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By D. Kwak, S. Han, J. Kim, Y. Lee

"INTRODUCTION In carbonate rocks, it is difficult to characterize due to the high degree of heterogeneity in pore geometry. Carbonate rocks have various types of pore systems such as fractures and vugs, and this heterogeneity should be considered for more realistic prediction of oil production in carbonate reservoirs. This study carried out water flooding experiments using five carbonate rock samples in order to observe the change of physical properties. Firstly, qualitative and quantitative analyses were conducted for each carbonate samples by use of XRD and XRF to evaluate the mineral content. All samples are mainly composed of CaCO3 and after that, the ICP experiments were carried out for the water passing through the carbonate. As a result, it was possible to measure the quantity of CaCO3, MgO, Fe2O3 component in water and due to this effect, the permeability of carbonate was altered especially in the front part of the core. Finally, after the carbonate was saturated by 30 API crude oil, water injection to enhance the oil recovery was repeated and it was confirmed that the oil-producing characteristics are different depending on the dissolution characteristics of carbonate rock samples. CORE SAMPLE ANALYSIS Porosity and Permeability Experiment Porosity and permeability were measured. The procedures are as follows (Figure 1). 1. Measure the diameter and length of the dry core using Vernier caliper. 2. Put the core in the core holder, run vacuum pump until the inlet and outlet pressure gauge equal. 3. Saturate the core using ISCO pump to inject water at 650 psi 4. Measure the amount of water and calculate the porosity 5. Set up the outlet pressure at 500 psi. 6. The flow rate measure when the equilibrium 7. Calculate the permeability through Darcy’s Law. 8. Cutting of core upstream and downstream about 13cm, and measure the each of permeability."

Jan 1, 2016

By V. Srivastava, T. Ghosh

"Modeling and Simulation of SAG Mill has been widely used in design and optimization of mill performance in terms of its power draw, processing capacity and product size distribution. However, these models are solved under steady approximation and do not provide any information on mill charge distribution in real time. This paper attempts to characterize mill contents by solving Whiten’s first order contents based model in Matlab/Simulink environment. The parameters in the model such as breakage rate (S), discharge rate (D) and appearance function (A) were estimated utilizing process and design data collected from a gold mine operating in Alaska coupled with nonlinear parameter estimation scheme. This model is then utilized to predict dynamic response of other key operational variables such as mill power, bearing pressure, charge level and product size distribution. The transient response of mill behavior with respect to changes in feed size distribution, tonnage and mill feed water is also presented. This dynamic simulation approach can be used for practicing different control strategy and training purposes. The observed response of mentioned variables was validated utilizing dynamic response data from the plant to encompass operational characteristics of SAG Mill behavior. Keywords: SAG Mill, Dynamic Modeling, Simulation, Nonlinear Parameter Estimation. INTRODUCTION Grinding in mineral industry is one the most important steps in the process of size reduction and plays a crucial role in determining the overall economics of the milling plant. Much of the efforts focused on improving the process efficiency using modeling and simulation have been practiced by researcher and engineers. However, up till now these models were simulated under steady state approximation because of their complex nature and difficulty in programming them in a dynamic framework. Steady state simulations have been successfully utilized in circuit designing, capacity planning and pre-flowsheet optimization. The maturity in steady state models is because of its applicability and regular use in steady state simulation packages such as JKSimMet, Limn, ModSim, etc. With the advent of equipment such as SAG and AG mill has been a recent shift in the simulating these models using dynamic approach. Because of the economic benefits of these devices and ability to act both as a primary grinding device and as secondary or tertiary crushing device they have gained a large popularity and are now universal to any milling plant. However, these device poses a real challenge to engineers and researchers in terms of operation and control. The major reason attributed to problems faced is because the ore constitutes the major portion of the charge in these devices when compared to ball and rod mill. This rock charge is subjected to disturbance such as changes in feed size distribution and ore hardness which results in unstable operation and frequent mill stoppages. One way to prevent this is to measure and control these external variables, however, lack of available instrumentation and unavailability of sensors to measure these variables has foiled the understanding of complete process occurring inside the mill thereby, inhibiting development of proper control system."

Jan 1, 2017

By J. J. Gusek

Passive treatment of mine drainage using constructed wetlands has been employed on coal and metal mine sites since about 1985. The technology has advanced significantly since then; there are currently over 600 of these systems treating coal mine drainage in the Eastern U.S. at flow rates of hundreds of liters per minute. Passive treatment performance at three metal mines discussed in this paper has been positive for a wide variety of flows, water chemistry, and climates. The sites include a high-altitude underground copper mine, acidic seepage from a gold heap leach pad, and pumped effluent from an active underground lead mine in Missouri.

Jan 1, 2000

By T. J. Jr. DeMull, F. G. Miller, J. P. Matoney

For some time a need had existed in the minerals processing field for a relatively efficient separator that would treat high tonnages of particles in the intermediate size range, i.e., those particles too large for froth flotation and too small for conventional gravity-type separa¬tors. Among those devices developed to meet this need are the centrifu¬gal specific gravity separators. These devices employ centrifugal acceleration to assist gravitational acceleration in separating light¬density minerals from heavy-density minerals. In the category of centrifugal specific gravity separators are the heavy-media centrifugal separator and the water-only cyclone. The two major centrifugal heavy-media separators, i.e., the heavy-media cyclone and the DynaWhirlpool, as well as the water-only cyclone, are discussed in terms of: design features, operating variables, operat¬ing data, and flowsheet design criteria. Examples of plant applications are given in the field of coal processing as well as the processing of other minerals such as iron ores, potash, and tin. Finally, the subject of the staging of centrifugal separators and their use in combination with other separators is discussed. PRINCIPLES For coarse sizes of minerals, efficient specific gravity separations have been possible for many years with open-bath vessels using the natural settling velocity or buoyancy of the particles. These bath ves¬sels process ore by utilizing micron-size solid particles suspended in the slurry fed to the separator. The inclusion of these particles in the slurry increases the effective density of the separating fluid to allow particle separations to be made at densities greater than that of water. However, if vessel size is to remain within economical limits, the particles processed in the bath vessel must have high settling rates in a IG gravitational field. Because of this requirement, heavy¬medium bath vessels are usually restricted to processing +V4-in. sizes. To extend efficient specific gravity separation to smaller sizes, the gravitational acceleration of particles is replaced by centrifugal acceleration. The settling of a small particle in a fluid in a centrifugal force field is similar to that found in a static bath except that the acceleration due to gravity, g, is replaced by a centrifugal acceleration where v, is the tangential velocity at radius r: V=kdm(P-P,), V'. (J) µ In more practical terms where the particles settle in a suspension of finer particles comprising the heavy media and with an effective suspension density p" V = kdm' (P P ) . v'. (2) U r To date the most effective use of this principle has been obtained with devices that rotate a liquid or suspension within a stationary enclosure in order to create centrifugal force. Cyclones are the most common devices used for this purpose, because they generate centrifu¬gal forces far greater than the force of gravity and therefore not only have high capacities but can treat finer sizes than bath-type vessels can. The two main types of cyclones used by industry are the heavy-media cyclone and the water-only cyclone. Also quite widely used is the DynaWhirlpool, which, though based on the same princi¬ple, differs in design from the conventional cyclone. HEAVY-MEDIA CENTRIFUGAL SEPARATORS Like the bath vessels, the heavy-media centrifugal separators em¬ploy media composed of micron-size particles suspended in water. However, the centrifugal force generated in these separators accentu¬ates the difference in settling rate between particles of different density and thus makes possible separations of finer size particles than can be treated in bath vessels. The two most common heavy-media centri¬fugal separators are the heavy-media cyclone and the DynaWhirlpool. Heavy-Media Cyclone Although cyclones were originally developed for use as classifiers or thickeners, it was later found that they could also effectively serve as heavy-media separators.63. 64, Design Features Fig. I I is a schematic of a typical cyclone developed to serve for any one of the following purposes: as a classifier, thickener, or specific gravity separator. The cyclone consists of a cylindrical section joined to a conical section, usually having an included angle of between 14° and 25°. Feed enters the cyclone tangentially through an orifice attached to the cylindrical section. The overflow orifice is located in the base plate of the cylindrical section. The vortex finder, a tube attached to the overflow orifice, extends into the cyclone from the base plate of the cylindrical section. The underflow orifice is located at the apex of the conical section. As some medium together with mineral particles is fed through the feed orifice, a vortex with a hollow air core extending from the overflow to the underflow orifice forms in the cyclone while hollow spray discharges form at each of these orifices. Under the influence of the centrifugal force, high specific-gravity particles move through the medium to the wall of the cyclone and descend in a spiral flow pattern to the underflow orifice. Those particles in the feed stream, lower in specific gravity than the feed medium, follow the major portion of the flow to the center of the core where they are caught in the high-velocity upward central current and are carried out through the overflow orifice. Fig. 12 shows a family of curves that illustrates how materials of varying specific gravity are recovered by a cyclone. Since the specific gravity of the medium is 1.40, the particles of 1.40 sp gr actually act as part of the medium and, regardless of the particle size, split between the underflow and overflow of the cyclone in proportion to the volume split of the medium. Particles higher in specific gravity than 1.40 are recovered in the underflow of the cyclone at increasing rates as the difference in specific gravity increases and the particle size increases. Particles lower than 1.40 in specific gravity are dis¬charged through the overflow orifice at increasing rates as the specific¬gravity difference increases and the particle size increases. However, all the curves originate at the fluid-flow ratio point for the finest particles of any gravity. The fluid-flow ratio is defined as the ratio of the rate of fluid flowing from the underflow to the rate of fluid

Jan 1, 1985

By R. Buchan

A number of mineral processing techniques have been adopted for the separation of the plastics making up a typical beverage bottle, and a complete flowsheet developed. Thus, size reduction, heavy media separation and flotation were used to separate PE, PVC and PET from their mixtures with cellulose fibers and aluminum, which makes up the cap of such bottles. It is shown that while heavy media separation allows the separation of a PVC/PET mixture from the solid waste, froth flotation can be readily used to separate PVC and PET from a mixture of the two. For this purpose, the differential action of an alkaline aqueous solution (PH=II) which contains methanol and MIBC as surface tension control agents has been found to be a suitable flotation medium. This paper reports some aspects of the flotation flowsheet developed for the separation of plastics from municipal solid waste mixtures and PVC from PET.

Jan 1, 1995

By R. G. Darmody

Longwall coal mining in southern Illinois occurs beneath some of the best agricultural land in the U.S. This region is characterized by highly productive, nearly level, and somewhat poorly drained soils. Subsidence from longwall mining causes changes in surface topography which alters surface and subsurface hydrology. These changes can adversely affect agricultural land by creating wet or ponded areas that can be deleterious to crop production. While most subsided areas show little impact from subsidence, some areas experience total crop failure. Coal companies are required by law to mitigate subsidence damage to cropland. The objective of this study was to test the effectiveness of mitigation in restoring grain yields to their pre-mined levels. The research was conducted on sites selected to represent conventional mitigation techniques on the predominate soils in the area. Corn (Zea mays L.) and soybean [Glycine max.(L.) Merr] yields in 1988, 1989, 1990, and 1991 from mitigated areas were compared to yields from nearby undisturbed areas. There was no significant (a=0.05) difference in soybean yields averaged over the four years. Average corn yields, however, were significantly lower than reference areas. The impact of subsidence and mitigation is variable and site specific. Results were also related to weather. In wet years, yields in mitigated areas tended to be depressed. This research demonstrated that mitigation of subsidence damage can be successful.

Jan 1, 1986

By C. B. Manula

The total systems model for underground coal mine planning and design (Master Design Simulator) is a set of computer programs which encompasses a realistic reproduction of the interaction among the geological, environmental, equipment, methods, and the health and safety aspects of the mining plan (Manula, Rivell, and Ramani, 1975). The total system includes nine major subsystems: geology and reserves, methane generator, roof support, subsidence, production, rail haulage, cost, water generator, and ventilation (Fig. 1). The subsystems themselves are divided into two categories based on the frequency with which they are executed: (1) event-oriented subsystems are executed either independently or at discrete intervals when certain specific events occur; and (2) dynamic subsystems function interactively during the production cycle, transferring data to or requesting data from event-oriented subsystems only when specific events occur (Fig. 2). Each subsystem has been tested and validated independently (Ramani, White, and Sutton, 1974; Ramani and Owili-Eger, 1974; Manula, Mozumdar, and Jeng, 1974a; Manula, Mozumdar, and Jeng, 1974b; Manula, et al., 1974; Manula, Rivell, and Sanford, 1974; Ramani, McClay, and Burgos, 1975; Manula and Owili-Eger, 1975; and Ramani, Owili-Eger, and Manula, 1975).

Jan 1, 1979

By C. Richard Tinsley

Investment activity in the Pacific Rim of Fire has seen a phenomenal surge from epithermal gold exploration. Individual countries are attractive because of lower up-front minerals lease costs (United States, Canada), better geological prospects (Chile, Indonesia), or cheaper equities (Australia). Since the October 1987 stock market crash, large companies are shedding minority joint venture interests to focus on core businesses. Some vertical integration is evident in Japanese coal investments in the Pacific Rim. This article does not cover the aluminum industry oligopoly, which is multinational in character. Nor does it cover the many Canada to US minerals investments. It will be interesting to see if the new US-Canadian free trade treaty will reverse that investment flow. Cross-border investments The following examples should dispel any doubts about the significance of cross-border investment in the Pacific Rim. BHP, Australia's largest public company, has invested $US 4.5 billion in the JS for the following transactions 1984 $2 billion Utah Minerals 1984 $500 million Energy Resources 1985 $745 million Monsanto Oil 1987 $400 million 50.7% Hamilton Oil 1989 $378 million Pacific Resources Placer Dome, mainly through 76% owned Placer Pacific, has the following gold mine developments in hand including the date the project began, Placer Dome's ownership, project name, its location, and capital expenditures: • 1985, 53.1 %, Kidston, Queensland, $A 139 million; • 1989, 37.9%, Big Bell, Western Australia, $A135 million; • 1989, 60.6%, Misima, Papua New Guinea, $C252 million; • 1990,45.5%, Granny Smith, Western Australia, $A95 million; • 1991, 50%, La Coipa, Chile, $US276 million; and • 1991, 25.3%, Porgera, Papua New Guinea, $C1.1 billion. Australia's Western Mining Corp. (WMC), through a foray of off-market acquisitions in late 1987, acquired con¬trol of five Canadian gold companies for a $A488-million outlay ($C452 million) as follows:

Jan 1, 1990

By William Harrison, Robert H. Trent

GENERAL DESCRIPTION History The most striking feature of mining in the United States has been the infrequent use of longwall systems. This system, which accounts for the majority of coal production in Europe, Japan, and other countries, is only recently growing out of its infancy in the mining of normal coal seams and is still untried in the mining of thick coal seams in the US. Its use in the mining of metal and nonmetal ore bodies has been virtually ig¬nored, except for isolated instances in trona, copper, and uranium. Longwall mining is believed to have originated in Shropshire, England, towards the end of the 17th cen¬tury (Laird, 1973). Although the method used would be considered primitive by today's standards, many of the basic concepts have remained unchanged. Longwall mining of coal in the US was first introduced before the turn of the century, but it never gained acceptance as it did in Europe. Historically, longwalling was a cyclic method where a single cut of coal was removed from the face on the producing shift each day, and the work of building stone packs in the gob and manually moving roof support was completed on the off shifts. Due to the amount of dead work, productivity was extremely low. In Europe, however, longwall methods were required despite the high costs involved, because only by this method could coal under heavy depth be mined with any reasonable degree of recovery. Reserves of coal lying under shallow cover, and therefore minable by room¬and-pillar methods, were long ago inadequate to supply most of Europe's coal requirements. In the US coal min¬ing has historically proceeded laterally with the new mines in virgin areas to replace old mines; in Great Britain, Germany, Japan, and many other countries, mining must proceed downward to greater depths. The depth of cover for most coal operations in the US is shallow, i.e., 61 to 305 m (200 to 1000 ft). This, combined with large reserves, has made room-and-pillar methods almost universally applicable. However, longwall systems were tried around the turn of the century. Whenever used, it was frequently noted that the opera¬tion was under the direction of men with foreign ex¬perience and was tried under ideal conditions. Some of the mines that were using longwall or had tried longwall prior to 1910 were the Radiant mine, CO; Vinton Coal Co., PA; Cambria Steel Co., Johnstown, PA; Grundy County and Spring Valley, IL; and unnamed mines in Washington, West Virginia, Kentucky, Iowa, and Kansas. As late as 1961, there was one circular longwall in operation at Centerville, IA. The first modern-day op¬eration to take advantage of European technology and longwall methods was Kaiser Steel Corp. at its Sunnyside mine near Price, UT. Due to deep cover and extremely poor roof conditions, combined with a need for in¬creased production, Kaiser management decided a new method was required and turned to longwall in 1961. The first longwall consisted of an Anderson Mavor shearer loader, British Jeffrey-Diamond conveying equip¬ment, and Dowty roof supports with a capacity made up of two and three 27-t (30-st) capacity props. After nor¬mal start-up problems, this unit averaged over 454 t (500 st) per shift (White and Palacios, 1976). During and after World War II, technology in hy¬draulics and controls had advanced to the point that self-advancing supports and hydraulic props were being developed. In 1960 only I % of West German produc¬tion was from mechanized longwall faces. This in¬creased to 37% in 1970 and 63% in 1973 (Kohlgruber, 1974). In 1976 there were 246 coal mines operating in the United Kingdom. Although this is only 50% of those operating ten years ago, the production has increased 42%, mainly through improvements in longwall equipment and methods (Hunter, 1976). In France and other European countries, the devel¬opment of longwall mechanization has been similar in seams up to 2.44 m (8 ft) thick. In seams that exceed 9.14 m (30 ft), a variety of longwall caving has been developed for coal seams with dips of 0 to 1.6 rad (0 to 90°). Those with the greatest success will be discussed later. As noted, the development of longwall mining to its present state of the art has mainly taken place since World War II with substantial gains in the last ten years. Mechanized longwall has been the result of several re¬lated major innovations (Jackson, 1975) 1) Development of the flexible armored face con¬veyor which can be installed along the face and moved forward without disassembly. 2) Development of face machines such as single and double drum shearer and coal plows which operate in conjunction with the armored conveyors. 3) Development of self-advancing hydraulic roof supports which now include chocks, chock shields, and shields. 4) Reliance of caving of the immediate roof based on proper planning and development. 5) Use of pneumatic slowing to enable extraction below overbuilt areas. The most recent developments in the mining of coal by longwall in the US include the introduction of shield supports at Kaiser's York Canyon mine in New Mexico, single-entry longwall development at Kaiser's Sunnyside mine, and Mid-Continent's advancing longwall system in Colorado. Metal and nonmetal longwall systems in the US have included the mining of copper at White Pine, MI; uranium in Utah and New Mexico, and trona in Wyoming.

Jan 1, 1982

By Kalyan Saikia

An integrated statistical-geostatistical modelling of gold exploration data of Gurahar Pahar prospect of Mahakoshal greenstone belt in Central India has been attempted. Statistical modelling of gold accumulation and width reveal a positively skewed 2-parameter lognormal distribution fit with an estimate of mean gold as 0.84 gram/tonne. Geostatistical modelling provided a spherical semi-variogram function fit with mean kriged estimate and mean kriging variance of gold as 0.76 gram/tonne and 0.23 (gram/tonne)2 -respectively. Ore inventory and grade-tonnage relationships for a selected part provided an estimate of 3,36,000 tomes of ore with an average gold of 0.76 gram/tonne at 0.5 gram/tonne cutoff grade.

Jan 1, 2002

By Douglas J. Kramm

This paper discusses the history and development of the Rotary Kiln in improved fuel economy. It discusses latest technology to optimize fuel economy in a long Rotary Kiln. It discusses the limestone preheater, the SF process for cement manufacture, and the flash calciner with suspension preheat and. suspension deheat for fine limestone.

Jan 1, 1977

By P. Worley

With Utah Power & Light Mining Division's commitment to operate the safest and most productive mines possible, a decision was made to purchase and install mine-wide monitoring systems for use in the mines. After review of several different systems the Conspec Senturion 200 system was chosen. Three separate systems were ordered to fulfill the monitoring requirements of the six mines in operation: one system for the Deer Creek Mine one for the Wilberg/Cottonwood complex, and one for the Deseret, Beehive and Little Dove complex.

Jan 1, 1989

JIM ARNOLD: Questions? Comments? Gary, were you gone when I made the comments about corporate puke? [laughter] SPEAKER: You were hiding. BRUCE CAVENDER, BHP Copper: Having worked in both places, I'd like to address the issue of the plant versus the corporate office. One thing to keep in mind is that we are all very engaged with the technical elegance of a lot of the work we do. There's some tremendous technical expertise in the plant. But remember, the guys in the corporate office are only thinking in one denomination, and that's dollars. So we'll see something like a spill, and for us it's a problem. At the end of the day, what the corporation cares about is the financial impact. So we've got to be careful to couch our solutions in dollar terms. JIM ARNOLD: Rebuttal? [laughter] DOUG HALBE: Are you going to rebut this one, Andy? ANDY CARTER, Oxidor Gold Corporation: No, I don't think so. I'm not up to it. I'd just like to address a question both to our panel and the floor. Those of us who've been in this industry any length of time have seen these same mistakes made over and over again. Wherever you go, year after year, plant after plant, you see the same problems. I guarantee you, Doug, that if we have a similar conference down the road, you're going to see the same thing. My question to the panel and to the floor is what is it about our industry that stops us from learning from our mistakes? What characteristic is it that prevents us from learning and makes us repeat the same mistakes over and over again? DOUG HALBE: That's a great question. Someone said in a meeting 10 years ago that if the people who design plants designed airplanes, the planes would be falling out of the air all the time. GARY SIMMONS, Newmont Gold Company: I've got an answer to your question as to why many plants are poorly designed. It's that the minute anybody demonstrates any sort of competence in plant design, they're promoted to a higher-paying job, and the talent pool is left with people of lesser experience. Just think about it: The people who have the experience and have demonstrated it more than once have moved up. JIM ARNOLD: I think that there's another reason, too. Seven or eight years ago I was chairing a session, and I challenged everyone in the session to some day publish an article about the design mistakes they'd made because we never talk about our mistakes. I'll

Jan 1, 1998

By R. Woods

"Comments on the paper ""Formation of hydrogen peroxide by chalcopyrite and its influence on flotation,""by A. Javadi Nooshabadi and K. Hanumantha Rao (Minerals & Metallurgical Processing, 2013, Vol. 30,No. 4, pp. 212-219)The formation of hydrogen peroxide from water during the grinding of chalcopyrite in a nitrogen-sparged environment, as reported by Javadi Nooshabadi and Rao (Minerals & Metallurgical Processing, 2013, Vol. 30, No. 4, pp. 212-219), is questioned on the grounds that oxidation of water by the mineral is unlikely to be thermodynamically feasible. It is argued that it is more likely that any peroxide that had been formed would have been generated from residual oxygen in the nitrogen-flushed system than from the oxidation of water.The formation of hydrogen peroxide by finely divided pyrite had been reported by a number of authors (Borda et al., 2001; Borda et al., 2003; Cohn et al., 2006; Schoonen et al., 2006; Schoonen et al., 2010; Jones et al., 2011; Javadi Nooshabadi et al., 2013). That hydrogen peroxide is formed in the presence of oxygen in solution can be comprehended from wellestablished mechanisms. Pyrite in aerated solution is known to oxidize by an anodic process that is coupled with the cathodic reduction of oxygen (Holmes and Crundwell, 2000). The latter process has been shown to occur through the formation of hydrogen peroxide (Biegler et al., 1975; Ahlberg and Broo, 1996). The pH dependence of cathodic oxygen reduction at other sulfide minerals, including chalcopyrite (Biegler et al., 1977; Rand, 1977), implies a similar mechanism at these surfaces."

Jan 1, 2015

By Kadri Dagdelen

New underground coal mines have become increasingly expensive to open. A simple drift mine producing a raw coal product can cost as much as $50 million while a new shaft mine producing a washed coal product can cost up to $200 million. As a result, few if any speculative new mines are constructed. Normally, a long term coal supply agreement is needed to justify new mine projects. Negotiating a supply agreement prior to production start is difficult. Pricing must be based on estimated rather than historic costs and coal quality must be estimated from core hole samples versus actual shipments. Further in todays competitive coal markets, there is little margin for error in either price or quality.

Jan 1, 1983

By J. Alderman

In modern industry, cost and productivity concerns and environmental concerns are sometimes incompatible, but at other times only appear to be incompatible. Surface disposal of wastes from coal preparation plants appears to be an area of the production system with little opportunity for initiating measures which cut costs and concurrently benefit the environment. However, improving the recovery efficiency of fine coal circuitry can cost-effectively reduce the plant waste environmental burden by a substantial amount. Studies at Jim Walter Resources indicate that fine-coal waste measuring 50% ash contains over 50% recoverable, marketable coal. Modifications to the plant circuitry which reduce the amount of misplaced coal in the fine-coal waste stream could substantially reduce the volume of fine waste disposed aboveground. Studies at Jim Walter Resources indicated that episodic overloads of the vacuum filters in the fine-coal circuits at the preparation plants were a source of misplaced coal in the fine-waste stream of the cleaning plants. To improve the filtration rate and reduce overload episodes, conventional rotary blowers were replaced with high pressure air blasters on most of the filters. Subsequent testing indicated that measurable benefits can be derived from this modification.

Jan 1, 1990

By Carl F. Austin

The subject of strata control in mining can be approached from both static or loading concepts or from dynamic or impulsive loading concepts. The fracture process itself appears to be primarily a dynamic process as is the gross creation of fractures through the use of impact, stress wave passage or in more general terms, the use of explosives. This paper presents experimental results which indicate that the understanding of the fracture behavior of rock that has been, established in the open literature is not always appropriate. In particular, the results of this experimental program have shown very interesting differences between the formation of fractures in rock and the formation of fractures in other materials such as metals and plastics which are often used as models for rock behavior studies Fracture patterns and causes of dynamic fracturing in various rock and artificial materials are presented.

Jan 1, 1965

By William J. Cavanaugh

In 1967, Lone Star Industries, Incorporated, established a program to carry out the necessary Research and Development work to bring the Snyder Process to commercial application. The purpose of this paper, is to present the detailed metallurgical results gathered in comparing the Snyder Process of Comminution to conventional grinding techniques for the milling and beneficiation of certain ores and other materials. The ore primarily dealt with in this paper is a fine-grained magnetite ore, containing approximately 23% acid-soluble iron, from the Lake St. Joseph ore body of Steep Rock Iron Mines, Ltd., (Canada). This particular example was selected for presentation in this paper because extensive comparative results with conventional methods of grinding were available. Also briefly described in the paper are the comminution of other ores and materials such as porphyry copper ore and alumina.

Jan 1, 1973

By Karl J. Ellefsen

A geophysical investigation can provide valuable geologic information needed to characterize sand-and- gravel deposits and can be an attractive complement to more common characterization methods such as drilling. Although such investigations have been conducted already, a comparison of the different geophysical methods used in these investigations apparently has never been done. For this reason, a study was initiated by the Mineral Resources Program of the U.S. Geological Survey to determine the advantages and the limitations of different geophysical methods when used to evaluate alluvial sand-and-gravel deposits. The study is focused on those geophysical methods that are commonly available, because these are most likely to be used by industry. Furthermore, the study is focused on surface geophysical methods. Heretofore, four different methods have been evaluated. Three of the four methods-time-domain electro-magnetic (TEM) soundings, frequency-domain electro-magnetic profiling, DC-resistivity soundings-are similar in that they all measure the electrical resistivity of the ground with depth. Ground-penetrating radar, however, maps changes in the dielectric permittivity and for the electrical resistivity with depth. For all, four methods, the objective is to relate the measured physical quantity to the stratigraphy of the alluvial sediments.

Jan 1, 1999

By M. M. Botz, F. W. DeVries

Discussion by F.W. DeVries Comments on natural cyanide attenuation. The paper by Botz and Mudder in the November 2000 issue of Minerals and Metallurgical Processing had one disappointing aspect. Table 1 (p. 229) failed to include a significant species - neutral copper cyanide (CuCN). This compound has been most trouble-some in many plant-scale cyanide cleanup processes, includ- ing acidification-volatilization- reneutralization (AVR), hy- drogen peroxide cleanup and air/SO2 cleanup. It has also plagued many pilot efforts to use ion-exchange (IX) resin technology. This author elucidated the concept that, under some conditions, copper cyanide failed to precipitate out of treated effluents and appeared to exist as a filterable colloid that reported as copper and cyanide, with the latter measured as WAD (weak-acid-dissociable) cyanide in that analytical method. The concentrations measured were very near the levels of 0.2 ppm, often the regulatory limit for WAD cyanide. The copper concentration, using the 1 : 1 ratio for this com- pound, would then be more than 0.4 ppm, which could also be unacceptable. We discovered that it was unsafe to assume that the Cu(CN),- would surrender both cyanide ions simultaneously and allow cupric copper to be removed subsequently as, say, cupric ferrocyanide (Hatchett's Brown). This compound could be ignored as safely as the "iron blues," as essentially an inert solid, stable in geologic time if not exposed to sunlight. Under poorly controlled oxidation of the cyanocuprite ions (copper with four, three or two cyanides complexed to the copper), CuCN could well be formed and could not be assumed to precipitate out as a solid. The authors of the paper, by failing to include the CuCN species in their model, may have left users of the model prone to ignore the possible occurrence of the colloidal(?) form in the discharge, thus finding an effluent that failed to meet regulatory limits. (See addendum below.) This somewhat ephemeral material may well have been responsible for some large-scale failures of cyanide destruction technology to succeed at sites in North America and elsewhere. Two specific references alluding to this occurrence may be found: Griffiths et al., 1987, "The detoxification of gold-mill tailings with hydrogen peroxide," Journal of the South African Institute of Mining and Metallurgy, September, p. 282. DeVries, 1989, "Improved understanding in detoxification of cyanide leach liquors using peroxide" Rand01 Gold Conference, Sacramento CA, p. 15 1. It is advisable for workers in this area of cyanide removal or recycle to avoid assuming that CuCN will, with certainty, precipitate out of solution, or that the dicyanocuprite ion will part simultaneously with both cyanide ions and allow cupric copper to be dealt with by other reactions. One further piece of work may be incomplete. That is, a definitive study of the long-term behavior of CuCN that does precipitate when exposed to other compounds present in neutralized tailings. Addendum. The extremely complex reaction of cupric ion on cyanide- which, of course, results in oxidation of cyanide to cyanate, probably through the intermediate stage of forming cyanogen [(CN)2] from oxidation of HCN with its hydrolysis to cyanate and cyanide ion - involves two cyanide moieties and the reduction of the cupric ion back again to the cuprous state. This, then, can form the CuCN potential "solid" that was already the undesirable species. In cyanide cleanup, with either air/SO2 or hydrogen peroxide, copper is generally employed as the catalyst, so it is unclear what happens when the CU(CN)2-1 is ultimately exhausted. Certainly, the field evidence is quite clear that all

Jan 1, 2002