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By Carl P. Maronde, William P. Barnett, Patricia A. Rawls

The commercial deployment of advanced fine-coal cleaning technologies depends on cost-effective approaches for efficient separation and ancillary operations in handling, dewatering, drying, and transporting coal fines. As a result of two solicitations under the High-Efficiency Preparation component of the Department of Energy Coal Preparation Program, several projects were initiated for testing and evaluation of emerging technologies and equipment that address operational difficulties associated with coal fines. This paper will update the status of those projects and discuss how the technologies they represent can ameliorate some problems associated with coal fines in today's preparation plants.

Jan 1, 1995

By Vanessa M. Torres

Diagnostic leaching tests provide a good indication of gold deportation in its various occurrence phases. With the results of these tests, possible flowsheets for difficult ore treatment can be established for further evaluation and plant operation can be optimized. The use of this technique can be extended, including heap leach evaluation and complex copper-gold ores. The results on the use of diagnostic leaching tests in gold ores from Companhia Vale do Rio Doce (CVRD) are presented and discussed, as well as the methodology to select steps and interpret results used at CVRD Technology Center (Sutec).

Jan 1, 1998

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 Shinya Ono, Tsuyoshi Katoh, Yuusaku Tominaga

In order to monitor/control airflow rate distribution in a complicated ventilation network installed many regulators, an integrated system composed of expert system, exerting programs for simulation to get macroscopic characteristics and drawing diagram, monitoring system and so on is introduced in this study. This system is made up of airflow velocity sensors and computers linked to an local area network. The main results of this study are as follows; 1) Combinations of two branches to monitor aerodynamic resistance change in a branch p in a network can be selected by comparing factor's value in a branch relation table. 2) When the combination of sensor branches for a branch p does not exist in the network at present condition, the system changes aero- dynamic resistances of appropriate branch q placed a regulator by referring branch relation table. And then the system asks other computer to get macroscopic characteristics under altered value of aerodynamic resistance of the branch q. 3) Dot pattern diagram shows airflow rate relation between an active branch and a passive branch. Three relations such as a) a straight line, b) a monotonous curve and c) extremums are displayed in different patterns for all the sets between an active branch and a passive branch at a time. 4) The ranges of airflow rate in coal faces by changing aerodynamic resistance of any one branch placed a regulator are shown in the Pareto diagram using values in the branch relation table. 5) Ventilation transfer diagram with two parameter, one shows airflow rate in a coal face and the other shows energy provided by main fans to overcome aerodynamic resistance in a net- work, is utilized to decide countermeasures for decreasing energy consumption in the network on increasing of airflow rate in the specified branch.

Jan 1, 1995

By Wen Lan Chen

In the plant where the 800m diameter cyclone was tested, 500 STPH of 50m x 0 raw coal was pulped in a heavy medium tank and pumped originally to four 700mm heavy medium cyclones. For the test one of these units was replaced by an 800mm diameter cyclone with the subsequent feed pressure for both units sets at approximately 15.0 psi. Since this was a feed to zero plant, an appropriate bleed of heavy medium to the dilute medium circuit was established to en- sure that the cleaning of the 500m x 0.5mm raw coal would not be adversely affected by high levels of 0.5mm x 0 fine coal present in the heavy medium. The medium gravity measured varied between 1.41 and 1.43. During a three-hour test on June 10, 1983, the raw coal sample was collected from the feed belt while the clean coal and refuse samples were collected separately at proper locations along the product streams of the two different diameter cyclones. All of these samples were shipped to the laboratory for screen and sink- float analyses. The raw coal screen and ash analyses are shown in Table 1.

Jan 1, 1984

By Rodolfo V. de la Cruz

The broad front concept is based on the principle that gasification can be achieved more efficiently and completely from a plane broad combustion front in contrast to other geometries obtainable with current methods of gasification. By restricting combustion to a plane broad front, the ideal condition for gasification is achieved. A plane broad combustion front can be developed in coal by initiating and propagating combustion from the walls of an oriented channel and collecting product gases from another similarly oriented channel. Flow will then be directed along the highest permeability of the coal bed, the available cross-sectional area for fluid flow is substantially increased and, more importantly, the increased flow will be uniformly distributed throughout the whole mass of coal. The success of the method is greatly dependent on how well an initial and rigorous permeability survey and associated corrective measures yield a well-characterized coal bed. To maintain uniform reaction rates, the advance of the combustion front is located with pressure- or mass flow-transducers. These sensors are then connected to servo-controlled mufflers for controlling segments of the fire front which are advancing ahead of others. Finally, the development of the concept to overcome problems of roof collapse, reactant and product gas leakages, and water invasion are briefly summarized.

Jan 1, 1976

By L. W. Pommier

In the field of minerals processing the concentration of valuable minerals normally takes place in suspensions of ore particles in liquids. The fluid resistance offered by Newtonian liquids to the movement of free settling spheres for the limiting cases of creep flow and turbulent flow is well described by Stokes' and Newton's Laws. However, these equations are not applicable to non-Newtonian fluids, since the relationship between applied shearing stress and resulting rate of shear is a non-linear function, and more than one viscosity parameter is necessary to describe their rheological properties. For this reason, the term "apparent viscosity," which has been commonly used to explain the flow resistance of the non-Newtonian systems including suspensions, may be misleading. A rigorous analysis of the mechanisms of momentum transport of solid-liquid systems is complex indeed. There are many variables that affect the properties of such systems, and precise limitations and assumptions are necessary in order to produce quantitative relationships for predicting their behavior. Very dilute suspensions of spherical particles in Newtonian liquids of identical density as the solids have been examined in the past (12); however, the study of suspensions in which there is a considerable difference in density, between the liquid and the suspended solids has been neglected.

Jan 1, 1968

By Graham A. Brown

Activities in offshore mineral exploration In Australia are increasing almost daily, at such a rate that this report will rapidly become out of date. At the time of writing, February 1967, there were no commercial discoveries of offshore minerals reported in Australia, although there has been definite encouragement in many fields. While this initial encouragement has not revealed any commercial mineral deposits offshore hopes are running high in Australia for success in 1967. Why should mineral deposits be expected offshore in Australia in the first place? The reasons are many. The minerals to be discovered also are many. The reasons are based on the history of alluvial and beach mining activities in Australia's past and at the present time, and on the physical environment of the vast Continental Shelf which surrounds the continent. A brief examination of the two primary features which are necessary before offshore mineral exploration can be contemplated should be, undertaken. Two favourable environments are necessary; firstly a Continental- Shelf to form a physical environment for the accumulation of the mineral deposits, and secondly a favourable political-legal environment to give the exploration companies adequate protection during exploration, and suitable long term arrangements for the exploitation of the deposits after discoveries have been made. Australia is well endowed with both of these.

Jan 1, 1967

By D. M. Wyslouzil

Conditioning, in the conventional sense, means providing sufficient agitation and contact time for the reagents to react with the minerals in the ground ore. High intensity conditioning (HIC) on the other hand, as described in this paper, recognizes the need to exceed this minimum power input over a suitable length of time to induce aggregation of the finest size fraction. Time alone is not sufficient to achieve aggregation. The threshold minimum power input, kW/m3, depends on many surface properties of the fine particles and can vary considerably. In addition, the mechanical aspects and the chemical conditions must be matched to achieve good aggregation. Treatment of complex sulphide ores, requiring fine grinding for liberation, offers a large field for the application of HIC. Improved flotation rates and enhanced selectivity are some of the benefits that can be expected. This unit operation has now reached the level of commercial application. Lakefield Research considered HIC not from a fundamental point of view but as a means of solving difficult mineral processing situations arising in actual operating plants. This paper summarizes the effects of the various chemical reagent combinations that had been applied to promote faster, more selective flotation, higher mineral recoveries and cleaner separations, using HIC.

Jan 1, 1995

By R. Fraher

The control of mine roof is of vital interest in underground coal mining not only for reasons of safety, but also to avoid the high costs of cleanup, resupport and production losses that can result from roof falls. The difficulty in determining roof stability mine-wide is due in large part to the broad variation of geologic and structural conditions that typically exist throughout a mining area. To ensure a stable roof over the entire mine, support systems must be selected to minimize the possibility of failure. The magnitude and cost of the support selected is a trade off against the cost of the number of falls that can still occur after it is installed. Because of the large number of variables involved in analyzing and optimizing roof stability versus support, a digital computer simulation was selected to find a cost effective solution to roof support design. A total cost approach is used which includes the actual cost of the roof support as well as the cost of the roof fall in terms of resupport and loss of production (Fraher 1990a). A Monte Carlo simulation program called ROCSIM (Roof control Optimization Cost SIMulation) has been developed for determining the optimum roof control system and design layout for underground room-and-pillar mining.

Jan 1, 1992

By F. C. Schwerer, C. R. McKee, J. C. Seccombe

Production of methane from coal seams requires hydrofracturing, and the length of a hydraulic fracture determines we11 spacing. Since the volume of fluid injected is known, the fracture length is the volume divided by average width and height. If the fracture is contained in the known height of the seam, then fracture width becomes the major factor con- trolling length. Width is proportional to coal compressibility; bulk compressibility is known to be larger than intrinsic compressibility. A method is given here to measure in-situ compressibility (a) from transient pressure testing. Theory linking flow in porous media with rock mechanical properties is reviewed. A consistent derivation of the porous flow equation is given incorporating 3-D deformation and the effective stress parameter "st' linking changes in effective stress and pore pressure. The relations for "st' in terms of a and intrinsic compressibility (ai) are substituted into the field measured porosity-compressibility product (net) and solved for a, the constrained matrix compressibility. In a field example, using 4 wells with an anisotropic analysis, the ratio of major to minor permeability was 17 for the Pratt A seam. a was found to be 6x10-5/psi as opposed to the laboratory value of 1.4x10-6/psi.

Jan 1, 1986

By F. A. Gates, Bengt Samuelson, James E. Edmunds, S. McCune, Neil Hario, Norman L. Weiss, J. M. Bertram, A. M. Cavaliere, F. M. Jr. Stephens, D. D. Chiang

DESIGN BASIS Size of Project The size of the project generally is expressed in tons of ore milled per day, but company policies differ widely in this respect with a few adhering to this set figure but many expecting the design capacity to be liberal. To some companies that follow the latter practice a 25,000-tpd milling plant that cannot reach 30,000 or 35,000 tpd with¬out major additions is a disappointment. The engineers responsible for planning the operation must know what is intended. Other projects are sized according to the tonnage of product rather than of mine ore; examples are iron ore mills that express size in terms of tons per year of pellets or high-grade concentrates, heavy minerals plants in tons per year of rutile or ilmenite, cement plants in barrels per year, potash in tons per year of muriate, phosphate in tons per year of washer rock and flotation concentrate, and others. However, tons per day milling rate is also the common denominator in most of those instances because the major equipment has to be selected on that criterion. Equally important are operating schedules, particularly the number of operating days per week and shifts per day for ore delivery, crushing, grinding, and processing. Hours per shift also are an impor¬tant factor in design, particularly in the case of ore delivery, and the lost time expected for maintenance, cleanup, inspection, preventive maintenance shutdowns, and many others, has to be taken into ac¬count. Frequently, the ore deposit will vary in hardness and grade to such a degree that the capacity of the mill will vary widely from year to year and cannot be expressed as a fixed figure, but rather as an average over a calculable period, such as ten years, or as a specific daily capacity over the first two years, next four years, etc., or some similar projection. A good example of this kind of situation is Asarco's Mission operation 15 miles southwest of Tucson, Ariz., described by Weiss and Vincent,1 where the major rock types differed widely in hardness, so that a change in the proportion of these types in the mill feed could have imposed difficult design problems if a constant tonnage rate had been expected. Expected Life The life of a mining operation depends upon the size of the deposit and the rate of mining. The latter is a policy decision based on an economic analysis2 which, in turn, is based on many factors. From the point of view of mill planning, the estimated life of the operation determines many criteria and affects many decisions on strength of structures and degree of protection of men and materials, the quality of the materials-handling and process machinery, the type of delivery systems for ore to the mill and concentrates to the smelter or market, environmental considerations, and many others. Costly installations that may be excellent investments for a 20-year project may be waste¬ful for a 5-year operation. An example is the comparison of different methods of crushing or grinding. Take single- vs. multiple-stage grind¬ing-the former may be found more economical for a 5-year operation, and the other, more costly method more economical for a 15- to 20-year life. Mining and Ore Transportation The mining method and the means of transportation of the ore to the first crushing stage have far-reaching effects upon mill design, particularly the crushing sections, and upon site selection (see Chapter 2, Situation of Mill). Consequently, mill design cannot advance until the mine planning has reached at least tentative decisions concerning these important matters, or reach the final stages until much is known about the ore that may be expected month by month and year by year for a reasonable period. Methods of ore transportation used in over 90 underground and open-pit mines are listed briefly in Section 32 (Table 1), and more detail is found later in this section and in Section 10, Storage and Transport. These methods include surface railroad, trucks, conveyors, surface skips, underground skips, and tramming from hoist or tunnel. In surface mining, transportation of the uncrushed ore by rail or truck to the primary crushing plant-conveniently located for lowest overall cost-is most common. Rail transportation provides low perton-mile costs. Truck transportation, though in some cases less eco¬nomical, is more flexible and more adaptable to mountainous terrain; furthermore, recent improvements have reduced the operating costs to keep trucks competitive on low-grade ores. The design of the primary crushing plant will be essentially the same whether delivery is by truck or rail, but the location of the plant is subject to more rigid restrictions in the latter case because of grade limitations, and these in turn may adversely affect the selec¬tion of the mill site as well. The influence of truck haulage in reducing the stripping ratio in open-pit mines is an added reason for predicting a minor role for rail transportation in the future. The use of conveyors to transport ore from the pit to the milling plant involves (in most cases) crushing the ore to a reasonable size (10 to 20 in. maximum with today's crushers) before conveying. The Twin Buttes system3 which went into operation in late 1969, utilizes primary crushers (two) and conveyors to receive rock waste, ore, and low-grade stockpile material from trucks, then transport them to the appropriate destination. Flexibility is dependent upon the porta¬bility of the primary crushers. In the face of this development, inclined skip hoists are no longer important to the mill designers. Underground mines generally pose fewer problems of design; these will be discussed in Chapter 2. Character of Deposit The degree of homogeneity of the ore in various parts of the mine is an important factor. The characteristics that concern the millman (approximately in order of importance) are: hardness, assay, metallurgical response, size distribution,4 and moisture content. Under metallurgical response may be included degree of oxidation, mineral¬ogy, clay content, and reagent consumption, as well as process re¬sponse in general. Short-term variations-hour-to-hour, day-to-day, or even week-to-week-make operation of the plant more difficult, require greater flexibility of process design and, perhaps, also require more instrumentation and manpower. Uniformity of the ore in the characteristics noted previously and

Jan 1, 1985

By Om P. Garg

The purpose of this paper is: 1) To summarize the capabilities and some of the limitations of the existing mine planning software. 2) To provide some guidelines for acquiring the software. 3) To identify problems and challenges in terms of how to justify increased use of computers (particularly the 32-bit microprocessor based super micro computers), for various activities related to a mining operation No attempt has been made to review the contents of available software packages in detail. Also the scope of this paper is limited to mine planning related computer applications. Applications related to accounting, inventory control, preventive maintenance, equipment scheduling, etc. have not been covered.

Jan 1, 1983

By Peter Amelunxen, Craig Lockhart

Significant effort was made in 2003 and 2004 to upgrade the existing instrumentation and process control infrastructure at the Phelps Dodge Bagdad copper concentrator. Specifically, • cameras were installed on the feed belt for online image analysis data, • ultrasonic level sensors were installed for froth height and sump level control, • a trial froth image system was installed on one of the rougher rows, and • a new expert system to tie everything together was integrated and tuned in-house. Control philosophy, observations, opinions, and general tips and tricks are discussed with the hope of assisting other plant personnel and expert system integrators.

Jan 1, 2005

By M. G. Ayat

In the previous work (1,2), initial developments in a novel tracing technique employing specifically prepared trace particiles were fully described. The synthetic tracers produced proved to represent coal particles in specific gravity based coal washing equipment in this work, a detection system has been developed that can detect the artificial tracers in the product or refuse part of the density-separating coal cleaning units and thus indicate the performance characteristics of the circuit. This system could not only be a simple, accurate, and inexpensive replacement for the usual time-consuming washability analysis, but it could also be used for diagnostic purposes in coal separatory devices.

Jan 1, 1987

By Norman F. Sweeney, H. John Hovland

Over one million yards of granite were excavated for the Helms Pumped Storage Project, including a large underground powerhouse complex. Site investigations and in situ stress measurements were essential elements of the project design and provided the necessary geologic parameters for executing a finite element study of the powerhouse. A construction monitoring program, of geologic mapping, field instrumentation, and rock mechanics testing was then designed and has been successfully implemented. This paper reports on the scope of this construction monitoring program and explicitly compares the measured deformations to those predicted. As a result of this recent field experience the assumptions used in the finite element program are reexamined.

Jan 1, 1981

By Dean J. Soderstrom

Soil and sands were contaminated with depleted uranium from weapons testing. This resulted in the formation of a complex mixture of uranium compounds. Characterization studies of the soil indicated the uranium was present as uranium metal, uranium oxides, silicon-bearing metallic uranium, and uranium silicates. A process was developed to selectively remove dense uranium compounds using gravity separation and a chemical extraction system to remove uranium which was not available for separation by gravity methods. Results from characterization studies and pilot scale testing are presented for background information. The primary purpose of this presentation is the report of the results achieved in the field application of the processes.

Jan 1, 1995

By A. Marabini, J. Cases, M. Barbaro

Outlined is a review of the application of new selective chelating reagents as flotation collectors; calculation methods for the selection of chelating structures, limitation of the function of commercial chelating agents as collectors, and the synthesis of two new classes of chelating collectors with mixed aliphatic-aromatic structure for oxidized lead-zinc ores. Given are: examples of substituted mercaptobenzothiazole and aminothiophenol structures, flotation and adsorption study of an alcoxyl-mercaptobenzothiazole on cerussite, comparison of adsorption of conventional and chelating collectors, study of the influence of the aliphatic structure1 component on the collecting power of chelating type reagent and the design of chelating collectors with optimal structure.

Jan 1, 1989

By Ernest Peters, Fiona M. Doyle

The leaching and bulk decomposition of sulfide minerals is of enormous commercial importance in several areas of the minerals industry. These include: direct leaching of ores or concentrates for the recovery of the contained metal values; decomposition of sulfides to recover associated values such as encapsulated gold; and the potentially hazardous oxidation of sulfides in waste disposal facilities. A significant challenge to successful future developments in these areas is to improve our fundamental understanding of the mechanisms of the chemical, electrochemical, and bacterially-mediated interactions between sulfides and aqueous solutions. The paper summarizes current understanding of these mechanisms, and discusses promising new directions for research.

Jan 1, 1989

By M. Menegaki

Restoration of abandoned mine sites is still one of the weak points of mining practice. The latter stands especially for the case of the surface coal and lignite exploitations, where the extended size of the disturbed land and the drastic changes to the geomorphologic features do not facilitate the implementation of a cost effective and environmentally sound reclamation plan. The paper examines the parameters involved towards the legal requirements for the reclamation of the first lignite exploitation in Greece, namely the ?Plakes? mine, located at Euboea, due to the particularities of the site. Then an integrated redesign procedure is presented, aiming at minimizing aesthetic degradation, confronting technical difficulties and preparing the site to accept new uses.

Jan 1, 2005