Optimization of the natural gas ladle baking process using pure oxygen-assisted staged combustion

Ladle preheating technology is critical to metallurgical production stability, product quality, energy efficiency, and emission control. However, conventional combustion approaches face multiple drawbacks. They suffer from insufficient combustion, uneven temperature distribution and high NO x emissions. In response, this study innovatively introduces a staged oxy-fuel combustion strategy for ladle preheating. A three-dimensional physical model of a 100t ladle was established, and numerical simulations of the staged pure oxygen combustion preheating process were conducted using computational fluid dynamics (CFD). The standard k-ε turbulence model, eddy-dissipation combustion model, and P-1 radiation model were employed. Simulation results were validated against measurements from a 1:3 scale experimental setup. Four cases were examined: conventional pure oxygen combustion, and three staged pure oxygen combustion configurations with O 1 :O 2 volume ratios of 3:7, 2:8, and 1:9. A systematic analysis was conducted to evaluate the effects of varying O 1 :O 2 ratios on the flow field, temperature distribution, flame morphology, lining temperature, and NO x formation characteristics inside the ladle. The results show that staged pure oxygen combustion enhances flow field organization, weakens the central jet intensity, achieves a more homogeneous momentum distribution, and mitigates erosion of the ladle bottom by high-temperature flue gas. Among the staged configurations, the O 1 :O 2  = 2:8 condition exhibits the best overall performance. It can form stable and well-proportioned flames with proper length and evenly distributed high-temperature regions. Under this condition, the lining heating rate reaches 57.9 K/h. Its inner wall temperature is 68.9 K higher than that under conventional pure oxygen combustion. Moreover, the radial temperature difference at the ladle bottom is only 29.35 K, indicating significantly improved temperature uniformity and reduced risk of thermal shock to the refractory materials. Furthermore, staged pure oxygen combustion establishes an oxygen concentration gradient within the combustion zone, effectively suppressing thermal NO x formation. Compared with conventional pure oxygen combustion, the O 1 :O 2  = 3:7 condition achieves a maximum NO x emission reduction of 82.5%, while the 2:8 and 1:9 conditions also yield substantial reductions. This study provides theoretical and technical support for the green and low-carbon optimization of industrial ladle baking. It can effectively guide the parameter adjustment of on-site ladle baking with O 1 (primary oxygen) and O 2 (secondary oxygen), reduce energy consumption and pollutant emissions, and promote the sustainable development of the steel industry.