Search Documents

By S. Corrent, F. A. V. Guimarães, M. G. Barbosa

"INTRODUCTION Moisture can be a villain, so new technologies have been explored to make more viable the production of high moisture iron ores. The current work presents the attempt of the utilization of a superabsorbent polymer (SAP) to aid in the screening process and in the ore handling process, such as stockpiles reclaiming and vessels/trains discharge in sub-zero temperature conditions. The results have shown that the polymer can be used in certain cases to improve productivity and increase safety in the process of handling the material (by increasing the TML). However, for size separation no advantages were found upon the use of the polymers. WATER ADSORPTION MECHANISMS The use of water in mineral processing is constant as its utilization brings an increase in the efficiency of separation. Although we have better results in the processing with water, materials with a high content of “natural” moisture can be very difficult to be treated by the conventional methods of separation. Nowadays many studies have been conducted in order to understand the effect of adsorption of water in the particles of complex minerals. Those studies have being divided in many different lines of research such as contact angle of a drop of water and the surface of the mineral to determine hydrophobicity, the particle size distribution and the porosity of particles. Mainly two forms of adsorption of water by the particles are possible: one the water is retained inside porosity of the particles. Laboratory tests developed in China have showed that capillary adsorption is faster in coarser particles that achieve the saturation degree earlier than finer particles (Xuewei Lv et al., 2011). The so called non-porous model considers the effect of water in the bulk sample of iron ores, in a physical connection when all the water works as a binder between particles as shown in the figure 1.If we take into account the compressibility of the system and compaction due to the weight of the bed over the particles, the thickness of the water film between particles is the same but the volume inside different particle size systems is much higher than in a system with particles of same size."

Jan 1, 2018

By D. Berberick

On January 5, 2012, the Mine Safety and Health Administration ordered the closure of the Silver Shaft, the primary underground access to Hecla?s Lucky Friday Mine, for removal of built up backfill material that accumulated over time on the shaft walls and furnishings. Lucky Friday and Cementation USA personnel worked quickly to identify the most effective means to get the mine back into production. The team developed a fast-track procurement and refurbishment plan utilizing shaft sinking winches, headframe modifications, a partial shaft sinking Galloway, and modified cages to not only complete clean-off of buildup, but also replace pipe brackets, shaft steel, and power and communications cables as needed in the 1,860 m (6,100 ft) deep shaft within 14 months.

Feb 23, 2014

By James M. Barker

The occurrence of borates and zeolites at Mesa del Alamo is well documented by McAnulty and Hoffer (1) and Lefond and Barker (2). Further investigation indicates the presence of priceite and meyerhofferite in addition to the howlite (1) and colemanite (2). Analcime occurs in addition to the clinoptilolite and phillipsite (2). The Mesa del Alamo area is about 200 !a south of Tucson, Arizona, and 13 km southeast of Magdalena, Sonora, Mexico, just south of the unpaved road to Cucurpe (Figure 1). The geology and mineralogy of northcentral Sonora is known only on a regional basis except for small areas mapped in detail during copper exploration. The study area is within the Basin and Range province of North America from which borates and zeolites are now produced in California. The borates and zeolites at Mesa del Alamo occur in geological environments similar to those of the Mojave and Death Valley regions of California (3, 4). Thus, a detailed exploration pro- gram in the Magdalena area could result in the discovery of economic borate and/or zeolite deposits.

Jan 1, 1979

By W. S. Weldon

The use of spiral separators for the beneficiation of fine coal typically in the size range -2+0.1mm is now well established process technology. Developments during the mid 1980's resulted in the production of cost effective, efficient large diameter coal spiral separators. Recent developments and research have been geared to optimize metallurgical performance, materials handling and equipment geometry of large diameter coal spiral separators.

Jan 1, 1997

By John Batchelder

The Copper Canyon Cu-Au-Ag deposits include two geologically distinct hypogene ore bodies developed primarily in late Paleozoic rocks adjacent to a 38-m.y.-old potassic-altered granodiorite, whose emplacement seems to have been controlled largely by the Virgin fault, a north-striking normal fault. Widespread but subeconomic concentrations of sulfides as fracture and cavity fillings in skarn apparently preceded the final intrusion of the granodiorite. In the west ore body, metals reached ore-grade concentrations through the massive replacement of andradite by chalcopyrite, pyrrhotite, and pyrite mineral assemblages. The east ore body probably formed after the granodiorite reached its present level. Calculated 6dD values of water in equilibrium with primary and secondary biotites range from -76 to -99 per mil at temperatures indicated by d180 values from coexisting quartz and biotite. The lightest values are in secondary biotite from the east ore body. These data suggest that fluids associated with potassic alteration here were most likely composed of magmatic water mixed with some meteoric water.

Jan 1, 1976

By J. D. McKay

Continuous column flotation parameter testing, to improve operating methodologies, using coarse bubbles on fluorite ore from Nevada, revealed that retention time is the predominant factor affecting column flotation fluorite recoveries. Column height and feed injection location affected fluorite grades and recoveries because they affected particle retention times in the collection and cleaning zones. Other parameters tested, including froth depth, wash water addition, and axial mixing, showed varying results. Four defined zones within the column were found to have characteristic rates of upgrading per vertical foot. Fluorite-gangue separation was more efficient in a column than in a conventional cell at all particle sizes.

Jan 1, 1987

By Qiang Wang, Jiaqiang Yu, Chunhui Fan, Yong Wang, Changyu Jin, Jun Bai, Yu Lu

Accurate ore blending necessitates an in-depth understanding of movement trajectories of fragments and the spatial evolution of the displacement field in the bench during blasting, Accurate ore blending is currently one of the most complex challenges faced by mining engineers. In light of this problem, a systematic study was conducted in this paper using neural network and numerical simulation based on field monitoring data. A nonlinear mapping relationship was established between the mechanical parameters of rock mass and the displacements of the monitoring points. The measured displacements of monitoring points under blasting were input into the neural network, which used back-calculation to derive the mechanical properties of the rock mass. These parameters were then applied in a forward calculation to analyze the movement trajectory of the monitoring points. The results showed that the calculated displacements were in good agreement with the monitoring results during the. The average relative errors in the horizontal and vertical displacements were 4.12% and 15.2%, respectively. Furthermore, the muckpile profile was in an inverted recumbent “S” shape after bench blasting, which was consistent with the actual shape of the muckpile. This verified the rationality and accuracy of the method proposed in this study. Finally, the movement trajectories of particles in the bench and the spatial evolution law of the displacement field during bench blasting were determined based on the calculation results, offering theoretical support and fundamental information for accurate ore blending.

Dec 16, 2023

By V. Steinbach

Non-renewable mineral raw materials are grouped into three categories to investigate ways leading to sustainable use of natural resources: 1.) metallic resources, 2.) non-metallic resources with the exception of the fertilizer minerals, and 3) the fertilizer minerals for the nutrients nitrogen (N), potassium (K), and phosphorous (P). With the exception of minerals in Group 3 which are essential for plant growth, mankind does not need raw materials as such, only the intrinsic property of a material that fulfils a useful function. This is especially true for non-metallic materials. Metallic resources have the best chance to become renewable if one makes optimal use of the resources of the man-made technosphere. For the fertilizer elements K and N there does not exist a problem, because sea water or air respectively provide an inexhaustible source for them. This does not apply to P however. So P is serving as one of our apposite case studies for solving sustainability challenges. For all the challenges along the road from a non-sustainable to a sustainable resource economy technology can be envisioned to come to the rescue provided conditions that are considered to be essential for sustainable use for all natural resources-- affordable renewable energy and human ingenuity to find new solutions for functions, to optimize processes and to minimize losses-- are satisfied.

Jan 1, 2011

By David Burgess

The paper describes experiments at the Somerset Mine, Colorado, under a cooperative agreement between U.S. Steel and the U.S. Bureau of Mines. A test was made of the tube bundle method of mine air sampling which was developed for European longwall mines; some 300,000 running feet of tubing provided continuous monitoring at 39 locations. Carbon monoxide concentrations were obtained with standard deviations of less than 1 ppm and oxygen concentrations with standard deviations of less than 0.20 percent. A base level of CO index (ppm CO evolved/pct 02 removed)) was determined to be 0-20 through most of the passageways of the mine. However, in one working section where the coal was initially hot (about 180°F within a pillar) the CO index was demonstrably higher, >20 trending upward to about 60 when smoke appeared and the section was sealed. The data are discussed in terms of laboratory experiments on CO evolution from coals.

Jan 1, 1975

Energy Developments Ltd. (EDL) has developed power plants at two Australian coal mines that featuring 94 gas-fueled Caterpillar G3516 engine/generator sets. They will convert to electricity 145 kt/a (160,000 stpy) of coal-seam methane gas for sale to a local utility. The $100-million project will cut the sites' methane emissions in half, provide a low-cost energy source and offset mine operating costs. The project began in May 1995. It is located at the Appin and Tower longwall underground mines, 80 km (50 miles) south of Sydney in New South Wales. The installation is one of the first to capture coal-seam gas from mine ventilation air and gas drainage systems. Coal- seam gas contains 40% to 60% methane, which fluctuates constantly. The system is expected to convert 578,000 m3/d (20.4 million cu ft/d) of coal-seam gas to 94 MW. It will also reduce greenhouse gas emissions by 3.5 Mt/a (3.8 million stpy) of CO, equivalent emissions. The Appin and Tower mines each produce 2 Mtla (2.2 million stpy) of clean coking coal. They operate around the clock with about 400 workers per site. The mines are owned by BHP Steel, Collieries Division, which will share the revenues from energy sales. The Appin Power Partnership consists of EDL and Lend Lease Development Corp.

Jan 1, 1997

By R. C. Kellner

Duval Sierrita Corporation, a wholly-owned subsidiary of Duval Corporation, operates an 86,000 STPD copper-molybdenum concentrator near Tucson, Arizona. Shortly after production commenced in February, 1970, it became apparent that the reduction crushing system represented a limitation to reaching the design capacity of 72,000 STPD. The development work performed on the reduction crushers in order to first meet design capacity, and to subsequently increase production to 86,000 STPD is described in this paper. The Sierrita plant is a conventional three stage crushing sys- tem. All crushers were supplied by the Allis-Chalmers Corporation and consist of two 58 x 89 Superior gyratories, four 138b EHD hydrocones, and ten 384 hydrocones. Screening is performed prior to and subsequent to secondary crushing and in closed circuit with the tertiary crushers. Typical throughput rates and equipment sizes are presented in Figure No. 1.

Jan 1, 1975

By Hans Ruge

The El Soldado copper mineralization occurs as relatively high-grade irregular ore bodies with assay contacts and with frequent inclusions of barren rock. The sampling method must be timely for production grade control purposes, as well as accurate and inexpensive. Sampling techniques evolved from sampling dump cars at the haulage level to sampling scooptrams at the loading pockets. These were abandoned in favor of sampling production blast holes. Several sampling alternatives are discussed. These involve the selection of optimum volumes and sampling frequencies while taking into consideration geological parameters and statistical analyses of sampling data.

Jan 1, 1984

By M. A. Bartkoski

Today?s surviving companies are being pushed to a heightened level of excellence due to market changes. Therefore, new business strategies must be explored. This paper offers a sequenced plan to retool, empower, and organize the entire team for a common goal. Integrity Process is an operating system that is very comprehensive and is integrated in every part of the business. It relies on a detailed prevention concept intertwined with accountability that produces individual efficiencies and team effectiveness. Integrity Process focuses on the importance between working from commitment motives versus compliance fears. The results are balanced in priority and truly yield a win-win for the owners, management, workforce, and the community. Integrity Process can and is being used in any industry that is challenged to optimize the relationship between people and process.

Feb 23, 2014

By Pramod C. Thakur

During the past ten years, the US coal industry has experimented with various ways to extract methane from coal seams. Drilling long horizontal boreholes in solid coal from mine workings and vertical gob degas boreholes are becoming standard techniques for methane recovery from coal seams. Prime motivations for such work have always been safety and productivity in mines, but the commercial value of gas so produced is encouraging utilization. The paper reviews various ways to produce methane from coal seams and discusses some utilization projects extant in the industry.

Jan 1, 1984

By C. G. Anderson

Extraction of valuable resources from complex orebodies will become more common. This is obvious for two reasons. First, the cleaner and more readily processed ores have continually been depleted through centuries of mining. Second, new technologies have evolved for effectively handling complex ores. One of these new processes has been in place at Sunshine since 1984. Based on sulfuric acid oxygen pressure leaching with nitric acid as an oxidizer, this patented technology allows silver and copper to be efficiently recovered from a complex sulfide concentrate. As efficient as it is, this process represents novel technology found nowhere else on an industrial scale. As such, a research program was undertaken in 1989 to optimize this leach process and to better understand it. From this study, several potential plant improvements were found and recommended. As a result, two of these options, nitric acid replacement by sodium nitrite and concentrate regrind are now used in day to day operation at Sunshine. Patenting of these changes was recently accomplished (1). Thus, the development, perceived mechanisms, plant integration and potential applicability of this technology will be covered in this paper.

Jan 1, 1994

By J. Diao

In order to understand the flotation kinetic behavior of coal and associated mineral matter, a detailed investigation was conducted in a 2-liter Denver flotation cell using three high sulfur coals at three feed sizes, minus 28. 100 and 200 mesh. Subsequently. the flotation products were sieved into different size fractions and analyzed for their ash and pyritic sulfur content in order to delineate the effect of particle size on the rate at which each constituent floats. The results were tested with several different flotation kinetic models and the best model for coal was then chosen. The flotation rate constant and the ultimate recovery calculated from a kinetic model were used to delineate the effect of particle size, collector (dodecane) and frother (MIBC) dosages on the flotation kinetics of coal, ash and pyrite.

Jan 1, 1992

By Edward S. Hsia

Pluor Utah has been closely associated with the engineering and construction of earth bottom thickeners for porphyry copper operations, for the counter-current decantation circuit of a gold cyanide plant and similar applications in mineral processing. During the past 13 years, some 18 of these thickeners have entered service and the bottoms have proved to be watertight structures with no particular problems encountered. In the course of this work, technological advances have been realized in the procedures for engineering and construction of these units to assure watertight basins and achieve all possible economies in construction. This paper describes the successful application of engineering and construction techniques for a number of these thickeners.

Jan 1, 1977

By F. Stanley, A. Noble, G. Luttrell

"The supply chain for coal-fired power stations involve a multi-stage network of mining units, preparation plants, blending facilities and transportation systems. Attempts to optimize the supply chain have historically been difficult due to the lack of communication/coordination between the various groups involved in coal production, transportation and utilization. In light of this issue, a new approach for globally optimizing the coal supply chain called Micro-Price Optimization has been developed to simplify the optimization problem and to provide coal producers with fundamental insight needed to improve the profitability of their operations. This fundamental concept assigns unit values to each particles (or groups of particles) passing through production units. Optimization occurs whenever the maximum tonnage of positive value particles are recovered and passed to market, while the minimum tonnage of negative value particles are recovered. Elements considered by the concept include factors such as target boiler cost/efficiency, waste disposal costs, coal quality parameters, emission penalties, transportation charges, or other quantifiable impact factors. This article reviews the basis for the micro-price concept and provides a detailed industrial case study involving the determination of optimum coal qualities that need to be supplied by mine operators to feed a coal-fired power station. INTRODUCTION The performance of coal preparation plants have long been known to play an important role in determining the overall profitability of mining operations. This significance is due to the fact that the misplacement of just 1 ton/hr of clean coal to reject resulting from poor plant performance can represent nearly $300,000 per year in lost revenues for a mine producing a steam market coal (i.e., 1 ton/hr x $50/ton x 6,000 hr/yr = $300,000/yr). This loss can be even more pronounced, occasionally approaching $1 million per year for each 1 ton/hr of misplaced clean coal, for operations producing high-quality coking coal products sold into the premium metallurgical market (i.e., 1 ton/hr x $150/ton x 6,000 hr/yr = $900,000/yr). Detailed economic studies indicate that improvements in plant yield resulting from increases in organic efficiency have one of the largest overall impacts on mine revenue when compared to other cost centers within the mining operation. One of the first studies to show this important financial impact was reported by Norton-Hambleton Consultants (Norton, 1979). Their study indicated that an unfavorable change in plant efficiency was second only to coal transportation in terms of its impact on profitability, while an unfavorable change in the cost of underground mining was a distance third. This longstanding realization has continued to provide a strong financial incentive for coal producers to optimize the separation efficiency of their coal processing and blending operations."

Jan 1, 2015

By G. S. S. Raman, M. S. Klima

The effects of pressure and cake thickness were studied using a split-plot design for pressure filtration of a fine refuse slurry obtained from a bituminous coal preparation facility. Pressure filtration offers the potential to significantly reduce the moisture content of the fine refuse stream with the addition of little to no flocculants, thereby minimizing the volume of refuse stored in impoundments and providing a recycle water stream for use within the plant. Experimental results showed that the final cake moisture decreased with increase in pressure and decrease in cake thickness. In addition, specific cake resistances calculated for the various tests indicated an increasing trend with increasing pressure and decreasing cake thickness. With increase in cake thickness, an increase in cake moisture and the weight of solids deposited in the cake was observed. An ANOVA analysis indicated that both cake thickness and pressure significantly affected the cake moisture, while only cake thickness statistically influenced the weight of solids in the cake. A regression model was developed with an R2 value of about 0.99 to relate cake thickness, the single largest statistically significant factor, with the weight of solids in the cake. Filter capacities were calculated in terms of the solids deposited per unit time based on a product specification of 25 percent cake moisture, and it was observed that the thinnest cake had the highest filter capacity.

By S. Frisch

Selenium (Se) in effluent waters has become a significant challenge for a number of industries. Toxicity studies and new reports of occurrence have certainly caused increased scrutiny and actions in the mining industry today (Sandy, DiSante, 2010). While initial activity in addressing selenium-laden waters were conducted in the coal mining industry, today a much broader range of mine types are beginning to search for solutions to selenium treatment of their mining waters, including both hard rock mining operations (gold, nickel, zinc, etc.) and soft rock mining (phosphate, uranium, etc.) Throughout North America, new regulations covering selenium discharge are either in place or being developed. While a number of physical/chemical approaches show promise in selenium treatment, when considering optimal cost and treatment efficacy issues, biological treatment ? particularly fixed-film biological treatment - is reported to be one of the most promising approaches to managing selenium-containing waters. Among biological treatment options, the fluidized bed reactor (FBR) has undergone extensive pilot testing for Se treatment in the last three years, including eight pilot programs, and the first FBR system is now operating at a coal mining site. In all tests, the FBR has been shown to be a highly cost-effective approach to selenium treatment based on its physical and performance characteristics. This is consistent with its history for reaching low levels of treatment in similar service for other oxyanions including perchlorate, nitrate and various metals. With the results from the most recent testing, the technology has been shown to be adaptable to an ever-broadening range of influent water conditions and flow rates, in varying terrains and weather conditions. Selenium occurs in various valence states from -2 to +6 (Sobolewski, 2005). The speciation of selenium plays a critical role in understanding the effectiveness of any approach for removal, especially to low levels. Elemental selenium is insoluble and has little effect on living organisms. Colloidal fractions are known to occur. In aqueous environments such as coal mining runoff, selenium is most often found as the oxygenated anions of selenite (SeO32-, Se4+) and selenate, (SeO42-, Se6+). Selenium is commonly found in mining waters in concentrations ranging from 3 to >12,000 µg/L. The U.S. National Primary Drinking Water Standard MCL is 50 µg/L for selenium (EU 10 µg/L; WHO 40 µg/L). The National Fresh Water Quality Standard is 5 µg/L for selenium. The U.S. Fish and Wildlife Service has recommended that the National Fresh Water Quality Standard be lowered to 2 µg/L to protect fish, waterfowl, and endangered aquatic species. Several states have followed with enforcement actions at these same low levels. In Canada, permits may require stakeholders to monitor levels in water or biota, or to comply with guidelines, at either the National or Provincial levels, which can be as low as 1 or 2 µg/L in surface waters. Treatment of selenium in all mining waters presents a series of challenges. It can be present in relatively dilute concentrations and in streams with variable and often high flow rates. It can be present in many soluble and particulate forms, which may affect process design and treatability. The conditions of influent selenium-containing waters can vary, with issues such as temperature, pH, total dissolved solids and other contaminants affecting the ability to remove selenium selectively and economically. Treatment of selenium often results in the generation of a concentrated by-product requiring disposal, and re-release from residuals can occur. Beyond these issues, the physical environment of a mining operation can offer challenges such as remoteness and harsh and/or cold weather. Currently available selenium treatment technology (Table 1) includes biological treatment and a number of physical-chemical processes ? such as ion exchange, membrane filtration and adsorption ? that vary widely in efficiency and cost. Most treatment options remain either too costly and/or unproven for selenium-containing streams for reasons that include poor removal efficiency, variability in volume and composition of influents, system sizing and logistics considerations, as well as operating requirements.

Feb 23, 2014