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By A. L. Mular

In order to simulate a grinding circuit, it is necessary to obtain valid mathematical models of the grinding mills and classifiers in the circuit. Several models of grinding mills Ova been proposed 1,2,3 and models of cyclone classifiers are available 4,5. Those models developed by Lynch et. al. 3,5 have been tested in the plant, so that some degree of reliability can be placed on them. Because of this, it is reasonable to assume that the Lynch models will apply for a given circuit, and then to test this assumption. Empirical modifications are made as necessary for a given situation. Usually, valid simulation models can be modified slightly to provide control models6,7. The purpose of this paper is to describe the results of an approach taken by Mular8 to obtain the Lynch models of parallel cyclone classifiers being used in the A-circuit of the new Strathcona Mill***.This was one of the projects undertaken by the fourth year Metallurgical Engineering Class of 1969, Queen's University, Kingston, Ontario, Canada, as part of their process design course which cooperates closely with the Canadian metallurgical industry.

Jan 1, 1970

By M. Manrique

Various pyrometallurgical methods for treating Ilmenite and Zircon concentrates are reviewed. Laboratory experiments, using a thermal plasma reactor, have been performed to evaluate: the conversion of ilmenite to TiC or TiC-Fe and the conversion of zircon to ZrC or ZrC-SiC. Results are examined and possible processing routes are identified.

Jan 1, 1996

By Stephen C. Moore

The Grossschloppen vein-uranium deposit, Bavaria, West Germany, was examined utilizing underground workings during 1980-82 by Esso Erz GMbH, an affiliate of Exxon Minerals Company (EMC). Geologic evaluation entailed dense drilling of a portion of the deposit from workings constructed specifically for the program. Discovered in 1977, the deposit was initially explored by surface diamond drillholes which allowed definition of a 30-60 m wide vein system discontinuously mineralized along a 1000 m strike length and to at least a 450 m depth. The underground program was conceived as a cost effective procedure to answer questions on vein correlation, grade continuity and variability. A 1200 m decline allowed access for detailed sampling of approximately 10% of the known area of mineralization. Fanned drillholes, logged by gaga probe, were spaced to provide intersections of veins at 10 to 20 m intervals. Six cross cuts also penetrate the pitchblende and uranophane mineralization which occurs in 0.1 to 2.5 as thick quartz veins. Detailed cross-sections and level plans were constructed for resource estimates of the intensively studied portion of the vein system. The program resulted in the discovery of local, high grade areas and an average grade in the evaluated area nearly double that expected from surface drilling.

Jan 1, 1983

By J. G. Pippenger

Rio Tinto Coal Australia (RTCA) developed Meandu Mine in Queensland, Australia in 1983 to supply thermal coal to the adjacent newly constructed Tarong Power Station (TPS). In designing the mine, RTCA selected Meandu?s best economic reserves for a 25-year life based on station owner Tarong Energy Corporation?s (TEC?s) estimated life for TPS. That 25-year plan changed dramatically in the early 2000s when TEC approved life extensions to TPS?s four existing units plus construction of a fifth unit. After reviewing Meandu?s remaining reserves, RTCA decided the nearby Kunioon reserve offered the more economic option for maintaining deliveries beyond 2010. Those plans changed yet again in 2007 when TEC chose to purchase the Meandu Mine and nearby reserves rather than extend RTCA?s contract. TEC then selected Thiess Pty Ltd (Thiess) to continue operating Meandu until the new mine at Kunioon could be developed.

Jan 1, 2011

By I. H. Gundiler

A pilot-plant flotation concentrate containing 21.6 g/t gold and 2 kg/t silver was used for this study. Base-line cyanide and thiourea tests showed 30-40% extraction of both gold and silver. After roasting (450-750C), the maximum gold extracted was 89% with thiourea and 76% with cyanide. Pressure oxidation tests were conducted following a statistical experimental design in a 2L laboratory autoclave at 10% pulp density, and the residues were subsequently leached in acidic thiourea solutions for 2h. Leach results were presented in the form of contour maps, and optimum autoclave conditions were determined for maximum gold extraction (93%). However, silver extraction was only 7% when gold extraction was maximized.

Jan 1, 1992

By W. Petruk

An investigation was conducted to determine the minimum number of samples that must be studied by image analysis of polished sections in order to characterize a mill product and to determine the apparent mineral liberation. It was found that a representive polished section cannot be prepared from an unscreened sample that has a wide size range of particles. Similarly individual screened' fractions are not representative of the sample because minerals are partitioned during screening. Consequently the quantities of soft brittle minerals are increased in fine grained fractions and quantities of hard minerals are increased in coarse grained fractions. It is assumed that results obtained by combining data for a series of narrow size range screened fractions (1 Tyler size range) are representative of the sample, and relatively accurate apparent mineral liberation data can be obtained for a mill product by analysing each fraction and combining the data. Somewhat less accurate data would be obtained by analysing a series of screened, fractions that have a wider size range of particles (5 Tyler size ranges). Mineral liberation analyses show that the most reliable apparent mineral liberation in each screened fraction is a value taken from a smooth curve drawn through the lowest points on a graph of % free vs size. A correlation between the apparent mineral liberation in screened fractions and calculated mineral liberations using Kings liberation model is good for sphalerite but not for chalcopyrite and galena.

Jan 1, 1985

By James W. Estep

The sulphur shortage that has occurred in the past two years has directed attention more and more toward sour natural gas reserves, Wellhead values of sour gas vary widely depending upon the acid gas composition, location, market conditions, and necessary processing charges. Preparation of a saleable residue gas is considerably more involved and expensive than that normally encountered in treating a sweet gas. Recent revisions in sales gas specifications have increased capital costs and processing charges. The presence of hydrogen sulphide and carbon dioxide in a natural gas contributes to shrinkage factors that may approach 50%. Fuel required by the gas sweetening process and sulphur slant tail gas incineration also contributes to a further reduction in the volume of residue gas available for sale. The additional processing facilities involving gas sweetening, mercaptan removal, expanded utilities, sulphur recovery and sulphur handling, all demand additional operating and maintenance staff. A favorable sulphur market under certain conditions may justify the processing of sour gas whereby sulphur is either a by-product or a co-product, Five typical cases involving different compositions of sour gas are presented for evaluation. Capital costs, operating problems, and operating costs are presented in detail for full economic evaluation

Jan 1, 1967

Lignite is a kind of easy-to-slime and low rank coal. It is hard to be separated by the conventional wet coal beneficiation technologies. Meanwhile, in recent decades, a large amount of fine coal (-6 mm) is generated as the mechanized mining technology has been progressively deployed in coal sector, which causes a great difficult for lignite beneficiation and upgrading due to lack of efficient technology available. In this paper, a vibrated gas-fluidized bed was used to separate the -6 mm fine lignite particles. Separation experiments of -6+3 mm and -3+1 mm lignite were carried out in a laboratory-scale vibrated gas-fluidized bed. The effects of several parameters including the superficial air velocity, vibration intensity, bed height and exterior moisture content on the separation performance were experimentally studied. The results show that the optimal separation performance was achieved when the superficial air velocity is 0.3, the vibration intensity is 1.4, the bed height is 50 mm, the exterior moisture content is below 4% (-6+3 mm) and 2% (-3+1 mm). And the probably error E values of -6+3 mm and -3+1 mm size fraction of lignite are 0.202 and 0.225 respectively. The results indicate that a vibrated gas-fluidized bed can provide an effective solution for -6 mm lignite separation.

Feb 23, 2014

By B. K. Cantrell

A miner working in an underground coal mine with diesel equipment is exposed to a wide array of pollutants from the diesel exhaust. These include CO, CO2, NO, NO2, SO2, diesel-exhaust aerosol, and a variety of hydrocarbon compounds. A quantitative definition of the health risk resulting from these exposures remains elusive, but during the past several years, progress has been made in defining the problem. Results from epidemiological studies by Garshick, et al. (1988); animal inhalation studies by Mauderly, et al. (1986); Iwai, et al. (1986); and Brightwell, et al. (1986); and in vitro studies by Lewtas, et al. (1986), have provided sufficient data for the National Institute of Occupational Safety and Health (NIOSH) to recommend that "whole diesel exhaust be regarded as a 'potential occupational carcinogen,' as defined in the Cancer Policy of the Occupational Safety and Health Administration," NIOSH (1988). NIOSH further stated that "though the excess risk of cancer in diesel-exhaust-exposed workers has not been quantitatively estimated, it is logical to assume that reduction in exposure to diesel exhaust in the workplace would reduce the excess risk."

Jan 1, 1990

By D. K. Dysinger

The U.S. Bureau of Mines investigated leaching of chalcopyrite with sulfuric acid-oxygen under conditions anticipated during in situ leaching. A central composite experimental design was chosen to study oxygen pressures of 150, 300, and 450 psi, leach temperatures of 35?, 65°, and 95° C, oxygen-to-chalcopyrite mass ratios of 0.5, 1.0, and 1.5, leach times of 8, 16, and 24 hours, initial acid strengths of 0.6, 1.2, and 1.8 g H2SO4/g chalcopyrite and pyrite to chalcopyrite mass ratios of 0, 1, and 2. The leaching kinetics were consistent with the shrinking core model. A quadratic response surface model was used to determine linear and interaction effects of the design factors on rate constants from Arrhenius correlations.

Jan 1, 1993

By F. G. Miller

It is generally accepted that sulfur exists in coal in three forms: (1) pyritic, (2) organic, and (3) sulfate sulfur. Sulfate sulfur usually makes up less than 1% of the total sulfur content. Pyritic and organic sulfur, make up almost all of the total sulfur and occur in varying amounts in different coals and can vary greatly in coal of the same seam Pyritic sulfurs of 20% to 80% of the total sulfur have been reported Other authors have shown that it is not possible to remove the organic sulfur without chemically altering the coal. Chapman and Jones (1) state: "Organic sulfur, unlike pyritic sulfur does not exist as discrete particles, but is intimately associated with the coal structure, and as such it is not possible to remove it or reduce its concentration by physical means." Any success in removing sulfur has come about by removing pyritic sulfur by physical means; therefore, removal of sulfur in the pyritic form is the subject of this investigation. The extent to which any impurities can be removed from a particular coal can be determined by a washability study. Outside of crushing coal, to finer sizes or chemically altering the coal, there are no known methods of changing this inherent washability characteristic. The efficiency of various methods used to remove impurities can be determined by comparison of results produced at a yield to the results as shown by a washability study. In recent years heavy media processes have proven their ability to wash plus 28 mesh coal and nearly produce results shown to be theoretically possible by the washability study. Therefore, it is the objective of this paper to show various methods of treating the finer fractions of the coal, in the hope of developing a process, which can effectively produce in the fine fractions the efficiency of heavy media devices in the coarse.

Jan 1, 1963

By A. Suarez, M. Menendez, M. R. Gent, P. Riesgo

"Recent requirements to reduce thermal coal plant emissions, and ultrafine coal's tendency to produce these emissions due to its typically high ash and moisture contents have limited the use of ultrafine coal. Ultrafine coal in beneficiation plants are usually either disposed of in tailing ponds at a loss in combustible material or disposed of by blending with coarser higher-grade products, resulting in a reduction in marketed product quality. A study of the options for processing ultrafine coal, consisting of < 200 µm hydrocyclone overflow, with 38.8 percent ash content is presented here. Ultrafine coal was processed based on 200-µm sieve bend and 10-µm hydrocyclone classifications, enhanced gravity separation (EGS) and froth flotation concentration as well as combinations of these. Yield, combustible material recovery (CMR) and product humidity were evaluated as test results.Depending on the processing applied, product ash content could be reduced up to 49.7 percent, and up to 95.8 percent CMR of the actual run of mill feed could be attained. All of the processing options analyzed could reduce produced thermal electric plant emissions due to ash and moisture from 22 to 38 percent of the actual unprocessed ultrafine coal product.Froth flotation was found to be the optimal process, yielding a product with the lowest ash content attained of 19.5 percent and CMR of 92.3 percent. Being the most versatile of the processes evaluated, it is capable of producing coal with varied ash contents but is subject to potential variations in coal flotability. The most complicated of the processing options, a combined sieve bend recovery of the > 200 µm fraction and EGS processing of the 10 to 200 µm fraction was found to be the next best option, attaining a combined 90.1 percent CMR and 25.0 percent ash content. IntroductionMunicipal, regional and national objectives to reduce fossil fuel combustion emissions and their effects on air quality and global weather changes are affecting thermal electric plant operations. Plans and regulations such as President Obama's Clean Power Plan (U.S. Environmental Protection Agency, 2015), the European Directive 2010/75/EU (European Commission, 2010) and China’s proposed Enhanced Actions on Climate Change (Wei, 2015) are of major significance to thermal electric plant operations. Although thermal plant efficiencies depend in large part on the losses of heat by plant components, the ash and humidity contents of thermal coal invariably reduce plant efficiencies and increase emissions of carbon dioxide (CO2), nitrogen oxides (NOx) and dust.Any noncombustible material present in thermal coal will result in higher CO2 emissions per unit of energy produced. Since no particle emission control can be totally effective, it is to be anticipated that any reduction in coal ash content will also result in reduced particle emissions. Kurose, Ikeda and Makino (2001) reported that NOx emissions also increase with coal ash content. The effect of coal moisture content during combustion is complex. Kurose, Ikeda and Makino (2001) showed that an increase in coal moisture content significantly reduces thermal NOx to total NOx production, and Bosoaga et al. (2006) showed that it tends to reduce NOx emissions. Since the humidity, pyrite and ash content of thermal coals directly affect thermal electric plant efficiencies and emissions, minimizing these factors should facilitate, at least in part, compliance with thermal electric plant emission limits. This, in turn, would affect the specifications and prices of the coal preparation plant products."

Jan 1, 2016

By W. W. Wen

Approximately 3 percent of the raw coal processed in U. S. Steel coal-preparation plants ultimately reports to slurry- tailing disposal. The usual disposal method is to pump the refuse slurry containing the minus-48 mesh (300 µm) refuse into dams or impoundments that are constructed of the coarse refuse. The failure of an impoundment at Buffalo Creek, Saunders, West Virginia and the sliding failure of a coarse refuse pile at Aberfan, Wales, England, resulted in an evaluation of refuse disposal methods by various regulatory agencies as well as coal producers. The result of this evaluation was the promulgation of Federal regulations dealing with the construction, operation, and final abandonment of coal refuse disposal areas. As a consequence of these regulations the use of the landfill/impoundment method of disposal became in some cases economically urlfeasible or technically impossible. U, S. Steel has studied a number of alternative methods of refuse disposal. During an investigation of mechanical dewatering with a pressure filter, Portland cement was added to the slurry to solidify the filter cake. Because of the success of the cement addition it was decided to study the stabilization of fine-coal-refuse slurry through use of cement-type additives.

Jan 1, 1979

By Yanan Zhang, Hongwei Deng, Feng Gao, Bo Ke

Recently, liquid carbon dioxide (L-CO2) blasting technology has attracted attention due to its good fracturing effect and safety performance, especially in coal seam permeability improvement. This paper analyzes the blasting effect of L-CO2 based on experiments and studies the fracturing mechanism from the perspective of stress wave action via theoretical analysis and peridynamic simulations. The results indicate that L-CO2 blasting achieves a good fracturing effect without forming a crush zone, and the loading rate and strength of the stress wave are key factors.

Jan 19, 2022

By Ulf B. Andersson, Christina Dahnér-Lindkvist, Bruno Figueiredo, Jessa Vatcher, Jonny Sjöberg, Joel Andersson

Hydraulic fracturing to precondition the rock mass in high seismic risk environments has great potential. Unfortunately, there are many unanswered questions about how to best implement a hydraulic fracturing program at individual mine sites, and even how to best use our engineering tools to evaluate these plans. To give the hydraulic fracturing field tests at LKAB’s Kiirunavaara Mine the best chance of success, fully-coupled, discontinuum numerical modelling Itasca’s 3DEC code was used together with statistical simulations of the fracture network. For modelling purposes, it was assumed that hydraulic fracturing successfully reduces seismic risk through 1) the creation of hydraulic fractures along a plane at each injection site, and 2) activation of existing discontinuities. A variety of scenarios for the mine were evaluated, which focused on site specific uncertainties (such as the spacing of the pre-existing discontinuities) and practical solutions (such as the hydraulic fracture spacing, selection of injection medium, and hydraulic fracture site location relative to production). The discrete fracture network (DFN) realizations were developed using available statistical data for discontinuities near where hydraulic fracturing was planned.

Apr 26, 2022

By CHONG WEI, TATYANA KATSAGA, DEREK APEL

This study provides an effective determination process of the interface microstructural parameters in the numerical modelling of the mechanical interaction between two different geomaterials involved with frictional-bonded interfaces, such as the interaction between backfill columns and the surrounding rocks, or the soil-structure interaction, by using the coupled finite-difference and discrete-element (FD-DE) method. Three-dimensional numerical direct shear tests were conducted on the coupled FD-DE model of the combined rock-cemented rockfill (R-CRF) specimens with the frictional-bonded interface. With the microstructural parameters determined, the macro-mechanical properties of the interface of the coupled model were calibrated to well fit with the theoretical values of the combined specimen under the direct shear condition assumed according to the Mohr–Coulomb strength criterion. Evident elastoplastic shear behaviour was observed on the interfaces, and excellent agreement was attained between the shapes of the theoretical and simulated shear stress-displacement curves of the coupled models at different servo-controlled normal stresses. Particulate-scale force chains inside the DE model of the CRF specimen were highly consistent with the force contour on the FD model of the rock specimen, demonstrating the shear stress evolution of the coupled model at different shear displacements. Parametric studies verified the effects of the deformation properties of the interface parallel bonds on the shape of shear stress-displacement curves of the coupled models. The test results validated the feasibility and rationality of the coupled FD-DE method for modelling the combined specimens with frictional-bonded interfaces or joints. Furthermore, this study provides valuable numerical modelling experience for investigating the shear behaviour at the interface between cemented backfill columns and surrounding walls by using the coupled FD-DE method.

Nov 2, 2021

By Piyush Rai, Suresh Kumar Sharma, Punit Paurush

The present study has been conducted in surface limestone mine to select the controllable blasting design parameters affecting the peak particle velocity (PPV) for assessment of ground vibration. The study aims at using two prominent statistical tools, namely, principal component analysis (PCA) and stepwise selection and elimination (SSE) techniques for identifying the key controllable parameters affecting the PPV. For determining the correlation coefficient between blasting design parameters and PPV from 44 field scale trial blasts, multi-variate linear regression (MLR) technique was done. It was found that the PCA and SSE eliminated a huge number of controllable parameters to identify the most important parameters, affecting the PPV. The PCA eliminated 6 number of parameters while SSE eliminated 5 number of parameters, and the coefficients of determination (R2) obtained were 0.616 and 0.584 for PCA and SSE respectively. The predictor equations were evolved, and these equations were used to validate the PPV results for another set of 21 field scale trial blasts. The predictor equations have been found to be fairly accurate in predicting the PPV values. Further, the PCA technique provides very near prediction of PPV with high degree of correlation in comparison to SSE technique. The paper highlights the role of state-of-art statistical tools in selecting the blasting design parameters affecting the PPV in field-scale blasting.

Mar 1, 2021

By AMIT SHARMA, BIBHUTI BHUSAN MANDAL

Operators of mining vehicles are exposed to high levels of whole-body vibration (WBV) and are therefore at risk of developing vibration-related health disorders. For implementing an effective control strategy, it is imperative to locate the source(s) of vibration, and the specific changes that might occur to the vibration signals during its transmission through the seats to the recipient human body. With this objective, Seat Effective Amplitude Transmissibility (SEAT) values of seat modules used in dumpers (n = 10) and other heavy earth-moving machines (n = 11) were evaluated in an iron ore mine. Vibration was measured simultaneously on the seat and on the cabin floor beneath the seat using tri-axial and uni-axial accelerometers. The study aims at determining the quality of seat modules of the transport and non-transport vehicles from the perspective of their natural resonance frequencies and capability of any such seat in reducing harmful vibration. The highest acceleration values were observed in the z-axis for all the dumpers. SEATrms values ranged from 78 to 133% and SEATvdv values ranged from 72 to 130% for the dumpers. For other HEMMs, SEATrms values ranged from 55 to 125% and SEATvdv values ranged from 56 to 123%. Mechanical vibration contains multiple frequency components. To understand the changes taking place to the different signals at these frequencies, 1/3 octave band analysis was carried out for the signals recorded both on the seat and the floor. There was significant attenuation (38 to 57%) at 4 Hz for three Dumper seats, whereas they resonated in the range of 1.6–2.5 Hz. The transmissibility(%) in the resonating frequencies ranged from 108 to 156%. Resonance frequencies for the remaining seven dumpers ranged from 3 to 8 Hz. The spine has been reported to resonate at 4 Hz, whereas resonance at 1.6 Hz has little significance to human beings in regard to WBV of a seated person. Hence, the characteristic resonant frequency of 4 Hz of seats as observed in the present study has the potential of causing adverse impacts on spinal health. Evaluation of SEAT factors and resonance characteristics of seats are therefore recommended to be examined while selecting a mining vehicle for regular deployment in mines.

Mar 12, 2021

By F. M. Benavides

The mining complex being analyzed consists of four mines and two processing plants located in an area where there are several existing modes of transportation. Figure 1 shows a map of the general layout of the four proposed mines and the two existing processing plants. The mines are identified by the numerals "I" through "IV" and the plants by the letters "A" and "B". A proposed overland conveyor would collect the product from all four mines and convey it to Processing Plant A. Alternate transportation systems are as follows: Railroad transport from Mines I and II to Plant B; Highway trucking from Mines I and II to Plant A; Off-the-road truck haulage from Mine III to Plant B and from Mine IV to Plant A. River transportation from the mines to the processing plants was not considered in this study under the assumption that the high capital investments for the loading and unloading facilities, in addition to difficult traffic problems, would make this mode of transportation unattractive.

Jan 1, 1980

By K. Terhaar

The objective was to determine operating protocols for a lead and silver column flotation cleaner, being considered for installation at Sunshine Mining & Refining Co.&apos;s Kellogg mill in Northern Idaho. In this column, tetrahedrite and galena were floated, and pyrite and other gangue minerals, including siderite and silica, were depressed. The procedure was to develop a dynamic simulation using a linear transfer function approach. The transfer function related cause and effect variables such as the influence of collector and depressant dosages on recovery and grades. Bench-scale flotation tests followed by pilot column testing provided the data used to develop a linear transfer function. The transfer function was derived using a spreadsheet. This model was applied to simulate how the flotation column could be made to respond to disturbances in feed grade. The results were that xanthate, zinc sulfate, and sodium cyanide were found to be suitable controls for grade and recovery. Simulations showed the best sequence of manipulations of these reagents, and these sequences were useful for future operator training. The conclusion was that linear transfer functions were able to simulate lead and silver recovery, develop scenarios for operator training, and provide a foundation for future on-line control.

Jan 1, 1999