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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

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lecture 5

Lecture 5

Grain Drying Fundamentals

the drying process
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
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
Developing a Uniform drying front
  • Uniform air flow
  • Parallel air flow
drying calculations
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
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
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 drying1
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

Natural Air Drying
other factors of natural drying
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
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