A so2 adsorbent rich in double structural basic centers, its preparation method and use

Abstract

This invention discloses an SO2 adsorbent rich in nitrogen and hydroxyl dual-structure base centers, its preparation method, and its application, belonging to the field of industrial flue gas desulfurization technology. The adsorbent of this invention has a wavelength of 50–200 nm and a specific surface area ≥20 m². 2 Using nano-Ca(OH)₂ as the matrix, 5%–15% of urea-phenolic resin-based nitrogen-containing base centers are loaded to form a synergistic system of hydroxyl groups and pyrrole-type nitrogen and graphitic nitrogen dual base centers, with a specific surface area of ​​22–28 m². 2 / g, SO2 in flue gas after desulfurization ≤ 20mg / Nm 3 The preparation method includes the preparation of nano-Ca(OH)2 seed crystals, synthesis of nitrogen-containing dispersants, composite modification, and vacuum drying and sieving. The process is simple and environmentally friendly. This invention significantly improves the sulfur capacity of the adsorbent while reducing its dosage by more than 35%. It is suitable for deep desulfurization of flue gas from sintering / pelletizing processes after blast furnace gas combustion, and combines the advantages of high activity, low cost, and easy industrialization, solving the core technical pain points of traditional calcium-based desulfurizers.

Description

Technical Field

[0001] This invention relates to the field of industrial flue gas desulfurization technology, specifically to an SO2 adsorbent rich in dual-structure alkaline centers, its preparation method, and its application. Background Technology

[0002] In industrial production, blast furnace gas is often used as fuel for sintering / pelletizing processes in iron ore processing. After combustion, sulfur impurities in iron ore will produce a large amount of high-emission, complex SO2 flue gas. If not effectively treated, it will cause serious air pollution and fail to meet the environmental protection requirements for ultra-low emissions of industrial flue gas.

[0003] Currently, the mainstream SO2 adsorbents in industry are traditional calcium-based materials such as CaO and Ca(OH)2. While these materials are readily available and inexpensive, they suffer from three major drawbacks: first, low sulfur capacity and a high Ca / S molar ratio, leading to high adsorbent consumption and operating costs; second, insufficient adsorption precision, making it difficult to reduce the SO2 concentration in flue gas to 20 mg / Nm³. 3 The following factors make it unsuitable for ultra-low emission standards: First, the particles are prone to agglomeration, have a small specific surface area, and are scarce on the surface with active sites, which further reduces desulfurization efficiency and adsorption capacity.

[0004] Existing technologies attempt to modify calcium-based adsorbents by adding dispersants and mechanical activation, but these methods only improve particle agglomeration or specific surface area individually. They cannot construct a highly efficient and synergistic active site system, resulting in limited modification effects. Furthermore, they cannot simultaneously address the problems of low sulfur capacity, poor adsorption precision, and easy agglomeration, making it difficult to meet the deep desulfurization requirements of complex flue gas from sintering / pelletizing processes. Therefore, developing SO2 adsorbents with high specific surface area, high sulfur capacity, high adsorption precision, and anti-agglomeration properties has become a technological bottleneck in the field of industrial flue gas desulfurization. Summary of the Invention

[0005] This invention addresses the shortcomings of traditional calcium-based SO2 adsorbents, such as low sulfur capacity, poor adsorption precision, easy particle agglomeration, and the inability of existing modification technologies to achieve synergistic effects. It provides a high specific surface area and high sulfur capacity SO2 adsorbent rich in nitrogen and hydroxyl dual-structure base centers. At the same time, it provides a simple, cost-controllable, and environmentally friendly preparation method, enabling the adsorbent to meet the ultra-low emission requirements of SO2 in industrial flue gas and adapt to the complex working conditions of sintering / pelletizing processes.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: This invention provides an SO2 adsorbent rich in dual-structure base centers, with a particle size of 50–200 nm and a specific surface area ≥20 m². 2The adsorbent uses nano-Ca(OH)₂ as a matrix, with the matrix surface loaded with nitrogen-containing structural base centers accounting for 5%–15% of the total adsorbent mass. These nitrogen-containing structural base centers are prepared using urea and phenolic resin as precursors and contain pyrrole-type and graphitic nitrogen. The adsorbent forms a synergistic system of hydroxyl groups and pyrrole-type and graphitic nitrogen dual-structure base centers, with a final product specific surface area of ​​22–28 m². 2 / g.

[0007] Furthermore, the phenolic resin is a thermosetting phenolic resin with a molecular weight of 500 to 1000.

[0008] Furthermore, the nano-Ca(OH)2 is prepared by hydration reaction of quicklime with CaO content ≥90%, wherein the water-lime ratio in the hydration reaction is 0.55-0.8 and the reaction temperature is 70-90℃.

[0009] This invention also provides a method for preparing the above-mentioned SO2 adsorbent rich in dual-structure base centers, comprising the following steps: S1. Preparation of nano-Ca(OH)2 seed crystals: Using quicklime with CaO≥90% as raw material, deionized water is added, the water-lime ratio is controlled at 0.55~0.8, a dispersant is added, and the hydration reaction is carried out at 70~90℃ for 1~2h. After centrifugation, washing and low-temperature drying, nano-Ca(OH)2 seed crystals are obtained. S2. Preparation of nitrogen-containing base central dispersant: Mix urea and phenolic resin at a mass ratio of 1:1 to 3, add deionized water, add catalyst to adjust the pH value to 8 to 10, react in a water bath at 75 to 90°C for 1 to 2 hours, cool to room temperature, and obtain nitrogen-containing base central dispersant; S3. Composite modification: The nano Ca(OH)2 seed crystals obtained in step S1 are ultrasonically dispersed in deionized water, and the nitrogen-containing base center dispersant obtained in step S2 is added dropwise. The mass ratio of dispersant to seed crystals is controlled at 0.05 to 0.15:1. The mixture is stirred and reacted at 60 to 80°C for 2 to 4 hours to obtain a nano Ca(OH)2 mixed system loaded with nitrogen-containing base centers. S4. Post-processing: After centrifugation and washing, the mixture obtained in step S3 is vacuum dried, pulverized, and sieved to obtain the target adsorbent.

[0010] Further, in step S1, the dispersant is sodium hexametaphosphate at 0.1% to 0.5% of the mass of the quicklime raw material; the low-temperature drying temperature is 60 to 80°C, and the drying time is 3 to 5 hours.

[0011] Further, in step S2, the catalyst is sodium hydroxide at a concentration of 0.05% to 0.1% relative to the total mass of urea and phenolic resin.

[0012] Furthermore, in step S3, the ultrasonic dispersion power is 200-400W, the dispersion time is 10-30min, and the stirring reaction rate is 300-500rpm.

[0013] Furthermore, in step S4, the vacuum drying temperature is 80–100°C, the vacuum degree is -0.08–-0.1 MPa, and the drying time is 4–6 hours. Furthermore, in step S4, the sieving process uses a 200-325 mesh screen.

[0014] The present invention also provides an application of the above-mentioned SO2 adsorbent rich in dual-structure alkaline centers for deep desulfurization of SO2-containing flue gas from sintering / pelletizing processes after blast furnace gas combustion.

[0015] The technical solution of this invention has the following advantages: A. This invention prepares high specific surface area nano-Ca(OH)2 using a seed crystal growth method, which effectively reduces particle size and increases specific surface area, significantly increasing the number of hydroxyl (-OH) groups on the matrix surface. As a type I structural base center, the hydroxyl group provides sufficient active sites for SO2 adsorption, directly improving the basic sulfur capacity of the adsorbent. At the same time, it significantly reduces the Ca / S ratio during the desulfurization process, improving the problems of insufficient active sites and high Ca / S ratio in traditional calcium-based adsorbents.

[0016] B. This invention introduces a nitrogen-containing structural base center in urea-phenolic resin, which forms a synergistic effect with the matrix hydroxyl groups, creating a dual-structure base center. The pyrrole-type nitrogen and graphitic nitrogen functional groups in the nitrogen-containing base center can further enhance the SO2 adsorption capacity, resulting in a significant increase in SO2 adsorption capacity compared to traditional calcium-based desulfurizers. At the same time, the nitrogen-containing base center also has a dispersing effect, which can effectively inhibit the aggregation of nano-Ca(OH)2 particles, prevent the active sites from being encapsulated, and continuously ensure adsorption precision and efficiency.

[0017] C. The specific surface area of ​​the adsorbent of this invention reaches 22-28 m². 2 / g, far exceeding that of traditional calcium-based desulfurizers (approximately 10 mg / g). 2 The larger specific surface area results in higher mass transfer efficiency and adsorption capacity; industrial application verification shows that the SO2 concentration in the flue gas treated by this adsorbent is ≤20mg / Nm³. 3 It fully meets the requirements for ultra-low emissions of industrial flue gas, while reducing the amount of adsorbent used by more than 35%, significantly reducing the overall operating costs of industrial desulfurization, including reagent consumption, transportation, and disposal.

[0018] D. The preparation method of this invention uses readily available raw materials and has controllable costs. It can be completed through conventional steps such as hydration, water bath reaction, ultrasonic dispersion, and vacuum drying. The operation is convenient and the conditions are mild, without the need for complex special equipment such as high pressure and high temperature. The entire preparation process has no harmful pollutant emissions, meets the requirements of green and environmentally friendly production, has strong process stability, and is easy to realize industrial mass production.

[0019] E. The adsorbent of this invention is specifically designed for the working conditions of large volume and complex composition of flue gas in sintering / pelletizing processes after blast furnace gas combustion. It can stably adapt to the deep desulfurization treatment of such complex industrial flue gas, and solves the three core technical defects of traditional calcium-based SO2 adsorbents in one go: low sulfur capacity, easy particle agglomeration, and difficulty in achieving ultra-low emissions. It has broad industrial application prospects in the field of sintering / pelletizing flue gas desulfurization in the steel industry. Detailed Implementation

[0020] This invention can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the inventive concept to those skilled in the art. All other embodiments derived by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention. Example 1

[0021] This embodiment provides an SO2 adsorbent rich in dual-structure base centers, prepared by the following method: S1 Preparation of nano-Ca(OH)2 seed crystals: Take 100g of quicklime with a CaO content of 92%, add 70g of deionized water (water-lime ratio 0.7), hydrate at 80℃ for 1.5h, add 0.3g of sodium hexametaphosphate; after reaction, centrifuge, wash 3 times, dry at 70℃ for 4h, to obtain a specific surface area of ​​22m². 2 / g, nano-Ca(OH)2 seeds with a particle size of 80-150nm; S2 Preparation of nitrogen-containing base-centered dispersant: Take 50g of urea, 100g of thermosetting phenolic resin with a molecular weight of 800, add 200g of deionized water, add 0.08g of sodium hydroxide, react in a water bath at 80℃ for 1.5h, and cool to obtain the dispersant; S3 composite modification: Add 100g of seed crystals to 500mL of deionized water, ultrasonically disperse at 300W for 20min, add 12g of dispersant (mass ratio 0.12:1), and stir at 70℃ and 400rpm for 3h. S4 Post-treatment: Centrifuge, wash twice, vacuum dry at 90℃ and -0.09MPa for 5 hours, and sieve through a 250-mesh screen to obtain the target adsorbent.

[0022] Test results: Specific surface area 25m² 2 / g, SO2 adsorption capacity increased by 2.2 times compared with traditional Ca(OH)2; SO2 concentration after desulfurization of sintering flue gas was 18mg / Nm 3 The amount of adsorbent used was reduced by 38%. Example 2

[0023] This embodiment provides an SO2 adsorbent rich in dual-structure base centers, prepared by the following method: S1 Preparation of nano-Ca(OH)2 seed crystals: Take 100g of quicklime with 90% CaO content, add 55g of deionized water (water-lime ratio 0.55), hydrate at 70℃ for 2h, then add 0.1g of sodium hexametaphosphate; after the reaction, centrifuge, wash 3 times, and dry at 60℃ for 5h to obtain a specific surface area of ​​20m². 2 / g, nano-Ca(OH)2 seeds with a particle size of 100-200nm; S2 Preparation of nitrogen-containing base-centered dispersant: Take 50g of urea and 50g of thermosetting phenolic resin with a molecular weight of 500, add 150g of deionized water and 0.05g of sodium hydroxide, react in a water bath at 75℃ for 2h, and cool to obtain the dispersant; S3 composite modification: Add 100g of seed crystals to 400mL of deionized water, disperse by ultrasonication at 200W for 30min, add 5g of dispersant (mass ratio 0.05:1), and stir at 60℃ and 300rpm for 4h. S4 Post-treatment: Centrifuge, wash twice, vacuum dry at 80℃ and -0.08MPa for 6 hours, and sieve through a 200-mesh screen to obtain the target adsorbent.

[0024] Test results: Specific surface area 22m² 2 / g, SO2 adsorption capacity is 2.0 times higher than that of traditional Ca(OH)2; SO2 concentration after desulfurization of flue gas from pellet plants is 19mg / Nm 3 The amount of adsorbent used is reduced by 35%. Example 3

[0025] This embodiment provides an SO2 adsorbent rich in dual-structure base centers, prepared by the following method: S1 Preparation of nano-Ca(OH)2 seed crystals: Take 100g of quicklime with 95% CaO content, add 80g of deionized water (water-lime ratio 0.8), hydrate at 90℃ for 1h, add 0.5g of sodium hexametaphosphate; after reaction, centrifuge, wash 3 times, dry at 80℃ for 3h, to obtain a specific surface area of ​​25m². 2 / g, nano-Ca(OH)2 seeds with a particle size of 50-100nm; S2 Preparation of nitrogen-containing base-centered dispersant: Take 50g of urea, 150g of thermosetting phenolic resin with a molecular weight of 1000, add 250g of deionized water, add 0.1g of sodium hydroxide, react in a water bath at 90℃ for 1h, and cool to obtain the dispersant; S3 composite modification: Add 100g of seed crystals to 600mL of deionized water, disperse by ultrasonication at 400W for 10min, add 15g of dispersant (mass ratio 0.15:1), and stir at 80℃ and 500rpm for 2h. S4 Post-treatment: Centrifuge, wash twice, vacuum dry at 100℃ and -0.1MPa for 4 hours, and sieve through a 325-mesh screen to obtain the target adsorbent.

[0026] Test results: Specific surface area 28m² 2 / g, SO2 adsorption capacity is 2.5 times higher than that of traditional Ca(OH)2; SO2 concentration after desulfurization by sintering / pelletizing combined process is 16mg / Nm 3 The amount of adsorbent used is reduced by 40%. Example 4

[0027] This embodiment provides an SO2 adsorbent rich in dual-structure base centers, prepared by the following method: S1 Preparation of nano-Ca(OH)2 seed crystals: Take 100g of quicklime with a CaO content of 93%, add 65g of deionized water (water-lime ratio 0.65), hydrate at 75℃ for 1.5h, add 0.3g of sodium hexametaphosphate; after reaction, centrifuge, wash 3 times, dry at 70℃ for 4h, to obtain a specific surface area of ​​23m². 2 / g, nano-Ca(OH)2 seeds with a particle size of 80-150nm; S2 Preparation of nitrogen-containing base-centered dispersant: Take 50g of urea and 100g of thermosetting phenolic resin with a molecular weight of 750 (mass ratio 1:2), add 200g of deionized water and 0.075g of sodium hydroxide, react in a water bath at 80℃ for 1.5h, and cool to obtain the dispersant; S3 composite modification: Add 100g of seed crystals to 500mL of deionized water, ultrasonically disperse at 300W for 20min, add 10g of dispersant (mass ratio 0.10:1), and stir at 70℃ and 400rpm for 3h. S4 Post-treatment: Centrifuge, wash twice, vacuum dry at 90℃ and -0.09MPa for 5 hours, and sieve through a 270-mesh screen to obtain the target adsorbent.

[0028] Test results: Specific surface area 25m² 2 / g, SO2 adsorption capacity increased by 2.3 times compared with traditional Ca(OH)2; SO2 concentration after desulfurization of sintering flue gas was 17mg / Nm 3 The amount of adsorbent used was reduced by 39%.

[0029] Comparative Example 1: Industrial-grade ordinary Ca(OH)2 was used without any modification. The particle size is in the micrometer range, and the specific surface area is 10 m². 2 / g.

[0030] Comparative Example 2: Only sodium hexametaphosphate was used to disperse and modify nano-Ca(OH)2, without loading nitrogen-containing base centers of urea-phenolic resin. The other raw materials and process parameters were completely consistent with those in Example 1.

[0031] Preparation method: quicklime hydration + sodium hexametaphosphate dispersion, without nitrogen-containing dispersant compounding step, direct drying and sieving to obtain single-dispersion modified nano Ca(OH)2 adsorbent.

[0032] Comparative experiment:

[0033] The conventional Ca(OH)₂ adsorbent of Comparative Example 1, the adsorbent of Comparative Example 2, and the adsorbents of Examples 1-3 of this invention were used in a flue gas with an initial SO₂ concentration of 1200 ppm and a flue gas flow rate of 2000 Nm³. 3 A comparison of desulfurization was conducted under the same operating conditions (h / h, adsorption temperature 80℃), and the results are as follows:

[0034] Comparative experimental data analysis: 1) In the embodiments of the present invention, the specific surface area is stable at 22-28 m². 2 / g, which is 120% to 180% higher than traditional Ca(OH)2 and 37.5% to 75% higher than the existing best dispersant modifier. The reason is that the present invention adopts a dual mechanism of controlling particle size by growing nanocrystals and inhibiting agglomeration by the steric hindrance of nitrogen-containing base centers in urea-phenolic resin, which completely solves the technical defects of easy agglomeration and low specific surface area of ​​calcium-based particles.

[0035] 2) The adsorbent of this invention achieves an SO2 adsorption capacity of 210–265 mg / g, which is 2.0–2.5 times higher than that of traditional agents and 29.6%–63.6% higher than that of existing modified agents. This improvement is far greater than the cumulative effect of single modification. This is due to the synergistic adsorption of hydroxyl groups with pyrrole-type nitrogen and graphitic nitrogen dual-base centers, resulting in a simultaneous enhancement of the number of active sites and adsorption intensity, representing a non-obvious technological breakthrough.

[0036] 3) The SO2 concentration after treatment in Comparative Examples 1-2 was 35-58 mg / Nm³. 3 It cannot meet the requirement of ≤20mg / Nm 3 The industrial ultra-low emission limits are met; after treatment in this embodiment, the SO2 concentration is stable at 16-19 mg / Nm³, all of which meet the standards, and can be stably adapted to the deep desulfurization process of sintering / pelletizing after blast furnace gas combustion.

[0037] 4) The adsorbent dosage of this invention is 7.5-7.9 kg / h, which is 35%-40% less than that of traditional agents. The Ca / S ratio is reduced to 1.1-1.25, the calcium source utilization rate is greatly improved, and the reagent, transportation and disposal costs of industrial desulfurization are significantly reduced, making it highly practical for industrial use.

[0038] In summary, this invention, through a composite technology combining nanocrystal seed regulation and dual-alkali center synergy, simultaneously solves the three core defects of traditional calcium-based desulfurizers: low sulfur capacity, easy agglomeration, and insufficient desulfurization precision. Furthermore, it significantly reduces the amount of adsorbent used and the Ca / S ratio is significantly lowered, effectively addressing the core defects of traditional calcium-based adsorbents and meeting the requirements for ultra-low emissions of industrial flue gas.

[0039] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A SO2 adsorbent rich in dual-structure base centers, characterized in that: With a particle size of 50–200 nm and a specific surface area ≥20 m², 2 The adsorbent uses nano-Ca(OH)₂ as a matrix, with the matrix surface loaded with nitrogen-containing structural base centers accounting for 5%–15% of the total adsorbent mass. These nitrogen-containing structural base centers are prepared using urea and phenolic resin as precursors and contain pyrrole-type and graphitic nitrogen. The adsorbent forms a synergistic system of hydroxyl groups and pyrrole-type and graphitic nitrogen dual-structure base centers, with a final product specific surface area of ​​22–28 m². 2 / g.

2. The adsorbent according to claim 1, characterized in that: The phenolic resin is a thermosetting phenolic resin with a molecular weight of 500-1000.

3. The adsorbent according to claim 1, characterized in that: The nano-Ca(OH)2 is prepared by hydration reaction of quicklime with CaO content ≥90%, the water-lime ratio in the hydration reaction is 0.55-0.8, and the reaction temperature is 70-90℃.

4. A method for preparing an SO2 adsorbent rich in dual-structure base centers as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Preparation of nano-Ca(OH)2 seed crystals: Using quicklime with CaO≥90% as raw material, deionized water is added, the water-lime ratio is controlled at 0.55~0.8, a dispersant is added, and the hydration reaction is carried out at 70~90℃ for 1~2h. After centrifugation, washing and low-temperature drying, nano-Ca(OH)2 seed crystals are obtained. S2. Preparation of nitrogen-containing base central dispersant: Mix urea and phenolic resin at a mass ratio of 1:1 to 3, add deionized water, add catalyst to adjust the pH value to 8 to 10, react in a water bath at 75 to 90°C for 1 to 2 hours, cool to room temperature, and obtain nitrogen-containing base central dispersant; S3. Composite modification: The nano Ca(OH)2 seed crystals obtained in step S1 are ultrasonically dispersed in deionized water, and the nitrogen-containing base center dispersant obtained in step S2 is added dropwise. The mass ratio of dispersant to seed crystals is controlled at 0.05 to 0.15:

1. The mixture is stirred and reacted at 60 to 80°C for 2 to 4 hours to obtain a nano Ca(OH)2 mixed system loaded with nitrogen-containing base centers. S4. Post-processing: After centrifugation and washing, the mixture obtained in step S3 is vacuum dried, pulverized, and sieved to obtain the target adsorbent.

5. The preparation method according to claim 4, characterized in that: In step S1, the dispersant is sodium hexametaphosphate at 0.1% to 0.5% of the mass of the quicklime raw material; the low-temperature drying temperature is 60 to 80°C, and the drying time is 3 to 5 hours.

6. The preparation method according to claim 4, characterized in that: In step S2, the catalyst is sodium hydroxide at a concentration of 0.05% to 0.1% relative to the total mass of urea and phenolic resin.

7. The preparation method according to claim 4, characterized in that: In step S3, the ultrasonic dispersion power is 200-400W, the dispersion time is 10-30min, and the stirring reaction rate is 300-500rpm.

8. The preparation method according to claim 4, characterized in that: In step S4, the vacuum drying temperature is 80-100℃, the vacuum degree is -0.08--0.1MPa, and the drying time is 4-6h.

9. The preparation method according to claim 4, characterized in that: In step S4, the sieving process uses a 200-325 mesh screen.

10. The application of an SO2 adsorbent rich in dual-structure base centers as described in any one of claims 1 to 3, characterized in that: Used for deep desulfurization of SO2-containing flue gas in sintering / pelletizing processes after blast furnace gas combustion.

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