JP2023032546A - Nozzle for atomizing pyrolysis plant or atomizing dryer - Google Patents

Abstract

To provide a nozzle for an atomizing pyrolysis device or an atomizing dryer capable of suppressing sintering irregularity or dehydration irregularity of mist.SOLUTION: A nozzle 100 for a spray pyrolysis device or a spray drying device includes a nozzle body 1 and a protective tube 3 covering an outer periphery of the nozzle body 1, wherein at an end of the nozzle body 1, a discharge port 2 for spraying liquid is provided. Between the nozzle main body 1 and the protective tube 3, a gap 4 is provided through which a cooling gas can flow, in the gap 4, a mechanism 5 capable of discharging a cooling gas toward the discharge port 2 while circling around the nozzle body 1 is provided.SELECTED DRAWING: Figure 1

Description

The present invention relates to nozzles for spray pyrolysis or spray drying.

For example, a spray pyrolysis apparatus or a spray drying apparatus is used as an apparatus for producing fine particles (Patent Documents 1 and 2). In these apparatuses, for example, a nozzle for spraying mist (droplets) of the raw material solution and a combustion burner for generating combustion gas are installed in the heating furnace. Fine particles are produced by spraying mist upward from a nozzle and thermally decomposing or drying the mist using combustion gas as a heat source.

Japanese Unexamined Patent Application Publication No. 2001-17857 JP 2019-25385 A

Since the nozzle is installed in a high-temperature heating furnace, measures such as covering the nozzle with a heat insulating material or adding a cooling mechanism to the nozzle are taken in order to keep the nozzle below the heat-resistant temperature. When providing the nozzle with a cooling mechanism, it is often the case that water is circulated around the outer periphery of the nozzle, or cooling air is circulated. However, according to the studies of the present inventors, it has been found that the following problems arise when the cooling air is circulated. That is, when cooling air is used, the cooling air is circulated in the gap between the nozzle body and the protective tube to cool the nozzle, while the cooling air is discharged around the mist and flowed into the heating furnace. However, the temperature of the cooling air flowing into the heating furnace varies depending on the position, and accordingly the amount of heat received by the mist also varies, resulting in uneven firing or uneven drying of the mist. As a result, fine particles generated from mist that causes uneven firing or uneven drying have a reduced particle strength, which causes variations in physical properties of the particles. Here, in this specification, the term "uneven baking or uneven drying" means that part of the mist is not sufficiently heated and becomes half-baked.
An object of the present invention is to provide a nozzle for a spray pyrolysis apparatus or a spray drying apparatus capable of suppressing uneven baking or drying of mist, and a spray pyrolysis apparatus or spray drying apparatus using the same.

As a result of studies in view of the above problems, the inventors of the present invention have found that a protective tube is provided on the outer periphery of the nozzle body, and cooling gas is circulated around the nozzle body in a gap between the nozzle body and the protective tube. This suppresses the variation in the amount of heat received by the mist and improves the dispersibility of the mist, so uneven firing or drying of the mist is suppressed, and the decrease in particle strength is suppressed. I found that it can be manufactured.

That is, the present invention provides the following [1] to [9].
[1] a nozzle body having a discharge port for spraying a liquid;
A protective tube covering the outer periphery of the nozzle body is provided,
Between the nozzle body and the protective tube, a gap is provided through which cooling gas can flow,
The gap is provided with a mechanism capable of discharging the cooling gas toward the discharge port while rotating around the nozzle body.
Nozzles for spray pyrolyzers or spray dryers.
[2] The nozzle according to [1], wherein the mechanism is composed of a plate unit installed in the gap.
[3] The nozzle according to [1], wherein the mechanism is an impeller that rotates by receiving rotational force from the cooling gas.
[4] The nozzle according to [1], wherein the mechanism is provided with a cooling gas introduction pipe for introducing the cooling gas in a tangential direction to the inner diameter of the protection pipe.
[5] The nozzle according to any one of [1] to [4], wherein two or more of the mechanisms are provided in the gap.
[6] The nozzle according to any one of [1] to [5], wherein the cooling gas is air.
[7] The nozzle according to any one of [1] to [6], wherein the nozzle body is a one-fluid nozzle, two-fluid nozzle, three-fluid nozzle, or four-fluid nozzle.
[8] a nozzle for spraying the raw material solution;
Equipped with a heating furnace that thermally decomposes or dries the mist of the raw material solution sprayed from the nozzle with the combustion gas of the combustion burner,
The nozzle is the nozzle according to any one of [1] to [7] above,
Spray pyrolysis or spray drying equipment.
[9] A mechanism for generating a swirling flow of the combustion gas is provided in the heating furnace,
The spray pyrolysis apparatus or spray drying apparatus according to the above [8], wherein the swirling direction of the combustion gas in the heating furnace is the same as the swirling direction of the cooling gas in the gap.

When the nozzle of the present invention is used, variations in the amount of heat received by the mist sprayed from the nozzle are suppressed, and the dispersibility of the mist is improved, so that uneven baking or drying of the mist is suppressed, and a decrease in particle strength is prevented. It is possible to produce microparticles with reduced variations in physical properties of the particles.

It is a schematic diagram which shows an example of the nozzle of this invention. It is a schematic diagram which shows an example of the nozzle of this invention. It is a mimetic diagram showing an example of an impeller concerning a nozzle of the present invention. FIG. 4 is a schematic diagram showing an example of a cooling gas introduction pipe according to the nozzle of the present invention; BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows an example of the spray-pyrolysis apparatus or spray-drying apparatus of this invention.

Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and overlapping descriptions are omitted. Also, for convenience of illustration, the dimensional ratios in the drawings do not necessarily match those in the description.

[Nozzle for spray pyrolysis device or spray drying device]
The nozzle of the present invention is exclusively for use in spray pyrolysis or spray drying equipment.
FIG. 1 is a schematic diagram showing an example of the nozzle of the present invention.
As shown in FIG. 1, the nozzle 100 includes a nozzle body 1 and a protective tube 3 that covers the outer circumference of the nozzle body 1. At the end of the nozzle body 1, a discharge port 2 for spraying liquid is provided. It is The nozzle 100 is provided with a gap 4 between the nozzle body 1 and the protective tube 3 through which the cooling gas can flow. It is characterized by having a mechanism 5 capable of discharging the cooling gas toward the discharge port 2 while swirling around the nozzle body 1 .

The nozzle body may be, for example, a fluid nozzle. More specifically, a one-fluid nozzle, a two-fluid nozzle, a three-fluid nozzle, or a four-fluid nozzle can be used. Among them, a two-fluid nozzle, a three-fluid nozzle, or a four-fluid nozzle is preferable, and a three-fluid nozzle or a four-fluid nozzle is more preferable.

For the nozzle main body, a commercially available nozzle suitable for the volume and specifications of the heating furnace may be selected. Also, it may be manufactured according to the specifications of the heating furnace.
The length of the nozzle body can be appropriately selected according to the volume and specifications of the heating furnace, and is, for example, 400 to 1500 mm.
Further, the outer diameter of the nozzle body can be appropriately selected according to the volume and specifications of the heating furnace.

Fluid nozzle systems include an internal mixing system in which the gas and the raw material solution are mixed inside the nozzle and an external mixing system in which the gas and the raw material solution are mixed outside the nozzle, and both can be employed. As the gas to be supplied to the nozzle, for example, air, inert gas such as nitrogen or argon, or the like can be used. Among them, air is preferable from the viewpoint of economy.

The protection tube is installed so as to cover the outer periphery of the nozzle body while maintaining a certain distance from the nozzle body.
The material of the protective tube is not particularly limited as long as it is heat-resistant, but examples include heat-resistant metals such as iron, stainless steel, Inconel, Hastelloy, and titanium, ceramics, bricks, and monolithic refractories.

The length of the protective tube may be shorter than the length of the nozzle body, and can be appropriately set according to the length of the nozzle body. For example, the length of the protective tube is 0.70 to 0.95 times the length of the nozzle body. Also, the inner diameter of the protective tube is, for example, 1.5 to 2.0 times the outer diameter of the nozzle body. Thereby, the discharging speed of the cooling gas can be adjusted.
When the protective tube is installed in the nozzle main body, it is preferable that the end of the protective tube protrudes outward from the discharge port of the nozzle main body. As a result, the nozzle body can be cooled by the cooling gas in a swirling state and discharged around the discharge port of the nozzle body, so the variation in the amount of heat received by the mist can be suppressed, the dispersibility of the mist can be improved, and the mist can be fired. It is possible to suppress unevenness or dryness unevenness.

A cooling gas for cooling the nozzle body is introduced into the gap between the nozzle body and the protective tube.
As the cooling gas, for example, air or an inert gas such as nitrogen or argon can be used. Among them, air is preferable from the viewpoint of economy.

The cooling gas introduced into the gap is discharged toward the discharge port of the nozzle body. A mechanism is provided.
Such a mechanism is not particularly limited as long as the cooling gas introduced into the gap can generate a swirling flow around the nozzle body, and for example, a plate unit can be used. Here, the term "plate unit" as used herein refers to a unit composed of one or more plate-like bodies. processed ones can be mentioned.
The shape of the plate-like body may be, for example, rectangular, circular, elliptical, tapered, arcuate, etc., and can be selected as appropriate.
The material of the plate-like body may be metal or ceramic, and is not particularly limited.
The plate-like body has a length of approximately 10 to 100 mm, a thickness of approximately 1 to 10 mm, and a width approximately equal to the width of the gap.
One or more plate units can be installed in the gap. The installation position of the plate unit can be set as appropriate. For example, when two units are installed, it is possible to install them at the ejection port side end of the nozzle main body and the substantially middle part of the nozzle main body, but the present invention is not limited to this.

As a specific example of the plate unit, for example, as shown in FIG. 1, a plate unit 5 in which a plurality of plate-like bodies 6 inclined at a predetermined angle with respect to the vertical direction are arranged in parallel along the horizontal direction. can be mentioned.
The number of plate-shaped bodies constituting the plate unit can be selected as appropriate as long as a swirling flow of the cooling gas can be generated around the nozzle body. 4 or more are preferable, and 4 to 10 are more preferable, because the ejection flow rate of the cooling gas is increased and the dispersibility of the mist is improved.
In addition, the installation angle of the plate-shaped body can be appropriately selected as long as a swirl flow of the cooling gas can be generated around the nozzle body, but from the viewpoint of improving the dispersibility of the mist, it is preferably 10 to 60° with respect to the vertical direction. , 15 to 45° is more preferred.
One or more plate units can be installed in the cavity.
The plate unit shown in FIG. 1 is composed of 10 rectangular plates inclined at 30° with respect to the vertical direction. One is installed at the end of the nozzle body on the ejection port side in a protruding state, and the other is installed at an approximately intermediate portion of the nozzle body.

Another aspect of the plate unit is, for example, the plate unit shown in FIG.
The plate unit shown in FIG. 2(a) is formed by arranging a plurality of tapered plate-like bodies inclined at a predetermined angle with respect to the vertical direction in a column along the vertical direction.
The number of plate-shaped bodies constituting the plate unit can be appropriately selected as long as a swirling flow can be generated around the nozzle body. Preferably, 2 to 4 sheets are more preferable.
The installation angle of the plate-shaped body can be appropriately selected as long as a swirling flow can be generated around the nozzle body. ° is more preferred.
The plate unit shown in FIG. 2(a) is composed of three bow-shaped plate-like bodies tapered at an angle of 30° with respect to the vertical direction. The height is different toward the gas introduction port), and it is installed oppositely along the outer periphery of the nozzle body.

Also, the plate unit shown in FIG. 2(b) is composed of a plurality of plate-like bodies installed so as to shield the cooling gas flow path.
The number of plate-shaped bodies constituting the plate unit can be selected as appropriate as long as it is possible to shield the flow passage of the cooling gas and generate a swirling flow around the nozzle body. From the viewpoint of improvement, 2 to 4 sheets are preferable, and 2 to 3 sheets are more preferable.
In addition, the installation angle of the plate-shaped body can be appropriately selected as long as it can shield the flow passage of the cooling gas and generate a swirling flow around the nozzle body. 10 to 70° is preferred, and 30 to 70° is more preferred.
The plate unit shown in FIG. 2(b) is composed of two rectangular plate-shaped bodies inclined at 60° with respect to the vertical direction, and the nozzle body discharge port side is arranged so that they intersect via the nozzle body. It is installed at the end.

Further, the plate unit shown in FIG. 2(c) is formed by providing a plurality of slits or holes in one plate-like body.
The shape of the slit or hole may be rectangular, circular, elliptical, arcuate, etc., and can be selected as appropriate.
The size of the slit or hole can be appropriately selected according to the size of the plate-like body so as to generate a swirling flow around the nozzle body.
The slits or holes are preferably installed symmetrically in order to generate a sufficient swirling flow around the nozzle body.
The slits or holes are preferably drilled at an angle to the vertical direction in order to circulate the cooling gas. The angle of the slits or holes is preferably 10 to 60°, more preferably 15 to 50°, with respect to the vertical direction.
The number of slits or holes is preferably four or more from the viewpoint of symmetrical perforation and sufficient swirl force of the cooling gas. The number of slits or holes is not particularly limited as long as the slits or holes can be formed symmetrically, and can be appropriately selected according to the size of the slits or holes and the size of the plate-like body.
The installation angle of the plate-like body is usually horizontal, but it may be inclined as long as a swirling flow of the cooling gas can be generated around the nozzle body.
The plate unit shown in FIG. 2(c) is composed of a single circular plate-like body having 12 round holes drilled at an angle of 30° with respect to the vertical direction. It is installed at the end.

Further, as another embodiment of the mechanism, for example, an impeller that rotates by receiving rotational force from the cooling gas can be cited. An example of an impeller is shown in FIG. As used herein, the term "impeller" refers to a rotating body composed of a plurality of blades attached to a hub.
The impeller shown in FIG. 3 is composed of a hub 9 that is rotationally driven by receiving rotational force from a cooling gas, and a plurality of blades 10 radially extending from the circumference of the hub 9. In 9, four blades 10 are arranged at equal intervals so that a pair of blades face each other. The number of blades to be installed and the size of the impeller can be appropriately selected according to the size of the gap between the nozzle body and the protective tube.

Furthermore, as another embodiment of the mechanism, for example, a cooling gas introduction pipe for introducing cooling gas in the tangential direction of the inner diameter of the protection pipe is installed in the protection pipe. An example is shown in FIG.
The cooling gas introduction pipe shown in FIG. 4 is provided with a cooling gas introduction pipe 7 on the side of the protective pipe 3 . Then, the cooling gas is introduced from the cooling gas introduction pipe 7 in the tangential direction of the inner diameter of the protective tube 3 to generate a swirling flow of the cooling gas in the gap.
It is preferable to install the cooling gas introduction pipe at a position as far away as possible from the discharge port of the nozzle body. As a result, it is possible to generate a sufficient swirling flow around the nozzle body while cooling a wide area of the nozzle body. Also, there may be a plurality of cooling gas introduction pipes. For example, by arranging the second cooling gas introduction pipe at a position diagonal to the first cooling gas introduction pipe, there is an effect of further strengthening the swirling flow of the cooling gas.

In the present invention, the above mechanisms may be combined. For example, as shown in FIG. 4, the plate unit shown in FIG. 1 can be combined with a mechanism for introducing cooling gas in the tangential direction of the inner diameter of the protective tube.

In the mechanism described above, the amount of cooling gas introduced into the gap must be an amount that can cool the nozzle main body to a heat resistant temperature or lower, but it is preferably smaller than the amount of gas introduced into the nozzle main body. However, since the mist has a straight traveling property, if the amount of gas supplied to the nozzle is too small, the effect of dispersing the mist is reduced. From this point of view, the amount of cooling gas introduced into the gap is preferably 50 to 95% by volume, more preferably 60 to 90% by volume, and more preferably 70 to 85% by volume with respect to the amount of gas introduced into the nozzle body. More preferred.

As described above, by using the nozzle of the present invention, the swirling cooling gas introduced into the gap between the nozzle body and the protective tube cools the nozzle body and is discharged around the mist, which will be described later. Since it flows into the heating furnace of the spray pyrolysis device or spray drying device, the temperature of the cooling gas is less likely to vary depending on the position. be done. As a result, uneven firing or drying of the mist is suppressed, and it is possible to produce fine particles with less variation in particle physical properties with suppressed decrease in particle strength. In addition, since it is easier to install the nozzle body in the center of the protective tube, for example, temperature variations such as the temperature on the left side of the nozzle body being low and the temperature on the right side being high are suppressed, and the heat exchange of the nozzle is improved. As a result of uniform heating, deterioration due to uneven burning of members such as the nozzle main body and packing is suppressed, so that they can be used for a long period of time without requiring replacement in a short period of time.

[Spray Pyrolyzer or Spray Dryer]
The spray pyrolysis apparatus or spray drying apparatus of the present invention is equipped with the nozzle of the present invention. A preferred embodiment will now be described with reference to FIG.

FIG. 5 is a schematic diagram showing an example of the spray pyrolysis apparatus or spray drying apparatus of the present invention.
The spray pyrolysis apparatus or spray drying apparatus 300 is of internal combustion type, and as shown in FIG. A heating furnace 101 for heating is provided. The combustion burner 102 is housed in a combustion tube 103 , and the combustion tube 103 is connected in a substantially horizontal direction with respect to the vertical heating furnace 101 and offset from the central axis of the heating furnace 101 . In this way, the heating furnace 101 and the combustion tube 103 are connected with their central axes shifted, so that when the combustion gas (hot air) generated in the combustion tube 103 passes through the heating furnace 101, it rises straight up. Instead, it causes a swirling flow and rises. As a result, the sprayed mist rises in the heating furnace 101 along with the swirling flow, ensuring a sufficient heating time.

The nozzle is not particularly limited as long as it is the nozzle of the present invention. In addition, the specific aspect of the nozzle is as described above.
One or more nozzles can be installed.

The materials of the heating furnace and the combustion tube are not particularly limited as long as they are used as furnace materials. Refractories can be mentioned.
The shape of the heating furnace and the combustion tube should be substantially cylindrical from the viewpoint of the fact that it can be fastened with a flange, the temperature unevenness in the heating furnace, and the suppression of uneven heat dissipation in the cross-sectional direction from the heating furnace and the combustion tube. preferable.

The size of the heating 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 10000 mm.
The size of the combustion tube is not particularly limited as long as it can accommodate the combustion burner, but the length of the combustion tube is preferably such that the flame generated from the combustion burner does not come into direct contact with the spray mist. However, if the distance between the flame generated from the combustion burner and the spray mist is too long, the thermal efficiency will be insufficient.
It is preferable that the inner diameter of the portion of the combustion tube connected to the heating furnace be smaller than the inner diameter of the heating furnace, since a strong swirling flow of hot air is likely to occur. For example, the internal diameter of the connecting portion of the combustion tube should be less than half the internal diameter of the vertical tube.

The deviation of the central axis between the heating furnace and the combustion tube is preferably 10% or more and 90% or less, taking the inside diameter of the heating furnace as 100%, in consideration of the degree of swirl flow generation, thermal efficiency, and influence on the heat resistance of the combustion tube. 20% or more and 80% or less is more preferable.

As for the combustion burner, considering the volume and specifications of the heating furnace, it is sufficient to select a commercially available burner suitable for this, or to manufacture a burner according to the specifications of the heating furnace.

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

Next, a method for producing inorganic oxide particles using a spray pyrolysis apparatus or a spray drying apparatus will be described.

First, a raw material solution is prepared. A raw material solution is a solution of a compound containing an element that constitutes an oxide.
The compound containing an element that constitutes an oxide is not particularly limited as long as it contains an element that constitutes an oxide and is soluble in a solvent such as water. Examples include inorganic salts, metal alkoxides, and the like. can. More specific examples include aluminum salts, titanium salts, magnesium salts, aluminosilicates, aluminum alkoxides, silicate alkoxides such as tetraethoxysilane and tetramethoxysilane. Examples of aluminum salts include inorganic salts such as aluminum nitrate, aluminum sulfate, aluminum chloride, aluminum phosphate, aluminum hydroxide, aluminum acetate and aluminum oxalate, organic metal compounds such as aluminum secondary butyrate, and aluminum compounds such as aluminum isopropylate. Dispersed ones are mentioned. Silicic acid alkoxides include tetraethoxysilane, tetramethoxysilane, and the like. A solution of aluminum oxide or silicon oxide dispersed in a solvent, or a sol solution of aluminum oxide or silicon oxide can also be used as the raw material solution. Furthermore, raw materials of other elements can be added in order to adjust the melting temperature, heat resistance and particle strength. Among them, one or more selected from aluminum salts, titanium salts, magnesium salts, aluminosilicates, aluminum alkoxides and silicate alkoxides are preferred.

Examples of inorganic oxides obtained from these raw material compounds include metal oxides, alumina, silica, oxides composed of aluminum and silicon, and the like. More specifically, alumina, silica, oxides composed of aluminum and silicon, titanium oxides, magnesium oxides, zinc oxides, zirconium oxides, barium oxides, cerium oxides, yttrium oxides, etc. Composite oxides obtained by combining these oxides are also included.

Solvents for dissolving or dispersing the compound containing the element constituting the oxide include water and organic solvents. Among them, water is preferable from the viewpoint of environmental impact and production cost.

The concentration of the compound containing the element constituting the oxide in the raw material solution is preferably 0.01 mol/L to saturated concentration, and 0.1 to 1.0 mol, in consideration of the density, strength, etc. of the inorganic oxide particles to be obtained. /L is more preferred.

Next, while supplying combustion gas (hot air) from a combustion burner housed in the combustion tube to the heating furnace, mist of the raw material solution is sprayed from a nozzle attached to the heating furnace. A pump may be used to feed the raw material solution to the nozzle, and the pressure and flow rate may be adjusted so as to achieve a desired mist ejection speed.

The flow rate of the gas supplied to the nozzle body is preferably at least 1000 times the volume of the raw material solution sent to the nozzle body. From the viewpoint of promoting salt precipitation, it is preferably 3000 times or less, more preferably 2500 times or less.

The flow rate of the cooling gas supplied to the gap between the nozzle body and the protective tube is preferably smaller than the amount of gas supplied to the nozzle body. For example, the amount of cooling gas supplied to the gap is preferably 50 to 95% by volume, more preferably 60 to 90% by volume, and even more preferably 70 to 85% by volume, relative to the amount of gas supplied to the nozzle body.

The temperature of the gas supplied to the nozzle main body and the gap is preferably below the temperature of the mist immediately after ejection, and more preferably below normal temperature (20±15° C.). The lower limit of the temperature of the supplied gas is preferably 1° C. or higher, more preferably 5° C. or higher, and even more preferably 10° C. or higher, for ease of temperature control.

The temperature of the mist immediately after spraying is a temperature not higher than 1/2 of the boiling point of the solvent in the raw material solution, and can be appropriately set according to the type of solvent in the raw material solution. For example, when the raw material solution is an aqueous solution, the temperature is preferably 1 to 50°C, more preferably 5 to 40°C, still more preferably 10 to 40°C. The temperature of the mist immediately after ejection can be controlled by installing a thermocouple at the tip of the nozzle so as to come into contact with the mist ejected from the nozzle. It is preferable that the thermocouple is installed within 5 cm from the tip of the nozzle. Moreover, in order to adjust the temperature of the raw material solution in the nozzle, the outer circumference of the nozzle may be covered with a heat insulating material. Examples of heat insulating materials include ceramic fibers, glass fibers, castables, and the like.

The ejection speed of the mist is usually 1 to 50 m/s, preferably 5 to 35 m/s, more preferably 10 to 20 m/s, from the viewpoint of promoting thermal decomposition or drying and preventing the generation of adherents on the wall surface of the heating furnace. .

The average particle size of the mist is preferably 0.5-60 μm, more preferably 1.0-20 μm, even more preferably 1.0-15 μm. It should be noted that the average particle size of the mist can be adjusted by adjusting the shape of the nozzle outlet and the pressure of the air.

The mist sprayed from the nozzle is heated in a heating furnace and thermally decomposed or dried to form a film containing an inorganic compound, from which inorganic oxide particles precipitate.
In the spray pyrolysis apparatus or the spray drying apparatus according to the present embodiment, as described above, the central axis of the heating furnace and the central axis of the combustion tube are connected with each other, so that the combustion gas generated in the combustion tube is When passing through the heating furnace, it does not rise straight up, but rises with a swirling flow. On the other hand, the cooling gas introduced into the gap between the nozzle body and the protective tube cools while swirling around the nozzle body and is discharged around the mist, and the combustion gas discharged from the combustion tube to the heating furnace. It is caught in the flow and rises in the heating furnace. As a result, the sprayed mist rides on this swirling flow and rises in the heating furnace, and a sufficient heating time can be secured, so that uneven baking or drying of the mist can be suppressed.
The swirl direction of the combustion gas in the heating furnace is preferably the same as the swirl direction of the cooling gas circulated in the gap between the nozzle body and the protective tube described above. By making the swirl direction of the combustion gas and the swirl direction of the cooling gas the same, a sufficient swirl force can be obtained, and variations in the amount of heat received by the mist can be suppressed, and the dispersibility of the mist can be improved. , uneven baking or uneven drying of mist can be suppressed.

The temperature in the combustion tube is not particularly limited as long as it is a temperature at which the solvent evaporates from the mist of the raw material solution.

The temperature in the heating furnace is not particularly limited as long as it is a temperature at which the solvent evaporates from the mist and the inorganic salt precipitates. .

Next, fine particles generated by thermal decomposition or drying are collected by being moved to a collection device by an induction fan from the downstream of the heating furnace, for example. Examples of recovery devices include a cyclone powder recovery machine and a bag filter. Moreover, in recovering microparticles|fine-particles, you may adjust a particle diameter by making it pass through a filter. Furthermore, dust removal and purification equipment such as a scrubber may be arranged downstream of the recovery device, if necessary.

The fine particles produced by the spray pyrolysis apparatus or spray drying apparatus 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 particle" as used herein refers to a particle having a structure that does not have a cavity inside, for example, a particle consisting of a single layer, and a core (also referred to as an inner core) and a shell layer. Particles having a (also called shell) can be mentioned. A "hollow particle" is 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. Furthermore, the term “porous particles” refers to particles having a large number of through holes connected from the particle surface to the inside. The size and shape of the through-hole are not particularly limited. Also, the particles may have closed pores inside.

Moreover, when producing inorganic oxide hollow particles, the surfaces of the inorganic oxide particles after thermal decomposition may be melted. As a result, the pores existing on the surfaces of the inorganic oxide particles are blocked, and inorganic oxide hollow particles having high particle strength without pores in the outer shell of the particles are obtained. In order to melt the surfaces of the inorganic oxide particles, for example, the temperature of the heating furnace may be controlled to the melting temperature of the inorganic oxide particles or higher.

As described above, by using the spray pyrolysis apparatus or the spray drying apparatus of the present invention, when the swirling cooling gas introduced into the gap between the nozzle body and the protective tube is discharged around the mist, The temperature of the cooling gas is less likely to fluctuate depending on the position, thereby suppressing fluctuations in the amount of heat received by the mist and enhancing the dispersibility of the mist. Together with the cooling gas, the mist is caught in the swirling flow of the combustion gas discharged from the combustion tube into the heating furnace and rises in the heating furnace, ensuring a sufficient heating time. As a result, uneven firing or drying of the mist is suppressed, and it is possible to produce fine particles with less variation in particle physical properties with suppressed decrease in particle strength.
In addition, the produced inorganic oxide particles can have the following characteristics.

The average particle size of the inorganic oxide hollow particles is usually 0.5 to 50 μm, preferably 1 to 20 μm, more preferably 2 to 10 μm. Here, the "average particle size" as used herein means the particle size (d50) corresponding to 50% of the cumulative distribution curve when the particle size distribution of the sample is created on a volume basis in accordance with JIS R 1629. do. As a particle size distribution measuring device, for example, Microtrac (manufactured by Nikkiso Co., Ltd.) can be used.

The particle density of the inorganic oxide particles is usually 0.1-2.5 g/cm ³ , preferably 0.2-1.5 g/cm ³ , more preferably 0.3-1.0 g. / cm ³ . In addition, the particle density can be measured by a gas replacement method in accordance with JIS R 1620. As a particle density measuring device, for example, a dry automatic density meter “Accupic (manufactured by Shimadzu Corporation)” can be used.

From the viewpoint of ensuring sufficient strength, the particle strength of the inorganic oxide particles is preferably 14 MPa or higher, more preferably 15 MPa or higher, and even more preferably 16 MPa or higher. Here, the term "particle strength" as used herein refers to the particle strength when the hollow particle residual ratio is 50% when the pressure is applied to the hollow particles by a pressure molding press. Specifically, it can be measured by the method described in Examples below.

The present invention has been described in detail based on its embodiments. However, the present invention is not limited to the above embodiments. Various modifications are possible for the present invention without departing from the gist thereof. For example, a spray pyrolysis apparatus or spray drying apparatus 300, as shown in FIG. It is not limited to this, and it is also possible to shift the central axis as described in JP-A-2020-32318 and JP-A-2021-69970, for example. Further, the combustion burner 102 may not be housed in the combustion tube 103 but may be attached to the side wall of the heating furnace. Furthermore, in the spray pyrolysis apparatus or spray drying apparatus 300, the nozzle 100 and the heating furnace 101 are vertically arranged, but the nozzles 100 are not limited to the vertical type, and may be horizontal or oblique.

EXAMPLES The embodiments of the present invention will now be described more specifically with reference to Examples. However, the present invention is not limited to the following examples.

1. Particle Density Measured by a constant volume expansion method using a dry automatic densitometer (Accupic 1340, manufactured by Shimadzu Corporation). That is, after putting a sample into the cell, the cell was filled with an inert gas, the volume of the sample was measured, and the particle density was obtained from this volume and the sample mass previously measured.

2. Average particle size The average particle size of the inorganic oxide particles is determined by using Microtrac (manufactured by Nikkiso Co., Ltd.) as a particle size distribution measuring device, creating a volume-based particle size distribution in accordance with JIS R 1629, and calculating the cumulative distribution curve. A particle diameter (d ₅₀ ) corresponding to 50% of the
Here, Microtrac has the characteristic of capturing the maximum diameter of a single particle as the particle diameter of that particle. indicates a tendency for the average particle size to increase.

3. Particle Strength Particle strength was measured by the following powder pressing method.
(1) Hollow particles and ethanol were mixed at a mass ratio of 4:1 to prepare a sample.
(2) The sample was placed in a pressure former, and a predetermined pressure (10 MPa, 20 MPa, 30 MPa) was applied with a hydraulic press.
(3) Leave for 1 minute while a predetermined pressure is applied.
(4) The sample was removed from the pressure former and dried at 80°C for 2 hours.
(5) The density of the hollow particles after pressurization was measured using a dry automatic densitometer "Accupic" (manufactured by Shimadzu Corporation).

Then, from the density of the hollow particles before and after pressurization, the residual rate for each predetermined pressure was calculated by the following formula, and the pressure at 50% residual was read from the graph of the residual rate and the applied pressure. The density was measured using the above-described density measuring instrument, and the true density of the hollow shell was measured after heating at the melting point or higher for 6 hours in a box-shaped electric furnace and cooling in order to remove voids.

Survival rate P [%] = (1-ρ/y)/ρ x (1/x-1/y) x 100

[In the formula, ρ represents the density after pressing, y represents the true density of the hollow shell, and x represents the density before pressing. ]

Example 1
Using the spray pyrolysis apparatus shown in FIG. 5, magnesium oxide hollow particles were produced by the following method. Specifically, 1985 g of magnesium acetate was dissolved in 100 liters of ion-exchanged water to prepare an aqueous magnesium acetate solution. Next, this aqueous solution was sprayed from a three-fluid nozzle having the structure shown in FIG. 1 into a heating furnace heated to a temperature of 1150° C., and magnesium oxide hollow particles were recovered using a bag filter. In addition, in the gap between the nozzle main body and the protective tube, as shown in FIG. 1, plate units each having a total of ten plates with an inclination angle of 30° were installed at two locations. Then, cooling air was circulated in this gap, and the cooling air was discharged toward the outlet of the nozzle body while swirling around the nozzle body. Further, spray pyrolysis conditions are as follows.

(Spray pyrolysis conditions)
・Amount of raw material solution sprayed: 14 L/h
・Nozzle air volume: 240L/min
・Amount of cooling air: 200L/min (ratio to nozzle air is 83%)
・ Baking temperature: 1150 ° C (burner control temperature. Position 5 cm from the nozzle tip)

Then, the particle density, average particle diameter and particle strength of the particles collected every hour after the start of production were measured. Table 1 shows the results.

Comparative example 1
Magnesium oxide hollow particles were produced in the same manner as in Example 1, except that the plate unit was not installed in the gap between the nozzle body and the protective tube. Then, the particle density, average particle diameter and particle strength of the particles collected every hour after the start of production were measured. Table 1 shows the results.

Comparative Example 1 is an example in which no plate unit was installed in the gap between the nozzle body and the protective tube. A decrease in particle strength was observed in the hollow particles obtained, and variations in particle physical properties were confirmed.
On the other hand, Example 1 is an example in which a plate unit is installed in the gap between the nozzle body and the protective tube, and the cooling gas is circulated there so as to swirl around the nozzle body. Variation in the amount of heat is suppressed, the dispersibility of the mist is improved, and uneven firing of the mist is suppressed, so that the obtained hollow particles have a suppressed decrease in particle strength, and variation in the physical properties of the particles is suppressed. was confirmed.

REFERENCE SIGNS LIST 1 nozzle body 2 outlet 3 protective tube 4 gap 5 mechanism (plate unit)
6 Plate 7 Cooling Gas Inlet 8 Slit or Hole 9 Hub 10 Blade 20 Impeller 100 Nozzle 101 Heating Furnace 102 Combustion Burner 103 Combustion Tube 200 Nozzle 300 Spray Pyrolyzer or Spray Dryer

Claims (9)

a nozzle body having an ejection port for spraying a liquid;
A protective tube covering the outer periphery of the nozzle body is provided,
Between the nozzle body and the protective tube, a gap is provided through which cooling gas can flow,
The gap is provided with a mechanism capable of discharging the cooling gas toward the discharge port while rotating around the nozzle body.
Nozzles for spray pyrolysis or spray drying. 2. A nozzle according to claim 1, wherein said mechanism consists of a plate unit installed in said gap. 2. The nozzle according to claim 1, wherein said mechanism is an impeller that rotates by receiving rotational force from said cooling gas. 2. The nozzle according to claim 1, wherein said mechanism comprises a cooling gas introduction pipe for introducing said cooling gas in a tangential direction of said protection pipe inner diameter. The nozzle according to any one of claims 1 to 4, wherein two or more of said mechanisms are provided in said gap. A nozzle according to any preceding claim, wherein the cooling gas is air. The nozzle according to any one of claims 1 to 6, wherein the nozzle body is a one-fluid nozzle, two-fluid nozzle, three-fluid nozzle or four-fluid nozzle. a nozzle for spraying the raw material solution;
Equipped with a heating furnace that thermally decomposes or dries the mist of the raw material solution sprayed from the nozzle with the combustion gas of the combustion burner,
The nozzle is the nozzle according to any one of claims 1 to 7,
Spray pyrolysis or spray drying equipment. A mechanism for generating a swirling flow of the combustion gas is provided in the heating furnace,
9. The spray pyrolysis apparatus or spray drying apparatus according to claim 8, wherein the swirling direction of the combustion gas in the heating furnace is the same as the swirling direction of the cooling gas in the gap.

Images