Catalyst for coal combustion, preparation method and application

Abstract

The invention discloses a coal combustion catalyst as well as a preparation method and application thereof. The coal combustion catalyst comprises a carrier, an active agent, a desulfurizing agent and an auxiliary agent in percentage by weight, the carrier is prepared from 60%-70% of TiO2 and an anatase phase gt; 90%; the specific surface area is 80-120m / g; the average particle size D50 is 5-15 [mu] m; the pore volume is gt; 0.2 cm / g; the active agent is a mixture of 12%-20% of Fe2O3 and CuO, the desulfurizing agent adopts CaO with calcium acetate as a precursor and accounts for 8%-12%, and the auxiliary agent is a mixture of MnO2 and WO3 with the content smaller than or equal to 5%. Compared with pure coal combustion, the coal combustion stability can be enhanced by adding the catalyst under the action of promoting free radical chain reaction by manganese sesquioxide and copper oxide, and the temperature fluctuation of a hearth is reduced by 15-20% under the working condition of low load or inferior coal, so that the fire extinguishing risk is avoided; meanwhile, through catalytic oxidation of the catalyst, carbon monoxide can be further oxidized into carbon dioxide, so that the emission concentration of carbon monoxide is greatly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical and metallurgical industries, in particular to a catalyst added in flames for improving combustion and reducing harmful substance emissions, and specifically to a coal combustion catalyst, a preparation method and an application thereof. Background Art

[0002] The main existing applications of coal include power generation, steel smelting, chemical raw material production and heating. In terms of power generation, coal is the main fuel for thermal power generation, and it generates steam through combustion to drive turbines to generate electricity; in the steel industry, coal is made into coke through the coking process, which is used as a reducing agent and fuel in the blast furnace ironmaking and steelmaking process; the chemical industry uses coal through gasification or liquefaction technology to produce basic chemical raw materials such as synthetic ammonia, methanol, and olefins; in addition, coal is also directly used in industrial boilers, civil heating and other heating scenarios, especially in areas with high heating demand in winter. It plays an important role. At the same time, some high-quality anthracite is also used for special purposes such as the manufacture of activated carbon and carbon materials. Despite the rapid development of renewable energy, coal is still an important part of my country's energy structure. In general, the application of coal involves all aspects of industry and life; but there are two main prominent problems in the combustion process of coal: First, varying degrees of incomplete combustion and varying combustion stability occur under different conditions. Second, combustion inevitably produces and emits large amounts of harmful substances, including nitrogen oxides and sulfides. Since coal currently holds an irreplaceable position in various sectors of society, improving coal combustion stability while simultaneously reducing harmful emissions is an extremely pressing issue in the current coal application sector. Summary of the Invention

[0003] In order to solve the problems of how to more effectively reduce the emission of harmful substances generated by coal combustion and how to improve combustion stability, the present application provides a coal combustion catalyst, preparation method and application. Compared with the existing technology, the present invention mainly solves one of the following technical problems existing in existing coal combustion through technical improvements in the following aspects: 1. The present invention utilizes the quaternary system of Fe, Cu, Mn and CaO to achieve combustion acceleration through the synergistic effect of components, while also solving the problem of integrated desulfurization. Compared with the existing single additive that cannot take into account both efficiency and environmental protection, it has a significant improvement.

[0004] 2. The present invention adopts an innovative nano-process, combined with ultrasonic assistance and ball milling to prepare CaO with a particle size of less than 100nm, which significantly improves the desulfurization activity and specifically solves the problem of low utilization rate of traditional calcium-based desulfurizers.

[0005] 3. The present invention adopts WO3 modified TiO2 carrier, and the specific surface area can reach or even exceed 35m after calcination at 750℃. 2 / g, with strong structural stability, which solves the problem that existing catalysts or additives are prone to sintering and causing catalytic failure in high-temperature environments with temperatures greater than 900°C.

[0006] 4. The present invention also specifically provides the optimal application scenario of the catalyst, so as to maximize the efficiency of the catalyst to improve the energy conservation and emission reduction efficiency of coal combustion. The present invention innovatively proposes a dual mode of adapting CFB bed material addition and coal powder micro-blending, which can not only play a catalytic role in the combustion process, but also play a role in treating harmful gases in the combustion emission stage.

[0007] 5. The present invention creatively proposes a technology combining the sulfur resistance of anatase TiO2 with the alkali metal poisoning resistance of WO3 to solve the problem of rapid catalyst deactivation and loss of catalytic effect caused by K / Na / S in existing coal ash.

[0008] In order to achieve the above objectives, the technical solutions adopted in this application are: A coal combustion catalyst comprises, in weight percentage, a carrier, an activator, a desulfurizer, and an auxiliary agent; the carrier is 60%-70% TiO2, with an anatase phase of >90%; the specific surface area is 80-120 m² / g; the average particle size D50 is 5-15 μm; and the pore volume is >0.2 cm³ / g; the activator is a mixture of Fe2O3 and CuO of 12%-20%, the desulfurizer uses CaO whose precursor is calcium acetate, accounting for 8%-12%, and the auxiliary agent is a mixture of MnO2 and WO3 of ≤5%.

[0009] In order to further optimize the carrier, preferably, the carrier also includes or is replaced by one or more of γ-Al2O3, CeO2, and composite carriers / modified carriers TiO2-Al2O3, CeO2-TiO2, CeO2-ZrO2; the active agent also includes or is replaced by one or more of copper oxide, manganese oxide, alkali metal oxide and precious metal, and the precious metal is Pt and / or Pd; the auxiliary agent also includes or is replaced by one or more of MoO3, ZrO2, K, Na.

[0010] The present invention also provides a catalyst preparation method for preparing the catalyst of the above volume, which specifically comprises the following steps: Step STP100, pre-dispersion of the nanoprecursor: dissolving the TiO2 carrier and Ca(CH3COO)2·H2O in a predetermined ratio, adding deionized water, heating to 60°C, and stirring for 30 minutes; after sufficient wetting and dispersion, dripping the mixture into the TiO2 suspension at a rate of 1-2 ml / min, maintaining a constant temperature and stirring for at least 60 minutes; ultrasonically cleaning the suspension and filtering it in a vacuum filtration apparatus; and drying the obtained filter cake to obtain a TiO2-loaded Ca(CH2COO)2 powder, denoted as Ti-CaA; Step STP200, stepwise impregnation of the active agent, weighing Fe(NO3)3·9H2O, Cu(NO3)2·3H2O, Mn(NO3)2·4H2O or 50% Mn(NO3)2 solution and (NH4)6H2W according to the preset mass parts. 12 A mixed salt consisting of O40·xH2O is dissolved in deionized water to obtain a mixed solution; the obtained mixed solution is then evenly dropped onto the Ti-CaA powder obtained and stirred in step STP100 at a rate of 1 ml / min in an equal volume impregnation manner. After the dropwise addition is completed, the mixture is sealed and allowed to stand for aging for 4 hours, and then dried to obtain a powder loaded with all active component precursors, which is recorded as FCMCa; Step STP300, high-energy ball milling dispersion and homogenization: the dried FCMCa powder was ground and passed through a 200-mesh sieve. The sieved powder was placed in a zirconia ball mill and ball-milled with anhydrous ethanol as the grinding medium. After ball milling, the slurry was vacuum filtered through a 0.45 μm filter and the filter cake was washed with a small amount of anhydrous ethanol. The filter cake was first dried at 80°C for 4 hours. Step STP400, programmed temperature calcination, the dried powder is placed in a corundum crucible, and then placed in a programmable temperature muffle furnace for programmable temperature calcination activation, and after calcination, it is ground and passed through a 200 mesh sieve to obtain a finished catalyst.

[0011] As one of the optimization methods for the preparation process, the pre-dispersion step of the STP100 nano precursor specifically includes: Step STP110, weighing and dissolving: weigh 70 g of the TiO2 carrier into a 500 ml three-necked flask, weigh 16.7 g of calcium acetate monohydrate Ca(CH3COO)2·H2O, dissolve it in 150 ml of deionized water, and stir until completely transparent; Step STP120, pre-wetting the support: add 100 ml of deionized water to the three-necked flask containing TiO2, turn on magnetic stirring, and heat the water bath to 60°C. Continue stirring for 30 minutes to fully wet and disperse the TiO2; Step STP130, nanodispersion and loading: pour the dissolved calcium acetate solution into a dropping funnel and slowly add the calcium acetate solution dropwise to the stirring TiO2 suspension at a rate of 1-2 ml / min. After the addition is complete, maintain the mixture in a 60°C water bath and continue vigorous stirring for 2 hours. Step STP140, ultrasonic treatment, transferring the suspension to a suitable container, placing it in an ultrasonic cleaner at 60°C, and ultrasonically treating it at a power of not less than 10 kW for 1 hour in an intermittent operation manner; In step STP150, the hot suspension is vacuum filtered using a 0.45 μm microporous filter membrane and the filter cake is washed multiple times with 200 ml of deionized water at 60°C to remove residual acetate ions. The filtrate is tested with silver nitrate solution until no chloride ion reaction or obvious white precipitate is observed. Step STP160, preliminary drying, transfer the filter cake to a watch glass, place it in a constant temperature drying oven, and dry it at 110°C for 12 hours to obtain TiO2 loaded with Ca(CH3COO)2 powder, recorded as Ti-CaA.

[0012] As one of the means of optimizing the preparation process, the stepwise impregnation of the STP200 active agent specifically includes: Step STP210, prepare a mixed salt solution by weighing 19.5g of Fe(NO3)3•9H2O, 19.5g of Cu(NO3)2•3H2O, 7.0g of Mn(NO3)2•4H2O or 4.6g of 50% Mn(NO3)2 solution and 1.3g of (NH4)6H2W 12 O 40 • A mixed salt composed of xH2O; dissolve the above salts in a total of 100 ml of deionized water. If using Mn solution, of course, the amount of water needs to be reduced accordingly. Stir until completely dissolved to obtain a clear or slightly turbid mixed solution; Step STP220, equal volume impregnation: Place 80 g of dried Ti-CaA powder into a 1000 ml three-necked flask; add water dropwise to another 3-5 g of Ti-CaA powder until just saturated with free water. Calculate the water absorption per unit mass of the Ti-CaA powder. Calculate the required volume V of the mixed salt solution based on the mass of the Ti-CaA powder and the measured pore volume. Using a dropping funnel or pipette, add volume V of the mixed salt solution dropwise to the Ti-CaA powder under continuous and gentle stirring at a rate of approximately 1 ml / min, with the temperature below 50°C. Step STP230, aging and drying. After the addition is completed, seal the bottle mouth with a sealing film and let it stand at room temperature for aging for 4 hours. Transfer the wet material to a watch glass, place it in a drying oven, dry it at 80°C for 6 hours, and then dry it at 110°C for 12 hours to obtain a powder loaded with all active component precursors, recorded as FCMCa.

[0013] As one of the means of optimizing the preparation process, the STP300 high-energy ball milling dispersion and homogenization step specifically includes: Step STP310, ball milling pretreatment, gently grind the dried FCMCa powder, pass it through a 200 mesh sieve, weigh 100 g of the sieved FCMCa powder and place it in a zirconia ball mill, add zirconia grinding balls, and then add 50 ml of anhydrous ethanol as a grinding medium, wherein the zirconia grinding balls account for 30% of the 10 mm diameter balls, 40% of the 5 mm balls, and 30% of the 3 mm balls, with a total ball-to-material ratio of 10:1; Step STP320, ball milling parameters are set, using a planetary ball mill with a rotation speed of 300 rpm, a ball milling time of 2 hours, alternating forward and reverse rotations, and reversing the direction every 15 minutes, or using a drum ball mill with a rotation speed of 60% of the critical speed for 24 hours; Step STP330, ball milling post-processing, after the ball milling is completed, the slurry is poured out, the ball mill jar and grinding balls are rinsed with an appropriate amount of anhydrous ethanol, the rinse liquid is combined, and the slurry is then vacuum filtered under 0.45 μm membrane conditions, and the filter cake is washed with a small amount of anhydrous ethanol. The filter cake is dried at 80°C for 4 hours.

[0014] As one of the optimization methods for the preparation process, the STP400 programmed temperature controlled calcination step specifically includes: Step STP410, placing the dried powder in a corundum crucible, spreading it into a thin layer less than 1 cm thick, and then placing it in a programmable temperature-controlled muffle furnace; Step STP420, roasting program setting, three-stage temperature rise setting: Stage 1 heating, room temperature - 250°C: heating rate 2°C / min, hold at 250°C for 2 hours; Second stage heating, 250°C - 550°C: heating rate 5°C / min, hold at 550°C for 3 hours; Three-stage heating, 550°C - target roasting temperature: heating rate 3°C / min; the target roasting temperature T can be set to either: T = 650°C, constant temperature for 4 hours or T = 750°C, constant temperature for 4 hours. After the roasting process is completed, turn off the power to the muffle furnace and let the furnace temperature naturally drop to below 200°C. Then open the furnace door and let it cool naturally to room temperature. Step STP430, final treatment, takes out the calcined catalyst block, grinds it lightly in a mortar, and passes it through a 200 mesh sieve to obtain the final catalyst.

[0015] The catalyst provided by the present invention has different performance in different application combustion environments. In order to better utilize the catalyst in reducing emissions and improving stability during coal combustion, the present invention also provides an application of the catalyst in reducing pollutant emissions. The catalyst is added to the furnace continuously or in batches together with fresh bed material or limestone at a ratio of 0.5-3 wt% of the total bed material of the CFB boiler.

[0016] As another preferred application of the present invention, the catalyst is uniformly mixed into the coal powder airflow at the coal mill outlet or before the coal powder feeder through a precision feeding device at a ratio of 0.1-0.5 wt% of the weight of the coal powder fed into the furnace.

[0017] Preferably, a high-temperature resistant catalytic element is arranged in the 700-900°C area in the furnace, and the catalytic element is an integral honeycomb ceramic carrier loaded with catalyst; at the same time, a catalytic reactor loaded with catalyst is set in the flue with a temperature of 300-400°C after the economizer and before the air preheater.

[0018] Still more preferably, a high-temperature resistant catalytic element is arranged in the 700-900°C area in the furnace, and the catalytic element is an integral honeycomb ceramic carrier loaded with catalyst; at the same time, a catalytic reactor loaded with catalyst is set in the flue with a temperature of 300-400°C after the economizer and before the air preheater.

[0019] Beneficial effects: 1. By adding the catalyst of the present invention, manganese trioxide and copper oxide promote the free radical chain reaction, the coal combustion stability can be enhanced compared to the combustion of pure coal. Under low load or low-quality coal conditions, the furnace temperature fluctuation is reduced by 15-20%, avoiding the risk of fire extinguishing. At the same time, through the catalytic oxidation of the catalyst, carbon monoxide can be further oxidized into carbon dioxide, which greatly reduces the emission concentration of carbon monoxide.

[0020] 2. The catalyst provided by the present invention can significantly reduce the ignition temperature of coal coke, reducing the ignition temperature of existing coal coke at 280℃-500℃ by about 75-100℃, and shortening the burnout time of the same mass of coal coke by 25%-38%. At the same time, under the action of the activator, it further catalyzes the carbon gasification reaction, further reduces the carbon content of fly ash, and improves combustion efficiency and calorific value.

[0021] 3. The use of nano-calcium oxide with a high specific surface area can efficiently capture sulfur dioxide gas produced by coal combustion, significantly increasing the original odor removal rate of sulfur dioxide; at the same time, under the catalysis of manganese dioxide, it can convert nitrogen monoxide into nitrogen dioxide, promoting subsequent SCR reduction, thereby reducing the generated nitrogen oxides into harmless nitrogen and water. The chemical reaction process is more thorough and reduces nitrogen oxide emissions.

[0022] 4. By adding the catalyst provided by the present invention, the burnout degree of coal is improved, so that the coal consumption can be effectively reduced by 2-4% when completing the same heating project. The use of high-utilization nano-calcium oxide can significantly reduce the amount of desulfurizer used compared to traditional limestone. Pre-desulfurization in the furnace can effectively reduce the tail FGD load and reduce the consumption of limestone slurry. Furthermore, since the carbon content of fly ash is greatly reduced, it can meet the standards of building materials raw materials, so that fly ash can be recycled, achieving the economic effect of turning waste into treasure, reducing costs and increasing efficiency. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0024] Example 1: A coal combustion catalyst comprises, in weight percentage, a carrier, an activator, a desulfurizer, and an auxiliary agent; the carrier is 60%-70% TiO2, with an anatase phase of >90%; the specific surface area is 80-120 m² / g; the average particle size D50 is 5-15 μm; and the pore volume is >0.2 cm³ / g; the activator is a mixture of Fe2O3 and CuO of 12%-20%, the desulfurizer uses CaO whose precursor is calcium acetate, accounting for 8%-12%, and the auxiliary agent is a mixture of MnO2 and WO3 of ≤5%.

[0025] Example 2: In this embodiment, the content ratio of each component is optimized based on Example 1. Specifically, the proportions of the carrier, activator, desulfurizer and auxiliary agent are adjusted to 70% TiO2, 12% Fe2O3 and 5% CuO, 10% CaO, 2% MnO2 and 1% WO3, respectively. The other formulas are not changed.

[0026] Example 3: In order to further optimize the carrier, in this embodiment, based on Example 1 or 2, the carrier also includes or is replaced by one or more of γ-Al2O3, CeO2, and composite carriers / modified carriers TiO2-Al2O3, CeO2-TiO2, and CeO2-ZrO2; the active agent also includes or is replaced by one or more of copper oxide, manganese oxide, alkali metal oxide and precious metal, and the precious metal is Pt and / or Pd; the auxiliary agent also includes or is replaced by one or more of MoO3, ZrO2, K, and Na.

[0027] Example 3: The present invention also provides a catalyst preparation method for preparing the catalyst of the above volume, which specifically comprises the following steps: Step STP100, pre-dispersion of the nanoprecursor: dissolving the TiO2 carrier and Ca(CH3COO)2·H2O in a predetermined ratio, adding deionized water, heating to 60°C, and stirring for 30 minutes; after sufficient wetting and dispersion, dripping the mixture into the TiO2 suspension at a rate of 1-2 ml / min, maintaining a constant temperature and stirring for at least 60 minutes; ultrasonically cleaning the suspension and filtering it in a vacuum filtration apparatus; and drying the obtained filter cake to obtain a TiO2-loaded Ca(CH2COO)2 powder, denoted as Ti-CaA; Step STP200, stepwise impregnation of the active agent, weighing Fe(NO3)3·9H2O, Cu(NO3)2·3H2O, Mn(NO3)2·4H2O or 50% Mn(NO3)2 solution and (NH4)6H2W according to the preset mass parts. 12 A mixed salt consisting of O40·xH2O is dissolved in deionized water to obtain a mixed solution; the obtained mixed solution is then evenly dropped onto the Ti-CaA powder obtained and stirred in step STP100 at a rate of 1 ml / min in an equal volume impregnation manner. After the dropwise addition is completed, the mixture is sealed and allowed to stand for aging for 4 hours, and then dried to obtain a powder loaded with all active component precursors, which is recorded as FCMCa; Step STP300, high-energy ball milling dispersion and homogenization: the dried FCMCa powder was ground and passed through a 200-mesh sieve. The sieved powder was placed in a zirconia ball mill and ball-milled with anhydrous ethanol as the grinding medium. After ball milling, the slurry was vacuum filtered through a 0.45 μm filter and the filter cake was washed with a small amount of anhydrous ethanol. The filter cake was first dried at 80°C for 4 hours. Step STP400, programmed temperature calcination, the dried powder is placed in a corundum crucible, and then placed in a programmable temperature muffle furnace for programmable temperature calcination activation, and after calcination, it is ground and passed through a 200 mesh sieve to obtain a finished catalyst.

[0028] Example 4: This embodiment refines the step STP100 based on the embodiment 3. Specifically, the pre-dispersion step of the nano-precursor comprises: Step STP110, weighing and dissolving: weigh 70 g of the TiO2 carrier into a 500 ml three-necked flask, weigh 16.7 g of calcium acetate monohydrate Ca(CH3COO)2·H2O, dissolve it in 150 ml of deionized water, and stir until completely transparent; Step STP120, pre-wetting the support: add 100 ml of deionized water to the three-necked flask containing TiO2, turn on magnetic stirring, and heat the water bath to 60°C. Continue stirring for 30 minutes to fully wet and disperse the TiO2; Step STP130, nanodispersion and loading: pour the dissolved calcium acetate solution into a dropping funnel and slowly add the calcium acetate solution dropwise to the stirring TiO2 suspension at a rate of 1-2 ml / min. After the addition is complete, maintain the mixture in a 60°C water bath and continue vigorous stirring for 2 hours. Step STP140, ultrasonic treatment, transferring the suspension to a suitable container, placing it in an ultrasonic cleaner at 60°C, and ultrasonically treating it at a power of not less than 10 kW for 1 hour in an intermittent operation manner; In step STP150, the hot suspension is vacuum filtered using a 0.45 μm microporous filter membrane and the filter cake is washed multiple times with 200 ml of deionized water at 60°C to remove residual acetate ions. The filtrate is tested with silver nitrate solution until no chloride ion reaction or obvious white precipitate is observed. Step STP160, preliminary drying, transfer the filter cake to a watch glass, place it in a constant temperature drying oven, and dry it at 110°C for 12 hours to obtain TiO2 loaded with Ca(CH3COO)2 powder, recorded as Ti-CaA.

[0029] Example 5: This embodiment further refines step STP200 based on embodiment 3 or embodiment 4. Specifically, the stepwise impregnation of the active agent includes: Step STP210, prepare a mixed salt solution by weighing 19.5g of Fe(NO3)3•9H2O, 19.5g of Cu(NO3)2•3H2O, 7.0g of Mn(NO3)2•4H2O or 4.6g of 50% Mn(NO3)2 solution and 1.3g of (NH4)6H2W 12 O 40 • A mixed salt composed of xH2O; dissolve the above salt in a total of 100 ml of deionized water (if using Mn solution, the amount of water needs to be reduced accordingly), and stir until completely dissolved to obtain a clear or slightly turbid mixed solution; Step STP220, equal volume impregnation: Place 80 g of dried Ti-CaA powder into a 1000 ml three-necked flask; add water dropwise to another 3-5 g of Ti-CaA powder until just saturated with free water. Calculate the water absorption per unit mass of the Ti-CaA powder. Calculate the required volume V of the mixed salt solution based on the mass of the Ti-CaA powder and the measured pore volume. Using a dropping funnel or pipette, add volume V of the mixed salt solution dropwise to the Ti-CaA powder under continuous and gentle stirring at a rate of approximately 1 ml / min, with the temperature below 50°C. Step STP230, aging and drying. After the addition is completed, seal the bottle mouth with a sealing film and let it stand at room temperature for aging for 4 hours. Transfer the wet material to a watch glass, place it in a drying oven, dry it at 80°C for 6 hours, and then dry it at 110°C for 12 hours to obtain a powder loaded with all active component precursors, recorded as FCMCa.

[0030] Example 6: This embodiment further optimizes the step STP300 based on any of the embodiments 3 to 5. Specifically, the high-energy ball milling dispersion and homogenization step includes: Step STP310, ball milling pretreatment, gently grind the dried FCMCa powder, pass it through a 200 mesh sieve, weigh 100 g of the sieved FCMCa powder and place it in a zirconia ball mill, add zirconia grinding balls, and then add 50 ml of anhydrous ethanol as a grinding medium, wherein the zirconia grinding balls account for 30% of the 10 mm diameter balls, 40% of the 5 mm balls, and 30% of the 3 mm balls, with a total ball-to-material ratio of 10:1; Step STP320, ball milling parameters are set, using a planetary ball mill with a rotation speed of 300 rpm, a ball milling time of 2 hours, alternating forward and reverse rotations, and reversing the direction every 15 minutes, or using a drum ball mill with a rotation speed of 60% of the critical speed for 24 hours; Step STP330, ball milling post-processing, after the ball milling is completed, the slurry is poured out, the ball mill jar and grinding balls are rinsed with an appropriate amount of anhydrous ethanol, the rinse liquid is combined, and the slurry is then vacuum filtered under 0.45 μm membrane conditions, and the filter cake is washed with a small amount of anhydrous ethanol. The filter cake is dried at 80°C for 4 hours.

[0031] Example 7: This embodiment further optimizes the step STP400 based on any of the embodiments 3 to 6. Specifically, the programmed temperature controlled roasting step includes: Step STP410, placing the dried powder in a corundum crucible, spreading it into a thin layer less than 1 cm thick, and then placing it in a programmable temperature-controlled muffle furnace; Step STP420, roasting program setting, three-stage temperature rise setting: Stage 1 heating, room temperature - 250°C: heating rate 2°C / min, hold at 250°C for 2 hours; Second stage heating, 250°C - 550°C: heating rate 5°C / min, hold at 550°C for 3 hours; Three-stage heating, 550°C - target roasting temperature: heating rate 3°C / min; the target roasting temperature T can be set to either: T = 650°C, constant temperature for 4 hours or T = 750°C, constant temperature for 4 hours. After the roasting process is completed, turn off the power to the muffle furnace and let the furnace temperature naturally drop to below 200°C. Then open the furnace door and let it cool naturally to room temperature. Step STP430, final treatment, takes out the calcined catalyst block, grinds it lightly in a mortar, and passes it through a 200 mesh sieve to obtain the final catalyst.

[0032] Example 8: The catalyst provided by the present invention has different performance in different application combustion environments. In order to better utilize the catalyst in reducing emissions and improving stability during coal combustion, the present invention also provides an application of the catalyst in reducing pollutant emissions. The catalyst is added to the furnace continuously or in batches together with fresh bed material or limestone at a ratio of 0.5-3 wt% of the total bed material of the CFB boiler.

[0033] Example 9: This embodiment is another preferred application of the present invention. The catalyst is evenly mixed into the coal powder airflow at the coal mill outlet or before the coal powder feeder through a precision feeding device at a ratio of 0.1-0.5 wt% of the weight of the coal powder entering the furnace.

[0034] Example 10: In addition to Example 8, this embodiment also includes arranging a high-temperature resistant catalytic element in the 700-900°C area in the furnace, wherein the catalytic element is an integral honeycomb ceramic carrier loaded with a catalyst; at the same time, a catalytic reactor loaded with a catalyst is set in the flue with a temperature of 300-400°C after the economizer and before the air preheater.

[0035] Example 11: In addition to Example 9, this embodiment also includes arranging a high-temperature resistant catalytic element in the 700-900°C area in the furnace, wherein the catalytic element is an integral honeycomb ceramic carrier loaded with catalyst; at the same time, a catalytic reactor loaded with catalyst is set in the flue with a temperature of 300-400°C after the economizer and before the air preheater.

[0036] Example 12: Although the above has objectively and fully theoretically deduced and explained the technical effects of the catalyst components, preparation methods, and effective active ingredients of the present invention, in order to further demonstrate that the technical effects of the catalyst of the present invention are significantly superior to those of existing catalysts, an experimental group was established in this example to conduct the following experiments: Experimental Group 1: The catalyst provided in Example 2 was used to simulate the working conditions of a pulverized coal furnace, and a trace amount of pulverized coal was added; Experimental Group 2: The catalyst provided in Example 2 was used to simulate the CFB boiler operating conditions and was added by mixing with the bed material; Control group: blank combustion without any additives; Existing technology group: using commercially available catalysts: specifically the composite coal-saving agent sold by Hebei Huashun Chemical Co., Ltd., denoted as coal-saving agent; and the SCR denitrification catalyst sold by Jiangxi Hanming Environmental Protection Technology Co., Ltd., denoted as denitrification catalyst, and mixed and added in a weight ratio of 1:1.

[0037] Experimental Standards: Coal char was prepared according to GB / T 30732-2014, "Methods for Industrial Analysis of Coal." Combustion kinetic parameters were determined using thermogravimetric analysis (TGA) according to ISO 11358:2014. Tested coal type: Shenhua bituminous coal pyrolyzed at 900°C for 30 minutes in a nitrogen atmosphere to produce finished char.

[0038] Experimental process: Take several samples of finished 200-mesh coal coke and divide them into 4 parts of the same mass for later use.

[0039] Experimental group 1: coal coke + 0.3 wt% catalyst of Example 2; Experimental group 2: coal char + 1.5 wt% catalyst of Example 2; Control group: pure coal char; Existing technology group: coal coke + 1.5 wt% coal-saving agent + 1.5 wt% denitrification catalyst; TGA test parameters: Instrument: NETZSCH STA 449 F5 Atmosphere: air (flow rate: 50 mL / min); heating program: room temperature → 1000°C, heating rate 10°C / min; sample size: 10.0 ± 0.1 mg.

[0040] Key data extraction: Ignition temperature: the temperature corresponding to 5% weight loss T5%, marking the start of combustion; Burnout temperature: the temperature corresponding to 95% weight loss T 95 %; Burnout time: T5% to T 95 % of the time interval Δt.

[0041] The experimental results are shown in Table 1 below. Table 1 is a comparison of the parameters of each experimental group. Preliminary conclusions show that the catalyst provided in Example 2 can reduce the ignition temperature by 75–82°C and shorten the burnout time by 39.9–42.6% compared to the control group; significantly better than the prior art group.

[0042] Example 13: This example follows the same grouping and experimental group ratios as in Example 12. Experimental Groups 1 and 2 were tested in the pulverized coal boiler and CFB application scenarios, respectively. The pulverized coal boiler experiments were conducted in accordance with GB / T 10184-2020, "Procedure for Performance Test of Power Plant Boilers"; the CFB boiler experiments were conducted in accordance with DL / T 1106-2020, "Procedure for Performance Test of Circulating Fluidized Bed Boilers." Experimental Group 1 used Shenhua bituminous coal, while Experimental Group 2 used Shanxi high-sulfur coal.

[0043] Experimental procedure summary: Boiler load: 100% rated load; Excess air coefficient: 1.25 for CFB furnaces and 1.20 for pulverized coal furnaces; Combustion temperature: 860–880°C for CFB furnaces and 1100–1200°C for pulverized coal furnaces. Catalyst addition methods were as follows: Experimental Group 1 used 0.3 wt% of the catalyst from Example 2 mixed into the pulverized coal at the pulverizer outlet; Experimental Group 2 used 1.5 wt% of the catalyst from Example 2; In the conventional technology group, a 1.5 wt% coal-saving agent was injected into the burner in the pulverized coal furnace; and in the CFB furnace, a 1.5 wt% denitrification catalyst was injected into the return leg. The control group did not use any additives.

[0044] Data Collection: Fly ash / slag carbon content was sampled every 30 minutes and determined according to the loss on ignition method specified in GB / T 35986-2018. CO concentration was monitored in real time using a Siemens LDS6 laser gas analyzer, with the average value taken during the stable period. SO2 concentration was analyzed using a Gasmet DX4000 UV differential absorption spectrometer. Temperature fluctuations were measured using a K-type thermocouple in the middle of the furnace with a frequency of 1 Hz, and the standard deviation σ of the temperature fluctuation over a 30-minute period was calculated. The following test results were obtained: Table 2 Comparison of fly ash carbon content Table 3 Pollutant emission reduction and temperature stability Table 4 In-situ sulfur dioxide removal rate Table 5 Temperature fluctuation (σ) Preliminary experimental conclusions: Tables 2-5 above show that the catalyst provided in Example 2 reduced the carbon content of CFB fly ash from 12.1% to 6.3%, an overall decrease of 47.9%; and in pulverized coal furnaces, from 7.5% to 4.9%, an overall decrease of 34.7%. CO emissions decreased by 56–58%, with an in-situ SO2 removal rate exceeding 58%. Furnace temperature fluctuations were reduced by 19–20%, and combustion stability was significantly improved. The SO2 removal rate in Experimental Group 2 reached 58.3%, far exceeding the 41.2% in the prior art group. This demonstrates that the ultrasonic-combined ball milling process significantly improves calcium utilization and the efficient desulfurization capability of nano-CaO. Experimental Group 1 reduced CO emissions by 56.7% in the pulverized coal furnace, while the prior art group only achieved a reduction of 18.7%, validating the synergistic oxidation capability of the Fe-Cu-Mn oxides. Furthermore, the standard deviation of furnace temperature decreased by over 19%, confirming the stabilizing effect of MnO2 on free radical reactions, significantly suppressing temperature fluctuations and improving coal combustion stability.

[0045] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for preparing a catalyst for coal combustion, characterized in that: The steps include: Step STP100, pre-dispersion of the nanoprecursor: dissolving the TiO2 carrier and Ca(CH3COO)2·H2O in a predetermined ratio, adding deionized water, heating to 60°C, and stirring for 30 minutes; after sufficient wetting and dispersion, dripping the mixture into the TiO2 suspension at a rate of 1-2 ml / min, maintaining a constant temperature and stirring for at least 60 minutes; ultrasonically cleaning the suspension and filtering it in a vacuum filtration apparatus; and drying the obtained filter cake to obtain a TiO2-loaded Ca(CH2COO)2 powder, denoted as Ti-CaA; Step STP200, stepwise impregnation of the active agent, weighing Fe(NO3)3·9H2O, Cu(NO3)2·3H2O, Mn(NO3)2·4H2O or 50% Mn(NO3)2 solution and (NH4)6H2W according to the preset mass parts. 12 A mixed salt consisting of O40·xH2O is dissolved in deionized water to obtain a mixed solution; the obtained mixed solution is then evenly dropped onto the Ti-CaA powder obtained and stirred in step STP100 at a rate of 1 ml / min in an equal volume impregnation manner. After the dropwise addition is completed, the mixture is sealed and allowed to stand for aging for 4 hours, and then dried to obtain a powder loaded with all active component precursors, which is recorded as FCMCa; Step STP300, high-energy ball milling dispersion and homogenization: the dried FCMCa powder was ground and passed through a 200-mesh sieve. The sieved powder was placed in a zirconia ball mill and ball-milled with anhydrous ethanol as the grinding medium. After ball milling, the slurry was vacuum filtered through a 0.45 μm filter and the filter cake was washed with a small amount of anhydrous ethanol. The filter cake was first dried at 80°C for 4 hours. Step STP400, programmed temperature calcination, the dried powder is placed in a corundum crucible, and then placed in a programmable temperature muffle furnace for programmable temperature calcination activation, and after calcination, it is ground and passed through a 200 mesh sieve to obtain a finished catalyst.

2. A method for preparing a catalyst according to claim 1, characterized in that: The pre-dispersion step of the STP100 nano precursor specifically includes: Step STP110, weighing and dissolving: weigh 70 g of the TiO2 carrier into a 500 ml three-necked flask, weigh 16.7 g of calcium acetate monohydrate Ca(CH3COO)2·H2O, dissolve it in 150 ml of deionized water, and stir until completely transparent; Step STP120, pre-wetting the support: add 100 ml of deionized water to the three-necked flask containing TiO2, turn on magnetic stirring, and heat the water bath to 60°C. Continue stirring for 30 minutes to fully wet and disperse the TiO2; Step STP130, nanodispersion and loading: pour the dissolved calcium acetate solution into a dropping funnel and slowly add the calcium acetate solution dropwise to the stirring TiO2 suspension at a rate of 1-2 ml / min. After the addition is complete, maintain the mixture in a 60°C water bath and continue vigorous stirring for 2 hours. Step STP140, ultrasonic treatment, transferring the suspension to a suitable container, placing it in an ultrasonic cleaner at 60°C, and ultrasonically treating it at a power of not less than 10 kW for 1 hour in an intermittent operation manner; In step STP150, the suspension is vacuum filtered while hot, and the filter cake is washed multiple times with 200 ml of deionized water at 60° C. using a 0.45 μm microporous filter membrane to remove residual acetate ions. The filtrate is tested with a silver nitrate solution until no chloride ion reaction or obvious white precipitate is observed. Step STP160, preliminary drying, transfer the filter cake to a watch glass, place it in a constant temperature drying oven, and dry it at 110°C for 12 hours to obtain TiO2 loaded with Ca(CH3COO)2 powder, recorded as Ti-CaA.

3. A method for preparing a catalyst according to claim 1, characterized in that: The stepwise impregnation of the STP200 active agent specifically includes: Step STP210, prepare a mixed salt solution by weighing 19.5g of Fe(NO3)3•9H2O, 19.5g of Cu(NO3)2•3H2O, 7.0g of Mn(NO3)2•4H2O or 4.6g of 50% Mn(NO3)2 solution and 1.3g of (NH4)6H2W 12 O 40 • A mixed salt composed of xH2O; dissolve the above salt in a total of 100 ml of deionized water and stir until completely dissolved to obtain a clear or slightly turbid mixed solution; Step STP220, equal volume impregnation: Place 80 g of dried Ti-CaA powder into a 1000 ml three-necked flask; add water dropwise to another 3-5 g of Ti-CaA powder until just saturated with free water. Calculate the water absorption per unit mass of the Ti-CaA powder. Calculate the required volume V of the mixed salt solution based on the mass of the Ti-CaA powder and the measured pore volume. Using a dropping funnel or pipette, add volume V of the mixed salt solution dropwise to the Ti-CaA powder under continuous and gentle stirring at a rate of approximately 1 ml / min, with the temperature below 50°C. Step STP230, aging and drying. After the addition is completed, seal the bottle mouth with a sealing film and let it stand at room temperature for aging for 4 hours. Transfer the wet material to a watch glass, place it in a drying oven, dry it at 80°C for 6 hours, and then dry it at 110°C for 12 hours to obtain a powder loaded with all active component precursors, recorded as FCMCa.

4. A method for preparing a catalyst according to claim 1, characterized in that: The STP300 high-energy ball milling dispersion and homogenization step specifically includes: Step STP310, ball milling pretreatment, gently grind the dried FCMCa powder, pass it through a 200 mesh sieve, weigh 100 g of the sieved FCMCa powder and place it in a zirconia ball mill, add zirconia grinding balls, and then add 50 ml of anhydrous ethanol as a grinding medium, wherein the zirconia grinding balls account for 30% of the 10 mm diameter balls, 40% of the 5 mm balls, and 30% of the 3 mm balls, with a total ball-to-material ratio of 10:1; Step STP320, ball milling parameters are set, using a planetary ball mill with a rotation speed of 300 rpm, a ball milling time of 2 hours, alternating forward and reverse rotations, and reversing the direction every 15 minutes, or using a drum ball mill with a rotation speed of 60% of the critical speed for 24 hours; Step STP330, ball milling post-processing, after the ball milling is completed, the slurry is poured out, the ball mill jar and grinding balls are rinsed with an appropriate amount of anhydrous ethanol, the rinse liquid is combined, and the slurry is then vacuum filtered under 0.45 μm membrane conditions, and the filter cake is washed with a small amount of anhydrous ethanol. The filter cake is dried at 80°C for 4 hours.

5. A method for preparing a catalyst according to claim 1, characterized in that: The step STP400 of programmed temperature controlled roasting specifically includes: Step STP410, placing the dried powder in a corundum crucible, spreading it into a thin layer less than 1 cm thick, and then placing it in a programmable temperature-controlled muffle furnace; Step STP420, roasting program setting, three-stage temperature rise setting: Stage 1 heating, room temperature - 250°C: heating rate 2°C / min, hold at 250°C for 2 hours; Second stage heating, 250°C - 550°C: heating rate 5°C / min, hold at 550°C for 3 hours; Three-stage heating, 550°C - target roasting temperature: heating rate 3°C / min; the target roasting temperature T can be set to either: T = 650°C, constant temperature for 4 hours or T = 750°C, constant temperature for 4 hours. After the roasting process is completed, turn off the power to the muffle furnace and let the furnace temperature naturally drop to below 200°C. Then open the furnace door and let it cool naturally to room temperature. Step STP430, final treatment, takes out the calcined catalyst block, grinds it lightly in a mortar, and passes it through a 200 mesh sieve to obtain the final catalyst.

6. A coal combustion catalyst, prepared by the catalyst preparation method according to any one of claims 1 to 5, characterized in that: Its components and contents specifically include a carrier, an active agent, a desulfurizer and an auxiliary agent in percentage by weight; the carrier is 60%-70% TiO2, with an anatase phase >90%; the specific surface area is 80-120m² / g; the average particle size D50 is 5-15μm; the pore volume is >0.2cm³ / g; the active agent is a mixture of Fe2O3 and CuO at 12%-20%, the desulfurizer uses CaO whose precursor is calcium acetate, accounting for 8%-12%, and the auxiliary agent is a mixture of MnO2 and WO3 at ≤5%.

7. A catalyst for coal combustion according to claim 6, characterized in that: The carrier also includes or is replaced by one or more of γ-Al2O3, CeO2, and composite carriers / modified carriers TiO2-Al2O3, CeO2-TiO2, and CeO2-ZrO2; the active agent also includes or is replaced by one or more of copper oxide, manganese oxide, alkali metal oxide and precious metal, and the precious metal is Pt and / or Pd; the auxiliary agent also includes or is replaced by one or more of MoO3, ZrO2, K, and Na.

8. Use of the catalyst according to any one of claims 6-7 in reducing pollutant emissions, characterized in that: The catalyst is added to the furnace continuously or in batches together with fresh bed material or limestone at a ratio of 0.5-3 wt% of the total bed material of the CFB boiler.

9. Use of the catalyst according to any one of claims 6-7 in reducing pollutant emissions and promoting coal combustion, characterized in that: The catalyst is evenly mixed into the coal powder airflow at the coal mill outlet or before the coal powder feeder through a precision feeding device at a ratio of 0.1-0.5 wt% of the weight of the coal powder entering the furnace.

10. Use of the catalyst according to claim 8 for reducing pollutant emissions, characterized in that: It also includes arranging a high-temperature resistant catalytic element in the 700-900°C area in the furnace, wherein the catalytic element is a monolithic honeycomb ceramic carrier loaded with catalyst; at the same time, a catalytic reactor loaded with catalyst is set in the flue with a temperature of 300-400°C after the economizer and before the air preheater; and it also includes arranging a high-temperature resistant catalytic element in the 700-900°C area in the furnace, wherein the catalytic element is a monolithic honeycomb ceramic carrier loaded with catalyst; at the same time, a catalytic reactor loaded with catalyst is set in the flue with a temperature of 300-400°C after the economizer and before the air preheater.

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