Search Documents

By K. V. S. Sastry

Pelletization, sintering, and pressure compaction are the most common methods used to agglomerate ore concentrates. Over the last 20 years agglomeration has grown enormously in popularity and has become a standard unit operation in the nonferrous, cement, fertilizer, and ceramic industries. However, it is in the processing of iron ores and the preparation of blast furnace feed that agglomeration is used most and its application has grown fastest (Ball, et al., 1973; and Sastry, 1977). This chapter deals with an account of the current practices and future trends in the application of computers relative to an overview of the process design and engineering considerations of the unit operation of agglomeration.

Jan 1, 1979

By M. S. Klima, M. Fofana

The use of a laboratory-scale magnetic fluid-based separator for coal separations was examined. A Frantz laboratory magnetic separator was modified by fabricating new pole pieces of the appropriate geometry to provide the proper magnetic field gradients. Two separation chambers, which were constructed of Plexiglas, were designed to fit between the pole pieces. A commercially available, water-based, ferromagnetic fluid was used as the separating medium. The separating density was changed by varying the current intensity of the electromagnet coil. Both batch and continuous separations were made using 0.59 x 0.50-mm and 0.18 x 0. 15-mm coal. The results are compared to those obtained using organic liquids.

Jan 1, 1998

By A. D. Agate

In developing nations, novel mineral processing methods like bacterial leaching are gaining prominence. The principles and practices for isolation and preservation of cultures used in bacterial leaching are discussed with special reference to cultures used in leaching copper from Indian ores. In all, 145 potentially useful microorganisms such as iron- and sulfur-oxidizing bacteria were isolated from various ecosystems of the copper mining areas in the country. The major organisms isolated by enrichment culture technique belonged to T. ferrooxidans and T. thiooxidans species. In addition, thermophilic cultures like Sulfolobus sp. and thermophilic thiobacilli were also isolated. The process of copper leaching was scaled up to the 300-kg level in PVC columns. Since the preservation of efficient cultures in active state was vitally important, a new method was devised that preserved the activity of thiobacilli for a period of more than two years. The novel method of storage in sterile chalcopyrite ore at 8°C can be considered an important advance.

Jan 1, 1987

By Paulo Roberto, S. M. Roberto, Francisco Valadares Póvoa, Evandro C. Silva

The market of mineral goods worldwide is characterized by a growing pressure on suppliers for better quality products, lower prices and productive processes which are energetically efficient and environmentally friendly. These pressures force the mineral industry to re-think not only the present models of exploitation of natural resources and production, but also their own model of techno- logical development. This paper outlines the model and the experience of Technology Strategic Planning (TSP) adopted by CVRD to face these demands, warranting and expanding its participation in the current markets and developing new businesses.

Jan 1, 1998

By Brij M. Moudgil, Shoulian Zhu, J. L. Pinault

A new technique, prompt neutron activation probe (PNAP), for analyzing phosphate rock slurry in-situ was evaluated both in the laboratory and at the plant. The technique yielded a high precision in the analysis of Ca, Si and H using 252Cf source. Low accuracy of the direct measurement of P using 241Am/Be in the laboratory tests was attributed to the interference of rare earth elements present in the samples, particularly Gadolinium. No significant effect of variables such as solids loading, particle size distribution, and flotation reagents was observed on the probe performance. The probe can detect the compositional changes of the feed, tailings and the concentrate streams in the plant.

Jan 1, 1993

By W. D. Monaghan, G. L. Mowrey, C. W. Ganoe

In addition to developing various types of coal-interface detection systems, the US Bureau of Mines is actively involved in developing a coal rib-thickness monitoring system for high wall mining applications. One particular system that shows promise uses a ground-penetrating radar system to detect the coal-air boundaries of coal ribs. Based on preliminary laboratory and field tests, results indicate that this method can be applied successfully in highwall mines to maintain a constant rib thickness. The coal seam should be relatively clean in the vicinity of the antenna (e.g., have minimal partings or dirt bands) for best results.

Jan 1, 1996

By W. Kemp Wait

Electronic ore sorting has been in use for over 15 years at many mining operations worldwide. Photometric ore sorting, which operates on the basis of measuring light reflectance levels of a rock surface, is in use at various locations on ores such as limestone, magnesite, gold, talc, spodumene, tungsten and coal. Radiometric sorters have been employed on uranium deposits in the western U.S.A. as well as at certain South African go1 d mines where preconcentrating gold is achieved using uranium association as a detector. A new ore sorter, employing two sensing parameters has been developed. Utilizing both photometric and conductivity sensing modes, this system has application to many gold ore types of North America. The first production machine has been installed at a gold mine near Beardmore, Ontario for the purpose of preconcentrating ore both from waste dumps from past production as well as within the ongoing mining operation.

Jan 1, 1987

By S. K. Kawatra, T. C. Eisele

Production of highly-cleaned coal for advanced utilization schemes requires close control of the coal ash content at very low levels. For this purpose, a sensitive, low-cost, robust on-stream ash analyzer is needed. The development of such an instrument based on x-ray backscatter and fluorescence is described, including features to improve its sensitivity at low ash levels. The performance of the resulting device in testing a real coal sample is discussed.

Jan 1, 1990

By Walter C. Labys

There has been considerable growth in public enterprise institutions involved in mineral commodity markets. These institutions typically consist of trading organizations (STO1s), regulatory agencies, and mixed agencies. The particular character of these institutions varies according to whether they reside in developing countries, in Eastern Europe (COMECON Countries), in industrialized countries, or in the form of international agencies. The purpose of this paper is to explain recent attempts to assess the growth of public enterprises as well as their impacts on mineral markets and trade. Some earlier analyses of market impact made by the author have been up- dated for four major mineral markets: copper, tin, bauxite and iron ore. Conclusions are drawn regarding the dynamics of market structure changes and their impacts.

Jan 1, 1986

By Charles D. Litton, Ronald S. Conti

This report describes the results of research conducted in the Bureau of Mines Experimental Mine at Lake Lynn Laboratory to determine the effects of air velocity, sensor spacing, and stratification of CO levels on the detection of slowly-developing coal/conveyor belt fires. In general, the time to detect a developing fire is calculated assuming an average CO level that has mixed completely with the ventilated airflow. The data indicate that CO sensors placed near the roof of an entry take advantage of buoyant- induced stratification of combustion products, resulting in earlier detection of developing fires. Even during the low-temperature, smoldering stage of a fire, the combustion products will tend to stratify near the roof, and once flaming occurs, the degree of stratification increases markedly. As one would expect, at higher air velocities, the degree of stratification is less than at lower air velocities, although still significant, especially during the flaming stages of the fire

Jan 1, 1993

By Bekta? Uz

In this research, geological characteristics of sand quarries around the village, Kemerburgaz Akpinar, are studied and the mineralogical, petrographical, chemical and technological characteristics (such as sieve analysis, relative density, water absorbtion etc.) of the sand samples, obtained from the area are explained. In the general area sand' quarries, being in lacustrine formations belonging to Neogen, the stratigraphic location of the sand occurences take place at high levels of these formations, geologically. All of this pattern, being under 1 mm with a ,particle dimension, it ranges from 0,5 mm in the quantity of 99 % to 0,25 mm in the quantity of 15 relative density is 2,65 g/cm3 ; water absorbtion is 0,9%. Mineralogically, the sand samples contain Quartz (84%), Feldspar (3%), Calcite + Aragonite (10%), Pyroxen+Amphibole (1-2%), Garnet+Tourmaline (0.5%), Olivine (0.1-0.5%). Besides, sand samples contain SiO2 with the quantity of above 90%. Containing Quartz at high levels for mineralogical, petrographical and chemical characteristics, Akpinar sand will be evaluated as silica sand when the carbonate mineral is removed with the method of ore preparation such as leaching.

Jan 1, 2005

By John O. Marsden

The project development metallurgist is faced with an interesting dilemma: The use of overly conservative metallurgical projections and cost estimates can kill a project that has the potential to provide needed jobs and growth to a company's bottom line. On the other hand if the metallurgist uses a highly aggressive approach by trimming capital and operating cost estimates to the bone and by applying highly optimistic metallurgical projections, there is a risk of creating a project that can never live up to expectations. The metallurgist must walk a tightrope between "sandbagging" and "overoptimism," and this tightrope is fraught with political intrigue and difficulty. This paper takes a some- what lighthearted look at some of the political aspects associated with this issue, and other issues, and offers a few guidelines for walking the "political metallurgical" tightrope.

Jan 1, 2001

By Tim Wolf, Barry Fink

Mine site managers reported occurrences of locking assembly bolt failures on the Enlow Fork Coal Mine's slope belt conveyor. The observations were made after a number of years of operation and raised questions as to the status of the assemblies in operation. These questions prompted a detailed review of the situation by independent consultants. Using operational history of the conveyor and confirmation of belt loads by static and dynamic methods, a locking assembly fatigue curve was created to suggest expected service life. From this work, suggestions were made to modify the pulley assemblies for extended service life.

Jan 1, 2002

By R. N. Chakravorty, R. J. Kolada

Explosions of methane in coal silos and coal ships is an ever present hazard. Recent investigations have shown beyond question that considerable accumulations of methane do occur in coal storage silos and numerous recent explosions in coal transport shipping strongly indicates that the same conditions also exist in ship storage holds. Investigations have shown that the main concentrations of methane occur within the actual coal pile. Within this region normal silo and ship ventilation systems are ineffective. The main 1ine of defence is therefore to exclude potential sources of ignition or to place the coal in an inert atmosphere, or both. This paper presents the results of a methane survey of all operating silos in Western Canada. These results demonstrate that a serious and widespread hazard of explosion exists. This paper also discusses various methods by which this hazard may be reduced including methods of venti1ation, inertization, microbiological control and early warning systems.

Jan 1, 1987

By Ch. Arvanitidis

This paper presents the design solution for an actual case of settlement tanks, for a wastewater treatment plant under construction, actually founded on swelling clay (the nature of which had not been appreciated beforehand) and suffering considerable damage as a result. Two points of interest prompted the use of a numerical model as an alternative approach to the traditional method of analysis: First, the desire to compare the in situ measured deformation and displacement of the tanks with the figures calculated by the numerical model. Second the need to check the validity of the suggested solution as a remedy, i.e. the replacement of a certain thickness of clay by graded material.

Jan 1, 2005

By G. P. Brahmaprakash, K. A. Natarajan, N. Jyothi, K. N. Sudha

Some important electrochemical aspects involved in the bioleaching of mixed sulfides have been discussed with reference to selective sphalerite dissolution from different binary mineral combinations. Combination potentials and galvanic currents were measured in different binary combinations of sphalerite with other minerals such as galena, chalcopyrite and pyrite in order to under- stand the electrochemical dissolution behaviour of sphalerite when coupled with other minerals. The effect of applied DC potential was also studied with reference to selective sphalerite dissolution from a binary mineral mixture. An application of a potential of -500 mV (vs SCE) was found to enhance bacterial growth as well as selective sphalerite dissolution. Factors influencing bioleaching of sphalerite under a negative applied potential are discussed.

Jan 1, 1989

By R. Ciccu

Permeable reactive barriers (PRB) are one of the most promising systems for groundwater remediation. PRB are constructed with the purpose to intercept the contaminated flow and to degrade it as a big reactive filter. The most common type of reactive barriers is realized by excavating a trench and by filling it with a substance able to treat the contaminants dissolved in the water. Another type of PRB is obtained by realizing a line of wells in which chemically active compounds are injected. A new method for barrier construction has been studied at DIGITA?s laboratories. It makes use of the waterjet technology to increase soil permeability and to inject active compounds. This technology is especially suitable in the case of deep contaminated aquifers where traditional construction methods are difficult to apply. The paper describes the experimental apparatus especially designed and constructed and the activities carried out to investigate the relationship between waterjet operative parameters and the penetration of the jet in the soil. In conclusion, on the basis of the experimental results, the economical feasibility of the technique is evaluated.

Jan 1, 2008

By Dick Lewis

The Misima deposit is on Misima Island in the Lousaide Archipelago, 240 km east-southeast of the Papua New Guinea mainland, and 600 km east of Port Morseby. Misima is a narrow mountainous island 40 km long and up to 10 km wide. The highest point is 1035 m above sea level. Gold mineralization is restricted to the eastern and less rugged third of the island. The Melanesian population lives in coastal villages. Subsistence agriculture is the main activity, although copra and cocoa are grown in plantations on the eastern and southern coasts. Prior to 1950, mining was important in the economy of the island. Climate is tropical, with little seasonal variation in temperature or rainfall. Tropical cyclones occur about every 10 years (Fig. 1).

Jan 1, 1990

By R. Harris, M. Misra

Column flotation technology has a demonstrated potential for recovering clean coal from high-ash waste fines. The effect of different variables such as air flow rate, frother addition, depressant addition, percent solids and particle size on the quality of separation are discussed. Results indicate that air flow rate and depressant addition are the important variables which control the selectivity in the flotation of fine coal in a column cell. Separation efficiency achieved with column cells is significantly better than that with conventional flotation cells. Under appropriate experimental conditions with a deep column, more than 80 percent coal can be recovered in the concentrate containing 10 percent ash from waste fines containing over 60 percent ash.

Jan 1, 1988

By A. Covelli, A. B. Cecala

Two recent US Bureau of Mines studies evaluated workers' dust exposures in automated pallet loading processes. The first study involved a Bureau designed dust control system using a push-pull ventilation technique. The unit was shown to reduce workers' dust exposures by 76% during pallet loading at a ground silica operation. A hydraulic lift table was used to automate the bag stacking process. This kept the loading height constant throughout the entire pallet loading cycle. The second study evaluated different commercial, automated-pallet loading systems. These systems automatically stack the bags onto pallets, shrink wrap the pallets, and deliver the pallets to a fork lift pickup location. Results from a ground silica evaluation site indicated respirable dust samples taken were below the Threshold Limit Value (TLV) as established by the Mine Safety and Health Administration (MSHA).

Jan 1, 1992