Strong Cl deposition was found together with moderate
sulfur, likely binding Ca, and weak aluminosilicate deposition
for blends containing Polish coal (60PC40RDF and
40PC60RDF blends in Fig. 7). Weak sulfur and strong aluminosilicate depositions were typically found with SAC/
RDF blends at all probe locations, and there was no Cl
deposition. On this basis, we suggest that sulfur could not
prevent alkali chlorides deposition with the blends studied
here. The protective power of the coal rather originated from
aluminosilicates.
Fig. 8 shows the results of spot analysis at lee-side of both
probes from the 40PC60RDF test. Points 1 and 2 show how
chlorine appeared together with S and Ca or with alkalies during weak deposition (Al+Si10 wt.%) prevented Cl deposition and
reduced alkali deposition. Potassium was present in amounts
up to 5 wt.%, however (point 5 in Fig. 8). These findings,
together with the result of bulk deposit analysis, strongly
suggest alkali aluminosilicate formation as the dominant path for alkali sequestration during combustion of the coal-containing
blends.