A STUDY OF SLAG IN LABORATORY, PILOT AND COMMERCIAL SCALE FURNACES USING FTIR MICROSCOPY, ELECTRON-MICROSCOPY AND NMR-SPECTROSCOPY

Scanning electron microscopy (SEM), electron probe microanalysis (EPMA), Fourier transform infra-red (FTIR) microscopy and Si-29 nuclear magnetic resonance spectroscopy (Si-29-NMR) have, been used to analyse the slag product from a drop tube furnace, a pilot scale testing facility and a commercial scale power plant. Essentially the same coal feed has been used in the three systems. It is shown that FTIR microscopy is a useful new tool for analysing slag deposits. Results obtained in the drop tube furnace demonstrate the formation of anorthite crystals at increased temperature (1400 to 1500-degrees-C) and reaction time (2-8 h). On the other hand data from the samples produced in the larger reactors demonstrate the significant increase in aluminium substitution in tetrahedral silica lattice with increasing temperature (1250 to 1350-degrees-C) and the formation of mullite, iron oxides and cristobalite. In the power station samples differences in amounts of these materials could be observed from the fire to the wall side of the furnace.