A method for preparing calcium hydroxide from carbide slag and calcium hydroxide thereof

Abstract

The application provides a method for preparing calcium hydroxide from carbide slag and calcium hydroxide thereof, and the method comprises the following steps: (1) performing slurry treatment on the carbide slag to obtain a first slurry, and then performing impurity separation treatment to obtain a second slurry; (2) mixing the second slurry in the step (1) with a surface modifier, and then performing superfine treatment, and obtaining the calcium hydroxide after solid-liquid separation. The method provided by the application improves the content of calcium hydroxide in the carbide slag through the impurity separation treatment, and the superfine treatment and the surface modifier synergistically act to solve the problem of particle agglomeration, so that the carbide slag particles are fully broken, and the specific surface area of the product calcium hydroxide is greatly improved. Moreover, the whole preparation process is simple in operation, high in economy and efficiency, and friendly to the environment, and the feasibility and economy of the preparation of high specific surface area calcium hydroxide from the carbide slag are significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization technology, and relates to a method for preparing calcium hydroxide from carbide slag and the calcium hydroxide thereof. Background Technology

[0002] Calcium carbide slag is an industrial solid waste generated during acetylene production, with annual emissions exceeding 30 million tons. Its main component is calcium hydroxide, which is widely used in power plant flue gas desulfurization and the preparation of calcium hydroxide powder. In the increasingly mature flue gas desulfurization process, calcium hydroxide is primarily used to neutralize acidic gases and ions such as sulfur dioxide, sulfur trioxide, fluoride ions, and chloride ions, ensuring that the sulfur content in flue gas emissions meets environmental standards. The desulfurization effect is directly influenced by the properties of calcium hydroxide; its specific surface area is a crucial factor determining the desulfurization effect. Generally, the larger the specific surface area of ​​calcium hydroxide, the better the desulfurization effect.

[0003] Calcium hydroxide prepared from carbide slag is used for desulfurization, but it is prone to agglomeration during the pulping process, affecting product quality. Therefore, improving the dispersibility and stability of calcium hydroxide crystals and preparing calcium hydroxide with a large specific surface area is of great significance for meeting the practical needs of flue gas purification and related applications.

[0004] CN202210514260.5 discloses a method for producing high specific surface area calcium hydroxide, including crushing, digestion, and screening. The quicklime has a calcium oxide content of over 93% by weight. The crusher is a hammer crusher or a roller crusher. The digesting agent is an aqueous solution of an organic compound with hydroxyl groups. The weight ratio of the digesting agent to granular quicklime is 5:1. The vibrating screen is a filtration-type mechanical separation device with a mesh size of 100-200 mesh. CN201911390295.7 discloses a method for preparing highly dispersible high specific surface area calcium hydroxide. Using quicklime as raw material, natural nanocellulose with abundant oxygen-containing groups is added as a template and sodium carboxymethyl cellulose surfactant during the digestion process. High-speed shearing and thorough mixing are performed, and calcium hydroxide nucleation and growth are achieved based on ultrasonic action. After washing, centrifugation, drying, and grinding, high specific surface area calcium hydroxide is obtained.

[0005] However, the aforementioned methods for preparing high specific surface area calcium hydroxide are costly and consume large amounts of reagents, making them unsuitable for large-scale industrial applications. Therefore, there is an urgent need for an efficient and low-cost method to directly prepare high specific surface area calcium hydroxide from carbide slag. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing calcium hydroxide from carbide slag and the resulting calcium hydroxide. The method provided by this invention increases the calcium hydroxide content in the carbide slag through impurity separation treatment. The synergistic effect of ultrafine treatment and surface modifiers solves the problem of particle agglomeration, ensuring thorough crushing of the carbide slag particles and significantly increasing the specific surface area of ​​the product calcium hydroxide. Furthermore, the entire preparation process of this invention is simple to operate, economical, efficient, and environmentally friendly, significantly improving the feasibility and economy of preparing high specific surface area calcium hydroxide from carbide slag.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing calcium hydroxide from carbide slag, the method comprising:

[0009] (1) The carbide slag is slurried to obtain the first slurry, and then impurities are separated to obtain the second slurry;

[0010] (2) The second slurry from step (1) and the surface modifier are mixed and then subjected to ultrafine treatment. After solid-liquid separation, the calcium hydroxide is obtained.

[0011] In this invention, ultrafine processing breaks down particles, reducing their size. The breaking process exposes fresh interfaces, causing surface atomic bonds to break and form unsaturated bonds, leading to a sharp increase in surface energy and chemical activity. This high surface energy drives the rapid aggregation of fine particles through van der Waals forces and hydrogen bonds. The added surface modifier solves the particle aggregation problem through molecular-level modification. The polar groups in the surface modifier are anchored to active sites on the particle surface, while the non-polar chains extend outwards. The modified particles become hydrophobic, reducing water molecule adsorption and decreasing slurry viscosity by more than 50%, thus improving the kinetic energy transfer efficiency of the grinding media. The modified particles have improved anti-agglomeration ability, preventing fine particles from enveloping larger particles to form a "cushion," allowing mechanical force to reach the unbroken particles directly. Therefore, this invention, through the coupled use of ultrafine processing and surface modifiers, effectively improves the crushing efficiency of carbide slag particles and significantly increases the specific surface area of ​​calcium hydroxide in carbide slag. Furthermore, the entire preparation process of this invention is simple to operate, economical, efficient, and environmentally friendly, significantly improving the feasibility and economy of preparing high specific surface area calcium hydroxide from carbide slag.

[0012] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0013] As a preferred technical solution of the present invention, the carbide slag in step (1) includes calcium hydroxide, and the mass percentage of the calcium hydroxide is 75wt%~85wt%, such as 75wt%, 77wt%, 80wt%, 82wt% or 85wt%.

[0014] As a preferred technical solution of the present invention, the pulping treatment in step (1) includes mixing carbide slag and water.

[0015] The method of mixing carbide slag and water includes a first stirring.

[0016] The first stirring speed is 50 rpm to 300 rpm, such as 50 rpm, 100 rpm, 150 rpm, 200 rpm, 250 rpm or 300 rpm.

[0017] The temperature of the pulping treatment in step (1) is 20℃~70℃, for example 20℃, 30℃, 40℃, 50℃, 60℃ or 70℃, and the time is 20min~600min, for example 20min, 1h, 2h, 3h, 5h, 8h or 10h.

[0018] In this invention, by controlling the stirring speed, temperature, and time during the slurry treatment process, the overall effect of impurity removal from carbide slag can be significantly improved. The aforementioned stirring speed not only ensures sufficient dispersion of the carbide slag in water, avoiding particle agglomeration, but also reduces the risk of material damage caused by excessive shearing. The aforementioned temperature helps improve processing efficiency while preventing unnecessary side reactions or component volatilization losses due to excessively high temperatures. The aforementioned time ensures that all components reach an optimal mixing state.

[0019] As a preferred technical solution of the present invention, the concentration of the first slurry in step (1) is 5wt%~25wt%, for example 5wt%, 8wt%, 10wt%, 15wt%, 18wt%, 20wt% or 25wt%, etc.

[0020] In this invention, by controlling the concentration of the first slurry within the above-mentioned preferred range, it can be ensured that the carbide slag is fully dispersed in water to form a uniform slurry, which helps in the subsequent impurity removal process and improves the removal efficiency of impurities in the carbide slag.

[0021] The impurity separation process in step (1) includes cyclone separation.

[0022] The cyclone separation is a multi-stage cyclone separation.

[0023] In this invention, either single-stage or multi-stage cyclone separation can achieve efficient separation of impurities in carbide slag. Multi-stage cyclone separation can more effectively capture residual coarse and fine mineral particles in the slurry, further improving the overall impurity removal rate. In this invention, two-stage cyclone separation is sufficient to meet high separation requirements.

[0024] The feed flow rate of the cyclone separator is 2m³. 3 / h~3m 3 / h, for example 2m 3 / h, 2.2m 3 / h, 2.4m 3 / h, 2.5m 3 / h, 2.7m 3 / h or 3m 3 / h, etc., with a feed pressure of 0.2MPa~1MPa, such as 0.2MPa, 0.3MPa, 0.5MPa, 0.7MPa, 0.9MPa or 1MPa, etc.

[0025] In this invention, by controlling the feed flow rate within the above-mentioned preferred range, it is possible to ensure that the slurry has sufficient residence time in the hydrocyclone, allowing impurity particles to be fully exposed in the hydrocyclone, thereby improving the impurity removal efficiency and avoiding the loss of calcium hydroxide due to excessive flow rate. By controlling the feed pressure within the above-mentioned preferred range, it is helpful to maintain the stable flow of the slurry in the pipeline and equipment, prevent blockage, and enhance the migration ability of solid particles in the hydrocyclone, which is beneficial to improving the capture efficiency of impurity minerals.

[0026] As a preferred technical solution of the present invention, in step (2), the mass ratio of carbide slag to surface modifier in the second slurry is 1:(0.005~0.05), for example 1:0.005, 1:0.008, 1:0.01, 1:0.015, 1:0.02, 1:0.025, 1:0.03, 1:0.04 or 1:0.05, etc.

[0027] In this invention, by controlling the mass ratio of carbide slag and surface modifier within the aforementioned preferred range, sufficient surface modifier can be ensured to participate in the reaction, improving the dispersion effect of calcium hydroxide particles and achieving a significant increase in their specific surface area. Simultaneously, unnecessary side reactions caused by excessive use of surface modifier are avoided. This achieves a significant increase in the specific surface area of ​​carbide slag while also considering cost-effectiveness, maximizing economic efficiency.

[0028] The mixing method in step (2) includes: adding a surface modifier to the second slurry in step (2) and performing a second stirring.

[0029] The mixing temperature in step (2) is 20℃~80℃, for example 20℃, 30℃, 40℃, 50℃, 60℃, 70℃ or 80℃, and the time is 20min~600min, for example 20min, 1h, 2h, 3h, 5h, 8h or 10h.

[0030] In this invention, controlling the mixing temperature of the surface modifier and carbide slag within the aforementioned range helps to enhance the efficiency of the surface modifier's action on the minerals in the carbide slag and improve its reactivity. Controlling the mixing time within the aforementioned preferred range ensures that the surface modifier has sufficient time to fully contact and react with the carbide slag, allowing the carbide slag particles to be fully broken down and increasing their specific surface area.

[0031] As a preferred technical solution of the present invention, the surface modifier in step (2) includes any one or a combination of at least two of coupling agents, surfactants, organic oligomers, unsaturated organic acids, water-soluble polymers or n-butanol.

[0032] It should be noted that, in this invention, organic oligomers refer to low molecular weight polymers formed by a small number of monomer molecules linked by covalent bonds, typically containing 2 to 20 monomer units.

[0033] In this invention, the surface modifier can cope with the complex mineral composition of carbide slag, reduce the surface energy of calcium hydroxide, and further improve the dispersion rate between particles. In practical applications, different types of surfactants can be selected according to the medium environment, thereby achieving flexible adaptation to different process conditions and meeting the needs of preparing calcium hydroxide with high specific surface area.

[0034] The coupling agent includes any one or a combination of at least two of titanate coupling agents, silane coupling agents, and aluminate coupling agents.

[0035] The surfactant includes any one or a combination of at least two of anionic surfactants, cationic surfactants, or nonionic surfactants.

[0036] The organic oligomer includes any one or a combination of at least two of polyolefin oligomers, polyethylene wax, or epoxy resin.

[0037] The unsaturated organic acid includes any one or a combination of at least two of acrylic acid, methacrylic acid, or butenoic acid.

[0038] The water-soluble polymer includes any one or a combination of at least two of polyacrylamide, polyethylene glycol, or polyvinyl alcohol.

[0039] In this invention, some groups in the coupling agent can react with various functional groups on the surface of carbide slag to form strong chemical bonds; surfactants can significantly reduce the surface tension of carbide slag slurry, changing the surface state of the system to produce wetting and anti-wetting; organic oligomers can form good wetting, adhesion, and coating effects with carbide slag powder; unsaturated organic acids have both unsaturated double bonds and carboxyl groups, which can better disperse carbide slag materials; water-soluble polymers are hydrophilic polymer materials containing a large number of hydrophilic groups, which is beneficial for the performance control of subsequent resource-based products; n-butanol can be adsorbed on the surface of carbide slag slurry, with its hydrophilic groups extending into the aqueous phase and its hydrophobic groups extending into the air phase, which can significantly reduce the surface tension of the liquid, thereby effectively dispersing particles in the carbide slag slurry. Furthermore, among the above types, n-butanol has the best effect, followed by water-soluble polymer materials, such as polyethylene glycol and / or polyvinyl alcohol.

[0040] As a preferred technical solution of the present invention, the ultrafine treatment in step (2) is carried out in a sand mill.

[0041] The rotational speed of the sand mill is 1500rpm~2500rpm, such as 1500rpm, 1600rpm, 1800rpm, 2000rpm, 2200rpm, 2400rpm or 2500rpm.

[0042] The ultrafine processing time is 25 min to 35 min, for example, 25 min, 26 min, 30 min, 31 min, 32 min, 33 min, 34 min or 35 min.

[0043] As a preferred technical solution of the present invention, after solid-liquid separation in step (2), filter cake and filtrate are obtained. The water content of the filter cake is 10wt%~50wt%, for example, 10wt%, 20wt%, 30wt%, 40wt% or 50wt%.

[0044] In this invention, by controlling the moisture content of the filter cake within the above-mentioned preferred range, it helps to ensure the smooth progress of subsequent processing steps, maintaining the good dispersibility of the carbide slag, preventing particle agglomeration, and preventing the material from becoming too dry, thus increasing the difficulty of operation.

[0045] The filter cake is then washed and dried sequentially.

[0046] The drying process includes vacuum drying.

[0047] The filtrate and the washing liquid are returned to the pulping process in step (1) for recycling.

[0048] In this invention, by recycling the filtrate and washing liquid, both the consumption of reagents and the discharge of wastewater are reduced.

[0049] In a second aspect, the present invention provides calcium hydroxide prepared by the method described in the first aspect.

[0050] As a preferred embodiment of the present invention, the specific surface area of ​​the calcium hydroxide is 30 m². 2 / g~60m 2 / g, for example 30m 2 / g、35m 2 / g、40m 2 / g、45m 2 / g, 50m 2 / g、55m 2 / g or 60m 2 / g etc.

[0051] The water content of the calcium hydroxide is ≤1wt%, for example, 0.1wt%, 0.2wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.8wt%, or 1wt%.

[0052] The D90 of the calcium hydroxide is 1.8μm to 2.2μm, for example, 1.8μm, 1.9μm, 2μm, 2.1μm or 2.2μm.

[0053] The purity of the calcium hydroxide is ≥90wt%, for example, 90wt%, 92wt%, 94wt%, 95wt%, 96wt%, etc.

[0054] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] 1. The method provided by this invention enables the preparation of calcium hydroxide with high specific surface area from carbide slag, while reducing processing costs and improving the overall economic efficiency of the process.

[0057] 2. This invention, through the coupled use of ultrafine treatment and surface modifiers, enables the carbide slag particles to be fully crushed, significantly increasing their specific surface area. Ultrafine treatment reduces particle size, dramatically increases surface energy, and enhances chemical activity, making the particles more prone to agglomeration. The added surface modifier, through molecular-level modification, prevents fine particles from enveloping larger particles to form a "cushion," allowing mechanical force to directly reach the uncrushed particles, thus solving the agglomeration problem.

[0058] 3. The entire preparation process of this invention is simple to operate, economical, efficient and environmentally friendly, significantly improving the feasibility and economy of preparing high specific surface area calcium hydroxide from carbide slag. Attached Figure Description

[0059] Figure 1 This is a schematic flowchart of the preparation method provided by the present invention. Detailed Implementation

[0060] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0061] 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; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms “comprising” and “having”, and any variations thereof, in the specification and claims of this invention are intended to cover non-exclusive inclusion.

[0062] Example 1

[0063] This embodiment provides a method for preparing high specific surface area calcium hydroxide from carbide slag, such as... Figure 1 As shown, the specific process is as follows:

[0064] (1) Mix carbide slag and water, and stir for 1 hour at 50℃ and 200 rpm to prepare a first slurry with a mass concentration of 15wt%. Then, feed the slurry at a flow rate of 2.5m³ / h. 3 A second slurry was obtained by two-stage hydrocyclone separation under the conditions of / h and feed pressure of 0.5MPa;

[0065] (2) According to the mass ratio of carbide slag to surface modifier in the second slurry being 1:0.02, n-butanol, a surface modifier, was added to the second slurry and stirred at 50°C for 1 hour. Then, it was placed in a sand mill and ground at 2000 rpm for 30 minutes to complete the ultrafine treatment. Subsequently, the ground slurry was subjected to solid-liquid separation to obtain filter cake and filtrate. The filter cake was then washed and vacuum dried to obtain the product calcium hydroxide powder. In addition, the filtrate and washing liquid were returned to the process of mixing carbide slag and water in step (1) for recycling.

[0066] Example 2

[0067] This embodiment provides a method for preparing high specific surface area calcium hydroxide from carbide slag, the method comprising the following steps:

[0068] (1) Mix carbide slag and water, and stir for 20 minutes at a temperature of 20℃ and a speed of 300 rpm to prepare a first slurry with a mass concentration of 5wt%. Then, feed the slurry at a flow rate of 2m³ / min. 3 Two-stage cyclone separation was carried out under the conditions of / h and feed pressure of 0.2MPa to obtain the second slurry;

[0069] (2) According to the mass ratio of carbide slag to surface modifier in the second slurry being 1:0.02, polyethylene glycol surface modifier is added to the second slurry and stirred at 20°C for 10 hours. Then, it is placed in a sand mill and ground at 1500 rpm for 35 minutes to complete the ultrafine treatment. Subsequently, the ground slurry is subjected to solid-liquid separation to obtain filter cake and filtrate. The filter cake is then washed and vacuum dried to obtain the product calcium hydroxide powder. In addition, the filtrate and washing liquid are returned to the process of mixing carbide slag and water in step (1) for recycling.

[0070] Example 3

[0071] This embodiment provides a method for preparing high specific surface area calcium hydroxide using carbide slag, the method comprising the following steps:

[0072] (1) Mix carbide slag and water, and stir for 10 hours at a temperature of 70℃ and a speed of 50rpm to prepare a first slurry with a mass concentration of 25wt%. Then, feed the slurry at a flow rate of 3m³ / h. 3 A second slurry was obtained by two-stage hydrocyclone separation under the conditions of / h and feed pressure of 1MPa;

[0073] (2) According to the mass ratio of carbide slag to surface modifier in the second slurry being 1:0.02, sodium dodecylbenzene sulfonate surface modifier is added to the second slurry and stirred at 80°C for 20 min. Then, it is placed in a sand mill and ground at 2500 rpm for 25 min to complete the ultrafine treatment. Subsequently, the ground slurry is subjected to solid-liquid separation to obtain filter cake and filtrate. The filter cake is then washed and vacuum dried to obtain the product calcium hydroxide powder. In addition, the filtrate and washing liquid are returned to the process of mixing carbide slag and water in step (1) for recycling.

[0074] Example 4

[0075] The difference between this embodiment and Embodiment 1 is that the mass ratio of carbide slag to surface modifier in the second slurry is 1:0.005;

[0076] The remaining preparation methods and parameters are consistent with those in Example 1.

[0077] Example 5

[0078] The difference between this embodiment and Embodiment 1 is that the mass ratio of carbide slag to surface modifier in the second slurry is 1:0.01;

[0079] The remaining preparation methods and parameters are consistent with those in Example 1.

[0080] Example 6

[0081] The difference between this embodiment and Embodiment 1 is that the mass ratio of carbide slag to surface modifier in the second slurry is 1:0.015;

[0082] The remaining preparation methods and parameters are consistent with those in Example 1.

[0083] Example 7

[0084] The difference between this embodiment and Embodiment 1 is that the mass ratio of carbide slag to surface modifier in the second slurry is 1:0.025;

[0085] The remaining preparation methods and parameters are consistent with those in Example 1.

[0086] Example 8

[0087] The difference between this embodiment and Embodiment 1 is that the mass ratio of carbide slag to surface modifier in the second slurry is 1:0.05;

[0088] The remaining preparation methods and parameters are consistent with those in Example 1.

[0089] Example 9

[0090] The difference between this embodiment and Example 1 is that the surfactant is propylene glycol;

[0091] The remaining preparation methods and parameters are consistent with those in Example 1.

[0092] Example 10

[0093] The difference between this embodiment and Embodiment 1 is that the slurry is ground in a sand mill for 40 minutes;

[0094] The remaining preparation methods and parameters are consistent with those in Example 1.

[0095] Comparative Example 1

[0096] The difference between this comparative example and Example 1 is that no surface modifier is added in step (2);

[0097] The remaining preparation methods and parameters are consistent with those in Example 1.

[0098] Comparative Example 2

[0099] The difference between this comparative example and Example 1 is that step (2) does not involve ultra-fine processing;

[0100] The remaining preparation methods and parameters are consistent with those in Example 1.

[0101] Comparative Example 3

[0102] The difference between this comparative example and Example 1 is that in step (2), the surface modifier is directly added to the sand mill without pre-mixing with the slurry;

[0103] The remaining preparation methods and parameters are consistent with those in Example 1.

[0104] Performance testing

[0105] The specific surface area of ​​the calcium hydroxide prepared in Examples 1-10 and Comparative Examples 1-3 was tested, and the test results are shown in Table 1.

[0106] Table 1

[0107]

[0108] As shown in Examples 1-3 of Table 1, the preparation method of the present invention can directly prepare calcium hydroxide with high specific surface area from carbide slag. A comparison of the data from Example 1 and Comparative Examples 1-3 in Table 1 shows that in the present invention, the surface modifier and ultrafine treatment work synergistically; omitting either step will significantly reduce the specific surface area of ​​the prepared calcium hydroxide.

[0109] A comparison of the data from Examples 1 and 4-8 in Table 1 shows that, with increasing amounts of surface modifier, the specific surface area of ​​the prepared calcium hydroxide exhibits a trend of first increasing and then decreasing, reaching its optimal effect when the mass ratio of carbide slag to surface modifier is 1:0.02, at which point the specific surface area of ​​calcium hydroxide can reach as high as 53.67 m². 2 / g; As can be seen from the comparison of the data of Example 1 and Examples 9-10 in Table 1, in this invention, the type of surface modifier and the time of ultrafine treatment also affect the specific surface area of ​​calcium hydroxide. By controlling them within the preferred range of this invention, it is more beneficial to improve the specific surface area of ​​calcium hydroxide.

[0110] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing calcium hydroxide from carbide slag, characterized in that, The method includes: (1) The carbide slag is slurried to obtain the first slurry, and then impurities are separated to obtain the second slurry; (2) The second slurry from step (1) is mixed with a surface modifier, and then subjected to ultrafine treatment. After solid-liquid separation, the calcium hydroxide is obtained. The surface modifier in step (2) is n-butanol, the mass ratio of carbide slag to surface modifier in the second slurry is 1:(0.015~0.05), the mixing time is 20min~600min, the ultrafine treatment is carried out in a sand mill, the speed of the sand mill is 1500rpm~2500rpm, and the ultrafine treatment time is 25min~35min.

2. The method for preparing calcium hydroxide from carbide slag according to claim 1, characterized in that, The carbide slag in step (1) includes calcium hydroxide, and the mass percentage of the calcium hydroxide is 75wt%~85wt%.

3. The method for preparing calcium hydroxide from carbide slag according to claim 1, characterized in that, The pulping process described in step (1) includes mixing carbide slag and water; The method of mixing carbide slag and water includes a first stirring; The first stirring speed is 50 rpm to 300 rpm; The temperature of the pulping treatment in step (1) is 20℃~70℃ and the time is 20min~600min.

4. The method for preparing calcium hydroxide from carbide slag according to claim 1, characterized in that, Step (1) The concentration of the first slurry is 5wt%~25wt%; The impurity separation process in step (1) includes cyclone separation; The cyclone separation is a multi-stage cyclone separation; The feed flow rate of the cyclone separator is 2m³. 3 / h~3m 3 / h, with a feed pressure of 0.2MPa~1MPa.

5. The method for preparing calcium hydroxide from carbide slag according to claim 1, characterized in that, The mixing method in step (2) includes: adding a surface modifier to the second slurry in step (2) and performing a second stirring; The mixing temperature in step (2) is 20℃~80℃.

6. The method for preparing calcium hydroxide from carbide slag according to claim 1, characterized in that, After solid-liquid separation in step (2), a filter cake and a filtrate are obtained, wherein the water content of the filter cake is 10wt%~50wt%. The filter cake is washed and dried sequentially; The drying includes vacuum drying; The filtrate and the washing liquid are returned to the pulping process in step (1) for recycling.

7. A calcium hydroxide prepared by the method according to any one of claims 1-6.

8. The calcium hydroxide according to claim 7, characterized in that, The specific surface area of ​​the calcium hydroxide is 30 m². 2 / g~60m 2 / g; The water content of the calcium hydroxide is ≤1 wt%; The D90 of the calcium hydroxide is 1.8 μm to 2.2 μm; The purity of the calcium hydroxide is ≥90wt%.

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