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By Behdeen Oraee

Constructing tunnels underground is generally described as a high-risk activity because conditions in the surrounding area tend to be unpredictable. This would and can create unique dangers in every situation. It is important to gain a deep understanding of the risks associated with tunneling in order to reduce the likelihood of their occurrence and severity of their consequences should they occur. For this to be achieved, different risks should first be evaluated and ranked according to their relative importance and criticality. The Amir Kabir tunnel is considered one of the most dangerous tunnels in Tehran, Iran, in terms of the risks involved in its excavation and their potential consequences. In particular, part T4 of the tunnel passes through a zone of different strata and also a compound of various soils. This paper studies part T4 of the Amir Kabir tunnel from a risk analysis and risk management point of view. In doing so, factors increasing total cost, causing delay in the project completion time, decreasing the operation rate and downgrading project quality were identified and ranked according to their importance using the aggregate primary index risk method. For this purpose, a comprehensive questionnaire was designed and completed by tunneling experts. By responding to the questionnaires, the experts determined the relative likelihood of occurrence of the studied factors and their potential consequences. As a result, the experts suggested several alternatives to reduce the risks involved in this particular study. Moreover, the experts completed new questionnaires whilst taking into account different alternatives. In the next step, the risks before and after applying the alternatives were compared. As a result of performing the said analyses, it was concluded first that the aggregate primary index risk is an effective tool in identifying the risks involved in such projects. Second, it was concluded that, by taking into account different alternatives when analyzing and ranking the risks, severity of the said risks can potentially be reduced. Also, by considering such matters when analyzing tunneling risks, the projects? efficiency can greatly increase as a result of reducing risks that threaten financial and human resources. The approach introduced in this paper, together with the methodology described, can be adopted by the mining design engineer in all similar situations. They will be of particular advantage in such methods as room and pillar mining, where the number of similar tunnels required is high.

Jan 1, 2014

By S. J. Ma

With the very effective depressant and collector developed by China Bluestar Lehigh Engineering Corp (hereinafter referred to as LEHIGH), satisfied results are obtained from laboratorial beneficiation tests on phosphate samples from Karatau, Republic of Kazakhstan by the direct flotation process. In this paper the effect of single factors on performance of flotation is studied and their applicable ranges are proposed. The final test results are described as follows: As the feed contains 23.20 % P2O5, and 3.96% MgO, a phosphate concentrate assaying 29.77%P2O5 and 1.54% MgO is produced, and the P2O5 recovery in concentrate is 88.28%. The beneficiation tests make it possible to simplify existing technology with fine grinding-desliming, followed by reverse & direct flotation system and consequently improve the concentrate grade and recovery for the future beneficiation plant

Jan 1, 2014

By E. Burdukova

This paper explores the relationship between the rheological behaviour and mineralogical nature of three different natural ore types. Rheological measurements performed here on Platreef, Kimber-lite and Norseman-Wiluna ores are correlated with the variation of phylosilicate mineral content in these ores and the corresponding physical properties of selected phylosilicate mineral groups. Preliminary results show that the clay mineral group (talc) has the least effect on both Bingham yield stress and viscosity of the three ore slurries tested, whereas the serpentine mineral group has a dramatic increasing effect on the Bingham yield stress especially at very low solid volume fractions. The Bingham viscosity of the mineral slurry appears to be the most influenced by the presence of the swelling clay mineral group (smectite). Significant increases in either Bingham yield stress or viscosity due to elevated contents of these problematic phylosilicate mineral groups are likely to cause negative effects on the processing and manageability of mineral slurries but it is unclear which is likely to have a more detrimental effect.

Jan 1, 2014

The University of New South Wales (UNSW Australia) has been a world leader in the development of innovative virtual reality technologies over the last 15 years. AVIE (Advanced Visualisation and Interactive Environment) was developed by iCinema as a collaborative venture between UNSW?s Faculties of Engineering and the College of Fine Arts. This is the world?s first 360°-surround, virtual reality (VR) stereo projection theatre system. The School of Mining Engineering at UNSW Australia has developed 18 different virtual reality modules aimed at mine safety training and mining engineering education. These modules are being regularly used in both the mining industry and the university. The School of Mining Engineering is continuously involved in the development of different modules. Research is also currently being conducted on the implementation of other technologies into this environment. Artificial intelligence (AI) and fuzzy logic are tools that the authors would like to consider implementing in future module development. This paper will review current research in both these areas and consider options for applying these technologies.

Jan 1, 2014

By Andrzej Luszczkiewicz, Alicja Bakalarz

The application of new collectors is considered to improve the beneficiation of Polish sedimentary complex copper ores from the Legnica-Glogow Copper Basin (SW Poland), the upgradeability of which becomes more difficult because of ores grade declining. One group of potential collectors is represented by nonpolar reagents. According to the available literature data, only selected sulfides float in the presence of the nonpolar liquids. The paper presents laboratory scale flotation results for the main sulfide minerals occurring in the Polish copper ores applying either thiol (potassium ethyl xanthate) or nonpolar (aqueous emulsion of n-dodecane) collectors. The investigated feed contained 1.91 % Cu in the form of sulfide minerals such as bornite, chalcopyrite, chalcocite and covellite. Other sulfide minerals including galena, pyrite and sphalerite were also present in the samples. Several flotation tests with various doses of each collector were conducted. Mineralogical analyses of flotation products were carried out and the results compared. A comparison of the results indicated that all sulfide minerals floated well with high recoveries ranging from 91 % to 99 % in the presence of the thiol collector. The use of the nonpolar collector provided results in flotation of sulfide minerals with different terminal recoveries from 61 % for chalcopyrite to 100 % for sphalerite. The most significant differences in flotation in the presence of both types of collector under various conditions of upgrading were observed for chalcocite, chalcopyrite and covellite. Similar flotation results were observed for sphalerite and galena for both collectors. The studies confirmed selective flotation of sulfides from the copper sulfide ores of the Legnica-Glogow Copper Basin in the presence of nonpolar collectors.

Jan 1, 2014

By C. A. Ozturk

The compressive strength of rock (sc) has an important effect on design of structures in rock engineering. Compressive strength can be determined in the laboratory using the uniaxial compressive strength (UCS) test. Some other index tests, such as the point load test, are also used, particularly when suitable samples for UCS are not available. The quantification of rock texture has introduced a new method in rock engineering for estimating the mechanical and physical properties of rock materials from microscopic investigations. The aim of this study is to quantify rock texture to estimate rock strength from the texture coefficient (TC), which is determined from a statistical assessment of thin section images. Rock texture is quantified by twelve different images from a single thin section to increase the reliability of texture analysis. A data-set is prepared to investigate correlations between TC and sc. The statistical correlations are computed after classifying of the rock samples based on their lithology as well as grain features. Equations derived based on the results of this study are used to predict the approximate value of compressive strength from the texture coefficient. This method is particularly useful for preliminary studies in rock engineering projects prior to detailed site investigation.

Jan 1, 2014

By X. J. Lu

Purified Na-montmorillonite samples were used as the starting materials to prepare organically modified montmorillonites (OM), and a series of OM samples were prepared by intercalation of al-kyl quaternary ammoniums with different alkyl chain length. The interlayer spacing (d001) of the OM was determined by small angle X-ray diffraction and its gelating performance was characterized by measuring the viscosity of OM/dimethylbenzene mixture. The effects of alkyl chain length, dosage of alkyl ammonium, intercalation duration and layer charge of the starting material on the OM structure and gelating properties were investigated. According to the results, the adsorption quantity of the alkyl ammonium is dependent on the hydrocarbon chain length, the dosage of the alkyl ammonium and the retention time. The adsorption quantity of the alkyl ammonium increases with the chain length and the dosage, and extra adsorption more than the CEC of the montmorillonite sample was observed under the dosages of more than 1.3 CEC. The interlayer spacing (d001) of the OM shows a dynamic variation with the dosage and the retention time, and super interlayer spacings greater than the length of the alkyl ammonium were observed under larger dosages and shorter retention times. However, the gelating performance of OM does not follow the variations of the adsorption quantity of alkyl ammonium, an optimum viscosity value of OM/ dimethylbenzene gel was observed with the moderate adsorption of the alkyl ammoniums. Furthermore, the layer charge plays an important role on the gelating performance of OM. The OM synthesized by the starting material with lower layer charge shows better gelating performance in the dimethylbenzene solution.

Jan 1, 2014

By Fiseha Tesfaye, Pekka Taskinen

"Thermodynamics of the equilibrium phase assemblage Ago_9Cul.lS-Cu2-xS-CuS have been studied by an EMF -method. The ternary phase was synthesized from the pure Cu2S and Ag2S in vacuum furnace at high-temperature and mixed with appropriate compositions of Cu2S and CuS to form the cathode electrode. The EMF-measurements were made on the solid-state galvanic cell Pt(-) I Ag I RbAg,ils I Ago9Cu1.1S-Cu2-xS-CuS I Pt(+), in a temperature range from 316 K to 498K.Based on the measured EMF vs. T relations, thermodynamic functions (?fG° , ?fS and ?fH°) of stromeyerite (Ag0.9Cu1.1S) in equilibrium with Cu2-xS and CuS have been determined. The obtained experimental values have been compared with the available literature values. New experimentally determined thermodynamic properties of the solid solution (Ag,Cu)2Sss were determined.IntroductionDue to intense mining of high grade sulfide ore minerals in the past, recently, the available sulfide ores are poor in metals and becoming increasingly complex; such that, the production of high grade metals by the conventional pyrometallurgical processes is compromised. Consequently, smelters are in need to modify their operating flow sheets and strategies for processing more complex feed materials economically, while meeting the strict environmental regulations. To make the appropriate modifications, accurate thermochemical data of phases and phase assemblages which exist in these complex ore minerals are essential.Silver-bearing sulfosalts are encountered in ore minerals for the production of base metals and are common sources of silver. Among the silver-based sulfosalts, stromeyerite (Ag0_9Cu1.1S) is relatively common ore mineral in most hydrothermal vein and replacement deposits [1]. Recently, the ternary chalcogenide compound Ago0.93Cu1,07S has been studied, intensively, due to its high ionic conductivity and gradual disorder in the sequential phase transitions [2]. Therefore, accurate knowledge of the thermodynamic properties of stromeyerite has considerable fundamental and practical interest in many aspects of extractive, chemical and physical metallurgy."

Jan 1, 2014

By Xiaojing Li, Yueyuan Zhou, Shengyao Ma

The paper presented the acnalysis of field intensity of rare-earth permanent magnet with high BH product and the research of magnet configuration with narrow pole pitch on open magnet surface, both using ANSYS. The possibility to separate micro-disseminated feebly magnetic minerals by improving the field intensity and the capture line distribution rate on open magnet surface were verified. The research on the method to pile up magnets to increase peak value of field intensity on the open magnet to 1.0T was done through correlation analysis between shape and dimensions of magnetic material and field intensity. And the research on technology method to improve capture line distribution rate in the separating field to 1.25×105/m2 was done through optimization design of magnet configuration of the open magnet with narrow pole pitch. Laboratory tests were performed with hematite sample from ore dressing plant such as Hainan mine, Qidong iron ore, etc. The separation results acquired were at the same level as using the electromagnetic separator, verifying the possibility to separate micro-disseminated feebly magnetic minerals with open magnet. The research suggested a new idea about the development of magnetic separator with high efficiency and low costs to separate feebly magnetic minerals and non-magnetic gangues.

Jan 1, 2014

By H. D. Yu

In this paper, an evaluation about the process mineralogy of the rich iron mine in Mongolia with comprehensive methods is given; this provides foundation of the comprehensive recovery of iron and cobalt in the ore. The research shows that the iron?s grade is 61.23%, Co?s grade is 0.02%, the ore is rich iron ore and its Co content also reaches border mining grade. For the ore, if want get high grade iron concentrate powder, must identify the mineral composition and the occurrence of iron and take into ac-count the recovery of Co content as associated resources. Chemical phase analysis results show that 86.35% of iron exists in magnetite, which means that the theoretical recovery ratio of iron is close to 86%. Minerals spectrum analysis confirmed that the magnetite containing a small amount of Mg, Al, and other impurities, the actual iron minerals to 70.28%, which means that theoretically iron grade iron concentrate only close to 70.28%. Based on the result of iron chemical phase analysis, by investigating the liberation of sulfide minerals and gangue, the recovery index of iron can be forecasted, when grinding fineness is 35%, 45%, 55% and 65% bellow 0.074mm,theoretical content of Fe in iron concentrate separately is 67.71%,67.88%,68.78%,and 69.43%,accordingly the theoretical recovery of Fe is 87.38%,87.05%,86.92% and 86.63%. From the perspective of process mineralogy, the forecast mineral beneficiation indicators show that the ore is easy sorting ore, iron processing operations have higher recovery rate, but wants sorting of high-grade iron ore concentrate still need appropriate grinding fineness. Furthermore, associated element Co, existing mostly in pyrite and pyrrhotite, is valuable in the ore. Pyrite and pyrrhotite have ideal liberation under grinding, so cobalt can be easily enriched in sulfide concentrate.

Jan 1, 2014

By I. Kairyakov

The present paper is about the restoration of the molybdenum production in the floatation plant of Ellatzite-Med AD in Bulgaria. The process, based on a working design, includes the construction of a new floatation molybdenum section in the existing molybdenum department of the Floatation Plant using the so called Vemco inert-gas floatation machines, made especially for the molybdenum floatation. While in the ordinary floatation machines, block impellers create suspension of the air, sucked from the atmosphere with the slime particles of the concentrate, which creates conditions for oxidizing the reagent, Vemco inert-gas floatation machines are covered with hermetic lids and the air inside the chamber is used. The technology, suggested by Geotechkoper Ltd. for making the working project, employs special machines from Dor Olliver Aimco, suitable specifically for molybdenum floatation in order to reduce the oxidizing of the reagent sodium hydrosulphate. Also the transport of the chamber product is done in hermetic conditions as the molybdenum flotation is done in two floatation rows and refining operations 3 to 8 are placed in the second row. Thus in the basic molybdenum floatation together with the first and second refining operations, which are hermetically closed, an ambient condition with low content of oxygen is created, that is about 8% for oxygen and about 92% of nitrogen, in which the oxidizing process is extremely reduced. This in turn results in reducing the consumption of the reagent depressor ? sodium hydrosulphate. In that way there is an improvement of the economical indices of the molybdenum production.

Jan 1, 2014

By P. Woo, N. Brodusch, R. Gauvin, H. Demers

The scanning electron microscope (SEM) was primary developed for imaging applications. With the introduction of the Si(Li) energy dispersive spectrometer (EDS), simultaneous imaging and x-ray microanalysis became possible. However, long working distance and high current were needed because the position and small solid angle of the EDS detector. The high spatial resolution is generally obtained at short working distance with a SEM. Unfortunately x-ray microanalysis is never performed in the best imaging conditions. The annular silicon drift detector system is inserted below the objective lens which gives a higher solid angle (up to 1.3 sr). In consequence, a lower working distance and probe current can be used. An improved spatial resolution becomes possible during x-ray microanalysis. With this x-ray detector installed on a cold-field emission scanning electron microscope, quantitative x-ray microanalysis with high spatial resolution at low beam energy and low current becomes possible with the possibility of using the various different type of imaging at the same time. Also, since the count rate can be as high as 1,500 kcps, which lowers significantly the detection limit of elements as well as the minimum feature sizes of different phases that can be distinguished.

Jan 1, 2014

By H. J. Liang

In this study, zeta potential and contact angle measurements of pyrite before and after interacting with Thiobacillus ferrooxidans are carried out to investigate the changes in its surface properties. The results show that, after pyrite interacting with Thiobacillus ferrooxidans and its metabolite, the surface electricity of pyrite changes obviously, resulting in a notable shifting of isoelectric point to lower pH value, but the contact angle varies little. Bacterial protein plays the most important role in the interaction. This work is helpful to disclose the mechanisms of Thiobacillus ferrooxidans de-pressing pyrite flotability.

Jan 1, 2014

"The Ernest Henry Mining (EHM) ore body is an iron oxide copper gold deposit with an average grade of 1.1 percent copper, 0.5 g/tonne gold and 22 percent magnetite. At the end of 2009, EHM converted the ball mill media charge from forged steel to high chrome media. At high pH values (above 10.5), forged media is passivated, so as the pH of the system drops the media corrosion rate increases and floods the system with corrosion products, affecting flotation. As the high chrome media is much more inert, pH has less of an effect on copper flotation response. Given this, the pH in the roughers was dropped from 10.6 to 9.6 and it was found that there was a slight increase in copper recovery and no statistical change in either the rougher or final copper concentrate grades for copper and gold. With the reduction in pH, there was a noticeable reduction in lime usage from 0.85 kg of lime per tonne of ore processed to 0.55 kg/t. This reduction in lime is equivalent to approximately $700,000 per annum at current production rates.INTRODUCTION The Xstrata Copper Ernest Henry Mine (EHM) is situated 38 km north east of Cloncurry, Australia. The mine began as an open-cut operation in 1998 and transitioned to a multi-sourced operation in December of 2011, utilising ore from the newly completed underground mine in addition to ore mined from the Mount Margaret Mining operations. EHM produces a combined copper gold concentrate containing 25 000 t of copper and 35 000 oz of gold annually, utilising a three stage grinding circuit along with a four stage flotation circuit. In addition to this EHM also produces 1 000 000 t of magnetite concentrate annually via a further grinding and three stage magnetic separation circuit. Based on metallurgical test work performed by Magotteaux between 2002 and 2008, the step to change from forged steel media to 18 percent chrome media was taken in 2009 in a bid to alter the pulp chemistry to improve the flotation performance in the plant (Greet, Kinal, Twomey, & Peatey, 2010). This plant trial resulted in: • Increased dissolved oxygen levels within the pulp, • A ball mill discharge Eh shift of 25 mV to more oxidising pulp potentials, and • An EDTA extractable iron percentage reduction. These improvements in the pulp chemistry resulted in an increase of 1.7 ± 0.6 percent in copper recovery and an increase of 2.9 ± 1.7 percent in gold recovery. As the plant trial using high chrome media was successful, the use of the media was adopted as the standard for the ball mill. This implementation opened the door for further process improvements around the flotation circuit."

Jan 1, 2014

"Chairman: Professor J. de V. Lambrechts Rapporteur: Mr R. HempPapers:Computer-aided design of a flash smelting installation by M. A. T. Cocquerel, R. T. Gates and L. A. GreenPlanning of mine ventilation by E. U. Reuther and A. DohrnenCoal mine ventilation systems in the U.S.A. by R. Stefanko and R. V. Ramani Heat flow models in ventilation planning by A. J. Dickson and A. M. StarfieldThe first of the papers in the session dealt with a flash smelter installation, while the remaining three papers dealt with mine ventilation. In view of this the Chairman proposed that the paper on flash smelting be introduced and discussed first, after which the remaining three papers would be introduced followed by discussion on all three.Dr Cocquerel, who presented the first paper, used some typical flow diagrams to illustrate the process and stated that the program considered only steady-state operations and did not take into account the dynamical changes. Subjective judgment was necessary for the preparation of input data and some degree of user appreciation was required.Dr Cocquerel said that no work bad yet been done on an optimization program, but that this was being considered. Such a program would require a large amount of physical and chemical data which were not yet available. The variables to be optimized were the energy and material consumptions and the loss of metal in the slag.The Chairman opened the discussion by asking Dr Cocquerel if he could give a brief description of the flash smelting process for the benefit of those not familiar with the subject. Dr Coquerel replied that in the Outokumpu process con¬centrates were injected directly into the furnace, and that the process was somewhat analogous to flash distillation or evaporation processes, but was perhaps closer to the burning of pulverized fuel.The process had two distinct advantages. First, the heat evolved in the smelting reaction was used to heat the furnace, which resulted in less fuel consumption, and, second, the effluent gases were cheaper to treat than the effluent gases from other pyrometallurgical processes. This was important particularly in view of the current interest in pollution problems.Mr P. Marais thought that the authors had done themselves an injustice by not including details of the very complex processes taking place in the furnace."

Jan 1, 2014

By Luis Bergh, Juan Yianatos, Luis Vinnett

"Process automation as an engineering discipline is more than control systems since it includes industrial instrumentation, such as sensors, transmitters and actuators, as well as control and supervision systems, collection and transmission of data and real-time software applications to supervise and control the operation of plants or industrial processes. In the last several decades, accelerated technological development has provided a variety of software and hardware tools to aid development, maintenance and continuous improvement of automated systems. These developments however seldom reach their full potential in real plants. There are many factors to be considered, among them human capital specific training and the organization model. In this paper, a methodology for training engineers in advanced control and supervision of flotation plants is presented based on study of the application of these technologies in hybrid pilot plants. Since experimentation in real plants may present undesirable risks and costs, and simulation studies are usually limited to some unrealistic conditions, a laboratory where on-line measurements of the hydrodynamic behaviour of a pilot plant is mixed with phenomenological models has been created. In this form, an environment as close as possible to a real plant can be recreated. A flotation column and a circuit of three pneumatic cells are fully instrumented and connected to a PLC and PC network. In the control room, students learn applications of classical PID control in a DCS environment, advanced predictive control, on-line process operation diagnosis, fault analysis, virtual sensors and expert-fuzzy systems. Several undergraduate and graduate courses and theses are supported by this Process Control Laboratory infrastructure. Examples of these applications are discussed."

Jan 1, 2014

By Tomohide Takeyama, Yuki Yoshida, Masaki Kitazume

"Abstract A series of centrifuge model tests was conducted to investigate the failure pattern and stability of cement treated clay ground having an unsupported vertical slope. The model ground was subjected to monotonically increasing centrifugal acceleration until it failed due to the enhanced self-weight. The test results were compared with the numerical analyses in which the treated soil was simulated by the Smoothed Particle Hydrodynamics (SPH) method. In the simulation, the Dracker- Prager model is employed as the constitutive model. In order to simulate the brittle behavior of the cement treated soil, it is assumed that the unconfined strength is gradually reduced to a certain value which corresponds to the residual strength due to accumulated plastic strain. It was found that the simulation by using SPH method can express the brittle failure observed in the centrifuge model tests.IntroductionBecause of economical and environmental concerns it has become more difficult in recent years to obtain enough soil to construct reclaimed land for airports, electric power plants, manufacture plants and so on. On the other hand, it has become difficult to find and construct disposal sites for waste subsoil or dredged soil. These circumstances have encourage geotechnical engineers at present to use these poor quality materials as filling materials more than they were used one or two decades ago. Several soil admixture methods have been developed to improve their properties and to manufacture high quality fill materials.The deformation and strength characteristics of cement treated soils have been investigated in Japan, which have revealed that the treated soil is characterized by a brittle behavior with quite high compressive strength and quite small strain at failure, and the treated soil with relatively high strength shows tensile failure instead of shear failure. Regarding to evaluate the stability of structures adjacent to or buried in the treated ground, Kitazume (1998) and Kitazume et al. (2003) investigated the earth pressure of cement treated ground by the centrifuge model tests. And they emphasized that the failure pattern of the cement treated ground was much different from that of ordinary ground. After the Hyogoken- Nambu earthquake in 1995, many design codes for the seismic stability were revised in Japan, so that seismic stability must be evaluated more precisely. The dynamic earth pressure of ordinary grounds is usually calculated by a pseudo-static limit equilibrium method based on the Mononobe- Okabe’s method (Okabe, 1924; Mononobe and Matsuo, 1929). This calculation method is also applied to the cement treated ground, although its applicability has not been thoroughly clarified."

Jan 1, 2014

By V. Nasri, S. Rashidi

The Baltimore Red Line Project is a proposed 22.7-km (14.1-mile) long east-west light rail transit (LRT) line envisioned to connect the areas of Woodlawn, Edmondson Village, West Baltimore, downtown Baltimore, Inner Harbor East, Fells Point, Canton and the Johns Hopkins Bayview Medical Center Campus. The Red Line LRT System has two tunnel segments - the Cooks Lane Tunnel (CLT) and the Downtown Tunnel (DTT). The CLT segment is roughly 1,920-m (6,300-ft) long. It commences at the west portal located at the highway ramp for I 70 (to be removed) and terminates at the east portal that is at the intersection of Edmondson Avenue (U.S. Route 40) and Glen Allen Drive. This segment of the project consists of the following construction components: approximately 1,458 m (4,786 ft) of tunnels, 143 m (469 ft) of cut-and-cover tunnel, and 318 m (1,045 ft) of retained cut (U) section. The approximate horizontal alignment for the Red Line LRT Project is shown in Fig. 1.

Jan 1, 2014

"Chairman: Professor J. C. Griffiths Rapporteur: Mr J. P. G. PRETORIUSPapers:Mine-mill production scheduling by dynamic programming by R. J. Roman Optimization of a large mining venture by J. C. Paynter, B. K. Loveday and C. G. Robinson Economic surface mining of multiple seams by T. V. Falkie and W. E. PorterIn introducing his paper, Mr Roman said that whereas in manufacturing plants the yearly production levels were usually chosen to produce the largest annual cash flow, in a mining operation, the raw materials (ore) were exhaustible so that the production had to be scheduled to maximize the total net present worth of the operation. This optimum production schedule could be determined by using dynamic programming. The required information was readily available to management at most mines. The 'possible operating range' of production rates lay between the rate with the highest profit per ton. and that with the highest profit per year. The optimum production rate started typically at the top of this range and decreased slowly as the deposit was depleted.Dynamic programming was used to determine several production schedules for a hypothetical mine-mill complex. The effects of changes in the ore grade estimates, size of deposit and acceptable rate of interest on the production schedule were taken into account. Apart from the fact that the net present worth of the overall profits was larger than that obtained by conventional methods, it appeared from the cases studied that the amount of metal recovered was also greater.Dr it P. King commented that this was a very interesting application of dynamic programming. He pointed out, however, that the market price of the metal was likely to vary significantly and randomly during the life of the mine, and he suggested that the problem should, therefore, be reformulated as a stochastic dynamic programming problem.If the price of the metal rose to abnormally high levels, a much higher than normal production rate could be expected. The results of analyses given in Table 5 showed that the production rate was a function of market price. In his view the stochastic problem could be solved just as easily as the deterministic problem.In reply to a question by Dr King as to whether the function relating recovery to production rate (Table I) was based on real data, the author replied that it was based on the results of an analysis conducted at the Union Carbide Corporation's Pine Creek tungsten mine in California.Dr D. M. Hawkins stated that costs were incurred when the production rate was altered, for example, in appointing or laying off staff, and that in practice it may be necessary to take these costs into account in finding the optimum production rate. Mr Roman replied that, while normal administrative costs were accounted for, the additional costs incurred in appointing and laying off staff were not taken into account."

Jan 1, 2014

By Kaustubh Joshi, Pradip, Beena Rai, Venugopal Tammishetti

"Rapid depletion of high grade iron ores coupled with the increasing demand for the blast furnace grade iron ore in recent times has shifted the research focus on the development of appropriate technologies for the utilization of low - grade alumina rich iron ore slimes. These slimes are currently being dumped into tailing ponds owing to their high alumina content. Typical constituent minerals present in the Indian iron ore slimes are hematite, goethite, gibbsite and kaolinite. Considering the fine particle size distribution (<37 microns) in the slimes, selective dispersion-flocculation seems to be one of the most appropriate process which has been explored by us. We present our successful results on a natural iron ore slime sample obtained from one of the mines in India. We have been able to achieve a concentrate assaying >67% Fe, and <3% Al2O3 and 2.8% loss on ignition (LOI) from the slime sample assaying 60.4% Fe, 7.7% Al2O3 and 5.45% LOI with an Fe recovery of 62-69% simply by adjusting the pulp pH. We have scaled up the process to a semi batch scale as a prelude to commercialize it for the beneficiation of low grade iron ore slimes."

Jan 1, 2014