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Four
kinds of woody biomass-Sawdust, Babul, Gulmahor and Eucalyptus-were
pyrolyzed in a nitrogen atmosphere at the heating rate of
10 ƒßC/min. up to 500 °C in a thermogravimetric
analyzer to investigate their pyrolytic characteristics. Three
stages- dehydration, devolatilization and solid decomposition-appeared
in the pyrolysis process. The thermograms could be directly
correlated with the thermal devolatilization. All four materials
were mainly devolatilized in the temperature range of 180-496
°C. A total volatile yield of about 70% was achieved from
each wood. The pre-exponential factor and activation energies
were calculated using differential method of analysis, assuming
different order of reactions. Linear regression was applied
and the value of order, which gives the highest confidence
level, was considered for the main devolatilization stage
(190-370 °C). The value of activation energy found was
in the following order: Eucalyptus>Babul >Gulmahor>Sawdust
and it was same for pre-exponential factor. The experimental
results may provide useful data for the design of pyrolytic
processing systems using woody biomass as feedstock.
The
prospect of producing clean, sustainable power in substantial
quantities from agricultural residues is now arousing global
interest, stimulated by increasing concern over the environmental
consequences of conventional fossil and nuclear fuel use.
The growing interest in renewable energies is accompanied
by the intensified research and development of technical processes
for the thermal conversion of biomass (Parikh et al.,
2002).
The
kinetic study of the biomass pyrolysis is of relevant importance
because plant design and scale-up bases on process simulation,
which needs reliable reaction models for the desired operation
conditions. There is a contention that the simple competitive
reaction model is a gross simplification of a number of very
complicated phenomena, and general agreement on the next level
of sophistication does not yet exist. It is again for this
reason that global mass loss models will continue to be attractive
as many issues continue to be sorted out. |
