Numerical simulation study on design optimization and layout of blast furnace oxygen-coal lances based on combustion enhancement mechanism

The tuyere raceway is the primary reaction zone for pulverized-coal combustion and gasification, while oxygen-coal injection is an effective strategy for enhancing low-carbon blast furnace ironmaking. However, the coupled effects of lance diameter, insertion mode, nozzle form, and double-lance layout on oxygen-coal mixing and competitive combustion are still not fully understood. In this study, a diameter-matching approach derived from Bernoulli's principle and pipeline pressure-drop analysis was combined with a three-dimensional Eulerian-Lagrangian CFD model to evaluate representative oxygen-coal lance configurations under identical blast furnace operating conditions. The novelty of this study lies in three aspects: oxygen-flow-based diameter matching, systematic comparison of structural parameters, and mechanistic interpretation of combustion enhancement through jet dynamics, gas-solid heat and mass transfer, and particle residence time. Under the investigated operating conditions, the 36 mm diameter, semi-through-type insertion, and recessed convergent nozzle generated a stronger thermal field and more effective gas-solid mixing than the other single-lance configurations, increasing the burnout rate from 67.48% to 72.23%. For the double-lance configuration, the horizontal layout exhibited a more symmetric distribution of temperature and species than the vertical layout. Horizontally opposed jets established a stronger central mixing zone, promoted synchronized particle dispersion, and increased the burnout rate from 78.54% to 82.38%. These findings demonstrate that appropriate lance geometry matching and a horizontal double-lance layout can effectively enhance oxygen-coal combustion performance under the present modeling and operating conditions.