Tests Performed with Raw Samples

Preliminary tests of reactivity and combustion behaviour of the single fuels and of their blends were carried out on the uncharred samples. Such tests included TPO analysis

Table 2. Volatile yields, residual ash after TGA and estimated char yield.

Sample

TGA

residue, %

Volatiles loss at the HTWM reactor, %

Estimated char yield*,

%

Ash **, %

Volatile matter **, %

Fixed carbon **, %

cocoa shells

7.45

82

11

7.68

71.89

20.43

coal К

15.10

37

48

13.57

30.46

55.77

wood chips

2.95

90

7

2.16

76.33

21.55

cocoa shells-coal К

14.37

44

42

wood chips-coal К

13.65

41

45

*Char yield was estimated as difference between volatile yield and ash residue after TGA of chars ■“determined according to the ASTM standards

in the thermogravimetric apparatus and CTO tests in the flow microreactor. SSA measurements of the samples were also performed. The main results of tests carried out on uncharred samples yielded the following indications:

a) the biomasses present double peak DTG profiles that reflect the presence of large amounts of volatiles (first peak). The coal, instead, present a single peak DTG profiles but, in this case a shoulder at the lower temperature end (about 600 K) of the peak is representative of the volatiles;

b) cocoa shells and wood chips have combustion profiles very similar each other (DTG profiles have a main peak at 600 К and a secondary peak between 650 К and 850 K) and ash amount significantly lower than coal K;

c) the measured values of the SSA of fresh blends made with coal К and biomasses differ significantly from the weighted average of those of the correspondent parent coal and biomass (Table 3).

Table 3. Measured SSA (m2/s) of various samples of single materials, and measured and calculated SSA of blends before and after charring.

Sample

raw

char

Measured

Calculated

Measured

Calculated

cocoa shells

0.11

13.34

wood chips

0.78

3.08

coal К (short charring times)

5.00

0.21

coal К

5.00

20.39

coal K-cocoa shells (short charring times)

1.98

4.50

1.06

0.26

coal K-cocoa shells

1.98

4.50

30,30

20.25

coal К – wood chips (short charring times)

3.86

4.58

0.57

0.62

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