Search Documents

By Terry I. Mudder, Michael M. Botz

Discharge regulations for mine waters require relatively low concentrations for cyanide and metals, and the trend is for discharge limits to be lowered. In the event conventional treatment practices are not sufficient to meet discharge limitations, advanced treatment technologies such as ion exchange and reverse osmosis may be considered. Though these technologies will provide discharge quality waters, they also require the disposal of a concentrated brine and are relatively complex and costly to operate. Many mine sites currently using activated carbon in precious metals recovery present the opportunity to economically operate an activated carbon water treatment plant for polishing of effluents. This paper presents summaries of six ( 6) mining operations which have evaluated or use activated carbon for treatment of water and which also use carbon in precious metals recovery processes.

Jan 1, 1997

By Andreas Rubo, Stephen Gos

In the days of increasing environmental and safety awareness many efforts have been made to prevent losses of both an evident economic nature and also less obvious losses. These losses could be associated with damages due to negative impact on the environment and also people coming into contact in a broader sense with any toxic chemical. This paper deals with how cyanide can be applied in a responsible manner at a modern gold mine. Responsible application is achieved by minimizing losses of reagent and avoiding negative impact on the environment as well as adopting a Responsible Care philosophy to the application of cyanide. It becomes evident that this is quite a complex system with a greater commitment than avoiding reagent losses for economic purposes.

Jan 1, 1997

Several years ago, North American mining companies began to realize they needed to expand their spheres to remain viable. This strategy has been successful, according to Robert W. Schafer. Today, companies from other continents have also recognized the need for an international view for long-term growth and viability, he said. Schafer is vice president for exploration with Kinross Gold. He was the program chairman and moderator of the keynote session at the 1997 SME annual meeting, held in Denver, CO, Feb. 23-27. The theme of the meeting was "Minerals - Serving the Global Community." A record attendance of more than 6,000 people participated in the meeting, which featured 415 exhibitors occupying 582 booths. The title of the keynote session was "Corporate Perspectives on a Global Minerals Industry." Each of the three keynote speakers discussed a different perspective of a global minerals industry.

Jan 1, 1997

By Bruno Sceresini

The Filblast Cyanidation Process incorporating intense high shear mixing, high gas mass transfer efficiency and high oxygen concentrations under conditions of elevated pressure has now been been successfully applied in gold cyanidation mills since May 1993. The first commercial unit had a slurry capacity of 110 cubic metres per hour. Since then 230 and 450 cubic metre per hour units have been installed and a 1,000 cubic metre per hour unit has been designed. Laboratory and pilot plant Filblasts have also been built. The reactor is a robust, compact in-line or end-of-line device and may be constructed out of a wide range of materials including wear and corrosion resistant alloys and ceramics. The Filblast Process may be applied to high temperature leaching of refractory gold ores and base metal concentrates. The development and application of the Filblast Gas Shear Reactor as a cyanidation tool has removed the constraints of plant size in cyanidation applications in mobile or readily transportable gold plants. A 250,000 tonne per annum fully modularised gold ore treatment plant with the Filblast and AARL Pump Cell as core technologies is nearing completion. This plant includes several novel features which are predicted to achieve widespread adaptation in modem cyanidation plants. This paper presents a briefreview of the development of the technology and the principles incorporated in the Filblast system. A number of case studies are presented which show significant financial benefits due to more efficient reagent utilisation, higher recovery and increased through-put.

Jan 1, 1997

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

By Gary Jobson

The Mt Todd Gold mine is situated near Katherine in the Northern Territory of Australia. Commissioning of an 8 Mtpa processing facility incorporating a four stage crushing circuit, ball mills, flotation, concentrate regrinding, high rate thickening and CIL processing was commenced during late 1996. A 4.5 M tonne /annum crushing and heap leach facility was commissioned during late 1994, and was subsequently upgraded to a nominal 6 M tonne / annum circuit during 1995. Processing equipment used included primary gyratory, secondary cone and tertiary Barmac VSI crushers. Some of the features of that crushing circuit and heap leach facility were presented at the Randol Perth 95 conference by myself. The location is described as sub tropical with average climatic conditions including 1100 millimetres annual rainfall, predominantly during the December. to March wet season, and 3000 millimetres evaporation and maximum temperatures ranging from around 26 to 46 °C. The main gold occurrence at the Mt Todd site is the Batman deposit, with current published Reserves of some 60 Mt@ 1.20 g Au / tonne ( 0.0425 oz Au / ton ). The primary ore from the Batman deposit is an extremely competent greywacke and is very hard at an average Bond Ball Mill Work Index of26.5 kWhrs/ tonne. Other indicators include a Bond Impact Crush Work Index of 20 kWhrs I tonne, an Abrasion Index of 0.15 and Ultimate Compressive Strength values of 100 - 200 MPa. The main gold occurrence is very finely disseminated free gold (at an average grain size of around 5 micron) within a combination of quartz and mixed sulphide. This gold bearing component is confined to largely parallel veins ranging from 0.5 to 25mm wide within a greywacke matrix. Although the gold is essentially non­refractory, there is a strong recovery versus grindsize relationship due mainly to the liberation characteristics and the relatively low permeability of the host greywacke rock.

Jan 1, 1997

By G. L. Simmons.

Many large. low-grade (refractory) sulfide gold resources exist in Nevada and other parts of the world that are not amenable to concentration by conventional flotation practice, Over the past several years Santa Fe Pacific Gold (SFPG) has investigated flotation process options to economically treat low-grade refractory resources of this type at Lone Tree and Twin Creeks. Conventional flotation technology applied to the original high-grade gold resources at Lone Tree and Twin Creeks was initially unsuccessful. Review and analysis of auriferous (gold-bearing) iron sulfide mineralogical characteristics and flotation chemistry provided a fundamental understanding that led to the development of a new flotation process that SFPG refers to as N2TEC. This paper discusses the development of this technology and compares N2 TEC results with conventional flotation practice.

Jan 1, 1997

By John A. Folinsbee

Placer Dome Canada owns and operates the Campbell mine and mill at Balmertown, in the north western corner of Ontario. The mine operates at 1.3 kt/d (1,500 stpd). It produced more than 9.3 t/a (300,000 oz/year) of gold during the last three years. Changes to the gravity concentration circuit have resulted in a 10% to 15% increase in gravity recovery. The mill head grade at the Campbell Mill is relatively high, averaging 18.5 g/t (0.54 oz/st) over the total reserve tonnage. During the past several years, the head grade was averaging close to 20 g/t (0.6 oz/st). Before 1994, gravity concentration was achieved by using a combination of conventional mineral jigs and tables. Jig concentrates were upgraded on shaking tables to produce a concentrate, which was refined to bullion. In May 1994, management decided to buy two Knelson CD 760-mm (30-in.) concentrators. The objective was to replace the existing jigs and increase gravity gold recovery by up to 15%. Gravity recovery with jigs averaged between 30% to 35%. Gravity recovery was anticipated to increase to about 50% with the Knelsons.

Jan 1, 1997

By L. A. Arrington-Webb

The International Standards Organization (ISO) 9000 series of quality standards was published in 1987. First initiated by the British in the mid-1970's to assure the quality of British goods and services. ISO 9000 certification demonstrated the capability of a supplier to meet the requirements of the customer. Thiele Kaolin Company has invested considerable time and money achieving and maintaining ISO 9002 certification. Through a regimen of process control and documentation, routine audits, and a commitment to quality management, this kaolin producer continues to be a competitive pigment supplier in a world-wide market.

Jan 1, 1997

By Raja V. Ramani

Worldwide, promulgation and enforcement of health and safety laws and regulations have been the primary means of ensuring minimum and uniform standards of health and safety in the mining industry. In U.S. coal mines, a new era was ushered-in in 1969 for the control of health hazards from respirable coal mine dust. Since then significant progress has been made on all aspects of the respirable dust problem-its definition, monitoring, reduction, and control. In the intervening years, our ability to monitor, analyze, and characterize the mine atmospheric environment and the health of miners has increased many fold. Also, advancements in production technology have far outdistanced enhancements in environmental control technology. Therefore, questions are continuing to be raised on the adequacy of the characterization and control measures with regard to both the airborne respirable dust in mines and the health effects of respirable dust. Late in 1995, the Secretary of Labor appointed an Advisory Committee on the Elimination of Pneumoconiosis Amona Coal " Mine Workers (Dust Advisory Committee) to review the progress towards elimination of coal worker's pneumoconiosis (CWP) and silicosis, and in the program to control respirable coal mine dust in underground and surface mines, and make recommendations including improved standards and other appropriate measures for the control of exposure to airborne coal mine dust. The Committee's report was released in October, 1996. In this paper, a summary of the recommendations of the Committee is presented. A brief discussion of the background, and the issues and findings leading to the recommendations is also presented. The Committee concluded that the progress made towards making mines safer from the health hazards of respirable coal mine dust is substantial but that it is not sufficient to achieve the intent of the 1969 Coal Act. The Committee's recommendations encompass a wide range of issues addressing permissible exposure limits (PELS), sampling, dust control plans, hazard and medical surveillances, role of miners, training, and research and development.

Jan 1, 1997

By Joseph M. Driscoll

After 30 years of successfully mining gold, Newmont Gold has temporarily ceased production from the original Carlin Pit. In late 1993, the Carlin East decline was driven and an extensive underground exploration program was started. Today, Newmont Gold produces refractory ore from the Carlin East Underground at the rate of 864 t/d (950 stpd). Annual production is more than 3.1 t (100,000 02). More than 70 underground miners will be employed during Carlin East's estimated six-year mine life. About 70% of the ore at Carlin East is mined by mechanized longhole stoping with delayed, cemented backfill. The remaining ore is mined by underhand drift and cemented fill methods.

Jan 1, 1997

By P. Riveros, J. Binvignat, V. M. McNamara, D. Koren

The feasibility of recovering cyanide and copper from a gold mill barren solution was evaluated in a small A VR pilot plant. The campaign lasted 64 hours, during which time about 4,000 L of gold mill barren solution were processed. The results showed that A VR is an effective technology for recovering cyanide and copper from barren solutions. Under the best conditions, the copper precipitation and the cyanide volatilization attained 94% and 98%, respectively. Using 5 MNaOH as the absorbent, practically all the HCN gas was recovered in the form of a concentrated NaCN solution containing 70 g/L free CN. Basic engineering design parameters applicable to a large-scale operation were obtained, including the Henry's Law constant and the mass transfer coefficient for HCN gas.

Jan 1, 1997

By F. P. van der Meer

Roller Press grinding has become an accepted technology in the cement industry, and finds a growing application in iron ore processing. Its introduction to the gold industry will depend on anticipated benefits such as a reduction in power requirements, the increase in throughput, and higher gold recoveries from the ground ore. The presentation highlights some of the specific features of the KHD Humboldt Wedag Roller Press and the effects of various operating parameters on the grinding result. Based on recent experiences examples are given on the use of the Roller Press in mineral applications. The anticipated reduction of grinding energy when using the Roller Press is discussed, together with the reduction in Bond Work Index.

Jan 1, 1997

By Andrew P. W. Briggs, Corale L. Brierley

A considerable economic and technical knowledge base has been amassed with the successful and sustained operation of commercial minerals bioleaching/biooxidation plants to extract copper from chalcocite ore and enhance precious metal recovery from sulfidic refractory ores and concentrates. Economic evaluation ofbio-processing must consider the value of the ore, the sulfide-sulfur requiring oxidation to achieve significant metal recovery, the time required for the biological process and, in the case of precious metal feed-stocks, the down-stream reagent consumption. Of these considerations oxygen requirement for the biologically-catalyzed oxidation of sulfide minerals is the prevailing determinant in the capital and operating costs of aerated, stirred-tank reactors for processing concentrates and bio-heaps for processing ores. Oxygen requirement is dictated by the amount of sulfide-sulfur requiring oxidation to achieve desired metal recovery. The testwork program to evaluate a project for application of biooxidation/bioleaching must be designed to insure that factors critical to economic assessment are fully quantified.

Jan 1, 1997

By Ethan B. Eilertsen

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, 1997

By B. A. Firth

The presence of misplaced ultra-fine particles has been shown to decrease the separation efficiency of unit operations used in coal preparation. Although the classification of fine coal was considered to be adequate for the needs of the coal industry during the 1970's and 1980's, it has become apparent that further improvements in the yield/ash/moisture relationship achieved by coal preparation plants will require increased efficiency in this size separation step. This paper describes the issues which are evolving in this area, and the capability of current and developing techniques to address the problems which need to be overcome.

Jan 1, 1996

Current scrubber capacities vary from 1.89 to 4.72 m3/s (4,000 to 10,000 cfm), and there is interest in using scrubbers with capacities up to 6.61 m3/s (14,000 cfm). This paper describes research to compare the effectiveness of blowing and exhausting face ventilation systems using high-capacity scrubbers with flows up to 6.61 m3/s. Tests were conducted in a surface ventilation gallery with exhaust and blowing systems operating under similar conditions. The mining machine was equipped with a machine-mounted scrubber. Methane gas was released at constant flow at the mining face and measured at several face locations. Effectiveness of exhausting and blowing systems was compared by determining average face methane concentrations. For each operating condition tested, blowing ventilation was more effective than exhausting for controlling face methane levels. Raising scrubber flow to 6.61 m3/s reduced methane levels for both blowing and exhausting systems.

Jan 1, 1996

By Boris V. Vlasenko, Vadim P. Potapov, Gennady I. Gritsko

In this paper we consider the elements of an information geomechanic monitoring system which is used in computerized mine planning and mining operations control. The automated sys tem is a technical means of geomechanic monitoring, as a complex system of regulated observations, estimation and prediction of changes in geomechanic state of rock mass and workings during underground mining of coal deposits. Geomechanic monitoring at coal mines and the automated system execute data collection, analysis and calculations of geomechanic situation in the panel during planning, development and carrying-out of mining operations for ensuring geotechnical stability of underground mining.

Jan 1, 1996

By Dr. -Ing. Karlheinz Timtner

This paper deals with the complicated and often misunderstood relationship between torsional windup, load sharing and peak torques in conveyor backstops. The principals apply in low speed, intermediate speed or high speed applications. Once the controlling factors are understood, a reasonable approach to selection procedures can be achieved.

Jan 1, 1996

By S. S. Peng

High horizontal stress has been well recognized as a significant factor in roof control. It can adversely affect roof stability if the panel is designed improperly. Mining experience has shown that it can cause a cutter roof. The effects of high horizontal stress on roof stability depend on many factors such as magnitude and direction of the maximum principal horizontal stress, ratio of the maximum to minimum principal horizontal stress, structure and mechanical properties of the immediate roof and mining sequence. However, little is known about the intrinsic mechanism of high horizontal stress effect on roof stability except some conceptual explanations. In order to design a stable entry, the redistribution and concentration of high horizontal stress around the openings must be fully understood. Using the 3-D finite element analysis technique, this paper presents the redistribution and concentration of high horizontal stress field for a three-entry system with different orientations of horizontal stress. Based on the horizontal stress redistribution, possible roof failure for different orientations of horizontal stress is analyzed.

Jan 1, 1996