US2348360A - Method of recovering minerals - Google Patents

Description

May 9, 1944. H. L REED METHOD 0F RECOVERINGMINERALS Filed Jan. 22, 1941 Patented May 9, 1944 "UNIT-Eo STATES PATENT OFI-ica aussen MErnon or nncovnnmc MINERALSY novara L. need, austin, Tex. application .mmm zz, 1941, sei-:1 No. 375,441

1s claims. (o1. 'z5-z) `This application is in part a continuation of my prior pending application Serial No. 342,075 iled June 24, 1940.l A

In another co-Dending patent applicationSerial No. 342,127 filed June 24, 1940, I have described land claimed a method of recoveringminerals from their ores, which consists of ilrst sulphidizing the minerals to be recovered and then separating' the sulphidized minerals from the gangue by various metallurgical processes, prefwhen this solvent was evaporated. The sulphidized ore, thus dried of liquid sulphur, was then pulverlzed in a rod mill and discharged v'therefrom as an aqueous suspension of mineral slimes.

This product was thence fed to a notation cell where the crystalline metallic sulphide particles were recovered by means of standard frothing reagents. 'lhese metallic, or basic, minerals were thus'iound to be readily sulphidized and eiliciently extracted by means of the foregoing treatment, which effected a concentration ratio of forty to one in the case ofcopper oxide or copper carerably by flotation. Thisuniqueprocess of treating crude ores with` molten sulphur has been found extremely desirable for many types of ores. particularly those which contain inappreciable values of non-basic, or semi-metallic, mineral constituents.

The., development of an eilicient method of economicallyextracting these. semi-metallic minerals from complex ores or concentrates, however, represents a very necessary objective of the science of metallurgy. For example, losses exceeding thirty per cent (30%) of the assayed tin content of certain complex Bolivian crude ores occur during the preliminary concentration thereof, exclusive` of the. excessive slag losses characterizing the subsequent smelting of such tin concentrates. Moreover, most of these tin concentrates, as finally imported from Bolivia, contain less than forty per cent (40%) of tin.

'I'he metallurgical refinement of crude antimony oxide mineral ores is similarly ineillcient. For example, almost an half million tons of such ore, assaying over five per cent (5%) antimony, several 'million dollars worth of mined and crushed mineral, has been abandoned by one company at a certain mining district in Mexico, for lack of a feasible process of concentration.

In van investigation for the purpose of providing a. feasible process of metallurgical concentration, many crude ores were treated with molten sulphur. The basic oxide minerals were found to'be readily altered to the corresponding metallic sulphides, respectively; and, thus sulphidized,

, were typically dissolved in the liquid sulphur medium' and subsequentlycrystallized therefrom bonate crude ores; that is, the rst notation concentrate, the so-called rough concentrate, was

forty times as rich in copperas the tailings.

However, certain minerals, particularly the non-basic, or semi-metalllaminerals. of which the native oxides of antimony and tin are notable examples, have a tendency to chemically combine not only withthe sulphur medium, during the vaporization thereof, but also with the limestone or other interfering basic, or metallic, substances whichrare frequently present in large amounts'asconstituents of the gangue material. Even in theabsence of these interfering basic substancesfthe sulphidation of the semi- Caa (SbS4) 2 produced in various proportions with the primary alteration product, antimony sulphide, SbzSa, and several secondary products such as calcium sulpho-antimonite, Caa(SbS3)z. These calcium compounds may be collectively termed ered by performing the snpnidizauon or the native ore at minimum temperatures, below the boiling point of sulphur; and by evaporating the A excess sulphur at minimum temperatures, such as ilve hundred degrees centigrade; but the latter vaporization temperature does not allow 'rapid lvaporization unless the particles of ore are relaing carbon dioxide to the water in the rod mill,

sodium carbonate, about one part ot the latter to ten parts oi' sulphur.l This mixture was heated rapidly and the excess sulphur vaporized. The

during the pulverizaton yof the sulphidized ore,`

`when injected by the rotor into the otation cell. A- small increase in the antimony content of the :dotation concentrate may thus be obtained; but the results are insuflicient to provide a realsolution to the problem. This problem of concentration of antimony oxide ores is a very important one because it has notV been solved by any prior standard method of metallurgical refining. f

It is an object of this invention, therefore, to eliminate the formation of the complex semimetallic sulphides of calcium during the process of sulphidization. Y Y

Another object is to accelerate the sulphidization of the semi-metallic minerals'. v

It is a further object to provide a continuous process in which the sulphidizing medium will produce a 'single product; and to provide a process in which such sulphidized product will be readily soluble in water so-that it may be more readily removed from the gangue.

It is a further object to provide a method whereby the dissolved sulphides of the semimetallic elements may be recovered by flotation,

In order that the invention may be readily understood, reference is had to the accompanying drawing, forming a part of this specification, and in which the single ilgure is in the nature of a diagram or ow sheet illustrating an ore crusher, rotary kiln, rod mill, otation cells, etc., used in carrying out the invention, and showing the relation of these. various pieces of apparatus to each other. In this drawing,` I have indicated optional steps or the optional addition of certain materials by dotted or broken arrows.

I have discovered that the formation of the complex semi-metallic sulphides of calcium may be inhibited during the sulphidization process and that the sulphidization process may be greatly accelerated by the previous introduction into the orev ofmaterial containing another or other elements which will combine with the sulphidized mineral much more readily and quickly than will the calcium. Numerous such materials may be employed. One such material, which has been round very suitable, is sodium carbonate. Cerresidue was then leached with plain water by.

, boiling the latter with the residue. The solution was filtered and thence injected with hydrogen sulphide gas, which decomposed-the dissolved sodium thioantimonate and thus precipitated antimony pente-sulphide. which was thence recovered by filtration. f

In large scale operations, the aqueous illtrate obtained from the ltered residue may be injected into a gas and liquid contact apparatus with the gases produced during the sulphidization of the crude ore.

This cause's'a precipitation of antimonypentasulphide uncontaminated with other products of sulphidization, this antimony sulphide being seventy-one per cent (71%) antimony by weight. The precipitation of this antimony sulphide is effected by the injection of the discharge nue gas from the rotary kiln where the. ore is first treated, which flue gas consists of carbon dioxide produced by the combustion of the fuel and also of sulphur dioxide produced by the sulphidization of the oxide minerals in the Both gases. when injected into the aqueous filtrate, acidify this solution of the complex sulphidization products of sodium and produce linsoluble antimony sulphide and soluble sodium thiosulphate by the preliminary neutralization of the excess alkali and by the decomposition of the complex semimetallic sulphides of sodium: 4

l it was stated that sodium carbonate and sodium sulphite are also produced; but I have found that if these latter substances are' produced they will both be immediately attacked by the sulphur dioxide gas and thus altered to sodium thiosulphate.

Y I have discovered that this sodium thiosulphate silicious gangue would be attacked thereby and altered to sodium' silicate:

Na2CO3-i-SiO2=Na2SiO3l-C0z Accordingly, the demineralid aqueous solu- .tion of regenerated sodium thiosulphate may be continuously returned to the rotary kiln, wherein the water solvent will be quickly evaporated as the crude ore mixture is heated.

The gradual progress of this'crude charge toward the interior of the slightly inclined, slowly rotating, cylindrical kiln is attended by increasing temperatures and by the spontaneous thermal decomposition of the sodium thiosulphate into sodium sulphate and molten penta-sulphide of sodium. 'I'he latter dissolves energetically in the 'liquid sulphur, which forms an ideal fusion medium with the sodium sulphate.

This alkalized sulphur medium, generated and maintained within the rotary kiln, vigorously attacks'the oxide minerals submerged therein by reducing them to sulphides, with the evolution of sulphur dioxide, and by simultaneously neu tralizing such sulphides while producing the soluble complex sulphidization products of sodiumz.

The continuous consumption or sodium pentasulphide, during the sulphidization ofthe oxide minerals, is continuously compensated by the regenerationof additional sodium penta-sulphide, as yperformed by the spontaneous thermal decomposition of the sodium thiosulphate. as delivered to the -kiln by the demineralized liquor:

l 4Nazs2o3=3Nazsor+Na2s5 Additional sodium penta-sulphide is reproduced by the sulphidization of a certain portionk of the sodium sulphate formed by thtoregoing .decomposition reaction. This sodium sulphate tends to be reduced, by molten sulphur, to sodium sulphite. This preliminary product is unstable at these temperatures; hence the sodium sulphite experiences spontaneous thermal decomposition, thus creating sodium sulphate and sodium sulphide. The latter product immediately reacts with molten sulphur, thus regenerating additional sodium penta-sulphide:

The chemical equilibrium of the foregoing reaction maintains a constant concentration of dissolved penta-sulphide of sodium in the molten sulphur medium. This equilibrium tends to be disturbed, of course, by the consumption of this alkali by the semi-metallic minerals; but such consumption is continuously compensated by the above phenomena of chemical regeneration of additional Penta-sulphide of sodium. Conseiuently, the sodium sulphate regenerant must Je considered as the primary sulphidizing rearent, in view of the fact that this salt constitutes the only source of sodium penta-sulphide which can maintain the chemical equilibrium of these kiln 'reactions By virtue of this process numerous economies are eiected. The rst which is apparent, is that the rst phase of the process, namely the reactions of the various materials within the kiln, produces gases which are employedto cause the precipitation of the antimony sulphide at the end of the process. Thus the necessity lfor providing any separate source of reagent for causing this precipitation is eliminated and great economy results therefrom.

Second, the result of the reaction during the precipitation of this antimony sulphide is a nonalkaline barren liquor h contains sodium thiosulphate: and this liquor is used in iormins the charge for the kiln in the ilrst step of the process so as to provide the sodium and a portion of the sulphur required for continuously charging 4the kiln. Thus the sodium is re-used again and again and the cost of sodium sulphate.

\ or other source of sodium, such as sodium thiosulphate. sodium sulphide or sodium carbonate.

is limitedtothecostofsuchamountsasarenecessary to replace leakage and unavoidable waste. At the same time, the use of this demineraiised vsodium thiosulphate liquor cuts down the necessary amount oi sulphur for the charge to the rotarykiln.

In addition to the economies just mentioned, the elimination of waste products avoids the necessity of providing for thedisposition of such products and provides s. continuous proc ess, which is highly useful and advantageous commercially. A y;

It is also to be noted that this process conserves heat because whereas sodium carbonate has a melting point of substantially 850 C., sulphur has a melting point of 120 C. and a boiling point of-445 C., approximately. The sodium penta-sulphide. which-fuses at 252 C., forms a fusion mediumwith molten sulphur and sodium sulphate which will very quickly react with the antimony oxide or tin oxide, or other semimetallic minerals, at. a temperature below 445 C.; whereas, in the-absence of such alkalized sulphur, a temperature laf-850 C. would be required to produce a water soluble antimony compound by means of sodium carbonate. Moreover, the excess sodium carbonate could 4not be retained in the kiln; whereas, the excess sulphur is automatically evaporated and refluxed and recondensed therein, thus conserving both heat and sulphur.' Finally, the heat required to melt,

.boil and vaporize sulphur is approximately one fourth of that required to convert ice into steam. The sulphidization equipment for the process described may be broadly similar to that employed for the calcination of limestone, and is diagrammaticaliy shown in the accompanying drawing.

The deminerallzed liquor will be fed to this rotarykiln, which is also fed continuously with the crude crushed ore and sulphur. The products from the rotary kiln are discharged into a rotary cooler and thence preferably fed to a rod mill, or the equivalent, and thence to any suitable filtering or separating apparatus where the solution may be separated from the insoluble tailings. This aqueous filtrate is then delivered to any suitable gas and liquid contact apparatus in the presence of the exhaust gases from the intake end of the rotary kiln, thus causing the precipitation of the antimony sulphide, or other semi-metallic sulphide, as above described. These precipitated sulphide: may then be separated from the barren liquor by filtration or by f any other suitable process.

. The. use of an `alkalized sulphidizing' medium I in accordancewith this invention makes Vposksible thejrecoveryof `tin from such ore without interference from the iron oxide or lsimilar basic compound because it causes the formation of a water soluble compound of tin, just vas in: the previous example a soluble compound of antimony was formed. AJust as the limestone in the previous example emerges from the kiln in the form of an insoluble compound, so in this instance the iron would .likewise emerge from the kiln in the form of an insoluble compound. vThe tin, in the form of thin-stannate of sodium, may then, of course, be removed by leaching the f sulphidized ore with water,`asin the case of the antimony. Anyof the various metallic oxides, or other basic compounds, presentl as a part of a semimetallic ore would behave in a similar soluble products of sulphidization.

If such tinor antirnony o rother semi-metallic Accordingly, the metallurgical refinement oi f complex minerals in general, and of theBolivian tin concentrates in particular, justified the fur ther development of this process,V since commercial quantities of copper and silvenas well as the tin content thereof, must be separately recovered from the ferrous gangue.

AS in the introductory problem of calcarious antimony oxide ores, the alkalized sulphur-mediumperforms the chemical decomposition and preliminary sulphidization of these .crude complex ores, such as the Bolivian tin oxide minerals.

This refractory crushed ore is fedto the cooler end. of, afrotary kiln, which is inclined toward its outlet end, having an annular partition or surface of the liquid ksulphur vmedium is attend- .ed by the dissolution'of the entrained'molten steel ribs, which promote an intimate diffusion of manner and be discharged from the kiln as inthe mineral constituents with the dissolved sodium pauta-sulphide.

The gradua1 descent of this sulphidizing charge through the shallow reservoir of agitated liquid sulphur is further characterized-by the evolution of sulphur dioxide which is thencevconveyed by thekiln gas toward the cooler end of the rotat-` ide minerals into the corresponding metallic sulphides, and of the semi-metallic minerals into the corresponding complex semi-metallic sulphides of sodium, identifies the character of the sulphidized products which, together with the inert calcareous or siliceous gangue material, finally arrive at the foot of the shallow sulphur 'reservoir where they are impeded by the steel ring which interrupts their gradual descent through the rotary kiln. f

These products of sulphidization, submerged in the molten sulphur medium, are thus temporarily impounded by a transverse circular dam, in effect, over which they continuouslyv spill as they are lifted from the alkalized sulphur reservoir by the action of the steel ribs secured to the interior surfaceof the slowly revolving cylindrical kiln. A portion of the liquid sulphur is conveyed by the ore which overows this annular darn into the evaporation zone ofthe rotary kiln.

During the progress of thismixture of sulphidized ore and alkali saturated sulphur toward the ring located below the mid-portion thereof; The

complex ore is automatically mixed with a saturated aqueous solution ofvsoclium thiosulphate during its continuous progress along the slightly inclined, slowly rotating, cylindrical kiln. Sulphur may or may not be added with this charge, the addition of sulphur being made unnecessary by the fact that suiiicient sulphur is provided from the decomposition of the sodium thiosulphate to perl mit the carrying out of the process. The translation of this raw mixture is attended by the evaporation of they entrained water during the preheating thereof by a counter-current of kiln gases. The slow and gradual descent of this mineralized chargev toward a central reservoir of alkalized molten sulphur, retained by said annular partition, is thus characterized by increasing temperatures and by the increasing condensation of sulphur vapor thereupon. Heat and sulphurare thus continuously absorbed by the advancing charge. Steel ribs, or lifting flights,

may, if desired, be secured to the interior surface of the revolving cylindrical shell, axially parallel to the spiralized motion imparted to the ore, in order to promote anv eiiicient vheat exchange between the ore thus distributed andthe counter-current of hot kiln gases.

The passage of this minerali'zed charge through the preheating zone of the rotary kiln witnesses the spontaneous thermal decomposition. of the entrained sodium thiosulphate into sodium sulphate 'and sodium pentasulphide, as well as'the rapid fusion of the latter.

The arrival of the preheated crude ore at the which is satirated with the dissolved products of sulphidization and particularly charged with sodium penta-sulphicle, produces a liquid resid.-

. uum of the latter` molten alkali which retains in solution the various metallic sulphides and complex semifmetallic sulphides of sodium. The sulphur vapor which distills from this sodium penta-sulphide residuum is conveyed, of course, by the counter-current of kiln gas toward the cooler zones of the kiln, where this refluxing sulphur vapor condenses upon the approaching charge of' raw complex ore, crude sulphur and sodium thiosulphate brine.

The foregoing liquid residuum as well as any products of crystallization, including minor amounts of sodium sulphate, are finally discharged with the inertgangue material from the lower end of the rotating kiln.

This unsintered aggregate of kiln products, dried of liquid sulphur, is received by an inclined, cylindrical, rotary cooler, wherein oxidation of the hot material is prevented by exclusion of air, which delivers them into a hopper which feeds the` rotating trunnion of a standard rod or ball mill. The latter is fed, of course, with water also; but only an absolute minimum thereof, since it is essential that the maximum concentration of dissolved penta-sulphide of sodium be continuously maintained during such aqueous di- 1ution,'which immediately precipitates the insoluble metallic or basic sulphides, in order to prevent the precipitation of the appreciably soluble sulphides of copper and bismuth.

This Arequirement of maximum concentration of dissolved alkali necessitates the continuous maintenance of a temperature exceeding 90 C.. during the pulverization and subsequent treatment of these hot kiln products. This maximum concentration of dissolved alkali may preferably be determined and indicated by a standiard pH- meter.

The hot pulverized material, thus super-saturated with sodium penta-sulphide, is discharged from the rod mill into a standard classifier, which delivers the usual aqueous suspension of slimes, whereas the coarser particles which settle therefrom are automatically returned to the rod mill.

This hot aqueous suspension may be conducted to a primary series of flotation cells, where the insoluble metallic sulphides win berecmfered.`

This preliminary flotation of the sulphides of manganese, iron, cobalt, nickel, zinc, cadmium, sill ver and lead, which are herein referred to as metallic, or basic, sulphides, will be performed in accordance with -the standard methods of iiota-y tion procedure, except that, for reasons which s will be hereinafter stated, the usual metallic sulphide froth will be produced in these cells by the injection of steam. rather than air, through the respective rotors thereof, The froth which overilows from this series of cells may be treated for the selective flotation of the'valuable constituents or followed by the cyanidation of the silver ',sulphide. The customary operations of settling phides, copper and bismuth, will be successively precipitated and extracted with the froth Droduced in these cells by the usual injection of air through the respective rotors thereof.

During the continuous progress of the hot mineralized iiltrate through any single series oi' these secondary cells, the gradual 'and cumulative decomposition of the dissolved sodium penta-sulphide will be performed by the oxygen content of the air injected therein:

'I'his production of sodium thiosulphate, a very soluble non-alkaline salt, attends the destruction of a portion of the dissolved alkali, sodiumpentacopper and bismuth, respectively. froma solution,

as distinguished from the usual flotation of sulphides from a suspension, represents an emclent and continuous method of metallurgical concentration of these pure sulphides, uncontaminated with the usual proportion of silicious or calcarious gangue particles, thus revealing an ideal eral parallel series, where the third group of- An analysis of this hot mineralized ltrate containing the so-.called soluble sulphides lof the semi-metallic elements, will indicate the principle by virtue of whichfthe mineral solute may be selectively extracted, in view of the respective characteristics of four types ofdissolved constituents, which may be identiiied and classied'as follows:

(l) 'I'he non-mineralized sodium compounds, e. g., sodium sulphate and sodiumpenta-sulphide; and I (2) Those mineral sulphides which are merely soluble by virtue 'of the maximum concentration of dissolved sodium penta-sulphide, e. g., copper and bismuth sulphides; or further dependent for such solubility upon the presence of tin sulphide. as is the prerequisite in the case of 'the dissolved copper sulphide; and Y (3) Those complex semi-metallic sulphides of sodium which are soluble in an aqueous solution of sodium thiosulphate and sodium sulphate by virtue of a limited or partial concentration of dissolved sodium pente-sulphide, i. e., the sulphides of mercury and tin; and

(4) Those complex semi-metallic sulphides of sodium which remain dissolved in a neutralized aqueous solution of sodium thiosulphate and sodium sulphate, in spite of the absence of sodium penta-sulphide, i. e.: sodium thioantimonate and sodium thio-arsenate.

Accordingly, this hot complex aqueous filtrate may be conducted to a second series of'iiotation cells, actually a system of several parallel series of cells, wherethe second group of mineral suldegree of flotation prociency.

The semi-neutralized liquor discharged from the secondary flotation stage will be received by a third system of notation cells, arranged in sevmineral sulphides, mercury and tin. will be successively precipitatedand extracted with the froth produced infthese cells by the injection of kiln gas, through the' respective rotors thereof.

During the continuous progress of the mineralized liquor `through any single Vseries of Vthese third class cells, the cumulative decomposition of the dissolved penta-sulphide of sodium will be continued by, and finally completed by, the sulphur dioxide content of the kiln gas injection:

' During this production of additional sodium thiosulphate, the complex semi-metallic sulphides ,of sodium are also attacked by the sulphur dioxide gas. For example,'this chemicalidecomposition of the dissolved sodium `thio-stannate produces the insoluble tin sulphide. .as well sodium thiosulphate:

3so2+`2 Na2si (susi) =2Nazsio3+2snsi+s The successive precipitation and hence the seas additional lective notation of the sulphides of mercury and tin, respectively,`represents a' continuous method of metallurgical concentration of these pure sulphides by means' of the simple expedient of simultaneous precipitation and notation.

The froth which overilows from'these third.

The nnai phase of @mineralization of uns neu- .tralized liquor may be similarly performed in a fourth system of flotation cells, wherein the sulphides of antimony and arsenic will be successively precipitated and hence selectively extracted "with the froth produced therein, either by the injection of kiln gas or by the injection of concentrated sulphur dioxide. 'I'he latter may be obtained by condensation, ifthe kiln gases are circulated through a gas-separator" at a pressure of fty pounds per sq.- in.

During the continuous progress of this neutralized liquor through any single series of these fourth class cells, the cumulative decomposition of the dissolved thio-antimonate of sodium will be performed by the sulphur dioxide injection:

-This precipitation and hence the flotation of antimony penta-sulphide is thusattended by the formation of additional sodium thiosulphate and,

, as usual, by the further conservation of the sulsolution will serve as a primary source of sodium thiosulphateand sodium sulphate.

During the subsequent evaporation of this solution in the preheating zone `of the rotary kiln, quantities of steam/will be produced and thence aspirated therefrom, together with the flue gas.

These aspirated vapors will also contain a portion of the very volatile arsenic penta-sulphide,

The principal feature. therefore, of the foregoing method of refining the condensate is emphasized by the applicability of this principle to the various phases of this process, whereby the specic recovery of the sulphur, as precipitatedl during the neutralization of the sodium pentasulphide, or during the decomposition of the complex semi-metallic sulphides of sodium, may be' performed prior to the flotation of the precipi- 10 tated mineral sulphides; whereas, the latter will thus remain in suspension until the secondary frothing reagent, as above, is added to the liquor arriving in the nal section of any single series 'of flotation cells. The sulphur thus extracted will be settled and thickened as usual, of course,

and thence returned to the rotary kiln.

This metallurgical process ofl continuously rening complex minerals by aqueous lixiviation e and by selective otation has produced individual concentrates of relatively pure sulphides of the semi-metallic elements. These sulphide products may be decomposed electrolytically, by virtue of their solubility, respectively, in a molten sulphur medium.

The significance of this nal expedient may be appreciated by consideration of the difficulties which are usually encountered during the electrolysis of metallurgical products, such as` the decoir'- "'ion of the electrolyte. A molten sulphur electrolyte, however, can not be decom-` posed, oi course. Moreover, this cheap medium has sufficient electrical resistivity to be maintained in a molten state by the conduction of the electrolytic current. Furthermore, this current may be regulated by the applied voltage,

which will automatically control the temperature of the sulphur solvent. In particular, if this temperature corresponds to the boiling point of sulphur, 445 C., then, in this case, the excess sulas produced by the thermal decomposition of phur produced by the electrolysis of the mineral sodium thio-arsenate during the distillation of the excess sulphur from the sulphidized ore and sodium penta-sulphide residuum, unless a sumcient excess of the latter solvent prevents such 45 tals, in the case. of tin, bismuth, lead, cadmium,

decomposition.

The recovery of the arsenic penta-sulphide may e be accomplished by circulating these aspirated kiln gases through a condensation trap, where` in the entrained steam will be condensed and discharged therefrom as an aqueous suspension of arsenic penta-sulphide.

units by the addition of a trace of pine oil to the aqueous suspension. This weak frothing reagent serves as a specic collector during this flotation of suspended sulphur.

The subsequent recovery of the arsenic pentasulphide will be readily performed in the second:

of these flotation units by the addition of a trace of amyl xanthate to'the aqueous suspension. This relatively stronger frothing reagent serves as a collector of any sulphidized mineral dur-'- ing the flotation thereof, either from the above condensate or from any of the mineralized media treated during the preceding phases of flotation. Y y

solute may be continuously removed as vapor from the electrolytic cell and subsequently condensed. Finally, this operating temperature permits the continuous production of liquid mezinc and arsenic, during the electrolytic decomposition of` their respective sulphides.

The objects hereinbefore expressed have thus been fully realized. The economical production of the individual concentrates of the semi-metalprecipitated and simultaneously floated from the filtered solvent medium and thus efficiently rened to a degree not hitherto achieved. The cost of the entire metallurgical rening process has been found to be very low, being approximately one cent per pound of sulphidizable elements fed to the sulphidization kiln. l Having described my invention, I claim: -l. In a continuous method of recovering mineral values lfrom a mass containing an element capable of forming a .water-soluble alkali compound with sulphur, the' steps of causing such mass to iiow in a substantially' continuous stream through zones of progressively increasing temperatures, mixing with such mass as it flows an 7l) excess of sulphur and an alkali, the temperature of the hottest of such zones being-suflicient to cause .a rapid sulphidization of said mass and vaporization of the excess sulphur, vcausing the sulphur vapor so produced to iow toward the 76 cooler of said zones, and condense upon the stream of material flowing toward the hotter of such zones, leaching with water the solid materials flowing from the hottest of such zones.k

drawing oil' the aqueous solution, treating said aqueous solution with the gases from said heated zones'to cause the precipitation therefrom of the insoluble sulphide of said element, collecting the barren liquor after such precipitation and mixing it with the stream of material entering said heated zones.

2. In a method of recovering mineral values from a mass containing an element capable of l forming a water-soluble alkali compound with sulphur, the steps of causing such mass to ilow in a substantially continuous stream through zones of progressively increasing temperatures,`

flowing toward the hotter of such zones, leaching with water the solid materials flowing from the hottest of such zones, drawing off the aqueous solution, and acidifying said solution to cause the precipitation therefrom of the linsoluble sulnhide of said element.

3. In 'a method of recovering minerals from a mass of ore containing compounds of copper, bismuth, tin, mercury, antimony. arsenic and other elements, the steps of sulphidizing such ore in the presence of an alkali, leaching the sulphidized ore in a non-oxidizing atmosphere with an amount of water insuicient to dissolve all of the alkali in said sulphidized ore, adding a frothing agent, injecting steam into the resulting mass to produce notation of insoluble metallic sulphides therefrom, filtering olf the concentrated alkaline solution of the soluble sulphides, injecting air into said solution to cause the simultaneous preto cause precipitation of insoluble sulphides and the simultaneous flotation thereof.

6. The method of recovering. valuable constituents from a mass containing elements capable of forming water-'soluble alkali sulpho-salt's where such mass contains also interfering substances, which comprises sulphidizing the mass in the presence of an alkali to` produce water soluble compounds, leaching the sulphidized mass with water to obtain a solution of such compounds,

drawing 01T the solution, adding a frothing agent,

and injecting acid kiln gas into the solution to cause precipitation of insoluble sulphides and the simultaneous llotatin thereof,

'1. The method of recovering valuable constituents from a mass containing elementscapable of forming water-soluble alkali sulpho-salts where such mass contains also interfering substances,

cipitation and notation of copper and bismuth y sulphides from said solution, injecting sulphur dioxide into said solution to cause the simultaneous precipitation and flotation of tin and mercury sulphides from said solution, injecting additional sulphur dioxide into said solution to cause simultaneous precipitation and flotation of antimony sulphide from said solution, and injecting sulphur dioxide and steam into said solution to cause the simultaneous precipitation and iiotation of arsenic sulphide therefrom.`

4. In a method of recovering minerals from a mass of ore containing elements, some of which are capable of forming water-soluble alkali compounds with sulphur, and others which are not, the steps of sulphidizing such ore in the presence of an alkali, leaching the sulphidized ore with an amount of water insufilcient to dissolve all of the alkali in said sulphidized ore, adding a frothing agent and injecting steam into the resulting mass toproduce flotation of insoluble metallic sulphides therefrom without removing the soluble sulphides.

which comprises sulphidizing the mass in Athe presence of an alkali to produce water soluble compounds, leaching the sulphidized mass with water to obtain a solution of such compounds, drawing oft the solution, adding a frothing agent, and injecting into the solution the gas resulting from the sulphidizing step to cause ecipitation of insoluble sulphides and the simult eous flotation thereof.

8. The method of recovering antimony from a mass containing antimonyl and limestone which comprises sulphidizing the mass in the presence of an alkali to produce a water soluble compound of antimony, leaching the sulphidized mass with water to obtain a solution of said compound, drawing oif the solution, adding a frothing agent, and injecting an acidifying gas into the solution to cause simultaneous precipitation and flotation of the antimony sulphide therefrom.

9. The method of lrecovering tin from a mass containing. the same where such mass contains iron oxide, which comprises sulphidizing the mass in the presence of an alkali to produce a water soluble compound of tin, leaching the sulphidized mass with water to obtain a solution of such compound, drawing off the solution, adding a frothing agent, and iniecting into the solution an acidifying gas to cause simultaneous precipit tation and flotation of the tin sulphide.

10. The method of recovering valuable constituents from substances containing an element of the group consisting of antimony, tin and bismuth which involves treating such substances with sodium thiosulphate in the presence of molten sulphur and then leaching the product with water.

l1. The continuous method of recovering mineral values from a mass containing an element capable of forming water-soluble alkali sulphosalts which involves treating such mass with sodium thiosulphate in the presence of molten sulphur, leaching4 the product with water, drawing o' this aqueous solution and injecting the same with sulphur dioxide gas in order to precipitate the sulphide of such element and in order to regenerate sodium thiosulphate; and re-using this non-alkaline compound to recover additional mineral values. h

12. A continuous process for recovering mineral values from a mass containing an element;` capable of forming a water soluble alkali sulphosalt, which comprises heating said mass with` an alkali in the presence of molten sulphur, dissolving the resulting alkali sulpho-salt out of the product, and adding sulphurous acid to the solution, whereby the insoluble sulphide is precipitated and alkali metal salts regenerated, and remass during the heating step.

13. A continuous process for recovering mineral values from av-mass containing an element capable of formingva water soluble alkalir sulphosalt, which comprises heating said mass With sodiumthiosulphate,r dissolving the resulting a1- kali sulpho-salt o ut o1' the product, and adding sulphurous acid to the solution, whereby the insoluble sulphide is precipitated and sodium thiosulphate regenerated. Y

14. A continuous process fol recovering mineral values from a mass containing an element capable of forming a water soluble alkali sulphosalt, rwhich comprises heating said mass with sodium thiosulphate in the' presence of other-.sodium compounds, dissolving the resulting'sodiuni sulpho-salts out of the product, adding sulphurous acid to the solution in order to precipitate the insoluble sulphide and to regenerate sodium salts, including sodium thiosulphate, and re-using such regenerated sodium salts to mix with said mass during the heating step.-

15. In a method of recovering minerals from a mass of ore containing e1ements,.some of which using such alkali. metal salts to mixl with said are capable of formingwater-soluble alkali compounds with sulphur and others which are not,

the steps of sulphidizing such ore-in the presence of an alkali, treating the sulphidized ore with water, adding a frothing agent and injecting steam into the resulting mass to produce flotation of insoluble sulphidized compounds therefrom without removing the soluble sulphidized compounds.

. 16. In a method of recovering minerals from a mass of ore containing elements, some'of which are capable of forming waterfsoluble alkali compounds with lsulphur and others which are not, the steps of sulphidizing such ore in the presence of an alkali, treating thev sulphidized ore with Water, adding a frothing agent, injecting steam

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