Toroidal Fluidised Bed^[1]

TORoidal fluidised BED or TORBED is used to describe this form of fluidised bed, often characterised as a reactor, hence TORBED Reactor being used as a generic description for such devices. A toroidal fluidised bed or TORBED reactor comprises a substantially circular chamber with an annular array of stationary deflectors or blades in its base. A process gas stream is introduced through these deflectors or blades such as to suspend particulates in a rapidly circulating fluidised band of material to be processed. The angle of entry of the gas stream with respect to horizontal is typically less than 45%. The shape of the slots formed in the annular array of blades is such that the circulating bed mixes toroidally thus generating the descriptive name.

TORBED Reactors contain a bed that is relatively shallow (<100mm in depth) compared to conventional fluidised beds (>100mm in depth) and hence with very much lower gas pressure loss in passing through the bed. This is particularly beneficial when considering the lower energy consumption in circulating the process gas stream through the bed.

The inlet velocity of the process gas stream as it impacts the base of the circulating bed is significantly higher than the terminal velocity of the particles in the bed. This allows the high impact velocities at the base of the bed to increase heat and mass transfer rates. The necessary retention time of the particles is thus reduced and the TORBED Reactor chambers are significantly smaller than traditional fluidised beds or rotary kilns.

TORBED Reactors are in everyday use in refineries, mineral processing plants, food processing, heat recovery, gas scrubbing, calcination, torrefaction, gasification, drying or cooling.