Pyrolysis and gasification of a thermally thick wood particle – Effect of fragmentation

• Macro-TGA wood pyrolysis and wood char gasification shows changes in their structure.
• Model of thermal conversion is implemented in the ANSYS Fluent.
• Wood pyrolysis and char gasification are simulated using the same approach.
• Effects of cracking, shrinkage or swelling prove to be rather unimportant for simulations.
• Wood char fragmentation is of crucial importance for gasification modelling.

A two-stage macro-TGA experiment on pyrolysis and gasification of a thermally thick wood cylinder showed that during pyrolysis at 400 °C particle shrinkage and cracking take place, but there is no fragmentation. The fragmentation became noticeable during wood char gasification at high temperature (930 °C). The experiment showed that wood char particles begin to break down shortly after gasification is initiated.A three-dimensional, transient model of biomass pyrolysis and gasification was proposed and implemented in the ANSYS Fluent CFD package. The results of simulations, corresponding to the macro-TGA experiment show that the effect of particle cracking and shrinkage may be neglected. However, the results also show that for successful modelling of gasification wood char fragmentation must be taken into account.