JPS5819608B2 - Manufacturing method of magnesium hydroxide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention combines a solution containing magnesium ions, such as seawater, brine, bittern, etc., with an alkaline substance or an aqueous solution thereof, such as quicklime, lightly calcined dolomite and its hydrate, carbide slag, sodium hydroxide, etc. The present invention relates to a method for manufacturing magnesium hydroxide (hereinafter referred to as a water mug) as a raw material, and particularly relates to a method for manufacturing a water mug with a low boron (hereinafter referred to as B2O3) content.

The main uses of water mugs are magnesium chloride, which is the raw material for magnesia clinker-1 metal magnesium, which is a raw material for basic refractories, and activated magnesia, which is obtained by calcining water mugs.
There is a demand for high-purity water mugs with few impurities, such as ceramics in the electronics field.

In particular, boron inhibits the agglomeration of metallic magnesium during the electrolysis of magnesium chloride, resulting in a decrease in production efficiency, so it is required to minimize the amount of boron.

Magnesia clinker is in high demand as a raw material for basic refractories, and along with magnesia (MgO) obtained by calcining natural magnesia (MgCoa), it has recently been used as seawater magnesia, which is made from seawater, brine, or bittern, with fairly high purity. It is indispensable as a refractory for steelmaking.

Naturally produced magnesia generally has a low B2O3 content, whereas seawater magnesia adsorbs and contains B2O3 in the raw material seawater, brine, or bittern into the magnesium hydroxide precipitate, so the B2O3 derived from this is usually quite high. The clinker contains 0.3 to 0.2 parts.

On the other hand, recent research results show that there is a strong demand for improving hot properties by reducing the amount of low-melting compounds other than magnesia, that is, for higher quality.In particular, compounds containing B2O3 form a melt at low temperatures. Therefore, reducing B2O3 is recognized as the most effective means for improving hot properties.

The B2O3 content in magnesia clinker is controlled by the B2O3 content of the water mug, which is its raw material.
20. The content is mainly B2 in seawater, brine or bittern.
Determined by O3 content.

Of course, some of the B2O3 in the water mug evaporates during the firing process, but
The rate of volatilization depends on the firing temperature, and is approximately 50%
It is difficult to volatilize more than %.

Therefore, B2O3 in magnesia clinker is 0.03
If you try to lower it to below, it will be at least B20a at the water mug stage.
/MgO must be 0.06% or less.

Research has also been conducted on volatilization accelerators, but they significantly impede physical properties at room temperature.

For example, the bulk density is significantly reduced.

Although it is possible to reduce B2O3 adsorption to water mags by increasing the pH during water mag production, this is not preferable because a large amount of CaO is co-precipitated, resulting in a decrease in quality.

Therefore, in order to produce high-grade, high-density, low-B2O3-containing magnesia clinker, B2 in seawater is
It is a reliable and advantageous method to remove O3 as much as possible and produce a water mug with low B2O3 content.

Based on the above facts, the inventors of the present application searched for a method of manufacturing a water mug with low B2O3 content and low content of other impurities. Focusing on the principle that B2O3 adsorbed in this water mug is easily released by an alkaline solution, we used a clever application method of using this repeatedly over and over again to generate and obtain magnesium ions in seawater as a water mug. At the same time B
This led to the invention of a B2O3 removal method that removes 2O3 from the system.

Regarding the B2O3 adsorption performance of various compounds with the purpose of obtaining B2O3 in seawater, brine, or bittern.

Various studies have been conducted on metal hydroxides, such as Fe (O
H) 3 , Mg (OH) 2 , Z r 02
+ ) G(20 is known to be a substance that adsorbs B2O8.

These adsorbents are commercially available, but their adsorption capacity is low and seawater magnesia clinker industry is unable to do so.

When a large amount of seawater is used, the use of these adsorbents is actually limited.

For example, in the method disclosed in Japanese Patent Publication No. 45-53, three types of water magnesia, a high B2O3 content water mug and a low B2O3 content water mug, are obtained, and therefore it is essential to produce two types of magnesia.

It is a condition.

The present invention solves this drawback and provides a method for producing a raw water mug for obtaining magnesia clinker with a low B2O3 content of 0.03% or less, for example.

The present invention is based on seawater removal B20. The process includes a water mug regeneration process, a water mug generation process, and is characterized by a configuration in which the water mug slurry generated in the water mug regeneration process is circulated to the seawater removal B2o3 process.

To remove B2O3 from seawater, a water mug is brought into contact with seawater, and the water mug that has adsorbed B2O3 is treated with an alkali to remove B2O3, and a water mug slurry and a high B2O3-containing solution are separated. This is a process in which B2O3 is removed from seawater by pouring it into fresh seawater to adsorb B2O3 again and repeating this operation continuously.

The amount of water mags that are recycled and reused in this process is more than four times the amount of dissolved MgO in seawater, and in principle there is no need for new water mags to be replenished.

It is desirable that the solid water mag concentration during adsorption is maintained at 1 og713 or more as MgO.

B in seawater can be reduced by recycling approximately 25 times the amount of dissolved MgO.
Almost all of the 2O3 can be removed, but the storage tank of the water mug becomes larger and the power of the circulation pump increases, so it is necessary to adjust it to the optimum point according to the target value of B2O3.

Alkali is added to the treated B2O3-free seawater to produce a water mug.

The principle of manufacturing water mugs produced using a solution containing magnesium ions and an alkali as raw materials is to obtain water mug precipitates obtained by the reaction Mg+++20H-+Mg(OH)2, and the method of the present invention also applies to the manufacturing process. The principle is essentially the same.

In the reaction between B2O3-free seawater and an alkaline solution, the pH of the reaction solution is not particularly limited, but preferably the pH is 1.
It is preferable to maintain it at 1.2 or higher.

When carrying out the present invention, if necessary, water mag produced by a known method is added to decarboxylated seawater, and at the same time, water mag recycled by the method described below is added so that the solid concentration of water mag in the seawater becomes MgO. As 10 f! It is appropriate to add the amount at least 14g/1, particularly preferably at least 14g/1.

At this time, the B2O3 in the seawater is adsorbed on the surface of the water mug, but better results can be obtained by uniformly dispersing the mixed liquid in the suspended layer of the water mug than by simply stirring.

The appropriate time for contact with the water mug is 30 minutes or more, but
About an hour is enough.

The water mug that has absorbed B2O3 is concentrated and alkali is added to B
Dilution water is added to increase the amount of 2O3 dissolved.

The alkali is preferably a strong base such as NaOH, KOH, or Ca(OH)2, and the dilution water is F solution, etc. after magnesium ions contained in fresh water or seawater are precipitated as a water mug by adding alkali. can be used.

The alkali concentration in the water mug regeneration process is [OH] and o
, ois gram ion/1 or more, preferably 0.025
Gram ion/1. above, the effect is sufficient at 0.035 gram ions/l or less, and the adsorbed B2O3 is CO
H': 80% at 10.018 g ions/l, 0.0
At 25 g ions/l, 100% desorption occurs.

Also, the solid concentration of the water mug is 60 f as MgO! /l~2
0 g/l is preferred.

The water mug is allowed to settle and concentrate again until it becomes a thick slurry.
The above-mentioned new raw material seawater is supplied, and the thickening tank overflow liquid, that is, the high B2O3-containing solution is discarded.

The effect of the present invention is regulated by the amount of water mag that is regenerated and circulated, but B20. When excluding B20 in seawater, the circulation of MgO, which is 15 times the amount of dissolved MgO in seawater, causes 15 times the amount of dissolved MgO in seawater. can be removed up to 65~/l.

The B10 content of the water mug obtained by adding alkali to the B2O3-free seawater obtained by the above continuous cycle is small, and is about 40% of the B2O3 content of the water mug obtained by the normal method.
Therefore, the B2O3 content of the magnesia clinker produced by firing this water mug is extremely low.

Example 1 This example was carried out by the steps shown in the drawings.

However, in the figure [A] is a B2O3 adsorption tank [B] is an adsorption concentration tank [
Ca is B20. The separation tank [D] is a separation and concentration tank.

In the figure, 1 is raw seawater, 2 is newly added water mug 3 is B2O3-free recycled water mug 4 is dilution water 5 is slaked lime milk 6 is B20-free. Seawater, γ indicates high B2o, containing liquid.

B20. with a diameter of 1.4 m and a volume of 4 d with a stirrer. Adsorption tank [A] Decarboxylation by adding phosphoric acid (4p as CO2)
pm) seawater 1 was supplied at an inflow rate of 877+"/Hr, and the water mug 2 prepared in advance was 16 kg/Hr as MgO.
was added at an addition rate of .

The mixed liquid is stored in a concentration tank with a diameter of 3.3 m and a height of 2 m and a volume of 17 m3.
B] was injected from the upper part of the tank, and the mixture was allowed to overflow uniformly from around the upper part of the tank.

This operation was carried out continuously to form a water mag layer in the adsorption/concentration tank [B] so that it was approximately half the height of the tank.

After that, stop adding a new water mug and move to the adsorption concentration tank [B].
The water mug at 80'Q/H is collected in the center by a rake.
A water mug corresponding to r is extracted and the volume with a stirrer is In
" was supplied to the B2O3 separation tank [Ca.

Slaked lime was added to the seawater, and the p liquid obtained by sedimentation and separation of the water mug was injected into the B2O3 separation tank at a rate of 2.5 m/Hr, and at the same time, the alkali in the liquid was reduced to 0.025 g ions/l as [OH]. 10 parts of Ca(OH)2 milk was supplied so that

The mixed liquid was supplied to a separation/concentration tank [D] having a diameter of 25 m, a height of 2 m, and a volume of 10 g, and the overflow liquid was discarded.

The concentrated water mug is collected in the center by a rake and converted into MgO at a rate of 80 kg/Hr with B20. It was circulated to the adsorption tank [A].

'□Continuing the above operations, the concentration of B2O3 in the raw seawater in an equilibrium state, the removal of B20. B20 in seawater. B2O3 content in water mugs at various concentrations, high B2o.

The B2O3 concentration of the containing solution was as shown in Tables 1 and 2.

The B2O3-free seawater contains B2O3 of <6.4 ■/l as described above, and Ca (OH) 2 milk was injected into this seawater and the reaction solution was kept at a pH of 11.4. The B2O3 content in the water mug is B2O3/MgO, which is 0.
．． It was 0.6%.

This water mug was concentrated to 200 g/11, washed with 15 times the amount of fresh water by volume, then dried, and 10 parts of water was added to this dried product to make 500ky7ct? The chemical composition and physical properties of the clinker, which was molded at a pressure of r and then fired at 1800°C for 1 hour, were as shown in the table.

In addition, the dried body was lightly baked at 1000°C for 2 hours, and 1000 kg
Table 3 shows the chemical composition and physical properties of Talinkar, which was molded at a pressure of /crit and then baked at 1800°C for 1 hour.

Example 2 Using the same equipment and method as in Example 1, a separation concentration tank [D
] B20. As a result of circulation in the adsorption tank [A), B20. Concentration, B2O3 content in water mug,
The chemical composition and physical properties of Talincar were as shown in Tables 4, 5, and 6.

[Brief explanation of the drawing]

The drawings are process explanatory diagrams for explaining the present invention in detail.

Claims (1)

[Claims] 1. An adsorption step in which a magnesium ion solution containing boron is brought into contact with magnesium hydroxide and the boron in the solution is adsorbed onto the magnesium hydroxide.An alkali is added to the magnesium ion solution deboronized in the adsorption step to produce magnesium hydroxide. a production step in which the magnesium hydroxide adsorbed with boron in the adsorption step is treated with an alkali to remove boron and separated into a magnesium hydroxide slurry and a high boron-containing solution; and a regeneration step in which the hydroxide from the regeneration step is A method for producing low boron-containing magnesium hydroxide, comprising a circulation step of circulating a magnesium slurry to an adsorption step.