Pyrolysis of large wood particles: a study of shrinkage importance in simulations☆

Shrinkage models have been developed and included in a model for the pyrolysis of large wood particles. Shrinkage is modelled in three different ways: uniform shrinkage, shrinking shell and shrinking cylinders. These models and a reference model without shrinkage are compared with experimental data for mass loss versus time during pyrolysis of birch cylinders at different temperatures. In the experiments a wood particle was introduced into a pyrolysis furnace held at constant temperature. The particle mass and volume were recorded using a balance and a video camera. Uniform shrinkage slows down the pyrolysis whereas shrinking shell and cylinder models enhance the pyrolysis rate. The effect was sufficiently small to be neglected given the uncertainty about some wood physical properties.