Grain Dryer

a machine for drying the grain of cereal and legume crops, the seeds of grasses and vegetable crops, and threshed clover. Grain dryers are also used to dry preground green clover, alfalfa, vetch and oats mixtures, and other grasses in order to obtain protein-vitamin feed.

Both shaft and rotary grain dryers are used, and they may be either stationary or movcable. In the shaft grain dryers the grain is dried while moving downward within the shaft, carried by its own weight. In this case the heat carrier (a mixture of furnace gases and air) enters through ducts in the shaft that are perpendicular to the direction of grain movement. In the rotary grain dryers the grain is dried in a rotating drum where it is mixed and moved along the drum in the stream of the heat carrier.

In shaft grain dryers, the temperature of the heat carrier when drying seed grain with a moisture content of up to 25 percent should not exceed 80°C; with a moisture content of over 25 percent the temperature should not exceed 70°C. When drying food grain with a moisture content of up to 25 percent the temperature of the heat carrier should not exceed 110°C, and the temperature for grain with a moisture content of over 25 percent should not exceed 100°C. In rotary dryers, when drying seed grain with a moisture content of up to 25 percent the temperature of the heat carrier should not exceed 145°–165°C, and when drying food grain with a moisture content of over 25 percent the temperature should not exceed 180°-210°C. In a single passage through a shaft grain dryer the moisture content of the grain is decreased by 6–12 percent, and in rotary dryers the decrease is 5–8 percent. The capacity of grain dryers is up to 8 tons per hour. Wood, coal, peat, or liquid fuel may be used as fuel for grain dryers.