US3190743A

US3190743A - Method and apparatus for manufacture of pellets or the like

Info

Publication number: US3190743A
Application number: US176635A
Authority: US
Inventors: Melvin J Greaves
Original assignee: Arthur G McKee and Co
Current assignee: Arthur G McKee and Co
Priority date: 1962-03-01
Filing date: 1962-03-01
Publication date: 1965-06-22
Anticipated expiration: 1982-06-22
Also published as: SE307965B; GB1029885A; ES285537A1

Description

June 22, 1965 M, J. GREAVES 3 METHOD AND APPARATUS FOR MANUFACTURE QF PELLETS OR THE Filed March 1, 1962 5 Sheets-Sheet 1 9 625 all ,4 rraenlsyr June 22, 1965 M. J. GREAVES 3,190,743

METHOD AND APPARATUS FOR MANUFACTURE OF PELLETS OR THE LIKE Filed March 1'. 1962 5 Sheets-Sheet 2 3 uzxxnn I III INVENTOR. MZ WM .2: 6;?54/55 147' 7 GPA/6 VS J n 22, 1965 A M. J. Gangs 3,190,743

METHOD AND APPARATUS FOR MANUFACTURE OF PELLETS OR THE LIKE Filed March-1, 1962 v 5 Sheets-Sheet 3 J0 INVENTOR.

June 22, 1965 M. J. GREAVES 3,190,743 METHOD AND APPARATUS FOR MANUFACTURE OF PELLETS OR THE LIKE Filed March 1, 1962 5 Sheets-Sheet 4 6/6 6 35a a 655 INVENTOR. Mlsz/m/ J GLPEAI/ES F) 6 BY J 50:14am, Sid 4404a.

Hal 14mm fi-knewed Juhe 22, 1965 r 3,190,743 METHOD AND APPARATUS FOR MANuFAcTunEpF PELLETS on THE LIK Filed March 1, 1962 I I M. J. GREAVES 5 Sheets-Sheet 5 m v M W W United States Patent 3,31%),743 METHOD AND APPARATUS FOR MANUFACTURE 0F PELLETS 0R THE LIKE Melvin .l. Greaves, Cleveland, Ohio, assignor to Arthur G.

McKee & Qompany, Cleveland, Ohio, a corporation of Delaware Filed Mar. 1, 1962, Ser. No. 1%,635 19 Claims. (Cl. 75-5) This invention relates to the handling of particulate materials as they are treated while traveling in a flat bed of substantial thickness.

Although the invention may be advantageously used for various purposes and with various materials, it will be primarily discussed below in connection with pelletizing on a traveling grate carrying a bed of balls containing finely divided iron oxide, such as iron ore, to form heathardened pellets having suificient strength and hardness to permit them to be handled, shipped, stored and charged into blast furnaces or other smelting apparatus. The

method and apparatus of the invention provides particular advantages in such use.

In the production of such heat-hardened pellets on a traveling grate water and finely divided ore, ore concentrate, flue dust, or other iron-bearing material, either alone or with fuel, flux materials or other substances, are mixed together to form a moist mud-like mass which is then formed into green balls by any suitable and well known means. To as great an extent as possible, these balls are of a uniform desired size, usually between about A to about 1" in diameter, and preferably between aboutF/s" and /2" in diameter. Pelletizing, involving proper drying and heating of these balls, will remove the moisture and strengthen them so that they may thereafter be handled,

shipped, stored and charged by conventional apparatus.

The usual elongated pelletizing machine of the traveling grate type used in handling such green balls comprises a number of pallets which, in the upper run of the grate, abut and define a traveling grate having a permeable bottom hearth and upwardly extending confronting side walls. machine, the green balls are deposited in a layer or bed of predetermined thickness at the charging end of the upper run of the grate as it travels longitudinally of the machine, and then the balls are pelletized by being subjected to drying, preheating, high temperature heating, and cooling or other treatments as the grate moves through the several zones of the pelletizing machine. This procedure involves passing air or other gas through the bed and the grate, either downdraft or updraft, or a combination of downdraft and updraft.

In practice it has been found that the green balls located in a layer of substantial thickness adjacent to each of the side walls and the balls in a layer of substantial thickness adjacent to the hearth of the traveling grate are not heat hardened and strengthened thoroughly and as uniformly as the pellets located in the remaining central portion of the grate. It appears that the transfer of heat to the pellets near the side walls and the hearth of the grate is less than the heat transfer to the pellets in the central portions of the grate. because the side Walls increase heat loss, and because the gas or air flow is substantially diiferent through the bed of pellets near the side walls than elsewhere in the bed of pellets on the grate due to gas or air leakage and different flow resistances near the side walls. Furthermore, in pelletizing machines in which the pellets are heated downdraft, the pellets in the bottom part of the bed near the hearth of the grate are also heated to a con siderably lesser extent than the pellets in the central portion of the grate above the pellets near the hearth.

In order to determine quickly whether the pellets have the strength, including hardness, characteristics suificient In a typical pelletizing operation on such ato withstand degradation or breakage from handling, shipping, stock piling and charging, a tumble test has been developed to establish an index of pellet resistance to degradiation, and hence an index of the strength of the pellets. This tumble test is essentially similar to that described in American Society for Testing Materials Designation D29450 entitled, Tumbler Test for Coke, published in ASTM Standards, 1958, Part 8, pages 1102-1103, but modified in that the screen used in the test is a 28 mesh screen and that the drum is rotated for 200 revolutions at 25 r.p.m.

Thus, if the traveling grate of a typical downdraft pelletizing machine is entirely filled with green balls, the pellets resulting from the green balls in the hearth and side layers will, under this tumble test, produce from about 10% to 20% or more of 28 mesh fines, which is an indication of very poor quality. The pellets in the remaining central portion of the grate, on the other nand, may produce as low as only 2% of 28 mesh fines on the tumble test, which is an indication of excellent quality. intensified competition among pellet manufactures has increased customer demand for high quality pellets to such an extent that pellet users want pellets which produce no more, and preferably less than, 5% of -28 mesh fines on the tumble test; therefore the substantial amounts of poor quality pellets produced in the side and hearth layers render impossible the achievement of such desired overall high quality output.

In attempting to eliminate or reduce the production of weak pellets in the hearth and side layers of traveling grate machines it has been proposed to feed previously heat-hardened undersized or broken pellets, or even other refractory materials, to form hearth and side layers on a traveling grate and define a through-shaped channel into which the green balls are fed. At the discharge end of the machine such materials are screened from the product pellets.

Such expedients greatly reduced the effective capacity of the traveling grate for the production of high quality pellets, consume large amounts of fuel in heating nonproductive materials in the hearth and side layers, and involve considerable difiicultics, capital investment, and expense in disposing of or storing and reusing the nonproductive hearth and side layer materials. Thus, in a typical traveling grate type pelletizing machine, such a large proportion of the cross section of the grate is occupied by side layer and hearth layer areas, which produce off-quality pellets or which heretofore have been filled by non-productive material, that only about 50% to 60% of the cross section of the grate is available for the production of pellets of the presently desired hi h quality. Since pelletizing machines and their associated equipment usually cost several millions of dollars, it is apparent that a very substantial portion of the capital investment and operating costs are devoted to the handling or production of unsalable materials.

A principal object of the present invention is to provide a new and improved process and apparatus for treating particulate material on a traveling grate which will greatly increase the production of satisfactory, high quality product from the grate at a moderate added cost in equipment and little, if any, increase in operating costs.

Another object is the provision of a new and improved process and apparatus for greatly increasing the output from a traveling grate of high quality strong, iron oxide pellets with substantial savings in fuel and other operating costs per ton of pellets produced.

These and other objects of the invention will be apparent from the following description of preferred and alternative embodiments thereof, reference being made to the accompanying drawings, in which:

FIGURE 1 is a side elevation of a pelletizing machine 3 embodying the invention, the apparatus being shown diagrammatically with the central portion of the machine and other parts broken away for the sake of clearness;

FIGURE 2 is a diagrammatic plan view of the machine of FIGURE 1, to the same scale, and with the central portion of the machine broken away for the same reason;

FIGURE 3 is a perspective view of the discharge end of the machine of FIGURE 1, the view being shown to a considerably larger scale;

FIGURE 4 is a somewhat diagrammatic cross section through the grate showing the hearth and side layer zones;

FIGURE 5 is a similar diagrammatic cross section showing a hearth layer of previously heat-hardened pellets and a superposed layer of green balls;

FIGURE 6 is a perspective view of the upper portion of the apparatus in FIGURE 3, to a somewhat larger scale, showing in more detail means for adjusting the position of the partitions which determine the thickness of the side layers of pellets to be segregated;

FIGURE 7 is a plan of the portion of the apparatus shown in FIGURE 3;

FIGURE 8 is a sectional elevation along line 8-8 of FIGURE 7;

FIGURE 9 is a side elevation of the discharge portion of the apparatus shown in FIGURE 3, parts being broken away better to show the arrangement of the discharge hoppers;

FIGURE 10 is a fragmentary view showing the adjustable means for feeding pellets forming the hearth layer;

FIGURE 11 is a side elevation of the lower portion of the discharge housing of another embodiment in which there is a screen for removing fines from side layer pellets before they are returned to the feed end of the machine;

FIGURE 12 is a plan of a different embodiment of the invention, comprising two pelletizing machines and means for temporarily storing the side layer pellets from both machines in a common hopper, from which the side layer pellets are withdrawn and deposited in the hearth layers on the traveling grates of both machines;

FIGURE 13 is a fragmentary elevational view from line 13-13 of FIGURE 12; and

FIGURE 14 is a side elevation of the discharge portion of another embodiment in which the side layer pellets are cooled after segregating on the pelletizing machine and in which the conveyors transporting such side layer pellets have rubber belts or the like.

As will appear from the following description, my method may be broadly described as including the steps of segregating, at the discharge end of a traveling grate on which particulate material is treated, imperfectly treated material such as that from adjacent the side walls of the grate and recirculating such imperfectly treated material back to the feed or charging end of the grate to form a hearth layer on which fresh untreated material is charged, so that the resulting product, which is separated from the imperfectly treated material at the discharge end of the grate, is formed of a mixture of treated material from the hearth layer which has been twice passed over and treated on the grate and material superposed on the hearth layer which has been once passed over and treated on the grate, the product formed of such mixture having an exceptionally high overall quality.

The apparatus of FIGURES 1 to 10 inclusive, as shown in FIGURES 1 and 2, comprises a pelletizing machine generally designated by reference numeral 1. This machine includes an endless traveling grate 2 of conventional design caused by suitable power driving means, not shown, to travel in the direction of the arrows. The upper run of the grate passes between an upper hood structure 3 and lower wind boxes 4 which subject green balls carried longitudinally through the machine by the upper run of the grate to drying, preheating, high temperature heating, cooling or other treatments, the method of operation for example being similar to that disclosed in either or both of O. G. Lellep Patents 2,750,272 and 2,750,273 issued June 12, 1956.

In the particular machine illustrated, the hood 3 is subdivided and equipped, and the wind boxes 4 are arranged and equipped, so that there is an updraft drying zone 5, a downdraft drying zone 6, a downdraft preheat zone 7, a long downdraft high temperature heating zone 8, and an updraft cooling zone 9 which is adjacent the discharge end of the apparatus.

Green balls may be supplied to the grate by any suitable means, That diagrammatically illustrated comprises a plurality of rotatable balling drums 10 in which the ore, ore concentrates and other ingredients are mixed with water to form balls which are as nearly as possible of uniform predetermined size; such balling drums may be like that described and claimed in J. F. Baler Patent 2,822,076 issued February 4, 1958. The means shown for feeding the green balls formed by the drums 10 onto the grate 2 is conventional. It comprises a power driven belt conveyor 11 on which green balls over a predetermined size are deposited from drums 10, and which discharge such balls onto belt conveyor 12. Conveyor 12, which is power driven, is mounted to be moved by a suitable power source not shown, about pivotal support 13 in a generally horizontal oscillatory path shown in full and broken lines in FIGURE 2, so that its discharge end 14 deposits green balls across the width of an intermediate conveyor 15 which in turn discharges the balls across the width of a vibratory screen 16. The ballcarrying widths of conveyor 15 and vibratory conveyor 16 are substantially identical to the ball-carrying width of the traveling grate 2. Balls over a predetermined size pass from the screen 16 onto the upper run of the traveling grate 2, while balls of less than the desired size pass through the screen onto a belt conveyor 17 from whence they return to the ball-making equipment.

As is apparent from FIGURES 3, 4, 8 and 9, the endless traveling grate is made up of a number of pallets 21 which extend transversely of the traveling grate with adjacent pallets abutting. Each of these pallets is so made that it comprises a perforate or gas-permeable bottom 22 and two upstanding end wall members 23. The bottoms and end wall members of the adjoining pallets 21 cooperate to form the longitudinal hearth 24 and longitudinal upwardly extending confronting side walls 25 of the grate 2. Each of the pallets 21 carries two rotatably mounted rollers 26 at each end adapted to travel in a guide track 27 defining an endless path at each side of the apparatus. The pallets in the upper run of the traveling grate abut and are pushed from the feed or charging end of the pelletizing machine toward its discharge end by suitable drive means (not shown).

The apparatus so far described may be of conventional construction and requires no further description.

It has been found that in a typical conventional pelletizing machine, when the channel cross-sectioned upper run of the traveling grate that is defined by the pellets is completely filled with green balls, and these balls are subjected to the sequence of treatments involved in the pelletizing operation, the balls located in thick side layers extending inwardly of the side walls of the grate and in a thick hearth layer extending a considerable distance upward from the hearth of the traveling grate produce pellets which are considerably less strong, and hence subject to greater breakage or degradation, than the pellets produced in other parts of the traveling grate. Referring to FIG- URE 4, which diagrammatically shows a cross section of the upper run of a typical traveling grate, the pellets from the side layers defined by the cross sectional areas A, B and A, B and the pellets from the hearth layer defined by cross sectional area C are considerably poorer in quality due to improper heat treatment than the pellets located in the central or remaining portion of the grate defined by the cross sectional area.

In a typical installation in which the width dimension W 3,1 eaves of the traveling grate is eight feet and the dimension H, which is the depth of which the grate may be filled with balls, is sixteen inches, it has been found that the thickness T of each of the areas A and A usually is approximately one foot and the thickness L of the hearth layer area C is approximately four inches. In such case the pellets produced in the portions of the side layers represented by areas A and A result in about or more of 28 mesh fines when subjected to the above indicated tumble test, the pellets produced in the portions of the side layers represented by areas B and B develop more than of 28 mesh fines during the tumble test, and the pellets produced in the portion of the hearth layer represented by area C result in about 10% or more of 28 mesh fines in the tumble test. On the other hand, the pellets produced in the central layer represented by area D are so strong that when subjected to the tumble test they may develop less than 2% of 2-8 mesh fines. Area D is only approximately 56% of the total cross sectional area of the grate, which means that only this portion of the theoretical capacity of the machine is eifective in producing high quality product. If it is attempted according to prior practices to prevent the production of poor quality product by filling the layers represented by areas A, A, B, B and C with previously pelletized or other non-productive material, then in such case there will still be only 56% of the theoretical capacity of the machine utilized in production of the desired product, although the heating requirements .are substantially those required for production at full theoretical capacity.

According to the present invention, the amount or" high quality pellets produced is very substantially increased by segregating at the discharge end of the pelletizing machine the insufficiently strong pellets in the side layers represented by areas A, B, and A, B of FIGURE 4, conveying them or similar insufiiciently strong pellets to the feed end of the pelletizing machine, and depositing such pellets to form a substantially uniform hearth layer 28 (FIGURES 2 and 5) represented by areas B, C and B of FIGURE 4. At the feed end of the apparatus, green balls are then deposed on such hearth layer in the form of a thick, substantially uniform layer 29 (FIGURES 2 and 5) represented by areas A, D, and A of FIGURE 4. The resulting composite longitudinally extending, fiat, substantially uniformly thick bed of green balls and pellets previously subjected to a pelletizing operation is represented in cross section by FIGURE 5. This bed, which has a width several times greater than its thickness, is moved by the traveling grate through the various treating zones of the pelletizing machine and discharged at the discharge end of the machine.

At the discharge end, pellets in the hearth layer represented by areas B, C and B of FIGURE 4 are thus those which have been subjected to two pelletizing operations, Whereas the pellets in the layer represented by areas A, D, and A are those resulting from a single pelletizing operation. At the discharge end of the pelletizing machine the pellets in the side layers represented by areas A and B, and A and B, are again recycled back to the feed end of the machine to form the hearth layer represented by areas B, C, B whereas the pellets in the intermediate layers represented by areas D and C are discharged as the final product, the above process being performed continuously so long as the pelletizing operation is carried out. This product is of high quality, it being possible according to the invention consistently to make such a product so it develops less than about 4% fines of 28 mesh in the standard tumble test.

The net gain in product output is represented by the pellets in the layer of area C. Depending on the size and proportions of the traveling grate, this gain can be from about 20% to 50% based onthe output represented by area D alone. With a grate having the cross sectional area dimensions indicated above, the gain is about 34%. This gain can be achieved with little if any greater fuel require- I'IlfilliS or operating expenses than are required to produce the high quality pellets in the central layer represented by area D alone and with only a relatively small increase in capital investment. Indeed, if the side layer pellets that are recycled back to form the hearth layer are not subjected to cooling sprays or the like, they have a substantial amount of heat which tends to reduce the heat which must be supplied by fuel.

FIGURES 1, 2, 3, 6, 7 and 8 of the drawings illustrate one form of means which may be advantageously employed in .the apparatus of FIGURE-S '1 to 10 inclusive to carry out such a method. As shown in FIGURES 3, 6, 7 and 8, such means includes a housing, generally indicated by numeral 3t}, located at the discharge end of the traveling grate for segreating from the pellets discharged from the grate those of substandard strength located in layers adjacent the side walls of the grate, and for carrying such weak pellets to suitable conveying means which transports them to the 'feed end of the traveling grate. Such housing means also acts to receive the pellets of satisfactory strength from the Zone of the traveling grate located between such side layers of pellets and to discharge such satisfactory pellets as product for subsequent handling.

This housing includes a rear hopper 31 the upper portion of which is located to receive pellets discharged from the pallets 21 of the traveling grate as they move downwardly into the return run. Hopper 31 has adjustable partitions 32a and 32b subdividing the flared upper portion of the hopper into two passages 33a and 33b which communicate through ducts 34a and 34b with outlet members 35a and 35b and also includes between these side partitions an intermediate opening divided by stationary central parti tion 36 into two passages 37a and 37b which communicate through ducts 38a and 38b with outlet members 39a and 3% through which the product is discharged.

The housing Stl also preferably includes a forward hopper 41 located to receive pellets dropping through the opening 42 (FIGURES 3 and 9) which develops between pallets 21 as the rearmost pallet moves by gravity from the upper run of abutting pallets down around the dis charge end of the machine toward the lower run. This hopper 41, similarly to the rear hopper 31. has a flared upper portion better to collect the pellets, which portion is divided by

adjustable partitions

43a and 43b which segregate the side layer pellets which are of substandard strength from the remainder of the pellets dropping through opening 42. The resulting side passages 44a and 44b communicate with

ducts

45a and 45b connected to the outlet members 35aand 35b connected to ducts 34a and 34b of the rear hopper. The intermediate upper portion of the forward hopper 41 is subdivided by stationary central partition 46 into passages 47a and 47b communicating with

ducts

48a and 48b discharging into the outlet members 39a and 3% which also receive the product pellets from the rear hopper 31.

In the illustrated embodiment, as is shown to particular advantage in FIGURES 3 and 6, the side partitions 32a and 32b of the rear hopper 31 are rigidly mounted on shafts 51a and 51b journaled in the rear hopper 31.

These shafts respectively have crank portions 52a and 5% connected to an air cylinder 53 by suitable linkage means generally designated by reference numeral 54, which is adapted to move simultaneously and to identical angular amounts in opposite directions the side partitions 32a and 3212. By control of cylinder 53, it is possible to adjust the width of the side layers of pellets discharging from the traveling grate into rear hopper .31 and passing through ducts 34a and 341) into the outlet members 39a and 3%.

The

partition

43a and 43b of the forward hopper 41 are also adjustable by bolts 55 (see FIGURES 6 and 8) extending through slots 56 in the inclined supporting portion 57 of each of the

partitions

43a and 43b and secured to the inclined walls of the hopper. Removable plates 58 permit ready access to such bolts for adjust- 7 ment of the partitions to variou positions as indicated by the full and broken lines in FIGURE 6.

Preferably, as shown in FIGURES 1, 2, 8 and 9, there is a hood 59 communicating with an exhaust duct 66, which hood extends over and encloses the discharge portion of the machine and the upper portion of hoppers 31 and 41, to remove dust which may arise from discharging pellets and to aid in cooling.

As is shown in FIGURES 1, 2, 3, 7, 8 and 9, the outlet members 3% and 39b discharge the product pellets onto short metal conveyors 61a and 6112 which discharge such pellets onto vibratory screens 62a and 62b. The final product pellets of a desired size predetermined by the screens discharge from the screens onto a conveyor 63 which transports them to finished storage or to shipping in the usual manner. The undersized pellets pass through the screens into conduits 64, and thereafter are handled conventionally. It should be noted that while in this embodiment the product pellets discharged from the machine are divided into two streams, as may be desirable when the output is so large that it cannot conveniently be handled by commercially available screening apparatus, the invention is not restricted to such a design but also contemplates that the product pellets can be discharged from the traveling gate in a single stream onto a single screening apparatus. The product conveyors 61a, 61b and 63, and the screening apparatus 62a and 6212, may be of conventional construction and hence require no further description.

The recycle side layer pellets from the side portions of the traveling grate are discharged through

ducts

34a and 45a, and 34b and 45b, into outlet members 35a and 35b which in turn discharge onto short conveyors 65a and 65b which carry the pellets to a cross conveyor 66. This conveyor 66 transports the pellets to and deposits them on an inclined conveyor 67 which conducts them to an elevated point at the feed end of the pelletizing machine as seen in FIGURES l and 2.

Another cross conveyor 68 receives the pellets discharged from the inclined conveyor 67 and conducts them to a feed hopper 71 located above the feed end of the traveling grate 2. The conveyors 65a and 65b and cross conveyors 66 and 68 shown are of conventional construction having metal troughs which will resist damage by the hot pellets and which are magnetically vibrated to advance the pellets along the troughs in the directions of the arrows. The inclined conveyor 67 is also of conventional belt-type construction having a material-carrying upper run made up of overlapping metal troughs which are not harmed by the hot pellets and which positively carry the pellets up the incline to the point of discharge.

The feed hopper 71 shown is of a conventional type, and has a bottom outlet which is as wide as the pelletcarrying width of the traveling grate 2. The hopper 71 includes a control valve member '72, shown in FIGURE 10, which may be adjusted to regulate the rate of feed, and hence the thickness of the hearth layer, of the recycle pellets discharged by gravity from the hopper onto the hearth of traveling grate 2. The feed hopper '71 is preferably sufiiciently large to provide for temporary storage of a substantial volume of pellets, thus providing for any irregularities in the rate at which recycle side layer pellets are delivered tothe feed end of the pelletizing machine.

In operation of the apparatus illustrated in FIGURES 1 to 10, inclusive, after start-up operations have been completed, the side layer pellets of substandard strength from adjacent the side walls 25 of the traveling grate 2, represented by zones A, B and A, B of FIGURE 4, are segregated from 16 remainder of the pellets by

partitions

43a and 43b of the forward hopper and by partitions 32a and 32b of the rear hopper of the housing 3% The remainder of the pellets in the intermediate portion of the grate, represented by areas C and D of FIGURE 4,

are discharged into passages 47a and 47b of the forward hopper and into passages 37a and 37b of the rear hopper of the housing 30, from whence they are discharged through outlet members 3% and 39]) onto conveyors 61a and 61b and screens 62a and 62b onto the product removal conveyor 63.

The pellets of substandard strength segregated by partitions 43:: and 4311 into passages 44a and 44b of the front hopper 41, and by partitions 32a and 32b into passages 33a and 33b of the rear hopper 31, are discharged through outlet members 35a and 35b onto conveyors 65a and 6511 which in turn discharge these pellets onto the common cross conveyor 66. This conveyor discharges the pellets onto the inclined conveyor 67 which carries them to and discharges them upon cross conveyor 68 which conducts them to the feed hopper 71.

The feed hopper 71 temporarily stores these pellets and the valve member 72 discharges them as a hearth layer of substantially uniform thickness across the full width of the hearth 24 of the traveling conveyor 2. By the means previously described, a layer of moist green balls is then deposited on top of such hearth layer, preferably in sufficient quantity to fill the traveling grate to the desired depth, as shown in FIGURE 5. The traveling grate, which is continuously moving during these feeding operations, conducts the bed, which is made up of the hearth layer of substandard side layer pellets and the superposed layer of moist green balls, through the various treatment zones of the pelletizing machine. In these zones the pellets and balls are subjected to pelletizing treatment as the grate conveys them to the discharge end of the pelletizing machine. Here the side layers of pellets are segregated as described above and returned to the feed end of the machine and the remainder of the pellets are discharged, screened and handled in the conventional manner as final product.

It will be observed that the pellets in the hearth layer formed of recycled side layer pellets are thus subjected to a second pelletizing operation, the two cycle pellets discharged as product from this layer, corresponding to those in the zone C of FIGURE 4, are of high quality and excellent strength, comparable to the single cycle pellets produced from green balls in the single pelletizing operation and discharged as product from the layer represented by zone D of FIGURE 4. This is true of the pellets resulting from zone C even though pellets resulting from a single treatment in this zone are of substandard strength. Consequently the product of the machine, made up of the pellets discharged from the composite layer made up of the layers represented by zones C and D of FIGURE 4 will be of exceptionally high quality and strength.

Preferably the widths of the side layers of pellets which are segregated and returned to the feed end of the pelletizing machine are identical. This width preferably is such that substantially all pellets in the side layers represented by areas A, B and A, B of FIGURE 4, which do not have the desired characteristics as compared with the pellets in the layer of area D of FIGURE 4, are segregated from the remaining pellets on the bed and returned to the feed end of the apparatus to form the hearth layer represented by areas B, C, B of FIGURE 4. Furthermore, it is preferable to adjust the transverse thickness of such side layers so that enough pellets are removed from the sides of the grate to form a hearth layer of sufiicient thickness that the final pellets discharged from the portion of the hearth layer represented by zone C at the discharge end of the machine, after these pellets have twice passed through the pelletizing operation, will have a hardness comparable to the pellets in area D. The optimum thicknesses of the side and hearth layers can be readily determined by simple experimentation or by experience based on the composition of the green balls and the characteristics of the pelletizing machine. The width of the side layers of pellets segregated from the remainder of the pellets at the discharge end of the machine can be adjusted by varying the positions of the

partitions

32a, 32b and 43a and 43b of the housing 39, and the thickness of the hearth layer can be adjusted by regulating the side layer thickness and the position of valve member 72 of the feed hopper 71, as previously described.

In this embodiment it is apparent that the pellets which are recycled to form the hearth layer are not segregated on the basis of size, but on the basis of their location in the bed, which location determines the characteristics, other than size, of the recycled pellets.

While in the embodiment described above the side layer pellets are not screened before being deposited in a hearth layer on the grate, in some cases such screening may be desirable. FIGURE 11 illustrates one means for perfiorming such screening. This figure shows a vibratory screening deivce 73 of conventional construction located to receive the side layer pellets from outlet member 3512-01 housing 30. The pellets over a predetermined size which do not pass through the screen 74 roll down to the cross conveyor 66 corresponding to the conveyor identified by the same reference number in the embodiment of FIGURES l10. The undersized material passing through the screen drops through discharge conduit 75 for disposition as desired. In this embodiment there is, of course, an identical screening device 73, not shown, which receives and screens the side layer pellets from outlet member 351) on the other side of the apparatus and deposits the pellets over a predetermined size on the conveyor 66, while similarly disposing of undersized material. The pellets on conveyor 66 may then be handled as described above.

While in the embodiment of FIGURES 1 to inclusive the pellets removed from the side layers of single pelletizing machine are returned to form the hearth layer of the same machine, it is possible according to the invention to segregate the insufiiciently hardened pellets from the side layers of a plurality of pelletizing machines, temporarily store such pellets, and then to use such pellets to form the hearth layers on a plurality of pelletizing machines. FIGURES l2 and 13 illustrate such an arrangement. In these figures parts which are identical to those of the embodiment in FIGURES 1 to 10 bear the same reference characters.

In FIGURES l2 and 13 there are two pelletizing machines, designated reference numerals 1' and 1". The machines and their apurtenant apparatus are substantially identical, except that the lower cross conveyors 66 and as extend in opposite directions toward each other and their discharge ends are offset to permit them to dis charge on the common inclined conveyor 81 located between the pelletizing machines.

More specifically, each of the pelletizing machines comprises a traveling grate 2 adapted to be driven in the usual manner between a hood structure 3 and wind boxes which subject the material on the grate to pelletizing treatments like those previously described. Each of these pelletizing machines includes means for forming a hearth layer 28 of pellets on the traveling grate, comprising a feed hopper '71 like that previously described. It also has associated with it balling drums 10 and apparatus and equipment for supplying green balls, and feeding a layer 29 of such green balls on the hearth, such means including a swinging conveyor 12.

At its discharge end each pelletizing machine includes a housing 34), identical with that previously described in connection with FIGURES 1-10, which isadapted to segregate side layers of substandard pellets from the discharge end of the traveling grate and convey them to conveyor 65a or 651) as the case may be. Each housing 30 is also adapted to receive the product pellets from the portion of the grate between the side layers and deposit them on conveyors dial and 61b from which they pass to the screening devices 62a and 62b and thence to the product removal conveyor 63.

In pelletizing machine I of FIGURE 12 the pellets of substandard strength from the side layers are deposited by conveyors 65a and 65b on cross conveyor 66, from which they pass to inclined conveyor 8-1. In pelletizing machine 1 of FIGURE 12 pellets from the side layers of the machine are deposited by conveyors 65a and 651) on the cross conveyor 66' from which they pass to the same inclined conveyor '81. Inclined conveyor 81 is generally similar to the conveyor 67 of the previous embodiment except that its width and angle of inclination are greater. Inclined conveyor 81 deposits the pellets carried by it into a common hopper 82 which temporarily stores the pellets. The pellets are withdrawn from hopper 82 by cross conveyors 68 and 68' (shown in FIGURES 12 and 13) which conduct them to the feed hoppers 71 of both machines. From the feed hoppers the pellets are deposited to form the hearth layers 28 as previously described,

The optimum transverse thickness of the wide layers which are segregated from the remainder of the pellets from the grates of machines 1' and I" can be readily established in the light of the considerations and by means similar to those previously described. These side layer pellets are mingled in hopper 82 which forms a reservoir or common supply of substandard pellets for forming hearth layers on machines 1 and I". As was previously indicated in discussing the apparatus of FIGURES 1-10, the width of the side layers removed from machines 1' and 1" is preferably such as to provide an adequate supply of substandard pellets in hopper 82 to form hearth layers on both machines 1' and I" of the proper thickness to produce in the hearth layers pellets of proper strength after the second pass over the grate.

It will be understood that although two traveling grate pelletizing machines 1' and I" are shown in FIGURE 12, any desired number of machines may be arranged in similar manner to be supplied with substandard hearth layer pellets from a common hopper or the like. In the preterred mode of operation of my method in a plurality of pelletizing machines the substandard pellets are removed from the side layers at the discharge ends of the machines at a volume and rate sufiicient to form the desired hearth layers on all of the machines. The common storage hopper (82 in FIGURE 12) could be initially filled with the substandard pellets at the start of an operation so that it will provide a bank or reservoir of substandard pellets which will be available to provide an adequate supply for all of the hearth layers on start-up and even if there should be temporary irregularity in the supply of pellets from the side layers of one or more of the machines.

In each of the embodiments described above, the side layer pellets are not cooled, but are transported by heatresistant conveying means toward the charging end of the machine, and are formed into the hearth layer while hot. This reduces fuel consumption. However, according to the present invention the side layer pellets may be cooled to a temperature low enough to permit them to be transported on less expensive but less heat resistant conveyors, such as belt conveyors having belts of reinforced rubber or the like. This modification is illustrated by FIG- URE 14, which represents the discharge end of a pelletizing machine which is identical with the machines of FIG- URES 1-10 and 12 except for the means for cooling, discharging, and transporting side layer pellets.

FIGURE 14 shows the pellet segregating housing lit? at the discharge end of the pelletizing machine, At each side of the machine this housing 30 discharges the side layer pellets into a hopper 9t) in which they are sprayed with cooling water from a pipe 91 controlled by valve 92. The cooled side layer pellets discharge from each hopper 99 onto an associated conveyor 93; the conveyor 93 from both sides of the machine discharge the side layer pellets onto a conveyor 94 from which they pass to the inclined conveyor 95 which transports them toward the charging end of the machine. Since the pellets are cooled to a sufiiciently low temperature, the conveyors 93, 94 and 95 may he belt conveyors having belts of rubber or the like.

If the inclined conveyor 95 corresponds to conveyor 67 of a single unit apparatus as shown in FIGURES 1 and 2, the upper cross conveyor 68 can be a similar belt conveyor. If conveyor 95 corresponds to inclined conveyor 81 of a multiple unit apparatus similar to that of FIGURE 12, then each of the upper cross conveyors 68 and 68' can be a belt conveyor with a belt of rubber or the like.

It is apparent that various modifications in addition to those indicated above may be made in the procedures an apparatus disclosed herein. For example, while each of the pelletizing machines illustrated provides downdraft preheat and high temperature heating zones it is apparent that the invention is also applicable to pelletizing machines and to operations in which the pellets are subjected to updraft preheat and/ or high temperature heating. Also while it is advantageous to provide storage hoppers, such as hoppers 71 and 82 of the embodiments, it is apparent that the recycled side layer pellet might be conveyed directly to the charging end of the grate and deposited thereon without an intermediate hopper. The side layer pellets may be both screened and cooled. Furthermore, the invention may be employed in connection with traveling grates other than those illustrated, including traveling grates in which the confronting side walls are differently shaped and positioned than the flat, vertical, parallel side walls shown. It will also be understood that the side layer pellets or other material which is to be recycled may be segregated on the basis of another standard than the indicated tumble test, and that the invention nay also be employed in connection with the treatment of various materials, other than iron oxide pellets, in which similar problems arise due to insufiicient treatment of materials in the side layers and hearth layers,

These and other modifications of the invention will be apparent to those skilled in the art. It is therefore to be understood that this patent is not limited to the forms of the invention disclosed herein or in any other manner than by the scope of the appended claims.

I claim:

1. The method of treating particulate material on a traveling support having a bottom and upwardly extending side walls and a charging end and a discharge end, which method includes the steps of depositing on said support near its charging end a transversely extending layer of said particulate material which has previously traveled over said support and been subjected to treatment thereon as a side layer adjacent at least one of its side walls, moving said particulate material on said grate through a treating zone providing treating conditions including heating, separating the material discharged at the discharge end of said traveling support into a side layer portion comprising material from adjacent at least one of said side walls and a product portion comprising the remander of the material discharged from said support, returning said side layer portion of material to the charging end of said support and utilizing it to form said transversely extending layer, whereby material which travels over said support in at least one side layer thereof is subjected to two treatments thereon, first as a side layer and second as a transversely extending layer.

2. In the treatment of particulate solid materials on a traveling support having a charging end and discharge end and also having a bottom and upwardly extending side walls which support travels through a treating zone providing treating conditions including heating for imparting desired characteristics to particulate material carried by said support, the improvement which comprises depositing on said traveling support near its charging end a substantially uniformly thick first layer of particulate material which has been previously subjected to treating conditions while carried through such treating zone on a similar traveling support in side layers adjacent the side walls of the support, depositing on said first layer a second layer of untreated particulate material, moving said traveling support carrying said first and second layers toward its discharge end through said treating zone, removing at the discharge end of said support the treated particulate material in side layers adjacent said upwardly extending side walls of said support, separately discharging from the discharge end of said support the treated particulate material located between said side layers, conveying said side layer material to the charging end of a traveling support, and utilizing said side layer material to form a first layer on said traveling support.

3. In the treatment of particulate solid materials on a traveling support having a charging end and discharge end and also having a bottom and upwardly extending side walls, which support travels through a treating zone providing treating conditions including heating for imparting desired characteristics to particulate material carried by said support, the improvement which comprises depositing on the bottom of said traveling support near its charging end a substantially uniformly thick first layer of particulate material which has been previously subjected to treating conditions while carried through such treating zone on said traveling support in side layers adjacent said side walls of said support, depositing on said first layer a second layer of untreated particulate material, moving said traveling support carrying said first and second layers toward its discharge end through said treating zone, removing at the discharge end of said support the treated particulate material in side layers adjacent said side walls of said support, separately discharging from the discharge end of said traveling support the treated particulate material located between said side layers, conveying said side layer material to the charging end of said support, and utilizing said side layer material to form said first layer on said traveling support.

4. In the treatment of particulate solid materials on a plurality of traveling supports each having a charging end and discharge end and also having a bottom and upwardly extending side walls, which support travels through a treating zone providing treating conditions including heating for imparting desired characteristics to particulate material carried by said support, the improvement which comprises depositing on the bottom of each traveling support near its charging end a substantially uniformly thick first layer of particulate material which has been previously subjected to treating conditions while carried through such treating zone on a traveling support in side layers adjacent the side walls of said support, depositing on said first layer on each traveling support a second layer of untreated particulate material, moving each traveling support carrying said first and second layers toward its discharge end through said treating zone, removing at the discharge end of each of said supports the treated particulate material in side layers adjacent the side walls of said support, separately discharging from the discharge end of each of said traveling supports the treated particulate material located between said side layers on said support, conveying said side layer material to the charging ends of said traveling supports, and utilizing said side layer material to form said first layers on said traveling supports.

5. In the pelletizing of moist green balls containing iron oxide on a traveling grate having a charging end and a discharge end and also having upwardly extending side walls and a perforate hearth, which grate travels through treating zones providing pelletizing conditions which heat harden said green balls carried by said grate into iron oxide pellets, the improvement which comprises depositing on the hearth of said traveling grate near its charging end a substantially uniformly thick hearth layer of iron oxide pellets which had been previously subjected to pelletizing conditions while carried on a traveling grate in side layers adjacent the side walls of the grate, depositing on said hearth layer a layer of said moist green balls containing iron oxide, moving said traveling grate carrying said layers toward the discharge end of said grate through said treating zones providing pelletizing conditions, re-

moving at the discharge end of said grate the side layer pellets in side layers adjacent the side walls of said grate, separately discharging from the discharge end of said grate the pellets located between said side layers, conveying said side layer pellets to the charging end of a traveling grate, and utilizing said side layer pellets to form a hearth layer on said grate.

6. In the pelletizing of moist green balls containing iron oxide on a traveling grate having a charging end and a discharge end and also having upwardly extending side walls and a perforate hearth, which grate travels through treating zones providing pelletizing conditions which heat harden such green balls carried by said grate into iron 'oxide pellets, the improvement which comprises depositing on the hearth of the traveling grate near its charging end a substantially uniformly thick hearth layer of iron oxide pellets which had been previously subjected to pelletizing conditions while carried on said traveling grate in side layers adjacent said side walls of said grate, depositing on said hearth layer a second layer of said moist green balls containing iron oxide, moving said traveling grate carrying said layers toward the discharge end of said traveling grate through said treating zones providing pelletizing conditions, removing at the discharge end of said grate the side layer pellets in side layers adjacent the side walls of said grate, separately discharging from the discharge end of said grate the pellets located between said side layers, conveying said side layer pellets to the charging end of said grate, and utilizing said side layer pellets to form said hearth layer on said traveling grate.

'7. In the pelletizing of moist green balls containing iron oxide on a plurality of traveling grates, each having a charging end and a discharge end and also having upwardly extending side walls and a perforate hearth which grate travels through treating zones providing pelletizing conditions which heat harden green balls carried by said grate into iron oxide pellets, the improvement which comprises depositing on the hearth of each traveling grate near its charging end a substantially uniformly thick hearth layer of iron oxide pellets which had been previously subjected to pelletizing conditions while carried on a traveling grate in side layers adjacent theside walls of the grate, depositing on said hearth layer on each traveling grate a layer of said moist green balls containing iron oxide, moving each traveling grate carrying said layers toward its discharge end through said treating zones providing pelletizing conditions, removing at the discharge end of each of said grates the side layer pellets in side layers adjacent the side walls of said grate, separately discharging from the discharge end of each of said grates the pellets located between said side layers on said grate, conveyingsaid side layer pellets to means providing temporary storage, and utilizing side layer pellets from said temporary storage means to form said hearth layers on said grates.

8. Apparatus for treating particulate materials comprising a generally horizontally disposed traveling support having a charging location and a discharge location and comprising a bottom and upwardly extending side walls; means for moving said traveling support so it travels from its charging location toward its discharge location; means for depositing particulate material on said support; means for subjecting said particulate material carried on said support to treatment including heating as said support travels; and diverting means at the discharge location of said support for segregating as layers the particulate material adjacent the side walls of said traveling support from the remainder of the particulate material discharged by said support.

9. Pelletizing apparatus comprising a generally horizontally disposed traveling grate having a charging end and a discharge end and comprising a gas permeable hearth and upwardly extending confronting side walls; means for moving said grate so its upper run travels from said charging end to said discharge end; means for depositing green balls on said grate; means for subjecting said balls on said grate to treatment including passing high temperature gases through the balls on the grate and through the bottom of the grate to form heat-hardened pellets as the grate travels; means for segregating pellets at the discharge end of the grate comprising an upwardly extending partition located near and spaced from each side wall of said grate at its discharge end for separating the pellets in side layers adjacent the side walls of the grate from the remainder of the pellets; means for transporting said side wall pellets to the charging end of said grate; means for depositing said side wall pellets on the hearth of said grate to form a hearth layer on which said green balls are deposited; and means for receiving the remainder of the pellets.

It). The apparatus of claim 9 in which said partition means are adjustable relatively to said side walls of said grate.

11. Pelletizing apparatus comprising a plurality of generally horizontally disposed traveling grates each having a charging end and a discharge end and comprising a gas permeable hearth and upwardly extending confronting side walls; means for moving each of said grates so its upper run travels from its charging to its discharge end; means for depositing green balls on each of said grates; means for subjecting said balls on said grate to treatment including passing high temperature gases through the balls on the grate and through the bottom of the grate to form heat-hardened pellets as the grate travels; means for segregating pellets at the discharge end of each of the grates comprising an upwardly extending partition located near and spaced from each side wall of said grate at its discharge end for separating the pellets in side layers adjacent the side walls of the grate from the remainder of the pellets; means for receiving and temporarily storing side wall pellets from said segregating means of said grates; means for depositing side wall pellets from said temporary storing means to form a hearth layer on each grate on which said green balls are deposited; and means for receiving the remainder of the pellets other than the side wall pellets from each of said grates.

12. The apparatus of claim 11 in which said partition means are adjustable relatively to said side walls of each of said grates.

l3. Pelletizing apparatus comprising a generally horizontally disposed traveling grate having a charging end and a discharge end and comprising a gas permeable hearth and upwardly extending confronting side walls; means for moving said grate so its upper run travels from said charging end to said discharge end; means for depositing green balls on said grate; means for subjecting said balls on said grate to treatment including passing high temperature gases downdraft through the balls on the grate and through the bottom of the grate to form heat-hardened pellets as the grate travels; means for segregating pellets at the discharge end of the grate comprising an upwardly extending partition located near and spaced from each side wall of said grate at its discharge end for separating the pellets in side layers adjacent the side walls of the grate from the remainder of the pellets; means for transporting said side wall pellets to the charging end of said grate; means for depositing said side wall pellets on the hearth of said grate to form a hearth layer on which said green balls are deposited; and means for receiving the remainder of the pellets.

14. Pelletizing apparatus comprising a generally horizontally disposed traveling grate having a charging end and a discharge end and comprising a gas permeable hearth and upwardly extending confronting side walls; means for moving said grate so its upper run travels from said charging end to said discharge end; means for depositing green balls on said grate; means for subjecting said balls on said grate to treatment including passing high temperature gases through the balls on the grate and through the bottom of the grate to form heat-hardened pellets as the grate travels; means for segregating pellets at the discharge end of the grate comprising an upwardly extending partition located near and spaced from each side wall of said grate at its discharge end for separating the pellets in side layers adajcent the side walls of the grate from the remainder of the pellets; means for separating said side wall pellets from those below a predetermined size; means for transporting said side wall pellets to the charging end of said grate; means for depositing said side wall pellets on the hearth of said grate to form a hearth layer on which said green balls are deposited; and means for receiving the remainder of the pellets.

15. Pelletizing apparatus comprising a generally horizontally disposed traveling grate having a charging end and a discharge end and comprising a gas permeable hearth and upwardly extending confronting side walls; means for moving said grate so its upper run travels from said charging end to said discharge end; means for depositing green balls on said grate; means for subjecting said balls on said grate to treatment including passing high temperature gases through the balls on the grate and through the bottom of the grate to form heat-hardened pellets as the grate travels; means for segregating pellets at the discharge end of the grate comprising an upwardly extending partition located near and spaced from each side wall of said grate at its discharge end for separating the pellets in side layers adjacent the side walls of the grate from the remainder of the pellets; means for cooling said side wall pellets; means for transporting said side wall pellets to the charging end of said grate; means for depositing said side Wall pellets on the hearth of said grate to form a hearth layer on which said green balls are deposited; and means for receiving the remainder of the pellets.

16. The apparatus of claim 8 in which said diverting means are adjustable to remove varying amounts of material in layers adjacent to said side walls of said traveling support.

17 The apparatus of claim 8 comprising means for depositing said segregated side layer material in a transverse layer on said support.

18. Apparatus for treating particulate materials comprising a generally horizontally disposed traveling support having a charging location and a discharge location and comprising a bottom and upwardly extending sidewalls; means for moving said traveling support so it travels from its charging location toward its discharge location; means for depositing on said support a layer of particulate material to be treated; means for subjecting particulate material carried on said support to treatment including heating as said support travels; diverting means at the discharge location of said support for segregating as layers the particulate material adjacent the sidewalls of said traveling support from the remainder of the particulate material discharged by said support; means for conveying said sidelayer particulate material to the charging location of said support; and means for depositing said sidelayer particulate material on said support in a different layer from the layer in which is deposited said particulate material to be treated.

19. Apparatus for treating particulate materials comprising a plurality of generally horizontally disposed traveling supports each having a charging location and a discharge location and comprising a bottom and upwardly extending sidewalls; means for moving each of said traveling supports so its travels from its charging location toward its discharge location; means for depositing on each of said supports a layer of particulate material to be treated; means for subjecting particulate material carried on each support to treatment including heating as said support travels; diverting means at the discharge location of at least one of said supports for segregating as layers the particulate material adjacent the sidewalls of said traveling support from the remainder of the particulate material discharged by said support; means for conveying said sidelayer particulate material to the charging location of one of said supports; and means for depositing said sidelayer particulate material on said support in a layer different from the layer in which is deposited said particulate material to be treated.

References Cited by the Examiner UNITED STATES PATENTS 1,926,032 9/33 Bunce et a1 26621 X 2,411,873 12/46 Firth 3 2,750,272 6/56 Lellep 75-3 2,821,469 1/58 Davis 75-5 2,980,291 4/61 Schuerger 75-5 BENJAMIN HENKIN, Primary Examiner.

DAVID L. RECK, Examiner.

Claims

1. THE METHOD OF TREATING PARTICULATE MATERIAL ON A TRAVELING SUPPORT HAVING A BOTTOM AND UPWARDLY EXTENDING SIDE WALLS AND A CHARGING END AND A DISCHARGE END, WHICH METHOD INCLUDES THE STEPS OF DEPOSITING ON SAID SUPPORT NEAR ITS CHARGING END A TRANSVERSELY EXTENDING LAYER OF SAID PARTICULATE MATERIAL WHICH HAS PREVIOUSLY TRAVELED OVER SAID SUPPORT AND BEEN SUBJECTED TO TREATMENT THEREON AS A SIDE LAYER ADJACENT AT LEAST ONE OF ITS SIDE WALLS, MOVING SAID PARTICULATE MATERIAL ON SAID GRATE THROUGH A TREATING ZONE PROVIDING TREATING CONDITIONS INCLUDING HEATING, SEPARATING THE MATERIAL DISCHARGED AT THE PORTION COMPRISING MATERIAL FROM ADJACENT AT LEAST ONE OF SAID SIDE WALLS AND A PRODUCT PORTION COMPRISING THE REMANDER OF THE MATERIAL DISCHARGED FROM SAID SUPPORT, RETURNING SAID SIDE LAYER PORTION OF MATERIAL TO THE CHARGING END OF SAID SUPPORT AND UTILIZING IT TO FORM SAID TRANSVERSELY EXTENDING LAYER, WHEREABY MATERIAL WHICH TRAVELS OVER SAID SUPPORT IN AT LEAST ONE SIDE LAYER THEREOF IS

8. APPARATUS FOR TREATING PARTICULATE MATERIALS COMPRISING A GENERALLY HORIZONTALLY DISPOSED TRAVELING SUPPORT HAVING A CHARGING LOCATION AND A DISCHARGE LOCATION AND COMPRISING A BOTTOM AND UPWARDLY EXTENDING SIDE WALLS; MEANS FOR MOVING SAID TRAVELING SUPPORT SO IT TRAVELS FROM ITS CHARGING LOCATION TOWARD ITS DISCHARGE LOCATION; MEANS FOR DEPOSITING PARTICULATE MATEIRAL ON SAID SUPPORT; MEANS FOR SUBJECTING SAID PARTICULATE MATERIAL CARRIED ON SAID SUPPORT TO TREATMENT INCLUDING HEATING AS SAID SUPPORT TRAVELS; AND DIVERTING MEANS AT THE DISCHARGE LOCATION OF SAID SUPPORT FOR SEGREGATING AS LAYERS THE PARTICULATE MATERIAL ADJACENT THE SIDE WALLS OF SAID TRAVELING SUPPORT FROM THE REMAINDER OF THE PARTICULATE MATEIRAL DISCHARGED BY SAID SUPPORT.