A Fluid Bed Dryer/Cooler system typically consist of a combination Dryer and Cooler in one machine. However, sometimes you also have 2 separate machines, and could be a combination of a Rotary Dryer with a Fluid Bed Cooler.
In any case, when you are using a Fluid Bed for Cooling,the discharged air is elevated to normally around 150 to 155 F and sometimes much higher if used in conjunction with a Rotary Dryer. Most Fluid Bed Dryers and Coolers will use approximately the same amount of air for drying as is needed for cooling. In a recirculation system, the baghouse or dust collector must be split, or have a separate section for the drying air which is very wet, and the cooling section, which is dry. The energy saved by reusing this dry clean air from the cooling section (since it must be passed through a dust collector anyway) is expressed in the following formula:
(Tdischarged air - Tambient air) X SCFMcooler fan = btu's saved/hr
An example: The outside air is 45 F and the discharged air off the cooling section is 155 F. You are using 20,000 SCFM in the cooling section and you also use 20,000 scfm in the drying section. How much energy is saved if we recirculated this air from the cooling section?
(155 - 45) X 20,000 = 2,200,000 btu's/hr
