AERATION and Cooling of stored grain.pdf

This article is on aeration and cooling of stored grain

1. AERATION AERATION
and COOLING and COOLING
of Stored Grain of Stored Grain
Mark Casada Mark Casada
, Ph.D., P.E. , Ph.D., P.E.
Agricultural Engineer Agricultural Engineer
USDA USDA
––
ARSARS
Grain Marketing & Production Grain Marketing & Production
Research Center Research Center Manhattan, Kansas Manhattan, Kansas
IAOM Pest Ma
nagement Workshop
IAOM Pest Ma
nagement Workshop

2. Professional Experience Professional Experience
GMPRC
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

3. AERATION AERATION
and COOLING and COOLING
of Stored Grain of Stored Grain
••
Introduction… Grain Storage Basics Introduction… Grain Storage Basics
¾¾
Grain Moisture: affect on storage Grain Moisture: affect on storage
••
Grain Temperature & Cooling Grain Temperature & Cooling
••
Grain Aeration Systems Grain Aeration Systems

4. Grain Storage Grain Storage
The Good News: The Good News:
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:
Always below 60°F, Always below 60°F,
below 50°F when weather allows. below 50°F when weather allows.

5. Grain Storage Grain Storage
The Bad News The Bad News
(grain storage threats) (grain storage threats)
::
‹‹
Insects Insects
‹‹
Fungi (molds) Fungi (molds)
‹‹
Sprouting Sprouting
‹‹
Loss of Germination Loss of Germination
‹‹
Handling Damage Handling Damage
‹‹
Rodents and Birds Rodents and Birds
‹‹
Other (Spoutlines, Moisture Migration, …) Other (Spoutlines, Moisture Migration, …)

6. Grain Storage Grain Storage
The Bad News The Bad News
(grain storage threats) (grain storage threats)
::
‹‹
Insects Insects
‹‹
Fungi (molds) Fungi (molds)
‹‹
Sprouting Sprouting
‹‹
Loss of Germination Loss of Germination
‹‹
Handling Damage Handling Damage
‹‹
Rodents and Birds Rodents and Birds
‹‹
Other (Spoutlines, Moisture Migration, …) Other (Spoutlines, Moisture Migration, …)

7. Stored Grain Factors Stored Grain Factors
‹‹
Grain Moisture Content Grain Moisture Content
‹‹
Initial Grain Quality Initial Grain Quality
––
soundness soundness
––
degree of contamination (fungi, insects, …) degree of contamination (fungi, insects, …)
––
amount of foreign material amount of foreign material
‹‹
Time in Storage Time in Storage
‹‹
Other (Oxygen Supply, pH, …) Other (Oxygen Supply, pH, …)
DryDry
CoolCool
Clean Clean
‹‹
Temperature Temperature

8. Stored Grain Factors Stored Grain Factors
‹‹
Temperature Temperature
‹‹
Grain Moisture Content Grain Moisture Content
‹‹
Initial Grain Quality Initial Grain Quality
––
soundness soundness
––
degree of contamination (fungi, insects, …) degree of contamination (fungi, insects, …)
––
amount of foreign material amount of foreign material
‹‹
Time in Storage Time in Storage
‹‹
Other (Oxygen Supply, pH, …) Other (Oxygen Supply, pH, …)

9. Dealing with the Threats Dealing with the Threats
The Top Two Threats The Top Two Threats
‹‹
Insects Insects
‹‹
Fungi (molds)
control w/ temperature control w/ temperature
Fungi (molds)
control w/ moisture control w/ moisture

10. GRAIN MOISTURE GRAIN MOISTURE

11. Dry vs. Wet Grain Dry vs. Wet Grain
‹‹
For this lecture: For this lecture:
––
Emphasis on dry grain (or over Emphasis on dry grain (or over
--
dry). dry).
‹‹
Moisture problems usually very limited. Moisture problems usually very limited.
––
Insects usually the bigger issue Insects usually the bigger issue (temperature). (temperature).
‹‹
Low moisture content may slow or stop Low moisture content may slow or stop some primary infesting insects. some primary infesting insects.

12. Grain Moisture Equilibrium Grain Moisture Equilibrium
Corn
M
o
i
s
t
u
re I
s
ot
h
erm
(
6
8
°
F
)
05
10152025
0
2
04
0
6
08
0
1
0
0
R
e
l
a
ti
v
e
H
u
m
i
d
i
ty, %
Equilibrium Moisture
Content, %

13. Grain Moisture & Mold Control Grain Moisture & Mold Control
‹‹
Moisture Content Moisture Content
Corn at 68°F Corn at 68°F
M.C.M.C.
ERHERH
16 %16 %
79 %79 %
15 %15 %
73 %73 %
14 %14 %
66 %66 %
the key to mold the key to mold
control control
60%
70%
80%
R
e
lat
iv
e H
u
m
i
d
i
t
y
, %
Storage Mold
Growth
Min.Max.
65%65%

14. Safe Storage Moisture Content Safe Storage Moisture Content
G
r
a
in St
o
r
e
d
O
n
e
Y
e
a
r
So
ut
h
C
e
n
t
r
a
l
N
o
r
t
h
Co
r
n
/M
ilo
1
3
1
4
1
4
S
o
y
b
eans
1
2
1
2
1
3
W
h
e
a
t/B
a
r
ley
11
12
13
S
u
n
f
lo
w
e
r
999

15. Grain Moisture Grain Moisture
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

16. Grain Moisture Grain Moisture
Cold
Air
Warm Grain
Moisture migration Moisture migration
causes additional causes additional moisture variation moisture variation
Aerate to eliminate Aerate to eliminate
temperature differences temperature differences
Wet grain

17. Grain Moisture Grain Moisture
Wet grain
Watch for Watch for
“simple problems” “simple problems”
A leak is a leak… A leak is a leak…

18. Grain Moisture Grain Moisture
Watch for Watch for
“simple problems” “simple problems”
Spouting can channel Spouting can channel
leaking water…
Wet grain
leaking water…

19. GRAIN TEMPERATURE GRAIN TEMPERATURE

20. Temperature & Insects Temperature & Insects
60
70
80
90
T
e
m
p
er
at
u
r
e, °F
Storage Insect
Growth
Min.Max.
60°F60°F
Temperature Temperature
is the key is the key
toto
insect control insect control

21. Temperature & Insects Temperature & Insects
9090 8080 7575 6060 5050 4040 <<
00
°F°F
ÖÖ
OO
ptimum for population growth ptimum for population growth
ÖÖ
Helpful to slow population growth Helpful to slow population growth
ÖÖ
Generally stops population growth Generally stops population growth
ÖÖ
Leads to eventual death of storage insects Leads to eventual death of storage insects
ÖÖ
Winter storage (stops moisture migration) Winter storage (stops moisture migration)
ÖÖ
Only way to achieve quick kill… Only way to achieve quick kill…

22. Insect Control in Stored Grain Insect Control in Stored Grain Meet Meet
SAMSAM
::
SS
anitation anitation
AA
eration eration
MM
onitoring onitoring

23. Insect Control in Stored Grain Insect Control in Stored Grain SS
anitation anitation ––
eliminate sources of infestation eliminate sources of infestation AA
eration eration
––
cool immediately to slow development cool immediately to slow development MM
onitoring onitoring
––
temperature & insect numbers temperature & insect numbers

24. Controlled Aeration Controlled Aeration
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

25. Controlled Aeration Controlled Aeration
‹‹
Simple aeration controllers are: Simple aeration controllers are:
––
cheap (pay off cheap (pay off
≤≤
one year) 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.

26. Controlled Aeration Controlled Aeration
Using thermostatic controllers to Using thermostatic controllers to
automate the aeration cycles automate the aeration cycles
A simple controller: A simple controller:
T
h
ermo
st
at
Hou
r
M
e
ter
R
ela
y
Fan

27. Grain Storage Cycle Grain Storage Cycle
‹‹
Cool grain immediately below 75°F Cool grain immediately below 75°F
‹‹
Cool to 60°F as soon as feasible (weather) Cool to 60°F as soon as feasible (weather)
‹‹
Maintain the grain Maintain the grain
––
monitor temperatures: monitor temperatures:
aerate as needed aerate as needed
––
monitor insects: monitor insects:
aerate/fumigate as aerate/fumigate as
required required
‹‹
Cool to 40°F for winter storage Cool to 40°F for winter storage
‹‹
Maintain the grain Maintain the grain
––
seal fan opening seal fan opening

28. Grain Storage Cycle Grain Storage Cycle
‹‹
Cool grain immediately below 75°F Cool grain immediately below 75°F
‹‹
Cool to 60°F as soon as feasible (weather) Cool to 60°F as soon as feasible (weather)
‹‹
Maintain the grain Maintain the grain
––
monitor temperatures: monitor temperatures:
aerate as needed aerate as needed
––
monitor insects: monitor insects:
aerate/fumigate as aerate/fumigate as
required required
‹‹
Cool to 40°F for winter storage Cool to 40°F for winter storage
‹‹
Maintain the grain Maintain the grain
––
seal fan opening seal fan opening

29. YearYear
--
Round Grain Storage Round Grain Storage
Receive Grain All Year Receive Grain All Year
‹‹
Insect infested grain mixed with clean grain Insect infested grain mixed with clean grain
‹‹
Insects move through the system with grain Insects move through the system with grain
‹‹
Insect numbers often higher than on Insect numbers often higher than on
--
farmfarm
‹‹
Segregate by infestation level and treat Segregate by infestation level and treat

30. YearYear
--
Round Grain Storage Round Grain Storage
Storage Fundamentals Storage Fundamentals
‹‹
Sanitation in and around grain bins Sanitation in and around grain bins
‹‹
Cooling grain (controlled aeration) Cooling grain (controlled aeration)
––
lower airflows ( lower airflows (
cfmcfm
//
bubu
) important for cost ) important for cost
––
pressure systems add more heat with deep bins pressure systems add more heat with deep bins
‹‹
Monitoring grain Monitoring grain

31. Grain Storage Safety Grain Storage Safety
––
Know & avoid equipment hazards Know & avoid equipment hazards
––
Always know the bin history Always know the bin history
‹‹
Practice lockout / Practice lockout /
tagout tagout
‹‹
Beware: flowing grain (stay out!) Beware: flowing grain (stay out!)
‹‹
Beware: bridged grain (stay off of it) Beware: bridged grain (stay off of it)
‹‹
Beware: steep piles (stay away from it) Beware: steep piles (stay away from it)
‹‹
Beware: dust/mold spores (wear mask) Beware: dust/mold spores (wear mask)
‹‹
Beware: CO Beware: CO
22
buildup (ventilate) buildup (ventilate)
Don’t be that Guy!
‹‹
Beware: grain dust & sparks (eliminate!) Beware: grain dust & sparks (eliminate!)
––
Stop grain dust fires & explosions Stop grain dust fires & explosions

32. Grain Storage Safety Grain Storage Safety
Hazards: Hazards:
‹‹
Grain dust is an airborne pollutant Grain dust is an airborne pollutant
––
LongLong
--
term effects under investigation term effects under investigation
––
Nuisance in surrounding residential areas Nuisance in surrounding residential areas
‹‹
Grain dust is a fire and explosion hazard 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

33. Grain Storage Safety Grain Storage Safety
Stopping Grain Dust Fires/Explosions Stopping Grain Dust Fires/Explosions
‹‹
Grain dust suspended in air Grain dust suspended in air
––
Design and manage to eliminate dust Design and manage to eliminate dust
‹‹
Sparks initiate a flame (at 400°F) 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 Confined area permits high pressure/explosion
––
Design to eliminate confined areas Design to eliminate confined areas

34. Grain Aeration Systems Grain Aeration Systems

35. Grain Aeration Systems Grain Aeration Systems
––
Fumigation w/ turning Fumigation w/ turning
––
Fumigation Fumigation
––
Turning Turning
––
Aeration Aeration
‹‹
Economics of Insect Treatments Economics of Insect Treatments
lower cost

36. Grain Aeration Systems Grain Aeration Systems
Reco
m
m
e
n
de
d Ai
rf
low
Ra
te
s fo
r D
r
y G
r
a
i
n
(Fo
ste
r & T
u
i
t
e,
19
82
):
R
ecom
m
e
nded rate*, cfm
/
bu
Storag
e
Ty
pe
Tem
p
erate
C
lim
ate
Subtropic
C
lim
ate
Ho
ri
zon
t
al
0.
0
5
→
0.
10
0.
1
0
→
0.
20
Vert
ical
0.
0
3
→
0.
05
0.
0
5
→
0.
10
*
Higher rates increase control, flexibility, and cost.
D
o
u
b
l
e

t
h
e
s
e

r
a
t
e
s

f
o
r
D
o
u
b
l
e

t
h
e
s
e

r
a
t
e
s

f
o
r
c
o
n
t
r
o
l
le
d

a
e
r
a
t
i
o
n
c
o
n
t
r
o
l
le
d

a
e
r
a
t
i
o
n

37. Grain Aeration Systems Grain Aeration Systems
Appro
x
im
ate Cooling Cycle Fan Ti
m
e
:
Airflow
rate (cfm
/bu
)
Season
0.
05
0.
10
0.
25
Su
mm
e
r
180 hr
90 hr
36 hr
Fall
240 hr
120 h
r
48 h
r
Wi
n
t
e
r
300 hr
150 h
r
60 h
r
Sp
rin
g
270 hr
135 h
r
54 h
r
C
o
o
li
n
g

t
i
m
e
s

a

li
t
t
le

l
o
n
g
e
r

C
o
o
li
n
g

t
i
m
e
s

a

li
t
t
le

l
o
n
g
e
r

w
i
t
h

c
o
n
t
r
o
ll
e
d

a
e
r
a
t
i
o
n
w
i
t
h

c
o
n
t
r
o
ll
e
d

a
e
r
a
t
i
o
n
H
i
g
h

h
u
m
i
d
it
y

i
n
c
r
e
a
s
e
s
H
i
g
h

h
u
m
i
d
it
y

i
n
c
r
e
a
s
e
s
c
o
o
l
in
g

t
i
m
es

(
e
v
a
p
o
r
a
t
i
v
e

h
e
a
t
)
c
o
o
l
in
g

t
i
m
es

(
e
v
a
p
o
r
a
t
i
v
e

h
e
a
t
)

38. Grain Aeration Systems Grain Aeration Systems
Fan
h
o
rsepower per 10
00 bu
of
whe
a
t
:
Airflo
w
ra
te (cf
m
/bu)
Dep
t
h, f
t
0.05
0.10
0.25
100
0.
20 hp
0.
79 h
p
6.
1 h
p
50
0.
057
0
.1
9
1
.3
20
0.
020
0
.050
0.20

39. Pressure vs. Suction Aeration Pressure vs. Suction Aeration Fan
Fan
Suction ( Suction (
downflow downflow
))
Pressure ( Pressure (
upflow upflow
))

40. Grain Aeration Systems Grain Aeration Systems
Airflow Options: Airflow Options:
‹‹
Pressure (push) System Pressure (push) System
‹‹
Suction (pull) System Suction (pull) System
‹‹
PushPush
--
Pull System Pull System
‹‹
Crossflow Crossflow
Aeration Aeration
System
TallTall
Silos Silos
System

41. Pressure System Advantages Pressure System Advantages
‹‹
Required if warm grain plac
ed on top of cool grain
Required if warm grain plac
ed on top of cool grain
‹‹
Last grain to cool is at top: easily monitored Last grain to cool is at top: easily monitored
‹‹
Natural convection aids aeration in deep bins Natural convection aids aeration in deep bins
‹‹
Fan energy compensates for too cool or moist air Fan energy compensates for too cool or moist air
‹‹
More uniform airflow in flat storages (long ducts) More uniform airflow in flat storages (long ducts)
‹‹
No solar heat pulled in from top to over dry grain No solar heat pulled in from top to over dry grain
‹‹
Won’t cause roof collapse if vents freeze Won’t cause roof collapse if vents freeze
Pressure vs. Suction Aeration

42. Suction System Advantages Suction System Advantages
‹‹
Excess moisture is easily detected at top Excess moisture is easily detected at top
‹‹
Allows you to smell th
e exhaust at ground level
Allows you to smell th
e exhaust at ground level
‹‹
Condensation Condensation
≈≈
below the grain; limited in duct below the grain; limited in duct
‹‹
High inlet brings in
less dirt and debris
High inlet brings in
less dirt and debris
‹‹
Eliminates potential to suck in winter snow Eliminates potential to suck in winter snow
‹‹
Can aerate spots in flat storages using plastic Can aerate spots in flat storages using plastic
Pressure vs. Suction Aeration

43. Aeration Duct Selection Aeration Duct Selection
‹‹
Arrangements: Arrangements:
“X” System “X” System
“Y” System “Y” System
Parallel “I” Parallel “I”

44. Aeration Duct Selection Aeration Duct Selection
Pad System Pad System
dd
wa
ll
wa
ll
= =
½½
grain grain depth depth
‹‹
Best “duct” Best “duct” arrangement: arrangement:
Close to full drying Close to full drying floor effectiveness floor effectiveness Less expensive than Less expensive than drying floor drying floor

45. Aeration Duct Selection Aeration Duct Selection
Aeration Fan Selection Aeration Fan Selection
……

46. Grain Storage Summary Grain Storage Summary
‹‹
Moisture Content Moisture Content
to Control Molds 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
‹‹
Temperature Temperature
to Control Insects 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
‹‹
Safety Safety
Practices to Control Hazards Practices to Control Hazards

47. Grain Storage Summary Grain Storage Summary
––
eliminate sources of infestation eliminate sources of infestation
––
cool immediately to slow development cool immediately to slow development
Remember Remember
SAMSAM
::
SS
anitation anitation AA
eration eration MM
onitoring onitoring ––
temperature & insect numbers temperature & insect numbers

48. Grain Storage on the Web Grain Storage on the Web
http://www. http://www.
gmprc gmprc
..
ksuksu
..
eduedu
//
––
http://pasture. http://pasture.
ecnecn
..
purdue purdue
..
eduedu
/~/~
grainlab grainlab
//
––
http://www. http://www
.
oznet oznet
..
ksuksu
..
eduedu
//
wheatpage wheatpage
//
––
http://www. http://www
.
baebae
..
umnumn
..
eduedu
//
extens extens
//
postharvest postharvest
//
––
http:// http://
brubru
..
gmprc gmprc
..
ksuksu
..
eduedu
//
projproj
//
sgasga
//
‹‹
..
‹‹ ‹‹
PostPost
--
Harvest Handling of Crops Harvest Handling of Crops
‹‹
Stored Grain Advisor Stored Grain Advisor

50. Aeration Duct Selection Aeration Duct Selection
‹‹
Three criteria: Three criteria: ––
Duct spacing Duct spacing
not “excessive” not “excessive”
‹‹
less than ½ grain depth to duct anywhere on floor 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 ft
22
per 25 cfm per 25 cfm

51. Aeration Duct Selection Aeration Duct Selection
‹‹
Miscellaneous: Miscellaneous: ––
Use well Use well
--
designed fan designed fan
--
toto
--
duct transition duct transition
––
Perforated ducts: minimum 10% open Perforated ducts: minimum 10% open
––
Roof vents: 1 ft Roof vents: 1 ft
22
/hp (pressure) /hp (pressure)
––
InIn
--
floor ducts don’t interfere with unloading floor ducts don’t interfere with unloading
––
Effective area = 75% for round ducts on floor Effective area = 75% for round ducts on floor

52. Aeration Fan Selection Aeration Fan Selection
1.1.
Select Select
lowest airflow ( lowest airflow (
cfmcfm
//
bubu
) for cooling rate ) for cooling rate
2.2.
Airflow: Airflow:
cfm/ft cfm/ft
22
= (0.8) x (depth) x ( = (0.8) x (depth) x (
cfmcfm
//
bubu
))
33
. Pressure drop: . Pressure drop:
∆∆
P = (inH P = (inH
22
O/ft) x (depth) + 0.4 O/ft) x (depth) + 0.4
4.4.
Total airflow: Total airflow:
cfm = ( cfm = (
cfmcfm
//
bubu
) x (total bushels) ) x (total bushels)
or:or:
cfm = (cfm/ ft cfm = (cfm/ ft
22
) x (floor area) ) x (floor area)
5.5.
Select fan Select fan
to deliver flow & pressure (fan data) to deliver flow & pressure (fan data)

53. Grain Aeration Systems Grain Aeration Systems
Double the Recommended
Airflows for Controlled
Ae
ration Syste
m
s
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.

54. Grain Aeration Systems Grain Aeration Systems
‹‹
Closed Closed
--
Loop Fumigation (CLF) Loop Fumigation (CLF)
––
More effective than probing More effective than probing
––
More efficient than probing More efficient than probing
‹‹
timetime
‹‹
fumigant fumigant
––
Safer than probing Safer than probing
‹‹
reduces exposure to fu
migant
reduces exposure to fu
migant
‹‹
reduces dust reduces dust
‹‹
eliminates enclosed space entry eliminates enclosed space entry