JPS6312639A - Production of spherical particle from melt - Google Patents

Abstract

PURPOSE:To obtain particles having roundness approximate by spherule by a simple means, by dripping drops of melt to a specific volatile liquid, gradually cooling and solidifying the drops in the volatile liquid in a state wherein the drops are covered with a vaporized gas of the volatile liquid. CONSTITUTION:In a method wherein drops of melt is dripped in a volatile liquid which is, practically, neither dissolved in nor dissolves the melt mutually and is not reacted with the melt to solidify the drops of the melt, the volatile liquid is heated to a temperature between the boiling point and the temperature 20 deg.C lower than the boiling point, the drops of the melt are dripped in the liquid and the drops of the melt are cooled and solidified in a state wherein the drops of the melt are covered with a gas of the volatile liquid. Caustic soda, caustic potash, calcium chloride, boric acid, urea, sulfur, a metal such as sodium, etc., are used as the melt. Trichloromonofluoromethane, dichloromethane, etc. are used as the volatile liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Use ¥f] The present invention relates to a method for producing spherical particles, and particularly to a method for producing spherical particles from a melt of caustic soda or the like.

[Prior Art] Various methods are conventionally known for obtaining particles by solidifying a molten liquid. These methods can be broadly divided into methods in which molten droplets are dispersed in the air and then cooled and solidified, and methods in which molten droplets are cooled and solidified in liquid.

Examples of the former method include a method in which molten droplets are dispersed into the air by centrifugal force from a rotating cylinder, as disclosed in Japanese Patent Publication No. 33-922, and Japanese Patent Publication No. 38-2959.
As disclosed in the above publication, there is a method that utilizes the combined effect of the centrifugal force of a rotating body and gravity in an air flow tower.

However, these manufacturing methods in an air stream generally
The molten drippings require a considerable amount of time to hang in the air before landing, leading to an increase in the size of the device. Furthermore, the molten droplets adhere to and scale the vessel wall during flight, requiring troublesome operations for removal.

On the other hand, the latter method of cooling and solidifying in a liquid includes Japanese Patent Publication No. 45-34384, Japanese Patent Publication No. 4B-9802, Japanese Patent Publication No. 2H7-1987, Japanese Patent Publication No. 48-88474, Japanese Patent Publication No. 48-88474, Japanese Patent Publication No. 48-88474,
No. 9-127898, JP-A No. 55-20839, and the like. Each of these publications discloses means for granulating molten droplets by mutually dropping them into an inert liquid, but all of them involve cooling means in which the molten droplets come into direct contact with the inert liquid. This is to disclose.

That is, in these methods, since the molten droplets are cooled by direct contact with the liquid, it is difficult to make the solidified particles spherical unless the droplets are made spherical in advance. Also-
1 It is practically difficult to form droplets into spherical particles in advance and bring them into contact with an inert liquid, and even if this is done, it is difficult to obtain spherical particles with truly good sphericity.

[Problems to be Solved by the Invention] Thus, the present invention provides by simple means spherical particles with good sphericity, which is difficult to achieve using conventional techniques.

[Means for Solving the Problems] Thus, the present invention provides a method for solidifying droplets of a molten liquid by making them exist in a volatile liquid that does not mutually dissolve or react with the molten liquid. The gist of the present invention is to provide a method for producing spherical particles, characterized in that the droplets are cooled and solidified by allowing a volatile gas of the volatile main liquid to exist around the droplets.

A preferred specific means for making the volatile gas of the volatile liquid exist around the droplets is to maintain the temperature of the volatile liquid as high as possible below its boiling point and bring it into contact with the droplets. According to the inventor's study, surprisingly, regardless of whether the temperature of the volatile liquid is below the temperature of the molten droplet, if the temperature is between the boiling point of the volatile liquid and a temperature 20°C lower than the boiling point, the droplet will melt. A phase of volatile gas is formed and maintained around the . The temperature range is more preferably between the boiling point and 10° C. below the boiling point.

The melt to which the present invention is applied is not particularly limited, but includes caustic soda, caustic potash, calcium chloride,
It is preferably applied to melts of metals such as boric acid, urea, sulfur, and sodium.

Apparatus for carrying out the invention may be of any type; for example, a tray-shaped vessel may be configured to flow a volatile liquid from one end of the vessel at a suitable flow rate toward the other end, and to The molten liquid is introduced into the liquid stream as a liquid column or as droplets.

At that time, it is preferable to heat the volatile liquid in advance to near its boiling point.

Thus, the molten liquid poured into the volatile liquid becomes droplets,
It is carried by a liquid stream towards the other end. Here, the volatile liquid surrounding the droplet is vaporized by the latent heat and/or sensible heat of the molten droplet, and the droplet is surrounded by vaporized gas, thereby preventing the droplet from cooling rapidly. As a result, while the droplets are slowly cooled, their surface tension makes them particles with a sphericity almost like that of a pearl. In the completely cooled and solidified state, there is no longer a gas phase around the spherical particles.
It settles in a volatile liquid and is removed from the bottom of the tank.

The spherical particles obtained by the method of the present invention have truly good sphericity, and most of the particles have a ratio of maximum diameter to minimum diameter of 1.5 or less, and even 1.3 or less. It is something.

The volatile liquid in the present invention must not cause mutual dissolution or reaction with the molten liquid, but there are no other restrictions. When the liquid is caustic soda, caustic potash or calcium chloride hydrate, halogenated hydrocarbons can be preferably used.

Specific examples of these include trichloromonofluoromethane, dichloromethane, 1,1.1-trichloromonofluoromethane, 1,1.2-)lichlorotrifluoroethane, 1,2-dibromotetrafluoroethane, n-per Examples include fluorooctane.

Example 1 A thin pipe was provided at the top of one end of the gutter-shaped horizontal tank to allow the melt to flow down, and from the end, the temperature was approximately 42°C in the horizontal direction.
1.1.2-Trichlorotrifluoroethane (R-i
13, boiling point 47.6°C).

An 80 wt % caustic soda melt at about 150° C. was poured into a liquid column from a thin pipe. The melt formed droplets in the R-113 stream and was carried toward the other end.

Then, the droplets were surrounded by the vaporized R-113 gas, and were gradually cooled while floating on the R-113 liquid surface, becoming solidified particles and settling to the bottom of the tank at the other end of the tank.

The obtained particles had an average particle diameter of 800 μm, and 90% or more of each particle had a sphericity with a ratio of maximum diameter to minimum diameter of 1.2 or less.

Comparative Example In Example 1, the temperature of R-113 put into the tank was changed to 2.
Everything was carried out in the same manner as in Example 1 except that the temperature was 0°C.

The surface of the droplets of the molten caustic soda poured into the tank instantly solidified, and they settled to the bottom of the tank without forming a gas phase around them.

The particles obtained are shell-shaped, hemispherical, or teardrop-shaped.
The particle size is also 3000-300μ with an average value of 1500μ.
It was distributed over a wide range.

Procedural amendment (method) % formula % ( 1. Indication of the case Patent Application No. 156193 of 1985 2. Name of the invention Method for producing spherical particles from a melt 3. Person making the amendment $ Relationship with the matter Patent application Address 2-1-2 Marunouchi, Chiyoda-ku, Tokyo (00
4) Asahi Glass Co., Ltd. Voluntary amendment based on the procedural amendment order dated September 30, 1986 (shipment date) 6. Number of inventions increased by the amendment None 7. Full text of the specification subject to the amendment

Claims (3)

[Claims] (1) A method in which droplets of a molten liquid are solidified by being present in a volatile liquid that does not substantially mutually dissolve or react with the molten liquid, in which the droplets are surrounded by the volatile liquid. A method for producing spherical particles, which comprises cooling and solidifying the droplets in the presence of a volatile gas. (2) The method for producing spherical particles according to claim (1), wherein the droplets are solidified between the boiling point and a temperature 20° C. lower than the boiling point of the volatile liquid. (3) The method for producing spherical particles according to claim (1), wherein the melt is selected from metals such as caustic soda, caustic potash, calcium chloride, boric acid, urea, sulfur, and sodium.