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By E. V. Manlapig, U. Erol, V. Ross, K. Tshimanga

Lonmin RoM ball mills are treating two types of feed ore produced by conventional mining and mechanised mining methods. It was reported that reduction in mill throughput was observed when treating the mechanised mining ore. Detailed grinding surveys were conducted for troubleshooting. Ore samples were collected for breakage characterisation using a JKRBT based on different particle density components. XRD analysis was conducted to investigate the association of minerals with density components. The plant surveys and the breakage characterisation tests all suggested that the two mining methods did not significantly affect either the ore breakage properties or the RoM mill performance. Instead, the mill discharge open area exerted a remarkable influence on mill throughput. The RoM ball mill operated at Lonmin K4 Concentrator has been proven to be a versatile mill that performed stably with variations in feed size distribution and feed ore changes by different mining techniques. The reasons are elucidated by the multi-component breakage characterisation and the plant surveys data.

Jan 1, 2012

By Wynne Potter

"On the west coast of Cape Breton Island four coal basins have been identified, varying in age and extending from Port Hood northeasterly to Chimney Corner. Those of Chimney Corner - St. Rose in the north and Port Hood in the south belong to the Pennsylvanian Riversdale Group while lying between them are the coal basins of Mabou and Inverness belonging to the younger Pictou Group. Almost all of the coal basins are submarine and coal mining was carried out on all basins at various times. The seams in all basins dip steeply seaward at angles from 10 to 20 degrees but were found to flatten seaward. The coal is ranked as a high volatile C bituminous coal. Ash and sulphur contents are high compared with Sydney coal and the coal has a tendency to spontaneous combustion when stored in large quantities.Of the four basins, the most significant is that of Mabou. At Mabou recent seismic and drilling investigations have indicated that although a sizable reserve of coal may be found offshore the structural problems, particularly faults, and the poor quality of the coal encountered will make it a resource of the future, if at all. Inferred resources have been calculated at 150 million tonnes in four seams over a 10 km2 area and extending 3 km from shore. The quality of the Mabou coals varies with ash, ranging from 5 to 25 per cent and sulphur up to 6 per cent. Calorific value ranges from 25.3 Mj I kg to 31. 7 Mj I kg. The Port Hood and St. Rose -Chimney Corner fields (Fig. 1) contain 16 million and 3 million tonnes respectively, but the Inverness basin is considered to have been depleted. The active mine in this area is the Evans Mine at St. Rose that is currently producing between 30 -50,000 tonnes a year from proven reserves of approximately 3 million tonnes."

Jan 1, 1985

By S. Gorzalczynski

The recent trend in underground mine developments is “bigger is better.” This is most certainly evident in the mine shaft and conveyances that operate within its compartments. Today, there are several new installations requiring mine cages that can transport up to 170 passengers. The technology in mine hoisting is advancing to address a combination of higher capacity requirements, deeper hoisting depths and faster winding rates, however, some areas of the hoist plant have not changed in the past 50 years. The most notable of these areas is the shaft compartment guide string and the conveyance mounted safety arrest mechanism. The technology in use today for the protection of passengers in a shaft conveyance from a hoist rope severance incident remains conceptually unchanged from Elisha Otis’ design of 1850. The actual retardation components, the safety dogs, have taken on several forms since Elisha’s invention with the last major design change occurring in the late 1940s. The arrest of a free falling shaft conveyance requires that the shaft guides withstand the energy imparted on them by the safety dogs. There are some very real limitations presented by the use of wood for this application. The new hoisting era will most certainly continue to demand larger capacity equipment, but also an increased awareness toward safety

Jan 1, 2002

By R. Brough

"Over 25 years ago, SKEGA pioneered the use of rubber linings in grinding mills and rubber is today widely accepted and almost standard material chosen for Regrind - and Secondary Hills. There are, however, only a few Primary Hills in operation with ""solid"" rubber linings because available materials and designs are often not cost efficient in comparison with steel alloys on a Cost per ton basis and/or downtime for liner replacement would be to a high.In other words, solid rubber has limits as any other material. However, 'SKEGA started to think, why not try to use the best properties of rubber as well as steel and combine the two materials together.Nearly 10 years ago SKECA started to test this concept in Rod Mills. A steel cap was vulcanized on to the leading face of the lifter bars, to be installed close to the feed end head (fig. 1)."

Jan 1, 1988

By Jared Onyirimba, Jim Viellenave, Hal Demuth, Dale Verran, Chad Sorba, Errol Lawrence, David Bronkhorst

As outlined within the Denison Mines Corp’s (“Denison”) Pre-Feasibility Study ("PFS") completed in late 2018, additional work is required to increase confidence and reduce risk associated with the application of the In-Situ Recovery (“ISR”) mining method at the Phoenix deposit, located on the Wheeler River Uranium Project (“Wheeler River” or the “Project”) in northern Saskatchewan. The successful application of ISR in any geological environment largely hinges on three fundamental requirements, 1) permeability (of the deposit), 2) containment (of the mining solution) and 3) leachability (of the mineralization). Denison has designed several staged technical programs to progressively reduce risk associated with these requirements as the Company advances the Project toward a Feasibility Study (“FS”) and Environmental Impact Assessment (“EIA”). This paper will discuss the scope and results of certain technical programs being undertaken as the Company aims to develop the first ISR mining operation in the Athabasca Basin.

Jan 1, 2020

By K. T. Aye

An investigation into the leaching of chalcocite and covellite in cyanide solutions at concentrations typically encountered daring gold cyanidation has been conducted. The results indicate that, for both minerals, the extent of leaching is greater under anoxic conditions, but is still incomplete even in the presence of free cyanide ions, with undissolved copper solids remaining in equilibrium with solution species. The speciation of the sulfur and cyanide reaction products in solution are interpreted in terms of the fast formation of a copper(I)- cyanide complexes in solution and a sulfur-rich copper(I) polysulfide solid phase, which then reacts more slowly to produce thiocyanate ions.

Jan 1, 2011

By Yong Kang, Bingyuan Yan, Dandan Zheng, Xiaochuan Wang, Dengfeng Su, Dongyang Li

"According to the characteristics of rock mass and the directional cutting technology of water jet, a new idea of light shock controlled blasting with water jet slotting was put forward. Based on the fracture mechanics theory and the stress wave theory, the mechanism of damping with water jet slotting was analyzed. On the basis of the above, the evolution law of the pressure wave and displacement field during the blasting were simulated by FEM software ANSYS/LS-DYNA. The result shows that: the oriented slot plays a good role in orientation during the blasting, and makes the energy generated by gas released by the explosives gather at the tip of the oriented slot, which makes it easier for the main crack to expand along the oriented slot and indirectly reduce the stress effect on the protected object. Meanwhile, the energy of the seismic wave is reduced while transmitting through damping slot. Finally, compared with the normal blasting with damping ditch, the maximum acceleration is reduced by 15.62%, the maximum velocity is reduced by 52.99%, and the maximum displacement is reduced by 68.32%. INTRODUCTIONIn recent years, with increasing demand for energy and space, an increasing number of underground projects have been under construction. Drilling-blasting method, as a traditional main method for rock excavation, is still an indispensable means in the engineering construction. As is known, blasting vibration will cause the deformation and unstable of the existing building structures, so how to reduce the influence on the existing building structures caused by the blasting vibration has become the focus. Traditional shock absorption measures mainly include three kinds: the first one is pre-splitting blasting, the second measure is to change the parameter of explosive filling, and the last one is to excavate damping ditch between the protected object and blastholes. However, engineering practices show that: the protected rock may be damaged in the process of pre-splitting crack construction by blasting, the second measure is difficult in operating, and the third measure is troubled by large work quantity (Song Guangming, 1999; Lou Jianwu, 2004; Lou Jianwu, 2005; Li Xibing et al., 2008)."

Jan 1, 2015

By L. C. Galloway, G. L. Tiley

"Mine hoist brakes must meet the following statutory performance criteria:- There should be two independent braking systems; at least one should act directly on the hoist drum.-If one brake fail s, the others should be able to retard and stop the hoist safely before the descending conveyance, carrying the rated load, reaches any obstruction.- When all brakes apply, decelerations should not be so violent that men travelling in the conveyance are injured.- The brakes shall not overheat and fade during an emergency stop.This paper discusses design principles and capacities of caliper and disc type brakes, when applied to double drum and friction hoists of equivalent capacity.IntroductionThis paper is about the brakes that are used on mine hoists; their functions, especially in emergencies, typical design, and how they are operated, controlled, tested, and adjusted.There are two basic types of mine hoists:1. Drum hoists, where the ropes are attached to, and coil on drums. The simplest system has only one drum. Most such hoists, however, have two drums, attached to a common shaft. Ropes are wound on each drum in opposite directions, so that when one conveyance is being raised, the other is lowered. The conveynaces may travel in vertical or inclined shafts. In the latter case, the hoist s are referred to as slope hoists.2. Friction hoist s, where the headropes are not attached to the wheel, but are in contact with it for an angle of lap of, typically, between 180 and 195 degree s. Forces are transmitted from the hoist wheel to the head ropes by friction.The lower ends of the conveyances are connected to balance ropes , approximately the same weight per foot as the headropes."

Jan 1, 1986

By Ernest A. Hodgson

A SERIOUS hazard which must be faced in some mines, though quite absent in others, is that of rockbursts. Bursts cannot be wholly avoided in such mines, but the hazard would largely disappear if they could be predicted. The problem of prediction resolves itself into that of measuring pressure in the mine and determining when that pressure nears a critical value. The geophysical approach to the problem lies in discovering some physical property of the rock, which varies with pressure, which can be measured for rock in place, and for which the indication of critical conditions is sufficiently definite and open scale. A physical property, suggested first in connection with earthquake pre-diction, is that of sub-audible snapping. It was argued that, as the pressure grows, the rock probably yields microscopically and that minute snapping occurs which is so faint as to be inaudible to the unaided ear. Experience has proved this to be the case. Following other earlier work begun early in 1939, experiments with this method were initiated at Lake Shore Mines in 1941, and equipment was slowly being developed in practice when, fortunately, it was found possible to by-pass this tedious development programme. Experiments with sub-audible snapping in mine rocks had been carried out by Dr. L. A. Obert of the U.S. Bureau of Mines and his associates over a period of about four years. An amplifier and a recorder were developed, each reasonably satisfactory in practice. Lake Shore Mines offers a tempting field for rockburst research. Dr. Obert was invited to test his equipment in this and other mines in Ontario and did so. As a result, he and the administrative personnel of the Bureau became interested in the Lake Shore experiments co the extent of most generously arranging for the manufacture of sets of their own designed equipment for use in this programme. The first three sets of recorders were ordered at once and were delivered in May, 1942. A second group of three sets, incorporating various improvements indicated by experience both in the United States and in Canada, reached Kirkland Lake in April, 1943. The pick-up devices, known as geophones, were made in the electronics laboratory at Lake Shore by Mr. Zack Gibbs, who has had charge of all the instrument development in this re-search.

Jan 1, 1943

By Bern Klein, Tichang Sun, Daozhen Gong, University of Science and Technology Beijing, Chunbao Sun, Stefan Nadolski

"This paper is focused on the effect of modifying the SAG mill/ball mill transfer size on the energy efficiency of SABC circuits. The transfer size is considered to be a parameter which provides operators with the opportunity to improve comminution circuit performance. In this study, the Moly-Cop tools package was employed to predict the energy consumption of SAG mill and ball mill circuits under different operating conditions. An Energy Benchmarking model was adopted to calculate grinding energy efficiency. The SABC circuit at the Huckleberry mine was selected for this case study. It was observed that after increasing circuit transfer size (T80) from the existing 3.3 mm to 4.8 mm, the Benchmark Energy Factor (BEF) of the SABC circuit decreased from 4.30 to 4.05. In terms of energy consumption of the SABC circuit, 1.17 kWh/t of specific energy saving was achieved through the transfer size optimization.It was also observed that when a transfer size was selected such that both SAG mill and ball mill circuits operated at their highest energy efficient states, the entire SABC circuit was the most energy efficient. The maximum energy efficiencies of these three circuits were all approximately 25% when compared to the minimum practical energy required to carry out an equivalent comminution duty. Single-particle compression breakage testing was used to determine the minimum practical energy associated with the Huckleberry mill feed. In combination with geo-metallurgical data, this study also provides an opportunity to perform dynamic optimization of SABC circuits."

Jan 1, 2016

By D. MOORE, A. REINSBAKKEN, A. J. Sinclair

The Gypo quartz vein lies near Oliver, British Columbia, and was quarried between 1955 and 1968 for decorative chips. The vein is one of many quartz veins hosted by the Late Jurassic Oliver Plutonic Complex, specifically by the porphyritic quartz monzonite phase of the pluton. The vein has a known length of 155m and a thickness of 46m. It strikes east-west and dips at 60 degrees to the south. Mineralogy is predominantly quartz with minor pyrite, muscovite, fluorite, calcite, apatite and manganese; trace amounts of chalcopyrite, pyrrh otite, marcasite and molybdenite also are present. Quartz in the vein is zoned. A thin grey quartz zone found near the margins of the vein fades gradually into white quartz, which comprises over 95% of the vein. Late-stage boxworks cut earlier mineralization, particularly fluorite, which occurs as pods in a zone fairly close to the hanging wall. Sulphide minerals are found in a centrally located zone in the quartz vein. The hanging wall of the Gypo veins is altered only slightly, but thefootwall is altered extensively to a greisen of muscovite and grey quartz. Evidence suggests that early in rhe vein development, the adjoining country rock was feldspathized. As grey quartz and muscovite was deposited, a period of intensive greisenization and fracturing occurred which so weakened the rock that a central block of greisenized country rock foundered. This provided the open space in which the vein was deposited.

Jan 1, 1984

By R. Vracar, D. Sinadinovic, Ž. Kamberovic

The paper presents a study on the oxidation of polymetallic gold ore by oxygen in an autoclave. It presents optimum parameters of autoclave leaching of sulphide refractory ore in self-generated sulphuric acid solutions aiming to get products with favourable technological characteristics from which precious and other useful metals can be recovered. A high partial oxygen pressure (1.5 MPa to 2 MPa), high leaching temperature (190°C to 200°C), pulp density 80 g/L to 240 g/L, ore fraction size 76 µm and leaching time up to 4 hours yield good results in rich ores. The full extent of copper and zinc conversion as well as a high extent of iron conversion has been achieved, while lead, gold and silver and a minor part of iron remain as a solid residue among gangue minerals.

Jan 1, 2001

By Gorzalczynski. Stan

The recent trend in underground mine developments is ?big is better?. This is most certainly evident in the mine shaft and the conveyances that operate within its compartments. Today, there are several new installations requiring mine cages that can transport up to 170 passengers. The technology in mine hoisting is advancing to address a combination of higher capacity requirements, deeper hoisting depths and faster winding rates, however, some areas of the hoist plant have not changed for the past fifty years. The most notable of these areas is the shaft compartment guide string and the conveyance mounted safety arrest mechanism. The technology in use today for the protection of passengers in a shaft conveyance from a hoist rope severance incident, remains conceptually unchanged from Elisha Otis? design of 1850. The actual retardation components, the safety dogs, have taken on several forms since Elisha?s invention with the last major design change occurring in the late 1940?s. The arrest of a free falling shaft conveyance requires that the shaft guides withstand the energy imparted on them by the safety dogs. There are some very real limitations presented by the use of wood for this application. The new hoisting era will most certainly continue to demand larger capacity equipment but also, an increased awareness toward safety.

May 1, 2002

By P. C. Parsons, G. C. Milligan

"IN FIELD WORK in the Cape Breton Highlands, which are heavily covered with vegetation, it is necessary to run traverses along the valleys of small brooks. We encountered difficulty in closing such traverses, and the following technique was developed to solve this problem. It has been tested in the field for four seasons by several people, and found to be simple, efficient and more accurate than any other compass-and-pace system of which we are aware. So far as we can find, the technique has not been described previously. It may be of use to others.The Cape Breton Highlands of Nova Scotia consist of hills of old intrusive and metamorphosed sedimentary rocks protruding up to 1,000 feet above the general level of the younger sediments which underlie the valleys. The flat hill-tops are the remnants of a plateau; drainage off the edge of this plateau has produced many small steep brooks. They occupy valleys which are up to 800 feet deep, and V-shaped in cross section, with steep sides covered by mixed conifers and hardwoods. The stream at the bottom is rarely more than a few feet wide, with a negligible meander belt, but with many bends, rapids and falls. Visibility along the stream, in consequence, is rarely more than a few hundred feet, and in many places much less.It was found impractical to map the streams by the method of meander lines, as described in many standard surveying texts and hand-books. The limited visibility, and the numerous bends of the brooks, necessitated many corners. Every corner introduces errors. To 'close' a survey with 40 or 50 such corners proved either very time-consuming or impossible. In most cases, however, the general direction of a valley may be obtained from an aerial photograph, or by direct observation, and this became the basis of the method adopted."

Jan 1, 1971

By H. C. Gunnings, C. O. Swanson

"The Sullivan mine; at Kimberley in southeastern British Columbia; is the largest silver-lead-zinc mine in the Empire and one of the largest in the world.The original discovery was made in 1892 by four prospectors. Until 1899, when the branch line of the Canadian Pacific railway from Cranbrook to Kimberley was completed, little work was done on the property. In 1900, systematic development was started, and during the next 3 years 5,000 tons of ore was shipped to the smelters at Nelson and Trail. By 1903, some 300,000 tons of ore was developed, and a smelter was started at Marysville, about 5 miles from the mine. However, this smelter closed down in 1907 because of metallurgical difficulties after treating 75,000 tons, and the property came under the control of the American Smelting and Refining Company. An option on the property was taken in 1909 by the Consolidated Mining and Smelting Company of Canada, who exercised their option in the following year. During the next 5 years by selective mining and sorting 188,000 tons of high-grade ore was produced and shipped to Trail. This tonnage came from the upper levels, about 4,600 to 4,800 feet in elevation. At the same time, deep drilling down to the 3,900-foot level showed the presence of an immense body of complex ore. In 1915, the main adit-the 3,900-foot level-was started, and by 1919 this had been driven a distance of 2 miles to develop the ore above this level. Meanwhile, progress was being made in overcoming the milling problems. An interesting account of this work was written by the staff ( 4). In 1923, the first unit of the present concentrator was erected, with a capacity of 2,500 tons a day, and thereafter the rate of production increased rapidly. In 1934 it was around 8,000 tons a day, and to date a total of about 30,000,000 tons of ore has been sent to the mill. In recent years, a considerable part of the production has come from levels between the 3,900-and 3,350-foot, which were opened by an internal incline shaft started in, 1930. In 1942, tin was added to the products separated at the concentrator."

Jan 1, 1954

By V Dolmage

Copper Mountain is the third largest copper mine in British Columbia, and is now producing close to 20 million pounds of copper per year, with which is recovered also 4,000 ounces of gold and. 13,800 ounces of silver. After a long and checkered career, during which the ownership and management changed several times, this deposit finally came into the possession of the Granby Consolidated Mining, Smelting and Power Company in 1923. It was not, however, until the end of 1925 that the mine, under the management of Charles Bocking and C. H. Smith, was successfully placed on a basis of profitable production. It is a low-grade deposit of the contact-metamorphic type, with refractory ores consisting of chalcopyrite and bornite in a gangue of altered andesitic and basaltic breccia. The ore is concentrated to a product carrying over 30 percent copper, which is smelted in Tacoma. The deposit is 12 miles south of the town of Princeton, which is on the Kettle Valley railway, 150 miles east of Vancouver and 40 miles north of the International Boundary line. Princeton is served also by a branch of the Great Northern railway, which leads clown the Similkameen, Okanagan, and Columbia valleys. Copper Mountain mine and camp are connected to Princeton by a good mo tor road extending up Wolf Creek valley, while the haulage level of the mine, which emerges on the steep side of the Similkameen valley 1,000 feet below the camp, is connected with Princeton by a spur of the Kettle Valley railway leading up the Similkameen canyon and passing en route through Allenby, where the concentrator is situated.

Jan 1, 1929

By F. Guo

"The leaching kinetics of zinc sulphide concentrate was studied under total pressures ranging from 0.3 MPa to 0.5 MPa and leaching temperatures ranging from 358 K to 378 K. The apparent activation energy of leaching reaction under different total pressures was calculated. The results show that for the extraction of zinc at low-temperature pressure leaching is controlled by an interfacial chemical reaction. This was supported mineralogical analysis of the leaching residue. The kinetic equation for low-temperature pressure leaching of zinc sulphide concentrate was further established by quadratic regression on the basis of shrinking core model.INTRODUCTIONThe Roast-Leach-Electrowinning Process (RLE) is the primary route for zinc production and responsible for more than 85% of the total zinc production (Souza et al., 2007). During the roasting of zinc concentrates, fugitive SO2 causes pollution. The prevention of SO2 emissions from the RLE process can be one of the challenges to this technology (Deller, 2005). In the 1980s, the Zinc Pressure Leach (ZPL) process changed the concept of zinc hydrometallurgy, in which zinc sulphide concentrate is directly leached at approximately 423 K and approximately 0.7 MPa oxygen overpressure and the sulphidic sulphur is oxidized into elemental sulphur so that the pollution by SO2 is completely avoided. Since 1981, five zinc plants have adopted the ZPL process either for expansion by integration with existing roasting facilities, or for the production of zinc without any roasting at all (Collins et al. 1994; Barth et al. 1998). The innovation of the ZPL process has made the zinc industries more competitive although it needs an autoclave. The direct leaching technology of zinc is still in development."

Jan 1, 2012

By K. M. Tait, M. M. McDonald

"An overview of the status of the development and application of Integrated Gasification Combined Cycle (IOCC) power generation is presented. Current projects in North America, Europe and Japan are described, together with the status of plans to apply the technology in Canada. A brief review of the technology is presented, including promising coproduction cycles and hybrid gasification fluid bed processes. The ability of the process to be modified for CO2 to be extracted for enhanced oil recovery or disposal is addressed. The environmental impact of IGCC technology is compared to those of other power generation technologies IntroductionDefinition and HistoryIntegrated Gasification Combined Cycle (IGCC) technology is a concept which has been around for about 50 years but has been generating increasing interest in the last 10 to 15 years. This paper focusses on coal as the feedstock for gasification. Other feedstocks used in gasification systems have included oil, biomass, tires and petroleum coke. IGCC technology integrates coal gasification with generation of electricity by means of a combined cycle system which fires the produced gas in the gas turbine. Figure 1 shows the basic components of an IGCC system which are the gasifier, the gas cleanup system and sulphur recovery plant, the gas turbine/generator set, the heat recovery steam generator (HRSG) and the steam turbine/generator set. The benefits of an IGCC system over a conventional Rankine Cycle pulverized coal (RCPC) fired system for the generation of electricity from coal are that the IGCC system has potential to have higher efficiency and lower emissions of NO., SO and CO2 per unit of power produced than the corresponding RCPC system."

Jan 1, 1994

By P. Hajiani

"It has been shown that the economics of the hydrometallurgy of a rare earth process depend upon the amount of acid needed to extract the metal per unit mass of the ore. In this paper, we show how to save a significant amount of acid treating a low grade ferrocarbonatite and extracting +99% constituent REEs. In order to save the acid, the alkali earth metals, originated from gangue minerals were removed prior to REE leaching. Moreover, the operating conditions of leaching reactor are optimized to leave iron behind and to leach REE selectively and effectively. Consequently, the hydrochloric acid consumption per ton of ore drops significantly compared to other processes.INTRODUCTIONThe viability of an extractive metallurgy process of rare earth elements (REEs) to produce an intermediate mixed concentrate depends upon a low-cost simple flowsheet (Bogner, 2014). It has been known that regardless of the mineral, the acid consumption is intimately associated with the operational cost (OPEX) of any REE project, particularly when the initial REE grade is low. Besides acid, the other reagents consumed in the process impact the OPEX. This makes minimizing acid consumption in an REE method a critical priority. The acid consumption in different projects has been reported to be equivalent of 100 kg to 1000 kg HCl (100%) per tonne of ore (Average: 500 kg/t HCl 100%) (Bogner, 2014). This value is strongly correlated with the grade of REE in the ore and therefore in the pre-concentrate.Previously, it has been stated that the Montviel flotation concentrate requires about 300 kg HCl (100%)/t ore to attain +99% REE recoveries using direct leaching (Yu, Verbaan, Pearse and Britt 2013). Hence, for an ore feed rate of 2500 t/d ROM, a large acid production plant (744 t/d HCl 100%) would be required for acid leaching of such concentrate. The equivalent Chlor-alkali plant is estimated to cost M$ 150 (CAPEX) and may require 100 MW power. Therefore, there is a necessity to improve the extractive hydrometallurgy and to reduce the acid consumption significantly."

Jan 1, 2016

By Elbasher M. E. Ahmed, Indresan Govender

"A mechanistic model of axial charge segregation in rotating drums is presented. We show that granular material composed of different frictional properties diffuse into axial bands as a consequence of concentration fluctuations in the free surface layer that is caused by friction-limited mobility. A Bagnoldian stress assumption ensures an asymmetric free surface profile thereby providing the essential ingredients for the evolution of axial bands and the subsequent band coarsening observed in the literature. The formulation is sensitive to the boundary conditions of tumbling mills, including particle size and density, mill speed, inter-particle bulk friction, end wall friction and drum geometry (length and diameter).INTRODUCTIONA mechanism to fully describe the axial segregation of charge in a rotating drum remains elusive to the mineral processing industry. With regard to low aspect ratio mills (like ball mills), current thinking favours the use of closed circuit mills with correspondingly low residence times to offset the completely random contact probabilities between particles and balls (Wills & Napier-Munn, 2006). Conical end caps are argued to exploit the centrifugal force to achieve a regular gradation of ball size along the mill with larger sizes at the feed end and smaller ones closer to the discharge. However; segregation along the length has been observed in the absence of conical end caps (Oyama, 1939; Levine, 1999): In these investigations, sufficient differences in the particle’s mechanical properties (particle size, density, shape, surface roughness) was enough to successfully achieve axial segregation. Figure 1 shows the segregation of a bimodal distribution (by size) into bands of larger (darker colour) and smaller (lighter colour) particles."

Jan 1, 2016