Simply, if a retort filled with a high grade (particle size and purity) of aluminium oxide
and is then subjected to any combination of process gases at the correct flow and pressure,
the oxide will exhibit similar characteristics to that of a fluid, hence the name fluidised bed.

The gas flow within the bed must be accurately controlled and uniformly distributed, this is
 perhaps the most critical aspect of fluid bed operation. Gas flow is controlled by the
'fluidisation plate' which is situated at the base of the retort, correct flow will produce +/- 2^oC
throughout the 'process envelope'.

Below graphically demonstrates the principals.

                                                                  Fluidisation Plate                                                                             Aluminium Oxide 

                            Gas Flow                                                     Fluidisation of Oxide                            Oxide reacts similar to a liquid

                                                'Liquid' oxide allows the placing                                     The component is heated
                                                  of components within the bed                                  and recovers to bed temperature

The graph below shows typical harden and double temper heat treatment cycle using a fluidised bed