Preparation method of calcium hydroxide with high specific surface area and high pore volume

Abstract

The application discloses a preparation method of calcium hydroxide with high specific surface area and high pore volume, which comprises the following steps: 1) uniformly mixing low-magnesium limestone particles and high-magnesium limestone particles to obtain limestone particle mixture; 2) mixing the limestone particle mixture, anthracite and aluminum dihydrogen phosphate and calcining to obtain calcium oxide; 3) crushing the calcium oxide and adding a composite modification additive to modify the surface of the calcium oxide to obtain modified calcium oxide; and 4) semi-dry digestion of the modified calcium oxide, and then flash drying in a flash dryer to obtain calcium hydroxide with high specific surface area and high pore volume. The preparation method of the calcium hydroxide has the advantages of simple operation, low cost, safety and environmental protection, and the prepared calcium hydroxide has high specific surface area, high pore volume and high purity, and is suitable for large-scale industrial application in the fields of high-end desulfurization and high-performance fillers.

Description

Technical Field

[0001] This invention relates to the field of alkaline inorganic powder preparation technology, specifically to a method for preparing calcium hydroxide with high specific surface area and high pore volume. Background Technology

[0002] Calcium hydroxide is an important alkaline inorganic powder with excellent neutralization and adsorption properties, and it is widely used in flue gas desulfurization, wastewater treatment, and rubber reinforcement. In flue gas desulfurization, calcium hydroxide is a mainstream desulfurizing agent that is both economical and environmentally friendly, as it can significantly reduce the emission of harmful gases by reacting efficiently with acidic pollutants such as SO2.

[0003] Currently, the mainstream industrial processes for preparing calcium hydroxide can be divided into the following two main categories:

[0004] 1) Dry process: Quicklime (CaO) is pulverized and then directly reacted with water in a dry digestion reaction to obtain the product. This process has a short flow rate and low energy consumption, but the specific surface area of ​​the prepared calcium hydroxide particles is relatively small (14m²). 2 / g~17m 2 / g), small pore volume (<0.1cm) 3 The pore structure is dense and poorly permeable. During the desulfurization process, the pores are easily blocked by products such as CaSO3 and CaSO4, which will hinder the continuous contact reaction between calcium hydroxide and SO2, and ultimately lead to a rapid decrease in the desulfurization efficiency of calcium hydroxide and premature deactivation.

[0005] 2) Wet process: This process involves wet digestion of quicklime with excess water, followed by dehydration and drying to obtain the product. The calcium hydroxide produced by this process has a relatively high specific surface area (25m²). 2 / g~35m 2 However, during wet production, the particles are prone to secondary agglomeration, and the pore structure is mostly closed or semi-through. Calcium hydroxide also has a relatively small pore volume, which cannot meet the rigid requirements (pore volume > 0.2 cm³) of high-end flue gas desulfurization scenarios (e.g., low-emission scenarios such as gas-fired power plants and steel sintering machines). 3 The wet production process requires additional dehydration and drying steps, which significantly increases energy consumption and production costs, while the wastewater treatment process is also prone to causing secondary pollution.

[0006] CN 121318184 A discloses a method for preparing a high specific surface area and high pore volume calcium hydroxide slurry. The steps include: S1, adding an alcohol reagent to water to obtain solution A; S2, adding an inorganic salt solution to solution A and mixing to obtain solution B; S3, adding reagent X, which is phenol or a mixture of triethanolamine, ethylenediamine, and ethylamine, and ultrasonically mixing to obtain solution C; S4, adding calcium oxide powder to solution C and continuously stirring and reacting to obtain a calcium hydroxide slurry. This method belongs to a typical wet process, with high production costs, making it difficult to promote large-scale application.

[0007] CN 121318185 A discloses a semi-dry method for preparing calcium hydroxide with high specific surface area and high pore volume. The steps include: S1, adding an alcohol reagent to water and mixing evenly to obtain solution A; S2, adding a composite cationic surfactant to solution A and dissolving it to obtain solution B; S3, adding an iron salt solution to solution B and mixing it evenly to obtain solution C; S4, adding triethanolamine to solution C and dissolving it by ultrasonication to obtain solution D; S5, spraying solution D into calcium oxide powder and continuously stirring and reacting to obtain calcium hydroxide with high specific surface area and high pore volume. This method involves a large number of additives (at least 6 types are required) and the process is cumbersome. In addition, the prepared calcium hydroxide still contains residual iron ions, which will accelerate the oxidation of desulfurization byproduct CaSO3, leading to rapid clogging of the pores of calcium hydroxide and thus aggravating the deactivation of the desulfurizing agent.

[0008] CN 121085563 A discloses a method for preparing high specific surface area calcium hydroxide, comprising the following steps: S1, mixing triethanolamine and diethanolmonoisopropanolamine with water to obtain an activator solution; S2, mixing quicklime with the activator solution to carry out a digestion reaction to generate crude calcium hydroxide; S3, sieving and drying the crude calcium hydroxide to obtain high specific surface area calcium hydroxide. This method belongs to a wet preparation process. Although this method can increase the specific surface area of ​​the prepared calcium hydroxide, it cannot effectively increase the pore volume of the calcium hydroxide.

[0009] In summary, existing calcium hydroxide preparation technologies generally suffer from the core problems of "performance shortcomings and dependence on additives": dry processes produce calcium hydroxide with low specific surface area and pore volume, resulting in insufficient desulfurization activity; wet processes, while increasing the specific surface area of ​​calcium hydroxide, have limited improvement on pore volume and are prone to secondary pollution; semi-dry processes and other improved processes rely on multi-component chemical additives (e.g., triethanolamine, iron salts, surfactants, etc.), which not only introduce impurities such as metal ions and organic residues, reducing the purity of calcium hydroxide products, but also accelerate pore blockage and shorten the lifespan of desulfurizing agents in desulfurization applications. At the same time, the complex additive system also significantly increases production costs, severely limiting the large-scale industrial application of calcium hydroxide in high-end desulfurization, high-performance fillers, and other fields.

[0010] Therefore, it is of great significance to develop a simple, low-cost, safe and environmentally friendly method for preparing calcium hydroxide, and to obtain calcium hydroxide with high specific surface area, high pore volume and high purity.

[0011] The above statements are merely background information related to the present invention and do not necessarily constitute prior art. Summary of the Invention

[0012] The purpose of this invention is to provide a method for preparing calcium hydroxide with high specific surface area and high pore volume.

[0013] The technical solution adopted in this invention is:

[0014] A method for preparing calcium hydroxide with high specific surface area and high pore volume includes the following steps:

[0015] 1) Mix low-magnesium limestone particles and high-magnesium limestone particles evenly, and control the magnesium oxide content to be 3wt%~5wt% to obtain limestone particle mixture;

[0016] 2) After the limestone granules, anthracite and aluminum dihydrogen phosphate are mixed evenly, they are added to a vertical kiln and calcined at 850℃~950℃ for 50h~65h to obtain calcium oxide.

[0017] 3) After pulverizing calcium oxide, a composite modifying agent is added for surface modification. The composite modifying agent consists of quaternized polyetheramine and polyaspartic acid to obtain modified calcium oxide.

[0018] 4) The modified calcium oxide was digested by a semi-dry method and then flash-dried in a flash dryer to obtain calcium hydroxide with high specific surface area and high pore volume.

[0019] Note: The calcination time mentioned in step 2) refers to the total time from when the material is fed into the vertical kiln to when it is discharged from the vertical kiln.

[0020] Preferably, the magnesium oxide content of the low-magnesium limestone particles in step 1) is ≤1 wt%.

[0021] Preferably, the particle size of the low-magnesium limestone particles in step 1) is 4cm to 6cm.

[0022] Preferably, the magnesium oxide content of the high-magnesium limestone particles in step 1) is 8wt% to 12wt%.

[0023] Preferably, the high-magnesium limestone particles in step 1) have a particle size of 4cm to 6cm.

[0024] Preferably, the mass ratio of limestone granular mixture, anthracite, and aluminum dihydrogen phosphate in step 2) is 1:0.075-0.085:0.015-0.020.

[0025] Preferably, the calcium oxide in step 2) has an activity ≥ 320 mL and a pore volume ≥ 0.15 g / cm³. 3 .

[0026] Preferably, the particle size of the calcium oxide after pulverization in step 3) is 80 mesh to 120 mesh.

[0027] Preferably, the mass ratio of calcium oxide to composite modifying agent in step 3) is 1:0.02 to 0.03.

[0028] Preferably, the mass ratio of quaternized polyetheramine and polyaspartic acid in step 3) is 1:2 to 4.

[0029] Preferably, the number-average molecular weight of the polyaspartic acid in step 3) is 1500 g / mol to 3000 g / mol.

[0030] Preferably, the surface modification in step 3) is carried out at a stirring rate of 300 rpm to 500 rpm for a modification time of 20 min to 40 min.

[0031] Preferably, the total water ratio of the semi-dry digestion in step 4) is 0.40 to 0.45, and the water temperature is 65°C to 75°C.

[0032] Preferably, the process parameters for flash drying in step 4) include: inlet hot air temperature of 300℃~350℃ and grading frequency of 35Hz~40Hz.

[0033] Preferably, the BET specific surface area of ​​the high specific surface area and high pore volume calcium hydroxide described in step 4) is >40 m². 2 / g, pore volume >0.2cm³ 3 / g.

[0034] The principle of this invention: This invention utilizes a multi-stage coupling effect of raw material lattice regulation, calcination aid synergy, modified gel support, and high-temperature residue removal and shaping to first directionally prepare calcium oxide with high pore volume, and then completely preserve the structural characteristics of calcium oxide in the final product, calcium hydroxide.

[0035] First, by precisely proportioning low-magnesium limestone particles to high-magnesium limestone particles, the magnesium oxide (MgO) content in the raw materials is stabilized at 3wt%–5wt%, promoting the growth of magnesium oxide (MgO). 2+ With Ca 2+The formation of CaO-MgO solid solution can disrupt the lattice integrity of CaO and reduce the lattice energy. This can make it easier for CO2 produced by the decomposition of CaCO3 during calcination to overflow and form initial pores, and can also inhibit the excessive growth of CaO grains, thus laying the foundation for the formation of porous structures.

[0036] Secondly, during the vertical kiln calcination stage, aluminum dihydrogen phosphate is used as an additive to decompose in situ at a calcination temperature of 850℃~950℃ to generate nanoscale aluminum phosphate (AlPO4) grains. These AlPO4 nanocrystals are uniformly germinating at the grain boundaries of CaO crystals. Through the Zener pinning effect, the high-temperature growth of CaO grains and grain boundary migration can be effectively inhibited, thereby allowing the pores left after CO2 escape to be retained and interconnected, ultimately generating active calcium oxide with high pore volume. At the same time, these uniformly distributed rigid AlPO4 nanoparticles can construct a micro-region rigid framework support between CaO grain boundaries, which can effectively resist the lattice expansion stress caused by water molecule intrusion during subsequent digestion, prevent pore collapse, and thus inherit the high pore volume structural characteristics to the final product.

[0037] Furthermore, in the dry modification stage, a flexible coating layer with gel strength is formed on the surface and pore walls of CaO particles using a composite modification agent (quaternized polyetheramine + polyaspartic acid). When this flexible coating layer comes into contact with water, it forms a stable gel network through hydrogen bonds and ionic bonds, which can effectively support the original porous structure of calcium oxide and prevent calcium hydroxide microcrystals from filling the pores during the subsequent semi-dry digestion process.

[0038] Finally, during the flash drying stage, the modifying additives are rapidly decomposed and removed at high temperature (without residue). At the same time, the rapid drying process avoids the collapse of the pore structure caused by slow dehydration, so that the calcium hydroxide product can fully retain the structural characteristics of high pore volume and high specific surface area, thereby significantly improving the desulfurization activity and mass transfer efficiency of calcium hydroxide.

[0039] The beneficial effects of this invention are: the calcium hydroxide preparation method of this invention has the advantages of simple operation, low cost, safety and environmental protection, and the calcium hydroxide prepared has high specific surface area, high pore volume and high purity, which is suitable for large-scale industrial application in high-end desulfurization, high-performance packing and other fields.

[0040] Specifically:

[0041] 1) By precisely controlling the raw material ratio, combining calcination synergists with dry modification process, this invention can prepare calcium hydroxide with high specific surface area, high pore volume and high purity, which can significantly improve the reactivity and mass transfer efficiency of calcium hydroxide in flue gas desulfurization scenarios, and reduce the risk of deactivation of calcium hydroxide and reduce the generation of hazardous waste.

[0042] 2) The calcium hydroxide preparation method of the present invention is compatible with existing vertical kiln production lines, with low additive residue and strong environmental protection. It has the dual advantages of optimizing production costs and upgrading product performance. The calcium hydroxide prepared can be widely used in high-end desulfurization, wastewater treatment and other fields, and has significant industrial application value and economic benefits. Detailed Implementation

[0043] The present invention will be further explained and described below with reference to specific embodiments.

[0044] Example 1:

[0045] A method for preparing calcium hydroxide with high specific surface area and high pore volume, comprising the following steps:

[0046] 1) Mix low-magnesium limestone particles (particle size 4cm-6cm, magnesium oxide content 0.82wt%) and high-magnesium limestone particles (particle size 4cm-6cm, magnesium oxide content 10.17wt%) at a mass ratio of 2:1 to obtain limestone particle mixture (magnesium oxide content 3.8wt%-4.0wt%).

[0047] 2) A three-section metering belt conveyor system is used to feed limestone granular mixture, anthracite, and aluminum dihydrogen phosphate into the vertical kiln's feeding hopper at a mass ratio of 1:0.08:0.018 (to achieve uniform mixing before entering the kiln). The mixture is then calcined at 880℃~900℃ for 56h±3h (from feeding to ash removal time), cooled, and calcium oxide is obtained (activity 342mL, pore volume 0.174g / cm³). 3 );

[0048] 3) Calcium oxide is crushed to a particle size of 100 mesh by jaw crusher and Raymond mill, and then conveyed to plow mixer. 2.5 wt% (based on dry calcium oxide) of composite modifier is added. The composite modifier is composed of quaternized polyetheramine and polyaspartic acid (number average molecular weight of 1500 g / mol) in a mass ratio of 1:3. The mixture is then mixed at 350 rpm for 30 min to obtain modified calcium oxide.

[0049] 4) The modified calcium oxide was semi-dry digested using a three-stage digester. The total water ratio for semi-dry digestion was 0.42, and the water temperature was 70℃. The digested material was then transported to a flash dryer for flash drying. The process parameters for flash drying were as follows: the inlet hot air temperature was 320℃, and the grading frequency was 38Hz, resulting in calcium hydroxide with high specific surface area and high pore volume.

[0050] Example 2:

[0051] A method for preparing calcium hydroxide with high specific surface area and high pore volume, comprising the following steps:

[0052] 1) Mix low-magnesium limestone particles (particle size 4cm-6cm, magnesium oxide content 0.37wt%) and high-magnesium limestone particles (particle size 4cm-6cm, magnesium oxide content 8.95wt%) at a mass ratio of 2:1 to obtain limestone particle mixture (magnesium oxide content 3.1wt%-3.3wt%).

[0053] 2) A three-section metering belt conveyor system was used to feed limestone granular mixture, anthracite, and aluminum dihydrogen phosphate into the vertical kiln's feeding hopper at a mass ratio of 1:0.075:0.020. The mixture was then calcined at 850℃~880℃ for 62h±3h, followed by cooling to obtain calcium oxide (activity 354mL, pore volume 0.178g / cm³). 3 );

[0054] 3) Calcium oxide is crushed to a particle size of 120 mesh by jaw crusher and Raymond mill, and then conveyed to plow mixer. 2.0 wt% of composite modifier is added. The composite modifier is composed of quaternized polyetheramine and polyaspartic acid (number average molecular weight of 3000 g / mol) in a mass ratio of 1:2. The mixture is then mixed at 350 rpm for 30 min to obtain modified calcium oxide.

[0055] 4) The modified calcium oxide was semi-dry digested using a three-stage digester. The total water ratio for semi-dry digestion was 0.45, and the water temperature was 65℃. The digested material was then transported to a flash dryer for flash drying. The process parameters for flash drying were as follows: the inlet hot air temperature was 300℃, and the grading frequency was 40Hz, resulting in calcium hydroxide with high specific surface area and high pore volume.

[0056] Example 3:

[0057] A method for preparing calcium hydroxide with high specific surface area and high pore volume, comprising the following steps:

[0058] 1) Mix low-magnesium limestone particles (particle size 4cm-6cm, magnesium oxide content 0.46wt%) and high-magnesium limestone particles (particle size 4cm-6cm, magnesium oxide content 9.16wt%) at a mass ratio of 1:1 to obtain limestone particle mixture (magnesium oxide content 4.7wt%-4.9wt%).

[0059] 2) A three-section metering belt conveyor system was used to feed limestone granular mixture, anthracite, and aluminum dihydrogen phosphate into the vertical kiln's feeding hopper at a mass ratio of 1:0.085:0.015. The mixture was then calcined at 920℃~950℃ for 53h±3h, followed by cooling to obtain calcium oxide (activity 328mL, pore volume 0.162g / cm³). 3 );

[0060] 3) Calcium oxide is crushed to a particle size of 80 mesh by jaw crusher and Raymond mill, and then conveyed to plow mixer. 3.0 wt% of composite modifier is added. The composite modifier is composed of quaternized polyetheramine and polyaspartic acid (number average molecular weight of 1500 g / mol) in a mass ratio of 1:4. The mixture is then mixed at 350 rpm for 30 min to obtain modified calcium oxide.

[0061] 4) The modified calcium oxide was semi-dry digested using a three-stage digester. The total water ratio for semi-dry digestion was 0.40, and the water temperature was 75℃. The digested material was then transported to a flash dryer for flash drying. The process parameters for flash drying were as follows: the inlet hot air temperature was 350℃, and the grading frequency was 35Hz, resulting in calcium hydroxide with high specific surface area and high pore volume.

[0062] Example 4:

[0063] A method for preparing calcium hydroxide with high specific surface area and high pore volume, comprising the following steps:

[0064] 1) Mix low-magnesium limestone particles (particle size 4cm-6cm, magnesium oxide content 0.27wt%) and high-magnesium limestone particles (particle size 4cm-6cm, magnesium oxide content 11.25wt%) at a mass ratio of 3:2 to obtain limestone particle mixture (magnesium oxide content 4.5wt%-4.7wt%).

[0065] 2) A three-section metering belt conveyor system was used to feed limestone granular mixture, anthracite, and aluminum dihydrogen phosphate into the vertical kiln's feeding hopper at a mass ratio of 1:0.080:0.018. The mixture was then calcined at 890℃~920℃ for 57h±3h, followed by cooling to obtain calcium oxide (activity 359mL, pore volume 0.179g / cm³). 3 );

[0066] 3) Calcium oxide is crushed to a particle size of 80 mesh by jaw crusher and Raymond mill, and then conveyed to plow mixer. 2.7 wt% of composite modifier is added. The composite modifier is composed of quaternized polyetheramine and polyaspartic acid (number average molecular weight of 2500 g / mol) in a mass ratio of 1:3. The mixture is then mixed at 350 rpm for 30 min to obtain modified calcium oxide.

[0067] 4) The modified calcium oxide was semi-dry digested using a three-stage digester. The total water ratio for semi-dry digestion was 0.42, and the water temperature was 75℃. The digested material was then conveyed to a flash dryer for flash drying. The process parameters for flash drying were as follows: the inlet hot air temperature was 330℃, and the grading frequency was 38Hz, resulting in calcium hydroxide with high specific surface area and high pore volume.

[0068] Comparative Example 1:

[0069] A method for preparing calcium hydroxide, except that in step 1), high-magnesium limestone particles were not used (the calcium oxide obtained by calcination has an activity of 286 mL and a pore volume of 0.122 g / cm³). 3 Except for ), it is exactly the same as in Example 1.

[0070] Comparative Example 2:

[0071] A method for preparing calcium hydroxide, except that in step 2), "aluminum dihydrogen phosphate" is replaced by an equal weight of "sodium chloride" (the calcium oxide obtained by calcination has an activity of 312 mL and a pore volume of 0.084 g / cm³). 3 Except for ), it is exactly the same as in Example 1.

[0072] Comparative Example 3:

[0073] A method for preparing calcium hydroxide, comprising the following steps:

[0074] 1) Use commercially available rotary kiln lime (activity 385 mL, pore volume 0.064 g / cm³) 3 The raw material, limestone (with an MgO content of approximately 4.3 wt% to 4.8 wt%), is crushed to a particle size of 100 mesh using a jaw crusher and Raymond mill, then conveyed to a plow-type mixer. 2.5 wt% of a composite modifier is added, consisting of quaternized polyetheramine and polyaspartic acid (number average molecular weight of 1500 g / mol) in a mass ratio of 1:3. The mixture is then mixed at 350 rpm for 30 minutes to obtain modified calcium oxide.

[0075] 2) Modified calcium oxide is digested in a three-stage digester using a semi-dry method. The total water ratio for semi-dry digestion is 0.42, and the water temperature is 70℃. The digested material is then transported to a flash dryer for flash drying. The process parameters for flash drying are as follows: the inlet hot air temperature is 320℃, and the grading frequency is 38Hz, to obtain calcium hydroxide.

[0076] Comparative Example 4:

[0077] A method for preparing calcium hydroxide, comprising the following steps:

[0078] 1) Calcium oxide (same as in Example 1) is crushed to a particle size of 100 mesh by jaw crusher and Raymond mill to obtain calcium oxide powder;

[0079] 2) The calcium oxide powder was semi-dry digested using a three-stage digester. The total water ratio for semi-dry digestion was 0.42. The digestion water contained 2.5 wt% (based on dry calcium oxide) of triethanolamine, and the water temperature was 70°C. The digested material was then conveyed to a flash dryer for flash drying. The flash drying process parameters were as follows: the inlet hot air temperature was 320°C, and the grading frequency was 38 Hz, to obtain calcium hydroxide.

[0080] Comparative Example 5:

[0081] A method for preparing calcium hydroxide is identical to that in Example 1, except that the inlet hot air temperature in step 4) is adjusted from "320℃" to "280℃".

[0082] Performance testing:

[0083] The BET specific surface area and pore volume test results of the calcium hydroxide prepared in Examples 1-4 and Comparative Examples 1-5 are shown in the table below:

[0084] Table 1. Results of BET specific surface area and pore volume tests for calcium hydroxide.

[0085]

[0086] Note: The BET specific surface area and pore volume of calcium hydroxide were tested according to "GB / T 19587-2017 Determination of Specific Surface Area of ​​Solid Substances by Gas Adsorption BET Method" (BJH mode).

[0087] As shown in Table 1:

[0088] 1) The BET specific surface area of ​​the calcium hydroxide prepared in Examples 1-4 is >40 m². 2 / g, pore volume >0.2cm³ 3 / g, with both high specific surface area and high pore volume, is suitable for large-scale industrial applications in fields such as high-end desulfurization and high-performance fillers.

[0089] 2) Compared with Example 1, the pore volume of the prepared calcium hydroxide was significantly reduced and the BET specific surface area was also reduced. This indicates that the ratio of low-magnesium limestone particles to high-magnesium limestone particles needs to be precisely controlled in order to prepare calcium hydroxide with both high specific surface area and high pore volume.

[0090] 3) Compared with Example 1, the pore volume of the prepared calcium hydroxide in Comparative Example 2 decreased significantly, and the BET specific surface area also decreased. This indicates that aluminum dihydrogen phosphate is needed to generate active calcium oxide with high pore volume. Conventional sodium chloride flux can only improve the activity of calcium oxide, but cannot improve the pore volume of calcium oxide at all.

[0091] 4) Compared with Example 1, the pore volume of the calcium hydroxide prepared in Comparative Example 3 decreased significantly, and the BET specific surface area also decreased. This indicates that the raw material lattice regulation process and the calcination aid synergistic process are indispensable processes for preparing calcium hydroxide with both high specific surface area and high pore volume.

[0092] 5) Compared with Example 1, the BET specific surface area of ​​the prepared calcium hydroxide in Comparative Example 4 was slightly increased, but the pore volume was significantly reduced, indicating that the modified gel support process is an indispensable process for preparing calcium hydroxide with both high specific surface area and high pore volume.

[0093] 6) Compared with Example 1, the BET specific surface area of ​​the prepared calcium hydroxide in Comparative Example 5 did not change significantly, but the pore volume decreased significantly, indicating that the inlet hot air temperature of flash drying directly affects the pore volume of calcium hydroxide.

[0094] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing calcium hydroxide with high specific surface area and high pore volume, characterized in that, Includes the following steps: 1) Mix low-magnesium limestone particles and high-magnesium limestone particles evenly, and control the magnesium oxide content to be 3wt%~5wt% to obtain limestone particle mixture; 2) After the limestone granules, anthracite and aluminum dihydrogen phosphate are mixed evenly, they are added to a vertical kiln and calcined at 850℃~950℃ for 50h~65h to obtain calcium oxide. 3) After pulverizing calcium oxide, a composite modifying agent is added for surface modification. The composite modifying agent consists of quaternized polyetheramine and polyaspartic acid to obtain modified calcium oxide. 4) The modified calcium oxide was digested by a semi-dry method and then flash-dried in a flash dryer to obtain calcium hydroxide with high specific surface area and high pore volume. In step 3), the mass ratio of quaternized polyetheramine to polyaspartic acid is 1:2 to 4.

2. The preparation method according to claim 1, characterized in that: The magnesium oxide content of the low-magnesium limestone particles in step 1) is ≤1wt%; the magnesium oxide content of the high-magnesium limestone particles in step 1) is 8wt%~12wt%.

3. The preparation method according to claim 1, characterized in that: In step 2), the mass ratio of the limestone granular mixture, anthracite, and aluminum dihydrogen phosphate is 1:0.075-0.085:0.015-0.

020.

4. The preparation method according to claim 1 or 3, characterized in that: Step 2) The activity of the calcium oxide is ≥320 mL, and the pore volume is ≥0.15 g / cm³. 3 .

5. The preparation method according to claim 1, characterized in that: In step 3), the mass ratio of calcium oxide to composite modifying agent is 1:0.02 to 0.

03.

6. The preparation method according to claim 1 or 5, characterized in that: Step 3) The number-average molecular weight of the polyaspartic acid is 1500 g / mol to 3000 g / mol.

7. The preparation method according to claim 1 or 5, characterized in that: Step 3) The surface modification is carried out at a stirring rate of 300 rpm to 500 rpm for a modification time of 20 min to 40 min.

8. The preparation method according to claim 1, characterized in that: Step 4) The total water ratio for the semi-dry digestion is 0.40 to 0.45, and the water temperature is 65℃ to 75℃.

9. The preparation method according to claim 1 or 8, characterized in that: Step 4) The process parameters for flash drying include: inlet hot air temperature of 300℃~350℃ and grading frequency of 35Hz~40Hz.

10. The preparation method according to claim 1 or 8, characterized in that: Step 4) The BET specific surface area of ​​the high specific surface area and high pore volume calcium hydroxide is >40m². 2 / g, pore volume >0.2cm³ 3 / g.

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