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By Charles V. Jude

This U.S. Bureau of Mines report presents a review and evaluation of existing and new backfilling materials and methods for their applicability to the problem of gate road stress reduction in deep retreat longwall coal mines. Candidate backfill materials include pulverized coal combustion fly ash, flue gas desulfurization, and fluidized bed combustion by-products from coal-fired electric power generation plants. Properties of both backfill and its component materials are presented, with particular emphasis on the unconfined compressive strength and elastic modulus of backfill mixtures. Hydraulic mix designs discussed in this report include high-water content slurry and low-water content paste fills. Three gate road stress-transfer-modification concepts are proposed to reduce abutment stresses in gate road systems. The first concept, packwalling, involves packwall construction behind the headgate shield inby the face and adjacent to the headgate pillars. The second concept, gob-filling, involves infilling a strip of gob inset from and parallel to the headgate using paste injection methods patterned after a technology recently developed in Europe. In the third concept, entry-filling, slurry fill methods are used to fill abandoned gate roads and crosscut entries inby the face.

Jan 1, 1995

By Gaballah Djona M.

Spent hydrorefining catalysts contain about 5 % of CoO and/or NiO, 12 % of MoO3 and up to 10 % of V205. They are generally supported by alumina and contain up to 25 percent of C, S and hydrocarbons. Such materials are potentially hazardous to the soil and to water resources. Selective chlorination of raw unroasted samples with Cl2 + air gas mixture had been investigated. At temperatures lower than 600 °C, it was possible to recover more than 90 % of nickel and cobalt chlorides, about 99 % of the molybdenum and up to 75 % of vanadium chlorinated compounds. CoCl2 and Ni/Cl2 were extracted from the chlorination residues by their dissolution with acidified water. Molybdenum and vanadium chlorinated compounds were recovered by selective condensation from the vapor phase. The chlorination of Al2O3 could be limited to less than 6 %. The scale up of this treatment was successful and a flow-sheet is proposed.

Jan 1, 1995

Overland conveyor belts that exhibit tracking problems under loaded and unloaded conditions can be tested to' determine the root cause of the mistracking. Moveable conveyors are more prone to mistracking due to structure alignment requirements. In addition, belting quality, splice straightness and carcass condition has a dramatic effect on the performance of a belt in relation to tracking. Methods are discussed that are proven to reduce belt mistracking and improve the operational reliability of the conveyor system.

Jan 1, 1995

By John A. Mavrogenes

The Texaco gasification system developed at the Monte Bello pilot plant efficiently bums petroleum-coke thereby producing syn-gas and electricity. This system produces more electricity than conventional burners, yet the only by-products are pharmaceutical grade sulfur and V -rich slag. Vanadium is known to exist in multiple valence states in compounds which possess a wide range of melting points and physical properties. Consequently, it becomes important to carefully regulate oxygen fugacity throughout the system in order to control vanadium valence state. Vanadium phase equilibria is presently poorly understood, in large part because of the multiple oxidation states of vanadium (-I, 0, +2, +3, +4, and +5) and the difficulty of unequivocally identifying the valence state(s) in many compounds. The operation of these gasifiers at approximately 1400°C is well above the melting point of V20S but considerably below the melting temperature of V02 and V 203. If J02 can be regulated to keep the burner within the V 205 field, slag material would more likely remain molten and more easily flow out of the bottom of the burner. In pure V oxides. the oxidation state is readily determined by microprobe analysis. where V20S (V+5) is 56% V, V02 (V+4) is 61.4% V, and V203 (V+3) is 68% V. However, V valence in multi-element phases (especially phases containing other elements of variable valence) cannot be resolved by microprobe analysis alone. Petroleum-coke gasification slags collected from within the gasifier under different oxidation conditions were studied by electron microprobe analysis (EMPA). X-ray diffraction (XRD). X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Raman spectrometry in conjunction with microprobe analysis was found to resolve the valence of vanadium in the phases of these slags. Raman spectra collected from homogeneous single phase V-oxide standards in vacuum at low temperatures (-150°C) yielded peaks characteristic to each valence state. Gasifier slag samples are, however, much more complicated. Oxidized samples contain: fine grained (Ca. Mg, Fe. V) oxide matrix of variable composition, (Fe. V, Ni) spinel. (Fe, AI, V, Ni, Mg) spinel, V205laths, AI-Si glass blebs and Ni sulfides. Reduced samples contain: crystalline Ca-siIicate matrix, subhedral to euhedral (V, Fe, Mg, AI) spinel, subhedral V02, Fe and Fe-Ni sulfides, Fe-Ni alloys, and complex Ca-oxide matrix. The different spinel assemblages, the characteristic V-oxides and the distinctly different character of the matrices makes the oxidized and reduced slags readily discernible.

Jan 1, 1995

By P. I. Prescott

Ground calcium carbonate (GCC) is used in the paper, plastics, paint, rubber, caulks, and sealants industries. The favorable properties of GCC include high whiteness and brightness, low hardness, and outstanding rheology in water systems. The quality of calcitic GCC ores, which include chalk, limestone, and marble, is dependent on calcite purity and the nature and quantity of ancillary minerals. Wet and dry grinding is used in the manufacture of GCC. Ore processed by optical sorting, flotation, and/or particle size classification has higher brightness and lower abrasion. GCC markets are a function of the product's properties, purity, and cost.

Jan 1, 1995

By Donna L. Bodine

The ability of oxidized Upper Freeport bituminous coal to adsorb Cu2+, Cd2+ and Mn(VII) from very dilute aqueous solutions has been studied. Low-rank coal is known to adsorb heavy metal ions from dilute, aqueous solutions, probably by ion exchange and/or chelation by acidic functional groups on the coal surface. However, it would be advantageous to use higher rank coals for water treatment. Coal samples were oxidized thermally or by 30% H202 to increase the surface concentration of phenolic and carboxylic groups, then portions were shaken with Cu2+ and Cd2+ solutions. Acidic KMnO4 was also used to oxidize coal, with concurrent sorption of the resulting Mn(IV) and Mn(ll). The effect of oxidation treatment, metal ion concentration, and solution pH on metal uptake kinetics was investigated. Potential applications for treating effluents, especially those containing oxidizing ions, are discussed, along with possible flowsheet options.

Jan 1, 1995

By R. J. Kuczynski

The U.S. Bureau of Mines Reno Research Center operated a batch pilot plant to demonstrate high-temperature cyanide leaching for recovering platinum group metals (PGM) from automobile catalysts. Approximately 1,600 kg of used pellet, monolith, and metal support catalyst containing 1,680 g (54 tr oz) of PGM were processed. Forty-five-kilogram batches of used catalyst were leached with sodium cyanide solution at 160° C for 1 h under basic conditions in a countercurrent processing sequence to dissolve the PGM. Extractions from the used pellet catalyst ranged from 94 to 95 pct for Pd, 95 to 97 pct for Pt, and 64 to 81 pct for Rh. Extractions from the used monolith catalyst ranged from 7B to BB pct for Pd, 75 to 90 pct for Pt, and 43 to 71 pct for Rh. Heating the pregnant leach solutions to 275' C for 4 h destroyed the PGM-cyanide complexes, resulting in over 99.7 pct of the PGM precipitating from solution. The PGM precipitate was predominantly a powder metallic concentrate, typically analyzing greater than 50 pct PGM. Heating destroyed cyanide to less than 0.2 mg/L. Both the pellet and monolith residues were evaluated for disposal using the EPA Toxicity Characteristic Leaching Procedure.

Jan 1, 1995

By John F. Papp

International and U.S. chromium material flow, losses, and environmental releases and transfers from mining through industrial processing, end use, and recycling are identified and quantified. Average (1983-92) U.S. consumption has been: metallurgical industry, 87 pct; chemical industry, 10 pet; and refractory industry, 3 pct. Average chromium content of aluminum, cobalt, copper, nickel, and titanium alloys and alloy, carbon, and stainless steel alloys was estimated. Anthropogenic chromium consumption was estimated for the cement and copper industries. N on-commodity cycle anthropogenic chromium mobilization resulting from U.S. fuel and fertilizer use was estimated. Commodity cycle anthropogenic world chromium loss from mining and primary consumer industry was estimated to be equivalent to about 56 pct of chromium contained in chromite ore production and represented a loss rate of 181 kt-Cr/Mt-CrOre. Chromium released to the atmosphere from natural and from anthropogenic sources were comparable in magnitude. Chromium released to soil was mostly from anthropogenic sources, and aquatic releases were all anthropogenic. Domestic product chromium losses exceed process losses by more than a factor of 10 showing the importance and potential environmental impact of post-consumer recycling. The location of historical and current domestic chromium industry processing sites in 23 States were reported. Chromium releases and transfers to the environment were estimated from 1973 through 2002 by primary consumer industry. A decrease in chromium releases and transfers to the environment was anticipated.

Jan 1, 1995

By G. T. Austin

This is an overview of the gemstone industry with special attention on particular states within the united states. The U.S. Bureau of Mines, Department of the Interior compiled and analyzed the information contained in this report. The report should be viewed as a current "still photograph" of a dynamic system. The information presented on a specific gemstone or for a specific state can and will change with time. This overview presents historical and reference information on the principal gemstones and their production in certain states. The report is not a definitive work on gemstones within the select states or United states.

Jan 1, 1995

By Corneille S. Ek

Flotation of several copper and lead-zinc ores has been carried out with mercaptobenzothiazole (MBT) as promoter. The results of laboratgory batch flotation tests have been compared with those obtained when using more common collectors like xanthates or dithiophosphates. It generally appears that MBT is an effective collector of all the sulfides, including pyrite, but that high selectivity is rather difficult to attain, except for gangue drop-out. Some kinetic tests have been performed to check the froth production rate by MBT as compared to other collectors.

Jan 1, 1995

Underground space can be defined as space below natural ground level which can be used as an alternative to an above ground location. While many of our above ground structures inherently involve underground excavation for foundations and services, the term underground space specifically refers to organised development of underground openings and of the underground domain. For example, the services to a city such as power, gas, sewerage, water and communications are installed in a congested array which usually requires roads to be dug up when the services need to be accessed. An underground space installation of services would involve a well planned conduit which is easily accessed without any excavation. The concept of using this virtually untapped land resource to the advantage of our expanding cities is gaining considerable interest in Australia. Overseas, in the Scandinavian countries and some Asian countries, underground space has been used for centuries; in Great Britain, France and the United States of America over the last century and in Japan for over a decade. This paper focusses on the types of underground space usage which should be competitive with above ground use and suggests areas in which the competitive edge may be improved in favour of underground space. In particular, considerable advantage is seen by using well-planned underground space developments in major cities, where the strategic central location of the development takes advantage of proximity to potential users. However, the largest single factor affecting the acceptance of underground space is the high capital cost of construction, even though an underground space development may result in lower operating costs and reduced long-term maintenance costs. While excavation methods and associated costs are very much site-specific, the importance of applying the latest technology in rock breakage, with consideration of ground vibration, excavation rates and ground support, remains a major challenge to the development of underground space.

Jan 1, 1995

By R. Reeves

Coal producers and utilities depend on automated coal blending systems to reduce costs and meet stringent environmental regulations. Over 30 systems installed in the United States since 1987 use on-line PGNAA (Prompt Gamma Neutron Activation Analysis) analyzers to accurately control the blending process. Experience and detailed engineering are required to integrate real-time data produced by the coal analyzer with a control system to meet demanding performance specifications. This article reviews successful installations and lists important features including interfacing analyzers with plant control systems, specifying feeders and weigh scales, and managing data.

Jan 1, 1995

By T. G. Hawkins, T. M. Naciuk

"The Katie Cu-Au deposit is situated in southeastern British Columbia, 425 km east of Vancouver. The deposit is a member of the alkaline group of porphyry Cu-Au deposits associated with potassically and propylitically altered andesitic volcanic rocks.The Katie porphyry system occurs in mafic to intermediate alkaline volcanic rocks of the Lower Jurassic Elise Formation of the Ross/and Group. Host metavolcanic rocks include andesitic to basaltic flows, flow breccia, massive fine tuff and crystal tuff Gabbroic intrusions alternate with the volcanic rocks in drill core. The lack of chilled margins and shear contacts, as well as their similar composition to the volcanic rocks, suggest that the gabbro was synvolcanic.Alteration exhibits a zonal pattern spatially related to zoned porphyry-style mineralization. Propylitic alteration is common and assemblages consist of epidote, chlorite, sericite and calcite. Potassic alteration zones are accompanied by elevated copper-gold grades and are composed of K-feldspar, plagioclase, quartz, biotite and chlorite. Narrow drillhole intervals of secondary magnetite, generally less than 2 m across, occur above the potassic alteration zones. A thick oxidized cap lies above the mineralized zones, although only local supergene enrichment has been identified. The lack of supergene enrichment is perhaps due to intense near-surface fracturing and leaching from a high energy groundwater environment.Sulphide mineralization consists mainly of pyrite within the propylitic halo, and pyrite and chalcopyrite with trace pyrrhotite, sphalerite, tetrahedrite, bornite and molybdenite within the potassic alteration core. Malachite, azurite and traces of chalcocite occur within the oxidized cap.Discovery and exploration techniques have included airborne geophysics, regional stream sediment sampling, prospecting, geological mapping, ground geophysical surveys, soil sampling surveys, and diamond drilling. Two primary targets of porphyry copper-gold mineralization have been identified by exploration. The Main zone strikes northwest, has an apparent true thickness ranging from 70 m to 135 m, and is a minimum of 500 m in length. The 17 zone strikes northwest, has an apparent true thickness of 90 m, and is a minimum of 300 m in length. The two zones are defined by grades that generally exceed 0.2% Cu and 0.25 g/t Au. Both zones are open along strike and to depth."

Jan 1, 1995

By B. J. Timmons

Depending upon which of two letters describing the theme of the session I chose to honor, the subject choices because either one or three. They were: "Applied Research and Exploration and Discovery" or "Applied Research in Exploration and Discovery." The final choice; to partially ignore both of them. That minor difference in meaning may be appropriate here, inasmuch as very minor research/exploration differences may also have profound impacts on discovery. To further set the stage, I consider myself an Industrial Minerals geologist, and more specifically primarily associated with basic construction materials crushed stone and sand & gravel. My remarks will apply primarily to those materials. Therefore, when the discussion instructions included emphasis on beneficial aspects (to name a few): "drill target definition; elimination of ore potential; ore forming environments; alteration studies, and isotope analysis," problems became apparent. Evidently, and although this was a form letter, the drafters of that letter had no idea what was involved in research for a construction materials source. My task may be great.

Jan 1, 1995

By S. Guo

In this paper, a model for the resin anchor bolt system is developed in which the smooth bar is modeled by using one-dimensional truss elements and the resin annulus is modeled by using axisymmetric elements. These two submodels are combined together and then incorporated into the' existing computer code ROOFBOLT. After this development, all of the components in the resin anchor bolt system including smooth bar, bearing plate and resin annulus can be correctly modeled.

Jan 1, 1995

By H. EI-shall

In this paper, the results of bench scale testing of five different flotation processes to separate dolomite from phosphate are discussed. The effectiveness of each process interms of phosphate recovery and MgO content in the concentrate is used together with the reagent consumption as the basis of comparison. The water quality is found to play a major role in the performance of these processes. Effect of water hardness as well as other parameters are discussed.

Jan 1, 1995

Grinding and energy input in stirred media mills are studied as functions of grinding time, stirring speed, media size and density, solid concentration, impeller and tank dimensions and design, and other relevant variables. Ground product size and surface area are determined with respect to the above variables. Changes in energy input and media/pulp rheological properties during grinding are described. The best conditions for grinding limestone in the laboratory stirred media mills have been identified. Equations for correlations involving power and modified Reynolds numbers have been established.

Jan 1, 1995

By T. J. DeMull

The business of heap leaching requires accurate forecasting of metal production from the heaps. Business forecasts typically follow a format that project periodic (monthly, quarterly, or annual) product shipments based on anticipated operating results, e. g., tons of ore placed, grade of ore, and rate of leach extraction. Since revenue and cash flow are dependent on the metal production stream, forecasts of metal production are very important for project evaluation and business planning purposes. Nevertheless, production forecasts, particularly for new heap leach projects, have been prone to errors. The present paper identifies some of the pitfalls that would be encountered in preparing production forecasts for new heap leach operations and provides a checklist of considerations to assist in preparing a forecast. Also, the paper presents a case study of copper production forecasting used for the Sanchez Project, a heap leach operation located near Safford, Arizona, that is presently under development by AZCO Mining, Inc.

Jan 1, 1995

By U. Paschedag

Today's modern longwalls have to produce high outputs with maximum availability and running time with the additional requirement of ever increasing panel width and length high-performance face conveyors require intelligent solutions for the integration of drive systems and chain tensioning devices into the overall longwall automation. The fully automated chain tensioning system allows the operation of an AFC with optimum chain tension at all times regardless of actual load on the conveyor. For the heavy-load start-up, the accurate load-sharing and an efficient overload protection of modern AFC's WESTFALIA and Dodge jointly developed the integrated WB/CST drive system.

Jan 1, 1995

By Bemd. E. Langner

At Norddeutsche AfFmerie the CollaMat is an important instrument for controlling the activity of glue in copper electrolyte. Thanks to on-line measuring of the glue activity appropriate action can to taken in the event of sudden changes, such as an intemption in the glue supply, as well as long-term trends, such as continuously decreasing glue activity over days or weeks. Laboratory tests on the dependence of glue degradation on temperature have shown that relatively small increases in temperature of only 3OC cause the half change value of the glue degradation to reduce by 25 %. It is a similar picture with the sulphuric acid concentration in electrolyte. An increase in the acid concentration from 160 g/l to 200 g/l can - depending on the temperature - likewise result in a decrease in the half change value of up to 25 %.

Jan 1, 1995