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By G. ALBORNOZ, S. Utili, A. AGOSTI, C. VALDERRAMA, R. PELL

The steepness of an openpit mine’s slopes has a substantial influence on the mine’s financial return. This paper proposes a novel design methodology where overall steeper pitwalls are employed without compromising the safety of the mine. In current design practice, pitwall profiles are often planar in cross section within each rock layer: that is, the profile inclination across each layer tends to be constant. Here, instead, a new geotechnical software, OptimalSlope, is used to determine optimal pitwall profiles of depth-varying inclination. OptimalSlope seeks the solution of a mathematical optimization problem where the overall steepness of the pitwall, from crest to toe, is maximized for an assigned lithology, geotechnical properties and factor of safety (FoS).

By I. V. Lunkin, E. B. Muhamedzhanov, A. B. Begalinov, B. R. Rakishev

Almost all the ore deposits of ferrous, non-ferrous and rare metals of Kazakstan, are exploiting by the open-cast method, are the complex-structural, multi-component ones. Their rational working requires precise organization of extracting works. In this connection it is necessary to set up the best intercommunications between drilling-blasting, excavating-loading and transport works. This requires the stable functioning of the quarry for dispatch of ore raw material of required quality with minimum of corresponding expenses. For this purpose, proceeding from the quarry’s ore output and the assumed parameters of the exploitation system, the first problem about rational arrangement of excavating-loading equipment in extracting faces is solved. By solving the problem the model with dynamic, adapting properties had been used. It was solved numerically by the method of statistical tests. By setting up the necessary link between type-sizes of excavating-loading and transport equipment, the minimum prime cost of loading and transportation of 1 ton of mining mass from the face to the receiving station was adopted as the criterion of optimality. Depending on the type of excavating-loading equipment, the efficiency function may be different. By using wheel loaders, their displacement between the faces is possible, therefore, the efficiency function of the problem may include expenses for their displacement. By using excavators like power shovel, the problem’s restrictions must exclude its displacement between the faces. The efficiency function consists of minimum expenses for loading, proceeding from set of volumes of extraction from the faces, satisfying required quality. The volumes of extraction from the faces, satisfying required quality of ore in output stream, are determined by the method of statistical tests. Sample range is given, proceeding from the restrictions for maximum productivity of the excavating-loading equipment. Volumes of extraction, not satisfying required quality, are cut off. The efficiency function meaning is then determined and minimized. Keywords: Excavating-loading equipment, its placing in extracting faces, optimal load-carrying capacity, specific expenses for loading and transportation of mining mass.

Jan 1, 2003

By M. Vulkov

The paper is focused on the optimal selection of grinding medium for a drum mill. The decision-making is based on the fuzzy multiple attribute approach. One way to optimize the grinding process in a tumbling mill is associated with the development and testing a new shape of grinding body. Family of new grinding bodies ? spheroidal tetrahedrons (tetraballpebs) has been manufactured. Two types of spheroidal tetrahedrons and a classical ball (sphere) with one and the same weight are compared. A fuzzy entropy method to calculate the weight of the attributes is suggested. A grinding body which is the best approximation to the fuzzy formulated technological conditions is selected. Keywords: grinding, spheroidal tetrahedrons (tetraballpebs), balls, fuzzy sets

Sep 1, 2012

By C. Guria

A modeling, simulation and optimization study of a complex industrial fluorspar beneficiation plant (Kadipani, Gujarat, India) with fourteen/ten flotation banks is carried out to find an optimum/near-optimum circuit for the given quality of feed ore. The phenomenological flotation model developed by Mehrotra and Kapur (1974) is used for circuit optimization. Two different optimization problems are formulated and solved. The first optimization problem involves a single objective function, which uses available plant data to estimate the feed-characterizing parameters, i.e., the flotation rate constants, by minimizing the weighted sum-of-square errors between the computed and plant values. The second optimization problem involves two objective functions to obtain several simplified circuits. The number of non-linking streams and the overall recovery of the concentrate, i.e., the acid-grade product, are maximized simultaneously in this problem. The single-objective variant (SGA-II-mJG) of the binary-coded elitist non-dominated sorting genetic algorithm with the jumping gene adaptation, NSGA-II-mJG, is used for the first problem, while NAGA-II-mJG (Guria et al., 2005 a) is used for the second problem. Simplified circuits with a few split streams are proposed on the basis of the present optimization study, which enhance the recovery of the acid-grade product without affecting its quality, for a given total volume of the flotation cell-bank. Even though the optimal solutions have certain drawbacks, they suggest a meaningful direction in using an iterative fitting of parameters to such optimal circuits, followed by re-optimization. Key words: Froth flotation, Mineral processing, Industrial fluorspar beneficiation, Feed identification, Circuit/network optimization, Global optimal, Jumping gene, Genetic algorithm, Multi-objective optimization

Jan 1, 2009

[Consider a square block W in an ore body S2, to be valued from one centre sample w, and one corner sample w2 (Fig. 9.1). The sample set is ws = Iw,;w21. We can estimate the block average µw by the average of the sample values x, and x2: µw = 'z (x, + xz). (9.1) The error made is measured by the estimation variance: o' (ws to W) = 2 - (ws; W) - - (ws;ws) - - (W; W). (9.2) However, we know that the centre sample w, gives more information about the block value than the corner sample w2. In the example studied in § 8.4, where w, and w2 were considered to be points, we found that of (w, to W) was nearly one third smaller than o2E (w2 to W), therefore when estimating W one should give more weight to w, than to w2. In general, when evaluating a block W from a set of n samples ws, where WS = l w;w2; ... wn1, a better estimator of µw can be obtained if we give different weights to the sample values, depending on the size and the positions of the samples. Some desirable properties of such an estimator µw are: ? It should be a linear function of the sample values xi: n µw = bi xi (9.3) =t where bi = weight given to sample x . ? It should be unbiased, i.e. its expected value should be equal to the true block value: E [µw - µw] = 0. (9.4) ? The mean squared error of estimation of µw should be a minimum E [(µw - µw)2] = a minimum. (9.5) The estimator which satisfies these properties is a minimum variance, linear and unbiased estimator, and is known as the kriging estimator. The corresponding error of estimation is the kriging error. This estimator is also known as the BLUE (for Best Linear Unbiased Estimator) estimator. This was named by Matheron in acknowledgement of the early work of Krige's in the optimization of the evaluation of the South African gold mines. The following notations will be used: µK kriging estimator. o2k = o2K (w,, to W) kriging error.]

Jan 1, 1978

By Stefano Utili, Robert Pell, Nelson Morales, Cristobal Valderrama, Andrea Agosti, Guillermo Albornoz

The overall slope angle (OSA) of pit walls plays a crucial role in the financial return of open pit mines. The work showcases a novel design methodology where non-planar geotechnically optimal pit walls with an OSA steeper than what is used in current design practices are employed without compromising mine safety, i.e. the optimal profiles are featured by the same Factor of Safety (FoS) than their traditional design counterparts. In the current design practice, pit wall profiles are often designed to be planar in cross-section and the profile in between ramps especially tend to be defined by a constant inter-ramp angle.

Sep 30, 2022

By B. Mbuya, A. F. Mulaba-Bafubianda, J. M. Mvita

The paper explains the main effects of input leaching parameters, such as addition of a reducing agent, acidity, agitation, temperature, and leaching system potential, in relation to observed and predicted yields of sought-after cobalt. An artificial neural network coupled with graphical probability networks was developed wherein the abovementioned input parameters were used to predict the percentage of dissolved cobalt. Furthermore, similarities and differences between the Bayesian and neural network approaches in terms of their key outcomes are compared with respect to study of the dissolution of cobalt in sulfuric acid. Key results indicate that there is a need to use neural network results to predict conditions for dissolution of cobalt, while using Bayesian network to explain inferences about conditions of the input parameters, thereby achieving realistic predictions.

Jan 1, 2023

Compressive crushing is applied in crushing plants used in mineral, mining, and aggregate in-dustry for fragmentation of rock materials. From a global perspective, the total volume of crushed rock is massive and corresponds to several billion tons. All societies have to fulfil a daily need of rock material products and its derivatives such as metals and minerals. The business for metals and minerals is global while the aggregates production is mainly a local industry. This paper presents a broader overview of optimisation with respect to product yield, use of natural resources and energy consumption. High level plant optimisation of compressive crushing plants is covered as well as real-time optimisation and optimisation of single production units. Each of three optimisation areas are presented and a discussion around how these three areas will be able to communicate with each other is given. Several models, e.g. process performance behav-iour with respect to wear, as well as fitness functions can be common for all three areas. Well-defined and representative fitness functions are of the utmost importance in order to assure that the optimisation results reflect the production targets. It is concluded that great benefits can be achieved by linking together different areas of optimisa-tion. The future for compressing crushing lies, without a doubt, in tailored processes both with re-spect to machines optimised for each customer, plant parameters and operation routines as well as an on-line adjustment, which takes into account current information and control possibilities.

Jan 1, 2014

By C Mann, S Swapp

"The mining industry is often challenged with the task of evaluating narrow vein open pit deposits. A realistic mineable solution from optimisation needs to accurately represent mining dilution and the practical limitations of mining equipment. Open pit dilution is driven according to mining method and fleet selection as this dictates the ‘selective mining unit’ (SMU) that can be practicably mined.Common evaluation methods represent dilution by:a mathematical dilution assumption addition of a dilution skin reblocking of the model to an appropriate SMU.This paper will explore an alternative method of applying dilution by adapting an underground stope modelling tool. By considering an SMU as a stope, automatic stope shape creators such as Datamine’s Mineable Shape Optimiser (MSO) can be used to create wireframes for each mining unit over the entire deposit. Using these wireframes, the model can be subblocked and assigned as either ore (inside the wireframe) or waste (outside the wireframe) prior to optimisation.The MSO process considers SMU geometry and a depth specific value-based cut-off. The result is an optimised solution for the deposit based on practical and achievable mining constraints rather than one based on generalised modifying factors.To evaluate the economic impact of the methods above, results have been costed and scheduled and a comparison of operating cash flows made.Citation:Swapp, S and Mann, C, 2016. Optimisation Improvements for Narrow Vein Open Pit Deposits Using Mineable Shape Optimiser, in Proceedings Ninth AusIMM Open Pit Operators' Conference 2016, pp 50–59 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Nov 15, 2016

By R LEATHAM

Long hole drilling underground has come a long way since 'down the hole' surface drills were first taken underground. The underground miners have progressively developed the use of long hole stope drilling from the 'quarry blast' to a precise and selective removal of ore while leaving the remaining structure as undamaged as possible. To reach this position has involved the development of equipment and explosives to give the desired results. This paper reviews some aspects of long hole stope production drilling.

Jan 1, 1992

By D Wyborn, P A. Dowd

The characterisation of rock fracture networks is an important component of rock engineering applications involving stability assessment or fluid flow analysis. However, the derivation of a reliable rock fracture model remains a very challenging problem in practice. This paper describes a Bayesian framework, in the form of Markov Chain Monte Carlo (MCMC) simulation, for the construction of such a model. Model conditioning using different data sources is discussed including seismic events recorded during hydraulic fracture stimulation, rock face fracture mapping data and downhole geophysical survey data. The freeware FracSim3D is used for the simulations.

Sep 26, 2011

By K H. Esbensen

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

Jan 1, 2005

By D R. Seaman, R P. Tooher, B A. Seaman

"Several mine scheduling tools exist for use in optimising and scheduling the reserve according to in situ value. These tools generally value the ore on a per block basis according to regressed recovery models based on ore grade and type. It is then the task of the plant metallurgist to ensure that these ore blocks are fed to the plant in a manner that satisfies the prevailing plant constraints. This task is often completed in complex Excel® spreadsheets that are modified over time with factors applied to account for plant modifications or limitations.It is the authors’ experience that this approach is difficult to audit and replicate in a consistent manner. Furthermore, operational decisions, such as primary grind size or autoclave oxidation are made on the metallurgist or managements’ perceived optimum value and does not necessarily represent a cash flow based optimum.Many processing plants contain multiple internal constraints. As ore feed grades and properties change over the life-of-mine (LOM), processing-bottlenecks shift from one unit process to another and different operating strategies need to be adopted to maximise cash generation from the process.This paper presents a unified optimisation approach to scheduling ore based on a circuit mass balance to describe the process plant with individual models for each significant unit operation. The approach allows for optimisation over multiple input variables and the inclusion of linear and non-linear constraints.This optimisation process has been applied to different complex gold operations. The end result is an automated scheduler that selects the optimum blend of ores as well as plant operating conditions that satisfy all internal plant and shutdown constraints while maximising the objective of choice (metal production or cash flow). The models are also valuable for evaluating expansion or debottlenecking opportunities of individual processing units. These models are coded in Matlab® R2016a provided by MathWorks®, and can be deployed to end users in a compiled version with significant savings in time to run different scenarios over the Excel®-based systems.Citation:Seaman, D R, Tooher, R P and Seaman, B A, 2016. Optimisation of Complex Gold Processing Plants with Multiple Unit Operation Constraints - the Newcrest Planning Scheduler, in Proceedings 13th AusIMM Mill Operators’ Conference 2016, pp 191–198 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Oct 10, 2016

By Drinkwater DJ, Watsford RMS, Johnson NW, Munro PD

This paper describes the use of modelling and simulation techniques in the analysis and optimisation of grinding circuits at the Lead/Zinc Concentrator of Mount Isa Mines Limited.The objectives of the studies were to: -1. improve primary grinding circuit performance by reducing the production of -0.006 mm galena fines.2. maximise the fineness of grind in the second existing grinding power and pumping capacitie The study has shown that quantitative models can operations. The models described plant operation,,and simulated the effect of process changes on plant performanc The use of automated scanning electron microscope technology tcliberation characteristics of the major minerals in the Mount isa Lead/Li ore is also described.

Jan 1, 1985

By D M R Stone

Failings di,posal presents many challenges at metal mines in Peru where the extreme relief yields very little useable land area. These challenges are amplified by other hazards such as the high seismic environment, high rainfall, and frequent debris torrents down the steep hillsides. As a result many mining operations have resorted to in-river disposal of mill tailings. This paper presents a case history of one underground metal mine located in the high Andes mountains of Peru where in-river disposal of tailings has been used for some 30 years. The paper outlines a comprehensive engineering study that was aimed at increasing the utilisation of tailings disposal underground. The scope of this study included modifications to the grinding and flotation circuits to produce a high sulphide and low sulphide tailings for underground and surface disposal respectively: mapping and cataloguing of abandoned stopes for hackfilling: modifications to the existing backfill system to improve icliahility and throughput, and a preliminary evaluation of alternatives Such as silicated and paste fills.

Jan 1, 1998

By F Kock, Y Sulianto, T Trott, B G. Putland, D Morgan

"Northparkes installed and commissioned a secondary crushing circuit in 2010 to debottleneck the semi-autogenous grinding (SAG) mill constrained grinding circuits. Following further improvements to the circuit (inclusion of a double deck vibrating screen), the project successfully delivered finer feed to the SAG mill. The result of this project was an increase in the milled tonnes from 5.6 Mt/a in 2012 to 6.0 Mt/a in 2013.The increased throughput rates introduced new challenges with the circuit becoming power limited. How to best optimise the available comminution power, while delivering the optimal particle size to the flotation circuit was made the key optimisation objective. To achieve this objective, Northparkes initiated a project that included engaging comminution experts. Recommendations included changes to the SAG mill including mill lifter design, increased grinding media charge levels and reduced grinding media size with aim of producing a finer grind size.Northparkes implemented these recommendations along with some other changes to SAG discharge grates and the mill discharge vibrating screen. This achieved a substantial reduction in the flotation feed particle size distribution (approximately 20 microns) by utilising increased average SAG power utilisation, in turn resulting in a two per cent increase in copper recovery.With power utilisation now maximised, the next phase of optimisation has moved to the throughput-grind-recovery relationship and the cost benefit analysis of installing additional grinding power.Citation:Sulianto, Y, Trott, T, Morgan, D, Bell, T, Kock, F and Putland, B, 2016. Optimisation of Installed Mill Power Post-installation of Secondary Crushing Circuit at Northparkes Mines, in Proceedings 13th AusIMM Mill Operators’ Conference 2016, pp 331–338 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Oct 10, 2016

By D Horacek, I K. Sheppard

Ok Tedi is in a period of transition. By 2008 mill feed will consist of higher levels of high-grade but metallurgically challenging skarn ores. Additionally, the Taranaki pit will start production in 2008 along with the start-up of a new pyrite concentrator. Taranaki ores are very high in sulfur. Sulfur is captured in a pyrite concentrate prior to tailing entering the Ok Tedi River. These and other complex scheduling issues will need to be resolved over a critical three-year period. With these requirements in mind, Ok Tedi contracted AMC Consultants to develop a custom version of the Life of Business Optimisation System (LOBOS¬) to assist medium-term production scheduling at Ok Tedi. LOBOS utilities enable Ok Tedi planning engineers to:import polygon-based reserve data (Blast Masters) from MineSightÆs Interactive Planning Tools (IP Tools); graphically construct block sequencing and material flow constraints; edit constraints defining standard scheduling, processing and financial relationships; define dump and stockpile attributes; and assign capacities to production systems, plants, dumps and stockpiles. LOBOS converts Ok TediÆs production scenario into a mixed integer program (MIP) and submits the resulting model to IlogÆs Cplex MIP Solver. The Solver seeks an optimal production schedule that maximises net revenue per mill hour while meeting all constraints. This paper introduces Ok Tedi and its production requirements and relates these requirements to the facilities developed for an Ok Tedi version of LOBOS.

Jan 1, 2007

By Z. Saw, C. Poveda, N. L. Mai

Optimising the throughput of a mining network comprising all equipment from shovels to semi-autogenous grinding (SAG) mills is a complicated task, yet the potential benefits can be significant. Key modelling challenges stem from the sheer number of possible routes which material can travel, different equipment operating under different constraints, and the rate of SAG mills being calculated through a nonlinear function of the blended materials’ rock attributes. Nevertheless, this is an ideal onapplication area of mathematical programming, a branch of operations research. This paper describes an application of mixed integer linear programming (MILP) to optimise the mining equipment network of one of the world’s largest copper mines.The model takes as input a year-long monthly mine schedule of shovels in different pits, pushbacks, sequences and faces which produce material to be moved through a network of crushers, conveyors, silos, distributors, stockpiles and SAG mills, ultimately outputting a daily operational plan for all equipment that maximises the throughput of the network. All operational constraints and business rules are considered, including three quality attributes of copper ore. Comparing model results with actual data shows an improvement of 4.47% in network throughput tonnage. Additionally, although the model is solved using a free, open-source solver, optimal solutions are still achieved within a practical timeframe.

Sep 1, 2021

Optimising drill performance has always been a primary goal of drilling and blasting managers. Improving drilling rates and utilisation will ultimately drive the cost per foot or metre downward. Additionally, more consistent production will ensure shovel or dragline performance goals are met and the chances of machine idle time is minimised. Over the past 20 years, many studies have examined rotary drilling factors and performance issues. In most cases a common theory points to energy input versus drilling output. Indexes such as specific energy and total work energy have been -developed to quantify the drilling process. As general engineering principles dictate, energy is required to drill rock by overcoming compressive and shear strengths. Concurrently, the greater the energy input, the faster the penetration output. Therefore, by examining the basic drilling energy parameters, optimisation is possible. The principles of rotary drilling are driven by five factors. When optimised individually and as a system, drill performance will improve. Most recent studies all agree that a performance relationship exists between bit load, bit rotation, and hole flushing. Additionally, proper bit selection and most of all, the operator, can have a tremendous effect on drill productivity. By analysing these factors and establishing the best case scenario, an overall drilling system can be engineered to match the mining characteristics. Furthermore, by balancing these factors, a lower cost will be achieved through increased production rates, maintenance costs, and effective drill utilisation.

Jan 1, 1995

Optimisation of the Advanced Automation System at Inmet Mining's PyhSsalmi Mine, Finland

Sep 13, 2010