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Corn Storage and Drying – Spring 2009

Corn Storage and Drying – Spring 2009. Kenneth Hellevang, Ph.D., P.E. Professor & Extension Engineer Agricultural & Biosystems Engineering NDSU Extension Service. Corn Flowability. 28% moisture freezes together 24% - 25% some binding <24% to assure flow Foreign material affects flow.

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Corn Storage and Drying – Spring 2009

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  1. Corn Storage and Drying – Spring 2009 Kenneth Hellevang, Ph.D., P.E. Professor & Extension Engineer Agricultural & Biosystems Engineering NDSU Extension Service

  2. Corn Flowability • 28% moisture freezes together • 24% - 25% some binding • <24% to assure flow • Foreign material affects flow

  3. Grain Hazards Bridging transfers load to the bin wall CAUGHT IN THE GRAIN! AE-1102

  4. Moldy Grain Health Hazard At least a N-95 rating

  5. 26% - 30% Moisture Corn • 28% corn @ 40°F AST = 30 days • Pile so can mechanically load • Aerate • High temperature dry by late February

  6. Holding 22% - 25% Corn • Cool to 20°F • High temperature dry by early March • Deterioration in early spring (AST)

  7. Grain Temperature Average Maximum Temp. February 1 - 15° March 1 - 27° April 1 - 45° May 1 - 65° Solar Radiation (Btu/ft2-day) Wall Roof Feb. 21 1725 1800 Jun. 21 800 2425 Periodically Cool Keep under 30°F

  8. Cable Temperature sensor Temperature indicator Fan Senses only grain near cable

  9. “Approximate” Allowable Storage Time for Cereal Grains (Days)

  10. Cooling Time 15 / cfm/bu = hrs Example: 42’ diameter, 36 ft depth, Corn 3 hp. Axial Fan, 0.15 cfm/bu Cooling time = 100 hrs. Aeration Airflow Rate Selection

  11. Fans Off During Snow/Rain/Fog

  12. Condensation may freeze over vents when outside air temperatures are below freezing

  13. Cover Fans When Not Operating • Prevents spring warm-up • Keep snow & pests out • Keep damp air out

  14. Storability Cracked, broken, immature corn spoils easier • Monitor: • Temperature • Moisture • Insects

  15. Let Stand Over Winter • Spring (March) moisture content ≈19% • Field losses unknown • Snow accumulation 40”= 4” water

  16. Rewetting or Drying Corn Equilibrium Moisture Content March 25°F & 76% RH, April 42°F & 71% RH

  17. Air Drying • 21% Maximum moisture content • 1.0 cfm/bu minimum airflow rate • Cool to 20°F for winter storage • Start drying early April

  18. Minimum Recommended Airflow Rate For Natural Air Drying Corn Airflow Moisture RateContent (cfm/bu) (%) 1.00 21 1.25 22 1.5 23 2.0 24 2.3 25 Wilcke and Morey, University of Minnesota Bu-6577-E, 1995

  19. “Approximate” Allowable Storage Time for Cereal Grains (Days)

  20. Natural Air & Low Temperature Corn Drying Spring Drying

  21. Air Drying

  22. Fan Power Required Limit Corn Depth 42 ft diameter bin, corn 36 ft deep, 1.0 cfm/bu Fan = 180 hp, static pressure = 17-inches wg. Not feasible

  23. Fan Type Comparison Corn: 21 ft. diameter, 20 ft. deep, 10 hp fan

  24. High Temp. Dryer Management • High temperatures, fast drying, fast cooling creates stress cracks & broken kernels • High moisture increases scorching potential

  25. Energy Efficiency Tips Energy requirements of a conventional high temperature cross-flow dryer as a function of drying air temperature and airflow rate. (University of Nebraska, about 1970) • Use maximum drying temperature that does not damage the corn • Airflow of Dryer Types • Mixed Flow ~ 40 cfm/bu • Cross-Flow ~ 70-90 cfm/bu • Airflow rate affects drying rate • Vacuum Cooling

  26. Drying Energy Cost Estimation High Temperature Drying~210°F Assumes 2,500 Btu/lb water Propane cost / bu- point moisture = 0.022 x price/gal $ 0.033/bu-pt = 0.022 x $1.50/gal @ $1.50/gal propane, estimated propane cost to dry corn from 25% to 15% is $0.033/bu-pt x 10 pts = $0.33/bu.

  27. Estimate Propane Quantity Needed Propane gallons = 0.02 x bu. x point moisture Propane = 0.02 x 1,000 bu x 10 pts = 200 gallons

  28. Moisture Meter Error • Electronic meters more sensitive to outside of kernel • Measure moisture content • Place sample in sealed container for several hours (6-12 hrs) • Recheck moisture • Adjust for temperature

  29. Moisture Shrink(Weight loss due to moisture loss) Moisture Shrink (%) = Mo – Mf__ x 100 100 – Mf Example: Corn dried from 25% to 15% moisture Shrink%= 25% – 15%__ x 100 = 11.76% 100% – 15% Shrink Factors (% weight loss/percentage point moisture loss) Example: The moisture shrink drying corn from 25.5% to 15.5% is 10pts x 1.1834 = 11.8%

  30. Adjustment added to the corn wet-harvest test weight to obtain an expected test weight after drying to 15.5 percent moisture. Affected by: * Kernel Damage * Drying Temperature * Variety Normally ¼ to 1/3 lb/pt.

  31. Dryeration Dump hot, temper without airflow 4-6 hrs, cool, move to storage Increases dryer capacity 50%-75%, Reduces energy by about 25%

  32. In-Storage Cooling Immediately cool, Airflow rate  12 cfm/bu-hr of fill rate Reduce condensation by partial cooling in the dryer

  33. For More Information http://www.ag.ndsu.nodak.edu/abeng Google: NDSU Corn Drying

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