2022 Volume 62 Issue 11 Pages 2236-2243
In-depth understanding of the existence state and migration behavior of K, Na, S, Ti in the BF hearth is essential to improve the campaign life and optimize the operation process of the blast furnace. In the study, deadman and carbon brick samples were extracted along the radial direction from a large commercial BF during dissection investigation. The microscopic morphology of the samples and the migration behavior of K, Na, S, Ti were analyzed. It was found that a layer of minerals existed on the surface of deadman coke in hearth, and high melting temperature phases such as CaS and TiN as well as slag with high aluminum were existed at the coke-slag-iron interface. K, Na compound present widespread in the deadman coke and carbon brick. The formation of mineral layer reduced the coke dissolution rate, thereby delaying the renewal rate of the deadman. With the dissolution of coke, minerals flow out from the surface of coke and precipitate as alumina and MgAl2O4 spinel, which reduces the voidage of the deadman. Meanwhile, slag is sufficiently desulfurized with the iron to form a large amount of CaS accumulation at the hearth sidewall, which intensifies the iron circulation and increases the erosion of carbon brick. When the slag is in contact with the refractory, the K, Na contained in the slag provides a source of alkalis attack on the carbon bricks, and the Ti in the slag provides the possibility of forming a protective layer containing titanium on the sidewall of the hearth.
