US3913242A

US3913242A - Preheater for grain dryer

Info

Publication number: US3913242A
Application number: US504997A
Authority: US
Inventors: Kenneth C Fackler; John O Bradford
Original assignee: M&W Gear Co
Current assignee: M&W Gear Co
Priority date: 1974-09-11
Filing date: 1974-09-11
Publication date: 1975-10-21
Anticipated expiration: 1992-10-21

Abstract

A concurrent-countercurrent flow, grain dryer of the type having an enclosed bin with a wet grain inlet at the top and a dry grain outlet at the bottom includes means for introducing hot air as a drying medium for the grain in a flow concurrent with the grain. Means are also provided at the bottom of the bin to introduce cool air which flows countercurrent to the grain flow. First exhaust ducts are provided intermediate and transverse the hot and cool air ducts. A second preheat exhaust is formed in combination with each hot air inlet duct so that a certain amount of the hot inlet air will flow upwardly in a countercurrent direction to the downward flow of the grain to preheat the wet grain immediately after it enters the enclosed bin of the dryer.

Description

United States Patent Fackler et a1.

Oct. 21, 1975 PREHEATER FOR GRAIN DRYER [73] Assignee: M & W Gear Company, Gibson City, 111,

[22] Filed: Sept. 11, 1974 [2]] Appl. No.: 504,997

[52] US. Cl. i. 34/170; 34/210; 98/55; 98/56 [51] Int. Cl. F26B 17/12 [58] Field of Search 34/6 1,623. I68, 170, 174. 34/210, 2l2, 33. 224, 225; 98/32, 33 A, 5256 [56] References Cited UNITED STATES PATENTS 3,373,503 3/1968 Kline et a1. 34/170 3,710,449 1/1973 Rathbun 34/170 3,727,323 4/1973 Meiners et a1. i i a 34/1 70 3,789,747 2/1974 Wasserman etal 98/32 Primary Examiner-John J. Camby Assistant Examiner-Henry C. Yuen Attorney, Agent, or FirmMolinare, Allegretti, Newitt & Witcoff 57 ABSTRACT A concurrent-countercurrent flow, grain dryer of the type having an enclosed bin with a wet grain inlet at the top and a dry grain outlet at the bottom includes means for introducing hot air as a drying medium for the grain in a flow concurrent with the grain. Means are also provided at the bottom of the bin to introduce cool air which flows countercurrent to the grain flow First exhaust ducts are provided intermediate and transverse the hot and cool air ducts. A second preheat exhaust is formed in combination with each hot air inlet duct so that a certain amount of the hot inlet air will flow upwardly in a countercurrent direction to the downward flow of the grain to preheat the wet grain immediately after it enters the enclosed bin of the dryer.

5 Claims, 2 Drawing Figures U.S. Patent Oct. 21, 1975 PREHEATER FOR GRAIN DRYER BACKGROUND OF THE INVENTION This invention relates to an improvement in a grain dryer and, more particularly, to the improvement of the preheater for a concurrent-countercurrent flow type grain dryer of the type disclosed in US. Pat. No. 3,727,323 issued Apr. 17, 1973 to Elmo R. Meiners and John 0. Bradford.

Grain, particularly corn is now often dried before storing to prevent wet pockets, mildew and consequent spoilage of the grain Fast, efficient drying may be effected by the introduction of a generally heated, low content drying medium (usually air) to the wet grain. The drying medium is moved relative to the grain and accumulates moisture from the grain. The moisture saturated drying medium is then removed from contact with the grain to provide grain having a relatively lower moisture content.

However, because the drying medium is usually heated to effect moisture transfer, sudden transition in the temperature of the grain may result or cause poor grain conditioning of the grain kernels. For example, the sudden transition of the grain from a relatively cool or ambient temperature to the high temperature of the drying medium may cause the grain to become scorched. That is, subjecting the cool grain to a hot (approximately 300F) blast of air will quickly evaporate moisture from the grain at and near the surface of the grain kernels. Simultaneously, very little moisture will transfer from the interior of the grain kernels to a position at or near the surface of the kernels. Conse quently, the kernels lose the protection against scorching initially provided by evaporative cooling of the moisture at or near the surface of the kernel.

Thus, prior art grain drying systems may cause scorching of the grain particularly when the ambient temperature of the grain is very low. Typically, ambient grain temperatures are very low during the late fall in the Midwest when outdoor temperatures are well below freezing.

To avoid such problems, the grain could be heated slowly. However, such a procedure would generally have to be done on a batch basis and would not be as efficient as continuous drying systems. Also, batch drying would be more expensive. Thus, in order to be commercially appealing, an improved drying apparatus which avoids scorching problems should be a continuous drying apparatus.

Concurrent-countercurrent grain dryers constitute a class of continuous type grain dryers which are very efficient and which normally do not produce an excess of cracked grain. Such dryers are continuous type dryers since grain continuously enters an inlet at the top of a drying bin and flows downwardly past upper hot air ducts, intermediate exhaust ducts. ower cool air ducts and out the bottom of the bin. The hot air flows concurrent with the grain to the intermediate exhaust duct. Cool air from the lower cool air ducts flows upwardly counter to the grain flow and exits at the same intermediate exhaust duct.

Although concurrent-countercurrent dryers are very effective, nevertheless when grain introduced at the top of the bin is especially cold due to the ambient conditions external the dryer, scorching and generally poor grain conditioning is quite likely to occur. That is, when a great temperature or moisture differential exists between the ambient condition grain and the drying medium, scorching will probably occur. Of course, scorching of the grain will undesirably reduce the value of the grain. Therefore, it is an object of this invention to provide an improved concurrent-countercurrent grain dryer which provides a means for preheating the grain to thereby avoid scorching and to provide better grain conditioning.

US. Pat. No. 3,727,323 refrered to above discloses a preheating structure for a grain dryer of the type similar to the present invention. The preheater in the reference patent is comprised of separate diamond shaped ducts positioned above and in alignment with hot air inlet ducts. The diamond cross section preheater ducts are perforated on all sides to receive a counterflow of hot air which preheats grain entering the bin. Additionally, the preheater ducts are vented at their opposite ends by adjustable shutters.

This specific preheater mechanism has proved to be very satisfactory and efficient. On the other hand, in stallation of such preheaters during the manufacturing process is a time consuming and burdensome expenditure, particulary in comparison with the improved structure of the present invention.

SUMMARY OF THE lNVENTlON In a principal aspect, the present invention comprises a grain dryer of the type having an enclosed bin with a wet grain inlet and a dry grain outlet. A plurality of spaced horizontal hot fluid inlet ducts are provided for directing fluid drying medium downwardly through a continuously moving bed of grain. Below the hot fluid inlet ducts are a plurality of spaced horizontal cold fluid inlet ducts for directing a fluid cooling medium upwardly through the same bed of grain. The cold fluid inlet ducts are spaced from one another to provide a plurality of grain discharges to the grain outlet. To provide for continuous downward grain bed movement or flow, means are provided for adding wet grain through the wet grain inlet and means are also provided for removing dry grain from the grain outlet. Intermediate the hot and cold fluid inlet ducts is a set of horizontal exhaust ducts positioned transverse the inlet ducts. The horizontal exhaust ducts exhaust the fluid from both the hot and cold fluid inlet ducts.

A manifold is provided at one end of the grain drying bin to supply hot fluid to the hot fluid inlet ducts and cold fluid to the cold fluid inlet ducts. The hot fluid inlet ducts are closed on three sides so that hot fluid may be discharged downwardly in a concurrent direction.

A perforated metal cap is positioned over the top of each hot fluid inlet duct. The cap is perforated metal so that hot fluid may be exhausted through the preheat exhaust duct formed by the perforated metal and the planar top of the hot fluid inlet duct. This upper preexhaust duct thus receives and exhausts hot fluid flowing in a direction countercurrent to the grain flow. This countercurrent flow of hot air preheats the downwardly flowing grain as it enters the bin and substantially prevents scorching of the grain during the drying operation.

It is thus an object of the present invention to provide an improved grain dryer having an improved preheater mechanism.

Another object of the present invention is to provide means in a countercurrent-concurrent type grain dryer for preheating the grain to thereby reduce or eliminate scorching, shattering of the wet grain and other deleterious effects which might occur by overheating or rap idly heating the grain during the drying process.

It is a further object of the present invention to provide an improved preheater mechanism for a concurrent-countercurrent type grain dryer wherein the preheat mechanism is formed from the least number of parts and with a minimum amount of alteration to dryers that do not include any preheat structure.

These and other objects, advantages and features of the present invention will be set forth in greater detail in the description which follows.

BRIEF DESCRIPTION OF THE DRAWING In the detailed description which follows, reference will be made to the drawing comprised of the following two figures:

FIG. 1 is a cut-away perspective view of a typical concurrent-countercurrent flow, column type grain dryer incorporating the improved preheat exhaust structure of the present invention; and

FIG. 2 is a cross-sectional view of the grain dryer of FIG. 1 illustrating the improvement of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The improved grain dryer of the present invention is substantially the same in construction as that shown and disclosed in US. Pat. No. 3,727,323. However, the preheat exhaust construction shown in US. Pat. No. 3,727.3 23 has been eliminated and the preheat exhaust construction of the present invention has been added.

Referring to the figures, the grain dryer of the present invention includes an enclosed bin comprised of opposed side walls and 12 end walls 14 and 16,

lower hopper walls

18 and 20 and

upper roof panels

22 and 24. Wet grain is conveyed to the interior of the bin formed by these respective walls through a grain inlet 25 by means of an auger 26 to form a bed. The wet grain bed 28 fills the interior of the bin and flows downwardly by means of gravity.

Positioned along the bottom-portion of the bin to form a plurality of spaced grain discharges are cold air inlet ducts 28. Each inlet duct 28 is formed by a triangular cross section duct running the length of the bin. Ducts 28 are perforated on the two top triangular sides 29 and 31 to permit discharge of cool fluid (air) in the upward direction.

The cold air inlet ducts 28 are separated from one another to define grain discharge outlets 30. Metering rolls 32 control the rate of grain discharge through the outlets 30. A discharge auger 34 removes the dried or lower moisture content grain from the lower apex formed by the

hopper walls

18 and 20.

Positioned above and transverse to the cold air inlet ducts 28 are horizontal perforated exhaust outlet ducts 36. The exhaust outlet ducts 36 havera diamond shaped cross section and are formed of metal which are perfo rated on all four sides of the diamond to permit exhaust of cold air flowing countercurrent to the grain flow as well as hot air flowing concurrent to the grain flow as explained below.

Positioned above and parallel to the cold air inlet ducts 28 are a plurality of horizontal hot air inlet ducts 38. Each hot air inlet duct 38 has a U-shaped cross section with depending

side walls

40 and 42 and a connecting top portion or crown 44. The hot air inlet duets 38 and in particular the walls forming the ducts 38,

walls

40, 42 and 44 are not perforated.

Hot air flowing into the hot air inlet ducts 38 is discharged downwardly or in a concurrent direction with the flow of grain in the bin. Both the hot and cold air fed to the

ducts

38 and 28, respectively, originate in a plenum chamber 46 adjacent one end of the

ducts

38 and 28. The plenum chamber 46 is split into two portions whereby a single fan 48 is operable to drive fluid directly into the cold air ducts 28 and through a heater 50 and hot air inlet 54 into the hot air ducts 38 to effect air movement through the bed 28 of grain in the bin. The air movement and construction of this portion of the dryer is much like that shown in Graham U.S. Pat. No. 3,302,297.

The improvement of the present invention relates to the preheat exhaust ducts 52 formed by the crown or top portion 44 and the

perforated side panels

48 and 49 extending the length of the bin. The

side panels

48 and 49 are preferably formed from a single sheet of metal which is bent to form an inverted V shaped cap which fits over the duct 38.

As illustrated in FIG. I, the exhaust duct 52 formed by the

side panels

48, 50 and top portion or crown 44 is vented to the atmosphere at the end of the bin opposite the hot air inlets 54. Thus, a triangular shaped exhaust opening 56 is associated with each preheat exhaust duct 52. An optional adjustable shutter 58 may be positioned over opening 56 to control the air flow rate from the preheat exhaust duct 52 to the atmosphere.

The acute angle of the

sides

48 and 50 with top portion 44 is preferably substantially equal to the angle of repose of the grain being dried. For example, the angle of repose for wet corn is approximately 4245. Thus, the downward flow of grain is not impeded by this construction and the grain will not collect and clog perfo rations 60 defined in the

panels

48 and 50.

In operation then, grain enters the top of the bin through grain inlet 25 and is spread in the bin via action of auger 26 and flows downwardly. Hot air enters ducts 38 and flows downwardly in a concurrent direction as illustrated by the arrows in FIG. 2. A certain amount of the hot air flows upwardly along the

sides

40 and 42 of the inlet ducts 38 and enters the perforations 60 of

panels

48 and 50 forming the preheat exhaust duct 52. Thus, a certain amount of hot air preheats the wet corn or grain prior to primary heating by the downwardly directed flow of hot air from ducts 38.

The moisture laden hot air ultimately exhausts through exhaust ducts 36. Of course, as preveiously described, a portion of the hot air exhausts through the preexhaust ducts 52 to effectively preheat the grain. The countercurrent flow of cold air entering through ducts 28 also exhaust through the exahust ducts 36. Adjustment of the flow rate amount through the preexhaust ducts 52 is effected by operation of shutters 58.

In this manner, a countercurrent flow of hot air is provided to preheat especially cold and wet grain. This slightly tempers the grain before it moves into the concentrated area of the hot air inlet ducts. Thus, the temperature differential between cold and wet grain and the hot fluid is small initially and increases gradually as the grain flows downward toward the region of maximum hot air flow and entry. This avoids scorching and sudden shock to the grain kernels resulting from the evaportion ofthe moisture at or near the surface of the kernel. ln this manner, more efficient removal of moisture from the grain is effected.

lmportantly, the preheater arrangement of the present invention provides structural advantages relative to the structure shown in U.S. Pat No. 3,727,323. It is a structure of substantially increased simplicity. That is, the utilization of additional separate diamond shaped ducts is no longer found necessary.

Finally, the structure of the present invention demonstrates improved preheating and grain drying results relative to the structure disclosed in US. Pat. No. 3,727,323. For example, the use of a preheat duct in association with each inlet duct provides improved preheat fluid flow throughout the grain bed. The preheat arrangement of the present invention thus permits an increase in the temperature of the inlet duct air to 325F. from the former temperature of 300F. As a result, we estimate improved dryer efficiency of 40% to 50%.

Therefore, the subject matter of the present invention is to be limited only by the following claims and their equivalents.

What is claimed is:

1. In a portable continuous flow grain dryer of the type having an enclosed bin with a wet grain inlet at the top of said bin and a grain outlet at the bottom of said bin, said bin including a plurality of spaced parallel horizontal hot fluid inlet ducts for directing a fluid drying medium downwardly through a bed of grain in said bin, a plurality of spaced parallel horizontal cold fluid inlet ducts for directing a fluid cooling medium upwardly through said bed of grain, said cold fluid inlet ducts positioned parallel to and below said hot fluid inlet ducts and spaced from one another to provide a plurality of grain discharges to the grain outlet fluid inlet means at one end of said inlet ducts, means for adding wet grain through said wet grain inlet, means for withdrawing dry grain from said grain outlet horizontal exhaust duct means intermediate said hot and cold fluid inlet ducts and perpendicular thereto to receive and exhaust fluid medium flowing from said hot inlet ducts in a concurrent direction to grain flow and also exhaust cold fluid medium flowing from said cold inlet ducts in a countercurrent direction to said grain flow, each of said exhaust duct means having outlets through said bin on op posite sides thereof, and means for providing hot fluid to said hot inlet ducts and cold fluid to said cold inlet ducts through said fluid inlet means at one end of said bin, the improvement comprising:

preheat exhaust ducts positioned over each of said hot fluid inlet ducts and coextensive therewith, each preheat exhaust duct being formed in part by a portion of a hot fluid inlet duct, each of said hot fluid inlet ducts including a substantially horizontal planar top and downwardly depending sides. said preheat exhaust ducts each including the planar top of said hot fluid inlet duct to form the bottom portion thereof and a perforated panel over and closed on said planar top to form a longitudinal duct. said preheat exhaust ducts being vented outside said bin.

2. The improved structure of claim I wherein said preheat exhaust ducts are vented at the end of the bin opposite the one end of the bin for providing hot fluid to the hot fluid inlet ducts.

3. The structure of claim 1 wherein said perforated panel is comprised of first and second intersecting perforated panels forming a longitudinal duct of triangular cross section with said planar top.

4. The improved structure of claim 3 wherein said first and second perforated panels each form an angle with said planar top substantially equal to the angle of respose of grain admitted to the bin.

5. The improved preheat ducts of claim 1 wherein each of said hot fluid inlet ducts is formed by a continuous single piece of material having an inverted U shaped cross section and said preheat exhaust duct is comprised of a single perforated panel having an inverted V cross-section forming a cap over the top of the

Claims

1. In a portable continuous flow grain dryer of the type having an enclosed bin with a wet grain inlet at the top of said bin and a grain outlet at the bottom of said bin, said bin including a plurality of spaced parallel horizontal hot fluid inlet ducts for directing a fluid drying medium downwardly through a bed of grain in said bin, a plurality of spaced parallel horizontal cold fluid inlet ducts for directing a fluid cooling medium upwardly through said bed of grain, said cold fluid inlet ducts positioned parallel to and below said hot fluid inlet ducts and spaced from one another to provide a plurality of grain discharges to the grain outlet fluid inlet means at one end of said inlet ducts, means for adding wet grain through said wet grain inlet, means for withdrawing dry grain from said grain outlet horizontal exhaust duct means intermediate said hot and cold fluid inlet ducts and perpendicular thereto to receive and exhaust fluid medium flowing from said hot inlet ducts in a concurrent direction to grain flow and also exhaust cold fluid medium flowing from said cold inlet ducts in a countercurrent direction to said grain flow, each of said exhaust duct means having outlets through said bin on opposite sides thereof, and means for providing hot fluid to said hot inlet ducts and cold fluid to said cold inlet ducts through said fluid inlet means at one end of said bin, the improvement comprising: preheat exhaust ducts positioned over each of said hot fluid inlet ducts and coextensive therewith, each preheat exhaust duct being formed in part by a portion of a hot fluid inlet duct, each of said hot fluid inlet ducts including a substantially horizontal planar top and downwardly depending sides, said preheat exhaust ducts each including the planar top of said hot fluid inlet duct to form the bottom portion thereof and a perforated panel over and closed on said planar top to form a longitudinal duct, said preheat exhaust ducts being vented outside said bin.

2. The improved structure of claim 1 wherein said preheat exhaust ducts are vented at the end of the bin opposite the one end of the bin for providing hot fluid to the hot fluid inlet ducts.

5. The improved preheat ducts of claim 1 wherein each of said hot fluid inlet ducts is formed by a continuous single piece of material having an inverted U-shaped cross section and said preheat exhaust duct is comprised of a single perforated panel having an inverted V cross-section forming a cap over the top of the hot fluid inlet duct.