Multicomponent devolatilization kinetics and thermal conversion of Imperata cylindrica

Abstract

Imperata cylindrica is a viable bioenergy crop with potential for conversion to clean energy through thermochemical processes such as pyrolysis, gasification and combustion. To facilitate further process development, a mathematical model that represents process kinetics is developed and validated on thermal degradation studies using thermogravimetric analyzer, over a temperature range of 30–1000°C, at four heating rates of 5, 10, 15, and 20°Cmin−1 under Nitrogen atmosphere. Model free and model fitting multicomponent methods are used for determination of pre-exponential factors (ko), activation energies (Ea) and fractional contribution (ξ). In addition, a novel approach is introduced to determine biomass (cellulose, hemicellulose and lignin) compositions by extending model fitting multicomponent method to identify components that correspond to each biomass composition using the pyrolysis temperature range. The model free methods of Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose gave average activation energies of 164.93kJmol−1 and 163.44kJmol−1 and average pre-exponential factor of 1.04×1025min−1 and 4.65×1018min−1 respectively. Using the multicomponent model fitting, the simulation was carried out for 3–14 pseudo components and the best quality of fit (0.75%) was for ten pseudocomponents at a heating rate of 15°Cmin−1 with an activation energy of 101.56kJmol−1, which compares favourably with the model free method. The novel biomass composition algorithm predicted the cellulose, hemicellulose and lignin as 66%, 24% and 10% respectively, varying from experimental composition by ±10%. The results strongly indicate that the pseudocomponent reaction modelling method could be employed to predict the experimental devolatilization rate and biomass composition with a high degree of success.