Search Documents

By P. G. Semple, K. W. Major, R. M. Nendick

As free milling oxide gold ore reserves are depleted, more mining companies are having to evaluate the available alternatives for treating refractory deposits. The selection of a treatment process can be very difficult; and, despite the claims of their respective proponents, there is no one process that will continuously prove superior. Selection of the optimum process for an individual deposit is contingent on the size of the deposit, the grade of the deposit and the refractory nature of the ore. Since extensive metallurgical test programs are usually required to determine the optimum extraction process, an inappropriate initial selection may prove costly and time consuming. This paper discusses the steps involved in evaluating a refractory ore in order to expedite the evaluation of the required process through the feasibility study stage.

Jan 1, 1990

By J. T. Ryan, Griffin. Wayne H.

This paper shows that if a drift has a brattice which is sufficiently leaky, changes in the operating point of the fan depend solely on the volumetric efficiency within the drift. Under this high leakage condition, an increase in the length of the drift causes very little shift in the fan operating point. For less leaky brattices, the operating point depends on both the fan characteristic curve and the volumetric efficiency. It is shown that for the fan curve and drift parameters used in this paper the fan operating point in a drift with a volumetric efficiency of 50% is essentially the same as a drift which has a zero efficiency. In this region of efficiency, an increase of 300% in the length of the drift causes only a 3% increase in fan operating pressure.

Jan 1, 1993

By M. S. Celik, G. Onal, S. Atak, A. A. Abramov

An oolitic phosphate ore composed of phosphate (mainly francolite) and carbonates as gangue has been tested for the suitability of the reverse flotation process. The samples were first ground autogeneously followed by the reverse flotation process. While the carbonates were floated by sodium oleate the phosphate was depressed by phosphoric acid. The effect of particle size, reagents type and concentration on flotation recoveries have been investigated to determine the optimum conditions. By this process, a run-of-mine ore containing 16.72 % P205 was upgraded to 28.00% P205 with a recovery of 77.0% The mechanism of optimum flotation with phosphoric acid observed at pH 6.3 is explained based on a relationship involving surface potentials and the ratio of required collector concentrations for the respective minerals.

Jan 1, 1993

By S. Subbarayan, S. Chander, M. S. Klima

A laboratory study was conducted to investigate the potential for recovering anthracite from coal preparation-plant tailings. The study included washability analyses, cyclone simulations and froth flotation testing Samples were collected from either the tailings streams or the slurry ponds of five anthracite-cleaning plants. From each sample, a washability analysis was conducted on the 28x100 and 100x200-mesh fractions. Using the above data, along with published partition data, simulations were performed with various cyclone-staging arrangements for both water-only and dense-medium cyclones treating the 28x200-mesh fractions. Separate froth -flotation tests were conducted on the 28x100- and 100x200-mesh fractions from three of the plant samples. The washability, simulation and flotation results are presented as grade-yield curves.

Jan 1, 1996

By Thornton L. Neathery

A small area in the Alabama Piedmont was studied to determine if metallic enrichment was associated with local magnetic anomalies. Cores from two holes in these magnetic anomalous areas have sulfide (pyrite, pyrrhotite, chalcopyrite) film on slicken-side and fracture surfaces. Two hundred and fifty soil samples were collected from the top of the "B" horizon on 1, 000 foot centers over the general trend of magnetic anomalies. Soil samples were leached with a 1:2. 7 mixture of HF and H2SO4 and the dilute filtrate analyzed for Cu, Pb, Zn, Ni, Co, Cr, Mo, and Cd, using atomic absorption methods. Concentration-value maps were prepared for each element. Small areas of anomalous concentrations were defined for Cu, Pb, Zn, Mo, and Ni. Some of these areas generally coincides with magnetic anomalies. Concentration values (ppm) range from: Cu 165.0 - 0. 5; Pb 265. 0 - 0.0; Zn 1386.0 - 43. 0; Ni 187.0 - 10.0; Co 207.0 - 6. 5; Cr 117.5 - 2.0; Mo 95.0 - 0.0; and Cd 32. 5 - 2.0. Studies of other magnetic anomalies appear warranted.

Jan 1, 1972

By Christopher Haycocks, Lawrence P. Johnson, George M. Neall, James M. Townsend

INTRODUCTION Conventional roof support methods such as mechanical and resin bolting provide adequate support for a wide variety of coal mine roof conditions. However, roof falls remain the single largest cause of death and injury in underground mines and seriously hamper production in many operations, demonstrating that these methods of roof support are not universally effective. One of the most recent and successful advances in coal mine roof control has been the introduction of the roof truss. Although past work on roof trusses (Gambrel1 and Haynes, 1970; Sheory, et al, 1973) shows little quantification of this support technique, numerous field examples have been cited where the truss effectively supported roof which could not be controlled by either mechanical or resin bolts (Kegel, 1969). The truss combines the advantages of both inclined roof bolts and post-stressing the roof. However, the full benefits of roof trusses will only be realized when design criteria to optimize support capacity are determined. The number of trusses required for a given roof condition can then be minimized, reducing installation time and making them economically more feasible. The purpose of this research is to develop roof truss design criteria based initially on laboratory studies of gravity-loaded multi-layered photoelastic mine models. Laboratory test results will then be modified where necessary following future field testing. The ensuing relationships should provide the field engineer with a reliable means of calculating optimum truss configuration, capacity, and spacing for a set of known roof conditions.

Jan 1, 1977

By R. D. Grove

The control of Florida phosphate flotation plants is largely based on the visual observations of experienced operators, both in recognizing good and bad froth conditions and in making judgments about the composition of feed, concentrate and tailing streams. Chemical analyses lag the process by at least two hours and, therefore, only assist in recalibrating the operators' vision when major deviations occur. An image analysis system was developed by IMC Fertilizer to improve the accuracy and precision of the composition estimation process. It still relies on the operator taking a representative sample, but provides a measurement in about 15 minutes after that sample is obtained. Background The search for a quick and inexpensive technique for estimating phosphate flotation stream composition continues. There have been attempts at using "wet chemistry," nuclearmagnetic resonance, neutron activation, X-ray diffraction and other techniques reported on in the past several years. None of these have yet found its permanent place in the flotation plants of the Florida phosphate industry. IMC attempted to use wet chemistry to provide 7.5-minute estimates of final concentrate insol and tailings BPL. This was aborted after 36 months of plant operation due to the high operating costs for chemicals and an operator. There was also no significant economic improvement in the plant's operation. Another factor was the necessity to limit these crude analyses to only a few process streams, which were insufficient to achieve improved plant operation.

Jan 1, 1993

By Harold D. Stevenson, Gerald G. Carlson

The Flow-Through Shares Program was set up by the Canadian Federal Government in 1978. While initial annual expenditures in flow-through shares was small, recognition of flow-through as a significant tax advantage combined with exploration successes, particularly in the gold sector, soon resulted in the majority of exploration dollars raised in Canada utilizing the flow-through share mechanism. What Are Flow-Through Shares As many exploration companies are non-taxable, they are not in a position to benefit from the tax deductions arising out of their exploration activities. Flow-through financing provides a mechanism for the exploration company to transfer these deductions to an investor. In addition to the deductions which an investor can apply against his personal income, the investor receives common shares in the exploration company (flow-through shares). To add to the attraction, the Federal government provides a 33 1/3 percent mark-up on qualifying expenses incurred by the exploration company, giving the investor a deduction of up to $1.33 for every $1.00 invested. By providing the investor with tax deductions in addition to the flow-through shares, flow through shares can often be sold at a premium to market which makes-the mechanism attractive to the exploration company as well. These shares are often sold through private placements and therefore have to be held for one year. The tax cost of the share is deemed to be ril, so the entire proceeds on disposal are

Jan 1, 1987

By Raja V. Ramani, Sachin Shankar

Re-entrainment refers to dislodgement of particles deposited by both atmospheric and nonatmospheric processes and their subsequent insertion into a flowing field. Formation of sand dunes, snow drifts, soil erosion and fugitive dust emissions are a few examples of the natural occurrence of re-entrainment. Re-entrainment studies have been done for the estimation of potential hazards from nuclear fallouts. The phenomenon of re-entrainment has been utilized for the cleaning of wafers and filters. Re-entrainment is associated with both surface and underground mining activities. However, studies on dust re-entrainment in mine atmospheres are limited. Understanding the re-entrainment phenomenon is important because dust particles lying seemingly harmless on the ground and adhering to numerous surfaces can get re-entrained and become a health and safety hazard. There are significant differences in the kind of re-entrainment encountered in underground mines and those in other fields of interest. These major differences are air velocity, direction of air flow, particle size, amount of particles, and time of exposure. While numerous studies have been done in other fields to identify the role of interacting variables and their contribution to the mechanisms of re-entrainment, no similar reported work is available for dust in mine atmospheres. In this paper, recent research efforts on re-entrainment are reviewed. The most suitable form of representing re-entrainment in underground coal mine atmosphere is presented. Various approaches to studying re-entrainment phenomenon in mines are also outlined.

Jan 1, 1991

By Keith G. Wallace, Gary K. Rogers

As a supplement to an analysis involving methodologies for the estimation of airflow resistance in shafts used for both ventilation and hoisting, a detailed shaft characterization survey was distributed worldwide. The survey provided detailed information which enabled verification of recommended velocities and established limitations on fill factors and relative velocities. This paper evaluates the information obtained for 37 shafts and presents a statistical evaluation of the results. Apart from airflow rates, conveyance rates, and physical characteristics, qualitative information regarding means of conveyance stability and velocity control techniques at unloading and loading points are also presented. Calculations of fill coefficient, free area velocity, and most importantly, relative velocity between the airflow and hoist, are conducted. These results are presented by frequency diagrams which illustrate the trends, as well as provide limitations for these parameters. The data illustrates that, commonly, the fill coefficient for two or more conveyances, does not exceed 30 %. A limit of 50% is suggested for a single conveyance shaft. A recommended free area velocity of 10 m/s (1,970 ft/min) for combined ventilation and hoisting shafts, is sup- ported by these results. Relative velocities of 30 m/s (5,905 ft/min) are most frequent and 50 m/s (9,840 ft/min) being a practical maximum.

Jan 1, 1987

By Wayne P. Myers

Electricity, as normally thought of by a layman's definition, is a man- made force that has no color, no odor, is not visible, cannot be heard, yet man can control it and make it perform his work for him. A person dare not cheat on it, for it then will master him. It has laws, rules, and regulations that must be strictly adhered to if it is to perform in the safest, most reliable, and economical manner. In the early days of coal mining the power source was man himself. Later man employed steam and compressed air to reduce his muscle power requirements needed in the extraction of coal. By the turn of the 20th century, electricity had become the most common source of power for the coal industry. Steam and compressed air are still found in use in isolated cases today for specific applications; however, they are rapidly being replaced by electricity. Electrical laws and regulations are quite extensive and somewhat complex for the proper generation and use of electricity. Man-made laws, rules, and regulations for the care and handling of electricity, designed for man's safety, are rigidly enforced by Mine Safety and Health Ad- ministration (MSHA), as well as the various state departments of mines.

Jan 1, 1981

By Peijian Zhang, Yansheng Liu, Yuusaku Tominaga

The directions for ventilation control are often given in linguistic styles such as "if the airflow rate measured is small, a high value of rotation on a local fan should be chosen." In order to control the underground climate using a computer instead of a human being, both the reliability of data values measured underground and the application of human recognition of data values are required. The efficiency of data transmission is dependent on a method of checking a signal which is changed by mixing noises resulting from cases of electrical and mechanical damage to cables. In the study, fuzzy reasoning is adopted to choose a checking method for underground conditions from a normally operating state to an emergency. Fuzzy reasoning is applied to control airflow rate under the linguistic control rules given. It is shown that an effective series of linguistic control rules derived by fuzzy-sets theory is available in ventilation control when used in conjunction with an air velocity sensor, a computer and a local fan with thyristor control. Moreover, a system to make an optimum series of linguistic control rules for ventilation control is introduced.

Jan 1, 1987

By Reese E. Mallette

This paper makes five major points which may be contributions to the art of limestone sinkhole engineering. First, solution cavity development in limestones is dependent in great measure on pyrite contained within the limestone. Second, rock failure is rarely involved in sinkhole problems, while soil failures are almost always the mode of occurrence. Third, draw down, depression of the water table, is a primary causative factor in sinkhole development. Fourth, lateral movement of vadose water along the soil-rock interface, sub-soil erosion, is the mechanism by which soil is stoped, raveled, piped, or removed from the soil cavern. Fifth, the ultimate or triggering factor in localizing a sinkhole collapse is any superposed mechanism which disrupts the continuity of an impermeable clay soil overburden. The above theses are presented as extensions of our observation and of published literature, with the suggestion that additional study of these mechanisms is warranted.

Jan 1, 1975

By J. Simmons, P. Ziemkiewicz

Acid-Base Accounting (ABA) is an analytical procedure that provides values to help assess the acid-producing and acid-neutralizing potential of overburden rocks prior to coal mining and other large-scale excavations. This procedure was developed by West Virginia University scientists during the 1960s. After the passage of laws requiring an assessment of surface mining on water quality, ABA became a preferred method to predict post-mining water quality,and permitting decisions for surface mines are largely based on thevalues determined by ABA. In order to predict the post-mining water quality, the amount of acid-producing rock is compared to the amount of acid-neutralizing rock, and a prediction of the water quality at the site (whether acid or alkaline) is obtained. We gathered geologic and geographic data for 56 mined sites in West Virginia, which allowed us to estimate total overburden amounts, and values for maximum potential acidity (MPA), neutralization potential (NP), net neutralization potential (NNP), and NP/MPA ratios for each site based on ABA. These values were correlated to post-mining water quality from springs or seeps on the mined property. Overburden mass was determined by three methods, with the method used by Pennsylvania researchers showing the most accurate results to actual overburden mass. A poor relationship existed between MPA and post-mining water quality, NP was intermediate, and NNP and the NP/MPA ratio showed the best prediction accuracy. In this study, NNP and the NP/MPA ratio gave identical water quality prediction results. Therefore using NP/MPA ratios, values were separated into categories: <1 should produce acid drainage, between 1 and 2 can produce either acid or alkaline water conditions, and >2 should produce alkaline water. On our 56 surface mined sites, NP/MPA ratios varied from 0.1 to 31, and six sites (11%) did not fit the expected pattern using this category approach. Two of eight sites with ratios <1 did not produce acid drainage as predicted (the drainage was neutral), and four of 40 sites with a ratio >2 produced acid drainage when they should not have. These latter four sites were either mined very slowly, had non-representative ABA data, received water from an adjacent underground mine, or had a surface mining practice that degraded the water. In general, an NP/MPA ratio of <1 produced acid or neutral drainage sites, between 1 and 2 produced mostly alkaline drainage sites, while NP/MPA ratios of >2 produced alkaline drainage with a few exceptions. ABA is a good tool to assess overburden quality before surface mining and to predict post-mining drainage quality after mining. The interpretation from ABA values was correct in 50 out of 52 cases (96%), excluding the four anomalous sites, which had acid water for reasons other than overburden quality.

Jan 1, 2003

By S. Bassignani, D. Ippolito

In Italy at the moment there is a program which involves for the future the exploitation of two uranium mines which are now in the research stage. About one hundred and fifty workers are at present employed in those facilities. An health physics surveillance program is under way and has been designed to fulfill the requirements due to the future exploitation of the two mines. A complete evaluation of the total dose (external + internal) received by the workers will be given together with a detailed analyses of the technical methods employed for such evaluations. The external doses are evaluated on the basis of individual TLD dosimeters, while the evaluation of the internal doses is mainly due to an enviromental survillance program of the radon and radon daughter air concentration inside the mines. The criteria established for the assessment of the sampling procedures, sampling intervals and dose evaluation related to the radon doughter exposure are reported. The external dose received by the workers are lower than 0.2 m Sv~month and the internal exposure less than 6.4 IO-3 J.h.m-3 /year or using the old units 2 WLM/year.

Jan 1, 1981

By Neil Jagger, Ian Arbuthnot, Mitchell Gordon

Ultra high density underflow is required in many thickener applications and in mineral processing is typically required for tailings to improve the thickened slurry rheology for either tailings dam development or for paste backfill applications. The improved liquid-solid separation resulting from the production ofultra high density underflow has both environmental and process benefits in the gold industry. Additional cyanide is recovered in the thickener overflow thus reducing plant cyanide costs and perhaps more significantly, a reduced quantity of cyanide is discharged to the tailings thus reducing either the toxic effect on the environment or the costs of cyanide destruction. Many gold and other mineral processing plants are situated in arid regions where the cost of water is high and the quantity often very restricted. Ultra high density thickened underflow results in increased recycle of tailings process water to the plant. In Countercurrent Decantation circuits, the wash efficiency is very dependent on the degree of liquid-solid separation in each thickener stage and the benefits ofultra high density underflow are either increased efficiency or decreased equipment costs as it may be possible to reduce the number of stages in the circuit.

Jan 1, 1995

By Kathryn C. Sole, Angus Feather, Leslie J. Bryson

A novel solvent-extraction route for the production of high­purity gold has been successfully demonstrated on a pilot-plant scale, and the first full-scale production plant is being commissioned. This plant, at Harmony Gold Mine in South Africa, is designed to refine 24 tons of gold per annum when operated for one shift per day. The commercial implementation of this process represents not only a significant advance in gold­refining technology, but may also be instrumental in initiating important changes in the legislation regulating the marketing of gold in South Africa. The Minataur™ Process (Mintek Alternative Technology for Au Refining) is able to produce gold of either 99.99% or 99.999% purity from intermediate process products having a wide range of gold contents. The process comprises oxidative leaching of the feed material, followed by selective solvent extraction of the gold from the leach liquor to reject impurities, and then precipitation of high-purity gold powder. This paper introduces the process, presents selected results of pilot-plant trials in which high-purity gold was produced from two significantly different feed materials, and illustrates some of the applicable cost benefits.

Jan 1, 1997

By G. A. Achilleos

The insufficiency of Boolean Logic and ?hard? decision making to represent and manage spatial data in set with their spatial errors comprises a remarkable difficulty for widely accepted estimation procedures, in realistic planning of space geometric problems and management through a GIS. Fuzzy logic as well as other theories such as the theory of Probabilities, Bayesian theory etc., contribute substantially towards this direction. Data are accompanied by their accuracy and are managed through the applications and modules of Spatial Analysis, aiming to access a decision with known accuracy and fuzziness. As it concerns the cases of waste sanitary landfill sites designing, which are based on the construction of a bank, the problem shown by this paper, seems to be quite serious. The determination of the theoretical waste disposals body in the landfill is based on an uncertain Digital Elevation Model (DEM). As this model is a result of a procedure enclosing errors and inaccuracies, it is for certain a non - error free model. Thus, the geometric computation of the excavation quantities and the waste disposals solid body volume, misquotes the expected standard theoretical computation and imports the need to decide and set a risk level for the project.

Jan 1, 2005

By G. E. S. Valadão

This paper is concerned with studying the dewatering behavior of three samples of iron ore products. The objective is to improve the industrial filtration performance by taking into account the laboratory results. Mineral samples came from the Iron Ore Quadrangle in the state of Minas Gerais, Brazil. These samples represent products from the industrial processing of hematitic ores. The samples have almost the same chemical and mineralogical compositions, but they have different size distributions and different specific surface areas. The filtration tests were performed using a modified Büchner funnel apparatus. The results indicate that size distribution and specific surface area have significant influences on dewatering behavior. For Sample 1, the addition of flocculant and/or surfactant was not essential to improving filtration performance. For Sample 3, the cake porosity and the cake thickness were influenced by the addition of the flocculant. On the other hand, the simultaneous addition of flocculant/surfactant decreased the cake formation time and reduced the cake moisture. For Samples 2 and 3, it was also observed that the industrial operation could be improved by taking into account these laboratory results. Key words: Dewatering, Iron ore, Hematite, Filtration, Flocculation, Surfactant

Jan 1, 2003

By D. R. Spears, D. A. Stanley

The US Bureau of Mines investigated the fundamental aspects of shear-flocculation using a rapid, in-situ particle size analyzer. Silica was stirred in the presence of an aliphatic amine to determine the effects of collector coverage, stirring speed and solids concentration on the kinetics of shear-flocculation. The results showed that shear flocculation is a two-stage process. In the first stage, which occurs during the first 1-2 min. of the reaction, the mean particle size increases rapidly, and in the second stage, an equilibrium is set up between the rates of floc growth and floc decay. Collector dosage affected the position of the equilibrium by altering the number of surface sites for particle-particle attachment. A minimum stirring speed was necessary for shear flocculation, which was dependent on solids concentration and collector dosage. This stirring speed was the minimum necessary for particles to overcome the electrostatic energy barrier, and that results in keeping the conditioned particles dispersed. Larger particles flocculated more rapidly. At very high stirring speeds, large flocs became unstable, resulting in a narrowed particle size distribution in the slurry.

Jan 1, 1995