JPH01275410A - Production of metal oxide fine powder - Google Patents

Abstract

PURPOSE:To reduce unreacted metal content in the title fine powder and to make the particle minute by ejecting high speed as from a fine tube equipped inside of a cylindrical burner having a specified structure to disperse metal powder, thereafter by ejecting the metal powder from a burner nozzle and by floating in a gas contg. oxygen to burn. CONSTITUTION:The metal powder of Mg, Al, Ti, etc., having <=200mu particle size is quantitatively supplied from a feeder 2, dispersed with the dispersing gas ejected at >=30m/s flow rate from the nozzle 5 for the dispersing gas and ejected at <=30m/s flow rate from the cylindrical burner nozzle 4 in a reaction chamber 9 of a vertical cylindrical reactor 6. The nozzle 5 for the dispersing gas is concentrically equipped on the axis of the cylindrical burner 3 and its caliber is below 1/3 one of the nozzle of the cylindrical burner. The caliber of the nozzle 4 of the cylindrical burner is preferably 2-50mm. The gas contg. >=1.2 times the theoretical oxygen amt. is supplied from a pipe 12.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a method for producing fine metal oxide powder having an average particle size of 1 μm or less, and more specifically, by using a burner with an improved structure, Improves powder dispersion,
The present invention relates to a method for producing metal oxide fine powder with less unreacted metal.

(Prior Art and Problems) Several proposals have already been made regarding methods for producing fine metal oxide powder by burning metal powder in an oxygen-containing atmosphere.

For example, JP-A-60-255602 and JP-A-60-255602
Japanese Patent No. 46905 discloses a method for producing fine metal oxide powder by supplying metal powder together with a carrier gas to a reaction chamber and burning it in an oxygen-containing atmosphere. According to these proposed methods, when the metal powder is supplied to the reaction chamber, the metal powder is not dispersed, so that the metal powder is supplied to the reaction chamber in a partially aggregated state. This aggregate causes fusion in the reaction chamber, becomes agglomerated, and reduces the surface area, so that oxidation ends only on the surface and is mixed into the produced metal oxide fine powder as unreacted metal. For this reason, in the production of metal oxides using combustion of metal powder,
There is a need for a method to prevent unreacted metal from remaining.

(Objective of the Invention) The object of the present invention is to provide a method for producing metal oxide fine powder that contains less unreacted metal, can be practically used as a raw material for ceramic sintered bodies, and as a filler, and has an average particle size of 171 m or less. There is a particular thing.

(Means for Solving the Problems) The present invention provides a 30 m
After dispersing the metal powder by ejecting high-speed gas of s or more,
The present invention relates to a method for producing fine metal oxide powder, characterized in that the metal powder is ejected from a nozzle of a cylindrical burner at a speed of 30 m/s or less, suspended in an oxygen-containing gas, and burned.

The metal oxide fine powders obtained in the present invention include magnesia (MgO), alumina (A(20,), titania (TiO□), spinel (MgO・An!O,), and forsterite (2MgO・SiO□). etc.

As the metal powder of the present invention, a metal powder or alloy powder corresponding to the composition of the above metal oxide is used, such as Mg,
/l! , Ti, Mg-A/! Alloy (atomic ratio 1:2),
Mg-Si alloy (atomic ratio 2:1) or the like is used.

The present invention will be explained below with reference to the drawings. In Fig. 1, 1 is a hopper, 2 is a feeder, 3 is a cylindrical burner, 4 is a cylindrical burner nozzle, 5 is a dispersion gas nozzle, 6 is a vertical cylindrical reactor, and 7 is a metal oxide fine powder produced. It is a collector.

The raw metal powder stored in the hopper 1 is quantitatively supplied by the feeder 2, dispersed by the dispersion gas ejected from the dispersion gas nozzle 5, and then transferred from the cylindrical burner nozzle 4 into the vertical cylindrical reactor 6. It is ejected into the reaction chamber 9.

The particle size of the metal powder 8 is preferably 2003 m or less. When the particle size of the metal powder 8 is larger than 200 μm, combustibility deteriorates and it becomes difficult to completely burn the metal powder.

The metal powder 8 needs to be sufficiently dispersed by the dispersion gas ejected from the dispersion gas nozzle 5 at a flow rate of 30 m/s or more, and then supplied to the reaction chamber 9. Flow velocity is 30 m/
If it is smaller than s, the metal powder 8 will not be sufficiently dispersed, and some of the metal powder 8 will be supplied to the reaction chamber in an aggregated state, and this aggregate will fuse in the reaction chamber and have a small surface area. The oxidation ends only on the surface, and unreacted metal is mixed into the generated metal oxide fine powder.

The dispersion gas nozzle 5 is preferably provided coaxially with the central axis inside the cylindrical burner 3, and its nozzle diameter is preferably ⅓ or less of the diameter of the cylindrical burner nozzle 4. Dispersion gas nozzle 5
If the diameter of the gas is larger than 1/3 of the diameter of the cylindrical burner nozzle 4, the flow rate of qt gas required to increase the flow velocity of the dispersed gas to 30 m/s or more increases, so that the gas is ejected from the cylindrical burner nozzle 4. This is not preferable because the speed of the metal powder 8 becomes greater than 30 m/s.

The diameter of the cylindrical burner nozzle 4 is preferably in the range of 2 to 50 mm. If the diameter is smaller than 2fflI11, metal powder may clog the nozzle, and if the diameter is smaller than 5
If the cylinder size is larger than 0, it is necessary to increase the flow rate of the dispersion gas excessively in order to disperse the metal powder.

The sufficiently dispersed metal powder 8 must be ejected from the cylindrical burner nozzle 4 into the reaction chamber 9 in the vertical cylindrical reactor 6 at a flow rate of 30 m/s or less. Since the combustion speed of the metal powder 8 is slower than that of metal vapor, it is not preferable to eject the metal powder 8 at a flow rate greater than 30 m/s because unreacted metal will remain.

When supplying the metal powder 8 to the reaction chamber 9, it is preferable to supply a backfire prevention gas to the cylindrical burner 3 from the pipe 10 in order to prevent backfire within the cylindrical burner 3.

As such a gas, an inert gas such as argon or helium is preferably used. For the same reason, tube 1
The dispersion gas supplied from 1 is preferably an inert gas.

The metal powder supplied to the reaction chamber 9 is combusted by the oxygen-containing gas supplied from the tube 12, producing fine metal oxide powder.

It is desirable that the oxygen-containing gas be supplied in an amount that is 1.2 times or more the theoretical amount of oxygen required to oxidize the supplied metal powder. In addition, the oxygen concentration of the oxygen-containing gas is 20 to 100
Preferably it is mol%.

If the amount of oxygen in the oxygen-containing gas is lower than 1.2 times the theoretical amount of oxygen, combustion of the metal powder will not be completed completely, and unreacted metal powder will be mixed into the fine metal oxide powder produced.

The flame temperature when the metal powder is combusted is preferably 1000°C or higher. If the temperature is lower than this, the combustion rate of the metal powder will be low, making it difficult to obtain a fine metal oxide powder with a small amount of unreacted metal.

Once the combustion of the metal powder is started, the combustion continues continuously, but at the start of the reaction, the combustion of the metal powder can be caused by a heating device 13 surrounding the vertical cylindrical reactor 6, such as an electric furnace. .

The generated metal oxide fine powder is collected by a collector 7, for example, a bag filter.

(Effects of the Invention) According to the present invention, there is less unreacted metal, and it can be practically used as a raw material for ceramic sintered bodies and as a filler.
Metal oxide fine powder having an average particle size of 1 μm or less can be efficiently produced using a simple device.

(Example) Next, examples of the present invention will be shown.

A metal oxide fine powder was produced using the apparatus shown in FIG. The diameter of the cylindrical burner nozzle 4 is 4 mm, the diameter of the dispersion gas nozzle 5 is 11TI111, and the inner diameter of the reaction chamber 9 is 105 mm.
mm, and the length was 1000 mm.

Examples 1 to 6 Metal powder 8 that passes through a 100-mesh sieve but does not pass through a 200-mesh sieve is fed at a rate of 12 g/min by feeder 2, and 51 g/min of argon gas is introduced from pipe 10 to prevent backfire. It was also conveyed to the cylindrical burner 3. Next, the metal powder 8 is introduced from the tube 11 at a rate of 22/min, dispersed by argon gas ejected from the dispersion gas nozzle 5 at a speed of 85 m/s, and then introduced from the cylindrical burner nozzle 4 at a speed of 10 m/s. 1 by electric furnace 13
It was ejected into a reaction chamber 9 heated to 100°C. At the same time, oxygen gas was supplied from the tube 12 to the reaction chamber 9 at 152/min.

Fine metal oxide powder generated by combustion of the metal powder was collected by a bald filter 7.

The particle size of metal oxide fine powder obtained by changing the type of metal powder as shown in Table 1 was measured using a transmission electron microscope,
In addition, unreacted metals were determined by thermal analysis. The results are shown in Table 1.

Table 1 Comparative Examples 1 to 6 Metal oxide fine powders were produced in the same manner as in Examples 1 to 6, except that the supply rate of the dispersion gas was O and the supply of argon gas for backfire prevention was 742/min. The results are shown in Table 2.

Table 2

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of an apparatus for implementing the present invention. ■・・・Hopper 2・・・Feeder 3・・・Cylindrical burner 4・・・Cylindrical burner nozzle 5・・・Dispersion gas nozzle 6・・・・
・Vertical cylindrical reactor 7...Collector 8・
...Metal powder 9 ...Reaction chamber 10
．． 11.12・Old・・Pipe 13・・・・Heating device

Claims (1)

[Claims] (1) After dispersing the metal powder by ejecting high-speed gas of 30 m/s or more from a thin tube provided inside the cylindrical burner, the metal powder is ejected from the nozzle of the cylindrical burner at a speed of 30 m/s or less. , a method for producing metal oxide fine powder, which is characterized by suspending it in an oxygen-containing gas and burning it. (2) The method for producing metal oxide fine powder according to claim 1, wherein the thin tube is provided coaxially with the central axis of the cylindrical burner, and the nozzle diameter is 1/3 or less of the nozzle diameter of the cylindrical burner. .