The equipment discussed in this section serves to dry solids. The process involves the removal of liquids, such as water or solvents, by adding heat to vaporize them. The types of dryers can be grouped into batch designs and continuous designs. The continuous dryers can be further subdivided on the basis of (1) whether the dryer itself is heated (nonadiabatic contact drying) or the dryer is unheated and the heat of vaporization is provided by preheated air (adiabatic convective drying); (2) for adiabatic dryers, whether the dryer is co-current (the solids and the drying air move in the same direction), countercurrent (hot air and solids move through the dryer in opposite directions), or fluidized bed; and (3) whether the dryer is operated under positive pressure or under vacuum. The control of each of these designs will be briefly discussed in this chapter.