Slag Viscosity Measurements.
Viscosity is the most important physical property of slag and ash, as it influences their ability to flow or develop strength. Using different viscosity models, MTI can predict the viscosity of a slag or ash. In some cases, actual physical measurements are necessary if the composition is outside the ranges where predictions are less accurate.
Viscosity of slags can be measured in either oxidizing or reducing environments. Viscosity in the range of 10-3000 poise is measured with a rotating-bob viscometer as the temperature drops from 1500°C to slag freezing. This method is accurate to ±5%.
T250 is the temperature at a viscosity of 250 poise, at which slag begins to flow (and develop strength). The method used to predict T250 of slag or ash is taken from U.S. Patent 4,009,605 “Method for Determining T250 Temperature.” The sample is placed in a furnace and heated at a steady rate. The test is monitored through the stages of melting; most tests are captured on video to better determine the T250.