JPS58156532A - Preparation of calcium hydroxide in high quality - Google Patents

Abstract

PURPOSE:To prepare calcium hydroxide of high purity at a low cost, by reacting calcium chloride with calcium hydroxide and/or calcium oxide, and decomposing only the resultant coarse particulate part of the calcium oxychloride. CONSTITUTION:Calcium oxychloride is crystallized from calcium chloride and calcium hydroxide and/or calcium oxide in an aqueous solution, and classified to give coarse particulate calcium oxychloride, which is then decomposed to prepare calcium hydroxide of high purity at a low cost without the influence of the variation in the kinds and content of impurities in the raw material. The calcium hydroxide or calcium oxide is preferably formed with water into a calcium hydroxide slurry, which is then classified to remove coarse sand, etc. and use only the coarse particulate part. Preferably, the calcium oxychloride is prepared by crystallizing as tribasic calcium chloride hydrate capable of easily forming coarse crystals containing no impurity.

Description

[Detailed Description of the Invention] In detail, calcium chloride, calcium hydroxide and/or
Alternatively, the present invention relates to a method for producing high-purity calcium hydroxide by obtaining calcium oxychloride from calcium oxide in an aqueous solution and decomposing the calcium oxychloride.

Calcium hydroxide is a strong alkali and neutralizing agent.

Used as a wastewater treatment agent in water supply and sewage systems, for pollution prevention, as a raw material for the production of bleach, as well as as a soil conditioner, construction materials, and sugar refining. It is a compound that is consumed in large quantities in a wide range of fields, such as food additives.

Calcium hydroxide is generally produced by burning limestone with coke or heavy oil to produce quicklime, and then digesting this quicklime with water to produce calcium hydroxide.

This method can produce calcium hydroxide cheaply and in large quantities, but because it directly uses a natural product called limestone as a raw material, there are many types and amounts of impurities derived from limestone, and there are many types and amounts of impurities derived from limestone. Due to the addition of impurities derived from chemicals, its purity is extremely low compared to general chemicals.

Therefore, even though it is the same strong alkali, it is used in crude fields that do not require high purity compared to caustic soda.
Or, it is limited to fields that have a method for removing impurities.

Impurities include solid and dissolved impurities, but most impurities exist inside calcium hydroxide particles and cannot be removed even if calcium hydroxide particles are washed with an aqueous solution or an organic solvent.

Impurities include CO2 (i.e. caco), sto,
, A40. .

Fe, O,, Mg0.804 (Ca80. or cas
o, ), etc., and these have a total weight of 1 to 5 wt-.

However, the amount and ratio vary widely depending on the production area of limestone and the type of coke or heavy oil. Moreover, there are Or, Mn, Ml, Cu, and Ph3 as trace metals, and these are contained in about 10 to 1.000 ppm.

Methods for obtaining high-purity calcium hydroxide from low-purity substances such as kernels include reacting high-purity caustic soda with high-purity calcium chloride, and treating a suspension of calcium hydroxide in a furnace. There are methods of concentrating the filtrate, but this is not economically viable except in very special cases.

That is, caustic soda has conventionally been used as a highly pure strong alkaline agent except in crude fields such as wastewater treatment. However, the price of caustic soda is rising and becoming tight due to the recent rise in energy costs and falling demand for chlorine. Under these circumstances, limestone, the main raw material for calcium hydroxide, is one of the few self-sufficient natural resources in Japan, and its supply is extremely stable. The appearance of calcium is desired in various fields.

In view of the above, the inventors of the present invention have conducted intensive studies to establish a method for producing calcium hydroxide with high purity and at low cost, regardless of the type and content of impurities in the raw materials. And/or after reacting calcium oxide with calcium chloride to generate calcium oxychloride crystals, classifying to obtain coarse particles of calcium oxychloride, and decomposing this to calcium hydroxide, high purity hydroxide can be obtained. They discovered that calcium can be produced and completed the present invention.

That is, the present invention crystallizes calcium oxychloride from calcium chloride, calcium hydroxide, and/or calcium oxide in an aqueous solution, classifies the calcium oxychloride to obtain coarse particles of calcium oxychloride, and then obtains the coarse particles. The present invention provides a method for producing high-purity calcium hydroxide, which is characterized in that calcium hydroxide is obtained by decomposing calcium oxychloride.

The present invention will be explained in more detail.

The essential requirements of the present invention are to crystallize calcium oxychloride from calcium chloride, calcium hydroxide, and/or calcium oxide in an aqueous solution, and to classify the calcium oxychloride to obtain coarse particles of calcium oxychloride. shall be.

As mentioned above, in calcium oxide produced from limestone and/or calcium hydroxide obtained by hydrating the calcium oxide, impurities are evenly distributed in these particles, and most of them are insoluble. Therefore, it cannot be separated by washing with water or organic solvents, or by mechanical operations such as classification.

However, according to studies conducted by the present inventors, when calcium oxychloride is produced by reacting calcium oxide and/or calcium hydroxide with calcium chloride, impurities contained in the raw materials are liberated as extremely fine particles. It was also found that the produced calcium oxychloride has very good crystal growth, resulting in extremely large crystals compared to fine impurity particles.

This release of fine particle impurities is because the impurities contained in calcium oxide and/or calcium hydroxide originally exist as extremely fine particles, and once calcium oxide and/or calcium hydroxide is This is thought to be because it melts and changes into calcium oxychloride, liberating impurities at this time.

A further important finding is that no free impurities are incorporated into the calcium oxychloride crystals. The reason for this is probably calcium hydroxide.

We believe that this is due to the fact that the crystal forms of calcium oxide and calcium oxychloride are different, and that impurities are essentially difficult to incorporate into the crystal, and that crystal growth is good and physical adhesion to the crystal surface can be prevented. There is.

As is clear from the above explanation, the product obtained is a mixture of calcium oxychloride crystals and fine particles of impurities, but there is a very large difference in particle size, and it is easy to eliminate impurities by adjusting the classification pressure. Crystals of calcium oxychloride can be obtained.

6 That is, the main purpose of the above requirements is not only to crystallize calcium oxychloride, but also to suspend and elute impurities contained in calcium hydroxide and/or calcium oxide in an aqueous solution, and to dissolve the crystallized oxychloride. The purpose is to classify calcium chloride and separate floating and eluted impurities from calcium oxychloride.

What is important in ζζ is the separation of impurities, that is, the crystallization of calcium oxychloride. In crystallization, a) calcium hydroxide and/or calcium oxide must be completely converted to calcium oxychloride, leaving no unreacted calcium hydroxide and/or calcium oxide containing impurities;
These are to prevent the crystallization of aggregated crystals of calcium oxychloride that easily envelops impurities, and to prevent the crystallization of fine calcium oxychloride that is difficult to classify from /9 impurities. For this purpose, it is important to adjust the crystallization rate of calcium oxychloride, and the crystallization rate is 20 to 2501F/hr*
j is desirable.

In addition, when crystallizing calcium oxychloride, an aqueous solution of calcium chloride or an aqueous solution of calcium chloride and sodium chloride, such as distilled V solution of the ammonia soda method (Solvay method), or a drainage solution of highly bleached powder can be used. But that's fine. In short, 4 for the crystallization of 1-oxycalcium chloride!
It is sufficient that calcium chloride with a certain pH is present.

Calcium hydroxide and/i or calcium oxide are
B) Slaked lime or lime milk obtained by digesting quicklime obtained by burning limestone, I) Those containing other components, such as calcium oxide obtained by burning dolumite, and water obtained by further digesting this. Examples include, but are not limited to, calcium oxide, and (2) calcium hydroxide produced by a reaction, such as a reaction between sodium hydroxide and calcium chloride.

In addition, calcium hydroxide and/or calcium oxide may be used, but it is preferable to make a slurry of calcium hydroxide in advance with water or an aqueous solution containing calcium chloride, and then classify this slurry to obtain water in the fine particle portion. A slurry of calcium oxide may also be used. In this case, coarse sand, coke residue, etc. can be removed. For classification, a Ceratra, a liquid cyclone, a wet sieve, etc. can be used.

A typical example of calcium oxychloride to be crystallized is tribasic calcium chloride hydrate ((acl, !!ca(
on), *si, o, s-11~1s), -Basic calcium chloride hydrate (OaO4αca(on),
eSR, O, s -1 to 4).

Tribasic calcium chloride tetrahydrate is easy to crystallize, and only 4
It is a desirable calcium oxychloride because it is a single crystal and easily forms coarse crystals, making it easy to separate from impurities. This crystallization can be performed under relatively mild conditions. That is, when the aqueous solution is a calcium chloride solution, the calcium chloride concentration is 1
0-30wtl.

Temperature 10~As℃, slurry, -concentration 10~40wt9g
The crystallization rate is 20 to 2509/'hr-1.

If salts other than calcium chloride coexist, reduce the calcium chloride concentration by the amount of salt in the pot.

Also, calcium oxychloride is cac4m cm (on)
, aH,O, the crystallization conditions are calcium chloride concentration 30
~40wt'j, temperature [2o ~120''C, threary concentration 10~40wt-dashi, crystallization rate #i20~25
It is 09/br-1.

The crystals obtained in this way are single crystals and contain almost no impurities of 10 microns or more, even several millimeters in size.) The impurities from the raw materials are mostly suspended as fine particles, and some are dissolved.

Furthermore, if seed crystals are added during crystallization of calcium oxychloride, the concentration of impurities contained in calcium oxychloride can be further reduced. This is also a fact discovered for the first time by the inventors. This is believed to be because the presence of seed crystals allows calcium dioxychloride to grow slowly, making it easier to separate it from impurities. The seed crystals preferably have an average particle diameter of 50 microns or less, more preferably 30 microns or less, and the amount added is preferably 'Aoa-'A of the production amount.

Seed crystals may also be prepared separately by the reaction of calcium hydroxide and calcium chloride, and the resulting calcium oxychloride may be ground and used.

Furthermore, although either a batch method or a continuous method can be applied to the crystallization method, a continuous method is preferable from the viewpoint of production efficiency.

Next, in order to separate calcium oxychloride and impurities, the relative coarse particles and fine particles distributed in the slurry are classified. Classification is extremely easy since impurities are fine and calcium oxychloride is coarse, and impurities can be almost completely removed. As a classification device, a Ceratra, a liquid cyclone, a wet sieve, etc. can be used, and a nine-crystallization and classification tank can also be used for both crystallization and classification. Dissolved impurities can also be removed by using a washed mother liquor during selection and classification.

The coarse particles of calcium oxychloride thus obtained may be directly decomposed to form calcium hydroxide, but may be subjected to K filtration before that. Dissolved impurities such as FjlK are completely removed. In addition, the filtrate at this time can be used as a washing mother liquor during classification.

Furthermore, the present invention requires that calcium oxychloride in the coarse particles be decomposed into calcium hydroxide.

The main purpose here is to separate calcium oxychloride to precipitate calcium hydroxide and dissolve calcium chloride.

Calcium oxychloride is easy to decompose, and there are various methods for decomposing it. For example, when decomposing tribasic calcium chloride hydrate, the temperature is increased or the salt concentration in the solution is decreased.

There is a correlation between temperature and salt concentration; the higher the salt concentration, the higher the temperature will be maintained. When decomposing in a calcium chloride aqueous solution, it can always be decomposed at a salt concentration of 30 wt- or less and a temperature of 40°C or more.

Furthermore, 0aC4.Ca(on)t.40 can also be decomposed in the same manner as tribasic calcium chloride hydrate.

Either L-batch type or continuous type can be applied as the decomposition type.

The concentration of calcium hydroxide obtained by decomposition is 5 to 30
vt- is appropriate. When calcium hydroxide is crystallized by decomposition, minute amounts of impurities contained in the coarse particles of calcium oxychloride float in the solution or are eluted and separated from calcium hydroxide. Most of the floating impurities are fine, several microns or less in size. Therefore, when calcium hydroxide is several microns or larger, impurities can be further reduced by classifying it to obtain coarse particles. Further, coarse impurities can be removed by classifying and removing coarse portions. For classification, commonly used Ceratra, liquid cyclone, wet sieve, etc. can be applied, and a classification crystallization type that serves both crystallization and classification can also be applied.

This classification removes 20-90% of impurities contained in calcium oxychloride. The removal rate of impurities increases when the calcium hydroxide crystal is a single crystal and is large, or when seed crystals are added during the crystallization of calcium hydroxide.

In this way, a slurry made of highly pure calcium hydroxide is obtained, and the slurry may be used as it is, or may be rolled into a cake, or further dried into a powder.

Drying, fluidized drying, belt dryer, etc. can be applied.

The following three points can be mentioned as unexpected features of the present invention. 1) Calcium hydroxide obtained by decomposition eventually becomes crystalline and has the shape of a hexagonal plate or a hexagonal column. Therefore, this calcium hydroxide is strong,
Dry products generate almost no dust. Moreover, it has a large bulk density and is easy to handle. 2) The obtained calcium hydroxide is active and highly reactive. This seems to be due to the extremely high purity of K. 5) The particle size of the obtained calcium hydroxide can be adjusted over a wide range from less than 1 micron to more than 100 microns. That is, by keeping the temperature higher or the salt concentration lower, the decomposition rate can be increased and the particle size can be reduced. Furthermore, if the decomposition rate is extremely high, for example, if the decomposition is completed within 5 minutes, an aggregate of calcium hydroxide that remains in the form of calcium oxychloride can be obtained.

These functionalities allow the range of applications of the calcium hydroxide of the present invention to be further expanded.

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

(1) Remove both insoluble and dissolved impurities contained in calcium hydroxide and/or calcium oxide,
High purity calcium hydroxide is obtained.

The amount of impurities in the obtained calcium hydroxide is CO.

α1Ls or less, 810.200 ppm or less, A/,
0.1100ppm or less, We, 0.50ppm or less, MgO500ppm or less, 110.100ppm
You can do the following.

Mortar) It is economical and does not require special drugs.

0) It is economical because there are no sophisticated unit operations and the process is simple.

(4) The obtained calcium hydroxide is crystalline.

Perhaps for this reason, compared to conventional products, dried products generate very little hard dust and have a large bulk density, making them easy to handle.

(6) The resulting calcium hydroxide is active and highly reactive. This seems to be due to the extremely high purity.

(@ The crystal grain size of the obtained calcium hydroxide can be adjusted over a wide range.

That is, while conventional products have amorphous shapes of several microns, the present invention can freely produce crystalline products ranging from 1 micron or less to 100 microns or more.

Next, examples of the present invention will be shown, but the present invention is not limited thereto. In addition, all parts and - shown in Examples and Comparative Examples are based on weight.

The analysis method was as follows.

CO3 Volumetric method using a small force type anhydrous carbon dioxide quantitative device (J-K8R90
11) After melting the precipitate by the 810° perchloric acid method in an alkali, colorimetric determination using 1-amino-2-naphthol-4musulfonic acid (
40 m After alkali-melting the precipitate resulting from hydration with ammonia in water, colorimetric determination with oxy/ (using a spectroscopic straight needle) 1., 0° Orthophenanthroline colorimetric determination (using a spectroscopic straight needle) MgO atom Nephelometry (using a spectroscopic straight needle) using 80° Ba804 purification, or
Mn, Ni Flameless atomic absorption method Example 1 A separable flask with an overflow tube equipped with a stirrer (1 t) 20 ml of lime milk obtained by calcining and digesting K limestone with coke (the impurity concentration is shown in Table 1). 1459
/hr, 5 sss calcium chloride aqueous solution to 215
It was introduced continuously at a rate of F/hr and the temperature was maintained at 25°C.

From the overflow pipe, the length is 20~500μ9, the width is 10~
A slurry of 20-diamond-shaped tribasic calcium chloride hydrate with a thickness of 5 to 200μ was produced for 56097'hr.
Obtained with. At this time, astringent brown impurities of several microns or less were floating in the mother liquor.

Next, slurry f of this tribasic calcium chloride hydrate
&lF into a t5t cylindrical classifier (cross-sectional area: 44cIl) with an inverted conical bottom (cross section area: 44 cIl), and a 20-calcium chloride aqueous solution was continuously poured into the classifier from the bottom at a rate of 4.8 // hr.
Introduced time.

In this way, a slurry containing 170 g of coarse tribasic calcium chloride hydrate was obtained in the classifier, and the slurry concentration was 2.
The supernatant liquid was removed by decantation and discarded as indicated by 0-.

Next, the slurry of coarse tribasic calcium chloride hydrate obtained by classification was placed in a separable flask with an overflow tube equipped with a 500 m stirrer.
The temperature was maintained at 40°C.

From the overflow pipe, the width is 5 to tO (1, the thickness is 5 to
30J hexagonal plate-shaped crystalline calcium hydroxide 89
g slurry was obtained at 2009/hr. This slurry is processed in a centrifuge at 300 Orpm for 1 minute, and then washed with 100 gK of calcium hydroxide for 1 minute with 209% water to obtain a calcium hydroxide cake with a water content of 10-. Table 1 shows the impurity concentration of the obtained calcium hydroxide.
Shown below.

The washing liquid was adjusted to CIL0420- with a washing liquid and used as a liquid introduced from the bottom of the classifier.

(9) The slurry flowing out from the upper part of the classifier (hereinafter referred to as flowing slurry) was passed through an a-S glass filter, and the concentration of impurities in the solid matter was measured.

The results are shown in Table 1.

Example 2 All procedures were carried out in the same manner as in Example 1 except that 20-scale milk of lime was used as the fine grain portion obtained by processing 20-scale milk of lime through a 200-mesh (Tyler Tsuta) sieve. .

The crystal forms of the obtained 93-basic calcium chloride hydrate and calcium hydroxide were the same as in Example 1, and the impurity concentration of calcium hydroxide was shown in Table 1.

Example 5 In the method of Example 2, seed crystals with a length of 10 to 30 μm and a thickness of 5 to 10 μm were added to the crystallization tank of tribasic calcium chloride hydrate.
J1. All operations were the same except that a slurry of 2091 tribasic calcium chloride hydrate having a thickness of 2-5 microns was introduced at 7 F/hr.

The resulting 93 basic calcium chloride hydrate has a length of 30 to 7
00μ1 width 10-300μ, thickness 10-200μ, yield of tribasic calcium chloride hydrate by classification is 9
Calcium hydroxide obtained by decomposition is crystalline and has a width of 5 to 1504 mm. The thickness was 5 to 50 μm, and the moisture content in the cake after centrifugation was 79 g. The impurity concentrations are shown in Table 1.

Example 4 Distillation waste liquid (OaC) of ammonia soda method (Solvay method)
/, 12%, Na015%) I 00 parts with quicklime obtained by calcining limestone with coke (the impurity concentration is shown in Table 1).
) was added and mixed, and after death, it was processed through a 200 mesh sieve to obtain a slurry of calcium hydroxide in the fine particles.

The composition is ca (oH), 10-.

C! LC4'' 0%, NaCl1L &-.

Next, the slurry of calcium hydroxide in the fine part was continuously introduced into a separable flask with an overflow tube equipped with a 1 ton stirrer at a rate of 322 f/hr and sodium chloride at a temperature of 18". Maintained CK.

Over 70 - Length 10~600μ9 Width 10~
400μ, thickness 5-150μ diamond-shaped tribasic calcium chloride hydrate 22-sla IJ- is 56097'h
Obtained with r.

Next, this slurry of tribasic calcium chloride was classified in the same manner as in Example 1 to obtain a slurry of coarse particles of tribasic calcium chloride hydrate. However, from the bottom of the classifier, Oa (
/47'lr, an aqueous solution of 20% NaCl was introduced. The temperature during the classification operation was 15-18°C.

Next, the obtained slurry of tribasic calcium chloride hydrate containing 20% coarse particles was decomposed in the same manner as in Example 1 to obtain a slurry of calcium hydroxide. However, the decomposition temperature Fi55℃
I went there.

From the overflow pipe, the width is 5 to 80μ, the thickness is 5 to 3
A slurry of 8 pieces of crystalline calcium hydroxide in the shape of a hexagonal plate of 0 μm was obtained, and this slurry was passed through a centrifuge using a V-filter.
After washing, a calcium hydroxide cake with a water content of 1291 was obtained. Table 1 shows the impurity concentration of the obtained calcium hydroxide.

Example 5 Limestone was calcined with coke in a separable flask with an overflow tube equipped with a 1 ton stirrer, and 30-milk of lime obtained by further digestion (the impurity concentration is shown in Table 1) was heated to 95
9. Ihr, 50- calcium chloride aqueous solution 29
59/br was introduced continuously and the temperature was maintained at 50°C. From the overflow pipe is a columnar cac4-ca with a length of 2 o~s OOμ, a convergence of 5~50Is, and a thickness of 5~50μ.
(oH), -H, oz o- slurry is 590 p/
Obtained in hr.

Next, this slurry of (!ac4・Ca(OH), aa, o) was operated in the same manner as in Example 1, and (acl,
- A slurry of ca(on)-5° was obtained. During this operation, an aqueous solution of calcium chloride at 40 DEG C. was introduced from the bottom of the classifier.

Next, the supernatant liquid of the slurry obtained by classification was extracted by a decantation machine to adjust the concentration to 50%,
The mixture was continuously introduced into a separable 7 flask equipped with an overflow tube equipped with a 500 sd stirrer together with water at 679/hr at 1359/hr. The temperature was maintained at 45°C.

From the overflow pipe, the width is 10 to 100μ and the thickness is 2
A slurry of crystalline calcium hydroxide in the shape of ~10jI hexagonal plates was obtained in 20097'hr.

This slurry was treated with a centrifuge in the same manner as in Example 1,
A cake of calcium hydroxide with a moisture content of 18-1 was obtained. Table 1 shows the impurity concentration of the obtained calcium hydroxide.

Example 6 In Example 3, 450 g of the slurry of calcium hydroxide obtained by decomposition was put into a 500-mm cylindrical classifier (cross-sectional area 25c11) with an inverted conical bottom, and 2091 calcium chloride was extracted from the bottom. The aqueous solution was introduced continuously at a rate of 75 r for 30 minutes and the effluent was discarded. Then, the flow rate from the bottom was increased by 1.2 μrK and continuously introduced for 1 hour. The supernatant water of the outflow slurry at this time was decanted using a decantation sink, the slurry concentration was increased, and the slurry was centrifuged in the same manner as in Example 1. The resulting calcium hydroxide cake was dehydrated using a hot air dryer, lightly loosened in a mortar to form a powder, placed in a test tube, and shaken to examine fluidity and generation of dust. As a result of visual observation, all were found to be highly free-flowing and no dust was generated.

Also, add 5 parts of calcium hydroxide powder obtained by drying to 1 part of water.
Suspend in a 200-cm beaker containing 0 (ld) and add 5 N/1 acetic acid 5 while stirring with a magnetic stirrer.
OWd was added all at once and the dissolved state of calcium hydroxide was observed.

As a result, the dissolution rate was 2 to 5 times higher than that of the raw material calcium hydroxide, even though the particle size was larger.

In particular, the dissolution rate of calcium hydroxide obtained in Example 6 was high.

Patent applicant: Toyo Ichida Kogyo Co., Ltd.

Claims (1)

[Claims] (1) Calcium chloride, calcium hydroxide and/or
Alternatively, calcium oxychloride is crystallized from calcium oxide in an aqueous solution, the skeleton calcium oxychloride is classified to obtain coarse grained calcium oxychloride, and then the core coarse grained calcium oxychloride is decomposed to produce calcium hydroxide. A method for producing high purity calcium hydroxide. ) The high purity calcium hydroxide according to claim 1, wherein the calcium hydroxide and/or calcium oxide is a slurry of fine particles of calcium hydroxide obtained by dividing a slurry of calcium hydroxide. Production method. (3) The method for producing high-purity calcium hydroxide according to claim 1 or 2, wherein the calcium oxychloride is tribasic calcium chloride hydrate.