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In sizing of wet coal by the horizontal vibrating screen, screen openings to be used is much restricted, because coal is sticky and its bulk density is little. The electrically heated screen and other various types of screen had been tried to screen raw coal and coal as raw materials at a few mm. However, they failed to realize satisfactory results. On the other hand, fine sizing of coal is requested by many fields. For example, raw coal is desired to be screened at the fine rate, before being fed to the coal preparation control system in order to transport undersizes as unprepared coal particles and to reduce load in coal preparation waste water treatment system.1) Coals fed to the fluidized bed boiler also should be sized at a few mm. Regardless of many requests on fine sizing of coal, it seems that there are many cases to omit the basic screening process, because the screening is very difficult on a industrial scale. Size control as pretreatment of coal as raw materials is presented as one of the basic screening processes. In 1979, Kinki Industrial Co., Ltd. and Nippon Steel Corporation jointly succeeded in developing the vertical centrifugal screen. Closed -circuit crushing system by the use of this screen has operated actually at N.S.C, Hirbhata .Works, and realized the anticipated result. Consequently, this system has established the position as the most basic technology in the coal preparation. 2), 3), 4) This system has been also introduced to Nakayama Steel Works, Ltd. in 1982. This system termed the CPC (Coal Preparation Control) Process has been operated smoothly in both N.S.C. and Nakayama. Reported herein is the practical application of the vertical centrifugal screen termed V3-Separator. (V3 means vertical, versatile and vibration.)

Jan 1, 1984

By Lowell B. Page

The White River Shale Project has completed a 5,000-foot production decline and a 30-foot diameter 1,010-foot deep shaft into its oil shale orebody in the Uinta Basin of eastern Utah. This is the first major underground access into these Green River deposits in this basin and provides an opportunity to establish and monitor in-situ rock mechanics stations as input to the mine engineering and planning of this large opening, high-tonnage mine. This paper discusses the history, mine development, and rock mechanics planning for this project.

Jan 1, 1984

By Edward C. Roper

Pegasus' Gold Ltd. operates two gold/silver heap leaching operations in the Little Rockies area of Montana. The Little Rockies has produced gold from underground operations on an intermittent basis from the 1880's to the early 1950's and from the open-pits on a continuous basis since 1979. Run-of-the-mine ore is drilled, blasted, sorted, loaded and hauled. The waste is dumped and compacted into 30 meter (100 foot) fills to be used for future leach pads. The leach pads have a central drain system and the impermeable membrane is constructed of bentonite and 30 mil PVC. The plants which have beenexpanded to 4900 Ipm (1300 gpm) capacity use the Merrill-Crowe process for gold and silver recovery. 4600 liters (1200 gpm) of the 9500 Ipm (2500 gpm) spray capacity is recycled through the old leach pads for upgrading before being processed. The gold/silver precipitate is smelted and the resultant dore' is shipped to a buyerhefiner. 1983 projected production is 2,177 kg (70,000 02s) of gold at a cost of less than $10/gm.

Jan 1, 1984

By Dyson NF

Nickel sulphide precipitated from waste liquors at the Yabulu plant of Queensland Nickel Pty Ltd was pressure leached under various conditions. Leaching at 130¦C and 700 kPa of air dissolved 95 per cent of the nickel as the sulphate in less than 2 h. Leaching at 130¦C and 350 kPa of oxygen dis- solved 95 per cent of the nickel in less than 1 h. Dissolution was faster with oxygen than with the equivalent pressure of air. Crystallization of hydrated nickel sul- phate from the resulting clarified leachate is readily achieved. Because the sulphide pre- cipitate also contains minor amounts of iron, copper and cobalt, the crystallization product contains these metals in excess of the amounts required for electrolytic-grade nickel sul- phate. This grade of product could only be produced if the contaminants were removed prior to crystallization. Alternatively, the "crude" nickel sulphate could find a market as a feed for the electrolytic production of Ni-Fe coatings.

Jan 1, 1984

"No questions.F Energy Consumption in Industrial Minerals : E.Joe No questions.g Automatic Dewaterinq at Mattagami : M. CaronE. Marcotte Is the control valve on the thickener underflow reducedFalconbridge as the pulp density reduces?Reply As the slurry density reduces the valve will constrict to reduce the flow and the density will re-establish itself.E. Marcotte Is there a stopper on the valve to prevent its closing too far?Reply We never shut it off completely because of the danger of sanding. It is just brought down to a normal level. It works very well within a given range and the operator is on hand to prevent any sanding out in the line."

Jan 1, 1984

By T. G. Rozgonyi

The basic goal of this investigation was to determine the degree of drying of high moisture lignite through the use of high temperature and pressure steam autoclaves. Specific items studied were: a) the effect of lignite particle size, b) steam temperature and pressure required, and c) the time of ahydration. Although removal of sodium, ash, sulfur and other ash-forming minerals was not the goal of this study, basic analysis of effluent water showed organic material and alkalai metal content. Removal of inherent moisture from run-of-mine lignite was tested by lock-feeding the lignite, which was previously sized by screening into 25 kg autoclaves. High pressure, up to 4.053 MPa (588 psi), saturated steam was then introduced into the pressure reactor. Reaction time, pressure, temperature, and depressurization rates were strictly controlled for each reactor test run. Results indicate that about 80% of lignite total moisture was removed, including some of the inherent moisture, yielding a non-oxidized, and thus stable, lignite product. As stated, a side benefit occurred as some reduction of non-combustible portions of the lignite also took place. The conclusion reached as a result of the tests is that the steam-drying process can be successfully applied to reducing moisture in lignite, and may be considered for additional studies on acceleration of the coalification process. On the basis of the data presented, the author believes that lignite can be economically upgraded in steam autoclaves by simultaneously reducing the moisture content by 80 percent and the sulfur content by at least 50 percent. Upgrading the lignite by this method will result in large energy and financial savings.

Jan 1, 1984

By R. E. Green

The Bureau of Mines undertook a bench-scale study of three different types of oxidized taconites3 from the Lake Superior district to improve the dispersion-selective flocculation-desliming process for beneficiating these materials. The response-surface contours of the effects of dissolved ionic species in the water and of three dispersion systems on the selective flocculation process were studied. Results of metallurgical data and chemical analyses of the aqueous phase showed that the water quality affects the performance of the selective flocculation process.

Jan 1, 1984

By Askew JE

The large, massive low grade gold orebody at Mount Charlotte has demanded an innovative approach to mining engineering. In the last five years several advances occurred in the areas of rock mechanics, mass blasting, blasthole drilling and truck haulage.Successive crown pillar failures throughout the life of the mine had resulted in a continuous geotechnical program, mostly utilisingconsultants. The culmination of this workwas the development of a successful crown pillar support system. Several stopes have incorporated the technique and the most notable success has been the relatively large F3 crown pillar.In hole hammer drilling was introduced to the mine in 1979, but little work had been done to develop a blasting system to suit the 165mm diameter holes. A non-electric sequential blasting system was adapted for use at themine and up to 600,000 tonnes have been fired successfully in an individual blast. Problems with ground vibration were addressed although this work remains incomplete.

Jan 1, 1984

By Brady KT, Pattenden G

A laboratory size solvent extraction apparatus has been constructed, which incorp- orates three stages of countercurrent extraction, followed by two stages of counter- current stripping. The model uses a gravity flow system from one stage to another and air lift pumps to recirculate organic and aqueous phases. A novel pump/mixer system is used to transfer solutions from the mixer compartments to the settler compartments. The model has proven valuable in the teaching of solvent extraction principles.

Jan 1, 1984

"The Archaean komatiite-associated nickel sulphide deposits at Kambalda, Western Australia, exhibit a number of stratigraphic features that are indicative of a strong volcanic control on ore localization, including (1) a restriction to specific basal cumulate metakomatiite host units, (2) confinement within distinctive synvolcanic embayments in the footwall and (3) variations in the internal structure and composition of overlying and adjacent barren metakomatiite flow's and the distribution of interflow metasediments with proximity to the ore zones.The high magnesium content of the host units (up to 45% MgO volatile-free) in comparison with that of aphyric or spinifex- textured lavas (16-32% MgO) has been considered previously to indicate either magmas/lavas rich in intratelluric olivine or selective accumulation of olivine phenocrysts. The marked linear trend of the oreshoots, basal host units, footwall embayments and the volcanic stratigraphic relationships have been used as evidence for local linear feeding fissures. Rare relict igneous olivine in some host units is, however, demonstrably not intratelluric, and there is no direct or indirect evidence of a proximal eruptive site (e.g. footwall feeders, pyroclastic breccias, ultramafic intrusives) at Kambalda such as at some other deposits of this type. Kambalda is interpreted as a distal rather than proximal volcanic environment.Emplacement of the komatiite sequence at Kambalda was probably controlled by the locations of a few specific eruptive sites relative to regional topographic gradients and influenced by the topography of the pre-existing volcanic surface. Olivine enrichment in the basal host units occurred by in-situ fractionation and cumulus crystallization of olivine during longitudinal lava flow within linear lava conduits, possibly centralized on depressions between non-overlapping footwall basalt flows. The distinctive stratigraphic relationships are attributed to localization of lava conduits along the volcanic pitchline, flanked by more slowly moving parts of the flows. There are analogies with the physical volcanology of Modern basaltic and Proterozoic komatiitic lava flows.A corollary of this model is that the lava conduits thermally eroded and assimilated sulphidic sediments, contributing additional sulphur to sulphur-saturated komatiites or possibly inducing sulphide separation in originally sulphur-undersaturated komatiites. The latter would account for the restriction of ores to linear cumulate komatiite host units (thermally active lava conduits) and the locally mutually exclusive, but stratigraphically equivalent, relationship between the ores and sulphidic metasediments at Kambalda."

Jan 1, 1984

By Lung Cheng

The Bureau of Mines has installed passive water explosion barriers in two operating mines to determine their usefulness in U.S. coal mines. The primary objective of this field trial was to determine the effect of the explosion barriers on mining operations. Data were also obtained on the ability of the barriers to withstand the mine environment and on the effect of the barriers on belt operation, ventilation, worker travel, and rock dusting. Fifty barriers were installed at three separate beltway locations, and periodic inspections were made. A year after installation, no defects of the barriers or support hardware were detected, nor was any complaint as to the presence of the barriers made by the mine personnel. To date, 2-1/2 years after installation, the barriers have had no detrimental ef-fect on rock dusting, belt operation, or ventilation. Costs of material, fabrication, and installation are reported herein.

Jan 1, 1984

By V. Lakshmanan, Dan Mackie, J. Melnbardis

"Crystalline Flake Graphite is a strategic mineral. Since 1954 nearly all North American consumption has been imported from offshore. The Bouthillier Project in Quebec, Canada, is Orrwell Energy's bid to enter the market, with plans to begin production of a 500 TPD operation in 1984.Milling of flake graphite is considered easy, yet more problems have been encountered in flowsheet and plant design than in most other minerals. A fresh approach to existing technology was taken, giving results that are highly satisfactory. The key to graphite liberation without flake deterioration is found to be in autogeneous grinding. In addition to producing marketable coarse graphite by such autogeneous grinding, flotation and tabling, super purity fines can be produced using repeated regrinding, elutriation and flotation. This paper discusses the design of a 500 TPD plant based upon the results obtained from bench and pilot plant studies. INTROOUCTIONWhen the Black Oonald mine at Calabogie Ontario ceased production in 1954 nearly all North American crystalline flake graphite had to be imported from offshore. Orebodies in the United States were too small or too low in grade to be exploited economically.The Houthillier Township near Mont Laurier in Quebec (Figure 1) was a known graphite-bearing area The Orrwell property in that area was delineated in 1957 Some test work including minor footage of diamond drilling was carried out by Italia Copper and the MHM Syndicate prior to 1981 when Orrwell acquired the property"

Jan 1, 1984

By M. P. Board, M. J. Reus

Instrumentation was installed during construction of the Silver Shaft in northern Idaho to evaluate lining behavior and rock deformation. Rock mass displacements were monitored with multiple-position borehole extensometers. Liner stress and strain were measured with concrete pressure cells and embedment strain gages. Rock displacement data from the 5,955-ft level indicate rock mass anisotropy. Liner stress and strain data reflect high in situ stresses and nearby station and raise construction. Continued monitoring and preliminary analysis indicate that concrete-lined, circular shafts are stable for high, unequal stress fields and anisotropy in deep level mines.

Jan 1, 1984

By Robert W. Bruhn

An investigation was made of ground response to pillar retreat mining in a 1.7 meter thick seam at 108 meter depth at a site in northern West Virginia. This paper describes mining-related stress changes and movements at mine level, displacements within the overburden, ground surface subsidence and groundwater level variations. Subsidence approached 40 per cent of the mine height and continued more than a year after mining. Water levels declined in certain deep-lying strata.

Jan 1, 1984

By Douglas J. Robinson

A pilot scale process has been developed to separate mercury, tin, silver, and copper from dental amalgam scrap. Laboratory research led to a process which was operated in 55 gallon drum sized reactors to treat 2000 Tr oz charges of scrap per day. This paper discusses the development work, presents a flowsheet and gives an indication of the equipment necessary to carry out the process on a commercial scale.

Jan 1, 1984

By Uros Bajzelj

To mine very weak carboniferous schists subjected to high ground pressures the underhand cut-and-fill stoping method was proposed using an artificial plate roof. An experimental stope was mined using three consecutive levels. Rock pressures, deformation of the reinforced concrete plate, and the quality of stowing were evaluated. It was found that roof deformations were minimized if the reinforced concrete plate and uncemented backfill were replaced with cemented backfill containing reinforcement near the bottom. The mining method prevented the occurrence of high rock pressures at the face. The method is suitable for mining subvertical ore bodies with large horizontal areas.

Jan 1, 1984

By J. W. Sterner

The Bureau of Mines conducted studies on four makes of Japanese automobiles, three 1981 and one 1982 model years, received from three manufacturers to determine if their materials composition would present problems to the current technology used to process junk automobiles for metal recovery. One of each make of automobile was hand-dismantled to determine the materials composition. In addition, two nearly identical automobiles of each make were shredded at a commercial operation where all metal products and rejects were collected for analysis to determine metal and nonmetal distribution. The average weight of the four automobiles to be dismantled, less batteries, tools, and fluids, was 1,938.3 lb. The weight was distributed as 1,472.9 lb. ferrous and 115.6 lb nonferrous metals, 275.2 lb combustibles, 72.3 lb noncombustibles, and 2.3 lb electrical components. The dismantled automobiles, less gas tanks, fluids, tools, wheels, tires, and batteries, which were all removed from the automobiles that were shredded, contained an average of 1,389.1 lb ferrous and 101.6 lb nonferrous metals, 305.7 lb nonmetals, and 2.3 lb electrical components. In comparison, materials collected from the shredded automobiles averaged 1,304 lb ferrous metals, 80 lb nonferrous metals, and 341 lb landfill materials. There were no materials used in the manufacture of the late model Japanese automobiles that should present handling or processing problems to the steelmaking or secondary metal recyclers.

Jan 1, 1984

By Jouko O. Kallioinen

The control of zinc flotation at Outokumpu Oy's Pyhasalmi and Vihanti mines is described. At Pyhäsalmi the zinc flotation circuit is partially open. Zinc and other metal assays of pulp flows are measured and direct assay control of concentrates in various flotation steps is adopted. Assay control is carried out by adjusting flotation air and pulp levels. Optimization with copper sulphate ensures high Zn- recovery and minimum copper sulphate consumption. A froth depth monitor is used to measure froth quality. At Vihanti the zinc flotation takes place in closed circuit. The most important control loop is the Zn-assay control of rougher concentrate by adjusting flotation air. The quality of froth is measured indirectly and thus copper sulphate consumption is altered. The circulating load is controlled also by flotation air in the three cleaning steps. The comparison of the control strategies shows that a more sophisticated control is adopted at Pyhäsalmi because the selective flotation of this massive sulphide ore is considered to be difficult. The control strategy includes numerous tests performed by the computer and control algorithms developed for the case. The control targets of the two zinc flotations described are also different: At Pyhäsalmi Zn-assay control of final concentrate including copper sulphate optimizing, at Vihanti the control of circulating load and Zn-assay of rougher concentrate.

Jan 1, 1984

By Kenneth E. Hjelmstad

In situ leach mining operations often encounter difficulty maintaining adequate leach solution flow into the are formation. Swelling and dis-persion of clay particles in the formation are often responsible for this permeability loss. Permeability and leaching tests were done in the laboratory on clayey ores to evaluate a clay-stabilizing polymer's effectiveness in preventing these problems. Test results indicate that treating the ores with the stabilizer could maintain permeabilities two to five times greater than the long-term permeabilities present in untreated ores. Both alkaline (pH 8.5) and acidic (pH 2.0) leaches were used in the permeability-leaching tests. Since in situ leaching throughput rate is directly related to permeability, these results also indicate a potentially beneficial effect on operating parameters such as capacity and injection pressure. To determine the reasons for the success of the clay stabilizers, an investigation was conducted to cieter-mine the effect of the stabilizer on clay swelling and dispersion. Clay-swelling tests indicated that the clay stabilizer reduced clay swelling. Zeta potential measurements made on fine clay particles treated with the stabilizer were compared to measurements made on untreated particles and indicated that the stabilizer was electropositive and, therefore, could reduce the degree of negative charge on the particles and their tendency to disperse or migrate.

Jan 1, 1984

By Wen H. Su

Multiple seam mining and its associated problems are very serious in Southern West Virginia where poor planning or lack of knowledge in seam interaction often results in complete loss of coal properties. Several measures have been proposed to alleviate the interaction problems under various multiple seam conditions, but few of them are specific in terms of mining plan. Two parallel approaches are adopted for this paper. One is field investigation which consists mainly of mine site visits and gathering of data. The other is the two-dimensional finite element simulation of mine workings using the data gathered as input. Two typical cases which represent the past and present multiple seam mining practice in West Virginia were investigated. Much attention is focused on the interaction problems experienced and the important parameters controlling interaction. Several key parameters controlling interaction in multiple seam mining were analyzed. Proper mining plans, by which the interaction problems can be minimized, are proposed for the individual cases after a better understanding of the interaction mechanism was realized through finite element analyses.

Jan 1, 1984