Method for preparing calcium hydroxide from carbide slag and calcium hydroxide thereof

Abstract

The invention provides a method for preparing calcium hydroxide from carbide slag and calcium hydroxide thereof.The method comprises the steps that 1, the carbide slag is subjected to slurrying treatment to obtain first slurry, and then impurity separation treatment is conducted to obtain second slurry; and (2) mixing the second slurry obtained in the step (1) with a surface modifier, then carrying out ultrafine treatment, and carrying out solid-liquid separation to obtain the calcium hydroxide. According to the method provided by the invention, the content of calcium hydroxide in the carbide slag is increased through impurity separation treatment, and the problem of particle agglomeration is solved through the synergistic effect of ultrafine treatment and the surface modifier, so that carbide slag particles are fully crushed, and the specific surface area of the product calcium hydroxide is greatly increased. In addition, the whole preparation process is easy and convenient to operate, economical, efficient and environmentally friendly, and the feasibility and economical efficiency of preparing the calcium hydroxide with the high specific surface area through the carbide slag are remarkably improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solid waste resource utilization, and relates to a method for preparing calcium hydroxide from carbide slag and calcium hydroxide prepared by the method. BACKGROUND

[0002] Carbide slag is an industrial solid waste formed in the production process of acetylene, with an annual discharge of more than 300 million tons. The main component of carbide slag is calcium hydroxide, which has been widely used in flue gas desulfurization of power plants, preparation of calcium hydroxide powder, etc. In the increasingly mature flue gas desulfurization reaction, calcium hydroxide is mainly used to neutralize acidic gases and ions such as sulfur dioxide, sulfur trioxide, fluoride ions and chloride ions, so that the sulfur content of flue gas emission meets the environmental protection standard. The desulfurization effect is directly affected by the properties of calcium hydroxide, and the specific surface area of calcium hydroxide is an important factor determining the desulfurization effect. Generally speaking, the larger the specific surface area of calcium hydroxide, the better the desulfurization effect.

[0003] The calcium hydroxide prepared from carbide slag is used for desulfurization, and is prone to caking during slurry preparation, affecting product quality. Therefore, improving the dispersibility and stability of calcium hydroxide crystals and preparing calcium hydroxide with a large specific surface area are of great significance to meet the actual needs of flue gas purification and corresponding applications.

[0004] CN202210514260.5 discloses a production method of high specific surface area calcium hydroxide, including crushing, digestion, screening, etc. The calcium oxide content of quicklime is more than 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 the granular quicklime is 5:1, and the vibrating screen is a filtering type mechanical separation equipment with a mesh size of 100-200. CN201911390295.7 discloses a preparation method of high dispersibility and high specific surface area calcium hydroxide, taking quicklime as raw material, adding natural nanocellulose with rich oxygen-containing groups as a template and carboxymethyl cellulose sodium as a surfactant during the digestion process, fully mixing under high-speed shearing, realizing calcium hydroxide nucleation and growth based on ultrasonic action, and obtaining high specific surface area calcium hydroxide through washing, centrifugation, drying and grinding.

[0005] However, the above-mentioned methods for preparing high specific surface area calcium hydroxide have high cost and large reagent consumption, which are difficult to meet large-scale industrial application. Therefore, there is an urgent need to provide a high-efficiency and low-cost method for directly preparing high specific surface area calcium hydroxide from carbide slag. SUMMARY

[0006] In view of the deficiencies of the prior art, the purpose of the present application is to provide a method for preparing calcium hydroxide from carbide slag and calcium hydroxide thereof. The method provided by the present application improves the content of calcium hydroxide in carbide slag through impurity separation treatment, and the synergistic effect of superfine treatment and surface modifier solves 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 of the present application is simple, economical and efficient, and environmentally friendly, which significantly improves the feasibility and economy of preparing high specific surface area calcium hydroxide from carbide slag.

[0007] In order to achieve the purpose of the present application, the following technical solutions are adopted in the present application:

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

[0009] (1) treating the carbide slag to obtain a first slurry, and then performing impurity separation treatment to obtain a second slurry;

[0010] (2) mixing the second slurry of step (1) with a surface modifier, and then performing superfine treatment, and obtaining the calcium hydroxide after solid-liquid separation.

[0011] In the present application, the superfine treatment breaks the particles, reduces the particle size, and exposes the fresh interface in the breaking process, so that the surface atomic bond is broken to form unsaturated bond, resulting in rapid increase of surface energy and increase of chemical activity. The high surface energy drives the fine particles to agglomerate rapidly through van der Waals force, hydrogen bond, etc., and the addition of surface modifier solves the problem of particle agglomeration. The polar groups in the surface modifier are anchored on the active sites on the surface of the particles, and the non-polar chains extend outward. The modified particles are hydrophobic, the water molecule adsorption is reduced, the slurry viscosity is reduced by more than 50%, and the kinetic energy transfer efficiency of the grinding medium is improved. The anti-agglomeration ability of the particles after modification is improved, which avoids the formation of "soft pad" by wrapping the fine particles around the large particles, so that the mechanical force directly reaches the unbroken particles. Therefore, the present application effectively improves the breaking efficiency of the carbide slag particles by coupling the superfine treatment and the surface modifier, and significantly improves the specific surface area of calcium hydroxide in carbide slag. Moreover, the whole preparation process of the present application is simple, economical and efficient, and environmentally friendly, which significantly improves the feasibility and economy of preparing high specific surface area calcium hydroxide from carbide slag.

[0012] The following is a preferred technical solution of the present application, but not as a limitation of the technical solutions provided by the present application. Through the following preferred technical solution, the technical purpose and beneficial effects of the present application can be better achieved and realized.

[0013] As a preferred technical solution of the present application, the calcium hydroxide in step (1) accounts for 75wt%-85wt% of the calcium carbide slag, such as 75wt%, 77wt%, 80wt%, 82wt% or 85wt%, etc.

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

[0015] The mixing of the calcium carbide slag and water includes first stirring.

[0016] The first stirring has a rotation speed of 50rpm-300rpm, such as 50rpm, 100rpm, 150rpm, 200rpm, 250rpm or 300rpm, etc.

[0017] The slurry treatment in step (1) has a temperature of 20℃-70℃, such as 20℃, 30℃, 40℃, 50℃, 60℃ or 70℃, etc., and a time of 20min-600min, such as 20min, 1h, 2h, 3h, 5h, 8h or 10h, etc.

[0018] In the present application, by controlling the stirring speed, temperature and time of the slurry treatment process, the overall effect of impurity removal in the calcium carbide slag can be significantly improved. The above stirring speed not only ensures the sufficient dispersion of the calcium carbide slag in water, avoiding the agglomeration phenomenon between particles, but also reduces the risk of material damage caused by excessive shearing. The above temperature helps to improve the treatment efficiency, while preventing unnecessary side reactions or component volatilization loss due to excessive temperature. The above time ensures that all components can reach the best mixing state.

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

[0020] In the present application, by controlling the concentration of the first slurry within the above preferred range, it can be ensured that the calcium carbide slag is sufficiently dispersed in water to form a uniform slurry, which is helpful for the subsequent impurity removal process and improves the removal efficiency of impurities in the calcium carbide slag.

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

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

[0023] In the present application, the impurities in the carbide slag can be efficiently separated by using one or more stages of cyclone separation, and the multi-stage cyclone separation can more fully capture the residual coarse and fine particles in the slurry, further improving the overall impurity removal rate. In the present application, two-stage cyclone separation can already meet the higher separation requirements.

[0024] The feed flow rate of the cyclone separation is 2m 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., and the feed pressure is 0.2MPa~1MPa, for example 0.2MPa, 0.3MPa, 0.5MPa, 0.7MPa, 0.9MPa or 1MPa, etc.

[0025] In the present application, by controlling the feed flow rate within the above preferred range, sufficient residence time of the slurry in the cyclone device can be ensured, so that the impurity particles are fully exposed in the cyclone, thereby improving the impurity removal efficiency, while avoiding the loss of calcium hydroxide due to excessive flow rate; by controlling the feed pressure within the above preferred range, it is helpful to maintain the stable flow of the slurry in the pipeline and the device, prevent the occurrence of blockage phenomenon, and enhance the migration ability of solid particles in the cyclone, which is beneficial to improve the capture efficiency of impurity minerals.

[0026] As a preferred technical solution of the present application, the mass ratio of the carbide slag to the surface modifier in the second slurry of step (2) 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 the present application, by controlling the mass ratio of the carbide slag to the surface modifier within the above preferred range, sufficient surface modifier can be ensured to participate in the reaction, improving the dispersion effect of calcium hydroxide particles and achieving a substantial increase in specific surface area; at the same time, unnecessary side reactions caused by excessive use of surface modifier are avoided. Not only the specific surface area of the carbide slag is substantially increased, but also the cost-effectiveness is taken into account, maximizing the economy.

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

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

[0030] In the present application, by controlling the temperature of mixing the surface modifier and the carbide slag within the above range, the efficiency of the surface modifier on the minerals in the carbide slag is enhanced, and the reactivity is improved. By controlling the mixing time within the above preferred range, the surface modifier has sufficient time to fully contact and react with the carbide slag, and the carbide slag particles can be fully broken down and the specific surface area is improved.

[0031] As a preferred technical solution of the present application, 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 the present application, the organic oligomer refers to a low molecular weight polymer formed by covalent bonding of a small number of monomer molecules, usually containing 2-20 monomer units.

[0033] In the present application, the surface modifier can cope with the complex mineral composition in the carbide slag, can 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, so as to realize flexible adaptation to different process conditions and meet the demand for preparing high specific surface area calcium hydroxide.

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

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

[0036] The organic oligomer includes any one or a combination of at least two of polyolefin oligomer, 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 the present application, part of the groups in the coupling agent can react with various functional groups on the surface of carbide slag to form strong chemical bonding; the surfactant can significantly reduce the surface tension of the carbide slag slurry, change the surface state of the system to produce wetting and reverse wetting; the organic oligomer can form good infiltration, adhesion and coating with the carbide slag powder; the unsaturated organic acid has unsaturated double bonds and carboxyl groups, which can make the carbide slag better dispersed; the water-soluble polymer is a hydrophilic polymer material containing a large number of hydrophilic groups, which is beneficial to the performance control of the subsequent resource product; n-butanol can be adsorbed on the surface of the carbide slag slurry, with the hydrophilic group extending to the water phase and the hydrophobic group extending to the air phase, which can significantly reduce the surface tension of the liquid, thereby effectively dispersing the particles in the carbide slag slurry. And among the above-mentioned 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 application, the superfine treatment in step (2) is carried out in a sand mill.

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

[0042] The superfine treatment time is 25 min to 35 min, such as 25 min, 26 min, 30 min, 31 min, 32 min, 33 min, 34 min or 35 min, etc.

[0043] As a preferred technical solution of the present application, the filter cake and filtrate are obtained after the solid-liquid separation in step (2), and the moisture content of the filter cake is 10wt% to 50wt%, such as 10wt%, 20wt%, 30wt%, 40wt% or 50wt%, etc.

[0044] In the present application, by controlling the moisture content of the filter cake within the above-mentioned preferred range, it is helpful to ensure the smooth progress of the subsequent processing steps, both maintaining the good dispersibility of the carbide slag and preventing particle agglomeration, and also not making the material too dry to increase the operation difficulty.

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

[0046] The drying includes vacuum drying.

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

[0048] In the present application, by recycling the filtrate and the washing liquid, both the reagent consumption is reduced and the wastewater discharge is avoided.

[0049] In a second aspect, the present application provides a calcium hydroxide prepared by the method of the first aspect.

[0050] As a preferred technical solution of the present application, the specific surface area of the calcium hydroxide is 30m 2 / g~60m 2 / g, such as 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%, such as 0.1wt%, 0.2wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.8wt%, or 1wt%, etc.

[0052] The D90 of the calcium hydroxide is 1.8μm~2.2μm, such as 1.8μm, 1.9μm, 2μm, 2.1μm, or 2.2μm, etc.

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

[0054] The numerical range of the present application includes not only the above-mentioned point values, but also any point values between the above-mentioned numerical ranges that are not mentioned. Due to the limited space and for the sake of simplicity, the present application does not exhaustively list the specific point values included in the range.

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

[0056] 1. The method provided by the present application realizes the preparation of calcium hydroxide with high specific surface area from carbide slag, while reducing the processing cost, which is conducive to improving the economic benefit of the overall process.

[0057] 2. The present application couples the use of superfine treatment and surface modifier, so that the carbide slag particles are fully broken, and the specific surface area is significantly improved. Superfine treatment reduces the particle size, sharply increases the surface energy, and increases the chemical activity, which leads to easier particle agglomeration. The addition of surface modifier avoids the formation of "soft pad" by wrapping fine particles around large particles, so that the mechanical force directly reaches the unbroken particles, solving the problem of agglomeration.

[0058] 3、The whole preparation process of the application is simple in operation, high in economic efficiency and friendly to the environment, and significantly improves the feasibility and economy of preparing calcium hydroxide with high specific surface area from carbide slag. BRIEF DESCRIPTION OF DRAWINGS

[0059] Figure 1 is a flowchart of the preparation method provided by the application. DETAILED DESCRIPTION

[0060] The technical solutions of the application will be further described through specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the application, and should not be regarded as specific limitations on the application.

[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 the application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the application; the terms "include" and "have" and any variations thereof in the specification and claims of the application are intended to cover non-exclusive inclusion.

[0062] Example 1

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

[0064] (1) Mix the carbide slag and water, stir at a temperature of 50℃ and a speed of 200rpm for 1h, prepare a first slurry with a mass concentration of 15wt%, then perform secondary cyclone separation under the conditions of a feed flow rate of 2.5m 3 / h and a feed pressure of 0.5MPa, to obtain a second slurry;

[0065] (2) According to the mass ratio of carbide slag to surface modifier in the second slurry being 1:0.02, add the surface modifier n-butanol to the second slurry, stir at 50℃ for 1h, then place it in a sand mill and grind at a speed of 2000rpm for 30min to complete the superfine treatment; then, perform solid-liquid separation on the ground slurry to obtain a filter cake and a filtrate, and then sequentially wash and vacuum dry the filter cake to obtain the product calcium hydroxide powder; in addition, the filtrate and the washing liquid are recycled to the process of mixing carbide slag and water in step (1).

[0066] Example 2

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

[0068] (1) The carbide slag and water were mixed, stirred at a temperature of 20℃ and a rotation speed of 300 rpm for 20 min to prepare a first slurry with a mass concentration of 5wt%, and then subjected to secondary cyclone separation at a feed flow rate of 2 m 3 / h and a feed pressure of 0.2 MPa to obtain a second slurry;

[0069] (2) The surface modifier polyethylene glycol was added to the second slurry according to a mass ratio of the carbide slag in the second slurry to the surface modifier of 1:0.02, and stirred at 20℃ for 10 h, and then placed in a sand mill and ground at a rotation speed of 1500 rpm for 35 min to complete the superfine treatment; subsequently, the ground slurry was subjected to solid-liquid separation to obtain a filter cake and a filtrate, and the filter cake was then sequentially washed and vacuum dried to obtain a product calcium hydroxide powder; in addition, the filtrate and the washing liquid were recycled to the process of mixing the carbide slag and water in step (1).

[0070] Example 3

[0071] The present example provides a method for preparing high specific surface area calcium hydroxide using carbide slag, which comprises the following steps:

[0072] (1) The carbide slag and water were mixed, stirred at a temperature of 70℃ and a rotation speed of 50 rpm for 10 h to prepare a first slurry with a mass concentration of 25wt%, and then subjected to secondary cyclone separation at a feed flow rate of 3 m 3 / h and a feed pressure of 1 MPa to obtain a second slurry;

[0073] (2) The surface modifier sodium dodecyl benzene sulfonate was added to the second slurry according to a mass ratio of the carbide slag in the second slurry to the surface modifier of 1:0.02, and stirred at 80℃ for 20 min, and then placed in a sand mill and ground at a rotation speed of 2500 rpm for 25 min to complete the superfine treatment; subsequently, the ground slurry was subjected to solid-liquid separation to obtain a filter cake and a filtrate, and the filter cake was then sequentially washed and vacuum dried to obtain a product calcium hydroxide powder; in addition, the filtrate and the washing liquid were recycled to the process of mixing the carbide slag and water in step (1).

[0074] Example 4

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

[0076] The rest of the preparation method and parameters are consistent with those of 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 rest of the preparation method and parameters are consistent with embodiment 1.

[0080] Embodiment 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 rest of the preparation method and parameters are consistent with embodiment 1.

[0083] Embodiment 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 rest of the preparation method and parameters are consistent with embodiment 1.

[0086] Embodiment 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 rest of the preparation method and parameters are consistent with embodiment 1.

[0089] Embodiment 9

[0090] The difference between this embodiment and embodiment 1 is that the surface active agent is propylene glycol;

[0091] The rest of the preparation method and parameters are consistent with embodiment 1.

[0092] Embodiment 10

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

[0094] The rest of the preparation method and parameters are consistent with embodiment 1.

[0095] Comparative example 1

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

[0097] The rest of the preparation method and parameters are consistent with embodiment 1.

[0098] Comparative example 2

[0099] The difference between this comparative example and embodiment 1 is that no superfine treatment is performed in step (2);

[0100] The rest of the preparation method and parameters are consistent with Example 1.

[0101] Comparative Example 3

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

[0103] The rest of the preparation method and parameters are consistent with Example 1.

[0104] Performance test

[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 can be seen from Examples 1-3 in Table 1, the high specific surface area calcium hydroxide can be directly prepared from carbide slag by using the preparation method of the present application. As can be seen from the data comparison of Example 1 and Comparative Examples 1-3, in the present application, the surface modifier and the superfine treatment are synergistic, and without any of the steps, the specific surface area of the prepared calcium hydroxide will be greatly reduced.

[0109] As can be seen from the data comparison of Example 1 and Examples 4-8, with the increase of the amount of the surface modifier, the specific surface area of the prepared calcium hydroxide shows a trend of first increasing and then decreasing, and the best effect is achieved when the mass ratio of the carbide slag to the surface modifier is 1:0.02, at which time the specific surface area of the calcium hydroxide can be as high as 53.67 m 2 / g; As can be seen from the data comparison of Example 1 and Examples 9-10, in the present application, the type of the surface modifier and the superfine treatment time will also affect the specific surface area of the calcium hydroxide, and by controlling them within the preferred range of the present application, it is more conducive to the improvement of the specific surface area of the calcium hydroxide.

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

Claims

1. A method for preparing calcium hydroxide from carbide slag, characterized by, The method comprises: (1) performing slurry treatment on carbide slag to obtain a first slurry, and then performing impurity separation treatment to obtain a second slurry; (2) mixing the second slurry of step (1) and a surface modifier, and then performing superfine treatment, and obtaining the calcium hydroxide after solid-liquid separation.

2. The method of preparing calcium hydroxide from carbide slag according to claim 1, characterized by, The carbide slag of step (1) comprises calcium hydroxide, and the mass fraction of the calcium hydroxide is 75wt%-85wt%.

3. The method of preparing calcium hydroxide from carbide slag according to claim 1, characterized by, The slurry treatment of step (1) comprises mixing the carbide slag and water; The mixing of the carbide slag and water comprises first stirring; The rotating speed of the first stirring is 50rpm-300rpm; The temperature of the slurry treatment of step (1) is 20℃-70℃, and the time is 20min-600min.

4. The method of preparing calcium hydroxide from carbide slag according to claim 1, characterized by, The concentration of the first slurry of step (1) is 5wt%-25wt%; The impurity separation treatment of step (1) comprises cyclone separation; The cyclone separation is multi-stage cyclone separation; The feed flow rate of the cyclone separation is 2 m 3 / h~3 m 3 / h, and the feed pressure is 0.2 MPa~1 MPa.

5. The method of claim 1, wherein the calcium hydroxide is prepared from carbide slag, characterized by, The mass ratio of the carbide slag to the surface modifier in the second slurry of step (2) is 1:(0.005-0.05); The mixing of step (2) comprises: adding the surface modifier into the second slurry of step (2), and performing second stirring; The temperature of the mixing of step (2) is 20℃-80℃, and the time is 20min-600min.

6. The method of preparing calcium hydroxide from carbide slag according to claim 1, characterized by, The surface modifier of step (2) comprises any one or combination of at least two of a coupling agent, a surfactant, an organic oligomer, an unsaturated organic acid, a water-soluble polymer, or n-butanol; The coupling agent comprises any one or combination of at least two of a titanate coupling agent, a silane coupling agent, or an aluminate coupling agent; The surfactant comprises any one or combination of at least two of an anionic surfactant, a cationic surfactant, or a nonionic surfactant; The organic oligomer comprises any one or combination of at least two of a polyolefin oligomer, a polyethylene wax, or an epoxy resin; The unsaturated organic acid comprises any one or combination of at least two of acrylic acid, methacrylic acid, or butenyl acid; The water-soluble polymer comprises any one or combination of at least two of polyacrylamide, polyethylene glycol, or polyvinyl alcohol.

7. The method of preparing calcium hydroxide from carbide slag according to claim 1, characterized by, The superfine treatment of step (2) is performed in a sand mill; The rotating speed of the sand mill is 1500rpm-2500rpm; The time of the superfine treatment is 25min-35min.

8. The method of preparing calcium hydroxide from carbide slag according to claim 1, characterized by, After the solid-liquid separation of step (2), a filter cake and a filtrate are obtained, and the moisture content of the filter cake is 10wt%-50wt%; The filter cake is sequentially washed and dried; The drying comprises vacuum drying; The filtrate and the washing liquid after washing are returned to the slurry treatment process of step (1) for recycling.

9. Calcium hydroxide prepared by the method of any one of claims 1-8.

10. The calcium hydroxide according to claim 9, characterized in that, The calcium hydroxide has a specific surface area of 30 m 2 / g~60 m 2 / g; The moisture content of the calcium hydroxide is ≤1wt%; The D90 of the calcium hydroxide is 1.8μm-2.2μm; The purity of the calcium hydroxide is ≥90wt%.

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