Kinetics and Mechanisms of Dolime Dissolution in Steelmaking Slag
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the steelmaking process, an effective and rapid slag formation during the oxygen blowing time has a significant impact on the refining reactions and is highly influenced by the rate of flux dissolution in the slag. Early slag formation with the desired properties greatly affects the process productivity and reduces the production costs. Reactive slag, which is rich in calcium oxide, is crucial for the effective removal of impurities from the metal. Dolime is added to the converter vessel to saturate slag with MgO and as the result to minimize the refractory lining degradation. Thus, the study of flux dissolution kinetics allows us to achieve effective slag formation with the desired composition and properties for better process control. When lime is charged to the converter its dissolution in the slag proceeds in three main stages[1]:
ELIZAVETA CHEREMISINA is with the K1-Met GmbH, 4020 Linz, Austria. Contact e-mail: [email protected] JOHANNES SCHENK is with the Montanuniversita¨t Leoben, 8700 Leoben, Austria. LUDWIG NOCKE is with the Voestalpine Stahl GmbH, 4020 Linz, Austria. ALEXANDER PAUL is with the Voestalpine Stahl GmbH Donawitz, 8700 Leoben, Austria. GERALD WIMMER is with the Primetals Technologies, 4020 Linz, Austria. Manuscript submitted October 3, 2018. Article published online March 29, 2019. METALLURGICAL AND MATERIALS TRANSACTIONS B
The penetration of flux pores by the liquid slag being heated from the jet impact zone. The viscosity of slag and the pore size of the dissolving material influence the extent of slag penetration. The reaction of the liquid iron silicate with solid lime/dolime with the formation of reaction products, such as liquid calciowustite and solid dicalcium silicate, which is well known for the formation of a dense layer around the dissolving flux particles and for limiting the dissolution process.[2–5] At the last stage of the blow, by raising the temperature and iron content in the slag, the solid dicalcium silicate layer softens due to the FeO attack. After the rapture of the solid product’s layer, the dissolution of flux progresses. Many studies have been conducted over the past decades on the topic of CaO and MgO dissolution in converter slag.[6–15] According to the studies[1–5] the dissolution of lime and MgO-based materials proceeds with the formation of dicalcium silicate and magnesiowustite with high melting points. Such compounds form a dense layer around dissolving particles, thus inhibiting the diffusion transport. In a study of the kinetic flux dissolution in the converter, Dogan et al.[2] confirmed the formation of solid magnesiowustite and dicalcium silicate on the surface of dolomite particles. It can be explained by the tendency of MgO to react with FeO, resulting in the formation of a high-temperature solid phase.
VOLUME 50B, JUNE 2019—1269
Deng[4] studied the dissolution behavior of lime and dolomite in the converter slag. It was concluded that a discontinuous dicalcium silicate layer and MgOÆFe2O3 magnesioferrite particles were found on the surface
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