Self-Baking Electrodes and Graphite Products for Non-Steelmaking Submerged Arc Furnaces: Applications

2025-11-07 16:05:45

In steelmaking, ferromanganese (FeMn) and ferrosilicon (FeSi) ferroalloys are used for deoxidation or composition adjustment. For producing calcium carbide (CaC₂), monocrystalline silicon, and phosphorus, carbon electrodes or self-baking electrode paste are employed. Self-baking electrode paste is a mixture composed of aggregates such as coke, graphite, and anthracite coal blended with coal tar pitch. This paste is filled into a metal cylindrical casing; after energization, it is gradually sintered into a conductive carbon electrode through resistive heating generated by the current itself and heat transferred from the furnace.

For large-scale furnaces, self-baking electrodes offer greater operational flexibility, eliminating the need for electrode jointing and simplifying handling. Their cost-effectiveness makes them the predominant choice for almost all non-steelmaking submerged arc furnaces. However, driven by environmental concerns, self-baking electrodes are now being replaced by carbon electrodes or Graphite electrodes.

Although not for steelmaking, calcium carbide (CaC₂) is likewise produced by melting quicklime (CaO) and carbonaceous materials (e.g., coke, anthracite coal) in an electric furnace at 2,000–3,000°C. This specialized submerged arc furnace functions as a resistance heating furnace where the carbon electrode tips are submerged in the raw material charge to suppress CaC₂ decomposition and enhance thermal efficiency. Molten calcium carbide is tapped from the arc-opened outlet at the lower sidewall of the furnace.

For operations requiring pre-drilled electrodes with diameters of 50–100 mm and lengths of 1,000–2,000 mm, artificial graphite electrodes are employed. In representative calcium carbide production furnaces (closed-type electric arc furnaces), phosphorus is manufactured by reducing phosphate rock with coke. This reaction involves a highly endothermic process at 1,400–1,500°C, consuming substantial electrical energy primarily as heat. Due to significantly lower electrode consumption compared to ferroalloy or industrial silicon production, baked carbon electrodes are commonly utilized