A method for preparing high specific surface area calcium hydroxide with low water-cement ratio by dry method

Abstract

The application belongs to the technical field of calcium hydroxide preparation, and particularly relates to a method for preparing high specific surface area calcium hydroxide by a dry method with low water-cement ratio. The application provides a method for preparing high specific surface area calcium hydroxide by a dry method with low water-cement ratio. In the lime digestion process, by adding special functional additives, the water-cement ratio required in the digestion process is reduced, and the water content of the product, high specific surface area calcium hydroxide, is also low, so that a complicated drying procedure is avoided, and the process for industrially preparing high specific surface area calcium hydroxide is simplified. The method not only simplifies the operation process, but also helps to realize large-scale application production.

Description

Technical Field

[0001] This invention belongs to the field of calcium hydroxide preparation technology, specifically relating to a method for preparing high specific surface area calcium hydroxide by a dry process with a low water-ash ratio. Background Technology

[0002] Sulfur dioxide is a colorless gas with a pungent odor at room temperature and is one of the major sources of air pollution. It is classified as a Group 3 carcinogen by the International Agency for Research on Cancer (IARC) of the World Health Organization, and is primarily produced by emissions from combustion processes. Sulfur dioxide can combine with water vapor in the atmosphere to form acid rain, posing a serious threat to human health and the ecological environment. Therefore, desulfurization of flue gas to reduce sulfur dioxide emissions is of great significance for sustainable social development.

[0003] With the increasing prominence of sulfur dioxide pollution in the atmosphere, flue gas desulfurization (FGD) technology has been widely developed. Based on the amount of water used in the desulfurization process, FGD technologies are classified into wet, semi-dry, and dry methods. Among them, limestone-gypsum wet FGD technology is a relatively mature and widely used FGD technology. This technology uses calcium hydroxide as the absorbent. Flue gas enters the spray tower from bottom to top, reacting with sulfur dioxide in the flue gas to form calcium sulfite, which is then further oxidized to calcium sulfate by air. In this process, the specific surface area of ​​calcium hydroxide is a key factor affecting the sulfur dioxide removal efficiency.

[0004] Traditional dry methods for preparing calcium hydroxide often require a high water-to-ash ratio to achieve a high specific surface area. At low water-to-ash ratios, calcium oxide and water cannot fully contact and react, resulting in a low hydration rate and consequently, low purity and specific surface area of ​​the prepared calcium hydroxide. Conversely, high water-to-ash ratios can cause clumping during digestion, preventing uniform reaction within the calcium oxide and resulting in high water content, substandard quality, and hindering flue gas desulfurization.

[0005] To ensure the product meets moisture content standards, companies often need to add a drying process, significantly increasing energy consumption and costs. Therefore, preparing calcium hydroxide with a high specific surface area at a lower water-cement ratio is an ideal preparation process. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention aims to provide a method for preparing calcium hydroxide with high specific surface area under low water-ash ratio conditions, and the prepared calcium hydroxide can be used for efficient flue gas desulfurization.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0008] A method for preparing high specific surface area calcium hydroxide using a low water-cement ratio dry process involves adding an additive during the quicklime slaking reaction. Based on the additive's effect of disrupting the surface water film tension of the powder particles, confined water molecules participate in the slaking reaction, thereby achieving the preparation of high specific surface area calcium hydroxide under low water-cement ratio conditions. The water-cement ratio is 0.3–0.4, and the specific surface area of ​​the calcium hydroxide is not less than 45 m². 2 / g.

[0009] Furthermore, the water content of the calcium hydroxide is not higher than 0.2 wt%.

[0010] Furthermore, the quicklime needs to be crushed and sieved to a particle size of less than 200 mesh, with an effective calcium oxide content of not less than 90%.

[0011] Furthermore, the additive is any one or more of trithiocyanate, calcium lignosulfonate, and sodium p-aminobenzenesulfonate.

[0012] Furthermore, the mass concentration of the additive is 0.1% to 0.5%.

[0013] Furthermore, the temperature range of the digestion reaction is 25°C to 45°C.

[0014] Furthermore, the rotation speed range of the digestion reaction process is 1000 r / min to 1700 r / min.

[0015] Application of high specific surface area calcium hydroxide prepared by the above method in efficient flue gas desulfurization.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] (1) This invention adds a special functional additive during the lime digestion process to promote the dispersion of calcium hydroxide particles, destroy the flocculation structure, release the encapsulated water molecules to participate in the digestion reaction, thereby reducing the water-ash ratio in the dry digestion process, resulting in a lower water content in the product calcium hydroxide, avoiding complex drying procedures, reducing energy consumption, simplifying the process of industrial preparation of high specific surface area calcium hydroxide, and helping to achieve large-scale application production.

[0018] (2) The hydrophilic side chains on the surface of the additive extend in the aqueous solution, forming a steric hindrance effect, increasing the specific surface area between calcium hydroxide particles, and improving the pore size and pore volume. Therefore, the obtained calcium hydroxide with high activity and high specific surface area has a high removal efficiency of sulfur dioxide in flue gas. Detailed Implementation

[0019] 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.

[0020] Example 1

[0021] Weigh 560g of 180-mesh quicklime with an effective calcium oxide content of 92%. Add 0.168g of trithiocyanate additive to 168g of tap water, with a water-to-lime ratio of 0.3 and an additive mass fraction of 0.1%. Disperse the mixture ultrasonically for 10 minutes. Add the quicklime and dispersion to a digestion reactor with an initial temperature of 25℃. Start stirring at a speed of 1700r / min. After digestion for 15 minutes, high specific surface area calcium hydroxide powder is obtained.

[0022] The target product, high specific surface area calcium hydroxide powder, has a specific surface area of ​​46.34 m². 2 / g, pore size 5.44nm, pore volume 0.068cm³ 3 / g, moisture content 0.13wt%, sulfur dioxide removal rate 98.4%.

[0023] Example 2

[0024] Weigh 560g of 180-mesh quicklime with an effective calcium oxide content of 91.7%. Add 0.672g of trithiocyanate additive to 224g of tap water, with a water-to-lime ratio of 0.4 and an additive mass fraction of 0.3%. Disperse the mixture ultrasonically for 10 minutes. Add the quicklime and dispersion to a digestion reactor with an initial temperature of 25℃. Start stirring at a speed of 1700r / min. After digestion for 15 minutes, high specific surface area calcium hydroxide powder is obtained.

[0025] The target product, high specific surface area calcium hydroxide powder, has a specific surface area of ​​47.03 m². 2 / g, pore size 5.64nm, pore volume 0.072cm³ 3 / g, moisture content 0.18wt%, sulfur dioxide removal rate 99.2%.

[0026] Example 3

[0027] Weigh 560g of 190-mesh quicklime with an effective calcium oxide content of 94.6%. Add 0.392g of calcium lignosulfonate additive to 196g of tap water, with a water-lime ratio of 0.35 and an additive mass fraction of 0.2%. Disperse the mixture ultrasonically for 10 minutes. Add the quicklime and dispersion to a digestion reactor with an initial temperature of 35℃. Start stirring at a speed of 1700r / min. After digestion for 15 minutes, obtain calcium hydroxide powder with a high specific surface area.

[0028] The target product, high specific surface area calcium hydroxide powder, has a specific surface area of ​​53.16 m². 2 / g, pore size 6.34nm, pore volume 0.085cm³ 3 / g, moisture content 0.19wt%, sulfur dioxide removal rate 98.5%.

[0029] Example 4

[0030] Weigh 560g of 190-mesh quicklime with an effective calcium oxide content of 92.8%. Add 0.851g of sodium p-aminobenzenesulfonate additive to 212.8g of tap water, with a water-to-lime ratio of 0.38 and an additive mass fraction of 0.4%. Disperse the mixture ultrasonically for 10 minutes. Add the quicklime and dispersion to a digestion reactor with an initial temperature of 30℃. Start stirring at a speed of 1700r / min. After digestion for 15 minutes, high specific surface area calcium hydroxide powder is obtained.

[0031] The target product, high specific surface area calcium hydroxide powder, has a specific surface area of ​​52.36 m². 2 / g, pore size 6.19nm, pore volume 0.079cm³ 3 / g, moisture content 0.19wt%, sulfur dioxide removal rate 99.2%.

[0032] Example 5

[0033] Weigh 560g of 175-mesh quicklime with an effective calcium oxide content of 93.5%. Add 0.425g of trithiocyanate and 0.2022g of sodium p-aminobenzenesulfonate to 179.2g of tap water. The water-lime ratio is 0.32 and the mass fraction of the additive is 0.35%. Disperse the mixture ultrasonically for 10 minutes. Add the quicklime and dispersion to a digestion reactor. The initial temperature of the digestion reactor is 30℃. Start stirring at a speed of 1700r / min. After digestion for 15 minutes, high specific surface area calcium hydroxide powder is obtained.

[0034] The target product, high specific surface area calcium hydroxide powder, has a specific surface area of ​​49.51 m². 2 / g, pore size 5.73nm, pore volume 0.089cm³ 3 / g, moisture content 0.17wt%, sulfur dioxide removal rate 99.6%.

[0035] Comparative Example 1

[0036] Weigh 560g of 180-mesh quicklime with an effective calcium oxide content of 93.2%, 196g of tap water, and a water-lime ratio of 0.35. Add the quicklime and dispersion to the digestion reactor. The initial temperature of the digestion reactor is 35℃. Start stirring at a speed of 1700r / min. After digestion for 15 minutes, high specific surface area calcium hydroxide powder is obtained.

[0037] The target product, high specific surface area calcium hydroxide powder, has a specific surface area of ​​27.35 m². 2 / g, pore size 4.28nm, pore volume 0.054cm³ 3 / g, moisture content 0.27wt%, sulfur dioxide removal rate 58.5%.

[0038] Example 6

[0039] Desulfurization performance test

[0040] (1) The BET specific surface area and total adsorption 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.

[0041] (2) Desulfurization performance was evaluated using a fixed-bed reactor on the products of five examples and one comparative example. The reactor inner diameter was 20 mm, and the desulfurization gas composition was SO2 700 mg / Nm³. 3 The concentrations were: CO2 5%, O2 21%, gaseous H2O 10%, and equilibrium N2; the reaction temperature was 200℃, the flue gas flow rate was 0.5 m / min, and the SO2 content was determined using an infrared flue gas analyzer.

[0042] The results are shown in Table 1. Compared with Comparative Example 1, which did not introduce additives, the specific surface area of ​​Examples 1 to 5 was significantly increased, and the desulfurization efficiency was greatly increased.

[0043] Table 1. Desulfurization performance test of different calcium hydroxides

[0044]

[0045]

[0046] The embodiments described above are merely specific examples of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing high specific surface area calcium hydroxide using a low water-cement ratio dry process, characterized in that, Additives are added during the quicklime slaking reaction. Based on the additives' ability to disrupt the surface water film tension of the powder particles, confined water molecules participate in the slaking reaction, thereby achieving the preparation of high specific surface area calcium hydroxide under low water-cement ratio conditions; the water-cement ratio is 0.3~0.4, and the specific surface area of ​​the calcium hydroxide is not less than 45 m². 2 / g, wherein the additive is any one or more of trithiocyanate, calcium lignosulfonate, and sodium p-aminobenzenesulfonate.

2. The method for preparing high specific surface area calcium hydroxide by a low water-cement ratio dry process according to claim 1, characterized in that, The water content of the calcium hydroxide is not higher than 0.2 wt%.

3. The method for preparing high specific surface area calcium hydroxide by a low water-cement ratio dry process according to claim 1, characterized in that, The quicklime needs to be crushed and screened to a particle size of less than 200 mesh, with an effective calcium oxide content of not less than 90%.

4. The method for preparing high specific surface area calcium hydroxide by a low water-cement ratio dry process according to claim 1, characterized in that, The mass concentration of the additive is 0.1% to 0.5%.

5. The method for preparing high specific surface area calcium hydroxide by a low water-cement ratio dry process according to claim 1, characterized in that, The temperature range of the digestion reaction is 25 ℃ to 45 ℃.

6. The method for preparing high specific surface area calcium hydroxide by a low water-cement ratio dry process according to claim 1, characterized in that, The rotation speed range of the digestion reaction process is 1000 r / min to 1700 r / min.

7. The application of high specific surface area calcium hydroxide prepared according to any one of claims 1 to 6 in efficient flue gas desulfurization.

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