Search Documents

By F. Rosenblum, P. Spira

"Techniques were developed to determine the oxygen demand of sulphide ore pulps in the laboratory and in concentrators. The effect of variables which influence oxygen demand was studied, and it is shown that the oxygen demand is a measure of the degree of oxidation of the sulphide surfaces. It is suggested that in investigating the significance of oxygen in flotation, the oxygen demand of the pulp is a more suitable parameter than the dissolved oxygen content.Oxygen demand measurements are being carried out with a view to determining the effect of aeration on mill metallurgy and devising improved methods of predicting aeration requirements of sulphide ores.The importance of pulp oxidation in the flotation of massive sulphide ores has long been recognized. At the Noranda concentrator, chalcopyrite could not be floated satisfactorily without a pre-flotation aeration step because the necessary dissolved oxygen was consumed by the large amount of pyrrhotite in the ore. With aeration, pyrrhotite and pyrite were depressed by surface •oxidization, and the resulting thiosulphate level in solution gave a good indication of the end of useful aeration. 1'he present study was prompted by the need to find an alternative criterion for cases where recycled mill water may contain a relatively high concentration of thiosulphate. Preliminary experiments suggested that the rate of oxygen uptake by the pulp -its oxygen demand -might be a practical measure of the end point of aeration as well as a significant parameter in the flotation of massive sulphide ores.Although it has long been realized that oxygen is an important variable in flotation, analytical difficulties precluded detailed plant investigations. Measurements of' dissolved oxygen in mill pulps were first reported by Ralston(i) in 1929. A titration method was used, and because of the delay occasioned by the preparation of clear solution samples, the values obtained were believed to be low. It was quite evident, however, that pulps in the grinding circuit had a lower oxygen content than in flotation. More recently, Woodcock(2,3) used a polarographic probe to carry out oxygen surveys in six Australian concentrators and he generally observed a similar pattern. A large number of other solution parameters were monitored, such as pH, redox potential, reducing power, and reagent and metal concentrations, with the aim of detecting correlations among the measured variables. A few potentin.lly useful relationships were found ""or specific operations in certain plants."

Jan 1, 1974

Project Located in northwestern British Columbia 70km West of Cassiar Highway Galore Creek Project and Road Access Corridors Designated For Mineral Development in Stikine-Cassiar Land Resource Management Plan (LRMP)Approved in 2000Strong BC Government, local community and Tahltan First Nation Support for Project

May 1, 2006

By Paulo F. T. Sachs

ERP systems have been widely implemented nowadays in several industries. However, ERP was originally designed to fit former MRP and MRP II users, and most of the ERP research has been focused on discrete manufacturing . On the other hand, process industries ? and mining in particular ? present many peculiar characteristics, which are difficult to comply with ERP systems standard functionalities. Again, very limited research has been developed covering enterprise management systems in mining. The objective of this paper is to identify, through an explanatory study that includes a case study methodology, how ERP systems manage the functional areas of the mining industry, and how they fit into the mineral value chain IT requirements. A secondary objective is to identify the gaps between ERP?s functional capabilities and the mining industry business requirements, and to point out the perceived benefits they generate to the companies.

May 1, 2004

By C. M. Davidson, D. J. Drexler

"Sulphuric acid treated with hydrogen peroxide to destroy organic contaminants could conceivably show increased corrosivity toward carbon steel shipping and storage vessels, caused by the persistence of a peroxide residual. This paper describes work performed to determine the effect of 0-200ppm hydrogen peroxide on the corrosion of carbon steel by 93% and 98% sulphuric acid at room temperature (23ºC) and 50ºC.Steel electrodes were exposed to acid containing several peroxide levels (0. 45, iOO and 200 ppm) for up to two weeks. Specimens were removed at intervals and weight loss, open circuit potential, depth of metal loss and residual peroxide concentration recorded.Hydrogen peroxide decomposes considerably over two weeks in iron-contaminated sulphuric acid. initial peroxide concentrations > l00 ppm suppress corrosion, but the effect is lost when concentration decays below about 60 ppm. Sustained peroxide levels in the range below 60 ppm may increase corrosion rates. These phenomena are interpreted by analogy with anodic passivation."

Jan 1, 1987

By P. Taskinen, D. Lindberg, H. Viitala

The formation of copper chlorides in flue dust or deposits in heat recovery boiler of copper smelters or waste-fired boilers may lead to formation of corrosive partially molten deposits on walls and heat exchangers of the boilers. These deposits can contain various other metals, such as alkalis, Fe, Zn, Pb together with oxides and sulfates. In the present study, a thermodynamic model for copper-containing binary and ternary metal chloride systems within multicomponent CuCl-CuCl2-FeCl2-FeCl3- PbCl2-ZnCl2 system has been assessed and optimized based on own experimental phase equilibrium data, as well as literature data. The thermodynamic properties of the liquid phase was modelled using the quasichemical quadruplet model and a thermodynamic database was optimized to predict all available experimental data within the experimental error limits. The thermodynamic database allows for more accurate predictions of potential corrosion-related issues in various heat recovery boilers and waste-fired boilers due to formation of copper chlorides. INTRODUCTION In the copper flash smelting, flue dust can cause severe problems in the gas train, used for separating dust from the SO2-rich off gas, by forming corroding accretions on the walls of the heat recovery boiler. Formation of dust build-ups in the boiler need to be cleaned regularly and potential corrosion damage checked, requiring costly and unscheduled shutdowns of the flash smelting process. Compounds of copper and zinc among other elements having high vapour pressures may volatilize during the smelting of the copper concentrate, forming dust when the process gas cools down. Also, particles of solid or liquid iron oxides originating from the ore get transported with process gas to the heat recovery boiler as a result of entrainment in the flue gas (Miettinen, 2008) The dust deposit build-ups on the boiler walls are formed partly by direct impact of particles and partly by vapour condensation on the boiler walls. The initial deposition takes place by the condensation of vapours that contain zinc, lead, arsenic and other metals having high vapour pressures. Also, low melting point eutectic components of alkali salts such as chlorides and sulphates can act as sticky cohesive particles attaching to the boiler walls. The fine particles landing on the surface of the porous dust deposit layer react in the SO2-rich atmosphere of the boiler to sulphates. The process gas within the boiler contains SO2, O2, SO3, H2O and N2 that diffuse into the porous accretions to form a stagnant gas layer within the dust deposit structure. The composition of this gas layer may differ greatly from the composition of the process gas that is flowing on the surface of the accretion layer. Locally HCl and H2SO4 are formed and even a reducing atmosphere may exist within the dust deposit layer, allowing new reactions to take place. The local micro-atmosphere may enable metal sulphates to be reduced to secondary sulphides and even metallic components. Within the accretion layer, components may be formed that would not be stable in the gas atmosphere inside the boiler (Miettinen, 2008). This may be the mechanism by which for instance chlorides of Cu, Fe and Zn are formed within the deposit layer.

Jan 1, 2019

In this paper, geostatistical techniques are applied to forecast the annual copper price in the short and medium terms (from one to five years ahead). These techniques allow the incorporation of monthly and multivariate information in the analysis and provide more accurate results than traditional approaches, especially as far as the one-year forecast is concerned. A second advantage of geostatistics stems from its ability to assess the uncertainty associated with the unknown future prices, thanks to estimation variances or confidence intervals, depending on the technique used. Such an assessment has a crucial importance in decision-making, from both macroeconomic and microeconomic points of view

Sep 1, 2004

By Carol J. Odell

As a mining social practitioner, social indicators are within the purview of required competencies. A situation, where the ER manager requested assistance in quickly deriving a few social indicators for the strategic plan motivates this paper: despite ample technical knowledge about indicators, a clear understanding of stakeholder aspirations and concerns, as well as familiarity with management priorities such a request required reflection to produce a satisfactory approach, which combined pragmatism with enough academic rigour to provide reliable measures, while being justifiable to management who are unfamiliar with many of the pertinent debates. Importance: Social indicators enable the identification of more and less effective mine-community engagement strategies as well as providing primary data to better understand how the mine-community social system responds to different interventions, thus guiding future engagement plans. In addition social indicators: ? Assist communication about social strategies with Engineering and Operations management, using a quantitative language that is familiar to them. ? Provides concrete data to engage stakeholders to discuss progress and challenges arising, to move discussions towards technically robust strategies and away from politically interested proposals. ? Finally, social measurement is required more and more in due diligence, covenants and ongoing monitoring in Independent Engineering assessments of projects for financing. This paper begins by considering some technical considerations that are useful to guide indicator development. It then introduces the field research informing this paper and discusses some useful results in the light of further applicable concepts from the literature. The paper ends by considering corporate aims in applying corporate social responsibility (CSR) programs and discusses the application of the research for practitioners at mining operations, in the light of these aims.

May 1, 2010

By Réjean Lévesque

SIDBEC-NORMINES a été incorporée en 1976. Depuis la fin de 1977, ses activités comprennent outre la concentration au lac Jeannine, près de Gagnon, du minerai de fer extrait du gisement du lac Fire, I'exploitation d'un atelier d 'enrichissement secondaire et une usine de bouletage à Port Cartier. L 'objectif principal de SIDBEC-NORMINES est de produire six millions de tonnes de boulettes d'oxyde de fer par année, dont trois millions auront une faible teneur en silice afin de répondre aux exigences de la réduction directe. Les installations de SIDBEC-NORMINES sont adjacentes aux installations portuaires de la Compagnie Minière Québec Cartier, à l'est de la ville de Port-Cartier. L 'ensemble est conçu pour produire les deux types de boulettes avec deux circuits d'agglomération installes en parallèle. La production de concentré enrichi (68% Fe et plus) est obtenue dans une usine d'enrichissement utilisant le precédé de séparation magnétique hum ide ahaute intensite (separateurs Jones). À l'usine de bouletage proprement dite, on effectue Ie broyage du concentré et sa mise en boulettes sur disques; l'in duration des deux types de boulettes est obtenue sur deux chaînes d'agglomération Dravo dont chacune a une capacité annuelle nominale de trois millions de tonnes.

Jan 1, 1979

By CIM Environmental, Social Responsibility Society

Within the mining industry, the pathway from exploration, to planning, construction, operation and closure has become more complex over the last few decades. The current financial, environmental and social influences present the mining industry with unprecedented challenges and opportunities. In addition, international environmental and social reporting standards and codes are becoming increasingly robust. The reporting requirements provide an added impetus for issuers to effectively manage environmental and social impacts and risks. Reporting requirements also provide the opportunity to be transparent. The intended audience for these Environmental, Social and Governance (ESG) Guidelines for Mineral Resource and Mineral Reserve Estimation includes practitioners, industry participants at all levels of skill and experience, corporate management and board members, government agencies, academic institutions and interested parties. For practitioners, this document provides underlying key principles of environmental, social and governance practices. The ESG Guidelines provide guidance for those using environmental, social, governmental and governance information when preparing and implementing mineral exploration programs and contributing to the preparation of mineral resource and mineral reserve estimates for mineral properties that are either at the study stage (i.e., scoping / preliminary economic assessment, pre-feasibility, or feasibility studies) or in operation. The guidelines can also be used to help mineral resource and mining companies apply good practice to manage their environmental and social risks and opportunities. Companies can identify and retain appropriate professionals to prepare environmental and social materials to support company studies. The guidelines are also a resource for companies developing effective environmental and social management strategies at any project stage. This document is not intended to be prescriptive and is not intended to provide exhaustive guidance on what to consider in terms of environmental, social, legal and governmental modifying factors in the preparation of MRMR estimates. Rather, it is intended as general guidance to assist companies and practitioners in considering and applying these modifying factors for MRMR estimates. This document is also not intended to guide environmental and social impact assessment (ESIA); however, the measures needed to manage impacts help inform the constraints and costs for defining mineral resources and mineral reserves and inform the costs and schedules of mineral project studies. All documentation of MRMR estimates made by an issuer and intended to be, or reasonably likely to be, made available to the public in a jurisdiction of Canada must comply with the requirements of National Instrument 43-101 Standards of Disclosure for Mineral Projects (NI 43-101), as amended from time to time (Canadian Securities Administrators, 2016a and 2016b). Disclosure is not addressed in these ESG Guidelines. Determination of what to include in disclosures is defined in the applicable Securities’ legal frameworks. Appendix A presents a summary table showing the linkage of the principles and topics in these ESG Guidelines to the potential effects on project costs, schedules, government permits and approvals, social licence to operate and financing.

Sep 8, 2023

By L. D. Smith

"Those who submit competing proposals for projects seek to present senior management with complete and fully supported material that will not fail under questioning. Hopefully, misleading notions and omissions will have been minimized and there will have been testing of the assumptions regarding the economic, social and political environments. A capital project evaluation team can do management and itself a service by including a sound approach to the impact of inflation (and its twin problem, interest) on a project and a great disservice with an inappropriate approach to inflation.InflationHandled deftly, inflation can alter a project evaluation to show almost any result the handler desires. It must be a constant source of frustration for design people and cost estimators to spend weeks perfecting the technical aspects of a project in order to minimize costs, only to have all of their efforts set awash in a sea of financial and economic assumptions that submerge all of the detail. In all of this, inflation is perhaps the largest offender, with inflation criteria often being brought to bear at the last minute, almost as an afterthought. Perhaps this tardiness reflects the difficulty of the subject and the belief that senior management will take its own approach to the problems of inflation. Such a belief is unfair to senior management, for it is entitled to not being misled by omission. It is entitled to the full use of the skills of the evaluating team, including respectable assumptions of the impact of inflation.Working in a consulting context, one has the opportunity to participate in the evaluation of a large number of projects. Reflecting the observation of a wide range of views regarding the subject of inflation, this paper will-address the impact of five different approaches to inflation on the evaluation of a single Canadian mining project."

Jan 1, 1987

By J. Molgaard, J. Masounave, J. Prinsen, P. Beaulieu, G. Huard

"A study carried out on behalf of the National Research Council (NRC) indicates that economic losses due to wear in the Canadian mining industry are in excess of $700 million annually. Severe wear, mainly by abrasion, was identified as the most important wear mechanism in terms of possible savings. One way to reduce losses would be the proper use of databases. A joint project of The Canadian Institute of Mining and Metallurgy (CIM) and NRC (Tribology laboratories at IMRI) has been initiated to create a factual database containing all relevant experience in the area of wear in the Canadian mining industry. As a first step, a prototype covering slurry pumps is being built. This should help to answer many questions, such as the number of people involved, interest from industry, cost vs benefits, etc.IntroductionTribology is concerned with the understanding of the mechanisms of friction, wear, and lubrication.Tribology is concerned with the correct use of materials for interacting solid surfaces, with the interaction of those surfaces with lubricants, with the chemistry, physics and use of lubricants and their additives. It is concerned with the reduction of friction and wear (or, in the case of belts, brakes, clutch plates, and similar devices, in achieving optimum friction with minimum wear) and is concerned with the avoidance of associated failures in machinery.Lubrication is usually the solution to a problem of friction and wear. Yet far from all the problems of friction and wear are solved by lubrication. The wear of grinding rods or shovel track pads can hardly be solved by lubrication, to name just two examples with which mining engineers will be familiar. There are indeed many situations of wear and friction where the surfaces in contact are unlubricated.In part, tribology is a matter of design. A major aspect, however, has to do with the choice of materials, to satisfy external constraints upon the component design or choice. The operating conditions for much industrial equipment, particularly in mining are, often very severe. The development of wear resistant materials, including materials which are applied as coatings, is clearly an important technology from the point of view of tribology."

Jan 1, 1987

By T. Norvell, R. Gosine, S. O’Young

"This paper describes the use of dynamic scheduling and discrete event control to provide coordinated control of multiple automated vehicles. This work has been carried out within ongoing research into multi-robot coordination developed around the underground mining scenario. Demonstrations using scaled laboratory models of underground mines illustrate the potential for this technology for full-scale implementation for mine-wide automation. IntroductionIn the past decade, the mining industry has been improving the efficiency of underground mining operations. Robotics and automation have demonstrated the potential to further reduce costs. Tele-operation of underground vehicles from above ground and autonomous navigation have reduced travel delays and allowed for single operator control of multiple vehicles (Bloomquist and Hinton, 2001). Other recent projects include the automation of the digging process as well as the drilling and blasting operations. Infrastructureless guidance systems are also being developed (Bloomquist and Hinton, 2001).Mine-wide automation requires significant developments at two levels: (1) the development of mining robots capable of performing tasks either autonomously or semiautonomously; and (2) the development of methods for automating operations at a systems level. This paper focusses on the latter, and describes a general framework for the coordination of multiple mobile robots in an unstructured or semi-structured environment."

Jan 1, 2003

By Marc C. Bétournay

A mine production locomotive, the world?s first applied industrial fuelcell vehicle, has been designed and tested in the context of a number of proof-of-concept projects supported by the Fuelcell Propulsion Institute, an international consortium of stakeholders dedicated to facilitate the commercialization of fuelcell vehicles. The locomotive?s simple electric-powered motor and controller system was ideal to study a number of requirements related to fuelcell power application: hydrogen power plant operation, underground hydrogen use, risk and regulatory requirements, production performance versus the conventional battery-powered locomotive version under measured duty cycles and production requirements, power plant design improvements for other fuelcell vehicles, and cost-benefit aspects. This article will focus on the design and testing aspects of this project which has led to successful performance demonstrations of the vehicle under surface and underground conditions at two mines. It will also present information on the creation of a safe, reliable and efficient power plant which fulfilled its design objectives, including longer productivity time for a given vehicle fill-up.

May 1, 2003

By G. E. Agar, W. B. Kipkie, V. K. Drylie

"This paper describes mineral processing test work on drill core samples from an ilmenite deposit in Terrebonne County just north of Montreal.Mineralogical examination showed that the intimate associa¬tion between ilmenite and hematite precluded their separation. The maximum concentrate grade was therefore limited to 22.9% Ti. Liberation of gangue from the hemo-ilmenite grains occurred around 400 µm, a size which proved to be too coarse for recovery by flotation.Other physical separation techniques, such as elec¬trodynamic, magnetic and jigging, were tried in order to take advantage of the relatively coarse liberation size. An all-flotation procedure and a combination of jigging and flotation yielded similar separations.IntroductionInco Metals Company, through its subsidiary Canico, optioned an ilmenite deposit in Terrebonne County, just north of Montreal, and conducted a drilling campaign to confirm previous geological assessments of the deposit and to provide core samples for mineralogical study. Parts of these core samples were used for mineral processing studies, which will be described in this report. The objective was to identify suitable upgrading procedures, to determine the optimum combination of concentrate grade and recovery, and to provide suitable batches of concentrate for further treatment."

Jan 1, 1980

By Norman O. Lotter, Dominic Fragomeni, Jorge Oliveira, Dee J. Bradshaw, Rebecca Monnapula

"The role of mixed collectors in enhancing the metallurgical performance of sulphide flotation processes was reviewed in 2008, and later published as an integrated theory by Lotter and Bradshaw, 2009. The theory proposed that xanthates, dithiophosphates and dithiocarbamates could be synergistically combined in an optimal formula to deliver improved grade and recovery. The approach uses a five-step structure, viz.1. A mineralogical study of the ore to be treated, identifying and quantifying the economic minerals (with hosting and association) and gangue species present.2. Selection of candidate collectors from this mineralogical information and from the known pulp conditions of that operation (e.g. Eh, pH).3. Design and execution of a factorial experiment to estimate and test the main effects and interactions, and to model the response surface for an optimum formulation [Box et al., 1978].4. Use of a High-Confidence Flotation Test platform in the factorial to reduce overall errors and allow for clearer observations [Lotter, 1995; Lotter and Fragomeni, 2010].5. Statistical design of a plant scale trial to measure and validate the gains [Napier-Munn, 1995; Lotter et al., 2009]. Eland Platinum, which was commissioned in November 2007, appointed a team to apply this theory to formulate an optimized mixed collector suite for use in the operation. The West Pit ore (UG2 - Normal ore) was sampled at site and brought to Xstrata Process Support, Sudbury, Canada, for mineralogical and metallurgical testing in 2008. Microprobe and QEMSCAN measurement characterized the type, grain size and textural association of the discrete Platinum Group Minerals (PGM) present. From the mineralogical data, it was clear that a mixture of dithiocarbamate and two xanthates would be a likely reagent suite selection. A factorially designed set of High-Confidence Flotation Tests studying these was performed, concluding that an optimal suite using certain amounts of these collectors was a viable formulation that would advance the grade and recovery performance at Eland above the standard PIBX by approximately 2.13% 4E PGE. The plant trial, which used a form of the replicated block design after Napier-Munn, 1995, and Lotter et al., 2009, exceeded this estimate with an overall PGE recovery gain of 2.48% (absolute basis) and a concentrate grade gain of 26.4 g/t PGE (absolute basis), as well as reducing chrome in concentrate from 2.04 to 1.62% (absolute basis). These gains proved to be statistically significant using the analysis of variance method, and have validated the theory."

Jan 1, 2011

By T. T. Chen, W. Petruk

The mineralogy of the feed, concentrates and tailings from the Heath Steele mill in New Brunswick was studied in detail to determine the liberation and recoveries of the major ore minerals, and to characterize the occurrence and distribution of the trace elements. The ore milled during August 1977 contained an average of 4.34 wt % Zn, 1.25 wt % Cu, 1.64 wt % Pb and 90 gr/ton Ag. The main trace elements in the ore are silver, cadmium, indium, cobalt, antimony, bismuth, arsenic, mercury, tin and gold. Silver is carried in solid solution in tetrahedrite-tennantlte, galena, Ag-Sb sulfosalts and Pb-Bi-Sb sulfosalts. Approximately half of the silver is recovered in the lead and copper concentrates and the remainder is lost in the tailings and Zn concentrate. As the major silver-bearing minerals also contain Sb and Bi, recovering silver by ore dressing would involve recovering elements that are troublesome in extraction metallurgy. Cadmium and most of the indium and mercury occur in solid solution in sphalerite and consequently are recovered in the zinc concentrate. Some indium is also recovered in the copper concentrate in a second unidentified indium-bearing mineral. Cobalt and arsenic occur principally in arsenopyrite, cobaltite, a Co-Fe sulfarsenide, pyrite and pyrrhotite, and follow these minerals into the tailings. Recovery of the valuable element cobalt, therefore, would involve recovering the environmentally hazardous element arsenic. Most of the tin and gold report to tailings. The ore was ground to about 80% minus 270 mesh. At this grind, 71 wt % of the sphalerite, 66 wt % of the chalcopyrite and 59 wt % of the galena were liberated. Recoveries of free sphalerite, free chalcopyrite and free galena in the Zn, Cu and Pb concentrates were 85 wt %, 76 wt % and 80 wt %, respectively; recoveries of unliberated sphalerite, unliberated chalcopyrite and unliberated galena in the respective Zn, Cu and Pb concentrates were 48 wt %, 5 wt % and 7 wt %. Some of the unliberated sphalerite and chalcopyrite grains in the tailings are large and would have been liberated at a finer grind.

Jan 1, 1980

By D. M. Doyle, P. J. Hannon

"The Canada/Nova Scotia Mineral Development Agreement (M.D.A.) is a subsidiary of a five-year Economic and Regional Development Agreement, signed on June 11, 1984. The objectives of the M.D.A. are to strengthen and diversify the Nova Scotian mineral industry and to coordinate federal and provincial policies and programs. The agreement outlines the activities and responsibilities of each government, including the division of the cost (60:40, federal: provincial) between governments. The agreement established a framework for joint planning to avoid overlap or duplication of programs.The M.D.A. programs are broadly divided into five sectors (Table 1 and Fig. 1): Geoscience, Minerals Technology, Development, Firm Specific and Public Information. Each sector is administered by a subcommittee composed of one federal member and one provincial member. The subcommittees report to a Management Committee. The Canada/Nova Scotia Mineral Development Agreement (M.D.A.) Management Committee is made up of Dr. Jack Reeves from EMR and Dr. Richard Potter from the NSDME.The Geoscience subcommittee, co-chaired by Peter Giles (NSDME) and William Poole (EMR), manages the regional geologic, geochemical and geophysical studies in the province. Included in this sector are studies into mineral deposits and the basic geological relationships between mineral deposits.The Mineral Technology sector is co-chaired by the authors, Don Doyle (CANMET) and Pat Hannon (NSDME). This sector of the M.D.A. conducts studies into mineral processing, sampling, deposit byproduct commodities and project feasibility analysis."

Jan 1, 1987

By R. Le Houillier, M. Nagamori, A. J. Plumpton

"Asbestos tailings are a typical serpentine, hydrated magnesium silicate, consisting primarily of antigorite and a few per cent of unrecovered fibrous chrysotile. Serpentine has unique thermal properties in that dehydroxylating calcination at 600 to 700°C can yield an amorphous structure in which most of the magnesia is liberated from the original bond with silica and thereby rendered chemically active. The amount of activated magnesia can be quantified by selective leaching with a weak acid such as acetic acid. Many wet processes have been proposed to extract magnesium values from calcined or natural serpentine by means of various acids and their ammonium salts. However, the only commercial utilization of serpentine today is found in dry processes such as the production of fused magnesium phosphate fertilizer .The present paper reviews the physical chemistry of the dehydroxylation of serpentine and also various wet and dry processes in order to provide a general view regarding the chemical transformation of asbestos tailings.IntroductionAsbestos fibers occur as chrysotile, a serpentine polymorph. More than nine tenths of mined asbestos ores consist of massive non-fibrous serpentine, primarily the polymorph antigorite, which is discarded as tailings after fiber extraction. For many decades, Quebec has been a world leader in the production of asbestos fibers. As a result, colossal tonnages of serpentine have accumulated in the Eastern Townships'!'. Serpentine minerals are found in large deposit s throughout the world, and significant research efforts have been made, particularly in Japan and the USSR, mostly in attempts to extract magnesia or silica values therefrom.The chemical composition of serpentine (chrysotile and antigorite) may be ideally expressed as Mg3Si2Os(OH). which corresponds to 43.7% MgO and 43.3% SiO2. Natural serpentines often contain a few per cent of Ni-bearing magnetite and other impurities, and therefore the contents of MgO and Si02are both about 40% or lower.Serpentine (hydrated magnesium silicate) is virtually insoluble in weak acids. However, when dehydroxylated under controlled conditions, ' it decomposes to an amorphous state in which magnesia and silica are isolated and chemically active. The magnesia so activated is readily soluble in weak acids. This unique characteristic of calcined serpentine, first discovered in 1942,, has since attracted the attention of innumerable researchers, whence many processes have been proposed."

Jan 1, 1980

By J. G. Price

"The paper reviews state-of-the art welding processes and consumables for structural and pressure equipment applications in offshore environments, particularly the Arctic. Optimum selection of consumables will be discussed with regard to the facility to meet tentative toughness requirements in weldments. Finally, the development of welding procedure specifications will be considered in relation to the prevention of hot or cold cracking and lamellar tearing.Welding RequirementsGeneralThe exploitation of Canadian frontier oil and gas reserves will require a fleet of various types of offshore structures. These will include fixed jacket types and semi-submersibles for the East Coast with huge man-made islands and icebreakers for the Arctic regions. Both these regions will also require supply and drill ships plus subsea pipelines and cargo tankers for transportation. Clearly the welding of these items will plays large part in the over-all integrity and safety of exploration and production operations.The required development in structural steels and pressure vessel steels, for current and future offshore structures, to improve properties, particularly toughness for lower temperature service, has also prompted welding researchers to develop process and consumable combinations to match the parent plate specifications. This development has had to consider particular aspects of weldability such as a low susceptibility to cold cracking and preventing low HAZ toughness. Current research has centred on attempts to increase HAZ toughness with higher heat input welding of newly developed structural steels.The installation of Arctic region pipelines has provided a sound base for future, more complex fabrications in the most severe service temperatures in the Canadian frontier although few of the installations have been designed to the lowest possible exposed temperature of -62°C."

Jan 1, 1987

By Franciszek Letowski

"Recovery of precious metals associated with a sulphidic matrix has an important economic effect on complex sulphide ore treatment. Because a significant portion of the silver and gold associated with pyrite are rejected to tailings during the selective flotation of pyritic Zn-Pb-Cu ore, other ore processing routes have been investigated.Direct leaching of the ore with ferric sulphate solution followed by separation of different components of the solid suspension by flotation was applied. Such a process allows for: production of zinc sulphate solution; transformation of galena PbS to insoluble lead sulphate PbS04 and its accumulation in a non-floatable fraction together with precipitated geothite FeOOH and other insoluble gangue minerals; separation of sulphur and non-decomposed sulphides in the floatable fraction.Laboratory research carried out on the ore samples from an Alaskan pyritic deposit from the Delta region indicates that gold and silver are mostly concentrated in the floatable fraction.Total recovery of zinc from the ore attains 96.5% to 98.5% after ferric sulphate leaching. About 85% of copper was extracted from the ore during the ferric sulphate and subsequent ferric chloride leaching, and about 6% of the copper remained in the non-floatable fraction and mixed fraction during the leaching-flotation step. Extraction of lead from the nonfloatable fraction during leaching with calcium chloride solution attained 98% to 99%. Extraction of silver from the floatable fraction during leaching with ferric chloride solution reached 98%. Extraction of gold from the floatable fraction during cyanide or thiourea leaching reached 71% to 89%. The results of the laboratory research are presented."

Jan 1, 1987