Search Documents

Flotation Circuit Optimisation - Towards More Sustainable Practice

Sep 13, 2010

By Edward Capillon

THE problem of scrap is probably of greater importance inn the production of gold, silver and other precious metal alloys than is the case for base metals and alloys. Remelting of gold and silver scrap in the shop is always a costly process because it involves losses by oxidation of the base metals in the alloy with a consequent increase in the percentage of precious metal. This is most marked in the case of alloys containing the low-boiling and easily oxidized metals zinc and cadmium. Since it is. not generally feasible to assay every shop remelt it follows that the possibilities of lost values are large. So-called rolled gold and silver plate is made by soldering or welding the precious metal alloys onto base, metal. Such plate when defective must be sent to the refinery to recover the gold and silver values, thereby involving additional expense in the form of refining charges. It is obvious therefore that gold and silver alloy scrap is an important item in manufacturing cost and must be reduced to a minimum. The amount of scrap resulting from poor metal will depend on a number of factors in the manufacturing operations, not least among which is the melting and casting practice. The notes which follow are a summary of experiments performed at various times to determine what variables in melting and casting are influential in the production of sound alloys.

Jan 1, 1930

By F. Malek

At Creighton Mine, magnitude events are a regular occurrence due to depth and major seismically-active structures. Over the last ten years, major advances have been made in research and development to develop strategies for the management of these major events. Today, the number of rockbursts has been drastically reduced at the mine and damage due to seismic events, when they occur, is often minimal. This paper describes the evolution and implementation of appropriate geomechanics strategies, designs, and practical ground control measures undertaken for the management of seismicity at Vale Inco?s Creighton Mine. A description of the research and development approach, implementation, and ground control strategy is provided for placement of enhanced support systems to manage the consequences of magnitude events at Creighton

May 1, 2009

By Vic Sterner

As cities and towns continue to grow, the need to install sewer, water, gas and other utilities becomes a necessity and the blasting of trenches for these service lines probably constitutes one of the most important forms of blasting in built-up areas. There f o re, understanding how explosives can be safely used in the most efficient manner is of prime importance. The need for protection against flyrock must be emphasized. The first consideration is that all explosive c h a rges should be located well down in the blastholes. The golden rule is to ensure that the depth of top stemming is never less than the burden on the hole. In the case of shallow holes, the minimum depth of stemming should not be less than 18 times the charge diameter, if airblast and flyrock are to be controlled. If there is a doubt, then additional cover and/or blasting mats should be used. Putting too much burden on blastholes is another possible cause of flyrock and raising ground vibration levels. Overburdening of explosive charges will also result in the blastholes not breaking to grade. This in t u rn re q u i res additional drilling of shallow holes down in the trench to achieve grade, thus further increasing the h a z a rd of flyrock .

Jan 1, 2004

By V. K. Alves, P. Lacoste-Bouchet

"In order to improve ball milling efficiency in pellet plants, Companhia Vale de Rio Doce (CVRD), experiments new technologies in Santa Luzia (M.G. – Brazil) research center facility. Pilot grinding tests have been conducted with small grinding media, size distributed from 5 to 12 mm (millpebs). Tests have been conducted on an ore from CVRD’s Usina 5 Nibrasco, in Vitória, Brazil. A sample of the regrind circuit feed was obtained and used in comparative grinding tests with two types of grinding charges: 100% balls and a blend of 70% balls and 30% millpebs by weight. According to the balls charge, the grinding media mixture has showed the following benefits: reduction of the power draw, increase of the mill capacity, reduction of the circulating load and a slight increase of the ore blaine. Following the results obtained, CVRD is going to further explore the regrinding potential of millpebs.INTRODUCTIONCompanhnia Vale de Rio Doce (CVRD) is the largest mining company in Brazil. CVRD is involved in iron, base metals, gold and bauxite industries. Moreover, CVRD operates several pelletizing plants in Brazil and in other countries.CVRD’s Center for Mineral Development (CDM) is equipped with a comminution laboratory where studies are carried out that are aimed at the optimization of existing plants at several mining sites as well as the technical and economical feasibility of new projects. The laboratory is equipped with a complete pilot plant with several mills and classifiers, enabling continuous grinding tests in grinding circuits of almost any capacity and characteristics.In January 2004, CVRD undertook to conduct pilot tests at CDM for evaluating the effect of small grinding media on ball milling efficiency. Generally speaking, it is not unusual for operators to add oversize grinding media in a conventional regrind mill. This fact originates mainly from prohibitive prices of grinding media below 25 mm due to a production capacity decrease of grinding media producers. The size of the grinding media is an important variable affecting ball milling efficiency. Use of oversize balls decreases the number of contact surface between which particles can be caught and broken."

Jan 1, 2005

By David Reddick

The mining industry is in the midst of dramatic change. Mining activities are moving from industrialized first world countries (Canada, Australia, and the United States) to the third world. This shift is occurring due to depleted reserves, tough environmental standards, and expensive labor in traditional mining countries. During a recent trip to South Africa, I was asked, owing to my educational background in economics and an international involvement in drilling and blasting, what changes could be anticipated in third world blasting practices as labor costs increase. It is from that beginning that this presentation has evolved.

Jan 1, 1997

By A. R. Biggart, A. Walters, G. J. E. Kramer

The Owner Procurement Process or OPP is a proven, viable alternative contract delivery method that is potentially applicable to many tunnel projects. Using the OPP, the owner specifies and procures major tunnel construction items such as tunnel boring machines and tunnel linings and provides them to a tunnel excavation contractor in order to manage risk and accelerate project schedule. However, due to industry perceptions regarding potential owner risk, it is seldom considered or is rejected out of hand. In fact, past performance demonstrates that the process significantly minimizes owner, contractor and over-all project risk and mitigates the impact of any claims and differing site conditions. The paper outlines how the process should be structured to achieve schedule, cost, quality and risk management benefits. Potential and perceived disadvantages are discussed and how the process can be structured to mitigate or avoid them. The planned implementation of this process on the tunnels for the Silicon Valley Rapid Transit Project in San Jose, California is discussed.

Jan 1, 2005

By R. S. Dean

"Interest in the nitrogen content of steel has increased sharply in the last few years. Investigations have indicated that its presence in steel has an important bearing on high temperature brittleness3, magnetic properties4, room temperature hardening5, and shock resistance. The steel producer may therefore look forward with certaintly to the necessity of controlling this element in a considerable proportion of his product. The literature, however, reveals a great many contradictory statements concerning the percentage of nitrogen which must be present to produce given effects on the properties of iron and steel. Most of these arise from a misunderstanding of the nature of the iron-nitrogen diagram near the iron end and a lack of recognition of the effect of state of aggregation on physical properties although both have been fairly well worked out.My thanks are due to Mr. J. L. Gregg, Prof. R. H. Dowdell, Mr, R. F. Mehl and Mr. H. C. Vacher for suggestions in connection with the preparation of this paper, and to Mr. C. H. Hefty and Mr. G. T. Motok for furnishing a valuable bibliography and translations of articles by Must and Duhr.The iron-nitrogen diagram in the solid state, so far as it concerns the nitrogen content of commercial iron and steel, consists simply in a solubility curve increasing with temperature. The important thing about this solubility curve is that without cold wore the iron nitride when precipitated does not go into solution on heating for long periods below 300°C. This slowness of solution is probably due to the fact that iron nitride when present as a separate phase has at these temperatures an equilibrium pressure of several thousand atmospheres7 and that therefore each particle of iron nitride surrounds itself with a layer of nitrogen. The precipitation of such an unstable crystal presents points of interest thermodynamically but we can not go into these here. It is quite well established that it precipitate. It can not diffuse then unless this layer is broken through or the temperature and pressure are increased to a point where the nitrogen is absorbed at an appreciable rate in the surrounding iron. This rate will depend on the degree of unsaturation of the iron and the excess pressure of the nitrogen above equilibrium pressure. The degree of unsaturation is determined by the temperature alone so that the temperature at which the rate of solution of the nitride becomes appreciable will depend on the pressure of nitrogen developed. This, in turn, will depend on the balance between rate of decomposition of the nitride and the rate o: flow of the iron. In annealed iron, this temperature of appreciable solution rate is between 300 and 350°C.8 By cold work, however, the elastic limit of the iron is increased, and conditions for the nitride to go into solution are reached at a much lower temperature, giving rise to the so-called blue brittleness. This brittleness and hardening is due to iron nitride going into solid solution and is not precipitation hardening."

Mar 1, 1931

In some parts of the world explosions in mines are more commonplace events. Even in the more developed nations explosions have occurred in recent times. In some cases these mines have significantly lowered their lost time injury frequency rates and as such considered themselves to be ?safe? operations. The consequence of these explosions has been devastating. It is not just the loss of those underground, but also to the families that have lost people in them and the broader community that has lost friends, income, business opportunities, and in many cases support and sponsorships. It begs so many questions, ?What went wrong??; ?Why were the circumstances not foreseen??; ?What could have been done to prevent it??; ?How is it that no one stopped it, reported it, fixed it etc.??. Being held accountable for negligence, should not be overlooked, however this may not aid the processes required to find all the answers. If the nature of explosions is understood, the circumstances and tools to prevent them are readily available then the occurrence and reoccurrence are due to weaknesses or inadequacies of the systems of work or in the implementation of them. This paper restates the fundamentals of gas explosions, examines the options to control the underground environment through ventilation, gas management and monitoring, education and training. Case studies have been used to examine systematic failures in ventilation management. In some of these cases it is not so much, the system that had been developed, but the interpretation and implementation of the system that resulted in the failure and subsequent loss.

Aug 1, 2013

By Andrew P. Jarosz

The present computerized mine planning systems use CAD-like and Data Base Management System (DBMS) environments for the handling of numerical, textural, and graphical data. These two environments are usually integrated, that the data provided by the DBMS are linked to any graphical element rendered by the CAD system. The subsidence monitoring, analysis and prediction process should be integrated with the mine design process. It should allow for the assessment of impacts of mining on surface, surface utilities, and structures. It should also provide for the measures to control mining, that will create only acceptable levels of negative impacts on the surface. The common data base, and graphical capabilities of the CAD interface, may be used with great advantage for both systems. The findings of the subsidence engineering modulus should be directly incorporated into the mine design system, and vice versa. In this paper the author suggests guidelines for the development of the comprehensive computer system, able not only to predict the vertical and horizontal components of the ground movement, but also assess the induced surface damages, and costs related to subsidence prevention and compensation.

Jan 1, 1995

By C. K. Leith

THE resolution presented at the Annual Meeting of the A.I.M.E., calling on Congress to provide now for postwar accumulation of mineral stock piles under Government control, expresses, I think, the nearly unanimous view of the mining industry. As a result of the trying experiences of the first World War, Mr. Baruch, in his report of Dec. 24, 1919, to the President, urged that steps be taken at once to ensure adequate supplies of raw materials for future emergency. In the twenty years that followed, the same program was vigorously urged on Congress by many individuals and agencies, public and private, including the Secretaries of War and Navy, many members of Congress, the Bureau of Mines, the Planning Committee for Mineral Policy appointed by President Roosevelt, the A.I.M.E., the Mining and Metallurgical Society, and others.

Jan 1, 1943

By R. R. Sayers

The contemplated use of dichloro-difluorco methane in domestic and commercial refrigerating appliances and in air-conditioning equipment for public buildings and possibly homes, brims attention to the health hazards involved in a wide potential exposure of the public to vapors of another new product, and for the first time to vapors of an organic fluorino compound. The objective in the development of this new refrigerant, however, has been the mitigation of health and explosion hazards in automatic refrigeration, and accordingly these factors have been given primary attention. Early in the development, the Bureau of Mines as requested to make a laboratory study of the toxicity and potential hazard, and it was ca the oasis of the results is of this work and the results of a preliminary investigation made in another laboratory6 that the compound has been selected for commercial use. The investigation conducted by the Bureau of Mines is still in progress, enough information has been obtained to indicate the order of the toxicity and the magnitude of the health hazards involved in the use of dichloro-difluoro methane as a refrigerant. The following is a summarized report of the work completed to date:

Jan 1, 1930

By A. C. Fieldner, SIDNEY GOTTLIEB

This report summarizes the research and technologic work of the Bureau of Mines on coal and coal products from July 1, 1947, to July 1, 1948. It is the thirteenth of a series presenting resumes based largely upon publications issued during the year . In some instances , research and testing results , not otherwise available in published form , are presented . The individual publications given as footnote references herein will provide further detail to the interested reader . The period covered by this report was marked by an ever -mounting concern for the adequacy of the Nation's fuel resources and for fuel shortages arising from an increasing demand for fuels at home and abroad . Several reports appeared which delineated the place of synthetic liquid fuels in the future fuel technology and economy of the Nation , emphasized the fact that eventually the principal raw material for the production of such fuels will bet,5,6 coal, and described the progress made by the Bureau of Mines in developing processes for the production of synthetic liquid fuels . heard testimony along similar lines . Increased awareness of the fuels problems confronting the Nation led to an authorization by the 80th Congress for the erection of an anthracite research laboratory at Schuylkill Haven , Pa . , to house expanded Bureau of Mines research on anthracite . Design of the structure was well under way by the end of the fiscal year . ( See fig . 1. ) Looking forward to expansion of Bureau research on lignite , the 80th Congress heard testimony on the problems and programs of lignite research10, 11 as a prelude to authorizing the construction of a lignite research laboratory in North Dakota .

Aug 1, 1949

ABSTRACTOperations Research and associated techniques have wide application in the Mining Industry and have been used in Mount Isa since 1961.Typical of the projects undertaken by the OperatIons Research staff are1. the development of a complex computer programme for use in economic evaluation of mineral deposits,2. development of a production scheduling and control system for a complex mining operation,3. SImulatIon of a metallurgical plant operation to test the adequacy of design specifications and4. analysis of vehicular accident data to valuate alternative courses of insurance action.

Jan 1, 1968

By Franco Oboni, Iain G. Bruce

The design of tailings containment structures relies on well-understood engineering methods being applied consistently. Unfortunately, not all facilities are designed or managed to the same level of competency. To standardize procedures, the Mining Association of Canada (MAC, 1998) prepared a “Guide to Tailings Management.” It recommended review of designs and an assessment of the risks associated with tailings impoundments be implemented during all phases of amine life. This paper describes how the quantitative risk assessment (QRA) process can be used to define risks associated with the design, construction and operation of a tailings management facility. And it discusses how, once the risk tolerability curves (RTC) are defined for a project, they can assist the risk management (RM) process.

Jan 1, 2002

By B. W. Gandrud

[This report presents the data of one of a series of investigations of the washability of Alabama coals as indicated by float-and-sink tests mode by the Bureau of Fines at the Southern Experiment Station in cooperation with the University of Alabama and Alabama coal producers. The Klandyke mine, operated by the Blocton Mining Co., is about 1 mile eat of Vest Blocton, Bibb County, Ala., floor the southwestern, extremity of the Cahaba coal field. The Bureau of Mines already has published three reports that deal with the, washability of Cahaba coals - one a washability study of the Clark bed at Marvel4/ one on the tabling of fine coal from the Thompson and Woodstock beds5/, and the third a washability study of the Henry Ellen bed at Acmar6/.]

Jan 1, 1939

IN the recent monograph on Broken Hill, N.S.W., by E. C. Andrews,* two independent petrological reports appear as Appendices 1 and n, by W. R. Browne and F. L. Stillwell respectively. In these considerable differences of opinion occur. Andrews contributes to some of the questions at issue, but no analytical review of the differences appears in the body of the report. Their development may invite question, and the following notes have been prepared partly in explanation and partly as a summary of some of the divergences. The soope of Browne's report extends over the whole district of Broken Hill, while Stillwell's deals with the rocks within 25 chains of the main lode. The more difficult and important rock-types occur in both areas, raising similar questions. In both cases observations extended beyond the limits of the prescribed areas. Broadly, Browne faces his problem as a study of a series of primary igneous rooks, acid and basio, whioh are intrusive into a series of sillimanite gneisses. The development of the sillimanite gneisses is regarded as belonging to an earlier period than the intrusion of the igneous rooks, while the gneissio structures of the latter are features which are incidental to their orystallization, and are not acquired subsequent to their consolidation. He finally produoes a picture in which his views of igneous injection and differentiation takes a prominent place. One direct result is the claim that three separate periods of metamorphism have oocurred in the Broken Hill area. Stillwell primarily examines the rooks as schists and gneisses since their present dominating features have been acquired during metamorphism. The effort is made to understand suoh differences as might arise from differing conditions of metamorphism upon rocks of similar and different oonstitution. The aim is to divest the rocks of those oharaoters which are due to metamorphism before approaching the questions of intrusive relatio'nships between igneous rocks andsediments.

Jan 1, 1924

By J. L. Robson, C. M. Bristow

mass flow rates of particles and air (the loading ratio).

Dec 1, 1994

By E. B. Kester

A study of the composition of the corresponding fractions of a primary and a high-temperature tar was undertaken to throw light on the net results of the pyrolysis of the primary products of coal decomposition in high-temperature coking practice, with reference both to total quantities of the chemically similar constituents and to their distribution throughout the boiling range. No exactly parallel investigations are on-record. The distribution of substances in high-temperature tars, however, is fairly well understood. Such tars are more or less similar, for they consist of the more stable phenols, aromatic and olefinic compounds resulting from the pyrolytic decomposition of a wide variety of primary tar constituents. For example, from a typical distillation curve for high-temperature tar phenols it may be seen that the greatest portion of the phenols distills between 180° and 220° C., a fairly narrow range. Low-temperature tars, on the other hand, are more complex, and hence exhibit dissimilarities from one to the next. Edwards, who has made a study of the acids, bases, and neutral oil of four low-temperature tar distillates, shows that the bases and neutral oil are evenly distributed among the fractions but that the concentration of the acids is greatest in the 200° to 230° fraction. Morgan and Soule find that in tar from the "Carbocoal" process, the 237° to 281° fraction has the highest acid content, whereas Davis and Parry find the 200° to 225° fraction of Freeport tar richest in phenols. Previous investigators have noted the following differences between primary and high-temperature tar: In the latter, naphthalene and anthracene occur in large quantities, the paraffins and naphthenes are negligible, the percentage of higher phenols is much lower than in primary tar, and the lower and more stable aromatic hydrocarbons have increased. In an endeavor to reconcile the change undergone when a primary is converted into a secondary tar, the writers have been unable to find references dealing with the extent of change which any one of the constituents of primary tar may undergo when subjected to secondary heating effects in the presence of other components, and the amount of the more stable compounds that may be expected from a given starting material.

Jan 1, 1932

Errors in ore reserve estimation can occur during drilling and sampling, sample preparation and analysis, geological logging and modelling, database construction, statistical or geostatistical evaluation, selection of economic parameters, selection of ore reserve method and assessment of mining constraints. Core sample recovery can be a major source of error, and it is proposed that the modelling of grade, metal accumulation and thickness should be accompanied by the modelling of core recovery (or core loss) so that for each ore block a weighted block recovery factor is obtained. This gives a good indicator of the reliability of a reserve estimate. It is suggested that a resource reliability rating (RRR) system be established to quantify what is meant by geological assurance and to combine this with an estimate of the precision of estimation as gained by geostatistical analysis. Proven and probable minable reserves would be those with an RRR better than 50% and a precision of estimation better than 20%

Dec 1, 1996