This is especially visible in the low temperature position B
(Figure 9). The deposits of sodium (Na), potassium (K),
chlorine (Cl) and sulphur (S) decrease using the additives. The
high amount of loose fly ash (that was removed before the
analysis) may protect the substrates from further particles
being accumulated on the substrate; however, this may not be
the case for the gravimetric measurements, where at least half
of the rings also cover the upper part of the heat exchanger,
where less fly ash was accumulated. The gravimetric
measurements in Figure 6 indicate increased amount of
deposits using the magnesium additives. Thus reliable
conclusions from the SEM-analysis cannot be drawn.