2.1.2. Dryer Description

The crossflow column dryer, shown in Figure 1, was fabricated at the Department of Agricultural and Biosystems Engineering, KNUST. It is a mobile drying system that can be transported from one place to another. The dryer consists of three main parts: a cylindrical drying bin, a portable biomass burner, and a fan (blower). The drying bin of 1.20 m height is made up of an inner and an outer wall cylinders that holds grains in the annular space of 0.25 m thickness. The inner and outer wall cylinders with radii 0.15 m and 0.40 m, respectively, make up the plenum and drying chamber of the dryer, respectively. Both the inner and outer wall cylinders were constructed with a perforated metal sheet to allow hot air movement across the inner bin, through the grains, and exit of moist air through the outer bin. The biomass burner serves as the primary heat-generating component of the dryer, and it is made up of heat exchangers. The burner is designed to accommodate a variety of biomass such as corn cobs, wood chippings, and rice husk. From a preliminary experiment conducted on just the biomass burner, corn cobs were fed into to burner at a feed-rate of 12 kg/h. After combustion of biomass, ashes fall through a grate in the combustion chamber for easy collection. The blower sucks air from the biomass burner through the heat exchangers and then forces the drying air through an air delivery tube to the drying bin. At the dryer's plenum, drying air is forced to pass through the drying chamber radially by restricting the movement of the drying air in the plenum by using a stopper.

**Figure 1.** CAD model of the crossflow column dryer showing all of its parts.
