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By J. Bouchard, A. Desbiens, M. Maldonado, R. del Villar

ABSTRACT: Despite many years of practical applications in mineral processing plants, the potential of column flotation has still not been fully exploited. The challenge in measuring some key variables is certainly an important contributing factor to this situation. Reliable online measurement of variables, such as the froth depth, bias, gas hold-up, frother concentration, bubble surface area flux, and bubble size distribution, provides opportunities for the application of various advanced control strategies and real-time optimization based on an economic criterion. For several years, Université Laval’sLaboratoire d’observation et d’optimisation des procédés researchers have been working on these opportunities. This paper describes the most recent advances and current research trends.

Jan 1, 2011

The accurate determination of trace level gold in ores, metallurgical samples and process solutions is required because of the value of gold, the efficiency of the cyanide leach process and because of the high gold recovery from these cyanide solutions. It is thus necessary to routinely analyse geological and metallurgical samples with gold concentrations of 3 g tonne (ug g- 1ppm) and process solutions with a gold concentration of 0.01 mgL 1 (ppm) preferably with sufficient accuracy to quote at least two significant figures. Several techniques have been reviewed for their suitability for the routine gold analysis of these samples which also contain signif- icant concentrations of other ions. The classic fire assay technique has achieved the respect and confidence of mining personnel because of the results achieved by very experienced assayers. Other extraction and concentration techniques have now been shown to be equally effective. The use of instrumental analytical techniques particularly atomic absorption spectrometry have shown that cheaper procedures, which are as reliable, are now available to gold producers for the routine analysis required to maintain an efficient gold recovery process.

Jan 1, 1982

A series of flotation experiments were carried out in a 2.25-dm3 laboratory-scale Rushton turbine cell using hydrophobic quartz particles. Flotation was performed at a constant mean bubble diameter over a range of superficial gas velocities and impeller rotational speeds. The overall flotation rate constant increased linearly with increasing superficial gas velocity (and hence bubble surface area flux). The rate constant also increased linearly with increasing energy dissipation, until a maximum value was reached. A further increase in energy dissipation had little effect on the rate constant. The dependency of the rate constant on energy dissipation is a reflection of the size range and hydrophobicity of the particles used in this study. The flotation rate constant increased with increasing particle size, except at the highest energy dissipation value examined, for which the flotation rate of the larger particles reached a plateau and, in some cases, decreased. Good agreement was obtained between the experimental results and those predicted by a fundamental flotation model using experimentally measured values for mean energy dissipation and the Sauter mean bubble diameter. The bubble velocity was adjusted to obtain the best fit to the experimental data. The inferred bubble velocity, based on the flotation model, was found to increase with increasing superficial gas velocity (and bubble surface area flux) and was found to decrease with increasing impeller rotational speed. While the inferred bubble velocities were significantly lower than experimentally measured bubble velocities, and, except at low superficial gas velocity values, significantly higher than the bubble swarm velocity calculated from gas holdup measurements, similar trends with impeller rotational speed and superficial gas velocity were observed in all cases.

Jan 1, 2007

By D. M. Baird

"Enormous deposits of gypsum of exceptionally high grade are readily accessible in southwestern Newfoundland. Coming large-scale production from one of these is resulting in renewed interest in deposits which have been known for more than a hundred and twenty years. General stratigraphy and structure of the Carboniferous rocks in which the gypsum occurs are de-scribed. The stratigraphic position of the basal gypsum-anhydrite zone is described. This massive evaporite horizon, which reaches a thickness of about 1,0001 feet, appears at Fishels-Heatherton, where it is largely undeveloped, and again on the nose of an anticline east of Flat bay, where a present production of 20,000 to 40,000 tons per annum is soon to be expanded to make it one of Canada's major producers. Detailed descriptions are given of the several types of gypsum, the relation of the gypsum and anhydrite, and the distribution of sodium chloride in the evaporite beds, and the bearing of all these on the origin of the gypsum are discussed. Brief reference is made to relation to world markets, mining and transportation, grade, and reserves."

Jan 1, 1959

By John L. Nieber

This information circular describes a computer program called VARSAT2D, a comprehensive unsaturated fluid flow simulator developed by the U.S. Bureau of Mines. VARSAT2D solves for either a vertical or horizontal, transient or steady-state solution in variably saturated, heterogeneous, anisotropic porous media using the Galerkin finite-element approach. Simplex triangular elements are used. Moisture retention characteristics are described by specifying either the Brooks and Corey, Brutsaert, or Van Genuchten power functions, with hysteresis described using the Maulem independent domain model. Boundary conditions may include any combination of time-varying seepage, pressure along solution domain, boundaries and/or at internal node points, unit hydraulic gradient at the lower boundary, and a uniform source and/or sink. This program should be a welcome addition for mining and environmental hydrologists, researchers, and engineers interested in modeling unsaturated fluid flow.

Jan 1, 1994

Laminated ceramics have received widely scientific and commercial attention because their properties, such as mechanical properties and electrical properties, can be tailored by adjusting the structure, thickness and composition of the different layers. For example, ferroelectric Bi4T13O12 (BIT) which has a positive temperature coefficient of dielectric constant (TE) can be used to modify the negative of typical microwave dielectric ceramic BaNd2Ti4O12(BMT). However, BaNd2Ti4O12/Bi4Ti3O12/BaNd1Ti4O12 (BNT/BIT/BNT) laminated ceramics could not be prepared by the general method because the optimal sintering temperature of BaNd2Ti4O12 ceramic (around 1350°C was much higher than that of Bi4Ti3O12 ceramic (around /1100°C). in this research, a new method of spark plasma sintering (SPS) combined with post-sintering was successfully proposed to prepare BNT/BIT/BNT laminated divided proposed to prepare ceramics. It was divided into three steps. In first step, the BaNd2Ti4O12 ceramics were prepared by conventional sintering method. In second mop, the calcined and pre-pressed Bi4Ti3O12 powders were sandwiched between BaNd2Ti1O12 ceramic pellets and spark plasma sintered at 900'C for 10min to synthesize BNT/BIT/BNT composite ceramics. In the last step, a post-sintering was employed to reoxidize the partially reduced BNT/BIT/BNT composite ceramics. The results of scanning electron microscopy (SEM) and electron probe mircoanalysis (EPMA) showed that BNT layer and BIT layer were well bonded and no significant interfacial infiltration between them was observed. The sandwiched BNT/B1T/BNT ceramic with 10.7% BIT in volume has a dielectric constant of 92.8, a low dielectric loss of 0.0068 and a small temperature coefficient of dielectric constant v/35 ppm/C at 1 MHz.

Jan 1, 2003

By Yong .. Jun Wu

Laminated ceramics have received widely scientific and commercial attention because their properties, such as mechanical properties and electrical properties, can be tailored by adjusting the structure, thickness and composition of the different layers. For example, ferroelectric Bi4Ti3O12 (BIT) which has a positive temperature coefficient of dielectric constant (,E) can be used to modify the negative tE of typical microwave dielectric ceramic BaNd2Ti4O12(BNT), However, BaNd2Ti4O12/Bi4TiO12/Bi4Ti3O12/BaNd2Ti4O12 (BNT/BIT/BNT) laminated ceramics could not be prepared by the general method because the optimal sintering temperature of BaNd2Ti4O12 ceramic (around 1350°C) was much higher than that of Bi4Ti3O12 ceramic (around 1100°C). In this research, a new method of spark plasma sintering (SPS) combined with post-sintering was successfully proposed to prepare BNT/BIT/BNT laminated ceramics. It was divided into three steps. In first step, the BaNd2Ti4O12 ceramics were prepared by conventional sintering method. In second step, the calcined and pre-pressed Bi4Ti3O12 powders were sandwiched between BaNd2Ti4O12 ceramic pellets and spark plasma sintered at 900°C for 10min to synthesize BNT/BIT/BNT composite ceramics. In the last step, a post-sintering was employed to reoxidize the partially reduced BNT/BIT/BNT composite ceramics. The results of scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) showed that BNT layer and BIT layer were well bonded and no significant interfacial infiltration between them was observed. The sandwiched BNT/BIT/BNT ceramic with 10.7% BIT in volume has a dielectric constant of 92.85, a low dielectric loss of 01068 and a small temperature coefficient of dielectric constant of 35 ppm/°C at MHz.

Jan 1, 2003

H. M. BOYLSTON, Cambridge, Mass.-I would first like to ask what machine Capt. Bellis used to make his tests on impact strength. I have made some tests with the Charpy impact machine, the specimen being supported at both ends and nicked in the middle, and, find that the results do not always agree with those obtained by the Izod and other machines. I would also like to ask what effect the composition and heat treatment of the tool steel had on the drilling of his rifle barrels, as compared, with the heat treatment of the steel itself? I notice that the analysis of the composition of steel used shows sulphur 0.050 and phosphorus 0.065; I should like to ask how those high limits of sulphur and phosphorus came to be allowed? I have some data which lead me to feel pretty certain that those high limits make for very unsafe steel in rifle barrels. It has never been explained to the satisfaction of all of us, why the manganese is so high: 1.22 per cent. I believe several reasons have been stated; among them, that it is high in order to compensate for the high sulphur, and also to increase the elastic limit and improve other physical properties of steel. Lastly, I wish to ask whether Capt. Bellis has tried any different methods of heat-treating his steel rifle barrels? Apparently these were all heat-treated before machining; has he had any experience with heat-treatment after machining, especially after drilling? Those questions may seem somewhat outside of the range of this -paper, but they are important, and if Captain Bellis can give us any information, it will be very helpful. Dr. J. A. MATHEWS,* Syracuse, N. Y.-The same subject was discussed here last year, and the earlier papers by Dr. Carle Hayward seem to indicate that nothing was gained by the length of time of 'tempering. (It should be borne in mind that his results were based upon electrical and magnetic measurements and not upon tensile tests.) That idea has been accepted as gospel by steel workers, until late years, and particu-larly in connection with alloy steels, on which there is no question that the effect of time of tempering is very marked.

Jan 4, 1918

Application of flotation for the removal of hydrophobic compounds from soils was studied. Bench scale flotation tests were conducted on artificially contaminated soil, using both conventional mechanically agitated machine and flotation column. Flotation parameters tested include surfactant collector type, conditioning time, flotation time, surfactant dosage, pulp pH, solid/liquid ratio in conditioning and pulp temperature. It is found that with conventional flotation 74% removal of the contaminant was achieved from soil particles in the range of 75-830 µm; with column flotation up to 80% of oil could be removed from the 250-830 µm soil fraction, and 65% from the 75-830 µm fraction. Flotation was found to have considerable potential for cleaning up contaminated soils.

Jan 1, 1998

By K. Rajani Kanth

Environmental problem is the major concern for any industry and there is a great need to that along green lines. Sangam Dairy being one of the most famous and wide spread Dairies in India, produces wide spectrum of milk products. The BOD levels of effluent water of this industry with MIF treatment were found to be around 100 ppm. Lot of research has been expended in the past to bring down the BOD levels to bare minimum. The main objective of the present study is to minimize the BOD level to the required level stipulated by environmental standards by employing various seeding materials. For this purpose microbes like Bacillus Subtiles, Pseudomonas, Aspergillas, Staphylococcus, and Pencilium have been employed and BOD levels were analyzed. Various Reagents, solutions with different dilution levels have been successfully prepared. Initial and final Dissolved Oxygen levels were determined before and after incubation. From the DO data, BOD was evaluated for all samples and comparison analysis of various seeding material was carried to suggest the efficient seeding material for the ETP plant. In the process, solutions of different dilutions have been prepared using difficult reagents. These samples are treated with above mentioned microbes and BOD levels are estimated. It has been observed that staphylococcus and Pseudomonas proved to be the best seeding materials. When there microbes have employed BOD levels fall to less than 10 and 20 ppm respectively

Jan 1, 2006

By Elisiane Maria Berton

Neste trabalho propõe-se o estudo do efeito do processo de SHTPN (Tratamento térmico de solubilização após nitretação por plasma), e do tratamento térmico de têmpera e revenido sobre a microestrutura, dureza e resistência à corrosão do aço inoxidável ferrítico AISI 409. Por meio do SHTPN obteve-se uma camada martensítica de nitrogênio na superfície do aço. Após o SHTPN as amostras foram temperadas de 950°C e revenidas nas temperaturas de 200, 400 e 600°C. A resistência à corrosão foi avaliada por meio da técnica de polarização cíclica e a dureza através de ensaios Vickers. Verificou-se que o SHTPN afetou significativamente a dureza do aço e o tratamento de têmpera refinou e melhorou a distribuição da martensita de nitrogênio. A camada martensítica formada apresentou espessura da ordem de 660 ?m. Os resultados indicam que é possível obter uma camada martensítica com dureza de 620 HV e aumento da região passiva, bem como do potencial de nucleação de pite quando comparado à condição não tratada (ferrítico). O melhor resultado de corrosão foi obtido para a amostra revenida na temperatura de 200°C.

Aug 8, 2018

By A J. Cornah

Critical decisions in iron ore project evaluation and production are based on global and local spatial estimates of primary mineral deposit properties (such as in situ geochemical grades) and geometallurgical responses (such as screened, washed or concentrated product yields and grades), which are derived from limited sample data. These spatial estimates are typically made using classical geostatistical techniques, which fundamentally assume that the attributes of interest behave additively. This assumption is generally appropriate for æprimaryÆ variables but æresponseÆ variables may behave non-additively and therefore their direct linear estimates may be biased.In this paper an existing additivity testing mechanism is used to quantify the bias resulting from direct linear estimation of a non-additive iron ore attribute. Data from a magnetite project are used to determine the circumstances under which such biases may be of material impact. The implications for iron ore resource estimation, geometallurgical modelling and grade control are outlined and discussed.CITATION:Cornah, A J, 2013. Assessment of the impact of non-additivity in the estimation of iron ore attributes, in Proceedings Iron Ore 2013 , pp 129-136 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013

By J. Mizera, J. Zdunek, K. J. Kurzydlowski, A. Dobkowska

This work concerns comparison of corrosion resistance of the aircraft aluminum alloy composed of Al - 2.3%Li - 0.1% Zr. The alloy was hot rolled (HR) from 13 mm to a thickness of 4 mm (e = 2.4) and 1 mm (e = 5.2). Corrosion resistance was investigated by Potentiodynamic Polarization Test. The investigation relied on exposure samples in two different corroding medium: 0.5 M NaCl solution and 0.01 M Na2SO4 solution with added 0.01% of Cl- at room temperature. Furthermore, the microstructure was analyzed using the optical microscope with polarized beam. The hardness was measured on lengthwise profile. It was stated that alloy after the largest deformation (equivalent total strain e = 5.2) is characterized by the best mechanical properties and the best corrosion resistance. The alloys in initial state and after deformation to 4 mm (e = 2.4) are characterized by worse corrosion resistance. It is associated with microstructure and density of dislocation in analyzing material.

Jan 1, 2015

By Donald J. Worth

INTRODUCTION Minera Real de Angeles makes a very interesting case study in more ways than one. To begin with, it represents the first time a bulk silver deposit has been put into production in Mexico. Second, the feasibility and financing stage spanned a period when the silver price ranged from $4 to $40 per ounce. Third, there was a major devaluation of the peso and a financial crisis in Mexico at completion of the project. Fourth, the composition of the partnership (a major Canadian mining company, a major Mexican mining company and the host government's own mining entity) is worthy of note. This paper gives considerable background on the project and how it came to fruition. The political risk aspects and how the major provider of funds perceived Mexican risk at the time of decision to participate and afterwards are highlighted. LOCATION AND HISTORY The Real de Angeles deposit is located at an elevation of 2300 meters in Central Mexico in the State of Zacatecas (Figure 1). The closest village is Noria de Angeles, three kilometers to the north. The closest cities are Aguascalientes, Zacatecas and San Luis Potosi. The first-mentioned is one hour to the southwest by automobile over good roads. Exploitation of the vein outcrops probably began towards the end of the sixteenth century by the Spanish. Evidence of past mining activity is shown by numerous shafts, manways, dumps and ruins. Also, there were remnants of two rudimentary concentrating mills now obliterated by pit development and in the nearby town of Noria de Angeles the ruins of a small smelter still exist. Compania Minera Gamma, an affiliate of a major international mining company, investigated Real de Angeles from 1969 to 1971. Its evaluation program included 20 drill holes and comprehensive geological engineering and metallurgical studies. The results were not encouraging and the option on the property was dropped. In late August 1973 geologists representing Placer Mexicana which was later renamed Explomin were advised of the availability of the property and liked the prospects sufficiently to make an option payment soon due and to agree to outright purchase by year-end. A series of 34 holes were drilled by Explomin and a preliminary study indicated that the prospect had mine-making potential if the silver price was right. [ ] DESCRIPTION OF THE PROJECT Real de Angeles is best described as a large, low grade open pit silver mine because at today's prices approximately 70% of the realizable revenue is derived from that metal. One must also keep in mind that the operation produces two concentrates - a lead concentrate with high silver content and

Jan 1, 1985

By C. O. Karacan, S. J. Schatzel, W. P. Diamond

In coal mining, longwall mining is a preferred method to maximize production by extracting large blocks of coal that have been outlined with a set of development entries. In U.S. mines, longwall panels are typically 305 m (1,000ft) wide (with a continual trend towards even wider panels), and usually over 3,050 m (10,000ft) in length. The increasing size of longwall panels, while helping to increase coal production, may also increase methane emissions due to the exposure of the mining environment to a larger area of fractured, gas-bearing strata. Thus, understanding the impact of increased panel widths on methane emissions, and designing gob gas ventholes and bleeder systems accordingly, can enhance the safety of the underground workforce by reducing their exposure to potentially explosive accumulations of methane/air mixtures. As part of its mine safety research program, NIOSH’s Pittsburgh Research Laboratory has initiated a reservoir modeling effort to better understand the interaction of the various geotechnical factors influencing gas flow within and to the underground longwall mining environment. A focus of this modeling effort has been 1) the prediction of the incremental amount of methane emissions to be expected due to increasing longwall panel widths, and 2) optimizing gob gas venthole completion practices to capture more of the gas in the subsided strata above longwall panels before it can enter the ventilation system of the underground workplace. The history matching phase of the study has been carried out on a 381-m (1,250ft) wide panel in the Pittsburgh Coalbed. Simulations have also been completed for a 442 m (1,450ft) wide panel to estimate the incremental increase in methane emissions and the performance of current gob gas venthole placement configurations. Additional venthole placement configurations were simulated to investigate options for optimizing methane capture from the subsided strata above the wider longwall panel.

The dissolution behavior of gold and copper from their elemental states and from Au/Cu alloys in cyanide solutions has been investigated using a rotating disc electrode. The anodic and cathodic reactions were studied separately and the resulting polarization curves were combined to examine the overall dissolution reactions. The dissolution rate of pure gold in the aerated cyanide solutions was inhibited by the anodic passivation on the gold surface, while the dissolution rate of pure copper was found to be mass-transfer-controlled. On the other hand, the dissolution of gold and copper from the alloys was partially controlled by electrochemical reaction and largely by mass transfer.

Jan 1, 1994

By K. Rainer Massarsch, Bengt H. Fellenius

"Abstract Vibration limits for buildings with respect to ground vibrations from pile driving published in international standards are reviewed. At first, relevant vibration parameters are defined and the evaluation of vibration records is described. The sensitivity of structures to different vibration parameters (displacement, velocity and acceleration) is discussed. Most vibration standards relate to blasting activities, the dynamic characteristics of which can be significantly different to those from construction activities and in particular, pile driving. Several vibration standards are reviewed. The Swedish vibration standard is described in detail, as it is the only one accounting for several important factors, such as ground conditions, building material, and type of building foundation. Many standards limit the guidance to values based on the dominant vibration frequency and a wide scatter of frequency-dependent vibration limits exists. It is difficult to compare limiting values of ground vibrations proposed in different standards.1. INTRODUCTIONFor poor ground conditions, placing structures on piles is the most common foundation solution, while sheet piles are widely used to support deep excavations. Piles and sheet piles must often be installed in the close vicinity to buildings, structures or installations in the ground, which can be affected by ground movements and vibrations, (Massarsch and Fellenius, 2014). In many areas, environmental concerns with respect to noise and ground vibrations can restrict or even prohibit driving of piles or sheet piles or reduce the efficiency of installation. The design engineer must prescribe – often at an early stage of a project — the permissible levels of ground vibrations in order to minimize the potential risk of building damage. When seeking guidance from the literature, little or practically no applicable information can be found on how to assess permissible levels of ground vibrations."

Jan 1, 2014

By Guanghui Li, Xuling Chen, Zhiyun Ji, Min Gan, Tao Jiang, Xiaohui Fan, Zhiyuan Yu

With the increase of proportion of biochar(without modified) replacing coke breeze, the physical strength of sinter decreases due to the faster burning speed of biochar. An investigation upon passivating biochar with boric acid was then conducted to strengthen sintering in this paper. A layer of thin film of B2O3 distributed in the surface of biochar was observed, which could reduce the contact between reaction gas and biochar. So the burning speed of biochar was decreased properly after passivation, and the combustion efficiency increased due to the inhibition of carbon gasification. The comprehensive effects of above changes could increase the maximum temperature of sintering bed, which facilitated to the mineralization of sintering mixtures. Eventually sintering indices got reinforced. Thus the indices of sinter as applying 40% passivated biochar were comparable with that of 100% coke breeze.

Jan 1, 2015

By J. G. Thompson

Determinations of the hydrogen content of irons and steels invariably are subject to two serious difficulties: (I) the determination of amounts of 0.001 per cent or less of any constituent requires an analytical procedure of unusual precision and accuracy, and (2) the hydrogen content of many samples is dccidedly not stable; i.e., there is no assurance that the content at the time the analysis is made is the same as it was when the sample was taken or at some previous time in the history of the piece. In respect to both the precision and speed of the determination, the vacuum-extraction procedure for the determination of hydrogen possesses advantages over the vacuum-fusion procedure, which has been the recognized standard for the detcrmination of other gaseous elements in sted-— oxygen and nitrogen for example. The basic facts upon which the vacuum-extraction procedure is based—i.e., the evolution of gas from solid steel when it is heated in vacuum, and the fact that the evolved gas is rich in hydrogen—were observed by Graham1 many years ago. Subsequent investigations have shown that hydrogen exists in steel chiefly as interstitial solid solution (i.e., in atomic dispersion) and perhaps to some extent as hydridcs that are unstable and decompose to form atomic hydrogen. In either case practically all of the hydrogen in steel at elevated temperatures exists in the atomic condition and consequently is able to diffuse readily through the metal. In contrast to this, other gaseous elements, such as oxygen and nitrogen, normally are present in steel chiefly in the form of relatively stable compounds such as oxides or silicates and nitrates; i.e., the oxygen and nitrogen atoms are fixed in stable combinations and are not free to migrate. The only oxygen or nitrogen that can diffuse in steel is the small amount in solution (atomically dispersed) and the rate of diffusion of these atoms is much less than that of hydrogen because of their greater atomic volume and lower mobility. Consequently, it is possible to extract most or all of the hydrogen from solid steel in a reasonable time at moderately elevated temperatures, but the procedure is not applicable to the determination of oxygen or nitrogen. It is only within the last decade that these observations have been developed into an analytical procedure for the determination of hydrogen. Apparatus and Procedure The apparatus used at the National Bureau of Standards,6 for the determination of hydrogen by the vacuum-extraction procedure, is shown schematically in Fig. I. The specimen, freshly cleaned and dried,* is suspended on a fine wire within the quartz furnace tube that is connected to the reservoir system and analytical train.

Jan 1, 1945

By Ljiljana Solujic

The need for the removal of mercury from the precious metals extraction circuits may be influenced by process, environmental, as well as by occupational hazard reasons. In these circuits mercury is mainly present as cyanide complexes. The effectiveness of any stabilization method will be influenced by the high thermodynamic stability mercury-cyano species exhibit in an aqueous solution. In this study, we have investigated the utility of the trisodium salt of trimmercapto-s-triazine (TMT) for precipitation of mercury from the corresponding cyano-complexes. The influence of pH molar ratio of TMT to Hg, coagulant and flocculant additions, excess of free cyanide, as well as the presence of other metal-cyano species on the effectiveness of mercury precipitation were investigated in detail. Also, a "teal world" precious metals mill effluent initially containing ~7 ug/mL (ppm) of Hg was treated and A was found that greater than 99.8% of the mercury was removed from the solution as am insoluble Hg/TMT complex.

Jan 1, 1996