Table of Contents
Advertisement
AERATION FAN – SUPER-FLOW FULL CENTRIFUGAL FAN
7.3. Grain Drying and Aeration Tips
• WHAT IS THE DIFFERENCE BETWEEN AERATION, NATURAL AIR DRYING, AND GRAIN DRYING WITH A
SUPPLEMENTAL HEATER? Aeration is used to control and provide uniform temperature for a grain mass.
Natural air drying is generally used for farm bins and is a method of drying grain without using supplemental
heat and is recommended at 1 cfm (13.4 L/s) per bushel of grain. Grain drying refers to adding supplemental
heat to lower the moisture content of a grain mass at a flow rate of greater than 1 cfm (13.4 L/s) per bushel
of grain. All three methods will help extend storage life for grain and prevent spoilage.
• HOW MUCH POWER DO I NEED TO DRY GRAIN? When natural air drying or when grain drying with a
supplemental heater you need roughly 1 HP (0.75 KW) for every 1000 BU (35.2 cubic meters of grain. When
aerating, you need roughly 1 HP (0.75 KW) for every 10,000 BU (352 cubic meters) of grain. These are
approximations only as the height of grain influences the required power as well. Consult your local dealer
to accurately size a fan.
• WHEN CAN I BEGIN TO HARVEST? With a complete natural air drying system in place, crops can be taken off
above normal moisture content (example: wheat 18%-20%). Under warm, low, relative humidity conditions
you should see 3/4–1% of drying taking place per day. This allows a 7–10 day advance on harvest time as
well as more harvesting hours per day.
Note
Natural air drying should be used as a management tool and not as a late harvest emergency drying
system. If late harvest conditions are cool and damp (conditions less than 50°F (10°C)) natural air
drying will be slow and adding supplemental heat is much more effective.
• AT WHAT TEMPERATURE DOES NATURAL AIR DRYING BEGIN? Grain drying begins at 50°F (10°C). Anything
less than 50°F (10°C) means the air is too cold and can only hold a small amount of moisture; therefore,
moisture removal from grain will be very slow.
• WHEN SHOULD I START MY FAN FOR NATURAL AIR DRYING?In order to create a uniform drying front, the
bin must be filled to the height of at least half of the bin's diameter above the system. (Example: A 14' (4.3
m) diameter bin needs to have a minimum of 7' (2.13 m) of grain above the system). The best uniform
drying front can be produced by filling your bin and then turning on the fan. Turning your fan on too soon
can cause uneven drying and negative results.
• WHEN SHOULD I START MY FAN FOR AERATION? The aeration fan should be started as soon as the
aeration ducts are covered with grain when filling. Once started, to prevent crusted grain, air flow through
the grain bin must be maintained until the bin reaches the desired temperature.
Table 2. Moisture Content of Grains
Wheat Equilibrium
Moisture Content %
Relative
at 25°C (77°
Humidity of
F)
Air %
58
12
64
13
70
14
75
15
79
16
83
17
86
18
CNA-3733 R2
Canola Equilibrium
Moisture Content %
at 10°C (50°
at 25°C (77°
F)
F)
13
7.5
14
8.2
15
9.0
16
9.8
17
10.8
18
12.0
19
13.4
Corn Equilibrium
Moisture Content %
at 10°C (50°
at 25°C (77°
F)
F)
8.6
12.2
9.4
13.0
10.3
14.0
11.1
15.0
12.0
15.8
13.2
16.9
14.5
17.8
7. APPENDIX
at 10°C (50°
F)
13.5
14.4
15.4
16.4
17.1
18.2
19.0
37
Advertisement
Table of Contents
