A parametric study on the effects of process conditions on dehydrogenation, wall shear and slag entrainment in the vacuum arc degasser using mathematical modelling

Karouni, Faris and Wynne, Bradley P and Talamantes-Silva, Jesus and Phillips, Stephen (2018) A parametric study on the effects of process conditions on dehydrogenation, wall shear and slag entrainment in the vacuum arc degasser using mathematical modelling. ISIJ International, 58 (9). pp. 1679-1686. ISSN 0915-1559 (https://doi.org/10.2355/isijinternational.ISIJINT-...)

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Abstract

The effect of vacuum pressure and argon flow rate on hydrogen degassing of molten steel in a triple plug, 100 tonne vacuum arc degasser has been examined using a three phase Eulerian CFD-mass transfer coupled model. The model takes into account the interaction between the slag, steel and argon phases over a 20-minute degassing period. Increasing the argon flowrate from 13-29 Nm3hr−1 produces a 10% increase in the hydrogen removal ratio, generating a faster melt velocity and larger slag eye. This also results in the maximum shear stress on the ladle walls increasing by a factor of 2.2 and the shear stress integrated across the wall increasing by a factor of 3.75, thus contributing to enhance refractory erosion. Within the same flowrate range the volume of entrained slag also increases by a factor of 1.4, which may result in increased nitrogen/oxygen pickup. Reducing the vacuum pressure maintains a low equilibrium hydrogen concentration and allows more efficient hydrogen removal, with a 38% reduction in the removal ratio between 102−104 Pa.

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