Biomass Fuel Quality Enhancement and Respiratory Quotient (RQ) for Ranking Fossil and Biomass Fuels Based on CO2 Emissions - Novel Combustion Concepts for Sustainable Energy Development - page 57

Table 3 Ultimate and
proximate analyses of
biomass components (Van de
Weerdhof 2010 ; Yoon et al.
2011 )

Hemicellulose Cellulose

Volatile matter (db) 74.11 91.64

Fixed carbon (db) 21.94 8.54

Ash (db) 3.95 0

C (daf) 43.77 43.58

H (daf) 5.91 6.09

O (daf) 50.26 50.27

N (daf) 0.05 0.05

S (daf) 0.02 0.01

Heating value (kJ/daf kg) 15,920 17,870

estimated for the bulk char percentage in the two samples were similar to the xed

carbon in mesquite and juniper on a dry ash-free basis (16.98 % for mesquite and
15.45 % for juniper from Table 2 ). The percentage of

fixed carbon in the three
components was used as a reference to determine the amount of volatile matter
released from the components during the torrefaction process. Amount of these
three components depends on the type of biomass. Hardwood was found to contain
higher percentage of hemicellulose when compared to softwood. Percentage of the
different components in hardwood and softwood was obtained from Liu et al.
( 2008 ). Table 4 shows the percentage of the three components along with the
kinetic constants for the three components which were determined using error
minimization technique.

Component Conversion and Mass Loss During Torrefaction: TCM

Volatilization of the three components at different torrefaction temperatures and
residence times was studied. The results obtained for torrefaction of mesquite which
is a hardwood at 240 C for a residence time of 60 min is shown in Fig. 6 . It was

assumed that the samples are heated from room temperature to the desired torre-
faction temperature at a heating rate of 20

°

° C/min.

Table 4 Composition of hardwood and softwood
Hemicellulose (%) Cellulose (%) Lignin (%)

Softwood (Liu
et al. 2008 )

12.27 53.26 26.66

Hardwood (Liu
et al. 2008 )

28.97 53.95 9.43

B (1/min) 6.66E+08 (Cozzani

et al. 1997 )

6.83E+16 (Orfao
et al. 1999 )

1,000 (Varhegyi
et al. 1997 )

E (kJ/mol) 103.2 (Cozzani et al.

1997 )

201 (Orfao et al.
1999 )

65 (Varhegyi et al.
1997 )