Search Documents

By V. I. Lakshmanan, Chris Dodson

Refractory gold ores or concentrates are pretreated in general by physical, chemical and biological oxidative pretreatment processes prior to cyanidation for the economic recovery of gold. The thermal treatment processes generally include fluid bed pro­cessing(!>, chemical with pressure<') or atmospheric (Caro's< ·'>, 3 Nitrox1')) pretreatment leaching and physical with ultrafine grinding!"). Roasting and aqueous pressure oxidation pretreat­ment methods have several commercial applications (Homestake, Barrick) and biological oxidation methods have recently found industrial applications in Africa. The roast pretreatment methods to treat refractory sulphide ores or concentrates transform iron sulphides generally to a porous iron oxide matrix assisting the lixiviant cyanide to effectively diffuse the calcine for cyanidation and hence with improved gold recovery. Jha and Kramer<') made an extensive review of roasting chemistty and practice to tt·eat refract01y gold ores. Industrially two stage pretreatment roasting is generally employed. During the first stage roasting is carried out under oxygen deficiency conditions to provide a low arsenic calcine, mainly magnetite and in the second stage magnetite is trans­formed to haematite under oxidizing conditions.

Jan 1, 1998

By Ian J. Corrans, Gary Johnson, John E. Angove

Activox® is a hydrometallurgical process used to oxidise sulphide concentrates. The process is based on two relatively simple, established unit operations; i.e. fine or ultra-fine milling (UFM) and pressure oxidation under mild conditions. An under-standing of, and ability to control the pulp chemistry during oxidation has resulted in the successful Activox® treatment ( on a batch scale) of a wide variety of sulphide flotation concentrates; • pyrite/arsenopyrite + gold • pyrite/chalcopyrite + gold • pyrite/chalcocite + gold • pyrite/enargite/tetrahedrite + gold Oxidation rates are rapid (1-2 hours retention time) and gold

Jan 1, 1995

By Kevin Phelan, Gary Johnson, Peter Sperring

The vast majority of tailings in the Western Australian Goldfields are deposited in purpose-built storage facilities. At mine-sites with open-pit mining operations there is also the requirement to mine and stack large volumes of waste rock, usually into surface waste dumps. As these dumps have typically 30% of their gross volume present as voids, there is the potential to use this void space for the storage of tailings. The concept of co-disposal is to store the tailings material in the void space of the waste dumps, eliminating the need for a separate tailings storage facility. Dominion Mining Limited have been investigating the possibility of using co-disposal as a means of tailings storage. Laboratory testwork has been used to understand some of the issues associated with the concept, and assist in the design of an on-site demonstration of the concept. Co-disposal offers a number of potential advantages, and despite a number of practical hurdles to overcome, considerable economic and environmental benefits could be realised if this concept can be demonstrated on a commercial scale. The major advantage of such a system is to remove the need to build, operate and rehabilitate a separate tailings storage facility. Rehabilitation can be incremental throughout the mine life as the co-disposal site will be virtually indistinguishable from a current waste dump in both size and form. Other potential advantages include more stable waste dumps, less land area disturbed on the project site, and better water recovery from the tailings.

Jan 1, 1995

By Harold Wahlborg, George Owusu

In a study using butyl diglyme as an organic extractant, essen­tially complete extraction of gold from chloride leach solution was achieved. The extraction kinetics are so fast that the process could be completed in 30 seconds. Except for iron, co-extraction of other ionic species was insignificant. Co-extracted iron species were successfully scrubbed from the loaded organic using 10% HCl solution. High grade, >99.9%, gold was recov­ered from the loaded organic using 5% oxalic acid solution as the stripping agent at a temperature of 70°C to 80°C. Over 99% of the organic-loaded gold was stripped from the organic phase. The butyl diglyme extractant is being tested on a variety of gold-bearing feedstocks. Presented here are results obtained from two gravity concentrates.

Jan 1, 1999

By V. Fred Swanson, J. Patrick Glynn

The environment for process engineers today is very different from 20 years ago. The ideas and mathematical description of models for a multitude of different unit operations is an ongoing development. The computer tools to deal with the mathematics are readily available and specialist companies have developed, tested and verified their models. The challenge for the process engineer is to know which package to use and to know whether a particular application is the most accurate for the specific process. Metallurgical simulation programs today are well known and proven. Certain programs are specialized while others are broader based. The needs of each user are dependent on the application. Typically, most users require the following operations: • Comminution • Flotation • Hydrometallurgy • Pyrometallurgy • Additional requirements could be defined as: • Thermodynamic capabilities for solids, phases, and gases • Dynamic simulation • Data analysis tools • Coal oriented operations • Diamond oriented operations

Jan 1, 1997

By Timo Niitti

Within the minerals industry, flotation is the predominant method when processing sulphide ores. There is hardly any competition in this area because of the high efficiency and low costs of flotation. When processing other ore types magnetic or gravity• methods are commonly used and sometimes leaching methods are selected. The wide variation of the properties of gold (high value, low ore grades, softness, high specific gravity etc.) sets challenging requirements to the processing methods and particu­larly for flotation machines, which should be able to effectively recover free fine gold, coarse gold and gold bearing minerals throughout the full size range. In gold processes the amount of concentrate is usually low, but in some cases large amounts of gold bearing sulphides e.g pyrites has to be recovered. In gold processing seldom does only one method provide the optimum results, but the recovery is usually made using several complementary technologies: gravity separation, leaching and flotation are the most common ones. Mineralogy is the determin­ing factor when selecting the method or methods to be used.

Jan 1, 1995

By P. Gelfi, G. Hill, A. Showell, V. Martins, R. Dunne, R. Jenkins

Carbon attrition losses are not usually a prime consideration for CIP equipment selection and CIP plant design. However, the costs as a result of carbon attrition and associated gold lost with carbon can be high. Recorded carbon losses for Newcrest operating gold plants were shown to vary widely from plant to plant. The Tuckabiana plant recorded an overall loss of only 0.3g carbon /t ore which is very low by industry standards. A comparative carbon management study was undertaken by Newcrest to highlight the reasons for the excellent record of Tuckabiana operation compared to other Newcrest plants. This paper discusses the results of the comparative study and high­lights areas of concern with respect to carbon attrition.

Jan 1, 1995

By Ken Criley, Marc E. Orman

Identifying the optimum ultimate height for heap leaching ore requires the consideration of a number of competing factors. A primary limitation is the reduction in the permeability of the ore with increasing heap heights. At low permeabilities the heap can blind off, cause serious ponding and runoff, and become very difficult to rinse at closure. The authors present a laboratory methodology that has been successfully used on several projects to identify the maximum height for controlling heap permeability.

Jan 1, 1996

By Brian Carr, Craig Brewer, Jeff Grubbs

This paper examines the role of the StemTite Blast Control Plug in explosive energy confinement and explores the benefits of its successful application in gold and silver mining operations. Prior studies involving this device are consolidated.

Jan 1, 1999

By James P. Sabogal

A control and monitoring system is being developed by Betz Laboratories for the heap leach process in gold recovery. Called Betz 14000GL, the system is designed to improve gold leaching and provide savings in chemical consumption by controlling and monitoring key parameters in the heap leach gold recovery circuit. The system uses information from on-line sensors to control antiscalant chemical addition, pH and cyanide levels. The proprietary graphics and report features of the computer system allows the user to monitor and critically evaluate the performance of the process.

Jan 1, 1998

By John Frostiak, Igor Gonzales, Kenneth G. Thomas, Ken Manning

The Pierina deposit was acquired in August 1996 when Barrick Gold Corporation purchased Arequipa Resources, a junior mining company with extensive land positions in Peru. At the time of acquisition, Arequipa ha.d developed two exploration tunnels and drilled 9 exploration holes on the property. Metallurgical tests, conducted on samples taken from the tunnels and the exploration holes indicated that the ore was amenable to heap leaching. Barrick's exploration team recognised from the outset, the potential of the mineralisation and convinced Barrick's senior management that this was indeed a world class deposit that should be pursued. On November 25, 1998, the fi was poured at Pierina, 27 months from the time of acquisition. During that period BmTick completed its exploration programme, prepared a development plan including capital and operating costs, production profiles and cash flow forecasts, and a schedule to develop a mine and construct a leach pad and gold recovery plant, including all supporting infrastructure. All permits and environmental approvals were obtained and all necessary land was acquired. The project was completed on schedule and under budget. This was the first greenfield mine development for Barrick outside of North America. This paper details, mainly, the research and development, engineering, construction and commissioning of the metallurgical process facilities.

Jan 1, 2000

By R. H. Lien, B. T. Waterman

Passive bioremediation can be a cost effective treatment for a variety of mine waters, including final draindown of closed cyanide heap leaches and seepage from tails dams. These solutions can contain noncompliance concentrations of arsenic, antimony, cyanide, mercury, nitrate, selenium, silver, etc. Passive bioremediation involves treating the contaminated solutions under anaerobic conditions. Contaminants such as mercury and nitrate are effectively removed in passive bioreactors whereas the effect of this treatment on TDS, cyanide, and sulfate is minimal. Several waters from gold heap leach operations were treated in the column tests. These tests determined the effectiveness of contaminant removal from each water and also provided important scaleup design information.

Jan 1, 1997

By Robert J. Storms, David J. Malone, Thomas E. Crandall

Corrosion and abrasion have been present in hydrometallurgical processes for many years. Ceramic lining materials have been used in several applications to protect process vessels from the corrosive and abrasive effects of a wide range of ore slurry processes. This paper reviews the history of ceramic lining systems utilized in hydrometallurgical vessels, the commercial benefits associated with their use, and additional areas of opportunity for the Mining Industry.

Jan 1, 1995

By Tony Weeks, J. Loah, Ian Mcgaffin

PT Newmont Minahasa Raya (PT NMR) operates a 700,000 tonne per annum open cut gold mine in the Minahasa region of North Sulawesi. The operation commenced production in the second quaiter of 1996 and is expected to produce an average of 150 000 to 180 000 ounces of gold per year for the mine life. The deposit is predominately refractory in nature and requires a complex treatment route incorporating dry milling and whole ore roasting followed by conventional cyanidation and adsorp­tion of the gold onto activated carbon. Gold is eluted from the carbon to produce <lore bars assaying approximately 94 percent gold. A scrubbing system for the removal of mercury from the roaster off gases was commissioned in late 1997. Due to the location of the operation, close to the coast and in seismic region with high rainfall submarine tailings placement (STP) was the preferred method of tailings disposal. Prior to dis­posal into the ocean the tailings from the CIP plant are detoxified in a three stage detoxification circuit to treat cyanide, arsenic and mercury. This paper reviews some of the design and operational fea­tures of the whole ore treatment process employed at the Minahasa Gold Mine.

Jan 1, 1998

By Sean E. Armstrong, Deepak Malhotra

Gold extraction from refractory ores as a percentage of total gold production is increasing. The processing technology options for treating difficult-to-process refractory ores are also increasing. The best processing option is dependent on many factors including feed grade and the cause for ore refractoriness. The causes for ore refractoriness are many foldCpreg-rob­bing, encapsulation in pyrite, arsenopyrite or silica, presence of cyanocides, presence of cyanide-insoluble gold compounds, etc.1. The first step in the process development of a refractory gold deposit is to determine the cause for ore refractoriness. The traditional approach of undertaking detailed mineralogical examination of ore types, major and minor mineral constituents and their association does not necessarily provide the metallur­gist all the information needed for characterization of gold-bear­ing ores. For process development programs it is desirable to complement traditional mineralogical methods with diagnostic leach testing, which attempts to quantify the deportation of gold in various mineral matrices. This paper briefly reviews the diagnostic leaching proce­dures and its applications for a wide range of gold-bearing refractory ores, both primary and by-product.

Jan 1, 1996

By Jim Johnson

The purpose of this paper is to summarize and discuss a variety of site specific conditions which are typically evaluated as part of the engineering design process for heap leach pads, solution control ponds, and associated facilities. The following sections will focus primarily on the topographic, climatologic, hydrologic, and geotechnical evaluations critical to selection of heap leach sites, and selection of a preferred heap leach configuration or method. Other important considerations in the design of a heap leach project, including evaluation of ore properties and leachability, pregnant solution processing requirements, spent ore neutralization/disposal requirements, and other anticipated reclamation requirements are beyond the scope of this paper are not addressed in any detail.

Jan 1, 1998

By Tong Deng, Yun Ma

Gold-copper ores have become important gold resources (von Michaelis, 1989), but the gold extraction from such materials posed a challenge due to the detrimental effect of copper species on gold cyanidation. Ammoniacal cyanidation process was rec­ommended (Muir et al., 1989) and practiced (Castello et al., 1992) for gold extraction from the gold ores which contain cop­per at moderate level mostly in form of oxide. This paper pro­vides an example to apply the ammoniacal cyanidation process to processing such a copper bearing gold ore.

Jan 1, 1996

By Marcos C. Filgueiras, Thomas A. Post, Michael A. Giralico, Daniel M. Adams

The leaching of copper, gold, and nickel in tanks requires mixing. Minerals require oxygen, acid and/or base [NH3] to assist in the leaching process. Two basic types of tanks are used for this operation. They are either vertical tanks or closed horizontal tanks called autoclaves. This paper discusses mineral leaching, it's mixing requirements, and autoclaves.

Jan 1, 1999

By Andrew Griffiths

The emphasis in the title of this paper should be placed on the world "Total", since the detoxification of cyanide in its free and weakly-complexed form with H202 has already found application in many areas, including the treatment of mining effluents. One of the most common forms of cyanide found in gold-mill effluents is hexacyanoferrate (usually ferrocyanide), which is included in measurements of total cyanide but is too stable to be oxidized by H202 or any other conventional oxidizing agent. This has led to the view that H202 cannot be used to detoxify effluents containing hexacyanoferrates, when a limit has been set on total cyanide. A process is described in this paper which does meet this requirement, and which has already been demonstated in two Canadian gold mills. Before describing the new process, the terms "free", "total" and "weakly-complexed" cyanide will be defined as they are used in this paper.

Jan 1, 1998

By J. R. Montgomery, T. A. Phillips, F. Blackham, D. J. Adams

Underground water, whether it is a mine seep, in situ leach solu­tion, or a pollution plume, is difficult to track and monitor. Monitoring wells are costly to drill and may be placed in the wrong spot. This report describes a test of an electromagnetic technique to track acid water draining from the Midnite Mine near Spokane WA. The tests successfully mapped the path of acid mine drainage being collected at the mine from two seeps. Several small side branches flowing to smaller seeps and a mix­ing zone where relatively clean water mixed with the acidic water, were also mapped. The study has changed previous opin­ions on the flow of water through the site and will be used as a basis for future site remediation planning.

Jan 1, 1996