RESULTS
Physical chemical, thermal characteristics and results of
elemental and proximate analysis are given in table 1. Paddy
husk has a higher heating value of 15.5 MJKg which supports
its use as fuel for furnaces and gasifiers. Silica and pentosan
content is high. Paddy husk thus has potential for use as a feed
stock for furfural and silica manufacture.
Thermogram of paddy husk at different heating rates and
under different atmospheres are shown m Figure l(a) through
(d) The temperature scale on these thermograms is not hear,
and has been adjusted to enable a more accurate dehydration
of the weight loss The degradation process is divided into
three &mct stages The first stage IS the dehydration&on of paddy
husk which occurred up to a temperature of 160 C The next
stage is the devolatilization followed by combustion of residual
matenal The second and third stages can also be attributed to
degradation of heim-cellulose and cellulose followed by
degradation of lignin m the thud stage The end of second
stage and start of third phase is indicated by mark 'B' on the
thermogram The first stage being the dehydration was not
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considered in calculating the kinetic parameters and the
effective two stages considered were stage 1 and stage 2.
The data owed fพom one thermogram (heating rate
10°C/w atmosphere-air) is given in Table3; the table also
mcludes the alpha values and time in seconds. This data was
used for the determination of activation energy and exponential
factor using the first order model suggested by
Bining (1992) and Agarwal(1987 and 1986), and also the
model of Coats and Redferm for various orders of reactions.
The results are summarized in table 4. A brief descriptions of
the models is given below.
Computation of kinetic parameters for the
principal conversion stage was done using an appropriate
integral solution. The multistage model using first order
kinetics provided good fit to experimental data. The
solution to the temperature integral of rate equation No. 7
used for the determination of kinetic parameters is as given
below: