2006 Volume 68 Issue 1 Pages 119-127
Soybean seeds, variety Tsurumusume, were dried using a re-circulating batch dryer of general use type, by connecting an outer heating system consisting of a jet oil heater, a flexible duct that sends warm air from the outlet of the jet heater to the upper part of the dryer, and a digital electric thermostat to control the temperature of the ventilating air flow in the dryer. The temperature of the air flow was manually adjusted to avoid the occurrence of seed-coat cracking and mechanically broken soybean seeds by considering the moisture content of the soybean seeds and the temperature and humidity of the ambient air. The conveying quantity of soybean seeds in the dryer was adjusted slightly so that the circulation cycle time was almost 2. 5 hours.
As a result, the soybean seeds were dried below 15%w.b. of uniform moisture content at an average drying rate of 0.22-0.35%/h, with no occurrence of seed-coat cracking. In addition, the ratio of mechanically broken soybean seeds during the drying process fell to less than 1% by ventilating the warmed air at the top of the layers. This method was effective at decreasing the mechanical damage to soybean seeds by screw conveyer and bucket conveyer impaction owing to the tempering process in the lower layers.
