US3012331A

US3012331A - Method for conditioning grain or similar materials

Info

Publication number: US3012331A
Application number: US724756A
Authority: US
Inventors: Oholm Gustav; Wallin Sven
Original assignee: Svenska Flaktfabriken AB
Current assignee: Svenska Flaktfabriken AB
Priority date: 1957-03-29
Filing date: 1958-03-28
Publication date: 1961-12-12
Anticipated expiration: 1978-12-12

Description

Dec. 12, 1961 5. OHOLM ETAL 3,012,331

METHOD FOR CONDITIONING GRAIN 0R SIMILAR MATERIALS Filed March 28, 1958 2 Sheets-Sheet 1 FIGI. 5

FIGZ. 25 4 6 FIGB. a

INVENTORSI SVEN WALL I N GUSTAV OHOLM BY WW Dec. 12, 1961 G. OHOLM ETAL ,33

METHOD FOR CONDITIONING GRAIN OR SIMILAR MATERIALS Filed March 28, 1958 2 Sheets-Sheet 2 FIG. 7 F 1 65 66 ,0? 4 4/ 60 i \"Q fl 2 i 5531 A I i: 1 4.2

INVENTORS SVEN V\ ALL|N GUSTAV OHOLM ATTYS.

atent fhce 3,912,331 Patented Dec. 12, 1 961 3 612 331 METHGD F8 CQI IDKTIGNING GRAlN QR SWEAR EEATERIALS Gustav Gholnr, Bromrna, Sven Wallin, Jot-limping,

Sweden, assignors to Alrtiebolaget Svensira Fiakttabrllren, Stockholm, Sweden Filed Mar. 23, 1958, Ser. No. 724,755 Claims priority, application Sweden Mar. 29, 1957 1 Claim. (Cl. 34-10) The present invention relates to a method for conditioning grain or similar materials conveyed as a layer on a supporting plane, the grain particles being passed and fluidized by a gaseous medium and thereby being first dried and then cooled during a treatment in two or more steps.

When drying grain and similar materials, which has to be stored after drying, it is necessary to reduce the temperature of the dried grain in order to avoid the damaging of the quality during the storing period. Generally, this cooling of the grain is efiected simultaneously with the drying of the grain in such a way that during its passage through the last part of the drying unit, cold outdoor air is blown through the grain. However, this cooling method has often proved insufiicient, or a relatively long treatment time has been required with a corresponding increase of the cost for the drying apparatus. Furthermore, it has been found that the quicker the drying is performed, the greater part of the treatment time will be required for the cooling of the grain.

The invention, which has for its object to eliminate this drawback and in the first place to enable a quicker cooling of the dried grain, is based on the knowledge'that the necessity for a long cooling thne depends upon the uneven moisture content created in the grain after the original drying. If the drying time is adjusted to obtain a certain mean moisture ratio in the discharged grain, the moisture ratio at the grain surface will be considerably below that value due to the delay-caused by the quick-dryingin the movement of the moisture from the inner portion of the grain and out to the surface of the same. As a consequence, the moisture ratio in the surface layer will often be below the hygroscopic equilibrium state of the outdoor air, and the grain therefore during the first part of the cooling absorbs moisture from the cooling air. Besides the disadvantage of an undesirable moistening of the grain there will be a surplus of heat resulting from the heat of condensation which prolongs the required cooling period. The super-dried surface layer will also prevent the outward movement of the moisture from the inner portion which is necessary for the moisture equalization, said moisture movement furthermore being delayed by a reduction of the temperature of the grain. Because of this prevention of the equalization of the moisture to the desired extent, the heat transmission necessary for the cooling is effected entirely by means of convection.

The method according to the invention is characterized by the fact that the material between the treatment steps is continuously transmitted to an equalizing zone, where the material is substantially isolated from the influence of the treatment medium.

Owing to the fact that the moisture equalization in the grain in this manner is performed at a fixed high temperature, the moisture movement will take place quicker and the grain will enter the cooling zone with so high a moisture ratio in the surface layer, that there is no risk of water absorption. Another object of the invention is a dividing, if desired, of the drying into two steps by providing a similar equalizing zone between the steps.

The invention also relates to a device for performing the method. Such a device consists of a unit in form of a rectangular box and equipped with inlet and outlet openings at opposite ends for the material to be treated and equipped with a substantially horizontal, perforated intermediate bottom wall, functioning as a supporting plane for the material, and one or more ventilators connected to the space below the intermediate bottom wall for supplying treatment medium and a discharge opening for this medium arranged above the intermediate bottom wall. A suitable embodiment of the device is characterized in that the supporting plane in the equalizing zone or zones is made without perforations or with perforations providing a considerably reduced flow area. According to another embodiment the space below the supporting plane is equipped with partitions at opposite ends of each equalizing zone and the equalizing zones are connected to supply means for a treatment medium of considerably lower pressure than that of the treatment zones. In sections where no air is blown through the grain particles, or at such a low velocity of the medium that fluidization does not take place, the conveyance of the material can be efiected by vibrating or shaking the supporting plane or by a scraping conveyor.

According to one embodiment, the device for performing the method according to the invention may consist of two or more units arranged one above the other and of equal dimensions, but a mirror image of each other and shaped as rectangular boxes. Each unit is equipped with inlet and outlet openings at opposite ends for the material to be treated and is provided with a horizontal, perforated intermediate bottom wall functioning as a supporting plane for the material, a ventilator connected to the space below the intermediate bottom wall for supplying treatment medium, and a discharge opening above the intermediate bottom wall for this medium. A characteristic feature of this embodiment is that the perforated intermediate bottom wall terminates some distance from the outlet end of its associated unit in a depending vertical partition, which defines a shaft-like space ending in the outlet opening for the material, said opening being arranged in the bottom of the unit.

According to all of the above mentioned embodiments of the device, the outlet for the discharged treatment medium can suitablyin order to prevent the grain from being caught by the descending treatment medium-be made as a slot in one or both of the side walls and have the same length as the perforated intermediate bottom wall. The slot terminates in an outlet duct arranged at the outer side of the unit having the same length as the slot and having a how area of about one and a half times as large as said slot. The outlet duct has an upwardlyfacing outlet opening which is defined by an inwardly bent edge, functioning as a catching rim. The side wall of the unit along the lower edge of said slot is formed with a V-shaped inwardly bent marginal portion or deflector for deflecting the material.

The invention will now be described more in detail with reference to the accompanying drawings, which show suitable embodiments of the devices for performing the method wherein:

FIG. 1 shows a vertical longitudinal section of an embodiment of the device.

FIG. 2 shows a cross section through the device along the section line 2--2 in FIG. 1.

FIG. 3 shows a vertical longitudinal section of another embodiment of the device.

FIG. 4- shows a cross section through the last mentioned embodiment of the device along the section line 44 of FIG. 3.

FIG. 5 shows a vertical longitudinal section through a modified embodiment of the device.

FIG. 6 shows a cross section through this modified embodiment along the section line 6-6 in FIG. 5.

FIG. 7 shows a plan view of the last mentioned device.

FIG. 8 is a fragmentary longitudinal vertical section showing a modification of the apparatus illustrated in FIGS. 1 and 2.

In the drawing, and more particularly FIGS. 1 and 2, the dryer comprises a rectangular box 1 formed as a unit with

end wall

2 and 2a, a bottom 7 and a roof 6 of sheet metal. The unit is provided with an inlet opening 3, made in the roof near the end wall 2 and an outlet opening 12 in the bottom of the section near the opposite end wall 2a. In the unit there is arranged a perforated intermediate bottom wall 8, supporting the material 9 to be dried and at the same time functioning as a distributing device for the treatment medium. A partition 28 depends from the intermediate bottom wall 8 at its end adjacent the end wall 2a to define therebetween the outlet opening 12. The material to be dried, i.e. the grain, is fed from a feeding hopper 4 and the feed of material is governed by means of an adjustable partition 5, in order to obtain a suitable layer of material 9. The space 16 below the perforated inter-mediate bottom 3 is connected'through a heater'Zt) to a ventilator 21 supplying the treatment medium.

According to the invention the intermediate bottom.

wall 8 is provided with ordinary perforations in the section A, while the bottom wall in the section B is provided with only small perforations to provide diminished'flow' of medium through the material 9 in this section. if

desired, the bottom wall in the section'B may be imperforate as shown at 8a in FIG. 8 to provide the diminished flow. discharge which functions as cooling zone, the intermediate bottom wall is provided with ordinary perforations.

'From the cooling zone the grain is emptied into an outlet trough 16 through the opening 12, from where the grain can be conveyed by means of an elevator 13, a

not take place, the conveyance of the grain can be ef fected by a scraping conveyor shown schematically at 29 t in FIGS. 1 and 2, or by vibrating the supporting plane for example by a vibrator shown at 29a in FIG. 8.

For the discharge of the treatment medium there are slot-shaped openings 11 of the same length as the per forated intermediate bottom arranged in the side walls of the section. The slot can be made with constant width as shown, or-for the purpose of an even distribution of medium-with varying width. The slot 11 terminates in an outlet duct 22 arranged on the outer side of the unit. one and a half times the flow area of the slot 11. The duct has along its top an outlet opening 24, defined by an inwardly bent edge 23 functioning as a'catching rim for catching grain particles, if any. Likewise, in order to prevent the grain from being caught by the discharged medium the side wall is along the lower edge of the slot provided with a V-shaped inwardly bent deflector 25 "for deflecting the material. In most 'cases it is sufiicient touse one single slot 'and an 'outlet'duct for the discharge of the treatment medium. The outlet duct of similar form at the other side of the unit can in such a case, as 1 shown in FIG. 2, be provided with a small door 26' which may be fo pened for inspection and testing of the material. For heating the treatment medium used in the drying zone in the case shown in 1, the ventilator '21 is connected to the chamber 10' throughthe heating coil 26 for heating by means of steam or hotwater. Airis supplied to the cooling zone either from a In the section C of the device next to the- The flow area of the duct 22 is preferably 49 in the upper unit 41a.

separate ventilator or, as in the case shown, from the same ventilator 21 through a by-pass 1S, equipped with an adjusting damper 19. A partition 17 is mounted in the space 10 for separating the drying and cooling mediums.

The embodiment of the device shown in FIG. 3 differs from that shown in FIG. 1 in that the space lfia below the supporting plane is provided with partitions 17a and 17b at opposite sides of the equalizing zone B. Furthermore, in this case the equalizing zones are connected to separate supplying means 21b for a treating medium of considerably lower pressure than in the treatment zones A, C to which treating medium is supplied by means of the ventilators 21a and 21c.' Tht supplying means 21b is in the case shown connected to the equalizing zone by means of a duct 27%), in which can be inserted a heating coil 28b. In similar manner a heating. coil 29a can be arranged in the duct 7a from the supplying means 21a to the treatment zone A. A duct 27c connects the supply means 210 to the cooling zone C.

In the device illustrated in FIG; 5 there are two closed super-imposed units 41a and 41b in form of rectangular boxes of equal dimensions, the second unit, however, being the mirror image of the first one.

The upper unit 41a has end walls 42 and 42a, a bottom 47, and a roof 46. The unit is provided with an inlet opening 43 near the end wall 42 which'is fed from a. feeding hopper 4-4. The feed of material is governed by an adjustable partition 45 to provide a suitable layer of fluidized material 49. A perforated bottom wall 48 is spaced upwardly from the bottom 47 to define therea heater 60 to a ventilator 51. Heated medium is thus supplied to the chamber 50 and passes upwardly through the perforated bottom Wall 48 to fluidize the material To discharge the treatment medium from above the material 49, openings 61 are formed in the side walls of the unit. The openings 61 may be of constant width, or, as shown, to provide an even distribution of medium with varying widths. The outlet opening 64 is similar to the opening 24 and need not be described further. The intermediate bottom wall 48 terminates at its end adjacent the end wall 42a in a depending partition 53'which defines an outlet 52from the upper unit 4-1a'between the partition 53 and the end wall 42a. The partition extends downwardly into the unit 41b to form a shaft-like space or chamber 54 isolated from the, treatment medium. The upper end of the chamber 54 forms the discharge opening for the upper unit 41a, and the lower end of the chamber 54 forms the inlet opening to the unit 41b. The sides of the inlet opening 55 is controlled by an adjustable partition 45b to determine the level of the material 491; in the lower unit. The lower unit has an' intermediate bottom wall 48b which defines a space 5% therebelow supplied with cooling medium by a ventilator 51b. The cooling supplied through the perforated Wall 48b passes upwardly through the material 4% and is discharged through a slot'61b and discharge openings 6% (FIG. 6) similarin con struction to the discharge opening 64. The perforated wall 48b terminates adjacent the reniote'end wall 42b of the lower unit 415 in a depending partition 53b which defines an outlet opening 52b from which the material is removed similarly to'themanner illustratedand describedin connection'with the embodiment illustratedin FIGS; 1 and Z. a

In this "embodiment said space 54 constitutes a resting space 54. should: suitably be dimensioned so that the equalizing time corresponds to at least of the drying time.

In this embodiment the heating coil 60 is as illustrated in FIG. 7 arranged on the suction side of the ventilator. This heating coil may also be substituted by a heat exchanger for indirect heating by means of flue gases or the necessary heat may also be supplied by direct addition of flue gases to the supplied out-door air. In order to increase the heat economy, part of the treating medium may be recirculated. The discharge duct of the treating medium may be recirculated. The discharge duct 62 is in such cases, as illustrated in FIG. 7 connected with the heating coil or the inlet of the ventilator by means of a duct 65, provided with a damper regulated inlet 66 for outdoor air. In order to make it possible to separate impurities accompanying the medium said return connection is suitably passing a dust settling chamber 67.

What we claim is:

A method of treating granular materials which comprises the steps of introducing the material into a first bed in a drying zone, passing a stream of drying medium up through the bottom of said first bed to fluidize the material therein, whereby said material is subjected to said drying medium for a predetermined time period, continuously withdrawing the dried material front one end of said first bed and introducing the material into an equalizing zone, interrupting the fluidization of the material in the equalizing zone by keeping the material in said equalizing zone substantially isolated from the effect oftreatment medium for a second predetermined time period at least one fourth said first predetermined time period to render the moisture content of the material uniform throughout, and then introducing the material from said zone into a second bed in a cooling zone, passing a stream of cooling medium upwardly through the bottom of said second bed to fluidize the material therein while cooling the same, and continuously withdrawing the cooled material from said second bed.

References Cited in the file of this patent UNITED STATES PATENTS 2,371,619 Hartley Mar. 20, 1945 2,582,688 Ford Jan. 15, 1952 2,635,684 Joscelyne Apr. 21, 1953 2,676,668 Lindsay Apr. 27, 1954 2,702,434 Richardson et al Feb. 22, 1955 2,715,282 Niven Aug. 16, 1955 2,797,908 Zubrzycki July 2, 1957