Modular column dryer for particulate material

A modular column dryer for particulate material including a housing with a removable module supported in the housing. The removable module includes at least one support member and a first pair of generally vertical side panels having perforations therein. The side panels are fixed to the support member to form at least a part of a first column for receiving particulate material and directing the material through the housing. Means is provided for introducing moist particulate material into a top portion of the column. Drying air is passed through the column for drying particulate material therein. A discharge mechanism is provided to remove the dried particulate material from a bottom portion of the column.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to gravity flow dryers for particulate 
material and, more particularly, to such a dryer having a drying column 
comprised of a removable module. 
2. Description of the Prior Art 
It is often necessary or desirable to dry freshly harvested grain before it 
is processed or stored. Storage of grain with excess moisture may cause 
quality deterioration and spoilage during subsequent storage. 
The need to dry grain prior to storage has long been recognized in the art 
and many grain drying systems have been developed to accomplish this 
purpose. In many such prior systems, the grain is heated by air at a 
predetermined temperature during a first drying process and then the grain 
is quickly cooled to a desired storage temperature by exposing the grain 
to a flow of ambient air. One such system is the cross-flow column type 
grain dryer in which grain flows downwardly by gravity through a column 
having perforate walls and heated air is forced transversely through the 
perforate walls of the column to contact the grain to dry the grain or 
remove moisture. Typical of such cross-flow grain dryers are the grain 
dryers shown and described in U.S. Pat. No. 2,732,630 to Markowich and 
U.S. Pat. No. 3,238,640 to Fry. 
The size of the perforations in the column walls in the typical prior art 
grain dryers has been set for the particular material to be dried. For 
example, if the dryer is to be used to dry corn, the perforations are 
somewhat smaller than the size of the corn. However, when drying smaller 
grains, such as rice, the perforations are smaller than when the dryer is 
designed for drying corn. Obviously, it is not feasible to dry small size 
grain in a dryer having large perforations in the walls defining the grain 
columns. Correspondingly, while it is possible to dry corn in a dryer 
having the small-sized perforations, as used in a rice or rope seed dryer, 
such drying is inefficient in that the air flow through the column is more 
restricted than desired. Thus, with the prior art dryers, it was necessary 
to have separate dryers for different types of grain or other particulate 
material to be dried. While some prior art dryers may have had perforate 
walls that were removed and replaced with walls having perforations of the 
same or a different size, such a conversion process was cumbersome and the 
dryers were not adapted to have removable modules for efficient and 
effective conversion involving a minimum of operator time and shut-down of 
the dryer. The present invention comprises a dryer having a removable 
module incorporating the columns, which can be quickly and conveniently 
removed and replaced to provide side walls having perforations 
appropriately sized for the material to be dried. 
SUMMARY OF THE INVENTION 
Briefly stated, the present invention provides a gravity flow grain dryer 
for particulate material comprising a housing and a removable module 
supported in the housing. The removable module is comprised of at least 
one support member and a first pair of generally vertical side panels 
having perforations therein. The side panels are fixed to the support 
member to form at least a first column adapted to receive the particulate 
material and direct the material through the housing. Means are provided 
for introducing moist particulate material into a top portion of the 
column and means are provided for removing dried particulate material from 
a bottom portion of the column. Means are also provided for introducing 
drying air into the column through the perforations in at least one of the 
side panels for drying the particulate material in the column.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawings, and particularly to FIG. 1, there is shown a 
column type gravity flow dryer for particulate material, for example, corn 
or other type grain. The dryer, generally designated 10, includes a 
generally square-shaped housing 12 comprised of a pair of solid end walls 
14 and 16 and a pair of side walls 18 and 20. Each of the side walls 18 
and 20 includes solid upper and lower portions 22 and 24, respectively, 
and a perforate intermedite portion 26. The housing 12 further includes a 
suitable roof 28 and is supported at the bottom by suitable support means 
or legs 30. At the top of the housing 12 is a means for introducing moist 
particulate material or grain into the top portion of the housing, in this 
embodiment, a suitably sized wet grain inlet 32. 
On the outside of the housing 12 adjacent end wall 14, is an assembly or 
means 34 for providing drying air and cooling air to the housing 12. The 
assembly 34, which is supported by a suitable support frame 36, generally 
includes a blower section 38 and a heater section 40. 
The blower section 38 comprises a pair of blowers or fans 42 and 44 both of 
which are mounted for rotation on a single shaft 46. The fan shaft 46 
extends outwardly through a generally circular cooling air inlet opening 
48 in the blower section 38 and is journaled for rotation within a 
suitable bearing 39. A suitable drive pulley 50 is mounted on the 
outwardly extending end of the fan shaft 46. The drive pulley 50 is driven 
to rotation by means of a standard drive belt system 52 which also engages 
a second drive pulley 54. The drive pulley 54 may be driven by any 
suitable means, for example, an electric motor or a power takeoff 
mechanism on a tractor or other vehicle (not shown). 
The fan 42, which is closest to the cooling air inlet opening 48, is the 
cool air fan and the fan 44, which is furthest from the air inlet opening 
48, is the hot air fan, the fans being separated by a vertical partition 
43 to form individual chambers surrounding each fan. Cooling air is drawn 
in through the inlet opening 48 by the cool air fan 42 and is directed 
into a pair of cool air ducts 56 which in turn direct the cooling air into 
the dryer housing 12. The hot air fan 44 draws air in through a second 
generally rectangular air inlet opening 49 located in the other housing 
end wall 16 at the opposite end of the housing and the hot air fan 44 
directs the flow of air upwardly into the heater section 40. The heater 
section 40 includes a burner 58 which heats the air received from the fan 
44. In the preferred embodiment, the burner 58 may be a standard Maxon gas 
burner. The heated air from the burner 58 passes into a collector chamber 
60 and thereafter is directed into the housing 12 by a pair of generally 
cylindrical hot air ducts 62. 
The heater section 40 and the blower section 38 are separated by a 
generally horizontally disposed partition 64 which contains an airflow 
control means, comprising in this embodiment, a plurality of adjustable 
dampers 66. The adjustable dampers 66 are provided to control the flow of 
air from the hot air fan 44 to the burner 58. In this manner, it is 
possible to effectively regulate the hot air flow into the housing 12 to 
efficiently dry a variety of different types of particulate material. For 
example, it may be desirable to provide a large hot air flow into the 
housing 12 for drying high moisture content corn and a much smaller hot 
air flow into the housing 12 for drying lower moisture content rice. Thus, 
the adjustable dampers 66 may be set in a substantially fully open 
position to apply a large hot air flow to dry corn or in a substantially 
closed position to apply a small hot air flow when drying rice. 
Referring now to FIG. 3, there is shown the interior configuration of the 
dryer of FIG. 1 with a slight variation which will hereinafter be 
described. The dryer 10 comprises a pair of generally vertical outer 
drying columns 68, each column being defined by first and second 
substantially parallel opposed spaced perforate walls 70 and 26. A wet 
grain hopper 72 is provided at the top portion of the dryer for receiving 
and temporarily storing the moist grain introduced into the top of the 
housing 12 through the wet grain inlet 32. The wet grain hopper 72 is 
defined by the roof panels 28, the side wall upper solid portions 22 and a 
pair of sloping interior hopper panels 74. The wet grain hopper 72 also 
functions to distribute the moist grain into the top portions of each of 
the outer drying columns 68. 
In order to provide for a more uniform and less restricted grain flow 
through the outer drying columns 68, the columns are tapered outwardly 
from top to bottom so that the width of each of the columns is greater at 
the bottom than at the top. By tapering the columns in this manner, the 
air flow is less restricted at the top of the columns (where the grain is 
wetter and provides a high air flow rate through the outer columns 68) 
than at the bottom of the columns (where the grain is drier, thereby 
providing for a more volume controlled airflow through the columns over 
their entire length. 
At the bottom of each of the outer drying columns 68 is a dividing wall 
means, in the present embodiment a generally vertical partition 76, for 
dividing the lower portion of each of the drying columns 68 into two 
generally parallel channels 78 and 80. Each of the channels 78 and 80 
preferably contains separate discharge means, in the present embodiment 
metering rolls 82 and 84, respectively, for discharging particulate 
material from the channels 78 and 80 at predetermined rates. Both of the 
metering rolls 82 and 84 are driven by a system of drive belts and pulleys 
generally designated 85. As shown, the drive pulley for the metering roll 
84 is of a smaller diameter than the drive pulley for metering roll 82. 
Accordingly, metering roll 84 rotates faster than metering roll 82 to 
thereby discharge grain from the innermost channel 80 at a faster rate 
than the grain is discharged from the outermost channel 78. The grain from 
both channels 78 and 80 is discharged by the respective metering rolls 82 
and 84 into a receiving hopper 86. 
As shown in FIG. 3, heated air from the hot air ducts 62 passes outwardly 
through the outer drying columns 68 to contact and dry the grain in the 
columns. Since the heated air enters each of the columns 68 through the 
inner perforated walls 70, the hottest driest air impinges upon the grain 
on the side of the drying columns adjacent inner perforated walls 70. As 
the heated air continues on its path across the columns, a certain amount 
of heat is lost to the grain in the columns and the air picks up and 
retains moisture from the grain. By the time the air reaches the grain 
adjacent the outermost perforate walls 26, a significant portion of the 
heat has been lost to the grain and the same flow of air is also somewhat 
moisture laden and not able to dry the grain as effectively. Thus, the 
drying of the grain is somewhat uneven across the column, the grain 
adjacent the inner perforate walls 70 becoming drier as it flows down the 
columns than the grain flowing down the columns adjacent the outer 
perforate walls 26. By controlling the downward flow rate of the grain 
through the columns 68 to have the grain adjacent the inner perforate 
walls 70 flow downwardly at a faster rate than the grain adjacent the 
outer perforate walls 26, as described above, the faster drying grain is 
more quickly removed from the columns and the slower drying grain is 
retained in the columns for a longer period of time and is exposed to the 
drying air for a longer period of time to promote more uniform drying 
across the column. In this manner, not only is all of the grain discharged 
into the receiving hopper 86 with a more uniform moisture content, but, by 
having the grain adjacent the inner perforate wall 70 moving more rapidly 
down through the columns, the problems of grain cracking and checking 
inherent in prior art grain dryers are reduced, since the rapidly dried 
grain is exposed to the hottest driest air for a shorter period of time. 
In order to further control the division of the grain into the channels 78 
and 80, the upper end of each of the partitions 78 are provided with an 
adjustable or pivotable section or divider 79. The adjustable or pivotable 
sections 79 may be adjusted depending upon the initial moisture content 
and type of grain being dried to change the relative proportions of the 
grain entering the channels 78 and 80 in order to further improve the 
uniformity of the drying across the columns. For example, when drying corn 
with a very high initial moisture content, it may be desirable to adjust 
the pivotable sections 79 to provide for a smaller portion of the grain 
flowing into channels 80 than is flowing into channels 78. In this manner, 
more of the corn is retained in the drying columns 68 for a longer time 
period. Correspondingly, when drying corn with a very low moisture 
content, it may be desirable to adjust the pivotable sections 79 to 
provide for a larger portion of the grain flowing into channels 80 than is 
flowing into channels 78, thereby discharging more of the corn from the 
dryer in a shorter time period. Thus, by adjusting the position of the 
pivotable sections 79 in conjunction with the predetermined discharge rate 
from each of the channels 78 and 80, more uniform drying of the grain is 
accomplished. 
The uniformly dried grain discharged from each of the channels 78 and 80 of 
the outer drying columns 68 is received and collected in the receiving 
hopper 86. Mounted generally in the center of the receiving hopper 86 is a 
tube member 88 which extends vertically upwardly into the dryer housing 
12. Located within the vertical tube member 88 is a conveyor means, for 
example, a grain carrying auger 90 which is driven to rotation by means of 
a suitable drive pulley 92 extending outwardly from the bottom of the 
receiving hopper 86. The drive pulley 92 may be driven by any suitable 
means, for example, an electric motor or the power takeoff from a tractor 
or other vehicle (not shown). 
The lower end of the tube member 88 contains a plurality of openings 94 
which allow the partially dried grain from the outer columns 68 which has 
accumulated within the receiving hopper 86 to pass into the tube member 
88. The grain passing into the tube member 88 is conveyed or transported 
upwardly by the rotating grain auger 90 and is discharged from the tube 
member 88 into a substantially enclosed inner chamber 96. In the present 
embodiment, the rotation of the grain auger 90 is sufficient to evenly 
distribute the grain discharged from the tube member 88 over the inner 
chamber 96. However, in a larger model of the dryer having a larger inner 
chamber 96, cross-augers or other suitable means (not shown) may be 
employed to provide an even distribution of the grain across the length 
and width of the inner chamber 96. 
The inner chamber 96 serves as a steeping or tempering chamber for the 
grain. By allowing the grain to steep or sweat as it moves downwardly 
through the chamber 96, the moisture removal efficiency, drying uniformity 
and quality of the grain is greatly improved. Preferably, the grain 
remains in the steeping chamber for at least one hour. The sloping lower 
walls 98 of the steeping chamber 96 are at an angle of not less than 
45.degree. in order to provide for an acceptable flow of the moist grain 
downwardly through the steeping chamber. The sloping lower walls 98 of the 
steeping chamber include suitable insulation 102 to prevent the grain 
flowing through the steeping chamber adjacent the lower walls 98 from 
becoming overheated due to its proximity to the incoming heated air 
passing through the hot air ducts 62. The upper walls 74 of the steeping 
chamber 96 are also sloped at an angle of not less than 45.degree. to 
assure an acceptable flow of the incoming moist grain from the wet grain 
inlet 32 into the outer drying columns 68. 
In order to provide for most efficient use of the steeping chamber 96, it 
should be preferably kept full of grain. To this end, the upper steeping 
chamber walls 74 include means, for example, a plurality of slots 106 
extending therethrough which allow some of the incoming moist grain to 
pass directly into the steeping chamber 96, in order to make up for any 
shrinkage of the grain which may have occurred as a result of the drying 
of the grain as it passed through the outer drying columns 68. The slots 
106 may also be employed to control the moisture content of the grain in 
the steeping chamber in a manner which will hereinafter become apparent. 
In the steeping chamber, the moisture in the grain tends to equalize for 
the grain in the chamber. 
The roof 28 may also contain a level control means 104 positioned slightly 
above the slots 106. The level control means 104 functions to actuate an 
elevator bucket or infeed auger (not shown) to maintain the grain in the 
wet grain hopper 72 at a level above the slots 106 in order to insure that 
there is sufficient moist grain available for adding to the steeping 
chamber 96 to make up for any shrinkage which may have occurred. 
The grain in the steeping chamber 96 flows downwardly at a controlled rate 
and passes into a pair of inner drying columns 100 which are also 
comprised of first and second perforate walls 108 and 110, respectively. 
The perforate walls 108 cooperate with perforate walls 70 and with the 
housing end walls 14 and 16 to form a pair of substantially enclosed 
plenum chambers 112. The plenum chambers 112 receive the heated air from 
the hot air ducts 62 and distribute the heated air so that it passes 
outwardly through the outer drying columns 68 and inwardly through the 
inner drying columns 100 along the entire length of the columns. The 
plenum chambers 112 may include suitable adjustable damper means 114 
extending across the plenum chambers 112 between the end walls 14 and 16 
to further control the distribution of the heated air to the inner and 
outer drying columns 68 and 100. The damper means 114 limits the amount of 
air which passes into the lower portion of the plenum chamber 112 to force 
more air through the upper section of the columns 68 and 100. In order to 
provide for a more uniform distribution of the heated air within the lower 
portion of the plenum chambers 112, the openings of the adjustable damper 
means 114 are tapered extending across the plenum chambers with the larger 
openings being adjacent end wall 14 or in close communication with the hot 
air ducts 62 to provide a generally uniform distribution of drying air 
into the lower portion of the plenum chamber. 
FIGS. 1, 4 and 6 show a slightly different structural arrangement for 
evenly distributing the heated air within the plenum chambers 112. As 
shown in FIGS. 1 and 6, a pair of tapered perforate tubes 116 (116' in 
FIG. 6) extend across the plenum chambers 112 between the end walls 14 and 
16. The larger end of the tapered tubes 116 are connected to and 
communicate with the hot air ducts 62 to receive the flow of heated air 
therefrom. Because the tubes 116 are tapered, the amount of heated air 
that passes along the length of the tube is restricted, thereby providing 
a uniform static pressure distribution along the length of the tube to 
insure a uniform airflow out of the perforations. The uniform air flow 
from the tapered tubes 116 provides a generally uniform distribution of 
the heated air along the tubes and throughout the plenum chamber 112, 
thereby providing a more uniform flow of the heated air through the 
columns 68 and 100 along their entire length. Alternatively, the tapered 
tubes 116 may be replaced with constant diameter tubes (not shown) having 
perforations varying in size and percentage of total opening along the 
length of the tubes, (the end of the tubes connected to the hot air ducts 
62 having the larger diameter perforations and greater percentage of 
openings) to provide the desired generally uniform static pressure 
distribution along the length of the tubes into the plenum chamber. 
Referring again to FIG. 3, the inner drying columns 100 also have a 
generally vertical partition 118, which divides each column into inner and 
outer channels 120 and 122 in a manner corresponding to the partitions 76 
for the outer drying columns 68. Discharge means in the form of metering 
rolls 124 and 126 are also provided for discharging grain from the inner 
and outer channels 120 and 122, respectively. As with the metering rolls 
associated with the outer drying columns 68, the metering rolls 124 and 
126 also turn at different predetermined rates for discharging the grain 
from the channels 120 and 122 at different rates. Preferably, the metering 
rolls 126 adjacent the first perforate walls 108 discharge the material at 
a rate faster than the metering rolls 124. 
As shown on FIGS. 1 and 3, a pair of distribution ducts 127 having 
triangular cross-sections extend across the plenum chambers 112 between 
the end walls 14 and 16. One end of the distribution ducts 127 is 
connected to the cooling air ducts 56 for receiving the cooling air flow. 
The ducts 127 have one wall provided by the perforated walls 108, which 
provide for the passage of cooling air into the lower portion of the inner 
drying columns 100. Adjacent each of the ducts 127 are small access or 
clean-out doors 129 to provide for the removal of debris which may 
accumulate within the plenum chambers 112. 
The inner drying columns 100 may also be wider at the bottoms than at the 
tops in a manner similar to that of the outer drying column 68 for 
substantially the same reasons as discussed above. Grain from the channels 
120 and 122 of the inner drying columns 100 is discharged into a second or 
inner receiving hopper 130. Grain from the second receiving hopper 130 may 
be removed from the dryer by means of a discharge tube 132 and may 
thereafter be transported to a suitable storage facility (not shown). 
The dryer 10 also includes a central inner chamber 134 surrounding the 
vertical tube member 88 and formed on opposite sides by the innermost 
perforate walls 100. The central chamber 134 extends the entire length of 
the dryer between end walls 14 and 16 (shown on FIG. 1) and provides the 
conduit between the hot air fan 44 and the second air inlet opening 49 for 
the movement of ambient air into the inlet of the hot air fan 44. The 
central chamber 134 also receives and collects both the heating and 
cooling air exhausted from the inner drying columns 100 and recycles or 
recirculates this exhausted air back to the hot air fan 44. By mixing the 
incoming ambient air with the air exhausted from the inner drying columns 
100 in this manner, the air entering the heater section 40 is effectively 
pre-heated, thereby requiring the addition of considerably less thermal 
energy to raise the air to the desired or requisite drying temperature. 
Although the benefits of recirculating or recycling air in a grain dryer 
are well known, recycling heated air through an interior chamber in this 
manner is highly desirable because the heated recycled air is insulated by 
the surrounding dryer structure, thereby preventing any substantial 
radiation loss of the heat energy contained within the recycled air. In 
addition, by employing such a central recycling chamber 134, the dryer 
structure can be greatly compacted. Furthermore, due to the insulation of 
the surrounding structure, moisture condensation and dripping problems, 
which have plagued some prior art recirculating dryers of other designs, 
are avoided. 
FIGS. 7, 8 and 9 show additional details of the lower portion of the dryer, 
including the grain discharge means. As shown on FIG. 9, metering roll 82 
is retained within a plurality of aligned spaced-apart tubular members 
136. Adjacent to and above the tubular members 136 are a plurality of 
inverted V-shaped members 138, which serve as deflectors to direct the 
downward flow of grain into the spaces 140 between the tubular members 
136. The metering roll 82 further comprises a horizontal rotating grain 
auger 142 disposed within the tubular members 136. The grain auger is 
supported by, for example, a suitable bearing 144 and is driven, for 
example, by means of a suitable drive pulley of the type hereinbefore 
described. Grain flowing downwardly in each of the channels of the drying 
columns is deflected by the inverted V-shaped members 138 into the spaces 
140 between the tubular members 136 where it is received and carried by 
the rotating grain auger 142 as shown by the flow arrows. Thereafter, the 
grain is discharged from the grain auger 142 through a plurality of 
openings 146 located between the lower portions of each of the tubular 
members 136 and the grain enters the receiving hopper 86, as shown in FIG. 
3. Each of the spaces 140 between the tubular members 136 is enclosed and 
includes a removable bottom panel 148, which is retained in place as shown 
by means of a pair of supporting side flanges 150 and a pair of suitably 
sized U-shaped clamps 152. By removing the U-shaped clamps 152, the bottom 
panels 148 may be conveniently removed for cleaning out the space 140 and 
the grain auger 142. The combination of the metering rolls and the 
inverted V-shaped members 138 provide for a uniform withdrawal of grain 
across each of columns of the dryer. Additional details concerning the 
structure and operation of the grain discharge means may be obtained from 
U.S. Pat. No. 4,152,841, which is hereby incorporated by reference. The 
other metering rolls 84, 124 and 126 operate and are constructed similarly 
to metering rolls 82. 
In cross flow dryers of the type shown, it is desirable to use the same 
dryer to dry particulate materials or grains of widely varying dimensions. 
For example, it may be desirable to dry either corn or rice in the same 
dryer. In order to be able to dry such different types of grains in the 
same dryer without any considerable loss of product or drying efficiency, 
it is necessary to have the ability to conveniently vary the size of the 
openings in the dryer's perforate walls forming the drying columns. 
Referring to FIGS. 5 and 6, the present invention employs removable modules 
160 to accomplish this result. Each module, generally designated 160, is 
complete in itself and comprises four generally parallel perforate side 
panels 110', 108', 70' and 26', which are fixed to a plurality of 
generally vertical support members or cross braces 172. In FIGS. 5 and 6, 
primes are used to designate component parts of the module 160, the primes 
being dropped when the module 160 is installed in the dryer 10 as shown on 
FIG. 4 (FIG. 3 does not show the modular construction features of the 
dryer 10). The perforate panels 110', 108', 70' and 26' may all be of one 
piece construction or may be made up of a plurality of individual smaller 
panels which are attached to the cross braces 172. The perforate panels 
110', 108', 70' and 26' cooperate to form a pair of drying columns 100' 
and 68' with a plenum chamber 112' therebetween. A tapered perforate tube 
116', a generally triangularly-shaped distribution duct 127' in 
cross-section having a perforated side wall 108' as a part thereof, and a 
clean-out door 129' are also included as part of the module 160 as shown. 
When a pair of complementary modules 160 are placed in position in the 
dryer housing 12 as shown in FIG. 4, they form essentially all of the 
drying columns 68 and 100. The upper and lower portions of the modules 160 
are suitably contoured to enable the modules to be appropriately 
positioned within the dryer housing 12 as shown in FIG. 4. The tapered 
perforate tubes 116 are connected to and cooperate with the hot air ducts 
62 (shown in FIG. 1) for the distribution of hot air within the plenum 
chamber 112. Likewise, the triangular-shaped air ducts 127 are connected 
to and cooperate with the cooling air ducts 56 (shown in FIG. 1) to 
provide a flow of cooling air when the modules 160 are in place within the 
dryer housing 12. Suitable sealing means (not shown) may be provided to 
prevent air leakage from around the connection of the perforate tubes 116 
and the triangular-shaped ducts 127 with the hot air ducts 62 and cooling 
air ducts 56. A number of small flanges 178 on the corners of the modules 
160 engage suitable complementary flanges 180 on the dryer housing 12 in 
order to properly position and retain the modules 160 in place within the 
housing 12. A plurality of sealing means, for example, neoprene flaps 182, 
are employed to close any gaps or openings which may occur along the joint 
lines where the modules 160 meet the dryer housing 12 and to prevent the 
leakage of any grain through any such gaps or openings. 
From the above description of the modules 160, it is readily apparent that 
the modules 160 may be installed or removed from the dryer housing 12 
shown in FIG. 4 with relative ease. Each dryer 10 has one or more pairs of 
such modules 160. Each pair of such modules 160 has perforate side panels 
110', 108', 70' and 26' with perforations of a different size than the 
other pairs of modules. For example, one pair of modules have perforations 
ideally suited for drying rice, whereas another pair of modules will have 
perforations ideally suited for drying corn. In this manner, greater 
flexibility and drying efficiency may be achieved with a single basic 
dryer structure. 
The dryer 10 may be operated as a batch-type dryer or as a continuous 
flow-type dryer. In either type of dryer operation, an operator makes a 
determination as to what type of grain is to be dried and the initial 
moisture content of the grain. The operator then selects the appropriate 
pair of modules 160 for the grain to be dried and installs the modules in 
the dryer housing 12 as shown in FIG. 4. The operator also adjusts the 
adjustable air flow dampers 66 (shown in FIG. 1) to the proper setting to 
provide the desired air flow to provide optimum drying for the particular 
grain being dried. Likewise, the operator adjusts the pivotable sections 
79 on the partitions 78 and 118 (shown in FIG. 1) to determine the 
relative portion of the grain which will be rapidly discharged from the 
grain columns 68 and 100 as described in detail above. 
In operation as a continuous flow dryer (referring to FIG. 3), the dryer is 
then activated and the grain to be dried is fed into the wet grain inlet 
32. The grain from the wet grain inlet 32 flows downwardly into the wet 
grain hopper 72 and is introduced into the top of the outer drying columns 
68. As the grain flows downwardly through the outer drying columns 68, 
heated air from the plenum chamber 112 flows outwardly through the grain 
to heat the grain and remove moisture therefrom. The drying air passes 
outwardly through the outer perforate wall 26 to the atmosphere. As the 
grain flows downwardly through the column, it becomes increasingly drier 
due to its continued contact with the heated air. As discussed in detail 
above, the grain flowing down the columns adjacent to perforate walls 70 
is dried more rapidly than the grain flowing down the column adjacent 
outer walls 26. Accordingly, as also discussed in detail above relative to 
FIG. 3, the grain flowing through the columns 68 adjacent perforate walls 
70 is discharged from the columns 68 at a faster rate than the grain 
flowing down the column adjacent the perforate walls 26. 
All of the grain discharged from the outer columns 68 is received and 
collected in the first receiving hopper 86. The collected grain flows 
downwardly within the hopper 86 and enters the vertical tube member 88 
through the openings 94. The rotating grain auger 90 within the vertical 
tube member 88 transports the grain upwardly to the top of the tube member 
88 where it is discharged into the steeping chamber 96. 
After an initial startup period, the steeping chamber 96 is generally 
filled with partially dried grain. Due to the relatively large size of the 
steeping chamber 96 with respect to the inner drying columns 100 which 
receive the grain discharged from the steeping chamber, the grain 
introduced to the top of the steeping chamber 96 moves slowly down from 
the steeping chamber 96 at a predetermined uniform rate. It is anticipated 
that the grain remains in the steeping chamber for at least a one hour 
period. While within the steeping chamber, the grain is steeped or sweats 
in a manner well known in the art. 
After passing out of the steeping chamber 96, the grain enters the inner 
drying columns 100 and passes downwardly therethrough. At the top of the 
inner drying columns 100, the grain is again exposed to a flow of heated 
drying air, which passes inwardly from the plenum chambers 112, through 
the columns 100 and into the central chamber 134, as shown in FIG. 3. As 
the grain moves further down the inner columns 100, it is exposed to the 
cooling air which passes inwardly from the cooling air distribution ducts 
127, through the columns 100 and into the central chamber 134. The dried 
and cooled grain is then discharged into the second or inner receiving 
hopper 130. The grain may then be removed from the dryer by means of the 
discharge tube 132 for subsequent storage and/or use. 
In addition to making up for the shrinkage of the grain within the steeping 
chamber 96, the slots 106 may be employed in conjunction with the metering 
rolls 124 and 126 at the bottom of the inner drying columns 100 to further 
control the moisture content of the grain discharged from the dryer 10. 
More specifically, by putting the metering rolls 124 and 126 on a separate 
drive (not shown), the amount of wet grain which enters the steeping 
chamber 96 through the slots 106 may be accurately controlled. For 
example, by having the metering rolls 124 and 126 turning faster than the 
metering rolls 82 and 84 of the outer drying columns 68, the flow of wet 
grain through the slots 106 is increased, thereby increasing the overall 
moisture content of the grain in the steeping chamber and, 
correspondingly, increasing the overall moisture content of the grain 
discharged from the dryer. By controlling the moisture content through 
grain mixing in this manner, the dryer 10 is better able to dry various 
types of grains having various initial moisture contents to a specified 
final moisture content. 
As discussed in detail above, the heated air passing through the inner 
drying columns 100 enters the central chamber 134 and is recycled back to 
the hot air fan 44 for reuse. Likewise, the cooling air which has passed 
through the inner columns 100 and has picked up heat from the heated grain 
within the columns is recycled back to the hot air fan 44 in the same 
manner. The heated air passing through the outer columns 68 is too 
saturated with moisture which has been removed from the grain, to be of 
desired use in recycling, and, thus, is exhausted to the atmosphere 
through the outer perforate walls 26. 
Referring now to FIGS. 2 and 10-14, there is shown an alternate apparatus 
generally designated 200 for providing a flow of heated air to the dryer 
10. The air heating apparatus 200 may be employed to provide direct or 
indirect heated air to the dryer 10. By direct heated air, it is meant 
that the air provided by the apparatus 200 to the dryer includes the 
combustion gas. By indirect heated air, it is meant that the air supplied 
by the apparatus 200 to the dryer contains no combustion gas. The air 
heating apparatus 200 may be employed as a replacement for the burner 58 
(shown in FIG. 1), when it is desirable to provide indirectly heated air 
to the dryer for drying certain particulate material, for example 
sunflower seeds, which are highly flammable. 
Referring now to FIG. 10, the air heating apparatus 200 comprises a 
generally vertical base portion generally designated 202 mounted on a 
suitable support frame 203 and includes a combustion chamber 204 having a 
burner or heater 206 therein. Directly above the combustion chamber 204 is 
a plurality of generally vertical exhaust tubes 208. A typical air heating 
apparatus may contain as many as 784 such open tubes, each tube being 
approximately 10 feet long. The lower end of each of the tubes 208 
communicates directly with the combustion chamber 204 for receiving the 
combustion gas from the burner 206. 
A reversible tubular structure 210 is releasably attached to the top of the 
base portion 202 by means of a plurality of nuts and bolts 212 which 
extend through cooperating aligned flanges 214 and 216 located 
respectively on the base portion 202 and the tubular structure 210. The 
tubular structure 210 includes a generally horizontal partition means or 
partition 218 for dividing the tubular structure into two generally equal 
sized chambers 220 and 222. The first chamber 220 (adjacent the base 
portion 202 on FIG. 10) has generally solid side walls, while the second 
chamber 222 (remote from the base portion 202 on FIG. 10) has side walls 
with perforations 223 providing air inlet means for admitting fresh 
ambient air into the air heating apparatus. The tubular structure 210 may 
be removed from the base portion 202 and turned over or reversed to a 
position as shown on FIG. 13, with the second (perforated wall) chamber 
222 adjacent the base portion 202, and with the first (solid wall) chamber 
220 being remote from the base portion 202. The reversal of the tubular 
structure 210 is accomplished by simply removing the nuts and bolts 212 
from the flanges 214 and 216, reversing end-for-end the tubular structure 
210, and replacing the nuts and bolts 212 through the corresponding 
aligned flanges 214 and 216'. Whether the tubular structure 210 is in the 
direct heating position as shown on FIG. 10 or is reversed to the indirect 
heating position as shown on FIG. 13, the chamber adjacent the base 
portion 202 serves as a heat exchange chamber, while the chamber remote 
from the base portion 202 functions as a manifold chamber. 
Referring again to FIG. 10, the vertical tubes 208 extend upwardly from the 
base portion 202, through the heat exchange chamber 220 and through a 
plurality of circular openings 224 in the horizontal partition 218, as 
shown in FIG. 12, one such opening for each tube 208. The partition 
openings 224 retain the upper ends of the vertical tubes 208 in position 
as shown, the partition 218 thereby cooperating with the tubes 208 to 
direct the flow of combustion gas into the manifold chamber 222. The lower 
ends of the vertical tubes 208 are retained and supported by a pair of 
generally horizontal plates 226 and 228 located in the base portion 202 
just above the combustion chamber 204. As best seen on FIG. 11, the 
uppermost of the horizontal plates 226 contains a plurality of generally 
circular openings 230, the diameters of which correspond to the outer 
diameters of the vertical tubes 208. The circular openings 230 in the 
upper horizontal plate 226 are the same in number and are aligned with the 
openings 224 in the horizontal partition 218. The lower of the horizontal 
plates 228 is parallel to and spaced apart from the upper horizontal plate 
226 and includes an equal plurality of aligned circular openings 232 
having diameters substantially the same as the inside diameters of the 
vertical tubes 208. In this manner, the vertical tubes are suitably 
supported by the lower horizontal plate 228 and are maintained in place by 
the partition 218 and the upper horizontal plate 226. One or more of the 
tubes may be conveniently removed for cleaning or replacement by simply 
removing covering member 229 and sliding the tube straight upwardly until 
it clears the partition 218. The covering member 229 is not essential to 
the operation of the air heating apparatus 200 and is provided only to 
protect the heating apparatus from the elements. 
The partition 218 further includes port means, for example, a second 
plurality of generally circular openings 236, as shown in FIG. 12, 
extending therethrough which provides a communication between the manifold 
chamber 222 and the heat exchange chamber 220. A suitably sized air 
exhaust means or opening 234, which is generally square in this instance, 
is provided in the right side of the base portion 202 to correspond to the 
lower portion of the second air inlet opening 49 to the dryer 10, the 
upper portion of opening 49 being closed by a plate or the like (not 
shown). In this manner, the hot air fan 44 of dryer through the central 
dryer chamber 134, dryer inlet opening 49 and aligned air heating 
apparatus opening 234 provides a means for moving air through the air 
heating apparatus 200 as will hereinafter become apparent. 
As shown on FIG. 10, the air heating apparatus 200 is set up to provide a 
flow of direct heated air. As shown, combustion gases from the burner 206 
are exhausted from the combustion chamber 204 by means of the vertical 
tubes 208. The combustion gases pass upwardly through the tubes into the 
upper or manifold chamber 222 of the tubular structure. As the hot 
combustion gases pass through the tubes 208, much of the heat is absorbed 
and retained by the tubes 208. As discussed above, the dryer hot air fan 
44 draws air into the dryer through the inlet opening 49 in dryer end 
panel 16. Since the inlet opening 49 communicates directly with the 
opening 234 in the air heating apparatus 200, the heater fan 44 also draws 
ambient air into the air heating apparatus 200 through the air inlet means 
or perforations 223 in the walls of the manifold chamber 222. The hot 
combustion gases exhausted into the manifold chamber 222 combine with the 
ambient air drawn in through the air inlet means 223 and the combined 
heated air flow is drawn through the circular openings 236 in the 
partition 218 and into the heat exchange chamber 220, (as shown by the 
flow arrows), where it comes in contact with the hot tubes 208 and is 
further heated. The combined heated air then passes further down between 
and around the vertical tubes 208 and through the opening 234 and into the 
dryer where it is used to dry the grain in the manner described in detail 
above. 
When employing the air heating apparatus 200 as an indirect heater as shown 
on FIG. 13, the tubular structure 210 is reversed end-for-end as described 
above and an additional plate 238 is placed on top of the partition 218. 
The plate 238 includes a plurality of circular openings 240, which 
correspond in number and alignment with the circular openings 240 in 
partition 218. The vertical tubes 208 extend through the circular openings 
240 in the plate 238. The plate 240 contains no other openings, so it 
functions to block off openings 236 in the partition 218, and thereby 
prevents the combustion gases exhausted from the vertical tubes 208 from 
passing downwardly into the heat exchange chamber. Instead, the combustion 
gases pass upwardly and are exhausted to the atmosphere as shown between 
covering member 229, which is supported by projections 241, and flange 
216. Ambient air is drawn into the apparatus through the air inlet means 
223 (now located in the heat exchange chamber) as shown in FIG. 13, passes 
around the hot vertical tubes 208 and is heated thereby. The heated 
ambient air is then drawn into the dryer 10 through the opening 234. 
A plurality of small openings or passageways 242 are provided in the base 
portion 202 adjacent the lower ends of the vertical tubes 208. The 
openings 242 allow a small flow of ambient air to be drawn into the air 
heating apparatus 200 for cooling the lower ends of the vertical tubes 208 
and the horizontal supporting plates 226 and 228. After serving its 
cooling function, the air drawn in through the openings 224 (which is then 
heated air) passes around the hot vertical tubes 208 where it is further 
heated and combines with the rest of the heated air for use in the dryer 
10. 
From the foregoing description, it can be seen that the present invention 
comprises a modular column dryer which may be utilized for drying 
particulate material of different sizes by simply selecting the removable 
modules with side wall perforations of the size particularly suited for 
efficient drying of the selected material to be dried. It will be 
recognized by those skilled in the art that changes or modifications may 
be made to the above-described embodiments without departing from the 
broad inventive concepts of the invention. It is understood, therefore, 
that this invention is not limited to the particular embodiments 
disclosed, but it is intended to cover all modifications which are within 
the scope and spirit of the invention as defined by the appended claims.