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By Nicholas Bonderoff, Amily Xu

The evaluation of battery electric vehicles (BEVs) in underground mines involves comprehensive business case analysis beyond just the capital and operating costs of the equipment itself. BEVs demonstrate benefits from an EHS perspective, reduced mine ventilation costs, lower energy operating costs, reduced overall GHG emissions (dependent on the source of electricity), elimination of DPM, lower equipment maintenance costs, and reduced cooling requirements in deep mines. When including batteries and supporting infrastructure, BEV capital costs are approx. 80% greater than that of diesel equipment. The project economics are highly dependent on the cost of electricity and diesel fuel, and these can vary widely depending on the location of the mining operation. Battery charging and swapping methodologies must be evaluated as there are a variety of approaches that can be employed which vary by manufacturer and type of equipment. Careful consideration of the cycle times, charging methodologies, and location of the battery charging infrastructure is necessary. Specific operating conditions must also be taken into consideration. For example, the time for blast gases to clear will be increased by reducing ventilation flow, and the potential impact on production needs to be evaluated. Similarly, the electrical distribution system needs to be evaluated for peak loading conditions when BEVs are charging. Criteria including maintainability, reliability, commercial availability, and performance need to be evaluated. BEVs have fewer components than diesel equipment and this correlates to lower overall maintenance costs, however, BEVs require maintenance personnel with specific skill sets in order to maintain the equipment. Battery lifecycle costs need to be considered as battery replacement incurs significant capital expense. Some manufacturers offer services to offset these capital costs through usage agreements. Recycling and disposal of batteries at the end of their lifecycles also need to be considered. With the increased selection of BEV equipment that will be available in the next 2-4 years, 100% BEV adoption is also possible. We recommend a holistic approach when evaluating BEVs for underground mines. This will ensure that everything is considered in order to evaluate the full impact of BEV implementation.

Jan 1, 2023

By I. I. Inculet, M. A. Bergougnou, J. D. Brown, R. M. Quigley, D. K. Faurschou

"Coal from Hat Creek, B. C., has been successfully beneficiated to remove ash while retaining calorific value by a dry electrostatic separation process using a fluidized bed for triboelectrification. Two samples of Hat Creek coal used in the beneficiation experiments have been characterized particularly with respect to their mineral and clay content. The calorific value recovery exceeds the simple dry coal recovery because of the heat lost in altering the clay minerals of the ash fraction during burning. Recoveries and ash contents of the beneficiated coal are comparable to recoveries by water washing, but the dry process avoids the potential water pollution problems.IntroductionProposals have been made which suggest an interim Canadian coal production target for the end of the century which will require a four- to fivefold increase over the 1977 production. This implies a nominal annual growth rate of about 6070 to achieve a production rate of 115 to 140 million tonnes/year. Whether or not this target is realistic, it is becoming increasingly evident that coal must be utilized more fully on a world-wide basis. The crisis in Iran has provided the latest stimulus to renewed interest in Canadian coals for domestic use and export.The emerging new era of coal utilization for fuel and chemical feedstock will not, however, generally tolerate the level of coal technology which prevailed prior to the availability of abundant cheap oil and natural gas. Economic, environmental and resource management considerations will necessitate, for example, the use of improved methods of beneficiating coal. Continued development and application of conventional processes, principally aqueous, involving heavy media and cyclones will solve many of the problems. However, less conventional processes may be preferable or necessary in certain applications."

Jan 1, 1980

By A. B. C. Stothart

"IntroductionIn the past four years Ontario Mines have made great progress in the development of reliable mine conveyance safety dogs. History shows that, prior to 1945, a rope failure on a descending conveyance was usually followed by unsatisfactory safety dog operation.It is proposed in this paper to discuss briefly;The history of this development. Progressive .development of one type (E. Long).Free fall testing of safety dogs. Anti-trailing rope device.HistoryOn February 2nd., 1945, a hoisting rope broke at the Paymaster mine. The safety dogs proved ineffective and permitted the cage to crash through to the bottom of the shaft, with disastrous results.Following this accident, the Ontario Government appointed a Technical Committee to investigate The Safety of Hoisting Equipment and Hoisting Practice in Ontario Mines. This Committee consisted of Dr. C. R. Young (Chairman) and Professors T. R. Loudon, E. A. Allcut, V. G. Smith, and Lloyd M. Pidgeon. The Ontario Mining Association (at the request of the Ontario Government) also appointed a Committee consisting of Messrs. R. E. Dye, R. D. Parker, and R. L. Healy."

Jan 1, 1950

By B. Chambers, M. Yunovich

"Corrosion monitoring is commonly used in a variety of industries as a means of effective corrosion control programs to extend the life of the asset and ensure safe operation of the facilities. The majority of the monitoring tools have limitations and tradeoffs – e.g., sacrificing the longevity of the probe for higher measurement resolution. Linear polarization resistance (LPR) probes have the advantage of providing the operator with accurate, real-time corrosion rate data; however, the probes can only be deployed in conditions where the measured environment possesses certain minimal conductivity. In many instances, utilization of LPR probes in conditions with intermittent wetting (for example, conditions where the temperature fluctuates above and below the dew point) presents a challenge. To address this limitation, a special-design cooled corrosion probe has been developed, commercialized and integrated into the distributed control system in the plants. In addition to high-accuracy measurement of corrosion rates, the probe allows for monitoring of pitting corrosion. The most innovative feature of the probe is the cooling circuit, which brings the temperature of the sensors below the dew point, forcing precipitation of moisture and thus permitting corrosion measurements. Additionally, the probe was found to be well-suited for monitoring corrosion in crude distillation unit (CDU) overhead space, where condensation of hydrochloric acid may take place at relatively high temperatures, which would require relatively moderate amount of cooling to be imparted to the probe sensors. This paper presents laboratory-based data from a test simulating CDU refinery environment. A case study is presented to demonstrate how the cooling probe can be effectively used in the plants for corrosion monitoring.INTRODUCTIONConventional corrosion-monitoring techniques such as weight-loss coupons to assess corrosion damage are commonly used in plants1. However, the use of coupons is not only labor-intensive, but also does not deliver real-time corrosion data, thus effectively serving as a “backwards-looking” monitoring tool. Linear polarization resistance (LPR) probes have the advantage of providing the operator with accurate, real-time corrosion rate data; however, the probes can only be deployed in conditions where the measured environment possesses certain minimal conductivity."

Jan 1, 2012

By N. Staroselsky

"Significant energy savings are often possible for centrifugal compressors operating in parallel by improved control strategy and improved instrumentation. Blow-off can usually be reduced by improved surge control combined with a better control strategy for loading and unloading the group of machines. More precise and stable pressure control then becomes possible. This improved control strategy will also decrease the frequency of operation near the dangerous limits of surge or overload or overspeed. A sample station of mixed centrifugal and reciprocating compressors is examined and a substantial energy saving with the recommended control strategy is projected from operating data. Present Operating Conditions of the Compressed Air StationThe Compressor StationThe compressor station described here has three centrifugal compressors and three reciprocating. It supplies a mine in New Brunswick.Compressed Air and Power ConsumptionFigure I and Figure 2 provide graphs of air consumption and pressure changes based on the owner's data.During the typical two-shift operating day (Fig . I) in the non-productive shift (midnight to 8:00 a.m.), the consumption stays at a level of 9,000 SCFM. This corresponds to a pressure of 110 PSIG. Then, after 8:00 a.m ., the air consumption starts to increase and th e pressure decreases. Around 10:00 a.m., the consumption reaches its maximum level at 97 PSIG. Around II :30 a.m., the air consumption starts to decrease because of the production drop during the lunch break of the first shift. Pressure increases again up to 109 PSIG. After the break, consumption rises to its maximum level over 16,000 SCFM andpressure drops to 97 PSIG.Around 2:30 p.m., the air consumption drops sharply to 9,000 SCFM because of the production decrease to zero level. This drop results from changing of shifts. The pressure at this time increases again up to 110 PSIG. The second shift (2:30 to II :30 p.m.) is an alogous to the first.During the three-shift operating day, the break around 4:00 . a.m . and the shift change around 6:30 a.m. cause sharp drops in air consumption. The pressure for almost the entire night shift stays near 110 PSIG because the station is working with blowing-off even under the maximum consumption. The analysis of Figures I and 2 shows that the pressure varies with the air consumption changes. During non -productive time (non-production shifts , shift changes and breaks) or during the night shift, the total station capacity is proportional to the discharge pressure. By decreasing the level of this pressure up to 97 PSIG, the flow of the station may be decreased during the non-production time as follow s:"

Jan 1, 1980

By Paul B. Batten

Shutdown is a generic term for what may be called an Outage, Turn Around (TAR) or Overhaul etc. Running a plant shutdown well has always been key to the financial contribution of a mine. However, something important has changed. The post pandemic reality is that it is harder to retain workers and many of those near retirement just didn’t come back to work. This is creating a shortage of experienced people and a workforce that changes employers easily. We are seeing the impact of this manifested in the erosion of established maintenance and supply chain processes that now struggle to yield the plant runtime that could once be taken for granted. The scope, cost and duration of a shutdown varies widely depending on the nature of the work and the equipment being renewed. The PM of an electric shovel might require a week of downtime and cost $100,000. A gold plant may need to go down for 3 days when its time to change mill liners and cost $500,000. A turnaround in a refinery can take more than a month and cost multi millions. Despite the huge differences.

Jan 1, 2023

By Robert B. Parsons

"The 1994 Quebec Budget included a significant overhaul of the mining duties sys-tem in that province: broadening the base and lowering the rate, all in the name of “ensuring the integrity of the taxation system"" and ""enabling the State to collect fair compensation "". The reforms hit hardest on the small, lightly-capitalized producer, by repealing the basic annual exemption, limiting the refund for losses, and significantly reducing the investment and processing allowances. There is some relief provided in the form of faster depreciation rates and a lower nominal tax rate, but the thrust of the overhaul is clear -higher taxes on the mining sector.IntroductionAlthough Quebec's mining tax regime represents under 10J0 of the province's revenue base, and was significantly reformed in 1979 and 1985, the May 13, 1994, provincial budget introduced further significant changes to the Mining Duties Act, The hope (on the part of the province) is to reduce the provincial ""subsidy"" for mining by $20 mil· lion per year by 1996."

Jan 1, 1995

By A. Supomo, H. Resendiz, C. Burbidge

"Freeport-McMoRan Inc. (FMI) commissioned the expansion of the Morenci Metcalf concentrator in 2014. The concentrator included many design and equipment innovations, including the first-of-its-kind Metso Hydraulic Roll Crusher (HRC), variable speed ball mills and variable speed crushers. In addition to the innovative design, FMI commissioned the Metso APC team to design a realistic process simulator and the plant APC. The process simulator was utilized to train operators before commissioning, which led to a smoother plant start up. The plant APC utilized the concept of dynamic constraint control, which controls the feed to the primary ball mills by “pulling” the tons from crushed rock storage bins, which then automatically are filled by the upstream HRC and secondary crushing circuits. The primary ball-mill control also adjusts the water addition to the cyclone clusters to avoid overload and achieve sufficient grind size. The constraints include in-circuit constraints for feeder capacity, screen-deck capacity, ball mill power, cyclone mass flow, pump capacity and pump motor capacity. The APC system was implemented shortly after the start of commissioning and immediately demonstrated increased throughput and an ability to highlight and quantify process constraints and bottlenecks. The following paper outlines the control strategy, discusses system implementation, results and challenges.INTRODUCTION The FMI Metcalf Concentrator is located in Morenci Arizona on the site of the old original Concentrator. The new Metcalf concentrator started operation in May of 2014. This plant was designed for an average of 63,500 tpd (70,000 stpd), increasing the total Morenci concentrator complex production to a nominal 113,400 tpd (125,000 stpd). The process flow diagram is shown below in Figure 1.The process consists of primary crushing feeding a coarse ore stockpile followed by secondary crushing operating in closed circuit with vibrating screen decks. The screen undersize feeds the first of its kind Metso hydraulic roll crusher (HRC) operating in a closed circuit with vibrating screens. The primary crusher is a Metso 60x110 gyratory crusher. Secondary crushers are Metso MP1250 Crushers with variable speed drives. Secondary crusher discharge is recycled to the dry screen feed bin and screened with oversize returning to secondary crushing and undersize feeding the Metso HRC3000. The product from the 3.0 meter X 2.0 meter roll crusher is wet screened with the undersize feeding the grinding circuit, which is comprised of two each 24-foot diameter by 40- foot-long variable speed ball mills running in parallel with each in closed circuit with a cyclone bank of 12 cyclones. The wet screen oversize is recycled to the HRC feed bin."

Jan 1, 2019

By SANDVIK WHITE

The mining industry produces approximately 4-7% of global greenhouse gas (GHG) emissions. It is fundamental for mining operations to take immediate sustainable action to actively contribute to an emissions-free future for the next generations. The mining industry has traditionally relied heavily on diesel technology and transitioning to more sustainable solutions requires change management to drive cultural acceptance and new product development. Sandvik was interested to find out the lifetime emissions of a single drill rig and to compare similar application diesel and BEV drill rigs with same use profile to each other. That led the calculation and pondering towards comparing different countries and mine sites as well

Jan 1, 2023

By Haipeng Li, Jacob Masliyah, Barun Gorain, Jian Huang, Qingxia Liu, Zhenghe Xu, AuTec Innovative Extractive Solutions Ltd.

"Froth flotation is widely used to selectively separate one or more minerals from an ore over a wide range of particle sizes with high efficiency. Bubble–particle attachment is one of the most critical steps in flotation. The objective of this project is to demonstrate the need for an innovative dual bubble generator to improve flotation efficiency. This dual bubble generator was designed to generate two different sizes (micron size and typical flotation size) bubbles. The micron size bubbles generated on the crevices of particle surfaces in venturi type of cavitation tubes enhanced the attachment of fine particles to the bubbles in conventional flotation systems. They also acted as a secondary collector, which has the potential to reduce operation cost and improve flotation recovery. The dual bubble generator was evaluated for a double refractory gold ore with 3g/t Au, 1.5 wt% TCM (total carbonaceous matter) and 0.7 wt% sulfides. The results were compared with those obtained using a commercial bubble generator. Compared with the commercial bubble generator, the dual bubble generator showed not only a higher gold recovery, but also an improved separation efficiency, demonstrating the potential of dual bubble generator in fine particle flotation.INTRODUCTIONFroth flotation has been widely used in mineral processing and waste water treatment. However, flotation has been proven inefficient for fine particle recovery although it becomes increasingly inevitable to process fine particles with the depletion of easy processing ores. The critical problem of fine particle flotation is the low attachment of fine particles to flotation size bubbles due to their low collision rate. Based on a commonly acceptable flotation model given by R =F*[Pc*Pa*(1-Pd)], the probability of bubble–particle collision (Pc), attachment (Pa) and particles detachment from air bubbles (Pd) collectively determines fine particle recovery (R) (Yoon and Luttrell, 1986). Since Pc = (3Dp/Db) where Dp and Db are diameters of particles and bubbles, respectively, bubble size and particle size impact the bubble-particle collision in opposite directions. It is evident that the probability of bubble–particle collision decreases with decreasing the size of particles, leading to a low recovery of fine particles. In this case, reducing the bubble size and/or increasing the apparent size of particles by fine particle aggregation are clear means to improve fine particle recovery."

Jan 1, 2016

By G. A. Frame, J. G. Patterson

The 24,000-tpd Frood-Stobie mill grinding circuit operation and control are described. Changes implemented during the past three years to improve grinding efficiency and capacity are discussed.

Jan 1, 1971

By V. Ushakov, P. Bogdan

Daily production scheduling in a highly dynamic smelter environment has always been a great challenge for the operation management due to a significant amount of uncertainties. Planned and unexpected equipment failures, various energy outages, inaccuracies in flow and mass balancing, manpower availability conflicts and other constraints make the job of daily production planning exceptionally difficult. This paper discusses a general scheduling approach utilized by the production management of the Phelps Dodge Miami Smelter (the Smelter). It also describes logical assumptions and some practical software solutions that have been exploited by the Smelter managers to assist the front line supervisors in dealing with daily planning activities for several years.

Jan 1, 2007

By B. Yamamoto, D. Post, J. De Leon, A. Meike

"This paper describes the theory, design, building, and testing of the passive magnetic bearing stabilizing system which is the core of the passive magnetic bearing system. The stabilizing system is made up of two large magnetic disks opposing themselves with a stabilizing disk in the center which allows the system to self-locate in a null position without the need for external power sources or sensors. When outside forces act upon the stabilizer, the magnetic fields interact with the stabilizing plate to return the system to its null position. Collaboration between two industry leaders has allowed an actual prototype to be built and tested providing real data to prove out the theory.INTRODUCTIONMagnetic bearing/stabilizer systems have many advantages over conventional mechanical bearing systems. These include near-zero drag losses and no need for lubrication since the rotating elements make no mechanical contact with the stationary elements of the bearing system. However all magnetic bearing systems must contend with a constraint known as Earnshaw’s Theorem in the early 1800’s, this theorem asserts the impossibility of constructing a stable, non-contacting, electrostatic or magnetostatic levitation system using only fixed charges or fixed magnetic poles, such as those produced by permanent magnets. Because of the constraint imposed by Earnshaw’s Theorem virtually all present-day commercial magnetic bearing systems are of the “active” type. That is, they employ electromagnets that are powered by amplifiers the inputs to which come from sensors embedded in the bearing system. These sensors are a part of a feedback loop that operates to keep the levitated rotating parts of the bearing stable and centered. The resulting complexity means that active magnetic bearings are expensive, require periodic maintenance, and continuously consume electrical power to energize their amplifiers and their electromagnets.Passive magnetic bearings are, of course, also subject to the constraints imposed by Earnshaw’s Theorem but they solve this problem in a straightforward and simple way, with only “passive” elements that take advantage of a loophole implicit in the derivation of Earnshaw’s Theorem. This loophole is that Earnshaw’s Theorem as derived applies only to static systems, i.e. an assembly of stationary permanent magnets arranged so as to levitate an object containing other permanent magnets. The theorem can be overcome if dynamic effects are taken into account. In active magnetic bearings the “dynamic effects” involve the afore-mentioned sensors, amplifiers, and electromagnets."

Jan 1, 2012

By B. H. Weber

"Industry generally has become noise-conscious and is realizing that damage to the human ear is expected to become more costly than any other compensation. Noise control has been recognized as a necessity and, fifteen years ago, in co-operation among different countries, inter-national organizations were set up to co-ordinate measures against dangerous noise and the development of silencing devices began. Rock drills for underground operations were particularly scrutinized because of the explosive nature of the noise developing from air escaping from exhaust. This paper describes the results and the present stage of development in the reduction and control of noise on rock drills, with special application to their use in mines."

Jan 1, 1970

By John Kostuik

AT the Sladen-Malartic mine, a number of orebodies have been mined, some by shrinkage and others by open sub-level scopes, from which the ore is handled either through a grizzly system or by mechanical loaders. This paper deals with the comparative costs and relative merits of the two handling arrangements. The facts brought out in this comparison have a bearing on the selection of a proper handling method. The mine is in Fourniere township, northwestern Quebec, about forty miles east of the town of Rouyn. It is served by the Rouyn-Senneterre branch of the Canadian National railways. Two vertical three-compartment shafts give access to the present workings. No. 1 shaft, at which the plant is centralized, is the main hoisting shaft, with five levels to 950 feet. No. 2 shaft, 2,400 feet east of No. 1, is under development, with four levels to 725 feet. At the main shaft, the ore is hand-trammed in 1 1/2 tons cars from the scopes to the stations o:i each level and hoisted in cages to surface at a rope speed of 900 feet per minute. Air-operated tipples are used to dump the ore through grizzlies of 14-inch openings into a surface bin of 150 tons capacity. The ore hoisted at No. 2 shaft is trucked from the headframe bin to the mill. Milling commenced in January, 1938, ar a daily rate of 250 tons. Within two months this rate was increased to the unit's maximum capacity of 325 tons. A second unit to treat a further 325 tons daily was installed in April, 1939. The orebodies mined at No. 1 shaft are parts of a silicified zone at the contact between syenite porphyry and greywacke. The zone is ten co sixty feet wide, strikes easterly, and dips to the south at 55 to 85 degrees. The hanging-wall of the zone is marked, though not precisely, by a strong gouge fault. Locally, the boundary of silicification may be as much as twenty feet either above or below the fault, but for practical mining purposes the fault is the hanging-wall of the ore-zone. The footwall roughly parallels the fault, but as an assay wall it is usually irregular in detail. The ore is dense and hard, a siliceous replacement of both porphyry and greywacke, mineralized with fine disseminated pyrite.

Jan 1, 1941

By J. F. MacGregor, M. Hou, D. Hodouin

"RésuméDe nouvelles méthodes efficaces sont maintenant devenues nécessaires pour traiter les quantités massives de données en temps-réel que collectent les ordinateurs industriels modemes. Les méthodes statistiques multi variables comme l'analyse en composantes principales et la projection sur des structures latentes sont des méthodes analytiques bien adaptées aux données industrielles bruitées et mal conditionnées. L'efficacité de ces méthodes est illustrée sur des données historiques collectées dans une usine de broyage et de flottation. Trois cent cinquante observations de quarante quatre variables de procède ont été utilisées pour démontrer les aptitudes de ces méthodes pour l'analyse préliminaire de données, la classification des régimes opératoires, le contrôle de qualité et la modélisation empirique des precedes.AbstractBecause of the availability of powerful industrial computers which collect huge amounts of real-time data in mineral processing plants, there is a need for efficient methods to extract relevant information from them. Multivariate statistical techniques, such as principal components analysis (PCA) and projection to latent structures (PLS), are well suited to analyze these large sets of noisy and ill-conditioned data. The power of PCA and PLS is illustrated on historical data from a grinding and flotation plant. Three hundred and fifty observations of forty-four process variables are used to show the capacity of these techniques for preliminary data analysis, classification of operating regimes, process monitoring, and process empirical modelling."

Jan 1, 1993

By A. C. Stevenson

"There are many critical application issues that affect all AC drives, but there are several that are absolutely mandatory for pulse width modulated (PWM) AC drives. If these rules are not followed, the drive system will have insulation, bearing EMI or noise problems. Pulse Width Output VoltageFigure 1 shows the output current of a typical pulse width modulated (PWM) drive. This is, of course, not a clean sine wave thus will have a lot of very significant harmonics. In fact, the harmonic spectrum is directly related to multiples of the carrier switching frequency plus side bands related to the basic output frequency. A typical spectrum for a PWM source bridge switching at 5 kHz is shown in Figure 2. Notice that the spectrum has multiples of the 5 kHz switching frequency and the number of side bands gets larger as the harmonic number increases.IGBT Switching TransientsWhenever we have PWM inverter switching, voltage transients are formed that propagate (usually at about half the speed of light) down the power cables to the motor just like in a radio frequency transmission line. If we do not terminate these transmission lines (motor cables) properly, the voltage pulses will be reflected when they reach the motor end and will be transiently increased up to twice their original amplitude.This transient voltage rise, shown in Figure 3, is important for three reasons:1. Insulation Voltage Stress — Higher voltage stress in the motor connecting cables and motor insulation will lead to a shorter insulation lifetime. If any of the voltage transient peaks exceed the insulation corona discharge level (partial discharge level), the insulation will gradually degrade with each voltage pulse. When it has been sufficiently degraded, it will then fail.Most new “inverter rated” motors have triple layer insulation which has a 1600 to 2000 volt partial discharge level. This will make them suitable to withstand the double voltage peak transient from a 600 volt inverter. It is wise to make sure of this fact, since a “standard” induction motor will only withstand about 1200 volts. Use of a standard motor in this application would shorten its life drastically. This can sometimes be as little as a matter of hours."

Jan 1, 2000

By C. Jewell, G. H. Rupay

"67 - 2:15-3:00Regeneration of Hydrochloric Acid from Waste Pickle Liquor Using a Fluidized Bed Reactor System. G. H. RUPAY and C. JEWELL, Dominion Foundries and Steel Ltd., Hamilton, Ont.The disposal of acidic waste liquors from pickling processes has always been a problem for the steel industry. With increased awareness toward environmental control and the problems acidic wastes create, processes utilizing recovery and regeneration of the waste acids are becoming more popular. This paper describes the Keramchemie/Lurgi process for regenerating hydrochloric acid from waste pickle liquor using a fluidized bed reactor system. The process parameters are outlined, together with a brief description of the equipment. This is followed by a discussion of the operating problems and concludes with economic data."

Jan 1, 2000

By D. Sammut, F. Houllis, J-L. Huens, J. Moyes

The Intec Gold Process has been developed as a halide-based alternative for the recovery of gold from refractory sulphide deposits. The halide medium allows sulphide oxidation and gold extraction to be performed concurrently at moderate temperature and atmospheric pressure sourcing oxygen from direct air injection. The dissolved gold is loaded onto activated carbon and stripped in a conventional Zadra circuit. High gold extractions have been achieved from a range of refractory gold concentrates at laboratory scale, which has led to a continuous locked-cycle pilot plant program. The pilot plant operated at >99% availability, with a maximum of 96.5% gold extraction from a concentrate containing 58.6 g/t gold. >99% of the dissolved gold was loaded onto carbon at up to 1% w/w, with no loss of carbon activity detected over five loading/washing/elution cycles. This paper describes the process and presents both laboratory and pilot plant results as well as economic data from two costing studies.

Jan 1, 2005

By S. E. Wolfe

AKNOWLEDGE of the density of a pulp or suspension is frequently required by the millman, to whom fluctuations in density, which occur in all mill circuits, are of importance and interest. There ,are many w.ays currently in use to determine density and probably the most common method is to take samples of the pulp. The proper sampling of the material is no easy matter, particularly when the pulp contains a sand fraction which settles rapidly. For example, when filling a liter container from the overflow of a classifier, it is al-most impossible to fill the can completely and yet prevent overflow. If there is an overflow, the pulp remaining in the can invariably has an excess of sand and the indicated density will be too high. To surmount such difficulties, and to obtain a continuous indication of the density of a pulp at any desired depth, the simple indicator shown diagrammatically in Figure l was designed by the writer in 1951. Its component parts, numbered as in Figure 1, are as follows.

Jan 1, 1958