US1952363A - Apparatus for coking agglomerates - Google Patents

Description

March 27, 1934.

E. H. BUNCE :1" AL APPARATUS FOR COKING AGGLOMERATES 2 Sheets-Sheet l Filed April 29 wkg INVENTOR EARL H. BUNCE .CLARENCE \ILE/VTZ I ATTORNEYS March 27, 1934. E. H. BUNCE ET AL APPARATUS FOR COKING AGGLOMERATES Filed April 29. 1931 2 Sheets-Sheet 2 INVENTOR EARL H.5l/NCE CZARENCE W LENTZ W ATTORN EYS Patented Mar. 27, 1934 PATENT OFFICE I 7 APPARATUS FOR come AGGLOMERATES Earl H. Bunce and Clarence J. Lentz, Palmerton, Pa., assignors to The New Jersey Zinc Company, New York, N. Y., a corporation of New Jersey Application April 29, 1931, Serial No. 533,720 7 Claims. (01. 202-117 This invention relates to the coking of agglom erated charges of mixed zinciferous material and carbonaceous reducing agent, and has for its object certain improvements in the coking of agglomerated zinciferous materials. The invention relates more particularly to improvements in apparatus for coking agglomerates 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 a coking 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 of fines 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, coking 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 requiresthe use of agglomerates that have suflicient initial strength to withstand the compression and the abrasion to which they are subjected in their passage through the vertical coking chamber. Adequate strength of the agglomerates to withstand this operation may only be obtained when the ingredients going into the agglomerates are carefully blended. Thus, when zinc ore is admixed with appropriate amounts of anthracite fines, 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 therefrom may be strong enough to be subjected in a vertical chamber to a colnng operation. A practice of this kind is disclosed and claimed in a copending application of Earl H. Bunce, Serial No. 391,825, filed September 11, 1929.

Such a vertical coking chamber practice, however, does not readily lend itself to the treatment of agglomerates formed of zinciferous material and a relatively large proportion of bituminous coking coal. When a large proportion of coking coal is present in the agglomerates, they tend to soften greatly during the heat treatment operation. This softening of the agglomerates causes operating difliculties. Thus, when the agglomerates are in a, coking chamber in the form of a columnar body, the undermost agglomerates 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 having heretofore been proposed.

In localities where bituminous 'coal alone is 0 readily available, and in which it is economically inadvisable to import anthracite coal fines or other suitable non-coking coal, at least in large quantities, there is therefore a distinct need for a coking operation adapted for the production of coked agglomerates of zinciferous material containing a large proportion of bituminous coal.- As a result of our investigations, we have determined that an apparatus may be employed that is peculiarly adapted for the production of coked 7 agglomerates of zinciferous material containing a relatively large proportion of bituminous coal.

The present invention accordingly contemplates an apparatus for producing coked agglomerates of zinciferous material and carbonaceous reducing agent, in which a porous charge of the agglomerates in the form of a relatively thin layer is progressively advanced through a substantially horizontal coking chamber. The charge of agglomerates is advantageously supported on a bed of fines carried by a traveling conveyor and preferably with a layer of coarse material disposed intermediate the bed of fines and the charge of agglomerates. During the course of their passage through the chamber, the agglomerates are heated to a sufficiently high temperature to coke the agglomerates. In the preferred embodiment of the invention, substantially non-oxidizing heating gases are brought in direct contact with the layer of agglomerates. The agglomerates may be subjected to heat treatment at successively higher temperatures as the charge is progressively ad,- vanced through the coking chamber.

According to the invention, a chamber with a traveling grate or hearth is employed in which to conduct the coking operation. A layer of fines 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 fines. A third layer, consisting of agglomerates of mixed zinciferous material and carbonaceous reducing agent, which may include a relatively large proportion of bituminous coking coal, is then spread on the layer of coarse material. The three superposed layers thus spread on the grate are progressiv'ely and simultaneously advanced 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 passage of gases therethrough, the heating gases then move laterally to side exits provided in the side walls of the coking chamber, 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, particularly 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 theagglomerates 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 coking chamber, the materials on the grate are dropped. Suitable screening devices may be used at this point to effect the separation of (1) the fines, (2) the coarse material, and (3) the coked agglomerates. The fines maybe returned to the other end of the coking chamber 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 layeryof 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, takenin conjunction with the following description, in which:

Fig. 1 is a side elevation in 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. 1;

Fig. 3 is a part side elevation partly in section 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 l0 resting on a plurality of concrete foundations 11. 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 upright sup ports.

A super-structure 15 rests on cast iron base members 16, which are in turn supported by the under-structure. The super-structure is built for the most part of refractory materials, and consists of longitudinal outer walls 17 resting on a 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 flue 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-supply flue 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 flues, advantageously connecting stacks or chimneys, not shown, for the withdrawal of spent heating gases. A suitable number of opening 2'7, 27, 27" 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 madeto Fig. 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 chamber are so built with respect to 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 bottom for the escape of spent heating gases.

The traveling hearth is of the endless conveyor type, and operates around sprockets 30 located at each end of the furnace structure, and appropriatelysupported 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. The upper rails are bent downwardly at 34 at the charging end of the furnace, and the lower rails are bent downwardly at 35 at the discharging end of the furnace to make an easy approach of the wheels to and on the tracks. The upper track or rail structure is supported by the understructure 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 more particularly 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 FJI tar, oil or the like.

or lowermost, compartment 38 is adapted to contain a charge of fines 39. These fines may advantageously consist of small anthracite coal particles, or the like. 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 In the assembly shown in the drawings, it will be noted that the compartments are adapted to dispose a layer of fines 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- supplyflues 22, 22', 22","22 etc. is provided above and communicating with the coking chamber. The fiues are separated from one another by dividing walls 47. In the case of the first gas-supply flue, at thecharging end of the coking chamber, it will be noted that its bottom 48 slopes downwardly into the coking chamber, lengthwise of the furnace. This slanting bottom, which of course likewise represents the top or ceiling 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 ports or holes 29 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 of the furnace, the desired structure may be obtained by using perforated cast iron side wall plates 49. Such plates are suflicient 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 elevated.

A hopper 50 is located at or near and crosswise of the discharge end of the coking chamber to contain sealing fines 51, such as anthracite coal. These fines are to be run onto the top layer of agglomerated charge materials coming through the coking chamber, and thus tend to seal the exit of the coking chamber to prevent ingress and egress of gases. The fines thus introduced are of course discharged from the coking chamber, together with the other materials supported on the grate. Since no sealing means is needed at the discharge 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 adapted to carry away dust particles, as well as gases.

As the materials are dropped from the traveling grate, dust tends to rise. The stack is adapted to 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 theminto a hopper 57; while the coked agglomerates 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 coke particles, and (3) the coked agglomerates of zinciferous material. Suitable provision may be made for conducting the fines and the coarse material separately to the other end ofthe 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 zigezag 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 2'7" leading to the upper gas-supply flue 22". Off-take pipes 61 communicate with each of the side gas-outlet flues 20". These off-take pipes are advantageously provided 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 110 through laterally extending pipes 63, provided with dampers 64 and merging with a pipe section 65 that leads downwardly into the upper gas-supply flue 22".

An inspection of this construction shows that 115 partially spent heating gases passing through the coking chamber below the gas-supply flue 22' I 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. e

The pipe section 65 merges with a fresh gasfeeding main 66, provided with a damper 6'7.' Fresh heating gases may, if desired, be passed through this gas main into the gas-supply fiue 22". It is thus seen that the partially spent heating gases introduced into this gas-supply flue from a previous coking operation may be augmented by fresh heating gases. It will of course also be evident that fresh heating gases may be introduced into the gas-supply fiue 22' without using partially spent heating gases coming from the gasoutlet fiues 20".

Off-take pipes 68 from the gas-outlet fiues 20 communicate with laterally extending pipe sections 69, provided with dampers '70; the pipe sections merging with aninlet pipe section '71 connecting with a suction-blower fan 72. An outlet pipe section 73 of the fan leads to the opening 2'7 of the gassupply flue 22". This fan operates to pull heating gases from one coking chamber to another and then to push heating gases through the coking chambers in series.

Ofi-take pipes 74 lead from the gas-outlet fiues 20' and connect with laterally extending pipe 145 sections 75, provided with dampers '76, which merge with an inlet pipe section 7'7 of a suction- -blower fan '18. Anoutlet pipe section 79 of the fan leads into the opening 27 of the gas-supply flue 22. Gas outlet pipes 80 connect with the gas- 150 outlet flues 20, and are preferably sufliciently high to create a natural stack or chimney draft.

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

Appropriateamounts 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 cokingoperations.

As the grate moves under the discharging bottoms of the hopper compartments, a layer of fines 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 fines. This layer, too, may be similarly regulated in thickness. A layer of agglomerated zinciferous material is then spread over the top of the layer of coarse material. This layer, too, may be suitably regulated in thickness.

Suitable heating gases are introduced through the openings 27, 27', 27" and 27" etc., into the gas supply flues 22, 22, 22", 22" etc. The gases are preferably substantially non-oxidizing. The temperature of these gases may be uniform throughout, for example, 900 C., but in the present preferred practice of the invention, the temperatures of the gases entering this series of gas supply flues are of'an increasing order, so that the agglomerates 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 fiue in the series is about 300 C., the second gas-supply flue abeut 500 to 550 C., the third gas-supply flue about 700 to 750 C., and the fourth and last gassupply flue 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 filled. The heating gases in gas-supply fiue 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 effect of the layer of fines 44, the downward movement of the heating gases is impeded, and the gases tend to spread out laterally, ultimately escaping through the multiplicity 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 flues 22, 22", 22" pass downwardly through their openings 24, and then pass through the agglomerated charge materials. In their progressive movement under each succeeding gassupply flue in the series, the agglomerates are subjected to 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 exciting flue .20 to the stack or chimney 61 or or both.

On being subjected to heating gases of the 'the coked agglomerates are still hot.

range of temperatures indicated, the agglomerated zinciferous material passes more or less uniformly through successive stages of (1) drying, (2) softening, (3) gasification of the volatile matter, and;.,4 hardening or final develgpment 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 fines tends to seal the discharge 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 fines, coarse material and coked agglomerates inter-mix freely. As the mixture passes over the screen 54, the fines 39 and 51, together with smaller amounts of fines 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 fines'are also returned to the hopper 51.

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 thehopper 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 In any event, the coked agglomerates should be collected out 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 agglomerated charge materials thereunder may be passed into the next supply flue in the series 22", and so on to the end of the series; and thus subject the agglomerates to the same heating gases repeatedly returned to the coking chamber. By the time the gases are returned to the last supply flue in the series, at the charging end of the furnace, the gases will have sufficient heat remaining at least to aid in a drying out step. This system of operation offers the advantage of fuel economy and the further advantage that tars and other volatile products can be recovered from the gases leaving the gasification zone of the coking chamber.

The procedure just outlined may 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 be in part by-passed from the system. Various procedural combinations become possible in practicing the invention.

In another modification of the practice of the invention, where the type of coal will permit, the gas-supply fiues need not be separated into difierent 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 of good bituminous coking coal, and of zinciferous material, such as zinc concentrates. 445 pounds of good coked agglomerates were 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 12 inches. The coarse material varied in thickness from 2 to 3 inches.

The practice above described offers a number of advantages: Agglornerates of zinciferous' material containing a relatively large amount of bituminous coal may be appropriately coked. Agglomerates of this character would be extremely difficult, 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 having low strength may be coked according to the practice of the present invention. Once the agglomerates are laid on the conveyor, they are not moved relatively to one another until they are 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 interm ittent 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 soften 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 non-coking carbonaceous materials, but where the oil or tar employed as a binding agent tends to soften during the heat treatment operation.

k The conveyor is exposed to the air on the one side and insulated by thebed of fines on the other, thus permitting high temperature treatment of the charge; while at the same time providing that all moving parts are kept thoroughly cool. The apparatus of this construction and this method of operation cuts to a minimum maintenance of the moving parts.

We claim:

I 1. In an apparatus for coking agglomerates of metalliferousiand carbonaceous reducing materials including a coking agent, the improvements comprising a relatively long and substantially horizontalcoking chamber, a traveling hearth adapted to convey a charge of the agglomerates supported on a layer of fines under conditions substantially avoiding relative movement of individual agglomerates through said chamber, a flue communicating with said coking chamber for introducing heating gases.in contact with the agglomerates, the side walls of the coking chamber being provided with ofitake ports above the level of the fines on the hearth for the withdrawal of spent heating gases that have traversed the bed of agglomerates, and a hopper near the discharge end of said traveling hearth for the introduction into the coking chamber and onto the charge supported by the traveling hearth of fines adapted to seal the end of the chamber against ingress or egress of gas.

2. An apparatus according to claim 1, in which the ceiling of the coking chamber slopes downwardly from the charging end towards the center and lengthwise'of the chamber.

3. An apparatus according toclaim 1, in which a plurality of separated flues overlay the coking chamber, each of said fiues being'provided with at least one opening for the passage of heating gases into the coking chamber.

4. An apparatus according to claim 1, in which a three-compartment hopper is provided at one end of the movable hearth, the first compartment being adapted to spread a bed of fines onto the traveling hearth, the second compartment being adapted to spread a coarse layer of material on said bed of fines, and the third compartment being adapted to spread a layer of agglomerates on said coarse layer of material.

5. An apparatus according to claim 1, in which a device is provided at the extreme end of the traveling hearth for receiving materials discharged therefrom,v said device consisting of a screening-chute adapted to make a three-way separation of fines, coarse material, and coked agglomerates.

6. An apparatus according to claim 1, in which a stack is provided at the discharge end of the traveling hearth for the withdrawal of dust.

'7. In an apparatus for coking agglomerates, the improvements comprising a substantially horizontal coking chamber, a traveling hearth of the endless conveyor type adapted to transport a layer of the agglomerates through said chamber, a gas supply flue overlaying the coking chamber, a plurality of passageways joining the flue with the chamber for the introduction of heating gases into the coking chamber, the side chamber walls being provided with a multiplicity of relatively small ports at the bottom level of the layer of agglomerates normally supported on the hearth for the withdrawal of spent heating gases and gaseous products resulting from coking operations, and a hopper near the discharge end of said traveling hearth for the introduction into the coking chamber and onto the charge supported by the traveling hearth of fines adapted to seal the end of the chamber against ingress or egress of gases.

EARL H. BUNCE. CLARENCE J. LENTZ.

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