JPS6221701A - Method for continuous production of ultrafine metal oxide powder and apparatus therefor - Google Patents

Abstract

PURPOSE:To obtain the titled ultrafine powder having uniform and stable quality, by forming a raw material containing finely pulverized metallic element in the form of briquette, reacting with chlorine gas and then subjecting to vapor-phase oxidation reaction. CONSTITUTION:Dried (101) and finely pulverized (102) raw material 1 containing metallic element is added with a reducing agent 2, pulverized and mixed (103), added with a granulation assistant 3 and formed in the form of briquette 10. The briquette 10 is calcined (105) in an inert atmosphere and subjected to chlorination reaction (106) by the following process. The briquette is supplied through the feeding tube 9 on a perforated rotary disk 12 in a vertical reaction tube 8, heated with the electrical furnace 16 surrounding the reaction tube 8, and rotated around its own axis by rotating the disk 12 and stopping the motion of the briquette 10 with the stopper 14. At the same time, chlorine gas 4 is supplied from under the disk 12 to and contacted with the briquette to produce a reaction product gas containing a metal chloride 5 and the gas is subjected to the fractional sublimation or distillation (107) to form a metal chloride 5, which is evaporated (108) again by heating and oxidized (109) in vapor phase to obtain ultrafine powder 7 of a metal oxide having a particle diameter of 0.01-0.1mum.

Description

[Detailed description of the invention] [Industrial application field] ZrO2゜Ti 02 , A, which is a sintering raw material for new ceramics, which is a new material with various functions as a structural material.
This article relates to a method and apparatus for continuous production of ultrafine powder of metal oxides such as l2O2, 5to2, etc., which produces submicron-sized ultrafine powders of metal oxides by gas phase oxidation reaction. Metal chloride is generated from raw materials containing metal elements, the generated metal chloride is heated to make it gaseous, and the metal chloride gas is oxidized in the gas phase to obtain ultrafine powder of metal oxide. The present invention relates to a method for producing ultrafine metal oxide powder and an apparatus directly used in the method.

[Conventional technology]

Conventionally, Zr0z, Ti0z, A1203
There are wet methods and dry methods for producing ultrafine powders of metal oxides such as metal oxides.

The wet method is a method for producing fine powder of a metal oxide from a water-H solution, and is a method for producing powder by decomposing a raw mineral with an acid or an alkali and then treating it with various chemicals.

On the other hand, the dry method is also called a gas phase reaction method, and there are two types: an evaporation condensation method that does not involve a chemical reaction, and a method that uses a gas phase oxidation reaction. The evaporation condensation method is a method in which raw materials are heated to a high temperature and vaporized, then cooled twice by a large temperature gradient of an arc or plasma flame, and condensed into fine particles. on the other hand,
The gas-phase oxidation reaction is a method of synthesizing the target substance through the oxidation reaction of volatile metal compound vapor. Of these two methods, the one based on gas phase oxidation reaction is easy to purify as the metal compound used in the reaction is volatile and does not require pulverization of the resulting powder, resulting in a highly pure product and the dispersibility of the resulting particles. It is widely used because it has the advantage that ultrafine particles with a narrow particle size distribution can be easily obtained depending on the reaction conditions. Conventionally, in a gas phase oxidation reaction, a metal chloride is generated using a raw material mineral containing a finely ground metal element, the generated metal chloride is turned into a gas by heating, and the metal chloride gas is converted into a gas phase. Ultrafine powder of metal oxide was obtained through oxidation reaction.

Here, the reason why metal chloride gas is first created is that metal chloride is easy to manufacture, has a high vapor pressure, and has relatively high reactivity.

On the other hand, since the method of synthesizing ultrafine powder such as metal oxides by gas phase oxidation reaction involves high temperatures with a high reaction rate, the properties of the product depend on the structure and temperature distribution of the reactor, the mixing state of the reaction gas, etc. significantly affect.

[Problem that the invention seeks to solve]

By the way, in the conventional gas phase oxidation reaction method, finely pulverized raw material minerals are directly supplied to a reactor and reacted with chlorine gas for reaction. This finely ground raw material mineral is t
It has poor kinetics, tends to cause unevenness in raw material supply, and makes delicate control of raw material supply difficult, impairing the stability of the reaction, and resulting in uneven particle size and unstable properties of the product, the ultrafine powder. It had the disadvantage of inviting

On the other hand, in the wet method, acid/alkali vapors generated during decomposition or by-products generated during chemical treatment are used. ! There is a problem in the processing of these materials, especially when the silica content in the raw materials is converted into sodium silicate gel during alkaline decomposition, making this processing difficult.

The present invention has been made in order to eliminate the above-mentioned drawbacks, and the first invention is to provide a method for producing ultrafine metal oxide powder by a gas phase oxidation reaction, with ease of reaction control and The second invention was made for the purpose of ensuring the stability of the first invention, and the second invention was made for the purpose of providing an apparatus that can be directly used in the first invention.

[Means for solving problems]

In order to achieve such an object, in the first invention, a finely pulverized raw material to which at least one of a reducing agent and a granulation aid is added as required is once formed into briquettes, and the briquettes are A metal oxide characterized in that it is brought into contact with 1 tl of reaction gas at high temperature to produce a reaction product gas containing a metal chloride, and the reaction product gas is fractionated and distilled to produce a metal chloride. This is a method for producing ultrafine powder.

Here, a reducing agent is added as necessary to first reduce the highly stable metal oxide mixed with the raw material in order to obtain a uniform powder of metal oxide, and then to generate gold-11 chloride. It was designed to do so.

Furthermore, although it is generally better not to add a granulation aid, it is added because sufficient crushing strength is often not obtained when briquettes are formed. However, when using a granulation aid, care must be taken that it must be sufficiently calcined at a high temperature in an inert atmosphere as a pretreatment before being subjected to the reaction. This is because if low-temperature volatile substances such as water and hydrocarbons derived from the granulation aid remain in the briquettes, they will cause damage to the mounting system.

On the other hand, in the second invention, the heating means is provided around the vertical tube, and the supply hole in the vertical tube wall is connected to the end of the supply tube with a small inclination for supplying briquettes. ii
A rotatable multi-hole rotary plate is provided in the vertical pipe below the supply hole described in 'ii, and the multi-hole rotary plate is directed from the vertical pipe wall toward the rotation axis of the multi-hole rotary plate near one side of the multi-hole rotation speed. This is a vertical reactor characterized in that a weir is provided in a protruding manner to prevent the second brigget from moving, and chlorine gas for reaction is introduced from below the porous rotary plate.

〔Example〕

Hereinafter, a metal oxide aWI powder continuous method according to an embodiment of the first invention and a vertical reaction tube as a vertical reaction apparatus according to an embodiment of the second invention will be explained based on the drawings.

As shown in the process diagram of FIG. 1, the embodiment according to the first invention involves pulverizing the raw material l of metal minerals dried in the drying step 101 in a pulverizing step 102 using an appropriate method, and A predetermined amount of powdered carbon material 2 as a reducing agent is added to l, and the mixture is pulverized and mixed in a pulverization and mixing step 103.

This powdered carbon substance 2 is combined with 115J contained in the mineral of raw material 1 to become carbon monoxide or carbon dioxide depending on the reaction temperature. Therefore, the predetermined amount of carbon material to be added is determined after determining whether carbon monoxide or carbon dioxide is produced depending on the set reaction temperature. It is preferable that this predetermined amount somewhat exceeds the amount of carbon calculated assuming that all the oxygen in the mineral of raw material 1 is converted to carbon monoxide or carbon dioxide. This is to take into account the amount lost by reacting with oxygen in the air. However, if the amount of excess carbon is too large, the excess amount will remain as unreacted carbon and inhibit the contact between Brichera) 10 and reaction chlorine gas 4, which will be described later. The raw material 1 that has been pulverized and mixed in the pulverization and mixing step 103 is molded into a spherical brigette 10 with a high crushing strength and a diameter of about 10 mm using a briquette machine or a pressure molding machine in the molding step 104. At that time, an appropriate amount of water or an organic binder is added as the granulation aid 3. After adding the granulation aid, a calcination step 105 is performed before the subsequent reaction.
As a pretreatment, the material is sufficiently calcined at a high temperature in an inert atmosphere such as N2.

Subsequently, in the chlorination reaction step 106, as shown in FIGS. 2 and 3, 9. Type reaction tube 8 is used.

The vertical reaction tube 8 according to this embodiment has the following configuration.
An electric furnace 16 is installed around the cylindrical vertical tube 13 as a heating means.
and a supply hole 15 bored and sunk in the vertical pipe wall 17.
and the end of the supply pipe 9 that supplies Briquella 10. The supply pipe 9 is connected to the supply hole 15 so as to have a gentle slope so as not to break the briquettes 10 when the briquettes 10 are supplied. Furthermore, a rotatable circular multi-hole rotary plate 12 is connected between the axis of the vertical pipe 13 and the multi-hole rotary plate 12 so as to prevent the Brigu 2 TolO from falling into the vertical pipe 13 below the supply hole 15 indicated by r'fJ. Insert it so that it matches the rotation axis. Near the upper surface of the multi-hole rotary plate 12, four rod-shaped weirs 1 are arranged parallel to the upper surface at equal intervals from the vertical pipe wall 17.
4 toward the rotation axis of the porous rotary plate 12.
Protrudingly installed to prevent the movement of Brichera) 10 on 2). Furthermore, the reaction chlorine gas 4 is made to flow in from below the porous rotary plate 12. Using this vertical reaction tube 8,
! To carry out the hydrogenation reaction, the briquettes 10 are placed in a vertical reaction tube B.
The chlorination reaction is carried out by supplying and filling the tank from the supply pipe 9.
At this time, the porous rotating disk 12 at the contact interface between the briquette packed bed 11 and the reaction chlorine gas 4 flowing from below is rotated slowly at an angular velocity of about 0.5 to 2 rp so as not to break the briquettes 10. let

Then, the briquette packed layer 11 placed on the porous rotating plate 12 also tries to rotate. However, since the weir 14 prevents the briquettes 10 from moving together with the porous rotating plate 12, the briquettes 10 will rotate on the spot. moreover.

The reaction residue in the form of fine powder generated as the reaction progresses is removed from the briquette-filled jflll, and the removed reaction residue is exhausted through the pores of the perforated rotary plate 12. In this way, the briquettes 1O and the reaction chlorine gas 4 are always brought into effective contact. A reaction product gas is produced using the metal chloride 5 obtained in this chlorination reaction step 106, and the reaction product gas is passed through several traps each held at a predetermined temperature to produce a metal chloride according to each temperature. 5 is separated as a solid or liquid, and in a fractionation sublimation step 107, it is sent individually to a sublimator or a vaporizer for fractionation and sublimation.

The metal chloride 5 that has been fractionated and sublimed is regasified by heating in a regasifying stage 10B, and then put into a burner flame together with a carrier gas in a gas phase oxidation reaction step 109 to cause a gas phase oxidation reaction in a high temperature oxidizing atmosphere. This produces ultrafine metal oxide powder 7 with a uniform particle size. Here, as the fuel to be supplied to the combustion burner necessary for the gas phase oxidation reaction, it is desirable to use a fuel that does not contain moisture in the combustion generated gas, such as carbon monoxide.

This is because the chlorine gas separated from the metal chloride 5 by the gas phase oxidation reaction reacts with water to generate hydrogen chloride, which causes contamination of the equipment and the like. Ultrafine powder 7 of the metal oxide
The particle size of the metal chloride 5 can be adjusted by changing the flow rate of the carrier gas containing the metal chloride 5 gas. O1~0. I Can be controlled within the IL layer.

Note that the chlorine liberated from the metal chloride 5 in the gas phase oxidation reaction step 109 is separated and recovered from the reaction exhaust gas 6 and used again as the reaction chlorine gas 4.

As is clear from the above configuration, according to the embodiment of the first invention, chlorine gas is extracted from the reaction exhaust gas 6 and reused as the reaction chlorine gas 4, thereby preventing environmental pollution and reducing costs. It turns out. In addition, in the gas phase oxidation reaction step 109 according to the present example, the gas containing the metal chloride 5 gas, which is the raw material gas, is directly introduced into the burner flame to perform the gas phase oxidation reaction. There are no factors that affect the properties of the ultrafine oxide powder 7, and it is mainly controlled by conditions related to the burner, such as flame temperature and oxygen flow, and the carrier gas mu. Therefore, if the conditions regarding the burner are kept constant, the properties of the ultrafine gold oxide powder 7 to be produced are determined only by the flow rate of the carrier gas.

In addition, in this embodiment, the metal chloride 5 generated in the chlorination reaction step 106 is immediately regasified in a sublimator or vaporizer after being separated and collected, and then subjected to the gas phase oxidation reaction step 109. This prevents subtle changes in power from occurring. This is because when a composition change occurs, the regasification temperature changes, making it difficult to quantitatively control the gasification process in the sublimator or vaporizer, and the gasification efficiency decreases due to a rapid increase in unsublimated residue. Because it invites you.

〔Effect of the invention〕

According to the first invention, instead of directly reacting finely pulverized minerals containing metal elements with chlorine gas at high temperatures as in the past, the finely pulverized minerals are first molded into briquettes of a predetermined standard, and then chlorine gas is reacted with chlorine gas. Since it is made to react with gas, it has better fluidity than conventional methods, allows for a stable supply of raw materials, and is convenient for mechanical control of processes.

In addition, according to the invention of fiS2, briquettes are replenished from a gently sloping supply pipe directly connected to the vertical pipe to prevent the briquettes from breaking, and the thickness of the briquette packed layer is kept constant, and chlorine for the supply reaction is By keeping the gas flow rate constant, the production rate and properties of metal chlorides can be stabilized. Furthermore, vertical ¥! Since the briquettes are filled into the pipe and reacted with the chlorine gas for reaction, 1
:The reaction progresses in order from the layered briquettes, and the rotation of the porous rotary plate always effectively brings the briquette surface into contact with the reaction chlorine gas, so the reaction progresses efficiently.

In this way, the gas phase oxidation reaction, which is susceptible to slight changes in reaction conditions, was stably controlled, making it possible to continuously produce ultrafine metal oxide powder with more uniform and stable properties.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing a gas phase oxidation reaction according to an embodiment of the first invention, FIG. 2 is a schematic diagram showing a vertical reaction tube according to an embodiment of the second invention, and FIG. 3 is a vertical reaction tube according to an embodiment of the second invention. FIG. 3 is a cross-sectional view taken along line mm of the reaction tube. 1...Raw material 2...Carbon material 3.
... Granulation aid 4 ... Chlorine gas for reaction 5
...Metal chloride 6...Reaction exhaust gas 7.
...Ultrafine powder of metal oxide 8...Vertical reaction tube 9...
・Supply pipe 10...briquette 11・
...briquette charge 1'i! I-layer 12... Porous rotating plate 13... Vertical pipe 14... Weir 15.
・・Supply hole 16・Itt air furnace 17・
・Vertical pipe wall

Claims (1)

[Claims] 1) Generating metal chloride from a raw material containing finely pulverized metal elements, heating the generated metal chloride to make it gaseous, and oxidizing the gas of the metal chloride in the gas phase. In the method for producing ultrafine metal oxide powder, the finely pulverized raw material is mixed with at least one of a reducing agent and a granulation aid as necessary, and then turned into briquettes. The briquettes are molded and brought into contact with reaction chlorine gas at high temperature to produce a reaction product gas containing metal chlorides, and the reaction product gas is fractionally sublimated or fractionally distilled to produce metal chlorides. A method for continuously producing ultrafine metal oxide powder. 2) The method for continuously producing ultrafine metal oxide powder according to claim 1, characterized in that a predetermined amount of carbon material is used as the ring-forming agent. 3) The method for continuously producing ultrafine metal oxide powder according to claim 1, characterized in that a predetermined amount of water or an organic binder is used as the granulation aid. 4) Ultrafine metal oxide powder according to claim 1, characterized in that the briquettes are heated at high temperature in an inert atmosphere when forming the briquettes with the addition of a granulation aid. continuous manufacturing method. 5) When performing gas phase oxidation of metal chloride gas, the metal chloride gas is directly introduced into a flame such as a burner together with a carrier gas to perform gas phase oxidation in a high temperature oxidizing atmosphere. A method for continuously producing ultrafine metal oxide powder according to claim 1. 6) A heating means is provided around the vertical pipe, and a supply hole in the wall of the vertical pipe is connected to an end of the supply pipe with a small slope for supplying briquettes, while a heating means is provided in the vertical pipe below the supply hole. A rotatable porous rotary plate is provided, and a weir is provided near the upper surface of the porous rotary plate to protrude from a vertical pipe wall toward the rotation axis of the porous rotary plate so as to prevent the briquettes on the porous rotary plate from moving. , and a vertical reactor characterized in that chlorine gas for reaction is introduced from below the porous rotary plate.