JP7708615B2 - Nozzles for spray pyrolysis or spray drying equipment - Google Patents

Description

The present invention relates to a nozzle for a spray pyrolysis device or a spray drying device.

For example, spray pyrolysis equipment or spray drying equipment is used as a manufacturing device for fine particles (Patent Documents 1 and 2). In these devices, for example, a nozzle for spraying a mist (droplets) of the raw material solution and a combustion burner for generating combustion gas are installed in a heating furnace, and the mist is sprayed upward from a nozzle installed below the heating furnace, and the mist is pyrolyzed or dried using the combustion gas as a heat source to produce fine particles.

JP 2001-17857 A 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 providing a cooling mechanism to the nozzle are taken in order to keep the nozzle below its heat-resistant temperature. When providing a cooling mechanism to the nozzle, water is often circulated around the periphery of the nozzle or cooling air is often circulated. However, according to the study by the present inventors, it has been found that the following problem occurs when 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 flows into the heating furnace. However, the temperature of the cooling air flowing into the heating furnace varies depending on the position, and the amount of heat received by the mist also varies accordingly, so that the mist is baked unevenly or dried unevenly. As a result, the fine particles generated from the mist with uneven baking or drying have a reduced particle strength, which causes variation in particle properties. In this specification, "uneven baking or drying" refers to a state in which a part of the mist does not receive sufficient heat, resulting in an undercooked state.
An object of the present invention is to provide a nozzle for a spray pyrolysis apparatus or a spray drying apparatus that can suppress uneven baking or drying of mist, and a spray pyrolysis apparatus or a spray drying apparatus using the same.

After considering the above problems, the inventors have found that by providing a protective tube around the outer periphery of the nozzle body and circulating a cooling gas in a swirling manner around the nozzle body in the gap between the nozzle body and the protective tube, the variation in the amount of heat received by the mist is reduced and the mist is well dispersed, thereby suppressing uneven baking or drying of the mist and enabling the production of fine particles with little variation in particle properties and with reduced reduction in particle strength.

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 an outer periphery of the nozzle body;
a gap through which a cooling gas can flow is provided between the nozzle body and the protective tube;
a mechanism capable of discharging the cooling gas toward the discharge port while rotating around the nozzle body is provided in the gap;
Nozzles for spray pyrolysis or spray drying equipment.
[2] The nozzle according to [1] above, wherein the mechanism is composed of a plate unit installed in the gap.
[3] The nozzle according to [1] above, wherein the mechanism is an impeller that rotates by receiving a rotational force from the cooling gas.
[4] The nozzle according to [1] above, wherein the mechanism comprises a cooling gas inlet pipe installed in the protective tube for introducing the cooling gas in a tangential direction of the inner diameter of the protective tube.
[5] The nozzle according to any one of [1] to [4] above, 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] above, wherein the nozzle body is a one-fluid nozzle, a two-fluid nozzle, a three-fluid nozzle, or a four-fluid nozzle.
[8] a nozzle for spraying a raw material solution;
a heating furnace for thermally decomposing or drying the mist of the raw material solution sprayed from the nozzle by a combustion gas of a combustion burner;
The nozzle is the nozzle according to any one of [1] to [7] above.
Spray pyrolysis equipment or spray drying equipment.
[9] A mechanism for generating a swirling flow of the combustion gas in the heating furnace is provided,
The spray pyrolysis apparatus or spray drying apparatus according to [8] above, 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.

By using the nozzle of the present invention, the variation in the amount of heat received by the mist sprayed from the nozzle is reduced, and the mist has good dispersibility, so uneven baking or drying of the mist is suppressed, and it is possible to produce fine particles with little variation in particle properties and with reduced reduction in particle strength.

FIG. 2 is a schematic diagram showing an example of a nozzle of the present invention. FIG. 2 is a schematic diagram showing an example of a nozzle of the present invention. FIG. 2 is a schematic diagram showing an example of an impeller for a nozzle of the present invention. FIG. 2 is a schematic diagram showing an example of a cooling gas introduction pipe for the nozzle of the present invention. FIG. 1 is a schematic diagram showing an example of a spray pyrolysis apparatus or a spray drying apparatus of the present invention.

Below, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings. Note that in the description of the drawings, the same elements are given the same reference numerals, and duplicated descriptions will be omitted. Also, for convenience of illustration, the dimensional ratios of 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 intended for use exclusively in spray pyrolysis or spray drying apparatus.
FIG. 1 is a schematic diagram showing an example of a nozzle of the present invention.
1, the nozzle 100 includes a nozzle body 1 and a protective tube 3 that covers the outer periphery of the nozzle body 1, and an outlet 2 for spraying a liquid is provided at the end of the nozzle body 1. The nozzle 100 is characterized in that a gap 4 is provided between the nozzle body 1 and the protective tube 3, through which a cooling gas can flow, and the gap 4 includes a mechanism 5 that can discharge the cooling gas introduced from a cooling gas inlet 7 at the end of the protective tube 3 toward the outlet 2 while swirling it around the nozzle body 1.

The nozzle body can be, for example, a fluid nozzle. More specifically, it can be a one-fluid nozzle, a two-fluid nozzle, a three-fluid nozzle, or a four-fluid nozzle. Of these, a two-fluid nozzle, a three-fluid nozzle, or a four-fluid nozzle is preferred, and a three-fluid nozzle or a four-fluid nozzle is even more preferred.

The nozzle body may be selected from commercially available nozzles that suit the volume and specifications of the heating furnace, etc. Also, a nozzle may be manufactured according to the specifications of the heating furnace.
The length of the nozzle body can be appropriately selected depending on the volume and specifications of the heating furnace, and is, for example, 400 to 1500 mm.
The outer diameter of the nozzle body can be appropriately selected depending on the volume and specifications of the heating furnace, and for example, if the nozzle is cylindrical, it is φ40 to 80 mm.

There are two types of fluid nozzles: an internal mixing type, in which the gas and raw material solution are mixed inside the nozzle, and an external mixing type, in which the gas and raw material solution are mixed outside the nozzle. Either type can be used. The gas supplied to the nozzle can be, for example, air or an inert gas such as nitrogen or argon. Among these, air is preferred from the viewpoint of economy.

The protective 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, and examples thereof include heat resistant metals such as iron, stainless steel, Inconel, Hastelloy, and titanium, ceramics, bricks, and unshaped refractories.

The length of the protective tube only needs to be shorter than the length of the nozzle body, and can be set appropriately 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. The inner diameter of the protective tube is, for example, 1.5 to 2.0 times the outer diameter of the nozzle body. This makes it possible to adjust the discharge speed of the cooling gas.
When the protective tube is installed in the nozzle body, it is preferable to install the protective tube so that the end of the protective tube protrudes outward beyond the outlet of the nozzle body. This allows the nozzle body to be cooled by the swirling cooling gas while being discharged around the outlet of the nozzle body, thereby reducing the variation in the amount of heat received by the mist and improving the dispersibility of the mist, thereby preventing uneven baking or drying of the mist.

A cooling gas for cooling the nozzle body is introduced into the gap between the nozzle body and the protective tube.
The cooling gas may be, for example, air or an inert gas such as nitrogen or argon, etc. Among these, air is preferred from the viewpoint of economy.

The cooling gas introduced into the gap is discharged toward the nozzle body outlet, and a mechanism is provided within the gap to cause the cooling gas to swirl around the nozzle body and be discharged around the nozzle body outlet.
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 may be, for example, a plate unit. Here, in this specification, the term "plate unit" refers to a unit composed of one or more plate-like bodies, and may be, for example, a unit in which a plurality of plate-like bodies are accumulated, or a unit in which a single plate-like body is processed.
The shape of the plate-like body can be appropriately selected from a range of shapes, including rectangular, circular, elliptical, tapered, and arched shapes.
The material of the plate-like body is not particularly limited and may be metal or ceramic.
The length of the plate is approximately 10 to 100 mm, the thickness is approximately 1 to 10 mm, and the width is approximately equal to the width of the gap.
It is possible to install one or more plate units in the gap. The installation positions of the plate units can be appropriately set, but for example, when installing two units, they can be located at the end of the nozzle body on the discharge port side and at a roughly middle part of the nozzle body, but are not limited to this.

A specific example of the plate unit is 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, as shown in FIG.
The number of plate-like bodies constituting the plate unit can be appropriately selected as long as a swirling flow of cooling gas can be generated around the nozzle body. However, as the number of plate-like bodies increases, the distance between the plate-like bodies becomes narrower, the discharge flow rate of the cooling gas increases, and the dispersibility of the mist increases. Therefore, four or more plates are preferable, and 4 to 10 plates are even more preferable.
Furthermore, the installation angle of the plate-like body can be selected appropriately as long as a swirling flow of 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, and more preferably 15 to 45°.
One or more plate units may be placed in the gap.
The plate unit shown in FIG. 1 is composed of ten rectangular plate-like bodies inclined at 30° to the vertical direction, one of which is installed at the end of the nozzle body on the outlet side with the end of the plate unit protruding outward beyond the outlet of the nozzle body, and the other is installed at approximately the middle of the nozzle body.

Another embodiment of the plate unit is, for example, the plate unit shown in FIG.
The plate unit shown in FIG. 2(a) is made up of a plurality of tapered plate-like bodies inclined at a predetermined angle to the vertical direction, arranged in a vertical row.
The number of plate-like bodies constituting the plate unit can be appropriately selected as long as a swirling flow can be generated around the nozzle body, but from the viewpoint of improving the dispersibility of the mist by increasing the discharge flow rate of the cooling gas, 2 to 5 plates are preferable, and 2 to 4 plates are even more preferable.
The installation angle of the plate-like body can be appropriately selected as long as a swirling flow can be generated around the nozzle body, but from the viewpoint of improving the dispersibility of the mist, it is preferably 10 to 60°, and more preferably 15 to 45°, from the vertical direction.
The plate unit shown in FIG. 2(a) is composed of three bow-shaped plate bodies tapered at an angle of 30° to the vertical direction, and these are arranged in staggered steps with their heights changed downward from the nozzle body outlet end (to the cooling gas inlet) and are disposed opposite each other along the outer periphery of the nozzle body.

The plate unit shown in FIG. 2(b) is composed of a plurality of plate-shaped bodies arranged so as to block the flow path of the cooling gas.
The number of plate-like bodies constituting the plate unit can be appropriately selected as long as it can block the flow passage of the cooling gas and generate a swirling flow around the nozzle body, but from the viewpoint of improving the dispersibility of the mist by increasing the discharge flow rate of the cooling gas, 2 to 4 plates are preferable, and 2 to 3 plates are even more preferable.
Furthermore, the installation angle of the plate-like body can be appropriately selected as long as it can block the flow passage of the cooling gas and generate a swirling flow around the nozzle body, but from the viewpoint of improving the dispersibility of the mist, it is preferably 10 to 70° with respect to the vertical direction, and more preferably 30 to 70°.
The plate unit shown in FIG. 2(b) is composed of two rectangular plate-like bodies inclined at 60° to the vertical direction, and is installed at the end of the nozzle body on the outlet side so that these intersect via the nozzle body.

Furthermore, the plate unit shown in FIG. 2(c) is a plate-like body having a plurality of slits or holes formed therein.
The shape of the slit or hole can be appropriately selected from a range of shapes, such as rectangular, circular, elliptical, and arched.
The size of the slit or hole can be appropriately selected according to the size of the plate-like body so that a swirling flow is generated around the nozzle body.
The slits or holes are preferably provided symmetrically in order to generate a sufficient swirling flow around the nozzle body.
In order to swirl the cooling gas, the slits or holes are preferably drilled at an angle to the vertical direction. The angle of the slits or holes to the vertical direction is preferably 10 to 60°, and more preferably 15 to 50°.
From the viewpoint of drilling the slits or holes symmetrically and obtaining a sufficient swirling force for the cooling gas, the number of slits or holes is preferably 4 or more. The number of slits or holes is not particularly limited as long as the slits or holes can be drilled symmetrically, and can be appropriately selected depending on the size of the slits or holes and the size of the plate-like body.
The plate-like body is usually installed at a horizontal angle, but may be inclined as long as a swirling flow of cooling gas can be generated around the nozzle body.
The plate unit shown in FIG. 2(c) is composed of a single circular plate having 12 round holes drilled at an angle of 30° to the vertical direction, and is installed at the end of the nozzle body on the outlet side.

Another embodiment of the mechanism is, for example, an impeller that rotates by receiving a torque from the cooling gas. An example of an impeller is shown in Figure 3. In this specification, the term "impeller" refers to a rotor that is made up of multiple blades attached to a hub.
The impeller shown in Fig. 3 is composed of a hub 9 that is rotated by the rotational force of the cooling gas, and a number of blades 10 that extend radially from the periphery of the hub 9. Four blades 10 are arranged at equal intervals on the hub 9, with each pair of blades facing each other. The number of blades and the size of the impeller can be appropriately selected depending on the size of the gap between the nozzle body and the protective tube.

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 protective tube is provided in the protective tube. An example of this is shown in FIG.
4 has a cooling gas introduction pipe 7 provided on the side of the protective tube 3. 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, generating 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. This allows a wide range of the nozzle body to be cooled while a sufficient swirling flow is generated around the nozzle body. In addition, there may be multiple cooling gas introduction pipes. For example, by arranging a second cooling gas introduction pipe diagonally to the first cooling gas introduction pipe, the swirling flow of the cooling gas can be further strengthened.

In the present invention, the above-mentioned 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 above mechanism, the amount of cooling gas introduced into the gap must be enough to cool the nozzle body below its heat-resistant temperature, but it is preferable that the amount is less than the amount of gas introduced into the nozzle body. However, since the mist has a tendency to move in a straight line, if the amount is too small compared to the amount of gas supplied to the nozzle, the effect of dispersing the mist decreases. From this perspective, the amount of cooling gas introduced into 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, of the amount of gas introduced into the nozzle body.

As explained 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 is discharged around the mist while cooling the nozzle body, and flows into the heating furnace of the spray pyrolysis device or spray drying device described below, so that the temperature of the cooling gas is less likely to vary depending on the position, and therefore the variation in the amount of heat received by the mist is suppressed and the dispersibility of the mist is improved. As a result, uneven baking or drying of the mist is suppressed, and fine particles with less variation in particle properties and reduced reduction in particle strength can be produced. In addition, since the nozzle body is easily installed at the center of the protective tube, temperature variations such as a low temperature on the left side of the nozzle body and a high temperature on the right side are suppressed, and the nozzle exchanges heat evenly, so that deterioration due to one-sided burning of components such as the nozzle body and packing is suppressed, and the nozzle can be used for a long time without the need for short-term replacement.

[Spray pyrolysis equipment or spray drying equipment]
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 be described below 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 device or spray drying device 300 is an internal combustion type, and includes a nozzle 100 for spraying a mist of the raw material solution, and a heating furnace 101 for pyrolyzing or drying the mist with the combustion gas of a combustion burner 102, as shown in FIG. 5. The combustion burner 102 is housed in a combustion tube 103, which is connected to the heating furnace 101 in a substantially horizontal direction 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 to each other with their central axes offset, so that when the combustion gas (hot air) generated in the combustion tube 103 passes through the heating furnace 101, it does not rise straight up, but rises by generating a swirling flow. As a result, the sprayed mist rises in the heating furnace 101 on this swirling flow, and a sufficient heating time can be ensured.

The nozzle is not particularly limited as long as it is the nozzle of the present invention. The specific embodiment of the nozzle is as described above.
One or more nozzles may be provided.

The material of the heating furnace and the combustion tube is not particularly limited as long as it is used as a furnace material, and examples thereof include heat-resistant metals such as iron, stainless steel, Inconel, Hastelloy, and titanium, ceramics, bricks, and monolithic refractories.
The shape of the heating furnace and the combustion tube is preferably approximately cylindrical, from the viewpoints of enabling fastening with flanges and suppressing uneven temperature inside the heating furnace and uneven heat dissipation in the cross-sectional direction from the heating furnace and the combustion tube.

The size of the heating furnace can be appropriately selected depending on the production scale. For example, when the furnace is a vertical cylinder, 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 by the combustion burner does not directly contact the spray mist. However, if the distance between the flame generated by the combustion burner and the spray mist is too long, the thermal efficiency becomes insufficient.
The inside diameter of the portion of the combustion tube that is connected to the heating furnace is preferably smaller than the inside diameter of the heating furnace, since this makes it easier to generate a strong swirling flow of hot air. For example, the inside diameter of the connecting portion of the combustion tube should be less than half the inside diameter of the vertical tube.

The misalignment of the central axis between the heating furnace and the combustion tube is preferably 10% to 90%, and more preferably 20% to 80%, of the inner diameter of the heating furnace taken as 100%, taking into account the degree of swirling flow generation, thermal efficiency, and the effect on the heat resistance of the combustion tube.

The combustion burner can be selected from commercially available products that suit the volume and specifications of the heating furnace, or it can be manufactured according to the specifications of the heating furnace.

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

Next, we will explain the method for producing inorganic oxide particles using a spray pyrolysis device or a spray drying device.

First, a raw material solution is prepared. The raw material solution is a solution of compounds containing elements that form oxides.
The compound containing an element constituting an oxide is not particularly limited as long as it contains an element constituting an oxide and dissolves in a solvent such as water, and examples thereof include inorganic salts and metal alkoxides. More specifically, examples thereof include aluminum salts, titanium salts, magnesium salts, aluminosilicates, aluminum alkoxides, and 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 therein. Examples of silicate alkoxides include tetraethoxysilane and tetramethoxysilane. In addition, a solution in which aluminum oxide or silicon oxide is dispersed in a solvent, and 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 these, one or more selected from aluminum salts, titanium salts, magnesium salts, aluminosilicates, aluminum alkoxides and silicate alkoxides are preferred.

Inorganic oxides obtained from these raw material compounds include, for example, metal oxides, alumina, silica, oxides of aluminum and silicon, etc. More specifically, examples include oxides of alumina, silica, aluminum and silicon, titanium oxide, magnesium oxide, zinc oxide, zirconium oxide, barium oxide, cerium oxide, yttrium oxide, etc., as well as composite oxides that combine these oxides.

Solvents for dissolving or dispersing compounds containing elements that constitute oxides include water and organic solvents. Among these, water is preferred from the standpoint of environmental impact and production costs.

The concentration of the compound containing the element that constitutes the oxide in the raw material solution is preferably 0.01 mol/L to the saturated concentration, more preferably 0.1 to 1.0 mol/L, taking into consideration the density, strength, etc. of the resulting inorganic oxide particles.

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

The gas flow rate supplied to the nozzle body is preferably 1000 times or more by volume relative to the amount of raw material solution delivered to the nozzle body, and the upper limit is preferably 3000 times or less, more preferably 2500 times or less, from the viewpoints of preventing solidification at the nozzle tip and promoting the evaporation of the solvent in the mist and the precipitation of inorganic salts.

The flow rate of the cooling gas supplied to the gap between the nozzle body and the protective tube is preferably less 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, of the amount of gas supplied to the nozzle body.

The temperature of the gas supplied to the nozzle body and the gap is preferably equal to or lower than the temperature of the mist immediately after ejection, and more preferably equal to or lower than room 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 mist temperature immediately after spraying is 1/2 or less of the boiling point of the solvent in the raw solution, and can be set appropriately depending on the type of solvent in the raw solution. For example, when the raw solution is an aqueous solution, the temperature is preferably 1 to 50°C, more preferably 5 to 40°C, and even more preferably 10 to 40°C. The temperature of the mist immediately after spraying can be controlled by installing a thermocouple at the tip of the nozzle so that it comes into contact with the mist sprayed from the nozzle. The thermocouple is preferably installed within 5 cm from the tip of the nozzle. In order to adjust the temperature of the raw solution in the nozzle, the outer periphery of the nozzle may be covered with a heat insulating material. Examples of heat insulating materials include ceramic fiber, glass fiber, castable, etc.

The mist is usually ejected at a speed of 1 to 50 m/s, preferably 5 to 35 m/s, and more preferably 10 to 20 m/s, from the viewpoint of promoting thermal decomposition or drying and preventing the formation of deposits on the walls of the heating furnace.

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

The mist sprayed from the nozzle is heated in a heating furnace and thermally decomposed or dried, forming a film containing an inorganic compound, from which inorganic oxide particles precipitate.
As described above, in the spray pyrolysis apparatus or spray drying apparatus according to this embodiment, the central axis of the heating furnace and the central axis of the combustion tube are offset when they are connected, so that when the combustion gas generated in the combustion tube passes through the heating furnace, it does not rise straight up, but rises while generating a swirling flow. Meanwhile, the cooling gas introduced into the gap between the nozzle body and the protective tube cools the mist while swirling around the nozzle body, and is discharged around the mist, and is caught in the flow of the combustion gas discharged from the combustion tube to the heating furnace and rises inside the heating furnace. As a result, the sprayed mist rises inside the heating furnace on this swirling flow, and sufficient heating time can be secured, so that uneven baking or drying of the mist can be suppressed.
In addition, the swirling direction of the combustion gas in the heating furnace is preferably the same as the swirling direction of the cooling gas circulated in the gap between the nozzle body and the protective tube described above. By making the swirling direction of the combustion gas and the swirling direction of the cooling gas the same in this way, a sufficient swirling force is obtained, the variation in the amount of heat received by the mist is suppressed, and the dispersion of the mist is improved, so that uneven baking or drying of the mist can be suppressed.

The temperature inside 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, but is preferably 100 to 500°C, more preferably 150 to 450°C, and even more preferably 200 to 400°C.

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, but is preferably 100 to 1800°C, more preferably 150 to 1500°C, and even more preferably 150 to 1200°C.

Next, the fine particles generated by pyrolysis or drying are moved from the downstream of the heating furnace to a recovery device by an induction fan, for example, and recovered. Examples of recovery devices include a cyclone powder recovery machine and a bag filter. When recovering the fine particles, the particle size may be adjusted by passing them through a filter. Furthermore, dust removal and purification equipment such as a scrubber may be installed downstream of the recovery device as 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, in this specification, "solid particles" refers to particles with a structure that does not have a cavity inside, and examples thereof include particles consisting of a single layer and particles having a core (also called an inner core) and a shell layer (also called an outer shell). Furthermore, "hollow particles" refers to particles with a structure that has a cavity (hollow part) inside and has a cavity surrounded by an outer shell. The number of cavities may be single or multiple. Furthermore, "porous particles" refers to particles with many through holes that are connected from the particle surface to the inside. The size and shape of the through holes are not particularly limited. Furthermore, the particles may have closed pores inside.

When producing inorganic oxide hollow particles, the surfaces of the inorganic oxide particles after pyrolysis may be melted. This closes the pores present on the surfaces of the inorganic oxide particles, resulting in hollow inorganic oxide particles with no pores in the particle shell and high particle strength. To melt the surfaces of the inorganic oxide particles, for example, the temperature of the heating furnace may be controlled to be equal to or higher than the melting temperature of the inorganic oxide particles.

As described above, by using the spray pyrolysis device or spray drying device 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 vary depending on the position, and as a result, the variation in the amount of heat received by the mist is suppressed, and the dispersibility of the mist is improved. Then, the mist, together with the cooling gas, is caught in the swirling flow of the combustion gas discharged from the combustion tube to the heating furnace and rises inside the heating furnace, ensuring sufficient heating time. As a result, uneven baking or drying of the mist is suppressed, and fine particles with little variation in particle properties with suppressed reduction in particle strength can be manufactured.
The produced inorganic oxide particles can have the following properties.

The average particle size of the inorganic oxide hollow particles is usually 0.5 to 50 μm, preferably 1 to 20 μm, and more preferably 2 to 10 μm. In this specification, the term "average particle size" means the particle size (d50) that corresponds 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. For example, a Microtrac (manufactured by Nikkiso Co., Ltd.) can be used as a particle size distribution measuring device.

The particle density of the inorganic oxide particles is usually 0.1 to 2.5 g/cm ³ , preferably 0.2 to 1.5 g/cm ³ , and more preferably 0.3 to 1.0 g/cm ^3. 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.

The particle strength of the inorganic oxide particles is preferably 14 MPa or more, more preferably 15 MPa or more, and even more preferably 16 MPa or more, from the viewpoint of ensuring sufficient strength. Here, in this specification, "particle strength" refers to the particle strength when the hollow particle residual rate is 50% when pressure is applied to the hollow particles using a pressure molding press. Specifically, it can be measured by the method described in the examples below.

The present invention has been described in detail above based on the embodiments. However, the present invention is not limited to the above embodiments. The present invention can be modified in various ways without departing from the gist of the invention. For example, as shown in FIG. 5, the spray pyrolysis device or spray drying device 300 has the combustion burner 102 housed in the combustion tube 103 and connected to the heating furnace 101 with the central axis shifted, but the present invention is not limited to this, and it is also possible to adopt a mode in which the central axis is shifted as described in JP 2020-32318 A and JP 2021-69970 A. In addition, the combustion burner 102 may not be housed in the combustion tube 103 and may be attached to the side wall of the heating furnace. Furthermore, in the spray pyrolysis device or spray drying device 300, the nozzle 100 and the heating furnace 101 are arranged vertically, but they may be horizontal or oblique, not limited to the vertical type.

The following examples are provided to further explain the embodiments of the present invention. However, the present invention is not limited to the following examples.

1. Particle density Measurement was performed by a constant volume expansion method using a dry automatic density meter (AccuPic 1340, manufactured by Shimadzu Corporation). That is, after placing a sample in a cell, the cell was filled with an inert gas and the volume of the sample was measured, and the particle density was calculated from this volume and the sample mass measured in advance.

2. Average Particle Diameter The average particle diameter of the inorganic oxide particles was determined by creating a volumetric particle size distribution in accordance with JIS R 1629 using a Microtrac (manufactured by Nikkiso Co., Ltd.) as a particle size distribution measuring device, and determining the particle diameter (d ₅₀ ) corresponding to 50% of the cumulative distribution curve.
Here, Microtrac has the characteristic of capturing the maximum diameter of a single particle as the particle diameter of that particle, so when there are many particles that have become elliptical or snowman-shaped due to interference from the mist, the average particle diameter tends to be larger.

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

Then, the remaining rate for each given pressure was calculated from the density of the hollow particles before and after pressure application using the following formula, and the pressure at which 50% remained was read from a graph of the remaining rate and applied pressure. The density was measured using the density measuring device described above, and the true density of the hollow shell was measured after heating above the melting point for 6 hours in a box-type electric furnace and then cooling in order to remove voids.

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

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

Example 1
Magnesium oxide hollow particles were produced by the following method using the spray pyrolysis apparatus shown in Fig. 5. That is, 1985 g of magnesium acetate was dissolved in 100 L of ion-exchanged water to prepare an aqueous magnesium acetate solution. Next, this aqueous solution was sprayed from a three-fluid nozzle having a structure shown in Fig. 1 into a heating furnace heated to a temperature of 1150°C, and magnesium oxide hollow particles were collected using a bag filter. In addition, in the gap between the nozzle body and the protective tube, plate units having a total of 10 plates with an inclination angle of 30° as shown in Fig. 1 were installed at two locations. Then, cooling air was circulated through this gap, and the cooling air was discharged toward the outlet of the nozzle body while swirling around the nozzle body. In addition, the spray pyrolysis conditions were as follows.

(Spray pyrolysis conditions)
・Raw material solution spray amount: 14L/h
Nozzle air volume: 240 L/min
Cooling air volume: 200 L/min (ratio to nozzle air is 83%)
Firing temperature: 1150°C (burner controlled temperature. 5 cm from the nozzle tip)

The particle density, average particle size, and particle strength of the particles collected were then measured every hour from the start of production. The results are shown in Table 1.

Comparative Example 1
Magnesium oxide hollow particles were produced in the same manner as in Example 1, except that a plate unit was not installed in the gap between the nozzle body and the protective tube. The particle density, average particle size, and particle strength of the particles collected every hour from the start of production were measured. The results are shown in Table 1.

Comparative Example 1 is an example in which a plate unit was not installed in the gap between the nozzle body and the protective tube. However, the amount of heat received by the mist varied, and the mist had poor dispersibility, resulting in uneven firing of the mist. As a result, the obtained hollow particles showed a decrease in particle strength, and variation in particle properties was confirmed.
In contrast, in Example 1, a plate unit was installed in the gap between the nozzle body and the protective tube, and a cooling gas was circulated therein in a swirling manner around the nozzle body. As a result, the variation in the amount of heat received by the mist was reduced, the dispersibility of the mist was improved, and unevenness in the firing of the mist was suppressed. As a result, it was confirmed that the decrease in particle strength of the obtained hollow particles was suppressed, and the variation in particle properties was suppressed.

REFERENCE SIGNS LIST 1 nozzle body 2 outlet 3 protective tube 4 gap 5 mechanism (plate unit)
6 Plate-like body 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 pyrolysis device or spray drying device

Claims (8)

A nozzle body having a discharge port for spraying a liquid;
a protective tube covering an outer periphery of the nozzle body;
a gap through which a cooling gas can flow is provided between the nozzle body and the protective tube;
The gap is provided with a plate unit having 4 to 10 plate-like bodies arranged in parallel along the horizontal direction, the plate bodies being inclined at an angle of 15 to 45 degrees with respect to the vertical direction, and the plate unit is capable of discharging the cooling gas toward the discharge port while rotating around the nozzle body by circulating cooling air therethrough.
Nozzles for spray pyrolysis or spray drying. 2. The nozzle according to claim 1, wherein the protective tube is disposed so that an end thereof protrudes outward beyond the discharge port of the nozzle body . 3. The nozzle of claim 1 or 2 , wherein the nozzle is of the internal mix type . The nozzle according to any one of claims 1 to 3 , wherein two or more of the plate units are provided in the gap. A nozzle according to any preceding claim, wherein the cooling gas is air. The nozzle according to any one of claims 1 to 5 , wherein the nozzle body is a one-fluid nozzle, a two-fluid nozzle, a three-fluid nozzle or a four-fluid nozzle. A nozzle for spraying the raw material solution;
a heating furnace for thermally decomposing or drying the mist of the raw material solution sprayed from the nozzle by a combustion gas of a combustion burner;
The nozzle is a nozzle according to any one of claims 1 to 6 .
Spray pyrolysis equipment or spray drying equipment. a mechanism for generating a swirling flow of the combustion gas in the heating furnace,
8. The spray pyrolysis apparatus or spray drying apparatus according to claim 7 , wherein a swirling direction of the combustion gas in the heating furnace and a swirling direction of the cooling gas in the gap are the same.