Characterization and Properties of Scaffold in a Dissected Blast Furnace Hearth

Abstract

The blast furnace scaffold can only be obtained while the blast furnace shut down after operating for many years. Its characteristics and properties are important for the blast furnace campaign life. The key to delaying the carbon brick corrosion in blast furnace hearth is the scaffold formed between the melt and the carbon brick. In an emergency shutdown blast furnace, the scaffold in hearth is completely preserved, and the scaffold on the surface of the carbon brick above and below the taphole in hearth are sampled. The purpose of this study is to describe the characterization and properties of the scaffold in hearth. The paper presents results from investigations using electron imaging techniques such as Transmission Electron Microscopy (TEM), Optical Microscope (OM), Scanning Electron Microscope combined with Energy Dispersive Spectrometer (SEM-EDS), Raman analysis and X-ray Diffraction (XRD). The main component of the slag skull above the taphole is similar to the final slag and is rich in harmful elements. The thermal conductivity of the scaffold is about 2 W/(m·K) and the viscosity as well as the solidus temperature are higher than the final slag. The slag skull acts to isolate and contain harmful elements. The phase on the hot surface of the carbon brick below the taphole is mainly consist of graphite and the large-grained graphite phase has a random spatial network distribution in the iron matrix. The slag skull and the graphite serves to segregate the melt and harmful element, thereby protecting the carbon brick and extending hearth life.