We have looked for cheaper sensors, able to measure ‘on-line’ the moisture content
in order to control the process with precision and rapidity.
Previous studies on the drying mechanisms (Abchir, 1988; Vasseur & Loncin,
1983) have shown that drying on a drum dryer takes place by boiling, since air
velocity around the dryer is under 6 m/s. That means that the product attains itsboiling temperature Tpe, which is a function of X, defined by the fact its steam
pressure at Tpe (i.e. PTpe) is equal to the total pressure P, over the product
(generally atmospheric pressure). Therefore, if product temperature is measured,
the corresponding moisture content X is known through knowledge of the
desorption isobar. This property facilitates the use of cheaper sensors, able to
measure on-line the moisture content with precision and rapidity.