SU43374A1 - Method for producing bleach - Google Patents

Description

It is known that when lime chlorine on calcium oxide hydrate is produced, it is prone, with a certain degree of chlorination, to become wet under the influence of water formed during this reaction, which proceeds according to the following scheme:

/ OS1

Ca (OH)., + C1, -Ca / Cl

This circumstance serves (especially in mechapic apparatuses) as the reason for the bleaching of lime loses its character to a fine scapula, forming agglomerated and cementing clods. A consequence of water absorption of bleaching lime is also the fact that, in the case of using iron apparatus, the latter is largely corroded. To eliminate these difficulties, various means were proposed, such as slow chlorination, the addition of significant amounts of air to chlorine, chlorination at low temperature, a decrease in the layer thickness, etc. However, all these means, achieving the goal only partially, suffer various disadvantages:

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in some cases, prolonged chlorination is inevitably associated with the decomposition of bleaching lime, in other cases these deficiencies are expressed in low productivity relative to the size of the apparatus and, above all, in the low content of active chlorine in the resulting bleaching lime.

It was also proposed to conduct the chlorination process in the presence of volatile organic indifferent solvents, but these methods are accompanied by inevitable losses of solvents, which significantly increase the cost of the product.

It is also known that wet and riddled with bleaches, the lime dye is more difficult to dehydrate, so that its decomposition becomes inevitable. That is why anhydrous bleaching lime has hitherto been available only to a very limited extent.

In the present invention, the authors succeeded in overcoming the above difficulties — water absorption during chlorination and the formation of lumps — and using various phases of chlorination and dehydration to obtain anhydrous bleach. The fact is that

if the calcium oxide hydrate is chlorinated in a discontinuously operating apparatus with a stirrer, then at first the reaction proceeds without the formation of lumps, for example, at a content of 10 ° C of active chlorine, the lime is still dry and dusty; with active chlorine, although it remains in the form of a powder, it is already beginning to be somewhat wet; when it deduces even more wet and the first small lumps begin to appear; at 30Vo and above, the formation of lumps continues, reaching a maximum at the highest chlorine content (37-Ze / o); in the latter case, the product is already wet and partly agglomerated.

We have found that if the chlorination is interrupted at that moment, when the bleaching powder, although it has already become wet, it still retains its powder character (which happens mainly at 25-28 / (, active chlorine) content, and immediately apply a high vacuum, The water formed during the reaction process is distilled off easily and quickly, which is most striking, at a lower temperature than in the products completely chlorinated. At the same time, it turned out that the removal of all the reaction water is disadvantageous because the product loses its ability to enter into th reaction with chlorine. Most advantageous to remove about / 5 formed water.

This partially labeled, low-percentage, but dry bleaching lime is again affected by chlorine; the latter enters a further reaction until the product reaches the maximum content of active chlorine (37-ZE / oX, which is important, since bleach retains the character of the powder. This fact is due to the fact that most of the water that is its accumulation would cause bleaching lime agglomeration, be removed in advance,

The dry, partially dehydrated and powdered product obtained in this way can already be directly put into use, as such, since it has greater strength and uniformity than ordinary limestone. If this product, immediately after its preparation, is again subjected to processing in the same apparatus, but under high vacuum, then, due to its special chemical and physical properties, it is fully dehydrated, without undergoing any noticeable decomposition. The result is an anhydrous, high-grade, stable powdered bleaching powder.

Thus, the combined, but alternating, phases of chlorination and dewatering represent significant advantages in obtaining bleach. Separating the dehydration process under high vacuum into two stages or one after obtaining the product chlorinated by / s, the other, at the end of chlorination, is compared with the known one-time dehydration to the end of chlorinated bleaching lime under high vacuum, the advantage of bleaching lime Chlorinated to Vs, water can be removed very easily and quickly and at a relatively low temperature. This is due to the fact that the water vapor of the bleaching lime chlorinated on / d turns out to be, according to our observations, significantly higher than the steam elasticity until the end of the chlorinated bleaching lime.

We further found that various chlorination and dehydration operations under high vacuum can be alternately and very advantageously carried out in a single mechanical, discontinuously operating apparatus, equipped with a double casing and a tube shaft agitator (casing and agitator with cold or warm water circulation for temperature control reactions and to remove water under high vacuum).

It is very remarkable that with the aid of this apparatus, very heavy lime is obtained. The weight per unit volume is greater than 1, while the apparent specific weight of all other grades of bleaching powder is approximately 0.6.

Example. 63 parts of calcium oxide hydrate are chlorinated in a device with a stirrer at a temperature of about 40 ° C (temperature is regulated with the help of circulating water). After absorption of 25 parts of chlorine, i.e., after the content of active chlorine in the product is 28.4%, the chlorination process is interrupted. A high vacuum (15–20 mm Hg) is immediately established, and at a temperature of 38–40 ° C, 5 parts of water are quickly released from the lime. The vacuum is turned off and chlorine is reacted again until bleach absorbs about 12 more hours of chlorine. In the thus obtained bleaching powder, there is active chlorine and only 4, of water; after that, the vacuum is again set (15-20 g) and now at 46-48 ° the product is completely dehydrated, depriving the remaining 4 parts of water. As a result, 91 parts of anhydrous powdered bleaching lime are obtained with a content of about 40% active chlorine and with a unit weight of about 1.15.

The very significant practical advantages of the proposed new method, compared with lead cameras or various mechanical continuously operating systems, Senclever, Backmann, Rudge, etc., are as follows. A new method, which allows to carry out discontinuous work, makes it possible to carry out chlorination in one simple iron apparatus with a bailout, in which the reaction is precisely controlled at each moment, since: a) the temperature can be regulated in any way; b) the chlorination process takes place simultaneously and in the same

degrees over the whole mass of calcium oxide hydrate and c) timely removal of the reaction water from the product chlorinated on Vs eliminates any corrosion of the apparatus.

With the help of a new method, which can be carried out with any concentration of chlorine, anhydrous bleaching powder in the form of a powder is obtained directly, which is extremely stable even at high temperatures in tropical countries.

- In other ways, obtaining such a product is only possible with extreme difficulty. The high proportion of bleach produced by the present method provides great savings in packaging costs and is of great importance for water transport.

The subject of the patent.

1. A method of producing anhydrous high-percentage bleaching lime by chlorine on calcium oxide hydrate followed by vacuum evaporation, characterized in that calcium hydroxide hydrated chlorinated only on Vs is removed by dehydrating in vacuum with 5% of water emitted during the chlorination reaction, and then chlorinated the lime is chlorinated again to obtain a product with a maximum content of active chlorine and evaporated using vacuum evaporation to an anhydrous state.

2. Application of the method described in paragraph 1, in one apparatus with alternate chlorination and dehydration under high vacuum.