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By B S. Petri, N T. Rouse

Underground limestone mines generally lack air pressure monitoring procedures and instrumentation guidelines. The blasting industry also lacks an applicable source for air overpressure levels that are produced by blasting operations in underground mines. This became apparent during the development of a new underground limestone mine, where overpressure levels from production blasting needed to be estimated. During the development phase of the mine, it was imperative that newly constructed underground structures be capable of withstanding the overpressure produced by blasting. Therefore, a study was conducted to (1) identify and review any published studies for data that may be applicable, (2) identify the appropriate equipment required to record the overpressure levels, (3) determine the proper procedures for setting up the equipment and recording overpressure, and (4) provide an understanding of the nature of the air overpressure in a developing mine.

Jan 1, 2014

By William Conger, Greg Schick

Grinding media consumption is a major cost variable in industrial mineral comminution circuits. Specifically, industrial SAG media consumption results from a combination of surface abrasion wear, media breakage, surface spalling and rejection size from the mill. Three main consumption rates; weight of media consumed per time, per kWh and per weight of ore ground are defined and compared. Recent industrial data has provided an opportunity to relate consumption in terms of weight of media consumed to weight of ore ground (g/tonne) and weight of media consumed per kWh of energy consumed (g/kWh) with SAG specific grinding energy consumed (kWh/tonne). Using relationships developed from this data it is possible to project SAG media consumption in future mineral comminution circuits.

Jan 1, 2014

By G. Zaitsev

In mining and mineral processing, ammonium and nitrate from residues of explosives and other sources are discharged to the aquatic environment. Nitrogenous compounds in mine water can adversely affect the aquatic environment. The aim of this work was to study the biological removal of nitrate from cold inorganic mine water at the pilot-scale in an operating underground mine. Seven-months pilot testing on biological removal of nitrate from inorganic mine water was successfully performed in denitrifying fixed-bed biofilm reactors. The feed to denitrification bioreactors contained 11 mg NO3--N/L. Methanol was added as an external carbon source to the denitrifying bio-reactor since the inorganic mine water contained only traces of organic compounds (<CODCr (50 mgO2/L). Nitrate removal reached 75 g NO3--N/m3/d with removal efficiencies above 95% at temperature below 4°C. Thus, removal of explosives-residues from cold inorganic mine water was shown in pilot-scale biofilm reactors.

Jan 1, 2014

With the advent of the First World Conference on Sampling and Blending (WCSB1) in Denmark in 2003 and the subsequent biannual meetings, together with other sampling conferences held on a regular basis, the central tenets of sound sampling practice and theory are spreading throughout the minerals industry. End-users and project houses, or groups who execute the projects, are all now better-informed about the principles of ?correct? sampling and preparation. To support this, many large mining companies now have their own in-house champion who will advise and ensure that the supply of sampling equipment is correct in terms of design and application, which further contributes to improved metallurgical accounting. The presence of a sampling champion also ensures that consistent and acceptable standards in regard to sampling practice are maintained throughout the group. This has, in turn, placed a greater degree of responsibility on the shoulders of sampling equipment suppliers, in terms of their equipment designs and product offerings, as well as applications knowledge for effective installation of equipment on client plants. This paper attempts to highlight the significant challenges that sampling equipment manufacturers often face with regard to complying with the newly understood requirements of best practice and sampling equipment design. Manufacturers invariably face issues with end-users or project houses, including project cost control, restricted headroom for samplers in plant layouts, and a lack of knowledge in certain quarters. These all have a potentially negative effect on the final outcome of a proposed sampling solution or implemented project. In reality, what is intended by all parties and what is ultimately installed are at times very different, with undesirable consequences for all concerned. Against this challenging background, there are, however, a number of instances where intent and implementation are complementary, with very satisfactory results. Keywords sampling, mechanical samplers, design, installation, sampling theory.

Jan 1, 2014

By Sydney Mantsho, Toni Streczynski, Manuel Gonzalez

"In 2013, the commissioning of the MillStar Stabilisation and FloatStar Stabilisation and Optimisation controllers were completed at the Cerro Bayo Silver (Ag) mine in Patagonia, Chile. The MillStar control system has stabilised the feed to the SAG mill as well as the density at the discharge end of the SAG mill and ball mill. The FloatStar Stabilisation and Optimisation controllers have successfully stabilised and optimised the flotation circuit to ensure consistent product quality within desired specifications.The mill feed is controlled utilising the MillStar Solids Feed controller. Additionally, the solids to liquid ratio into the SAG mill was controlled utilising the Mill Inlet Ratio controller in conjunction with the Solids Feed controller. The discharge end of the milling process is a highly interactive and complex system. The use of a Robust Nonlinear Model Predicative Controller (RNMPC) was ideally suited to control this section of the process. On the Cerro Bayo milling circuit, the RNMPC was used to control the mill discharge sump level and the primary cyclone feed density to produce a more consistent feed to the flotation circuit.Three levels of the FloatStar control system were installed, for flotation stability, concentrate flow stability as well as grade optimisation. The Level Stabiliser was used to stabilise the level control on 6 flotation banks. The Flow Optimiser was commissioned on the Rougher, Scavenger and Cleaner concentrate sumps to stabilise concentrate flow from the flotation cells. The Grade Recovery Optimiser was commissioned on the Roughers section. A number of instrumentation challenges were identified which limited the overall benefit derived from the system. Once these were addressed, the performance was optimised. The overall benefit provided by the system was observed in terms of the improvements in Ag recovery."

Jan 1, 2014

By Graeme Jameson

"In current flotation circuits it is customary to grind the whole of the mill feed to an initial size, which is determined by the liberation characteristics of the ore, and the ability of the flotation machines to float the fully liberated particles. Usually, the product of the primary mill will be ground further in a ball mill, to improve the liberation of the values and hence the product grade, before passing to rougher flotation cells. The final grind size is ore-dependent, and is a balance of factors including the relation between surface liberation and grind size, the grain size of the valuable particles within the host rock, and the feed grade. The P80 for the feed to flotation may be as high as 300 µm for free-milling copper ores, and as low as 53 µm for finely disseminated complex ores. The grinding of the feed ore requires considerable input of energy. The rate of replacement of wear components such as mill liners and media, is proportional to the energy input. The costs of these two factors - energy and wear - are usually comparable and together they form the major part of the running costs of a concentrator, and indeed, of the whole mining operation. The energy required increases as the final grind size decreases. This talk will focus on the reduction of milling costs that could be achieved, using a fluidized bed flotation technology that can give high recoveries at coarse particle sizes. A number of different circuit designs will be presented, using the new technology. Calculations show that reductions in the running costs of a mine and associated concentrator of the order of ten to twenty percent could be achieved."

Jan 1, 2014

By Xin-liang Gao, Qing Li, Gui-qin Fu, Duo Jin, Miao-yong Zhu

"Optical microscope together with alternative wet-dry cyclic accelerated corrosion tests and XRD, SEM were employed on bridge weathering steel samples with different Mn and Ni contents which were vacuum induction melted and rolled to study their effects on the microstructure and rust layer evolution in er' containing condition. The results show that the microstructure is mainly ferrite and pearlite when Mn and Ni contents are 0.75 %, 0.42 %, respectively. Both the increase of Mn and Ni contents will make pearlite disappear while granular bainite appear, meanwhile the grain size decreases. With the increase of Mn content, the corrosion rate decreases in the initial stage, but the effect becomes little in the later stage. The increase of Ni not only improves the corrosion resistance of steel base at the initial stage but also hinders the tendency of further corrosion. As Mn content increases, a-FeOOH contents in rust layer decreases. With increase of Ni content, the content of a-FeOOH in the rust increases while that ofy-FeOOH decreases.IntroductionWeathering steels had been ~radually applied in manufacture of bridges owing to reducing the corrosion rate remarkably [I- l .Good weldability was needed for high performance bridge weathering steels. Since carbon was thought to be bad for weldability, low carbon content steel was adopted and Mn was added to amend the mechanical strength loss. Some scholars[6, 7l believed that Mn was beneficial for increasing corrosion resistance performance of the steel in marine atmospheric environment. Some scholars [S, 9l thought that Mn had little effect on corrosion resistance in marine atmospheric environment. Presently, the effect of Mn on bridge weathering steel in marine atmospheric environment still remained poorly understood. Ni was considered to be beneficial for increasing corrosion resistance performance in marine atmospheric environment [JO-l4l However, the high cost limited its application range. What would bring to the rust and corrosion by decreasing Ni content needed further research.Most researchers assumed that microstructures only affected the corrosion behavior of bare steel. But the study of Guo et al. P5l showed that the homogenous microstructures were beneficial for the corrosion resistance of steels. The effect of Mn, Ni content change on microstructure and microstructure on corrosion still remained poorly understood. In the present work, the effect of Mn and Ni on the microstructures of steel matrix, as well as the microstructures on the rust and corrosion was investigated."

Jan 1, 2014

By Turgay Gurun

"Digital simulation can be used as an analytical tool to optimize the design of crushing plants without need for large-scale experimental programs.General mathematical description of a crushing operation permits the simulation of a crushing plant flowsheet under various operating conditions. The process model encompasses multistage open- and closed-circuit crushing of hard and soft rock. Crushing balances are analyzed in the light of crusher and screen performance and a comparison of different closed-circuit arrangements is made in terms of process and layout criteria.The simulation model allows comparison of process alternatives to be made in terms of equipment selection and capital and operating cost estimation. It thus provides the pertinent practical information to maximize plant efficiency, and to minimize expenditures in such items as equipment, structures, power consumption, and so on."

Jan 1, 2014

By William Reisz

Managing the blast site at almost any operation can be a daunting task. There are so many details that must be observed, understood, and acted upon. It goes without saying that there are no two locations that have the exact same challenges and concerns. The level and the extent of these challenges can vary widely.

Jan 1, 2014

By A. S. H. Kabir, I-H. Jung, J. Su, S. Yue, M. Sanjari

The final mechanical properties of wrought magnesium alloys are mostly controlled by microstructure and crystallographic orientation or texture. In common magnesium alloys, grain coarsening occurs during annealing process and formation of undesirable basal texture cannot be changed markedly. The aim of this work is to investigate the effect of static precipitation on microstructure and texture evolution during annealing at 250 °C after warm rolling of Mg-Al-Sn alloy. Mg-3Al-3Sn (wt. %) alloy has been designed using thermodynamic modeling software, FactSageTM, based on forming target stable and incoherent Mg2Sn precipitate within the industrial deformation temperature range. Microstructures and precipitation were investigated by optical and scanning electron microscopes and macro-texture was measured by X-ray diffraction (XRD) techniques. It was found that static precipitates form in a large scale at the recrystallized grain boundaries and retards the grain growth during annealing. Slight weakening in basal texture was also observed during annealing.

Jan 1, 2014

By Kyle P. Flynn, Frank J. Hrach, James D. Bittner

ST Equipment & Technology, LLC (STET) has developed a processing system based on tribo-electrostatic belt separation that provides the mineral processing industry a means to beneficiate fine materials with an entirely dry technology. In contrast to other electrostatic separation processes that are typically limited to particles greater than 75µm in size, the triboelectric belt separator is ideally suited for separation of very fine (<1µm) to moderately coarse (300µm) particles with very high throughput. The high efficiency multi-stage separation through internal charging/recharging and recycle results in far superior separations that can be achieved with a conventional single-stage free-fall tribo-electrostatic separator. The triboelectric belt separator technology has been used to separate a wide range of materials including mixtures of glassy aluminosilicates/carbon, calcite/quartz, talc/magnesite, and barite/quartz. An economic comparison of using the tribo-electrostatic belt separation versus conventional flotation for barite / quartz separation illustrates the advantages of dry processing for minerals.

Jan 1, 2014

By T. Gerritsen, R. MacRosty, R. Pula

For several years Hatch has been installing fibre optic temperature sensors on the copper cooling elements of smelting furnaces to improve monitoring capabilities in critical locations. The metal/matte tapblock is a key area to monitor in the furnace as it undergoes severe wear from the molten material repeatedly drained through it. The high wear rate around the tapblock means downtime is necessary to perform refractory repairs. A good understanding of the tapblock condition allows the operation to maximize safety and production; consequently the metal/matte tapblocks have been the focus of this study. Fibre optic technology allows the installation of numerous sensors in locations that are very sensitive to refractory thickness, thereby providing information previously unavailable with traditional measurements. The transient nature of the thermal response to tapping and the three-dimensional geometry of the tapblock confound the interpretation of refractory thickness from temperature measurements. This paper focuses on the analysis of both plant data and thermal modelling simulations and details the progress made in relating the temperature measurements to the refractory thickness in front of the copper tapblock.

Jan 1, 2014

By D. Z. Wei

Amine collectors with different structures and length of carbon-chain have been widely used in oxide minerals flotation. In this paper, we synthesized one kind of binary amine, N-dodecylethyl- enediamine, and studied its flotation performance. From the results, we can see N-dodecylethylenediamine which has excellent frothability, is a new type of chelating surfactants. And it also has fine catchability to quartz and hematite. The recoveries of quartz and hematite increase with the augment of N-dodecylethylenediamine concentration. When the dosage of collector reaches 100g/t, the recoveries of quartz and hematite achieve 95.30% and 87.89% respectively. Meanwhile, the influence of pH on the flotation recovery of hematite is studied and test results showed that, as pH increases, the flotation recovery rises until pH=9. And the recovery reaches its maximum in alkalescence. The collector has better flotation capability to quartz than to hematite. And the maximum recovery of quartz is gained in alkaline media, which reaches 97.87%. Finally, the flotation mechanism of N-dodecylethylenediamine is discussed through the measurement of infrared spectroscopy.

Jan 1, 2014

By Wilky Desrosin, Alicia E. Ares, Carlos E. Schvezov

"In the present research the horizontal directional solidification Zn-Sn alloys (Zn-4wt. %Sn, Zn- 6wt. %Sn, Zn-10wt.%Sn and Zn-30wt.%Sn) was carried out by extracting heat in two opposite directions. For this purpose, ceramic molds, a muffie, a horizontal furnace with two heat extraction systems at the ends, a measurement, acquisition and recording temperature system, eight K-type thermocouples and an electronic recorder were used. The main parameters involved in the columnar-to-equiaxed transition, CET, were: the moment of start and end of solidification at each position under consideration, cooling rates, the average temperature gradients and critical temperature gradients at the CET, the average speed of liquid and solid interphases left and right, advancing in opposite directions. Also, solidification kinetics was found to be different between horizontal solidification two-way heat extractions, with preliminary results of the vertical unidirectional solidification. In the solidification experiments, the velocity and accelerations of the liquidus and solidus interphases usually occurs at the end solidification zone of the samples.IntroductionSolidification of metal alloys, which starts in the external equiaxed region (chill), results in two basic types of structures in a single solidified alloy sample: columnar and equiaxed. The presence of both structures indicates the occurrence of the colunmar-to-equiaxed transition phenomenon[!].Studying the colunmar-to-equiaxed transition, CET, is of great technological interest for the evaluation and design of the mechanical properties of the solidification products. To this end it is necessary to understand the mechanisms by which it occurs. As found in previous studies [2-5], the CET occurs by competition between columnar and equiaxed growth. Mainly is controlled by the parameters of casting, such as the alloy composition, the density of the present nuclei in the liquid, the cooling capacity of the metal I mold, and the degree of convection in the liquid [7-10]."

Jan 1, 2014

By J. K. Williams, M. P. Wells

"As part of the planning system at each division of Nchanga Consolidated Copper Mines, Limited, the Mine Planning Department is required to produce a detailed production schedule for each shaft.Because of the difficulties in producing a schedule which satisfies all the mining constraints, and because of the large clerical effort involved, the full range of possible schedules can never be considered.It has been found possible to produce a schedule using linear programming which satisfies the majority of the many varied mining constraints. Computer programs have been written to enable the mine planning department to use this mathematical system without assistance.The system has a large degree of flexibility to enable the planner to include conditions which cannot be incorporated readily in the linear program. This system permits the more efficient production and evaluation of schedules and reduces the amount of clerical effort."

Jan 1, 2014

By Y. B. Zhang

China is rich in iron ore resources, but most of these ores are low-grade, polymetallic and refrac-tory ones. Furthermore, with the rapid development of chinese iron & steel industry, the comprehen-sive recovery of these ores is becoming more and more important. The tin, zinc-containing complex iron ores are typical polymetallic and intractable ones, and great reserves of them are found in China. At present, they have not been efficiently utilized. In this paper, based on the investigation of basic physicochemical properties of the tin, zinc-bearing iron concentrates, taken from a mineral processing plant, the mineralogy reason that these concentrates are so intractable and refractory is found out, using advanced microscopic testing methods, such as optical microscope (OM), Scanning Electronic Microscope (SEM), X-ray diffrac-tion (XRD), etc. It is found that the symbiotic relationship of iron, tin and zinc metallic minerals are very complicated, and magnetite in the concentrate is closely symbiotic or enwrapped by fine cassi-terite and sphalerite. So it is difficult to separate tin and zinc completely from the iron concentrates by simple regrinding and physical separation method. This investigation provides theoretical guid-ance for developing new approaches for utilizing these concentrates.

Jan 1, 2014

By Michael Nicol

A quantitative description of hydrometallurgical operations depends primarily on an understanding of the kinetics of the chemical and physical processes that take place in such operations. This paper will review the current status of kinetics in hydrometallurgy in terms primarily of the author’s experience in diverse unit operations. A distinction will be made between the popular use of models based on limited kinetic data and mechanisms which reflect the actual elementary chemical or physical steps involved in an overall process. Several examples will be used to illustrate this distinction. The proliferation of published papers of declining quality has resulted in the bequest to later researchers of outdated and often incorrect conclusions by a process that is often difficult to reverse. Some examples of these mysterious concepts will be examined and hopefully reversed. Finally, several examples will be given that identify significant gaps in our understanding of the kinetics of important processes that remain unresolved.

Jan 1, 2014

By Adriaan van Seters

"Abstract The content of Eurocode 7 – Part 1 and Part 2 – with respect to piled foundations is outlined. The important role of pile testing is presented and the derivation of the characteristic value of pile bearing resistance is explained. Recommendations for the use of correlation factors are given. The ongoing work of the Evolution Groups on piling is to prepare a revision of Eurocode 7 after 2019. Future topics and changes are highlighted.General outline of pile design by Eurocode 7In his paper for this conference Frank (2014) outlined the various aspects of standardisation for pile foundations, which involves Eurocode 7 as leading for pile construction in Europe. Standards for pile testing and execution of piling works were established in the last 15 years.This paper focuses on the design of piled foundations according to the design code Eurocode 7, which consists of 2 parts:EN 1997-1 Geotechnical design - Part 1: General Rules (CEN, 2004);EN 1997-2 Geotechnical design – Part 2: Ground investigation and testing (CEN, 2007) In Eurocode 7-1, Section 7 – Pile Foundations - deals with the design of piles. The safety concept for pile design is given in Section 2 – Basis of Geotechnical Design - for the three Design Approaches.In Section 7 presents the design of piles according to four methods:1. Results of static load tests2. Empirical or analytical calculation methods3. Results of dynamic load tests4. Observed performance of a comparable pile foundation.Guidelines for the ground investigation for piles is provided in Eurocode 7-2, Annex B.3. In the Annexes of Eurocode 7-2 examples of analytical methods to determine the bearing resistance of a single pile based on the results of various ground investigation techniques are given. Thus calculation models are presented based on design using the results of Cone Penetration Tests (D.6 and D.7) and Pressuremeter Tests (E.3). The Annexes of Eurocode 7-2 are informative.For the interpretation of Eurocode 7, reference is made to Frank et al (2004) and Bond and Harris(2008)."

Jan 1, 2014

By Collin Bartlett, H. Storch

"Modern metallurgical processes operating with oxygen enriched air, such as the Outotec Flash Smelter and Flash Converter, generate very concentrated SO2 off-gas, which in combination with Outotec sulphuric acid plant technology allows the production of high pressure steam to be used for power generation. Outotec combines well proven technology of sulphur burning plants for this purpose with metallurgical plants.The application of Outotec’s proven LURECTM process enables processing of SO2 gas of up to 25 vol.-%. This process maximizes the energy recovery from the SO2 oxidation at a suitable high temperature level which can be turned into high pressure steam. The application of the Outotec HEROSTM heat recovery system enables the generation of low pressure steam from the absorption energy released at the intermediate absorption step. Additionally, energy is also recovered in the acid coolers for boiler feedwater pre-heating.The concept of integration of high and low pressure steam in combination with the pressurized operation of the boiler feedwater deaerator, thus heating up the boiler feed water to temperatures around 160…170°C, enables indirect transfer of low pressure steam (for deaerator operation) into more valuable high pressure steam, which improves the degree of heat recovery. This is the characteristic of Outotec’s HEROS+TM process.The increased generation of high pressure steam will in turn enable the generation of more electricity when compared to a standard traditional sulphuric acid process."

Jan 1, 2014

By G. R. Forbes

Flotation froth machine vision systems provide consistent real-time measurements pertaining to the state of the flotation cell being monitored. Typical measurements include froth velocity, froth colour, froth texture and froth stability. This paper presents the results from test work conducted on the molybdenite rougher circuit at the Kennecott Utah Copper Concentrator during February 2006. Machine vision results show that it is not possible to accurately determine bubble size distribution information for the molybdenite froth, despite using state-of-the-art methods. Instead, it is necessary to make use of texture measurements to classify the various different froth states. Numerous combinations of texture measurements and classifiers are used to determine the best combination. Results show that the Fourier ring based texture measurements perform the best when both K nearest neighbour and Gaussian mixture model classifiers are used. The concentrate grade of the flotation cell is modelled using combinations of froth velocity and froth texture descriptors. The results show that by using a linear combination of these descriptors rather than either one by itself it is possible to account for a much larger percentage of the variation observed in the concentrate grade data. Adjusted R2 values of 92% and 84% are achieved when modelling the copper and the molybdenite concentrate grade respectively.

Jan 1, 2014