Drying High Moisture Corn Drying High Moisture Corn –– Challenges of the 2009 Harvest SeasonChallenges of the 2009 Harvest Season

Grain Journal WebinarGrain Journal Webinar

October 30, 2009October 30, 2009

Dirk E. Maier, Ph.D., P.E.Dirk E. Maier, Ph.D., P.E.Grain Science & IndustryGrain Science & IndustryKansas State UniversityKansas State University

dmaier@kdmaier@k--state.edustate.edu

Objective of DryingObjective of Drying

To reduce the harvest moisture To reduce the harvest moisture content of grains and oilseeds to content of grains and oilseeds to levels that are… levels that are… –– safe for storage, and safe for storage, and –– optimum for marketingoptimum for marketing

Safe Storage Moisture Content in Equilibrium with Intergranular Air at 65% Relative Humidity (Chung'89)

11

12

13

14

15

16

0 5 10 15 20 25 30 35

Temperature (C)

Moi

stur

e C

onte

nt (%

)

SorghumCornSoybeansWheat, Hard

DryingDrying SystemSystem

CategoriesCategories

Drying System CategoriesDrying System Categories••

Low TemperatureLow Temperature••

Natural air or air heated by up to 5Natural air or air heated by up to 5--1515°°FF••

InIn--bin (or inbin (or in--storage)storage)

••

Medium TemperatureMedium Temperature••

kernel temps kernel temps below 110below 110°°FF

for seed and food grains, and for seed and food grains, and below below 140140°°FF

for all others (incl. #2 yellow corn, waxy, HOC)for all others (incl. #2 yellow corn, waxy, HOC)••

InIn--bin or columnbin or column

••

High TemperatureHigh Temperature••

kernel temps above 140kernel temps above 140°°FF••

InIn--bin or columnbin or column

••

CombinationCombination••

Med temp plus Med temp plus dryerationdryeration

or inor in--bin coolingbin cooling••

MedMed--low temp 2low temp 2--stage dryingstage drying

CrossflowCrossflow

HotHotDryingDrying

AirAir

MoistMoistExhaustExhaustAirAir

Conventional Conventional CrossflowCrossflow

DryerDryer

Fan

Filling Auger

GrainGrainColumnColumn

Fanand

Heater

WetHolding

Bin

Heated Air Plenum

Cooling Air Plenum

Unloading AugerGrain Meter++ ++

Drying RequiresDrying Requires

••EnergyEnergy••Forced airForced air••TimeTime

The higher the drying air temperature…The higher the drying air temperature…

……the the faster faster andand

…the …the more efficientmore efficient

the drying process will be!the drying process will be!

Dilemma #1:Dilemma #1:

The The higher the drying air temperaturehigher the drying air temperature and the and the faster the drying processfaster the drying process

……

… the … the lower the end use qualitylower the end use quality of of

the dried grains and oilseeds!the dried grains and oilseeds!

Relative Magnitude of Factors Causing Breakage Susceptibility

BreakageBreakage SusceptibilitySusceptibility

Interior Damage:Interior Damage:Stress failure of the endosperm Stress failure of the endosperm resulting in stressresulting in stress--cracked and brittle cracked and brittle kernelskernels

Causes:Causes:Excessive compressive or tensile stresses Excessive compressive or tensile stresses during or after drying, cooling or during or after drying, cooling or rehydration (conditioning)rehydration (conditioning)

ZeroSingleDoubleMultiple

Effect of Final Moisture Effect of Final Moisture on Breakageon Breakage

0%

10%

20%

30%

40%

11% 13% 15% 18%

MoistureMoisture

BreakageBreakage

Effect of Drying Method on Effect of Drying Method on Stress CracksStress Cracks

••Low temperatureLow temperature

<5%<5%

••Medium temperatureMedium temperature& slow cooling& slow cooling

1010--35%35%

••High temperature High temperature 5050--100%100%

Wet Milling Quality – Effect on Extractable Starch

-0.5

0

0.5

1

1.5

2

2.5

3

3.5

130 150 170 190 210 230 250

Drying Air Temperature (F)

Extr

acta

ble

Star

ch R

educ

tion

(pts

)

Dryer 1Dryer 2

200ºF

Grain Kernel TemperatureGrain Kernel Temperature versusversus

Drying Air TemperatureDrying Air Temperature

Grain Grain TypeType –– End Use End Use

–– Maximum Kernel TemperatureMaximum Kernel Temperature

CORNCORN DryDry

MillingMilling

& & SeedSeed 100100--110110°F°FWet MillingWet Milling 130130--140140°F°FFeedFeed

UseUse 160160--180180°F°FWHEATWHEAT SeedSeed

(> 24%)(> 24%) 110110°F°FSeedSeed

(< 24%)(< 24%) 120120°F°FFlourFlour 120120--170170°F°F

SOYBEANSSOYBEANS SeedSeed 100100°F°FOil Oil CrushingCrushing 120120°F°F

SUNFLOWERSUNFLOWER FoodFood 140140--170170°F°FOil CrushingOil Crushing 170170--195195°F°F

RICERICE MillingMilling

(>20%)(>20%) 105105°F°FMillingMilling

(<20%)(<20%) 110110°F°FBARLEYBARLEY MaltingMalting 105105--120120°F°F

FeedFeed 165165--185185°F°FEDIBLE BEANSEDIBLE BEANS Food UseFood Use 100100°F°F

MaximumMaximum DryingDrying

RatesRates

Grain Grain TypeType % % MoistureMoisture LossLoss

CornCorn, , SorghumSorghum, , SunflowerSunflower

LessLess thanthan

5% / 5% / hourshours

WheatWheat LessLess thanthan

4% / 4% / hourshours

SoybeansSoybeans LessLess thanthan

3% / 3% / hourshours

RiceRice Less than 2% / hoursLess than 2% / hours

Effect of Excessive Drying Air TemperatureEffect of Excessive Drying Air Temperature

392°F5 min

392°F10 min

320°F10 min

320°F30 min

Dilemma #2:Dilemma #2:

Temperature and Temperature and Moisture Distribution Moisture Distribution

in Dryersin Dryers

CrossflowCrossflowTemperatureTemperature

AAIIRR

TTEEMMPP

OOUUTT

MEANMEAN

ININ

HotHotDryingDrying

AirAir

MoistMoistExhaustExhaustAirAir

CrossflowCrossflow

OOUUTT

MEANMEAN

ININ

Grain MoistureGrain Moisture

TemperatureTemperature

AAIIRR

TTEEMMPP

OOUUTT

MEANMEAN

ININ

HotHotDryingDrying

AirAir

MoistMoistExhaustExhaustAirAir

Drying Corn from 25% Drying Corn from 25% to 19% at 230° Fto 19% at 230° F

DistanceDistance

GrainGrain

MoistureMoisture

BreakageBreakagefrom Air Inletfrom Air Inlet

TemperatureTemperature

ContentContent

SusceptibilitySusceptibility

inchesinches

°F°F

%%

%%

0.5

215

10

483.0

172

20

11

5.5

124

24

10

Modified Modified CrossflowCrossflow DryerDryer

GrainMeter

Filling Auger

Heated Air Plenum

Unloading Auger

HeatingChamber

Warm Warm Air OutAir Out

CoolingCoolingAir InAir In

Control BoxControl Box

Effect of Exhaust Air Effect of Exhaust Air Recirculation Recirculation

AirAir

MoistureMoisture

SpecificSpecificTemp.(°F)Temp.(°F)

GradientGradient

Energy (Btu/lb)Energy (Btu/lb)

No recirculationNo recirculation

154154

5.05.0

3,0003,000

Recirculation/Recirculation/

149149

1.31.3

2,1002,100Suction CoolingSuction Cooling

--74%74% --30%30%

Grain Column Grain Column Turning Turning

DifferentialDifferential Grain Grain SpeedSpeed

DryerDryer

Dilemma #3:Dilemma #3:

Initial KernelInitial Kernel--toto--Kernel Kernel Moisture Variability Moisture Variability

Average moisture content (MC), moisture content range, percentage point differential, and standard deviation (SD) in maize kernels collected at the inlet and outlet of commercial crossflow (CF), concurrent-flow (CCF), and mixed-flow (MF) dryers. (Source: Montross et al. 1994)

Dryer Type

Average MC (%)

MC Range (%) Point Differential

Standard Deviation

InIn OutOut InIn OutOut InIn OutOut InIn OutOut

CFCF 20.820.8 15.015.0 10.0 10.0 ––

33.133.1 8.5 8.5 ––

31.531.5 +23.1+23.1 +23.0+23.0 3.923.92 4.824.82

CCFCCF 21.721.7 14.714.7 14.5 14.5 ––

37.537.5 7.0 7.0 ––

34.034.0 +23.0+23.0 +27.0+27.0 4.424.42 4.574.57

MFMF 22.422.4 14.814.8 8.5 8.5 ––

38.538.5 8.0 8.0 ––

35.535.5 +30.0+30.0 +27.5+27.5 4.234.23 4.194.19

Segregating Segregating Initial MoisturesInitial Moistures

Silo 1 = 22-25%

Silo 2 = 19-22%

Silo 3 = 16-19%

Tempering (steeping)Tempering (steeping)

Medium Temperature Medium Temperature Drying Drying

andand Slow CoolingSlow Cooling

Slow Cooling Methods:Slow Cooling Methods:

•• InIn--bin coolingbin cooling••DryerationDryeration••Combination highCombination high--lowlow••Continuous slow coolingContinuous slow cooling

High Capacity Drying followed High Capacity Drying followed by by DryerationDryeration

MediumTempBin Dryer

••

66--12 hours tempering of 12 hours tempering of hot grainhot grain

••

0.50.5--1.5 1.5 cfm/bucfm/bu

cooling cooling airflowairflow

••

1212--24 hours cooling time24 hours cooling time••

22--3 points moisture loss 3 points moisture loss during coolingduring cooling

••

Transfer cooled & dried Transfer cooled & dried grain to final storagegrain to final storage••

batch or continuousbatch or continuous

Effect of Tempering on Single Kernel MC and Stress Cracks

Single Kernel Moisture Test 1

0

5

10

15

20

25

0 1 2 3 4 5 6

% M

C

Hour 0Hour 1Hour 2Hour 3Hour 4Crack Test

10/29/2003

Crac

k

2.45 2.39 1.96 1.40 1.09

1.30 1.17 1.26 1.04 0.87

MC s.d.

SC s.d.

Continuous-Flow Dryeration System

Dilemma #4:Dilemma #4:

Hybrid Effects on Hybrid Effects on Drying CapacityDrying Capacity

0.6

0.7

0.8

0.9

1

0 5 10 15 20 25 30 35 40 45Tim e , m in

Moi

stur

e R

atio

C1

C2

C3

C4

Drying Times for Four Corn Hybrids – Conditions: 22.5%

15% mc at 180°F (82°C)

Drying time difference of 2x

Drying Times for Soybean Varieties (Giner 1995)

0 20 40 60 80 100 120 140

Torcaza 63Tancacha INTA

OFPEC Juan FeOFPEC 627Norking 641

MitchellMartineta 50Inriville INTA

Hood SCAHood 75

Federada 1 INTAFarnailla 841Farnailla 837

Deltapine 345Crawford

Copetona 53Coker 237Bragg SCBigua 54

Asgrow 6381Asgrow 5502Asgrow 5306Asgrow 3127

Minutes

Series2Soybeans were dried at 140°F (60°C) from 22 to 13% moisture

+55%

Managing Energy CostsManaging Energy Costs

••Energy efficiencyEnergy efficiency––Hot corn transfer (Hot corn transfer (dryerationdryeration, in bin cooling), in bin cooling)––Vacuum/suction coolingVacuum/suction cooling–– Exhaust air recirculationExhaust air recirculation

••Avoid drying on extremely cold daysAvoid drying on extremely cold days––Natural gas use penalties may applyNatural gas use penalties may apply

••Alternative fuelsAlternative fuels––BiofuelsBiofuels

(biodiesel)(biodiesel)

Drying FrostDrying Frost--Damaged CornDamaged Corn

Milk StageMilk Stage•• low yield, difficult to pick & shell, chaffylow yield, difficult to pick & shell, chaffy•• green chop or ensile whole plantsgreen chop or ensile whole plants

Dough StageDough StageDent StageDent Stage

Drying FrostDrying Frost--Damaged Corn Damaged Corn –– Dough Stage Dough Stage

Low yields & TW (50 lb/Low yields & TW (50 lb/bubu and less)and less)High kernel MCsHigh kernel MCs

•• Soft dough 60Soft dough 60--62% MC; field dry to 35% MC before harvest62% MC; field dry to 35% MC before harvestHigh cob MCsHigh cob MCs Kernel (%)Kernel (%) 1010 1515 2020 2525 3030 3535 4040

Cob (%)Cob (%) 99 1818 3333 4545 5252 5656 5959

•• “Drier Damage” of doughy kernels at high drying air “Drier Damage” of doughy kernels at high drying air temperaturestemperatures

•• Wrinkled, blistered, darkened, brown Wrinkled, blistered, darkened, brown •• max grain kernel temp below 120max grain kernel temp below 120--140140°°FF

•• Dry to 14% MC for shortDry to 14% MC for short--term winter storageterm winter storage•• Longer storage increases risk for selfLonger storage increases risk for self--heatingheating

Drying FrostDrying Frost--Damaged Corn Damaged Corn –– Dent StageDent StageBelow normal TWBelow normal TW

•• >50 lb/>50 lb/bubu similar feeding valuesimilar feeding value•• <50 lb/<50 lb/bubu may contain…may contain…

•• hard to digest free sugarshard to digest free sugars•• less oilless oil•• incompletely developed proteinincompletely developed protein

MC at frozen stageMC at frozen stage•• early dent: 50early dent: 50--55% MC55% MC•• late dent: 40% MClate dent: 40% MC

Harvest at 30Harvest at 30--35% MC35% MC•• If blackIf black--layered before frost, corn is physiologically maturelayered before frost, corn is physiologically mature

Dry but keep max grain kernel temp below 120Dry but keep max grain kernel temp below 120--140140°°FFDry to safe storage moisture contentDry to safe storage moisture content

Average rate of grain moisture loss for three corn Average rate of grain moisture loss for three corn hybrids planted in late April to early May in Indiana hybrids planted in late April to early May in Indiana

Source: Nielsen 2002

SummarySummary

Dilemma 1:Dilemma 1:••

High temperatures and rapid drying results in High temperatures and rapid drying results in poor grain qualitypoor grain quality––

breakage susceptibility, stress cracks, processing breakage susceptibility, stress cracks, processing quality, end use qualityquality, end use quality

Solution:Solution:••

Do not exceed maximum grain temperaturesDo not exceed maximum grain temperatures

•• Do not exceed maximum drying ratesDo not exceed maximum drying rates

•• Use medium and low temperature drying systemsUse medium and low temperature drying systems

SummarySummary

Dilemma 2:Dilemma 2:••

High temperature, high capacity High temperature, high capacity crossflowcrossflow

drying systems cause temperature and moisture drying systems cause temperature and moisture content gradientscontent gradients

Solution:Solution:••

Use modified Use modified crossflowcrossflow

dryers with …dryers with …

––

suction coolingsuction cooling––

column inverterscolumn inverters––

variable column speedsvariable column speeds••

Use mixed flow (rack) or concurrentUse mixed flow (rack) or concurrent--flow dryersflow dryers

SummarySummary

Dilemma 3:Dilemma 3:••

High temperature, high capacity drying High temperature, high capacity drying systems cannot improve the initial kernelsystems cannot improve the initial kernel--toto--

kernel moisture content variabilitykernel moisture content variability

Solution:Solution:••

Segregate grain based on initial moistureSegregate grain based on initial moisture

•• Use multiple drying and tempering stagesUse multiple drying and tempering stages

•• Use continuousUse continuous--flow flow dryerationdryeration

processprocess

SummarySummary

Dilemma 4:Dilemma 4:••

Capacity of high temperature, high capacity drying Capacity of high temperature, high capacity drying systems can be significantly affected by hybrid systems can be significantly affected by hybrid drying rate differencesdrying rate differences

Solution:Solution:••

Choose dryer based on 70Choose dryer based on 70--80% of rated drying 80% of rated drying capacitycapacity

•• Utilize moistureUtilize moisture--based automatic drying control based automatic drying control systemssystems

•• Use stochastic dryer controlUse stochastic dryer control

SummarySummary

••When drying poor quality, frostWhen drying poor quality, frost-- damaged corn, …damaged corn, …

–– don’t exceed maximum grain kernel don’t exceed maximum grain kernel temperatures of 120temperatures of 120--140 F on doughy kernels 140 F on doughy kernels to avoid/minimize “dryer damaged” kernelsto avoid/minimize “dryer damaged” kernels–– don’t plan to store low quality corn past the don’t plan to store low quality corn past the

cold winter periodcold winter period–– dry and store at 14% to avoid storage dry and store at 14% to avoid storage

problemsproblems

“Leaders & Knowledge for the Global Grain Industry”

Dr. Dirk E. Maier, Ph.D., P.E.Professor and HeadDept. of Grain Science & IndustryKansas State UniversityManhattan, Kansas, U.S.A.www.grains.k-state.edu