US1798255A

US1798255A - Copper-extraction process

Info

Publication number: US1798255A
Application number: US159450A
Authority: US
Inventors: William E Greenawalt
Original assignee: Individual
Current assignee: Individual
Priority date: 1927-01-06
Filing date: 1927-01-06
Publication date: 1931-03-31
Anticipated expiration: 1948-03-31

Description

March 31, 1931. w, GREENAWALT 1,798,255

COPPER EXTRACTION PROCESS Original Filed Jan. 6, 1927 M me Slag S clcm Elecbric E'u mace .Low Grad Concentra Roasbng PPF" Fu mace Anodcs Pur C 50 5olfmt1 gn Co er Ta s No i 5 o uuon Acid. Soluhon I Tar e s ES \5 .Acld. Soluhon 4 H25 Gcncrafor Copper Saulphlde T Impure lectrolyhc 7 Pure Ellecholghc Copper CllCUlt Copper CIICUlt lNVENTOR Patented Mar. 131, 1931 earner oFFIcE WILLIAM E. GREENAWALT, OF DENVER, COLORADO COPPER-EXTRACTION PROCESS Application filed January 6, 1927, Serial No. 159,450. Renewed August 18, 1930.

The object of the process is to combine the hydrometallurgy of copper with the pyrometallurgy in such a way as to produce an economical treatment for copper ores at the mines, which is capable of being operated either in small or in large units as occasion may require, with the production of the cop per as the electrolytic metal. If there are precious metals associated with the copper, l these may also be recovered in elemental form.

Copper ores, as mined, are usually concento eliminate barren material, or gangue. The concentrate is then usually smelted to matte, the matte blown to blister 13 copper, the blister copper is then refined to obtain the electrolytic metal. Or, the concentrate may be roasted, leached with sulphuric acid, and the copper deposited elec-,

vtrolytically to obtain the electrolytic metal. ilil The concentrate may be obtained from the original ore either by gravity or flotation concentration, and the concentrate will usually vary from 15% to copper, depending on the nature of the ore, but principally on the mineralogical combinations in which the copper occurs.

the concentrate is smelt-ed, roasting is usually necessary, and usually considerable liuxing is required to slag oif gangue material associated with a low grade concentrate, and the gangue material also requires fuel for smelting. By smelting a relatively low grade concentrate, a relatively large plant is required, relatively large amounts of fuel :75 and flax must be provided, and the labor item is high; all of which means increased expense.

l the concentrate is treated by roasting,

leaching, and electrolysis, the copper can be converted directly into the electrolytic metal,

but the roasting of a concentrate containing fro 15% to 25% copper, presents some difficulties, both of the extraction of the copper and the fouling of the acid leach solu tions. Much progress has been made in roasting high grade copper ore 0r concentrate to get a high extraction of the copper, and "he fouling of solutions is not necessarily harmful, and may be beneficial, as set forth for example in my Patent No. 1 388,056, Feb. 51) 5, 1924, nevertheless, if a treatment can be evolved which largely overcomes the difiiculties mentioned, as in the present process, a considerable advantage would result at least under many conditions. 55

In describing the process reference may be made to the accompanying drawing, which is a flow sheet of the process in diagrammatic plan.

Most mines, or mining districts, produce large amounts of low grade copper ore, usually in the form of sulphide, or as the sulphide and oxide (including carbonate) mixed. In either case the general method of procedure is to separate the sulphide mineral from the gangue to form a concentrate. This concentrate is usually of relatively low grade, as compared with the theoretical percentage of copper in the mineralogical combination of the copper minerals, and is so contaminated with iron, silica, alumina, etc, that vigorous fluxing is required for good smelting conditions, and this makes a smelting process expensive to install and expensive to operate in most mining districts. Where power is cheap and fuel is costly, electrio smelting would appear to present some advantages, but the complications arising from the fiuxing of large quantities of material and the large amount of electricity so required to smelt a relatively low grade ore or concentrate, has led to failure or disappointment wherever it has been tried.

In the concentration treatment of mine ore, either by gravity or flotation, a certain 3:, amount of very high grade concentrate may be separated from the large amount of the ordinary sulphide concentrate, but the relatively small amount of very high grade concentrate will contain a relatively large [iii amount oi? the total copper. Usually this relatively small portion of high grade concentrate Will be in the form of the relatively pure minerals, chalcocite, bornite, and chalcopyrite. Pure chalcocite contains 79.8% copper and 20.2% sulphur; pure bornite contains 5!.5870 copper, 28.6% sulphur, and 16.36% iron; pure chalcopyrite contains alto O copper, 3d.9% sulphur, and 30.5% 1ron.

The conditions of concentration can best be illustrated by taking a specific case in the treatn'ient off 100 tons of ore assaying 1.5%, or 30 pounds, of copper per ion, or containinna total of 3000 pounds of copper. It the ratio of: concentration is into i, we Would have, as the result of the concentration treatment:

on tons tailing, 0.25% copper (5117s.)... 450 lbs. total 10 tons concentrate, 12.75% copper 2,550 lbs. total The ten tons of concentrate may be separated into:

1.5 tons high grade concentrate, copper (1,000 lbs.)

1,500 lbs. total 8.5 tons low grade concentrate, 6.12% copper (121 lbs.) 1,0

nere should not be a great deal of diiiiculty under most conditions in getting a 50 or a copper concentrate in relatively small amounts as indicated, it much of the copper in the ore is in the form of either bornite or chalcocite. The 00% copper concentrate is preferred and will be assumed for the purpose oi illustration, altho it will be understood that the process is not particularly limited to the percentage of copper in the high grade concentrate, but that the higher the grade of the high grade concentrate, the better the process can be operated.

If there is gold or silver in the ore, the high grade concentrate will contain the precious metals in about the same proportion as it contains the copper from the original ore. That is to say, of the total precious metal content in the concentrate, 415% will be in the one ton of 60% copper concentrate, and will be in the 9.0 tons of 7.5% copper concentrate.

Having made the separation of the mineral from the gangrue and divided the mineral into a relatively small amount of high grade concentrate and a relatively large amount of low grade concentrate, the method of procedure is as follows:

The high grade concentrate, asiumed consisting of 60% copper with its combined sulphur and a small amount of iron with its combined sulphur, is preferably smelted in an electric fur ace, to dissociate or volatilize the sulphur and to slag elf the relatively small amount of iron, so as to obtain. a, nearly as possible, pure copper sulphi' The first atom of sulphur of the iron of the concentrate is easily volatilized. The sulphur of the resulting matte which is combined with the iron, and With the copper as cupric sulphide, CuS, is easily volatilized at a comparatively low temperature, but it requires a high. temperaturepractically a White heatto volatilize the sulphur from cuprous sulphide, Cu S. It is usually preferred therefore to maintain the temperature of the electric furnace such that the sulphur of the iron sulphide and the cupric sulphide are quickly volatilized While avoiding the higher temperature necessary for the complete dissociation of the cuprous sulphide. The extent or the reduction of the cugrous sulphide may vary to suit the operator to get the greatest ultimate economy. There is no definite end point in the process, but the object would be to get all or nearly all of the copper in the condition of cuprous sulphide, and if circumstances indicate greater econor by coni'zinuing, the reduction so to obair. a portion of the copper in elemental form, that may al- 'o be done, as "will be described later. For the present it may be assumed that the copper after being; treated in the electric furnace is in the form of practically pure copper sulphideprincipally as cuprous sulphide. The charge in the electric furnace is treated so as to slag;- off or eliminate the iron as completely as practical.

The volatilized sulphur can be condensed and recovered a? the elemental sulphur, and the elemental sulphur Will usually be an asset in the operation.

On account 01"" the high grade of the concentrate charged into the furnace, its easy iusibilit-y, and the relatively low temperature necessary to volatilize sulphur and slag: oii impurities, the cost of smelting- Will he very low, per charge, and still relatively smaller, per pound of copper produced. The power. or electric energy required to smelt such material is quite Within good economy at ordinary prices for electricity, and vvl re power is cheap, the economy will be marked.

If the charge is smelted to cuprous sulphide. a ton of the original charoje will he concen trated into C11 3, Weighing about 1500 pounds, as a result of the elimination of; the iron l most of the sulphur. This relatively pure copper sulphide is then ground to a suitable fineness and roasted. The resulting copper oxide is then leached with, acid, pret erably vith dilute sulphuric acid, and the copper is then deposited from the resulting" pure copper sulpl ate solution as the very pure electrolytic metal.

One of the principal points in this connection is, that by eliminating; the iron by cheap smelting of the high grade concentrate. no territes or ferrates are formed in roa ting, and hence the extraction or solution of the copper from the resulting copper oxide can be made complete or practically so. The one outstanding difficulty in the treatment of copper ores or concentrates by roasting, leaching, and electrolysis, has been the mation of ferrites and ferrates in roasting, vhich makes it difiicult, if not at times impractical, to get the high extraction necessary or desired in the treatment of high, grade copper concentrate. By the method of procedure of this process, the extraction of the copper, as also the precious metals, i'roin high grade copper concentrate can he made practically complete, and the diiiiculty incident tothe formation of ferrites and ferrates, in roasting, is confined to the low grade concentrate, and will not usually large.

Another outstanding point of interest is, that with the elimination of the iron from the h gh grade concentrate, electrolytic diiii culties, due to the presence of iron in the electrolyte, are entirely avoided, or practically so, and this makes possible high eiiiciencies and smooth operation in the deposition of the copper. It also makes possible easy stripping of the waste copper solution, should it be necessary to strip solutions either on account of excess acid or relatively small amounts of impurities which may accumu late in the cyclic operation or the process.

it will he seen that with the elimination of the iron from the high grade concentrate by fusion, the resulting copper sulphide, amounting to ah three fourths of 7 i: al concentrate, is quicklyand easily roasted and quickly and easily leached with dilute sulphuric acid. This indicates a minimum roasting and leaching expense both of intion and operation. If the concentrate ins rare or precious metals they will be round in convenient form in the leached residue, from which they are easily recovered or separated.

The initial acid for leaching may be obned as such, but this will not be neces- Some of the concentrate may he roastto sulphate, and the resinting copper sulphate when electro yzed will give the acid to make the process cyclic and continuous.

The pure, or relatively pure, copper suln solution flows frointhe leaching tank o the settler, and "from the settler the clarilied copper sulphate solution flows into the le trolytic copper tanks No. 1, where the copper is deposited and an equivalent of acid is regenerated. Theoretically, by this procthe amount of acid consumed in dissolv- 3 or "from the copper OXlClG will regene ed in the deposition of the copper, so that theoretically, at least,'the process requires very little care in regulating solutions, and if the solutions are maintained at the desired copper content, an eiliciency ap preaching the theoretical should be realized in the deposition of the copper.

t is thought, therefore, that this method e5 oi procedure, involving cheap smelting, easy roasting, the elimination of iron in injurious amounts from the electrolyte, and with copper of exceptional purity as the end product, 05ers decided advantages over ordinary roasting, smelting, converting, and the refining of the resulting blister copper, and that it also offers advantages over the general hydrometallurgical process, involving roasting, leaching, and electrolysis, in the treatment oi the entire concentrate, with its atten diiliculties in roasting and leaching to get a high extraction, and the difiiculties incident to the fouling of solutions, where such fouling is undesirable.

ln trea ing the high grade concentrate in an electric furnace, it may be desirable at times, or always, to reduce some of the copper to elemental metal, altho this eleimpure. In such a mental metal will case, the impure copper from the electric furnace is cast ito anodes, and refined in the pure, or iaatively pure, electrolyte obtained from leaching the pure, or relatively pure, copper oxide resulting from roasting the pure, or relatively pure, copper sulphide. One advantage of this method of procedure would he that less power would be required to deposit the copper, in the proportion o from to .4 volt with soluble copper anodes, compared with about 1.75 to 2.0 volts for insoluble anodes. The volume or" current would he the same in both cases. f\ L a? n I v11 the ObliGi hand more power would be required in reduc the cuprous sulphide to the elemental and further disadvantage would be the exwork in casting anodes and changing them, whereas, with insoluble anodes the operation would he reduced to extreme simplicity, an-l should be preferred where the cost 01"" electric power is cheap or normal, and the alternative method where the cost of electric power is excessively high. A small amount of metallic copper in the sulphide, if fine, would he converted into the oxide by roasting, and if some of the copper is in the form of shot, it can be dissolved with ferric sulphate in the treat nent of the low grade concentrate.

The low gr-" le concentrate, assumed nine tons centa .ing 7.5% copper, is roasted with the view or making as much as possible of the copper soluble in water, and a high percentage lulne in dilute acid. It is not difficult to roast a low grade concentrate to make from '?5% to 85% or" the copper soluble in water, and from 85% to 95% soluble in dilute acid. practical, to roast copper ore or concentrate so as to niche high percentage of the cop per soluble water or dilute acid without the same time making some of the iron le. This soluble iron in the leach som is usually considered detrimental if the copper is to be deposited electrolytimetal in the electric furnace,

It is difiicult, if not im- -s electrolytically depo lted from lly free from iro l, as delactic referred to also d isle a large copper obtained .-.ro11 leachd loi grade concentra e, from U euro and rich copper solution. do this the 15 astod low .de concen- With The Water will dissolve the Wat oluble cop ,ci, as sulphate, amounting to about 75% oi the total a solu scribce, i

trate is first leached L )-\l L o The resulting copper solution can he made very rich in copper, especially sir co the vater will be hot as a reslnt hot A Water saturatea r asted concentrate. solution of copper s1 cont: in 12.93% copy l l 'e at T deg. C. Wil 1nd while the SOlL- hehly never be iilicul bout copion from one r1935 Wafer soluurated. there should taining' per. i charge ca 1 tion for t e next charge. The rich water solution of copper sulphate will be practically neutral and will not contain a great deal of iron, for, as i well known, the amount 0 water soluble iron in r asted copper ore o concentrate is sn all as compared with tha= soluble in di ute t ci The Water solution of copper sulphate from l aching the roasted low grade concenrate is flOWQ l into the water CUSQ, solution a t is treated with the relatively re copper oxice obtained "from roasting the copper sulphide from the smelting furnace. lhe iron is precipitated, While an equivalent of copper goes into solution. This rich copper solution, practically free from iron in injurious amounts, is then transferred to the electrolytic circuit for denositing copper obtained from leaching nk, Where i' L the high grade copper oxide. in this Way, under the assumed COllCllllOllS, from to oi the total copper in both the h gh grade and low grade concentrate can he oeposited as the electrolytic metal from a solu tion practically free iron". injurious impurities, and the copper so obtained should be of exceptional purity, even for electrolytic copper.

It is evident that it the copper solution obtained from leaching; the roasted lou grade concentrate with water, is transferreztl to the high grade concentrate circuit, excess acid will. be produced, since the copper dissolved as the Water soluble sulphate will, on electrolysis, re ider an equivalent of acid Without consuming acid. In order to maintain the best conditions for electrolysis for practically all of the copper deposited electrolytically, the copper solution in the cop per tank. should he as nearly normal as pos sihle in acidity and the copper content of the solution should he such as to give the highest ampere etiiciency for the current density used, and the current density under toe conditions, can he naintained fairly high.

( ennel conditions can be practically e -e l bleeding oil the excess solution, ir the solution which is too high in acid, rich should become too impure, and stri oin the copper from the bled solution er stripping tanks. It should be iinpoverish the solution in the cin tanks to as low 0.10% to .irly high ampere ciliciency duction of excellent copper. JQ-ssary nor desirable to strip as that, since the excess *e the copper from the concentrate which is not W, o s

5i i ition, impoverished in copper, transferred to the circuit for leaching the on grade concentrate to extract the er which is not soluble in Water, but iia dilute acid solution.

iii dissolve the acid soluas also a considerable amount ol 11 a1 1 other acid soluble impurities. The pper solution flows into the acid r solution tank, or reducer, Where it is orably treated with copper sulphide, preierzbly as obtained from smelting the high grade concentrate, or from recipitating copper from lean and foul solutions with hydrogen sulphide. This reduces t harm- Ale t'ul ierr c iron to the practically harmless ferrous iron, and makes practical a high current etliciency in the deposition of the copper from solutions high in iron. The impure copper solution, contai Zng salts of iron, flow-s into copper tanks No. 2, Where the copper is deposited and acid and ferr c iron are regenerated. Ferric iron is injurious largely in proportion to its presence in the electrolyte; the solution is therefore circulated in a sort of closed circuit liietvieen the solution tank, or reducer, containing copper sulphide, and the copper tanks to keep down the ferric iron. The solution issuing from the copper tanks No. 2, should not contain over 0.25% ferric iron, and this should be almost completely reouced in the solution tank, or reducer. lVhen the solution is sutficiently impoverished in copper, he resubing; acid solution, or a portion of it, is returned to the roasted low grade concentrate leaching tank N0. 2. Excess acid Will be produced in the electrolysis of the solutions obtained from treating the roasted low grade concentrate as described. If the concentrator tailing does not contain any copper as oxide (including carbonate) soluble in an acid solution, the lean solution may be treated with a precipitant, such as hydrogen sulphide, and the copper precipitated. The

solution may then be wasted.

If, however, the concentrator tailing con tains copper worth recovering at no ext acid expense, the concentrator tailing is treat-- ed, without any particular refinements, With the excess acid produced the leaching and electrolytic circuits. The resulting soiiition will be very dilute in copper and quite heavily charged with all k nds of soluble impurities. It is preferred therefore, to precipitate the cop oer from these lean and foul solu tions chemically, preferably with hydrogen sulphide. The hydrogen sulphide may be conveniently and economically generated from iron matte and the relatively pure and strong acid solution obtainedfrom electrolyzthe relatively rich and pure copper solution in the high grade concentrate circuit. The solution and the precipitate flow into the separator, where the copper sulphide pre cipitate settles very quickly. The overflowing acid solution may be wasted or returned to the concentrator tailing. leaching tank. The copper sulphide precipitate may be transferred to the solution tank, or reducer, of the low grade concentrate leaching and electrolytic circuit, Where the copper s redissolved with the reduction of ferric iron, and the re-dissolved copper is then deposited as the relatively pureelectrolytic metal.

If a portion of the copper solution from leaching the concentrator tailing is rich enough, it may be transferred to the electrolytic circuit of the low grade concentrate, and the copper deposited therefrom directly as the electrolytic metal.

If power for electric smelting is expensive, or if the high grade concentrate contains considerable amounts of impurities, it Will usually be desirable to smelt the high grade concentrate in a blast furnace to slag off most of the iron and other impurities and run the molten matte into the electric furnace for the further elimination of iron and to concentrate the copper to the condition desired. It is di licult to get the desired elimination of the iron in the electric furnace Without producing slag fairly high in copper. The high copper slag from the electric furnace is therefore returned to the blast furnace, so that the only metal loss in the slag is that in the blast furnace slag, and this will usually be quite small. If desired, air or steam may be introduced into the electric furnace to assist in the desired reactions. p

The total elimination of the iron so as to produce pure copper sulphide is probably im practical on a commercial basis, and while a chemically pure copper sulphide is not contemplated in this process, it is desirable to eliminate the iron as completely as practical, consistent with economical commercial operation. The small amount of iron remaining in the copper sulphide will largely be converted into the insoluble oxide on roasting. If a small amount of iron goes into solution on leaching, it will, or may, be precipitated out of the solution by the large amount of copper oxide, obtained from roasting the copper sulohide, which acts as a strong base. Thus the iron may be kept out of the solution, except in amounts so small as not to be noticeably injurious in the commercial deposition of the copper from the leach solution.

The tendency in leaching the practically pure copper oxide, containin perhaps var'able amounts of ooppersulphate, is to produce excess acid. Bleeding of the solution may be regulated so that the acid and impurities in the leach solution and electrolyte may be kept at a desired standard. In any event, the amount of impurities in the solution in the high grade concentrate leaching and electrolytic circuit can be kept exceedingly low.

ln eliminating iron in the electric furnace and producing as nearly practical pure copper sulphide, when the copper concen trate reaches the composition of chalcocite, @11 5, or about 80% copper, some of the copper is likely to separate out as the elemental metal. Under certain conditions it may be desirable to carry the treatment in the electric furnace so far as to obtain some of the copper in the form of sulphide and some in the form of theelemental metal. The sulphide would then be roasted and leached as described, and the elemental impure copper, or even copper sulphide containing elemental copper, would be cast into anodes, and the anodes would be refined in the relatively pure copper solution obtained from leaching the relatively pure copper oxide, resulting from roasting the relatively pure copper sulphide. The separation between the sulphide and the metal, in the electric furnace, need not be carefully made if a little sulphide get-s mixed with the copperin the anodes, it will do no particular harm, and if some finely divided copper gets mixed with the sulphide, the elemental copper, like the sulphide, will be converted into the oxide on roasting. Should any metallic copper be left in the residue after leaching, it can be returned to the electric furnace.

The production of metallic copper may be facilitated by adding high grade copper oxide to the fused high grade sulphide. The copper oxide may be obtained from roasting a high grade sulphide, obtained from roasting a high grade copper concentrate, or the high grade copper sulphide obtained from smelting. The copper sulphide and the copper oxide in the electric furnace will react to produce elemental copper and sulphur dioxide, a reaction which is well known.

Where power is expensive, the saving in power in the deposition of the copper from a soluble anodes as compared with depositing the copper with insoluble anodes, would be considerable. N o strict line of demarcation between the sulphide and metallic copper would have to be followed, but the process admits of wide variation, without much special apparatus.

If a portion of the copper sulphide is reduced to the metallic state in the electric turnace, partor the copper, on electrolysis, will be deposited from soluble copper anodes and another portion will be deposited from the leach solution with insoluble anodes. Antimonial lead anodes seem to be tl e most satisfactory for this purpose, for insoluble anodes.

In roasting the concentrated copper sulphide obtained by smelting the high grade concentrate, some copper sulphate is formed, but this copper sulphate does not interfere with the general working 01 the process. The relative amounts of copper oxide and copper sulphate in the concentrated copper oxide may be controlled in the roasting. The excess acid produced by leaching the concentrated copper oxide, including the sulphate if present and eleetrolyzing the resulting copper solution, may be used in extracting copper from lean oxidized ore, or from the concentrator tailing.

Copper ores frequently contain small amounts of rare or precious metals, which in the usual methods of treatment by solvent processes would not be worth the extra step for their recovery. In the present process the rare or precious metals will be concentrated by gravity or flotation in about the same proportion as the copper. 'lhat is to say, about 117.5% of the total precious metal content of the concentrate will be in the high grade concentrate and 1 2.5% in the low grade concentrate, under the assumed conditions. In or der to facilitate and cheapen the recovery of any residual copper and the rare or precious metals in the high grade concentrate leached residue, the residue is returned to the smelting furnace until the precious metals have accumulated sutliciently to make their recovery in elemental form most profitable, and then the leached residue is given a specia treatment for the recovery of the rare or precious metals by any of the well known methods.

By separating the concentrate into a high grade concentrate a. d a low grade concentrate, the low grade concentrate leached residue can also be treated with greater tacili y for the recover of the precious metals, especially with cyanide. Copper is astrong cyanicide, and in high grade or medium grade copper concentrate it is extremely ditficult, and highly uncertain, to get the copper leached residue sufiiciently low in copper to make economic cyaniding practical for the recovery of the precious metals. it is easily practical, however, in leaching roasted low grade concentrate, to the copper so low in the residue that cyaniding of the residue will not present any unusual ditliculty. The separation of the concentrate into a high grade and a low grade concentrate otters certain definite advantages in the recovery of the precious metals by the process described.

In leaching the roasted low grade concentrate to dissolve the water soluble copper, it may be desi able to add a little of the regenerated acid solution to the water to make a very dilute acid solution with which to dissolve the water soluble copper. This will dissolve an appreciable amount of the acid soluble copper, but only a very small extra amount oi"? the acid soluble iron. The idea would be to leach the water soluble copper with an acid solution so dilute that the solution after leaching would be neutral or nearly so, and that the small amount of iron dissolved would be precipitated with the excess, or concentrated, copper oxide. lhe iron precipitated out of the solution with the copper oxide would be redissolved by the acid leaching of the roasted low grade concentrate, but as this copper solution, containing salts of iron is electrolyzed under conditions in which the iron is not particularly harmful and may even be beneficial.

In leaching the copper leached residue in leaching tank No. 1 to extract the precious metals, it is not necessary to make a close extraction of the precious metals if the leached residue is returned to the smelting furnace, since the residual copper and rare or precious metals will be recovered in a new matte or copper sulphide, so that the only metal loss would be that in the slag from the smelting furnace and that escaping as fume.

I claim:

1. A process comprising, treating copper ore to separate a high grade and a low grade copper concentrate, roasting the low grade concentrate, smelting the high grade concentrate to produce highly concentrated copper sulphide, roasting the concentrated copper sulphide to produce concentrated copper oxide, leaching a portion oi": the concentrated copper oxide with an acid solution to extract the cooper, electrolyzing the resulting copper solution to deposit the copper and regenerate acid, returning the regenerated acid solution to the concentrated copper oxide, leaching the roasted low grade concentrate to extract av portion of the copper, treating the resulting copper solution with a portion 01"? the concentrated copper oxide, and elect-rolyzing the resulting purified copper solution with the copper solution obtained from leaching the concentrated copper oxide;

Inn

2. A process comprising, treating copper ore to separate a high grade and a lou grade p concentrate, roasti g the low grade conicntrate to malre a portion of the copper mater soluble and a portion a d soluble, smelting the high grade conccn to proluce nghly concentrated ,coppi sulphide, ti e concentrated copper sulphide to 1 "nice trated copper oxide, leaching ncentrated copper oxide With. an acid t. to extract the copper, electrolyzingi he resulting copper solution to deposit the opper and regenerate acid, returning, the re {encrated acid solution to the concentrated op er oxide and repeating the cycle, leach- 11g the roasted low grade concentrate to exra ct the Water soluble copper, and adding the wet r soluble copper solution to the concencopper oxide leaching and electrol' tic cry A process comprising, treating copper ore to separate a high grade and a low grade concentrate, roasting the low grade concentrate, sine ting the high grade concentrate to produce concentrated copper sulphide, roasting the concentrated copper sulph de to produce concentrated copper oxide, separately leaching the roasted lowgrad concentrate and the concentrated copper oxide, adding the richer and purer portion of the copper solution resulting from leaching the roasted low grade concentrate to the richer and purer solution obtained from leaching the concentrated copper oxide, and eiectro-lyzing the solution.

4:. A process comprising, treating copper ore to separate a high grade and a low grade concentrate, roasting the low concentrate, smelting the high grade concentrate to produce concentrated copper sulphide, roasting the concentrated copper sulphide to produce concentrated copper oxice, separately leaching the roasted low grade concentrate and the concentrated copper oxide to extract t 1e copper, electrolyzing the richer and purer copper solution obtained from leaching the roasted low grade concentrate and the concentrated copper oxide in one electrolytic circuit, and electroi uzing the relatively lean an l impure copper solution obtained from leacl the roasted low grade concentrate and the concentrator copper oxide in another electrolytic circuit.

A process comprising, treating copper ore to produce a copper concentrate, smelting the concentrate to matte, treating the matte to eliminate sulphur and slag oil iron so as to produce a concentrated copper sulphide, roasting a portion or" the concentrated copper sulphide to produce concentrated copper oxide, leaching the concentrated copoxide to extract the copper, electrolysing the resultin copper solution to deposit the Lw 0 copper and regenerate acid, treatmg another portlon of the concentrated copper sulphide *rodcs in the copper solution obtained from leach r t 1e concentrated copper oxide.

6. A. proce. s comprising, smelting copper o centrate to matte, treating the matte to etminate lphur and iron as to produce concentrated copper sulphide, roasting a por .tion out the concentratedcopper sulphide to croouce concentrated copper oxide, leachinga portion or the concentrated copper e: do to extract the copper, electrolyzing the resulting copper solution to deposit the copper and regenerate acid, applyinga portion of the concentrated copper oxide to a portion of the heated copper. sulphide to eliminate sulphur so as to produce impure metalliccopper, casting the resulting impure metallic copper into anodes, and electrolytically refining the anodes with the copper solution obtained from leaching a portion of the concentrated copper oxide.

7. A process comprising, treating copper ore to separate a high grade and a low grade copper concentrate, roasting the low grade concentrate, leaching the roasted low grade concentrate to extract the copper, smell-i the high grade concentrate to proouce conceitrated copper sulphide, roasting the con- 1 copper sulphide to produce copper centrateo oxide, applying the copper oxide to the copper solution obtained from leaching the roasted low grate concentrate, and clectrolyzing the solution.

8. A process comprising, treating copper ore to separate a high grade and a low grade copper concentrate, roastingthe low grade concentrate, treating the high grade concentrate to convert a portion of the copper to the concentrated copper oxide and a portion. to the impure metallic copper, leaching the roasted low grade concentrate to extract the copper, treating the resulting copper solution With the concentrated copper oxide and refining the impure metallic copper in the copper solution the electrolyte.

9. A process comprising, separating copper ore into ahigh grade and a low grade copper concentrate, roastin the low grade concentrate, to make a portion of the copper Water soluble and a portion acid soluble, leaching the roasted low grade concentrate to extract the Water soluble copper, smelting the high grade concentrate to produce concentrated copper sulphide, roasting th concentrated copper sulphide to produce concentrated copper oxide, applying the concentrated copper oxide to the Water soluble copper solution to precipitate iron and other imp rities from the solution, and electrolyzing the purified solution to deposit the copper.

10. A process comprising, treating copper ore to separate a high grade copper concena low grade copper residue, treating gn grade concentrate to produce conccntrated copper oxide, leaching the concentrated copper oxide with an acid solution to extract the copper, electrolyzing the cop or solution to deposit the copper and regenerate acid, treating metal sulphide With the regenerated acid solution to produce hydrogen sulphide, and precipitating copper from lean or foul solutions with said hydrogen sulphide.

11. A process comprising, treating copper ore to separate a high grade copper concentrate and a low grade copper residue, smelting the hi l grade concentrate to produce concentrated copper sulphice, roasting the concentrated copper sulphide to produce concentrated copper oxide, leaching the concentrated copper oxide with an acid solution to extract the copper, electrolyzing the copper solution to deposit the copper and regenerate acid, and applying the regenerated acid solution to the low grade copper residue to extract the copper therefrom.

12. A process comprising, treating copper ore containing rare or precious metals to separate a high grade and a low grade copper concentrate, smelting the high grade concentrate to obtain concentrated copper sulphit e, roasting the concentrated copper sulphide to obtain copper oxide, leaching the copper ide to extract the copper, returning the leached residue to the smelting furnace and repeating the cycle until the residue is de sirably enriched in the rare or precious metals, and then treating the residue to recover the rare or precious metals.

13. A process comprising, smelting copper concentrate containing precious metals to concentrate the precious metals into concentrated metal sulphide, roasting the concentrated metal sulpnide, leachin the resulting roasted material to extract the copper, smelting the leached residue to concentrate the precious metals and residual copper into an impure concentrated copper product, and electrolytically refining the impure concentrated copper product to separate the precious metals and recover the copper as the electrolytic metal.

1%. A process comprising, treating copper ore to produce a copper concentrate, roasting a portion of the concentrate, leaching the roasted concentrate to extract portion oi? the copper so as to obtain a relatively pure and relatively rich copper solution, then separately leaching the roasted concentrate to extract the remaining copper and thus obtaining a relatively lean and relatively impure copper solution, smelting another por-- tion of the concentrate to produce an impure concentrated copper product, casting the impure concentrated copper product into an odes, and refining the anodes with the rel: tively pure and-relatively rich copper solution obtained from leaching the roasted copper concentrate as the electrolyte.

15. A process of treating copper concentrate comprising, smelting the concentrate to matte, electrically heating the matte to dissociate the sulphur and iron so as to produce concentrated copper sulphide, roasting a por tion of the concentrated copper sulphide to produce concentrated copper oxide, and adding the concentrated copper oxide to the electrically heated copper sulphide to eliminate more sulphur.

16. A process comprising, treating copper ore to separate copper concentrate, roasting a portion of the concentrate to make a portion of the copper Water soluble and a portion acid soluble, leaching the roasted concentrate to first extract the Water soluble copper and then leaching the roasted concentrate to extract remaining acid soluble copper, separately precipitatin the copper from the Water soluble and from the acid soluble copper solutions, smelting another portion of the concentrate to produce a highly concentrated fused copper product, casting the highly concentrated fused copper product into anodes, and electrolytically refining the anodes in the water soluble copper solution obtained from leaching the roasted concentrate.

17. A copper extraction process comprising, treating copper ore to separate a high grade and a low grade copper concentrate, roasting and leaching the low grade concentrate to extract the copper, smelting the high grade concentrate to produce concentrated copper sulphide, electrically heating the concentrated copper sulphide, adding concentrated basic oxide to the electrically heated copper sulphide to eliminate the sulphur and to produce impure metallic copper, castii'ig the resulting impure metallic copper into anodes, and electrolytically refining the anodes.

WILLIAM E. GREENAWALT.