AERATION AERATION and COOLING and COOLING of Stored Grain of - - PowerPoint PPT Presentation
AERATION AERATION and COOLING and COOLING of Stored Grain of Stored Grain Mark Casada , Ph.D., P.E. , Ph.D., P.E. Mark Casada Agricultural Engineer Agricultural Engineer USDA ARS ARS USDA Grain Marketing & Production Grain
Mark Casada Mark Casada , Ph.D., P.E.
, Ph.D., P.E. Agricultural Engineer Agricultural Engineer USDA USDA – – ARS ARS Grain Marketing & Production Grain Marketing & Production Research Center Research Center Manhattan, Kansas Manhattan, Kansas
IAOM Pest Management Workshop IAOM Pest Management Workshop
1981: 1981: B.S. Mechanical Engineering (P.E.) B.S. Mechanical Engineering (P.E.) 1980s: 1980s: corn, tobacco, peanuts (Ky. & NC) corn, tobacco, peanuts (Ky. & NC) 1990s: 1990s: wheat, barley, & potatoes (Idaho) wheat, barley, & potatoes (Idaho) 2000s: 2000s: wheat, corn (Kansas) wheat, corn (Kansas) 20+ years: 20+ years: crop storage & handling crop storage & handling research and teaching research and teaching
Introduction… Grain Storage Basics
Grain Moisture: affect on storage
Grain Temperature & Cooling
Grain Aeration Systems
Cool, dry, clean Cool, dry, clean grain stores very well: grain stores very well: we expect we expect no quality loss no quality loss. . Aeration is the tool to keep grain cool: Aeration is the tool to keep grain cool: Alw ays below 6 0 ° F, Alw ays below 6 0 ° F, below 5 0 ° F w hen w eather allow s. below 5 0 ° F w hen w eather allow s.
Insects
Fungi (molds)
Sprouting
Loss of Germination
Handling Damage
Rodents and Birds
Other (Spoutlines, Moisture Migration, …)
Insects
Fungi (molds)
Sprouting
Loss of Germination
Handling Damage
Rodents and Birds
Other (Spoutlines, Moisture Migration, …)
– – soundness soundness – – degree of contamination (fungi, insects, …) degree of contamination (fungi, insects, …) – – amount of foreign material amount of foreign material
Dry Dry Cool Cool Clean Clean
– – soundness soundness – – degree of contamination (fungi, insects, …) degree of contamination (fungi, insects, …) – – amount of foreign material amount of foreign material
control w/ temperature control w/ temperature
control w/ moisture control w/ moisture
– – Emphasis on dry grain (or over Emphasis on dry grain (or over-
dry).
Moisture problems usually very limited.
– – Insects usually the bigger issue Insects usually the bigger issue (temperature). (temperature).
Low moisture content may slow or stop some primary infesting insects. some primary infesting insects.
Corn Moisture Isotherm (68°F)
5 10 15 20 25 20 40 60 80 100
Relative Humidity, % Equilibrium Moisture Content, %
Moisture Content
the key to mold the key to mold control control
60% 70% 80% Relative Humidity, % Storage Mold Growth
Min. Max.
65% 65%
Average Moisture Content Average Moisture Content – – Very little grain is at the “average” Very little grain is at the “average” moisture content moisture content Must deal with the Must deal with the highest highest moisture content in the bin moisture content in the bin
Cold Air Warm Grain
Moisture migration Moisture migration causes additional causes additional moisture variation moisture variation
Wet grain
Wet grain
Watch for Watch for “simple problems” “simple problems” A leak is a leak… A leak is a leak…
Watch for Watch for “simple problems” “simple problems” Spouting can channel Spouting can channel leaking water…
Wet grain
leaking water…
60 70 80 90 Temperature, °F Storage Insect Growth
Min. Max.
60°F 60°F
Temperature Temperature is the key is the key to to insect control insect control
90 90 80 80 75 75 60 60 50 50 40 40
< < 0
°F °F
Optimum for population growth ptimum for population growth
Helpful to slow population growth
Generally stops population growth
Leads to eventual death of storage insects
Winter storage (stops moisture migration)
Only way to achieve quick kill…
– – eliminate sources of infestation eliminate sources of infestation
– – cool immediately to slow development cool immediately to slow development
– – temperature & insect numbers temperature & insect numbers
Using thermostatic controllers to Using thermostatic controllers to automate the aeration cycles automate the aeration cycles Objective: Objective: keep grain within 10 keep grain within 10 – – 15°F of 15°F of average ambient temperature average ambient temperature Three Cooling Cycles Three Cooling Cycles Summer: Summer: Cool grain immediately below 75°F
Cool grain immediately below 75°F
Fall: Fall: Cool below 60°F as soon as weather
Cool below 60°F as soon as weather permits permits
Late Fall: Late Fall: Cool to 40°F for winter storage
Cool to 40°F for winter storage
Simple aeration controllers are:
– – cheap (pay off cheap (pay off ≤ ≤ one year)
– – easy to use (thermostat + hour meter) easy to use (thermostat + hour meter) – – effective and efficient effective and efficient – – and should be on every grain bin. and should be on every grain bin.
Thermostat Hour Meter Relay Fan
Cool grain immediately below 75°F
Cool to 60°F as soon as feasible (weather)
Maintain the grain
– – monitor temperatures: monitor temperatures: aerate as needed aerate as needed – – monitor insects: monitor insects: aerate/ fum igate as aerate/ fum igate as required required
Cool to 40°F for winter storage
Maintain the grain – – seal fan opening seal fan opening
Cool grain immediately below 75°F
Cool to 60°F as soon as feasible (weather)
Maintain the grain
– – monitor temperatures: monitor temperatures: aerate as needed aerate as needed – – monitor insects: monitor insects: aerate/ fum igate as aerate/ fum igate as required required
Cool to 40°F for winter storage
Maintain the grain – – seal fan opening seal fan opening
Insect infested grain mixed with clean grain
Insects move through the system with grain
Insect numbers often higher than on-
farm
Segregate by infestation level and treat
Sanitation in and around grain bins
Cooling grain (controlled aeration)
– – lower airflows ( lower airflows (cfm cfm/ /bu bu) important for cost ) important for cost – – pressure systems add more heat with deep bins pressure systems add more heat with deep bins
Monitoring grain
– – Know & avoid equipment hazards Know & avoid equipment hazards – – Always know the bin history Always know the bin history
Practice lockout / tagout tagout
Beware: flowing grain (stay out!)
Beware: bridged grain (stay off of it)
Beware: steep piles (stay away from it)
Beware: dust/mold spores (wear mask)
Beware: CO2
2 buildup (ventilate)
buildup (ventilate)
Beware: grain dust & sparks (eliminate!)
– – Stop grain dust fires & explosions Stop grain dust fires & explosions
Hazards: Hazards:
Grain dust is an airborne pollutant
– – Long Long-
term effects under investigation – – Nuisance in surrounding residential areas Nuisance in surrounding residential areas
Grain dust is a fire and explosion hazard
– – Powerful and deadly explosions Powerful and deadly explosions – – Requires three ingredients Requires three ingredients
Grain Dust is the Big One Grain Dust is the Big One
Grain dust suspended in air
– – Design and manage to eliminate dust Design and manage to eliminate dust
Sparks initiate a flame (at 400°F)
– – Design and maintain to avoid sparks/hotspots Design and maintain to avoid sparks/hotspots
Confined area permits high pressure/explosion
– – Design to eliminate confined areas Design to eliminate confined areas
– – Fumigation w/ turning Fumigation w/ turning – – Fumigation Fumigation – – Turning Turning – – Aeration Aeration
lower cost
Recommended Airflow Rates for Dry Grain (Foster & Tuite, 1982): Recommended rate*, cfm/bu Storage Type Temperate Climate Subtropic Climate Horizontal 0.05 → 0.10 0.10 → 0.20 Vertical 0.03 → 0.05 0.05 → 0.10
*Higher rates increase control, flexibility, and cost.
Fan Fan
Suction ( Suction (downflow downflow) ) Pressure ( Pressure (upflow upflow) )
Required if warm grain placed on top of cool grain
Last grain to cool is at top: easily monitored
Natural convection aids aeration in deep bins
Fan energy compensates for too cool or moist air
More uniform airflow in flat storages (long ducts)
No solar heat pulled in from top to over dry grain
Won’t cause roof collapse if vents freeze Pressure vs. Suction Aeration
Excess moisture is easily detected at top
Allows you to smell the exhaust at ground level
Condensation ≈ ≈ below the grain; limited in duct below the grain; limited in duct
High inlet brings in less dirt and debris
Eliminates potential to suck in winter snow
Can aerate spots in flat storages using plastic Pressure vs. Suction Aeration
“X” System “X” System “Y” System “Y” System Parallel “I” Parallel “I”
Pad System Pad System
d dwall
wall =
= ½
½ grain
grain depth depth
Close to full drying Close to full drying floor effectiveness floor effectiveness Less expensive than Less expensive than drying floor drying floor
to Control Molds ERH < 65 % for long term storage ERH < 65 % for long term storage Use the highest moisture in the bin Use the highest moisture in the bin
to Control Insects T ≤ 40°F in winter (always < 60°F) T ≤ 40°F in winter (always < 60°F) Watch the highest temperature in the bin Watch the highest temperature in the bin
Practices to Control Hazards
– – eliminate sources of infestation eliminate sources of infestation – – cool immediately to slow development cool immediately to slow development
– – temperature & insect numbers temperature & insect numbers
– – http://pasture. http://pasture.ecn ecn. .purdue purdue. .edu edu/~ /~grainlab grainlab/ / – – http://www. http://www.oznet
.ksu ksu. .edu edu/ /wheatpage wheatpage/ / – – http://www. http://www.bae bae. .umn umn. .edu edu/ /extens extens/ /postharvest postharvest/ / – – http:// http://bru bru. .gmprc gmprc. .ksu ksu. .edu edu/ /proj proj/ /sga sga/ /
.
Post -
Harvest Handling of Crops
Stored Grain Advisor
Three criteria: – – Duct spacing Duct spacing not “excessive”
not “excessive”
less than ½ grain depth to duct anywhere on floor
– – Air velocity Air velocity< 2500 fpm for pressure system
< 2500 fpm for pressure system < 1500 fpm for suction < 1500 fpm for suction
– – Perforated Perforated surface area surface area = 1 ft
= 1 ft2
2 per 25 cfm
per 25 cfm
Miscellaneous:
– – Use well Use well-
designed fan-
to-
duct transition – – Perforated ducts: minimum 10% open Perforated ducts: minimum 10% open – – Roof vents: 1 ft Roof vents: 1 ft2
2/hp (pressure)
/hp (pressure) – – In In-
floor ducts don’t interfere with unloading – – Effective area = 75% for round ducts on floor Effective area = 75% for round ducts on floor
1 . 1 . Select Select lowest airflow ( lowest airflow (cfm cfm/ /bu bu) for cooling rate ) for cooling rate 2 . 2 . Airflow: Airflow: cfm/ft cfm/ft2
2 = (0.8) x (depth) x (
= (0.8) x (depth) x (cfm cfm/ /bu bu) ) 3 3 . Pressure drop: . Pressure drop: ∆ ∆P = (inH P = (inH2
2O/ft) x (depth) + 0.4
O/ft) x (depth) + 0.4 4 . 4 . Total airflow: Total airflow: cfm = ( cfm = (cfm cfm/ /bu bu) x (total bushels) ) x (total bushels)
cfm = (cfm/ ft cfm = (cfm/ ft2
2) x (floor area)
) x (floor area) 5 . 5 . Select fan Select fan to deliver flow & pressure (fan data) to deliver flow & pressure (fan data)
Double the Recommended Airflows for Controlled Aeration Systems Recommended rate*, cfm/bu Storage Type Temperate Climate Subtropic Climate Horizontal 0.10 → 0.20 0.20 → 0.40 Vertical 0.05 → 0.10 0.10 → 0.20
*Higher rates increase control, flexibility, and cost.
– – More effective than probing More effective than probing – – More efficient than probing More efficient than probing
time
fumigant
– – Safer than probing Safer than probing
reduces exposure to fumigant
reduces dust
eliminates enclosed space entry