In this book CFD simulations of the hydrodynamic behaviour of a fluidized bed reactors are described and shown. Two main topics have been analyzed: the transition from bubbling to slugging fluidization regimes (in the first section) and the evolution of volatiles from a submerged gas-emitting particle (in the second section). Both the analysis have been performed with a commercial code (CFX 4.4) using the granular kinetic theory. The fundamental principles of fluidization and the two-phase flows physics as well the basic approaches to computational fluid dynamics modelling and numerical...