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By Scott Hopkins

Simulation tools are preferred for evaluating complex systems due to its ability to mimic reality and quickly evaluate many different what-if scenarios and find global solutions. A simulation model is capable of representing variable and dynamic disturbances that are typically encountered in day-to-day operations; this is where spreadsheet models or linear programs fall short because they cannot account for the dynamic behavior and relationships. The simulation model used for this work was developed by Xstrata-Nickel (previously Falconbridge). The simulation tool is very flexible and can be used to simulate different mining and development methods. The scope of the modeling included production mining, geology, equipment fleets, equipment maintenance and random failures, manpower, shift schedules, and cycle activity times. A case overview of the 170 Orebody will be presented along with the challenges associated with data collection for the model inputs. Results and lessons learned will also be discussed.

May 1, 2008

By Joseph L. Fournier

Suncor Oil Sands employs delayed coking technology in converting bitumen into synthetic crude oil. Currently up to 10,000 m3 of delayed coke (coke) is produced per day as a byproduct of the upgrading process, of which up to 9,000 m3 per day is placed in dry storage on Lease 86/17. A review was completed to examine the case history of leachate potential experiments from the dry storage of coke and the environmental relevance of coke leachate studies conducted over the past decade. The review included an evaluation of the potential impacts of environmental conditions within the location of coke storage, including precipitation pH, as well as daily and annual ozone trends. Coke leachate potential has historically been characterized using standard leachate testing protocols (i.e., TLCP, SPLP) together with other studies that have employed strong acids and oxidizing agents in the extraction fluids. The present paper highlights prevailing conditions in the Athabasca Valley air-shed with emphasis given to ambient ozone (oxidizers), as well as precipitation pH and acid input deposition rates, and will demonstrate that TCLP / SPLP tests lack the intended environmental relevance relative to the conditions under which coke is stored.

May 1, 2011

By Manqiu Xu, Glen Robertson, Steve Wilson, Pete Quinn

"The middlings circuit, once called the pyrrhotite rejection circuit, at Inco’s Clarabelle mill was a single flotation stage. It used to process a combined feed consisting of the main flotation scavenger concentrate and the non-magnetic portion of the magnetics flotation circuit tails. The typical circuit metallurgy was 55% nickel recovery at 6.5% Cu+Ni concentrate grade. In the past few years, a research project with the objective of improving the circuit metallurgy was initiated between Inco’s research laboratory and the Mill’s Process Technology group. This project has gone through three steps: a) initial laboratory studies, b) on-site pilot plant investigation, and finally c) full plant implementation.The present paper describes the initial laboratory test work. The development of a two-stage circuit consisting of separate rock and pyrrhotite rejection stages to replace the simultaneous rejection of both rock and pyrrhotite in a single stage is discussed. A two-stage circuit simulation based on batch laboratory flotation data is also presented. Further development work, including the on-site pilot plant test work and the plant implementation of the new circuit design, will be described in a later publication.INTRODUCTIONThe milling operation at Inco’s Clarabelle mill, Copper Cliff, Ontario processes a rich complex sulfide ore from several large production mines around the Sudbury basin (Agar, 199 1). The sulfide mineralization is simple, consisting of chalcopyrite (Cp), pentlandite (Pn) and pyrrhotite (Po). The main gangue minerals are pyroxene, feldspar and quartz with minor amphibole and talc. Estimates of mineral composition are routinely calculated from Cu, Ni and S assays. In the mineralogical calculations, all gangue minerals are conveniently grouped and treated as rock (Rk)."

Jan 1, 2000

By J. Miettunen

"The lining of a grinding mill has an important role in creating the conditions for the grinding process. The main purpose of the lining is to transfer the energy taken by the mill motor to the contents of a mill. The power draw curve of the mill, if measured with sufficiently short intervals, describes how well the lining works in lifting and mixing the material to be ground.The power draw curve can also be used for determining the volumetric filling of a mill. This new measuring technique was developed at the Pyhasalmi concentrator in 1989-90. The measuring device with its PC-connections offers an excellent tool for controlling volumetric mill filling, for maximizing throughput and for research purpose (e.g. process studies, mill linings design).The paper describes the new method and the results achieved at Outokumpu's concentrators.INTRODUCTIONVarious methods have been developed for measuring mill load; weighing, noise, etc. Weighing is one of the most reliable methods but installing the sensor to existing mills is often difficult. Besides the load measurement does not indicate the volumetric filling if the specific gravity of the mill feed fluctuates. Noise measurement has often failed with its sensitivity to various disturbance sources.As known, the power draw measurement is one of the most accurate measurements in grinding circuits and therefore it has been utilized in sophisticated control, e.g. in power peak seeking algorithms for maintaining maximum grinding efficiency.About 10 years ago power oscillation measurement was developed at Pyhasalmi concentrator. In this method the amplitude of the oscillation caused by the lifters was measured. The oscillation amplitude and the mill filling has quite a good correlation and together with the power draw measurement it could be used for maximizing mill throughput (Koivistoinen and Miettunen, 1989). The main difficulties in this method were that the dependence between mill filling and the amplitude is unlinear and that the dependence also is individual for each mill.The method developed during 1989-90 is also based on the power oscillation but on its phase shift. In principle level of the material in a mill is measured. The method has been successfully used for maximizing throughput at Pyhasalmi and Enonkoski concentrators and at Harjavalta slag concentrator."

Jan 1, 1991

By G. Simard, M. J. Gagnon, A. Charette, G. Péloquin

"In the Bayer process, flocculants are introduced in the feed well to enhance the aggregation of red mud particles. To gain a better understanding of the flocculation process taking place in the feed well, shearinduced flocculation was achieved using concentric rotating cylinders (Couette system). Our previous work has shown the effect of the shear rate on the aggregate’s settling rate and on residual turbidity of the Bayer liquor. In this study, the data demonstrated that the aggregates at selected shear levels appear as a population with a widespread size distribution. By using an imagery apparatus, it was possible to measure the size, the shape, and the sedimentation velocity of the larger red mud aggregates. Marked differences were noticed in the characteristics of the aggregate populations obtained under various shear conditions. IntroductionIn the Bayer process, red mud particles are separated from the liquor in primary clarifiers and washing circuits under the action of synthetic polymers. The agitation in the feed pipe and in the feed well affects the flocculation since the aggregates are formed by the interaction between the red mud particles and the polymers. A minimum shear rate is needed to initiate the aggregation process of fine particles (Warren, 1975).Different systems have been used to study the effects of shear on the flocculation process (Tampo and Watanabe, 1979; Klimpel and Hogg, 1986; Scott et al., 1996; Biggs and Lant, 2000). The Couette flow system has been used in some studies on shear-flocculation (Oles, 1992; Farrow and Swift, 1996a, 1996b). The importance of the physical properties of the aggregates in determining the efficiency of the solid-liquid separation process within a given gravity thickener has been demonstrated (Farrow and Warren, 1989a)"

Jan 1, 2002

By Jan E. Nesset, Phillip J. Mackey, Joo Y. Kim, Giovanni Di Prisco, André R. Laplante

Understanding the appropriate gold recovery to associate with copper recovery when assessing laboratory testing on porphyry deposits is often complicated by several factors including variable and/or complex mineralogy, and the variability contributed by the low Au content of the various flotation products. As a result, gold recovery is often underestimated and the value contributed by the gold to project economics is less than it should be, a problem that could influence overall project viability. Typically, for these types of deposits, the gold recovery is found to be lower than the copper recovery. In this unique project, having the objective of seeking a better understanding of gold recovery relative to copper recovery, mill feed samples from a selection of six operating world-class Cu-Au low-grade deposits were collected along with the mill metallurgical results for the corresponding sample periods. The samples were subjected to laboratory flotation tests, as well as the Laplante gravity recoverable gold (GRG) test, mineralogical assessment and cyanidation leaching. The aim was to better understand the copper and gold recovery relationship, the links between laboratory and plant flotation performance, the influence of mineralogical differences, and the potential for enhancing gold recovery by gravity recovery techniques. A new correlation of copper and gold recoveries based on the results is presented in the paper. The results showed that the link between copper and gold recoveries established in the best laboratory tests were maintained in the plant results, and further, that the potential for improving Au recovery by gravity or flash flotation methods is directly proportional to the amount of gold greater than 75 microns.

Jan 1, 2005

By S. Stefanizzi

In the present paper, numerical simulations based on a finite/discrete element approach are used to study deformation and failure process during standard rock mechanics. FEM/DEM modeling has been used as available with the ELFEN code, which explicitly model the transition from continuum to discontinuum. The transition is simulated through a crack nucleation and propagation that obeys to the Griffith?s failure criterion. If the fracture criterion within the intact rock (represented by FEM) is met, a new crack (represented by DEM) is initiated. Remeshing allows the fracture process through the FEM mesh to be tracked and visualized, thus contact properties can be assigned to pre-existing fractures and newly generated fractures. In this study, compressive tests of rock samples are simulated. The applicability of ELFEN to properly and efficiently simulate typical laboratory rock mechanics tests, with reference to the rock fracture process, is described in detail. In addition, an indirect validation of the extensional strain criterion proposed by Stacey (1981) is given.

May 1, 2009

By T. Belem

The main objective of this study is to better understand the effect of underground CPB placement conditions on its microstructural, hydro-mechanical and geochemical properties. To reach this objective, three PVC columns, each 3 m high, were built, and were filled with CPB material. The columns allow simulating undrained (UD), half-drained (HD) and fully-drained (FD) conditions along with the measurement of resulting self-weight consolidation settlement of the CPB. Bleed and drainage waters were also collected from each column for geochemical analyses (pH, Eh, EC, SO42- content). After 90-days of curing time, a total of sixty CPB samples were cored from the backfill columns and subjected to uniaxial compression tests followed by physical characterization (Gs, void ratio, water content, degree of saturation, specific surface area). The results showed that the total drainage water and the maximum observed settlement occur mainly within the first 72 hours after the columns are filled. The corresponding volumetric strains suggest that in situ backfilled stopes simulated behave in a similar way to the fully-drained (FD) or the half-drained (HD) conditions. The MIP test results show that the pore structure varies between the top and the bottom of each column.

May 1, 2007

By Norman O. Lotter, André R. Laplante

"The pursuit of concentrator surveying for purposes of metal accounting or process optimization has not yet connected with the well-published realm of geostatistics. The reality of lognormality in time has seldom been discussed. One publication by Krige, 1962, examined such effects for a gold concentrator in South Africa, towards an information system that would provide feedback to the mining and surveying teams on grade control of ore mined.During present studies which are designing and testing a new survey model, called statistical benchmark surveying, it was found that the distributions of feed, concentrate and tailings bear significant residual signs of the parent lognormality in space. The multiple hosting of paymetals in different mineral species complicates the understanding of these distributions. These features have to be recognized and treated in order to perform appropriate quality control on the diagnostic sampling performed in the pursuit of statistical benchmark surveying.It is shown in this paper that the above two features can actually be used to advantage in the diagnosis of continuous periods of operations data ahead of such surveying, including the estimation of recoverable paymetals in flotation tailings from a graphical method.INTRODUCTIONAssessment of Concentrator PerformanceMilling and flotation, sometimes accompanied by gravity separation, are well-established unit processes, which have traditionally been used to treat ore that has been mined. This is because these processes liberate, then separate, the valuable minerals, which contain paymetals, from host gangue. This is often done by a combination of crushing and grinding processes, or autogenous grinding, to liberate the paymetal minerals, followed by gravity separation and/or flotation, to separate these valuable minerals into a concentrate, or several concentrates. These concentrate(s) have a lower bulk than the parent ore from which they are derived. Further, they contain a high percentage of the valuable minerals. Accordingly, they are more economically treated in subsequent beneficiation processes than the ore from which they were produced."

Jan 1, 2005

By Yum Xiaoquan, Turgut Yalcin

"A laboratory study was carried out to determine the potential role and effect of ultrasonic irradiation in the flotation of a Sudbury copper-nickel sulphide ore. The use of ultrasound was tested separately at the pulp preconditioning, collector conditioning and flotation stages. While no significant benefits were evident in the latter two cases, ultrasonic preconditioning of pulp improved the grade-recovery performance and had the prospect of reducing reagent consumption rates. Tests were conducted on both the normal and oxidized ore samples, and several variables were investigated, including ultrasound frequency (25 kHz and 45 kHz), ultrasonic power (up to 1.6 W/cm2), duration of ultrasonic treatment (up to 60 minutes), and the intensity of pulp agitation employed during the application of ultrasound. Ultrasound frequency of 25 kHz and duration of 15 minutes yielded satisfactory results. Changes were found to occur in the temperature, pH and Eh of the pulp during ultrasonic processing. The favorable effects of ultrasound observed in this study were attributed primarily to its surface cleaning capability.INTRODUCTIONThe use of ultrasound for the surface cleaning of objects is well known. Ore flotation is based essentially on the surface properties of minerals, and hence stands to benefit from ultrasonic treatment which may help restore mineral surface characteristics that might have been lost or modified through oxidation, etc. Expected outcomes of this method of treatment include improved flotation kinetics, higher recovery, better selectivity, and savings in reagent consumption, as has been demonstrated by various researchers (Aldrich and Feng 1999, Celik 1989, Ozkan 2002, Letmathe et al. 2002, Nicol et al. 1986)."

Jan 1, 2005

By Denis Thibodeau

The selected mining method for the Rodeo lower Zone is slot and slash. Initial design indicated that the stope height should be limited to a maximum of 18 m, thus six levels were needed to extract the ore. Higher stope height in the Rodeo Lower Zone means less development thus less capital required to extract the available reserves. It was proposed to eliminate one level by establishing 30 m and 24 m level intervals. To ensure that no stability problems will be encountered by eliminating one level, a Matthew analysis, based on diamond drill core information, was performed for the Lower Rodeo Ore Body. In addition, comparisons between the rock mass quality of Meikle Main Zone below 1825 L and Meikle East Zone between 1600 L and 1750 L with the rock mass quality of the Lower Rodeo were made

May 1, 2002

By P. O. Sandstrom

"Atlas Copco is introducing a new patented method for full-face boring. This paper presents the basic principles of the boring action and discusses the present experience regarding performance and costs. The Atlas Copco ""Full-facers"" are designed for hard-rock applications, although they are successfully boring in soft ground without major changes. The unique patented boring principle referred to as the 'Undercutting Method' permits these machines to bore, economically, in harder ground than machines based on the 'crushing principle'. This is mainly due to considerably lower cutting-tool costs, as the tungsten carbide tips only are in contact with one-third of the bored volume. The remaining rock is 'undercut' and peels off from a slight back pressure.The undercutting method also permits boring of non-circular headings and Atlas Copco has already manufactured two machines for rectangular drifts. This concept could revolutionize development work in mines employing trackless equipment."

Jan 1, 1971

By Ike Isagon

Backfilling has become an integral process in underground mining operations, with varying cost-effective forms of application. This study is a part of an overall investigation into the backfill practices at Copper Cliff North Mine (CCNM). The mine is well-diversified in terms of backfill methodologies and practices. The mine employs different fill methods such as cemented and un-cemented rock fill, slag fill, and cemented hydraulic fill (or a combination of them) in order to fill the voids created by mining activities. The history of backfilling at CCNM has been dominated by cemented and un-cemented slag fill. Each fill method requires operating and engineering guidelines for a cost effective quality control system. The purpose of this paper is to briefly discuss the backfill methods and applications, operating guidelines, and engineering requirements at CCNM.

May 1, 2011

By T. B. Armstrong

"The developing world energy crisis and spiraling fuel costs have created a new public awareness and general acceptance of the need for energy conservation.Plants will have different objectives for an energy conservation program but there appears to be a common approach on how to save electrical energy.Data for a 180tph Rod Mill powered by a 750 hp motor will be used to demonstrate the relationship of energy input and production levels and to seek an optimum operating condition.Energy Conservation:Plants that have examined ways of dealing with the energy situations have concluded that energy conservation has important benefits for industry, including reduced costs, fewer production slowdowns inthe event of fuel shortages and a continued competitive position.There have been some ""startling"" conservation achievements attained through such simple plant maintenance and operating practices as reducing unnecessary lighting in buildings and yards, turning off' equipment not needed at night or over week-ends, through planning maintenance and production schedules to minimize energy use and through improving quality control to eliminate waste.Significant reducti.ons in energy use have been achieved by some rather simple but vigorous maintenance and plant engineering efforts directed at finding and fixing energy ""leaks"" rather than technological advances or major rework or redesign of facilities and equipment.An Energy Conservation Program often must overcome such obstacles as historic operating practices and emp1-oyee indifference, i.e. the ris.ing costs of fuel should result in re-examination of so1ne basic attitudes to energy conservation. Some measures, rejected in the past largely on the grounds of capj.tal. expenditure, now make economic sense in the light of future escalating energy costs."

Jan 1, 1978

By R. E. Barbosa

Seepage forces generated during tunnel excavation affect the ground response and may cause severe instability problems, including total ground collapse and flooding into the tunnel. This paper presents a new closed-form analytical solution, for stresses and displacements around a cylindrical tunnel excavated in a porous water-bearing elasto-plastic material, which includes the effects of seepage forces. The analysis is carried out in terms of effective stresses and pore water pressures. The solution shows that seepage forces may have a major effect on the effective stresses around the tunnel, on the extent of the plastic zone, on the radial displacements, and on the tunnel support requirements. The conditions for development of a ?flowing ground? condition at the tunnel face have been identified. The paper presents a procedure for the hydromechanical ground-support interaction analysis, to determine the excavation induced inflow and the pressures acting on the lining, throughout the progressive driving of the tunnel, including the effective pressures exerted by the ground and the pressures generated by the water.

May 1, 2009

By T. G. Joseph

A strain-softening constitutive relationship is introduced that describes the post-failure stress-strain curve for rock regardless of whether the rock is intact or broken. The core of this relationship is an ?apparent friction? concept that relates the post-failure apparent cohesive and frictional characteristics of the rock to the strain. The relationship can be determined for a given rock via a series of tri-axial strength tests establishing the peak strength and corresponding strain for a range of confining pressures, together with the determination of the base angle of friction via a simple tilt test. The postulates and assumptions used in deriving this relationship are verified from results of tri-axial tests on both intact and broken rock.

May 1, 2002

By Eugene Nel, Johan Theron, Chris Martin, Hans Raabe

"Impala Platinum Limited is the world’s second largest platinum producer, producing more than 1.7 million ounces of the precious metal last year, much of this from the UG-2 reef located in the Bushveld Complex, South Africa. As part of Impala’s ongoing expansion programme, tonnage through their principal UG-2 processing facility, near Rustenburg, was increased 40% in 2001.To accommodate the increased throughput, the role of the existing primary mills was converted from conventional semi-autogenous grinding units, to attrition and selective grinding units, operating in fully autogenous mode. The finer chromite and coarser silicate components in the mill discharge are then separated by screening and processed in dedicated circuits downstream. This way, the need to spend considerable capital to increase primary grinding capacity was averted.In the last year, considerable work has been conducted to evaluate and optimise the two downstream circuits. This has involved an optimisation programme of sampling and diagnostic flotation testing, supported with QemSCAN analysis. This paper will describe the operation of the new circuit. It will also describe some of the more novel aspects and interesting findings from the optimisation programme.INTRODUCTIONThe South African platinum industry is the world’s largest producer of platinum and the world’s second largest producer of palladium. Located in a wide area north of Johannesburg, the industry mines ores from the Bushveld Complex, one of the world’s great mineral treasure chests, containing over 70 percent of the world’s platinum, as well as extensive reserves of the other PGE (platinum group elements), chrome, manganese and vanadium. The industry employs about 180,000 people in, predominantly, underground mines, which together form an almost unbroken circle of mining operations 200 km in diameter."

Jan 1, 2004

By Glenn K. Nolan

"Today, more than any other time in recent history, aboriginal communities are looking for ways to be understood as more resource development companies continue to explore and develop Canada's vast resource potential.Recent Supreme Court rulings have affirmed the need to engage aboriginal communities early on in resource development projects. There are many conflicting ideas on how, who, and when to engage. Given the large number of communities and varied cultures, each resource development company must equip itself with a better understanding of the people they are planning to work with.The lecture will begin with a basic historical perspective on treaties and the various societies across Canada. We will also explore the current situation many communities find themselves in today. Building a meaningful relationship with a community is the foundation for a lasting partnership. Every community is unique and every approach to engage communities must be just as unique. The lecture will outline some basic steps that can lead to a better relationship building process between the communities and companies."

Jan 1, 2008

By Jason Clarke, André R. Laplante

"The gravity-recoverable gold (GRG) ore characterization test was developed 15 years ago and has been applied to hundreds of ore samples. The test accurately determines the size distribution of GRG, at which grind it is recoverable, and the extent of its liberation above 150 µm. This contribution shows how the test can be simplified, what are the likely problems to occur, and what information is then lost. Two simplified versions of the test are presented, of which the simplest, grinding a 20-kg sample to a P80 of 75 µm, is retained as the best one. A database of 18 comparative tests is presented. The choice of the full GRG test vs. the simple test is discussed, as is the deportment of the GRG recovered in the standard test but not in the simplest test.INTRODUCTIONThe GRG test was developed in 1990 to characterize the progressive liberation of gold in representative samples of ores, with the primary objective of generating data for a gold gravity recovery model (Woodcock and Laplante, 1993; Laplante et al., 2000). Characterization includes the size distribution of GRG as well as the grind size at which it becomes recoverable. This is achieved in a 3-stage protocol of liberation and recovery using a laboratory centrifuge unit, a Laboratory Knelson Concentrator 3 inches in diameter (KC MD3). This protocol is shown in Figure 1. The first stage takes place at a F100 of 850 ?m (F80 of ~550 ?m), the second at F80 of 180 ?m, and the third at a P80 of 75 ?m. The rationale for the three cycles is the desire to preserve the original size distribution of the gold grains in the ore and to obtain a recovery grind size curve. The feed is a representative sample of ore that can be extracted from ore samples (e.g. drill core reject) or stream products of the grinding circuit other than circulating loads or product having undergone hydraulic classification (e.g. rod mill discharge or SAG screen undersize). Ideally the samples should weigh between 60 and 100 kg, depending on feed grade and gold top size. It is beyond the scope of this paper to fully discuss measures of representativity in the ore sample, for example Gy’s minimum sample mass model (Gy, 1979). However, further work in this regard may be an opportunity. The large initial weight facilitates representativity and minimizes weight and sulphide recovery to the concentrate (since concentrate weight is relatively constant at ~100 g), which limits the recovery of gold in nonsulphide gangue or gold carriers (i.e. sulphides). Thus, the 100 g concentrate carries principally discrete gold species, such as electrum, and native gold. The concentrate and a 600-g representative sample of gangue of each stage are screened down to 20 ?m and each size class is fire assayed (the concentrates to extinction, the tails up to 30 g per size class). The five coarsest size fractions of stage-1 concentrate are individually upgraded using a hydrosizer and the concentrates examined with an optical microscope to assess the degree of liberation of the gold phase. Scanning electron microscope work has established that the GRG has an excellent degree of liberation below 150 ?m in stage 1 and generally a good degree of liberation in stages 2 and 3 (Guerney et al., 2003); as a result the size distribution of the GRG has been found to approach closely that of gold grains (Nesset et al. 2005)."

Jan 1, 2006

By Manqiu Xu, Peter Wells, Gord Bacon

"A methodology is proposed for milling flowsheet design using flotation rate, selectivity and residence time distribution data. The flotation rate data and the difference in flotation rates between the main minerals to be separated are determined from laboratory batch tests. The residence time distribution (RTD) data is calculated using the tanks-in-series model assuming each flotation cell is a perfect reactor. The rate, selectivity and RTD data can be used to calculate the optimum flotation cell number in a bank for rougher/scavenger in a commercial plant.This methodology is demonstrated in a case study of a nickel sulfide ore. It is shown that miniplant rougher/scavenger data can be closely predicted from a batch test using the proposed methodology.INTRODUCTIONIt has been the trend in the past several decades that large flotation cells are increasingly used. This is largely driven by the economics as ore grades are getting lower and the rate of ore processing must be increased in order to keep mining operations economically viable. The development and evaluation of 250 to 500 m3 WEMCO SmartCell and Outokumpu TankCell flotation machines are well in progress. There are many advantages in using large cells: fewer cells, less floor space, lower power cost (although this is now being questioned for fine particle flotation), simpler circuit, simpler control, and lower auxiliary equipment cost (Arbiter, 1999). As flotation cells are getting larger, the importance of cell hydrodynamics, namely, air/slurry dispersion, power intensity, froth transfer, residence time distribution (RTD) and short-circuiting are being fully recognized (Jonaitis, 1999; Weber, et al., 1999; Gomez and Finch, 2002). It is not the intention of this paper to discuss flotation cell scale-up. The intention is to answer what is the optimum number and size of cells in a flotation bank for a given throughput. Figure 1 illustrates this problem facing design engineers. The same mean residence time required for a given throughput can be achieved in a single large cell, or many smaller cells in a row. A few cells of large size may be more cost-effective but they may not be as effective as more cells of smaller size in achieving the optimum metallurgy."

Jan 1, 2005