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By J. P. Grau, J. Z. Lu

"Thickeners/clarifiers are widely used in coal preparation plants, potash processing and other mineral processing facilities. Thickeners play a very important role in slurry treatment systems to accomplish solid/liquid separation. The demand for larger plants and the increased thickener handling capacities sometime require thickener diameters as large as 200m. The development and use of high capacity thickeners makes it possible to increase the handling capacity of these thickeners by several to more than 10 times compared to conventional thickeners. Hence, for a given slurry rate, selection of a high capacity thickener will significantly reduce the footprint of the thickener. Much higher handling rate, higher concentration of underflow, clearer overflow and lower capital cost are obvious advantages of high capacity thickeners; however, some process requirements and the concerns of operational cost, especially the flocculant cost of a high capacity thickener operation, keep some engineers selecting conventional thickeners and staying away from the high capacity thickeners. Forty years after the first high capacity thickener was developed, there are still arguments in the selection of conventional thickeners or high capacity thickeners in mineral processing. The arguments will continue unless there is a clear picture of capital cost vs. operational cost for each of the thickener types. The purpose of this paper is to analyze these costs and to provide guidelines for selection of thickeners. INTRODUCTIONThickeners/clarifiers are widely used in various slurry treatment systems. For mining and mineral processing, thickeners are an integral part of the solid/liquid separation system. The feed to the thickeners are processing slurries. The fundamental mechanism for the solids/liquid separation is for the solid particles in the slurry to gravity settle inside the thickener tank. The clear water overflows from the top of the thickener tank and is typically reused in the processing circuit, and the concentrated underflow is discharged to different downstream process systems depending on the application of the thickeners. The general requirements for a thickener operation include high density of underflow and clear overflow. Since thickener operation consists of continuous feeding, overflow and discharge of underflow, the solid particles will gravity settle against an upward flow with its velocity dependent on the feed rate and the underflow discharge rate. Higher feed rates to a given thickener produce higher upward velocities. Underflow discharge is typically relatively small compared to the amount of overflow. The upward flow tends to take particles up to the overflow. Only those particles having a settling velocity greater than the upward flow velocity will possibly settle out. Hence, thickener feed rate has to be controlled so that the required overflow water clarity can be achieved."

Jan 1, 2012

By H. B. Farnam

"THE IRON ORE Company of Canada has been using do-it-yourself type explosives for three years. During the last 12 months we have used over 10 million pounds of ammonium nitrate-fuel oil explosives and either purchased or formulated one million pounds of slurried explosives.W e have been moving approximately one million cubic yards of stripping and ore per month and we expect our production rate to in-crease. Eighty per cent of our strip-ping and ore is soft enough to be blasted successfully with ammonium nitrate-fuel oil mixtures. Twenty per cent of our material is extremely hard and requires an explosive having greater strength than an AN-fuel oil mixture.W e had been using canned am-monium nitrate base explosives and TNT pellets to give maximum bottom loading density to fracture hard rock. As AN -fuel oil became widely used, it was apparent that other types of explosives could be formulated to fit our blasting requirements. Dr. M. A. Cook of the University of Utah was consulted regarding new explosives and together we developed the blasting slurries.Figure 1 shows a general view of one of our hard rock pits. The foot wall is on the right-hand side and this material is called iron forma-Figure 1.-General view of hard rock pitstion by our Company but is called 'Taconite by the operators on the Mesabi Range. This material runs 35 to 45 per cent iron and many pieces are hard enough to scratch glass. The formation is tilted at an angle of 55 degrees as can be seen in Figure 3.The bedding planes of this rock are about 24 to 36 inches apart and if the material is not well broken or fragmented, large chunks or slabs must be handled by the shovels which reduces shovel capacity and efficiency and increases maintenance costs."

Jan 1, 1960

By H. Tsuruta, A. Fujibayashi, I. Sumi, A. Murao, R. Murai

Injection of biomass into blast furnace as alternative reducing agent is so effective for the purpose of mitigation of carbon dioxide emissions from steel industries, because biomass is considered to be carbon neutral raw materials. Certain amount of Palm Kernel Shell (PKS) is abandoned after Palm oil extraction process. To use as a reducing agent of blast furnace, PKS was carbonized and classified by 100 mesh sieve. To examine the gasification behavior of PKS carbide under the blast furnace conditions, several combustion experiments were conducted using hot model experimental furnace. The experimental results showed that the gasification efficiency of PKS carbide increased as the quantity of volatile matter increased. This tendency is the almost the same for the pulverized coal, so carbide of PKS can be used at blast furnace at appropriate amount of volatile matter that can be controlled by carbonization condition. In addition, the pressure drop of the furnace tends to decrease because the amount of ash in PKS carbide may be smaller than that of pulverized coal. PKS carbide is a suitable reducing agent in that respect.

Jan 1, 2015

By John D. Smith, Robert J. Mitchell

"There is a world-wide trend toward underground bulk mining methods employing hydraulically placed backfill. This trend is recent and therefore there is little in the literature to assist an operator in the design of backfill properties, the design of drainage facilities, the calculation of the operating forces on a bulkhead, and the control procedures considered necessary before, during and after pouring. This paper presents recommended procedures that are based on over to years of experience in the various aspects of backfilling large openings. Free-draining timber or concrete block bulkheads are shown to be a viable alternative to massive reinforced concrete bulkheads for the containment of backfill pours. Hydrostatic pressures cannot develop in backfills provided adquate drainage facilities are installed.IntroductionThe increasingly adverse relationship between mining costs and mineral values has led mining companies to develop more productive, lower-cost, bulk mining methods. This has led to the increasing use of large, more or less continuous, hydraulically placed backfill pours to enable the recovery of a higher proportion of pillar ore. The success of any bulk mining method depends on the degree of stability maintained during the stoping operations with reference to the mining rate, the performance of the backfill with respect to the per cent extraction of pillar ore, and the control of the mine structure with respect to safety and productivity. One such method has been previously described(I) where a steeply dipping orebody is being mined with a sub-level method that employs large, hydraulically placed tailings pours for delayed pillar recovery. The paper describes the rock mechanics analysis undertaken to establish the stope and pillar geometry and the approach taken to establish backfill strength requirements to prevent dilution during pillar recovery. Production with this method started in 1970 and because few, if any, large bulk pours had previously been used in- this way (judging by the lack of information in the literature), design data and criteria were needed for several aspects of the work. Methods to establish backfill quantities and pertinent ""in-place"" fill properties are described in 2, 3 and 4 in the list of references. Results of field measurements taken to establish fill pressures for bulkhead design purposes are described in 5 and 6. Laboratory large-scale model tests undertaken to confirm a fill strength design equation, which takes into account fill arching, have recently been completed. A paper describing these tests and the results will be forthcoming in the near future."

Jan 1, 1982

By M. Krasowska

Dynamics of collision and kinetics of the bubble attachment to hydrophobic solid plates (Teflon) of different surface roughness were investigated. The experiments were carried out in such a way that probability of the collision and probability that the detachment will not occur were equal always 100%. Thus, it was possible to determine effect of the surface roughness on the bubble attachment (three phase contact formation, TPC) only. A high-speed camera (1182 Hz) was used to record the velocity variations, bouncing and time of attachment of the bubble colliding with Teflon plates having different surface roughness (5 different plates). Roughness of the plate surfaces was modified in a mechanical way using different abrasive papers. It was found that the roughness had a crucial influence on the time-scale of the TPC formation and attachment of the bubble colliding with the Teflon plates. Despite high hydrophobicity of all plates (contact angles 1100 -115º) it was observed that at the smoothest surfaces (called "Teflon I" and "Teflon II" and having surface roughness below 1 um) there was no attachment during the bubble first collisions. Prior to the attachment four or more "approach?bouncing" cycles of the colliding bubble were observed there and simultaneously the bubble shape varied rapidly within time intervals below 0.85 ms. Time of contact of the colliding bubble with the Teflon plates was very short; 2-3 ms. These results indicate that during that short time of the collision the liquid layer separating the colliding bubble and the solid surface did not reach a critical thickness of its rupture.

Jan 1, 2006

By C. R. Machado

Sossego Mine was the first Vale SAG mill operation to process copper-gold ore. It is located in the state of Para, in the south-eastern Amazon region of Brazil. In the first six years of continuous operation, Vale investigated different alternatives for improving circuit performance by investigating operating conditions, mainly focusing on the SAG mill. Today, after a steady increase over five years the annual production rate seems to have stabilized. It is hoped this work will show how the SAG operating practice have been perfected with time and as new data are collected. Historical data of mill grind-outs and crash stops helped create operation curves depending on the ball charge volume and total charge volume. Also noted were impacts on throughput due to the effect of reducing liner weight and the ore type characteristics.

Jan 1, 2012

By M. P. Sinha, Rashmi, Tata Steel Ltd., S. Jaiswal, A. Bhatnagar, P. Garg

Reagents form a crucial part of flotation process as they have the power to control the surface properties of minerals. In case of coal flotation, collectors and frothers are two the important and commonly used reagents. But other types of reagents such as promoters, modifiers and depressants are also finding wide applications because of their availability to improve selectivity and increase recovery. Because of these chemicals the scenario has changed from flotation being used mostly for high rank hydrophobic coals to low rank, oxidised or inferior coals. In the present work a case is presented in which two non-ionic surfactants (abbreviated as A & B) known to act as emulsifier have been studied to get a better flotation performance for a preparation plant with varying feed characteristics. Laboratory flotation tests were conducted with both the surfactants using three feed samples of the plant by varying the dosage at three different levels. The highest combustible matter recovery (more than 80%) was obtained for surfactant B at a dosage of 75 ppm (parts per million) for feed 1. But at the same dosage the recovery decreased by 21% and 10.2 % respectively for feed 2 and 3. On the other hand surfactant A showed a consistent result for all the three feed samples giving the highest value at a dosage of 50 ppm followed by a decrease beyond this point. The tests were complemented by contact angle measurements that demonstrated the same trend. In addition to this the reproducibility of data for Surfactant A was checked and found that the standard deviations for both separation efficiency and combustible matter recovery were within the permissible range (less than 5%). Finally an in-plant process optimization study to evaluate the performance and applicability of surfactant A at industrial level was done and has been discussed.

Jan 1, 2016

By G. W. Evatt

This paper presents the scientific framework underpinning the Resource Valuation and Optimisation Model (RVOM). The RVOM is a Real Options software package, which helps mine owners optimally plan their operations, understand their project risks, and make defensible valuations. This is achieved in the presence of both financial and physical uncertainty. The three key outputs from the RVOM are: Valuation, Optimal Decision and Probability of Decision, where a decision can include any combination of: normal operation, expanded operation, care and maintenance, and abandonment (and variants thereof). This paper presents a clear example of the RVOMs usage to a case-study gold mine.

Jan 1, 2011

By A. G. Spencer, A. D. Taylor

This paper discusses some of the advantages and problems associated with the selection of large unit equipment for a metallurgical plant. A given flowsheet and material balance for an iron ore concentrator is assumed. Then two plant designs are developed, one utilizing a number of smaller-size equipment units and one utilizing the largest available equipment units. The mechanical and electrical problems are discussed and a comparison of capital costs is made. Finally, brief consideration is given to a plant de-sign using units larger than those which are currently available.

Jan 1, 1968

By R. Bonifaz, R. Subiabre

The Chagres Smelter, part of the Anglo American plc group, situated 80 Km north of Santiago in Chile, completed a series of operational improvement in 2005 resulting in an optimum capacity in its operational units. At present the Chagres Smelter has developed an operational strategy which seeks to reduce bottle-necks in the production process. In this way we have managed to lower operational cost, decrease energy consumption and maximize the capacity of the Acid, Oxygen, and Smelting, Converting, Refining and Casting units. A constant review of international benchmarks together with continuous staff improvement and the latest smelter technology have combined to place Chagres among the finest smelting works in the world. In response to environmental challenges, we have studied various options for investment that will yield a suitably profitable business to benefit both Anglo American and Chile. The most relevant technical indicators are: energy consumption=6,3 GJ/ton fine copper (1st in the world), intensity of smelting rate in Flash Smelting unit of 6,900 ton of copper concentrate/m2 of furnace area (1st in the world) and to be one of the top five smelters in achieving the lowest direct cash cost .

Jan 1, 2007

By C. S. Gibson

"MOST of the mines in the Province of Ontario in Canada are multi-level operations in steeply dipping veins; yet there is an appreciable number whose de-posits are relatively flat-lying, ranging up to 45° inclination.The veins vary in width up to several hundred feet and may or may not be branching systems. The depths of mines range from a few hundred to 8,000 feet, approximately. The primary products of the underground group are asbestos, gold, silver, cobalt, copper, nickel, iron, uranium, talc, fluorspar, gyp-sum and salt.There are a few open-pit mines. The majority are temporary in type because, as the outcrops are removed, mining is continued be-low surface. Primary products of the open pits are copper, nickel, iron, magnesium and nepheline syenite.The industry as a whole employs about 50,000 persons, approximately 60 per •cent of whom have dust-exposure occupations. The definition of a dust-exposure occupation and the requirements for •dealing with same are set forth in The Mining Act of Ontario.Results of extensive and continuing studies on the incidence and progression of silicosis have been reported periodically for years past, in annual reports of the Mines Accident Prevention Association of Ontario and in papers presented at Conferences sponsored by Mcintyre Research Foundation of Toronto, all of which have been published. The information provided therein proves the effectiveness of the means being used to prevent silicosis and allied disorders."

Jan 1, 1960

By G. Rong, W. Du

Stability of some potential unstable blocks in the left bank slope of Baihetan hydropower station is evaluated in this paper using the three-dimensional (3D) limit equilibrium method. The Baihetan hydropower station is in the downstream of Jinshajiang River, China. The geological condition in the river valley is complex, and many large discontinuities are detected in the slope of the two banks. As a result, much attention should be paid to the stability of the slope in the feasibility study stage. Because the left bank slope is an oblique consequent one, we mainly focus on the slope stability analysis in the left bank. Comprehensive geological exploration is conducted in the studied area and the detected discontinuities are well researched. By building a 3D geological model of the left bank slope, three potential unstable blocks which are close to the dam site are detected. An irregular wedge analysis method is then used to calculate safety factors of the three blocks under three conditions, which are natural condition, rainfall condition, and seismic condition, respectively. It is found that the safety factors of the block 1# and the block 2# are quite low when compared to the suggested values. Extra care must be exercised when excavating the slope near the block 1# and the block 2#. A preliminary reinforcement is also suggested.

Jan 1, 2015

By V. L. Eardley-Wilmot

Introduction We are all familiar with the bright and attractive colours of the roofs of our suburban houses and country cottages, but few of us fully appreciate the complex and highly technical nature of the business which produces these roofings. Roofing granules consist of small broken particles of certain types of rocks, burned clay products, or slag. They are used either in their natural state or artificially coloured and are affixed onto one surface of asphalt sheeting. Their main functions are to protect the roof against external fire hazard, prolong its life, and enable it to withstand extremes of weather over a period of years without deteriorating. Pleasing designs and colours are added attractions. The reverse, or inner side, of the sheeting is coated with a film of talc or fine mica to prevent it sticking when rolled up for convenience of handling for transport. The finished sheets or strips are cut into a variety of shapes for roofing shingles, or for sidings which resemble rows of bricks separated by mortar. In Canada, the consumption of roofing granules has increased fourfold in the past decade and indications are that the industry will continue to expand. At present, fourteen plants are engaged in manufacturing granule-coated roofings, but, apart from a relatively small output of natural granules by two producers in British Columbia, only one eastern producer makes both natural and coloured granules in Canada, and these only for its own use. The annual consumption is now over 77,000 tons of roofing granules valued at more than $1,600,000, but about 62 per cent of the tonnage is imported. It is thus apparent that the production of Canadian-made granules, both natural and coloured, could be considerably increased. This paper is presented in order to give an outline of the industry and at the same time to point out its difficulties and pitfalls.

Jan 1, 1946

By Nicholas C. Williams

This paper presents the development of a demand reduction and responsive strategy capable of reducing the electrical power demand, particularly during peak conditions. The work presented includes a case study of a UK colliery. Areas explained are the equipment installation at the mine; the development of the demand reduction strategy including the load profile database and prediction optimisation model. Some live production data from the power meter installation at the mine is also presented.

Aug 1, 2013

By Jaeheon Lee, Junmo Ahn, Doyun Shin

"Many alternative leaching systems including bacterial leaching have been introduced to avoid passivation on the surface of chalcopyrite and to increase the leaching efficiency of copper from chalcopyrite. Recently, glycine, one of the simplest amino acids, has been emerging as an efficient and environmental-friendly lixiviant to recover copper. In the present study, an alkaline glycine–peroxide lixiviant system was used to leach copper from chalcopyrite concentrate and the leaching mechanisms were also investigated by a suite of kinetic studies under different conditions. The chalcopyrite concentrate contains 28.8% copper with 30.8% sulfide sulfur. The effect of concentration of glycine and hydrogen peroxide of the leaching solution was investigated. Glycine concentration was varied from 0.5 to 1.0 M and the hydrogen peroxide concentration was changed between 3 to 5%. Leaching time and pulp density were also varied. Hydrogen peroxide is an oxidant of the system and the leaching efficiency with periodic additions of the peroxide was also studied. A mineralogical study was performed using XRD and SEM. To investigate the surface of the residue materials, XPS was used to see if any passivating layer was formed during the leaching. Detailed results from mineralogical, chemical, and metallurgical studies will be presented and discussed.INTRODUCTION The greatest global resource of copper is low-grade chalcopyrite and heap bioleaching may be the only economic option for its processing. However, formation of a passivating layer on the surface of chalcopyrite slows down the oxidation reaction and reduces the efficiency of the process."

Jan 1, 2017

By Michael Harley, E. Guy Charleworth

"Bedding-parallel thrust-hosted gold veins are developed in the Sabie-Pilgrim's Rest goldfield, eastern Transvaal, South Africa. The reefs display a complex history characterized by temporally and spatially overlapping events of similar mineralization and deformation. Recognition of the episodic reactivation of these low angle (5° to 10°) thrust faults implicates high fluid pressures (equalling or exceeding lithostatic pressures). Geochemical constraints limit the amount of fluid-rock interaction and the occurrence of transgressive mineralization within the Archaean granitoid basement suggests that the high pressure fluids originated at depth beneath the Transvaal Basin.Similarities exist between gold deposits of Sabie-Pilgrim's Rest and Telfer, Western Australia as well as Passagem de Mariana, Minas Gerais, Brazil. All deposits are sub-parallel to the enclosing bedding which is shallowly inclined. Furthermore, they are also hosted by contractional deformational structures and are clearly epigenetic in origin."

Jan 1, 1994

By B. R. Johnston, K. D. Streeter

"ABSTRACTCoal Mountain Operations is the newest of Fording Coal’s operations although it is the oldest in terms of its historical production. In October, 1994, Fording purchased the former Corbin Creek/Byron Creek Mine. The mine is located in southeastern British Columbia, approximately 150 air kilometers from Calgary, Alberta. It was first developed in 1905 and has gone through a variety of owners in its 90-year history.This paper will deal with the remobilization strategy and the mining plans for the operation which are being implemented to make this operation competitive in the world export coal market. IntroductionIn October 1994, following a due diligence process, Fording Coal Limited purchased Coal Mountain Operations from Corbin Creek Resources, an employee group which had previously owned the mine. The purchase awarded Fording Coal Limited with 100% of the assets, and control of all the coal leases at Coal Mountain.The mine is located in southeastern British Columbia, southeast of Sparwood at the hamlet of Corbin, (Fig. 1).Rehiring of laid-off employees started in November 1994, with mining activities also recommencing in November. The coal preparation plant was restarted in December with one shift, went to two shifts in January 1995, and had four-shift, full-time operation in April 1996."

Jan 1, 1997

By R. B. Nourse, R. Hundermark, B. Masters, H. Joubert

The new 30 MVA slag cleaning furnace at Waterval Smelter, Rustenburg Platinum, South Africa, has been in operation since 10 March 2003. The furnace design and operation face a number of challenges including a wide variety of feed materials and resulting bath conditions. Furnace feed varies in combinations of granulated Waterval Ausmelt Converter Slag (WACS), hot fed Peirce-Smith converter slag, concentrate and reverts. Coke is added as reductant. The resulting slag composition varies considerably and regularly. For the case feeding WACS an almost pure fayalitic slag (60%+ FeO, 30%+ SiO2) with a very low viscosity results. Due to the widely varying slag conditions, including a superheated fayalitic slag with high fluidity, a robust sidewall design is required adjacent to the slag bath. For this reason the furnace sidewall is equipped with Pyromet's MAXICOOL® high intensity copper cooling system. The design and installation of the copper coolers as well as tap holes are discussed. To cope with the variation in bath conditions and high slag superheat (350°C when tapped at 1650°C), the copper coolers are capable of removing peak sidewall heat fluxes above 500 kW/m2. Feedback is included on the performance of the Pyromet MAXICOO® copper cooling system for the first two years of operation. The paper further includes an overview on the design and performance of the tap holes, furnace shell, furnace roof and copper slag spouts.

Jan 1, 2005

By B. K. Ayres

Modern management of uranium mine or mill waste storage facilities (WSFs) often requires that they be remediated or decommissioned with a cover system. In addition to creating a self-sustaining landscape that supports the end land use, cover systems are intended to reduce long-term risks to human and ecological receptors from the stored waste to acceptable levels. The performance and longevity of a cover system will be strongly influenced by the features or shapes of the WSF final landform. Hence, cover systems and landforms must be thought of as an integrated design. Based on the author’s experience, the most important elements of the design process for maximizing the potential of WSF final landforms / cover systems being sustainable over the long term are noted in this manuscript. Several key items that must be considered and addressed during the planning phase of constructing a WSF final landform are also described. Various methods for monitoring performance of a WSF final landform are also reviewed. Key aspects associated with decommissioning a tailings WSF and waste rock pile at the former Cluff Lake uranium mine in northern Saskatchewan are included to illustrate many of the practical insights provided in this paper.

Jan 1, 2020

By Ning Zhang, Yan Chen, Qikang Yi, Linjian Ma, Guoan Wang

Laboratory tests were performed to explore the effects of frequency on the deformation property of rock salt subjected to cyclic loading under confining stress condition. A two-stage (transient and steady) evolution law of axial cumulative strain was obtained through cyclic stress-strain curves complied from the loci of minimum load of each cycle. The unloading modulus decreases with loading cycles/time as a negative exponential function. The damage of rock salt under cyclic loading is reflected by the degradation of elastic modulus. A unified damage evolution equation considering the effects of frequency and time was established based on the experimental results. A new creep damage model for rock salt was proposed by introducing the non-stationary modular components in Burgers creep equation according to the Lemaitre equivalent strain theory. Comparative study indicates that the new model can accurately describe the creep deformation and damage evolution of rock salt under different loading frequencies. This paper provides a more reasonable model and relevant mechanical parameters for the stability analysis of compressed-air storage cavern in the injection and withdrawal durations.

Jan 1, 2015