In the present study, paddy husk was subjected to
Thermogravimetric Analysis at heating rates of 10 and
100°C/min. in a thermal analyzer. The analysis was
carried out in air and mixture of oxygen and nitrogen
(5: 95%) atmosphere. Reaction kinetic parameters such
as activation energy, frequency factor and order of
reaction have been evaluated and reported. These are
relevant to the design of paddy husk fired gaslfiers,
furnaces and other thermochemical conversion
equipment. The results of the thermochemical studes
and their potential applications are presented in the
paper.
INTRODUCTION
Production of paddy husk
Rice is the major cereal crop in the world and in
Inha. The area under paddy crop in 1992-93 (Anon, 1994)
was about 42 million hectares-the largest under any single
crop in India. The current annual production of paddy husk
in India is estimated to be around 25 million tons, where as
the annual production of paddy husk in the world is
estimated to be over 90 million tons.
Applications of Paddy Husk
Paddy husk is used in several ways. The
applications are location specific. The major uses of are:
cattle feed, fuel for furnaces and gasifiers, feed stock for
chemical and paper board industries and silica industries.
The calorific value of paddy husk is reported to be 15.5
MJkg (Jain, 1988). It has potential to be used as fuel in
boiler furnaces for production of steam and hot water in
small and med" industries.
A survey was conducted by Bhatnagar and Sehgal (1990)
regarding the use of paddy husk as fuel in boiler furnaces
in industries in Ludhiana district of Punjab, India. It was
observed that the thermal efficiency of husk fired furnaces
is in the range of 28-35% and these furnaces cause serious
environmental pollution due to emission of fly ash and
smoke from the boiler chmney. The furnaces covered in
the survey included inclined grate, horse shoe and step
grate type furnaces.
The main objectives of paddy husk management are two
fold: 1) use of paddy husk as a source of energy in most
efficient manner, and 2) minimization of environment
pollution resulting from inefficient utilization. In th~s
context, it is very essential to have efficient designs of husk
fired furnaces and gasifiers. For proper designing of the
furnaces or gasifiers the basic requirement is adequate and
reliable data on the characteristics and reaction kinetics of
thermal degradation of paddy husk. The characteristics
data for paddy husk, specially for the husk available in the
local environment, is lacking at present.
A study was therefore undertaken to determine the
characteristics and reaction kinetics during thermal
degradation of paddy husk. Paddy husk was subjected to
thermal analysis under air and a mixture of nitrogen and
oxygen (95:5%) at different heating rates. Reaction
kinetics parameters i.e. energy of activation and preexponential
factor and order of reaction are determined
and reported in the paper.
LITERATURE REVIEW
Paddy husk characterization
A nu" of publicitions containing thermodynarmc property
data for biomass have wed (Jain, 1988; Bhng & Jenkins,
1985; Jain, 1988; Kjellstrom, 1982; Rossi, 1984). Properties
relevant to both thermochemical and biologd conversion
processes are reported, although comprehensive data on the
properhes of paddy husk is inadequate.
Charactenstics of paddy husk as reported by various authors
are given m Table 1. A close look at the reported data on the
characteristics of paddy husk reveal sigtllscant inconsistency
in the reported values. This may be because of Werences in
the variety of paddy grown, sod conditions and other
environmental factors prevahg in the Werent regions. As is
0-7803-3547-3-7116 $4.00 0 1996 IEEE 2274
evident from the Table 1, some very important data on
characterization is not reported in the literature.
Thermal degradation of paddy husk
For thermal degradation studies, Merent research groups
have used non-isothermal and isothermal degradation
techniques. In non-isothermal, biomass material is heated
under a pre-set programmed or linear heating rate and weight
loss data is recorded as a function of temperature or time, on a
thermal analyzer. The process is characterized by finely
ground small parbcle size and low weight samples. The
instrumentation is well developed for non-isothermal
degradation. On the other hand the isothermal degradation is
characterized by large samples, bigger size and is carried out
in specially designed therm0 balance.
Dunng the last 30 to 35 years thermogravimetric data to
evaluate kmetic parameters of solid state decomposition
reactions involving weight loss and temperature have been
investigated by several research workers. A common
methodology/models used for the determination of energy of
activation, pre-exponential factor and order of reaction adopted
by most of the scientists is given below. Most of researchers
have assumed solid state decomposition according to the
following reaction.
as mechsm is unkely to be the predormnant mechs