US2555516A

US2555516A - Spray drier

Info

Publication number: US2555516A
Application number: US72427A
Authority: US
Inventors: Alan C Stoneman
Original assignee: Purex Corp Ltd
Current assignee: Purex Corp Ltd
Priority date: 1949-01-24
Filing date: 1949-01-24
Publication date: 1951-06-05
Anticipated expiration: 1968-06-05

Description

n 5, 19 1 A. c. S'i'ONEMAN 2,555,515

' SPRAY DRIER Filed Jan. 24, 1949 ALAN C: STONE/WAN I 0 4 IN VEN TOR.

HrroeusK Patented June 5, 1951 UNITED STATES PATENT OFFICE SPRAY DRIER Alan C. Stoneman, San Marino, CaliL, assignor to Purex Corporation, Ltd., South Gate, Calif., a corporation of California Application January 24, 1949, Serial No. 72,427

12 Claims.

This invention has to do generally with drying systems operable to separate and substantially solidify materials out of fiuid mixtures or solutions by vaporization of the liquid solvent or carrier. Particularly the invention is directed to improvements in spray drying equipment wherein a fluid or slurry composition containing the material to be recovered is subjected to extended surface contact with air and resultant concentration of solids, by spraying the liquid downwardly within a chamber and concurrently or countercurrently with a drying air stream.

As illustrative, the invention is applicable to the spray drying of materials capable of solidification in the form of hollow globular, porous or cellular particles characterized by their friability, and hence requiring carefully controlled handling to prevent their disintegration and dusting. Typical of such materials are solidifiable detergents including various soaps and wetting agents, such as the aliphatic sulphates and sulphonates, alkyl aryl sulphonates, generally the sulphated or sulphonated petroleum derivatives, or derivatives of alcohols, ethervs,

esters or amids, etc. Also contemplated is the cooling or drying of proteins (e. g. eggs) and the like, as well as inorganic substances such as,

200 F. to 350 F., for an extended period of time.

Also particularly contemplated are improvements in a continuous course of drying whereby the product is conditioned against physical deterioration during and following its collection from the spray drier, by first assuring its reduction to a state of substantially completed dryness or rigidity, in the absence of which the product may be subject to excessive dusting. It is found that where required cooling of the product is permitted to continue after collection of the particles on a conveyor or thereafter in storage, marked deterioration occurs by reason of such efiects as lumping, and weakening of the particle structure upon crystallization of its salts (typically in the case of solid detergents) as cooling and drying proceed to completion. In accordance, with the invention, theproduct particles are subjectedto such rapid and complete cooling and dryingwhile in divided or suspended condition as to assure attainment of the desired final structure and condition of the particles in advance of their collection and storage. Thus the product may quickly attain not only a stable physical form but also chemical stability immediately upon drying, thus avoiding degradation (e. g. nutritionally) of such products as the amino acids, which suffer from being subjected to excessive or prolonged heating.

The invention has the further and important practical advantage of substantially increasing the capacity of a given size drier, in that the ability to accomplish quick and thorough final drying of the product all in a continuous drying sequence, permits a material throughput considerably greater than the capacity of the conventional dryer whose throughput is primarily limited by its inability to accomplish final drying comparably in time or thoroughness.

structurally, the invention is directed primarily to final drying of the product after its travel down through a spray chamber during which the bulk of the liquid content of the material may have become vaporized and the product approaches substantially solid form. The invention is predicated upon the concept of then contacting the product with such quantities of atmospheric air as may be required for quick cooling and drying, and while the particles are caused to have such gentle falling motion as will prevent their disintegration. Specifically the particles falling from the spray chamber are directed desirably in a series of downwardly cascading, streams, preferably of annular form. transversely through which streams of atmospheric air are passed, as by induction into a chamber at the inside of the stream series.

All the features and objects of the invention, as well as the details of certain illustrative embodiments, will be understood more fully and to best advantage from the following detailed description of the accompanying drawing, in which:

Fig. 1 is a view showing in side elevation a spray drier representing one embodiment of the invention, certain portions of the structure appearing in section;

Fig. 2 is a fragmentary enlargement of the bottom portion of the structure shown in Fig. 1;

, and

Fig. 3 is a fragmentary sectional view illustrating a variational embodiment of the invention.

or forced from conduit II a flow of air which 2 passes downwardly through the chamber as hereinafter described, to the induction outlet conduit during the course of their concurrent flow to thev bottom of the chamber.

The drying chamber bottom is formed by 'a'n" ,1

inverted frusto-conical section lqhaving a discharge opening l from which the air stream. is

discharged into an annular'space is within the concentrically spaced, frusto-conical outer duct or jacket l'l. Upon entering thespace [6, the air stream undergoes a flow reversal so that by virtue of gr avity and inertia effects, the incompletely dried product particles travel. on downwardly to the, bottom of. the secondary chamber [8. c The inductionconduit l2, which, may be connected to a 'suctionblower (not shown) communicates with the air passage l 6 at circularly spaced intervals through theseriesof ducts indicated at [9.

As previously indicated, upon discharge from the spray chamber throughopening I5, the particles have lost most of their liquid content but nevertheless may be still sufficiently cohesive that if permitteddirectly to drop onto the conveyor and thencetaken to storage while in heated and'incompletely dried condition, the particles would tend tolurnp together and deteriorate upon crystallization of their salts, all as mentioned in the introduction. Also if given no accelerated cooling, certain classes of materials would undergo chemicalimpairment as aresult of prolonged maintenance of the particles at elevated temperatures'. Accordingly, in order to insure the product against either physical or chemical degradation, I provide. at the bottom of the secondary chamber I8 a cooling arrangement generally indicated at 2| which assures immediate completed solidification and chemical stabilization of the product. V

,, Referring now to Fig. 2, opening 22 in the bottom of the air jacket I? contains a vertical coaxial conical baffle 23 centered with relation to cles, excepting those reduced to dust size being withdrawn-in thegair streams going to the ducts f9, 'fallIupon "and are uniformly deposited about the-baffle 23. Below this baffle is a series of suitably supported angularly reversed conical bafiies 2 3, 24 amaze, three being shown as typical, in 00- axial alinement with a fourth bafiie 26 discharging into the collector baiiie 2l and thence onto the conveyor 20. Thus annular streams of the product flow from opening 22 downwardly in a series of cascading streams in passing over the baflie'series 23 to 21 and in falling through the spacesbetween them. The bafiie angularities and their diameters preferably are such in relation to the quantity of material flowing over them, that the material is subjected to such low viscosity and gentle deflecting eiiects as not to rupture the hollow bead-like or globular form of theparticles, thus reducing any dusting tendencies to a minimum.

In the course of its cascading flow downwardly over the bafiie series, the product is cooled by. mechanically created drafts of atmospheric air flowing transversely through the product stream 3M0 the conical bafile wall.

' By controlling the rate of air induction into the pipe, the rate of atmospheric air flow in- -Ward1y. through thebafiie series and cascading product streams may be so controlled as to eifect quick final cooling of the product to the temperalture desired, while simultaneously drying the particles' to give them the necessary hardness that c the axis of opening I5 so that the product partia willprevent any consequental cohesion or disinagrarian at and beyond their deposition on the conveyor.

' Fig. 3 illustrates a variational embodiment of the invention, accordin to which the passage of final drying and cooling air through the prod-' not beyond the spray chamber outlet I5, is effected by atmospheric air induction into chamber It. Here I may use instead of the previcusly described continuous wall .baflie 23, a suction ofspaced conical baiiles' I33, 34 and 35 pcsitioned within the bottom outlet end of the jacket I! and in axially centered relation to the chamber outlet is so that the product is permitted to fall uniformly over the bafile series and in cascading streams from each to th baffle below. The reduced pressure in chamber I 8 causes the induction of atmospheric air upwardly within the

baflie series

133, 34 and35, and outwardly through the spaces '36 and 31 between jthem, and of course transversely, but in this instance outwardly throughthe cascading particle "streams. From the "lower, bafiie 35, the product may be dropped onto the conveyor 38, or otherwise collected. 7.

, It will be understood that the drawings are to beeregarded as 'illus'trative of the invention in certain of itsv typical and preferred forms,'and that various changes and modifications may be made without departure from the invention in.

its intendedspirit and scope.

Iclaim: t

1. A spray drier comprising a vertically ex-' tended'shell forming a drying chamber'and having a bottom converging to a discharge opening,"

means for spraying within saidchamber in contact withdrying'air therein, liquid particles pass 7 in downwardly withinthe chamber'to be dried to substantially solid particles, bafile means at said openingextending transversely of the path of the fallingpar'ticles and forming and direct-1 ing a stream of incompletely dried particles downwardly from saidfopenin'g, there being a cooling spacebelow said bafiie extending about an insidezone and through which the particles fall, ablower and a conduit connected to the blower and terminally positioned in proximate relation to said cooling l'space so that coolingair is displaced through the cooling space andthe falling stream from one side to the other side thereof.

, 2. A spray drier comprising a vert'ically extended. shell forming a, drying chamber and having a bottom converging to a discharge opening, means for spraying within'said chamber in contact with drying air therein, liquid particles passfall, a blower, and a conduit connected to the blower and communicating with said zone so that cooling air is displaced through said coolin space from about said falling stream inwardly therethrough into said zone.

3. A spray drier comprising a vertically ex- 7 tended shell forming a drying chamber and having a bottom converging to a discharge opening, means for spraying within said chamber in contact with drying air therein, liquid particles passing downwardly within the chamber to be dried to substantially solid particles, a vertical series of baiiies extending transversely of the path of the falling particles positioned at and directly below said opening, there being cooling spaces between said bafiies so that incompletely dried particles pass downwardly in a succession of cascading streams over the baffles and through the cooling spaces and in a pattern extending about an inside zone, a blower and a conduit connected to the blower and terminally positioned in proximate relation to said coolin spaces so that cooling air is displaced through the cooling spaces and the cascading streams from one side to the other thereof.

4. A spray drier comprising a vertically extended shell forming a dryin chamber and having a bottom converging to a discharge opening, means for spraying within said chamber in contact with drying air therein, liquid particles passing downwardly within the chamber to be dried to substantially solid particles, a vertical series of baiiles extending transversely of the path of the falling particles and exposed openly to the atmosphere at and directly below said opening, there being coolin spaces between the baflles so that incompletely dried particles pass downwardly in a succession of cascading streams over the bafiies and through the cooling spaces and in a pattern extending about an inside zone, a blower, and a conduit connected to the blower and communicating with said zone so that atmospheric air is drawn through said cooling space from about said cascading streams inwardly therethrough into said zone.

5. A spray drier comprisin a vertically extended shell forming a drying chamber and having a bottom converging to a discharge opening, means for spraying within said chamber in contact with drying air therein, liquid particles passing downwardly within the chamber to be dried to substantially solid particles, an upwardly convergent circular baflie within said opening forming and directing a stream of incompletely dried particles downwardly from said opening, there being a coolin space below said baflie extending about an inside zone and through which the particles fall in an annular stream, a blower and a conduit connected to the blower and terminally positioned in proximate relation to said cooling space so that cooling air is displaced through the cooling space and radially and uniformly through said annular stream from one side to the other side thereof.

6. A spray drier comprising a vertically extended shell forming a drying chamber and having a bottom converging to a discharge opening,

o 6 means for spraying within said chamber in contact with drying air therein, liquid particles passing downwardly within the chamber to be dried to substantially solid particles, an upwardly convergent circular baflie within said opening and an annular baille directly below and spaced from said circular baiile to form a cooling space between the baffles, incompletely dried particles being directed by said circular bailie in an annular stream falling through said cooling space onto said annular baffle and about a zone within the baflles, and blower and conduit means communicating with said zone and operating to draw atmospheric air inwardly through said cooling space and stream into said zone.

'7. A spray drier comprising avertically extended chamber having a bottom converging to a discharge opening, means for spraying downwardly within said chamber a liquid to be dried to substantially solid residual particles, means for passing drying air through said chamber, an upwardly convergent substantially conical bafiie within said opening onto which incompletely dried particles are deposited from said chamber and fromwhich the particles are dropped in an annular stream, a plurality of spaced coaxial frusto-conical baffles of reverse angularity below said opening and conical baffle and over i which the particles fall in a succession of cas cading streams, and a suction blower communicating with and drawing air from the interiors of said baffles and inducing separate streams of air inwardly between the baiiles and radially inwardly through said stream.

8. A spray drier comprising a vertically extended chamber having a bottom converging to a discharge opening, means for spraying downwardly within said chamber a liquid to be dried to substantially solid residual particles, means for passing drying air through said chamber, an upwardly convergent substantially conical baflle within said opening onto which incompletely dried particles are deposited from said chamber and from which the particles are dropped in an annular stream, a plurality of spaced coaxial frusto-conical baiiies of reverse angularity below said opening and conical bafile and over which the particles fall in a succession of cascading streams, and an induction pipe extending into a space within said baflies, air being drawn from the atmosphere inwardly between the baffles and through said streams into the induction pipe.

9. A spray drier comprising a vertically ex-- tended shell forming a drying chamber and having a bottom converging downwardly to an upper discharge opening, means for spraying downwardly within said chamber a liquid to be dried to substantially solid residual particles, said shell including a downwardly convergent wall spaced about said bottom of the chamber and having in its bottom a lower discharge opening and having also a suction outlet through which a now of drying air is induced downwardly through the chamber, upwardly convergent baffle means axially alined with said upper discharge opening and positioned in said lower discharge opening and in spaced relation to the wall edge forming the opening, and a conduit communicating with the inside of said bafiie means and through which a flow of atmospheric air is induced transversely and inwardly through a stream of incompletely dried particles deposited on and falling from said bafiie means.

10. A spray drier comprising a vertically ex! tended shell forming a drying chamber and havn a bottom conver in downwardly to a upper discharge openin means :for spraying downwardly within said chamber a liquid to be dried to substantially solid residual particles, said shell including a downwardly convergent wall spaced about said bottom of the chamber n having in its bottom a lower discharge opening and having also a suction outlet through which a flow of drying air is induced downward- 1y through the chamber, upwardly convergent bafiierneans axially alined with said u per opening and positioned in said lower opening and spaced relation to the wall edge forming the opening, atmospheric air .flow being induced to said suction outlet through a falling stream of incompletely dried particles deposited on said baflle means.

11. A spray drier comprising a vertically ex.- tended shell forming a drying chamber and haying a bottom converging downwardly to an upper discharge opening, means for spraying downwardly within said chamber a liquid to ;be dried to substantially solid residual particles, said shell including .a downwardly convergent wall spaced about said bottom of the chamber and having in its bottom a lower discharge opening and also having .a suction outlet through which a flow of drying air is induced downwardly through the chamber, upwardly conyergent baflie means axially alined with said upper opening and positioned in said lower opening'and in spaced relation :to the wall edge forming the opening, :a plurality of spaced coaxial frusto-conical bafllles of reverse tangularity below said conical bafille and over which the particles fall in a succession of cascading streams, and means for inducing atmospheric air inwardly between the bafiles and transversely through said streams.

.12. A spray drier comprising a vertically extended shell forming a drying chamber and havine e' batten conv nes downwa d y t a upper di a s o ni g m an f s ray n dcw war with n said chamb a l u t e d ied t substant al y s l d i al pa t c s, said .e in l dmg a downwardly c nvergen "spaced about said bottom of the chamber andhaying in its bottom a lower discharge open a of drying air is induced downwardiry throu h t ch mb up ar ly n ergent a le means axially a i-ned wi h d upper penand nes ticned n said lower op g an i spacd relation to the wall edge forming the open ng, a plurality of spaced coaxial frustoc nica lea-flies of rever ns e it b l w d conica baflle and ove wh the Pa tic e a n a suc es on o ca cadin am nd an lduction Pipe x e d a e a y i a Space in said baffles and thence upwardly therein, being drawn from the atmosphere inwardly between the bafiles, and through said streams into t e induct n ipe- ALAN C. STON-EMAN.

, REFERENCE rrE Ihe following references are of record in the file o this patent:

UNITED STATES PATENTS ing nd haying also a suction outlet through