ABSTRACT
In the wet agglomeration, water is used as a binder to promote the adhesion between powders. Thus, the degree of wetting, which is referred to as moisture content, seriously affects the physical properties of the final agglomerates. In powder handling processes, there exist no sensors which can measure moisture content directly. The electric-resistance-type moisture sensor has two types of its construction; in the cell-type sensor, the moisture content is determined by measuring the change of electric resistance due to the increase or decrease of moisture. The microwave moisture sensor is able to measure the moisture content continuously without touching the powder bed. Wet granulation is one of the most sensitive operations to the moisture content. The microwave and infrared (IR) are available to detect the moisture optically. The IR sensor and fluidized bed vessel is connected by optical fibers and heated purge air is blown at the extremity of the sensor to prevent the powder sticking.
