Comparative study on pyrolysis characteristics and kinetics of lignocellulosic biomass and seaweed

Abstract

The pyrolysis characteristics and kinetics of lignocellulosic biomass (cotton stalk) and seaweed (Gracilaria lemaneiformis) were studied comparatively. Results of the thermal degradation processes showed that the pyrolysis occurence of G. lemaneiformis is easier than that of cotton stalk. However, G. lemaneiformis released less volatile components and produced more solid residues. As the heating rate increased, the maximum mass loss rates for cotton stalk were decreased, while those for G. lemaneiformis were increased. Results of the kinetic analysis by Popescu method indicated that the pyrolysis mechanism of cotton stalk is three-dimensional diffusion, which can be described by Zhuralev, Lesokin, and Tempelmen (Z–L–T) equation \((G(\alpha ) = \{ [1/(1 - \alpha )]^{1/3} - 1\}^{2} )\), whereas that of G. lemaneiformis is random nucleation and nuclei growth, which can be described by Avrami–Erofeev equation \((G(\alpha ) = [ - \ln (1 - \alpha )]^{1/4} )\). The average activation energy values (192.17 and 146.11 kJ mol−1, respectively) of cotton stalk and G. lemaneiformis obtained by Popescu method are similar with those (189.88 and 153.79 kJ mol−1, respectively) calculated by Flynn–Wall–Ozawa (FWO) method. Moreover, the average activation energy of G. lemaneiformis is lower than that of cotton stalk.