US1773991A - Process of purifying zinc ore - Google Patents

Description

Aug. 26, 193& o. GERLACH PROCESS OF PURIFYING ZINC ORE Filed Dec. 31, 1927 4 Sheets-Sheet 1 E/KYJTTZZTW: JEQ ZZY I WW Aug. -5, 1930. OVGERLACH PROCESS OF PURIFYING ZINC ORE Filed Dec. 51, 1927 4 Sheets-Sheet 2 TLLOOL aw Aug. 26, 1930. o, GERLACH 1,773,991

PROCESS. OF PURIFY ING ZINC ORE Filed Dec. 31, 1927 '4 Sheets-Sheet 3 05W Ganbcz/olv PROCESS OF PURIFYING ZINC ORE Filed Dec. 51, 1927 4 Sheets-Sheet 4 ROASTED ORE COARSE LUMPS CHARGEH ACHINE H 9 ;I C1 SCALPING +0 E #1 smrsnzo ORE +H Q COARSE MATERIAL .S CREEN'.

'L v PARTLY-SINTERED ORE COARSE LuMPs m 4 v 3 l H z CARBON CHARGE 2 MACHINE +H Q n: 3 E52" 1:. Q SCALPING zsmrsaso ORE; COARSE MATERIAL,

' SCREEN COARSE. LUMPS 1 PARTLY 5 NTERED ORE E1 677157 0560/ Gar/6m JMA%O w y/z wz Patented Aug. 26, 1930 UNITED STATES PATENT OFFICE OSCAR GERLACH, 0F PERU, ILLINOIS, ASSIGNOR TO MATTHIESSEN & HEGELER ZINC 00., OF LA SALLE, ILLINOIS, A CORPORATION OF ILLINOIS BBOCESSOF PURIFYING ZINC ORE Application filed December 31, 1927. Serial No. 243,840.

This invention relates to an improved process of purifying zinc and other ores and to the apparatus employed in carrying on said process and its purpose is to provide improved means and an improved method for more efficiently effecting the purification which has heretofore been carried on chiefly by electrolytic means. The principal purpose of the invention is to provide a method for removing from zinc sulfide, carbonate, or other zinc ores-the lead and cadmium compounds and other compounds which are frequently present and which ordinarily volatilize readily when the zinc ore is heated.- A further object is to provide an improved method of purifying zinc ores by the application of heat. Another object is to provide an improved method of purifying zinc ores according to which the crushed ore is heated in the presence of a reducing agent. Still another object is to provide an improved method of purifying zinc ores by the application of heat in separate heating stages, the residue obtained from the operation of one heating stage being treated in the next heating stage of the process. An important feature of the invention is the discovery that the purification of zinc ores may be effected by a modification of the sintering apparatus which is emplo ed with iron ores and the like. Other ob ects of the invention relate to various features of the process and apparatus which will'appear more fully hereinafter.

Zinc ore most frequentlyv exists in the form of zinc. sulphide (ZnS) and in the practice of the present invention this ore is first crushed to a sufiiciently fine condition to enable it to pass through a ten mesh screen, that is, a screen having ten divisions to the inch. and the screened ore is then roasted in the usual roasting furnace at a temperature of from 1600 degrees Fahrenheit to 1800 degrees Fahrenheit to remove therefrom the larger portion of the sulphur (about 90%),

roasting furnace is taken therefrom and' crushed and screened after which it is put into a sintering machine through a hopper, preferably along with a quantity of previously treated ore which is taken from the discharge of the same or another sintering machine. The crushed and screened ore from the roasting furnace and the coarse materials from the discharge of'the sintering.

machine are thoroughly wetted with water before being introduced into the pans of the sintering machine to facilitate the passage of heat through the crushed material and to aid in the reducing process. The ore which is thus placed in the pans of the sintering machine is conveyed in these pans at a relatively low rate of speed, for example, at the rate of six inches per minute, and the ore is thus brought under a sintering hood equippedwith gas burners or other burners for producing a high temperature therein, preferably a temperature between 2600 degrees F. and 2800 degrees F. A number of burners are preferably provided in this hood, the first ones being fed with air and oil or gas to produce an oxidizing flame while the later ones of the series are fed with steam and oil or Water gas to form a reducing flame and to cause the production-of free hydrogen which is made use of in freeing the Zinc ore of the cadmium oxide therein. Preferably, a, two inch layer of line zinc ore is put on top of'a one-half inch layer of coarse ore. The object of putting the coarse more with the result that the upper por-.

' tions of the ore in the sintering pans are flames. It would appear that the lead and substantially freed of both lead and cadmium compounds. The lead is driven out of the layer of ore penetrated by the flames and collects partly in the ore beneath the same in the form of sulphate (while partescapes as such through the fan and stack to the air), and the cadmium likewise is driven out of the upper layer and collects partlyv in the lower 1a er in the form of sulphate and sulphide while art escapes. The zinc oxide in the upper ayer is not driven out in the limited time during which the ore is exposed to the cadmium in the upper layer are reduced and then volatilized a recombine in the vaporous state with sul hur and oxygen to form" the Sn] hates an sulphides in the lower layer. Thus, the upper portions ofthe crushed materials in the pans of the sintering machine are substantially freed ofcadmium and lead compounds; According to the present invention, this upper portion of the ore is scraped or otherwise removed from the lower layer of ore in the pans before the pans reach the end of their upper path of travel in the machine. The zinc ore which is thus removed is subsequently distilled with carbon rated and returned to the inlet end of the machine as referred to above for the protection of the pans and to prevent the clogging of the openings in the bottoms of the pans, while the fine materials are introduced into a hopper along with a quantity of carbon, preferably in the form of finely divided anthracite coal. The mixture discharged from this hopper is then elevated by a conveyor,

F wetted with water, and fed into another after which the coarse materials are returned to the inlet end of the second machine while the fine materials are mixed with carbon and fed to a third sintering machine. By carryon the process in a. number of successive steps substantially all of the zinc in the ore may be freed of the cadmium and lead compounds and at the same time the sulphur di-' oxide gas which is liberated in the several machines of the series may be drawn off and made use of in the manufacture of sulphuric acid. The escaping vapors of lead and cadmium sulphates may also be saved (by a Cottrell separator) and made use of. Although various forms of apparatus might be employed in carrying on the process described above, there is illustrated in the accompanying drawings an improved sinter-' ing machine which is adapted for that purpose. I

In the drawings, Figure 1 shows a side elevation of the sintering machine;

Fig. 1 shows a side elevation of a second sintering machine which is arranged to receive the discharge from the first sintering machine shown in Fig. 1;

Fig. 2 is an enlarged vertical section on the line 2-2 of Fig. 1;

Fig. 3 is an enlarged section through one of the cutting and scraping devices for removing materials from the upper parts of the sintering pans, and

Fig. 4 is a diagram of the flow sheet of the'improved process carried on by the pres ent invention.

As illustrated in the accompanying drawings, the apparatus comprises two sintering machines 10 and 10*? which are shown in Figs. 1 and 1, respectively, and which are similar in construction so that a description of one will sufiice for both. Each sintering machine comprises a plurality of sintering pans 12 which are mounted to follow an endless path of travel and which form a substantially continuous series so that each pan is located closely adjacent to the next leading and following pans of the series, except at the discharge end of the machine where a gap 13 is provided to allow the pans to drop a short distance to facilitate the dumping of the contents thereof. The sintering pans 12 are supported by a frame 14 comprising a plurality of vertical frame members 15 and a number of transverse frame members 16. This frame 14 serves as a support for certain track members which are provided to coact with rollers 17 mounted to revolve on trunnions 18 projecting laterally from opposite sides of the sintering pans 12, there being two rollersi17 at each side of each pan. In the upper horizontal portion of the path of travel ofthe sintering pans, the rollers 17 coact with horizontal trackways 19 having depending flanges 19 which are secured to brackets 20 attached to the longitudinal side frame members 21, as shown in Fig. 2. At their rear ends, the track members 19 are curved downwardly in semicircular fashion as shown at 19 and they are arranged to cooperate with upturned semicircular en tremities 22' o'f the lower track members 22 which are attached to. the vertical frame members 15. The lower track members'22 are inclined downwardly towards the forward end of the machine and arethence curved upwardly in a semicircle, as shown at 22", thus guidingthe sintering pans in their upward movements at the forward end of' the machine. Each roller 17 has an annular flange 17f which projects over the edge of the adjacent track members 19 and 22 so that lateral displacement of the sintering pans isprevented. .The movement of the sintering pans 12 on the trackways 19' and 22 is effected vided with teeth 24 arranged in pairs, the

teeth of one pair being spaced apart from those of thenext adjacent pair in such amanner that the teeth will engage behind the rollers 17 on thesintering pans 12, as shown in Fig. 1, when the sintering ans have rolled by gravity from the rear en to the forward end of the machine, whereupon the sintering pans are elevated concentrically with the curved portions 22'? of the lower trackway and are thus elevated to the forward end of the upper horizontal trackways 19 where the sintering pans are moved rearwardl' by the enga ent therewith of the following pans whicfi ai re continuously elevated by the driving wheels 24. The driving wheels 24 are actuated by a large gear 28 fixed on the shaft 25 and arranged to mesh with a inion 29 I fixed onan auxiliary shaft 30 havmg bear- 'ingscarried by vertical frame members 15.

The shaft 30-has fixed thereon a worm wheel 31 meshing with a worm 32 attached to the rear end of a longitudinal driving shaft 33. The shaft.33 is connected at its forward end by bevel gears 34 with a transverse shaft 35 which may be driven by an electric motor or other suitable driving means. This driving meclianism serves. to actuate the driving the horizontal wheels 24 in such a manner that the sintering pans have relatively 'slow travel in a rearward directionon the up er horizontal trackways 19, as heretofore exp ained. When a sintering pan 12 reaches the rear ends of rtions of the trackways 19, it falls by avity through the distance provided b the gap 13, thus discharging the materia s contained-therein.

The sintering ans 12 are provided with upwardly extending side walls 12' connected by transverse bars 12 and the side walls 12" have ledges on which are mounted the opposite sides of the grates 123 on which the crushed ore is ioaded. The sintering pans are open their ends so that when they are arranged in close spaced reiatiou on. the up per trachways 19, as shown in it, they form acontinuous trough for the reception of the crushed ore. In the region beneath the sintering pans which are mounted on the upper trac ways 19, there is located a casing 3 which forms a vacuum chamber 38 upper edges of the walls of the casing 3i being connected to a rectangular frame 39 which -is seated on. and secured to the inturned flanges 21 of the side frame members and which forms a funnel for directing materials downwardly into the chamber 38. The chamber 38 has a'pipe 40 leading from the lower part thereof and connected to a suction pump or other suitable apparatus adapted for maintaining a vacuum in the chamber 38 so that the sulphur dioxide and other gases which are liberated in the ore. and not the condensed and deposited therein are drawn downwardly into'the chamber 38 and thence outwardly through the pipe 40. In order to form a seal between the vacuum chamber and the sintering pans while these pans are in the upper part 0 their path of travel, a sealing plate 41, of somewhat flexible construction, is mounted along each lateral ed e of the'frame 39, bein held in position by c amping members 42 threadedly engagin studs 43. By adjusting the clamping mem ers 42, the upper edges of the sealing plates 41 may be caused to engage in the desired manner the grooves 44 which are formed in the side members of the sintering pans on the under sides thereof,

as shown in Fig. 2, in such a manner that the grooves in successive pans ali accurately with each other. A seal is 't us formed so that the gases from the sintering pans may be drawn downwardly into the vacuum chamber without actual loss.

The crushed and Wetted materials to be a treated in the sintering pans are introduced thereto through a-l'eeding hopper 45 secured to u wardly projecting portions of frame mem rs adjacent the orward end of the machine. 'The relatively coarse materials from the discharge of the sintering machine are fed to the inlet end,thereof through an auxiliary hopper 46 which is mounted adjacent the hopper 45. As the sintering pans travel beneath the hoppers 45 and 46 they are filled so that the upper surface of the material therein lies flush with the upper edges of their side walls 12" and, after being filled, the sintering pans m ve rearwardly on the trackway's 19 and are brought successively into position beneath the sintering hood 48 the walls of which extend downwardly and terminate closely adjacent to the upper surfaces of the sintering pans. The hood48 is lined with refractory material as shown at 48 and which the relatively high temperature before referred to is produced within the sintering hood. After emerging from the sintering hood, the pans 12' continue their travel rearwardly over the vacuum chamber 38 until,

position so that its lower edge divides the material in the pans along a definite horizontal plane. If desired, the plate or chute 51 may be adjustable so that ditlerent depths of material may be scraped from the sintering pans. As the pans move rearwardly, the upper portion 52 of the material in each pan is pushed upwardly onto the upper-side of the plate or chute 51 and is conveyed up-' wardly thereover by means of a plurality of transverse conveying members 53 which are carried by conveying chains 54. mounted on s rocket gears 55. These gears are fixed on siafts 56, one of which is driven so that the chains 54 are actuated in the direction indicated by the arrows 57. It will be under-- stood that the chutes 51 are inclined upwardly and rearwardly and also laterally so that the quantities'of zinc oxide ore which are scraped upwardly thereover are eventually deposited from the upper end of thechute 51 into a conduit 58 which is located at one side of themachine and which conveys the zinc oxide ore away for subsequent treatment in separating the metallic zinc.

Each sintering pain; after passlng the lower end of the device 50, drops by gravity through the space 13 and thus automatically discharges the remainder of its contents onto a screen 59 located over a hopper 60. .Tl1e coarse materials which do not pass through the screen are taken from the lower edge of the screen and conveyed by suitable means to the feeding hopper 46 at the inlet end of the first machine while the fine materials which drop into the hopper 60 are mixed therein with a quantity of carbon, preferably in the "form of anthracite coal and thoroughly wetted with water, preparatory to treatment in a subsequent smterlng machine of the series.

Between each adjacent pair of sinterlng machines of the apparatus employed, there is located an elevating device 61 for elevating the mixture of discharged material and carbon which drops from the hopper 60 into an open vessel 62 where it is picked up by the buckets 63 of the elevating device 61. The buckets 63 are carried by endless chains 64: and are in upright position whencarrled by the upper stretches of thesechains so that the quantities of materials picked up in the buckets are conveyed upwardly and thence dumped into the hopper 65 at the upper end or? the elevating device, as shown particularly in Fig. l. The hopper 65 discharges into a chute 66 which conveys the material to the feedinghopper 45 of the next sintering machine of the series. The chains 64 of the elevating device are mounted to travel on sprocket gears 67 andthe sprocket gears at in an inclined position and which may be supported by the frame 14 of the adjacent sintering machine. By this means a number of sintering machines, similar to those ordinarily employed in the sintering of iron ore, are

adapted for the use of the present process by the application thereto of the modified features described above. 4:

Although one example of the improved process of the present invention and one form of apparatus for carrying on that process have been setforth above by way of illustration, it will be understood that the improved process may be practiced in various ways and that various forms of apparatus inay be employed without departing from the scope of the appended claims.

I claim:

1. A process of freeing zinc ores from lead and cadmium contained therein which comprises subjecting a portion of a body of the ore to a temperature an atmosphere at which lead and cadmium vaporize while maintaining another portion of the ore at a substantially lower temperature whereby the lead and cadmium are volatilized from the first named portion and condensed in the second named portion, and separating the two portions.

2. A process of freeing zinc ores from lead and cadmium contained therein which comprises subjecting a.portion of a body of the ore to a temperature at which lead and cadmium vaporize while maintaining another portion of the ore at a substantially lower temperature whereby the lead and cadmium are volatilized from the first named portion and condensed in the second named portion, separating the two portions, and again subjecting the second named portion to the same process.

3. A process of freeing zinc ores from lead and cadmium contained therein which comprises subjecting a portion of a body of the ore to a temperature at which lead and cadmium vaporize while maintaining an-l other portion of the ore at a substantially lower temperature whereby the lead and cad mium are volatilized from the first named portion and condensed in the second named portion, separating the'two portions, mixing the second named portion with fresh inatcrial and subjecting it to the same process.

42. A. process oi freeing zinc ores "from lead and cadmium contained therein which comprises subjecting a portion'of a body out the ore to a temperature at which lead and cadmium vaporize while maintaining another portion of the ore at a substantiall lower temperature whereby the lead and cad mium are volatilized from the first named portion and condensed in the/second named portion, separating the two portions, screening the second named portion andsubjecting the coarser materials thereof to the same process.

5. The process of purifying zinc ore which consists in crushing and wetting the ore, heating a portion of the body of ore to vaporize certain ingredients thereof, pausing said vaporized ingredients to be condensed in another portion of the same body of ore, and separating the first-mentioned portion of said ore which is thus freed of said ingredients.

6. The process of purifying zinc ore which consists in heating the" ore to vaporize certain ingredients thereof, causing the vaporized ingredients to be withdrawn from a portion of said ore, separating said portion of said ore, again heating the remaining portion of said ore to vaporize certain ingredients thereof, causing saidlast mentioned vaporized ingredients to be withdrawn from a part of said remaining portion of said ore, and separating said part of said ore from which said vaporized ingredients'are withdrawn. 7

7. The process of purifying zinc ore which consists in placing the ore in a conveyor, subjecting the ore to the action of heat while moving in said conveyor to vaporize certain ingredients thereof, subjecting said heated ore to the action of suction and causing the vapors to be condensed in the lower part of the moving body of ore, and continuously removing the upper portion of the moving body of ore which is freed of said vaporized ingredients.

8. The process of purifying zinc ore which consists in placing the ore in a conveyor, subjecting the ore to the action of heat while moving in said conveyor to vaporize certain ingredients thereof,v subjecting said heated ore to the action of suction and causing the vapors to be condensed partly in the lower part of. the moving body of ore, continuously removing the upper ortion of the movin body of ore which is 're'ed'of said vaporize ingredients, and extracting the zinc from said last mentioned portion of the ore after it has been removed.

9. The process of purifying zinc ore which consists in placing the ore in a conveyor, subjecting the ore to the action of heat While moving in said conveyor to vaporize certain ingredients thereof, subjecting said heated ore to the action of suction and causing the vapors to be condensed in the lower part of the moving body of ore, continuously removing the" upper portion of the moving body of ore whichis freed of said vaporized 1ngredients, discharging the residue of said ore from said conveyor, mixing carbon with said residue, placing said mixture in another conveyor, su jecting said mixture in said last mentioned conveyor to the action of heat to vaporize certain ingredientsthereof, then subjecting said mixture to the action of suction and condensing said vapors in the lower portion of the moving ore mixture, separating the upper portion of the ore mixture from'which said va ors are withdrawn, and extracting the zinc i separated portion. V

10. The process vof purifying zinc which consists in crushing and wetting the zinc ore placing said ore in a conveyor, causing said ore to pass beneatha heating means Whereby certain ingredients of the ore are vaporized, then subjecting the ore to the action of suction means located beneath, the moving body of ore, thereby causing the vapors to rom said last mentioned be condensed in the lower portion of the body ofv ore, then removing the upper layer of the body of ore from which the vaporized ingredients have been withdrawn, and sepawhich is so removed.-

11. The process of purifying zinc ore which'comprises the steps of crushing the ore, highly heating the ore to vaporize certain ingredients thereof while retaining the zinc content of the ore in an unvaporized I state, causing said vaporized ingredients to consists in crushing t e ore, heating the body of the ore to vaporize certain ingredients thereof while leaving certain other valuable ingredients unvaporized, causing said vaporized ingredients to be condensed in a portion of the same body of ore, and separatingthe portion of the ore from which the vaporize ingredients have thus been re moved.

13. The process of purifying zinc ore which comprises the steps of crushing the ore, highly heating a portion of the ody of ore to vaporize certain ingredients thereof while leaving certain other valuable ingredients unvaporized and retaining the remaining portion of the ore at a lower temperature, causing said vaporized ingredients to be condensed in said portion of the same body of ore retained at a lower temperature, and separating the portion of the ore from which the vaporized ingredients have been thus removed.

14. The process of purifying zinc ore whic comprises the steps of crushing the ore, heating a portion of the body of the ore while it Is in motion to vaporize certain ingredients thereof while'leaving the zinc content 90 rating the zinc from the upper layer of'ore of the ore unvaporized and retaining the remaining portion of the body of the ore at a lower temperature, causing said vaporized ingredientsto be condensed in said portion of said ore retained ata lower temperature, and then separating the portion of the ore from which the vaporized ingredients'have been removed While the body of ore is inmotion. 7 r

In testimony whereof I have subscribed my name, r

OSCAR GERLACH.

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