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By Chris Lynagh, Lisa Smiley

INTRO PAGE

Jun 13, 2021

By Wolfgang Baum

The objective of this presentation is to demonstrate the utilization of process mineralogy to improve the plant performance of a large gold-silver operation. From raw ore to tailings, from concentrate to off-gases, nearly all aspects of the recovery process have benefited from the mineralogical work. The involvement of a process-oriented mineralogist on a routine basis permitted the plant to "unlock" the reasons for process problems and to take corrective measures such as adjusting and modifying the mill circuit and the process parameters. Process mineralogy has also been of substantial value for the selection and operation of equipment. This resulted in a more cost-effective operation with improved precious metals recovery and better by-product quality. Specific modifications made in recent years are largely related to mineralogical factors, particularly the inherent precious metals mineralogy and alteration characteristics of the ore.

Jan 1, 1998

By Peter Erlynne

Rising costs have affected the cost of operating and install­ing crushing circuits, just as they have affected every other area and there is little possibility that the cost cycle is about to be reversed - power costs, wear materials costs and labour costs continue to increase but a basically stable gold price makes little allowance for these cost increases. Additionally, lower grades of ores being worked, and harder feed materials have a significant effect on the potential for higher processing costs. There are, of course, options for size reduction - some of them newer than others - some are suitable for certain types of ores and less suitable for others and it can sometimes be difficult to ascertain the accuracy of anticipated results before plant design and con­struction are completed - by which time the capital outlayed will preclude a change to another method ofreduction. Nordberg's patented WaterFlush Technology has the potential to change the way that Ball Mill Feed production is viewed: Some of the elements that must be considered are: • Capital Cost • Operating Cost • Efficiency • Flexibility • Availability • Control • Support Efficiency • Expertise • Spares availability • Environmental considerations

Jan 1, 1995

By Kevin Bell

The TRAC™ Program was developed to provide our clients with a mechanism that allows them to better manage site remedia­tion and closure costs. This program provides a fixed-price contract for site remediation and case closure and is well suited for large pro­jects with multiple PRPs, such as Superfund sites. Because Kvaerner is a large engineering/construction firm and not a consult­ing firm, we can offer this type of contracting mechanism that envi­ronmental consulting firms are hesitant or unable to provide. With TRAC™, Kvaerner assumes financial and technical responsibilities for carrying a site through the closure process for a fixed price. Liabilities carried on our client's balance sheet for site closure can be removed when they sign up forTRAC™. In many instances, a profit can be realized as the liability on the balance sheet may exceed our TRAC™ fixed-price cost to close the site. Bonds and other sureties securing the site can be released and set­tlement with other involved parties can be quickly reached. For a project to be considered for this program, it typically meets the following criteria: 1) The project site should be physically separated from other contaminated sites 2) A reasonable quantity of site investigation data must be avail­able including site-usage history with or without a projected fea­sibility study(ies) and/or remediation design 3) Access to perform all necessary work must be available. After a review of all site data, K vaerner develops a "risk menu" to manage financial risks. In this "menu", each compo­nent of the project is assigned a level of probability that the costs will occur. Then the base cost of each activity is "weighted" by multiplying the potential cost growth by the probability. This analysis assures that the financial risks are appropriately defined, weighted, and mitigated and a realistic fixed price is developed. Upon acceptance of our proposal and conclusion of contract negotiations, Kvaerner takes over future responsibility for clos­ing your site. This allows the client to: 4) Release reserves obligated on financial statements for the site (and potentially realize a profit if the TRAC™ fixed-price cost is less than our client's booked obligation) 5) Finalize cost settlement with other responsible parties, insur­ers, etc. 6) Redirect resources involved in the environmental manage­ment of the site 7) Cap legal and administrative costs In addition to performing the site cleanup and closure work, at our client's request we are able to: 8) conclude lease obligations for property 9) dispose of equipment and buildings

Jan 1, 1998

By Leslie M. Burnside, Gene E. McClelland, Roy R. Cellan

Revegetation of neutralized heap leach material in the arid environment of the Great Basin represents a challenge of avail­able technology. The chemical and physical environment of spent and neutralized ore is inhospitable for germination and establishment of desirable long term vegetation. Common soil amendments were tested to dete1mine if the heap material could be made more conducive to plant growth. Decommissioned heap material profile samples were collected and reconstructed in columns at bench scale. The column profiles were amended and subjected to three leaching regimes, and representative meteoric conditions. The soil amendments provided positive results for ameliorating the heap material limitations and providing a medi­um conducive to plant growth. The bench scale study also pro­vided insight for the future of heap leach planning and design with successful reclamation in mind at the forefront.

Jan 1, 1998

By S. Healey, P. Jean, G. Deschenes, M. Fulton

Three years ago, the New Britannia Mine started a project to improve productivity of its cyanidation plant. Results indicated that gold dissolution was strongly influenced by sulphide minerals and that the slower gold dissolution rate had a detrimental effect on overall gold recovery. The leaching strategy had to be modified to address this issue. Changes to the leaching circuit proved to be very successful. The first action was to introduce lead nitrate in the leaching circuit. The strategy of addition of lead nitrate was upgraded in three steps. An on-line free cyanide analyser was installed and the strategy of cyanide addition automated. The enhancement of the leaching kinetics have resulted: an 4% increase of gold recovery, from 87.8% in 1996 to 91.9% in 1999, which represents a reduction of 0.17 git Au in the leach residue; an average of 1330 additional extracted gold ounces per year from 1997 to 1999; a 21 % reduction in the cyanide consumption; the shut down of the cyanide destruction plant; and finally a contribution to the 27% reduction in the overall production cost per tonne of ore.($ 3 per ton). The significant increase of the throughput was instrumental in the reduction of the processing cost. In 1999, the improvement of gold recovery represented an additional gross revenue of $c""l.9 Million. The project is discussed in details in this paper.

Jan 1, 2000

By Ivan Caetano Machado

Good morning ladies and gentleman. During 1995 Prof. R. P. King (University of Utah Comminution Center) presented 2 papers on new horizons in comminution: "Comminution Research in the United States " was presented at the 1995 Meeting of the National Mining Association, while "Comminution: Meeting the Needs of Fundamental Research in the Mineral Industry" was presented at the 2nd SME Research Forum - 1995. In both papers a very interesting graph named "Energy usage for various comminution schemes" illustrated some poignant issues proposed by Prof. King. We do think that some of Prof. King's ideas might very well serve as "warm-ups" for this Comminution Panel Discussion, which are ultimately the goals to be reached by the 3-minute presentations. Thus, we shall be addressing in the sequence Prof. King's most relevant ideas (as well as introducing his graph), intending therefore show how important creative and state-of-the-art Mill Modeling is, if it is to become a Tool to Effective Cost-Saving Optimization Strategies.

Jan 1, 1996

By F. P. de Kock, P. West-Sells, B. Wassink, D .. B. Dreisingerl

During the cyanide leaching of gold ores containing copper minerals, aurocyanide (Au(CN)f) is produced and typically recovered using activated carbon. However, free cyanide, as well as cyanide associated with cuprous cyanide complexes, are generally not recovered from the barren liquor. This results in a significant economic penalty in high cyanide consumption due to the dissolution of copper. 1\vo different configurations of a novel method for the treatment of barren liquor streams for cop­per recovery and cyanide recycle are described. Recovery of copper and cyanide is affected using solvent extraction (XI 7950). Loaded organic is stripped with a high copper, high caus­tic solution which is electrowon to produce copper metal. Depleted electrolyte is treated with sulfuric acid to recover cyanide which is returned to the leaching circuit. Results of benchscale and mini-pilot plant experiments are presented.

Jan 1, 1996

By W. T. Plummer

• The SuperBowl is a fluidized bed, semi-continuous, enhanced gravity separator for gravity gold recovery. The market for this type of equipment has, until recently, been dominated by a single supplier. Many mineral processors have encouraged the SuperBowl designers to develop competitive equipment for obvious reasons. • The primary beneficiary of competition in this field will be the mineral processing community because legitimate competition fosters continuous improvement in product and price.

Jan 1, 1996

By Peter Bourke

It was in 1982 that the first SK-80 flash flotation machine was introduced at Hammaslahti concentrator in Finland to produce a final grade copper/gold concentrate. Since then the size and number of flash flotation units has steadily developed with the SK-240 being introduced in 1984 and the SK-500 unit in 1990. To date over 130 units have been installed worldwide many of which have been used to maximise the recovery of precious metals such as gold and platinum by preventing overgrinding in the grinding circuit prior to flotation. This paper briefly describes results achieved at several major gold mines in Australia and overseas that operate large flash flotation cells.

Jan 1, 1995

By Gary E. Geiger

laboratory studies were performed to assess the calcium carbonate inhibition performance of phsophonates and polymeric dispersants at high hardness and high pH conditions. Based on the results of these studies, a new calcium carbonate treatment program was developed that shows excellent Inhibition characteristics and Is not sensitive to calcium hardness.

Jan 1, 1998

By David Martin Menne, Chris Campbell-Hicks

Optimisation of many oxide gold processing facilities, in most cases, either does not really take place or if it does take place it happens too late or takes too long. This is unf01tunate as extra profits and early cash flows are lost, in new projects, and/or may not be realised at all in others. The situation is easily avoid­ed by ensuring that the plant optimisation happens immediately following commissioning or for an established operation simply 'biting the bullet' and making it happen immediately as a 'better late than never' decision. This type of optimisation requires intense undiluted focus on each and every problem or restriction that contributes to reduced plant performance or bottlenecks, without letting go, until the predetermined outcome is produced. Thus a dedicated person with specific quantative goals is required for these tasks. Methodology and strategies for optimi­sation are discussed and numerous examples presented. The secret of successful heap leaching is discussed.

Jan 1, 1998

By HJ Marais, J A. van Niekerk

An investigation was initiated by BILLITON Process Research and Gold Fields Limited for the efficient removal of thiocyanate and cyanide from leach solutions. This led to the development of the ASTERTM process, an acronym for Activated Sludge Tailings Effluent Remediation. The biological degradation of thiocyanate and cyanide in effluents provides an alternative treatment to the more traditional processes. This occurs with a large number of micro-organisms which include bacteria, actinomycetes and fungi. Cyanide and thiocyanate are degraded to ammonia and carbon dioxide. Most forms of cyanide-metal complexes are generally removed through a co.mbination of oxidation and sorption into the biofilm/biomass. Since the ASTER™ process has commercial applications, a patent has been lodged for the ASTER™ process. A culture containing thiocyanate degrading organisms has been deposited with the Australian Government Analytical Laboratories (AGAL). The identification of the bacteria is in progress. Tailings arising from a cyanidation process tend to contain cyanide and thiocyanate. The presence of these species prevents the recycling of this water upstream to a bioleach circuit due to its toxicity to the bacterial culture. Increasingly stringent legislation for the land disposal of cyanide containing solutions also necessitates the treatment of the solutions before disposal.

Jan 1, 2000

By Jeffrey R. Kelly, Paul M. Kubera, Richard A. Howk

Mixing of solid-liquid slurries is a unit operation that is widely encountered in the minerals processing industry. Applications may range from simple slurry storage in open tanks to complex chemical reaction systems under extreme conditions of temperature and pressure. The specific process requirements dictate both the degree of mixing required and the type of agitation employed to achieve the desired results.' Many continuous-flow process applications feature tanks operating in series to provide a discrete number of stages and a known residence time for the slurry. Because these tanks operate at a constant level in an overflow mode, the mixer must maintain uniform solids concentration and size distribution throughout the tank; failure to achieve uniformity results in accumulation of coarse solids in the tank, ultimately leading to a process or mechanical failure. Downward-pumping, axial-flow mixing impellers are widely employed to produce uniform solids suspension. The specific impeller type, number, size, and power draw is a function of each given situation. The use of high-efficiency, fluid-foil impellers (Figure I) has evolved as a recognized standard for these flow­controlled applications. Recent small-scale experimentation and full-scale experience has demonstrated that, when uniformity is required, capital and operating expense can be minimized by employing an additional upper impeller pumping in the upward direction.

Jan 1, 1995

By David Lunt, Evan Kirby, Peter Mason, Ian Ritchie

The treatment of refractory gold ores, in particular the "competing" technologies and their relative advantages and economics, has become a major segment of most mineral technology oriented conferences in recent years. A common theme is the increasing refractory nature of gold ores being treated. This is despite ores such as those at Kalgoorlie having required roasting for liberation since the last century. Papers on refractory gold treatment have examined the characteristics of refractory ores and the causes of reduced recovery (eg La Brooy 1994), the available technologies and their relative economics eg Litz 1990), and the selection of a suitable process route (eg Nicholson 1993, Weston 1994). The most comprehensive collation of data on such processes is provided in the different editions of Randol. A variety of classifications and definitions of "refractory ore" have been published. Due to the many factors which can impact on the recovery of gold it is perhaps not feasible to develop a universal characterisation that can be applied to all gold bearing rocks. La Brooy et al have provided the framework for characterisation shown in figure 1.

Jan 1, 1995

By Andre R. Laplante

Gravity gold recovery can be of significant economic importance for gold copper ores that cannot be directly cyanided. Gravity is typically followed by flotation to produce a smeltable copper concentrate. Flotation tails gold values are often too low to justify a cyanidation circuit. Given this typical scenario, a very effective gravity circuit can yield higher overall gold recoveries (i.e. gravity + flotation), and also improve the NSR of gold. Typical scoping work, whilst well suited to investigate the downstream circuit, be it flotation or cyanidation, often overestimates ore variability to gravity recovery and fails to yield the data needed to predict plant gravity recovery and design the optimum gravity circuit. This presentation examines why typical scoping work fails to address gravity recovery adequately and shows how a standard test to characterize gravity recoverable gold (GRG) can provide the missing data. Case studies are presented and used to illustrate the concepts of recovery effort and aggressive gravity recovery.

Jan 1, 2000

By Wendi H. Cooksey

This paper examines two comminution circuits on a hypo­thetical gold ore deposit with both small-scale (1,000 short tons per day) and large-scale (35,000 short tons per day) production rates. The most appropriate circuit is dependent on the highest economic performance with a combination of crushing and grinding equipment to achieve the desired product size. The selected circuit is dependent on costs associated with project cri­teria, equipment selection and ore characteristics. Factors influ­encing the selection of the comminution circuit require system­atic evaluation to optimize plant performance and maximize eco­nomic return. The small-scale circuit economics responded best to three-stage crushing followed by a single-stage ball mill. The large-scale plant favors a primary crusher followed by SAG milling and ball milling. The conclusions from this paper indi­cate that each project must be evaluated separately to determine the most economic means of reducing the size of the ore.

Jan 1, 1998

By S. R. LaBrooy, M. C. Costello, A. C. Bax

Nickel is present in a number of gold ores in Australia, Africa and the United States. The effects and behaviour of the nickel during the cyanidation and adsorption processes, and also during the elution and electrowinning processes have been examined by a number of researchers, usually as a part of a larger investigation. This paper examines the available data on the behaviour and effect of nickel during cyanidation and its associated unit processes. The presence of nickel is often not considered to be particu­larly important as it does not cause the same degree of problems across the circuit as those experienced in the presence of copper. It can however lead to increased cyanide consumption during leaching, and reduced adsorption of gold onto carbon. A proportion of nickel cyanide may be removed from carbon prior to elution by carrying out a hot (90° C) acid wash. The nickel which remains on the carbon will be partially eluted during the main elution step, and, dependent on its concentration in the pregnant solution, part of it may be deposited during electrowinning. There is always a risk that any nickel remaining on the carbon after the elution step will be reduced to metallic nickel during the regeneration step. This may ultimately result in an increasing base level of nickel on the carbon, as metallic nickel is insoluble in both cyanide and hydrochloric acid.

Jan 1, 1995

By Rebecca A. Miller, Terry M. Hertel

In-pit identification of neutral waste rock at the Zortman and Landusky minesites in Montana, by visual and chemical analy­ses, will assist in proper segregation and placement of rock so that soil and water resources can be protected. The use of too few or very general segregation criteria to identify neutral waste rock can result in ineffective waste rock segregation. Conversely, the use of overly restrictive criteria can result in the unnecessary loss of valuable reclamation material that would otherwise have to be mined elsewhere and hauled to the site. Recognition of nonre­active materials can be accomplished on a site specific basis with the use of visual observation and simple chemical analyses. The choice of chemical parameters used to analyze rock samples is constrained by the length of time needed to conduct the test. These analyses must require no more than 24 hours to complete so mining can proceed without delay. Limits set for the chosen parameters must be reasonable and defensible. To achieve these objectives over one thousand samples were collected at the Zortman and Landusky minesites and clas­sified by rock type, total sulfur content, paste pH, and net neu­tralizing potential (NNP). In addition, over 22 humidity cell kinetic tests were conducted to help corroborate static results for waste rock. Another 8 humidity cells were configured in series to test waste rock blending and waste rock/limestone capping alternatives as mitigation for acid rock drainage. Leachates were analyzed for pH, conductivity, alkalinity, acidity, sulfate, Al, Cd, Cu, Fe, Mn, Zn, Mg, and Cr in some cases. Petrographic analysis, as well as total sulfur content, paste pH, and static and kinetic test results identified three geochem­ically different waste rock groups: 1) Archean amphibolite gneiss and Paleozoic carbonates and shales, 2) Tertiary syenite porphyry, and 3) other less abundant Tertiary igneous and Archean metamorphic rocks.

Jan 1, 1996

By K. Barbetti, D. C. Wright, L. J. Warren, J. A. Rumball

This paper describes the advantages and disadvantages of cyanide sensors in gold processing operations, and their role in reducing process variability and lowering cyanide consump­tion. The importance of understanding the chemistry of the sensing principle, and the role of impurities, in order to choose the correct sensor setting, is demonstrated.

Jan 1, 1997