Electric Arc Furnace: Analysis of the Advantages of Bottom-Blowing Technology

Electric Arc Furnace: Analysis of the Advantages of Bottom-Blowing Technology

Bottom-blowing technology in electric arc furnaces (EAFs) provides several key metallurgical and operational benefits:

(1) Enhances Scrap Melting and Reduces Cold Zones

The stirring action promotes scrap melting and helps eliminate the "cold zones" that typically exist in the EAF steelmaking process. This reduces the "soft melting" phenomenon in these areas, leading to more uniform heat distribution.

(2) Accelerates Metallurgical Reactions

Bottom stirring increases the reaction rate at the steel-slag interface. This enhances the adsorption and removal of non-metallic inclusions, accelerates dephosphorization and decarburization, and positively contributes to shortening the overall smelting cycle.

(3) Improves Bath Homogeneity and Reduces Tapping Temperature

Increased molten steel velocity within the bath helps eliminate temperature stratification. This leads to a more thermally uniform molten pool, which can allow for a lower tapping temperature without compromising process requirements.

(4) Optimizes Slag Chemistry and Reduces Iron Loss

The stirring promotes equilibrium conditions at the steel-slag interface, reducing the iron oxide (FeO) content in the slag. This directly benefits metallic yield by minimizing iron loss to the slag.

(5) Extends Furnace Lining Life

The combined effect of a lower tapping temperature and reduced FeO content in the slag results in less thermal and chemical attack on the refractory lining, thereby extending its service life.

Operational Considerations

During the first heat of a new campaign, bottom blowing is typically not initiated. The permeable plugs (tuyeres) can be replaced when severely worn, using a procedure similar to replacing an EBT (Eccentric Bottom Tapping) assembly.

The optimal gas supply pressure generally ranges from 0.3 to 1.2 MPa. The specific flow rate (at standard conditions) for effective stirring is typically controlled within 0.001 to 0.002 m³/(min·t).

Common bottom-blowing gases include nitrogen, carbon dioxide, and argon. Using argon can help reduce the nitrogen content in the final steel. To optimize costs, some manufacturers implement gas switching, using different media (e.g., nitrogen, CO₂) during various stages of the heat, reserving argon for the final refining period.

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