A Model for Estimation of Viscosity of Molten Silicate Slag

Osaka University, Suika, Ōsaka, Japan
ISIJ International (Impact Factor: 1.07). 01/2005; 45(5):651-656. DOI: 10.2355/isijinternational.45.651

ABSTRACT A model to evaluate the viscosity of silicate melts is proposed on the basis of the bonding states of oxygen, i.e. non-bridging oxygen and free oxygen ions, in the silicate structure, considering the flow mechanism of the melts with the network structure. Gaye's model is applied to evaluate the bonding state of oxygen ions using thermodynamic databases. The present model can reproduce the composition dependence of the viscosities for silicate melts in binary systems with a single model parameter, as well as the composition dependence of the viscosities for ternary systems in a wide composition range.

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    International Journal of Materials Research (formerly Zeitschrift fuer Metallkunde) 11/2008; 99(11):1185-1194. DOI:10.3139/146.101752 · 0.68 Impact Factor
  • International Journal of Materials Research (formerly Zeitschrift fuer Metallkunde) 11/2008; 99(11):1195-1209. DOI:10.3139/146.101753 · 0.68 Impact Factor
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    ABSTRACT: The viscosity of slag and the thermal conductivity of ash deposits are among two of the most important constitutive parameters that need to be studied. The accurate formulation or representations of the (transport) properties of coal present a special challenge of modeling efforts in computational fluid dynamics applications. Studies have indicated that slag viscosity must be within a certain range of temperatures for tapping and the membrane wall to be accessible, for example, between 1,300 °C and 1,500 °C, the viscosity is approximately 25 Pa·s. As the operating temperature decreases, the slag cools and solid crystals begin to form. Since slag behaves as a non-linear fluid, we discuss the constitutive modeling of slag and the important parameters that must be studied. We propose a new constitutive model, where the stress tensor not only has a yield stress part, but it also has a viscous part with a shear rate dependency of the viscosity, along with temperature and concentration dependency, while allowing for the possibility of the normal stress effects. In Part I, we reviewed, identify and discuss the key coal ash properties and the operating conditions impacting slag behavior.
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