ABSTRACT

This study presents the numerical simulation of biomass pyrolysis under isothermal condition following a two-step parallel kinetic reaction scheme in a single reactor. Biochar, one of the end products of this process is considered an efficient vector for soil conditioning and sequestering carbon to offset atmospheric carbon dioxide. The properties of mild steel and poultry litter were used to develop a numerical model using finite element method (FEM). This model considered heat transfer in a novel batch reactor and mass transfer during pyrolysis of biomass. The numerical solutions to the system of pyrolysis kinetic model were used to investigate the mass loss of pyrolysis products at different residence time and temperatures. The simulation study found that the reactor should be heated on all sides (furnace heating) for maximum heat transfer in order to achieve a two-step reaction in which biochar can be produced at two stages. Also, significant mass loss occurred at 573.15K between 7200s and 9000s (0.0847kg and 0.051kg). Biochar yield declined at higher temperatures as 33.72%, 27.84%, and 22.28% at 573.15K, 673.15K and 773.15K during primary reaction. At secondary reaction char yield varies between 9.18%, 11.56 and 12.08%. The model was validated by comparing the predicted values with experimental result from literature. Additionally, good agreements were established between the present result and that of past works. It is therefore expected that this study will enhance the understanding of the pyrolysis process involving primary and secondary reactions in a single reactor by giving physical insights into the various factors and the parameters affecting the process including the heat transfer rate within the reactor body.