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Several processes are now available for the recovery of free and WAD cyanide from gold plant solutions and pulps. In the past, the incentive for evaluating cyanide recovery in gold plant flowsheets has been economic. In many cases, it has been possible to demonstrate (at least in the laboratory and on paper), an improvement in process economics by; (i) reducing the costs of tailings detoxification, (ii) recycling cyanide at lower cost than the purchase/delivery price of new cyanide, and (iii) generating additional revenue via by¬product sales. Despite these convincing arguments, few cyanide recovery plants have been built at operating gold mines. Also, there is arguably an even more compelling reason for mining companies to consider cyanide recycling. With the growing storm of negative public opinion that the use of cyanide in the mining industry is attracting - following several highly publicized spills over the last couple of years - the time has come for the gold industry to demonstrate environmental diligence and stewardship in the use of this commodity that is so vital for their industry. There is no doubt that the widespread implementation of cyanide recycling will reduce the impact of the cyanidation process on the environment, both by reducing the risk of spills (with less cyanide being transported from manufacturing plants to gold mines), and by reducing the loading of toxic and non-toxic metals and ions in the tailings. In this paper, the various processes that are available for cyanide recovery are discussed, along with the process chemistry. Results of several laboratory and pilot plant trials that have been conducted over the last few years are also presented.

Jan 1, 1998

By Kenneth N. Han

Thermodynamic and kinetic aspects of nickel and cobalt leaching from metals. minerals and ores in various media have been reviewed and discussed in this paper. A kinetic model developed to delineate the leaching mechanisms for these metals has been discussed in view of experimental observations. The current review also includes the dissolution behavior of nickel and cobalt from various minerals such as oxides, sulrides. ocean floor manganese nodules, and laterites. A particular emphasis has been extended to similarities and differences of the dissolution behavior of these two metals in various media. The leaching of nickel as well as cobalt metal in acidic solutions and arnmoniacal solutions exhibits in most part mass transfer controlling. although at some pH's, chemical controlling or mixed controlling mechanisms seem to prevail. The leaching of nickel and cobalt from oxides in acids and ammoniacal solutions. on the other hand, can be described best by chemical controlling mechanisms.

Jan 1, 1993

By W. J. Guay

Scrubbing of simulated copper reverberatory furnace gases containing 1.0 percent sulfur dioxide with the minus 74 ~m fraction of the San Manuel tailings has shown sulfur dioxide removals of almost 100 percent over an effluent pH range of 3.1 to 4.6 and a wide range of liquid to gas ratios with absorptions of 11 to 17 Kg of sulfur dioxide per tonne of minus 74 um slimes. The high reactivity of the tailings slimes with S02 indicates that the reaction rate is not controlled by the slow dissolution of calcium carbonate in sulfurous acid which characterizes scrubbers using ground limestone. The interpretation of these results has been considerably enhanced by wet chemical analysis and emission spectrographic analysis which show that calcium and iron account for about 90 percent of the SO2 absorption with the rest being accounted for by aluminum, magnesium, potassium, and sodium. Mineralogic examination confirms the, chemical and spectrographic analyses showing that the major constituent removed from the slimes is calcium carbonate, with lesser amounts of chlorite and montmorillonite (silicates containing iron, magnesium, aluminum, and calcium) being removed.

Jan 1, 1981

By J. Avraamides

Some operational difficulties have been encountered in the transfer of carbon-in-pulp technology to Australian conditions. Many gold mines? are located in remote and arid areas where the available ground water is highly saline. There is a gradual depletion of free milling oxidised gold ore reserves resulting in the necessity to treat deeper primary sulphide .deposits which can be refractory. Some near-surface ore-bodies and tailing dumps are contaminated by natural vegetative matter which can interfere with the adsorption of gold from the cyanided pulp,. Advances which have been? made include potable water conservation in elution, a new type of regeneration kiln, inter-stage screens, alternative leaching systems transportable carbon-in-pulp plants and efficient open-cut mining methods. Academic and applied research is well supported by government and industry and the results are normally rapidly disseminated and put into practice by the gold mining industry.

Jan 1, 1989

By A. Valenzuela

During the last years, Chile has been the largest copper producer, either as concentrates or cathodes. Copper obtained via pyrometallurgy is produced by seven smelters, which have carried out modernization plans to increase smelting capacity or to achieve environmental regulations established in the Chilean legislation. Thus, the present work updates technological innovations in smelters, environmental regulations and presents solutions for SO2 handling, particulate matter and arsenic. Also, the authors emphasize the important role of CODELCO Chile, the most important state-owned copper company, in developing technologies such as EI Teniente Converter and EI Teniente Slag Cleaning Furnace,

Jan 1, 2003

By S. Castro, P. Alfaro, C. Moctezuma

IMMSA operates a conventional roasting-leaching-purification-electrolysis plant for the production of zinc from concentrates in San Luis Potosi, Mexico. The leaching circuit was designed to take into consideration a feed mixture to the roaster with a maximum iron content of 7%. Since the start-up of the plant in 1982, the zinc recovery increased to 94.5%. However, an increase in the iron content in 1997 caused an important decrease in the global zinc recovery. Two new steps were added to the leaching circuit and modifications were made to the other steps in order to increase zinc extraction. Two new automated press filters were installed to replace the original vacuum drum filters and to minimize soluble zinc losses. Additionally, the residue treatment steps in purification were modified and a calcium removal circuit is just starting operation. These actions, besides improving the operations, have as the main objective to increase the global zinc recovery to levels above 94.5%.

Jan 1, 2000

By R. J. Chesher, J. C. Anzalone, T. F. Krusmark

The BHP Copper Refinery at San Manuel, AZ employs conventional electro-refining technology, plating at a current density of 335 A/m2 on six kilogram copper starter sheets. In 1995, a combination of variable anode chemistries and increasing current density in the tankhouse created periods of increased bismuth in cathode. Bismuth in electrolyte was minimized by bleeding electrolyte to the nearby BHP leaching facility. However, the expected drop in cathode bismuth was not achieved. Investigations indicated that starter sheets contained a significant concentration of bismuth. The bismuth was found to occur in combination with antimony on the surface of the sheet adjacent to the mother blank. Studies were conducted to determine the mechanism by which Group VB elements are incorporated into the starte sheets. Operational practices were introduced to minimize bismuth in starter sheets and improve cathode quality.

Jan 1, 1997

By D. M. Hausen

Multiple drill sections through many of the numerous breccia pipes in the American Eagle copper deposit at Copper Creek, Arizona, have been evaluated by means of alteration and geochemical data. Contoured plots indicate vertically plunging, concentric, cylindrical shells of alteration and mineralized rock that are similar in structure, geometry, magnitude and petrology to the San Manuel-Kalamazoo Deposit, located about 14 miles to the southwest. Both deposits are similar in dimension and consist of multiple, irregular, rod-shaped injections of porphyry into a granodiorite host. Analogous to the San Manuel-Kalamazoo Deposit, most of the porphyry plugs are oriented parallel to the cylindrical axis of the "ore shell". A continuously mineralized, elliptical shell, inferred from deep drilling, is capped by a flatter zone of copper mineralization. Above this flat zone, copper-bearing fluids were channeled upward along conduits that correspond with quartz-sericite "breccia pipes". At depth, zones of sericite and K-feldspar alteration products exhibit conformable relationships with the copper deposition. A "bullet-shaped" ore shell, with a nearly vertical axis, is proposed to explain the conformable zones of altered and mineralized rock. The "nose" or top of the "bullet" is 1800 to 2300 feet below the surface, and structurally controlled in part by steeply dipping Hi and ENE faults. If correct, this model suggests that the vertical ore shell may extend to great depth.

Jan 1, 1988

By T. W. Turk

In May 1984, Davy McKee Corporation was awarded a contract for engineering design, procurement assistance, project management and startup services for two gold recovery plants? in the People's, Republic of China (PRC). The basic design of these two projects was to be accomplished by a combined effort of the Chinese and Davy McKee Corporation (DMC). The, design goals were to provide a state-of-the art plant while maintaining Chinese standards and design practices whenever possible. Chinese-manufactured equipment was to be used as much as possible. This paper discusses the project organization and procedures developed to accomplish the design goals, the process selection and design, and the selection and procurement of equipment outside of the PRC. Design development for grinding, leaching and carbon adsorption, and gold recovery are discussed in detail. The major goal of process selection and design was to provide common criteria for both plants. Equipment .sizing and selection was identical for carbon-in-leach adsorption, gold recovery, acid washing, and carboo regeneration for both plants. Of special importance is the design of the wastewater treatment system. Due to the cl0se proximity of a major population area, slurry discharging from these mines must be treated to meet drinking water standards. The process development and design of this system is also discussed in detail.

Jan 1, 1989

By Makiko Takahashi

A tool is being developed to predict and visualize the microstructural evolution of steels during quenching. This tool utilizes experimental data and reference data that are stored in a database to predict the microstructural development. The visualization tool animates qualitative representation of two- dimensional microstructure drawings as well as the quantitative volume fractions of phases present as a function of time. This is achieved by superimposing the Jominy End-Quench test results over the Continuous Cooling Transformation diagram of the alloy. The predicted microstructure is presented through the web browser to maximize the ease of use. In addition, a parallel coordinate system is used to aid in identifying similarities within the data set by presenting the large number of data at a glance. The results for 4140 steel that was quenched in a wide variety of quenchants will be presented to illustrate the prediction and visualization tools. Keywords: Quenching, Microstructure Prediction, Simulation, Data Visualization, Database, Applet, Animation

Jan 1, 2003

By Li Xi

This paper describes how a back-propagation neural network is built for predicting the properties of engineering materials from their other properties, compositions or processes. A predicted result of the impact toughness of a 12Cr-2Ni-1.5Mo stainless steel from its tempering temperature is presented. Furthermore, the combination of this neural network for prediction is able to supplement the unpredictability of the expert system outside its domain of expertise. An integrated system may perform more intelligently and solve more complex problems as well as human expert, in some case even better.

Jan 1, 1992

By S. S. Chabot, S. E. James

A recent survey of CEOs from major steel companies worldwide revealed the importance of recycling zinc units from EAF dust, mill scale, blast furnace dust, and other zinc containing streams in their plants. Many processes were developed and installed in response to this challenge. The most successful approach involves the production of a crude zinc oxide and selling it to primary zinc producers to recover the metal value. The problem with this process is the high concentration of halides in the crude oxide. This type of material cannot be processed directly in an electrolytic zinc plant because of corrosion problems it will cause in electrolysis. In 1999, BRZ installed a zinc oxide receiving and washing plant to minimize the impact of halides to its circuit. A description of the washing plant and initial operating results are included.

Jan 1, 2000

An iridium oxide coated titanium electrode was tested as anode in copper electrowinning. Initial results confmed that the DSA-type anode was significantly more active for oxygen evolution than traditional lead anodes. However, during longer runs, the anode potential was observed to increase linearly at a rate of 220 mV/year. Scanning elecuon microscopy (SEM) and energy dispersive spectroscopy (EDS) showed that the anode passivation could be attributed to elecuochemical dissolution of the coating. The effect on the anode potential of organic additives (glue and thiourea) and lead in solution was also examined. A preliminary economic evaluation of the anodes is given.

Jan 1, 1992

By Larry M. Southwick, Phillip J. Mackey, A. E. (Bert) Wraith, Albert Pelletier

In 1881, the first commercial pneumatic Bessemer-type converter treating copper matte was successfully introduced by Pierre Manhes at the Eguilles copper plant near Vedène in France. This development followed over a year of testing on a smaller scale at a foundry in Vedène, during which the vertical tuyeres of the conventional Bessemer converter had been successfully replaced by horizontal tuyeres in an effort to avoid the freezing of copper which had occurred in the bottom of the vessel having vertical tuyeres. The Manhes Converter, as it became known, was the first successful large-scale adaptation of the Bessemer concept of using compressed air blown into a melt for metal refining and treatment. Within a few years, Manhes Converters utilizing horizontal tuyeres in either the original type of vertical converter, or a later and more enduring horizontal barrel converter, were in operation at over a dozen copper smelters around the world. It was this process that Messrs Peirce and Smith essentially improved with the introduction of the larger converter which bears their name and the development celebrated at this Symposium. The present paper briefly traces the original development by Pierre Manhes in the early 1880s and which set the stage for the later Peirce-Smith adaptation. The paper observes that the original development by Manhes was in part driven by the need to reduce coal (energy) consumption and hence the production cost in order for Eguilles to remain competitive with the larger plants in Swansea, Wales, where a ready supply of cheap coal helped keep smelter treatment terms of the day low. These themes are eerily resonant of today where booming copper production in China has impacted the industry, and also where energy consumption, closely linked to today’s more familiar theme of ‘climate change’ remains an important challenge currently confronting the entire industry. The paper concludes with comments on these seemingly parallel situations today and offers some thoughts for the future.

Jan 1, 2009

By G. B. Harris

Much has been written over the past decade concerning the disposal of arsenic from metallurgical processes. In Canada, there are proposed regulations which would classify arsenic in the Primary Group of twenty one persistent, toxic pollutants to be banned or phased out. Since many nickel and cobalt ores, not to mention those of copper, gold and uranium, contain significant amounts of arsenic, it is pertinent to assess the current state-of-the-art of its disposal. The literature is reviewed, and it is demonstrated that from a purely chemical point of view, the family of ferric arsenates largely immobilize arsenic. There is clear evidence from laboratory studies that both crystalline ferric arsenate (scorodite) and amorphous ferric arsenates in which the molar Fe/As ratio is at least three (Fe/As = 3) have very low arsenic solubility; plant data are given to support this. The debate over the long term stability of these compounds continues however; the evidence presented for long term stability and for compound breakdown is critically reviewed in the light? of the recent structural studies, and the role of base metals in these compounds evaluated. Finally, conclusions are drawn as to the viability of a purely chemical process for the long term disposal of arsenic from metallurgical processes.

Jan 1, 1993

By J. S. Becker

Technology developed and first implemented in the United Kingdom enables very low grade aluminum scraps containing oils, organics, plastics and ferrous metals to be directly charged, without pretreatment, into a unique melting furnace. The system has been in full scale production for over three years. The oxy-fuel-based furnace design incorporates internal afterburning in the furnace's hot zone, producing excellent thermal efficiency and very low emissions. The furnace is inherently low in NOx. This paper will provide both theoretical background and extensive operating results for this new melting concept. Applications describing both purpose built new furnaces and retrofits of existing reverberatory furnaces will be presented. Extensive operating emissions data will be presented.

Jan 1, 1996

By Susanne Pignolet-Brandom

Reflected light microscopy, and scanning electron microscope energy dispersive spectroscopic analysis and backscatter electron images were used to determine if a "slick dross" with undesirable handling properties has an assemblage of phases distinct from normal dross. This study has found that in the normal dross the most abundant lead phases are lead sulfide and lead metal and the most common copper phases are copper-iron sulfide and copper sulfide. In the slick dross, the most abundant copper phase is copper-lead sulfide and the most common lead phases are copper-lead sulfide and lead sulfide. The resulting mineralogical information has provided additional insight into the causes of the handling problem and the reaction mechanism for the formation of normal and slick dross

Jan 1, 1988

By Carl C. Nesbitt

A study was conducted to examine the treatment of metal-bearing effluents by precipitating the metals as sulfides and simultaneously collecting the particles by flotation. The precipitant was hydrogen sulfide gas which was introduced into a bench-scale column cell with air. The study included experiments of various flotation reagents and column configurations in treating solutions containing dissolved copper, lead, mercury, iron, zinc and cadmium. An acidic laboratory waste from a local copper operation was used to test the column with a solution containing several metals and arsenic. Precipitates were observed to form at the gas/liquid interface when the gas mixtures were rich in H2S. Copper, mercury, lead, and cadmium were precipitated from solution as sulfides to concentrations near detection limits. The flotation of these precipitates was enhanced with small amounts of S-7151 promoter from American Cyanamide Company and Dowfroth 1263 mixed with the feed. The recovery of the precipitates in this manner produced a smaller volume slurry which was easier to dewatering than a slurry produced by conventional precipitation techniques. The low pH and high oxidation-reduction potential in the cell from H2S addition was not conducive to form precipitates of iron, zinc or arsenic. However, these ions were precipitated as sulfides by raising the pH of the column discharge.

Jan 1, 1994

By J. Wong

We report a successful use of x-ray absorption spectroscopy to probe the chemical and structural environment of trace elements in coal. When applied to vanadium in coal, it was found that vanadium exists in at least two environments: a trivalent site 6-fold coordinated by oxygens at ca. 2.0~ and a tetravalent site 5-or 6-fold coordinated also by oxygens, one of which forms a short V=O bond at ca. 1.6a. No evidence of nitrogen (porphyrin)1'or sulfide environment was found. It was also found that the vanadium environ-ments in the raw coal did not survive unchanged in a liquefaction process. These findings have implications for coal cleaning processes and for trace element release into liquefaction process streams.

Jan 1, 1982

By P. J. Mackey

Over the course of Dr. Robertson’s career, the ferrous and non-ferrous plants have seen enormous changes in technology and increases in plant capacity, essentially amounting to a “technological revolution”. In iron and steel, the “mega” blast furnace of some 6,000 m3 working volume is now standard (~10,000 tonnes (mt) of pig iron/day). Similar huge changes in process technology and plant size have occurred in the non-ferrous industry. As an example, the fuelfired reverberatory furnace, once the mainstay of the copper industry, has disappeared - replaced by large capacity flash and bath smelting technologies. The energy consumption per unit mass of metal produced has also been reduced considerably. Our understanding of the thermodynamics and mechanisms of metallurgical reactions, a field to which Dr. Robertson has significantly contributed, has made great strides. This paper reviews these changes with particular reference to the copper smelting industry, providing also comments on expected future trends.

Jan 1, 2014