Date of Award
Master of Science (MS)
The feasibility of applying differential thermal analysis techniques to relate variance in the chemical analysis of fouling and non-fouling lignite ashes to specific differential temperature peaks was investigated.
Analysis was accomplished by heating powdered samples (minus 200 Tyler mesh) at an average heating rate of 13° F per minute from ambient conditions to 1*850° F in an oxidising atmosphere. The samples were contained in a cylindrical nickel sample cell and temperature was monitored with ehromel-alumel thermocouples.
Boiler flyash samples* laboratory ashed samples of natural lignite and synthetic ash mixtures based on the chemical analysis of the natural lignites were prepared and subjected to DTA analysis.
Reactions* transitions and melting points were characterized using cumulative synthetic mixtures. Peaks were obtained for silica* magnesium oxide* calcium oxide* potassium sulfate and sodium sulfate.
The fouling properties of the original lignites could not be detected by DTA analysis of boiler flyash samples. The natural fouling and non-fouling ash samples exhibited dissimilar DTA curves during initial heatings which could be used to differentiate fouling lignite from non-fouling lignite. It was found* however, that the differences observed in the DTA curves were eliminated after repeated high temperature exposure.
Before definite conclusions concerning the acceptance or rejection of a lignite based on the differences in DTA curves* the effect of prior temperature exposure must be thoroughly examined and additional natural lignite ash samples must be analyzed.
DTA techniques show considerable promise as a means of determining fouling properties of lignite and the technique should he used at higher temperatures to enable DTA analysis during the fusion of the lignite ash.
Bredahl, Robert G., "Differential Thermal Analysis of Lignite Ash" (1965). Theses and Dissertations. 4007.