[0001] This invention relates generally to gravity flow dryers for particulate material
and, more particularly, to a multi-stage gravity flow dryer for particulate material
wherein the discharge of the dryer is channelized.
[0002] 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.
[0003] 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 US-A-3238640
and DE-C-717052.
[0004] While the prior art cross-flow type grain dryers are generally effective in drying
grain, the entire quantity of grain is not uniformly dried. A further drawback associated
with this type of prior art drying system has been that the rapid temperature change
occurring as a result of exposing the wet grain to a flow of high temperature air
has tended to result in stress cracking of the grain. Although several different attempts
have been made to improve the cross-flow grain dryers to alleviate stress cracking,
as well as to improve the quality of the grain, such attempts have had mixed success
and have resulted in greater complexity in the grain drying structure. The present
invention provides a multi-stage cross-flow type grain dryer which provides a greater
uniformity of drying of the grain, while minimizing the problems associated with stress
cracking of the grain.
[0005] What constitutes the invention is defined in the following claim 1, the classifying
portion of which is based on the known cross-flow dryer described in DE-C-717052.
[0006] The foregoing summary, as well as the following detailed description of preferred
embodiments of the present invention, will be better understood when read in conjunction
with the accompanying drawings, in which:
Fig. 1 is a perspective view, with parts broken away, of a grain dryer in accordance
with the present invention;
Fig. 2 is a side elevational view of the dryer shown in Fig. 1 with the addition of
an alternative air heating system;
Fig. 3 is a sectional view of a slightly modified version of the dryer of Fig. 1;
Fig. 4 is an end elevational view of the dryer of Fig. 1 and showing the end wall
removed;
Fig. 5 is a slightly enlarged end elevational view of a module portion of the dryer
of Fig. 4 and showing the module removed from the housing;
Fig. 6 is an enlarged plan view of the drying column module of Fig. 5;
Fig. 7 is an enlarged side sectional view with parts broken away of the lower portion
of the dryer of Fig. 2;
Fig. 8 is a sectional view taken along the lines 8-8 of Fig. 7;
Fig. 9 is an enlarged side elevational view of one of the dryer arrangements of a
portion of Fig. 7 and showing parts broken away;
Fig. 10 is a side elevational view, with parts broken away, of the alternative air
heating system as shown added to the end of the dryer in Fig. 2;
Fig. 11 is a greatly enlarged sectional view of a portion of the heating system of
Fig. 10 taken along the lines 11-11, thereof;
Fig. 12 is a sectional view of the heating system of Fig. 10 taken along the lines
12-12, thereof;
- Fig. 13 is a side elevational view with parts broken away of the heating system
of Fig. 10 with the upper tubular structural portion reversed; and
Fig. 14 is a sectional view of the heating system of Fig. 13 taken along the lines
14-14, thereof.
[0007] 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 intermediate 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.
[0008] 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.
[0009] 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).
[0010] 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.
[0011] 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.
[0012] 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,
which define an unrestricted column for the flow of grain in the column as indicated
in Fig. 3. 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 walls
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.
[0013] In order to provide for a more uniform and less restricted grain flow through the
outer drying columns 68, the columns are gradually tapered outwardly from top to bottom
so that the width of each of the columns is greater at the bottom than at the top,
and as shown in Fig. 3, the inner walls 70 are gradually tapered outwardly from top
to bottom with respect to the outer generally vertical walls 26. 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.
[0014] At the bottom of each of the outer drying columns 68 is output or flow directing
means including a dividing wall means, in the present embodiment a generally vertical
solid partition 76, for dividing the lower portion of each of the drying columns 68
below the perforate portion of the columns into two generally parallel channels 78
and 80 below the treating zone in the columns. 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 to provide a differential grain flow in the unrestricted
column in the treating zone for more particulate material passing through the column
to be discharged through the metering roll 84. Hence, it should be apparent that more
grain will flow through the innermost channel, and as grain flows down the unrestricted
column, it is permitted to flow from wall 26 toward wall 70 where the faster drying
and discharge is taking place. The grain from both channels 78 and 80 is discharged
by the respective metering rolls 82 and 84 into a receiving hopper 86.
[0015] 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
the inner perforated walls 70. As the heated air continues on its path across the
columns in the treating zone, 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 adjacent wall 70 is more quickly removed
from the columns and the slower drying grain adjacent wall 26 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.
[0016] 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 is provided with an adjustable or pivotable
section or divider 79 below the treating zone. 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.
[0017] 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 centre 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).
[0018] 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.
[0019] 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° 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° to assure an acceptable
flow of the incoming moist grain from the wet grain inlet 32 into the outer drying
columns 68.
[0020] 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 be uniformly distributed amongst
all the grain in the chamber.
[0021] 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 ensure that there is sufficient moist grain
available for adding to the steeping chamber 96 to make up for any shrinkage which
may have occurred.
[0022] 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 portions 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 each plenum chamber.
[0023] 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 ensure a uniform airflow out of the perforations therein.
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.
[0024] Referring again to Fig. 3, the inner drying columns 100 also have a generally vertical
solid partition l18, 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.
[0025] 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 cool 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.
[0026] The inner drying columns 100 may also be wider at the bottoms than at the tops in
a manner similar to the gradually tapered arrangement 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).
[0027] 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 110. 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 inner 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.
[0028] 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 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 spaces 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 US-A-41528
41. The other metering rolls 84, 124 and 126 operate and are constructed similarly to
metering rolls 82.
[0029] 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.
[0030] Referring to Figs. 5 and 6, embodiments of the invention employ 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.
[0031] When a pair of complementary modules 160 are placed in position in the dryer housing
12 as shown in Fig. 4, they form 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.
[0032] 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.
[0033] 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 76 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.
[0034] 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.
[0035] 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.
[0036] 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.
[0037] 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
in the treating zone 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.
[0038] 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.
[0039] 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.
[0040] Referring now to Figs. 2 and 10-14, there is shown an alternative 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.
[0041] 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 3 metres 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.
[0042] 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 in 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.
[0043] 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 in 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.
[0044] 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.
[0045] 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.
[0046] 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 the 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.
[0047] 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.
[0048] From the foregoing description, it can be seen that the present invention comprises
a multi-stage gravity flow dryer for particulate material in which the particulate
material is discharged in a channelized manner in order to provide improved uniformity
of drying, as well as prevents overheating and cracking of the particulate material
being 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 scope of
the invention as defined by the following claims.
1. A gravity flow dryer (10) for particulate material comprising a generally vertical
drying column (68) having first and second opposed spaced walls (70, 20), each of
said walls having a perforate portion, the column being adapted to receive particulate
material and direct the material through the dryer, means (32) for introducing moist
particulate material into a top portion of the column (68), means (40, 62) for passing
drying air into the column (68) through the perforate portion of the first wall (70)
and out through the perforate portion (26) of the second wall (20) for drying the
material in a treating zone in the column (68), and output means (82, 84, 76, 79)
for removing dried particulate material from a bottom portion of the column (68),
characterised in that said output means (82, 84, 76, 79) is located generally below
the treating zone of the column (68), the output means (82, 84, 76, 79) including
a first discharge means (84) and a second discharge means (82) at the bottom of the
column (68), the first discharge means (84) being adjacent the first wall (70) and
the second discharge means (82) being adjacent the second wall (20), the first discharge
means (84) being adapted to discharge particulate material at a rate faster than the
second discharge means (82) to provide a differential flow of particulate material
in the column (68), said column (68) being unrestricted to the flow of particulate
material in the treating zone so as to permit particulate material to flow from the
second wall (20) toward the first wall (70) as the particulate material passes down
the column in the treating zone, so that more particulate material is discharged through
the first discharge means (84) to enable faster drying particulate material adjacent
the first wall (70) in the column (68) to pass through the column (68) faster for
a channelized discharge through the first and second discharge means (84, 82).
2. A dryer as claimed in claim 1, characterized in that said output means (82, 80,
76, 79) includes dividing wall means (76, 79) extending between the first and second
walls (70, 20) generally below the treating zone in the column (68) for dividing the
particulate material directed through the column into first and second channels (80,
78) after said particulate material has been exposed to said drying air in the treating
zone.
3. A dryer as claimed in claim 2, characterized in that said dividing wall means (76,
79) includes a generally vertical solid partition (76) extending generally parallel
to the first and second walls (70, 20) generally below the perforate portion (26)
of at least one of the first and second walls (70, 20) and generally below said treating
zone.
4. A dryer as claimed in claim 1, characterized in that a second generally vertical
drying column (100) substantially the same as the first drying column (68) is provided,
the first and second drying columns (68, 100) being spaced part to provide a plenum
chamber (112) between the first walls (70, 108) thereof, the drying air passing into
the plenum chamber (112) before entering the perforate portion of the first walls
(70, 108) into the treating zones of the drying columns (68, 100).
5. A dryer as claimed in claim 4, characterised in that second dividing wall means
(118) extend between the first and second walls (108, 110) of the second drying column
(100) generally below the treating zone of the second column (100) for dividing the
particulate material directed through the second column (100) into first and second
channels (122, 120) after said particulate material has been exposed to said drying
air in the treating zone of the second column; third discharge means (126) associated
with one of the channels (122) of the second column (100) and fourth discharge means
(124) associated with a different channel (120) of the second column (100) than the
third discharge means (126), the third discharge means (126) being adjacent the first
wall (108) of the second column (100) and being adapted to discharge particulate material
at a rate faster than the fourth discharge means (124).
6. A dryer as claimed in claim 5, characterised in that said second dividing wall
means (118) includes a generally vertical solid partition (118) extending generally
parallel to the first and second walls (108, 110) of the second column (100) generally
below the treating zone of the second column.
7. A dryer as claimed in any preceding claim, characterised in that the or each drying
column (68, 100) is substantially rectangular in cross section and at least one of
the first and second walls (70, 20) of the drying column (68) is gradually tapered
outwardly from top to bottom so that the column (68) has a greater width between the
first and second walls (70, 20) at the bottom than at the top.
8. A dryer as claimed in claim 2, characterised in that at least an upper portion
(79) of the dividing wall means (76) is adjustable to vary the relative sizes of the
channels (78, 80).
9. A dryer as claimed in claim 8, characterised in that the relative sizes of the
channels (80, 78) of the first column (68) and the relative rates of discharge of
the first and second discharge means (84, 82) are coordinated to provide for preferred
drying of particulate material.
10. A dryer as claimed in any preceding claim characterised in that the first and
second discharge means comprise separate metering rolls (80, 78).
11. A dryer as claimed in claim 5, characterised in that at least an upper portion
of the second dividing wall means (118) is adjustable to vary the relative sizes of
the channels (122, 120) of the second column (100).
12. A dryer as claimed in claim 11, characterised in that the relative sizes of the
channels (122, 120) of the second column (100) and the relative rates of discharge
of the third and fourth discharge means (126, 124) are coordinated to provide for
preferred drying of particulate material.
13. A dryer as claimed in claim 4, characterised in that a steeping chamber (96) is
provided to receive material from the first and second discharge means and to permit
the partially dried material to steep therein prior to feeding the material on to
the second drying column (100).