JPH1061907A - Rotary kiln - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rotary kiln for raising the temperature of a powder and grain in which the temperature raising rate is increased by increasing the thermal conductivity for a powder and grain layer. SOLUTION: A flow controller 5 is disposed at the powder and grain inlet end of a cylindrical rotary kiln made of a refractory material 1. A powder and grain feeder 2 comprising a screw feeder is passed movably through the central part in order to feed in a powder and grain 4. The powder and grain 4 is transferred while turning in the kiln and heated with hot air 3 to raise the temperature thereof. The flow controller 5 comprises an outer piece and an inner piece and since a hot air path formed between both pieces is inclined and enlarged toward the inside, temperature raising rate of the powder and grain 4 can be increased by decreasing the current velocity of hot air 3 at the central part of rotation and increasing the current velocity in the vicinity of wall face or on the surface of powder and grain layer thereby increasing the thermal conductivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary kiln having improved heat-raising characteristics of a material to be heated and heated.

[0002]

2. Description of the Related Art FIG. 7 is a sectional view of a conventional rotary kiln. In the figure, the structure of the rotary kiln is a cylindrical container structure made of a refractory material 1, and the powder 4 is supplied by a powder supply device 2 such as a screw feeder, and the supplied powder 4 is transported. The hot air 3 is sent while rotating, and heated and heated by the hot air.

[0003]

The conventional rotary kiln is a cylindrical container made of the refractory material 1 as described above.
It has a very simple structure, the shape of the powder 4
Although it is characterized by being less susceptible to type restrictions, it has a drawback that the gas convection heat transfer coefficient is poor, and therefore the rate of temperature rise of the powder 4 is slow. As a countermeasure, a method of increasing the length of the rotary kiln is used, so that the size of the apparatus is increased and the cost is increased.

[0004] An object of the present invention is to provide a rotary kiln capable of increasing the rate of temperature rise of a granular material layer by improving the heat transfer coefficient of gas convection in order to solve the above problems.

[0005]

Therefore, according to the present invention, a hot air is sent from one gas inlet and a processed material such as a granular material is charged. The processed material is transferred to the other while rotating the same while rotating. In a rotary kiln of an external hot air heating type that warms or dries, a gas flow control device having a hot air passage at the gas inlet is provided, and the hot air passage has an inner wall surface or a surface of a granular material layer which is higher than the hot air gas flow velocity at the center of rotation. A rotary kiln provided to increase a gas flow rate in the vicinity.

In the present invention, the flow control device is attached to the gas inlet as described above, and the flow control device is provided with a hot air passage, and the hot air passage increases the hot air near the inner wall surface of the rotary kiln or near the surface of the granular material layer. As compared with the conventional gas flow velocity distribution, the flow velocity at the center of rotation is reduced, and the gas flow velocity near the wall surface or the gas flow velocity near the surface of the granular material layer is increased accordingly. As a result, the convective heat transfer coefficient of the portion increases, and the rate of temperature rise of the granular material layer can be increased.

[0007]

Embodiments of the present invention will be specifically described below with reference to the drawings. 1 is a cross-sectional view of a rotary kiln according to a first embodiment of the present invention, FIG. 2 is a plan view of a flow control device used in the rotary kiln in FIG. 1, and FIG. 3 is a cross-sectional view along AA in FIG. In these figures, reference numerals 1 to 4 are the same as those in the conventional example, and thus the same reference numerals are used and the description will be made with reference to the same reference numerals.
The feature of the present invention resides in that a flow control device indicated by reference numeral 5 is provided. Hereinafter, this characteristic portion will be described in detail.

In these figures, the structure of the rotary kiln is a cylindrical container structure made of the same refractory material 1 as in the conventional example, and the granular material 4 is supplied from a granular material supply device 2 such as a screw feeder. 4 is heated and heated by the hot air 3 while being transported while rotating.

A flow control device 5 is provided at the gas inlet end of the cylindrical container, and the flow control device 5 has a central portion through which the powder supply device 2 is movably inserted, and a hot air passage around the periphery. , And a structure for guiding the hot air 3 to the inside. The hot air 3 reduces the gas flow velocity at the center of rotation by a hot air passage as described later,
Accordingly, the gas flow velocity around the wall surface or the gas flow velocity near the layer of the granular material 4 is increased.

FIG. 2 shows a flow control device 5 according to the first embodiment of the present invention. The flow control device 5 combines a conical inner piece 8 in an outer piece 7 and passes a hot air passage through a circumferential gap therebetween. The hot air passage 6 is provided to be inclined so as to expand inward. By such an inclination, the gas flow of the hot air 3 flowing in can be forcibly deflected near the wall surface. In the first embodiment, the hot air and the particles of the granular material 4 are of the co-current type, but may be applied to the counter-current type.

FIG. 3 shows a flow control device 15 of a rotary kiln according to a second embodiment of the present invention, wherein (a) is a plan view and (b) is a side view thereof. The second embodiment is the same as the first embodiment except for the flow control device 15, and therefore only this part will be described. In the figure, a flow control device 15 is provided with a plurality of swirlers 9 between an outer piece 17 and an inner piece 18, a hot air passage 16 is provided between the swirlers 9, and at the same time a hot air gas is deflected near a wall surface, A swirling flow is generated in the circumferential direction.

FIGS. 4A and 4B show a rotary kiln flow control device 25 according to a third embodiment of the present invention, wherein FIG. 4A is a plan view, and FIG. The third embodiment is also the same as the first embodiment except for the flow control device 25, and thus only this portion will be described. In the figure, a flow control device 25 is formed by providing a plurality of holes as hot air passages 26 around a disk-shaped flow control device main body so as to be inclined so as to expand inward. In the third embodiment, the holes are provided in a row in the circumferential direction. However, a plurality of holes may be provided in the radial direction. With the flow control device having such a structure, the gas flow can be deflected near the wall surface.

FIG. 5 is a diagram showing a heat transfer pattern in the rotary kiln in the case of relatively low-temperature hot air (hot air of about 500 ° C.). In the figure, the heat transfer form related to the temperature rise of the powder
One is transmitted directly from the gas to the layer of the granular material 4 by convective heat transfer as shown in (a), and the other is transmitted to the wall once by convective heat transfer from the gas as shown in (b), Then, it can be broadly divided into those which are radiated as shown in (b) -1 or those which are transmitted to the layer of the granular material 4 by contact heat transfer as shown in (b) -2.

Therefore, by providing the rotary kiln flow control devices 5, 15 or 25 as described above, the hot air from the hot air passages 6, 16 or 26 is deflected near the wall surface or near the surface of the granular material layer. In the figure, by increasing the convective heat transfer (a) and (b), the rate of temperature rise of the granular material can be improved.

According to the rotary kilns of the first to third embodiments described above, the width of the hot air passage 6 in the first embodiment, and the number and inclination of the swirlers 9 in the second embodiment, or In the third embodiment, it is possible to arbitrarily set the flow velocity in the vicinity of the wall surface by appropriately selecting the hole diameter, and realize the gas flow velocity distribution A shown in FIG. In particular, in the second embodiment, since a swirling flow can be generated in the circumferential direction, the gas convection heat transfer coefficient can be significantly improved, and the rate of temperature rise of the granular material layer can be increased. .

[0016]

As described above in detail, the present invention provides a gas flow control device having a hot air passage at a gas inlet of a rotary kiln, and a gas convection heat transfer coefficient on an inner wall surface or a surface of a granular material layer. By appropriately selecting the width of the hot air passage, the flow velocity near the wall surface can be set arbitrarily, and the gas flow velocity distribution on the wall surface can be increased more than the center of rotation. it can. Thereby, the convective heat transfer coefficient to the granular material layer is increased, and the rate of temperature rise of the granular material layer can be increased.

Also, a plurality of swirlers are provided in the flow control device,
If the configuration is such that a hot air passage is provided between the blades, the same gas flow velocity distribution as described above can be obtained by appropriately selecting the number and inclination of the swirling blades. Further, since a swirling flow can be generated in the circumferential direction, the gas convection heat transfer coefficient can be greatly improved. The rate of temperature rise of the granular material layer can be further increased.

[Brief description of the drawings]

FIG. 1 is a sectional view of a rotary kiln according to a first embodiment of the present invention.

FIGS. 2A and 2B show a flow control device used in the rotary kiln according to the first embodiment of the present invention, wherein FIG. 2A is a plan view thereof, and FIG. 2B is a sectional view taken along line AA of FIG.

3A and 3B show a flow control device used in a rotary kiln according to a second embodiment of the present invention, wherein FIG. 3A is a plan view and FIG. 3B is a side view.

4A and 4B show a flow control device used in a rotary kiln according to a third embodiment of the present invention, wherein FIG. 4A is a plan view and FIG. 4B is a sectional view taken along line BB of FIG.

FIG. 5 is an explanatory diagram showing a general heat transfer mode in a rotary kiln.

FIG. 6 is a diagram showing a gas flow rate distribution in a rotary kiln of the present invention and a conventional example.

FIG. 7 is a sectional view of a conventional rotary kiln.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Refractory material 2 Granular material supply device 3 Hot air 4 Granular material 5,15,25 Flow control device 6,16,26 Hot air passage 7,17 External piece 8,18 Internal piece

Claims (1)

[Claims] 1. An external hot-air heating rotary kiln that sends hot air from one gas inlet and feeds processed materials such as powders and granules, and transfers the processed material to the other while rotating and heating or drying. In the above, a gas flow control device having a hot air passage at the gas inlet portion is provided, and the hot air passage is provided so as to increase the gas flow velocity near the inner wall surface or the surface of the granular material layer than the hot air gas flow velocity at the rotation center portion. A rotary kiln characterized by that.