JPH08198620A - Treatment of sodium chloride-containing material for preventing low temperature solidification - Google Patents

Abstract

PURPOSE: To obtain a treating method of a sodium chloride-containing material for preventing low temp. solidification capable of preventing the sodium chloride- containing material consisting essentially of the sodium chloride from being solidified and eliminating a handling time of an indoor storage and a breaking of solidified particles. CONSTITUTION: >=0.05wt.% at least more than one kind compounds containing Al<3+> , Mg<2+> , Ca<2+> , Sr<2+> , Mn<2+> , Cu<2+> , Zn<2+> , Fe<3+> , or Ni<2+> , being an ion having a heat of hydration larger than that of Na<2+> per pulverized salt is added to a pulverized salt. The pulverized salt mixed with the compd. isolating the ion having the heat of hydration larger than that of Na<+> does not cause the low temp. solidification even if stored at -15 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a treatment of a sodium chloride-containing substance for preventing a so-called low-temperature solidification, which prevents the sodium chloride-containing substance containing sodium chloride as a main component from solidifying under a low temperature condition. Regarding the method.

[0002]

2. Description of the Related Art Sodium chloride has the following formula (1) when the product temperature (temperature) falls below 0.1 ° C. in the presence of water.
The above reaction occurs to change to a dihydrate. NaCl + 2H ₂ O → NaCl · 2H ₂ O (1) Usually, the water content of sodium chloride is attached to sodium chloride crystals as a saturated solution of sodium chloride. Since the sodium chloride solubility of this water decreases as the temperature decreases, fine crystals of sodium chloride precipitate, but when the temperature falls below 0.1 ° C, the reaction of the above formula (1) causes sodium chloride to dissolve. Dihydrate is precipitated. Precipitation of this sodium chloride dihydrate lowers the sodium chloride concentration in the water and makes it unsaturated, and the sodium chloride dissolves in this water. Such precipitation and dissolution are repeated, and sodium chloride dihydrate is produced until the water adhering to the crystal surface disappears [D. W. K
aufmann: Sodium chloride (1993), 47th
See page 8 (Translated and published by Salt Science Research Foundation)].
Since most of the water content of sodium chloride crystals exists on the crystal surface, the above-mentioned reaction occurs on the crystal surface. As a result, the generated sodium chloride dihydrate cross-links between a plurality of adjacent crystals, and the sodium chloride crystals are bonded to each other to cause so-called low temperature consolidation. Particles of sodium chloride solidified at low temperature have little fluidity and are difficult to handle.

In regions such as Hokkaido where the temperature drops below freezing in winter, in order to prevent the low temperature solidification of the sodium chloride particles, for example, indoors where the room temperature is kept higher than the freezing point by using a jet heater or the like. It should be stored in a container, warmed at the time of use, destroyed with a hammer etc. to break up the solidified sodium chloride particles, or stored in a dissolved state when dissolving sodium chloride at the time of use. It is being appreciated.

[0004]

However, when the amount of sodium chloride is large, it is not economical to store it indoors as described above because heating equipment is required. In addition, it is troublesome to operate and complicated to warm up or break a solidified sodium chloride particle group with a hammer or the like during use. Further, storage in a dissolved state can be applied only when it is dissolved at the time of use. Therefore, it is desired that the sodium chloride particles can be prevented from solidifying at low temperature.

In particular, when sodium chloride is used as an antifreezing agent for preventing freezing of road surfaces, low temperature solidification often becomes a problem. That is, this antifreezing agent is loaded and sprayed on the spray truck. Therefore, since a large amount of the antifreezing agent is used at a time, dozens of 1-ton packaging bags are usually stacked and stored outdoors. In addition, when the packaging unit is large in this way, the weight of the antifreezing agent itself tends to cause solidification. Therefore, the antifreezing agent often solidifies at a low temperature.
The low-temperature solidified antifreeze must be crushed before it can be loaded into the spray truck. In addition, during the spraying of the antifreezing agent, the sodium chloride particles, which are the antifreezing agent, loaded on the spray truck may be solidified at a low temperature and may not be sprayed. In recent years, the use of spiked tires has been banned to prevent dust pollution, so the demand for sodium chloride as an antifreezing agent has increased rapidly, and there is a strong demand for antifreezing agents that do not freeze at low temperatures.

According to the present invention, it is possible to prevent the sodium chloride-containing substance containing sodium chloride as a main component from being solidified at a low temperature, and there is no need to store it indoors or to destroy the solidified sodium chloride particles. Provided is a method for treating a sodium chloride-containing substance to prevent low temperature solidification.

[0007]

According to the present invention, at least one compound that releases ions having a heat of hydration larger than that of Na ⁺ is added to a sodium chloride-containing substance containing sodium chloride as a main component. Provided is a method for treating a sodium chloride-containing substance to prevent the characteristic low temperature solidification.

The present invention will be described in more detail below.

In order to prevent the low temperature solidification of the sodium chloride-containing substance, (i) the product temperature should not be lower than 0.1 ° C,
(Ii) For example, it is conceivable to prevent the formation of sodium chloride dihydrate by removing the water adhering to the surface of the sodium chloride crystal by heating and drying. But,
All of these methods require a great deal of cost and are not practical.

Therefore, the present inventors have found that sodium chloride dihydrate is produced due to the presence of ions having a heat of hydration larger than Na ⁺ (sodium ion) in the water attached to the surface of sodium chloride. Find that you are prevented,
The present invention has been completed.

That is, as described above, sodium chloride dihydrate is produced by decreasing the solubility of sodium chloride due to a decrease in temperature and precipitating from water adhering to the crystal surface saturated with sodium chloride.

Therefore, ions having a larger heat of hydration than sodium ions (hereinafter referred to as additive ions) are added to the sodium chloride-containing substance. The heat of hydration is a change in the amount of heat that occurs when a solute is infinitely diluted with water as a solvent under constant pressure, and corresponds to the binding energy of the solute to water. Therefore, the larger the heat of hydration of the ion, the larger the binding energy between the ion and the water molecule. The additive ion has a larger heat of hydration than the sodium ion, and has a larger binding energy with the water molecule than the sodium ion. Therefore, at room temperature, when the additive ions are dissolved in water saturated with sodium chloride adhering to the surface of the sodium chloride crystal, the additive ions and water molecules bond to form a hydrate. This hydrate behaves like one ion in water. Due to the formation of such hydrates, sodium chloride in water is available for dissolution,
Since the amount of free water decreases, the solubility of sodium chloride in the water decreases. As a result, excess sodium ions are deposited as sodium chloride.

When the product temperature of the sodium chloride-containing substance drops to below freezing point, the untreated sodium chloride-containing substance adheres to the surface of sodium chloride crystals, and sodium chloride significantly reduces the solubility of sodium chloride in saturated water. To do. Therefore, sodium chloride 2
A hydrate is formed.

On the other hand, a sodium chloride-containing substance added with an ion having a larger heat of hydration than the above-mentioned sodium ion, when the product temperature drops to below freezing point, is sodium chloride of water adhering to the surface of the sodium chloride crystal. The decrease in solubility is smaller than that in the untreated case. Also,
Since water forms hydrates with additive ions, there is less free water available when sodium chloride precipitates. Therefore, generation of sodium chloride dihydrate from the water is suppressed, and low-temperature solidification can be prevented.

Here, the larger the amount of additive ions added, the smaller the decrease in the solubility of sodium chloride in the water adhering to the crystal surface due to the decrease in the product temperature. In addition, as the amount of the additive ions added increases, the amount of water available for forming sodium chloride dihydrate in the water adhering to the crystal surface decreases, so the amount of sodium chloride dihydrate formed decreases. Become. Also, the larger the heat of hydration of the additive ions, the greater the effect of preventing low temperature solidification.

Sodium chloride solidifies even at room temperature.
Conventionally, disodium phosphate, potassium ferrocyanide, magnesium carbonate, magnesium chloride and the like have been used as anti-caking agents for preventing caking of sodium chloride at room temperature (hereinafter referred to as "caking at room temperature"). But,
It is known that room temperature solidification occurs due to precipitation of fine crystals of sodium chloride due to absorption and release of water on the surface of sodium chloride crystals [D. W.
Kaufmann: Sodium Chloride (1993), 4th
Page 68 (Translated and published by Salt Science Research Foundation), Tsutomu Masawa: Mol, Vol. 7. No. 7, P.I. 32 (19
69)]]. Therefore, the mechanism of room temperature consolidation is
Since it is different from the case of low temperature solidification, the anti-caking agent for preventing room temperature solidification is not all effective in preventing low temperature solidification. That is, in order to prevent low-temperature solidification, it is necessary that the ion liberated when the additive is dissolved in the water adhering to the surface of the sodium chloride crystal has a larger heat of hydration than the sodium ion.

Table 1 shows whether or not various additives have the effect of preventing room temperature solidification and low temperature solidification, and the heat of hydration of the additive ions.

[0018]

[Table 1]

The additive ion added to the sodium chloride-containing substance is not particularly limited as long as it has a larger heat of hydration than sodium ion. The heat of hydration of sodium ions is 96.5 kcal / mol. As an additive ion,
For example, alkaline earth metals such as magnesium ion (Mg ²⁺ ), calcium ion (Ca ²⁺ ), strontium ion (Sr ²⁺ ), aluminum ion (A
l ³⁺ ), iron (I) or iron (II) ions (Fe ²⁺ , Fe
³⁺ ), nickel ion (Ni ²⁺ ), manganese ion (M
Inorganic cations including metal ions such as n ²⁺ ), zinc ions (Zn ²⁺ ) and copper ions (Cu ²⁺ ) can be used.

Addition of the additive ion is carried out by adding a compound capable of liberating the ion to the water adhering to the surface of the sodium chloride crystal (hereinafter referred to as additive) to the sodium chloride-containing substance. The additive is selected in consideration of economy, use of the sodium chloride-containing substance, and the like.
For example, magnesium chloride (MgCl ₂ ), calcium chloride (CaC
l ₂ ) is preferred. Bitter soup containing magnesium chloride as a main product, which is a by-product of salt production, is also suitable. In addition, an aluminum compound such as aluminum chloride (AlCl ₃ ), an iron compound such as ferric chloride (FeCl ₃ ), a nickel compound such as nickel chloride (NiCl ₂ ) and the like can be used. Further, at least two kinds of these compounds may be added together to the sodium chloride-containing substance.

The method for adding the above-mentioned additive to the sodium chloride-containing substance is not particularly limited, but it is most preferable to add the solution after dissolving the additive in a suitable solvent in that both can be easily mixed uniformly. However, it may be added as powder.

In principle, the amount of additive added is the amount of hydrate,
That is, it should be determined by the molar concentration of each additive. When the content of sodium chloride-containing substance is 0.05% by weight, the effect of reducing the solidification strength due to low-temperature solidification appears, and the addition amount is preferably 0.1% by weight or more. The upper limit of the amount added is not particularly limited, but it should be determined in consideration of economic efficiency. In addition, when determining the amount to be added, the type of additive and the use of the sodium chloride-containing substance should be taken into consideration.

Examples of the sodium chloride-containing substance to which the method for treating a sodium chloride-containing substance for preventing low-temperature solidification of the present invention is applied include salt, a road surface antifreezing agent,
Examples include livestock feed compounding agents, soda industrial salt, food processing salt and the like. In particular, sodium chloride, which is used as a road surface anti-freezing agent, is often stored outdoors in a large amount below freezing as described above, and is also sprayed in large quantities on the road surface. Therefore, by applying the treatment of the present invention, it is possible to prevent low-temperature solidification in advance, and it is not necessary to destroy the solidified sodium chloride particles before the spraying of the road surface deicer, and again during the spraying work. It is prevented that the sodium chloride particles are solidified at a low temperature and cannot be sprayed.

More specifically, the road surface antifreezing agent has a composition of, for example, about 97% by weight of sodium chloride, about 1% by weight of other salts, and about 2% by weight of water. By adding the above-mentioned additives to such a road surface antifreezing agent, low temperature solidification can be prevented.

[0025]

EXAMPLES Examples of the present invention will be described in detail below.

1. Changes in Solubility of Sodium Chloride Due to Additives Changes in solubility of sodium chloride were investigated when potassium chloride, magnesium chloride, calcium chloride and aluminum chloride were added to water at 0.5 ° C. at different concentrations. The results are shown in the characteristic diagram shown in FIG. As is clear from FIG. 1, it was confirmed that the higher the concentration of the additive, the lower the solubility of sodium chloride. Therefore, by adding an additive to the sodium chloride particle group, the number of free water molecules that can be used for dissolution of sodium chloride in the water is reduced, so that the solubility of sodium chloride in the water adhered to the surface of the sodium chloride crystal is reduced. However, as a result, it was inferred that excess sodium was precipitated as sodium chloride.

2. Change in Solubility of Sodium Chloride by Additives at Each Temperature When magnesium chloride was added to water at different concentrations,
The solubility of sodium chloride in the aqueous solution at 0.5, -5 and -15 ° C was examined, respectively. The result is shown in the characteristic diagram of FIG. As is clear from FIG. 2, it was confirmed that the higher the concentration of magnesium chloride, the smaller the difference in the solubility of sodium chloride due to the temperature difference. Therefore, the addition of the additive almost eliminates the decrease in the sodium chloride solubility of the water adhering to the surface of the sodium chloride crystal due to the decrease in the product temperature of the sodium chloride particles, and prevents the formation of sodium chloride dihydrate. It was speculated that.

3. Change in production amount of sodium chloride dihydrate due to additive Add sodium chloride to an aqueous solution of magnesium chloride or calcium chloride prepared at different concentrations at 0.5 ° C. until saturated, and further add sodium chloride to 100 g of water. After adding at a rate of 25 g, add each aqueous solution to -15 ° C
The mixture was stirred for 72 hours in the constant temperature bath. Cooled. The amount of sodium chloride dihydrate produced thereby was measured. The result is shown in the characteristic diagram of FIG. As is clear from FIG. 3, the higher the concentration of the additive, the more sodium chloride 2
It was confirmed that the amount of hydrate produced was reduced.

4. Change in solidification strength of sodium chloride particle group due to additives Add potassium chloride, magnesium chloride, calcium chloride, and aluminum chloride to the pulverized salt having an average particle diameter of 1100 μm at different ratios to the pulverized salt, and uniformly Mixed. These additives were added by dissolving the additives in water so that the water content of the salt after treatment was 3% by weight. 65 g of these treated salts were placed in a cylindrical container having an inner diameter of 40 mm, and a load of ² kg / cm ² was applied to produce a test piece. After leaving these test pieces in a constant temperature bath at -15 ° C for 48 hours, the breaking load was measured according to JIS-R5201, and this was taken as the consolidation strength. The results are shown in the characteristic diagram of FIG.

As is clear from FIG. 4, when magnesium chloride, calcium chloride and aluminum chloride were added, it was confirmed that the larger the amount of these additives added, the lower the consolidation strength of the treated salt. It was In particular, it was found that the solidification strength of the treated salt was remarkably lowered when the addition ratio was 0.1% by weight or more. On the other hand, with respect to potassium chloride, which has a smaller heat of hydration than sodium ion, no decrease in the caking strength was observed at any addition amount of treated salt.

5. Effect of Preventing Low Temperature Solidification by Various Additives To the pulverized salt having an average particle diameter of 1100 μm, the additives shown in Table 2 were separately added at a ratio of 0.1% by weight based on the pulverized salt, and uniformly mixed. These additives were added by dissolving the additives in water so that the water content of the salt after treatment was 3% by weight. 65 g of these treated salts were placed in a cylindrical container having an inner diameter of 40 mm, and a load of ² kg / cm ² was applied to produce a test piece. After leaving these test pieces in a constant temperature bath for 48 hours, the breaking load was measured according to JIS-R5201, and this was defined as the consolidation strength. The results are shown in Table 2. The heat of hydration of the ions liberated from these additives is also shown in Table 2 [Chemical Society of Japan; Chemical Handbook Basic Edition II, 808 (1966) Maruzen].

[0032]

[Table 2]

As is clear from Table 2, a decrease in the caking strength was observed by the treatment with the additives except for potassium chloride, which has a lower heat of hydration of the ions liberated from the additives than sodium ions. No difference was observed in the effect whether the additive was chloride or sulfate. Also,
Strontium compounds, manganese compounds, copper compounds, zinc compounds appear to be less effective. However, since the ions liberated from these have a relatively large atomic weight, the number of hydrates is smaller than the magnesium compounds and aluminum compounds in which the atomic weight of the liberated ions is relatively small when added on a weight basis. . Therefore, if the addition amount is the same based on the molar concentration, there is no great difference in the effects of both.

6. Application to the production of pulverized salt In the production process of pulverized salt, magnesium chloride dissolved in water and powder are added separately to pulverized salt (average particle size 1100 μm) to be conveyed on a belt conveyor after pulverization. Then, it was packaged in a 1-ton packaging bag. The water content of the ground salt after the treatment was 3% by weight, and the amount of magnesium chloride added was as shown in Table 3. The crushed salt contained in these packaging bags was stored in a refrigerator at -15 ° C for 7 days, and then the packaging bag was opened, and the consolidation strength of the crushed salt was measured according to the method described in Test 5 above. The results are shown in Table 3.

[0035]

[Table 3]

As is clear from Table 3, the effect of preventing low temperature solidification by the addition of magnesium chloride was confirmed in the actual manufacturing process of the pulverized salt. Further, no significant difference was observed in the effect whether the addition method was solution addition or powder addition.

[0037]

As described above, according to the method for treating a sodium chloride-containing substance for preventing low temperature solidification of the present invention, an ion having a larger heat of hydration than sodium ion is added to the sodium chloride-containing substance. As a result, it is possible to prevent the sodium chloride-containing substance from solidifying at a low temperature. For this reason, since heating to maintain the product temperature of the sodium chloride-containing substance above the freezing point is unnecessary,
Equipment costs and fuel costs can be reduced. In addition, it does not take time and effort to disintegrate the low temperature solidified sodium chloride-containing substance before or during use. Further, even if the packaging unit becomes large, it can be stored outdoors, and even if the sodium chloride-containing substance itself is weighed, it does not easily congeal, so there is no restriction on the storage location or packaging unit.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing the relationship between additive concentration and sodium chloride solubility.

FIG. 2 is a characteristic diagram showing the relationship between magnesium chloride concentration and sodium chloride solubility.

FIG. 3 is a characteristic diagram showing the relationship between the additive concentration and the production amount of sodium chloride dihydrate.

FIG. 4 is a characteristic diagram showing the relationship between the additive concentration and the solidification strength of ground salt.

Claims (4)

[Claims] 1. To prevent low-temperature solidification, which comprises adding at least one compound containing an ion having a heat of hydration larger than Na ⁺ to a sodium chloride-containing substance containing sodium chloride as a main component. Method for treating substances containing sodium chloride. 2. The method for treating a sodium chloride-containing substance for preventing low-temperature solidification according to claim 1, wherein the amount of the compound added is 0.05% by weight or more based on the total amount of the sodium chloride-containing substance. 3. The sodium chloride-containing substance for preventing low temperature solidification according to claim 1, wherein the amount of the compound added is 0.1% by weight or more based on the total amount of the sodium chloride-containing substance. Processing method. 4. The ions are Al ³⁺ , Mg ²⁺ , C
In order to prevent low temperature solidification according to claim 1, which is at least one selected from the group consisting of a ²⁺ , Sr ²⁺ , Mn ²⁺ , Cu ²⁺ , Zn ²⁺ , Fe ³⁺ and Ni ^2+. Method for treating substances containing sodium chloride.