Formation Mechanism of the Brittle Layer in Carbon Brick of Blast Furnace Hearth

Abstract

The brittle layer of carbon brick in a Chinese 4000 m3 blast furnace hearth is investigated in detail, and its formation mechanism is proposed correspondingly. The occurrence form of the brittle layer in carbon brick is characterized by chemical analysis, X‐ray diffraction, and scanning electron microscopy–energy dispersive spectroscopy. The results show that obvious harmful element (K, Na, and Zn) erosion on the sidewall of the blast furnace hearth is observed, in which Zn erosion is dominant. The K2O, Na2O, and KCl produced in the carbon brick by K and Na are the inducement of the brittle layer formation, and the ZnO formed by Zn is the main reason for the brittle layer formation. The thermal stress caused by temperature gradients in carbon brick is greater than its bending strength, which will increase the microcracks in carbon brick. The brittle layer has a lower thermal conductivity due to higher porosity, resulting in a large temperature difference. The resulting thermal stress will aggravate the embrittlement degree.

Erosion Mechanism of Carbon Brick in Hearth of 4000 m3 Industrial Blast Furnace

“…Among them, Zinc vapor may enter the carbon brick through the cracks and holes. As zinc vapor continues to deepen, the temperature decreases, and the zinc vapor liquefies and reacts with the CO to form ZnO [13][14][15], as shown in Equation (1). The iron phase in the carbon brick may be oxidized to form iron oxide in the process of overhauling the furnace, as shown in Equation (2).…”

“…The pressure generated by molten iron is opposite to the direction of the surface ten- According to the law of thermodynamics, the change in surface energy should be the same as the work performed by the external force, that is, the change in surface energy should be the same as the work performed by the additional pressure generated. dG = δW 1 = 4πR 2 P 1 .dR (15) It can be obtained:…”

The Effects of Different Zn Forms on Sintering Basic Characteristics of Iron Ore

“…Hence, the chemical composition of the sinter significantly affects the operation stability of the blast furnace. Zn compounds in sinter are reduced to Zn vapor in the high-temperature area of the blast furnace, most of Zn vapor is oxidized to ZnO, which is adsorbed on the surfaces of charges and furnace wall, resulting in the worsening of permeability of the charges and corrosion of refractories [ 4 , 5 , 6 , 7 ]. In recent years, domestic steel enterprises have regarded metallurgical dust generated in the steel production process as sintering raw materials to control the cost and reduce the pollution [ 8 , 9 ].…”