Principles of Grain Drying
36
As air enters grain it picks up some moisture, which cools the air slightly. When the air moves through a deep
grain mass, the air temperature is further lowered and its relative humidity is increased until the air approaches
equilibrium with the grain. If air reaches equilibrium with grain, it passes through remaining grain without any
additional drying. If air with high relative humidity enters dry grain, some moisture is actually removed from air and
enters grain. This slightly dried air will begin to pick up moisture when it reaches wetter grain.
Overdrying
Overdrying grain costs money in two ways:
1 An excessive amount of energy is used to dry the grain.
2 Crop is worth less because of shrinkage.
Table 11
below details extra costs associated with marketing overdried corn. As stated before, stirring machines
are an excellent way to eliminate overdrying and are essential when a heater is used with a drying bin.
Table 11
- Costs of Marketing Overdried Corn Based on $1.00=€1.30, $.06 kW/hr (€.046 kW/hr) and $1.00/gal LP (€.266/L LP)
Moisture
Content (%)
Extra Drying Costs
Extra Shrinkage
Total Overdrying
Dollars ($)
Euros (€)
Dollars ($)
Euros (€)
Dollars ($)
Euros (€)
14
0.035
0.031
0.044
0.040
0.079
0.071
13
0.061
0.055
0.072
0.065
0.133
0.120
12
0.087
0.078
0.099
0.089
0.186
0.167
11
0.117
0.105
0.126
0.113
0.243
0.218
Grain Cooling
Grain dried with a heater must be cooled following drying. Run fans without heat until air coming out of bin is
same temperature as that going in, usually a couple of days. Insufficient cooling of grain will result in moisture
condensation and grain spoilage during storage.
Fans
Axial fans
are the most common type of fan used for aeration. They require a relatively low initial investment and
operate well at static pressures below 3 to 4 inches (76 to 100 mm or 750 pa) water gauge. However, axial fans
are noisy, and should be directed away from residences if possible.
Centrifugal fans
deliver a fairly consistent airflow over a wide range of static pressures, but require a higher
initial investment than axial fans. Centrifugal fans, however, are much more quiet and efficient. When aeration is
required for tall bins or small grains, both of which create high static pressures, 3,500-rpm centrifugal fans are
recommended.
Use of Sukup software with a personal computer is recommended to ensure optimal fan is selected for the
application. Select a fan according to the manufacturer’s rating tables to deliver required air volume at expected
static pressure.
Airflow Requirements
Use Table 12 to help determine airflow needed in specified aeration applications. Requirements are
presented in standard and metric units.
Table 12
- Airflow Requirements
Aeration Application
CFM/Bu
m³/hr/MT
Normal Storage
1/20 to 1/5 (usually 1/10) 4 to 15 (usually 8)
Cooling Hot Grain from Dryer *
1/2
38
Cooling in Bin
1/2 to 1 (usually 1/2)
38 to 76
Wet Holding Tank
1/4 to 1/2
19 to 38
Roof Dryer
12 to 22
911 to 1670
In-Bin Drying: Natural Air
1 to 3
76 to 228
Low Temp (2ºF to 5ºF temp rise) 1 to 3
76 to 228
High Temp (120ºF max for corn) 1-1/2 to 5
114 to 380
* If basing airflow on dryer capacity, CFM = 12 x bu/hr capacity of dryer.
Summary of Contents for Fastir
Page 4: ...Limited Warranty 4 LIMITED WARRANTY...
Page 50: ...Appendix A Wiring Diagrams 50 Figure 52 Double Auger Fastir Wiring Diagram...
Page 51: ...Appendix A Wiring Diagrams 51 Figure 53 Triple Auger Fastir Wiring Diagram...
Page 52: ...Appendix A Wiring Diagrams 52 Figure 54 Quadruple Auger Fastir Wiring Diagram...
