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By Graham Davey

"Ultrafine grinding of minerals has been in wide spread use in the industrial mineral field for over 30 years. Within the last 10 years the metalliferous industry has shown interest in the ability to produce ultrafine particles, as chemical, physio-chemical and physical separation processes have advanced to be able to treat ultrafine metalliferous particles. Also as the primary mineral deposits are depleted, new more difficult deposits must be mined. Existing operations are also looking to maximize economic return from existing deposits, requiring new thinking and technologies.The recent development of industrially proven and cost efficient technologies for ultrafine grinding has opened up another processing option for the treatment of finegrained metalliferous and refractory gold ores. The current commercial designs are variations of stirred mills used in the industrial minerals sector for the past 30 years. For the purposes of this paper ultrafine grinding is considered to be P80 of less than 15 microns.Attrition milling to fine grind sizes presents some challenging issues relating to scale-up including the dearth of information on the quantitative impact of feed and operating conditions, as well as the precise and accurate measurement of particle size distributions. Two examples from recent installations will be analyzed including Thalanga Copper and Century Zinc Mines. Both have diverse grind size targets for the SMD, yet both have realized significant metallurgical gains."

Jan 1, 2002

By K. Terhaar, K. Prisbrey

The objective was to determine operating protocols for a lead and silver column flotation cleaner being considered for installation at Sunshine Precious Metals Inc. 's Kellogg mill in Northern Idaho. In this column, tetrahedrite and galena were floated, and pyrite and other gangue minerals, including siderite and silica, were depressed. The procedure was to develop a dynamic simulation using a linear transfer function approach. The transfer function related cause-and-effect variables such as the influence of collector and depressant dosages on recovery and grades. Bench-scale flotation tests followed by pilot column testing provided the data used to develop a linear transfer function. The transfer function was derived using a spreadsheet. This model was applied to simulate how the flotation column could be made to respond to disturbances in feed grade. The results were that xanthate, zinc sulfate and sodium cyanide were found to be suitable controls for grade and recovery. Simulations showed the best sequence of manipulations of these reagents, and these sequences are useful for future operator training. The conclusion was that linear transfer functions were able to simulate lead and silver recovery, develop scenarios for operator training and provide a foundation for future on-line control.

Jan 1, 2002

By Y Zhuang, S La Brooy

The selection of the optimum process route for a new project has traditionally consisted of investigating existing options and ranking them in terms of cost, technical risk and environmental acceptability. With the current focus on sustainable development other factors now need to be considered. Life Cycle Assessment (LCA) of the process options can be used to extend the assessment in terms of their potential for earning renewable energy credits and in judging their ability to achieve greenhouse gas emission reductions. A rigorous life cycle assessment is demanding in terms of setting the baseline for comparisons and evaluating the elements that make up the emission profiles of the process options. However, a simplified LCA can provide a useful tool for comparing different process options. This approach can be combined with traditional assessment criteria to rank the options available to the project. GRD Minproc has been intimately involved in executing LCA calculations for different municipal waste treatment options. This paper applies a similar LCA methodology to investigate the greenhouse gas implications for different options for copper processing. The process options considered are:concentrator û sale of concentrate to smelter, concentrator û on-site mini smelter, and concentrator û leach SX/EW. The paper then goes on to consider the operating cost implications that could arise with the introduction of carbon taxes or carbon credits and how these might impact on the future choice of flowsheet.

Jan 1, 2002

By Henk Dijkman

Existing metallurgical operations can be optimized by implementing engineered bioreactor systems in the process configuration. For instance, metals can be recovered safely and economically from process and waste streams using biogenic sulfide. This paper focuses upon possible applications of high rate biotechnology in metallurgy and mining. Metal recovery from liquid streams (process bleed streams, leach water, waste streams), integrated removal of (fugitive) SO2, treatment of acid blowdown and other options will be described. Practical examples are given. A large-scale application of biotechnology at Pasminco's Budel Zink refinery is described. Here, acid plant blowdown is treated together with electrolyte magnesium bleed. Concentrated zinc sulfide (10 tpd) is produced biologically, eliminating the production of gypsum and closing the refinery sulfur cycle. Recovery of metals from solution at Kovehute Pribram in the Czech Republic is the second practical example. In this case, H2S is produced on-site for metal removal from an alkaline slag dump leachate. At the Caribou mine in New Brunswick, Canada, acid mine drainage is treated with biogenic sulfide. This plant is situated upstream of a lime neutralization plant. As a result, reusable ZnS is produced, the volume of the sludge (gypsum and hydroxides) from the lime plant is reduced by 50%, the sludge is free of heavy metals and the final effluent concentration of heavy metals is in the ppb range. In the second phase of this project, metals will be recovered from stored tailings, resulting in significant revenues.

Jan 1, 2002

By J. Wagner, P. Eger

Although lifetime estimates for sulfate reduction based on total substrate carbon typically range from 20 to 30 years, field and laboratory experiments showed that rates of sulfate reduction decreased over time as readily available organic material was consumed. When the rate of acid input exceeded the rate of sulfate reduction, alkalinity was removed from the substrate, the pH decreased and metals increased. Output pH increased from 4 to more than 6 after the system was shut down for several weeks and the rate of acid input was reduced. Successful long-term treatment requires a design based on the input pH and the long-term organic decomposition rate.

Jan 1, 2002

By J L. Mauk

The Favona low-sulfidation epithermal deposit in the Hauraki Goldfield is less than one kilometre southeast of the world-class Waihi deposit. The veins are hosted by Miocene andesite of the Waipupu Formation, have a total strike length of over 900 m, a vertical extent of at least 350 m and are on average 1-3 m wide. Individual veins have been traced for 200 m with vein widths up to 25 m. The dominant vein textures are massive, crustiform and colloform banded veins and vein breccias, with subsidiary textures including comb, zonal, flamboyant, lattice-bladed, ghost-bladed, microbotryoidal, feathery, ripple and dune, and mosaic. Quartz is the dominant gangue mineral in the veins at Favona. Accessory gangue minerals include pyrite, chlorite, adularia, illite, calcite, and apatite. Electrum is the only gold-bearing mineral and is associated with acanthite, tetrahedrite, pyrite, sphalerite, chalcopyrite, and rare galena. Whole rock geochemical analyses indicate that gold grades correlate with textures/vein types. The highest gold and silver grades are associated with vein breccias and banded veins, with the former containing 28 g/t Au and 136 g/t Ag on average. To date, veins with significant base metal sulfide minerals, and massive and crystalline quartz veins lack significant precious metals (Au and Ag), except for one banded base metal sulfide-rich vein at Favona. An overall zonation of the veins exists, with base metal sulfide minerals dominant at depth (1050 m RL) of the system are characterised by massive quartz veins.Fluid inclusions from a total of 31 quartz, amethyst, and platy calcite veins reveal homogenisation temperatures of ~190-250¦C, with final ice melting temperatures between 0.0 and -0.8. Ice melting temperatures correspond to apparent salinities of 18O value of the water that formed these veins is approximately -4.3 per mil, which is similar to meteoric water-dominated, near neutral chloride fluids in geothermal systems in the Taupo Volcanic Zone.

Jan 1, 2002

By N Davies, M J. Coward, P L. Hissey

Mount Isa Mines has four mining operations in Mt Isa with the X41 and Enterprise Mines producing copper and the Lead Mine and George Fisher producing lead zinc and silver. Each stream contributes ore to their respective concentrator at a feed rate and therefore metal ratio set out by the monthly schedule. Mine Planning and scheduling lead to a sales and operating plan (S&OP) and revenue projections which ultimately derives actual revenue /tonne and therefore cost/tonne. At Mount Isa, both the copper and lead/zinc streams produce ore from relatively new operations to be blended with material from more mature operations. It is critical to accurately predict the metal contribution from each operation in order to gauge the relative performance of each mine. Development mining ore contributions are estimated and reconciled, as are stope and bench sources. Performance is continually measured and assessed during extraction and grade adjustments are made to account for underbreak, overbreak and design modifications. It is critical to not understate or overstate the contribution from one operation relative to the other as this can produce a false picture of operational performance. Identifying process improvements are key to improving the business overall. Ore from the lead stream passes 17 measurement stations and two midstream reconciliation points before delivery to the heavy media plant (HMP), where the metallurgical circuit begins. From this point two concentrates are produced. A zinc concentrate for treatment off site and a lead concentrate for further on site processing. The lead smelter takes 100 per cent of Isa concentrates as well as a contribution from BHP-BillitonÆs Cannington Mine.

Jan 1, 2002

By D. D. Tannant

An experimental and numerical study was conducted on the geomechanical behaviour of oil sands during penetration tests in which a steel wedge with an apex angle of either 20 degrees or 30 degrees was forced into compacted oil sands. The boundary conditions simulated in the laboratory tests are similar to shovel penetration into oil sands. The objective of the laboratory tests was to measure the force required to push a steel wedge into compacted oil sands. A wedge penetration test differs from conventional triaxial tests in that much more shear is generated. The laboratory data was needed to improve calibration of micro-mechanical input parameters for a two-dimensional discrete element model of oil sands constructed with Particle Flow Code (PFC). Initial model calibration was performed with triaxial test data and then a PFC model of the wedge penetration test was constructed. The measured force-displacement behaviour of the steel wedge was compared with PFC modelling results. It was found that different combinations of PFC particle and bond parameters could equally well replicate the laboratory triaxial compression data for bitumen-rich oil sands. When the wedge model was run, it was found that the resulting force required to penetrate the wedge into the oil sands was about four to six times higher than that measured. This clearly indicates that further research is required to improve the predictive capability of PFC models of oil sands.

Jan 1, 2002

By M Nombe

Based on the analysis of a case study at POWELTON No.2 MINE, it was determined that mine stability problems had occurred due to floor softening. A fireclay (underclay) layer in the immediate floor was softening after coal extraction and failing under pillars load. The thickness of soft floor was considered as the governing factor in the determination of the magnitude of floor displacement. The effect of floor thickness on floor displacement was evaluated by creating seven models that were input into the LAMODEL program. The properties of the soft floor were determined from a bearing capacity test performed in the Mains close to the area where mine stability problems had occurred. Moisture increase was considered in the reduction of floor bearing strength. Various strain-softening properties were allocated to the materials representing the soft floor. The LOW GAP POWELTON No.2 MINE was modeled and LAMODEL program was used to determine stress and convergence on both the coal seam and the fireclay seam. The results of critical stress and convergence obtained from modeling were compared with the actual floor failure area in the mine.

Jan 1, 2002

By J. P. Constantinea

The use of fluidized beds for the roasting of zinc sulphide concentrates marked a milestone in the electrolytic production of zinc. Stable operation of a fluidized bed for zinc roasting requires a particle size distribution that minimizes the risk of defluidization and helps control carryover to manageable levels. However, the understanding of the roasting process is limited, and changes in operating conditions mainly rely on intuition, experience, and trial and error. A research program has been initiated at UBC to study the phenomena that influence the particle size distribution of fluidized bed zinc roasters. In preparation for the experimental phase, this paper reviews the current literature on the phenomena that affect the particle size distribution during fluidized bed roasting and other fluidized bed processes.

Jan 1, 2002

By S. A. Osterberg, J. L. Breckenridge, R. S. Popielak

Multidisciplinary investigations were completed to prove the availability of water resources for the proposed San Cristóbal silver-lead-zinc mine in the arid Altiplano of Bolivia. Surface water resources are scarce, of poor quality, and unsuitable for development. Therefore, hydrogeological reconnaissance targeted alluvial aquifers for development. Follow-up resistivity, refraction, and water quality assessments were used to prioritize areas with prolific production potential. Pumping tests and regional water balance analysis indicate an alluvial aquifer can sustain the required approximately 40 000 m3 per day production for the life of the mine and predict no significant negative environmental effects on local groundwater users and the environment.

Jan 1, 2002

By J. J. Gusek

There are hundreds of passive treatment systems accepting mining influenced water (MIW) throughout the world. Some systems do not perform to design expectations while others, including volunteer systems, have successfully operated relatively unattended for decades. The primary reasons for this situation include the common misconceptions that (1) a “cookbook” approach to design is valid for a wide array of MIW chemistries and site conditions, and (2) low maintenance means “no maintenance.” Passive treatment systems for MIW are typically manmade ecosystems that are designed to handle a specific range of metal loading conditions and MIW geochemistry. Thus, when design conditions are exceeded, the suite of microbial to macroscopic ecosystems may be slow to recover or mature. This should be no surprise to designers. But when a particular system fails, it may be inappropriately attributed to the technology, not the design. This paper presents a standard “phased” design protocol that appears to work and provides examples of sub-par performance of selected passive treatment systems.

Jan 1, 2002

By Steve Kral

The mining industry is no stranger to hard times. Throughout its history, the industry has faced the ups and downs of commodity prices, difficult-to-mine-and-process ore bodies, labor issues and other problems. Throughout it all, though, the mining industry continues to provide the materials needed for society —even in the face of attacks by those who seek to cripple the industry or have it go away. The reason the mining industry survives, of course, is that mankind requires the products the industry produces. And, in recent decades, the industry has developed new technologies and improved on existing ones to produce those products in environmentally sound ways. At the same time, the economic benefits have been enormous to communities throughout the world where mining takes place.

Jan 1, 2002

By G B. Siddall

The paper examines the current state of equipment and circuit design, with reference to Australian practice. Following a review of the changes in milling applications over the last 15 years, developments in mill design are examined. Current issues include trunnion versus shell support; drive type and economic analysis for comparison of the various systems; the efficiency of the mill discharge system for slurry and pebble removal, and lining configuration. Peripheral problem areas such as pebble crushing and classification are briefly examined. Circuit design issues are reviewed. The decision to modify the traditional primary crushed feed is examined with reference to recent and proposed installations. A retrospective look at fully autogenous installations and their successes is presented, and current views on increasing throughput are assessed. Finally, future developments are anticipated in mill design and control, and competing processes are identified.

Jan 1, 2002

By Axel Preusse

Stowing or waste fill is common in the German mining industry since the beginning of mining activities, With increasing mechanization, flat and gently inclined seams (0 -- 18) were mined. These mines were located within the densely populated areas close to important infrastructures such as industrial complexes, roads, highways, railroads, rivers and canals. These buildings and infra¬structures were rarely protected against subsidence influences and other ground movements and dump capacities close to the mines were exhausted. For subsidence reasons and because of the low dump capacities pneumatic stowing methods were continuously developed and used in German longwalls until 1997. Due to techni¬cal standards and because of some restrictions pneumatic stowing in Germany is only used at a minimum seam thickness of 2.00 m and average costs of this method are $20 - 30 per ton. A significant reduction of the disturbance potential and by that a decrease in expenses for subsidence regulations due to reduced subsidence and ground movements could not be achieved. In this paper the experiences with pneumatic stowing in the Ger¬man mining industry are described. Possible subsidence reduction and economic aspects of pneumatic stowing are taken into account.

Jan 1, 2002

By B Faulkner, M. Weinecke

In 1997, Sveciala began a program to develop a process to convert waste tires into valuable commodities. A review of numerous approaches revealed shortcomings that were process related or mechanical related, while some of the approaches emphasized he production of low-value products. A market study revealed that a process that could produce a good grade of carbon black would be economically feasible. This paper discusses the laboratory and pilot-plant development and commercial plant design of such a process.

Jan 1, 2002

By M. M. Botz, F. W. DeVries

Discussion by F.W. DeVries Comments on natural cyanide attenuation. The paper by Botz and Mudder in the November 2000 issue of Minerals and Metallurgical Processing had one disappointing aspect. Table 1 (p. 229) failed to include a significant species - neutral copper cyanide (CuCN). This compound has been most trouble-some in many plant-scale cyanide cleanup processes, includ- ing acidification-volatilization- reneutralization (AVR), hy- drogen peroxide cleanup and air/SO2 cleanup. It has also plagued many pilot efforts to use ion-exchange (IX) resin technology. This author elucidated the concept that, under some conditions, copper cyanide failed to precipitate out of treated effluents and appeared to exist as a filterable colloid that reported as copper and cyanide, with the latter measured as WAD (weak-acid-dissociable) cyanide in that analytical method. The concentrations measured were very near the levels of 0.2 ppm, often the regulatory limit for WAD cyanide. The copper concentration, using the 1 : 1 ratio for this com- pound, would then be more than 0.4 ppm, which could also be unacceptable. We discovered that it was unsafe to assume that the Cu(CN),- would surrender both cyanide ions simultaneously and allow cupric copper to be removed subsequently as, say, cupric ferrocyanide (Hatchett's Brown). This compound could be ignored as safely as the "iron blues," as essentially an inert solid, stable in geologic time if not exposed to sunlight. Under poorly controlled oxidation of the cyanocuprite ions (copper with four, three or two cyanides complexed to the copper), CuCN could well be formed and could not be assumed to precipitate out as a solid. The authors of the paper, by failing to include the CuCN species in their model, may have left users of the model prone to ignore the possible occurrence of the colloidal(?) form in the discharge, thus finding an effluent that failed to meet regulatory limits. (See addendum below.) This somewhat ephemeral material may well have been responsible for some large-scale failures of cyanide destruction technology to succeed at sites in North America and elsewhere. Two specific references alluding to this occurrence may be found: Griffiths et al., 1987, "The detoxification of gold-mill tailings with hydrogen peroxide," Journal of the South African Institute of Mining and Metallurgy, September, p. 282. DeVries, 1989, "Improved understanding in detoxification of cyanide leach liquors using peroxide" Rand01 Gold Conference, Sacramento CA, p. 15 1. It is advisable for workers in this area of cyanide removal or recycle to avoid assuming that CuCN will, with certainty, precipitate out of solution, or that the dicyanocuprite ion will part simultaneously with both cyanide ions and allow cupric copper to be dealt with by other reactions. One further piece of work may be incomplete. That is, a definitive study of the long-term behavior of CuCN that does precipitate when exposed to other compounds present in neutralized tailings. Addendum. The extremely complex reaction of cupric ion on cyanide- which, of course, results in oxidation of cyanide to cyanate, probably through the intermediate stage of forming cyanogen [(CN)2] from oxidation of HCN with its hydrolysis to cyanate and cyanide ion - involves two cyanide moieties and the reduction of the cupric ion back again to the cuprous state. This, then, can form the CuCN potential "solid" that was already the undesirable species. In cyanide cleanup, with either air/SO2 or hydrogen peroxide, copper is generally employed as the catalyst, so it is unclear what happens when the CU(CN)2-1 is ultimately exhausted. Certainly, the field evidence is quite clear that all

Jan 1, 2002

By J. Paraszczak

With regards to the cost and profitability of a mining operation, the performance of the equipment employed is one of the key issues. Cost and profitability depend on, among other factors, the reliability and availability of the equipment. In an attempt to reduce equipment downtime, it is indispensable to collect and analyze reliable data and information on failures and maintenance actions. This paper reviews common problems encountered in this respect, with particular emphasis on the lack of uniform terminology and methodology. Recommendations concerning the standardiztion of reliability and maintainability concepts and measures are given. Regarding the benefits that the latter may bring, the paper concludes with a proposal for an industry-wide initiative in this respect.

Jan 1, 2002

By J. Ran

"Hangingwall sloughing is the major cause of unplanned stope dilution in open stope mining. Understanding the hangingwall sloughing mechanism can guide the stope design in minimizing the unplanned dilution and improving muck size and therefore mining efficiency. Though the modified stability graph method may be adopted to assess the hangingwall stability, for mines where the hangingwall is inaccessible, the required parameters are difficult to define and some of the simple influential factors cannot be easily identified in this method to provide guidelines for stope design.This paper identifies the main modes of hangingwall sloughing in open stope mining based on detailed data collected from mined-out stopes and site observations, applies the voussoir beam notation to analysis of the hangingwall sloughing mechanism, compares the model analysis results with the collected stope data, and provides guidelines for stope design and model application. Finally, examples are given to demonstrate the time and support effects on hangingwall sloughing and stope dilution."

Jan 1, 2002

By C. R. Edwards

"The Cigar Lake project will develop the world’s second largest high grade uranium deposit. The Cigar Lake Phase 1 orebody contains approximately 226 million pounds U3O8 at an average grade of 20.7% U3O8. The mine, to be operated by Cameco Corporation, will use a unique water jet boring mining method to cut previously frozen ore. A distinctive ore handling design is required to handle the high grade ore slurry exiting the mining machines. The ore will be crushed and ground underground, with the ore slurry then pumped to surface. Loaded into purpose-designed containers on tractor-trailer units, the ore slurry will be trucked to Cogema Resources Incorporated’s McClean Lake mill. McClean Lake will leach all of the ore. Forty-three percent of the resulting uranium solution will remain at McClean Lake for processing into yellowcake. The other 57% of the uranium solution will be shipped to Cameco’s Rabbit Lake mill for processing into yellowcake there. Detailed design for the Cigar Lake project is now underway. Barring regulatory or market delays, production could start up as soon as early 2005.INTRODUCTIONThe Athabasca Basin in northern Saskatchewan hosts a number of large uranium mining and milling operations, including Cluff Lake, Key Lake, McArthur River, McClean Lake and Rabbit Lake. (Edwards 1988, Edwards 1992, Fielder 1998, Edwards and Oliver 2000, Edwards 2001) The latest project in the Athabasca Basin is the Cigar Lake project."

Jan 1, 2002