JPH0346785A - Heater with nonsoaking type sic protective tube - Google Patents

Abstract

PURPOSE:To extend the service life and to improve the thermal efficiency by gearing a sleeve of the quality having a fixed specific resistance at the circumference of a rod-form heater to form a protective tube contact, and covering the sleeve with an SiC protective tube. CONSTITUTION:At the circumference of a rod-form heater 1 furnishing cold terminals 2 for electric connection at both ends, a sleeve 3 of the quality having a specific resistance 100OMEGAcm or more is geared to form a protective tube contact, and the sleeve 3 is covered with an SiC protective tube 4. In this case, in the SiC protective tube 4, an aperture such as a slit for heat radiation is provided near the heating part of the heater. As the quality of the SiC protective tube for gas cutoff in the furnace, a recrystallization type SiC, a slef-sintering SiC, or an SiC injection SiC is used normally.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention improves the life expectancy of a non-immersion type SiC heater used for melting molten materials such as glass or as a heat source for firing ferrite, etc. Non-immersion type heater with SiC protection tube that improves efficiency [Conventional technology] SiC heaters are widely used as a simple high heat source in various industries, especially non-immersion type heaters for melting glass, holding molten metal, or firing ferrite. There is a lot of demand as a mold heater.

The shape of the non-immersion type heater is usually a bar with a circular cross section, and has a structure in which cold terminal parts for electrical connection are provided at both ends, and a central part sandwiched between the cold terminal parts serves as a heat generating part.

Separately, there is an immersion type heater for melting aluminum, and various systems have been developed, including a structure that isolates the heater in molten metal from the molten metal, as well as systems that break down the separation wall.

The heat generating part constituting the main body of the non-immersion type heater is subjected to various coating treatments such as plasma spraying on its periphery in consideration of corrosion resistance.

Due to the surface coating that provides insulation and internal protection functions, its lifespan is approximately 400 hours at most, and the complexity and cost of maintenance such as replacing the heater is a bottleneck to improving operational safety and productivity. .

Unlike the molten metal isolation wall technology of immersion type heaters, improving the lifespan of heaters under gas contact requires a structure that achieves the harmonious benefits of suppressing increases in power consumption and reducing costs by extending lifespan. It has not been started.

[Problem that the invention seeks to solve]

Problems that were not considered important with immersion type heaters using molten metal isolation wall technology, namely, a means to overcome the limit of life extension due to surface coating, and a means to overcome the problem to enable sufficiently advantageous cost reduction in terms of power consumption and total cost. Development issues are essential for non-immersion heaters.

For example, even though the heater for glass melting, which is in high demand, has a coating mainly made of glass on its surface, the SiC itself, which is the heater material, is corroded by the alkali metals contained in the glass atmosphere in the melting furnace. , so-called burnout phenomenon occurs.

When the thinning phenomenon occurs, the apparent resistance of the heating part increases, and with this increase in resistance, the amount of heat generated also increases, accelerating the corrosion rate, and as a result, the rapid progress of thinning and consumption limits the life of the heater. .

Therefore, when cutting off the glass atmosphere from the heater in order to suppress the thinning phenomenon, it is important to consider the extent of the effect of this blocking on the heater's radiant heat, the lowest possible cost structure required to do so, and the electrical structure that can withstand high voltage loads. In addition to developing the structure, we also clarified the existence of an advantageous balance between the degree of increase in power consumption and cost reduction due to increased lifespan.

[Means for solving problems]

In order to overcome the above-mentioned problems, the present invention provides a non-immersion type SiC heater used as a heat source for melting low-melting materials such as glass or for firing ferrite, etc. , specific resistance is 10
A sleeve made of a material with a resistance of 0 Ω■ or more is fitted to form a protection tube contact part, and the sleeve is covered with an SiC protection tube, and an opening such as a heat radiation slit is provided near the heat/emission generating part. We have developed a heater equipped with a protective tube.

The protective tube material for in-furnace gas cut-off to prevent corrosion is as follows:
From the viewpoint of thermal conductivity, SiC or a material with a high SiC content is preferable, and usually recrystallized SiC% self-sintered S
iC or St-implanted SiC is preferred.

However, since the SiC material itself is electrically conductive, electrical insulation from a heater that loads a high voltage becomes a problem.

When voltage is applied, current is shunted not only to the heater but also to the protection tube.
Power loss becomes large and the power used is wasted, making it impossible to suppress the increase in power consumption.

Therefore, it is necessary to use a material with high insulating properties for the material of the sleeve interposed at the contact part between the heater and the protective tube, and detailed experiments have shown that the specific resistance at room temperature is 100Ωc.
It has been found that I11 or higher is preferable.

[Function and Examples]

The functions and examples of the non-immersion type heater with SiC protection tube of the present invention will be described in detail below. It goes without saying that the present invention is not limited to this embodiment.

Figure 1 shows a cross-sectional view of the non-immersion type heater with SiC protection tube of the present invention, which has a diameter of 20+ m and a length of 700 mm.
Cold terminal parts (2) for electrical connection with the same diameter and length of 15 mm are arranged on both sides of the iC heater (1) body, and the cold terminal parts (2) have a diameter of 40 + n and a step of 34 mm for supporting the protective tube. , a sleeve (3) with a length of 20 irises is brought into fitting contact, and with the sleeve (3) interposed, an outer diameter of φ401n, an inner diameter of φ35,
The heater (1) is covered with a SiC protection tube (4) having a length of 9° OW.

The material for the sleeve can achieve the required electrical insulation with a material having a specific resistance of 100 ΩG or more, and the material is not particularly limited as long as cost, workability, durability, etc. are taken into consideration.

Figure 2 shows the effect of the heater structure with a protection tube on heating efficiency and testing of better corrective measures. The slit was cut and formed on the SiC protection tube (4) with the above dimensions in the projected shape of the slit and circular hole.
It has an oval shape of 0wm x 6 dragons, and the circular holes are φ61m at intervals of 50m.

The above shape and dimensions can be appropriately selected in consideration of heat radiation efficiency, strength, etc., and are not particularly limited.

Table 1 compares the lifespan of the non-immersion type heater with a SiC protection tube of the present invention and the case without a protection tube in a glass melting furnace.
- A dramatic improvement of 10 times.

Electric power will increase by 30 to 40%, but if you take into account the melting furnace shutdown and replacement work to replace the heater, the total cost will improve significantly.

Table 2 compares the power consumption of the heaters (4 heaters) with and without the heat radiation windows.The heat radiation efficiency of the heater is increased by providing the heat radiation windows to reduce power consumption. It is clear that this method is effective in suppressing the increase in power consumption.

Table 1 Test No. in Table 2 above: Test No. 2 with slits and no holes; Test No. 3 with slits on the melt side; Test No. 4 with 12 holes on the opposite side of the melt; Test No. 4 with 21 slits on the opposite side of the melt. It is a protection tube. No current loss to the protection tube (4) was observed.

The reason why the usage time was short in Test No. 2 is that because the slit was provided on the melt side, the vaporized glass atmosphere came into contact with the heat generating part of the heater, and the heat generating part was corroded.

The heater structure, which provides electrical insulation using the SiC protection tube (4) and the sleeve (3) provided at the contact part with the SiC heater, prevents the adverse effects of melting furnace gas to a high level and suppresses increases in power consumption. , thermal efficiency can be maintained at a high level by forming windows for heat radiation.

〔Effect of the invention〕

The non-immersion type heater with a SiC protection tube of the present invention suppresses corrosion of the heater body due to the structure with the protection tube, increasing durability and extending the lifespan by 5 to 10 times. Windows increase thermal efficiency and reduce power consumption, contributing to energy savings.

[Brief explanation of drawings]

FIG. 1 shows a cross-sectional view of the SiC heater protection tube of the present invention,
FIG. 2 is a projected view of a heat radiation window provided on the SiC heater protection tube. (1) (2) (3) (4) (5) Heater cold terminal sleeve protection tube heat radiation window

Claims (1)

[Claims] 1. In a non-immersion type SiC heater used as a heat source for melting low-melting materials such as glass or for firing ferrite, etc., a rod-shaped heater having cold terminals for electrical connection at both ends has a specific resistance of 100 Ωcm at the outer periphery. A non-immersion type heater with a SiC protection tube, characterized in that a sleeve made of the above material is fitted to form a protection tube contact portion, and the sleeve is covered with an SiC protection tube. 2. A non-immersion type heater with a SiC protection tube, characterized in that the above-mentioned SiC protection tube is provided with an opening such as a heat radiation slit in the vicinity of the heater heat generating part.