Heated Air Drying
Whether in drying bins or in wagons, is usually done at air flow rates of 15 to 40 CFM/bu.
For in storage heated air drying , air flow rates can be considerably lower than state above, although minimum air flow of a CFM /bu is considered tolerant with small kernel seeds and low temperatures, it is generally recommended that the minimum air flow rate be 8 to 10 CFM /bu for all seeds. There are limits to the drying temperatures to which all seeds should be subjected. Using drying temperature above this maximum can result in deterioration of seed quality.
The use of lower temperature in drying reduces the danger of fire while giving all the drying capacity needed, if adequate air flow volume is used.
Procedure for Heated Air Drying in Bins:
The following is a generalised procedure for drying seeds with heated air.
1. Charge seed into bin to the recommended depth, maintaining uniform distribution of trash air broken kernels.
2. Operate dryer at recommended temperatures for that seed. This can be done manually, or by setting the control thermostat, if available to the desired temperature.
3. When drying is completed, continue blowing air through seed, without heat, to bring seed temperature down to air temperature, or to 50 0 F , if air temperature is lower. This will require from thirty minutes to two hours, depending upon the quantity being dried and the air temperature.
High drying temperature dry the exterior of the seed kernel considerably more than the interior. Some moisture testers, which measure primarily the surface moisture of the kernel, may then indicate that the seed is dry. After a few days of storage, the moisture redistributes itself through the kernels and the same moisture tester will indicate that the grain has picked up 2 or 3 percent moisture. From this, the farmer may erroneously conclude that he cannot safely store heated air dried seed. This difficulty is largely overcome by using recommended drying temperatures.