An Empirical Method for the Prediction of Coal Ash Slag Viscosity

Abstract

A new method for the prediction of the viscosity of coal ash slags, in the Newtonian region, is presented. The technique is modeled on experimental viscosity data less than 1000 Pa s and hence is most reliable in that region. The capability of the model in predicting the viscosity of slags from coal ash was found to be superior to a number of the most commonly used empirical models found in the literature, which are based on simplified oxide melts or British coal ash slags. The method also provides an indication of the relative fluxing strength of the basic oxides usually found in coal ash slags. It was found that the fluxing strength is related to the inverse of the cation radius.

Effects of Design/Operating Parameters and Physical Properties on Slag Thickness and Heat Transfer during Coal Gasification

“…Because of the difficulty in measuring the viscosity at high temperatures, several correlations based on the slag composition have been proposed [23,[27][28][29][30]. However, these correlations exhibited deviations from the measured data depending on the ash samples [31][32][33] and with each other [34].…”

Computational Modelling of a Tangentially Fired Boiler With Deposit Formation Phenomena

“…To be useful for deposition modelling, ash viscosity must be described as a function of particle temperature and ash composition. In the current paper a model proposed in (Browning et al, 2003) is used. The model is a function of mole fractions of Si, Al, Ca, Fe, Mg, Na, K, Mn, Ti, S and provides improvements over other models in matching experimental data.…”

Slag Behavior in Gasifiers. Part II: Constitutive Modeling of Slag

“…Browning et al [15] provide a brief review of the various slag viscosity models, and they observed that the Kamanovitch-Urbain method is the most accurate for SiO 2 -Al 2 O 3 -CaO-MgO slags. They also suggested an empirical method to obtain the viscosity of the slag that depends on finding the temperature shift, among other parameters.…”

“…Such a sharp gradient causes various types of responses including the creation of different sub-layers. Studies have indicated that slag viscosity must be within a certain range of temperatures for tapping and for the membrane wall to be accessible, for example, between 1,300 °C and 1,500 °C, the viscosity is approximately 25 Pa·s [15].…”