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@[email protected]
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
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