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By D. L. Leach

This report covers laboratory experiments simulating in situ copper recovery from primary sulfide ores in sulfuric acid systems pressurized with oxygen. Copper extraction and acid consumption data are correlated with temperature in the range 50-150°C and quenched pH in the range 0.25-2. Adverse changes in the chemical composition of the leach solution and the formation of gangue-mineral alteration products and secondary sulfides can severely limit the extraction of copper above 90°C. Keeping the pH below the self-buffered value of about 2 and the temperature below about 110°C produces the maximum extraction rates. Forcing the pH too low not only results in excessively high acid consumption but may also limit the extraction of copper at temperatures above 100°C.

Jan 1, 1975

By C. G. Hunkin

In situ, or in-place leaching is concerned with the extraction of metals from natural mineral disseminations without removal from their geologic location which, in many cases, amounts to the reversal of the deposition process accompanied by a presumed increase in velocity of the processes, if the project is to be profitable. Solution mining processes involve removal of minerals such as sulfur, common salt, and potash, generally leaving cavernous voids, in contrast to in situ leaching which term is applied to the selective dissolution of a mineral from its gangue without sensible disturbance of the formation. Where such a process can be operated, the advantages are manifold and have been so recognized by miners from the earliest days of mining. Recent technological developments have encouraged a reassessment of the status of in situ leaching, and it now appears possible to extend the application of the method from a few isolated special situations to many uranium and copper deposits. Anaconda's interest in the techniques stems from long experience with vat and heap leaching, 'dump leaching, and natural leach activities associated with several established mines. Increasing activity through-out the industry has been noted, particularly in leaching low grade pillars and the peripheral zones of operating mines, often by the introduction of leach solutions via boreholes drilled from surface. Reactivation of dormant mines] using similar techniques has been successful. Over the long term, environmental improvement activity will lead to excess sulfuric acid production, even to a disposal problem. The cost of leach solutions and reagents must be reexamined in this light. The mineral industry now classifies as uneconomic deposits of readily soluole minerals whose potential value, on a per acre basis, may De several times that of many currently profitable oil field reser-

Jan 1, 1971

By H. V. Fairbanks

It is estimated that millions of tons of coal fines are unsaleable each year due to difficulty of drying them economically with conventional mechanical dewatering and thermal drying equipment. The difficulty is due to the fact that coal of small particle size presents a large surface area with polar groups which have a great affinity for water. In order to remove this water thermally, a high temperature is necessary which oxidizes the surface of the coal. This substantially reduces the heating value of the coal. If drying could be satisfactorily carried out at a lower temperature, much more of the heating value of the coal fines could be retained. It was conjectured that acoustic energy applied during the drying process might prove to be of value since acoustic energy has the property of producing cavitation at a liquid-solid interface when the intensity is sufficiently great. This cavitation process produces water at room temperature which can be carried away from the solid surface by a flow of relatively cool air. Hence, moisture removal is made possible at a lower temperature.

Jan 1, 1966

By Jeffrey Mitsopoulos

King County?s (KC) Brightwater Conveyance Project in Seattle, Washington involves the construction of approximately 21 kilometers (13 miles) of bored tunnel, in three contracts, with four TBM?s which produce large amounts of real-time digital mining data. To facilitate the management of TBM data with a single interface and assist in project Quality Assurance, KC?s Construction Manager (Jacobs Engineering) recommended the use of the software TPC (Tunneling Process Control), developed by Babendererde Engineers GmbH. The paper demonstrates how TPC was used for oversight, analysis and QA on a complex tunneling project and how contemporaneous review and management of data results in a better understanding of TBM performance than can be obtained by retrospective analysis of data.

By A. Chieregati

"A heterogeneity study was conducted at Erdenet Copper Mine in Erdenet, Mongolia, to determine the fundamental sampling error associated with blasthole sampling. Using a custom designed sector sampler, six large blasthole samples were collected to perform the test that was developed by Pierre Gy, to estimate the constitutional heterogeneity factor for several types of ore. The study investigated the entire sampling protocol, from mine site to analytical laboratory, and quantified the contributions to fundamental sampling error (FSE) of the various stages of sampling and sample preparation. The total relative standard deviation (RSD) of sampling error was determined to be ±32% and ±49.4% for copper and molybdenum respectively. A classical statistics analysis conducted on the data confirmed the level of RSD. About 95% of the sampling error was produced from only one step in the sampling protocol: when the 1 kg sample was reduced to 50 g sample for chemical analysis. Therefore, it is recommended that the 1 kg sample be reduced to 50g using a slightly different protocol to minimize the FSE. The 1 kg sample should be first crushed to 0.2cm size. A 250g split should then be taken and fine ground. A 50g split should then be taken from the 250g fine ground split. These two simple steps will reduce the FSE to ±7.9% and ±17% for copper and molybdenum respectively. The modified sampling protocol effectively reduces the probability of misclassification of low grade ore to zero. INTRODUCTION The Erdenet copper-molybdenum open pit mine is located in Erdenet, in Orkhon province, Mongolia. The Erdenetiin-Ovoo copper-molybdenum deposit is between 1.5 and 3 km wide, and about 25 km in length (Erdenet Mining Corporation, 2016). Chalcopyrite, bornite covellite and chalcocite are among the major minerals found in the deposit. The mine processes approximately 26 million tons of ore annually. A study was conducted to evaluate the fundamental error associated with the blasthole cuttings and sampling protocol at the mine. The open pit mine uses 215mm diameter Russian drills to drill 17.5m holes for 15m benches. The total weight of blasthole cuttings for a 215mm diameter hole and 15m bench height is between 1.5 and 2 tonnes. This amount of sample is difficult and time consuming to collect and analyze. Therefore, a sector sampler was designed for the Russian drills to collect large samples that were representative of the blasthole cuttings (Ganguli et al., 2016). In order to eliminate the delimitation and the extraction errors, researchers consider sector samplers to be ideal for sampling blastholes (Pitard, 2008; Chieregati and Pitard, 2009). This method was intentionally more rigorous than the blasthole sampling protocol at the mine to ensure that the blasthole cuttings were properly sampled. This study was part of a broader study that also looked at the relationship between particle size and grade. The samples collected by the custom designed sector sampler were very large (195 kg on average), and therefore, sufficient for both studies. The relationship between particle size and grade has been reported in Ganguli et al. (2016)."

Jan 1, 2017

By R. D. Cook, J. L. Johnson

"Measuring mud bed level in a sedimentation device is an important control variable. Methods used to date for this purpose have had limited success providing continuous, consistent measurements at a reasonable price. This paper describes a new instrument for detecting the mud bed / liquor interface as well as bed density profiles. The state of the bed is measured directly with sensors located in the thickener. Data from bench-scale and full-scale tests show that the bed level is well defined and easily detected. In addition, full-scale testing revealed unprecedented information about thickener beds. Variation in bed density gave new insight into thickener bed dynamics, providing design and control opportunities never before possible. This novel instrument can significantly improve thickener control by providing reliable and consistent bed level measurements. It is also capable of measuring bed density profiles that can potentially identify significant operating problems early enough to take corrective action before experiencing costly shut downs. INTRODUCTION Numerous studies and papers have been devoted to the subject of thickener design and operation to achieve specified throughput and discharge densities. Mathematical models have been developed that present methods for sizing thickeners and predicting performance under varying process conditions. The compression effect of deeper beds on dewatering performance is a recognized phenomenon (Wilhelm and Naide 1981). This is one variable of many that are inter-related and influence thickener performance. For example in the steady-state, continuous operation of a thickener, if the solids feed rate increases and the bed level remains the same, the underflow discharge rate must increase with the result of solids concentration being lower. The interactions of these parameters are at the heart of thickener models. One such model (Burger and Narvaez 2007), predicts solids concentration profiles increasing downward and discontinuities between settling zones. This model uses sediment height (bed level) as a parameter that influences capacity calculations to achieve the specified solids concentration of the underflow. Knowing the bed depth is critical to maintaining stable thickener operation. Implicit in these modeling strategies are some basic assumptions such as homogeneous distribution of solids in the different settling zones, plug flow of solids through the settling zones and steady state operation of the thickener. The accuracy of these assumptions has not been verified because there has been little visibility inside the bed of full size operating thickeners. Testing of the instrument presented in this paper demonstrates that it provides a degree of visibility of the dynamics in a thickener not previously possible and indicates that the basic assumptions of the modeling strategies may not be completely accurate."

Jan 1, 2015

By L. Martin, M. Raffaldi, M. Stepan, D. Benton

The Office of Mine Safety and Health Research, Spokane Mining Research Division, is continuing its high-energy, high-displacement testing of field-scale shotcrete panels. A test program was developed to determine the relationship between applied force, displacement and energy for both unreinforced and reinforced shotcrete panels. Reinforcement options consisted of synthetic macro-fibers, sprayed polyurea liners, chain-link mesh, welded-wire mesh and combinations of them. During testing, photogrammetry was used to measure the geometric changes of the panels, including volume changes and panel cracking. These measurements were correlated with the load and displacement data, allowing visual observation to be related to the applied force and displacement. The test results provide a comparison of the mechanical performance of the various panel types and can assist in interpreting the condition of installed surface support. Visual assessment of the loading cycle and strength capacity of shotcrete in underground excavations will improve mine safety by providing a means to better quantify the stability of installed shotcrete support.

Jan 1, 2016

By James R. Dunn

The mineral industry" has made and will continue to make important contributions to the growth of our economy. However, the industry is presently under continuous and increasingly severe attacks by organizations and individuals interested in the preservation of our environment. Yet neither the public interest value of preservation nor the public interest value of our mineral industry is known. In the absence of such values, judgments about best land use where minerals are involved are nearly always made on emotional grounds. An example of the sort of problem that has been created is in the New York Metropolitan Area. Because of institutionally-created shortages stemming largely from zoning decisions and building over deposits, the effective cost of fine aggregate delivered at dockside at Manhattan rose from $2. 65/cubic yard in July, 1969, to $4.10/cubic yard in May, 1970, this in spite of approximately ;l0,000 years of reserves on Long Island. The cost of fine aggregate for New York City alone has "Increased over $S million annually within one year, with the cost increase for the Tri-State Metropolitan Area (coastal Connecticut, New Jersey, and New York)" exceeding $10 million annually. The ab0ve situation has created a cost increase which is clearly the result of non-conservation of a mineral resource. That is, in readily measurable values, it Is costing the public about $10 million per year because good conservation practices were ignored-a public-interest loss. Admittedly, this is not the whole story because the public is simultaneously obtaining other values from the land surface that would otherwise have had to be dedicated, temporarily to be sure, to mineral recovery-a public-interest gain. However, the point is that we do not know where the balance lies-the net public interest value; it may lie one way for deposits zoned out of existence by a growing suburb, another for areas designed as permanent greenbelts, and still another for areas under new highways

Jan 1, 1971

By O. Lopez

"Stringent regulations and increased arsenic presence in ore bodies being exploited have created the need for cost effective and environmentally compliant technologies to remove selenium and arsenic from mine waters and metallurgical waste streams. Existing treatment methods have high life cycle costs and/or produce residues that, due to their unknown stability over the long-term, may represent future liabilities. This results in high compliance costs and uncertainties which negatively impact existing operations and projects in permitting. Selen-IX™ is a new ion exchange based process that selectively removes selenium from mine impacted waters down to 1 ppb while producing a stable inorganic iron-selenium product. Results of piloting completed on streams generated from coal and copper-gold deposits are presented along with preliminary equipment sizing and life cycle costs of full scale treatment. An example of a commercially available system for arsenic removal using sulphide precipitation is presented. The benefit of this treatment method is discussed based on recently completed technical feasibility assessment including laboratory testing and preliminary engineering design. INTRODUCTION Selenium Due to the chemical similarity between selenium and sulfur, selenium substitutes sulfur in many minerals that can be found in a wide range of deposits including coal, base metal, precious metal, phosphate, and uranium. One of the main environmental challenges facing the industry in North America today is related to the removal of hexavalent selenium, e.g. selenate, to ultralow levels, typically between 1 to 10 ppb, from large flows of often cold water containing less than 1,000 ppb of selenium. Recent studies commissioned by the industry identified biological selenium reduction systems as the best available technology. Although the biological selenium reduction process is commercially proven in certain applications to remove selenium to ultralow discharge levels, the technology has been primarily applied to relatively low and constant flows of warm water produced by the Flue Gas Desulfurization (FGD) scrubbers in the power generation industry. The wide spread adoption of this treatment method by the mining industry is hindered by high capital and operating costs associated with treating large flows of cold water, lack of data and knowledge about the long term stability of solid residues produced by this treatment, and limited capacity of biological systems to respond to sudden changes in flow and/or mass load of contaminants. Furthermore, it has been reported that reaching discharge limits less than 3 ppb could be a challenge and that polishing treatment for the removal of BOD and phosphate maybe required to avoid the impact of the biological treatment which requires organics and nutrients, on aquatic environment downstream of treatment plants. Alternate treatment systems are being developed to overcome and/or completely avoid some of the challenges of biological systems. One such treatment system is BioteQ’s Selen-IX™ process which is purely physico-chemical treatment system."

Jan 1, 2015

By G. F. Revey

All underground operations have limiting factors that influence overall profitability. Hoisting, hauling, available headings, labor, milling capacity and other factors limit how much material can be removed from an underground mine. Consequently, when mines use limited labor to handle the additional rock from overbreak and to perform extra ground support tasks, productive activity is replaced by non-productive work. Mining economics are further penalized when overbreak causes dilution of ore grades. This paper reviews organizational systems that mines have used to create environments which foster the creation of successful overbreak control programs. Actual case histories document the various quality improvement techniques, worker incentives, and practical project management systems used by these mines. A brief review of controlled blasting technology sources and overbreak measurement tools is also included.

Jan 1, 1997

By T. Krichler

"Current mine control stations are either single-position systems with high engineering effort or all-in-a-box solutions with low integration possibilities of third-party devices. Above all, both approaches are cost-intensive and not feasible for small companies. This paper shall be an inspiration of how to enhance the productivity and monitoring of an existing mining system in a modular way by introducing a proven technique of the ongoing digital revolution: A Wi-Fi network based on the communication protocol OPC UA. The starter kit consists of a single-board computer, a WLAN access point and any electronic sensor. INTRODUCTION The majority of the European mining industry is run by small and medium deposits (Europe Geology, 2017). This is due to the fact that most ore mines in Europe are widely distributed within the continent, are generally small and additionally they are often steeply inclined. Such ore bodies are normally mined with underground mining methods and must be excavated with high selectivity because of their small thickness. That is why the economy of scales, higher efficiency through bigger machines, cannot be used in most deposits in Europe except for lignite mines. It is important to find an alternative possibility to improve the efficiency of European mines for making them competitive internationally. For cost optimization and profit maximization it is necessary to use the trends of industry 4.0 and to broadcast these into the mining industry to reach a technological advantage. The goals of the EU within the Horizon 2020 funded project are to shorten the actualisation of the mine and block model to hours, improve the communication with Through the Earth (TTE) via very- or ultra-low frequency for long-time monitoring of the abandoned workings, and develop a cost-effective mine control station for optimization of mining processes in Small and Medium Enterprises (SMEs) as well. This paper deals specifically with the new approach for data acquisition, transmission and visualisation of a mine. SCADA AND ERP IN MINING There are already many Supervisory Control and Data Acquisition (SCADA) and Enterprise Resource Planning (ERP) programs on the market, but these are normally not developed for the mining industry. At the moment this leads to three options. • To hire a system integrator, who shall build a complete control station for one mine that requires a high amount of knowledge in programming and cannot be maintained by the mining company itself. • To buy different types of out-of-the-box systems, whereby every system can include some of the used technology. In this case a huge amount of project engineers and operators – at least one per system and shift- is required. • To buy every machine and program from one company including the service contracts."

Jan 1, 2018

By Peiwei Xiao, Xiang Li, Biao Li, Haoyu Mao, Nuwen Xu

As an advanced method of rock engineering construction safety monitoring, microseismic monitoring technology can monitor the micro-fracture of rock masses within an effective range, and then perform forecast analysis of rockburst, cracking, falling blocks and other disasters. Although the application of microseismic monitoring technology has become more mature, how to improve its application efficiency remains to be further studied. At present, artificial intelligence has been extensively developed, and the use of intelligent algorithms to improve the efficiency of rockburst forecast can provide a valuable reference for the safe construction of underground engineering. To this end, this paper proposes a microseismic multi-parameter rockburst early warning model based on dynamic Bayesian networks. First, the sensitivity of microseismic source parameters to rockburst forecast is analyzed based on microseismic monitoring data and actual rockburst information of a hydropower station. Second, the main seismic source parameters and their data are selected and imported into a dynamic Bayesian network for learning to obtain the rockburst forecast model. The model is confirmed in its self-validation and K times cross-validation, and the receiver operating characteristic curve of the model is also analyzed, it is found that the area under the curve is close to 1, indicating that the model has good accuracy. Finally, the analysis of the influence strength of the parent and child nodes in the model reveals that the moment magnitude and source scale are the most sensitive parameters, which can be used as an important reference for rockburst forecast.

Apr 26, 2022

By Y. Lizotte

The purpose of this paper is to describe a stochastic simulation program used to assess several dispatching rules applicable to small scale computerized systems for optimizing truck/shovel productivity. The system studied is semi-automated with a dispatcher communicating instructions by two-way radio. The simulation program is structured on an advance clock approach which enables the insertion of dispatching rules at various points in the haulage net- work. The rules tested include minimize shovel idle time, maximizing immediate truck use and assigning trucks to shovels to meet specific production objectives. A variation of the traditional "Match Factor" is implemented to maintain fleet balance throughout the shift. A mine case study demonstrates how the dispatching rules increase productivity of such semi-automated dispatching systems. Practical problems involved in the implementation of small computerized dispatching systems are also discussed.

Jan 1, 1986

By Carlos Kovacs-Figueroa

Because of air pollution control regulations in the early 701s it became necessary to clean effluent gases from the Morenci Reduction Works Smelter. Feasibility studies indicated that this could be accomplished most efficiently by using the smelter gaseous effluent to feed a sulfuric acid plant. Complying with air pollution control regulations thus created the need to dispose of relatively large amounts of concentrated sulfuric acid. Typical Morenci ores contain substantial amounts of oxidized copper minerals which are not recoverable by flotation. In addition, there is low sulfide, high oxide material which can be leached, but is not suitable for flotation concentration. Early in 1971 sufficent data had been accumulated to show that a leaching plant for the Morenci tailings could use a large portion of the sulfuric acid produced by the Smelter. It was determined that for all practical purposes leaching of the available copper was complete in two hours or less. Capital expenditures could not be justified for more than two stages of counter current decantation for recovery of the leached copper, and the plant was designed with these criteria in mind.

Jan 1, 1976

By N. L. Parduhn

Populations of Bacillus cereus spores are elevated in soils over four subsurface gold deposits in the western United States. Large deposit-to-background ratios of B. cereus populations were obtained in soil traverses over the Minnesota vein deposit, Empire District, Colorado (maximum 50:1); the Shasta (maximum 3,500:1), and Evening Star maximum 18,000:1) vein deposits, Shasta County, California; and the Hog Ranch disseminated gold deposit (maximum 40,000:1) in Washoe County, Nevada. Small increases in the concentration of toxic metals in the soil may be responsible for the elevated spore populations. The observed elevation of B. cereus spore populations near these gold deposits indicates that the method should be further investigated as a potential exploration tool.

Jan 1, 2013

By N. Harrigle, Tsutsumi

Very fine wet sizing of minerals such as kaolin, precipitated calcium carbonate, lime milk, and clay slip is a difficult process to achieve using standard vibrating screens. With particle sizes ranging in the sub-microns combined with the agglomerating tendencies of certain materials, screen blinding becomes a serious issue. Sizetec, Inc. has developed an innovative screening equipment to help solve this problem. The High Performer Screen uses powerful linear vibrations to help break apart agglomerated particles and prevent screen blinding. Optionally fitted with the Air Explosion Screen Cleaning System, compressed air can be periodically injected into the screen underflow chamber to clean the screen surface without the use of water sprays. This paper highlights some of the key features of the Sizetec High Performer Screen and describes typical performance that can be expected based on results from various trials conducted in the kaolin industries.

Jan 1, 2002

By W. J. Douglas

The mine manager in today's environment is faced with a wide variety of problems and challenges which must be addressed if efficient and profitable operations are to be achieved. Expansion of operations has, in many instances, resulted in inexperienced work crews, face supervisors, and superintendents. The complexities of a mining system preclude rapid movement through the learning curve for moat personnel. The management of production suffers both from this inexperience and the lack of standard procedures and methods for planning, schedul ing and analyzing production systems. The lack of visibility of information, as well as of the operations themselves, due to their remoteness, adds to the problem of production management.

Jan 1, 1980

By George H. Willis

In the second half of the nineteenth century, bimetallism progressively replaced by gold standard. After World War I and 1931-33 depression, gold mainly reserved for official international transactions and internal use restricted. Changes since 1971 have shrunk official international use of gold. International payments deficits and surpluses now financed by private and official credit, rarely by gold. Historical review covers evolution of: (1) internal and external private use, (2) internal official use, (3) external official use, (4) role in IMF and (5) use as unit of account.

Jan 1, 1978

By James L. Hendrix, Michael R. Straka, Emil B. Milosavljevic, Ljiljana Solujic, Neil P. Gallagher

Analysts that utilize the classical distillation procedures for cyanide analysis are often frustrated by the poor reproducibility and repeatability of these techniques. Capital intensive business decisions and environmental management regulations are exas­perated by the fact that the EPA/ASTM approved cyanide deter­mination methods produce data of questionable quality. Reliable cyanide values are important in monitoring the effec­tiveness of the cyanide detoxification procedures. Efficiency and cost of gold and silver cyanidation recovery can also be improved by precise cyanide monitoring in the process itself.

Jan 1, 1996

By Vincent Tricot, Daniel Altier, Roger Storry

"INTRODUCTION The Liantang / Heung Yuen Wai Boundary Control Point (BCP) project, located in the north-east New Territories of Hong Kong, will form the seventh land crossing between the Hong Kong Special Administrative Region (HK) and Shenzhen in China (Figure 1). The BCP project comprises an 11km long dual two-lane trunk road linking the border crossing facility to the existing road infrastructure in HK and when completed it will facilitate future regional development and alleviate frequent traffic congestion at the existing Boarder control points.In December 2013 Dragages Hong Kong (a member of the Bouygues Construction Group) was awarded the 5.4km long Contract 2 section of the project, including the 4.8km long Lung Shan Tunnels, by the Civil Engineering and Development Department of the Government of the HK SAR. To overcome the difficult ground conditions anticipated along the Contract 2 section of the project the tunnels will be constructed using mechanical and drill and blast (D&B) excavation techniques together with a 14.1m diameter multi-mode Earth Pressure Balance Tunnel Boring Machine (TBM). Land constraints imposed on the project alignment require that the final 500m section at the northern end of the Lung Shan tunnels, under Princess Hill (Figure 2), takes an almost 90 degree turn towards the north. The resulting 354m radius curve restricts the sight-line of road users to below the minimum 110m at 80km/hr hence, the internal span of the tunnels needs to be increased from 12.6m, in the standard straight section, to 15.4m in this curved section to accommodate a widened shoulder which will provide the required sight-line distance."

Jan 1, 2016