Consider options when selecting on-farm grain dryer
Farmers are increasingly building their own grain handling systems and by-passing local elevators. Grain dryer systems are an integral part of farm grain storage, and there are many choices, according to Dr. Kenneth J. Hellevang, PE, Extension Agricultural Engineer of North Dakota State University.
Natural drying has no restrictions on the amount of grain dried but has a limit on the initial moisture and can take several weeks to accomplish. Layer drying is similar but grain with higher moisture can be dried as long as the amount is limited in depth to what the fan can move air through. A layer that is too deep will spoil because the air cannot penetrate the grain. Both of these systems are common to smaller, older grain storage bins
Many farmers use bin batch dryers, some with a stirring device to reduce moisture variation throughout the bin. Some batch bins have a sweep auger that removes dry grain and transfers it to another cooling bin for storage.
Column dryers can be portable and the drying action takes place outside the storage bin. 2-3 hours per batch of up to 1,000 bushels may be possible with a column batch dryer. The normal cycle is fill-head-cool-unload. Some column dyers are continuous fill.
To increase efficiency, you can partially dry a batch using the high-temperature method and finish with a natural air system. Another way to attain efficiency is to use dryeration. Hot grain is removed from the drying bin about 1-2% wetter than desired allowed to temper without airflow for up to 6 hours. After the temperature equalizes in the kernel, the cooling fan is turned on and the temperature is taken down to the desired level.
This publication is a good introduction to grain drying.