US2333089A

US2333089A - Grain drier

Info

Publication number: US2333089A
Application number: US378508A
Authority: US
Inventors: George J Burkhardt
Original assignee: Individual
Current assignee: Individual
Priority date: 1941-02-12
Filing date: 1941-02-12
Publication date: 1943-11-02
Anticipated expiration: 1960-11-02

Description

Nov. 2, 1943. G. J. BURKHARDT GRAIN DRIER Filed Feb.

12, 1941 2 Sheets-Sheet l grwe wbo'n 13-1- EURKHARDT 1943. G. J. BURKHAIRD'IH GRAIN DRIER 1941 '2 Sheets-Sheet 2 Filed Feb. 12

E J .EJURKHARD TI Patented Nov. 2, 1943,

ur OFFICE.

George J. Burkhardt, Riverdale, Md. Application February 12, 1941, Serial No. 378,508

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 1 Claim.

This application is made under the act of March 3, 1883, as amended by the act of April 30, 1928, and the invention herein'described and claimed, if patented, may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment to me of any royalty thereon.

My invention relates to apparatus for drying grain. It is well known that grains of various kinds vary considerably with regard to the amount of moisture contained at the time of harvesting, the actual percentage of moisture varying with the kind of grain and, more particularly, according to weather conditions obtained during and immediately preceding the period of harvesting. It is well understood by grain handlers generally, that grain having too high a moisture content cannot be safely held in bulk storage for any length of time owing to the tendency of such grain to become self-heating when so stored.

Heating of stored grain may occur through either.

the rapid germination of mould spores which are carried along with the grain and become active under appropriate conditions of moisture and temperature, or may occur through metabolic processes taking place within the grain kernels themselves, which processes are materially accelerated by the presence of excessive moisture in the grain. The temperature rise of the grain, resulting from either of these processes, or both in combination, is at first gradual, but becomes more pronounced as the grain temperature increases, the process being self-accelerating, and sooner or later results in a rapid increase of the temperature to values at which rancidity and mustiness quickly develop, together with more or less complete loss of germinating power, all of which markedly depreciate the value of the grain.

The only practicable means so far found of keeping such grain in sound condition is the reduction, by drying, of the moisture content of the grain to a value at which it will be stable in bulk storage. Various means and methods of drying grain have been used but drying apparatus hitherto employed have been unsuited to farm use. by reason of being too cumbersome and costly, or, if constructed of small size, were either of inadequate grain handling capacity or incapable of removing moisture at a suiliciently rapid rate.-

My invention provides a grain drying apparatus of simple and compact type and of moderate cost and relatively high grain drying capacity in pro portion to its size and weight, capable of effecting a pronounced reduction in moisture content with a single pass of the grain through the apparatus, drying being efiected at a high thermal efficiency, under controlled temperatures without danger to grain from overheating.

I obtain the aforementioned important advantages by means of the apparatus herein described and shown in the accompanying drawings, in which Fig. 1 is a side elevation of a apparatus;

Fig. 2 is a vertical section of the drying chamber of the apparatus shown in Fig. 1 along the line AA in Fig. 3;

Fig. 3 is a horizontal section of the drying chamber along the line B--B in Fig. 2;

Fig. 4 is a vertical section through the lower portion of the drying chamber and the plenum chamber;

Fig. 5 is a vertical section through the drying chamber of a modifi d form of my invention.

Similar figures of references refer to similar parts in the several iews.

Moist grain to be dried is received in a hopper I at the top of a vertically extending drying chamber 2, at such a rate as to keep the chamber constantly filled with the grain. The grain moves downward by gravity through said chamber and is removed from the bottom thereof at a constant controlled rate and elevated by means hereinafter described, and is discharged at 3 by grain discharge spout 4. As the grain moves downwardly in chamber 2, it contacts and passes between horizontal heating pipes 5 adapted to receive and convey a heating fluid, such as hot water or steam, said heating pipes extending transversely of said chamber in parallel spaced arrangement, the grain also contacting and pass ingbetween vertical heating plates or fins 6 also extending transversely of chamber 2 inparallel spaced arrangement and transversely of pipes 5 and secured to said pipes by welding, brazing or shrinking, etc., wherebythe surfaces of said plates become virtually, for heat conducting purcomplete drying poses, extensions of the outer surfaces of said pipes, thereby providing within a limited space. a relatively large area for heat conduction to the grain descending between said pipes and said plates or fins. and making possiblea high total rate of heat transfer from the heating fluid in said pipes to said grain, with a relatively small difference between the temperatures of said fluid and said grain.

The downwardly moving grain in drying chamber 2 is constantly subjected to the action of an upwardly moving current of air drawn from the chamber. 8 immediately below drying chamber 2. The bottom of drying chamber 2 is formed of wire netting surfaces 9 of such mesh as to retain the grain in the drying chamber but permit air to pass freely from plenum chamber 8 into the grain over nearly the entire bottom of drying chamber 2. Instead of wire-netting, surfaces 9 may be'of any other material; as for example, perforated sheet metal, adapted to retain the grain in chamber 2 while allowing air to passfreely into the same from the plenum chamber 8. The air passes upwardly through the grain,

passing between heating pipes 5, andheating plates or fins 6, and being heated by contact therewith, and emerges from the grain into outlet flues IDA adapted to extend transversely of the drying chamber, the bottoms of outlet flues IDA being open to the grain, and returns togthe atmosphere through the open ends of said outlet flues.

Grain passing downward through drying chamber 2 and passingbetween and around airoutlet ducts IDA, into the space below said ducts, en-

' has been heated, partly by heat absorbed by the air from heated grain and partly by heat received directly from portions of heating pipes and heating plates or fins 6. The heating sur face of the heating element comprised by pipes 5 and plates or fins 6, is so generally distributed over the cross section of drying chamber 2, as may be noted in Fig. 3, that a large proportion of the kernels in the grain make contact with some portion ofsaid' heating surface and are forced into intimate contact with the same by the pressure due to the weight of the grain in the chamber above said heating element, thereby provid ing conditions favorable for rapid conduction of heat from said heating element to the grain. Each kernel of grain so heated makes contact with the heating surface on only a. relatively small proportion of its total perimeter. Much of the remainder of said perimeter is, at the same time, subjected to the action of the current of air rising through the grain, and is therefore giving up both heat and moisture to said air current. The thermal conditions provided by, this arrangement are, therefore, favorable to a rapid transfer of both heat and moisture from the grain ,to the air. The continuous removal of heat from the grain while it isreceiving heat 'from the heating element, tends to preventthe accumulation of heat within the'grain and thereby avoids overheating of the grain.

The'portion of drying chamber 2 extending between said heating element and plenum chamber 8 constitutes a heat exchanger in which the heated grain and cool air from the atmosphere move in countercurrenh the grain moving down- ;wardlyand the air upwardly. The downwardly moving heated grain gives up heat, in both sensible and latentform; to the upwardly moving air current, the sensible and latent heat content of theair being correspondingly increased. The temperature of the grain and the vapor pressure of its moisture content, both tend to approach the corresponding values for the incoming air, the grain being both dried and cooled as it moves downward through'the said space.v

The wire netting surfaces 9 which form the bottom of drying chamber 2 and separate said drying chamber from the plenum chamber 8, are

aasaose steeply inclined to right and to left in alternation, forming a plurality of V-shaped troughs, extending in parallel contiguous arrangement. The lower edges of the surfaces 9 which form each such trough do not meet but are somewhat separated leaving a narrow slot-like grain discharge opening ID at the bottom of the trough into which the dried grain descending in chamber 2 I is guided by-the inclined surfaces 9 and through which the dried grain exits from said chamber.

'Each discharge opening I0 is connected to a plurality of grain discharge hoppers H which receive the dried grain issuing from drying chamher 2 through openings I0 and guide said grain into closed grain spouts I2 which extend through the bottom l3 of plenum chamber 8. The lower end of each spout i2 is provided with a grain discharge wheel I4 of conventional type adapted to discharge grain at a controlled rate determined by the rate at which said wheel is rotated. Wheels M are carried upon and rotated by shafts 15 which are driven at a controlled speed by means hereinafter described. Wheels 14 dis- 'charge the dried grain into trough l6.

conveyor ll, operating in trough l6 conveys the dried grain to the foot of dried grain elevator i8 which elevates the grain and delivers it into grain discharge spout 4, the dried grain being discharged at 3.

Air vent openings i9 are provided in the walls of spouts 12 below the bottom R3 of plenum chamber 8, said openings being adapted to permit the free escape to the atmosphere of such air as may be forced through the grain in hoppers l i and spouts 12 by the pressure of air in plenum chamber 8, thereby preventing the building up in spouts l2 of air pressure which might affect the delivery of grain by wheels Hi.

The drying apparatus shown in Fig. l is arranged for utilizing water as the heating fluid circulated through the heating pipes in the drying chamber. As shown in that figure, the water is heated in boiler 20, of a conventional type, and is circulated by circulating pump 2| through said boiler 20, flow pipe 22, flow header 23, heating pipes 5, return header 24 and return pipe 25, back to pump 2|. The heating system being of 1 the closed type is conventionally equipped with (ill rate of flow of the hot water through heating pipes 5 in drying chamber 2 may be regulated by valve 3| in return pipe 25, and the temperature of the hot water observed by thermometer 30, and regulated as required by manipulation of conventional draft controls of boiler 20. Water is supplied to the heating system when required through water supply valve 32 and water suppl; pipe 33, extending from a suitable source, not shown. Drain valve 34 permits the heating sys tem to be drained, when required.

While I prefer to employ hot water as the neating fluid circulated through heating pipes it is evident that any other heating fluid, such as.

' for example, steam, could be similarly employed without departing from the essential principle of my invention.

The moving members of the drying apparatus are operated by electric motor 35, which drives countershaft 36 by means of belt 3?. Instead of the electric motor 35, the moving members be driven by any other suitable means as, for example, an internal combustion engine. From countershaft 36, fan 7 is driven by belt 38, the dried grain elevator 18 by twisted belt 39, and

Spiral 2,838,089 circulating pump 2! by belt 40. Spiral conveyor I! is directly connected to the shaft, not shown,

carrying the bottom pulley of elevator 18 and receives its motion therefrom.

Grain discharge wheels l4 chain 4!, speed changing transmission 42 and chains 43 and 44 driving sprocket wheels 45 on shafts i5. Transmission 42 is of a conventional type, having speed adjusting means, such as a handwheel 46, by operation of which the speed of wheels l4 may be varied as required.

In operation, in drying grain, the rate of flow of hot water through heating pipes 5 is controlled by adjustment of valve 3|, the temperature of the hot water regulated by adjustment of conventional draft controls of boiler 20, the rate of movement of the grain through the drying chamber is controlled by adjusting the speed of the wheels I4 through manipulation of handwheel 46, and the volume of air forced upwardly through the grain in the drying chamber, is controlled by adjustment of shutter 41 on intake of fan 1.

I have found it essential to the proper periormance of my drier to employ fins or plates 6 in addition to having two rows of pipes 5. These fins or plates 6 should be properly spaced at substantially 24 per foot.

Under an alternative application of my invention, shown in Fig. 5, I may arrange heating pipes in a plurality of banks, as for example, in three banks, 48,49, and 50, each of said banks comprising heating pipes 5, heating plates or fins 6, flow header 23 and return header 24, connected and arranged, as hereinbefore described, said banks being positioned, one above another in said drying chamber 2, but separated, one from another, by intervening spaces, 5| and 52 in said chamber. I have found this arrangement to be advantageous where grain of high moisture content is to be dried and its moisture content reduced in relatively large proportion, requiring a correspondingly large amount of heat in relation to the quantity of grain handled. This modification of my invention enables relatively large are driven through reductions to be made in the moisture content of grain, with a less total expenditure of heat than is required with heating pipes in a single bank, thereby accomplishing the drying at a higher thermal efficiency with less tendency to overheat the grain.

While I have shown three banks of heating pipes, it is to be understood that I do not limit myself to this particular number of banks, since it is evident that my invention may be practiced with any other number of such banks without departing from the essential principle of my invention.

While grain drying apparatus has been employed having horizontal heating pipes in vertically extending drying chambers in connection with means for forcibly passing currents of air upwardly through the grain in said chambers, I have found that such structure is not adapted for the type of apparatus which has a capacity for high moisture removal; high ratio of heat conducting surface area to the volume of grain to be handled, and a high rate of moisture removal without subjecting the grain to dangerously high temperatures; and, the combination of these features in a compact, portable apparatus as hereinbefore described.

Having thus described by invention, what I claim for Letters Patent is:

A grain drier comprising a vertically elongated chamber adapted to be filled with a column of grain, means for introducing grain into the top of said chamber, a foraminous support for the column of grain at the bottom of the chamber, means for forcing air into the chamber belowthe foraminous support, whereby the air will pass upward through said support and through the column of grain, controllable positive means for removing grain from said support to the exterior of the chamber, and a radiator in said chamber above said support, said radiator having members spaced to permit the column of grain passing therebetween to be uniformly heated.

GEORGE J. BURKHARDT.