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By W. K. Gummer

"THE LOCATION of Canada's present aluminum industry is determined by availability of hydroelectric power, and ready access to ocean transport facilities. The chief raw material for the production of the metal is imported by ship over several thousand miles of water. In times of freedom of shipping and uncontested movement this provides the industry with its cheapest method of operation. However, during the early part of the last decade the general conditions of ocean and rail transportation were such that interest in the treatment of materials other than bauxite was greatly stimulated. This was the case not only in Canada, of course, but in most other countries.Canada has no deposits of bauxite and much research was carried out on other aluminous materials, chiefly silicates, in an effort to develop more or less economic and feasible methods of treatment. In the United States, this research was considerably more extensive. Some projects were early shown to be of little or no value, whereas others, including the widely publicized lime-sinter and soda-lime-sinter methods, became important. In North America, however, apart from the application of the sinter method to the hitherto waste-product (red mud) of the normal Bayer plant operation, none of these processes contributed appreciably to the production of aluminum during the war. In certain European countries, on the other hand, largely because of their situation with regard to bauxite deposits, they had a more general application, and Germany, for example, produced alumina from clay, ashes, and slag by at least four methods."

Jan 1, 1952

By F. Sorenson, P. A. Castellarini, F. Garbarino, M. N. Garcia

"Recently, significant efforts to improve productivity from the tight intervals of the Mulichinco Formation within the Sierra Chata Field in the Neuquén Basin have been ongoing. Because conventional high quality reservoirs were being developed in this field, a proper reservoir understanding and completion approach was applied. After developing these high permeability reservoirs, the operator began evaluating the tight intervals and new areas within the field, but a completely different approach was necessary to achieve motivating production improvement.An extensive study to help enhance reservoir understanding and identify key factors controlling productivity of these tight intervals (which tend to be in the range of 5 µD) has been ongoing. Some of the issues discussed in this study are 1) petrophysical review, 2) rock properties calibration, 3) geomechanics understanding, 4) faulting and micro faulting/lineaments description, 5) stimulation and completions review and, 6) understanding key production drivers.As in many other tight reservoir projects, a considerable area of the reservoir must be effectively stimulated during the hydraulic fracturing process to achieve economic productivity. Two critical issues hinder these objectives. First, the low permeability in addition to a pore pressure close to or even lower than hydrostatic are critical characteristics when attempting to flow back the well and clean up fractures. Second, very high horizontal stress anisotropy resulting from a strike slip stress regime promotes the generation of simple planar bi-wing fractures. It is well-known that this fracture geometry will contact much less reservoir area compared to more complex fractures, as the operator would normally intend to create at very low permeability reservoirs.This paper discusses these issues and how they were addressed. A pilot drilling and completion program was initiated during 2012 to validate this study. Key factors include well location relative to formation unconformities, their orientation relative to the far field principal stresses, hydraulic fractures generated, and overall completion design."

Jan 1, 2015

By M. Nusheh, C. Bumby, A-H. Puichaud

"Vanadium-bearing titanomagnetite ironsand deposits occur along a 480 km stretch of the west coast of New Zealand. In the present study, the leaching behaviour of NZ ironsand was investigated in hydrochloric acid (2–10 M) solution at 50–80°C for 2 h. The resulting leaching liquors exhibited Fe/V ratios in the range 150–180. The distribution of trace element contaminants between solution and solid residue was investigated, and processing conditions have been determined for rapid and efficient dissolution of Fe, Ti and V into the leaching solution. In addition, mineralogical analysis of raw ironsand and leached residues was performed in order to study the leaching mechanism. Samples were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy (EDX), X-ray fluorescence spectroscopy, qualitative and quantitative X-ray diffraction and inductively coupled plasma mass spectrometry (ICP). Results indicate that the dominant dissolution process follows shrinking particle mechanism. However, ironsand particles containing ex-solution lamellae exhibited a different leaching behaviour compared to homogenous titanomagnetite particles.INTRODUCTION Titanomagnetite ironsand (blacksand) forms Quaternary onshore beach and dune deposits and offshore marine deposits (Figure 1) along 480 km of coastline from Kaipara Harbour south to Wanganui on the west coast of the North Island (Christie, 2016). It attracted the attention of scientists from the earliest times (Galbreath, 1998). The principal minerals in ironsand are titanomagnetite (TTM), ilmenite, quartz and ferromagnesian minerals such as augite, hornblende, diopside, and olivine with smaller amounts of rutile and apatite (Mauk, 2016).Several large ironsand deposits have been discovered and exploited since the late 1960’s. The Waikato North Head and Taharoa mines are currently operating and they have a 2015 measured resource of 400 million tonnes in total and provide over 2 million tonnes of concentrate per year by simple cost effective magnetic separation process (Christie, 2016; Christie & Brathwaite, 1997). The concentrate contains not only 7–8% TiO2 and 56–60% SFe, but also 0.3–0.6% V2O5, is both a valuable titanium mineral and a source of vanadium. All the production is used for steelmaking industries. The other potential for utilizing more of this resource without requirement of integration into an iron and steel producing plant is to develop a hydrometallurgical route with advantages of higher efficiency along with lower emissions. Currently, there is no existing commercial process capable of extracting all three of these elements as industrial-grade commodity products. Acid leaching of TTM concentrate with higher degrees of recovery and selectivity is a key step in any possible hydrometallurgical route."

Jan 1, 2017

By G. Morin, F. Chiesa, B. Duchesne

The Quality index is a useful tool allowing to assess the metallurgical quality of aluminium AlSiMg foundry alloys (A356/357). Its value is calculated from the ultimate tensile strength and elongation; it increases with the metallurgical quality of the casting, i.e. with finer dendrites, lower microporosity and inclusion count and lower iron content. This Quality index does not depend on the degree of temper applied during the heat treatment (aging time and temperature). After defining the Quality index, it will be explained how it can be predicted from the knowledge of the local solidification conditions obtained from modelling. The paper will then present four case studies of castings for which the prediction of the Quality index by modelling was made. These case studies from different authors will involve the three most common casting processes used for producing high integrity aluminium castings, namely: sand casting, permanent mould casting and investment casting (lost wax). In all cases, the accuracy of the prediction will be assessed by comparing the predicted Quality index distributions to the experimental values based on the published measured values of the local tensile properties.

Jan 1, 2006

By K. L. Boyd

"Can the increasing tonnages of ore and waste mined today be accommodated simply by using bigger and better crushers? This paper reviews the latest primary crushing and large cone crusher designs. It highlights how—in addition to using the larger crushers now available—maximizing the utilization percentages in each stage of the rock size reduction circuit will assist in meeting the larger production requirements of existing and new mining operations. Its goal is to help consultants and operators select the optimal equipment and custom-designed items in material handling from the mine to the mill, maximizing operating hours per year.RÉSUMÉ Le recours à des concasseurs plus grands et plus performants suffit-il à gérer l’augmentation du tonnage du minerai et des déchets que l’on extrait de nos jours ? Cet article examine les tous derniers modèles de concassage primaire et de grands concasseurs à cône. Il montre que, pour satisfaire aux exigences de production plus conséquente des exploitations minières existantes et nouvelles, il est important d’optimiser les taux d’utilisation à chacune des étapes du circuit de réduction de la taille des roches, en plus d’utiliser les concasseurs plus grands actuellement disponibles. L’objectif de cet article est d’aider les sociétés d’experts-conseils et les exploitants à sélectionner le meilleur équipement ainsi que des articles fabriqués sur mesure pour la manutention de la mine au concentrateur, en optimisant les heures d’exploitation par année.INTRODUCTIONAre larger crushers the answer to meeting the demands of existing or new mining projects for increased tonnage? Boyd (2002) predicted that larger crushers for primary and fine crushing would be beneficial and contribute to the further development of mineral processing. Larger crushers for primary and fine crushing applications have since become available.The rock size reduction process from the mine to the selected milling process facility has not changed since a person first broke a rock to get at the interesting mineralization within. The rock size reduction process circuit from the mine to the mill can be summarized in four stages:• stage 1: mining (rock breakage and fragmentation);• stage 2: prescreening (scalping);• stage 3: primary crushing; and• stage 4: fine crushing (secondary, tertiary, and quaternary).Plant throughput and ore delivery schedule will form the basis for flowsheet design and equipment selection. Once the project design criteria and the mine plan have been established, the circuit’s utilization percentage (percentage of hours when the circuit is being utilized) can be optimized for each of the four stages. The mining and process departments play a key role in the selection of the final comminution circuit, and both departments should be familiar with and contribute to the design of the circuit."

Jan 1, 2017

By A. H. Burns

"Regenerative and recuperative burner systems require advanced combustion techniques to minimize NOx emissions. Various methods of pollutant minimization and furnace design considerations are described. Cited examples are a large high temperature furnace and a small Zinc vaporizing furnace. The concept of total carbon footprint is introduced. The application of Biomass combustion as an effective method of cost and green-house gas (GHG) reduction is discussed. Practical considerations of scale, location and process limitations are discussed. Two examples of biomass fired equipment are cited. Ideal sites have large biomass resources available locally. Processed biomass fuels will be an important substitute for fossil fuel. INTRODUCTIONIn 1992, I presented a paper entitled Combustion Strategies In The Modern Industrial Environment (1992). At that time an abundant supply of cheap fossil fuel made many of the measures I talked about difficult to justify for anything but new equipment.Since 1992 we, as a society, have demonstrated an ability to accelerate the pace of industrial and societal change. The term industrial revolution applied to this age of incessant change is completely meaningless, implying a discrete moment in historical time. What our society has built is a system capable of unfettered, continuous and accelerating technological change. With this change comes an increasing demand for energy and materials.This year is the anniversary of the Titanic disaster, a moment in time when technological certainty met the caprice of nature and gave us a brutal reminder of what can happen to us if we underestimate that power (Mowbray, 1912). In the intervening interval we have regained the technological arrogance that was lost in 1912 bringing us back to the problems of climate change and the need for sustainable industrial activities.We use advanced mathematics to describe many complex systems, sometimes with disastrous results. For example there has been a recent attempt to model the global economy as a completely deterministic system. This premise is flawed at its foundation as human nature and emotion are indeterminate constants in the equations, yielding probabilistic solutions at best. As engineers we are all familiar with stiff problems. The solution to such a problem is meaningless and we have all had the misfortune to live through and rue the effects of that miscalculation over the last few years."

Jan 1, 2012

By B. MohammadSadeghi, S. Bakhshivash, M. Haghshenas, F. Rahimi

"Constrained groove pressing (CGP), as a severe plastic deformation (SPD) technique, is one of the applicable methods for sheet metal forming capable of producing ultra-fine grained materials (UFGMs). In CGP, processing and die design parameters can significantly affect the deformation response of sheet metal specimen. Having said this, in the present research the effects of die design variables and processing parameters (i.e. shear angle and friction) on the deformation behaviour of an Al-Mg-Si Alloy are studied thoroughly. Finite element analysis (FEA), was used to evaluate the effectiveness of mentioned parameters on the deformation homogeneity, strain distribution and pressing load variations. Also, mechanical properties of the deformed sample in term of micro-hardness was analyzed. It is observed that with increasing the shear angle, effective stress, strain and pressing load are enhanced. Moreover, by increasing the coefficient of friction, pressing load enhances. The color coded micro-hardness measurement showed a good agreement with the strain distribution obtained from FEA (higher hardness for the zones associated with higher shear plastic strain values).INTRODUCTIONWork hardening results in enhanced mechanical properties upon cycles of deformation (Hosford & Caddell, 2007). However, the formability of the processed products are affected by work hardening reducing the possibility of processing in subsequent deformation cycles. Therefore, many industrial processes cannot be performed on sheet metals to produce products with desired mechanical and physical properties (Valiev, Islamgaliev, & Alexandrov, 2000). Severe plastic deformation (SPD) is an effective grain refining technique which can impose large plastic strains through cold working on a metallic specimen (Bisadi, Rastgou, Payganeh, Zeynali, & Ghahremani, 2010). SPD techniques are mainly categorized into three types; sheet, bulk and tube forming. Among SPD sheet forming methods, Constrained Groove Pressing (CGP) (Shin, Park, Kim, & Park, 2002), Accumulative Roll Bonding (ARB) (Saito, Tsuji, Utsunomiya, Sakai, & Hong, 1998) and Repetitive Corrugation and Straightening (RCS) (Zhu, Lowe, Jiang, & Huang, 2001) possess potential applications in manufacturing industries."

Jan 1, 2016

By Shichang Liu, Hongli Jia, Zhaolian Wang, Maotang Liu, Ltd. Shandong Huate Magnet Technology Co., Fengliang Liu

"Introduce and promote a latest technology and equipment for magnetite. It’s featured of purifying concentrate, lowering tailing grade, high concentrate recovery rate and stable operation. HUATE® New Style Elutriation Electromagnetic Separator is an equipment to obviously upgrade magnetite. The slurry is fed into separation area through feeder. Generated by excitation coil, the working magnetic field distributes specially in separation area. Under the combined effect of the background field, excitation and demagnetic field and gravity, the mineral particles float downwards in the form of magnetic chains, and interact with the rising water. The gangue, non-magnetic particles, lean intergrowth,etc will be discarded as tailing via overflow tank and pipe. While the magnetic will be discharged from concentrate pipe. Its grade is 2%-10% higher than that of traditional magnetic separation equipment. It adopts the technologies of transformer oil cooling, alternative and uniform pulsation magnetic field controlling the tailing grade, larger drum feed-in device, more uniform umbrella scattering discharge and stabler output current, and realizes lower coil temperature raise, stabler magnetic field, more uniform discharge, effective isolation of weak-magnetic area from non-magnetic area, more obvious upgradation and recovery rate and lowering tailing mFe%. It’s more suitable to purify and thicken the high grade and ultrafine iron powder. Compared with traditional elutriation equipment, it adopts new technologies in removing impurities, operation, large-scale, process simplification, water-saving, remote control, etc. It optimizes the comprehensive beneficiation index, expands its application scope, reduces resource wastes and increases economic benefits.INTRODUCTIONMagnetite accounts for a comparatively great proportion in various iron resources. As it’s a kind of strong magnetic mineral, we must adopt the weak magnetic separation equipment in magnetic separation process to realize removing Si and lowering impurities. While it cannot do very well to use the common weak magnetic separation equipment in the final cleaning to remove Si and lower impurities. At present, the plants, adopting single magnetic separation process to realize cleaning and removing Si and lowering impurities, are in the minority. Most magnetite plants adopt the flotation separation process to remove Si, lower impurities and purify the concentrate. Though with stable indexes and high Fe recovery rate, the flotation process is very complicated, high-cost and with lots of environmental pollution. If adopting the weak magnetic separation equipment can realize removing Si, lowering impurities and the final cleaning, the magnetic separation process should be the primary choice."

Jan 1, 2016

By W. A. Lang

Introduction Under our present civilization, industrial developments will be greatest in those areas in which energy .can be most economically produced and efficiently used, where labour is in adequate supply, and where markets for the products of industry are available. A knowledge of fuels- the present major sources of energy- and of their utilization is therefore of vital importance. With that in mind, the aim in this paper will be to outline the known reserves of fuels in Alberta, to give their characteristics, to indicate the markets served by each, and to offer some suggestions for the future development of the coal industry. The paper should be regarded as a compilation of published data rather than as an original treatise. Alberta is richly blessed by having large reserves of mineral fuels. The estimated reserves of coal are 46,562 million tons. Alberta is the oil and gas province of Canada. The world's largest deposit of bituminous sand occurs along the Athabaska river in Alberta. In addition, there are large areas of forested land in the northern and western sections of the Province, and the rivers serve for the development of hydro-power.

Jan 1, 1949

By L. Tong

The nickel laterite ore is composed of soft and hard minerals, and nickel distributes preferentially into the soft mineral rather than in the hard. Selective comminution of saprolitic and goethitic nickel laterites is investigated to upgrade nickel into the fine fraction using stirred milling. The optimal selective grinding conditions were determined through a kinetic study and the limit of selective grinding and nickel upgrade was analyzed. The breakage rates of minerals, grinding time, and the weight ratio of soft and hard minerals in the feed play an important role in selective grinding. A small breakage rate on hard minerals and a large breakage rate difference between the minerals are optimum for selective grinding. The soft mineral grade decreases with grinding time and the optimum grinding time is a trade-off of the soft mineral upgrade and recovery. The minerals weight ratio determines the limit of selective grinding. The effect of nickel upgrade is determined by both the conditions that influence selective comminution and the nickel grades in both the soft and hard minerals. The nickel grade in the soft mineral determines the limit of nickel upgrade.

Jan 1, 2015

By Jan E. Nesset, Phillip J. Mackey, Joo Y. Kim, Giovanni Di Prisco, André R. Laplante

Understanding the appropriate gold recovery to associate with copper recovery when assessing laboratory testing on porphyry deposits is often complicated by several factors including variable and/or complex mineralogy, and the variability contributed by the low Au content of the various flotation products. As a result, gold recovery is often underestimated and the value contributed by the gold to project economics is less than it should be, a problem that could influence overall project viability. Typically, for these types of deposits, the gold recovery is found to be lower than the copper recovery. In this unique project, having the objective of seeking a better understanding of gold recovery relative to copper recovery, mill feed samples from a selection of six operating world-class Cu-Au low-grade deposits were collected along with the mill metallurgical results for the corresponding sample periods. The samples were subjected to laboratory flotation tests, as well as the Laplante gravity recoverable gold (GRG) test, mineralogical assessment and cyanidation leaching. The aim was to better understand the copper and gold recovery relationship, the links between laboratory and plant flotation performance, the influence of mineralogical differences, and the potential for enhancing gold recovery by gravity recovery techniques. A new correlation of copper and gold recoveries based on the results is presented in the paper. The results showed that the link between copper and gold recoveries established in the best laboratory tests were maintained in the plant results, and further, that the potential for improving Au recovery by gravity or flash flotation methods is directly proportional to the amount of gold greater than 75 microns.

Jan 1, 2005

By H. J. H. Pieterse

Agitation requirements in oxidation autoclaves can vary widely depending on the mineralogy of the feed material and the specific process selected. Before selecting an agitation system it is important that the client specify the desired throughput, mineralogy, chemistry, kinetics, compartments, overall retention time, and the desired oxygen utilization. In selecting the agitation system, the factors mentioned above as well as oxygen solubility, oxygen mass transfer coefficients, and specific power are evaluated. Much research effort has been directed toward open tank systems for fermentation and oxidation processes. However, for high pressure autoclave oxidation processes little information is available. In this review the author's experience in the autoclave industry and some of the available literature are utilized to compare the installed power per unit volume with some of the methods proposed for open tank oxidation. Equations that appear to give results close to that experienced in the industry have been identified. Further work is required in this area to develop a higher degree of confidence in the ability to predict the power required for any given case.

Jan 1, 2004

By William E. Roscoe

"Mineral exploration properties are those on which an economically viable mineral deposit has not yet been discovered. Such properties are bought, sold, optioned and joint ventured on the basis of their perceived potential for the existence and discovery of a viable mineral deposit. The intrinsic value of an exploration property is therefore based on the exploration potential. One measure of the exploration potential is the amount that can be justified to spend on exploration for a viable deposit.The appraised value method uses a cost approach to value exploration properties. It is based on the premise that an exploration property is worth the meaningful past exploration expenditures plus warranted future costs to test remaining exploration potential. Results of past exploration work are analyzed in order to retain only those past expenditures that are productive in terms of identifying remaining potential. Warranted future costs comprise a reasonable exploration budget to test that potential.INTRODUCTIONThe purpose of this paper is to describe a cost approach to the valuation of mineral exploration properties and to provide some valuation examples. The particular cost approach described is the Appraised Value Method, which is best applied to mineral properties at the exploration stage.At present there are no comprehensive regulations or guidelines in Canada which specify what approaches and methods to use for the valuation of mineral properties. In this paper, the Appraised Value Method described is one method that the writer considers to be accepted industry practice for mineral properties at the exploration stage.Mineral properties are valued for a number of reasons, including mergers and acquisitions, non arm's length transactions, pricing of initial public offering of stock, support for property agreements, litigation, expropriation, and insurance claims."

Jan 1, 2003

By F. A. Auld

"Traditionally deep shaft sinking from the ground surface was carried out using drill and blast methods. Although large diameter blind shaft drilling has been carried out successfully on numerous occasions previously, including as early as 1852 in Germany (Auld, 1995), little attempt has been made until more recently to mechanise the shaft sinking excavation process using down-the-hole machines. This paper reviews the development of deep shaft sinking machines from the early 1970’s up to the present day. INTRODUCTION Mechanical excavation methods can significantly improve excavation performance, in order to access natural resources faster, and labour safety is increased compared to drill and blast operations. However, shaft sinking machines need to be capable of accommodating all the basic requirements for deep shaft sinking, namely: 1. Excavation and muck removal 2. Ground stability control 3. Groundwater ingress control 4. Temporary lining installation 5. Permanent lining installation and watertight sealing 6. Ventilation 7. Secondary means of egress for personnel In addition, how the machine operates in the shaft is an important factor, either slung on ropes from a surface headgear or on its own in the bottom of the shaft. An all-embracing machine which can deal with all of the above conditions is impossible but many of these requirements can be incorporated into a single machine. Deep shaft sinking also differs greatly from normal tunnel construction which employs the use of either a roadheader arm installed within a shield or a full-face tunnelling machine for excavation. Hydrostatic pressure and ground stability problems increase with depth, whereas in tunnelling the depth is normally relatively shallow and the aforementioned factors remain approximately constant along the tunnel length. DEEP SHAFT SINKING MACHINES All the shaft sinking carried out previously in the UK was by the traditional method of drill and blast. Elsewhere, in other parts of the world, attempts have been made to mechanise the process."

Jan 1, 2019

By L. S. Rivett, U. M. Oko

The Strathcona mine, with a large new underground operation and concentrator, was recently brought into\ production by Falconbridge Nickel Mines Ltd. The tailings disposal and water utilization problems at Strathcona are described in this paper, with sections devoted to the Moose Lake watershed system, tailing impounds, the construction of dams and the operation of the Moose Lake neutralization plant for the elimination of acidity, including the equipment used.

Jan 1, 1971

By J. Visman

"SummaryThis paper is presented as part of a programme to show the steps taken by industry and others interested in supplying a solid fuel of constant quality to 'satisfy a consuming market. The paper deals with the general principles underlying quality control in coal preparation plants, namely, constant quality and close adherance to acceptance limits. It also describes how control of ash content is ""generally hampered by the problem of coal sampling .and the long duration of the ash analysis and how these difficulties may be overcome.Quality control can be effected in several ways. Thorough blending wll reduce variations appreciably, except those of long trend. The latter can be detected by automatic sampling and quick ash analysis. At present, under favourable conditions, a system of half-hourly ash determinations with an accuracy of 0.5 to 1.0 per cent can be realized, to the effect that trends with a 'wave length' of more than two hours cu be eliminated within the limits of accuracy of the ash figures. The general solution of the problem is a combination of blending, accurate sampling, quick ash determination, and statistical analysis of the pattern of ash distribution.The use of statistical methods of analysis, such as the t test and F test, is •discussed at some length in order to emphasize the importance of the correct evaluation of observational data if there is to be confidence in the validity of test results.General ConsiderationsCOAL, as a fuel, is too cheap for a long haul across the country. The limiting distance depends on the price of the local competitive fuels, and, as the price depends to a great extent on quality, so does quality, to the same extent, command the market."

Jan 1, 1952

By L. H. Van Loon, E. G. Crayston, A. F. Heather

"IntroductionTHE PROPERTY of Madsen Red Lake Gold Mines. Limited. comprises fifty-eight claims located between Russet and Faulkenham lakes in Baird and Heyson townships of the Patricia portion of the District of Kenora. The mine is seven miles •by road from the hamlet of Red Lake. This latter centre is .connected to the Trans-Canada Highway at Vermillion Bay, Ontario, by provincial highway No. 105 which has a total length of one hundred and thirteen miles.The Madsen property went into production on August 11th, 1938, with a milling plant rated at 300 tons per twenty-four hours. Changes made in the crushing plant during October, 1938, allowed a •finer feed to be delivered to the mill and increased the milling •capacity to 400 tons per twenty-four hours. During 1948, steps were taken to add an additional 400-ton capacity unit to the milling plant. This latter work was completed by May, 1949, giving the present total milling .capacity of 800 tons per twenty-four hours.It was realized in the early 1940's that, eventually, considerable material suitable for backfilling in the mine would be required. As there were no large deposits of gravel or sand anywhere near the mine, officials of the Company considered it advisable to investigate the feasibility of using mill tailings for mine •backfill. Since Madsen mill tailings contain approximately 80 per •cent of minus-200-mesh material, it was not considered practical to use them for underground backfill without first removing the finer material. as the slimes present in a product of this fineness would without doubt preclude any drainage whatsoever. Table I gives a sizing analysis of Madsen mill tailings and Table II a quantitative chemical analysis of the ore."

Jan 1, 1954

By P. H. Jennings

Commercial tellurium commonly contains heavy basemetal impurities such as lead, copper, iron, etc., as well as selenium and oxygen. The base metals may be removed by vacuum distillation or by zone melting. Vacuum distillation is a convenient method for treating moderate quantities (~ 100 kg.) for the production of a material having a total content of heavy metals in the 10-30 ppm range. By zone melting, it is possible to lower all the heavy metal impurities tm below the limits of spectrographie detection. Neither vacuum distillation nor zone melting is effective for the removal of selenium, but treatment of molten tellurium with hydrogen converts selenium to hydrogen selenide. This procedure is too s low to be considered except as an adjunct to zone melting. In the course of air-melting, many of the more easily oxidized impurities form a dross and may thus be readily removed. Substantial refinement with respect to iron, tin, chromium, aluminum, sodium, silicon, magnesium, calcium and manganese can be achieved in this way. Although tellurium can be electrodeposited from either acid or alkaline solutions of the dioxide, various factors militate against successful electro-refining, amongst which may be mentioned the brittleness of cast tellurium anodes and the tendency for the metal to be deposited in dendritic form, even at low current densities.

Feb 1, 1966

By P. H. Jennings, J. C. T. Farge

Commercial tellurium commonly contains heavy base-metal impurities such as lead, copper, iron, etc., as well as selenium and oxygen. The base metals may be removed by vacuum distillation or by zone melting. Vacuum distillation is a convenient method for treating moderate quantities ( 100 kg.) for the production of a material having a total content of heavy metals in the 10-30 ppm range. By zone melting, it is possible to lower all the heavy metal impurities tm below the limits of spectrographie detection. Neither vacuum distillation nor zone melting is effective for the removal of selenium, but treatment of molten tellurium with hydrogen converts selenium to hydrogen selenide. This procedure is too slow to be considered except as an adjunct to zone melting. In the course of air-melting, many of the more easily oxidized impurities form a dross and may thus be readily removed. Substantial refinement with respect to iron, tin, chromium, aluminum, sodium, silicon, magnesium, calcium and manganese can be achieved in this way. Although tellurium can be electrodeposited from either acid or alkaline solutions of the dioxide, various factors militate against successful electro-refining, amongst which may be mentioned the brittleness of cast tellurium anodes and the tendency for the metal to be deposited in dendritic form, even at low current densities.

Jan 1, 1966

By V. L. Eardley-Wilmot

Introduction We are all familiar with the bright and attractive colours of the roofs of our suburban houses and country cottages, but few of us fully appreciate the complex and highly technical nature of the business which produces these roofings. Roofing granules consist of small broken particles of certain types of rocks, burned clay products, or slag. They are used either in their natural state or artificially coloured and are affixed onto one surface of asphalt sheeting. Their main functions are to protect the roof against external fire hazard, prolong its life, and enable it to withstand extremes of weather over a period of years without deteriorating. Pleasing designs and colours are added attractions. The reverse, or inner side, of the sheeting is coated with a film of talc or fine mica to prevent it sticking when rolled up for convenience of handling for transport. The finished sheets or strips are cut into a variety of shapes for roofing shingles, or for sidings which resemble rows of bricks separated by mortar. In Canada, the consumption of roofing granules has increased fourfold in the past decade and indications are that the industry will continue to expand. At present, fourteen plants are engaged in manufacturing granule-coated roofings, but, apart from a relatively small output of natural granules by two producers in British Columbia, only one eastern producer makes both natural and coloured granules in Canada, and these only for its own use. The annual consumption is now over 77,000 tons of roofing granules valued at more than $1,600,000, but about 62 per cent of the tonnage is imported. It is thus apparent that the production of Canadian-made granules, both natural and coloured, could be considerably increased. This paper is presented in order to give an outline of the industry and at the same time to point out its difficulties and pitfalls.

Jan 1, 1946