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By A. Saki, P. Gebski, W. Ying

Industrial smelting furnaces are subjected to significant structural changes and deterioration caused by the conditions under which they operate. The current methods for the structural assessment of furnaces include visual inspections, analysis of thermal data, acousto ultrasonic-echo (AU-E) of the refractory lining and surveying of the key structural elements. Acoustic Emission (AE) non-destructive testing (NDT) technique has proven its capabilities for continuous monitoring of industrial installations and structures. Recently, Hatch Ltd. has been successful in applying acoustic emission for monitoring furnace tapblocks, and expanding the scope of the acoustic emission monitoring to the structural integrity of the entire furnace. The capability of detecting emissions related to the fracture development in the furnace shell, movement of the refractory, electrode arcing, combined with efficient source location algorithms makes an acoustic emission system a comprehensive tool for the real-time furnace integrity monitoring. In this paper the concept of such state of the art system for structural integrity assessment is presented. The initial results of the acoustic emission monitoring together with data analysis techniques are discussed.

Jan 1, 2011

By G. F. Raymond, W. P. Armstrong

"At the time of this study, the Valley mine was producing 23 000 tonnes of ore per day from a large, low-grade porphyry copper orebody. Sulphide mineralization, principally bornite and chalcopyrite, occurs in a stock work of quartz veins in one phase of the Guichon Creek batholith. The property was explored from 1967 to 1982, and was placed in production in 1983.Using a three-parameter lognormal approximation developed by G.F. Raymond at Similkam een and Mount Isa Mines, a geo- statistical conditional probability ore reserve was estimated prior to mining. Comparisons with blasthole kriging and milled ore for the first 17 months of production showed close agreements at all cut-offs between conditional probability estimates and mineable ore. This was not true of either kriging or polygon estimates. An important part of this work was identifying and correcting for bias in both exploration and blasthole samples.IntroductionCominco's Valley lake deposit is a large, low-grade, porphyry copper orebody in the Highland Valley of British Columbia. Total indicated plus inferred ore reserves are 700 M tonnes at ore grade of 0.47070 Cu. At the time of writing, ore milling is at a rate of 23 000 tI d through the old Bethlehem mill. Mining is in 10m horizontal benches using 9.8 m3 shovels and 90 tonne trucks. Since this paper was written, Valley and nearby Lomex have been combined into Highland Valley Copper with a combined oreproduction of about 120 000 tI d.Copper mineralization, principally bornite and chalcopyrite, is regularly distributed throughout the deposit as disseminated low-grade within a granodiorite host rock, and as higher grade veinlets within a stock work of near-vertical quartz veins generally 10 cm or less in width. It is likely that problems with sample variability and sample bias are mainly related to mineralization within quartz veining. Valley geology has been described in detail by Allen and Richardson and by Osatenko and Jones (2). The exploration sampling program and identification of diamond-drill sample bias have been discussed by Armstrong and Newman'»."

Jan 1, 1988

By Adrianus (Adrian) Halim, Tomas Bolsöy, Stina Klemo

"This paper describes the ventilation system used in underground hard rock mines in Sweden and Finland, which is very different than the system used in other major mining countries such as Australia, Canada, South Africa, and USA. The system utilizes auxiliary fans with Variable Speed Drive to distribute primary airflow to working levels instead of regulators that are commonly used in other countries. Descriptions about Ventilation on Demand in this system and ventilation regulations in Sweden and Finland are presented in this paper. This paper also quantifies a comparison between the Nordic and the system used in other countries. KEYWORDS Auxiliary fan, Regulation, Ventilation on demand (VOD), Variable speed drive (VSD) INTRODUCTION The primary objective of an underground mine ventilation system is to provide sufficient airflow to dilute atmospheric contaminants that are produced by mining activities. Typically, a mine ventilation system consists of one to four primary fans, regulators to control primary airflow distribution to levels or panels, and auxiliary fans that distribute airflow to dead-end workings via ducts. Depending on circuit geometry, underground booster fans are sometimes used. This system is widely employed in many countries such as Australia, Canada, USA, United Kingdom, and South Africa. However, mines in Nordic countries such as in Sweden and Finland employ a different system, in which auxiliary fans instead of regulators are used to control primary airflow distribution, as well as distributing airflow to dead-end workings. This paper describes the general layout of Nordic ventilation system, its VOD and heating system, its comparison with the system that is widely used in other countries which is referred as “Non-Nordic ventilation system” in this paper, and the current ventilation regulations in Sweden and Finland. The comparison was quantified by doing simulations using Ventsim Design 5 software. DESCRIPTION OF NORDIC VENTILATION SYSTEM General System Layout Figure 1 shows a schematic of typical ventilation system used in Swedish and Finnish mines. The schematic was drawn by Franzen, Myran, Larsson, and Rustan from Stiftelsen bergteknik forskning (Swedish Rock Engineering Research Foundation) and the English translation is written next to the Swedish terminologies. The system is generally a push-pull system. None of Swedish and Finnish mines use exhaust system. As shown in Figure 1, the primary airflow is distributed to levels by auxiliary fans that are bolted to a bulkhead located in the access to intake raise/shaft. These intake fans are attached to ventilation ducts that distribute airflow to all working faces. The exhaust auxiliary fans, which are not attached to any ducts and also are bolted to a bulkhead located in the access to exhaust raise/shaft, then flow the exhaust airflow into the exhaust shaft. A small quantity of this exhaust air is directed into the ramp, which acts as another main exhaust airway. The deepest level is also equipped with booster fan(s) that draw air from the intake shaft/raise and direct it into the ramp to provide fresh air in the ramp. There is no free split in this system. Figure 2 shows a schematic of a level ventilation layout in the Nordic system. Figure 3 shows a photo of these auxiliary fans."

Jan 1, 2019

By H. C. Cooke

Geological examination of the underground workings of the Horne and Aldermac mines during the summer of 1927 has brought out the following facts: (1) That the ores tend to replace bodies of breccia or tuff rather than massive lava or dyke material; (2) That the faulting and folding at the Horne has had a pronounced effect in localizing the ore-bodies; (3) That there is a tendency in cert?-in cases for ore-bodies to be localized beneath gently dipping dykes, which acted as impervious roofs; (4) That there is a great difference in age between the chalcopyrite part of the ore-bodies and the pyrite-pyrrhotite portion. A statement of the development to date at the Aldermac mine is also included in the paper. ALDERMAC MINE The Aldermac property is made up of eight claims in the western half of Boischatel township, Quebec, including 747 acres in all. The mine itself is approximately three miles, 25 chains from the west boundary, and four miles, 55 chains from the north boundary, of the township.

Jan 1, 1928

By Paul Guliov

Potash dominates the industrial mineral scene in Saskatchewan accounting for 44% of total provincial mineral production in 1981. More than 7 million tonnes of potash have been produced annualy in recent years; ten underground mines are presently (1983) active. Sodium sulphate and cement are also important mineral products. Construction aggregates, clay products, bentonite, salt, peat moss and sulphur complete the list of industrial mineral products.

Jan 1, 1984

By P. Archer

The Blondeau Formation has been examined in a stratigraphic drill section at Barlow Lake. The formation contains pyroclastic flows and volcanogenic sediments throughout, but epiclastic sedimentary rocks dominate the upper parts of the section. Five distinct types of pyroclas tic flows are known in the section, as well as minor mafic lava flows. Volcanogenic sediments are commonly intercalated with the true volcanic rocks. Sedimentary rocks include fine-grained intraclastic sandstones, heterolithic sandstones and green and black shales. Interpretation of the origin and relative disposition of the volcanic and sedimentary rocks favours a model of near-emergent vulcanism in an upward shoaling environment.

Jan 1, 1984

By J. E. Quinn, S. Wolstencrof, K. H. Soldenhoff

Ion Exchange (IX) using Strong Base Anion Exchange (SBA) resins is conventionally used to purify uranium from sulfuric acid pregnant leach solutions (PLS), particularly when uranium grades are relatively low. However, the presence of chloride in the PLS interferes negatively with conventional SBA based IX processes, by reducing the uranium loading on the resin. Chloride can be present in the PLS due to the use of saline bore or seawater in leaching, or chloride containing leach/IX reagents. ANSTO has been examining strategies to combat this problem for several years. ANSTO previously reported that a recently developed high-capacity SBA resin was capable of extracting uranium efficiently from saline leach liquors produced at Boss Resources’ Honeymoon in-situ recovery mine in South Australia. The resin was tested successfully in a 2017 Field Leach Trial carried out onsite in the existing wellfield area. While the piloting was extremely promising, the elution was more challenging, with eluate tenors limited to 2 g/L U3O8 using NaCl. This is due to the resin’s strong affinity for the uranium complex, which makes it difficult to elute efficiently by standard methods. In this paper, we describe a novel elution process developed for strong base resins that significantly improves upon conventional methods. The process, developed by ANSTO, is based upon conversion of the extracted uranyl sulfate species to uranyl carbonate, followed by elution with sodium chloride. The loading and elution process was demonstrated in continuous locked-cycle piloting conducted at ANSTO in 2019. The results were excellent, with eluate tenors of 8–9 g/L U3O8 achieved from Honeymoon PLS containing 50 mg/L U3O8, with very little transfer of impurities. In subsequent test work, the eluate was shown to be amenable to uranium peroxide precipitation. The results represent a huge step forward for the purification of uranium from saline leach liquors.

Jan 1, 2020

By E. W. Mountjoy

THE Exshaw formation is a thin but very persistent black shale unit generally well exposed along the easterly scarp faces of the fault blocks comprising tl1e front ranges of the Rocky mountains. It is over lain by the Mississippian Banff shales and silty shales and underlain by the massive Palliser Limestone formation of late Devonian age. The Exshaw continues eastward under the plains of Alberta and on into Saskatchewan, with little change until it reaches the surface of the Palaeozoic-Mesozoic unconformity. During the summer of 1953, the writer was working- with a field party under Dr. J. L. Usher in the front ranges of the Alberta Rocky mountains. This party, sent out by the Mobiloil Company, conducted a geological survey of Devonian rocks between the towns of Banff and Jasper. The writer helped to describe and map these Devonian rocks and obtained first-hand information concerning the Exshaw shale and its relationship to the underlying and overlying sediments. Additional information was obtained from reference material and from a number of geologists whom the writer has consulted. Grateful acknowledgment is offered to them, to the Mobiloil Company for releasing field information, and to F. W. Beales and W. P. Hancock who helped edit the original paper for publication. Information from areas north and smith of that studied and from bore holes on the prairies is referred to. Localities mentioned may be found in Figure 1.

Jan 1, 1956

By S. Tavani, T. Rees

The current mining operations at Newmont Boddington Gold Mine (NBG) commenced in 2008, and commissioning of the processing plant started in the latter half of 2009. Metso Process Technology and Innovation were engaged to assist NBG with commissioning and project ramp-up through the implementation of a comprehensive “Mine-to-Mill” Process Integration and Optimisation project. This methodology entailed extensive data collection which included drill and blast audits, ore characterisation, comprehensive comminution circuit surveys and review of operational data to assess the limitations within the current mining and processing operations. The results of these investigations have been used to define the operating base line of both the mining and processing areas and identify improvement opportunities. The use of modelling and simulations, utilising actual production data, has allowed for multiple scenarios to be evaluated, minimising the requirement for actual trials and thereby minimising impact on the operation. Improvements implemented to date include: the introduction of routine rock strength measurement for inclusion in block models, modifications to blast design improving ROM fragmentation and downstream comminution process performance, and changes to improve performance of secondary crushing and grinding circuits. Close cooperation between the mine and plant personnel is playing a significant role in overcoming the challenges presented to this operation and further improvements are targeted for the second full year of process plant operation.

Jan 1, 2012

By Robert Macdonald, William Coombe, John F. Lewry

Gold occurrences have been known in the La Ronge Domain for many year . Mineable reserves have more recently been outlined and there is every prospect of a major gold camp being established in the domain within this decade. The La Ronge Domain lies in the Lower Proterozoic 'Trans-Hudson Orogen' and is part of a collage of Early Proterozoic crust comprising volcanoplutonic arcs, batholiths, associated volcaniclastics and volcanogenic sediments lying between the Superior Craton to the outheast and the reworked Archean basement/Aphebian cover terrain to the northwest. The domain has several lithostructural subdivisions, the most important of whjch , from a gold exploration point of view, is the Central Metavolcanic Belt. This belt is composed dominantly of a range of metavolcanic rocks and gabbroic to granitic intrusives, which geochemically resemble younger subduction-generated 'primitive' arcs developed on oceanic crust. U-Pb zircon geochronology indicates that the arc volcarusm and pre- to late-kjnematic plutonism occurred about 1890 Ma to 1850 Ma ago. The belt has an attained grade of upper greenschist to amphibolite facies and is relatively undeformed , though high strain zones occur locally. Most gold occurrences in the La Ronge Domain have been found in the Star-Waddy Lakes area of the Central Metavolcanic Belt, and in the Sulprude-MacKay Lakes area to the south which is interpreted as a tectonically dismembered part of the main belt. Both tratiformand vein-type gold occurrences are present in the domain; vein-type predominate and form nearly 90 per cent of the occurrences. The stratiform-type occurrences show a regional lithological a sociation with iron-rich sediments within proximal felsic volcanjc sequences. Some vein-type occurrences appear related to brittle fracturing associated with intrusive emplacement (the magmatic-hydrothermal "syn:' and "subvolcanic" veins) and faulting. However, most of the vein-type occurrences exhibit a spatial association with regionalscale ductile shear and other high strain zones, and were probably formed by metamorphichydrothermal processes.

Jan 1, 1986

By Jean-Luc Collins

"This new tool can be used as a quick guide f or the assessment of the potential economic wealth of any risky capital project. It does provide an unambiguous recommendation of the type ""go or no go"" to the decision-maker simply by comparing two different ratios profit/investment. One ratio determines the minimum value required to at least break even while the other measures a probable value based on the asymptotic theory of statistical extremes.Its application is briefly illustrated by means of an underground gold mine extension project, an oil sands mine project and a polymetallic open pit project.Once a favourable recommendation has been obtained then a detailed ""cash flow after taxes"" analysis can be carried out for the project.IntroductionMany tools are used in financial decision-making such as the payback period, the discounted cash flow, the internal rate of return and the wealth growth rate (Berry , 1971).These tools are useful and meaningful in evaluating normal projects closely related to regular business where the number of assumptions made is usually very small and where the cost of capita! is usually selected as a discount rate or a hurdle value. In situations where a significant number of assumptions have to be made,two problems can emerge, namely:I. the risk involved is underestimated leading to a potential financial disaster; or2. a good opportunity is lost because the approach used in evaluating the project is too conservative.Each assumption has its own degree of uncertainty and it is well known that combining uncertainties together can lead to a total uncertainty of critical proportion. The easiest way to account for risk is to increase the discount rate or the hurdle value, but this approach alone is quite subjective and can easily lead to the problems described above."

Jan 1, 1993

By Wayne N. McKee, Scott A. Lewis

"Introduction to the Syncrude OperationSyncrude Canada Ltd., located 42 km north of the city of Fort McMurray, Alberta, (Fig. I) is an integrated operation that has produced synthetic crude oil from the Athabasca oil sand deposit since 1978.The operation, consisting of a surface mine, an extraction plant, a bitumen upgrader, and a utilities plant, is currently capable of producing over 60 million barrels of crude oil per year. Production is expected to increase to 70 million barrels of crude oil per year over the next five-year period with no major changes to equipment or process planned.The Syncrude surface mine, producing a total of 675 000 tonnes of ore and waste per day, rates as one of the largest mines in the world. A strip mining method is utilized, with two or three operating benches necessary to excavate a total depth varying between 60 m and 70 m. The 20 m to 30 m of overburden is removed by electric and hydraulic shovels and 200-ton haul trucks, and dumped in the mined-out pit for final storage. The overburden operation creates a flat bench near the top of the ore zone on which the four 60 m3 draglines operate. The draglines excavate interbanded ore and waste in the highwall, with ore placed on the operating bench in windrows, and waste returned to the mined-out pit. The windrowed ore is reclaimed by four bucketwheel reclaimers, and discharged onto a conveyor system for transfer to the extraction plant."

Jan 1, 1993

By C. Yanqui

"Discontinuum Mechanics is based on two foundations: the idealization of the internal structure of substances, and the principle of the arithmetic mean value. For a linear discontinuum, the methods of Crystallography are used to describe their structure, in which nodes stands for the position of the homologous points such as molecules, grains, or any other motif. The principle of the mean value states that the value of any discrete function at a node is equal to the arithmetic average of the values of this function at the neighboring nodes. This principle leads to an elliptical linear differential equation of the second order, with coefficients given by the statistical second moments of the Cartesian components of the metric vector. As long as those coefficients are components of a symmetric second-order tensor, there are three mutually perpendicular directions, in which the variances reach their extreme values and the covariances are zero, showing that the mean value principle transforms the discontinuum into a statistically equivalent orthotropic continuum.The application of Discontinuum Mechanics to linear rock masses is simple and direct. It is sufficient to define the motif as the plane of geological discontinuity, and the metric vector as the normal vector to this plane, whose magnitude is the spacing between two consecutive planes belonging to the same set of discontinuities. Furthermore, heterogeneities of rock masses can be also included in this description by substituting the plane of discontinuity by a zone of weakness. In this way, the magnitude of the normal vector results from the product of the spacing and the RQD or the RMR. In going further in this theory, at least three conclusions show up. First, in the evaluation of rock masses, it is necessary to determine the orientation, spacing, and RMR for each set of discontinuities. Second, the conventional method of finding the principal families from the contours of equal concentration of poles on the stereographic projection excluding the spacing does not have any physical meaning. Third, any problem of rock mechanics can be solved in a rigorous and reliable way by integrating the differential equation of the mean value."

Jan 1, 2015

By A. K. Chetin, W. W. Fitkin

"The reservoirs of Mississippian Mi-dale beds and Frobisher beds found in the Weyburn field lie at the north-western termination of a broad productive belt extending 120 miles along the northeastern rim of the Williston basin. These carbonates, and inter-bedded evaporites, originated during cycles of marine transgression and regression, and were deposited as rock types characteristic of shoal, lagoon, and basinward shelf environments. The Frobisher-Alida Beds, which form a secondary reservoir to the main Midale Beds of producing zone are composed of oolit1c, fragmental-bioclastic, vugular limestone capped by an impervious dolomitic mudstone. Production is controlled by localized structural features resulting from de-positional build-up. Excellent reservoir conditions are accompanied by an active water drive. The Frobisher Evaporite, consisting of massive primary anhydrite with dolomitic veinlets, forms the floor seal for the Midale beds oil accumulation. A significant facies transition into an oolitic, bioclastic, vugular limestone characterizes this unit. Beyond the depositional margin of the evaporitic facies, marked increases in porosity and permeability of the en-tire reservoir are noted. Carbonate units overlying the areal extent of the Frobisher Evaporite exhibit a greater degree of metasomatism, dolomitization, and more abundant secondary anhydrite.Porous carbonates comprising the producing zone of the Midale beds are divided into an oolitic, fragmental bioclastic, vugular limestone, and an overlying granular marly lime-stone unit, capped, by the Midale Evaporite. Oil is accumulated in a stratigraphic trap bounded above and be-low by primary anhydrite and truncated by the post-Mississippian erosional surface. Mississippian strata dip basinward from this erosional surface in a broad homocline exhibiting only minor irregularities. Rapid lateral and vertical porosity and permeability variations are common. Localized, separated, porous lenticles contain interstitial water in areas where the Midale beds are underlain by the Frobisher Evaporite. The major portion of the field, however, is capable of water-free production. Bottom and edge waters are found in certain portions of the field. Productive limits are tentatively defined around most of the present field perimeter. A large area along foe southern edge of the field remains open to future development. Probable ultimate remaining recoverable crude oil reserves, as of September 30th, 1958, were estimated by Mc-Daniel Consultants Ltd. to be in excess of 330 million barrels."

Jan 1, 1959

By S. H. Schulz

100 YEARS AGO, on the first of August, 1877, the mining engineer Friedrich Koepe was granted the patent rights for a hoist driving ropes on the principle of friction. It was named after him: the Koepe hoist. On the occasion of this centenary, the main features of the Kcepe principle are described.

Jan 1, 1977

By C. J. Newman, K. Molnar, A. G. Storey, G. Macfarlane

"The Kidd Creek copper smelter started operation in June 1981 using the Mitsubishi Continuous Smelting Process. A steady increase in plant production rates has been demonstrated, and the annual tonnage of concentrate smelted is now double the original design rate. This paper summarizes recent modifications made to increase concentrate feed rates, increase on-line time, reduce copper losses and control the impurity level in anode copper. It includes improvements made to furnace design, improvements to reduce downtime f or boiler cleaning, and improvements made to the acid plant to allow handling of increased gas flowrates and higher gas strengths while maintaining low acid plant emission rates. IntroductionThe Kidd Creek Division of Fal conbridge Limited operates a base-metal mining and metallurgical complex, located in Timmins, Ontario, which includes an underground mine, a 13 500 tonne/day concentrator, a 130000 tonne/year zinc plant and a copper smelter and refinery, The copper smelter and refinery were commissioned in 1981, with an installed capacity of 59 000 tonnes/ year of cathode. The smelter, utilizing the continuous smelting technology of the Mitsubishi Process, has subsequently been expanded in production capacity, and in 1991 produced 113 500 tonnes of blister copper The capacity of the refinery, which uses Onahama No. 3 tankhouse technology, has been increased to 96 000 tonnes/year of cathode. The capacity increase at the smelter has been realized through the input of additional oxygen to both the smelting and converting furnaces, without increasing the process off-gas flowrate through the associated waste heat boilers.In this paper, a brief review of smelter operation and modifications in the period 1982 to 1987 is presented, together with a more detailed discussion of operation during 1988 to 1991, and a discussion of future planned improvements."

Jan 1, 1992

By A. C. Ross

"The paper will deal with non-destructive testing in general, and its advantages to those responsible for the maintenance of wire rope. An outline of the main features of the M.D. 6 Defectograph will be given, and the method of operation and results obtained will be described.The instrument will accommodate ropes at 7 /16-to 2 %-inch diameter at reasonable speeds, and is capable of detecting the most minute defects in even the largest-diameter wire ropes."

Jan 1, 1969

By Peter A. Hacquebard

"Two continuous coal zones occurring in a 2500f t (762 m) thick section of the Upper Carboniferous Pictou Group (Westphalian C and D) have been encountered in five offshore wells drilled f or oil and gas in the Gulf of St. Lawrence. They correlate, by means of fossil spores, with thick coals of the Mabou and Inverness coalfields situated at the eastern margin of the Basin. Therefore, the presence of a large submarine coalfield of at least 18000 sq mi. (46 620 km'] is indicated. This compares with an estimated size of 14 000 sq mi. (36260 km' ) for the Sydney Coal Basin.Accessibility is provided only by the small onshore parts of the Mabou and Inverness fields, because farther offshore the coals lie too deep to be mined (below 4 OOO f t ([ 219 m)).Two near-shore coal exploration wells indicate that at Mabou Mines the younger Inverness coals occur at a mineable depth to at least 5 km from land. A structure contour map of this area shows a reserve of 125 million tons in two Inverness equivalent seams that are 8.5 ft (2.6 m) and 4.5 ft (f.4 m) thick. The Mabou coals, however, reach too great a depth close to shore to possess mineable resources.A structure contour map of the Inverness submarine area, based on mine data and one off shore seismic profile, indicates inferred mineable resources of 160 million tons, in two seams that are 7ft (2.1 m) and 4.5 ft (f.4 m) thick . A detailed deep seismic survey will be necessary to substantiate the structure and resource estimates"",Maceral and coal quality percentage diagrams of five column samples of these seams (the 7 Foot and 13 Foot Seams of Inverness Equivalents) show a bright banded coal, high in reactive macerals, which will produce a weak coke unsuitable f or metallurgical purposes. A thermal coal with a rank of H. V. ""B"" Bituminous (0.64% Ro) is present, averaging 12000 btu llb (6 660 kcai/kg), 10% ash and 6% sulphur, of which 60 to 80% is derived from pyrite.Microlithotype profiles of the major Mabou and Inverness coals show characteristic successions that can be used f or seam identification and proved valuable f or structural interpretations.The time of faulting in the major fracture zone on the eastern margin of the Gulf of St. Lawrence Basin has been deduced from coal rank variations. It occurred in pos tPermian, probably Early Triassic time."

Jan 1, 1986

By G. Binks

In 1997, the Zinifex Hobart Smelter ceased ocean disposal of jarosite and the flowsheet was converted to reject iron as paragoethite. This paper describes the evolution of the flowsheet since the changeover and considers future flowsheet developments. The major change to the flowsheet has been an increase in the silica content of the calcine resulting from treating increasing levels of Century concentrate. The high silica levels impacted on the paragoethite precipitation stage, causing a deterioration in the settling and filtration characteristics of the paragoethite and an increase in the contained zinc level. The implementation of a two stage neutral leach step has enabled the flowsheet to cope with the higher input silica levels. Future developments include an understanding of the form of the zinc in the paragoethite and options to lower the zinc level to improve the overall zinc recovery.

Jan 1, 2006

By J. A. Drozdiak, W. Tse, P. P. Rosario

"In a recent publication (SAG 2015), we presented a non-conventional high pressure grinding roll (HPGR)-ball mill circuit as a lower capital cost alternative to the “standard” HPGR circuit. The circuit was designed for the treatment of a hard ore and relatively high tonnage (50,000 t/d). That paper provided details such as flowsheets, layouts, and equipment lists for the two options and compared their calculated capital costs demonstrating significant savings for the proposed circuit. This paper extends the analysis to a third option, a traditional semi-autogenous ball crushing circuit, giving the same level of details and now including the operating cost estimates for all three options for a more comprehensive analysis. Moreover, this work also provides information about the strengths and weaknesses of the non-conventional HPGR circuit when compared to the “standard” HPGR option.This study demonstrates that the proposed non-conventional HPGR-based circuit not only provides a lower overall capital costs for the project if compared to a “standard” HPGR circuit but also brings the capital cost to the level of the traditional semi-autogenous grinding (SAG)-ball mill circuits. In addition, the innovative HPGR circuit provides similar operational cost savings of the “standard” HPGR and thus a significant advantage when compared to the SAG option. With the current capital cost sensitivity for most greenfield projects, the proposed alternative circuit should help make HPGR-based circuits more competitive and thus promote the utilization of a technology that enables higher energy efficiency and reduced greenhouse gas emissions. INTRODUCTIONThe application of high pressure grinding roll (HPGR) technology in comminution circuits is well established for the processing of cement, diamonds and iron ore (Broeckmann & Gardula, 2005), and over the past 10–15 years, this technology has slowly been applied to hard ores in high-tonnage precious and base metal operations. Unfortunately, under the current economic climate, the ability to finance large capital projects has become very difficult and companies tend to have an easier time securing funding if the capital expenditures (CAPEX) are low with a proven process method. The traditional semi-autogenous grinding (SAG) mill / ball mill circuits easily fit into this mould, having been installed in countless plants around the world over the past 30 years with relatively low capital requirements. In contrast, it has been well-documented that HPGR-based circuits are capital intensive with complex material handling systems (Seidel, Logan, LeVier, & Veillette, 2006). Although these circuits benefit from reduced operating costs with the increase in energy efficiency and the elimination of steel grinding media (Rosario, Boyd, & Grundy, 2009), if the company is unable to secure financing to build the plant, these advantages remain out of reach. With the current trend to retrofit existing SAG circuits with a secondary crushing circuit to achieve design throughput, the opportunity to circumvent this gross inefficiency by making HPGR-based circuits more capital friendly would greatly benefit the industry."

Jan 1, 2016