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By P Bourke, S Ronkainen

Since the early days of flotation, process technicians have known that the speed at which the froth is recovered over the lip of the cell has a very direct and consistent influence on the grade and recovery of the circuit. No plant would deny that, even to this day, one of the most important aspects of a process technicianÆs job is ensuring that the froth is moving at a desired and controlled speed over the lip. Unfortunately, process technicians cannot watch the froth throughout the entire shift, as there are always other problems to attend to. A considerable amount of work has thus been done to develop a æsystemÆ that automatically measures the speed of the froth. This measurement would then be used in simple controllers to emulate the steps taken by the process technician in correcting deviations of the froth speed from its desired level. Many of the earlier attempts to measure speed were ineffective, as they were unable to cope with turbulence on the froth surface. The FrothMasterÖ instrument makes use of machine vision technologies to measure the speed of the froth over the lip of a cell at a very high sampling rate. This instrument produces an extremely reliable and accurate measurement of the froth speed (as well as other parameters such as bubble size and froth stability). As we will show, the effectiveness of the speed measurement in controlling the performance of the plant is a testimony to its reliability. Three FrothMasterÖ units have recently been installed on the Cadia Hills Gold Mine in New South Wales (Australia). The objectives of this installation were:to control the mass-recovery of two Tank Cells in series on the same level where differences in the hydrostatic head between the two cells result in the cells pulling inconsistently with respect to each other; control of the concentrate grade (per cent copper) from the first rougher; reduction in the frother consumption in the rougher circuit by monitoring the froth speed. A simple controller was designed to react to disturbances in the same way that human operators react. This was done after consultation with the metallurgists and the process technicians at Cadia. The controller had two functions: Stabilisation: The stabilising controller made use of three manipulated variables (level, frother addition rate and aeration rate) to control the froth speed to a setpoint. Optimisation: The optimising controller adjusted the froth speed setpoint based on deviations of the grade (measured in real-time by the OSA) from a setpoint. The plant metallurgist adjusted the grade setpoint based on information about the ore. The results from a 21-day trial have shown the following:The ratio of concentrate mass-recovery between two cells in series on the same level has been successfully balanced, thereby overcoming problems due to differences in hydrostatic heads. It is possible to control the speed of the froth, in mm/s, to within five per cent of its setpoint using the aforementioned manipulated variables. It has also been shown that, for reliable control, it is necessary to control more than just one variable (eg level or air). The grade of the first rougher concentrate has been controlled to within 0.3 per cent of the grade setpoint for long periods of time, which has important implications for the circuit recovery. The frother consumption has been reduced significantly. This paper will thus show that substantial progress has been made to demonstrate the value of using on-line froth speed measurements in flotation plant control to obtain real financial benefits.

Jan 1, 2000

By P Williams

The Sunrise deposit is one of AustraliaÆs largest and most profitable gold deposits. It has consistently and spectacularly outperformed every resource model created. Currently over the life of the Sunrise pit there has been a 50 per cent under estimation of ounces mined. Without a solid basis for predicting the tonnes and grade or the spatial location of mineralisation, mine planning becomes problematic. Recently, through a better understanding of the mineralising processes the reconciliation of the resource model has improved to be in the order of ten per cent under on ounces mined. This paper will describe how the mine geologists at Placer Granny Smith have implemented the changes required to improve the resource model. Work began with the development of a three-dimensional lithological and structural model based on historical drilling and pit mapping. Continual updating of the geological model with grade control logging, assays and in pit face mapping, now allows for the on-going improvement of the resource model and the planning of mine development drilling.

Jan 1, 2000

By Kallioinen Jouko

"Advanced Flotation Technology is the application driven design of Don-Oliver flotation cells to achieve the optimum performance for each type and grind of flotation. Optimum performance is the combination of both recovery and selectivity.Optimized performance is the combined product of optimized mixing and effective froth removal. Optimized mixing is applied to roughers, scavengers, cleaners and specialty cells such as those to float hydrocyclone underflows in both primary and regrind circuits in order to reduce overgrinding. Effective mixing for fine material is easy, but overmixing reduces selectivity in frothbed.Selectivity in flotation is an important target, especially when treating complex ores, and parameters in frothbed have been examined to improve the separation of minerals and eliminate circumstances that reduce separation rate.Advances in process control have been achieved with expert controls and instructive operator information data. This has gained a higher degree of understanding of cell operation and ore type being processed to be used in future process development work. Excellent results of this Advanced Flotation Technology have been achieved and designs through 7000 cu ft (200 m3) are currently available for high capacity concentrators. This paper will detail how flotation cells are more responsive to the exact requirements of the duty specified."

Jan 1, 2000

By D. Duvris

The main objective of this work was to quantitatively investigate exhaust emission levels relative to maintenance (service) intervals during the operation of diesel-powered equipment at an underground bauxite mine in Greece. Such emissions depend on a great number of parameters, including the type of engine (technology) and its tuning, the type of work performed (as related to the engine workload), the suggested maintenance intervals, the altitude, the temperature and humidity of the atmosphere in the underground mine, the properties of the fuel and the operator's training and experience levels. The necessary ventilation quantities were calculated based on exhaust gas-concentration measurements and site-specific relationships between pollutants and adjusted air-quality indices. Diagrams comparing the necessary and recommended airflow for several equipment groups, featuring two engine types and different maintenance intervals, are presented.

Jan 1, 2000

The objectives of mining grade control are presented and examples of the techniques used in various open pit and underground mines are used to define the attributes of good grade control. Reasons are discussed for the success of various improved practices. The progressive development of grade control is presented and the balance between quantitative and qualitative data is analysed. The skills and resources required for grade control on mine sites that are using best practice are also presented. A number of problems in grade control have been solved recently however there are still issues that need to be addressed. Examination of the grade control process frequently stops after sample quality has been examined. There is much more beyond this that can now be optimised using conditional simulation models. Other future directions of mining grade control are also suggested. An extensive bibliography of published papers on grade control is included that will be maintained and updated on a website.

Jan 1, 2000

By Philip L. Hageman, Paul H. Briggs

An important tool for use in the geochemical assessment of abandoned mine-waste piles is a leach procedure that can easily be done in the field and used for on-site screening of historic mine-waste material. We have developed a simple field leach test that is an effective indicator of waste pile geochemistry and can be used in order to establish the relative geochemical fingerprint for a given pile. This simple procedure also provides indication of the potential chemical composition of run-off from the weathered surface of these piles. As part of developing the technique, a comparative study was carried out on eight mine-waste composite samples from different deposit types. Splits of all eight composites were leached using the field leach test procedure and a modified version of EPA Method 1312 (SPLP). We found that the field leach test consistently provides relative indication of leachate geochemical trends comparable to leachate data derived from the more regulated, time consuming and laborious EPA Method 13 12 (SPLP).

Jan 1, 2000

By L. M. Scovell

The Internet and its related technologies will radically change the way that mines manage and control their maintenance, repair, and operating supply chains. The Internet is creating new distribution channels and offers new technology platforms with significant advantages over more traditional methods. Mines will have to re-evaluate both the strategies and the tactics employed in these areas. Mines will use e-commerce to integrate their maintenance, repair, and operating supply chains. The integration will extend beyond traditional trading partners to a worldwide network of communities with similar interests and goals. The changes will transform the way mines operate, lower mining costs, and thereby increase their chances of success in an increasingly competitive environment.

Jan 1, 2000

By J. Wong, M. G. Lipsett, L. K. Daneshmend

"Current trends of increased size, complexity, and automation of surface mining equipment necessitate more comprehensive and objective techniques for equipment comparison and selection. The field of reliability analysis provides tools to generate quantitative bases for maintenance and reliability aspects of such comparisons. Results from statistical analyses of failure and repair time data are used to perform the comparison. A case study is presented which analyzes five machines of two different technologies and three different designs.IntroductionThe surface mining industry is currently faced with a rapid evolution in production equipment. The more obvious trend in this evolution is the steady introduction of even larger machines. Parallel, and complementary, to this increase in size is the introduction or adaptation of new technologies. Together, these two trends result in new surface mining equipment designs; these designs are often more complex and may feature technologies that have yet to be proven for the application or at the scale they are now fielded.The prospect of significant automation of open pit equipment is also bound to add complexity to future equipment designs. Semi-automated features, such as drilling controllers (Aquila, 2000), have already been commercialized. Fully autonomous haul trucks have been demonstrated in open pit mines (Jackson and Zoschke, 2000). Design concepts for comprehensive teleoperation of open pit operations have been formulated (Lipsett, 1998).With this rapid availability and deployment of new technology and equipment, managers and maintainers are faced with a multitude of decisions regarding what equipment to acquire and what maintenance strategies to implement. In light of this evolution in mining equipment, it is necessary to develop better methods for making equipment management decisions (Dessureault et al., 1999; Paraszczak, 1999). The incentive for development of such techniques is that a large portion of an open pit mine’s operating cost is maintenance related, as shown in Table 1."

Jan 1, 2000

By Cindi Byrns, Andy Davis, Amy Tisdale

The Robinson district, Ely, Nevada is a hydrogeologically complex system with several distinguishable geologic blocks, each with a distinct background groundwater chemistry. To discriminate between background and mine-impacted groundwater, background wells, monitoring wells, pit lakes, waste rock seeps, and surface water samples were analyzed for a suite of major cations and anions, together with trace and precious metals, rare earth elements, 2H-deuterium and 18O/16O. The data allowed identification of groundwater flow paths, verification of hydrochemical source areas and characterization of natural attenuation mechanisms (e.g., mixing, dilution and mineral precipitation) that control the concentration and migration of metals at the site.

Jan 1, 2000

By H. M. Lima, P. Wathern

There are many different words to describe mine closure, including rehabilitation, reclamation, restoration and decommissioning. Closing mining operations, mainly open pit mines, has required resolution of numerous issues. Mine closure plans involve environmental-protection issues, regulatory issues and community issues. The obvious, and often most expensive of them, is the physical rehabilitation of the disturbances and the elimination of long-term commitments and maintenance. This paper outlines mine closure planning and its important component, mine-site rehabilitation. Community consultation and involvement are also referred to as an important component of the mine-closure plans, which are required to ensure satisfactory mine site rehabilitation. Considerations of socioeconomic impact of mine closure and long-term responsibilities are presented.

Jan 1, 2000

By K. S. Han, M. Yoshimuura, H. Fujita, Y. Sato, S. W. Song

"Film of LlCoO2 as cathode material for rechargeable lithium microbatteries has been fabricated on the platinum metal substrate by electrochemical-hydrothermal method in concentrated LiOH solution at 200 °C as Soft Solution-Processing. The film fabrication has been understood in terms of dissolution of cobalt metal powders and subsequent oxidative deposition on the substrate. The film structure was characterized using scanning electron microscope, X-ray diffraction analysis; X-ray photoelectron spectroscopy and micro-Raman spectroscopy.IntroductionRapid growth of wireless communications and emerging integrated optoelectronic circuits caused the miniaturization· cif electronic devices, thus the demand for high energy density microbatteries as a power source for the microelectronics increases. In this regard, all solid-state lithium microbatteries including LiCoO2 and LlMn2O 4 [l-4], the most promising intercalation cathode material, have been developed. However, major difficulty of .fabrication of a lithium microbattery arose from the preparation of cathode film, according to a· recent report on Rare Metal News [5]. Although many attempts have been made to deposit the cathode films, all those methods are mostly chemical vapor deposiiton (CVD), various evaporation, sputtering techniques and spray pyrolysis. These methods require preparation of bulk cathode materials cir its precursor, then deposition with complicated instruments including high· vacuum system, and even postsynthesis annealing to obtain desire electrochemical 'properties. It is clear that all of these techniques are neither economic nor environmentally friendly. Compared to those methods, film form.ation from an aqueous solution is thought to be simpler and more economical, and requires much· less energy consumption. Our .group has demonstrated the utility of Soft SolutionProcessing [6,7], which is defined as environmentally friendly processing using (aqueous) solutions, to produce films of a variety of functional solid materials. According to the Pourvaix's diagram [8], some metal can be dissolved in an alkaline solution and consequently combined with hydroxyl group or oxygen anion forming metalate or metalite. Cobalt also seemed to form cobaltite, HCoOi in strong alkaline solution in the Pourvaix's pH-potential diagram. Based on this information, it was expected that LiCoO2 could be prepared using the cobalt metal in Li OH solution by Soft Solution-Processing. Recently, we reported the successful single step fabrication of electrochemically active LlCoO2 films on the cobalt metal substrate by hydrothermal methods without any post-synthesis annealing as Soft SolutionProcessing [9,10]. Film formation mechanism could be elucidated by the following evidences. . As expected from Pourvaix's diagram, cobalt metal was dissolved in concentrated LiOH solution forming dissolved cobalt species which was detected by an observation of absorption band in UV-VIS absorption spectrum [10]. Thus the reaction was assumed to be started from dissolution. Time dependent potential of Co electrode exhibited only one-step evolution with 0.6 eV from Co metal to LiCoO2 [10]. Another strong evidence was the finding of LiCoO2 powder precipitates at the bottom of tetlon beaker after the reaction [11]. Based on those experimental findings, it was understood that film is formed by dissolution-precipitation mechanism [9-11]."

Jan 1, 2000

By M. Vallée

Several reviews of mineral project performance in the past 35 years indicate a pattern of occasional, but recurrent, mining project failures due to shortcomings in geological information and estimation, mineral processing and metallurgical testing, feasibility study objectives and requirements, and project start-up methods. A commitment to quality assurance and continuous improvement methods and to obtaining “ENOUGH DATA, OF APPROPRIATE QUALITY” is essential. Recent international and Canadian proposals for mineral resource and ore reserve definitions have taken a nonprescriptive stance that will undermine the formulation of requirements, guidelines and industry standards for efficient deposit delineation and estimation, and for the determination of project feasibility. To help reduce problems, every feasibility study supporting a mine development and production decision should be based on objectives and methods adequate to reach completion targets similar to the bankers’, as a good business target for a profitable project. In a resource/reserve system, the use of reserve should be restricted to a project that meets required technical, economic and legal feasibility requirements for successful project implementation, and the definitions of these categories should provide explicit limits. Current shortcomings will limit the ability of the Qualified Person to provide “adequate professional practice,” fulfill his/her professional responsibilities to his employer or client and provide adequate information to the investing public. We must take advantage of present opportunities for Setting New Standards for the new Millennium.

Jan 1, 2000

By André Vien, Pedro Gonzalez, Julio Palomino, Rob Perry

"In many mineral processing plants ore is reclaimed from a stockpile using multiple feeders. The discharge from these feeders is combined onto a single conveyor from which total tonnage is measured. Typically, operators set feeder output ratios to adjust the proportion of total tonnage drawn from each feeder. From a process control perspective, this system is not easy to control because the response time of each feeder depends on the distance from the feeder to the weightometer. This paper proposes a simple and elegant process control strategy to manage feeder ratio changes and the associated long and varying process dead-times. Changes in feeder speed are delayed and filtered to compensate for transport delays between feeders. The strategy was evaluated by simulation and installed on a mill feed system.ResumenEn numerosas plantas procesadoras de minerales, el mineral es extraido desde una pila de almacenamiento usando varios alimentadores. La descarga de estos alimentadores es recibida por zinica correa transportadora, en la cual se mide el tonelaje total. Comzinmente, los operadores colocan un valor determinado en cada controlador de razdn para ajustar la proporcidn del tonelaje total extraido por los alimentadores. Desde el punto de vista del control automatic0 de procesos, este sistema es dijkil de manejar debido a que el tiempo de respuesta de cada alimentador depende de la distancia de este respecto a la ubicacidn del pesdmetro. Este trabajo, propone una estrategia de control, simple y elegante, para compensar los cambios de razdn a cada alimentador y los tiempos muertos del proceso largos y variables. Los cambios en la velocidad de los alimentadores son retardadas y filtradas para compensar los retardos del transporte entre alimentadores. La estrategia fue evaluada por simulacidn, instalada y probada en un sistema de alimentacidn a molino."

Jan 1, 2000

By M P. Sandy, J B. Simpson

The empirical stope design techniques developed by Mathews et al (1981) and refined by Potvin (1988) and others, have gained rapid acceptance in Australia in the 1990s as a simple, æfirst-passÆ means of designing primary stopes. However, it is recognised that these æstability graphÆ methods can only provide broad design guidelines. Recently published stability graphs (Hutchinson and Diederichs, 1996) encompass a wide range of geological environments, which are not discussed, and the influence of time and blasting practices cannot be easily reviewed. The æscatterÆ in the graphs must reflect, to some degree, different operating practices as well as subtle but important differences in the pre-mining conditions that are not adequately accounted for in the æmodified stability numberÆ. Development of a ælocalÆ, site-specific stability graph may overcome some of these problems. At NormandyÆs Golden Grove Operations, Western Australia, detailed reviews of stope stability performance, including Cavity Monitoring System (CMS) surveys, are undertaken for every stope, with the objective of developing a series of local stability graphs, customised to site conditions and calibrated in terms of æAverage Falloff ThicknessÆ (AFT). Cablebolting of stope hangingwalls is used to develop reinforced æbeamsÆ on each sublevel, effectively dividing the full span into smaller, more stable æsubspansÆ. By analysing stope stability performance in terms of fall-off, cost-benefit studies can be undertaken of the effect of cablebolting and other options for modifying stope spans. The approach used to develop the local stability graphs, and their integration into routine stope design procedures at Golden Grove, is described. The experience gained during stope extraction in the Scuddles orebodies has been successfully applied to the Gossan Hill æC-PanelÆ orebody. This methodology should be applicable to other underground mining operations.

Jan 1, 2000

By Dany Pelletier, Yeves Breau, Ahmed Bouajila, Claude Gagnon

"In flotation circuits, direct measurement of the volumetric flow rate delivered by electromagnetic flowmeters is often difficult to obtain particularly due to piping and flow constraints. However, on-line material balance calculation could offer a reliable alternative to flow rate sensing. This paper describes an on-line material balance software package as applied to a copper flotation circuit for mass flow rate estimation mainly based on the output of an x-ray fluorescence onstream analyser. Rule-based procedures for the management of the main calculation modules are designed and integrated to a Comdale expert system. Attempts to diagnose the flotation process from mass flow rate data are also discussed.INTRODUCTIONThe need for improved process diagnosis, control and optimisation has become more evident for the mineral processing industry in the last decade. Therefore, new process variables need to be inferred or measured particularly in highly multivariable processes such as flotation. This process is subject to a wide variety of disturbances mainly generated by frequent and sometimes abrupt changes in physical and chemical characteristics of the ore and due to some irregularities in manual process operating procedures.A flotation circuit scheme is always a complex network counting more than two dozens of slurry streams. Information about those streams (%solids, metal content analysis, and flow rates) are important for process diagnosis, performance evaluation control and optimization (1,3).On-line sensing instruments such as x-ray fluorescence (XRF) on-stream analysers (OSA), gamma density gauges and electromagnetic flowmeters have been developed for the measurement of those variables. Unlike the other variables, stream flow rates could be determined by different ways:"

Jan 1, 2000

By D. A. Robbins

Remote sensing for environmental measurements is already being used. Aircraft-mounted imaging spectroscopy has been used to evaluate historical mining operations, as well as active mine sites. To the extent that remote sensing can provide more sensitive, cost effective and timely monitoring potential, the technology is of interest to the industry. Questions, however, remain about the application and validation of the data and concerning the availability of the technology in the private sector. This paper discusses some of the potential uses, benefits and concerns related to remote sensing. And it discusses efforts to monitor the technology's development.

Jan 1, 2000

By Joseph J. Feiler

Fires in underground coal mines are persistent problems anywhere in the world that coal is mined. Coal fires pose safety and health hazards in the form of mine subsidence, loss of energy reserves, destruction of property and surface improvements, and air pollution. In 1995, the US Bureau of Mines (US-BM), in cooperation with the Colorado Division of Minerals and Geology (CDMG),entered into a contract with Goodson & Associates Inc. (GAI) to design and field test the effectiveness of a new foamed grout technology called ThermoCell. GAI is a Lakewood, CO geotechnical and mining reclamation engineering firm. The company developed ThermoCell to control and extinguish underground coal fires. The viability of the special grout and the technology of application were established during a full-scale field demonstration at the abandoned IHI Coal Mine fire, near Rifle, CO. Following acquisition of additional funding by CDMG in 1999, Goodson returned to the site in April to continue the grouting to fully extinguish the IHI fire.

Jan 1, 2000

By N. Kuyucak

Acid rock drainage (ARD) resulting from the natural oxidation of sulfide mineral wastes has become a major concern to the mining industry, both during the operational period and after mine closure. ARD is generally characterized by high acidity and high concentrations of dissolved metals and sulfates. If the generation of acid cannot be prevented or controlled, it must be treated to eliminate acidity and to reduce the concentration of heavy metals and suspended solids before release to the environment. Microorganisms play an important catalytic role in the generation of ARD. Several prevention, control and treatment technologies that are based on microbiological activities have been developed. The role of microorganisms and biotechnology in the generation of ARD and their role in the methods used for prevention, control and treatment are discussed in this paper. Recently developed passive and biological treatment processes that have been implemented at mine sites are emphasized in this paper. Benefits, limitations and design criteria for passive biological processes are also presented.

Jan 1, 2000

By Gennaro G. Marino

During the preliminary design stages of the Illinois Division of Natural Resources(DNR) building, it was discovered that an old coal mine was present some 70 m (220 ft) beneath the building site. The new DNR building to be constructed is 36 m (120 ft)wide and 134 m (440 ft) long. It has three stories above grade and abasement level. The building is oriented north-south and has east and west ponds next to it (Fig. 1). The building is located on the State Fairgrounds in Springfield, IL. Given the history of surface subsidence of these underground coal mines in the Springfield area, there was concern about the potential for future subsidence at the building site. Mine subsidence events in the area have resulted in more than 0.9 m (3 ft) of settlement and have caused significant structural damage.

Jan 1, 2000

By Patrick R. Taylor

Glass is used for immobilization of radioactive and hazardous wastes due to its durability and ability to accept a variety of waste constituents into its network structure. Alternative high temperature vitrification techniques have the advantage of increased throughput, increased waste loading and being applicable to variable and heterogeneous waste streams. However, the increased processing temperature places further concerns on the increased volatilization of contaminants, and increased corrosion and erosion of me Iter components. A database of melt properties at higher temperatures, such as partitioning, viscosity, density and electrical conductivity, in the temperature range of 1400-20000 K are being developed.

Jan 1, 2000