Revisiting shrinking particle and product layer models for fluid–solid reactions – from ideal surfaces to real surfaces

A general model based on an arbitrary geometry was developed for reactive solid particles which have surface defects and porosity. The model equations comprising intrinsic kinetics as well as mass transfer effects through the product layer and the fluid film surrounding the solid particle were derived for shrinking particle and product layer models. From the model equations, the fluid (gas or liquid) concentrations at the reaction surface can be calculated and the change of the solid phase can be predicted. The approach was illustrated with monodisperse particle distributions in batch reactors. Complex kinetics as well as simpler special cases were treated. In general, the model predicts a higher reaction order with respect to the solid component than the previous ideal models, which assume slab, cylindrical or spherical geometries for solid particles.