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 52

TGA Thermograms - Mesquite Nitrogen vs. Carbon-dioxide
Comparison

100

Pyrolysis - Nitrogen
Pyrolysis - Carbon-dioxide
200°C - Nitrogen
200°C - Carbon-dioxide
220°C - Nitrogen
220°C - Carbon-dioxide
240°C - Nitrogen
240°C - Carbon-dioxide
260°C - Nitrogen
260°C - Carbon-dioxide
280°C - Nitrogen
280°C - Carbon-dioxide
300°C - Nitrogen
300°C - Carbon-dioxide

90

80

70

60

50

40

30

20

0 100 200 300 400 500 600 700 800

Temperature (°C)

Fig. 2 Comparison of thermograms from pyrolysis and torrefaction of mesquite wood using N 2
and CO 2 as the purge gases, adapted from Eseltine ( 2011 )

than samples torre ed using nitrogen. This is due mainly to chemical reactions

occurring between CO 2 and the carbon within the fuel which will be discussed in
further detail in a subsequent section.

3.2.2 Juniper

Data obtained from torrefaction and pyrolysis of juniper wood chips were analyzed
in the same manner as the data from mesquite wood pyrolysis and torrefaction. The
shape of the thermograms from juniper wood follows the same trends as the
thermograms from mesquite wood. The only noticeable difference between the
pyrolysis curves of mesquite and juniper is being the weight percent remaining after
the active pyrolysis zone. Juniper wood loses more weight during the initial active
pyrolysis zone when compared to mesquite due to differences in the chemical
composition of the two biomasses.
Comparing the weight loss from the torrefaction of mesquite and juniper wood,
it can be seen that mesquite wood has a higher amount of weight loss at a given
torrefaction temperature. This is due mainly to differences in the chemical com-
position of both biomasses. Prins et al. ( 2006a ) have stated that deciduous woods,
such as mesquite, have a hemicellulose fraction comprised of mostly xylan. Xylan
is being more reactive than mannan, the main constituent of the hemicellulose
fraction found in coniferous woods (such as juniper). Due to the temperature range
over which hemicellulose breaks down, a signi cant portion of the weight lost

during torrefaction occurs from the decomposition of hemicellulose. Therefore, the