Preparation method of calcium hydroxide desulfurizer based on functionalized graphene modification

Abstract

The application belongs to the technical field of calcium hydroxide preparation, and particularly relates to a preparation method of a modified calcium hydroxide desulfurizer based on functionalized graphene. The method comprises the following steps: uniformly mixing quicklime and amino-functionalized graphene, adding water, and performing digestion reaction to obtain the modified calcium hydroxide desulfurizer. In the lime digestion process, the amino-functionalized graphene is added, which on one hand promotes the uniform dispersion of calcium hydroxide particles in the two-dimensional graphene network, inhibits the agglomeration of calcium hydroxide particles, forms a steric hindrance effect of the silane branched chain, increases the specific surface area between the calcium hydroxide particles, and improves the pore size and pore volume, so that the calcium hydroxide with high specific surface area is obtained; on the other hand, the amino functional groups on the surface of the functionalized graphene provide new high-density basic sites, which can synergistically strengthen the host-guest interaction, thereby greatly improving the adsorption capacity of sulfur dioxide and the efficiency of flue gas desulfurization.

Description

Technical Field

[0001] This invention belongs to the field of calcium hydroxide preparation technology, specifically relating to a method for preparing a calcium hydroxide desulfurizing agent based on functionalized graphene-modified calcium hydroxide. Background Technology

[0002] With rapid industrial development, sulfur dioxide in coal-fired flue gas has become one of the major sources of air pollution. Therefore, controlling sulfur dioxide emissions and improving air quality has become an urgent requirement and important goal for sustainable social and economic development.

[0003] Flue gas desulfurization (FGD) refers to the removal of sulfur oxides (SO2 and SO3) from flue gas or other industrial waste gases. FGD systems are classified into three main categories based on whether water is added during the process and the dry / wet state of the desulfurization products: wet, semi-dry, and fully dry. Dry FGD technology is increasingly used in desulfurization systems for coke oven gas in coking plants, flue gas from gas-fired power plants in steel mills, and flue gas from kilns in glass, cement, and smelting heating processes, as well as magnesium metal kilns. This technology is mature and operates stably. The SDS desulfurization process, using sodium bicarbonate as the alkali source, offers advantages such as high desulfurization efficiency, a wide range of desulfurizing agent sources, and low engineering implementation difficulty. Under the action of high-temperature flue gas, ultrafine sodium bicarbonate powder decomposes into highly active sodium carbonate (Na2CO3) and carbon dioxide. The highly active Na2CO3 reacts chemically with SO2 and other acidic media in the flue gas, resulting in absorption and purification to meet emission standards.

[0004] The "desulfurization ash" produced by SDS desulfurization mainly consists of sodium sulfate and sodium sulfite, and also contains impurities such as sodium carbonate and dust. Due to the large number of impurities, it cannot be comprehensively utilized. Sodium sulfate has high solubility in water, easily polluting environmental water sources, making landfilling impossible. Approximately 5 million tons of desulfurization ash are produced annually nationwide. The revised "Law of the People's Republic of China on the Prevention and Control of Environmental Pollution by Solid Waste" came into full effect on September 1, 2020, adding relevant responsibilities to solid waste generating enterprises and clearly stipulating severe penalties for illegal activities, significantly increasing the pressure on enterprises. Furthermore, the price of sodium bicarbonate desulfurizing agent increased several times between 2019 and 2022, leading to a substantial increase in the desulfurization costs for these enterprises.

[0005] Calcium hydroxide is a white, hexagonal, powdery crystalline powder with a density of 2.243 g / cm³. 3Calcium hydroxide is a strong alkali and has wide applications in water treatment and environmental pollution control. It is particularly effective as a desulfurizing agent in mature dry and semi-dry flue gas desulfurization processes. The flue gas purification process using calcium hydroxide generally utilizes the gas-solid contact between acidic gases in the flue gas and calcium hydroxide, leading to acid-base reactions or related adsorption. The key factors determining this reaction are the specific surface area of ​​calcium hydroxide and the number of alkaline sites. Therefore, preparing calcium hydroxide with a high specific surface area and abundant alkaline sites is crucial for improving flue gas desulfurization efficiency.

[0006] Compared to baking soda, calcium hydroxide desulfurizer with high specific surface area and high activity has the characteristics of being porous, highly active, well-dispersible, and highly utilized, with a specific surface area (BET) of 40 m². 2 With a specific surface area of ​​over 85%, it is 3-4 times more potent than ordinary calcium hydroxide, enabling it to rapidly adsorb and absorb SO2 in flue gas with a utilization rate exceeding 85%. High-surface-area calcium hydroxide exhibits excellent fluidity, preventing pipe blockage during use. The desulfurization product is gypsum, which can be used as a building and cement material. The desulfurization process does not involve carbon dioxide emissions, thus avoiding the use of corporate carbon emission quotas. No grinding or pulverization is required during use, simplifying the process. High-surface-area calcium hydroxide offers significant economic advantages.

[0007] Currently, the preparation of high specific surface area calcium hydroxide often requires the addition of various organic additives. For example, patent document CN116903270B discloses a method for preparing highly reactive and high specific surface area calcium hydroxide powder, which involves adding hydrochloric acid aqueous solution, ammonia water, and ammonium carbonate aqueous solution as additives during the digestion process. The strong acid and alkali additives added cause serious environmental pollution. However, there are few reports on adding environmentally friendly solid additives during the digestion reaction to increase the specific surface area of ​​calcium hydroxide. Summary of the Invention

[0008] To address the technical problems existing in the prior art, the present invention provides a method for preparing a desulfurizing agent based on functionalized graphene-modified calcium hydroxide, and the prepared calcium hydroxide can be used for efficient desulfurization of flue gas.

[0009] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0010] A method for preparing a modified calcium hydroxide desulfurizer based on functionalized graphene includes: mixing quicklime and amino-functionalized graphene evenly, adding water, and carrying out a digestion reaction to obtain the modified calcium hydroxide desulfurizer.

[0011] Furthermore, the quicklime is crushed and screened to a particle size of no more than 300 mesh, and the effective calcium oxide content is no less than 85%.

[0012] Furthermore, the bonding molecules of the amino-functionalized graphene include at least one of 3-aminopropyltrimethoxysilane, N-aminomethyl-3-aminopropyltrimethoxysilane, and N-aminoethyl-3-aminopropyltrimethoxysilane.

[0013] Furthermore, the mass ratio of quicklime to amino-functionalized graphene is 10:1 to 25:1.

[0014] Furthermore, the mass ratio of water to quicklime is 0.3 to 0.7.

[0015] Furthermore, the conditions for the digestion reaction are: temperature 25°C. ～ 70℃, rotation speed 1200 rpm to 1500 rpm.

[0016] A modified calcium hydroxide desulfurizing agent prepared by the method described above has a specific surface area of ​​45 m². 2 / g or more.

[0017] Application of a desulfurizing agent as described above in efficient flue gas desulfurization.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] (1) This invention uses amino-functionalized graphene for in-situ modification during the lime digestion process, which promotes the high dispersion of calcium hydroxide particles in the two-dimensional layered network of graphene, destroys the flocculation structure, releases the encapsulated water molecules to participate in the digestion reaction, thereby inhibiting the aggregation of calcium hydroxide particles. The steric hindrance effect of the silane branching chain greatly improves the specific surface area, pore size and pore volume of calcium hydroxide.

[0020] (2) The abundant amino functional groups on the surface of amino-functionalized graphene provide new high-density alkaline sites for the removal of sulfur dioxide, which can synergistically enhance the host-guest interaction, thereby greatly improving the adsorption capacity of sulfur dioxide and improving the flue gas desulfurization efficiency.

[0021] (3) The present invention uses amino-functionalized graphene as a solid modifier, which is environmentally friendly and suitable for large-scale production of calcium hydroxide with high specific surface area. Detailed Implementation

[0022] To facilitate understanding of the present invention, a more comprehensive description will be given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0023] The BET specific surface area and total pore volume of the products in the examples and comparative examples were tested and analyzed using a specific surface area analyzer according to the method in GB / T 19587-2017 "Determination of Specific Surface Area of ​​Solid Substances by Gas Adsorption BET Method".

[0024] The desulfurization performance was evaluated using a fixed-bed reactor with an inner diameter of 15 mm. The desulfurization gas composition was 600 mg / Nm³ of SO₂. 3 The composition was 7% CO2, 21% O2, 8% gaseous H2O, and the remainder was equilibrium N2. The reaction temperature was 220℃, the flue gas velocity was 0.5 m / min, and the SO2 content was determined using an infrared flue gas analyzer.

[0025] Aminofunctionalized graphene was prepared by the following method: graphene oxide was dispersed in a certain amount of wastewater toluene, sonicated for 2 hours, and one or more of 3-aminopropyltrimethoxysilane (APTMS), N-aminomethyl-3-aminopropyltrimethoxysilane (AMAPTS) and N-aminoethyl-3-aminopropyltrimethoxysilane (AAPTMS) were added, refluxed for 12 hours, and dried overnight in a vacuum oven at 60°C.

[0026] Example 1

[0027] Weigh 850g of 180-mesh quicklime (effective calcium oxide content 87.4%) and 85g of 3-aminopropyltrimethoxysilane (APTMS) functionalized graphene, add 255g of tap water, add the dispersion to the digestion reactor, the initial temperature of the digestion reactor is 25℃, start stirring, the speed is 1300 rpm, after digestion for 10 minutes, modified calcium hydroxide powder is obtained.

[0028] The specific surface area of ​​modified calcium hydroxide is 47.20 m². 2 / g, pore size 5.28nm, pore volume 0.187cm³ 3 / g, sulfur dioxide removal efficiency 96.9%.

[0029] Example 2

[0030] Weigh 850g of 180-mesh quicklime (effective calcium oxide content 90.2%) and 60g of N-aminomethyl-3-aminopropyltrimethoxysilane (AMAPTS) functionalized graphene, add 340g of tap water, add the dispersion to the digestion reactor, the initial temperature of the digestion reactor is 40℃, start stirring, the speed is 1500 rpm, and after digestion for 15 minutes, modified calcium hydroxide powder is obtained.

[0031] The specific surface area of ​​modified calcium hydroxide is 49.84 m². 2 / g, pore size 5.63nm, pore volume 0.154cm³ 3 / g, sulfur dioxide removal efficiency 95.7%.

[0032] Example 3

[0033] Weigh 850g of 180-mesh quicklime (effective calcium oxide content 89.5%) and 54g of N-aminoethyl-3-aminopropyltrimethoxysilane (AAPTMS) functionalized graphene, add 520g of tap water, add the dispersion to the digestion reactor, the initial temperature of the digestion reactor is 40℃, start stirring, the speed is 1300 rpm, and after digestion for 20 minutes, modified calcium hydroxide powder is obtained.

[0034] The specific surface area of ​​modified calcium hydroxide is 52.36 m². 2 / g, pore size 5.18nm, pore volume 0.262cm³ 3 / g, sulfur dioxide removal efficiency 97.2%.

[0035] Example 4

[0036] Weigh 850g of 180-mesh quicklime (effective calcium oxide content 91.6%), 26g of 3-aminopropyltrimethoxysilane (APTMS) functionalized graphene, and 39g of N-aminoethyl-3-aminopropyltrimethoxysilane (AAPTMS) functionalized graphene. Add 590g of tap water and add the dispersion to a digestion reactor. The initial temperature of the digestion reactor is 55℃. Start stirring at 1450 rpm. After digestion for 10 minutes, modified calcium hydroxide powder is obtained.

[0037] The specific surface area of ​​modified calcium hydroxide is 55.12 m². 2 / g, pore size 6.26nm, pore volume 0.178cm³ 3 / g, sulfur dioxide removal efficiency 98.1%.

[0038] Example 5

[0039] Weigh out 850g of 180-mesh quicklime (effective calcium oxide content 93.7%), 15g of 3-aminopropyltrimethoxysilane (APTMS) functionalized graphene, 35g of N-aminomethyl-3-aminopropyltrimethoxysilane (AMAPTS), and 13g of N-aminoethyl-3-aminopropyltrimethoxysilane (AAPTMS) functionalized graphene. Add 450g of tap water and add the dispersion to a digestion reactor. The initial temperature of the digestion reactor is 65℃. Start stirring at 1500 rpm and digest for 20 minutes to obtain modified calcium hydroxide powder.

[0040] The specific surface area of ​​modified calcium hydroxide is 58.36 m². 2 / g, pore size 6.71nm, pore volume 0.185cm³ 3 / g, sulfur dioxide removal efficiency 99.5%.

[0041] Example 6

[0042] Weigh out 850g of 180-mesh quicklime (effective calcium oxide content 92.0%), 30g of 3-aminopropyltrimethoxysilane (APTMS) functionalized graphene, 19g of N-aminomethyl-3-aminopropyltrimethoxysilane (AMAPTS), and 26g of N-aminoethyl-3-aminopropyltrimethoxysilane (AAPTMS) functionalized graphene. Add 490g of tap water and add the dispersion to a digestion reactor. The initial temperature of the digestion reactor is 25℃. Start stirring at 1400 rpm and digest for 10 minutes to obtain modified calcium hydroxide powder.

[0043] The specific surface area of ​​modified calcium hydroxide is 49.65 m². 2 / g, pore size 5.21nm, pore volume 0.248cm³ 3 / g, sulfur dioxide removal efficiency 96.8%.

[0044] The above description is only for better explaining the embodiments of the present invention and is not intended to limit them. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention shall fall within the scope of the present invention.

Claims

1. A method for preparing a functionalized graphene-modified calcium hydroxide desulfurizing agent, characterized in that: Quicklime and amino-functionalized graphene are mixed evenly, and then water is added to carry out a digestion reaction to obtain a modified calcium hydroxide desulfurizer.

2. The preparation method of a functionalized graphene-modified calcium hydroxide desulfurizer according to claim 1, characterized in that: The quicklime is crushed and screened to a particle size of no more than 300 mesh, and the effective calcium oxide content is no less than 85%.

3. The preparation method of a functionalized graphene-modified calcium hydroxide desulfurizer according to claim 1, characterized in that: The bonding molecules of the amino-functionalized graphene include at least one of 3-aminopropyltrimethoxysilane, N-aminomethyl-3-aminopropyltrimethoxysilane, and N-aminoethyl-3-aminopropyltrimethoxysilane.

4. The preparation method of a functionalized graphene-modified calcium hydroxide desulfurizer according to claim 1, characterized in that: The mass ratio of quicklime to aminofunctionalized graphene is 10:1 to 25:

1.

5. The preparation method of a functionalized graphene-modified calcium hydroxide desulfurizer according to claim 1, characterized in that: The mass ratio of water to quicklime is 0.3 to 0.

7.

6. The preparation method of a functionalized graphene-modified calcium hydroxide desulfurizer according to claim 1, characterized in that: The digestion reaction conditions are: temperature 25-70℃, rotation speed 1200-1500 rpm.

7. A modified calcium hydroxide desulfurizing agent prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The modified calcium hydroxide desulfurizer has a specific surface area of ​​45 m². 2 / g or more.

8. The application of the desulfurizing agent according to claim 7 in efficient flue gas desulfurization.