Drier

June 2, 1936. o. s. anderson et al

2,042,979

DRIER

Filed April 18, 1934

Sheets-Sheet 1

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June 2, 1936

O. S. ANDERSON ET AL

2,042,979

DRIER

Filed April 18, 1934

Sheets-Sheet 2

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June 2, 1936.

O. S. ANDERSON ET AL

2,042,979 !Q

DRIER

Filed April 18, 1934

Sheets-Sheet 3

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June 2, 1936. o. s. anderson et al

2,042,979

DRIER

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June 2, 1936. o. s. anderson et al 2,042,979

DRIER Filed April 18, 1934 7 Sheets-Sheet 5

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June 2, 1936. o. s. anderson et al 2,042,979

DRIER

Filed April 18, 1934 7 Sheets-Sheet 6

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3nt>entors, ΟτΆ'77 S. J77r<Terso7i

8s ¢3 dttornegs.

June 2, 1936. o. s. anderson et al 2,042,979

DRIER Filed April 18, 1934 7 Sheets-Sheet 7

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Patented June 2, 1936

2,042,979

UNITED STATES PATENT OFFICE

2,042,979

DRIER

Orlin S. Anderson, Cleveland, and Raymond Tuttle Anderson, Berea, Ohio, assignors to The V. D. Anderson Company, Cleveland, Ohio, a corporation of Ohio

Application April 18, 1934, Serial No. 721,226

Claims. (CI. 257—92)

This invention relates to driers, and pertains more particularly to that type wherein the material to be treated is introduced at or adjacent one end of the structure and travels toward a 5 / discharge opening at the other end, the material during its movement being cascaded over a cage or series of heated pipes carried by a rotary structure located within a stationary outer casing. Mounted upon and movable over the pipes are 10 scrapers which act to remove any accumulated material from the pipes, and the manner of connecting and actuating the scrapers forms one feature of the invention.

In driers of the general type above described, 15; particularly where the material is adherent, the scraper elements, or certain of them, have a tendency to compact the material against the ends or heads which support the pipes. One of the objects of the present invention is to provide 20 means whereby this compaction is precluded, or, if it inheres, the compacted mass is disrupted so that the resultant pieces or particles may be readily picked up and cascaded.

With this and other advantages of structure 25 and operation in view, reference is had to the annexed drawings, wherein:

Figure 1 is a side elevation, with parts broken away, and the cover and pan in section, of the forward end of the drier, and illustrative more 3Q particularly of the variable feed mechanism, the driving means, and the exhauster or suction fan;

Fig. 2, a transverse vertical sectional view taken on the line II—II of Fig. 1;

Fig. 3, a plan view, partly in section, with the 35 cover or enclosing shell removed;

Fig. 4, a vertical sectional view of the intake end of the machine, illustrating more particularly the driving means for rotating the cascading drum and the heating pipes located therein, as 40 well as moving the scrapers to and fro over the pipes;

Fig. 5, a sectional view on a somewhat enlarged scale, illustrative of certain details of the mechanism employed for driving the scrapers back and; 45forth;

Fig. 6, a detail sectional view on the line VI—VI of Fig: 5;

Fig. 7, a vertical sectional view of the discharge end of the drier, disclosing the outlet for dried 50’ material and the means whereby the heating medium is caused to flow through the pipe elements;

Fig. 8, a detail sectional view on the line VIII—VIII of Fig. 10, of the annular spreader for 55 the compacted material at the discharge end of the apparatus and illustrative more particularly of its cross-section form and the manner in which it .is secured to the adjacent head;

Fig. 9, a transverse vertical sectional view, taken on line IX—IX of Fig. 4, showing the pan, 5. the drum and allied parts looking toward the intake end of the drier;

Fig. 10, a similar view, looking toward the discharge end and; taken on the line X—X of Fig. 7;

Fig. 11, a perspective view of the drum body; 10

Fig. 12, a like view illustrating two of the pipe scraper elements, showing the manner in which they are connected and also the attachment of the forward one (at left of figure) to the shaft employed to reciprocate the scrapers; 15

Fig. 13, a sectional elevation of the annular cone-shaped member employed to disrupt the compacted material at the discharge end of the drier;

Figs. 14 and. 15, transverse vertical sectional 20 views taken on the lines XIV—XIV and XV—XV, respectively, of Fig. 7 and illustrating more particularly the passages for the flow of the heating medium through one of the drum and pipe-supporting heads; and 25

Fig. 16, a longitudinal sectional view taken on the line XVI—XVI of Fig. 10, and depicting the passages just referred to, together with the pipes.

In the drawings, I denotes a base or frame upon which is mounted and secured a bottom 2 semi- 30 circular in cross section and closed by ends 3 and ¢, thus in effect forming a semi-circular trough.

Secured to the base I and extending along each of the upper longitudinal edges of the trough are angle irons 5 and 6, respectively, with one ele- 35 ment extending outwardly and forming a seat for a cover 7, Fig. 1. Said cover extends throughout substantially two-thirds of the length of the structure and stands well away at its upper portion from the drying means shortly to be de- 40 scribed, so that the vapor driven off as the result of the drying action can readily rise away from the material and thus preclude a cooking action in the drier. An exhaust fan 8 is connected to the upper portion of cover 7 and draws 45 off any vapors. A second and lower cover 9, Figs, 1 and 2, is employed to enclose the forward or intake end of the machine.

The heating pipes with which the material to be dried comes into contact, are denoted through- 50 out by. i I and are associated, with and serve to rotate the two heads 12 and. 13 through means later described. Said heads are located at opposite ends of the drying chamber (members 2, 3, 4, 7 and 9). 55

2,042,979

The construction of the head 12 is such that the pipes II extend through openings formed therein, or, more specifically, through openings formed in the inclined faces of the annular material spreader 14, which is cone-shape in cross section, (see more particularly Figs. 3 and 4), and which, in the form shown, is integral with the head 12. In the instant case, the pipes are shown as provided with blocks or closures ll^a inward of the cone-shape spreader or deflector 14, which blocks are permanently held within the pipe. This is brought about by abutting adjacent ends of pipe sections and welding the same together, and to a block I l^a which projects into the adjacent ends of the pipe sections. See Figs. 3 and 4.

By leaving the outer ends of the pipes open, air may freely enter the same and maintain those portions of the pipes which extend from the block outwardly through the deflector in a relatively cool condition. At the opposite end, the pipes extend through openings formed in a second cone-shape deflector or spreader 16 (see Figs. 7, 8 and 13), and are threaded into openings formed in the inner face of an annular exhaust chamber 17 formed upon or in the head 13. See more particularly Fig. 16.

A series of smaller diameter pipes 18 is connected with a supply chamber 19, Fig. 7, formed in head 13 extending into and through pipes 11, the opposite ends of the pipes 18 terminating short of the blocks I l^a (Figs. 3 and 4). Said pipes are preferably arranged in two spaced annular series, the pipes in each series being spaced from each other as most clearly indicated in Fig. 14.

The annular spreader 16, (see Figs. 7, 8, 13 and 16), is formed separate from head 13 and is secured to the inner face thereof by machine screws 21 passing through openings 22 and into threaded openings formed in the head. Head 13 is formed on its outer face with two concentric outwardly extending collars or annular flanges 23 and 24, to the former of which is secured an elongated and substantially tubular member 25. At its inner end, said member is so contoured as to be in communication with exhaust chamber 17 through the space between the collars.

A steam supply pipe 26 extends through member 25 in spaced relation thereto and is in direct communication with the supply chamber 19. A washer 27 secured to the outer end of collar 24 encircles pipe 26 and shuts off communication at that point between the inlet and exhaust passages. As will be best seen upon reference to Figs. 14, 15 and 16, the head casting 13 is so cored as to ensure proper flow of the heating medium.

Member 25 forms one of the axles or supports for the rotatable elements of the drier, (see Fig. 7). It extends through bearings denoted generally by 28 mounted and secured within a box-like housing 29, adjustably carried for alignment with the bearing elements at the opposite end of the mechanism by a rigid bracket structure 31. At its outer end, member 25 carries a stuffing box 32 into which pipe 26 is secured in communication with a steam supply 33. An exhaust pipe 34 also opens into the chambered portion of the box. Any suitable form of mounting for the head 13 may, of course, be employed with other features of the invention.

Heads 12 and 13 are secured to each other in rigid spaced relation by a drum, preferably of the form shown in detail in Fig. 11. It may be said to be formed of two metallic sheets 35 and 36, each of semi-circular form. One edge of each section is provided with an inwardly projecting flange 37, while the opposite edge is cut away to produce a plurality of arms 38, the ends whereof 5 are bent inwardly as at 39, said ends overlying the flange of the adjacent flange to which they are riveted or otherwise secured.

To each side of each of the arms, the metal on the downgoing side or edge of each of the ele- 10 ments 35 and 36 is bent outwardly, forming scoops or lifters 41 which act to gather the material from the lower portion of the drier and to introduce it into the drum through the longitudinally disposed openings formed to each side of the 15 straps. The drum at each end, see Figs. 3 and 11, is formed with a series of longitudinally extending arms or Angers 42, which overlie the heads 12 and 13 and to which they are rigidly secured.

As the drum is rotated, the material thus picked 20 up is cascaded onto the reel of heated pipe within the drum, where it is not only heated but to a great degree broken up should it be in masses. As will be seen upon reference to Figs. 9 and 10, the material as it drops will pass out through the 25 then lowermost opening and be again picked up by the next moving scoop or element 41.

To the inner face of each arm, and so positioned that they abut the respective annular spreaders 14 and 16, are wedge elements 43, V- 30 shaped in cross-section and inclined to the inner surface of the drum. In other words, each of : these elements presents an exposed inclined edge . which slants upwardly toward the outer end of the drum or the adjacent annular spreaders, and 35 two side faces which latter diverge toward the . end of the drum at which they are located. These wedge-shaped elements likewise act as disrupters or spreaders upon the material as the same is or may be compacted through the action of the 49 pipe scrapers. Said scrapers, see more particu- . larly Figs. 3 and 12, may be said to comprise a series of spaced plate-like members, annular in outline.

Three of such members are shown and are 45 numbered 44, 45 and 46, respectively, and each is . provided with openings as 47 through which the heating pipes 11 extend. These scrapers are not rigidly affixed to each other but are connected \ somewhat loosely by rods 48 having nuts on 50 their ends with spacing tubes 49 placed on the rods and intermediate adjacent plates. This manner of connection permits the scrapers to ac- commodate themselves to any moderate degree of sag of the pipes which may occur after ex- 55 tended use.

The length of the spacing tubes is made slightly shorter in the aggregate than the overall length of the rods 48 between the nuts secured upon the outer ends thereof, so as to GO provide a degree of lost motion in the movement of the scrapers back and forth. Being suspended ' loosely upon the rods, the scraper plates take different bearing positions on the pipes during the revolution of the same, thus securing a 65 scraping of pipes on all sides as the scrapers do not reach the same position on the pipes when a certain pipe is at a certain part of the arc of its travel around the center of the drier. Thus the weight of a loosely controlled scraper falls 70 against all sides of all pipes eventually in a number of passes back and forth over such pipes. In this manner, the pipes are kept free of accumulated material.

The reciprocation of the scraper elements and 75 the rotation of the drum, including the heads &lt; and; the pipes, are effected, through a mechanism about to be described, alii of the driving- paxts for producing such motions being: located outside ^{5 th}ScSper element 46 is formed with an pro j ecting annular flange 51, and extending inwardly therefrom are. a series? ofc spokes 52 winch terminate, at their inner ends: in. a hub-hte eleio ment 53; Said hub is.ffittedl on ttein^r reduced ¹ end· of a shaft 54; being keyed thereto as at 55.

cover Plate 56 of a diameter such as to cover the. shaft, end: as well as the adjacent end. of _ hub is· secured in place by a plurality of ap screws: 57 passing through the plate and into the shaft end. This plate,, white; assisting m se,~ Sring the hub to the shaft, likewise provides a cover and prevents, ingress: of material: undergoing treatment or the oil therefrom from.pass90 ing in between the shaft and hub. c.

It is to be noted that the edge of. eachspoke 52 which faces toward the head 12. is beveled brought, to a. sharp edge: 52^e„ see. Figs. 4 and; . It will also be apparent upon, an°

-’ > Fig. 4, that said edges, he parallel to the inner edge of webs 58, extending inwardly from the m ner face of: the head 12 and terminating m the centrally disposed cylindrical hub-hke element .

Extending, through the hub and surrounding 30 the adjacent portion of relation thereto is an elongated hollow shaft or sleeve 61, the same being keyed at 54-to.head. Ϊ2 and likewise to a gear· 62. The: hollow shaft adjacent gear 62 is, supported in a noted generally by- 63, secured to affix ber 64 of the machine frame·,, (see more particu ^1&amp; To provide a support, for the shaft 54 adjacent the head 12; the innermost end .of the hollow shaft 61 is cut out to increase its internal· diam- ⁴⁰ IS forming a. seat for a bearing sleeve 65. Collar 66 is mounted on the outer end of toe— low shaft and is. secured! thereon by an ^el®toent 67. Mounted within the collar or ,- are two contracting, rings 68 and 69, the ^J bearing directly against the; adjacent end of the Se e· and serving to proper position. Furthermore, the rings pre elude passage of oil along the shaft in either

- direction. The construction as above set forth, ^ϋϋ ensures a proper- support: for the. intake end of the drum and its allied parts, white still perm!ttog freT movement of the shaft 54 to. move the qeraners as will now be described.

-,-, outward of gear 62 ^the shaft extends through ' a bearing 71, composed of upper and lower se tions supported by affixed frame element 72 rath an intprnosed babbitt bearing i3.

mS η .is formed with an annular groove 74 exteriorly thereof and a transversely extending of 'the groove, the key, (see Figs. 5 and 6) , li e wise- extending through the seat formedm. th_ inner face of the babbitt at such point, which bab

,.- bitt in turn extends upwardly into a transversely “ Xdlta 0Pe»lW jUTn unner portion of the frame element 72. &amp; set screw 78 extends through frame element 72, and at its lower end contacts key 75 preferably ad- iacent one end thereof, thus locking the key against any movement under normal operation ^0ίΤ1Ϊ upperⁿportion of bearing 71 is provided with an Extension 79 and provided with a similar extension 81 and aligning

2,042,979 openings are formed therein. Mounted in each of these, elements: is a tubular “^emb^ ⁸?

83, respectively, preferably formed of hard stad and extending: through which is a shear pm. 8 produced, from: a softer steel.. This pin holdsthe 5, parts in the position shown under normal operation of the: machine, but should the scrapers become; wedged or prevented from their normal paths,, the member 71 to rotate,, thereby shearing pm 84 and thus djs- 10 connecting the parts and permitting tM member 71 to rotate so that reciprocation of shaft 54,. which is normally effected through means shortly to be described, is precluded. _

By placing set screw 78 toward one end of key 15 75 the part 71 is; not held against rotation when the shear pin is disrupted by abnormal ^eoncb' tions, as might be the case were the screw located directly^ over the center of the bearing and shaft. S Sto armwment ha, »«» trtwe a tendency to clamp the parts ^and to rotation of the member 71 when pin 84 is b^ken The babbitt is designed to stand a compression S of approximately 3000 lbs. Said .member 71 is provided with an integral projection 25 85 in which there is formed a vertically tosposed socket 86,. designed to receive the stem 81_ of a, follower or shoe 88. Member 71, rath which the follower 88 is: associated, may be termed the re^taFolkmer-88 is designed to coact with ^{a cylib} drical cam formed upon the ™^ter· portion of shaft 54, there being present right and left handspiral. grooves 89 and. 91, the grooves passing, info each other at their ends. . ., ⁰

A housing 92 is employed to enclose the shaft, _a~ seen in Fig. 4, the same; being: secured to element 71; Any suitable means may· be_employe. to impart: motion to the shaft, and in the instant case an electric motor 93 secured to member 6 40 in any suitable, manner is shown.

A shaft 94 driven by the motor carries affievel pinion 95 which meshes with the bevel gear 96 secured to a shaft 97, which latter lies parallel to shaft 54.. Said shaft 97 carries a pinto ^{93 45}which in turn meshes: rath: the gear 62 keyed to the elongated sleeve or hollow ^dnv1^ ,, Said shaft is likewise keyed to. the_ head, 12 through a key 54», and upon rotation of the shaft ttooX the gearing above described, rotary mo- 50 35 the- cage of heating pipes, and, of necessity, the scrapers which are mounted upon· said pipes. Thus it wilt be. seen that all of the movable eleSASL the «« «I»”¹»' “ from the shaft 61, and inasmuch as the- hub 53 £ £ye?W stall M. as _M SS, tion is likewise imparted to said shaft 5*.

As will· be readily appreciated, all of the mechanism tor actuating the shaft 54 is without the 60 drier proper and, consequently, is not subjected ^t° j£^eabove indicated,, the material to be treated is introduced, into the head end of the drierr _ adjacent head 12, and is discharged at thejapnosite end as through an opening 99, Figs.. Ί and 10 The material to be treated may be direttly introduced if so desired and the rate nassage of the material through the drier will be controlled by the rate of feed and Hkewise 70 by the inclination of the bottom 2 toward the rifarharffe ©nd; either or both. .

Tn the instant case, a feeding device, adjustable as to rate of feed is showm see may be said: to comprise a hopper 101 which 7o discharges into trough 102 in which is mounted a feed screw or worm 103 which underlies the hopper and terminates at the upper end of a chute 104, the lower end whereof stands in a 5 tangential relation to the drum on the downgoing side thereof, see Fig. 2.

The feed screw is actuated by a sprocket chain deriving its motion from shaft 97, the chain at the upper portion passing over a sprocket 105, 10 associated with adjustable and variable mechanism denoted generally by 106, to vary the rate of rotation of the feed screw or worm and consequently the amount of material introduced into the drier during any given period.

1·> As will be seen upon reference to Fig 1, the variable feed mechanism is such that it may be readily removed and a large opening left at the upper or intake end of the chute. This enables _o the introduction of material into the drier di-0 rectly from an attrition mill or other pre-treating mechanism.

It is thought that the operation of the machine will be clearly understood from the foregoing description, but a brief resume will be given.

Assuming that material is introduced into the drier by the feed mechanism shown in Fig. 1, or directly from an attrition mill, it would pass -n ^d°^wnwardIy onto the rotatable drum and even^uJ tually some of it will pass in through the openings in the side of the drum, assuming that one of said openings is uppermost at that time· otherwise, the material will pass to the bottom _ of the pan and be picked up by the blades 41 and cascaded over the heating pipes as the drum rotates.

During this operation, the scrapers are moved to and fro over the pipes, keeping the surfaces clean and free of any adherent material, which 4u. if permitted to rest thereon would cake and char, this latter assuming that the heating is sufficiently high to bring about such charring and possible burning action.

As the scrapers move to the left in Figs. 3 and ⁴ⁱ·»· 4, some of the material will be carried forward by the scraper 46 and as it nears the end of its stroke, that is when it comes within a short distance of head 12, there will be an accumulation _p,,„ ^{of ma}torial ahead of the same. This material <>υ would naturally be compressed by the scraper and prevent the scraper from reaching the end of its stroke were it not for the presence of the deflectors or disrupting elements 14, or 14 ., ^ad(t ⁸³’ ^or and 43, as the case may be, which °‘^J members serve to deflect the material inwardly and outwardly, as well as laterally, this latter by the members 43. So, too, the sharpened edges 52' of the spokes 52 coacting with the webs 58, tend to cut up or further disrupt any compacted material.

In this manner, any compacted material is disrupted and drops away from the scraper, and passes into the drum or through the opening in G5 the drum to the pan 2. The material is not carried by the scrapers in the sense that all the material in the drier is moved at one time there- ., -----------_uuuliuu( by; probably not more than 5% or 10% or there- ^material. However, actual feeding tests about of the material in the drier tends to com70 pact at the end of the scraper travel.

On some materials which are granular and not sticky, the scraper may possibly be omitted; however, wherever the material is adherent and may be compressed and sticks together, the de75 * Sectors or disrupters are found highly efficient

2,042,979

I so that the scrapers may be operated without ^! any stoppage or breakdown of the apparatus.

It is evident, of course, that the disrupting element at the discharge end of the machine where the material has become dried to the de- 5 sired extent may be omitted in some instances for when the material reaches this point it is no longer sticky or adherent, unless the material is sticky by nature even when moisture-free.

It may be stated that when drying material 10 for use in presses of the type shown in Letters Patent to Anderson, No. 1,773,771, and others of like import, the material is dried below atmospheric moisture. Most driers of which we are aware are made to dry from high percentages 15 of moisture, say 50% to 15%, down to 8% to 10% moisture, and on materials which are granularlike, such as whole corn, whole soya beans, whole barley, etc. When ground or rolled, there is produced a certain percentage of flour-like ma- 20 tenal which readily adheres to all surfaces, especially when the material contains moisture, or is damp. With the present drier, the moisture content may be reduced to below 1% to 2% moisture from products containing from 8% to 10% 25 moisture, the materials being usually introduced in a ground or rolled condition. In drying copra, for instance, with a view of expressing the oil therefrom, it is dried to A% to 1% moisture from 4% to 5% moisture. ₃₀

The scrapers are in these instances necessary to prevent sticking and crusting or burning of the material on the pipes, and to maintain the drier at as near maximum efficiency as possible.

In operation where steam say at 200° F. to 35 350° P. is used, depending upon the steam pressure employed, burning will take place if the mass of material becomes encrusted, producing charcoal in time, which when it falls off becomes admixed with the other material passing through 40 the drier and results in a dark colored meal and a dark colored oil.

• ^ch^arred material has been known to burst mto flame, which is both dangerous and costly to subdue By drying as low as we can with the 45 present structure, we also prevent the loss of considerable protein or ammonia from the material when subjected to high pressure in a press of the Anderson type.

It may be stated that when drying materials for 50 y^se_A^ln P^{resses of} the type shown in Letters Patent to Anderson, ^No· ^773,771, and others of like import, the material is dried below atmospheric moisture, and the process of drawing off the moisture or vapor as fast as it is evaporated 55 when drying before pressing, improves the protein content of the cake or meal after it is pressed m the type of press mentioned above By the usual process of cooking the meal preparatory to pressing in a hyraulic press, the cooking 60 action on the material has a tendency of changing certain of the proteins into an indigestible SgertMe^{16 the άΓΥίη&amp; Pr}°^{CeSS IeaTCS the prot}^ⁿUlgCollUlc,

The usual chemical analysis for protein does 65 *?®^{rence ln} Proteins contained in —----------- auvucti leeaing- tests carned out by various State experimental stations have proven this to be a fact. This is clearly shown in a bulletin published by the Ohio State 70 Agricultural Experiment Station at Wooster Ohio, entitled “Soybeans and Soybean Oil Meal’ for Pigs”, by W. L. Robison, Bulletin #452

It has also been found that the casein is nre- served in meals that are dried before pressing, so 75

2,042,079 that they may be used in the manufacture of casein glues. The usual cooking process on the other hand, cooks the casein so that it is not suitable to be used for glue.

δ Where the material is cooked, at high moisture content, some protein or ammonia is driven off in the form of vapor. When, however, the material is dried at low temperatures, as low in moisture as.above stated, this loss is practically eliminated 10 when it is further processed in a tempering apparatus and .press of the type:above specified. The temperature of the material passing through the drier will be regulated and maintained so that the.material will not reach-a. temperature above 15 boiling point, and in most cases, the temperature range will be approximately 150° F. The material does not stay in the apparatus for any .considerable period of time, fifteen minutes being all sufficient in most cases, and varying of course 20 with the material undergoing treatment.

As above noted, the member 7 stands well away from the drum so that the vapor can readily arise from the material and not produce a cooking action in the drier. This high domed section also 25 ..prevents the exhaust fan from drawing out the fine particles of the material, because the movement of the vapor is not rapid adjacent the drum.

As will.be readily appreciated from the description above given, if for any reason the movement SO of the scrapers should be impeded and they should become locked, the shear pin will be disrupted and the reciprocating movement of shaft 54 arrested. The shaft, however, will still continue to rotate so¹ long as the motor 93 remains 35 .in action.

The actuating mechanism for the shaft 54 employed.to reciprocate the same is relatively simple and as above noted, stands well away from the body of the drier so that it is not subjected :40 to temperature changes.

It has been, found that wet material, or material having a high moisture content, passing into the feed end of the drier, will bum upon the heating pipes between the head 12 and the nearest po45 -sition that the scraper 46 may assume with reference to said head, due to the fact that it is impossible to scrape the pipes at this point. This deposit grows in a relatively short time until it eventually obstructs the scraper 46 from com:50 pleting its stroke toward the head ί 2, with the re- suit , that; the shear pin is ruptured. When this occurs; it will readfiy be appreciated that the deposit whichhas accumulated upon the pipes, must be scraped off and another shear pin in55 stalled before the drier may be again put into operation.

By providing means whereby the outer ends of the pipes II may be maintained in a relatively cool condition, this caking or burning of the ma:60 terial is avoided. At the outlet end· of the drier such caking does not take place, by reason-of the fact that the moisture content of the material is so -lowered before it reaches that end, that the material will not adhere to the pipes or other :65 ..elements; to any considerable'extent.