Fluidised Bed Reactors and Combustion

Solid materials to be sent to combustion systems are typically characterised by a particle size distribution; therefore, this chapter opens with a presentation of the concepts of particle size distributions and characteristic mean diameters. As fluid dynamic precursors of fluidised bed reactors, fixed bed reactors are presented, up to the characteristic equations which determine the condition of minimum fluidisation of a bed of granular material. Fluidised beds are illustrated in their main characteristics (presence of dense phase/bubbles and their role, elutriation phenomena), highlighting in particular their advantages when considering solid–gas applications such as biomass combustion. The chapter closes with a technical-historical focus on fluidised bed combustors.