Lecture 5 Grain Drying Fundamentals
The Drying Process Moisture removed from one point to another at a rate dependant on the difference in water vapor between the two locations Air passed through the bed of grain will either gain or lose moisture Air passing through wet grain will gain moisture Airflow rate Too fast-not as much removed Too slow- not as much removed
Drying Zones Grain does not dry uniformly Especially bin type dryer with low air flow Three Zones Dried Zone Drying Zone-most potential for drying Undried Zone-rewetting zone, condensation occurs here
Developing a Uniform drying front Uniform air flow Parallel air flow
Drying Calculations Size of bin Rating of fan Moisture of grain currently & desired Temp of drying air RH of drying air
Size Groupings of Drying Systems Low Capacity Less than 10,000 bushel/yr & 500 bu/day Medium Capacity 10,000-30,000 bu/yr & bu/day High Capacity More than 30,000 bu/yr & 1,500 bu/day
Natural Air Drying Only energy required is that to run the fan Occurs if RH allow a net moisture transfer Equipment Needed Perforate floor & fanspreader, sweep auger Stirring devices are not needed Portable auger-sized to handle harvest needs At least 500 bu capacity/hr
Natural Air Drying Advantages Most energy efficient Low Cost Move grain only one time ( usually) Disadvantages Slowest method Greatest potential for spoilage Highest level of management More time needed for inspection spoilage Insect problems
Other factors of Natural Drying Rate of drying directly related to the airflow delivered & the RH Quantity of grain may effect air flow Depth of grain Dockage of grain Settling of grain
Concerns with fans Fans of same Hp are not always capable of same air flow Doubling air flow increases energy requirements by 5 times Systems have limited auxiliary drying capacity May require you to partially dry in the fall & complete drying in the spring Maximize efficiency by adding layers, & watching grain temp