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By Cudmore JF, Rowlands D

Incidents associated with spontaneous combustion of coal have resulted in the loss of many lives and considerable capital and equip- ment. Nevertheless, the factors controlling the propensity of coal to spontaneous combustion are not clearly understood and there is a need for research to study the effects of rank, petrog- raphy, moisture contents, etc. This has been attempted in a study of the propensities of selected Queensland coals to spontaneous combustion. An adiabatic calori- meter was constructed to study the self-heating of a large number of coals. Chemical and petro- graphic analyses of the coals were determined and an attempt was made to relate these propert- ies to the self-heating characteristics of the coal. The results show a strong relationship between rank and self-heating characteristics and that petrographic composition of coal may also be of importance. Some observations on the application of the laboratory results to the practical situation are made as are recommendations for future research.

Jan 1, 1981

By Wood P. D, Pettifer G. R

In the upper coal surface in the Latrobe Valley, craters known locally as fireholes have developed due to prehistoric coal fires. They can be several hundred metres across and up to fifty metres deep, and are now filled with overburden materials varying from hard baked clays to very soft lacustrine clays. In addition to reducing coal reserves, continuous mining operations are seriously affected by fireholes. Large undulations in the upper coal surface result in a mixture of coal and overburden on the upper mining levels. The very soft lacustrine clays are unstable in the mine batters and the overburden dump, are difficult to handle on the bucket wheel excavator/conveyer system, and have insufficient bearing capacity for the large bucket wheel excavators. Early identification is essen- tial and both drilling and dynamic core penetrometer have been exten- sively used. However, this has not proved adequate in locating and defining the extent of all fireholes, due largely to their irregular shape. To overcome this a range of geophysical techniques has been trialled with very promising results. A trial area has been covered on a twenty metre grid using gravity and Geonics EM34 conductivity measurements and the same area has been covered at a closer spacing with high resolution magnetics. Image processing of contoured magnetic, EM34 conductivity and residual gravity data has resulted in very good correlation with drilling data.

Jan 1, 1989

By K Hskansson

In earlier studies along a mining region recipient (the river VormbScken, northern Sweden), the fraction of certain trace metals recovered in the particulate phase has been found to increase with increasing concentrations of particulate iron. This study was conducted to see if the pattern could be reproduced by adding minor amounts of ferrous iron, simulating groundwater inputs. When the iron is oxidised in the near neutral river water, it will form iron oxyhydroxides and precipitate. Trace metals may be either co-precipitated along with the iron, or adsorbed onto the freshly formed precipitates. If this is the case, such a mechanism may be incorporated as a part of a final polishing step in a mine drainage treatment system based on natural attenuation processes. The experiments were performed at 0¦C and 22¦C, on authentic river waters collected during the winter and summer of 2002, respectively. In order to investigate the influence of particles and bacteria initially present, filtered river waters (4 solution were added to the experimental beakers, increasing the iron content of the waters by 0 - 1.5 mg/L. The oxidation and precipitation processes were followed by means of filtration (0.2 ¦m) for up to seven days. In order to be able to compare the experimental results with the actual field situation, on both experimental occasions, surface water samples were collected also from three stations situated along the river. The samples collected were analysed for iron, calcium, and trace metals by AAS and ICP-MS. The iron oxyhydroxides formed in the experiment did not influence the partitioning of As, Cu, and Pb to the same extent as the particulate iron encountered along the river appeared to do. Cd and Zn were recovered mainly in the dissolved (

Jan 1, 2003

By C J. Moran

The Gladstone region, as one of the most industrially intense regions in Australia, uses significant quantities of fresh water. Awoonga Dam, situated on the Boyne River, is the only major source of water in the region. The current typical annual usage is 53 GL (Porteous, 2006) and approximately 80 per cent of the water is used by heavy industry (Gladstone Area Water Board, 2004). Until relatively recently, there has been ready and easy access to raw water for industrial use. The recent drought, which resulted in severe water restrictions in 2002 and 2003, emphasised the importance of water for a dominant industrial region like Gladstone. Although now in the process of changing, the typical contractual arrangements in the past have provided little financial incentive for efficient water use. From research undertaken on potential water reuse opportunities, several key questions have emerged related to water management in an industrial region such as Gladstone. This paper highlights these key questions, presents findings from recent regional strategies and assesses the potential for water reuse. Even though there is no clear-cut financial incentive for reusing water, there could be stronger regional and risk mitigation drivers for doing so. Initiatives to incorporate adaptive capacity through collaborative industrial synergies would allow for robustness and resilience in water security, leading to long-term sustainable water management across the Gladstone region.

Jan 1, 2006

By A Halim

The European Union (EU) have recently issued new Threshold Limit Value-Time Weighted Average (TLV-TWA) for diesel exhaust contaminants, which are CO, NO2 and DPM. The new limits for CO and NO2 were issued in 2017 whilst the one for DPM was issued in 2019. However, in order to allow EU mines to formulate strategies to comply with these new limits, the EU granted a transition period in which mines could use the old limits until the new limits are enforced. The new limit for CO and NO2 will be enforced from 21 August 2023 whilst the one for DPM will be enforced from 21 February 2026. The new limit for NO2 and DPM is very low, 0.5 ppm for NO2 and 0.05 mg/m3 of Elemental Carbon (EC) for DPM. Combination of these two limits would be the lowest among all mining jurisdictions worldwide. It poses a huge compliance challenge to EU mines if they keep using diesel machines. Therefore, a study and a field trial were carried out by the author in 2019–2021 to investigate whether replacing diesel machines with Battery Electric Vehicles (BEVs) would be the best answer to this challenge. This paper outlines results of this study and field trial.

Oct 12, 2022

Jan 1, 2004

The applicability of Bieniawski and Hoek-Brown empirical strength criteria has been assessed for different groups of coal and various types of intact rocks by using a vast number of published triaxial test data from various places. Analysis of individual data sets revealed that the traditional forms of the criteria do not have a perfect agreement with the data. A strong negative correlation has been observed between B in Bieniawski's criterion and m in Hoek and Brown's criterion with uniaxial compressive strength of materials. Both criteria have been modified and empirical relationships have been introduced for coal as follows:m = 62.903 - 34.213 (log pc) 0.9772B = 10.152 - 4.709 (log pc )0.8889Similar relationships have been developed for different rock types as well.A comparison between the applicability of each of the above approaches with the conventional criteria reveals a very significant advantage for new approaches and a supremacy for the Bieniawski criterion in all cases particularly in the case of coal.The modified Bieniawski criterion fits coal as well as different types of rocks with excellent accuracy.The modified Hoek-Brown criterion gives a good result for rocks but does not fit coal data quite well. In other words, Hoek-Brown criterion is not an suitable one for coal.

Jan 1, 1998

By Moorrees C

Carbonic acid leaching of crude iron-containing magnesia derived from Savage River magnesite yields a magnesium bicarbonate leachate with a substantial soluble iron concentration. The iron concentration depends upon the leaching conditions (particularly time, temperature and pulp density) but is generally in the range 0.005-0.5 g/litre. If this soluble iron is not removed prior to the precipitation of the magnesium as a hydrated carbonate, then this product will be contaminated by the iron, and will not yield a final product (high-purity magnesia) that meets specifications.The soluble iron content of the magnesium bicarbonate leachate can be reduced to an acceptable level by addition of solid aluminium sulphate either during carbonic acid, leaching of the crude calcine or to the clarified leachate. Chemical analysis and X-ray diffraction revealed that the iron is precipitated as an iron-containing hydrotalcite-type compound, [Mg6(Al,Fe)2(OH)16]CO3.4H2O. The actual composition of the precipitate depends on the amount of aluminium sulphate added and the precipitation technique used. Because precipitation of iron in this manner also results in reduced magnesium recovery from the leachates, It WIll be necessary to develop methods for recovering the magnesium component of the precipitates.

Jan 1, 1984

By P Mason, J F. Huntington, K M. Scott

Short-wave infrared (SWIR) spectral reflectance of the hydrothermally altered volcanic rocks in the footwall of the Hellyer Zn-Pb massive sulfide deposit was measured with a portable PIMATM infrared spectrometer. The Al-OH absorption band was used to derive information on the cation composition of white mica. The wavelength range of the Al-OH band from 2194 nm to 2222 nm reflects variation in the number of octahedral Al (Alvi) in white mica from 3.9 to 3.2 (based on four octahedral cations per formula). This Alvi range indicates a substantial compositional variation, covering most of the compositional region between muscovite (Alvi = 4.0) and phengite (Alvi = 3.0). Moreover, the spectral reflectance data show that the compositional variations of white mica are spatially related to the hydrothermal alteration zoning, such that the white mica of more phengitic composition tends to form in the main upflow fluid channels in the centre of the footwall alteration system. The results suggest that the octahedral Al content of white mica, which is spectrally definable by the wavelength of the Al-OH band using a field instrument such as the PIMATM, can be used to map fossil hydrothermal systems and potentially as vectors to mineralisation.

Jan 1, 2004

Silica and limestone fluxing levels in copper smelting slags were studied. Copper concentrates with flux additions were smelted to matte (55.5 per cent Cu) and slag in a pilot scale submerged combustion furnace.Results indicated that oxidic and sulphidic copper levels in slags were minimised with a slag Si02 level of 36 per cent and a SiO2/CaO ratio of 5.5. Total copper losses in slags were 0.6 per cent under these conditions.To produce the desired slag chemistry, additions of bulk silica and limestone to copper concentrates of fluctuating grades were predicted numerically. The method employed the solution of two simultaneous equations, each respectively for silica and limestone calculations.The predicted flux additions were applied in a further series of tests and the resultant stages were found to be satisfactory. The method is applicable to smelting 'operations which employ two flux bins, with weigh feeders, so that slag chemistry may be controlled with the flux/concentrate feed mix.

Jan 1, 1985

By Umetsu Y, Su Qing-quan

The electrical conductivity of electrolytes is very important in metal electrowinning and electrorefining processes as it has a very large influence on the energy consumption. There are few measurements of the electrical conductivity of zinc electrowinning electrolytes available. The electrical conductivity of zinc electrowinning electrolytes were measured over the following range of concentrations, 100 to 200 g/L H2SO4, 0 to 80 g/L Zn and 0 to 20 g/L Mg, at temperatures from 25 to 60 C. The specific conductivity of zinc electrowinning electrolytes may be expressed as a function of concentrations of sulphuric acid, zinc and magnesium and temperature by the following equation: k(S/cm) = 0.004 + 0.00115 t + 0.00282 [H2SO4] t - 0.00114 [M] t + 0.3442 [H2SO4] - 0.0451 [1-12SO4]2 - 0.1058 [M]ò[H2SO4] - 0.0224 (M] + 0.0286 [M] 2 where t is temperature (C), [H2S04](moI/L) is sulphuric acid concentration and [M](mol/L) is a sum of zinc and magnesium concentrations, ([Zn]+[Mg]). The specific conductivity of zinc electrolytes is a function of the concentrations of the hydrogen ion and free water molecule, which are calculated by taking into account the second ionisation constant of sulphuric acid and the stability- constants of zinc-sulphate and magnesium-sulphate complexes at 25 C.

Jan 1, 1993

By Andersen AK

As part of a research program sponsored by Continental Copper and Steel Industries, Inc. (cos), investigations have been conducted by the Colorado School of Mines Research Foundation, Inc. to study the effect of high current densities on electrolytic processes. The importance of high current densities has long been recognized, particularly in the deposition of copper, and the results of considerable research on the subject have been reported in recent years (19 29 39). This is not surprising because, besides plant capacity, current density is the other major factor which will determine the process economics. In the production of electrolytic copper, current efficiency, steam consumption, number of cells, building area, metal inventory, cathode purity, and power consumption are all affected by current density. The ability to maintain a high current efficiency and satisfactory cathode purity while increasing the current density to twice or three times that commonly practiced could result in considerable saving of capital investment and reduce the operating cost per ton of metal produced. The optimum current density i.e., that current density of which production cost would be at a minimum, can be established from an analysis of the various inter- relating factors (49 59). A review of.all operating electrolytic plants (electrowinning and electrorefining) will indicate that most of these plants are operating at 50% or less of the optimum current density (6). One of the reasons for not using the optimum current density may be attributed to the fact that conventional electrolytic tank- house equipment does not perform satisfactorily at high current density operations. Various investigators (19 79 8) have attempted to overcome this limitation by modifying the design of the electrolytic cell, virtually unchanged since it was first introduced in the late 1800's. Previously, these attempts have not resulted in,a cell design suitable for commercial application. However, recently, a cell has been designed which performs efficiently under such conditions. This is a CCS development (patents applied for).

Jan 1, 1969

By E Nunes, R Mendes, D Jacobson, G Cota, T Machado, E Santos, J Almeida, E Pereira9, B Raso

Grinding circuits are known to be the highest consumer of energy used in the ore comminution process, with high operational costs and sensitivity to ore conditions. The mining industry is being encouraged to look for more energy efficient processes while increasing the mass and metallurgical recovery; a specific example is projects with lower iron ore grades, which demands a higher level of liberation and resulting higher energy consumption. This has led to increased usage of high-pressure grinding roll (HPGR) technology as an alternative design within the comminution circuit. A growing use of the HRC™ HPGR technology has been used to generate concentrate through a more sustainable process. In the Brazilian state of Minas Gerais, the readaptation of iron ore beneficiation circuits has been initiated, replacing the traditional crushing-to-grinding flow sheet with circuits using crushing-to-HPGR flow sheets, with the main driver being reduced energy consumption. Utilising results from sampling campaigns and analysis of experimental data collected in an industrial plant, the work herein presents a case study from the JMN Mineração operating plant, where the HRC™ HPGR was used as an alternative to traditional grinding using horizontal mills. The results show that the HRC™ HPGR performance in this iron ore processing plant showed benefits in terms of reduced energy consumption as compared to the projected performance with a traditional grinding circuit.

Sep 18, 2023

By D J. D'Astoli, M D. Goodz

In 1993 a detailed review of drill sample yuuluy was rouxluard through twin and triplet drill holes using open hole, crossover suhreverse circulation (RC) and diamond drill methods. Advances in face-sampling RC methods demanded a further review of the validity and reproducibility of drill sample data. A program was undertaken to drill three RC holes using the latest technology (new face- sampling bits, dust suppressers, cyclones and compressors). Volumetric and mass studies were undertaken to review sample recoveries. Modal analyses on indicator minerals were logged to interpret the relative degree of mineralisation. Ambiguities in the results were immediately apparent and the consensus was for follow-up twin diamond holes using HQ3 coring tubes. The most mineralised RC hole was selected for the first twin diamond hole. This RC hole (MS 313) encountered one intersection of >0.47 g/t; in contrast the diamond hole (MS 342) had nine intersections at > I g/t. Results at hand show definitively that face-sampling RC drilling is not acceptable as a method of exploration for gold deposits of the Woods Point type. Furthermore it is demonstrated that RC drilling should not be used for any type of exploration of high-grade gold vein deposits related to highly fractured or porous hostrock, or areas of previous mining activity. Methods are proposed for reviewing of rates of sample recovery, distribution and cross-contamination. Comparisons also show that in limited metreage reconnaissance drill programs, diamond drilling is more similar to percussion in per metre costs, than it is credited with, and always provides more bang for the Buck.

Jan 1, 1997

By D Hatton, S Wilson, F Orrante, M Taghimohammadi, F van der Walt, N Arslan, M Westcott

"Cayeli Bakir Isletmeleri is an underground copper-zinc mine in turkey. The ore is highly variable with feed grades ranging from 1–4 per cent copper and 1–10 per cent zinc. Due to this variability, ore characterisation and blending strategies are crucial for performance optimisation.This paper presents a case study for a multidisciplinary approach to process optimisation, integrating Geometallurgical and advanced control methods to achieve optimised plant performance. The results from comprehensive metallurgical tests and surveys were used to develop a mathematical model utilising SGS’s Integrated Geometallurgical Simulator® (version number 2.5.24.0). The model was employed to determine the most appropriate operational settings required to ensure that optimised grades and recoveries are achieved for each ore type.SGS’s Modular Expert Technology (MET) expert system was then implemented to target these optimum operational ranges utilising online grade and froth velocity measurements. The successful conversion and deployment of the modelled process parameters into an expert system has resulted in significant improvements in overall recovery and circuit stability.Citation:Arslan, N, Westcott, M, van der Walt, F, Hatton, D, Taghimohammadi, M, Orrante, F and Wilson, S, 2016. A Multidisciplinary Approach to the Optimisation and Control of a Copper-zinc Grinding and Flotation Circuit, in Proceedings 13th AusIMM Mill Operators’ Conference 2016, pp 115–122 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Oct 10, 2016

By Tonkin D. A

Poor performance in the several stages of the magnetite recovery circuit, coupled with poor desliming through inefficient and over- loaded desliming screens, led to excessive magnetite consumption. An accurate and reliable sampling programme was established covering all outlets of the plant. Emphasis was placed on frequency of increments in an endeavour to detect extreme conditions of short duration. Systematic checking of the entry points to these outlets than identified those sections of the recovery circuit at fault, namely magnetite recovery separators and the heavy media cyclone product rinsing screens. More product rinsing water was provided, and modifications to the rinsing screens improved the efficiency of these units. Consistency of operation through automatic control of level eliminated the sudden massive losses in the magnetic separators. Load on the recovery circuit was then reduced by improvements to the raw coal desliming screens. A 50 per cent reduction in magnetite consumption was achieved.

Jan 1, 1974

By Redman P. G, McMahon B. K

A simple technique for evaluating the field stress ratio is presented, based on the results of extensometer or convergence tape measure- ments taken in an advancing tunnel. This tech- nique also yields a value for the rock mass modulus, provided Poisson's Ratio is assumed. The results of two case studies are presented illustrating the effectiveness of the method.

Jan 1, 1981

By J Rayo

Andean countries (Chile, Peru, Bolivia and Argentina) have 42 semi-autogenous mills (SAG) in operation and there are more than 30 projects in the pipeline that consider SAG mills. At the end of the next decade, the total amount of SAG mills in this area will likely be close to 100.There is a lot of reliable operational information collected by JRI Ingenieria Sociedad Anonima, the author’s engineering company, for more than 20 years and processed by statistical software, to be used as a reference for design basis of future projects or to improve operations by comparison. JRI Ingenieria Sociedad Anonima has reliable information related to the performance of more than 50 per cent of the Andean SAG plants.The paper presented considers a set of graphs that summarise the collected and verified SAG plants technical data. The figures will show key parameters as circuits and equipment data, energy consumption, technical availability, utilisation rates, throughput variability, pebble productions, steel consumption and others.The data is compared with typical design basis of several engineering companies and the main differences are analysed and/or commented on.CITATION:Rayo, J, 2014. Comparison of semi-autogenous mills operations in Andean countries, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 283–296 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

By Gupta A, Fung C. C

The hydrocyclone parameter d5Oc is estimated by the application of Artificial Neural Network (ANN). Results indicate that ANN performs equally well as compared to statically derived analytical formulae. Results also show that ANN will also be convenient in the on-line control of hydrocyclones.

Jan 1, 1996

By Gilbert DJ, Lemon NM

A case history of a two year study of low grade ores in the Middleback Range area with the objective of defining possible areas of interest from a combination of geological- petrological-metallurgical criteria. Covering the general geology of the area and ore types; the results of metallurgical testwork and the pattern of evolution of these tests; the petrological explanation of the results of the testwork; the culmination of the work in the selection of areas of best potential for more intensive work. Jaspilites consisting of magnetite, hematite and limonite with quartz and silicate-carbonate-sulphide minerals are hosts to high grade iron mineralisation but also constitute a large low grade iron Reserve.

Jan 1, 1975