US2166351A - Vacuum drier - Google Patents

Description

July 1s, 1939. c, HAGEN 2,166,351 l VACUUM DRIER Filed Feb. 6, 1936 5 Sheets-Sheet 1 I l 1x11 N (WW Hingis* July 18,' 1939.

.C HAGEN VACUUM DRIER .5 Sheets-Sheet 2 Filed Feb. e, 195s July 18, 1939. i c. HAGEN 2,166,351

VACUUM DRIER Filed Feb. 6, 1936 5 Sheets-Sheet 3 July 18, 1939. C, HAGEN 2,166,351

VACUUM DRIER Filed Feb. 6, 1956 5I Sheets-Sheet 4 July 18, 1939. 1 Q HAGEN 2,166,351

VACUUM DRIER Filed Feb. 6, 193' i 5 SheetS-She'et 5 Aas .Ig

8J '1 I y Inl/enig? [lar] ,ditto/MT5.;

Patented July 18, 1939 VACUUMv Damn.

Carl Hagen, Park Ridge, lll., assigner, by mesne assignments, to Corn Products Reiining Company, New York, N. Y., a corporation of 'New Jersey Application February s, 193s.. semi No. 62,625

s claims. (c1. 344-23) This invention relates to improvements in vacuum driers and has vfor its principal object the provision of a 'vacuum drier which i's so constructed that materials of various character may be passed through the apparatus and dried therein by a continuous operation.

Another object of the invention is to provide an apparatus of the,above character in which the material being dried is caused to pass over l0 one Vor more heat radiating surfaces positioned in a sub-atmospheric zone, whereby the drying operation is effected by the direct contact of the material with the heat radiating surface, thereby effecting substantial saving in fuel cost by reason 15,1 of the low temperatures required for vaporizing the surplus moisture under sub-atmospheric pressure and by reason of the direct contact of the material with said heat radiating surface.

Another object is to provide, in apparatus of the above character, improved means for distributing the material over the heated surfaces 1 and for keeping it in agitation so as to take advantage of the maximum efficiency of the heat radiating surfaces.y

A more specific object is to provide a continu- 'ous drier of the above character for quickly and uniformlyv drying materials which are likely to be altered in character or quality by 'the use of high temperatures. In this connection the invention includes the provision of an apparatus in which starch. containing approximately 45% of moisture may be quickly and uniformly dried by a continuous operation in a partial vacuum, the apparatus including means whereby the evaporation of moisture and the temperature of the starch can be so controlled as to avoid danger ofgelatinizing the starch and at the same time maintain conditions which aidin the production of thicker boiling starch. than is obtained with the drying apparatuses now in general use.

While the apparatus of the present invention is not limited in its utility to the drying of starch, it has been designed in view of the various problems encountered in connection with the handling and drying of suchjmaterial. 'I'he apparatus herein shown willbe, therefore, described herein in connection with the drying of starch.

'I he starch drying apparatuses now in'igeneral use ordinarily employ heated air as a drying medium, the heated air being circulated through drying tunnels or other chambers so as to come into direct contact with the starch. Such air usually contains dirt and other impurities which become mixed with the starch being dried. If the old type of apparatus is of 'a construction adapted to Akeep the starch in agitation during the drying operation. the air becomes impregnated with the dry starch dust so as to form a combustible mixture. If the starch is dried in sizeable quantities. for example, in trays or forami- 5 nous containers. the drying operation must be carried on for a relativelylong period and at low temperatures in order to avoid gelatinizing the starch. Such apparatuses also require large lfloor space and the labor and fuel cost required 10 for handling thestarch is relatively high as compared with the low operating cost of the present improved apparatus.

The present invention, in addition to overcoming the above mentioned and other objections by l5 effecting economy in operation, eliminating contaminating foreign 4matter, and otherwise improvingthe quality of the product, includes various other improvements relating to particular problems encountered in connection with the20 dryingof starch. The rapid evaporation of moisture from the wet starch and also the tendency of the wet starch to adhere to the surfaces over which it is moved are likely to form lump portions in the materialA which must be 26 brok'enup in order to insure uniform drying thereof. The present improvement, therefore, includes the provision of improved devices for disintegrating the starch lumps so as to facilitateuniform distribution of the starch over the 30 heating surfaces. The disintegrati'ng means are themselves of novel construction so that they will operate efciently on the wet and the partially dried starch, as' -well as on the thoroughly dried starch. 35

The drying tables over which the starch is caused Vto lpass from the inlet-to the outlet o! the drying chamber are so arranged as to provide circuitous paths for the starch and the vapors emitted therefrom during the drying op- 40 eration; the vapors being adapted to contact the bottom surfaces ofthe drying tables so as to be superheated and thereby avoid condensation of the vapors within the drying chamber. .The vaporspass through the starch at lthe locations 46 Where the starch is discharged from one table to another. The dry starch .dust suspended in the vapors is therefore collected from the vapors by contact with the damp starch in the upper portion of the drying chamber. The dry starch dust thus collected reduces, to some extent, the tendency which the wet starch has to adhere to the dryingtables. When found desirable, a quantity of the dry starch from a suitable source, for example, from the discharge valve of the drier, 55

may be mixed with the wet starch fed into the machine and thereby reduce the tendency of such starch to adhere to the inlet valve and other parts of the apparatus.

The present embodiment of the invention is illustrated in the accompanying drawings wherein Fig. 1 is a vertical section through the drying apparatus and shows the arrangements and general constructions of the principal parts ofthe apparatus.

Fig. 2 is a plan view of the drying chamber, the inlet valve and the means for operating said valve. l

Fig. 3 is a sectional plan view taken on line 3-3 of Fig. 1.

Figs. 4, 5 and 6 are fragmentary views illustrating the constructions of three of the drying tables. k

Fig. 'I is a fragmentary illustration, on a larger scale, of the elements shown in Fig. 3 for moving the starch over the top surface of the drying table and for disintegrating the lumps present in the starch.

Fig. 8 is an end view of the lump disintegrating rollers shown in Fig. 7.

Figs. 9 and 10 are side and cross sectional views respectively of one of the scraper members for distributing the starch over a drying table and for moving it toward one edge thereof.

Eg. 11 shows one of a plurality of brackets secured to the inner wall of the drying chamber for supporting the drying tables.

Fig. 12 is a fragmentary section of one edge portion of a drying table.

Figs 13 and 14 are plan and vertical sectional views, respectively, illustrating the construction of the valves for controlling the inlet and outlet ports of the drying chamber, and

Fig. 15 is a sectional view taken through one of the windows provided for vobserving the material being dried and showing improved means for removing `any dust which may collect on the inner surface' of the window.

The drier illustrated in the drawings may be generally described as comprising a closed drying chamber Ill-which is connected at its upper end with an evacuator II of any suitable construction for maintaining a suitable vacuum 1n the chamber. Preferably a vacuum of approximately 2'1 to 28 inches of mercury is maintained so that themoisture in the starch will vaporize at a relatively low temperature.

'I'he wet starch is introduced into the drying chamber by means of a rotary valve I2 which is constructed, as hereafter described, so that the vacuum in the chamber III will assist the discharge of the -wet sticky starch from the valve. A -plurality of steam heated tables designated I3, I4 and I5 are arranged in vertically spaced relation in the drying chambers. 'I'he starch is spread overthe several tables and discharged from one onto another by means of distributing and forwarding mechanism, designated as a whole by the reference numeral I6. This mechanism includes a plurality of scraper devices I1 and lump disintegrating devices I3, positioned marginal portions of the underlying tables I4.

It is moved inwardly onthe three tables designated I4 and discharged'through a central opening 2l onto the central portions of the underlying tables I3-I5. The starch is discharged by means of a rotating valve I2* which is the same in construction as the inlet valve.

The vapor emitted from the drying starch is discharged from the top of the chamber through the vapor outlet 2|. The said vapor follows the same general course as the starch, but in the opposite direction, -and is superheated by contact with the bottom surfaces of the drying tablesV so as to avoid condensation thereof within the drying chamber. 'I'he dry starch suspended in the vapor is removed therefrom by contact with the wet starch in the chamber.

Referring now to the specific arrangement and construction of the various parts: The casing of the drying chamber I0 is preferably cylindrical and comprises a top section 22, a bottom section 23 and a plurality of intermediate sections 24. The intermediate sections 24 are preferably formed witha number of windows 25 positioned at different locations around the chamber, so that the operator may observe the o-peration of the parts enclosed within the chamber. Any dust which may collect on the inner surface of the window, may be removed by opening the valve 25 momentarily (Fig. 15) so as to permit air to rush through the pipe 25b and into the vacuum chamber, thereby dislodging any collection of dust on the inner surface of the window.

A plurality of brackets 26, preferably three for each table, project inwardly from the inner wall of the chamber I0 for loosely supporting the drying tables I3-I4.

The drying tables I3 are in the form of disc shaped steam chests, each chest comprising a dished body casting 21 formed with a plurality of concentric upstanding ribs 28. The said ribs divide the body into a plurality of steam passages 29, 30, 3| and 32, the open sides of which are closed by a removable cover plate 33 which forms the top surface of the drying table. The said cover plate is preferably made of bronze and is' clamped in position by means of bronze fiat headed, bolts 34 which extend through openings in the said ribs 28. The open ends of the several steam passages communicate with a common inlet passage 35 which is connected by means of branch pipe36 to a steam supply pipe 31 located outside of the drying chamber. The water of condensation is discharged from the steam passages through separate ports 38, 39, 40 and 4I which communicate with suitable steam traps 42 so as Ato insure a thorough drainage- `tables I4, however, are each formed with a central opening 20, previously referred to, and are v of larger diameter than the tables I3 so as to receive the starch discharged over the outer edges of the table I3. The spaces between the peripheries of the tables I4 and the wall of the drying chamber are closed by means of sealing strip members 43 to prevent the passage of starch and vapor around the outer edges of the tables. The

bottom table I5 seats on an upstanding rib 44 which forms one side of a channel 45 for receiving the dried starch discharged from thefsaid table. The steam inlet pipe l36h and the ports 75 38h, 39h, 4I)b and 4|b for the discharge of water of condensation are formed in the bottom face of the table I5 so as to avoid interference with the starch distributing and forwarding mechanism I6.

The starch distributing and forwarding mechahism for the several tables comprise the shaft I9 whic-h is journaled in upper and lower bearings 46 and 41, respectively. 'I'he shaft is operatively connected with a `motor 48 by means of a gear 49, a pinion 50 and a variable gear reduction mechanism'SI, of well known construction. The Variable gear reduction includes a manually operated hand wheel 52 whereby the speed of rotation of the shaft I9 and the memf bers carried thereon may be varied in accordance with the time required for properly drying the starch. A plurality of horizontally disposed arms 53 extend outwardly from the shaft I9 at locations above each of the several drying tables. The said arms are connected to the shaft by means of hub members 54 and are rigidied by truss rods 55 extending from ,the tops of the hubs to collar fittings 56 secured to intermediate portions of the arms.

The said arms are further rigidied and connected together by means of horizontally disposedtie rods 5'I and turn buckles 58 v(Fig. 3). A group of Scrapers I1 comprising blade portions 58 and shank portions 60 are secured to each of the supporting arms 53. The scraper blades for each table are arranged at suitable angles relative to the path of movement and the blades of one group are disposed in staggered relation to those of another, whereby the starch is agitated by movement thereof from one position to'another on the tables. The damp particles of the starch are therefore brought into direct contact with the heated surface of the table. The angular arrangement of the Scrapers also serves to distribute the starch over the entire area of the tables and move the starch, by a step by step' movement, toward the edge of the table from which it is discharged onto the next underlying'table. It will be observed in this connection, that the Scrapers for the three tables designated I3, and for the bottom table I5, are positioned to move the starch from the central portion ofthe tables toward their outeredges and that the Scrapers for the three tables designated I4 are positioned to move the starch from the outer edges of the tablestoward the central discharge openings 28.

Both the rapid evaporation of the moisture inthe starch and the movement of the wet starchv vgeneral form of conical rollers or cages and are preferably positioned near the outer edges of the tables. Each of the-said disintegraters comprises inner and outer head .members 6I-62, respectively (Fig. 7). The said head members are keyed or otherwise fixed on reduced erid portions 63-64 of an axle 65. Shoulders 68-61 at opposite ends of the axle hold the head members lil- 62 in proper spaced relation. The inner faces of the head members are provided with a number of bearing pockets in which are loosely fitted the trunnion end portions 88-68 of a plurality'of roller bars 68. Said bars are preferably made by twisting bars, square in cross section, so that the twisted corner portions of the bars form helical edges extending the full length of the bars. A U-shaped frame comprising a flat metal strip 10 and bearings 1I engag the projecting ends 'IL-'I3 of the axle. Resilient metal strips 14, l5 and I6 secure the disintegraters I8 to the scraper `arms A53 so that resilient force is exerted'on vthe starch as the disintegraters are rolled over it. 'Ihe helical roller bars 69 are free to turn about their own axes. This independent movementgof Ythe bars together with` their helical configuration serve to dislodge any accumulation of wet starch on y the bars and to break up any lumps which may be pressed into the spaces between the bars. By the time the starch reaches the bottom table of the drier, the starch lumps are thoroughly broken up and dried. Consequently the lump disintegraters I8 may be omitted from the table I5. The starch is discharged from the bottom' are of the same construction and comprise a casing made up of a central ring 18* and upper and lower head members I9 and 80, respectively. The ring 188L is clamped between the upper and lower heads by means of a plurality of bolts 8|. The rotating valve member 82 is provided with a plurality of pockets 83. When the valve member 82 is in the position indicated in Figs. 13 and 14, one of the pockets 83 communicates with an inlet passage 84 in the top portion of the valve cas- )ing and another pocket 83 communicates with a discharge passage 85 formed in the bottom of the casing. Valve member 82 is rotated by a suitable connection with a beveled gearv 86 secured to one end of a shaft 81 which in turn is keyed to the rotating valve 82. The inlet passage 84 and the discharge passage 85 of the valve casing are preferably positioned at remote points to each other so that the partitions 88 between the several pockets and the inner, walls 89 thereof lwill serve as Sealing members to prevent the passage of atmosphere frmthe inlet passage 'to the outlet passage, when the valve Vis employed as an inlet valve to the drier and to prevent admission of air into the drying chamber when the valve is as a discharge valve. Y

The position of the inlet valve, as shown in Fig. 1 of the drawings, is' an inverted position with relation to' the position of the valve illustrated in Figs. 13 and 14. It is operated by mechanismA comprising a. bevel pinion 90 which meshes with the bevel gear 86, a shaft" 9| on which the bevel pinion is mounted, a large sprocket l2 on the shaft which is connected by means of a. chain S3 to a sprocket pinion which forms part of a speed reduction mechanism 94 and an electric motor 95. The speed of rotation of the inlet valve may be varied, by operation of the hand wheel 95e, so as to vary the movement lof the valve in accordance with the speed of operation of the distributing andforwarding mechanism I6 within the drying chamber. The means by which the mechanism 94 operates to vary the speed of the shaft atmospheric pressure enters above the starch to force the wet sticky starch into the drying chamber. Further rotation of the valve, for example, in the direction of the arrow indicated in Fig. i3, moves. the pocket Il* into the position now ocy cupied by the pocket designated u in Fig. 13,

f the drying chamber.

and consequently closes communication between the air valve 9i andthe pocket. The said pocket, however, is still in communication with the evacuated drying chamber. Consequently any air remaining in the pocket when it reaches the position indicated at Il will be withdrawn so that when this pocket moves around lto thel position beneath the inlet passage of the valve, the vacuum in the pocket will serve to draw the wet starch into the pocket, thereby insuring that each pocket will be completely nlled and thereby provide a relatively uniform feed of wet starch into the drying chamber.

When the said valve structure is used as a discharge valve for the dry starch, the air valve 96 is closed and an opening is tapped at thelocation indicated by the numeral 91 for a suction line Il. The other end of the suction line is tapped into the vapor discharge passage 2| from the drying chamber. The air in the empty pocket is therefore withdrawn before the pocket movesinto a position to receive a charge of dry starch .from Bywithdrawing they air from the empty pocket in the manner thus described, `there is no interference to the movement of the dry starch in the discharge passage, nor formation of starch dust clouds, such as would take place by sudden expansion of air if the air were not exhausted from the valve pockets.

'I'he operation of the drying apparatus may be summarized as follows: a vacuum is maintained in the drying chamber by means of the evacuator I I. The rotary inlet valve I2 receives a charge of wet starch from the source of supply and discharges it into the drying chamber; this discharge being effected quickly by, reason of the atmospheric pressure which enters through the air valve 96 above the charge of wet starch. Any atmosphere entering the drying chamber with the wet starch is immediately discharged from the drying chamber through the vapor outlet 2| before the said air cancome inw contact with the partially dried starch. Before the valve pocket is moved out of communication with the interior of the drying chamber, a vacuum is created in the said valve pocket. This condition hastens the recharging of the pocket with wet starch when it moves into communication with wet starch sup- The wet starch discharged from the inlet valve drops onto the upper table il and is spread over the upper surface thereof by means of theangularly disposed scrapers |1 and is at the same time moved outwardly toward the periphery of the table i3 where it is discharged onto the outer portion ot -the underlying table il. It is spread over the table Il in the same manner as previously described and is moved inwardly toward the central'discharge opening 2l, where itis discharged onto the next underlying table i3. This spreading and movement of the starch is carried out in connection with its movement over each of the tables until it is discharged into the collecting channel 45 in which it is moved by the starch dust is held in suspension in the air. The

vapor emitted from the drying starch is discharged irom the top of the drying chamger. In its movement to the discharge passage 2| the vapor passes in contact with the bottom surfaces of the steam heated drying tables and is thereby super-heated to a temperature which will prevent condensation. In order to further guard against condensation of the vapor, the walls of the drying chamber and the discharge valve or any part thereof may be covered with insulation, for example, as indicated at 99 in Fig. 1. The rotary discharge valve I2* being operated by gear connections |00, lill and |02 with the vertical shaft i9 operates at a predetermined speed with relation to the starch distributing and forwarding mechanism. Ordinary commercial starch contains from 10 to 14 per cent of moisture. 'Ihe moisture content of the starch dried in the present apparatus can be varied at will by varying the amount of vacuum contained in the chamber, by varying the steam supply to the drying tables or by varying the speed of movement of the starch through the drying apparatus. The degree of dryness can be maintained at any fixed point because the starch, as it passes over the tables, is maintained in a pulverulent state by means of the lump disintegrater i8.

While the present invention illustrates as a preferred construction an arrangement and construction of tables together with distributing and forwarding means for moving the starch across the f tables transversely of the drying chamber, it will be obvious Vto personrsfamiliar with the art that the said mechanisms might be'constructed to operate so as to give a different movement to the starch than is described herein. It may be understood, however, that the present invention contemplates all modifications in structure coming within the scope of the appended claims.

The improvements of the inlet and discharge valves |2|2n are shown and described herein for the purpose of making a full disclosure of the drying apparatus-as a whole. However, I do not claim herein the said valve improvements per se, since these Yimprovements are disclosed and claimed in my copending' divisional application Serial No. 186,946, filed January 26, 1938.

I claim:

l. In apparatus for drying pulverulent and adhesive materials, the combination of a drying table positioned to receive a continuous supply of material to be dried, means for moving the material over the table, and means for disintegrating the lump portions of the material so as to. insure uniform distribution and movement thereof; said disintegrating means comprising a roller structure, the peripheral portion of which includes a plurality of separately movable roller bars of helical configuration whereby the configura-tion of the bars disintegrates the lump material without compressing the same and relative movements of thebars effects a self clearing action.

2. In apparatus for drying pulverulent and adhesive materials, the combination of a drying table positioned to receive a continuous supply of material to be dried, means comprising a plurality of angularly disposed scraper elements for agitating and forwarding the material over the table, and means for ,disintegrating the lump portions of the material so as to insure uniform distribution and movement thereof; said disintegrating means comprising a cage roller structure, the peripheral portion of which includes a plurality of roller bars of helical configuration which are spaced apart and separately movable, whereby the conguration of the bars disintegrates the.

lump material without compressing the same and the separate movements of the bars effect a self clearing action.

3. In apparatus for drying pulverulent material, the combination of a closed drying chamber having a transparent window closure for facilitating the inspection of the material being dried, means for maintaining a vacuum in the chamber, means utilizing the difference in the internal and external air pressures for removing deposits of dust from the innersurface of said window closure comprising an air nozzle positioned to direct air into contact with the inner surface of said window closure and a hand valve for opening said nozzle to admit inflow of air under atmospheric pressure.

4. A starch drying apparatus comprising, in

combination, a drying chamber, a plurality ofl ing in the form of relatively flat steam chests, each formed with a plurality of concentric passages of substantially equal length for distributing the steam throughout all portions of th'e chest.

5. A starch drying apparatus comprising, ,in combination, a drying chamber, a plurality of drying tables positioned inthe chamber in vertically spaced relation, and means for spreading the starch over the several tables and discharging it from one table onto another; the said tables being in the form of relatively at steam chests, each formed with a plurality of concentric steam passages for heating substantially uniform areas of the chest and communicating with a common steam inlet and having separate discharge openings, whereby the steam is distributed throughout the chests in accordance with the requirements of the several passages thereof and the condensate and the 'non-condensible gases in each passageis discharged therefrom through its discharge opening.

6. In a continuous drier for pulverulent and adhesive material, the combination of a closed chamber, a pluralityr of circular steam heated dry- -grators comprising cone shaped cage rollers for

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