JP3640677B2 - Production method of calcium hypochlorite - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method for producing calcium hypochlorite using calcium oxide as a raw material directly instead of conventionally used calcium hydroxide.
Calcium hypochlorite is used as a water disinfectant and is often used for pools and sewage treatment.
[0002]
[Prior art]
(1) Technical background Calcium hypochlorite is produced by emulsifying calcium hydroxide in water or the filtrate after the reaction, and blowing chlorine gas into the emulsion to produce calcium hypochlorite for filtration and recovery. A method of post-drying into a product is common.
In addition to calcium hydroxide, the alkali source may be used in combination with sodium hydroxide.
Calcium hypochlorite is dissolved in the filtrate (mother liquor) after the product is recovered, and discarding it necessitates neutralization, leading to loss of yield and high manufacturing costs .
For this reason, in the conventional manufacturing method, a method of using this filtrate as an emulsified solution of calcium hydroxide is also employed. However, the water balance cannot be achieved with this alone, and a part of the filtrate is discarded, and an improvement measure for this is desired.
(2) Similar technology US Pat. No. 321,647 discloses a method of evaporating and concentrating excess mother liquor under low temperature and reduced pressure in order to facilitate the growth of salt crystals and separation from calcium hypochlorite crystals. The salt crystals are still accompanied by a large amount of calcium hypochlorite crystals, so that the quality of the salt is not sufficient, and there is a disadvantage that a large amount of energy is required to evaporate the excess mother liquor.
[0003]
[Problems to be solved by the invention]
An object of this invention is to provide the manufacturing method of the efficient calcium hypochlorite which does not produce | generate an excess mother liquor.
[0004]
[Means for Solving the Problems]
(1) Constitution of the Invention The method for producing calcium hypochlorite of the present invention comprises the following constitution.
Calcium oxide is used in place of calcium hydroxide as a raw material for the chlorination reaction.
(2) Detailed description In production of calcium hypochlorite, calcium hydroxide is used as a main raw material in addition to chlorine. Depending on the process, caustic soda may be used in combination.
Conventionally, the reason why calcium oxide was not used in place of calcium hydroxide could not be considered because of the fact that direct contact between water and calcium oxide may cause considerable heat generation and difficulty in forming a uniformly dispersed emulsion. This is because the.
In order to reduce the excess mother liquor, calcium hydroxide may be emulsified in the mother liquor, but this alone usually makes it difficult to balance the water, and some excess mother liquor is produced as a by-product. In addition, when calcium oxide is used instead, rapid heat generation occurs upon contact with water, and calcium hypochlorite in the mother liquor is decomposed, leading to yield loss.
[0005]
As a measure for improving this, a method of attaching a jacket or coil to the reaction vessel and cooling with brine is conceivable. However, since heat generation occurs at the moment when calcium oxide and water come into contact with each other, sufficient measures cannot be taken.
However, it was discovered that when calcium oxide was emulsified after mixing caustic soda into the mother liquor, the temperature rise due to heat generation was greatly reduced and a uniform emulsion was obtained without decomposition of calcium hypochlorite.
[0006]
【Example】
Although the Example of this invention is shown, this invention is not limited to these.
[0007]
Example 1
Chlorination raw material liquid for the production of calcium hypochlorite (liquid obtained by appropriately treating various liquids including mother liquor recycle liquid) After mixing 380 g of 49% sodium hydroxide with 455 g, calcium oxide powder with stirring Is gradually mixed to make a uniform emulsion. During this time, the temperature rise of the emulsified liquid was about 2 ° C. and did not exceed 25 ° C., even though external cooling was not performed. The composition of 9,308 g of this emulsion was 12.6% calcium hypochlorite, 16.3% sodium chloride, 7.7 alkali, 62.8% water, and 0.6% others.
While stirring the emulsion, chlorine gas was blown in for about 3 hours to complete chlorination. The composition of the chlorinated solution after completion of chlorination was 17.7% calcium hypochlorite, 20.1% sodium chloride, 0.9% alkali, 60.4% water, and 0.9% for others.
In this case, the decomposition of calcium hypochlorite was very slight.
Hypochlorous acid when this liquid is processed into a normal product (calcium hypochlorite crystal and solution are separated, the crystal is dried and the product is recycled, and the solution is recycled as a raw material for chlorination). The calcium concentration was 76%, which was inferior to that of a normal product.
[0008]
Comparative Example 1
In the same manner as in the example, 473 g of calcium oxide powder was mixed with 8,455 g of chlorination raw material liquid (liquid obtained by appropriately treating various liquids including mother liquor recycling liquid) in the production of calcium hypochlorite. As soon as calcium oxide came into contact with the liquid, the heat generated intensely, and the liquid temperature suddenly exceeded 30 ° C from 21 ° C, and gas generation (which is considered to be a decomposition gas of calcium hypochlorite) occurred. Interrupted.
[0009]
Comparative Example 2
Chlorination raw material liquid (liquid obtained by appropriately treating various liquids including the mother liquor recycle liquid) 9,504 g mixed with 428 g of 49% caustic soda, and then stirred with calcium hydroxide. The powder is gradually mixed with 515 g to make a uniform emulsion. During this time, the temperature rise of the emulsified liquid was about 2 ° C. and did not exceed 25 ° C., even though external cooling was not performed. The composition of 10,447 g of this emulsion was 12.5% calcium hypochlorite, 16.3% sodium chloride, 7.4 alkali, 63.2% water, and 0.6% others.
While stirring the emulsion, chlorine gas was blown in for about 3 hours to complete chlorination. The composition of the chlorinated solution after completion of chlorination was 17.3% calcium hypochlorite, 20.1% sodium chloride, 0.9% alkali, 60.9% water, and 0.8% others.
In this case, the decomposition of calcium hypochlorite was very slight.
This solution is subjected to ordinary treatment (calcium hypochlorite crystals and solution are separated, the crystals are dried and the product is recycled, and the solution is recycled as a raw material for chlorination), and the calcium hypochlorite concentration is 76. % Products obtained. However, in this case, even if the necessary mother liquor was recycled, 319 g of mother liquor remained.
[0010]
【The invention's effect】
By using calcium oxide instead of calcium hydroxide, the water balance of the entire reaction system can be improved by the amount of water required for calcium oxide to react with water to produce calcium hydroxide, and the excess mother liquor By-product can be prevented.

Claims (1)

  In the method of producing calcium hypochlorite by chlorinating an emulsion containing calcium hydroxide, after adding caustic soda to the solution containing the filtrate (mother liquor) after filtration of the calcium hypochlorite-containing solution, oxidation A method for producing the emulsion by adding calcium.