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By A. W. Khair

This paper presents an analysis of respirabie dust generation due to the action of a continuous miner. Underground coal cutting by a drum-type continuous miner was simulated in the laboratory using a specially designed unique automated rotary coal cutting simulator (ARCCS). An analysis of -400 mesh particles was done on gravity collected material. Samples of entrained dust were collected through the use of cascade impactors. Both samples were analyzed for size distribution and particle shape. Using the simulated coal cutter permitted variation of operating and in-situ parameters to provide information on the effects on generation of -400 mesh particles. In these tests coal blocks with an approximate dimension of 18 in. x 15 in. x 6 in. (45.7 cm x 38.1 cm x 15.2 cm) were first subjected to confining pressures, equivalent to in-situ conditions. Such blocks were then cut by the cutting head of the ARCCS, thus simulating the action of the continuous miner in underground coal mining. During the tests under a particular set of in-situ and operating parameters a number of other parameters such as 1) penetration of bit into coal, 2) penetration resistance (thrust and cutting pressures), 3) rotating velocity of cutting head, and 4) acoustic emission activity in the coal block were monitored. After each cutting cycle the fractured surfaces were photographed and a velocity survey was conducted by using a sonic technique. At the end of each experiment the cutting paths of the bits in coal were photographed using an optical microscope with an attached camera.

Jan 1, 1985

By C. Alan Tapp

Introduction Mine sampling determines the practicality of any mining operation. Improper sampling can result in an incorrect appraisal of present production and future potential. Therefore, the mine department in charge of ore-reserve calculations and mine sampling should be overseen by competent and experienced professionals with technical backgrounds qualifying them to produce accurate results. Sampling is a process by which portions of an ore body are collected and analyzed to estimate the average mineral content of the entire ore body. It is incorrect to assume that a large number of samples eliminates any errors in the sampling method. To obtain unbiased samples, proper sample location with respect to rock type and mineralization is just as important. The sampling procedure must yield correct results for the type of mineral deposit, and careful consideration should be given to whether or not the sampling technique has been developed to an extent sufficient to eliminate as much human error and bias as possible. Only after the ore has been mined and milled is the sampling accuracy known. Sampling also provides information about the bulk composition of the ore for mineralogical and metallurgical tests that determine the economic ore-waste boundaries and the geologic trends for exploration. Actual mining plans can be developed from this information to maximize profits. Accurate sampling is critical, and thus must be approached in a scientific manner. Sampling Techniques Sampling practices and techniques are as varied as the mines in which they are used. The method(s) chosen must be tailored to suit the company and mining needs. For instance, tabular uranium deposits, vein gold deposits, and porphyry copper deposits pose special problems in conducting unbiased sampling. The mine geologist or engineer in charge must develop a sampling method, test it in a sample area, and then critically evaluate the results. If the results from the test area are accurate within the economic limits established by the company, they then may be adopted for general use in the mine. Four routine sampling methods are suitable for specific sampling objectives in the daily mine routine: (1) channel sampling, (2) chip sampling, (3) grab sampling, and (4) bulk sampling. The final sampling results depend upon how the four methods are combined to accurately determine the grade of the ore body. When used in conjunction with each other during different stages of mine development, the channel, chip, grab, and bulk sampling methods provide an in-house check or a comparison by which mining methods and sampling procedures can be evaluated. However, the most valid check is based upon the daily mill production. Channel Sampling Channel samples consist of cuttings collected from a groove cut into the rock about 102 mm (4 in.) wide and 19 mm (0.75 in.) deep. Various tools ranging from a 1.8-kg (4-lb) hammer and moil to a pneumatic chisel can be used to cut the sample. Accessibility and rock hardness determine the applicable sampling tools. Before attempting to take a sample, the rock surface must be cleaned thoroughly; the method of cleaning depends upon the amount of mine dust accumulated on the surface or the degree of alteration of the rock surface. Typical cleaning methods 'employ a wire brush, water, or chipping a fresh surface. Next, the sample outline is marked on the prepared surface, taking care to choose appropriate sample loca- tions. After determining the proper sample outline and length, the sample can be chiseled out, catching the rock fragments on a canvas tarpaulin on the floor, in a powder box, in a canvas bag to avoid contamination, or by some other suitable means to capture all of the sample. Vertical veins present a special problem because the drift's back usually is arched, not square. For example, Fig. 1 shows that if sample intervals are measured from A' to D', the length of the sample interval is greater than the true vein width, resulting in an incorrect calculation of the ore reserves. The correct method would collect three samples at A'-B', B'-C', and C'-D', using either actual measurements in the mine represented by A-B, B-C, and C-D or trigonometric calculations to determine the true ore thickness. Then, each sample can be weighted by grade and true thickness for the vein. Channel lengths usually are a maximum of 1.5 m (5 ft), and it is good practice to divide longer samples into smaller intervals according to structures, changes in rock types, or differences in rock hardnesses. The influence of those features on the mineralization then can be determined. Chip Sampling Chip sampling is a variation of channel sampling used when the rock is too hard to channel sample economically or when little variation in the mineral content indicates that this sampling method will yield results similar to those of channel sampling. Rather than cutting a channel in the rock, small chips are flaked off at regular intervals over the entire face or area being the mine. sampled. Care must be taken to assure that the sample is representative of variations in the rock hardness and type. hi^ method is fast and useful in preliminary evaluations, but it should not be used for quantitative ore-reserve calculations. Grab Sampling Grab sampling is a fast method for double checking either channel or chip-sampling procedures, and, in some instances, mine production can be estimated from carefully taken grab samples. Grab sampling takes equal amounts of material at selected intervals over a mine dump, a muck pile, or from an ore car to estimate its Channel Sampling mineral content. Generally, this method is not considered reliable. Many independent variables can affect this type of sampling process. Thus, if the ore occurs in the softer fraction and a proportional amount of the result-

Jan 1, 1982

By R. Keith Evans

Potential large scale uses in secondary battery systems and fusion reactors together with a steady increase in demand for conventional applications, particularly in aluminum smelting, has resulted in an increasing interest in lithium and its compounds. Current world requirements are met from both granitic pegmatites and non-pegmatitic sources and although the emphasis in this short paper is on the pegmatitic minerals, and, in particular, on their "direct usage" applications, a short summary of other sources and requirements for chemical production is included for the sake of completeness.

Jan 1, 1977

By Timothy D. Gardner, Christopher Mark

Coal mines in the Illinois Basin have not engaged in pillar recovery for many decades. In large part, this is due to the exceptionally weak nature of much of the roof in the region. But, as room-and-pillar mining is conducted at greater depths, and larger pillars become necessary, recovering them becomes more attractive. Recently a western Kentucky coal mine became the first in recent times to successfully employ full pillar recovery. This paper describes the many challenges that were overcome during the process. From the beginning, the focus was on protecting the miners from roof instability, using cable bolts, mesh, mobile roof supports (MRS), and engineered final stumps. Two short test panels were extracted first, and the results were used to adjust the support pattern and mining sequence. Further adjustments were made based on subsequent experience. To date, seven panels have been recovered without a ground fall injury.

Jul 1, 2023

By John E. Edkins

Metal sulfides, chiefly pyrite and mFnor sphalerlte zssociated with che Herrin (No. 6) coal member of the Pennsylvania Carbondale Formation, have been concentrated in a coal refuse deposit in southern Illinois. Oxidation of pyrite has produced highly acid waters with high concentrations of iron, zinc (up to 200 parts per million) and toxic trace elements that have leached downward to a water system perched on glacial drift. Chemical, petrographic, low-temperature ashing and x-ray diffraction were performed on cores. The data show that economic recovery of zinc and other trace metals is unlikely at this site. Energy (coal) recovery at the Superior Washer site is possible if resultant environmental problems are considered in the planning.

Jan 1, 1981

By L. R. Chirinos

The Tintaya mine of BHP Copper, located in Southern Peru, includes a copper oxide deposit hosted in a mineralized skarn zone. The ore contains large amounts of clays and high acid consuming species resulting in low heap leaching performance. A treatment scheme was proposed that included a wet screening separation. The coarse fraction would be treated by heap and the fines by agitation leaching. The dissolved copper would then be recovered through solvent extraction and electrowinning (SXEW). Testwork determined the optimum heap leaching conditions to treat the oxide in on/off pads of 3 meter height with an initial acid cure followed by variable acid strength during irrigation. The method resulted in a reduced acid consumption and good copper recoveries.

Jan 1, 1997

By Peter Zhang

The immediate roof at the test site consisted of laminated clay shale that is likely to be susceptible to weathering. With seasonal dry-wet cycles in the mine ventilation air, the roof in the intake air would deteriorate and lose integrity over time. In many instances, the weathering-prone roof would gradually scale off piece by piece between bolts and over the entry corners. In some long-term entries, roof weathering could develop up to 2-3 ft deep with columns of bolted roof hanging under the upper intact roof. If wire mesh is used, the roof bags down and reduces the entry height, and the weight of the bagged roof tends to pull the bolts out and poses a safety hazard. An effective measure is always sought to support this type of weak roof that is sensitive to moisture degradation. One solution is to seal the roof shortly after entry development to prevent moisture penetration so that roof integrity can be maintained for the long term. In this application, a polymer-based sealing material was tested in the Rockspring mine for weathering protection and reinforcement. The material is a one-component polymer powder for spray application onto the roof and rib. The sealant material is mixed with water in the spraying nozzle to apply to the roof and rib as a paste. The product sets within 5-10 minutes and forms a membrane as thin as about 1/8-in. The membrane will quickly develop tensile and bonding strength within minutes and completely cure within a few days. Through sealing, bonding and lateral reinforcement, the integrity of the weak roof can be maintained. The material has been tried in a long-term evaluation over several months in a set of main entries in the Rockspring mine owned and operated by Rockspring Development, Inc., affiliate of Foundation Coal. Preliminary evaluation has shown that the material is an effective and economical solution to ensuring the long-term stability of weathering-prone roof.

Jan 1, 2009

By Steve Wirch, Robert Jankowski

The issue of dust control in underground coal mines has been extensively studied by both government and industry. This research work has resulted in many techniques which control the dust or help miners avoid it. Control techniques either prevent the dust from becoming airborne or cleanse the air before it can be inhaled. Avoidance measures minimize the exposure of miners to the airborne dust by blowing the dust away from work areas or making it unnecessary for a miner to occupy a dusty region. One of several successful dust control measures in continuous miner sections is the use of a machine mounted scrubber which cleanses the air and helps to prevent the contaminated air from reaching areas frequented by mine personnel. Research on the application of scrubbers on longwall shearers began in the 1970s and continued into the 1980s. The most successful projects showed only moderate improvement when a scrubber system was mounted on a longwall shearer, and the less successful projects actually increased worker dust levels. There are many reasons that scrubbers have not been successfully applied on longwalls. The most significant of these is that longwalls have across the face ventilation and generally have high face air flows. Scrubbers tend to work best when they are the primary cause of ventilation. Therefore, their capture efficiencies on longwalls tend to suffer because of the exposure of the drums to the primary airflow. Other reasons scrubbers have not been implemented on longwall s include the successful application of an excellent water spray system, effective cutting techniques, and dispersion of dust sources. These techniques can help control drum generated dust, increase production, and limit the relative effectiveness of a scrubber.

Jan 1, 1995

By Hans von Michaelis

Metallurgists are trained to seek synergisms and to optimize trade-offs in the selection of processes and flowsheets. The subject of my paper and the focus of this entire conference is on synergisms involving more than just metallurgical recovery, but encompassing mining and environmental management too. Operators have always known that by recycling tailings water they could recover some cyanide and lime values or reduce the amount of new flotation reagent additions. The trade-offs have changed at many US mines today where concern about avian mortality necessitates that water in the tailings pond be detoxified. This is just one example of how selection of processes and technology today requires integration of environmental management. MUDDER & GOLDSTONE (1989) showed how cyanide can be recovered from tailings slurries by an acidification­volatilization-reabsorption (A VR) process which was installed in New Zealand, and which in 1992 is being commissioned also at Nerco DeLamar Silver Mine as described by OMOFOMA & HAMPDEN (1992). FRICKER (1990) and FRICKER & OWERS (1992) show how using A VR to recover cyanide from pregnant pulps ahead of gold recovery improves the yield of recoverable cyanide while improving the performance of the gold recovery step and detoxifying the tailings. This is an excellent example of the synergisms that can be achieved ,y applying a "systems approach."

Jan 1, 1992

By Rainer Antretter

"THE CHALLENGE The 14km long, Arlbergtunnel, closed for public traffic during summer 2015, receiving a comprehensive and substantial renovation from 2015 to 2017. The main works discussed here, carried out during 2015, comprise 37 drill and blast SEM/NATM emergency escape tunnels from road level to the ventilation duct plenum have to be constructed as well as eight additional lay-by niches and three transformer tunnels. This presentation comprises the construction ventilation design, designed according to national regulations, suitable for 150 employees working 24/7 simultaneously at more than 40 single working sites lined up along the tunnel. The ventilation-system chosen was utilising two existing shafts for intake/discharge and a cross passage to surface, to handle a total fan power of 1.600kW. DESCRIPTION OF RENOVATION WORKS Linking Tyrol and Vorarlberg, two Federal States of Austria, the Arlbergtunnel is a single tube two-way road tunnel with vent duct plenum, constructed in the mid-1970s. According to latest EU legislation, additional escape exits have become obligatory. The existing seven cross passage links to the adjacent Arlberg Railway Tunnel, with average spacing of about 1.500m constructed in 2007, an additional upgrade to shorter escape spaces of approx. 400m was now required to comply with the updated legislation. Additional transformer tunnels, lay-by niches and small niches for emergency maintenance use, cleaning and other purposes, as well as a the installation of a new fire main in the invert, coupled with the simultaneous replacement of virtually the entire power and signaling cables, generated several dozen small and large single sites distributed along the 14km of tunnel.Purpose of the 37 walkable emergency escape tunnels is to reach the “upper deck” of the Arlbergtunnel, the vent duct plenum. These have an 180deg curve in plan, inclined at 10% and approx. 60m (65yd) long tunnels, excavated using drill and blast method starting from road level and working upwards to the level of an “intermediate soffit”, the vent duct plenum in the crown of the tunnel. The vent duct plenum is separated into a fresh air part and an exhaust air part, shown in Figure 1. The escape tunnels end with a pressure door in the fresh air section of the ventilation duct plenum. From there illuminated signs show the shortest escape route to the safe area between the road tunnel and the railway tunnel, as shown in Figure 2."

Jan 1, 2016

By D. Tahija

"Hecla's Greens Creek silver-gold-lead-zinc mill began using carbon dioxide rather than sulphuric acid to control pH in April, 2015. High pH levels in the grinding and lead flotation circuits are caused by the presence of re-mined cemented paste backfill in mill feed and need to be lowered to achieve good flotation response. Carbon dioxide has proven to be quite effective at controlling pH in the lead circuit with greatly improved pH target attainment. The allowable amount of carbon dioxide used is not limited by effects on lead-zinc selectivity and by poor froth characteristics, as was the case with sulphuric acid. Startup and implementation went smoothly, with few operational issues needing to be resolved. Early results from implementation of the system and its effects on mill performance will be presented. INTRODUCTION Hecla Greens Creek is a silver-gold-lead-zinc mine producing flotation lead and zinc concentrates, as well as a gravity gold concentrate. Besides their base metal contents, both the lead and zinc concentrates carry precious metals. The circuit is largely conventional, with SAG and ball mill grinding being followed by graphite removal preflotation, then conventional lead flotation and conventional zinc flotation. Both rougher concentrates are treated in regrind steps, followed by cleaner flotation. The cleaners tails are treated in an unorthodox bulk circuit to produce a low-grade zinc-lead concentrate marketed to Imperial Process smelters (1). BACKGROUND Backfill and Flotation pH The Greens Creek mine is an underground operation in which mined areas, after ore extraction, are backfilled, using rammed paste or pumped slurry. The backfill consists of mill tailings to which approximately five percent Portland or similar cement is added to enhance its compressive strength. Later mining near backfilled areas inevitably results in a considerable amount of old backfill being mixed with new ore before being shipped to the mill. Depending on orebody geometry, mining methods etc., the amount of backfill in mill feed is often 20% to 25% and sometimes even higher. Commercial cement, and consequently backfill prepared using it, contains excess lime. Because of this, backfill in mill feed is indistinguishable from the addition of a large amount of lime, so mill natural pHs often range above 10 or even 11. Similar situations have been recognized for many years at mines throughout the world (2)."

Jan 1, 2016

By John Armstrong, Michael Savill, David Powell

Hong Kong is an intensively developed region and has the highest vehicle densities in the world. In 2000 there were 6.6 million people and 580,000 vehicles using 1,890 km of road covering the 1084 km 2 territory. The high vehicle and population densities together with the difficult terrain have seen road tunnels emerge as key components both in the current and future road transportation network. Currently there are eleven operating highway tunnels in Hong Kong, seven government owned and the remaining four “build, operate and transfer” franchises, see Figure 1. The very first tunnel was the dual two Lions Rock Tunnel completed in 1967and the latest the dual 3 lane Tai Lam Tunnel opened in mid 1998. Figure 2 shows the alignment and statistics for all 11 Hong Kong tunnels. Looking ahead, Hong Kong has embarked on the study and design of the next generation of major highways and as many as a further seven tunnels are currently under feasibility study or detailed design. This seems an opportune year to produce a broad appreciation of the fire strategy, life safety and ventilation practices in Hong Kong not only for the existing tunnels but the new standards and requirements for the next generation of Hong Kong tunnels. This paper provides an overview of the fire strategy, life safety and ventilation of Hong Kong’s existing and planned tunnels. The paper pays particular attention to the areas where the unique conditions and requirements in Hong Kong impacts on tunnel and systems design and the solutions adopted to overcome these challenges.

Jan 1, 2001

By Jamal Rostami, Tala Tahernia

TBM utilization rate is a component of machine performance prediction and critical for developing a reliable estimate of the construction completion time and cost of the tunnel. Estimation of the utilization rate involves identifying and quantifying the time dedicated to each activity in a tunneling jobsite. Ring building is a common activity in TBM tunneling and takes a large amount of tunnel excavation time when using shielded TBMs. This paper concentrates on the effect of tunnel diameter on the duration of downtimes related to ring building and examines the impact of machine diameter on downtimes. For this purpose, the dependency of segment installation time to segment configuration, and also the diameter of the tunnel was investigated. Furthermore, the ring building time for four tunnels with different sizes of diameters and a variety of ring arrangement were analyzed and the relationship between TBM diameter and segment installation time and consequently TBM utilization was evaluated.

Jun 13, 2021

By S. R. Maynard

The Ortiz Mountains lie 25 mi (40 km) northeast of Albuquerque, New Mexico in Santa Fe County (Figure 1). Approximately 350,000 ounces (11,000 kgs) of gold have been produced from the Ortiz Mountains since the 1820s. The 100 square mile (260 square km) Ortiz Mine Grant was secured from the Mexican government in 1833 by Jose Francisco Ortiz for the purpose of mining gold. The Grant has remained more or less intact to the present. The mineral rights are currently owned by Ortiz Mines, Inc. of Joplin, Missouri and are leased to LAC Minerals, USA, Inc. (west half) and to Gold Fields Mining Corporation (east half).

Jan 1, 1989

By Wayne Wride, Amy Lamb, Debra Sonntag

In today's "information age", we have the ability to collect volumes of data about a company's performance. The challenge is to turn that data into information employees can understand and use to fine-tune equipment, modify work processes, and ultimately manage production. Software programs have increasingly given end users control over what data is used and how it is presented. Kennecott has implemented an information system capable of collecting and storing data at the primary level. This enables plant personnel to transform historical data into information for action. Kennecott plans to expand its data collection and use trending and reporting capabilities to move toward a fully optimized operation.

Jan 1, 2000

By William S. Pintz, William A. Vogely, Charles J. Johnson

This chapter on the role of minerals in developing economies is oriented toward economic policy issues. The discussion and analysis cut across the technical, economic, legal, and policy fields. The goal of this chapter is to pro- vide relevant background information important to individuals involved with the minerals sector in developing countries. Where possible, trends are shown to provide a basis for understanding the evolving role of minerals in developing economies. This chapter is divided into the following five sections: (1) characteristics of developing countries (which presents selected statistical comparisons); (2) government objectives in developing countries; (3) government policy formulation in developing countries; (4) determinants of future trends, and (5) a summary of the chapter's major points combined with the authors' view. CHARACTERISTICS OF DEVELOPING COUNTRIES There are 155 nations in the world categorized as "developing countries." In total these nations represent about one third of the value of the world's mineral production, three quarters of the world's population, and over half of the world's land surface area. The group of so-called developing countries is quite diverse and there are exceptions to almost any general observation about the group as a whole. Most definitions of the term "developing country" are based on levels of per capita income. However, if per capita income is the sole criterion used in categorization, then several oil-exporting countries would jump from the category of developing country to the category of developed country.a Obviously, this results in a poor fit with respect to other measures. In general, the majority of developing countries can be characterized by relatively low per capita income, high population growth rates, high levels of unemployment, low levels of education, short average life ex- pectancies, income distribution skewed toward the highest 20% of the population, and a large share of exports represented by primary commodities. b For the purposes of this chapter a slightly modified version of the widely used World Bank system of classification (shown in Table 1.2.1) is used. As summarized in Table 1.2.1, developing countries are divided into three main groups based on estimated gross national product (GNP) per capita. It should be noted that the high- income, oil-exporting countries have characteristics of both developing and industrialized countries; however they are included for most statistical comparisons within the group of developing countries. Of the 155 developing countries in the world, approximately half produce minerals other than common building materials, and only 32 account for more than five percent of world pro-

Jan 1, 1985

By R. L. Miller

"Why should we care about diesel quality amidst the complexity of mining for minerals? Mining companies use a large amount of diesel fuel in their worldwide operations, both for moving ore from the mine to the processing mills or transportation hubs, and to generate power for onsite processing. This creates a large carbon footprint and poses both environmental risk with the production of emissions, and public perception of how those companies do their business as stewards of the environment while incurring a huge fuel expenditure. To improve diesel quality and create incremental value and greater environmental stewardship, the opportunity is broken down into several segments: 1. Mining industry diesel consumption 2. Fuel quality issues 3. Impacts on operations, economics, and emissions 4. Potential solutions 5. How improved fuel quality saves fuel expenditures 6. Economics of improved fuel quality 7. Recommended testing process 8. Fuel quality analysis checklist MINING INDUSTRY DIESEL CONSUMPTION The average grade of mined Australian ore bodies has halved, while the waste removed to access the minerals has more than doubled over the last 30 years, thus increasing energy consumption by 70%, (http://eex.gov.au/industry-sectors/mining/). Energy consumption and intensity in mining and mineral processing is rising at around 6% per annum. The mining industry is a huge consumer of diesel fuel worldwide, and the SRS Rocco Report of 4 August 2014 gives a better picture of recent trends. To better understand the reasons to reduce both fuel costs and consumption, we need to compare metrics on the amount of diesel consumed per each ounce of gold produced over the last decade. The rate of diesel consumption in gallons per each ounce of gold produced for the top five worldwide gold producers has doubled in the last 8 years from 12.7 gallons per ounce in 2005 to 25.8 in 2013 as shown in Figure 1 below.This is caused by 1) lower ore grades requiring more hauls to get same amount of finished gold product, and 2) haul trucks moving ore from deeper sources in open pit and underground mines. For one large multi-national gold mining company, the 2005 waste rock / production ratio was 52 metric tons/gold ounce; by 2013 that ratio had grown to 113 metric tons/gold ounce per the same SRSrocco 4 August 2014 report. Using the metrics above, the top 5 gold miners used over 591 million gallons of diesel fuel in 2013. The cost of diesel in dollars per ounce of gold has increased from $30.48 in 2005 to $101.14 in 2013, an annual appreciation of 16.2% as shown in Figure 2 below."

Jan 1, 2017

By Paul F. Ph. D. Ziemkiewicz, Courtney D. Black

According to the American Coal Ash Association, 105 million tons of coal combustion products (CCP) were produced by the power generating utilities in 1997. Of that total, 1.68 million tons were used in mining applications (ACAA, 1997). Results have ranged from the environmentally beneficial to neutral and, in some cases, detrimental. Twenty years ago coal ashes: bottom and fly ashes constituted nearly all CCPs. With the shift to new emission control technologies at power plants, however, large volumes of new products are being generated. Many do not lend themselves to traditional ash applications such as cement formulation. Many CCP disposal sites are not documented with reliable pre and post application monitoring. In this report we discuss types of CCP, their relevant characteristics and the mining environment. We have attempted to identify a range of documented applications and to draw conclusions about their environmental effects including benefits and adverse impacts.

Jan 1, 2000

By M. Brändström, R. Dube, J. Moyo, T. Perkins, G. Bermudez, L. Bartsch, C. Smith, R. Sorensen

The Kennecott Copperton concentrator is currently the bottleneck for the Kennecott operation and several projects have been initiated to increase throughput. This increase in grinding circuit throughput has resulted in a coarser grind size which has impacted flotation circuit recovery. Metso Outotec 300m3 forced air tank flotation cells are currently utilized in the rougher flotation circuit at the Copperton concentrator. Higher overall recoveries have been observed on the newer Outotec tank cells compared to the original 85m3 self-aspirated flotation cells they replaced. However, coarse particle flotation response on these large, forced air cells did not show encouraging results when compared to smaller previously installed cells. This coarse recovery loss has been attributed to the longer froth transport duration and transport distance on large cells (100m3 and larger). Cell manufacturers addressed the risks of additional coarse particle losses in large cells by installing concentric circumferential launders and crowders (also called center launders). These are designed to reduce froth transport time and distance in the last cells in rougher stages where low residual floatable minerals causes a lack of froth mobility. The center launders also increase froth crowding, which also helps to increase froth transport velocity and increases copper and molybdenum recoveries. A trial set of the center launder retrofits were installed on the last three tank cells in one of the parallel rougher flotation rows at Copperton. The launder retrofits were installed at the end of October 2020 and monitored until March 2021. This six-month trial showed statistically significant improvements in copper and molybdenum flotation recoveries through the rougher circuit.

Mar 2, 2022

Unplanned ore dilution can have severe impact on the economics of a mining operation. The paper discusses and distinguishes between controllable and natural parameters influencing ore dilution, and how it can be minimized in longitudinal mining systems of narrow vein orebodies. It is shown through data of surveyed stope profiles and numerical modelling that unplanned ore dilution is a function of stope design and construction, orebody geometry, and rock mass characteristics.

Jan 1, 2010