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By M Edwards

The paper outlines the successful application of some of the on-belt technologies available from Scantech International Pty Ltd and how these have provided benefits in a number of mining and mineral processing operations. Effective process control requires real time analysis so quality can be fed back to the previous process and fed forward to a subsequent process. A range of on-belt analysers that allows for full stream, continuous, non-contact analysis of conveyed materials is available to achieve this. Real time results can provide timely information for effective process control. Benefits of on-belt analysis systems become more evident once the true variability of material quality and moisture content in conveyed flows is measured. To obtain economies of scale in mineral processing operations large material flows are achieved using conveyors. The cost and effort to sample representatively increases as conveyor flows increase. One sample may represent a few tonnes or up to 10 000 tonnes of material. The turnaround time between sampling and availability of sample analysis data does not allow real time process control. Tonnage flow rate, moisture content and elemental or mineralogical composition are required to perform effective process control of most conveyed streams. Tonnages can be effectively measured using belt weighers. The analyses derived from small samples supplied by conveyor-based sampling systems contain high variability. On-belt, continuous analysers see all the material and, through short term compositing of analyses, supply less variable results. Real time analysis helps operators develop a better understanding of material variability. Analysers can be effectively utilised to improve the consistency of product quality through bulk sorting and blending control. Many existing users of the technologies have gained competitive advantages through their ability to supply a more consistent quality product to the market.

Jan 1, 2008

By D Flint, O Rindriatmoko

PT FreeportÆs Deep Ore Zone (DOZ) Mine is the latest block cave mine within the East Ertsberg Skarn System (EESS).Issues with undercutting and stress concentrations at the extraction level were experienced, leading to reduced pillar strength.The extraction level-related issues became more pronounced, leading to local panel drift collapse, in an area that was over 100 per cent extraction. A review of ground conditions, panel collapse descriptions, and factors contributing to panel collapse are presented in this paper.

Jan 1, 2005

By D Morgan, D Sato, B Lumsden, S Senanayake

Laboratory flotation tests on fresh cyclone overflow samples are a useful tool to troubleshoot and indeed to improve plant performance; however, reproducibility between laboratory flotation test and plant performance is important for interpretation of the laboratory tests and hence their usefulness. Chemical reproducibility can be achieved with the addition of the required reagents; however, reproducing the physics of forces and energy in a 5 L cell compared to a 50 000 L plant cell or a 500 000 L plant cell is not generally studied or discussed. For some tests such as collector evaluation the physics of the flotation process may not be critical, but for some evaluations in the laboratory, it can be important.All flotation plants suffer from losses of valuable <20 µm mineral. Selective mineral aggregation has long been recommended to improve the poor flotation recovery of <20 µm sulfide minerals; however, successfully testing any type of selective sulfide mineral aggregation’s effect on flotation recovery in the laboratory on practical plant samples requires reproducing plant cell physics. The energy input per litre and the forces in a laboratory cell are vastly different to a plant cell. Reproducibility between laboratory and plant tests requires that these differences be minimised. The physics of the laboratory flotation cell is particularly important when fine mineral aggregation tests are carried out.This paper outlines a modified laboratory aggregation and flotation method that closely reproduces plant performance in a laboratory test.CITATION:Sato, D, Lumsden, B, Senanayake, S and Morgan, D, 2014. Development of a laboratory flotation method to test plant mineral aggregation, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 173–178 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

By N Cusworth, W R. Mackenzie

"In 2007, the authors presented a framework for the conduct of resource project feasibility studies and provided guidance on minimum standards and best practice (Mackenzie and Cusworth, 2007).This paper will present the authors’ observations in relation to feasibility studies undertaken to support investments made during the unprecedented period of resource project capital investment since 2007. It will also provide comments on general trends in the mining industry’s approach to project assessment and update recommendations on best practice.CITATION:Mackenzie, W R and Cusworth, N, 2016. The use and abuse of feasibility studies – has anything changed?, in Proceedings Project Evaluation 2016, pp 133–148 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 8, 2016

By Kellerwessei H, Oberheuser G

A major breakthrough in extending the life of the wear material of high pressure roll crushers when treating moist, highly abrasive material has removed the last impediment to the widespread acceptance of high pressure comminution in the minerals industry. The system is very energy efficient. It has been demonstrated that in the cement industry energy savings of up to 50 per cent have been achieved compared to conventional hall milling. Besides being energy efficient, the process provides some remarkable and useful effects; ò better liberation of mineral constituents (as proven for diamond liberation). ò preferential comminution where induced micro fissures follow grain boundaries. ò higher reactivity of the product due to micro fissures. All these points will be described here together with a review of current flowsheet design and incentives for the use of this method of Comminution.

Jan 1, 1993

By X Feng, X Zhang, W Sun, Y Zhe, K Hou, B Zhao, H Liu

Pulang Copper Mine, being China's largest newly built mine using block caving, boasts an annual production capacity of 12.5 million tons. Production level and roadway stability hold the key to the successful application of block caving. However, with Tong Kuangyu being the only mine in China which has applied such a method, we currently lack relevant experience in the successful application of the method. This paper has studied the influence of different rock mass zonings, fault thickness, fault dip angles, on-site construction quality on the production level, roadway stability of block caving through numerical simulation and analysed the roadway stability in different kinds of support solutions so as to ensure the successful application of block caving in Pulang Copper Mine. The results have shown that the existing support method in Pulang Copper Mine can meet the requirement of roadway support in zone II and III, but could not satisfy the demand in terms of support strength in the relatively fragmented zone I area. When roadway passes through the fault, the deformation of surrounding rock and plastic zone of roadway will gradually decrease with the increase of fault dip angle; the deformation of surrounding rock and plastic zone of roadway will gradually increase with the increase of fault thickness. An ideal support effect can be achieved through the joint support of grouting and bolting when roadway passes through the fault. In the measured model of on-site construction, there is stress concentration in the intersection between the access and transverse drift of ore removal. Therefore, the stability of the roadway can be improved by improving the construction quality. CITATION:Sun, W, Hou, K, Zhang, X, Feng, X, Liu, H, Zhe, Y and Zhao, B, 2018. Research on supporting technology for production level roadways of block caving in Pulang Copper Mine, in Proceedings The Fourth Australasian Ground Control in Mining Conference (AusRock), pp 95–106 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 30, 2018

By A Esfahanipour, M Osanloo

Determination of cut-off grade?strategy is one of the most important stages of open pit mine planning and design. It is the parameter directly influencing the financial, technical, economic, legal, environmental, social and political issues in relation to mining operation. Choosing the optimum cut-off grade strategy that maximises the economic outcome has been a major topic of research workers for nearly one century. Many researchers have contributed in devising methods and algorithms, such as dynamic programming, linear programming, optimal control and so on for various aspects of its determination. In this paper, a non-linear mathematical programming for cut-off grade strategy optimisation is presented, considering the three main stages of mining operation introduced by K F Lane. In this model maximisation of net present value of mining operation, under the three constraints of mining stagesÆ capacities, considered as the optimisation criteria. Due to the discrete representation of the mining resource, the proposed non-linear formulation is approximated by a non-linear signomial geometric programming. According to non-convexity and the complexity of the proposed model, an augmented Lagrangian genetic algorithm was used to find the optimum cut-off grade strategy under varying and fixed price circumstances. To validate the proposed non-linear model efficiency, the results were compared with the results obtained by the K F Lane methodology. It was found that the proposed non-linear model works efficiently in the determination of cut-off grade strategy. According to the simplicity of the structure of non-linear programming modelling in comparison with dynamic programming it is hoped that, further development of this model would certainly provide the ability of considering managerial and technical flexibilities as well as incorporating more real mining conditions in the determination of cut-off grade strategy optimisation.

Sep 26, 2011

By Y Yang, J Skrypniuk

The Jinfeng mine is Sino Gold's flagship project and is the second largest gold mine in China. Sino Gold Limited (SGL) holds 82 per cent equity in the Sino-Foreign joint venture Sino Guizhou Jinfeng Mining Limited (SGJML) with a Chinese partner. Jinfeng is located in a relatively remote site in southwestern Guizhou province. The orebody is considered to be the largest known Carlin type deposit in China. Jinfeng Plant has the world's third largest BIOX« bacterial oxidation facilities (790 t/d), treating highly refractory concentrate generated from crushing, semi-autogenous grinding (SAG) and ball milling and bulk sulfide flotation operations. The Jinfeng Plant construction started in February 2005, commissioning was completed in April 2007, and commercial gold production was achieved in September 2007. This paper describes the successful operations of Jinfeng Plant over the last two years. The key events of the project development are described, from the project background and process design, through to the commissioning and achieving design mill throughput of 3600 t/d resulting 180 000 ounces of gold per year. Process aspects of the BIOX« and carbon-in-leach (CIL) operations over the last two years are discussed which illustrate a very high BIOX« oxidation rate (more that 97 per cent) and excellent CIL recovery (more than 96 per cent). The management of the Jinfeng plant CIL tailings detoxification and filtration is described, and Jinfeng has became the first BIOX« processing plant to have achieved dry stacking of detoxified and pressure filtered CIL tailings. Current efforts to recover cyanide from CIL detoxified solution and the achievement of a zero discharge site water balance are also introduced. Many improvement projects have been made over the last two years which have culminated in a 15 per cent increase in mill throughput over the design and BIOX« CIL recovery increasing from 92.5 per cent to 96 per cent. Significant operating cost reductions from lowered of acid, lime and cyanide usage through process modifications and technical innovations are discussed.

Jan 1, 2009

By M Camarda, A Pirson, F Vasconcelos, J Mesquita

ArcelorMittal Prijedor is a goethitic iron ore mine located in the north-west of Bosnia and Herzegovina, which mainly supplies ArcelorMittal’s European subsidiaries. Annual production of the asset stands at the level of 1.5–2.1 million tons of iron ore product which is sent to ArcelorMittal Zenica steelmaking plant. Two types of products with approximately 50 per cent Fe are generated in Prijedor through a process composed by crushing, screening, and magnetic separation stages. Within this process one of the tailings produced is called ‘ultrafines’. The ‘ultrafines’ product corresponds to the desliming hydrocyclones overflow in Prijedor plant, which is classified in a size fraction below 25 μm and corresponds to about 5 per cent of feed. This material is richer in iron than the coarser size fractions of the ore but do not present a good performance in concentration processes. In this way, several studies have been carried out during the last years to find solutions to use the ‘ultrafines’ material without success. In this context, the possibility of dehydroxylate the goethite contained in the material transforming the mineral into hematite and thus increasing the iron grade of the final product was investigated. During the research, several dehydroxylation tests with different temperatures and time of exposure were performed. Using dihydroxylation process at temperatures higher than 800°C it was possible to produce a material with 43 per cent Fe from the original 39 per cent Fe ‘ultrafines’ sample. In addition, the dehydroxylation tests confirmed that goethite becomes completely transformed into hematite at 400°C (with an exposure time of 60 mins) and material is completely sintered at 1200°C. A simulation study based on dehydroxylation tests results showed that it would be possible to use a ‘ultrafines’ product with Fe grade higher than 45 per cent to produce a material with 50 per cent Fe through a complete dehydroxylation process.

Sep 18, 2023

By J D. Goldsworthy

The McPhee Creek bedded iron deposit is a recent discovery made by Giralia Resources NL (Giralia) in the northern Pilbara of Western Australia. The deposit lies 30 km north of the town of Nullagine along the southeastern margin of the East Pilbara Granite-Greenstone Terrane (EPGGT).The McPhee Creek area is located in the Kelly Greenstone Belt in the southeastern part of the EPGGT. The Archaean aged greenstone belt consists of volcanic and sedimentary sequences including the Warrawoona Group and the Gorge Creek Group. The McPhee Creek iron ore deposit lies within banded iron formation (BIF) rocks of the Gorge Creek Group. The structure of the McPhee Creek area is dominated by a northeast trending, upright synform (Sandy Creek Syncline) and associated folding that is truncated by northeast trending faults in the east. Iron ore mineralisation is predominantly stratabound and follows the dip of the bedding – however, in some areas, particularly in the southwest of the deposit, mapped steep to moderate dips of bedding planes are at odds with underlying fl at mineralised zones in drill sections. Zones within the deposit that contain substantial thickness of iron ore correspond to areas of complex folding suggesting structural control and iron enrichment in fold hinges. Petrographic analyses confirm mineralisation is goethite dominant and the deposit is strongly supergene enriched.Giralia initially identified iron ore potential in the McPhee Creek area through the presence of a small known channel iron deposit (CID) mesa. Giralia began exploration in 2008 by re-drilling a portion of the CID (subsequently named Crescent Moon) and reported a small low-grade Inferred Mineral Resource. Target generation in the wider area utilising Geological Society of Western Australia maps and Ikonos satellite images identifi ed strongly ferruginous outcrops associated with major structures along an 8 km long range located 2.5 km to the west north-west of the Crescent Moon CID deposit. In late July 2008, a total of 62 rock chip samples were collected during a helicopter supported sampling program conducted at McPhee Creek. Samples taken from haematite-goethite enriched BIF and canga zones outcropping intermittently over the 8 km length of the western and central areas of the prominent range assayed up to 63 per cent Fe. These zones represent the discovery outcrops and surface expression of the McPhee Creek main range iron ore deposit.Follow up sampling, geological mapping, bulldozing of access tracks and ramps and reverse circulation (RC) drilling commenced in September 2009. A maiden Inferred Mineral Resource was announced by Giralia to the Australasian Securities Exchange (ASX) on 15 December 2009.The current Indicated and Inferred Mineral Resource at December 2010 stands at 260 Mt grading 56.2 per cent Fe, 0.12 per cent P, 6.7 per cent SiO2, 2.3 per cent Al2O3 and 9.5 per cent LOI at a 50 per cent Fe cut-off. McPhee Creek is one of the largest iron deposits found in Archaean BIF in the northern Pilbara.

Jul 11, 2011

Safe, efficient production is a common objective for all large open pit mines. Despite comprehensive policies, procedures and regulations aimed at protecting workers, several people die each year in mining equipment-related collisions. The limited sightlines of heavy equipment operators coupled with difficult operating conditions are major contributing factors to the majority of mining equipment collisions. Off road haul trucks are the most common type of machinery involved in surface accidents. These vehicles represent the primary target for improving safety performance by mine operators. Although several commercial products have been introduced to address these issues, none have achieved significant market acceptance. The current collision avoidance solutions lack integration with onboard fleet management and equipment health systems. To achieve acceptance in industry, any collision avoidance system must offer high reliability, minimal false alarms, and value for money. With these criteria in mind, this paper will examine the pros and cons of the various technological approaches to collision avoidance in an open pit mining environment. The unique global positioning systems (GPS) and camera-based proximity detection solution on offer from Modular Mining Systems will be described. This solution uses intelligent filters to minimise false alarms. Tight integration with fleet management provides context information to enhance warnings and enable back-office near-miss analysis. Available today, this combination creates a practical solution to improve the situational awareness of heavy equipment operators, at a compelling price point. Future directions for maximising heavy equipment operator situational awareness will also be examined.

May 1, 2010

By K Williams, A Lavrinec, V Gurung, D Ilic

The moisture content of iron ore during handling can range from the dust extinction moisture at the point of arrival at the port to the transportable moisture limit at the point of loading ships for maritime transport. Moisture content and ore composition, specifically fines content, have a large influence on ore flowability. Typically, elevated moisture can result in bottlenecks, downtime and lost productivity due to build-up, conveyor carry-back and blockages, increasing maintenance costs. On the other hand, low moisture can result in increased dust emissions influencing the environmental footprint and product losses. Managing the use of water across the supply chain is therefore critical for service life of equipment, productivity, but also has environmental and social impacts, affecting the social license to operate. Previously, experiments have shown that oscillations induced in iron ore during handling and transport can result in movement of moisture through the ore. This kind of moisture migration depends on the nature of these oscillations, such as the undulation of idlers during conveying, the inherent ore properties and the initial moisture content. Moisture has been observed to move either upwards and/or towards the bottom of the burden. These effects can be exploited to remove excess water from the ore influencing handleability and operation, however, the actual mechanisms of moisture migration are currently poorly understood. The study presented herein involves the use of simulation to examine moisture and ore interactions. Simulations using discrete element method (DEM) and coupled with smoothed particle hydrodynamics (SPH) are implemented to investigate the behaviour of moisture in wet ore in the presence of oscillation. This is conducted at a fundamental level first using glass beads and water which is then compared to iron ore at high moisture content. The results of the modelling are discussed in view of experiments conducted.

Sep 18, 2023

By G Gilchrist, S C. Dominy, T Jashashvili, R C. A Minnitt

The grouping and segregation error is one of Gy’s seven errors that cannot be measured in any qualitative manner because of its transient and changing characteristics each time the sample is handled mechanically. Attempts to calculate the mean and variance of the segregation error is considered by some as ‘an exercise in futility’ that would not help us achieve representative sampling. This research is aimed at understanding the process of segregation of dense, finely divided and dilute particulate materials supported in a clean quartz substrate during intense agitation. Several mixtures of fine-grained materials including steel, tungsten carbide and gold grains were used in these experiments. Four hundred grains of each of the minerals and metals at a top size of 2 mm were mixed with approximately 600 g of finely ground quartz material (95 per cent passing 2000 microns) in a 500 ml plastic jar with a sealable lid. The mineral–?metal mixtures were analysed in three steps using microfocus X-ray computed tomography. Step one consisted of rolling the containers on a flat surface in an attempt to concentrate the mineral and metal grains in the core of the supporting substrate; this is a base case that can be reconstructed after each session of analysis. The second step involved gentle and vigorous shaking of the mixtures in order to segregate the denser minerals and metals from the supporting quartz substrate. In some cases, a third step involved splitting the sample through a riffle splitter. Three-?dimensional images of the surface of each grain, its volume and its X-, Y- and Z-coordinates, before and after intense agitation of the container, were interpreted from the reconstruction of the tomographic X-ray data. The spatial analysis of grains using cell declustering and 3D variography provided a useful means of characterising the distribution of the grains in space and the extent to which they had become segregated during the process of agitation. Spatial analysis indicates that in general, grouping and continuity of grains is weakly developed. The modelled nugget effect remains high for most tests, indicating that grains of similar size did not group together strongly. Agitation through rolling provided the best continuity, although not consistently in the long axis of the plastic jar. The nugget effect was consistently highest, and the range of continuity shortest in samples that had been split, indicating that the grouping and continuity were reduced through splitting the sample. Initial results indicate that very little segregation of the minerals and metals occurs in the quartz substrate. This is somewhat counter-intuitive, but suggests that the effects of agitation on mixtures of dense minerals and metals in substrates of lower density do not lead to excessive segregation. Differences in behaviour between dense materials in response to agitation are evident. Grains of different composition and shape did not group and segregate in a predictable manner in response to the agitation methods. Initial results indicate that the degree to which a material groups and segregates relates more to the characteristics of the denser material itself, rather than the agitation method employed.CITATION:Minnitt, R C A, Jashashvili, T, Gilchrist, G and Dominy, S C, 2017. Quantifying segregation of minerals and metals in particulate materials using computed X-ray tomography and variography, in Proceedings Eighth World Conference on Sampling and Blending , pp 173–182 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2017

By N Esmaeili, M Saghaeian, L Hosseini, V Sheikhzadeh, R Hejazi

Ore roasting has long been used for beneficiation and assay upgrading of different ores. In this process, which is mainly used for sulfide ores, the ore is heated to a high temperature. More specifically, it is a metallurgical process involving gas-solid reactions at elevated temperatures. Some types of Iron ore are weak in magnetic properties. Hematite, goethite and limonite are classified in this group. Unlike magnetite, which shows strong magnetic susceptibility, these ores are hard to beneficiate through magnetic separation route. Many researches have focused on gravity separation and flotation routes for upgrading these ores and these methods have also been utilised in the industry. One of the methods to whose industrial application less attention has been paid is magnetising roasting in which the non-magnetic iron ore is transformed to magnetite which is further beneficiated through magnetic separation. In this study, magnetising roasting tests have been performed on one goethite sample in order to check the feasibility of using this method for this specific ore in industrial scale. It is worth mentioning that high intensity magnetic separation have been performed on this sample before but the achieved results were not promising. Results have revealed that through magnetising roasting magnetite content of the ore could be increased from 1.7 per cent up to about 25 per cent. FeO content of the feed sample was increased from 1.03 per cent up to around 9.25 per cent. Also optimum size distribution for achieving the best results in magnetising roasting for this sample has been determined through this study. The best results were achieved when the ore size was 0–10 mm. The effect of coal ratio, time and temperature on the process have also be studied. A coal ratio of 5 per cent, time of 30 min and a temperature of 850°C were determined to be the optimum conditions. Finally, the technical feasibility of utilising magnetising roasting for this specific ore has been confirmed.

Aug 24, 2022

By M P. Sandy, V Louchnikov, V Eremenko, M Orunesu, O Watson

"Surface support is a key component of most ground support systems which are applied as a means of reducing the risk of rockfall occurrence and maintaining serviceability of mine development. Surface support has two primary functions: distributing the applied load throughout the system by providing connection between rock bolts retaining smaller rocks that unravel between rock bolts.Confinement is also provided to the rock mass, which may increase its capacity to resist further degradation or loosening.Surface support has been routinely installed in most underground mines around the world for many years, yet the operators are still not always certain which type is best suited for deformable ground conditions. A number of factors need to be taken into consideration prior to selecting the type of surface support liner, such as its capacity, availability, practicality of installation, manual handling and loading conditions (static or dynamic) to ensure the system’s optimal performance in terms of safety and costs.This paper presents an overview of the surface support types currently used in underground mines in Australia. Shotcrete, weld mesh, high-tensile chainlink mesh, reinforced weld mesh and high energy absorption (HEA) mesh are discussed. A detailed description of each system is provided in terms of capacity, energy absorption, installation cycle and costs. The cost of each system has been normalised to the units of energy absorbed. The information presented in this paper can be used by underground operators as a reference guide when deciding on suitable surface support type for deformable ground conditions.CITATION:Louchnikov, V, Sandy, M P, Watson, O, Orunesu, M and Eremenko, V, 2014. An overview of surface rock support for deformable ground conditions, in Proceedings 12th AusIMM Underground Operators’ Conference 2014, pp 57–66 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 24, 2014

By Yucheng H, Baogui Y, Wenyong L

High-water rapid-solidifying material, called 'high-water material', is a new material developed by the authors over many years. The material can solidify nine times its volume of water into solid. The material is a fine kind of binder with special properties. The solidifying body of high-water material with water has quite a high early strength. The compressive strength of the material within three days can reach the same strength as conventional Portland in 28 days. One ton of the material can replace three tons of conventional Portland cement as binder. Some important achievements have been made in application of high-water material. In metal mines, based on the material, a new full-tailing cemented backfill technology has been developed. The characteristic of the new technology is that high-water material is used as binder and full tailing or alluvial sand is used as backfill aggregate. Because of the application of the new technology, major technical problems in backfill technology such as classifying of tailing, dewatering, transportation of pulp, low strength of hackfill body. environmental contamination and so on, have been solved.

Jan 1, 1998

By C J. Greet

Oil can enter a flotation circuit from a number of sources (for example, from mining equipment, oil leaks from the grinding equipment and coatings on the grinding media, but to name a few). Folklore generally states that any oil that contaminates the ore entering the flotation circuit is considered to have a negative impact on flotation. That is, a loss in concentrate grade and recovery.This represents a dilemma for some grinding media suppliers, who use a variety of quenching medium (air, polymer, oil or water) to achieve the desired physical properties of the ball. In the case of high chrome grinding media it is necessary, in some instances, to quench in oil to give the ball the right degree of toughness, which invariably leads to these balls having a thin film of oil on their surface. Once the grinding media arrives on site and site personnel recognise that the balls are “covered” in oil, they generally insist that the oil will have a deleterious impact on flotation performance.Obviously, any supplier “worth their salt” would take remedial action at the point of manufacture to minimise this problem. However, does quenching oil actually present a significant “threat” to the flotation process? This paper provides both laboratory and plant data describing the effect quenching oil has on the flotation of copper sulphide ore, with surprising results!

Aug 8, 2011

Vertical flow systems (SAPS, vertical flow wetlands) are increasingly used for passive treatment of mine drainage that is net acid. Data on 30 systems in eastern US show that well designed systems typically add about 40 g/d/m2 of alkalinity to influent net acid water. If they are designed with a conservative loading rate of 25 g/d/m2 and carefully constructed, they produce net alkaline water. Alkalinity added depends on influent acidity, Fe, pH, and retention time, and ranges widely, from 7 to 484 mg/L, so this is not a useful design criterion. Some waters may benefit from retention times longer than the conventional 12 - 16 hours, but the design must be partly based on cost-benefit considerations. Systems with fine limestone added to the compost layer perform better than average, perhaps to an alkalinity generation rate of 80 g/m2/d. A variety of problems are noted in the 30 systems and others reported in the literature. Systems with high influent Fe (> ~75 mg/L, varying with pH) tend to gradually decrease in flow rate because of precipitation and settling of Fe hydroxides on top of the compost layer. Some high-Fe systems precipitate Fe in the limestone layer, suggesting inadequate compost thickness, or short-circuiting through thin spots. Systems with Al exceeding about 10 mg/L tend to plug because of Al hydroxide precipitation in the limestone layer. Flushing only removes a small part of this precipitate, but can extend life. Some systems are ineffective because of failure of the inflow system. Some systems are uneconomic because they are oversized. A continuing program of inspection and maintenance is necessary for long-term performance.

Jan 1, 2003

By M F. Gazley

The amphibolite-facies metabasaltic rocks of the Mine Mafic Package at Plutonic Gold Mine, Marymia Inlier, Western Australia, contain an estimated total endowment of 12.2 Moz of Au, which includes 4.71 Moz of past production and 2.77 Moz of reserves and resources; the remainder comprises lower-grade inventory. Over 65?000 multi-element analyses of whole-rock core and face channel samples from the underground workings of the deposit have been collected by portable X-ray fluorescence (pXRF) using a handheld Innov-X Omega pXRF unit. The analyses were performed on pulverised samples through paper bags, and were corrected using a pulverised, matrix-matched, reference standard. This method of data correction compares favourably with conventional XRF analyses performed on the same samples.A preliminary study based on pXRF analyses from a small number of drill holes found that a geochemical stratigraphy was evident in the pXRF data, and that this stratigraphy strongly controlled the location of Au mineralisation. The present study incorporates a much larger pXRF data set that samples a greater volume of diamond drill core and face channel samples and presents the data in a three-dimensional (3D) framework.This data set allows an investigation of the mineralogy of Au mineralisation with varying geochemical associations across the deposit. Historically, there has been a strong relationship identified between As and Au, which has caused issues with metallurgical performance, rendering some areas of the deposit only marginally economic. Utilising seamless data integration of the pXRF data set allows for recognition of the different styles of Au mineralisation using elemental concentrations and ratios from the multi-element analyses (Au:As, Au:As:Cu, As:Cu vs. K:V), and to visualise the distribution of these different mineralogical associations in 3D. The results of the 3D modelling and geochemical characterisation of the different styles of Au mineralisation are currently the focus of an extensive metallurgical testing program, the preliminary results of which are presented here.

Aug 22, 2011

By E Rubio, N Morales

A common practice in the mining industry is to decompose the planning process into different tasks, so the overall process and specific schedules can be constructed easily. Nevertheless, currently there are some adverse effects, such as not capturing the real value of a project by not taking into account the construction of several underground drifts and general infrastructure. Then the common practice is to compute mining sequence and cut-off grade profiles over the life of the mine without constitutively integrating the development schedule as a means to measure the constructability of a given mine design and sequence. Thus, the investigation summarised in this paper shows a novel, integrative way of treating an underground mine sequence and production schedule while considering drift development scheduling. Moreover, it is thought that, because of this original model, the whole underground production scheduling exercise must concentrate on combining the development and the production scheduling to compute a robust and a feasible production schedule.In order to quantify the effect of the conventional way of viewing the planning, the concept of the building information model (BIM) needs to be used, which was postulated by Charles Eastman and has been used extensively since the late 1970s. BIM takes other aspects of a project into account, considering at the same time the spatial relationships, quantities and properties of building components, but especially some kind of model visualisation, which is the advantage to be incorporated. This paper presents the basis for an optimisation model that allows for defining the sequence of the mining development so that the production plan can be achieved. For this, the model considers the space dimensions, time, pattern or strategy, cost or benefit, precedence and resources available. Tests were performed considering a block caving and sublevel open stoping method. Finally these tests showed the main conclusion, that production sequence changes when the building capacity is considered.

Sep 26, 2011