Continuous-flow grain steeping and cooling system

A continuous-flow, slow grain cooling process including the charging of hot, partially dried grain from a heated-air grain dryer into the top of a grain container in an even layer. The downward flow of grain through the grain container is regulated at a rate that allows the grain to remain in a top steeping zone for from four to twelve hours. After the initially charged grain is held at the steeping temperature for a predetermined steeping time, a controlled upward flow of ambient air is provided to cool the grain in a bottom cooling zone. The air flow is provided at a rate that allows grain to remain in the cooling zone until it is cooled close to the ambient air temperature, but the upward flow is controlled such that it will not cool any grain until it has been properly steeped. Cooled dry grain from a layer near the bottom is then discharged from the bottom of the grain container.

TECHNICAL FIELD 
This invention relates to a method of conditioning grain, and more 
particularly to a process for slowly cooling grain partially dried in a 
heated-air grain dryer. 
BACKGROUND ART 
Slow grain cooling is a proven, widely adopted and effective technique to 
cool grain that has been dried in a heated-air grain dryer. Steeping 
(short-term storage without aeration) and slowly cooling hot, dried grain 
will efficiently remove an additional one to four points of moisture. 
There are three recognized main advantages of slowly cooling grain that 
has been dried in a heated-air dryer: increased drying capacity, reduced 
operating costs for drying, and improved grain quality. 
Specific known processes utilizing slow grain cooling include in-bin 
cooling, combination high-temperature/low temperature drying and 
dryeration. Of these processes, dryeration has the greatest potential for 
rapidly and efficiently reducing moisture content in grain. 
In the dryeration process, hot, dried grain is discharged from a heated-air 
dryer into a grain bin, tank or other grain container where two separate 
grain conditioning sub-processes occur. The hot grain is first stored 
without aeration in a container at its removal temperature from the dryer 
for a predetermined period of time to permit the grain to steep. The 
removal temperature is the temperature the grain is discharged from the 
heated air grain dryer, typically 140.degree. F. to 160.degree. F. During 
this time, usually from four to twelve hours, temperature and moisture 
tend to become uniform within each kernel. Then the steeped grain is 
cooled by moving ambient air through it. This dryeration process (steeping 
and then cooling by aeration) has been commonly found to remove up to four 
additional points of moisture from the grain after the grain leaves the 
heated air grain dryer, in addition to the points of moisture removed in 
the dryer. 
The amount of moisture removed in the grain steeping and cooling process is 
dependent upon the difference of the grain temperature entering and the 
grain temperature leaving the process and the time the grain is steeped. 
Although not well verified by research, considerable experience indicates 
adequately steeped grain will lose 0.20 to 0.25 percentage points of 
moisture for each 10.degree. F. temperature reduction. The temperature at 
which the grain leaves the dryer and enters the steeping process is 
dependent upon the drying air temperature and the efficiency of the heated 
air grain dryer. Common grain temperatures of grain leaving a dryer 
operating between 180.degree. F. and 200.degree. F. is 140.degree. F. to 
160.degree. F., but both higher and lower dryer operating temperatures and 
therefore grain temperatures also do occur. The grain temperature will 
remain at this temperature during steeping and until the grain enters the 
cooling process, when it is cooled by aeration with ambient air. The 
temperature of the grain leaving the cooling process is a few degrees 
below the ambient air temperature. Although an ambient temperature range 
of 50.degree. F. to 60.degree. F. is common during the fall, both higher 
and lower temperatures are frequently encountered. Following are two 
examples of approximate low and high expected moisture reductions during 
the grain steeping and cooling process: 
EQU low, [(100.degree. F.-70.degree. F.)+10.degree. F.].times.0.20 
points/10.degree. F.=0.60 points 
EQU high, [200.degree. F.-20.degree. F.)+10.degree. F.].times.0.25 
points/10.degree. F.=4.50 points 
One problem with the dryeration process as currently employed is that it is 
normally practiced as a batch process requiring two grain bins or tanks. 
Thus, a substantial capital investment is required. 
Those concerned with these and other problems recognize the need for an 
improved slow grain steeping and cooling process. 
DISCLOSURE OF THE INVENTION 
The present invention provides a continuous-flow, slow grain steeping and 
cooling process. The process includes the charging of hot, partially dried 
grain from a heated-air grain dryer into the top of a grain container in a 
layer of approximately uniform thickness. The downward flow of grain 
through the grain container is regulated at a rate that allows the grain 
to remain in a top steeping zone for a predetermined period of time, 
typically from four to twelve hours. After the initially charged grain is 
held at the steeping temperature for a predetermined steeping time, a 
continuous upward flow of ambient air is provided to cool the grain in a 
bottom cooling zone. The air flow is provided at a rate that allows grain 
to remain in the cooling zone for a predetermined cooling time depending 
on the airflow rate in cfm/bu (cubic feet of air per minute per bushel). 
Cooled dry grain from a layer near the bottom is then discharged from the 
bottom of the grain container. 
An object of the present invention is the provision of an improved slow 
grain steeping and cooling process. 
Another object is to provide a continuous-flow slow grain cooling process 
that may be practiced in a single grain container.

BEST MODE FOR CARRYING OUT THE INVENTION 
Referring now to the drawings, FIG. 1 illustrates the flow of the grain 
from harvest as wet grain, through heated-air grain drying, through the 
continuous-flow grain container, to longer term storage or transported as 
cool dried grain. 
Continuous-flow grain steeping and cooling systems utilize existing or 
modified equipment commonly used for continuous-flow in-bin drying or 
newly developed equipment on an existing grain bin, grain tank, 
self-contained column grain dryer, silo, remodeled or converted corn crib, 
grain wagon, etc. adapted to incorporate continuous grain flow capability. 
In the process of the present invention, grain flows into the container at 
or near the top and is discharged at or near the bottom. 
The process is a continuous process that combines grain steeping and grain 
cooling. The grain container is equipped with continuous-flow grain 
handling equipment and airflow equipment. Appropriate controls regulate 
both the flow of grain through the grain container after a predetermined 
and adequate steeping time and also the discharge of cooled grain from the 
grain container. 
In operation, newly harvested wet grain commonly having a moisture content 
of approximately 20-26% is transferred from the harvesting equipment to a 
heated-air grain dryer. The heated-air dryer commonly reduces the grain 
moisture content to a level of about 16-18% and the partially dried grain 
is discharged from the dryer without being cooled, e.g. generally, at a 
temperature of about 140.degree.-160.degree. F. This hot, partially dried 
grain is then charged into the grain container through an opening at or 
near the top. 
During the start-up phase, hot partially dried grain is laid into the grain 
container in a layer of approximately uniform thickness by use of a 
conventional grain spreader or other suitable devices. When the first 
grain charged into the grain container has achieved a predetermined 
residence time, typically from four to twelve hours, which can be 
controlled manually or with an appropriate timing device, a continuous 
flow of ambient air is directed upwardly through the grain to begin the 
cooling process. A cooling front travels upwardly through the grain mass 
while hot, partially dried grain is added to increase the depth of the 
grain mass. The grain mass is divided into an upper steeping zone and a 
lower cooling zone as the grain container is filled to a predetermined 
capacity to complete the start-up phase. 
After the initial start up, hot partially dried grain is charged into the 
top of the grain container in a layer of approximately uniform thickness. 
The continuous downward flow of grain is regulated at a rate that allows 
the grain to remain in the steeping zone for a predetermined period of 
time typically from four to twelve hours. The upward flow of ambient air 
through the grain mass is provided at a rate that allows the grain to 
remain in the cooling zone for a predetermined cooling time as determined 
by the fan airflow rate in cfm/bu. The upward flow of ambient air is 
interrupted so that the cooling zone does not enter the grain in the 
steeping zone before that grain has been adequately steeped. Cooled dry 
grain having a temperature approximately equal to ambient air and a 
moisture content of about 12-14% is discharged from an approximately 
uniform thickness layer of grain at the bottom of the container by a 
bottom mounted sweep auger or augers or other suitable equipment. 
The moisture content of the dried grain can be monitored with appropriate 
grain moisture testing equipment. This equipment and the electrical wiring 
circuits within the equipment can be designed to select one of two 
discharge conveyors. One discharge conveyor would move grain that has been 
adequately dried to storage or to be transported as dried grain. The other 
discharge conveyor would move grain that is not adequately dried to the 
wet grain holding bin or tank or to the dryer. 
One variation of the present invention is the utilization of the 
continuous-flow principle to remove hot adequately steeped grain from the 
grain conditioning container prior to cooling. The hot, steeped grain can 
be cooled in a storage container, such as a grain bin, equipped with a 
properly sized fan and air distribution system, such as a perforated floor 
or duct system. This cooling process will remove approximately the same 
amount of moisture as the above preceding process. One caution with 
cooling hot, steeped grain in a storage bin is the possibility of 
excessive water condensation on the sidewalls, that can run down into the 
grain and cause serious grain deterioration and storage problems. 
Thus, it can be seen that at least all of the stated objectives have been 
achieved. 
Obviously, many modifications and variations of the present invention are 
possible in light of the above teachings. It is therefore to be understood 
that, within the scope of the appended claims, the invention may be 
practiced otherwise than as specifically described.