Fluidised bed conveyor systems use air at a very low pressure and do not resort to piping in which to flow the material. Their driving force is gravity, so they are only able to operate with a downward tilt, albeit at an angle of a few degrees.
Gravity conveyors consist of a channel divided longitudinally by a continuous porous membrane over which the material flows, as illustrated in the figure above. The operating principle of these systems is based on the introduction of a small amount of air at low pressure through the membrane.
Fluidised channels are capable of handling bulk material up to 100 metres and are suitable for flow rates up to 300 m3. In general, materials with a grain size of 40 to 500 μm and a density of between 1400 and 5000 kg/m3 are the easiest to transport and will flow very smoothly down shallow slopes.