JP2021069970A - Spray pyrolysis apparatus - Google Patents

Abstract

To provide a spray pyrolysis apparatus capable of producing fine particles having a uniform shape and a particle diameter without requiring a pyrolysis furnace having a large diameter when a plurality of spray devices is used.SOLUTION: A spray pyrolysis apparatus 100 comprises: a drying pipe 1 to dry a sprayed raw material solution; and a pyrolysis furnace 2 to pyrolyze dried particles generated from the raw material solution. Two or more sets of the drying pipes 1 are arranged at one end of the pyrolysis furnace 2 and have a structure where a vertical pipe part 1a extending in a vertical direction and a horizontal pipe part 1b extending in a horizontal direction toward the vertical pipe part 1a are coupled. In the vertical pipe part 1a, a spray device 3 for spraying the raw material solution is housed.SELECTED DRAWING: Figure 1

Description

The present invention relates to a spray pyrolysis apparatus.

As an apparatus for producing inorganic oxide particles, for example, a spray pyrolysis apparatus is used (Patent Documents 1 and 2). This spray pyrolysis device is equipped with a fluid nozzle for spraying the mist of the raw material solution and a combustion burner for generating combustion gas in the pyrolysis furnace, and is installed below the pyrolysis furnace. Inorganic oxide particles are produced by spraying mist upward from a fluid nozzle and heat-treating the mist using combustion gas as a heat source. Then, the inorganic oxide particles are moved to the bag filter by the attraction fan and collected as a product. As the fluid nozzle, a two-fluid nozzle or a three-fluid nozzle is usually used, and in mass production, a plurality of fluid nozzles or a single large nozzle are used.

Japanese Unexamined Patent Publication No. 2001-17857 Japanese Unexamined Patent Publication No. 2019-25385

However, according to the studies by the present inventors, it has been found that there are the following problems in the production of inorganic oxide particles using the conventional spray pyrolysis apparatus. That is, when a plurality of fluid nozzles are used, the mists sprayed from the adjacent fluid nozzles interfere with each other (collision), the mist diameter increases, and it becomes difficult for the particles to become fine particles. In order to solve such a problem, it is conceivable to install fluid nozzles at predetermined intervals, but it is unavoidable to increase the diameter of the pyrolysis furnace. Increasing the diameter of the pyrolysis furnace not only increases the amount of heat required, but also makes it difficult to perform uniform heat treatment. In addition, when the diameter of the pyrolysis furnace is increased, it is conceivable to install a large nozzle, but it takes a long furnace length for the mist to diffuse to the vicinity of the inner diameter of the pyrolysis furnace, thereby heating the mist. The time is shortened and the heat treatment is insufficient. Furthermore, it is conceivable to suppress the spread of the mist sprayed from the adjacent fluid nozzle, but if the spread of the mist is suppressed, the mist extends in the vertical direction (straight direction of the spray), so that the residence time in the furnace is shortened. , The heat treatment varies, and it becomes difficult to obtain uniform fine particles.
An object of the present invention is a spray pyrolysis device capable of producing fine particles having a uniform shape and particle size without requiring an increase in the diameter of the pyrolysis furnace when a plurality of spray devices are used, and an inorganic substance using the spray pyrolysis device. The purpose is to provide a method for producing oxide particles.

As a result of examination in view of the above problems, the present inventors have found that an increase in mist diameter due to interference between mists sprayed from a plurality of spraying devices causes the mist to dry in the thermal decomposition furnace of the conventional spraying pyrolysis device. It turned out to occur only before. Therefore, the present inventors individually house the spraying device and provide a spray pyrolysis device provided with a drying tube for drying the mist sprayed from the spraying device so that the sprayed mist can be collected in the drying tube. Since it dries quickly and moves to the pyrolysis furnace as dried particles, the increase in mist diameter due to interference between mists is suppressed, and even if multiple sprayers are used, fine particles with uniform shape and particle size can be produced. Found that it can be manufactured.

That is, the present invention provides the following [1] to [9].
[1] A drying tube for drying the sprayed raw material solution and
Equipped with a pyrolysis furnace for thermally decomposing dry particles generated from the raw material solution
Two or more drying pipes are installed at one end of the pyrolysis furnace, and have a structure in which a vertical pipe portion extending in the vertical direction and a horizontal pipe portion extending in the horizontal direction toward the vertical pipe portion are connected.
A spraying device for spraying the raw material solution is housed in the vertical pipe section.
Hot air is supplied from the horizontal pipe to the vertical pipe.
Spray pyrolysis device.
[2] The spray thermal decomposition apparatus according to the above [1], wherein the drying pipe is connected with a horizontal pipe portion and a vertical pipe portion with their central axes offset from each other.
[3] The spray thermal decomposition apparatus according to the above [1] or [2], wherein the horizontal pipe portion is connected to the vertical pipe portion at an inclination angle of 10 to 80 °.
[4] The spray pyrolysis apparatus according to any one of [1] to [3] above, wherein the inner diameter of the horizontal pipe portion of the portion connected to the vertical pipe portion is smaller than that of the vertical pipe portion.
[5] The method for producing inorganic oxide particles according to any one of [1] to [4] above, wherein the spraying device is a fluid nozzle.
[6] The spray pyrolysis apparatus according to any one of [1] to [5] above, wherein the pyrolysis furnace has an auxiliary heat source.
[7] The spray pyrolysis apparatus according to [6] above, wherein the auxiliary heat source is one or more selected from a combustion burner, a hot air heater, and an electric heater.
[8] Inorganic oxide particles comprising a step of spraying a mist of a raw material inorganic compound-containing solution from the spray device and thermally decomposing it using the spray thermal decomposition device according to any one of the above [1] to [7]. Manufacturing method.
[9] The above-mentioned [8], wherein the raw material inorganic compound is one or more selected from aluminum salt, titanium salt, magnesium salt, calcium salt, borate, aluminosilicate, aluminum alkoxide and silicate alkoxide. Method for producing inorganic oxide particles.

According to the spray pyrolysis device of the present invention, the spray device is individually housed in a drying tube, and the mist sprayed from the spray device is quickly dried in the drying tube and moved to the pyrolysis furnace as dry particles. The increase in mist diameter due to interference between mists is suppressed, and even if a plurality of spraying devices are used, fine particles having a uniform shape and particle size can be easily produced. In addition, since it is possible to prevent the generation of sticking substances on the inner wall of the drying pipe, it is possible to stably and efficiently produce inorganic oxide particles.

It is a schematic diagram which shows an example of the spray thermal decomposition apparatus of this invention. It is an enlarged view of the drying tube part which concerns on the spray thermal decomposition apparatus of this invention. It is a schematic diagram which shows an example of the conventional spray thermal decomposition apparatus.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate description will be omitted. Also, for convenience of illustration, the dimensional ratios in the drawings do not always match those described.

[First Embodiment]
FIG. 1 is a schematic view showing an example of the spray pyrolysis apparatus of the present invention.
As shown in FIG. 1, the spray thermal decomposition apparatus 100 includes a drying tube 1 for drying the sprayed raw material solution and a thermal decomposition furnace 2 for thermally decomposing the dried particles generated from the raw material solution. Is. Two or more drying pipes 1 are installed at one end of the pyrolysis furnace 2, and a vertical pipe portion 1a extending in the vertical direction and a horizontal pipe portion 1b extending in the horizontal direction toward the vertical pipe portion 1a are connected to each other. It has a structure, and a spraying device 3 for spraying a raw material solution is housed in a vertical pipe portion 1a. A pump 6 for feeding the raw material solution contained in the raw material solution tank 5 is installed on the upstream side of the spraying device 3, and the amount of the raw material solution fed is controlled by the flow meter 7.

Any material used as the furnace material can be used as the pyrolysis furnace, and the pyrolysis furnace may be selected in consideration of the heating temperature and the like. Further, it is common to use refractory bricks, heat insulating bricks, castables, etc. alone, in layers, or in combination thereof on the inner wall of a metal shell.
The shape of the pyrolysis furnace is preferably a rigid cylindrical shape in that a swirling flow can be generated in the pyrolysis furnace.
The size of the pyrolysis furnace can be appropriately selected according to the production scale. For example, in the case of a rigid cylindrical shape, the inner diameter is preferably 600 to 1600 mm, and the height is preferably 3000 to 3000. It is 10000 mm.

The drying pipe may be installed at either the upper end or the lower end of the pyrolysis furnace, but it is preferable to install the drying pipe at the lower end of the pyrolysis furnace from the viewpoint of preventing mist from adhering to the inner wall of the drying pipe.
The number of drying tubes is not particularly limited as long as it is 2 or more, but 2 to 4 tubes are preferable. It is preferable that the drying tubes are installed in parallel at equal intervals along the inner circumference of the pyrolysis furnace.

The materials of the vertical pipe portion and the horizontal pipe portion are not particularly limited as long as they are heat resistant, and examples thereof include metals such as iron, stainless steel, Inconel, Hastelloy, and titanium, ceramics, bricks, and amorphous refractories.
The shape of the vertical pipe portion and the horizontal pipe portion is preferably substantially cylindrical from the viewpoint of ease of connection and suppression of temperature unevenness and dissipated heat unevenness.

The size of the vertical pipe portion and the horizontal pipe portion can be appropriately set according to the size of the pyrolysis furnace. For example, in the case of a substantially cylindrical shape, the inner diameter is preferably 150 to 400 mm. The height is preferably 300 to 1000 mm.
The inner diameter of the portion of the horizontal pipe portion connected to the vertical pipe portion is preferably smaller than the inner diameter of the vertical pipe portion. As a result, a swirling flow is generated in the drying pipe by the hot air supplied from the horizontal pipe portion to the vertical pipe portion, and mist can be entrained in this swirling flow, so that it is possible to prevent the mist from adhering to the inner wall of the drying pipe. it can. The inner diameter of the connecting portion of the horizontal pipe portion is preferably 90% or less of the inner diameter of the vertical pipe portion from the viewpoint of easily generating a swirling flow in the drying pipe and preventing mist from adhering to the inner wall of the drying pipe.

The horizontal pipe portion is preferably connected to the vertical pipe portion by inclining upward, and more preferably connected to the vertical pipe portion at an inclination angle of 10 to 80 °. As a result, the hot air supplied from the horizontal pipe portion to the vertical pipe portion generates a stronger swirling flow in the drying pipe, and mist can be involved in this swirling flow, so that the mist adheres to the inner wall of the drying pipe more highly. Can be prevented at the level. As shown in FIG. 2, the "tilt angle" referred to here is a horizontal plane passing through the intersection of the central axis of the inner diameter of the horizontal pipe portion and the central axis of the inner diameter of the vertical pipe portion, and the central axis of the horizontal pipe portion. The angle θ formed by. The range of the inclination angle is preferably 20 to 80 °, more preferably 30 to 75 °, from the viewpoint of easiness of generating a swirling flow in the drying pipe and prevention of mist from adhering to the inner wall of the drying pipe.

Further, in the vertical pipe portion and the horizontal pipe portion, it is preferable that the horizontal pipe portion and the vertical pipe portion are connected by shifting their central axes. As a result, a stronger swirling flow is generated in the drying pipe by the hot air supplied from the horizontal pipe portion to the vertical pipe portion, and the sprayed mist rides on this swirling flow and is quickly dried. It is possible to prevent the adhesion of mist. The term "shifting the central axis" as used herein means that, as shown in FIG. 2, the central axis of the inner diameter of the horizontal pipe portion and the central axis of the inner diameter of the vertical pipe portion are displaced at the connecting portion. The deviation of the central axis is preferably 10% or more and 90% or less, more preferably 20% or more and 80% or less, assuming that the inner diameter of the vertical pipe portion is 100%. As a result, the speed of the swirling flow is sufficiently increased, so that the adhesion of mist to the inner wall of the drying pipe can be suppressed at a higher level.

One spraying device is housed in the vertical pipe portion.
The spraying device is not particularly limited as long as it can be accommodated in the vertical pipe portion, and examples thereof include a fluid nozzle. Examples of the fluid nozzle include a 1-fluid nozzle, a 2-fluid nozzle, a 3-fluid nozzle, and a 4-fluid nozzle. Among them, a two-fluid nozzle, a three-fluid nozzle, and a four-fluid nozzle are preferable, and a three-fluid nozzle and a four-fluid nozzle are more preferable. In the spray pyrolysis apparatus shown in FIG. 1, one fluid nozzle is installed upward in the vertical pipe portion. The spray device may be protected by a heat insulating material or the like, if necessary, in consideration of heat resistance.

The fluid nozzle method includes an internal mixing method in which the gas and the raw material solution are mixed inside the nozzle and an external mixing method in which the gas and the raw material solution are mixed outside the nozzle, both of which can be adopted. As the gas supplied to the nozzle, for example, air, an inert gas such as nitrogen or argon, or the like can be used. Above all, air is preferable from the viewpoint of economy.

At the end of the horizontal pipe portion, a heat source device for supplying hot air from the horizontal pipe portion to the vertical pipe portion can be installed. Examples of such a heat source device include a combustion burner, a hot air heater, and an electric heater, but the heat source device is not particularly limited as long as it has a sufficient amount of heat for drying the mist.
One or two or more such heat source devices can be installed, but preferably one. In addition, in the spray pyrolysis apparatus shown in FIG. 1, one combustion burner 4 is installed in a horizontal pipe so that combustion gas flows in the direction of the vertical pipe portion.

Any of the combustion burners, hot air heaters, and electric heaters that are generally sold can be used. Considering the volume, specifications, etc. of the pyrolysis furnace, the model suitable for this may be selected. Further, it may be manufactured according to the specifications of the pyrolysis furnace.

The fuel used for the combustion burner is not particularly limited, and examples thereof include gas fuel, liquid fuel, and solid fuel, and two or more of these fuels may be co-fired. Examples of the gaseous fuel include LPG, city gas, and vaporized organic matter. Examples of the liquid fuel include liquefied organic substances such as kerosene, light oil, heavy oil and recycled oil. Examples of the solid fuel include powdered coal, charcoal, wood and the like.

When the combustion burner is installed in the horizontal pipe portion, the length of the horizontal pipe portion is preferably such that the flame generated from the combustion burner does not come into direct contact with the spray mist. A mechanism capable of moving the combustion burner in the front-rear direction may be provided so that the flame of the combustion burner does not come into contact with the spray mist, and may be adjusted as necessary.

As shown in FIG. 1, an auxiliary heat source 8 may be installed on the outer periphery of the pyrolysis furnace 2. As a result, a sufficient amount of heat dissipated can be imparted, so that the temperature and holding time required for the synthesis of the inorganic oxide particles can be stably secured with good reproducibility.
Examples of the auxiliary heat source include one or more selected from a combustion burner, a hot air heater, and an electric heater. The number of auxiliary heat sources installed may be one, but depending on the length of the pyrolysis furnace, two to six may be installed. In the spray pyrolysis apparatus shown in FIG. 1, six electric heaters are installed as auxiliary heat sources.

Further, by arranging the auxiliary heat source in the same swirling direction as the swirling flow from the vertical pipe portion, the swirling flow can be supplemented by the hot air generated from the auxiliary heat source.
Further, the auxiliary heat source may be installed at a different surface or height in order to adjust the temperature in the furnace and the swirling flow. The installation surfaces may be arranged vertically or facing each other in the pyrolysis furnace. The installation height may be the same height (on the same circumference) or different steps.
When a combustion burner is used as an auxiliary heat source, it is preferable to install it so that the flame does not come into direct contact with the dry particles in order to prevent excessive reaction and melting or deformation of the particles. In order to prevent the flame of the combustion burner from entering the furnace, a mechanism capable of moving the combustion auxiliary burner in the front-rear direction may be provided and adjusted according to the length of the flame.

A recovery device 9 and an attraction fan 10 can be installed at the other end of the pyrolysis furnace 2. As a result, the fine particles are moved to the collection device 9 by the attraction fan 10 and collected. Examples of the recovery device include a bag filter.
Further, cooling recovery may be performed by providing a space on the other end side of the pyrolysis furnace into which cooling air can be introduced and introducing cooling air into the space. As a means for introducing the cooling air, an installation of a cooling air suction unit, a means for sending the cooling air from a fan or a blower, or the like can be adopted. These may be performed from a plurality of places. Further, instead of the cooling air, water cooling may be performed, and ion-exchanged water, clean water, or the like can be used. Further, a cyclone may be arranged on the upstream side of the recovery device in order to reduce the load of the recovery device and recover coarse particles and foreign substances. .. On the other hand, dust removal and purification equipment such as a scrubber may be arranged on the downstream side of the recovery device, if necessary.

Next, a method for producing inorganic oxide particles using the spray pyrolysis apparatus according to the present embodiment will be described.

First, a raw material inorganic compound-containing solution is prepared.
The raw material inorganic compound-containing solution may be prepared by mixing the raw material inorganic compound and the solvent. The mixing method of the raw material inorganic compound and the solvent may be such that both are added at the same time and mixed, or the other is added to one and mixed, and the mixing method is not particularly limited.

The raw material inorganic compound is not particularly limited as long as it is a compound containing an element constituting an inorganic oxide and dissolved in a solvent such as water, and examples thereof include an inorganic salt and a metal alkoxide. Examples of the inorganic salt include aluminum salt, titanium salt, magnesium salt, calcium salt, borate, zinc salt, zirconium salt, barium salt, cesium salt, yttrium salt and aluminosilicate. Examples of the metal alkoxide include aluminum alkoxide and silicate alkoxide. As the raw material inorganic compound, one kind or two or more kinds can be used.

Examples of the aluminum salt include aluminum nitrate, aluminum sulfate, aluminum chloride, aluminum phosphate, aluminum hydroxide, aluminum acetate, and aluminum oxalate. Examples of the magnesium salt include magnesium nitrate, magnesium sulfate, magnesium chloride, magnesium phosphate, and magnesium hydroxide. Examples of the calcium salt include calcium nitrate, calcium chloride, calcium hydroxide, calcium formate, calcium acetate, and calcium propionate. Examples of the borate include metaborates such as sodium borate and potassium borate, tetraborates such as sodium tetraborate and potassium tetraborate, and pentaborates such as sodium pentaborate and potassium pentaborate. Borate can be mentioned. Examples of the silicate alkoxide include tetramethyl orthosilicate (TMS), tetraethyl orthosilicate (TEOS), tetrapropyl orthosilicate (TPOS), and tetrabutoxysilane. Further, a solution in which aluminum oxide and silicon oxide are dispersed in a solvent, and a sol solution of aluminum oxide and silicon oxide can also be used as a raw material solution.
Among them, as the raw material inorganic compound, one selected from aluminum salts, titanium salts, magnesium salts, calcium salts, borates, aluminosilicates, aluminum alkoxides and silicate alkoxides because the effects of the present invention can be easily enjoyed. Alternatively, two or more are preferable, and one or two or more selected from aluminum salts, magnesium salts, calcium salts, borates and silicate alkoxides are more preferable.

Examples of the oxide obtained from the raw material inorganic compound include oxides composed of metal oxides, alumina, silica, aluminum and silicon. More specifically, examples thereof include oxides composed of alumina, silica, aluminum and silicon, titanium oxides, magnesium oxides, zinc oxides, zirconium oxides, barium oxides, cerium oxides and yttrium oxides. A composite oxide that combines these oxides can also be mentioned.

Examples of the solvent include water and organic solvents. Of these, water is preferable from the viewpoint of environmental impact and manufacturing cost.

The concentration of the raw material inorganic compound in the raw material inorganic compound-containing solution is preferably 0.01 mol / L to a saturated concentration, preferably 0.1 to 1.0 mol, in consideration of the particle size distribution, density, strength, etc. of the obtained inorganic oxide particles. / L is more preferable.

Next, while supplying hot air from the horizontal pipe portion of the drying pipe to the vertical pipe portion, the mist of the raw material inorganic compound-containing solution is sprayed from the spraying device mounted on the vertical pipe portion of the drying pipe. As a result, the mist caught in the flow of hot air supplied from the horizontal pipe portion to the vertical pipe portion evaporates the solvent and dries quickly, and inorganic salts (dry particles) are deposited on the mist surface. The hot air supply source may be a combustion burner, a hot air heater, or an electric heater.

The temperature inside the drying tube is not particularly limited as long as the solvent evaporates from the mist of the raw material inorganic compound-containing solution, but for example, 100 to 500 ° C. is preferable, 150 to 450 ° C. is more preferable, and 200 to 400 ° C. is further preferable. preferable.

A fluid nozzle is preferable as the spraying device. The specific embodiment of the fluid nozzle is as described above.

The average particle size of the mist is preferably 0.5 to 60 μm, more preferably 1 to 20 μm, and even more preferably 1 to 15 μm. The average particle size of the mist can be adjusted by adjusting the shape of the ejection port of the spraying device and the pressure of the gas supplied to the spraying device.

Then, the inorganic salt (dry particles) precipitated on the mist surface is thermally decomposed by applying heat by the auxiliary heat source of the thermal decomposition furnace, and the inorganic salt is oxidized to generate inorganic oxide particles. The auxiliary heat source may be a combustion burner, a hot air heater, or an electric heater.

The temperature in the pyrolysis furnace is preferably 400 to 1800 ° C, more preferably 600 to 1500 ° C, further preferably 700 to 1400 ° C, still more preferably 900 to 1200 ° C. If it is less than 400 ° C., the thermal decomposition reaction tends to be insufficient, and if it exceeds 1800 ° C., it is difficult to sufficiently cool the particles when they are discharged to the outside of the thermal decomposition furnace, and the particles tend to aggregate with each other.

Next, the inorganic oxide particles generated by the thermal decomposition reaction are recovered. For example, in the spray thermal decomposition apparatus shown in FIG. 1, the inorganic oxide particles are transferred from above the thermal decomposition furnace to the recovery apparatus 9 by the attraction fan 10. Moved and recovered. Further, when recovering the inorganic oxide particles, the particle size may be adjusted by passing the particles through a filter.

[Second Embodiment]
The spray pyrolysis device according to the first embodiment is different from the spray pyrolysis device according to the first embodiment in that the pipe for sending the exhaust gas from the recovery device is connected to the horizontal pipe portion of the drying pipe. .. That is, in the spray pyrolysis apparatus 100 shown in FIG. 1, a combustion burner 4 is attached to the horizontal pipe portion 1b of the drying pipe 1 as a hot air supply source, whereas the spray pyrolysis apparatus according to the present embodiment has the same. The difference is that such a heat source device is not installed, and a pipe for sending the exhaust gas from the recovery device is connected to the horizontal pipe portion of the drying pipe.
Since the exhaust gas usually has a heat of about 200 to 300 ° C., the mist of the raw material solution sprayed from the spraying device is discharged by sending the exhaust gas from the horizontal tube portion to the vertical tube portion of the drying tube. The solvent can be evaporated and dried while being involved in the flow of the gas to produce dry particles.

The pipe for feeding the exhaust gas from the recovery device is not particularly limited as long as it has heat resistance, and examples thereof include metals such as iron, stainless steel, Inconel, Hastelloy, and titanium. A metal fitting such as a bolt, a pin, or an L-shaped metal fitting can be used to fix the pipe to the horizontal pipe portion.
The other configurations of the spray pyrolysis apparatus according to the present embodiment are as described in the first embodiment.

Next, a method for producing inorganic oxide particles using the spray pyrolysis apparatus according to the present embodiment will be described.
Also in the present embodiment, the inorganic oxide particles can be produced by the same method as in the first embodiment. First, a raw material inorganic compound-containing solution is prepared. Next, while supplying the exhaust gas from the recovery device from the horizontal pipe portion of the drying pipe to the vertical pipe portion via a pipe, the mist of the raw material inorganic compound-containing solution is sprayed from the spraying device of the vertical pipe portion of the drying pipe to dry it. Inorganic oxide particles can be produced by generating dry mist particles in a pipe and thermally decomposing them in a thermal decomposition furnace. Then, the inorganic oxide particles are moved to the recovery device by the attraction fan and recovered.

The inorganic oxide particles produced by the method of the present invention may be solid particles, porous particles, hollow particles, or a mixture of two or more of these. Here, the term "solid particles" as used herein means particles having a structure having no internal cavity, for example, particles composed of a single layer, and a core (also referred to as an inner core) and a shell layer. Particles having (also called an outer shell) can be mentioned. Further, the “hollow particle” refers to a particle having a structure having a cavity (hollow portion) inside and having a cavity surrounded by an outer shell. The number of cavities may be singular or plural. Further, the “porous particle” refers to a particle having a large number of through holes connected from the surface of the particle to the inside. The size and shape of the through hole are not particularly limited. Further, the particles may have closed pores inside.

When producing the inorganic oxide hollow particles, the surface of the inorganic oxide particles after thermal decomposition may be melted. As a result, the pores existing on the surface of the inorganic oxide particles are closed, and the inorganic oxide hollow particles having no pores in the outer shell of the particles and having high particle strength can be obtained. In order to melt the surface of the inorganic oxide particles, for example, the temperature of the auxiliary heat source may be controlled to be equal to or higher than the melting temperature of the inorganic oxide particles.

Further, the inorganic oxide particles produced by the method of the present invention have a substantially spherical shape, and the average circularity thereof is usually 0.85 or more. Here, the "average circularity" in the present specification means a value calculated by the following method, and the closer the shape of the particle is to a true sphere, the closer the average circularity is to 1. When the projected area (A) and the perimeter (PM) of a particle are measured from a scanning electron micrograph and the area of a perfect circle with respect to the perimeter (PM) is (B), the circularity of the particle is A / B. expressed. Therefore, assuming a perfect circle having the same perimeter as the perimeter (PM) of the sample particles, the perimeter is PM = 2πr and the area is B = πr ² , so B = π × (PM / 2π) ² Therefore, the circularity of this particle is calculated as circularity = A / B = A × 4π / (PM) ^2. Then, the circularity is measured for 100 particles, and the average value is used as the average circularity. The inorganic oxide particles of the present invention preferably have an average circularity of 0.90 or more from the viewpoint of dispersibility, mixability, etc. when mixed as various fillers.

The average particle size of the inorganic oxide particles is usually 0.1 to 50 μm, preferably 0.3 to 30 μm, and more preferably 0.5 to 20 μm. In the present specification, the “average particle size” means the _{particle size (d 50} ) corresponding to 50% of the integrated distribution curve when the particle size distribution of the sample is prepared on a volume basis in accordance with JIS R 1629.

Hereinafter, embodiments of the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

1. 1. Measurement of average circularity The circularity was measured for 100 inorganic oxide particles photographed with a scanning electron microscope (manufactured by JEOL Ltd.), and the average value was taken as the average circularity.

2. Measurement of average particle size The average particle size of inorganic oxide particles is calculated by using Microtrac (manufactured by Nikkiso Co., Ltd.) as a particle size distribution measuring device and creating a volume-based particle size distribution in accordance with JIS R 1629. _{The particle size (d 50} ) corresponding to 50% of the distribution curve was determined.
Here, since the microtrack has a characteristic that the maximum diameter of one particle is regarded as the particle size of the particle, when there are many particles that are elliptical or snowball-shaped due to the interference of mist. Shows a tendency for the average particle size to increase.

Reference example 1
Inorganic oxide particles were produced using the conventional spray pyrolysis apparatus shown in FIG.
As shown in FIG. 3, the spray pyrolysis apparatus 200 includes a bag filter 9 and an attraction fan 10 on the downstream side of the pyrolysis furnace 2. The size of the pyrolysis furnace 2 is 1000 mm in inner diameter × 5000 mm in height, and six electric heaters are installed as auxiliary heat sources 8 on the outer periphery thereof. Below the pyrolysis furnace 2, one three-fluid nozzle is installed as a spraying device 3 so as to spray mist upward. A pump 6 for feeding the raw material solution contained in the raw material solution tank 5 is installed in the fluid nozzle, and the amount of the raw material solution fed is controlled by the flow meter 7.

First, a raw material inorganic oxide-containing solution prepared by dissolving 0.04 mol of aluminum nitrate and 0.16 mol of tetraethyl orthosilicate in 1 L of distilled water was put into a raw material solution tank. Next, the raw material inorganic oxide-containing solution is pumped to the fluid nozzle together with compressed air (liquid supply amount: 6 L / h), sprayed in the form of mist from the nozzle ejection port, and an electric heater (internal temperature) in the pyrolysis furnace. It was thermally decomposed by 1000 ° C.). Then, the inorganic oxide particles were recovered by a bag filter. The average circularity and the average particle size of the obtained inorganic oxide particles were measured. The results are shown in Table 1.

Comparative Example 1
Inorganic oxide particles were produced by the same operation as in Reference Example 1 except that two 3-fluid nozzles were installed below the pyrolysis furnace. The two fluid nozzles were installed so that the distance between them was 300 mm. The average circularity and the average particle size of the obtained inorganic oxide particles were measured. The results are shown in Table 1.

Example 1
Inorganic oxide particles were produced using the spray pyrolysis apparatus shown in FIG.
In this spray pyrolysis apparatus, two drying pipes are installed below the thermal decomposition furnace, and each drying pipe houses one three-fluid nozzle in the vertical pipe portion and one combustion burner in the horizontal pipe portion. In that respect, it differs from the spray pyrolysis apparatus shown in FIG. The two drying tubes were installed so that the distance between the fluid nozzles was 300 mm. Other device configurations are as described in Reference Example 1. The height of the drying pipe was 700 mm, the inner diameter of the vertical pipe portion was 200 mm, and the inner diameter of the horizontal pipe portion was 170 mm. Further, the horizontal pipe portion was connected to the vertical pipe portion at an inclination angle of 30 °, and the deviation of the central axis was 25% with the inner diameter of the vertical pipe portion as 100%.

A raw material inorganic oxide raw material solution was prepared in the same manner as in Comparative Example 1, and this was put into a raw material solution tank. Next, the raw material solution is pumped to each of the three fluid nozzles together with compressed air (liquid delivery amount: 6 L / h), sprayed in the form of mist from the nozzle ejection port, and the mist is placed on the swirling flow of the combustion gas of the combustion burner. It was dried in a drying tube (internal temperature: 300 ° C.) and pyrolyzed in a thermal decomposition furnace by an electric heater (internal temperature 1000 ° C.). Then, the inorganic oxide particles were recovered by a bag filter. The average circularity and the average particle size of the obtained inorganic oxide particles were measured. The results are shown in Table 1.

Example 2
Inorganic oxide particles were produced using the same apparatus as the spray pyrolysis apparatus shown in FIG. 1, except that a pipe for feeding the exhaust gas from the bag filter was connected to the horizontal pipe portion of the drying pipe. That is, a raw material inorganic oxide raw material solution was prepared in the same manner as in Comparative Example 1, and this was put into the raw material solution tank. Next, while the exhaust gas (200 ° C.) from the bag filter is blown from the horizontal pipe portion to the vertical trunk portion of the drying pipe via a pipe, the raw material inorganic compound-containing solution is pumped to each of the three fluid nozzles together with compressed air. Liquid feed amount: 6 L / h), sprayed in the form of mist from the nozzle outlet, put the mist on the swirling flow of exhaust gas, dry it in the drying pipe (internal temperature: 200 ° C), and electric heater in the thermal decomposition furnace. It was thermally decomposed by (internal temperature 1000 ° C.). Then, the inorganic oxide particles were recovered by a bag filter. The average circularity and the average particle size of the obtained inorganic oxide particles were measured. The results are shown in Table 1.

In Reference Example 1, since only one fluid nozzle was installed in the pyrolysis furnace, there was no problem of an increase in mist diameter due to interference between mists. Therefore, uniform inorganic oxide fine particles having a high average circularity were obtained.
On the other hand, in Comparative Example 1, since two fluid nozzles were installed in the conventional spray pyrolysis apparatus used in Reference Example 1, the mists sprayed from the adjacent fluid nozzles interfered with each other, the mist was deformed, and the mist diameter was increased. Has increased. Therefore, inorganic oxide particles having a low average circularity and a large average particle size were obtained.
On the other hand, in Examples 1 and 2, since the spraying devices were individually housed in the drying tube and the mist was sprayed into the drying tube from the spraying device to dry, the increase in mist diameter due to the interference between the mists was suppressed. Therefore, even if a plurality of spraying devices were installed, uniform inorganic oxide fine particles having a high average circularity were obtained. Moreover, when the inner wall of the drying pipe was visually observed, no adhered matter was confirmed.

1 Drying pipe 1a Vertical pipe part 1b Horizontal pipe part 2 Pyrolysis furnace 3 Atomizer 4 Combustion burner 5 Raw material solution tank 6 Pump 7 Flow meter 8 Auxiliary heat source 9 Recovery device 10 Attracting fan 100 Atomized pyrolyzer 200 Atomized pyrolyzer

Claims (9)

A drying tube for drying the sprayed raw material solution,
Equipped with a pyrolysis furnace for thermally decomposing dry particles generated from the raw material solution
Two or more drying pipes are installed at one end of the pyrolysis furnace, and have a structure in which a vertical pipe portion extending in the vertical direction and a horizontal pipe portion extending in the horizontal direction toward the vertical pipe portion are connected.
A spraying device for spraying the raw material solution is housed in the vertical pipe section.
Hot air is supplied from the horizontal pipe to the vertical pipe.
Spray pyrolysis device. The spray thermal decomposition apparatus according to claim 1, wherein the drying pipe is connected with a horizontal pipe portion and a vertical pipe portion with their central axes offset from each other. The spray thermal decomposition apparatus according to claim 1 or 2, wherein the horizontal pipe portion is connected to the vertical pipe portion at an inclination angle of 10 to 80 °. The spray pyrolysis apparatus according to any one of claims 1 to 3, wherein the inner diameter of the horizontal pipe portion of the portion connected to the vertical pipe portion is smaller than the inner diameter of the vertical pipe portion. The method for producing inorganic oxide particles according to any one of claims 1 to 4, wherein the spraying device is a fluid nozzle. The spray pyrolysis apparatus according to any one of claims 1 to 5, wherein the pyrolysis furnace has an auxiliary heat source. The spray pyrolysis apparatus according to claim 6, wherein the auxiliary heat source is one or more selected from a combustion burner, a hot air heater, and an electric heater. A method for producing inorganic oxide particles, which comprises a step of spraying a mist of a raw material inorganic compound-containing solution from the spray device and thermally decomposing it using the spray thermal decomposition device according to any one of claims 1 to 7. The inorganic oxide according to claim 8, wherein the raw material inorganic compound is one or more selected from aluminum salt, titanium salt, magnesium salt, calcium salt, borate, aluminosilicate, aluminum alkoxide and silicate alkoxide. How to make particles.

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