US1763758A - Apparatus for subjecting materials to the action of indirect heat - Google Patents

Description

June 17, 1930. MCGARVEY CLINE APPARATUS FOR SUBJECTING MATERIALS TO THE` ACTION OF INDIRECT HEAT Filed June 17. 192e 5 slves-'sheet APPARATUS EOE SUBJEGTING MATERIALS To THE ACTION 0E INDIRECT HEAT vJune 17, 1930. MCGARVEY CLINE s sheets-sheet '2 Figld June 17. 1926 June 17, 1930. MQGARVEY LlNE I 1,763,758

APPARATUS FOR SUBJEGTING MATERIALS TO THE ACTION OF INDIRECT HEAT Filed June 17, 1926 Y A 5 Sheets-Sheet MGGARVEY CLINEv APPARATUS'FOR SUJECTING MATERIALS TO ACTION OF INDIRECT HEAT Filed June l7, 1926 .Tune I7, 1930.

Mull

Patented June 17, 1930 'I UNITED STATES PATENT OFFICE MCGAIWEY CLINE, OF JACKSONVILLE, FLORIDA, AssIGNOR To Woon PROcss COM- PANY, INC., OF EASTPORT, FLORIDA, A CORPORATION or FLORIDA APPARATUS FOR SUBJECTING MATERIALS T0 THE ACTION OF INDIRECT HEAT Application filed .Tune 17,

This invention relates to an apparatus for subjecting substances to the action of indirect heat, and has been designed more particularly for the destructive distillation of comminuted wood in the form of sawdust, pulp and chips, shavings, etc. Y

The apparatus of my present invention employs a structural principle disclosed and claimed in my former Letters Patent No. 1,589,838, dated June 22, 1926, wherein I have disclosed a retort characterized by the employment of a series of spaced superposed stationary heating plates, a rotatable shell surrounding the plates, scrapers resting on the plates and connected to and driven by the shell, means for admitting the stock to be treated onto the top plate of the series, means for passing the material from each plate to the next underlying plate, means for heating the material, and means for discharging the material from the lower end of the retort, My present invention employs the broad feature of stationary heating plates with means for depositing the material successively onto said plates, and a rotatable shell encircling the plates and constituting a driver for the scraper arms; but in my present invention I have provided a novel and improved means for heating the plates well adapted forl the use of gaseous products of combustion as a heatting medium, and adapting the apparatus for destructive distillation when the stock operated upon requires or is adapted to that type of distillation.

One structural feature of the present apparatus resides in hollow heating plates for supporting the material treated during the intermittent travel of the latter from top to bottom of the retort. Hollou7 heating plates of this character have'heretofore been used in a distillation apparatus, but considerable ditliculty has been experienced in effecting a thorough circulation of the gaseous heating medium through the plates so as to thoroughly and efficiently heat up the latter. Also former structures have not been adaptable to circulating a gaseous heating medium in large volume through the heating elements due to restricted areas available for the passage of the heating medium. Ample areas 1926. Serial N0. 116,520. i

for the passage of the heating medium have been obtained by increasing the size of the heating units which greatly increases the bulk and cost of the machine. One object of my present invention is to provide an im proved means for very thoroughly and effectively circulating the heating medium through the hollow plates, and for. increasing the area of passages for circulating the heating medium without increasing the size of the heating elements.

Another object of the invention is to provide an apparatus that with slight changes may be built to operate .either as a single stage apparatus or as a multiple stage apparatus; that is, an apparatus wherein the heating medium may be simultaneously admitted to all of the heating plates, or to one, two, three or more of said plates successively or in successive stages, as desired or required by the nature of the material treated, thus permitting having all the heating elements simultaneously in contact with a heating medium at a constant temperature or dividing the heating elements into groups maintained at different temperatures.

A further object of the invention is to provide, in a distillation apparatus using products of combustion from a. furnace as the heating medium, a novel combination of retort and furnace whereby the waste from the retort, when of a fuel-bearing character, suoli as coke or charcoal, may be delivered directly in whole or in part to the fire box of the furnace by the discharging mechanism of the retort, thereby saving much time and labor in the handling of the furnace fuel. fuel coming from the-retort being at the ignition temperature, burns immediately when ,itv comes in contact with the air in the furn'ace chamber, thus insuring a clean hotl fire and economy in fuel.

Other objects are to provide an improved structure of retort which will readily facilitate access to the interior thereof for cleaning and repairs; and to provide a new and simplified means for operating Scrapers of the heating plates which will permit the removal of the rotating outer shell of the retort from which the drive to the scrapers is The better understood by reference to the follow' ing detailed description, taken in connection with the accompanying drawings wherein I have illustrated one simple andpractical embodiment of the principle of the invention, and in which- Fig. 1 is an elevation, partly in Vertical section, of the complete apparatus;

Fig. 2 is a top plan View, omitting the foundation or base;

Fig. 3 is a transverse section, on an enlarged scale, taken on the line 3 3 of Fig. 1;

Fig. 4 is a further enlarged horizontal section taken in the plane of the line 4-4 of Fig. 5 just beneath the lowermost heating )late 1 F ig?. 5 is avertie-al section through the lower portion of the apparatus, including the rotatable support for the outer shell, the diseharger and the upper portion of the foundation on the irregular line 5 5 of Fig. 4, with the lowermost heating plate appearing in edge elevation;

Fig. G is an enlarged top plan view of one of the heating plates;

Fig. 7 is a half edge elevation and half vertical section of the heat-ing plate;

Fig. 8 is a vertical section through the charging mechanism;

Fig. 9 is a fragmentary Vertical section through one of the hand holes of the outer shell showing the edge portions of several heating plates, the Scrapers thereon, and the drive from the shell to the scrapers;

Fig. 10 is a horizontal section on the'line 10-10 of Fig. 9;

Fig. 1l is a vertical transverse section through the discharger;

Fig. 12 is a top plan View of a. pair of adjacent heating plates, illustrating the relation of the discharge openings therein; and

Fig. 13 is an edge elevation of Fig. 12, Viewed from the bottom of the latter.

Referring to the drawings, 10 designates a supporting base or foundation herein shown as of brick work and hollow to provide a fire chamber or furnace which may lsupply a heating medium in the form of gaseous products of combustion. On the foundations 10 are a series of piers 11, on top of which are mounted hollow radially disposed chairs 12 (Fig. 1) attached to the piers by anchor bolts 13 and themselves sup porting a base-plate 14. To the peripheral portion of the upper surface of the base-plate 14 is secured a. channel ring 15 provided at intervals with filler blocks 16, in which latter and the ring 15 are mounted studs 17 on which are journaled a series of flanged wheels 18; said ring studs and wheels constituting a turntable support for the rotary housing or outer shell of the retort. 19 designates as an entirety the cylindrical outer shell or casing of the machine, to the lower end of which is attached a ring 20 (Fig. 5) resting and riding on the wheels 18 and formed on its outer periphery with a ring gear 21, through which the shell is rotated by mechanism hereinafter described. Y

The base plate 14 is additionally supported on a central hollow pedestal or vertical eX- tension 22 of the brick work foundation, which at its lower end communicates with the combustion chamber of the furnace. In the structure of furnace herein shown', the fire box 23 is located eccentrically ol' the retort, and the gases of combustion flow there from through a circular flue passage indicated by the dotted lines 24, nearlyy entirely around` the axis of the retort,.entering the central duet of the pedestal 22 through a radial passage 25. The base-plate 14 also overlies the pedestal 22 and is formed with a central opening registering with the bore of the latter.

Mounted on the base-plate 14 coaxially with the latter and attached thereto and to, thepedestal 22 as by anchor bolts 2G is a foundation ring 27 which supports a series of superposed stationary hollow heating plates mounted within and coaxially with the rotating shell 19. The detailed structure of these heating plates, which are all substantially alike, is well illustrated in Figs. G and 7. By reference to these views itwill be seen that each of these plates is a circular hollow structure comprising an annular top wall 28 formed with a narrow neck 29 on its inner periphery, an annular bottom plate 30, at its outer periphery merging into the outer periphery of the top plate 28 and formed on its inner periphery with a short dependening neck 31 equipped at its lower end with an inwardly directed flange 32 adapted to rest upon and be attached to the neck 29 of the next underlying heating plate; the flange 32 of the lowermost heating plate resting upon and being attached to the top flange of the base ring 27 as clearly shown in Fig. 1. The interior of the heating plate is preferably subdivided by radial partitions 33 into a considerable number of sector-shaped chambers or compartments 34, the inner ends of which are open to an annular axial shaft or flue formed in part by the combined inner peripheries of the stack of heating plates, as shown in Figs. 1 and 7. Each heating plate is formed at one point between adjacent partitions 33 with a sector-shaped discharge open: l

tially entirely around said underlying plate before it encounters the discharge opening of the latter, with the shell 19 rotating in the direction in which the openings are staggered from bottom to top.

The topmost plate of the group, or, in a' Imiltiplestage apparatus such as that herein illustrated, the topmost plate of the group Vin each stage, is also formed with three or more inwardly projecting lugs 85 which may conveniently consist of integral extensions of the partations 83; and these lugs form supports for a group of inner shells 36, each pref-` erably, and as herein shown, having the form of an inverted frustum of a cone, each of these shells having at its open upper end a circumferential flange 87 resting on the lugs 35, by which the shell is suspended coaXially within the central opening of a group of underlying vheating plates, with its flange 37 forming a joint with neck 29'ofthe plate on which it is suspended These inner shells 36 form' the 'inner wall of the annular shaft or flue above referred to, their flanges 37 serving to divide the flue into a plurality of sections corresponding to the several v.stages of heating plates. In the instance herein shown three such shells are employed, cach having a depth corresponding to five heating plates, but manifestly the number of shells and the number of heating plates lserved thereby may be varied as desired. Mounted in each of the shells 86 are vertically spaced groups of radially extending tubes'38, the tubes of each group extending across the annular flue and passing .through the open inner ends of the several compartments 34 of the heating plate served thereby and extending nearly to the outer limit of the chamber of the plate. In the bottom of each shell 36 is formed a manhole. preferably of elliptical form as shown in Fig. 8-,. normally closed by a cover 89. The purpose of the elliptical form is to facilitate removal of the lower manhole cover through the manhole lof an upper shell whenever it may be necessary to clean or repair t-he tubes or other interior parts. From the foregoing it will be seen that the interior of each of the inner shells 36, except the topmost', communicates through its open upper end with theannular flue section of the next higher group or stageV of heating plates.

The outer rotary shell 19 is formed, preferably on opposite sides, with groups of vertical handholes 40 closed by covers 41, the groups on the two sidesbeing so relatively offset that access may be had therethrough to all of the heating plates of the stack, while said handholes may be utilized for the mounting of driving means for the scrapers next to be described.

Resting upon the upper peripheral pvor-v of said ring are radially disposed arms 43 that overlie the upper surface of the heating plate in sweeping contact with the latter, eX-

tending approximately to the hubs of the plates, with a slight clearance. Secured to the outer periphery of the ring 42 is a short lug 44 (Figs. 9 and 10) adapted tobe drivingly engaged by an inwardly projecting lug 45 formed on a strip 46 attached to one side wall of the handhole opening 40. By this simple device the rotating movement of the shell 19 is transmitted to the ring 42 and, through the latter', to the entire series of sweeper arms 43. To maintain the radial positionof the sweeps 48 against the load of the material and the friction on the plate, their inner ends are preferably threaded on a rod or wire ring 47 extending through the entire series of sweeps, as shown in Fig. 3.

Theinterior of the retort is sealed, preferably by means of the uppcrland lower liquid seals illustrated in Fig, 1. The lower seal is formed by an annular well formed between the ring 15 and an inner ring 48 mounted on the plate 14, and a rotating ring 49, attached to and depending from an annular plate 50 that is secured to the lower end of the shell 19, and extending into the well; the latter being filled with any suitable liquid. The upper seal is of' the same character, except that the well is formed on the upper end of the shell between the latter and an inner ring 51 attached thereto, while the ring 53 that dips into the well depends from a stationary covere plate 54.

Attached to and resting upon the hub of the topmost heating plate is a channel ring 55 to which the cover-plate 54 is attached, and said cover-plate 54 is centrally apertured to register with the lower end of a smokestack section 56 mounted on the cover-plate, the top or side ofwhich stack section may communicate with a discharge flue (not shown).

Into the cover-plate 54 is also fitted a discharge pipe 57 thatcommunicates with the annular space above the topmost heating plate and provides a discharge conduit for the Vapors and gases driven off from the material treated. A safety discharge pipe for the vapors and gases is shown at 58 in Figs. 1 and 5, the same being fitted into'the base-plate 14 and communicating with an annular chamber 59 formed between the base ring 27 and the inner wall 48 of the lower seal. The top wall of the chamber 59 is formed by an annular' plate 60 secured at its outer edge to the inner wall 48 of the lower seal and, on its inner periphery,formed with an upstand-ing circular flange 61 encircling but spaced from the ring 27 and the neck of the lowermost heating plate, so as to provide an angular flow passage downwardly' for gases or vapors into the chamber 59. A portion of the flange v61 on either side of the discharged hopper is extend` ed up into Contact with the lower side of the lowermost heating plate, as shown at 61 in Fig'.5, so that gases and'vapors descending through the dischargeopen-ing in the lowermost heatingplate will be compelled to pass 5 somedistance laterally and rearwardly in a circular path to iind access to the annular chamber 59 through the arcuate port between the flange 61 and the neck of the heating plate. These gases and vapors, resulting for the most part from exothermic reactions in the material treated, are accompanied by cnosiderable dust, most of which settles on the annular plate 60; and to remove this dust I preferably attach one or more radial sweeper arms 60 to a depending flange 50 on the annular plate 50, by which the dust is scraped into the discharge hopper below described.

The discharge opening 33 ofthe lowermost heating plate directly overlies a discharge hopper 62 conveniently formed by down-4 wardly bent walls of the plate 60, and. the lower end of the hopper communicates through a neck 63 with an underlying dis,- eharger. This latter, which is best shown in Figs. 5 and 11, comprises a generally rectangular box 64 formed with a fixed vertical rear wall 65, a removable front wall or cover-plate 66, and a flat bottom wall 67. Directly below the box 64 is mounted, on the foundation 10,

the tubular housing 68 of' a conveyor screw 69. The opposite ends of the box 64 commu- -nicate with transverse openings or ports in the screw housing 68, as clearly shown in Fig.

5, and the side walls of the box, opposite said ports, are extended downwardly and inwardly as shown at 70 in Fig. 11 into contact with p the lower edges of the ports, thereby forming hoppers for passing the material directly into the field of action of the conveyor screw. At-

tached to the under side of the top wall of the box is a wear plate 71 portedto register with the hopperl neck 63, and mounted on the bottom wall 67 is a co-operating wear plate 72, the ends of which are lipped down across the ends of the bottom plate 67 to prevent endwise displacement. Between the wear plates 71 and 72 is slidably mounted a measured-charge valve comprising a block 7 3 having spaced vertical cells 74 and 75 adaptedto be alternately brought into register with the neck 63 and the discharge ports and hoppers leading to the screw. Adjusting screws 76 (Fig. 11) threaded through the bottom plate 67 into contact with the wear plate 72 permit upward adjustment ofthe latter to compensate for wear and thus maintain a snug sliding fit of the valve. The feeding mechanism at the top of the retort is best shown in Figs. 1 and 8 and comprises a tubular casing 77 mounted on the cover-plate 54 and equipped with a hopper 78, and a plunger 79 slidable in the casing 77 through wear rings 80 and packing81 adapted to carry lubricant. The inner end of the casing 77 enters a hood or cap 82 attached to the cover-plate 54 directly over the central opening of the latter.

The discharge valve 73 and the feed plunger' 79 are simultaneously operated through a connected operating mechanism herein shown as comprising a vertical roeking beam 83 pivoted between its ends at 84 to a bracket 85 secured to any suitable sup-- port, and links 86 and 87 connecting the lower and upper ends of said rocking beam to a stem 88 of the valve 73 and the feed plunger 79 respectively. lVhen discharging granular material, such as sawdust or comminuted wood, into the retort, the best results are ob` tained by retracting the plunger only part way across the throat oi the hopper, and on its forward stroke advancing it some distance beyond the throat of the hopper thereby sharply compressing the material and avoiding the bulging oi the material upwardly into the neck of the hopper as the plunger passes the same; this latter being avoided by reason oiE the fact that as the plunger retraets it leaves an empty space bcyond the neck of the hopper into which the succeeding charge can fall, and be moved before the compression stage is reached. lt will also be observed that the presence of the wear rings 8O leaves a small annular clear- 'ance between the plunger and its casing,

which avoids wedging of slivers between the relatively moving surfaces such as would tend to cause the plunger to stick. 'lhls clearance has the further advantage of admitting the ready backward escape of air squeezed by the plunger out oi the body of stock compressed by it, thus avoiding the carrying over ol' an appreciable amount of air into the retort with the stock.

It is also desirable to vary the size of the opening from the neck of the hopper into the plunger casing to correspondingly vary the size of each charge; and this may be secured through the employment et adjusting means in the plunger operating mechanism which varies the path of the plunger without varying the extent of its stroke.

A simple means for this purpose is that illustrated in Fig. 8 wherein Athe connecting link between the rocking beam 83 and the plunger is made lengthwise adjustable. Such link is herein shown as made up of an eye screw 89 pivoted `to the rear end of the plunger at 90, a nut 91 on said eye screw, a sleeve 92 at one end screwed into the nut 91, and a rod 93 litted into the sleeve 92 and connected thereby by cross-pins 94 and formed at its outer end with an eye 95 pivotally connected to the upper end of the rocking beam 83.

Any suitable or convenient mechanism for imparting power to the rotatable shell 19 and to the rocking beam 83 may be eru'iloyed within the purview of the invention, ut in Figures 1 and 4 I have illustrated a simple power drive for this 'purpose consisting of a power shaft 96.having at one end a crank 97 connected by a link 98 to the rocking beam 83, whereby the latter is oscillated; said shaft also carrying a bevel gear 99 meshing with and driving a bevel gear 100 fast on the lower end of a short vertical shaft 101 journaled in a bearing 102, said vertical shaft carrying a spur pinion 10S meshing with and driving the large gear 21 on the rotating shell 19.

lVhere the apparatus is used in treating material, such as wood or coal, yielding a Combustible residuum, a pronounced economy in operation maybe effected by delivering the spent material or residuum directly into the iire Chamber of the furnace; and for this purpose I have shown in Figs. 1 and 5 the casing 68 of the discharge conveyor screw formed on its lower side with a short branch 104 registering with a duct or port 105 through the portion of the top wall of the furnace forming the roof of the iire chamber 23. The amount of charcoal or coke thus delivered directly to the fire chamber may be regulated by a slide valve 106 controlling the branch 104. The charcoal or coke discharged from the retort is already at a high temperature, and as soon as it meets the oxygen in the fire chamber bursts into flame giving off the hot gases that are em- 'ployed as the heating medium in the retort.

This expedient thus effects a considerable economy not only of time and labor, but also of heat.

The mode of operation is probably apparent from the foregoing description of the structural features of the invention, but may be briefly outlined, together with some of the advantages thereof, as follows.

The material treated passes in successive charges through the charging mechanism onto the topmost heating plate of the series, and, under the rotation of the outer shell and the spreaders driven by the latter, is advancedv in a thin uniform film over the surface of the topmost plate, dropping through' the discharge opening thereof onto the next under` lying plate over which it is, advanced in the same manner by the scrapers of that plate, and so on from top to bottom of the series. By reference to Fig. 3 it will be observed that I preferably employ a large number of.

' scraper arms spaced at short intervals, which effect a very uniform and even spreading of the material in a thin layer and prevent the piling up of any considerable body thereof on the surface of the plate, thereby greatly conducting to the thorough and uniform heating of allthe particles of the material. Simultaneously with this intermittent or step-by-step downward progression of the material through the retort there is an upward iiow of the gaseous products of combustion from the furnace through the central annular Hue, the several heating plates, and

the inner shell or shells 36. In the multiple stage arrangement illustrated in Fig. 1, these heated gases flow first into thelowermost annular line section and thence into the heating plates of the lowermoststage, returning by way of the radial tubes 38 to the interior of the lowermost inner shell 86, From the latter the heated gases flow upwardly into the second annular flue section and through,r theseveral heating plates of the second stage, thence back through the tubes of that stage into the intermediate inner shell 3G, whence they flow upwardly and into and through the topmost annular flue section and the hollow heating plates of the topmost stage returning by way of the tubes of that stage into the topmost inner shell 36, whence they pass through the top ring 55 and flue section 56 to the discharge flue of the apparatus. 1t will be observed that the above-described structure presents an area for the passage of the heating gases equal to the area of all of the radial tubes that enter the pla-tes constituting one stage. Manifestly, the larger the number of heating plates in a stage the greater will be the number of tubes available for the passage of the flue gases, andA vice versa. The apparatus is thus flexible in point of construction to secure either uniform heatin of all the plates and a consequent uniform veating of the material throughout the retort, by employing only a single stage; or variable heating, and increased economy of the heat, byemploying a plurality of stages, wherein the material will be subjected to gradually increasing heat as it passes from the plates of an upper stage to' those of a lower stage.

vThe generated vapors are designed to be normally passed off through thetop outflow the lower seal, by opening a valve in said pipe or by providing the .latter with a safety valve.

1 have herein illustrated and described one simple practical physical embodiment of che principle of the invention more especially adapted to the distillation of wood and kindred oil-bearing products, but also advantageously usable as an apparatus for subjecting any kinds of material to the action of indirect heat for any of `various purposes,

such as drying; but it is manifest that the structural details may be widely variedto suitv the particular conditions and materlals treated without involving any departure from the essential principle of the apparatus or sacricng any of the benefits and advan tages inhering therein. Hence, I do nQt limit the invention to the particular embodiment herein presented, or to its use with any particular class of materials or the heating of the latter for any particular purposes, but re serve all such variations,l modifications and mechanical equivalents as fall within the spirit and purview of the appended claims.

I claim- 1. In a retort for distilling oil from solid\ substances, the combination of a vertical series of spaced superposed hollow annular heating plates open through their inner peripheries, an outer shell encircling said plates, an inner shell having a closed bottom and an open top, said inner shell extending through and spaced from the inner peripheries of said plates, tubes mounted in said inner shell and extending into said hollow plates, means for charging material to be treated onto the top plate of the series, means for moving the material from'each plate to the next underlying plate, means for supplying a gaseous heating medium between said inner shell and said plates, means for discharging spent material from the lower end of said retort, and means for conducting vapors from said retort.

2. In a retort for distilling oil from solid substances, the combination of a stack of hollow annular heating plates open through their inner peripheries and formed with discharge openings staggered around their axis, an outer shell encircling said plates and rotat- 'able relatively thereto, Scrapers overlyingl and movable relatively to said plates, an inner shell having a closed bottom and an open top, said inner shell extending through and spaced from the inner peripheries of said plates, tubes mounted in said inner shell and extending into said hollow plates, means for charging material to be treated onto the top plate of the series, means for supplying a gaseous heating medium to the lower end of the space between said inner shell and said plates, means for discharging spent material from the lower end of said retort, and means for yconducting vapors from said retort.

3. A formpf claim 1, wherein the heating plates are divided by partitions into a' lurality of compartments, and the inner s ell carries tubes extending into each compartment of each plate respectively.

4. A form of claim 1, wherein the heating plates are divided by radial partitions into a plurality of sector-shaped compartments, and the inner shell carries straight radial tubes extending into each compartment of each plate respectively.

5. form ofclaim 1, wherein the flue member is suspended at its upper end from the topmost heating plate of the series.

6. A form of claim 1, wherein the topmost heating plate is formed with inwardly projecting lugs on its inner periphery, and the inner shell is formed on its upper end with an external flange resting on said lugs.

7 A form of claim 1,lv wherein the inner shell takes the form of a Jrustum of a cone disposed with its wide end'uppermost.

8. A form of claim 1, wherein the inner shell has a manhole in its bottom normally closed by a cover.

9. A form of claim 1, wherein the flue member takes the form ofa frustum of a cone disposed with its wide end uppermost and has a manhole in its bottom normally closed by a cover.

10. A form of claim 2, wherein the heating plates, inner shell, and tubes are stationary, and the shell rotates around the plates and drives the Scrapers over the latter.

11. A form of claim 2, wherein the heating plates are stationary and the outer shell rotates around the plates, and wherein also the scrapers take the form of radially disposed arms attached at their outer ends to rings lying on the plates and rotated by the shell.

12. A form of claim 2, wherein the heating plates are stationary and the outer shell rotates around the plates, the Scrapers consist of radially disposed arms attached at their outer ends to rings lying'on the plates, and said rings and shell are equipped with cooperating contact lugs whereby the rings arel driven from the shell.

13. In a multiple stage retort, the combi' nation ofa series of spaced superposed hollow annular heating plates open at their inner peripheries, an outer shell encircling said plate, a vertically arranged group of inner shells having closed bottoms extending through and spaced from said plates, tubes mounted in said respective inner shells extending into laterally opposite groups of plates, means for charging material to be.

treated onto the top plate of the series, means for moving the material from each plate to the next uuderlying'plate, means for supplying a gaseous heating medium between the lowermost inner shell and the plates encircling the same, means for discharging spent material from the lower end of said retort, and means for conducting vapors from said retort.

14. In a multiple stage retort, the combination of a series of spaced superposed hollow annular heating plates open at their inner peripheries, an outer rotatable shell encircling said plates, Scrapers on said plates driven by said shell, a vertically arranged group of tapered inner shells having closed bottoms and open tops extending through and spaced from said plates, radial tubes mounted in said respective inner shells extending into laterally opposite groups of plates, means for charging material to be treated onto the top plate of the series, means for passing the mathe next higher stage.

"terial from eachplaie to the next underlying plate, means for supplying a gaseous heating medium' between. the lowerniost inner shell and the plates encircling' the same, means for discharging spent material from the lower end of s'aid retort, and means for conducting vaporsitrom said retort.

15;- In an apparatus lfor subjecting material to indirect heating, the combination ot a flue having transverse partitions dividing the same into a plurality of sections, a stack of ,annular hollow heating plates encircling" and communicating through their inner peripheries With said flue, said heating plates-being grouped in stages corresponding to the sections of'said Hue, means for effecting downward travel of the material successively over said heating plates, means for supplying a heating medium to the lowermost section of the flue, and means independent of said Hue partitions for directing the flow ot the heating medium from the interiors of the heating plates ot each underlying stage into the flue section associated with the heating plates of MCGARVEY CLINE.

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