The temperature of molten glass in glass furnace forehearth is higher than 1100 ℃, thus requiring electric heating electrode material to have good high temperature performance. Besides, the contact resistance of electrode to molten glass should as small as possible and the electrode should not pollute molten glass or small pollution. Molybdenum electrode has high temperature, corrosion resistance and other properties. Besides, it react with molten glass will produce colorless products, which will not affect glass’ quality. What’s more, the price is reasonable. So molybdenum electrode is an ideal electrode material for glass furnace forehearth. Molybdenum electrode has many excellent characteristics, so China domestic and foreign glass furnace forehearth electric heating all use molybdenum electrode. And molybdenum electrodes have rod-shaped and plate-shaped two kinds.
Rod-shaped and Plate-shaped Molybdenum Electrode
Rod-shaped electrode is installed by heat, which is until the molten glass in forehearth reached a certain height, then the electrode directly inserts into the high-temperature molten glass. Installing electrode by this way can prevent electrode being oxidized. The advantage of this installment is, easy to replace, install and maintain, on the other hand, the disadvantage is uneven heating. This is mainly because rod-shaped electrode has small conductive area, and not on the same plane, so the power line which is electric field distributes in the forehreath is uneven. What’s more, rod-shaped electrodes have large usage amount and investment. To make forehearth molten glass can reach sufficient thermal uniformity, so in the forehearth there should install dozen of molybdenum electrodes, or even more.
Plate-shaped molybdenum electrode can be installed to the side wall of the forehearth in refractory martial, which can eliminate the temperature difference between central and both sides molten glass and the center of the glass material channel. At the same time the contact area of electrode glass in molten glass is large. Besides, the electric field distribution uniform, low current density, uniform heating, it is good to improving molten glass uniformity and thermal stability. However, plate-shaped electrode is easily oxidized and difficult to install, thus greatly limiting its application. T-type structure determines plate-shaped molybdenum electrodes should install by cold way. At the same time, in order to prevent electrode oxidation should take certain protective measures, such as using glass fiber to cover electrode, to avoid prolonged flame baking, and to lead the molten glass in a short time.