JPS5829245B2 - Method for producing coarse calcium hypochlorite dihydrate - Google Patents

Description

Detailed Description of the Invention The present invention uses semi-basic calcium hypochlorite as a starting material for producing calcium hypochlorite trihydrate, and uses columnar calcium hypochlorite trihydrate as a seed crystal. The present invention relates to a method for producing calcium chlorite trihydrate.

More specifically, in the method for producing calcium hypochlorite trihydrate, (1) a suspension of calcium hydroxide and/or dibasic calcium hypochlorite is chlorinated to produce semibasic hypochlorite; (2) When the semi-basic calcium hypochlorite obtained in (1) is chlorinated to crystallize calcium hypochlorite trihydrate, a, b, Using columnar calcium hypochlorite trihydrate in which the ratio of each c axis is 0.5≦b/a≦2.0 c/a≧1.5 and the C axis is 5 microns or more, the species is The present invention relates to a method for producing coarse calcium hypochlorite trihydrate by growing crystals.

Calcium hypochlorite trihydrate is a well-known substance that has been studied for a long time.

There are a wide variety of manufacturing methods, and it is currently manufactured and sold around the world as an important intermediate or main component of highly bleached powder.

However, in any production method, calcium hypochlorite trihydrate has fine and poor crystals, and separation from the mother liquor is extremely difficult.

If calcium hypochlorite trihydrate with good coarse separation properties could be produced, it would significantly reduce fixed and variable costs and provide an economical method for producing high-quality advanced bleaching powder. .

Calcium hypochlorite trihydrate belongs to the tetragonal crystal system, and its shape is either oblate square plate crystals (hereinafter simply referred to as oblate crystals) or aggregate twin crystals in which the oblate crystals are stacked with plane symmetry ( (hereinafter simply referred to as a layered crystal).

Conventionally, these crystals were also called di,pentahydrate or trihydrate, but the correct name is dihydrate.

In order to facilitate understanding of the present invention, the present invention will now be described with reference to the drawings.

FIG. 1 is a schematic diagram of an oblate crystal.

With the center of the crystal as the origin, the a-axis and b-axis are the well-developed directions, that is, the width direction, and the C-axis is the direction that is less developed, that is, the thickness direction.

Normally, the ratio of the lengths of the a-axis and the b-axis is approximately equal, and the ratio of the lengths of the a-axis and the a-axis is approximately equal.
The ratio of the axial lengths (hereinafter referred to as c/a) is 0.1 or less.

As can be easily seen from the shape of the oblate crystals, the growth rate in the a-axis and b-axis directions is high, but the growth rate in the c-axis direction is extremely slow.

Calcium hypochlorite trihydrate in such a shape is very brittle and is easily crushed into fine particles by a slight mechanical impact.

Moreover, when separating from the mother liquor, the mother liquor 0 passage is blocked because it is flat.

Therefore, zero separation of the oblate crystals is extremely difficult.

A layered crystal disclosed in US Pat. No. 2,469,901 is an example of an improved separation property.

As shown in the second sketch, the width direction is the a-axis and the b-axis,
The thickness direction is the C axis.

Normally, the lengths of the a-axis and b-axis are approximately equal, and c / a
is 1.0 or less.

Here, the C axis is the sum total of the C axes of the oblate crystals constituting the laminated crystal, and c/a of the constituent oblate crystals is 0.1.
It is as follows.

These laminated crystals have a coarse appearance, but because they are twin crystals, they contain a large amount of mother liquor between the constituent oblate crystals, and are brittle and can be crushed into fine particles by mechanical impact.

Therefore, separation of the layered crystals becomes difficult.

In addition, British Patent No. 487009 and U.S. Patent No. 246990 disclose a method in which separation properties are improved by growing oblate crystals and laminated crystals as seed crystals.
The specification of No. 1 describes a so-called seed crystal addition method.

This method has some effects.

However, the growth rates of the a-axis and b-axis are not so high, and the growth rate of the c-axis is extremely low.

Therefore, it is necessary to add a large amount of seed crystals, and the crystals that are grown are flat.

Therefore, it is brittle and easily crushed by mechanical impact into fine particles, and in the case of laminated crystals, a large amount of mother liquor is contained between the constituent oblate crystals.

That is, even in the seed crystal method, it is difficult to separate the crystals obtained.

If separation from the mother liquor is difficult, it is necessary to use an extremely powerful separator or to perform the separation operation for a long time. Weight) x (looo
) (wet cake weight) is high, the decomposition rate of calcium hypochlorite increases in the drying process, and the energy required for drying increases.

As mentioned above, various methods have been tried to improve the separability of calcium hypochlorite trihydrate, but none of the methods has been able to provide a fundamental solution.

Here, the disadvantages of poor separation of calcium hypochlorite trihydrate and mother liquor will be listed.

(1) Separation is burdensome and requires an expensive and powerful separator.

Also, the number of separation-like cardinalities increases. (2) The rate of adhesion of the mother liquor in the wet cake obtained by separation increases, and impurities in the mother liquor are transferred to the product, resulting in poor quality.

(3) The moisture content in the wet cake increases, increasing the amount of energy required for drying.

In addition, in this case, the decomposition rate of calcium hypochlorite increases,
As a result, the content of decomposition products such as calcium chloride, calcium chlorate, and calcium carbonate increases.

(4) Oblate crystals contain a large amount of mother liquor, which increases the viscosity of the slurry during crystallization.

Therefore, it is necessary to lower the slurry concentration, which increases the size of the device.

Additionally, the amount of mother liquor circulated increases, and the amount of calcium hypochlorite decomposed during circulation increases.

(5) Calcium hydroxide must be used that has a low content of calcium carbonate, etc., which cause water-insoluble components.

(6) There are difficult problems in continuous formation, such as crystals becoming even more flat due to continuous formation.

There are many disadvantages such as.

Furthermore, conventionally, when producing calcium hypochlorite trihydrate, sodium hydroxide was used in an amount approximately equivalent to that of calcium hydroxide.

The reason for this is that when only calcium hydroxide is chlorinated, calcium chloride grows, inhibits crystal growth, and impairs the storage stability of the product.

If sodium hydroxide is used in combination, this harmful calcium chloride will not be produced, but harmless sodium chloride will be produced.

However, sodium hydroxide is expensive and increases variable costs, so it is desired to avoid its use.

Calcium hypochlorite trihydrate is generally produced by chlorinating calcium hydroxide, a mixture of calcium hydroxide and sodium hydroxide, dibasic calcium hypochlorite, or a mixture thereof. At that time, heat is generated, which is usually a huge amount of 360 kcal per KP of chlorine.

If this reaction heat is not removed, the temperature will rise rapidly and the following equation (1
) and (2) reactions proceed and calcium hypochlorite decomposes.

Ca(CIO)2−”CaCl2+02
(1)3 Ca (C10)2 →Ca (C103
)2 + 2CaC12 (2) Therefore, heat removal is required, and a large amount of cooling energy is required for this purpose.

If the cooling energy can be reduced, it will provide an energy-saving manufacturing method.

In other words, in order to produce calcium hypochlorite trihydrate that is economical and has excellent product quality, the following three points must be solved.

(1) Improve separation from mother liquor.

(2) Remove unnecessary sodium hydroxide.

(3) Reduce S dynamic energy.

In order to solve many of these problems, the present inventors have made extensive studies on the crystal growth, separability, product quality, cooling energy, etc. of calcium hypochlorite trihydrate.

As a result, when semi-basic calcium hypochlorite is chlorinated to crystallize calcium hypochlorite trihydrate, columnar calcium hypochlorite trihydrate, which has a completely different shape from conventional crystals, is produced. The present invention was completed by discovering that all the problems could be solved by using this as a seed crystal and growing it.

That is, the present invention provides a method for producing calcium hypochlorite trihydrate, which includes: (1) chlorinating a suspension of calcium hydroxide and/or dibasic calcium hypochlorite to produce semibasic trihydrate; Crystallizing calcium chlorite, (2) When chlorinating the semi-basic calcium hypochlorite obtained in (1) to crystallize calcium hypochlorite trihydrate, the previously applied specification ( carboxylic acids shown in Japanese Patent Application No. 53-24576 (see Japanese Patent Publication No. 57-243);
The ratio of the a, b, and c axes of columnar calcium hypochlorite trihydrate obtained by adding one or more types of modifier selected from carboxylates and carbohydrates is 0.5≦b/a. ≦2. O c / a ≧ 1.5, and the C axis is 5 microns or more, preferably 0.5≦b / a ≦ 2.0 c / a ≧ 3.0, and the C axis is 10 microns or more. The present invention provides a method for producing coarse calcium hypochlorite trihydrate using columnar calcium hypochlorite trihydrate as a seed crystal.

As is well known, semibasic calcium hypochlorite is obtained by chlorinating calcium hydroxide and/or dibasic calcium hypochlorite at high temperatures, and is usually shaped like a bamboo leaf and is easily separated from the mother liquor. .

The present invention chlorinates this semi-basic calcium hypochlorite to crystallize calcium hypochlorite trihydrate, and essentially does not require sodium hydroxide.

In addition, calcium hypochlorite trihydrate can be crystallized by chlorinating calcium hydroxide and/or dibasic calcium hypochlorite instead of semibasic calcium hypochlorite, but the calorific value at that time is chlorination of calcium hydroxide and/or dibasic calcium hypochlorite is not included in the present invention.

Further, mere chlorination of semi-basic calcium hypochlorite results in fine oblate crystals, that is, calcium hypochlorite trihydrate with extremely poor separation properties.

However, when columnar calcium hypochlorite trihydrate is added as a seed crystal during crystallization and the seed crystal is allowed to grow, coarse calcium hypochlorite trihydrate with extremely improved separability can be obtained. .

That is, in the present invention, when semibasic calcium hypochlorite is chlorinated to crystallize calcium hypochlorite trihydrate, columnar calcium hypochlorite trihydrate is added as a seed crystal, and the seed crystal is It is an essential condition to grow calcium hypochlorite trihydrate to produce coarse calcium hypochlorite trihydrate.

The columnar calcium hypochlorite trihydrate used as a seed crystal in the present invention is calcium hypochlorite trihydrate in which C@ has abnormally developed and the growth of the a-axis and b-axis is extremely suppressed. The shapes are shown in Figure 3: A: cylindrical, B: square prism,
C: Including all four-sided truncated conical shapes and shapes intermediate thereto.

When the columnar calcium hypochlorite trihydrate according to the present invention is used as a seed crystal, its growth property is very good and it instantly becomes coarse calcium hypochlorite trihydrate.

In particular, the growth rate of the a-axis and b-axis is high (2 to 3 times faster than that of conventional crystals).

Also, the longer the C-axis, the larger it becomes. Furthermore, the growth rate of the C axis is a
It is small compared to the axis and b axis.

Therefore, as the growth progresses, c/a becomes smaller, that is, it changes to a quadrangular prism shape or a quadrangular bipyramidal shape, but at the time of the seed crystal, the C axis has a length that far exceeds that of conventional crystals. The thickness is thick.

Therefore, the grown crystals are coarse and thick, and do not have twinning, resulting in coarse calcium hypochlorite trihydrate, which could not be predicted by conventional methods.

In addition, columnar calcium hypochlorite trihydrate not only has a very long C axis, but also short a and b axes, so the amount added as a seed crystal can be extremely small, and the coarse hypochlorite that is usually produced can be It is very efficient, requiring less than 20 wt% of calcium chlorate dihydrate.

In other words, the present invention solves the drawback of calcium hypochlorite dihydrate, which is that the growth of the C-axis is very poor. By cleverly using columnar calcium hypochlorite dihydrate as a seed crystal, this drawback is overcome and coarse calcium hypochlorite trihydrate, which is coarse and extremely easy to separate, is produced.

Hereinafter, the method for producing coarse calcium hypochlorite trihydrate according to the present invention will be explained in more detail.

The starting process for calcium hypochlorite dihydrate is a known method for producing semibasic calcium hypochlorite. Chlorination of a suspension of calcium hydroxide and/or dibasic calcium hypochlorite The temperature at that time is preferably 30 to 60°C.

If the temperature is lower than 30°C, fine needle-like crystals will form, and if the temperature is higher than 60°C, the decomposition of calcium hypochlorite according to the above-mentioned reaction formulas (1) and (2) will become more intense.

At 30 to 60°C, coarse bamboo leaf-like crystals with sufficient crystal growth are obtained, and since the concentration of calcium hydroxide in the parent liquor is high, the decomposition of calcium hypochlorite is small.

In particular, a temperature of 40 to 55°C is desirable. Further, as for the chlorination method, both continuous and batch methods can be applied, but from the standpoint of simplifying the operation and crystal growth, the continuous type % type % chlorination tank may be of the tank type, DTB, or DP type.

Chlorine gas is usually introduced as a gas, but the rate is 10
-2009/hr[ is appropriate.

Note that chlorination generates heat, and if left as it is, the temperature will rise, so heat must be removed, but the crystallization temperature can be raised, so cooling water can be used to remove heat, and brine is not necessary.
Therefore, only a very small amount of electric power is required for heat removal.

Although chlorination can be controlled by calcium hydroxide concentration, it is more convenient to use redox potential.

The main composition of the mother liquor is 5-15w% calcium hypochlorite.
, calcium chloride is 17 to 35 w%, but may also contain a small amount of sodium chloride.

In addition, the concentration of semi-basic calcium hypochlorite is 10 to 30
W% is appropriate.

The slurry of semi-basic calcium hypochlorite obtained by chlorination may be classified and concentrated using a super decanter, a Ceratra liquid cyclone, etc., and calcium carbonate and clay may be removed.

In this case, the calcium carbonate and clay content contained in the slurry of coarse calcium hypochlorite trihydrate are extremely reduced, the separability is further improved, and a high-quality product with extremely low water-insoluble content can be obtained.

This is a major unexpected feature of the present invention.

In addition, the mother liquor or slurry with a high calcium carbonate and clay content obtained by classification may be purged as is to maintain the water balance and calcium chloride balance, but calcium hydroxide is added to this and dibasic hypochlorite is added. After crystallizing calcium chlorate, the mother liquor with a reduced concentration of calcium hypochlorite may be purged.

In addition, the entire slurry of semi-basic calcium hypochlorite may be used for the production of coarse calcium hypochlorite dihydrate, but a portion of it may be separated from the mother liquor as it is and further dried before being sold commercially. A 60 degree bleaching powder may also be produced.

In addition, when one or more substances selected from carboxylic acids, carboxylates, and carbohydrates are present during the crystallization of this semi-basic calcium hypochlorite, the growth in the thickness direction is promoted, resulting in a bamboo leaf-like or rhombic shape. crystals are obtained, and their classification and separation properties are further improved.

Particularly effective are polybasic carboxylic acids and their salts.

Next, crystallization of coarse calcium hypochlorite trihydrate will be explained.

Coarse calcium hypochlorite dihydrate is produced by chlorinating semi-basic calcium hypochlorite. At this time, columnar calcium hypochlorite dihydrate (hereinafter referred to as columnar seed crystals) is used as a seed crystal. This is used to grow and manufacture the product.

This columnar seed crystal is for calcium hypochlorite trihydrate.
Although it is added in a saturated or supersaturated state, it may be added in a cake state or in a sterilized state.

Further, it may be added continuously or intermittently.

The crystallization tank used may be a complete mixing tank type, DTB,
DP type is also fine.

The amount added can be selected arbitrarily, but coarse calcium hypochlorite trihydrate is produced due to problems with the production equipment for columnar seed crystals and the influence on the particle size of the coarse calcium hypochlorite trihydrate produced. The content of the compound is 20 wt% or less, preferably 10 wt% or less.

In addition, when adding columnar seed crystals directly as a slurry,
The modifier used in the production of columnar seed crystals will accompany it, but since the amount added is small, it will be in extremely small amounts, which will affect the growth of columnar seed crystals, the decomposition of calcium hypochlorite, and the highly bleached powder that becomes the product. However, if the columnar seed crystals are used as a cake or washed, these modifiers will be completely eliminated.

Crystallization temperature is usually 5 to 50℃, but 15 to 40℃
This is more desirable than suppressing zero decomposition of calcium hypochlorite according to reaction formulas (1) and (2) and increasing the growth rate of columnar seed crystals.

The apparent crystal residence time is usually 1 to 10 hours.

If it is too short, fine calcium hypochlorite dihydrate will be generated, and if it is too long, the crystallization tank will become larger.

The concentration of coarse calcium hypochlorite trihydrate, that is, the slurry concentration, has a slurry viscosity that is significantly lower than that of the conventional method, and can be extremely high at 10 to 40 w.
t% is desirable.

The slurry composition contains 10 to 45 w of calcium hypochlorite.
Preferably 18 to 38wt, and calcium chloride is 8wt.
-45 wt%, preferably 10-30 wt%, calcium hydroxide content is 0-20 wt%, preferably 0.3-1.0 wt%
% range.

However, when the sodium chloride accompanying the columnar seed crystals eutectoids, it is necessary to slightly lower the concentration of coarse calcium hypochlorite dihydrate.

Chlorine is usually introduced into the crystallization tank as a gas, and the appropriate introduction rate is 10 to 2001/hr-(l).

Note that chlorination generates heat, and if left as it is, the temperature will rise, so the heat must be removed.

Since the crystallization temperature is relatively low, heat removal is performed using a refrigerator and brine.

Therefore, the electricity cost will be higher, but since the calorific value is lower than when the substance to be chlorinated is calcium hydroxide and/or dibasic calcium hypochlorite, the electricity cost will be 115~21
5 is enough.

In addition, if chlorine absorption is poor, overchlorination occurs and the decomposition reaction shown in equation (2) proceeds rapidly.

Control of the reaction is therefore important, and sufficient monitoring must be performed by pH or redox potential.

The growth of columnar seed crystals is determined by the calcium chloride concentration in the mother liquor being 40%.
wt%, or even 50 wt%, and the obtained coarse calcium hypochlorite trihydrate has an a-axis and a b-axis of 10 to 1.
000 microns and a C-axis of 5 to 300 microns in the shape of a four-sided hermaphrodite trapezoid or a thick square plate.

In addition, this chlorination can also be operated at the eutectoid point of coarse calcium hypochlorite dihydrate and semi-basic lucium hypochlorite.

In this case, the separation of crystals in the next step will be slightly reduced, but the advantage is that the available chlorine content of the product can be adjusted.
It has the advantage of decomposing calcium hypochlorite and reducing its size.

The eutectoid point is preferably controlled by the supply rate of chlorine and semi-basic calcium hypochlorite.

On the other hand, the slurry of coarse calcium hypochlorite dihydrate may be separated as is, but before that, it must be separated using a liquid cyclone.
It is preferable to separate the slurry of concentrated coarse calcium hypochlorite trihydrate obtained by fractionating fine calcium hypochlorite dihydrate, calcium hydroxide, calcium carbonate, clay valve, etc. using a Ceratra etc. , it is easy to separate, and a high-quality highly bleached powder with little water-insoluble content can be obtained.

In particular, it can be used when low-grade calcium hydroxide or chlorine gas with a high carbon dioxide concentration is used.

However, as mentioned above, when a slurry of semi-basic calcium hypochlorite is classified to remove calcium carbonate and clay valves, the classification can be carried out simply by concentrating the coarse calcium hypochlorite. is easy.

Incidentally, the classification operation for removing calcium carbonate and clay valves can be easily carried out using a slurry of semi-basic calcium hypochlorite.

A basket type centrifuge is usually used for separation.
Continuation is also possible.

The separated mother liquor may be directly circulated to the crystallization process or may be partially purged, but calcium hydroxide is added to it to crystallize dibasic calcium hypochlorite, and the water and calcium chloride balance is In order to remove calcium hypochlorite, it is recommended to purge the mother liquor with a reduced concentration of calcium hypochlorite and supply the remainder to a semi-basic calcium hypochlorite crystallization tank.

The wet cake obtained by separation has a low adhesion mother liquor rate (20 wt% or less, 5 wt%, calcium hypochlorite content is 55 to 75 wt%, and calcium chloride content is 1 to 10 wt%).

The wet cake may be dried directly, but if the calcium chloride concentration in the wet cake is high and adversely affects the quality of the highly bleached powder product, water, sodium hypochlorite aqueous solution, sodium chloride, etc. It can be easily removed by washing with an aqueous solution that does not substantially contain calcium chloride, such as an aqueous solution.

The washing step is usually combined with the separation step and processed in the same separator.

Naturally, therefore, serialization is easy. It is best to handle the washed mother liquor in the same way as the separated mother liquor.

The washed cake obtained by washing contains 55 to 75 wt % of calcium hypochlorite and 1 wt % or less of calcium chloride.

The wet cake or wash cake is preferably mixed with a diluent such as IJum (chlorinated for the purpose of adjusting the available chlorine content) and dried.

Drying is very easy because the percentage of adhering mother liquor is low and the crystals are coarse, so a flash dryer, fluidized bed dryer, etc. are used.

The energy required for drying is small, and the decomposition rate of calcium hypochlorite during drying is small, and the highly bleached powder obtained is of high quality and has an effective chlorine content of 50 to 95%, which can be freely adjusted.

Next, the features of the present invention will be listed.

(1) Because the crystals are coarse and not twinned, the separation from the mother liquor is very good, and the percentage of mother liquor attached to the wet cake is 30 wt% or more, sometimes reaching 50 wt%, in the case of conventional crystals. It is surprisingly small and can reach 20 wt% or less, especially 5 wt%, with a simple ordinary separator and a short processing time.

(2) Since the adhesion mother liquor ratio of the wet cake is small, drying is easy and requires less energy.

Furthermore, the decomposition rate of calcium hypochlorite during drying is reduced.

Therefore, highly bleached powder of high yield and high quality can be obtained.

(3) The crystals are extremely strong and difficult to be crushed by mechanical impact, and the generation of fine particles is extremely reduced.

Therefore, in addition to improving the yield, it does not harm the health of operators, general handlers, etc., and is extremely beneficial in terms of hygiene management.

(4) Because the crystals are coarse, the slurry concentration in the crystallization process is low, and the slurry concentration is 15W in the case of conventional crystals.
L% was the limit, but it can be increased from 20wt% to 40wt%, making it possible to significantly downsize the equipment.Also, by maintaining a high slurry concentration, the amount of circulating mother liquor is reduced, and calcium hypochlorite is reduced during circulation. The amount of trihydrate decomposed becomes smaller.

(5) The concentration of calcium hypochlorite in the wet cake can be as high as 98 wt% on a dry basis, and when producing highly bleached powder, the effective chlorine content can be easily adjusted from 50 wt% to 95 wt%.

(6) Calcium chloride concentration is 25wt% or less 50wt%
Even in this case, the growth of columnar seed crystals is good, and coarse calcium hypochlorite trihydrate can be obtained.

Therefore, expensive sodium hydroxide is not required.

(7) The amount of heat generated during crystallization of coarse calcium hypochlorite trihydrate is extremely small, and less electricity is required for heat removal.

(8) By classifying a slurry of semi-basic calcium hypochlorite, calcium carbonate and clay can be easily removed, and the content of water-insoluble matter in the product can be extremely reduced.

(9) By separating and drying a slurry of semi-basic calcium hypochlorite, a 60% highly bleached powder can be produced.

Another unexpected feature was that semi-basic calcium hypochlorite was extremely easy to chlorinate, and when thick slaked lime cake was chlorinated, no calcium oxyoxide was observed, although it was a small amount of precipitated calcium oxide. There is.

Although the present invention requires a separate process for producing columnar seed crystals, since the amount of columnar seed crystals added is small, a small amount of equipment is required, and variable costs are negligible.

In addition, although it was difficult to perform a continuous method in the conventional method, it is easy in the present invention, and productivity is significantly improved.

The present invention has many and remarkable features as described above, and has a large economic effect, greatly reduces fixed costs and variable costs to zero, improves product quality, and is extremely useful for hygiene management. This is an extremely effective manufacturing method for producing calcium hypochlorite trihydrate and highly bleached powder.

Next, examples according to the present invention will be shown, but the present invention is not limited thereto.

Also, all measurements are based on weight.

Example 1 (Production of semi-basic calcium hypochlorite) In a cylindrical crystallization tank equipped with an overflow tube and equipped with a stirrer, 160 ml of 35% calcium hydroxide θ slurry was added while maintaining the temperature at 45°C. chlorine gas was introduced separately and continuously at 45 g/hr to produce a semi-basic calcium hypochlorite Q) slurry, which was withdrawn from the overflow tube at 205 E//hr.

The composition of this slurry is 20.9% calcium hypochlorite.
%, calcium chloride was 17.7%, calcium hydroxide was 4.5%, and calcium chlorate was 0.7%.

Also, semi-basic calcium hypochlorite has a length of 100 to 5
00 microns, width 50-150 microns, thickness 1
It was a bamboo leaf-like crystal with a size of 0 micron or less.

A portion of this semi-basic calcium hypochlorite slurry was processed in a basket-type centrifuge, and the resulting wet cake was processed in a hot air dryer maintained at 90°C. A 60% highly bleached powder containing 65.0% calcium, 6.7% calcium chloride, 233% calcium hydroxide, and 4.4% moisture was obtained.

Incidentally, during the production of semi-basic calcium hypochlorite, heat was generated, but the heat was removed very easily using tap water (room temperature 25°C).

(Manufacture of columnar seed crystals) 10% citric acid aqueous solution 30. ? , calcium hydroxide 11
2. ? 239g of 148% caustic soda aqueous solution, 449g of water
was placed in a one-flood crystallization tank equipped with one stirrer, and while maintaining the temperature at 15° C., 201 d of chlorine gas was introduced at a rate of about 1509/hr −1 .

Q) pH at the end of chlorination is 10.3, a axis, b axis is 5 to 15 microns, C axis is 20 to 120 microns, c
A slurry of columnar seed crystals was obtained from which columnar calcium hypochlorite trihydrate having a value of about 7 was obtained.

(Production of coarse calcium hypochlorite trihydrate) A slug of the semi-basic calcium hypochlorite described above was placed in a cylindrical crystallization tank equipped with an overflow pipe and equipped with a stirrer at 1°C maintained at 20°C. ．． ! i'/hr.

Chlorine gas 8.1 El/hr, slurry 1 of the columnar seed crystals
Chlorination was carried out by continuously feeding 0.6 g/hr of each separately.

At the same time, slurry was extracted from the overflow pipe at 2099/hr.

The growth of columnar seed crystals was good, and 45 hours after the start of operation, the a-axis, b
A slurry of coarse calcium hypochlorite trihydrate having an axis of 20 to 400 microns and a C axis of 20 to 150 microns having a nearly four-sided hermaphrodite shape was obtained.

The slurry composition contains 24.0% calcium hypochlorite;
Calcium chloride is 23.2%; calcium chloride is 20.
3%, calcium hydroxide was 0.4%, and the slurry concentration was 24%.

When 50 liters of the slurry was processed in a basket type centrifuge at 300 rpm for 1 minute and further washed with 3 liters of pure water at 3,000 rpm for 1 minute, calcium hypochlorite content was 70.3%. Calcium chloride is 0.
5%, calcium hydroxide is 1.0%, and the adhesion mother liquor rate is 1.
125 g of a 1.3% wash cake was obtained.

Next, 10 liters of this wash cake (I-chloride with a purity of 99%)
1) After adding and mixing 2 Cl of rum powder, it was treated in a hot air dryer maintained at 90°C, and the calcium hypochlorite was 73.4
%, sodium chloride is 21.0 hi, calcium chloride is 0.
9%, calcium hydroxide 1.8%, water 25% 7
A 0% highly bleached powder was obtained.

In addition, when producing coarse calcium hypochlorite, heat is generated, but the amount of heat generated is about 115 when producing coarse calcium hypochlorite trihydrate by chlorinating calcium hydroxide. was extremely easy.

Example 2 (Production of semi-basic calcium hypochlorite) A 37% calcium hydroxide slurry (calcium carbonate) was added to a cylindrical crystallization tank equipped with an overflow tube and a stirrer at 1°C while maintaining the temperature at 55°C. concentration 1.5%) to 154. ! ? /hr, chlorine gas 4.59/hr, 10% citric acid aqueous solution6.
0. ? /hr separately and continuously for chlorination to produce a slurry of semi-basic calcium hypochlorite, which was withdrawn from the overflow tube at 205 ji/hr.

The composition of this slurry is 20.2% calcium hypochlorite.
%.

Calcium chloride is 18.2%, calcium hydroxide is 4.
6%, and calcium carbonate was 13%.

Also, semi-basic calcium hypochlorite has a length of 50 to 30
0 micron, width 50-150 micron, thickness 5-3
0 micron Q) rhombic crystals.

This semi-basic calcium hypochlorite slurry was heated at 45°C.
The mixture was classified and concentrated using a Ceratra with an upward flow rate of 20 Crn/hr.

A concentrated semi-basic calcium hypochlorite slurry was obtained from the lower part of the Ceratra, and its composition was 28.9% calcium hypochlorite, 16.0% calcium chloride, and 6.2% calcium hydroxide. , calcium carbonate was 0.3%.

(Production of coarse calcium hypochlorite trihydrate) A cylindrical crystallization tank equipped with an overflow tube and equipped with an IL stirrer maintained at 20°C was charged with the above-mentioned concentrated semi-basic calcium hypochlorite slurry. -114ji/hr, aqueous solution of 10.6% calcium hypochlorite and 21.4% calcium chloride 77g/hr, chlorine gas 6.8.9/hr, columnar seed crystal slurry 10, 69 of Example 1 / hr were separately and continuously supplied to each of the reactors to produce a slurry of coarse calcium hypochlorite trihydrate.

At the same time, 208 fl/ml of the slurry was pumped from the overflow pipe.
C was extracted at hr.

The growth of columnar seed crystals was good, and 45 hours after the start of operation, the a-axis, b
A slurry of coarse calcium hypochlorite trihydrate having an axis of 20 to 300 cyclones and a C axis of 20 to 150 microns having a nearly quadrangular trapezoidal shape was obtained.

The concentration of calcium carbonate in the slurry was 0.2%, and when the slurry was treated in a basket-type centrifuge in the same manner as in Example 1, the concentration of calcium hypochlorite was 72%.
5 excellent, calcium chloride 0.3%, calcium hydroxide 1. %, calcium carbonate was 0.3%, and the adhesion mother liquor percentage was 8.0%.

After adding 20g of sodium chloride powder with a purity of 99 or above to this cake 10 (l) and mixing, it was treated in a hot air dryer maintained at 90°C to contain 74.3% calcium hypochlorite and 0.8% calcium chloride. , 1.5% calcium hydroxide, 0.5% calcium carbonate, 20.7% sodium chloride.
, a 70-high bleaching powder with a moisture content of 1.6 was obtained.

Further, the calorific value due to chlorination was very small as in Example 1.

In addition, the semi-basic calcium hypochlorite 0 slurry was classified using a set slurry, and chlorinated using columnar seed crystals without concentration to produce a slurry of coarse calcium hypochlorite trihydrate, which was similarly separated. As a result, the separability was poor, and the adhesion mother liquor ratio of the washed cake was 15.3%, and the calcium carbonate content was as high as 2.3%.

[Brief explanation of the drawing]

Figure 1: A copy of flat rectangular plate-shaped calcium hypochlorite trihydrate; Figure 2: A copy of laminated calcium hypochlorite trihydrate (agglomerate twins); Figure 3: Book. In the invention, a copy of columnar calcium hypochlorite trihydrate used as a seed crystal. A...Cylindrical crystal, B...quadrangular columnar crystal,
C: Quadrilateral bipyramidal truncated crystal.

Claims (1)

[Claims] 1. In a method for producing calcium hypochlorite trihydrate, (1) a suspension of calcium hydroxide and/or dibasic calcium hypochlorite is chlorinated to produce a half-basic (2) When the semi-basic calcium hypochlorite obtained in (1) is chlorinated to crystallize calcium hypochlorite trihydrate, as a seed crystal. Columnar shape in which the ratio of a, b, and c axes of calcium hypochlorite trihydrate is 0.5≦b / a≦2.0 c / a≧1.5, and the C axis is 5 microns or more A method for producing coarse calcium hypochlorite trihydrate, which comprises adding calcium hypochlorite trihydrate.