Note: Descriptions are shown in the official language in which they were submitted.
-- lO90S6Z
This invention relates to a grain drying bln for controlling the
drying and cooling of field-harvested seeds in storage. This application
is a division of application Serial No. 238,392 filed October 27, 1975.
The technique of early harvesting including field shelling and
subsequent conditioning of corn and other cereal grains in storage is
becoming increaslngly popular. The present methods of conditioning or
drying these cereal grains range from simply storing the seeds and letting
them dry in the atmosphere, to placing them in drying bins and passing
heated air through the grain seeds. In more recent years, complicated
mechanical devices for agitating the stored grain or for removing the
bottom-most layer of stored grain have increased equipment and operational
expenses and severely damaged both the phyRical and food properties of the
grains and not infrequently the storage structure itself.
Grain exposed by storing in atmospheric air frequently is
inadequately driet. In most cases, the drying process is so slow that
problems of mold and biochemical changes result in serious losses to the
Etored grain. Also, drying of this type is interruptet by undesirable
weather conditions,~e.g., high humidity or prolonged wet and rainy periods,
both of which result in accelerated degradation of the stored grain.
Wet graln that is artificially dried by flow of heated air in a
drying bin i8 frequently damaged due to the fact that commercial drying
techniques often use drying air temperatures from 100F. to 140F., and
sometimes even as high as 200F., with resultant destruction of enzymes and
amino acid proteins and other volatile ingredients.
The early harvesting techniques used in producing corn today
frequently involve field shelling of the corn when it is at a moisture
content of 27X. At this moisture level, grain deteriorates rapidaly and
becomes mold infested. Corn approaches physiological maturity when its
moisture content is 20%. The maturing process involves not only the re-
moval of moisture, but also chemical stabilization. Because mature corn
B
--` lO90S6Z
is more stable, it may be stored ~afely over long periods under proper con-
ditions while storing of corn with excessive isture inhibits or even
prevents the natural occurrence of biological maturity. Maturing involves
the chemical stabilization of starch and protein which constitutes 85~ of
the corn kernel. In the maturing process, sugar molecules bond together
to form starch molecules which are more complex carbohydrates and are more
stable chemically. Similar processes are involved with proteins and amino
acids. In these processes water is eliminated, and thus drying or the
elimination of water is an essential aspect of maturing of grain. Tempera-
ture and moisture are both factors in grain stabilization; however, abovecertain isture levels, chilling of grain does not prevent deterioration
of the seed. The following table shows germination loss in stored,
refrigerated corn.
; GERMINATION LOSS IN STORED, REPR~GERATED CORN
GERMINATION- EMERGENCE*
MOISTURE AFTER 6 MOS.: APTER 18 MOS, AFTER 6 MOS. AFTER 18 MOS.;
Above 24% 17X 0% 0% 0Z
18 - 24% 4ZX 13X 33% 53%
16 - 18% 74% 71% 59% 88%
14 - 16% 70% 73% 56X 86%
12 - 14% 75% 75% 47% 93
10 - 12% 65Z 69% 70% 91%
Under 10% 74% 73% 75% 84Z
AVERAGE56.5% 82.5
Storage temperature approximately 35~F.
*Percentage Emergence within`five days of plantlng
- 2 -
1090562
It is not uncommon for the drying air used in conventional pro-
cesses to be at a temperature of 110F. to 140F., and occasionally even
higher, e.g., up to 200F. It would seem that such temperatures would
~speed drying, but because of the sharp contrast with ambient temperatures
as the air approaches the surface, resulting in moisture condensation and
blockage to air flow, the drying process is slowed. When the grain is
stirred, condensation in bin walls is intensified because of contrasting
temperatures, resulting in rusted wall and rotted grain. Destruction of
protein, loss of corn oils and other heat-suscepible ingredients can
result in as much as five pounds per bushel loss of weight when high heat
drying is utilized.
Commonly, hydrocarbon fuels, e.g., propane, are used as a heat
source. The combustion of these fuels is associated with the production
of water. The BTU per hour output of heaters commonly employed range from
500,000 to 3,000,000 so that the per day production of water as a product
of combustion can range from 75 to 500 gallons. This vapour is in the air
that goes through the grain.
The seriousness of this problem is attested to by the fact that
nearly every drying bin has crusted and sprouting surface grain, overdried
bottom grain, rusting of bin walls and rotting of grain.
Present principles and practices of drying stored grain rest on
the assumption that obtaining saturated, exhaust air is desirable. In the
prior art, specific zones in the grain bulk are referred to, i.e., the dry
zone, the drying zone and the wet zone.
Weight losses of 1% of the dry matter have been found to corre-
late to a 20% loss of germination, and in today's economy~ such deteriora-
tion can amount to as much as 20¢ per bushel loss in value. Since loss of
germination means loss of value, it is desirable to maintain maximum
germination. Therefore, maximum control provides maximum germination, and
the induction of dormancy from the earliest time following the harvest of
lO90S62
the grain by exposing the harvested grain to controlled air flow and
moisture removal is desirable. Dormancy is a state of retarded respirs-
tion; accelerated respiration increases kernel food consumption and
weight loss. Respiration is the conversion of_oxygen to carbon diox de
(the carbon being derived from the consumed sugar)
and is exothermic, i.e., heat is generated. Thus, when high-moisture _orn
is exposed to warm saturated air, the rapid development of mold and heating
of grain is intensified by the exothermic process of respiration as well
as by the external addition of heat.
In the case of excessive differential, overdried grain will
result~ if saturated air is obtained, deteriorative conditions are estab-
. _
lished. The proces~ of this invention proposes to maximize utilization
of natural air, and to maximlze preservation of seed quality and market
weight and value. The equilibrium corn moisture obtained during ventilation
is shown in the following table.
Si~ilar moisture equilibrium charts can be-prepared for other
grains. ~~ ~~~
a; 1(t90~6'~
,__ ~ E~ ~ 0 ~
C~ H ~ O~
P~ X
P~ ~
. P P ~ ~ ~ ~ ~ ~ ~ i~ a~
E-~ H 1-/ 0 ~ ~D O ~ u~ I` O
~ ¢ H c~ ~ t` -J ~ ~t -;t u~
.~ , , . 1~ ~ X
,,, P~ ~3 P
: a ~
0~
U~ ~ ~ ~ ~ ~ ~ ~ P~
~ O O O O O O O O
P ~ O
z~ ~
~ .
HO
E~ ~ ~ i~ ~ ~ ~ ~ ii~
P~ ~ O ~ U~
_1 E~ O ~
~ H ~1 ~ _1 ~1 ~1 ~ ~1 --I
P ~Y ~~X
~_1 F~
P ~
~ E~ ~ p~
X ~1: P E~ ~ ~ ~ ~ a~
E~ ~ ~ H H c~ u~ o u~ 0 0
~ E~ ~ ~ ~ ~ ~ ~ u
H H X ~ X
O ¢ P~ ~ P
E-l P~
P m
a: o 0
~ ~Y o~
O E~
~ cn ~J
~ X ~
o P ~ ~ O O O O O O O O O O
X Z ~ E~ o u~ o u~ o u~ o u~ o u~
~ ~ ~ ~ ~ ~ u~ ~ 0
~ .
~ ._
P
H
m P ~ ~ ~ "~
H E-l ~ -1 0 0 o~ D `;t C`l O 0~ 1~ 1
~ P~ Z U~ . .
H O PS H u~ ~t) It) u~ ~ ~ ~ '$ ~S ~ C'~ ~ c~
' tY ~ ox
P~
E~
'1: ~ E~
~ 1-1 H
~ E~ ~ ~! il~ 1~ il`~ ~C ~ a~ ~ ~ ~ ~ ~ ~
X ~ H o ~1 u~ O ~ ~
E-~ ~ X ~
~ . .
~-
~ ~ ~ ~ ~ P~ ~ P~ ~ ~ ~ ~ P~ ~ ~ ~
P~ ooooooooooooo
Z ~ ~ U~ O U~ O U~ O U~ O U~ o U~ o U~ .
~ ~ ~ 0
P~ ~
-- 5 --
lO90S6Z
Accordingly, it is an ob~ect o a broad aspect of this invention
to provide a grain drying bin for conditioning grain to controlled dormancy
and moisture, and to maximize weight and market value for specific markets
while maintaining optimum seed conditions.
It is an ob~ect of a further aspect of this invention to provide
a grain drying bin for "cool-drying" grain by reference to the temperature
differential between dry-air and wet-air in which the dry-air temperature
is automatically regulated and the source of heating the drying air can be
inactivated when the difference between the wet-air temperature (exhaust)
and the dry-air temperature (plenum) is greater than the preset tolerance,
allowing for fluctuations of the plenum-air temperature that occur
seasonally.
By one aspect of this invention, a grain drying bin is provided
which is of the type having a plenum chamber formed in the lower part
thereof and a gas-pervious floor forming the top of the plenum chamber,
the grain drying bin comprising: means for introducing atmospheric air
into the plenum chamber; and electrical heating means for adding heat
energy to the air in the plenum chamber, the electrical heating means
including a plurality of heat lamps mounted on the lower part of the bin
ad~acent the plenum chamber.
By one variant thereof, the grain drying bin further includes:
means for determining the temperature of air in the plenum chamber; means
for determining the temperature of air as it exhausts the bin; thermostat
means responsive to the temperature of the air in the plenum chamber for
controlling the operation of the meating means; and means, adapted to over-
ride the thermostat controlling the heating means and to inactivate the
heating means when the temperature difference between the drying air in the
plenum chamber and the air exiting the bin is greater than a predetermined
amount.
By a variation thereof, the grain drying bin further includes:
-- 6 --
-- 109056Z
a plurality of heat lamps spaced about the bin wall ad~acent the plenum
chamber and having a total output of 10 to 40 watts per one hundred bushels
of bin capacity.
By another variation, the grain drying bin further includes: a
plurality of fans distributed about the wall of the plenum chamber; each
fan being individually controlled and including closure means to prevent
air from exiting the plenum chamber when the fan is inactivated.
By yet another variation, the grain drying bin further includes
transparent heat lamp mounting plates detachably secured to the bin wall.
By a still further variation, the grain drying bin further
includes means for indicating the amount of air being introduced into the
plenum chamber.
By another variant, the heat lamps emit radiant energy.
By another variant, the heat lamps emit radiant energy in the
infrared wavelengths in the electromagnetic spectrum.
By a further aspect of this invention, a grain drying bin is
provided which is of the type having a plenum chamber formed in the lower
part thereof, a gas-pervious floor forming the top of the plenum chamber
and an upstanding plenum chamber wall forming the sides of the plenum
chamber, the grain drying bin comprising: means for introducing atmos-
pheric air into the plenum chamber, including at least one fan tube
attached to the plenum chamber wall; and electrical heating means for
adding heat energy to the air in the plenum chamber, the electrical heating
means comprising a plurality of heat lamps attached to and spaced around
- the plenum chamber wall, the plurality of heat lamps also being spaced
i from the fan tube on the plenum chamber wall.
By a variant thereof, the heat lamps include means for emitting
infrared rays.
By another variant, the graln drying bin further includes a
plurality of fan tubes having fans therein spaced around and attached to
_. .
- 7 -
lO90S6Z
the plenum chamber wall, each of the fan tubes and the heat lamps being
spaced apart from each other around the plenum chamber wall.
By a further aspect of this invention, a grain drying bin is
provided of the type having a plenum chamber formed in the lower part
thereof and a gas-pervious floor forming the top of the plenum chamber,
the grain drying bin comprising: means for introducing atmospheric air
into the plenum chamber; and electrical heating means for adding heat
energy to the air in the plenum chamber, the electrical heating means
comprising a plurality of heat lamps spaced about the plenum chamber.
According to one embodiment of this invention as now provided
by the present Divisional Application, grain to be conditioned or dried is
placed in a storage bin, generally of the type having a means for blowing
drying air into a plenum chamber below the body of grain to be dried.
The roof of the plenum chamber, which is also the floor of the storage
bin, is pervious to gas flow and allows the drying air to percolate up
through the body of grain to be dried. Bins of this type are quite common
in the prior art, but they usually include a blower furnace as the means
for supplying drying air to the bin.
In the present invention as now provided by the present Divi-
sional Application, in one of its embodiments,:the drying which is effectedmuch more closely approximates what can be termed natural drying. Specifi-
cally, it utilizes a flow of air and a particularly specified heat source
which is more controllable and less destructive to the grain than prior
art techniques. Strictly natural air drying is not fully adequate to
reduce grains to moisture levels safe for long-term storage, due to
humidity and temperature conditions that exist in fall and early winter,
as noted in the following table.
-- 8 --
10~056Z
'~ !
NAT~RAL AIR GRAIN DRYNESS* BY THE MONT~ ~IOWA)
AVG. CORN WET-BULB** AVG. CORN WET-BULB** ¦
MOISTUR~ DEPRESSION MOISTUR~ DEPRESSION
Jan.20Z 1 - 2 July 11 1/2% 7 - 10-
Feb.l9X 1 - 3 Aug. 12% 7 - 9
March i7% 2 - 5 Sept. 13Z 6 - 8
April 16Z 5o _ 70 Oct. 14Z 5 _ 70
May13 1/2Z 7 - 8 Nov. 16% 3 _ 5
June13 1/2Z 7 - 8 Dec. 19~ 1- - 3-
. _ . .
*Varies With Dlfferent Grains; also with varietal and sea-
son-l differences.
**Average Mean Wet-Bulb DepreggIong From U.S. Weather Bureau
Data.
The grain drying bin of aspects of this invention as now provided
by this Divisional Application departs fundamentally from this generally
accepted assumption and employs a controlled balance of volume of air flow
to grain volume and of air dryness to grain dryness while substantially avoiding
the clash of warm grain air temperatures with cool or cold ambient temperatures.l
The effect is to maintain a relative humidity in the exhaust air below
saturation so that some drying can occur within the entire bulk of grain
and thus substantially eliminate the "wet zone" of high-moisture perishable
grain exposed to saturated air; accelerated rates of respiration (in the
grain itself and in molds and other micro-organisms exposed to warm, humid
conditions) that intensify losses of weight and food value are likewise sub-
stantially prevented. - j
The grain drying bin of aspects of this invention as now
provided by this Divisional Application utili~es the fact that as water
evaporates from a surface, the surface becomes cool. Therefore, as dry
air is passed through the body of moist grain, evaporation takes place and
cools the grain air a certain amount; t~he amount of cooling is dependent upon
a number of factors, e.g., the particular grain being dried, the temperature
of the drying air, the moisture content of the grain, and the relative
I
.
1090S6Z
humidity o~ the drying air. The effect of eyaporatiye cooling is to
render the kernel and micro-organism dormant and thus to stabilize the
kernels and micro-organisms. It is a feature of an aspect of this inven-
tion as now provided by this Divisional Application that the drying air is
not heated to such an extent that the grain can be damaged thereby or
overdried. It is desired to approximate as closely as practicable the
conditions of natural air drying, and accordingly, the drying air is pre-
ferably conditioned only to control its dryness or relative humidity with-
out greatly raising it above ambient temperatures.
The temperature of the plenum air is controlled, e.g., by a
thermostat or other similar modulating or cycling device. According to
one aspect of the invention as now provided by this Divisional Application,
the temperature differential between plenum air and exhaust air is moni-
tored, and the specified heating means is inactivated when the differential
exceeds a preselected value.
Specifically, according to an aspect of this invention as now
provided by this Divisional Application, a controlled flow of ideal,
natural "harvest air" is maintained within the stored grain with an
apparatus for measuring and controlling natural air dryness or relative
humidity so as to control grain dryness and dormancy. The addition of
dry energy (heat) to the drying air is selectively controllable so as to
determine the extent of drying that can occur within the grain. This is
accomplished by obtaining a measure of the "dry-bulk" temperature and the
"wet-bulb" temperature depression that occurs within the grain with the
addition of heat only when the wet-bulb depression is less than the pre-
determined tolerance.
Since only a small rise in temperatu~e of the drying air is
required in the use of the grain drying bin of an aspect of this invention
as now provided by this Divisional Application, electrical heating means
are ideally suited, and because of their extraordinary safety, convenience
--.10 --
lO90S62
and serviceability, heat lamps are preferred as a means for heating the
drying air. Heat lamps distributed about the plenum chamber uniformly
warm metal floor and floor supports, giving good distribution of the
added heat. The exceptional economies of light energy as a heat source
are well known.
Additionally, radiant heat energy from electrical sources is
totaly dry energy and does not aggravate problems of moisture condensation
as does the combustion of hydrocarbon fuels.
In summary, the grain drying bin of aspects of this invention as
now provided by this Divisional Application provides that, because of the
sensitive nature of seeds and other products with similar sensitivities,
the application of heat as used in conventional drying of non-living pro-
ducts is excessive and intolerably damaging, and that preservation of
weight and food value in grain is accomplished only in preserving the
biological integrity of the seed.
Further, even when drying is accomplished with low levels of
heat, these can be excessive because of the adverse environment created
by the heat in increasing seed respiration and in causing stratification
of moisture within the grain which allows for mold infestation.
Because of high costs of energy and limitations of energy
resourc~s, their wise management, especially in drying grains, is obviously
urgent because of the vast expenditure of energy resulting from the growing
practice of drying food grains.
More specifically, this invention in another of its aspects as
now provided by this Divisional Application includes a grain drying bin
operated in such a way that the biological integrity or living character
of biological products, especially food grains, is preserved by drying,
chilling and conditioning in a controlled storage environment. Such con-
trol of storage environment is by ventilation, which maintains a balanced
ratio of air-volume to grain-volume, and which substantially prevents
-- 109056Z
stagnation of and accumulation of moisture in the interstitial grain-air.
Throughout the conditioning process inherent in the use of the apparatus
of aspects of this invention as now provided by this Divisional Applica-
tion, the temperature of the product in storage remains colder than
ambient temperatures and that when the product has achieved the desired
equilibrium moisture, it is at the same temperature as the ambient air.
Furthermore, monitoring means indicate the extent of heat expen-
diture or evaporative cooling during ventilation, i.e., the differential
temperature observéd from the time the air enters the grain to the time
it exhausts, thereby providing direct indication of equilibrium moisture
being achieved within the grain at any time. Control means are provided which
automatically activate or deactivate heat sources in response to evapora-
tive cooling and make possible the selective control of moisture content
in the grain by selective control of differential temperatures.
In the accompanying drawings,
Figure 1 is a side elevation view, partically cut away, showing
a grain bin equipped according to one aspect of this invention;
Figure 2 is an exploded view showing the details of heat lamp
mountings according to one aspect of the invention;
Figure 3 is a front elevation view showing a control panel for
use in accordance with one aspect of this invention;
Figure 4 shows a schçmatic operational circuit diagram for the
operation of the grain bin of one embodiment of the in~ention;
Figure 5 shows a schematic opërational circuit diagram for the
operation of the grain bin of another embodiment of the invention; and
Figure 6 is a partial perspective view of the interior bottom of
the grain bin equipped with a multiple fan arrangement according to one
aspect of this invention, with certain portions removed for clarity.
According to one embodiment of this invention as now provided by
this Divisional Application, a grain drying bin is now provided which has
!
- 12 -
~ 1090S6Z
the ability to produce grain having precisely controlled levels of moisture
and also provides that these levels are obtained in a manner which results
in minimum germination loss of the grain with resultant maximum quality for
ultimate use. Some processing techniques require specific moisture levels,
and the ability to supply grain with these specific levels will produce
competitive advantages in certain cases.
A feature of one aspect of this invention as now provided by
this Divisional Application is that the ultimate grain moisture can be
obtained by selected settings of the controls. These controls include a
thermometer mounted so as to measure plenum-air temperature, and a tempera-
ture cycling control, e.g., a thermostat, that activates or deactivates
heat sources in response to the plenum-air temperature. A second thermo-
meter, sensing the temperature of the exhaust air, provides a differential
reading of temperature from the plenum-air so as to provide an indication
of grain moisture and extent of drying taking place. The differential
reading, when greater than a preset level, causes the heat sources to be
inactivated regardless of the thermostat setting.
Incorporated in aspects of this invention as now provided by this
Divisional Application is specified electrical apparatus including a
specific type of heating means which provide indirect and direct condition-
ing of the air.
By means of electrically powered fans, a controlled volume of
air is kept flowing through the grain according to grain moisture content
as has been described in the aforementioned United States Patent No.
3,408,747, according to the following chart. Because of chilled-air tem-
peratures, the process involving the use of the grain bin of an aspect of
this invention allows for reduced volumes of air (by 40X) over previously
cited recommendations.
- 13 -
-- 109056Z
REQUIRED C.F.M./BU.
Percent moisture: c.f.m./bu.
30 . . . . . . . . . . 9.0
28 . . . . . . . . . . 7.0
25 . . . . . . . . . . 5.0
22 . . . . . . . . . . 3.5
20 . . . . . . . . . . 2.5
18 . . . . . . . . . . 1.5
Indirect electrical heating is obtained by fan blade friction
and by the heat given off by electric motors powering the fans. Also, the
pressure in the plenum would be above atmospheric, and the higher pressure
gives greater drying capacity to the air as is well known. The combination
of fan blade friction, electric motor heat and pressurized air may in some
cases raise the temperature as much as from 2 to 5F. This temperature
increment together with ideal weather conditions can, in some cases, pro-
vide adequate capacity for accomplishing the desired degree of grain dry-
ness. However, during most seasons the supplemental adtition of some
heat energy will be required. Electrical sources are ideally suited for
this additional heat. Advantages obtained by electrical heating include
greater safety, ln that the fire hazard is reduced compared to that when
conventional blower furnaces are used or when propane burners are used.
Service requirements are at a minimum and only require changing a light or
heat element in most cases. Additionally, the well-known sanitizing advan-
tage of infrared renders certain bacteria and mold spores inactive upon
exposure,which effect is of great value in stabilizing a safe-keeping
environment for food grain. The present invention in one of its aspects
as now provided by this Divisional Application minimizes problems resulting
from conventional high heat drying including uneven drying, overdrying,
condensation of moisture within the grain causing accelerated biochemical
activity, and moisture condensation on the bin walls. Conventional high-
- ~4 -
- 109056Z
heat drying generally includes introducing the products of combustion into
the drying bins, and as a result, large amounts of water are introduced
into the grain.
Referring now to Figure 1 of the drawings, a grain storage bin
11 is shown having side walls 12, a conically shaped roof 13, and an
opening 14 in the top of the roof. The bin has a foundation 15 and floor
supports 16 supporting a floor 17 which is pervious to gas flow. A body
of grain to be conditioned is indicated at 18, and fan 19 and duct 20
leading from the fan for introducing air into the plenum chamber are shown.
A group of heat lamps 21 mounted in frames 40 are located around the outer
wall of the plenum chamber formed between the bin foundation 15 and the
bin floor 17, and control panel 22 is located on the side wall 12 of the
bin. According to one simple aspect of this invention as now provided by
this Divisional Application, the heat lamps 21 distributed about the lower
part of the grain bin side walls 12 are simply turned on and left on during
the entire drying procedure, which may take several weeks. In some cases,
the heat lamps 21 may be thermostatically controlled to maintain a desired
temperature level in the plenum chamber. The kilowatt input accomplished
with lamps is generally within a range from 1/4 to 3/4 watt per bushel of
bin capacity.
According to a variant of the invention also shown in Figure 1,
a temperature sensing means 37 is shown in the top of the body of grain 18
and is located preferably near the center of the bin to minimize the effects
of heat loss through the bin wall. Plenum air thermostat 33 (see Figure 3)
with differential sensor 36 closes the circuit supplying power to cable 47
within the range of preset tolerances,~i.e., if the exhaust air drops
below the preset tolerance of cooling, the circuit is opened, or if the
plenum-air temperature rises above the thermostat setting the circuit is
broken.
As an alternative to the use of fan l9 and duct 20 as shown in
lO90S62
Figure 1, a plurality of small fans 24 could be spaced about the bin
directly on the lower bin wall, (which is also seen in Figure 1). These
smaller fans would preferably be individually operable to guard against
a surge of electrical load if all the fans were turned on togetherr and
would include suitable closure means on each fan (not shown) substantially to
prevent pressurized air from the plenum chamber from exiting through a fan that
is not running.
A preferred embodiment of the heating means to be utilized in an
aspect of this invention as now provided by this Divisional Application
is illustrated in Pigure 2. As shown therein, a window frame 40 which may
- be round, square, or rectangular, attaches to the bin wall 12 by means of
bolts 41 or other suitable means through holes in bin wall 12. Heat lamp
42 is carried by receptacle 43 carried on transparent window 44. Window
44 can be removed for changing a burned out lamp or for providing access
to the plenum chamber for cleaning or inspection simply by removing bolts
45. Some of the advant~ges provided by this embodiment include ease of
maintenance, access to plenum for inspection or cleaning, illumination of
both plenum and grQunds outside the bin, and substantial prevention of mildew. j
This embodiment also reduces fire hazards which arelpresent when flame heaters
.
are used, and substantially eliminates the pollution resulting from flame
heaters or glowing resistance elements.
Figure 3 shows a grain dryness control panel 22 suitable for
mounting on the lower side wall of the bin below the floor 17.
The control panel includes: a thermostat 32 with a remote sensor
37 that measures the exhaust air temperature; a thermostate 31 that
measures the plenum air temperature; a cycling (thermostat humidstat)
and/or moldulating means 33 with remote sensor 36; and differential
(humidity/temperature) selector 34; a light 38 indicating when the circuit
is open or closed; a power cord 47 supplying power to the heat sources;
and a manometer 35 that indicates air flow.
B - 16 _
1090562
In Figure 4 the power cord 47 is connectet to a power source
(not shown) and forms a circuit having a heat lamp 42, a thermostat 33,
and a differential temperature controller 34 all connected in series. The
thermostat 33 responds to warming through sensor 46. Thermometer 31
indicates the temperature in the plenum at sensor 46, and this temperature
reading is also carried to thermostat 33 and differential controller 34
by lines 33' and 34', respectively. The temperature of the exhaust chamber
of the grain bin is measured by sensor 36, which temperature reading is
indicated on thermometer 32 and is also input into differential controller
34.
In Figure 5, the power cord is likewise connected to a power
source (not shown) and has connected, in series therewith, a thermostat
53, and a heat lamp 42. Thermostat 33 operates exactly as described in
the Figure 4 embodiment, i.e., it responds to warming. mermostat 33
closes the contact when the temperature at sensor 46 is below the setting
thereon, and the contact is opened when the temperature at sensor 46 rises
to the temperature set on the setting, or above the setting. mermostat
53 works in an opposite fashion in that it responds to chilling, i.e.,
when the temperature sensed by sensor 46 is lower than the setting thereon,
the thermostat 53 contact is open and when the temperature sensed by sensor
36 is at the setting or above, the circuit is closed. It will be under-
` stood that the heat lamp 42 operates only when the contacts of both thermo-
stats 33 and 53 are closed. This arrangement, like that of the embodiment
of Figure 4, is fully automatic.
Figure 6 shows a view of the base of the grain drying bin,
including the side walls 12 resting on the foundation 15 and floor supports
16 which support a floor 17 which is pervious to gas flow. The group of
heat lamps 21 are shown disposed around the perimeter of the floor
supports 16, and the fans 19 and ducts 20 leading therefrom for introducing
air into the plenum chamber are shown to be spaced around the perimeter of
109056Z
the floor support and between the heat lamps 21. The ducts 20 are pro-
vided with air controlling registers 54.
The operation of the control panel shown in Figure 3 is based
upon the following considerations:
When corn moisture is above 26%, sufficient water is present so
that evaporation and evaporative cooling approximates that of water from a
free surface. Therefore, the temperature depression measured in the ex-
haust air when compared with that of the plenum air provides the wet-bulb
temperature reading. This being so, the previously cited moisture equili-
brium chart (TABLE 1) provides a meaningful guide (based on psychometricwet-bulb depression) as to how dry the grain is becoming.
To obtain 13% moisture corn, the wet-bult depression to be main-
tained should be 7F. approximately.
As the grain dries, its hygroscopic property (i.e., internal seed
forces holding water) increasingly resists evaporation, and as evaporation
decreases evaporative cooling also decreases. When grain moisture reaches
equilibrium with air moisture, the plenum air and exhaust air temperatures
will be the same ant no drying will take place.
Therefore, the comparison of these two temperatures provides
positive indication as to when drying does or does not ta~e place and as
to how dry the grain is becoming; heretofore, the farmer could only guess
about these situations. More complete charts can be supplied as a valuable
aid to the producer in co~trolling drying, e.g., the chart shown in Table I.
The ultimate dryness of the grain is determined by the ultimate
dryness of the air. It can be observed from a psychrometric chart that a
5F. wet-bulb depression at 70F. represents 74% relative humidity (14.0
corn moisture); while a 10F. wet-bulb depression at 70F. represents a
55% relative humldity and 11.4% corn moisture; while a 20~F. wet-bulb de-
pression represents a 36Z relative humidity and corn moisture under 9~.
Similarly, relative humidities and equilibrium corn moisture can be found
- 18 -
.losns~z
for all other normally occurring temperatures. The actual wet-bulb depres-
sion observed in the surface grain may be somewhat less than the real wet-
bulb depresæion as the grain dries, and increasingly so the closer grain
moisture approaches equilibrium moisture with the atmosphere, so that
actual grain dryness being achieved would, in fact, be lower than that
suggested by the observed temperature differential. The corn equilibrium
chart contained in the aforesaid United States Patent No. 3,408,747 gives
corn moisture levels below those cited on the chart contained in this
invention and represents an accommodation to the changing hygroscopic
characteristics of grain as it dries, and may therefore more accurately
represent grain moisture being achieved.
-- 19, --
--` TABLE 1 ~09056Z
GRAIN MOISTURE EQUILIBRIUM. CORN ROUGH RICE SOYBEANS.
~ i
... . U o~ o~ ~ I
~ . ~ ~1 o
o . ~: ~ ~ ~ . . .
U~ ~ o ~ o ~ ~ ~
o . U ~ O~J D ~ ~ ~> ~ u~ ~
O Z; ~ ~ 0~ 0 OP' ~ ~ O U~
X ~ ~c~ ~ ~ 1
u~ P u ~: ~ p, a~o~ o-~lu) ~
_I H t~ ~ ~ ~ O O O ~ ~ O ~ ~ u~
o ~ . ~ ~o ~ u~ ~ o ~ ~ ~ ~ ~
o P w q~ C o ~ o ~ ~ ~ ~ 1 ~
0~ . ~ ~S U C OD ~ u~ 0 ~ ~ O ~ u~ e~ CO O ~ u~
~: ~ U ~, C ~ j_l~ ~ 1 ~ _~ OCI~ ~ ~
o~4 U~ ~0 ~ 0 ~ 4 O ~ O ~ U~ ~ o~ u7 1~ o
o o PS C o O ~ _l ~ ~ ~ ~ ~ o o <~
.C ~d ~ ~ ~ _~ ~1 ~ ~ 1 ~ ~ ~J
P6 o Z 4 ~ 0 h :~ ~ 0 0 1~ o~ ~ ~ u~ 0 ~ O ~ u~
p u~ 'C ~O~ ~ ~ ~ O ~0 0 _1 _1 ~ ~ O o~l~ co ~ u~
U C ~O.n ~D 0 _1 ~ U~ ~ _~ ~ ~ _l ~ ~ ~ O~
~ o ~ u~ S~ ~ ~ . . . . . . . . . . . . . .
P~ O ~ C O O O ~ O o~ ~ ~ u~ u~ ~ O~ I~ ~O
X ~ ~.~: ~ C~ ~1 ~1 _1 ~1 ~ 1 ~ 1
E~ ~ vC ~0 ~ ~ ~ o ~ u~ ~ ~ u~ 1~ 0 O~
PS P~ O O ~ O ~ r~ ~ O u~ ~ O~ ~ `D ~
c ~rC ~ c~ ~ _l ~ ~ _l ,. ,1 _1 c~ ~ ~ .c
VC ~0 ~ ~1 ~ ~ 1~ o~ C~l O 1~ vl O ~1 u~ 1~ O rl ~U
E- `~ ~a ~ . . . . . . . . . . . . .
~q O ~ ~ O O O ~1 0 CO ~ ~ O U~ ~ ~ ~ OD ~ U~ ~J _
,C ~ ~ ~1 ~ ~ ~1_1 c~ 0
~ ~ OO,n ~ O ~ ~ ~ ~ ~ ~ O
X o ~ . . . . . . . . . . . . . . V~
u~ O O O O O a~ ~ ~ ~ ~ o~ D u~ ~ V O
U~ ~ ~ ~ ~ ~ ~ o
U~ I~ o o ~ U~ U~ I~ o ~ o U~ 1~ o
~ O . . . . .,. . . . . . . . . .
:~ o o~o~ ~1~ ~ C~l`~ U~ .¢
~O _l ~ . ~ 1 ~ 1 ~ ~ ~ V
~ ~ ~ ~ ~ ~ I~ ~o a~ _~ c~ ~1 ~
o . . . . . . . . . . . C
U~ ~oo~ ~ ,~u~ ~C~ ~
~D ~ ~ 1 ~ ~ ~ ~ ~J O
1~ O~ ~ ~ ~ ~ ~O r~ y~ ~ . O
o ~ 1~ ~D ~ ~ ~ V O
` ~ 1 ~ 1 ~ o ~
~ 'D t _l a~t o ~ ~ v
o ~o to~ ~ ~t ~ _~ ~; ~`- ~ o t~
1 ~ t
~ c~
O ~ ~ O
t
o o o o o o o ' o o o --
O t~lt O tJ~ O tJlt o u~ o t ~ , t~ ,
I DRY, PLENUM-AIR TEMPERATURE
,
- 20 -
~090562
The measure of wet-bulb depression is a measure o relative
humidity; it is obvious, therefore, that controlling wet-bulb depression
controls relative humidity.
~ When the setting on thermostat 33 is below the temperature
observed on thermometer 31, the contacts of the thermostat are open and
light 38 will be on.
When drying begins, thermostat 33 is set as desired (e.g., 6F.
above ambient) by turning the knob of 33 in the direction of "increase"
indicated by the arrow.
When the thermostat 33 setting is above the plenum temperature,
the contacts close to activate the heat source and light 38 goes out.
When the temperature of the plenum is the same as the thermostat setting,
the heat sources are deactivated. It can happen that because of low rela-
tive humidities in the natural air, overdrying can occur even though the
temperature of the plenum air would never reach the thermostat setting.
Undesirable overdrying would result if the heat source were not deacti-
vated. Such conditions are indicated if the exhaust air temperature drops
excessively below the plenum temperature, e.g., 10F. An adjustable
temperature differential control means 34 is provided in conjunction with
the thermostat 33. Differential control means 34 is adapted to determine
the differential between plenum air and exhaust air, and automatically to
open the thermostat circuit, thereby deactivating the heat source, when
the differential exceeds the value preset on control means 34.
The manometer 35 measures static pressure (inches water) and
indicates the volume of air being delivered by the fan(s).
The required ratio of air-volume to grain-volume varies with the
grain moisture, By knowing the actual and the required ratios, the operator
knows how fast the bin can safely be filled. The required ratios (cfm/Bu.)
for heated ai~ drying are defined in the sforesaid United States Patent
-- 30 No. 3,408,747, but because of chilled air temperatures are less:than
- 21 -
109056Z
those required in the above identified patent, ag has been observed previously.
Filling of the bin can continue as long as ratios are maintained.
By fixing the depth of grain (8 - 14'), a prescribed horsepower
requirement can be defined to maintain a certain level of air.
By maintaining horsepower application of 1/2 to 1-1/2 h.p. per
1000 bushels of corn, an air-to-grain ratio of 3 cfm/Bu. can be maintained
and substantially complete filling of the structure allowed. For example, a
10 H.P. is recommended for 10,000 bushels of corn; a 33~ diameter bin is
required to obtain 10,000 bushels in a 12 - 14' depth. As grain depth increases,
pressure increases and air flow decreases, thus decreasing the safe fill
rate. Air volume has to be maintained according to grain moisture content
as previously cited, which principle is basically applicable to all grains.
Heretofore it has been customary to use single fans. The appli-
cation of multiple fans offers distinct advantages: control of air flow
according to grains need lower electrical requirements; increased air
flow; more uniform air flow, more easily serviced; more direct attachment
to the bin by sizing fan housing to plenum depth and a more flexible appli-
cation of horsepower to fit a wide variation of systems.
The fans 19 have flap closures around the plenum chamber which
allow the respective fans to introduce air into the plenum chamber, but
which substantially prevent air from leaving the plenum chamber when that
same respective fan is not operative. Furthèr, it becomes practicable to
prefabricate an electrical harness that attaches in series to the previous
fan providing a simple "add on" approach to increase fan numbers in a given
system.
It is a feature of this invention as now provided by this
Divisional Application that grain can be dried in a manner more closely
approximating natural drying, and over-heating and over-drying of the
grain can be avoided. Specifically, satisfactory drying rates may be
obtained without using supplemental heat sources e.g., the heat lamps 21
-`` 109056;~
so long as the dryness of the air is consistent with the desired equili-
brium dryness that will be obtained in the grain. When the outside air
temperature is too cold and/or when it has a high humidity, the supple-
mental heat source can then be activated to provide the necessary dryness
in the air to obtain proper drying rates.
The differential setting for the operation will vary with the
particular grain being dried and the ultimate moisture content desired .
A~ setting of 7 - 10 F. may be best for corn, while a 5 - 8F. differen-
tial may be best for rough rice and a 3 - 6F. differential for soybeans.
It must be emphasized that adequate air flow must be provided
in any drying operation of this type. As has been said, a thorough dis-
cussion of the importance of air volume to the drying operation appears in
the aforesaid United States Patent No. 3,408,747.
Dryness of the air determines dryness of the grain, while the
volume of air employed and the temperature determines how long it will
take to complete drying.
Calculated averages for dryness, for time required, as well as
probability of weight and germination losses (as described in the afore-
said United States Patent No. 3,408,747) can be determined according to
differing conditions of air flows.
For exampleJ 26% moisture corn harvested on November 1, using
1-1/2 cfm/Bu. generally requires 44 days to dry to 13-1/2% moisture with
a 64Z probability of losing 0.5% of dry matter (approximately 10% germina-
tion); doubling the air volume (3 cfm/Bu.) reduces the probability of
weight loss to zero and reduces drying time to 22 days.
The application of this gradual process of moisture removal does
not limit harvest capacities since under certain moisture levels (25%)
instant and total filling of the bin is possible. Even now, structures up
to 48' diameter are available with capacities in excess of 20,000 bushels.
The operation of one embodiment of the invention as now provided
~090~i6Z
by this Divisional Application will now be illustrated by reference to
Figures 1 and 3 of the drawings. A grain bin 11 is filled with grain to
be conditioned, e.g., by filling through the opening 14 in the roof 13
of the bin. After the grain 18 is in the bin and has been levelled, tem-
perature sensor 37 and sensor 36 for the differential temperature control
are placed in the bed of grain near the surface thereof. Depending upon
the ambient temperature and humidity conditions, a desired drying tempera-
ture is set on the thermostat 33 and a setting selected for maxmimum
tolerable differéntial. During fan 19 operation, air is forced into the
plenum chamber and up through the floor 17 into the body of grain 18 and
eventually out the opening 14. As the drying air passes through the body
of grain, moisture will tend to be removed from the grain into the air,
and the resultant evaporation will cause a lowering of the temperature of
the air. The extent of the temperature lowering will be indicative of
the rate of removal of water from the grain, and can be observed by the
operator by reference to the thermometers 31 and 32. If the temperature
differential indicated by thermometers 31 and 32 exceeds the differential
setting of control 34, this indicates that overdrying would occur, and
the differential control 34 will function to inactivate the supplemental
heating means. Drying will then continue utilizing air which has not had
supplemental heat added thereto, other than the small amount resulting
from the operation of the fan and motor. The differential temperature
then will tend to work back toward the range set on the differential con-
trol 34, and if the differential temperature becomes less than the amount
set on control 34, the thermostat may again cause the heat lamps 21 to
become activated, adding heat to the drying air.
Now, with respect to the embodiment shown in Figure 4, in its
operation, the heat lamp 42 will only operate when the contacts of both
the termostat and the differential controller 34 are closed. Consequently,
in order for the heat lamp to operate, the temperature sensed in the plenum
~09056Z
by sensor 46 must be below the preset temperature of thermostat 33 in order
to have the contact in thermostat 33 closed, and the different$al tempera-
ture between 36 and 46 (in the exhaust and plenum chambers, respectively)
must be less than the differential setting on differential controller 34.
It will be understood that thermostat 33 and differential controller 34
respond automatically to close the contacts as well as to open them to
provide a fully automated control.
- 25 -
