Fall always seems like a good time to review grain drying terms such as low temperature drying, high speed drying and combination drying.
High speed drying refers to a grain handling system that rapidly lowers moisture content to acceptable levels for storage. In such a system, air, usually heated by propane, is forced through the grain mass by one or more fans. The rapidly heated grain then goes through a cooling process in storage or is moved to storage following a cooling process.
Low temperature drying refers to a grain handling system that also utilizes fans. The system is often used in October and November when relative humidity is around 80%. Sometimes a second drying season may occur in March and April. The goal of the producer using this method is to get relative humidity to about 65% inside the bin by raising the temperature of the air passing through the bin. This allows grain in the mid-twenty percent moisture range to dry down to acceptable moisture levels for storage. Sometimes, the producer uses natural air flow through the fan. This results in a natural increase of about two degrees and can usually reduce moisture to short-term storable levels. Often a small amount of supplemental heat via electricity or propane is used to reduce moisture content to 14 or 15% for long-term storage. For overall grain quality, this method usually proves very beneficial since it reduces the damage to kernels created by a rapid, high speed dry down. Unfortunately, this type of dry down may sometimes take the better portion of a week or two weeks, and drying may slow down further if the weather turns too cold since cold air has a much harder time removing moisture. Additionally, harvest may surpass drying capacity creating storage problems.
Combination drying is probably the most popular method of the three. In this system, high speed drying and low temperature drying are combined. The grain initially is passed through a high speed dryer such as a continuous flow dryer or it is placed in a bin dryer such as the common drying bin with stirrators found on many farms. In this process, wet grain is dried down to a point where natural air can accomplish "the rest of the drying task." Such a system often results in both decreased energy costs, since not as much propane or electricity is used, and increased storage capacity, since high speed drying bins are rapidly emptied into low temperature bins.
Source: Matt Montgomery, Extension Educator, Local Food Systems and Small Farms, firstname.lastname@example.org
Pull date: September 17, 2012