Numerical approaches for thermochemical conversion of char
Nils Erland L. Haugen, Brandon Loong, Reginald E. Mitchell
Abstract
This paper gives a review of the current state of the art for numerical simulations of char conversion. In particular, it presents models that have been developed to describe the physical and chemical phenomena that characterize thermochemical char conversion. All particle sizes are covered, ranging from pulverized particles to wood logs. The aim of the paper is to give the reader the required starting point in order to develop his own simulation tool. Two fundamentally different approaches are studied in detail, namely the resolved particle approach and the point particle approach. In the resolved approach, both the char particle itself and the surrounding boundary layer is resolved. This means that heat, mass and momentum transfer are accurately handled. For the point particle approach, which is computationally much cheaper, one has to rely on suitable models to estimate for example the heat, mass and momentum transfer. Finally, the paper also gives detailed descriptions of how to handle ash inclusions in the char in addition to particle fragmentation and thermal annealing.