JP2798776B2 - Dryer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a dryer used particularly for debinding a ceramic molded body.

<Conventional technology> A ceramic molded body that requires complicated processing after molding, for example, an alumina shaft, or a sheet-shaped ceramic molded body by injection molding or extrusion using ceramic powder such as ceramic sintered magnet powder In the case of producing a binder, a binder such as wax, paraffin, methacrylic copolymer, polystyrene, low-density polyethylene, polybutyl methacrylate, or polyvinyl butyral is used to maintain its form during processing or molding. It is necessary to add 3 to 10 times the amount used in the molding method, more specifically, up to about 13% by weight.

When firing a ceramic molded body containing such a large amount of binder after molding or processing, for example, a temperature of 1200
When sintering under normal sintering conditions of about ℃, the binder, which is a polymer compound, is rapidly evaporated or decomposed.
Evaporation may occur, causing rupture or cracking of the ceramic molded body in the sintering furnace.

For this reason, usually, before firing, a step of removing the binder in the ceramic molded body in a drying step called a binder removal treatment is employed. In this drying process,
Generally, the temperature in the processing tank is gradually increased to about 300 ° C. in a state where the ceramic molded body is disposed in the processing tank of the dryer, that is, the scattering speed of the binder due to evaporation or evaporative decomposition is increased at the heating rate. A batch process for removing the binder while controlling is performed.

By the way, the exhaust gas discharged from the processing tank at the time of this binder removal treatment contains the combustible gas which is obtained by evaporating the binder, which is a polymer material, into a low molecular weight as described above.

Therefore, in a dryer used for this type of debinding treatment, for example, as shown in FIGS. 4 (A) and 4 (B), a heater for raising the temperature of air flowing in from the outside to a predetermined temperature is used.
It is necessary to prevent this flammable gas from turning into the inside of the unit 15.
While increasing the wind speed at 16 and sending the gas into the processing tank 17, the gas generated in the processing tank 17 is forcibly exhausted to the outside of the dryer by suction of an exhaust fan 19 connected to an exhaust hole 18, which is a so-called one-type.
A pass-type structure is adopted.

In this dryer, the external air is supplied to the exhaust fan 19.
After being taken into the dryer by the suction of, and heated by the heater 15, the speed is increased by the stirring fan 16 and sent into the processing tank. In the figure, reference numeral 20 denotes a heat exchanger that functions to exchange heat in exhaust gas discharged from the dryer with external air taken into the dryer, and reference numeral 21 denotes a damper.

<Problems to be Solved by the Invention> However, in the case of performing the binder removal treatment using the dryer having the one-pass system described above, the wind speed distribution in the treatment tank becomes large due to the so-called short path. For this reason, there is a problem that the wind speed decreases at a place far from the stirring fan in the processing tank.

This is because the air accelerated by the stirring fan collides with a resistor such as the ceramic molded body or the inner wall of the processing tank placed in the processing tank and generates a reverse flow, so that the speed in the forward direction is offset. It is considered that the so-called turbulent flow is formed due to deceleration or omnidirectional formation, and air stagnation occurs in the processing tank.

For this reason, although a sufficient wind speed can be obtained at the inlet side of the processing tank near the stirring fan, a required wind speed cannot be obtained as the distance from the processing tank increases.

The debinding treatment is greatly affected by wind speed and temperature, and the processing efficiency is determined by the wind speed and temperature in the vicinity of the ceramic molded body. Therefore, when the wind speed distribution is large as described above, the wind speed and As a result, it is difficult to perform the binder removal process in the stagnation portion compared to other portions, and as a result, the portion of the processing tank far from the stirring fan is used for the binder removal process. It could not be used as a space, resulting in poor processing efficiency.

In particular, since this kind of binder removal treatment is not a continuous treatment but a batch treatment as described above, if the entire surface of the treatment tank cannot be used, a large decrease in mass productivity cannot be avoided. .

An object of the present invention is to provide a dryer having a high processing efficiency, which is suitable for the binder removal treatment of a ceramic molded body to which a large amount of a binder is added as described above.

<Means for Solving the Problems> The dryer of the present invention has an independent suction path for heating the external air with a heater and sending it to the processing tank, and a circulation path for forcibly circulating the air in the processing tank by the circulation fan. In addition, a straightening plate is provided at least on the inlet side of the processing tank, and the external air heated by the heater and the air in the circulation path are straightened by the straightening plate and flow into the processing tank. And

The above-mentioned rectifying plate functions to rectify the air flow in the processing tank, and for example, a perforated plate having a large number of holes having appropriate sizes provided at appropriate intervals may be used. The rectifying plate may be provided at least on the inlet side of the processing tank, but is more preferably provided on the outlet side of the processing tank.

Further, in an actual dryer, an exhaust path provided with an exhaust fan may be provided on the outlet side of the processing tank, and a part of the exhaust gas in the circulation path may be discharged to the outside of the dryer through the exhaust path. .

Further, it is preferable that the inflow direction of the external air in the intake path coincides with or is substantially the same as the circulation direction of the air in the circulation path. If these directions are reversed, air in the circulation path may be mixed into the intake path, depending on the internal structure of the dryer.

<Operation> An independent path of an intake path for heating the external air with a heater and sending it to a processing tank as described above, and a circulation path for forcibly circulating the air in the processing tank by a circulation fan as described above. By separating the flammable gas discharged from the processing tank through the heater, the binder can be removed while the processing tank is warmed by the circulation method without passing through the heater.

At that time, since a rectifying plate is provided at least on the inlet side of the processing tank, the external air heated by the heater and the air in the circulation path flow into the processing tank in a state where the air is rectified by the rectifying plate, As a result, an air flow having a large wind speed and a small wind speed distribution, that is, a laminar flow can be formed in the processing tank.

And the laminar flow state is maintained in the processing tank by the above-mentioned circulation path, so that there is no decrease in wind speed,
The direction does not change. In addition, since forced circulation is performed by the circulation fan, the higher the density of the object to be processed, the higher the wind speed in the vicinity thereof. Further, since the wind speed in the processing tank can be increased in this way, the temperature distribution in the processing tank can be remarkably improved. As a result, the entire processing tank can be used as a space for the binder removal processing, and the processing efficiency is significantly improved.

In addition, since the air in the processing tank is laminar as described above, even if the size of the processing tank is increased in the width direction, the wind speed distribution can be suppressed small, and the processing efficiency is further improved. Is also a great advantage.

<Example> An example will be described below.

FIGS. 1 to 3 show the structure of a dryer according to the present invention. The dryer includes an intake path 1 for feeding external air into a processing tank after heating, and the heated external air and the inside of the processing tank. A circulation path 2 for forcibly circulating the air is provided.

The suction passage 1 is connected to a treatment tank 3 provided inside the dryer from a suction passage 1a for suctioning external air provided at the top of the dryer.
Is formed so as to communicate with the perforated plate 4 provided on the inlet side of the plate. A heater 5 such as an electric heater is provided in the middle of the intake path 1.
As shown in FIG. 3, the air flows in the clockwise direction and reaches the perforated plate 4 as shown in FIG.

The perforated plate 4 is provided with a large number of through holes at appropriate intervals, and the perforated plate 4 partitions the inlet side of the processing tank 3. A similar perforated plate 6 is also provided on the outlet side of the processing tank 3, and the outlet side of the processing tank 3 is partitioned by the perforated plate 6.

In the processing tank 3, a large number of ceramic molded bodies to be subjected to the binder removal processing are arranged at appropriate intervals, for example, on a shelf provided in the processing tank.

On the other hand, the circulation path 2 is a series of paths formed by communicating the circulation path 2a provided in the upper part of the dryer, the perforated plate 4, the processing tank 3, and the perforated plate 6, and the circulation path 2 includes: A circulation fan 7 including a power source such as an electric motor is provided. By the operation of the circulation fan 7, a circulating airflow is formed in the same clockwise direction as the intake path 1 as shown by a dotted line in FIG.

On the outlet side of the perforated plate 6, an exhaust path 8 as shown by a two-dot chain line is formed. The exhaust path 8 includes an exhaust hole 9 provided in a part of the outer wall of the dryer, an exhaust pipe 10 connected to the exhaust hole 9, and a power source such as an electric motor attached to the exhaust pipe 10. Exhaust fan 11 provided
Consists of The capacity of the exhaust fan 11 is set smaller than the capacity of the circulation fan 7, and a part of the circulation airflow is discharged to the outside of the dryer through the exhaust pipe 10 by the function of the exhaust fan 11.

Further, the outlet side of the exhaust pipe 10 is connected to the heat exchanger 12. This heat exchanger 12 also has the above-described intake passage 1a.
The inside of the heat exchanger 12 is connected to the high-temperature gas discharged from the exhaust pipe 10 and the intake passage.
Heat exchange is performed with the low-temperature external air flowing into the intake path 1 via 1a, and the external air
For example, it flows into the intake path 1 while being heated to about 70 to 80 ° C. As such a heat exchanger 12,
For example, a convection type may be used.

In the dryer having the above structure, the external air heated as described above by the heat exchanger 12 flows into the dryer through the intake passage 1a, and is heated to a predetermined temperature by the heater 5 in the intake passage 1. After that, it flows into the processing tank 3 through the perforated plate 4. At this time, the heated external air is rectified and flows into the processing tank 3 in a laminar flow state by the action of the perforated plates 4 and 6.

The temperature in the processing tank is gradually increased to about 300 ° C. by controlling the temperature by the heater 5, and
By controlling the wind speed by adjusting the output of the above, the binder removal processing of the ceramic molded body placed in the processing tank 3 is quickly performed.

In the above dryer, the output of the circulation fan 7 is set to 140 m ³ /
min, and the output of the exhaust fan 11 is 6 m ³ / min, the wind speed at the inlet of the processing tank 3 is about 1.2 m / sec, and the wind speed at the lower part of the outlet where the wind speed is the smallest is about 1.0 m / sec. Yes, the wind speed distribution in the processing tank was kept small.
Further, the temperature distribution in the processing tank was small, and when the inlet of the processing tank was set to the set value, the temperature in the processing tank was lower by 5 ° C. than the set value even at the lowest part below the outlet of the processing tank.

On the other hand, a dryer having the same size as the dryer of the embodiment and having the structure shown in FIGS. 4A and 4B was manufactured, the output of the stirring fan 16 was set to 135 m ³ / min, and the output of the exhaust fan 19 was changed. 3.3 output
When a similar experiment was conducted with m ³ / min, the wind speed in the processing tank was 1.0 m / sec at the processing tank inlet side near the stirring fan 16, while 0.1 m / sec at the lower part of the processing tank outlet. And the temperature distribution was large, and the lower part of the processing tank outlet side was lower by 10 ° C. than the set value.

From the above, in the dryer having the structure of the present invention, the wind speed distribution and the temperature distribution in the treatment tank could be significantly improved as compared with the conventional dryer.

In the above-mentioned conventional dryer, the loading efficiency of the ceramic molded body in the processing tank is limited due to the problem of the wind speed distribution and the temperature distribution, and only about 86% of the space in the processing tank can be used for debinding. On the other hand, in the case of the structure of the embodiment, the temperature distribution and the wind speed distribution are improved, the space in the processing tank can be used almost 100%, and the yield after the processing at this time is also the same as that of the dryer having the conventional structure. This was the same as when processing was performed with reduced loading efficiency.

Except that the width in the width direction was doubled, the same dryer as in the above embodiment was made, and the wind speed distribution in the processing tank in this dryer was examined. The wind speed was 1.2 m / sec near the circulation fan. On the other hand, even on the side farther from the circulation fan, the wind speed distribution was 1.0 m / sec. Therefore, even when the width of the processing tank in the width direction is doubled, approximately 100% of the space in the processing tank can be used as a space for the binder removal treatment. The yield in this dryer was substantially the same as the dryer of the above embodiment.

In the above-described embodiment, the intake path and the circulation path are provided in the upper part of the dryer. In addition, for example, a circulation path is provided in the upper part of the dryer, and the intake path is formed on the circulation path. Needless to say, this may be done.

<Effects of the Invention> As described above, according to the present invention, the wind speed in the processing tank can be improved, and the wind speed and temperature distribution can be significantly improved, so that the space in the processing tank can be effectively used by about 100%. ,
It is possible to provide a dryer having a high processing efficiency, which is suitable for the binder removal processing of the ceramic molded body.

[Brief description of the drawings]

FIG. 1 is a perspective view of the dryer of the embodiment, FIG. 2 is a front view of the dryer, FIG. 3 is an explanatory view showing the flow of air in the dryer, and FIGS. 4 (A) and (B) are conventional figures. It is explanatory drawing of the structure of the dryer of FIG. 1 ... intake path, 2 ... circulation path, 3,17 ... treatment tank, 4,
6 ... perforated plate, 5 ... heater, 7 ... circulation fan, 8 ...
… Exhaust path, 11,19 …… Exhaust fan.

Claims (1)

(57) [Claims] 1. An air intake path which is heated by a heater and sent to a processing tank, and a circulation path for forcibly circulating air in the processing tank by a circulation fan are provided as independent paths. A dryer provided with a rectifying plate on a side thereof, wherein the external air heated by the heater and the air in the circulation path are rectified by the rectifying plate and flow into the processing tank.