Environment and Operating Conditions of Electric Arc Furnaces

Environment and Operating Conditions of Electric Arc Furnaces

Electric arc furnaces (EAFs) employed for smelting typically operate in three distinct characteristic stages:

1.  Melting Stage: At the onset, solid charge materials are melted. This phase has the highest energy demand of the entire cycle.

2.  Initial Refining and Heating Stage: This stage follows the primary melt.

3.  Refining Period: During this stage, the energy input is primarily required to offset thermal losses and maintain the process.

A typical AC electric arc furnace has a smelting cycle ranging from approximately 3 to 8 hours. This duration depends on factors such as the power supply circuit parameters, the furnace capacity, and the specific smelting process. The melting period itself lasts about 0.5 to 2 hours. During this time, the furnace acts as a highly unbalanced three-phase impact load, with extremely unstable current and substantial power consumption, accounting for roughly 60% to 70% of the total energy used. In contrast, during the oxidation and reduction refining periods, both voltage fluctuations and power consumption are significantly reduced.

The operational behavior of an electric arc furnace during scrap metal smelting is characterized by:

   Frequent arc extinction and re-ignition at the beginning of the melt.

   Continuous arc fluctuations throughout the full melting period, leading to sharp and rapid current variations.

   Occurrence of short circuits due to the collapse of charged material.

The power factor at the operating point of a standard electric arc furnace circuit typically ranges from 0.8 to 0.85. For high-power electric arc furnaces, this value is often lower, between 0.7 and 0.8. A lower power factor inherently results in reduced power efficiency for the furnace operation.

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