6. Conclusions
The composition of deposits suggested that the formation of
alkali aluminosilicates is the main path for the sequestration of
alkali chlorides from flue gas of the studied feedstocks.
Chlorine deposition was weak during strong deposition of Al
and Si and vice versa. Kaolinite was the most common
aluminosilicate in the studied coals and capable of alkali
chloride capture. Kaolinite content in South African coal was
10 T2 wt.% in fuel db and in Polish coal 5 T2 wt.%
correspondingly. When South African coal is fired with RDF,
chlorine concentrations in deposits tend to be negligible. Polish
coal did not prevent chlorine deposition as effectively.
The main differences between the results obtained with the
100 kW and 4 MW CFB reactors were in the direction of Cl
deposition. On average, Cl deposition was fairly similar in the
two reactors. Temperature of the flue gas passing the probe was
lower and the mean size of fly ash particles larger in the 4MW
CFB. As a result, alkali chlorides condensed more on coarse fly
ash particles, which tend to deposit on the wind-side by inertial
impaction rather than condensing or diffusing to the lee-side.