US2924887A

US2924887A - Dryer for granular, fibrous and like material

Info

Publication number: US2924887A
Application number: US559626A
Authority: US
Inventors: Jr William R Marshall
Original assignee: Proctor and Schwartz Inc
Current assignee: Proctor and Schwartz Inc
Priority date: 1956-01-17
Filing date: 1956-01-17
Publication date: 1960-02-16
Anticipated expiration: 1977-02-16

Description

eb- '16, 1960 w. R. MARSHALL, JR ,887

DRYER FOR GRANULAR, FIBROUS AND LIKE MATERIAL 1 Filed Jan. 17, 1956 3 Sheets-Sheet 1 FIG. I.

2 I Q9 1 IIIH HHHHMHIM g a INVENTORI WILLIAM R. MARSHALL JR.

BY War/7W ATTYS.

Feb. 16, 1960 w. R. MARSHALL, JR 2,924,887

DRYER FOR GRANULAR, FIBROUS AND LIKE MATERIAL Filed Jan. 17, 1956 3 Sheets-Sheet 2 INVENTOR WILLIAM R. MARSHALL JR.

ATT Y5.

Feb. 16, 1960 w. R. MARSHALL, JR 2,924,887 I DRYER FOR GRANULAR, FIBROUS AND LIKE MATERIAL Filed Jan. 17, 1956 s Sheets-Sheet :s

' FIG.

INVENTOR ATTYS.

Unit States Patent I 1 DRYER FORGRANULAR, FIBROUSAND ,1

LIKE MATERIAL William R. Marshall, In, Madison, Wis., assignor to I Proctor 8: Schwartz, Inc., Philadelphia, Pa., 3 corporaf tion of Pennsylvania Application January 17, 71956, Serial No. 559,626

.zc ar ns. (31. 34-57 I The present invention relates to dryers wherein a wet dispersible' material is introduced into 'a high velocity stream of gaseous dryingmedium, for example at 200- 800 ft. per second, which creates highly turbulent initial drying conditions to produce very high drying rates.

. The invention has particular utility in dryinggranuilar, fibrous and like material which can be fed and dispersed in a high velocity gaseous stream to'remove ex- 1 ternal and internal moisture.

, A primary object of the present mvention isto provide apparatus of the stated character which produces high initial turbulence and dispersion of the Wet material so that it dries in a very short retention time, thereby permitting higher initial drying temperatures, but at ,the same time, minimizing the possibility of product degradation.

, Another object of the present invention is to provide ,a dryer which effects drying of the material while it is dispersed, thereby preventing the formation of clumps in the finished product. Rapid dispersion in the wet state may obviate the need for subsequent size reduction. More specifically, the invention contemplates a dryer in which the high velocity fluid stream carrying the maimparting a special condition of turbulence as aresult of the combined efiect of the tangential and axial velocity components.

A further object of the present invention is to provide a dryer of simplified construction and operation in which the gaseous drying medium is the sole means for conveying the product in contrast to those dryers which depend on the motion of-mechanical parts for conveying the product. I e

4 These and other objects of the invention and the various features and details of the construction and operation thereof are more fully set forth hereinafter with reference to the accompanying drawings in which:

Fig. 1 is a vertical sectional view of one embodiment of a dryer-made in accordance with the present invention; I Fig. 1a is a fragmentary view of a modified discharge .arrangement for the dryer shown in Fig. l;

- Fig. 2 is a horizontal sectional view taken on the line 2-2 of Fig. 1;

Fig. 3 is a view similar to Fig. 1 showing a modified form of the invention; and,

Fig. 4 is a view similar to Fig. 1 showing a further modified form of the invention.

Referring now to the drawings and more particularly to Figs. 1 and 2 thereof, the dryer chamber comprises a generally cylindrical chamber 11 which is closed at its upper end by a top wall 12 and is formed at its lower end with a funnel-shaped bottom portion 13 terminating in a discharge; conduit 14.

ill?! accordance with the invention, heated gaseous drymg medium is injected into the drying chamber 11 from an injector in the form of a high velocity vortex chamber 15., As shown in Fig. l, the high velocity chamber "comprises a generally cylindrical inlet portion 16 and a generally cylindrical outlet nozzle portion 17 which passes centrally through the top Wall 12 of the drying chamber 11 as shown coaxially with the cylindrical chamber 11. The nozzle portion 17 may range from to /3 of the cross sectional area of the inlet portion 16 and to this end, the two portions are connected by a tapering mid-portion 18. By reason of the reduced cross sectional area of the nozzle portion 1. the drying medium introduced into the inlet portion 16 is substantially; accelerated as it passes through the nozzle porition, attaining an axial velocity in the range of 150 to 0 feet .per second and tangential velocities in this samerange, The high axial and tangential velocities of th e idrying medium in the portion 17 greatly contribute to thehigh efficiency afiorded by the invention, as will be more fully set forth hereinafter. I

Air is introduced into the inlet portion 16 of the chamber .15 in a tangential direction. To this end, 'an inlet conduit 21, as shown in Fig. 2, is disposed tangentially to the, inlet portion 16. As shown in Fig. l, airor other gaseous drying medium is supplied under pressure to the inlet conduit 21 by means of a blower 22 which forces the air through a heater 23, and from the heater into the conduit 21. Of course, the blower acting as an exhauster, maybe connected to the discharge conduit 14 to draw the air through the dryer, ora blower and exhauster may be used respectively at the inlet and the discharge. ends. As shown, the conduit 21 is cylindrical at its intake end 24 and is rectangular at its discharge end 25 where it joins with the inlet portion 16 of the chamber 15, although the intake end may be square or rectangular. The tangential arrangement of the conduit 21 imparts a swirling motion to the'air or other drying medium as it is introduced into the chamber 15, as suggested by the arrows in Fig. 1. e

In the embodiment shown in Fig. 1, the material to be'dried is introduced by suitable means into the air stream prior to its admission into the vortex chamber 15, and the subsequent injection of the air stream into the drying chamber '11. The material as it enters the vortex chamber 15 is picked up by -the swirling high velocity air stream and is. carried into the ,body of the drying chamber 11. In the illustrated embodiment, the feed means comprises a screw 28 which feeds the material into the conduit 21 from ahopper 29, but other feeding devices and methods are possible Within the scope of the present invention. Further, the location of the feed point can be located at different points prior to the inlet to the vortex chamber, depending on the particular problem involved. i e

In accordance with the invention, when the-airorother drying medium is introduced into the drying chamber 11, it expands into the greater cross sectional area of the drying chamber as compared to the reduced area of the nozzle 17; The expansion of the drying medium in the drying chamber reduces the velocity of fiow and gives a prolonged drying time to insure achieving .of the de-. sired final moisture content. At this point in the dryer, the drying medium has cooled sufficiently to remove any possibility of overheating the product. H

The swirling motion imparted to the air stream by the tangential inlet conduit 21 is maintained-throughout the drying chamber. The swirling motion in the vortex chamber 15 imparts both high turbulence'and a centrifugal force to the particles carried by the stream of drying medium, which combinedto break up clumps or masses of the material which may be present due to the moist condition thereof. The drying medium, as 1t enters the drying chamber, continues to exert a centrifugal force on the material as well as a dispersing action. The combined eifect of these forces insures that the material is continually subjected to intimate contact with the drying medium throughout the drying cycle. The rapid drying occurring in the high velocity of the type described herein.

When the material reaches the bottom of'the chamber 11, itis substantially dried. The dried material is *then exhausted with the air stream through the discharge conduit 14 to a separating cyclone or the like.

An-alternate discharge arrangement is shown in Fig. 1a. This arrangement effects separation of the product from the exhaust air stream within the drying chamber. To this end, the drying chamber 11a is connectedto the discharge conduit 14a through the down turned terminal portion of the conduit 14a This arrangement affords separation of the exhaust air from the product which falls by gravity to the bottom of the chamber 11a where it is conveyed away by a suitable'conveyor, such, for example, as shown at 30 in Fig. 1a.

-Another embodiment of the present invention'is 'illustrated in Fig. -3. In this embodiment of the invention, the drying chamber comprises a cylindrical body portion 31 which'communicates with an exhaust duct '32 by an inverted funnel-shaped upper section 33. i The lower portion of the drying chamber may taper inwardly as indicated at 34 and terminatesin a funnel-shaped bottom portion 35 which opens to a product conveyor 36, which may be of the screw type shown. ln this embodiment of the invention, the gaseous medium carrying the 'material to be dried is introduced into the drying chamber by an injector in the form of a vortex chamber 41 similar to the chamber 15. In this instance, the injector is inverted to direct the stream of drying medium upwardly-through the drying chamber. It should be noted that the inlet conduit 42* enters the inlet portion'43 of the vortex chamber tangentially as shown at 44 to effect a swirling flow of the medium in the injector. is of reduced crosssection to accelerate the flow of gases and solids prior to their admission into the drying chamber 31. The material to be dried is introduced into'the air stream in advance of the inlet conduit 42, for example by a screw communicating wi-th'a hopper'47.

Inthis embodiment of the invention,'as inthe pre- The exhaust nozzle 45 of the chamber viously described' embodiment, the gaseous medium conveyingthemate'rial to be dried is driven with a swirling movement and-isaccelerated in the vortex chamber 41. As 'itis exhausted-"from the vortex chamber into the drying chambenthe 'medium is greatly expanded, by reason of the greater cross sectional area of thedrying chamber. Thus,the material isacted upon by a violent expansion force resulting from" the centrifugal force in the vortex'chamber and is carried upwardlytoward the exhaust conduit 32.

The centrifugal force, in this instance, efiects a separation-of the *heavier particles from the gaseous stream and 'these particles fall to "the bottom of the drying chamber where they are'conveyed awayby the conveyor 36. These heavier particlesare cooled in the conveyor and advanced to a product receiver. The particles not' separated from the medium are conveyed through the exhaustdu'ct '32 to a'cycloneor other-"separating unitwhich collects the product from the gaseous medium.

' As'in the-previously described embodiment, the construction "describedherein permits-the use of a higher temperaturedrying medium than ordinarily used. In addition, the possibility of clumps forming in the dried "product are greatlyreduced-by the apparatus of the "52. The nozzle 52 comprises a cylindrical inlet portion 53, a converging portion,and a cylindrical outlet throat portion 54 which passes through the end wall of the drying Chamber 51, and through which the drying medium passes at high velocity. o

The inlet and outlet portion of the nozzle 52 has relative dimensions in the same range as the chamber 15 described above and operates to accelerate theair "stream prior to its admission into' the drying chamber. Preferably; the air issupplied to the chamber-52 under 20 56. Since the air is injected centrally of the nozzle heatand pressure, for example, by a heater-55 and fan 52, the air is not given a swirling motion, but it has been found'that the acceleration and turbulencein the throat of the nozzle 54 and the subsequent'expansion and deceleration in the dryer chamber. 51 creates a high degree of dispersion of the material injected into the '"air stream prior to its admission into the drying chamber51.

If desired, swirling motion may be imparted to the'air priorto the nozzle by installing stationary vanes in the duct section 53 of the nozzle 52.

In thepresent instance, the material is introduced into the'air'stream in the high velocity or throat section 54 of the nozzle 52. Thedrying medium in the high velocity section may be at reduced pressure. Howev'erfthe pressure at '54 will depend on the resistance to flow after the chamber 51. The illustration shows a: screw feeder 57 for the material fed from a hopper 58, but'any suitable feed means may be employed. As

the material from the feeder 57 enters the air stream, the velocity differential between the feed and air creates a high degree of turbulence which breaks up the material and disperses it into the drying chamber. This method permits the meet higher temperatures with a consequent reduction of drying time. From the drying chamber 51, the material is discharged into a separating cyclone or the like, for example, as shown'at'59.

While particular embodiments of the presentinvention have been herein illutsrated and described, it is not intended to limit the invention tosuchdisclosure but changes and modifications may be made therein and comprising a generally cylindrical dryingrch'amber, a

flow nozzle adjacent one end of said chamber, said nozzle having an enlarged hollow cylindrical inlet'pontion, a tapering midportion and a reducedelongated hollow cylindrical outlet throat portion for injecting the gaseous drying medium into said chamber, said elongated throat portion being positioned centrally in said chamber adjacent said one end coaxially with said chamber and being opened toward the opposite end thereof,- said outlet throat being smaller in cross section than" the cross sectional area of said cylindrical drying chamber to elfect an abrupt expansion of the gaseous mediumupon injection'into 'said chamber, a tangential: inlet conduit in the enlarged inlet. portion of said nozzle, means to intro duceheatedpr'es'surized drying medium into said nozzle through said inlet conduit to efiect a swirling movement ofsaid rnediumth'rough said elongated throat'portion, means to introduce said'material into said drying medium prior to 'its'passage through saidelongated outlet throat and'its'injecti'oninto said chamber whereby saidmaterial isthoroughly intermixed with said: heated drying medium and is heated thereby in said"elongatedoutlet throat,

and means at the oppositeend of said chamber-to exhaust the drying medium therefrom.

2. Apparatus for drying of fibrous, and like material, comprising an upright generally cylindrical drying cham ber, a tapered flow nozzle adjacent the lower end of said chamber, said nozzle having an enlarged inlet portion and a reduced cylindrical outlet throat portion for injecting the gaseous drying medium into said chamber,

"said throat portion being positioned centrally in said chamber adjacent said lower end coaxially with said chamber and being opened toward the upper end thereof, said outlet throat being smaller in cross section than the cross sectional area of said cylindrical drying chamber to effect an abrupt expansion of the gaseous medium upon injection into said chamber, a tangential inlet conduit in the inlet portion of said nozzle, means to introduce pressurized drying medium into said nozzle through said inlet conduit, means to heat said drying medium prior to its injection into said chamber, means to introduce said material into said drying medium prior to its injection into said chamber, means at the upper end of said chamber to exhaust said drying medium, and means at the lower end of said chamber to convey material away therefrom.

References Cited in the file of this patent UNITED STATES PATENTS 1,478,526 Merrell Dec. 25, 1923 1,840,857 Testrup et a1. Jan. 12, 1932 1,914,895 Peebles June 20, 1933 2,368,699 Arnold Feb. 6, 1945 2,435,927 Manning et a1. Feb. 10, 1948 2,460,546 Stephanoif Feb. 1, 1949 2,538,833 DeRycke Jan. 23, 1951 2,702,949 Parker Mar. 1, 1955 2,770,052 Morrison Nov. 13, 1956