Date of Award


Document Type


Degree Name

Master of Science (MS)


Chemical Engineering


A suitable technique for preparation of lignite ash deposits for electron microprobe analyses was developed. Six samples were prepared and systematically analyzed on the microprobe for chemical concentrations and distribution relationships at four separate positions on the tube deposit. The six samples were collected on air cooled tubes placed in the combustion gas stream during combustion of four high sodium lignites and two low sodium lignites in the Bureau of Mines pilot plant combustor.

Sodium-sulfur compounds were found in a layer completely surrounding the tube. The thickness of this layer was reduced when covered by the bulk of the deposit.

Sodium concentration in high sodium lignites and iron concentration in low sodium lignites were highest near the tube and decreased consistently toward the outer edge of the deposit. Silicon and aluminum concentration were consistently higher in the deposit than in the laboratory-prepared ash, while the concentration of sulfur was one-third as large in the deposit as in the original ash.

Beam scanner photographs show the relationships among chemical constituents in the deposits. Forty-two distinct groups of elements were found, each of which may represent more than one chemical compound.

A mechanism of deposition was proposed.