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By B. Andersen

An accurate knowledge of Interactions among mineral particles and between such particles and dissolved and precipitated species Is Important in developing efficient separation processes. In this investigation interactions in Florida phosphatic clay waste, that are relevant to dispersion and selective reagent adsorption, the two main prerequisites for selective flocculation, were studied. Initial studies with artificial slimes, consisting of pure clay and phosphate minerals, showed dispersion of artificial slimes to be relatively easy. The problems that were encountered during selective flocculation of the artificial slime were due to unselective polyacryllc acid adsorption on clay, which was caused by the presence of multivalent calcium ions on the exchangeable cation positions on the clay surfaces. This problem could be solved by exchanging calcium for sodium, which reduces the interaction between the polymer and the clay surface. This procedure, however, was not successful for mineral mixtures. Natural slimes were found to be much more difficult to disperse. This was attributed to the presence of cementing materials such as humic substances and Ai and Fe (hydr)oxide precipitates. Selective removal of these cementing materials resulted in good dispersion and partial separation. Further increase in separation of natural slime is likely determined by the presence of calcium on the clay surfaces, as was found for the artificial mixtures.

Jan 1, 1992

By Z. Man, X. Zhu, Y. Xian, Y. Tao

"Fine coal separation has been always concerned. The froth flotation is not efficient in desulfurization because of the low rate of sulfide liberation from raw coal, the natural hydrophobicity caused by sulfur concentration on the surface of sulfide, and the presence of large amounts of middling feed. An efficient centrifugal gravity separator was employed to separate for Shandong –0.5mm high sulphur coal, the partition curve of centrifugal separator was obtained with conclusion that the Ecart probable error value of the separator is 0.095, the imperfection I value is 0.128. Finally, comparing with the coal flotation using progressive release method, the result shows that the effect of the desulfurization with centrifugal gravity force field based on density difference between coal and minerals are much better than that of the floatation which operates based on the difference in surface properties. It provides a efficient technical way for fine coal separation. INTRODUCTION Coal plays the most important role in the energy consumption in China. Although natural gas, wind energy, nuclear power has made great progress in recent years, but the share of coal in the final energy consumption accounts for 70-80%, which is determined by energy storage of China. Under the requirement of environmental protection, the clean utilization of coal resources becomes more and more important, and the need has already been identified. Coal washing and processing plays an important role in the process of high-efficiency and clean utilization of coal. For the separation of fine coal, flotation is a traditional method for effective separation and has been used in large scale industrial applications in coal preparation plant. However, for the separation of difficult-to float coal, especially fine oxidized coal and low–rank coal with hydrophilic surface, flotation is usually inefficient [1-3]. Although many pretreatment methods have been adopted, including grinding, microwave pretreatment, new flotation reagents, the problem of efficient separation has not been completely resolved [4-6]. Thus, an enhanced gravity separation method using particle density difference rather than hydrophobic difference was proposed for the separation of fine coal. Many research results have proved that this is a practical and effective method of sorting. R.Q. Honaker used Falcon C10 concentrator, Knelson centrifugal separator and spiral separator to clean the fine coal with size of 600*210 µm and 210*37µm, the effects of different operating parameters on the separation index was discussed. The results show that the separation density of Falcon can reach 1.6, and the Ep value can reach 0.1-0.15. This paper revealed that for the separation of fine coal with high sulfur content or fine grained content. Falcon has high separation efficiency with low cost. Separation results present in another paper showed that the desulfurization efficiency of inorganic sulfur was better than that of flotation [7-8]."

Jan 1, 2017

By Renee Royer, Allan Punkkinen

As mines progress to ever increasing depth, new challenges are encountered with serious concerns for rock excavations in highly stressed conditions. New procedures have been undertaken or are under way to remove workers from the workface, mitigating risk and exposure to hazardous conditions. Rockbolting crews are at particular risk as they are the first line of defense in the installation of the ground support systems. One such initiative for removal of workers from danger has been with remote bolting. Equipment manufacturers have had the ability to remotely inject resin pneumatically into boreholes for several years, but it has not been recognized as a very effective method due to a variety of complications. This makes the installation of dynamic support system components such as the D-Bolt® increasingly difficult. More recently, hollow-core bolts have become popular providing far more effective installation when installed with pumpable, two component urea-silicate injection resins. Normet has developed high energy dissipation self-drilling dynamic bolts (SDDB®) to meet these challenges. Following several inquiries as to the effectiveness of pumpable resins for use with dynamic support components, Normet Canada performed comprehensive testing of the bolt and resin system at CanmetMINING in Ottawa to dispel or substantiate any preconceived beliefs. Several dynamic and static tests in direct and indirect loading were carried out. Results include tests in shear and early strength UCS of the resin to measure the performance of the SDDB compared with the established D Bolt as an effective dynamic ground support component. Underground field observations, installation methodology and in-situ testing are investigated.

Apr 26, 2022

By J. J. Gusek

An 81 hectare (200 acre) tailings impoundment at a taconite operation in Wyoming that ceased operations in 1983 has been a source of blowing dust. The site qualified for reclamation under Wyoming's Abandoned Mine Land (AML) reclamation program. The ultimate reclamation construction included: incorporating commercially available organic amendments and fertilizers into a 300 mm (12 in) thick "cap" of a sterile clay loam cover material, lowering the water level in an adjacent flooded mine pit that was feeding uncontrolled seeps into the tailings basin, constructing a wide tailings pond spillway that allows flood control while minimizing seasonal water level fluctuations in the pond, and building rock berms and rock snow fences for wind erosion control and soil moisture preservation. Tree planting in the protective wind/snow shadows of rock berms and rock snow fences, and the plugging of a decant pipe are planned for future work.

Jan 1, 1998

By D. Newman

"The U.S. stone industry is in a transition from surface quarries to single and multiple level underground stone mines. The factors driving this transition include surface quarries; ? reaching their economic stripping ratio, ? encroaching on the mineral reserve boundary where the remaining reserves are below the active pit, ? dust, noise, and blast vibration concerns as suburban neighborhoods and development move into formerly rural areas. Ground control is critical to the success of a safe and productive, mining operation. The primary focus of the ground control engineer in an underground stone mine is the stability of the roof or back, development and benched pillar stability, stability of the sill pillar between vertically adjacent mining levels, and floor stability. Roof stability begins with the selection of a stable back horizon based upon the presence of a thin shale parting, stylolite, or other discontinuities from which the production shot can easily ""peel"" away leaving a stable back stratum. Room width and the decision of whether to bolt the roof, the bolt length, bolt type, bolt diameter, and spacing of the support is controlled by the thickness, fracture spacing, jointing, and material properties of the back strata. Horizontal stress controls the header and crosscut azimuth as to avoid driving perpendicular to the maximum horizontal stress direction. Stable pillar dimensions depend upon the interaction of the; ? vertical stress resulting from overburden thickness and multiple level interaction of overlying level(s), ? mining height during development and the final mining height after floor shots are taken while benching, ? presence of faults, folds, or joints passing through the pillar, and ? stone lithology recognizing that the presence of oolitic bands, shale partings, and bentonite beds create zones of weakness that can destabilize an otherwise competent pillar. Floor stability is typically not a significant issue for underground stone mines because the bearing capacity of the stone exceeds the vertical pressure transferred through the pillar. However, floor heave can be a ground control issue where shale partings, moisture sensitive strata, weak stone bands, or horizontal stress is present. Roof stability and pillar stability problems can be initiated as the floor heave enables the pillar and roof to settle. The ground control issues for underground stone mines are most clearly presented through a series of case histories. The case histories presented in this paper are a mix of ground failures and successful mining. The focus is on the geotechnical data required for underground stone mine ground control for roof, pillar, and floor design and stability analysis."

Jan 1, 2016

By Colin Irwin, Adrian Naranjo-Castillo, Christopher Petta, Eric Zarobila

The Shoreline Consolidation Sewer is a CSO control project in Cleveland, Ohio that requires the installation of 5,000 feet of 72-inch inside diameter pipe using microtunneling methods. After award, the contractor submitted a value engineering proposal to eliminate two deep shafts and install the tunnel in two drives instead of four. In an example of successful collaboration, owner, contractor, and engineer worked together during the initial construction stages to modify the design and update the contract documents. This paper examines the importance of exible requirements in contract documents and a collaborative environment between all parties to successfully deliver a project.

Jun 23, 2024

By J. L. Arola

Since start-up of fluxed pellet production in August: 1987, the Minorca Mine has made a number of process changes to improve pellet quality and productivity. Quality improvements include: 1. Installation of a contraction t:ester. 2. Installation of on-line calcium and silica analyzers. 3. Process autocation changes. Productivity improvements include: 1. A second fluxstone storage bin and feeder. 2. A new vacuum pump and disc filter. 3. A filter aid addition system. 4. Enclosing the filter cake reclaim feeder. 5. A new grate bar cleaner.

Jan 1, 1989

By M. D. Bishop

Early solvent extraction circuits in the uranium industry utilized bona fide kerosenes as diluents for extractant chemicals. These kerosenes were used successfully in the uranium industry; however, at least one plant was destroyed by fire resulting from the use of a low flash point kerosene. Although the term "kerosene" is used throughout the solvent extraction industry, the authors have been unable to find any use of kerosene in copper solvent extraction circuits. A term that is occasionally used with reference to diluents is "metallurgical kerosene." Such a term is unrecognizable in the petroleum industry. Kerosene [or kerosine] is a flammable hydrocarbon mixture that is less volatile than gasoline. It is produced for combustion purposes and may have variable compositions of organic compounds including alkanes, alkenes, alkines, and aromatics. Diluents are constant composition hydrocarbon mixtures developed specifically for use in solvent extraction processes. These products usually have much lower vapor pressures and higher flash points than kerosene. In solvent extraction systems, they typically comprise 70 to 95 v/o percent of the circuit organic. The primary purpose of the diluent is to adjust the extractant concentration to the working range of the operation. The diluent and extractant must be completely soluble or miscible with each other. Secondary diluent effects are to promote transfer kinetics, optimize phase disengagement, and minimize both organic in aqueous and aqueous in organic entrainment.

Jan 1, 1996

By C. Van Landingham, A. Bailey, R. A. Schoof

A residential metals abatement program has been underway in Butte for more than 20 years. More than 1,350 yard and attic cleanups were completed by the end of 2018; most triggered by lead. While the focus is on remediation of residential soil and house dust, the program also includes a blood lead monitoring program with identification and abatement of additional sources of exposure for children with elevated blood lead levels (BLLs). As specified in the remediation program, studies are being conducted every 5 years to assess BLL data collected from Butte children. The first two studies have evaluated over 6,000 BLLs from 2003 through 2017 and evaluated trends over this time period, by Butte neighborhood, and as compared to areas outside of Butte. These studies showed that rates of elevated BLLs (i.e., those above 5 µg/dL) in Butte children have declined dramatically since 2002 but have been declining much more slowly since 2011. Improved rates of confirmation testing are needed to verify the rates of elevated BLLs. While the RMAP likely has contributed to these declines in BLLs the magnitude of impact cannot be quantified.

Mar 2, 2022

By T. Krumins, L. Zunti, R. Frischmuth

"Titanium and titanium alloys are commonly selected for pressure oxidation autoclave vent piping and pressure control valve components, as well as autoclave internals and other process piping. In the autoclave vent application, titanium ignition risk is controlled by limiting oxygen concentration, and preventing high gas velocity gas impingement on surfaces. Oxygen concentration is dependent on the autoclave pressure and temperature operating conditions and therefore oxygen concentration and the associated titanium ignition risk is dependent on standard operating procedures, process control interlocks and permissive conditions. It is not uncommon for these standard controls to be deficient during atypical operating conditions, or for operations to deviate from the operating procedures, increasing the potential for a titanium ignition incident. Titanium ignition risk caused by elevated oxygen concentration in autoclave vent systems can be reduced with the introduction of an online autoclave overpressure calculation and the configuration of associated interlocks and permissive conditions. INTRODUCTION High temperature pressure oxidation (>190°C) is a well recognized and versatile metallurgical oxidative pre-treatment process commonly used to liberate gold from refractory sulphide ores and concentrates before conventional leaching with cyanide. Titanium and titanium alloys are highly corrosion resistant in pressure oxidation process conditions and are therefore commonly selected as materials of construction for many components including: autoclave internals, agitators, process piping, and components in autoclave vent systems. Operations that anticipate or have experienced aggressive corrosion in the vent system often have little choice in material selection other than the use of titanium (Krag & Henson, 1992). Titanium is not suitable for use with elevated oxygen concentrations and is considered a restricted material because of its high pyrophoricity and combustion propagation properties (Beeson, Smith, Stewart, 2007). Several serious incidents have occurred in which titanium materials have ignited in autoclave applications (Zawierucha, McIllroy, Million, 1995). In autoclave vent applications, titanium ignition risk is reduced by preventing elevated oxygen concentrations, maintaining low gas velocities, and minimizing the potential for gas impingement on surfaces. Oxygen concentration in the autoclave vapour phase and vent system is dependent on the autoclave operating pressure and temperature conditions and therefore titanium ignition prevention controls typically include process interlocks and operating procedures based on the selected nominal design operating conditions. However, it is not uncommon for these controls to be deficient or for operations to deviate from the nominal operating conditions over time, increasing the risk of titanium ignition. The introduction of an online calculation of autoclave overpressure and a maximum target autoclave pressure as well as associated process control interlocks and permissive conditions can alert the autoclave control room operator and prevent an elevated oxygen concentration from developing, and therefore reduce titanium ignition risk in autoclave vent systems."

Jan 1, 2016

By K. Zhang

Real option value (ROV) method is considered to be more practical and advanced compared to net present value (NPV) method in evaluating a mining project, in particularly when there is substantial uncertainty in the commodity market as well as possible operational flexibility embedded in the project. Usually, it may take months or even years for the commodity product to be available in the market after the mining activation decision is made. The impacts of postponing the delivery of commodity product on the mine?s ROV and NPV are assessed based on the proposed real option method. Postponing the delivery of the products leads to declined NPV and ROV compared to the non-postponing scenario and extended postpone results in higher lost values in NPV and ROV. For a mine with lower mining cost, by postponing the delivery, the exercising threshold of commodity price is lower because the mine owner anticipates that commodity price may rise during the time of postponing. A mine with higher mining cost requires a higher exercising price threshold to ?lock up? the profit when there is ambiguity of market situation due to the postponing of the delivery.

Feb 23, 2014

By George E. Edwards

Pacific Rim markets for export coal already represent a larger market than the total tonnage imported into the European Community countries and they will continue to expand. The largest importers will continue to be in the sector comprising Japan, Korea, Hong Kong and Tai- wan. It is likely that the total Pacific Rim markets will reach 206 m.t.p.a. by 1990 and 290 m.t.p.a. by 2000, with the major growth in steam coal demand. Australia has an efficient coal industry, represents a stable long term source of supply and is favourably situated geographically to continue to be the largest single supply source.

Jan 1, 1982

By R. E. Nivens

In the past, Newmont Gold Company relied on cement for their ore agglomeration process. With assistance from Betz Industrial, Newmont began Investigating the use of polymers for ore agglomeration. If gold recovery would not be jeopardized, then polymers could replace cement and possibly reduce operational costs associated with cement agglomeration. The following outlines the preliminary testing conducted to determine the feasibility of polymer agglomeration with Newmont's ore and the results of the test heap, which was constructed so the program could be examined under actual operating conditions. Similar polymer agglomeration testing has been successfully performed in other Nevada gold operations. By eliminating the need for cement, a polymeric agglomeration program could improve material handling operations, as well as offer the following additional savings. First, the polymer application uses only lime for adjusting basicity, the polymer does not contribute any alkalinity to the heap. Because lime is more soluble than cement, detoxification of the heap becomes much faster and less costly for the mine relative to rinsing cement alkalinity. The following graph compares the detoxification rate of cement and polymer over a 33 day cycle.

Jan 1, 1993

By P. Stanley Jacobsen, Hemant B. Gala, Richard E. Hucko

Coal is the nation's most abundant fossil energy resource. However, its use is limited because of the nature and amount of associated impurities, such as mineral matter, sulfur, trace elements, and moisture. The moderate-to high- sulfur content of many U.S. coals is of particular concern as current and newer, potentially more stringent, regulations require reduction in sulfur oxide emissions. Release of particulates, NOx, and other pollutants during the coal-use cycle is also of concern. The current practice of controlling sulfur oxide emissions in the major steps of the coal- use cycle is limited mainly to coal preparation by physical beneficiation and, to a smaller extent, to post-utilization cleanup (flue gas desulfurization). Approximately two-thirds of the coal from states east of the Mississippi river is physically cleaned, whereas only 15% to 20% of the operating boilers in the utility industry are equipped with scrubbers to desulfurize the flue gas (Henzel, 1988). Physical beneficiation methods can be very effective in removing mineral matter, including pyritic sulfur, from coal. These processes take advantage of the differences in physical proper- ties between coal and mineral matter to achieve the separation. In a typical physical cleaning operation, raw coal is crushed to about a 50-mm (2-inch) top size. It is then screened into coarse, intermediate, and fine sizes. Crushing the coal liberates some of the ash-forming minerals, including a portion of the sulfur that is not chemically bound to the coal. The per- centage of impurities freed from the coal matrix generally increases as the coal particle size decreases. The coarse- and intermediate-sized coals are typically subjected to a cleaning pro- cess based on differences in specific gravity between coal particles and the associated impurities. Such cleaning processes used include jigs, dense-medium baths, cyclone systems, and concentrating tables. The fine-sized (typically less than 0.5-mm) coal, if beneficiated, is typically cleaned using a froth flotation technique based on the differences in surface proper- ties between coal and its associated impurities. At fine sizes, greater cleaning potential exists because a greater portion of the impurities is released from the coal matrix. However, this potential is not fully realized owing to inefficiencies in separating fine particles using state- of-the-art flotation technology. Overall, current commercial coal preparation processes are estimated to remove up to 60% of the ash and 10% to 30% of the sulfur, depending on the coal characteristics, with product weight recoveries rang- ing from about 60% to 90% and thermal recoveries of about 85% to 98% (Versar, 1985; Science Applications International Corporation, 1987; Hoffman- Muntner Corporation, 1978). For many U.S. coals, grinding to sizes finer than those used in current coal preparation plants is required to liberate most of the physically bound impurities from the coal matrix. As noted, conventional coal-cleaning methods are not very effective at these fine sizes. Accordingly, the expanded use of domestic coal requires the development of advanced coal cleaning technologies that can provide economic performance while reducing environmental impacts. Program Goals and Objectives The overall goal of the U.S. Department of Energy (D0E)'s Coal Preparation Program is to provide the scientific and engineering knowledge base that industry can utilize to produce economically competitive and environmentally acceptable clean-coal products for introduction as market conditions warrant. The coal preparation process(es) should remove undesirable components from coal and improve its handling characteristics, thus making the product coal technically, as well as economically, viable as a competitor with petroleum-derived fuels and natural gas, and with alternative environmental control technologies. The coal preparation process must be applicable to a wide variety of bituminous and low-rank coals. The cleaning process should reduce the variability among clean-coal products from various raw coals, thus significantly increasing the range of potential end uses for each raw coal. To the extent that deeply cleaned coal products have greatly reduced levels of

Jan 1, 1988

By B. Blaschuk

The Freeport McMoRan Bagdad Solvent Extraction (SX) circuit is the oldest plant of its kind currently in operation. The plant was commissioned in 1969 and was the second SX-EW operation to be built following the Ranchers Bluebird solvent extraction and electrowinning (SX-EW) plant near Miami, Arizona. Over the years of operation, the configuration of the SX has gone through many changes to accommodate a variety of pregnant leach solution (PLS) grades and flows. Although modifications to the original plant configuration are numerous, the Bagdad SX circuit has maintained its general form consisting of multiple long and narrow settlers. The unique configuration of the Bagdad SX circuit presents a variety of operational advantages and challenges; however, it continues to operate at a level recognized in the industry as excellent.

Jan 1, 2010

By Madan M. Singh

With the current emphasis on ecology, safety, and conservation of natural resources, some consideration should be given to methods of mining that reduce surface damage, make the mining of coal less hazardous, and allow exploitation of a larger percentage of the coal in situ. One method that can be helpful toward attaining these objectives is the use of packing or stowing. Stowing involves the replacement of the ore that has been removed by waste material obtained from within the mine or elsewhere. Evidently, it would be most beneficial if this waste for packing were available from the mine being worked, but generally this is not possible. If complete stowing is adopted, it is necessary to bring in packing material from other sources. Stowing tends to reduce surface subsidence, but not eliminate it. It enhances roof support and curtails accumulation of methane in the gob, making the mining operations safer. It may also allow one to obtain a larger amount of coal. Currently, in the United States, a substantial amount of coal is left in place as pillars, in the hope that it will support the overburden indefinitely. Some of these could be extracted with stowing. The mining of thick, steep, or contiguous seams would also be facilitated.

Jan 1, 1974

By M. A. Anderson

After mope than fifty years Of Continuous operation, the Nevada Mines Division found itself faced with declining ore headings and metallurgical efficiencies, and rising operating costs. Although intensive process improvement programs had been initiated at various times in its history, insufficient return on investment served to defeat plans for any major changes in circuitry. The advent of practical large-volume flotation machinery, along with the success of long-range exploration drilling programs, complimented the results of an intensive program of research and development. The result of laboratory testing, pilot plant testing, and full scale plant tests was the proven indication of metallurgical improvement given increased flotation residence time and the effect of mechanical agitation in flotation.

Jan 1, 1975

By Harrison R. Cooper

The expanding use of digital control in the metallurgical industry is a significant recent development. From 1970 to 1975, approximately forty metallurgical plants throughout the world have adopted automation techniques based on digital controls (see Table 1). Several recent technical reports have described development of digital control systems in concentrator grinding control, 1,2 flotation,3 and smelter operations.4,5

Jan 1, 1975

By J. L. Fuller

Thousands of mine air samples are taken underground each year by MSHA inspection personnel in order to further assure that miners have a safe and healthy environment in which to work. While most air samples are taken with stain tubes, many samples are obtained in evacuated containers and returned to a laboratory for more accurate analysis on a gas chromatograph. In order to enhance the accuracy, reliability and repeatability of the samples taken with evacuated containers, improved procedures have been developed, which are described in this report, for filling two different types of evacuated sample containers using either mechanical or electrical pumps. In those instances, such as when sampling strata gases in drill holes, where mathematical calculations may be required for proper sampling, example calculations are provided. The use of a third type of evacuated container, which is generally restricted to non-specific sampling of the ambient mine atmosphere, is also described.

Jan 1, 1986

By Elmer H. Citron

The Monterey Coal Company, a wholly owned subsidiary of The Carter Oil Company of Houston, Texas, recently awarded a contract to build the Monterey No. 1 Preparation Plant, which will be located near Carlinville, Illinois, to the McNally Pittsburg Manufacturing Corporation. The preparation plant will be one of the most modern jig preparation plants in the State of Illinois. Illinois No. 6 coal will be delivered by a 48" slope belt having 35-degree carrying idlers, operating at 650 FPM and operating on an incline of nearly 17 degrees. The slope belt is driven by two 450 BP motors and will deliver the mined coal at the rate of 1800 TPH to a stationary step-type ' screen having six-inch openings. The overproduct from the stationary screen will discharge into a 10' x 24' McNally Rotary Breaker and the underproduct will bypass the rotary breaker. The rotary breaker is equipped with heavy manganese screens with 6 ½" diameter openings. The sized 6" x 0 coal from the stationary step screen and the rotary breaker will be discharged by gravity to a 4%" raw coal incline storage belt. The 48" raw coal storage belt will deliver the 6" x 0 sized coal at the rate of 1800 T?H to an 8000 ton concrete raw coal silo, 70 feet in diameter and 1x7 feet high. The 6" x 0 sized coal will be drawn from the concrete storage silo by seven (7) 36" wide reciprocating plate feeders. Five feeders are to have constant speed drives at a rated capacity of 145 TPH each. Two (2) feeders will have remote con- trolled variable speed drives, to provide a varying feed.

Jan 1, 1970