ABSTRACT
Powder handling processes are mainly categorized into wet and dry processes. 1,2 In wet processes, the degree of wetness (moisture content) seriously affects physical properties (size, shape, density, etc.) of the fi nal products. In order to produce the desired product effi ciently and continuously without diffi culty, monitoring and control of moisture content are required. Even in dry processes, moisture content sometimes causes problems. Generally, powder materials contain moisture, to some extent as water of hydration, bound water, and so forth, which exists on the powder surface or forms liquid bridges between powders. Moisture on the powder surface greatly changes the powder’s properties such as fl owability and internal friction, causing handling problems. The liquid bridges generate agglomeration of powders and adhesion to the vessel wall. In all cases, control of moisture content is necessary in order to avoid problems.
