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By R. M. G. S. Berezowsky

An atmospheric ammoniacal thiosulphate leach system was developed to recover gold and silver from residues of the ammoniacal oxidation leaching of sulphidic copper concentrates. Extractions of 88 - 95% Au and 83 - 98% Ag were attained within 2 to 4 hours at 40 - 60°C in thiosulphate leaching of the oxidation leach residues of Manitoba chalcopyrite concentrates analyzing 24.6% Cu, 0.18 oz/ton Au and 4.26 oz/ton Ag and a complex British Columbia chalcopyrite/tetrahedrite concentrate analyzing 18.5% Cu, 0.27 oz/ton Au and 276 oz/ton Ag. Parameters affecting the Au and Ag solubilization included thiosulphate, ammonia, and cupric ion concentrations, temperature, retention time and the degree of Cu extraction and sulphide oxidation in the primary oxidation leach. The precious metals were recovered from the thiosulphate liquors by zinc dust cementation.

Jan 1, 1979

THE township of Costerfield is situated in the parish of Costerfield, county of Dalhousie, and lies 6 miles east of Heathcote and 30 miles south-east of Bendigo. It is separated from Heathcote by the Mt. Ida Range, which forms the western boundary of the Silurian formation. It is situated at the head-waters of Tin-pot Creek, a small southerly tributary of the Deegay Ponds Creek, which flows east to the Goulburn River.The field was discovered in 1860 by two prospectors, Coster and Field, who were guided there by a shepherd, M Nicol Coster and Field had already discovered an antimony lode about three miles nearer Heathcote, when M Nicol offered to guide them to the larger outcrop. The main Costerfield reef at that time projected above the surface, and was white through oxidation, though the bluey sulphide showed on fracture. No alluvial gold of any consequence was obtained at Costerfield, but a little was obtained, at Redcastle, 7 miles to the north, and in some of the gullies to the east.Following its discovery there came a period of prosperity to Costerfield, while the mining operations were confined to the oxidized zone. The early success of mining at Costerfield was due to the gold values, and it is probable that the oxidized zone was secondarily enriched. The earliest available record of values is a crushing of Coster and Co. on the Antimony reef (now known as the Costerfield reef), when 200 tons from a depth of 70 ft. averaged 4 oz. per ton in July, 1861. At this time a crushing mill had not yet been erected at Costerfield, and the ore was carted and treated at Redcastle. The massive antimony ore, consisting of mixed oxides and sulphides, was separated by hand-picking as "marketable ore," and the remainder crushed for gold. A higher average is recorded from South Costerfield in September, 1861, when a 15' cwt. parcel...

Jan 1, 1922

By N. Snyders, I. Mwandawande, S. M. Bradshaw, M. Karimi

"Computational fluid dynamics (CFD) was applied to predict the average gas holdup and the axial gas holdup variation in a 13.5 m high cylindrical column 0.91 m diameter. The column was operating in batch mode. A Eulerian-Eulerian multiphase approach with appropriate interphase momentum exchange terms was applied to simulate the gas-liquid flow inside the column. Turbulence in the continuous phase was modelled using the k-_ realizable turbulence model. The predicted average gas holdup values were in good agreement with experimental data. The axial gas holdup prediction was generally good for the middle and top parts of the column, but was over-predicted for the bottom part of the column. Bubble velocity profiles were observed in which the axial velocity of the air bubbles decreased with height in the column. This may be related to the upward increase in gas holdup in the column. Simulations were also conducted to compare the gas holdup predicted with the universal, the Schiller-Naumann, and the Morsi-Alexander drag models. The gas holdup predictions for the three drag models were not significantly different. IntroductionColumn flotation is an important concentration technology that is used in the mineral processing and coal beneficiation industries. The growing interest in the use of column flotation in mineral processing has been attributed to the simpler flotation circuits and improved metallurgical performance compared to conventional flotation cells (Finch and Dobby, 1990). Flotation columns have also found other applications outside mineral processing, such as de-inking of recycled paper (Finch and Hardie, 1999).In column flotation, a rising swarm of air bubbles generated by means of air spargers is employed to collect the valuable mineral particles and separate them from the gangue minerals in a countercurrent process. Wash water, which is continuously fed at the top of the column, is used to eliminate entrained particles and stabilize the froth. The column volume can be divided into two sections – the collection zone in which the bubbles collect the floatable mineral particles, and the cleaning zone (or froth zone) where product upgrading is enhanced through the removal of unwanted particles entrained in the water mixed with bubbles from the collection zone."

Jan 1, 2019

By Makoto Ohlsuka

The ternary Ni2MnGa intermetallic compound is an intelligent material which has both a ferromagnetic property and a shape memory effect (SME). The use of the shape memory alloy films for an actuator of micro-machines is very attractive because of its large recovery force. The purpose of the present study is to investigate the effects of fabrication conditions and to clarify the relationships between these properties and fabrication conditions of the Ni-Mn-Ga films. The Ni-Mn-Ga films with a thickness of nearly 5 um were deposited with a radio-frequency magnetron sputtering apparatus using a Ni50Mn25Ga25 or Ni52Mn24Ga24 target. They were heat-treated at various temperatures between 873 and 1273 K for homogenization and ordering and then cooled in a furnace. The composition of the films depended on the sputtering power. The as-deposited films were crystalline and had columnar grains. After the heat treatment the grains widened and the grain boundary became indistinct with the increasing heat treatment temperature. The martensitic transformation temperature of the heat-treated films increased with increasing nickel content. Furthermore the effect of plastic deformation and constraint aging on SME is also investigated. After plastic deformation, the two-way SME was shown through the martensitie transformation and its reversion, The intensity of X-ray diffraction peaks from stress-induced martensitie phase was found. The constraint-aged films also showed the two-way 3ME by thermal cycling.

Jan 1, 2003

By Henry F. Hebley

INTRODUCTION How often has the thoughtful observer pondered the apparent contradictions experienced in the weather? One can take records of two days, one in the winter and one in the summer. The "degree days" indicate that space heating and domestic load were present in one case and not in the other. The Business Index may be about the same, indicating that the industrial activity of the area and its concomitant use of fuel were about the same. Thus the volume of the products of combustion released to the atmosphere varied only as related to the space heating demand. Yet on one day in winter the atmosphere may be clear and bracing, while on a summer's day the air is thick and murky and the visibility sharply reduced. The situation may be reversed. What are some of the factors that contribute to the creation of these conditions? These few notes have been prepared to indicate some of the influences that are exerted on the problem. THE SOURCES OF ATMOSPHERIC POLLUTION The industrial area of Pittsburgh, Pa., has been a dominant center for the production of iron and steel for over one hundred years. In fact, with the growth of the numerous auxiliary processes Allegheny County which contains Pittsburgh is probably the most industrialized county in the world. In addition, the type of manufacture carried out in this area is predominant dependent on thermal energy (heat). That energy is supplied from coke and coal produced in the vicinity of Pittsburgh. Indicative of the stupendous quantities of fuel that are employed in this industrial area's economy, the following (Table No. taken from the U. S. Census (1940) may I of interest. An influence that has never been fully appreciated by many individuals is the fact that no matter what adventures the gases of combustion experience as they pass through the various processes, ulti¬mately the spent gases are discharged through chimneys to the atmosphere.

Jan 1, 1948

By M. van de Vijfeijken

This paper will first give a short overview of the Copper Mountain project in British Columbia, which just has started commercial operation earlier this year. The grinding process with one 34' x 20' SAG mill and two 24' x 39.5' ball mills will be briefly discussed. All three mills are gear driven by a ring gear, dual pinion and two low speed synchronous motors. Copper Mountain has installed on all three mills, the new state-of-the art dual pinion mill drives. All the inherent operation and maintenance features of this drive technology will be discussed, as well as the advantage of having variable speed control also on the ball mills. The installation and commissioning of the mills and drives at Copper Mountain will be briefly reviewed. Finally the first field measurements on these low speed mill drives will be presented, with the main focus on the low mechanical stress impact of these mill drives on the pinion and ring gear, as well as the accuracy of the load sharing between the two motors.

Jan 1, 2012

By Nader Shahcheraghi, Verya Nasri, Mehdi Bakhshi, Ali Haghighat

An accidental fire load is one of the major loads considered in design of segmental linings in transit tunnel. Typically, a two-dimensional coupled thermo-mechanical finite element analysis (FEA) is conducted. The conventional approach involves using standard fire curves (temperature-time curves) which can lead to a significant overestimation of fire load and tunnel lining thickness in metro tunnels. The focus of this paper is on the cutting-edge approach, using 3D computational fluid dynamics (CFD) analysis of real train fires in metro tunnels and coupled thermo-mechanical finite element analysis (FEA) to accurately and cost-effectively design fiber-reinforced concrete (FRC) segmental tunnel linings for large-scale metro projects.

Jun 23, 2024

By Mingming Zhang, Ramana G. Reddy

"Carbon dioxide (CO2) is one of the most common by-products produced during light metals production. It is considered to be the cause of greenhouse effects. Efficient reduction of CO2 can help minimize the rate of global warming and improving energy sufficiency. In this paper, a novel light metal production process was developed using ionic liquid electrolytes. This process has significant advantages compared to the traditional high temperature processes such as zero CO2 and CF4 emission, low energy consumption due to the low temperature operation and nonconsumable electrodes. Two types of anode materials (graphite, extruded carbon) were tested in electrolysis experiment. The results showed that both anode materials were stable (negligible weight loss). However, the extruded carbon was found to be superior to graphite in terms of current density and current efficiency. The calculated energy consumption for aluminum production was less than 10 kWh/kg at current densities up to 300 A/m2.IntroductionGlobal demand for ultra-light, ultra-strong, recyclable metals is growing as the world switches to low-emission vehicles, energy-saving devices and sustainable products. Aluminum demand is forecast to climb by 30 percent; magnesium demand by 200 percent, while for the emerging industrial light metal, titanium, the demand is expected to be at least double in the next decade. However smelting of light metals is the most energy intensive among all the steps of light metals production. For example, on an average it takes about 15.7 kWh of electricity to produce one kilogram of aluminum from alumina [1, 2, 3]. Advancements in energy efficiency have been steady, but slow, and most U.S. aluminum smelting production operates at 95% current efficiency. Besides high energy consumption, another major concern of the light metals smelting process is the emissions of greenhouse gases (GHG). Electrolysis green house gas emissions in the Hall-Héroult process can be split into three groups: 1) reduction reaction emissions, carbon dioxide (CO2) and carbon monoxide (CO); 2) process upset perfluorocarbons emissions; and 3) hydrogen fluoride (HF) formed from the moisture (H2O) present in the raw materials [2, 3]. Hydrogen fluoride gas can be captured and returned to the cells by the alumina dry scrubbing system used in modern facilities. A total of 5.31 kilograms of CO2 is generated from the reduction process for each kilogram of aluminum produced in the average U.S. primary facility. The perfluorocarbon emissions are related to the “anode effect.” If the concentration of alumina in the bath becomes too low, other reactions between the carbon anode and the bath occur and tetrafluoromethane (CF4) and hexafluoroethane (C2F6) are generated. These gases have high global warming potentials (GWP), which is a ratio developed to compare the ability of each greenhouse gas to trap heat in the atmosphere relative to carbon dioxide"

Jan 1, 2008

By R. O. Dannenberg

The Bureau of Mines investigations described in this report were undertaken to devise a process to economically recover precious metals and copper from low-grade, complex electronic scrap generated in large quantities by military and civilian electronic operations. Leaching with various media is applicable to certain selected items of electronic scrap but cannot be practically applied to complex mixtures of scrap. A process comprising incineration, caustic leaching to remove aluminum, smelting with a siliceous slag, and electrolysis recovered 99.9-percent-pure copper metal and anode slimes assaying more than 7,000 ounces per ton of combined precious metals. Silver, gold, and copper recoveries were 93, 95, and 87 percent, respectively. Cost analysis indicated that an alternative process using direct smelting of the scrap to make assayable products for sale to a custom smelter would provide better overall financial returns.

Jan 1, 1972

By E. M. Stiles

THE Wellington Lake power plant of the Consolidated Mining and Smelting Company of Canada, Limited, about 25 miles from Goldfields, Saskatchewan, is the second hydro-electric project operating in that Province, the first being the Island Falls plant of the Churchill River Power Company which serves the operations of the Hudson Bay Mining and Smelting Company at Flin Flon, Manitoba. The Churchill River project develops 90,000 h.p. at 56-ft. head; the Wellington Lake plant 3,300 h.p. at 75-ft. with pro-vision for an additional 3,300 h.p. unit. Churchill River power is trans-mitted at 110,000 volts over a 58-mile line of steel towers to Flin Flon and an additional 45 miles over a wooden pole-line to Sherritt-Gordon. Our steel tower-line is 22 miles long, and the voltage is 60,000; this choice be-cause certain such equipment was available from Trail. The diversion of 15,000? second-feet at 56-ft. head for 90,000 h. p. at Churchill river dwarfs our 500 second-feet flow at 75-ft. head for 3,300 h.p. In both cases, the main obstacles to be overcome during plant construction were the lack of transport facilities and the short open season. Let it be noted here that this paper deals mainly with those phases of plant construction which were particularly interesting to the writer. With-out these variations from the ordinary routine, this is just another power project whose story is better told by the accompanying charts and pictures. To many members of the Institute it is still just that; but I am writing for those who, like myself, have been too seldom responsible for major under-rakings at an appreciable distance from a railway siding. When it was planned in early 1937 to erect a 1,000-ton mill at our Box mine, both hydro and Diesel power were discussed. With ten years' ore in sight, even an expensive hydro project, such as ours turned out to be, produces kilowatts materially below the 2-cent operating cost of a Diesel plant using fuel-oil at 14 cents a gallon.

Jan 1, 1940

By G Dunstan

The Ridgeway gold mine has been an enigma of the international underground hard rock community for nearly 20 years. It nearly didn’t eventuate as it was more than 500 m below a farmer’s paddock in Central New South Wales when the exploration team, looking for open pit deposits, got a sniff on its last attempt and then drilled the high-grade discovery hole. It took separate studies to find an economic mining approach. Newcrest, then a mid-tier mining company, took the venture that set it on a path of growth and built what was to become the backbone of the company for the next 15 years.The initial mining method was sublevel caving (SLC) for the upper 300 m of the orebody. The nameplate production rate for the SLC was 4 Mt/a, which was reached in June 2002 shortly after the commissioning of the materials handling system. The ultimate production rate was subsequently lifted to around 6 Mt/a through a series of innovative and efficiency initiatives. In June 2007, approval was granted for the development of a block cave (BC) operation to extract the ore reserve situated immediately below the existing SLC operations, Ridgeway Deeps. The BC was designed at approximately 6 Mt/a to match the concentrator and a systematic improvement process through the entire underground system again saw delivery rates consistently around 10 Mt/a.In line with the production rate increases, Newcrest was also committed to advancing caving knowledge through a number of targeted research and development experiments and new processes. These were primarily related to improving cave ore recovery through systematic draw marker trials, cave propagation through preconditioning techniques with associated monitoring systems. New technologies were also developed to improve the safety and efficiency of the mine through data collection, cave establishment techniques, production dispatching and autonomous loading.CITATION:Dunstan, G, 2016. The truth is stranger than fiction – the story of Ridgeway gold mine, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 19–30 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By J. Tuominen

Outokumpu Direct-to-Blister Flash Smelting is currently in operation in two smelters, a third one is under construction and a fourth one is in the design phase. The two smelters in operation are the Glogow 2 smelter of KGHM Polska Miedz S.A. in Poland and the Olympic Dam smelter of BHP Billiton in Australia. The Outokumpu Direct-to-Blister smelter of Konkola Copper Mines Plc. in Zambia is under construction and the new smelter of Glogow 1 is under design and waiting for final go-ahead decision. Additionally, the Garfield smelter of Kennecott Utah Copper Corp. makes blister copper out of matte in a Flash Converting furnace. A similar operation is under construction for Y anggu Xiangguang Copper Co. in China. The slag cleaning process, which is needed to clean the slag of the Direct-to-Blister Flash Smelting Furnace, has different requirements depending on the feed to the flash furnace. These differences are discussed in the paper. The differences between the processes and slag produced are discussed as well as the metallurgical requirements for slag cleaning. The Direct-to-Blister process, where the blister copper is produced directly from concentrate in one step, requires at least a partial treatment of the slag in an electric slag cleaning furnace. The existing impurities determine the specific requirements of the actual cleaning process. The different processes are discussed in the paper. The newest developments of Outokumpu Technology Oy for electric slag cleaning furnace design are presented as well as the characteristics which the furnace shape gives to the process.

Jan 1, 2007

The object of this paper is to give a description of the new office and changehouse building and equipment at the Zinc Corporation Limited, the office section of which has now been in full use for approximately three years, and the changehouse section for approximately two years. As the expectations of the design have been fully realized, it is thought that this description will be of interest to members and possibly of some use to others faced with similar problems.GENERALIn the centralization of the surface plant around the new main shaft the combined office and changehouse building forms a prominent feature, being located between the shaft and the mill and facing the workshops on the northern side.The scheme for housing all employees in one building was proposed by the Manager, Mr. A. J. Keast, who was familiar with a similar successful structure built at the McIntyre Porcupine Mines Ltd. in Ontario, Canada.The principal features of this building were adopted as a basis for design, and the present layout evolved to suit the particular requirements of this mine.Some of the advantages of the design are:(a) Economy in first cost and space occupied when compared with plants having separate office and changehouse buildings.(b) Easier and more constant supervision of employees and of the plant by the senior staff members.(c) Close contact between officials of all departments.(d) Close covered connection between changehouse and shaft.(e) Avoidance of duplication of ,essential services such as electric power, water, heating plant, sewerage, etc.The Managing Director, Mr. W. S. Robinson, further instructed that the following requirements be adhered to in the new building:(a) Ample accommodation to be provided for office staff and other employees.(b) Special attention to be paid to lighting, both natural and artificial.(c) Working temperatures to be controlled to facilitate comfort and efficiency.(d) The buildings and equipment' to be of a permanent nature with furnishings and fittings of modern design.

Jan 1, 1941

By Eduardo M. Sacris

The performance of the grinding circuit, from the initial stages of operation to the present, is discussed. The mill efficiency as measured by the Bond grindability data and the operating work index is presented. The objective has been to produce a sand cyclone overflow containing not more than 6% +65 mesh. However, this has never been attained even at low milling rates. On the other hand, significant improvements in throughput were achieved by instituting some equipment changes and process modifications within the grinding circuit. The latest approach to solving the coarse grind problem is also discussed.

Jan 1, 1983

By Thomas M. Harris

Cation exchange is not sufficiently selective to be used for the removal of heavy metal ions from a general industrial wastewater. However, if the metals can be converted to polyvalent anions through complexation, they may be removed both selectively and efficiently by anion exchange. This approach, referred to as chelation-assisted anion exchange (CAAE), has been examined using industrial wastewater samples contaminated with Ni2+ and Cr3+. For this particular application, the Ni2+ is complexed with 8-hydroxyquinoline-5-sulfonic acid, and the Cr3+ with sulfosalicylic acid. Removal efficiencies and adsorption isotherms for both the complexants and the complexes were determined in batch-mode tests.

Jan 1, 1994

By N Weatherstone

A consistent and reliable international approach to public reporting of a mining companyÆs main assets, its Mineral Resources and Mineral Reserves, has become of increasing importance in recent years with the rapid globalisation of the mining industry. Through the efforts of the Committee for Mineral Reserves International Reporting Standards (CRIRSCO), a committee representing national resource/reserve reporting committees in Australia, South Africa, UK/Ireland/Western Europe, Canada, USA and Chile, the reporting standards in most æwesternÆ countries use almost identical resource and reserve definitions and are generally around 90 - 95 per cent compatible. New codes based on the CRIRSCO model are being developed or considered in other countries, including Peru and the Philippines. This unified approach has provided the mining industry, regulators and investors with a common framework to report and interpret mineral resource and reserve estimates, thereby facilitating funding to the mining industry through improved investor understanding and confidence. The common reporting standards are reflected in the CRIRSCO International Template, available on CRIRSCOÆs web site, a document that is kept æliveÆ by reflecting the best of the most recently published CRIRSCO-type national standards. In a significant exception to this unified industry approach, the USA Securities and Exchange Commission (SEC) requires adherence to its own standard, only partly compatible with CRIRSCO-type standards, with adverse and costly implications for companies listed in the USA. A major industry submission was presented to SEC in April 2005 which, if accepted, would bring about considerable compatibility of CRIRSCO and SEC standards. The UN Economic Commission for Europe (UN-ECE) has, since 1992, been developing its Framework Classification (UNFC) as a single global system for harmonising all existing national and international resource/reserve reporting systems, covering both government and industry requirements and both the hydrocarbon and solid minerals sectors. While few mining companies report their resources and reserves using the UNFC, the system is accepted or is being examined as a basis for reporting by some governments, including those of Russia, China and India. The UN-ECE agreed in 1999 to incorporate CRIRSCO definitions into the UNFC for those categories of resources and reserves used for market-related reporting, but a more recent edition of the UNFC removed or changed the definitions, requiring re-engagement by CRIRSCO to ensure compatibility. Since 2005, CRIRSCO and the Society of Petroleum Engineers (SPE) have been involved in discussions with the International Accounting Standards Board (IASB), which plans to develop a new Accounting Standard for the Extractive Industries as part of its International Financial Reporting Standards. At the request of the IASB, CRIRSCO and SPE have been examining any potential for convergence of resource/reserve definitions between the mining and hydrocarbon industries. Each of these systems is described in this paper and high level comparisons made.

Jan 1, 2006

By Y. M. Shneerson, P. V. Zaytsev, I. V. Fomenko, M. A. Pleshkov

A thermodynamic description of the equilibrium in liquid and gas phases under specific conditions of refractory gold pressure oxidation was generated using the HKF theory. The gold behavior was considered at 190-225°C in the presence of 1-100 mg/L of chloride ion, and under oxidationreduction potential (ORP) of +700 to +1030 mV. The calculations show that the predominant form of gold(I) occurrence is [AuOH]° compared to [AuCl2]?. High ORP favors the formation of [AuCl4]? as a predominant form of gold(III). It is noted that this complex is responsible for the gold losses buildup during POX. Laboratory test results for double refractory concentrate POX are shown. The combined negative effect of (i) organic carbon of the concentrate and (ii) dissolved chlorides in POX slurry on gold recovery is demonstrated. The effects of carbonate blending to the POX feed concentrate and incomplete oxidation of sulfides on POX performance were studied. The pilot tests results of continuous pressure oxidation are also shown and generally confirm the laboratory results and theoretic dependencies. A comparison of the experimental data with the results of thermodynamic calculations is made. As a result of current research, an effective process for POX treatment of carbonaceous sulfide concentrates in the presence of chlorides was developed.

Jan 1, 2014

By Robert A. Jankowski, Charles A. Babbitt, Natesa I. Jayaraman

The U. S. Bureau of Mines, through a contract research program with Foster-Miller, Inc., has identified guidelines for the selection of the most effective water spray system and water flow rates for use on continuous mining machines. Specifically, these parameters were modified to obtain maximum dust control with regard to quartz dust exposure and more stringent respirable dust standards due to quartz. A novel water spray system, consisting of flat fan spray nozzles, mounted across the top of the mining machine, along with high flow, flat fan and higher pressure hollow cone nozzles mounted under the boom has been identified and tested. The anti-rollback/underboom spray system minimizes dust rollback while increasing dust knockdown by its unique positioning of spray manifolds and orientation of spray nozzles. Respirable dust suppression characteristics of the system acted in three ways: - by wetting the surface of the broken coal material to prevent dust from becoming airborne; - by controlling the airflow pattern at and near the face to minimize dust rollback to the operator Is control location; and - by dust knockdown, i.e., airborne capture, or scrubbing of airborne dust from the air. During underground trials, the anti-rollback/ underboom spray system reduced dust levels at the operator's position and in the immediate return by 55 and 15 pct, respectively, when compared to a conventional spray system. Quartz dust levels at the operator '8 position were essentially eliminated, while quartz dust levels in the immediate return were reduced by 57 pct. Applying the concepts of this technique throughout the mining industry should reduce the health hazard associated with excessive exposure to respirable quartz dust, as well as allow coal mine operators to comply with the associated, more stringent, respirable dust standards.

Jan 1, 1987

By James S. Graham

Specifications for treated round wood piling are presented for the engineers consideration. Included in the text are background information, technical committees, Chellis, quality, treatment, static and dynamic stresses, accessories, and existing codes and standards. The specifications are also available using Word Perfect on 3.5 or 5.25 inch size disks provided by the National Timber Piling Council. Note: DFI recommended wording is wood, head, and toe, instead of timber, butt, and tip.

Jan 1, 1992

By Jochen Petersen, Caroline Muzawazi

The technical feasibility of ammonia leaching of PGM bearing Platreef flotation concentrates was investigated as an alternative method for the recovery of base metals prior to precious metal recovery. The composition of the concentrates includes 2.02% Cu and 3.17% Ni, and the major base metal minerals are chalcopyrite and pentlandite. Optimal leaching conditions were initially established in shake flask experiments to be a solution containing 4 M NH4OH, 4 M (NH4)2CO3 and a pH range between 9 and 10. These were used as base case conditions in column and batch stirred tank reactor tests, where the effects of total ammonia concentration and operating temperature were explored further. At optimal conditions nearly 100% Cu and Ni extraction were obtained in the batch stirred tank reactor, and 95% Cu and 60% Ni extraction was obtained in columns. The activation energy for chalcopyrite and pentlandite was 36 kJ/mol and 16 kJ/mol, respectively, in both reactors, indicating different reaction pathways for the two minerals. Gas-liquid mass transfer appears to be the limiting reaction step in columns much more than in tanks, and the degree of ammonia loss to air is significant. This initial test work indicates the feasibility of using ammonia leaching for this and similar materials as an alternative route to conventional smelting and refining prior to PGM recovery, but a number of technical challenges still need to be overcome.

Jan 1, 2014