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By Rodrigo Toro, Ivan Yutronic N

"The Copper Concentrator Plant of Compañía Minera Doña Inés de Collahuasi (CMDIC) is composed of three grinding lines, the third one being the largest. Due to the capacity feature of the third line, specially its SAG mill, it is a priority that the advanced process control team of the Company deploys a supervisory control strategy that allows this unit to operate in an optimal way, in order to achieve the maximum productivity at minimum cost. It is in this kind of tasks where advanced control applications play a key role in obtaining the best economic profit of the process.The advanced process control team, formed by people from Informatics, Automation and Operations of CMDIC have assumed the challenge of generating the transition from a manual SAG Mill 1011 operation (40 x 22 feet, the largest copper SAG mill of the world), to a fully automatic SAG Mill using a multivariable control strategy instead of a rule based on expert control system (widely used in industrial mining process control applications).Therefore, CMDIC decided to work together with Honeywell APC Team implementing an advanced automatic control strategy for the SAG Mill 1011, using for this purpose a technology called Model Based Predictive Control (MPC), based on a variety of control methods that uses dynamical models of the process, obtained from input/output data, in order to print the process knowledge into a group of mathematical relationships that links the constraints (controlled variables) with available commands (manipulated variables) and measured disturbances.The main objective of the advanced control strategy is to ensure process government, tending to throughput stability and optimization, by the execution of coordinated control actions, proactively avoiding measured disturbances effects and the SAG mill overloading.The most important benefits of using a multivariable control strategy are: the automated operation of SAG mill 1011 (that was manually operated before the implementation of this application), a safer, more coordinated and more stable process operation, achieving through this an increase of throughput and a decrease of specific energy consumption, controlling the amount of oversize material production, power consumption, mill loading, noise and torque. In addition to the operational results, this challenge has consolidated a control team, with the participation of engineers and operators, diminishing the typical implementation time and achieving a greater use of the application in a short time."

Jan 1, 2010

By Christopher F. Gleeson, Roger D. Thomas

"Abstract - Wawa has long been a center of mineral exploration activity and diamonds have been reported in the area since the 1930s. However, diamond exploration did not begin in the area in earnest until 1991. In 1993, Sandor Surmacz and Marcelle Hauseux of Saminex began a prospecting program in the area which culminated in their discovery of the "Sandor" diamond occurrence in an outcrop on the east side of the Trans-Canada Highway. They subsequently optioned the property to Spider Resources Inc. who obtained the necessary exploration permits from Algoma Central Corporation and undertook an exploration program. The diamonds at the "Sandor" diamond occurrence are hosted in the matrix of a spessartite dike composed of actinolite, biotite, and albite. Of the 64 similar dikes that have been sampled and analyzed to date, eight have been found to contain a total of 231 diamonds. Most of the diamonds are of high quality, although they are small.The dikes are non-magnetic and do not have any other geophysical characteristic that can be used to differentiate them from the adjacent country rock. All of the dikes discovered to date have been found by prospecting or by geological mapping by the Ontario Geological Survey. The dikes do not contain pyrope garnet or chrome diopside, two of the commonly used kimberlite indicator minerals. Instead, low Mg, high Cr, Zn-rich chromite, and ilmenites of variable composition, some of which lie within the field of kimberlitic Mg-ilmenite compositions, characterize the diamondiferous dikes. A regional-scale till sampling program for heavy minerals, and geochemical analysis of the <0.177 mm fraction, was used to further define the areas of occurrence of the spessartite dikes and to indicate additional areas for diamond prospecting. Heavy minerals in till that were most useful include: actinolite, chromite, and ilmenite. Geochemical analyses of the dikes show them to contain elevated concentrations of Ni and Cr and to be enriched in Ba, Co, V, Ca, Fe, and Mg relative to the surrounding rocks. Elevated concentrations of Ni and Cr in till occur overlying and down-ice of known lamprophyre dikes."

Jan 1, 2000

By A. Baydusa, K. Barron

A theory for cutter roof failure in coal mines has been developed. It is shown that the key parameters influencing the likelihood of cutter roof failure are the rock strength, the vertical stress (depth) and the horizontal to vertical stress ratio. The support force necessary to prevent the development of this mode of failure is, in most cases, so high as to make it impractical to apply a force of such magnitude. It is, therefore, better to allow the failure to occur and to design a bolting system to support the dead weight load of the failed block. This is probably best achieved by using a yielding bolt system (such as split set bolts) which is anchored well beyond the top of the potential failure block. The maximum potential caving height determined from this theoretical approach compares favourably with field observations reported in the literature.

Jan 1, 1999

By Benoit Bissonnette

"The need for production of a competent fill was recognized early by the project partners. Consequently, a 4000 Ud paste fill plant was constructed and commissioned in early August 1994.In order to fine tune the process without risk to the underground workings, a closed pumping loop was devised on surface. After two months of this exercise, the first underground slope was filled according to specifications obtained from the pilot plant trials.This paper will focus on the operational problems encountered and the solutions adopted so far, and on a comparison between expected and actual fill production and characteristics.RésuméLa nécessité de produire un remblai de propriétés mécaniques suffisantes a été rapidement reconnue par les partenaires du projet. Conséquemment, une usine de production de remblai en pate, utilisant les residus du concentrateur d'une capacité de 4000 t/j a été construite et l'opération a débuté au mois d'aôut 1994.Dans le but de roder le précedé sans mettre en danger les installations souterraines, l'usine a été testée dans un circuit de surface. Après deux mois d'essais, le premier chantier souterrain a été rempli avec du remblai en pate selon les specifications dérivées de l'usinage pilote.Cet article présente les problemes d'opération rencontrés et leurs solutions, en plus de faire une comparaison entre les résultats prévus et ceux actuellement obtenus sur la production et sur les charactéristiques du remblai."

Jan 1, 1996

By J. A. Finch

"Gas dispersion in flotation defines the efficiency of the process once the chemistry has been established. There are three measurements, superficial gas velocity, gas holdup, and bubble size, which along with the derived quantity bubble surface area flux, are used to define “gas dispersion.” Sensors for measuring gas dispersion in industrial machines have been developed. This communication describes the working principle of the techniques and illustrates their potential to detect problems and to improve the operation of individual cells, banks and circuits. IntroductionFlotation is the most widely used process to separate minerals and is finding increasing application in other chemical and environmental fields. The process exploits natural and induced hydrophobicity to collect selected particles on the surface of a bubble. Once the process chemistry to control hydrophobicity has been established, the efficiency depends on dispersion of air to generate the necessary bubble surface area. Bubble surface area flux, Sb, the interfacial area generated per unit time and unit area of the machine, is emerging as one of the most useful variables to quantify gas dispersion (Gorain et al., 1997, 1998) although not without its critics (Heiskenan et al., 2001).For a bubble population of mean size db at a superficial gas velocity (or rate) Jg, the bubble surface area flux can be derived from geometric considerations (Finch et al., 1999):"

Jan 1, 2002

By D. Imeson, T. Grammatikopoulos, M. Aghamirian, M. Oliazadeh

"More than 70% of potash is produced worldwide by froth flotation. Flotation of potash was developed in the early 1930s. Amines are widely used for flotation of sylvite (KCl) from halite (NaCl) and insoluble materials such as clays. Amine collector is also absorbed by clays. Therefore, clays are usually separated by scrubbing and de-sliming prior to flotation. Alternatively, slimes can be floated ahead of potash flotation. Flotation recoveries of sylvite are commonly in the range of 85%, while losses can occur in slimes, flotation tailings and make-up of process brine. Ores containing free coarse-grained sylvite are generally screened, whereas both fine and coarse fractions are conditioned and floated separately. The unique features of potash flotation include solubility of sylvite in water, the size of particles floated and fast kinetics. Particles up to 2.3 mm can be floated and about 50% of flotation feed can be removed in the rougher stage in few minutes. The main challenges in potash flotation are the recovery of potash from slimes, flotation efficiency in the presence of carnallite and recovery of coarse potash grains. A review of potash flotation shows that there is still room for improvement in both coarse and fine potash flotation. The present paper reviews the most significant flotation parameters including reagent type and dosage, flotation circuits, flotation equipment size and new developments in potash flotation. The latter include new reagents, flotation technologies (Hydrofloat, Jameson and column cells) larger flotation cells and slimes flotation.INTRODUCTION Potash is the common industrial term for potassium in various chemical combinations and minerals soluble in water. About 90% of potash produced worldwide is used as agricultural fertilizers. Flotation is the main treatment process of sylvinite (KCl-NaCl) ores for recovery of sylvite (KCl). Potash concentrate should contain a minimum of 95% KCl and be relatively free from 0.2 mm KCl fines. The flotation process for beneficiation of potash ores was developed in United States and Russia concurrently in the early 1930s. In 1934, Potash Corporation of America applied flotation process in a commercial scale (Tippin R.B. and Huiatt J.L). In the initial application, halite (NaCl) was selectively floated by employing lead chloride as an activator and soap as collector. The sylvite concentrate was reported in the cell underflow."

Jan 1, 2012

By P. A. Witt

"Highland Valley Copper is a conventional truck-shovel mining and flotation concentrator operation located 75 km southwest of Kamloops, British Columbia (Fig. 1).The ore is situated within a porphyry copper deposit and is mined at a rate of 135,000 mt/day from two separate open pits. The nearby mill produces concentrates containing 375 million pounds of copper and 5 million pounds of molybdenum metal yearly. In the Valley pit, head grades are roughly 0.40% Cu at a 0.23% Cu equivalent cut-off. The Valley pit strip ratio currently sits at 0.55:1 with waste quantities made up of separate rock and unconsolidated overburden units. From the mill, concentrates are trucked to nearby Ashcroft and then hauled by rail to ocean port facilities in Vancouver. The mine employs 950 people and is planned to operate until 2009. The operation is a partnership between Teck Cominco (63.9%), BHP Billiton (33.6%), and others (2.5%). Management is shared by the two principal owners and directed by a management committee."

Jan 1, 2005

By C. M. Davidson, D. J. Drexler

"Sulphuric acid treated with hydrogen peroxide to destroy organic contaminants could conceivably show increased corrosivity toward carbon steel shipping and storage vessels, caused by the persistence of a peroxide residual. This paper describes work performed to determine the effect of 0-200ppm hydrogen peroxide on the corrosion of carbon steel by 93% and 98% sulphuric acid at room temperature (23ºC) and 50ºC.Steel electrodes were exposed to acid containing several peroxide levels (0. 45, iOO and 200 ppm) for up to two weeks. Specimens were removed at intervals and weight loss, open circuit potential, depth of metal loss and residual peroxide concentration recorded.Hydrogen peroxide decomposes considerably over two weeks in iron-contaminated sulphuric acid. initial peroxide concentrations > l00 ppm suppress corrosion, but the effect is lost when concentration decays below about 60 ppm. Sustained peroxide levels in the range below 60 ppm may increase corrosion rates. These phenomena are interpreted by analogy with anodic passivation."

Jan 1, 1987

By Shawn Healey, Ray Norcross

"Site IdentificationNew Britannia MineA 50/50 WX Gold Inc. - High River Gold Mines Ltd. Joint VentureTVX Gold Inc. is the OperatorLocationThe New Britannia Mine is located in the town of Snow Lake, Manitoba, which is situated between Flin Flon and Thompson, 420 miles north of Winnipeg.Brief Description of OperationNew Britannia Mine processes 2000 tonnes per day at an average grade of 4.5 g/t. Mill recoveries are currently 91 YO, accounting for forecast of 98,000 ounces for 1998.New Britannia Mine's mill complex incorporates conventional crushing, grinding and carbon-in-pulp technology. The design capacity of the New Britannia Mine mill is 1850 tonnes per day. The mill has processed upwards of 2300 tonnes per day, with no required upgrades.Gold recovery averaged 89.8% for 1997 compared to the planned 87% recovery expected from projected metallurgical test work. Year to date recovery mid December 1998 stands at 91.1 %Cash costs for the 1998 year to date were down to U.S. $221.49 per ounce, down 12% from the 3rd quarter of 1997. Milling costs for 1998 YTD were at Cdn. $9.38 per tonne and Cdn. $73.50 per ounce.Geology - (Orebody Description)The Snow Lake gold deposit is located within the Aphebian Flin Flon / Snow Lake Greenstone belt. This belt is composed of an assemblage of poly-deformed volcanosedimentary supercrustal sequences intruded by pre and sin tectonic ultra mafic and mafic intrusions and sin to post tectonic granitoid.The principal gold bearing rock at the New Britannia Mine is made up of quartzcarbonate material in sequence of basic and acidic volcanic rocks contained within a shear zone. The ore itself is gold associated with the sulphide mineral arsenopyrite and contains some pyrite, pyrotite, plus chalcopyrite. Proven and probable reserves at December 31, 1997 were at 4.04 million tonnes at 4.6 g/t and underground exploration continues to confirm the extension of the ore zones to depth."

Jan 1, 1999

By Dave Rose, David G. Meadows, Mike Westendorf

"Copper Mountain’s concentrator was commissioned in May 2011. The circuit consists of a 34’ x 20’ EGL SAG mill, a Raptor 900 pebble crusher and two 24’ x 39’6” ball mills. Each mill is equipped with a 2 x 8500 HP dual pinion drive system. The plant was designed to process 1585 mtph of SAG feed. From startup, the mill struggled to meet the required production rates. Over time, a major initiative that involved blasting and fragmentation, optimization of the SAG mill in terms of discharge grates, ball size and slurry density, and operation of up to three mobile pre-crushing plants resulted in significant increases in throughput. In parallel, a number of modeling tools, including JK SimMet, were run based on plant benchmarking exercises. Samples collected at the mine site during ramp up confirmed the very competent nature of the ore with drop weight - A*b values of less than 24 being recorded on a variety of plant feeds and lithologies. After due consideration including demonstration of proof of concept, a new pre-crushing circuit incorporating an XL2000 cone crusher and associated screening equipment was designed, constructed and commissioned at the site in August 2014. This paper reviews the history of the original circuit design, the various optimization steps taken and impacts, together with the final pre-crushing circuit and net results.IntroductionThe Copper Mountain Mine is located approximately 20 km south of Princeton, British Columbia, Canada (refer to Figure 1). The region has a long history of copper mining dating back to 1923. The Copper Mountain camp occurs in the 'eastern volcanic belt' of the Nicola Group (Monger, 1989). It is an alkali copper-gold deposit in which the volcanic strata are intruded by early Jurassic dykes, sills, irregular plugs and zoned plutons (Woodsworth et al., 1992). The stratified rocks are relatively fresh with slight metamorphism in the local contact regions."

Jan 1, 2016

By E. S. Moore

"The Centre of the silver-producing section of the Gowganda area lies about 55 miles northwest of Cobalt, and the village of Gowganda is 71 miles by road from New Liskeard. The geological similarities of the Gowganda and Cobalt areas led prospectors westward from the rich Cobalt field, first to Elk Lake and then on to Gowganda, where mineralization was found in 1907. A year later many showings were found, and rich hand-picked ore was shipped. Most of the ore has come, however, from two mines, both of which are still operating; the Miller Lake-O'Brien, which was purchased by Siscoe Metals of Ontario Ltd. in 1945, and the Castle-Trethewey. The annual production of these two mines runs over one and one-half million ounces of silver and considerable cobalt. The total production of the camp has reached about 32,000,000 ounces of silver and a large amount of cobalt, the total not recorded.General GeologyThe general geology of Gowganda is in many respects much like that of Cobalt. There are areas of Keewatin basic and acid Javas mixed with tuffs and basic intrusions. These rocks are deformed and partly altered to schists, and have been intruded by some Haileyburian basic and ultra-basic rocks and by Algoman granite. These were followed by a large number of porphyritic Matachewan quartz diabase dykes. After a period of extensive erosion the Huronian sediments were deposited on a pene-planed surface over all the older rocks; these sediments include large quantities of conglomerate (partly tillite), quartzite, and greywacke. The Keweenawan rocks include the Nipissing quartz diabase sill, later quartz diabase dykes, and one long olivine diabase dyke, the latest Precambrian rock. The area has been extensively glaciated.Structural FeaturesThere has been little folding in the area since the Algoman batholiths were intruded, and the Huronian sediments lie nearly flat, with dips of 10, 15, or rarely 25 degrees. The Matachewan dykes show a remarkably uniform, nearly north strike, indicative of east-west tension when they were intruded. On the other hand, the dykes later than the sill strike nearly east, tangentially to the northeasterly and northwesterly strikes of the Miller Lake basin."

Jan 1, 1949

By Eric Konigsmann, Doug Spence, Scott Jones

"The Williams Gold Mine is located in the Hemlo camp of Northwestern Ontario and is one of Canada’s largest gold producers with annual gold production of 400,000 ounces. The operation is owned and operated as a 50:50 joint venture between Teck Cominco Limited and Barrick Gold Corporation.In July 2002, the decision was made to introduce paste backfill produced from mill tailings as the primary backfilling method in the mine and to decommission the existing cemented rock fill system. This required a fast track design to be completed for both a surface paste backfill plant and an underground paste distribution system followed by an intensive construction phase through the fall and winter of 2002/2003. The paste system was commissioned on schedule in late April 2003 and was in full production within 4 weeks of the initial start up. Overall, the project duration was only 42 weeks from initial project release to commissioning and it was completed $2 million under the budget of $14 million.This paper presents an overview of the lab testwork and process flowsheet design, process control methodology and describes the construction and commissioning phases of the project. Preliminary paste plant performance and operating cost data is also presented.IntroductionThe Williams Gold Mine is located in Northwestern Ontario adjacent to the Trans Canada Highway in the Hemlo Gold Camp as shown in figure 1. The mine currently produces approximately 400,000 ounces of gold annually and is owned and operated as a 50:50 joint venture between Teck Cominco and Barrick.The deposit was discovered as part of the Hemlo gold discovery in 1981 which led to the development of three mining operations within a 2 kilometre radius. The neighboring operations are the Golden Giant Mine, currently owned and operated by Newmont Gold, and the David Bell Mine, currently owned and operated by the same joint venture which is running Williams. David Bell ore is blended and milled in the Williams concentrator."

Jan 1, 2004

By Tapiwanashe Chenje, David Hewitt, Peter Radziszewski

"Steel media wear is a major cost component in mineral processing. In the case of existing operating mill, steel media wear prediction can be used to help compare the performance of steel media from different suppliers before completing marked ball tests. It can also be used to investigate how ores from different site of a given mine affect steel media wear. In the case of Greenfield cases, steel media wear prediction can be used to estimate the cost of steel media for a given feasibility study.This paper presents a wear testing and prediction methodology that ties together abrasion wear and corrosion wear testing results through the use of a simplified discrete element charge motion model. The experimentation dimension to this methodology takes samples for steel media, mine site ore and water to determine abrasive and corrosive wear parameters of a given media, ore, water set.The test methodology development is illustrated along with a comparison of wear predictions with observed wear rates in some operating mills. A case study is included that illustrates how this methodology was used to estimate steel media wear performance. The paper closes with a discussion on the use of parts of the experimental methodology to investigate other abrasive wear conditions such as liner wear, paste backfill piping and ore breakage as well as avenues for future test development.INTRODUCTIONThe cost of comminution processes represents a significant part of the overall costs of a mining operation. Grinding media/liner wear alone accounts for 15-25% of the total operating cost. The annual steel grinding media consumption is approximately 2.5 mtpa or 0.3% of total world steel production [Smorgon Steel Group, 2005]. Using an estimated grinding media cost of about US$0.75/kg [Halbe and Smolik, 2002], gives a media cost of over US$1.875 billion per annum. Mining continues to shift towards exploitation of lower grade ores as the higher grades get depleted. These low-grade ores require finer grinding for the liberation of the value minerals, and hence it can be assumed that grinding media consumption will also continue to rise.The Bond abrasion test, dating back to 1963, [Weiss, 1985] is still used to estimate the total mill media wear. This is a purely empirical test based on the ore. From Bond abrasion index tests, it is possible to determine a wear rate using the following function:"

Jan 1, 2009

By C. A. Olivier

Le Ministère des Richesses naturelles du Québec has continued development work on the process/or direct reaction 0/sodium carbonate with lithium-bearing silicates(Canadian Patent No. 643,843). Recent process improvements have involved continuous pressure leaching, rather than batch leaching, and higher solution concentrations (over 55 g/l Li2CO3. These improvements have been demonstrated on a pilot scale operating on decrepitated spodumene from the Sullivan Mining Group&apos;s Quebec deposit. The new process is expected to be very competitive with the conventional sulphuric acid route. The improved flowsheet and main process steps will be described along with pilot-plant results.

Jan 1, 1979

By B. K. Gorain

"Mining of low grade deposits along with the necessity to design and operate flotation plants with high throughput presents unique metallurgical and environmental challenges that need to be addressed to reduce project risks, improve project economics and to sustain the profitability of operations over the life of a mine.Some of the key challenges include poor recovery of valuables and concentrate quality issues due to complex mineralogy, the need to use poor quality water such as brackish or sea water, reduce environmental impact from the process, integrate flotation with hydrometallurgy to maximize precious metals recovery, escalation of capital and operating costs, use of unproven technology and constant use of larger equipment, high ore variability, worldwide constraints on resource availability and an ever increasing need for reliable metallurgical input to financial models to evaluate economic viability of projects.The need to develop effective solutions to these problems in a short time frame is becoming a key to the success of any new project and for sustaining the profitability of a mining operation. An integrated multi-disciplinary approach to problem solving is crucial with the need for a more lateral thinking along with strategic partnerships and collaboration involving the right players. This paper presents some of the key findings based on experiences from a large number of challenging projects and operations focused on solving complex flotation problems.INTRODUCTIONThere are various challenges to successful development of mineral resources. Most of the ore bodies being developed worldwide are of lower grades requiring high throughput to be economical. Many of these lower grade ore bodies have significant occurrences of deleterious and penalty elements that could render a deposit unworthy of development unless there are technological solutions to process them economically in a sustainable manner with minimal environment impact. Even in a high metal price scenario, the economics for some of these low grade ore deposits is marginal. From a metallurgical perspective, these ore bodies have complex mineralogy and use of any off-the-shelf technology is not always effective. Development of innovative processes are often required, which is expensive, time consuming and sometimes risky.This paper will provide a broader perspective on the steps involved in solving flotation problems for operating plants and for greenfield development projects. In addition, some of the key challenges in flotation of complex low grade ore bodies along with the economic benefits in developing solutions to these problems will be presented."

Jan 1, 2013

Risk management has taken on renewed vigor since the economic crisis of the late 2000s. The resources of governments, individuals, and corporations are being stretched to a point where only the most promising projects move forward. Risk management is a crucial part of the decision making process, yet it remains a broad term that includes disciplines from engineering to finance. A collaborative effort will be necessary to ensure that the most auspicious and appropriate projects are the ones moving forward. Risk management can be quantified to an extent by comparing the likelihood of an instance with the result of consequence of the instance occurring. In this manner it is possible to assign risk factors to instances and ultimately, begin to associate monetary value to the instance. Carbon sequestration is an emerging field that has a number of unique challenges. Risk management and mitigation must be an integral part of the overall picture. This begins with the planning and design phase, continues through implementation and production, site closure, and does not cease until termination of liability. The ability of carbon sequestration projects to successfully assess, mitigate, and recover from leaks will be a decisive characteristic of overall success. The costs of mitigation and failure will need to be analyzed on a test level, but will still need to be reliable enough to extrapolate to a commercial level operation. This paper will build a risk management profile based on case studies and field tests in Tennessee and Virginia. These tests are scheduled to commence in late 2013 and consist of small-scale injection tests in unconventional storage reservoirs with an emphasis on enhanced coalbed methane (ECBM) recovery and enhanced gas recovery. The ultimate goal will be to provide a clear and concise direction to move carbon sequestration from the test phase to commercial scale. While it is necessary from a risk management perspective to analyze all risk points, the scope of this paper will focus on pre-injection risk assessment for carbon dioxide (CO2) leakage potential. Despite the differences between the two tests, CBM compared to shale among other differences, a framework for analysis and mitigation can be developed pertaining to leakage risk. The probability of each type of failure will be assessed and analyzed, and plans to mitigate or reduce these risks will be reviewed.

Aug 1, 2013

By K. J. Fair, H. W. Smith, D. R. Francis, J. M. Toguri

"Bench-scale batch milling and screening tests were carried out on secondary aluminum dross 10 produce an aluminum concentrate. To complement these tests, an analysis of a commercial plant was also performed by sampling dross at various stages in the plant&apos;s milling and screening circuit. These studies have indicated that benefits of increased capacity, grade and recovery of aluminum metal can be realized by addition of screens before the ball mill, longer grinding period and by grinding the smaller size fractions more efficiently.To test the predictions, a plant test was performed on the milling of100tons of secondary dross. The recycling of the large size fraction (+1/8 in.) of aluminum dross through the impact mill rather than through the rate limiting ball mill resulted in a comparable aluminum grade. The ball milling of the _1/ 8 in. + 10 mesh size gave a dross grade of71% AI. A lower feed rate to the ball mill resulted in a higher final grade. With minor modifications, secondary dross can be processed in 22% of the time it takes with the present circuit without a sacrifice in grade.IntroductionSecondary aluminum dross is a mixture of metallic aluminum, aluminum oxides and salts (alkali halides). Any comminution process deforms or slowly grind s the malleable metal phase and reduces the size of the friable, brittle, oxide-salt phase relatively fasterr(1).The milling of aluminum dross is performed to upgrade the metallic aluminum fraction. Figure I shows a flowsheet for the milling of secondary dross as presently practised at Metals and Alloys Co. Ltd., Toronto, Ontario. At point A, large acceptable grade material is hand picked for refurnacing, the unacceptable off-grade material is sent to the sweat furnace and the remaining, + 2 in. fraction is recycled through the 3.9 ft by 4.1 ft impact mill. For simplification, three ball mills are shown. However, in reality there is only one, a 5 ft by 10 ft ball mill used in a semi-batch mode. The 2 in. + 3/8in. and 3/8 in. + 10 mesh products are remilled in the ball mill. The -10 mesh material is discarded as waste."

Jan 1, 1987

By G. Auld

"A simple method is presented whereby the additional quantity and static pressure necessary to compensate for ventilation duct leakage may be estimated using the circular reference functions of modern spreadsheets. Favourable comparisons have been made to the National Coal Board (United Kingdom) design charts and to a case study analysis. IntroductionIn mining, most ducted systems are applied to the development of access tunnels, and most of these systems leak to some extent. When the ventilation duct fails to deliver the required quantity of air to the work place, there is a significant contribution to the development costs, either directly or indirectly.Directly — More air and more pressure are required to compensate for the leakage, more capital development (ventilation shafts, parallel drives) are required because ventilation systems cannot push the fresh air far enough, and longer re-entry times to ensure toxic blast fumes to be diluted.Indirectly — There is a reduction in productivity because of the inclement atmospheric conditions, and/or closure of development ends because of unacceptable atmospheric conditions at the working place. This has been exacerbated over the last few decades because of the increased use of diesel equipment of ever increasing power, and the more stringent Occupational Health and Safety requirements demanding more air flow per kilowatt of diesel power.The leakage from a duct must, therefore, be reliably estimated in order to assess the effectiveness and construction of the system; assess the effectiveness of the maintenance or repair of the duct; appreciate the cost of the leakage, and therefore apply effective maintenance and installation procedures; and engineer safer, healthier and more cost-effective ventilation systems."

Jan 1, 2002

By R. Grant, C. Bazin

"Brunswick Mining has investigated grinding media optimization for the purpose of improving the flotation feed and regrind product size distributions to enhance metal recoveries. This paper presents the findings of on-going testing of various sizes and shapes of grinding media. Plant observations combined with estimated breakage rates demonstrate the importance of appropriate selection of media sizes on the milling operation.IntroductionBrunswick Mining and Smelting is located near Bathurst, New Brunswick, and operates one of the world&apos;s largest lead and zinc mines. The ore mineralogy and processing flowsheet have been described elsewhere (Petruk and Schnarr, 1981; Shannon et 01., 1993). Despite the 25 years&apos; milling experience, there has been considerable disagreement as to the required grind size (Grant et 01., 1991). Since 1964, fineness of the flotation feed ranged from 60% to 80% passing 400 mesh (37 um) and averaged slightly above 71% in 1992. Results from mineralogical analysis (Petruk and Schnarr, 1981), laboratory and pilot plant experiments, as well as plant sampling (Grant et al., 1991; Hendriks and Ounpuu, 1985; Shannon et al., 1993) indicate that improved metal recoveries can be achieved by an increase in the fineness of grind, and more specifically by maximizing the amount of material in the 15 urn to 25 um range.This paper shows the results obtained so far from the evaluation of the effect of grinding media size and shape on grinding mill efficiency. The problem of finding optimum grinding media size, shape and composition has been recogrtized since the early 19405. The main criterion for the selection of media size is the size of the material to be ground (Bond, 1958). Although several relationships have been proposed to assist in the selection of grinding media size, none of them are entirely satisfactory (Wills, 1988). Other approaches using the breakage rates and process simulators were developed to help in the selection of grinding media size (Austin et al., 1976; Lo and Herbst, 1986; Concha et 01., 1992; Samskog et al., 1990; Martinovic et al., 1990). Although considerable effort was put into the analysis of grinding media size, very little information is available on the effect of grinding media shape (Norman and Decker, 1985, p. 3C-4). Norris (1952), Kelsall et al. (1973) and Herbst and Lo (1989) have shown that balls are more efficient than other shapes of grinding media including truncated cones and cubes."

Jan 1, 1994

By Peter Barker, Terry Jones

"The Kelsey Centrifugal Jig (KCJ) utilizes the application of centrifugal force (and the resultant enhanced gravitational field) to conventional jigging technology principles to successfully and efficiently process materials where the valuable constituent particulates are very fine and/or where there is a small specific gravity differential between these and the gangue minerals.The KCJ is applicable to a broad range of fine mineral recovery duties, with current installations in the mineral sands, tin, tantalum, gold and nickel industries. Other areas of application are being developed with mineral commodities including tungsten, base metals, iron ore, chromite and apatite/feldspar.Information on the principles of operation of the KCJ, typical performance figures in a number of application areas, comparison to centrifugal concentrators, key elements for a successful KCJ operation and recent developments with the KCJ are presented in this paper to demonstrate the capabilities of the KCJ.INTRODUCTIONAfter a number of years of development by inventor Chris Kelsey, the first commercial KCJ unit was installed at the Renison Bell tin mine in Tasmania, Australia, in 1992. The subsequent decade saw the installation of further KCJ units in applications including tin, tantalum and mineral sands.Development and improvement in KCJ hardware continued and culminated in the introduction of the high-capacity Model J1800 KCJ and standard features such as an automatic screen cleaning system. This opened up further markets and resulted in Model J1800 KCJ installations in the gold and nickel industries, as well as further KCJ installations in the mineral sands and tin industries. In recent years, work has continued on application of the KCJ to many other duties in industries including tungsten, base metals, iron ore, chromite, apatite/feldspar, etc."

Jan 1, 2007