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By Olli Korhonen

Dado el alza de precio de la energía y el progreso realizado en el control de la misma, se mostró que las máquinas de flotación de gran volumen son insuperables en cuanto ahorro y avance tecnológico. En este sentido, el objeto del texto radica en señalar la utilidad de las máquinas de gran concentración, a comparación de las pequeñas plantas de concentración, bajando los costos de la operación y optimizando los resultados metalúrgicos. Como ejemplo más inmediato está la compañía Outokumpu Oy, ya que es la primera compañía minera que ha desarrollado su propio mecanismo de flotación adecuado para ser usado en celdas grandes y ha posibilitado el funcionamiento de 10 máquinas en la mina.

Oct 14, 1980

By I. R. Muirhead, S. Frimpong

"The mechanization of mining operations in underground coal mines has led to faster cutting rates of coalfaces with increased levels of emission of gaseous and particulate contaminants in the workings. Consequently, the fresh air streams from the main ventilation systems reaching distant workings are often insufficient, ineffective or inadequate and have to be supplemented by auxiliary ventilation systems to create and maintain the required working environments underground. The efficiencies of auxiliary ventilation systems are largely affected by drivers of the system such as the type and capacity of the fan; the type, length, diameter and condition of the ventilation ducting and the distance from the discharge end of the intake ducting to the face. Traditionally, single point measurements of methane gas concentrations using either flame safety lamps or hand-held measuring instruments have been used to assess how safe underground coal workings were. Unfortunately, such occasional measurements of methane gas concentrations do not give an accurate picture of the real gas concentration in the working as they are often taken from the easily accessible locations in working. Continuous monitoring of the methane gas concentration in development headings enables a better assessment of the environmental conditions prevailing there. All variations in the methane concentrations are more easily captured on a continuous monitoring basis than by instantaneous single point measurements. The approach adopted in this work was to continuously monitor the concentration of methane very close to the face and about 60 m outbye in development headings, observe the types of auxiliary ventilation equipment and their sizes being used in the working as well as noting the lengths from the discharge ends of the forcing and exhaust ductings to the face.In this paper, empirical methods are used to calculate the mean efficiencies of the auxiliary ventilation systems in selected development headings in coal mines in North America. This enables the assessment of the effectiveness of the auxiliary ventilation systems and the identification of the system drivers in them. The results show that the efficiencies of the forcing systems ranged from 17.02% to 96.81% while the efficiencies of the overall systems varied from 6.04% to 54.16%. The distance from the discharge end of the intake ducting to the face appeared to be the strongest driver in the performance of the auxiliary ventilation systems studied. It was also noted that when the discharge end of the intake ducting to the face does not exceed 7 m, there were faster purging rates of methane at the face and the efficiencies of the overall auxiliary ventilation system were greater than 50%. These findings are very important in underground coal mining in North America as they will assist to avert calamities, such as the Westray coal mine disaster in 1992 which resulted from the explosion of methane gas, by identifying which components of the ventilation system need special attention to create safe working conditions underground."

Jan 1, 2003

To provide a flexible, low-maintenance, low-cost continuous mine air monitoring system as an alternative to conventional fixed-point, electronic monitoring systems. Background Continuous monitoring of mine air is highly desirable (and often required) not only to improve miner safety, but also to increase mine productivity. Continuous air monitoring systems can provide earl" warning of developing fires, excessive methane accumulation, reduced oxygen levels, and other developing problems in remote, inaccessible or sealed areas, and in active workings. Fixed-point, electronic systems require one Sensor for every gas to be measured at every defined monitoring location. As the number of monitoring locations increases, so does the cost, along with increases in the time required for routine maintenance and calibration of the sensor System cost also increases when monitoring locations are identified for mine areas requiring permissible electrical equipment.

Jan 1, 1988

By Rajagopala Reddy Kallu

After the Sago and Darby No. 1 mine incidents, the new regulatory standards for the design of mine seals in underground coal mines of the United States require the mine seals to withstand higher explosion standards. This necessitated for the development of new design approaches and standards. For development of any new design standards or approaches a detailed understanding of effect of key influencing parameters on the stability of mine seal is a must. This paper attempts to address one of the factors, i.e. roof convergence, that play an important role in the stability of mine seal under explosion loading. Initially a couple of three dimensional numerical models were built and tested for different levels of roof convergence. These models confirmed that roof convergence has great influence on seal stability. A detailed study is undertaken, with some simple assumptions, to establish typical influence of roof convergence on the stability of mine seal under different levels of static explosion pressures. Three dimensional distinct element code 3DEC is used for this purpose.

Jan 1, 2007

Kinetics of Reclamation of E-Waste by a Bioleaching Route

Sep 13, 2010

By Susana Marraccini Giampietri Lebrão, Jorge Alberto Soares Tenório, Renato Souza e Silva, Guilherme Wolf Lebrão, Viviane Tavares de Moraes

Os resíduos eletroeletrônicos podem ser compostos por equipamentos ou parte deles, que se tornaram obsoletos, pararam de funcionar ou ainda por apresentar defeitos durante a sua produção. As placas de circuito impresso (PCIs) são peças presentes em equipamentos eletroeletrônicos compostos por materiais metálicos, cerâmicos e poliméricos. Para alguns destes metais já existem processos para recuperação, contudo estes processos baseiam-se em técnicas pirometalúrgicas que podem liberar substâncias tóxicas. A fim de minimizar os impactos ambientais propõe-se o beneficiamento das PCIs através de rota hidrometalúrgica para a obtenção de cobre em solução e, posteriormente fazer a redução do cobre. Para tanto se fez a moagem das PCIs, seguida de caracterização química. Partiu-se para rota hidrometalúrgica em meio ácido e em meio oxidante. A solução resultante de cobre foi reduzida para cobre metálico por reação de redução com ácido ascórbico. Os resultados apresentam recuperação de 97 % de cobre das PCIs com obtenção de cobre metálico.

Oct 11, 2019

By J. T. Popp

This Bureau of Mines study reviews the geological factors that affect methane in the Beckley coalbed in southern West Virginia, including overburden, coalbed structure, type of and changes in lithology above and below the Beckley coalbed, and presence of fractures in the coal and rock adjacent to the Beckley. Depending on the depth, the Beckley coalbed emits from 216 to 520 ft3 of methane per ton of coal mined, and the Bureau estimates that methane emission in a deep, extensively developed mine in this area may exceed 3,000 ft3 per day per ton of coal mined. Average face cleat and butt cleat trends in the Beckley coalbed measured underground are N 33° W and N 53° E, respectively. Close cleat spacing con¬tributes to the friable nature of the Beckley and provides easy movement for methane and water. Because rider coals, splits, and carbonaceous shales may contribute methane to mine emissions, predictions of methane emission based on gas content of the Beckley coalbed alone may be conservative. Beckley coalbed reserves in the study area are 234 million tons. The gas content of the Beckley coalbed averages 407 ft3/ton, and the coalbed gas reserves are 108 billion ft3.

Jan 1, 1976

By Truman P. Stauffer

Secondary use of mined-out space in underground limestone quarries is emerging in the Kansas City area where abandoned quarry sites are being renovated into warehouses, factories, and offices. Mining techniques, ceiling heights, and pillar distribution are being altered as planning for the secondary use of mined-out space is combined with the quarrying process. Even the historic urban- quarry land use conflict invites a reappraisal in that this development provides a potential resolution of the problem. Mutual subsidization by dual rock and space interest is changing the economics of rock production. A city is much more than a surficial adjunct superimposed upon the topography of an area. Its development and growth are deeply rooted in the resources, benefits and problems of its underlying geology. The environmental geologist must address himself to more than the quality of a particular resource. He must comprehensively relate resource extraction and processing with the urban emphasis of optimal use which favors long term usage of land over one time economic ventures. Limestone quarrying, closely allied with the growth of many cities, has commonly left a series of scarred landscapes in the path of the burgeoning metropolis. These abandoned quarry sites are barriers to orderly city growth and fail to serve the people as useful and taxable land. Where quarries are functional, supplying the city with needed growth minerals, problems of blasting damage, noise, and dust exist. Technology faces the challenge of making mineral production and processing good neighbors to the urban market they serve. Continued growth of cities may require more efficient use of space below as well as above the surface optimizing land usage so that long term economic benefits may be reflected in improved mining methods.

Jan 1, 1973

Detailed investigation was carried out on the dephosphorization of a number of phosphorus-rich manganese or samples of India by leaching with dilute sulphuric acid. Various process parameters like concentration of acid, liquid-solid ratio, temperature of leaching, time of leaching, and particle size of the ore were studied in detail for the three samples of manganese ore from central India, and optimum values were worked out on a laboratory scale. Preliminary studies show that certain ores which are not easily amemlible to appreciable dephosphorization by leaching with dilute sulphuric acid can be made amenable by :roasting to 700-900°C before leaching.

Jan 1, 1974

By M. J. Senk, A. Lusin

Federal regulations require that methane liberated at the face be diluted and removed to maintain methane gas concentrations below 1 pct (CFR) in working places and intake air courses. The delivery and distribution of intake air at the face is critical for effective face ventilation. Improved techniques for monitoring the movement of intake air to the face are needed. A test system was developed and a computer program written for using a three-axis ultrasonic anemometer to measure airflow in a simulated mine entry. Results of tests conducted in the entry showed that the anemometer is a valuable tool for measuring mine airflow conditions near the face.

By O. Lashkari

Manipulation of pouring temperature is an efficient way to produce different microstructural features. In order to characterize the microstructure of rheocast billets due to different superheats of 615-695 °C, the parallel plate compression method was employed. Foundry 356 Al-Si alloy with different morphologies of primary a-Al particles were tested at different initial pressures of 4,8, 11,2 KPa, The resulted strain-time graphs were further treated mathematically to calculate viscosity of SSM billets. The interrelationships of viscosity, the microstructure and primary phase flow during compression are discussed, It is shown that the dendritic primary a-Al structure has the highest viscosity number which is almost three orders of magnitude greater than those for globular morphology, The current research have, for the first time, shown the validity and reliability of "parallel plate compression viscometry" method in characterizing microstructural evolution of Rheocast SSM billets.

Jan 1, 2005

By P. Ventura

Reliability of the liquefaction analysis is based on data plotted as by piezocone, as by deep vibrocompactation monitored tests. The negative porewater pressure, re lated to hydrostatic value, recorded by piezocone, is a good marker of the absen ce of the liquefaction. Systematic measures of the ground settlements, inside the vibroinfixed steel pipe, allow to locate the liquefable strata with loose density. Experimental study of the combined soil improvement by stone columns is carry out in particular in sea bed. The interaxis of the columns for the best efficiency is valued as of the vibrocompactation, as of the drainage effects, especially during earthquake.

Jan 1, 1989

By J. L. Holman

The Bureau of Mines has extended its previous development of cast Mn-Cu damping alloys to powder metallurgy (P/M) consolidation of alloys containing 55 to 75 wt-pct Mn. Blends of minus 200-mesh elemental powders were compacted cold in directional and isostatic presses. With 1 pct binder, typical green densities ranged between 76 and 80 pct of theoretical when pressing at 30 or 48 tsi. Green strength increased with compacting pressure and copper content. As-sintered tensile strengths ranged to 60,000 psi fox a hydrogen, sintered 60Mn-40Cu alloy, along with 5-pct elongation. Sintered densities ranged between 90 and 96 pct of theoretical. Sintering (a as effective when holding for 1 hr at maximum temperatures of 900° to 1,040` C, dependent on composition. Strength and ductility were considerably lower than for equiva¬lent cast alloys. When aged to the damping condition, alloys containing 60 to 70 pct Mn exhibited >40 pct specific damping capacity (SDC) at 5,000-psi stress, considerably higher than values reported for equivalent cast material. Effects of 1 or 3 pct Sn or Zn additions on SDC and other properties were assessed. Trials were conducted on consolidating rings and gears of the 65Mn-35Cu alloy on industrial-type P/M equipment.

Jan 1, 1979

This paper discusses how elemental analysis of conveyed bulk flows in real time using PGNAA (Prompt Gamma Neutron Activation Analysis) technology has resulted in significant improvements in advancing plant control in mineral processing operations. Basis of operation of the PGNAA through belt, full stream, continuous, multi-elemental, real time analysis technology is explained. Capabilities and limitations in plant operating environments are discussed including comparison with other real time, online technologies through review of published information available for on-conveyor minerals applications. Case studies demonstrate benefits provided by this technology in two operating mines. An iron ore company had prior experience with the PGNAA analyser technology, implementing an early model in a minerals application in 2003 to develop confidence in its measurement performance and usefulness of the data. A number of analysers were subsequently included throughout the new plant design for extensive measurement and control of conveyed bulk flows, from conveying after mining through to rail load-out. A copper-gold company installed an analyser to address copper ore blending issues where an on-belt system was the only viable option for the degree of control required. Analyser suitability was evaluated through test work on site samples to determine customised multi-element precision guarantees for each application. Analyser results from normal operation are compared against laboratory analyses of multiple cross stream samples collected from conveyed flows to assess performance. Both projects discussed were able to realise benefits previously unattainable for plant quality control, surpassing capabilities of traditional technologies which were either unsuitable for measuring conveyed flows with adequate accuracy or in real time. Equipment payback within a few months was achieved for both sites. Through proven performance in these applications, the companies consider the technology an essential component in advanced plant control necessary in new process flow sheet designs, rather than an optimisation tool.

Jan 1, 2014

Control of flotation processes is mostly managed by plant operators, who assess the performance of the plant based on their own experience and other heuristic rules. These rules tend to be subjective or ill-defined, since most of them are concerned with the structure of the flotation froth, such as colour, bubble size and shape distributions, froth mobility and froth stability. These phenomena are very difficult to quantify objectively, and inexperience on the part of the operators, human error, etc., can lead to significant inefficiencies in plant operation. In this paper the development of a fuzzy system to support the control decisions of plant operators is described, which leads to significantly smoother control action and more stable plant operation than could be obtained with crisp sets of rules or manual control strategies. Keywords: flotation, fuzzy logic, image analysis, genetic algorithms, rule induction

Jan 1, 2000

By Aline Kemp

O objetivo deste trabalho é estudar o efeito da composição química e dos parâmetros de lingotamento convencional na ocorrência de trincas superficiais em barras laminadas. Faz-se um estudo dos parâmetros que podem influenciar na formação deste tipo de defeito e uma análise da morfologia de trincas. Com relação à composição química, foi alcançada redução na ocorrência de trincas superficiais em barras laminadas através da adição de Ti e redução do teor de Al no aço. Maior temperatura e menor velocidade de lingotamento correspondem à melhor combinação para alcançar redução da ocorrência desse tipo de defeito.

Oct 30, 2017

By William R. Archibald

This report presents the results of a program demonstrating the technical and economic feasibility of hydraulic borehole mining of uraniferous sandstone. This mining technique involves the drilling of a borehole from the surface down into the ore body. A borehole mining tool consisting of a high-pressure cutting jet and a slurry jet pump is lowered down the borehole. Water from the high-pressure cutting jet cuts into the sandstone formation generating a water-sand slurry which flows to the slurry jet pump and is pumped to the surface. The cutting jet is rotated and moved up and down from the surface, thereby generating a cavity in the formation. When the cavity size reaches a point beyond the effective radius of the cutting jet, the mining tool is moved to an adjacent borehole and the process is started again. This program was carried out in four phases. Phase I included modifications to the borehole mining system (built and tested under a previous contract, No. H0252007, for the mining of coal) and factory tests of the jetting system. Phase II covered the field tests and a public demonstration. Phase III involved nozzle and equipment modifications and factory tests. Field testing continued under Phase IV along with an evaluation of this method. The field tests were conducted successfully on Rocky Mountain Energy Company's Nine Mile Lake property near Casper, Wyoming. Results indicate that; hydraulic borehole mining of uranium is technically feasible (300 tons of uraniferous sandstone were mined from a depth of 90 ft) and the hydraulic borehole method is economically attractive. However, additional testing is required to clearly define the economic feasibility.

Jan 1, 1978

By Robert E. Barieau

General expressions for evaluating various thermodynamic properties applicable to the van der Waals equation of state have been derived. These formulas were subsequently used to evaluate various thermodynamic functions in the two-phase region. The results indicate that, for a van der Waals fluid, there is a finite discontinuity in the second derivative of the vapor pressure curve, in the second derivative of the chemical potential or Gibbs free energy at the critical point, and in the heat capacity at constant volume measured at the critical density. Numerical values are tabulated and graphs are presented for all functions calculated.

Jan 1, 1967

By A-A. Bogno, Ch. -A. Gandin, A. Maitre, H. Henein

Most metallic materials are produced from their liquid state. In order to control the properties of industrial products, it is very important to understand their solidification path and the resulting microstructures which can be significantly affected by melt undercooling. High undercooling results in rapid solidification and a refined microstructure with minimal microsegregation. This paper reports on the analysis of rapidly solidified Al-Cu droplets obtained by a single fluid atomization process, Impulse Atomization. A quantitative analysis by Rietveld refinement method of the Neutrons Diffraction data was carried out to determine the fraction of the intermetallic Al2Cu. Knowing the fraction of Al2Cu, the eutectic fractions and corresponding dendritic and eutectic undercoolings were estimated using the metastable extensions of solidus and liquidus lines of the Al-Cu system calculated by Thermo-Calc. In addition to this work, a model of microsegregation coupled with ThermoCalc software via TQ (application programming interface of ThermoCalc) and the Wang-Beckerman model for dendritic growth velocities has been developed for binary alloys. This has led to the development of a phenomenological relationship between primary phase undercooling and initial growth velocity. A comparison of estimated primary undercoolings using a coarsening model with the adiabatic undercoolings for each alloy composition has confirmed that solidification occurs under adiabatic conditions during recalescence.

Jan 1, 2014

Separation of Iron Particles from Banded Haematite Quartzite (BHQ) Ore by Selective Magnetic Coating The separation of fine iron particles from banded hematite quartzite (BHQ) has been studied using selective magnetic coating. The BHQ ore assays as 38.9 per cent Fe, 42.5 per cent SiO2 and 1.0 per cent Al2O3. Mineralogically, the ore contains hematite and quartz as the major mineral phases where as goethite and magnetite is present in minor entities. Natural magnetite of very fine size and oleate-magnetite in colloidal form, prepared synthetically in the laboratory are used as the coating material on the surface of hematite particles. The selective coatings of oleate-magnetite on BHQ surfaces followed by magnetic separation studies have indicated that, it is possible to achieve 62.3 per cent Fe with 8.5 per cent SiO2 at 85.4 per cent iron recovery. The recovery of iron values is found to be superior in comparison to the conventional magnetic separation techniques. The selectivity of coating for enhancing the magnetic response of iron particles is achieved by controlling the surface properties of the particle via electrokinetic potential adjustment by controling pH and addition of oleate-magnetite. In the separation process, the effects of pH, magnetic intensity and addition of oleate-magnetite are studied to achieve the maximum grade and recovery of iron values. The optimum separation is observed at pH of 7.5, oleate-magnetite concentration of 0.25 ml/g of BHQ ore and a magnetic intensity of around 0.8 Tesla. The X-ray diffraction (XRD), Infra-red spectroscopy (IR) and UV-visible spectroscopic studies strongly suggest preferential coating of magnetite on hematite surfaces. Scanning electron microscopy (SEM) studies have brought out the semi-quantitative features of BHQ ore. The recovery of iron values from a lean grade ore such as BHQ is carried out looking into the future needs of this ore in India for iron and steel making.

Sep 13, 2010