US1840946A - Lead refining apparatus - Google Patents

Description

A. E. HALL LEAD .REFINING APPARATUS s sheets-sheet 1 Filed NOV. 8, 1929 www@ Jan. 12, 1932. A. E. HALL v LEAD REFINING APPARATps Filed Nov. 8. 1929 3 Sheets-Sheet 2 Jan. l2, 1932. A. E. HALL 1,840,946

LEAD REFINING APPARATUS Filed Nov. 8, 1929 3 Sheets-Sheet 5 .A50 crystalsweretransferred Parental Jn. 12, 1932 y PATENT OFFICE LRTHUB E. HVAIL, OF PERTH AMBOY, NEW J' EBSEY 'LEAD REFINE@ APPTUS Application filed November 1929. Serial No. 405,5?8.

This invention relates to lead reining and is more particularly directed to a process and pparatus ier the removal of bismuth from sad.

The metal bismuth is found as an impurity in lead and whenpresent in even small quantities, say upwardsof 6.15%, renders the lead unsatistaetorn to a large portion of the lead consumers. able sheathing, lead pipe, sheet lead, battery plate grids and lead for paint making purposes and, other purposes will not tolerate lead containing even small quantities such as 0.15%. If the bismuth content is reduced to 0.034% or less the lead produced i5 is satisfactory to the trade. At the present time it is possible to produce lead containing such low quanties of bismuth by the electrolytic process of refining, and by segregating ores, but the electrolytic process is an expenzo sive one and its expense increases as the quantity of bismuth in the lead increases. Where Y lead bismuth contains less than approximately 97% lead it has been Jound advisable to apply both a re process and later an electro- 2.5 lytic process on the same lead with the combined cost of a little less than le per pound for such treatments. Y

In 1900 Stephen Tredinnick who had been wor 0 at a plant in Nevada where the separationof silver from lead was being practiced, was granted a U. S. Patent No. 662,836 for an apparatus for refining and desilverizing lead, and somewhat later it was attempted to employ the apparatus described in his patent for the removal of bismuthY from ead and the concentration of the bismuth .in a relatively small amount of lead. The apparatus involved' included a. 'number of kettles which were separately heated and agitated in 40 an attempt to insure uniform heating throughout by blowing steam into the kettles.

Ater heating up of a charge in one kettle, 1t was allowed to crystallize in part and the kettle was then lifted by a hydraulic ram and the molten contents were allowed to flow into a second and adjacent kettle, after which the remaining crystals were melted in the first kettle and then, this kettle still bein elevated by means of the hydraulic ram, 't e melted by gravity to a third vand adjacent kettle. Theprocess was not a continuous one andV involved a large percentage of idle equipment containing metallic lead whose processing was awaiting the release of other apparatus in the refining group. The apparatus also presented consderable other diiiculties in operation which resulted in a relatively small output and an exorbitant cost along with poisonin of the operatives due to the production of ne particles of dross blown up b the steamused in agitation of the kettles. .'Illiese disadvantages resulted in abandonment of the Tredinmck apparatus for the purpose mentioned and since then it has l,been necessar to rely on the costly and laborious electro ytic process.

The principal object of this invention accordingly is to provide a simple, inexpensive, and eflicientv apparatus for refining lead to lower its bismuth content which shall do away with vthe disadvantages of the electrolytic process and practice mentioned under the Tredinnick patent. Another object of the invention is to provide a simple eiiicient. apparatus which shall permit a continuous separation of bismuth from lead, which shall avoid holding large masses of lead idle while waiting for available a paratus for processing, which shall permit a simple effective control to`be maintained for the production of lead containing desired percentages of bismuth and in accordance with the bismuth conj tent of the raw material as received. Other objects will be in part obviousl and in part pointed out hereinafter.

' The invention accordingly comprises the 'novel vapparatus and combinations thereof, speciicjembodiments of which are described herein by way of example only and in accordance with the manner in which I now prefer to ractice the invention.

urther and 'more specific objects, features and advantages will clearly appear from the detailed description given below taken in connection with the accompanyin drawings which form a part of this speci catibn and illustrate by way of example one embodiment of the invention.

In the drawings, Fig. 1 is a diagrammatic plan view of a preferred embodiment of my by continuously rotating screws and partially.

and alaunderLlserv' a heated kettle on the right;

Fig. 4 is a diagrammatic end elevation of the series of crystallizers and kettles;`

Fig. 5 is a sectional plan view of a part of the series ofcrystallizers and kettles taken on the line 5 5 of Fig. 3, certain parts being omitted for the sake of clearness; and

Fig. 6 is a sectional elevationtaken on the line 6-6 of Fig. 5,

Referring now to the drawings, and particularly to Figs. 1 and 2, I have designated a series of crystallizers or baths there shown r as C1 to C13 inclusivecandthe kettles corresponding thereto and into which each crystallizer or bath delivers to K1 to K13 respectively and inclusive. These crystallizers and kettle units constitute a series at one end of which, namely at K1, lead of the lowest bismuth -content produced is obtained and at the opposite end of the series lead with the highest bismuth tcontent is obtained.

These crystallizer-kettle units, C1, K1, C2, K2, C3, K3 and so on are positioned so as to maintain therethrough a continuous and unobstructed avity flow of leadbismuth in which the ismuth is increasing and an opposite flow which is partially by gravity of lead-bismuth with-increasing content of lead. To accomplish the gravity ilow, each c' stallizer, for example C1, is set at a he1ght,preferably 6 inches above the next c stallizer C2 inthe series. In accordance wlth this arrangement, the

' metal level of C2 is at a height of 6 inches higher than the metal level of C3, and the metal level of C3 isv at a hei ht of 6 inches i higher than thexnetal levelo C4, and so on through the series. Between each crystal-l lizer or bath is asubstantially horizontal o n launder serving to convey molten leaid-y is-l muth alloy from one crystallizer or bath to the next -b gravity due to the head existing between e crystallizers, thus between C1 and C2 is a launder L1, between C2 and C3 -is a launder L2 and 4so on throughout the series of launders L8 to L12 occur, L12 being positioned'between crystallizer C12 'and C13 as an exit for-the lead containing higher bismuth. Y

'The ow of lead-bismuth alloy in which themnount of lead is increasing is maintained The crystallizers or baths are maintained at a suitable temperature to keep a'molten mass of combined lead and bismuth with crystals of lead-bismuth, which crystals will naturally:

contain less bismuth than the bismuth content of the molten mass, and correspondingly more A lead; The proportion of vlead-bismuth crystals to molten metal in the baths will be-maintained at a ratio which will give ldesired results'. I find 57% crystals and 43% molten metal maintains proper grades in the case` where the raw. material containing 0.164% bismuth is charged into K6 when-a product from K1 is desired containing` 0.034% bismu'th, but other grades of raw material and other desired grades of products may indicate other proportions. v

The crystals are moved out of the crystallizer or bath by thev rotating screws, each screw delivering into its corresponding kettle at a pre-determined rate depending upon the l area of the screw and of course upon the proportion of crystals to molten metal present as determined by the temperature` maintained. In each kettle the crystals received are melted by an oil burner or other source of heat and in melted condition are allowed to'flow by gravity throu h a series of open ducts or launders` D1 to 12 inclusive. The duct leadin from the kettle K2. to crystallizer C1 is esignated as D1, from the kettle K3 to C2 isdesignated as D2 and so on to the end of the series. from the kettle K1 and is an outletvfor the lead containing the lowest content of bismuth. The launders L1 to L12 inclusive 1 of concrete or other suitable material. The bottom 2 of the crystallizer is inclined at an angle of about 90 tothe lower end wall 3 ofy rIhe duct D13 leads l -material such as cast iron mounted-.in a base the crystallizer and the bottom wall is set at about an angle of 40 to the horizontal being heldin position by the concrete base 1. Mounted in suitable bearings on the end walls is a rotatable shaft 4y which is'rotatedby an outside source'bf power .not shown,

and is in the form of a helix being perforated throughout with drawing holes about fg inches, preferably, in diameter. The bath of lead-bismuth 6 contains approximately the ratio 57% crystals to 43% molten mass-and the screw 6 as it rotates moves these crystals out of the molten bath, draining-back any Y molten material through the perforations 5,

the crystals being deposited in the kettle K6. The kettle K6 is mounted on suitable pillars of refractory material 7 and is surrounded by a refractory lire wall 8 through which an oil burner 9 for supplying heat to the kettle K6 is provided. The crystals passing into theV burner 9.

The arrangement for heating the upper portion of the crystallixzersds shown in Figs.

. 5 and 6. The description of one heating means for a crystallizer will sufiicefor all as the heating means is preferably identical throughout. As shown in Figs. 5 and 6, the gases passing from the burner 9 pass under the kettle K6 and up through two ducts 10 and 11 at the end of the kettle on either side of the .crystallizen These ducts are controlled by hand-operated dampers 12 and 13 to allow part or all of the gas to pass upwardly without passing around the crystallizer C6 or else part or substantially all of the burner gases may pass along the side walls of the crystallizer in order to heat that part ofthe crystallizer above the level of the lead therein. For this purpose openings 14 and'15 are provided respectively in the ducts 10 and 11 at a oint between the lead level in crystallizer 6 and the top of the crystallizer tank. This duct leads respectively into flues 16 and 17, each of which is 'shaped to follow the outline of the crystallizer wall above the lead level. At the end of the crystallizer away from the ducts 10 and 11 the flues 16 and 17 are Hattened out as shown in Fig. 5 joining one another to make'a flattened iue 18 which communicates by a branch 19 with a common pipe 20 leading to the stack 21. Gases from flues 10 and 11 after passing therethrough may also be led to the stack 21 by connections not shown. Dampers. 12 and 13 are provided with handles so that they may be moved in the ducts 10 and 1l and positioned to cause all of the gases to pass up the conduits 10 and 11 when it is not desired to heat the upper part of the cry stallizers or to divert part or all of the gasesalong'tie ues 16 and 17 te sired.

Each of the iiues 16 and 17 has a crystallizer wall forming one vertical side of it in each case, the other walls of the 4fiuesas well as the walls of the ducts being made of suitable refractory material. These heated iiues serve thepurpose of preventing solid chills on the inner side of the wall above the molten metal level thereof. Such chills are to be avoided because they not only impede the rotary movement of the screws but cause a solid lead bismuth compound to form which may be different from the constitution of the crystals in the crystallizers.

Each of the screw conveyors S1 to S13 is driven in a manner similar to that shown with the screw conveyor S6 in Fig. 3. A common shaft 22 drives the( various screw conveyors. A'tooth pulley 23 is mounted opposite eachcrystallizer tank communicating through a chain 24 with tooth pulley 25 mounted to drive a worm 27 mounted on the crystallizer and driving a worm wheel 28.. The latterv is mounted on the end of the shaft 4 of the screw conveyor S6. I preferably maintain the revolutions per kminutejofxall screw conveyors the same. Once started the speed of these conve ors need not be adjusted. [he rate of crystal elivery into the ketties is controlled as heretofore Vpointed out by the temperature maintained in the crystallizers and hence the quantity of crystals produced. This temperature is adjusted by means of the oil burners underneath the various kettles and control of the plant by control of the heat supplied to these burners so that a greater or less tonnage to be produced at the endsV of the series -is secured.

The typical crystallizerand kettle shown in Fig. 3 1s repeated in each of the other crystallizers and kettles represented inthe group C1 to C13 inclusive and K1 to K13 inclusive, including the inclination of the crystallizer, the form of the conveyor, positioning of the kettle and the oil burner, ducts and iiues for adjusting the temperature thereof.

As shown particularly in Figs. 1 and 2, the respective diameters and areas of the kettles, crystallizers and screws varies, the larger ones being on the left andA being graduated to the smallest on the right of the series.

This graduation is arranged proportionately to the amount of work done by each unit,

The overflow levels for the various crystallizers for crystals 'being moved into the respective kettles are designated respectively as' O1 to O13 inclusive, see particularly Y Fig. 4.

In carrying out the process of separating lead from bismuth, lead containing bismuthv in the proportion of .164% as an example, is available as astarting material and is employed in the process although it will beunderstood thatv lead with higher or lower bismuth contents may be employed to commence the process. Thls material is melted and charged into the crystallizer C6 where it attains a temperature such that` the mass will contain approximately 57% of lead-bismuth with crystals and about 43% of molten material approximately 317 to 327 C. The screw conveyors S1 to S13 are started to rotate and the oil burners for kettles K1 to K13 are started to bring the temperatures in these various kettles up to the proper points, all of the crystallizers having been brought to and being maintained at a suitable temperature for providing the desired ratio of crystals to molten .material therein .as received. The crystals.A are continuously transferred from the crystallizer into the melting kettle K6 which is now at a suitable temperature to melt the crystals whereupon they flow through D5 into crystallizer C5 which is at a suitable temperature to maintain the ratio of crystal to molten-condition of 57% to 43% or any desired ratio. The screw conveyor there removes these crystals as they form and moves them into the kettle K5 where they vare melted.` The molten material in C5 due to theposition of C5 above C6 tends to iow and in part flows through L5 back into C6 where it joins molten material already there.

C6 is maintained by the molten metal flowingr from K7'and also by the heated-gases from the combustion chamber of K6 at a' slightly 'lower temperature than C5 Where temperature is'maintained by iniiowing molten metal 'from K6 and also by re j lated diversion of heated gases from com ustion chamber -of K5 so that from the molten material flowing from C5 to C6 through L5 some crystals form and these join crystals forming from molten material already present in C6 and these combined crystals are moved as indicated'by S6 into the kettle K6. C6 is supplied, of course, it will be understood by fresh lots of theraw material containing bismuth of approximately 164%. The molten material in C6 will tend to flow from it to C7 due to the height of C6 above C7.r C7 ismaintained at slightlower temperature than C6 and crystals therein, these crystals being removed from S7 into K7. In K7 a similar process.

to that occurring in K6 results and K7' being. 6 inches higherthan C6.the melted crystals flow back into C6. The molten material in C7 passes through- L7 into C8. The

Vcrystals of lead-bismuth containing a higher content of lead `are those flowing by combined screw action and avity in a direction towards K1 from which the material kettles. In this case it is shownas connected toK6 (see Fig. 1) and is intended to su ply as there connected, lead containing pre erably a bismuth content of about 0.164%.` If lead with a lower bismuth content were su plied this tank could be connected to kett e K4, K3, or if lead with a higher bismuth content were supplied the tank could be connected to K7, K8, etc. Tank T is connected to kettle K6 by means of a pipe in which is connected a centrifugal pump which is intended to continuously feed the molten raw material at a temperature slightly above its melting point into the crystallizer. Asshown on Fig. 1, the successive degrees of the average bismuth content of the whole ma in each crystallizer or bath from C13 to C1 are 1.46%, 1.00%,

'l` he molten material is flowing entirely by gravity as I prefer from C1 to C2,`from C2 to C3 and so on through the series, C1 to C13 having successive degrees in bismuth content of .05% to. 2.00% in the same stages just mentioned but in the reverse direction.

On the other hand the molten material is flowing entirely by gravity as I prefer, through the series K13 to C12, K12 to C11, and so on from K13 to K1 to final product issuing from K1 of a grade lof 0.034% bismuth, according to the stages first mentioned.

The crystals `collected in K1 therefore will4 have a bismuth -content of approximately 0.034% or less and a lead content of approxlmately 99.9%

On the other hand the molten material containing the higher contents ofl bismuth is Sflowing entirel by gravity, as I prefer, through theserles of kettles from K1 to K13 with a bismuth content increasing from 042% to 1.460% bismuth, according to the stages just mentioned, in the reverse direction. l

shown and describedin the specification the production of a lead containin 2.00% of bismuth, the content of bismuth 1n the product passing from C13 may range to higher percentages of bismuth towards that alloy of leadand bismuth which has the lowest melt- It will be understood that although I havev 'zov ing point and contains a higher percentage of4 bismuth.

The'apparatus and process mentioned are 4simple and eicient. The rate of flow is all controlled automatically, there are no troublesome valves to get out of order uiring manual manipulation, the only contro being exercised `by proper regulation of the tempera-ture provided by the oil burners, which "in turn controls the relative percentage of crystals and liquid in the crystallizers and hence the delivery of crystals from the crystalhzers to the kettles. The sepation of crystals from.molten material by the rfcrated screw conveyors is` clean and e ective and the melting of the crystals introduced into the kettles is eiliciently performed because a relatively small mass of unmelted material is dropped into a large mass of molten material. Theprovision of a V6 inch head of molten metal throughout the system insures that no great pressure of this material will be exerted on theV connectionsbetween the various pieces of apparatus so that a long` life is assured to them and to -the apparatus. In case it is necessary to make replacements, however, these may be made promptly and inexpensively. In addition capital outlay for the building of such a plant is relatively small. The apparatus is so arranged in addition that there is no violent agitation or large exposure of molten metal surface and hence a minimum' oxidation of lead occurs with minimum presence of fume and danger opoisoning of the operatives is thus avoided. Y

rIhe process is continuous and eliminates delay in the units. There. is no mass o molten material waiting for a kettle or crystallizer to be free before it can be'processed. After the temperatures have been adjusted throughout the units the process canbe operated without change of temperature in the units as long as the raw material being supplied is ot approximately the same bismuth content and it is desired to produce a lead of approximately the same lowered bismuth content. One advantage resulting from the maintenance of a uniorm temperature is that it is not necessary to cool down or heat up large masses of refractory material which are naturally poor conductors radiators and absorbers of heat. The process is applicable of course to lead materials with varying bis' muth contents and `in accordance with thetemperature control, the poundage or tonnage, issuing from either the low bismuth end or the high bismuth end may be adjusted. The desired fiow of metal, namelylead concentrate in one direction and bismuth concentrate in the opposite direction is automatically obtained by reason of the established levels of the crystallizers and kettles and iiow in any other direction is prevented.

, While I have described my invention in considerable detail and with respect to a pre- 'ferred form thereof.v I do not desire to be limited to such details or forni-since many changes and modifications may be made and the invention embodied in widely diierent forms without departing from the spirit and scope thereof .in its broader aspects. Therefore, I desire to cover all modifications and bination, a kettle and a crystallizer, autoy matic means for continuously moving crystals out of the crystallizer into the kettle,l

means for melting said crystals in the kettle and delivering them in molten condition outside of said kettle, and means to conductl molten material away from the crystallizer.

2. In apparatus for refining lead, in combination, a crystallizer-kettle unit having a kettle and crystallizer, means for moving crystals out of the crystallizer into the kettle, means for melting said crystals in the kettle and delivering them in molten condition to another crystallizer-kettle unit, and means to conduct the molten material away from the crystallizer to a third unit. l

3. In apparatus for refining lead in combination, a crystallizer-kettle unit having a kettle and crystallizer, means for moving crystals out of the crystallizer into the kettle, means for melting said crystals in the kettle and delivering them in molten condition to the crystallizer of another erystallizer-kettle unit and means to conduct molten material away from the rst mentioned crystallizerv to the crystallizer of a third crystallizer-kettle' unit.

4. In apparatus for refining lead, in com' bination, a series of crystallizer-kettle'units arranged in a sequence to provide an unobstructed 'gravity flow of molten] l'ead containing an increasing amount of impurities such as bismuth in one direction, and providing a vflow of lead containing decreasing amounts of impurities such as bismuth in an opposite direction, each unit having a kettle and a crystallizer, means for moving crystals out of the crystallizer into the kettle, means for melting said crystals in the kettle and delivering them in molten condition outside of said unit, and means to conduct molten material away lfrom the crystallizer.

5. In apparatus for refining lead, in com-A bination, a series of crystallizer-kettle units arranged in a'se uence to provide an unobstructed gravity ow of molten lead containing impurities such as bismuth in one direction, and providing a flow of lead containing decreasing amounts o? impurlties such as bismuth in an opposite direction, each unit having a kettle and a crystallizer, a. conveyor in each crystallizer for conveying crystals out of it into the kettle, a heater for melting crystals in the kettle, a duct connecting said kettle with the next crystallizer on one side of the series and being positioned to allow a gravity flow of molten material from the kettle to said other crystallizer and a duct for conducting molten material away from the crystallizer to the next lcrystallizer on the other side of the series.

6. In apparatus for reininglead, in combination, a series of crystallizer-kettle units arranged in a sequgnce to provide an unobstructed 'gravity ilow of molten lead containing an increasing amount of impurities'such as bismuth in one direction; and providing a fiow of lead containing'decreasing amounts of impurities such as bismuth yin an opposite direction, each unit having a kettle, a crystallizer and a conveyor for moving c stals out kettle to the crystallizer of the unit on one creasing impurit cual moving "'10.'A'crystal1izer side for delivering melted crystals by gravity from the kettle to said crystallizer, and a,

launder leading from the last mentioned crystallizer to the first mentioned crystallizer for delivering molten lead containing inby avity, to the first mentioned crysta zer, tile crystallizer-kettle unit on the other side having a duct leading from its kettle to the first mentioned crystallizer and deliverin melted crystals containing increasing l content by lgravity to the crystallizer, and a launder lea ing from the first mentioned crystallizer to the crystallizer of the last mentioned unit to deliver molten lead containing increasing impurity by gravity. to the crystallizer of the last mentioned unit, the crystallizer-kettle units at either end being connectedin a-similar manner te that described on the other units but being connected to deliver, respectively, outside the series-for molding or otherwise, material of the highest lead content andmaterial of the lowest lead content. A

7. In apparatus for refining lead, in combination, a series of crystallizers and kettles` arranged in a sequence to provide a flow of molten lead containing an increasing amount of impurities such as bismuth in onedirection and providing a flow of lead containing decreasin amounts of bismuth in an opposite direction, each crystallizer havinga conveyor-for moving crystals out of the crystallizer intotlie kettle, connections between the kettles and crystallizers inthe series, the dimensions of the crystallizers, kettles and conveyors being proportioned to the amounts of material to be handled b each. v n 8..',In'apparatus for m ing lead, in combination, a vessel for holding molten lead crystalsand a device for continuy crystals out of the lead while leaving the molten material behind.A

9. In apparatus for refining lead, in combination, a vessel for holding molten lead containing crystals anida: clililve or for crystals'outo eea w'eeaving the molten matei-'La behind.

ining1 having in combination, a crystallizing f 'w into a'kettle and a device for moving :fromthecryst'allizingtrough inw am kes. 11. A-crystalliaer-kettle unit for leadrenin having in combination' a crystallizing trough feeding im s -kaisnnd a 'rotating screw conveyor for moving crystals vfrom the Atro'ughinto the kettle. 12. A ,iinitfor lead reinto t e lin' having'in combination, a

Iscrew conveyor, having holes ierced therein for allowing molten lead to rain from lead crvstals, for moving crystals from the crystallizing trough into the kettle.

13. A crystallizer-kettle unit. for lead reiining having in combination, a crystallizing trough feedin into a kettle and a device for movin cr sta s from the crystallizing trough ettle, and a heater for melting crystals delivered to the'kettle.

14. A crystallizer-kettle unit for lead refining having in combination, a crystallizing trough feeding into a kettle and a rotating screw conveyor for movingcrystals from-the crystallizing trough into the kettle, and a heater for melting crystals delivered to the kettle. Y

15. A crystallizer-kettle unit for lead ref ining having in combination, a crystallizing trough feeding into a kettle and a rotating screw, havingholes pierced therein for allowing molten lead to drain from lead crystals, for moving crystals from the crystallizing trough into the kettle, the crystallizing l trough and screw being set at an angle to the horizontal whereby the cr stals are moved upwardly out of the solution on an incline and de osited in the kettle.

16. crystallizer-kettle unit for lead refining having in combination, a crystallizing trough feeding into a kettle and a rotating screw conveyor, having holes pierced therein for allowing molten lead to drain from lead crystals, for moving crystals from the crysta lizing trough into the kettle, the crystallizing trough and screw being set at an anl gle4to the horizontal whereby the crystals are lmoved upwardly out of the solution on an inclineand deposited in the kettle, a heater delivering products of combustion to said kettle for melting crystals deposited therein,

Y and ducts positioned on the walls of said crystallizer above the level of the lead bath therein for conveying said products of combustion past said crystallizery to su lply heat ,to'the portions thereof situated a ve said bath. In testimony whereof I have signed my name to this specification.

. ARTHUR E. HALL.

kettle unit `for lead reies

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