Catalyst composition for reducing NOx emission of ammonia-doped combustion circulating fluidized bed boiler as well as preparation method and application of catalyst composition

Abstract

The invention discloses a catalyst composition for reducing NOx emission of an ammonia-doped combustion circulating fluidized bed boiler as well as a preparation method and application of the catalyst composition, and the catalyst composition comprises the following components by weight: (1) 25-60 wt% of spinel with the general formula of FeM2O4; (2) 10 to 30 weight percent of modified red mud; (3) 5 to 20 weight percent of CFB boiler fly ash; (4) 10 to 35 weight percent of one or two of kaolin and attapulgite; and (5) the balance of one or two of aluminum sol and silica sol. The catalyst composition is added into a CFB hearth, under the NH3-doped combustion working condition, conversion from NH3 to NO can be inhibited, the generated NO and NH3 are catalyzed to react with reducing substances generated in the coal burning process, NO is reduced into N2, and therefore the purpose of effectively removing NOx is achieved; meanwhile, due to the proper particle size distribution of the catalyst, the reduction reaction of NH3 and NO is catalyzed, NH3 escape is reduced, and the fuel utilization rate is increased.

Description

Technical Field

[0001] The present invention relates to the field of catalysts, and in particular to a catalyst composition for reducing NOx emissions from a circulating fluidized bed boiler using ammonia-doped combustion, and a preparation method and application thereof. Background Art

[0002] Circulating fluidized bed (CFB) boilers have seen rapid growth due to their perceived advantages, including good fuel adaptability, excellent load regulation, and convenient ash and slag utilization. However, they are also a major source of CO2 emissions. Energy conservation and emission reduction measures, including the use of renewable energy, can reduce or offset CO2 emissions from CFB boiler combustion. NH3, a hydrogen-rich, carbon-free fuel, offers advantages such as high energy density, low cost, and safe storage and transportation. Its combined combustion with coal is considered a rapid and effective method for reducing CO2 emissions from CFB boilers.

[0003] CFB boilers operate at low combustion temperatures, generally not exceeding 950°C, and contain very few hydrocarbon radicals. Therefore, the NOx in their flue gas is primarily fuel-based. Furthermore, due to their staged combustion and the presence of a large amount of reducing materials within the furnace, CFB boilers inherently offer the advantage of low NOx emissions. However, when CFB combustion is mixed with NH3, NH3, as a nitrogen-containing fuel, becomes another major source of fuel-based NOx in the flue gas, often leading to elevated NOx levels. Research has shown that elevated NOx emissions and NH3 slip are the primary challenges facing NH3 fuel combustion.

[0004] Staged combustion at the front, such as air staged combustion and NH3 staged combustion, step-by-step combustion, NH3 combustion organization optimization (such as fuel-rich combustion, NH3 injection location, method and NH3 mixing ratio), and selective non-catalytic reduction (SNCR), selective catalytic reduction (SCR) and low-temperature ozone oxidation and their combination at the back can effectively reduce NOx emissions from ammonia-combined combustion CFB boilers. However, NOx control measures in the front combustion process either have limited NOx control levels, or affect combustion efficiency or lead to increased emissions of other pollutants (such as NH3 slip); for the back flue gas treatment, when the NOx concentration in the flue gas increases significantly, the denitrification load and denitrification cost will increase significantly. The use of a dedicated ammonia-combined combustion and nitrogen reduction control system or a denitrification catalyst is an effective denitrification method.

[0005] Chinese patent CN202210327223.3 discloses a coal-fired boiler ammonia-blended combustion and nitrogen reduction control system and operation method. The boiler burner is configured as an ammonia-coal mixed combustion burner. Several pure ammonia burners are connected in parallel and connected to an ammonia supply device, which is in turn connected to the ammonia supply device. An ammonia multi-nozzle spray gun is arranged in the boiler furnace and connected to the outlet of a hydrogen-ammonia mixing control device. The outlets of the ammonia supply device, hydrogen supply device, and compressed air source are connected to the hydrogen-ammonia mixing control device. A flame temperature visualization device is provided above the ammonia multi-nozzle spray gun. A rectifier device and a flue gas continuous online monitoring device are sequentially arranged in the horizontal flue downstream of the boiler economizer. The flame temperature visualization measuring device, hydrogen-ammonia mixing control device, flue gas continuous online monitoring device, and all flow control devices are connected to the DCS control center. This invention can maximize the unit's carbon and nitrogen reduction levels while achieving stable and efficient combustion of ammonia coal in the furnace.

[0006] Chinese patent CN201811405693.7 discloses a denitration catalyst, its preparation method, and a method for reducing nitrogen oxide emissions from a circulating fluidized bed boiler. The method comprises adding a denitration catalyst to the dense phase bed of a circulating fluidized bed boiler. The catalyst is prepared by calcining green pellets prepared from activated alumina, fly ash from a coal-fired circulating fluidized bed boiler with a carbon content of less than 6.0 wt%, a lanthanide salt, a transition metal salt, and a binder to produce a denitration catalyst comprising at least 15-50 parts by weight of activated alumina, 12-45 parts of fly ash from a coal-fired circulating fluidized bed boiler with a carbon content of less than 6.0 wt%, 1-7 parts of a lanthanide oxide, 2-15 parts of a transition metal oxide, and 15-25 parts of a binder. During the CFB combustion process, the denitration catalyst, under the action of the catalyst, converts NOx in the flue gas in situ within the boiler combustion chamber, thereby reducing NOx levels. This patent is more applicable to in-furnace denitration in conventional coal-fired CFB boilers.

[0007] The denitrification methods involved in existing technologies are mostly used in conventional coal-fired CFB boilers or adopt complex control methods, which can effectively remove NOx to a certain extent. However, when applied to high-ammonia CFB boilers, they face problems such as low NOx removal efficiency and large amounts of NH3 escape. Summary of the Invention

[0008] In response to the problems of low NOx removal efficiency and large amounts of NH3 leakage during the combustion process of high-ammonia CFB boilers in the prior art, the present invention proposes a catalyst composition for reducing NOx emissions from a circulating fluidized bed boiler burning ammonia, as well as its preparation method and application. The catalyst can inhibit the conversion of NH3 to NO and catalyze the reduction reaction of NH3 with the generated NO, thereby reducing NH3 leakage while removing NOx and improving fuel utilization.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] A catalyst composition for reducing NOx emissions from a circulating fluidized bed boiler using ammonia as the combustion medium comprises the following components, based on the weight of the composition: (1) 25-60 wt% of spinel having the general formula FeM2O4; (2) 10-30 wt% of modified red mud; (3) 5-20 wt% of CFB boiler fly ash; (4) 10-35 wt% of one or both of kaolin and attapulgite; and (5) the remainder being one or both of alumina sol and silica sol.

[0011] Preferably, the catalyst composition comprises the following components, based on the weight of the composition: (1) 30-55 wt% of spinel having the general formula FeM2O4; (2) 15-25 wt% of modified red mud; (3) 8-15 wt% of CFB boiler fly ash; (4) 12-30 wt% of one or both of kaolin and attapulgite; and (5) the balance being one or both of alumina sol and silica sol.

[0012] Preferably, the spinel is one or more of FeMn2O4, FeAl2O4, FeCo2O4, and FeNi2O4.

[0013] Preferably, the preparation method of the spinel is as follows: iron salt is mixed with one or more of manganese, aluminum, cobalt, and nickel salts to obtain a mixed solution, and then the mixed solution is added dropwise to a solution containing sodium hydroxide and sodium carbonate, and stirring is continued after the addition is completed. After nucleation and crystallization, the mixture is cooled, filtered, and washed until neutral to obtain the spinel.

[0014] Preferably, the temperature of the mixed solution is 60-85° C., the dropping time is 0.5-1.0 h, the pH of the solution containing sodium hydroxide and sodium carbonate is controlled at 8-10, and the stirring time is 6-18 h.

[0015] Preferably, the modified red mud is prepared as follows: weigh an appropriate amount of red mud, grind it into fine powder, stir it continuously and wash it with deionized water until it is neutral, add boric acid solution for modification, and dry it to obtain the modified red mud.

[0016] Preferably, the red mud is ground into fine powder with a particle size of 10 to 30 μm, the concentration of the boric acid solution is 0.1 to 1 mol / L, and the mass ratio of boric acid to red mud is 0.01 to 0.05.

[0017] Preferably, the specific surface area of ​​the catalyst composition is not less than 35m 2 / g, and the wear index is not higher than 0.8% / h.

[0018] Preferably, the specific surface area of ​​the catalyst composition is 45 to 60 m2 / g, and the wear index is 0.5~0.75% / h.

[0019] The present invention also provides a method for preparing the catalyst composition, comprising the following steps:

[0020] (a) adding modified red mud, calcined CFB boiler fly ash, and one or both of kaolin and attapulgite to deionized water in sequence under stirring, stirring once, adding nitric acid dropwise after stirring, then adding spinel, stirring twice, and finally adding one or both of aluminum sol and silica sol, stirring three times to obtain a slurry;

[0021] (b) spray-drying the slurry to obtain a catalyst composition, followed by drying, calcining, and sieving.

[0022] Preferably, in step (a), the first stirring time is 1 to 3 hours, the second stirring time is 3 to 5 hours, the third stirring time is 5 to 12 hours, and the volume concentration of nitric acid is 10%.

[0023] Preferably, in step (a), the calcination temperature of the CFB boiler fly ash is 500-700° C., and the calcination time is 3-5 hours.

[0024] Preferably, in step (b), the spray drying molding conditions are as follows: the spray drying furnace temperature is 320-480°C, the outlet temperature is 220-260°C, and the spray pressure is 40-70 atmospheres; the drying treatment conditions are drying at 120-150°C for 6-10 hours; and the roasting conditions are roasting at 800-900°C for 8-12 hours.

[0025] The present invention also claims to protect the use of the catalyst composition in an ammonia-compounded combustion circulating fluidized bed boiler.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention provides a catalyst composition for reducing NOx emissions from a circulating fluidized bed boiler with ammonia-doped combustion, which uses a spinel component (M = Mn, Al, Co or Ni) of the general formula FeM2O4 and a mixture thereof as an active component. Under CFB boiler operating conditions, it inhibits the conversion of NH3 to NO, catalyzes the reaction of already generated NO with NH3 and a large amount of reducing substances (such as carbonaceous particles and CO in flue gas) generated during coal combustion, and reduces NO to N2; red mud is a waste generated during the production of alumina, and the content of metal oxides such as aluminum oxide, iron oxide and titanium oxide that can promote the reaction of NO with NH3 is relatively high. High, through washing and boric acid modification, the alkalinity and pore structure of red mud are changed. The addition of red mud can also reduce costs and recycle waste; CFB boiler fly ash contains relatively high denitrification active metal elements, and its carbon content is reduced by roasting to improve the strength of the catalyst composition; kaolin, attapulgite and their mixtures are used as carriers of the catalyst composition, and their higher pore volume and specific surface area provide good dispersion effect for the active components, further improving the denitrification performance of the active components; aluminum sol or silica sol or their mixtures are used as binders, which interact with kaolin, attapulgite and their mixtures to improve the strength of the catalyst composition.

[0028] In summary, the catalyst composition provided by the present invention can inhibit the conversion of NH3 to NO, catalyze the reaction of already generated NO with NH3 and other reducing substances produced during the coal combustion process, and reduce NO to N2, thereby achieving the purpose of effectively removing NOx; at the same time, due to the suitable particle size distribution of the catalyst, it catalyzes the reduction reaction of NH3 and NO, reduces NH3 escape, and improves fuel utilization. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments. Of course, the specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0030] Unless otherwise specified, the chemical reagents and materials in the present invention are purchased from commercial sources or synthesized from commercially purchased raw materials.

[0031] The present invention provides a catalyst composition for reducing NOx emissions from a circulating fluidized bed boiler in which ammonia is mixed with combustion. The catalyst composition comprises the following components by weight:

[0032] 25-60 wt% of spinel of the general formula FeM2O4, which may be 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, preferably 30-55 wt%;

[0033] 10-30 wt% of modified red mud, which may be 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, preferably 15-25 wt%;

[0034] 5-20 wt% CFB boiler fly ash, which may be 5 wt%, 8 wt%, 11 wt%, 14 wt%, 17 wt%, 20 wt%, preferably 8-15 wt%;

[0035] 10-35wt% of one or both of kaolin and attapulgite, which may be 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, preferably 12-30wt%;

[0036] The balance is one or both of aluminum sol and silica sol.

[0037] Specifically, the spinel is one or more of FeMn2O4, FeAl2O4, FeCo2O4, and FeNi2O4.

[0038] Specifically, the preparation method of spinel is as follows: iron salt is mixed with one or more of manganese, aluminum, cobalt, and nickel salts to obtain a mixed solution, and then the mixed solution is added dropwise to a solution containing sodium hydroxide and sodium carbonate. After the addition is completed, stirring is continued, and after nucleation and crystallization, the mixture is cooled, filtered, and washed until neutral to obtain spinel.

[0039] Specifically, the temperature of the mixed solution is 60-85°C, which may be 60°C, 65°C, 70°C, 75°C, or 80°C; the dropwise addition time is 0.5-1.0h, which may be 0.5h, 0.8h, or 1h; and the pH of the solution is controlled at 8-10, which may be 8, 9, or 10.

[0040] Specifically, the modified red mud preparation method is as follows: Weigh an appropriate amount of red mud, grind it into a fine powder, stir it continuously, and wash it with deionized water until it is neutral. Boric acid solution is added to modify it, and then the modified red mud is dried. Red mud is a waste product generated during the alumina production process. It contains aluminum oxide, iron oxide, titanium oxide, and other components that are beneficial for denitrification. Boric acid solution is added to modify it to change its acidity and alkalinity and pore structure.

[0041] Specifically, the usage ratio of boric acid to red mud is 0.01 to 0.05.

[0042] Specifically, the red mud is ground into fine powder with a particle size of 10 to 30 μm, and the concentration of the boric acid solution is 0.5 mol / L.

[0043] Specifically, the specific surface area of ​​the catalyst composition is not less than 35m 2 / g, preferably 45 to 60m 2 / g; the wear index is not higher than 0.8% / h, preferably 0.5-0.75% / h.

[0044] The present invention also provides a method for preparing the catalyst composition, comprising the following steps:

[0045] (1) adding modified red mud, calcined CFB boiler fly ash, and one or both of kaolin or attapulgite to deionized water in sequence under stirring, stirring once, adding nitric acid dropwise after stirring, then adding FeM2O4 spinel, stirring twice, and finally adding one or both of aluminum sol or silica sol, stirring three times to obtain a slurry;

[0046] (1) The slurry is spray-dried to form a catalyst composition, which is then dried, calcined, and sieved.

[0047] Specifically, in step (1), the first stirring time is 1 to 3 hours, which may be 1 hour, 2 hours, or 3 hours; the second stirring time is 3 to 5 hours, which may be 3 hours, 4 hours, or 5 hours; the third stirring time is 5 to 12 hours, which may be 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours; and the volume concentration of nitric acid is 10%.

[0048] Specifically, in step (2), the conditions for spray drying molding are that the spray drying furnace temperature is 320-480°C, the outlet temperature is 220-260°C, and the spray pressure is 40-70 atmospheres. The furnace temperature can be 320°C, 350°C, 380°C, 400°C, 450°C, 480°C, the outlet temperature can be 220°C, 230°C, 240°C, 250°C, 260°C, and the spray pressure can be 40 atmospheres, 50 atmospheres, 60 atmospheres, 70 atmospheres; the drying conditions are drying at 120-150°C for 6-10 hours, the drying temperature can be 120°C, 130°C, 140°C, 150°C, and the drying time can be 6h, 7h, 8h, 9h, 10h; the calcination conditions are calcining at 800-900°C for 8-12h, the calcination temperature can be 800°C, 850°C, 900°C, and the calcination time can be 8h, 9h, 10h, 11h, 12h.

[0049] The present invention also claims to protect the use of the catalyst composition in an ammonia-compounded combustion circulating fluidized bed boiler.

[0050] Example 1

[0051] (1) Preparation of FeMn2O4 spinel

[0052] 1) Add 500g H2O, 110g NaOH and 34.8g Na2CO3 to beaker 1 and stir evenly at 55°C; 2) Add 500g distilled water to beaker 2 and stir, then add 187.7g Fe(NO3)3.9H2O and 111.1g Mn(NO3)2.4H2O in sequence to completely dissolve them; 3) While stirring, slowly add the solution in beaker 1 dropwise to beaker 2 for 0.6h. After the addition is complete, continue stirring for 15h for nucleation and crystallization, then cool, filter and wash until neutral to obtain FeMn2O4 spinel.

[0053] (2) Preparation of modified red mud

[0054] 1) Weigh 500 g of red mud, grind and sieve to obtain a fine powder of 10 to 30 μm; 2) Wash repeatedly with deionized water while stirring until neutral; 3) Modify the red mud with a 0.5 mol / L boric acid aqueous solution (3 h) at a mass ratio of boric acid to red mud of 0.04, and dry at 120° C. to obtain modified red mud.

[0055] (3) Composition molding preparation

[0056] 500 g of deionized water was added to a reactor, and during the stirring process, 30 g of modified red mud obtained in step (2), 20 g of CFB boiler fly ash that had been roasted (600° C., 4 h), and 42.9 g of kaolin (70.0 wt% on a dry basis) were added in sequence, and stirred for 3 hours. 45 g of nitric acid with a volume concentration of 10% was added dropwise; the FeMn2O4 spinel obtained in step (1) was added and stirred for 4 hours. Finally, 111.1 g of aluminum sol (18 wt% on a dry basis) was added and stirred for 8 hours to obtain a slurry; the slurry was spray-dried to form a slurry, and the spray drying furnace temperature, outlet temperature and spray pressure were controlled at 390° C., 240° C. and 50 atmospheres. After spray drying and forming, the slurry was dried at 120° C. for 8 hours, roasted at 850° C. for 10 hours, and sieved to obtain product 1.

[0057] Example 2

[0058] (1) Preparation of FeMn2O4 spinel

[0059] 1) Add 500gH2O, 110gNaOH and 34.8gNa2CO3 to beaker 1 and stir evenly at 55℃; 2) Add 500g distilled water to beaker 2 and stir, then add 211.6gFe(NO3)3.9H2O and 196.8gAl(NO3)3.9H2O in sequence to completely dissolve them; 3) While stirring, slowly add the solution in beaker 1 dropwise to beaker 2 for 0.8h. After the addition is complete, continue stirring for 16h for nucleation and crystallization, then cool, filter and wash until neutral to obtain FeAl2O4 spinel.

[0060] (2) Preparation of modified red mud

[0061] 1) Weigh 500 g of red mud, grind and sieve to obtain a fine powder of 10 to 30 μm; 2) Wash repeatedly with deionized water while stirring until neutral; 3) Modify the red mud with a 0.5 mol / L boric acid aqueous solution (2.5 h) at a mass ratio of boric acid to red mud of 0.04, and dry at 120° C. to obtain modified red mud.

[0062] (3) Composition molding preparation

[0063] 500 g of deionized water was added to a reactor, and during the stirring process, 40 g of modified red mud obtained in step (2), 15 g of CFB boiler fly ash that had been calcined (600° C., 4 h), and 42.9 g of attapulgite (70.0 wt% on a dry basis) were added in sequence. The mixture was stirred for 3 hours, and 45 g of nitric acid with a volume concentration of 10% was added dropwise. The FeAl2O4 spinel obtained in step (1) was added and stirred for 5 hours. Finally, 133.3 g of aluminum sol (18 wt% on a dry basis) was added and stirred for 8 hours to obtain a slurry. The slurry was spray-dried to form a slurry, and the spray drying furnace temperature, outlet temperature, and spray pressure were controlled at 390° C., 260° C., and 55 atmospheres. After spray drying and forming, the slurry was dried at 130° C. for 8 hours, calcined at 870° C. for 10 hours, and sieved to obtain the target product 2.

[0064] Example 3

[0065] (1) Preparation of FeCo2O4 spinel

[0066] 1) Add 500gH2O, 110gNaOH and 34.8gNa2CO3 to beaker 1 and stir evenly at 55℃; 2) Add 500g distilled water to beaker 2 and stir, then add 137.8gFe(NO3)3.9H2O and 98.7gCo(NO3)2.6H2O in sequence to completely dissolve them; 3) While stirring, slowly add the solution in beaker 1 dropwise to beaker 2 for 1.0h. After the addition is complete, continue stirring for 20h for nucleation and crystallization, then cool, filter and wash until neutral to obtain FeCo2O4 spinel.

[0067] (2) Preparation of modified red mud

[0068] 1) Weigh 500 g of red mud, grind and sieve to obtain a fine powder of 10 to 30 μm; 2) Wash repeatedly with deionized water while stirring until neutral; 3) Modify the red mud with a 0.5 mol / L boric acid aqueous solution (3 h) at a mass ratio of boric acid to red mud of 0.04, and dry at 120° C. to obtain modified red mud.

[0069] (3) Composition molding preparation

[0070] 500 g of deionized water was added to a reactor, and during the stirring process, 36 g of modified red mud obtained in step (2), 24 g of CFB boiler fly ash that had been roasted (600° C., 4 h), and 57.1 g of kaolin (70.0 wt% on a dry basis) were added in sequence, and stirred for 3 hours. 45 g of nitric acid with a volume concentration of 10% was added dropwise; the FeCo2O4 spinel obtained in step (1) was added and stirred for 5 hours. Finally, 80.0 g of silica sol (25 wt% on a dry basis) was added and stirred for 10 hours to obtain a slurry; the slurry was spray-dried to form a slurry, and the spray drying furnace temperature, outlet temperature and spray pressure were controlled at 400° C., 260° C. and 55 atmospheres. After spray drying and forming, the slurry was dried at 130° C. for 8 hours, roasted at 900° C. for 10 hours, and sieved to obtain product 3.

[0071] Example 4

[0072] (1) Preparation of FeNi2O4 spinel

[0073] 1) Add 500gH2O, 110gNaOH and 34.8gNa2CO3 to beaker 1 and stir evenly at 55℃; 2) Add 500g distilled water to beaker 2 and stir, then add 130.5gFe(NO3)3.9H2O and 84.1gNi(NO3)2.6H2O in sequence to completely dissolve them; 3) While stirring, slowly add the solution in beaker 1 dropwise to beaker 2 for 1.0h. After the addition is complete, continue stirring for 18h for nucleation and crystallization, then cool, filter and wash until neutral to obtain FeNi2O4 spinel.

[0074] (2) Preparation of modified red mud

[0075] 1) Weigh 500 g of red mud, grind and sieve to obtain a fine powder of 10 to 30 μm; 2) Wash repeatedly with deionized water while stirring until neutral; 3) Modify the red mud with a 0.5 mol / L boric acid aqueous solution (2.5 h) at a mass ratio of boric acid to red mud of 0.04, and dry at 120° C. to obtain modified red mud.

[0076] (3) Composition molding preparation

[0077] 500 g of deionized water was added to a reactor, and during the stirring process, 50 g of modified red mud obtained in step (2), 30 g of CFB boiler fly ash that had been roasted (600° C., 4 h), and 42.8 g of attapulgite (70.0 wt% on a dry basis) were added in sequence. The mixture was stirred for 3 hours, and 45 g of nitric acid with a volume concentration of 10% was added dropwise. The spinel of FeNi2O4 obtained in step (1) was added and stirred for 5 hours. Finally, 80.0 g of silica sol (25 wt% on a dry basis) was added and stirred for 10 hours to obtain a slurry. The slurry was spray-dried to form a slurry, and the spray drying furnace temperature, outlet temperature and spray pressure were controlled at 450° C., 280° C. and 60 atmospheres. After spray drying, the slurry was dried at 150° C. for 8 hours, roasted at 900° C. for 12 hours, and sieved to obtain the target product 4.

[0078] Example 5

[0079] (1) Preparation of FeMn2O4 spinel

[0080] 1) Add 500gH2O, 110gNaOH and 34.8gNa2CO3 to beaker 1 and stir evenly at 55℃; 2) Add 500g distilled water to beaker 2 and stir, then add 150.2gFe(NO3)3.9H2O and 89.5gMn(NO3)2.4H2O in sequence to completely dissolve them; 3) While stirring, slowly add the solution in beaker 1 dropwise to beaker 2 for 1.0h. After the addition is complete, continue stirring for 18h for nucleation and crystallization, then cool, filter and wash until neutral to obtain FeMn2O4 spinel.

[0081] (2) Preparation of modified red mud

[0082] 1) Weigh 500 g of red mud, grind and sieve to obtain a fine powder of 10 to 30 μm; 2) Wash repeatedly with deionized water while stirring until neutral; 3) Modify the red mud with a 0.5 mol / L boric acid aqueous solution (3 h) at a mass ratio of boric acid to red mud of 0.04, and dry at 120° C. to obtain modified red mud.

[0083] (3) Composition molding preparation

[0084] 500 g of deionized water was added to a reactor, and during the stirring process, 36 g of modified red mud obtained in step (2), 24 g of CFB boiler fly ash that had been calcined (600° C., 4 h), and 57.1 g of attapulgite (70.0 wt% on a dry basis) were added in sequence. The mixture was stirred for 3 hours, and 45 g of nitric acid with a volume concentration of 10% was added dropwise. The FeMn2O4 spinel obtained in step (1) was added and stirred for 4 hours. Finally, 80.0 g of silica sol (25 wt% on a dry basis) was added and stirred for 10 hours to obtain a slurry. The slurry was spray-dried to form a slurry, and the spray drying furnace temperature, outlet temperature and spray pressure were controlled at 420° C., 270° C. and 55 atmospheres. After spray drying and forming, the slurry was dried at 140° C. for 8 hours, calcined at 900° C. for 8 hours, and sieved to obtain the target product 5.

[0085] Example 6

[0086] (1) Preparation of FeMn2O4 spinel

[0087] 1) Add 500gH2O, 110gNaOH and 34.8gNa2CO3 to beaker 1 and stir evenly at 55℃; 2) Add 500g distilled water to beaker 2 and stir, then add 232.8gFe(NO3)3.9H2O and 216.5gAl(NO3)3.9H2O in sequence to completely dissolve them; 3) While stirring, slowly add the solution in beaker 1 dropwise to beaker 2 for 0.9h. After the addition is complete, continue stirring for 15h for nucleation and crystallization, then cool, filter and wash until neutral to obtain FeAl2O4 spinel.

[0088] (2) Preparation of modified red mud

[0089] 1) Weigh 500 g of red mud, grind and sieve to obtain a fine powder of 10 to 30 μm; 2) Wash repeatedly with deionized water while stirring until neutral; 3) Modify the red mud with a 0.5 mol / L boric acid aqueous solution (3 h) at a mass ratio of boric acid to red mud of 0.04, and dry at 120° C. to obtain modified red mud.

[0090] (3) Composition molding preparation

[0091] 500 g of deionized water was added to a reactor, and during the stirring process, 30 g of the modified red mud obtained in step (2), 16 g of CFB boiler fly ash that had been calcined (600° C., 4 h), and 21.5 g each of kaolin and attapulgite (70.0 wt% on a dry basis) were added in sequence, and stirred for 4 hours. 45 g of nitric acid with a volume concentration of 10% was added dropwise; the FeAl2O4 spinel obtained in step (1) was added and stirred for 5 hours. Finally, 67.7 g each of aluminum sol and silica sol (18 wt% on a dry basis) was added and stirred for 8 hours to obtain a slurry; the slurry was spray-dried to form a slurry, and the spray drying furnace temperature, outlet temperature and spray pressure were controlled at 4500° C., 260° C. and 60 atmospheres. After spray drying and forming, the slurry was dried at 140° C. for 10 hours, calcined at 850° C. for 12 hours, and sieved to obtain the target product 6.

[0092] Example 7

[0093] (1) Preparation of FeCo2O4 spinel

[0094] 1) Add 500gH2O, 110gNaOH and 34.8gNa2CO3 to beaker 1 and stir evenly at 55℃; 2) Add 500g distilled water to beaker 2 and stir, then add 155.0gFe(NO3)3.9H2O and 111.0gCo(NO3)2.6H2O in sequence to completely dissolve them; 3) While stirring, slowly add the solution in beaker 1 dropwise to beaker 2 for 0.8h. After the addition is complete, continue stirring for 18h for nucleation and crystallization, then cool, filter and wash until neutral to obtain FeCo2O4 spinel.

[0095] (2) Preparation of modified red mud

[0096] 1) Weigh 500 g of red mud, grind and sieve to obtain a fine powder of 10 to 30 μm; 2) Wash repeatedly with deionized water while stirring until neutral; 3) Modify the red mud with a 0.5 mol / L boric acid aqueous solution (3 h) at a mass ratio of boric acid to red mud of 0.04, and dry at 120° C. to obtain modified red mud.

[0097] (3) Composition molding preparation

[0098] 500 g of deionized water was added to a reactor, and during the stirring process, 30 g of modified red mud obtained in step (2), 30 g of CFB boiler fly ash that had been roasted (600°C, 4 h), and 57.1 g of attapulgite (70.0 wt% on a dry basis) were added in sequence. The mixture was stirred for 3 hours, and 45 g of nitric acid with a volume concentration of 10% was added dropwise. The FeCo2O4 spinel obtained in step (1) was added and stirred for 5 hours. Finally, 80.0 g of aluminum sol (25 wt% on a dry basis) was added and stirred for 10 hours to obtain a slurry. The slurry was spray-dried to form a slurry, and the spray drying furnace temperature, outlet temperature and spray pressure were controlled at 420°C, 270°C and 55 atmospheres. After spray drying and forming, the slurry was dried at 130°C for 10 hours, roasted at 900°C for 12 hours, and sieved to obtain the target product 7.

[0099] Example 8

[0100] (1) Preparation of FeNi2O4 spinel

[0101] 1) Add 500gH2O, 110gNaOH and 34.8gNa2CO3 to beaker 1 and stir evenly at 55℃; 2) Add 500g distilled water to beaker 2 and stir, then add 167.8gFe(NO3)3.9H2O and 108.1gNi(NO3)2.6H2O in sequence to completely dissolve them; 3) While stirring, slowly add the solution in beaker 1 dropwise to beaker 2 for 1.0h. After the addition is complete, continue stirring for 18h for nucleation and crystallization, then cool, filter and wash until neutral to obtain FeNi2O4 spinel.

[0102] (2) Preparation of modified red mud

[0103] 1) Weigh 500 g of red mud, grind and sieve to obtain a fine powder of 10 to 30 μm; 2) Wash repeatedly with deionized water while stirring until neutral; 3) Modify the red mud with a 0.5 mol / L boric acid aqueous solution (3 h) at a mass ratio of boric acid to red mud of 0.04, and dry at 120° C. to obtain modified red mud.

[0104] (3) Composition molding preparation

[0105] 500 g of deionized water was added to a reactor, and during the stirring process, 30 g of the modified red mud obtained in step (2), 20 g of CFB boiler fly ash that had been calcined (600° C., 4 h), and 42.8 g of kaolin (70.0 wt% on a dry basis) were added in sequence. The mixture was stirred for 3 hours, and 45 g of nitric acid with a volume concentration of 10% was added dropwise. The FeNi2O4 spinel obtained in step (1) was added and stirred for 5 hours. Finally, 80.0 g of silica sol (25 wt% on a dry basis) was added and stirred for 10 hours to obtain a slurry. The slurry was spray-dried to form a slurry, and the spray drying furnace temperature, outlet temperature, and spray pressure were controlled at 440° C., 260° C., and 55 atmospheres. After spray drying, the slurry was dried at 150° C. for 8 hours, calcined at 900° C. for 12 hours, and sieved to obtain the target product 8.

[0106] Comparative Example 1

[0107] Unmodified red mud was taken, and the remaining components were the same as those in Example 1, and comparative example composition 1 was prepared according to Example 1.

[0108] Comparative Example 2

[0109] Unmodified red mud and uncalcined CFB boiler fly ash were taken, and the remaining components were the same as those in Example 1. Comparative Example Composition 2 was prepared according to Example 1.

[0110] Examples 11 to 21

[0111] The denitration performance of the catalyst compositions for reducing NOx emissions from ammonia-compounded circulating fluidized bed boilers prepared in the above-described examples and comparative examples was evaluated as follows. The denitration performance evaluation test was conducted in a quartz tube fixed-bed reactor. The denitration catalyst composition was mixed with CFB boiler circulating ash at a concentration of 2.5 wt % of the circulating ash. The quartz tube reactor was loaded with 1.0 g of the catalyst mixture, and the reaction gas was (5.0 vol % NH 3 , 5 vol % CO, 2500 mg / m 2 ). 3 The reaction mixture was stirred at a flow rate of 120 ml / min, a reaction temperature of 900°C, and a reaction pressure of atmospheric pressure. The NO and NH3 contents in the reaction tail gas were analyzed using a flue gas analyzer. The denitrification and NH3 removal performance of the catalyst composition were evaluated based on the NO removal rate and NH3 conversion rate, as shown in Equations (1) and (2). The performance evaluation results are shown in Table 1.

[0112]

[0113] Where: DeNO is the removal rate of NO, C NO is the NO concentration in the mixed gas after the reaction mg / m 3 , C NO0 is the NO concentration in the mixed gas before the reaction mg / m 3 .

[0114]

[0115] Where: η NH3 is the NH3 conversion rate, C NH3 is the NH3 concentration in the mixed gas after the reaction, vol%, C NH3a is the NH3 concentration in the mixed gas before the reaction (vol%).

[0116] Table 1 Combustion-supporting performance of ammonia combustion-supporting catalyst

[0117]

[0118]

[0119] 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 contents of the present invention and implement them accordingly. The scope of the patent of the present invention cannot be limited by these embodiments alone. That is, any equivalent changes or modifications made to the spirit disclosed by the present invention still fall within the scope of the patent of the present invention.

Claims

1. A catalyst composition for reducing NOx emissions from a circulating fluidized bed boiler using ammonia as the combustion medium, characterized in that: The composition comprises the following components, calculated on the weight of the composition: (1) 25 to 60 wt% of spinel having the general formula FeM2O4; (2) 10 to 30 wt% of modified red mud; (3) 5 to 20 wt% of CFB boiler fly ash; (4) 10 to 35 wt% of one or both of kaolin and attapulgite; and (5) the balance being one or both of alumina sol and silica sol.

2. The catalyst composition according to claim 1, characterized in that The composition comprises the following components, calculated on the weight of the composition: (1) 30 to 55 wt% of spinel having the general formula FeM2O4; (2) 15 to 25 wt% of modified red mud; (3) 8 to 15 wt% of CFB boiler fly ash; (4) 12 to 30 wt% of one or both of kaolin and attapulgite; and (5) the balance being one or both of alumina sol and silica sol.

3. The catalyst composition according to claim 1, characterized in that The spinel is one or more of FeMn2O4, FeAl2O4, FeCo2O4, and FeNi2O4.

4. The catalyst composition according to claim 3, characterized in that The spinel preparation method is as follows: iron salt is mixed with one or more salts of manganese, aluminum, cobalt, and nickel to obtain a mixed solution, and then the mixed solution is added dropwise to a solution containing sodium hydroxide and sodium carbonate. After the addition is completed, stirring is continued, and after nucleation and crystallization, the solution is cooled, filtered, and washed until neutral to obtain the spinel.

5. The catalyst composition according to claim 4, characterized in that The temperature of the mixed solution is 60-85° C., the dropping time is 0.5-1.0 h, the pH of the solution containing sodium hydroxide and sodium carbonate is controlled at 8-10, and the stirring time is 6-18 h.

6. The catalyst composition according to claim 1, characterized in that The preparation of the modified red mud comprises the following steps: weighing the red mud and grinding it into fine powder, then continuously stirring and washing it with deionized water until it is neutral, then adding a boric acid solution for modification, and drying to obtain the modified red mud.

7. The catalyst composition according to claim 6, characterized in that The red mud is ground into fine powder with a particle size of 10 to 30 μm, the concentration of the boric acid solution is 0.1 to 1 mol / L, and the mass ratio of boric acid to red mud is 0.01 to 0.

05.

8. The catalyst composition according to claim 1, characterized in that The specific surface area of ​​the catalyst composition is not less than 35m 2 / g, and the wear index is not higher than 0.8% / h.

9. The catalyst composition according to claim 8, characterized in that The specific surface area of ​​the catalyst composition is 45 to 60 m 2 / g, and the wear index is 0.5% / h~0.75% / h.

10. A method for preparing the catalyst composition according to any one of claims 1 to 9, characterized in that: The steps include: (a) adding modified red mud, calcined CFB boiler fly ash, and one or both of kaolin and attapulgite to deionized water in sequence under stirring, stirring once, adding nitric acid dropwise after stirring, then adding spinel, stirring twice, and finally adding one or both of aluminum sol and silica sol, stirring three times to obtain a slurry; (b) spray-drying the slurry to obtain a catalyst composition, followed by drying, calcining, and sieving.

11. The preparation method according to claim 10, characterized in that: In step (a), the first stirring time is 1 to 3 hours, the second stirring time is 3 to 5 hours, the third stirring time is 5 to 12 hours, and the volume concentration of nitric acid is 10%.

12. The preparation method according to claim 10, characterized in that In step (a), the calcination temperature of the CFB boiler fly ash is 500-700° C., and the calcination time is 3-5 hours.

13. The preparation method according to claim 10, characterized in that In step (b), the spray drying molding conditions are as follows: the spray drying furnace temperature is 320-480°C, the outlet temperature is 220-260°C, and the spray pressure is 40-70 atmospheres; the drying treatment conditions are drying at 120-150°C for 6-10 hours; and the roasting conditions are roasting at 800-900°C for 8-12 hours.

14. Use of the catalyst composition according to any one of claims 1 to 9 in an ammonia-blended combustion circulating fluidized bed boiler.

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