Preparation method of high specific surface calcium hydroxide

Abstract

The application relates to the technical field of calcium hydroxide, in particular to a preparation process of calcium hydroxide, which comprises the following steps: S1, crushing and screening calcium oxide; S2, performing ball milling organic coating pretreatment on the calcium oxide in S1 to obtain a base material, and the selected coating agent is ethylene glycol, triethanolamine, ethylenediamine, polyethylene glycol, glucose, ethanol or glycerol; and S3, performing digestion treatment on the base material in S2, and obtaining high specific surface calcium hydroxide after drying.

Description

Technical Field

[0001] This invention relates to the field of calcium hydroxide technology, specifically to a method for preparing high specific surface area calcium hydroxide. Background Technology

[0002] Calcium hydroxide, as a low-cost alkaline inorganic material, is widely used in various fields such as flue gas desulfurization and denitrification, especially as a core desulfurization adsorbent in dry and semi-dry flue gas desulfurization processes. However, calcium hydroxide prepared by traditional processes has significant drawbacks: rapid crystal growth, small specific surface area (only 20~30 m² / g), simple pore structure, and strong exothermic hydration of calcium oxide, which easily leads to particle agglomeration and uneven hydration, resulting in low calcium utilization and desulfurization efficiency. At the same time, it is prone to carbonization during storage and transportation, forming a calcium carbonate film on the surface, which further reduces reactivity and cannot meet the long-term, high-purity requirements of industry. To address the aforementioned issues, coating modification technology has become one of the key optimization pathways. A functional film is formed on the surface of calcium oxide using a coating agent, blocking direct contact to slow down the hydration rate and inhibit agglomeration, while simultaneously guiding crystal growth and optimizing the pore structure. Ma Junbiao (Dry Desulfurization Lime Digestion Process [J]. Huadian Technology, 2010, 32(05):74-79.) found that even with a single additive, the BET concentration using a dry digestion process could only be increased to a maximum of 30 m² / g. Hao Zhifei (Wet Modification for Preparation and Characterization of High Specific Surface Area Calcium Hydroxide [J]. Inorganic Salt Industry, 2015, 47(12):3.) added a single hydroxyl-containing organic additive during the digestion process, which increased the specific surface area of ​​calcium hydroxide to 47.4 m² / g. However, the single additive had limited regulatory effect on crystal growth and insufficient inhibition of hydration agglomeration. Combining core patented technologies with existing research findings, this patent selects multi-component organic coating agents such as ethylene glycol, triethanolamine, and ethylenediamine. These agents not only possess the stability and environmental advantages of both alkanolamine and polyol coating agents, but also address the pain points of particle agglomeration and insufficient specific surface area in traditional processes by reducing solid-liquid interfacial tension and delaying hydration reactions. This further enhances the dispersibility and reactivity of the product, making it suitable for the long-term, high-purity requirements of industrial desulfurization and denitrification scenarios. Summary of the Invention

[0003] To address the problems existing in the prior art, the present invention provides a method for preparing calcium hydroxide, which utilizes an organic coating agent to coat calcium oxide. The organic coating layer on the surface of calcium oxide slows down the reaction rate during the hydration process, prevents agglomeration during the hydration process, and increases the specific surface area of ​​calcium hydroxide.

[0004] The specific solution in this invention is as follows: S1: Raw material preparation, calcium oxide is selected as the raw material; S2: Raw material pretreatment, calcium oxide is coated to obtain base material, ready for use; S3: Deionized water and base material are added simultaneously in a digestion reactor according to the set water-cement ratio to digest calcium hydroxide. S4: The calcium hydroxide particles after digestion in S3 are sent to a rapid dryer for drying to obtain dried calcium hydroxide powder. Preferably, the water-cement ratio in S3 is the percentage of the amount of water added for digestion to the amount of calcium oxide used, and the water-cement ratio is 50 wt% to 100 wt%, wherein the preferred water-cement ratio is ≥75 wt%. Preferably, the temperature of the deionized water in S3 is ≤35 ℃, and more preferably ≤30 ℃. Preferably, the organic coating agent is one or a mixture of ethylene glycol, triethanolamine, ethylenediamine, polyethylene glycol, glucose, ethanol, and glycerol, and the concentration is 0.5 to 8 wt%, preferably 1 to 3 wt%. Preferably, the drying temperature is 130–250 °C, more preferably 150–180 °C. Preferably, the planetary ball mill has a rotational speed of 600-900 r / min and a preferred milling time of 2-8 h; the drum ball mill has a rotational speed of 120-220 rpm and a preferred milling time of 5-20 min; the total weight ratio of the milling steel balls to the coating agent and calcium oxide is 10-40:1; and the high-speed disperser has a dispersion time of 5-20 min. Preferably, the product drying temperature is controlled at 140~180 ℃, and the drying time is preferably controlled at 10~20 min. The calcium hydroxide product has a multi-point BET specific surface area of ​​30 m². 2 / g or more. Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention. The positive and progressive effects of this invention are as follows: The preparation method of the present invention is simple to operate and requires less manpower and material resources; The calcium hydroxide of this invention has a high specific surface area; This invention can be mass-produced, reducing production costs. Attached Figure Description

[0005] Figure 1 This is a table showing all process conditions and test analysis data in the preparation method of high specific surface area calcium hydroxide according to the present invention. Detailed Implementation

[0006] The present invention is further illustrated below by way of embodiments, but this does not limit the invention to the scope of the embodiments described. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the invention should be considered equivalent substitutions and are included within the protection scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or according to the product instructions.

[0007] Example 1 Raw material preparation: Chemically pure calcium oxide (particle size range of 20-40μm) was selected as the raw material. The method for pretreatment of raw material coating is as follows: 50 g of calcium oxide and 0.5 g of ethylene glycol are simultaneously added to a high-speed disperser and dispersed for 10 min. Take out the coated powder, add 20 g of the coated powder and 16 ml of deionized water into the digestion reactor at the same time, insert a thermometer to record the temperature, and stir until the digestion temperature is below 55 ℃ and then stop stirring. The reacted calcium hydroxide powder was placed in a rapid dryer and dried at 160 °C for 15 min. The BET of the dried calcium hydroxide powder was measured to be 40.25 m. 2 / g Example 2 Raw material preparation: Chemically pure calcium oxide was selected as the raw material. The method for pretreatment of raw materials is as follows: Install the ball mill jar and the planetary ball mill, add 50 g of calcium oxide and 2.5 g of triethanolamine into the ball mill jar at the same time, adjust the rotation speed to 600 rpm, and the ball milling time to 2 h, and start ball milling. Take out the ball-milled powder, add 20 g of the ball-milled powder and 20 ml of deionized water to the digestion reactor at the same time, insert a thermometer to record the temperature, and stir until the digestion temperature is below 55 ℃ and then stop stirring. The reacted calcium hydroxide powder was placed in a rapid dryer for drying at a temperature of 160 ℃ for 15 min. The BET of the dried calcium hydroxide powder was determined to be 48.4 m. 2 / g . Example 3 Raw material preparation: Chemically pure calcium oxide was selected as the raw material. The method for pretreatment of raw materials is as follows: Install the ball mill jar and the drum ball mill, put 50 g of calcium oxide and 1.5 g of triethanolamine into the ball mill jar at the same time, adjust the speed to 150 rpm, and the ball milling time to 30 min, and start ball milling. Take out the ball-milled powder, add 20 g of the ball-milled powder and 16 ml of deionized water to the digestion reactor at the same time, insert a thermometer to record the temperature, and stir until the digestion temperature is below 55 ℃ and then stop stirring. The reacted calcium hydroxide powder was placed in a rapid dryer for drying at a temperature of 160 ℃ for 15 min. The BET of the dried calcium hydroxide powder was determined to be 48.1 m. 2 / g . Example 4 Raw material preparation: Chemically pure calcium oxide was selected as the raw material. The method for pretreatment of raw materials is as follows: Install the ball mill jar and planetary ball mill, add 50 g of calcium oxide and 1.5 g of ethylene glycol into the ball mill jar at the same time, adjust the rotation speed to 600 rpm, and the ball milling time to 2 h, and start ball milling. Take out the ball-milled powder, add 20 g of the ball-milled powder and 14 ml of deionized water to the digestion reactor at the same time, insert a thermometer to record the temperature, and stir until the digestion temperature is below 55 ℃ and then stop stirring. The reacted calcium hydroxide powder was placed in a rapid dryer for drying at a temperature of 160 ℃ for 15 min. The BET of the dried calcium hydroxide powder was determined to be 45.7 m. 2 / g . Example 5 Raw material preparation: Chemically pure calcium oxide was selected as the raw material. The method for pretreatment of raw materials is as follows: Install the ball mill jar and the drum ball mill, put 50 g of calcium oxide and 1.5 g of glycerol into the ball mill jar at the same time, adjust the speed to 150 rpm, and the ball milling time to 30 min, and start ball milling. Take out the ball-milled powder, add 20 g of the ball-milled powder and 18 ml of deionized water to the digestion reactor at the same time, insert a thermometer to record the temperature, and stir until the digestion temperature is below 55 ℃ and then stop stirring. The reacted calcium hydroxide powder was placed in a rapid dryer for drying at a temperature of 160 ℃ for 15 min. The BET of the dried calcium hydroxide powder was determined to be 46.23 m. 2 / g . Example 6 Raw material preparation: Chemically pure calcium oxide was selected as the raw material. The method for pre-treatment of raw materials is as follows: 50 g of calcium oxide, 0.5 g of glycerol, 0.5 g of ethanol and 0.5 g of glucose are simultaneously put into a ball mill jar, the speed is adjusted to 600 rpm, the ball milling time is 2 h, and the ball milling begins. Take out the ball-milled powder, add 20 g of the ball-milled powder and 18 ml of deionized water to the digestion reactor at the same time, insert a thermometer to record the temperature, and stir until the digestion temperature is below 55 ℃ and then stop stirring. The reacted calcium hydroxide powder was placed in a rapid dryer for drying at a temperature of 160 ℃ for 15 min. The BET of the dried calcium hydroxide powder was determined to be 47.23 m. 2 / g . Comparative Example 1 Raw material preparation: Chemically pure calcium oxide was selected as the raw material. Add 20 g of calcium oxide and 16 ml of deionized water to the digestion reactor simultaneously, insert a thermometer to record the temperature, and stir until the digestion temperature is below 55 ℃ and then stop stirring. The reacted calcium hydroxide powder was placed in a rapid dryer for drying at a temperature of 160 ℃ for 15 min. The BET of the dried calcium hydroxide powder was determined to be 18.32 m. 2 / g . Comparative Example 2 Raw material preparation: Chemically pure calcium oxide was selected as the raw material. Add 20 g of calcium oxide and 16 ml of 5% triethanolamine solution to the digestion reactor simultaneously. Insert a thermometer to record the temperature and stir until the digestion temperature is below 55 ℃. The reacted calcium hydroxide powder was placed in a rapid dryer for drying at a temperature of 160 ℃ for 15 min. The BET of the dried calcium hydroxide powder was determined to be 44.25 m. 2 / g .

[0008] Performance testing: The calcium hydroxide prepared in Examples 1, 2, 3, 4, 5, Comparative Example 1, and Comparative Example 2 were subjected to performance tests, and the test data were recorded in [the relevant documentation]. Figure 1 .

Claims

1. A method for preparing calcium hydroxide, characterized in that: Includes the following steps: S1: Crush and sieve the calcium oxide, and select calcium oxide with a particle size range of 80~800 mesh as raw material; S2: Calcium oxide is ball-milled and coated with a coating agent to obtain a base material; S3: Digestion treatment, the base material and deionized water are mixed and treated to obtain calcium hydroxide. S4: The calcium hydroxide particles after digestion in S3 are rapidly dried to obtain calcium hydroxide powder.

2. The method for preparing calcium hydroxide according to claim 1, characterized in that, The method for pre-treatment of raw materials is as follows: calcium oxide and a coating agent are coated for 0.5 to 12 hours to complete the pre-treatment of raw materials and obtain a base material coated on the surface of calcium oxide with the coating agent.

3. The method for preparing calcium hydroxide according to claim 2, characterized in that: The organic coating agent used for coating is one or more of ethylene glycol, triethanolamine, ethylenediamine, polyethylene glycol, glucose, ethanol, and glycerol, and the concentration is 0.5-8 wt%.

4. The preparation process of calcium hydroxide according to claim 2, characterized in that, The method for coating calcium oxide with the coating agent is as follows: the coating methods for organic coating agents include planetary ball milling, drum ball milling, and high-speed dispersion.

5. The preparation process of calcium hydroxide according to claim 2, characterized in that, The process of coating calcium oxide with the coating agent includes planetary ball milling, drum ball milling, and high-speed dispersion.

6. The method for preparing calcium hydroxide according to claim 1, characterized in that: The water-ash ratio in S3 is the percentage of the amount of digestion water added to the amount of calcium oxide used, and the water-ash ratio is 50 wt% to 100 wt%, the digestion water temperature is 20 to 60 ℃, and the digestion time is 10 to 30 min.

7. The method for preparing calcium hydroxide according to claim 1, characterized in that: Deionized water and base material are added simultaneously in a digestion reactor according to the set water-cement ratio. Calcium hydroxide is obtained when the temperature in the digestion reactor drops to 40-60 ℃.

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