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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 Gordon R. Wicker, Peter V. Avotins, Steven S. Ahlschlager

Laterite ore slurries exhibit Bingham plastic behavior and can be characterized by the magnitude of their yield point and Bingham viscosity. These two parameters are affected by ore composition, solids concentration, and temperature and are used to predict the pressure drop in pipelines and heat transfer coefficients in shell-and-tube heat exchangers. In cycloning of laterite slurries, the calculated cut size is corrected by factors obtained from the rheological parameters.

Jan 1, 1979

By Ross W. Smith, Xiapeng Zheng, Peggy J. Arps

The adhesion (and de-adhesion) of Bacillus subtilis to dolomite was determined under a number of conditions of initial concentration of the organism, agitation, mineral particle size and temperature. Rate equations curves for both adhesion and de-adhesion were constructed, with the rates of de-adhesion being about half that of adhesion. From the temperature data the energy of adhesion was determined to be about 1.02 kcal/mol. Adhesion of dolomite to B. subtilis follows a Langmuir isotherm. Equilibrium constants, adhesion capacity and Gibbs free energy of adhesion of B. subtilis to dolomite (at pH 6.6) were determined. These values were compared to similar data for adhesion of B. subtilis to apatite and dolomite.

Jan 1, 2002

By Kotaro Ohga, Kiyoshi Higuchi, Zhang Xun Tao

In Japanese coal mines, drivage works of in-seam gate roads are mainly carried out by blasting methods. Changes of methane concentration in gate roads are recorded by centralized monitoring systems in general. To obtain useful information from the recorded data, authors analyzed changes of methane concentration for 3 hours after blastings. As a result, the changes of methane concentration with time can be divided into five distinct patterns. It is thought that appearance of the each pattern depends upon the geological conditions of the surrounding of the headings. Therefore, we attempted to confirm such observations by simulations using mathematical models.

Jan 1, 1989

By Wolfgang Sand, Alex Schippers, Tilman Gehrke, Thore Rohwerder, Peter-Georg Jozsa

Metal sulfides are degraded via thiosulfate (pyrite) or via polysulfides and sulfur (sphalerite, galena, chalcopyrite) by leaching bacteria The attack on the crystal lattice is either effected by only iron(III) ions or by iron(III) ions and protons, respectively. Consequently, different endproducts are formed. For a control of ARD-processes, these reactions need to be hown to regulate them. Experiments in percolators up to 65 m3 with inorganic compounds like fluoride, concrete, or SDS resulted in differently lasting inhibition. Microcalorimetric measurements of microbial leach activity allow monitoring of these effects with respect to active bacterial cells, and, in addition, the amount or rate of dissolved metal sulfide allowing prediction of possible endangerment by ARD.

Jan 1, 2000

By Thomas H. Koenning, William E. Bruce

Determination of the state of a mine fire is an important function during firefighting and during rescue and recovery operations. It is imperative that an accurate, up-to-date assessment of fire conditions be available for persons directing such activities in order to avoid unacceptable risk to mine rescue teas and/or fire fighters. Many indicators which consist of ratios of the concentrations of fire gases have been developed over the years for determining the state of a mine fire. Results from numerous gas sample analyses are necessary for determining the trend of the fire. Some indicators are preferred because the influence of sample dilution, a frequent problem, is said to be eliminated. Definitions and examples of indicator6 found to be useful in diagnosing recent western U. S. coal mine fires are presented. Mine gas explosibility is an important subject also requiring rapid assessment. Example explosibility calculations are presented applying one widely used method. Establishing limits for withdrawal of personnel are discussed.

Jan 1, 1987

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

The major cost in comminution is energy consumption, which can be as high as 50% of the operating cost. Improvements in plant operations have resulted in up to a 15% reduction in energy usage (kw-hr/t). These improvements have been made through the optimization of grinding efficiency and the use of expert model-based control systems. Optimization involves the determination of the levels of the critical-operating conditions that result in the most efficient breakage of ore in the mill. These optimal levels are identified through plant/laboratory test work and through computer simulation using advanced process models. Model-based expert control achieves the maximum performance from the grinding circuit by identifying the characteristics of the ore in the mill with an optimal on-line estimator. Using this information, the control system dynamically determines the operating point that will yield the optimal performance. Two industrial applications of grinding-circuit optimization and model-based control are presented to demonstrate the power of this new technology.

Jan 1, 1997

By Donald L. Bott

A computer model called the Quality Compliance Model was developed to optimize the mine planning and sequencing in area coal mining with respect to the limit on pounds of sulfur dioxide per million BTU imposed by regulations. The objective of the model is to maximize the amount of high sulfur coal mined from various benches while meeting the specified compl'ance standards. Given multiple seams and multiple benching operations, the mining sequence from each pit is simulated. The rate of mining is controlled such that the in-pit blending will maximize the usage of high sulfur coal and meet compliance standards. The compliant coal can be stockpiled for usage at a later date, or it can be disassociated. This calculation can be based on any given rate of production, i.e., from as small a unit as a unit train to as large as monthly or yearly production.

Jan 1, 1982

By P. Tsakiris

The increasing social interest for the environmental issues, forces the authorities to enact more rigorous regulations. The mining industry is one of the sectors that concentrate vigorous remonstrance. It is an absolutely justified reaction, as a result of the numerous contaminated and polluted sites that have been inherited by previous operations and they remain unremedied. The lack of a consolidated global legislation, transfers the burden of decisions to the national level. This paper consists of two parts. At the first part, it discusses the critical role of the state to form an effective environmental policy, feasible for the context of the national economy. Afterwards it analyses two of the main points, which must be considered by the regulator for the excavation activity, the abandoned sites and the duration of the mining investment. The aims are to defuse, in the short-term, the public pressure, protecting the economic growth and, at the same time, to form a basic structure for the development of the corporate social responsibility. The second part presents an alternative financial instrument for the Greek regulatory framework, conformed to the characteristics of the Greek Economy, and analyses the expected benefits both for the business and the social welfare.

Jan 1, 2002

By Andrew H. Stearn, Robert O. Agbede, Edward F. Divers

The ability to compete profitably in a competitive, demanding and specialized market, requires all components of productivity to be optimized toward the same manufacturing goal. This ever present requisite is seldom more apparent than with the quality control (PC) considerations that confront the super-refined metallurgical production necessary for today's exacting technical applications. In a work-place that already exceeds all environmental standards for cleanliness, this paper describes the development of specific environmental mechanisms and controls implemented at a titanium processing facility to impact both the minimal air-borne particulate contaminants and excessive process heat generation which are believed to degrade product purity. Based on the analysis of a carefully structured and instrumented field survey, two alternative solutions were proposed to modify the present facility utilizing a forced air (blowing) system. The first scenario requires ambient air to be drawn from a louvered rooftop installation and ducted to specific zones within the plant with appropriate weighted louvers and wall and roof exhausters designed into the system for air control. The second scenario incorporates a properly sized baghouse to be used in conjunction with the first system.

Jan 1, 1991

By David R. Zuchelli, Elio L. . Checca

Two case studies of methane gas explosions and their effect on the operation of underground coal mines are presented. The studies detail the recovery operations and investigations at each mine site. These include the circumstances prior to the explosions and the effects on the surface and underground ventilation control systems. Various ignition sources such as surface and underground electrical power systems, degasification sites, ventilation shafts, test well casings, and lightning activity were investigated. In each case, a lightning report from the National Lightning Detection Network1 was used in conjunction with the physical evidence and eyewitness accounts to confirm lightning strikes as the ignition source for the explosions.

Jan 1, 1995

By Donald Lau, Adrian Crawford

In the field of grouting, practitioners fre¬quently advocate procedures that are often unique and contradictory. As a result there has been considerable debate as to what constitutes optimum grouting practice. A knowledge of both the rheological properties and the flow characteristics of grouts is essential to the development of a rational understanding of the grouting process. Flow models and viscosity experiments have been conducted using cement grouts comprising High Early Strength Portland and Microfine cements. The addition of superplasticizers was found to enhance the flowability of the grouts as well as to reduce the effective groutability ratio. Steady state flow equations and design charts for predicting the radial penetration of cement grouts have been developed.

Jan 1, 1986

By Jonathon M. Hanson, John F. Schatz

A combined theoretical and laboratory test program is described with the purpose of providing a useful model of the multiple radial fracturing process. A non-quantitative conceptual model is developed as the basis for detailed mathematical modeling and test planning. The model includes borehole pressurization, flaw rupture, and gas- driven fracture propagation phases. The laboratory tests are carried out in blocks of scaled rock simulant loaded to a true three-dimension stress state and with miniature propellant/explosive charges in a wellbore as the fracturing energy source. The conceptual model, fracture initiation modeling, and laboratory test setup have been completed and are described. The remaining work is ongoing

Jan 1, 1986

By K. Biswas

A finite-element algorithm was developed for an axisymmetric heat-transfer problem involving phase change. The finite-element treatment of the phase-change problem was dealt with by using the enthalpy method. The finite-element algorithm was subsequently applied to model the heat exchange between mine ventilation air and frozen ground in the presence of roof bolts in an underground mine with permafrost. This paper analyzes a single bolt in the problem domain with the convection boundaries at the roof level of the mine airway. A short-term study, comprising the evaluation of roof bolting (friction-anchored type), was conducted, and recommendations were made regarding the applicability of roof bolts as a support system for a given thermal condition.

Jan 1, 1996

By K. R. Price, M. Gauna

Jim Walter Resources No. 4 mine produces coal through retreat longwall mining at 610 to 670 m (2000 to 2200 ft) of depth. A three entry, total yield pillar, longwall development experimental region was established for three adjacent longwall panels utilizing 6.1 m (20 ft) wide gate section pillars. Presently, the first longwall panel is completed with roadway deformational behavior monitored for a ground control assessment of the mining system. Data illustrate that the total yield pillar gate section design at No. 4 mine is presently comparable to gate section designs having large equal size chain pillars. Ground conditions will continue to be monitored during the mining of subsequent longwall panels in order to determine the ground control implications from multiple panel extraction.

Jan 1, 1986

By Julian S. Edwards, C. Frederick C. Pearson, Sevket Durucan

Information gained at the site investigation stage of the Carsington aqueduct project led the designers to suspect that methane might be encountered during tunnelling and therefore gas detection techniques, including emergency shutdown systems, were introduced. After construction, on completion of the excavation and lining of the tunnels, a survey showed that methane was entering the aqueduct dissolved in infiltrating groundwater. General body air concentrations were very low but on closure methane concentrations rose rapidly within the aqueduct. A research project has now been initiated to investigate the mechanism of methane generation and entry rate into the system, the results of which are being taken into account in the preparation of future operating procedures.

Jan 1, 1989

By D. Tao

The presence of insoluble slimes in potash ore poses a serious processing problem to the potash industry. These insolubles must be removed prior to potash flotation because of their high adsorptive capacity for amines which are generally used as collectors in the subsequent sylvite flotation. This is usually accomplished by scrubbing of the ore in brine followed by hydrocyclone classification to separate slimes from the salt particles. Insoluble slimes that remain in the ore after the desliming procedure are depressed by reagents such as guar gum or starch during sylvite flotation. In this research, the feasibility of using GP clay binders to replace guar gum for potash flotation was investigated. Batch mechanical flotation tests were conducted with the potash samples provided by a leading potash company. It has been found that GP clay binders increased potash concentrate yield and recovery at the same product grade. Effects on potash flotation efficiency of flotation process parameters such as impeller rotation speed, slurry temperature, binder type, dosage and conditioning time have been investigated to establish the optimum conditions for flotation. Binder GP374G33 has been identified as the optimum substitute for guar gum as slime depressant in potash flotation.

Jan 1, 2008

By Jorgen Elbrond

The economic environment of mining is particular and requires special methods for seeking the economic optimization of mining and guiding the construction of logical production planning systems. An interactive program system which generates sequences of mining rates and cutoff grades, using as it's core an open-ended dynamic programming algorithm, is described. The program system is built not with the aim of obtaining a single mathematical optimum, but on the concept of satisfying the mine planner by producing several alternative mine plans and testing various schedules under conditions of uncertainty.

Jan 1, 1982

By Shouci Lu, Sun. Keji

Most phosphate ores in China are characterized by fine dissemination of the intergrown minerals and high content of carbonates. Therefore, in order to recover phosphorus minerals by flotation, some technological problems must be solved, such as fine particle flotation and separation of phosphate from carbonates. For effective flotation of finely ground phosphate ores and selective separation of phosphorus minerals from carbonates, S-series and L339 modifiers have been developed. A series of combined collectors with improved collector ability and selectivity have been developed and applied in several flotation plants in China. In this paper, CCLS, a combined collector for phosphates and PA-31 and a collector for reverse flotation of carbonates, are described. It has been found that some surfactants added with fatty acids function well in flotation at lower temperature, hence heating pulp in winter may be excluded. It is important for energy savings. The synergy mechanism of these additives in fatty acid flotation is discussed in this paper.

Jan 1, 1999

By John F. Schat, T. William Thompson

Laboratory data on the time-dependent compaction of porous rocks are presented, and various attempts to model this behavior are described. These lead to a discussion of the problems that arise in using laboratory data to estimate long-term effects. A method is suggested for combining laboratory data with information from the geologic record to estimate long term effects.

Jan 1, 1986