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By A. Manouchehrian, M. Cai

"Rockburst, which often occurs around underground openings in highly stressed hard rocks, is a sudden and violent unstable rock failure and is associated with energy release. Rockburst is very dangerous to workers and mining equipment, and it has been a major concern for deep underground construction and mining. Before excavation, rocks are loaded under a true-triaxial condition. Upon excavation, the rocks at the excavation boundaries are loaded in the maximum principal stress direction and unloaded in the minimum principal stress direction and this provides a necessary condition for unstable rock failure to occur. Understanding rock behavior under true-triaxial unloading condition is critical for developing measures to control unstable rock failure in underground construction.In this article, an explicit FEM tool is used to simulate rock behavior under true-triaxial unloading condition, with a focus on analyzing stable and unstable failure and the released energy during failure. Firstly, a uniaxial compression test was simulated. The results indicated that the adopted numerical tool was able to simulate stable and unstable failure by varying the Loading System Stiffness (LSS). In this research, Loading System Reaction Intensity (LSRI) was proposed as an indicator to identify stable and unstable failure. Secondly, unstable rock failure under true-triaxial unloading condition was simulated. A rock specimen was loaded in three directions; the lateral pressures (s3 and s2) were kept constant and the vertical stress (s1) was increased to a pre-defined stress. The specimen was suddenly unloaded in the minimum principal stress direction (s3) and loading in the s1 direction was continued until failure occurred. Different LSS values were considered and the results showed that the LSS influenced the failure mode; a soft loading system resulted in more violent failure and released more energy than that in a stiff loading system. The influence of specimen height to width ratio on rock failure was also investigated. It was found that failure in taller specimens was more violent than that in shorter specimens. Insights gained from the simulation are useful for better understanding of the influencing factors on the released kinetic energy during unstable rock failure and to find means to control rockburst damage in engineering practice."

Jan 1, 2015

By V. G. Papangelakis, G. A. Moldoveanu

"Rare earths adsorbed on clay minerals are easily recovered via ion exchange during leaching with inorganic monovalent salt solutions. The leaching efficiency of various salts at 0.5M and 25°C was investigated as a function of cation type and salt system (sulphates vs. chlorides). (NH4)2SO4 was identified as the lixiviant of choice and a procedure was established to investigate the influence of lixiviant concentration, temperature, pH and agitation on desorption kinetics and REE extraction levels. It was determined that the kinetics were fast and the optimum leaching conditions (for >80% total REE extraction) required pH below 5 and moderate temperatures (<50°C). INTRODUCTIONRare earth elements (REE) are at the core of numerous advanced applications due to their various uses in high strength permanent magnets, lasers, automotive catalytic converters, fiber optics/superconductors, and electronic devices (as phosphors in TVs and display screens for computers and cell phones). Because of the ongoing development of new technologies, there is an increased demand for REE in the international market, with emphasis on identifying new resources to insure an adequate supply for present and future use. World production of rare earths is dominated by China, the United States and Australia; however, in terms of resources, China dominates the world potential with reserves estimated to be over 90% of the total (Chen, 2011).The main commercially significant REE sources, as reviewed by O’Driscoll (1991) are bastnasite (carbonate) and monazite (phosphate) minerals, containing up to 70% wt. rare earth oxides (REO). In spite of being high grade, these ores are associated with elevated recovery costs due to difficulty in mining, separation and beneficiation. Moreover, aggressive conditions are required to solubilize the REE from the mineral, such as leaching with hot, concentrated acids or baking in 70% NaOH (Gupta & Krishnamurti, 2005)."

Jan 1, 2012

By O. S. Perry, G. H. Charlewood, K. Griffin, S Ogryzlo, H. Hopkins, G. MacIntosh

"The gold mines of Kirkland Lake are in Teck township, Timiskaming district, Ontario, latitude 48°9'N. and longitude 80°3'W., at an elevation of 1,038 feet above sea-level.There are seven contiguous producing mines in a length of 3;1/2 miles along the general east-west strike of the deposits. The seven mines are, in order from west to east, Macassa, Kirkland Lake, Teck-Hughes, Lake Shore, Wright-Hargreaves, Sylvanite, and Toburn.The first discovery of gold in the zone was made by W. H. Wright in 1911 on the east claim of the Wright-Hargreaves property, and the following year the Tough brothers and H. Oakes found gold in what is now the No. 1 vein_ at the Toburn. Production began at the Toburn in 1915, followed by Teck-Hughes in 1917, Lake Shore in 1918, Kirkland Lake Gold in 1919, Wright-Hargreaves in 1921, Sylvanite in 1927, and Macassa in 1933.To the end of 1946, 31,938,350 tons of ore had been milled at the Kirkland Lake mines, from which 16,132,700 oz. gold, having a value of $498,517,600, were recovered. The bullion varies from mine to mine between 800 and 900 fine, the average for all the mines being 853. The average fineness of the native gold is 941.The workings of some of the mines are more than 6,000 feet deep and sinking to depths below 7,000 feet is now in progress.GENERAL GEOLOGYThe regional structural geology of the area in which the mines of Kirkland Lake occur is described in a preceding paper in this volume by J. E. Thomson."

Jan 1, 1954

By W. R. Bacon

"IntroductionTHIS IS a brief discussion of certain regional and economic aspects of the Coast Range of British Columbia. Between Portland canal and the 60th parallel of latitude, only the eastern margin of the Range is in Canada. The solely British Columbia interval extends from Portland canal to Burrard inlet. Personal observations in various parts of this area form the basis for much of this paper.Regional GeologyGranitic RocksSome of the best, most continuous exposures in the Coast Range are found at sea level. Reconnaissance study of the coastline has shown that the Range is predominantly granitic in character, but there simplicity ends, for the term 'granitic' as applied to the Coast Range covers a variety of mineralogical compositions. Actual granite is quite uncommon, occurring mainly in irregular or dyke-like masses that do not achieve batholithic dimensions. It is commonly pinkish, relatively homogeneous, and exhibits few of the deformational features that are obvious in much of this plutonic complex.Most of the granitic rocks of the Range fall well within the compositional limits of quartz diorite and granodiorite. The problem of resolving the great mass of these rocks into smaller coherent units is in general a difficult one. As noted above, granitic rock of uniform composition and texture is found in restricted areas and can be outlined without much difficulty. One such body occurs on the southern shore of Nelson island."

Jan 1, 1955

By T. Lu

Microwaves have considerable potential as an energy source in both mineral processing and metals extraction. In this research, the utilization of microwave radiation for the heating of a gibbsite type bauxite ore was investigated. Firstly, thermogravimetric studies were performed in order to characterize the dewatering processes of the ore. Secondly, both the real and the imaginary permittivities, which are the fundamental properties that determine the interaction of microwaves with any given material, were measured for the bauxite ore as a function of temperature. The changes in the permittivities were shown to be related to the dewatering processes. Subsequently, the effects of operating variables such as processing time, sample mass, particle size, microwave power, sample bulk density and carbon and magnetite additions on the sample temperature in a microwave field were studied. The results showed that under suitable conditions the bauxite ore could be readily heated. Therefore, there is considerable potential for the application of microwaves for the heating of bauxite ores.

Jan 1, 2007

By José L. Carvalho

"Time-dependent swelling deformation of several shaley rock formations in Ontario is a wellknown phenomenon. In shales and mudstones with a higher salt concentration in the pore fluid than the ambient fluid, the outward gradient generates an osmotic pressure which acts as the driving force for swelling. The swelling phenomenon appears to be related to ion exchange between the rock porewater and the surrounding water.The swelling potential is expressed as the percent swelling strain that occurs per log cycle of time, in either the vertical (perpendicular to bedding) or horizontal (parallel to bedding) directions. In addition, the swelling potential is also noted to be stress dependent. In practice, therefore, the conditions required for swelling are (i) the accessibility to water, and (ii) an outward salt concentration gradient from pore fluid of the rock to the ambient fluid. The relief of in-situ rock stress during excavation serves an initiating mechanism (Lo and Micic, 2010).INTRODUCTIONTime-dependent swelling deformation of several shaley rock formations in Ontario is a well-known phenomenon. In shales and mudstones with a higher salt concentration in the pore fluid than the ambient fluid, the outward gradient generates an osmotic pressure which acts as the driving force for swelling. Swelling is also controlled by the inter-particle bonding; if the bond strength exceeds the osmotic pressure, swelling will not occur, and vice-versa. The bond strength can be reflected by the calcite content which forms cementation bond between rock particles."

Jan 1, 2015

By G. C. Bateman

THE cause of silicosis and its prevention have held the attention of medical men and mine operators for many years and at the present rime the study of this disease is more than ever to the fore, even though a considerable abatement in the incidence of silicosis has been noted of late. This abatement is due to individual and collective efforts. The Industry is keenly alive to the situation and much research is being carried on. Silica dust is assumed to be a contributing factor in the cause of silicosis. How it acts progressively in the early silicoric is nor fully understood. As the study advances, more effective measures of control may be evolved. At present the Industry has three known methods of reducing the incidence: 1. By thorough X-ray examination of all applicants, with special reference to chest conditions. Those who are considered to be susceptible to the disease are prevented from entering the industry. 2. Thorough ventilation of the mine. 3. Control of tuberculosis in mining centres and removal of miners when first symptoms of tuberculosis become apparent. In 1934, the Ontario Mining Association formed a Committee, known as the Technical Silicosis Research Committee, to study and supervise work on problems related to silicosis. This Committee obtained the full-rime services of a mining engineer to carry our research work at the mines in the Province of Ontario. The Ontario Mining Association has also provided funds for the purpose of carrying on research work along pathological and biological lines. This work is being done in the Department of Medical Research of the University of Toronto, in the Banting Institute, under the supervision of Sir Frederick Banting. The Silicosis Committee work in full cooperation with the doctors in the Banting Institute and provide material from the mines for the it use.

Jan 1, 1936

By Hans Lundberg

PREFACE THE successful conclusion of all geophysical work depends on the operator&apos;s skill and sound judgment, as well as on his knowledge of geology and geophysics. We have been fortunate enough to have as co-workers a number of very good men. Some results of their work are summarized in this paper, and it is a pleasure to acknowledge their cheerful spirit of co-operation and the enthusiasm and loyalty with which they have assisted in the building of a geophysical organization to serve the Canadian mining industry HISTORY Geophysical prospecting is commonly, but quite erroneously, regarded as something new. The name is modern, but the principle of applying physical laws to reveal the presence of hidden ore is several hundred years old. Already, at the beginning of our civilization, the need was strongly felt for methods that could indicate the presence of ore in regions where the ore-bodies were completely masked or hidden from the eye. Particularly in countries where the rocks have been eroded during periods of glaciation and later covered by a thick mantle of glacial debris, all kinds of mysterious schemes were invented to locate the hidden ore. Often magic was resorted to (for example, the divining rod), but methods based on sound principles were also developed. Such features as topography, colour and taste of surface waters, and the growth and occurrence of trees and plants, were used to reveal certain types of ore deposits. For finding bodies of iron ore, the compass was very early in use. The fact that objects of iron attract a compass needle was utilized in prospecting long bef01:e the time of Columbus, and a systematic search for bodies of iron ore by this method was organized as early as the year 1600. There are still in existence documents, dated a little over 300 years ago, which show that the Swedish Chancellor of that day, Axel Oxenstiorna, ordered dozens of sun-dial compasses from instrument makers in Germany. The Swedish Government at that time employed a great number of prospectors to search systematically for iron ore. This Government undertaking must have been quite successful, as a number of iron ore-bodies were found in areas covered by heavy overburden. These prospectors were simply Government &apos;geo-physicists&apos;, although they were not known by this fancy name.

Jan 1, 1937

By D. Auerswald, M. Kotze, V. Yahorava, T. Udayar

Uranium can be recovered from lower grade uranium ores (<800 mg/kg U3O8), leach residues, and waste dumps cost-effectively via resin-in-pulp (RIP). Using this technology, no solid/liquid separation or washing of the leach residues are required. Furthermore, the uranium recovery can be higher than with conventional methods. RIP technologies have, however, been perceived negatively due to concerns around potential resin fouling and losses. This paper highlights the advancements made in RIP and discusses a number of potential applications where the technology could deliver economic and consequential environmental benefits by reducing the uranium levels in the waste.

Jan 1, 2014

By M. R. KEYS

"The property is about 120 miles north of Red Lake in the Favourable Lake area, district of Kenora ( Patricia part) , Ontario. The original discovery was staked by K. Murray in December, 1927. The first development work was done by the Favourable Lake Mining and Exploration Company. In 1936 Newmont Mining Corporation acquired control of the property and developed it to production by September, 1939. Production to the end of 1945 had a value of $7,534,656 from 441,457 tons of ore, an average value of $17.04 a ton . This production was mainly from gold and silver, with lead and zinc of subordinate importance.The rocks in the vicinity of the mine trend in a north-south direction. From east to west the sequence is: (1) A dark-coloured, massive rock, presumably a flow, composed mainly of quartz and biotite. ( 2) A buff- coloured, scricitized rock locally containing quartz phenocrysts and black hornblende. This is an alteration product of the dark variety and is later than the folding. It occurs mainly within the dark rock. (3) A series of sediments comprising thin beds of greywacke, grit, quartzite, conglomerate, and iron formation. ( 4) A gabbro sill, now largely altered to amphibolite.With the exception of the buff type, these rocks dip 80°E. The buff rock has a very irregular outline in comparison with the other rocks and appears to dip somewhat more flatly east. Felsite and diorite dykes are also present. These have a general strike of S.60°E. and dip 65°S .W. A post-ore diorite dyke trending N.15°E. occurs about 2,000 feet east of the mine area."

Jan 1, 1954

By I. Donohue, M. Pearson, E. Barrette

"This paper presents the technique and benefits of the finite element approach for designing the refractory lining in pressure oxidation autoclaves. One-dimensional equations are used to develop an initial refractory design. ANSYS Parametric Design Language (APDL) scripts are then used to build and analyse a more accurate three-dimensional finite element model to verify the refractory thickness, determine weld overlay requirements, and assess mechanical stability. The APDL scripts provide a cost effective means to quickly evaluate various boundary conditions and multiple designs to determine the optimal lining configuration and nozzle layout.INTRODUCTIONNew ore processing facilities demand increased capacity, requiring hydrometallurgy processes that have larger reactor vessels operating at higher pressure and temperature. Many pressure hydrometallurgy operations require vessels with an impermeable membrane and one or more courses of refractory or ceramic brick. The membrane provides corrosion protection for the vessel shell and the brick provides thermal protection for the membrane. Designing a refractory lining with an economic service life as a thermal barrier requires the refractory to be erosion resistant, chemically compatible with the process fluid, and mechanically stable. A fundamental understanding of the factors affecting the lining system is essential as designs move further away from the industry’s experience base.During basic engineering the refractory lining design is developed using one dimensional cylindrical conduction equations for heat transfer and classical hoop stress-strain relationships for determining mechanical stability. The results of the thermal calculations specify the refractory thickness that should prevent the membrane temperature from exceeding the design limit. Mechanical stability of the lining is determined by examining the sensitivity of lining stability with respect to various parameters. There are three criteria that must be satisfied to conclude mechanical lining stability:"

Jan 1, 2012

By E. Krause, V. G. Papangelakis, S. Garg, R. Mahadevan, E. Edwards

"Bioleaching uses iron and sulfur-oxidizing bacteria to extract base metals from sulfide minerals. As bioleaching involves breaking the iron-sulfur bonds by ferric attack, the biologically mediated rate of iron oxidation is recognized to play a key role in influencing the overall kinetics. In this study, we investigate the catalytic ability of an indigenous AMD culture for oxidizing Fe(II) in solution. This culture was subsequently adapted on pyrrhotite tailings (0.6% Ni) by gradually increasing the solids loading. Results from this study show that such an adaptation reduces the initial lag phase in the biotic oxidation of Fe(II), thereby allowing for a higher Ni extraction when compared to experiments with an un-adapted culture at a similar solids loading. The use of adapted cultures also helps to reduce the residence time for bioleaching of Ni from pyrrhotite tailings. INTRODUCTIONAs the world demand for pure base metals grows; the mining industry is increasingly faced with the burden of processing lower grade ores and mining waste streams in order to recover the occluded metal VALUES ((Watling, 2006). The extractive metallurgy of nickel from sulfide minerals focuses on using a combination of mineral processing, pyrometallurgical (smelting) and hydrometallurgical techniques to extract Ni from its ore bodies.Pyrrhotite (Fe1-xS) is commonly found in association with pentlandite and chalcopyrite in sulfidic Ni ores, such as those found in Sudbury, Ontario, and in Russia, e.g. Norilsk. The vast majority of this pyrrhotite needs to be removed using mineral processing techniques, in order to minimize the Fe and S contents of the concentrates that proceed on to smelting. If all pyrrhotite were left in the concentrate, much more slag and SO2 would be produced, and the smelter throughput would be limited. Beneficiation of Ni sulfide ores leads to the rejection of unwanted constituents as mining wastes, which may still contain extractable amounts of Ni (Edgar Peek et al., 2010)."

Jan 1, 2012

By K. H. Poulsen, C. J. . Hodgson

Synvolcanic, layered gabbro-anorthosite sills at Rainy Lake, Northwestern Ontario, reflect a combination of igneous processes including fractional crystallization, wall rock assimilation and possibly liquid immiscibility. Chalcopyrite-pyrrhotite mineralization at the base of the Grassy Portage intrusion accumulated by crystallization of a sulphide liquid during cooling. Upward enrichment of Fe and Ti in this intrusion and also in the Bad Vermilion Lake anorthosite complex culminated with the crystallization of lenses of disseminated to massive magnetite+ apatite+ ilmenite+ rutile. Regional low to medium grade metamorphism and accompanying deformation resulted in recrystallization and local remobilization of ore minerals.

Jan 1, 1984

By David A. Orava, Richard C. Swider

"The technical knowledge and practical experience accumulated by industry and others in abating acid mine drainage (AMD) is being proactively applied at every phase of the mine life cycle. This paper traces the mine life cycle from exploration to post closure monitoring and maintenance, and reviews AMD abatement measures that have become an integral component of exploration and mining activities.Attention is increasingly being given to evaluating AMD potential as part of exploration work, and studies related to project feasibility and design. Mining, mineral processing, and waste management options are selected taking into consideration their suitability to inhibit AMD. These inhibition measures are typically committed to in closure plans submit-ted at the permitting stage. Mines are operated and decommissioned, often progressively, as planned and in accordance with environ-mental protection policies."

Jan 1, 1996

By J. Gogal

Cameco's Cigar Lake Operation (CLO) started commercial uranium ore production in 2015. Initial mining was focused in areas of the ore body with relatively low concentrations of elements of concern (EOCs). As mining progressed into areas of the ore body that were richer in EOCs, some statistically significant behavior of certain analytes was noted in the water treatment circuits. It was ultimately found that the CLO ore body natively hosts numerous alkyl arsine compounds in addition to inorganic arsenide minerals. The alkyl arsines were found to be recalcitrant to typical adsorption on ferrihydrite, with the degree of recalcitrance associated with the degree of alkylation. A number of changes to the process circuits and water balance were performed and planned in order to inhibit the transport of alkyl arsines from the ore stream into the process water stream, and to optimize the overall site water usage. In some instances, the interactions of equipment in conjoined circuits of the process had controlling effects on the behavior of the overall circuit. Work continues to iterate upon the capital design features in order to further tighten the water balance, and to optimize water usage and operating costs.

Jan 1, 2020

By A. D. Mufch, G. P. Mitchell

"THE HARDY MINE of Falconbridge Nickel Mines Limited is located in Lot 9, Concession 1, Levack Township, Sudbury District, Ontario, 20 miles northwest of the city of Sudbury, and a mile west of the town of Levack. The ore deposit is one of the many nickel-copper sulphide bodies found on, or near, the lower contact of the well-known Sudbury norite-micropegmatite irruptive, and is one of a family of ore deposits which occur on the northwest rim of the irruptive.The property was acquired by purchase in 1935. In the same year a magnetometer survey along the footwall contact of the norite, which is covered by about 150 feet of glacial sands and clays, first indicated the location of the orebody. Drilling from 1935 to 1942 outlined the extent of the ore. Shaft sinking was commenced in the fall of 1951, and the mine is now approaching full production at a rate of about 300,000 tons per year.There are several major differences between the geology of the Levack area and the Falcon bridge area, which lies at the opposite extremity of the irruptive, 28 miles to the east. The purpose of this paper is to describe the essential features of the geology of the Levack area as seen in the Hardy mine, and to supplement the recent papers on other properties in the Sudbury area by Davidson (1), Lochhead (2), and Yates (3).General GeologyA recent review of the regional geology and an extensive bibliography of the Sudbury area can be found in the two papers by H. C. Cooke (4, 5). Some of the recent related references are: Jas. E. Thomson (6), E. M. Abraham (7), Franc. R. Joubin (8), W. G. Q. Johnstone (9)."

Jan 1, 1949

By J. D. Little

"THE SALMO PROPERTIES of Canadian Exploration, Limited comprise forty-one Crown-granted mineral claims situated on Iron mountain between Sheep creek (on the north) and Lost creek, some eight miles southward from Salmo, in the Nelson mining division (see Figure 1). On these claims there are at present four operating mines. These are, from north to south, the Dodger, Feeney, and Emerald, all tungsten mines, and the Jersey, a lead-zinc mine, about 7,000 feet south of the Dodger. About midway between the Dodger and the Jersey is a fifth mine, the Emerald lead-zinc mine, which was the first producer in the area but has been inactive since 1926. The locations of the mines are shown in Figure 2.Records of prospecting and claim staking on Iron mountain -which owes its name to the presence of large iron-stained outcrops -go back to 1895. The first recorded owner of the claims that form the old Emerald lead-zinc mine was John Waldbeser who, in 1908, did considerable work and produced 426 tons of lead ore valued, at the then price of lead, at $7,000. This ore was chiefly lead carbonate and was taken from the surface outcrops of two bands of ore that form the Emerald orebodies. In 1909, the Emerald was the largest lead producer in the Nelson mining district."

Jan 1, 1953

By J. F. K. Brown

WHEN I first received the kind invitation extended to me by the Mining Society of Nova Scotia, I read over very carefully the suggested title-"The importance of long-distance planning and budgetting in modern methods of mining, and the advisability of working to some definite plan". I came to the conclusion that I might as well confess my inability to handle properly such a vast and intricate subject within the scope of any one paper. More properly, I think a round-table discussion should be indulged in-a sort&apos; of symposium carried on in similar fashion to the World Power and Coal Conferences- you know, a committee for this, a committee for that, and, finally, a committee to see what the committees are doing. Weil, your Secretary&apos;s suggestion is just like that- much too comprehensive for any half-hour&apos;s presentation. As a paper, also, it either becomes too general and therefore uninteresting, or i.t descends into detail and describes means and methods to the end desired, which have little attraction because they were designed to meet quite different conditions than those my audience would mentally be considering. Of the two evils facing me, I have chosen the one that sticks to the generalities. Your Secretary&apos;s query almost automatically divides itself into two distinct phases: First, the importance, and second, the advisability, of planning. Let us dwell for the moment on the second, because, if we can prove advisability, that leads to desirability and, finally, to doing. Proving is the difficult part of the little problem. Here was something I, personally and as a mining engineer, had been battling for all my corporate life without being able to prove it to anybody. Then I saw the way out of that. I perceived I could put that little question of advisability on another basis altogether-:put it in the class of "coming- some day- soon" whether you or l or anybody else liked it or not; call it, if you please, mandatory, certain, necessary, enforceable planning. All of which means that the problem of advisability has rather suddenly become the very practical one of "how to do it". Why?

Jan 1, 1937

By C. Bazin

"Discrete transfer functions which use the grinding circuit feed tonnage to predict mass flowrates at reagent addition points in the flotation circuit were calibrated using a dynamic grinding/flotation simulator. Predicted values are multiplied by g/t ratios to calibrate reagent flow. The transfer functions are currently integrated into the distributed control system at Les Mines Selbaie.INTRODUCTIONThe development of adequate tools for the control of flotation processes is a continuous challenge. Since the early 1970's there have been numerous publications dealing with practical applications of flotation process control. A review of that literature shows that basic feedback and feedforward controls are the two preferred strategies for flotation processes. Some advanced control schemes started to emerge (e.g. Zaragoza and Herbst, 1988). Feedforward and feedback aim at reducing the effect of the following flotation process disturbances (e.g. McKee, 1991):0 Changes in throughput;0 Changes in feed grade;0 Changes in particle floatability (size, liberation, surface oxidation ... );0 Deliberate changes of set-point;Feedforward strategy acts on manipulated variables, mainly reagent addition, to attenuate the effect of disturbances such as changes of feed rate and grade. The feedforward strategy is driven by measurements of disturbances. Feedback control acts to compensate unmeasured disturbances, such as ore floatability, and to bring process variables to targeted set-points of concentrate or tails grades. The feedback control action is driven by set-point error, caused by either a deliberate change of set-point or unaccounted disturbances.This paper proposes a way to improve feedforward control schemes by addition of a simple model of solids transportation. The feedforward strategy considered in this paper is of ratio type, i.e. the manipulated variable is changed according to a predefined ratio between this variable and the measured disturbances. A typical example is the ratioed reagent addition to mass flow of ore."

Jan 1, 1993

By Egbert Burchardt

The challenge of "ore bodies getting steadily harder and lower in grade" was brought to light during the first oil crisis in the 70&apos;s. Shortly afterwards, HPGRs appeared on the scene with the promise of saving energy. This combined with developments in wear protection for the rolls ushered in a period of trade-off studies that considered the HPGR as an option to improve project economics or to even make projects feasible at all. Since then, applications of HPGRs at Cerro Verde (Freeport), PTFI Grasberg (Freeport), Mogalakwena (Anglo Platinum), Tarkwa (Goldfields), Boddington (Newmont), Penasquito (Goldcorp), and others have contributed to the creation of a formidable basket of operating experience. Collected through years of successful operation, this information has been used to validate design criteria, scale-up factors and establishing a clearer picture of what "to do" and what "not to do". This paper compares results from various mining operations using HPGRs in their processing plants. Some of the lessons learnt in different operating environments are reviewed in order to support proper implementation and operation of HPGR&apos;s. Some of the development programs that have been initiated to improve wear life of the tyres and to reduce overall operating costs are reviewed. It is timely to summarize today?s experience and analyse its implications for existing and new operations.

Jan 1, 2012