JPH04126533A - Method and apparatus for producing inorganic sphered particles - Google Patents

Abstract

PURPOSE:To sphere inorg. powdery starting material at a high rate of sphering by radially jetting a mixture of combustible gas with the starting material from a nozzle set in a burner and jetting combustion improving gas from the inner wall of the burner so that a whirling flow is generated. CONSTITUTION:A high temp. flame and inorg. powdery starting material are jetted in a furnace and the starting material is melted and sphered. At this time, the starting material is previously mixed with combustible gas and fed to a burner 1 for jetting the high temp. flame and the mixture is radially jetted from the ejection holes 3 in a nozzle 4 set in the burner 1. Combustion improving gas is further jetted from the ejection holes 2 in the inner wall of the burner 1 so that a whirling flow is generated. The inorg. powdery starting material can efficiently be sphered with a small amt. of the combustible gas at a high rate of sphering.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing molten spheroidal inorganic particles used, for example, as a sealing material for tC, and an apparatus used therefor.

[Conventional technology]

IC encapsulants are required to have functions such as electrical insulation and low coefficient of thermal expansion. Therefore, in general, a thermosetting resin such as an epoxy resin is mixed with melt-treated inorganic particles such as amorphous silica particles, and this mixture is used for sealing. In recent years, it has been found that the use of spherical particles as the inorganic particles has the advantage of superior fluidity and ease of resin sealing, and spherical molten inorganic particles have come to be widely used. A method for producing spherical inorganic particles is disclosed, for example, in Japanese Patent Application Laid-open No. 145613/1983. In this conventional method, the furnace consists of a spheroidizing chamber and a cooling chamber connected to the bottom of the spheroidizing chamber, and a flame is injected from the top of the furnace along with the raw material powder to melt the surface or the entire raw material powder, and the surface tension The raw material powder is spheroidized. The raw material powder spheroidized in this manner is cooled and solidified in a cooling chamber, and then guided to a subsequent collection system. The collection system is equipped with a collection device such as a cyclone or a bag filter.

An example of a conventional burner is shown in Figs. 6 and 7. In this burner, the inside of a cylindrical block is tapered to form a combustion section, and the upper part of the tapered surface contains 8 pieces of combustible gas. A discharge hole 13 is formed, and eight auxiliary gas discharge holes 14 are formed slightly below the center. Inorganic particles as a raw material are supplied from a raw material supply pipe 15 connected to the upper part of the combustion section.

[Problem to be solved by the invention]

However, in the conventional method described above, as shown in Fig. 6, a type of burner is used that injects combustible gas and auxiliary gas toward the center in parallel or facing each other, and forms a flame downstream. I am using it. In this burner, the high-temperature flame region effective for melting and spheroidizing the raw material powder is a very limited and narrow area directly below the burner. the result,
Since a considerable amount of the raw material powder does not pass through the high-temperature flame section, it is not completely melted and spheroidized, and the spheroidization rate (weight of spheroidized powder/weight of recovered product powder) is low.

In addition, in order to increase the spheroidization rate, it is necessary to increase the amount of combustible gas used, and there is also a problem that the amount of combustible gas used per product spherical body increases, resulting in a large fuel consumption rate. Furthermore, in this type of burner, if a large amount of raw material powder is continuously supplied, the raw material powder tends to agglomerate.
As a result, there was a problem that the aggregated raw material powder was not melted and spheroidized, resulting in a low spheroidization rate.

[Means to solve the problem]

The present invention solves the above problems and provides a means for efficiently spheroidizing inorganic raw material powder with a high spheroidization rate using a small amount of combustible gas.

According to the present invention, in a method of melting and spheroidizing raw material powder by injecting a high-temperature flame and inorganic raw material powder into a furnace, the inorganic raw material powder is mixed in combustible gas in advance and supplied to a burner that injects high-temperature flame, A method for producing inorganic spheroidized particles, characterized in that a mixture of a combustible gas and the raw material powder is injected radially from a nozzle provided in a burner, and an auxiliary gas is injected from an inner wall of the burner so as to generate a swirling flow. The present invention relates to an apparatus used in the method.

The high-temperature flame may be anything that has a temperature and heat amount that can melt the inorganic raw material powder and make it spherical, such as hydrogen gas, methane, ethane, propane, butane, ethylene, acetylene, hydrocarbon gas such as LNG, LPG, benzene, etc. It is formed by mixing a combustible gas such as a hydrocarbon that is liquid at room temperature, such as toluene, gasoline, diesel oil, or kerosene, with an auxiliary gas such as oxygen and burning the mixture.

The inorganic raw material powder is silica, alumina, magnesia, etc., and the particle size is about 0.1 to 500 nm, preferably 3 to 40 nm.
．． A value of about n is appropriate.

The mixing ratio of combustible gas and inorganic raw material powder depends on the type of combustible gas,
It varies depending on the type of inorganic raw material powder, particle size, etc., but usually 1
Appropriately selected from the range of ~100 (kg raw material 7 NII 3 fuel). Experiments can be conducted as necessary to determine a preferred blending ratio.

The apparatus used in the method for producing spheroidized inorganic particles of the present invention is a furnace equipped with a burner that injects high-temperature flame.

The burner is provided with a nozzle for injecting a mixture of combustible gas and inorganic raw material powder, and an auxiliary gas discharge hole.

The combustible gas and the inorganic raw material powder may be mixed by a conventional method, and the powder may be supplied in a fixed amount while stirring if necessary, and added to the combustible gas air flow pipe. In addition, an ejector etc. can also be used.

The nozzle for spraying the mixture is configured to spray the mixture radially. For this purpose, a plurality of discharge holes for the mixture may be provided in the nozzle, for example, three or more discharge holes may be provided at approximately equal intervals in the circumferential direction, or slits may be formed all around the circumference.

The discharge angle of the mixture (θ in Figure 1) should be set so that the burner center axis and nozzle center axis are aligned in order to prevent melting of the inner wall of the burner body and to ensure uniform dispersion of raw material powder into the furnace. 20” to the burner center axis if
It is desirable to set the angle in the range of ~80° and 30'~50°. The discharge angle of each discharge hole may not be constant.

The auxiliary gas discharge hole is formed to generate a swirling flow from the inner wall of the burner main body. Assisting gas discharge angle (φ in Fig. 2
) is preferably 20° or more to ensure the effect of swirling flow.
On the other hand, if the swirling flow becomes too strong, the amount of raw material powder adhering to the inner wall of the furnace will increase and the product recovery rate will decrease.

The discharge angle of the auxiliary gas with respect to the burner axis direction is not limited to a right angle.

Regarding the axial distance L between the mixture discharge hole and the auxiliary gas discharge hole (see Figure 1), (+) indicates that the mixture discharge hole is closer to the burner opening than the auxiliary gas discharge hole;
-), if L is (-), the tip of the fuel gas nozzle may be damaged by melting, and the (+) side may be 0.
Combustion may become unstable in a range exceeding 25D (D: internal diameter of the burner body, see Figure 1), so
It is desirable to set it within a range of 0.25D.

The burner in the furnace is usually installed at the top of the furnace, but is not limited thereto, and may be installed at the side wall or bottom depending on the structure of the furnace.

Other equipment of the apparatus may include a cooler, a collector, a classifier, etc. for the molten spheroidized particles discharged from the furnace.

[Effect]

In the process of melting and spheroidizing raw material powder by directly blowing it into a high-temperature flame, it is important to know how to form a high-temperature flame region over a wide range and stably. An important technique is how to inject the powder evenly. In the present invention, in order to uniformly blow the raw material powder into a high-temperature flame, the raw material powder is mixed into combustible gas in advance, and the raw material powder is supplied to the burner in a sufficiently mixed state in the combustible gas. This further enhances the effect of uniformly dispersing the raw material powder by the burner. In addition, the reason why the auxiliary gas discharge hole has a swirling angle φ is to generate a swirling flow in the auxiliary gas within the burner body, and this swirling flow forms a negative pressure area inside the burner, and this negative pressure As the gas recirculates, combustion is promoted and rapid combustion is achieved, creating a wide and stable high-temperature flame region. Furthermore, the raw material powder injected into the furnace by this swirling flow passes through the hot combustion gas in a uniformly dispersed state. As a result, heat transfer between the raw material powder and the gas occurs instantaneously, promoting molten spheroidization.

〔Example〕

The apparatus shown in FIG. 3 equipped with the burner shown in FIGS. 1 and 2 was used.

In the burner 1, a tubular nozzle 4 coaxially protrudes inward from a closed end of a burner tile inner wall 5, which is an inner tube of a double-tubular burner main body. The tip of the nozzle is closed and its inner surface protrudes conically, and eight mixture discharge holes 3 are bored at equal intervals at an angle of 45'' with respect to the axial direction of the nozzle on the side near the tip. In the burner tile inner wall 5, 16 auxiliary gas discharge holes 2 are bored in the same direction at equal intervals and at an angle of 45° with respect to the normal direction. 0. ID from discharge hole 3
It's retreating.

This burner 1 has a two-stage cylindrical furnace body 9 with an enlarged diameter at the bottom.
is attached to the top of the A combustible gas supply pipe is connected to the nozzle, and there is a branch part 8 in the middle of the pipe that mixes the raw material powder.
is provided. The branching part 8 has a hopper 7 for raw material powder.
are connected via a stationary feeder (not shown).

The furnace main body 9 is composed of a melting zone for spheroidizing the melt and a cooling zone connected to the lower part of the melting zone, and a cyclone 11 is installed from the cooling zone via a cooling chamber 10. 12
is a prower.

With the above-described device, L P is released as combustible gas from the burner
G 15N+w3/hr, oxygen 75N as auxiliary gas
When a molten spheroidization test was conducted by injecting silica powder with an average particle size of 30n as a raw material powder into the furnace at a rate of 150 kg/hr, the spheroidization rate (95%
), high-grade fused spheroidal silica particles free from impurities were obtained.

For comparison, the results of a spheroidization test using the burner shown in FIG. 6 are shown as a comparative example in Table 1 along with the results of this example. Microscopic photographs of the spheroidized particles are shown in FIGS. 4 and 5.

Table 1 [Effects of the Invention] According to the present invention, it is possible to widen the flame area where high-temperature melting is possible, and at the same time, by uniformly dispersing the raw material powder in the high-temperature gas, the raw material powder and the gas can be Since heat transfer occurs instantaneously, molten spheroidization is promoted. As a result, the spheroidization rate is higher than in the conventional method. Further, even when obtaining the same spheroidization rate, melting can be performed with a smaller amount of combustible gas than in the conventional method, and there are advantages such as a reduction in fuel consumption.

According to the present invention, there is an advantage that highly pure inorganic spheroidized particles can be obtained very efficiently and stably.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the main part of a burner used in an embodiment of the present invention, and FIG. 2 is a vertical cross-sectional view taken through both ridge holes. FIG. 3 is a schematic diagram of the apparatus used in the embodiment of the invention. FIG. 4 is a micrograph showing the structure of the molten spheroidized particles obtained in the Examples, and FIG. 5 is a photomicrograph substituted for a drawing showing the structure of the molten spheroidized particles obtained in the Comparative Example. FIG. 6 is a sectional view of an example of a conventional burner, and FIG. 7 is a plan view thereof. 1... Burner 2... Combustion auxiliary gas discharge hole 3... Mixture discharge hole 4... Nozzle 5... Burner tile inner wall 6... Burner tile outer wall 7... Raw material hopper 8... Branch Part 9... Furnace body 10... Cooling chamber 11... Cyclone 12... Blower

Claims (2)

[Claims] (1) Inject high temperature flame and inorganic raw material powder into the furnace,
In a method of melting and spheroidizing raw material powder, inorganic raw material powder is mixed in combustible gas in advance and supplied to a burner that injects a high-temperature flame, and the mixture of combustible gas and raw material powder is radially ejected from a nozzle installed in the burner. and the auxiliary combustion gas is injected from the inner wall of the burner so as to generate a swirling flow. (2) In a device equipped with a burner that injects a high-temperature flame into the furnace, a nozzle that injects a mixture of combustible gas and inorganic raw material powder radially is provided in the center of the burner, and the burner is provided with a swirling auxiliary gas from its inner wall. An apparatus for producing spheroidized inorganic particles, characterized in that an auxiliary gas discharge hole formed to generate a flow is provided, and the opening end of the nozzle is provided closer to the burner opening end than the auxiliary gas discharge hole.