Search Documents

By M. C. Williams, T. P. Meloy

For over thirty years the Population Balance Model, PBM, has been the mainstream modeling method for comminution unit operations and comminution circuits. For commercial comminution circuits the method is based on erroneous physics and dubious numerical mathematical methods leading to non unique solutions that have little extrapolative value and faulty control strategies. In short the PBM is wrong. Given is a detailed analysis showing a number of non trivial flaws in the linear PBM. Moreover, a simpler model is presented that leads to a solution of the comminution circuit predicting the size distribution output over a variety of conditions. Because the linear PBM is firmly entrenched, an award is offered, $10,000, to any researcher that can use the linear PBM and its present numerical methods to predict the typical straight line, self similar, output of wet mills over a variety of grinding times.

Jan 1, 1992

By K. N. Han, P. B. Queneau, Bruce W. Cavender

Measures of metallurgical performance, such as recovery rates or mass balances, are frequently based on point estimates of operating conditions in the system of interest. Because the processes being measured are dynamic, a range of uncertainty accompanies each measurement; this uncertainty is reflected in the accuracy with which the calculated result describes the true metallurgical performance. In stochastic modeling, a range of probable values is used in place of a point estimate to describe each variable. The calculated result takes the form of a distribution, delineating both the magnitude and probability of potential outcomes.

Jan 1, 1993

By H. Habenicht, E. Urschitz

Three mining methods for full extraction in flat coal seams - i.e., longwall (L W), shortwall (SW), and rib pillar extraction (RPE) - are com- pared with each other in view of the introduction of a mechanized, self-advancing roof support. Features are shown according to which RPE appears most attractive under certain conditions. In this presentation, the mining methods are outlined and discussed. The new support (Alpine Breaker Line Support, ABLS) is described, and its employment is explained. A trial operation in RPE using the ABLS has been conducted successfully in a South African coal mine. The results and improvements are stated.

Jan 1, 1988

By Gordon H. Jardine

The cost of performing equipment maintenance is an increasingly significant component in the total operating cost of today's capital-intensive, large-scale mining operations. Because of the interdependence o f equipment maintenance on other functional areas of the minesite, an integrated approach to the monitoring and control of maintenance costs is essential. An important element of the introduction of computer-based systems in a mine is the acceptance of the systems by the users. The development history and major features of a minesite-developed system, which emphasises the user's importance, is described. The system outlined is designed to provide information for decision-making to the place where the company's maintenance money is actually spent - on the shop floor.

Jan 1, 1986

By R. J. Snoby, P. Grotjohann

In processing heavy-mineral sands, the low feed concen¬tration and respective high value of the desired minerals require high-capacity production and sharp classification/ separation techniques to reduce the specific production costs. This paper describes the new allfux® separator, which can economically accomplish these criteria. The separator is a two-stage process that combines rising current and fluidized-bed technology. This allows for the treatment of ex¬tremely high mass flows in a single unit. This paper reports on test work performed on coal, iron ore and heavy minerals.

Jan 1, 2000

By M. J. Wilhelm

Bromine is the intermediate member of the halogen family of elements between iodine, a solid, and chlorine, a gas. The name is derived from the Greek bromos, meaning stench. Bromine is the only nonmetallic element that is liquid at room temperatures, with a melting point of -7.2°C and a boiling point of 58.78°C. Reddish brown in color, it dissolves easily in water to yield a red solution. Bromine volatilizes at ordinary temperatures to a red vapor that is very irritating to the eyes, nose, and throat. Density of the liquid is 3.12, and gas weighs 7.59 gpl in standard conditions. Because the element is highly active, it exists in nature only as bromide compounds. Bromine was discovered by Antoine Jerome Balard in seawater bitterns in 1825 and began to find commercial applications shortly thereafter in photography, medicine, and dyes. The first commercial production of bromine was in 1846 in Freeport, PA, followed by production in Germany in 1865. OCCURRENCE Bromine is widely distributed in nature, and compounds occur in solution in natural brines, in seawater, saline lakes, oil and gas well brines, and in evaporite chloride minerals. The concentration of bromine salts ranges from 60 to 65 ppm in seawater to several thousand ppm in oil well brines and saline lakes. The distribution of bromine in marine evaporite minerals and in the solutions from which they crystallized was determined many years ago by H.E. Boeke (1908). Theoretical aspects regarding the geochemistry of bromine have been published in numerous papers (Raup and Mite, 1969). Bromine occurs in solid solution in carnallite and sylvite associated in potash deposits, in halite in salt beds, salt in oil shales, and in trona deposits. Its presence is useful as a guide in geochemical exploration. The analysis of small amounts of bromides in the presence of large amounts of chlorides is discussed by W. Schwerdtner (1963). Manganese, iron, and iodine may interfere with the determination. Other analytical methods are discussed at length in literature (Stenger and Atchison, 1964).

Jan 1, 1994

By D. R. East

Recent experiences within certain sectors of the international mining industry suggest an underestimation of the environmental risk associated with the design of mine waste management facilities. These experiences show that the technical and managerial challenge of responsible mine waste management is not always fully appreciated. Unfortunately, the image of the mining industry's environmental performance is negatively impacted by a relatively few number of failures. This negative view overrides the many positive contributions made by the majority of mining companies. The fact that these failures continue to occur to this day in both developed and developing countries is indeed remarkable, and indicates a degree of risk-taking approaching unacceptable levels. The design requirements for tailing storage facilities are, in many cases, more demanding than those of conventional water dams, because seepage of fluids which contain dissolved metals may pose a greater threat than the mere loss of water.

Jan 1, 1999

By S. Hardcastle

Kidd Creek mine has recently completed upgrades of its primary ventilation systems enabling it to maintain a delivery of 1200 m3/s to continue mining ore zones extending to over 3000 m below surface. Following these upgrades the mine initiated a multi-stage review of their ventilation usage. The focus of these reviews, ranged from a brainstorming session of invited experts, through an evaluation of production plans to a detailed analysis of production data to determine if the ventilation system could be run more efficiently, thereby reducing the mine?s power consumption and associated operating costs. The initial review identified 1500 kW of installed fan power that could be eliminated from the primary ventilation system. The benefits of the subsequent analyses, so far, are not as measurable. The second and third analyses, respectively using long range production plan data and historic production data to determine ventilation requirements based upon diesel equipment, did not agree. Both were shown to have limitations, the future based analysis underestimating, and the historical analysis overestimating the requirements. Regardless of the failings of each method, important outcomes were achieved from the detailed analyses, namely, the ability for a mine to meet a forward analysis prediction of airflow depends on its ability to adjust the ventilation to meet the dynamic nature of the mining process. Also, to minimize total ventilation requirements, a mine must regularly redistribute its airflow; this not only reduces the total volume requirement but also increases the variability of the delivered flows which can provide further operational savings. Since the detailed analyses, the Kidd Creek mine has implemented a more frequent ventilation review and redistribution procedure; consequently, it now operates with an average delivery of 930 m3/s, which is 23% lower than in 2005 at the start of the review process.

Jan 1, 2009

By Rex C. Bryan

An accurate and dependable ore reserve estimate is important to any mining company. It is also essential for development drilling and production planning to know about the distribution of the ore within the area to be mined. This paper will show that in the case of more variable deposits such as uranium, the use of geostatistics is superior to conventional techniques. Unlike conventional methods, geostatistics includes the importance of spatial orientation of measured variables. With the use of variograms in conjunction with kriging, a point or a block may be estimated along with its error of estimation. The existence of disequilibrium can create a severe problem in uranium 'ore reserve estimation, and mine and production planning. Disequilibrium can be simply defined as the ratio of chemical or assay values to gamma equivalent values calculated from the downhole geophysical gamma-ray logs. Various methods for adjusting for disequilibrium have been proposed. Most, however, have side stepped the consideration of disequilibrium itself being a regionalized phenomena; or its, relation to surrounding geology. This paper presents methods of incorporating both aspects. The East Dilts Pit at the Bear Creek Uranium Mine in Wyoming, has been used as a case study. Polygonal, triangular, and lognormal kriging and various disequilibrium adjusted methods, including multi-factor cokriging have been com- pared with the mining experience.

Jan 1, 1982

By D. R. East

Recent experiences within certain sectors of the international mining industry suggest an underestimation of the environmental risks associated with the design of mine waste-management facilities. These experiences show that the technical and managerial challenges of responsible mine waste management is not always fully appreciated. Unfortunately, the image of the mining industry's environmental performance is negatively impacted by a relatively few number of failures. This negative view overrides the many positive contributions made by the majority of mining companies. The fact that these failures continue to occur in developed and developing countries is indeed re¬markable and indicates a degree of risk-taking approaching unacceptable levels. The design requirements for tailings storage facilities are, in many cases, more demanding than those of conventional water dams because seepage of fluids that contain dissolved metals may pose a greater threat than the mere loss of water.

Jan 1, 2000

By Carlos Andrade

An engineering endeavor involves the creation of an expansive, environmentally conscious reinforced sloped MSE wall system. The objective is to enlarge a flat mining work area. Situated in southern Arizona, this mine is dedicated to extracting essential resources such as Manganese, zinc, silver, and lead, crucial for advancing clean and renewable energy initiatives. The project necessitates the implementation of a Mechanically Stabilized Earth retention system. This system aims to both expand the mine’s working area and facilitate access to underground tunnels. The expansion pad must be robust enough to endure the substantial loads exerted by heavy mining machinery. The wall’s reinforcement components are strategically designed to counteract the challenges posed by aggressive soil conditions with low resistivity. Furthermore, they must be resilient against potential damage during installation. The system’s ease of transportation is crucial due to challenging access conditions, and its design must allow for efficient drainage. A significant consideration is the integration of a face system that fosters vegetation growth and seamlessly merges with the existing flora of the area. In addition, plans include the construction of an access road downslope from the wall. The chosen solution involves a reinforced sloped system with a 70-degree incline. The wall’s surface is adorned with an erosion control mat, intended to promote the proliferation of vegetation. For added durability, the wire basket units are equipped with galvanized wire featuring a polymer coating. High tensile strip bonded geogrids, featuring a robust polyester core, provide essential reinforcement. The completed wall is an impressive feat, spanning 1500 feet in length and soaring to a height of 45 feet. It stands as a testament to innovative engineering in harmony with environmental and functional considerations.

Feb 1, 2024

By I. Yaniv

The magneto-hydrostatic method can be used today to separate slightly magnetic or non-magnetic particles according to differences in their specific gravities and magnetic susceptibilities. The classical approach is to effect stratification prior to separation. This paper discusses some of the significant parameters which bear on the design and pattern of the expected stratification in the separation cell. As the characteristics of the magnetic field, and consequently those of the magnetic forces, are determined by the geometry of the poles, this subject is treated first. In this context a new approach, whereby the range of stratification is extended, using positive as well as negative gradients, is presented. Finally, the effect of the relative size and shape of the particles on stratification is discussed.

Jan 1, 1978

By V. I. Lakshmanan, Chris Dodson

Refractory gold ores or concentrates are pretreated in general by physical, chemical and biological oxidative pretreatment processes prior to cyanidation for the economic recovery of gold. The thermal treatment processes generally include fluid bed pro­cessing(!>, chemical with pressure<') or atmospheric (Caro's< ·'>, 3 Nitrox1')) pretreatment leaching and physical with ultrafine grinding!"). Roasting and aqueous pressure oxidation pretreat­ment methods have several commercial applications (Homestake, Barrick) and biological oxidation methods have recently found industrial applications in Africa. The roast pretreatment methods to treat refractory sulphide ores or concentrates transform iron sulphides generally to a porous iron oxide matrix assisting the lixiviant cyanide to effectively diffuse the calcine for cyanidation and hence with improved gold recovery. Jha and Kramer<') made an extensive review of roasting chemistty and practice to tt·eat refract01y gold ores. Industrially two stage pretreatment roasting is generally employed. During the first stage roasting is carried out under oxygen deficiency conditions to provide a low arsenic calcine, mainly magnetite and in the second stage magnetite is trans­formed to haematite under oxidizing conditions.

Jan 1, 1998

By Greg Barfoot, K. Payne

Condition monitoring of conveyor belting has become an established tool for maintenance programming, replacement strategies and quality assurance for belt conveyor systems. What is less well known is that the condition of the conveyor belting is usually a symptom of problems in other areas rather than the problem source. This paper presents an overview of the state of the art in belt monitoring and the move towards on-line NDT systems. The use of belt monitoring data as an indicator for overall system design, maintenance and operation is also discussed.

Jan 1, 1996

By Deepak Malhotra, Sean Armstrong, Linda Baltich

The economic profitability of any mineral company is dependent upon maximizing mineral recoveries while minimizing costs. The effectiveness of any strategy to meet this objective is dependent upon firstly obtaining quantitative information concerning the steady-state metallurgical balance of the plant, and secondly, how efficiently this information is used to improve/optimize plant performance. This two-step approach can be designated as a "plant audit." Plant audits on a routine basis can be very expensive and time-consuming. Most plants have reduced staffs to cut costs. The remaining staff has to spend time to solve production/operation problems, thereby leaving limited resources (i.e., people, time, and money), for plant auditing. This paper briefly reviews plant auditing categories, and a systematic approach to auditing which has been successfully used at several operations. An example illustrating the use of this approach in gold operations is discussed in this paper.

Jan 1, 1992

By Harleigh V. S. Tingley

Investment in the mining industry has increased substantially throughout the world in recent years. So have acquisitions, divestitures, and financial restructurings. The return of outside investors to the industry is welcomed. The trend toward stockholder litigation is not so welcomed. Both have provided the impetus for commissioning outside professional due diligence studies of potential minerals transactions. For a number of reasons, some unique to the industry, evaluation of mining investments is a challenging task for the investor. Investments in exploration prospects and undeveloped properties have a high speculative content. Buyers pay for uncertain future prospects. Alternatively, most developed mining investments are large and long-lived and cannot easily be modified during that life. Even so, to be successful, they must compete in an environment in which their reserves - the source of their profits - are often imperfectly known. And markets, competition, technology, and politics are among the many continually changing factors that affect investment performance. Minerals investment evaluation is further complicated because each minerals investment has its own singular combination of risks and opportunities. Each ore type and each ore body presents different problems in reserve evaluation, mining, and extraction. Each minesite has its own often unique combination of mine, infrastructure, political, environmental, and other risks. And the key requirements for commercial success differ substantially among various minerals.

Jan 1, 1990

By George H. K. Schenck

Decisions to develop deposits of calcareous materials for cement production are based largely on anticipated markets for heavy construction which utilizes concrete. The geologist should understand the fundamental factors that underlie such management decisions, so that his field work and reports will more effectively relate to the information requirements of managers in the cement industry. The paper examines the relationships that exist between exploration and development of calcareous raw materials for cement manufacture and changing factors in the marketing of cement. Continued overcapacity, improved technology, changing distribution patterns, ease of entry, economics of scale, and the nature of product demand are some of the characteristics of the cement industry that are basic to decisions regarding exploration programs and property development.

Jan 1, 1966

By A. J. Hudson, M. R. Yenchek

Faulty insulators on mine trolley/track haulageways may allow leakage of currents into the mine roof, which may ultimately result in the combustion of the roof material. The National Institute for Occupa¬tional Safety and Health (NIOSH), Pittsburgh Research Laboratory (PRL), devised a passive means to detect overheating insulators on di¬rect current systems. The detector consists of a spring- loaded car¬tridge that ejects a reflective streamer of white Teflon tape when subjected to elevated temperatures. The cartridge assembly can easily be installed over the outer metallic shell of an existing trolley line insu¬lator. If an insulator overheats due to ground leakage currents, the vis¬ible streamer alerts mine personnel traveling on the haulageway.

Jan 1, 2000

The recovery of coarse particles has been widely recognized as being limited by the froth in mineral flotation. In response to this, FLSmidth has developed the Selective Froth Recovery (SFR) System. The SFR System is an extraction system that vacuums material from select locations within the froth and separates the recovered solids into coarse and fine fractions with a hydrocyclone. The SFR is supported and located by an actuator connected to the cell?s level control so that the suction heads are maintained at an offset distance from the slurry level. This can increase the recovery of coarse material by selectively recovering the material close to the bottom of the froth where drop-back of coarse particles typically takes place. The SFR System has been tested at two separate mine sites, and has been proven to increase the copper recovery in both trials. TEST RESULTS The SFR prototype was installed in a copper recovery circuit, on a rougher scavenger 160-m3 flotation cell. Figure 1, shows the SFR System, which consists of four conical skimmer heads that are plumbed together and share a common actuator. The SFR System, raised out of the froth prior to a test, can be seen in Figure 2. The SFR prototype was able to maintain a variety of set points using the level control to determine the slurry height.

Feb 27, 2013

By T. P. Weldum, B. J. Mahoski, R. S. Rasmussen

A case study of a systematic approach to grinding circuit steady-state optimization is presented. After an overall review of the flow-sheet, two operating circuits were prepared for detailed testing. Functional performance analysis was chosen as the primary modeling system, and, on this basis, a quality-assurance program for data gathering was implemented. A number of circuit-design and operating variables were investigated. Statistical analysis of plant-test results revealed relationships previously unquantifiable by any other modeling technique. Improvements in the classification system and in mill grinding efficiencies were demonstrated. As a result, there was significant energy cost savings.

Jan 1, 2000