Nozzle for spray pyrolysis apparatus or spray drying apparatus

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

Technical Field

[0001] The present invention relates to a nozzle for a spray pyrolysis apparatus or a spray drying apparatus.

Background Art

[0002] As a microparticle manufacturing apparatus, for example, a spray pyrolysis apparatus or a spray drying apparatus is used (Patent Documents 1 and 2). In these apparatuses, for example, a nozzle for spraying a mist (droplet) of a 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 microparticles are manufactured by thermally decomposing or drying the mist using the combustion gas as a heat source.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Since the nozzle is installed in a high-temperature heating furnace, measures such as coating the nozzle with a heat-insulating material or providing a cooling mechanism for the nozzle are taken to keep the nozzle below its heat-resistant temperature. When a cooling mechanism is provided for the nozzle, water is often circulated on the outer periphery of the nozzle or cooling air is made to flow through. However, according to the study by the present inventors, it has been found that there are the following problems when cooling air is made to flow through. That is, when using cooling air, while cooling the nozzle by making the cooling air flow through the gap between the nozzle body and the protective tube, the cooling air is discharged around the mist and made to flow 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 in the mist. As a result, the particulate matter generated from the mist with uneven firing or uneven drying has a reduced particle strength, which becomes a factor in the variation of particle physical properties. Here, in this specification, "uneven firing or uneven drying" means that a part of the mist does not receive sufficient heat and is in a state of being underfired. 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 firing or uneven drying of a mist, and a spray pyrolysis apparatus or a spray drying apparatus using the same.

Means for Solving the Problems

[0005] As a result of investigations in view of the above problems, the present inventors provided a protective tube around the outer periphery of the nozzle body, and by making the cooling gas flow through the gap between the nozzle body and the protective tube so as to swirl around the nozzle body, the variation in the amount of heat received by the mist is suppressed, and the dispersibility of the mist is also improved. Therefore, uneven firing or uneven drying of the mist is suppressed, and it has been found that fine particles with less variation in particle physical properties and with a reduced decrease in particle strength can be produced.

[0006] 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 and comprising 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 mechanism capable of discharging the cooling gas toward the discharge port while swirling around the nozzle body. A nozzle for a spray pyrolysis apparatus or a spray drying apparatus. 〔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 a 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 of the inner diameter of the protective tube into the protective tube. 〔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, 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 with combustion gas of a combustion burner is provided, the nozzle being the nozzle according to any one of 〔1〕 to 〔7〕. A spray pyrolysis apparatus or a spray drying apparatus. 〔9〕The spray pyrolysis apparatus or the spray drying apparatus according to 〔8〕, further comprising a mechanism for generating a swirling flow of the combustion gas in the heating furnace, wherein a swirling direction of the combustion gas in the heating furnace is the same as a swirling direction of the cooling gas in the gap.

Advantages of the Invention

[0007] By using the nozzle of the present invention, the variation in the amount of heat received by the mist sprayed from the nozzle can be suppressed, and the dispersibility of the mist is also improved. Therefore, uneven firing or uneven drying of the mist is suppressed, and fine particles with little variation in particle properties with suppressed decrease in particle strength can be produced.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0009] 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 denoted by the same reference numerals, and redundant descriptions are omitted. Also, for the sake of illustration, the dimensional ratios in the drawings do not necessarily match those in the description.

[0010] 〔Nozzle for Spray Pyrolysis Apparatus or Spray Drying Apparatus〕 The nozzle of the present invention is exclusively used for a spray pyrolysis apparatus or a spray drying apparatus. 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 periphery of the nozzle body 1. At the end of the nozzle body 1, a discharge port 2 for spraying liquid is provided. And the nozzle 100 is provided with a gap 4 through which a cooling gas can flow between the nozzle body 1 and the protective tube 3. The gap 4 has a mechanism 5 that can discharge the cooling gas introduced from the cooling gas inlet 7 at the end of the protective tube 3 toward the discharge port 2 while swirling around the nozzle body 1.

[0011] Examples of the nozzle body include fluid nozzles. More specifically, single-fluid nozzles, two-fluid nozzles, three-fluid nozzles, or four-fluid nozzles can be mentioned. Among them, two-fluid nozzles, three-fluid nozzles, or four-fluid nozzles are preferred, and three-fluid nozzles or four-fluid nozzles are more preferred.

[0012] The nozzle body may be selected from commercially available nozzles according to the volume and specifications of the heating furnace, etc. Alternatively, one 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, etc. For example, it is 400 to 1500 mm. Also, the outer diameter of the nozzle body can be appropriately selected according to the volume and specifications of the heating furnace, etc. For example, when the nozzle is cylindrical, it is φ40 to 80 mm.

[0013] Regarding the type of fluid nozzle, there are an internal mixing type in which gas and the raw material solution are mixed inside the nozzle and an external mixing type in which gas and the raw material solution are mixed outside the nozzle, and either can be adopted. As the gas supplied to the nozzle, for example, air, or inert gases such as nitrogen and argon can be used. Among them, air is preferred from the perspective of economy.

[0014] The protective tube is installed 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 has heat resistance. For example, heat-resistant metals such as iron, stainless steel, Inconel, Hastelloy, titanium, ceramics, bricks, and refractory castables can be mentioned.

[0015] The length of the protective tube only needs to 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 discharge speed of the cooling gas can be adjusted. When installing the protective tube on the nozzle body, it is preferable to install it with the end of the protective tube protruding outside the discharge port of the nozzle body. Thereby, while cooling the nozzle body with the swirling cooling gas, it can be discharged around the discharge port of the nozzle body, so that the variation in the amount of heat received by the mist is suppressed, the dispersibility of the mist is enhanced, and the firing unevenness or drying unevenness of the mist can be suppressed.

[0016] 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, inert gases such as nitrogen and argon, etc. can be used. Among them, air is preferable from the viewpoint of economy.

[0017] The cooling gas introduced into the gap is discharged toward the discharge port of the nozzle body, but in the gap, a mechanism is provided for discharging the cooling gas around the nozzle body while swirling around the nozzle body and discharging it around the discharge port of the nozzle body. 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. For example, a plate unit can be mentioned. Here, in this specification, the "plate unit" refers to something composed of one or two or more plate-like bodies. For example, those obtained by integrating a plurality of plate-like bodies or processing a single plate-like body can be mentioned. The shape of the plate-like body includes, for example, a rectangle, a circle, an ellipse, a tapered shape, a bow shape, etc., and can be appropriately selected. The material of the plate-like body may be metal or ceramic, and is not particularly limited. The length of the plate-like body is generally 10 to 100 mm, the thickness is generally 1 to 10 mm, and the width is substantially equal to the width of the gap. In addition, 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 can be at the discharge port side end of the nozzle body and at the substantially middle part of the nozzle body, but it is not limited thereto.

[0018] 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 cited. The number of plate-like bodies constituting the plate unit can be appropriately selected as long as a swirling flow of the cooling gas can be generated around the nozzle body. However, as the number of plate-like bodies increases, the dimension between the plate-like bodies becomes narrower, the discharge flow rate of the cooling gas increases, and the dispersibility of the mist increases. Therefore, 4 or more are preferable, and 4 to 10 are more preferable. Also, the installation angle of the plate-like body can be appropriately selected as long as a swirling flow of the cooling gas can be generated around the nozzle body. However, from the viewpoint of improving the dispersibility of the mist, 10 to 60° with respect to the vertical direction is preferable, and 15 to 45° is more preferable. One or more plate units can be installed in the gap. The plate unit shown in FIG. 1 is composed of 10 rectangular plate-like bodies inclined 30° with respect to the vertical direction. One of them is installed at the discharge port side end of the nozzle body with the end of the plate unit protruding outside the discharge port of the nozzle body, and the other is installed at the substantially middle part of the nozzle body.

[0019] Also, as another aspect of the plate unit, for example, the plate unit shown in FIG. 2 can be cited. 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 vertical column. 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. However, from the viewpoint of improving the dispersibility of the mist by enhancing the discharge flow velocity of the cooling gas, 2 to 5 sheets are preferable, and 2 to 4 sheets are more preferable. Also, 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. However, from the viewpoint of improving the dispersibility of the mist, an angle of 10 to 60° with respect to the vertical direction is preferable, and an angle of 15 to 45° is more preferable. The plate unit shown in Fig. 2(a) is composed of three tapered bow-shaped plate-like bodies inclined at 30° with respect to the vertical direction. These are arranged in steps with different heights from the end of the nozzle body discharge port downward (toward the cooling gas inlet), and are installed opposite to each other along the outer periphery of the nozzle body.

[0020] Also, the plate unit shown in Fig. 2(b) is composed of a plurality of plate-like bodies installed so as to shield the flow path of the cooling gas. The number of plate-like bodies constituting the plate unit can be appropriately selected as long as the flow path of the cooling gas is shielded and a swirling flow can be generated around the nozzle body. However, from the viewpoint of improving the dispersibility of the mist by enhancing the discharge flow velocity of the cooling gas, 2 to 4 sheets are preferable, and 2 to 3 sheets are more preferable. Also, the installation angle of the plate-like body can be appropriately selected as long as the flow path of the cooling gas is shielded and a swirling flow can be generated around the nozzle body. However, from the viewpoint of improving the dispersibility of the mist, an angle of 10 to 70° with respect to the vertical direction is preferable, and an angle of 30 to 70° is more preferable. The plate unit shown in Fig. 2(b) is composed of two rectangular plate-like bodies inclined at 60° with respect to the vertical direction, and these are installed at the end of the nozzle body discharge port side so as to intersect via the nozzle body.

[0021] Furthermore, the plate unit shown in Fig. 2(c) is a plate-like body provided with a plurality of slits or holes. The shape of the slit or hole includes, for example, rectangular, circular, elliptical, arcuate, etc., and can be appropriately selected. 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. In order to generate a sufficient swirling flow around the nozzle body, it is preferable to symmetrically provide the slits or holes at the installation positions of the slits or holes. In order to swirl the cooling gas, the slit or hole is preferably drilled at an angle with respect to the vertical direction. The angle of the slit or hole is preferably 10 to 60° with respect to the vertical direction, and more preferably 15 to 50°. From the viewpoint of symmetrically drilling 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 symmetrically drilled, 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 in the horizontal direction, 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, and this is installed at the end on the discharge port side of the nozzle body.

[0022] As another embodiment of the mechanism, for example, an impeller that rotates by receiving a rotational force from the cooling gas can be mentioned. An example of the impeller is shown in Fig. 3. Here, in this specification, the "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 a rotational force from the cooling gas and a plurality of blades 10 that radially extend from around the hub 9. Four blades 10 are arranged on the hub 9 at equal intervals and in such a way that a pair of blades face each other. The number of installed blades 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.

[0023] 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 protective pipe may be installed in the protective pipe. An example thereof is shown in FIG. 4. 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 pipe 3 to generate a swirling flow of the cooling gas in the gap. The cooling gas introduction pipe is preferably installed at a position as far as possible from the discharge port of the nozzle body. Thereby, while cooling a wide range of the nozzle body, a sufficient swirling flow can be generated around 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 diagonal position of the first cooling gas introduction pipe, there is an effect of further strengthening the swirling flow of the cooling gas.

[0024] In the present invention, the above-described mechanisms may be combined. For example, as shown in FIG. 4, the plate unit shown in FIG. 1 and the mechanism for introducing cooling gas in the tangential direction of the inner diameter of the protective pipe can be combined.

[0025] In the above-described mechanism, the amount of cooling gas introduced into the gap needs to be an amount capable of cooling the nozzle body to a heat-resistant temperature or lower, but it is preferably less than the amount of gas introduced into the nozzle body. However, since the mist has straightness, if it is too less than the amount of gas supplied to the nozzle, the effect of dispersing the mist is reduced. From such a viewpoint, the amount of cooling gas introduced into the gap is preferably 50 to 95% by volume, more preferably 60 to 90% by volume, and still more preferably 70 to 85% by volume with respect to the amount of gas introduced into the nozzle body.

[0026] 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 is discharged around the mist while cooling the nozzle body, and flows into the heating furnace of the spray pyrolysis apparatus or spray drying apparatus described later. Therefore, the temperature of the cooling gas is less likely to vary depending on the position, and accordingly, the variation in the amount of heat received by the mist is suppressed, and the dispersibility of the mist is enhanced. As a result, firing unevenness or drying unevenness of the mist is suppressed, and fine particles with little variation in particle properties and suppressed reduction in particle strength can be produced. In addition, since it becomes easier to install the nozzle body around the protective tube, for example, 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 as a result of uniform heat exchange of the nozzle, deterioration due to uneven baking of members such as the nozzle body and packing is suppressed, and it can be used over a long period without requiring replacement in a short period.

[0027] 〔Spray pyrolysis apparatus or spray drying apparatus〕 The spray pyrolysis apparatus or spray drying apparatus of the present invention is equipped with the nozzle of the present invention. Hereinafter, a preferred embodiment will be described with reference to FIG. 5.

[0028] 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 an internal combustion type. As shown in FIG. 5, it includes a nozzle 100 for spraying a mist of a raw material solution, and a heating furnace 101 for thermally decomposing or drying the mist with the combustion gas of a combustion burner 102. The combustion burner 102 is housed in a combustion tube 103. The combustion tube 103 is substantially horizontal with respect to the vertically oriented heating furnace 101 and is connected while being offset from the central axis of the heating furnace 101. In this way, by connecting the heating furnace 101 and the combustion tube 103 with their central axes offset from each other, 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 generates a swirling flow and rises. As a result, the sprayed mist rides on this swirling flow and rises in the heating furnace 101, ensuring a sufficient heating time.

[0029] 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 can be installed.

[0030] The materials of the heating furnace and the combustion pipe are not particularly limited as long as they are used as furnace materials. For example, heat-resistant metals such as iron, stainless steel, Inconel, Hastelloy, and titanium, ceramics, bricks, and refractory castables can be mentioned. As for the shapes of the heating furnace and the combustion pipe, from the viewpoints of being able to perform fastening by a flange, temperature unevenness in the heating furnace, and suppressing heat dissipation unevenness in the cross-sectional direction from the heating furnace and the combustion pipe, it is preferably substantially cylindrical.

[0031] The size of the heating furnace can be appropriately selected according to the manufacturing scale. For example, when it is in 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 pipe is not particularly limited as long as it can accommodate the combustion burner. However, the length of the combustion pipe is preferably such that the flame generated from the combustion burner does not directly contact 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. In addition, it is preferable that the inner diameter of the portion of the combustion pipe connected to the heating furnace is smaller than the inner diameter of the heating furnace in terms of easily generating a strong swirling flow of hot air. For example, the inner diameter of the connection portion of the combustion pipe is preferably set to be half or less of the inner diameter of the vertical pipe.

[0032] The deviation of the central axes of the heating furnace and the combustion pipe is preferably 10% or more and 90% or less, more preferably 20% or more and 80% or less, with the inner diameter of the heating furnace being 100%, in view of the degree of generation of the swirling flow, thermal efficiency, and the influence on the heat resistance of the combustion pipe.

[0033] The combustion burner can be selected from commercially available ones in consideration of the volume and specifications of the heating furnace, etc., or ones manufactured according to the specifications of the heating furnace can also be made.

[0034] The fuel used in the combustion burner is not particularly limited, and examples thereof include gaseous fuels, liquid fuels, and solid fuels, and two or more of these fuels may be co-combusted. Examples of the gaseous fuel include LPG, city gas, and vaporized organic substances. 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, and wood.

[0035] Next, a method for producing inorganic oxide particles using a spray pyrolysis apparatus or a spray drying apparatus will be described.

[0036] First, a raw material solution is prepared. The raw material solution is a solution of a compound containing an element constituting the oxide. The compound containing an element constituting the oxide is not particularly limited as long as it contains an element constituting the oxide and is soluble in a solvent such as water, and examples thereof include inorganic salts, metal alkoxides, etc. More specifically, examples include aluminum salts, titanium salts, magnesium salts, aluminosilicates, aluminum alkoxides, tetraethoxysilane, tetraethoxysilane, and other alkoxysilanes. Examples of the aluminum salt include inorganic salts such as aluminum nitrate, aluminum sulfate, aluminum chloride, aluminum phosphate, aluminum hydroxide, aluminum acetate, and aluminum oxalate, organometallic compounds such as aluminum secondary butyrate, and those in which an aluminum compound such as aluminum isopropylate is dispersed. Examples of the alkoxysilane include tetraethoxysilane and tetramethoxysilane. In addition, 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 the raw material solution. Furthermore, in order to adjust the melting temperature, heat resistance, and particle strength, raw materials of other elements can also be added. Among them, one or more selected from aluminum salts, titanium salts, magnesium salts, aluminosilicates, aluminum alkoxides, and alkoxysilanes are preferable.

[0037] Examples of the inorganic oxides obtained from these raw material compounds include metal oxides, alumina, silica, and oxides composed of aluminum and silicon. 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. can be mentioned, and composite oxides formed by combining these oxides can also be mentioned.

[0038] Examples of the solvent for dissolving or dispersing the compound containing the element constituting the oxide include water and organic solvents. Among them, water is preferred from the viewpoints of environmental impact and manufacturing cost.

[0039] The concentration of the compound containing the element constituting the oxide in the raw material solution is preferably 0.01 mol / L to the saturation concentration, more preferably 0.1 to 1.0 mol / L, considering the density, strength, etc. of the obtained inorganic oxide particles.

[0040] Next, while supplying combustion gas (hot air) from the combustion burner housed in the combustion tube to the heating furnace, the mist of the raw material solution is sprayed from the nozzle attached to the heating furnace. Note that it is possible to use a pump for feeding the raw material solution to the nozzle, and the pressure and flow rate may be adjusted so as to achieve a desired mist discharge rate.

[0041] The gas flow rate supplied to the nozzle body is preferably 1000 times or more in volume ratio with respect to the liquid feed amount of the raw material solution to the nozzle body. The upper limit value is preferably 3000 times or less, more preferably 2500 times or less, from the viewpoints of preventing caking at the nozzle tip, promoting solvent evaporation of the mist, and promoting inorganic salt precipitation.

[0042] The gas flow rate of the cooling gas supplied to the gap between the nozzle body and the protective tube is preferably less than the gas amount supplied to the nozzle body. For example, the gas amount of the cooling gas supplied to the gap is preferably 50 to 95% by volume, more preferably 60 to 90% by volume, and still more preferably 70 to 85% by volume, with respect to the gas amount supplied to the nozzle body.

[0043] The temperature of the nozzle body and the gas supplied to 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). Note that the lower limit of the temperature of the supplied gas is preferably 1°C or higher, more preferably 5°C or higher, and still more preferably 10°C or higher for ease of temperature control.

[0044] The temperature of the mist immediately after spraying is a temperature equal to or lower than half 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, it is preferably 1 to 50°C, more preferably 5 to 40°C, and still more preferably 10 to 40°C. Note that for temperature control of the mist immediately after ejection, a thermocouple may be installed at the tip of the nozzle so as to contact the mist ejected from the nozzle. The installation position of the thermocouple is preferably within 5 cm from the tip of the nozzle. Further, in order to adjust the temperature of the raw material solution in the nozzle, the outer periphery of the nozzle may be covered with a heat insulating material. Examples of the heat insulating material include ceramic fiber, glass fiber, and castable.

[0045] The ejection speed of the mist is usually 1 to 50 m / s, and from the viewpoints of promoting thermal decomposition or drying and preventing the generation of deposits on the heating furnace wall surface, 5 to 35 m / s is preferable, and 10 to 20 m / s is more preferable.

[0046] The average particle diameter of the mist is preferably 0.5 to 60 μm, more preferably 1.0 to 20 μm, and still more preferably 1.0 to 15 μm. Note that the average particle diameter of the mist can be adjusted by the shape of the nozzle outlet and the air pressure.

[0047] The mist sprayed from the nozzle is heated in the heating furnace to undergo thermal decomposition or drying, forming a film containing an inorganic compound, and inorganic oxide particles precipitate starting from this film. As described above, in the spray pyrolysis apparatus or spray drying apparatus according to this embodiment, since the central axis of the heating furnace and the central axis of the combustion tube are offset and connected, when the combustion gas generated in the combustion tube passes through the heating furnace, it does not rise straight up, but generates a swirling flow and rises. On the other hand, the cooling gas introduced into the gap between the nozzle body and the protective tube is discharged around the mist while swirling around the nozzle body and cooling, and is entrained by the flow of the combustion gas discharged from the combustion tube to the heating furnace and rises in the heating furnace. As a result, the sprayed mist rides on this swirling flow and rises in the heating furnace, ensuring a sufficient heating time, so that uneven firing or uneven drying of the mist can be suppressed. Note that it is preferable that the swirling direction of the combustion gas in the heating furnace is the same as the swirling direction of the cooling gas flowing through 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 can be obtained, the variation in the amount of heat received by the mist can be suppressed, and the dispersibility of the mist can be enhanced. Therefore, uneven firing or uneven drying of the mist can be suppressed.

[0048] The temperature in the combustion tube is not particularly limited as long as it is the temperature at which the solvent evaporates from the mist of the raw material solution. For example, 100 to 500 °C is preferable, 150 to 450 °C is more preferable, and 200 to 400 °C is even more preferable.

[0049] The temperature in the heating furnace is not particularly limited as long as it is the temperature at which the solvent evaporates from the mist and inorganic salts precipitate. However, 100 to 1800 °C is preferable, 150 to 1500 °C is more preferable, and 150 to 1200 °C is even more preferable.

[0050] Next, the fine particles generated by pyrolysis or drying are moved and recovered to a recovery device by an induced draft fan, for example, from the downstream of the heating furnace. Examples of the recovery device include a cyclone powder collector and a bag filter. Also, when recovering the fine particles, the particle size may be adjusted by passing them through a filter. Further, dust removal and purification equipment such as a scrubber may be arranged on the downstream side of the recovery device as necessary.

[0051] 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 having a cavity (hollow part) inside and having a cavity surrounded by an outer shell. The number of cavities may be single or multiple. Furthermore, "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 holes are not particularly limited. Furthermore, the particles may have closed pores inside.

[0052] In addition, 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, and the inorganic oxide hollow particles having no pores in the particle shell and high particle strength are obtained. 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.

[0053] 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.

[0054] The average particle diameter 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. Here, in this specification, the "average particle diameter" means the particle diameter (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. For the particle diameter distribution measuring device, for example, Microtrac (manufactured by Nikkiso Co., Ltd.) can be used.

[0055] The particle density of the inorganic oxide particles is usually 0.1 to 2.5 g / cm 3 and preferably 0.2 to 1.5 g / cm 3 and more preferably 0.3 to 1.0 g / cm 3 Here, the particle density can be measured by the gas displacement method in accordance with JIS R 1620. As the particle density measuring device, for example, a dry automatic densitometer "Accupic (manufactured by Shimadzu Corporation)" can be used.

[0056] From the viewpoint of ensuring sufficient strength, 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. Here, in this specification, the "particle strength" means the particle strength when the residual rate of the hollow particles is 50% when applied to the hollow particles with a compression molding press. Specifically, it can be measured by the method described in the examples below.

[0057] As described above, the present invention has been described in detail based on its embodiments. However, the present invention is not limited to the above embodiments. The present invention can be variously modified without departing from its gist. For example, in the spray pyrolysis apparatus or spray drying apparatus 300, as shown in FIG. 5, the combustion burner 102 is housed in the combustion tube 103 and is connected offset from the central axis of the heating furnace 101. However, the present invention is not limited to this. For example, it is also possible to adopt the mode of offsetting the central axis described in JP-A-2020-32318 and JP-A-2021-69970. 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 arranged vertically, but the present invention is not limited to the vertical type and may be horizontal or diagonal.

Example

[0058] Hereinafter, embodiments of the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

[0059] 1. Particle density It was measured by the constant volume expansion method using a dry automatic densitometer (Accupic 1340, manufactured by Shimadzu Corporation). That is, after putting a sample into the cell, an inert gas was filled therein to measure the volume of the sample, and the particle density was determined from this volume and the sample mass measured in advance.

[0060] 2. Average particle diameter The average particle diameter of the inorganic oxide particles was measured using a 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 the particle diameter (d 50 ) corresponding to 50% of the cumulative distribution curve was determined. Here, since Microtrac has the characteristic of regarding the maximum diameter of a single particle as the particle diameter of that particle, when there are many particles in an elliptical or snowman shape due to the interference of mist, the average particle diameter tends to be large.

[0061] 3. Particle strength The 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) It was left standing for 1 minute while applying the predetermined pressure. (4) The sample was taken out of the pressure former and dried at 80 °C for 2 hours. (5) Using a dry-type automatic densitometer "Accupic (manufactured by Shimadzu Corporation)", the density of the hollow particles after pressing was measured.

[0062] Then, from the densities of the hollow particles before and after pressing, the residual ratio for each predetermined pressure was calculated by the following formula, and the pressure at 50% residual was read from the graph of the residual ratio and the applied pressure. For the density measurement, the above-described density measuring machine was used, and the true density of the hollow shell was measured after heating in a box-type electric furnace at a temperature above the melting point for 6 hours and then cooling to remove the void part.

[0063] Residual ratio P [%] = (1 - ρ / y) / ρ × (1 / x - 1 / y) × 100

[0064] 〔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.〕

[0065] Example 1 Using the spray pyrolysis apparatus shown in Fig. 5, magnesium oxide hollow particles were produced by the following method. That is, 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 the magnesium oxide hollow particles were recovered using a bag filter. Note that, in the gap between the nozzle body and the protective tube, plate units each having 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 discharge port of the nozzle body while rotating the periphery of the nozzle body. Also, the spray pyrolysis conditions are as follows.

[0066] (Spray pyrolysis conditions) · Raw material solution spray rate: 14 L / h · Nozzle air flow rate: 240 L / min · Cooling air flow rate: 200 L / min (ratio to nozzle air is 83%) · Firing temperature: 1150°C (burner control temperature. Position 5 cm from the nozzle tip)

[0067] Then, the particle density, average particle diameter, and particle strength of the particles recovered every hour from the start of production were measured respectively. The results are shown in Table 1.

[0068] Comparative Example 1 Magnesium oxide hollow particles were produced by the same operation as in Example 1 except that no plate unit was 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 recovered every hour from the start of production were measured respectively. The results are shown in Table 1.

[0069]

Table 1

[0070] Comparative Example 1 is an example where the 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 moreover, the dispersibility of the mist was poor, resulting in uneven firing of the mist. As a result, the obtained hollow particles showed a decrease in particle strength, and variations in particle physical properties were confirmed. In contrast, Example 1 is an example where a plate unit was installed in the gap between the nozzle body and the protective tube, and a cooling gas was circulated there so as to swirl around the nozzle body. However, variations in the amount of heat received by the mist were suppressed, the dispersibility of the mist was improved, and uneven firing of the mist was suppressed. Therefore, it was confirmed that the obtained hollow particles had a suppressed decrease in particle strength and suppressed variations in particle physical properties.

Explanation of Signs

[0071] 1 Nozzle body 2 Discharge port 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 apparatus or spray drying apparatus

Claims

1. A nozzle body having a discharge port for spraying a liquid, and a protective tube covering the outer periphery of the nozzle body are provided, and a gap through which a cooling gas can flow is provided between the nozzle body and the protective tube, and in the gap, there is a plate unit in which 4 to 10 plate-like bodies inclined at an angle of 15 to 45° with respect to the vertical direction are arranged in parallel along the horizontal direction, and a plate unit capable of discharging the cooling gas toward the discharge port while swirling around the nozzle body by flowing the cooling air is provided. A nozzle for spray pyrolysis or spray drying.

2. The nozzle according to Claim 1, wherein the end of the protective tube is installed so as to protrude outside the discharge port of the nozzle body.

3. The nozzle according to Claim 1 or 2, wherein the nozzle is an internal mixing type.

4. The nozzle according to any one of Claims 1 to 3, wherein two or more of the plate units are provided in the gap.

5. The nozzle according to any one of Claims 1 to 4, wherein the cooling gas is air.

6. 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.

7. A nozzle for spraying a raw material solution, and a heating furnace for thermally decomposing or drying the mist of the raw material solution sprayed from the nozzle by the combustion gas of a combustion burner are provided, and the nozzle is the nozzle according to any one of Claims 1 to 6, a spray pyrolysis device or a spray drying device.

8. The spray pyrolysis device or the spray drying device according to Claim 7, further comprising a mechanism for generating a swirling flow of the combustion gas in the heating furnace, 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.

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