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By Wooller R

The 3-D regular block model used for long term mine planning at Hamersley Iron did not fulfil the requirements for short term mine planning in terms of accurate representation of geological structures, contacts and boundaries in the orebodies. A computer model, based on zone plans, is being created as a single orebody model for all phases of mine planning. The zone plan is the primary interface between the geologists and mining engineers. It is essentially a bench plan at mid-bench height showing geological structure, material type boundaries, the grade and physical characteristics of ore blocks. The method allows for the dilution of ore zones by waste material. The stratiform nature of the orebodies allows zones of varying grade to be readily delineated on the plans. The Zone Plan Model (ZPM) is the interface between geological and mine planning computer systems. It is the basis of all mine planning with applications including long and short term mine plans, reconciliations, general ore reserve estimations, pit design and general model enquiries. The system was designed to be user driven. The user has complete control at all times as all computer generated data are fed back to the user who may then elect to override the computer. Various controls were built into the system to ensure model validity and integrity. The system has proved to be invaluable as a tool for users with little or no computing experience.

Jan 1, 1986

By Jorgensen FRA, Moyle FJ, Turner TM

Laminar flow furnace techniques and thermal analysis were used to study the combustion of Kambalda nickel concentrate and Collie coal. The study was made to ascertain the suitability of the latter as a replacement for the fuel oil currently burnt in a flash furnace at the Kal- goorlie Nickel Smelter. The coal was found to ignite at temperatures between 500-600¦C which was the same as that required for the most reac- tive component of the concentrate, namely py- rite. The rates of reaction of both the coal and concentrate were dependent on oxygen con- centration. Sulfur dioxide hindered the combus- tion of concentrate and of coal, the effect on the concentrate being the more pronounced. The effects of moisture content and the tendency for spontaneous combustion of the coal were also noted.

Jan 1, 1982

The mechanisms of fragmentation in homogeneous materials and structured rock mass are reviewed. A method previously used to predict vibration damage to the remaining rock is extended and shown to be valid for the prediction of fragmentation in the rock mass removed by blasting. The effectiveness of different explosives in different types of rock blasting is discussed.

Jan 1, 1990

By J C. de Vries

When times are tough in the mineral industry û as they have been for some time û typical responses by mining companies are to cut costs and/ or increase production. The latter is seen to spread fixed costs, thereby also reducing unit costs per tonne mined. However, most mineral deposits respond to increased production rates by lowering ore grades, so the reduction in cost per tonne of ore does not necessarily result in a reduced cost per unit of metal produced. The authorsÆ experience is that this process often leads to a mine plan that is a long way from optimal. Producing to the point where marginal cost equals marginal revenue may work well in a manufacturing operation, but it is not necessarily the best strategy for a mining company with a depleting resource. Variations in tonnage and grade with depth, ore reserve optimism and a variety of other factors conspire to produce variations in production rates and grade that often result in suboptimal outcomes and potential mine failure. Added to this is the focus of industry analysts and senior corporate management on such measures as unit costs and ounces in reserves. This is perceived to have the perverse effect of driving the share price down when strategies are adopted that actually improve the value of the mining operation, and vice versa! Many mine failures can be prevented by a close examination of the tonnage grade curve and an understanding of how margins, net cash flows and resulting business risk change with cut-off grades and rates of production. A few relatively simple analyses early in the evaluation of a project can demonstrate the tradeoffs between the main decision parameters, leading to right-sizing of the operation. Once major commitments to major capital items have been made, and reserves have been publicly reported, optimisation of the operation becomes much more difficult than if it had been done earlier. Such investigations can also identify the upside potential and downside risks associated with factors outside the companyÆs control. Many strategies that may enhance value in the good times significantly increase the downside risk in the bad times. What is often called risk analysis typically looks at superficial issues, and does not evaluate the major factors leading to the potential for financial disaster. This paper illustrates some of these major risks, and demonstrates how they may be fully evaluated so that corporate decision makers can make fully informed decisions that take account of the real risks.

Jan 1, 2003

By Quinlan M. J, Ratcliffe J. S

Chemical kinetics is a dependent process which usually correlates the rate at which a reaction proceeds with the mechanism descriptive of the manner by which reactive particles interact. Given the latter, the object gen- erally is to find the reaction rate dependency in terms of an intensive property of the system - number of reactive particles present, and of the energetics of the system - usually temperature. Chemical kinetics depend on a dem- onstration that reaction considerations alone control the phenomenological process under study. For these rea- sons, chemical kinetics are usually involved in homogeneous gaseous systems. Even in liquid homogeneous sys- tems earliness or lateness of reactant mixing rather than chemical kinetics may be controlling. Considerations of transport phenomena are involved in heterogeneous systems and often control the observable rate:an additional problem in such systems is to apportion the rate due to mass transfer - usually a linear process - and that due to reaction which may be linear or non-linear. Experimentally, conditions are often chosen so that only one consideration controls but this becomes more difficult where solid phases are involved. Kinetic modelling involves considerations of chemical kinetics, transport phenomena, and factors attributable to the physical environment in which the process takes place. The latter two considerations may be quite different as between experiment and plant. The kinetic model may be a mathematical representation of a conceptual mech- anistic model of the reaction. Alternatively, it may be an empirical relationship resulting from, for example, some curve fitting procedure applied to experimental data. The latter approach may be necessary where the system is particularly complicated.

Jan 1, 1975

By A R. Bonani, M P. Pe±a

The optimisation of slope angles, that is to say, increasing them, compared to the original design is always the subject of analysis of stability for geotechnical engineers and economic analysis for planning engineers. Questions to be answered include: What is the acceptable risk? What factor of safety? What probability of failure or reliability? The Rosario Open Pit has a history of failure, poor quality rocks and high pore pressures. It was decided to deepen the pit below the programmed design to test the practicality of different design approaches, which if successful, could be used to improve the economics of mining at Collahuasi. The revised slope design has factors of safety in the range of 1.0 to 1.2, probabilities of failure of ten to 38 per cent, and increased slope angles of between 3¦ and 5¦ with respect to the original design. The pit deepening with these design slopes will deliver an extra two million tonnes of ore which will have a significant positive impact on mining economics.

Jan 1, 2007

By Fabjanczyk M. W

A limitation to present theoretical roof reinforcement design methods is the inability to derive accurate and quantitative information about the roof rock condition and the action of reinforcement at various excavation stages. To obtain the information required to assess roof rock stability, detailed monitoring of the in-situ behaviour of reinforcement and roof strata is required. Reliable instru- mentation and techniques have been developed for use in underground coal mines to identify the geometry and magnitude of displacements occurring in roof rock and the forces generated in reinforcement. The use of such instrumentation allows an accurate assessment of the in-situ capability of reinforcement and the mode of reinforcing action developed. In-situ monitoring can supply data required for the practical design of reinforce- ment and assess the potential stability of current designs. The use of such data together with mine wide appraisal of rock and stressfield considerations, can allow roof reinforcement to be designed on the basis of a predicted roof Response.

Jan 1, 1986

By Sofoulis I

Recent studies in the Archaean of the Kalgoorlie-Norseman area show that the layered rocks can be subdivided into two main units, both containing basic igneous rocks and sediments. The lower unit is distinguished by the presence of acid volcanic flows and sills. In some areas, clastic sediments become coarser and,pas-s into conglomerates. This passage is accompanied by thinning of the beds. These features and their distribution suggest a basin of subsidence flanked-by areas of shallow-water deposition. -.

Jan 1, 1964

The rapid industrialisation of the world was driven by an improved ability to utilise chemical energy. Unfortunately harnessing explosive energy did not come cheaply given the hundreds of lost lives. However, the modem explosives industry has made significant technological achievements, for explosives are now considered to be both safe and extremely effective. Upon closer inspection, it would appear the key to this achievement has been the development of initiation systems. While the focus may have been originally on safety, modem developments have concentrated upon harnessing the benefits of initiation control. Before attempting to gaze into the future, it is worth reviewing some of the significant advances that have occurred.

Jan 1, 1990

By Cudmore JF, Rowlands D

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

Jan 1, 1981

Jarrah Decline is currently the only underground operation at the Boddington Gold Mine, (BGM). The mine is located 120 km SE from Perth in WA, with mineralisation hosted within deeply weathered felsic and intermediate intrusions and volcanic rocks of the Saddleback Greenstone Belt (Morley and McBride,1995). Open cut operations commenced in April 1987 with a mill throughout of 3.OMtpa. A number of upgrades have since taken place, with the oxide material throughput currently milled at a rate of 7Mtpa. In 1992 a separate circuit, the supergene mill, was commissioned to treat copper material from the open cut and now ore from the Jarrah Decline. Current throughput in the supergene plant is 30,000 tonne per month, with a varied blend according to mill requirements. Total gold production from the Jarrah Decline in 1994 was 60,000 ounces from 90,000 tonne of ore.

Jan 1, 1990

By R Dwyer

Iron ore currently mined in Australia generally requires very little beneficiation. However, depleting high-grade resources means that in the future low-grade iron ore deposits will need to be mined to meet the increasing demands of the global steel industry. Along with the increased demand, the industry faces additional pressure to reduce the environmental impact of mining and mineral processing. This has stimulated research beyond incremental improvements to conventional processing into alternative low-impact processes, including biotechnological approaches to mineral processing.Bioflotation and bioflocculation have emerged as relatively recent technologies, in which bacteria and/or their extracellular material may be used as flotation reagents (collectors or modifiers), enabling improved selective separation of minerals. The primary advantage is the production of a selective, environmentally-benign alternative to conventional flotation reagents. A biotechnological approach may also be taken in the beneficiation of high-phosphorous iron ores utilising bacteria capable of iron reduction and phosphorous solubilisation.Samples from three iron ore deposits in Western Australia were examined for bacteria suitable for iron ore benefi ciation. A number of common soil microorganisms including Pseudomonas spp, Limnobacter thiooxidans, Paenibacillus spp, and Ralstonia insidiosa were identified using culture-independent molecular techniques. A number of anaerobic species belonging to the genus Clostridium were also identified in the core samples. Selected aerobic species were enriched and isolated on high nutrient media in the presence of haematite. Several of the isolated strains showed an affinity for iron ore, attaching to haematite in enrichment cultures and further demonstrated through adhesion studies. Other isolated species such as Ralstonia isidiosa and Pseudomonas stutzeri are known to solubilise rock phosphates in soils and have potential for the removal of phosphorous from Australian iron ores.

Jul 11, 2011

Answers to many questions arising in the different phases of exploration, estimation and production of a mineral deposit, can be found in the geostatistical theory of G. Matheron. It is shown that all these questions regarding sample size, number of samples, shape of drilling pattern can be answered as soon as the continuity of the mineralization is quantitatively characterized by means of a variogram. Next a formula which gives the variance of the error associated to any estimation procedure (i.e., any method and any sampling pattern) is given. Applications to the computation of the standard error of the'mean for various sampling patterns are shown, as well as how to use the formula to simulate several possible sampling strategies and choose the best one. Altogether it is shown how to answer the often heard question, "what happens if such and such sampling procedure is used?", rather than giving an hypothetical "optimal" solution.

Jan 1, 1976

By Isobe K, Muchi I, Hsieh YS

Theoretical and experimental studies have been made-to clarify the physical and chemical behavior of the tuyere combustion zone of blast furnace. Gas streamlines around this zone were visualized by the use of the two-dimensional equip- ment. Close agreement between the observed stream- lines and the calculated ones is found. The three- dimensional experimental studies have revealed that there exists a so-called dry zone in the neighbor- hood of the raceway and the trickling liquid be- haves approximately like a continuum. A kinetic model is develdped to describe the behavior of coke combustion in the tuyere zone. The model is based on the reaction kinetics, the differential balances of heat and mass, and the mechanics of gas flows. Regarding-the-axial distribution of gas composition in the tuyere zone, good agreement is obtained be- tween the model prediction and the data observed in a working furnace by the other investigators. Cal- culated results-show that the maximum consumption of coke occurs at the intermediate region of the raceway. For the blowing of oxygen-enriched or high -humidity blast, the position at which the maximum consumption of coke occurs is shifted toward the tuyere nose. Similar effect is found when the par- ticle diameter of coke in the tuyere zone is de- creased. The solid flow pattern around the tuyere combustion zone was visualized by the use of the two-dimensional equipment in which the sublimation of dry ice particles in front of the tuyere was

Jan 1, 1981

By Lee H. G, El-Rahaiby S. K

The literature relating to reduction of sulphides by carbon using lime as sulphur-absorbent is reviewed. A stage-wise thermodynamic model is employed to evaluate the practical feasibility of the direct reduction smelting of galena (PbS) concentrates with a carbon reductant in the presence of lime; a coke-rate of 65 kg/ton Pb is predicted by the model. The experimental data on the reduction of PbS:4CaO:4C mixtures under nitrogen were correlated by means of a finite difference numerical method and the values of the intrinsic rate constant I1 were derived. The results for the uncatalysed reduction are represented satisfactorily with log I1 = 1.247(±0.522) - 5540(±610)T-1.The catalysed PbS:4CaO:4C mixtures contained 2.5 wt% of ternary (K, Li, Na)2CO3 catalyst. For the catalysed reduction it was found that log I1 = 3.981 (±0.301) -7790(±353)T-1, where I1 (in both relations) is expressed in moles.(g.C.)-1.atm-1.s -I. The catalytic enhancement faclor was found to be quite large in the 1068 to 1262°K temperature range investigated here.

Jan 1, 1991

By I R. F MacCulloch

Bacterial oxidation of sulfide minerals is a familiar and commercially available process to enhance gold recovery with problem ores. Pintail Systems, a Colorado, USA based company had developed bio-processes for gold recovery based on natural mineral formation and transformation in a global mineral cycle. The biological recovery of precious metals from ore involves a number of mechanisms that are dependent on the metal-mineralogical association. These processes include: partial bio-oxidation of sulfide ores; oxidation of gangue minerals exposing gold to leaching; surfactant properties of bacteria/nutrient solutions that improve wettability of ores and solution contact with leachable gold and silver; and microbial production and excretion of trace amounts of gold lixiviants, and bio-fracturing or biological alteration of ore minerals. Pintail has demonstrated enhanced recovery of precious metals during cyanide detoxification of spent heaps at the end of mine life. Biological recovery processes also have the potential to be applied to in situ mining technologies. The in situ process application could recover gold from subgrade deposits, small deposits or those ore bodies with uneconomic stripping ratios for conventional mining. In situ biomining can be accomplished at a fraction of the cost of conventional mining and leaching and does not have the environmental liabilities associated with many conventional gold lixiviants.

Jan 1, 2004

By Atalla YM

Steel rolling mill product finishing pro cesses gradually become or often already are unsuited for current production and marketing conditions. Indications are made as to what has been done to (i) rectify situations of this kind and, (ii) to reduce both product finishing time and costs. The principal features of two separate case studies are reviewed, these being (a) the finishing-end of B.H.P.'s Newcastle o.2 Merchant Mill and, (b) a mixed functions finishing yard and warehouses group (known as he Merchant Mills Loading Yard) which has been perating for a number of years. The areas in ach case are identified as a system while the arious functions, principal product streams nd processing equipment are respectively iden- ified as sub-systems and system elements. etails are given of the models used in each Sub-system dependency on the system as a le is traced by means of an information and ision analysis or by time studies and the sonableness of the system elements is deter- ed by computer programming or by simple com- ison methods. The-accumulated data is used derive improved mill finishing-end or Load Yard,functioning concepts according to pro- rules whilst at the same time considering

Jan 1, 1975

By de Lassar de Pressigny Y

IRSID has in its laboratories two experi mental counter-current reduction furnaces allo- wing the simulation of the physico-chemical conditions of reduction in any gas-solid coun- ter-current process, including the blast furnace and direct-reduction shaft-furnaces. The counter current is realized by an electric furnace mo- ving along a laboratory tube filled with the material to be tested. The reducing gas stream in the tube travels in the same direction as the furnace After reduction, twenty samples, with dif- ferent degrees of reduction and which can be related to different levels of an industrial furnace, are taken from the tube and subjected to various quality tests. Experiments were realized to determine the behaviour of various types of industrial pellets when reduced under either blast furnace or shaft furnace conditions. The results show the large influence of the reducing conditions on any pa- rameter characteristic of the quality of the pellets : reduction efficiency, swelling, cru- shing strength and disintegration.

Jan 1, 1974

By Gray N. B, Grimsey E. J

A steady state heat and mass balance simulation of the Western Mining Kalgoorlie Nickel Smelter (KNS) flowsheet was developed within the framework of the commercial software METSIM. The KNS simulation can achieve all plant setpoints through the adjustment of controlled process inputs, and provides a useful tool for the evaluation of the current flowsheet and potential flowsheet developments The simulation model and a number of applications are discussed in this paper.

Jan 1, 1991

By S van der Sluijs, M van Ende, Y Tang, A Emami

This paper presents a phenomena-based model for investigating the possibility of scrap melting in an Open Slag Bath Furnace (OSBF) for green ironmaking. The goal of this study is to enhance the circularity of the steelmaking process by utilising scrap as a green source of iron in OSBFs. The model takes into account the fundamental differences between OSBFs and traditional processes such as Electric Arc Furnaces (EAFs) and Basic Oxygen Furnaces (BOFs). The model considers three primary regions where scrap heating and melting occur: the solid feed pile, slag and hot metal. It accounts for factors such as the furnace geometry, scrap charging mechanism and specific heat and mass transfer properties of the reactor. The model was validated using literature data and was used to investigate the heating and melting behaviour of individual scrap particles under various process parameters. The study finds that the scrap melting process in OSBFs involves three stages: shell formation, shell remelting and subsequent melting of the parent scrap. The carbon content of the scrap and the liquid hot metal plays a critical role in determining the melting behaviour. Depending on the carbon concentration and temperature, the melting process can be heat transfer controlled or mass transfer controlled. The paper also examines the scrap feeding methods in OSBFs, including direct charging into the slag or charging through a feed pile. The model provides insights into the melting rate of scrap compared to Direct Reduced Iron (DRI) in OSBFs and highlights the role of carbon in this process. Overall, this phenomena-based model contributes to the understanding of scrap melting behaviour in OSBFs and provides valuable insights for optimising the circularity and efficiency of green ironmaking processes. The findings of this study can inform the design and operation of OSBFs, paving the way for increased utilisation of scrap as a sustainable feedstock in the steel industry.

Jun 19, 2024