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By Sukumar Bandopadhyay

A present dominant problem is that of high downtime of the longwall shearer used in the coal production process. The means by which this problem can be overcome are many, but one of, the most important ones is that the-use of an expert system can reduce diagnostic and repair time. In this paper, a fault-diagnostic expert system model is presented. Specifically, the diagnostic architecture of the longwall shearer expert system and its use for diagnostic reasoning are discussed.

Jan 1, 1989

By L. G. Austin

The paper summarizes the current state of development of simulation models for SAG and FAG mills, and gives the results of recent investigations of the physical processes occurring in autogenous grinding. The breakage process is treated as the sum of three regions of breakage actions: normal breakage caused by nipping of particles between media (steel balls or pebbles); abnormal breakage caused when the particle or lump is too big in relation to the media to be readily nipped; self-breakage resulting from the chipping fracture and abrasion of the tumbling action of rock lumps. Each region of breakage action has associated specific rates of breakage and primary progeny fragment distributions.

Jan 1, 1989

By A. J. Getz

The paper reviews the status of the major precious metals projects in Australia, Papua New Guinea, Indonesia, the Philippines, and New Zealand. The projects may be at the stage of exploration, development, operation, or expansion. The paper covers project location, reserves, method of resource exploitation, anticipated production, and other unique conditions.

Jan 1, 1990

By Long An, Chao Wu, Yuanhui Li, Xing Sun, Shuai Xu, Changyu Jin

Stage open stope mining (SOSM) maintains the stability of excavation openings by leaving a large number of rib pillars. Affected by the strong unloading due to stage mining and the low width-to-height (w/h) ratio of the pillars remaining, largescale destabilization disasters of rib pillars or excavation openings easily occur when the distribution of ground stress or the size of rib pillars is unreasonable. In view of these problems, a physical SOSM model test was carried out based on an underground metal mine in Chifeng City, China, revealing the deformation and failure characteristics of the SOSM pillar group by overloading. The physical model test results of SOSM and room-and-pillar mining (RPM) with a weak pillar were compared, and the failure process of the SOSM pillar group showed the characteristics of rapid and severe damage. The strength difference between a weak pillar and the adjacent pillars enhanced the stress rebalancing effect and extended the failure process of the pillar group. Similar to the SOSM pillar group with a low w/h ratio, some high-strength pillars can be used to avoid large-scale destabilization disasters caused by the synchronous failure of pillars.

Mar 8, 2023

By Fredy A. Elorrieta Agramonte, Gabriel von Rickenbach, Roberto Luis Fonseca, David Córdova Rojas, Rolando Romero, Rico Brändle

The mine’s economic life is dynamic by nature. Some factors that create this scenario are the need to recognize new exploitation areas, the evolution of the mineral prices and the development of new technologies to access them. The dynamics of mining development, especially in the underground environment, changes significantly as the stages unfold. In many cases the final solution differs greatly with the initial. The frequent presence of new conditions and factors often cause the mine to develop in a quasi-permanent transition stage, which could be characterized by the generation of dynamic micro-seismic events that could cause rockburst damage in some specific areas. Although they may be infrequent, these dynamic events can have an important adverse impact on mine safety and causes serious losses. Also, changes in the production schedule during exploitation could be a big issue if the problem is not effectively addressed. When the transition of the mine to an active micro-seismic environment begins as an unforeseen scenario, it is frequent to use static ground support systems as they are readily available. Traditionally, the support systems used are reinforced shotcrete with a middle layer of Welded Standard Wire Mesh (WSWM) and Chain Link Standard Wire Mesh (CSWM) of reduced gauges, i.e. wires less or equal than 4 mm in diameter. Although, this support system is used to control static instability problems, there is no good reference of its energy absorption capacity under dynamic load conditions, creating uncertainty in the effectiveness of controlling rockburst events. These support systems are analyzed at the present paper, testing the reinforced shotcrete layer with 4 mm diameter of WSWM and CSWN under dynamic load. Additionally, the influence of the use of high tensile strength steel wire in the meshes (HSWM) compared to the previous ones, is analyzed to assess the scope in controlling rockburst events and keeping the safety of underground environment.

Apr 26, 2022

By T. T. Chen, J. L. Jambor, J. E. Dutrizac

A reconnaissance study of the neutralization potential of 30 diverse minerals, 28 of which are silicates and aluminosilicates, has shown that most of these minerals contribute minimally to the neutralization potential (NP) in standard static tests. Feldspars in particular give low NP values and would not be expected to attenuate the acidity to any significant extent in acid rock drainage settings. The BET-determined surface areas of the minerals vary considerably, and the large surface areas of some of the pulverized samples have clearly affected the NP values even though the standard static-test protocol was used for the preparation of the samples. The low NP values of most silicates and aluminosilicates are in general agreement with the laboratory-determined slow dissolution rates for these minerals. The results suggest that, in the prediction of whether rocks will be acid-producing, the most realistic measure is that of the carbonate content. In mine wastes from metalliferous ore deposits, the contribution to the NP by the non-carbonate gangue assemblage is unlikely to be more than a token amount until well after the establishment of an acid rock drainage situation.

Jan 1, 2000

By E. T. Tuzcu

Microscale information about single particle fracture can be incorporated into the macroscale model of the whole size reduction process in the mill. The ultrafast load cell (UFLC) device provides a substantial amount of information about fracture characteristics of a particle under impact loading. UFLC captures high-resolution compressive force signals during particle breakage. The measurement of the compressive force at the instant of fracture of the particle allows computation of a number of comminution-related particle properties, as well as the energy absorbed during fracture. In the current study, limestone particles 50 mm in size were fractured to obtain specific fracture energies. Then, based on the experimental data, two models were proposed to quantify the fracture process. The specific fracture energy distribution of the particles in the range of 6 to 50 mm was defined by the well-known Weibull distribution. The other model is a probabilistic fracture model. This model is a link between energy events occurring in a grinding mill and the breakage rates of particles. The impact energy spectra or energy events occurring in a grinding mill can be obtained with a discrete element method (DEM) simulation. One can model the breakage rates of the mill material by combining the energy spectra with the probabilistic fracture model. This novel approach for the modeling of breakage rates via DEM and UFLC is shown here.

Nov 1, 2011

By E. T. Tuzcu

Microscale information about single particle fracture can be incorporated into the macroscale model of the whole size reduction process in the mill. The ultrafast load cell (UFLC) device provides a substantial amount of information about fracture characteristics of a particle under impact loading. UFLC captures high-resolution compressive force signals during particle breakage. The measurement of the compressive force at the instant of fracture of the particle allows computation of a number of comminution-related particle properties, as well as the energy absorbed during fracture. In the current study, limestone particles 50 mm in size were fractured to obtain specific fracture energies. Then, based on the experimental data, two models were proposed to quantify the fracture process. The specific fracture energy distribution of the particles in the range of 6 to 50 mm was defined by the well-known Weibull distribution. The other model is a probabilistic fracture model. This model is a link between energy events occurring in a grinding mill and the breakage rates of particles. The impact energy spectra or energy events occurring in a grinding mill can be obtained with a discrete element method (DEM) simulation. One can model the breakage rates of the mill material by combining the energy spectra with the probabilistic fracture model. This novel approach for the modeling of breakage rates via DEM and UFLC is shown here.

Jan 1, 2011

By Nagashi Ogushi

Geochemical prospecting method using stream sediments, soils and rock chips has been tested to see the applicability for the typical Kuroko field in Japan. Three independent anomalies have been detected in maps being shown by grav densities of cells which are represented by the results of factor analysis as well as distribution of minor elements scaled in logarithm. A small vein type mineralization which has outcrops could be attributed to the origin of them whereas the one near the surface of known Kuroko deposit to a coincidence. The addition of drill core geochemistry is required to complete the interpretation.

Jan 1, 1982

By Y. T. John Kwong

Modified after procedures for assessing acid-generating potential of coal spoils, most acid-base-accounting (ABA) analyses inadequately characterize highly varied metal deposits. Although mineralogy critically controls acid generation and metal leaching, acquisition of appropriate data and their interpretation are poorly developed. Metal loading rates are commonly determined by kinetic testing, which rarely duplicate actual field samples and conditions. Accurate predictions and reduced assessment costs can conceivably be achieved by (i) use of geochemical analyses to define surrogate indicators; (ii) intelligent acquisition and use of mineralogical data; and, (iii) compilation of geo-environmental ore-deposit models to validate inference based on detailed geology.

Jan 1, 2000

By M. R. Yalamanchili

Recently, noequilbrium electrokinetic measurements using laser-Doppler electrophoresis were reported by Miller et al. (1992) for alkali halides and the sign of their surface charge thus determined. These results are generally as expected from simplified lattice ion hydration theory with KCI, under normal circumstances, being the most significant exception. In this regard, lattice defects (F centers and oxygen imperfections) have been found to influence the surface charge of KCI and its electrophoretic mobility. In particular, the presence of oxygen defect states in the crystal lattice has been found to be responsible for KCI's unexpected behavior. The concentration of oxygen defect states in KCI, as characterized by UV/Vis absorption, was varied in order to study their influence on the electrokinetic behavior and subsequently on the flotation response of KCl. At low oxygen contents « 60 ppm) KCI is positively charged as expected from lattice ion hydration theory. However, typically, KCI contains substantial oxygen (>300 ppm) sufficient to impart a negative surface charge which accounts for the selective flotation of KCI from NaCl by hetero-coagulation with oppositely charged alkyl amine hydrochloride collector colloids.

Jan 1, 1994

By M. K. Larson, J. K. Whyatt

Proper employment of numerical stress analysis design tools is based on the demonstrated ability of a model to capture key elements of the geologic site model and accurately simulate how these elements interact with a mine design. While these tools have progressed markedly, they are, at heart, a gross simplification of the abundant complexity of a natural setting and its response to mining. A generic deep longwall site model was developed that includes aspects of the geology of deep coal mines in the Wasatch Plateau and Book Cliffs coal fields of Utah. The site model contains a set of common features and observations of how these features typically respond to mining. This site model was the basis for evaluating use of empirical, boundary element and volume element stress analysis tools to analyze the distribution of stress around a deep longwall panel. More specifically, this evaluation examined shifting of stress to panel abutments and gob, distribution of stress in the abutment and deformation and failure of bridging strata. Measurements of abutment stress changes at two sites in the Wasatch Plateau region were used to illustrate model calibration. Overall, these comparisons highlight the considerable differences between methods. Volume element tools can incorporate considerable detail and have fewer underlying assumptions, but this detail carries a considerable computational cost. Boundary element tools are much more efficient. However, this efficiency comes at the cost of added assumptions. These assumptions were challenged by the presence of a strong sandstone unit in the overburden, leading to boundary element results that depart significantly from volume element results. Empirical rules are the simplest, but are even more burdened by assumptions, many of which are implicit in underlying cases. Insight into the nature and impact of underlying assumptions in each method is essential to the proper use of results in mine design.

Jan 1, 2009

By Jurgen H. Kleinau

This paper details Keeler/ Dorr-Oliver's experience with the application of fluid bed combustion technology to the burning of coal-mining waste. The designs of two stage fluid bed combustors/dryers are demonstrated as useful in the drying of coal, slag and coke, using coal and coal refuse (gob) as fuel. Anthracite mining refuse (culm) is more than abundant in Northeastern Pennsylvania. After demonstration at Shamokin, Pennsylvania, a full commercial-sized fluid bed boiler using culm is used for district heating in Wilkes-Barre, Pennsylvania. Limited research work has shown the utility of using fine coal as filter aid in sludge in¬cineration. With the rising avenues of the suitability of coal as auxiliary fuel in fluid bed sludge incineration, an expansion of these concepts combines the use of coal or coal refuse as filter aid and auxiliary fuel. Lime¬stone addition controls SO2 emission.

Jan 1, 1985

By B. C. Bhowmick, B. B. Dhar

Central system of ventilation, adopted almost universally in coal mines of India and elsewhere in the world, has often proved deficent in providing a cost effective solution to the acute ventilation problems of remote workings in many mines. Loss of air due to leakage through a number of stoppings, doors etc. and accumulation of heat and moisture by intake air on its way to a working through long and circuitous route are the main unavoidable reasons for low efficiency of the system, sluggish and oppressive ventilation of workings. Multi-zonal ventilation system using large diameter bore holes for feeding fresh air in the mine close to a working has been proposed as a viable economic alternative. The method promises to provide congenial environment at working faces without resorting to air conditioning or use of booster fan. Optimum location and diameter of bore holes as well as general design procedure have been dealt in the paper. Finally, the technical as well as economic advantages of the method over the conventional design have been highlighted with the help of a case study where ventilation system of an extensive shallow mine in Central India has been redesigned according to the old and the new concepts. The methodology is general enough for adoption elsewhere in other mines under similar circumstances.

Jan 1, 1993

By A. E. Isaacson

The U.S. Bureau of Mines is investigating a systems approach to metals recovery from leach liquors produced by in situ leach mining techniques. A successful in situ leaching process requires a thorough under-standing of the complex interrelationships that exist between leaching chemistry and metals recovery. Laboratory research is addressing these interrelationships in the solution mining of a copper oxide deposit. Laboratory tests have been conducted to gather baseline data related to the design and operation of continuous leaching-solvent extraction-electrowinning circuits. This paper addresses the findings of the baseline studies. Specific results include the characterization of simulated in situ leach liquors produced by leaching chrysocolla and chrysocolla-atacamite-bearing copper ores. Metal recovery procedures, utilizing four commercial solvent extraction reagents, are also characterized, and potentially troublesome leach liquor contaminants that may complicate waste management procedures are identified.

Jan 1, 1990

By Quanjun Liu, Rongping Lin, Rongdong Deng

Arsenic contamination significantly affects the quality of copper concentrates, presenting challenges during smelting processes. Considering that covellite and enargite have similar surface properties, they are difficult to separate by flotation, resulting in copper concentrates with excessive levels of arsenic. To address this issue, this study systematically investigated the flotation separation of covellite and enargite in microflotation and bench-scale flotation tests using calcium lignosulfonate as a depressant, with the results indicating that calcium lignosulfonate can be used to separate covellite and enargite because it enables the separation of arsenic-bearing copper minerals into high- and low-arsenic (As 0.57%) copper concentrates. According to contact angle and adsorption tests, scanning electron microscopy–energy dispersive spectroscopy, and X-ray photoelectron spectroscopy, the differential adsorption of calcium lignosulfonate onto covellite and enargite is the primary reason for their distinct flotation behaviors in the presence of calcium lignosulfonate. The selective depressive effect of calcium lignosulfonate provides a novel approach for improving the flotation separation of arsenic-bearing minerals from copper sulfide minerals.

Feb 28, 2024

By T. Tamagawa, I. Iwasaki, N. X. Fu, M. Kobayashi

A three-stage fluidizing-bed process consisting of chlorination, selective oxidation and sulfur chloride conversion was tested for processing chalcopyrite concentrate. It was found that the use of excess oxygen was essential for the stable operation of the oxidation reactor. The excess-oxygen gas inevitably causes the oxidation of the sulfide concentrate in the chlorination and sulfur chloride conversion reactors. A new flowsheet is proposed to separate the chlorination and selective oxidation steps with separate flow paths of the fluidizing gases, thereby, preventing the passage of excess-oxygen gas in the chlorination and sulfur chloride conversion reactors. The feasibility of the proposed flowsheet was demonstrated in a laboratoryscale fiuidizing bed setup.

Jan 1, 2002

By Deli Hu, Xiangze Shu, Cai Wang, Hongfu Liu

To detect the place and range of fire is one of the key technologies in the extinction of coal mine underground fire. A fire-prevention and extinction research team of Shanxi Mining College have successfully carried out a program detecting the place of fire with radon. In the past four years the authers have done the detecting work in several mines in Shanxi Province, such as Gujao, Xuangang Louan and Ningwu. The place and scope and the trend of underground fire of coal mine can be now exactly estimated. The data and information from detecting provide a reliable basis for drawing up the scheme to extinguish underground fire and extract mineral coal securely. The principle and method of fire detecting based on radon on surface, the data processing and analysis are discussed in this paper.

Jan 1, 1991

By A. Gupta, S. C. Srivastava, K. K. Saroj

Bacterial degasification of methane and conventional methane drainage for generation of power have become accepted practice. Comparative economies of both the techniques have been described. Authors have discussed an alternative technique, involving complete methane biocycle. The first stage of the entire process involves gasification of coal using a consortia of bacteria to generate methane. The generated methane has been proposed to be pumped,as in conventional methane drainage. Technique described is basically similar to underground coal gasification, with the difference that in place of coal combustion, degradation of coal to lower molecular weight compounds by one set of bacteria and then methanogenesis by methanogens, producing methane have been described. Brief account of communities of bacteria that may be employed have been dealt with. Three arguments in favour of proposed technology as an alternative to conventional coal mining are: 1.Total elimination of hazardous operation. 2.Availability of power plants based on methane drainage, assuring comparative economies. 3.Possibility of utilisation of fuel cell technology for power generation giving higher efficiency. All the three phases of complete blocycle viz (1) methane generation from coal (ii) conversion of methane to hydrogen and oxygen (iii) conversion of products so obtained to methane, thereby completing the cycle have been discussed. INTRODUCTION Drainage of methane by conventional pumping process (Boxho,et.al.,1980) not only is helpful in maintaining safe extraction of coal, but with utilisation of extracted gas for power generation, also helps in over all economy of coal mining. This is gradually becoming standard practice for mining of coal in highly gassy mines. An alternative technique (Thakur et. al., 1991) of bacterial degasification of coal seams is also gradually gaining ground. The bye products of this process that is carbondioxide and water, do not contribute towards economy of coal extraction process. However the technique has its own advantage particularly in goaf area for avoiding fire hazard and drainage of methane from coal seams prior to initiation of mining operation. Either of these techniques could be applied in specific situations with success.

Jan 1, 1993

By Ehsan Alavi, Eren Kusdogan

The City of Toronto’s Coxwell Bypass Tunnel is currently being constructed by North Tunnel Constructors ULC, a joint venture of Jay Dee Canada, C&M McNally Tunnel Constructors and Michels Canada. This project includes construction of approximately 10.5 km of 6.3 meter finished diameter rock tunnel, five 20 meter diameter storage shafts and eleven tunnel connection drop shafts, along with associated deaeration and adit tunnels. This paper describes progress on the project to date and reviews the risk mitigation measures utilized on the project to move the project forward through tough geological conditions during shaft excavation and tunneling phase of the project.

Jun 13, 2023