Search Documents

By I. Farr, H. Wittens

"In 1989 and 1990 abnormally high levels of arsenic in ore from the Thompson Open Pit Mine threatened Manitoba Division's electro-nickel production. The paper will discuss our development of a flotation process to separate pentlandite and gersdorffite (the prime nickel and arsenic bearing minerals).The presentation will focus on the development of the process from conception, through lab and plant test work, to plant optimization and full scale production. The paper will conclude with the benefits and cost of the completed project.INTRODUCTIONRejection of arsenic from nickel sulphide ores was not a primary concern in the Manitoba Division until 1989. At that time increased production in the Thompson Open Pit mine, which contains high arsenic ore zones, resulted in excess amounts of arsenic in the Thompson Refinery affecting electro-nickel quality. This problem was resolved through extensive efforts by Mill personnel. The purpose of this paper is to familiarize the reader with- the Thompson Mill.- the mineralogy of the Thompson orebody.- the evolution of Ni/As separation in the Mill.- the metallurgical impacts of the separation on the Mill.- the importance of the separation to the Manitoba Division."

Jan 1, 1991

By Neil Campbell

"The gently-dipping Devonian dolomite beds south of Great Slave lake in northern Canada are nearly every-where concealed by a cover of glacial drift and muskeg. Nevertheless, in 1898 or earlier, four small outcropping areas of dolomite, richly mineralized with lead and zinc sulphides, were discovered. Exploration work performed here up to the end of 1930, included intensive trenching and drilling of the showings, together with mapping and wide-spaced drilling in the surrounding region. This work proved that the discoveries are isolated pockets of mineralization much too small to be commercially valuable by themselves. No evidence of orebodies elsewhere was reported.Meanwhile, mapping by the G.S.C. in the Shield far to the east disclosed major Precambrian faults, some of which can be projected southwesterly (under a cover of Paleozoic sediments) to the vicinity of Pine Point. During the period from 1940 to 1947, consideration was given, by The Consolidated Mining and Smelting Company Ltd., to evidence of a theoretical possibility that, although apparently dormant in Paleozoic times, these faults may have provided a structural control and a source of ore-bearing solutions in some post-Devonian period. From this, it was postulated that the breaks might have created, in the overlying dolomite, a linear array of orebodies concealed by overburden but lying in a belt of considerable length and in a position predictable within practical limits. A program of drilling designed to test and exploit this specific concept was conducted from 1948 to 1955.he drilling within the new, theoretically-defined search area resulted in the discovery of many lead-zinc ore-bodies, none of which was exposed at the surface. Some of these are large and (as indicated by 1965 production records) very rich. They are situated 1 to several miles distant from, and apparently not connected to, the earlier-known surface discoveries. The drilling also disclosed that the ore, which consists of disseminated sphalerite and galena replacements together with colloform sphalerite and coarse galena cavity fillings, occurs mainly at certain stratigraphic horizons within a large, coarsely-recrystallized dolomite barrier reef. Considerable fracturing and folding was found. It has been suggested that reef development was influenced by post-Precambrian tectonic movements associated with the old faults in the basement complex. The ore may have been deposited by solutions moving from distant sources to favourable structural and chemical environments in or related to the reef.In more recent exploration performed in the course of preparing for mining production, the rate of ore discovery within the same general geological context has been greatly accelerated by the use of new geophysical techniques and drilling equipment. Reserves of 21.5 million tons, averaging 4 per cent lead and 7.2 per cent zinc, were reported in 1965, and production from open pits at the rate of approximately 248,000 tons of concentrates per year is in progress"

Jan 1, 1966

Cameco Corporation is in the process of revitalizing the Key Lake mill. As part of this process, the company is considering installing the Rabbit Lake style strong acid stripping in solvent extraction. This would lead to using hydrogen peroxide for uranium precipitation. The process currently employs ammonia stripping and ammonia precipitation. As part of the process evaluation, an indirect fired drier pilot plant test was conducted. This paper will discuss the results of that test work, including the relationships between the following: ? Drying temperature and product grade ? Drying temperature and product colour ? Drying temperature and product reactivity with water ? Drying temperature and energy input requirements ? Drying temperature and shipping costs

Aug 1, 2010

By H. A. Halupka, I. A. Mozer

"At its plant in San Juan, Peru, Marcona Mining Company operates two grate pelletizing furnaces for the agglomeration of 3.5 million long tons of magnetic concentrates annually. Line One, installed in 1963, was built by Lurgi as a downdraft process furnace utilizing a furnace fan for the recuperation of hot gases from the cooling zone. This line was modified in 1966 to include both updraft drying and downdraft drying, and the original roof burners were converted to side-wall burners. Line Two, a Dravo-Lurgi furnace with an annual capacity of 2.4 million long tons, was built in 1966. This line, in contrast to the modified Lurgi furnace, employs direct recuperation of hot gases from the cooling zone and utilization of process gases from the firing zone for updraft drying.At its plant in San Juan, Peru, Marcona Mining Compa-ny operates two grate pelletizing furnaces for the agglo-meration of 3.5 million long tons of magnetic concentrates annually. Line One, installed in 1963, was built by Lurgi as a downdraft process furnace utilizing a furnace fan for the recuperation of hot gases from the cooling zone. This line was modified in 1966 to include both updraft drying and downdraft drying, and the original roof burners were converted to side-wall burners. Line Two, a Dravo-Lurgi furnace with an annual capacity of 2.4 million long tons, was built in 1966. This line, in contrast to the modified Lurgi furnace, employs direct recuperation of hot gases from the cooling zone and utilization of process gases from the firing zone for updraft drying. 5 per cent increased capacity, 30 per cent lower fuel oil consumption, and approximately 400 per cent reduction in grate bar and pallet corrosion. Firing of the pellet bed was improved by conversion from roof to side-wall burners. This modification also permitted utilization of monolithic refractory in place of pre-fired shapes, thereby improving over-all furnace availability and reducing refractory stock requirements from 154 different shapes to 18.Data are presented to compare operating performance of the Dravo-Lurgi furnace and the modified Lurgi furnace. These data show 30 per cent lower fuel oil consumption and 10 per cent higher capacity per unit grate area for the Dravo-Lurgi furnace, which also averages higher availability due to greater operating flexibility."

Jan 1, 1970

By C. T. Harper, B. J. Fryer, R. P. Taylor

"IntroductionThe Maurice Bay deposit is one of a number of uranium deposits that have been found in recent years in the Athabasca Basin of northern Saskatchewan (Tremblay, 1982). This deposit, along with the others, belongs to the unconformity type deposits (Beck, 1977). They are, for the most part, polymetallic, being characterized by a suite of metals which include U, Ni, Co, Cu, Pb, Zn, Mn, V, Ag, Au, Pt-group elements, S, As, Bi, Se, Te, and Mo, some of which, besides U, are present in economic concentrations (Amok, 1974; Ruzicka, 1975; Tapaninen, 1976; Hoeve and Sibbald, 1978; Dahlkamp, 1978). The Maurice Bay deposit was known to be a small low grade deposit in which the ore was essentially monomineralic, consisting mainly of pitchblende (Harper, 1978). However, the occurrence of trace amounts of some of the elements common in the larger polymetallic ore bodies (e.g. Key Lake, Cluff Lake D) was anticipated. Thus a lithogeochemical sampling project was undertaken in 1979 across part of the Maurice Bay deposit (Harper, 1979). Major oxides (SiO2, Al2O3, FeO, Fe2O, MgO, CaO, K2O, Na2O, MnO, P2O5, and TiO2) and a group of the most common trace metals (U, Ni, Co, Cu, Pb, As, Au, V, and Se) were analyzed to determine whether any elemental patterns (halos or depletions) could be detected which would reduce the number of pathfinder elements needed for exploration purposes. In addition to the above metals, Th was also checked because some conglomerate strata in the Maurice Bay area are known to be thorium-enriched (Harper, 1978). Only the trace metal distributions will be discussed in detail in this report.General GeologyThe Maurice Bay area is underlain by three major groups of rocks, the White Lake metamorphic complex, an unnamed granodiorite complex, and the Athabasca Group, described previously (Fig. 1; Harper, 1979). Table 1 summarizes the stratigraphic features as deduced by geological mapping and the examination of drill cores."

Jan 1, 1986

By Raju S. Sagi

This paper deals primarily with the different types of drilling methods used by the Iron. Ore Company of Canada for sampling the soft and friable hematite-limonite (secondary) iron ore deposits found in the Scheferville area. The problems associated with drilling, sampling, sample handling and sample preparation. for chemical analysis of these ores are discussed. Systematic evaluation of the various drilling methods led to the selection of an integrated drilling system. This system consists of a rotary dual- tube - reverse-circulation drill, with tricone bit, polymer mud and mechanical sample splitter, The historic al development of this drilling system is described in detail, as are the equipment , sample flow and quality control checks carried out to obtain representative samples. This integrated drilling and sampling system has been used satisfactorily on a routine basis for determining the grade and tonnage of ore for the various deposits for the last five years (1972-76) in the Schefferville area.

Jan 1, 1977

By D. Racicot, T. Hanel, E. H. Chown

Over thirty plutons in the Chibougamau-Desmaraisville belt were examined briefly in the field and sampled, in addition to the few masses that have been studied in detail. The survey indicates that the intrusions may be conveniently grouped in four main categories, based on their time of intrusion. These are; remobilized basement domes, pre-kinematic intrusions, syn-kinematic intrusions and postkinematic intrusions. Basement domes, as exemplified by the Lappa rent Massif, are composed of migmatized tonalite-diorite gneiss that has undergone at least two periods of mafic dyke intrusion and at least three major deformational periods. The rise of the basement domes was accompanied by extensive mylonitization and the intrusion of syn-tectonic plutons. Pre-kinematic plutons, such the Chibougamau pluton, are diori te-tonalite in composition, and were intruded into the supracrustal pile and partly eroded before the main deformation of the belt. Syn-kinematic plutons occur principally as marginal intrusions bordering the belt (Barlow), or as discrete intrusions along structural highs (La Dauversiere), and are either hornblende monzodiorite or tonalite in composition. Post-kinematic plutons, such as Muscocho, are principally granodiorite and often porphyritic intrusions locally deforming the enclosing rocks. The close relationship between mineralization and high-level intrusions such as the pre-kinematic and some of the post-kinematic plutons is discussed.

Jan 1, 1984

By A. Saigal

The effect of temperature on the cutting forces during machining of alumina reinforced aluminum composites was investigated, Aluminum 6061, 10% Al2O3 reinforced composite and 20% Al2O3 reinforced composite were tested, A 5/8-inch diameter high-speed steel end mill, a Micro 100 TiN coated single edge endmill cutter and a two-fluted solid carbide insert cutter were used for tooling, The results, in general, showed an increase in the cutting forces as the temperature of the material increased, From the raw data, there are temperatures ranges in which the force data did decrease but they were insignificant with regards to predicting a downward trend. A regression analysis was used to understand which variables had the greatest affect on the forces being generated, The correlation and regression analysis showed that at 600 rpm (velocity: HSS- 98,2 sfpm, Micro 100 cutter - 78,5 sfpm, solid carbide cutter - 192,4 sfpm) the tooling, the workpiece material, built up edge, and temperature were statistically significant factors in the test, Tooling was a significant variable in all testing, The smallest forces recorded during machining were generated with the solid carbide two-fluted endmill cutter, Visually, the solid carbide tooling produced a better surface finish during the testing which made it the tool of choice, In addition, the force data proved that as the cutting speeds were increased, the cutting forces decreased.

Jan 1, 2005

By Forrest A. Kerr

Northern British Columbia is a term which probably conveys to various individuals quite different meanings. To the average person it signifies an area of indefinite size and indefinite position which may start at Prince Rupert, Stewart, or somewhere else, and end at Alaska or .the Yukon. Many people, in their conception, fail to encompass in their mind's eye that vast tract of land lying ~o the east of the panhandle of Alaska. Few realize that the area north of an east-west line through Stewart represents more than one-third of the Province and is, of course, the part most appropriately designated as northern British Columbia. This section, more especially the northernmost 100,000 square miles, from political, geographic, and economic viewpoints stands isolated perhaps more than any other part of British Columbia. Unlike the rest of the Province, it has no coast line, being cut off from the Pacific ocean by a narrow strip of Alaska. It is bounded on the north by the Yukon, and on the east by Alberta. In the south this northernmost 100,000 square miles is limited by a divide of rugged mountainous country separating the drainage basins of the Stikine and Liard rivers from those to the south.

Jan 1, 1929

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 W. A. Green

Introduction While pilot-mill operations were being carried on at Flin Flon, as described by R. E. Phelan (1), a detailed topographic map was being made of the area in the vicinity of the ore-body for later use in laying out plans for the final plant. The area covered by this survey was 6,600 feet by 6,600 feet, with contours on 2-foot intervals. As mentioned by Mr. Phelan, it was definitely decided at the end of November, 1927, to take up the option on the Flin Flon property and to proceed immediately with the plans for construction of a metallurgical plant at Flin Flon to treat 3,000 tons of ore per day, and of a hydro-electric power plant at Island Falls, Saskatchewan, to supply power for the future operations at Flin Flon. Railway Built From The Pas to Flin Flon Just as soon as the decision was made to go ahead with the construction work and opening-up of the property, it was of course essential to give immediate attention to the building of a railway to the mine. Many years previously, a preliminary survey had been made for a railway to branch off the Hudson Bay railway at a point 4.7 miles northeast of The Pas, and, during certain negotiations in 1925, the Provincial Government of Manitoba had agreed to guarantee the railway bonds necessary to finance the building of the line, so that it was possible to organize for this work immediately. A contract was let by the newly organized Manitoba Northern Railway Company to the Dominion Construction Company, Ltd., and Tomlinson, for the building of the railway to the mine, a distance of approximately 87 miles (see Figure 1). The Manitoba Northern railway is a subsidiary to the Canadian National railway, and all engineering and supervision of the contractors was done by the Canadian National engineers. Actual construction work was started in January, 1928. The first 52 miles of the railway from The Pas to Cranberry Portage is over fairly level, although slightly rolling, country, and a considerable portion of the route is over muskeg area. Rails were laid on top of the frozen muskegs. Gravel deposits were opened-up along the line and, before warm weather; sufficient ballast .was distributed in the muskeg areas to prevent thawing under the track, and thus give the necessary support to allow uninterrupted transportation over the line.

Jan 1, 1935

By G. F. Flaherty

THE property of Tashota Goldfields, Limited, in the Lake Nipigon area, Ontario, is located about 4 miles west of Onaman lake and 16 miles by winter road south-southeast of Tashota station on the transcontinental line of the Canadian National railways. The mine, formerly developed to a limited extent under the name of Tashota Gold mine, has, since late in 1933, been under the management of Minefinders Limited, who, in 1935, brought it into production on a 60-ton per day basis. During the winter of 1934-35, the writer was geologist at the property. The geological structure in the immediate vicinity of the mine workings lends itself well to analysis on the basis of the mechanical principles of folding. Since structure is of prime importance in the localization of the ore-shoots and of the host shear-zones at the property, the correlation of all structural details and their mechanical interpretation forms a working hypothesis of structural control for the direction of exploration and development work. It is believed that the structural relations here set forth may be found applicable in part, or at least suggestive, in working out the relations of ore-shoots to structure in the Sturgeon River area to the south, and in the Little Long Lac area to the southeast (Figure 1).

Jan 1, 1936

By D. M. Muir

Many plants produce iron(II)/(III) waste liquors which must be treated by neutralisation and precipitation to remove the iron. Iron can be precipitated as crystalline goethite or jarosite by controlled oxidation at low pH and as magnetite by controlled oxidation at high pH, but only at elevated temperatures (>70°C). This study focuses on the characterisation and settling properties of the iron oxides produced at ambient temperatures using various neutralising agents in order to improve the performance of thickeners. It was found that two-stage addition of caustic to FeC12 solutions produced a fast settling material characterised by Mossbauer spectroscopy and XRD as maghemite and magnetite. However, lime and magnesia additions resulted in more ferrihydrite formation and much lower settling rates because of the enhanced oxidation of Fe(II) by air. Settling rates decreased significantly as the proportion of Fe(III) to Fe(II) in the liquor increased. The mechanism of iron oxide precipitation is discussed together with some reasons for the different behaviour of the neutralising agents.

Jan 1, 2006

By Mike Dry, Rod Dry

If humanity is truly serious about reducing emissions of carbon dioxide into the atmosphere, today’s power plants burning fossil fuels will have to be replaced by power plants that do not emit CO₂. Unless carbon capture/sequestration becomes practical, the new power plants will be hydroelectric, wind, solar or nuclear installations. Hydroelectricity requires the appropriate geography. Solar installations can only deliver power as and when sunshine is available, and wind installations when the wind blows. Therefore, power from these sources will be intermittent, but the demand for electricity does not follow the patterns of sun and wind. That will require large-scale electricity storage and/or load following by the remaining power suppliers, increasingly so as the use of fossil fuelled power generation declines. Modern nuclear power plants are designed for demand following. However, operating at lower than design output has a negative impact on the economics of nuclear power plants because the overall cost of the electricity they generate is dominated by capital cost. Primary (blast furnace) iron smelting is responsible for a significant part of global CO₂ emissions because the reagent used is carbon. Were it available in sufficient quantity (and at a low enough cost), hydrogen could replace carbon in the manufacture of raw direct reduced iron (DRI), using technology such as modified HYL (Tenova Hyl, 2018) or Midrex (Ravenscroft, 2017). This paper examines a scenario in which, instead of demand following, nuclear power stations are operated at their design capacities and surplus power is used to generate hydrogen in off-peak periods. This hydrogen is then used to replace carbon in the manufacture of raw steel.

Jan 1, 2020

By Yves Gagnon, Nicole Gauthier, Daniel Kelly, Michel Rocheleau

"The Larder Lake-Cadillac Tectonic Zone in Rouyn-Beauchastel area (a 20 km long segment) contains distinct lithotectonic units bounded by artastomosing or sub-parallel shear zones. The gold deposits in the area are located within highly strained portions of E-W striking shear zones. The ore-zones are structurally controlled disseminated and vein-type lodes. They are spatially related either to megascopic z-shaped folds which refold E-W shears, or to areas of intersection between E-W shear zones and late NE-striking faults. Several ore bodies are enclosed within ultramafic rock units or at their contacts with adjacent units. All the lenses are elongated down dip and distributed, both loterally and vertically, ""en echelon"" . The ore zones tend to decrease in size and number away from the hinge zone of the megascopic z-shaped folds.Two main styles of mineralization are recognized at the Astoria deposit and at for most of the deposits in the Rouyn-Beauchastel segments a discontinuous ""Carbonate Ore"" and a more continuous, albitic sulphide-bearing ""Flow Ore"" (terminology used at the Kerr Addison mine).The typical ""Carbonate Ore"" zones are found within strongly arbonatized blocks bounded by conjugate late NE or NNW-striking fralls. The carbonatized blocks display features characteristic of llrittle to brittle-ductile deformation developed in shear zone system. Vein systems in the ""Carbonate Ore"" occur within shear fractures(D R)tension fractures (T), or within brecciated rocks adjacent to NS llrilcing faults. The ""Carbonate Ore"" zones are displaced by numer IU lole E-W, NNE, NW and N-S faults.The ""Flow Ore"" zones are found within predominantly ductile portions of E-W shear zones. The sulphide mineralization is finely disseminated and regularly distributed within mylonitic foliation or associated with veins and veinlets sub-parallel or oblique to the mylonitic foliation, in which case the mineralization is coarser grained. The gold mineralization is a late Archean event postdating the formation of the penetrative fabric, and synchronous with the end of the dextral oblique-slip motion."

Jan 1, 1990

By T. Krumins, L. Zunti, R. Frischmuth

Mercury is known to occur in sulphide-bearing refractory gold deposits in the form of sulphide minerals or elemental inclusions. These deposits typically require an oxidative pre-treatment process, such as pressure oxidation or roasting, to achieve economic gold recovery. However, these processes also have the potential to liberate mercury, a portion of which may then be released to the environment through gaseous emissions. Mercury emissions from mine processing operations have been of particular interest in recent years, as governments impose lower emission targets and organizations adopt better industry practices to reduce the environmental and health aspects of releasing mercury into the environment. This paper describes various mercury removal technologies with respect to pressure oxidation gas handling circuits, with a focus on key design variables and technology selection criteria.

Jan 1, 2014

By Ming’an Wei, Qifu Duan, Jianmin Wu, Lusheng Zhou, HMR Group Limited / HMR Technology Canada Ltd., Wenjian Wu

"The development and industrial applications of magnetic liners have been around for decades. A Swedish company Skega first introduced rubber magnetic liners, and then followed by the Chinese invention of metal magnetic liners. Traditionally, both liners were used in secondary ball mills and regrind ball mills for industrial applications, especially for ores containing magnetic materials. Mostly steel balls or equivalent forged steel balls, usually below 60 mm in diameter, were used as grinding media. With the development of mineral resources over the years, SAG mills and larger ball mills have become the dominating components for comminution circuit design. Due to the development of larger diameter ball mills and thus larger ball charge diameter (up to 80mm) especially in non-ferrous metal mining operations, the application of magnetic liners have been very limited. Based on “Magnetism theory” and the development of new materials, the HMR Group Limited has been conducting researches on examining the structures of magnetic liners, associated materials and magnetic circuits which led to the invention of the Nano Alloy Steel Magnetic Liner (NSML). Recently, NSML had a successful application in a 5.5 m diameter × 6.5 m ball mill at the Erdenet Copper Mine in Mongolia. The NSML successfully handled a ball size up of to 80 mm, while achieving a service life of nearly 24 months, which is almost 3 times wear life of the original manganese steel liners.INTRODUCTIONDuring the development and utilization of mineral resources, mineral processing is an indispensably operation. The effective separation of various useful minerals depends on sufficient monomer dissociation of minerals in the ores. The crushing and grinding operation is prior operation of mineral processing. Ball mills are used in different concentrators. As the main consumption parts of mill, liners have been studied constantly. As a new kind of liners, magnetic liners besides can meet the requirement of production, and also have characteristics with maintenance-free, saving energy and increasing efficiency. So the magnetic liners are worth to be spread and applied world widely."

Jan 1, 2016

By R. P. Chapman

The geochemical interpretation of results of statistical analysis of published multi-element stream sediment data from southwest and northern New Brunswick is presented. Element concentrations in southwest New Brunswick are low and comparable to element concentrations in background areas in northern New Brunswick. Deposits of copper and nickel are indicated in southwest New Brunswick. Anomalous element concentrations occur in several areas in northern New Brunswick and the elements most commonly associated with these anomalies are Cu, Pb, Zn, As and Ag; and also Mo, Wand Sb. Bedrock geology greatly influences element concentrations and may cause false anomalies. Manganese has a pronounced effect on the dispersion patterns of Co and also Zn, Mo, Pb, As, Ba and Ni. Nickel and Cr are strongly sympathetically related and this association is independent of bedrock type.

Jan 1, 1977

By E. C. Harder

BRITISH Guiana, Great Britain's only South American colony, may be reached by very comfortable steamers, both from North America and Europe. The trip from North American Atlantic ports requires about 12 to 14 days; that from Europe about 18 to 20 days. A number of steamship lines, including Canadian, American, and Dutch, have regular sailings between North America and British Guiana, with calls en route at various interesting ports in the West Indies and northern South America. Moreover, several lines, including British, German, and French, have steamships operating regularly between Europe and the West Indies. Indeed, so popular have the West Indian voyages become in recent years that, during the winter months, special cruises in considerable number are organized for many vessels that ply in the trans-Atlantic service in the summer. A trip to British Guiana, therefore, has become a delightful experience. After visits at the various attractive Leeward and Windward islands and Trinidad, the approach to the low, flat, British Guiana coast, with its muddy coastal waters extending for many miles offshore, is somewhat of a contrast. Arrival in Guiana waters is signalled by the appearance of the modern high-power Demerara Light, located "on a shoal about twelve miles from the mouth of Demerara river. From this point, if the tide is right, a pilot takes the steamer across the bar, eight to ten miles offshore, and into Georgetown harbour. At high tide, the water above the bar ranges from 15 to 18 feet in depth, depending on whether it is neap tide or spring tide; at low tide, the corresponding depths are 9 to 11 feet. As the bar is of soft mud, however, it is usually possible for vessels to pass over it with a draught of about two feet in excess of that indicated by the tide tables. Upon nearing the shore, one sees first the Georgetown wireless towers, then the light-house and the tall chimneys of sugar mills and of various factories in Georgetown, and finally the palms and other tropical trees and the houses of Georgetown itself along the sea shore and the east bank of Demerara river. Extensive wharves operated by various exporting and importing companies stretch along the river bank and activity prevails in Georgetown harbour. The principal exports are sugar, rice, gold, diamonds, bauxite, balata, lumber, fruit and other tropical products. The imports are food-stuffs, wearing apparel, and manufactured materials of many kinds.

Jan 1, 1936

By Paul Toor

The operation of SAG mills is variable over time due to their continually changing liner shape, mass and subsequent load motion. However, this tends to be poorly accommodated in liner design and mill control, with only limited compensation made for this influence, usually in the first few weeks after a new liner is installed. With ever-increasing ore competency, increasing energy costs and decreasing ore grades, simplified design and operational approaches that compromise the achievable mill efficiency are no longer adequate. This paper presents a methodology that has been developed to measure and account for the changes in mill performance as the liner wears. This involves monitoring all liner profiles ? in other words the three-dimensional liner shape - over the life of the liner, then conducting controlled surveys at different stages of the liner wear life, and correlating the mill performance to the liner profiles. The measured liner mass is modelled to provide an ongoing meaningful load mass measure that excludes the liner mass.

Jan 1, 2012