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By P. Bevilacqua, G. Ferrara, M. C. Williams, T. P. Meloy

Tabling is an old environmentally friendly separation unit operation. This paper models shaking tables and explores the action and design of riffles on shaking tables. By reassessing riffle shape and riffle patterns, significant improvements in tabling performance appear feasible. While table sales appear at their nadir, a high-tech environmentally friendly table may have a significant market in the coming decade. Riffles on a shaking table impact particle separation. Particles are affected by riffles and their exit position on the table is dramatically changed, Riffle shape determines how much the riffle will influence a given material. Moreover, riffle patterns influence the concentration of a given material and its exit points on a table. This effect of riffle placement and design is modeled in a spreadsheet. Major performance and separation improvements may he expected by improved table design. Two physical laws of tabling have been derived. These laws aid in the design of sophisticated high-tech tables.

Jan 1, 1995

By R. Herrera-Urbina, D. W. Fuerstenau

A large number and a wide variety of chemical reagents are used in flotation processes for wettability and Eh control, particle agglomeration/dispersion and bubble stability. A historical account of the use of flotation reagents through the years since flotation was introduced as a viable and economic process for the concentration of sulfide minerals is given and a review of old and modern postulates of their interaction with minerals is presented. Although the results of surface and colloid chemistry studies with well characterized mineral/flotation reagent systems have advanced our understanding of the role played by these chemicals in the flotation process, many questions remain unanswered. Moreover, new flotation reagents are needed to solve the challenge posed by the treatment of problematic-type ores and fuel deposits that have increasingly become the source of our raw and energy materials. Because of the depletion of high-grade and relatively easy-to-process ores, flotation scientists and engineers are confronted with finding more specific and selective flotation chemicals to effectively and economically concentrate minerals. The development of new flotation reagents is vital for cleaning fine coal and processing polysulfide, polymetallic ores, and mixed oxide/sulfide ores.

Jan 1, 1989

By Barry A. Hillman

Respirable (PM-10) crystalline silica is regulated by the State of California as a carcinogen. The risk-management of this material by the State exemplifies the inherent problems in the development of regulations based on current risk-assessment practices. The influence of extremely conservative risk-assessment and risk-management can be expressed in economic impacts including the increased cost of production, reduced competition, increased prices, reduced employment and redistribution of income. This paper attempts to contrast theoretical risk- assessment and risk-management with current application using crystalline silica as an example. Based on health information pertaining to silica, the paper examines federal and State of California regulatory and public policy positions. Using current risk factors and empirical data for the Central Valley of California, the projected incidence of lung cancer in humans is examined. While such an analysis would project an extremely high incidence of lung cancer as well as silicosis, not a single case of either lung impairment has been recorded within the study area or throughout the world in the general population. This suggests that sound guidelines for the analysis of scientific information have given way to the assumption that virtually any information representing a substance as a carcinogen is to be considered valid with little or no qualification.

Jan 1, 1992

By C. P. Mangelsdorf, Richard A. Allwes

At the request of the U.S. Department of Labor, Mine Safety and Health Administration (MSHA), the U.S. Bureau of Mines evaluated the suitability of using tri-sets for protecting mine personnel in roof-fall prone areas. A steel-set arch provided by MSHA served as a basis for evaluating the performance of the tri- set. All tests and analyses were conducted according to the arch canopy test and design procedures developed by the Bureau. Theoretical resistance functions were established for the steel-set arch and tri-set and were representative of their experimental behavior. The resistance functions were used to determine the energy absorption capacity of the structures and to predict their dynamic response to impact loading. The dynamic tests demonstrated that the arch canopy design procedure is appropriate for tri -sets and yields conservative designs for both steel-set arches and tri-sets. As a result of this work, it is recommended that tri-sets may be considered for protection against roof falls, provided that the arch canopy design procedure is utilized for each application and that the principles underlying the design procedure are understood.

Jan 1, 1992

By Frederick W. Bauer

The potential worldwide "market" for metallurgical bauxite is about 94 million MT. The high degree of concentration of the alumina sector, combined with the high percentage of long-term contractual relationships, results in a small spot market with an illdefined price structure. Further segmentation occurs based on bauxite quality and alumina plant design. The potential 'free" market is estimated to be about 18 million MT that represent the requirements of nonintegrated alumina producers. It, too, is covered almost entirely by multi-year supply contracts.

Jan 1, 1984

By Fathi Habashi

THE UNIT process of adsorption involves two steps: 1) Loading of the adsorbent. 2) Recovery of metal values from the adsorbent. Charcoal is the adsorbent commonly used in extractive metallurgy. The discovery of the adsorptive power of charcoal from solutions is generally accredited to Lowitz (1785), who observed that several dissolved organic substances were precipitated on charcoal. Graham was the first to demonstrate that inorganic substances were also adsorbed on charcoal. In 1830, he reported that iodine dissolved in KI solution was adsorbed on charcoal. Also calcium ions were adsorbed from limewater, as were lead ions from lead nitrate solution. The use of charcoal in metallurgy was first applied

Jan 1, 1970

By K. V. Viswanathan, P. Sornasundaran, S. E. El-Mofty

Dolomite is found to undergo preferential dissolution in aqueous solutions and this is found to be strongly dependent on the solid to liquid ratio (SIL). Electrokinetic studies done under the sump conditions revealed that the mineral surface charge is also affected markedly by the solid content in the suspension. Conditioning of the dolomite at low SIL ratios for short time intervals showed preferential dissolution of calcium leading to a magnesium-enriched dolomite surface. At higher SIL ratios and longer conditioning times, calcium depletion from the solution and a calcium-enriched dolomite surface resulted. The results are discussed in terms of surface precipitation and/or bulk precipitation and surface conversion of dolomite to the calcium-enriched phase (calcium carbonate and/or magnesian calcites).

Jan 1, 1990

By James G. Tilton

Throughout the world, sedimentary basins are exploited for many different minerals. Frequently, the extractive methods conflict with one another. A case in point is the proximity of oil and gas operations and the mining of coal. Generally, the interference between the two industries lies in the fact that the reserves over- lie or underlie one another. Mining of coal generally is developed on a rectangular pattern in a horizontal mode while oil and gas drilling is developed on a radial pattern in a vertical mode. Coal mining has exhausted vast acreages in various basins with many of those basins being drilled for oil and gas. Those existing wells create problems by requiring the unrecoverable coal pillars to support the well bore, or to make special provisions in order to mine through an existing well. The system works ... more or less; but there are little or no provisions made for additional drilling unless the vast majority of those new wells are drilled through mined-out sections (gob) of those mines. Many states have rules and regulations governing the drilling of oil and gas wells through gob; but, some companies and some regulatory agencies or personnel have deemed such drilling as a hazard to the mining operations. This paper explores the history, technical standards, and safety aspects of drilling oil and gas wells though the gob of worked-out and active mines. It is the opinion of the author that such drilling can be conducted safely while eliminating the re- quired changes in mine projections and the loss of recoverable coal in the form of well pillars.

Jan 1, 1997

By E. Kenneth Siroky

The concept of ultrasonic measurement was originally applied to marine operations. Sonar . . . standing for Sounding, Navigation and Ranging, was developed for military uses. Today Sonar has become very important to the fishing fleets and marine construction industries where its applications cover a wide range of uses our company, in addition to the inair ultrasonic equipment as discussed in this paper, is also deeply involved in marine sonar and works primarily with oceanographic research and fishing industries. Ultrasonics, by simple definition, are sound waves beyond the audible range of the human ear and are generally accepted to be waves over 20,000 cycles per second. When applied to level measurement, the principles of ultrasonics are basically quite simple. A sound pulse is initiated at a point in time and the time interval for the echo from that pulse to return can be interpolated into distance. The speed of sound in air under standard conditions is approximately 1,100 feet per second, or if converted into more meaningful information as related to distance measurement, the time required for sound to travel one foot round trip is 1.78 milliseconds. An early application for ultrasonic level monitoring equipment was in large grain elevators. Prior to ultrasonics, the common practice of inventory measurement was to have an employee walk around the top of these large grain elevators, which are often over 100 feet above ground level, and drop a weighted rope or chain down into the silo to determine the level of the grain. Needless to say, this was a slow process and could be extremely unsafe, especially during windy and snowy weather conditions. An alternate

Jan 1, 1971

By H. Zhu

Qualitative and interpretative information as obtained from geological and/or geophysical studies, in addition to precise measurement, is incorporated into the estimation process through an indicator variable. The indicator conditioned estimator is formulated as a cokriging and its expression is data value dependent as opposed to that of the traditional kriging estimators. The solution of the dual cokriging system pro-vides simultaneously an estimate of the unknown and an estimate of the conditional probability that the unknown belongs to a specific population or class. Being an unbiased and minimum-error-variance estimator by construction, the indicator conditioned estimator is better in the least square sense than the ordinary kriging estimator because it uses additional information carried by the indicator data.

Jan 1, 1989

By Glenn H. Damon

Concern about environmental pollution goes back many centuries, but until recently most efforts to control it have been perfunctory and spasmodic, aimed largely at coal smoke and other visible pollutants. Air pollution is to a large degree a byproduct of our economic development, and scientific knowledge of the causes and character of such pollution is more extensive than the technology to handle the waste byproducts of our industrial civilization. The removal of all constituents foreign to the air from the effluents produced by an industrialized society is obviously impractical at this time. There is widespread difference of opinion regarding acceptable ambient air concentration levels for the Various pollutants produced by combustion processes, but there is basic agreement that the pollution of the atmosphere must be controlled and eventually reduced. The magnitude of the air pollution problem has been increasing rapidly because our expanding economy calls for an ever-increasing consumption of energy, and fossil fuels are a principal source of energy. For example, the consumption of electricity has been increasing at an average annual rate of approximately 8 percent over the last 10 or 1.5 years. Table 1 shows the estimated emission of the principal pollutants into the atmosphere in 1966. The approximately 90 million automobiles, trucks, and buses on American highways contribute the largest proportion of pollutants to the atmosphere, but that fact does not alter the growing problems of the coal industry. You will note that sulfur oxides, particulates, and nitrogen oxides are all products of the combustion of coal. Of these air contaminants, sulfur oxides are now receiving major emphasis in terms of research to develop effective means for control, Table 2 shows that the combustion of coal produces approximately 60 percent of the sulfur oxides discharged to the atmosphere. While the utilization of coal is the principal source of particulate matter, this is not considered as serious a problem as it was in the early part of the century because of technological developments that have produced sound methods for the removal of particulates from waste gas streams.

Jan 1, 1968

By K. T. Valsaraj, L. J. Thibodeaux

Solvent sublation, the separation process for the removal of two hydrophobic compounds (penta- and trichlorophenols) from the aqueous phase, is discussed, as is a steady-state mathematical model for fire process. Solvent Sublation "'as conducted in a continuous countercurrent mode. The underlying mechanisms, theory and experimental details on the effects of process variables on removal efficiency are reported.

Jan 1, 1994

By Eric K. Albert

Computer oriented simulation techniques can be effective in the design and analysis of complex mining systems. In fact, a number of computer software products are available for mine systems simulation. However, previous models have tended toward being either data-intensive and deterministic, or data-limited and highly stochastic. The need for a fully integrated package with a simplified user interface has never been more apparent. In this paper, the design of a surface mining simulation model documented in Albert (1986) is described. The basic features of the surface mining system and their counterparts in the simulation model are discussed. The methods and algorithms used to implement these subsystems are presented. Considerations of information management and software design are illustrated, especially as they apply to the application of the package by a mining engineer. An example is provided to demonstrate the concepts embodied in the model and to show how a surface mine is simulated from mine parameters.

Jan 1, 1989

By Jerry Grott

Southwest Salt Company is solution mining the Luke Salt Body of probable late Miocene age. The discovery hole, from which the first core was recovered, was drilled in 1968. The deposit was encountered at a depth of 880 feet, and the bit was still in salt at the bottom-hole depth of 4,500 feet. The solar ponds, developed on land formerly dedicated to agriculture, have an annual capacity of about 90,000 tons. Because land values are very high, mining rates and procedures are governed by the need for near-saturated brine to minimize land requirements. Because of the frequency of dust storms, the salt operation uses a unique wet-harvesting method. Most inventory is kept in the ponds under brine and harvested only a few days before shipment. Studies of the nature of crystal growth and the distribution of windblown and brine impurities led to the development of procedures for processing salt of high chemical purity and low insolubles content. Chemical purity exceeds that of most salt produced in fuel-fired evaporators. Salt is shipped from Phoenix as tar east as west Texas and as far west as central California. Occasional shipments have been made to Hawaii and Alaska.

Jan 1, 1987

By Chris J. Conway, Bruce W. Atkinson, Graeme J. Jameson

The flotation of coal in the fie and coarse particle size ranges presents particular problems. Fine or ultra-fine coal less than 100 microns presents a challenge to conventional flotation machines because the rate of capture of the coal particles can be very low, so longer residence times are needed. Also, conventional mechanical cells are not normally designed with froth properties in mind. Froth drainage may be inadequate, leading to excessive entrainment of ash. The upper limit of flotation of coal is normally put at about 500 um (30 mesh). It appears that, in mechanical cells, coarser particles tend to be torn away from bubbles in the turbulent environment created by the impeller. In this paper, results are presented from plant trials of a high-intensity flotation column of novel design, namely the Jameson cell. Extensive trials have been conducted on coal slurries with a top size of around 1 mm. Size-by size analysis shows that it is possible to achieve high yields of low ash product over the whole particle size range.

Jan 1, 1995

By J. P. Golightly

The structure and occurrence of nickeliferous laterite profiles are described and explained in terms of mineral solubility and drainage conditions. Complete profiles, from top to bottom, include: limonite zone; nontronite or silica zone; and saprolite zone. The middle zone is present only where drainage is sufficiently slow to allow saturation conditions to build up with resulting quartz or smectite precipitation. This precipitation may occur in any climate at a water table or in tropical climates with a long dry season. The degree of serpentinization of the laterite parent rock is important in determining the nature of the saprolite zone. Unserpentinized peridotite produces saprolite ores with hard residual rock cores, nontronitic or amorphous saprolitic rims, and fracture fillings of garnierite and quartz. Ser-pentinites yield relatively homogeneous serpentine saprolite, with minimal quartz or garnierite.

Jan 1, 1979

By Eddy J. Jacques

When the automatic control of a ventilation process is considered, and supervising expert systems need to be designed, an important problem to address is: what will be the optimal set points of the regulators that should meet a certain number of independently formulated requirements, distributed over a ventilation network? The set of these requirements, expressed in terms of air flow quantities or differential pressures in certain airways, need not be consistent. Their number is not limited by the number of available regulators, nor by their nature, i.e. passive or active. Moreover, they may be subject to upper or lower limit values. The method described here addresses this problem and tries to provide a tool that should allow to calculate the set points of all the regulators as a global and optimal solution with respect to this set of distributed requirements. The pure mathematical developments in this paper are kept as short as possible in order to allow more room for the description of a relevant example.

Jan 1, 1991

By Huang Kong Xuan, Li Yun Teng

Reviewing the development of resin-in-pulp (RIP) technology for the extraction of gold in the world, especially in South Africa and USSR, and the chemistry of interaction between aurocyanide ions and anion-exchange resins. RIP benchtest and pilot plant investigations show that the resin of the weak-base and strong-base can absorb gold in the cyanide pulp and gold can be eluted from the strong-base resin by electro-elution. The possibility of future application of RIP technology in China fa also briefly discussed.

Jan 1, 1998

By S. E. Phillipson, S. Romberger

The Late Miocene San Cristobal Ag-Zn-Pb deposit represents syngenetic and epigenetic mineralization with low- and high-sulfidation characteristics. The geology of the deposit is characterized by barren dacitic ring fracture domes, mineralized resurgent rhyodacite domes, strongly altered and mineralized tuffaceous lacustrine sedimentary rocks and an extensive crystal-lithic tuff debris apron. The orebody is hosted by intracauldron sedimentary rocks and breccias. Fluid inclusion data suggest that silver, lead and zinc were transported as chloride complexes and precipitated by cooling in veins from <5% (by weight) NaCl eq. fluids at 170° to 215°C. Silver spatially and perhaps temporally associated with resurgent rhyodacite was transported as a chloride complex and precipitated by increased H2S activity or increased fluid pH.

Jan 1, 2002

By Rasik H. Raythatha

Calcium carbonate is perhaps the most widely used mineral in the world. With total consumption of all calcium carbonate exceeding over 25 million tom per year, within this class of filler, a relatively smaller segment of precipitated calcium carbonates (PCC) is often misunderstood as a commodity product and bundled in the same category as ground calcium carbonate. However, each material has a distinctly digerent role and characteristics. Precipitated calcium carbonates are used to influence specific performance in a specific application whereas ground calcium carbonate is used primarily to reduce cost in many applications. In this paper, attempts are made to demonstrate the role of nano-fine-PCC in improving shear-thinning characteristics of common and specialized sealants and automotive underbody coating and how such "nano-particle" cal- cium carbonate properties can be exploited to process PVC plastics while reducing overall cost. We also review the role of precipitated calcium carbonate as "nano" material and why it must be viewed as a specialty additive.

Jan 1, 2003