US1483056A

US1483056A - Metallurgical process

Info

Publication number: US1483056A
Authority: US
Publication date: 1924-02-05
Anticipated expiration: 1941-02-05

Description

Feb; s, 1924. V, 1,483,056 W. E. GREENAWALT METALLURGICAL PROCES S v Filed Dec. 6. 1921 Patented Feb. 5, 1924.

UNITED STATES WILLIAM E. GREENAWALT, OF DENVER, COLORADO.

METALLURGICAL PROCESS.

Application filed December 6, 1921. `S era1 No. 520,241.

T 0 all whom it may concern.'

Be it known that I, WILLIAM E. GREENA- WALT, a citizen of the United States, residing in the city and county of Denver and State of Colorado, have invented 'certain new and useful Improvements in Metallurgical Processes, of which the following' is a specification.

The invention refers more particularly to the hydrometallurgical extraction of copper from its ores, and has as its particular obiect the economical treatment of both oxidized and sulphide ores of copper by combining the treatment of both into one readvisable, with ordinary acid leaching.

In leaching low grade oxidized ores, it usually takes from three to ive pounds of acid to extract one pound of copper; `If iron is used as the precipitant, it willusually take from one to two pounds of iron, per pound of eopper'precipitated. Excess acid is neutralized at the expense of the iron, so that where there is an appreciable amount of excess acid, both excess acid and iron are wasted. Then, too, the resulting cement copper is quite impure and has to be treated much the saine as a high grade copper ore, or concentrate, to obtain inerchantable copper.

It is evident, that with the consumption of from three to five pounds of acid and from one to two pounds of iron, per pound of copper extracted, and with the copper in the form of an impure metal, the process becomes prohibitive. Acid plants are expensive to install, and even if installed on a small scale, the cost of acid is excessive. If the acid is purchased, it will usually cost not less than 1.5 to 2.0 per pound, delivered at the mine.

One of the most difficult problems, in leaching copper ores, has been to overcome this acid expense. yThis difficulty is solved by the present invention, and one of the principal objects of this invention is lto provide sufficient acid, by a regenerative process, in the treatment of oxidized and sulphide ores to make the process self sustaining in acid for both.

Usually, sulphide and oxide ores occur in the same deposit. The oxides occur at or near the surface, the sulphides at depth, and a mixture of both in the intermediate zone. The oxides and sulphides may come from the same mine, or from different mines: the origin of the ore, for the purpose of this invention, is immaterial.

As a preliminary to the description of the present process, it might-be Well to consider some matter bearing directly on it. In

carrying out the processes described in my Patents, No. 1,314,742, September 2, 1919, and No. 1,353,995, September 28, 1920, it was found that 1.4 lbs. of copper could be deposited per k. w. h., with the simultaneous regeneration of 3.0 lbs. of acid, from a solution containing as much, or more than 3.0% iron. It was also found that with a solution containingv 4.0% copper and 3.0% iron, the copper could be reduced to 1.0%, and the acid could be regenerated up to as high as 10.0%, before it was necessary to return the solutionto the ore. The ferrie salts in the solution were under vgood control, and it was this control which made these results possible.

It was also found, by carefully roasting ya sulphide concentrate, containing, say, 15.0% copper, and roasting as described in my pending application, Serial No. 485,885, filed July 19, 1921, that from to 75% of the copper could be made soluble in water, as the copper sulphate. The remaining copper in the roasted concentrate, is soluble, to a very high percentage, in dilute acid, with an 'acid consumption not greatly exceeding the theoretical, or practically, about 1.75 lbs. of acid` per lb. of copper so extracted. The excess acid produced, with a concentrate containing 300 lbs. of extractible copper. with 50% of the copper in the roasted concentrate soluble in water,` would be about as follows:

` Lbs. acid.

300 lbs. copper 3.0 lbs. acid, per lb 900 150 lbs. copper 1.75 lbs. acid consumed 263 Excess acid, per ton concentrate 637 This excess acid is then applied to the oxidized ore. It is evident that vabout 13 tons of low grade oxidized ore, Vcontaining 2.0% copper, and with an acid consumption of 3.0 lbs. of acid, per lb. of copper, could be treated with this excess acid. It is believed that over 20 tons of oxidized ore could be treated, in the treatment of one ton of concentrate, if the copper extracted from f I 20 tons of 2% oxidized ore, with acid regenerated in the regular operation of the process, with the use of the sulphur dioxide gas from the roasting furnace as a reducing Q agent.

The present process will now be described, reference may be made to the accompanying flow sheet, in diagrammatic plan.

l The mixed sulphide and oxide ore is concentrated in the usual Way to separate the sulphides from the oxides. The oxide tail ing, or ore, 'is charged into a leaching vat, Where it may be treated either by agitation or percolation, preferably by percolation,

- if the ore can be leached effectively in that way. The sulphide concentrate, containing about 15% extractible copper, is sent to the roasting furnace, where it is roasted at a low temperature, to make as much as possible of the copper soluble in water. Usually there will be no difliculty in making from 50% to 75% of the copper in the roasted concentrate soluble in water. The roasted concentrate is then leached, preferably, by agitation, on account of its high grade. The resulting copper solution will be fairly high in both copper and iron: and may be assumed to contain about 4.0% copper and 3.0% iron. The amount of iron in the copper solution is quite immaterial, in the operation of this process, for the reason that by t-he use of sulphur dioxide, as indicated, the iron can be maintained quite closely in the ferrous condition, and this is of importance. The solution from the copper concentrate leaching tank is flowed into a closed chamber, designated as S()2 reducer, No. 1, where thesulphur dioxide gas from the roasting furnace is applied to it. The sulphur dioxide gas reduces the ferrie salts to the ferrous condition. The solution is maintained in a pool in the SO2 reducers. The gas is maintained over the pool. The reducer is arranged so that the liquid in the pool may be treated with the gas confined over it. The reduction of the ferrie salts is not a rapid reaction, with sulphur dioxide, and this arrangement provides sufiicient time for effective work. The reduced solution flows into the settling tank, where the solution is clarified, after which it is flowed through the electrolytic units. These units consist, essentially., of an SO2 reducer and a number of electrolytic copper depositing cells, arranged so that a continuous iow of reduced electrolyte, or solution, may be maintained from the reducer to the cells and a return flow of oxidized electrolyte from the cells to the reducer. The copper solution is owed from the settling tank into the copper electrolytic cells, No. 1, where a portion of the copper is deposited and acid and ferrie salts regenerated. The flow is regulated so that the outflow from the cells will not, preferably, exceed 0.25% ferric iron. The ferrie iron may conveniently be less. A flow of reduced solution is maintained from the reducer to the cells, and a return flow of oxidized solution from the cells to the reducer, while a portion of the solution, the advance flow, is advanced to reducer No. 2, and from reducer No. 2, to the second set of electrolytic copper depositing cells, where, again, a portion of the solution is circulated between the reducer and the cells, While another portion is returned to the roasted concentrate, and another portion, the advance flow, is applied to the oxidized ore in the leaching tank. The copper in this solution, as returnedto the con centrate and as advanced to the oxidized ore, will amount to about 1.0% and the acid may be from 5.0% to 10.0%. In this way the copper concentrate is treated until the copper is suiiiciently extracted, and the leach tailings wasted.

The regenerated acid, or advance solution, is applied to the ore in the oxidized ore leaching tank, where copper and soluble impurities are dissolved, and the acid practically neutralized, so that the resulting solution contains considerable copper, and somewhat more iron and other impurities. This solution is then treated with sulphur dioxide in reducer No. 3, and flowed into the third series of electrolytic cells. As before, a portion of the electrolyzed solution is returned to the reducers, while another portion, the advance flow, is owed'into reducer No. 4, where it is again treated with sulphur dioxide, and then electrolyzed in the fourth series of electrolytic cells. The solution, issuing from the last series of electrolytic cells, will contain considerable regenerated acid, some ferric iron, and a small percentage of copper', usually from 0.25% to 0.50%. A portion of this solution is returned to the oxidized ore leaching vat, while another portion, the advance How, or a portion of it, is passed on tothe chemical copper precipitator, where the small remaining amount of copper is precipitated chemically out of the solution, and the solution wasted. vAny method of chemically precipitating the copper from the waste solution may be used. 'Hydrogen sulphide is preferred, for the reason that the copper is effectively precipitated from acid solutions with hydrogen sulphide, whereas, other precipitants, such as metallic iron, act on t e acid as well as on the copper, and this would require a large amount of precipitant per unit of copper precipitated. Water is necessarily added to the solution in amounts at least equal to the quantity of foul solution wasted: a large portion of this fresh water is conveniently added to the solution from the moisture in the oxidized ore in the oxidized ore leaching tank, and wash waters resulting from washing the leached residues of both the roasted concentrates and oxidized ore.

The sulphur gas from the roasting furnace is preferably passed through the respective reducers, in series, as shown, by means of an exhauster communicating with the last reducer. The order of the reducers is not of great importance, so far as the application of the sulphur gas is concerned, altho it is preferred to apply the strongest gas, direct from the roaster, to the fresh copper solution, or the solution flowing from the roasted sulphide concentrates. This method of operation keeps the dissolved impurities within workable limits. The amount of impure solution wasted will be mostly determined by the amount of soluble iron, but, as the electrolysis, under the conditions, is practically independent of the amount of iron in the electrolyte, the iron content may be maintained quite high, and this means that the amount of solution wasted may be kept relatively small.

The control of the ferrie salts is a vital factor in the operation of the process. By maintaining a flow of reduced solution from the reducer to the electrolyzers, and of oxidized, or electrolyzed, solution from the cells to the reducers, while advancing a portion of the solution through the entire system, the ferrie salts may be kept at a very low limit, usually considerably below 0.25% ferrie iron, and this serves to get a high energy efficiency, a high acid regeneration, and 'freedom from annoyances invariably accompanying high ferrie iron in the electrolyte.

A ttention is called to the desirability of having a fairly strong acid solution, especially in the leaching of concentrate. ln the ordinary operation of electrolytic processes, the ferrie salts accumulates so rapidly in the electrolyte, and its presence is so harmful, that a high regenerated acid solution is diiiicult, and in fact, quite impractical. A low acid solution greatly complicates the leaching operation. A high acid solution greatly simplifies it.

By the operation of this process, the fol lowing results may be expected: First, the deposition of about 1.4 lbs. of copper, per k. w. h. (E. M. F. measured across the bus bars of the cells) Second, use of the SO,

from the roasting furnace, as a reducing agent for the ferric salts formed, with the regeneration of 3.0 lbs. of acid, per lb. of copper deposited: Third, the regeneration of suiicient acid in the entire operation of the process itself to make it self-sustaining in acid for the treatment of one ton of 15% copper sulphide ore or concentrate, and from fifteen to twenty tons of about 2.0% oxidized copper ore, as indicated. This will ordinarily come within the range of the treatment of copper ores which are amenable to acid leaching.

The SO2 reducer-s may conveniently be made as shown in my Patent, No. 1,353,995, September 28, 1920; or as shown in my pending application, Serial No. 485,884, filed July 19, 1921. The reducer consists, essentially, of a covered chamber adapted to contain a. pool of liquid and to confine a gas over the pool, and arranged so that the liquid of the pool may be treated `with the gas. This may be done by spraying the liquid of the pool into the gas, which saturates, or supersaturates the fine liquid spray, and this spray falling into the pool, also saturates, or absorbs the gas in the liquid in the pool, so that the entire liquid of the pool is under the action of the gaseous reducing agent. As rapidly as the gas in the pool reacts with the liquid, fresh gas is absorbed due to the liquid spray. This, effectively, brings in the element of time, so essential in the reduction of ferrie salts with sulphur dioxide. It maintains the entire pool of liquid under continuous treatment with the gas. The liquid flows into the pool at one end and out of the pool at the other end. The time factor is dependent on the size of the pool.

It is desirable to apply the impure gas (gas containing dust etc.) from the roaster` to the impure copper solution from the leaching tank or agitator. By this arrangement the gas is washed and purified for the subsequent reducers, and by allowing the reduced solution to settle, the impurities in the solution are also eliminated for subsequent electrolysis in the various series of cells. Practice has shown that there is no dificulty in passing the gas through the various reducers in series, by means of an exhauster communicating with the last reducer. The suction is always inwardly and fumes do not esca-pe to contaminate the surrounding atmosphere.

The pools of solution, or electrolyte, in the reducers are preferably fairly large. The definite amount of electrolyte in the pools will be determined by the amount of reduction of the ferrie salts desired. The ferrie salts should be very effectively reduced to get good, or the best, results in the electrolyzers. n

The process is advantageously applied to low grade roasted sulphide ore, instead of the oxidized ore in the oxidized ore leaching.

. tended to limit it to this application.

The process has been described particu-- larly in reference to sulphate solutions. lt is also applicable to chloride and other solutions.

This application is intended to cover, in part, the process disclosed in my apparatus patent 'referred to, No. 1,353,995, Septemher 28, 1920.

I claim:

1. A process of treating sulphide and oxide ores of copper comprising, treating the sulphide ore to get a sulphide concentrate, roasting the concentrate, leaching the roasted concentrate With a dilute acid solution, treating the resulting copper solution with sulphur dioxide obtained from roasting the sulphide concentrate, electrolyzing the solution to deposit the copper and regenerate acid, returning a portion of the regenerated solution to the roasted concentrate to extract lthe remaining copper, applying the excess regenerated acid solution to the unrcasted oxidized ore to extract the copper therefrom, precipitating the copper from the resulting solution obtained from leaching the unroasted oxidized ore, and then Wasting the solution.

2. A process of treating sulphide and oxide ores of copper comprising, concentrating the sulphide ore to obtain a concentrate relatively high in copper and sulphur, roasting the concentrate to make a portion of the copper soluble in Water and a portion soluble in dilute acid, leaching the roasted concentrate With a dilute acid solution, treating the resulting copper solution with sulphur dioxide obtained from roasting the sulphide concentrate, electrolyzing the solution to deposit the copper and regenerate acid, returning a portion of the regenerated acid solution to the roasted concentrate, applying the excess regenerated acid solution to the unroasted oxidized ore to extract the copper therefrom, precipitating the copper from the resulting solution with the simultaneous regeneration of acid, returning a portion of the regenerated acid solution to the unroasted oxidized ore, and discarding another portion.

3. A process of treating sulphide and oxide ores of copper comprising, treating the sulphide ore to obtain a concentrate relatively high in copper and sulphur, roasting the concentrate to make a portion of the copper soluble in Water and a portion soluble in dilute acid, leaching the roasted concentrate with a dilute acid solution, treating the resulting solution with sulphur dioxide, electrolyzing the solution to deposit the copper and regenerate acid, returning a portion of the regenerated acid solution to the roasted concentrate, applying the excess acid solution to the unroasted oxidized ore to extract the copper therefrom, precipitating the copper' from the resul-ting solution with the simultaneous regeneration of acid, returning a portion of the foul .re enerated acid solution to the unroasted oxi ized ore,y and discarding another portion.` y

4. A process of treating sulphide and oxide ores of copperI comprising, treating the sulphide ore to obtain a concentrate higher in copper and higher in sulphur than the original ore, roasting the concentrate to make a portion of the copper `soluble in Water and a portion soluble in dilute acid, leaching the roasted concentrate with a dilute acid solution, treating the resulting copper solution with sulphur dioxide, elec` trolyzing the solution to deposit the copper and regenerate acid, returning a ortion of the regenerated acid solution to t e roasted concentrate, applying the excess acid to the unroasted oxidized ore to extract the copper therefrom, applying sulphur dioxide to the resulting copper solution, precipitating the copper from the solution with the simultaneous regeneration of acid, returning a portion of the resulting foul regenerated acid solution to the unroasted oxidized ore, and discarding another portion.

5. A process of treating sulphide and oxide ores of copper comprising, roasting the sulphide ore to makel a portion of the copper soluble in Water and another por- 100 tion soluble in dilute acid, leaching the roasted ore with a dilute acid solution, treating the resulting copper solution with a reducing agent, electrolyzing the solution to deposit the copper and regenerate acid, returning a portion of the regenerated acid solution to thev roasted ore, applying another portion to the oxidized ore, applying a reducing agent to the resulting copper solution from the oxidized ore, precipitating the copper therefrom with the simultaneous regeneration of acid, returning a portion of the regenerated acid solution to the oxidized ore, and discarding another portion so that by adding an equivalent of Water to the leach solution the impurities in the solution may be maintained Within desired limits.

6. A process of treating sulphide and oxide ores of copper comprising, treating the sulphide ore to obtain a sulphide concentrate, roasting the concentrate to make a portion of the copper soluble in Water and another portion soluble in dilute acid, leaching the roasted concentrate with aV dilute acid solution, treating the resulting copper solution with the sulphur dioxide obtained from roasting the sulphide concentrate, electrolyzing the solution to deposit the cop per and regenerate acid, returning a portion of the regenerated acid solution to the Vil() roasted concentrate, applying another portion to the unroasted oxidized ore, treating the solution from the unroasted oxidized ore with sulphur dioxide obtained from roasting the sulphide concentrate, precipitating the copper from the resulting solution With the simultaneous regeneration of acid, returning a portion of the regenerated acid solution to the unroas'ted oxidized ore, and discarding another portion.

T VA process of treating sulphide and oxide ores of copper comprising roasting the sulphide ore to make a portion of the copper soluble in Water and another portion soluble in dilute acid, leaching the roasted ore with a dilute acid solution, treating the solution with sulphur gas obtained from roasting the sulphide, electrolyzing the solution to deposit the copper vyith the simultaneous regeneration of acid, returning a portion of the regenerated acid solution to the roasted ore, applying another portion to the oxidized ore, applying a reducing agent to the resulting copper solution from the oxidized ore, electrolyzing the solution to deposit the copper and regenerate acid, returning a portion of the resulting foul acid solution to the oxidized ore, and discarding another portion.

8. A process of treating sulphide and oxide ores of copper comprising, roasting the sulphide ore, leaching thev roasted ore With a dilute acid solution to extract the copper, applying a reducing agent to the copper solution, electrolyzing the reduced solution and repeating the cycle of alternate reduction and electrolysis until the solution is suiiiciently depleted in copper and regenerated in acid, then returning a portion of the regenerated acid solution to the roasted ore, applying another portion to the. oxidized ore, precipitating the copper from the solution obtained from the oxidized ore, and discarding the solution.

9. A process of treating sulphide and oxide ores of copper comprising, roasting the sulphide ore,"leaching the roasted ore with a dilute solution of acid, treating the resulting copper solution containing salts of iron with the sulphur dioxide obtained from roasting the sulphide, electrolyzing the solution to deposit the copper and regenerate acid and repeating the cycle of reduction and electrolysis until the solution is suiiiciently depleted in copper and regenerated in acid, then returning a portion of the regenerated acid solution to the roasted ore to complete the extraction of the copper and applying another portion to the oxidized ore to extract the copper therefrom, treating the resulting copper solution from the oxidized ore with the sulphur dioxide obtained from roasting the sulphide ore, electrolyzing the solution to deposit the copper and regenerate acid and repeating and electrolysis until the solution is suiiicientiy depleted in copper and regenerated in acid, then returning a portion of the regenerated acid solution to the roasted ore and applying another portion to the ox-,l

idized ore to extract the copper therefromf treating the resulting copper solution from the oxidized ore with the sulphur dioxide obtained from roasting the sulphide ore, electrolyzing the solution to deposit the copper and regenerate acid and repeating the' cycle of reduction and electrolysis until the solution is sufficiently depleted in copper and regenerated in acid, then returning a portion or' the regenerated acid solution to the oxidized ore, chemically precipitating the small amount of remaining copper from another port-ion and discarding the resulting barren solution.

11. A process of treating sulphide and oxide ores of copper comprising, roasting the sulphide ore, leaching the roasted ore With a dilute acid solution, applying sulphur dioxide to the resulting copper solution, electrolyzing the solution to deposit the copperr and regenerate acid, .cycl'ically circulating a portion ot the regenerated acid solution betweenthe roasted ore the sulphur dioxide reducer and the electrolyzer until the copper in the ore is suiiiciently extracted, advancing another portion of the regenerated acid solution 'to the oxidized ore tov extract the copper therefrom, applyingl sulphur dioxide to the resulting solution from vthe oxidized ore, precipitating the copper from the solution With the simultaneous regeneration of acid, returning a portion of the regenerated acid solution to the ore and discarding another portion.

12. A process oic treating sulphide and oxide ores of copper comprising, treating the sulphide ore to obtain a sulphide concentrate, roasting the sulphide concentrate to make a relatively large portion of the copper soluble in Water, leaching the copper from the roasted concentrate with a dilute. acid solution, applying the sulphur dioxide from the roasting concentrate to the resulting copper solution, electrolyzing the solution to deposit the copper and regenerate acid, and

` trolyzing the solution to deposit .the copper and regenerate acid, returning a portion of the regenerated acid solution to lthe roasted concentrate to complete the extraction otI the copper, and` applying the excess acid solution tothe unroasted oxidized ore to extract the copper therefrom.

14. A process of treating sulphide and oxide ores of copper comprising, treating the sulphide ore to obtain a sulphide concentrate, roasting the sulphide concentrate, leaching the roasted concentrate with a dilute `acid solution. to extract a portion ot' the coppe-napplying sulphur dioxide obtained from roast-lng the sulphide concentrate to the copper solution containing salts ot iron to 'reduce the ferrie salts to the ferrous condition, electrolyzing thesolution to deposit the copper and regenerate acid and ferric salts, circulating a portion of the solution in a vclosed circuit between the reducer and electrolyzer and alternately subjecting it to reduction and electrolysis, and then when the solution is sufficiently depleted in copper and regenerated in acid returning a portion of lthe regenerated acid solution to the roasted concentrate and applying the excess acid to the unroasted oxidized ore to extractthe co per therefrom.

15. n the electrolysis ot copper solutions obtained from leaching ores and containing salts of iron, a process comprising, a progressively advancing the solution through a series of electrolytic units comprising a reducer and electrolyzer, circulating a portion of the solution in its advance tlow between vthe reducers and electrolyzers ot ithe respeccontaining salts of iron, a process comprising progressively advanoi ng ithe solution through a 'serieslof electrolytic units comprising a. reducer vand electrolrzer, circulating a por tion of the `solution between. the electr-olv fr and reducer ot one electr-olytic unit and a terna'tely subjectingit to 'reduction and electrolysis, and advancing a portion to another elcctrolyt-ic unit and repeating the cycle until the solution is suiliciently dep `cited in copper and regenerated in acid, and then returning the regenerated acid solution to the ore 17. A process of treating ores of copper comprising, leaching the ore to extract the copper, progressively advancing the resulting copper solution containing salts ot iron through a series ot electrolytic units coniprising a reducer and an elcctrolyzer, subjee-ting the solution alternately to the action oit electrolysis and to the action of sulphur dioxide in the reducers in the respective electrolytic units, progressiiv'ely advancing the sulphur dioxide through the respective reducers, circulating a port-ion oi the so lution in closed circuit between the reducers and electrolyzers of one electrolytic unit and advancing another portion to the next electrolytic unit o't' the series and repeating t-he cycle until the solution is sufficiently depleted in copper and regenerated in acid and then returning the regenerated acid solution to the ore.

18. A process of treating ores of copper comprising leaching the ore to extract the copper, passing the resulting copper solution containing salts of iron through a series ot electrolyzers, passing the copper solution through a series of pools of the solution so that the inflow/ing solution Will mingle With the pool, treating the solutions ot the pool with sulphur dioxide, circulating a portion ot' the solution in a closed circuit between the respective pools and electrolyzers, and progressively advancing a portion of the solution. through the series of pools and electrolyzers until the solution is sufficiently depleted in copper and regenerated in acid and returning the regenerated acid solution to the ore.

19. A processof treating orcs oit copper comprising, leaching lthe ore With a dilute acid solution, alternately subjecting the solution containing salts of iron to the action of sulphur dioxide and to the action of the electric current in a series ot reducers and electrolyzers, progressively advancing a portion ot the solution from one series of reducers and electrolyzers to the next until the solution is sufficiently depleted in copper and regenerated 'in acid, and then returnin the rogruinerated acid solution to the ore.

20. A process ot treating copper ores comijirising, leaching the ore With a dilute acid solution, alternately subjecting the resulting copper solution containing salts of iron to the action ot sulphur dioxide' and to the action of the electric current in a series ot reducers and electrolyzers, and progressively advancing the sulphur dioxide from one reducer to the next olf the series.`

2l. A process of treating copper ores comprising, leaching the ore with a dilute acid solution, alternately subjecting the resulting copper solution containing salts of iron to the action of sulphur dioxide and to the action of the electric' current in a closed circuit in a series of electrolytic units containing a reducer and an electrolyzer, progressively advancing a portion of the solution from one electrolytic unit to the next of the series, and when the solution is sufficiently depleted in copper and regenerated in acid, returning the regenerated acid solution to the ore.

22. A process of treating ores of copper comprising, leaching the ore with a dilute acid solution, alternately subjecting the resulting solution containing salts of iron to the action of a gaseous reducing agent and to the action of the electric current in a closed circuit in a series of electrolytic units containing a reducer and electrolyzer, progressively advancing a portion of the solution from one electrolytic unit to the next of the series, and when the solution is suciently depleted in copper -and regenerated in acid returning the regenerated acid solution to the ore.

23. A process of treating copper ores comprising, leaching the ore With. a dilute acid solution, alternately subjecting the resulting copper solution containing salts of iron to the action of a reducing gas and to the action of the electric current in a closed circuit in a series of electrolytic units containing a reducer and an electrolyzer, progressively advancing a portion of the solution from one electrolytic unit to the next of the series, and progressively advancing the reducing gas from one reducer to the next of the series.

24. A process of treating copper ores comprising, leaching the ore with a dilute' acid solution` electrolyzing the resulting copper solution containing salts of iron to deposit the copper with the simultaneous regeneration of acid and ferrie salts, reducing the 'lerric salts formed by the electrolysis to the ierrous condition by applying sulphur dioxide to a series of pools of the solution alternating with the electrolyzers, progressively advancing the solution through the series of electrolyzers, progressively advancing the solution through the series ot pools of the electrolytev` and treating the electrolyte of the pools with the sulphur dioxide.

25. A process of treating cop-per ores comprising, leaching the ore With a dilute acid solution, electrolyzing the resulting copper solution containing salts of iron to deposit the copper and regenerate acid and ferrie salts, reducing the ferrie salts formed by the electrolysis by applying a reducing gas to a series of relatively large pools of the solution alternating With the electrolyzers,

progressively advancing the solution through the series of electrolyzers, progressively advancing the solution through the relativeljv large pools of the electrolyte and treating` the electrolyte of the pools with a reducing gas, and When the solution is sufficiently deplet-ed in copper and regenerated in acid returning the regenerated acid solution to the ore.

26. A process of treating mixed sulphide and oxide ores of copper comprisings crushing the ore, separating the sulphide from the oxide, roasting the sulphide, leaching the roasted ore with dilute acid solution, treating the resulting copper solution with the sulphur dioxide obtained from roasting the sulphide, electrolyzing the solution and repeating the cycle of reduction and electrolysis until the solution is suiciently depleted in copper and regenerated in acid, and then applying the regenerated acid solution to the oxidized ore to extract the copper therefrom.

27. A process of treating copper ores comprising, leaching the ore with a dilute acid solution, flowing the solution through a series of electrolyzers to deposit the copper and regenerate acid and ferrie salts, maintaining a series of relatively large pools of the electrolyte in communication with the electrolyzers, treating the electrolyte of the pools with sulphur dioxide, circulating a portion of the electrolyte in a closed circuit through the respective pools and electrolyzers, and progressively advancing the electrolyte through the respective pools and electrolyzers until the solution is suiiciently depleted in copper and regenerated in acid and then returning the regenerated acid solution to the ore.

28. A process of treating copper ores comprising, leaching the ore with a dilute acid solution, passing the resulting copper solution through a series of reducers and treating it therein with sulphur dioxide, passing the solution through a series of electrolyzers to deposit the copper and regenerate acid and ferrie salts, circulating the solution in a closed circuit between the respective reducers and electrolyzers of the series, progressively advancing the solution through the series of reducers and electrolyzers until the solution is sufficiently depleted in copper and regenerated in acid, and when the solution is suiciently depleted in copper and regenerated in acid returning the solution to the ore.

29. A metallurgical process comprising treating copper ore with a dilute acid solution to extract the copper, alternately sub-A jecting the resulting copper solution containing salts of iron to the action of sulphur dioxide in a series of reducers containing relatively large pools of the solution and vto the action of the electric current in a series of electrolyzers. progressively advancing the solution from one reducer and electrolyzer to the next reducer and electrolyzer of the series ot' reducers and electrolyzers until the solution is sufliciently depleted in copper and regenerated in acid, and then returning the regenerated acid. solution to the ore.

BO. A metallurgical process comprising5 treating copper ore with a dilute acid s0- lution to extract the copper, alternately subjecting the resulting copper solution containing salts of iron to the action of a reducing gas and to the action of an electric current in a series of reducers and electrolyzers, progressively advancing the Solution from one reducer and electrolyzer to the next reducer and electrolyzer of the series until the solution is suiiciently depleted in copper and regenerated in acid, and then chemically precipitating the remaining copper from the electrolyzed solution With the simultaneous regeneration of acid.

31. A metallurgical process comprising treating copper ore vWith a dilute acid `solution to extract the copper, alternately subjecting the resulting copper solution containing salts of iron to the action of sulphur dioxide in a series of reducers containing relatively large pools of the solution and to the action of the electric current in a series of electrolyzers, and progressively advancing the solution from one reducer and electrolyzer to tlie next reducer and electrolyzer of the series of reducers and electrolyzers until the copper in the solution is sulficiently depleted.

32. A metallurgical process comprising treating copper ore with a dilute acid solution to extract the copper, alternately subjecting the resulting copper solution con-l taining salts of iron to the action of sulphur dioxide and to the action of an electric current in a series of reducers and electrolyzers, progressively advancing the solution from one reducer and electrolyzer to the next rei ducer and electrolyzer oi' the series until the solution is sufficiently depleted in copper and regenerated in acid and then returning the regenerated acid solution to the ore.`

WILLIAM E. GREENAWALT.