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By Roger J. Araujo

A photochromic material is one which undergoes a change of color when exposed to light and reverts to its original color when the light is removed. Review articles carrying extensive bibliographies have been written by Brown and Shaw (1) and by Schwab and Bertelson (2). Organics. Schwab and Bertelson divide the reactions in different organic photochromic materials into some half-dozen categories; Windsor (3) reduces these to the following three main classes of general interest, based on how they work. 1. Stereoisomers. Absorption of light breaks one of the chemical bonds in a. ring molecule, thus allowing the molecule to unwind and form a different geometrical arrangement. The reverse process is a reforming of the bond. Examples of this class are the spiropyrans and the anils. 2. Dyes. A triphenyl methane dye, for example, is oxidized by energetic light; the absorption characteristics of the positive ion so formed are different from those of the original electrically neutral benzene rings. 3. Triplet States. In the class of polynuclear aromatic hydrocarbons, ground-state molecules are excited first to a singlet state by irradiation, and then go, via the lowest triplet state, to an excited triplet state. Visible light is absorbed in the triplet-triplet transition.

Jan 1, 1970

By S. M. Carpenter

In response to the FY2008 Consolidated Appropriations Act (H.R. 2764; Public Law 110?161), the United States Environmental Protection Agency (USEPA) issued the final Mandatory Reporting of Greenhouse Gases Rule (MRR). The rule, signed by the USEPA Administrator, Lisa Jackson, on September 22, 2009, requires reporting of greenhouse gas (GHG) emissions from large sources and suppliers in the United States, and is intended to collect accurate and timely emissions data to inform future policy decisions. The MRR will go into effect on January 1, 2010, and a report of the total emissions for calendar year 2010 will be due to the USEPA by March 31, 2011. Under the final MRR, suppliers of fossil fuels or industrial greenhouse gases, manufacturers of vehicles and engines, and certain facilities that emit 25,000 metric tons or more per year of GHG emissions are required to submit annual reports to the USEPA. The gases covered by the rule are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFC), perfluorocarbons (PFC), sulfur hexafluoride (SF6), and other fluorinated gases as outlined in Table A-1 of Subpart A of the MRR, which is also provided in Appendix A of this report.

Jan 1, 2011

What decision making tools and methods are available to a project owner when there is no clear differentiator between construction alternatives? A team led by a joint venture of Parsons Brinckerhoff and PGH Wong Engineering (PB/Wong) has been providing preliminary engineering services to the San Francisco Municipal Transportation Agency (SFMTA). The SFMTA and PB/Wong team developed several alternative construction methods for the tunnels and stations of the San Francisco Central Subway Project, none of which could be judged clearly better than another using traditional approaches and metrics. The team employed a risk assessment and analysis frame-works as a means of comparative analysis, drawing upon the knowledge of industry experts in the geotechnical, tunneling and construction fields to assist in the effort. This paper presents the approach and results of a cost and schedule risk analysis for two such analyses designed to answer two different questions regarding the advisability of different construction approaches. These assessments paved the way for key decision making in the preliminary engineering phase of the project and formed the foundation for continuing risk management efforts on the project. The focus of this paper is primarily the first two stages of risk management?identification and assessment?and some of the organizational dynamic issues that arise in such efforts.

By D. L. Ogonowski, J. O. Marsden

The Candelaria copper-gold mine is located approximately 25 km south and east of Copiapo in Region III, Chile. The original concentrator was designed to treat 28,000 t/d (30,800 stpd) of chalcopyrite-bearing ore through a circuit consisting of a single 11.0 m(36 ft) diameter SAG mill, two ball mills, conventional rougher and scavenger flotation, column cell cleaner flotation, and ceramic disc filtration. The plant was commissioned in August 1994 and quickly reached design capacity and expected levels of metallurgical performance. In May 1996, a decision was made to double the capacity of the concentrator by the addition of a second line of equipment. The expanded facilities were commissioned in October 1997, less than 18 months after the decision to proceed, and well within the budget. The original concentrator facilities were replicated or duplicated as much as possible, however, a number of important equipment changes were made to take advantage of industry developments since the original concentrator was designed. These included the use of Eimco 120 m3 (4,200 ft3) cells for rougher and scavenger flotation and the installation of a Svedala VTM-800Vertimill for regrinding. This paper describes the rationale behind these changes and explores the reasons for the success of the project.

Jan 1, 1999

By K. Hanson

When done properly, benchmarking is an extremely effective tool for assessing ones performance, finding areas for improvement, and identifying strengths. However, when done improperly it can be an exercise in futility and result in incorrect observations and conclusions. A primary pitfall of benchmarking is collecting too much unreliable information. Surprisingly, the evolution of data storage and the ease of data collection are not helping with better data collection. Instead, it is just allowing one to collect more information, while at the same time inundating one with too much data. Additionally, the process of data collection can be tedious and is often times delegated to the least experienced individual resulting in unreliable and incorrect data collection and entry. Another primary pitfall of benchmarking is metrics that are cost based or poorly designed. Cost based metrics typically involve comparing unit mining costs ($/tonne). Between mines, unit mining costs are not very well correlated and have become further complicated by significant regional cost variations and mining inflation in the last years. Likewise, poorly designed metrics lead to poor benchmarking results. Examples of poorly defined metrics include: metrics that rely on information that is difficult to collect, metrics that are poorly defined, metrics which are too site focused, and metrics that measure low consequence practices.

Jan 1, 2011

Traditional fine grinding mills in mineral processing relied on the use of steel medium for particle size reduction. The successful development of the Isa Mill(a horizontal stirred mill with 3000 litres of net chamber volume and 1120 kW rated motor power)adopted a novel product separator design that has led to a major revision of medium use in fine grinding. The Isa Mill separator has also successfully operated with a wide variety of medium types such as silica sands, river gravel, smelter slag, run-of-mine ore fractions and steel shots, with size ranges from 0.5 to 10 mm. A great flexibility of the Isa Mill operations has been achieved for processing a feed as coarse as 120 um to a product as fine as 5 µm. This paper discusses the performance of two inert grinding media used in the Isa Mills in Mount Isa Mines of Australia for processing galena and sphalerite bearing ores to below 10 microns. They are the copper reverberatory furnace slag (CRFS)and the heavy medium plant rejects (HMPR). A methodology was also demonstrated for comparing the medium performance and for scaling up the Isa Mills from a 1.5-litre laboratory batch mill to a full scale 3000-litre mill.

Jan 1, 2000

By Hassell E. Hunter

The Wyoming Mineral-Conoco Crownpoint Project represents the first time that big hole drilling has been exclusively used to develop totally a privately financed mine below a depth of 1000 feet. Three shafts, one ten feet in diameter and two six feet in diameter, were successfully drilled to depths of 2243', 2188' and 2188' respectively and cased with hydrostatic designed steel casing. The largest shaft is to be used to handle muck and water from station excavation and enlargement of the other two shafts. A reverse circulation system with potassium chloride base mud was used for drilling. The mud was cleaned by settling in steel lined tanks with assistance by cyclone type separators. Deviation was monitored by gyroscopic surveying at 30 foot intervals and did not exceed 16 inches off plumb. Casing was designed to withstand hydrostatic pressures with a 1.5 safety factor to the large shaft and 1.25 safety factor for the smaller shafts. All casing welds were x-ray tested prior to lowering the casing in the hole. Cementing the annular space completed the operation. The total time to mobilize, drill and move off the three shafts was 363 days. The drilling operation was completed ahead of schedule and under budget.

Jan 1, 1983

By David G. Van Hersett

The single most unique design feature of the Centralia Coal Mine is the public information program. Just what the heck does public information have to do with the development of a coal mine? The utilities of today have had to build larger and larger plants to keep down the costs of power to the consumer. The large plants require huge amounts of capital, take up large areas of real estate, consume unprecedented amounts of coal, and generate large quantities of waste products which have to be reckoned with. Coal mines supplying these plants have also increased in size and production to meet the power plants' unending appetite for coal. This means the disturbance of great areas of land and significant alterations to the landscape. Today's public is greatly concerned about the environment in which he is living. The great size of a power plant with its large stacks, coal piles, and the coal mine with its large earth movers, disturbed acreages and the resulting waste products of both operations appears to present a threat to his environment. Because of this,' many power plants and coal mines are having public acceptance problems. This has resulted in the passage of stringent legislation and in some cases brought upon construction delays for major power plants.

Jan 1, 1970

By S. Chander, S. W. Musselman

The molecular structure of hydrophobic and hydrophilic groups in nonionic surfactants has been related to the wetting and dispersion of selected pigments. The nonionic surfactants included in this study are acetylenic diol based surfactants and ethoxylated alkyl phenols. The Langmuir model could be used to fit adsorption data. Further analysis of the data showed that the free energy of adsorption was a function of adsorption density of the surfactants at the interface. The change in free energy with adsorption density could be interpreted by considering a change in the orientation of the adsorbed molecules. Acetylenic diol based surfatants were found to have an area per molecule of 2-3 times that of similarly ethoxylated alkyl phenols. The wetting and dispersion properties of lamp black, a model hydrophobic surface, by these surfactants were investigated by contact angle measurements and particle size analysis. Acetylenic diol based surfactants with ethylene oxide contents between3.5 and 10 moles per molecule and alkyl phenol based surfactants with approximately 9 moles of ethylene oxide per molecule were found to provide superior wetting abilities. Longer ethylene oxide chains were required for superior dispersion capabilities within each family of surfactants. Complete wetting and dispersion was found to occur above the critical micelle concentration of the surfactants.

Jan 1, 2000

By Wen Lan Chen

In the plant where the 800m diameter cyclone was tested, 500 STPH of 50m x 0 raw coal was pulped in a heavy medium tank and pumped originally to four 700mm heavy medium cyclones. For the test one of these units was replaced by an 800mm diameter cyclone with the subsequent feed pressure for both units sets at approximately 15.0 psi. Since this was a feed to zero plant, an appropriate bleed of heavy medium to the dilute medium circuit was established to en- sure that the cleaning of the 500m x 0.5mm raw coal would not be adversely affected by high levels of 0.5mm x 0 fine coal present in the heavy medium. The medium gravity measured varied between 1.41 and 1.43. During a three-hour test on June 10, 1983, the raw coal sample was collected from the feed belt while the clean coal and refuse samples were collected separately at proper locations along the product streams of the two different diameter cyclones. All of these samples were shipped to the laboratory for screen and sink- float analyses. The raw coal screen and ash analyses are shown in Table 1.

Jan 1, 1984

By S. J. Stokowski

An extensive drilling and laboratory testing program indicates that diagenetic dolomitization of the Oligocene Sombrerito Fm. limestone, southwestern Dominican Republic, is detrimental to the usefulness and quality of the potential construction aggregate resource. The first part of this program was the collection, photographing, and geologic logging of diamond drill cores to allow lithologic subdivision of the strata into potential quarry layers. The primary lithostratigraphic units are: I (youngest) approximately 10 m of white, dense marine limestone; II, approximately 5 m of white, interbedded dense and chalky marine limestone; III, 2+ m of tan, chalky calcitic dolomite. Unit I has been often altered by lateritic weathering and/or dolomitization; Unit II is often altered by dolomitization. The quarry layers were individually crushed, by core, into coarse aggregate sizes for chemical and physical (specific gravity absorption, MgSO4 soundness, sand equivalent, and LA degradation) analyses. The non-weathered units decrease in coarse-aggregate yield and quality with depth and dolomitization. Dolomitization typically causes about 5% lower yield of coarse aggregate, a sand equivalent of about 20 units below the original value, an increase in absorption of about 3%, an increase in the LA of up to 13%, and a decrease in the average 5-cycle MgSO4 soundness by about 17%.

Jan 1, 1987

In recent years there have been significant advances in computing power and programming technology, enabling more complicated processes to be modelled in greater detail. This has led to increased understanding of these complex processes, including mineral processing circuits. JKSimMet was developed over the past 35 years, incorporating outcomes from various research projects conducted at the Julius Kruttschnitt Mineral Research Centre (JKMRC), part of the Sustainable Minerals Institute at The University of Queensland. It is a steady-state software program that allows the user to mass balance, model fit and simulate crushing, grinding and classification circuits. JKSimFloat has been developed over the past 20 years, incorporating outcomes from the JKMRC and other institutions around the world through the AMIRA International P9 project ? The Optimisation and Simulation of Mineral Processing Circuits. It is also a steady-state software program, similar to JKSimMet, but is focused on analysing flotation circuits. Both programs have been used in a wide variety of optimisation and design projects over many years. This paper provides an overview of both JKSimMet and JKSimFloat and examples of how both programs have been used to better understand, develop and optimise mineral processing circuits around the world.

Feb 27, 2013

By Walter N. Campbell

The Simon Silver Mine is located near Mina, Nevada, approximately 50 miles northwest of Tonopah and 40 miles east of Hawthorne. It is an old property which was last worked in 1932 and closed operations due to problems arising from low metal prices. Federal Resources Corp. acquired the property in 1963 and undertook a completely new development program since the old surface plant and underground workings were beyond feasible repair. The deposit of silver, lead, zinc and copper is predominantly replacement of limestone. In the summer of 1964, a new surface plant was constructed and on December 2, 1964, sinking of a three compartment vertical shaft started and was completed to a depth of 1088 feet in April of 1965. Following the sinking program an 850 foot crosscut was driven to intersect the mineral zone on the 1000 level after which drifting, crosscutting and raising totaling some additional 4280 feet has been completed along with considerable diamond drilling and long holing into the walls. To date, two ore bodies have been encountered and test stoping operations are underway together with development of the 800 level for servicing, ventilation and access. The present development of ore is directed towards substantiating sufficient reserves to warrant the construction of a flotation mill.

Jan 1, 1967

By M. Bennett, L. Twidwell

Montana Tech has embarked on a coordinated series of studies to delineate the characteristics of the Berkeley Pitlake containing over 36 billion gallons of acidic, metal-contaminated water formed after the cessation of open-pit copper mining in Butte, Montana, USA. The objectives of the overall series of studies are to summarize presently available information and to generate new and needed information to formulate a conceptual environmental model for the pitlake and to provide characterization data for the development of advanced treatment technologies. In this presentation, the chemistry of the Berkeley Pitlake water is partially reviewed. It is known that the pitlake consists of two distinct layers of water referred to as surface and deep water. Samples of deep water were collected and placed in a 12-ft high and 6-inch diameter column and exposed to different wavelengths of UV radiation as well as atmospheric conditions. Measurements of pH, redox potential (EH), dissolved O2, turbidity, conductivity, temperature, and elemental composition show that the water reacts differently and indicates that the diurnal effects of sunlight likely play a major non-biological role in its chemistry. Resulting technology could be useful for developing an alternative to treating acid-rock drainage.

Jan 1, 2007

By E. M. Haynsworth

The disposal of phosphatic clays has presented a problem to the phosphate industry since the mining of phosphate rock first began. As the flotation process was introduced in the late 1920's, the problem of clay disposal was increased significantly since clay is present in proportionally greater quantities in reserves yielding flotation concentrates. Because of their physical character and the tremendous surface area per unit volume, these clays have the characteristic of retaining large volumes of water as they are slurried during processing. The phosphatic clays with which we are dealing consist primarily of apatite, wavellite and montmorillonite. In the beneficiation process, we remove the -150 mesh material as waste. However, the particles are essentially smaller than -325 mesh, and more than 70% are smaller than three microns. The disposal of clay and the recovery of a portion of the water require settling areas with a capacity ranging up to 2 cubic feet for each cubic foot of phosphate matrix mined. According to a recent study by the Bureau of Mines, the average cost for disposal of these wastes is 24.5 cents per ton of, product (U. S. Bureau of Mines Circular 8404). This is a major cost of phosphate rock production.

Jan 1, 1970

By P. M. Soupios

An integrated suite of environmental methods was used to characterize the hydrogeological, geological and tectonic regimes of the study area, to determine the geometry of the landfill (depth and spatial extent of electrically conductive anomalies), to define the anisotropy caused by bedrock fabric fractures and to locate potential zones of electrically conductive contamination. The study area which covers an area of about 0.08 Km2 is a municipal solid waste site (MSW), located 20Km West of Herakleion in the central part of Crete (S. Greece). The landfill is located in a northwest oriented valley with highlands to the northeast and southwest. The combination of geophysical methods and chemical analysis are commonly implemented for characterization and management of land-fills. At the particular site, geophysical methods were focused on studying the electrical insolating properties of the materials, electrical con-ducting properties of fluids (leachates) and electromagnetic properties of the disturbed regolith materials in the burial zones. Three different types of geophysical surveys were performed: 1) 2D electrical tomography (ERT), 2) electro-magnetic measurements using very low frequencies (VLF) and 3) electromagnetic conductivity (EM31). Furthermore, in order to calibrate the geophysical methods dielectric spectrometry measurements are conducted. To evaluate the environmental degradation of the area, soil and liquids samples were collected.

Jan 1, 2005

By Alfredo Menendez, Alberto Sarmentero

A B S T R A C T The Los Pijiguaos bauxite is one of the largest accumulations of trihydrate alumina ore recently discovered; it is a plateau type, with no overburden, relatively soft tertiary quartz-bearing bauxite developed on a pre-Cambrian Rapakivi Granite batholith. The deposits are found in the northwestern rim of the Guiana Shield, State of Bolivar, Venezuela, and were discovered in 1976 after a grass-roots exploration campaign. Target areas were mainly selected on the basis of geological and geo¬morpholigcal criteria, guided by correlation with known deposits elsewhere in the Guiana Shield. The vertical. lateritic profile consists of an upper concretionary zone, followed by a mottled zone, a palid zone and finally the weathered rock merging into fresh granite. The upper concretionary zone displays a cellular, pisolitic or spongy texture and contains the following minerals: gibbsite (60-90%),quartz (5-10%), hematite (5-10%), goethite (under 5%), boehmite (traces), kaolinite (traces). The gibbsite content decreases sharply downward from the lower limit of the concretionary zone and the kaolinite and quartz content increases in the underlying mottled zone. The mottled and palid zones display a pseudo rapakivi texture and quartz, kaolinite and mica are the. essential minerals.

Jan 1, 1984

By A. B. Cecala

Enclosed cabs have been used on surface mining equipment for many years to protect equipment operators from health and safety hazards. The surface mining and quarrying process is a highly mechanized process that generates large quantities of respirable dust. Due to economic factors, more older mining equipment is being used today than in years past. With this older equipment, it is common to observe deterioration of many components on the enclosed cabs which greatly reduce their protection effectiveness. NIOSH has performed a number of different field studies, as well as a comprehensive laboratory study evaluating various factors and parameters regarding enclosed cabs. NIOSH has recently completed a cooperative research effort with Sy-Klone International and Vulcan Materials Company to evaluate the effectiveness of a newly designed uni-directional filtration and pressurization system that brings all the clean filtered air in at the roof of the cab and extracts all recirculated air near the floor. This design provides the highest air quality to the equipment operator. Testing on this new system showed an almost 10-fold reduction in respirable dust inside the enclosed cab. The uni-directional design is easy to incorporate and should be considered for all new and retrofit systems in surface mining equipment.

Jan 1, 2009

Samples collected during the exploration phase of mining represent baseline conditions at the site. As such, they can be very important in forecasting potential environmental impacts should mining proceed, and can become measurements against which future changes are compared. Constituents in stream water draining mined and mineralized areas tend to be geochemically, spatially, and temporally variable, which presents challenges in collecting both exploration and baseline water-quality samples. Because short-term (daily) variations can complicate long-term trends, it is important to consider recent findings concerning geochemical variability of stream-water constituents at short-term timescales in designing sampling plans. Also, adequate water-quality information is key to forecasting potential ecological impacts from mining. Therefore, it is useful to collect baseline water samples adequate for geochemical and toxicological modeling. This requires complete chemical analyses of dissolved constituents that include major and minor chemical elements as well as physicochemical properties (including pH, specific conductance, dissolved oxygen) and dissolved organic carbon. Applying chemical-equilibrium and appropriate toxicological models to water-quality information leads to an understanding of the speciation, transport, sequestration, bioavailability, and aquatic toxicity of potential contaminants. Insights gained from geochemical and toxicological modeling of water-quality data can be used to design appropriate mitigation and for economic planning for future mining activities.

Jan 1, 2011

By H. Savasci, G. Yarim, J. S. Chung

As part of ongoing deep-ocean mining research, hydraulic transport systems as well as status of deep-ocean mining systems are reviewed in the aspects of manganese nodules and crusts from 8006,000-m depth. The emphasis of the investigation of hydraulic transport is placed on the shape effect of particles on the pressure gradients and flowrates. Series of tests are being conducted to study the lift characteristics of a 2-phasevertically upward hydraulic transport of 2 types of small solid particles in a PVC pipe of 1-in (2.54 cm) diameter: irregular-shaped silica sands and equivalent spherical glass beads. Pressure drops and mass as well asvolumetric flow rates were measured by electromagnetic(EM) flowmeter and mass flowmeter. The particle sizes used are 8-10 mesh. The results in turbulent flow range of 101045Re show that pressure gradients or friction factors are smaller for the spherical beads than the sands. The larger the concentration of the particles are, the larger the pressure gradients become. The larger the particle concentration is, the less the effect of particle shape on pressure gradients becomes. The shape effect is greater for the minimum particle transport velocities than for the settling velocities.

Jan 1, 1999