Search Documents

By Lech Bolinski, Joe Shirley

Over two dozen Resin-in-Pulp (RIP) plants have been in operation in the fonner Soviet Union since the beginning of 1970. Currently approximately 50% of the gold produced in Russia, Uzbekistan and Kazakhstan, which equates roughly to 10% of the total world output, is recovered using the RIP technology. An alternative to activated carbon, ion-exchange resin has several advantages for the recovery of gold. Resins are less prone to clay or organic foul­ing and do not require thennal regeneration. They also have poten­tially higher loading capacities, faster adsorption kinetics, and are more resistant to abrasion. The original Russian RIP process was based on engineering expertise developed for uranium ore pro­cessing and has a few major drawbacks. The biggest problem is an 18-30 day resin stripping process, which results in a huge gold lock-up. The problem was recently overcome by the development of a new stripping technology which cuts the time to 12-24 hours. Currently, there is rather limited practical knowledge of the Russian RIP process in the West, but often Western mining com­panies developing gold mines in the fonner Soviet Union are hard pressed by their local joint venture partners to take a serious look into RIP. It is probably only a matter of time before one of these companies will cross Soviet technology with Western engineering and develop a modem RIP process as an attractive option to the current CIP and CIL technologies.

Jan 1, 1996

By Richard M. Crowell, John W. Shield

GeoBiotics has developed a biooxidation technology (patents pending) which involves coating refractory precious metal sulfide concentrates onto a support material and biooxidizing the sulfides in a heap configuration. The concentrates are produced from low or high grade sulfidic refractory ores or existing mine tailings. The process has been found to achieve high gold recoveries asso­ciated with stirred tank biooxidation, but at the low operating and capital costs associated with whole ore heap biooxidation. Improved gold recoveries of up to 98% after biooxidation are reported for 4 representative mines or deposits. The sulfide flotation concentrates were studied using 3 and 6 in. diameter columns or 3 in. drained vats. The refractory sulfide concen­trates biooxidize rapidly in 3 to 12 weeks with substantial increases in subsequent gold recovery.

Jan 1, 1996

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 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 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 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

By Jeffery S. Thompson

In this report, the effect of catalytic amounts of activators on gold dissolution in clear solutions with gold disks and with slur­ries of gold ores is presented. Activators are nitrogen and sulfur aromatic heterocyclic compounds, which catalyze the gold dis­solution reaction in cyanide and other lixiviant solutions. Gold dissolu!ion studies in clear solutions indicate that the catalyst must bmd to the gold surface to catalyze the dissolution reac­tion. A concentration dependence for activation is observed· the optimum catalyst concentration depends on choice of activtor lixiviant concentration, and solution agitation. Nitrogen and sul fur aromatic heterocycles catalyze gold dissolution in slurries of gold ores with cyanide and other lixiviants. The typical proce­dures of agitated leach and rolling bottles were used to evaluate gold leaching rates. Activation has been demonstrated with a variety of ore types.

Jan 1, 1996

By James L. Hendrix, Michael R. Straka, Emil B. Milosavljevic, Ljiljana Solujic, Neil P. Gallagher

Analysts that utilize the classical distillation procedures for cyanide analysis are often frustrated by the poor reproducibility and repeatability of these techniques. Capital intensive business decisions and environmental management regulations are exas­perated by the fact that the EPA/ASTM approved cyanide deter­mination methods produce data of questionable quality. Reliable cyanide values are important in monitoring the effec­tiveness of the cyanide detoxification procedures. Efficiency and cost of gold and silver cyanidation recovery can also be improved by precise cyanide monitoring in the process itself.

Jan 1, 1996

By Paul Hamilton, Brian Jones

Traditionally,relatively large gold mines in developing countries have relied on imported process plant engineering, design, pro­ject management and advisory skills. In 1995, there was a significant departure from this in Zimbabwe, when a locally based engineering company under­took and completed the construction of a one hundred and twen­ty thousand tonne per month capacity gold extraction plant for the treatment of sands/slimes residues integrated with run of mine ore. This paper describes the challenges of designing, construct­ing and commissioning a Carbon in Leach (CIL) gold extraction plant in a developing country, and discusses the various con­straints associated with it. In addition, the paper reviews the application of technology which is innovative to Zimbabwe, including the use of dewatering cyclone clusters, and two and a half tonne capacity elution/electrowinning convection units.

Jan 1, 1996

By Richard H. Johnson

The Castle Mountain Mine (CMM) is located in the eastern por­tion of San Bernardino County, Southern California, 70 miles south of Las Vegas. The CMM is a joint venture between Viceroy Gold Corp. (75% and operator) and MK Gold (25%). The CMM initially started gold production with an 8,000 tpd cyanide heap leach operation in February, 1992 when the first ore was crushed and delivered to the leach pads. Even during construction and commissioning, design work was under way to engineer and construct a 1,200 tpd Mill circuit to process the higher grade fraction of the ore through use of pulp agglomera­tion. The need for a grinding circuit became evident with the quantity of high grade material delineated during drilling and the amount of visible gold that the geologists were finding in the drill core and R.C. cuttings. Viceroy did not want to stack the higher grade ore on the heap, and it was clear that permitting a tailings pond would, at best, be a long drawn-out affair. An alternative to a tailings facility had to be found.

Jan 1, 1996

By G. A. Plakhin, A. V. Luganov, V. A. Luganov, G. V. Gorbatenko

In order to extract gold from the complex sulphur-arsenic bear­ing raw materials and to remove arsenic and sulphur from the process in an ecologically safe form we have studied oxidizing roasting of highly arsenic gold bearing concentrates with soda, leaching of cinders, processing of the obtained solution and extraction of gold from the cake. There were processed concen­trates containing from 5 to 28% of arsenic, 12-20% of sulphur in the form of pyrite and arsenopyrite. The content of gold in the concentrates was 4-75 git. The roasting temperature was changed in the range of 773-l 173K, the consumption of calcined soda was 75-200% of stoichiometric necessarily for bonding of arsenic and sulphur into the water soluble compounds, the dura­tion of the process was varied in the range of 10-120 minutes. Under roasting in optimal conditions up to 97% of arsenic and 95% of sulphur go into water soluble compounds. The out­put of cake is 65-70% of the concentrates. The extraction of gold from the cake is higher than from the raw concentrates. The technology has been tested on a pilot plant scale

Jan 1, 1996

By Brad Hewitt

Since Campbell Mine began processing ore, there has been a gravity gold recovery circuit. From 1947 to 1982, gravity gold was concentrated through the combination of jigs and mercury amalgamation. In 1982, jigs with concentrating table upgrading commenced and was utilized until the end of 1994. As of January of 1995 to the present, Knelson Concentrators in com­bination with concentrating tables have been employed to achieve a refinable product. An evaluation of the justification used for the last change is the focus of this paper.

Jan 1, 1996

By Paul D. Chamberlin

There are many unit operations applicable to the processing of gold/copper ores. Deciding which are most applicable to your ore can be done using a series of tree diagrams. The diagrams show generalizations, not definitive rules. And the listing of process alternatives on the diagrams is very limited although there are dozens to choose from. Three questions help point the way to proper process selec-tion: 1. How much gold is in the ore? 2. How much copper is in the ore? 3, What is the cyanide consumption when leaching the ore?Halogens can also effectively leach gold ores and gold/cop

Jan 1, 1996

By K. G. Thomas

New developments in gold exploitation over the past few decades have been extensive and promise to be exciting for the foreseeable future. They cover all phases of gold mining from developments in mining, processing, computer and finance. This presentation will cover these different disciplines and show how Barrick Gold Corporation ("Barrick") has used these devel­opments to enhance shareholder wealth. The developments can be grouped into disciplines as shown in the following table.

Jan 1, 1996

By R. Bruce Thorndycraft

This paper will describe several modifications to design of con­ventional oxide gold heap leaching. They are targeted at reduc­ing costs and simplifying heap operations. These modifications were conceptualized during consulting work on over 90 differ­ent heap leaches. In 1995, a unique opportunity arose to imme­diately apply all of these design concepts to the permitting and construction of a new facility at the American Girl Mine in southeastern California. American Girl Mine has operated since 1987. In April 1995, the mine faced a situation with grave consequences for cash flow. Approval for mining of a new ore zone, Oro Cruz, had just been granted, after lengthy delays by California regula­tors. All existing pad space would be filled by October. Only 6 months were available, and new pad siting and design were still undecided. Permitting of a new pad had not begun. Options were quickly reviewed. A strong criteria for pad site selection and design was ease of permitting. There was also a strong desire to install a system that would achieve better met­allurgical recovery and reduced operating costs, compared to previous heaps at this mine. One site offered the best chance for rapid permitting. It was the site of the original 1987-90 heap leach. This already dis­turbed ground contained 1.6 million tons of heaped ore. The old heap had just completed detoxification and was about to be signed off as a Group C waste, ready for reclamation. Instead of recontouring and revegetating the old heap, which the reclamation plan anticipated, we offered BLM and the County something even better. We proposed to off-load much of the detoxed old heap, and reuse the space. The off-loaded material would be back-filled into the original open pit, imme­diately adjacent. While the footprint of the proposed new pad was much larger, the reuse of disturbed ground, and backfilling of the open pit, had very strong appeal to the regulators. Our permitting strategy included the technical design of the proposed new facility. Many of the new design details also appealed to the regulators, particularly the "zero active ponds" concept.

Jan 1, 1996

By Christopher J. Pritchard

Federal mine safety regulations prohibit the recirculation of face air In a gassy Class III metal-non metal mine. Tg Soda Ash, Inc, operates a 2.0M ton/yr (2.2 million st/yr) underground gassy Class III trona mine In southwest Wyoming, currently liberating approximately 5,700 m3/day (200,000 ft3/day) of methane. Because of the low methane emissions and the incombustibllity of trona, it was decided that Tg would be an excellent environment to test recirculation at a U. S. gassy mine, for possible future use by Industry. A research program was begun with the cooperation of MSHA, the U.S. Bureau of Mines, the University of Utah, and Tg. Initial testing centered around re-using shop air under¬ground. Next, conduct a continuous miner section recirculation test to see how the face contamination was affected by 305m (1,000 ft) and 610m (2,000 ft) recirculation distances. A district test followed to examine the effects of the critical parameter - respirable dust. Finally, a long-term program to study respirable trona dust transportation and deposition in mine airways to plan for district fan siting and effects on face air dust levels.

Jan 1, 1995

By S. P. Liebenberg

During the past fifteen years significant progress has been made on carbon-in-pulp (CIP) technology for the extraction of gold. While most research on the mechanisms and kinetics of CIP sub-processes has focused on the adsorption step only, auxiliary unit operations such as elution have received less attention. The mathematical models which have been developed for elution at the University of Stellenbosch can be used for design as well as process optimisation by incorporation into an overall CIP simulation program. Except for these models, no other comprehensive models for the complex elution process are available. It is the aim of this paper to review recent modelling work on competitive elution from activated carbon.

Jan 1, 1995

By A. K. Bakshi

In cold regions, rinsing of spent cyanide from leach heaps is stopped during winter and is resumed again after the snow melts. The effect of this idle time on the overall removal process was studied in this experiment. Samples were collected for rinsing tests from one heap at a gold mine near Fairbanks, Alaska. Continuous and interrupted rinsing of this sample were carried out in test columns. The rinse solution was analyzed at regular intervals to determine the rate of cyanide removal from the solids. It was found that total cyanide concentration per rinse cycle for interrupted rinsing test was higher than for the corresponding continuous rinsing test. As a result, interrupted rinsing required less rinsing cycles than continuous rinsing.

Jan 1, 1995

By M. Dondi, M. Surracco, G. Alfano, P. Saba

Recent investigations on fine grinding with jet mill miprototypes of original design, constructed at the DIMM and Centro Studi of the National Research Council at Cagliari University, have led to the realization of a third generation micronizer characterized by large capacity and high efficiency. The new model and its distinctive features are described here and the results are presented of grinding tests on typical, high grade Sardinian minerals used for quality products. The operating principles of the jet mill are described in relation to the mechanico-elastic properties of the minerals treated. In particular the efficacy of the comminution process is demonstrated in terms of both solid treated and of impact, attrition and shearing forces generated in the micronizer. Particle size distribution of the finished products are reported, that satisfy the most stringent market specifications for the different minerals, as well as energy consumptions. The alternative operating options for solving particular grinding problems and minimizing energy consumption are discussed. Lastly, the main developments of the jet mill for a possible application at industrial scale are suggested.

Jan 1, 1995

By Carl-Eric Dr. Nilsson

Energy cost for mine ventilation in Sweden is high, especially during winter time when air must be heated. This paper presents the result from a project entitled ventilation-as-required. The term ventilation-as-required means that the required volume of fresh air should be distributed only to such areas, where mining work is going on and to be reduced to a minimum in the rest of the mine. Ventilation-as-required is a monitoring system that controls the operation and capacity of the fans and measure the air pollutant gases, i.e. carbon monoxide, nitrogen and sulphur dioxide at strategic points. It is an active system that responds when equipment is under operation. MITU proposed in 1991 a project to develop a ventiation-as¬required system and such components as transmitters and receivers for the communication between the equipment and the fans. The mining companies, Boliden Mineral AB, LKAB, Outokumpu and Ammeberg Mining Corporation joined the project and have financed a joint research and development programme supported with a grant from the Swedish Government through NUTEK. MITU proposed a second project in 1992 to the mining companies to develop an improved "intelligent" fan for scope ventilation. Boliden Mineral and LKAB joined the project and have financed a joint research and development project supported by the Swedish Government through NUTEK. The Government even made a commitment to support the investment of the first 50 fans ordered with a grant of 25% of the investment cost. The result from projects show that the target set up in the plans is more than achieved, with an energy reduction that exceeds 30% compared to previous consumption. No environmental influence due to reduced ventilation is observed in the stope when work is under progress. Dilution of exhaust gases from diesel fuel decreased from 6.000 m3/L consumed diesel fuels to 3,600 m3/L. The automatic data processing and sensor system is even increasing the security of the work so that it can be done under safer environmental conditions.

Jan 1, 1995