US3463630A

US3463630A - Process for producing zinc and related materials

Info

Publication number: US3463630A
Application number: US531503A
Authority: US
Inventors: Lamar S Todd
Original assignee: LAMAR S TODD
Current assignee: LAMAR S TODD
Priority date: 1966-03-03
Filing date: 1966-03-03
Publication date: 1969-08-26
Anticipated expiration: 1986-08-26

Description

Aug. 26, 1969 Filed Marclh 5, 1966 L. S. TODD PROCESS FOR PRODUCING ZINC AND RELATED MATERIALS Sheets-Sheet 1 ZINC Cu .5 M67725)? Q) ow mflcra? Z/A/c Z/A/C con/051x55? 2 EI/fl/DPW SVAQOP/JCVS .9 a/vLs I upu/a INVENTOR.

ATTORNEYS Aug. 26, 1969 Filed March 8; 1966 1.. 5. won

PROCESS FOR PRODUCING ZINC AfiD RELATED MATERIALS 5 Sheets-Sheet 3 INVENTOR BY M4 ATTORNEYS.

L- S. TODD Aug. 26, 1969 PROCESS FOR PRODUCING ZINC AND RELATED MATERIALS Filed March 5. 1966 3 Sheet-Sheat 3 R N vb INVENTOR warn-$3 k w E mini Rum stmvw ATTORNEY-5f United States Patent RELATED 14 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a new process for the treatment of complex sulfide substances to make high value metallic end-products. The process accomplishes this by reducing the mineral sulfide with molten copper in the metal extractor to make molten cuprous sulfide matte and a molten copper alloy of the metal being reduced. The matte goes to a converter where it is reacted with gaseous oxygen to make molten copper and gaseous sulfur dioxide. The molten copper is returned to the metal extractor. The copper alloy made by the sulfide reduction in the extractor goes to an evaporator where the volatile metal is evaporated from the molten copper alloy and the resulting molten copper goes to the converter. Any metal can be produced by this process if the metal sulfide can be reduced by copper and the metal has a lower boiling point than copper. Two or more metal sulfides can be simultaneously reduced in the metal extractor to make a copper alloy containing copper and two or more metals. One or more of the metals can be volatilized from the complex copper alloy in a metal evaporator. The volatile metals can be separated by fractionation and condensation.

This invention relates to the metallurgy of a process for the separation of the elements in a complex sulfide mixture. More particularly, the invention concerns a pyrometallurgical process for the extraction of zinc and other materials from substances that are rich in zinc sulfide like a sphalerite ore concentrate.

The most common zinc mineral of commercial value that occurs in nature is sphalerite which is a zinc sulfide (ZnS). It can occur in sufficient concentrations of about 5% or more to be classed as zinc ore or it can be a lesser constituent of complex multisulfide mineral deposits.

The raw material for Zinc production processes is usually a relatively pure zinc mineral. This requires that the zinc mineral has to "be removed and concentrated from the ore. This is commonly efiected by grinding and flotation or some other type physical concentrating or upgrading. The endproduct sphalerite ore concentrate is usually about 90% zinc sulfide. The remaining percentage is typically made of minerals like covellite (CuS), chalcocite (C11 5, galena (PbS), pyrite (FeS pyrrhotite (FeS), greenockite (CdS), lime (CaO), silica (SiO gold (Au), and silver (Ag). The substances can occur as separate crystals or complex homogeneous mixtures.

All commercial metallic zinc production processes require the presence of zinc oxide (ZnO) as an intermediate step. Therefore, the sphalerite ore concentrate must be changed to zinc oxide. This is commonly brought about by roasting (combustion in air) by the following reaction:

3,463,630 Patented Aug. 26, 1969 This reaction is quite exothermic but it is difficult to apply this energy directly to other endothermic metallurgical processes required for zinc production. The gas that is produced is quite often used to produce sulfur chemicals like sulfuric acid.

There are two basic commercial processes for producing metallic zinc from the oxide: pyrometallurgical and electrolytic. Each process has advantages and the proper choice is made after economic evalution of many factors.

The pyrometallurgical process is based upon the reduction of zinc oxide with carbon at about 1100 C. as according to the following reaction:

ZnO+C- Zn+CO (2) Zinc vapor is condensed from the resulting gas stream. The reaction is endothermic and requires the application of energy by means of external combustion heating of the reactor, internal electric resistance heating, or electric arc heating. The zinc blast furnace developed by Imperial smelting, Ltd. of England does use internal combustion of coke as a source of energy but coke is relatively expensive and much of it is incompletely burned to carbon monoxide. The resuting metallic zinc contains sufficient lead and cadmium to limit the general commercial usefulness and application of this product.

The evaporation of impure zinc and the subsequent fractionation of the resulting vapors will produce some of the most pure zinc known to mankind. The New Jersey Zinc and the Amex refining processes have been developed to purify the zinc produced by the zinc oxide-carbon reactions. The resulting products are high purity zinc, a lead-iron rich residue, and a cadmium-rich zinc alloy.

The electrolytic method uses direct currentto decompose an aqueous zinc sulfate solution and deposit high purity zinc upon plates suspended in the solution. Sulfuric acid is also made in the electrolytic cell and it is used to dissolve more roasted sphalerite. Occasionally, some of the residues or solution of this process are treated1 for metal recovery with cadmium being of principal va ue.

There is an important point to consider when metals are recovered from a complex sulfide ore that contains significant quantities of zinc, copper, lead, and iron. Copper, lead, and zinc metals are produced by diflerent metallurgical processes. When one of these metals is being produced, the other metals are looked upon as impurities which require additional processing or refining steps to remove. It would be industrially desirable to recover all of these metals from a complex sulfide ore concentrate with a single simple process. Since the metals that are being treated are not of great value, some ores and concentrates cannot be commercially utilized or their sale value is penalized unless the initial physical separation of the mineral sulfides is good.

The object of this improvement is the disclosure of a new, improved, and novel process for the treatment of complex sulfide substances to make high value metallic end-products. The process accomplishes this by reducing the mineral sulfide with molten copper in the metal extractor to make molten cuprous sulfide matte and a molten copper alloy of the metal being reduced. The matte goes to a converter where it is reacted with gaseous oxygen to make molten copper and gaseous sulfur dioxide. The copper goes back to the metal extractor. The copper alloy made by the sulfide reduction goes to an evaporator where the volatile metal is evaporated from the molten copper alloy and the resulting molten copper goes to the converter. Any metal can be produced by this process if the metal sulfide can be reduced by copper and the metal has a lower boiling point than copper. The copper alloy can contain more than two metals.

The procedure involved in carrying out the improvement according to this invention may be most clearly understood by reference to the accompanying drawings in which:

FIG. 1 shows an arrangement including a converter, a zinc extractor, a zinc condenser and a zinc evaporator in which there is a countercurrent flow between the zinc extractor and the converter;

FIG. 2 shows the maximum solubility of sulfur in brass in percentage as compared to the percent of zinc in a brass composition and the temperatures at which the products were obtained;

FIG. 3 shows the ratio of the percentage of zinc in brass and the percentage of Zinc in the matte and the temperatures at which certain results were obtained; and

FIG. 4 shows a flowsheet for the treatment of a sphalerite ore concentrate. The principal mode of movement of some of the major elements from the extractor is shown. The flow sheet shows the use of the converter gases to heat the extractor in treating solid sphalerite. A copper alloy is produced from which copper and brass may be obtained. All materials are liquid unless otherwise noted.

The subject matter of the four figures will be discussed in further detail later in this specification.

The basic fiowsheet of the process to make zinc is given in FIG. 1. The diagram shows the movement of the materials including their physical state and the four basic operations. Note that copper and cuprous sulfide serve as intermediates within the process and are recycled. Copper does not have to be consumed as a raw material or produced as a product of the overall process. For simplicity, the process is described by the use of zinc sulfide. Materials that are rich in zinc sulfide such as a sphalerite ore concentrate can be used to make zinc by the invention.

A balanced chemical equation for the overall process is given below:

Oxygen appears to serve as the reducing agent instead of carbon or direct current electricity as in commercial processes. If oxygen (air) is reacted directly with zinc sulfide without the use of the copper intermediate, roasting will occur to produce a less valuable product. This is a unique improvement in zinc pyrometallurgy.

The zinc extractor is the most unusual unit in the process and the two simultaneous reactions that occur in it are as follows:

Reaction 4 is the reduction and reaction 5 shows the formation of brass with an excess of copper. The formation of brass prevents the boiling of the zinc (the boiling point of pure zinc is 907 C. at 760 millimeters of mercury). The cuprous sulfide product contains unreduced zinc sulfide and the brass contains a small amount of dissolved sulfide. These factors are a function of the zinc content and temperature. FIGS. 2 and 3 show graphi cal information on the maximum solubility of sulfur in brass and the ratio of zinc between the brass and matte respectively. These two figures are taken from the MS.

Crr -l-Zne Brass 4 thesis The Boundaries and Tie-Lines of the Two-Liquid Field of the Copper-Zinc-Sulfur Ternary Diagram by Lamar S. Todd, University of Arizona, 1964.

To facilitate the production of a brass with the highest zinc content and a matte (mixed sulfide) with the lowest zinc content, the zinc extractor will be operated in a countercurrent manner. The copper and zinc sulfide are fed into the opposite ends of the zinc extractor. The zinc extractor would be a long refractory-lined trough with baffles placed in it to increase the length of flow. The solid zinc sulfide that is added to the zinc extractor forms a slurry with the matte that is already present in the reactor. As the slurry moves down the trough, the solid zinc sulfide disappears. The brass of intermediate zinc content becomes richer in zinc as it flows in the opposite direction of the slurry. The brass at maximum zinc content is removed from the end extraction reactor. Even though the solid zinc sulfide is removed from the matte slurry, it is desirable to reduce the dissolved zinc sulfide in the matte. Therefore, the matte continues within the same unit to move counter current to a stream of copper that has been added to the extractor. The copper forms a brass of intermediate zinc content as the copper flows opposite to the matte. The end-products of the extraction are brass and an essentially pure cuprous sulfide.

There are several factors to be considered for the proper operation of the zinc extractor. It is desirable to make a brass of as high a zinc content and of as low a sulfur content as possible. The cuprous sulfide matte leaving the zinc extractor should contain as little zinc in the sulfide as possible. FIG. 3 shows that higher temperatures favor the zinc going into the brass because the ratio of zinc in the brass to zinc in the matte is larger. For example, by careful examination of the data in FIG. 3, the ratio of the zinc in the brass to zinc in the matte improves from 1.8 at 1125 C. to 2.0 at 1250 C. when the zinc content of the brass is 2.0%. The data in FIG. 2 shows that lower temperatures decrease the sulfur content of the brass. For example, for a brass that contains 10% zinc, it will dissolve 1.11% sulfur at 1200 C. and 0.92% sulfur at 1150 C. In summary, the data shows that for optimum operation, the copper inlet of the zinc extractor can and should be at a higher temperature than that of the brass efiluent. This means that superheated copper and/ or the flame from fuel combustion and/ or hot gases can be applied to the copper inlet end of the brass extractor. The copper and/ or gas will become cooler as they/or it fiows through the zinc extractor because of the endothermic reduction and by heat losses from the equipment.

Data from test runs shows that the optimum temperature of the brass leaving the zinc extractor should be about 1200 C. The brass can contain between 1% and 17% zinc. A typical brass should contain about 13% zinc and 1.0% sulfur. Brass with significant amounts of Zinc can be made at 1125 C. to 1250 C. Brass can be made at temperatures up to 0 C. but the zinc percentage is small. The cuprous sulfide matte product should contain about 1% zinc.

The brass that is made in the zinc extractor is treated in the zinc evaporator to remove the zinc content by volatilization. This unit takes advantage of the fact that zinc has a significant vapor pressure in brass. The minimum operating pressure should be 0.15 millimeter of mercury because at lower pressures, the zinc will solidify in the condenser. The inlet temperature of the brass should be sufiiciently high to keep it molten and the exit temperature must be above the 1083 C. melting point of copper. The copper product should contain about 0.5 zinc.

The use of a vacuum on the zinc evaporator allows the unit to operate at temperatures approaching the melting point of copper and it would consume less energy than a unit operating at atmospheric pressure. The brass enters and the copper leaves the unit continuously through barometric legs. Zinc would leave the unit continuously as the vapor. The brass must be heated to effect the evaporation of the zinc. This is best accomplished by causing the brass to flow through a long channel which is heated by passing electricity through the metal. The cross-sectional area of the channel is varied to control the heat generated in the various portions within it. About 1200" C. is a good operating temperature for this unit.

The zinc can be evaporated from brass at atmospheric pressure as described in U.S. Patent No. 2,429,584, This unit consumes large amounts of electricity because temperatures of 1650 C. must be maintained to make copper containing 0.5% zinc from brass. If this type of unit is used in the process described in this patent, it is best to send the copper to zinc extractor instead of the converter as shown in FIG. 1. This is done because of the high zinc content and the temperature of the copper. It is best to add this copper at some intermediate point in the zinc extractor and add the copper from the converter to the end of the zinc extractor. This copper enters the zinc extractor at an intermediate point between the ends because it is best to have the very low zinc copper from the converter contact the matte as the matte is leaving the zinc extractor.

There is an approach to the zinc evaporation that is a combination of the two previous alternatives that is potentially the very best method. It consists of two units that operate in series at different pressures and temperatures. The first unit obtains the brass from the zinc extractor and heats the brass to about 1400 C. at atmospheric pressure to evaporate part of the zinc. The brass of intermediate zinc content made by the previous unit is then passed into a vacuum vessel where the residual zinc flash evaporates. No energy is added to the vacuum vessel because the lowering of the temperature of the copper supplies the energy for the zinc evaporation. The copper goes to the converter. This approach makes eflicient use of the electrical energy and does not require that heating be done in the vacuum evaporator.

The zinc condenser changes the zinc vapor to liquid by lowering the temperature of the vapor. Liquid zinc is removed from the condenser.

The copper of the cuprous sulfide matte that is produced from the zinc sulfide reduction in the zinc extractor must be recovered to make the process economically feasible. To those acquainted with the art of copper smelting, converting is used to make copper from copper matte. An oxygen-bearing gas which is customarily air is brought in contact with the matte and the following reaction occurs:

This reaction is mildly exothermic and it is brought about in a horizontal refractory-lined cylinder of which the Peirce-Smith is a common type. The unit operates on the batch principal and the unit rotates on its axis during the operating cycle. Air enters the molten bath through ducts (tuyeres) that exit the gas below the surface of the bath. A converter has operated at Messina in the Union of South Africa that uses a stationary hearth.

A stationary continuous converter is the best unit to use for the invention described herein because the converter could accept various materials continually and it would make more efficient use of the heat generated. It probably is necessary to use oxygen or oxygen-enriched air for the converter because a high temperature must be maintained, the copper from the zinc evaporator will cool the converter, and little iron will be present in the matte. Water-cooled lances are used for injecting the oxidizing gas into the bath. The converter should operate at as high a temperature as possible. The temperature required for the copper product and the attack of the converter lining are the two principal items to be considered in selecting a temperature. Operating temperatures of up to 1350" C. should be easily obtained with temperatures of up to 1600 C. The high temperatures and large volumes of oxidizing gas will cause the residual zinc in the copper from the zinc evaporator and matte from the zinc extractor to volatolize and oxidize to a zinc oxide fume. The zinc oxide can not be readily recovered or changed to metal by the process. Therefore, the production of zinz oxide should be minimized and the best method of accomplish ing this is to prevent zinc from entering into the converter. A rich continuous high temperature stream of sulfur dioxide bearing gas will be produced. This gas will be a good source of heat and sulfur dioxide for chemicals. The gas could be used to heat the zinc extractor or waste heat boilers.

It should be noted that all of the materials within the process are liquid or gases. This means that continuous transfer of these materials between units of the invention should be simple. A pump should be placed in the system for the continuous movement of copper or brass. The best position for the pump is between the zinc extractor and the zinc evaporator. The vapors or gases in the process will readily move by creating a pressure differential. One distinct improvement of the invention is accomplished by direct attachment of the converter and the zinc extractor. This would greatly simplify the transfer of copper, matte, converter gas, and slag between the zinc extractor and the converter. Those acquainted with the art of commercial copper converting realize that the liquid and solid feed and the products of a converter are moved separately in batches.

As an example according to which the process may be conducted, the following details of procedure have been satisfactorily followed.

Examples were made by mixing copper shot or powder and zinc sulfide powder. This charge was placed in a cylindrical graphite crucible and covered with charcoal to prevent oxidation. The crucible was placed i a splittube graphite resistance furnace for heating. The temperature was taken with an optical pyrometer from the top. After reacting, the crucible was removed from the furnace and the contents poured into another graphite crucible at room temperature. After cooling, the samples were sectioned and polished for microscopic examination. There was a sharp line that separated the brass and matte phases. The following data was obtained on several samples:

Zinc sulfide (g 19. 48 14. 61 4. 87

Cuprous sulfide 31. 83

Temperature 0.)- 1, 1G01,220 1,165-1, 200 1,1901,450

Time in furnace (min) 70 Final wt. (g.)- 63. 69 75. 71 Brass analysis:

Copper (percent) 87. 7 87. 93. 9

Copper (percent) 56. 7 71.8 80.1

Zinc (percent) 19. 2 9. 2 9

Sulfur (percent) 23.0 22. 4 20. 8

No. 1 was solidified in a fireclay crucible instead of a graphite crucible.

It is discovered by sample #2 that a brass containing about 13% zinc can be made at about 1200" C. It is also discovered that brass of low zinc content can be made at temperatures up to 1450 C. The separation of the brass and the matte phases is excellent as was observed after sectioning. Therefore, each phase can be readily withdrawn from the zinc extractor and treated. It should be noted that the reaction does not extract all of the zinc into the brass from the zinc sulfide in a single batch-type reaction.

Additional samples were carefully prepared to support the data found by samples 1-3. The first step was to prepare a matte of copper and zinc sulfide. The combinations of copper, zinc, and brass were reacted with the matte in a horizontal graphite capsule. The capsule was cooled very rapidly after reacting to preserve the composition of the two phases that existed in the sample preparation temperature. Data on the preparation and properties of important samples are given below:

Matte preparation:

Fused granular Cuzs (g.) 1. 35 3. 25 1. 35 2.50 Powdered CuS (g.) 90 .05 90 Powdered ZnS (g.) 90 O5 .90 Temperature C.) 1, 325 Time (hrs.) :15 :15 :15 Final weight (g.) 2. 88 3. 26 2. 89 Sample preparation:

Matte (g.) 2. 79 3. 27 2. 77 N 0. Cu wire (g.) S. 92 9 Fine granular Cu (g.) 9. 12 .48 9. 31 26 20 mesh Zn (g.) .10 13 Temperature 0.)... 1, 200 1, 250 1, 250 1,125 1, 125 Time of treatment (hrs.) 1: :48 :33 2:29 1:30 Final Weight g. 12. 76 11. 79 12. 805 12. 09 Cleaned brass weight (g.)..- 8. 94 9. 8715 9. 2596 7. 563 9. 779 Brass composition:

Percent zinc 17. 12 1. 18 16. 84 7. 68 1. 54 Percent copper- 81. 83 97. 19 82. 20 91. 19 97. 34 Percent sulfur. 0. 84 1. 12 1. 00 0. 92 1. O4 Matte composition:

Percent. zinc. 18. 93 0. 56 16. 68 5. 70 O. 80 Percent copper 58. 19 79. 87 60. 75 73. 59 79. 35 Percent sulfur 21. 58 19. 46 22. 31 20. 99 19. 68

These samples and others prepared in a similar manner were used to construct FIGS. 2 and 3.

Samples 4 through 8 show more accurately the composition of the phases that would occur in the zinc extractor. The data shows that brass can be made down to a temperature 1125 C. E. Strohfeldt (1936) published some data on samples prepared in a manner similar to the samples indicated in this improvement 'but at 1550- 1600 degrees.

Improved operating conditions for the invention were discovered by the samples described above. He claimed to have prepared a brass containing 22.7% zinc.

The various examples are only batch reactions but the data shows that continuous countercurrent liquidliquid extraction can occur which will concentrate the Zinc in the copper to make brass.

The zinc production process can be modified to produce a low sulfur brass if copper-bearing raw materials are used and another unit is used. It has been discovered that the brass that is produced by the zinc extractor can be refined to lower the sulfur content. The refining action is brought about by cooling between the temperatures of 1250 C. and 1125 C. as is shown by FIG. 2 and will continue down to the melting point of the brass. The excess sulfur will float to the top of the melt as a mixed copper-zinc sulfide and form a separate phase which would be returned to the zinc extractor. This refining action is observed in samples 1 and 2 because the sulfur contents are lower than the values given in FIG. 2 for the corresponding reaction temperatures and zinc concentrations. The residual sulfur content of the refined brass could be lowered by adding a metal that will reduce copper or zinc sulfide. The brass refining operation and unit could be used with the zinc production process to decrease the amount of sulfur going into the zinc evaporator.

There are many other elements that occur in a sphalerite ore concentrate which are of value. One of the major improvements of this invention is that it can recover other metals. Most other zinc production processes do not recover other elements readily, the elements are recovered as complex mixtures of compounds of low value, or the efficiency of the recovery is low. This process will recover most of the principal metals in a complex sphalerite ore concentrate as pure metals, fairly pure metals that could be refined, or alloys which would be of high value on the commercial market.

Cadmium can be extracted from a sphalerite ore concentrate. The two simultaneous reactions for reducing cadmium sulfide in the metal extractor are given below:

CdS +2Cu- Cu S +Cd (7) Cd-l-Brass Cadmium-bearing Brass (8) Pb+Brass- Lead-bearing-Brass The lead can volatilize from the alloy in the metal evaporator with difliculty. Lower vacuums and/ or higher temperatures might be necessary to remove the residual lead from the copper.

The purity of the zinc, lead, or cadmium depends upon the design of the fractionation unit. The zinc, lead, and cadmium that are produced are materials whose major component is one of these metals.

Copper is readily recovered from a sphalerite or concentrate. The copper sulfide minerals that enter the zinc extractor are not reduced to metallic copper but leave with the matte. The matte is then reduced to copper in the converter. The excess copper that is produced can be removed from the converter or the excess copper can be passed back through the metal evaporator and then removed from the process as copper. Copper can be removed from the system as brass.

Iron is one of the more common elements in a sphalerite ore concentrate. It is not Worth recovering as the metal but it does serve several very useful purposes. Iron is of essentially no value in other commercial zinc production processes. The iron sulfide in the matte will tend to preferentially oxidize, therefore, it will protect the zinc sulfide from oxidation by the gases in the metal extractor. If zinc oxide is formed or enters the metal extractor with the sphalerite, the following reaction will generate zinc sulfide:

ZnO-l-FeS- ZnS+FeO (11) In general, most of the iron sulfide that enters the process will be carried along with the matte and become oxidized in the converter. This oxidation will generate heat which is desirable. For the high temperature operation of the converter, it will be necessary to decrease the silica in the converter slag and increase the magnetite content to decrease the attack on the refractories. The slag will be removed from the converter periodically to prevent accumulation.

The gold and silver can be classed together because they react in a similar manner. Neither element will oxidize out of the copper in the converter and only silver will show a slight tendency to vaporize in the evaporator. This means that gold and silver will accumulate in the system. Copper can be removed from the process and electrolytically refined to recover these and other precious metals.

Small amounts of calcium, aluminum, and silicon oxides are present in sulfide mineral concentrates. These and related oxides will tend to float to the top of the matte in the metal extractor and form a slag. This slag is of some value because it will decrease zinc volatility in the metal extractor and it will help prevent the reaction of the brass and matte with the metal extractor gas atmosphere.

There are many improvements in the invention described herein compared with commercial zinc production processes. Some of the advantages are listed below:

(1) The process produces many metals or alloys from a complex sphalerite-bearing o're concentrate. Some of the metals are zinc, cadmium, and lead. The alloys are brass and copper containing gold and silver.

(2) Many metals are separated from a complex sphalerite-bearing ore concentrate in a few units.

(3) All of the materials within the process are liquids or gases and therefore can easily be transported.

(4) No reducing agents such as carbon or direct current electricity is required. Oxygen appears to be the reducing agent.

(5) The theoretical energy requirements for the reduction of zinc sulfide are much less than for the principal reducing reaction in commercial zinc production processes.

(6) The labor costs for the process should be relatively low.

(7) The process has the potential of being highly automated.

I claim:

1. A process for producing metals from a mixture of metal sulfides including zinc sulfide, lead sulfide, cadmium sulfide, and copper sulfide, which process comprises passing said mixture of metal sulfides through a metal extractor wherein the said mixture is contacted with molten copper to form a phase of alloys of the zinc, lead and cadmium with copper and a phase of copper sulphide, removing the copper sulphide phase from said metal extractor and treating it with oxygen in a converter whereby the copper is recovered, returning the recovered copper to the metal extractor, removing the copper alloy phase from the metal extractor, passing said alloy phase through a metal evaporator unit wherein the more volatile metals are vaporized, passing the volatilized metals to a fractionation unit wherein the volatilized metals are separated, and separately discharging the metals from said fractionation unit, and returning the residual liquid copper phase from said evaporator unit to said metal extractor.

2. A claim of the type defined in claim 1 in which a sphalerite ore concentrate is used as the mixture of metal sulfides and zinc is discharged from the fractionation unit.

3. A claim of the type defined in claim 1 in which a sphalerite ore concentrate is used as the mixture of metal sulfides and vaporized zinc from said fractionation unit is condensed.

4. A claim of the type defined in claim 1 in which a sphalerite ore concentrate containing lead is used as the mixture of metal sulfides and zinc and lead are separately discharged by the fractionation unit.

5. A claim of the type defined in claim 1 in which a sphalerite ore concentrate containing cadmium is used as the mixture of metal sulfides and zinc and cadmium are separately discharged by the fractionation unit.

6. A claim of the type defined in claim 1 in which a sphalerite ore concentrate containing copper serves as the mixture of metal sulfides, and zinc is discharged from the fractionation unit and excess copper is removed from said copper alloy phase.

7. A claim of the type defined in claim 6 with the excess copper being removed from the copper discharged from said evaporator unit.

8. A claim of the type defined in claim 1 in which a sphalerite ore concentrate containing lead, cadmium, and copper is the mixture of metal sulfides, and the metal extractor is operated with recovered copper from said converter and said mixture of metal sulfides being fed thereto in counter current manner at about 1200 C.

9. A claim of the type defined in claim 1 in which a sphalerite ore concentrate containing lead, cadmium, and copper is the mixture of metal sulfides, and the metal extractor is operated with recovered copper from said converter and said mixture of metal sulfides being fed thereto in countercurrent manner in the range of 1125 C. to 1450 C.

10. A claim of the type defined in claim 9 in which the copper alloy phase that is produced by the metal extractor contains about 13% zinc.

11. A claim of the type defined in claim 9 in which the copper alloy phase that is produced by the metal extractor contains 1% to 17% zinc.

12. A claim of the type defined in claim 9 in which the copper inlet portion of the metal extractor is at a higher temperature than the copper alloy phase exit.

13. A claim of the type defined in claim 1 in which the copper from the evaporation unit is fed to the converter from which it passes to the metal extractor.

14. A claim of the type defined in claim 1 in which a sphalerite ore concentrate serves as the mixture of metal sulfides and the vaporized metals discharging from the said evaporator unit are condensed to make impure zinc.

References Cited UNITED STATES PATENTS 807,271 12/1905 Imbert -86 X 894,383 7/1908 Imbert 75-86 X 1,002,037 8/1911 Clerc 75-86 1,749,126 3/1930 Bunce et al. 75-86 L. DEWAYNE RUTLEDGE, Primary Examiner HENRY W. TARRING II, Assistant Examiner US. Cl. X.R.