Transcript Lecture 5 Grain Drying Fundamentals

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
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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 & 500-1500 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
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