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High Temperature Properties of BOF Slag and its Behaviour in the Blast Furnace
Author(s) -
Ökvist Lena Sundqvist
Publication year - 2004
Publication title -
steel research international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.603
H-Index - 49
eISSN - 1869-344X
pISSN - 1611-3683
DOI - 10.1002/srin.200405844
Subject(s) - slag (welding) , metallurgy , blast furnace , wüstite , smelting , raceway , coke , ground granulated blast furnace slag , tuyere , materials science , steelmaking , electric arc furnace , pellets , softening point , melting point , magnetite , composite material , cement , lubrication
Slag formation in the bosh and raceway is an important issue in the blast furnace process. SSAB works in Luleå operate with 100 % olivine pellets. A small amount of basic fluxes is added from the top, slag and limestone are used. To improve the control of slag formation, a concept with injection of BOF slag was evaluated and tested in the LKAB experimental blast furnace (EBF). In this paper, the behaviour of BOF slag as a slag former, when it is top‐charged or tuyere‐injected, is evaluated based on the results from a laboratory study including reduction tests, softening and melting tests, XRD analyses and SEM analyses. Samples taken from the EBF during excavation, and with a burden probe during operation, are examined. The evaluations show that the melting point of BOF slag is quite low and will not be increased, because of the partial reduction that occurs in the BF shaft. When carbon is present at high temperatures, reduction proceeds and a high basicity slag with a high melting point, consisting of di‐ and tricalcium silicates, is formed. When pellets with a basicity of B2 ~ 1 are used, a slag with similar properties can be formed as a result of interaction with the BOF slag. BOF slag in combination with olivine pellets with a low basicity generates a slag with intermediate basicity and the reduction of iron oxides in the slag has a small effect on the melting temperature. The BOF slag decreases the melting point of coal and coke ashes.