cuprex process
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Overview
The Cuprex Metal Extraction Process: Recovering Copper from Sulfide Ores
R.F. Dalton, G. Diaz, R. Price and A.D. Zunkel
The Cuprex™ metal extraction process produces cathode-grade copper using a hydrometallurgical process based on chloride leaching of sulfide ore concentrates. The process incorporates several novel steps to overcome the major problems associated with earlier chloride-based processes, including mild leaching conditions usingferric chloride as leachant and solvent extraction of copper using a novel reagent. This produces a highly concentrated cupric chloride electrolyte from which cathode-grade copper is electrowon in the Metclor cell. The technical viability and robustness of the core technology have been proven in a series of large-scale pilot trials. More recent work has concentrated on supplementary processes to convert the copper powder product to an article of commerce and to recover valuable by-products. A fully integrated scheme is now being developed with updated cost estimates.
INTRODUCTION
Recent years have seen a considerable increase in activity in the development of hydrometallurgical processes. There are a number of reasons for this increase. For example, hydrometallurgical procesSes permit the recovery of metals from lower-grade feedstocks, are often more environmentally acceptable than conventional pyrometallurgy, and provide a means of processing complex concentrates that cannot be handled simply or economically by pyrometallurgy. It is probably not without significance that most recent hydrometallurgical processes for the recovery of base metals from sulfide ores are based on chloride leaching systems, and that the majority of these processes are aimed primarily at, or at least include, the production of copper. Chloride hydrometallurgy has been described as a logical choice for treating unconventional concentrates that smelters cannot readily handle, 1 and the technology is regarded as particularly suitable for on-site, small-tonnage refining of copper in remote areas. In view of these positive attributes, it is not unreasonable to question why chloride hydrometallurgy has so far found very limited practical application.
CHLORIDE LEACHING PROCESSES
The history of chloride leaching dates back almost a century, and it has long been recognized as a highly efficient
1991 August. JOM
process capable of producing concentrated leach solutions. Ferric chloride and cupric chloride solutions have been the favored leachants, particularly for chalcopyrite concentrates, because of their high leaching efficiency and the fact that sulfur is liberated in the elemental form:1.2
CuFeS2 + 3CuCI2 -7
4CuCI + FeCI2 + 2S (1)
CuFeS2 + 4FeCI3 -7
CuCIz + 5FeCI2 + 2S (2)
Initially, chloride-based processes found little application because of the highly corrosive nature of the solutions, but these problems have been largely overcome with the advent of modern materials of construction such as fiberreinforced plastic, polypropylene, butyl rubber and titanium.
Over the past 20 years, research and development work on chloride-based hydrometallurgical processes have burgeoned, and at least 12 processes are said to have progressed beyond the "laboratory beaker" stage of evaluation. These earlier processes have been reviewed and discussed in some detail in References 2-8. Essentially, however, they can be broken down into three main classes: • Those such as the Canmet9,10
Minemet Recherchell,lz and Broken Hill Associated Smelters (BHAS)13 processes, in which copper is finally electrowon from sulfate solution. In these processes, copper is recovered by solvent extraction using an 0-
hydroxyaryloxime reagent, followed by stripping with sulfuric acid and conventional electrowinning from sulfate solution, Leach solutions in these processes are generally of lower copper concentration and acidity or steps have to be taken to adjust and control pH.
• Those such as Cyprus Metallurgical's Cymet process,14,lS which employ mixed ferric chloride and cupric chloride leachants to produce cuprous chloride that is then isolated from the reaction mixture. The precipitated cuprous chloride is reduced to metallic copper using hydrogen in a fluidized bed reactor.
• Those processes such as Duval's copper leach, electrolysis and regeneration (CLEAR) process,1.2,S,16,17
the U.S. Bureau of Mines (USBM) process18,19 and the Dextec process20 in which copper is produced directly by electrolysis. The CLEAR and USBM processes were developed primarily for the treatment of chalcopyrite concentrates, the principal leachants being cupric chloride and ferric chloride, respectively. Both processes produce cuprous chloride solutions from which copper is electrowon in diaphragm cells and leachant regeneration takes place in the anode compartment. The overall cell reactions for the CLEAR process and the USBM process are given in Equation 3 and Equation 4, respectively,
2CuCI -7 Cu + CuCI2 (3)
CuCI + FeCI2 -7 Cu + FeCI3 (4)
The Dextec process involves the anodic dissolution of copper from a chalcopyrite concentrate in a brine solution in the presence of oxygen. The reaction is carried out in a diaphragm cell and the copper is deposited at the cathode,
A number of these processes progressed well beyond the laboratory development stage and some, such as the CLEAR process, advanced to full-scale production. Like so many of the other early chloride-based processes, however, the CLEAR process was not a commercial success; and the 30,000 t/y experimental plant at Sierrita, Arizona closed in 1981 for various technical and economic reasons. S
Notably, very few of the processes outlined above permit the direct production of high-purity copper, even when applied mainly to clean chalcopyrite concentrates. In most cases, further expensive fire refining and electrorefining are necessary to produce wire bar- or cathode-grade material. For example, the CLEAR process produced only blister-grade copper and, similar to the Cymet process, contained all the silver present in the original leach solution, thus necessitating further electrorefining.s
The very efficiency of chloride leaching brings its own problems. Many other base metals, minor metals and metalloids which are present as reactive sul-
51
fides (e.g., Zn, Pb, Ag, As, Sb, Bi, Cd and Hg) are all leached very effectively in chloride media:
Ag2S + 2FeCl3 ~ 2AgCl + 2FeCl2 + S (5)
ZnS + 2FeCl3 ~ ZnCl2 + 2FeCl2 + S (6)
PbS + 2FeCl3 ~ PbC~ + 2FeCl2 + S (7)
This is a factor that cannot be overlooked since, without a purification stage, the presence of these metals has a very serious effect on the quality of the copper produced.21
Chloride-based processes that produce pure copper by means of solvent extraction using o-hydroxyaryloxime reagents are constrained by the performance of these extraction agents.
Cu2+ (aq.) + 2RH (org.) f--)
RzCu (org.) + 2H+ (aq.) (8)
Since Equation 8 (where RH is the 0-
hydroxyaryloxime extractant) is governed by hydrogen ion concentration, the practical result is that only relatively dilute copper solutions can be treated (as in the Canmet process), or careful pH control or adjustment is necessary (as in the Minemet Recherche process). This negates one of the very attractive features of chloride leaching-its ability to produce very concentrated copper solutions. It is therefore clear that, while solvent extraction has a great deal to offer because high-purity copper can be produced directly, the o-hydroxyaryloximes are far from being ideally suited for this task and are, at best, a compromise choice dictated by their availability.
Cu Concentrates
FeO'OH + Other Metals
Bleed to Effluent Treatment
NEW SOLVENT EXTRACTION TECHNOLOGY
Recognizing the need for an extractant capable of capitalizing on the attractions of chloride leaching of copper concentrates, Imperial Chemical Industries (lCI) (Manchester, United Kingdom) embarked on a program of research aimed at devising such a reagent. The successful outcome of this was the novel extractant DS5443,6,7,22 a commercial formulation of which is now available as Acorga™ CLX50 from ICI Specialties. This reagent is ideally suited for the extraction of copper from chloride media, since the loading and stripping operations are governed by the concentration of chloride ion in the aqueous phase (Equation 9, where L represents the extractant DS5443).
Cu2+ (aq.) + 2Cl- (aq.) + 2L (org.) ~ L2CuCl2 (org.) (9)
Thus, the extraction process takes place at the high chloride ion concentration encountered in chloride leach solutions, and the stripping process takes place at low chloride ion concentration. Further, Acorga CLX50 meets all the other requirements for a successful solvent extraction reagent (viz., high selectivity for copper, fast extraction and strip kinetics, good phase-disengagement properties, and high stability).
In essence, Acorga CLX50 is capable of transferring large amounts of copper with no need for pH adjustment or control and with very high selectivity over a wide range of metals and metalloids. Thus, the reagent can produce pure cupric chloride solutions from highly
.--.S
Figure 1. The flow sheet for the Cuprex metal extraction process.
52
impure, concentrated chloride leach solutions. The extraction behavior of Acorga CLX50 is quite sensitive to temperature. Thus, extraction at ambient temperature (25°C) gives high copper recoveries, while stripping at 6Q-65°C facilitates the attainment of very concentrated pregnant copper electrolyte solutions (>90 gil Cu) with a completely stripped organic phase using only two extraction and three strip stages.
NEW CHLORIDE ELECTROWINNING
TECHNOLOGY
Another development which led to improvements in chloride hydrometallurgy is the electrowinning of copper from chloride solution in the Metclor cell, developed by Tecnicas Reunidas (Madrid, Spain). 23,24 For this cell, the pure concentrated cupric chloride electrolyte produced by Acorga CLX50 is an ideal feed.
Traditionally, copper is electrowon or electrorefined from a sulfate solution; such processes are well understood, relatively easy to carry out, and in common practice worldwide. By comparison, electrowinnhtg of copper from chloride solution is not such a common practice and, though well researched, is recognized as carrying with it certain inherent technological difficulties. These arise mainly from the existence of two stable oxidation states of copper in chloride solution, the existence of copper in solution as complex anionic chloro species such as CUCl32-, the liberation of chlorine rather than oxygen at the anode, and the production of a powder or dendritic form of copper rather than smooth sheet
r--------------. Cu
Depleted Brine
Solid Residue
JOM • August 1991
15.00 125.00
r-f .-I ""- ..... t7'I 12.00 t7'1100.00 0 CIJ
:::J C 0 CIS
9.00 Q)
C)
a/A 2.2 :::J 75.00 a/A B.O ~ c-o « c c ~ 6.00 .~ 50.00 Q) a. a. a. a 0 0 u
3.00 U '25.00
0.00 -fI'----r--....--....,......---r-0.00 B.OO 16.00 24.00 32.00
Copper in Aqueous gil
O.OO--f"-----,----.-----r--~-
0.00 2.50 5.00 7.50 10.00 Copper in Organic gil
a b Figure 2. Isotherms for (a) extraction (25°C) and (b) stripping (65°C) of copper by 50% Acorga CLX50. Feed: 25 gIl Cu, 5.5 M CI. Strip: 5 gIl HC!.
cathodes at anything other than low current densities.
The Metclor cell is a two-compartment deSign, the cathode and anode compartments being separated by a reinforced cation-selective ion-exchange membrane such as Dupont's Nafion™ 417. It utilizes coated, dimensionally stable anodes to facilitate chlorine evolution at minimum voltage and a unique design of perforated hollow titanium cathode through which catholyte is pumped so as to create high agitation and good mass transfer at the cathode surface.
THE CUPREX METAL EXTRACTION PROCESS-CORE
TECHNOLOGY
Following the highly encouraging preliminary studies conducted by ICI and T echnicas Reunidas, Nerco Minerals Company (Vancouver, Washington) became interested in the development of a hydrometallurgical process for the treatment of sulfidic copper ores that incorporated the two key technical advances. This led initially to a small-scale pilot trial (750 glh copper) jointly operated by the three companies. This smallscale trial had the objective of demonstrating the compatibility of the three main sections of the process-leaching, solvent extraction and electrowinningand the ability to produce top quality copper directly. The outcome was sufficiently encouraging for the three companies to form a joint venture partnership, known as Hydrometals IV, to develop what is now known as the Cuprex™ metal extraction process (CMEP).
1991 August • JOM
The next stage in the development was the construction and operation o(a larger scale demonstration pilot plant (12 kg/h) to prove the technical and economic viability of the process. This objective has now been accomplished.
The CMEP flow sheet is shown in Figure 1. In the process, sulfidic ore concentrate is leached at atmospheric pressure with ferric chloride solution at about 95°C to produce a solution in which all the copper is in the divalent oxidation state (Equations 10 and 11) and reactive sulfides are converted to elemental sulfur (Equation 12).
CuFeS2 + 4FeCl3 -7
CuCl2 + 5FeCl2 + 2S (10)
Cu2S + 4FeC13 -7
2CuCl2 + 4FeCl2 + S (11)
MilS + 2FeCl3
-7
MI!C1z + 2FeC1z + S (12)
The reaction mixture is then cooled, passed to a thickener, and filtered. The leach residue, which filters easily, consists of gangue, pyrite and up to 65% sulfur, depending upon the grade of concentrate used. It also contains any gold or molybdenite present in the original ore.
The pregnant leach solution is cooled to 25°C, and any sulfate introduced with the concentrate is removed by the controlled addition of calcium chloride to precipitate gypsum. The clarified pregnant liquor containing copper, iron and minor impurities (mainly zinc, lead and silver) and 5.5 M to 6 M chloride ion is sent to the extraction stage of the sol vent extraction circuit. In this stage, it is contacted at ambient temperature with a
kerosene solution of Acorga CLX50, and the copper is transferred selectively to the organic phase. The loaded organic solution is scrubbed with spent anolyte to remove traces of impurities and is then stripped in accordance with Equation 13 by contacting with water at 65°C to produce an aqueous solution containing over 100 gil copper.
L2CuC1z (org.) -4
2L (org.) + Cu2+ (aq.) + 2Cl- (aq.) (13)
Typical isotherms and McCabe-Thiele diagrams for the extraction and stripping of copper with Acorga CLX50 are shown in Figure 2.
The chloride ion content of the aqueous extract is increased by the addition of sodium chloride to enhance its conductivity and to minimize the possibility of precipitation of cuprous chloride. It is then sent to the electrolysis section as catholyte.
The mode of operation of the Metclor cell and the way in which it is integrated with the appropriate sections of the solvent extraction circuit are diagramed in Figure 3. Copper deposition takes place in the cathode compartment and the electronic balance in the catholyte is maintained by transfer of sodium ions from the anolyte through the ion-exchange membrane. The copper is removed continuously from the cells, washed, and processed to an article of commerce. The spent catholyte, which contains copper in the cuprous and cupric oxidation states and sodium chloride (corresponding to that added to the aqueous extract and the deposited copper), is sent to the reforming stage.
In the reforming stage, monovalent
53
FEED ---,
EXTRACTION
RAFFINATE TO----' REGENERATION
Solvent
NaCI
H20
NaCI Solution
CuCI2 + NaCI
Figure 3. The simplified flow circuit for the Metclor cell.
copper in the spent catholyte is oxidized to the divalent oxidation state using some of the chlorine produced in the anode compartment of the cell. The reformed spent catholyte then passes to the depletion stage of the solvent extraction circuit, where it is contacted with organic solvent from the stripping stage.
In two stages of depletion carried out at a high organic-to-aqueous phase ratio (8:1), the copper concentration in the reformed spent catholyte is reduced to approximately 0.1 gil. The copper-depleted aqueous solution is fed to the electrolysis cell as anolyte. The organic solvent phase, now containing a small amount of copper, is advanced to the extraction stage of the solvent extraction circuit.
Silver present in the concentrate is leached and reports in the raffinate from the solvent extraction stage. Since the copper concentration in this solution is very low, silver may be recovered by cementation. Excess iron present in the leach raffinate resulting from leaching of chalcopyrite is removed as goethite (FeO·OH) in a pressure oxidation stage that simultaneously regenerates part of the leachant (Equation 14). The remainder of the leachant is regenerated using chlorine from the electrolysis stage (Equation 15).
6FeCl2 + 1.502 + Hp ~ 2FeO·OH + 4FeCl3 (14)
2FeCl2 + Cl2 ~ 2FeC13
(15)
Copper in the scrubbing and washing liquors may be precipitated as copper sulfide and returned to the leaching stage. Other metal cations may be precipitated by a combination of liming and sulfide treatment to produce environmentally acceptable solid and liquid effluents.
54
PILOT TESTING AND PROCESS OPTIMIZATION
All of the steps comprising the core technology of CMEP-namely leaching, solvent extraction, electrowinning, leachant regeneration and treatment of liquid effluents-have been tested in a continuous demonstration pilot plant at the Tecnicas Reunidas Research Center in Torrejon, Spain.
The plant, with the capacity to process one tonne of concentrate per day, was operated round the clock during a series of trials, each of which lasted up to three weeks. The plant was highly automated and contained as much on-line instrumentation as would be required in a commercial scale plant. All instrument readings were fed to a master control computer. A second computer was used for continuous logging of data.
The plant employed a single-stage leaching operation comprising five reactors arranged in series. The pilot operations were carried out using a southwestern U.s. chalcopyrite concentrate of composition shown in Table 1.
Copper leach efficiencies of greater than 96-97% were obtained with a residence time of 9-10 hours at 95-100DC, leading to an overall copper recovery in the process of greater than 96%. Flocculant was added to the pulp from the leaching operation, which separated readily in the thickener. The underflow from the thickener passed to a drum filter where final separation and washing of the leach residue was accomplished without problems.
In the pilot plant operations the pregnant leach solution was cooled to 25°C, and calcium chloride was added in a stirred vessel to precipitate sulfate introduced with the concentrate as gypsum.
DEPLETED BRINE
The solution then passed to a second preCipitation vessel and on to a thickener, from which some of the underflow was returned to the first stirred vessel to seed the gypsum precipitation. The clarified pregnant leach solution was forwarded to solvent extraction containing approximately 25 gil copper, 120 gil iron and 6 M in chloride ion.
The solvent extraction circuit comprised two extraction, two scrub, four strip and two ~epletion stages and employed a 50 vol. % solution of Acorga CLXSO in Escaid 1 00. Extraction raffinates containing less than 0.5 gil copper were consistently obtained, and the use of four strip stages produced advanced aqueous electrolytes containing up to 110 gil copper. The solvent extraction circuit proved to be robust and relatively insensitive to fluctuations in conditions. Neither decomposition nor deterioration in the performance of the extraction reagent was detected during the entire period of operations.
Table I. Composition of Concentrate Used in Demonstration Pilot Plant Runs
Element Cu Fe Zn Pb As Sb Bi Mo Ag Hg Ca Mg SiOz S (total) 504 Moisture
Amount
27.5wt.% 26.1 wt.% 0.26wt.% 0.08wt.% 235 ppm 110ppm 25 ppm
140 ppm 90 ppm 10 ppm 0.5 wt.%
0.12 wt.% 12.0wt.% 28.5wt.% 3.0wt.% 1.8 wt.%
JOM • August 1991
Electrowinning was carried out in three full-size cells with some opportunity taken to experiment with slight design variations. The cells were of a multiple two-compartment design, the anodes and cathodes being separated by a reinforced, cation-selective, ion-exchange membrane such as Nafion 417. Cathodes were titanium and anodes were coated titanium rods.
Electrowinning operated well, with copper being electrowon at a current efficiency greater than 94% and current density of 1.5 kA/m2. Mean power consumption in the cells during the demonstration plant trials was 2.66 kWh per kilogram of copper produced.
No problems were encountered in the depletion and regeneration stages, and excess iron was successfully removed from the extraction raffinate as a filterable goethite precipitate. Similarly, no problems were encountered in liming and sulfide precipitation of metals from effluent streams.
The pilot trials achieved the initial objective of demonstrating the technical viability of the process and its ability to produce cathode-grade copper. A typical copper analysis, produced under normal operating conditions but following copper powder washing and drying, is shown in Table II.
In summary, the pilot trial demonstrated the mutual compatibility of the four main sections of CMEP: leaching, solvent extraction, electrowinning and leachant regeneration. Inevitably, problems were encountered, but satisfactory splutions were found and implemented during the course of the demonstration plant operations. Possibly the most important result to emerge from the pilot operation was the ability of CMEP to produce copper of a quality matching that of the highest standards in the industry when operating under optimum conditions.
Table II. Copper Product Quality Under Normal Operating Conditions
Impurity Element Content (ppm)*
Al Sb As Bi Cd Cr Co Fe Pb Mg Mn Ni Se Si Ag Te Sn Zn
0.42 3.7 0.3 ND 0.05 ND 0.7 3.2 ND 3.7
0.36 ND ND ND 0.5 0.5 ND ND
II- Spark emission analysis. NO-Not detected.
1991 August • JOM
ASTM Standard B115 (ppm)
5 5 2
12 8
8 4
25 2 10
THE ENHANCEMENT PROGRAM
As indicated previously, the main emphasis of the pilot plant runs was on a successful demonstration of the core technology of the process. Supplementary processes to produce a copper article of commerce and to recover valuable byproducts from copper concentrates were not fully developed at this time. Recognizing that a fully integrated process had to be demonstrated technically and environmentally, and that capital and operating costs for the integrated process had to be developed, the Hydrometals joint venture has since undertaken an enhancement program. Good progress is being made on the enhancement program, and final technical results and cost estimates for the integrated CMEP are expected by the end of 1991. The main thrusts of the work are as follows:
Recovery of Sulfur and By-Products
Processes are being developed by a Canadian technology vendor for the recovery of sulfur, molybdenite and unleached chalcopyrite from the leach residue by a combination of flotation and melt filtration, and for the recovery of gold by cyanidation.
Copper Powder Processing
This work is aimed at the production of an article of commerce from the electrowon copper powder. Washing, drying, briquetting, melting and direct conversion of copper powder to copper wire and copper rod are being evalua ted by several process development contractors and equipment vendors in the United States and the United Kingdom. The key challenge is to maintain the cathode quality of the copper through to the final article of commerce.
Silver Recovery
Tecnicas Reunidas has developed a cementation procedure for recovery of silver from solvent extraction raffinate with iron powder. This is now being integrated into the process flow sheet.
Environmental Assessments
Process residues such as goethite and sludges from lime precipitation have been subjected to toxicity tests at an environmental laboratory in the United States. They have been found to meet u.s. Resource Conservation and Recovery Act criteria and are not considered hazardous wastes. The liquid effluents are being evaluated to confirm their adherence to U.S. standards.
Technology Integration and Cost Estimation
The peripheral technologies and the recovery and recycle of salt from the depleted brine are being integrated with
the core technology by a Canadian engineering contractor. The capital and operating costs for the integrated process are being estimated for five locations worldwide-the southwestern United States, the Iberian Peninsula, western Canada, Chile and Australia.
On the basis of data accumulated during the demonstration plant trials, the estimates shown in Tables III and IV have been made for units of consumption of reagents and utilities for the particular ore concentrate used. The particular case study was based on recovery of salt in the process by forced steam evaporation. (In the southwestern United States and other warm arid locations, solar evaporation may be viable and less expensive.) The consumptions listed may vary, depending upon the mineralogy of the particular ore concentrate, though they are not expected to vary widely. Precise estimates can be made on the basis of laboratory-scale leaching trials and a computed mass balance for the process circuit. Clearly, actual operating costs will be very dependent on local factors, particularly the cost and availability of reagents, utilities and manpower. Table V gives estimated staffing levels for a 30,000 t/y CMEP copper production facility.
FEATURES OF CMEP
Long operating experience and analysis of the pilot-plant data leads to the conclusion that the technical viability of
Table III. Reagent Consumption
Reagent
Chlorine HCl (33%) NaCl CaCl2 Ca(OH)2 NaHS Oxygen Scrap Iron Flocculant Acorga CLX50 Kerosene
Consumption (per tonne Cu)
0.20 tonnes 0.608 tonnes 0.203 tonnes 0.072 tonnes 0.265 tonnes 0.031 tonnes 0.329 tonnes 0.118 tonnes
0.242 kg 1.00 kg 5.00 kg
Table IV. Utilities Consumption
Utility
Power Steam Process Water Cooling Water
Consumption (per tonne Cu)
4.00MWh 7.41 tonnes
33m3
321 m3
Table V. Estimated Labor Requirements
Salaried Personnel
Senior Mgt. and Admin. Laboratory Staff Operations /Engineers
Hourly Personnel
Foremen/Lead Operators Operators Maintenance/Electricians
Number
8 8 7
6 28 29
55
CMEP has been clearly demonstrated; indeed, it may prove to be particularly attractive in a number of situations. The particularly attractive features may be classified as both physical and chemical and are listed below.
Physical Features
• Lower capital costs than a smelter and refinery of eqUivalent capacity.
• Economically viable for both large and small operations, down to 10,000-30,000 t/y.
• Permits mine site production of copper in small operations in remote locations. This in turn eliminates concentrate shipping, cuts inventory costs, and gives mine operators the option of marketing their own copper with added value for their final product.
• Modular construction is possible, allowing design flexibility and plant portability.
Chemical Features
• Efficient leaching reactions give high copper recovery at moderate temperatures and pressures.
• The process is environmentally clean since elemental sulfur is produced rather than sulfur dioxide.
• Production and marketing of sulfuric acid is avoided.
• Pyrite, gold and molybdenite are not leached.
• The process is capable of treating many feed materials, including "dirty" and low-grade concentrates. This reduces penalties for undesirables in concentrates, eliminates the need for cleaner flotation, and gives better metal recoveries.
• The process can be extended to include most major metals found in complex, copper-bearing deposits.
ACKNOWLEDGEMENTS The authors express their appreciation for
the contributions and help of numerous colleagues in their respective organizations and in organizations assisting with work on the enhancement program in bringing about the successful demonstration of the technical viability and evaluating the economics of the Cuprex metal extraction process, and in enabling this paper to be written. Thanks are also due to the managements of Imperial Chemical Industries, Tecnicas Reunidas and Nerco Minerals Company for their permission to present this paper.
References 1. D.C McLean, "Chloride Leaching of Copper Concentrates, Practical Operational Aspects," presented at the AIME Annual Meeting, Dallas, TX (February 14-18, 1982). 2. E. Peters, N Application of Chloride Metallurgy to Treatment of Sulphide Minerals," Chloride Metallurgy (Brussels: Benelux Metallurgie, 1977), p. 1. 3. K.J. Edmiston, "An Update on Chloride Hydrometallurgical Processes for Sulphide Concentrates," SME T echnical Paper 84-114 (Golden, CO: SME, 1984). 4.0.5. Flett, J. Melling and R. Derry, "Chloride Metallurgy for the Treatment of Complex Sulphide Ores," report LR461 (ME), (Stevenage, UK: Warren Spring Laboratory, 1983). 5. A.W. Fletcher, "Future Potential for Chloride Metallurgy," paper presented at SME Annual Meeting, New Orleans, LA (March 3-5, 1986). 6. R Price, P.M. Quan and B. Townson, "Novel Solvent Extractants for Copper from Chloride Media-Their Application in the Processing of Complex Base Metal Concentrates," presented at the Joint EEC-Canada Seminar on the Treatment of Complex Minerals, Ottawa, Canada (October 12-14,1982). 7. RF. Dalton et aI., "Novel Solvent Extractants for Recovery of Copper from Chloride Leach Solutions Derived from Sulphide Ores," Reagents in the Minerals Industry (London: IMM, 1984), p. 181. 8. R.F. Dalton et al, "The CUPREX Process-A New Chloride Based Hydrometallurgical Process for the Recovery of Copper fromSulphidicOres," Separation Proc. in Hydrometall., ed. G.A. Davies (London: Ellis Horwood, 1987), pp. 466-476. 9. G.M. Ritcey, B.H. LucasandKT. Price, "Evaluation and Selection of Extractants for the Separation of Copper and Zinc from Chloride Leach Liquor, Hydrometallurgy (1982), p. 197. 10. G.M. Ritcey, B.H. Lucas and K T. Price, "Extraction of Copper and Zinc from Chloride Leach Liquors Resulting from Chlorination Roast Leach of Fine-Grained Sulphides," Proc. ISEC'SO, vol. 3, (Liege, Belgium: Association des Ingenieurs Sortis de I'Universite de Liege, 1980), paper 80-71. 11. J,M. Demarthe, L. Gandon and A. Georgeaux, "A New Hydrometallurgical Process for Copper," Extractive Metallurgy of Copper, ed. J.C Yannopoulus and J.C Agarwal (Warrendale, PA: TMS, 1976), p. 825. 12. J.M. Oemarthe,A. Sonntag and A. Georgeaux, U.S. Patent no. 4,023,964 (1977). 13. N.E. Meadows and M. Valenti, 'The BHASCopper Lead Matte Treatment Plant," Proc. Non Ferrous Smelting Sympo-
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siurn (Victoria, Australia: AusIMM, 1989), p. 153. 14. J.H. McNamara et aI., "A Hydrometallurgical Process for Copper," paper presented at the AIME Annual Meeting, Denver, CO (February 26-March 2,1978). 15. W.C Hazen, for Cyprus Metallurgical Process Corporation, USA. Canadian Patents nos. 1,012,089 (1977) and 1,028,651 (1978). 16. F.W. Schweitzer and R Livingstone, "Duval's CLEAR Hydrometallurgical Process," paper presented at the AlME Annual Meeting, Dallas, TX (February 14-18, 1982). 17. C.E. Atwood and CH. Curtis for Duval Corporation, U.S. Patents nos. 3,785,944 (1974) and 3,879,272 (1975). 18. TA. Phillips, "Economic Evaluation of a Process for Ferric Chloride Leaching of Chalcopyrite Concentrate," Rl 7474 (Washington, D.C.: U.S. Bureau of Mines, 1971). 19. F.P. Haver, RD. Baker and M.M. Wong, "Improvements in Ferric Chloride Leaching of Chalcopyrite Concentrates," Rl8007 (Washington, D.C: U.S. Bureau of Mines, 1975). 20. P.K. Everett, 'The DEXTEC Copper Process," Ex/raction Metallurgy'S1 (London, U.K: IMM, 1981), p. 149. 21. E. Anderson et aI., "Production of Base Metals from ComplexSulphideConcentratesbytheFerricChlorideRoute ina Small Continuous Pilot Plant," Complex Su/phideOres,ed. M.J. Jones (London, U.K: IMM, 1980), pp. 186-192. 22. RF. Dalton, R. Price and P.M. Quan, "Novel Solvent Extractants for Chloride Leach Systems," Proc. In/. Solvent Extraction Conference, [SEC 'S3, Denver, CO (1983), p. 189. 23. E.D. Nogueira, "Recent Advances in the Development of Hydrometallurgical Processes for the Treatment of Base Metal Sulphides," Int. Conf. on Mineral Science Technology (South Africa: M1NTEK, 1984). 24. E. Hermana Tezanos, U.s. Patent no. 4,776,941 (1988).
ABOUT THE AUTHORS ____ _
R.F. Dalton received his Ph.D. in chemisty from the University of Manchester, United Kingdom, in 1969. He is currently senior scientist at ICI Specialties Research Centre.
G. Diaz received his graduate degree in industrial chemistry from the University of Valladolid, Spain, in 1975. He is currently director of the R&D Center at Technicas Reunidas.
R. Price received his Ph.D. in chemistry from the University of Nottingham in 1960. He is currently a consultant at Ray Price Consultants, Shropshire, United Kingdom. Dr. Price is also a member of TMS.
A.D. Zunkel received his D.Sc. in metallurgical engineering from the Colorado School of Mines in 1967. He is currently president of A.D. Zunkel Consultants. Dr. Zunkel is also a past president of TMS.
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JOM • August 1991
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