JPS6317772B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for concentrating an aqueous calcium chloride solution. Specifically, it is a method for concentrating a calcium chloride aqueous solution for the purpose of obtaining a concentrated calcium chloride aqueous solution suitable for manufacturing solid calcium chloride products such as granules and flakes.

Conventionally, the ammonia distillation effluent in the ammonia-soda method or the effluent after distilling ammonia by adding calcium hydroxide to an ammonium chloride aqueous solution is an aqueous solution whose main component is calcium chloride, and is used as a raw material for calcium chloride products. commonly used as One such product is a solid calcium chloride product in the form of granules, flakes, etc. The solid calcium chloride product is usually produced by evaporating and concentrating the distillation waste liquid to form a concentrated calcium chloride aqueous solution, and then dripping the concentrated calcium chloride aqueous solution from a nozzle and solidifying it into granules by contacting with cold air, or by using a rotary drum flaker. It is manufactured in flake form.

The concentration of concentrated calcium chloride aqueous solutions obtained by conventional concentration methods is as low as 71 to 72% by weight, and solid calcium chloride products obtained from the aqueous solutions tend to solidify, which can lead to the occurrence of defective products, especially during the rainy season. There are many. Furthermore, the solid calcium chloride product is brittle and easily generates dust, which not only adversely affects the working environment but also causes product loss. In order to solve the above problem, it is possible to further concentrate the calcium chloride aqueous solution and granulate it using a more concentrated calcium chloride aqueous solution, but in the conventional concentration method, if the concentration exceeds about 72% by weight, Normally, this would not be possible because crystals of calcium chloride monohydrate would precipitate and the solution would solidify. Therefore, the current method of concentrating it to 72%, granulating it, leading it to a drying process and drying it, and then cooling it with a cooling equipment to make the final product is adopted. This makes the equipment more complex and
This results in an increase in manufacturing costs.

As a result of extensive research in order to solve the above-mentioned problems, the present inventors have found that by making common salt exist in a specific ratio in a calcium chloride aqueous solution and performing evaporation concentration, the aqueous solution solidifies in the evaporator. It has been found that a highly concentrated calcium chloride aqueous solution can be obtained without any problems. Furthermore, the inventors have discovered that when the above-mentioned concentration is carried out to a calcium chloride concentration of 72.5% by weight or more, the solid calcium chloride product obtained from the concentrated calcium chloride aqueous solution is free from caking, and its strength is also improved, leading to the completion of the present invention. .

That is, in the present invention, when evaporating and concentrating a calcium chloride aqueous solution,
This is a method for concentrating a calcium chloride aqueous solution, which is characterized in that common salt is present at a NaCl/CaCl ₂ weight ratio in the range of 0.025 to 0.041, and concentration is carried out to a calcium chloride concentration of 72.5% by weight or more at a temperature at which the salt does not precipitate.

In the present invention, as the calcium chloride aqueous solution, an aqueous solution in which calcium chloride is dissolved as a main component can be used without particular limitation. For example, typical examples include ammonia distillation effluent in the ammonia-soda method, and ammonia distillation effluent after adding calcium hydroxide to an aqueous ammonium chloride solution to distill ammonia.

In the concentration method of the present invention, the calcium chloride aqueous solution has common salt present, and the common salt is NaCl/
_CaCl2 weight ratio 0.025~0.041, preferably 0.028~
It is necessary to adjust it to 0.038.
If the salt content is less than the above range, crystals of calcium chloride monohydrate will precipitate during concentration to a desired concentration by the concentration operation described later, and the solution will solidify.
Furthermore, if the amount of salt exceeds the above range, salt crystals will precipitate and grow during the concentration, resulting in clogging of piping and nozzles during granulation. That is, by adjusting the salt concentration in the calcium chloride aqueous solution within the above range, the concentration of the calcium chloride aqueous solution can be concentrated to the desired concentration by preventing solidification of the solution or precipitation of salt by the concentration operation described later. can do. There are no particular restrictions on the means for adjusting the salt concentration in the calcium chloride aqueous solution within the above range.
For example, if the calcium chloride aqueous solution is the ammonia distillation effluent in the ammonia-soda method, the liquid composition usually has a calcium chloride concentration of about 10 to
11% by weight, and the salt concentration is about 4-5% by weight. If the NaCl/CaCl ₂ weight ratio exceeds the above range, the calcium chloride aqueous solution may be concentrated as it is, depending on the case, to an appropriate concentration, and the excess salt may be precipitated at a temperature that allows it to precipitate. A method of separating common salt is preferred.

In the above method, a mutual solubility curve of calcium chloride and common salt at each temperature is created in advance, and based on the mutual solubility curve, the temperature at which the saturated solubility of common salt is within the above range at the calcium chloride concentration of the calcium chloride aqueous solution is determined. Those skilled in the art can easily carry out the separation of common salt at the desired temperature. To give a specific example, if the ammonia distillation effluent in the ammonia-soda method is concentrated to 38% by weight and the salt precipitated at a temperature of 45°C is filtered, an aqueous calcium chloride solution with a NaCl/CaCl ₂ weight ratio of about 0.04 is obtained. can be obtained. Also,
As another method, it is also possible to adjust the NaCl/CaCl ₂ weight ratio by adding calcium chloride or a calcium chloride aqueous solution with a low salt content to the calcium chloride aqueous solution. On the other hand, NaCl/CaCl ₂
When the weight ratio is lower than the above range, for example, when the calcium chloride aqueous solution is a waste liquid obtained by adding calcium hydroxide to an almost pure ammonium chloride aqueous solution and distilling ammonia, the calcium chloride aqueous solution Add salt ingredients inside
The NaCl/CaCl ₂ weight ratio may be within this range. The method of adding the salt component to the calcium chloride aqueous solution is not particularly limited. For example, a method of adding the necessary amount of salt directly to the calcium chloride aqueous solution, or a method of directly adding the required amount of salt to the calcium chloride aqueous solution, or a method of adding the calcium chloride aqueous solution as it is or after concentrating it to an appropriate concentration and forming a salt layer at a temperature such that the saturated solubility of salt in the aqueous solution falls within the above range. Typical methods include a method in which a calcium chloride aqueous solution having a high salt concentration is added to the calcium chloride aqueous solution.

In the present invention, an aqueous calcium chloride solution whose NaCl/CaCl ₂ weight ratio is adjusted within the above range is evaporated and concentrated at a temperature at which common salt does not precipitate. Although the temperature cannot be absolutely limited, it is generally set to the boiling point of an aqueous calcium chloride solution at normal pressure.

Concentrating the calcium chloride aqueous solution has a calcium chloride concentration of 72.5% by weight or more, preferably 73.0% by weight.
It is necessary to do the above. If the calcium chloride concentration is lower than the above range, the solid calcium chloride product obtained using the calcium chloride aqueous solution is likely to caking, its strength is reduced, and dust is likely to be generated. The higher the calcium chloride concentration, the more effective it is in preventing the above phenomenon, but if it is too high, calcium chloride monohydrate will precipitate. The upper limit of the concentration varies somewhat depending on the proportion of salt contained, but is generally 74.5% by weight, preferably 74.0% by weight.
And it is sufficient.

As understood from the above explanation, according to the concentration method of the present invention, an aqueous calcium chloride solution can be concentrated to a high concentration without precipitation of calcium chloride monohydrate. Therefore, the concentrated calcium chloride aqueous solution obtained by concentration can be made into a solid calcium chloride product that does not solidify and is strong simply by granulating and flaking. It is very economical as there is no need to provide a drying process etc. afterwards.

Examples are shown below to specifically explain the present invention, but the present invention is not limited to these Examples.

In addition, in the Examples and Comparative Examples, the bending strength was measured by the following method.

Γ Bending strength measurement method As shown in Figure 2, a piece of wood 1 (6cm long x 2cm wide)
× height 3 cm) were placed in parallel at intervals of 4 cm, and test piece 2 was placed on top of these. Further, a cardboard container 3 having a volume of 4 cm in length x 2 cm in width x 8 cm in height was placed in the center of the test piece 2, and mercury 4 was gently dropped into the container, causing the test piece to break. By the way, I quickly weighed it. The bending strength (g/cm ² ) was determined by dividing the weight by the cross-sectional area of the load applied to the test piece. Therefore, it can be said that the higher the bending strength, the harder the calcium chloride is, and the less likely it is to generate dust.

Example 1 Calcium chloride 10.8g/100c.c., salt 4.5g/
The ammonia-soda process distillation waste containing 100 c.c. was concentrated at normal pressure to 120°C, then cooled to 45°C.
The solution was kept at 45° C. and the precipitated common salt was filtered off. The composition of the obtained calcium chloride aqueous solution was 38.5% by weight of calcium chloride, 1.5% by weight of common salt (NaCl/
CaCl ₂ =0.039). This calcium chloride aqueous solution was concentrated at normal pressure to 178° C. to give a calcium chloride concentration of 72.9% by weight. The calcium chloride aqueous solution after the above concentration is 2cm wide, 10cm long, and 0.5cm deep.
The sample was poured into a 1 mm deep SUS304 frame and cooled to prepare a test piece, and its bending strength was measured. As a result, the bending strength was 42 g/cm ² . Further, when the above two test pieces were stacked and a weight of 100 g was placed on them, and the test pieces were left in a room with a humidity of 80% for one week and the state of caking was observed, there was no caking at all. Furthermore, the calcium chloride aqueous solution was concentrated until it solidified, and the temperature and calcium chloride concentration (hereinafter referred to as concentration limit temperature and concentration limit concentration) at normal pressure were measured. As a result, the concentration limit temperature was found to be
At 182°C, the critical concentration was 74.2% by weight.

Example 2 NaCl/CaCl ₂ obtained in the same manner as Example 1
= 0.039 calcium chloride aqueous solution is heated to dissolve the calcium chloride to prepare a calcium chloride aqueous solution of NaCl/CaCl ₂ = 0.034, and this is heated at normal pressure to 182
It was concentrated until the temperature reached ℃, giving a calcium chloride concentration of 74.0% by weight. A test piece was prepared in the same manner as in Example 1 using the above concentrated calcium chloride aqueous solution,
The bending strength was measured and found to be 78 g/cm ² . Further, when the caking state was observed in the same manner as in Example 1, there was no caking at all. Furthermore, the concentration limit temperature of the calcium chloride aqueous solution after the adjustment is 183°C,
The critical concentration was 74.3% by weight.

Example 3 NaCl/CaCl ₂ obtained in the same manner as Example 1
=0.039 calcium chloride aqueous solution was heated to dissolve the calcium chloride to prepare a calcium chloride aqueous solution of NaCl/CaCl ₂ =0.025, and this was heated at 180℃ at normal pressure.
It was concentrated to give a calcium chloride concentration of 72.5% by weight. A test piece was prepared in the same manner as in Example 1 using the concentrated calcium chloride aqueous solution, and the bending strength was measured, and it was found to be 40 g/cm ² . Further, when the caking state was observed in the same manner as in Example 1, there was no caking at all. Furthermore, the concentration limit temperature of the calcium chloride aqueous solution after the adjustment is 180°C,
The critical concentration was 73.2% by weight.

Example 4 After adding calcium hydroxide to an aqueous ammonium chloride solution and distilling ammonia, salt was added to the effluent (calcium chloride concentration 10.8% by weight).
A calcium chloride aqueous solution with NaCl/CaCl ₂ =0.038 was prepared. The calcium chloride aqueous solution was heated to 178% at normal pressure.
It was concentrated to ℃ to give a calcium chloride concentration of 73.1% by weight. A test piece was prepared in the same manner as in Example 1 using the concentrated calcium chloride aqueous solution, and the bending strength was measured to be 45 g/cm ² . Also,
When the caking state was observed in the same manner as in Example 1, there was no caking at all. Further, the concentration limit temperature of the calcium chloride aqueous solution after the above adjustment was 182° C., and the limit concentration was 74.3% by weight.

Comparative Example 1 In Example 1, the overtemperature of the common salt was changed and the overheating of the common salt was carried out to obtain 38.5% by weight of calcium chloride,
A calcium chloride aqueous solution with NaCl/CaCl ₂ =0.055 was obtained. This calcium chloride aqueous solution was heated to 170℃ at normal pressure.
When the mixture was concentrated to a concentration of 67.0% by weight, it began to become cloudy, so a test piece was immediately prepared in the same manner as in Example 1 and its bending strength was measured. The result was 35 g/cm ² . Moreover, when the solidification state was observed in the same manner as in Example 1, it was found that the solidification was firmly solidified.

Comparative Example 2 A test piece was prepared in the same manner as in Example 1 except that the concentration temperature was 172°C and the calcium chloride concentration was 70.9% by weight, and the bending strength was measured.29
g/ ^cm2 . In addition, when the solidification state was observed in the same manner as in Example 1, it was found to be firmly solidified.

Comparative Example 3 NaCl/CaCl ₂ obtained in the same manner as Example 1
= 0.039 calcium chloride is heated to dissolve the calcium chloride to prepare a calcium chloride aqueous solution of NaCl/CaCl ₂ = 0.018, and this is concentrated at normal pressure to 173°C to give a calcium chloride concentration of 70.7% by weight. did. A test piece was prepared in the same manner as in Example 1 using the concentrated calcium chloride aqueous solution, and the bending strength was measured. The result was 18Kg/ ^cm2 . Moreover, as a result of observing the solidification state in the same manner as in Example 1, it was found that the solidification state was firmly solidified. Further, the concentration limit temperature of the calcium chloride aqueous solution after the above adjustment was 174° C., and the limit concentration was 71.1% by weight.

[Brief explanation of the drawing]

FIG. 1 shows the apparatus used to measure bending strength.
In the figure, 1 is a wooden piece, 2 is a test piece, 3 is a container,
4 represents mercury.

Claims (1)

[Claims] 1. When concentrating a calcium chloride aqueous solution by evaporation, common salt is present in the calcium chloride aqueous solution with a NaCl/CaCl ₂ weight ratio in the range of 0.025 to 0.041, and the calcium chloride concentration is 72.5 at a temperature at which the salt does not precipitate.
A method for concentrating an aqueous calcium chloride solution, the method comprising concentrating an aqueous solution of calcium chloride to more than % by weight. 2. By precipitating and separating the salt in the aqueous solution containing calcium chloride and common salt, NaCl/
The method according to claim 1, wherein the concentration is carried out after adjusting the CaCl ₂ weight ratio to a range of 0.025 to 0.041. 3 Adding salt components to calcium chloride aqueous solution
The method according to claim 1, wherein the concentration is carried out after adjusting the NaCl/CaCl ₂ weight ratio to a range of 0.025 to 0.041.