CA1195108A - Multi-stage particulate material dryer having channelized discharge - Google Patents

Abstract

GRAVITY FLOW DRYER FOR PARTICULATE
MATERIAL HAVING CHANNELIZED DISCHARGE
ABSTRACT
A gravity-flow grain dryer for particulate material comprises a generally vertical drying column having first and second opposed spaced perforate walls, the column being adapted to receive particu-late material and direct the material through the dryer. An input is provided for introducing moist particulate material into a top portion of the column and a discharge mechanism is provided for removing dried particulate material from a bottom portion of the column. A
blower and heater are also provided for passing drying air into the column through the first perforate wall and out through the second perforate wall, the air drying the material within the column. A
dividing wall extends between the perforate walls for dividing at least a portion of the column into at least two channels, of the channels containing a discharging mechanism for removing particulate material from the channel. A first discharge mechanism is associated with a first of the channels and a second discharge mechanism is associated with a second of the channels, the first channel being adjacent the first perforate wall and the first discharge mechanism is adapted to discharge particulate material at a rate faster than the second discharge mechanism.

Description

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This application is a divisional of Application Serial No. 405,450 filed June 18, 1982.
BACKGROUND OF THE INVENTION
-Field of the Invention This invention relates generally ~o gravity flow dryers for particula~e material and, ~ore particularly, to a multi~stage gravity flow dryer for particulate material whe~rein the discharge of the dryer is channeli~ed.
Summary of the Prior Art It is often necessary or desirable to dry freshly harves~ed grain before it is processed or stored.
Stor~ge of grain with excess rnoisture may cause quality de~erioration and 6poilage during subsequent storage.
The need to dry grain prior to storage has long been recognized in the art and many grain drying syste~s 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 flo~s downwardly by gravity ~hrough a col~mn 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 mois~ure. Typical of such cross-flow grain dryers are the grain drvers shown and described in U.S. Patent No. 2,732,630 to Markowich and U.S. Patent No.
3,238,640 to Fry.
While the prior art cross-flow type grain dryers are generally effecti~e in drying grain, the entire qUaRtity of grain is not uniforrnly dried. A further drawback associated with ~his type of prior art drying system has been tha~ the rapid temperature change occurring as a resul~ of exposing the wet grain to a flow of high temperature air has tended ~o 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 attemp~s have ~ad mixed success and have resulted in greater complexity in the grain drying structure. The present invention provides a cross-flow type grain dryer which provides a greater uniforrrlity of drying of the grain, while minimizing the problerns associated with s~ress cracking of the grain.
Summary of the Invention Briefly sta~ed, the present invention provides a gravity flow grai.n dryer for particulate material comprising agenerally vertical drying column having first and second opposed spaced perforate walls~
The drying column is adapted to receive particulate material and direct the material through the dryerO Means are provided for introducing moist particulate material into a top portlon of the colurnn and means are provi.ded for removing dried parti-culate material from a bottom portion of the column. Meansare also provided for passing drying air into the column for dryi.ng the material, the air entering the column throuyh the first perforate wall and leaving the column through the second perforate wall~ Dividing wall means extends between the spaced perforate walls for dividing at l.east a portion vf the ~ 3 column into at least to separate channels. A first dis-charge means is associated with a first of the ch~nnels and a second discharge means being associat~d with a second of the channels at predetermined rates with a first discharge means, the first channel being adjacent the first per~orate wall and the first discharge means being adapted to discharge particulate material at a rate faster than the second discharqe means.

1~ Br~ef De~crip~ion of the_Drawlngs The foregoing summary, as well as the following detailed description of perferred embodiments of the present inven~ion, will be better understood when read in conjunction with the accompanying drawings, in which:
Figo 1 is a perspective view, with parts broken away, of a grain dryer in accordance with the present inven t i on;
Fig. 2 is a side elevational view of the dryer shown in FLg. 1 with ~he addition of an al~ernate air heating system;
~ ig. 3 is a sectional view of a slightly modified ~ersion of the dryer of Fig. l;
Fig. 4 is an end elevational view of ~he dryer of Fig. 1 and showing the end wall removed;

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Figo 5 is a ~lightly enlarged end elevatiorlal view o a module portion of the dryer of Fig. 4 and showing ~he module removed from ~he housing;
Fig. 6 is an enlarged plan vi.ew 9f the drying column module of Fig~ 5;
Fig. 7 is an enlarged side sectional vlew with part.s broken away of the lower portion of the dryer of Fig. 2~
Flg~ 8 is a sectional view taken along the lines 8-8 O:L~ FLgo 7;
Fig. 9 is an enlarged side elevational view of one o~ ~he dryer arrangements of a portion o Fig. 7 and showlng parts broken away;
Fig. 10 is a side elevational view, with p~rts broken away, of the alternate air heating syste~-as shown added to the end of the dryer in Fig~ 2;
Flgo 11 is a greatly enlarged s~ctional view of a portion of ~he heating sy~tem of Fig. 10 ~aken along the lines 11-11;
Fig~ 12 is a sec~ional vie~d of the heating system of Fig. 10 taken along the lines 12-12;
Fig~ 13 is a side elevational view with parts bro~en away of the heating system of Fig. 10 with the upper tubular ~tructural por t ion rever s ed; and Fig. 14 is a sectional view of the hea~in~ system of Fig. 13 taken along the lines 14-140 Description of the Preferred Embodiment Referring to the drawings, and particularly to Figo 1~ there is shown a column type gravi~y flow dryer for particu`late material, for example, corn or other type grain. The dryer, generally designated 10~
includes a generally square-shaped housi~lg 12 co~pri.sed of ~ pair of ~olid end walls 14 and 1~ and a pair of ~5~

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 260 The housing 12 further includes a suitable roof 28 and 5 ls supported at the bot~om by suitable support means or legs 30O At the top o the housing 12 is a means for introducing moist particulate material or grain into the top portion o~ the housing, in this embodiment, a suitably sized wet grain inlet 32.
On the outside of the housing 12 adjaeent end wall 14, is an assembly or means 34 for providing drying air and cooling air to the housing 1~. 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 ~hrough a generally circular cooling air inlet opening 48 in the blower section 38 and is journaled for ro~ation 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 ~4 may be driven by any suitable means, for example, an electric motor or a power takeoff mechanism on ~ 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 inle~ opening 48, is the hot air fan, the fans being separated by a vertical ~ 5~'~J~

parti~ion 43 to form individual chambers surrounding each fan. Cooling air is drawn in through tne inlet opening 48 by the cool air fan 42 and is directed into a pair of cool air duc~s 56 which in turn direct the cooling air into ~he 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 ehe flow o~ air upwardly into the 'neater 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 duct~ 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 pl~rality of adjustable dampers S6. 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 ~ypes of particulate material. For example, it may be desirable to provide a large hot air flow into the housing 12 for drying high mois~ure content corn and a much smaller hot air flow into the housing 12 for drying lower moisture content riceO Thus, the adjustable dampers 66 may be set in a substantially fully open posi~ion to apply a large hot air flow to dry corn or in a substan~ially closed position ~o apply a small ho~ air fl.ow when drying rice.
* trademark ~s~

Referring now to Fig. 3, there is shown the interlor configuration of the dryer of Yig. 1 with a slight variation which will hereinaf~er be described.
The dryer 10 comprise~ a palr of generally vertical S outer drying columns 68, each cclumn being defined by first and second substantially parallel opposed spaced perfcrate walls 70 and 260 A wet grain hopper 72 i8 provided at the top portion of ~he dryer or receLving and temporarily storing ~he moist grain introduced into the ~op of ~he housing 12 through the wet grain inlet 32. The wet grain hopper 72 is defined by ~he roof panels 28, the side wall upper solid portions 22 and a pair cf sloping interior hopper panels 740 The wet grain hopper 72 also functions ~o distribute the moist gr~in in~o the ~op portions of each of the outer drying columns 68.
In order to provide for a more uniform and le~s res~ricted grain flow through the outer drylng columns 68~ the columns are ~apered outwardly from ~op to bottom 60 that the width of each of the column~ is greater a~ 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 or a more volume controlled airflow ~hrough the columns over their entire length.
At the bottom of each of the o~ter drying columns 68 is a dividing wall means, in ~he present embodiment a generally vertical par~ition 76, for di~iding the lower portion of each of the drying columns 68 lnto two generally para~lel channels 78 and 80. Each of ~he ~ ~ 5 ~3~

channels 78 and 80 preferably contains ~eparate discharge ~ean~, in ~he present embodlment metering rolls 82 and 84, respectively, for discharging particulate ma~erial fro~ the channels 78 and ~0 at S predetermined rates. Both of ~he metering rolls 82 and ~4 are driven by a system of drive belts and pulleys generally designated 85. As shown, the drive pulley for the me~ering roll 84 is of a smaller dlameter than the drive pulley for metering roll 82. Accordingly, metering roll 84 rotates faster than metering roll 82 to ~hereby discharge grain from the innermost channel 80 at a faster rate ~han ~he grain is discharged from the Qu~ermos~ 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~
~ s shown in Fig~ 3~ heated air from the hot air ducts 62 passes ou~wardly 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 ~he inner perforated walls 70, the ho~test driest air impinges upon ~he grain on the side o the drying columns adjacent inner perforated walls 70. As the heated air continues on its path across the columns, a certain amoun~ 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 outermos~ perforate walls 26, a significant portion of the heat has been lost to the grain and the same flow of air is also somewha~
mois~ure laden and not able to dry the grain as effectively. Thus, the drying of the gra~n is somewhat uneven across the column, ~he grain adjacent ~he inner perfora~e walls 70 becoming drier as .it flows down the columns than the grain flowing do~m the columns adjacent the outer perfora~e walls 26. By controlling the downward flow ra~e of the grain through the columns 68 to have the grain adjacent the inner perforate walls 70 1OW downwardly at a faster rate than ~he grain adjacent the outer perora~e walls 26, as described above, the faster drying grain is more guickly removed from the columns and the slower drying grain is re~ained 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 columnO
In this manner, not only is all of the grain discharged into the receiving hopper 86 with a more uniform moisture conten~, but, by having the gr~in adjacent the inner perforate ~all 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 ~urther control the divi~ion o the grain into ~he channels 78 and 80, the upper end of each of the partitions 78 are provided with an adjustable or pivotable sec~ion or divider 79. The adjustable or pivotable sections 79 may be adju~ted depending upon the initial moisture content and type of grain being dried to change the relative propor~ions 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 inieiaL moisture content, it may be desirabLe to adjust the pivotable sections 79 to provide for a smaller portion of the grain flowing in~o channels 80 than is flowing into channels 78. In this manner, more - lo -of the corn i8 retained in the drying columns 68 for a longer ~ime periodO Correspondingly, when drying con~
with a very low moisture content, i~ may be desirable to adjus t the plvotable sections 79 to prov~de for a 5 larger portion of the grain 10wing into channels 80 than is flowing into channels 78, ~hereby discharging more of ~he corn from ~he dryPr in a shorter time period. Thus, by adjusting the position of the pivotable sections 79 in conjunction with the predetermined discharge ra~e 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 cent~r of the receiving hopper 86 is a tube member 88 which extends vertically upwardly into the dryer housing 12. Loca~ed within the vertical tube member 88 is a conveyor means, for example, a grain carrying augcr 90 which is driven to rotation by means of a sui~able drive pulley 92 extending outwardly rom 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 takeof from a tractor or other vehicle (not shown).
The lower ~nd of the ~ube member $8 contains a pLurality of openings 94 which allow the partially dried grain from the outer columns 68 which has accumulated within the reeeiving hopper 86 to pass ;nto the tube member 88. The grain passing in~o the ~ube member 88 is csnveyed or transported upwardly by ~he rotating grain auger 90 and is discharged from the ~ube ~5~

member 88 into a substantially enclosed inner chamber 95. In the presen~ embodimen~, the rotation of the ~rain auger 9Q is sufficient ~o evenly di.stribute the grain discharged from the tube member B8 over the lnner chamber 96. However, in a larger model of the dryer having a larger inner chamber 96, cross-augers or other sui~able means (not shown) may be employed to provide an even distribution of ~he grain across the length and width of ~he inner chamber 96.
The inner chamber 96 serves as a steeping or ~empering chamber for the grain. By allowin~ the grain to steep or sweat as i~ 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 th~n 45 in order to provide for an acceptable flow of the moist grain downwardly through 20 the steeping chamber. The sloping lower walls 98 of the steeping chamber include suitable i~sulation 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 ~han 45 to assure an acceptable flow of the incoming moist grain from the we~ grain inlet 32 into the vuter drying columns 68c In order to provide or most efficient use of the s~eeping chamber 96, i~ should be preferably kept full of grain. To this end, the upper s~eepin~ chamber walls 74 include means, for example, a pl~rality of slots 106 extending therethrough whicll allow some of the inco~ing moist grain to pass directly into ~he steeping chamber 96, in order to make up or any ~hrinkage 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 810ts 106 may al80 be employed to control ~he moisture content of the grain in the steeping chamber in a manner which will hereinafter becsme 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 sligh~ly above the slots 106. The level control means 104 functions to actuate an elevator bucke~ 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 ~he steeping chamber 96 to make up or any shrinkage which may have occurred.
The grain in the steeping cha~ber 96 flows downwardly at a con~rolled rate and passes into a pair of inner drying columns 100 which are also comprised of first and second perforate walls 108 and 110, respec~ively. The perforate walls 108 cooperate wi~.h perforate walls 70 and with the housing end walls 14 and 16 to orm a pair of substantially enclosed plenum chambers 112. The plenum chambers 112 receive the heated air from the ho~ air ducts 62 and distribu~e the hea~ed air so that i~ passes outwardly through the outer drying columns 68 and inwardly ~hrough 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 ou~er drylng columns 68 and 100. The damper means 114 limits the amount of air which pas~es into the lower portion of ~he plenum cha~ber 112 to force more air through the upper section of ~he columns 68 and 100. In order to provide for a more uniform distribution of the heated air within ~he lower portion 10 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 general'y uniform distribution o 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 hea~ed air within the plenum chambers 1120 As shown in Figs. 1 and 6, a pair of tapered perforate tubes 116 (116' in Fig. S) extend across the plenum chambers 112 between ~he end walls 14 and 16. The larger end of the tapered tubes 116 are connected to and communicate with the hot air ducts S2 to receive the flow of heated air therefrom. Beca~se the tubes 116 are tapered, the a~ount of heated air that passes along the length of the tube is restricted, thereby providing a uniform sta~ic pressure distribution along the length of the tube to insure a uniform airflow out of the perforationsc The uniform air flow from the tapered tubes 116 provides a generally uniform distribu~ion of the heated air along the ~ubes and throughou~ the plenum chamber 112, thereby providing a more uniform ~3 10w of the heated air through the columns 68 and 100 along their entire length. Alternatively, the tapered tubes 1~6 may be replaced with constant diameter tubes (not shown) having perforations varying in size and S percentage of total opening along ~he length of the ~ubes, ~the end of the tubes connected to the hot air duc~s 62 haYing the larger diameter perfora~ions and greater percentage of openings) to provide the desired gen~rally uniform sta~ic pressure distribution along the length o the tubes into the plenum chamber.
Referring again to Fig. 3, the inner drying columns 100 also have a generally vertical par~ition 118, which divides each column into inner and outer channels 120 and 122 ln a manner corresponding to ~he partitions 76 for the outer drying columns 68.
Discharge means in the form of metering rolls 124 and 125 are also provided for discharging grain from the inner and outer channels 120 and 1?2, respectivelyO As with the metering rolls associated with the outer drying columns 68, the metering rolls 124 and 126 also turn at different prede~ermined rates for disrharging the grain from the channels 120 and 122 at different rates. Preferably, the metering rolls 126 adjacent the irst 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 dis~ribution ducts 127 having triangular cross-sections extend across the plenum chambers 112 between the end walls 14 and 160 One end of the distribution ducts 127 is connected to the cooling air ducts 56 for receiving the cooling air flo~O The ducts 127 have one wall pro~ided by the perforated walls 108, which provide for the passage of cooling air in~o the lo~er portion o the inner drying columns 100. Adjacent each of the duct~
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 di~cussed above. Grain from ~he channels 120 and 122 of the inner drying columns 100 is discharged into a second or inner recei~ing hopper 130.
~rain 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 sui~able storage facility ~not shown).
The dryer 10 al50 includes a cen~ral inner chamber 134 surrounding the vertical tube member 88 and formed on opposite sides by the innermos~`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 inle~ of the hot air ~an 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 recircula~es ~his 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 ~hiS manner, the air entering ~he heater section 40 is effectively pre~heated, thereby requiring the addition of considerably less thermal energy ~o raise the air to the desired or requisite drying temperature. Although ~he benefits of recircula~ing 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 ls insulated by the surrounding dryer struc~ure, thereby prevenSing any substantial radiation loss of ~he heat energy contained within the recycled air~ In addi~ion, by e~ploying such a central recycling chamber 134, the dryer structure can be greatly compacted. ~urthermore, due to ~he insulation of the surrounding structure, moisture condensation and drippi~g 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 aligl-ed 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 flo~ of grain into the spaces 140 between the ~ubular 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 sui~able 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 deflec~ed by ~he inver~ed V-shaped members 138 into the spaces 140 be~ween the tubular members 136 where i~ is received and carried by the rotating grain auger 142 as shown by the flow arrows.
Thereaf~er, the grain is discharged from ~he grain auger 142 through a plurality of openings 146 loca~ed between ~he lower portions of each of ~he tubular members 136 and the grain enters the receiving hopper 86, a~ shown in Flg. 3O ~ach Qf the spaces 140 between ~he ~ubular members 136 is enclosed and includes a removable bottom panel 148, which is retained in place as shown by means of a pair of suppor~ing side flange~
150 and a palr o s~itably sized U-shaped cLamps 152.
By removing the U shaped clamps 152, the bo~torn panels 148 way be convenien~ly removed for cleaning out the s9pace 140 and the grain auger 142. The combination of the me~ering rolLs and the inverted V~shaped members 138 provide for a uniform withdrawal of grain across each of columns of the dr.yer. Additional details concerning ~he structure and operation of the grain discharge means may be obtained from U . S . Paterlt 4,152,841, The other metering rolls 84, 124 and 126 operate and a~e constructed similarly to metering rolls 82.
In cross flow dryers of the ~ype shown, it is desirable to use the same dryer to dry particula~e materials or grains of widely varying dimensions. For example, it may be desirable to dry either corn or rice in the sarne dryer. In order to be able to dry such different types of grains in the same dryer without any cor9siderable 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 formirlg the drying columns~
Referring to ~igs. S and 6, ~he present invention employs removable modules 160 to accornplish this result~ Each modllle, ~enerally designated 160, is complete in. itself and comprises four generally parallel perforate side panels 110', 108'9 70' and 26', which are fi~ed ~o a pll~rali~y of generally ver~ical ~s~

support members or cross braces 172. In Fi~s. 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 construetion or may be made up of a plurality of individual smaller panels which are a~tached ~o the cross braces 172. The perforate panels 110', 108', 70' and 26' coopera~e to form a pair of drying columns 100' and 68' with a plenu~ chamber 112' there.between. A tapered perforate ~ube 1161, a generally triangularly-shaped distribu~ion duct 127' in cross-sec~ion having a perforated side wall 108' a~ a part thereo, and a clean-out door 129' are al50 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 for~ the drying columns 68 and lO0. The upper and lower portions o the modules 160 are suitably contollred 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 Ll20 Likewise, the triangular-shaped air ducts l27 are connected to and cooperate with the cooling air ducts 56 (shown in Fig.
1) to provide a flow of cooling air when ~he modules 160 are in place within the dryer housing 12. Suitable sealing means (not shown~ may be provided to preven~
air leakage from around the connec~ion of ~he perfora~e tu~es 116 and the triangular-shaped ducts 127 with the -~ 9-hot air ducts 62 and cooling air ducts 56. A number of small flanges 1-~8 on the corners of the modules 160 engage sui~able 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 ~he modules 160 meet ~he dryer housing 12 and to prevent the leakage of any grain through any such gaps or openirlgs.
From the above description of Lhe 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 ~han the other pairs of modulesO For exa~ple, one pair of modules have perforations ideally suited for drying rice, whereas ano~her 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 ~hen selects the appropriate pair of modules 160 for the grain to be dried and ins~alls the modules in the dryer housing l? as shown in Fig. 4. The operator also adjusts the adjus~able air flow dampers 66 ~shown in Figo 1) ~0 the proper setting to provide the desired -~o-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 11~
(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 de~all above.
In operation as a continuous flow dryer (referring to Fig. 3), the dryer is then activa~ed 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 ~he we~ 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 25 to the at~osphere. As the grain flows downwardly through the colu~n, it becomes incressingly drier due to its continued contact with ~he heated air. As discussed in detail above, the graîn flowing down the columns adjacent ~o perforate walls 70 is dried more rapidly than the grain flowing down the column adiacent 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 ra~e than the grain flowing down ~he 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 collec~ed grain flows do~wardly within the hopp~r 86 and enters the vertical tube member 88 through the openings 94. The ro~ating grain auger 90 within the vertical tube member 88 transports the grain upwardly to the top of the tube member ~8 where it i8 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 ~he 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 ou~ of the steeping chamber 96, the grain enters the inner drying columns 100 and passes downwardly there~hrough. At the top of the inner drying columns 100, the grain is again exposed to a flow of hea~ed 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 in~o the second or inner receiving hopper 130. The grain may then be removed from the dryer by means of ~he discharge ~ube 132 for subsequent storage and/or use.
In addition to making up for the shrinkage of the grain wi~hin the steeping chamber 96, the slots 106 may be employed in conjunction with the me~ering rolls 124 ~5~

and 126 at the bottom of the inner drying columns 100 to ~ur9;her control the moisture content of the grain discharged from the dryer 10. More specifically, hy puttirlg the me~ering rolls 124 and 126 on a separate drive (not ~hown), the amount of wet grain which enters the steeping chamber 96 through the slots 106 may be accurately con~rolled. For example, by having the metering rolls 124 and 126 turning faster ~han the metering rolls 82 and 84 of the outer drying columns 68, ~he flow of wet grain through the slo~s 106 is increased, thereby increasing the overall moist~re 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 ~o a specified final moisture content.
As discussed in detail above, the heated air passing ~hrough the inner drying columns 100 enters the central chamber 134 and is recycled bac~ 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 manneru The heated air passing through the outer columns 68 is too saturated with mois~ure which has been removed from the grain, to be of desired use in recycling9 and, thus, is exhausted to the atmosphere through ~he outer perforate walls 26.
Referring no~ 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 ~ ~ 5~ ~ ~

air heating apparatus 200 may be employed to provide direct or indirec~ hea~ed air to the dryer 10. By direct heated air, it is meant that the air provided by the apparatus 200 tv the dryer includes the combustion gas. By indircct heated air, Lt is meant tha~ the air supplied by the apparatus 200 to the dryer contains ns combus~ion 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 1Q heated air to ~he 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 ~he combustion chamber 204 is a plurality of generally vertical exhaust tubes 208. A typical air heating appara~us may contain as many as 784 such open ~ubes, each tube being approximately 10 feet long. The lower end of each of the tubes 208 communieates 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 ~ubular structure 210. The tubular structure 210 includes a generally horizontal partition means or partition 218 for dividing the tubular struc~ure into t~o 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 Z02 on Fig. 10~ has side walls with perforations 223 providing air inlet means or admitting fresh ambient air into the air heating apparatus. The ~ubular structure 210 ~ay 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 2020 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 ~he 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 ehamber 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 partitivn 218, as shown in Fig. 12, one such opening for each tube 208. T~e 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 S openings 230, the diameters of which correspond to ~he outer diameters oE ~he vertical tubes 208. The circular openings 230 in ~he upper horizontal plate 226 are the same in number and are aligned with the openings 224 in the horizontal parti~ion 218. The lower of the horizontal plates 228 is parallel to and spaced apart from the upper horizontal plate 2~6 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 parti~ion 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 par~ition 218 further includes port means, for example, a second plurality of generally circular openings 236, as shown in Fig. 12, extending therethrough which prov~des a communica~ion between the manifold chamber 222 and the heat exchange chamher 220.
A suitably sized air exhaust means or opening 234, which is generally square in this instance, is provided in ~he righ~ 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 openlng 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 23bl provides a means for moving air ~hrough the air heating apparatus 200 as will hereinafter become apparent~
As shown on Fig. 10, the air heating apparatus 200 is set up ~o 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, ~he 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 ~ases 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 dra~n 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 con~act with the hot ~ubes 208 and is further heated. The combined heated air then passes fur~her down between and around the 5~

vertical tubes 208 and through the opening 234 and into the dr5~er where it is used to dry the grain in the manner described in detail above.
When employing the air hea~ing apparatus 200 as an 5 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 parLition 218. The plate 238 includes a plurality of circular openings 240, which correspond in number 10 and alignment with the circular openings 240 in partition 218. The vertical ~ubes 208 extend through ~he 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 15 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 !:he atmosphere as shown between covering member 229, which is supported 20 by projections 241, and flange 2160 Ambient air is drawn into the apparatus through the air inlet means 223 (now loca~ed 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 25 drawn into the dryer 10 through the opening 234.
A plurality of small openings or passageways 242 are provided in the base portion ~02 adjacent the lower ends of the vertical tubes 208. The openings 242 allow a small flow of ambient alr to be drawn into the air 30 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 func~ivn, the air drawn in through the openings 224 (which is ~hen v~

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 gravity flow dryer for particulate material in which the particulate ~aterial is discharged in a channelized manner in order to provide improved uniformity of drying, as ~lell as 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 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 eover all modifications which are within the scope and spirit of the invention as defined by the appended claims.

Claims (8)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A gravity flow dryer for particulate material comprising:
a generally vertical drying column having first and second opposed spaced walls, a corresponding portion of each of said walls including perforations therein, the column being adapted to receive particulate material at the top and direct the material through the dryer to the bottom and being unrestricted in the column to the flow of particulate material so as to permit particulate material to flow from the second wall toward the first wall as the particulate material passes down the column;
means for introducing moist particulate material into a top portion of the column;
means for passing drying air into the column through the perforate portion of the first wall and out of the column through the perforate portion of the second wall for drying the material in a treating zone in the column;
output means located below the perforate portion of the column for removing dried particulate material from the bottom of the column below the treating zone in and including a first discharge means at the bottom of the column and a second discharge means at the bottom of the column, the first discharge means being adjacent the first wall and the first discharge means being adapted to discharge particulate material at a rate faster than the second discharge means 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 first discharge means, whereby the faster dried grain adjacent the first wall in the column passes through the column faster for a channelized discharge through the discharge means.

2. The dryer as recited in Claim 1 wherein drying column is substantially rectangular in cross section and at least one of the opposed spaced walls of the drying column is gradually tapered outwardly from top to bottom so that the column has a greater width between the opposed spaced walls at the bottom than at the top.

3. The dryer as recited in Claim 1 wherein the drying column having the first and second opposed walls provides a first drying column, the dryer further including:

a second generally vertical drying column substantially the same as the first drying column, the first and second drying columns being spaced apart to provide a plenum chamber between the perforate portions of the first walls of each column, the drying air passing into the plenum chamber before entering the perforate portions of the first walls of the drying columns;
a second generally vertical solid partition at the bottom portion of the second column extending generally parallel to but below the perforate portion of said walls of the second column, the second partition for dividing the particulate material directed therough the second column into first and second channels after said particulate material has been exposed to said drying air; and third discharge means associated with the first channel of the second column and fourth discharge means associated with the second channel of the second column, the third discharge means being adjacent the first wall of the second column and being adapted to discharge particulate material at a rate faster than the fourth discharge means.

4. The dryer as recited in Claim 2 wherein the wall gradually tapered outwardly is the first wall.

5. A gravity flow dryer for particulate material comprising:
a generally vertical drying column having first and second opposed spaced walls, a corresponding portion of each of said walls including perforations therein, the column being adapted to receive particulate material and direct the material through the dryer;
means for introducing moist particulate material into a top portion of the column;
means for passing drying air into the column through the perforate portion of the first wall and out of the column through the perforate portion of the second wall for drying the material in the column;
means located below the perforate portion of the column for removing dried particulate material from the bottom of the column and including a generally vertical solid partition extending generally parallel to but below the perforate portion of the column walls for dividing the particulate material directed through the column into first and second channels after said particulate material has been exposed to said drying air, at least a portion of the partition being adjustable to vary the flow of material that passes through the channels;

a first discharge means associated with the first channel and a second discharge means associated with the second channel, the first channel being adjacent the first wall and the first discharge means being adapted to discharge particulate material at a rate faster than the second discharge means.

6. The dryer as recited in Claim 5 wherein the relative channel sizes and the relative rates of discharge of the first and second discharge means are coordinated to provide for preferred drying of particulate material.

7. A gravity flow dryer for particulate material comprising:
a generally vertical drying column having first and second opposed spaced walls, a corresponding portion of each of said walls including perforations therein, the column being adapted to receive particulate material and direct the material through the dryer, the dryer column having the first and second opposed walls providing a first drying column;
means for introducing moist particulate material into a top portion of the column;
means for passing drying air into the column through the perforate portion of the first wall and out of the column through the perforate portion of the second wall for drying the material in the column;
means located below the perforate portion of the column for removing dried particulate material from the bottom of the column and including a generally vertical solid partition extending generally parallel to but below the perforate portion of the column walls for dividing the particulate material directed through the column into first and second channels after said particulate material has been exposed to said drying air, a first discharge means associated with the first channel and a second discharge means associated with the second channel, the first channel being adjacent the first wall and the first discharge means being adapted to discharge particulate material at a rate faster than the second discharge means;
a second generally vertical drying column substantially the same as the first drying column, the first and second drying columns being spaced apart to provide a plenum chamber between the perforate portions of the first walls of each column, the drying air passing into the plenum chamber before entering the perforate portions of the first walls of the drying columns;

a second generally vertical solid partition at the bottom portion of the second column extending generally parallel to but below the perforate portion of said walls of the second column, the second partition for dividing the particulate material directed through the second column into first and second channels after said particulate material has been exposed to said drying air, at least a portion of the second partition being adjustable to vary the flow of material that passes through the channels of the second column; and third discharge means associated with the first channel of the second column and fourth discharge means associated with the second channel of the second column, the third discharge means being adjacent the first wall of the second column and being adapted to discharge particulate material at a rate faster than the fourth discharge means.

8. The dryer as recited in Claim 7 wherein the adjustment of the second partition and the relative rates of discharge of the third and fourth discharge means are coordinated to provide for preferred drying of particulate material.