Search Documents

By I. K. Choi

In a recent paper by Smith and Wen(1) the adsorption of sodium dodecylsulfate and trimethyldodecylammonium chloride on kaolinite was studied. As would be expected considering the general negative character of kaolinite, except perhaps at quite' acid pH values (2,3,4), it was found that trimethyldodecylammonium chloride adsorbed strongly on kaolinite at basic pH values. Furthermore, it was found that sodium dodecylsulfate adsorbed strongly on kaolinite at acid pH values, particularly at initial 1H values below pH 3 (final pH values near pH 4). It is interesting to note that adsorption of the anionic surfactant was strong under conditions where the kaolinite was apparently slightly negatively charged (2). The present paper reports on an extension of the work by Smith and Wen. In this paper the effects of the presence of dodecyl alcohol and sodium hexametaphosphate on adsorption of sodium dodecylsulfate and trimethyldodecylammonium chloride on kaolinite are considered.

Jan 1, 1967

By T. F. Tomb

on' January 6, ,1992, the Mine Safety and Health Administration (MSHA) issued an Advanced Notice of Proposed Rule Making (ANPRM) for diesel particulate (DP). The ANPRM identified five areas where the Agency was seeking additional information to assist in the rule making process. These areas were exposure 'limits, risk assessment, consideration of other information, sampling and monitoring methods, and feasibility. The period for submitting information relative to the ANPRM closed July 10, 1992. Prior to issuance of the ANPRM, the agency was involved in conducting studies to evaluate sampling and control technologies and to gather information with respect to occupational exposures to diesel particulate in underground mining operations employing diesel-powered equipment. Since issuance of the notice, additional studies have been conducted to provide supplementary information in these specific areas. Results of these additional studies indicate that average DP levels in coal mines not using aftertreatment range from 0.9 to 2.1 mg/m3. Aftertreatment devices can reduce these levels by approximately 50 to 90 percent. Studies conducted in metal and nonmetal mines showed average DP levels ranging from 0.3 to 1.6 mg/m3.

Jan 1, 1994

The surface of chalcopyrite was studied in situ in aqueous solution by an atomic force microscopy (AFM). The AFM images showed that some absorbate in patches was detected on the mineral surface, after the chalcopyrite sample was soaked in 5x10-4M potassium ethyl xanthate (KEX) solution at pH 11 for 10 minutes. These patches increased in size with time elapsing. At the same time, as shown by the obtained AFM force curves, the adhesion between the AFM tip and the substrate increased greatly due to the adsorption. Rinsing with ethanol removed the absorbate from the chalcopyrite surface, as well as the big adhesion observed in KEX solution.

Jan 1, 2010

By Paul Soros

A major share of the increase in the energy demands of Ontario province in the next decade will be supplied by bituminous coal mined in the U,S, To be competitive with alternative sources of energy, it is essential that the delivered cost of coal, inclusive of all transportation charges, be kept at a minimum. The Bessemer aid Lake Erie Railroad Company and the Pittsburgh and Conneaut Dock Company are currently building a shiploading terminal at Conneaut, Ohio, to service this tonnage, together with expected increases in coal consumption in the Eastern Lake Erie - Lake Ontario area, (see Fig, 1).

Jan 1, 1965

By P. Somasundaran, D. R. Nagaraj, Tarun Bhambani, P. Patra

Flotation separation and recovery of value minerals from ores containing fibrous silicate minerals are known to be quite challenging. Earlier studies have established that the metallurgical challenges (poor selectivity and recovery, high energy consumption, etc.) arise from the impact of the fibrous minerals (with high aspect ratio) on pulp rheology, which was found be rather complex. The complex rheological behavior of ore suspensions containing particles with high aspect ratio and its influence on flotation outcome are investigated in this study. Flotation tests and rheological measurements were carried out with both ores (containing fibrous minerals) and a model system comprising nylon fibers (chemically inert) added to a copper ore that had no fibrous mineral. These studies allowed the determination of contributions of physical properties of the fiber to pulp rheological behavior. Optical microscopy images of the fiber pulp indicated that the fibers entangled to form two levels of microstructures: two-dimensional (2D) aggregates under semi-dilute (< 20% solids) conditions and three-dimensional (3D) microstructures at concentrations > 30% solids. The yield stress (σ) values determined for the fiber pulp were logarithmically related to the volume fraction of the 2D/3D structures. The relationships developed here for different ARs showed that the yield stress of a flotation pulp changes with respect to shape, size, and the concentrations of the microstructures. Implications to the effects of such entangle networks on selectivity of flotation separation are discussed.

Bioleaching of solid wastes lithium ion battery industries was carried out in this investigation. A new method for recovery of cobalt, potentially the basis of an economic and environmentally friendly process was examined. The present study was conducted using chemolithotrophic and acidophilic bacteria Acidithiobacillus ferrooxidans and some mixed thiobacilli collected from abandoned mine drainage. These organisms were able to utilize sulfur and ferrous ion as energy source. Bio-dissolution of cobalt was found to be faster than lithium. The effect of initial Fe(II) concentration, initial pH and solid/liquid (w/v) ratio were studied in detail. With increase of time of leaching the dissolution of cobalt was found to be increased and this must be due to competitiveness of the mixed thiobacilli for utilizing the energy source among them. Since the bacteria are belonging to acidophilic group the higher pH studies revealed a decrease trend in metal dissolution. Higher solid/liquid ratio also found to be detrimental for the bacterial activity. It seems bacteria are not resistant to higher concentration of the metal. The optimized conditions for bio-dissolution were sol-id/liquid (w/v) ratio - 10 g/L, initial Fe(II) concentration - 5 g/L, elemental sulfur - 1% (w/v). In the optimized conditions, cobalt dissolution was observed to be about 75 % whereas that of lithium was 15% after 25 days.

Jan 1, 2006

By Thomas Camus

"STATE OF THE ART The current situation of ground prediction in TBM is of great concern for tunnelling contractors, and the subject has been quite widely addressed over recent years, for instance by the French Eupalinos 2000 programme, which tested a variety of technological approaches. A number of interesting projects were executed, such as the SOUND and OnSITE projects, part of the German Geotechnologien programme: these projects are focused on seismics, while other techniques such as radar are not considered. Little information and even less industrial applications have been released apart from lab simulations and numerical modelling. A number of field tests in different configurations have been carried out for compression waves, but the results were often not reliable or convincing, and therefore little has been reported in open literature. The advances seem somewhat promising as far as hard rock tunnels are concerned, but ignore the problem raised by concrete lined tunnels such as those bored by a TBM in soft ground. In such tunnels, sending and receiving seismic waves reliably through the lining (and the grouting behind) is quite illusory. A careful analysis of the seismic prediction research results show that the main problem is the source which is poorly controlled and poorly coupled (for instance in concrete lined tunnels, or in approaches that use the TBM cutter head vibrations as a source). Generating waves perpendicular to the tunnel axis is also a problem: aligning with the tunnel axis makes more sense. Radar (Ground Penetrating Radar - GPR) has been used in geotechnical surveys for decades, and also for tunnel inspection. Attempts have been made at using it on a TBM (for example in Japan by Taisei) but mainly using off-the-shelf GPRs, which are not adapted to work in the specific environment of a TBM (because of its huge mass of metal, to start with). Very few results have been published, probably due to the somewhat disappointing performance of such implementations. At present, no TBM has a GPR incorporated in its cutter head that is able to predict ground characteristics while drilling. Another characteristic and drawback of most current methods is that they require dedicated periods of time during which other tunnel construction activities must be stopped. Due to the duration of such operations this leads to performing ground prediction on a weekly basis only, and therefore to a requirement for an investigation range of 100 metres approximately (in order to cover the TBM advance over the coming week). This is not achievable with boreholes made from the TBM, even less if a reasonable accuracy is required, as is usually the case."

Jan 1, 2016

By W. A. Yuill

A process has been developed for increasing the grade of chalcopyrite concentrates from about 25 percent copper to about 60 percent copper. The concentrates are treated with two steps of autoclaving and then by flotation. Because of the lower associated weight, copper in the concentrates could be shipped and smelted at less cost than untreated concentrates. Use of the process can also increase overall yield from an orebody if a lower grade concentrate is sent to enrichment than would be sent to a smelter. Potential applications of the process would be for treating concentrates that must be transported a long distance for smelting or for treating concentrates so as to increase the capacity of a smelter.

Jan 1, 1984

By Ted C. Mathews

Pre-concentration by sorting is as old as the mining industry. Inevitably waste rock is broken with ore. Separation may take place in the stopes by selective mucking and transport, or selective loading and transport of ore and waste by 12-cu, yd. shovels and 100-ton trucks in large open pit operations. Hand sorting of 1" to 16" pieces, formerly widely practiced at underground chutes and prior to or following first stage crushing, has greatly diminished in the United States with its high per hour labor cost, although still widely practiced in other countries and, surprisingly, in some of the most modern mills where inexpensive labor is available. The economics of pre-concentration by sorting is attractive since elimination of waste at any cost less than the total milling cost will show a profit. The size at which sorting should be under- taken is determined by the size at which liberation is secured to yield a product of ore and waste, and greatly influences cost and the point in the flowsheet where sorting can be undertaken. In some instances mining costs can be reduced where an inexpensive sorting system to eliminate waste is combined with a less selective and less costly mining method. This is particularly true in deep mines where hoisting capacity determines the rate of extraction and sorting is performed underground, with waste utilized for fill. Hand sorting, while efficient, is expensive because of low sorting rates. Peale (1) quotes man hour capacity at 1/3 ton per hour on sizes 3/4" to 3" copper ore, and up to 5 tons per hour on rich iron ore sized from 4" to 16".

Jan 1, 1974

By Johan Bosch, Wout Broere, Minh Ngan Vu

"INTRODUCTION Shield tunnelling is often used in constructing underground infrastructure in cities due to the ability to limit settlements and damage to existing buildings. However, in an urban environment with soft overburden and buildings on pile foundations such as the North-South Line project in Amsterdam, there is a tendency to design the tunnel well below the surface and below the pile tip level in order to reduce interaction between tunnelling process and piles. This results in deep tunnels and deep station boxes. When the tunnels are located close to the surface and above the pile tip level, this would reduce the required depth of the station boxes and the construction cost. Moreover, other benefits of shallow tunnels are the low operational cost in the long-term and shorter traveling time from the surface to the platforms. Still, the tunnels should be constructed in such a manner that existing buildings are not structurally damaged, which results in a minimum required distance between tunnelling process and existing buildings. In this paper, the extent of the area that is influenced by tunnelling will be investigated in order to determine the limit distance from tunnelling to existing foundations without inducing too large building deformation. From analysing empirical data of many shield tunnels, Peck (1969) firstly presented the settlement trough on the surface induced by tunnelling in soft soil as a Gaussian distribution. This is also confirmed by other authors (Cording and Hansmire, 1975; Mair et al., 1993; Ahmed and Iskander, 2010). In this study, the Gaussian curve is used to investigate the ground movement when tunnelling in order to find the effects on existing structures. Based on the results from centrifuge test and empirical data, Mair et al. (1993) showed that the subsurface settlement profile distributes as the Gaussian curve also. The width of settlement trough at the depth z depends on the depth of the tunnel z0 and a coefficient K depending on depth. Other studies by Moh et al. (1996), Grant and Taylor (2000) and Jacobsz (2003) based on Mair et al. (1993) proposed a limited change of K in various kinds of soil."

Jan 1, 2016

By J. J. Fallon

Las Vegas is a place of many distractions. It is difficult for one to apply himself to sophisticated technical matters in the midst of gambling, liquor, scantily clad young ladies and the top entertainment available in the United States. But, I know that the men and women of SME are made of stronger stuff and will not be tempted by these things.

Jan 1, 1989

By Dennis A. Fenton

This paper presents some techniques and data required to design large ball mills. The advent of larger size mills leads to consideration of the gearless drive as a practical solution to utilize large horsepowwers. The particular shell structure under consideration is subjected to thermal as well as magnetic loads. The magnitude of the inertia, magnetic and shell temperature characteristics have a very significant effect on the design and performance of the hydrodynamic pivoted shoe bearing. Particularly since these bearings have lower frictional resistance properties than hydrostatic trunnion tee rings. The structure of the mill is designed for long life. Parameters involved with the fatigue life of the structure are discussed together with some of the more important aspects of the design.

Jan 1, 1975

By M. T. Errington, P. C. Miller, W. E. Hardwick

Paper discusses in general terms the techno economic merits of various types of aerated biological reaction systems. The current status of the technology leaves many questions unanswered and hence the choice of the best system to employ is open to discussion. Reasons are given for the choice of the reactor system to be built and operated by Davy McKee. The pilot plant has been designed to provide answers to a number of the questions posed by this technology.

Jan 1, 1998

By Angelus S. C. Owili-Eger

The investigation into the hydrologic and hydrogeochemical influence of longwall coal mining in the Appalachian coal basin was under- taken in response to the need to technically address problems of damaged or impaired well yields, and quality deterioration. Prior to this study, issues regarding reduced aquifer yields and degraded water quality had to be handled in a very qualitative manner. Such an approach would, in the long run, claim a heavy toll on the mining industry. The primary objective of this undertaking, therefore, was to provide sufficient and reliable information base for the determination of the local and possibly the regional effects of longwall mining on well yields, and the hydraulic and hydrogeochemical parameters of the immediate surface and subsurface water systems. Specifically, the program was designed to supply definitive data to answer the following series of questions: 1. Does longwall mining affect the quantity and quality of water in local wells above and adjacent to longwall panels and barrier pillars? 2. If the water quality is affected as soon as mining takes place, does it heal? or if it is not affected immediately, does it change over a longer period of time? 3. How do the aquifer water transmitting characteristics respond to induced physical ad hydrologic variations? 4. What is the extent of the various changes in quantity and quality of the water resources? 5. Should and can standard hydrologic evaluation techniques be used to determine the hydraulic properties of highly fractured zones located within a larger and less permeable aquifer?

Jan 1, 1983

By Morgan M. Sears

The LaModel program is widely used to calculate stresses and displacements on thin tabular deposits, particularly when multiple seams or complex mining geometry is encountered. The program itself allows the user to create multiple mining steps to show a progressive sequence of mining. However, LaModel considers each individual step as an independent steady-state condition, and any previous loading conditions of the materials are not tracked. It also does not consider any sort of dynamic stress change during the mining process. In certain circumstances, especially in multiple-seam situations, modeling a scenario of the seam of interest without considering the previous mining sequence in the off seams can potentially lead to inaccurate results. The primary objective of this paper is to present a situation where a potentially dynamic, unstable mining condition was encountered. It was not evident until the previous loading conditions in the off seams and the impact of dynamic stress changes in the active seam were considered. It is important to make the mining community aware of these potential modeling scenarios where the path-dependent nature of the mining sequence is of key importance. This paper presents a case history where room-and-pillar retreat mining was being conducted in a relatively deep cover stress regime where multiple seam interactions were present from both undermining and overmining. Mining in the active seam was being conducted with roomand- pillar mining techniques consisting of a series of parallel production panels being successively developed and retreat mined along a set of Mains. In this situation, the traditional global LaModel analysis without any path-dependent adjustments did not fully identify the area of poor conditions that were encountered. This paper explores the impacts of mining in the active seam on the lower seam which, in turn, has a negative impact on the active seam. This provided a solid foundation for the subsequent analysis of the three seams simultaneously. Based on the calibrated model, it is likely that retreat mining in the active seam resulted in increased stresses in the underlying seam that conceivably resulted in additional convergence and, most likely, additionally convergence of the pillars under the panel being developed. This in turn could have caused active subsid- The LaModel program is extremely useful for analyzing multiple-seam mining scenarios. As multiple-seam situations become even more prevalent, the potential for encountering a path-dependent mining scenario also increases. To successfully model path-dependent mining scenarios, the ground control engineer will be required to make sound judgments on the condition of pillars in sub-adjacent seams. These engineering judgments should be based not only on the current state of stress, but also on any prior or future states of stress. This means considering the stresses from over or undermining as well as stresses applied to the sub-adjacent seams from actively mining the seam of interest.

Jun 25, 2024

By Daniel T. Brian, O&apos

Exploration targets and results in the mining industry are commonly summarized in terms of tonnage and grade. Business appraisals require, as additional information, the expected profit or loss implied by the physical summary. The early incorporation of knowledge gained through financial analysis computations can provide a means for economically resolving many common exploration and development problems. Examples of such applications from the activities of exploration planning, reconnaissance, land acquisition, and development planning are presented in this paper.

Jan 1, 1969

By W. K. Pincock

Accident prevention can be portrayed as a science that deals with facts and natural phenomena and must be dealt with in the same manner as any other operating problem. Safety at the Copper Queen Branch dates back to 1913 when a Safety Organization was started and rules formulated for underground mining. Since then the mining industry has made substantial progress in the elimination of accidents and when the Lavender Pit was started in 1951, it adopted the general plan in use at all Phelps Dodge properties. Following is a brief description of the Pit Operations:

Jan 1, 1959

By C. Maltesh

Anionic conditioning of phosphate ores prior to fatty acid flotation is a very critical step that determines the eventual selectivity, recovery and hence the economics of the process. However the chemical mechanisms operating during this conditioning step are not established. Several studies have been conducted in the past to determine the mode of interaction of collectors with the phosphate fractions however these have been done on a laboratory scale using pure phosphate minerals. In order to test the relevance of the observed effects to plant practice in this work a comprehensive survey of plant practice was first conducted and then adsorption on flotation feed and francolite were studied under simulated plant conditions. Effects of conditioning energy and water chemistry as well as solids loading and fuel oil were determined. Most importantly, different adsorption mechanisms were found to be dominant under laboratory and plant conditions. In plant water, there was some physisorption of oleic acid on phosphate flotation feed and francolite in addition to chemisorption. However, in distilled water under laboratory conditions only chemisorption was detected. Fuel oil reduced the residual oleic acid in solution after adsorption, which explains the beneficial role of extender in phosphate flotation. The dissolved species in solution arising from the flotation feed or plant processing water are shown to clearly play a major role in determining the adsorption of oleic acid on the substrates. The study also specifically demonstrates the importance of conducting research tests under plant mixing conditions and plant water chemistry for the results to be useful commercially.

Jan 1, 1996

By Z. Yu

The effect of particle size on coal dewatering has been well recognized However, there are no systematic studies on ultrafine coal dewatering. The results discussed last year revealed the effect of flocculant type and coal wettability on the filtration of ultrafine coal In this paper, the differences in dewatering between -25 µ m ultrafine and -500 µ m fine coal with addition of flocculants, surfactants and oil-emulsions in vacuum filtration are further investigated Significant differences were observed in the reduction of the cake moisture. The utilized emulsions were found to be very powerful and promising filtration aids for both ultrafine and fine fractions of hydrophobic and hydrophilic coal

Jan 1, 1995

By Z. Henderson, J. Saylor, L. R. Mendoza

"Diesel particulate Matter (DPM) is a byproduct of fuel combustion in diesel engines. It is classified as a carcinogen, with associated respiratory and cardiovascular health effects. The composition, size, and concentration of DPM is dependent on factors such as engine type, loading and fuel composition. Though a number of DPM abatement and control strategies currently exist, particularly in underground mining environments, occupational exposures remain a serious health concern. As a novel abatement approach, DPM scavenging by fine water or “fog” droplets has been proposed and a laboratory set-up has been built to test the efficacy on engine exhaust. Here, we describe a series of tests that varied engine load, system flow rate and fog drop number density. While none of these factors had overwhelming effects on the results within the ranges tested, the improvement in DPM mass removal attributed to the fog treatment was about 45% on average in comparison to no treatment. INTRODUCTION Diesel engines have seen widespread use for well over a century due to their relatively high thermal efficiency and fuel economy1. More recently, however, adverse health risks of diesel exhaust have become increasingly clear. Many of these risks are associated with the physical and chemical properties of exhaust components1–3. The term diesel particulate matter (DPM) is used to refer to the solid components of diesel exhaust, which are a mixture of elemental and organic carbon (EC and OC) and minor constituents including sulfates and metal ash3. The OC fraction of DPM results from unburned fuel and lube oil, whereas EC or soot is formed during the combustion of locally rich regions within the fuel. DPM is classified as a carcinogen6,7 and epidemiological studies have demonstrated a positive correlation between long-term exposure to DPM and other combustion-related fine particulate and increased cardiovascular and pulmonary diseases8,9. Diesel engines operate in relative fuel rich/oxygen lean conditions and are characterized by relatively high emissions of particulate as compared to spark-ignition engines2,3,10. Typically, these emissions range from 107 – 109 particles/cc and cover two primary size ranges: the nuclei mode where particles have diameters less than about <50 nm, and the accumulation mode where diameters are from about 50-10,000 nm. Most OC resides in the nuclei mode as semi-volatile compounds, while most EC is in the accumulation mode3. The physical and chemical properties of DPM vary with the type of engine, fuel (e.g., petro- vs. bio-diesel) and operating conditions such as loading (i.e., a function of torque and rotational speed)2,3,9,11,12. Loading is a particularly important factor with respect to DPM toxicity9,13,14, and on the effectiveness of after-treatment technologies2,3,15. Engine load alone can affect the EC/OC ratio, and the size distribution and number density of DPM. For diesel engines, the load is roughly proportional to the equivalence ratio3, defined as the actual fuel/air ratio over the stoichiometric fuel/air ratio for complete combustion. Light loads generally favor the formation of OC and small particles. As load is increased the volatiles are oxidized leading to larger soot particles (i.e., EC), but lower total number density of DPM. With further loading, the formation of soot offsets the decrease in volatiles, resulting in increased DPM mean size and number density3."

Jan 1, 2017