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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

Corn Storage and Drying – Spring 2009

Kenneth Hellevang, Ph.D., P.E.

Professor & Extension Engineer

Agricultural & Biosystems Engineering

NDSU Extension Service


Corn flowability
Corn Flowability

  • 28% moisture freezes together

  • 24% - 25% some binding

  • <24% to assure flow

  • Foreign material affects flow


Grain hazards
Grain Hazards

Bridging transfers load to the bin wall

CAUGHT IN THE GRAIN!

AE-1102


Moldy grain health hazard
Moldy Grain Health Hazard

At least a N-95 rating


26 30 moisture corn
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
Holding 22% - 25% Corn

  • Cool to 20°F

  • High temperature dry by early March

    • Deterioration in early spring (AST)


Grain temperature
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


Senses only grain near cable

Cable

Temperature sensor

Temperature indicator

Fan

Senses only grain near cable


Approximate allowable storage time for cereal grains days
Approximate” Allowable Storage Time for Cereal Grains (Days)


Aeration airflow rate selection

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




Cover Fans When Not Operating temperatures are below freezing

  • Prevents spring warm-up

  • Keep snow & pests out

  • Keep damp air out


Storability temperatures are below freezing

Cracked, broken, immature corn spoils easier

  • Monitor:

  • Temperature

  • Moisture

  • Insects


Let stand over winter
Let Stand Over Winter temperatures are below freezing

  • Spring (March) moisture content ≈19%

  • Field losses unknown

  • Snow accumulation 40”= 4” water


Rewetting or drying
Rewetting or Drying temperatures are below freezing

Corn Equilibrium Moisture Content

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


Air drying
Air Drying temperatures are below freezing

  • 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 temperatures are below freezing

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 days1
temperatures are below freezingApproximate” Allowable Storage Time for Cereal Grains (Days)


Natural air low temperature corn drying
Natural Air & Low Temperature temperatures are below freezingCorn Drying

Spring Drying


Air drying1
Air Drying temperatures are below freezing


Fan power required
Fan Power Required temperatures are below freezing

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
Fan Type Comparison temperatures are below freezing

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


High temp dryer management
High Temp. Dryer Management temperatures are below freezing

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

  • High moisture increases scorching potential


Energy efficiency tips
Energy Efficiency Tips temperatures are below freezing

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
Drying Energy Cost Estimation temperatures are below freezing

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
Estimate Propane Quantity Needed temperatures are below freezing

Propane gallons = 0.02 x bu. x point moisture

Propane = 0.02 x 1,000 bu x 10 pts = 200 gallons


Moisture meter error
Moisture Meter Error temperatures are below freezing

  • 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 temperatures are below freezing(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
Dryeration obtain an expected test weight after drying to 15.5 percent moisture.

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
In-Storage Cooling obtain an expected test weight after drying to 15.5 percent moisture.

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

Reduce condensation by partial cooling in the dryer


For More Information obtain an expected test weight after drying to 15.5 percent moisture.

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

Google: NDSU Corn Drying


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