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By P. J. Bhonde, R. D. Angal

Conventionally low carbon ferromanganese is manufactured globally by refining high carbon ferromanganese in liquid state. This process is an expensive and lengthy technique. Hence, the present work was undertaken with the objective of understanding the feasibility and kinetics of the solid state refining of ferromanganese. The process involved transformation of carbon rich carbides viz. Mn3C2, Mn7C3 into metal rich carbide i.e. Mn15C4, Mn23C6 by subjecting the alloy powder to a flowing stream of carbon dioxide. Effect of the process governing parameters such as time, temperature, particle size, pressure on the extent of decarburization was studied. Without any loss of manganese in the form of fumes or slag, it was observed that, there was substantial reduction, viz. 65 per cent in the total carbon content, by this technique. Subsequently, the process was investigated to find out the mechanism of carbon removal. Depending upon the temperature and the particle size, it was found that the rate controlling mechanism changes from chemical reaction control to product layer (ash) diffusion control. The activation energy for each of the aforesaid mechanism was computed. The values thus obtained substantiated the aforesaid mechanisms.

Jan 1, 2004

By R. Vernon Helm

Four tables listing values for the various physical properties of those sulfur compounds most likely to occur in petroleum and petroleum products are given herein. The data necessary to bring the first compilation2/ in this subject up to date are given in table I -Revised and Additional Data, which includes boiling points, refractive indices, densities, and freezing points. Tables 11-, III, and IV are published for the first time and include refractive indices for the F, C, and G' lines of hydrogen and the helium D:3 line; surface tensions and viscosities, and refractivity intercepts, specific dispersions, specific refractions, and parachors. The need for information concerning the sulfur compounds in petroleum is becoming-more urgent because of the necessity of refining larger quantities of high-sulfur crude oil to meet the rising demand for petroleum products. For a number of years the Bureau of Mines has been engaged in research to make available more information concerning the properties of the sulfur compounds in petroleum. The petroleum industry has recognized the value of such studies, and as a result the American Petroleum Institute has established Research Project 48A to study sulfur compounds. The investigations under this Project are to be done in Bureau of Mines laboratories as a cooperative project in connection with the work already started.

Jan 1, 1949

By Ji-He Wei

Keywords: stainless steel, AOD refining, side and top combined blowing, mixing characteristics, water modeling The fluid mixing characteristics in the bath during the side and top combined blowing AOD (argon-oxygen decarburization) refining process of stainless steel have preliminarily been studied on a water model unit of a 120 t AOD converter. The geometric similarity ratio between the model and its prototype (including the side tuyeres and the top lances) was 1:4. On the basis of the theoretical calculations for the parameters of the gas streams in the side tuyeres and the top lances, the gas blowing rates used for the model have more reasonably been determined. The influence of the tuyere number and position arrangement, and the gas flow rates for side and top blowing on the characteristics has been examined. The results demonstrated that the liquid in the bath underwent vigorous circulatory motion during gas blowing, without obvious dead zone in the bath, resulting in a well mixing effectiveness. The gas flow rate of the main tuyere had a governing role on the characteristics, a suitable increase in the gas flow rate of the subtuyere could improve mixing efficiency, and the gas jet from top lance could make the mixing time prolong. Corresponding to the oxygen top blowing rate specified by the technology, a roughly equivalent and good mixing effectiveness could be reached by using six side tuyeres with an angle of 27° between each tuyere, and five side tuyeres with an angular separation of 22.5° or 27° between each tuyere. The relationships of the mixing time with the gas blowing rates of main-tuyeres and sub-tuyeres and top lance, the angle between each tuyere, and the tuyere number have been obtained.

Jan 1, 2005

The modern theory of sampling of particulate minerals essentially consists of a recent generalization of the procedures for applying and calibrating the formula usually known as ?Gy?s Formula? for sampling variance control, in which the central concept is a parameter called the liberation factor l. A model which can be experimentally adjusted was proposed by one of the authors several years ago, based on geostatistical considerations. This new model, which relates the liberation factor to the sizes of the fragments and mineral grains, solves the usual difficulties faced in the past, and permits predictions that are well verified in practice. Unfortunately, an older, arbitrary and less general formula is still widely used. The vast majority of today?s misapplications of Sampling Theory of Particulate Materials can be traced back to the use of this antiquated and generally incorrect model. Following a brief history of the models used for the liberation factor and a description of its main variable, the liberation size, and to illustrate the importance of proper modelling of l, this paper presents demonstrative calculations of the absurdity of the incorrect model using the particular case of gold mineralization as an example, followed by some more positive examples of application.

Jan 1, 2002

Methods for Improving the Flotation Recovery of the Coarse Fraction of a Nickel Ore

Sep 13, 2010

Following the Coalbrook Colliery disaster in 1960, Salamon and Munro (1967) established the well known empirical coal pillar strength formula in South Africa. This formula has prevented further violent multiple pillar failures. In 1996, a back analysis of the collapsed and uncollapsed cases in Australia led to the development of the Australian empirical coal pillar strength formulae. The original collapsed and uncollapsed coal pillar database of Salamon and Munro (1967) was updated in 2006. This study introduced various strength formulae for different coalfields and seams in South Africa through back analyses of collapsed and uncollapsed cases. Today, the resultant pillar strength formulae from these previous studies and the behaviour of coal pillars are mostly well understood and applied with confidence. However, it was assumed in the previous studies that the behaviour of pillars is not time dependent; therefore, the formulae established do not provide an associated time to failure of coal pillars. This paper attempts to evaluate the so called 'Geometrical Limits' concept to provide the Australian coal mining industry with a tool to assess the long-term behaviour of bord and pillar workings where the pillars are prone to failure due to spalling of ribs. In order to achieve this outcome, the principles of the safety factor concept and the probability of failure calculated using the coal pillar strength formulae have also been evaluated and practical design examples are presented in this paper.

Nov 25, 2010

By Mohammad Noaparast, Babak Fotoohi

"Due to certain advantages in (semi-)Autogenous-Ball mill circuits in most of the high-throughput ore grinding units of mineral processing plants, much attention is paid to optimize the mill performance. Despite the maturity of the grinding mill mechanical design, there had been made less attention to the efficiency of the grinding media in the past. In this research, the possibility of establishing a relationship between liner/lifter wear rate and variations in the composition of the iron ore (from Chadormalu mine) is investigated.Measurements and determination of liner/lifter wear rates and patterns concluded in recognition of critical liner segments exposed to much abrasion during the ore grinding. After metallurgical analysis of liner materials and correlation of wear rate with the ore composition, the homogeneity in the metallurgical microstructure of the alloyed steel (such as the uniform distribution and amounts of the constituent phases) was determined as the most influential factor in the response of the liner/lifter to the variations in the ore composition. Magnetite with greater abrasion index than hematite, in finer particles, is responsible for additional abrasion of liners; hematite with greater work index exists in the mill with larger particle sizes, thus it could produce wear on liner parts with less tolerance to impact as is the situation for martensitic steels.INTRODUCTIONThe mineralization in Chadormalu plutonic iron ore deposit is consisted of mostly magnetite, hematite, martite, apatite, quartz and carbonates. The average composition of the ore is presented in Table 1. In the processing circuit, the gyratory crushed ore reduced to 30 cm would finally be the feed to three similar 32’ semi-autogenous mills in parallel processing lines. The pulp in the mill would have the characteristics mentioned in Table 2. The quality of the mill output has its direct effect on the downstream processes either physically or chemically (e.g. in cycloning or flotation respectively). In order to take advantage of optimum performance for these circuits, a close control of the ore grinding conditions is necessary; because any shortages in throughput, liner/lifter damage or changes in ore composition could bring the unexpected casualties. In this work, it has been attempted to find (possibly) a reasonable relationship between variations in ore characteristics together with liner quality and the amount of wear rate in different liner/lifter segments of a semi-autigenous mill. Liner/lifter segments are supplied by three different domestic steel making companies. The alloy structure of the liners/lifters is made up of pearlitic chromoly steel."

Jan 1, 2005

By D. Washington

The US economy and the demand for nonfuel minerals grew at lower rates in 1995 than in 1994. Demand for major metals, such as aluminum, copper and steel, was mixed but relatively stable. The building industry, including highway construction, helped to support modest overall growth in demand for industrial minerals. The value of processed materials of nonfuel mineral origin produced in the United States during 1995 was estimated to be $395 billion, an increase of almost 10%compared with 1994 (Fig. 1). The estimated value of US raw nonfuel minerals production during 1995 was $38billion, about 7% more than in 1994. The value of US minerals production has increased in 30 of the last 35years.

Jan 1, 1996

By Mike Higgins

"Data management is emerging as a major concern for miners. Engineers today are faced with anextensive array of data from varying sources, and are required to consolidate and analyse thisinformation to produce an effective and efficient mine plan. The viability of a mining operation canbe dependent on the outcomes of this process. With so much at stake, it is no surprise that mostengineers prefer a standard approach to blasting which is designed to minimise risk rather thanoptimise performance."

Jan 1, 1998

By Dean H. Ambrose

This paper presents the results of a study using computer human modeling to examine machine appendage speed. The objective was to determine the impact of roof bolter machine appendage speed on the likelihood of the operator coming in contact with. A contact means two or more objects intersecting or touching each other, e.g., appendage makes contact with the operator?s hand, arm, head or leg. Incident investigation reports do not usually contain enough information to aid in studying this problem and laboratory experiments with human subjects are also not feasible because of safety and ethical issues. As an alternative, researchers developed a computer model approach as the primary means to gather data. By simulating an operator?s random behavior and machine?s appendage velocity, researchers can study potential hazards of tasks where it is not possible to perform experiments with human subjects. Analysis information is helpful to the mining industry in terms of making recommendations that reduce the likelihood that roof-bolter operators experience injury due to contact with a moving boom. Data analysis of roof bolter simulations show that the virtual-operator?s response time has little effect on the number of contacts experienced. Based on frequency and cross-tabulation, regardless of other variables, contact incidents were always greater when the boom was moving up, were always greater on the palm, and were always greater for the boom part of the machine. Also, regardless of boom speed, the 25th-percentile-sized operators experienced more contacts than did other operator sizes. Furthermore, regardless of boom speed, the 152-cm mine seam experienced more contacts than did other seam heights tested. Results of a survival analytic approach suggest that controlling the boom speed is the most important factor in determining the risk of an operator making contact. Based on the data collected, boom speed greater than 41 cm/s results in a substantial increase in risk to the roof bolter operator and should probably be avoided. At speeds less than or equal to 25 cm/s are associated with a more modest relative risk, which represents an acceptable level of risk. Also, at speeds between 25 and 41 cm/s, there could be a particular boom speed in this range at which a significant inflection point in the relative risk estimates occurs. Based on the results, this issue needs to be addressed by future research.

Jan 1, 2003

By Werner Wenzel

Whisker growth during the reduction of iron ores The phenomenon of whisker growth can be observed in a number of solid-state crystallisation reactions, which, apparently, appear in6 the first instance as though they are two independent processes. From such reactions, one can find the whisker type of crystallisation on solid bodies. These examples show, that the whisker growth is neither due to certain crystal forms with predetermined temperature and pressureranges, nor to parameters, which, ad hoc, are necessary for the crystallisation. In all cases the whisker formation seems to depend on nucleation and the availability of crystallizing material in direct environment of such a nucleus, under given parameters of a system. One can generally state, that the research of whisker growth with the aim of establishing proper physical laws, to determine the foundamentals of whisker formation and whisker growth, is at present under active study. We can conclude that, although a great number of hypothesis have been proposed; no concluding theory has yet been arrived at. In the institute for ferrous metallurgy of the technical university of Aachen, research works are undertaken to find an explination to various metallurgical phenomena through help of whisker growth which was observed under varying conditions of iron ore reduction. This was possible by using refined microscopic techniques through which the whisker growth on solid oxyde substrates is detected. This refined technique combines the latest methods of surface examination with the help of stereo-scan-electron-microscope and proper and carefull preparation of surface to be stereo-scanned.

Jan 1, 1971

By Timothy C. Siegel

Accurate representation of the geotechnical resistance distribution is critical in evaluating the performance of piles and pile groups for design. A current practice is to infer the geotechnical resistance distribution based on measured changes in strain during conventional top load pile testing. Especially for drilled and bored piles, the residual load is typically assumed to be negligible both during testing and after the application of the structure load. A practical result is that the compressive structural load is anticipated to be opposed primarily by the shaft resistance with little or no mobilized toe resistance. The predicted top deflection is estimated as the combined elastic compression plus the movement necessary to mobilize shaft resistance. The development of residual load (and associated negative skin friction) results in a significantly different design condition. Negative skin friction tends to force the pile into the ground and develops residual load in the pile that contributes to the internal compressive load. Significant toe resistance can be mobilized in order to resist the combination of negative skin friction and the sustained compressive load. The pile movement becomes a function of the toe penetration required to mobilize sufficient resistance to reach a balance of forces. In an effort to study the development of residual load in augered cast-in place (ACIP) piles, the authors installed and monitored strain gages that were embedded in an 18-inch diameter ACIP pile at a site in southeast Georgia. The results of this study indicate that residual load develops over time and reaches a distribution that is consistent with the principles of the unified design of piles. It is concluded that residual load develops in ACIP piles (as well as all drilled and bored piles by the same mechanisms) and that the residual load should be considered in the interpretation of load tests and in the pile design, particularly in the estimation of the single pile and pile group settlement.

Jan 1, 2009

By Robert Boehnke, Bernd Mueller

Despite enormous efforts over the last decades there are still many unanswered questions with respect to calculation and modeling of the blast process using appropriate physical laws. Most calculations of explosive charges of a blast design are based on experience, empirical observations or blasting theories with serious shortcomings. This paper presents a new theory for the design and calculation of a rock blast that is based on the momentum. It offers a clear-cut method for the calculation of blast processes. The theoretical results will be compared with on-site measurements by means of a newly developed strain sensor and further measuring equipment. The momentum theory helps better to explain physically the processes of a blast. On the basis of long-term statistical investigations a momentum balance can be carried out with the volume-based blasting momentum and the measurable momentum associated with the muckpile and the remaining rock mass. This type of consideration requires a complex procedure which includes the blastability of the rock masses. Realis tic strain measurements open a new interpretation possibility and judgment criteria for the most probable building damage, the dynamic impact on general types of buildings and also for the blast process itself. The blast-induced stress and the momentum generated could be back-calculated using a geophone profile and the strain sensor. The strain owing to a dynamic impact can be influenced by the changing of the drill-, blast- and shotfiring technique like the until now measured vibration velocity. In this way it is possible today to make a complex preparation, calculation and evaluation of blasts. The new techniques of measuring in connection with the momentum theory bring about an increase of the safety and a clearcut method of improving the blast processes. This procedure offers new possibilities for the precise calculation, simulation and modelling of blasts and resulting vibrations and leads to an increase of the safety as well as economic adaptation of the drill-, blast- and shotfiring techniques to a pre-determined blasting result.

Jan 1, 2003

By Derek J. Fray

"In order to extend the application of fused salts in\the electrowinning and electrorefining of metals, it is necessary to maximise the current density, minimise the voltage drop and greatly increase the area of electrode surface so as to compete with the space-time yield of pyrometallurgical reactions. The various designs of electrowinning cell are reviewed and it is shown that by the application of a modest centrifugal field it is possible to reduce the anode to cathode interelectrode spacing to 4 mm whilst still maintaining a current efficiency of 85-90%.The thermodynamic potential for electrorefining is far less than for electrowinning yet fused salt electrorefining is only applied in limited cases. The reasons for this are discussed and the important design parameters evaluated. It is concluded that by using packed bed electrodes, separated by a diaphragm, the possibility of electrorefining with very low energy consumption can be achieved. Carbothermically-produced metals are always cheaper than those produced by electrolysis but suffer from the disadvantage of low purity. It is proposed that fused salt electrorefining may offer an energy efficient way of upgrading the metal. IntroductionThe majority of metals can be deposited from fused salts (1,2) but as commercial production is restricted to the more reactive elements, it is worthwhile considering the advantages and disadvantages of fused salt electrolysis as' compared to smelting and aqueous electrolysis. The advantages over aqueous extraction are as follows:1) the much higher conductivities and diffusivities result in much lower IR losses and higher current densities can be achieved at modest voltages;2) the elevated temperatures of operation result in larger exchange currents which give rapid kinetics and lower activation polarisation for the electrode reactions;3) the absence of water as a solvent means that it is not necessary to consider the evolution of hydrogen as a competing cathodic reaction. Furthermore, alkali halide salts, often used as solvents in fused salt electrolytes, have high deposition potentials;4) molten salts generally are mutually soluble and, therefore, concentration polarisation effects are minimised."

Jan 1, 1988

By Michael Wieland

For shooting rock properly, some relatively fixed quantity of rock work is required from the total charge mass, while keeping the overall toxic fumes to a minimum. The overall fumes weighted for the toxicity of different species and taken per unit charge mass, ??, are represented by a relative fume toxicity (RFT) formula. The worst two contributions are often carbon monoxide {CO} and total nitrogen oxides {NOX}, so the traditional Russian formula RFT-R formula suffices, though a generalized form RFT-G with more terms is worth checking. Using the work-principle model from thermodynamics, the rock work per unit charge mass, ??, is found from the reduction in internal energy for the reaction zone. This resolution technique for rock-work invokes the usual assumption that the quick irreversible process occurs without notable heat transfer to the rock (adiabatic); rock-work is not resolved, when this restriction is untenable. The ratio of ?? to ?? yields the weighted toxic fumes divided by the rock work or the readjusted fume toxicity ??, where ?? = ??/??. For convenience, graphical trends of ??, ?? and ?? were normalized using reference results for a stoichiometric (ANFO) mixture of ammonium nitrate (AN) and fuel oil (FO) shot under nominal rock confinement, noted later.

Jan 1, 2006

By P. J. van der Walt

Some 30 years ago exposure to dense-medium separation in South Africa, culminated in the adaptation of the process for the treatment of -0.5 mm fines. The first commercial plant at Greenside Colliery apparently operated for some 18 years. Three further plants followed, including one treating tin ore. It is gratifying to learn, therefore, that there is renewed interest. The objective of making the process easier to operate (?more practical??) is commendable but the cumbersome technical approach could be counter productive. Perhaps a brief outline of the original thinking might be helpful when analysing the problem.

Jan 1, 2003

A 3-D computerised model of the southern part of Greymouth Coal Limited's Coal Mining Licence area has recently been completed. This model, and associated 3-D CAD tools, has/is being used to optimise drillhole spacing during exploratory data collection and as a visualisation and interpretation aid. This model will also provide the basis for future mine planning, with the emphasis on an optimal mine outline to maximise safety and profitable coal extraction. Previous use of computer techniques was restricted to drillhole database entry, storage and log production. Recently a 3-D geological/structural model was created for the Southern Rapahoe Sector of the Greymouth Coalfield. Geostatistical analysis of the database highlights the inadequacy of the present drillhole spacing for preliminary mine planning. The sparsity of hard data at depth results in a lower level of confidence in the accuracy of the 3-D model. Nevertheless, the model and 3-D CAD techniques has been used to target and refine ongoing resource evaluation, and provides the basis for initial reserves. In the future the geologic model will be used as the basis for preliminary and later (optimal) mine planning. It is also expected to accommodate other forms of data input in seam drilling and seismic. Development of the 3-D computer model was a first in the Greymouth Coalfield and highlights both the use of computerised techniques for resource evaluation and mining, and the effects of wide spaced drillhole data on model accuracy. The computer will continue to provide the most efficient and cost effective tool for optimal resource evaluation and mine planning as Greymouth Coal Limited moves from feasibility/mine planning to full production. The increased use of computer-based methods for mine planning should be seen as part of 'The Changing Face of West Coast Mining' in line with the theme of this Conference.

Jan 1, 1996

Recovery of Pentlandite and Chalcopyrite from Tailings by Bi-Cyclone Powerful Flotation Column

Sep 13, 2010

By W. P. Diamond, S. L. Cario, F. Garcia, J. D. Byars, T. P. Mucho

The National Institute for Occupational Safety and Health (NIOSH) has been conducting research at a Pittsburgh Coalbed longwall mine to evaluate and optimize bleeder ventilation and gob gas venthole longwall methane control systems. Gas flow into these two methane control systems was investigated using a combination of Sulphur Hexafluoride (SF6)tracer gas studies and gob venthole pressure monitoring experiments. The insights gained from this research has facilitated the development of a longwall subsided strata methane control system conceptual model. This model provides the basis for design suggestions to increase the efficiency of the gob gas venthole system to permit the bleeder ventilation system to become a "safety net" for methane control.

Jan 1, 2000

By L. C. IlsLey

The increasing use of Diesel engines for operating equipment on trunk-line railroads and for power-plant units has stimulated interest in the use of Diesel engines for other lines of work, among which is the possibility of substituting Diesel locomotives for trolley locomotives for mines. The possibility of developing Diesel locomotives for duty in American mines is not as remote as it might seem, particularly in view of the fact that locomotives of this type are already used in considerable numbers in European mines. A study of Diesel locomotives in Europe is contained in Report of Investigations 3320, Diesel Mine Locomotives - Development and Use in European Coal Mines, by George S. Rice and F. E. Harris.

Jan 1, 1938