Nickel-Cobalt 97 International Symposium

Technical Program

of the 27th Annual Hydrometallurgical Meeting of CIM

held in conjunction with the 36th Annual Conference of Metallurgists

Laurentian University, Sudbury, Ontario, Canada

August 17-20, 1997

Monday, August 18, 1997, AM

Session 2: Nickel Recovery from Sulfide Concentrates or Mattes

Room: FA-054, Fraser Building

Chair-persons:

Paper 2.1 - 10:30

The Hydrometallurgy of Nickel Sulfides

F. Habashi, Department of Mining and Metallurgy, Laval University, Quebec City, Quebec, Canada

The hydrometallurgy of nickel sulfides with elemental sulfur formation is a neglected area of research although it is the only route to solve the pollution problems associated with smelters. A review of the early attempts to apply this technology, the advances recently made in pressure hydrometallurgy, and an evaluation of the present situation is given. Attention is drawn to the difference in behaviour between nickel and iron sulfides in hydrometallurgical systems using acid medium. While both sulfides liberate elemental sulfur, nickel sulfide consumes acid and the Ni2+ ion goes into solution, while ferrous sulfide does not consume acid and the iron precipitates as Fe2O3. This is a great advantage when treating pentlandite - pyrrhotite type concentrates where pyrrhotite is many times more than pentlandite.

Paper 2.2 - 10:55

Hydrometallurgical Processing Options for Nickel Sulphide Concentrates

D.J. Honey, D.M. Muir and P.R. Hunt, WMC Resources Ltd, Perth, Western Australia, Australia

Obtaining nickel metal directly from concentrate without the need for a pyrometallurgical intermediate process is potentially economically attractive. This is especially the case for difficult to smelt concentrates which are low grade or contain problem elements such as arsenic and magnesium. Two commercially operated nickel concentrate processes are described, the Outokumpu "HIKO" Process and the Sherritt Process. WMC Resources Ltd. (WMC) initially used the Sherritt Process to treat nickel concentrate, but the process is energy intensive and WMC subsequently moved to treating nickel matte to improve economics.

There are, however, a number of possible process options for nickel sulphide concentrates, ranging from bacterial oxidation to roast/leach processes. This paper evaluates alternative nickel concentrate leaching options and considers some of the environmental, technical and cost issues. This provides a rationale for accepting or rejecting processing options. It is concluded that both pressure leaching in sulphate media and atmospheric leaching in chloride media warrant further investigation. Some results of leaching a nickel concentrate under various conditions in these media are compared.

Paper 2.3 - 11:20

Commissioning of the Stillwater Mining Company Base Metals Refinery

L. Newman, Stillwater Mining Company, Columbus, Montana, USA

M. Makwana, Sherritt International Consultants, Fort Saskatchewan, Alberta, Canada

Stillwater Mining Company (Stillwater) operates a mine and milling facilities at Nye, Montana to produce a nickel-copper sulphide concentrate which contains a significant amount of platinum group metals (PGM). The concentrate is processed at Stillwater's smelter located in Columbus, Montana to produce a nickel-copper-PGM matte. In 1995, Stillwater constructed a Base Metals Refinery (BMR) adjacent to the smelter to process the matte using an acid leach process. The process consists of extracting essentially all of the nickel, copper and sulphur from the matte in an atmospheric leach step followed by a pressure leach step to produce a PGM-rich concentrate, which is refined elsewhere.

The Stillwater BMR was successfully commissioned in April, 1996 and design conditions were achieved in a relatively short time. This paper describes the design and commissioning of the BMR and highlights the performance of the plant.

Paper 2.4 - 11:45

The First Commercial Plant of Pressure Extraction of Nickel in China

Qiu Dingfan, Beijing General Research Institute of Mining and Metallurgy, Beijing, China

Pressure leaching is used worldwide for nickel recovery, particularly in the treatment of copper-nickel matte. The Beijing General Research Institute of Mining and Metallurgy pioneered and made substantial contributions to the development of extraction metallurgy and pressure leaching in China. This paper describes a new process for copper-nickel separation, first tested in the pressure leaching pilot plant at the Institute. Based on the pilot plant data, a commercial plant treating copper-nickel matte was started in 1993 which has been successfully operating since then.

Monday, August 18, 1997, PM

Session 10: Novel Nickel/Cobalt Recovery Processes

Room: FA-054, Fraser Building

Chair-persons:

Paper 10.1 - 14:00

A Review of the Hydrometallurgical Recovery of Cobalt from Sulphide Ores

D.K. Xia and C.A. Pickles, Dept. Materials and Metallurgical Engineering, Queen's University, Kingston, Ontario, Canada

In this presentation, the current state of cobalt production from sulphide ores will be discussed in terms of process technology, capacity and feed sources. The recovery methods strongly depend on plant location, size, type and composition of the reserve. Recent research activities on cobalt-containing complex ores and concentrates are discussed.

Paper 10.2 - 14:25

Process Development for International Curator's El Boleo Copper - Cobalt Project

T. Bolles, Hazen Research Inc., Golden, Colorado, USA

R. McElroy, Fluor Daniel Wright Ltd., Vancouver, British Columbia, Canada

D. Griffiths, International Curator Resources Ltd., Vancouver, British Columbia, Canada

International Curator's El Boleo Project is based on mining copper-cobalt ores from stratiform deposits near Santa Rosalia, Baja California Sur, Mexico. Project plans involve the use of open pit and underground mining to exploit a resource that includes substantial amounts of highly variable and complex near surface oxide ores in addition to sulfide ores. Process development has focused on sulfuric acid leaching in sea water to recover economic metals, copper and cobalt.

The resulting flowsheet involves selective precipitation and flotation of copper followed by selective precipitation and flotation of cobalt and zinc. The flowsheet avoids copper precipitation complications and a very difficult solid-liquid separation. The copper product is a saleable concentrate (35-50% Cu as CuS) containing minimum cobalt. The mixed cobalt/zinc concentrate, containing about 6% Co, requires further processing.

The presentation will chart the development effort, including bench and pilot scale process research and engineering trade-off analyses, all focused towards an economically optimized process for this complex resource.

Paper 10.3 - 14:50

The CESL Process for Nickel-Cobalt-Copper Sulphides

D.L. Jones, Cominco Engineering Services Ltd., Vancouver, British Columbia, Canada

Cominco Engineering Services Ltd (CESL) has developed a novel hydrometallurgical route to processing Ni-Co-Cu sulphide concentrates. All three metals are recovered in very high yield as refined products. The process uses pressure oxidation together with SX/EW. Sulphur oxidation to sulphate is minimized, with most sulphide reporting as elemental sulphur. The process has been tested in a fully integrated pilot plant, treating about 120 kg/day of concentrate. The key pressure oxidation process has been operated for over 3,000 hours. Preliminary analysis indicates that the process will compete with, and even replace, the conventional smelting/refining route and will have less environmental impact. The process can also be adapted to treating laterites.

Coffee Break (15:15-15:45)

Paper 10.4 - 15:45

Sulfur Compounds Conversion and Metal Recovery Using Bioprocess Technology

A.L. de Vegt, Paques, Inc., Exton, Pennsylvania, USA

C.J.N. Buisman, Thiopaques Sulfur Systems B.V., Balk, The Netherlands

Paques has developed and installed metal and sulfate removal systems based on biotechnological processes. A Paques treatment system has been in operation at a zinc refinery since May 1992 treating a flow of 5000 m3/day. Sulfate is reduced to below 200 mg/L while metal removals exceed 99%. In North America, pilot testing has demonstrated that copper and zinc can be selectively recovered from mine waters using biologically produced hydrogen sulfide. Using efficient bioreactors and hydrogen gas as a reductant, hydrogen sulfide can be produced economically at ambient pressure and temperature, from a variety of readily available sulfur sources such as flue gas, acid mine drainage, acid plant blow down, and elemental sulfur. This paper will address the costs associated with the biological production of hydrogen sulfide and discuss possible applications of sulfate reduction and sulfide precipitation in nickel/cobalt metallurgy.

Paper 10.5 - 16:10

The BioNIC Process: Description of the Process and Presentation of Pilot Plant Results

D.M. Miller and D.W. Dew, GENCOR Process Research, Randburg, Republic of South Africa

A.E. Norton, GENCOR Minerals Technology, Marshalltown, Republic of South Africa

P.M. Cole and G. Benetis, MINTEK, Randburg, Republic of South Africa

The BioNIC Process is being developed by GENCOR in cooperation with MINTEK as a competitive process to conventional smelting for the recovery of nickel from low-grade sulphide ores. The process involves bioleaching of the metal sulphides followed by pH adjustment for iron removal and solid/liquid separation; further metal recovery proceeds by sulphide precipitation or concentration and purification of the process liquor by ion-exchange or solvent extraction to produce an upgraded electrolyte followed then by either nickel electrowinning or hydrogen reduction to produce nickel powder.

The bioleaching technology has been developed by GENCOR from its BIOXâ Process, which is commercially applied for the treatment of refractory gold ores. A demonstration pilot plant, producing about 20 kg of cathode nickel per day, will be operated at GENCOR Process Research in the first half of 1997, to prove the viability of the BioNIC Process for commercial treatment of the Maggie Hays ore body in Western Australia. This paper will focus on the process flowsheets developed, and will present results from the laboratory and pilot plant operations.

Paper 10.6 - 16:35

Bioleaching of Cobalt Arsenides

J. Frenay, Métallurgie et Traitement des Minerais, Université de Liège, Liège, Belgium

A two-step process is developed to recover the cobalt from arsenitic ores. First, the ferrous iron in the solution is subjected to bacterial oxidation to ferric. Then, in a second reactor, the ore is leached using the ferric iron solution leading to cobalt dissolution and arsenic precipitation with iron as scorodite. The key to this two-step process, in comparison with the usual bacterial leaching, is that the two step reactions can be optimized independently. In this presentation, the chemistry of the process, the properties of microorganisms such as adaptation and tolerance, along with the results of the tests are described.

Tuesday, August 19, 1997, AM

Session 18: Electrolytic Processes

Room: FA-054, Fraser Building

Chair-person: J. Lipkowski (University of Guelph, Guelph, Ontario, Canada)

Paper 18.1 - 9:00

Removal of Copper and Other Minor Elements in the MCLE Process

S. Makino, N. Kemori, N. Matsumoto and S. Matsumoto,

Niihama Nickel Refinery, Sumitomo Metal Mining Co. Ltd., Niihama, Ehime, Japan

In the MCLE (matte chlorine leach electrowinning) process, which is Sumitomo Metal Mining's original technology for producing high purity electrolytic nickel, metallic elements such as Ni, Cu, and Co are leached from raw nickel matte using chlorine gas as oxidant. Among the impurities present in the resulting leach chloride solution, copper is of particular importance because cuprous and cupric ions act as electron carriers in the chlorine gas leaching process. Furthermore, copper is among the major impurities in the nickel matte which also accumulates in the leaching circuit.

In the MCLE process, copper is removed by electrowinning from the chloride solution in a metallic powder form. This is rarely practiced on a commercial scale, and details of this copper removal as well as of other minor impurities will be presented.

Paper 18.2 - 9:25

Electrochemical and Atomic Force Microscopy Studies of Nickel Electrodeposition from Watts Electrolyte

G. Szymanski, M. Pogoda, B. Campbell and J. Lipkowski

Department of Chemistry and Biochemistry, University of Guelph, Guelph, Ontario, Canada

Atomic Force Microscopy (AFM) has been employed to study Ni electrodeposition from Watts electrolyte of a variable chloride to sulfate ratio. The AFM images revealed that the electrolyte composition significantly influences the morphology of the electrodeposited metal. Digital image analysis has been performed to quantify these morphological changes. It has been shown that the morphology of electrodeposited Ni can be conveniently described in terms of the surface roughness and the distribution of grain sizes. The dynamic scaling analysis has been used to describe the surface roughness as a function of the scaling length and deposition time. The distribution of the grain sizes was approximated by the distribution of the surface heights. It has been demonstrated that the information about the morphology of the electrodeposited metal may be encoded in the magnitude of a few numerical parameters.

Paper 18.3 - 9:50

Electrochemical Kinetics of the Anodic Dissolution of Nickel Matte and Synthetic Ni3S2

X. Zhu, J. Li, M. Wadsworth and R. Woods

Department of Metallurgical Engineering, University of Utah,Salt Lake City, Utah, USA

Commercial nickel matte anode material (International Nickel Company) and synthetic Ni3S2 were oxidized anodically under a variety of conditions. Reaction products were identified by cyclic voltammetry, X-ray diffraction analysis, Raman spectroscopy, and X-ray photoelectron spectroscopy. Kinetics of surface film growth were measured using chronoamperometry techniques. Variables considered include maximum scan potential, time at a fixed potential, temperature, solution pH and the effect of stirring. Electrochemical reactions occurring on the nickel sulfide surface are proposed based on electrochemical measurements and identification of surface reaction products. The results obtained for nickel matte were compared with those from synthetic heazlewoodite (Ni3S2).

Coffee Break (10:15-10:45)

Paper 18.4 - 10:45

The Ammonia-Ammonium Nitrate Leaching of Nickel Matte

Suratman and Pramusanto, Mineral Technology Research and Development Centre, Bandung, Indonesia

Nickel sulphamate solution is one of the electrolyte solutions used in nickel electroless and electroplating industries. Laboratory leaching process has been investigated in which PT INCO nickel matte, containing more than 76% nickel, is dissolved under an atmospheric pressure with a mixture of ammonia-ammonium nitric and sulphate solution to produce nickel sulphamate solution. The effect of pH, composition of pregnant solution and residue was determined. Work on the development of direct nickel matte leaching process for the production of nickel sulphamate is presented with an emphasis on its application to the nickel sulphamate salt recovery process.

Tuesday, August 19, 1997, AM

Session 19: Novel Nickel/Cobalt Separation Processes

Room: FA-441, Fraser Building

Chair-persons:

Paper 19.1 - 9:00

Nickel Cobalt Separation with Superoxidants

G.M. Dunn, BKS Hatch (Pty) Ltd., Gallo Manor, Republic of South Africa

H.W. Schubert, Western Platinum Ltd., Marikana, Republic of South Africa

H.E. Holliday, BKS Hatch (Pty) Ltd., Gallo Manor, Republic of South Africa

Pilot plant campaign results for the separation of cobalt from nickel in sulphate media using Caro's acid and ozone as oxidants are presented. Ozone utilisation data at varying pH, temperature, and retention time are discussed. The residues were upgraded employing a classical low pH leaching to a Co:Ni ratio of approximately five and several hundred employing a novel extraction process.

Paper 19.2 - 9:25

Complexane Types of Chemically Modified Chitosan: Novel Chelating Adsorbents for Separating Nickel and Cobalt

K. Inoue, Saga University, Saga, Japan

Novel chelating adsorbents were synthesized by chemical modification of chitosan with ethylene di-amine tetra-acetic acid and di-ethylene tri-amine penta-acetic acid. Adsorption of various metal ions from sulfuric acid solution was examined and the selectivity series of base metals was found to be as follows: Cu(II) ³ Mo(VI) > Ni(II) > V(IV) >> Zn(II) ³ Co(II) > Al(III). Breakthrough and elution tests, performed with a packed column containing these adsorbents, demonstrated successful nickel/cobalt separation as well as considerable aluminum rejection.

Paper 19.3 - 9:50

Development Of Synergistic Solvent Extraction System for the Recovery of Nickel and Cobalt from Spent Hydrodesulfurization Catalysts

K. Inoue, P. Zhang and Y. Koga, Saga University, Saga, Japan

H. Eguchi, Catalysts and Chemicals Industries Co. Ltd., Kitakyushu, Japan

For the purpose of recovering cobalt and nickel from spent hydrodesulfurization catalysts, a novel solvent extraction system, using two types of synergistic mixtures, was developed to selectively extract small amounts of nickel and cobalt in the presence of large quantities of aluminum in sulfuric acid solution at low pH. The first type represents mixtures of LIX 63 and di-alkyl phosphinic acids such as Cyanex 272 and PIA-8. The second type comprises mixtures of di-alkyl naphthalene sulphonic acids and picolylamines.

Coffee Break (10:15-10:45)

Paper 19.4 - 10:45

Nickel and Cobalt Separation and Recovery by RecofloŽ Ion Exchange Technology

M. Sheedy and D. Swaine, Prosep Technologies Inc., Pickering, Ontario, Canada

RecofloŽ ion exchange technology utilizes fine mesh resin beads, a fully packed resin bed, and counter-current regeneration. These features help improve exchange kinetics, reduce regenerant consumption, and increase the concentration of strip solutions. RecofloŽ technology has been extensively used in the metal finishing industries for nickel recovery since the mid 1970s.

More recently, this technology has been evaluated for the recovery and separation of nickel from cobalt using Dow Chemicals' XFS 4195 chelating resin. Laboratory pilot plant tests were conducted using cobalt electrolyte from Inco Ltd.'s Port Colborne refinery. A typical run with this feed, containing 93.3 g Co/L and 1.44 g Ni/L, resulted in a purified electrolyte with 84.8 g Co/L and 0.4 g Ni/L, and a nickel bleed and rinse stream with 7.0 g Co/L and 2.9 g Ni/L. A comparison of the RecofloŽ system to the existing conventional ion-exchange equipment indicated a reduction in acid and water consumption of 30% and a reduction in resin volume of greater than 90%. Case studies are also presented for full scale systems treating a nickel and cobalt bearing ammonium sulfate effluent stream, a rinsewater stream from a zinc-nickel electrogalvanizing plant, and a rinsewater from a duplex nickel plating operation.

Paper 19.5 - 11:10

A Hydrochloric Acid Process for Nickeliferous Laterites

R.W. Gibson and N.M. Rice, Department of Mining and Mineral Engineering, University of Leeds, Leeds, UK

The development of a hydrometallurgical hydrochloric acid based leaching process for the treatment of nickeliferous laterites of various types is described. A key step is the separation and concentration of the nickel in the leach liquor (1-5 g/L) from magnesium and/or iron to a tenor compatible with electrowinning or hydrogen pressure reduction. This can be achieved using solvent extraction with Cyanex 301, Cyanex 302 or Versatic 10 which displayed the best extraction characteristics. Cyanex 301 showed excellent selectivity for Ni but was very difficult to strip except with high concentrations of acid. Cyanex 302 seemed suitable but co-extraction of magnesium was appreciable.

Paper 19.6 - 11:35

Solvent Extraction - Electrowinning of Cobalt Using PC88A - A Case Study

K.S. Rao, P.C. Rath, B.R. Reddy, S.C. Das, T. Subbaiah, S.K. Gogia, K. Sanjay and R.P. Das,

Regional Research Laboratory (CSIR), Bhubaneswar, Orissa, India

Electrolytic cobalt was produced from a solution containing nickel and other metallic impurities employing solvent extraction - electrowinning technique. The solution was generated in batches by leaching superalloy scrap. The purified solution contained about 7-12 g Co/L, about 35-50 g Ni/L, as well as Zn and Cu in small quantities. The organic extractant was a partially neutralised PC 88A (bis-2-ethylhexyl phosphonic acid) diluted in kerosene. Cobalt from the metal-loaded organic phase was stripped by dilute H2SO4 / acidic CoSO4 solution. The resulting CoSO4 solution, enriched to ~45 g Co/L, was used as the electrolyte for cobalt electrowinning.

The results from the laboratory and bench scale studies could be reproduced in the subsequent continuous pilot plant testing with minor deviations. More than 98 % cobalt and about 0.2% nickel were transferred from the leach solution to the cobalt electrolyte from which cobalt metal was electrodeposited with a current efficiency of ~65%. Smooth cathode deposits were obtained with 99.3% purity. A few process problems such as a third phase formation and crud formation were encountered and they could be solved with modification to process conditions.

Tuesday, August 19, 1997, PM

Session 30: Recent Advances in Solvent Extraction for Nickel/Cobalt Separation

Room: FA-054, Fraser Building

Chair-persons:

Paper 30.1 - 14:00

The Treatment of Cobalt/Nickel Solutions Using CyanexŽ Extractants

W.A. Rickelton and D. Nucciarone, Cytec Canada Inc., Phosphine Technical Centre, Niagara Falls, Ontario, Canada

Bis(2,4,4-trimethylpentyl) phosphinic acid, R2P(O)OH, is available from Cytec as CYANEXâ 272 extractant. Originally developed in the early 1980's, its use to recover cobalt from nickeliferous solutions is now well established with commercial plants operating in Europe, South America, Africa, Australia, Canada and China. The properties which make CYANEXâ 272 an almost ideal extractant for cobalt recovery are discussed in both theoretical and practical terms. Additionally, the potential use of its dithio analogue, bis(2,4,4-trimethyl pentyl) dithiophosphinic acid, in cobalt-nickel recovery is described briefly.

Paper 30.2 - 14:25

Cobalt Recovery by Solvent Extraction from Acid Leach Solutions of Caron's Process Mixed Ni/Co Sulfide

R.V. Martínez, E.G. Liranza, B.R. Bárzaga, A.M. Daudinot, Laterite Research Center, Moa, Holguín, Cuba

This paper presents a summary of the results for the selective recovery of cobalt by solvent extraction using Cyanex 272 extractant from solutions produced by acid leaching of nickel/cobalt sulfides product of the Caron's process. Data from laboratory and miniplant tests using basic nickel carbonate acid leaching solution as aqueous feed are also presented.

Paper 30.3 - 14:50

Cobalt/Nickel Separation from Acidic Leach Liquors

C. Bourget, M. Cox and D.S. Flett, Division of Chemistry, University of Hertfordshire, Hatfield, United Kingdom

This paper describes the recovery and separation of cobalt and nickel from acidic leach liquors derived from the leap leaching of laterite ores. Flowsheets based on the use of organophosphorus acids and synergistic mixtures of organophosphorus acids and a -hydroxyoximes are discussed and critically assessed. The flowsheet finally chosen for detailed study involves the bulk extraction of cobalt and nickel at pH 7-8 using the magnesium salt of Versatic acid to eliminate pH control. Good recoveries of cobalt and nickel are achieved in a two-stage counter-current extraction, however with some co-extraction of manganese. This can be scrubbed along with residual magnesium and calcium in the organic phase by contact with a small amount of strip liquor. Stripping of cobalt and nickel from the organic phase is possible with 1.0 mol/L sulphuric acid to give a strip liquor concentration of 52 g/L nickel, 4.2 g/L cobalt from a loaded organic phase containing 1 g/L nickel and 0.8 g/L cobalt. Preparation of the magnesium Versatate salt, by contacting the Versatic acid in a hydrocarbon diluent with powdered magnesium hydroxide in the absence of water, proved troublesome and experiments are proceeding to try to devise a more suitable procedure.

Coffee Break (15:15-15:45)

Paper 30.4 - 15:45

Treatment of Leach Liquors Containing Cobalt and Nickel by ZENECA Development Extractant DS6001

J.R. Lawson and M.A. Cox, ZENECA Specialties Research Centre, Blackley, Manchester, United Kingdom

A novel class of solvent extraction agents has recently been developed by ZENECA at its Specialties Research Centre in Blackley, Manchester, UK. The chemical and physical properties of one of these reagents appear to offer an elegant route to isolating pure nickel and cobalt streams from mildly acidic aqueous leachates. The performance of the development reagent DS 6001 in both laboratory batchwise tests and mini-rig trials is examined using simulated leach solutions. The data collected indicate that a typical laterite leach liquor may be processed considerably more efficiently using DS 6001 than with currently available reagents. An authentic acidic leachate derived from a lateritic ore will be used in the next phase of the work.

Paper 30.5 - 16:10

The Solvent Extraction Recovery of Copper, Cobalt and Zinc from Seawater Based Leach Solutions

D. Dreisinger, University of British Columbia, Vancouver, British Columbia, Canada

T. O'Kane, O'Kane and Associates, Vancouver, British Columbia, Canada

L. Gormely, H.A. Simons Engineering, Vancouver, British Columbia, Canada

C. Fleming, Lakefield Research Ltd., Peterborough, Ontario, Canada

The leaching of copper, cobalt and zinc containing ores in an acidic sea water solution has been studied in the development of a metallurgical flowsheet for International Curator's El Boleo orebody. Copper can be recovered from the solution by solvent extraction using conventional hydroxyoxime reagents. However, a chloride wash step is required to prevent chloride transfer from the sea water to the strip solution. Further zinc and cobalt recovery and separation is achieved by solvent extraction using a quaternary amine (Aliquat 336). Experimental data, including from continuous pilot plant solvent extraction circuit operation, will be presented.

Paper 30.6 - 16:35

QNI Limited Cobalt Refinery - Process Development, Installation and Operation

J. Fittock, Queensland Nickel Pty. Ltd., Townsville, Queensland, Australia

QNI's nickel and cobalt refinery located at Townsville in north-east Australia is capable of processing 3.6 million wet tonnes of lateritic nickel ore each year. Laboratory bench scale and pilot plant studies to produce a high purity cobalt product were conducted in 1990 to 1996. A novel process in which the impurities are eliminated by a combination of solvent extraction and ion exchange resin treatment was patented. A 2,000 tpa nominal capacity cobalt plant was constructed during 1996 and full scale production of QN Cobalt Oxide Hydroxide containing low levels of impurities commenced in 1997.

Wednesday, August 20, 1997, AM

Session 40: Nickel/Cobalt Recovery from Lateritic Ores: Current and Advancing Operations

Room: FA-054, Fraser Building

Chair-persons:

Paper 40.1 - 9:00

The Acid Pressure Leach Process for Nickel and Cobalt Laterite, Part I: Review of Operations at Moa

M.E. Chalkley and I.L. Toirac, Moa Nickel S.A., Moa, Holguín, Cuba

The acid pressure leach process for the treatment of low magnesium lateritic ore has been in operation at the Pedro Sotto Alba Plant in Moa, Holguín, Cuba, since 1959. The plant was originally constructed by the Moa Bay Mining Company, a subsidiary of Freeport Sulphur, and was taken over by the Cuban Government in 1960. The plant re-commenced operations in 1961, under Cuban management. After a series of problems, encountered during start-up, were eliminated production gradually increased and improvements were made to the recovery of nickel and cobalt. In December 1994, Sherritt Inc. announced the formation of a Combined Enterprise with General Nickel S.A., a state-owned company of the Cuban Government, to mine, process and refine cobalt and nickel contained in the lateritic ores located near Moa. The nickel and cobalt sulphides produced in Moa by Moa Nickel S.A. are transported to the nickel and cobalt refinery at Fort Saskatchewan, Alberta, Canada for processing to pure metal products.

This paper describes the process flowsheet at Moa, together with plant performance data. Progress in the initial twenty-four months of the Combined Enterprise is discussed with particular emphasis on production improvements and preliminary work on environmental issues.

Paper 40.2 - 9:25

The Acid Pressure Leach Process for Nickel and Cobalt Laterite, Part II: Review of Operations at Fort Saskatchewan

D.G.E. Kerfoot and P.D. Cordingley, Sherritt International Corporation, Fort Saskatchewan, Alberta, Canada

The nickel-cobalt sulphides produced from limonitic laterite ores by Moa Nickel S.A. in Cuba are shipped to the Corefco nickel-cobalt refinery in Canada. This refinery is the former Sherritt Gordon nickel refinery in Fort Saskatchewan, Alberta, which has been in operation since 1954. Major changes to the refining process were required to handle the Moa sulphide feed with its unusually high cobalt content. While the ammonia leach and hydrogen reduction circuits were retained with only minor modifications, major changes were made in the processes for the separation and recovery of cobalt. A totally new cobalt-nickel separation was successfully developed, in which most of the cobalt is separated from the ammoniacal nickel sulphate leach solution by precipitation as a cobalt-nickel hexammine salt, using anhydrous ammonia as the reagent. This salt, which contains equal amounts of cobalt and nickel, is refined to a pure cobaltic hexammine salt by selectively leaching nickel with water, and recrystallizing the resulting impure cobaltic hexammine salt in ammonium sulphate solution. The recrystallized cobalt hexammine salt has a Co : Ni ratio of over 2000 : 1, and contains very low levels of copper, zinc and cadmium. It is redissolved in ammonium sulphate solution and converted to cobalt powder by hydrogen reduction. This paper describes the changes made to the refinery processes since 1991, and reviews recent operating performance with emphasis on the treatment of Moa sulphides.

Paper 40.3 - 9:50

Industrial Experience with the Ni/Co Sulphides Precipitation Process

R.R. Matos, General Nickel Co., Moa, Holguín, Cuba

Design parameters related to the Ni/Co sulphide precipitation process are presented and compared with actual results obtained during sulphides precipitation. The paper focuses specifically on the predicted theoretical advantages and benefits of the sulphide seeding process.

Coffee Break (10:15-10:45)

Paper 40.4 - 10:45

The Cawse Nickel/Cobalt Laterite Project Metallurgical Process Development

J.H. Kyle and D. Furfaro, Oretest Pty. Ltd., Kewdale, Western Australia, Australia

The Cawse Nickel Project is one of the exciting new developments in nickel laterite ore treatment, currently under construction in Western Australia. The Cawse orebody has a number of distinct advantages over tropical and other temperate laterites in its ore mineralogy, low moisture content, and ability to be upgraded prior to pressure acid leaching.

The flowsheet developed by Centaur Mining and Exploration Limited for the Cawse Project includes ore upgrading, pressure acid leaching, iron oxidation and removal, precipitation of a nickel/cobalt hydroxide, ammonia re-leach of the precipitate, solvent extraction to produce a pure nickel sulphate solution for nickel electrowinning, and cobalt precipitation as a sulphide. Novel aspects of the flowsheet include a combination of an acid dissolution and an ammoniacal downstream solution route, and the addition of sulphur to the autoclave to control chromium(VI) formation during treatment of high grade siliceous cobalt ores. The main aspects of the flowsheet are discussed, with results coming from both batch and continuous testing, which were often occurring in parallel during 18-month fast-tracked process development.

Paper 40.5 - 11:10

Application of the Pressure Acid Leach Process to Western Australian Nickel/Cobalt Laterites

G. Motteram and M. Ryan, Anaconda Nickel Ltd., West Perth, Western Australia, Australia

R. Weizenbach, Sherritt International Consultants Inc., Fort Saskatchewan, Alberta, Canada

Western Australian nickel cobalt laterite ores, as being developed at Murrin Murrin, Bulong and Cawse, represent an unusual form of mineralization which is suitable for treatment using the Pressure Acid Leach process. The significant difference between the Western Australian ores and those treated at Moa Bay is the preponderance of smectite or nontronite clays, in comparison to the Cuban limonitic ores. These clay based ores contain lower iron and aluminum but higher magnesium levels than limonitic ores, resulting in up to 50% higher acid demand. The presence of local calcretes for neutralization and the high evaporation rates provide the ability to lock bleed water and residue streams into environmentally safe impoundments.

Issues associated with the development of the acid leach process for Western Australian laterites include: handling of viscous pulps through the slurry section, systems for preheat of viscous pulps prior to autoclave leaching and, the corrosive nature of the acid slurries when using chloride bearing groundwaters. Otherwise, the circuit adopted for Murrin Murrin will be largely conventional, using mixed sulphide precipitation of nickel and cobalt from the main leach solutions and refining of the mixed sulphide to high purity metal products. The Murrin Murrin project will be commissioned in mid-1998 and will be capable of producing 100 million pounds of nickel and 6.6 million pounds of cobalt per year.

Paper 40.6 - 11:35

The Calliope Project: Pressure Acid Leaching of New Caledonian Laterite Ore

M.D. Faris and M.J. Collins, Sherritt International Consultants Inc., Fort Saskatchewan, Alberta, Canada

G.S. Becker, P.J. Matheson and G.A. Lennard, Calliope Metals Pty Ltd., Brisbane, Queensland, Australia

Nickeliferous laterite ore from New Caledonia is currently processed by smelting of saprolite to produce ferronickel and by reduction roasting and ammonia leaching of limonite to produce nickel metal and cobalt by-products. Calliope Metals proposes to operate a refinery near Gladstone, Queensland, Australia, to recover 20,000 tonnes per year of nickel plus cobalt from limonite and limonite/saprolite transition ores imported from New Caledonia using the pressure acid leach process.

Target ore grades of 1.6% Ni and 0.17% Co will provide additional revenue, relative to projects treating lower grade ores near their source, to offset ore purchase and shipping costs. Pre-feasibility estimates place the cash cost of operations at US$ 1.29 per pound of nickel in sulphides after cobalt credits. Continuous laboratory testwork and process design conducted by Sherritt have demonstrated that high metallurgical recoveries of Ni and Co as sulphides can be achieved. This paper provides an overview of the ore supply strategy, process development work, plant design and pre-feasibility economic estimates for the project.

Wednesday, August 20, 1997, PM

Session 49: Nickel/Cobalt Recovery from Lateritic Ores: Recent Developments

Room: FA-054, Fraser Building

Chair-persons:

Paper 49.1 - 14:00

High Temperature Acidic Pressure Leaching: An Omnivorous Process to Treat Nickel-Cobalt Feedstocks

C.J. Ferron, R. Molnar and R.G. Williamson, Lakefield Research Ltd., Peterborough, Ontario, Canada

High temperature autoclaves are being used increasingly in the gold industry for the treatment of refractory ores, and their success in this field has renewed interest in extending their use to other areas of the metallurgical sector. The high temperature and, if required, oxidizing conditions in an autoclave create an extremely reactive environment and the process can be applied to a variety of nickel-cobalt feedstocks. Examples of autoclave applications are presented for various feedstocks including: nickel cobalt sulpho-arsenides, spent catalysts, sulphide concentrates, mattes and laterites.

Several options exist for recovering metals from leach liquors, depending on the specific cases and metal markets. Processes that are briefly discussed here are: mixed sulphide precipitation, solution purification by selective precipitation and solvent extraction.

Paper 49.2 - 14:25

Sulfuric Acid Leaching of Nickeliferous Laterites

E. Krause, A. Singhal and B.C. Blakey, Inco Ltd., Mississauga, Ontario, Canada

V.G. Papangelakis and D. Georgiou, Dept. Chem. Engineering and Appl. Chemistry, University of Toronto, Toronto, Ontario, Canada

Nickeliferous lateritic ores are the product of ultramafic bedrock weathering in warm and humid climates. Two ore types are important for the production of nickel by the sulfuric acid pressure leaching process. These are limonite, which analyses 1.0-1.6 wt% Ni, and contains goethite as the predominant mineral phase, and saprolite, which analyses 1.6-3 wt% Ni and consists mainly of Mg-silicates.

Transmission electron microscope (TEM) analyses of different lateritic ores revealed that goethite particles consist of aggregates of very fine needles (<0.02 m m diameter, 0.2-0.3 m m long). TEM analyses also revealed that goethite dissolves during leaching, and that iron re-precipitates as spherical hematite (~0.2 m m diameter). The leach kinetics depend mainly on the leach temperature and the acid addition. The acid requirement depends mainly on the Mg (saprolite) and Al contents of the ore. At the high leach temperatures (240-270° C), bisulfate ions predominate over sulfate. Consequently, an acid supply significantly in excess of the stoichiometric requirement is needed to provide sufficiently acidic conditions during leaching. The excess acid increases with increasing Mg content of the ore.

The micro structure of goethite affects the rheological properties of aqueous laterite slurries and the settling properties of incompletely leached laterites. The settling characteristics of leached lateritic ores worsen with increasing saprolite content of the ore. Some leach residues may exhibit particularly poor settling due to the presence of clay minerals. Hematite-alunite scale forms mainly in those compartments where acid is added and the degree of super-saturation (excess acid) is highest.

Paper 49.3 - 14:50

Settling Rates of Nickel-Laterite Clay-Rich Residues from High-Temperature Acid Leaching

G.P. Tindall, Mineral Science Department, Murdoch University, Perth, Western Australia, Australia

D. M. Muir, WMC Resources Ltd., Perth, Western Australia, Australia

Treatment of a clay rich fraction from a Western Australian nickeliferous laterite by high temperature acid leaching results in hematite-silica residues. Decantation of these siliceous residues has proven difficult, due to slow settling rates and low under-flow densities. In this study, leach temperature, agitation, time and acid concentration were varied in order to improve settling rates. Measurement of the electrophoretic mobility of leach residues suggests variations in surface chemistry account for the differences in settling performance. However, changes in operating practice can have a significant effect. Acid addition at 150° C is recommended prior to nickel extraction at 250° C to optimise silica precipitation. It is shown that saline process water leads to jarosite formation and higher under-flow volumes. The effect of Eh and Cr(VI) on settling rates of these clay rich ores requires further investigation.

Coffee Break (15:15-15:45)

Paper 49.4 - 15:45

Acid Leaching of Nickel Laterites in the Presence of Sulphur Dioxide at Atmospheric Pressure

G.K Das, S. Anand and R.P. Das, Regional Research Laboratory (CSIR), Bhubaneswar, Orissa, India

D.M. Muir, WMC Resources Ltd, Perth, Western Australia, Australia

G. Senanayake, P. Singh and G. Hefter, Dept. Min. Science & Chemistry, Murdoch University, Perth, Western Australia, Australia

Atmospheric acid leaching of a West Australian lateritic nickel ore and an Indian chromite overburden ore were found to be much more effective using sulphur dioxide as a reductant. The effect of acid concentration, SO2 and the catalytic behaviour of Cu(II) during leaching were examined. Aqueous SO2 alone readily leached cobalt and manganese with little iron, but nickel was leached by the addition of mineral acid in direct proportion to the dissolved iron. Kinetic treatment of the data indicate that the iron dissolution follows a shrinking sphere model. Leaching rates in three different acids were found to be in the order of HCl > H2SO4 > HClO4. The difference in acid reactivity appears to be mainly related to the speciation of Fe(II) and Fe(III), Eh of the solution and proton activity. An Eh-pH diagram has been constructed which considers the different species involved during reaction.

Paper 49.5 - 16:10

Extraction of Nickel and Cobalt from Greek Low-Grade Nickel Oxide Ores by Heap Leaching

S. Agatzini-Leonardou, D. Dimaki and E. Boskos

Department of Mining and Metallurgical Engineering, National Technical University of Athens, Athens, Greece

Statistically designed experiments were conducted to study and optimize column leaching, simulating heap leaching, of low-grade nickel oxide ores with sulphuric acid at ambient temperature. The ore tested was hematitic laterite with Ni 0.91%, Co 0.065%, Fe 31.97%, Mg 1.65%, Al 3.14%, Cr 1.54%, Ca 0.065% and SiO2 33.49%. Leach columns were made of PVC with internal diameter 25 cm and height 2.5 m. The variables studied were: feed grain size, sulphuric acid concentration in the leach solution, ratio of the leach solution volume to the ore weight and leach solution flow-rate. Responses measured included: nickel, cobalt, iron, magnesium aluminum, chromium, calcium, silicon, potassium and manganese percent extraction, Fe/Ni ratio in the leach liquor and sulphuric acid consumption. Nickel recoveries of up to 85% were obtained in less than 40 days. The Fe/Ni ratio in the leach liquors averaged 4/1, much lower than the value of this ratio in the ore (35/1). Mineralogical analyses of the leach residues were also conducted and the mechanism of laterites heap leaching was established.

Paper 49.6 - 16:35

State of the Art, Potentials and Limits to the Fluid Bed Pyrohydrolysis Technology with Special Emphasis on Nickel Chloride

C. Kögler, F. Bärhold and W. Engelhardt, Process Engineering Division, Keramchemie GmbH, Siershahn, Germany

G. Van Weert, Oretome Ltd, Caledon East, Ontario, Canada

Fluid bed pyrohydrolysis of metal chlorides by the Keramchemie technology is reviewed, including the production of hydrochloric acid for recycle to process. To date, this technology has mainly been used by the steel industry to regenerate its pickling acid.

Application of fluid bed pyrohydrolysis shows great promise, especially for the minerals and metals industry. Using chloride-based circuits, environment-compatible waste solids can be produced. For 15 years a similar technology was used by Falconbridge at its Norwegian refinery. This operation is reviewed, with an emphasis on the air/fuel system supplying the fluid bed, in which dried nickel chloride crystals were pyrohydrolyzed.

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