• • Optimal gas−liquid mixing is achieved at melt viscosities of 0.01 and 0.5 Pa·s, whereas minimal splashing occurs within 0.1−0.25 Pa·s (approximately 1076−1100 °C); this non-overlapping window forces operators to prioritize either mixing or splash suppression, directly affecting reaction completeness and metal recovery.
• • Shear stress on the furnace lining increases with melt viscosity and rises particularly rapidly in the 0.1−0.25 Pa·s range, making this interval a critical erosion-risk zone that accelerates refractory wear and shortens campaign life.
• • The regions surrounding the oxygen lances are the most susceptible to erosion, identifying localized lance-adjacent refractory as the primary failure point and directing maintenance and design efforts to this area.
• • A recommended operating viscosity of 0.01−0.1 Pa·s minimizes erosion while maintaining acceptable mixing, providing a concrete control target for industrial bottom-blowing lead smelting that co-processes lead-containing waste materials.