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By A. L. Mular

"IntroductionThe mining industry has made slow but steady progress toward the automation of mineral processing plants over the last 35 years. The stimulus to automate is associated with important economic and hidden benefits, so that today, the latest in instrumentation and technology is being employed.This chapter assesses the status of instrumentation justified economically, defines levels of control and certain fundamentals of feedback control loops, describes typical sensors employed in concentrator circuits, summarizes control strategies employed therein, and briefly highlights trends in integrated plant control.Current Status of AutomationAs early as 1948, the mining industry began to show interest in automation, probably because of its close association with the petroleum industry. By 1958, some regulatory control had been achieved in various sections of a concentrator, particularly in crushing circuits. Successes were attributed primarily to the reliability of sensors employed in the corresponding control scheme. By 1961, computers had appeared on the scene, initially, for data logging purposes.From 1958 to 1965, very few new control strategies had been implemented. Guidelines in vogue at this time appeared to be:- Install proven automation, unless a good instrumentation department exists at the concentrator.- Do not bite off too much instrumentation at one time.- Do not purchase on price alone; instrumentation must function in the concentrator environment.- Do not purchase automatic control equipment to be fashionable.Such guidelines were employed1 because of a lack of: (a) quantitative process knowledge, (b) reliable primary sensors, (c) initiative to try something new, (d) trained personnel, and (e) understanding that older concentrators could justify automation in many situations."

Jan 1, 1989

By W. E. MacDonald

This paper relates the story of 100 years of mining in the Harbour Seam at the Princess Colliery, Sydney Mines, Nova Scotia. Several interesting anecdotes are included along with the discussion of the evolution of coal mining methods in the area. Finally, some of the recently introduced equipment at Princess Colliery is described, and prospects for the future of the industry are outlined.

Jan 1, 1968

IDS: The Company IDS Ingegneria Dei Sistemi, founded in 1980, is a world leader as a high technology solution provider in selected niche defense and civil market sectors ? Private and Independent ? IDS?s Quality System is certified ISO 9001 Ed. 2000 ? IDS has the highest Military Clearance ? Continuously measure (24x7) mine wall movements with sub-millimetric accuracy at long distance (up to 4 Km) ? Provide reliable early warning for progressive slope movements potentially leading to mining wall failures ?Map the long term evolution of slow moving slopes to get a better knowledge of the rock mass strength

Aug 1, 2013

"A numerical procedure based on Smoothed Particle Hydrodynamics (SPH) is developed for rock blasting phenomena involving multiple intersecting joints. In this procedure, an elasto-plastic damage constitutive model has been applied in the framework of SPH to simulate yielding response of the surrounding rock medium. In this paper, a square shape rock medium with centrally located emulsion explosive in a borehole is numerically blasted with and without the presence of two diagonal rock joints. The model is simulated by assuming all four sides of the rock medium as free surfaces. The paper elaborates the propagation of stress wave, expansion dynamics of gaseous products, and development of fracture, fragmentation of the medium and dissipation of energy due to damage.INTRODUCTIONDamage prediction of rock mass and its mean fragmentation size are of important to design blast parameters for a given explosive. Current blasting practice solely depends on empirical relationships between fragmentation sizes to those blast design parameters while mathematical descriptions of the physical laws governing the process of rock blasting are limited. A constitutive relationship based on properties of explosives and rock mass is of special interest because of its capabilities in describing the key features of rock fracture and fragmentation, resulting in understanding of the physical process involved in rock blasting. It is well known that blast-induced damage and fragmentation of rock mass occur due to detonation induced stress wave and product gas driven fracture propagation. Nevertheless, the fundamental mechanism of the failure process and the behavior of rock characteristics under these two different loading are not well understood in many cases, which are closely related to growth of fractures and interaction of cracks under different loading conditions.Continuum damage mechanics is considered to be appropriate to describe the failure process under such high-amplitude stress wave. Based on this approach, several theoretical models have been developed to analyze the dynamic damage of brittle material such as rock and concrete with microstructure (Chen, 1999; Taylor et al., 1986; Wu et al., 2004; Yazdchi et al., 1996). These models are mostly based on the theory of damage mechanics or fracture mechanics with some statistical treatment to incorporate random distribution of microcracks. In the application of fracture mechanics theory, sometimes it is difficult to estimate the micromechanical parameters such as crack density and fracture toughness in different modes. In this study, damage in rock material is evaluated according to the earlier model developed by Grady and Kipp (1980), which is a fracture model coupled with a material description for stress wave propagation to predict quantitatively fracture and fragmentation under explosive loading conditions."

Jan 1, 2015

By G. S. Hume

Research thrives on ideas, and the theoretical considerations of today are either the discarded notions or the proven facts of tomorrow. The progress made in the past fifty years in the acquisition of knowledge of petroleum geology is no less astounding than is the tremendous increase in the production of oil on the North American continent from 61 million barrels in 1897 to 1,917 million barrels in 1947, an increase of 3,300 per cent, with production of natural gas expanding from less than 400,000 Mcf in 1897 to approximately 4,500,000,000 Mcf, or an increase of 11,000 fold in the same period. In the search for and discovery of the oil and gas fields that have yielded such prolific wealth, no idea has had a more profound effect than has the ?anticlinal? theory of oil accumulation, propounded in 1844 by Sir William Logan, the founder of the Geological Survey of Canada, after noting the position of oil seepages on the crests of anticlines in Gaspe peninsula. Sir William apparently was not much impressed with his own idea at this time, but after the Drake well discovery in 1859 and the publication by Henry D. Rogers, of Glasgow University, formerly of the Pennsylvania Geological Survey, of a paper in which he pointed out that the seepages in Pennsylvania were on anticlines, T. Sterry Hunt, an associate of Sir William Logan on the Geological Survey of Canada, published a reasonably comprehensive statement of the anticlina theory in the Montreal Gazette on March 1st, 1861. Hunt recognized the fact that the oil ?being lighter than the water which everywhere penetrates the rocks below the water level, naturally rises and accumulates along the crown of these anticlines". This was a recognition of the fact that gas, oil, and water in an anticlinal structure separate according to buoyancy or specific gravity. For some years the anticlinal theory does not seem to have attracted much attention, but when I. C. White in 1883 revived it and put it to practical use by prospecting for 'anticlinal' oil an gas structures in Pennsylvania, West Virginia, and Kentucky, its real value not as a theory but as a fact became widely recognized. Even today, the search for anticlines as oil and gas structures is being vigorously continued. In the past fifty years, however, it has become widely recognized that petroleum and natural gas collect in many different types of structures, and these have become known by the general name of 'traps'. About 1890, terrace structures were highly regarded because it was thought certain oil fields in Pennsylvania, New York, and Ohio were directly related to them. However, as Wilson (2, p. 437) has pointed out, it is recognized to day that ?'wherever the surface evidence is complete and dependable, other factors (than the terrace structure) are found to be in control'.

Jan 1, 1948

By Jian Li, Robbie McDonald, David Robinson

"The pressure oxidation of sulfide minerals at temperatures above 200°C enables the extraction of base metals, improves the extractability of gold from refractory ores, enables solubilisation of PGEs and can be used to hydrothermally upgrade base metal-containing feeds. Fundamental studies reveal that the solution chemistry (and mineralogy of the solids) during pressure oxidation can be manipulated with outcomes that include (1) increased leaching rates, (2) lower oxygen requirements and (3) the formation of chemically more stable residues. This paper presents examples describing how these outcomes might be achieved based upon fundamental investigations.INTRODUCTION The application of pressure oxidation to the processing of gold ores and concentrates dates back several decades and continues to be the process of choice at operations such as Pueblo Viejo (pyritic gold) which host the largest autoclave of its kind in the world (Barrick Gold Corporation, 2016). Commercial application to the processing of base metals and PGMs resides with long established processes such as the Sherritt process, ore specific applications such as by Noril’sk, at Sepon etc. or has not proceeded to date beyond pilot scale testing (e.g. Phelps Dodge, CESL, Activox, Platsol). Recently there has been significant interest in hydrothermal upgrading options for concentrates including the NONOX and Toowong processes (Rohner et al., 2016; Weidenbach et al., 2016). The latter options suggest directions where sound knowledge of the underlying fundamentals enables novel outcomes and efficiencies to be obtained. It comes as no surprise that investigations similar to those underpinning these developing processes can be traced back several decades. It is not the subject of this paper to provide a historical perspective of the relevant autoclave chemistries but rather, to present some potential opportunities suggested by studies in our laboratories. Topics to be discussed in this paper include (1) control of metal extraction rates, (2) control of iron-residue composition and (3) control of sulfur oxidation and hence acid generation and oxygen requirements. The work described will focus upon the pressure oxidation of a nickel concentrate."

Jan 1, 2017

By André van Wageningen

Since the beginning of this century Boliden Mineral and Atlas Copco have worked together in stages on improving the accuracy and quality of drilling. Navigation of the drill rigs with IREDES has been in use in the Boliden mines for several years. Recently the capability of the system has extended with map navigation to more accurately follow the ore in cut&fill mines. The system allows for changes on the individual round level to follow the ore without changing the whole design for the heading. Those changes are done in a CAD-system and remove the need for face markings and will allow for even better accuracy in both height and wall position. All the information between the CAD-system and the drill rigs is exchanged using the IREDES standard. This paper describes the workflow and the use of the IREDES standard.

Oct 1, 2009

By T. Ivankina, T. Lokajícek, H. Kern, T. Svitek

The knowledge of 3D velocity distribution of P- and S-waves in rocks is very important parameter for interpretation and understanding the nature of seismic anisotropy observed in the earth’s crust and upper mantle. A new high-pressure measuring head was designed and constructed to enable ultrasonic sounding of spherical rock samples in 132 independent directions under up to 60 MPa of acting hydrostatic pressure by means of simultaneous longitudinal and transversal sounding. New measuring system enables ultrasonic sounding of spherical rock samples by using a pair of P-wave sensors and two pairs of perpendicularly polarized S-wave sensors (TV and TH) see Fig.1. Shear wave sensors polarization is oriented according to rotation axis of the sample. Special shear wave gel was used to transfer shear waves between the sample and sensors under acting hydrostatic pressure. An isotropic glass sphere was used to check and calibrate the new measuring setup. A spherical sample of a biotite gneiss from the Outokumpu scientific drill hole was used for testing measurement. There is shown that both, P- and S-wave velocities, can be measured simultaneously up to 70 MPa, respectively. We report data of the 3D velocity distribution of P- and Swaves measured for the first time on a sample sphere of biotite gneiss. We rely, in particular, on the directional dependence of compressional and shear wave propagation and their relationship to the crystallographic (CPO) and shape preferred orientation (SPO) of major rock-forming minerals. The 3D seismic measurements revealed a strong foliation-related directional dependence (anisotropy) of P- and Swave velocities. Ultrasonic measurements were compared with 3D velocity calculations based on neutron diffraction measurements of crystallographic preferred orientation (CPO) of major minerals. Comparison of 3-D velocity distribution (P, S1, S2 and S1-S2) determined by two completely different methods ultrasonic sounding and neutron diffraction is presented. Measurements showed that the intrinsic bulk anisotropy is basically caused by the CPO of biotite constituting about 23 vol.% of the rock.

Jan 1, 2015

By Angus D. Campbell

Introduction In the Twentieth Annual Report of the Mcintyre Porcupine Mines, Limited, for the year ending March 31st, 1932, the General Manager, Mr. R. J. Ennis, said: "During the period under review, the plans outlined in last year's report have been completed, and all operations have been centralized in the new plant adjacent to No. 11 shaft. The new mill went into operation on May 27th and attained its rated capacity of 2,000 tons per day on November 15th. The new shops, warehouse, change-house, and general offices were occupied on December 1st, consummating the change from the old to the new plant ... "Silicosis is now definitely recognized as an industrial disease, and progresses rapidly when associated with tuberculosis. In an effort to combat its prevalence and progress, the new change-house was designed to build up the men's resistance to this and other forms of disease. It provides for a complete change from underground to street clothing, with a shower bath and solarium treatment in the interval. 'Unfortunately, in almost every goldmine, a very small percentage of the work-men are not adverse to taking some of the high-grade ore for their own purpose. This, in turn, tends to cast suspicion upon the honourable as well as the dishonorable employees. The new change-house routine discourages this practice and eliminates unjust suspicion, to the satisfaction of all concerned with the Company's operations".

Jan 1, 1933

By Hevina S. Dashwood

This paper proposes to build on my previous research (Dashwood 2012), which analyzed how and why the norm of sustainable development became institutionalized in the global collaborative corporate social responsibility (CSR) initiatives of major mining companies. Since the late 1990s, the majority of major global mining companies have employed the norm of sustainable development to frame their individual CSR policies and to inform industry collaboration at the global level through the International Council on Mining and Metals (ICMM). This paper proposal seeks to address lingering questions from that research, by developing an explanation for how the normative frame of sustainable development has translated into specific CSR standards adopted by the mining industry. Preliminary findings suggest that, although the global mining industry has reached broad consensus on the meaning of sustainable development in the context of mining, there remains considerable variation between mining companies in terms of which specific global standards they adopt. As members of the ICMM, major mining companies are required to report according to the Global Reporting Initiative (GRI) indicators relevant to mining, and there has been wide-spread up-take of the ISO 14,001 environmental management system standard. However, other global standards, such as the International Finance Corporation (IFC) Performance Standards and the Extractive Industry Transparency Initiative, have not been uniformly adopted by the mining industry. What explains this variation? The paper employs a three-level institutional framework (rational choice institutionalism, historical institutionalism and the ?new? institutionalism in organization theory) to explain the influences on the adoption of CSR standards in the global mining sector. Existing research confirms that institutional context is an important factor in explaining CSR adoption in the mining sector (Dashwood 2012). Are similar forces at work in explaining the variation in adoption of specific CSR standards? A three-level institutional analysis lends itself to uncovering influences both external to mining companies (such as pressures from stakeholders), as well as internal company dynamics (such as managerial discretion). Furthermore, the framework can incorporate dynamics operating at the global level (such as isomorphism), the national level (such as the regulatory regime) and the local level (such as community needs and environmental challenges). The theoretical significance of this framework is that the influences on CSR adoption are more complex than can be explained in a single approach (such as narrow rational choice/cost benefit explanations). On a practical level, insights into how global standards get interpreted and acted upon by individual companies could lead to the development of more appropriate and effective global standards.

Aug 1, 2013

By The Hollinger Mill Staff

ALTHOUGH cylindrical grinding mills have long been used, there is wide divergence of opinion as to what constitute best operating conditions. Questions such as mill diameter, diameter-length ratio, revolutions per minute, type and size of grinding media, volume of charge, circulating load, pulp level, pulp consistency, liner design, and size of feed, have all been given serious consideration by competent scientific investigators as well as by operators. While many laboratory and plant tests have been made that would seem to justify certain definite conclusions, there is a dearth of definite data giving actual results obtained when a grinding mill working between fixed limits is operated at its maximum capacity under varying conditions as to ball load, circulating load, speed, etc. In tests conducted recently at the Hollinger, extending over a period of thirteen months, to determine the best operating conditions for a ball-mill 6 ft. 6 in. diameter inside the liners, some very interesting facts have been ascertained. This paper is presented in the desire to make public the results of these tests and not with the idea that the last word has been spoken in regard to grinding. We feel, however, that these facts justify certain definite conclusions and hope that, by the fullest and frankest criticism and discussion, the essentials necessary for the correct design and operation of grinding mills will become better known.

Jan 1, 1937

By Mike Smith, George Chung

"A 23 million dollar Flotation Plant has been commissioned at the Iron Ore Company of Canada in 1998. Nine OK-50 cells &re used to float silica in this 1,400 tomes per hour plant. The paper details project development, construction and operating results. This plant gives IOC the capability to produce not only high quality blast furnace pellets of varying silica, CaO and MgO levels, but also a high iron, DR grade pellet. The first activity was simply to sit down with the suppliers, Outokumpu, Wemco. GL&V and Svedala, to discuss applications and share experiences. We learnt what each supplier had to offer, what features would particularly suit this application, what options were offered, what were the materials of construction, how the equipment is maintained, which wear parts require replacement, etc., etc. We tried to learn as much about the equipment as the suppliers themselves knew. Then we tried to learn more: we contacted users and asked about any weak points, which options were worth incorporating and which items were not. We then discussed these points with the suppliers and established how potential problems might be overcome."

Jan 1, 1999

By M. F. Ameur, M. Habak, H. Aouici, M. Kenane

Present study interest by aluminium alloy (Al 7175-T5173) drilled without cooling fluid. The influence of the machining parameters (spindle speed and feed rate) on the holes quality was analyzed. Drilling tools are made of carbide (WC); high speed steel (HSS) and TiN coated carbide (WC-Ti).The Experiment design was reinforced by the application of statistical analysis of variance (ANOVA).The results show that the thrust force is influenced principally by the spindle speed and feed rate. Though, both feed rate and tool materials have statistical significance on the surface roughness. In addition, the objective of correlations between spindle speed and feed rate with the evolution of the machining parameters was established. These correlations were obtained by quadratic regression using the response surface methodology. Finally, useful to select optimum values of drilling parameters, that would minimize thrust force, torque, cutting temperature and surface roughness.

Jan 1, 2015

By Unknown

We are indebted to the Consolidated Mining and Smelting Company of Canada Limited for the several pictures in this issue showing the progress made in new construction at Tadanac and at Bonnington Falls, B.C. Plate No. 1 shows the down-stream side of the No. 1 hydro-electric station of the West Kootenay Power and Light Co. Limited at Bonnington Falls, on the Kootenay river, at which 17,500 k.v.a. will be developed to meet the requirements of the enlarged zinc and lead refineries at Tadanac. The generators, exciters and switch apparatus were supplied by the Canadian General Electric Company and the step-up transformers by the Canadian Westinghouse Company Limited. The plant throughout was designed, manufactured and erected by Canadians. Plate No. 2 shows the casting room of the new lead-plant and plate No. 3 the new tank-room of the electrolytic lead refinery at Tadanac. These additions will increase the capacity of the lead refinery by some 150 tons daily. The extensions also include practically doubling the zinc plant, and the gold and silver refineries. With the exception of the new stack, all designing construction and installation of the various plants is being done by the Company's own employees at Tadanac. Plate No. 4 shows the progress made in the construction of the new reinforced concrete stack at Tadanac. This stack, of 21 feet inside diameter at the top, will be brick lined and when completed will rise 400 feet above its foundations: the tallest of its kind in the world. The construction is in charge of the Rust Engineering Company of Pittsburgh, Pa. Plate No. 5 is a panorama of the Tadanac smelters and refineries. The photograph was taken from the roof of the lead smelter and gives an excellent idea of the size of the plant and its surroundings. Tadanac produces electrolytic lead, zinc and copper and fine gold and silver. During 1924 the company treated 1,333,523 tons of ore and produced: 161,400,- 769 pounds of lead; 92,197,824 pounds of zinc; l,382,750pounds of copper; 4,074,044 ounces of silver, and 26,976 ounces of gold.

Jan 1, 1925

By M. F. Goudge

BRUCITE associated with highly metamorphosed Precambrian limestone was discovered in the vicinity of Rutherglen in northern Ontario by the writer during field work on the limestones of that district in 1937, and later was identified in similar limestone at Bryson and Wakefield, Quebec. The brucite occurs as granules disseminated through the limestone (Figure 1) and comprises from 20 to 35 per cent of the rock. Such rocks may be referred to as predazzites or pencatites, depending on the proportions of the constituent minerals. In this paper, however, the general term brucitic limestone is used to designate limestone containing brucite. In none of the deposits does the magnesia content of the rock approach that of magnesite, and in the deposits near Bryson and Wakefield the magnesia content is only that of dolomite. Therefore, without some method of concentrating the brucite, the deposits would be of little or no more value as a source of magnesia than is ordinary pure dolomite, which is abundant in many parts of Canada. Investigations in the laboratories of the Bureau of Mines have, however, resulted in the development of a method whereby, from certain of the deposits, pure calcined brucite, or magnesia, in granular form can be obtained, apparently at a cost that will enable it to compete in eastern Canada with imported magnesia. The granular magnesia so obtained appears to be highly suitable for use in basic refractories, for making magnesium metal, and for various other purposes for which magnesia is commonly used. Prospecting in the neighbourhoods of the original discoveries has resulted in a number of other deposits being found in each of the three areas, and there is now apparently available s1.dficient brucitic limestone of a grade that will lend itself to commercial exploitation to supply for many years a large part of the present and prospective Canadian market for magnesia and its products. Furthermore, it is expected that additional deposits will be discovered as prospectors and others become more familiar with the appearance of brucitic limestone.

Jan 1, 1940

We describe a new method of characterising the effect of dissolved materials on the rate of coalescence of bubbles in aqueous media. Single bubbles were allowed to rise to meet the surface of an aqueous solution, and the time of persistence between arrival and bursting of bubble was measured as a function of solute concentration. A laser beam was placed just above the surface of the liquid, with a detector in the light path, so that any disturbance at the surface could be seen as a break in the beam. The arrival of a bubble at the surface could be detected from the behaviour of the trace on an oscilloscope, and when the bubble broke, another significant change in the signal could easily be seen. The time between disruptions was reported as the persistence time. The effect of a homologous series of n-alcohols (C1 to C8) on the persistence time was measured, in aqueous solution. It was found that with increasing concentration of a particular solute, the persistence time increased up to a point, and then declined. However the magnitude of the persistence time was found to increase with increasing numbers of carbon atoms in the molecule. Bubbles of 1, 2 and 3 mm diameter were used. Persistence time increased with increasing bubble diameter, the maximum values observed being of order 100 secs. For a given solute, the persistence (drainage) time increased with increasing bubble diameter. The concentration Cmax at which the maximum persistence time was observed, was found to be independent of the bubble size. It decreased uniformly as the carbon number increased, and was well correlated by the function y1/2 (dy /dc) -2 I dc)-2 . There was no apparent correlation with the surface excess at maximum persistence time.

Jan 1, 2006

By V. A. Ettel

Current practices in electrolytic winning and refining of copper , nickel and zinc are reviewed from the point of view of their respective energy requirements. The electrical energy requirements of these processes are broken down in to the individual components, which belong to two basic categories: (a) thermodynamic energy requirements (G of the desired reaction) : (b) energy losses (anode and cathode polarizations, ohmic drops in the electrolyte and in the cell hardware, energy losses due to unwanted side reactions and electrical shorts). The individual energy components are separately examined for each electrolytic process and the potential for energy saving in these processes is discussed. It is shown that many potential energy-saving measures are uneconomical at the present time, as they increase over-all operating costs. The discussion is focused on those approaches which hold most promise for the future.

Jan 1, 1977

By R. B. Hyde

"Severe drilling conditions and difficult mud problems are briefly out-lined as the major cost items in all production operations. The chief problems discussed are abnormal pressures, high temperature, trouble-some shales, and low rates of penetration. These problems have been eliminated or greatly reduced in many areas by• the proper application of recently developed drilling mud products and techniques. These severe problems and their solutions are discussed generally: the application of high-density weighting materials to overcome abnormal pressures; surfactant muds with sodium polyacrylate as a solution for deep and high-temperature drilling; shale control muds and new dispersants for severe shale problems; and low-solids emulsions and •extreme-pressure lubricants for greatly improved rates of penetration."

Jan 1, 1959

By David Scott, Denis V. Lachance, Daniel Marcotie

"LocationThe Heath Steele mine is located 50 km northwest of Miramichi, New Brunswick.Brief DescriptionHeath Steele is a 2700 t/d, copper-lead-zinc operation which employs conventional crushing, grinding, and differential flotation.HistoryThe Heath Steele mine is located in northeastern New Brunswick approximately 50 km northwest of the city of Miramichi and 65 km southwest of Bathurst. The massive sulphides containing ore values in zinc, lead, copper and silver were discovered in 1953 as a result of a joint venture between the American Metal Company and the International Nickel Company of Canada. The discovery was named after Mr. Heath Steele, manager of exploration for Amco at the time of the discovery.Mill production began in February 1957; however, the mine was forced to shutdown in 1958 due to depressed metal prices and metallurgical problems. It was re-opened in 1962 and milling operations resumed at 725 t/d until 1968 when the milling capacity was boosted to 1450 t/d and then to 2700 t/d in 1969.OreThe main ore zones are massive sulphides with very fine mineral grain. The chalcopyrite, galena and marmatitesphalerite occurrences are finely disseminated.Liberation is accomplished by grinding to 68% to 72% <400 mesh. Average mill feed assays are 0.8% to 1.2% copper, 1.8% to 2.5% lead, and 5.5% to 6.5% zinc, with 60 to 75 g/t silver."

Jan 1, 2000

By R. Q. Honaker

A significant problem in ultrafine particle classification is the significant amount of submicron particle by-pass to the coarse particle stream. In classifying cyclones, submicron particle by-pass to the underflow stream can be reduced by decreasing water recovery. Past studies have shown that a reduction can be realized when the feed solids concentration is increased or the apex diameter is reduced. However, both adjustments tend to increase the particle size cut point and negatively affect classification efficiency due to the impact on slurry rheology. The addition of a viscosity modifier to the feed stream of a classifying cyclone improved the classification performance and decreased the particle size cut point over a range of feed solids concentrations. The detailed test program investigated the use of the modifier in conjunction with varying apex diameters to identify conditions that minimize ultrafine by-pass. With small apex sizes, roping conditions were readily eliminated by the addition of viscosity modifiers. The addition of the modifier had no deleterious effect on froth flotation performance, which commonly serves as a downstream separation process. The fundamental and practical benefits of viscosity modifiers in classification processes are discussed in this publication.

Jan 1, 2006