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By S. Chander

A comparison of gold, platinum and sulfide ion selective electrodes was made for determination of Eh in solutions containing hydrosulfide ions as a model system. The comparison was made in terms of the accuracy of the measured response, response time, pH dependence, and reproducibility of measurement. The sensitivity of each electrode towards changes in hydrosulfide ion concentration was measured in terms of the change in measured Eh per decade change in concentration. On the basis of a detailed investigation of the electrode processes occurring at the surface of gold and platinum electrodes, it was postulated that within the pH range investigated these electrodes respond to changes in the hydrosulfide ion concentration in solution. In comparison, the sulfide ion selective electrode is known to respond to changes in the sulfide ion activity in solution. Although the potentials measured with gold and platinum electrodes were mixed potentials, pretreatment procedures can be used to obtain a signal suitable for process control. For control of hydrosulfide ions in flotation pulps, the use of a gold electrode pretreated at 1.0 V with respect to a standard hydrogen electrode is recommended.

Jan 1, 1992

The nickel refinery at Yabulu consumes an average of 118,000 kg/h of low pressure steam in stripping operations to-recover ammonia and carbon dioxide from product liquor and ore tailings streams. The steam used in the stripping operations is produced from the 25 MW power generation plant at the refinery. The back pressure on the non condensing steam turbines is maintained at 60 kPa.Studies have been carried out to determine the optimum amount of steam required to be generated for stripping operations. When steam production is increased, the product liquor flow from thewashing thickeners can be increased. This results in improved washing efficiency of the thickeners and therefore improves the plant nickel recovery. A computer thickener wash model was used to predict nickel recoveries at varying steam consumption rates.The studies have shown that in most plant situations, it is not economical to-generate more steam than that already available from existing power production.The studies also highlighted the necessity to use all steam generated from power production at all times to maintain maximum nickel recovery.

Jan 1, 1985

By P Krauss, S Harpalani

Methane emitted from underground coal mines, along with ventilation air and known as ventilation air methane (VAM), constitutes the largest component of coal mine methane (CMM) emissions. Atmospheric methane, on the other hand, is a potent greenhouse gas with a significant adverse impact on the atmosphere. This has led to the development of various technological alternatives for its use as an energy fuel. Techniques involving oxidation of VAM, usually consisting of very low concentrations of methane, have been validated in the past. Prominent among these technologies are the thermal and catalytic flow reversal reactors, ancillary fuel technologies, lean fuel gas turbines, and concentrators and gasifiers. However, the efficiency of any VAM utilisation technique depends on the amount and concentration of methane in the ventilation exhaust air. Therefore, quantification of VAM emission from a coal mine is the first step towards identifying the most suitable technology for its utilisation for energy production. This paper presents an evaluation of the efficacy of VAM as an energy source. It provides details of a case study aimed at developing a technique to accurately quantify VAM emission from a coal mine. It further discusses the various VAM utilisation techniques available, and presents an economic evaluation of the alternatives. Based on the findings of the study, the most feasible method for VAM utilisation is identified for the mine. The paper summarises the procedure for quantifying VAM emissions and selecting the most suitable utilisation technique.

Jan 1, 2005

By R. D. Reiswig, D. J. Mack

THE use of pyrophoric alloys in ignition devices dates back more than fifty years to a German patent granted to Carl Auer von Welsbach in 1903.' This patent named a composition essentially the same as that used in most present-day cigarette lighter "flints:" 70 pct mischmetal, 30 pct Fe, referred to here as "Auer alloy." Among the few current exceptions to this composition are those "flints" based on titanium or zirconium. The rare-earth metals of which mischmetal is composed are so similar chemically and physically remarkable similarity in their alloying behaviors would be expected. Comparison of the binary phase diagrams2 of these elements with nonrare-earth metals shows that this is true to a striking degree, so much so, in fact, that it appears that a mixture of these elements may be treated as a single component of alloys without fear of serious error. In considering alloys containing mischmetal, therefore, the mixture of rare-earth elements will be referred to merely as "cerium," the predominant element in mischmetal. In polishing cerium alloys for metallographic examination, it was soon discovered that aqueous polishing media were highly corrosive. Free cerium in the alloys acts similarly to calcium (though not quite so rapidly) in evolving bubbles of hydrogen at the metal-water interface; thus, special metallographic techniques are required. The simplest polishing technique found to be satisfactory consisted of slow hand grinding on dry emery papers through

Jan 1, 1956

The correct design and effective operating strategies of metallurgical plants require a constant analysis of data gathered for process control, or for due accountability. Conventional, oldfashion statistical tools often fall short of helping management, either because they are too complicated and ambiguous, or because they fail to address structural problems leading to causes of setbacks. This paper focuses on three statistical tools known for their practicality and the in-depth perspective they offer in attempts to retrieve important information from existing data. These tools also provide a better appreciation of the importance of carefully selected data quality objectives. Chronological data are meticulously gathered and stored at considerable expense: They have value, and it is the duty of management to take full advantage of them. These three selected tools are the variogram and its auxiliary functions, the moving average and its auxiliary functions, and the relative difference plot. This paper offers solutions, and a reference for managers to optimise metallurgical plants.

Jan 1, 2002

By W. W. Little

At the United Verde mine the 9-2D stope on the 4050 ft level is located within the north sulphide mass lying some 800 ft north of the main sulphide ore body. In 1948 it was estimated that this block contained 85,000 tons of ore at 4% copper and 9.2% zinc. The north ore body is a lenticular replacement deposit in the black schist, extending from about 100 ft above the 3750 level to a distance below the 4500 level yet to be determined. Although the mineralized zone approaches 1000 ft in length, only 300 ft is of economic importance. In width it varies from a maximum of 60 ft to about 3 ft at the north end, and is characterized by pinching and swelling in the ore zone. One of these larger swells is being mined as the 9-2D stope. Mining costs at greater depth, together with the expected grade of ore after dilution, necessitated a low cost mining method to permit profitable stoping operations. Based on the results obtained in a number of Canadian mines, it was decided to develop the ore body for stoping by the Aldermac or bench method of diamond drill blastholes; however, this plan was subsequently changed and the radial or ring method adopted. Such a method seemed to offer the advantage of large tonnages at low cost, and obviate the necessity of waste fill. This latter point was of particular importance, since the present waste system does not extend below the 3000 level.

Jan 4, 1950

By A. W. Edelen

THE Teziutlan copper-zinc deposit is supposed to be of late Cambrian or early Paleozoic age. The country rocks are a series of schists or phyllites, flat lying and in the form of a plunging anticline. The ore deposit occupies a single horizon in the schist for a known horizontal extent of 1200 meters. Along its strike occur four large lenses or ore bodies. These ore bodies occupy positions along the flank and extend to the crest of the anticline. The primary mineralization is in the form of quartz, pyrite, sphalerite, chalcopyrite and galena, with a few scattered silver anti-monides. Quartz and pyrite form the mineralization between the ore lenses. In the ore lenses the sulphides appear as a massive, very fine-grained intergrowth of minerals. The intergrowth suggests a contemporaneous deposition of the heavy sulphides. The grain size, usually under 0.09 mm., makes the separation difficult and fine grinding important. The ore bodies were formed at great depth by solutions probably originating in the same basic magma that gave rise to the dolerite sills that are so common in their vicinity.

Jan 1, 1937

By Oscar Aguilar, Jin-ichi Nakamura, Kazuo Nakamura

Michiquillay deposit is porphyry copper type with over 500 million tons of 0.70% Cu ore. In order to reflect the true nature of the orebody as to shape and value distribution and to compensate for insufficient data in the outer perimeter and lower portion, "Triangular Interpolation Method" is used in the computation, wherein block grades are determined by "Plane Regression". The results thus obtained are compared with the data from additional investigation and are found to match well with each other. Aside of total Cu, assays of Fe, S, MoS2 and geological data such as alterations, rock types, faults, mineralogical compositions are also stored in the computer. By this system, their distribution and relation to alteration become clear and classification of ore into types affecting recovery become possible. The outputs of this system make clear the characteristics of the orebody and furnish valuable geological data on the orebody.

Jan 1, 1976

By J. C. De Haven, Harry Seltz

INTERMETALLIC compounds are formed in many binary metal systems. Some compounds are stable to their melting points, and others decompose at lower transition temperatures. Even those of the first class are dissociated in the liquid state, as indicated by the continuous form of their solubility curves at their melting points'. While the lattice structures of some of these compounds' have been determined, their thermodynamic properties have not been investigated. In this paper is described the determination of the free energy and heat of formation of the compound CdSb, which is of the first class mentioned above, melting congruently at 455° C. This compound shows a rhombic structure, and the lengths of the edges of the elementary cell containing four molecules are: a = 6.52,b=8.60,c=4.16Å2 There are three possible methods of determining the free energy of formation of a compound of this type. The first method, applying the third law of thermodynamics, requires the measurement of its heat capacity preferably to liquid hydrogen temperatures, and a calorimetric determination of its heat of formation. The second method involves the study of the equilibrium of the compound in some gas reaction, such as: CdSb + CO2 = CdO + CO + Sb. From the known free energies of formation of, CdO, CO2 and CO the free energy of formation of CdSb could be calculated. The third method measures the electromotive force of a galvanic cell in which the cell

Jan 1, 1935

By M. A. Marticorena, R. Stratton-Crawley, C. I. Basilio

Diethylenetriamine (DETA) is a selective depressant for nickeliferous pyrrhotite during pentlandite flotation. Laboratory flotation tests conducted on ore and process samples showed that pyrrhotite rejection is greatly improved by small additions of DETA; however, the effectiveness of this depressant is most noticeable when the mineral sample is oxidized. LIMS and XPS analyses conducted on flotation products and pyrrhotite specimens showed that the difficulty in pyrrhotite rejection arises from inadvertent activation of the mineral by heavy metal ions, such as Ni2+, cu2+ and Ag+, that are present in the process water. In the presence of DETA, however, the mineral is deactivated under oxidizing conditions. The deactivation mechanism may involve oxidation of the activation products, which are likely in the form of heavy metal sulfides, followed by solubilization by DETA. FTIR spectra of pyrrhotite electrodes contacted with DETA showed no trace of the reagent on the surface, substantiating the view that its role is one of complexing agent that enhances the dissolution of activation products under oxidizing conditions. FTIR spectra of pyrrhotite contacted with amyl xanthate solutions showed that both dixanthogen and iron xanthate are formed on the surface, the latter becoming more predominant at higher potentials. In the presence of DETA, however, only a small amount of xanthate is adsorbed on the mineral at potentials (Eh) approximately 200 mV higher than the case without DETA.

Jan 1, 1995

By D. H. Newland

CERTAIN observations from the field and laboratory suggest the need for recasting some of our ideas about gypsum as a rock-forming mineral and in relation to supplies for industrial use. Until about 25 years ago, the use of gypsum was confined almost entirely to agriculture. During the past quarter century, though, its usefulness has been greatly developed, particularly in the building trades, which now absorb most of the gypsum produced. In 1919, according to the U.S. Geological Survey, the output of crude gypsum was 2,240,163 tons, a gain of 912 per cent. in 25 years. About one-half of this production was mined in New York, Ohio, and Michigan, where the proved supplies can hardly be regarded as over-large when viewed in relation to the rapid expansion of industrial requirements. The occurrence of gypsum in the United States is treated by R. W. Stone and others.1 The deposits of Canada are described by L. H. Cole.2 Several states, including Kansas, Oklahoma, Iowa, Michigan, and New York, have had special surveys made their of gypsum deposits, but the reports, as a rule, refer to conditions as they existed from 15 to 20 years ago.

Jan 9, 1921

By Eckley B. Coxe

At the first meeting of the Institute, a paper was read by Mr. Rothwell, calling attention to the importance of at once considering the great waste of anthracite coal under the present system of mining and preparing that fuel for market, and a committee was appointed to examine and report upon the method now in use. About the time the committee were selected, a general resumption of work, after the long strike, took place in the coal regions, and the members of the committee have not in consequence had as much leisure to devote to the study of the question as its importance demands. In the present preliminary report we shall merely sketch out the . plan which we propose to pursue in our investigations, so that when our fellow-members are called upon to assist us in our work by furnishing statistics, etc., they may understand more clearly for what object our inquiries will be made. As one of the most practicable methods of obtaining the information requisite for an intelligent consideration of our subject, we propose to send, from time to time, to members and others interested in the mining of anthracite coal, printed sets of questions relating to points under consideration. We would here impress upon our fellow members the importance of filling up these papers as far as they can from their own knowledge. We would, of course, wish each question to be answered as fully as possible, but we do not expect every one to answer them all. One question well answered would be of more use to us than the whole paper filled up with answers, many of

By W. Rostoker, S. Spachner

A N alloy of 50 pct Ni-50 pct Fe is currently manu- factured in tape thickness down to 1/8 mil. In the annealed form, this alloy produces an almost square hysteresis loop. This has generally been related to the fact that by proper rolling and annealing practice a sharp cube, (100) [OOl], texture can be developed. As part of a program directed toward an understanding of the relationships between magnetic properties and structure of tape core materials, analyses were made of preferred orientations in tapes of various thicknesses. Annealed tapes of this alloy in 2, 1, 1/2, ¼, and Y' mil gages were acquired from commercial sources. Pole figures constructed for the 2 and 1 mil tapes showed the expected sharp cube texture. However, the ½, ¼, and ? mil annealed tapes showed no evidence of any preferred orientations. A comparison of two transmission patterns is shown in Fig. 1. The origin of the absence of texture in the tapes of less than 1 mil thickness was explored in some detail. The basic questions were whether the heat treatment for the thinner tapes was wrongly selected, whether the initial cold worked textures were different, or whether the actual thickness of the tape exercised some influence on its annealing characteristics. Quantities of the five gages of tape were acquired in the as-rolled condition just prior to the final anneal. Pole figures of the cold worked textures were constructed for each of the tapes. Eye estimates of in-

Jan 1, 1956

By Luís Tavares Ribeiro

Nowadays there is a greater need for detailed reservoir modelling in the oil industry. It is generally recognized that nearly all reservoirs are heterogeneous and idealization of rock characteristics in flow calculations is unrealistic regarding actual physical and textural conditions encountered in geologic formations. The heterogeneity of oil reservoirs considerably influences the distribution of fluids, as well as their displacement. It would be advantageous if a reservoir petroleum engineer was able to construct a precise mathematical model of the detailed reservoir rock variability characterizing the degree of reservoir heterogeneity in an unambiguous way. This paper presents a geomathematical model describing the spatial behaviour and distribution of the principal reservoir properties. The model is based on the Theory of Regionalised Variables and the Kriging technique. The model is performed by a set of computing programs and is tested on an Abu Dhabi oil reservoir in United Arab Emirates.

Jan 1, 1986

Renison Goldfields Consolidated Limited (RGC) and Consolidated Gold Fields Plc (CGF) purchased New Guinea Goldfields Limited (NGG) in 1982 as an exploration venture. Following an intensive drilling programme in the Upper Ridges area sufficient ore reserves were outlined to justify the installation of a new 700 tonnes of ore per day gravity gold extraction plant. Major considerations in the design of the new plant were to minimise production inter- ruptions in the existing plant and to include simple, but technically efficient, equipment that could be operated and maintained by a workforce with limited experience in modern technology. These goals were achieved over a six month period, commissioning being carried out in April, 1983. Mining the epithermal gold deposit is by open cut benching and truck haulage. The gravity concentrator includes a scrubber, wet hammer mill and rod mill, to crush, grind and prepare the ore for sizing and desliming. Gold recovery units consist of a jig, spirals, shaking tables and amalgam barrels. Although the majority of the gold is in the minus 100 plus 20 microns size fraction a recovery of 63 percent, from a head grade of 2.0g/tonne, is Achieved.

Jan 1, 1984

By R. D. Schmidt, S. E. Follin

Introduction Mineral recovery from an in situ leaching operation is determined by the often complex interaction of hydrology, mass transport, and chemical kinetics. The operating conditions of many pilot and production scale uranium leaching operations involve heterogeneities in aquifer permeability. Differences in permeability may be naturally occurring, the result of differences in main size or cementation, or they may be induced by leaching activity. Variations in permeability directly affect the fluid flow streamline pattern, fluid flux, and so also leaching geochemistry and uranium recovery. An in situ leaching hydrology model (ISL) and a mass transport-oxidation rate model (ISLGC) have been developed for use in making site specific predictions of the leachability and productive potential of heterogeneous ore deposits, and for the optimal design of leachant injection and recovery operations. The two models are linked by output and input requirements. The ISL hydrology model generates a leachant flow streamline pattern between injection and recovery points in a flow domain incorporating regions of arbitrary permeability. The ISLGC transport model describes the changing solution concentrations of uranium and oxygen and the changing mineral concentrations of uranium and pyrite resulting from convection, longitudinal dispersion, and oxidation reactions. ISL hydrology model Basic equations The differential equation for steady-state two- dimensional flow in an isotropic porous medium is

Jan 1, 1988

By J. Jolly

THIS short note on the probable character of the organic sulfur compounds in coal can do no more than indicate lines of research. We have no new experimental work to describe, nothing comparable in value with the careful studies of American coals by Powell and Parr1 and Yancey and Frazer.2 A study of the manner in which sulfur compounds exist in British coals (and their behavior on heat treatment) is rendered increasingly necessary by the fact that the British reserves of good coking coals of reasonably low sulfur content are fast being depleted. We believe that it is essentially by a study of the modes of formation, occurrence, and decomposition of the various types of inorganic and organic sulfur compounds in coal that it will be possible, with hope of success, to attack the problem of purifying coals, otherwise eminently suitable for coking, from these objectionable ingredients. Sulfur, so far as is at present known, does not normally occur in the free state in the coal conglomerate, but is chiefly distributed, irregularly, in three forms: 1. As primary constituents of the coal conglomerate, organic in nature and probably associated with those molecular complexes that have resulted from the degradation of the proteins of the plant tissues responsible for the formation of the coal mass. These constituents can be classed as "organic sulfur." 2. As metallic sulfides, e.g., iron pyrites. 3. As metallic sulfates, e.g., calcium sulfate and ferrous sulfate. (The occurrence of these compounds varies with the occurrence and degree of degradation of class 2.)

Jan 3, 1925

Expect Labrador Iron Ore Shipments by 1954 Iron ore shipments from the Quebec-Labrador area are a "definite expectation" by late summer, 1954, according to William H. Durrell, general manager of the Iron Ore Company of Canada. About $120 million have been invested in the project, with a total of $200 million expected to be reached before a ton of ore is shipped, Mr. Durrell said. According to the general manager approximately 418 million tons of open pit highgrade ore have been proven in the project. Deposits lie several hundred miles north of the mouth of the St. Lawrence River in territory which was without transportation of any kind. Construction of a railroad from Seven Islands to Knob Lake, about 360 miles, is an important part of the development plan. The railroad will be the first to adopt complete roller bearing applications. Construction is on schedule with 215 miles of the route graded. Completion involves two tunnels through rock, one of almost half mile length, a 700-ft bridge and several smaller spans.

Jan 3, 1953

By Ronald J. Roman

The shrinking core model for coarse particle leaching has been generally accepted as describing the leaching of a copper oxide or sulfide ore. However, when a mixed oxide/sulfide ore-is leached this model can not be used in its simple form because at least two and possibly three separate leaching processes are occurring simultaneously (dissolution of oxide copper minerals, secondary copper minerals and primarily copper minerals). It has been impossible to isolate their individual leaching curves from the recovery/time curve generated by the column leach test. This paper describes a tests program carried out at the Groupo Mexico, Mexicana de Cobre's La Caridad operation in which the individual recovery/time curves for the leaching of copper oxide mineral, secondary copper mineral and primary copper minerals were developed from standard column leach tests. Once the individual recovery/time curves were developed scale-up of the column leach test results to the commercial heap leaching operation is possible by using the shrinking core model.

Jan 1, 1999

By Anthony Iannacchione

One of the more pressing engineering problems for deep longwall mines in the Southern Appalachian Basin is to design longwall systems that will eliminate catastrophic coal pillar failure from the working environment. The purpose of this study is to quantify the behavior of a particular size abutment pillar prone to burst or bump. Because the 24.4-111 (80-ft) square abutment study pillar is within the pillar size commonly used in this region, understanding the behavior of this pillar should aid in future efforts to design optimum mining strategies. This research has attempted to construct the pillar stress and roof-to-floor convergence profiles in order to evaluate the ultimate strength, deformation modulus, visco-elastic deformation, and violent failure characteristics of the pillar during longwall mining. This information reflects the overriding influence of the local geologic characteristics on bursts, provides the field measurements needed to verify concurrent modeling studies, and suggest some basic mechanisms associated with the coal pillar bursts discussed in this paper.