JP7554136B2 - Spray Pyrolysis Equipment - Google Patents

Description

The present invention relates to a spray pyrolysis device.

A manufacturing device that utilizes the spray pyrolysis method is used to manufacture hollow particles. The internal combustion spray pyrolysis device used in this manufacturing method has a furnace body consisting of a vertical tube. A combustion tube is connected to one part of the outer periphery of the furnace body, and a combustion burner for generating combustion gas is installed in the combustion tube. A spray device (spray nozzle) for spraying an aqueous solution is installed in the furnace body. The nozzle used here is called a two-fluid, three-fluid, or four-fluid nozzle, and the aqueous solution is sprayed from the tip simultaneously with compressed air to form a mist and fine particles. These fine particles are dried inside the furnace body and become the product. In order to obtain the target specific gravity and particle size, a certain level of processing time and processing temperature are required as processing conditions.

In general, compared to externally heated spray pyrolysis devices, internal combustion spray pyrolysis devices have a larger total gas volume in the furnace body because not only gas caused by mist but also combustion gas generated by the combustion burner flows into the furnace body. This causes a problem that the gas flow rate in the furnace body increases and the target processing time (residence time in the furnace) of the particles cannot be secured. As a result, particles are generated that are not sufficiently melted and have low strength. This can be solved by making the device larger, or by arranging multiple combustion burners as in Patent Documents 1 to 3, generating a swirling flow in the furnace body and allowing the particles to remain in the furnace body for a long time. This also makes it possible to suppress temperature unevenness in the furnace body.

JP 2004-292223 A JP 2007-84355 A JP 2001-137699 A

However, even when a swirling flow is generated inside the furnace body using a combustion burner, depending on the relative positions of the combustion burner and the spray device, heat exchange between the combustion gas and the particles may not be sufficient, resulting in hollow particles with high particle density and low strength.

Therefore, the object of the present invention is to provide a spray pyrolysis device capable of producing hollow particles with low particle density and high strength.

The spray pyrolysis apparatus of the present invention comprises a furnace body consisting of a vertical tube,
At least one combustion tube connected to the outer circumferential surface of the furnace body;
A combustion burner is disposed at an end of the combustion tube opposite to the furnace body and generates a flame toward the furnace body;
A spray nozzle is disposed on the tube axis at the bottom of the furnace body and sprays the aqueous solution upward;
The combustion tube is arranged so that the discharge direction of the combustion gas from the combustion tube does not intersect with the tube axis of the furnace body,
The combustion tube has a throttle at a connection portion with the furnace body,
When viewed from a direction perpendicular to the discharge direction and horizontally, the intersection B between the discharge direction and the tube axis of the furnace body is located with a lower limit of 1/2 times the inner diameter of the furnace body below the tip A of the spray nozzle and an upper limit of 3 times the inner diameter of the furnace body above the tip A of the spray nozzle.

According to this configuration, by misaligning the direction of combustion gas discharge and the tube axis of the furnace body, when the combustion gas discharged from the combustion tube passes through the furnace body, it does not rise straight up, but rather creates a swirling flow and rises. The mist and particles sprayed into the furnace body rise inside the furnace body on this swirling flow, ensuring sufficient reaction time (processing time). In addition, by positioning the combustion tube so that the intersection B between the direction of combustion gas discharge and the tube axis of the furnace body is located within the above range relative to the tip A of the spray nozzle, the mist and particles sprayed from the spray nozzle can be sufficiently dispersed by the swirling flow. As a result, sufficient heat exchange is performed between the combustion gas and the particles, and hollow particles with low particle density and high strength can be produced.

In the spray pyrolysis apparatus of the present invention, the combustion tubes are provided in a plurality of groups at different positions in the vertical direction,
the plurality of combustion tube groups includes a first combustion tube group that is closest to the spray nozzle in a vertical direction,
When viewed from a direction perpendicular to a first discharge direction from the combustion tubes belonging to the first combustion tube group and from a horizontal direction, an intersection B1 between the first discharge direction and a tube axis of the furnace body is located at a lower limit of 1/2 times the inner diameter of the furnace body and an upper limit of 1/2 times the inner diameter of the furnace body with respect to a tip A of the spray nozzle,
The combustion tube groups other than the first combustion tube group may be positioned above the first combustion tube group.

With this configuration, the combustion gas discharged from the multiple combustion tubes can be linked together to generate a sufficient swirling flow within the furnace body. In addition, by providing multiple combustion tubes, it is possible to provide heat equivalent to the heat dissipated by the furnace body, and the temperature and retention time required for the synthesis of hollow particles can be reproducibly and stably ensured.

In addition, in the spray pyrolysis apparatus of the present invention, the inner diameter of the outlet of the throttle may be 1/2 or less of the inner diameter of the furnace body.

By providing a throttle, the flow rate of the combustion gas discharged from the combustion tube can be increased. For example, when the composition is changed and the firing temperature is lowered, the amount of fuel fired by the combustion burner is reduced, and the flow rate of the combustion gas discharged from the combustion tube decreases as the amount of combustion gas decreases, resulting in insufficient swirling flow. Therefore, by providing a throttle, the flow rate of the combustion gas discharged from the combustion tube can be maintained and sufficient swirling flow can be generated, even if the amount of combustion gas decreases when the firing temperature is lowered.

1 is a schematic cross-sectional view showing an example of a spray pyrolysis apparatus according to the present invention. FIG. 1 is a plan view showing an example of a spray pyrolysis apparatus according to the present invention. FIG. 13 is a plan view showing a spray pyrolysis apparatus according to another embodiment; FIG. 13 is a plan view showing a spray pyrolysis apparatus according to another embodiment; Cross-sectional schematic diagram showing the relative positions of the combustion tube and the spray nozzle Cross-sectional schematic diagram showing the relative positions of multiple combustion tubes and spray nozzles FIG. 1 is a plan view showing a schematic configuration of a furnace body and a combustion tube according to an embodiment of the present invention; FIG. 1 is a plan view showing a schematic configuration of a furnace body and a combustion tube according to a comparative example; FIG. 1 is a plan view showing a schematic configuration of a furnace body and a combustion tube according to a comparative example; 1 is a plan view and a side view of a spray pyrolysis device according to another embodiment; 1 is a plan view and a side view of a spray pyrolysis device according to another embodiment; 1 is a plan view and a side view of a spray pyrolysis device according to another embodiment;

Below, one embodiment of the spray pyrolysis apparatus will be described with reference to Figures 1 to 5. Note that in each figure, the dimensional ratios in the drawing do not necessarily match the actual dimensional ratios, and the dimensional ratios between the drawings do not necessarily match either.

Figure 1 is a cross-sectional schematic diagram showing an example of a spray pyrolysis apparatus according to the present invention. Figure 2 is a plan view showing an example of a spray pyrolysis apparatus according to the present invention. The spray pyrolysis apparatus 100 of this embodiment is an internal combustion type, and is equipped with a furnace body 1 consisting of a vertical tube, and at least one combustion tube 2 connected to the outer circumferential surface of the furnace body 1.

The material of the outer walls of the furnace body 1 and the combustion tube 2 is preferably a heat-resistant metal, such as iron, stainless steel, Inconel, Hastelloy, titanium, etc. The furnace body 1 and the combustion tube 2 are preferably substantially cylindrical in shape, since they can be connected by flanges, and they suppress temperature unevenness in the cross-sectional direction within the furnace body 1 and unevenness in heat dissipation in the cross-sectional direction from the furnace body 1 and the combustion tube 2.

The material for the furnace body 1 and the inner wall of the combustion tube 2 may be any material that has the necessary heat resistance, such as ceramics, metal, bricks, and castable refractories.

The furnace body 1 consists of a vertical tube extending in the vertical direction. The combustion tube 2 is preferably connected to the furnace body 1 at an angle of 5 to 90 degrees, with the vertical downward angle being 0 degrees. If this angle is 5 degrees or more, the speed of the swirling flow is sufficiently high, preventing the occurrence of non-uniform turbulence within the furnace body 1 and suppressing the variation in the resulting particle characteristics. If the angle is 90 degrees or less, the exhaust of hot air is promoted and heat build-up can be suppressed.

At the end 2a of the combustion tube 2 opposite the furnace body 1, a combustion burner 3 is disposed, which generates a flame toward the furnace body 1. Either liquid fuel or gaseous fuel can be used as fuel for the combustion burner 3. Specifically, gaseous fuels such as LPG, city gas, and vaporized organic matter, and liquid fuels such as kerosene, light oil, heavy oil, and recycled oil can be used.

The length of the combustion tube 2 is preferably such that the flame generated by the combustion burner 3 does not come into direct contact with the spray mist. However, if the distance between the flame generated by the combustion burner 3 and the spray mist is too long, the thermal efficiency will be insufficient.

At the bottom of the furnace body 1, a spray nozzle 4 is disposed, which sprays the aqueous solution upward. The spray nozzle 4 is disposed on the tube axis 1c of the furnace body 1. The spray nozzle 4 is preferably a 2-4 fluid nozzle, and the aqueous solution may be sprayed using compressed air as carrier air, with the spray nozzle 4 being doubled so that an air shield is formed around the spray mist. In addition, the spray nozzle 4 may be protected with insulation, etc., as necessary, taking heat resistance into consideration.

The combustion tube 2 is connected to the furnace body 1 at the end 2b. A constriction 21 is provided at the connection of the combustion tube 2 with the furnace body 1. The constriction 21 is tapered, and the inner diameter gradually decreases toward the furnace body 1. By providing the constriction 21, the flow rate of the combustion gas discharged from the combustion tube 2 can be increased. The inner diameter d21 (see Figure 2) of the discharge port 21a of the constriction 21 is preferably 1/2 or less of the inner diameter d1 (see Figure 1) of the furnace body 1.

The "throttle" in this specification may be any structure capable of increasing the flow rate near the discharge port of the combustion tube 2, and is not limited to the tapered throttle 21 as in this embodiment. The "throttle" may be, for example, a throttle-like structure that increases the flow rate near the discharge port of the combustion tube 2 by locally reducing the cross-sectional area of the combustion tube 2.

The orifice 21 may be provided on the end 2b side of the combustion tube 2, and the position of the outlet 21a of the orifice 21 may be any of the outlet of the combustion tube 2 (see FIG. 3), the inside of the combustion tube 2 (see FIG. 4), and the inside of the furnace body 1 (see FIG. 2). The material of the orifice 21 may be heat-resistant bricks, fire-resistant bricks, amorphous refractories, ceramics, metals, etc., and is appropriately selected based on the operating temperature, operating environment, etc.

The gradient θ of the orifice 21 is not particularly limited, but taking into consideration the ease of flow of the combustion gas generated by the combustion burner 3 (resistance due to the orifice 21) and the heat storage in the combustion tube 2 (if the gradient θ is large, the resistance of the combustion gas increases and heat is trapped inside the combustion tube 2), a gradient θ between 5 and 75° is preferable.

As shown in the plan view of FIG. 2, the combustion tube 2 is arranged so that the discharge direction 20 of the combustion gas from the combustion tube 2 does not intersect with the tube axis 1c of the furnace body 1. In this embodiment, the discharge direction 20 of the combustion gas is the tube axis direction of the combustion tube 2 and also the axial direction of the throttle 21.

By misaligning the combustion gas discharge direction 20 and the tube axis 1c of the furnace body 1 in this way, when the combustion gas discharged from the combustion tube 2 passes through the furnace body 1, it does not rise straight up, but rather creates a swirling flow and rises. The mist and particles sprayed into the furnace body 1 ride this swirling flow and rise within the furnace body 1, ensuring sufficient reaction time (treatment time).

The discharge direction 20 of the combustion gas is preferably parallel to the tangent direction of the inner circumferential surface of the furnace body 1. This allows the combustion gas to efficiently generate a swirling flow.

FIG. 5 is a schematic diagram for explaining the positional relationship between the combustion tube 2 and the spray nozzle 4. In FIG. 5, the throttle 21 is omitted for convenience of explanation. When viewed in a direction perpendicular to the discharge direction 20 of the combustion gas and in a horizontal direction, specifically, in a direction perpendicular to the paper surface of FIG. 5, the intersection B between the discharge direction 20 and the tube axis 1c of the furnace body 1 is located at a lower limit of 1/2 times the inner diameter d1 of the furnace body 1 and an upper limit of 3 times the inner diameter d1 of the furnace body 1 with respect to the tip A of the spray nozzle 4. If the intersection B is located below the lower limit of 1/2 times the inner diameter d1 of the tip A, the temperature of the nozzle tip (the surrounding area after the mist is discharged) will be lowered, and the drying speed of the mist will be slowed, so that the mist will collide with the furnace wall or the mist will interfere with each other, resulting in a deterioration in the quality of the particles. If the output of the combustion burner 3 is increased in order to raise the temperature of the nozzle tip, the temperature inside the furnace body 1 (furnace temperature) will become too high, resulting in a deterioration in the quality of the particles.
Furthermore, if the intersection point B is located above the tip A by more than three times the inner diameter d1, the mist or particles sprayed from the spray nozzle 4 cannot be sufficiently dispersed by the swirling flow.

A bag filter can be installed on top of the spray pyrolysis device 100 to collect the hollow particles produced. A cyclone can be installed in front of the bag filter to reduce the load on the bag filter and collect coarse particles and foreign matter. In addition, it is preferable to install a heat exchanger, as this allows for the use of residual heat and the reduction of exhaust gas volume. A dust removal and purification device such as a scrubber can be installed after the bag filter as necessary.

By using the spray pyrolysis device 100 of this embodiment, the sprayed mist and particles are carried by the swirling flow and react in the reactor for a long time, so that it is possible to stably and efficiently obtain fine hollow particles. When spray pyrolysis is performed using a raw material liquid that is a raw material for inorganic oxides, if the raw material droplets do not directly contact the flame, a drying reaction will proceed first, and the mist will become hollow particles. If the pyrolysis reaction proceeds next, inorganic oxide hollow particles will be obtained. Here, examples of inorganic oxides include metal oxides, alumina, silica, calcia, magnesia, oxides made of aluminum and silicon, and more specifically, oxides made of alumina, silica, aluminum and silicon, titanium oxide, magnesium oxide, calcium oxide, sodium oxide, potassium oxide, lithium oxide, boron oxide, phosphorus oxide, zirconium oxide, barium oxide, cerium oxide, yttrium oxide, and the like, and also include composite oxides that combine these oxides.

Examples of solvents for dissolving or dispersing the raw materials of the elements constituting these oxides include water and organic solvents, but water is preferred from the viewpoints of environmental impact and production costs, and an acid or alkali may be added as a pH adjuster for the solution. Examples of acids that can be used include hydrochloric acid, nitric acid, sulfuric acid, and organic acids, and examples of alkalis that can be used include sodium hydroxide, calcium hydroxide, and potassium hydroxide.

In the example shown in Figures 1 to 5, there is only one combustion tube 2, but multiple combustion tubes 2 may be provided at the same height, and multiple groups may be provided at different positions in the vertical direction (hereinafter, multiple combustion tubes provided at the same height will be referred to as the 0th combustion tube group). Note that even when only one combustion tube is provided at the same height, it is still referred to as a "group." By linking the combustion gas discharged from the multiple combustion tubes 2 with each other, a sufficient swirling flow can be generated within the furnace body 1. In addition, by providing multiple combustion tubes 2, it is possible to provide heat equivalent to the heat dissipated by the furnace body 1, and the temperature and holding time required for the synthesis of hollow particles can be reproducibly and stably ensured.

Figure 6 shows an example in which two combustion tubes, a first combustion tube 2A and a second combustion tube 2B, are provided. For convenience of explanation, the orifice 21 is omitted in Figure 6. The first combustion tube 2A belonging to the first combustion tube group is disposed closer to the spray nozzle 4 than the second combustion tube 2B belonging to the second combustion tube group, that is, the first combustion tube group is disposed closest to the spray nozzle 4 in the vertical direction. The direction of discharge of the combustion gas from the first combustion tube 2A is the first discharge direction 20A. At this time, when viewed from a direction perpendicular to the first discharge direction 20A and from a horizontal direction, the intersection B1 of the first discharge direction 20A and the tube axis 1c of the furnace body 1 is located at a lower limit 1/2 times lower than the inner diameter d1 of the furnace body 1 and at an upper limit 1/2 times higher than the inner diameter d1 of the furnace body 1 with respect to the tip A of the spray nozzle 4.

The second combustion tube 2B is disposed above the first combustion tube 2A. The direction in which the combustion gas is discharged from the second combustion tube 2B is the second discharge direction 20B. When viewed from a direction perpendicular to the second discharge direction 20B and from a horizontal direction, the intersection B2 between the second discharge direction 20B and the tube axis 1c of the furnace body 1 is located above the tip A of the spray nozzle 4 by an upper limit of three times the inner diameter d1 of the furnace body 1.

When three or more combustion tube groups are provided, the third and subsequent combustion tube groups are positioned above the second combustion tube group. For example, if the direction of combustion gas discharged from the combustion tubes belonging to the third combustion tube group is the third discharge direction, when viewed from a direction perpendicular to the third discharge direction and from a horizontal direction, the intersection point between the third discharge direction and the tube axis 1c of the furnace body 1 is located at an upper limit three times the inner diameter d1 of the furnace body 1 relative to the intersection point B2. The fourth and subsequent combustion tube groups are similar to the third combustion tube group. In other words, if n is an integer of 3 or more, the intersection point B(n) between the (n)th discharge direction and the tube axis 1c of the furnace body 1 is located at an upper limit three times the inner diameter d1 of the furnace body 1 relative to the intersection point B(n-1) between the (n-1)th discharge direction and the tube axis 1c of the furnace body 1.

Specific examples are presented below to explain the present invention in more detail, but the present invention is not limited to these examples.

Examples 1 to 4
A spray pyrolysis apparatus having a furnace body 1 and a combustion tube 2 as shown in Fig. 7 was installed. The inner diameter of the furnace body 1 was 500 mm. The inner diameter of the combustion tube 2 was 500 mm, and the inner diameter near the outlet of the combustion tube 2 was 250 mm due to a tapered structure (throttled portion length 400 mm, gradient 17°). The material of the combustion tube 2 was steel as the base material and monolithic refractory as the lining fireproof material.

Comparative Examples 1 to 4
A spray pyrolysis apparatus having a furnace body 1 and a combustion tube 2 shown in Figures 8 and 9 was installed. The inner diameter of the furnace body 1 was 500 mm. The inner diameter of the combustion tube 2 was 500 mm or 250 mm, and no throttle structure was provided.

Next, 100 L of ion-exchanged water was mixed with 1992 g of tetraethyl orthosilicate, 131 g of aluminum nitrate nonahydrate, 455 g of magnesium nitrate hexahydrate, 516 g of calcium nitrate tetrahydrate, 1666 g of sodium tetraborate decahydrate, and 1 L of concentrated nitric acid, which was then poured into the solution tank and stirred. The raw material solution was sprayed in the form of a mist through the spray nozzle 4 by the liquid delivery pump and passed through the furnace body 1.

At least one combustion tube (first combustion tube) was provided as the combustion tube 2, and up to three combustion tubes (first to third combustion tubes) were provided. The installation positions of each combustion tube 2 relative to the tip of the spray nozzle 4, that is, the position of the intersection (B1 in FIG. 6) between the discharge direction of the first combustion tube and the tube axis 1c of the furnace body 1, the position of the intersection (B2 in FIG. 6) between the discharge direction of the second combustion tube and the tube axis 1c of the furnace body 1, and the position of the intersection (not shown in FIG. 6) between the discharge direction of the third combustion tube and the tube axis 1c of the furnace body 1, when the position of the tip A of the spray nozzle 4 is set to "0", were as shown in Table 1. In Table 1, "+" indicates upward and "-" indicates downward. In Example 4 and Comparative Example 4, a third combustion tube was provided, but the third combustion tube was provided at the same height as the second combustion tube, and the third combustion tube and the second combustion tube belong to the second combustion tube group described above.

The combustion burner 3 was an LPG burner, and the temperature inside the furnace was controlled to 900°C by the amount of LPG burner fired. The raw material solution was sprayed from the spray nozzle 4 at 30 L/h, and the particles were rapidly cooled to 300°C at the outlet of the furnace body 1 with cooling air, and the hollow particles were collected in a bag filter at the downstream stage.

The recovered hollow particles were evaluated as follows. The evaluation results are shown in Table 2.
Measurement of Average Particle Size The average particle size of the inorganic oxide hollow 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 size (d50) corresponding to 50% of the cumulative distribution curve.

Measurement of Particle Density The particle density of the inorganic oxide hollow particles was measured in accordance with JIS R 1620 using a dry automatic density meter "AccuPic (manufactured by Shimadzu Corporation)."

Measurement of Particle Strength Particle strength was measured by the following powder pressing method.
(1) A sample was prepared by mixing inorganic oxide hollow particles and ethanol in a weight ratio of 4:1.
(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 inorganic oxide hollow particles after pressure application was measured using a density measuring device (Accupic, manufactured by Shimadzu Corporation).
The remaining rate for each predetermined pressure was calculated from the density of the inorganic oxide 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 versus applied pressure.
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.)
The true density of the hollow shell was measured by heating at or above the melting point in a box-type electric furnace for 6 hours in order to remove voids, and then cooling and measuring the true density with a density measuring device.

As can be seen from Tables 1 and 2, in Examples 1 to 4, the flow rate of the combustion gas was at an appropriate value due to the throttle structure and the installation of the first combustion tube (combustion burner) at an appropriate position, which resulted in a swirling flow within the furnace body and ensured retention time. As a result, hollow particles with low particle density and high particle strength were produced.

The spray pyrolysis apparatus 100 is not limited to the configuration of the above-mentioned embodiment, nor is it limited to the above-mentioned action and effect. Of course, various modifications can be made to the spray pyrolysis apparatus 100 without departing from the spirit of the present invention. For example, the configurations and methods of the above-mentioned embodiments may be arbitrarily adopted and combined, and further, one or more of the configurations and methods of the various modified examples described below may be arbitrarily selected and adopted in the configurations and methods of the above-mentioned embodiment.

In the above embodiment, the combustion tube 2 is connected to the furnace body 1 at an angle of 90°, and the orifice 21 is tapered such that the axis of the orifice 21 coincides with the axis of the combustion tube 2 as shown in FIG. 10(a), but is not limited thereto. For example, the outlet 21a of the orifice 21 may be a square shape as shown in FIG. 10(b), or may be a polygonal shape such as a hexagon. Also, for example, as shown in FIG. 10(c), the combustion tube 2 may be connected to the furnace body 1 at an angle of less than 90°. Also, for example, as shown in FIG. 10(d), the orifice 21 may be shaped such that the axis of the orifice 21 is offset from the axis of the combustion tube 2.

When multiple combustion tubes are provided, they may be provided at different heights or at the same height. When multiple combustion tubes are provided at the same height, the multiple combustion tubes are provided at intervals in the circumferential direction of the furnace body 1. In the example shown in Figure 11, three combustion tubes 2 are provided at different heights and are provided at equal intervals in the circumferential direction of the furnace body 1.

In the above embodiment, one each of the combustion tube 2, the first combustion tube 2A, and the second combustion tube 2B is provided, but this is not limited to this. For example, multiple combustion tubes 2 may be provided at the same height. Similarly, multiple first combustion tubes 2A may be provided at the same height.

Also, for example, as shown in FIG. 12, multiple combustion tubes 2 may each be connected to the furnace body 1 at an angle of less than 90°.

100: spray pyrolysis apparatus 1: furnace body 1c: tube axis of furnace body 2: combustion tube 2A: first combustion tube 2B: second combustion tube 2a: end of combustion tube 2b: end of combustion tube 3: combustion burner 4: spray nozzle 20: discharge direction of combustion gas 20A: first discharge direction 20B: second discharge direction 21: orifice 21a: orifice outlet A: tip of spray nozzle B: intersection of combustion gas discharge direction and tube axis of furnace body B1: intersection of first discharge direction and tube axis of furnace body B2: intersection of second discharge direction and tube axis of furnace body d1: inner diameter of furnace body d21: inner diameter of orifice outlet

Claims (3)

A furnace body consisting of a vertical tube;
At least one combustion tube connected to the outer circumferential surface of the furnace body;
A combustion burner is disposed at an end of the combustion tube opposite to the furnace body and generates a flame toward the furnace body;
A spray nozzle is disposed on the tube axis at the bottom of the furnace body and sprays the aqueous solution upward;
The combustion tube is arranged so that the discharge direction of the combustion gas from the combustion tube does not intersect with the tube axis of the furnace body,
The combustion tube has a throttle at a connection portion with the furnace body,
The combustion tubes are provided in a plurality of groups at different positions in the vertical direction,
the plurality of combustion tube groups includes a first combustion tube group that is closest to the spray nozzle in a vertical direction,
When viewed from a direction perpendicular to a first discharge direction from the combustion tubes belonging to the first combustion tube group and from a horizontal direction, an intersection B1 between the first discharge direction and a tube axis of the furnace body is located at a lower limit of 1/2 times the inner diameter of the furnace body and an upper limit of 1/2 times the inner diameter of the furnace body with respect to a tip A of the spray nozzle,
the second combustion tube group is disposed above the first combustion tube group,
When viewed from a direction perpendicular to a second discharge direction from the combustion tubes belonging to the second combustion tube group and from a horizontal direction, an intersection B2 between the second discharge direction and a tube axis of the furnace body is located at an upper limit three times the inner diameter of the furnace body 1 with respect to a tip A of the spray nozzle,
The third and subsequent combustion tube groups are disposed above the second combustion tube group ,
A spray pyrolysis apparatus in which, when viewed from a direction perpendicular to the (n)th discharge direction from a combustion tube belonging to the (n)th combustion tube group and a horizontal direction, an intersection B(n) of the (n)th discharge direction and a tube axis of the furnace body is located up to three times the inner diameter of the furnace body relative to an intersection B(n-1) of the (n-1)th discharge direction and a tube axis of the furnace body, where n is an integer of 3 or more . 2. The spray pyrolysis apparatus according to claim 1 , wherein an inner diameter of the outlet of the throttle is equal to or smaller than half an inner diameter of the furnace body. 3. The spray pyrolysis apparatus according to claim 1, wherein the gradient θ of the throttle is 5 to 75°.