Failure mechanisms of blast furnace tuyeres and mitigation strategies: A comprehensive review

Iron blast furnace is a gigantic counter-current reactor and contributes to the majority of ∼1.9 billion tonnes of steel produced annually. Among various components of the blast furnace, tuyeres made of high-purity copper with protective coatings are the most critical in nature from the viewpoint of smooth furnace operation without interruptions. These water-cooled copper tuyeres inject preheated blast between 1200–1300 °C into the furnace for oxidation of coke and subsequent reduction of iron ore from the gaseous reductants. In the present review article, different failure mechanisms of the tuyeres are clarified, and the underlying reasons are stated from the viewpoint of the manufacturing aspects of the tuyeres, its design and application of coatings, operational effects and the quality of raw materials being used in the blast furnace. Predominant failure mechanisms include melting loss due to slag and liquid iron, erosion caused by pulverized coal, thermal fatigue exacerbated by the metallurgical segregation and heterogeneities within the coatings, Zn-diffusion induced Brass formation and subsequent deterioration due to reduced thermal conductivity and chloride induced corrosion cracking. A state-of-the-art review of various strategies for improved reliability and service life of Cu tuyere and way forward for further research is proposed in this work. It is expected to benefit the blast furnace operations as well as failure analysts and researchers working to improve the reliability of the tuyeres and other components made of Cu.