Part of one briquette was submitted for TG analysis (Fig. 4). TGA
data show that the organic concentration in the briquette increased
to 53% and the ash decreased to 35%. These changes in values
are associated with the sieve process and the addition of the
binder (organic material). TGA data (shown in two peaks) are discussed
after the next figure.
Fig. 5 displays thermal analysis results using DSC obtained for:
(a) a briquette prepared by boiling the mixture of charcoal, starch
and water (before pressing); and (b) a briquette obtained by pressing
charcoal powder mixed with a binder (starch and water heated
at 100 C). Sample (a) demonstrates a doublet between 450 and
500 C; the first peak is associated with the charcoal burning,
and the second peak is associated with the polymer burning. In
(b) there is only one large peak, indicating a blend formation with
only one peak burning, i.e., a more homogeneous charcoal–polymer
mixture. After these results, all the samples were prepared
by the second method.
Curve (b) in Fig. 5 shows two nearby peaks at 300 and 500 C
that are in agreement with the loss of mass observed in the TG record
(Fig. 4). These peaks indicate the presence of organic matter
not decomposed (cellulose and lignin) in the bulk of the charcoal.
The high volume of bagasse fired and the high rate of firing probably
did not carbonize the bulk of the larger particles of bagasse
farther from burning points.
The density of the briquettes measured with a balance and caliper
varied from 0.91 to 1.33 g/cm3. These values are smaller than
the values obtained from eucalyptus charcoal (1.41 g/cm3) using
tar as a binder (Brito and Nucci, 1984) but are in good agreement
with the values (1.08 g/cm3) obtained using others kinds of binders
and wood (Fontes et al., 1991).
The calorific value (the mean of three samples) was 25,551 kJ/
kg, as determined by using a calorimeter according to the guide-