Modélisation et simulation de la combustion du charbon vert dans un brûleur à lit fixe

Abstract

The main objective of this thesis is to develop a computational tool for simulating the combustion of green charcoal derived from household and agricultural waste, aiming to reduce environmental pressure and greenhouse gas emissions associated with traditional fuels. This biofuel, a promising alternative for rural households, is the focus of the study. The work began with a 1D two-phase (solid-gas) model of combustion in a refractory-walled stove, using global reaction kinetics, mass and energy balances, BDF spatial discretization, and LSODE for time integration. The model predicts temperature, gas production, and solid mass evolution over time, accounting for all solid combus tion stages and showing good agreement with experiments, particularly regarding refractory-induced temperature rise and post-combustion cooling. Due to limitations of the 1D model especially in geo metry handling a 3D model was developed, incorporating variable bed porosity and a two-equation gas-phase combustion mechanism. Parametric studies showed that lower porosity and moderate air inlet velocities (0.3 m/s) improve ef ciency, while high velocities (0.4 m/s) extinguish the ame front. A laminar combustion model was then introduced, enhancing temperature predictions. Radiative heat transfer was assessed using the P1 and MeanTemp models, revealing major differences in tempera ture pro les and energy release. The P1 model increased energy release by 7.63%, demonstrating the critical role of radiation modeling in optimizing xed-bed biochar combustion systems