System for conditioning grain

A system for conditioning grain in a sealed container through the removal of liquid from a bushel of grain by sequentially evacuating high relative humidity air from the sealed container and thereafter allowing dry environmental air to reenter the sealed container. A sensor in the sealed container detects the relative humidity therein and supplies a controller with a signal to operate a pump which evacuates high relative humidity air from the sealed container. Thereafter, a pressure sensor detects a vacuum in the sealed container and supplies the controller with a signal which terminates the operation of the pump to allow dry environmental air to reenter the sealed container. The replacement of high relative humidity air with dry environmental air continues until the liquid content per bushel of grain is at a desired level.

This invention relates to a system for conditioning grain through the 
removal of liquid from a sealed container by sequentially evacuating high 
relative humidity air from the sealed container and thereafter replacing 
the same with dry environmental air. 
For all grains there is an optimum harvest efficiency where grain loss is 
at a minimum. Unfortunately, the time period for this optimum harvest is 
limited to dry weather conditions and grain maturity. Grain can be 
harvested at any time when the moisture content is below 25% but in order 
to store such grain for an extended period of time, it must be dried to 
about 15% moisture. For instance, after corn reaches a dent condition, and 
progresses toward the harvest Condition, before it can be stored without 
spoilage the moisture content must be below 17%. 
A bushel of corn has a set volume and weighs 56 pounds. At 15% moisture, 
the solid matter in a bushel of corn has been established at 47.32 pounds 
and the liquid content is 8.68 pounds. Liquid content in a bushel may 
change but the solid content always remains constant. Thus, it is 
important to remember that as grain is dried, the resulting weight occurs 
from the evaporation of water from within each kernal of grain. 
The cheapest way to dry grain is through an equilibrium system wherein 
environmental air is continually passed through stored grain. However, in 
such a system if the air is too dry, the grain overdries whereas if the 
relative humidity of the air is too high, the grain never dries properly. 
A more effective manner of drying grain is to use a non-equilibrium system, 
wherein hot, dry air is continually forced through the stored grain. 
In both of these systems there exists a drying front in the storage bin. A 
drying front is a zone where grain has reached a point of equilibrium 
below the front with wet grain above the front. Unfortunately, in the 
non-equilibrium system, if equllibrium occurs, the grain overdries 
resulting in excessive shrink and cracking. To avoid such over-drying, the 
grain must be moved by either a conveyor to another bin, or continually 
mixed by a stirrer until a desired moisture content is achieved. 
Unfortunately, the stirring action can create a column in the grain from 
the top to the bottom of the storage bin which causes an air leak. An air 
leak is a volume of air that moves in the center area and is under a lower 
static pressure than the static pressure near the walls of the storage 
bin. Within such columns, air is exhausted without being saturated with 
water. Under such conditions, the cost of drying is unnecessarily 
increased. To avoid air columns, an upper limit for air flow exists such 
that the velocity of the air entering a bin should not exceed about 1750 
ft./minute If the velocity is greater than this, a uniform drying front is 
not achieved and uneven air drying columns are produced. In addition, when 
grain is not dried at a uniform rate it is possible to cause moisture 
build up on the top of the storage bin which can produce mold in the 
grain. Tests have shown that an air flow of 1 cfm/bu can dry about 3/4ft. 
of grain per day. 
In the present invention it has been discovered that grain in a storage bin 
can be dried to a desired moisture content through an air equilibrium 
system by sequentially evacuating air from a sealed bin and replacing the 
same with dry environmental air. Dry environmental air is presented to the 
sealed bin and after a period of, the moisture in the grain evaporates to 
thereafter raise the relative humidity of the air in the sealed container. 
A first sensor in the sealed bin provides a controller with an initial 
signal indicative of the moisture content in the grain while a second 
sensor detects the relative humidity of the environmental air and provides 
the controller with a second signal. As long as the signal from the first 
sensor indicates a moisture content in the grain which is above a desired 
moisture content, and the relative humidity is below a set level as 
indicated by the second signal, the controller responds by supplying a 
solenoid valve with an operational signal. Operation of the solenoid 
terminates communication of dry environmental air to the sealed bin and a 
pump is supplied with an operational signal. Thereafter, the pump 
evacuates the high relative humidity air from the sealed bin. When the 
fluid pressure in the sealed chamber reaches a vacuum level of between 
20-22 in. Hg in the sealed bin, a sensor supplies the controller with a 
termination signal to switch off the pump and open the solenoid valve to 
again allow dry environmental air to reenter the sealed bin. Should the 
relative humidity of the environmental air be above about 80%, the 
operational signal to the the solenoid valve is delayed or the relative 
humidity of the environmental air is lowered to a level where it can hold 
more moisture by passing the same through a dehumidifier. The evacuation 
of high humidity air from the sealed bin and replacing it with dry 
environmental air continues until the first sensor detects that the 
moisture level per bushel of grain is at a desired level. 
An advantage of drying grain according to this invention occurs as dry 
environmental air eliminates a vacuum throughout an entire sealed bin at 
substantially the same time to uniformly dry the entire quantity of grain 
in the sealed bin. 
An advantage of the system of drying grain as disclosed in the instant 
invention occurs since moisture build up in stored grain is eliminated as 
dry environmental air is communicated to the entire sealed chamber to 
uniformly eliminate a vacuum created therein through the evacuation of 
high humidity air from the sealed bin. 
Another advantage of grain drying as disclosed in the present invention 
occurs since the temperature, pressure, and relative humidity of grain in 
a sealed container is substantially uniform throughout the entire sealed 
container. An objective of this invention is to provide a grain drying 
system for a sealed bin with sensing means to detect the moisture content 
in a bushel of grain and provide a controller with an operational signal 
for the actuation of a pump to evacuate high relative humidity air from 
the sealed bin and in the process remove moisture from the grain stored 
therin. These advantages and objectives should be apparent from reading 
this specification while viewing the single figure in the drawing

DETAILED DESCRIPTION OF THE INVENTION 
The grain conditioning system 10 as shown in the drawing is designed to 
uniformly and substantially simultaneously remove water from each bushel 
of grain in a sealed bin or silo 12. Grain harvested from a field is 
directly placed in the silo or sealed bin 12. After the grain is placed in 
the bin 12, opening 18 in an inflatable and movable seal 20 is closed and 
after a period of time, the relative humidity of the air in the now sealed 
bin 12 and correspondingly each bushel of grain therein is detected by a 
first sensor 14. The first sensor 14 provides controller 16 with an 
initial signal corresponding to the relative humidity in the sealed bin 
12. Controller 16 also constantly receives an environmental signal from 
sensor 22 that detects the relative humidity of the air in the surrounding 
environment. If the relative humidity as detected by sensor 22 is above 
80%, controller 16 remains in an inactive condition. However should the 
relative humidity of the environmental air be below 80%, controller 16 
responds to the actuation signal from sensor 14 and environmental signal 
from sensor 22 to supply a first timer 15 with an activation signal. When 
timer 15 is activated, a signal actuates power relay 26 to simultaneously 
supply solenoid valve 28 and pump 36 with an actuation signal. Solenoid 
valve 28 closes and interrupts communication of environmental air through 
conduit 32 to conduit 34 connected to the sealed bin 12. Conduit 34 also 
connects the sealed bin 12 with pump 36. With solenoid valve 28 closed, 
pump 36 begins to evacuate air from the sealed bin 12. As air is evacuated 
from the sealed bin 12, flexible seal 20 moves toward the grain as the 
fluid pressure therein is lowered. A pressure sensor 30 detects the fluid 
pressure in the sealed container or bin 12 and when a predetermined vacuum 
level is achieved, a termination signal is transmitted to timer 38. 
Timer 38 in turn supplies timer 15 with a termination signal to switch 
power relay 26 to an off position. With relay 26 in the off position, 
power to pump 36 and solenoid valve 28 is also terminated. Without 
electrical power, a spring moves a plunger in solenoid valve 28 to open 
conduit 32 and allow dry environmental air to enter the sealed bin 12. As 
air enters bin 12, the vacuum is eliminated as the fluid pressure therein 
approaches atmospheric pressure. When the vacuum is eliminated, the dry 
environmental air that enters the sealed container or bin 12, picks up 
moisture from each kernal of grain. Sensor 14 measures the liquid per 
bushel of grain and continually supplies controller 16 with an update of 
the relationship between the solid and liquid content per bushel of grain. 
An external heat source is not required in this system 10 since heated air 
creates an undesirable drying front. Should conditions be such that the 
temperature of the environmental air is below 60 degrees Fahrenheit, in 
order to increase the moisture carrying capacity of the environmental air, 
sensor 43 receives an input signal from controller 16 and directs the 
environmental air through a dehumidifier 42 before it passes through the 
valve 28. Controller 16 controls the actuation of sensor 43 such that only 
when environmental air is presented to bin 12 is the dehumidifier 
actuated. Further, only when environmental air above relative humidity of 
80% will the controller supply sensor 43 with an operational signal. 
A temperature sensor 40 located in the sealed bin 12 supplies controller 16 
with a signal indicative of the temperature of the grain. 
As long as sensor 14 detects the moisture content in grain in the sealed 
bin 12 is above the desired dryness, the controller 16 continues to cycle 
the solenoid valve 28 and pump 36 to evacuate moisture laden air from the 
sealed bin 12 and replace the same with dry environmental air. This cycled 
flow provides for uniform drying throughout the entire sealed bin 12. 
In an actual test with a natural drying equilibrium system and the grain 
conditioning system 10 of the present invention, the following conditions 
were observed. 
In both systems, 7500 bushels of corn was placed in each bin. In the 
conventional bin, air was continually passed through the grain, while in 
the conditioning system 10, the bin 12 was sealed. The moisture content in 
each bushel of grain was detected to be 20%. 
A standard bushel of corn being defined as having a weight of 56 pounds and 
having a moisture content of 15.5% moisture. Since the dry or solids in 
such a bushel of corn remain constant at 47.32 pounds, the liquid content 
is fixed at 8.68 pounds. 
In a bushel of corn with 20% moisture, the total weight is 59.15 pounds. 
Since the solids remain constant at 47.32 pounds, the liquid in such a 
bushel is 11.83. Thus 3.15 pounds of water per bushel must be removed to 
dry the corn to a safe storage level. 
In the test, it was decided to evaluate the difference in the two systems 
when the corn was dried from 20% moisture to 17% moisture. A bushel of 
corn with 17% moisture weighs 57.01 pounds and its liquid content is 9.69 
pounds. Thus, 2.14 (11.83 -9.69) pounds of water per bushel must be 
removed to reach 17% moisture in the corn. 
The total water needed to be removed from each bin is 2.28 lb./bushel 
.times.7500 bushel =17,100 pounds. 
In the natural drying system, a 10 HP fan having a rating of 10,000 CFM was 
used. At the end of 28 days, the moisture in the bin had reached 17%. From 
this we are able to calculate that 403,200,000 cu. ft. of environmental 
air had passed through the bin (10,000 CFM .times.60 minutes .times.24 
Hours .times.28 days). The cost of operating the 10 HP can be calculated 
as follows: 28 days .times.24 hours =672 hours .times.10 KW =6720 KWH 
.times.$0.05 per KWH (average cost of electricity) =$336. The cost per 
bushel is $336/7500 bushel =$0.0448 per bushel or $0.0149 per 1% moisture 
that is removed. 
In the grain conditioning system 10, pump 36 was rated as 15 HP and 220 
CFM. At the end of 119 hours of operation of the pump, the moisture in the 
tin had reached 17%. On the average, the pump 36 had operated for 15 
minutes while it took 20 minutes for the dry, environmental air to reach 
equilibrium with the moisture in the grain within the sealed bin 12 and 
complete a cycle of operation. The moisture in the system 10 had reached 
17% after the completion of 477 cycles of operation. Since the pump 36 
only operated for 15 minutes per cycle, the actual pump operational time 
is 15 minutes .times.477 cycles =7155 minutes or 119 hours. The pump cost 
i calculated as follows: 119 hours .times.15 HP =1788 KWH .times.$0.05 
cents/KWH =$89.43 or $0.012 cents per bushel, which can also be expressed 
as $0.004 cents per 1% removal of moisture from the corn. 
From the above test, it has been demonstrated that the grain conditioning 
system 10 is effective, efficient and economical in reducing the moisture 
content in grain to a level where spoilage does not occur when store in a 
sealed bin.