JP3201818B2 - Spray pyrolysis method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a spray pyrolysis method and apparatus.

[0002]

2. Description of the Related Art Finer properties of fine ceramics can be obtained only by controlling the purity, chemical composition and fine structure of raw materials. Manufacturing processes, especially the synthesis of raw materials, are often key to product development. It is required that the raw material powders have high purity, high composition uniformity in the case of compounds and mixtures, and fine and high reaction activity. Various synthesis methods have been devised to obtain ceramic powders having such properties.However, as a synthesis method to satisfy the requirements of fineness, high purity, and high composition uniformity, synthesis via the gas phase or liquid phase is required. There is a law. Unlike the case where a conventional solid phase is used, it is considered that each constituent element is mixed in the atomic order in the synthesis method via the liquid phase. The liquid phase method is a method in which a metal element existing in a solvent is precipitated as a hydroxide, a nitrate, a sulfate, a carbonate, or the like, and is thermally decomposed to synthesize an oxide fine powder. Many methods have been developed for the liquid phase method, depending on the method of depositing metal salts and the method of thermal decomposition, and the spray pyrolysis method is one of the methods.

[0003] In the spray pyrolysis method, a metal salt solution is sprayed as fine droplets in an atmosphere maintained at a temperature higher than the temperature at which thermal decomposition occurs, and evaporation of a solvent, deposition of a metal salt, and In this method, thermal decomposition is performed to synthesize oxide (non-oxide) fine powder. The powder obtained by this method has advantages of composition uniformity on an atomic scale and uniform dispersibility of a trace component element, and fine particles having good dispersibility can be obtained.
And even if there is a non-uniformity of the composition due to drying and thermal decomposition, it is physically limited within the divided fine particles, so that there is little composition separation due to rearrangement of components. Also,
The proportion of components contained in each sprayed solution is very close to that of the conditioned solution, so that the dispersion of the components can be tightly controlled.

As described above, in the spray pyrolysis method, a metal salt solution as a raw material of fine ceramics or oxide superconducting material is sprayed in a mist state at a high temperature of, for example, 500 to 1300 ° C. This is a method for producing fine powder by performing thermal decomposition / reaction or synthesis in a short time.

[0005]

However, such a conventional spray pyrolysis method has only a very small test scale, has a short operation time, and has a small continuous operation time, even in a laboratory stage. There was no one that considered drivability. Further, in the product recovery, a method has been adopted in which product fine particles deposited in a lower portion of the reaction chamber are recovered after the operation is completed, each time the operation is completed. Accordingly, an object of the present invention is to solve the conventional problems as described above and to provide a spray pyrolysis method and apparatus capable of continuously collecting products.

[0006]

According to the present invention, an undiluted solution is sprayed into the reaction chamber from the upper part of the vertical reaction chamber, and the sprayed undiluted solution is solidified in the reaction chamber and then thermally decomposed. In the spray pyrolysis method of taking out the obtained powder from the lower part of the reaction chamber, the lower part of the reaction chamber is inclined at an angle of 40 to
80 ° inverted truncated cone with a powder outlet at the bottom
And the inner partition wall for the half-duplex structure consisting of an outer partition wall surrounding it, the cooling gas A between the partition walls of the semi double structure
By introducing it towards the outer surface of the inner bulkhead ,
While cooling the outer surface of the partition wall to indirectly cool the solid-gas mixture after spray pyrolysis , the cooling gas is applied to the inner partition wall.
After colliding with the outer surface and reducing the flow velocity,
And then further cooling the solid-gas mixture with the solid-gas mixture .

Further, according to the present invention, in a spray pyrolysis apparatus including a vertical reaction chamber and a sprayer disposed above the reaction chamber, the lower part of the reaction chamber has an inclination angle of 40 to 80 °. <br/> In addition to forming an inverted truncated cone , a powder outlet at the bottom
A spray pyrolysis apparatus is provided, which has a half-duplex structure including an inner partition wall having the inner partition wall and an outer partition wall surrounding the inner partition wall, and a cooling gas inlet is provided in the outer partition wall below the reaction chamber. In the spray pyrolysis method of the present invention, the type of cooling gas varies depending on the stock solution to be sprayed, but it is generally preferable to use air, N ₂ gas or Ar gas,
The temperature of the cooling gas is preferably from 40 to 120C. Further, it is preferable to cool the gas temperature accompanying the powder to 70 to 260 ° C. with a cooling gas in view of the heat resistance of the solid-gas separation device such as a cyclone and a bag filter on the downstream side.

On the other hand, in the spray pyrolysis apparatus, it is preferable to provide a heating furnace outside the reaction chamber so as to surround the reaction chamber in order to keep the atmosphere in the reaction chamber higher than the pyrolysis temperature. When the undiluted solution and gas come into contact with each other and become hot due to reaction heat such as combustion, a heating furnace is not particularly necessary .

[0009]

In order to continuously recover the product fine particles without deteriorating the quality of the product fine particles and without affecting the reaction inside the reaction chamber, the present inventor has made various attempts to lower the temperature of the obtained product fine particles. As a result of the investigation, it was found that if the cooling gas was directly injected into the lower part of the vertical reaction chamber, the gas flow inside the reaction chamber was disturbed, which was not preferable for spray pyrolysis. Therefore, in the lower part of the vertical reaction chamber,
Stop the injection of the cooling gas flow in such a way as to make direct contact with the carrier gas that carries the product particles, and adopt a configuration in which the lower part of the reaction chamber has a semi-semi-double structure.
The cooling gas was injected in such a way as to make indirect contact.

That is, in the semi-double structure at the lower part of the reaction chamber, the inner structure forms an inner partition having an inverted truncated cone shape and a powder outlet at the bottom, and the outer structure surrounds the inner partition. Having a structure. Since the cooling gas is injected toward the outer surface of the inner partition wall, the outer surface is cooled to perform heat exchange with the carrier gas accompanied by the powder in the lower portion of the reaction chamber. By colliding with the outer surface of the inner partition, kinetic energy is lost and the flow velocity is reduced. Next, the cooling gas further cools the carrier gas by mixing with the carrier gas from the powder outlet at the bottom of the inner partition wall, mixes the product fine particles that have fallen with the carrier gas, stirs, and cools. I do.

As a result, fine particles of the product at an appropriate temperature are entrained in the mixing chamber of the cooling gas and the carrier gas at the lower part of the reaction chamber, which communicates with a solid / gas separation device such as a cyclone and a bag filter arranged on the downstream side. You can get gas. Further, the side surface of the inner partition wall can prevent the influence of heat radiation from the reaction chamber to the mixing chamber. Since the side surface of the inner partition wall is cooled from the outside by the injected gas, it is not necessary to use a high heat-resistant material for the side surface, and a normal metal material such as Inconel, Hastelloy, or stainless steel can be used. The inclination angle α of the inner partition wall 6 is
In order to make the product fine particles flow easily, the angle is formed at 40 to 80 °, preferably 45 to 75 °.

[0012]

Next, embodiments of the present invention will be described in more detail with reference to the drawings, but the present invention is not limited to these embodiments. (Embodiment 1) FIG. 1 is a schematic sectional view showing an example of the spray pyrolysis apparatus of the present invention. In FIG. 1, a spray pyrolysis apparatus 1 includes a vertical reaction chamber 2, a furnace 3 surrounding the outside of the vertical reaction chamber 2, and a two-fluid nozzle 4 serving as a sprayer disposed above the vertical reaction chamber 2. It has. The lower part 5 of the vertical reaction chamber 2 has an inverted frustoconical inner partition wall (hopper) 6 having a powder outlet 8 at the bottom, an inverted frustoconical outer partition wall 7, and a continuous downward from the outer partition wall 7. And a semi-double structure. Further, a cooling gas injection port 10 is provided in the outer partition 7,
Each of the mixing chambers 9 is provided with a suction port 11 that communicates with a solid-gas separation device such as a downstream bag filter (not shown).

The vertical reaction chamber 2 has a size of 300 mmφ × 10
A 00 mm (height) quartz tube 12 was employed. The furnace 3 is composed of an electric heater capable of adjusting the temperature and a refractory, and a space 15 is provided between the furnace 3 and the quartz tube 12. The upper and lower parts of the furnace 3 are each held by a refractory material 14,
A heat retaining member 13 is provided outside the furnace 3 to prevent heat loss. The inclination angle α of the inner partition wall (hopper) 6 was set to 60 °. The inclination angle β of the outer partition 7 having the shape of an inverted truncated cone was set to be about 10 ° larger than the inclination angle α of the inner partition 6.

The raw material solution is a solution prepared by adding water and ethanol (50:50 vol%) so that the composition of mullite of aluminum nitrate and ethyl silicate (3Al ₂ O ₃ .2SiO ₂ ) becomes 0.2 mol / l. The operation was performed under the conditions shown in Table 1 using air as the atomizing gas, the carrier gas, and the cooling gas of the two-fluid nozzle, and the results shown in Table 1 were obtained.

[0015]

[Table 1]

From the results shown in Table 1, air was injected from the cooling gas inlet 10 under the conditions shown in Table 1, and the temperatures of the carrier gas and the product fine particles after the reaction were reduced, and the condition of the lower portion 5 of the reaction chamber were examined. Injecting a cooling gas at a temperature below 40 ° C.
When the temperature is too low locally, dew condensation occurs on the wall surface, and product particles adhere to the portion. It was also found that the metal member in the lower part 5 of the reaction chamber was easily corroded. 120 ° C
Injecting a cooling gas having a temperature exceeding the above, the cooling effect is small, and a large amount of gas needs to be introduced. Therefore, it was found that the optimum temperature of the cooling gas was 40 to 120 ° C.
By using the cooling gas in such a temperature range, the cooling effect in the semi-duplex structure in the lower part 5 of the reaction chamber can be maintained, so that the hopper 6, the outer partition 7, the mixing chamber 9, As the members of the cooling gas injection port 10 and the suction port 11, ordinary metals such as Inconel, Hastelloy, and stainless steel were used, but there was no particular problem.

(Example 2) Using the same apparatus and the same raw material solution as in Example 1, the structure of the mixing chamber below the reaction chamber was changed as shown in FIGS. The influence of the turbulence of the gas in the room and the temperature on the lower part of the mixing room was investigated. In FIG. 2, a mixing chamber 22 was formed by extrapolating an outer partition 21 outside the inner partition (hopper) 6 into the reaction chamber 2. FIG. 3 shows a situation in which the lower part of the reaction chamber 2 of the spray pyrolysis apparatus 1 is used as it is as the mixing chamber 31, and the cooling gas inlet 10 is provided at the center of the lowermost part thereof so as to face the suction port 11. Table 2 shows the conditions and results.

[0018]

[Table 2]

In evaluating the results shown in Table 2, if there was turbulence in the gas in the reaction chamber, the powder was unevenly deposited in the reaction chamber. The average particle size of the product fine particles was 2 μm. From the results in Table 2, it was found that when the inclination angle of the inner partition wall (hopper) 6 was 40 to 80 °, the gas in the reaction chamber was not turbulent and the powder was hardly deposited. Further, as shown in FIG. 3, it was also confirmed that the gas in the reaction chamber was largely disturbed in the structure without the inner partition.

[0020]

As described above, according to the spray pyrolysis method and apparatus of the present invention, the carrier gas and the product after the pyrolysis can be produced without causing the turbulence of the gas in the reaction chamber even by introducing the cooling gas. The fine particles can be cooled. Further, there is almost no accumulation of powder, and continuous operation for continuously extracting product fine particles becomes possible. Further, since the hopper at the lower part of the reaction chamber is cooled by the cooling gas, there is no need to use a material having high heat resistance, and a normal metal material can be used.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one example of a spray pyrolysis apparatus of the present invention.

FIG. 2 is an explanatory view showing an example of a structure of a lower part of a reaction chamber.

FIG. 3 is an explanatory view showing another example of the structure of the lower part of the reaction chamber.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Spray pyrolysis apparatus 2 Reaction chamber 3 Furnace 4 Two-fluid nozzle 5 Lower part of reaction chamber 6 Inner partition wall (hopper) 7 Outer partition wall 8 Powder outlet 9 Mixing chamber 10 Cooling gas inlet 11 Suction port 12 Quartz tube 13 Heat insulation Member 14 Refractory 15 Space 21 Outer partition wall 22 Mixing chamber 31 Mixing chamber

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Takashi Ito 3847 Ikebe-cho, Midori-ku, Yokohama-shi, Kanagawa Prefecture Inside Okawara Kakoki Co., Ltd. 94533 (JP, U) Hira 2-52300 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B01J 19/00 B01J 19/00 301 B01J 2/04

Claims (6)

(57) [Claims] 1. A spray pyrolysis method in which a stock solution is sprayed into a reaction chamber from the upper part of a vertical reaction chamber, and the sprayed stock solution is solidified in the reaction chamber and then pyrolyzed, and the obtained powder is taken out from a lower part of the reaction chamber. in the tilt angle 40 and the reaction chamber lower portion
80 ° inverted truncated cone with a powder outlet at the bottom
And the inner partition wall for the half-duplex structure consisting of an outer partition wall surrounding it, the cooling gas A between the partition walls of the semi double structure
By introducing it towards the outer surface of the inner bulkhead ,
While cooling the outer surface of the partition wall to indirectly cool the solid-gas mixture after spray pyrolysis , the cooling gas is applied to the inner partition wall.
After colliding with the outer surface and reducing the flow velocity,
And further cooling the solid-gas mixture with the solid-gas mixture . 2. The cooling gas is air, N ₂ gas or Ar.
The spray pyrolysis method according to claim 1, which is a gas. 3. The spray pyrolysis method according to claim 1, wherein the temperature of the cooling gas is 40 to 120 ° C. 4. The spray pyrolysis method according to claim 1, wherein the temperature of the gas accompanying the powder is cooled to 70 to 260 ° C. by the cooling gas. 5. A spray pyrolysis apparatus comprising a vertical reaction chamber and a sprayer disposed above the reaction chamber, wherein the lower part of the reaction chamber is formed into an inverted truncated cone having an inclination angle of 40 to 80 °. And an inner bulkhead having a powder outlet at the bottom
A spray pyrolysis apparatus characterized in that it has a half-duplex structure composed of outer partition walls surrounding the reactor, and a cooling gas inlet is provided in the outer partition wall below the reaction chamber. Outside of 6. The reaction chamber, spray pyrolysis apparatus according to claim 5, wherein the heating furnace is provided surrounding the reaction chamber.