2013 Volume 30 Pages 69-83
Thermal drying is a highly energy-consuming process found in almost all industries accounting for between 10–20% of national industrial energy consumption in the developed economies of the world. It is arguably the oldest unit operation and yet R&D in this area is only a few decades old. Over 50% of products consumed by humans are in particulate form so that drying of wet particulates as well as feedstock such as solutions, suspensions or pasty solids is of great industrial interest. Efficient drying technologies must produce engineered dry particulates of desired quality at minimum cost, low carbon footprint and little environmental impact. This article attempts to provide a global overview of recent advances in drying technologies most of which represent evolutionary innovations. In order to reduce investment costs one needs to enhance drying rates within limits imposed by the product properties and end product quality requirements. Several novel gas-particle contactors for example have been evaluated for drying. Combined modes of heating and hybrid dryers can improve drying performance in some cases. Recent interest in production of nanoparticles by wet processing also has stimulated interest in drying to produce nanoparticles. Drying of heat sensitive biotech and pharmaceutical products also pose new challenges. A capsule overview is presented of recent developments including enhancements in conventional drying technologies as well as more innovative new technologies.
