Pyromechanics: A solid mechanics approach to deformation during pyrolysis

Abstract

During pyrolysis, organic materials undergo morphological changes that are important to predict, particularly in the field of thermochemical conversion. This work proposes an approach to model deformations during pyrolysis combining elastic, thermal expansion, and pyrolysis contributions. A three-dimensional anisotropic pyromechanics model is derived for porous media by volume averaging. It includes pyrolysis kinetics, mass, momentum and energy conservation for both solid and gas phases. A key advantage of the pyromechanics model lies in its physical framework, which effectively captures the effect of internal stresses on the overall deformation. Implemented as open-source within the Porous material Analysis Toolbox based on the OpenFOAM framework (PATO) using an incremental approach, the model is specifically applied to wood in this study. Two experimental validations are conducted using pyrolyzing cylindrical wood particles to verify the model’s predictions concerning temperature profile evolution and shrinkage effects. Importantly, the model’s capability to estimate stress distribution holds promise for further investigations into crack distribution and propagation.