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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 Jaczkowski B

The lower orebody (LOB) at Chingola Divi- sion of Nchanga Consolidated Copper Mines Limited (NCCM) accounts for approximately 30 per cent of the total copper production for the company. The uniformity of the geology of the orebody lends itself readily to a computer based ore reserve calculation and accounting system. The mining units are physically defined such that a hierarchical type of com- puter file organisation can reflect the existing physical interdependencies. In 1972, a project team consisting of one representative from each of the mine planning, operational research, and computer services departments was formed to investigate and to define the technical mining requirements of the dynamic ore reserve system (DORS). The system was finally implemented in 1975ò

Jan 1, 1977

By Guerney P. J

A suspension of finely powdered ferrosilicon in water is the dense medium used in the gravity upgrading of iron ore, diamonds and other minerals. Ferrosilicon can he lost in the plant through corrosion. The greatest corrosion losses occur when

Jan 1, 1997

By W A. Peppin, D N. Riley, N W. Schulenburg

In June 2008, a joint airborne collection using hyperpspectral systems was tested on a single Twin Otter aircraft. This experiment was designed to incorporate two airborne hyperspectral sensors for geological and environmental projects. Mineral exploration and environmental impact statements are two areas where full spectrum hyperspectral data can document the mineralogy at the surface prior to mining operations. Many previous hyperspectral remote sensing collections were collected on a single aircraft with a single sensor. Mineral mapping using hyperspectral sensors that measure in complimentary regions of the electromagnetic spectrum is cost effective as it allows for the mapping of clays, sulfates, carbonates, feldspars, quartz, garnets and many other minerals. This report describes the experiment using the following two hyperspectral sensors: ProspecTIR, a visible near and shortwave infrared (VNIR-SWIR) sensor with 356 channels and spectral range of 0.4 to 2.5 ¦m, along with a spatially enhanced broadband array spectrograph system (SEBASS), a midwave and longwave infrared (MWIR-LWIR) sensor with 128 channels from 2.5 to 5.3 ¦m and 128 channels from 7.6 to 13.5 ¦m. SpecTIRÆs ProspecTIR system and The Aerospace CorporationÆs Spatially Enhanced Broadband Array Spectrograph System (SEBASS) are pushbroom sensors, have high signal to noise ratios, have similar swath widths and instantaneous fields of view. Examples of data collection experiment will be shown with a focus on mineral/lithologic identification and mapping along with environmental assessment in the western United States. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

By S B. Sheldon

Wall control programs tend to be expensive and consequently require financial justification in order to get approval for the expenditure required. The difficulty faced in getting this approval is that the outcomes of a wall control program are all subjective – a prediction of wall stability and what the wall would do with and without the program. Determining a net benefit is difficult and often justification of a wall control program is based on gut feel, history and a good selling campaign to build a perceived need.This paper outlines a simple solution to this problem by applying risk management principles to wall control. The process is to identify the risks to the operation associated with current wall conditions and then build a risk database for different potential scenarios for each risk. A financial impact is assigned to each risk scenario to complete the database. A consequence and likelihood analysis of each of the risks is undertaken and a formula applied to estimate the projected cost to the operation for the current risk profile. The process is repeated for the predicted wall control conditions after the application of the wall control program. A successful wall control program will reduce an operation’s risk profile so this projected cost should be less than that calculated for the current scenario. The difference in the two projected costs is the value that the wall control program has produced and this value can be used to determine the net financial benefit potential for the wall control program.This methodology can also be applied to other improvement programs that focus on risk reduction such as vibration control.

Nov 8, 2011

The mostly submerged New Zealand sub-continent has a complex geological history and an active oceanographic regime that provides opportunities and challenges for offshore mineral exploration. Known deposits include polymetallic Fe-Mn nodules and crusts, polymetallic massive sulfides, phosphatic nodules, titanomagnetitie ironsands and placer gold deposits. Currently exploration interest is high with some 3.5 per cent of the EEZ under prospecting permit or application.   Article 76 of the UNCLOS convention allows coastal states to have sovereign rights over areas of the seafloor that are natural prolongations of the landmass that constitute submerged parts of the continental margin as extended continental shelf. New Zealand has substantial areas of elevated ridges and plateaux beyond the 200 M EEZ that form extended continental shelf. New Zealand has nearly completed a ten year, $44.4 M programme to define its outer extended continental shelf. New Zealand will lodge its outer limits of the extended continental shelf with the UN-appointed Commission on the Limits of the Continental Shelf in 2006, which if accepted, will enclose ~1.8 million km2 beyond the existing EEZ. Ocean Survey 20/20 is a follow-on marine mapping programme to underpin resource exploration and environmental management of the EEZ and extended continental shelf.

Jan 1, 2005

By Y Zhu, W Liang, P Knights

In recent years, Chinese companies have invested billions in Australian mineral exploration, development and processing. In 2008 - 2009 alone, the Foreign Investment Review Board approved $26.4 B of investment. Much of this investment has been by merger and acquisition (M&A) of Australian resources companies. This paper sets out to investigate how Australian CEOs perceive the cultural and institutional challenges in operating Australia mining companies recently acquired by Chinese interests. HofstedeÆs cultural dimensions and institutional theory from management science were used to develop a structured questionnaire, which was subsequently used to conduct telephone interview of the CEOs of six recently acquired mining companies. Analysis of the survey results indicated that, in all cases, few changes were made to the operational management of the Australian companies post-M&A. The three major benefits for Australian companies as a result of the M&A are the ability to; access long-term debt at lower cost; secure finance for growth plans in financially volatile times; and maintain existing management structures. Some perceived negatives involved longer and more convoluted decision-making as a result of Chinese state approval required for investment decisions. The study identified building æGuanxiÆ and an aversion to losing æfaceÆ as important cultural learnings for Australian CEOs. Maintaining effective communications is regarded as key for successful cultural integration.CITATION:Liang, W, Zhu, Y and Knights, P, 2012. Cultural challenges in Chinese/Australian mining mergers and acquisitions - A CEOÆs perspective, in Proceedings International Mine Management 2012, pp 251-260 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 20, 2012

By P Lindsay

A numerical model has been developed to simulate the effectiveness and costs of a number of conceptual remedial measures aimed at reducing acidity and metal concentrations in the Ngakawau River and its tributaries near the Stockton Coal Mine, situated on the West Coast of New Zealand. The Stockton Coal Mine has been in operation over the past 100 years. During that time, seepage from waste rock dumps has contributed to elevated acidity and metal concentrations in the Ngakawau River and some of its tributaries. The yearly mean rainfall at the mine site is 6000 mm. The model, developed using GoldSim software, simulates rainfall, run-off and stream discharge for 26 tributaries. It then calculates acidity and metal concentrations in the mine impacted tributaries and the dilution downstream from the mine. The model has been calibrated to measured flow and acidity and metal concentrations in the Ngakawau River and some of its tributaries. Acidity and metal loads are removed from the system in accordance with specified efficiencies and capacities of the respective conceptual remedial measures. The user can compare specific remedial measures, or a combination of conceptual remedial measures. The model predicts the acidity and metal concentrations at a number of monitoring stations for any remedial strategy selected by the user. It also calculates the capital and operational costs for that particular remedial strategy. This paper presents the development of the numerical model and describes how the end-user can use it to compare the efficiency and costs of various remedial strategies by running different æwhat ifÆ scenarios.

Jan 1, 2006

By P J. Marsh, P J. Bartsch, N J. Semler

Iron Road Limited is currently studying the feasibility of producing 20 Mt/a of high-grade (67 per cent Fe) magnetite concentrate from a 2.6 Bt resource (JORC) located at Warramboo on the central Eyre Peninsula in South Australia. Bulk concentrate has been tested at a relatively coarse grind size of -106 ¦m. The preliminary flow sheet has been confirmed based on initial mine plans and comprehensive metallurgical testing across the range of mineralisation. Extensive Davis tube testing to predict magnetite recoveries has been conducted over the resource, however this was completed at settings different to the optimised settings developed in the metallurgical test work program.This paper outlines the development of an ore treatment simulation in SysCAD which utilises the mine production plan, the Davis tube test data from the resource, data from metallurgical test work and process design criteria to predict magnetite concentrate deliveries. Mineralogical data, including QEMScan results and metallurgical assessments, were a fundamental basis of the process models which enable predictions of concentrate yield and quality. Power and water requirements are also calculated within the model. SysCAD dynamic simulation has been used to assist with the design of the process plant and downstream infrastructure. The simulation has been set-up to allow iterative integration and optimisation of the mine plan when it becomes available.CITATION:Semler, N J, Marsh, P J and Bartsch, P J, 2013. Iron RoadÆs prediction of magnetite concentrate production from the Central Eyre Iron Project, in Proceedings Iron Ore 2013 , pp 539-546 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013

By McKay AD

The bulk of Australia's uranium resour- ces was delineated in the last 18 years when a total of $563 million (1984 dollar values) was spent on uranium exploration. Australia's share of the low-cost Reasonably Assured Re- sources in the World Outside the Centrally Planned Economies Area (WOCA) increased from 1.5% in 1967 to 29% by the end of 1984 and its share of the low-cost Estimated Additional Resources (Category I) then stood at 25%. As of December 1984, Australia's uranium resour- ces were estimated by the BMR to be: Cost range US$80/kg U (US$30/lb U301) Reasonably Assured Resources 463 000 t U Estimated Additional Resources(I) 251 000 t U Cost range US$80-130/kg U (US$30-50/lb U308) Reasonably Assured Resources 63 000 t U Estimated Additional Resources(I) 126 000 t U The increases in Australia's resources was sustained by a group of large and rela- tively high-grade deposits which were disco- vered during the period 1969 to 1975. Austra- lia's share of the low-cost resources was also enhanced by a contraction of WOCA's low-cost resource base due to escalation of production costs for smaller low-grade deposits. Most of Australia's uranium resources are contained in the Proterozoic unconformity- type deposits of the Alligator Rivers uranium field and the stratabound deposit at Olympic Dam on the Stuart Shelf. Most of the remain- der of Australia's uranium resources is con- tained in calcrete-type deposits. Less than 10% of Australia's uranium resources are in sandstone-type deposits. Total Australian production to the end of 1984 amounted to 26 241 t U, representing 3.4% of WOCA's cumulative production. Aus- tralia's share of WOCA's annual production has steadily increased from 1.3% in 1977 to 11.2% in 1984 (4390 t U). The increases in Austra- lian production took place in the face of reductions of production in WOCA countries, principally the US, from a record level of 43 988 t U in 1980 to about 39 000 t U in 1984. New low-cost production centres, mainly in Australia and Canada, have partly compen- sated the decline in US production. The Department of Resources and Energy (1985) reported that Australian exports of yellowcake are expected to reach 10 000 t U308 (8480 t U) by 1993/94, representing an in- crease of about 13% oer annum.

Jan 1, 1986

Two key elements in the design of a pastefill or high density hackfill system are the preparation of the backfill material and its distribution underground. This paper examines these two areas. Owing to the essentially impervious nature of total mill tailings, preparation of pastefill and high density fill from current tailings involves a physical dewatering process. There are currently three methods available for this process: I. Vacuum or pressure filters. These represent the 'traditional' approach to the preparation of pastefill. 2. Paste production storage mechanism. This is a thickening/storage mechanism developed with the specific objective of producing paste/high density backfills. 3. Fluidization. This system utilises silos fitted with simple dewatering devices and nozzles. Recently developed by CANMET, it provides the simplest and most economical approach. This paper describes and compares the three preparation methods, from a practical and an economic point of view. Once the pastefill/high density fill has been prepared and binder added, the backfill must be distributed underground into the stopes. A fundamental factor in the design of a distribution system is the rheology of the material- No two materials will exhibit the same properties, and a sequence of rheological and related testing is required prior to the completion of the design of the underground distribution system. This paper covers the testwork normally required and discusses the fundamental design parameters of pastefill distribution systems. The final section of this paper summarises the use of pastefill at three mincsin Canada.

Jan 1, 1998

By D Kepert

It is the role of the exploration geologist to create wealth through the discovery, delineation and characterisation of economic mineralisation. This requires a critical depth of geological understanding.Unfortunately, the resource industry is well known for its cyclic nature. Many of the current generation of workers have only ever experienced the boom of the ‘super-cycle’ and are only just discovering the negative side to the business. For the case of the geologist and especially the exploration geologist, the magnitude of peaks and troughs are usually amplified and may become destructive to all parties. During the uptime a healthy stream of exploration good news becomes the staple diet of company releases, in particular those of junior companies attempting to bolster the share price. The geological knowledge and experience gained thus forms a significant and integral part of the value and therefore, future of a company. On the downturn it is often viewed that geologists are a luxury, an optional extra and a burden on the bottom line with companies entering a period of memory loss and myopia.Retention of geological knowledge however remains critical as projects, companies and cycles mature. Beyond exploration per se, this knowledge becomes both fundamental in de-risking and commercialising an asset (through development or divestment) and in positioning the company for cyclic or counter-cyclic opportunities.The growth and retention of this knowledge base is difficult to quantify in terms of direct value but becomes one of a successful resource companies greatest assets. At worst, its loss can lead to millions of investors’ funds wasted on missed opportunities, drilling, or poorly designed plant and mine.But the rocks are around for the longer haul and pay little notice to the vagaries of the scurrying of Man.This paper reflects on some of the authors own observations through 25 years of iron ore exploration, in why it is critical to always rigorously question the prevailing geological (mis)understanding and the technical and commercial benefits which that may bring, and looks forward to the future.CITATION:Kepert, D, 2015. Geology – the affirmative case, in Proceedings Iron Ore 2015, pp 285–298 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By M J. Nimmo

extremely powerful tools for building predictive and generative models. ML can be used for building highly accurate regression and classification models. But without careful data science and statistical analysis, a regression or classification model could be highly biased and completely wrong – and we may not even realise. An example rock density estimation task will be used to illustrate the potential gains and possible pitfalls in using ML and AI in Mineral Resource estimation. What could possibly go wrong? Nothing! For most simple regression or classification problems, very little. For density estimation, using the global mean may be all that is possible, but the resource classification would need to reflect the uncertainty in global estimation of tonnage. Everything! From data collection and measurement, from selecting ML and AI techniques and designing the analysis workflow to our own cognitive bias. The things that could go wrong are vast and may include but not limited to asking the wrong question, not asking questions, data bias, measurement errors, insufficient data coverage, not collecting the right variables, not collecting enough observations, collecting clustered samples, unbalanced data, filtering out data without reason (outliers), clipping data (outliers), relying on automatic feature selection, including irrelevant variables, excluding relevant variables, geological interpretation, changing context, blindly following best practice, splitting small data sets, subsetting large data sets, using the wrong tool for the task, insufficient budget to complete the analysis, not allowing enough time for testing and experimentation (the science), focusing too much on building the model (the engineering), not learning from the data, our assumptions, our preconceptions, and our skill. This paper will explore the question of how training regression models to predict rock density are affected by gaps in the data (missing observations and missing variables). What could possibly go wrong?

May 24, 2023

The Louvicourt Mine is located 600 km north of Montreal in the province of Quebec, Canada. The owners are Aur Resources Inc (30 per cent), mine operator, Novicourt Inc (45 per cent) and Teck Corporation (25 per cent). It is an underground mechanised operation with a total work of 290 employees. Since 1994, the mine production is 11 120 456 tonnes at 3.60 per cent Cu, 1.51 per cent Zn, 26.07 g/mt Ag and 0.96 g/mt Au. At a rate of 4300 tonnes per day 365 days per year. Louvicourt Mine is a copper operation since 80 per cent of our revenue is from copper. The mining method is transverse blasthole stoping, mining primary and secondary stopes. The stope dimension is 15 m wide by 30 m high and 10 m to 80 m long for primary stopes. The secondary stopes are limited at 25 m long. Close to 100 000 metres of production drilling per year is required for 115 mm and 165 mm diameter holes. Backfilling is done with pastefill from the start of the operation in 1994. The binder ratio is 4.5 per cent in primary and two per cent in secondary stopes (80 per cent slag and 20 per cent cement). Development requirement to maintain production was 5000 m from 1996, 1997, 1998, 4200 in year 1999, 3200 m in year 2000 and an average of 2500 m in 2001 and 2002. Typical 6.0 m + 4.3 m, 4.9 m + 4.6 m and 4.5 m + 4.6 m headings. In addition more than 1500 metres of development will be excavated in/under paste backfill before 2004. A total of 60 mobile units are required among which for lateral development (three two boom electric hydraulic jumbos û AC Boomer 322, four electric hydraulic roofbolters û Maclean MEM-928 and AC Boltec PL350 and two anfo loader truck û Dux) and for production (four ITH drills û MTI, one electric hydraulic longhole drill û AC Simba H1357, eight LHD û AC-Wagner ST8-B, 1 LHD ST-1000 and two haulage 30 tons trucks û Dux. The 1 January 2002 reserves are 4.1 M tonnes grading 3.1 per cent Cu and 1.9 per cent Zn at an NSR (Net Smelter Revenue) of $US 53. The operating mining costs were at an average of $US 23 from 1996 to year 2000 and $US 25 in 2001. The operating costs ranged from a low of $US 0.41 per pound of copper in 1999 to a high of $US 0.49 per pound of copper in 1998.

Jan 1, 2002

By Hoskings R

Conceptual studies of the run of mine stockpiling and reclaiming requirements com- menced in 1975. Final selection of equipment was made in 1978 and the equipment was commissioned in June, 1979. Equipment selection was made after extensive investigation and visits to existing facilities throughout the world. The equipment selected is described and com- pared with the alternatives. Foundations were designed to minimise clean up effort and to ensure stability of equipment under design wind loading without storm bays. Program- mable logic control enables the stacking and reclaiming facility to provide a blended feed to the coal preparation plant.

Jan 1, 1980

Crandallite and millisite in Christmas Island 'B' and 'C' phosphate ores are rapidly decomposed by sodium hydroxide solutions at about 80QC. As these phosphates generally contain less than 1% silica, an alkaline extraction process can be designed, in which up to 95% of the sodium hydroxide used, may be recycled. The insoluble residue consists of an impure, highly reactive apatite, which in pot trials, has given good responses as a direct application fertiliser; alternatively this residue can be underacidulated to give a granular product with fertiliser potential. The hot leaching solution contains up to 95% of the alumina and approx- imately half of the phosphate from the original ore. Simple crystallising techniques have been developed on a laboratory-scale to use this leaching solution for producing smelter-grade alumina and detergent-quality trisodium phosphate. As the demand for detergents is limited, an investigation was made of the reaction between trisodium phosphate and slaked lime, derived from a high-grade New Zealand limestone occurring near Oamaru. The product is calcium phosphate, containing up to 40% P205, and less than 0.2% each of iron, aluminium and fluorine, and it should be a useful raw material for phosphoric acid manufacture. A preliminary economic evaluation of the whole process looks promising, And warrants further investigations, including pilot-plant work.

Jan 1, 1971

By L Soebari, W Sunyoto

The Wabu Ridge Gold Skarn deposit is located at elevations of up to 3100 metres above sea level, in the Central Highlands of Irian Jaya, Indonesia, 35 km NNW of the Grasberg porphyry deposit. Wabu is a grass-roots discovery in an area with no previous gold mining history or record of gold mineralisation. A geological resource of 117.26 million tonnes at an average grade of 2.16 g/t Au (1.0 g/t Au cut-off) has been defined to-date. Mineralisation is hosted within a skarn occurring along the southern boundaries of the Late-Miocene age monzonite-diorite Pagane intrusive complex. The intrusive complex occurs in the footwall of a major EW structure, the Derewo fault, which displays sinistral strike-slip and reverse fault movement. The Derewo fault separates Derewo metamorphic units to the north from platform sediments of the Australian craton to the south. The skarn has a strike length of 6 km and is up to 1.5 km wide. It is developed within calcareous shelf sediments of the Tertiary New Guinea limestone group and is dominated by prograde garnet development. Gold mineralisation was deposited during retrograde alteration and is directly associated with arsenophyrite and bismuth minerals. Retrograde alteration is distinguished by a sequence of clinopyroxene , magnetite, epidote and hornblende, biotite and chlorite and lastly carbonate. Gold is associated with the biotite/ chlorite phase together with sulphides and precipitated as the result of fluid mixing. The Wabu Ridge Gold Skarn deposit was identified in April 1990 during a regional program of helicopter assisted stream sediment sampling of -80 mesh (180 microns) fraction and panned concentrate sampling. The initial discovery sample site was situated 15 km down stream from the deposit and returned 1.49 ppm Au for the stream sediment sample and 138 ppm Au for the panned concentrate sample. A regional airborne helicopter magnetics survey, conducted in early-1992, helped defined the main magnetite associated skarn zone and the extent of associated igneous rocks. Detailed follow-up commenced in May 1992 and consisted of detailed mapping, soil sampling and ground magnetics prior to drilling the first hole in October 1992. Drilling to-date has delineated a contained geologic resource of 8.1 million ounces of gold and potential exists for a larger resource.

Jan 1, 1999

By J Benn, V Kuznetsov, G Timms, A Spain

Earthen covers are now widely used in the mining industry to control the generation rate and/or release rate of low quality drainage from piles of sulfidic minewastes. Covers are usually designed to reduce the water infiltration rate and in some cases may also reduce the oxygen flux to the underlying sulfides. Engineered covers have only been used since the 1980s, however, and there is very little field data on their performance in the longer term. This lack of information has implications for the degree of confidence that can be placed on the predictions of the environmental impacts of sulfidic minewastes, for the acceptance of close-out criteria by regulatory authorities and for the financial liability of the mining industry. Covers were placed on sulfidic waste rock dumps at the abandoned Rum Jungle uranium mine during 1984 - 1985. These covers were designed to reduce the water infiltration to less than five per cent of incident rainfall by both water shedding and storage-release mechanisms. Regular monitoring by the Australian Nuclear Science and Technology Organisation (ANSTO) demonstrated that the covers performed better than the design criterion for around ten years, but infiltration rates have subsequently increased. There is a 66 per cent probability that the infiltration rate now exceeds five per cent of incident rainfall. The cover on the largest pile, WhiteÆs heap, was sampled in pits dug at eight locations. Sampling was carried out at the end of the monsoonal wet season and again at the end of the ædryÆ season. This, together with laboratory testing, enabled cover performance to be assessed against five criteria: design, construction, cover material characteristics, physico-chemical characteristics and biological characteristics. We are of the opinion that the design of the cover was suitable to achieve the objectives of stability, water shedding, storage-release, and provision of a substrate for vegetation growth. Over most of the surface of the heap, the construction of the covers, drains and erosion prevention structures was in accordance with design specifications. However, several small and localised bare patches on the upper surface of WhiteÆs heap coincide with a reduced cover thickness, which is likely to have been due to poor construction in those patches. The construction of covers on minewastes is dependent on an adequate source of material meeting design specifications. From our limited examination, it appears that there was shortage of material for each of the three zones û a lower impervious clay layer, the moisture storage-release layer and the upper erosion-resistant layer for vegetative growth. An indication of this was that the upper layers in some areas were observed to be thinner than specified. We are of the opinion that this shortage of suitable material has been responsible for some of the changes observed ten years after emplacement. Physical and geotechnical testing indicated that the cover materials no longer meet the original specifications. In particular, the permeability at the 8 locations was found to be greater than specified, by up to several orders of magnitude. The higher permeability may explain the higher observed rainfall infiltration and moisture content of the waste rock. This increased permeability appears to be due to a combination of biological and physical processes û galleries formed by termites and ants and an extensive system of shrinkage/desiccation cracks formed by the development of a polygonal blocky structure involving the entire lower clay layer. The desiccation cracks may fill with coarser illuviated materials and form a conduit through which roots access the underlying waste rock. Measurements were made of oxygen flux into the heap as cover layers were excavated in the pits. They indicated that the full cover currently reduces the oxygen flux to 20 - 23 per cent of that into bare waste and that this reduction seems to be proportional to the cover thickness. It was also found that the oxygen flux into the cover is about four times higher at the end of the dry season than at the end of the wet season and that the difference is due primarily to the difference in moisture content of the cover. Recommendations are made for the design and construction of covers.

Jan 1, 2003

By K H. Esbensen

Optimisation of a real-time at-line monitoring system for control of industrial granule coating quality is presented. The system is based on a fluorescence imaging system, because fluorescence originates in the interiors of enzyme granules but is significantly quenched by a polymer coating (which is needed due to environmental precautions). We have developed an image analytical system for direct prediction of coating quality, which is based on application of the Angle Measure Technique (AMT) for image complexity characterisation; AMT is briefly described. The first part of the presentation addresses pixel sampling strategies within a digital industrial image, inherent in application of AMT, in which the unfolded image is regarded as a one-dimensional object in analogy with 1D process sampling in Theory of Sampling (TOS). The effects of random, stratified and systematic pixel selections in the unfolded image are evaluated. Also factors such as the fraction of image pixels and the effects of specific unfolding strategies (there are three principal strategies, termed æchopÆ, æsnakeÆ and æspiralÆ respectively) are investigated. It turns out that unsuspected artifacts are sometimes produced, related to the specifics of the unfolding procedure, which interferes with a straightforward 1D TOS process sampling analogy. These artifacts have a wider interest û among others, for 2D sampling û and therefore receive special attention in this presentation. The optimal pixel selection strategy for the AMT algorithm is found to be systematic or stratified sampling (not surprising according to TOS) of 500+ initiating points, but need to be unfolded in the novel spiral- or snake-wise fashions in order to effectively counteract these artifacts. This also has a general impact on various suggested standard schemes for 2D grid-sampling, among others, from the geoscience realms. The second part of the presentation is directed towards optimal image analytical sampling of a continuous series of fluorescent images (imaging of conveyor belts of æinfinite lengthÆ), ie optimisation of process image sampling. The minimum number of images needed to uphold a sufficiently good on-line estimate of the quality control (QC) parameter in question is found to correspond to the relatively high sampling rate of 15 - 20 per cent, which can be shown to be related to an intrinsic very high measurement error level (25 per cent) of a mandated analytical reference method.

Jan 1, 2005

By C Chen, T Kan

The distribution ratio of Pb (LPb s/m) between three types of slags (FeOx–SiO2, CaO–FeOx and FeOx– CaO–SiO2) and molten copper after equilibrium was measured at 1300°C and oxygen partial pressure (pO2) of 10-10–10-6 atm. Results showed that for FeOx–SiO2 slag, the LPb s/m increased from 0.024 to 2.57 with pO2 increased from 10-10 to 10-6 atm. The LPb s/m with CaO–FeOx slag was lower than the FeOx–SiO2 slag at the same pO2, ranging between 0.015 and 0.53. Using the FeOx–CaO– SiO2 slag generated LPb s/m values (0.02–1.6) in between. The oxygen partial pressure in the investigated range had no obvious effect on the activity coefficient of PbO (γPbO) which was averagely 0.44, 1.70 and 0.71 for FeOx–SiO2, CaO–FeOx and FeOx–CaO–SiO2 slags, respectively. The increases in the (CaO+MgO)/SiO2 mass ratio of the FeOx–CaO–SiO2 slag induced the decrease in the LPb s/m and the increase in the γPbO value. However, the variation in the Fe/SiO2 mass ratio didn’t exert obvious effects.

Jun 19, 2024