Preparation method of high-purity nano calcium hydroxide

Abstract

The invention relates to the technical field of calcium hydroxide preparation, and particularly discloses a preparation method of high-purity nano calcium hydroxide, which comprises the following steps: a digestion link, a crushing link and a dehydration link, by optimizing raw material selection and treatment flow and controlling the purity of calcium oxide, the problem of unstable purity possibly caused by external purchase of raw materials is avoided. Meanwhile, an efficient purification technology is adopted in the preparation process, impurities are further removed, it is ensured that the purity of the final product high-purity nano calcium hydroxide reaches the extremely high level, and the strict requirements of the high-end application field are met. The production cost is effectively reduced while the high quality of the product is kept.

Description

Technical Field

[0001] The present invention relates to the technical field of calcium hydroxide preparation, and in particular to a method for preparing high-purity nano calcium hydroxide. Background Art

[0002] Calcium hydroxide, as an important inorganic chemical raw material, has shown wide application potential in many fields such as environmental protection, building materials, medicine and food. With the continuous advancement of nanotechnology, high-purity nano calcium hydroxide has gradually become a hot spot for research and application due to its unique physical and chemical properties, such as high specific surface area, excellent dispersibility and enhanced reactivity. However, there are still a series of technical difficulties in the preparation of high-purity nano calcium hydroxide, which limits its large-scale production and application promotion.

[0003] In traditional methods, the preparation of nano-scale calcium hydroxide usually involves the digestion process of quicklime or high-purity calcium hydroxide, followed by coating with surfactants and further refining the particles through ball milling or ultrasonic crushing technology. Although these steps can achieve nano-size particles to a certain extent, there are the following key issues that need to be solved urgently.

[0004] Difficulty in controlling the purity of raw materials: In the prior art, the purity of calcium oxide, as the starting raw material, directly determines the purity of the final product. However, due to the diverse sources of raw materials and the lack of effective purification methods, calcium oxide often contains a variety of impurities, which are difficult to completely remove in subsequent processing, seriously affecting the purity and performance of nano calcium hydroxide. Although ball milling and ultrasonic crushing can effectively reduce the particle size, the existing physical screening technology is limited by its resolution and cannot achieve precise screening at the nanometer level. This means that in the subsequent processing process, regardless of the quality of the particles, they are all processed together, resulting in uneven particle size distribution in the final product, making it difficult to obtain a nano-scale calcium hydroxide product with a high degree of consistency. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing high-purity nano calcium hydroxide to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for preparing high-purity nano calcium hydroxide comprises the following steps:

[0008] S1. Digestion process: select high-quality calcium oxide blocks with a purity of not less than 86% to ensure that the active ingredients of the raw materials are high. The ratio of calcium oxide blocks to water is solid-liquid ratio: 1:9. The digestion temperature is controlled between 20℃ and 95℃. Stirring is performed to ensure that the calcium oxide blocks are fully in contact with water and react evenly. Digestion time: until the calcium oxide blocks react completely and inactive calcium oxide and calcium carbonate settle to the bottom.

[0009] S2. Crushing stage: A vibrating screen with an aperture of 0.5 mm is used to screen the mixed liquid after digestion to remove impurities and unreacted solid particles. A crushing tank with a volume of 0.5 mm is selected according to the production scale to ensure that it can accommodate the mixed liquid after screening. The liquid flows in two dimensions inside the crushing tank under the action of the guide plate and the stirring paddle. The guide plate and the stirring paddle are designed as follows: the guide plate is 30 degrees to the tank wall, and the stirring paddle speed is controlled at 100-300 rpm to achieve two-dimensional flow of the liquid. After the liquid flows from the bottom to the top liquid level along the tank wall, it is brought into the bottom of the tank by the vortex; under the continuous action of the guide plate and the stirring paddle, the liquid continues to flow upward along the tank wall; it fully collides with the ultrasonic wave, so as to achieve the degree of crushing to the nanometer level;

[0010] The crushing tank is equipped with an ultrasonic generator, with ultrasonic frequency of 20-40kHz, ultrasonic power of 500-2000W, and crushing time of 30-180 minutes;

[0011] S3, dehydration step: after the crushing step, select a rotary horizontal screw centrifuge or a plate and frame filter press, the centrifuge speed is 2000-6000rpm, after centrifugal drying, the moisture content of the obtained wet solid calcium hydroxide is controlled between 48-52%, the purity of the product is higher than 98%, and the particle size reaches the nanometer level, that is, a high-purity nano calcium hydroxide finished product.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] The present invention controls the purity of calcium oxide by optimizing the raw material selection and processing flow, thereby avoiding the problem of unstable purity that may be caused by purchasing raw materials from outside. At the same time, an efficient purification technology is used in the preparation process to further remove impurities, ensuring that the purity of the final product, high-purity nano calcium hydroxide, reaches an extremely high level and meets the strict requirements of high-end application fields. The present invention effectively reduces production costs while maintaining high product quality. On the one hand, strict control of raw material purity reduces unnecessary waste; on the other hand, efficient purification and screening technology improves production efficiency, reduces energy consumption and material consumption, and promotes the promotion of industrial production of high-purity nano calcium hydroxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The purpose of preparing transmission electron microscope images at 100 nanometer scale for the present invention;

[0015] Figure 2 The purpose of preparing a transmission electron microscope image at a scale of 500 nanometers for the present invention;

[0016] Figure 3 The purpose of preparing a transmission electron microscope image at a scale of 10 microns for the present invention;

[0017] Figure 4 The transmission electron microscope image intention at 2 micrometer scale is prepared for the present invention;

[0018] Figure 5 It is a schematic diagram of the internal structure of the crushing tank of the present invention. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] Embodiment 1:

[0021] See also Figures 1 to 4 As shown,

[0022] A method for preparing high-purity nano calcium hydroxide comprises the following steps:

[0023] S1. Digestion

[0024] Raw material selection: Choose high-quality calcium oxide blocks.

[0025] Water was added for digestion, and the solid-liquid ratio was 1:9.

[0026] Reaction environment: Carry out in excess water to ensure that only calcium oxide with sufficient activity can react with water to form calcium hydroxide. The digestion temperature is controlled at 65℃.

[0027] Impurity treatment: Inactive impurities such as calcium oxide and calcium carbonate will automatically settle during the reaction.

[0028] Purity improvement: Avoid the use of ball milling and ultrasonic crushing to improve the purity of the product.

[0029] 2. Crushing link

[0030] Pretreatment: The upper flowable mixed liquid after the digestion reaction is screened through a vibrating screen.

[0031] Crushing equipment: Special crushing tank, with ultrasonic device installed on the outside.

[0032] Crushing mechanism:

[0033] The liquid flows in two dimensions under the action of bottom diversion and stirring, that is, after flowing from the bottom to the top liquid level along the tank wall, it is brought into the bottom of the tank by the vortex.

[0034] Under the continuous action of the guide plate and the stirring paddle, the liquid continues to flow upward along the tank wall.

[0035] Achieve sufficient collision with ultrasound to achieve fragmentation to the nanoscale level.

[0036] Crushing time: generally lasts 50 minutes.

[0037] 3. Subsequent processing

[0038] Dehydration: Since the obtained paste has too high water content (over 85%), it is not conducive to storage and transportation.

[0039] Drying method: centrifugal drying or plate and frame filtration.

[0040] Finished product characteristics: obtain moist solid calcium hydroxide containing 50% water, that is, a high-purity nano calcium hydroxide finished product.

[0041] When the guide plate is at an angle of 30 degrees to the tank wall, it can effectively guide the liquid flow to the axial direction of the stirring device, causing the liquid flow to roll up and down. This flow mode is conducive to the full and uniform mixing of the material and liquid, reduces the mixing time, and improves the mixing quality.

[0042] Embodiment 2:

[0043] 1. Raw material preparation

[0044] A batch of calcium oxide blocks with a purity of 86% was selected as the production raw material to ensure that the raw material has high active ingredients and low impurity content. This batch of calcium oxide blocks has been strictly screened and tested and meets the production requirements.

[0045] 2. Digestion

[0046] Mixing ratio: Add 100 kg of calcium oxide blocks and 900 kg of water (according to the solid-liquid ratio of 1:9) into the digester. The digester is made of stainless steel, which has good corrosion resistance and high temperature resistance.

[0047] Temperature and stirring control: Set the temperature of the digester to 70℃ and turn on the stirring device. Set the stirring speed to a medium level to ensure that the calcium oxide blocks are fully in contact with the water and react evenly. At the same time, observe the reaction in the digester to avoid excessive foaming.

[0048] Reaction completion: After a period of reaction, observe the mixture in the digester and find that the calcium oxide blocks have completely reacted and the inactive calcium oxide and calcium carbonate have settled to the bottom. At this point, it can be considered that the digestion process has been completed.

[0049] 3. Crushing and screening: The digested mixed liquid is screened through a vibrating screen with a pore size of 0.5 mm to remove impurities and unreacted solid particles. The vibrating screen is made of stainless steel, which has good corrosion resistance and wear resistance.

[0050] Crushing tank operation: Add the screened mixed liquid into a crushing tank with a volume of 2 cubic meters. The crushing tank is designed with a guide plate and a stirring paddle. The guide plate is at a 30-degree angle to the tank wall, and the stirring paddle speed is set at 200rpm. Turn on the stirring device and ultrasonic generator to allow the liquid to fully collide with the ultrasonic wave under the continuous action of the guide plate and stirring paddle. The frequency of the ultrasonic generator is set at 30kHz and the power is set at 1000W.

[0051] Crushing time control: The crushing time is set to 90 minutes. During this period, the reaction in the crushing tank is regularly observed to ensure that the liquid fully collides with the ultrasonic wave and is crushed to the nanometer level.

[0052] 4. Dehydration

[0053] Centrifuge selection: Use a rotating horizontal screw centrifuge for dehydration. The centrifuge is made of stainless steel, which has good corrosion resistance and wear resistance.

[0054] Centrifugal parameter setting: Set the speed of the centrifuge to 2000-6000rpm. Add the crushed mixed liquid into the centrifuge and start the centrifuge for dehydration.

[0055] Product collection and testing: After dehydration is completed, open the valve at the bottom of the centrifuge to discharge and collect the moist solid calcium hydroxide. The product is tested for purity and particle size, and the results show that the product purity is higher than 98% and the particle size reaches nanometer level.

[0056] In summary, developing a method for preparing high-purity nano-calcium hydroxide that can effectively control the purity of raw materials, achieve nano-level precise screening, and provide detailed particle size data and microstructure evidence is of great significance for promoting technological progress and industrial upgrading in this field.

[0057] It will be appreciated that in the development of any actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but will be a routine task of design, fabrication, and production for those of ordinary skill having the benefit of this disclosure without undue experimentation.

[0058] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing high-purity nano calcium hydroxide, characterized in that: The following steps are involved: S1. Digestion process: select high-quality calcium oxide blocks with a purity of not less than 86% to ensure that the active ingredients of the raw materials are high. The ratio of calcium oxide blocks to water is solid-liquid ratio: 1:

9. The digestion temperature is controlled between 20℃ and 95℃. Stirring is performed to ensure that the calcium oxide blocks are fully in contact with water and react evenly. Digestion time: until the calcium oxide blocks react completely and inactive calcium oxide and calcium carbonate settle to the bottom. S2. Crushing process: A vibrating screen with an aperture of 0.5 mm is used to screen the mixed liquid after digestion to remove impurities and unreacted solid particles. A crushing tank with a volume of 0.5 mm is selected according to the production scale to ensure that it can accommodate the mixed liquid after screening. The liquid flows in two dimensions inside the crushing tank under the action of the guide plate and the stirring paddle. The guide plate and the stirring paddle are designed as follows: the guide plate is 30 degrees with the tank wall, and the stirring paddle speed is controlled at 80-500rpm to achieve two-dimensional flow of the liquid. After the liquid flows from the bottom to the top liquid level along the tank wall, it is brought into the bottom of the tank by the vortex; under the continuous action of the guide plate and the stirring paddle, the liquid continues to flow upward along the tank wall; it fully collides with the ultrasonic wave, so as to achieve the degree of crushing to the nanometer level; The crushing tank is equipped with an ultrasonic generator, with ultrasonic frequency of 20-40kHz, ultrasonic power of 500-2000W, and crushing time of 30-180 minutes; S3, dehydration step: after the crushing step, select a horizontal spiral sedimentation centrifuge or a plate and frame filter press, the centrifuge speed is 2000-6000rpm, after centrifugal drying, the moisture content of the obtained wet solid calcium hydroxide is controlled between 48-52%, the purity of the product is higher than 98%, and the particle size reaches nanometer level, that is, a high-purity nano calcium hydroxide finished product.

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