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By J Carter, B J. Armstrong

Best practice for the submission of samples to an internal or commercial laboratory requires quality control materials to be included for the purpose of independently and comprehensively assessing laboratory performance. These quality controls include the use of certified reference materials (CRMs) and may be blind to the laboratory. Iron ore companies purchase these materials from reputable manufacturers from stock of run-of-mine materials at the appropriate grades. The international standard, ISO 17034 (ISO, 2016), specifies the competency requirements for organisations manufacturing reference materials, and includes rigorous requirements for the assessment of homogeneity, stability and establishment of property values and their uncertainties. Homogeneity is one of the most important measures of suitability for all certified reference materials and refers to the degree to which the composition and properties of a sample are uniform throughout the batch, relative to the analytical precision of the method. More specifically, homogeneity studies of candidate reference materials should be assessed for both within sample variance and between sample variance with appropriate statistical controls. The design and application of homogeneity studies are discussed as they apply to both crushed and pulverised reference materials. Crushed certified reference materials have been utilised by the iron ore industry for a number of years and provide the user with a critical assessment of variances in sample preparation in addition to analysis. Crushed reference materials are similar in presentation to an RC sample and are generally used as discrete parcels of material submitted to the laboratory from the field. Pulverise certified reference materials miss the sample preparation step and are subsampled from th delivered sachet at the point of analysis. This paper compares the relative homogeneity performance of crushed and pulverised certified reference materials by grade across key iron ore chemical constituents. Outcomes are benchmarked to the international standard ISO 9516 (ISO, 2003) for the determination of various elements in iron ores by lithium borate fusion and X-ray fluorescence. Practical implications are discussed with reference to a case study from an iron ore laboratory in the Pilbara.

Sep 18, 2023

By J Say, M Hawtin, L Carlon, P Cann

Historically, production from sublevels of the Ernest Henry Mine (EHM) started from blind uphole rises at the end of slot drives. Where previous investigations considered removing these slot drives and starting production with independent ore drives, any development savings were consumed when drives were extended to minimise ore loss. Since 2017, EHM and Orica have been investigating opportunities to optimise drill and blast practices by implementing Orica’s Wireless Electronic Blasting System (WEBS). To reduce ore drive development metres, a novel design was proposed utilising the WebGen™ 100 system to combine a rise with pre-charged widening firings. Initially these new rise and widening firings achieved results similar to previous EHM designs, achieving on average 81 per cent of design height and width. Due to poor performance of the fourth trial a significant re-design was required. Modifications included drill hole re-positioning, in-hole primer relocation and initiation delay adjustments. Since the re-design a step change in rise performance has been observed with rise and pre-charged widening shots averaging 95 per cent of design height and width. With rise and widening performance exceeding expectations, the removal of slot drives has allowed a substantial reduction in lateral development. Development savings of 165 m and 169 m from the RL1325 and RL1300 levels have been achieved. Primary draw and ore recovery has also increased due to the later addition of pre charged forward stripping rings. Level design changes have also significantly improved the mining cycle by allowing for a reduction in required ground support, improved secondary ventilation, a reduction of critical path development, simpler production scheduling and less wear and tear on machinery. Future mine level designs now incorporate key learnings and are proving beneficial to a variety of scenarios including changing orebody boundaries at depth.

Mar 15, 2021

By P Collier

From 1972 until 1989 when operations were suspended Bougainville Copper Limited (BCL, owned 53.58 per cent by Rio Tinto Limited) operated a large open pit mine and processing facility at Panguna on Bougainville Island, Papua New Guinea producing copper concentrate containing significant quantities of gold and silver.BCL has a stated vision of recommencing operations at Panguna. In 2008, Rio Tinto, on behalf of BCL, conducted a multi-disciplinary study to assess the technical and financial viability of redeveloping the Panguna operation. One of the key outputs of the study was a Joint Ore Reserves Committee (JORC) Code compliant mineral resource statement based on the existing block model and fundamental data, archived since mine closure. Historical data (including the resource block model and drill hole data) was recovered from computer archives by a former Panguna mine employee familiar with the various obsolete data formats, thus maintaining an unbroken chain of custody of the data by Rio Tinto since operations were suspended. No additional data were collected as part of this study.The extensive data and documentation archive facilitated a sufficiently detailed evaluation of the fundamental data and model to support an updated resource statement. Table 1 of the JORC Code was used to guide the model validation process.Reconciliation of blasthole and metallurgical plant data with the reserve model, indicated that the copper and gold drill hole composite database was significantly biased towards underestimation in several key domains due to a combination of the following: mineralisation loss during core loss, core loss (minor), vertical drill holes failing to intersect sufficient subvertical mineralised fractures and veins, drill hole spacing too wide, and variable diamond drill hole core size. The resource model evaluation was based on three material types (all previously mined at Panguna), that were defined based on cut-off grade and rock type parameters: direct feed ore – material for delivery directly to the plant, preconcentration and screening ore – subeconomic material beneficiated to produce fines of economic grade, and waste. Three pit shells and designs were generated based on three separate sets of economic parameters. These economic parameters were also used to assign material types to the block model. The three resulting models were then evaluated against the corresponding pit shells.Classification of the resource was approached conservatively due to the inherent bias in the drill hole data. Consequently only Indicated and Inferred resources were tabulated.The study highlighted the importance of maintaining detailed documentation pertaining to resource estimates and operational history, particularly reconciliation, and the value that can be added by a simple, low-cost data compilation exercise.

Aug 22, 2011

By J T. Carswell, K Sutton

Quality control (QC) of reverse circulation drill sampling commonly involves regular duplicate subsampling to monitor the extent of imprecision or random error in the subsampling system. In gold mining in Australia, the subsampling tool is usually a cone splitter.Other sources of error, including delimitation error and bias (systematic error) in the subsampler are often assumed to be negligible or ignored for being too difficult to QC.This paper describes actual sampling errors and error mitigation based on quality assurance and quality control (QA/QC) of surface and underground reverse circulation drill sampling at a high-nugget gold mine at Sunrise Dam, Western Australia.CITATION:Carswell, J T and Sutton, K, 2014. Sources of sampling error and implications for quality assurance and quality control in surface and underground reverse circulation drilling, in Proceedings Sampling 2014 , pp 65–70 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 29, 2014

By R Crosbie, K C. Runge, E Tabosa, J K. McMaster

Flotation feed density is an operating parameter which is currently not well understood. Most models of flotation only incorporate its effect on particle residence time, but it is likely to have additional effects within both the pulp and froth phases of the machine. Test work was performed in MetsoÆs 3 m3 RCS test rig to investigate the effect of flotation feed density on metallurgical performance. The rig was operated at Rio TintoÆs Northparkes operation using flotation feed and scavenger tail. For each feed, tests were performed at different feed densities, and measurements were performed to estimate the pulp and froth recovery as well as other key flotation parameters (eg bubble size, turbulence and froth stability). Results of this test work have shown that the pulp density does affect key parameters of the flotation process in both the pulp and froth phases. Pulp phase kinetic rates decrease at high density and this is attributed to a reduction in the turbulence within the cell. Froth phase recovery, however, improves presumably because of a stabilising effect due to a greater loading of solids on bubble surfaces.There is a need for more research to be done to better understand these interactions so that metallurgists can determine the optimum flotation feed density to use at a particular operation, or within a section of a flotation circuit.CITATION:Runge, K C, Tabosa, E, Crosbie, R and McMaster, J K, 2012. Effect of flotation feed density on the operation of a flotation cell, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 171-178 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

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 R Schmitt, Y Ghorbani, I McElroy, N J. Bolin, M Parian

Aitik is a large copper porphyry type deposit located in northern Sweden, currently exploited at an annual rate of approximately 45 Mt. The ore’s exceptionally low head grade of 0.25 per cent Cu and varying degrees of hardness across the entire deposit pose challenges to the two fully autogenous grinding lines, each of which comprises a primary autogenous mill in series with a pebble mill. The variability in ore grindability frequently leads to fluctuations in mill throughput. Within the framework of a geometallurgical approach, the present study investigated the relationships between ore grindability and modal mineralogy. For this purpose, drill core samples from different lithologies were subjected to Boliden AB’s in-house grindability tests. This fully autogenous laboratory-scale test generates a grindability index mainly related to abrasion breakage, which is a significant breakage mechanism within autogenous mills. The test results suggested divergent degrees of grindability within and across the selected rock types. A combination of scanning electron microscopy, X-ray powder diffraction, and X-ray fluorescence analyses was performed for the grinding products and bulk mineral samples. The resulting mineralogical and elemental properties were subsequently correlated to the parameters from the grindability tests. It was shown that the main mineral phases, such as plagioclase, quartz, and micas, correlate well with the grindability indices. Similar correlations were found regarding the sample’s chemical composition, attributable to the main mineral phases. A further inverse correlation was established between the sample’s calculated average Mohs hardness and the grindability indices. Moreover, mineral liberation information provided by scanning electron microscopy was associated with the parameters mentioned earlier. The identified relationships between grindability, modal mineralogy, and element grades may help Boliden develop a predictive throughput model for Aitik based on the mine’s block model.

Aug 24, 2022

By D Clarke, I Minniakhmetov

The Olympic Dam deposit is truly a world-class IOCG-Ag deposit, the world’s fourth largest deposit of copper and the world’s largest known single uranium deposit. Traditional and non-traditional methods have been used to accurately model the geology and mineralisation of the Olympic Dam deposit. Conditional simulation models have long been used as the most robust method for estimating risk and uncertainty in mine planning decisions at other mines around Australia and the world. There are many challenges associated with simulating the Olympic Dam deposit at a selective mining unit size sufficient for underground mine planning purposes. These include the size of the deposit, resulting in hundreds of millions of grid blocks; the disseminated nature of the zoned sulfide mineralisation. And lastly the direct relationship of the relative abundances of the sulfide mineral species that are crucial to the Olympic Dam smelter performance. Several geostatistical techniques have been utilised in the workflow for the Olympic Dam Conditional Simulation model to address these challenges. The key techniques are: • Projection Pursuit Multivariate Transform to de-correlate the main elements before simulation. • Pluri-Gaussian implicit boundary simulation method to simulate the mineralisation domains. • Spectral simulation method of de-trended and de-correlated attributes with account of local varying variance. The resulting conditional simulation models have been validated against histograms, grade-tonnage curves, cross-plots and assessed for variogram reproduction. This paper presents how the final conditional simulation models compare to benchmarking models created using alternate estimation techniques of ordinary kriging and local uniform conditioning. It also presents a validation process using historical samples to test final estimate accuracy of the simulation models.

May 24, 2023

By J Caron, M Athayde, F Lavoie, R Joyce

Decarbonisation has become a major challenge for the global steelmaking industry, turning towards new technologies aimed at carbon footprint reduction, which on its own accounts for approximately 9 per cent global emissions. The iron and steel industry represents a ‘hard to abate’ sector, where much of efforts are currently being deployed into initiatives aiming to decarbonise the ironmaking through the use of green hydrogen, carbon capture utilisation and storage and state-of-the-art operation of current technologies, while little efforts being deployed to find carbon-efficient solution to iron ore burden preparation, where high-grade iron concentrate will increase in importance to ironmaking regardless of the chosen reduction route. Quebec Iron Ore (QIO), a subsidiary of Champion Iron Limited (Champion), produces high-grade hematite concentrate with one of the lowest carbon global footprints. Still, QIO is partnering with its clients to the development of burden solutions to minimise CO2 emission, in the seek for a decarbonised steel. In a strong technological partnership, Binding Solutions Limited (BSL) has developed a novel, coldbinding technology to provide a cleaner, more cost-effective alternative to induration. The technology allows miners and steel producers to reduce Capex significantly and reduce energy consumption and CO2 emissions by 90 per cent. QIO and BSL have partnered to adapt the disruptive cold binding technology developed by BSL to QIO’s concentrate to produce a high-quality low emissions iron ore agglomerate. This paper describes the efforts taken to further develop BSL’s cold binding technology and its application to QIO’s high-grade iron ore concentrate to produce a hematite cold bonded briquette (hCBB) showing comparable performances with high quality seaborne fired pellets.

Nov 8, 2021

By J Westh, S Rashleigh, L Gallagher

Mining companies are moving towards automated haul trucks and other equipment. One reason for this is that if automated trucks can operate in a standard pattern over and over again without variation, then human error is reduced, if not eliminated.The challenge for mining production leaders/managers is to ensure operators follow standard operating procedures for load and dump operations, with each operator doing the same thing, every time. However, operators are only human and inconsistent performance is rife at every mine site. The finger may be pointed at the operators for not doing as instructed. The clarity and variability of trainer instructions may be considered causal to the problem. Herein lies the problem. Almost all operators believe they are following the procedure very closely; moreover, they all demonstrate a strong desire to conform to instruction.Using video analysis and feedback, each operator can be shown where and by how much they differ from the benchmark set by their company. Operators, often for the first time, can see definitively what they are doing, compared to industry best practice.The technology utilised by real-time video (RTV) crews measures time, distance and angles. It can overlay the video of the operator at the load site, with video of the perfect pass. Operators are amazed when they see how near to, or how far they are from best practice.The footage and data gathered by RTV assists operators in understanding exactly what adjustments are required to increase proficiency. It also assists load and dump superintendents to identify where in the process they are losing time. When translated to overburden removal or mineral/resource extraction, the result is large production economies without the need for large capital investment in new automated technology.CITATION:Westh, J, Gallagher, L and Rashleigh, S, 2012. Improving safety and mine productivity using real-time video technology, in Proceedings International Mine Management 2012, pp 173-188 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 20, 2012

By A L. Randriamanjatosoa, G Small, C Greet

In flotation simulation models, the effects of pulp chemistry other than pH are often ignored and reduced to particles hydrophobicity or contact angle, neither of which can be measured readily in real time in an operating plant. The flotation response of a given sulphide mineral is known to be influenced and can be improved by changing the chemical characteristics of the pulp during grinding and flotation. The on-line measurement of pulp pH, potential, dissolved oxygen, temperature and oxygen demand of a process stream was completed with the PCM® (Pulp Chemistry Monitor) developed by Magotteaux in this study. The data generated together with relevant plant operating parameters were used to construct an empirical model and simulate the metallurgical performance of the ore. The same approach was also applied to laboratory flotation tests data using various grinding media types. The flotation models better fit the actual data when the chemistry of the pulp is taken into account.CITATION:Randriamanjatosoa, A L, Greet, C and Small, G, 2018. Effects of pulp chemistry on plant and laboratory flotation modelling, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 423–432 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

By M Carr, C Wheeler, M Lurie, B Chen

The demand for steel products in modern society is prompting the iron ore industry to optimise their operations to ensure sustainability of fines and lump products. One of the key components in the iron ore transportation chain are belt conveyors. The energy consumption of modern belt conveyor systems has reduced considerably over the past few decades, however, there is still significant scope for further reductions, especially when heavily loaded long overland belt conveyors are considered. A new rail based continuous bulk material transportation system has been developed by researchers at the University of Newcastle to reduce the energy consumption of heavily loaded and long overland conveyors. The Rail-Running Belt Conveyor technology is a state-of-the-art continuous belt conveying technology which provides an innovative and novel departure from conventional continuous bulk material transportation systems with significant energy and economic benefits. This paper presents an overview of a Rail-Running Belt Conveyor variant which considers an enclosed belt. Enclosed belt conveying has the benefits of encapsulating the bulk material, and thereby reducing dust emissions and moisture ingress, in addition to being able to negotiate smaller radius horizontal and vertical curves leading to greater flexibility. To quantify the primary differences between conventional conveying technologies, the Denver office of thyssenkrupp Industrial Solutions (USA) developed a case study for an 11 km long conveyor. The conveyor design throughput was 2750 t/h and included a small net elevation loss of 10 m. When considering CAPEX the Rail-Running Pipe Conveyor equipment supply cost is approximately 45 per cent of the cost of a conventional pipe conveyor, while savings upwards of US$50M emerge for CAPEX combined with five years of OPEX. The savings vary with the topography and density of the bulk commodity, with iron ore generally showing increased savings because the high bulk density increases rubber losses in conventional conveyors.

Nov 8, 2021

By R Battison, R Duggan, S Esen, K Henley, P Dare-Bryan

Increased catch bench crest loss has been observed in recent years at Barrick’s Cowal Gold Mine situated in central New South Wales, Australia. A project was initiated to diagnose the cause of the crest loss, and evaluate ways to limit its effect on final walls.A range of different blast measurement techniques were utilised to evaluate the progressive damage caused to catch berms by presplit, production and trim blasts. Techniques employed included; single point vibration measurement, cross-hole seismic analysis, precision berm surveys, horizontal p-wave velocity measurements, crest loss volume calculation and water level changes between blasts.Blast measurements showed that the majority of damage to the catch berm was caused by the presplit blasts, which registered vibrations greater than 700 mm/s at 5 m behind the presplit line. As a result, considerable changes were made to the blast designs after a series of computer simulations via mechanistic blast modelling (MBM). The uncharged presplit collar was increased from 2 m to 4 m, and every second hole was left uncharged. Vibration modelling using a multiple seed wave (MSW) model was used to optimise trim blast delay timing. Burden relief was changed from 16 ms/m to 27 ms/m using one hole firing per 4 ms time window, and the initiation angle was changed from shallow to steep. These changes in the presplit loading and trim timing helped reduce catch bench crest loss by 1–2 m.Trim shots using a high strength bulk emulsion explosive were also identified as contributors to berm damage after analysis of blast monitoring and MBM modelling. The modelling study resulted in the generation of alternative blast designs to minimise the crest loss, including the use of low-density/low-velocity of detonation (VOD) bulk explosive product (Flexigel™ Advantage) in trim pattern designs. This was trialled on the Northern and Eastern pit walls to evaluate the damage to catch berms on final walls. The trials demonstrated that berm vibration was reduced significantly; fragmentation was similar (or slightly blockier) compared to the fragmentation using the old blast designs; displacement of the berm was reduced, so increased catch bench widths were attained. This paper summarises the trials, and presents a summary of the crest loss to date.CITATION:Battison, R, Esen, S, Duggan, R, Henley, K and Dare-Bryan, P, 2015. Reducing crest loss at Barrick Cowal Gold Mine, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 189–202 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

Rather like the mythical "Economic Man" "an employer" in this context must necessarily be an abstraction, and the views possessed by such an abstraction, a composite of many views known to have been expressed. Not even the complex Conciliation and Arbitration legislation in this country provides any helpful specifications, except in one peculiar particular. The Australian Conciliation and Arbitration Act provides an almost totally tautological definition, except in that one oddity referred to above. It is this : "An employer means any employer in any industry, and includes any person who is usually an employer in an industry, and also includes a Club." No doubt there is some perfectly justifiable reason for such specific and unique particularity in an otherwise meaning- less definition. That need not trouble us in this exercise.

Jan 1, 1982

The Pacific Rim countries ofAustralia, New Zealand, Papua New Guinea, Indonesia, Fiji, Philippines and Solomon Islands will be reviewed from an equity investors perspective.   The following areas will be covered: Country risks Exploration spending and activity Project development Taxation Relative cost of doing business Environmental considerations Political/bureaucratic situations Capital raising Equity markets as a source of funds Developing market funds The aim of the paper will be to outline the most attractive areas for investment by equity and private funds plus documenting the changes needed in the less favourable countries if they are to attract investors.

Jan 1, 1995

By A Halim

"There is still debate about who should ultimately be responsible for the ventilation system in anunderground mine. The Queensland Coal Mining Safety and Health Regulation 2001, states that adedicated ventilation offi cer is the person, while Western Australian Mines Safety and InspectionRegulation 1995 states that it is the mine manager who is responsible; the ventilation offi cer actsas the managerÆs principal ventilation advisor. This paper outlines a comparison between bothapproaches."

Jun 1, 2012

Exploration for uranium in Australia commenced only during the 1940s, but in this short period has been very successful as one third of the world's low cost uranium reserves have been discovered in Australia. Total uranium exploration expenditure in Australia up to the end of 1983 was $A(1983) 554 million; this discovered 20 potentially economic deposits and official reserves of 560 000 tonnes of uranium oxide at an average cost of $1 per kg of U 0 . An exponential 8 eserves indicates distribution of uranium r that there could be 54 undiscovered uranium deposits in Australia, each with reserves of 20 000 tonnes U308 or more, in addition to smaller deposits. Using a constant uranium price of $A(1983) 79 per kg, no deposit is economic at a grade below 0.12 per cent U 08 or with reserves of less than 3 000 tonnes. Selecting deposits with reserves of 5 000 tonnes U 0g or more as prime exploration targets, only 39 per cent of discoveries will yield a real internal rate of return (IRR) of 10 per cent or more. After committing a minimum exploration budget of $10 million to this search, an explorer has one chance between 7 and 12 of discovering a deposit that will repay the exploration investment.

Jan 1, 1984

By P Myers, T Elkington, S Wonday

Sierra Rutile LimitedÆs (SRL) heavy mineral sand mining operation in Sierra Leone, West Africa, is embarking on a new phase of its life. After confronting many challenges during the 1990s and 2000s, SRL is embarking on a strategy of growth to recover maximum value from the mine over the rest of its life. Sophisticated linear programming techniques have been used to develop an optimum strategy for extracting SRLÆs many known deposits of economic grade, while considering options for expansion and for a variety of mining and processing methods and combinations. CITATION:Myers, P, Elkington, T and Wonday, S, 2012. Strategic optimisation at Sierra Rutile - A case study in maximising project value, in Proceedings Project Evaluation 2012 , pp 59-66 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 24, 2012

By M R. Dehghan, H Mansouri, A Hakami, M A. Ebrahimi Farsangi, F Faramarzi

Today, it is accepted that rock fragmentation by blasting affects loading and hauling operations, and also directly influences on downstream processes such as crushing and grinding. In this research, the influence of rock fragmentation by blasting on the performance of three mills at Gol-e-Gohar iron ore mine No 1 was studied. Firstly, the fragmentation of conventional blast patterns in iron ore (5 × 6 m) was studied using image analysis and the performances of three mills were monitored. Then, a new blast pattern (4 × 5 m) was designed and nine blasts were carried out using this pattern. Increasing the powder factor form 1650 gr/m3 to 2480 gr/m3 by changing the blast pattern design showed that mill throughputs increase five per cent to 30 per cent for the new pattern.CITATION:Hakami, A, Mansouri, H, Ebrahimi Farsangi, M A, Dehghan, M R and Faramarzi, F, 2015. Study of the effect of blast pattern design on autogenous and semi-autogenous mill throughput at Gol-e-Gohar iron ore mine, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 315–320 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By J K. Claflin, S R. La Brooy, A M. Claflin

Rotary kilns have been in service in the gold industry to regenerate carbon for 65 years. At the time oxide ores with gold head grades of 8 to 10 g/t were being treated. Carbon could be regenerated adequately at 650°C and solution losses were less than 1%. Forty years ago, research indicated that heavily fouled carbon from flotation circuits had to be held at 750 to 850°C for ten to twenty minutes for full reactivation (Avraamides and La Brooy, 1987), gold head grades were typically 5 g/t and solution losses typically 0.02 ppm – still less than 1%. In 2017 it was determined (Claflin et al., 2017) that a residence time of less than 1 minute at 750°C can be adequate to reactivate carbon fouled with organics sufficiently to achieve 0.005 ppm solution losses in a flotation tailings leach plant.With the potential for discovery head grades to drop below 0.6 g/t, solution losses of 0.02 ppm represent over 3% loss. Tight operation of the whole carbon circuit is required to keep gold solution losses below 1% going forward.There are alternatives to a rotary carbon kiln, e.g. vertical kilns of which the Minfurn, Rintoul and Combustion Air kilns are examples. The alternative kilns can be heated using electrical heating elements, induction, and microwave. These kilns can operate successfully under the right conditions, however, they are almost exclusively for small carbon throughputs and are not suitable for the large carbon advance rates that are required to process low head grade ore deposits. Large throughput carbon kilns are are almost exclusively fossil fuel fired rotary kilns and the subject of this paper. In the view of the principal author, a fossil fuel fired vertical carbon kiln is preferred to a rotary kiln, however, it is not currently used in the industry.Thermal regeneration of activated carbon has a major impact on gold recovery in the carbon circuit. The carbon kiln and associated equipment constitute 3 to 5% of the capital cost for an oxide processing plant and up to 10% of the capital cost if flotation tails are leached. Despite the capital cost and impact on recovery, the carbon kiln is often poorly selected, operated and maintained.Six years ago Ausenco embarked on the Carbon Kiln Initiative to reduce solution gold losses. This body of knowledge has been published in a series of papers culminating in this paper on how to:1. Select a kiln appropriate for the flowsheet;2. Maintain the kiln to achieve design operation; and3. Operate the kiln to minimise costs and maximise reactivation.CITATION:Claflin, J K, La Brooy, S R and Claflin, A M, 2018. Carbon kiln selection, operation and maintenance, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 251–274 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018