Kinetic studies in pyrolysis of garden waste in the context of downdraft gasification: Experiments and modeling

The disposal and management of dry leaves litter (biomass) from roads and gardens in urban areas is a challenging task. It is beneficial to use this waste as an energy source in thermal applications through pyrolysis and gasification. Downdraft gasifier is one such promising reactor that can be employed to achieve this task in a decentralized manner. A distinct pyrolysis zone is established in the gasifier during its operation, and it influences the performance significantly. Hence, the present work is undertaken to study the kinetics of pyrolysis in conditions that prevail in gasifier. A fixed-bed laboratory reactor that uses biomass pellets is employed to analyze the gases generated during pyrolysis process. Carbon dioxide and carbon monoxide evolve at relatively lower temperatures while methane and hydrogen form at higher temperatures. A simplified single-step power law kinetic model is used to fit the experimental data for the gas evolution in fixed bed reactor experiments and the respective kinetic parameters are estimated. The model thus developed is used successfully to predict the flow rate and the composition of gas leaving the pyrolysis zone of gasifier, showing the utility of this approach to obtain an insight into the gasifier operation. (C) 2020 Elsevier Ltd. All rights reserved.