SU1201655A1 - Furnace for producing silicon carbide - Google Patents

Description

The invention relates to the construction of electric furnaces for continuous production of silicon carbide and can be used in abrasive and other industries.

The purpose of the invention is to improve the quality of the product and its output.

The drawing shows a furnace for the production of silicon carbide, vertical section.

The furnace for producing silicon carbide contains a shaft 1 lined with refractory material in the form of a steel cylindrical casing 2; Mine 1 contains heating zone 3, reaction zone 4 and cooling zone 5. The lining at the end of the cooling zone is made with a taper of 5-7 ° to ensure a more uniform discharge of the charge.

The upper electrode 6 is axially mounted in the shaft 1 of the furnace and made in the form of a circular graphite or carbon rod with the possibility of axial movement. The lower ring electrode 7 is made with a height equal to 0.3-0.5 of the internal diameter of the furnace shaft, and is mounted concentrically in the side walls of the mine. To accommodate the annular electrode 7 in the lining of the shaft is made annular groove 8. Graphite conductor 9 is introduced through the side walls of the mine. The annular space of the furnace, limited to the annular electrode 7, is the reaction zone 4 of the furnace. The height of the heating zone 3 is 4.5-5.5 heights of the annular electrode 7, i.e. reaction zone. In the lower part of the cooling zone 5, a device 10 is placed to destroy the block of the finished product, made in the form of rotating finned disks 11, and a mechanism 12 for unloading the product. To load the charge, there is a loading opening 13 and a loading mechanism (not shown). For exhaust gases is the pipe 14.

The selected ratio of the height of the annular electrode and the internal diameter of the furnace shaft allows to increase the current density in the electric arc space, which provides a more intense resistive heating of the charge and a more complete reaction between the components. This is facilitated by the fact that the mixture in the reaction zone by increasing the height of the heating zone comes more heated (up to 1100-1300 ° C),

When the height of the annular electrode is less than 0.3 of the internal diameter of the furnace shaft and the small length of the heating zone (less than

4.5-5.5 heights of the ring electrode) The charge practically does not have time to warm up to the reaction temperature and fully react, in addition there is fusion of the charge with the electrode surface and termination of its continuous descent along the charge. Perform ring electrode

with a height of more than 0.5 of the internal diameter of the furnace shaft and the heating zone with a height of more than

4.5-5.5 height of the ring electrode leads to a decrease in current density so that the reaction between the components with their stoichiometric ratio becomes almost impossible.

The furnace for the production of silicon carbide works as follows.

The granulated mixture consisting of quartz sand and coke, taken in a stoichiometric ratio, is continuously fed to the preheating zone, where it is heated by the reaction exhaust gases to 1100–1300 ° C and enters the annular space between the upper electrode 6 and the annular electrode 7, i.e. to reaction zone 4. In this zone, the charge is heated in a combined resistive-arc mode with the passage of electric current through the circuit of the upper electrode - charge - ring electrode. The temperature in the reaction zone rises to 2000 ° C and higher, while in the zone of the ring electrode it is lower than in the zone of the upper electrode. As a result, a layer of fine-crystalline silicon carbide is formed in the area of the ring electrode, which is looser and weaker. Under pressure of the charge column, this near-wall layer is destroyed and does not interfere with the progress of the silicon carbide block along the shaft.

With the passage of the charge of the annular space with a height of 0.3–0.5 of the internal diameter of the furnace shaft, the reduction of silicon dioxide to carbide is almost completely completed. The block of the finished product passes the cooling zone with cooling devices (not shown in the drawing), in its lower part it is destroyed by rotating finned discs 11 and the product unloading mechanism 12 is continuously removed from the furnace.

Regulation of the heat load of the furnace is carried out using a furnace transformer (not shown), as well as by axial movement of the upper electrode 6.

The invention allows to increase the yield of silicon carbide by 6-7%, while the product is obtained co-crystalline, with virtually no unreacted charge and with a low content of impurities of the carbon-containing component. The resulting silicon carbide, intended for the abrasive industry, does not require sorting it with the aim of separating the unreacted charge, which is currently carried out manually, and thus significantly reduces labor costs and increases the production culture.

The use of the stoichiometric charge makes it possible to reduce by 10–15%

petroleum coke consumption.

Claims (2)

FURNACE FOR PRODUCING SILICON CARBID containing a refined, lined mine with heating, reaction and cooling zones, an upper electrode axially mounted in the furnace shaft, a lower ring electrode and loading and unloading mechanisms, characterized in that, in order to improve the quality of the product and its output, the annular electrode is made with a height equal to 0.3— 0.5 internal diameter of the furnace shaft, and the height of the heating zone is 4.5—5.5 of the height of the annular electrode. 1201655 12 2 one 1201655