US2054441A - Method and apparatus for drying liquid containing materials - Google Patents

Description

Sept. 15, 1936.

NETHODAND APPARATUS FOR DRYING LIQUID CONTAINING MATERIALS Filed" Jan 29, 1952 3 Sheets-Sheet 1 INVENTOR;

.Darzd .DPeebZes,

D. D. PEEBLES 2,054,441 I Sept. 15, 1936. 2,054,441

METHOD AND APPARATUS FOR DRYING LIQUID CONTAINING MATERIALS D. D. PEEBLES Filed Jan. 29, 1931 3 Sheets-Sheet 2- INJ ENTOR. Dav/0' 0. Peeblea;

a A TTORNE Y Sept. 15, 1936. PEEBLES 2,054,441

' 'METHODAND APPARATUS FOR DRYING LI UID CONTAINING MATERIALS Filed Jan. 29, 1932 3 Sheets-Sheet s INVENTOR. flan J A TTORN YS.

Patented Sept. 15, 1936 PATENT OFFICE- METHOD AND APPARATUS FOR DRYING LIQUID CONTAINING MATERIALS David D. Peebles, Eureka, Calif., assignor to Western Condensing Company, San Francisco, Calif., a corporation of California Application January 29, 1932, Serial No. 589,645

11 Claims.

This invention relates to the drying of liquidcontaining materials, by evaporation of liquid therefrom, and particularly to the dehydration of solid or liquid materials containing water, by

contact with a heated gaseous drying medium.

In the methods' heretofore used for this purpose, it has been customary to bring the material, in a state of suitable sub-division, into contact with a gaseous drying medium at a temperature sufficient to eifect removal of liquid from such material, but in many cases difiiculty has been experienced in obtaining a uniform degree of liquid removal from all the particles ofmaterial. This diificulty may be due 5 in part to difierences in initial liquid content of different particles of the material, in part to differences in size or physical structure of the par-- ticles, by reason of which the smaller particles,

or those particles which are of less dense structure, tend to undergo a more complete liquid removal than the larger or more dense particles, and in part to a failure to obtain uniformly efiective contact and uniform time of contact of all the particlesof material with the gaseous drying medium. These factors have frequently resulted in insufiicient drying of some of the particles of material, and excessive drying of other "particles, and in some cases have caused buming, hardening or other injury to some of the particles. Under such non-uniform conditions,

if it is attempted to insure drying of all the particles to less than a certain liquid content, by.

using a drying medium at sufliciently high temperature and providing a sufliciently long time 5 of contact to cause drying to the desired 'extent of even the largest and densest of the particles and the particles having the highest original liquid content, as well as those particles which are subjected to the least effective contact with the drying medium, the-result is not only an increase in cost of operation due to the greater amount of heat consumed in unnecessary and expensive heating of some of the more easily dried particles, but also, in many cases, serious injury to the material, due to heating of some of these particles to excessive temperatures, and to excessively prolonged treatment of such particles at these temperatures.

This latter objection is particularly serious in 50 the case of organic materials or other materials susceptible to injury by heat. For example, in the dehydration of certain vegetables and fruits, which has long been practiced for the purpose of preserving the same and reducing the weightthereof, it has been found that the flavor, appearance, and other properties are injuriously afiected if the material is subjected to excessively high temperature for an unduly long period. The same is also true in the treatment of heat sensitive liquid materials such as milk or milk 19 products.

The principal object of the present invention is to provide for drying liquid-containing particles in such manner to produce material of a uniform degree of dryness, regardless of variations in the size of such particles, and at a minimum cost.

A further object of the invention is to minimize the heat required to remove a certain amount of liquid from liquid-containing materials, and par- 0 ticularly from liquid-containing materials in the form of particles diflering from one another in size or physical structure, or in original liquid content.

A further object of the invention is to provide for the uniform drying, to any desired degree of dryness, of liquid-containing material susceptible to injury by heat, and to prevent any of such material from being subjected tohigh temperature for an excessive period of time. A particular object of the invention is to provide a method and apparatus for the above purpose, in which each particle of material is subjected to only such temperature and for only such length of time, as is required to efiect the-desired removal'of liquid from that particular particle.

A particular object of the invention is to obtain an eflicient and economical removal of liquid from materials containing the same, without causing burning, hardening or other injurious eifects on such material, and also without causing excessive heating or hardening of the surface of the particles of such material.

A distinguishing feature of the present invention is that the movement of the particles of liquidcontaining material through and out of the drying zone is controlled in accordance with the amount of liquid remaining in such particles, in such manner that, as-the liquid content of each particle is reduced to a certain desired point,

' such particle is removed fromthe high tempera- .ture zone and thus prevented from injury by continued subjection to high temperature and also prevented ,ilrom taking up additional heat from the drying medium.

A further distinguishing feature is that the liquid-containing particles are'subjected to heating and drying in an elongated drying chamber and that the temperature of the drying medium within said chamber is caused to be progressively reduced in the direction of travel of such particles therethrou'gh, and the particles are introduced first into -a zone of relatively high temperature and are progressively carried into zones of decreasing temperature in accordance with the degree 01' removal of liquid therefrom.

According to a preferred embodiment of the pension, The lighter particles are carried upwardly by the gas stream until the upward velocity or the gas is sufficiently reduced to just balance the force of gravity on such particles, while the heavier particles, namely, particles of greaterv size or inherent density. or having relatively high liquid content, remain in the lower portion of the gas stream and are subjected to the maximum temperature thereoi. As the liquid content of each particle, and consequently the weight thereof, is reduced, the particle is carried upwardly by the gas stream to progressively higher levels where it is subjected to further drying action by gas of progressively lower temperature, until the liquid content is'so reduced that the particle becomes sufliciently light to be carried to the top, of the ascending column of gas. The spent gaseous drying medium together with dried particles carried away in suspension therein, is conducted from the top of the ascending column to suitable means ior separation of the dried particles therefrom.

The liquid-containing material may be introduced at any suitable level in the ascending column, but is preferably introduced at or adjacent the lower end or said column.

I-- also prefer to provide means for producing vortical motion or the gaseous drying medium and suspended particles in the upper portion of the ascending column, such vortical motion being preferably effected by withdrawing 'a portion of the gaseous medium and suspended particles from one point in said upper portion and reintroducing the same at another point in said upper portion, such removal and reintroduction being carried out in a tangential direction with respect to the periphery-oi the ascending column, and inthe same rotative direction so as to maintain whirling or vortical movement of the gaseousmedium and suspended particles in the'upper portion or the column 'and cause prolonged contact oi the heavier particles of material with the drying medium, due to the greater tendency of such heavier particles to be thrown outwardly toward the periphery of the whirling gaseous medium by the action or centrifugal force. The gaseous drying mediumis caused to leave the ascending column through a restricted central opening at the top of the column and or less diameter than the column at the region of such vertical motion,

so that no particles are permitted to'be carried out through such openings until they are sumciently light to be carried inwardly by the gas against the action of centriiugal iorce. vMeans are-,also preferably provided for utilizthereof will be either apparent from such de-- scription or specifically pointed out.

The accompanying drawings illustrate typical forms of apparatus according to the present invention, and in which the method of my invention may be advantageously carried out. Refer- Fig. 24s a horizontal-section on line 2*! in Fig. 1.

Fig. 3 is a vertical section of the lower portion of the drying chamber showing a modified means for introducing divided solid material thereto.

Fig. 4 is a vertical section of the lower portion of the drying apparatus, showing a modification of such apparatus and of the material introducing means particularly adapted for the treatment of liquid materials.

Fig. 5 is a partly sectional side elevation oi amodified form of drying apparatus, in which the liquid-containing material is introduced at a level somewhat above the bottom of the ascending .as-a furnace or heat inter-changer indicated generally at I, a vertically elongated drying chamber Ill and a partial separator or concentrator 30 for receiving the spent gaseous drying medium and suspended dried material and eifecting a partial separation of such material from said drying medium and a concentration of such material in a relatively small proportion 01 such medium.- :The drying chamber is shown as comprising a vertically disposed casing of. circular cross-sec tion and having a height equal to several times its greatest diameter. Said casing is of upwardly increasing cross-sectional area throughout the greater portion of its height, increasing from a diameter d1 near its lower end lto a diameter d: near its upper end, which latter diameter may be for example from 2 to 6 or more times as great as the first-mentioned diameter. The height h of the casing, from-the point of lesserdiameter to the point of greater diameter is equal to several times the greater diameter, for example, said height may be from 3 to 6 or more timm as great as said diameter. This major portion or the casing therefore has the form oi as narrow, gradually tapering inverted irustum ofa cane.

The lower end oi the drying chamber is connected by a suitable entrance housing I l to the source of gaseous drying medium. Such entrance chamberis shown as being of elbow shapeandmay advantageously be orsomewhat greater diameter than the minimum diameter tho! the main drying chamber, so as to provide a restricted throat .l2 at the base of said drying chamber. Suitable means are provided for introducing the material to be dried into said drying chamber adjacent the lower end thereof and preferably at or near said restricted throat. For example, for'the treatment of solid material in divided condition, such means may comprise a hopper-like receptacle l3 having a spout I4 leading from the lower end thereof into a conduit 15 which extends into the entrance chamber II and is provided with an upwardly extending portion 16 opening at its upper end I1 into' the drying chamber at substantially the level of said throat. Said conduit preferably opens upwardly into the drying chamber and substantially centrally thereof. The conduit I5 may be connected at its other end to the atmosphere or to any suitable source of air or other gas at atmospheric temperature or at any other desired temperature, and at atmospheric or any other suitable pressure. According to a preferred embodiment of the invention, such conduit is open to the atmosphere, and'the necessary velocity of air therethrough for conveying the dividedsolid material into the drying chamber is created by the reduction of pressure produced at the restricted throat l2 due to the high velocity of the gaseous drying medium at this point past the open end I! of said conduit, the velocity of said gaseous medium at said point being sufficient to cause a reduction of pressure below atmospheric pressure. The delivery of divided solid material from the spout 14 into the gas stream in conduit l5 may be facilitated by inclining said spout downwardly and forwardly in the direction of gasn flow through said conduit and by providing said spout with an opening l8 at its lower end which is disposed forwardly in the direction of such gas flow.

The casing I0 is shown as provided with an upper end portion l9 formed as a frustrum of a cone, extending upwardly and inwardly from the point of maximum diameter of .said casing to a restricted centrally disposed outlet opening 20. Said opening 20 is of considerably less diameter than the maximum diameter (12, and may, for example, be approximately equal to the minimum diameter d1, The converging upper portion 19 is of considerably greater inclination to the ver tical than the main casing portion Ill, and is consequently of relatively small height as compared to said main casing portion. The interior of the casing I0 is shown as being entirely unobstructed between the restricted throat l2 at the lower end thereof and the central outlet opening 20 at the upper end thereof. A conduit 2| leads from said outlet opening 20 to the partial separator or concentrator 30, and is shown as opening tangentially into said separator orconcentrator, as indicated at 22. m Means are also preferably provided for producing vertical or whirling motion of the gas in the upper portion of the drying chamber, such means being shown as consisting of circulating means comprising a conduit 23 communicating substantially tangentially with the interior of the drying chamber adjacent the periphery thereof as shown at 24 and leading to a fan or blower 25 and a conduit 26 leading from the outlet of said fan or blower and opening substantially tangentially into said drying chamber adjacent the periphery thereof as shown at 21. The conduits 23 and 26 are so disposed as to respectively withdraw and reintroduce gas from and to said chamber in the upper portion of said chamber.

same rotative direction, so as to maintain an active whirling or vertical motion of the gas in the The conduit 23 is shown as disposed somewhat above the conduit 26, but this relationship is not essential to the invention. The vertical distance between these two conduits may be varied as desired, or the relative disposition thereof with respect to the height of the drying chamber may even be arator housing, from a level considerably above 0 the lower end, thereof downwardly through said lower end, and opens at its upper end into the interior'of the separator housing as shown at 35.

The point of communication of said outlet conduit with the separator housing may, for example, be adjacent the level of the lower end of the cylindrical portion 3! and is, of course. substantially centrally disposed with respect to said housing. If desired, a suitably shaped hood or baifle 36 may be mounted over the upper end of said outlet conduit, but spaced somewhat above the same so as to permit outward flow of gas into said conduit. The other end of said outlet conduit may lead, as shown, to a suitable device such as a fan or blower 31 for creating the desired 35 flow of gas through the apparatus. In case it is desired to remove any suspended particles which may remain in the gas discharged through outlet conduit 34. the discharge of said fan or blower may be connected by conduit 38 to any suitable means for collection of such material.

Another outlet pipe 39 opens substantially tangentially into the interior of the separator housing adjacent the periphery thereof and at or adjacent the lower end of the downwardly converging portion 32 thereof, and said conduit leads to a suitable device such as fan or blower 4| for withdrawing gas and suspended particles therethrough. The discharge of said fan or blower may be connected by conduit 42 to any suitable means, not shown, such as a centrifugal separator or filter, for separation and collection of the treated material from that portion of the. gaseous medium which is removed from the separator 30 along with such material.

In the operation of the above described apparatus the several fans 25, 31 and 4| are set in operation, and the furnace or other heating apparatus I is also operated, so as to cause gaseous drying medium at suitable temperature C to be delivered from said heating apparatus and containing water or other liquid, either chem-.

ically or physically associated therewith, is de livered to the feed receptacle l3' and thence through spout l4 into the current of air or other gas which is induced to flow through conduit.

15 by the reduced pressure created at the restricted throat l2. and suspended in said current of air or other Such material is mixed with and is carried thereby through said conduit and delivered ,upwardly through the opening I! into the lower portion of the drying chamber. Such material is thus brought into contact with the ascending column of gaseous drying medium. in said chamber and is simultaneously heated and carried upwardly thereby, the rate of such upward movement and consequently the duration of the drying operation being dependent upon 'the size and weight of the individual particles. The velocity of upward gas flow at the lower end of the drying chamber is suilicient to exert a great enough upward force to hold all the par-- ticles of material in suspension. Each particle,

approximately desired amount of liquid, so that each particle is caused to remain in the drying chamber'for whatever length of time may be necessary to reduce its liquid content to this desired point. Furthermore, particles of relatively high liquid content and consequently of relatively large weight are caused to remain at a lower level in the drying chamber than particles of relatively low liquid content, and are thus subjected to contact with the drying medium at relatively higher temperatures, since it be observed that the temperature of the gaseous drying medium progressively decreases in its upward' movement through the drying chamber due to transfer of heat to the solid particles 5 a feature which is of particular advantage in preand to utilization of such heat in evaporating liquid therefrom. Thus the temperature to which each particle is subjected, is progressively decreased, as the liquid content thereof decreases,

venting burning or other injury to the material being treated. when the liquid content of such material is relatively high, burning or injury is preventeddue to the rapid utilization of heat evaporating such liquid, and probably also dr{e in part to the presence of an envelope of liberated vapors around such particle; as the liquid content decreases the particle becomes more susceptible to injury by heat, but such in- 55 jury is prevented according to this invention by a corresponding reduction in the temperature to which the particle is subjected. As the particlesapproach the desired state of dryness, and when their susceptibility to injury by heat is a maxi- 50 mum, they-. are subjectedsonly to the relatively low temperature of the drying medium at or near the upperpart of the drying chamber; The automatic removal-of particles fro'mxthe zone of v highest temperature before the liquid content 05 thereof is reduced below a certain point also prevents excessive heating and hardening of the surfaces of the particles, which would not only result in direct injury to the product, in certain cases, but would also tend to prevent the desired 70 evaporation of liquid from the interior portions of the particles;

'Furthermore,-particles of relatively large size are moved upwardly within the drying chamber somewhat more slowly than particles of rela- 75 tively small size. as buoyant effect of the gas on the suspended particles increases to a less extent with increased sizeof particle than does the downward pull exerted by the force of gravity. This is advantageous, since somewhat more prolonged heat treatment is required to remove a given proportion of liquid from a largeparticle than from a small particle, due to the longer time required for the entire particle to become heated and also to the greater difliculty of escape of vapors therefrom. The same is also true of particles of relatively high specific gravity,

as" these particles are carried upwardly moreslowly than particles of relatively low specific gravity, and also require-more prolonged heat treatment due to the fact that they are generally of -a more dense structure and consequently giveup their liquid by evaporation less readily.

In the upper portion of the drying chamber, a portion of the gaseous medium is continually withdrawn tangentially from the periphery of the chamber through conduit 13 and reintroduced tangentially adjacent the periphery of said chamher throughconduit 26, and the gaseous medium in this portion of the chamber together with the suspended solid particles contained therein are thereby caused to whirl about the axis of said chamber at relatively high velocity. Any particles which might tend to pass through the drying chamber due to the initial upward momentum thereof, are caught in this whirling gas and; due to the relatively large weight thereof, are driven outwardlyby centrifugal force and are either recirculated with the gas through said conduits .23 and or are carried around with the whirling gas in the upper portion of the drying chamber until they are suiilciently dried so that their weight becomes sufliciently small to permit them to be carnied upwardly and inwardly by the gas, against-the action of centrifugal force,

' and to reach the restricted central outlet opening 20. I is, therefore, seen that the use of this restricted central outlet opening is of importance in connection with the whirling gas movement in the upper portion of the drying chamber, as noparticle can move inwardly to said opening and against the action of centrifugal force until its weight is reduced to a certain predetermined point corresponding to a certain liquid content.

It is evident therefore that both the force of gravity and centrifugal force are utilized according to this invention for controlling the duration of the drying action and for causing all particles to remain in the drying chamber for just sufficient time to dry the same to the desired extent.

The gas discharged through opening, together with the suspended particles carried thereby, passes through conduit 2] and enters tangentially into the separator 30. .Said gas passes downwardly with a whirling motion within the housing portions 3| and-32, and the major portion of the gas is drawn inwardly by the exhausting action of fan 31 and passes through opening 35 and conduit 34 to saidfan. However, due to the centrifugal action on the suspended particles, suchparticles are prevented from being drawn inwardly with the gas and are concentrated principally or wholly in the outer layer of the whirling gas and against the walls of the separator housing, and are eventually carried downwardly to the lower end of said housing and are drawn oil through the discharge conduit 39, together with a relatively small proportion of gas, by the action of fair 4 I. From said fan this concentrated suspension of solid particles in a relatively small volume of as is delivered through ing the vapors evaporated from the material beconduit 82 to the above-mentioned means for separating such suspended particles from this small volume of gas, and for collecting the dried material.

One advantage of the use of a centrifugal separator 30 of the down-draft type, such as abovedescribed, is that it provides for removal of both gas and separated solids from the lower portion of the separator, instead of requiring that a gas outlet flue be carried up above the top of the separator housing, as is the case in separators of the ordinary cyclone type. Since the drying chamber itself is necessarily of considerable vertical height, and since it is advantageous to have the conduit 2| extend substantially horizontally from a position above the drying chamber outlet opening 20 to the tangential inlet of the separator 30 in order to minimize the draft loss in said conduit, it is evident that a considerable practical advantage in the way of minimizing the total height of the apparatus is realized .by providing a separator of such type that no additional head room is required above thetop of such separator.

The temperature of the gaseous drying medium used, as well as the nature and quantity of such medium, may be varied in accordance with the nature and quantity of material to be treated and the amount of liquid to be removed therefrom. For example, in one specific instance where it was desired to substantially dry alfalfa containlng'approximately 75% water, good results were obtained by using furnace gases at a temperature of approximately 625 F. at the point of entrance into the drying'chamber. In any event the quantity of gas used and the initial temperature thereof should be suflicient so that the temperature of the gas at the outlet of the drying chamber and throughout the separating and collecting appa ratus is above the dew-point of the gas containing treated, so as to prevent condensation of liquid in any part of the" system. Preferably, the final temperature. of the gases is above the boiling point of the liquid which is to be evaporated.

For example, in the specific instance above-mentioned, the quantity of gases used was such that the temperature of the gas at the outlet of the drying chamber was approximately 220 F.

The relative quantity of gas circulated through the conduits 23 and 26, for maintaining whirling motion within 'the drying chamber, as compared to the total gas flow through the system may also be varied according to the requirements of a y particular operation. For example, in the drying of alkalfa as above-mentioned, good results were obtained by circulation of from 600 to 800 cubic feet of gas per minute through said conduits, while the total gas volume discharged through fan '31 (not including the relatively small quantity of gas discharged through fan II) was from 4500 to 4800 cubic feet per minute, both these volumes being calculated at approximately 220 F.

The upward velocity of the gaseous medium within the drying chamber, as well as the relation between the initial velocity at the diameter di and the final velocity at the diameter 412, may also be varied according to the nature. of the material to be treated and other conditions. For example, the initial upward velocity at thebottom of the drying chamber may be from 50 to feet or more per second, and the minimum upward velocity at the top of the drying chamber may be from A; to 1/20 of the initial velocity. It

will, of course, be understood that all of the above values are given only by way of example, and are not to be considered as limiting the invention to these particular values.

In the drying of alfalfa with the above-described apparatus, the alfalfa may be delivered to the receptacle IS in shredded, chopped or otheradvantageously be dried by this method are vegetables, such as carrots or the like, and various kinds of fruits, which may also be reduced to shredded or chopped condition and introduced in the same manner as described above for alfalfa.

Other means may be used for introducing the liquid-containing material into the drying chamber. For example, in Fig. 3, the feed conduit I5 is shown as extending'straight downwardly into a receptacle B5, to a position near the bottom of said receptacle, and divided solid material, such as one of the materials above-mentioned may be delivered to said receptacle as by means of screw conveyor 46, in such manner as to maintain a body of such material within said receptacle, as indicated at 41, up to or somewhat above the lower open end of conduit IS. The conduit l5 opens, as before, into the restricted throat I! of the drying chamber [0; in such manner that the reduced pressure created at said throat serves.

to draw the divided solid material from said receptacle upwardly through said conduit and into the drying chamber.

In Fig. 4 I have shown a form of feed means particularly adapted for use in the drying of liquid'materials, such as milk or the like, which contain solids in solution or suspension therein. In this case the feed conduit l5" extends downwardly into a receptacle 49, into which the liquid marelatively small size, I prefer to provide a pipe 53' which extends upwardly within the pipe 15',

through which air, steam, or other gas, may be introduced. Said pipe v53 terminates in an opening adjacent the opening of pipe 15", in the well known manner of spraying or atomizing devices of this type. a

For use in the treatment of liquids, I also prefer to provide means for introducing air or other gas at relatively low temperature into the drying chamber and between the ascending column of high temperature gas and the walls of said chamber; such relatively cool gas being also preferably introduced in an upward direction so as to form a protecting layer which not only tends to prevent contact of the'liquid material with the side walls but also to lower the temperature of the side walls sumciently to prevent burning or injury to any particles of material which may come in contact therewith. For this purpose, the lower end of the drying chamber In is shown as provided with a downwardly and outwardly extends upwardLv and inwardly toward the interior of the drying chamber.

In the treatment of liquid materials in this form oi apparatus, the liquid is drawn up through the conduit l" due to the reduced pressure at the throat l2". its such liquid emerges from said conduit it is atomized, or subdivided by the combined action of the gas admitted through pipe 53, preferably under suitable pressure, and the gas passing upwardly at high-velocity around the tip portion 52 of said conduit. The material thus introduced is heated, and liquid is evaporated therefrom in substantially the same manner as described above in the treatment of solid materials, and the apparatus acts as beiore to insure the desired degree 01' removal of liquid from all of the particles, without injury or excessive heating of any of the particles, due to the fact that the size and weight of the particles decreases as liquid is evaporated therefrom. -In

this way, the solids contained in milk, or other liquid products, may be recovered in dry pow-,

dered condition, without danger of injury thereto by excesively prolonged contact with gas at high temperature.

annular opening 5| passes upwardly along the walls of the drying chamber, as indicated by' the arrows at- 58, and assists in preventing the suspended liquid particles from. contactingsuch side walls and also in maintainingsuch walls at a suiilciently low temperature so that any particles which may come in contact therewith are not injured or caused to stick to said walls.

The remainder of the operation, including the 4 whirling of the gas and suspended particles in the upper portion of the drying chamber, the removal of the gas and dried particles from said chamber, and the subsequent separation "of such particles from said gaseous medium, may be cara ried out in substantially the same manner as above described.

The form of'apparatus shown in Fig. 5 com- I prises a vertically elongated drying chamber I 0 0! substantially the same type as shown in Fig. 1,

59 means Ila for introducing heated drying medium from any suitable source,..upwardly into the lower end of said chamber, and a flue 11a for conducting the spent drying medium and died particles from the upper end of said cham- The principal distinction of this form of apparatus from that shown in Fig. 1 is that the liquid-containing material is introduced into. the drying chamber at a level somewhat above so the lower end thereof. In case thematerial to be treated consists of solid material "in divided condition, the means for introducing such material may comprise a pipe BLopening into the interior of said chamber at a level somewhat above the lower end thereof, but ata considerable distance below the upper end of said chain'- Q bar, and preferably having its inner end portion ii directed downwardly. a stream of air or 1 other suitable conveying fluid may be introduced through said pipe, and the divided solid material, containing liquid which it is desired to' remove therefrom, may be introduced into'said lfluid stream by means of hopper I31; and spout 'a. It will be understood that any other suit-- 15 able means for introducing liquid containing ma- -vided with means for maintaining whirling mo- The relatively cool air drawn inthrough the terial. at an intermediate level in the dryin chamber may be substituted for the means above described. In case such material is .of a liquid nature, it may be either sprayed or atomized I directlyv into the gaseous drying medium at the li desired level or may be sprayed into a separate 1 stream oi conveying fluid, such as air, and carried therebyinto the drying chamber.

The apparatus may in this case also be pro- 10 tion of the gaseous medium and suspended material in the upper portion of the drying chamber. Such means may comprise, as before, a fan or blower 25a. and conduits 23a and 26a opening tangentially into said chamber adjacent the periphery thereof. In this case, however, the pipe 23d. leading from the drying chamberto the inlet of said fan is-shown as disposed at a somewhat lower level than the conduit 260 which leadsfrom the fan back to the drying chamber, but this relative disposition is not' essential.

In the operation of the form of apparatus last described the flow of drying medium into and through the drying chamber is substantially the same as before. The material to be dried, however, is delivered into the ascending column of drying medium at an intermediate level therein, and preferably in a downward direction. The lighter particles of such material are more quickly arrested in their downward movement and carried upwardly, while the heavier particles continue to fall 'to successively lower levels until-their downward movement is flnally arrested by the entrain- -ing efiect of the upwardly moving gas, it being understood that the upward velocity of the gas 35 at the bottom of the ascending column, that is, at the point indicated at 65, is preferably maintained sufilciently high to cause substantially all of the particles of material to be arrested in their downward movement and thus prevent the discharge of any appreciable quantity of such mae terial through the lower end of the drying chamber. The particles of material are, as before, carried to progressively higher levels in the drying chamber as their liquid content and consequently 45 their weight is progressively reduced, and are thus brought into contact with drying medium at progressively lower temperature. Furthermore, all

the particles are caused to remain within the drying chamber until their liquid content, and consequently their weightybeizomes sufliciently small to permit the same to be carried upwardly to the point of minimum gas velocity at the top of the drying chamber and thence out through conduit Ila. The whirling gas movement within the upper portion of the drying chamber also acts in substantially the same manner as before, to prevent particles of excessive weight and liquid content from being prematurely carried out of the drying chamber, and increases the period of subjectionof such particles to contact with the drying medium.

The apparatus shown in Fig. 6 also comprises a drying chamber II of substantially the same type as above described. provided with inlet means I id for delivering drying medium upwardly into the lower end thereof and outlet means Zia for conducting the spent drying medium and dried material from the upper end thereof. A pipe 62 extends downwardly into the drying chamber and is preferably disposed substantially axially thereof; and said pipe'opens at.its lower end 63 into the interior of 'the drying chamber at a level adjacent the upper end thereof. The material to be treated may be delivered through said pipe in any suitable manner, for example in a manner similar to that in which it is delivered through the pipe iii in Fig. 5. Any other means 'for introducing material of a solid or liquid nature, in divided condition, into the gaseous medium adjacent the upper end of the ascending column, may be substituted for the means above described. 7

In this case the apparatus is not shown as pro vided with means for maintaining whirling movement in the upper portion of the drying chamber.

' In carrying out the drying operation in this form of apparatus the material is delivered downwardly from pipe 62 into the drying chamber, as

indicated by the arrow at 64. The initial downdescend toa relatively low level in said column before their downward motion is completely arrested, while the lighter particles will descend to a less distance and will remain at relatively high levels in the drying chamber. As before, the upward velocity of the drying medium at the lower end of the drying chamber is suificient to substantially prevent outflow of any of the particles of liquid-containing material into the inlet means Ila, and such upward velocity progressively decreases throughout the height of the drying chamber, due to the increasing cross-section thereof. pended particles, the progressive movement of such particles to higher levels and consequently to points of progressively lower temperature, and the final removal from the drying chamber of particles whose liquid content is reduced to the desired point are carried out in this formof ap- V para us in substantially the same manner as above described, except for the eifect of the whirling movement in the upper portion of the drying chamber, which in this case is omitted.

I claim:

1. The method of drying liquid-containing materials which comprises establishing an ascend-- ing column of gaseous drying medium of upwardly decreasing velocity and temperature, introducing liquid-containing material in divided condition into said column so as to cause removal of liquid-from such material by evaporation and cause particles from which liquid is so removed to be carried upwardly in said column, the drying .region of such whirling movement.-

' 2. The method of drying liquid-containing, materials which comprises establishing an ascending column of gaseous drying medium of upwardly decreasing velocity and temperature, introducing liquid-containing material in divided condition into said column so as to cause removal of liquid I from such material by evaporation and cause par-.

The removal'of liquid from the susing such gaseous medium substantially tangentially into the upper portion of said column so as to maintain whirling movement in said upper portion about the axis of said column, and removing gaseous medium and suspended particles from said column above the region of such whirling movement, and separating such gaseous medium and suspended particles from one another;

3. The method of drying liquid-containing materials which comprises establishing an ascending column of gaseous drying medium of upwardly decreasing velocity and temperature, introducing liqu d-containing material in divided condition into said column so as to cause removal of liquid from such material by evaporation and cause particles thereof from which liquid is so removed to be carried upwardly by said ascending column, the drying medium in the lower portion of said column being caused to move substantially vertically upward, maintaining whirling movement of gas and suspended particles in only the upper portion of said column about the axis thereof, and removing gaseous medium and suspended material from said column above the region of such whirling movement and solely at a position disposed centrally of said column and wholly within an area of considerably less diameter than the maximum diameter of said column.

4. An apparatus for drying liquid-containing material comprising a vertical chamber of upthroat, means for introducing liquid containing .material in divided condition into the gaseous medium in the lower portion of said chamber, said chamber having an upwardly and inwardly directed opening at said restricted throat for introducing relatively cool gas upwardly into said chamber adjacent the side walls thereof at a level adjacent the point of introduction of such liquid-containing material, and means for removing gaseous medium and suspended particles from the upper portion of said chamber.

5. An apparatus for drying liquid-containing material comprising a vertical chamber of circular cross-sectionand of upwardly increasing diameter, means 'for introducing gaseous medium at relatively high temperature upwardly into the lower portion of said chamber, means for delivering liquid-containing material in divided condition into the gaseous medium within said chamher, meansconnected to the upper portion of said chamber for withdrawing gaseous medium therefrom and re-introducing the same tangentially into the upper portion thereof, so as to create whirling movement of gaseous medium and suspended particles in only the upper portion of said chamber and about the axis thereof, and means for removing gas and suspended particles from the upper portion of said chamber.

6. An apparatus for drying liquid-containing material comprising a vertical chamber of circular cross-section and. of upwardly increasing diameter, means for introducing gaseous medium at relatively high temperature upwardly into the lower portion of said chamber, means for delivering liquid-containing material in divided condition into the gaseous medium within said chamber, circulating conduit means communicating substantially tangentially with said chamber at two separate positions, fan means connected in said conduit means for effecting withdrawal of gaseous medium from said chamber at one of said removing gaseous medium and suspended particles from said chamber at a lating conduit means.

7. An apparatus for drying liquid-containing materials comprising a vertical chamber of circular cross-section and of upwardly increasing diameter, means for introducing gaseous medium at relatively high temperature upwardly into the lower portion of said chamber, means for delivering liquid-containing material in divided condition into the gaseous medium in said chamber, means at the upper portion of said chamber for maintaining whirling movement of gaseous medium and suspended particles in said upper portion of the chamber about the axis thereof, .means closing the upper end of said chamber and providing a restricted centrally disposed outlet opening whose diameter is considerably less than the maximum diameter of said chamber, and means .for removing gas and suspended particles through.

said outlet opening, said means for maintaining whirling movement in the upper portion of the chamber comprising conduit means opening at each end into said chamber tangentially and in Y opposite directions and at different levels, and fan means connected in said conduit means.

' 8. An apparatus for drying liquid-containing materials comprising a vertical chamber of circular cross-section and of upwardly increasing diameter, means for introducing gaseous medium at relatively high temperature upwardly into the lower portion of said chamber, means for delivering liquid-containing material in divided con-.

I dition into the gaseous medium within said chamber comprising conduit means opening at each "'tively cool gaseous edium upwardly into said her, means at the upper portion of said chamber for maintaining whirling movement of gaseous medium and suspended particles in said upper portion and about the axis of the chamber, said chamber having an upwardly converging portion at its upper end above the region of such whirling movement and extending from the point of maxi- -mum diameter upwardly to a restricted central outlet opening, and means for removing gaseous medium and suspended particles through said outlet opening, said means for maintaining whirling movement in the upper portion of the chamand is of considerably greater height than dlameg position above said circu-' ter and whose upper portion converges upwardly from the upper end of said major portion to a restricted central outlet opening, means for introducing gaseous medium at relatively high temperature upwardly into the lower end of said major portion of the chamber, the interior of said chamber being substantially unobstructed be tween said lower end and said restricted central outlet opening, means for delivering liquid-containing material in divided condition into the gaseous medium within said chamber, means connected to the upper porton of said chamber for withdrawing gaseous medium therefrom and reintroducing the same tangentially into the upper portion thereof, so as to create whirling movement of gaseous medium and suspended particles in bnly'the upper portion of saidchamber about the axis thereof, and means for removing gaseous material and suspended particles from said chamher through said restricted central outlet opening.

10. An apparatus for drying'liquid-containing 7 materials comprising a. vertically extending chamber of circular cross-section and of upwardly increasing diameter, said chamber increasing uni iormly in diameter from a point of minimum diameter near the lower end thereof to the upper end thereof, a frusto-conical member connected directly to the upper end of said chamber and provided at its upper end with a centrally disposed outlet opening, means for delivering heated gaseous medium substantially vertically upwardly into said chamber at said point of minimum diameter, means for introducing liquid-containing material in divided condition into the lower portion of said chamber, and means for maintaining whirling motion of the gaseous medium in the upper portion of said chamber, about the axis thereof.

through a restricted throat at the lower end thereof, the velocity of said gaseous medium at said restricted throat being sumcientto create a reduced pressure at this point, introducing liquid-containing material in divided condition into the ascending gaseous drying medium at the region of reduced pressure adjacent said restricted throat so as to eilect removal of liquid from such material by evaporation and cause particles thereof from which liquid is so removed to becarried upwardly in said column, introducing a relachamber adjacent t side walls thereof at a point of reduced pressure adjacent said restricted throat, and removing gaseousimedium and sup-. ported particles fromthe upper portion of said chamber. r

D. PEEBLES.

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