ANS:B - Indirect arc

An indirect arc furnace is a type of electric arc furnace (EAF) where the electric arc is generated outside the furnace vessel, and the heat is transferred to the metal charge indirectly. In an indirect arc furnace, the arc is established between two or more carbon electrodes or graphite rods, and the heat generated by the arc is radiated or transferred through a refractory lining to the metal charge inside the furnace. Here's a breakdown of how an indirect arc furnace works:

1. Arc Generation: The electric arc is generated between the carbon electrodes or graphite rods located outside the furnace vessel. This arc generates intense heat, reaching temperatures of several thousand degrees Celsius.
2. Radiation and Conduction: The heat generated by the arc is radiated and conducted through the refractory lining of the furnace vessel. The refractory lining serves as insulation and helps to contain the heat within the furnace.
3. Heating the Metal Charge: The intense heat from the arc transfers through the refractory lining to the metal charge inside the furnace vessel. The metal charge, typically consisting of scrap metal or raw materials, begins to melt and undergo the desired metallurgical processes, such as refining or alloying.
4. Control and Operation: Indirect arc furnaces offer flexibility in operation and temperature control. By adjusting the power input and electrode positioning, operators can regulate the temperature and energy input to the furnace to achieve the desired melting and refining conditions.
5. Applications: Indirect arc furnaces are commonly used in steelmaking processes, particularly for melting and refining ferrous metals. They are suitable for melting a wide range of steel scrap and raw materials, making them versatile in steel production.