Effect of cooling rate on coal slag viscosity under a reducing atmosphere

Abstract

Coal slag viscosity was measured under constant cooling rate conditions. Low cooling rates of 2, 5, and 8 °C/min were employed to determine the deviation in viscosity from the equilibrium viscosity, and rapid cooling rates of several hundreds °C/min to investigate the changes in the slag viscosity under slag tap conditions. A concentric cylindrical slag viscometer was modified to allow for rapid cooling of slag. The rapid cooling was obtained by injecting water around the crucible. The temperature was measured on the outside of the crucible, and the actual cooling rate of the slag was calculated from the transient heat balance. As expected, higher cooling rates gave lower viscosities, showing 25°C deviation in Tcv even at a cooling rate of 2°C/min, compared to the isothermal measurement. Under rapid cooling rates, two slag samples remained fluid to below 1000 °C at the highest cooling rate attained.