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By J. M. Carter, Rodney H. Sergent, L. E. Kun, J. T. Pressly

Underground mine service water in South Africa is used for dust suppression and cooling the environment as well as the pneumatic rock drills. Although the chilled water is not intended for potable use, it is often used as drinking water by mining personnel. Furthermore, droplets sprayed are liable to be inhaled. The water is recirculated on a continuous basis and is a potential source of infection by intestinal microorganisms or water-borne diseases such as cholera or typhoid. In order to protect the health of the underground workforce it is customary to disinfect the chilled service water, The bacteriological quality of the water is monitored by enumerating total aerobic bacteria (TAB), total coliforms (C C) and Escherichia coli (E Coli). E coli is an indicator of human faeca_l __ - -- contamination, The bacteriological standard specified by the Anglo American Corporation for mine service water is less than 3000 TA B per 100ml, less than 2 CC per ml and the total absence of E Coli. There are several disinfecting agents available for use. Among these are UV irradiation, ozone, chlorine dioxide and compounds that produce hypobromous and hypochlorous acids. Historically, the methods of treatment have been chlorine based and include the use of gaseous chlorine (surface installations only), calcium hypochlorite granules or tablets, chlorinated cyanurate tablets, sodium hypochlorite solutions and hypochlorite produced by electrolysis.

Jan 1, 1991

By Trent Temple, Curtis Johnson, John Mudge

Newmont Gold Company uses centralized carbon handling facilities to strip loaded carbon from five mills and four leach facilities located along a 38 mile stretch of the Carlin Trend in Nevada. Both Zadra and AARL elution processes are employed at this centralized facility which is located near the company's Gold Quarry operations. The Zadra elution circuit was commissioned in 1985 and later expanded in 1987. This circuit can strip carbon at a rate of 24 tons per day. The AARL elution circuit, commissioned in 1988, also has the capacity to strip 24 tons of carbon per day. Two horizontal, rotating, regeneration kilns are used to reactivate approximately 60% of the stripped carbon before it is returned to the mills or leach facilities. One kiln is located in the Zadra plant, while the other is located in the AARL plant.

Jan 1, 1990

By E. Haug, Quamrul Ahsan, R. Norcross

Cyanide leaching is the most common process employed in the majority of the gold extraction plants. These gold extraction plants naturally generate tailings and/or effluents that contain highly toxic cyanides, In geographic locations with excess precipitation and therefore net positive water balance, a portion of these tailings must be discharged. Before these highly toxic cyanide-containing effluents can be discharged to the waterways, cyanide and any other toxic substance must be destroyed. Geographic locations with high evaporation and low precipitation, as in the western USA, result in net negative water balance and therefore these plants can operate with a zero discharge option. However, with the current stringent environ­mental regulations and concerns for bird and wildlife mortality, even these operations may be required to partially treat their tailings to preclude potential harm to wildlife. Furthermore, heap leach opera­tions are now generally required to detoxify the heaps before abandonment. It is, there­fore, apparent that all gold extraction plants may be required to install some form of effluent treatment in order to achieve the above objectives,.

Jan 1, 1990

By J. L. Waldron

This paper presents a theoretical tool used to analyze gold recovery problems at Dee Gold Mining Co. The first step in addressing the problem was realizing that lower gold extraction was linked to high silver grades, and could not be correlated to either the carbonaceous or sulfidic content of the ore. Analyses of metallurgical testwork, blasthole, and mill recovery data demonstrated that decreases in gold extraction correlatP� well to increases in silver extraction. Figure 1 illustrates this for 1991 mill operations. This was the starting point for the work described in this paper.

Jan 1, 1992

By Len H. Steele

To date VMD have designed, built and supplied nine autoclaves to various mining companies in Canada, the US, and Papua New Guinea. Initially, completely fabricated and lead lined units were shipped. The logistics of Placer Dome's Porgera PNG Project necessitated fabricating and lead lining each autoclave in five sections for transportation to site, each piece weighing approximately 30.5 tonnes. Support equipment such as turning rolls, automatic and manual welding machines had to be set up on site to facilitate assembly of these units which was a challenge in planning. This on site erection programme was completed in three months.

Jan 1, 1992

By P. G. Semple, K. W. Major, P. Eng.

The recent increase in development of refractory gold deposits has resulted in changes to the traditional treatment processes. The selection of the preferred refractory treatment process is dependent on the mineralogy of the ore. One process, which has recently gained increasing attention, utilizes dry grinding and roasting of the whole ore. This paper will discuss some of the considerations to be addressed during the design of the process fl owsheet and what the effects of the various alternatives will be on the plant capital and operating costs. The paper will be based, in part, on current experiences with dry grinding, roasting plant design and start-up.

Jan 1, 1990

By Rick T. Richins

Despite what may be overwhelming evidence that natural degradation of cyanide and cyanide attenuation in hydrogeochemical processes are capable of reducing or eliminating potential water quality problems associated with heap leach facilities, the recent sharp increase in the price of gold and wide interest in the cyanidation process has focused all regulatory eyes on cyanide leaching. Regulations continue to increase, design criteria are more strict, and detoxification requirements approach or exceed the level of detectability. Current governmental regulation of mining and milling operations using cyanide varies considerably from state to state. The lack of regulatory consistency at this level is largely attributable to the current Bevill Amendment exclusion of mine wastes as potentially hazardous wastes, the undefined status of the Environmental Protection Agency's ongoing mine wast study effort, and the mining industry's reluctance to develop a consistent policy regarding state versus federal mine waste regulation.

Jan 1, 1998

By David Martin Menne

Introduction

Jan 1, 1991

By Deepak Malhotra, Sean Armstrong, Linda Baltich

The economic profitability of any mineral company is dependent upon maximizing mineral recoveries while minimizing costs. The effectiveness of any strategy to meet this objective is dependent upon firstly obtaining quantitative information concerning the steady-state metallurgical balance of the plant, and secondly, how efficiently this information is used to improve/optimize plant performance. This two-step approach can be designated as a "plant audit." Plant audits on a routine basis can be very expensive and time-consuming. Most plants have reduced staffs to cut costs. The remaining staff has to spend time to solve production/operation problems, thereby leaving limited resources (i.e., people, time, and money), for plant auditing. This paper briefly reviews plant auditing categories, and a systematic approach to auditing which has been successfully used at several operations. An example illustrating the use of this approach in gold operations is discussed in this paper.

Jan 1, 1992

By J. A. Meech, C. A. Harris

Expert Systems are being used in the Mineral Industry with ever­increasing frequency. A major advantage of these systems over conventional computer programs is that the knowledge and intelligence of human experts can be captured directly onto a computer for transfer to novices or other lesser experts. These programs allow rapid construction of process models that are not well-understood in fundamental terms, but for which good operational reasoning exists. In addition, user-friendly access to "high-tech" knowledge can be provided to unsophisticated personnel who otherwise might be turned off by unintelligible jargon. As such, these systems can be important training tools for new operators. This paper describes the features of Expert Systems that relate to gold processing plants. Applications include grinding circuit control, supervisory control of reagent addition and pulp density, monitoring and control of CIP/CIL carbon inventories and the operation of carbon stripping and regeneration facilities. A consultative Expert System is described that provides advice on laboratory cyanidation testwork

Jan 1, 1992

By H. G. Linge

Pyrrhotite (FeS1+x ,0<x<0.15) is an iron sulfide which is considered to be a pest in carbon-in-pulp/ leach (CIP/L) gold processing [l].The perceived influence of pyrrhotite on gold processing by CIP/L is a competing consumption of 02 and CN­as the pyrrhotite dissolves by oxidation [1,2]. The few studies of the oxidation chemistry, kinetics and mechanism of the oxidation ofpyrrhotite are reviewed in detail elsewhere [3].There is broad agreement that the surface of pyrrhotite is very rapidly oxidized to form a thin (e.g. 10 nm) ferric hydroxy-oxide layer which overlays an iron-deficient sulfide lattice covering the original pyrrhotite. The reaction can be summarized thus:

Jan 1, 1995

By Steve R. La Brooy

Techniques for dealing with copper-gold ores are reviewed. Cyanide has little selectivity of gold over copper, and depending on the reactivity of the copper minerals cut-off grades for gold recovery by direct cyanidation are generally below 0.5% copper for oxide ores and 1 % for sulfide ores. Non-cyanide gold leachants also tend to be reactive to copper. The cheapest option for sulfidic ores is to produce a flotation concentrate for smelting, while transition ores generally need a sulfidisation pre-treatment. The requirement for the concentrate to have a high enough copper grade to be acceptable to a smelter may compromise copper and gold recovery. This can lead to significant gold grades in the flotation tailing, and copper levels in the tailing that are too high for direct cyanidation to be able to recover the gold. Oxidised ores, flotation tailing or other material not amenable to flotation represent the greatest grey area for gold recovery. Copper removal by acid, alkaline or ferric pre-treatment is possible though not generally used. Cyanide pre-leaching to remove copper, followed by copper and cyanide recovery represents a potential option that has been installed at one Australian gold plant, where copper is recovered onto carbon, ahead of the slower leaching gold. Actual cyanide recovery depends on ore mineralogy, allowing for losses as cyanate, thiocyanate, carbonate and ferrocyanide. Alternative options for gold recovery following cyanide leaching include precipitation, ion exchange and solvent extraction of the gold. Ammonia-cyanide leaching may offer another option for more selective gold dissolution from flotation tailing and oxidised materials. A plant is currently under construction in Mauritania.

Jan 1, 1992

By Stuart K. Nicol, Malcolm D. Engel, Neville T. Moxon

Ion flotatir,n of gold is a process being developed to selectively float extremely dilute aurocyanide liquors using a novel surface active complexing agent. The principle of ion flotation is also applicable to a wide range of other metal-containing solutions. The market potential of the gold flotation process would be enhanced by the possible combination of the gold recovery capabilities with both cyanide recovery and metal removal. For example, recovery of copper cyanides from a return liquid strean1 would be a useful means of reducing operating costs and satisfying environmental pressures to treat tailings dams. Experimental work is described where samples of tailings solution from a far north Queensland gold mine were subjected to ion flotation to remove copper cyanide species from a clear recycle solution. The form in which these products was removed was of secondary importance compared to the need to produce a clean solution for use in the plant. Recovery of the anionic copper cyanide species was accomplished using a quaternary ammonium surfactant.

Jan 1, 1991

By Michael Brittan

For every million ounces/year of gold produced by mining and process operations, each 1 % loss to tails represents 10,000 oz/year of production sacrifice. Recovering this lost gold would generate aditional revenue of $3 million/year at $300/oz. Similarly, if the average recovered grade is say 0.15 oz/st, every $0.45/st reduction in operating costs will result in equivalent annual savings of $3 million. This paper describes the application of a technique to realize such cash flow benefits for milling operations.

Jan 1, 1999

By A. N. Islam, C. Simons, M. N. Hughes, J. Barrett

The effluent from the bio-oxidation of arsenopyrite contains high concentrations of iron(III) and arsenic(V), the pH being in the range 1.0-1.3. The use of lime to increase the pH causes the precipitation of calcium sulfate, calcium arsenate and a mixture of solids containing calcium, iron and arsenic. The presence of calcium is due to slaked lime encapsulated by the iron arsenate precipitates. These iron arsenate solids are related to known minerals. The use of sodium hydroxide to effect the precipitation of iron and arsenic produces solids which are more stable than those produce by using slaked lime. The use of limewater produces an initial precipitate of calcium arsenate.

Jan 1, 1991

By J. W. C. Wong, S. D. Miller, J. J. Jeffery

Pre-mining identification of acid forming mine and waste materials is of concern to the mining industry because of the potential for the generation of acid mine drainage, acid rock drainage, and soil acidity problems. Accurate identification of acid forming material is essential for developing appropriate waste management strategies to reduce environmental problems related to acid generation from sulphide containing wastes. The acid-base accounting procedure, in its various forms , is commonly used for pre-mining screening of mine and mine waste materials. The procedure is generally effective when used and applied correctly but is prone to incorrect interpretation of results which can have significant financial and environmental implications. This paper examines the acid-base accounting Procedure and the possibility of misuse of this method with special emphasis on the sampling method, the sulphide forms, the acid neutralization capacity, and the interpretation of results. Data from numerous coal, base metal, and gold mining operations are used to illustrate the application of the acid-base account. The data base indicates that overall, approximately 1/3 of all waste generated by mining and mineral processing is potentially acid forming indicating the need for correct identification and management. Problems associated with simple application of 'absolute' acid-base criteria for classifying acid forming material are highlighted and the need for developing site specific or 'relative' criteria is discussed and illustrated by case study.

Jan 1, 1991

By Joe D. Allison, Tom D. Baugh

The analysis for total cyanides (CN, or the cyanide due to the combination of free, weakly associated and refractory cyanide complexes) is required by most regulatory agencies for determination of effluent compliance. This method requires a distillation of the sample at low pH's and is most often sent to contract laboratories at a high time and monetary cost. This paper describes a new micro­distillation apparatus which allows for a multiple of CN,"' analyses to be carried out simultaneously saving both time and money. It can be used in the field, since only electrical power is required for the method. While not being appropriate for reporting values to the respective regulatory agencies as of yet, it is quite valuable for screening a large number of samples prior to submission of the samples to a contract lab for "official" reporting.

Jan 1, 1990

By Ali Sogue, Steven Schurman, R. Jensen

This paper presents the results of the remediation of the Gregory Gulch #1 Superfund site, an EPA Clear Creek Superfund project located in central Colorado. The Gregory Gulch #1 site was an historic gold mine and mill located within the city limits of Central City, Colorado. Remediation efforts included the use of the Envirobond™ additive to chemically bind the metals in 3,000 tons of acid generating mine waste that contained high levels of arsenic, lead, zinc and mercury. The toxicity of the mine waste amended with Envirobond™ was not only reduced to RCRA TCLP standards but also to the more stringent UTS standards. The final cost of the treatment was much less than standard industry solidification processes and significantly less than offsite disposal options.

Jan 1, 1999

By Rakesh Sehgal, Pushkar Verma, Mohit Sharma

"SJVN Limited successfully commissioned its Rampur HEP (412 MW) in 2014. The project has been planned to operate in tandem by directly utilizing the Tail Water of SJVN’s prestigious Nathpa Jhakri Hydro Power Station 1500 MW located upstream. The initial filling of voluminous water conductor system of RHEP with 10.50 m diameter, 15 Kilometer long Head Race Tunnel, involved more than 1.5 million m3 of water. The filling operation of such a large diameter tunnel constructed in young folded Himalayas which always offer less ideal sites for tunnelling and their subsequent operations under pressurized conditions is worth sharing with tunnelling fraternity. The paper covers meticulous planning, execution, precautions taken, and performance monitoring during filling process keeping in view the fragile geology, low rock cover zones, shear zones in close vicinity of thickly inhabited areas, squeezing zones, hot water zones encountered during excavation.1.0 RAMPUR HYDRO POWER STATION IN BRIEFRampur Hydroelectric Project (412 MW), is located in Himachal Pradesh (India). This project is a downstream development of Nathpa Jhakri Hydro Power Station (1500 MW) constructed on river Satluj and commissioned during 2003. Both the projects today are now successfully working in tandem. The upstream NJHPS has been constructed on the left bank of the river while the downstream Rampur HPS is located on right bank of the river (Figure-1).The major length of HRT of Rampur project lies on right bank of river before it crosses under the river in its initial reach (Figure-2). The main features of the project are as below:• 10.50 m diameter 15 km long HRT ending in a 155.75 m deep, 38.00 m diameter surge shaft.• 3 steel lined pressure shafts, 5.4 m dia, 211-220m long.• Surface valve house 69 m long x 10.50 m wide x 23 m high housing 3 No. butterfly valves• 3 No. surface penstocks 5.4m dia 368-382m long, bifurcating into six penstocks, each of 3.80 mdia. to feed six generating units of surface power house 158 m long x 24.50 m wide x 48 m high, with Francis turbines each of 68.67 MW capacity."

Jan 1, 2016

By G. Meschke

"This paper reports on computational and experimental research, performed at the Collaborative Research Center “Interaction Models for Mechanized Tunneling” at Ruhr-University Bochum, Germany. Research covers a broad spectrum of topics relevant for mechanized tunneling in soft soil conditions. This includes advances exploration methods and models for the characterization of the in-situ ground conditions, the interaction of the face support and the tail gap grouting with the porous soil, multi-scale models for the design of fiber reinforced segmental linings with enhanced robustness, computational methods for the numerical simulation of the tunnel advancement, the soil excavation and the material transport in the pressure chamber, logistics processes and risk analysis in urban tunneling.INTRODUCTIONMechanized Tunneling has proven itself as an economical and flexible construction method that continues to undergo a dynamic evolution process. Shield diameters continue to increase, and the application range of tunnel boring machines is being extended to an ever-increasing variety of geotechnical conditions. In order to maintain economic viability and to ensure an environmentally friendly construction process, realistic and reliable numerical models are required in order to make informed decisions during planning and construction. To provide a reliable numerical prognosis, it is necessary to accurately assess and understand the interactions between the components involved in mechanized tunneling with the surrounding site, the ground, and any pre-existing structures. Heterogeneous geological conditions and often only approximated ground parameters create, in contrast to other engineering projects, special demands. This necessitates new insights to new problems that can only be effectively solved through truly interdisciplinary research. To address these challenges, the German Research Foundation (DFG) has established the Collaborative Research Center “Interaction Models for Mechanized Tunneling” (SFB 837) at the Ruhr-University in Bochum in 2010. Collaborative Research Centers are interdisciplinary scientific research groups in which cooperative research is conducted under the umbrella of a central research theme. With a research budget of ca. 10 Million Euros for the second 4-year funding period, and a research team composed of 13 project leaders along with approximately 35 scientific assistants the SFB 837 is currently one of the largest research groups conducting fundamental research in tunneling related topics worldwide.RESEARCH TOPICSThe research topics of the SFB 837 encompass a number of relevant planning and construction related aspects in mechanized tunneling (Figure 1). These research themes are each supported by computational models and laboratory investigations and are all included in an SFB overarching Tunnel Information Model (TIM). Interaction groups integrate and combine the results of different submodels through prototypical cause-and-effect relationships, and through the analysis of the Wehrhahn metro line (WHL) project in Düsseldorf, which has been adopted as the reference project for the SFB 837."

Jan 1, 2016