] Example 3

[0068] (1) Preparation of denitrification agent A: 4 parts of waste vanadium-based denitrification catalyst, 3 parts of cerium-zirconium solid solution, 11 parts of spinel-type composite metal oxide, and 1 part of carbide slag were mixed evenly and then ground to form denitrification agent A; the particle size after grinding was ≤80μm (less than 14% sieve residue), wherein the spinel composition was Co. 0.3 Zn 0.7 Fe 0.5 Al 0.5 O4;

[0069] (2) Preparation of denitrification agent B: Crush 3 parts of raw coal lumps and 5 parts of coal gangue into small particles of a certain size, and mix them evenly with 2 parts of limestone powder to form denitrification agent B; the particle size of the crushed coal lumps and coal gangue is 0.01~1mm, and the particle size of the limestone powder is ≤80μm (less than 14% sieve residue);

[0070] (3) Preparation of denitrification agent C: Mix 2 parts copper oxide with 1 part cerium oxide, 1 part cobalt oxide and 1 part iron oxide evenly, then add 2 parts electrolytic manganese slag and 1 part red mud and mix evenly, then grind to a certain particle size to form denitrification agent C; the powder size of denitrification agent C is ≤40μm (less than 8% sieve residue),

[0071] The mass fractions of denitrification agents A, B, and C are 1 part of denitrification agent A, 6 parts of denitrification agent B, and 1 part of denitrification agent C. The total mass fraction of denitrification agents A, B, and C is 0.3% of the raw meal mass.

[0072] The background emission concentration of nitrogen oxides at C1 outlet is 400 mg / Nm³. 3 After adding denitrification agents A, B, and C according to the above method, the nitrogen oxides in the exhaust gas decreased to 45 mg / Nm³. 3 .

[0073] The embodiments described above are only used to illustrate the technical ideas and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The patent scope of the present invention should not be limited by these embodiments. That is, all equivalent changes or modifications made in accordance with the spirit disclosed in the present invention still fall within the patent scope of the present invention.

Claims

1. A denitration method using CO in cement kiln flue gas as a reducing agent, characterized in that, It comprises the following steps: (1) mixing the denitration agent C with the coal powder uniformly, and adding it into the cement production system from the decomposing furnace; (2) adding the denitration agent B into the rear end of the decomposing furnace outlet; (3) mixing the denitration agent A with the raw material, and then grinding, and adding the mixed raw material from the connecting air pipe between the cyclone C1 and C2 at the kiln tail; The total denitration material accounts for 0.1‰-1% of the mass of the raw material, wherein, according to the mass fraction, the denitration agent A accounts for 1-2 parts, the denitration agent B accounts for 3-8 parts, and the denitration agent C accounts for 1-3 parts in the total denitration material; The preparation of the denitration agent A comprises uniformly mixing the crushed waste vanadium-based denitration catalyst, cerium-zirconium solid solution, carbide slag and spinel-type composite metal oxide according to a certain mass ratio, and then grinding to form the denitration agent A; The preparation of the denitration agent B comprises crushing the raw coal block and coal gangue into small particles of a certain size, uniformly mixing the small particles with limestone powder to form the denitration agent B; The preparation of the denitration agent C comprises uniformly mixing a certain mass of copper oxide with one or more of cerium oxide, zirconium oxide, lanthanum oxide, manganese dioxide, cobalt oxide and ferric oxide, and then adding electrolytic manganese slag and red mud, uniformly mixing and grinding to a certain particle size to form the denitration agent C; The particle size of the denitration agent A mixture after grinding is ≤80 μm, and the sieve residue is less than 14%. The A site of the spinel-type composite metal oxide is Co 2+ with Mg 2+ , Cu 2+ , Ni 2+ , Mn 2+ , Zn 2+ , Cd 2+ , or a combination of one or more of them; the B site is Fe 3+ with Al 3+ , Co 3+ , or a combination of one or more of them, wherein Co 2+ accounts for more than 20% of the A site, and Fe 3+ accounts for more than 30% of the B site.

2. The method according to claim 1, wherein the cement kiln flue gas is used as a reducing agent. According to the mass fraction, the waste vanadium-based denitration catalyst accounts for 2-5 parts, the spinel-type composite metal oxide accounts for 10-13 parts, the cerium-zirconium solid solution accounts for 2-8 parts, and the carbide slag accounts for 1-3 parts.

3. The method according to claim 1, wherein the cement kiln flue gas is used as a reducing agent for denitration. According to the mass fraction, the particle size of the crushed coal block and coal gangue is 0.01-1 mm, the particle size of the limestone powder is ≤80 μm, the sieve residue is less than 14%, the coal block particles account for 3-5 parts, the coal gangue particles account for 5-8 parts, and the limestone powder accounts for 1-2 parts.

4. The method according to claim 1, wherein the cement kiln flue gas is used as a reducing agent. According to the mass fraction, the particle size of the denitration agent C powder is ≤40 μm, the sieve residue is less than 8%, wherein the copper oxide accounts for 1-2 parts, the cerium oxide accounts for 0-1 part, the zirconium oxide accounts for 0-1 part, the lanthanum oxide accounts for 0-1 part, the manganese dioxide accounts for 0-1 part, the cobalt oxide accounts for 0-1 part, the ferric oxide accounts for 0-1 part, the electrolytic manganese slag accounts for 1-2 parts, and the red mud accounts for 1-2 parts.