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By John A. Herbst, William T. Pate, A. Edward Oblad

Dynamic optimization is a cost-effective means to increase production or improve product quality in a plant. Several model-based approaches to dynamic optimization of mineral processing operations have been developed and implemented in plants. This paper reviews the phenomenological models that are the basis for dynamic optimization and the alternative methods of mathematical optimization. These methods range from theoretically complex and costly to implement to intuitively comprehensible and readily implemented.

Jan 1, 1990

By A. Zorychta, T. Cyrul, Z. Kleczek

INTRODUCTION Underground mining causes disturbances of the primary state of stresses. Resulting from those disturbances a loss of stability of rocks that surround excavation may occur interrupting the production and creating life danger for the personnel. One of the manifestations of such an instability is a rock burst phenomenon which mainly occurs at great depths. From the mechanical mint of view the rock burst is a loss of stability /Filcek et a1.,1984; Pietuchow and Linkow, 1976/ due to : - quasi-static stress changes in the surrounding rocks; we will call it s seam burst , - dynamic stress changes in the surrounding rocks caused by rock shocks ; we will call it roof burst. Possibility of the rock burst occurrence Is uniquely determined by the state of stresses existing in the rock mass. In the following sections of the paper we will consider different aspects of this question. Moreover distributions of displacements and failure criteria for a coal seam at longwall mining will be defined. STATEMENT OF THE PROBLEM Determination of the vertical stresses and displacements resulting from longwail mining will be based on the Budryk’s idea of a stress wave /Salustowicz, 1955/. The idea originates from the analysis of a roof plate /beam/ resting on the deformable foundation /Sean/ and subjected to the cylindrical bending. Equation of the bending lice uniquely defines vertical stresses and displacements which are induced in the seam. The equation will account only the shear force effect. Elimination of the bending moment has been shown and discussed by Zorychta and Bcrecki /Zorychta, 1985; Borecki and

Jan 1, 1986

By Gregory B. Baecher, Walter Steiner, Herbert H. Einstein

1. INTRODUCTION Empirical methods have always been important in tunneling in contrast to many other branches of engineering. Beginning in the late 19th century, when engineering entered the phase of formal modeling, this dichotomy could be seen to emerge even in the work of individuals. Culmann (1), Ritter (2) Kommerell (3) and others simultaneously were developing analytical approaches to bridge and building design and empirical approaches to tunnel design. The dichotomy remains. Empirical or simple analytical methods are used at most in the preliminary design of bridges and buildings, while they are used in all phases of tunnel design and construction. In fact, the past decade has seen a resurgence of interest in empirical methods, and with it discussion and controversy. This discussion has centered on the suitability of various methods. In some applications identical results are obtained with differing methods and in some cases radically different ones. On certain occasions the discussion has focused more on the methodological rather than empirical by taking issue with the appropriateness of particular parameters or the structure of some methods. This paper attempts to establish a basis for judging the suitability of empirical methods in tunnel design, and their applicability to particular cases. The paper makes no claim of exhaustiveness, and instead emphasizes basic requirements for application. Various methods are reviewed against this background. A detailed comparison of empirical methods and a description of their concept and background is now being prepared (4). Specifically the paper first defines empirical methods, and their purpose (Section 2), describes their structure (Section 3), and focuses on the basic requirements each must satisfy (Section 4). Then

Jan 1, 1979

By Hayward B. Oblad, Gary F. Meenan

Two optoelectronic detectors were developed by CONSOL R&D for fine coal processing applications. One sensing device is used to estimate the amount of fine coal in the solids fraction of the froth flotation tailings slurry. The other probe, based on similar technology, is capable of measuring sol ids concentrations as high as 10 weight percent in fine coal slurry streams. These patented optoelectronic sensors are installed in several CONSOL coal preparation plants and are an integral part of the fine-coal control systems.

Jan 1, 1993

By Nader Shahcheraghi, Verya Nasri, Mehdi Bakhshi, Ali Haghighat

An accidental fire load is one of the major loads considered in design of segmental linings in transit tunnel. Typically, a two-dimensional coupled thermo-mechanical finite element analysis (FEA) is conducted. The conventional approach involves using standard fire curves (temperature-time curves) which can lead to a significant overestimation of fire load and tunnel lining thickness in metro tunnels. The focus of this paper is on the cutting-edge approach, using 3D computational fluid dynamics (CFD) analysis of real train fires in metro tunnels and coupled thermo-mechanical finite element analysis (FEA) to accurately and cost-effectively design fiber-reinforced concrete (FRC) segmental tunnel linings for large-scale metro projects.

Jun 23, 2024

By Howard M. Wells

Investment in minerals development usually entails big financial outlays. which will remain at risk for a long time before the venture can begin to generate a return cash flow. Before 'committing himself to such a venture the investor would be wise to carefully examine the possible consequences of his exposure to risk. In this context risk is defined in multiple terms, which relate the magnitude of possible loss with the probability that such loss may occur--normally the probability will decrease as the amount of possible loss increases. The analysis of risk is an essential component of the decision making process, especially so in the case of low grade high tonnage mining ventures where a very real possibility exists that future unfavorable circumstances may lead to losses that could cripple or ruin even the richest corporation. Wells (1979) postulates a rationale for making the investment decision under uncertainty based on the comparison of two independent risk criteria: 1) the risk inherent in the venture represented by the negative portion of the cumulative distribution of the net present value (NPV), as derived by a stochastic evaluation procedure, 2) the limits of risk the decision maker is willing to accept, taking account of the financial capacity-of the 'firm to absorb various levels of future cash shortfall should the venture prove disappointing. The chance the investor would be prepared to accept can be expected to decrease as the amount of the possible shortfall increases. The limits of acceptable risk are-defined by a curve called the "LL-curve" which can be directly compared with the cumu¬lative NPV curve. A positive investment decision is implied if the limits of acceptable risk are not exceeded.

Jan 1, 1982

By D. A. Harman

The U.S. Environmental Protection Agency recently recognized Newmont and other mining companies, along with the Nevada Division of Environmental Protection for their voluntary work in reducing mercury air emissions. One example of this voluntary effort is the installation of a reactive scrubber to capture mercury vapor from the exhaust of a carbon regeneration kiln at Newmont’s Twin Creeks Mine. After considering the available technologies, a proprietary reactive scrubber, developed by ADA Technologies, Inc., was selected and is currently being commissioned. Mercury removal rates greater than 90% have been documented.

Jan 1, 2004

By Yoginder P. Chugh, M. Silverman

Premining investigations involve the determination of roof, floor, and coal seam characteristics to delineate areas of troublesome ground control prior to development of a mine. Data obtained can be useful in mine design, equipment selection, estimation of face productivity, development of ground control plans and assessing ground control costs, and in conducting feasibility studies and financial analyses. This paper discusses 1) the causative factors associated with ground instability, 2) how useful data can be obtained for these factors during premining investigations, and 3) analysis techniques to delineate probable areas of ground instability.

Jan 1, 1982

By P. Zhu

The leaching behavior of copper powders recovered from waste printed circuit boards (WPCBs) was investigated using electrogenerated chlorine and aeration in a sulfuric acid solution with added NaCl and CuSO4. Various parameters were studied to understand the mechanism of the copper leaching. When the current density increased from 0 to 0.1 A/cm2, the temperature from 30 to 60° C, agitation speed from 100 to 400 rpm, and the size ranged from below 75 to 150 µm, the leaching ratios of copper powders increased. The leaching kinetics were analyzed using a shrinking core model: 1-(1-X)1/3 = kt, and the leaching process was chemically controlled with an activation energy of 14.7 kJ/mol due to Cl- ion catalysis. The ratios of [Cu+]/[Cu2+] at various temperatures (30, 40, 50, 60 and 70° C) showed a periodic variation with the increasing of the leaching time. The redox potentials of the leaching solution and copper leaching ratios in different conditions were measured. The result indicates that dissolved oxygen achieved the dissolution of coppers and electrogenerated chlorine can promote the dissolution of copper powders and improve the reaction rate of kinetics in the presence of oxygen.

Maximising margins in competitive markets demands superior productivity. Unfortunately, management systems developed early this century for other industries often drive counterproductive behaviours choking mining productivity. Many executives and managers waste valuable time and effort relying on simply training and communicating to improve managerial practices and attitudes. In covering practical human behaviour, the paper explains why this fails - and explains how to use systems to successfully drive improved managerial practices and attitudes. It highlights use of modern performance Measurement, Analysis and Reporting systems to drive behaviours and improve margins - without capital investment - and make executive and managerial work easier and more effective.

Jan 1, 1999

By P. W. Johnson, H. Fan, S. B. Patton, T. Novak, R. L. Sanford

A computer model is presented that quantitatively uses the relationship between the interactive and dynamic processes of methane drainage, mining, and ventilation. The model includes simulation of the coalbed methane reservoir for prediction of gas-emission rates under the influence of degasification wells and longwall mining, ventilation network-generation and ventilation simulation. As mining progresses step-wise through the coalbed-methane reservoir, the ventilation network is created and subsequently simulated, iteratively determining fan requirements to safely reduce methane concentrations. The model can be used to quantitatively study the effectiveness of methane degasitication on the ventilation system in a longwall panel.

Jan 1, 1995

By D. L. Slyter

Coeur d'Alene Mines Corporation's Thunder Mountain project in Valley County, Idaho, is one of the most remote active mining operations in the US. High altitude, heavy snows, and proximity to wilderness complicate operations in this environmentally sensitive area. Mining is conducted by conventional open pit techniques while processing utilizes on-off heap leaching and Merrill-Crowe zinc precipitation. The project is one of a few similar operations which detoxify the leached ore prior to its removal from the leach pads. Both leaching and neutralizing ( detoxifying) circuits are closed and independent loops. After leaching, alkaline chlorine solutions destroy residual cyanide in the heaps. Calcium hypochlorite solution for the cyanide destruction is prepared by injecting chlorine gas into milk of lime solution.

Jan 1, 1998

By D. Belin

Treatment of dilute acid mine drainage and similarly polluted water is becoming increasingly complicated. The pressure of economics is now exacerbated by legislation which classifies as hazardous waste the precipitates from conventional lime treatment plants. Since acid mine drainage invariably contains sulfate ions, one solution is to use anaerobic Desulfovibrio type bacteria to reduce the sulfate into sulphide ions which could then be used to precipitate out the heavy metals. Results are presented for both batch flask cultures and continuous column tests. Compost was used as the bacterial substrate in the column test which simulated heaps. Conditions changed from aerobic to the required anaerobic deep in the columns. Polluted feeds (up to 700 mg/l zinc) gave effluent containing well below I mg/l zinc over extended periods. Direct transfer of sulphide ions through a stream from an isolated container of bacteria is a good alternative.

Jan 1, 1991

By H. Yoon

Several processes involving injection of sorbent and humidification water downstream of the air preheater in a coal-fired boiler unit, are being developed as low capital cost retrofit S02 control options. Extensive laboratory work, pilot plant programs and larger scale programs have developed performance data and design information. Many of these programs were supported by the U. S. Department of Energy (DOE) as "proofs-of-concept" of three different processes proposed by Dravo, Bechtel and General Electric. Based on these project results, DOE formulated a comprehensive in-duct sorbent injection development program to fully commercialize the technology by 1992. Also, EPRI will conduct a 4 MWe pilot program to develop its HYPAS process. The Consol Coolside process is scheduled for utility demonstration in 1989 on a 104 MWe unit at the Ohio Edison Edgewater Station under partial sponsorship of the DOE Clean Coal Technology Program.

Jan 1, 1989

By J. W. Carson

Introduction Many bulk solids such as coal, limestone, and fine moist ores often flow unpredictably out of bins, hoppers, and boreholes. Vast amounts of time and money are spent-with or without success-on flow promoting devices. In addition, many solids segregate in storage, feed erratically, flood, arch, rathole, and stick to bin walls reducing the live capacity. This article discusses bulk solids flow properties and provides guidelines for designing storage bins, hoppers, and feeders to provide reliable flow. Bulk Solids A bulk solid is a granular material consisting of discrete solid particles-submicron to several inches in size-that is handled in bulk form (for example, in a bin or silo). The gas filling the voids is generally insufficient to fluidize the material and the liquid (usually water) content is assumed to be less than saturation. Types of Flow Problems To design an efficient storage system, an engineer must be aware of problems that can arise during storage and flow of bulk solids: • No flow. A stable arch or pipe (rathole) develops within the solid, stopping flow. • Erratic flow. Momentary arches form within the solid, (ratholes), partly or completely empty out, and then collapse. • Flushing. Powders become fluidized, aerate, and flush uncontrollably through the bin outlet. • Lack of design capacity. A large part of the stored material remains stable around a rathole. Manual prodding, severe vibration, and even explosives may be used to restore flow. • Segregation. Smaller particles tend to sift through the voids between larger particles causing accumulations of fines and coarse in various areas of the bin. • Product degradation. Some materials spoil, cake, or oxidize if they remain in a bin too long. This is usually caused by a first-in-last-out flow sequence. • Level control. Measuring the volume of material left in a bin is difficult if a rathole develops. In one portion of the bin the level control device may indicate the bin is full; in another portion it may indicate it is empty. Eliminating Flow Problems All flow problems can be minimized or prevented by suitable design of the bin/feeder unit. This involves knowing the flow properties of the solid, then choosing the appropriate type of bin and feeder to establish the desired flow pattern. There are three types of flow patterns that may occur in a bin: funnel flow, mass flow, and expanded flow. Funnel flow occurs when some of the material in the bin is stationary while the rest is in motion. Funnel flow bins, shown in Fig. 1, are characterized by: • Low head room. A flat bottom or shallow hopper bin has large storage capacity with minimum height. Unfortunately, all this storage capacity may not be usable ("live"). • First-in-last-out flow sequence. The first material put into a funnel flow bin is the last material withdrawn because the flowing material is concentrated in the region directly above the outlet. • Ratholes. Because of the flow channel that forms, a stable rathole develops if the material has sufficient cohesive strength. • Erratic flow. Once a rathole becomes partially or completely empty, it may collapse creating a stable arch and erratic flow. • Flushing. Collapsing ratholes cause flushing and flooding of fine material. • Segregation. If a bulk solid has a tendency to segregate, this tendency will be accentuated as the material is discharged from a funnel flow bin. Funnel flow bins are suitable for coarse, free flowing, nondegrading solids, when segregation is not important. Mass flow occurs when all the material in a bin is in motion whenever any is withdrawn. Char-

Jan 3, 1983

By K. G. Sutterer, R. J. Sweigard, U. Graham, T. C. Hopkins

The prevalent use of coal combustion byproducts in engineering applications has been with Class C and Class F fly ash as admixtures in structural concrete. But, the use of fly ash and bottom ash byproducts from modern desulfurization processes is receiving increased attention. The University of Kentucky has been conducting research into civil- and mining-engineering applications of these products. The studies have included extensive investigation of the geomechanical behavior of the materials and the effect of mineralogy on this behavior. These studies indicate important mineralogical considerations in the selection of materials for a specific application and highlight the importance of quality control before and during usage on specific projects.

Jan 1, 1998

By J. C. Cawley

Improvements in today's maintenance practices are mandatory as more complex and productive machines evolve in the mining industry. By keeping machine reliability high through improved maintenance procedures, overall mining costs can be reduced. The Bureau of Mines is investigating diagnostic maintenance systems for underground mining machinery. A hydraulic expert diagnostic system and an electric motor predictive diagnostic system have been designed and installed on a Joy 16CM continuous miner. An electrical diagnostic system has been designed and installed on a Joy 14CM continuous miner. Each system is functionally described and the relative merits of expert diagnostic systems versus algorithmic diagnostic systems are discussed.

Jan 1, 1992

By S. G. Malghan

Flotation is the primary method for copper minerals separation from porphyry ores. The need to process difficult-to--float porphyry copper ores presents challenges to engineers and scientists in several areas. This paper is concerned with summarizing generalized problems faced in processing porphyry ores and treatment methods to overcome them. Though some of the problems are interrelated, they are classified into three broad categories. The case studies of some of the successful applications of innovative methods to solve problems related to ore mineralogy, metallurgical aspects of ore treatment, and process variables show that quite often the problems are solvable by a judicious choice of flotation variables.

Jan 1, 1987

By J. W. Choung, J. A. Finch

Acid rock drainage (ARD) is a recognized environmental challenge facing mining industries. An ambient temperature ferrite (ATF) process has been investigated for treating ARD. Most nonferrous metal and calcium ions present in typical ARDs were found to be detrimental to the ATF process. Three approaches were examined, including C02 aeration, addition of complex agents and use of magnetic seeds. By introducing magnetic seeds in the ATF process, the interferences were minimized and all the precipitates formed with lime neutralization were magnetically recovered from a simulated ARD. The residual concentrations of major metal ions in the treated water were environmentally acceptable. The XRD pattern confirmed the spinel ferrite crystal structure of the products

Jan 1, 2000

By M. E. Mellado

In this paper, we present an a posteriori validation of a heap leaching analytical model using sensitivity analysis. The model is suitable to represent the process of heap leaching of solid reactants from porous pellets and is based on a combination of the leaching kinetics at two levels: particle and heap. The validation is simple, and a sensitivity analysis can easily be performed. The simplicity of the analysis provides insight into the control and optimization of the heap leaching process without strong mathematical complexities. The model and the corresponding sensitivity analysis include the effects of heap height, particle sizes, flow rates and several operation-design variables. Using a case study, we discuss the importance of model validation based on sensitivity analysis. We also comment on several choices for optimizing the process. We had three goals in this work: a posteriori validation, highlighting the importance of model validation and providing insight into optimization choices. We can conclude that the model has good internal logic and there are no extra variables; i.e., all of the variables in the model are necessary.

May 1, 2012