The amount of air required for a dryer is largely determined by its temperature and the amount of water to be removed.  The higher the dryer gas temperature the less gas is needed.  The heat balance over each bed section determines the temperature of the bed and the off-gas.  The good contact of the fluidized beds assures that the gas is only a few degrees warmer that the bed and they are often the same temperature.  When water is readily available on the surface of the chips (down to about 30% MC) the dryer gas will be almost 100 saturated (at dew point), and the temperature will be very low (usually less than 120F).

As the chips dry the rater removal slows and the bed temperature rises.  The gas temperature should be reduced by admitting cold ambient air through inlet vents in the side of the dryer.

Rotary dryers in the US are often run with up to 600F inlet air and sometimes higher.  To maintain high delta Ts for heat transfer the outlet temperature can run over 150F.  The effect of these high temperatures is a tendency to form “blue haze”.  There is always a temperature limit where blue haze becomes a problem.

In belt dryers the dryer gas temperature must be kept lower to prevent the chips on the bottom of the belt from being over heated.

So, the dryer gas rate for the fluidized bed dryer may be a little higher than for a rotary dryer, but much less than required for the belt dryer.