JP2600181B2 - Method for producing oxide powder - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for producing a relatively large-particle-size oxide powder by burning metal powder, and more particularly, to a method using a small-particle-size oxide powder as a core. The present invention relates to a method for producing an oxide powder that performs grain growth during combustion.

[Prior Art] Japanese Patent Application Laid-Open No. 60-255602 discloses a method for producing ultrafine oxide particles, in which a chemical flame is formed by a burner in an atmosphere containing oxygen, and a metal powder is formed into a dust cloud in the chemical flame. There is a disclosure of a production method of synthesizing ultrafine oxide particles of 5 to 100 nm by adding a possible amount and burning.

[Problems to be Solved by the Invention] Oxide fine particles produced by the method of JP-A-60-255602 and the like produce high-temperature liquid particles due to the oxidation reaction of metal powder, and they collide and coalesce. The grains grow by
The particle size is approximately several nm to 100 nm (= 0.1 μm). If particles having a larger particle size are required, they cannot be formed as they are, and the reactor must be extended to increase the grain growth time and to be externally heated to keep the particles in a liquid state. Therefore, a manufacturing problem occurs.

The present invention uses the above-mentioned reactor as it is,
An object of the present invention is to provide a production method capable of easily producing a large-diameter oxide powder having a particle diameter of m.

[Means for Solving the Problems] The present applicant previously disclosed in Japanese Patent Application Laid-Open No. 61-224360 a compound oxide of ultra-fine particles of 1.0 μm or less, which was burned with a mixture of a metal powder and a carrier gas using a burner. And proposed a synthesis method.

The production method of the present invention comprises: a first step of supplying a metal powder constituting an oxide together with a carrier gas into a reaction vessel;
A second step of igniting a flame in the reaction vessel to form a flame and burning the metal powder to synthesize an oxide powder. A mixture of the oxide and the metal powder is supplied, and the second step is characterized in that grains are grown by an oxide synthesized by burning the metal powder with the metal oxide as a nucleus.

The first step is a step of supplying a substance to be burned into the container. A carrier gas, an oxide-forming metal powder, and a metal oxide having a small particle diameter serving as a nucleus for grain growth are supplied. As a carrier gas, oxygen gas can be mainly used.

Aluminum, magnesium, silicon, zirconium, titanium, and other aluminum powders and silicon powders as metal powders mixed with mullite composition, magnesium powder and aluminum powders as powders mixed with spinel composition, and cordierite composition as metal powders Aluminum powder, magnesium powder, and silicon powder can be used as the metal powder. As the metal oxide having a small particle diameter, it is preferable to use the same kind of metal oxide or composite oxide as the metal forming the oxide.

The metal oxide can be supplied as a mixture with the metal powder, or can be supplied into the container at a fixed rate from another hopper. When the amount of the metal powder is smaller than that of the oxide, the grain growth hardly occurs and the oxides are aggregated with each other, so that the particle size distribution becomes too large. If the amount of the metal powder is too large, grain growth hardly occurs, and it becomes difficult to obtain a large-grain oxide.

The reaction vessel preferably has an ignition source. The ignition source can be one that produces a spark. The reaction vessel is preferably lined with a heat insulating material such as alumina brick.

In the second step, a flame is formed by igniting in the reaction vessel, and the metal powder is burned to cause grain growth using oxides present in the flame as nuclei. When the metal powder burns to form an oxide, it causes grain growth with the oxide powder particles as nuclei, and they collide and coalesce into larger particles, so the particle size of the oxide powder finally obtained Is 1 to 2 digits larger than the particle size of the added oxide powder. The second step is usually 10
Since it is performed at a high temperature of 00 ° C. or more, a high-temperature flame is formed. In this case, a flame can be formed by the propane gas and the oxygen gas.

The synthesized oxide powder is collected together with the combustion exhaust gas. In this case, generally, it can be performed by connecting the container and the dust collector and driving the dust collector. As the dust collector, an electric dust collector, a bag filter, a collecting drum type fine powder collecting device, or the like can be used.

Further, by using a collecting device having a two-stage structure, only oxide particles having a desired particle size or more can be collected in the first stage, and particles having a smaller particle size can be collected in the second stage. The small particles collected in the second stage can be introduced into a container and used as nuclei for grain growth.

[Effects of the Invention] In the present invention, in a first step, a mixture of a metal oxide having a small particle diameter and a metal powder is supplied, and in a second step, the mixture is synthesized by burning the metal powder using the metal oxide as a core. This is a method for producing an oxide powder, wherein the particles are grown with an oxide. According to this method, a spherical oxide powder having a relatively large particle diameter (1 to several μm) can be easily and inexpensively produced with little modification of the apparatus.

This manufacturing method can be applied not only to the synthesis of oxides but also to the synthesis of powders of mullite, spinel and cordierite, which are composite oxides.

Embodiment FIG. 1 shows a manufacturing apparatus according to a manufacturing method of the present invention. This manufacturing apparatus mainly includes a reaction vessel 10 having an inner wall surrounded by a heat-resistant brick 10a and having a discharge passage 11a on a side wall, and a burner 9 forming a flame 8 on an upper wall of the reaction vessel 10.

The burner 9 is connected with a powder supply device 1 for supplying metal powder and oxide powder, and a conduit 4 provided with an oxygen supply pipe 40 and an LPG supply pipe 5 for supplying LPG for pilot fire. .

A powder collecting device 11 is provided in the discharge passage 11a, and exhaust gas is sucked into the powder collecting device 11 by a blower 12.

The following reaction was carried out by the reactor configured as described above to obtain an oxide.

First, the oxygen supply pipe 40 and the valve 50 of the LPG supply pipe 5 were opened, the burner 9 was ignited, the inside of the reaction vessel 10 was sufficiently dried, and deoxidation was performed. 8 m ³ / hour of carrier gas flow,
LPG was supplied into the reaction vessel at a flow rate of 0.4 m ³ / hour. Next, aluminum powder was supplied from the powder supply device 1 and burned.

By operating the blower 12 and sucking the combustion exhaust gas containing the oxide powder, the collection and installation 11 collected the oxide powder. The particle size of the obtained aluminum oxide powder was 100 nm or less.

The ultrafine aluminum oxide powder and the metal aluminum powder obtained above were mixed at a ratio of 1: 1 and placed in a powder supply device of a hopper and burned in the same manner as described above. When the metal aluminum powder burns to oxides, it causes grain growth with the resupplied oxide powder particles present in the flame as nuclei,
Furthermore, because they become larger particles due to collision coalescence,
The particle size of the collected aluminum oxide powder is 10 ~ 20μm
And the resupply was greater than the aluminum oxide.

In the case where the above-mentioned grain growth during combustion is insufficient and small-sized oxides are mixed even in a small amount, a collecting device having a two-stage structure is used as shown in FIG. A filter that collects only oxides is provided, and those with a small particle diameter that have passed through are collected in the second stage, transported to a separately provided hopper, and re-supplied into the reaction vessel, where large particle diameters with uniform particle diameters are obtained. Was obtained. Therefore, a metal oxide of a large particle size can be continuously obtained without increasing the number of steps or changing the apparatus.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a manufacturing apparatus according to an embodiment, and FIG. 2 is a schematic cross-sectional view of a manufacturing apparatus that reuses small fine particles in a modification of the embodiment of FIG. 1, 1 '... powder supply device, 4 ... conduit 5 ... LPG supply pipe, 40 ... oxygen supply pipe 8 ... flame, 9 ... burner 10 ... reaction vessel 11, 11' ... powder collection Container, 12 ... Blower

Claims (2)

(57) [Claims] 1. A first step of supplying a metal powder constituting an oxide together with a carrier gas into a reaction vessel, igniting in the reaction vessel to form a flame, burning the metal powder and burning the oxide powder A first step of supplying a mixture of a metal oxide having a small particle size and the metal powder, and a second step of converting the metal oxide to A method for producing an oxide powder, wherein grains are grown by an oxide synthesized by burning the metal powder as a nucleus. 2. The method according to claim 1, wherein the metal oxide having a small particle diameter is obtained by classifying the generated metal oxide.