Search Documents

By Joe W. Siefke

The world-class Kramer sodium borate deposit is being developed by modern open pit operations near Boron, California. The deposit is a bedded, lenticular sedimentary sequence of borax and kernite crystals together with claystone. The borates dip south into a structural basin-bounding fault and were formed in the bottom muds of a permanent shallow lake. The lake was fed boron and sodium-rich solutions from a thermal spring source of volcanic origin. In addition to deposit geology, present day geotechnical concerns such as groundwater and slope stability will be discussed.

Jan 1, 1995

By K. E. Doud

An unusually pure grade of rutile and several grades of aplite rock are produced in a unique mining and mineral dressing operation in Hanover County, Virginia. The ore body is an aplite rock of gnessic structure, having a sari ace exposure extending over several hundred acres, heavily leathered and containing rutile, ilmenite, and other titanium and iron minerals. The physical nature and mineral composition of the ore body has permitted the use of a relatively economical and unusual processing circuit. The flowsheet was designed to take full advantage of the remarkable liberation of the minerals at relatively coarse rinds. It permits flexibility in changing the product mix, and maintains high levels of purity in both rutile and aplite rack. The mineral processing is discussed in some detail below.

Jan 1, 1962

By T. J. van der Walt

This paper proposes a new methodology to model ill- defined processing operations using neural nets (NN's). A process with many variables (large dimensionality) cannot be modelled adequately if limited process data are available. This problem of multi-dimensionality is addressed and an approach suggested to reduce the dimensionality using NN's. The result of this modelling methodology is a combined model of phenomenological expressions and NN's. The model can successfully be incorporated in a dynamic simulator of the process. A new approach to conduct modelling on the basis of continuous data collected directly from an industrial processing unit, is also proposed. The modelling methodology is applied to a typical processing operation, the resin-in-pulp (RIP) process.

Jan 1, 1992

By E. A. Brecke

The Cave-In-Rock Flourspar District is located in the northeast part of Hardin County, Illinois and is the most northeasterly occurrence of flour spar of the Illinois-Kentucky Flour spar Area. The occurrence of these deposits is confined to an area about one and one-half miles wide and five miles long parallel to the Peters Creek Fault (Fig. 1) The delineation of several features that may be described as breccia pipes has permitted the definition of the point of ascent of solutions to the host horizon and the lateral spread from these points.

Jan 1, 1962

Overview In 1992, US coal supply and demand were shaped more by weather conditions and the export market than by the economic recovery. Preliminary data compiled by the Energy Information Administration (EIA) (Table I) show that coal production declined slightly to 902 Mt (994 million st). Consumption, though, rose by about 1 % to 811 Mt (894 million st), trailing the 2.1 %growth in Gross Domestic Product. Contributing to the decrease were a sizable drop in coal exports and some coal stock withdrawals. Consumption increased largely because electric utilities turned to coal to offset a shortfall in hydroelectric generation caused by a drought in the Northwest. Apart from this, the demand for coal-fired generation was dampened by a mild winter in the northwestern and northcentral United States, and a cool summer in the central and eastern parts of the Nation. Coal use by other consumers was about the same as in 1991. The average delivered prices of coal to all consuming sectors decreased slightly in 1992, reflecting soft coal markets (Fig. 1). US coal exporters experienced a set-back in 1992 mostly because of losses in the European market. Total coal exports fell by 6% to 93 Mt (103 million st), the first decline since 1987. Coal stockpiles at the end of 1992 were about 1.8 Mt (2 million st) below 1991, despite stock buildups by some electric utilities in the East. Stocks were built up as a hedge against possible coal miners' strikes after the Feb. 1, 1993, expiration of the contract between the United Mine Workers of America and the Bituminous Coal Operators' Association.

Jan 1, 1993

By A. K. Sheik, W. G. Pariseau

A small underground mine in northern Idaho was used as an experimental facility for studying the role of water in the analysis of mine-opening stability. Laboratory test data, borehole measurements and geological mapping assisted in the construction of a coupled finite element model of the rock mass. The model was used to make quantitative estimates of rock stress, strain and displacement changes and to make estimates of the water pressure and flow velocity changes that occurred during historical mining. Stope cuts and wet fills were included in the analysis. The stability of the crown pillars between stopes was of particular interest. The relatively low effective stress and high rock-mass strength showed that water pressure changes were of no great consequence, which is in agreement with experience. The computational tools used in the analysis may be applied to other wet mines with appropriate changes to site-specific data.

Jan 1, 2002

By D. A. Swanson

Predicting when and at what rate seepage will occur from waste-rock facilities is becoming an integral part of permitting and closure at mines situated in dry climates. Such predictions require development of a conceptual framework that accurately describes how water will percolate through a waste-rock facility. Also needed is a detailed hydrological characterization of the waste-rock facility, including measurement of the hydraulic properties of the waste rock and any potential cover materials. This paper presents a conceptual framework describing unsaturated water flow in a waste-rock facility and describes methods for characterizing the hydrology of a waste-rock facility in a dry climate. The methods are designed to collect site-specific data to support accurate and defensible predictions of long-term seepage rates.

Jan 1, 1998

By M. J. Sanzotti, C. J. Bise

This paper examines the potential for controlling longwall-induced subsidence by pneumatically backstowing waste rock into the void created by mining. The paper also examines scheduling the process as a unit operation of the mining activity. Based on a review of background literature and interviews with representatives of various mining companies, public-interest groups and state and federal regulatory agencies, a hypothetical case-study evaluation of pneumatic stowing at a southwestern Pennsylvania mine was conducted. The study indicated that current stowing technology cannot keep pace with the production potential of longwall systems in the United States. Further, at the mine used in this case study, concomitant stowing would reduce subsidence by only 50% of what would normally be incurred during full longwall caving, and the longwall coal-production rate would decrease from 3,630 t (4,000 st) per shift in the nonstowing case to 1,360 t (1,500 st) in the stowing case. A preliminary cost analysis reveals that pneumatic stowing would add from $5.79 to $11.57 per t ($5.25 to $10.50 per st) to the operating cost of producing coal at the case-study site.

Jan 1, 1997

By N. T. Cowper

Slurry viscosity ultimately affects the majority of mineral extraction processes. However, to date its role has been disguised because mineral processing equipment has been conservatively designed to operate at minimal slurry viscosity. With most ores this still meant acceptable solids concentration was achieved. However, with the advent of treatment of weathered ores the resulting higher slurry viscosity (rheology) has meant solids concentration has had to be reduced, often to unacceptable levels. To permit operation at higher solids concentration chemical dispersants are employed. These dispersants are expensive and their addition should be controlled. Slurry Systems Pty Limited (SSPL) has developed an On-Line Viscometer to monitor and control slurry viscosity, whether by controlling water addition or by controlling dispersant addition. Using this instrument the slurry rheology can be controlled at the optimum level, maximizing solids throughput, and minimizing water, reagent, and dispersant addition. This paper discusses rheology of typical mineral slurries, the relationship between slurry rheology and percent solids in a slurry, and the need for rheological control in mineral processing. The effects of rheology on various process steps, and the use of dispersants are reviewed. The paper concludes with summarizing actual case histories and cost impact of Theological control.

Jan 1, 1992

By D. S. Holmes

Biological processes for metal solubilization and ore beneficiation are in widespread use today. There are also some promising new applications of biotechnology in the areas of metal concentration and toxic metal cleanup. Recent progress in genetic engineering promises both to revolutionize the existing biological process and to expedite the adoption of the new biological applications. But before it can do so effectively, progress must be made in many areas of fundamental research and in biochemical engineering. These issues are addressed with special reference to the biotechnology of semi-enclosed containers (bioreactors), dumps, heaps, in situ and under- ground leaching, and with respect to the biotechnology of metal concentration. Finally, certain biological considerations for bacterial strain improvement are discussed.

Jan 1, 1987

By E. F. ‘Pat’ Nelson, Richard Broom

Our portion of this afternoon’s session is dedicated to the operation of automatic process control associated with small to medium size primary or SAG milling circuits. In recognition of the subject matter of this symposium, specifically precious metals, our historical reference is Rosario Dominicanna in the Dominican Republic, one of the largest gold producers in the Western Hemisphere. Plus a backward glance to review very briefly the initial performance of the big primary mills at Island Copper in British Columbia and Pima IV in Arizona. We will then get to the subject at hand with a discussion of a retrofit control logic recently installed on a 5000 hp primary mill. The focus of this review is the simple, inexpensive, and cost effective character of this retrofit installation.

Jan 1, 1984

By Kal V. S. Sastry, Stephen N. Little

Computer simulation of comminution systems is found to provide significant cost savings by enabling efficient circuit design and development of control systems. These simulation systems are based on sound mathematical models and numerical methods. Nevertheless, they are found to be hard-to-use and hard-to-modify to carry out more elaborate process analysis. This paper discusses the fundamental principles and practical aspects of an advanced, highly functional, and user-friendly SIMulator for COMminution, SIMCOM, that is being developed at Berkeley by incorporating state-of-the-art software engineering principles.

Jan 1, 1992

By G. D. Schena

A decision support system for the management of the mineral resources of a developing country has been derived. The system allows the evaluation of the impact of a mineral project in a developing country in the broad context of its economy. The analysis permits the assessment of the overall socio-economic consequences of mineral prospects and allows incorporation in the evaluation of issues that are broader in scope than the pure financial objectives. The system is built around the Leontief framework of economic analysis. The original input-output model, enhanced to incorporate country-specific behaviour is integrated with cost-benefit analysis and shadow pricing. The analysis leads to synthetic measures of profitability at market and shadow prices. These measures are useful to direct the mineral policy of a developing country through the exploitation of those mineral resources which are most likely to bring about economic growth and social advancement.

Jan 1, 1992

By C. R. Stephan, N. B. Greninger, W. A. Slivensky

The U.S. Bureau of Mines and the U.S. Mine Safety and Health Administration (MSHA) are participating jointly in a research program to evaluate strength characteristics and air-leakage resistance of various proposed seal designs for use in underground coal mines. Over 20 full-scale seals were constructed in the Bureau's experimental mine at the Lake Lynn Laboratory, air-leakage tested, then subjected to pressure pulses of 0.14 MPa or greater. A discussion on the experimental procedure, construction techniques, and the explosion and air-leakage test results is presented. Four types of construction material were used during this seal testing program: solid-concrete-blocks, low-density foam blocks, cementitious foam, and wood blocks. Only one of the solid-concrete block designs using a mortared thick wall survived the explosion and air-leakage tests. Most of the low-density foam block and cementitious foam seal designs were judged to meet the requirements to be considered a coal mine seal. One of the wood block convergence seal designs failed explosion testing. Based, in part, on these research findings, several alternative seal design constructions using low-density foam blocks, cementitious foam, or wood have been approved by MSHA for use in coal mines.

Jan 1, 1993

By G. Chi, M. C. Fuerstenau, R. C. Bradt, A. Ghosh

With increased emphasis on controlled blasting, which is the first and least-costly stage of comminution, ore grindability and plant throughput can be increased by 5% to 10%, and energy savings of up to 10% appear possible. Crushing and grinding efficiencies are presented for ore blasted under regular and adjusted field conditions. An economic analysis of drilling and blasting through crushing and grinding is presented, suggesting that cost savings approaching 10% may be achieved.

Jan 1, 1998

By L. J. Dahl, S. E. Paulson, H. L. Kuhlman

To provide basic information on the processes occurring during in situ leaching, the US Bureau of Mines developed a geologic characterization research program. This includes laboratory experiments wing leaching apparatus that can accommodate whole core samples. Whole core experiments result in a higher proportion of ore mineral contact by the leach solution than packed column experiments. They also allow for the assessment of permeability changes taking place as the result of mineral dissolution, precipitation, and clay swelling within the flow channels of the rock. The leaching apparatus developed can be wed for either constant-pressure or constant- flow rate experiments and allows for the control of flow rate, pressure, and temperature during the experiments. Details of the experimental apparatus are presented, as well as preliminary results from the first series of experiments on an oxide copper ore from the Casa Grade, AZ area.

Jan 1, 1988

By V. W. Skema, M. W. Smith

Pennsylvania has 4,000 km (2,500 miles) of streams that do not meet water-quality standards due to acid mine drainage (AMD), making AMD the greatest cause of water pollution in the state. The problem is mainly caused by abandoned coal mines. To abate AMD, Pennsylvania is using a watershed-based approach that includes remining as a key component of a comprehensive restoration strategy. The Tangascootack Creek Water-shed was targeted for AMD restoration through remining. Geologic mapping and overburden data were analyzed using Earth Vision software to identify areas of coal reserves that could be remined to improve water quality. Incentives are offered to encourage mining in these designated areas.

Jan 1, 2002

By Raj K. Singhal

Three principal activities are involved in planning and developing a surface mine. These are 1) definition of economic and technical feasibility, 2) design, procurement and construction, and 3) mining and reclamation. The last is the only activity which begins in the feasibility study and continues throughout the life of a mine. It is also the activity which depends heavily on use of computers. This paper deals with a method of selecting mining software and dwells on the recent progress, made in this area. Discussed also is the status of computerized equipment management and information systems: a microprocessor based technology applied to dispatch systems, monitoring of equipment health and performance, wireless data transmission to a centralized data processing unit, and mine- wide information and reporting system. Reference has been made to upcoming developments which offer the potential- of transforming the surface mine of the year 2000 into a "manless pit". Canadian achievements in all of these areas have been highlighted at appropriate places in the text.

Jan 1, 1989

By Johannes Wageneder

As a reaction to the fire accidents in tunnels in Europe Designers nowadays have to demonstrate the integrity of underground structures such as metro systems, railway and road tunnels in case of fire load wherever as a consequence of a lining collapse surface infrastructures or residential areas could be affected. To respond to this FLAMDOCS allows to calculate the stability of reinforced concrete structures during fire load for a series of prede?ned time steps. Elementary theories of non linear material properties and reinforced concrete structures are used.

Jan 1, 2003

By R. D. Doepker, P. L. Drake

The dissolution of metals from various metal- mine tailings has been studied through a series of submerged tailings batch tests at US Bureau of Mines laboratories. Tailings selected for this study included both reactive (as determined by column leaching studies) and benign tailings. Metal mobilization in aerated (97% saturated with oxygen) samples appeared to be consistently greater than metal dissolution from stagnant (79% or 70% saturated with oxygen) waters. In the early weeks of the study, sulfate concentrations increased with solid-liquid contact time, while calcium dissolution remained early constant. Metal concentrations varied in relation to solid-liquid contact time and aeration. Leachate pH appeared to be nearly independent of solid-liquid contact time for basic tailings. Reactive tailings having both a submerged and a surface component demonstrated increased metal mobility.

Jan 1, 1991