Feasibility of BF Hearth Protection Using Spinel Formation by Slag Composition Control

Abstract

The formation of titanium carbonitride has been used as a conventional method to protect the refractory wear in the hearth. Because titanium carbonitride is formed only in the molten iron, the area that can form a protective layer in the hearth is limited. There is another possibility to protect the refractory wear by introducing the compounds with high melting point in the slags. If the compounds with high melting point are simultaneously formed in the molten iron and slag by adding TiO2, it might be more effective to form the protective layer and to prevent the refractory wear of hearth. However, the change of slag compositions and the formation of slag compounds can affect the slag viscosity and critical temperature, which might cause serious problems with blast furnace operation.In this study, to find the slag compositions for the effective compounds formation with maintaining the slag fluidity, the viscosity measurements, in-situ observation of compound formation by a confocal laser scanning microscopy and thermodynamical evaluation by FactSage has been carried out. Based on these results, the suitable slag compositions were suggested to form a protective layer in the hearth.

Thermodynamic Properties and Viscosities of High-Titanium Slags

“…The heat capacity and enthalpy change of the slag reflected the temperature resistance to the fluctuation of the slag under a specific heat input, which can be defined here as thermal stability. The heat capacity and enthalpy change of the slag can be estimated according to formulas [1] through [9] due to the crystal transformation heat, phase transformation heat, and chemical reaction heat in the slag during the melting processes. We used a FactSage computer package to conduct accurate thermodynamic calculations in this study.…”

“…Feng et al 8) investigated the effect of TiO 2 on the phase compositions of titanium-bearing slag by Fourier transform infrared spectroscopy (FTIR), showed that the polymerization degree in the slag decreased and the content of perovskite phase in the slag increases with the increase of TiO 2 content. Although the influence of TiO 2 and basicity on the viscosity of slag has been widely researched, 9) much less attention has been paid to ultra-high titanium slag from the perspective of heat input.…”

“….......................................... (5) ............................... (7) .......................................... (8)¦ ............................. (9). …”

Effects of Sulfur and Titanium Interaction in Molten Pig Iron on Erosion of Carbon Brick

“…On the other hand, raw materials containing titania charged in BF is an effective measure to protect the hearth at the end of the service. [15][16][17][18] The titania in iron ore is reduced to form titanium and the titanium is dissolved into molten…”

Economical and Efficient Protection for Blast Furnace Hearth

“…It is the concern for operators to choose the economical ore containing titania for protection. [10][11][12] The effect of titania content on metallurgical properties of the ore was investigated by many papers, 13,14) the evaluation of the economy only based on price was concluded to be one-sided, few people synthetically evaluate the economy of the ore containing titania based on the price, the flux amount, the iron production and the slag amount. 15) In addition, the evaluation index of the protection effect is lacking, the stability of the protection effect can't be guaranteed due to the change of operation, the time to increase titanium load becomes the key for operators.…”