ABSTRACT
Drying of liquid materials on inert solid carriers is a relatively new commercial technology to produce powders from solutions, suspensions, slurries, and pastes. Although this technique was developed in the former Union of Soviet Socialist Republics (USSR) in the 1950s and used for industrial drying of pigments, fi ne chemicals, pharmaceuticals, and certain materials of biological origin (e.g., Kutsakova et al., 1964; Reger et al., 1967; Minchev et al., 1968; Anonymous, 1992), it was not widespread, mostly because of the language barrier. Over the past two decades, however, drying on inert particles has found a renewed interest mainly because of its ability to produce powders even from the coarsely dispersed liquid feed at evaporation rates competitive to spray, drum, and fi lm-rotary dryers (Strumillo et al., 1983; Adamiec et al., 2007; Kudra and Mujumdar, 2007; Reyes et al., 2008). Extensive studies, carried out in Poland, Brazil, England, New Zealand, and Australia, have resulted in several pilot units and custom-made installations (e.g., Anonymous, 1986; Grbavcic et al., 1998). In addition, fl uid bed dryers with inert particles have recently been marketed by companies such as Carrier Vibrating Equipment Co., United States, and Euro-Vent, England, as well as PROKOP INOVA in the Czech Republic that offer dryers utilizing a swirling bed of inert particles (Kutsakova et al., 1990, 1994). Recently, the idea of drying of liquids sprayed on the surface of inert particles has been extended to drying of highly wet materials such as the granules of pressed yeast (70% moisture content), which were dried as a fl uidized mixture with inert polyethylene beads (Alsina et al., 2005).
