Cu-modified red mud-fly ash flue gas desulfurizer, preparation method and application thereof

Abstract

This invention belongs to the field of red mud and fly ash solid waste recycling and flue gas desulfurization technology. To address the problems of high energy consumption, investment and operating costs, wastewater treatment, and ultra-low emissions in existing coal-fired flue gas desulfurization technologies, this invention provides a Cu-modified red mud-fly ash flue gas desulfurizer, its preparation method, and its application. Red mud and fly ash are mixed at a mass ratio of 8:1 to 1:1, hydrated, and then calcined at a medium temperature of 200-300℃ to obtain a red mud-fly ash matrix. This matrix is ​​then modified by impregnation in a Cu(NO3)2·3H2O solution, dried, and calcined at a high temperature of 450-650℃ to obtain the Cu-modified red mud-fly ash flue gas desulfurizer. The active component (CaO) is utilized within the 200-600℃ temperature range. 12 The synergistic effect of (Al2O3)7 and 2MgO·SiO2, hydroxyl groups, and active adsorption oxygen removes SO2 from flue gas with an average removal efficiency of ≥93%. Using solid waste red mud and fly ash as raw materials to prepare flue gas desulfurizers allows for the treatment of waste with waste, achieving high-value utilization of solid waste resources.

Description

Technical Field

[0001] This invention belongs to the field of red mud and fly ash solid waste recycling and flue gas desulfurization technology, specifically involving a Cu-modified red mud-fly ash flue gas desulfurization agent, its preparation method and application. Background Technology

[0002] Coal-fired power generation produces a large amount of SO2. As an acidic gas, SO2 emitted into the atmosphere can cause great harm to the ecological environment and human health. Therefore, controlling SO2 in flue gas is an important part of air pollution control.

[0003] Currently, the most mature industrial flue gas desulfurization technology for coal-fired power plants is the limestone-gypsum wet desulfurization method. This method has high SO2 removal efficiency, but it suffers from drawbacks such as high energy consumption, high investment and operating costs, and wastewater treatment. The latest national ultra-low emission standards for coal-fired power plants require SO2 emissions to be below 35 mg / m³. 3 Therefore, it is imperative to develop an effective dry flue gas desulfurization agent that meets the requirements of ultra-low emissions.

[0004] Red mud is a waste product from alumina plants, mainly composed of Al2O3, SiO2, Fe2O3, and MgO. It is highly alkaline and can cause soil alkalization and freshwater pollution. Fly ash is a solid waste product from coal-fired power plants, primarily composed of metal oxides such as SiO2, Al2O3, Fe2O3, CaO, and MgO. Its accumulation occupies large amounts of land and causes serious damage to the ecological environment. The chemical compositions of both red mud and fly ash indicate that they have certain recycling value.

[0005] The components of fly ash mainly exist in a glassy form, exhibiting low activity and limited adsorption capacity. Therefore, it cannot be directly used for SO2 removal and requires modification to improve its adsorption performance. This can be achieved by modifying fly ash with strongly alkaline red mud, thus enhancing the utilization of both red mud and fly ash. Consequently, red mud, fly ash, and metal additives can be used to prepare desulfurizing agents with economic and social benefits for the efficient dry removal of SO2 from coal-fired flue gas, thereby achieving ultra-low SO2 emissions and realizing the goal of treating waste with waste. Summary of the Invention

[0006] To address the problems of high energy consumption, investment and operating costs, wastewater treatment, and ultra-low emissions in existing coal-fired flue gas desulfurization technologies, this invention provides a Cu-modified red mud-fly ash flue gas desulfurizer, its preparation method, and its application.

[0007] This invention is achieved by the following technical solution: a Cu-modified red mud-fly ash flue gas desulfurizer, wherein the Cu-modified red mud-fly ash flue gas desulfurizer is obtained by mixing red mud and fly ash at a mass ratio of 8:1-1:1, hydrating and then calcining at a medium temperature of 200-300℃ to obtain a red mud-fly ash matrix, then impregnating it in Cu(NO3)2·3H2O solution for modification, drying and then calcining at a high temperature of 450-650℃, which is the Cu-modified red mud-fly ash flue gas desulfurizer.

[0008] The fly ash is fly ash from a pulverized coal furnace, and the red mud is aluminum red mud produced by the sintering method.

[0009] The method for preparing the Cu-modified red mud-fly ash flue gas desulfurizer comprises the following steps:

[0010] (1) Raw material grinding and screening: The raw red mud and fly ash are mechanically ground and screened to obtain red mud and fly ash with a particle size of less than 0.15 mm for later use;

[0011] (2) Preparation of red mud-fly ash matrix: The red mud and fly ash obtained by sieving are mixed at a mass ratio of 8:1-1:1. The mixture is mixed evenly with deionized water at a volume ratio of 1:3-1:20. The mixture is hydrated in a water bath at 60-95℃ for 1-8h. The hydrate is then dried at 60-100℃ for 4-10h and calcined at 200-300℃ for 1-4h to obtain the red mud-fly ash matrix.

[0012] (3) Preparation of Cu-modified red mud-fly ash flue gas desulfurizer: Mix red mud-fly ash matrix with 0.01-0.4 mol / L Cu(NO3)2·3H2O solution evenly, the volume ratio of red mud-fly ash matrix to Cu(NO3)2·3H2O solution is 1:3-1:10, soak in a water bath at 60-95℃ for 1-3h, then separate the solid and liquid, dry the obtained solid at 80-100℃ for 6-10h, calcine at 450-650℃ for 1-3h, and cool naturally to room temperature, which is the Cu-modified red mud-fly ash flue gas desulfurizer.

[0013] The above-mentioned Cu-modified red mud-fly ash flue gas desulfurization agent is used to remove SO2 from flue gas.

[0014] The specific method is as follows: the desulfurizing agent utilizes the active component (CaO) within a temperature range of 200-600℃. 12 The synergistic effect of (Al2O3)7 and 2MgO·SiO2, hydroxyl groups, and active adsorbed oxygen removes SO2 from flue gas with an average removal efficiency of ≥93%.

[0015] SO2 is removed from flue gas; the reaction gas consists of 5% O2 and 500 mg / m³. 3The mixture consists of SO2 and N2 as a balance gas, with a desulfurizing agent mass of 1g. The experiment was stopped when the average removal efficiency was lower than 93%.

[0016] During the hydration process of red mud and fly ash, the strong alkalinity of the red mud disrupts the glassy structure on the fly ash surface, thereby improving the pore structure of the red mud-fly ash mixture. This effectively improves the SO2 gas transport performance and enhances the desulfurization capacity of the desulfurizing agent. Simultaneously, the hydration process generates numerous hydroxyl groups, which can effectively oxidize SO2, further improving the desulfurization capacity of the desulfurizing agent. Further drying and medium-temperature (200-300℃) calcination of the hydrated red mud-fly ash mixture will form a new substance (CaO). 12 ·(Al2O3)7 and 2MgO·SiO2 are the main active substances for SO2 removal; Cu(NO3)2·3H2O-modified red mud-fly ash enhances the activity of CaO. 12 The formation and uniform distribution of ·(Al2O3)7 and 2MgO·SiO2, and the partial release of active substances (CaO) during the high-temperature (450-650℃) calcination of the red mud-fly ash matrix impregnated with Cu(NO3)2·3H2O. 12 (Al₂O₃)₇ decomposes into CaO and Al₂O₃, further enhancing the desulfurization capacity of the desulfurizing agent; component Cu exists within the desulfurizing agent as Cu + and Cu 2+ Cu exists in the form of Cu during the desulfurization process. + To Cu 2+ The conversion can effectively promote the conversion of actively adsorbed oxygen, thereby improving the desulfurizer's catalytic oxidation and removal capacity of SO2. Therefore, Cu-modified red mud-fly ash flue gas desulfurizer is based on the active component (CaO). 12 SO2 is removed through the synergistic effect of (Al2O3)7 and 2MgO·SiO2, hydroxyl groups, and actively adsorbed oxygen. The prepared desulfurizer can effectively remove SO2 from coal-fired flue gas in the temperature range of 200-600℃, with an average removal efficiency of ≥93%. Using solid waste red mud and fly ash as raw materials to prepare the flue gas desulfurizer can achieve waste-to-waste treatment.

[0017] The Cu-modified red mud-fly ash flue gas desulfurizer prepared in this invention can fully meet the latest ultra-low emission standard for thermal power plants, which requires SO2 emissions to be below 35 mg / m³. 3 Requirements. Attached Figure Description

[0018] Figure 1 The SO2 removal efficiency curve of desulfurizing agent C in Example 3 is shown. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains, and all materials publicly cited herein and cited by them are incorporated herein by reference.

[0021] Equivalent technologies of the specific embodiments described herein that are readily apparent to those skilled in the art through routine experimentation are included in this application.

[0022] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the instruments and equipment used in the following examples are all standard laboratory instruments and equipment; unless otherwise specified, the experimental materials used in the following examples were all purchased from regular biochemical reagent stores.

[0023] Example 1: A Cu-modified red mud-fly ash flue gas desulfurizer, specifically prepared as follows: The original red mud and fly ash are mechanically ground separately. The red mud and fly ash particles with a diameter less than 0.15 mm obtained by sieving are mixed at a mass ratio of 1:1. This mixture is then mixed evenly with deionized water at a volume ratio of 1:3. The mixture is hydrated in a 95°C water bath for 1 hour, then dried at 100°C for 4 hours, and then calcined at 250°C for 4 hours to obtain a red mud-fly ash matrix. The red mud-fly ash matrix is ​​then mixed evenly with a 0.01 mol / L Cu(NO3)2·3H2O solution at a volume ratio of 1:3. The mixture is then impregnated in a 95°C water bath for 2 hours, filtered to obtain a solid, and then dried at 100°C for 6 hours, and then calcined at 650°C for 1 hour. The solid is then naturally cooled to room temperature, yielding Cu-modified red mud-fly ash flue gas desulfurizer A.

[0024] An experiment to remove SO2 was conducted at 200℃. The reaction gases consisted of O2 (5%) and SO2 (500 mg / m³). 3 It consists of N2 (balance gas) and 1g of desulfurizing agent. The experiment is stopped when the average removal efficiency is lower than 93%. The cumulative sulfur capacity of the desulfurizing agent in the desulfurization experiment is 46.33mg / g, and the highest removal rate of 100% can be maintained for 12min.

[0025] Example 2: A Cu-modified red mud-fly ash flue gas desulfurizer, specifically prepared as follows: Raw red mud and fly ash are mechanically ground separately. Red mud with a particle size less than 0.15 mm obtained by sieving is mixed with fly ash at a mass ratio of 8:1. This mixture is then mixed evenly with deionized water at a volume ratio of 1:20. The mixture is hydrated in a 95°C water bath for 8 hours, then dried at 90°C for 10 hours, and finally calcined at 300°C for 2 hours to obtain the Cu-modified red mud-fly ash flue gas desulfurizer. Red mud-fly ash matrix is ​​prepared by mixing red mud-fly ash matrix with 0.2 mol / L Cu(NO3)2·3H2O solution at a volume ratio of 1:10. The mixture is then immersed in a 90°C water bath for 2 hours, filtered to obtain a solid, and dried at 90°C for 10 hours. After drying, the solid is calcined at 450°C for 3 hours, with the remaining steps being the same as described in Example 1. The mixture is then naturally cooled to room temperature to obtain Cu-modified red mud-fly ash flue gas desulfurizer B.

[0026] An experiment to remove SO2 was conducted at 400℃. The reaction gases consisted of O2 (5%) and SO2 (500 mg / m³). 3 It consists of N2 (balance gas) and 1g of desulfurizing agent. The experiment is stopped when the average removal efficiency is lower than 93%. The cumulative sulfur capacity of this desulfurizing agent in the desulfurization experiment is 75.62mg / g, and the maximum removal rate of 100% can be maintained for 24min.

[0027] Example 3: A Cu-modified red mud-fly ash flue gas desulfurizer, specifically prepared as follows: The original red mud and fly ash are mechanically ground separately. The red mud and fly ash particles with a diameter less than 0.15 mm obtained by sieving are mixed at a mass ratio of 5:1. This mixture is then mixed evenly with deionized water at a volume ratio of 1:5. The mixture is hydrated in a 90°C water bath for 2 hours, then dried at 90°C for 10 hours, and then calcined at 300°C for 2 hours to obtain a red mud-fly ash matrix. The red mud-fly ash matrix is ​​then mixed evenly with a 0.02 mol / L Cu(NO3)2·3H2O solution at a volume ratio of 1:6, and impregnated in a 90°C water bath for 2 hours. The mixture is filtered to obtain a solid, which is then dried at 90°C for 10 hours, and then calcined at 500°C for 2 hours. The solid is then naturally cooled to room temperature, yielding the Cu-modified red mud-fly ash flue gas desulfurizer C.

[0028] An experiment to remove SO2 was conducted at 500℃. The reaction gases consisted of O2 (5%) and SO2 (500 mg / m³). 3 The desulfurizer consists of nitrogen (N2) and nitrogen (N2) (balance gas). The mass of the desulfurizer is 1g. The experiment was stopped when the average removal efficiency fell below 93%. The cumulative sulfur capacity of this desulfurizer in the desulfurization experiment was 193.91 mg / g, and the highest removal rate of 100% could be maintained for 65 minutes. The SO2 removal efficiency curve of this desulfurizer C is shown below. Figure 1 As shown.

[0029] Example 4: A Cu-modified red mud-fly ash flue gas desulfurizer, specifically prepared as follows: Raw red mud and fly ash are mechanically ground separately. Red mud and fly ash with a particle size less than 0.15 mm obtained by sieving are mixed at a mass ratio of 5:1. This mixture is then mixed evenly with deionized water at a volume ratio of 1:5. The mixture is hydrated in a 90°C water bath for 2 hours, then dried at 90°C for 10 hours, and then calcined at 300°C for 2 hours to obtain a red mud-fly ash matrix. The red mud-fly ash matrix is ​​then mixed evenly with a 0.4 mol / L Cu(NO3)2·3H2O solution at a volume ratio of 1:6, and impregnated in a 90°C water bath for 2 hours. The mixture is filtered to obtain a solid, which is then dried at 90°C for 10 hours, and then calcined at 500°C for 2 hours. The solid is then naturally cooled to room temperature, yielding Cu-modified red mud-fly ash flue gas desulfurizer D.

[0030] An experiment to remove SO2 was conducted at 600℃. The reaction gases consisted of O2 (5%) and SO2 (500 mg / m³). 3 It consists of N2 (balance gas) and the mass of the desulfurizing agent is 1g. The experiment is stopped when the average removal efficiency is lower than 93%. The cumulative sulfur capacity of the desulfurizing agent in the desulfurization experiment is 108.13mg / g. The maximum removal rate of 100% can be maintained for 26min.

[0031] Example 5: A Cu-modified red mud-fly ash flue gas desulfurizer, specifically prepared as follows: The original red mud and fly ash are mechanically ground separately. The red mud and fly ash particles with a diameter less than 0.15 mm obtained by sieving are mixed at a mass ratio of 6:1. This mixture is then mixed evenly with deionized water at a volume ratio of 1:10. The mixture is hydrated in a 60°C water bath for 5 hours, then dried at 60°C for 7 hours, and then calcined at 200°C for 1 hour to obtain a red mud-fly ash matrix. The red mud-fly ash matrix is ​​then mixed evenly with a 0.4 mol / L Cu(NO3)2·3H2O solution at a volume ratio of 1:6, impregnated in a 60°C water bath for 1 hour, filtered to obtain a solid, and then dried at 80°C for 8 hours, and then calcined at 500°C for 2 hours. The solid is then naturally cooled to room temperature to obtain Cu-modified red mud-fly ash flue gas desulfurizer E.

[0032] An experiment to remove SO2 was conducted at 500℃. The reaction gases consisted of O2 (5%) and SO2 (500 mg / m³). 3 It consists of N2 (balance gas) and the mass of the desulfurizing agent is 1g. The experiment is stopped when the average removal efficiency is lower than 93%. The cumulative sulfur capacity of the desulfurizing agent in the desulfurization experiment is 124.08mg / g. The maximum removal rate of 100% can be maintained for 43min.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A Cu-modified red mud-fly ash flue gas desulfurizer, characterized in that: The Cu-modified red mud-fly ash flue gas desulfurizer is prepared by mixing red mud and fly ash in a mass ratio of 8:1-1:1, hydrating, calcining at a medium temperature of 200-300 DEG C, then dipping the red mud-fly ash matrix obtained in a Cu(NO3)2.3H2O solution, drying, and calcining at a high temperature of 450-650 DEG C.

2. The Cu-modified red mud-fly ash flue gas desulfurizer according to claim 1, characterized in that: The fly ash is pulverized coal furnace fly ash, and the red mud is sintering process aluminum red mud.

3. A process for the preparation of the Cu-modified red mud- fly ash flue gas desulfurizer according to claim 1 or 2, characterized by: The steps are as follows: (1) raw material grinding and screening: grinding the raw red mud and fly ash by a machine respectively, and screening to obtain red mud and fly ash with a particle size less than 0.15 mm for standby; (2) preparing a red mud-fly ash matrix: mixing the screened red mud and fly ash in a mass ratio of 8:1-1:1, mixing the mixture with deionized water uniformly, the volume ratio of the mixture to deionized water being 1:3-1:20, hydrating the mixture in a water bath at 60-95 DEG C for 1-8 h, then drying the hydrate at 60-100 DEG C for 4-10 h, and calcining at 200-300 DEG C for 1-4 h to prepare the red mud-fly ash matrix; (3) preparing a Cu-modified red mud-fly ash flue gas desulfurizer: mixing the red mud-fly ash matrix with a Cu(NO3)2.3H2O solution of 0.01-0.4 mol / L uniformly, the volume ratio of the red mud-fly ash matrix to the Cu(NO3)2.3H2O solution being 1:3-1:10, dipping the mixture in a water bath at 60-95 DEG C for 1-3 h, then separating the solid from the liquid, drying the obtained solid at 80-100 DEG C for 6-10 h, and calcining at 450-650 DEG C for 1-3 h to obtain the Cu-modified red mud-fly ash flue gas desulfurizer.

4. Application of the Cu-modified red mud-fly ash flue gas desulfurizer in claim 1 or 2 to removal of SO2 in flue gas.

5. Use according to claim 4, characterized in that: The specific method is that the desulfurizer uses active component (CaO) in 200-600 ℃ temperature range 12 ·The synergistic effect of (Al2O3) 7 and 2MgO·SiO2, hydroxyl groups and active adsorbed oxygen removes SO2 in flue gas, and the average removal efficiency is ≥93%.

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