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By S Jackson, I Arbuthnot

The use of High Rate Thickeners has gained wide acceptance in the mineral treatment industries. The design of these units is characterized by an efficient deaeration and flocculation chamber, and introduction of the flocculated feed solids into a preformed floc bed zone. By these means the settling process is accelerated and consequently High Rate Thickeners achieve a significantly higher throughput per unit area than conventional thickeners.   The object of a control system on a High Rate Thickener (HRT), as on a conventional thickener, is to obtain the required underflow density and overflow clarity at all feed conditions. The feed conditions which may vary include volumetric and mass feed rate, pulp density, particle size and particle type. A conventional thickener has a large volume and cross sectional area, and changes in performance occur slowly û the operator has time to observe and react to these changes to maintain control. On a HRT, there is a much reduced residence time and therefore control parameters need to be reset more frequently. Although manual control is possible, the use of automatic control systems is therefore desirable to avoid excessive operator attention, while optimizing control of density and clarity. Automatic control of a conventional thickener is usually achieved by an underflow density loop which regulates the rate of withdrawal of underflow. A turbidity meter is sometimes used to measure overflow clarity and regulate the addition of a coagulant or polymer flocculant. These measures are not adequate on a HRT, because they would not give optimum control and could lead to excessive flocculant use. To achieve optimum operation in a HRT, the floc bed level should be maintained above the feed inlet point in the thickener. This bed level has become the key variable around which most control systems have been designed. However, a number of problems have occurred which has resulted in poor control, or only partial control of thickener performance. We will describe some of these problems, and a solution which is simple and effective.

Jan 1, 1990

By Norman C. Stines

Russia's mineral potential is a secret that has been effectively kept by the Iron Curtain. There is no conclusive data and because of its extreme importance to the Free World, the subject is greatly discussed. Opinions range from those presented by Paul Tyler in his article "Russia's Mineral Potential," June issue of MINING ENGINEERING to those of Norman C. Stines, presented herewith. Mr. Stines is a consulting mining engineer of Los Gatos, Calif. He was in Russia, China, and Manchuria from 1909 to 1918 as a mining executive. From 1917 to 1919 he served as assistant military attache Intelligence Branch U. S. Army in Petrograd, Russia.

Jan 11, 1951

By L. E. Djingheuzian

Introduction Cylindrical grinding mills have been used for a long time, but during many years of testing no methods were established that gave consistent results. The work by both scientific investigators and operators led very often to contradictory conclusions, and each millman was very much 'on his own' when trying to find the limits for working of his ball-mills. Fred C. Bond, in the introduction to his paper on Wear and Size Distribution of Grinding Balls, freely states that the mathematical immaturity of the grinding process "is the cause of many inefficient designs and installations as well as of much poorly oriented experimental work", and evidently he sees the solution of all our grinding problems in the discovery of the fundamental laws "which can change the empirical art into a mathematically exact science". While the writer is in complete agreement with Mr. Bond that grinding is governed by fundamental laws which can be expressed by mathematical formulae, there are so many variables in grinding, all interwoven with each other and mutually influencing each other, that the coalescing and merging of all these variables into a harmonious mathematical whole appears to be a homeric job. However, a light appeared on the horizon when it was proposed that power be used as an index of the grinding operation. It is pertinent to quote Gow, Guggenheim, Campbell, and Coghill from their paper on Ball Milling, in which they say: "Much of the past literature devoted to the subject has been concerned with the Kick-Rittinger dispute over evaluating grinding, or with dissertations on ball paths and the closely allied impact versus attrition hypotheses or with the exclusive consideration of certain specific variables, such as mill speed or circulating load, irrespectve of the other factors in operation. Such subjects may be dismissed with but little discussion in what may be called, by comparison a new philosophy in the stud of ball milling. Briefly this 'new philosophy' consists ' of using power as an index of the mill operation, and investigating grinding from the standpoint of set and induced variables with emphasis on the latter". But it is safe to assume that it was the work by E.W. Davis, H. E. T. Haultain, F. C. Dyer, A: M. Gaudin, J. Gross, S. R. Zimmerley, and others, that cleared the path for the authors of Ball Milling and induced them and A. W. Fahrenwald to look farther afield and thus to establish a far-reaching relationship between the power and capacity and the diameter of the ball-mills.

Jan 1, 1949

By Hugo Cabrera-Real

This work investigated the chemical and mineralogical properties of CaO-SiO2-CrOx-CaF2- MgO slags. Synthetic slags were prepared and the effect of the slag basicity (CaO/SiO2) and MgO contents on the stability of the mineralogical species formed was analyzed. The morphology and composition of the slags were analyzed by XRD and SEM-EDS, whilst their chemical stability was evaluated by leaching with an aqueous acetic acid solution. It was found that in slags with CaO/SiO2 = 1, the main Cr-compound was MgCr2O4 spinel, which forms octahedron crystals. Small amounts of CaCr2O4 and CaCrO4 were also observed. It was found that increasing the slag basicity from 1 to 2 the compounds MgCr2O4 and CaCr2O4 were formed together with the Cr(V)-containing compound complex Ca5(CrO4)3F which forms hexagonal crystals. The results showed that the highest chromium concentration levels in the leaching liquors corresponded to slags with CaO/SiO2 = 2, probably owing to the formation of Ca5(CrO4)3F.

Jan 1, 2010

By Noel N. Moebs

Bureau of Mines studies of mine roof fall problem in the Pocahontas No. 3 Coalbed of southern West Virgania and southwestern Virginia have established that type and sequence of rock are significant factors in roof competence. The poorest conditions occur where the immediate roof consists of slump structures and slickensided rock. The best conditions occur where the roof consists of a sequence that coarsens upward from shale to massive sandy shale. A small manual of color photographs of rock types was devised to aid in identifying drill cores. Proper identifications should enhance the prediction of areas of potential roof problems in advance of mining.

Jan 1, 1981

By AIME AIME

AT FOUR O'CLOCK members gathered in the auditorium for the annual business meeting of the Institute which, according to its charter, must be held on the third Tuesday of February each year. President Turner presided and after the usual formal action on minutes announced that he would create a precedent by transferring the President's annual address (which by tradition has always been delivered at the banquet on Wednesday evening) to the business meeting, and, furthermore, would only present a brief abstract of it. Since it appears in full on pages 127-131 of this issue it can be followed with the careful attention its thoughtful analysis of current conditions deserves.

Jan 1, 1933

By Y. A. Attia, M. Elzeky

Thiobacillus ferrooxidans bacteria were used in this work to study the effect of bacterial adaptation on the bioleaching of three iron-bearing sulfide minerals, namely, pyrite, chalcopyrite and arsenopyrite. The change in the pH during the bioleaching process was observed and the mechanism of the bacterial action were discussed. It was found that bacterial adaptation prior to bioleaching, enhanced the degree of sulfide leaching by 2-4 folds over that of non-adapted bacteria. A1 so the bacterial activity was enhanced by 2-4.8 folds. The pH of leaching solutions was decreased by the increase in both adaptation period and bioleaching time. It was also concluded that the mechanisms of bioleaching of iron-bearing sulfide minerals involved both the direct and indirect bacterial action simultaneously.

Jan 1, 1989

By F. D. Ayhan

The aim of this study was to investigate the effects of various water mediums on desulfurization and deashing of a coal sample using flotation. For this purpose, experimental studies were conducted on a coal sample containing high ash and sulfur contents. The effects of pH, solid concentration, collector amount and frother amount on the flotation were investigated separately in Mediterranean Sea water, Çermik thermal spring water, snow water and tap water. Flotation results indicated that, when comparing the various water mediums, the following order for the ash content was obtained: snow water < Çermik thermal spring water < tap water < the Mediterranean Sea water. For the reduction of total sulfur, the following order was obtained: snow water > Çermik thermal spring water > Mediterranean Sea water > tap water. When snow water was used as a flotation medium, it was found that a concentrate containing 3.01% total sulfur and 27.64% ash with a total sulfur reduction of 57.06% was obtained from a feed containing 7.01% total sulfur and 41.17% ash.

Jan 1, 2009

By L. A. Haas

In this Bureau of Mines investigation, conditions were determined to form an iron sulfide adherent coating with a metallic golden luster on steel upon anaerobic heat treatment with sulfur. The sulfide formation rate was determined in the temperature range of 105° to 500° C with reaction times up to 68 hours. The optimum temperature and time to form an adhering decorative coating on mild steel was in the range of 105° C for about 70 hours to 285° C for 1 hour. The golden coating consisted of an inner layer of pyrrhotite and an outer layer of pyrite. At temperatures higher than about 300° C, the outer layer thickness decreased owing to the decomposition of pyrite to pyrrhotite.. Small quantities (<0.5 wt-pct) of petroleum oil accelerated the sulfide growth rate. The sulfide coating decreased the corrosion rate of steel in a neutral aqueous medium by a factor of two. The dissolution of pyrite in water was dependent on particle size and surface area with the flat pyrite coatings exhibiting the lowest dissolution rate.

Jan 1, 1974

By R. K. Dunham, D. J. Reddish, X. L. Yao

Paper presented at the conference: Risk assessment in the extractive industries, held in Exeter, UK, 23-24 March 1994, and first published London: IMM, 1994, preprint volume, 10pp., 10 refs. The integrated approach combines a powerful ground movement prediction program with a knowledge-based expert system. ESDAS (Expert Structural Damage Assessment System) was developed to evaluate mining subsidence damage in the form of risk and in terms of the three vital contributing components (mining factors, site factors and structural factors). Using a certainty factor risk assessment technique, the system can be used to predict the likely damage to a particular structure subjected to mining subsidence. A previously developed powerful ground movement prediction program, SWIFT (Subsidence With Influence Function Techniques), has been combined with the expert system to allow the mining factor to be more accurately determined in a broader range of mining layout. Since SWIFT can be calibrated to any particular coal field using local subsidence data, it is believed that the integrated system could be used in any coal field worldwide for the assessment and control of mining subsidence damage risks

Dec 1, 1995

By M. Kalin

"SUMMARYWaste management in general, and the water treatment of mine and mill effluents, has become an ever increasing burden for mining operations. A reduction in these expenditures would undoubtedly be desirable if this could in fact be achieved within effluent guidelines and monitoring requirements.A brief summary is presented of the research which has as its aim the development of methods which would reduce such costs and lead to solutions for environmentally acceptable close-out conditions for acid generating mine waters. The basic concepts of Ecological Engineering and Biological Polishing are presented, together with an indication of the present state of these research efforts. Details are provided of the progress of various experiments which aim to promote reducing conditions, organic matter production and the establishment of biological filters which remove metals from the water which are then retained within the waste management areas. These conditions should lead to a curtailment of acid drainage and an improvement in effluent quality.A description is provided of the first pilot demonstration using this approach to achieve a walk-away condition for the close-out of a massive sulphide tailings resulting from 10 years of operating a copper/zinc concentrator in Northern Ontario.1.0 INTRODUCTION1.1 Waste management and close-outIt is recognized that the achievement of a cost-effective and competitive mining operation, from the commencement of exploration for ore bodies through to the day-to-day efficient operation of the mine, requires a certain expertise and sophistication. However, the environmental effects of these activities are considered peripheral issues and their importance as an integral part of the planning and development of the mine/mill, is not always appreciated."

Jan 1, 1988

By Marcela Teixeira Dalboni Garcia

Neste trabalho é apresentado uma metodologia para caracterização de propriedades ópticas e espessura de óleo depositado em folha-de-flandres por elipsometria. Folhas-de-flandres precisam receber ao final do seu processo de produção um fino filme de óleo para proteger a folha contra abrasão e facilitar o desempilhamento quando é armazenada em fardos. Para medida da espessura desta camada de óleo foi desenvolvido um procedimento eficaz com o uso de um Elipsômetro Espectrométrico (ou Espectral) de Polarizador Rotativo. Foram comparados os resultados com estudos feitos pelo método da balança de hidrofil, técnica utilizada atualmente, mostrando um aumento na sensibilidade da medida.

Aug 16, 2017

Development of a Froth Dropback Measurement Device

Sep 13, 2010

By M Eggers, H Baxter

This paper discusses the geotechnical condition of bedding shears and small- and large-scale faults and shears in Archean banded iron formation (BIF) bedrock, based on observations of core and televiewer images. Information that can be collected includes the orientation of defects, infill thickness, strength and material type, defect shape and surface roughness.The spacing and continuity of bedding shears may be critical to slope design where performance is structurally controlled with bedding dipping out of a wall. The intensity of development of the bedding shear is a useful indicator of the amount of shearing a bedding surface has been subjected to. This can allow for engineering judgement to be used in adopting peak or residual shear strengths along defect surfaces when developing the design.The spacing and continuity of bedding shears may also contribute to the blockiness and degradation of a rock mass where the structural orientation is otherwise favourable. Additionally the condition, thickness and strength of infill of major fault structures can affect slope design and performance, depending on orientation.Comparison of the condition of structures observed in core with the corresponding in situ televiewer image has been made to assess what characteristics are most accurately captured by each technique and whether the additional information gathered from using the televiewer technique is justified by the cost. The question of whether the data collected by a televiewer is sufficient to ultimately replace the need for core is considered.CITATION:Baxter, H and Eggers, M, 2013. Fault and shear characterisation in archean banded iron formation bedrock - a comparison between core and televiewer data collection techniques, in Proceedings Iron Ore 2013 , pp 47-56 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013

On July 1, 1969, the Explosives Research Center merged with the Health and Safety Research and Testing Center to form the Safety Research Center, with facilities at Pittsburgh and Bruceton, Pa. Subsequently, passage in December of the Federal Coal Mine Health and Safety Act of 1969 (Public Law 91-173) had a major influence on the activities of the new center. These activities were conducted under two main programs, Coal Mine Safety Research and Explosives Research. The Coal Mine Safety Research program was concerned primarily with two categories of hazards: health-related hazards associated with the mine environment, due to such factors as respirable dust, toxic gases and vapors, and excessive noise; and accidents due to mine fires, explosions, and roof falls.

Jan 1, 1972

By A. H. G. Mitchell

Most, if not all, of the six recognised post-Cretaceous, predominantly andesitic mineralised belts in the region are now thought to be subduction-related magmatic arcs. The Inner Carpathian arc and the Eastern Bosnia or Drina-Rhodope arc host numerous vein and replacement deposits with epithermal features and Zn-Pb+/-Ag as the predominant economic minerals. In contrast, the south Apuseni Mountains have produced over 1 600 t Au from epithermal veins but very little Zn-Pb. Recent age determinations and geophysical data from the Baia Mare district of the Inner Carpathians suggest that mineralisation succeeded volcanism by 1-2 m.y. and accompanied crustal extension and the cooling of a large, mushroom-shaped pluton whose boundaries define the mineral district. In the south Apuseni district, mineralisation can be explained by mixing of meteoric with low-salinity metamorphic water expelled during intrusion of mafic rocks into the middle or lower crust. The more continental or cratonic crust in the Drina-Rhodope and Inner Carpathian arcs precluded the input of low-salinity, Au-bearing metamorphic water; the Zn-Pb deposits formed where convecting meteoric water mixed with saline water, possibly introduced through carbonate rocks in the basement

Aug 1, 1996

By J L. Mauk

Golden Cross is a volcanic-hosted, low-sulfidation, epithermal Au-Ag deposit in the Hauraki Goldfield. Irrespective of the rock type (andesite versus dacite), hydrothermally altered wallrocks are enriched in K, Rb, As and Sb around Au-Ag mineralised veins of the Empire vein system and stockwork. Sodium and Sr are strongly depleted around these veins, whereas Mg and Fe are locally depleted. Calcium and Si display mixed behaviour, varying from unchanged to depleted to enriched. Other elements including Al, Ti, Mn, Zr, Y, and Nb show little change or are immobile during hydrothermal alteration. Element enrichment and depletion trends are directly related to the degree of alteration and the alteration mineralogy. Addition of K and Rb and converse loss of Na and Sr in intensely altered wallrock surrounding veins corresponds to the replacement of igneous plagioclase by hydrothermal adularia. Sodium and Sr occur in moderately altered rocks on the margins or in æhard barsÆ that contain plagioclase. Locally, elevated Si concentrations and depletion of Mg adjacent to the Empire vein system reflects intense silicification of the wallrocks and the replacement of mafic minerals by quartz rather than by chlorite. The geochemical zonation patterns at Golden Cross are very similar to those at the McLaughlin deposit California, and shallow levels of the active Broadlands Ohaaki geothermal system. Therefore, determination of K, Na, Rb, Sr, and Ca enrichment and depletion patterns provides insight into alteration intensity and mineralogy that is complimentary to traditional trace element analysis of As, Sb, Hg, Au, Ag, Zn, and Pb used in the exploration of shallow level (&lt; 500 m) epithermal Au-Ag deposits.

Jan 1, 2000

By M. M. Hajdasinki

A project&apos;s rates of return (RORs)1, be it the internal rates return (IRRs) or one of the many IRR surrogates, frequently needs to be approximated. The success and efficiency an ROR- approximation procedure depend on the quality the approximation-initiating parameters, such as bounds or seed values (guesses). The existing approximation procedures commonly use bounds and guesses suggested by intuition rather than supported by mathematical considerations. This paper presents three mathematically founded ROR-bounding and eleven ROR-guessing approaches and examines their suitability by using examples of typical project cash-flowpatterns (CFPs). The calculated bounds and guesses not only improve the approximation efficiency, but also allow the process of the ROR discovery to be automated, thereby making it more convenient and reliable.

Jan 1, 1999

By Ronald M. Lewis

Quadratic functions, Q(hkl), are given to six places in increments of 0.01° for 2? from 00 to 90° for FeKa and from 25° to 180° for FeKa1. The wavelengths used for Fe in the computation are those agreed upon by the Editorial Commission of the International Tables for X-ray Crystallography (1950): FeKa1 1.93597 A.; Feka2 1.93991 A. INTRODUCTION At the Federal Bureau of Mines laboratory, Norris, Tenn. X-ray diffraction crystallography using tubes with iron targets revealed a need for a handy reference for the quadratic functions of iron radiation. The tables presented here were prepared to satisfy that need. The quadratic form Q(hkl) may be expressed in terms of the Bragg diffraction angle 2? and of the wavelength ? as

Jan 1, 1961

By L. Flett, S. Woods, C. Deredin

"Following a significant reduction in world Imperial Smelting Furnace (ISF) capacity from 2003 to 2008, a major optimization initiative was successfully carried out on the lead upgrading and bulk (zinclead) flotation circuits in the Brunswick Concentrator.This paper describes the process improvements that have taken place in order to reduce the quantity of bulk concentrate:•,Increase in lead upgrading rougher flotation circuit capacity•,Installation of a closed-circuit bulk regrind utilizing MillPebs and 150 mm Cavex hydrocyclones•,Installation of two additional cleaner flotation stages on the bulk circuit•,Optimization of the manipulated variables in the lead upgrading and bulk circuitsINTRODUCTIONThe Brunswick Mine (Xstrata Zinc Canada) is located near Bathurst, New Brunswick and is one of the world’s largest lead/zinc mines. Milling of ore commenced in 1964 from the No. 12 orebody, with an expansion in 1966 to accommodate ore from the No. 6 open pit mine. The planned closure of the mine will take place at the end of the first quarter in 2013. The ore is a complex massive sulphide, consisting of approximately 20% valuable minerals, 60% pyrite and 20% silicates.A simplified flowsheet for the concentrator is given in Figure 1. The overall flowsheet involves SAG milling, secondary ball milling, selective flotation, and dewatering by thickening, filtering and drying. The complexity of the flowsheet evolves from the requirements for fine grinding and the production of four concentrates: zinc (sphalerite), lead (galena), copper (chalcopyrite) and bulk (sphalerite plus galena).Primary hydrocyclone overflow feeds the copper-lead aerator-roughers for flotation at pH 9.0 with soda ash. Plant xanthate (80-20 sodium isopropyl and potassium amyl) and AP407 are used as collectors in the copper-lead circuit. The rougher concentrate is directed to the copper-lead regrind circuit and the tailings are fed to the secondary grinding circuit. The secondary hydrocyclone overflow from the secondary grinding circuit feeds the copper-lead rougher-scavenger banks. Rougher concentrates are reground to a P80 of 28 µm prior to three stages of copper-lead cleaning. The first stage of cleaning is done in an open circuit with the tail reporting to the cleaner scavenger. The cleaner scavenger concentrate reports to the regrind circuit and the cleaner scavenger tail combines with the rougher/scavenger tail to feed the zinc circuit. The second and third stages of cleaning are performed in closed circuit with the cleaner tail being recycled to the copper-lead regrind circuit. The average final concentrate grades 23% Pb, 3% Cu and 704 g/t Ag, and is fed to the copper separation circuit."

Jan 1, 2013