JPH08110177A - Hot air circulation furnace - Google Patents

Abstract

PURPOSE: To provide a hot air circulation furnace in which productivity can be improved and a high purity control over atmospheric gas can be realized under a simple configuration not using any equipment and the like. CONSTITUTION: There are provided a heat treatment chamber 3 having item to be processed stored therein ; a gas circulation passage 4 arranged at an outer circumference of the heat treatment chamber 3, connected to the heat treatment chamber 3 and for causing atmospheric gas G flowed even in the heat treatment chamber 3; a gas supplying pipe 6 inserted into the gas circulation passage 4, arranged along a circulating direction of the atmospheric gas G and to which external atmospheric gas is supplied. To the extremity end of the gas supplying pipe 6 is fixed a gas injection nozzle 7 for use in injecting the atmospheric gas G.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot air circulating furnace, and more particularly to a method of circulating atmospheric gas supplied to a heat treatment chamber.

[0002]

2. Description of the Related Art Conventionally, when a heat treatment such as firing is performed on a ceramic product, a hot air circulating furnace configured as shown in the vertical sectional view of FIG. 4 has been used. That is, in heat transfer in a temperature range of about 500 to 600 ° C. or less, convective heat transfer is more dominant than radiant heat transfer. This is because it is convenient to use the hot air circulating furnace configured to perform the above in order to reduce the variation in the temperature distribution inside the furnace. And
This hot-air circulation furnace has a furnace body 11 having a heat insulating structure, a muffle 12 which is a heat treatment chamber, that is, a muffle 12 made by combining a heat-resistant metal plate, and the muffle 12
And a furnace body 11, and a gas flow passage 13 through which an atmospheric gas G such as nitrogen supplied from the outside and heated is circulated.

Further, at this time, the muffle 12 is supposed to house a box (not shown) containing a ceramic product or the like to be processed in a multi-tiered manner. A large number of vent holes 14 through which the atmospheric gas G is circulated are formed in each of the side plates that constitute the above and face each other. In addition, a gas supply pipe 15 for supplying the atmospheric gas G introduced from the outside is drawn into the gas circulation path 13 located on the muffle 12, and a sirocco fan for circulating the supplied atmospheric gas G is also provided. 16 and an electric heater 17 for heating the circulating atmospheric gas G to a required temperature are respectively arranged. The sirocco fan 16 is connected to an electric motor 19 via a sealed bearing 18, and the electric motor 19 It is designed to be rotated.

[0004]

By the way, in the hot air circulating furnace having the above-mentioned conventional structure, it is necessary to use equipment such as a sirocco fan 16 having excellent heat resistance and a sealed bearing 18 having a high degree of shaft sealing performance. Not only does this lead to an increase in cost, but it is not possible to improve productivity by further raising the temperature of the atmosphere gas G due to restrictions imposed by the materials and performance of these devices. Was becoming. Further, since the sealed bearing 18 is greatly affected by the temperature difference between the inside and outside of the furnace, deterioration of the shaft seal performance is unavoidable, and the atmospheric gas is controlled to have a high purity while preventing the intrusion of air (oxygen) from the outside of the furnace. There was also the inconvenience that it became difficult.

The present invention was devised in view of these inconveniences, and a hot air circulation furnace capable of improving productivity and controlling high purity of atmospheric gas with a simple structure without using any equipment. The purpose is to provide.

[0006]

A hot-air circulation furnace according to the present invention is provided with a heat treatment chamber in which an object to be treated is housed, and the heat treatment chamber is arranged around the outer periphery of the heat treatment chamber and is connected to the heat treatment chamber.
A gas circulation path in which the atmospheric gas that also circulates in the heat treatment chamber circulates, and a gas supply that is inserted in the gas circulation path and is arranged along the circulation direction of the atmospheric gas and that is supplied with the atmospheric gas from the outside And a pipe, and a gas jet nozzle for jetting an atmospheric gas is attached to the tip of the gas supply pipe. The gas circulation path at this time is connected so that the atmospheric gas flows in the heat treatment chamber in either the horizontal or vertical direction.

[0007]

According to the above structure, the new atmospheric gas supplied from the outside through the gas supply pipe is ejected through the gas ejection nozzle, and the atmospheric gas existing around the gas ejection nozzle is regenerated. After being drawn along the circulation direction by the jetting action of the atmospheric gas jetted to the heat treatment chamber, the gas flows into the heat treatment chamber in the gas circulation path and then flows in the heat treatment chamber.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a vertical sectional view showing a schematic structure of a hot air circulating furnace according to this embodiment, and FIGS. 2 and 3 are vertical sectional views showing modifications thereof.

The hot air circulating furnace according to the present embodiment is called a batch type furnace, in which a furnace body 2 having a heat insulating structure in which an electric heater 1 is embedded and a ceramic product which is an object to be treated are housed. The heat treatment chamber that accommodates the boxes (not shown) stacked in multiple stages, that is, the muffle 3 made of a combination of heat-resistant metal plates, and the muffle 3 is arranged along the outer periphery of the muffle 3 and Gas G that is connected to the muffle 3 and that also flows through the muffle 3.
And a gas circulation path 4 that circulates. In addition, the gas circulation path 4 at this time is configured by using a pipe material made of a heat-resistant metal, and the atmosphere gas G heated by the electric heater 1 while circulating in the gas circulation path 4 flows in the muffle 3. The atmosphere gas G is connected to the muffle 3 in a state of flowing along the horizontal direction, and is connected to the gas circulation passages 4 of the side plates that constitute the muffle 3 and are opposed to each other. A large number of vent holes 5 are formed to circulate.

Further, a gas supply pipe 6 for supplying an atmospheric gas G introduced from the outside is inserted in the gas circulation passage 4, and the gas supply pipe 6 in the form of a straight pipe circulates gas in the longitudinal direction. It is arranged fixedly along the circulation direction of the atmospheric gas G in the passage 4. A gas injection nozzle 7 is attached to the tip of the gas supply pipe 6 located near the center of the gas circulation path 4 in the longitudinal direction, and the atmospheric gas G supplied by the gas supply pipe 6 is supplied.
Is squeezed by the gas ejection nozzle 7 and is circulated in the gas circulation path 4
It is supposed to squirt inward.

Therefore, in the hot air circulating furnace according to the present embodiment, a new atmosphere gas G supplied from the outside through the gas supply pipe 6 will be ejected after passing through the gas ejection nozzle 7, and the inside of the gas circulation passage 4 will be ejected. Gas injection nozzle 7
The atmospheric gas G existing around the is attracted in the circulation direction by the ejection action of the newly ejected atmospheric gas G. That is, at this time, the momentum of the newly supplied jet of the atmospheric gas G diffuses and affects the surrounding atmospheric gas G, and the affected atmospheric gas G surrounds the periphery of the jet. It will be attracted as a surrounding flow. Then, the new atmosphere gas G and the attracted atmosphere gas G flow toward the muffle 3 in the gas circulation path 4 while being heated together by the electric heater 1 embedded in the furnace body 2, and then the ventilation hole 5 In addition to flowing into the muffle 3 through, the ceramic product, which is the object to be processed, is fired while flowing through the muffle 3.

Although not shown, it is a matter of course that an exhaust hole for discharging the used atmosphere gas G corresponding to the supply amount of the new atmosphere gas G is provided in the gas circulation path 4 in advance. is there. In addition, it is needless to say that the circulation amount of the atmosphere gas G can be proportionally adjusted by adjusting the supply amount of the new atmosphere gas G at this time, and according to the study conducted by the inventor of the present invention, It is also possible to obtain a circulation amount close to 7 times the supply amount.

Furthermore, in this embodiment, an oxygen concentration meter or the like is provided at the inflow portion of the gas circulation path 4 into which the atmospheric gas G, which has been obtained by firing the ceramic product while flowing through the heat treatment chamber 3, flows in. A sampling port S connected to the gas component detection device is attached. In the case of such a configuration, an accurate oxygen concentration control is performed by detecting the components of the atmosphere gas G that has just passed through the periphery of the ceramic product being processed through the sampling port S. Atmosphere gas control can be performed.

By the way, the gas circulation path 4 in this embodiment
Is connected so that the atmospheric gas G is oriented to flow in the muffle 3 along the horizontal direction. For example, as shown in the modification of FIG. 2 or 3,
The gas circulation path 4 may be connected to the muffle 3 so that the atmosphere gas G flows in the muffle 3 along the vertical direction. 2 and 3, those parts and portions that are the same as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

First, in the hot air circulating furnace according to the first modification shown in FIG. 2, the gas circulation passage 4 is connected to the muffle 3 so that the atmosphere gas G flows in the vertical direction in the muffle 3. The gas circulation path 4 here constitutes a muffle 3 and is connected to each of a ceiling plate and a bottom plate which face each other vertically. At this time, a large number of vent holes 5 are formed in the ceiling plate and the bottom plate, and the atmospheric gas G flowing in from the bottom plate side is in the muffle 3.
It flows through the inside from the bottom to the top and then flows out from the ceiling board side. By the way, when such a configuration is adopted, the variation of the temperature distribution in the muffle 3 in which the boxes (not shown) accommodating the ceramic products and the like are stacked and stacked in multiple stages are shown in FIG. It is considered to be improved over the case of the above configuration.

In the hot air circulating furnace according to the second modification shown in FIG. 3, the gas circulation passage 4 is connected to the lower half of each of the side plates constituting the muffle 3, while the gas circulation passage 4 is connected. In this hot-air circulating furnace, the atmospheric gas G flowing from the lower side of the muffle 3 flows upward in the muffle 3 as well. Will be done. Further, also in the hot air circulating furnaces according to the first and second modified examples, the gas component detecting device is provided at the inflow portion of the gas circulation path 4 into which the atmospheric gas G flowing in the heat treatment chamber 3 flows. A sampling port S to be connected is attached. In the case of these modified examples, the atmospheric gas G that has passed around the ceramic product
Will flow intensively through the inflow site of the gas circulation path 4, for example, the gas outflow pipe 8, and it will be possible to perform highly accurate component detection as much as the atmospheric gas G is concentrated.

In the hot air circulation furnace described above, the electric heater 1 for heating the atmospheric gas G is embedded in the furnace body 2. However, the present invention is not limited to this, and the electric heater 1 is a furnace. Needless to say, it may be arranged on the inner surface of the body 2 or may be arranged in the gas circulation path 4. When the electric heater 1 is embedded in the furnace body 2 or disposed on the furnace body 2, not only the atmospheric gas G but also the muffle 3 is directly heated by the electric heater 1. As a result, it is possible to improve the temperature distribution in the furnace and the thermal responsiveness in the furnace. Furthermore, in the above description, it is assumed that the hot air circulating furnace is a batch type, but it goes without saying that the scope of application of the present invention is not limited to the batch type. That is, for example, a plurality of muffles 3 are connected to each other, and then a gas circulation path 4 and a gas supply pipe 6 are provided.
If the gas ejection nozzle 7 is provided for each muffle 3, it is possible to configure a hot air circulating furnace called a continuous type.

[0019]

As described above, according to the hot air circulating furnace of the present invention, the ambient gas newly supplied from the outside can be jetted out without using any equipment for circulating the ambient gas. This makes it possible to circulate the ambient gas existing around the gas ejection nozzle. Therefore, it is not necessary to use equipment such as sirocco fan and power for driving them, which not only makes it possible to reduce costs, but also has an effect that high purity control of atmosphere gas can be easily performed. To be Further, it is possible to raise the temperature of the atmospheric gas to 900 ° C. or more before use without being restricted by the equipment, and as a result, it is possible to obtain the effect that the productivity can be improved. .

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a schematic structure of a hot air circulating furnace according to this embodiment.

FIG. 2 is a vertical cross-sectional view showing a schematic structure of a hot air circulating furnace according to a first modification.

FIG. 3 is a vertical cross-sectional view showing a schematic structure of a hot air circulating furnace according to a second modification.

FIG. 4 is a vertical sectional view showing a schematic structure of a hot air circulating furnace according to a conventional example.

[Explanation of symbols]

 3 Muffle (heat treatment room) 4 Gas circulation path 6 Gas supply pipe 7 Gas ejection nozzle G Atmosphere gas S Sampling port

Claims (4)

[Claims] 1. A heat treatment chamber (3) for accommodating an object to be treated.
And a gas circulation path, which is arranged on the outer periphery of the heat treatment chamber (3) and is connected to the heat treatment chamber (3), and in which the atmosphere gas (G) circulating in the heat treatment chamber (3) circulates (4)
And a gas supply pipe (6) inserted into the gas circulation path (4) and arranged along the circulation direction of the atmospheric gas (G) and supplied with the atmospheric gas (G) from the outside. A hot-air circulation furnace, characterized in that a gas jet nozzle (7) for jetting an atmospheric gas (G) is attached to the tip of the gas supply pipe (6). 2. The gas circulation path (4) comprises an atmospheric gas (G).
The hot-air circulating furnace according to claim 1, wherein the heat-air circulating furnace is connected in such a manner as to flow in the heat treatment chamber (3) along a horizontal direction. 3. The gas circulation path (4) is provided with an atmospheric gas (G).
2. The hot-air circulation furnace according to claim 1, wherein the hot air circulation furnace is connected in such a manner that the heat flows in the heat treatment chamber (3) along a vertical direction. 4. An inflow part of a gas circulation path (4) into which an atmospheric gas (G) flowing in the heat treatment chamber (3) flows,
The hot-air circulation furnace according to claim 1, further comprising a sampling port (S) connected to the gas component detection device.