JP3677518B2 - Fine powder heating method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for heat-treating a fine powder, particularly a fine powder having a particle size of 75 μm or less, in a large amount and uniformly.
[0002]
[Prior art]
A rotary kiln is generally used for heating a powder having a relatively large size because a large amount of continuous processing is possible. However, if this is used for fine powders with a particle size of 75 μm or less, the particles will not move smoothly, so they cannot be heated uniformly, and dust is generated, making it difficult to handle industrially. There are many problems to be solved.
[0003]
Therefore, a fluidized furnace using mainly sand as a dispersion medium is used for heating such fine powder. For example, as a method of manufacturing fine hollow glass spheres by heat treatment of volcanic glassy sediment fine powder, pulsating air flow is sent from below the dispersion part filled with solid glass spheres and silica sand, and dispersed There is known a method in which fine powder supplied to the upper part is conveyed and raised at a speed of 10 to 100 cm / second and foamed by a foaming part heated to 900 to 1100 ° C. (Japanese Patent Laid-Open No. 8-73232).
[0004]
FIG. 4 is a cross-sectional view for explaining an apparatus used in the conventional method, and FIG. 5 is a cross-sectional view showing the structure of the dispersion layer. This apparatus incorporates a dispersion layer C formed by filling a glass solid sphere 9 and silica sand 8 on a perforated plate 7, and a dispersion chamber A having a raw material supply port 2 opened above the dispersion layer C. And an upright cylindrical heating furnace B connected to the upper part thereof, and the heating furnace B has a focusing tube structure 3 in which 3 to 20 narrow tubes are converged.
[0005]
According to the conventional method, the fine powder D is conveyed by the screw feeder from the hopper 1, supplied from the raw material supply port 2 to the dispersion chamber A, and pulsating airflow sent from the pulsating airflow inlet 5 below the dispersion layer C. It is dispersed in the dispersion layer C, heated from the surroundings by the focusing tube 3 disposed in the heating furnace B above the dispersion layer C, foamed, and taken out from the powder discharge port 4. At this time, if necessary, air can be introduced from the air intake 6 provided on the side wall or the upper portion of the heating furnace B to facilitate recovery.
However, the method using such an apparatus is not suitable as an industrial method that requires a large amount of processing because the amount of processing is limited and scale-up is impossible.
[0006]
[Problems to be solved by the invention]
In the present invention, when heat-treating a fine powder, particularly a fine powder having a particle size of 75 μm or less, it can be processed in a large amount, and the temperature history of individual particles can be made uniform, thereby obtaining a product of equal quality. In order to provide an improved method and apparatus.
[0007]
[Means for Solving the Problems]
As a result of various researches on a method and an apparatus for heat-treating a fine powder uniformly and in large quantities, the present inventors have found that in the method using the apparatus shown in FIG. 1 and FIG. It is found that by arranging a focusing tube and arranging a combustion burner so that the individual fine powder rising in the focusing tube is heated uniformly, uniform heating is performed and mass processing becomes possible. Based on this finding, the present invention has been made.
[0008]
That is, the present invention supplies fine powder to be processed on the granular dispersion medium filling zone, and is carried by a pulsating air flow sent from below the filling zone, and rises at a speed of 10 to 100 cm / sec. In the heat treatment method, the fine powder is raised by the divided paths, and the divided paths are converged to form at least three units, and each unit is ejected from the side. A fine powder heating method characterized by heating uniformly by a heated gas flow, a dispersion chamber A having a fine particle supply port 2 having a built-in granular dispersion medium packed bed and opened above the packed bed, and dispersion In a fine powder heating apparatus composed of an upright cylindrical heating furnace B hermetically connected to the upper part of the chamber A and heating means of the heating furnace B, a plurality of thin tubes are focused in the upright cylindrical heating furnace B. Upright focusing tube 3 A fine powder heating apparatus characterized in that at least three are arranged in parallel and a plurality of injection-type combustion burners 11 are attached at appropriate positions on the wall surface of the heating furnace in an eccentric radial manner at substantially equal intervals to serve as heating means. Is to provide.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Next, the method and the device of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic longitudinal sectional view showing an example of the apparatus of the present invention, FIG. 2 is a transverse sectional view along the line XX, and the raw material fine powder D is transferred from the hopper 1 to the upper part of the dispersion chamber A by a screw feeder. Is supplied to the dispersion chamber A through the supply port 2 provided in the upper part, and ascends from the dispersion chamber A through the plurality of upright focusing tubes 3,. Taken from.
[0010]
The dispersion chamber A has the same structure as that of the conventional apparatus, and the dispersion layer C is formed by filling the upper part of the perforated plate 7 with granular dispersion media 8, 9 such as silica sand or solid glass spheres. Below the layer C, a pulsating airflow inlet 5 is provided.
[0011]
The heating furnace B is composed of an upright cylindrical main body B ′ and a conical top portion B ″. The uppermost portion of the conical top portion B ″ is opened and an exhaust port 10 is provided.
A plurality of injection-type combustion burners 11,... Are attached to the middle wall surface of the upright cylindrical main body B ′ of the heating furnace in an eccentric radial manner at substantially equal intervals.
Here, the eccentric radial shape means that the injection direction of each combustion burner 11,... Is made to coincide with the tangent line of the concentric circle a having a diameter smaller than the diameter of the circle of the cross section of the heating furnace body, as shown by the one-dot chain line in FIG. The state that is attached.
[0012]
As described above, by arranging the combustion burners 11,..., The fine powder D rising in the upright focusing tubes 3, which are arranged in parallel in the heating furnace B, is heated uniformly. The rising speed of the fine powder D in each of the upright focusing tubes 3,... Is selected within a range of 10 to 100 cm / second. Moreover, although the heating temperature of this fine powder D is influenced by the objective of a process, it is 500-1300 degreeC normally, Preferably it is the range of 900-1100 degreeC.
[0013]
As shown in FIG. 3, each of the upright focusing tubes 3,... Is composed of a plurality of focusing tubes 12,... It is built up and built in. Each of the tube bodies 12,... Is composed of an elongated tube having an inner diameter of 10 to 20 mm, and 10 to 30 tubes are bundled.
The fine powder D heat-treated in the heating furnace B having such a structure is collected from the upper outlet of each focusing body via the discharge pipes 13,.
[0014]
【Example】
EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited by these.
[0015]
Example 1
In this example, volcanic glassy deposits (produced in Iizaka-cho, Fukushima City, commonly known as Fukushima Shirato) were crushed as the raw material powder, and 10-30 μm powder classified at 10 μm and 30 μm was used. The proportion of particles exceeding 30 μm contained in this raw material powder was 15% by weight or less, and the proportion of particles having a particle size of less than 10 μm was 15% by weight or less.
[0016]
The raw material powder was supplied to the heating apparatus shown in FIG. This heating device has an exhaust port 10 at the center upper part of the heating furnace, and 18 focusing tubes 3,... In a cylindrical vertical furnace installed so that the flow of hot air is rotated by gas burners 11. Are installed separately.
[0017]
First, the raw material powder is put in the hopper 1, and the dispersion layer C having a cross-sectional area of 475 cm ² filled with 475 g of silica sand having a particle size of about 200 μm is placed on the perforated plate 7 at a rate of 10 kg per hour by a screw feeder. Then, pulsating air with a pulsation rate of 30 times / second was sent from the lower part of the dispersion layer at a rate of 0.855 m ³ per minute. The particles dispersed in this way were raised through 18 vertically arranged focusing tubes. In addition, each focusing tube was configured by bundling 19 elongated tubes having an inner diameter of 13.3 mm. The maximum temperature inside the focusing tube was maintained at 1000 ° C. by adjusting the gas burners 11.
[0018]
In order to suppress heating air and cooling of the foam and condensation of moisture in the foam recovery part, air was introduced from the air inlet 6 at the top of the heating furnace. The amount of introduction was adjusted by adjusting the flow rate of the suction blower directly connected to the foam recovery unit.
The produced foam was collected and its density and strength were measured. As a result, a volcanic glassy foam having a bulk density of 0.50 g / cm ³ , a particle density of 0.85 g / cm ³ , a coarse particle content of 1.5% by weight and a strength of 90.6% by weight was obtained. In addition, this intensity | strength represents the content rate of the nondestructive particle | grains after hold | maintaining for 1 minute under the hydrostatic pressure of 8 MPa.
[0019]
【The invention's effect】
According to the present invention, a fine powder of 75 μm or less can be heat-treated in a large amount and uniformly.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal sectional view of an example of an apparatus of the present invention.
FIG. 2 is a cross-sectional view taken along line XX in FIG.
FIG. 3 is a cross-sectional view of the focusing tube of the present invention.
FIG. 4 is a schematic longitudinal sectional view of a conventional example.
FIG. 5 is a cross-sectional view of a dispersion layer in a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Hopper 2 Raw material supply port 3 Upright focusing tube 4 Powder discharge port 5 Pulsating air flow introduction port 6 Air intake port 7 Perforated plate 8,9 Granular dispersion medium 10 Exhaust port 11 Combustion burner 12 Tube 13 Discharge tube A Dispersion chamber B Upright cylindrical heating furnace C Dispersion layer D Fine powder

Claims (2)

The fine powder to be processed is supplied onto the granular dispersion medium filling zone, and is carried by the pulsating air flow sent from the lower side of the filling zone, and is heated at a rate of 10 to 100 cm / sec. In the method, the fine powder is raised by the divided paths, and these divided paths are converged to form at least three units, and each unit is made uniform by the heated gas flow injected from the side. A fine powder heating method, characterized by heating. A dispersion chamber having a granular dispersion medium packed bed and a fine powder supply port opened above the packed bed; an upright cylindrical heating furnace hermetically connected to the upper part of the dispersion chamber; and heating means of the heating furnace In the fine powder heating apparatus constituted by the above, at least three upright focusing tubes in which a plurality of thin tubes are converged in the upright cylindrical heating furnace are arranged in parallel, and a plurality of at a suitable location on the heating furnace wall surface. A fine powder heating apparatus characterized in that a jetting combustion burner is attached in an eccentric radial manner at substantially equal intervals to serve as a heating means.

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