JP2000247659A - Auxiliary heater for float bath - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heater which is used as an auxiliary heater of a silicon carbide heating element used mainly in a float bath furnace for melting glass and is capable of prolonging the life of the float bath furnace. SOLUTION: The heating device of the float bath furnace comprises the reaction sintered silicon carbide heating element 1, a protective tube 2 which is manufactured of an SiC-Si composite consisting of 70 to 90 wt.% SiC and 30 to 10 wt.% Si and having a porosity of <=1% and is closed at one side end and a heating element support 4. The supporting and wiring of the device comprising these members only on one side of the furnace are possible. Independent temperature control is executed by building a thermocouple 3 of the heater into the protective tube.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an auxiliary heater for a furnace in a float bath furnace for melting glass.

[0002]

2. Description of the Related Art A float bath furnace for melting glass is generally used at a temperature of about 1100 ° C., and a silicon carbide heating element is mainly used as a heating element. However, the use of the silicon carbide heating element causes a gradual increase in resistance when used, and causes a shortage of electric power required for the furnace. Therefore, it was necessary to periodically replace the heating element.

[0003]

The float bath furnace has the following features.
Although the heating element is replaced in about 0 years, the replacement of the heating element requires dismantling the ceiling of the furnace, and since the float bath furnace is a large facility, the replacement cost becomes large. In addition, the replacement time is greatly increased, and production during that time is stopped. Therefore, it has been required to extend the operation time of the furnace even a little.

[0004]

Means for Solving the Problems A structure in which a heating element can be taken in and out during operation of the furnace is provided with a one-terminal type heating element so that it can be inserted from one side of the furnace, and the heating element is protected from the alkali atmosphere in the furnace. A protective tube made of a SiC-Si composite material and an auxiliary heater having a heating element support are provided, and the heating element used so far is used as auxiliary heating of electric power, which is insufficient. It is to extend the operating time. In order to independently control the temperature of the heater for auxiliary heating, it is desirable to insert a thermocouple into a protective tube made of a SiC-Si composite material. Japanese Patent Application Laid-Open No. 3-46785 proposes a method of covering a SiC heater with a SiC protection tube. In this method, the protection tube is an open end tube and has a terminal on both sides. Since the float bath furnace is required to be cantilevered from the side, its structure and purpose are different from those of the present invention. As for the protection tube, it is not sufficient to protect the heater from an alkaline atmosphere coming out of a float bath furnace with a simple protection tube made of SiC. Furthermore, the present invention provides a SiC 70 to 90 wt
And Si having a porosity of 1% or less composed of Si and 30 to 10% by weight
When the C-Si composite material is used, if the SiC content is 90% or more, it is too dense to impregnate Si and the porosity increases, and if the SiC content is 70% or less, the strength becomes insufficient at high temperatures and the creep characteristics deteriorate. If the amount exceeds these ranges, the conditions required for the float bath furnace cannot be satisfied.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Inside a silicon carbide protective tube, a silicon carbide heating element capable of realizing a one-terminal structure by cutting a spiral is used as a heating element, a support for supporting the heating element, and further a silicon carbide heating element. It has a structure in which a thermocouple is inserted inside the protection tube. When a thermocouple is inserted, the purpose is to perform temperature control independent of the main heating device side, and there is no problem if power control is performed even when there is no thermocouple.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described based on embodiments. FIG.
Indicates a heater composed of a silicon carbide heating element, a silicon carbide protection tube, a heating element support, and a thermocouple. The protection tube is φ110 × L1600 and recrystallized SiC
Is used in a 20% melt-impregnated SiC-Si composite material. The heating element is φ55 × 1100 (heating section) ×
A spiral single-terminal heating element of 700 (non-heat generating part) is made of SiC which has been sintered by reaction. The heating element support includes porous Al ₂ O ₃ —S
Using the iO ₂ system of brick. As the thermocouple, a mullite (3Al ₂ O ₃ , 2SiO ₂ ) protection tube was fixed to the inner surface of the heating element in addition to the R thermocouple. With the above configuration, the heating element is protected from the alkali atmosphere in the furnace, and independent temperature control is possible by incorporating a thermocouple. Further, since the device can be inserted from one side of the furnace, the device can be taken in and out without stopping the furnace, and can be replaced without stopping production. FIG. 2 shows a state where the present invention is set in an actual furnace,
Table 1 summarizes the temperature data when an output of 18 kw (temperature in the protective tube 1310 ° C.) was applied. In addition, Table 2 summarizes the results of tests performed under the conditions of a furnace temperature of 1100 ° C., a nitrogen atmosphere, alkali addition, and holding for 500 hours as an evaluation test of the material of the protective tube.

[0007]

As described above, by using the auxiliary heater of the present invention, in order to compensate for the power shortage caused by the main heating element alone, the furnace is shut down by inserting the necessary amount of power. Power can be supplemented, and the life of the float bath furnace can be extended.
Further, the present invention can be used not only for a new furnace but also for an existing furnace by forming a mounting hole on a side surface. Further, when the auxiliary heater is deteriorated due to its use and the power becomes insufficient, the furnace can be replaced while the furnace is being operated, thereby completely satisfying the demand for extending the life of the float bath furnace.

[Brief description of the drawings]

FIG. 1 is a diagram showing a heater assembled with an apparatus according to the present invention.

FIG. 2 is a view showing a state in which the apparatus according to the present invention is set in a furnace and measurement positions of respective surface temperatures.

[Explanation of symbols]

1. Heating element 2. Protection tube 3. Thermocouple 4. Heating element support 5. Terminal

Claims (2)

[Claims] 1. A heater in a float bath furnace, wherein a silicon carbide heating element, 70 to 90 wt% of SiC and Si
SiC-S composed of 30 to 10 wt% and having a porosity of 1% or less
It is characterized by comprising a protective tube having a closed end on one side made of i-composite material, and a heating element support, and a device composed of these can be supported and wired only on one side of the furnace. Heater. 2. The heater according to claim 1, wherein the heater can be independently controlled in temperature by incorporating a thermocouple in a protection tube.