US1357495A

US1357495A - Metallurgical process

Info

Publication number: US1357495A
Authority: US
Publication date: 1920-11-02
Anticipated expiration: 1937-11-02

Description

W. E GREENAWALT.

METALLURGICAL PROCESS.

MPLQCATION FILED JUNE 10.. 1918.

Patented Nov. 2, 1920.

2 SHEETS-SHEET 1.

IM'EM OK w. E GREENAWALT.

METALLURGICAL PROCESS.

APPLICATION FILED JUNE [0. 1918.

1,357,495, Patented Nov. 2, 1920.

2 SHEETSSHEET Z 16 WIT/155859, 4:

luvs/v TOR WILLIAM E. GREEI l'AWALT, 01? DENVER. COLORADO.

PATENT c rries.

METALLURGICAL PROCESS.

Specification 0! Letters Patent.

Patented Nov. 2, 1.920.

" Application filed June 10, 1918. Serial No. 289.255.

To ail whom it concern.

Be it known'that 1, Warrant E. GREENA- wAL'r, a citizen of the United States, residmg in the city and county of Denver and :State of Colorado, have invented certain new and useful Im rovements in Metallurgical Processes, 0 which the following is a specification.

- The invention has for its more immediate object the rendering harmless, or mitigating the evils, in the electrolysis of impure electrolytes, especially electrolytes obtained from leeching'ores and containing salts of the variable valent elements.

This prooess'may be regarded as a continuation of m co-pend ng applications, Sigriai No. 15,5 3, and Serial 0. 132,273, and. like those applications, will be described more particularly in reference to the treatment of copper ores, although it is not intended tolimit it to any particular use;

In the electrolysis of impure copper solutions, as for example those obtained from leaching copper oreswit'h an acid sulfate solution, there is always present iron sulfate, which injuriously ali'ects the operation.

Ferrous sulfate in the electrolyte is not particularly harmfuhbut the ferric sulfate is hi hly detrimental.

f a solution of copper sulfate, containing ferrous sulfate, is elcetrolyzod, copper is deposited at the cathode while sulfuric acid and ferric sulfate are produced at the anode, as shown by the following equations:

1. (31130 +H O+Electrol sis:

*' 2 t y Cu+H,SO,+O

2. CuSO +2FeSO +Electrolysis:

I (lu-l-FeASOJ,

The ferric sulfate. finding its way to the cathode, combines with the deposited copper, and is again reduced to the ferrous condition, thus: p

The lossofefiiciency due to this cause is more-or less proportional to the amount of ferric-sulfate inthe electrolyte, and under certain conditions ma be very large. In aggravatedrases \the use of eilicicncy may be so great'that the copper is dissolved as rapidly as it is deposite If, however, the ferric sulfate can hereduced at" the expense of a comparatively cheap reducing a out, such as hydrogen sulfid or co per su lid, then acid is regenen, ated, and t e iron in the electrolyte, being reduced to the ferrous condition; loses its ability to combine with the deposited cop'- per, as shown by the equations:

In the treatment of copper ores by solvent processes there are produced rich and lean copper solutions. The rich copper solutions usually result from the application of the standard solution, while the lean copper solutions usually result from the application of wash water to wash out the soluble values from the ore after the rich solutions have been withdrawn.

Usually, if the rich solutions are electrolyzcd or not, the lean solutions are chemically precipitated and the precipitate so obtained usually plays no further wart in the general metallurgical scheme. ne of the objects of this process is to use the sulfide precipitated from the lean, or from the foul solutions, to reduce, or eliminate, the difliculties in the electrolysis of the rich solutions, and have as an end product for both, the pure electrolytic metal.

The process can best be described more in detail by referring to the accompanying drawings, in which Figure 1. is a diagrain matic longitudinal section, and Fig. 2, a diagrammatic plan, of the general scheme and apparatus carrying it out. In the draw ings, 1 is a leaching vat, or other suitable apparatus, for applying an acid solution'to the ore to dissolve the copper. The rich copper solution flows into the storage tank 2, and forms the electrolyte. The lean copper solution, or washwater, flows into the pump 20, and is elevated through the pipe-line 21 to the weak solution storage tank 2 From tank 22 the lean solution flows in a reguiated stream into the precipitator 23, in which the solution is violently agitated, sp yed, or atomized, in the presence of hydroge suitid,

produced in the hydrogen sulfid generator 24. The copper is precipitated as the sulfid, with the simultaneous regeneration of acid, as set forth in the following equation:

The resulting sludge, consisting of the precipitated copper sulfid and regenerated Weak acid solution. flows into the separator in which the sulfid settlesby gravity and is worked toy". rd the central opening in the bottom and into the distributing pipe line 26 by the rotating mechanism Within the tank, while the clear supernatant solution flows into the oxidizer 28, through the pipe line 27. This oxidizer is preferably an electrolyzer in which the oxygen released by the electrolytic action, oxidizes any excess of hydrogen sulfid from the reducer, so that the excess cannot precipitate copper in the ore as the more or less insoluble sulfid, and also to convert the ferrous salts into the ferric condition, which is desirable, since ferric salts act on both the sulfid and oxidized copper in the ore to bring it into solution. It oxidation is not desired, the solution flows through the by-pass 29. The washwater after having its copper precipi tatcd and an equivalent of acid regenerated, and preferably also electrolyzed to convert the ferrous salts into the ferric condition, stored in tank 30 for re-use an acid wash on the ore. as desired.

The electrolyte having the copper in solution and containing iron usually in both the ferric and ferrous condition, flows from the storage tank 2 in a regulattal stream into the redu ing: unit 3, where the ferric salts are converted to the ferrous salts by means of copper sullid. then to th electrolyzcrs 4, then to the reducing unit 5. to the second series of clcctrolyzcrs to the third reducing unit T. t the third series of electro lyncrs and so on, until the electrolyte is solucicntly impoverished in copper and rcgenerated in acid. The rcducinp units consist of agitators, l, 5'. and. 7. ol' separators, 3 5 and 7". and of air-lifts, l. and 1", or other device, for creating a return flow from the bottom of the separator to the top of the agitator. The copper sultid precipitate from the separator 25 is flowed in a regulated stream into the agitators Il". 5", and 7, through the distributing pipe 26. The Elmtrolytc and copper sull'ld prccipitatc being in this way brought into intimate contact, the ferric salts are quickly reduced to the ferrous condition. In order to make a clear separation of the precipitate and electrolyte after reduction. the overflowing reduced soluti n. still containing some copper sultid in suspeut n. i passed to the thicken rs or separators ii. and 7'. Where complete separation tak s place; the clear overflowing reduced solution going to the electrolyzers 4, (l, and 8, while the settled precipitate at the bottom of the separators is returned to the agitators. 3, 5, and 7. In this Way the copper sulfid precipitate is consumed and the electrolyte reduced and enriched in copper sulfate, as shown by.

equations

5 and 6. The electrolyzers 4, (l, and 8, are representative of a series of as many cells as desired.

The electrolyte on entering the cells is practically completely reduced. \Vhen electrolysis begins, copper is deposited at practically the theoretical rate, while acid is regenerated according to equation 1, and some of the ferrous salts converted to the ferric condition, according to equation 2. It is desirable to hold the ferric salts down to as low as 0.109. ferric iron; it should not, in any event, greatly exceed 0.25% ferric iron.

This may be conveniently done by b ing the cells in compound series and by regulating the rate of flow through the system. The ferric salts, formed in alternate series of elcctrolyzers, is reduced in alternate reducers, and this is continued until the elec troiyte is suliiciently impoverished in copper and regenerated in. acid, when it flows into the pump 15, and through the pipe line 16 into the oxidizer and acid generator 17. This oxidizer is an electrolyzer in which the oxygen liberated by the electrolysis of the acid solution, oxidizes the ferrous iron to the ferric condition, so as to enable the solvent to act more energetically on the sultids in the ore. which are unattached by sulfuric acid. The solution may also ,be enrichcd in sulfuric acid by introducing sulfur dioxid. from the sulfur dioxid generator 18, into the oxidizer 17. where it is oxidized by the action of the electric current to sol furic acid. lfoxidatlon of the solution is not In-ccssary or desired, it may be by-passcd through the pipe line 31, into the storage tank ill. In either case the rcgcm-ratcd acid solution is stored in tank 1:7 to be applied to tho orc in the leaching vat, as desired. The sulfuric acid acts on the oxids and carbunnies. and the ferric iron on the sulfids. To this Way a. close extraction of the copper can be made-usually closer than by ordinary acid leaching.

The copper sullid from the separator .25 may be directly distributed, through the pi pc line "26, to the agitators 3", ii, and T. It is preferred, however. to introduce all the freshly precipitated copper sulfid into the first reducing agitator. 3*, and regulate the overflow in such a way that a. considerable portion of the copper sulfid flows into the separator 3, and then. as the settled sultid is elevated by the air lift t", pass it (in to the nest reducing agitator 5. Where the cycle is repeated. and then on to the next reducing agitator, 7, Where the cycle is again re posted, and so on for the entire series of alternatc reducers and electrolyzcrs. \Vhon the impoverished sullid sludge; containing also considerable quantities of sulfur as shown by equation ilxissucs from the last 6 reducer, it is conducted to a filter 38, and the M arid, and partially into the filtrate returned to the circuit through the pipe '13, while the sludge goes to ihe roasting furnace it) to have the Mil l'ur hurncd oil. and i the cupric sulfid partially converted into the cuprous sulfid by the elimination of one atom of sulfur. 'l he ouprous sulfid is more cllcctive in reducing the ferric salts than the cupric sulfid. The sulfid precipitate, treated to eliminate some of its sulfur, is again put into the circuit 26 through the eonveycr in. The suli'ur dioxid from the furnace may be conducted, through i the pipe line ll to thioxidizers, and acid generators. 28 and 17.

Instead of using air in the air lills. 3 5", and 7, it might be desirable to introduce a gas into the air lift to act on the electrolyte. Either sulfur rlioxid or hydrogen sullid may be cfl'ectivcly intrruluced in this way. It niight be desirable lo introduce sulfur dioxid in the electrolyte in the first reducer, 3*, and then maintain the ferric salts reduced with copper sulfirl in the remaining reducers.

A partial reduction of the variable valcnt salts'may be made with sulfur dioxid, by diverting some of the gas from the sulfur 'dioxid generator 18, to the sulfur dioxid re ducer 4.8, shown in .2. 9.1Fe (S(),),,-i-S() -{-lLO:

' I QFeSO l-H SO Acid may be regenerated in this n ay from What would otherwise boa waste gas in many 'lnetallurgical works, while at the same time reducing some of the t'crric salts.

The pro ess is applicahlc to chlorid as well as to sull'at solutions.

The reducing action of the precil'iitated copper sulfid. q iouitirc in both hot and cold solutions. lnhot solutions containing 3.5 grams ferric iron per liter, (0.35% a at a temperature of 145-deg. R, with occasionalstirring: under the same conditions, at

{52 deg. F., 56% of the ferric iron can he rei dncfld. Under the same conditions, in either hot or cold solutions, the ferric iron can be 'com 'iletcly reduced in one minute by violently shaking in a bottle or violently agitating with air, when the amount of copper in fsuspension is equal to that in solution; As "t" advisable to carry out the electrolytic position at a temperature of about 125 F., there should be no trouble in having completely reduced electrolyte in the renccrs, and effective depolarization in the cells, with considerably reduced power for do position.

"I claim:

1, A metallurgical rocess which consists copper and containing salts of the variable ralent elements to deposit the copper whereby thc salts of the variable valent elen'ients are raised from a lower to a higher valency, treating the lean copper solutions to prccipitate the metal as tho sulfid, applying sulfur dioxid to the rich solutions, and then maintaining the solution reduced with the copper sulfid obtained from the lean solutions.

2. A metallurgical process which consists in applying sulfur dioxid to a copper solution obtained from leaching ores and oontaining salts of the variable valent elements, clcctrolyzing the solution whereby the coppcr is deposited and the salts of the variable ralen't elements raised from a lowcr to a higher valency, maintaining the electrolyte reduced with copper sulfid until the electrolyte is suliiciently impoverished in copper and regenerated in the solvent, and then returning the clmtrolyle to the ore to dissolve more copper.

3. A process of clcctrolyzing a metal salt of a polybasic acid obtained from leaching ores and containing salts of the variable valent elements which consists in alternately elcctrolyzii'ig and reducing the electrolyte by adding copper sulfid as a reducing agent in the first of the series of reducers and then carrying a portion of the reducing agent from the first to the last of the series of reducers, and finally separating the impovof reducer-s and then carrying a portiono! the copper sulfid from the first to the last of the series of reducers, and finally separating the impoverished copper sulfid from the electrolyte impoverished in copper and rturning the electrolyte to the ore and treating the impoverished copper snlfid to reduce its sulfur content and again treating the electrolyte therewith.

5. A process which consists in treating ores of copper with an acid solution to dissolve. the metal, maintaining separate the rich and the lean ooppersolutions, electrolyzing the solutions rich in. copper and containing salts of the variable valent elements to deposit the copper, precipitating the cop per from the lean solutions with a chemical precipitant, applying the chemical precipiv tate to the electrolyte to reduce the higher valency salts formed by the electrolysis to a lower valency, and then before returning the electrolyte to the ore electrolyzing it under different conditions to convert the lower valency salts to a higher valency.

6. A process which. consists in treating ores of copper with an acid solution to dissolve the copper, maintaining separate the rich and the lean resulting copper solutions, electrolyzing the rich copper solution containing salts of the variable valent elements to deposit the metal, precipitating the lean copper solutions with hydrogen sulfid, separating the sultid precipitate from the weak acid solution, applying the copper sulfid to the rich solution to maintain the ferric salts reduced, and oxidizing the precipitated lean solutions b electrolysis and returning the regeneratet \veak acid solutions to the orc.

7. In the electrolysis of a solution of a 'metal salt of a polybasic acid obtained from leaching ores and containing salts of the variable valent elements, theprocess which consists in applying sulfurdioxid to the solution to reduce the salts of the variable "alcnt elements from a higher to a lower valency in the first stages of the electrolysis, and then continuing the reduction of the higher valency salts formed by the electrolysis by means of copper sulfid precipitate, and then when the solution is sufliciently impoverished in the metal being deposited and re generated in acid returning the solution to the ore.

8. In the electrolysis of a solution, of a metal salt of a polybasic acid obtained from leaching ores and containing salts of the variable valent elements, the process which consists in applying sulfur dioxid to the solution to reduce the salts of the variable valent elements from a higher to a lower valency in the first stages of electrolysis, and then continuing the reduction of the higher valency salts formed by the electrolysis by means of concentrated copper sulfid, and then when the solution is suiliciently impoverished in the metal being deposited and res generated in acid returning the solution to the ore.

9. In the electrolysis of a solution of a metal salt of a polybasic acid obtained from leaching ores and containing salts of iron, the process which consists in electrolyzing the rich metal solutions to deposit the metal and regenerateacid and ferric salts, precipitating the metal from the lean solutions as the sulfid, applying the. metal sulfid precipitube to the electrolyte to reduce the ferric I salts in the electrolyte and liberate sulfur from the precipitate, separating the residual recipitate from the electrolyte and reducmg its sulfur content, and then again applying the precipitate reduced in sulfur to the electrolyte. A

It]. In the electrolysis of a solution of a metal salt of a polybasic acid obtained from leaching ores and containing salts of iron, the process which consists in withdrawing the electrolyte from the clcctrolyzcrs into )ools at different points of the system. treating the withdrawn clm-troLytc at different points of the system with a solid rcdlwing agent distinct from the ore by agitation, returning the reduced electrolyte to the electrolyzcrs, and finally when the electrolyte is sufliciently impoverished in the metal being deposited and regenerated in acid returning the solution to the ore.

11. In the electrolysis of a solution of a metal salt of a polybasic acid containing salts of iron, the process which consists in reducing the ferric iron formed by the elec trolysis to the ferrous condition by applying a reducing agent to a series of pools of the electrolyte, progressively advancing the electrolyte through a series of elcctrolyzers, and progressively advancing the electrolyte through a series of pools communicating with the electrolyzers and containing a reducing agent for the ferric salts.

12. In the electrolysis of a solution of a metal salt of a polybasic acid containing salts of iron, the process which consists in reducing the ferric iron formed by the electrolysis to the ferrous condit on by applying a reducing agent to a series of pools of the electrolyte, progressively advancing the electrolyte through a series of elcctrolyzcrs, progressively advancing the. electrolyte through a series of pools communicating with the electrolyzers and containing a reducing agent for the ferric salts, and progressively advancing the reducing agent through the series of pools of the electrolyte.

13. A metallurgical process which consists in treating ores of copper with an acid solution to dissolve the copper, electrolyzing the resulting solutions rich in copper and containing salts of iron to deposit the cop er with the simultaneous oxidation of the erprecipitating the copper'from the leanand foul solutions with hydrogen sulfid, separating the resulting copper sulfid precipitate from the precipitated solution as a thick- -rous salts to the ferric condition, chemically ened sludge, and applying the copper sulfid precipitate in the form of a sludge to the rich copper solutions to reduce the ferric salts formed by the electrolysis to the ferrous condition.

i WILLIAM E. GREENAWAl/I. \Vitnesses MARY II. W'ooLsnY,

IRMA GREENAWALT.