Abstract:
In-depth thermodynamic and kinetic, synergistic effects of the coal and rice husk blends
on co-pyrolysis have been investigated for bioenergy production. The thermo-kinetic
rate parameters were determined for chemical, one-dimensional diffusional, and phase
interfacial reaction models especially when fitted to the Coats-Redfern method. The
fitted models exhibited thermo-kinetic rate parameters. The thermogravimetric analysis
in view of the thermodynamic parameters including enthalpy, Gibbs free energy, and
entropy imparted the prominent degradation temperature ranges (Stage A: 200 °C-400
°C, Stage B: 410 °C-560
°C) for co-pyrolysis reactions of blends. The proportional
increase of rise husk into coal for Stage A caused an increase in the apparent values of
activation energy, enthalpy specifically for one-dimensional diffusional, and phase
interfacial reaction models. In case of Stage B, the increasing share of rice husk into coal
proved to be beneficial in decreasing values of activation energy and enthalpy. Positive
synergies for 80:20 and 60:40 coal-rice husk blends were calculated. In addition to
characterization analysis of all samples; co-pyrolysis and co-gasification experiments
were completed in a tubular fixed bed reactor at Stage B and onwards temperatures for
synergized blends. The resultant co-pyrolysis biochar samples revealed honeycomb
structure useful in adsorption applications. The gas chromatography-mass spectrometry
analysis of the bio-oil yields 23% phenols, 11% acids, and methoxy phenols for the
60:40 coal-rice husk blend. The product gas composition of 2% H2, 14% CH4, and 4%
CO2 for the 80:20 coal-rice husk blend increased to 3% H2, 12% CH4, and 5% CO2 for
the 60:40 blend. The co-gasification process substantially increased the production of H2
up to 14%-17% when compared to co-pyrolysis results. The approach used in this study
can be utilized to capitalize on synergy to enhance co-pyrolysis of appropriate blends
and their products can be used in further future applications upon upgradation.
