JPH05279018A - Production of magnesium hydroxide - Google Patents

Abstract

PURPOSE:To improve the digestion reaction property, shorten the reaction time, and enhance the reaction rate by improving the digestion method, in a production of magnesium hydroxide by a digestion reaction of calcined magnesium oxide. CONSTITUTION:In a digestion reaction reactor 1, the digestion of the calcined magnesium oxide and water is performed. Also while a magnesium hydroxide layer which is formed on a particle of the calcined magnesium oxide is ground with a surface pulverizing means 2, the digestion reaction is advanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing magnesium hydroxide which is useful as a neutralizing agent for effluent and an alkaline agent for flue gas desulfurization.

[0002]

2. Description of the Related Art As one of the methods for producing magnesium hydroxide, after calcining magnesium carbonate ore such as magnesite at a relatively low temperature, it is usually used with a crusher (hammer-crusher) or a fine crusher (Raymond mill). There is a method of subjecting so-called light-burned magnesium oxide obtained by dry pulverization to a particle size of 100 μm or less to a digestion reaction with water.

[0003]

However, this method has a slow digestion reaction rate and requires a long time of 5 to 16 hours even if the preheating temperature of water is as high as possible. Even if it is applied, a reaction rate of about 85 to 90% is usually obtained. This is because lightly burned magnesium oxide has uneven calcination conditions due to the size of massive ores during calcination, which causes the inclusion of substances that are difficult to undergo a digestion reaction.

In view of the above-mentioned conventional circumstances, the present invention aims to improve the digestion reactivity by shortening the reaction time and increase the reaction rate by improving the digestion method of light burned magnesium oxide.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in order to achieve the above-mentioned object. As a result, first, the digestion reaction of light-baked magnesium oxide occurs from the particle surface, and the water on the particle surface is accompanied by this. It was considered that the magnesium oxide layer was generated and the diffusion of water into the inside of the particle through this layer was the rate-determining factor for the digestion reaction.

Therefore, in order to facilitate the above diffusion,
While advancing the digestion reaction while subjecting the generated magnesium hydroxide layer to so-called surface pulverization, in which the particles are crushed by collision, dispersion, peeling action, etc., it was found that the digestion reactivity was significantly improved. This invention has been completed.

That is, according to the present invention, when magnesium hydroxide is produced by a digestion reaction of light-burned magnesium oxide, the digestion reaction is advanced while milling the magnesium hydroxide layer formed on the surface of the particles of light-burned magnesium oxide. The present invention relates to a characteristic method for producing magnesium hydroxide.

[0008]

The magnesium hydroxide layer formed on the surface of the light-burned magnesium oxide particles is much weaker than the light-burned magnesium oxide serving as the core, and is therefore easily ground. When the digestion reaction proceeds while the particle surface layer is pulverized in this way, the particle surface is always kept in an active state, and the digestive reactivity is dramatically improved.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a structural example of an apparatus applied to the manufacturing method of the present invention.

In the figure, 1 is a digestion reaction tank equipped with a water supply means 1a, a light burned magnesium oxide introduction means 1b, a stirrer 1c, and a warmer 1d, 2 is a surface crushing means consisting of a bench lily tube, and 3 is a stirrer 3a. Equipped magnesium hydroxide water slurry storage tank, P1 is a pump, V1 and V2 are valves.

In the digestion reaction tank 1, about 3 water from the water supply means 1a.
Hot water of about 0 to 60 ° C. is supplied to the introducing means 1b.
A lighter burned magnesium oxide is introduced, and uniform stirring is performed by the stirrer 1c to carry out the digestion reaction.

[0012] This digestion reaction liquid opens the valve V1,
The light is circulated by the pump P1 through the circulation path L1 for a predetermined residence time, and is generated on the particle surface of the light-burned magnesium oxide by the surface crushing means 2 composed of a bench lily pipe arranged in the path L1. Grind the magnesium hydroxide layer.

That is, the digestion reaction liquid introduced into the bench lily tube is accelerated in its flow velocity at the narrowed portion 2a thereof, and is subjected to the abrasion and peeling action due to the strong collision with the particles or the wall surface. The magnesium oxide layer is easily scraped off.

When the digestion reaction proceeds while milling in this manner, the reaction rate becomes remarkably faster than the conventional method (method in which the digestion reaction is carried out in the digestion reaction tank 1 while performing normal stirring), and the power to be applied is increased. Usually 1/3 to 1 / depending on the strength of
The reaction is completed in a short time of about 10. Whether or not the reaction is completed can be easily confirmed by examining the state of temperature increase due to viscosity increase or reaction heat.

By such a digestion reaction, the light-burned magnesium oxide becomes a water slurry of magnesium hydroxide,
When the valve V2 is opened, it is guided to the storage tank 3 having the stirrer 3a and stored in a stirred state. This water slurry is used as it is in various industrial fields as a neutralizing agent for effluent, an alkaline agent for flue gas desulfurization, and the like.

In the above example, a bench lily tube is used as the surface crushing means 2, but an orifice or a nozzle having the same function as this may be used, and a static mixer whose flow direction changes at a steep angle. Etc. may be used.
Further, a household-use mixer having a high-speed rotating blade or blade and collision, dispersion, and peeling action between the fixed wall and the like may be made of a wear-resistant material.

FIG. 2 shows another structural example of the apparatus applied to the manufacturing method of the present invention. The circulation path L1 in FIG. 1 is omitted, and the surface crushing means 2 is directly placed in the digestion reaction tank 1. It is provided. In this case, as the crushing means 2, a high-speed stirrer shown in the figure, for example, Micro Agitator manufactured by Shimazaki Seisakusho Co., Ltd. is preferably used.

In this high-speed agitator, a stirring blade 23 is provided on the lower tip side of a shaft 22 which rotates at a high speed by a motor 21 as shown in FIG.
4 is attached to the fixed support cylinder 25. The digestion reaction solution is
It is sucked from the opening 26 and the lower end side of the support cylinder 25, surface-crushed between the blade 23 and the fixed wall 24, and flows out from the gap 27.

Needless to say, the stirrer 1c provided in the digestion reaction tank 1 is for stirring and mixing the light burned magnesium oxide as a raw material and magnesium hydroxide as a reaction product so as not to settle at the bottom of the tank. This is a normal stirrer, which does not have a surface crushing action like the high speed stirrer 2 described above.

After the digestion reaction is carried out in this manner, it is led to the storage tank 3 having the stirrer 3a by the pump P2 and stored in a stirring state. According to this device configuration, the circulation path L1
Since it can be omitted, it can be made more compact than that of the apparatus configuration of FIG. 1, and can further contribute to downsizing and cost reduction of the digestion reaction apparatus.

[0021]

As described above, according to the present invention, since the digestion reaction is advanced while milling the magnesium hydroxide layer formed on the surface of the particles of light-burned magnesium oxide, the digestion reactivity is remarkably improved, The reaction time can be remarkably shortened as compared with the conventional one, and a reaction rate of 100% can be obtained.

Therefore, in the digestion reaction, it is not necessary to raise the preheating temperature of water so much, the consumption cost of steam is reduced accordingly, and the digestion reaction apparatus can be downsized, and the digestion reaction can be continued. Is also easy. In addition, since the light-burned magnesium oxide used can be expected to have a good digestion reaction even if the particle size is relatively coarse, good results can be obtained in reducing the power during pulverization and downsizing the pulverization equipment, and also in terms of apparent specific gravity. As a result, the volume for long-distance transportation will decrease, and the fare will be cheaper.

[Brief description of drawings]

FIG. 1 is a schematic view showing one structural example of an apparatus applied to a manufacturing method of the present invention.

FIG. 2 is a schematic view showing another configuration example of an apparatus applied to the manufacturing method of the present invention.

3 is a cross-sectional view taken along the line AA of FIG.

[Explanation of symbols]

 1 digestion reaction tank 1a water supply means 1b light burned magnesium oxide introduction means 2 surface crushing means (bench lily tube, high speed agitator) 3 magnesium hydroxide water slurry storage tank

Claims (1)

[Claims] 1. When producing magnesium hydroxide by a digestion reaction of light-burned magnesium oxide, water is characterized in that the digestion reaction proceeds while milling a magnesium hydroxide layer formed on the surface of particles of light-burned magnesium oxide. Method for producing magnesium oxide.