Ore Heat-Treating Furnace

an electric-arc furnace used in reducing operations. Ore heat-treating furnaces are usually equipped with sealed crowns; these are called closed, or hermetic, furnaces. Less often, the furnaces have a vat that is open on top; these are known as open furnaces. The vat may be round, triangular, or rectangular and either stationary or rotary. The steel furnace shell is lined with refractory materials. An electric current is passed through the vat, which is filled with a burden, across the furnace transformers, a short network of copper or aluminum conductors, and self-baking electrodes (less often, carbon or graphitized electrodes).

Although ore heat-treating furnaces generally have three electrodes arranged at the apexes of an equilateral triangle or six electrodes arranged in a line, some furnaces have one, two, 12, or 24 electrodes. The furnace transformers, which are installed in separate rooms close to the furnaces, use high operating currents (up to 150 kiloamperes) and have from 17 to 46 levels at which power can be supplied to the furnace (from 100 to 600 volts). The nominal capacities of the furnaces vary from 16.5 to 72 megavolt-amperes. The charge materials are heated and melted mainly by the powerful electric arc and by the heat generated by passing the current through the charge and melt. The temperature in the reaction zone ranges from 1500° to 2000°C.

Ore heat-treating furnaces are used in ferrous and nonferrous metallurgy, for example, in the smelting of ferroalloys, pig iron, and copper and nickel mattes, and in the production of fusible refractory materials and synthetic slags. They are also used in the chemical industry, in the production of phosphorus and calcium carbide.