Corn storage and drying spring 2009
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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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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


Grain Hazards

Bridging transfers load to the bin wall

CAUGHT IN THE GRAIN!

AE-1102


Moldy Grain Health Hazard

At least a N-95 rating


26% - 30% Moisture Corn

  • 28% corn @ 40°F AST = 30 days

  • Pile so can mechanically load

  • Aerate

  • High temperature dry by late February


Holding 22% - 25% Corn

  • Cool to 20°F

  • High temperature dry by early March

    • Deterioration in early spring (AST)


Grain Temperature

Average Maximum Temp.

February 1 - 15°

March 1 - 27°

April 1 - 45°

May 1 - 65°

Solar Radiation (Btu/ft2-day)

WallRoof

Feb. 21 17251800

Jun. 21 8002425

Periodically Cool Keep under 30°F


Cable

Temperature sensor

Temperature indicator

Fan

Senses only grain near cable


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


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


Fans Off During Snow/Rain/Fog


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


Cover Fans When Not Operating

  • Prevents spring warm-up

  • Keep snow & pests out

  • Keep damp air out


Storability

Cracked, broken, immature corn spoils easier

  • Monitor:

  • Temperature

  • Moisture

  • Insects


Let Stand Over Winter

  • Spring (March) moisture content ≈19%

  • Field losses unknown

  • Snow accumulation 40”= 4” water


Rewetting or Drying

Corn Equilibrium Moisture Content

March 25°F & 76% RH, April 42°F & 71% RH


Air Drying

  • 21% Maximum moisture content

  • 1.0 cfm/bu minimum airflow rate

  • Cool to 20°F for winter storage

  • Start drying early April


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


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


Natural Air & Low Temperature Corn Drying

Spring Drying


Air Drying


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


Fan Type Comparison

Corn: 21 ft. diameter, 20 ft. deep, 10 hp fan


High Temp. Dryer Management

  • High temperatures, fast drying, fast cooling creates stress cracks & broken kernels

  • High moisture increases scorching potential


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


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.


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


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


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%


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.


Dryeration

Dump hot, temper without airflow 4-6 hrs, cool, move to storage

Increases dryer capacity 50%-75%,

Reduces energy by about 25%


In-Storage Cooling

Immediately cool, Airflow rate  12 cfm/bu-hr of fill rate

Reduce condensation by partial cooling in the dryer


For More Information

http://www.ag.ndsu.nodak.edu/abeng

Google: NDSU Corn Drying


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