US3594286A - Carbonizing multiple layers of material by maintaining reducing atmosphere in bed and oxidizing atmosphere above bed - Google Patents

Abstract

A PROCESS OF DEVOLATILIZING MATERIAL CONTAINING VOLATILES WHICH INVOLVES THE FEEDING OF SUCH MATERIALS ONTO A MOVING HEARTH IN A SERIES OF SUCCESSIVELY APPLIED SHALLOW LAYERS WHEREIN EACH SUCH APPLIED LAYER IS AT LEAST PARTIALLY DEVOLATILLIZED BEFORE APPLICATION OF THE NEXT SUCCESSIVE LAYER AND UNDER THE ACTION OF THE RADIANT HEAT OF A PRECEDING LAYER AND RADIANT HEAT DERIVED FROM COMBUSTION OF EVOLVED VOLATILES.

Description

July 20, 1971 Original Filed Feb. 9, 1966 J. L. KEMMERER, JR 3,594,286 CARBONIZING MULTIPLE LAYERS OF MATERIAL BY MAINTAINING REDUCING ATMOSPHERE ABOVE BED 5 Sheets-Sheet 1 INVENTOR JOHN L. KEMMERER JR.

ATTORNEY y 20, 1971 J. L. KEMMERER, JR 3,594,286 CARBONIZING MULTIPLE LAYERS OF MATERIAL BY MAINTAINING REDUCING ATMOSPHERE ABOVE BED ATTORNEY y 20, 1971 J. KEMMERER, JR 3,594,286

CARBONIZING MULTIPLE LAYERS OF MATERIAL BY MAINTAINING REDUCING ATMOSPHERE ABOVE BED Original Filed Feb. 9. 1966 3 Sheets-Sheet I INVENTOR JOHN LKEMMERER JR United States Patent CARBONIZING MULTIPLE LAYERS 0F MATERIAL BY MAINTAINING REDUCING ATMOSPHERE IN BED AND OXIDIZING ATMOSPHERE ABOVE BED John L. Kemmerer, In, Short Hill, N..I., assignor to Wise Coal & Coke Company, New York, NY.

Continuation of abandoned application Ser. No. 526,245,

Feb. 9, 1966. This application Mar. 31, 1970, Ser.

Int. Cl. Cb 47/20 US. Cl. 201-27 8 Claims ABSTRACT OF THE DISCLOSURE A process of devolatilizing material containing volatiles which involves the feeding of such materials onto a moving hearth in a series of successively applied shallow layers wherein each such applied layer is at least partially devolatilized before application of the next successive layer and under the action of the radiant heat of a preceding layer and radiant heat derived from combustion of evolved volatiles.

This application is a continuation of application Ser. No. 526,245, filed Feb. 9, 1966, now abandoned.

This invention relates to treating materials which contain volatile matter which can be released through the application of heat.

-In one of its aspects the invention relates to the coking, devolatilization, and/or calcining of carbonaceous material by continuously feeding a first relatively thin layer of undevolatilized material to a devolatilizing zone wherein the layer is subjected to a luminescent flame to heat the layer to at least partially devolatilize the same, thereafter, in a continuous operation, feeding a second layer onto the first layer in a devolatilizing zone, and heating the second layer to at least partially devolatilize the second layer and to thereafter add as many layers of carbonaceous material of such depth as to continuously feed a supply of untreated material to the oven as will be necessary to obtain suflicient 'volatiles thereform so as to support a condition which will permit for the autogenetic action for coking and/ or calcining of the product under treatment once the furnace or oven has been put into operation and has attained the desired operating temperatures, that is, a temperature which will insure the material under treatment to give off some of its volatile gases and to utilize such gases to support combustion within the structure housing the material under treatment.

In another of its aspects, the invention relates to a process for devolatilizing a mass of carbonaceous material as hereinbefore described wherein the first layer of material is a thin layer and the second layer of material is a relatively thinner layer and each successive layer of material being thinner than the next preceding layer of material, although it will be appreciated that the thickness of the additional layers of carbonaceous material may not necessarily be thinner than the next preceding layer of material, but vary according to the volatiles contained within the material under treatment, the temperatures at which they will be driven off the carbonaceous material, and the amount of volatiles obtained from such carbonaceous material, which when combined with air or oxygen from an outside source, are caused to combust so as to maintain a substantially uniform temperature within the furnace with material on a continuously moving hearth with carbonaceous material thereon undergoing a coking and/ or calcining operation.

In a still further aspect, the invention relates to a process for devolatilizing carbonaceous materials as hereinbefore described wherein a plurality of thinner layers are successively added to the bed and subsequently heated whereby a coked or calcined product is produced.

In a still further aspect, the invention relates to a process as hereinbefore described wherein the volatiles evolved from the layers of material are collected and are used as a source of heat.

In a still further aspect the invention relates to a process as hereinbefore described wherein the bed of successive layers of material are stirred prior to the addition of another layer.

In a still further aspect, the invention relates to an apparatus for carrying out the processes of this invention.

Many methods have been employed for devolatilizing and calcining of carbonaceous materials, limestone and the like. One such method employs the use of radiant heat to heat a thin bed of carbonaceous material. In a continuous process, employing the radiant heat, the maximum capacity is related to the rate of heating of the moving bed. It has generally been found that thicker beds yield stronger material but take longer to heat. Although the time for heating varies with a given temperature environment with the square of the bed thickness, the thinner beds of carbonaceous materials do not necessarily heat at a proportionately faster rate because of the formation of fluff or foamed coke on top of the moving bed. As the bed becomes thinner and the rate of heating increases, the formation of the porous coke absorbs a greater percentage of the heat. The porous coke or fluff is a good insulator and thus inhibits the flow of heat to the lower extremities of the bed. A process for making such a porous coke or fluff is disclosed and claimed in the co-pending application of Asquini, Ser. No. 230,424, filed Oct. 15, 1962, now Patent No. 3,227,627.

Generally, the time required for devolatilization of calcinable material subjected to radiant heat varies as the square of the diameter of a given particle. In a moving bed operation as hereinbefore described, if no disturbances of the bed are made, the time for devolatilization using radiant heat varies as the square of the thickness of the bed. To speed up the heating process and the devolatilization process, rabbles or stirrers such as those described in co-pending application of John L. Kemmerer, Jr. et al., Ser. No. 423,197, filed Jan. 4, 1965, have been provided.

I have now discovered that the process of calcining on a moving bed can be substantially improved by using the advantage of both the above-mentioned systems. I use a thin bed of material which is continuously being devolatilized, heating at a high rate. This is accomplished by providing a plurality of layers each of which is at least partially devolatilized prior to the addition of another layer of material thereto.

It is well known in the art that one can coke a liquid hydrocarbon by spraying the same alone or combined with solid material onto a moving bed of coke. However, heretofore, it was not recognized that the time required for calcining limestone for coking carbonaceous materials in a luminescent flame heat operation could be significantly reduced by subjecting a plurality of the layers of uncalcined materials to the luminescent flame, and also to the heat emanating from the material already under treatment on a hearth or the like. In this manner,

the raw carbonaceous material to be treated is immediately exposed to two sources of heat, one from the bed of material under treatment and the other from the aforesaid luminescent flame.

'By various aspects of this invention, one or more of the following objects can be obtained.

It is therefore an object of this invention to provide a continuous process for devolatilizing carbonaceous materials containing volatile matter wherein the rate of throughput is increased and the fuel requirement for devolatilization is decreased.

It is a further object of this invention to provide a continuous process for coking carbonaceous materials wherein thinner layers of material are devolatilized.

It is a further object of this invention to provide a process for calcining a calcinable material wherein the rate of calcining is greatly increased with or without the use of rabbles.

It is a still further object of this invention to provide a process for calcining or devolatilizing of carbonaceous materials containing volatile matter wherein the process is carried out with or without the addition of extraneous heat.

It is a still further object of the invention to provide a process for coking and/or calcining volatile containing matter with the employment of an apparatus such as an oven or hearth which may be operated on a continuous basis and which may be driven at a slower speed than heretofore thought feasible for accomplishing a given coking and/or calcining operation, which reduction in driving speed results in reduced wearing of the parts employed in such continuously operating ovens or furnaces.

It is a still further object of the invention to provide an oven or furnace of the continuous type which will permit the addition of material to be coked and/or calcined at vantage points along the oven or furnace so as to insure the maintenance of a substantially constant temperature throughout the area of the oven or furnace.

It is a still further object of this invention to provide an apparatus to carry out the process as hereinbefore described.

Other aspects, objects, and the several advantages of this invention are apparent from a study of this disclosure, the drawings and the appended claims.

According to the invention, there is provided a continuous process wherein a layer of material containing volatile matter is calcined. Successive layers of materials are fed to a devolatilizing zone wherein they are subjected to heat from a luminescent flame, and also to the heat derived from the preceding layer or layers of volatile containing matter undergoing treatment. Therefore, it will be appreciated that the raw or untreated volatile containing matter which is layer loaded onto an apparatus for carrying out the objects of the present invention is exposed to both the heat of the bed of material already undergoing treatment and the heat derived from the luminescent flame, aforesaid. Each layer is at least partially devolatilized prior to the addition of another layer. Preferably, the volatile matter driven off is combusted above the bed and in the case of carbonaceous material, it is the source for the luminescent flame which heats the material to calcining temperatures. In a preferred embodiment of the invention, the second layer which is put on top of the first, is thinner than the first layer and each successive layer is thinner than the next preceding layer of material. The successive layers of materials may not necessarily be thinner than the next preceding layer, although this has been found to be the most effective manner of carrying out the process of layer loading in a devolatilization operation.

It has been found that when a plurality of thin layers are exposed to radiant heat for a time suflicient to partially devolatilize the material, the time necessary to devolatilize a similar bed of material substantially the same thickness as the resulting thickness of the plurality of layers is appreciably reduced. This can be accounted for by reason of the fact that as the raw material is being layer loaded onto a partially devolatilized bed of material on a moving oven or hearth, it is exposed to the heat emanating from the bed of material already under treatment and also the heat derived from the luminescent flame which is ever present over the material under treatment by reason of burning of the volatiles derived therefrom, combined with oxygen to combust the same.

In a preferred embodiment of the invention, a thin layer of carbonaceous material is fed into a furnace where it is exposed to radiation from a luminescent flame which heats the bed to at least partially devolatilize the material. Before the material becomes completely devolatilized, however, a second, preferably thinner layer is fed on top of the first layer. The heat from the first layer as well as the heat from the luminescent flame, heats the second layer to drive off volatile components from it. The second layer is preferably added prior to complete devolatilization of the coking material in the first layer. More layers can similarly be added until the total desired thickness of the bed is reached.

Prior to the addition of each layer to the bed, the bed can be stirred with rabbles or the like, which stirring will result in a final product of loose granular coke.

The invention is applicable to coking, calcining or other devolatilization process in which volatile materials under heat are expelled from solid or solid-like materials.

The materials to which the invention is applicable include but are not liimted to limestone, carbonaceous materials such as non-coking coals, anthracite coals, green petroleum coke pellets or briquettes containing controlled percentages of bituminous coking coal or other carbonaceous material or inerts either with or without a bituminous binder.

The invention will be further described with reference to the accompanying drawings in which FIG. 1 is a schematic, showing an embodiment of the invention as applied to a continuous process using a conveyor belt;

FIG. 2 is another embodiment of the invention showing the invention as applied to a pancake furnace having rabbles;

FIG. 3 FIG. 2;

FIG. 4 is a top plan view with parts broken away of an embodiment of the invention as applied to a rotary donut type oven.

Referring to FIG. 1 there is provided a conventional type furnace having a base 2, side walls 3 and a top 4, all composed of suitable refractory material such as fire brick or the like. Mounted for rotation within the furnace is a continuous conveyor belt mechanism 5 mounted on suitable rollers 6 which are driven by any suitable driving means. The conveyor belt mechanism 5 comprises belt 7 formed of any suitable material, suffice it to say, that it is made of material which will withstand the heat developed within the furnace and is of a flexible nature thereby enabling the belt to be trained over the aforesaid rollers 6 for carrying out the objects of the present invention.

Mounted in the top wall 4 of the furnace are a plurality of baflle plates 8 formed of a suitable material and are secured to the wall 4 in any suitable manner. The baflle plates 8 as clearly shown in FIG. 1 of the drawings provide a series of chambers 9.

Mounted in wall 4 of the furnace are a plurality of chutes 10, 20 and 30 and these chutes are positioned closely adjacent to the aforementioned baffle plates 8. The chutes 10, 20 and 30 extend within the furnace and terminate the outlets '11.

The chutes 10, 20 and 30 are constructed of any suitable material capable of withstanding the heat generated within the furnace and as will be observed from the drawings in FIG. 1, the outlets 11 of the chutes 10, 20 and 30 are arranged at differing heights for a purpose to be more fully described hereinafter.

A discharge opening 12 is formed along one of the side walls 3 of the furnace for permitting the discharge of material from within the furnace to any suitable conveying means such as a roller conveyor structure generally indicated by reference character 13. The roller conveyor is mounted for rotation on a suitable bearing 14 formed is a partial top view of the furnace shown in on an extension of a scraper plate 15 which extends within the discharge opening 12 and terminates in close proximity to the roller 6 at the discharge end of the furnace.

A number of ports 16 are provided in the wall of the furnace for feeding air into chambers 9. It will be noted that the ports 16 are arranged at differing heights so that air which is admitted into the chambers 9 will be admitted at the desired elevation so as to insure combustion of the volatiles in chamber 9 in a manner to be more fully described hereinafter. The material to be coked which is generally indicated by reference character 17 feeds downwardly by gravity onto the conveyor belt mechanism during operation of the furnace illustrated in FIG. 1 of the drawings.

In operation, chute 10 feeds a thin layer of material 18 onto moving conveyor belt 5. The baflle plate 8 which is positioned closely adjacent to the outlet 11 of chute .10 serves to level off the material being fed onto the conveyor mechanisms and to likewise limit the amount of material which is to be received on said conveyor mechanism, the baffles 8 serving in the manner of a leveling plate. The thin layer of material passes into the first chamber 9 where it is subjected to the heat of a luminescent flame produced either by the volatiles evolved from the material under treatment combining with the air from ports 16 when the temperature within the furnace proper is sufiicient to volatilize some of the material under treatment, or if the heat within the furnace proper is not suflicient to cause partial devolatilization in the aforementioned chamber 9 then an external source of heat can be furnished at this point of the furnace so as to heat the material under treatment and to thereby cause the same to release some of its volatile matter. Following the treatment of the material in the first chamber 9 as shown in FIG. 1 of the drawing, a chute 20 which also contains material to be treated feeds by gravity the material to be treated onto the partially devolatilized layer 18. It will be observed that the outlet 11 for chute 20 terminates a short distance above the first layer .18 and serves to deposit a second or additional layer of material onto the partially devolatilized layer within the first chamber 9. A second baffie 8 serves to level off the material fed from chute 20 and it Will be observed that in the second chamber 9 there are shown ports 16- for the admission of air within this second chamber. The air is delivered within the chamber 9 at a level above the top of the bed of material under treatment to oxidize the volatile matter in the upper portion of the chamber of furnace so as to heat the top and side walls of the furnace which will radiate heat onto the material on the conveyor to volatilize such material while effectively maintaining a reducing temperature about the material under treatment. Following the partial devolatilization of the material under treatment in the second chamber 9, additional material to be treated is fed onto the second layer of material in a thin layer and as many added layers as desired can be introduced onto the material under treatment as is desired. While FIG. 1 of the drawings discloses chute 30 as depositing a thin layer of material to be treated on a somewhat heavy bed of material, it will be understood that the furnace employed for carrying out the object of the present invention ion contains feeding chutes between chutes 20 and 30 for building up the height of the material on the conveyor to the extent shown in FIG. 1 of the drawings.

It should be pointed out at this time that the furnace shown in FIG. 1 of the drawings can be caused to operate autogenetically. As will be understood, once the furnace has been in operation for such a time as to cause the walls of the furnace to become heated by reason of the same being exposed to the luminescent flame generated in each of the chambers of the furnace, any material containing volatiles will be at least partially devolatilized by reason of being exposed to the inherent heat of the furnace wall 6 structure and to heat derived from the already formed bed of material undergoing treatment, the volatiles, upon mixing with air which is fed into the various chambers being spontaneously ignited.

It will be noted that vents 19 are provided in the top wall 4 of the furnace and these vents can, when desired, be employed for the removal of volatiles from within the chambers with which they are associated and to deliver these volatiles, by suitable piping, not shown, to any of the chambers along the path of flow of material under treatment so as to supplement the volatiles in such chamber so as to increase the heat in the chambers where the volatiles have been directed. It will therefore be seen that once the heat within the furnace structure has risen to a point suflicient to partially devolatilize the material at the entrance end of the furnace, that such partial devolatilization coupled with the admission of outside air will cause such volatiles to combust and may render the operation of the furnace completely autogenetic. As previously stated, however, outside heat sources can be employed wherever the material under treatment does not contain sufiicient volatilizable material therein to support an autogenetic action in carrying out the objects of the present invention. Also, if desired, rabbles or stirrers can be employed in chambers 9 so that the material under treatment in passing from one chamber to the next will be caused to be moved or stirred on the conveyor so as to expose different portions of the material under treatment to the luminescent flame and to the heat derived from the already formed layer of material undergoing treatment to thereby increase the efficiency of the operation of the process.

Referring now to FIGS. 2 and 3 there is shown an apparatus similar to that described in co-pending application of John L. Kemmerer, Jr. et al., Ser. No. 423,197, filed Ian. 4, 1965, which application is incorporated herein by reference.

In FIGS. 2 and 3 there is provided a furnace having a rotary hearth 40 with an inner hearth surface 41 sloping from the outer periphery of the furnace downwardly to a central soaking pit 42 integral with and depending from the hearth 40. While FIG. 2 of the drawings describes the inner hearth surface 41 as sloping downwardly to a centrally located soaking pit, it is obvious that inner hearth surface 41 can extend on a truly horizontal plane for carrying out the objects of the present invention. The rotary hearth 40 is supported on spaced rollers 43 mounted on a furnace frame 44 and is driven by a motor and a rack and pinion drive in any conventional manner for rotary hearth furnaces. Curb 45 of the furnace extends vertically above the hearth surface 41 at its outer periphery and carries a trough 46 with sand or liquid 47.

The furnace frame 44 carries roof beams 48 which support a refractory roof 49 which has a central flue 50. The roof has a depending wall 51 carrying flange 52 which extends into the sand or liquid 47 carried in trough 46, thus forming a rotary seal between the stationary roof portion 49 and the rotary hearth 40. The roof 49 is provided with air ports 53 leading from a suitable header mechanism 54 mounted on the furnace frame 44 in any suitable manner. Depending walls 51 are provided with air ports 55 and 56 and lead to a suitable header mechanism 57 with valve means 58 and 59 mounted in the pipeline so as to regulate the amount of air issuing from ports 55 and 56. Ports 55 and 56 direct air generally across the hearth in a radial direction and are so positioned in the depending wall 51 so as to cause the introduction of air within the furnace at a level above the top of the material undergoing treatment on the hearth to oxidize the volatile matter derived from the material under treatment and to mix with the same in the upper portion of the furnace and to combust in that area thereby heating the roof and side walls of the furnace so that the heat radiates onto the material on the hearth to devolatilize such material while maintaining a reducing atmosphere about such material under treatment. Burners 60, only one of which is shown in the drawings, are spaced about the roof 49 and these burners are employed for bringing the furnace to operating temperature and to provide additional heat for those reactions which are not completely autogenetic. A radially substantially V-shaped rabble pit 61 is formed in the roof of the furnace from the flue 50 of the roof wall 49 to the side wall 62. The bottom of the pit 61 is provided with slots adapted to receive rabbles 63. These rabbles may be solid or of hollow-like structure with inner vertical batfies for internal cooling depending upon the temperature required for calcining or for otherwise treating the material on hearth 40. For higher temperatures, the latter type rabble is preferred.

A rotary discharge table 64 is provided beneath the soaking pit 42 to receive the output of material from within the soaking pit. A fixed discharge spout 65 is mounted in frame 44 between the soaking pit and discharge table 64. The spout 65 is provided with a peripheral trough 67 carrying sand or liquid 68 into which a depending flange 69 on the soaking pit extends to form a seal between these parts.

According to the invention, there is provided a series of vertical chutes 70, 71, 72, 73, 74, 75, 76 and 77 which are employed for feeding material to be calcined or otherwise treated into the furnace structure. It will be observed that each vertical chute 70 to 77 inclusive is disposed at different levels with respect to the inner hearth surface 41, the first chute 70 lying closely adjacent to the inner hearth surface 41, whereas chut e 77 terminates at an elevation substantially higher with re spect to the inner hearth surface 41 with the intermediate chutes being graduated in spacing also with respect to the inner hearth surface 41. By so spacing chutes 70 to 77 inclusive with respect to inner hearth surface 41 the thickness of each layer of material which is fed onto the rotating hearth can be regulated. As will be seen from FIG. 3 of the drawings the vertical chutes 70 to 77 inclusive are directly behind or downstream of rabbles 63 so that the material being calcined or otherwise treated is stirred or turned prior to the addition of another layer of material thereon. The vertical chutes 70 to 77 inclusive can be of any material, it being sufiicient to state only that they are made of a material suitable for withstanding the heat generated within the hearth of the furnace.

The layer loading of the material undergolng treatment through chutes 70 to 77 inclusive allow more material to be exposed to the radiant heat within the furnace structure thus providing faster heating of the bed of material undergoing treatment. While FIGS. 2 and 3 of the drawings disclose the principle of layer loading through aforementioned chutes 70 to 77 inclusive along with rabbles 63, it is obvious that a furnace of this type can be operated without the rabbles 63, however, the furnace is preferably operated with the layer loading mechanism chutes 70 to 77 inclusive as well as with rabbles 63 to maximize the efiiciency of the operation in the treatment of material whether it be for calcining, or for other diverse type treatment of materials.

While FIGS. 2 and 3 of the drawings disclose the employment of burners so as to supply heat necessary to raise the temperature within the furnace sufiiciently high as to cause the material under treatment to release some of the volatiles contained therein, it is obvious that once the furnace disclosed in FIGS. 2 and 3 has reached a temperature sufficiently high as to cause any material fed therein to devolatilize by reason of the heat radiated from the wall and hearth surfaces as well as from the heat derived from the already formed bed of material undergoing treatment, that air can be supplied to the interior of the furnace in the manner hereinbefore described so as to mingle with the evolved volatiles and to thereby combust so as to heat the interior of the furnace and to maintain a temperature therein which will render the operation to proceed autogenetically. While there is shown but one set of air ports 55 and 56 in FIGS. 2 and 3 of the drawings, it will be obvious that such air admission ports are located at desired locations along the periphery of the stationary or upper portion of the furnace. The spacing of the air admission ports 55 and 56, one above the other, permits the admission of air within the furnace at different levels, thereby permitting the treatment of varying depth of material on the rotating hearth, the lower air admission port being employed when there is a relatively shallow bed on the rotating hearth whereas the upper air admission port is employed when a relatively thick bed of material is undergoing treatment on the rotating hearth.

FIG. 4 of the drawings discloses a modification of the invention wherein there is disclosed the principle of layer loading as applied to a rotary or donut type furnace. The furnace may be of the type described and claimed in the application of Robert J. Asquini, Ser. No. 230,424, filed Oct. 15, 1962, now Patent No. 3,227,627 which is herewith incorporated by reference.

The furnace shown in FIG. 4 can be operated autogenetically or the heat necessary to carry out the process of the instant invention can be furnished from external sources where the material undergoing treatment does not permit for an autogenetic process.

There is shown in FIG. 4 an annular hearth which is caused to rotate at desired speeds through any suitable mechanism. The hearth 90 extends between an inner wall 91 and an outer wall 92 and rotates in the direction of arrow A as shown in FIG. 4. A roof structure 93 extends for 360 over the rotating hearth 90 and the inner wall 91, outer wall 92 and the roof structure 93 form a substantially closed oven-like chamber. The structure shown in FIG. 4, except for the manner of layer loading material to be treated therein, forms no part of the present invention and it is sufficient to set forth that the material to undergo treatment in the furnace depicted in FIG. 4 is admitted into the oven-like structure at the inlet section 94 following which, a leveler 95 levels the material prior to its introduction into a first heating zone generally indicated by reference character 96. Following the treatment of the material in the said first heating zone the material passes to successive heating zones 97, 98, 99, 100, and 101 defined by a series of baffles plates 102, 103, 104, 105 and 106 and to a quenching zone 107 of the conventional type, and thence to a plow mechanism 108 which scrapes off the material from the top surface of the rotating hearth and directs such material to any suitable conveyor or storage container. The heat required for the material under treatment within the oven or hearth can be supplied from extraneous sources such as burners, not shown, positioned either in the roof and inner and outer walls of the hearth or the heat necessary for driving off the volatiles from within the material under treatment on the annular hearth or the heat necessary for driving off the volatiles in the chambers of zones 96, 97, 98, 99, 100 and 101. The volatiles can be burned within the oven structure in a manner similar to that described and claimed in aforesaid application Ser. No. 230,424, filed Oct. 15, 1962 now Patent No. 3,227,627. For the operation of the furnace shown in FIG. 4 of the drawings on an autogenetic basis, there is schematically shown, piping lines 109 which lead for instance from an outlet 110 formed in the roof structure 93 wherein hot gases from within the heating zone 110 defined by bafiles 104 and 105 can be diverted to the initial or first heating zone designated by reference numeral 96, formed between baffies 102 and 103. The hot gases taken from the chamber or zone 100 enter the initial or first heating zone 96 by means of suitable piping generally indicated by reference characters 111 and 112 which direct the flow of gases therethrough and through openings 113, 114, 115 and 116 formed in the inner and outer walls 91 and 92 of the furnace structure. As can be appreciated, any number of piping arrangements can be utilized for transferring hot gases from one chamber or zone to another chamber or zone where it is desired to elevate the temperature in a second zone during the processing of the material under treatment. Also, this will permit for the apparatus to operate on an autogenetic basis after the furnace has been fired for a sufficient period of time so as to permit the partial devolatilization of material being fed into the first heating zone, and it becomes necessary that additional volatiles be fed to the first heating zone in order that with the added volatiles at this stage, when combined with air, will ignite and produce a luminescent flame above the bed of material undergoing treatment.

Means are provided for reheating the hearth during its rotation, after it has been cleared of material thereon by the plow mechanism 108 and this means is shown schematically by a conduit 117 which extends from the area defined by the bafiles 105 and 106 and connects with pipe 118 which direct these hot gases through openings 119 and 120 formed in the inner and outer walls as shown in FIG. 4 of the drawings. The hot gases directed by conduit 117 in the manner aforesaid will heat that portion of the hearth as it passes into zone 121 prior to the deposit thereon of the material to be treated through the material inlet section 94 which can be in the nature of a hopper or the like. By thus reheating the hearth at zone 121, the temperature of the material deposited thereon -will be elevated sufficiently as to cause some of the volatiles therein to be driven otf and to unite with air which is supplied in any suitable manner to the first heating zone 96 and to cause said volatiles and said air to combust so as to maintain the temperature sufficiently high in the first heating zone 96 as to cause a partial devolatilization of the material under treatment and the burning of said evolved volatiles for continuously furnishing the heat necessary for making the process one which will be substantially fully autogenetic resides primarily in the manner of layer loading the material onto the rotating hearth 90. As will be observed, a plurality of inlet chutes 122, 123, 124, 125, 126 and 127 are provided at spaced intervals throughout the circumferential area defined by the furnace structure. The inlet chutes aforesaid, are placed upstream of the bafiles 102, 103, 104, 105 and 106 and are so positioned with respect to the floor structure of the annular hearth 90 as to feed materials to be treated within the furnace in thin layers beginning with a thin layer applied at the first heating zone designated by reference character 96 and applying a still second thin layer of material to the first such layer of material by the next inlet chute 122 and thereafter at successive inlet chutes, additional thin layers are caused to be added to the already formed layers on the hearth until such time as the desired depth of material on the hearth has been attained.

It should be pointed out that the layer loading of material to be devolatilized by the process of the instant invention provides that in all modifications of the apparatus shown for carrying out the instant process, the material to be treated which is added near the discharge end of the apparatus and to the already layered material undergoing treatment is a relatively thin layer of material so as to permit the same to be exposed to both the heat of the bed of material thereunder and to the luminescent flame above as to cause the same to properly be coked and/or calcined before reaching the exit or discharge end of the apparatus.

As will be seen from FIG. 4 of the drawings, the inlet chutes 122, 123, 124, 125, 126 and 127 extend outwardly of the roof 93 and are adapted to contain material to be fed on the rotating hearth. The inlet chutes are constructed of a material which will withstand the temperatures generated within the furnace and may be in the form of a funnel or like structure, enabling material to be processed to be housed therein and to feed by gravity onto the rotating hearth as successive thin layers of material. The inlet chutes and battles aforesaid are disposed within the oven structure in somewhat the same manner as the baflle plates 8 and chutes 10, 20 and 30 described in FIG. 1 of the drawings. That is, the inlet chute adjacent the first heating zone 96 and bafile means 102 associated therewith are so positioned within the furnace as to permit the deposit of but a thin layer of material onto the moving hearth and as the hearth continues its rotation, the next successive chute and baflle means associated therewith permit the addition of a second thin layer of material, and so on, until such time as the hearth completes its complete revolution when the final layer of material is added to the already formed bed of material. As the material passes from one zone to the other during rotation of the hearth, the material is exposed to heating zones and, as stated previously, by reason of being able to withdraw gases of one section and to divert the same to another section along the path of rotation of the hearth, the temperatures in the varying heating zones can be regulated so as to improve the efficiency of operation of the furnace.

As will be evident from the aforegoing disclosure, the practice of the invention allows a given hearth or conveyor furnace to devolatilize more material in a given period of time with the same temperatures being applied to the material under treat-ment. In other words, more devolatilization can take place for a given thickness of material if the material is devolatilized in stages or layers than if one layer of material is devolatilized at one time. Thus, for a given amount of material, less heat is lost through the roof, hearth and walls of the devolatilizing chamber and less heat is required per unit of devolatilized material to carry out the operation.

Further, for a given amount of charge material, a given furnace will reach a higher temperature by the layer loading of the invention than by the conventional one layer method. Thus, the outside heat requirements by such a process are reduced from that required by the conventional methods, and in some cases as has been hereinabove disclosed, an autogenetic operation can be provided. Additionally, by the use of the invention, heat can be applied to both sides of the material on an impervious hearth to further increase the efliciency of the operation without the necessity of disturbing the bed with plows or rabbles.

Reasonable variation and modification are possible within the scope of the foregoing disclosure, the drawings, and the appended claims to the invention, the essence of which is that there is provided a process and apparatus by which an undevolatilized material containing volatilizable matter is devolatilized by continuously supplying the material to a devolatilizing zone wherein at least partial devolatilization takes place, continuously supplying at least one more layer of material to said first layer and devolatilizing the one more layer prior to addition of other layers.

I claim:

1. A continuous process for devolatilizing material containing volatiles comprising continuously feeding a first layer of uncalcined material onto an imperforate hearth housed within the lower portion of a devolatilizing zone, while in said devolatilizing zone, effectively maintaining a reducing atmosphere around the materials being treated while simultaneously maintaining an oxidizing atmosphere in the nature of a luminescent flame in the upper portion only of said devolatilizing zone to at least partially devolatilize said first layer, continuously feeding a second layer onto the said first layer to at least partially devolatilize said second layer while continuing the devolatilization of the first layer.

2. A process for devolatilizing material according to claim 1 wherein said first layer is fed onto a moving bed and both layers are covered as a calcined product.

3. A continuous process for devolatilizing a mass of undevolatilized material according to claim 2 wherein 11 said volatile material is collected and used as a source of heat in the process.

4. A continuous process for devolatilizing a mass of undevolatilized material according to claim 3 wherein said volatiles are mixed with oxygen in the upper portion of said devolatilizing zone to burn said volatiles, thus providing heat for the process so that an autogenetic process is effected.

5. A continuous process for devolatilizing a mass of undevolatilized material according to claim 2 wherein said first layer is stirred prior to the addition of said second layer.

6. A continuous process for devolatilizing a mass of undevolatilized material according to claim 2 wherein a plurality of layers are added to said first two layers, each layer being added after at least a partial devolatilization of the previously added layer.

7. A continuous process for devolatilizing material containing volatiles comprising continuously feeding a first layer of uncalcined material in a thin layer onto a rotary circular hearth into a heated oven chamber adjacent to the outer periphery thereof to form a thin bed thereon, and subjecting said first layer to the heat of a luminescent flame to at least partially devolatilize said first layer, the hearth and the material thereon being moved with respect to a plurality of rabbles disposed above the hearth and spaced progressively outwardly from the center thereof, thin layers of material to be treated being continuously delivered onto said bed at spaced points along the hearth downstream from said rabbles, the material being progressively advanced toward a material outlet at the center of the hearth by disposing said rabbles so that they extend into the bed at an angle of attack that moves the bed progressively inwardly toward said material outlet, said bed being turned over prior to the addition of said thin layers during its progressive move toward said material outlet, and the treated material being discharged into the material outlet at the center of the hearth.

8. A process according to claim 7 wherein the volatile material is collected above said bed and mixed with oxygen to provide the heat for the volatilization.

References Cited UNITED STATES PATENTS 1,906,755 5/1933 Karrick 20124 1,927,968 9/ 1933 Willson. 1,952,363 3/1934 Bunce et al. 2,668,760 2/1954 Bryer et al. 2,672,412 3/1954 Burrow et al. 2,676,006 4/ 1954 Martin. 3,260,513 7/1966 Connell. 3,370,937 2/ 1968 Tsujihata et a1.

NORMAN YUDKOFF, Primary Examiner D. EDWARDS, Assistant Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No- 3 Dated Julv 20 1971 Inventor) John L Kemmerer Jr It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading to the printed specification, lines 6 and 7, "Wise Coal & Coke Company, New York, N.Y." should read Salem Corporation, Pittsburgh, Pa. a corporation of Pennsylvania Signed and sealed this 18th day of April 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents :ORM 7394050 USCOMM-DC 60376-P69 a U S, GCIVERNMENY PBlNYING OFFICE |9B9 0-36613

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