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By Robert S. Shoemaker

The development of a metallurgical project is a business venture rather than a technical exercise, and its real objective is to obtain the maximum return on investment consistent with the limitations imposed by company policy and the requirements of society. Demand for profits is the driving force for technical advances and naturally leads to improvements in processes, equipment and plant designs. In the mineral dressing field there have been virtually no new processes developed since the introduction of flotation, and the steady erosion of profits by inflation has been offset only by increasing equipment size. Unfortunately, in recent years, plant designers have not always utilized the largest equipment or the opportunities for functional and economic design presented by the development of larger equipment. Lower cost plants can be developed providing that unrealistic restraints arising from the prejudice of past practices are avoided. As an illustration of this premise, three different approaches were taken toward the design of a clearly delineated but hypothetical copper concentrator of 20, 000 tons per day capacity. While the same flowsheet was used in each case, designs were produced for a conventional plant, an alternate using the largest available equipment, and a third scheme utilizing large equipment and the most functional design which could be developed, including features derived from many plants in many different industries. Capital costs were developed for the three separate designs based on a location in the southwestern United States. Ancillary facilities were identical in each case and included a mine truck shop, a maintenance shop, a general office, and a nominal starter dam for tailings disposal within 5000 feet of the plant. Water supply within 1000 feet of the plant, and power furnished to the property boundary has been assumed in each case. The flowsheet of the three plants is shown in Figure 1 and represents the treatment of a typical sulfide copper ore by three- stage crushing followed by single-stage ball milling. Concentration is by flotation roughing and scavenging followed by regrinding of the concentrates and two stages of cleaning.

Jan 1, 1971

By G. A. Grandy, P. F. Thomas, C. D. Danecki

When considering the mill drive system for a grinding application, a large number of questions must be answered. Depending on the mill size and type, the mill can be driven by several configurations of drive systems: a single low-speed motor connected to a pinion driving a ring gear, two low-speed motors connected to two pinions and driving a ring gear, or a gearless motor mounted directly. In addition, a gear drive system can have a reducer placed between a high-speed motor(s) and pinion(s) or a power path splitting pinion stand. In some designs the reducer is integral with the pinion stand driven by a high-speed motor. The technical and commercial implications of several mill drive options are presented. Initial cost, cost of installation, cost of commissioning, and cost of operation and maintenance are presented for each drive option considered. The impact of each drive system on the design, cost and operation of the overall plant electrical system is discussed. Also, consideration is given to mill drive availability, and the potential cost resulting from delays in plant production.

Jan 1, 2001

By Robert L. Russell

Production at Freeport Indonesia's Ertsberg open pit copper-gold mine started in 1972 at a rate of 7.5 kt/d (8270 stpd). Mill throughput remained at that rate for several years until the discovery of the Ertsberg East (GBT) ore body. This discovery prompted three succes¬sive expansion stages from 1981 to 1988 that boosted production to 20 kt/d (22,000 stpd). In 1988, the discovery of the huge Grasberg porphyry copper deposit launched an era of much larger expansions. The first of these was the installation of a fourth primary mill in 1989 that increased throughput to 32 kt/d (35,270 stpd). That was followed by an expansion of the crushing and screening plant and in 1991 the addition of a new south concentrator to bring production to 57 kt/d (62,830 stpd). The addition of a primary ball mill and the changeout of the original Denver flotation cells in 1993 brought production to its current level of 66 kt/d (72,750 stpd).

Jan 1, 1994

By G. Van Weert

Mining project feasibility is projected from a geological model and a mining plan. Ore grade is assumed to be continuous, based on drill hole assays as much as 80 m apart. Eighty meter is 80,000,000 micron. Base metal concentrators may be said to work at 80 micron, for flotation at least. In short, metallurgical and financial performance in green field metal mining is forecast on rejecting waste after comminuting the ore down by roughly a volume factor of 1,000,000,000,000,000,000 (1018) from the feasibility/banking study parameters. This is the gap between mine and mill, between present sulphide mining practices and mineral dressing capabilities, and ultimately between lenders/shareholders expectations and mine/mill performance. By inserting a new upgrading technology in this gap, new opportunities for reserve enhancement and cost reduction are created, and risk could be reduced. Blast holes for extracting the outlined ore might be 8 m apart. Most ore bodies do not abruptly change composition at 8 m intervals; nor are they homogeneous in grade at the 8 cm (3?) rock size, optimum size for sorting. Mining in 8 m blocks will inevitably cause dilution of the mill feed and ore losses in the waste rock. This is well recognized in the mining industry. Much work is going on applying the vast data storage and manipulation capability of computers to mine scheduling. One only has to consult the SME Annual Meeting presentations. At the 2007 Meeting, Clark and Dagdelen described the challenges faced by Newmont at its operations and the application of sophisticated software tools and methods in its search of solutions to mining optimization. Block models can often contain in excess of one million blocks. Additional complexity exists when multiple grades are modeled for each block. The authors identify the main optimization problem as the system?s ability to cater to large scale problems in an acceptable timeframe; in other words, still larger computers are needed. At the same Meeting, Menabde et al (2007) presented a new pit development planning tool called Blasor, developed by BHP Billiton Technology, and its co-developed Blasor IPD (In Pit Dumping), (Zuckerberg et al (2007)). For purposes of this paper, Blasor/IPD incorporates options on processing capacity constraints and blending targets, eliminating arbitrary up-front decisions about cutoff grades for each block of material in the extraction sequence.

Jan 1, 2008

By V. Svalbonas

Everybody has an opinion what the quality of a grinding mill head casting should be, yet extremely few take the time, or get the opportunity, to compare their opinions against fitness-for-purpose data. The real question is not how flawless the casting should/could be, but rather how long will ?this? casting survive in operation. To validate an opinion on this topic one needs either extensive historical data, or comprehensive experimental data, or preferably, a combination of both. The same data can also be used to establish the conservativeness, or lack thereof, of analytical prediction methods.

Jan 1, 2009

By Michel Fontaine, Bruno St-Cyr

"The mission of the CENTRE DE RECHERCHE INDUSTRIELLE DU QUEBEC (CRIQ) is to stimulate economic development by guiding businesses in their pursuit of innovation.With a comprehensive approach to their needs, CRIQ provides businesses with expertise based on the most recent developments and insights in the fields of:Research and Development ServicesAutomation and production processesDevelopment of industrial equipmentEnvironmental biotechnologiesTesting and Product Qualification Services Industrial and Technological Information ServicesConsultancy and competitive intelligence servicesIndustrial information bankStandardization ServicesElaboration of standards and product certificationSystems registrationEXPERTISE COMPETENCE, INNOVATIONSince its founding in 1969, CRIQ has been involved in over 100,000 projects. The results of its research and development services have enabled it to build over one hundred pieces of equipment, almost all still in operation today. CRIQ has been and remains the driving force of innovation and expertise on the industrial scene, offering highly competitive solutions to a clientele from numerous industrial sectors.CRIQ became a crown corporation operating on a commercial basis on June 30, 1997. This change in its corporate structure has enabled it to put a marked emphasis on trade and implement an array of new operational practices.The formation of marketing companies with private partners, the opening up to corporate business and international markets, the new directions for internal research and the strengthening of its marketing component are among the activities CRIQ has initiated over the last fiscal year to finally reach its cruising speed."

Jan 1, 2000

By L. S. Urbanoski

This presentation describes a major modernization project at the Geco concentrator. The objectives of the program were to replace obsolete flotation equipment and upgrade process controls.Noranda Minerals Inc. — Gecc Division is located at Manitouwadge in Northern Ontario. The community is situated north of Lake Superior approximately equidistant from Thunder Bay and Sault Ste. Marie.Milling operations began in September, 1957. The mill processes a complex base metal ore by differential flotation techniques to produce copper, lead and zinc concentrates. To date some 43 million tons have been milled, qualifying Geco as a rather major base metal deposit.II. BACKGROUND:The Geco concentrator was designed and constructed in the mid 50's. A number of features specific to a concentrator of that vintage provided the justification for the modernization efforts described herein.Firstly, the mill was constructed without any instrumentation, not even pneumatic controls. Solid state electronics, computers and related instrumentation were unheard of, or rather primitive by today's standards.Secondly, some of the major equipment, in particular the flotation equipment, did not compare favourably to that in use today. MacIntosh flotation machines (more commonly known as Mac cells) were installed at Geco. These cells were prevalent in a number of concentrators built by Noranda, including Quemont Mining Corporation Limited, Gaspe Copper Mines Limited and Noranda — Horne Division. The Mac cells were used for copper and zinc rougher and scavenger operations. Some units were also installed for a pyrite recovery circuit that was never operated. In total, 104 Mac cells were installed in the main flotation area of the concentrator.

Jan 1, 1987

By P. R. Richardson

"Milling is the weak link in the process chain of many mineral operations. While this activity accounts for only a relatively small proportion of the direct costs of most mineral processing complexes, there are intangible and indirect costs associated with milling which are extremely large. For example, significant opportunity costs are associated with the relatively low yields which characterize this stage of the process.There are changes abroad in the world which I believe are going to cause us to reformulate the whole concept of milling. Increased competition in mineral markets are going to force managers to look anew at the high mineral values reporting to tailings which are a high opportunity cost for many operations. Tailings recovery plants are not the ultimate solution to this problem. Greater environmental concerns are going to increase the costs associated with tailings disposal and force the mining industry to look for other ways to dispose of waste products. Technology changes currently underway in manufacturing and other process industries, such as the automated 'lights-out' plant are going to be brought into this industry, and the changes will be dramatic.These are major long term changes which probably seem rather remote to many managers and professionals in existing operations which are faced with much more mundane challenges arising from day-to-day operations. However, I believe that milling is increasingly a 'lean and keen' operation involving fewer and fewer people, but who are increasingly skilled and professional. Traditional cost management approaches are no longer adequate and the industry has to take a new look at the nature of cost reduction in this core activity. This stage in the mineral process provides opportunities for value creation leading to a significant unit cost advantage for the corporations willing to adopt a total cost approach."

Jan 1, 1988

By Steve Hubbard, Brad Marchant, Rolando Cuadra

"Triton Mining Corporation acquired the rights to Mina El Limon in Nicaragua in 1993 by international bid. The bid included the gold operations at Limon and an exploration concession of approximately 4000 km2. Triton assumed control of operations and exploration in May 1994.The Limon mine is located in west-central Nicaragua, approximately 100 kilometers northwest of Managua. The climate is tropical, characterized by a wet season from May through October, and a dry season November through April. Gold at Limon is associated with both banded quartz and silicified breccia veins in Tertiary volcanic rocks, belonging to the lower Coyol Group. Mining is from two open pits and one mechanized underground operation. A second underground mine is currently under development for production during 1997.This paper describes the expansion of the milling facility at El Limon from a nominal capacity of 400 tonnes/day, producing approximately 20,000 ounces of gold annually, to the existing 900 tonne per day mill operation. Engineering of the new mill facility was initiated in September 1994 and construction was completed a year later."

Jan 1, 1997

By P Rubie, B Morgan, J Russell, C Stewart

The relationship between efficient liner exchange, concentrator availability and concentrator profitability is well documented. Russell Mineral Equipment’s (RME) relationship with OZ Minerals’ Prominent Hill site personnel enabled sound collaboration between the two parties. Both parties worked together to identify the sources of productivity and efficiency loss and developed solutions to reverse them.This paper chronicles the identification of production inefficiencies and the resulting removal of mill relining from the critical path through the materialisation of mill relining optimisation strategies. Furthermore, this paper outlines other recent mill relining optimisation strategies developed by RME and tested at Prominent Hill, to demonstrate and achieve further productivity, efficiency and safety improvements.CITATION:Rubie, P, Russell, J, Morgan, B and Stewart, C, 2017. Mill relining optimisation – a story of collaboration, in Proceedings MetPlant 2017, pp 335–345 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 11, 2017

By V. K. Gupta

"Effect of mill speed on grinding kinetics has been investigated with a view to using mill speed as a manipulated variable for control and optimization of the grinding circuit performance under variable ore hardness conditions. Dry and wet batch grinding tests were carried out for quartz, limestone and cement clinker in a 29 cm x 18 cm laboratory ball mill. Mill speed values selected were 55 and 70% critical. In the case of dry grinding operation, with an exception of quartz, for all materials studied the effect of mill speed on grinding rate was found to be insignificant for sizes finer than about 35 mesh. In the case of wet operation, grinding rates were found to be approximately proportional to the mill speed. The implications of these results are discussed.INTRODUCTIONIt is well known that mill speed has a considerable effect on the grinding rate of the ore particles l-3 For particles of a given size there is an optimum speed at which mill grinding efficiency is maximum (i.e. specific energy consumption is minimum) 3•4. Mill speed can, therefore, be effectively used as a manipulated variable to deal with the disturbances arising from changes in the size and hardness (grinding rate) of the ore being fed to the grinding circuit. Though, it has not been the case so far, with recent developments of ring motors2 and frequency inverters5 a continuous variation of mill speed has now become feasible, and it is expected that mill speed control will soon be a regular feature of plant operation2,6."

Jan 1, 1985

The Millennium deposit, located in northern Saskatchewan between the McArthur River mine and the Key Lake mill, has considerable potential for becoming an operating mine. Located in the Athabasca Basin, Millennium is blessed with both the riches and the challenges that this basin offers. The potential for ground water inflows during shaft sinking, and the unconventional challenges associated with underground uranium mining, render the successful development of a new mine in this area especially rewarding. The preliminary design and engineering of the Millennium Project has tapped into the experience of other operations in the area, and has utilized new applications of geophysics technology to enhance the understanding of the local geological structure. This discussion will focus on the innovations, and the challenges specific to uranium mining, for a deposit that is poised to be one of the next mines to supplement Saskatchewan's uranium resources.

May 1, 2008

By F. D. Ford, Z. Dai

"Vale’s Ontario Operations re-introduced Cu/Ni separation at Clarabelle Mill in 2006. The mill processes ores from a number of mines in the Sudbury basin. A saleable Cu concentrate is produced at 30-60% Cu recovery from mill feed, which has to meet the quality specification. In particular, Ni content in Cu concentrate must be less than 0.6%, otherwise, penalties will apply and diminish the value of Cu concentrate, in addition to the lost Ni value. Generally, a Ni grade of less than 0.4% is obtained in Cu concentrate. More recently, while processing Cu-rich ore, Cu concentrate contained more than 0.6% Ni which is abnormally high. Detailed mineralogical investigation shows that Cu-rich ore contains more millerite in comparison to typical Sudbury Ni sulphide ore. Millerite is found to be more floatable than pentlandite and is much more difficult to depress using high-lime aeration conditioning, which is the standard practice in Cu/Ni separation to float chalcopyrite while depressing pentlandite. The current operation uses sodium cyanide at 20 g/t to depress pentlandite and pyrrhotite. However, it is found that a high dosage is required to depress millerite. It is also shown that starch and dextrin are promising in millerite depression.INTRODUCTIONPrior to bulk smelting in 1991, Cu/Ni separation was carried out at Vale’s Copper Cliff Mill, Ontario Operation. The typical Cu concentrate grade was around 30% Cu and 1% Ni. This is very high in comparison to today’s value of 0.4% Ni and would not be acceptable for external processing. However, the Cu concentrate was processed internally at the Copper Cliff smelter/refinery, so the Ni contained in Cu concentrate was not lost and no actual penalties applied. During the SO2 abatement initiative, bulk smelting was chosen because of the perceived simplicity and consequently, Cu/Ni separation was eliminated (Agar, 1991) and the Copper Cliff mill was subsequently demolished. In 2005 and after more than one decade of bulk smelting, business changes required the removal of some Cu concentrate from Clarabelle Mill bulk concentrate to provide smelter capacity for Voisey’s Bay concentrate in the Copper Cliff smelter. In essence, this strategy calls for Cu removal at Clarabelle Mill (Lawson, 2006). In this case, Cu concentrate is sold externally and it must meet the quality requirement of less than 0.6% Ni."

Jan 1, 2011

IN presenting a'description of milling and treatment methods at the Waihi mine, it is advisable to first traverse a good deal of the past history of the mine, and show the various steps which have led up to present-day practice. The record of the company is one of steady, solid advancement, both in metallurgical and financial results. This is illustrated by the following figures, dating back from 1897...

Jan 1, 1912

By K. Mikulash

"Agnico-Eagle Mines Limited is located at Joutel in North-Western Québec. The mine is about four miles north-west from the town on the left bank of the Harricana River. The present mining is 1,800 feet deep with an extensive geological development below this level.HISTORY The development of the ore body started sometimes in 1967 and then the operation ceased in 1969 and again reopened in 1973 due to higher prices of gold. During these periods of active development, a considerable metallurgical research has been done by different laboratories and research and design companies.The original capacities of the Mill differed as much as 30%. So did the concept of the ore treatment. The original design of the mill was for 200 TPD of ore with straight cyanidation. The problems with low gold extraction, high reagent consumption and poor filtration resulted in a decrease of the expected mill output to an initial 550 TPD with gold recoveries in the order of 40 to 60%.Although the studies and research work done on the ore varied, all of them had a common conclusion: a very fine grind is needed to expose gold. The mining method (sub-level blast hole mining) now provides the ore that differs from that on which the metallurgical test work was conducted and the original capacity calculations had been done.These variations in the concept consequently led to the conclusion that the size of gold is a determining factor for the process.Kilborn Engineering provided the original design with the Leslie Eng¬ineering completing the design. The metallurgical test work has been done by the Department of Energy, Mines & Resources, Lakefield Research of Canada, Kilborn Engineering and Sidam Incorporated.The new flotation section with secondary grinding has been designed and put into operation by the company in December 1975 with the results yet to be evaluated."

Jan 1, 1976

By J. R. Hart, V. C. Smith, V. P. Babarovich-Hansen, J. H. Schubert

"An introduction and case study of Mintek's latest generation of Milling Circuit controller, the MillStarTM with IES (Interpreting Expert System) is presented. This paper also describes as a case study its installation on a Southern African base metals concentrator plant which has demonstrated improved operation, greatly reduced variation in product quality, as well as increased capacity and availability of the circuit.In this case study, the MillStarTMw as installed along with several other enhancements, including hydrocyclone underflow monitoring, product particle size estimation and flotation circuit stabilisation. MillStarTM utilised the particle size measurement to control grind to within 2% of setpoint, all the while ensuring sump level control, density control as well as mill power optimisation. Mintek' s expertise in the modelling of tumbling mills allowed the development of a specialised optimising controller that ensured the mill was kept in the most efficient operating region.MillStarTM augments the automatic control with useful user interface features, such as on-line trends of any logged variables, historic data warehousing and retrieval and production summary reports.A novel feature that distinguishes the MillStarTMi s the IES (Interpreting Expert System). This is a feature of the software that works with the automatic control code to generate explanations for control actions made by the controller. Often complex control systems are mysterious in nature, reducing trust and eventually resulting in them being switched off. The IES method of exposing the heart of the controller has proved popular and is seen to have potential as a training tool. 314"

Jan 1, 2000

By E. Wolmarans

Dowding, Reynard and Associates Mineral Projects (DRAMP) was approached by the ARM/Lion Ore JV during July 2006 to conduct a feasibility study and control budget estimate for a new greenfield project for their NKOMATI Nickel mine 45 km east of Machadadorp. The scope included the evaluation and review of previous studies as well as a techno-economic trade-off on four possible comminution circuits ranging from conventional crushing and ball milling to fully autogenous milling. The following document encapsulates the thought process, decisions and the references used in selecting the final comminution route for the new 375 ktpm MMZ concentrator. Apart from the pilot test work performed, design simulations from a number of sources, performance results from a recently commissioned 100 ktpm MMZ concentrator, together with an understanding of the geology and mineralogy of the orebody and possible variations in the characteristics of the orebody over the life of mine were assessed. The results from all the above-mentioned work indicated that it would be possible to treat the MMZ ore at the desired throughputs to the desired grind sizes in a fully autogenous grinding (ABC-type) circuit. Autogenous milling is generally considered to be one of the higher risk milling circuits. This is mainly due to the fact that the ore, which is utilized as the grinding media, could be variable in terms of hardness and mineralogy/geology. Nevertheless, it is a very popular route as the cost benefits, more specifically the operating cost, are normally very attractive. This is especially the case when large low grade orebodies are evaluated. In North/South America, autogenous and semi-autogenous grinding circuits have been successfully employed during the past 20 years on large scale low grade operations. Taking all the above factors into account, the DRA/Nkomati project team recommended an autogenous circuit with the option to add steel to both the primary and secondary mills (if required) for the new operation in order to create the opportunity for significant operating cost savings. One has to bear in mind that all the new design simulations and decisions are based on previous work and potential unknown variations within the orebody will never be fully understood until the pit is operational for some time.

Jan 1, 2009

LOCATIONThe property of the Mount Isa Mines Ltd. is situated in Western Queensland, 603 miles by rail west of Townsville, the nearest seaport. All supplies and the bullion are railed between Mt. Isa and Townsville. The climate is semiarid, and operations are conducted throughout the year without difficulty.WATER SUPPLYThe mill make-up water is obtained from the mine, and also from Rifle Creek reservoir, which is situated 20 miles from Mount Isa. The domestic supply of water is obtained from a series of bores on the company's leases.POWER SUPPLYElectric power at 3300 volts, 3-phase, 50 cycles, is supplied from the company's steam power plant, consisting of two units, each unit comprising one Babcock & Wilcox boiler, supplying steam at 300 lb. pressure per sq: in. to one 5000 kW. turbo-alternator. Pulverized coal is used as fuel, and power is being generated at a cost of 0.45d. per kilowatt hour. The coal used is supplied from the State Coal Mine, Bowen, costing 42/- per ton delivered at Mt. Isa.

Jan 1, 1933

By P. W. Godbehere, B. W. Brooks

"This paper deals with the milling of slags from the Noranda Continuous Process, in the Horne Concentrator at Noranda, Quebec. The milling of copper slags, although novel in Canada, has been practiced in Japan, Finland and elsewhere for several years.In March 1973, the prototype Noranda Continuous Process furnace or ""reactor'' came on-stream, In this pyrometallurgical process (see Fig. 1), copper concentrates mixed with flux are smelted in a single furnace to form copper or a high grade copper matte, and slag. The conventional smelting processes of roasting, reverberatory smelting and converting have been incorporated in a single 17 ft. diameter by 70 ft. long steel cylindrical vessel (l, 2). The copper or matte is tapped from the bottom of the reactor into ladles and transferred to an anode furnace or to a converter. The slag is tapped into 40 ton capacity ladles, cooled, crushed, and conveyed to the concentrator. At the present time, the reactor is operated to produce matte. The matte slag* containing 4 - 6 per cent copper is milled using conventional ore dressing grinding and flotation equipment. A flotation concentrate assaying 35 - 40 per cent copper is recycled to the reactor. Crushing, conveying, grinding, flotation and tailing disposal equipment previously used for over 40 years for ore treatment has been modified to suit the requirements of slag milling. Slag milling is essentially the scavenger circuit of a pyrometallurgical process."

Jan 1, 1977

By Eric Konigsmann

"Omai Gold Mines is a large scale open pit gold mining operation located in central Guyana, South America with a 12,000 tonne per day milling facility. Mill operations were initiated in December 1992 with commercial production beginning in January 1993. The entire operation employs approximately 120 expatriates and some 800 Guyanese nationals and is expected to produce in excess of 250,000 ounces of gold per year. The total mineable reserves contain 2.5 million ounces of gold with a projected mine life of twelve years.The milling circuits feature an SABC grinding circuit, gravity concentration and a conventional CIP gold recovery circuit. This paper will review the mill start up and ""run-in"" phase during the first year of operation. Emphasis will be placed on descriptions of start up problems and circuit modifications, mill performance trends in 1993, and personnel training and development. An outlook for 1994 is also given.IntroductionOmai Gold Mines is a large scale, open pit gold mining operation located in the Potaro district of Guyana, South America, some 160 kilometers south of the capital city Georgetown. Although there are numerous small scale gold mining ventures in Guyana, particularly with the dredging operations on the rivers, Omai is the first hard rock, open pit mine to be developed in the country. At present, this mining operation is one of the largest gold mines in South America.The Omai gold deposit has been exploited for over one hundred years. In the late 1800's, a German syndicate used hydraulicing with subsequent gravimetric separators such as sluice boxes and trommel screens to recover gold from saprolite, a soft, oxidized, claylike mineral which covers much of the claim area. Through the early 1900's and up until the 1950's, numerous mining companies including Anaconda Mining Co. Ltd. explored and drilled the Omai deposit but the technology and low gold price of the day made the reserve uneconomic to develop."

Jan 1, 1994