US2207779A - Process and apparatus for zinc smelting - Google Patents

Description

July 16, 1940. F. e. BREYER 2,207,779

PROCESS Imp APFARATUS FOR z INc SMEL'IING I Filed May 18, 1938 3 Sheets-Sheet 1 INVENTOR FRANK 6. 62571-7? BY g ATTORNEYS.

July 1 6, 1940.

F. G. BREYER PROCESS AND APPARATUS FOR ZINC SIELTIflG Filed May 18,1938.

3 Sheets-Sheet 2 INVENTOR FRANK 6.8REYEE ATTORNEYS July 16, 1940. F. G. BREYER 2,207,779

PROCESS AND XPPARATUS FOR ZINC SMELTING 7 Filed lay 18, 1958 3 Sheets-Sheet 3 INVENTOR ATTORNEYS FRANK 6, 'BREYEE UNITED STATES PATENT: oFFicE PROCESS AND APPARATUS FOR ZINC SMELTmG Frank G. Breyer, Wilton, Conn.

Application May 1a, 1938, Serial No. 208,553

15 Claims. (01. 75-87) I This invention relates to the production of ingly small charges must be employed for satismetallic zinc by the smelting of the zinc-bearing factory results. Zinc ores and reducing materaw materials. rials supplied to the retorts must be of high' The production of metallic zinc by pyrometalquality and of selected physical condition. There 5 lurgical processes up to a few years ago had inare many types of zinc-bearing materials which 5 variably been accomplished by the use of relaare not suitable. Moreover, the introduction of tively small gas-tight refractory retorts or mufcharges into the many retorts, their discharge, fies which extend directly into small individual and the drawing of liquid zinc from the small condensers. The liberation of zinc as a vapor condensers are burdensome operations which from the solid residues in these retorts requires require a great deal of labor in thepresence of 10 a reduction reaction at high temperature and with high temperatures, dust and fumes, which makes considerable absorption of heat. The heat necworking conditions undesirable. essary to sustain the reaction is generated by Still another disadvantageous feature of the the combustion of fuel, like coal, coke or gas, conventional processisthat the fuel requirements outside the retorts and conductedto the charges are very great because all of the CO generated 1 therein" through the refractory retort walls. within the retort isburned in the air and lost The condenser, luted into thefront end of the and by far the larger portion of the heat genretortand extending out of the heating zone erated by combustion around the retorts is wastinto cooling air, is nothing more than a tapereded. Only a relatively small portion of the heat down prolongation of the retort, or zinc liberatis conducted through the retort walls and into 20 ing chamber, and the zinc vapors generated in the poorly heat-conducting residues for use in the retort move directly into the condenser where reacting the charge. they are chilled and condensed to a pool of liquid These limitations of the conventional zinc zinc. A zinc furnace is a battery of these indismelting process have long been recognized in vidual small retorts and condensers positioned the art, and various means have been tried with 25 horizontally and enclosed in aflre brick setting the purpose of overcoming them. Animproveand fired as a unit. ment, which involves the use of vertical retorts Each retort and its'condenser of this convendeveloped by my co-workers and myself and de-; tional process constitute essentially a single scribed in United States Letters Patent Nos.

chamber or environment, and conditions in the 1,678,607, 1,680,726, 1,712,132, 1,712,133, 1,811,910, 80 condenser are controlled by conditions in the 1,832,354, and 1,832,356, has served to some ex-' retort. Not only must sufficient heat to sustain tent to separate the furnace, which eliminates the the reduction reaction be conducted into the rezinc from the residues, from the condenser and to 'tort through its walls, but the fumes released in permit some degree of independent control of the retort must be in a condensable condition so these two stages of the process. This develop- 35 that when they reach the condenser and are ment, however, has by-no means provided a-satischilled the zinc content may there condense factoryzincsmeltingsystem, since the zinc releasout as a liquid pool of metal and be withdrawn ing furnace must still produce zinc vapor in an from time to time manually, environment from which combustion gases are.

40 One of the limitations of this conventional excluded in order that the vapor may be con- 40 process is that combustion or firing gases must densed to liquid zinc when it reaches the conbe scrupulously excluded from the charge in a denser. This necessity still restricts the process retort, since the admission of such gases results to the use of retorts or muflles of relatively small in the formation of blue powder or uncoalesced cross section and still subjects it to limiting raw zinc particles in the condenser, instead of liquid material requirements, expensive preparation, 4,5

zinc. For example, as soon as a zinc retort cracks 'and wasteful methods of indirect heating. and fire gases penetrate into the charge the If there is any one aspect of the problem that vapors will not condense and coalesce to liquid. may be said to be dominant when smelting zinc In order to avoid wasting the zinc-as oxide the by the use of equipment comparable in capacity charge is promptly withdrawn from the retort to that used in lead and copper smelting, it is when this occurs. I the problem of conducting heat into a porous .Another limitation-of the usual process is that body of charge gf any appreciable dimensions the nature of the charges supplied to the retorts without the aid of rapidly moving fire gases, must be carefully controlled, and retorts of very Using the charge as an electric resistor and ll small cross section accommodating corres'pond-. thereby generating heat within the charge itself is a solution for certain types of ore, but it has not worked satisfactorily or economically on ores of low fusion point or low zinc content. On the other hand, if the heat could be generated by combustion of fuel in immediate and close contact with ore, the zinc could be eliminated from residues at a very rapid rate, as witness the very great tonnages of zinc eliminated from ore in a small space by the mechanical zinc oxide process. See article by Breyer in The Mining Magazine, London, April, 1936.

Rapid elimination of the zinc by direct firing.

fuels and permits liquid metallic zinc to be re- .covered from the resulting mixture of zinc vapor,

suspended zinc compounds and combustion gases.

Another object of the invention is to provide an improved zinc smelting process, and apparatus for carrying out the same, which enable the handling of really large charges of zinc-bearing raw materials and fuels, permit the use of ores or other zinc-bearing materials of either low or high grade as well as cheaper fuels, reduce the labor requirements in zinc smelting andmaterially improve the conditions under which the operators of the prdcess must work.

Another object of the invention is to provide a zinc smelting process involving several steps which are carried out in independently controlled chambers so as to avoid limitations imposed on the zinc releasing and condensing operations by known processes. 1 Another object is to provide a process for producing both metallic zinc and zinc oxide as separate products by the fire reduction of the same charge of zinciferous raw material.

Another object is to provide a process for smelt ing zinc from raw material in which the heat ofreduction is supplied by combustion in the releasing chamber, and which produces gaseous products having a relatively high zinc content from which metallic'zinc may be condensed.

Another object is to provide a zinc smelting process in which zinc-bearing fumes are released from raw material in a chamber heated by inter- 1 nal combustion and the resulting fumes are subjected to rapid reduction and conditioned for effective condensation in a chamber controlled independently of the zinc releaser.

A further object of the invention is to provide a zinc smelting. process comprising new and improved methods and means for efficiently extracting zinc values from dilute or rich gases containvide a process which may be controlled and adapted for changing conditions of operation and for the production of metallic zinc from various types of zinciferous raw materials.

I have found that the foregoing and other desirable features and advantages may be accomplished by an entirely new sequence of separately environed and controlled process steps and apparatus. I have discovered that the introduction of a fume conditioning furnace intermediate the zinc eliminator and the condenser permits the elimination of zinc from the raw material, on the one hand, and the condensation of the zinc, on the other, to be carried out independently in environments which are maintained under individual chemical, thermal and mechanical controls, and that the resulting freedom from limitations here'- tofore imposed upon zinc smelting operations may be utilized to modify the elimination step or the condensation step, or both, so that metallic zinc may be produced practicably by elimination from ore or the like in a chamber where combustion occurs.

. My process consists of three or more distinct stages which, though closely related to each other, are susceptible of a wide degree of variation and. independent control. In the first stage I release zinc from zinciferous raw material in a furnace by the action of carbonaceous reducing material, the heat of reduction being supplied by combustion in the furnace chamber. in the furnace chamber preferably is kept in a relatively high range to influence the composition of the 'fumes' favorably and to permit large outputs of products, and the operations incident to the elimination of the zinc preferably are con- "trolled so as to obtain relatively large concentrations of zinc in thefumes issuing from the fur- ,nace. The, charge is preheated to approximately the reaction temperature before introduction into the chamber. The combustion-supporting gas preferably is preheated, audit may be enriched with oxygen in order to enhance the zinc content of the fumes. In a preferred embodiment I supply a large proportion-of the heat necessaryfor continuous reduction in the furnace by reoxidizing, or combusting, part of the zinc vapor and carbon monoxide which have previously been generated from the charge. It also is advantageous when using certain raw materials and under certain conditions of operation to produce both metallic zinc and zinc oxide as separate The temperature products from the same charge material by treating the relatively rich fumes generated during the early period of the reduction for the recovery of metallic .zinc according to my process, and thereafter burning to zinc'oxide the more dilute fumes later generated.

The fumes generated in the first stage of the process contain variable amounts of zinc vapor, carbon monoxide, carbon dioxide, nitrogen, and suspended reoxidized zinc. The content of carbon dioxide and reoxidizedzinc depends largely upon the degree of reoxidation permitted in the furnace, and may vary from a small proportion to a verylarge proportion when reoxidation is utilized as the principal source of heat for the reaction. These fumes, in a condition precluding satisfactory condensation, are swept out of the furnace by pressure of the reaction products and are carried into a closed conditioning chamber containing a gas permeable charge of very hot, active reducing material, such as low temperature coke, lignite char or charcoal. The reducing material has been preheated, deoxidized and degasified before being contacted by the fumes from the furnace. During the flow of. fumes through this material the influx of appreciable quantities of air or other gases, except from the eliminating 75 atom-r9 3 furnace, is prevented, and heat is supplied by means other than combustion within the chamber to sustain and complete the reduction of reducible constituents of the fumes in the gaseous or suspended form. The conditioning chamber provided for this purpose is of a size, appropriate to the capacity of the connected zinc eliminating furnace, which will subject the fumes passing therethrough to heating and reducing conditions for a period of time sufficient to eflect substantially complete reduction of their content of 002, H and zinc oxide. Its charge of reducing material is kept readily pervious to the fumes so as to permit large through-puts and to avoid excessive pressure losses between the eliminating furnace and the condensers. Q

In this conditioning furnace, by the final reduction of oxidized materials in theifumes with or without other special treatments, fumes from which liquid zinc otherwise would not be obtainable are converted to a condensable condition. The treatment in the conditioner results in thedelivery of completely reduced, dust-free vapors to the next stage of the process-the condensation stage. In addition, non-uniformities in the materials leaving the eliminating furnace can be treated variably and ironed out by suitable con trol of the conditioning chamber, which may be equipped to treat a variable supply and discharge a uniform exit product. In one embodiment of the process zinc waste material, such as zinc dross, zinc scrap, zinc die-castings and the like, may be redistilled by the sensible heat of the conditioned gases passing out of the chamber, resulting both in cooling the vapors for condensation and in enrichment of the vapor laden gases while' going to the condensing apparatus. The

gases leaving the conditioning chamber also may be subjected to treatment with sodium or other chlorides, or other surface fluxes or reducers of surface tension, in order to improve the coalescence. In still another embodiment, traces of sulfur and other substances which interfere with the condensation and the quality of the metal product may be removed by contacting the gases in the conditioning furnace with scrap iron, scrap copper or other drag-downs, corresponding to precipitants in wet process purification process thereby eliminating impurities which otherwise would be condensed with or entrapped by the condensing zinc vapors.

The condensation of fully reduced, vapor laden gases leaving the conditioning furnace may be carried out in various types of condensers. When the gases are quite low infzinc vapor two condensers in series may be,-used to advantage-a liquid condenser and a powder condenser. In the liquid condenser, in addition to whatever cooling has occurred, e. g., through redistillation of zinc after reduction, the vapors are contacted with molten zinc metal to take advantage of the fl'ects of evaporation. They arethen cooled be-/ low the saturation point to collect the liquid product and thereafter preferably cooled rapidly in the powder condenser to deposit their residual zinc content as zinc dust, or blue powder. This powder may be returned to the upper part of the conditioning chamber to be redistilled by the sensible heat of the gases, enriching them to the point where a higher percentage of liquid is condensed and-a lower percentage of powder. This system will ultimately come into equilibrium and all the metal will be recovered as liquid;

When the gases in the powder condenser are quite dilute and require a large loss of heat' through its walls, I may cool these walls by air and subsequently use the hotair to combust fuel gases, when such are used to heat the conditioning furnace, or to blast the zinc eliminating furnace, or to preheat the solids going to either furnace.

By the use of the process described in general above I am able to release zinc from residue by any procedure'best suited for the specificzinc raw material. and the availability of fuels or electric power, as a relatively concentrated fume and without regard to the condensibility of the fumes as they leave the eliminating furnace. This process might-be said to be a fire concentration of the zinc with subsequent reduction of the metal in gaseous suspension-in a separate furnace. By its use all the advantages of fire concentration of zinc are to be had without the low heat economies and the collecting and hendling and reworking costs of the ordinary process where the gases are cooled down and the zinc and other suspended matter separated and collected, densified and reworked in another furnace as a charge for metal or oxide.

The importance of the flexibility of my new process will be readily apparent to persons skilled. in the art. Since the elimination of the zinc from the residue may take place in directly fired furnaces the problem of carrying heat economically into a bulk of porous ore and coal is solved. Only the final conditioning of the resulting fumes in the conditioning chamber need be accomplished by indirect or more expensive heating methods. In this conditioning chamber heat transfer is mostly to gases and solids in extremely fine suspension which, by theirvelocity, have. high transfer rates and because they are extremely finely divided, reduce easily. The process is freed from other limitations which are inherent in the usual retort practice. farge charges of zinc-bearing rawmaterials, .of almost any quality and physical condition, may be treated satisfactorily, and fuels of an inexpensive and readily accessible type may be used for combustion. Mechanical furnaces can beused which will handle one hundred tons or more of zinc charge per day, the fumes from which are passed through closely controlled conditioning columns for treatment therein and thence to communicating condensers where they condense to liquid zinc.

Other features 'and advantages of'the invention will be made more apparent by the ensuing detailed description of illustrative embodiments when considered in connection with the accompanying drawings illustrating suitable apparatus which I have provided for practicing the invention. In the drawings,

Figure l is a front elevation, partly in section, of a complete zinc smelting assembly, including a zinc eliminating furnace, a conditioning chamer and a condensing system together with provision for producing zinc oxide from the same charge as used in the eliminating furnace.

Figure 2 shows an assembly of another form of'apparatus which may be used instead of the Figure 4 shows another form of zinc elimi-iv nating furnace in combination with another form 'of conditioning furnace and a condenser.

In the practice of the invention by the use of apparatus of the types illustrated in the several 'figures of the drawings, the elimination of zinc from residue is carried out in a furnace chamber designated generally by the character A, and the furnace fumes from the zinc eliminating chamber A, including zinc and zinc compounds in suspension, pass to a conditioning chamber B where reducible constituents thereof are reduced and the fumes are conditioned for condensation. From chamber B the zinc laden gases flow into condensation apparatus C where metallic zinc is recovered. Each of these stages of treatment is kept under individual control and adapted for best performance of the whole under varying conditions of operation, as described in greater detail below.

In the practice of the invention according to one embodiment I may employ a modified travelling grate furnace such as illustrated in Figure l for the elimination of zinc from the residue. The furnace is composed of suitable refractory furnace walls i0 which define chambers within the furnace, separated by arches 29, and enclose a traveling grate upon which the charge of zinc-bearing raw material, reducing materials and fuel is continuously fed. The grate l2 comprises a plurality of interconnected sections forming a continuous conveyor, the sections being made of heat-resisting material and spaced to permit the passage of combustion-supporting gas therebetween but to prevent the sifting of briquetted material therethrough. This grate l2 passes over appropriate sprocket wheels l4 and I6, respectively, and beneath its upper flight air boxes i8, 20, 22 and 24 are provided which extend across the furnace structureat appropriate intervals and serve to supply regulated streams of combustion-supporting gas, such as air, to the under side of the grate. The grate is arranged to pass beneath hoppers 2'6 and 28, respectively, the former for briquetted fuel and the latter for briquettes of zinc-bearing raw material and carbonaceous reducing material. Intermediate these hoppers the grate passes through a fuel ignition chamber 30. Beyond hopper 28 is 'an additional combustion chamber 32, for bringing the charge to a reaction temperature, and beyond this chamber are located larger, zinc eliminating chambers 33 and 34 in which combustion and reduction of the charge take place. In the walls of the zinc eliminating chambers, above the grate, inlets for combustion-supporting gas are provided, for example as shown at 33a and 34a, for a purpose hereinafter described.

In the operation of the furnace, as the grate moves beneath hopper 26 a bed of fuel is'fed onto the grate and then carried into the fuel ignition chamber 30 where it is ignited and from which combustion gases are withdrawn through a. suitable stack 36. The bed of ignited fuel is then carried beneath the hopper 2B for the charge materials, and briquettes of zinc-bearing raw material, such as 'zinciferous ore, and reducing material, such as coke, are fed into the ignited bed of fuel at this point. The layers of material are then carried into combustion chamber 32 where the entire charge is brought up to a reaction temperature and from which gases are withdrawn through a stack 38. As the grate proceeds in its movement it then carries the ignited materials, at a reaction temperature, into the zinc eliminating chambers 33 and 34 where there occur continuous combustion, generation of heat and continuous reduction of .the zincbearing raw material with consequent evolution of zinc-laden fumes. p In the preferred manner of eliminating the zinc at A in Figure 1, a relatively small volume of air or other combustion-supporting gas is 5 fed upwardly into the charge through the grate l2, enough to keep the grate relatively cool and to maintain active reduction in the lower portion of the charge. The remaining oxygen necessary for combustion to keep the materials well above the reduction temperature is supplied by passing air, or an oxygen-enriched gas, preferably preheated as high as practicable, into the chamer A at a point above the charge where part of the zinc vapor and carbon monoxide already generated will be reoxidized to carbon dioxide and suspended particles of zinc oxide. In this manner the zinc content of the fumes leaving the furnace may be greatly increased as compared with a process in which the heat required for the reduction reaction is supplied substantially .entirely by burning carbon. Assuming no heat losses and all of the reaction materials preheated to reaction temperature, the reduction would be maintained on a continuous basis, with no burning of carbon, by reoxidizing less than half of the zinc vapor and carbon monoxide. In practice, when using the traveling grate type of eliminating furnace, a part of the heat necessary to sustain the reactions is supplied by the combustion of carbon and the remainder by combustion of zinc vapor and carbon monoxide, and fumes containing a relatively high proportion of zinc and zinc compounds arecontinuously discharged from sections 33 and 34' of the zinc eliminating chamber A through heat insulated off-takes 40 and 42. The fumes are carried by the respective off-takes into conditioning chambers B where further treatment takes place, as hereinafter de-' scribed, in order to condition them for recovery of their zinc content.

tion the charge on the grate I2 is kept in chambers 33 and 34 untilthe rate of reaction becomes retarded, which may occur after about threefourths of the zinc content is exhausted, and it then passes into chamber 35 where it is fired by an air blast from beneath the grate. The fumes from this chamber are then conveyed by' an ofltake 44 into a burner E for the production of zinc oxide. With this system the proportions of metallic zinc and zinc oxide produced from the charge may be varied over a wide'range, depending upon market conditions, etc., and requirements for both products may be supplied by the operation of the same furnace on the same raw materials.

The fire reduction which takes place in the reduction chambers 33 and 34 is capable of utilizing various types of zinc residues and fuels as the raw materials and of producing larg e' 'volwires of fumes for the recovery of metallic zinc. The temperature in these chambers is keptv in a high range to foster rapid reduction and the maintenance of pressures sufficient to drive the fumes through the other stages of the process. A suitable balance of pressures between chambers 33 and 34 and adjacent chambers 32 and 35 can be effectedby appropriate venting of the latter.

The conditioning apparatus used in the second (ill stage of the present process may be substantially the same regardless of whether a zinceliminating. furnace of the type illustrated in Figures 1, 2 and 4, or of other types, is used. It preferably comprises a column of granulated coke or other active carbonaceous reducing material heated' to a temperature considerably above the reducing point of zinc oxide, carbon dioxide and water vapor and operated so that such compounds in the fumes entering the column are reduced substantially entirely and the resulting gases conditioned for effective condensation of liquid zinc in the condensation stage of the process. The carbonaceous reducing mate-.

rial is contained in a gas-tight chamber to which heat may be supplied either by burning fuel outside the chamberand transferring the heat through its walls or by making the column itself a resister in an electric circuit and generating the required heat electrically within the chamber itself. Provision is made for feeding preheated and deoxidized coke at the top of the column and for removing reducing material at the bottom before its efflciency for conditioning the fumes has been substantially impaired. The

' column itself should provide considerable space for carrying out the reduction reactions, and its heating capacity should be ample so as to ensure thorough reduction of oxidized compounds in the fumes and to permit large through-puts of gases. I

The higher the temperatures maintained in the column the lower its volume may be per unit' gas-tight walls including an outer metallic shell 52 and an inner layer of flre brick or other refractory material 54. Adjacent its top end it is formed with a restricted neck 50 which is normally kept closed by a rotatable gate valve 58 permitting the introduction of solid material into the chamber at will, but normally excluding air from the chamber. Through valve 58 the chamber communicates with a hopper 60 for the reception of conditioningmaterial from a charging floor 62. The top of hopper B is usually covered by a movable gate which may be moved to an open position to permit the'introduction ,of material into the hopper from a car 64. The lower part' of chamber 40 includes a restricted neck 86, also normally closed by a rotatable gate valve 68, through which material from the chamber may be discharged into a suitable receptacle on a floor 10. Since the fumes from the zinc eliminating. furnace and off-take 40 pass upwardly through the chamber and the conditioning material is introduced into the chamber at the top, the described arrangement provides descending columns which result in eillcient utilization of the material therein and enable easy adaptation of the rate of flow to requirements of the process. 7

Each conditioning chamber may include a bleeder 1| extending from the top portion of the I chamber and controlled, for example, by a valve 1 la for regulating the flow of gases therethrough, The purpose of the bleeder is to permit any oxidizing gases introduced into the top of the chamber by the charge materials to be bled off. so that passage of such gases into the condensation apparatus with zinc laden gases may be avoided.

The heating means illustrated in Figure '1 includes an upper series of electrodes 12 extending into material in the chamber and a lower series of electrodes 14. With a column of coke in the chamber electrical current may be passed through these electrodes and through the coke to raise the temperature of the material to the proper point andto maintain such temperatures while fumes from the releasing furnace pass through the chamber. Heating the column in this way permits'ready control over the temperatures and conditionsof reaction therein. The heat required in the column is the heat generated by reoxidation in the eliminating furnace plus an losses which occur after the fumes leave the eliminator. Since the materials being reduced are composed of gases and very finely divided suspended compounds, reduction is very rapid, and heat transfer, whether from electrically heated coke or through the walls of the conditioning chamber, is efllcient. The large throughputs of materials per unit volume of equipment and the freedom of selection of materials in the several stages of the process render operations economical and efficient in comparison with known smelting practices.

. In addition to reducing material, such as coke, lignite, charcoal and activated carbon, I may introduce in like manner, controlled amounts of zinc scrap material, such as zinc dust, zincdross, zinc scrap, zinc die-castings and the like into the upper part of the conditioning chamber, 1

and redistlll the same'by means of the sensible heat of the previously reduced gases. I may also I introduce "drag-downs or condensation promoters as described hereinabove. These practices accelerate the subsequent condensation of molten zinc from the gases and at the same time purify the scrap materials introduced into the chamber.

From the conditioning chambers 46 and 48,

whether of the type just described or of" other types to be described below, completely reduced and conditioned zinc-laden gases pass outwardly through conduits 82 and 84 and thence into condensing apparatus 0, which may be of any suitable construction or, when the gases are relatively lean in zinc vapor, preferably is adapted specially for efiicient recovery of metallic zinc, for example, as illustrated in Figure 2 or 4.

In the embodiment shown in Figure l, the condensing apparatus comprises chambers I6 and I8 having inside baflies which cause the gases to swirl through the chambers and to condense on the walls thereof and collect in a well or sump 88, whence liquid zinc may be withdrawn through a port 90 adjacent a floor level 92. The chambers are cooled, for example, by fins 19 or other cooling means. The residual gases from which zinc vapor has been condensed are withdrawn from the condensers through stacks 94 and 96 and then carried off for combustion uses or for other purposes, for example, in the conduit 99 which also receives combustion gases from chamber 32 of the travellinggrate furnace.

It will be noted that conduits 40 and 42 from the zinc eliminating furnace enter the conditioning chambers 46 and 48 at a point where the entering fumes immediately contact very hot conditioning material. This is important to satisfactory operation, since it prevents chilling of the fumes, subjects them to conditioning treatment underthe optimum circumstances, and

avoids loss of zinc'values which otherwise might occur to an objectionable extent upon contact-between the fumes and cooler material.

By use of the present'process, I am able to release fumes from the metalliferous charge in the zinc eliminating furnace which include what have heretofore been considered objectionable combustion gases and to condition these fumes before they are introduced into the condensing apparatus so that they are no longer objectionable and so that an eflicient recovery of liquid zinc is obtained. As already indicated, the process permits variations in the type of apparatus used in each stage. Several preferred variations are illustrated in Figures 2 to 4 of the drawings.

Figure 2 illustrates an assembly in which a blast furnace of the slagging type is used for the elimination of zinc from zinciferous ore and in which special condensing apparatus is employed to enhance the recovery of metallic zinc from relatively lean zinc-laden fumes. The eliminatingfurnace is designated I in Figure 2, and is constructed in a well known manner to provide a chamber A in which the reaction of a charge of fuel, ore and reducing material takes place. A

hearth I 02 is located at the bottom of the furnace chamber, and a well I04 communicates with the hearth for the collection of lead and matte when rial. A header I06 for a blast of combustion- .supporting gas surrounds the furnace and is connected with a series of tuyeres I00 for the introduction of a blast of air or other gas, preferably preheated, into the charge. Solid material forming the charge is dropped into the furnace chamber from a bin IIO through a restricted neck I I 2, controlled by a bell valve H4. The furnace gases containing the zinc leave the furnace chamber through a port H6 and a flue I I8 connected with a conditioning chamber I20. The chamber I20 illustrated in Figure 2 is constructed like chambers 46 and 48 of Figure 1, although other types of conditioning apparatus may be used in its place. Conditioned fumes from the chamber I20 leave through a flue I56 adjacent the upper end of the chamber. and thence pass to the condensing apparatus which is illustrated in greater detail in Figure 3. v

The condensing apparatus illustrated in Figures 2 and 3 includes a liquid condenser and a powder condenser. Chamber C is a liquid zinc condenser similar to those shown in Figure 1. Chamber D is a zinc dust or blue powder condenser with large metal surface cooling areas I50 and ample baiiling I52 to settle out the last of the zinc in the reduced gases. It is providedwith conveying means, for example, a screw conveyor I54, at the bottom or hopper'portion, so that the collected powder may be continuously or intermittently returned to the chamber .for revolatilization by the sensible heat of the previously reduced gases. The conditioned gases-from B enter C by way of the port and flue I56. Molten metal condenses out in C anrl may be tapped off from the tap hole I 58; The partially condensed gases pass then into the blue powder condenser D where, due to the intense cooling, the last of the zinc is dropped out. The non-condensable gases of high fuel value leave this condenser through a flue I60 to beused for any suitable purpose, such as in the degassing and deoxidizing. furnaces for the metalliferous charge and the conditioning chamber coke. I may also burn it in regenerators or recuperators to preheat the blast for the furnace A or use it conditioning for indirectly heating the conditioning chamber B instead of the electric resistance method shown in Figure 2.

Charge materials introduced into the blast furnace I00are preheated, degasified and freed of substances which readily oxidize zinc vapor before introduction into the combustion chamber of the furnace. The materials may be prepared in this manner by the use of apparatus com-' municating with the bin IIO including a hopper,

solid materials passing through the kiln are kept in a state of agitation, and preliminary deoxida-e tion and degasiflcation thereof are facilitated. Burner I34 extends axially into the kiln through one of its ends so that solid materials approaching the burner are thoroughly treated before they leave the kiln through conduit I36. Gases from the kiln pass off through a waste stack I46. Solid materials entering conduit I36 are conveyed into bin IIO, for example, by a screw conveyor I48. By the use of apparatus of this type a suitably proportioned mixture of deoxidized, degasifled and preheated ore and carbonaceous mate-p rial maybe introduced into bin I I 0 at the desired rate, and from bin IIO these materials may be charged into the furnace chamber through restricted neck II2 simply by lowering the bell valve H4. The conditioning material fed into chambers B may be degasified, deoxidized and preheated and thenfed to these chambers by similar apparatus.

As fuel for burner I34, I may use powdered coal, oil or gaseous fuels,- but I, prefer to use residual gases taken off from the condensation stage of the process because of the economic advantage thus obtained. It will be understood that burner I34 may communicate in any suit able manner with a gas take-01f from a condensing apparatus, such as the take-off I60 illustrated in Figure 3 of the drawings.

A further assembly of apparatus suitable for use in the improved process is illustrated in Figure 4. The zinc eliminating chamber A in this figure is the furnace of the Waelz kiln type,"in-

'cluding an elongated tube 300 that connects The kiln is usually supported on a preheated charge including zinciferous andcarbonaceous reducing materials and fuel into the entry end of the kiln, for example, through a delivery chute 3I4. Adjacent the lower end of the kiln the header 304 is equipped with means 3I6 for introducing combustion-supporting gas, preferably highly heated air, into the furnace,

ment is provided by an indirectly fired vertical retort 200.

The waelz -type kiln is advantageous for use i in the economical elimination of zinc from raw materials'of low grade. In operatioman inclina tion and rate of rotation of the kiln are adopted which subject the charge to reaction conditions for a considerable period of time. The constant revolution of the kiln maintains a degree of agitation and mixing of the constituents of the charge which promotes a high elimination of their zinc content. The heat and blast require ments of this type of operation are relatively low because of its adaptability for the reoxidation of a. large proportion of the zinc vapor and carbon monoxide initially liberated from the charge before the gases leave the furnace, so that the endothermic heat requirements of the reduction 'reaction are substantially compensated by the exothermic reoxidation of the zinc and carbon monoxide. The operation of this apparatus thus. produces gases of relatively high zinc content, and the condition of the gases is such that they may be passed through a conditioning chamber B in accordance with my-invention and there contacted with reducing material while heat is supplied so as to convert them to a condensible condition.

The conditioning furnace illustrated in Figure 4'comprises a vertical retort 200, similar .to the conventional vertical coke retort, which includes one or more conditioning chambers B and is heated indirectly by the combustion of gases. A. column 202 of coke or other reducing material is maintained within chamber B, degasifled and deoxidized reducing material being fed into the chamber through an overlying hopper 204, for example as in Figure 2. A valve-controlled bleeder Il may communicate with the top portion conduits 2|. and H2 which supply suitable gaseousfuel taken from a pipe 2 l4, preferably gases exiting from the zinc condenser system, and they also communicate with upper and lower conduits M6 and 2I8 that receive combustion-supporting gas such as air from preheating chambers 220 and 222, respectively. By this means cornbustionmay take place alternately from the upper and lower ends of the flues, and the combustion gases exit through the idle chamber 220 or 222 so that combustion-supporting gases later passed through the chamber become preheated before use. A retort of this type is described in greater detail in United States Letters Patent No. 1,908,632.

The condensing system shown with the apparatus of Figure 4 embodies connected condensing chambers C and D for the condensationof liquid zinc and powder, respectively. Fumes from the zinc eliminating furnace are carried into the conditioning chamber B of the retort'through the flue 320, and they pass upwardly through the column of reducing or other conditioning material in a direction counter-current to the movement of the conditioning material. Heat sufiicient to sustain and complete the reactions in the chamber is supplied efllciently from the flues 208,

but without introducing oxidizing material intov the chamber or diluting thegases flowing there- I through. The conditioned gases leave chamber B through a flue 224 and .then pass into the liquid condenser 0. Here they first flow through a section 230 in which the gases are cooled rapidly to approximately their saturation temperature by intimate contact with liquid or solid zinc. The cooling at 230 may be regulated by cooling means 232. so that part of the zinc content of the gases is condensed and flows downwardly over bafiies or the like in contact with the rising vapors. From section 230 the gases go into a condenser 240 in which the liquid zinc is collected, and from this they pass to the powder condenser D in which the residual zinc vapor is collectedas powder or' zinc dust. The remaining gases, containing a large proportion of carbon monoxide, leave D through a flue 242 and may be returned to the retort 200 for combustion. The blue powder collected in D is continuously or intermittently returned to the upper region of the conditioning chamber B or to the cooling section 230 of condenser C, an arrangement for the latter including a screw conveyor 244 being illustrated in Figure ,4. If desired, preheating of the air used to combust the gases in flues 208 or for other purposes may be carried out by forcing the air through sheet metal work surrounding the condensers C and D.

My improved process may be modified in many ways other than those specifically mentioned above once its freedom from limitations inherent in conventional retort smelting practice has been realized. For example, an arc furnace may be used in the first or zinc eliminating operation of the process with good results, particularly when non-volatile values are to be recovered from ore in addition to volatile-metals such as zinc. A great deal of freedom may also be used in the selection of apparatus, treatments and controls for the second or conditioning operation of the process and for the third operation in which the conditioned fumes are converted to desired zinciferous products.

It will be a parent. to persons skilled in the art that my improved process and apparatus are capable of practical embodiment in many different forms. I therefore desire that the invention be accorded a scope suflicient to embrace equivalents, in keeping with the spirit of the specification and the requirements of the claims. I

, I claim:

1. In the pyrometallurgy of zinc, the process which comprises releasing zinc from a reducible zinciferous charge in a chamber and supplying heat for the reduction by combustion of oxidizable material within the chamber, conducting the fumes including zincvapor, suspended reoxidized solids and combustion gases into a hot reaction zone of a separately controlled and independently heated conditioning chairmen-passing the fumes in the conditioning chamber througha gas-permeable bed of hot reducing material while. supplying additional heat to reduce constituents of the fumes without externally diluting their zinc content, and condensing molten zinc from the conditioned gases in separately controlled con-.

2. In the pyrometallurgy of zinc, the process which comprises releasing zinc from a reducible zinciferous charge in a chamber and supplying heat for the reduction by combustion of oxidizable material within the chamber, conducting the fumes including zinc vapor, suspended reoxidized solids and combustion gases into a hot reaction zone of a separately controlled conditioning chamber, contacting the fumes in the conditioning chamber with hot reducing material while supplying heat to reduce constituents thereof without externally diluting the zinc content, contacting the reduced gases with condensation-promoting agents in the conditioning chamber, and condensing molten .zinc from the conditioned gases in separately controlled condensing means.

3. In the pyrometallurgy of zinc, the process which comprises releasing zinc from a reducible zinciferous'charge in a chamber and supplying heat for the reduction by combustion of oxidizable material within the chamber, conducting the fumes including zinc vapor, suspended reoxidized solids and combustion gases into a hot reaction zone of a separately controlled conditioning chamber, contacting the fumes in the conditioning chamber with hot reducing material while supplying heat to reduce constituents thereof without externally diluting the zinc content, contacting the reduced gases with an inorganic chloride in the conditioning chamber, and condensing molten zinc from the conditioned gases in separately controlled condensing means.

4. In the pyrometallurgy of zinc, the process which comprises releasing zinc from a reducible zinciferous charge in a chamber and supplying heat for the reduction by combustion of oxidizable material within the chamber, conducting the fumes including zinc and zinc compounds in gaseous suspension out of the liberating chamber -and into a hot reaction zone of a separately con trolled and independently heated conditioning chamber, passing the fumes through a porous bed of hot reducing material which moves through said'zone countercurrent to the flow of the fumes and simultaneously heating said material and fumes to reducing temperatures without supplying oxidizing substances thereto, thereafter conducting the fumes out of the conditioning chamber and into cooling and condensing means and condensing metallic zinc therefrom.

5. The process of zinc smelting which comprises reducing zinc-bearing raw material in a first chamber to produce a mixture including zinc vapor, reoxidized zinc and gases capable of oxidizing zinc vapor before condensation thereof, flowing the mixture from the first chamber through a gas-permeable bed of hot reducing material in a second chamber'and there heating the reducing material and mixture independently of said first chamber, reducing said reoxidized zinc to zinc vapor and reducing said gases to non-oxidizing form without substantial external dilution of the zinc vapor concentration of the mixture, and thereafter condensing zinc vapor in the mixture to metallic zinc in another chamber.

6. The process of zinc smelting which comprises reducing zinc-bearing raw material in a first chamber to produce a mixture including zinc vapor, reoxidized zinc and gases capable of oxidizing zinc vapor before condensation thereof,

flowing the mixture. from the first chamber through a gas permeable'bed of hot reducing material in a second chamber and there heating the reducing material and mixture independently of said first chamber, reducing said reoxidized zinc to zinc vapor and reducing said gasesito nonoxidizing form without substantial external dilution of the zinc vapor concentration'of the mixture, distilling zinc in the second chamber and adding the resulting zinc vapor to the reducing mixture, and thereafter condensing zinc vapor in the mixture to metallic zinc in another chamber.

7. The process of zinc smelting which comprises reducing zinc-bearing raw material in a first chamber to produce a mixture including zinc vapor, suspended zinc compounds and gases capable of oxidizing zinc vapor before condensation thereof, flowing the mixture into a second chamber and into contact with reducing material hotter than the mixture, maintaining such contact for a period of at least several seconds and rewhich comprises releasing zinc from a reducible.

zinciferous charge in a chamber and supplying heat for the reduction by combustion of oxidizable materialwithin the chamber, conducting the fumes including zinc vapor, suspended reoxidized solids and combustion gases into a hot reaction zone of a separately controlled conditioning chamber, passing the fumes in the conditioning chamber through a gas-permeable bed of hot reducing material while supplying heat independently of said combustion chamber to reduce constituents of the fumes without externally diluting their zinc content, thereafter condensing molten zinc from the conditioned gases in one condenser and extracting the remaining zinc content ofthe residual gases as solid metallic zinc in another condenser.

9. Inthe pyrometallurgy ofzinc, the process which comprises releasing zinc from a reducible zinciferous charge in a chamber and supplying heat for the reduction by combustion of oxidizable material within the chamber, conducting the fumesincluding zinc vapor, suspended reoxidized solids and combustion gases into a hot reaction zone of a separately controlled conditioning chamber, contacting the fumes in the conditioning chamber with hot reducing material while supplying heat to reduce constituents thereof without externally diluting the zinc content, thereafter condensing molten zinc from the conditioned gases in one condenser, extracting the remaining zinc content of the residual gases as solid metallic zinc in another condenser, and

conveying solid metallic zinc from said other reoxidized zinc and combustion gases into a second chamber and through a gas permeable bed of hot reducing material therein, heating said reducing material and fumes independently of said first chamber, while excluding oxidizing substances, and thereby reducing reducible constit uents of the fumes and conditioning the gases for condensation, and thereafter condensing metallic zinc from the conditioned gases. I

11. The process of smelting zinc which comprises releasing zinc from a zinciferous charge in a chamber by heating the charge in the presence of reducing.material and combusting carbonaceous material, supplying most of the heat of reduction by combustion of zinc vapor and carbon monoxide generated from the charge, passing the resulting fumes including zinc vapor, reoxidized zinc and combustiongases into contact with hot reducing material while excluding oxidizingsubstances and thereby reducing reducible constituents thereof and conditioning the gases for condensation, and thereafter condensing metallic zinc from the conditioned gases.

12. The process of producingmetallic zinc and zinc oxide as separate products from the same charge of zinciferous raw material which comprises releasing zinc from the charge byheating the charge in the presence of reducing material, supplying a substantial part of the heat of reduction by combustion of zinc vapor and carbon monoxide generated from the charge, passing the, resulting fumes into a separate conditioning chamber and substantially completely reducing and condition-v ing them for condensation therein, condensing metallic zinc from the conditioned gases, releasing additional zinc from the charge after the reduction reaction becomes retarded by combustion of carbon in contact therewith, and burning the resulting additional fumes to collect zinc oxide.

13. The process of smelting zinc which comprises releasing zinc from a preheated zinciferous charge in a chamber by further heating the charge in the presence of reducing material, supplying part of the heat of reduction by combustion of carbon andthe remainder by reoxidation of generation of fumes including zinc vapor and suspended reoxided compounds, condensing means for condensing zinc vapor to metallic zinc, separately controlled conditioning means including an enclosed bed of reducing material intermediate the furnace and condenser for receiving said fumes from the furnace, conditioning the fumes for improved condensation of metallic zinc therefrom and passing conditioned gases onward to the condenser, means for supplying heat to said material to convert the fumes to reduced condition without substantial external dilution of the zinc vapor concentration thereof, means for carrying fumes from said furnace and for introducing the same into said conditioning means in the heated portion thereof, and means for carrying conditioned gases from said conditioning means into said condensing means, said condensing means including a condenser for collecting molten zinc and another, communicating condenser for collecting zinc powder, and means for returning said powder into said conditioning means.

15. The process of zinc smelting which comprises releasing zinc from a reducible zinciferous charge in a chamber and supplying heat for the reduction by combustion of oxidizable material within the chamber, conducting the fumes in--' cluding zinc and zinc compounds in gaseous suspension out of the releasing chamber and into a hot reaction zone of a separately controlled and independently heated conditioning chamber, deoxidizing a supply of carbonaceous reducing material for the conditioning chamber, maintaining a gas-permeable bed of the previously deoxidized material in said reaction zone, passing said fumes through said bed and simultaneously supplying heat to said bed and fumes, without supplying oxidizing substances thereto, to reduce the zinc compounds to zinc vapor and conditioning the fumes for condensation of metallic zinc, thereafter conducting conditioned gases out of the conditioning chamber and into cooling and condensing means and condensing metallic .zinc therefrom, and from time to time removing material from said bed and adding fresh deoxidized material thereto so that the material in said bed moves in a direction counter-current to the flow of fumes therethrough.

FRANK G. BREYER.

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