Preparation method of high-purity calcium hydroxide

Abstract

The application relates to the technical field of calcium hydroxide, and discloses a preparation method of high-purity calcium hydroxide, which comprises the following steps: adding calcium oxide into a digestive juice for digestion to obtain calcium hydroxide; the calcium oxide is obtained by calcining lime and an additive; the additive is composed of molybdenum hydroxide and ferrous oxide; and the digestive juice contains water. Through the technical scheme, the problems of low purity and low yield of calcium hydroxide in the prior art are solved.

Description

Technical Field

[0001] This invention relates to the field of calcium hydroxide technology, and more specifically, to a method for preparing high-purity calcium hydroxide. Background Technology

[0002] Calcium hydroxide, also known as carbon dioxide absorbent or slaked lime, is a white, powdery solid. It is suitable for wastewater treatment, power plant desulfurization, paint fillers, and chemical industries. It can also be used to produce calcium carbonate, epichlorohydrin, bleaching powder, and neutralizing agents. Currently, calcium hydroxide is typically prepared from quicklime, but this method suffers from low purity and low yield, leading to increased costs and failing to fully meet market demand. Summary of the Invention

[0003] This invention proposes a method for preparing high-purity calcium hydroxide, which solves the problems of low purity and low yield of calcium hydroxide in related technologies.

[0004] The technical solution of the present invention is as follows: This invention proposes a method for preparing high-purity calcium hydroxide, comprising the following steps: adding calcium oxide to a digestion solution for digestion to obtain calcium hydroxide; wherein the calcium oxide is obtained by calcining lime and an additive; wherein the additive is composed of molybdenum hydroxide and ferrous oxide; and wherein the digestion solution contains water.

[0005] As a further technical solution, calcium oxide is added to a digestive solution for digestion and maturation to obtain calcium hydroxide.

[0006] As a further technical solution, the curing temperature is 80~90℃ and the curing time is 1~2h.

[0007] As a further technical solution, the admixture is 0.3% to 0.5% of the mass of lime.

[0008] As a further technical solution, the stirring speed during the digestion reaction is 40~60 r / min.

[0009] As a further technical solution, the digestive fluid also contains additives; the additives are one or more of triethanolamine, sodium tripolyphosphate, and polyvinylpyrrolidone.

[0010] The addition of additives to the digestive fluid of this invention can accelerate the formation of calcium hydroxide, obtain higher quality calcium hydroxide, and optimize the performance and characteristics of the product.

[0011] As a further technical solution, the mass ratio of molybdenum hydroxide to ferrous oxide is 1:1.5~2.5.

[0012] As a further technical solution, the mass ratio of molybdenum hydroxide to ferrous oxide is 1:2.

[0013] As a further technical solution, the mass ratio of water to calcium oxide in the digestive fluid is 3~5:1.

[0014] As a further technical solution, the additive in the digestive fluid is 0.2% to 1% of the mass of calcium oxide.

[0015] As a further technical solution, the digestion time is 30-40 minutes.

[0016] As a further technical solution, the calcination is carried out in two stages. The calcination temperature of the first stage is 400~500℃ and the calcination time of the first stage is 2~3h. The calcination temperature of the second stage is 900~1000℃ and the calcination time of the second stage is 10~20min.

[0017] As a further technical solution, the heating rate to the first stage calcination temperature is 10~20℃ / min.

[0018] As a further technical solution, the heating rate to the second-stage calcination temperature is 15~25℃ / min.

[0019] By limiting the heating rate to the first-stage calcination temperature in this invention, the additives can better exert their effects, making calcium oxide more active and improving the yield and purity of calcium hydroxide.

[0020] The working principle and beneficial effects of this invention are as follows: The additives composed of molybdenum hydroxide and ferrous oxide in this invention can promote the decomposition of calcium carbonate in lime and reduce the calcination time. On the one hand, this makes the prepared calcium oxide more active, and on the other hand, it can improve the yield and purity of calcium hydroxide. This not only reduces production costs but also improves the quality of calcium hydroxide and expands its application range. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1 A method for preparing high-purity calcium hydroxide includes the following steps: S1. After the lime and additive are mixed evenly, they are fed into a rotary kiln and heated to 500℃ for 2 hours at a heating rate of 10℃ / min. Then, they are heated to 900℃ for 20 minutes at a heating rate of 15℃ / min. After that, the material is discharged, ground, and cooled to obtain calcium oxide with a particle size of 40mm. The additive is 0.3% of the mass of lime and is composed of molybdenum hydroxide and ferrous oxide in a mass ratio of 1:1. S2. Add calcium oxide to the digestion solution, digest at 40 r / min for 30 min, then let stand at 80℃ for 2 h to mature, filter, wash, dry, and pass through a 200 mesh sieve to obtain calcium hydroxide; the digestion solution consists of water and additives (composed of triethanolamine and polyvinylpyrrolidone in a mass ratio of 1:1), the mass ratio of water to calcium oxide is 3:1, and the mass of the additives is 0.2% of the mass of calcium oxide.

[0023] Example 2 A method for preparing high-purity calcium hydroxide includes the following steps: S1. After the lime and additives are mixed evenly, they are fed into a rotary kiln and calcined at 450℃ for 2.5 hours at a heating rate of 15℃ / min. Then, they are calcined at 950℃ for 15 minutes at a heating rate of 20℃ / min. After calcination, the material is discharged, ground, and cooled to obtain calcium oxide with a particle size of 40mm. The additives are 0.4% of the mass of lime and are composed of molybdenum hydroxide and ferrous oxide in a mass ratio of 1:1. S2. Add calcium oxide to the digestion solution and digest at 50 r / min for 35 min. Then, let it stand at 85℃ for 1.5 h to mature. Filter, wash, dry, and pass through a 200 mesh sieve to obtain calcium hydroxide. The digestion solution consists of water and additives (composed of sodium tripolyphosphate and triethanolamine in a mass ratio of 1:1). The mass ratio of water to calcium oxide is 4:1, and the mass of the additives is 0.8% of the mass of calcium oxide.

[0024] Example 3 A method for preparing high-purity calcium hydroxide includes the following steps: S1. After the lime and additive are mixed evenly, they are fed into a rotary kiln and calcined at 400℃ for 3 hours at a heating rate of 20℃ / min. Then, they are calcined at 1000℃ for 10 minutes at a heating rate of 25℃ / min. After calcination, the material is discharged, ground, and cooled to obtain calcium oxide with a particle size of 40mm. The additive is 0.5% of the mass of lime and is composed of molybdenum hydroxide and ferrous oxide in a mass ratio of 1:1. S2. Add calcium oxide to the digestion solution and digest at 60 r / min for 40 min. Then, let it stand at 90℃ for 1 h to mature. Filter, wash, dry, and pass through a 200-mesh sieve to obtain calcium hydroxide. The digestion solution consists of water and sodium tripolyphosphate. The mass ratio of water to calcium oxide is 5:1, and the mass of sodium tripolyphosphate is 1% of the mass of calcium oxide.

[0025] Example 4 The only difference between this embodiment and Example 1 is that the additive in S1 is composed of molybdenum hydroxide and ferrous oxide in a mass ratio of 1:3.

[0026] Example 5 The only difference between this embodiment and Example 1 is that the additive in S1 is composed of molybdenum hydroxide and ferrous oxide in a mass ratio of 1:1.5.

[0027] Example 6 The only difference between this embodiment and Example 1 is that the additive in S1 is composed of molybdenum hydroxide and ferrous oxide in a mass ratio of 1:2.

[0028] Example 7 The only difference between this embodiment and Example 1 is that the additive in S1 is composed of molybdenum hydroxide and ferrous oxide in a mass ratio of 1:2.5.

[0029] Example 8 A method for preparing high-purity calcium hydroxide includes the following steps: S1. After the lime and additive are mixed evenly, they are fed into a rotary kiln and heated to 500℃ for 2 hours at a heating rate of 15℃ / min. Then, they are heated to 900℃ for 20 minutes at a heating rate of 15℃ / min. After that, the material is discharged, ground, and cooled to obtain calcium oxide with a particle size of 40mm. The additive is 0.3% of the mass of lime and is composed of molybdenum hydroxide and ferrous oxide in a mass ratio of 1:1. S2, same as Example 1.

[0030] Example 9 A method for preparing high-purity calcium hydroxide includes the following steps: S1. After the lime and additives are mixed evenly, they are fed into a rotary kiln and heated to 500℃ for 2 hours at a heating rate of 20℃ / min. Then, they are heated to 900℃ for 20 minutes at a heating rate of 15℃ / min. After that, the material is discharged, ground, and cooled to obtain calcium oxide with a particle size of 40mm. The additives are 0.3% of the mass of lime and are composed of molybdenum hydroxide and ferrous oxide in a mass ratio of 1:1. S2, same as Example 1.

[0031] Comparative Example 1 Compared with Example 1, this comparative example does not contain molybdenum hydroxide and ferrous oxide.

[0032] Comparative Example 2 Compared with Example 1, this comparative example does not contain ferrous oxide.

[0033] Comparative Example 3 Compared with Example 1, this comparative example does not contain molybdenum hydroxide.

[0034] Test case The activity, yield, and purity of calcium oxide in Examples 1-9 and Comparative Examples 1-3 were determined. The method for determining the activity of calcium oxide was as follows: the prepared calcium oxide was made into a sample with a particle size of 6 mm. 50 g of the sample was placed in water at 40 °C. Phenolphthalein was used as an indicator. The sample was titrated with 4 N hydrochloric acid under stirring with an electric stirrer until the red color disappeared within 10 min. The total volume (mL) of hydrochloric acid consumed was the activity of calcium oxide. The results are shown in Table 1.

[0035] Results of the determination of calcium oxide and calcium hydroxide in Examples 1-9 and Comparative Examples 1-3

[0036] Compared with Example 1, Comparative Example 1 did not add molybdenum hydroxide and ferrous oxide, Comparative Example 2 did not add ferrous oxide, and Comparative Example 3 did not add molybdenum hydroxide. The results showed that the activity of calcium oxide in Comparative Examples 1 to 3 was lower than that in Example 1, and the purity and yield of calcium hydroxide were also lower than those in Example 1. This indicates that the simultaneous addition of molybdenum hydroxide and ferrous oxide can improve the activity of calcium oxide and the purity and yield of calcium hydroxide.

[0037] Compared to Example 1, Examples 4-7 varied the mass ratio of molybdenum hydroxide to ferrous oxide. The results showed that the activity, purity, and yield of calcium oxide in Examples 5-7 were all higher than in Examples 1 and 4. This indicates that a mass ratio of molybdenum hydroxide to ferrous oxide of 1:1.5-2.5 further improved the activity, purity, and yield of calcium oxide. Furthermore, a mass ratio of 1:2 further enhanced these parameters.

[0038] Compared with Example 1, Examples 8 and 9 changed the heating rate of the first stage calcination. As a result, the activity of calcium oxide, the purity of calcium hydroxide, and the yield of calcium hydroxide in Example 8 were all higher than those in Example 1, indicating that when the heating rate of the first stage calcination is 15℃ / min, the activity of calcium oxide, the purity of calcium hydroxide, and the yield of calcium hydroxide can be further improved.

[0039] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for producing high-purity calcium hydroxide, characterized by, Includes the following steps: Calcium oxide is added to a digestion solution for digestion to obtain calcium hydroxide; the calcium oxide is obtained by calcining lime and an additive; the additive consists of molybdenum hydroxide and ferrous oxide; the digestion solution contains water; The calcination is carried out in two stages. The calcination temperature of the first stage is 400~500℃ and the calcination time of the first stage is 2~3h. The calcination temperature of the second stage is 900~1000℃ and the calcination time of the second stage is 10~20min.

2. The method for preparing high-purity calcium hydroxide according to claim 1, characterized in that, The digestive fluid also contains additives; the additives are one or more of triethanolamine, sodium tripolyphosphate, and polyvinylpyrrolidone.

3. The method for preparing high-purity calcium hydroxide according to claim 1, characterized in that, The mass ratio of molybdenum hydroxide to ferrous oxide is 1:1.5~2.

5.

4. The method for preparing high-purity calcium hydroxide according to claim 1, characterized in that, The mass ratio of water to calcium oxide in the digestive fluid is 3~5:

1.

5. The method for preparing high-purity calcium hydroxide according to claim 2, characterized in that, The additive in the digestive fluid is 0.2% to 1% of the mass of calcium oxide.

6. The method for preparing high-purity calcium hydroxide according to claim 2, characterized in that, The admixture is 0.3% to 0.5% of the mass of lime.

7. The method for preparing high-purity calcium hydroxide according to claim 1, characterized in that, The digestion time is 30-40 minutes.

8. The method for preparing high-purity calcium hydroxide according to claim 1, characterized in that, The heating rate to the first stage calcination temperature is 10~20℃ / min.

9. The method for preparing high-purity calcium hydroxide according to claim 1, characterized in that, The heating rate to the second-stage calcination temperature is 15~25℃ / min.

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