JPH09156920A - Granule of metal iodide and method for granulating the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain granules of a metal iodide excellent in workability and having no harmful influence caused by scattering of coase particulates in various uses and to provide an effective granulation method of the metal iodide. SOLUTION: In granulating a metal iodide expressed by the formula, MIn [M is an alkali metal or an alkaline earth metal in the periodic table, I is iodine atom and (n) is 1 or 2], an aqueous solution of the metal iodide is continuously fed into a fluidized bed spray granulating dryer and dry-granulate the metal iodide.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to metal iodide granules used as raw materials for industrial chemicals, medicines, additives or materials in various fields, and a method for granulating the same.

[0002]

2. Description of the Related Art Metal iodides are used for various chemical reactions such as production of organic compounds by Sandmeyer reaction,
Of course, it is useful as a reagent for analysis,
Some of them are medicines as an anti-inflammatory agent, a diuretic, and an altering agent, and are materials for photographic emulsions, single crystal lenses for scintillation counters, etc., and recently, nylon fiber additives, liquid crystal displays (LCD), polarizing films. The number of applications as a raw material is increasing, and it is expected to supply inexpensive and high-purity metal iodide.

As a method for producing an aqueous solution of metal iodide, an iron reduction method of treating iodine with iron powder, formic acid,
Reduction with organic acids such as oxalic acid or its metal salts, reduction with hydrazine hydrate, reaction of iodine with metal hydroxides to remove by-produced metal salts of iodic acid, aqueous hydroiodic acid solution and metal water Various methods such as a neutralization reaction method with an oxide have been proposed, and an aqueous solution of metal iodide provided by any of these methods is concentrated by an appropriate method to precipitate a part of the metal iodide. The conventional formulation was a method of collecting powdery metal iodide by filtering, drying, pulverizing or completely drying and pulverizing.

However, since powdered metal iodides are scattered during handling, bag filters,
It requires extra capital investment such as a local exhaust system, and washing powder metal iodide scattered around with water causes troubles such as killing bacteria during treatment of activated sludge, and if stored, The workability was remarkably deteriorated because of a form such as blocking and caking which tend to be secondary aggregated.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and is excellent in workability in an effective granulation method of metal iodides and various uses, and has a harmful effect due to dust scattering. The aim is to provide metal iodide free granules.

[0006]

Means for Solving the Problems Accordingly, the present inventors have:
In order to achieve the above-mentioned object, the workability is excellent, and as a result of diligent study on the granules of metal iodide and the granulation method thereof, which does not have a harmful effect due to dust scattering, the conventional aqueous solution of metal iodide was concentrated by an appropriate method. Therefore, metal iodide is not hygroscopic, but rather is separated by filtration, drying, crushing or total solidification and crushing to collect powdered metal iodide. For example, by using the fluidized bed spray granulation method, which was considered to be unsuitable for granulation of metal iodide because of the tendency of secondary aggregation such as blocking and caking, It has been found that granules having a distribution) can be obtained, and the present invention has been completed based on this finding.

That is, the above-mentioned object is obtained by formula (1) MIn (wherein M is an alkali metal or alkaline earth metal of the periodic table of elements, I is an iodine atom, and n is 1). Or granulating the metal iodide represented by 2), an aqueous solution of the metal iodide is continuously supplied to a fluidized bed spray granulation dryer to dry granulate the metal iodide. This is achieved by a method for granulating a metal iodide, which is characterized in that

Another object of the present invention is that the granules of the metal iodide represented by the general formula (1) granulated by the above method are 99% by weight or more having a particle size of 250 μm or more. This is achieved by the characteristic metal iodide granules.

Further, an object of the present invention is that the metal iodide granules have characteristics such as a repose angle of 45 ° or less, a spatula angle of 55 ° or less, a compressibility of 25 or less, and a fluidity index of 80 or more. It is also achieved by the metal iodide granules described above.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In accordance with the embodiment of the present invention,
This will be described in detail below.

First, the concentration of the aqueous metal iodide solution used in the present invention is not particularly limited, but is preferably about the solubility of the metal iodide at room temperature. If it is made extremely dilute, extra energy is required to remove water and the cost increases, which is not preferable. The aqueous solution of metal iodide contains a fine powder of undissolved metal iodide which forms a colloidal substance. In addition, metal iodide is soluble in alcohol as well as water, but if a solvent other than water is used, it will harm the surrounding environment if the vaporized solvent is directly exhausted to the atmosphere. Direct exhaust is regulated from the viewpoint of environmental protection, and it is not preferable because it costs more because it is necessary to separately provide a device for recovering the solvent or burning the solvent. Further, as a method for producing an aqueous solution of a metal iodide, as described above, an iron reduction method of treating iodine with iron powder, formic acid, reduction with an organic acid such as oxalic acid or a metal salt thereof, reduction with hydrated hydrazine, A method produced by any method such as a method of reacting iodine with a metal hydroxide to remove a metal salt of iodic acid produced as a by-product, a neutralization reaction method of an aqueous solution of hydroiodic acid and a metal hydroxide is also used. be able to.

Further, as the kind of the metal iodide,
A metal represented by the general formula (1) MIn (wherein M represents an alkali metal or alkaline earth metal in the periodic table of the elements, I represents an iodine atom, and n represents 1 or 2). Iodide (hereinafter, also simply referred to as metal iodide) is applicable, and examples thereof include alkali metal iodides such as lithium iodide, sodium iodide, potassium iodide, rubidium iodide, and cesium iodide, and beryllium iodide. , Magnesium iodide, calcium iodide, strontium iodide, barium iodide and other alkaline earth metal iodides.

The metal iodide granulation method of the present invention is based on a fluidized bed spray granulation method using a fluidized bed spray granulation dryer. Here, the fluidized bed spray granulation method according to the present invention will be described in detail by taking as an example a case where an aqueous solution of potassium iodide is used as an aqueous metal iodide solution and the potassium iodide is dried and granulated continuously. .

First, the average grain size as a seed crystal is 60 to 97 μm.
The finely powdered potassium iodide of m was charged in a fluidized bed type spray bed granulator / dryer, and 100 to 15
Sending dry hot air at 0 ℃, flow rate 1.6 ~ 2.0m
/ S is adjusted to form a fluidized bed, and an aqueous potassium iodide solution is sprayed downward from the spray provided in the upper part of the bed to the spray air pressure of 2.5 to 5 kg / cm ² G,
The amount of sprayed air is adjusted to 15 to 48 Nm ³ and sprayed. By continuously supplying an aqueous potassium iodide solution at a constant flow rate so as to always form a fluidized bed and performing granulation drying, potassium iodide granules having a constant particle size (250 μm or more) can be continuously obtained. The quality (purity) of this product is almost the same as that of the seed crystal used or a fine powder product dissolved in an aqueous solution, and further, its granule strength and stability over time are sufficient.

As described above, in the granulation method using the fluidized bed spray granulator / dryer of the present invention, it is necessary to use the seed crystal that becomes the nucleus of the granule during granulation. As such seed crystals, it is preferable to use a fine powder of the same metal iodide as the granules to be granulated. The size (average particle diameter) of the seed crystals is usually 60 to 100 μm, preferably 65 to 90 μm. If the size of the seed crystal is less than 60 μm, it may cause clogging of the bag filter, and if it exceeds 100 μm, classification may be deteriorated and undried.

The type of the fluidized bed spray granulator / dryer used in the present invention is not particularly limited.
For example, a fluidized bed type in which a powder (seed crystal) is fluidized with hot air, and a liquid binder (aqueous solution, colloidal solution, etc.) which is the aqueous solution of the metal iodide of the present invention is sprinkled from this to perform agglomeration granulation In this case, in the case of a powder (seed crystal) having a particle size of about 150 μm or more, coating granulation is possible depending on the operating conditions), the same as the above case, but in the powder (seed crystal) in the layer A modified fluidized bed type that gives a circulating flow and discharges a relatively large grown granule by utilizing a classification effect, and a metal of the present invention from spraying coarse particles (seed crystals) by utilizing the characteristics of a spouted bed A spouted bed type granulating apparatus is used in which an iodide aqueous solution (colloidal solution) or the like is attached and coated granulation is performed at the same time while being dried.

In the granulation method using the fluidized bed spray granulator / dryer of the present invention, the operating conditions during granulation are:
The metal iodide aqueous solution is appropriately determined according to the type of metal iodide used, the type of fluidized bed spray granulation dryer, the particle size and particle size distribution of the target metal iodide, the flow characteristics, etc. The size of the liquid droplets during spraying (spray) (the size of the spray of the device) is usually 1 to 100.
μm, preferably 30 to 40 μm. When the size of the droplet is less than 1 μm, when the metal iodide is present in the aqueous solution in the form of colloid or the like, it may cause clogging of the spray or form seed crystals after spraying. It dries before adhering and stays in the layer as a dry fine powder, which may cause clogging such as exhaust filters, and the dry fine powder may adhere to the surface of the seed crystal that is wet with droplets. Adhesion is not preferable because it forms granules of relatively weak strength. Further, the size of the droplet is 100 μm.
When it exceeds the range, the droplets do not stay in the layer due to the jet stream and spontaneously fall quickly, so the frequency of contact with the seed crystals decreases, and the number of droplets that reach the bottom of the layer without adhering increases. However, it is not preferable because a large number of seed crystals may be adsorbed on the droplet particles to form aggregated particles.

Of the above operating conditions, the spraying speed (spraying amount) varies depending on the size of the apparatus used and the like, but the spraying air pressure is normally 2.5 to 5 kg / spraying air pressure.
It is preferable to adjust to cm ² G, preferably 4 to 5 kg / cm ² G and to continuously supply at a constant flow rate. The amount of sprayed air is not particularly limited because it varies depending on the size of the device used and the like, and should be appropriately determined according to the device used. When the atomization air pressure by continuous supply is less than 2.5 kg / cm ² G, the growth rate of granules is slow and the economic efficiency is poor, and the atomization air pressure is 5 kg / cm ² G.
If the amount exceeds the above range, the excessive drying of the seed crystals may not catch up with the adhesion and drying of the seed crystals, and droplets of the metal iodide may adhere to the undried seed crystals one after another. It is not preferable that the droplets condense and reach the bottom of the layer without being attached due to spontaneous fall. Further, if the spray is not continuously supplied, the crystals rub against each other to form fine powder, which is not preferable.

Of the above operating conditions, the liquid temperature of the droplets during spraying is not particularly limited, but is usually room temperature to 35 ° C., preferably 25 to 35 ° C.

Further, among the above operating conditions, the temperature of the dry hot air in the fluidized bed spray granulation dryer, that is, the granulation temperature, is usually 80 to 150 ° C, preferably 100 to 150 ° C.
It is. If the granulation temperature is lower than 80 ° C., it takes a long time to dry the granules in the fluidized bed, and it is necessary to keep the spray rate of the aqueous solution of the metal iodide low. When the temperature exceeds 150 ° C., depending on the size of the droplet of the aqueous solution of the metal iodide to be sprayed, the metal iodide is dried before it adheres to the seed crystal and is discharged as fine powder particles from the inside of the fluidized bed to the outside of the system. It is not preferable because it may cause clogging of the dust collecting filter. Furthermore, the flow rate of the fluidized bed formed by the dry hot air is usually 1.6 to 2.0 m / s, preferably 1.8 to
The range is 2.0 m / s. The flow velocity is 1.6 m / s
When the flow rate is less than 2.0 m / s, it is difficult to form and control the fluidized bed due to the self-weight of the seed crystal and the granulation operation using the entire bed becomes insufficient. It is not preferable that the granules violently collide with each other due to swirling of the laminar flow in the bed, or the granules violently collide with the inner wall of the bed and a part of the grown granules is lost.

Next, the size (and particle size distribution) of the metal iodide granules formed by the above-described granulation method of the present invention is usually not less than 250 μm and not less than 99% by weight, preferably 250 to 1000 μm. Is 100% by weight. When the granules are included in the above range, metal iodide granules having high granule strength can be obtained, and fine powders of the metal iodide (about seed crystals) or massive solids of the metal iodide (agglomeration of the granules) can be obtained. In comparison with the above (1), the fluidity is extremely good and there is no dusting at all, so the workability is remarkably improved in various applications using the metal iodide granules, and the harmful effects caused by dust scattering are eliminated. In particular, the metal iodide granules according to the present invention are convenient in terms of workability and handling at the time of packaging and use of the granules, and have uniform reaction, etc. ° or less, spatula angle 55 ° or less, compression degree 25
Hereinafter, the fluidity index is 80 or more, preferably the angle of repose 31 to 3
5 °, spatula angle 32-38 °, compression degree 20-22,
It is desirable to have various fluidity characteristics with a fluidity index of 80-89. At this time, the fluidity used here is a powder physical property diagram, published on May 1, 1975, 1st edition, 1st edition, edited by Japan Society for Powder Engineering, Japan Powder Industry Association, published by Industrial Technology Center Co., Ltd., R. et al., Pages 147-149. L. It was measured by Carr's fluidity evaluation method. Table 1 (corresponding to Table 7.3 "Powder Fluidity Index Table" on page 149 of the above document) is shown below as a guide for the degree of fluidity.

[0022]

[Table 1]

That is, since the granules obtained by the granulation method according to the present invention have a good fluidity such as a small angle of repose, when the granules are used as a raw material, the granules can be prepared, for example, from a hopper or the like. When supplying the granules, not only is there no generation of dust, and there is no blockage due to cross-linking or agglomeration of the granules and there is no clogging. In addition, since the granules are in a granular form, the small contact area between the granules contributes to prevention of caking during storage of the granules. Further, in the fluidized bed spray granulation method of the present invention, by appropriately selecting appropriate operating conditions, it is possible to obtain granular particles whose particle size is controlled so as to fall within a substantially uniform particle size distribution as described above. The granules thus obtained do not undergo rapid dissolution, and have a stable dissolution rate and can promote a stable and homogeneous reaction as compared with conventional fine powder products and lump solid products.

[0024]

EXAMPLES The present invention will be described in more detail based on the following examples.

Example 1 33 kg of potassium iodide fine powder was dissolved in 27 kg of water to prepare an aqueous potassium iodide solution having a specific gravity of 1.2 and a solid content of 55% by weight potassium iodide. A fluidized bed spray granulator / dryer (Mixgrad MGD-5, manufactured by Okawara Seisakusho Co., Ltd.) was charged with 25 kg of potassium iodide fine powder as seed crystals, and the temperature was 150 ° C.
Was blown in to form a fluidized bed of fine powder of potassium iodide. The flow rate was adjusted to 1.8 to 2.0 m / sec, and the previously adjusted aqueous potassium iodide solution was continuously sprayed for 4 hours at a rate of 1.5 kg / hr by a metering gear pump. At this time, the exhaust temperature was 80 ° C., the spray air pressure was 2.5 kg / cm ² G, and the spray air amount was 3.5 Nm ³ . The obtained potassium iodide granules had a water content of 0.2% by weight or less and a particle size of 250 to 1000 μm, and the amount obtained was 44 kg. The amount of stay in the bed at this time is 1
It was 6 kg. In addition, the flow characteristic test result shows that the angle of repose is 4
The flow index was good at 3.5 °, the spatula angle of 33.3 °, and the compression degree of 4, which was 85. Quality is JIS K 8913
-1992 was passed.

Example 2 Potassium iodide granules were obtained in the same manner as in Example 1 except that the aqueous potassium iodide solution was prepared by reducing iodine with formic acid. The flow characteristics test results of the obtained potassium iodide granules were as follows: repose angle 43.5 °, spatula angle 52.
At a compression degree of 5, the flow index was as good as 80. The quality passed JIS K 8913-1992.

Example 3 117.5 kg of sodium iodide granules were continuously prepared in the same manner as in Example 1 except that 183.3 kg of an aqueous sodium iodide solution (110 kg as NaI) was prepared by reducing iodine with formic acid. Obtained. The flow characteristics test results of the obtained sodium iodide granules were a very good flow index of 90 at a repose angle of 35 °, a spatula angle of 30 °, and a compression degree of 12. Quality is JIS K 8913-1992.
Was passed.

[0028]

INDUSTRIAL APPLICABILITY In the fluidized bed spray granulation method of the present invention, by appropriately selecting appropriate operating conditions, it is possible to obtain granular particles having a large particle size and controlled so as to be contained in a substantially uniform particle size distribution. The granules thus obtained do not undergo rapid dissolution and have a stable dissolution rate as compared with conventional fine powder products and lump solid products, and can promote a stable and homogeneous reaction, It can be widely used as a raw material for medicines, medicines, and additives or materials in various fields. Furthermore, in the granulation method of the present invention, the apparatus is relatively simple, auxiliary equipment is not required, and a high-purity fine powder product (seed crystal and metal iodide soluble in water) easily available as a raw material is used. )
Since it is possible to use, there is almost no contamination of impurities during the manufacturing process, and water is used as the solvent, it is possible to obtain inexpensive and highly pure metal iodide granules, and the number of which is increasing recently. It can be said that it is an excellent granulation method capable of providing the granules used for a certain nylon fiber additive, a liquid crystal display (LCD), and a polarizing film material.

Further, the granules obtained by the granulation method according to the present invention have a good fluidity such as a small angle of repose, so that when the granules are used as a raw material, the granules can be prepared from, for example, a hopper. When supplying granules, there is no generation of dust and no adverse effects due to dust scattering, and there is no blockage due to cross-linking or agglomeration of granules, and there is no clogging, so workability and handling during use of granules are improved. Excel. Further, since the granules are in a granular form, the small contact area between the granules contributes to prevention of secondary aggregation such as blocking and caking during storage of the granules.

Claims (3)

[Claims] 1. General formula (1) MIn (wherein M represents an alkali metal or alkaline earth metal of the periodic table of the elements, I represents an iodine atom, and n represents 1 or 2) When granulating the metal iodide represented by, a fluidized bed spray granulation dryer is continuously supplied with an aqueous solution of the metal iodide to dry granulate the metal iodide. Granulation method of metal iodide. 2. The metal iodide granules represented by the general formula (1) granulated by the method according to claim 1 have a particle size of 25.
A metal iodide granule comprising 0% or more and 99% by weight or more. 3. The angle of repose of 45, wherein the metal iodide granules are
3. The metal iodide granule according to claim 2, which has the following properties: a spatula angle of 55 ° or less, a spatula angle of 55 ° or less, a compressibility of 25 or less, and a fluidity index of 80 or more.