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By T. C. Rao, Vanangamudi. M., J. P. Barnwal

Experiments were carried out on 76 mm laboratory heavy medium cyclone treating -2.0 t 0.5 mm coal and on two 600 mm industrial heavy medium cyclones treating coal in the size range -13.0 t 0.5 mm. The variables studied were spigot diameter and feed medium gravity. The generalised distribution curve for the separation of coal in these heavy medium cyclones has been defined by the equation [ ] The specific gravity of separation SG has been found to increase linearly with increase in feed medium, gravity (SGf). The relationship for SG of industrial cyclone is given as 50 SG = -6.801 t 6.463 SGf t 0.0327 Spig 50 -0.02625 SGf. Spig. Further, the probable error for the separation has been found to be linearly related to (SG50 - SGf ) according to the equation [ ] The model equations developed have been used to select appropriate levels of operating conditions to achieve an increase in the yield by about 2 to 4% without affecting the quality of the product.

Jan 1, 1990

By B. S. Treiber, R. A. Lohnes, S. M. Levorson

As part of a research program to develop a coal-handleability index that would predict the ease with which a coal would flow through a handling system, an apparatus was developed to directly measure the unconfined Yield strength and bulk density of consolidated-coal samples. The new test apparatus provides a fast and simple method for determining the strength and compressibility parameters that are associated with the handling characteristics of crushed coal. Comparative tests were conducted using a low-stress triaxial-test apparatus. To check the accuracy of the new method, four coals with a variety of moisture contents and gradations were tested using the new method. These tests indicate that the new test device yields valid results. Further, the speed and ease of operation of the new device makes it suitable for quality control and quality assurance in plants.

Jan 1, 1996

By B. C. Cornilsen, X. Shan, D. H. Carlson, J. H. Johnson

Airborne respirable Diesel Particulate (DP) presents an additional health hazard in that it has been shown to be mutagenic. This problem is of increasing concern as more coal mines introduce diesel vehicles. If the DP present in coal mine air is to be controlled it must first be measured. This paper describes development of the laser Raman spectroscopic measurement of the amount of DP in DP/coal mixtures collected on filters in the laboratory and in coal mines. The Raman technique provides a chemical measure of the carbonaceous material in each component, and is not dependent upon particle size. When this work was begun there were no known analytical methods for this measurement. Side-by-side in-mine comparisons of the results obtained from Raman, neutron activation analysis, and size selective analyses (MOUDI and personal samplers) are presented. The neutron activation and size selective analyses were obtained by the USBM Twin Cities Research Center and University of Minnesota. Good agreement has been found among these three methods.

Jan 1, 1991

By E. Azrag, A. MacDonald

A hydrogeologic investigation was conducted to predict inflow to underground mine workings and mining-induced hydrologic impacts for a proposed underground mine beneath a lake in northern Canada. Flow and shut-in tests were conducted to determine hydraulic conductivity values and to estimate the hydraulic head. A conceptual hydrogeologic model was developed and incorporated into a numerical ground-water flow model (utilizing MINEDW, a three-dimensional, finite-element code with special attributes designed for mine dewatering). The mining sequence was represented in detail(e.g., driving ramps and drifts, extracting panels, and backfilling mined areas). Due to limited field data, a quantitative assessment of uncertainty was implemented to estimate limits of possible inflows.

Jan 1, 2003

By B. Cristol, G. Benier

Laboratory and pilot tests have shown that the grinding of some aluminas makes two populations appear : agglomerates’ and ultimate crystals’. Classical breakage functions (Size Mass Balance Method) aren't able to describe correctly this kind of grinding. So we have optimized a particular breakage matrix which takes into account the fact that the agglomerates can either be reduced in size or either be blown up to liberate the ultimate crystals. The models which were developed using this breakage matrix are in good agreement with the experimental results of the pilot tests. The industrial breakage functions were estimated from pilot breakage functions, using scale up prediction procedures and plant tests. The agreement between predicted and actual plant performance is excel1ent.A 20 % increase in capacity was predicted to be available by improving the grinding circuit classifier performances.

Jan 1, 1992

By Don W. Murphy, Don M. Larsen

Advanced process control has been implemented at the Jerritt Canyon Mill. Plant production prior to 1997 was limited by grind circuit capacity. The installation of additional mill horsepower and an optimizing supervisory control system achieved a throughput increase in excess of 12 percent. The controller application utilized a seamlessly integrated fuzzy logic expert system for real-time mill control coupled with a neural network predictor for closed-loop feedback of particle size constraints. In late 1998, a second supervisory controller was installed to operate the fluidized bed roasters. The second controller optimized roasting conditions, increased plant throughput and improved metallurgical recovery.

Jan 1, 2000

By J. H. Tylczak, R. Blickensderfer, D. J. Singleton

As part of its research on wear of mining and mineral processing equipment, the US Bureau of Mines evaluated the erosion-corrosion characteristics of 12 alloys in phosphoric acid waste water. Tests were conducted on 2- and 5-cm-diam specimen8 in 12- and 60-cm-diam ball mills by grinding phosphate rock in gypsum pond water with an initial pH of 1.6. For comparison, grinding tests also were conducted in tap water. Static corrosion tests in gypsum pond water also were carried out. For all alloys tested, the wear by erosion-corrosion was greater than the sum of erosion plus static corrosion. A low-alloy, high-carbon steel and a high-manganese, nitrided stainless steel were the most cost-effective materials

Jan 1, 1987

By Selamet G. Ercelebi, Mahmut Yavuz

An inherent aspect of longwall mining is moving the equipment from a mined-out panel to a newly developed panel. Moving times may be reduced by detailed preplanning. A very useful tool for planning is MS Project. Using MS Project, one can efficiently plan, manage and coordinate a project from conception to conclusion. The critical path analysis identifies potential critical activities which may cause excessive time delays. Changes to the tasks on the critical path can have significant impact 0.n the completion of a project. Assigning additional resources to these tasks (either moving labor from other tasks to critical tasks or providing labor overtime work) may reduce the move time. Simultaneous activities are the candidates for moving the labor from an activity to another. Each time a change is made, the critical path should be recalculated. MS Project quickly recalculates schedules and lets you see how changes in one part of the project will affect the overall plan. In this fashion it is possible to minimize the longwall move time.

Jan 1, 2002

By M. Cambridge

The design process must anticipate all construction and operational conditions and make an allowance for all eventualities. Prevention of failure during operational life, and in some cases post abandonment, requires that a risk assessment is undertaken during the design stage which defines not only the factors of safety to be used but the criteria for the structure during its operating life. These operating criteria should clearly identify the at-risk structures and the inspection and monitoring routines required to ensure compliance with the design objectives. On a mine site, it is the role of mine management to ensure that the operating rules be applied throughout the mine life and that a system of inspection and monitoring procedures be instigated. Where the risks are significant, high-level auditing by an independent engineer will also be required. Within the inspection and auditing framework, the designer needs to incorporate instrumentation to enable the operators and management to confirm that the facility meets the requirements of safety, stability and environmental compliance whilst continuing to meet its operational function. This paper reviews the use of inspection and monitoring to prevent failure and provides, in summary, examples of where monitoring has been undertaken and prevented failure. A tabulated review of legislation, regulations and technical guidance generated as a result of previous failures or untoward events is provided.

Jan 1, 2005

By J. C. Ransdell

A conventional paddle-type mixer and a gravity-flow mixing device were evaluated for conditioning of fine phosphate feed (- 35 + 150 mesh) with fatty acid and fuel oil, and for acid scrubbing prior to cationic flotation. Gravity-flow mixing re- quired less residence time but slightly higher reagent concentrations to achieve recovery levels similar to conventional conditioning. Grade was less sensitive to reagent concentration using the gravity-flow mixer. For acid scrubbing, the gravity-flow mixer proved equally effective. In this paper, the effect of time, pulp density, reagent concentration, and emulsification on conditioning and acid scrubbing efficiency of the two devices is discussed.

Jan 1, 1987

By Edward R. Torak

The Ohio Coal Testing and Development Research Facility (OCTAD) was commissioned in 1992 by the Ohio Coal Development Office and the Ohio Power Company to support evolving process technologies that will lead to increased environ- mentally sound use of coal. OCTAD is equipped with advanced physical concentration devices and processes capable of beneficiating coal to levels beyond conventional practice. The first task of OCTAD operators was to test the cleanability of the Meigs Creek Seam Coal in advanced circuitry and compare the results to conventional cleaning levels. In testing the seams, OCTAD circuitry was configured to produce middlings on the coarse and intermediate size fractions. These middlings were subsequently crushed to a finer size (28M x 0) and subjected to cleaning in fine heavy-media cyclones and advanced froth flotation circuitry. Nearly thirty-six full-scale production runs at various operating conditions were completed during the campaign. The results of the test program are examined in this paper.

Jan 1, 1995

By Fathi Habashi

SELENIUM AND tellurium are by-products of electrolytic copper refining. Copper anodes contain 0.01-0.2 % Se and up to 0.04 % Te; during electrolysis these deposit as a slime at the bottom of the cell. Such slimes contain 2-15% Se and 0.5-8 % Te, as selenides and tellurides of gold, silver, and copper. The following compounds have been identified in the slimes: (Ag, Au)Te2, Ag2Se, Ag2Te, CuAgSe, Cu2Se, Cu2Te. Anodic slimes from copper electro¬lytic refining are a grayish black powder, minus 200 mesh. When this complex mixture is decomposed in an acid medium, elemental selenium and tellurium can be obtained, while in an alkaline medium, both metals go into solution. Acid leaching The slime is charged in acid digesters of 800-900 lb capacity, heated to 260°C with 78 % H2SO4, for 8-12 hr. During digestion the following reactions take place:

Jan 1, 1970

By J. Mersch Ward

Homestake Mining Company has identified a significant native sulfur resource at its Cinnabar Canyon prospect in Mono County, California. Elemental sulfur occurs as replacements, fracture coatings and breccia fillings in a thick sequence of Miocene-Pliocene intermediate volcanic rocks. The deposit extends along a northwest trending regional fault and measures approximately 900' in width, at least 1800' in length, and has a thickness in excess of 200'. The deposit lies approximately 150' below the surface and is covered by a silicified cap of volcaniclastic strata. The deposit has been delineated by rotary and core drilling. Utilizing a grade cutoff of 5% elemental sulfur, the delineated deposit has a probablelpossible resource of 16.1 million tons of ore averaging 17.9% elemental sulfur containing 2.57 million long tons sulfur. Assay grades within the resource area range up to 40% sulfur over a 40-foot intercept.

Jan 1, 1992

By Steve Kral

The power industry throughout the world is in the midst of a significant transition that will result in a major restructuring. Deregulation of utilities in the United States is continuing, resulting in increased competition among power providers. The traditional ways that electric power is globally bought, sold and delivered will also change. However, according to the Department of Energy's (DOE) Pat Godley, one thing is clear: "Those who provide the power during the 21 st century will be those who are willing to change - those who are willing to accept new ways of doing business and willing to employ new technologies." Godley is assistant secretary of fossil energy with DOE. Her comments came during the opening remarks at the Fourth Annual Clean Coal Technology Conference, held in Denver, CO, Sept. 5-8, 1995. The conference was sponsored by DOE and the Center of Energy and Economic Development. Under the theme "Global Opportunity," more than 300 coal and utility executives spent three days discussing the new face of the electric-power industry throughout the world and the new, mostly clean coal technologies (CCT) that will be available to power providers.

Jan 1, 1995

By Thomas P. Meloy

A brittle solid broken by crushing or impact, results in a mass size distribution curve having a straight line segment when plotted on log-log paper. Depending on the mineral, the slope of this straight line segment ranges from a maximum of one for materials like glass and quartz to values of one half or less. Theoretical derivations of the size distribution, such as the Gaudin-Meloy model, yield a slope of one and only one. When the Gaudin-Meloy model is modified to assume that not all cracks terminate on a preexisting surface, the new model predicts that size distribution slopes, depending on the type of brittle solid, will be less than one. There is a measurable physical parameter that will predict the slope. In addition the model predicts that particles from such a size distributions will have negative corners and peaks - indentations. Moreover the model predicts that particle shape will systematically change with decreasing particle size. Finally, this new physical model of comminution may be experimentally tested.

Jan 1, 1995

By F. G. Boehm, T. S. Golosinski

This paper identifies the components of belt conveyor shifting force as a vertical force, Pv, a lateral force, Ph, and a longitudinal force, Pl. A method for estimating these forces is proposed that relates each of their values to the properties of the conveyor structure and rails, the shifting operation parameters, and other site-specific conditions. The effect of this force on the shifter behavior is analyzed, and guidelines are developed for selecting a suitable shifter. As well, other equipment requirements for the shifting operation are discussed.

Jan 1, 1988

By G. P. Dvoichenkova, E. A. Trofimova, M. V. Zaskevich, V. A. Chanturiya

The paper presents theoretical and practical aspects of directed adjustment of physicochemical properties (pH,Eh) and ion composition of recycle and mine water by electrochemical treatment. Treatment is run in the conditioners of diaphragm-type with production of alkaline catholyte of pH value up to 12 and acidic anolyte of pH up to 2. In process of water electrolysis the directed motion of Mg2+ and Ca2+ ions is observed from anode volume to cathode one, were they precipitate as hydroxides and carbonates; it leads to decrease of salt content in anolyte and catholyte. The anolyte has been concentrating anions, it is being saturated with oxygen, which reaches 20-35 mg/L. The results of experimental and industrial testing of electrochemical technique for mine and recycle water in flotation of diamond-containing and sulphide-scheelite, hematite, phosporite, apatite-nephelite, bauxite ores indicated the increase of recovery up to 2-1 5% and grade up to 0,5-2%, concurrent with decrease of reagent consumption from 15 to 50 %. Modules of industrial conditioners of different type capacity have been developed.

Jan 1, 1995

By Michael D. Balen

The plate-glass windows in the bus were cracked and mud-coated. Nevertheless, they afforded an excellent view of the many head-on collisions we narrowly avoided along the route from the Magadan airport to town. Apparently the driver thought the left side of the road was smoother than the right side, for he drove in the wrong lane at all possible times, even in the face of oncoming traffic. As far as we could tell, neither side of the road was any better than the other. Either way, we had to hang on just to stay in our seats. We careened past trucks and pedestrians, nearly always in the face of impending disaster. When the bus finally pulled into the parking lot of the Okean Hotel in Magadan, we had to thank the driver, not only for safely delivering his passengers, but also for the lasting first impression he gave us of the Russian Far East.

Jan 1, 1995

By Y. M. Jiang

Longwall faces can move at high advancing rates, but many geological variations can cause unexpected instabilities and production losses. The rapid movement makes it necessary to evaluate different geologic conditions in the rock mass as fast as possible to assess their effects on the longwall face and shields. It is believed that prompt awareness of geologic conditions is the key to preventing instability at a longwall face. This paper introduces the application of fuzzy set theory for characterizing and evaluating roof conditions. Real-time monitored data coupled with fuzzy set analysis provides valuable information, such as shield leg pressure, developing load on shields, intervals of periodic weighting and the ratio of developing loads during periodic to normal times.

Jan 1, 1997

By Gülhan Özbayoglu, Yusuf Ziya Akgök

The effect of cooling rate on the flotation behaviour of copper slags of flash smelter plant in Samsun was investigated. Fresh molten slag was solidified in laboratory scale in three different ways. All the samples were characterized by chemical and mineralogical analyses. The chemical analyses showed that samples prepared from fresh slag had 0.9 to 1 % Cu with 40 % Fe and 30 to 32 % SO2. Old pit slag samples contained between 1 to 3% copper. Microphotographs showed that rapidly cooled slags showed fine size distributions, e.g. the copper grains in granulated slag had sizes in 1-2 microns. On the other hand, the size of copper grains in slowly cooled slags increased above 40 microns. Flotation tests carried out by using potassium amyl xanthate and Flotanol-C showed that slowly cooled slag reduced the copper losses in the tailing and improved the grade of concentrate. Under the light of laboratory investigation, the pit dimensions of Samsun Plant have been modified which resulted in a pronounced improvement of the grade and recovery of concentrate produced at Samsun slag flotation circuit.

Jan 1, 1995