SU50797A1 - Heating resistance for electric ovens - Google Patents

Description

Usually in electric furnaces high-resistance is used as resistance, for example, nichrome wire or carbon or silitic (carborundum) rods, connected in series in series. All such kind of heat bodies, especially silicic, and even more so carbon rods, are oxidized from the surface at high heating temperatures of between 1000 and 1500 ° C and, moreover, when turned on and off again, they become very brittle, but the nichrome wire for temperatures above 900 ° not applicable at all.

In large steel-smelting furnaces of the Steinberg and Gramolin type, despite the extreme simplicity of their arrangement, a great inconvenience is the need for very frequent changes of carbon rods (every 4-6 hours) due to the fact that they become thin due to oxidation from the surface. In addition, when changing them, there is always the danger of their fragments falling into the charge.

In order to eliminate these drawbacks, it has already been proposed that a carbon or silicate rod, heated by current, be enclosed in a tube of refractory material, which is actually a heating body for the furnace space, with some gap remaining between the tube and the rod from outside air access.

The invention relates to a similar type of heating resistance for electric furnaces and consists in a special form of their implementation, providing, for her very long service life, considerable strength and non-acidity of the surface during the entire service life. Due to their mechanical strength, such resistances can be made of any desired length without fear of their deflection in a heated state. In addition, they can be made for temperatures of the order of 1200 °, and much higher, for example, 1600 ° or even e, e higher.

In the accompanying drawing, several exemplary embodiments of the inventive invention are presented, with FIG. 1 shows the structure of such a heating resistor for muffle or

industrial type crucible furnaces; FIG. 2 shows another embodiment of the resistance of FIG. 1, composed of two spliced along the length of the rods; FIG. 3-resistance for larger furnaces, for example, such as Steinberg and Gramolin.

As seen in FIG; 1, a coarse, silitic or similar rod /, filled with its ends into carbon, graphite, silitic or the like tips 2, is protected from the oxidizing action of outside air by a refractory tube 4 supported by the ends on the wall 10 of the furnace and the lining 11 impaled with their ends on the lugs 2. Metal, best of all, iron or stainless steel pins 3, tightened with lock nuts 5, are screwed into the ends of the lugs 2. The sleeves 6, the diameter of which is approximately equal to the inner one, are screwed onto the ends of the pins 3 the diameter of the tubes 4, and two nuts 7, 6, between which the cable lug of the current-carrying wire is fixed. The space 9 between the lock nut 5 and the sleeve 6 is packed with asbestos. In this way, current is supplied and the ends of the tube are sealed against the penetration of external air into it.

For operating temperatures of the order of 800-1300 ° A porcelain tube can be used as a protective shell without danger of bending it in a hot state. At the same time, the initial amount of air enclosed in the gap between the rod and the tube oxidizes some insignificant amount of the material of the rod, and after that the resulting gases play the role of a protective atmosphere for it against further oxidation. Heat is transferred from the rod to the tube by radiation, and the temperature is only slightly (approximately 50 °) higher than the temperature of the tube itself, which is the heating body for the furnace space itself.

For higher operating temperatures, of the order of 1500-1700 °, it is advisable to manufacture protective

tubes of corundum or similar material.

If, depending on the larger dimensions of the furnace, rods are thin but long, then it is possible, as shown in FIG. 2, be composed of two or more rods interconnected by a transition sleeve 72 of the same material as the rods or their tips. In order for the sleeve 12 not to come into contact with the tube, two or three support rods / 5 are inserted into it from the same material as the tube 4. Similarly, the transition sleeve 12 can also be worn over a solid, thin, but long carbon or silicite a rod to prevent it from sagging inside the tube, in the case of applying heating resistance to high temperatures.

In this way, it is possible to cover the furnace space of 1.0-1.5 meters without any fear of breakage or sagging of the heating resistance during heating.

For larger steel-making, glass-smelting or other furnaces, in which it is expedient to produce water cooling of the inlets, the latter can be arranged as tubular coils 14–15 sealed into the furnace walls and cooled with running water, through which heating resistance tubes are passed. Such a design, due to the complete independence of the heating resistances from the cooling system, makes it extremely easy and quick to change them if necessary without stopping the cooling effect.

The suggested resistances are applicable both in laboratory practice and in production furnaces, for example, for steel smelting, glass melting, etc., and the protective tube eliminates the possibility of fragments of coal falling into the bath, as in the Steinberg and Gramolin furnaces.

The subject matter of the invention.

Claims (2)

1. Heating resistance for electric furnaces consisting of coal, silicon or the like like a rod with thickened tips, protected from the heat of external air in a state of refractory tube, forming a closed space between it and the rod, and the heating body for the furnace space itself is a tube that receives heat from the current-heated rod by radiation, which differs the fact that said tube 4 is put on thickened tips 2 of rod 1, into which ends the current supply pins 3 are screwed with lock nuts 5 and the ends of the tubes are closed E b, the space between which is filled with asbestos locknuts 5 to protect against penetration of air into the tube. 2. With a heating resistance according to claim 1, use a cooling system consisting of coils embedded in the walls of the furnace with water circulating in them through which the heating resistances are passed. 95 7 U /////: ///// U-l 4 1 Ig 7. .... / s, with . 2 F & G. / / -,one WTTTM / 2U