Coal-saving desulfurization ash-removal decoking agent applied to boiler

Abstract

The invention belongs to the technical field of additives for coal-fired boilers, and particularly relates to a coal-saving desulfurization ash-removal decoking agent applied to boilers. The coal-saving, desulfurization, ash-removal and coke-cleaning agent is prepared from the following components: a component A, a component B and a component C, wherein active components CaO, HoFeO3 and CeO2 are loaded on a carrier SrO-MgO; the component B is prepared by loading the active components MgCO3 and KNO3 on the carrier BaFe12O19; the component C is Cu-doped CoFe2O4, and the component C is Cu- The mass ratio of the component A to the component B to the component C is (5-8): (2-3): 1. The coal-saving desulfurization ash-removal coke cleaning agent can effectively save fuel, improve the sulfur fixation efficiency, reduce generation of coke scales on the furnace wall, remove old coke scales, improve the working condition of a circulating fluidized bed boiler and greatly reduce the operation and maintenance cost of the circulating fluidized bed boiler.

Description

Technical Field

[0001] The invention belongs to the technical field of additives for coal-fired boilers, and particularly relates to a coal-saving, desulfurizing, ash-removing and coking agent used in boilers. Background Art

[0002] A circulating fluidized bed (CFB) boiler is a specialized type of boiler that crushes coal to a specific particle size and distributes it evenly above the air distribution plates at the bottom of the furnace. Combustion air is introduced from beneath the air distribution plates, achieving fuel combustion through fluidization technology. These boilers offer advantages such as high combustion efficiency, strong fuel adaptability, a wide load turndown ratio, convenient and rapid load regulation, and low pollutant emissions. The operating principle and structural design of CFB boilers give them numerous unique features that distinguish them from traditional layer-fired and pulverized coal-fired boilers. Based on their unique combustion mode and gas-solid two-phase fluidized combustion mechanism, CFB boilers are filled with inert bed materials such as quartz sand and limestone. The fuel (coal, biomass, etc.) and bed material are fluidized (similar to a boiling liquid) by the primary air flow, resulting in intense gas-solid mixing and heat transfer. Compared to traditional boilers, CFB boilers incorporate key components such as a dense phase fluidized bed, cyclone separators, a return device, and an external heat exchanger. It is precisely the uniqueness of circulating fluidized bed boilers that makes the desulfurization and anti-coking of coal in circulating fluidized bed boilers different from those in other boilers.

[0003] As we all know, coal produces SO2, smoke, NO x , CO and other harmful gases, among which SO2 has the most serious impact on the environment. High concentrations of SO2 will endanger human health and form "acid rain", which directly pollutes the soil. To achieve the purpose of desulfurization, unlike the tail wet desulfurization used in traditional boiler desulfurization, the circulating fluidized bed boiler uses in-furnace limestone desulfurization. Limestone is used as a desulfurizer and enters the furnace together with pulverized coal. At the normal operating bed temperature of 850-900℃, the limestone powder is calcined into calcium oxide. CaO reacts with SO2 generated by coal combustion to form CaSO4, which is discharged in solid form, thereby achieving a desulfurization effect combined with sulfur dioxide.

[0004] When a circulating fluidized bed boiler is in operation, the bed material in the furnace is primarily composed of ash from the feed coal, unreacted limestone, and limestone desulfurization reaction products. The bed material is fluidized by the primary air introduced under the air distribution plate and the secondary air introduced above it. Some particles are entrained by the flue gas and move upward within the furnace. At different heights in the furnace, some solid particles fall along the furnace walls, forming an internal circulation of the material. The remaining solid particles are entrained by the flue gas and enter the separator for gas-solid separation. The vast majority of the separated particles are returned to the furnace through the return valve, forming an external circulation of the material.

[0005] When limestone is added to a circulating fluidized bed boiler as a desulfurizer, it undergoes an endothermic decomposition reaction at temperatures above 800°C. This requires a certain amount of fuel to generate the heat required for the decomposition reaction, thus increasing the boiler's coal consumption. Based on a coal sulfur content of 3-5%, a calcium-sulfur molar ratio of 2:1, and a desulfurization efficiency of 85%, adding limestone to a circulating fluidized bed boiler desulfurization process will increase coal consumption by 9.3%-11% compared to desulfurization without limestone. Therefore, the increased coal consumption caused by adding limestone to a circulating fluidized bed boiler should not be ignored.

[0006] Furthermore, due to limitations in the reaction conditions of circulating fluidized bed boilers, such as residence time and temperature window, the amount of limestone added during actual production is at least double the theoretical value. While this improves desulfurization efficiency to a certain extent, 50% of the added limestone does not react with SO2, but instead decomposes during combustion and heat, resulting in CaO in the ash. The remaining 50% of the limestone only has an 80% desulfurization efficiency. This not only results in low desulfurizer utilization and increased raw material costs, but also increases ash volume by 25%-35%, increasing the pressure on solid waste disposal. When the CaSO4 generated by desulfurization circulates with the bed material to high-temperature zones (such as the dense phase zone), it may decompose due to localized oxygen deficiency or high temperatures (CaSO4 + C → CaO + SO2 + CO). The released SO2 then re-reacts, further reducing desulfurization efficiency.

[0007] The fluidized bed of a circulating fluidized bed boiler contains dense phase zones, dilute phase zones, and a recirculation system. Although the overall temperature is controllable, localized temperatures can exceed the ash melting point (typically 1100-1300°C) due to uneven air distribution (such as worn air distribution plates or clogged air caps), uneven fuel particle distribution (such as large particle deposition), or localized accumulation of desulfurizer, leading to the formation of coke. If material flow within the recirculation system is poor, prolonged retention time can cause the temperature to rise, leading to coking and ultimately disrupting the entire material circulation system. Therefore, circulating fluidized bed boilers require the addition of inert materials such as kaolin to inhibit alkali metal coking, but this can reduce the fluidization performance of the bed material.

[0008] Increasing limestone dosage to improve desulfurization efficiency in the circulating fluidized bed (CFB) of a circulating fluidized bed boiler (CFB) can increase bed material alkalinity due to excessive CaO, promoting the formation of low-melting-point compounds and exacerbating coking. Coking within the bed disrupts fluidization, leading to interrupted material circulation, uneven bed temperature distribution, deteriorating desulfurization reaction conditions, and reduced desulfurization efficiency. This, in turn, prompts increased desulfurizer dosage, creating a vicious cycle of "coking—reduced desulfurization efficiency—more desulfurizer—more coking." Currently, there's no effective solution to the coupling between desulfurization and coking prevention in CFB boilers. Summary of the Invention

[0009] The purpose of the present invention is to provide a coal-saving desulfurization, ash removal and coke cleaning agent for use in boilers, which can effectively save fuel, improve sulfur fixation efficiency, reduce the formation of coke scale on the furnace wall and remove old coke scale, improve the working condition of circulating fluidized bed boilers, and greatly reduce their operation and maintenance costs.

[0010] While researching how to effectively address the coupling issue between desulfurization and coke prevention in circulating fluidized bed boilers, the present inventors discovered that the fundamental problem lies in the low efficiency and single efficacy of existing coal additives. Even though there are existing coal additives with multiple functions, each function remains separate and independent, lacking effective synergy, resulting in low overall efficiency. Therefore, the components of the coal-saving, desulfurization, ash removal, and coke removal agent described in the present invention work together to significantly improve efficiency.

[0011] The specific technical solutions are as follows: A coal-saving, desulfurizing, ash-removing and coking agent for boilers, comprising the following components: Component A: The active components CaO, HoFeO3 and CeO2 are loaded on the carrier SrO-MgO; wherein the mass ratio of CaO:HoFeO3:CeO2 is (10-15):1:(2-5); the molar ratio of SrO:MgO in the carrier is (2-4):1.

[0012] First, the primary active component in Component A is CaO, rather than limestone (CaCO3). Therefore, instead of consuming the heat generated by the fuel for endothermic decomposition, sulfur can be directly fixed, thus saving coal. Loading CaO on the SrO-MgO carrier significantly increases the contact area between CaO and SO2, improving sulfur fixation efficiency.

[0013] After SO2 is adsorbed on the surface of HoFeO3, it is oxidized to SO3 and reacts with O in the HoFeO3 lattice. 2- Combined to form stable sulfate. In addition, at furnace temperature, HoFeO3 can also release lattice oxygen, replenish O2 in the gas phase, enhance the full combustion of coal and reduce coking.

[0014] CeO2 forms oxygen vacancies at high temperatures, which promotes the oxidation of SO2 to SO3. CeO2 reacts with SO3 to generate thermally stable cerium sulfate. The decomposition temperature of cerium sulfate is relatively high and it is relatively stable under furnace temperature conditions.

[0015] As can be seen from the above, component A fixes sulfur from multiple dimensions and different angles, and the active components complement each other to avoid the occurrence of "dead corners" in sulfur fixation.

[0016] SrO-MgO not only acts as a carrier, increasing the contact area between the active components of sulfur fixation and SO2, thus improving the sulfur fixation efficiency, but also inhibits the high-temperature decomposition of calcium sulfate, further improving the sulfur fixation efficiency. The details are as follows: SrO reacts with CaSO4, formed by the sulfur fixation of the main active component, CaO, under the normal operating bed temperature of 850-900°C in a circulating fluidized bed boiler: SrO + CaSO4 → SrSO4 + CaO. The resulting SrSO4 decomposes at a temperature of 1600°C, higher than that of CaSO4. Furthermore, the main active component, CaO, can be regenerated, allowing it to continue to participate in sulfur fixation, further improving sulfur fixation efficiency.

[0017] In addition, MgO can also form a solid solution with CaSO4 or generate magnesium sulfate, and together with SrO, it solves the problem of circulating fluidized bed boilers that when CaSO4 circulates with the bed material to the dense phase zone, the SO2 released by decomposition participates in the reaction again, resulting in a further reduction in desulfurization efficiency.

[0018] Component B: Active components MgCO3 and KNO3 are loaded on the carrier BaFe 12 O 19 ; Among them, the mass ratio of MgCO3:KNO3 is (2-3):1.

[0019] In the initial stage of coal combustion, the BaFe 12 O 19 Under furnace temperature conditions, the active component MgCO3 produces a first micro-explosion in the coal seam, which makes the coal seam bulky, improves its permeability, and fully participates in the combustion of the coal's combustible components. As the temperature gradually rises, the oxidant reacts sequentially, and the carbon powder produced by the first micro-explosion reaches a high concentration in the local space, causing a secondary deflagration, further strengthening the micro-explosion effect. This not only significantly reduces the blackness of the exhaust smoke, but also reduces the carbon content of the slag, thereby improving the combustion efficiency of the boiler. In addition, the decomposition of MgCO3 produces MgO, which acts as a catalyst to reduce the activation energy of coal combustion.

[0020] KNO3 decomposes under furnace temperature conditions to produce oxygen, which can increase the local oxygen concentration. After mixing with the combustible gas, it expands the ignition range of the combustible gas and makes the suspended carbon particles burn more thoroughly.

[0021] The carrier BaFe 12 O 19 It has a magnetoplumbite structure and is ferrimagnetic. It is a tiny magnetic particle that can maintain its magnetism in the absence of an external magnetic field. This allows component B to achieve magnetic suspension for a long time in the high temperature environment of the furnace, achieving a longer retention time in the furnace.

[0022] Component C: Cu-doped CoFe2O4, chemical formula is Cux Co 1-x Fe2O4, 0.3≤x≤0.5.

[0023] Cu-doped CoFe2O4 has a spinel structure that acts as an oxygen carrier, promoting oxygen transfer. This effectively accelerates the gasification reaction of coal char in coal-fired environments and reduces the accumulation of solid coke. The surface of Cu-doped CoFe2O4 is rich in acidic sites, which promote the adsorption and decomposition of sulfur and nitrogen compounds in coal char, further reducing coking.

[0024] During the research process of the present invention, it was found that when the molar amount of Cu doping is in the range of 0.3-0.5, the degree of regulation of the lattice distortion and active site distribution of CoFe2O4 can promote more complete combustion of combustible gases, suspended carbon particles and semi-coke in the coal seam in the furnace, which helps to prevent coking. However, when the molar amount of Cu doping exceeds 0.5, it has a counterproductive effect on the catalytic performance of CoFe2O4.

[0025] The mass ratio of component A:component B:component C is (5-8):(2-3):1.

[0026] Furthermore, in the coal-saving, desulfurizing, ash-removing and coking agent used in circulating fluidized bed boilers, in component A, the mass ratio of active components CaO:HoFeO3:CeO2 is 12:1:4; and the molar ratio of SrO:MgO in the carrier is 3:1.

[0027] Furthermore, the chemical formula of the coal-saving, desulfurizing, ash-removing and coking agent used in circulating fluidized bed boilers is Cu in component C. 0.4 Co 0.6 Fe2O4.

[0028] Furthermore, the mass ratio of component A: component B: component C in the coal-saving, desulfurization, ash removal and coke cleaning agent used in circulating fluidized bed boilers is 6:2:1.

[0029] In the present invention, the coal-saving, desulfurizing, ash-removing and coking agent used in circulating fluidized bed boilers has a particle size of component A of 0.2-0.4 mm, a particle size of component B of 20-50 μm, and a particle size of component C of 10-25 μm.

[0030] After the three components of the coal-saving desulfurization, ash removal and coking agent are mixed with the fuel coal, the degree of coking can be further reduced through the gradient grading method. According to production practice statistics, the coking amount of circulating fluidized bed boilers has decreased by 78%-86%, and the annual maintenance and coking cost can be saved by at least 3.5 million yuan.

[0031] In the present invention, the coal-saving, desulfurizing, ash-removing and coking agent for circulating fluidized bed boilers, component A of which is prepared by the following steps: (1) Preparation of carrier SrO-MgO: First, a 30wt%-40wt% Sr(NO3)2 aqueous solution and a 20wt%-25wt% Mg(NO3)2 aqueous solution are stirred and mixed to obtain a mixed solution; wherein the molar ratio of metal ions Sr:Mg in the mixed solution is (2-4):1; Then, the pH value of the obtained mixed solution is adjusted to 10-11, and ammonia water with a concentration of 1-2 mol / L is added to the mixed solution under stirring at room temperature to carry out a precipitation reaction; After precipitation is completed, the mixture is aged at room temperature for at least 12 hours; filtered, washed, and dried; and the precipitate is calcined at 600-800° C. for 4-6 hours to obtain a SrO-MgO composite oxide.

[0032] (2) Preparation of component A: S1. Prepare a Ca(NO3)2 aqueous solution with a concentration of 2-3 mol / L as the impregnation solution a and set aside; S2, prepare a Ho(NO3)3 aqueous solution with a concentration of 0.5-1.0 mol / L and a Fe(NO3)3 aqueous solution with a concentration of 0.5-1.0 mol / L, mix the Ho(NO3)3 aqueous solution and the Fe(NO3)3 aqueous solution in a molar ratio of 1:1, and adjust the pH value to 4-5 to form an impregnation solution b, which is set aside; S3, prepare a Ce(NO3)3 aqueous solution with a concentration of 1.0-1.5 mol / L as the impregnation solution c, and set aside; S4. According to the mass ratio of the active components, measure the impregnation solution a, impregnation solution b, and impregnation solution c required for impregnation and set aside; S5. Immerse the carrier SrO-MgO obtained in step (1) in the impregnation solution b prepared in S4, stir at room temperature for 1-2 hours, and let it stand for 12 hours; filter and dry to obtain the impregnation precursor of this step; place the obtained impregnation precursor in a muffle furnace and heat it to 650-700°C at 2-4°C / min, and calcine it for 3-5 hours; cool it to room temperature to obtain SrO-MgO loaded with HoFeO3; S6. Immerse the HoFeO3-loaded SrO-MgO obtained in S5 into the impregnation solution c prepared in S4, stir at room temperature for 3-4 hours, let stand for 24 hours, filter, and dry to obtain the impregnation precursor of this step; place the obtained impregnation precursor in a muffle furnace and heat it to 550-650°C at 1-2°C / min, and calcine it for 4-5 hours; cool it to room temperature to obtain SrO-MgO loaded with CeO2 and HoFeO3; S6. Immerse the HoFeO3-loaded SrO-MgO obtained in S5 into the impregnation solution c prepared in S4, stir at room temperature for 3-4 hours, let stand for 24 hours, filter, and dry to obtain the impregnation precursor of this step; place the obtained impregnation precursor in a muffle furnace and heat it to 550-650°C at 1-2°C / min, and calcine it for 4-5 hours; cool it to room temperature to obtain SrO-MgO loaded with CeO2 and HoFeO3; S7. Immerse the SrO-MgO loaded with CeO2 and HoFeO3 obtained in S6 into the impregnation solution a prepared in S4, stir at room temperature for 7-9 hours, let stand for 48 hours, filter, and dry to obtain the impregnation precursor of this step; place the obtained impregnation precursor in a muffle furnace and heat it to 800-850°C at 1-2°C / min, and calcine it for 6-8 hours; cool it to room temperature to obtain component A, SrO-MgO loaded with CaO, CeO2 and HoFeO3.

[0033] In the present invention, the coal-saving, desulfurizing, ash-removing and coking agent for circulating fluidized bed boilers, component B of which is prepared by the following steps: (1) Preparation of BaFe carrier 12 O 19 : First, dissolve Ba(NO3)2 and Fe(NO3)3 in deionized water, add citric acid, stir until uniform, and adjust the pH value to 5-6; heat in a water bath at 80-85°C to form a gel; Then, the gel was dried and calcined at 700-800℃ for 3-5h to obtain BaFe 12 O 19 .

[0034] (2) Preparation of component B: First, MgCO3, KNO3 and BaFe 12 O 19 Stir the powder to mix evenly; Then, ethanol is added and stirred to obtain a slurry; the slurry is placed at 70-75° C., stirred, and dried; after drying, the slurry is placed at 150-200° C. for heat stabilization treatment for 1.5-2 hours to obtain component B.

[0035] In the present invention, the coal-saving, desulfurizing, ash-removing and coking agent for circulating fluidized bed boilers, wherein component C is prepared by the following steps: First, the metal sources of cobalt nitrate, iron nitrate and copper nitrate are dissolved in deionized water according to the molar ratio, citric acid is added, and stirred until completely dissolved to obtain a metal salt mixed solution.

[0036] Then, the metal salt mixed solution is heated in a water bath at 80-85° C. to form a sol, and then the temperature is further raised to 125-130° C. to obtain a gel.

[0037] Finally, the obtained gel was calcined at 650-750°C for 5-7h to obtain Cu-doped CoFe2O4.

[0038] In the present invention, the coal-saving, desulfurizing, ash-removing and coking agent used in a circulating fluidized bed boiler is used in an amount of 0.15% to 0.2% of the amount of coal loaded into each boiler of the circulating fluidized bed boiler.

[0039] The specific operation of the method for using the above-mentioned coal-saving, desulfurization, ash removal and coke cleaning agent for circulating fluidized bed boilers is as follows: First, the coal is crushed to obtain pulverized coal with a particle size of 1-6 mm; Then, the components A, B and C of the coal-saving, desulfurizing, ash-removing and coking agent are sequentially added into the pulverized coal and ground and mixed thoroughly.

[0040] The beneficial effects of the present invention are as follows: the coal-saving, desulfurization, ash removal and coke cleaning agent applied to a circulating fluidized bed boiler according to the present invention can effectively save fuel, improve sulfur fixation efficiency, reduce the formation of coke scale on the furnace wall and remove old coke scale, thereby improving the working condition of the circulating fluidized bed boiler and greatly reducing its operation and maintenance costs.

[0041] First, this coal-saving desulfurization, ash removal, and coke cleaning agent provides excellent oxygen supply and oxygen enrichment, allowing the suspended carbon particles and combustible gases in the combustion chamber to fully combust, thereby reducing the carbon content of the slag and the combustible content of the fly ash, and improving combustion efficiency. Practice has proven that using this coal-saving desulfurization, ash removal, and coke cleaning agent can save over 7% of coal in circulating fluidized bed boilers.

[0042] The coal-saving desulfurization, ash removal, and coke cleaning agent then converts the sulfur in the coal into solid sulfides, which are discharged with the slag, thereby significantly reducing the emission of sulfur dioxide gas, which is a serious air pollutant. Test analysis shows that the use of the coal-saving desulfurization, ash removal, and coke cleaning agent can achieve a desulfurization rate of over 93% in boilers.

[0043] In addition, the use of the coal-saving, desulfurizing, ash-removing and coking agent can also reduce the content of combustibles in slag and fly ash due to complete combustion.

[0044] The coal-saving desulfurization, ash removal and coke cleaning agent can be retained in the furnace for a long time. On the one hand, it prevents the formation of coke, reduces the coking rate by at least 70%, and controls the steam temperature fluctuation within ±5°C; on the other hand, it can gradually loosen and fall off the coke, which can greatly improve the heat conduction efficiency of the boiler, reduce the exhaust gas temperature, and at the same time reduce the corrosion and wear caused by scaling and coking, extend the inspection cycle and service life of the boiler, reduce the number of inspections and maintenance of the boiler, reduce the annual maintenance cost by at least 30%, and maintain the safe and economical operation of the boiler. DETAILED DESCRIPTION

[0045] The technical solution of the present invention is described in detail below. Example 1

[0046] The coal-saving, desulfurizing, ash-removing and coking agent for circulating fluidized bed boilers is composed of the following components: Component A: The active components CaO, HoFeO3 and CeO2 are loaded on the carrier SrO-MgO; wherein the mass ratio of CaO:HoFeO3:CeO2 is 12:1:4; and the molar ratio of SrO:MgO in the carrier is 3:1.

[0047] The component A is prepared by the following steps: (1) Preparation of carrier SrO-MgO: First, a 40 wt% Sr(NO3)2 aqueous solution and a 20 wt% Mg(NO3)2 aqueous solution were stirred and mixed to obtain a mixed solution; wherein the molar ratio of metal ions Sr:Mg in the mixed solution was 3:1; Then, the pH value of the obtained mixed solution was adjusted to 11, and 1.5 mol / L ammonia water was added to the mixed solution under stirring at room temperature to carry out precipitation reaction; After precipitation is completed, the mixture is aged at room temperature for 12 hours; filtered, washed, and dried; and the precipitate is calcined at 700° C. for 5 hours to obtain a SrO-MgO composite oxide.

[0048] (2) Preparation of component A: S1. Prepare a 2.5 mol / L Ca(NO3)2 aqueous solution as the immersion solution a for later use; S2, prepare a 1.0 mol / L Ho(NO3)3 aqueous solution and a 1.0 mol / L Fe(NO3)3 aqueous solution, mix the Ho(NO3)3 aqueous solution and the Fe(NO3)3 aqueous solution in a molar ratio of 1:1, and adjust the pH value to 4 to form an impregnation solution b, which is set aside; S3, prepare a Ce(NO3)3 aqueous solution with a concentration of 1.5 mol / L as the impregnation solution c, and set aside; S4. According to the mass ratio of the active components, measure the impregnation solution a, impregnation solution b, and impregnation solution c required for impregnation and set aside; S5. Immerse the carrier SrO-MgO obtained in step (1) in the impregnation solution b prepared in S4, stir at room temperature for 1 hour, and let it stand for 12 hours; filter and dry to obtain the impregnation precursor of this step; place the obtained impregnation precursor in a muffle furnace, heat it to 650°C at 3°C / min, and calcine it for 4 hours; cool it to room temperature to obtain SrO-MgO loaded with HoFeO3; S6. Immerse the HoFeO3-loaded SrO-MgO obtained in S5 into the impregnation solution c prepared in S4, stir at room temperature for 4 hours, let stand for 24 hours, filter, and dry to obtain the impregnation precursor of this step; place the obtained impregnation precursor in a muffle furnace and heat it to 600°C at 2°C / min, and calcine it for 4 hours; cool it to room temperature to obtain SrO-MgO loaded with CeO2 and HoFeO3; S7. Immerse the SrO-MgO loaded with CeO2 and HoFeO3 obtained in S6 into the impregnation solution a prepared in S4, stir at room temperature for 9 hours, let stand for 48 hours, filter, and dry to obtain the impregnation precursor of this step; place the obtained impregnation precursor in a muffle furnace, heat it to 850°C at 1.5°C / min, and calcine it for 8 hours; cool it to room temperature to obtain component A, SrO-MgO loaded with CaO, CeO2 and HoFeO3.

[0049] Component B: Active components MgCO3 and KNO3 are loaded on the carrier BaFe 12 O 19 ; Among them, the mass ratio of MgCO3:KNO3 is 3:1.

[0050] The component B is prepared by the following steps: (1) Preparation of BaFe carrier 12 O 19 : First, Ba(NO3)2 and Fe(NO3)3 were dissolved in deionized water, citric acid was added, stirred until homogeneous, and the pH value was adjusted to 5; then heated in a water bath at 85°C to form a gel; Then, the gel was dried and calcined at 750 ° C for 4 h to obtain BaFe 12 O 19 .

[0051] (2) Preparation of component B: First, MgCO3, KNO3 and BaFe 12 O 19 Stir the powder to mix evenly; Then, ethanol was added and stirred to obtain a slurry; the slurry was stirred and dried at 75° C.; after drying, it was placed at 200° C. for thermal stabilization treatment for 2 hours to obtain component B.

[0052] Component C: Cu-doped CoFe2O4, chemical formula is Cu 0.4 Co 0.6 Fe2O4.

[0053] The component C is prepared by the following steps: First, dissolving metal sources cobalt nitrate, iron nitrate, and copper nitrate in deionized water according to the molar ratio, adding citric acid, and stirring until completely dissolved to obtain a metal salt mixed solution; Then, the metal salt mixed solution was heated in a water bath at 85°C to form a sol, and then the temperature was further raised to 130°C to obtain a gel; Finally, the obtained gel was calcined at 50 °C for 6 h to obtain Cu-doped CoFe2O4.

[0054] The mass ratio of component A:component B:component C is 6:2:1. Example 2

[0055] The coal-saving, desulfurizing, ash-removing and coking agent for circulating fluidized bed boilers is composed of the following components: Component A: The active components CaO, HoFeO3 and CeO2 are loaded on the carrier SrO-MgO; wherein the mass ratio of CaO:HoFeO3:CeO2 is 10:1:2; and the molar ratio of SrO:MgO in the carrier is 2:1.

[0056] The component A is prepared by the following steps: (1) Preparation of carrier SrO-MgO: First, a 30 wt% Sr(NO3)2 aqueous solution and a 20 wt% Mg(NO3)2 aqueous solution were stirred and mixed to obtain a mixed solution; wherein the molar ratio of metal ions Sr:Mg in the mixed solution was 2:1; Then, the pH value of the obtained mixed solution was adjusted to 10, and 1 mol / L ammonia water was added to the mixed solution under stirring at room temperature to carry out a precipitation reaction; After precipitation is completed, the mixture is aged at room temperature for 12 hours; filtered, washed, and dried; and the precipitate is calcined at 600° C. for 6 hours to obtain a SrO-MgO composite oxide.

[0057] (2) Preparation of component A: S1. Prepare a 3 mol / L Ca(NO3)2 aqueous solution as the immersion solution a for later use; S2, prepare a 0.5 mol / L Ho(NO3)3 aqueous solution and a 0.5 mol / L Fe(NO3)3 aqueous solution, mix the Ho(NO3)3 aqueous solution and the Fe(NO3)3 aqueous solution in a molar ratio of 1:1, and adjust the pH value to 4 to form an impregnation solution b, which is set aside; S3, prepare a Ce(NO3)3 aqueous solution with a concentration of 1.0 mol / L as the impregnation solution c, and set aside; S4. According to the mass ratio of the active components, measure the impregnation solution a, impregnation solution b, and impregnation solution c required for impregnation and set aside; S5. Immerse the carrier SrO-MgO obtained in step (1) in the impregnation solution b prepared in S4, stir at room temperature for 2 hours, and let it stand for 12 hours; filter and dry to obtain the impregnation precursor of this step; place the obtained impregnation precursor in a muffle furnace and heat it to 700°C at 4°C / min, and calcine it for 3 hours; cool it to room temperature to obtain SrO-MgO loaded with HoFeO3; S6. Immerse the HoFeO3-loaded SrO-MgO obtained in S5 into the impregnation solution c prepared in S4, stir at room temperature for 4 hours, let stand for 24 hours, filter, and dry to obtain the impregnation precursor of this step; place the obtained impregnation precursor in a muffle furnace and heat it to 550°C at 2°C / min, and calcine it for 5 hours; cool it to room temperature to obtain SrO-MgO loaded with CeO2 and HoFeO3; S7. Immerse the SrO-MgO loaded with CeO2 and HoFeO3 obtained in S6 into the impregnation solution a prepared in S4, stir at room temperature for 7 hours, let stand for 48 hours, filter, and dry to obtain the impregnation precursor of this step; place the obtained impregnation precursor in a muffle furnace and heat it to 850°C at 2°C / min, and calcine for 6 hours; cool it to room temperature to obtain component A, SrO-MgO loaded with CaO, CeO2 and HoFeO3.

[0058] Component B: Active components MgCO3 and KNO3 are loaded on the carrier BaFe 12 O 19 ; Among them, the mass ratio of MgCO3:KNO3 is 3:1.

[0059] The component B is prepared by the following steps: (1) Preparation of BaFe carrier 12 O 19 : First, Ba(NO3)2 and Fe(NO3)3 were dissolved in deionized water, citric acid was added, stirred until homogeneous, and the pH value was adjusted to 6; then heated in a water bath at 80°C to form a gel; Then, the gel was dried and calcined at 700 °C for 5 h to obtain BaFe 12 O 19 ; (2) Preparation of component B: First, MgCO3, KNO3 and BaFe 12 O 19 Stir the powder to mix evenly; Then, ethanol was added and stirred to obtain a slurry; the slurry was stirred and dried at 70° C.; after drying, it was placed at 200° C. for heat stabilization treatment for 1.5 hours to obtain component B.

[0060] Component C: Cu-doped CoFe2O4, chemical formula is Cu 0.3 Co 0.7 Fe2O4.

[0061] The component C is prepared by the following steps: First, dissolving metal sources cobalt nitrate, iron nitrate, and copper nitrate in deionized water according to the molar ratio, adding citric acid, and stirring until completely dissolved to obtain a metal salt mixed solution; Then, the metal salt mixed solution was heated in a water bath at 85°C to form a sol, and then the temperature was further raised to 125°C to obtain a gel; Finally, the obtained gel was calcined at 750 °C for 5 h to obtain Cu-doped CoFe2O4.

[0062] The mass ratio of component A:component B:component C is 5:2:1. Example 3

[0063] The coal-saving, desulfurizing, ash-removing and coking agent for circulating fluidized bed boilers is composed of the following components: Component A: The active components CaO, HoFeO3 and CeO2 are loaded on the carrier SrO-MgO; wherein the mass ratio of CaO:HoFeO3:CeO2 is 15:1:5; and the molar ratio of SrO:MgO in the carrier is 4:1.

[0064] The component A is prepared by the following steps: (1) Preparation of carrier SrO-MgO: First, a 40 wt% Sr(NO3)2 aqueous solution and a 20 wt% Mg(NO3)2 aqueous solution were stirred and mixed to obtain a mixed solution; wherein the molar ratio of metal ions Sr:Mg in the mixed solution was 4:1; Then, the pH value of the obtained mixed solution was adjusted to 11, and 2 mol / L ammonia water was added to the mixed solution under stirring at room temperature to carry out precipitation reaction; After precipitation is completed, the mixture is aged at room temperature for 12 hours; filtered, washed, and dried; and the precipitate is calcined at 800° C. for 4 hours to obtain a SrO-MgO composite oxide.

[0065] (2) Preparation of component A: S1. Prepare a 2 mol / L Ca(NO3)2 aqueous solution as the immersion solution a for later use; S2, prepare a 1.0 mol / L Ho(NO3)3 aqueous solution and a 1.0 mol / L Fe(NO3)3 aqueous solution, mix the Ho(NO3)3 aqueous solution and the Fe(NO3)3 aqueous solution in a molar ratio of 1:1, and adjust the pH value to 4 to form an impregnation solution b, which is set aside; S3, prepare a Ce(NO3)3 aqueous solution with a concentration of 1.5 mol / L as the impregnation solution c, and set aside; S4. According to the mass ratio of the active components, measure the impregnation solution a, impregnation solution b, and impregnation solution c required for impregnation and set aside; S5. Immerse the carrier SrO-MgO obtained in step (1) in the impregnation solution b prepared in S4, stir at room temperature for 1 hour, and let it stand for 12 hours; filter and dry to obtain the impregnation precursor of this step; place the obtained impregnation precursor in a muffle furnace, heat it to 650°C at 2°C / min, and calcine it for 5 hours; cool it to room temperature to obtain SrO-MgO loaded with HoFeO3; S6. Immerse the HoFeO3-loaded SrO-MgO obtained in S5 into the impregnation solution c prepared in S4, stir at room temperature for 3 hours, let stand for 24 hours, filter, and dry to obtain the impregnation precursor of this step; place the obtained impregnation precursor in a muffle furnace and heat it to 650°C at 1°C / min, and calcine it for 4 hours; cool it to room temperature to obtain SrO-MgO loaded with CeO2 and HoFeO3; S7. Immerse the SrO-MgO loaded with CeO2 and HoFeO3 obtained in S6 into the impregnation solution a prepared in S4, stir at room temperature for 9 hours, let stand for 48 hours, filter, and dry to obtain the impregnation precursor of this step; place the obtained impregnation precursor in a muffle furnace and heat it to 800°C at 1°C / min, and calcine for 8 hours; cool it to room temperature to obtain component A, SrO-MgO loaded with CaO, CeO2 and HoFeO3.

[0066] Component B: Active components MgCO3 and KNO3 are loaded on the carrier BaFe 12 O 19 ; Among them, the mass ratio of MgCO3:KNO3 is 2:1.

[0067] The component B is prepared by the following steps: (1) Preparation of BaFe carrier 12 O 19 : First, Ba(NO3)2 and Fe(NO3)3 were dissolved in deionized water, citric acid was added, stirred until homogeneous, and the pH value was adjusted to 5; then heated in a water bath at 85°C to form a gel; Then, the gel was dried and calcined at 800 °C for 3 h to obtain BaFe 12 O19 ; (2) Preparation of component B: First, MgCO3, KNO3 and BaFe 12 O 19 Stir the powder to mix evenly; Then, ethanol was added and stirred to obtain a slurry; the slurry was stirred and dried at 75° C.; after drying, the slurry was placed at 150° C. for heat stabilization treatment for 2 hours to obtain component B.

[0068] Component C: Cu-doped CoFe2O4, chemical formula is Cu 0.5 Co 0.5 Fe2O4.

[0069] The component C is prepared by the following steps: First, dissolving metal sources cobalt nitrate, iron nitrate, and copper nitrate in deionized water according to the molar ratio, adding citric acid, and stirring until completely dissolved to obtain a metal salt mixed solution; Then, the metal salt mixed solution was heated in a water bath at 80°C to form a sol, and then the temperature was further raised to 130°C to obtain a gel; Finally, the obtained gel was calcined at 650 °C for 7 h to obtain Cu-doped CoFe2O4.

[0070] The mass ratio of component A:component B:component C is 8:3:1. Example 4

[0071] The difference from Example 2 is that the component C in this example is Cu-doped CoFe2O4, with the chemical formula Cu 0.5 Co 0.5 Fe2O4.

[0072] The rest is the same as Example 2. Example 5

[0073] The difference from Example 2 is that the molar ratio of SrO:MgO in component A of this example is 4:1.

[0074] In the preparation step (1) of the component A, the molar ratio of metal ions Sr:Mg in the mixed solution is 4:1.

[0075] The rest is the same as Example 2.

[0076] Comparative Example 1

[0077] The difference from Example 1 is that the weight ratio of component A:component B:component C in this comparative example is 6:1:1.

[0078] The rest is the same as in Example 1.

[0079] Comparative Example 2

[0080] The difference from Example 1 is that in component A in this comparative example, the mass ratio of CaO:HoFeO3:CeO2 is 5:1:1.

[0081] The rest is the same as in Example 1.

[0082] Comparative Example 3

[0083] The difference from Example 1 is that in component B in this comparative example, the mass ratio of MgCO3:KNO3 is 1:3.

[0084] The rest is the same as in Example 1.

[0085] Comparative Example 4

[0086] The difference from Example 1 is that in component C of this comparative example, Cu-doped CoFe2O4, the chemical formula of which is Cu 0.7 Co 0.3 Fe2O4.

[0087] The rest is the same as in Example 1.

[0088] Comparative Example 5

[0089] The difference from Example 1 is that the operation of step (2) of the preparation method of component A in this comparative example is as follows:

[0090] S5. Immerse the carrier SrO-MgO obtained in step (1) in the impregnation solution c prepared in S4, stir at room temperature for 4 hours, let it stand for 24 hours, filter, and dry to obtain the impregnation precursor of this step; place the obtained impregnation precursor in a muffle furnace and heat it to 600°C at 2°C / min, and calcine it for 4 hours; cool it to room temperature to obtain SrO-MgO loaded with CeO2; S6. Immerse the CeO2-loaded SrO-MgO obtained in S5 into the impregnation solution b prepared in S4, stir at room temperature for 1 hour, and let it stand for 12 hours; filter and dry to obtain the impregnation precursor of this step; place the obtained impregnation precursor in a muffle furnace and heat it to 650°C at 3°C / min, and calcine it for 4 hours; cool it to room temperature to obtain SrO-MgO loaded with HoFeO3 and CeO2; S7. Immerse the SrO-MgO loaded with HoFeO3 and CeO2 obtained in S6 into the impregnation solution a prepared in S4, stir at room temperature for 9 hours, let stand for 48 hours, filter, and dry to obtain the impregnation precursor of this step; place the obtained impregnation precursor in a muffle furnace and heat it to 850°C at 1.5°C / min, and calcine for 8 hours; cool it to room temperature to obtain component A, SrO-MgO loaded with CaO, CeO2 and HoFeO3.

[0091] The following is a performance test experiment on the coal-saving, desulfurization, ash removal and coke cleaning agent described in each embodiment and comparative example.

[0092] 1. Experimental purpose: To test the coal saving rate, desulfurization rate, fly ash carbon content and large slag carbon content of the circulating fluidized bed boiler after using the coal saving, desulfurization, ash removal and coke cleaning agent of the present invention compared with the blank control group.

[0093] 2. Experimental method: The No. 1 atmospheric pressure circulating fluidized bed boiler of a thermal power plant of a certain company was used as the experimental object. The test period was the winter heating period, and the boiler was operating normally at full load.

[0094] Taking one working condition as a unit, the SO2 emission rate (kg / h) of the boiler is recorded on time and the desulfurization rate (%), coal consumption per ton of steam (kg / h), fly ash carbon content, and large slag carbon content are calculated by respectively adding the coal-saving desulfurization, ash-removing and coking agent described in each embodiment and comparative example at 0.2% of the amount of coal loaded in each pot of the circulating fluidized bed boiler; and adding the coal-saving desulfurization, ash-removing and coking agent described in Example 1 at 0.6% of the amount of coal loaded in each pot of the circulating fluidized bed boiler.

[0095] Specific operation: First, the coal is crushed to obtain pulverized coal with a particle size of 5-6mm; Then, the components A, B and C of the coal-saving desulfurization, ash removal and coke cleaning agent are sequentially added to the pulverized coal and ground and mixed thoroughly. The particle size of the component A is 0.3-0.4 mm, the particle size of the component B is 40-45 μm, and the particle size of the component C is 15-20 μm.

[0096] Note: The flue gas flow rate remains stable during the test; the quality of the boiler coal remains unchanged during the test; before conducting the next operating condition test, it must first be stabilized for 5 hours before the test is carried out.

[0097] The test results are shown in Table 1.

[0098]

Claims

1. A coal-saving, desulfurizing, ash-removing and coking agent for boilers, characterized in that: It is composed of the following components: Component A: Active components CaO, HoFeO3 and CeO2 are loaded on a carrier SrO-MgO; wherein the mass ratio of CaO:HoFeO3:CeO2 is (10-15):1:(2-5); the molar ratio of SrO:MgO in the carrier is (2-4):1; Component B: Active components MgCO3 and KNO3 are loaded on the carrier BaFe 12 O 19 ; Wherein, the mass ratio of MgCO3:KNO3 is (2-3):1; Component C: Cu-doped CoFe2O4, chemical formula is Cu x Co 1-x Fe2O4, 0.3≤x≤0.5; The mass ratio of component A:component B:component C is (5-8):(2-3):

1.

2. The coal-saving, desulfurization, ash-removing and coke-cleaning agent for circulating fluidized bed boilers according to claim 1, characterized in that: In the component A, the mass ratio of active components CaO:HoFeO3:CeO2 is 12:1:4; and the molar ratio of SrO:MgO in the carrier is 3:

1.

3. The coal-saving, desulfurization, ash-removing and coke-cleaning agent for circulating fluidized bed boilers according to claim 1, characterized in that: In the component C, the chemical formula of Cu-doped CoFe2O4 is Cu 0.4 Co 0.6 Fe2O4.

4. The coal-saving, desulfurizing, ash-removing and coking agent for circulating fluidized bed boilers according to claim 1, characterized in that: The mass ratio of component A:component B:component C is 6:2:

1.

5. The coal-saving, desulfurization, ash-removing and coke-cleaning agent for circulating fluidized bed boilers according to claim 1, characterized in that: The particle size of component A is 0.2-0.4 mm, the particle size of component B is 20-50 μm, and the particle size of component C is 10-25 μm.

6. The coal-saving, desulfurizing, ash-removing and coking agent for circulating fluidized bed boilers according to claim 1, characterized in that: The component A is prepared by the following steps: (1) Preparation of carrier SrO-MgO: First, a 30wt%-40wt% Sr(NO3)2 aqueous solution and a 20wt%-25wt% Mg(NO3)2 aqueous solution are stirred and mixed to obtain a mixed solution; wherein the molar ratio of metal ions Sr:Mg in the mixed solution is (2-4):1; Then, the pH value of the obtained mixed solution is adjusted to 10-11, and ammonia water with a concentration of 1-2 mol / L is added to the mixed solution under stirring at room temperature to carry out a precipitation reaction; After precipitation is completed, the mixture is aged at room temperature for at least 12 hours; filtered, washed, and dried; and the precipitate is calcined at 600-800° C. for 4-6 hours to obtain a SrO-MgO composite oxide; (2) Preparation of component A: S1. Prepare a Ca(NO3)2 aqueous solution with a concentration of 2-3 mol / L as the impregnation solution a and set aside; S2, prepare a Ho(NO3)3 aqueous solution with a concentration of 0.5-1.0 mol / L and a Fe(NO3)3 aqueous solution with a concentration of 0.5-1.0 mol / L, mix the Ho(NO3)3 aqueous solution and the Fe(NO3)3 aqueous solution in a molar ratio of 1:1, and adjust the pH value to 4-5 to form an impregnation solution b, which is set aside; S3, prepare a Ce(NO3)3 aqueous solution with a concentration of 1.0-1.5 mol / L as the impregnation solution c, and set aside; S4. According to the mass ratio of the active components, measure the impregnation solution a, impregnation solution b, and impregnation solution c required for impregnation and set aside; S5. Immerse the carrier SrO-MgO obtained in step (1) in the impregnation solution b prepared in S4, stir at room temperature for 1-2 hours, and let it stand for 12 hours; filter and dry to obtain the impregnation precursor of this step; place the obtained impregnation precursor in a muffle furnace and heat it to 650-700°C at 2-4°C / min, and calcine it for 3-5 hours; cool it to room temperature to obtain SrO-MgO loaded with HoFeO3; S6. Immerse the HoFeO3-loaded SrO-MgO obtained in S5 into the impregnation solution c prepared in S4, stir at room temperature for 3-4 hours, let stand for 24 hours, filter, and dry to obtain the impregnation precursor of this step; place the obtained impregnation precursor in a muffle furnace and heat it to 550-650°C at 1-2°C / min, and calcine it for 4-5 hours; cool it to room temperature to obtain SrO-MgO loaded with CeO2 and HoFeO3; S7. Immerse the SrO-MgO loaded with CeO2 and HoFeO3 obtained in S6 into the impregnation solution a prepared in S4, stir at room temperature for 7-9 hours, let stand for 48 hours, filter, and dry to obtain the impregnation precursor of this step; place the obtained impregnation precursor in a muffle furnace and heat it to 800-850°C at 1-2°C / min, and calcine it for 6-8 hours; cool it to room temperature to obtain component A, SrO-MgO loaded with CaO, CeO2 and HoFeO3.

7. The coal-saving, desulfurizing, ash-removing and coking agent for circulating fluidized bed boilers according to claim 1, characterized in that: The component B is prepared by the following steps: (1) Preparation of BaFe carrier 12 O 19 : First, dissolve Ba(NO3)2 and Fe(NO3)3 in deionized water, add citric acid, stir until uniform, and adjust the pH value to 5-6; heat in a water bath at 80-85°C to form a gel; Then, the gel was dried and calcined at 700-800℃ for 3-5h to obtain BaFe 12 O 19 ; (2) Preparation of component B: First, MgCO3, KNO3 and BaFe 12 O 19 Stir the powder to mix evenly; Then, ethanol is added and stirred to obtain a slurry; the slurry is placed at 70-75° C., stirred, and dried; after drying, the slurry is placed at 150-200° C. for heat stabilization treatment for 1.5-2 hours to obtain component B.

8. The coal-saving, desulfurizing, ash-removing and coking agent for circulating fluidized bed boilers according to claim 1, characterized in that: The component C is prepared by the following steps: First, dissolving metal sources cobalt nitrate, iron nitrate, and copper nitrate in deionized water according to the molar ratio, adding citric acid, and stirring until completely dissolved to obtain a metal salt mixed solution; Then, the metal salt mixed solution is heated in a water bath at 80-85°C to form a sol, and then the temperature is further raised to 125-130°C to obtain a gel; Finally, the obtained gel was calcined at 650-750°C for 5-7h to obtain Cu-doped CoFe2O4.

9. The coal-saving, desulfurizing, ash-removing and coking agent for circulating fluidized bed boilers according to claim 1, characterized in that: The usage of this coal-saving desulfurization, ash removal and coking agent is 0.15%-0.2% of the coal loading amount per boiler of the circulating fluidized bed boiler.

10. The method for using the coal-saving, desulfurization, ash removal and coke cleaning agent for a circulating fluidized bed boiler according to any one of claims 1 to 9, characterized in that: The specific operations are as follows: First, the coal is crushed to obtain pulverized coal with a particle size of 1-6 mm; Then, the components A, B and C of the coal-saving, desulfurizing, ash-removing and coking agent are sequentially added into the pulverized coal and ground and mixed thoroughly.

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