JPH02199004A - Production of metal oxide particle - Google Patents

Abstract

PURPOSE:To coarsen fine particles by oxidizing metal powder with combustion of an oxidizing gas, forming fine metal oxide particles, applying the fine particles to fibrous carbon according to a specific method, forming a fibrous carbon composite material and burning the resultant composite material with an oxidizing gas. CONSTITUTION:Metal powder, such as Al, is ignited in a vessel containing an oxidizing gas present therein to form the first combustion frame and afford fine metal oxide particles having about 0.1mum particle diameter. A hydrocarbon gas, such as propane gas, is jetted on the periphery of the first combustion flame to cool the fine metal oxide particles and prevent grains from growing. The hydrocarbon gas is simultaneously incompletely burned to form fibrous carbon and the fine metal oxide particles are then applied thereto to form a composite material. An oxidizing gas is subsequently introduced into the composite material to form the second combustion flame and incinerate the fibrous carbon in the composite material. The sticking fine metal oxide particles are aggregated and melted to afford coarse grains having 1-5mum average grain diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing metal oxide particles by a metal powder combustion method, and more specifically to a method for producing coarse metal oxide particles.

[Prior Art] A conventional method for producing metal oxide particles by combustion of metal powder involves forming a combustion flame with an oxidizing gas and metal powder,
Metal powder was evaporated and burned to collect metal oxide particles from the combustion exhaust gas.

The particle size of the metal oxide particles obtained by this method is controlled by adjusting the amount of metal powder and the temperature of the combustion flame. For example, JP-A-60-2
Publication No. 5602 discloses a method for producing ultrafine metal oxide particles by supplying metal powder in an amount sufficient to form a powder cloud and burning it in a flame. The metal oxide particles obtained by this method are spherical or spherical polyhedral and have a particle size of 5 to 11
It is 00n. Furthermore, Japanese Patent Application Laid-open No. 63-252910 discloses that metal powder is supplied into a flame, the metal powder is oxidized to form fine oxide particles, and cooling gas is jetted around the outer periphery of the flame to cool the fine oxide particles. There is a disclosure of a method for obtaining metal oxide fine particles having a particle size of 0.1 μm or less by inhibiting grain growth.

[Problems to be Solved by the Invention] Metal oxide particles may require not only fine particles but also coarse particles depending on the application. In order to produce metal oxide particles with a large particle size, it is considered that the metal oxide fine particles generated after combustion should be made to collide and aggregate to become coarser. However, when the formed metal oxide fine particles become coarse due to natural aggregation, particles that have become larger due to aggregation and those that remain fine particles coexist, making it difficult to obtain uniform particle sizes and particles with a wide particle size distribution. Become.

The present invention aims to solve the above-mentioned problems, to coarsen metal oxide particles and to sharpen the particle size distribution.

[Means for Solving the Problems] The method for producing metal oxide particles of the present invention includes a first combustion flame formed by a metal powder and an oxidizing gas, and a first combustion flame formed by oxidizing the metal powder to form metal oxide fine particles. 1 oxidation step, and jetting hydrocarbon gas around the periphery of the first combustion flame to cool the metal oxide particles and prevent grain growth, and to incompletely burn the hydrocarbon gas to form fibrous carbon. ,
an adhesion step of forming a composite in which the metal oxide fine particles are attached to the IIi fibrous carbon; and a second combustion flame is formed by the composite and oxidizing gas to burn out the fibrous carbon and remove the metal oxide. It consists of a second oxidation step in which fine particles are melted and coarsened.

This metal powder includes aluminum, magnesium,
Mixed metal powder of aluminum and silicon mixed with calcium, silicon, zirconium, titanium and other mullite compositions,
A mixed metal powder of magnesium and aluminum blended in a spinel composition, a mixed metal powder of magnesium, aluminum, and silicon blended in a cordierite composition, etc. can be used.

This oxidizing gas is oxygen or air. This oxidizing gas is used for combustion oxidation of metal powder and combustion removal of fibrous carbon and the like. Hydrocarbon gas is propane gas,
Butane gas, LPG, LNG, etc. are used. This hydrocarbon gas is ejected around the periphery of the first combustion flame within the reaction vessel, and is incompletely combusted by the combustion heat of the first combustion flame to form fibrous carbon.

In the first oxidation step, the metal powder is transported to a reaction vessel using an oxidizing gas such as oxygen gas as a carrier gas, is ignited, forms a first combustion flame, and produces metal oxide fine particles (about 0.1μ
m) is formed in the first combustion flame.

In the adhesion step, hydrocarbon gas is ejected around the periphery of the first combustion flame, absorbs the combustion heat of the first combustion flame, cools the generated metal oxide fine particles, and prevents grain growth. This burnt hydrocarbon gas is incompletely combusted to form 41M carbon. To achieve incomplete combustion of this hydrocarbon gas,
This can be done by using less oxidizing gas than the reaction equivalent of hydrocarbon gas. The fibrous carbon adheres to the metal oxide fine particles formed in the first combustion flame to form a composite. In order to uniformly adhere metal oxide fine particles to the fibrous carbon produced at this time, it is preferable to agitate the product by ejecting hydrocarbon gas from the side wall, for example. This composite precipitates in the form of, for example, a bunch of grapes. In addition, the ratio of the amount of oxygen gas and the amount of hydrocarbon gas ejected in the deposition process (502/C3H
The particle size of the metal oxide fine particles can be controlled by e >. In particular, it is preferable that the ratio is in the range of 1.0 to 0.8 because it brings about good results in the formation of the composite and the coarsening of the metal oxide particles.

In the second oxidation step, an oxidizing gas such as oxygen gas or air is introduced into the composite produced in the deposition step to form a second combustion flame and burn out the fibrous carbon of the composite. At this time, when the fibrous carbon of the composite is burned, the attached metal oxide fine particles coagulate, are melted, and become coarse. Therefore, by adjusting the ratio of the amount of oxidizing gas and hydrocarbon gas flowing into the reaction vessel, the generation of fibrous carbon can be controlled, and the number of metal oxide fine particles attached to the fibrous carbon can also be changed. do. For this reason, it is thought that the amount of agglomeration of metal oxide fine particles during combustion and melting changes, and the particle size of the metal oxide particles, which become coarse, is controlled. Further, the amount of metal oxide fine particles adhering to the fibrous carbon is considered to be approximately the same per fibrous carbon, and the particle size distribution of the coarse particles becomes sharp. The produced metal oxide particles have, for example, an average particle size of 1 to 5 μm.

The generated metal oxide particles are easily separated from by-products such as combustion exhaust gas, for example, by a bag filter.

[Function] In the method for producing metal oxide particles of the present invention, the metal oxide fine particles generated in the first oxidation step are cooled by the hydrocarbon gas introduced to the periphery of the first combustion flame, and grain growth is inhibited. , by attaching metal oxide fine particles to the fibrous carbon produced by incomplete combustion of the hydrocarbon gas to form a composite, and in a second oxidation step, introducing an oxidizing gas to this composite and burning it. The fibrous carbon is burned and removed, and the attached metal oxide particles are aggregated and melted to form coarse particles. Further, the ratio of the metal oxide fine particles attached to the fibrous carbon to the fibrous carbon is considered to be almost the same, and the particle size distribution of the coarse particles becomes sharp. By this method, coarse metal oxide particles having an average particle size of 1 to 5 μm can be easily obtained.

[Example] The present invention will be specifically explained below using Examples.

FIG. 1 shows a schematic cross-sectional view of the reaction apparatus used in this example. This reaction vessel 5 has metal powder, powder and oxygen gas 3 on the upper wall.
A supply section 1 from which propane gas 4 is ejected through a nozzle is provided on the side wall, a propane gas supply port 12, an oxygen gas ejection lower, and a discharge section 10 for discharging products and the like.

The reaction vessel 5 has a space for protecting the combustion flame 8 and the flame 9, and the inner wall is insulated with firebrick. The inside of the reaction vessel 5 is divided by a partition wall 6 made of a heat insulating material into an upper chamber 5a where the first oxidation step and the adhesion step are carried out and a lower chamber 5b where the second oxidation step is carried out. This upper chamber 5a and lower chamber 5
The partition wall 6 separating the parts b has an opening 6a as shown in FIG. 2 through which the two communicate. A propane gas supply port 12 is provided in the side wall of the upper chamber 5a. As shown in Fig. 3, there are four oxygen gas ejection lowers on the upper side wall of the lower chamber 5b.
Further, in the lower part, there is provided a discharge section 10 consisting of a bag filter 11 for separating metal oxide particles and a blower 11a for discharging exhaust gas to the outside of the system.

At the upper W5a of the reaction vessel 5, the lower mouth of the hopper 2a is connected to a conveying pipe 3a, and the filled aluminum powder 2 is supplied from the upper part to the first combustion flame 8 in the reaction vessel 5 through a nozzle with oxygen gas 3. At the same time, a supply pipe 4a for propane gas 4 is provided in the nozzle portion of the transport pipe 3a for oxygen gas 3, and a nozzle for ejecting the gas to the outer periphery of the first combustion flame 8 is disposed.

Furthermore, there is a propane gas supply port 12 at the lower part of the side wall of the upper chamber 5a, which blows out propane gas to stir and mix the gas and metal oxide fine particles in the upper chamber 5a, and adjusts the oxygen gas/propane gas ratio. Promotes the formation of composites.

In the lower chamber 5b, the composite formed in the upper chamber 5a and the combustion exhaust gas are guided through the opening 6a of the partition wall 6, and oxygen gas is further introduced from the lower blowout in the side wall to form a second combustion flame 9 and burn it. The metal oxide particles and combustion exhaust gas are then discharged from the discharge section 1o.

Aluminum powder with a purity of 99.9% (#
350) 2 is supplied to the reaction vessel 5 with oxygen gas 3.

Oxygen gas 3 was passed at a flow rate of 4 Nml/hour to transport metal aluminum powder 2 to reaction vessel 5, and ignited it in upper chamber 5a to form first combustion flame 8. Near the center of this first combustion flame 8, the metal aluminum powder is oxidized and the particle size becomes 0.
．． The result is aluminum oxide fine particles of about 1 μm.

Attachment step Propane gas 4 is applied to the periphery of this first combustion flame through the nozzle 4a.
The first combustion flame 8 is supplied at a flow rate of 1 Nml/hour to prevent the fine particles of aluminum oxide produced by cooling the first combustion flame 8 from growing. Further, the ratio of oxygen gas and propane gas is adjusted to cause incomplete combustion of propane gas 4 to form fibrous carbon. In addition, in order to increase the production rate of fibrous carbon and l! In order to bring the fibrous carbon into sufficient contact with the metal oxide fine particles to increase the production rate of the composite, and to ensure that the metal oxide fine particles uniformly adhere to each fibrous carbon, the jet is ejected from the spout 12 at the bottom of the side wall. Further, propane gas was jetted out at a flow rate of 0.3 Nrl/hour to mix and stir. At the periphery of the first combustion flame 8, fibrous carbon is generated due to incomplete combustion due to combustion heat, and oxide fine particles falling from the first combustion flame are attached to form a composite.

The generated composite and combustion exhaust gas are discharged through the opening 6 of the partition wall 6.
from a to the lower chamber 5b.

The composite material and combustion exhaust gas introduced into the lower chamber 5b through the opening 6a of the second oxidation step partition wall 6 are oxidized to the second oxidation step by newly injected oxygen gas.
A combustion flame 9 is formed and combustion occurs.

At this time, in order to improve the combustibility of the composite and the combustion exhaust gas generated in the adhesion process in the lower chamber 5b, a partition wall 6 is provided to separate the first combustion flame from the first combustion flame. The lower chamber 5b is opened by an opening 6a provided at a certain position. Oxygen gas injected into the lower chamber is 1ONml
The composite was ejected from four ejection lowers at a flow rate of /hour to form a second combustion flame 9 and burn it. This blowout lower blows out oxygen gas from four locations to stir the contents in order to obtain the effect of stirring to improve the combustibility of the burnt material forming the second combustion flame and loosening the composite. In this second combustion flame, the fibrous carbon of the composite is burned and removed, and the attached aluminum oxide fine particles are aggregated and melted to become coarse particles. The products are separated from the combustion exhaust gas by a bag filter 11 of the separator. The separated metal oxide particles had an average particle size of 5 μm.

In the above manufacturing method, if the ratio of oxygen gas and propane gas introduced into the upper chamber 5a of the reaction vessel 5 is changed, the particle size of the obtained particles changes. The results are shown in FIG. The horizontal axis represents the ratio of oxygen gas to propane gas, and the vertical axis represents the specific surface area of the particles to show the relationship between the two. The ratio is 1.
The range 0-0.8 showed the minimum specific surface area. The reason for this is that as the number of gaps between hydrocarbon gases increases, the number of metal oxide fine particles adhering to the fibrous carbon per unit decreases, so the relative amount of metal oxide fine particles that aggregate during combustion and melting decreases, resulting in coarse particles. It is thought that the particle size of the particles becomes smaller. In addition, when the amount of oxygen gas increases, the amount of fibrous carbon produced decreases, so i1M per unit
As the number of metal oxide fine particles that adhere to the shaped carbon increases, more particles are melted and the particles become coarser. However, if the amount of oxygen gas increases too much, cooling in the first combustion flame becomes insufficient, particle growth occurs, and adhesion to the fibrous carbon becomes insufficient, making it impossible to control coarsening and reducing the particle size. Therefore, the particle size can be controlled by adjusting the ratio of oxygen gas to propane gas.

[Effect] According to this method for producing metal oxide particles, metal oxide particles that are coarse and have a sharp particle size distribution can be easily produced with good reproducibility.

Furthermore, the particle size of the metal oxide particles obtained can be controlled by adjusting the ratio (502/C3Ha) of oxygen gas and hydrocarbon gas introduced into the upper chamber of the reaction vessel.

[Brief explanation of the drawing]

FIG. 1 is a schematic longitudinal sectional view of a reaction apparatus used in an embodiment of the present invention, and FIG. 2 corresponds to the A-A cross section of the partition wall between the upper chamber of the reaction vessel and the royal room in FIG. 1. FIG. 3 is a cross-sectional view of the reaction vessel corresponding to the A'-A-section of the oxygen gas outlet in the lower chamber of the reaction vessel in FIG. 1; FIG. 4 is a diagram showing the relationship between the ratio of oxygen gas/propane gas introduced into the upper chamber and the particle size of the generated aluminum oxide particles. 1. Supply section 2. Metal powder 3. ...Oxygen gas 4...Propane gas 5...Reaction container 5a...Upper chamber 5b...Lower chamber 6.
...Partition wall 7...Oxygen gas outlet 8...Combustion flame 9...Flame 10...Discharge part 12...
・Propane gas supply port

Claims (1)

[Claims] (1) A first oxidation step in which a first combustion flame is formed using metal powder and an oxidizing gas, and the metal powder is oxidized to form metal oxide fine particles; and hydrocarbon gas is ejected around the periphery of the first combustion flame. to cool the metal oxide particles and prevent grain growth, and to incompletely burn the hydrocarbon gas to form fibrous carbon;
an adhesion step of forming a composite in which the metal oxide fine particles are attached to the fibrous carbon; and a second combustion flame is formed by the composite and oxidizing gas to burn out the fibrous carbon and remove the metal oxide fine particles. A method for producing metal oxide particles, comprising a second oxidation step of melting and coarsening the metal oxide particles.