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Lecture 5

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

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  1. Lecture 5 Grain Drying Fundamentals

  2. 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

  3. 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

  4. Developing a Uniform drying front • Uniform air flow • Parallel air flow

  5. Drying Calculations • Size of bin • Rating of fan • Moisture of grain currently & desired • Temp of drying air • RH of drying air

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

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