| The formation of a liquid phase is particularly important for clinkering, agglomeration, fouling, and slagging. The calculation of the composition of the liquid was done by the SOLGASMIX program which minimized the total free energy of the system. The composition of the liquid was then used to calculate the viscosity from a comprehensive computer program which incorporated six major viscosity models. The viscosity program was interfaced with SOLGASMIX so that the predicted liquid phase composition automatically selected the most appropriate viscosity equation.;The test results from the combined SOLGASMIX-viscosity program for thirty-three chosen materials showed that the best equation for prediction of viscosity differed according to the variation of coal ash composition. To find the best equation for prediction of viscosity, the tested materials were subdivided into seven groups. The appropriate classifications of the tested materials are the key to a successful application of the combined SOLGASMIX-viscosity program to predict the viscosity of coal ash slag before a viscosity test of coal ash is carried out. They were based on the base-to-acid ratio, silica ratio, lignite factor, and percentages of SiO;In sintering tests of three different particle size fractions of ASTM coal ashes, the sinter point of coal ashes by the electrical resistance method, and the thermophysical and thermochemical changes of coal ashes were measured in a sintering furnace. For sintering tests in a drop tube furnace, the ashing temperature was determined as the temperature at which any degree of sintering of ash was not observed in the SEM photomicrograph of each coal ash. The minimum sintering temperature of coal ashes was also determined in the drop tube furnace. The bonding of the particles is governed by the sintering equation developed by Frenkel. The viscosity calculated from the Frenkel equation was compared with the viscosity predicted from the combined SOLGASMIX-viscosity program. The results of these two viscosities did not agree. Therefore, Frenkel's model is not suitable for routine testing of sintering characteristics of coal ash. |
