Fluidization converts a packed bed of particles into an expanded, suspended bed that possesses many of the properties of a fluid: the bed has zero angle of repose, seeks its own level, and assumes the shape of the containing vessel.

Fluidization is an interdisciplinary field of inquiry; after more that fifty years of research process, chemical and mechanical engineering, physics and mathematics still find challenging problems to tackle. Fluidized beds are used successfully in many processes, catalytic and noncatalytic. Despite its apparent simplicity, fluidization encompasses a variety of patterns (bubbling, fast, turbulent, spouted three-phase, fixed or circulating). It is affected by such operations as mass and heat transfer, erosion and attrition, entrainment and elutriation, and separation. It finds application in power generation, in the chemical industry (e.g., phthalic anhydride and acrylonitrile production), in the petrochemical industry (e.g., hydrocarbon cracking and production of synfuels via Fischer-Tropsch reaction), in the incineration of hazardous waste, in coal and biomass gasification, in the processing of minerals (alumina, limestone and phosphate rocks), and in the biochemical, pharmaceutical and food industries. These processes and applications make fluidization a challenging field for fundamental and applied research.