SCALE-UP OF PNEUMATIC CONVEYING DRYERS

Scale-up of pneumatic conveying dryers has until now been largely empirical. A theoretical model is outlined which predicts dryer performance effectively. It depends on some uncertain parameters, notably agglomeration and wall friction, bur these can be found more accurately by checking the predictions against results from the small-scale dryer. The model can then be used to scale up to the full size dryer. The required duct length falls as the gas velocity is reduced and the duct diameter increased, subject to satisfactory conveying and dispersion at the feedpoint.