ABSTRACT
One of the most important functions of the pilot plant is to study the showering characteristics of the solid in the dryer. Some materials will stick or ball up in the dryer, and other materials will not tolerate the falling action. Mass transfer in the solid is the major resistance to drying. When selecting a dryer, there are several questions that need to be answered for all types of dryers. Rotary dryers will be used to illustrate problems because they dry more material than any other dryer. In direct-fired dryers, heat economy dictates a temperature which is far too high for most products, so parallel flow dryers are usually more economical. Steam tube rotary dryers are highly efficient units and handle much of the industrial drying load. The initial cost is greater than that of a hot air dryer, but in many cases steam is available and gas for heating is in short supply.
