LOCAL-STRUCTURE OF A LIGNITIC COAL ASH SLAG AND ITS EFFECT ON VISCOSITY

The increase of viscosity with decreasing temperature for Beulah, ND, coal ash is explained by changes in the local structure of the slag re sulting from the growth of microphases. The local structure of quenche d slag was investigated by infrared (IR) and Mossbauer spectroscopies, differential thermal analysis (DTA), electrical resistivity, and X-ra y diffraction (XRD) and scanning electron microscopy (SEM). The IR tes t was performed on samples quenched from temperatures ranging from 110 0 to 1500-degrees-C. IR spectra showed seven visually resolved bands c entered at 750, 870, 950, 1090, 1150, 1250, and 1350 cm-1. The intense broad bands in the region of 950-1250 mum-1 were assigned to antisymm etric stretch vibrations of Si-O-Si and Si-O-Al modes of silica tetrah edra. The band at 1350 em-1 seems to pertain to an impurity in the sla g with a lower force constant than that of Si-O. The Fe3+/SIGMAFe rati o determined by Mossbauer spectroscopy for Beulah slag is larger at 14 00-degrees-C (0.96) than at 1500-degrees-C (0.88). DTA and electrical resistivity of Beulah melt indicated on rearrangements of clusters (st ructural units) likely resulted from the agglomeration of individual c lusters.