Alkaline flux dissociation in blast furnace tuyere bird’s nest: Part 1: CaO dissolution kinetics and slag physicochemical evolution in the coal-coke-slag

• Published in: Fuel (Guildford) 2024-09, Vol.372, p.132179, Article 132179
• Main Authors: Guo, Ziyu, Zong, Yanbing, Zhang, Jianliang, Zhao, Puzhuo, Xu, Zhe, Liu, Yanxiang, Ye, Cuiting, Jiao, Kexin
• Format: Article
• Language: English
• Subjects: Alkaline flux dissolution kinetic; Bird’s nest area; Blast furnace; Coal-coke-slag; Low carbon
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2024.132179

[Display omitted] •The dissolution limit content of CaO dissolved in coal-coke-slag was characterized.•The dissolution rate of CaO and properties evolution of coal-coke-slag were analyzed.•The dissolution mechanism of CaO dissolved in coal-coke-slag was revealed.•The injected content of CaO in the blast furnace tuyere was quantified. In the pursuit of optimizing smelting efficiency and minimizing carbon emissions in blast furnace operations, the strategic introduction of the tuyere alkaline flux injection, particularly in managing the viscosity of the coal-coke-slag in the bird’s nest region, is investigated. This study focused on exploring the dynamics of CaO dissolution within the slag of the coal-coke-slag in the bird’s nest area of a 2200 m3 blast furnace in China, particularly under conditions of instability. Quantitative analysis revealed that at 1550 °C, the CaO maximal dissolution capacity reached 62.05 wt%, with an average rate constant of dissolution observed at 4.65 × 10−4 s−1. The dissolution mechanism was characterized by interfacial dissociation, mass transfer diffusion, and the attainment of a dynamic equilibrium, predominantly influenced by the Ca2+ concentration gradient within the slag. This process facilitates the depolymerization of the slag’s network structure, heavily influenced by the aluminum oxide tetrahedron, effectively reducing slag viscosity. Further, the study quantified the optimal CaO injection content through the tuyere, suggesting a range of 4.00–5.32 kg/tHM, contingent on the use of high-quality raw fuel and advanced high wind temperature technology. This work contributes valuable theoretical insights towards enhancing the efficiency and sustainability of smelting operations, applicable to both conventional and high pellet blast furnaces, marking a significant step forward in the development of low-carbon metallurgical processes.