World Grain - July 2011 - 52

GRAINOPERATIONS

Aeration strategies
There are many different ways to use air movement to maintain grain quality
by Harmon Towne

My ﬁrst experience out of college in 1963 was working with farmers and country elevators on drying and storage of grain. One of the main topics that I discussed at meetings was aeration. The U.S. Department of Agriculture (USDA) had done a lot of work in the 1940s on maintaining the quality of grain during storage. Although much of the initial research had to do with ﬂat storage, by the early 1960s this information was being used for concrete silos as well as steel grain bins. Research had shown that as the temperatures changed with the seasons, convection currents were active in the bin because of temperature differences in the grain mass. Since grain is a good insulator, the central core temperatures remained fairly constant while grain next to the wall and on the surface changed with the ambient temperatures. With cool air settling along the wall of the bin and warm air rising in the center, minute amounts of moisture were transferred to the surface, and condensation took place. This eventually led to spoilage and if the core temperatures remained above about 50 degrees F, insect activity also occurred. By using small amounts of air movement through the grain, the grain mass temperatures could be equalized, eliminating moisture migration and insect activity. Air ﬂows of 1/20th CFM (cubic feet per minute) per bushel were recommended because this was thought to simulate the natural air ﬂow. Tests showed that at these low rates it took about 300 hours of continuous fan operation to equalize the temperature of the grain to the ambient temperature. The recommendations were also to use a suction system to keep condensation from occurring on the top of the grain pile. As the size of storage structures increased and the desire to cool the grain faster became more prevalent, airﬂows were increased to 1/10th CFM per bushel. This reduced the time to cool the grain in half. As electricity supplied to the farms improved, larger fans became more practical. The trend of higher airﬂow has continued for today’s operations. It is now quite
52

A centrifugal fan manufactured by Brock. Photo courtesy of Brock.

A vane axial fan manufactured by GSI. Photo courtesy of GSI.
July 2011 / World Grain / www.World-Grain.com

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World Grain - July 2011

Table of Contents for the Digital Edition of World Grain - July 2011

World Grain - July 2011
from the editor-in-chief - Industry must move to avoid public opprobrium
CALENDAR OF EVENTS
News review
GRAIN MARKET REVIEW - Oilseeds
COUNTRY FOCUS - Focus on Israel
Combating volatility
FEATURE - Keeping a close eye on corn
BIOFUELS QUARTERLY - Ready for an ENERGY REVOLUTION
BIOFUELS QUARTERLY - Biofuels News Review
GRAIN OPERATIONS - Aeration strategies
FEATURE - BUSY FALL FOR IAOM
FEATURE - North American supplier profiles
SUPPLIER NEWS
PRODUCT SHOWCASE
ADVERTISER INDEX
World Grain - July 2011 - World Grain - July 2011
World Grain - July 2011 - 2
World Grain - July 2011 - 3
World Grain - July 2011 - 4
World Grain - July 2011 - 5
World Grain - July 2011 - from the editor-in-chief - Industry must move to avoid public opprobrium
World Grain - July 2011 - 7
World Grain - July 2011 - CALENDAR OF EVENTS
World Grain - July 2011 - 9
World Grain - July 2011 - News review
World Grain - July 2011 - 11
World Grain - July 2011 - 12
World Grain - July 2011 - 13
World Grain - July 2011 - 14
World Grain - July 2011 - 15
World Grain - July 2011 - 16
World Grain - July 2011 - 17
World Grain - July 2011 - 18
World Grain - July 2011 - 19
World Grain - July 2011 - GRAIN MARKET REVIEW - Oilseeds
World Grain - July 2011 - 21
World Grain - July 2011 - COUNTRY FOCUS - Focus on Israel
World Grain - July 2011 - 23
World Grain - July 2011 - 24
World Grain - July 2011 - 25
World Grain - July 2011 - 26
World Grain - July 2011 - 27
World Grain - July 2011 - Combating volatility
World Grain - July 2011 - 29
World Grain - July 2011 - 30
World Grain - July 2011 - 31
World Grain - July 2011 - 32
World Grain - July 2011 - 33
World Grain - July 2011 - FEATURE - Keeping a close eye on corn
World Grain - July 2011 - 35
World Grain - July 2011 - 36
World Grain - July 2011 - 37
World Grain - July 2011 - 38
World Grain - July 2011 - 39
World Grain - July 2011 - BIOFUELS QUARTERLY - Ready for an ENERGY REVOLUTION
World Grain - July 2011 - 41
World Grain - July 2011 - 42
World Grain - July 2011 - 43
World Grain - July 2011 - 44
World Grain - July 2011 - 45
World Grain - July 2011 - 46
World Grain - July 2011 - 47
World Grain - July 2011 - BIOFUELS QUARTERLY - Biofuels News Review
World Grain - July 2011 - 49
World Grain - July 2011 - 50
World Grain - July 2011 - 51
World Grain - July 2011 - GRAIN OPERATIONS - Aeration strategies
World Grain - July 2011 - 53
World Grain - July 2011 - 54
World Grain - July 2011 - 55
World Grain - July 2011 - 56
World Grain - July 2011 - 57
World Grain - July 2011 - FEATURE - BUSY FALL FOR IAOM
World Grain - July 2011 - 59
World Grain - July 2011 - FEATURE - North American supplier profiles
World Grain - July 2011 - 61
World Grain - July 2011 - 62
World Grain - July 2011 - 63
World Grain - July 2011 - 64
World Grain - July 2011 - 65
World Grain - July 2011 - 66
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World Grain - July 2011 - 77
World Grain - July 2011 - 78
World Grain - July 2011 - 79
World Grain - July 2011 - 80
World Grain - July 2011 - 81
World Grain - July 2011 - SUPPLIER NEWS
World Grain - July 2011 - 83
World Grain - July 2011 - 84
World Grain - July 2011 - 85
World Grain - July 2011 - 86
World Grain - July 2011 - 87
World Grain - July 2011 - PRODUCT SHOWCASE
World Grain - July 2011 - 89
World Grain - July 2011 - ADVERTISER INDEX
World Grain - July 2011 - 91
World Grain - July 2011 - 92
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