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By Upfold RW, Velzeboer MD

An underground mine fire will influence the ventilation equilibrium in several ways which results in a redistribution of the ventilating quantities and pressures throughout the whole mine. The ventilation carries the combustion products which constitute the greatest danger of mine fires through the mine and provides the oxygen on which the intensity of the fire depends. However, as a result of the ventilat- ion disturbances created by the fire, changes in airflow patterns can take place which are not always obvious, especially when the mine is being served by several fans. The use of com- puter simulation techniques allow for the likely effects to be tested and the different ventilation options to be evaluated as an integral part of the overall emergency/rescue planning and control procedures.

Jan 1, 1981

By S Coward, S Jackson, S Moayer, J E. Vann

The variability and uncertainty of mineralisation, coupled with subsequent uncertainty in mining and processing, is often paid scant regard or overlooked during the evaluation of mining projects. In many instances, when the project transitions to the operational phase, the reality of feed or product variability and the consequences of unquantified uncertainties throughout the value chain become obvious. The outcome is the familiar picture of frequent ramp-up underperformance and failure to deliver on planned targets and objectives.Both mine and exploration geologists are expected to generate mineral deposit models that are based on an integration of diverse sources of data. These multifaceted deposit models already play a pivotal role in the design, development and optimisation of mining project value, and the trend to a fully digitally engineered future means that this importance is increasing. It is therefore vitally important that tools be made available to the geologist (as well as mining engineers and metallurgists) that enable them to characterise and assess variability and uncertainty via appropriate deposit models and thus articulate their impact on potential project configurations and decisions. Scenario-based project evaluation (SBPE) provides a framework for full and proper analysis of the downstream impacts of inherent deposit variability and uncertainty on project performance.SBPE has been developed by the authors over several years and aims to propagate geological uncertainty and variability through the mining value chain. The outcomes of SBPE can be tested against future external scenarios capturing financial, economic and socio-political factors that also drive project performance. Stochastic representations of the orebody (via conditional simulation (see Chilès and Delfiner, 1999)) that explicitly incorporate variability and represent uncertainty are propagated through the value chain on a block-by-block basis (ie on a much more granular basis than traditional project evaluation approaches).Conventionally, metallurgical processes are modelled with deterministic equations (eg regression models) based on limited data. The SBPE approach allows for the modelling of process performance uncertainty using geometallurgical sampling fully. Multiple outcomes of SBPE are passed through financial modelling, which can also incorporate stochastic components, thus allowing full quantification of the risks and opportunities of a set of project alternatives. The value of the SBPE system is that once a base case has been established, multiple engineered alternatives coupled with external scenarios are easily evaluated and compared in terms of incremental value.A new case study of SBPE is presented that shows how, by analysis of the various aspects of variability and uncertainty, project managers are able to focus on the areas that have the greatest ability to reduce risk and/or add significant value. This can lead to sufficient flexibility being built into operations that allow operators to cope with the real orebody delivered to the plant.CITATION:Jackson, S, Vann, J E, Coward, S and Moayer, S, 2014. Scenario-based project evaluation – full mineral value chain stochastic simulation to evaluate development and operational alternatives, in Proceedings Ninth International Mining Geology Conference 2014 , pp 21–32 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 18, 2014

By N S Melkoumian

While improvements in occupational health and safety (OHS) in the mining industry have decreased fatalities and accidents, little attention has been paid to the cultural confound of 'safety' in the increasingly multicultural mining industry. Occupational health and safety processes often contain assumptions of cultural understanding that may not be shared or understood by mining employees. There are potentially dangerous and costly implications of cultural difference in the mining environment. Some people have been enculturated with high levels of anxiety concerning catastrophe and uncertainty while others have a more laissez faire attitude to accidents and disaster. The level of cultural anxiety about uncertainty can be a major factor in the acceptance of OHS processes. OHS manuals based on a comprehensive set of rules and procedures may assume that the authority of 'rules' is shared by all employees regardless of a variety of cultural understandings when this may not be the case. Similarly, cross-cultural employees may not share a background or acceptance of expensive technological innovation and so resist/avoid the application of new safety equipment. Then too, OHS staff may not realise the significance of religious belief or personal responsibility on employees' attitudes to safety in the workplace environment. A lack of consideration of these cultural elements could have fatal and expensive results. This paper explores the impact of cultural difference in the understanding of OHS in the Mining Industry, presents a model to improve the understanding of the cultural confound in safety, improves analysis of OHS in practical multicultural situations, provides assistance for those involved in OHS training and may become a basis for developing OHS policy and procedure.

Dec 6, 2010

By D J. Brake

The risk from fire remains one of the most serious of underground mine disaster scenarios. The impacts of mine fires on the underground ventilation system and the production of toxic gases have been difficult to model and therefore assessments have relied largely on empirical data, historical precedent and subjective opinions. Underground fire modelling software has had limited availability and been technically challenging and time consuming to use especially for routine mine investigations. There has also been no well-accepted set of assumptions for fire modelling in mines, which has resulted in a lack of confidence in adopting its use more widely. This paper describes modelling of three critical fire scenarios in underground hard rock mines: a fire (LHD) in an underground diesel refuelling facility, a fire in an underground explosives magazine and a fire on an underground ore transport conveyor. Modelling was undertaken using VentsimÆs VentFIREÖ fire simulation module. It describes the basis of design, the key assumptions, the methodology used and provides examples of the outputs, conclusions and recommendations. It reviews the impacts of these fires on egress and entrapment strategies in the mine. Some general principles regarding improvements to ventilation circuit design based on this analysis are also recommended. Whilst the fire scenarios were based on actual case studies, they have been disguised for this paper.CITATION:Brake, D J, 2013. Fire modelling in underground mines using Ventsim Visual VentFIRE software, in Proceedings The Australian Mine Ventilation Conference , pp 265-276 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 1, 2013

By A Grigg, L Hackett

Alcoa operates two bauxite mines at Huntly and Willowdale, located within the jarrah forest south-east of Perth in Western Australia. Ore reserves are shallow but extensive, and mining pits averaging around 20 ha in size are distributed across a mining region in a mosaic pattern, linked to a centrally-located crusher by a radiating network of haulroads. A mining or crusher region is defined partly in terms of economic haul distances, and new regions are opened once the current regions’ reserves have been mined. Since commencing in 1973, the Huntly mine has constructed and progressively closed three previous mining regions and is presently in a transition from the fourth and current region of McCoy to the new region of Myara. At present rates of production, approximately 450 ha is cleared, mined and rehabilitated each year.The value of topsoil in returning a diverse mix of native jarrah forest plant species and supplying nutrients, organic matter and soil biota to rehabilitated areas has long been recognised. Managing the topsoil resource is therefore a critical element in the success of rehabilitation outcomes, but the distribution and dynamic nature of mining operations pose significant planning and logistical challenges. The regionalised approach to mining at Huntly also presents a range of issues for what are, in effect, soil management plans for episodic mine closure. The nature of mining and rehabilitation operations are described, together with the planning processes that Alcoa follows to quantify, track and report on soil movement. A case study of the Huntly mine demonstrates that an integrated operational and life-of-mine planning process is essential for successful and cost-effective mine rehabilitation.CITATION:Hackett, L and Grigg, A, 2014. Topsoil management for long-term mine operation and closure – a case study from Alcoa's bauxite mining operations in south-west Australia, in Proceedings Life-of-Mine 2014 , pp 609–614 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 16, 2014

By K Ehrig, V Liebezeit, Y Li, B Pewkliang, M Smith, E Macmillan

Pre-concentration of low grade ores via the rejection of low/no value materials based on fragment size is the subject of many published papers and studies over the past decade. However, the possibility of upgrading should not limited to low grade ores given the high cost of capital, energy, water, reagents, and ultimately tailings storage across the mining industry. Mining and processing facilities at Olympic Dam consist of an: 1) underground mine where ore is extracted via sublevel open stoping and 2) integrated processing plant located on the surface which produces Cu-cathode, Au-Ag bullion and uranium oxide concentrate. Blasted ore is trucked/trained to underground crushers which produce an ore feed with a product size P80 = -145 mm. Crushed ore is then hoisted to the surface and delivered to the ROM pads via an overland conveyor. The typical copper grade of mill feed is approximately 2 wt%. A rapid assessment of the potential to upgrade Olympic Dam mill feed prior to the ROM pads via rejection of low value materials based on fragment size was completed using existing data. Three separate datasets were utilised to assess the deportment of Cu, U, Au across size ranges of 200 mm down to sub-8 m. Cumulative grade vs cumulative mass distribution graphs for each element were produced. This data clearly demonstrates that Cu, U, Au grades remain constant down to ~212 m, which happens to be the liberation size of the sulfides. Hence, no potential to upgrade the ore stream via rejection of +200 mm - to ~212 m sized materials prior to milling. Mineralisation within the Olympic Dam Fe-oxide Cu-U-Au-Ag deposit (IOCG) occurs as disseminated sulfide grains within granite- to hematite-rich breccias. The typical sulfide grain size is sub-200 m that supports the outcomes of the grade deportment by fragment size study.

Nov 10, 2020

By Egan J. R

Changes have recently been applied to the Sullivan Concentrator lead and zinc circuits to treat fine-grained ores which make-up the majority of ore reserves in the mine. Pilot plant testwork conducted in 1990 - 91 indicated that concentrate grades would be substantially improved by reducing the particle size (Pao) of the lead from 38 to 15 ¦m and the zinc from 45 to 24 ¦m. Circuit revisions involved installation of major new equipment including: two 600-kilowatt Vertimills for regrinding, a four metre diametre column flotation cell and a four metre diameter hyperbaric pressure filter for dewatering. Duties of the existing regrind mills were Reassigned.

Jan 1, 1993

By C Vejrazka

Northparkes is located 27 km north of the township of Parkes in central New South Wales, Australia. The operations consist of underground block cave mines and an ore processing plant that produces high-grade copper and gold concentrate. Production is currently sourced from the E48 Lift 1 block cave mine and open cut stockpiles. Mining commenced at Northparkes in 1994 as an open cut operation. Underground block cave mining began in 1997. Northparkes was the first mine in Australia to use the highly efficient block cave mining method, which relies on gravity and natural rock stresses to fragment the ore.The occurrence of air blasts is one of the principal mining hazards in block caving operations between the time of first undercutting and breakthrough of the cave to surface. As such, it needs to be managed continuously, and risk assessments need to be reviewed on a regular basis for applicability to changing conditions. Unfortunately, there is little literature on how to practically approach air blast risk assessments in a way that can be incorporated in the day-to-day operation of a mine. Previous methods of assessing air blast risk were tedious and results were often unrepeatable.With the extension of the E48 Lift 1 extraction level, it was necessary to assess the air blast risk for the extension drives and develop operational guidelines for production from the extension. A review of the methodology for assessing air blast risks revealed substantial improvement opportunities.This paper outlines the principles used for air blast risk assessments at Northparkes Mines and the methodology employed to achieve efficient, repeatable and auditable results.CITATION:Vejrazka, C, 2016. Northparkes Mines’ current air blast risk assessment practices for block caving operations, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 257–264 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By U König, N Norberg

Traditionally, quality control of iron sinter has relied on time-consuming wet chemistry. However, the mineralogical composition that defines the physical properties, such as strength or reducibility, is not monitored.X-ray diffraction (XRD) analysis in combination with Rietveld quantification and statistical data evaluation using partial least squares regression (PLSR) has been successfully trialled to determine the mineralogical composition and process parameters such as the FeO (Fe2+) content and basicity of iron sinter within an analysis time of less than eight minutes per sample. The results were compared with wet chemistry data.PLSR does not require pure phases, crystal structures or complex modelling of peak shapes. The analysis is therefore easy to set up and ideal if only one property needs to be analysed. PLSR results show an accuracy for the FeO content of ±0.3 per cent for the samples analysed in this case study.Both the PLSR and Rietveld methods take the full XRD pattern into account and can be simultaneously applied on the same measurement. PLSR was found to be the more robust method if only FeO and basicity results are required. The Rietveld method helps to predict other parameters, such as the compression strength of the sinter, by monitoring all existing phases (eg larnite C2S or silico-ferrite of calcium and aluminium phases).CITATION:König, U and Norberg, N, 2015. Iron sinter process control using x-ray diffraction, in Proceedings Iron Ore 2015, pp 53–60 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By A L. de Ambrosis, F M. Weir, M Fowler

Traditional kinematic and statistical analyses of geological structure for geotechnical engineering applications, while considered industry standard practice, have some limitations and unrealistic assumptions. An improved approach involves a discrete fracture network (DFN), a numerical model that explicitly represents how defects may be spatially distributed through the rock mass. The DFN technique utilises the structural data in stochastic analyses to give a range of possible models used for visualisation and stability analyses.The early development of the DFN approach was largely associated with modelling fractured hydrocarbon reservoirs and nuclear waste isolation programs. With recent improvements to computational power it has become recognised internationally as a valuable tool for modelling some geomechanical problems encountered when designing excavations in fractured rock masses. For tunnelling or slope stability projects DFN modelling provides visualisation of a rock mass and identification of likely failure mechanisms.This paper presents a suite of DFN modelling undertaken for the design of a tunnel within the Ashfield Shale unit of the Sydney Basin, Australia. The necessary input parameters and derivation of these, along with the importance of both an accurate engineering geology model and validation of the synthetic fracture network are demonstrated. Multiple realisations of the DFN were analysed to provide an indication of the number and volume of unstable blocks for the proposed tunnel geometry, enhancing support design. One fracture network realisation was sliced along multiple sections for use in finite element modelling.CITATION:Weir, F M, de Ambrosis, A L and Fowler, M, 2014. Discrete fracture network modelling for tunnel design in the Sydney Basin, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 219–226 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By J W. Dong, Y M. Li, J L. Tian, Z H. Jiang

Electroslag remelting is widely used to produce various special steels, mainly because of its ability to provide high cleanliness and excellent homogeneity of ingot. Undoubtedly an optimal slag plays a key role in removing inclusions and enhancing the mechanical properties of a specific special steel. In order to improve the metallurgical performance of the slag in electroslag refining of die steel, a variety of slags have already been developed using traditional trial-and-error methods. Nonetheless, these slags may not be inherently optimal for the specific requirements of actual die steel refining processes. In this work, we have designed a CaF2-CaO-Al2O3-SiO2-MgO quinary slag system using genetic algorithms method aiming to remove the existing large size inclusions (D and Ds type) in high quality die steel. The comprehensive effects of five components (CaF2, CaO, Al2O3, SiO2 and MgO) were studied based on existing fundamental theory. The slag composition was screened considering the parameters such as melting point, electrical conductivity, calcium ion concentration, and appropriate viscosity etc. Furthermore, the candidate optimal slag was applied in the industrial production of die steel by electroslag remelting method. The detection results indicate that majority large inclusions (D and Ds type) have been successfully removed, showing significant advantage to traditional slags. This result has demonstrated the genetic method to be efficient and reliable. In addition, depending on the personalised demand of other steel and alloys, this method allows for the adjustment of the screening frameworks and processes to develop the candidate optimal slags. This method has not been reported previously in the field of electroslag composition design, and compared with the traditional trial-and-error method, the new method will save a lot of time and experimental costs.

Jun 19, 2024

By G Harbort, D Clarke, D Morgan, C Sola

Northparkes Mines commenced production in 1994 and the mine has significant reserves to allow operation into the future. There are a number of potential future concentrator feed sources with variable sulfide mineralogy and grades.In February 2012 a comprehensive flotation survey was conducted to allow mass balancing and evaluate the operation of the flotation circuit. A rudimentary, copper element only, unsized flotation simulator was developed to evaluate high level potential for optimisation and improvement. In 2013 this flotation model was expanded to produce a mineral based, floatability component model to estimate the effect of future concentrator feed source on metallurgical performance. This revised model allows various circuit configurations to be simulated to provide a high level blueprint for the long-term planning to maximise performance.This paper provides a review of the process followed to develop the model, including an analysis into the mineral floatability component model and its calibration against plant operations. The effect of varying feed mineralogy and feed quality on future performance has allowed an internal review of potential circuit changes needed to accommodate the changing future feed.CITATION:Clarke, D, Harbort, G, Morgan, D and Sola, C, 2014. Northparkes Mines – flotation and planning for the future, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 203–208 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

By B Armstrong

The Proterozoic poly-metallic Trilogy deposit was discovered in 1997, and until recently, mining evaluation was stalled due to poor metallurgical performance. Unlocking the substantial economic value of the deposit required a coming together of geologists, mineralogists, metallurgists and mining engineers, who by working collaboratively, uncovered the detail necessary to allow the required metallurgical breakthroughs to occur. The deposit itself is described as a sedimentary exhalative (SEDEX), with an enriched lead-zinc-silver core surrounded by a broader envelope of copper-gold mineralisation. The geological domains were defined in broad terms based on the style of mineralisation, assay values and lithology. These domains, while adequate for the resource estimation process, failed to translate into representative metallurgical domains. Additional work with new techniques defined regions in the deposit with altered processing properties which could not be recognised by conventional geological logging. Such additional complexities could not be appreciated at the outset of the metallurgical test work program.These regions were defined by applying the EDTA analysis method for recognition of where the valuable sulfides, particularly galena, had been partially modified by oxidising conditions. Hence, the flotation response of the valuable sulfide minerals was diminished and the increased amount of heavy metal cations available in the system significantly reduced selectivity in the flotation process.Understanding the detail of this complexity was essential in determining representative metallurgical domains, which was the first step in the long road of development.

Sep 5, 2011

By A J. Weston

Block or panel caving technology is far removed from that of the top slicing and block caving of the late nineteenth or early twentieth centuries. The rapid mechanisation and expansion of these methods in the late twentieth century was as much a result of the change of the technology of the unit operations of development, ground support, drilling and blasting and transport as it was of the advances in geotechnical understanding and practice. The small footprint gravity and scraper block caving mines with boundary weakening, rail transport and shaft hoisting of the early to mid-twentieth century have been replaced by massive high lift panel caves using preconditioning of the ore, large load-haul-dump units, adjacent crushers and conveyors to surface. The technology changes in the unit operations are described and the drivers for these changes examined.CITATION:Weston, A J, 2016. The evolution of block caving technology, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 265–274 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

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 A T. Spathis, M L. Lawlor-O’Neill

A methodology for the inversion of a scaled charge weight superposition model to predict peak particle velocity (PPV) has been examined. The inversion involves two steps: first simulated annealing is used to get an initial estimate of the model parameters; and second, these parameters are used as input to a quasi-Newton non-linear optimisation method, used to refine the value of the parameters. The methodology recovers the three required parameters (two charge weight scaling parameters and a time window width) and does this directly from a single production blast for a given point of interest. It has been tested on a synthetic example and recovered the input model parameters successfully in the presence of introduced noise with a coefficient of variation ranging up to ten per cent. Another test used the vibration measurements of three tunnel blasts monitored during the construction of the Citybanan tunnel in Stockholm. In this case, the three model parameters are found from one blast and for a given point of interest, and the PPV at the same point of interest is predicted for the second and third blast fired in the same vicinity as the first blast. The three blasts used different firing sequences. The predicted PPV limits use a confidence interval determined from the scatter in the peak levels obtained from the single calibration blast. The methodology was able to predict an upper bound for the PPV in 21 of the 26 tunnel blast vibrations studied. These predictions improve on a previous study involving the same model but which did not use the inversion process above. Given this reasonable success, further testing of the method on other data sets and alternative forward prediction models is recommended.CITATION:Lawlor-O’Neill, M L and Spathis, A T, 2015. An inversion method for the prediction of peak particle velocity in blasting, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 97–108 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By Ward B

Central Colliery was developed to exploit large underground reserves in the German Creek lease. It was planned from the outset as a retreating longwall operation and is the first longwall mine in Queensland. Longwall mining is not new to Australia but all previous experience has been confined to the coalfields of New South Wales. There was no precedent for longwall extraction in the markedly different geological setting of the Bowen Basin in Central Queensland. Various investigations were thus carried out during the initial development of Central Colliery, prior to the installation of the longwall, to ascertain the geotechnical characteristics of the coal seam and the adjacent strata and to predict the performance of the heading and pillar design as mining proceeds to depth. Laboratory tests showed the coal to be weak with an unconfined compressive strength of 9.6 MN/m2. Site inspection and geophysical correlation revealed a shear zone and extensive intraformational shear planes in the seam. The latter were found to exert a controlling influence on rib reaction in the headings. This behaviour was predicted by finite element modelling of the development headings which indicated that mining induced stresses in the coal would be relieved by block movement of the ribs. A chain pillar width versus depth curve was established for yielding pillar design based on empirical and computational methods. This gave pillar widths from 25m to 48m over the proposed depth range of 150m to 300m. Finite element modelling of the 25m pillars chosen for the first gateroads confirmed the overall stability of the design but suggested that rib spall could be significant in the adjacent tailgate. (1) Chief Mining Engineer, Capricorn Coal Management Pty. Ltd., German Creek Mine, Queensland (2) Senior Engineering Geologist, Coal Division, The Shell Company of Australia Limited, Melbourne

Jan 1, 1986

By M Uceda, E Guerra, Y Choi, J L. Shepherd

In this paper we describe the leaching characteristics of pure gold in thiosulfate solutions that contain a known chelator; meso-2,3-dimercaptosuccinic acid (DMSA). The interfacial and chemical characterisation of the system was accomplished using both electrochemical methods and inductively coupled plasma mass spectrometry (ICP-MS) analysis after pure gold samples were exposed to solutions composed of 65 mM Na2S2O3, 1 mM NaOH and a range of DMSA concentrations. In the absence of DMSA, cyclic voltammetry revealed the onset of thiosulfate mediated gold dissolution, the degree of which was reduced at more positive potentials due to the formation of oxidised thiosulfate products on the gold surface. The addition of small amounts of DMSA (<10 ¦M) to the electrolyte resulted in minor changes to the voltammograms indicating a subtle interaction of the additive with the gold surface that may improve leaching. However, at higher concentrations of DMSA (up to 100 ¦M), electrochemical evidence suggests the formation of new oxidation products in solution as well as the formation of more compact monolayers of DMSA on the surface, which contribute to partial repassivation of the surface. The influence of DMSA on thiosulfate leaching of pure gold electrodes at the open circuit potential for a period of 90 minutes was tested and the corresponding gold leaching performance evaluated with ICP-MS analysis. Our data shows that small amounts of DMSA (1 ¦M) doubled the amount of total gold in solution when compared to the same study in the absence of the additive. However, higher concentrations (5 ¦M DMSA) reduced the overall amount of dissolved gold. These results may point to a mechanism where small amounts of DMSA improve leaching by adsorbing onto the surface in a highly defective monolayer that partially blocks or disrupts the formation of passivation products caused by thiosulfate oxidation, but excess DMSA can limit the leaching process itself by forming too coherent a monolayer on the gold surface.CITATION:Uceda, M, Choi, Y, Shepherd, J L and Guerra, E, 2013. Investigating the influence of meso-2,3-dimercaptosuccinic acid on thiosulfate leaching of bulk gold electrodes, in Proceedings World Gold 2013 , pp 207-214 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

By P K. Singh

Recent advancements in understanding the detonation process are noteworthy, but they are still based on somewhat hypothetical situations. The actual variables that are essential parts of normal blasting practice have not yet been taken into account in such treatments. These include the various initiation practices employed to detonate a column of explosive, from single point initiation to multi-point initiation in blast holes, and the effect on detonation characteristics of both detonators and explosives under multi-deck and multi-hole blasting conditions. The in-the-hole velocity of detonation (VOD) of an industrial explosive is dependent on explosive’s charge diameter and blasthole diameter. The relationship between blasthole diameter and VOD provides a fundamental guideline to the rate of energy conversion and energy release within the detonation front on the interaction of explosives with the confining medium.The in-the-hole VOD of explosives was measured at four experimental sites in India for different blasthole diameters, ie 150 mm to 311 mm, but for identical explosive composition being same particle size, density, viscosity and loaded into blastholes with the same degree of confinement. The results of the studies demonstrated that there is definite relationship in in-the-hole VOD of the explosive and the diameter of the blast hole. The study also confirmed that the explosives initiated with concentrated boosters yielded higher VOD in comparison to those explosives that were initiated with multi-point priming. The measured increase in VOD of explosives for increasing diameter of holes was up to 24 per cent. The rate of change in in-the-hole VOD of explosives increases with increasing blasthole diameter. It can be further stated that the in-the-hole VOD of the explosive reaches a fairly constant value after reaching a limiting/threshold diameter of 311 mm.

Nov 8, 2011

By Wong KY, Woodcock JT

Previous results have shown how con- trolled-potential sulphidization (CPS) can give improved metallurgy during rougher flo- tation of mixed oxide-sulphide copper ores. Results in this paper, using different samples and different equipment, confirm the previous results and extend the application of CPS to cleaner flotation. By using CPS, faster flotation of copper minerals (chalcocite and malachite) from clay was obtained in roughing and cleaning, and improved concentrate grades and recoveries were achieved over those by conventional manual control. The optimum sulphidizing potential (i.e. the potential of a sulphide ion-selective electrode versus a saturated calomel electrode) was -500 mV, and could be controlled to ¦5 mV, during four rougher- scavenger and three cleaner-re cleaner stages. This optimum gives the best balance between copper recovery, concentrate grade, and sodium sulphide consumption. Five cleaning circuits and five ore com- posites of different composition (0.55-1.50 per cent Cu) were examined as well as the effect of feed size and pulp density. Better results were obtained at 20 per cent solids in a Denver cell than at 33 per cent solids in an Agitair cell; this may have been related to the high clay content of the ore. Commercial equipment for pilot plant or full-scale plant application of CPS is cur- rently being developed.

Jan 1, 1986