ABSTRACT
This chapter focuses on non-conventional spray drying techniques. Superheated steam drying has been well established for many forms of solid-based drying. Application of superheated steam as the drying medium in wood, sludges, food, and agricultural products has shown that the medium improves product qualities such as porosity, and prevents and minimizes undesired quality changes such as off-flavours and oxidation reactions. There are, however, minimal scientific reports on the use of superheated steam as a medium for spray drying. In this section, some recent experimental work in this area will be discussed with more emphasis on how superheated steam can be used in spray dryers with reference to its effect on powder functionality development. The counter current spray drying technique is then introduced as a useful spray drying configuration for in-situ crystallization control. This unique capability is mainly due to the relatively longer drying time scale in the counter current spray dryer. In contrast to the conventional dehydration of liquid, the spray dryer can also be potentially used as a droplet-absorption-dehydration process for functional particle production. The antisolvent vapour precipitation technique is discussed and this process utilizes each sprayed droplet as micron-size precipitation ‘vessels’.
