ELECTRIC GLASS FURNACE WITH ZONE TEMPERATURE CONTROL

摘要

An improved furnace for electrically heating material such as molten glass. At least one and, preferably, a plurality of controlled thermal zones are established transverse to the direction of glass flow through the furnace. For each thermal zone, at least two electrical circuits supply power to at least three submerged electrodes for heating the glass. A control circuit is provided to maintain substantially constant the square of the average current in each circuit. If a predetermined permissible temperature variation is exceeded in the molten glass in any thermal zone, power to all electrodes for such thermal zone is either reduced or interrupted. The thermal zones may also be interdependent for maintaining a desired temperature profile in the material flow direction.