US2130731A - Apparatus for treating material - Google Patents

Description

Sept. 20, 1938. B. M. CARTER I APPARATUS FOR TREATING MATERIAL original- Fil ed Jan. 3, 1933 2 Sheets-Sheet l \o INVENTOR ,3. M far/er 70 ATTORNEY Sept. 20, 1938.

B. M. CARTER APPARATUS FOR TREATING MATERIAL Original Filed Jan. 3, 1933 2 Sheets-Sheet 2 INVENTOR B. M. C'ar/er *7 ATTORNEY Patented Sept. 20, 1938 UNITED STATES PATENT OFFICE 2,130,731 APPARATUS ron TREATING MATERIAL Bernard M. Garter, Montclair, N. 1., asslgnor to General Chemical Company, New York, N. Y., a corporation of New York Original application January s, 1933, Serial No. 649,786. Divided and this application April 28, 1937, Serial No. 139,478

K 9 Claims. (01. 34-4) primarily directed to rotary drum or. cylinder drying apparatus. Drying material in such apparatus has been heretofore proposed In prior operations, it has been customary to continuously pass the material to be .dried through an'elongated rotary drum against a countercurrent flow oi. heated drying medium such as air. Because of the low melting point of the salts or similar materials being dried, it is necessary in practical operations that the highest temperature of the drying air be relatively low, i. e., considerably less than the softening point of the material. In countercurrent drying, the nature of the operation is such that the temperatureof the heated drying air is greatest at the air inlet-salt outlet end of the drying zone or chamber. The temperature of the heated drying air decreases as the air current passes through the drying zone, and is at a minimum at the point where the air leaves the salt inlet-air outlet end of the drying zone. Hence, the moisture-carryingcapacity oi the air current is at a minimum as the air stream leaves the drying chamber. moisture-carrying capacity of the air as it is discharged from the drier, together with other factors, limits the production of dry material by a single unit of apparatus.

The invention aims principally to provide apparatus for drying salts and similar materials of such construction that the output of a unit of given size may be largely increased. A further understanding of the objects and advantages of the invention may be had from a consideration of the following description taken in connection with the accompanying drawlngaln which Fig. 1 is a vertical, longitudinal section of one end of the dryer, showing in elevation an axially Fig. 4 is a transverse section on line 4-4 of- Fig. 3;

Fig. 5 is a transverse section on' theline 55 01. Fig. 3;

Accordingly, the

Fig. '6 is a transverse section on line 6-6 of Fig. 1;

Fig. 7 is a'similar transverse section on line 1-1 of Fig. 1;

Fig. 8 is an enlarged view, partly in section, of 5 that portion of the gas distributing pipe between sections M and 5-6, Fig. 3;

Fig. 9 isa transverse section on line Fig- H of Fig. 10 is a-developed plan of a damper in the 10 gas distributing pipe;

Fig. 11 is an end elevation of the damper taken on the line ll-ll'of Fig. 10;

Fig. 12 shows temperature curves, the purpose of which will be hereinafter noted, and 15 Fig. 13 is an elevation taken approximately on the line Iii-l3 of Fig. 1.

Referring to Fig. 1 of the drawings, the reference numeral 5 indicates one end of a cylindrical drum providing a drying chamber 6. The drum carries several longitudinally spaced, circumferential tires 1 resting in supporting rollers 8. The end of the drier, not shown, has mounted thereon an annular gear meshing with a drive pinion through which the drum is rotated from a source of power. The salt outlet end 9 of the drum pro- Jects into a flxed housing 10 into the bottom of which material is continuously discharged from the drum. One vertical side wall of the housing I I0 has attached thereto a circular flange ll engaging'a flange I2 carried by the tire I, flanges H and I2 forming a substantially gas-tight joint laden air from the apparatus; Such fixed hous- 40 ing is also equipped with conventional means for continuously feeding "material into the salt inlet end 01 the rotary drum. As is customary in ape paratus of this type, the salt inlet end of the cylinder is elevated slightly to facilitate movement of, material gradually toward the salt discharge end in fixed housing ill. The drum is rotated in the direction of the arrow 15 in Fig. 6. Reference numeral I, Figs. 1 and 2, indicates a blower, driven by motor ii, the pressure side or the blower'being connected through conduit l8 and opening I! with the interior of housing III.

In operation, drying medium, such as heated air, is fed into the-salt discharge end 9 of the drum from the housing Ill, passes through drying 5 chamber 5 countercurrent to the direction of movement of the salt, and flows from the salt inlet end of the drum into a fixed housing similar to housing ill, from which the air is eventually discharged to the atmosphere.

As shown in Figs. 1' and 7, projecting from the inner face of the cylinder 5 are longitudinal angle irons 20 to which are attached serrated staggered relation, near the salt discharge end are baflies or grilles 23, 24 and 25 shown in side and end elevations in Figs. '1 and 7 respectively. The baflies are-screen-like frames, connected at longitudinal edges 26 and 21 with adjacent serrated plates 2l. The baflies prevent lumps from passing through with dry salt, and effects. more thorough cascading of fine, nearly dried material than is secured by the serrated angles. At these grilles, the nearly dry salt is effectively showered through the drying atmosphere in a manner which could not be eflected at the opposite end of the kiln where the salt is wet.

Additional quantities of heated drying medium are fed. into the drum through an axially disposed, longitudinal distributing pipe 30 shown in elevation in Fig. 1, and in enlarged section in Fig. 3. The inlet end of pipe 30 iwfixedly supported at 3i in outer side wall 32 of the housing i0. Pipe 30 is cylindrical from wall 32 to section 5-5 in Fig. 3. From this point, pipe 30 tapers uniformly toward the small end 33, which is closed off by a circular disk 34. Rigidly connected to and extending through disk 34 is a stub shaft 35, the outer end of which passes through a bearing 35 supported by a spider, the

arms 31 of which are riveted at the outer ends to angle irons 20 and at the inner ends to the circularv flange 38 of thebearing 36. Hence, the

small end of the fixed pipe 30 is maintained in position by hearing 35. The gaseous drying medium, such as air, is fed into pipe 30 from an inlet conduit 40. The top side of pipe 30 may advantageously be covered with insulating material, such as asbestos, to prevent overheating and possible melting of salt material falling on top of the pipe during rotation of the drum- The tapered portion 4i of the air pipe 30, between transverse sections 4-4 and 5-5, is provided on the lower side with a plurality of elongated openings 45, 46, 41, 40, 49, and 50 of uniform length and width. The openings are separated by the shortsections 5i left uncut to avoid weakening of the pipe. In effect, all of the openings together. may be considered as constituting,

' a single elongated slotin the underside of tapered section 4|. As noted, the drum rotates in the direction of the arrow i5 in Fig. 6, andaccordingly theshell, in conjunction with angles 20 and plates 2|, tends to carry material upwardly through the left half 53 (Fig. 6) of dry-.

ing chamber 5. In order to cause air entering the drying chamber 6 through openings -50 to be directed toward thesalt ibeing dried, the longitudinal center line of openings 45-50 is displaced circumferentially from the vertical a distance equal to an angle A as indicated particularly in Fig. 8, and also'in Figs. 4"and 5.

Angle A may for example be about 20. The openings are therefore oil the vertical center in the direction of rotation of the cylinder so that the hot air is directed toward the surface of the bed of salt at a point at which the bed is of substantial depth.

The passage of air through openings 45-50 is controlled by an eccentric damper indicated generally by reference numeral 50, and shown in Fig. 10 in plan. In Fig. 10, the damper is curved upwardly out of the plane of the paper as will be seen from Fig. 11. The curvature of the damper is such that the convex surface conforms with the inner surface of tapered section 4i of the air pipe 30. The damper is rigidly connected through hangers 5| to a longitudinally extending pipe 52, the inner end 53 of which fits over and may oscillate about the inner end of fixed stub shaft 35. The opposite end of pipe 62 is rotatably supported in a fixed bearing 55 shown in Figs. 1 and 3. Keyed to the outer end of pipe 62 is an operating handle 65 (Fig. 13) and since the inner end of the pipe is rotatably carried by stub shaft 35 andthe outer end of the pipe is rotatably supported in bearing 55, the position of the damper 60 relative to the openings 45-50 may be controlled by manipulation of handle 65.

Referring to Fig. 10, line 63 represents the center line or crest of the damper. When the latter is positioned to close all openings 45-50, as shown in the large section Fig. 8, line 53 coincides with the longitudinal center of openings 45-50 indicated by the dotted line between points B and C (Fig. 8). In the particular damper illustrated, although specific dimensions are immaterial, dimension .D (Fig. 10) is slightly posed in different angular relation with respect to center line 58, that is, the taper of edge I2 with respect to line 58 is sharper than the taper of edge I3 with respect to center line 05. When the damper is in place in pipe 30 and adjusted so that all openings 45-50 are closed, longitudinal edges 12 and 13 and transverse edges represented by dimensions D, F, E, and G oc-, cupy the positions shown in Fig. 8.-

The gas distributing pipe 30 is also provided at I5 (Fig. 1) with a plurality of openings 15 shown in section in Fig. 9. Openings I5 are to the right of thevertical (Fig. 9) and are arranged similarly to, openings 45-50 so that hot gas entering the drum through openings is directed into the body of salt beingvcarried up wardly in the'direction of the arrow ii of Fig.

6. Openings 10 are controlled by a longitudinally sliding damper I8 (Fig. 3) comprising a ring 19 carried by spider arms 30, the inner ends of which are connected to a sliding sleeve ll extending outwardly through bearing (Fig. 1).

Attached to the outer end of sleeve 0| is a lug 84 (Fig. 3) to which is plvotally connected at 35 an operating handle 05 one end of which is, ,pivoted at 31 to the end of a link 30 pivoted to a fixed bracket 30, shown more clearly ln-Fig. 1.

The invention may be employed in practicesubstantially as follows:

As noted, the invention is directed particularly softening or liquefaction at relatively low temperatures, and hence should be dried at temperatures below-the softening point. For convenience and by way of illustration, the operation of apparatus of the invention will be described in connection with the drying of trisodium phosphate, a salt containing considerable quantity of however, that the apparatus of the invention is applicable for use not only to the drying of salts drying or treatmentof any material from which water or other vaporous constituents must be evaporated at temperatures below that at which I liquefaction or incipient fusion of the material treated would take place.

In customary commercial practice, trisodium phosphate crystals, containing 12 molecules of water, are first separated from the mother liquor by means of a filter, and may bc'washed with I water to remove mother liquor ordinarily retained by the dewatered crystals. For example, after gal filterdelivers a product containing from to 8% free water. Initial dewatering of the crystal slurry and the apparatus employed constitute no part of this invention.

To meet certain trade requirements on trisodium phosphate crystals, for example, all free water and a small amount of the water of crystallization must be removed from the centrifuged equivalent of not less than about 101.5% of Na3PO4.12H2O and such water is removed by exposure of the wet salt to a heated gaseous drying medium such as hot air. Heretofore, drying has been accomplished in operations .involving counter-current flow of salt and hot air through a rotary drum, the hot air initially introduced into the drier at the salt discharge end being heated to thedesired temperatures by any convenient means. In such operations, involving countercurrent flow of salt and drying the amount of salt which may be dried in any given apparatus is dependent upon the diiference in water content between the air entering the salt outlet end and leaving the salt inlet end-of the per unit of time is more or less dependent upon in summer than in winter on account of the higher temperature and the humidity of the atmosphere in warm weather. a

The basic features of the process aspects of the invention may be more clearly understood from a brief consideration ofsome of the fundamental principles involved. In summer in the temperate zone, temperatures of about 80 F. and relative humidity of about 70% frequently prevail. Under these conditions, atmospheric air contains about 7.6 grains of water per cubic foot.

On heatingathe volume increases, and the moison heating.to 100 F.,contains about 7.4 grains of water per cubic foot, and has a relative humidity of about 38%. On further heating to, say, 120 F., such air, as introduced into the salt outlet end of the drier, would contain about 7.1 grains ofwater per cubic foot'and the relative v humidity decreases to about 21%. Since in practical-operation, complete equilibrium is not obto apparatus for drying material subject to water of crystallization. It is to be understood,

5 containing water of crystallization', but to the.

the water wash, one well-known type of 'centrifu by refrigeration, drying, etc.

salt so that the dried product will contain. the

drier. Furthermore, the output of such a drier atmospheric conditions, the capacity being lessture carrying capacity is raised so-that such air tained, the humidity of the heated air discharged from the salt inlet end ofthe drier decreases as the temperature increases. Thus, air leaving the salt inlet end of the drier at about 100 F. and relative humidity of about 60% would carry about 11.6 grains of water per cubic foot, or about 4.2 grains per cubic foot in excess of entering atmospheric air heated to about 100 F., having a relative humidity of about 38% and containing about 7.4 grains of water per cubic foot. Further, air leaving the salt inlet end of the drier at about 120 F. and a relative humidity of about 50% would carry about 17.2 grains of water per cubic foot, or about 10.1 grains per cubic oot in excess of entering atmospheric air heated to about 120 F.', having a relative humidity of about 21% and containing about 7.1 grains of water per cubic foot. Accordingly, a given volume of air leaving the drier at about 120 F. and about 50% relative humidity would dry more than twice the amount. of. wet salt that would be dried by the same amount of air leaving the drier at about 100) F. and about 60% relative humidity.

It will be understood the output per unit of time of a drier' of a given size is determined by quantity of airv employed, moisture content of such air, and the temperature to which-the air is heated prior to introduction to the drier. The initial moisture content of the air is determined by atmospheric conditions, and is not subject to control, unless the air is previously conditioned The remaining two controllable factors are also subject to limitation. The volume of drying air employed cannot be in excess of that at which it would tend to carry the material out of the drier in suspension, and on the other hand, the temperature of the drying air cannot be raised above that at which the materials being treated would bedeleteriously affected. a

In the present description of the operation of the process, it is to be understood the reference to specific temperatures, volumes of dryingair, and dimensions of the drier are illustrative; and

are mentioned only to facilitate description of .one embodiment of the invention.

140 F. without creating a sticky condition that Produces undesirable caking. Thus, in practice it is not desirable to allow the maximum temperature of the drying air to exceed about 135 F. In prior practice, it has been customary to pass the salt continuously through a rotary drum in contact with a stream of air flowing countercurrent through the drier, the temperature of the drying being about 135 F.

It has been found'that in prior practice, e. g. where wet salt and drying air pass countercurrent through thedrier, the temperature of the drying air drops of! rapidly, in the first onethird of the length of the drying chamber, and thereafter remains substantially constant until the air leaves the salt inlet end of the drier. In Fig.12, the "abscissa represents the length of the the temperature of the drying air. Dotted curve K approximately indicates the temperatureconditions existing in the drierwhen operated in accordancewith prior practice; From this curve, it will be. seen that while passing through approximately the first third of the drier, the temperature drops from approximately 135 F. to say air introduced intothe salt outlet end of the drier drying chamber 6, and the ordinate represents about 110-l12 F., and thereafter, during the subsequent two-thirds of passage through the drier, the temperature of the drying air decreases gradually to about 100 F., at which temperature the drying air passes out of contact with the wet salt being fed into the salt inlet end of the drier.

In accordance with the present invention, operations are conducted so that the temperature of the drying air leaving the drierisconsiderably raised, thus largely increasing the water carrying capacity of the drying air at the time of last contact with wet salt. By means of the present method and apparatus, conditions in the drying chamber may be so controlled that the temperature of the air leaving thedrier may be regulated as desired within certain limits. From a consideration of the temperature curve K of Fig. 12, it will be seen that if properly regulated quantities a of drying gas, heated to proper temperatures, are

introduced into the drier beginning at points beyond approximately the first third of the drier (measuring from the salt outlet end), the temperature of the drying atmosphere in the subsequent two-thirds ofthe drying chamber may be raised, and the water carrying capacity of the drying air, as discharged from the salt inlet end of the drier, largely increased. In the present invention, such temperature control in the drier may be had by introducing heated gas into the drying chamber 5 through the gas, distributing pipe 30, by suitable regulation of dampersv 50 and I5.

In the apparatus illustrated, it may be assumed for example, drum 5 is about feet long. The

taper of pipe 30 begins at section 5-5, Fig. 3,

about '7 feet from the salt outlet end 9 of the drum, and at a point which is indicated by a corresponding line 5-5 on Fig. 12. As the temperature of the drying air has dropped materially at about line 5-5 (Fig. 12), to accomplish the purposes of the invention, controlled quantities of *air heated to proper temperatures are introduced into the drying chamber through one or more of the openings -50 of pipe 30. It is noted, section line 4-4 (Fig. 3), corresponds approximately with line 4-4 on Fig. 12. The particular portion of the drier, between lines 5-5 and 4-4 (Fig. 12) into which hot gas from pipe 30 is introduced is selected by manipulation of the damper 50.

I In Fig. 8, the damper is shown in such position that all openings 45-50 are closed. It will be recalled fromthe foregoing description that edges I2 and 13 are pitched oppositely and at different angles with respect to center line 58 of damper 0.

Referring to Fig. 8, it will be seen that movement of damper in the direction of the arrow 95, first uncovers a portion or the whole of opening 45 nearest the small end of tapered section 4|. Thus, a comparatively short downward movement of handle (Fig. 13) uncovers the opening 45, and admits heated air from the pipe 50 into the interior of the drum at the point at which opening 45 is positioned. Because of the relatively sharp pitch of edge I2, with respect to center line 58 of the damper 50, it will be seen that continued movement of damper 50 in the'direction of the arrow 55 successively uncovers, openings 45-50 in the order named, until when the handle 55 is in the position of the dotted line 55 (Fig. 13), all openings 45-50 are uncovered, and because of the taper of pipe 30 substantially qual quantitles of air pass "through each opening into the drum. Thus, when it is desired to introduce air as noted above where the damper was fully of the tapered section, and then progressively to- In one particular series of tests, carried out in to temperatures of about 400F. was fed into the than salt outlet end 5, handle 55 is moved downwardly, and as many 0! the openings as necessary may be uncovered, and additional hot gas admitted to selected portions of the drum.

In other situations arising in practice, it may desirable to introduce additionalhot gas only or I initially in portions of the drying chamber nearer the salt discharge end of the drum. This may be accomplished by raising handle 55 which ,causes movement of damper 50 in the directionof 1 the arrow 91 in Fig. 8. As'edge E of the damper is shorter thanedge F, it will be seen that such movement of the damper first uncovers the opening 50 adjacent the section-line 5-5 of Fig. 3. On account of the pitch of edge 13, with respect 1 to center line 58 of damper 50, further movement of the damper in the direction of the arrow 51 uncovers opening 50-45 progressively in the order named. When handle 55 is in the position of dotted line 59, all openings are uncovered, and air enters drying chamber 5 in the same manner opened by downward movement of handle 55.

Thus, by moving handle 55 downwardly, air is introduced into the drier first at the small end ward the larger section, if downward movement of handle 55 is continued. On the other hand by lifting handle 55, air is introduced into the drum first through the opening 50 adjacent section hne 5-5 of Fig. 3, and thereafter, on further upward movement of handle 55, through openings progressively nearer the small end of a distributing pipe 30. Accordingly, by adjustment of the position of the damper to suit spe- ClfiC operating conditions, additional quantities of hot drying gas may be introduced into any portron of the drying chamber, and the temperature conditions therein controlled as required. It will be seen that by reasm of the difference of pitch of edges '|2 and 13 with respect to center line 55 of the damper, all the openings 50-45 may be more rapidly opened or closed by raising handle 55 or lowering the same to the horizontal positron, thus in effect using edge-I3 as the working" edge of the damper. On the other hand, downward movement of handle 55 and raising the same to the horizontal position makes edge I! the working edge, and as the pitch of edge I! is sharper, with respect to center line 58, the openings 45-50 are uncovered or covered at a less rapid rate. In practice, it has been found generally desirable to admit additional hot drying gas nearer the salt inlet end, say through openings 45, 45 and 41, rather than near the salt outlet end. Thus, handle 55 is manipulated so that edge 12 is employed as the workin damper. g edge of the midsummer over an extended period of time, and at an average atmospheric temperature of about F. and about 10% relative humidity, operations were conducted so that approximately 40 tons of dried trisodium phosphate were produced by the drier in 24 hours, about 10.8% free and combined water having been removed from the wet salt. The total quantity of drying medium employed was about 5,000 cubicfeet per minute. About half this volume of air, at temperatures about 131 'F., was fed into the drier from the fixed housing l0. An equal volumejconsisting of products of combustion from an oil' burner, heated distributing pipe 50 from pipe 40, and introduced into the drier with all the openings 45 -50 uncovered. The combined volume of gas left the drier at temperatures of about 122 F., the temperature prevailing in the drum being indicated approximately by the curve L, in Fig. 12. In the abovetests, the followlng results were obtained:

Food Product Percent Percent Na;PO .12H,0 92. 96 103. 04 NaOH l. 60 1. 25 Na|C0,. .78 1.21

By proceeding in accordance with the above,

the output of the drier was approximately doubled over operations carried out in a drier of the same size, but built and operated as in the prior practice. It will be seen from Fig. 12, the temperature of the drying medium leaving the drier is about 20 higher than previously obtainable,

thus eiTecting the largely increased capacity of the drier.

By operation of damper I8 controlling openings 16 positioned relatively near the salt disfrom the housing l may be at temperatures of about 100 F., thus cooling the dried salts, to some extent, just prior to discharge from the drier, such cooling advantageously. permitting packaging of the product without caking', and without the use of additional equipment to cool the product prior to packaging.

Where air or other gaseous heating medium is introduced into the drying chamber from house ing l0 at lower temperatures of about,"say, 100 F., the temperature in the drying chamber just beyond the salt outlet end 9 may be rapidly raised to the desired maximum temperature by opening the damper 18, and. permitting admission of hot gases through openings I6. By this operation in conjunction with manipulation of damper 88, a temperature curve in the drier approximating curve M may benobtained, which curve, as will be seen, converges with curve L at a point near the salt outlet end of the drier, the temperatures thereafter approximating those which prevail in instances where the drying air is initially introduced at 131-132' F. I

In the above specific example, it will be noted the hot combustion products entering the drier through pipe 30 were heated to temperatures of about 400 F. No particular temperatures for the high temperature gas supply need be employed. Improved results, over prior practice, may be obtained where the hot gases entering through pipe 80 are at any temperature above that of the gas entering the drier from housing I 0. The higher thetemperature of the gases entering the drier from pipe 30, the higher the temperature of the combined gas stream leaving the salt inlet end of the drier, and accordingly the greater the output of the drier and the emciency of the dryingoperation. To obtain substantially improved in- -crease in the drier capacity, the temperature of the gas introduced through pipe 30 should not be less than about, say, 250 F. The upper limit of the temperature of the gas from pipe 30 is 'controlled by the nature of the material being treated.

enough to raise the temperature of the combined gas stream in the drier sufficient to cause softening or injury to the material being treated. The volume of the combined gas stream in the drier should not be in excess of that at which material would be carried away in suspension. i

It will also be understood any suitable gas may be used for both the high and low temperature supply. Air heated by heat exchange may be employed for either or both low and high temperature supply, and also combustion gases, if sootless, may be utilized for either or both the low andhigh temperature supply, thus eliminating use of steam heaters previously employed, and thereby eil'ecting economies in cost of heat supplied to the drier.

I claim:

1. Apparatus for treating material comprising a rotary drum forming a treating chamber, means for introducing solid material to be treated-into one end of the chamber, means for moving the material through the chamber, means for introducing a primary stream of gas into the opposite end of the chamber, means'for passing the gas stream through the chamber countercurrent to the movement of the solid material, a fixed'conduit projecting into the chamber from said opposite end and terminating in a tapered section extending longitudinally through a substantial part of the chamber, an elongated slot in the underside of and extending substantially the lengthof the tapered section of the conduit, a damper in the conduit for closing the slot, said damper having oppositely pitched edges so formed as to close off, on movement of the damper, the whole of the slot or variable portions of either end of the slot, a

second opening in the conduit adjacent said oppo 3. Apparatus for treating material comprising,

a rotary drum forming a treating chamber, means for introducing solid material to be treated into one end of thechamber, means for moving the material through the chamber, means for introducing a primary stream of gas into the opposite end of the chamber, means for passing the gas stream through the chamber countercurrent to the movement of the solid material, a fixed con-,

duit projecting into the chamber from said opposite end and terminating in a tapered section extending longitudinally through a substantial part of the chamber, an elongated slot in the underside of and extending substantiallythe length of the tapered section of the conduit, a damper in the conduit for closing the slot, said damper having oppositely pitched edges so formed as to close off, on movement of the damper, the whole of the slot or variable portions of either end of the slot.

, 4. Apparatus for treating material comprising a chamber, means for introducing materia to be treated into the chamber, a conduit in the chamber for introducing treating medium, an opening in the conduit and a damper associated with the opening, said damper having opposite edges disposed at different angular relation with respect to the intervening center line of the damper and so formed as to close oil? on movement of the damper the whole of the opening or variable portions of either end of the opening.

5. Apparatus for treating material comprising a chamber, means for introducing material to be treated into the chamber, a conduit in the chamber for introducing treating medium, an opening in the conduit and a damper associated with the opening, said damper having opposite converging edges so formed as to close off on movement of the damper the whole of the opening or variable portions of either end of the open ing.

6. Apparatus for treating materials comprising a chamber, means for introducing material to be treated into the chamber, a conduit in the chamber for introducing treating medium, an opening in the conduit and a damper associated with the opening, said damper having oppositely pitched edges so formed as to close off on movement of the damper the -whole of the opening or variable .portions of either end of the opening.

said damper having oppositely pitched edges so, formed as to close ofi on movement of the damp er the whole of the opening or variable portions of either end of theopening.

8. Apparatus v for treating material comprising opening.

a chamber, means for introducing solid material to be treated into one end 01' the chamber,

means for moving the material through the chamber, means for introducing a primary stream of treating medium into the opposite end of the chamber, means for passing said primary stream through the chamber countercurrent to the movement of the solid material, a conduit projecting into the chamber for introducing further quantities of treating medium, said conduit extending longitudinally through a substantial part of the chamber, an elongated opening in the conduit and a damper associated with the opening,said damperhaving oppositely pitched edges so formed as to close 011 on movement of the damper the whole of the opening or a variable portion of either end of the opening. a

9. Apparatus for treating material comprising a rotary drum forming a treating chamber,-

means for introducing solid material to be treated into one end of the chamber, means for moving the material through the chamber, means for introducing a primary stream of gas into the opposite end of the chamber, means for passing the gas stream through the chamber countercurrent to the movement of the solid material, a conduit projecting into the chamber from said opposite end for introducing further quantities of treating medium, said conduit terminating in a tapered section extending longitudinally through a substantial part of the chamber, an opening in the tapered section of the conduit and a damper associated with the opening, said damper having oppositely pitched edges so formed as to close oif on movement of the damper, the whole of the opening or a variable portion of either end of the BERNARD M. CARTER.

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