structures clearly indicates the effect of fuel on the morphology of
accumulated ashes, and almost no individual ash grains are seen in
sample cross-sections except the test No. 3. The lack of individual
particle boundaries indicates some surface reactions and interactions
between neighboring particles probably due to the
presence of potassium components quite significant in the case of
sunflower pellets and agromass (cf. the data in Table 6). Long-time
co-combustion of those type of fuels may thus be associated with
increased fouling and boiler operational problems since the significant
presence of alkali and chlorine in the biomass ashes brings
about that the deposits are thicker and more ‘aggressive’ to the
steel surfaces. The results shown in Table 7 confirm that sunflower
pellets (test No. 1) are more dangerous in comparison to fuels from
other tests since for this fuel the presence of chlorine was detected
not only in the outer layer of the deposits but also on steel and
deposit boundaries. However, it has to be emphasized that the
content of chlorine in the investigated fuels was not very high and
thus the results were only valid for a given set of fuels.