US1926032A - Treatment of metalliferous material - Google Patents

Description

Sept. l2, 1933. E. H. BuNcE Er AL TREATMENT QF METALLIFEROUS MATERIAL 2 sheds-sheet 1 Filed April 29, 1931` YINVENTOR ATTORNEYS Sept. 12, 1933. E. H. BuNcE ET AL TREATMENT OF METALLIFEROUS MATERIAL File'd April 29, 1931 Sheets-Sheet' 2 A d jllll. DID. 4. PEL P LFI Patented Sept. `12, l1933 y' PATENT OFFICE TREATMENT F METALLIEROUS MATERIAL I Earl ILJBunce and Clarence J. Lentz, Palmerton, Pa., assignors to The New Jersey Zinc Company, New York, N. Y., a corporation of New J ersey- Application :April 29, 1931. .Serial No. 533,721

Claims.

` This invention relates to the coking of agglomerated charges of mixed zinciferous material and carbonaceous reducing agent, and has for its object certain improvements in the coking o agglomerated zinciferous materials. Ihe invention relates more particularly to improvements in the method of coking agglomeraties of mixed zinciferous and carbonaceous reducing materials including a coking. agent.

Various proposals to coke zinciferous materials `have been advanced. Thus, heaps of mixed zinc ore and bituminous coal have been subjected to acok'ing operation, the resulting coked mass then being broken up and introduced into a smelting furnace for the recovery of the zinc values. Such a proposal is objectionable because of the formation of large amounts of7 lnes and of irregularly sized lumps resulting from the crushing operation.

A recent proposal to coke agglomerates of mixed zinciferous and carbonaceous reducing materials` including a cohlng agent is to pass a charge of the agglomerates in the form of a continuous column through a vertically disposed coking chamber. Such a procedure requires the use oi agglomerates that have sumcient initial strength to withstand the compression andthe abrasion to which they are subjected in their passage through the vertical` coking chamber. Adequate strength of the agglomeates to withstand this operation may only be obtainedwhenl the ingredients going into the agglomerates are carefully blended. Thus, when zinc ore is admixed with appropriate amounts of anthracite unes, or other suitable hard-non-coking carbonaceous material, such as coke breeze, and a narrowly limited, amount of bituminous coal of good coking quality, agglomerates formed there- Y from may be strong enough to be subjected in a vertical chamber to a coking opration. A practice of this kind is disclosed and claimed in a copending application of Earl H. Bunce, Serial No. 391,825, filedv September ll, 1929. l Such a vertical coking chamber practice, however, does not readily lend itself to the treatment of agglomerates formed of zinciierous material and a relatively large proportion of bituminous coking coal. When a large proportion of coking coal is present inthe agglomerates, they tend to soften greatly during the heat treatment operation. This softening of the agglomerates causes operating diiculties. Thus, when the agglomerates are in a coking chamberin the orm oi a columnar body, the undermost agglom- 55 crates are squashed and stick together. The

net result may be to coke the agglomerates into a mass closely approximating the heaps of coked material first described above as havingy heretofore been proposed.

1n localities where bituminous coal alone is 60 readily available, and in which it is economical- 1y inadvisable to import anthracite coal fines or other suitabler non-coking coal, at least inlarge quantities, there is therefore a distinct need for a c'oking operation adapted for the production of 65 coked agglomerates of zinciferous material containing a`large proportion ofbituminous coal. As a result of our investigations, we have determined that a method' may be employed that isy peculiarly adapted for the production of coked 7o agglomerates of zincferous material containing a relatively large proportion of bituminous coal.

The present invention accordingly contemplatesffa method of producing coked agglomerates of zinciferous material and carbonaceous 7g reducing agent, in which a porous charge ci the agglomerates in the iormof a relatively thin layer is progressively advanced through a substantially horizontal coking chamber. 'The charge of agglomerates is advantageously supso ported on a bed of fines carried by a traveling conveyor and preferably with a layer oi coarse material disposedy intermediate the bed of fines and the charge of agglomerates; During thek course of their passage through the chamber, the agglomerates `are heated to a sufficiently high temperature to coke the agglomeraties. In the preferred embodiment of the invention, substantially non-oxidizing heating gases are brought in direct contact with the layer oi agglomerates. The agglomerates may be subjected to heat treatment at successively higher temperatures" as the charge is progressively advanced through the coklng chamber.

According to the invention, a chamber with a traveling grate or hearth is employed in which to conduct the vcoking operation. A layer of nes'is disposed on the traveling hearth, which may consist of a traveling pan conveyor, at one end of the furnace. A layer of coarse material, such as residues resulting from a reduction operation, is next spread over the layer of nes.

vanced through the length of the furnace chamber.

During the course of their passage through the chamber, the agglomerates are heated to an elevated temperature adapted to effect their coking. In the present preferred practice of the invention, heating gases are passed downwardly through and in direct contact with the agglomerates. During the course of their travel, the heating gases ultimately find their way down in and among the particles in the layer of coarse material. Since the layer of fines is substantially impervious to the passagefof gases therethrough, the heating gases then move laterally to side exits provided in the side walls of the furnace, where they make their escape. The heating gases may be passed through the furnace either by suction applied to the side exits or by pressure applied to the gas inlets.

The layer of agglomerated charge materials containing the zinciferous material should be carefully selected with reference to its depth, so that the undermost agglomerates will not be squashed by the uppermost agglomerates, par. ticularly when the agglomerates during the heat treatment operation pass through their softening stage. The thickness of the layer of agglomerates may be made to fit given operating conditions. It will of course be clear that the desired thickness of the layer will vary according to the manner in which the agglomerates have been formed. Thus, the larger the proportion of bituminous coking coal to the amount of zinciferous material, including other substantially inert` non-coking material present, the thinner should be the layer of agglomerates to avoid'squashing and sticking together.

As the agglomerates are advanced through the coking chamber, they may be passed through heat treatment zones maintained within varying temperature ranges. For example. the agglomerates may in the first zone be subjected to a temperature adapted to effect not much more than a drying-out of the agglomerates. As the agglomerates are successively. passed through other heating zones in the series, their temperature may be raised to a point where the final coking operation is completed in the last zone.

When the traveling hearth moves over and around the far end of the furnace, the materials on the grate are dropped. Suitable screening devices may be used at this point to effect the separation. of (l) the fines, (2) the coarse material and (3) the coked agglomerates. The fines may be returned to the other end of the furnace and again introduced onto the traveling hearth as a bottom or cushioning layer. The coarse material, likewise, may be returned to provide the desired layer of coarse material. Freshly agglomerated zinciferous charge materials are then introduced onto the layer of coarse material. In this manner, the coking process may be made a substantially continuous one.

These and other novel features of the present invention will undoubtedly be better understood if reference is made to the accompanying drawings, taken in conjunction with the following description, in which:

, Fig. 1 is a side elevationin section of an apparatus adapted for a practice of the invention;

Fig. 2 is a transverse end elevation in section of the apparatus shown in Fig. l:

Fig. 3 is a part side elevation partly in section Amafiosa of a modified form of apparatus; taken on the line 3-3 of Fig. 4; and

` Fig. 4 is a plan view of the apparatus shown in Fig. 3.

The apparatus shown comprises a structural steel under-structure 10 resting on a plurality of concrete foundations l1. The under-structure is preferably open, so that it is exposed to the open air for cooling. It consists of spaced and oppositely placed upright supports 12, to which longitudinal bracing `beams 13 are permanently attached. Lateral cross-members 14 rest upon the longitudinal members, and are advantageously spaced between oppositely located uprightsupports.

A super-structure 15 rests on cast iron base members 16, which are in turn supported by the under-structure. 'I'he super-structure is built for the most part of refractory materials, and consists of longitudinal outer walls 17 resting one. refractory bottom 18, and spaced inner walls 19; together with end walls. A gas-outlet flue 20 is provided between each inner and outer wall.

The space between the'two inner walls is subdivided by a refractory partition 21 into an upper gas-supply i'lue 22, and a lower coking chamber 23. An opening or openings 24 in the partition wall permits the passage of heating gases through the gas-supplyiiue to and into the coking chamber. A ceiling 25 surmounts the super-structure, which is provided with a suitable number of openings 26 into`the gas-outlet ilues, advantageously connecting stacks or chimneys, not shown, for the withdrawal of lspent heating gases. I 2'? are also provided in the ceiling -to connect the gas-supply flues with a source of heating gases to be employed in the coking operation.

If reference is more particularly made to Fig.

A suitable number of openings 2, it will be seen that the coking chamber is defined at its sides by the inner walls, and at its top by the dividing partition between the inner walls, and on the bottom by the hearth of a traveling end conveyor 28. The traveling hearth device and the side walls of the coking 4chamber are so built with respectto one another that the coking chamber may be made as tight as practicable. A multiplicity of holes or ports 29 are provided through the inner walls at or near their h bottom for the escape of spent heating gases.

The traveling'hearth is of the endless con- `veyor type, and operates around sprockets 30" located at each end of the furnace structure, and appropriately supported in bearings resting on concrete foundations, as more particularly shown in Fig. 1. The hearth is provided on its under side with spaced axles and wheels 31, operating on an upper set of tracks or rails 32; and on a lower set of tracks or rails 33. 'I'he upper rails the furnace, and the lower rails are bent downwardly 35 at the discharging end of the furnace tovmake an easy approach of the wheels to and on the tracks. The upper track or rail structure is supported by the under-structure steel assembly, as shown; while the-lower track or rail structure is supported on a structural steel assembly 36; which is 'in turn supported by the concrete foundations. The traveling conveyor is of course operated by a motor, not shown.

Referring moreparticularly to Fig. 1, a hopper arrangement 37 is located at one end of the furnace for the. introduction of charge materials into the coking chamber by depositing them on 135 are bent downwardly 34 at the charging end of `thracite coal particles, or the like.

the traveling hearth. The hopper arrangement shown comprises three sloping individual and separated compartments, each of which is adapted to dispose a layer of material on the traveling hearth; or one layer upon another. The rst, Y or lowermost, compartment 38 is adapted to contain a charge of nes 39. These nes may advantageously consist of small an- The second compartment 40 is adapted to contain porous coarse material 41, such as coke; or residues from a previous smelting operation, and the like. The coarse material should be considerably larger than the fines, so that passageways are provided between contacting coarse particles to provide for a flow of heating gases therethrough when the particles are disposed in the coking chamber. The third compartment 42 is adapted to contain agglomerated charge materials 43 consisting of zinciferous material and carbonaceous reducing material including a coking agent, such as bituminous coal, with or without an appropriate binder, such as tar, oil or the like. Inthe assembly shown in the' drawings, it will be noted that the compartments are adapted to dispose a layer of iines 44 on the traveling hearth; a layer of coarse material 45 on the layer of fines; and a layer of agglomerated zinciferous material 46 on the layer of coarse material.

While referring to Fig. 1, it will be noted that a series of gas- supply ues 22, 22', 22", 22"', etc.,

is provided above andA communicatingwith the` Yits bottom 48 slopes downwardly into the coking chamber, lengthwise of the furnace. This slanting bottom, which of course likewise represents the top or Vceiling of that end of the coking chamber, compensates for the settling of the charge as it advances through the coking chamber, so that the coking chamber roof remains at an approximately uniform distance above the upper level of the charge.

As pointed out above, a multiplicity of holes ,are provided in the side walls of the coking chamber for the withdrawal of spent gases that have passed through the agglomerated charge materials. In the case of the side walls at or near the charging end ofthe furnace, the desired structure may be obtained by using perforated cast iron side `wall plates 49. Such plates are sufiicient when the temperatures employed are not extremely high. In the case of the side walls at or near the discharge, end of the coking chamber, however, it is preferable to use refractory walls, as indicated; because the temperatures there employed are highly ele ated.

A hopper 50 is located at or near an crosswise of the discharge end of the coking chamber to contain sealing ilnes`51, such as anthracite coal. These linesv are to be run onto the top layer of agglomerated charge materials coming through the coking chamber, and thus tend to seal the exit ofthe coking chamber ,to prevent ingress and egress of gases. 'Ihe fines thus introduced are of course discharged from the coking chamber, together with the other materials supported on ther grate. Since no sealing means is needed at thedischarge end of the .furnace when it is operated under pressure, the hopper 50 may be omitted in this case.

A stack or chimney 52 is provided at the discharge end of the coking chamber, and is adapty ed to carry away dust particles, as well as gases. As'thematerials are dropped from lthe traveling grate, dust tends to rise. 'll'he stack is adapted Ato take away the dust particles while permitting-the fines, the coarse material. and the coked agglomerates to proceed downwardly.

An enclosed screening device 53 is located at the end of the furnace to receive the discharged materials. This screening device preferably consists of a screen 54 adapted to separate the fines and drop them into a receiving hopper 55; and a coarser screen -56 adapted to separate the coarse materials and drop them into a hopper 57; while the cokedagglomerates continue to the end of the screening device, where they are separately collected. With a structure of this kind, an effective separation may be obtained between (1) the anthracite fines, (2) the coarse cokevparticles, and (3) the colxed agglomerates of zinciferous material. Suitable'provision may be made for conducting the fines and the coarse material separately to the other end of the traveling grate, where they .may be re-used.

A modified form of apparatus is shown in Figs. 3 and 4, according to which heating gases may be passed in a zig-zag manner through the coking chambers of the furnace in series, provision being made for adding fresh heating gases to one or more of the chambers, if desired. Thus, a gas supply main 58 communicates with a combustion chamber 59, having `an air inlet 60, and communicating with the opening 27"' leading to the upper gas-supply ue 22"'. Oil-take pipes 61 communicate with each ofthe side gasoutlet iues4 20"'. These off-take pipes are advantageously providedv with dampers 62 that may be utilized either to withdraw partially spent heating gases in whole or in part away from the system, or to conduct these heating gases in whole or in part through laterally extending pipes 63, provided with dampers 64, and merging with a pipe section 65 that leads downwardly into the upper gas-supply ue 22".

An inspection of this construction shows that 120 partially spent heating gases passing through. the coking chamber below the gas-supply flue 22"' may be passed in whole or in part into the next gas-supply flue 22" in the series, or, the partially spent gases may in whole or in part be taken away from the system.

The pipe section 65 merges with a fresh gasfeeding main 66, provided with a. damper 67.. Fresh heating gases may, if desired, bepassed through this gas main into the gas-suply flue 22". It is thus seen that the partially spent heating gases' introduced into this gas-supply flue from a previous coking operation maybe augmented by fresh heating gases. It will of course also be evident lthat fresh heating gases may be introduced into the gas-supply iiue 22" without using partially spent heating gases coming from the gas-outlet nues 20".

Oil-take pipes 68 from the gas-outlet flues 20" communicate with laterally extending pipe sections 69, provided with dampers 70; the pipe section merging with an inlet pipe section "l1 connecting with a suction-blower fan /72. An outlet pipe section '73 of the fan leads to the' 145 opening 27 of the gas-supply flue 22". .'This fan operates to pull heating gases from one coking chamber to another and then to push heating gases through coking chambers in series. y y

OIT-take pipes "I4 lead from the gas-outlet 150 nues 20', and connect with laterally extending pipe sections 75, provided with dampers 76, which merge with an inlet pipefsection 77of a suction-blower fan 78. An outlet pipe section 79 of the fan leads into the opening 27 of the gas-supply flue 22. Gas outlet pipes connect with the gas outlet ilues 20, and are preferably sufficiently high to create a natural stackl or chimney draft.

The above described apparatus may be operated as follows in a practice of the invention:

Appropriate amounts of fines 39, coarse material 41, and agglomerated zinciferous material 43 are placed 'in the hopper compartments 38, 40 and 42, respectively. The traveling hearth or pan conveyor 28 is set in motion. As indicated in the drawings, the hearth moves from right to left through the coking chamber 23. The rate of movement of the traveling grate may be regulated to fit desired and optimum coking operations.

As the grate moves under the discharging bottoms of the hopper compartments, a layer of iines 44 is'spread on and across the hearth. This layer of fines may be regulated in thickness by suitably regulating the size or height of discharge from compartment 38. A layer of coarse material 45 is next spread on and across the layer of nes. This layer, too, maybe similarly regulated in thickness. A layer of agglomerated zinciferous material is then spread over the top of the layer of coarse material.-

'I'his layer, too, may be suitably regulated in thickness.

Suitable heating gases are introduced through the openings 27, 28', 27" and 27"' etc., into the gas supply ilues 22, 22', 22", 22"' etc, The gases are preferably substantially nonoxidizing. The temperature of these gases may be uniform throughout, for example, 900 C., but inthe present preferred practice of the invention, the temperatur'es of thegases entering this series of gas-supply flues are of an increasing order, so that theagglomerates are subjected to increasingly greater temperatures as they are progressively advanced through the coking chamber. Thus, in one practice of the invention, the temperature of the gases entering the first gas-supply fluev in the series is about 300 C., the second gas-supply flue about v500 to 550 C.; the third gas supply-flue about 700 to`750? C.; and the fourth and last gas-supply ilue about 900 to 950 C.

As the traveling hearth moves through the coking chamber and around the sprockets 30, the layers of charge materials supported on the grate are progressively advanced through the coking chamber; until the coking chamber is illled. The heating gases in gas-supply flue 22 pass through its openings 24 into the coking chamber. The gases contact with the coked agglomerates of zinciferous material in the layer 46, as they seep completely through the layer into the sub-layer of coarse material 45. Due to the sealing eiect of the layer of vfines 44, the downward movement of the heating gases is impeded, and the gases tend to spread out laterally, ultimately escaping through the mutiplicity of side openings 29 in the side walls 19. These openings should be located at or above the upper level of the fines, and directly adjacent to the layer of coarse material.

In a similar manner, the heating gases of the gas supply nues 22', 22", 22"' pass downwardly .'.5`-through their openings 24, and then, pass through the agglomerated charge materials. In

their progressive movement under each succeeding gas-supply ue in the series, the agglomerates are subjected tol successively higher temperatures. After passing through the multiplicity of side openings 29, the spent gases, together with 'volatilized products resulting from the coking operation, pass upwardly through the gas exiting iiue 20 to the stackV or chimney.

On being subjected to heating gases of the range of temperatures indicated, the agglomerated zinciferous material passes more or less uniformly through successive stages vof (1) drying, (2) softening, (3) gasification of the volatile matter, and (4) hardening or final development of a coked structure.

During the transit of the charge materials through the coking chamber, a supply of fines, such as anthracite dust coal, 51, is continuously dropped from the hopper 50 onto the layer of coked agglomerates leaving the chamber. The disposition of these nes tends to seal the dislcharge end of the coking chamber against ingress or egress of gases.

When the traveling grate passes around and under the far end of the coking chamber, the charge materials are discharged into the sloping screening device 53, where the nes, coarse material and coked agglomerates inter-mix free- 1y. As the mixture passes over the screen 54, the fines 39 and 51, together with smaller amounts'of nes that may have been formed during the coking operation, fall through screen 54 into the collecting hopper 55. These fines are for the most part returned to the charging end of the furnace, and are introduced into the compartment 38. Some of the nes are also returned to the hopper 51. 1

The coarse material 41, on the other hand, together with any other coarse material of substantially similar size that may result from the coking operation, is dropped through screen 56 into the collecting hopper 57. This coarse material is returned to the hopper compartment 40, where it is re-used.

The coked agglomerates of zinciferous material are, however, separately-collected at the end of the screening device, for a subsequent reduction operation; which is preferably done while the coked agglomerates are still hot. In any event, .the coked agglomerates should be collected'ou't of continued contact with the atmosphere, to avoid oxidation.

Instead of resorting to the use of successive stages of increasing temperatures, heating gases of substantially the same temperature may be employed throughout the entire length of the' coking chamber. Various other modifications of the coking operation may be employed. Thus, heating gases may be introduced into the last gas-supply flue in the series 22"', as shown in Figs. 3 and 4, and the gases that have passed' through the agglornerated charge materials thereunder may be passed into the next supply ilue in the series, 22", and so on to the end of 12 inches.

The procedure just ouuinedmay be varied somewhat, as will be evident from Figs. 3 and .4. Thus, fresh heating gases may be added to partially spent heating gases passing from one coking zone to another. In this manner the mean temperature of the mixed heating gases may be made higher than would be the case if the partially spent heating gases alone were used; Should the partially spent heating gases have suered too large a temperature drop, they may bel in part by-passed from the system. Various procedural combinations become possible inbpracticing the invention. f

In another modification of s the practice 4of the invention, where the type of coal will permit, the vgas-supply flues need not be separated into diierent compartments as shown. In other words, the dividing partitions or walls 47 may be eliminated.

Some specific figures may be useful to arrive at a better'understanding of the practice of the invention. Excellent results were obtained when the agglomerates contained 40% of good bituminous coking coal, and 60% of zinciferous material, such as zinc concentrates. 445 pounds of good coked agglomerates vwere produced per hour. The conveyor had a width of 2 feet 6 inches on the inside, and an overall length of 30 feet from sprocket to sprocket. The bottom layer of dust coal varied in thickness from 8 to The coarse material varied in thickness from 2 to 3 inches.

The practice above described oers a number of advantages: Agglomerates of zinciferous material containing a relatively large amount of bituminous coal may be appropriately coked. Agglomerates of this character would be exf tremely diicult, if not impossible, to coke in a vertical coking chamber, due to softening of the coal, and sticking `due to overhead weight. Freshly formed or green agglomerates khaving low strength may be coked according to thepractice of the present invention. Once the agglomerates are laid on the conveyor, they are not moved relatively to one another until theyare discharged; and there is no excessive overhead load. The use of binders may for the most part be eliminated. The apparatus lends itself to continuous as well as intermittent feeding of fresh agglomerates and the discharging of coked agglomerates. Such a practice also permits the use of oil and tar binders in agglomerates that normally have a tendency to softenA the agglomerates during the early stages of coking. This practice is effective even when relatively small proportions of bituminous coking coal are employed in conjunction with appreciable quantities of noncoking carbonaceous materials, but where the oil or tar employed as a binding agent tends to soften-during the heat treatment operation.

The conveyor is exposed to the air on the one side arid insulated by the bed of lines on 'the' other, thus permitting high temperature 1,926,039 i l L5 through a substantially horizontal coking chambei-,said charge of agglomerates being supported on a bedof nes carried by a .traveling conveyor with a layer ofrcoarse material disposed intermediate the bed of nes and the charge of agcharge of agglomerates is subjected to heat treatment at successively higher temperatures as the charge is progressively advanced through4 the coking chamber.

4. Process according to claim `l, in which the charge of agglomerates is subjected to heattreatment at successively higher temperatures as the charge is progressively advanced through the 'coking chamber, substantially non-oxidizing gases being brought in direct contact with the agglomerates 'until they are coked. ,i

5. In a process of producin Icoked agglomerates of zinciferous material a a carbonaceous coking agent, the steps which comprise passing a. porous charge of the agglomerates in free contact with one another through a substantially horizontal and directly heated coking chamber on a traveling conveyor without substantial squashing and sticking of the agglom-g crates during their entire passage through the chamber and under conditions substantially avoiding relative movement of individual agglomerates, said charge of agglomerates being spread out in the form of .a layer having a depth adapted to avoid squashing and sticking of the lowermost agglomerates by overhead agglomerates,` the agglomerates being conducted through the chamber with a gentle movement' adapted to avoid objectionable jarring and abrading of the agglomerates, heating the agglomerates in direct contact with hot gases during the course of their passage through said chamber to a sufliciently high temperature to coke the agglomerates, the hot gases being passed downwardly through the charge agglomerates, and then withdrawing the spent gases laterally from the agglomerates at or near the bottom of the layer.

6. Process according to claim 5, Vin which the charge of agglomerates is supported on a bed of lines adapted to cushion the agglomerates against jarring movement of the traveling conveyor.

7. Process according to claim 5,' in which the .heating lis effected by hot substantially nonloxidizing gases introduced into the coking chamber in zones maintained at predetermined temperature levels.

8. Process according tol claim 5, in which green agglomerates are introduced into they cok ing chamber un-dried.

9. Process according to claim 5, in which the agglomerates are introduced into the coking chamber dried.

10. Process according to claim 5, in which the agglomerates consist of an admixture of zinciferousmaterial and bituminous coal.

11. Process according to claim in which the agglomerates consist of an admixture of zinc` iferous material and bituminous coal present in amount not more than about 45%.

12. In a process of producing coked agglomerates of zinciferous material and a carbonaceous coking agent, the steps which comprise progressively advancing a charge of the agglomerates in .free contact with one another and in the form of a layer through a substantially horizontal coking chamber, said charge of agglomerates being supported by a traveling hearth moving through the coking chamber, graduallylraising the temperature of the agglomerates in direct contact with heating gases until the agglomerates are coked, the heating gases being passed downwardly through the layer of agglomerates after which the gases are moved laterally and are withdrawn through openings provided in the side walls of the coking chamber.

13. Process according to claim 12, in which the agglomerates are successively passed through zones o! heating gases introduced into the coking chamber at increasing temperatures.

14In a process of producing'coked agglomerates of zinciferous material and a carbonaceous coking agent, the steps which comprise supporting a layer of the agglomerates in free contact with one another in a substantially horizontal coking chamber, introducing heating gases at or above coking temperatures into the coking chamber at one end thereof, and withdrawing spent heating gases from the other end of the chamber, the hot gases being passed downwardly through the layer of agglomerates after which the spent gases are withdrawn laterally through openings provided in the side walls of the coking chamber.

15. Process according to claim 14, in which the layer oi' agglomerates is progressively advanced through the coking chamber in a' direction generally opposite to that in which the heating gases move.

16. In a process of producing coked agglomerates oi' mixed zinciferous material and a carbonaceous coking agent, the steps which cpm` prise progressively advancing a charge of the agglomerates in free contact with one another and in the form of a layer through a substantially horizontal coking chamber, said charge of agglomerates being supported by 'aq traveling hearth moving through the coking chamber, and heating the agglomerates to their temperature ofvcoking by heating gases of substantially uniform temperature lbrought into direct contact with the agglomerates, the hot gases being passed downwardly through the charge of agglomerates, and then withdrawing the spent gases laterally from the agglomerates at or near the bottom of the layer.

17. In a process for producing coked agglomerates of zinciferous material and a carbonaceous coking agent, the steps which comprise progressively advancing a charge of the agglomerates in the form of a layer through a substantially horizontal coking chamber, said charge of agglomerates being supported by a traveling hearth moving through the coking chamber, and gradually raising the temperature of the agglomerates in direct contact with heat-v ing gases until the agglomerates are coked, the heating gases being passed downwardly into the layer of agglomerates, after which the gases move laterally and arewithdrawn through openings provided in the side walls of the coking 'chamber at or near the bottom of the layer of agglomerates.

18. Process according to claim 17, in which the agglomerates are successively passed through zones of heating gases introduced into the ook4 ing chamber at increasing temperatures, the heating gases first being introduced into the heating zne next to the discharge end of the furnace, passed downward through the layer of agglomerates, then removed laterally through holes in the side-walls, conducted to the next heating zone, and passed downwardly through the layer of 'agglomerates in that zone.

19. Process according to claim 17, in which the layer of agglomerates is supported on a bed of fines.

20. Process according to claim 17, in which the layer of agglomerates is supportd on a bed of coarse refractory material o1.' smaller size than the agglomerates and the coarse refractory material is supported on a bed of nes; the coked agglomerates, coarse refractory material and nes being separated by screening after discharge from the coking furnace.

EARL H. BUNCE.

l CLARENCE J. LENTZ.

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