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By Jed H. (Original by) Mosgrove

Good mine ventilation starts at the drawing board. A coal mine will either be adequately ventilated or not, depending upon how good a job was done in the planning. Poor planning will not only result in inadequate ventilation, but may also lead to low productivity. A mine foreman cannot achieve high productivity while trying to maintain 4.2 ma/s (9000 cfm) of air at his last open crosscut.

Jan 1, 1981

By R. A. Jankowski, R. Gong, R. Bhaskar

Full-scale laboratory studies were performed to evaluate the effect of passive barriers and spray airmovers on airflow patterns at a continuous miner face and in reducing underboom boilout and operator exposure to dust. Tasks included baseline data collection, smoke trace tests, detailed performance testing using tracer gas, and data analyses. Data collection was performed using a state-of -the-art gas analysis system and custom-developed software. The data were used to calculate operator exposure at various locations and to develop gas profile maps to analyze airflow patterns. The effects of the proposed underboom airflow modification devices on operator exposure and airflow patterns were examined. Based on the results obtained from the study, the base case condition, with no barriers, appears to result in the lowest operator exposure.

Jan 1, 1992

By Richard E. Ray, George N. Aul, Fred Garcia, William P. Diamond

Increasing longwall panel dimensions, particularly face width in gassy coalbeds, may result in unexpected increases in methane emissions. To investigate this problem, continuous longwall face emission monitoring studies were conducted at two adjacent mines operating in the Pocahontas No. 3 Coalbed, where longwall faces were to be extended from 229 to 305 m (750 to 1,000 ft). It was predicted by regression analysis of methane emissions data from 229 m (750 ft) wide longwall faces that extending faces to 305 m (1,000 ft) would increase methane emission rates by only 7 percent (0.6 m3/min (20 cfm)), to 8.6 m3/min (304 cfm) at the VP-1 Mine. In contrast, it was predicted that extending faces at the VP-3 Mine could increase methane emissions by as much as 13 percent (1.8 m3/min (65 cfm)) to 16.1 m3/min (567 cfm). The geologic and mine design factors in¬fluencing the variation in face emissions between the two mines will be discussed.

Jan 1, 1997

By Russell. A. Smith

This paper describes some recent work on the identification and development of new chemical reagents aimed at improving the industrial processing of phosphate ores by froth flotation. In particular, three chemical product families which will be discussed appear to offer enhanced flexibility by: 1) utilizing a small amount of a silica control reagent which can significantly reduce the amount of anionic (carboxylic) collector required for a given P2O5 recovery level; 2) utilizing a new anionic collector family which offers high P2O5 recovery and selectivity versus standard carboxylic collectors; and 3) utilizing another new anionic collector family which has, in some tests, allowed for selective removal of dolomite from apatite. Examples and use characteristics of each of these new chemical ideas will be presented.

Jan 1, 1993

By Edward C. Dowling

Cleveland Cliffs and affiliated companies have established a commitment to the development and use of integrated process control. Substantial capital investments in process control, coupled with the dedication of human resources to effectively use the information, have generated meaningful business results. Improvements in productivity, operating costs and product quality have been realized. This paper presents an overall process control and information strategy, specific case studies, lessons learned and the current view of the next steps in the continued journey toward integrated process control and information management.

Jan 1, 2000

By O. Olajide, E. H. Cho

A laboratory study of the jigging process with Pittsburgh seam coal has been conducted. The laboratory-scale Baum jig used in this study was a McNally-Norton LO30X Right Hand Model Baum jig with an effective screen area of 0.186 m2 Feed material was prepared by selecting a size range from 6 mesh to 1.91 cm. Solid feed rates were 27.2 kg/min and 32.7 kg/min. Water flow rates were varied from 37.9 to 94.6 L/min. It has been found that smaller particles give higher values of density of separation and lower efficiency of separation. Increasing water flow rate increases the discharge rate of clean coal at a constant solid feed rate. It appears that the efficiency of separation increases by increasing water flow rate up to a certain value, and then levels off upon increasing the flow rate further.

Jan 1, 1988

There has been some confusion over the selection of discount rates when performing stochastic simulations of a project's net present value (NPV) using risk- adjusted discounting techniques. Some argue that lower discount rates should be used when performing stochastic valuation simulations. This creates higher NPV values and improves the attractiveness of a project. Others argue that the discount rate should not be lowered for these simulations. This paper exposes the source of this confusion. It demonstrates that stochastic simulations do not remove the risk inherent in a project and, therefore-do not improve a project's value to the risk-averse investor. Risk-adjusted discount rates should, therefore, not be adjusted downward when performing stochastic NPV simulations. Stochastic simulations are, however, shown to he useful in several aspects of project valuation.

Jan 1, 1996

By K. Sasaki, T. Murakami, S. Akibayashi, Q. Wei

A numerical analysis and an experiment were done on groundwater flow past a bore hole with a cylindrical obstacle at its center. Flow around the obstacle in the bore hole was studied in detail. Two dimensional governing equations to simulate this flow were written for the hydraulic head and seepage velocity in a porous medium and for the vorticity, stream function, and velocity in the bore hole. These equations were non-dimensionalized and solved by using the alternating direction implicit and successive-over-relaxation finite difference methods. Flow visualization experiments and velocity measurements in the bore hole were done with a two dimensional model composed of a porous medium. The numerical analysis procedures were validated by a comparison of numerical and experimental results. Effects of the Reynolds number and obstacle size on flow in the bore hole are clearly shown in the velocity and streamline profiles. The quantitative relation between the seepage velocity in the porous medium and the velocity of flow around the obstacle in the bore hole also were estimated.

Jan 1, 1996

By K. A. Natarajan, M. K. Yelloji Rao

The electrochemistry of sphalerite and chalcopyrite was investigated under both open-circuit and applied potential conditions. Emphasis was placed on the selective dissolution of sphalerite from a mixture of sphalerite-chalcopyrite flotation concentrates as a function of applied potential, acid concentration, pulp density, and time. Morphological studies using a scanning electron microscope (SEM) were also carried out with chemically leached, galvanically leached, and unleached surfaces of sphalerite and chalcopyrite. Selective dissoulution of sphalerite could be achieved if the mixed chalcopyrite-sphalerite concentrate slurry was maintained at a negative applied potential of -0.4V (SCE). Probable mechanisms involved in the selective dissolution of zinc are disscussed.

Jan 1, 1990

By Martin L. Smith

Mine waste characterization and risk assessment currently focesses on water quality and largely ignores boththe charteristics of the wastes themselves and how wastes interact with the environment. Characterization of the parameters that control contamination of pore waters and their migration can quantitatively assess risk and remediation strategies in terms of cost effectiveness and risk reduction. Since mine waste characteristics are spatial, geostatistical methods should be used for characterization and assessment. A number of geostatistical methods are reviewed in terms of their application to mine waste sampling, modeling and risk assessment and management.

Jan 1, 1995

By M. J. Laurila

Utilizing data compiled from a drilling program and bulk samples taken from a coal reserve, flowsheet performance for a coal preparation plant can be calculated using a desktop computer. Sets of equations defining material balances involving coal preparation plant unit operations are employed to depict plant performance. Techniques are discussed for interpolating washability data and extrapolating size distributions and other critical data to expand on oftentimes limited sets of quality data to a useable data base from which projections can be made. Simulation of flowsheets can be done for a number of different conditions and configurations while still remaining in a limited working memory capacity of 32,000 bytes. Presented within this paper are several pertinent examples.

Jan 1, 1982

By R. Hogg, M. Polat, S. Chander

A fresh dust generator was designed and built in order to study the agglomeration behavior and other characteristics of freshly generated airborne dust. The size distribution of the freshly generated quartz airborne dust produced by the generator was measured both directly in air and after dispersion in water. It was observed that same dust particles had an apparently coarser size distribution in air than in water, suggesting possible agglomeration of the dust particles. It was also observed that the size distribution obtained by a cascade impactor was very similar to the liquid dispersed size distribution, implying deagglomeration by the impactor. The agglomeration was confirmed by microscopic observations of particles in air and those collected on a microscope slide. The extent of agglomeration played a decisive role on the fraction of the dust actually becoming airborne. It was also found that contamination of the airborne dust by the rolls of the crusher was almost twice as much as that of the product.

Jan 1, 1991

By R. Q. Honaker, D. P. Patil, A. Sirkeci

Because of increasing production of fine coal during mining over the past century and because of inefficient fine-coal recovery technologies, a vast reserve of high-quality coal now exists in refuse ponds. A novel finecoal circuit, consisting of a hindered-bed classifier, an enhanced gravity concentrator and a flotation column, was evaluated for the recovery of fine coal from refuse ponds. The treatment of a pond derived from Pittsburgh No. 8 seam coal resulted in the production of a premium fuel containing less than 5% ash and a calorific value of about 30,170 kJ/kg with 60% mass yield. Results from the treatment of two refuse pond materials are presented in this paper.

Jan 1, 2002

By C. E. Zebula, F. F. Aplan, R. S. Datta

The hydrophobicity of oil shale was found to follow the sequence R-5 > Mahogany >> Eastern. Further, hydrophobicity was found to correlate with the total organic carbon (TOG) content, decreasing with increasing specific gravity of raw oil shale pieces. Differences in hydrophobicity from piece to piece indicate that gravity preconcentration would be much more effective for Western than for Eastern oil shales. Purified kerogen concentrates and low specific gravity fractions (<2.0) of raw Western oil shale samples show critical surface tension of wetting values of [y]c = ~35 mNm -1, and for a kerogen concentrate from an Eastern oil shale [y]c = ~46 mNm-l. This infers that dust from oil shale mining operations can be suppressed by surfactant solutions similar to those used to suppress coal dust.

Jan 1, 1988

By Joseph Lynch, John DiPonio

This report refers to the Chicago Deep Tunnel Contract 13A, which was the first contract let in the City of Chicago requiring the construction of deep drop shafts for the transportation of high level sewage to the deep tunnel system. The basic contract required the contractor to construct certain drop shafts designed to deliver surface and high level sewage to the deep tunnel system approximately two hundred feet below. The design of the drop shafts was in a degree affected by their proximity to the existing deep tunnel. The tunnel, approximately three and one-half miles long, was to have five shafts dropping sewage at five locations. Four of the drops were approximately one-half mile apart and spaced from the dead end of the tunnel. One shaft divided the remaining two miles from the existing work shaft at the southeast end of the tunnel wherein a 220&apos; deep pumping station was to be built. The existing tunnel had been built some time previously and all dewatering had stopped, allowing the tunnel and main shaft to fill with water. According to the plans, the drop shafts were all between fifty and ninety feet north or south of tunnel center line, and located in heavily built-up residential and industrial property. This then defines the problems: How do we control the water. If we excavate from the top down, how do we handle the slurry and the muck from five locations. How shall we construct the connecting tunnel between

Jan 1, 1997

By William C. Cooley

Modern tunnel boring machines are subject to excessive cutter wear and bearing failures when used in hard and abrasive rock. In very hard rock, the high cost of cutter and bearing replacement, combined with slower excavation progress, make it more economical to drive tunnels by conventional drill and blast methods. The use of high pressure water jets to break rock provides a promising alternative. Experimental data indicate that the specific energy (the energy expended per unit volume of rock broken) decreases as the water jet pressure increases. Continuous jets are generally limited to pressures below 100,000 psi, whereas pulsed jets from a water cannon can attain much higher pressures. Therefore, the Federal Railroad Administration of the U. S. Department of Transportation has sponsored the design (Ref. 1 & 2) and the fabrication and testing (Ref. 3 & 4) of a water cannon to determine its effectiveness in rock disintegration at very high pressures. This paper reports the results of laboratory tests with pulsed jets against large rock samples at pressures of 125,000 to 650,000 psi and field tests against dolomitic limestone and granitic gneiss at pressures near 450,000 psi. Although initial tests were made with a small nozzle, operating at off-design conditions (Ref. 4), this paper only covers results with the full-size nozzle, including 55 laboratory test shots and 67 field test shots.

Jan 1, 1974

Over the past few years, the School of Mines of Paris has carried out a program of research* on the grade-tonnage relationships in the border zones of porphyry copper deposits. The initial problem was quite difficult : how does the grade vary at the border of the known orebodies? Does it decrease regularly, or do some thresholds exist, where the grade diminishes abruptly? The answer to these questions have important repercussions on the prediction of the future reserves in the fringe of the orebodies. If the grade decreases regularly, very important reserves could exist; if not, there would be strong limitations to the possible recoverable reserves. The first step of our study was a critical study of previous work done on the subject. It appeared that, following Lasky&apos;s pioneering paper (Lasky, 1950), most of the authors used what we can call an historical approach to the problem. In this, the grade-tonnage relationships are calculated from the available figures for production and reserves and the results are then extrapolated to the future. The strong limitation of this model are brought out in this article.

Jan 1, 1982

By R. Addison, P. V. Avotins, D. W. Kestner, M. F. Dibble, L. A. Haas, M. D. Flavel, D. Halbe, D. J. Barratt, G. V. Jergenaen

Mineral processing in 1980 can be described by several key words, familiar to the industry throughout the past decade: complex, low grade, environmental, energy, high tonnage, and economics. Flowsheets have become more complex in order to treat lower-grade, finer-grained, more complex ores and still meet environmental and economic constraints. Operators and researchers have had to cope with these problems, which have resulted in marked trends in mineral processing. The use of advanced instrumentation in process monitoring, control, and modeling has been increasing to deal with fluctuating ore grades, higher plant capacities, rapidly rising operating costs, and process complexities. The industry has been presented with new generations of equipment that reportedly do the job more efficiently and at a reduced cost. The need to meet stricter air and water environmental standards has resulted in a concerted effort by the mineral industries to obtain an appropriate balance between the needs of mining and mineral processing and the requirements for proper environmental, safety, and health protection. Energy and economic considerations have led to increased equipment size, particularly in grinding, flotation, and conveying. Throughout all phases of mineral processing there has been an effort to reduce energy consumption. One avenue followed by researchers and operators was the testing and use of chemicals to reduce energy requirements.

Jan 5, 1981

By H. Soto, J. Jara, F. Nava, J. B. Hiskey, B. J. Scheiner

Laboratory tests showed that ozone can destroy free cyanide and weakly complexed cyanide (copper and zinc cyanides). The iron cyanide complexes were resilient to ozonation but they were effectively eliminated by precipitation with Fe (II) ions under controlled pH conditions. Tests carried out with effluents from a number of gold mills confirmed the results obtained previously in the laboratory. The industrial samples contained cyanide in the form of free cyanide and also complex copper, zinc and iron cyanides. Solutions that contained up to 184 mg/L total cyanide, after the ozone treatment analyzed only 2-3 mg/L dissociable cyanide and 50-90 mg/L CN(t) (accounted for by iron complexes). After precipitation with ferrous ions total cyanide was reduced below 1.5 mg/L. For most solutions ozone consumption ranges from 3 to 6 g per g of cyanide destroyed. However, certain impurities (such as SCN and S203 ), present in some effluents, increase ozone consumption and make it more difficult to reduce copper concentration to satisfactory levels.

Jan 1, 1993

By J. A. Herbst, J. E. Bohrer, Y. C. Lo

A systematic approach has been developed to analyze a phosphate grinding circuit with a view toward determining promising alternatives for increasing mill capacity. This analysis was carried out and capacity increases were predicted in the context of detailed population balance models developed for the plant ball mills and classifier systems. Model development and verification was performed using data obtained in a series of batch tests and two plant test campaigns. The effects of feed rate, percent solids, ball size, and mill material filling, etc., on grinding were investigated in the laboratory and plant. Residence time distribution tests were also performed to determine the transport behavior in the mill. The population balance models were found to provide accurate predictions of full-scale grinding circuit performance. Based on the findings of this study, additional capacity in excess of 25% was predicted for these ball milling circuits by a proper combination of ball size change, mill dilution, and adopting screen classification in place of hydro-cyclones. These predictions have been confirmed by plant tests in which the recommended operating changes have been implemented. Understanding the effects of operating variables on breakage kinetics and the interplay between kinetics, transport, and classification has contributed significantly to increasing the mill capacity.

Jan 1, 1988