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By Steve Rule, Jose Roberto Vago, Walter de Moura

Cerro Vangaurdia Gold Mine is a joint venture between AngloGold (the operator), Perez Companc and Formicruz and is situated in the southern province of Santa Cruz, in Argentina, approximately 2,150 km south of the capital, Buenos Aires. The mine is located in a severe, semi-arid environment with very cold winters and little annual rainfall (200mm). It is an open-pit operation, mining several narrow, shallow epithermal quartz veins with . gold and silver mineralisation. Commissioning of the plant commenced in September 1998 and the first dore bar was poured towards the end of the same month. The nominal capacity of the plant is 55,000 tonnes per month, with a design capacity of 60,000 tonnes per month. Prior to finalising the design, an extensive testwork programme was undertaken at Nova Lima, in Brazil, in which all parts of the process were evaluated together on a pilot-plant scale. The process flowsheet selected at Ce1rn Vanguardia is quite novel, in that it includes milling in cyanide, as well as a cyanide recovery and recycling plant on the tailings section of the treatment plant is included. The cyanide recovery process selected was a version of the acidification - volatilization - reabsorption (AVR) process, known as Cyanisorb™. The selection of the Cyanisorb™ process in the plant design was as a direct consequence of two factors:

Jan 1, 2000

By Hans von Michaelis

Welcome to RANDOL GOLD FORUM 88. It is clear from the list of delegates and speakers that this conference will lead to excellent discussions of the latest developments in this fast-moving industry. Less than a year ago Randol International Ltd. published an eleven-volume report titled "Innovations in Gold and Silver Recovery - Phase 111". In the short space of time since then, many new developments have been noted, many of which will be described in this Forum. I believe that some of the more significant innovations currently under development are those that address the following:

Jan 1, 1998

By L. J. Warren

Recent research at the Parker Centre in Pe1ih, Western Australia, has provided opportunities to reduce gold production costs by: reducing lime costs in the carbon-in-pulp process, understanding the mechanism of selective extraction of gold over copper using ammoniacal cyanide, and increasing throughput and improving overflow clarify in thickeners. This paper reviews the work of these three Parker Centre project teams, and highlights those instances where the results have been applied to plant practice.

Jan 1, 1998

By D. D. Carda, S. Dunn, W. E. Dunn, T. Storbeck

Gold chlorination which will be presented in this paper is limited entirely to the use of gaseous chlorine in a fluidized bed reactor at elevated temperatures in the absence of aqueous water. The only water used in this process is that which is used in scrubbing the effluents. Low temperatures are defined as those below 500°C. All experimentation for this paper was carried out on a laboratory scale, with all calculations extrapolated frpm this. Some of the data is drawn from work with other projects which have been operated at pilot and larger scale.

Jan 1, 1998

By Stuart Ratcliffe, Denis Kidby

The development of Vitrokele™ Technology over the last 10 years is reviewed with reference to mine site piloting and com­mercial applications. The first mine site piloting was conducted in Australia in 1989 followed by a further six continuous site trials in Australia, Canada and the USA. These major pilot plant studies are complemented by over 50 laboratory scale batch and pilot testwork programmes. The first commercial plant using Vitrokele™ Technology was the Connemara project commissioned in Zimbabwe in 1995. Subsequent to this, three commercial scale projects have been designed using Vitrokele™ to recover precious metals, base met­als and cyanide. The various projects are discussed with relation to the differ­ing flowsheets applied to each particular case.

Jan 1, 1998

By Stephen R. Brown

Current conditions in the gold market demand that mine and plant operators make budgeted production targets at the lowest possible unit costs. For those companies bringing new gold pro­duction capacity on-line, achieving budgeted production levels as quickly as possible after start-up is vitally important to mini­mize unit costs and to begin a positive cash flow. Whether the objective is to simply improve unit costs or successfully start-up a new, complex plant, success will be strongly influenced by the skill levels of the operators and supervisors. The only way to assure return on plant investment, and to survive during depressed metal prices, is to ensure that plant operators have the knowledge to effectively run the plant. Technology available in computer-based, multimedia training systems, including: inter­active animation, videos, voice-overs, schematics, and text can now be used to train operators at their own pace using plant-spe­cific information. Additionally, it has been shown that learning through multimedia provides a higher degree of long term reten­tion than more traditional learning methods.

Jan 1, 1998

By Malcolm Wills

Boddington Gold Mine commenced operation in 1987 with an initial production of 3.0 Mt/y at a grade of 3.5 git. Head grade has reduced over the life of the mine and the major response to the drop in grade has been to increase mining rates and increase plant throughput. A capital expansion was carried out in 1996 increasing the throughput to 6.0 Mt/y and since that date tonnage has been increased without major capital expenditure. BGM's current mill throughput is 8.77 Mt/y ( 1999). In 1999 the combined basement plant and direct leach plant processed 8,770,055 tonnes to produce 233,507 ozs or 7.262882 tonnes of gold at an average head grade of 0.83 git. With grades of 0.83 git, and gold price at record lows, $US251.95loz in August 1999 or $A393.67loz it has been necessary to make and maintain major cost savings to remain profitable. Boddington Gold Mine has achieved this by a number of steps including a productivity study by outside consultants.

Jan 1, 2000

By D. A. Bulled

• "What does it look like?" - describes the appearance. • "How does it work?" - outlines the operation. e "Why does it work?"- explains the principles. • "What about controls?" - indicates possible automatic systems. • "How is it sized?" - discusses the necessary testwork and evaluation. • "What are the results?" - demonstrates test and operating results. • "What's the benefit?" - concludes with gains for the user.

Jan 1, 1999

By Donald D. Gullickson

The entire system is built around pre-designed and pre-engineered modules which are assembled to meet the metallurgical and production parameters of the project. The carbon vessels are the key to the flexibility of the system. The vessels are made of a coated mild steel, which allows the carbon vessels to be used in the adsorption, desorption and acid wash cycles. In the adsorption mode, the solution is pumped up-flow through four (4) vessels in series at 250 gpm fluidizing the carbon bed. When the carbon in the lead vessel is loaded, it is disconnected from the adsorption circuit via rubber hoses with quick-disconnect fittings. The second vessel is then made the lead vessel and a stripped carbon vessel is added to the end of the adsorption circuit.

Jan 1, 1998

By Donald D. Haas

Contract mining has a definite place in the mining industry, both in the United States and around the world. A mine owner should evaluate the utilization of contract mining in the devel­opment and production of mining properties. This evaluation of contract mining should be performed at various times in the life of a mining prope1iy from the development and initial operation of a new mining project, periodically throughout the mine's life, and at mine closure. Many factors must be considered in ana­lyzing and evaluating the potential of contract mining and those factors are both quantitative and qualitative. Quantitative factors are those factors for which costs or measures can be determined or estimated objectively; and qualitative factors are those factors for which costs or measures must be determined subjectively and do not lend themselves to objective determination or estimation. Some of the qualitative aspects may provide only yes, maybe, or no answers while others will provide a tendency or partiality toward one answer or the other without a quantified cost. The major quantitative aspects include operating and capital costs, monitoring costs, capital preservation, acquisition and disposal of new and used equipment, direct payroll and administrative costs, recruiting and training costs, and employment and termi­nation of staff and hourly personnel. The major qualitative areas include corporate philosophy, risks associated with capital and operating costs, financing the project, operating control, operat­ing flexibility, recruiting and training of personnel, employment and termination, administrative concerns, and owner/contractor relationship.

Jan 1, 1998

By John G. Banker, Arthur L. Forrest

Titanium solves corrosion, maintenance and environmental problems in many reactor and autoclave applications. Titanium clad construction permits autoclave designers a great deal of flexibility combined with significant cost reduction. Titanium alloys can be selectively applied in specific regions of the auto­clave to accommodate local environmental conditions. Resistance to general corrosion, crevice corrosion, abrasion, and ignition conditions can be accomplished selectively and eco­nomically. Explosion clad pressure vessel fabrication and perfor­mance have been proven through three decades of experience.

Jan 1, 1996

By Fred W. De Vries

The history of mining-industry regulations on cyanide indicates a trend to set criteria based on generalized inferences related to its high toxicity. As toxic-inventory-motivated regulations are framed, material balances are expected to imply atmospheric releases of HCN as a major factor. A review of atmospheric data shows the probable triviality of any environmental impact of such releases, and suggests a very deliberate approach to any proposed regulations regarding these emissions.

Jan 1, 1996

By Gordon Lewis

The Penjom Gold Mine is one of the world's worst preg-robbing gold ores, yielding very low recoveries from traditional CIL methods. Gold recovery from the cyclone underflow was targeted to recover as much gold as possible in the absence of the fine preg-robbing carbon. Gold is recovered by intensive cyanidation and tabling of a gold concentrate produced by gravity from the cyclone underflow. The circuit was designed together with Gekko Systems and uses their InLine Pressure Jig and InLine Leach Reactor technology to reject the preg-robbing carbonaceous material and obtain high recoveries from the gravity concentrate before over grinding the carbon and sulphides. The gravity and intensive cyanidation circuit now recovers almost 50% of gold in new mill feed, with unit recovery in intensive cyanidation of up to 90%, the highest unit recovery in the plant. Operating costs for the gravity and intensive cyanidation circuit are under US$2.50 per oz, while the cost to recover gold from the cyclone overflow is -US$200 per oz. (not including common costs of milling, stripping and electrowinning). Figure 1 shows the increase in gold recovery due to the gravity and ILR circuit coming on line at Penjom.

Jan 1, 1999

By Jacques Monette

Gold and silver cyanide complexes are presently desorbed from activated carbon by means of hot caustic elutions. These solutions may or may not contain additional sodium cyanide. There are several parameters which affect the rate of stripping. Some of these include pH, ionic strength, and tempera­ture. Stripping is conducted in recirculating (ZADRA) or once through (AARL) circuits. This paper describes the development of a new chemical eluant which increases the rate of stripping of both gold and silver cyanide complexes from carbon. Two case history applications are described.

Jan 1, 1995

By John W. Greene

ennec?tt's Bameys Canyon Mine personnel developed an mnovahve process to extract gold from a small (1.8 million tons) sulfide ore zone in an oxidized ore body located at the Bameys Canyon Mine. This approach consists of extracting the sulfides from the ore via flotation, shipping the concentrate to Kennecott's new smelter, and mixing the flotation tailings with the oxide ore, agglomerating the mixture, and stacking the resultin tailings/oxide ore combination on the heaps. Conventional heap leaching technology is utilized to recover the gold from the mixed materials. Overall, the total gold recovery from the sulfide ore is esti­mated to be 90%. This approximation is based on a smelter gold recovery of 98% from the concentrate and an 88% recovery from the tailings during heap leaching

Jan 1, 1996

By W. R. Mackenzie, C. A. MacDonald

Oxide copper was discovered in 1946 at Guelb Moghrein. Early work culminated in the construction in 1970, by a consortium headed by the Anglo American group, of a project producing copper concentrates from 1,000,000 tonnes per annum of oxide ore. The process used was the TORCO (Treatment Of Refractory Copper Ores) process, which reduced oxide copper minerals to elemental copper by roasting in fluidised beds at 800°C with salt and coal. The roaster product was then floated to yield a high grade smelter concentrate, which was exported. The project closed in 1976, due to low copper prices and increased energy prices, leaving an open pit, the old TORCO plant, a water pipeline, and more than 2,000,000 tonnes of tail­ings, which contained remnant copper, as well as an average of 3 git of gold. After several attempts to recommence operations at Akjoujt, recovery of gold from the old TORCO tailings was started in 1992 by a joint venture company known as MORAK (Mines d'Or d'Akjoujt). This company comprises General Gold Resources N.L. of Australia, who are the managing partner, SAMlN (La Societe Arabe des Mines d'Inchiri) and the International Finance Corporation. Because the tailings are high in copper (0.1-0.3% Cu), the project used the 'Hunt' process, which uses a combination of cyanide and ammonia to leach gold while suppressing copper extraction. The gold is recovered from leach liquor by carbon absorption.

Jan 1, 1996

By Antonio Dominguez-Perez, Annette Dickmann, Roy Norcross, Andreas Rubo, Stephen Gos

With increasing cost pressure in the production costs of gold, there have been great efforts made to reduce the gold production costs as much as possible and a great deal of effort and lateral thinking is required to maintain a cost effective gold production facility. In a difficult economic environment, there is always the danger of saving in the wrong place. Just like it can be fatal to cut down on innovative research and development for long-term existence and sustainability in most industries, savings in safety and visionary planning of regulations expected in the future can become very costly on the long run, if preventative measures are not taken, observed or ignored. This paper deals with some current topics pertinent to the gold mining industry with regard to the interaction between potential risks, regulations and the costs that arise and can be saved in relation to these. Only an optimal combination of cost effective, safe and technically feasible regulations enable an operation to work economically.

Jan 1, 1999

By Bruno Sceresini

Prospectors and small scale mmmg companies have long expressed the wish for a highly mobile mineral processing plant. This is especially so in the case of gold mining as relatively small deposits can be highly profitable due to the relative ease of producing a marketable product when compared with the refming and marketing costs incurred with base metals. This paper will concentrate on gold ore treatment in fitting with the theme of the 1996 Randol Gold Forum but the principles may also be applied to base metal ores. The development and application of the Atomaer Filblast Gas Shear Reactor as a cyanidation tool has removed the con­straints of plant size in pulp cyanidation applications. KC Dodd and Associates, Consulting Engineers and Australian Mining Advisers, Pty Ltd, have designed a 1,000,000 and a 250,000 tpa fully modularised ore treatment plant. Various module configu­rations can be arranged to treat a wide variety of ores ranging from simple gold ores to gold-copper and base metal ores. This paper will limit the discussion to comparing the capital and operating costs of a conventional and a modularised 1 million tpa gold treatment employing a number ofnovel concepts which complement the compact, high capacity Filblast Cyanidation Process and the AARL pump Cell Adsorbers. The design described in the paper not only reduces equip­ment sizes and allows for rapid deployment of a sizeable capac­ity plant but also offers significant capital and operating cost benefits.

Jan 1, 1996

By Tony Treasure, Ian Ewart

The EMEW® cell has been developed to overcome a number of inherent limitations in conventional electrowinning technology, particularly the high cost and restricted process windows characteristic of conventional hardware. The EMEW technology has been widely demonstrated to achieve high performance for various metals under chemical conditions well outside the limits required for efficient operation of conventional cells. In particular application of the EMEW cell for recovery of silver offers significant operating and capital cost advantages over conventional Merrill Crowe technology used for cyanide based solutions. The cell also offers process advantages for direct silver recovery from nitric acid solutions. The performance of the EMEW® cell on silver cyanide solutions, producing high grade silver metal in a single step, is accomplished by providing a physical mechanism which presents metal ions to the cathode on a highly efficient and continuous basis. The simplicity of design and operation of the EMEW cell offers the following advantages for silver recovery from cyanide or nitrate based solutions: • High grade product in a single step. • Selective for silver over other metals in the electrolyte. • Wide operating concentration range (100,000 - 5ppm). • Ability of the cell to operated in a variety of acid or alkaline electrolytes. (Cyanide, Nitrate). • Simple liquor reticulation. • No pretreatment required - Clarification, deaeration or zinc dust. • High cmTent density and current efficiency compared to conventional electrowinning cell. • Modular design allows for flexible operation and production rate. • Pilot plant results using full scale cell result in accurate scale up design. • Easy/fast installation - cell banks are delivered pre configured with piping and wiring. • Enclosed cell minimizes corrosive vapor and liquid losses in the circuit.

Jan 1, 2000

By John Batty, Rennie Stallknecht, Dave Dew, Rennie Marais

GENCOR was contracted by Lonrho Plc of London to design a treatment plant for the benificiation of ores from the Amantaytau Goldfields in Uzbekistan (CIS). The testwork required for determining the design parameters was conducted at GENCOR Process Research in Randburg South Africa, on large bulk samples of ore shipped from the CIS. The initial milling and flotation testwork was designed to both optimise the conditions for maximum gold recovery, and to provide flotation concentrate for subsequent testwork. The concentrate produced was fed to a pilot scale BIOX® plant, and at the client's request a portion was shipped to specialists in roasting and pressure oxidation technology for comparison. Besides the testwork conducted at the GENCOR Process Research Laboratories in South Africa, the client also requested that the testwork be repeated at the Ingichki Research centre in Uzbekistan to demonstrate to their CIS joint venture partners that the results obtained in South Africa are reproducible and to demonstrate the ease of operation of a BIOX® plant. Pilot scale equipment was air freighted to Ingichki where the results of the testwork obtained in South Africa were successfully duplicated. BIOX® technology was shown to achieve higher gold recoveries than either roasting, whole ore roasting or pressure oxidation.

Jan 1, 1995