JPH0220920B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat treatment furnace for new ceramics and other new materials, and in particular to an improvement in a high-temperature electric furnace for continuously roasting the above-mentioned types of granular materials.

Conventionally, Tammann furnaces using graphite existed for experimental purposes, but these furnaces require batch loading and unloading of the material to be processed, which is time-consuming and inconvenient, and it is difficult to use them in combination with ceramic tubes, etc. For this reason, the maximum heat treatment temperature is approximately 1800℃, and therefore,
It is not suitable for roasting powder or granular materials that require higher temperatures, and furthermore, since the Tammann furnace is used as a heating element, crucibles, boats, etc. This is not only uneconomical, but also complicated and difficult, making it unsuitable for production.

Therefore, in order to eliminate the above-mentioned drawbacks, the present applicant has proposed Japanese Patent Application No. 58-18154 (filed on February 8, 1988).
A means for feeding objects to be processed, a furnace main body, and objects to be heated at high temperature, which are to be sequentially arranged on a longitudinal axis, as disclosed in Japanese Patent Application Laid-open No. 145478/1983 (published on August 20, 1982). and a discharge means, in this case,
A cylindrical highly heat-resistant heating element made of carbon or graphite is vertically installed in the center of the furnace body, a refractory is placed around the heating element, a protective atmosphere space is formed, and electricity is directly applied to the heating element. A high-temperature electric furnace is proposed, which is characterized in that the material to be processed is continuously fed, heated at high temperature, and discharged by generating heat. Objects can be continuously heat-treated at temperatures as high as 2000°C (up to 3000°C possible), and because the object to be treated and the heating element are placed in direct contact with each other, heat conduction is improved. The heat treatment is improved, the temperature rise of the heating element is suppressed, and leakage of the protective atmosphere gas is prevented as a whole, so that the heat treatment can be carried out continuously, efficiently and economically.

However, in the high-temperature electric furnace according to the original patent application as described above, if the object to be processed is conductive, current passes through it and generates heat locally, making it difficult to uniformly heat the object. Furthermore, due to the chemical and physical wear and tear caused by the material to be treated, the heating element also serves as the furnace core tube, which has an adverse electrical effect and makes it impossible to achieve uniform heating as before. There is.

In contrast, the present invention aims to provide a high-temperature electric furnace capable of eliminating the above-mentioned drawbacks, and the gist thereof is a means for feeding the workpieces to be sequentially arranged on the longitudinal axis. and a furnace body and a means for discharging the high-temperature heated material, and in this case, a plurality of furnace core tubes made of carbon or graphite are arranged vertically in the center of the furnace body. A rod-shaped heating element made of a material is provided, a refractory is placed around the furnace core tube and the heating element, a protective atmosphere space is formed, and each of the heating elements is directly energized to generate heat. The present invention consists in that the object to be treated is continuously fed, heated at high temperature, and discharged, and thus, according to the present invention,
Since heating elements are installed separately and independently around the furnace core tube, current flows through the heating elements, so even if the object to be treated is conductive, heat will not be generated locally, and the heat generated by the object itself will not be generated. It has the advantage that there is no adverse electrical effect even in the event of chemical or physical wear and that the design and arrangement of the heating element can be made independent of the dimensions of the furnace core tube.

Furthermore, by arranging a plurality of sets of furnace core tubes and heating elements in series, the throughput of the material to be processed can be increased.

Next, the present invention will be explained in more detail with reference to the embodiments shown in FIGS. 1 to 4.

In Fig. 1, 1 is an upper hopper, 2 is a rotary valve, 3 is a lower hopper, 4 is a furnace body, 5 is a connecting heat-resistant tube, 6 is a water-cooled jacket tube, and 7 is a feeding means such as a screw conveyor. The upper hopper is covered with a lid 8, and the internal air is appropriately exhausted from an exhaust pipe 9 to be connected to a vacuum pump (not shown), and the rotary valve is for delivering a certain amount of the material to be processed, such as a non-metallic inorganic material, such as carbonaceous or ceramic powder, charged into the upper hopper to the lower hopper, and a supply pipe 10 is installed in the lower hopper. An inert or neutral gas such as nitrogen or argon is fed through. Structure 1
A water-cooled upper power supply terminal 12 and a water-cooled lower power supply terminal 13 are respectively attached to the upper surface and the lower surface of the furnace body 4 to be installed in the furnace body 4. Or a plurality of rod-shaped heating elements 15 made of carbon or graphite to be installed in a concentric arrangement around a furnace core tube 14 made of graphite.
are the upper and lower terminal parts 1 integrated with this
6 and 17, and the refractory 18 surrounding these furnace core tubes and heating elements is filled with inert gas such as nitrogen or argon to prevent oxidation at high temperatures. The gas inlet 19 and outlet 20 are provided at appropriate locations in the furnace body so as to be placed in a neutral gas atmosphere, and the outermost periphery is made of a metal plate or the like to maintain a certain degree of airtightness. It is configured as a furnace shell 21, and a space 22 for forming a protective atmosphere for the gas is formed around the furnace core tube and heating element, except for the two terminal portions.

As the refractory material 18 to be loaded around the furnace core tube 14 and heating element 15, it is desirable to use a board made of carbon, ceramic fibers, etc. or graphite powder particles distributed according to the heat-resistant temperature range.
Further, the conductors 23 and 24 that conduct electricity to the upper and lower power supply terminals 12 and 13 may have a flexible water-cooled tube structure in order to cope with the high temperature near the two power supply terminals, and furthermore, the conductors 23 and 24 that conduct electricity to the upper and lower power supply terminals 12 and 13 may have a flexible water-cooled tube structure. The bodies or objects to be processed can also be charged continuously at the inlet side or by a feeding means such as a rotary valve or a screw conveyor.

In the high-temperature electric furnace according to the present invention having the above configuration, a material to be treated such as carbonaceous or ceramic powder is charged into the upper hopper 1 in advance by the feeding means as described above, When the rotary valve 2 is operated, a predetermined amount of the material to be treated is caused to fall by gravity into the lower hopper 3 into which an inert or neutral gas such as nitrogen or argon is to be fed from the supply pipe 10, and then the object is stopped. From the lower end of the screw conveyor 7 to the water-cooled jacket 6, the connecting heat-resistant tube 5, the furnace core tube 14, and the lower hopper 3 are deposited in order, resulting in a full state. Next, the operation of the rotary valve 2 is stopped, and while direct current or alternating current is applied to the upper power supply terminal 12 and the lower power supply terminal 13, an inert or neutral gas such as nitrogen or argon is supplied from the supply port 19 as required. When held for a period of time, the heating element 15 will heat up to 2000℃ (or more up to 3000℃) due to Joule heat.
The object to be processed is heated to a high temperature by contact conduction heat, radiation, and convection conduction heat from each of the heating elements, and is roasted.

Next, if the rotary valve 2 is activated at the same time as the transport mechanism such as the screw conveyor 7 is driven, the workpiece is continuously lowered from above to below using gravity, but is still heated at first. The unroasted workpiece is continuously filled into the water-cooled jacket pipe 6 and the connecting heat-resistant tube 5, and then the workpiece that has been heated and roasted by the heating element 15 is continuously filled as before. forced to be discharged. At the same time, when the rotary valve 2 is driven to send the workpiece that has been previously fed into the upper hopper 1 into the lower hopper 3, the workpiece will be heated to a high temperature by the conduction heat from each heating element 15. It is heated to a temperature of 100%, is continuously discharged downward, and then can continue to perform a prescribed roasting operation.

Next, another embodiment of the present invention shown in FIG. 2 will be described, with the same parts as in FIG. 1 being given the same reference numerals.

The refractory 18 loaded in the furnace body 4 with the hopper 3 provided on the top has a double structure of ceramic fibers 18 ₁ on the outside and carbon fiber or felt 18 ₂ on the inside, and fills the atmospheric space 22. An inert or neutral gas such as nitrogen or argon to be heated is fed from a gas supply pipe 25 installed around the water-cooled lower power supply terminal 13, thereby feeding the furnace core tube 14, heating element 15, and The refractory 18 surrounding these is prevented from oxidizing at high temperatures. In addition, discharge means such as double shutters 26, 27 and a chute 28 are attached to the lower ends of the connecting heat-resistant tube 5 and the water-cooled jacket tube 6, respectively, so that a fixed amount of the material to be treated can be removed intermittently. In this case, the double shutter directly serves to convey the material to be processed, and also has the function of blocking communication with the outside air and preventing leakage of protective atmosphere gas. There is.

In the above embodiment, a case has been described in which a plurality of rod-shaped heating elements 15, for example eight, are arranged concentrically around one furnace core tube 14 having a circular cross section, but according to the present invention, As shown in FIG. 3A and FIG. 4A, it is possible to increase the throughput by connecting the heating element and the furnace core tube arranged in the same way as before, and also, as shown in FIG. As shown in FIG. 3B, the furnace core tube 14 may have a rectangular cross-sectional shape, and a plurality of rod-shaped heating elements 15, for example, 10, may be installed vertically around the core tube 14. Fourth
As shown in Figure C or Figure 4 D, a plurality of rod-shaped heating elements 15 are installed horizontally through the furnace body 4 on both sides of the furnace core tube 14 having a circular or rectangular cross section and at equal intervals above and below. However, the same objective can be achieved.

Additional relationship The original patent application, Japanese Patent Application No. 58-18154
145478) is equipped with a means for feeding the material to be treated, a furnace body, and a means for discharging the material to be heated at high temperature, which are arranged in sequence on the longitudinal axis, and in this case, carbon or graphite is placed in the center of the furnace body. A cylindrical highly heat-resistant heating element is installed vertically, a refractory is placed around the heating element, and a protective atmosphere space is formed, and the heating element is directly energized to generate heat. A high-temperature electric furnace is described, which is characterized in that it is configured to continuously feed, heat, and discharge materials at high temperatures.

However, in the original patent application, if the object to be processed is an electrically conductive object, there is a drawback that the object to be processed cannot be heated uniformly because current passes through it and generates heat locally. In contrast, in the present invention, the heating element also serves as the furnace core tube, which has a negative electrical effect and prevents uniform heating as before. Since the heating elements are installed separately and independently around the core tube, the current flows through the heating elements, so even if the object to be treated is conductive, it will not generate heat locally, and therefore the object to be treated will be uniformly heated. chemical heating of the object to be processed,
This has been improved so that it does not have any adverse electrical effects even when subjected to physical wear and tear, and the design and arrangement of the heating element can be made independent of the dimensions of the furnace core tube.

[Brief explanation of drawings]

FIG. 1 is an axial longitudinal cross-sectional view showing a high-temperature electric furnace according to the present invention, FIG. 2 is a drawing similar to FIG. 1 showing another embodiment of the present invention, FIGS. 3 A, B, and 4. stomach,
B, C, and D show still other embodiments of the present invention, and FIG. 3 is a sectional view taken along the - line in FIG.
FIG. 4 is a broken sectional view taken along the - line in FIG. 2. Note that the correspondence relationship between the main parts shown and the symbols is as follows. 1... Upper hopper, 2... Rotary valve, 3... Lower hopper, 4... Furnace body, 5... Heat-resistant connecting pipe, 6... Water-cooled jacket pipe, 12... Water-cooled upper power supply terminal, 13... Water-cooled lower power supply terminal, 14... Furnace core tube, 15... Heating element, 16... Upper terminal portion, 17... Lower terminal portion, 18... Refractory, 22... Protective atmosphere space, 26, 27... ...double shutter,
28...Shoot.

Claims (1)

[Scope of Claims] 1. A furnace comprising a feeding means for a material to be treated, a furnace body, and a discharge means for a material to be heated at a high temperature, which are arranged in sequence on a longitudinal axis, and in this case, a furnace body is provided with a feeding means for a material to be treated which are to be sequentially arranged on a longitudinal axis, and a means for discharging a material to be heated at high temperature. A plurality of rod-shaped heating elements made of the same material as before are arranged around a hollow furnace core tube made of carbon or graphite to be installed, and a refractory is placed around these furnace core tubes and heating elements. A high-temperature electric furnace is characterized in that the workpiece is continuously fed, heated at high temperature, and discharged by directly supplying electricity to the heating element to generate heat, and forming a protective atmosphere space. . 2. The electric furnace according to claim 1, wherein the furnace core tube has a circular or rectangular cross-sectional shape, and the heating element is arranged vertically around the furnace core tube. 3. A high-temperature electric furnace according to claim 1, in which a plurality of rod-shaped heating elements are installed horizontally through the furnace body on both sides of the furnace core tube and at equal intervals vertically.