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By H. Cho, P. T. Luckie

A study was undertaken to investigate the liberation behavior of coal macerals through size reduction and density separation. It was seen that the liberation of coal macerals could be achieved by size reduction, allowing selective separation of coal organic components. However, the degree of liberation was dependent upon the comminution history. Even for the same fineness, the extent of liberation might not be the same depending on how the material was generated. The liberation of coal macerals was analyzed by examining the liberation index. It was seen that, although comminution produced fine particles enriched in inertinite (primarily fusinite and semifusinite), these particles were less liberated than coarser particles. However, the liberation of macerals increased when all the feed was ground to a finer size.

Jan 1, 1999

By B. Bringhurst, J. J. McClelland

A filter consisting of a synthetic fibrous material has been determined to be a viable alternative to the wire mesh panels currently used in irrigated filter dust collection systems. An extensive laboratory investigation of the material showed that it removed a higher percentage of both respirable coal and quartz dust from the air entering a collector than did the flat and pleated wire mesh panel designs. This improvement in dust collection efficiency reduced the amount of coal and quartz dust discharged from the collector exhaust by approximately 44%. Since continued exposure to excessive levels (>5%) of respirable quartz dust presents a severe health hazard, this alternative filter medium could be of use to those mines required to comply with more stringent dust standards due to quartz.

Jan 1, 1992

By Wei Wu

A computer-aided method for optimization of bench blast design in surface mines is presented. The design procedures basically consist of two steps. Firstly, a series of normalized, full- scale bench crater tests must be carried out in the field to find the optimum burden that produces the largest amount of acceptable fragments and other parameters that defines the effective fracture zone. Next, the locations and initiation sequence of blast-holes will be determined in such a way that each hole, at its time of firing, will be responsible for same amount of burden rock and will be in a position favorable to effective fracture of burden rock. A computer software "B.B." which can assist the second step of the design is fully introduced and its application is illustrated by an example.

Jan 1, 1992

By Brian W. Hester

All gold occurrences in Tanzania are of Precambrian age and in geological settings similar to gold deposits in other parts the world. The three main areas of interest are perhaps the least prospected of areas of gold mineralization in Precambrian rocks in non- aligned, or market economy nations. Historic production exceeds 77.660 kg (2.5 million oz). Current results by small scale workers go unreported, but have been estimated to be as high as 11.000 kg (350.000 oz) annually. Gold occurs in both lower and upper Precambrian rocks. In the older. gold is associated with greenstones and iron formations typical of many cratonic areas of Precambrian age. The Tanzanian Craton lies in the north west quarter of the country where it is flanked on both east and west sides by mobile belts involving upper Precambrian rocks of high metamorphic grade. Gold occurs in fractures in the western belt within two distinct areas.

Jan 1, 1989

By Robert W. Bartlett

Pretreatment of sulfidic refractory gold ore by biooxidation in coarse-crushed ore heaps is a promising new technology, especially for low-grade ores that cannot afford pressure leaching or roasting. An algebraic equation for determining the economically optimum biooxidation of the sulfide minerals in the ore is provided that is based on the empirical biooxidation rate constant for the ore, the project's financial discount rate, the ore grades of both refractory and non-refractory gold, and the gold price. Then, the economically optimum duration of bioheap pretreatment, t$, is determined from its logarithmic relation to the optimum fractional extent of ore biooxidation, F$, through the ore's biooxidation rate constant. In doing so, it is assumed that the ore is adequately crushed and amenable to bioheap pretreatment and that the cumulative oxidation of the ore with time is known from ore testing so that the rate constant can be determined.

Jan 1, 1995

By Jerzy Matuszewski

Under conditions of high methane content in the seams and the descending of exploitation to greater depths, methane hazard control is becoming more and more difficult. This is due both to the amount of methane released and to the technical possibilities of diluting and capturing it. The removal of excess methane from mine workings only by means of the ventilating current has become a problem. Therefore many countries designate large sums of money for research work in the field of controlling dangerous methane accumulations and for introducing this control into mining practice. In Poland the Central Mining Institute is leading in this field. Its Safety-in-Mines Institute, Barbara Experimental Mine in cooperation with collieries has recently carried out interesting investigations on the distribution of methane concentrations in gobs behind the front of longwalls mined with caving.

Jan 1, 1980

By L. E. Baker, M. J. Leck

OSIRIS is a continuous monitoring system for respirable dust which has been specifically designed for mining and related industries. By using the latest microprocessor technology, OSIRIS provides a sophisticated dust measuring system which is a cost effective alternative to regular gravimetric sampling. The system is certified intrinsically safe for use underground. Up to eight underground OSIRIS sensors can be controlled and monitored by a single IBM PC computer located at the mine surface. This computer provides continuous and instantaneous information about the dust concentrations at the sites being monitored. Information is available in tabular and graphical form. The paper gives details of proving trials of the OSIRIS system in some UK coal mines. During these trials, adjacent OSIRIS sensors placed on the same underground roadway cross-section gave virtually identical results. Throughout a good correlation was obtained with conventional gravimetric dust samples. The OSIRIS equipment proved both reliable and easy to operate. OSIRIS was designed and developed by the Safety Engineering Laboratory of the UK Health and Safety Executive. It is now available commercially and is being

Jan 1, 1987

By Jon C. Yingling

Techniques for optimization of mineral processing flowsheets are reviewed. Though not yet widely used in the minerals industry, approaches for chemical process optimization based on successive quadratic programming (SQP) algorithms may be employed to determine optimum unit design and control settings for a mineral processing flowsheet. Moreover, in certain mineral processing flowsheet applications, specialized techniques can be applied because of the nature of the system relations. These techniques offer advanta es in efficiency. Moreover, their capability exceeds that o f the SQP approaches since simultaneous optimization of circuit configuration and unit controls can be addressed.

Jan 1, 1990

By S. C. Suboleski, J. W. Oberholzer

This paper describes research being undertaken by the Chamber of Mines Research Organization (COMRO) to assist the continuous miner operator and section foreman in the performance of their jobs. The project will initially provide visual assistance to the miner operator, and later it will semiautomate the mining (cutting) process. Using a technique known as "RF tagging," the project will also provide the section foreman with real-time or near-real-time information about the performance of the loading and hauling units. This data will allow the section foreman to quickly detect problems and take action where appropriate. The project is based upon the application of currently available technology, and in-mine testing results from the first phase are now available.

Jan 1, 1994

By M. H. Kotze, M. J. Virnig, G. Steinbach

Earlier work at Mintek on the development of gold-selective resins culminated in a plant-manufactured batch of the first generation of Minix resin. A subsequent pilot-plant campaign at a South African gold mine identified some problems with that resin. These included lower capacity and selectivity for gold compared with the laboratory prototype, and a slow but progressive loss in capacity as the resin was eluted and reloaded cyclically. These problems were overcome by chemical modification of the resin structure. Examples of these improvements are presented. The commercialization of a new resin for a new metallurgical application presents problems, which are exacerbated by the initial lack of demand for the resin because the process is unfamiliar to the mining industry. Progress in the commercial development of Minix is discussed in this context.

Jan 1, 1993

It doesn't take any special acumen to note that US engineering and construction firms are busier than ever with mining projects in this mineral conscious world. This special issue of Mining Engineering takes a look at E&C companies-their expanding role, their special capabilities, and their challenges and problems. ME sent a questionnaire to a representative sample of E&C firms. Information was sought about officers, ownership, and amount of business. ME also asked about types of projects and commodities dealt in as well as market distribution and forms of payment. The accomnanying charts show how the 17 responding E&C firms answered these and other questions. Other ME survey questions, and a review of company literature, yielded information about financing techniques and special challenges for E&C firms. Insights were gained concerning government impacts, customer-generated problems, and promising areas for development-including synfuels-in the minerals industry. These areas are discussed later in this article. Accompanying articles in the special issue discuss the E&C company's role in mining projects, research and development in E&C firms, one approach to contract work used by an E&C firm, and an E&C project case study.

Jan 10, 1980

By I. Iwasaki, H. Dho

The role of sodium silicate in the anionic flotation of a Florida phosphate ore was investigated using laboratory continuous flotation tests, frothabiliry tests and SEM observations. In the absence of sodium silicate, Ca I+ promoted the unwanted activation of quartz by forming calcium bearing precipitates. The addition of sodium silicate enhanced the flotation efficiency through: 1) the removal of impurity minerals and calcium-bearing precipitates from quartz surfaces by dispersion, 2) drier and more persistent froths stabilized by oily droplets containing calcium silicate precipitates, and 3) higher specific flotation rates of phosphate relative to quartz, leading to faster flotation rates and increased selectivity of separation.

Jan 1, 1991

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 Peter Sullivan, Johan van Heerden

Increased use of continuous miners and roadheaders in the underground coal mining industry in South Africa has led to improved productivity and efficiency of operations. Of major concern, however, is the increased amount of airborne dust generated during mining. Dust is a health hazard in terms of respiratory diseases, can impede productivity and is the major contributor to the potential of underground explosions. The concern of the South African coal mining industry with regard to the underground dust problem has led to the establishment of a Dust Control Section in the Coal Mining Division of COMRO. In the field of dust suppression system evaluation and design, collaborative work has been undertaken by COMRO and FLOSEP. This paper gives a review of the application of Computational Fluid Dynamics (CFD) in evaluating and improving environmental conditions in continuous miner and roadheader sections. A brief history of the development of the CFD model as well as a discussion of a typical application is included.

Jan 1, 1993

By R. K. Devala

In this paper, numerical approximation schemes, for solution of the mass transfer problem in mine ventilation have been developed by using three implicit finite difference schemes. Results from these schemes have been compared with the analytical solution for spatial and time increments, using the concept of Root Mean Square error. For implicit finite difference schemes, in general, the modified central difference scheme is better than the two other schemes at lower velocity. Also, at lower air velocities, implicit schemes underpredicted the concentration values. At higher air velocities, the Crank-Nicholson and Laasonen schemes provided better results than the Modified Central Difference scheme.

Jan 1, 1994

By Charles D. Litton

Introduction The successful performance of a mine-wide fire detection system depends upon its ability to detect the presence of a fire rapidly and reliably. It should be sufficiently rapid so that there remains enough time to either safely evacuate a mine or successfully extinguish and control the fire or both. It should be reliable so that false alarms are minimized without sacrificing sensitivity or time response. Systems should also be durable enough to withstand the mine environment over long periods of time while maintaining a high degree of re1iability. Maintenance and calibration of the system should be simp1 e and not require the expenditure of excessive time and manpower to keep it operational. Sensitivity, reliability, and durability of mine fire sensors and their electronic support systems have been the subject of significant Bureau research within recent years. The bulk of this type of information, along with the reports from which the remainder of this paper is derived, can be found in the Bibliography. It suffices to say that there exist commercially available systems for use in mines. This paper addresses a strategy for the use of such sensors and systems. Many factors influence the design of a mine-wide fire detection system, such as the potential sources and modes of ignition, the types of combustibles involved and the quantities avai1able for fire growth and flame spread. Mine air ventilation influences the growth and spread of a fire and also serves to transport the products-of-combustion to other areas of a mine remote from the fire. Fire sensor alarm thresholds place limits on the sizes of fires that can be detected. The time to respond to a detected fire, either in terms of evacuation or control and extinguishment, place additional time constraints on the design of fire detection systems. These factors interact with each other, often in complex ways, and it is the definition and understanding of these factors and their interactions that hold the key to the design of adequate and re1iable fire detection systems. Our level of understanding of the problem has increased dramatically within recent years and it is the intent of this paper to discuss the progress that has been made and how the information can best be used to improve the level of fire detection in underground mines.

Jan 1, 1986

By Frank E. Dalton, Bart T. Lynam, Forrest C. Neil

The Tunnel and Reservoir Plan (TARP) is the largest tunneling program in the history of the metropolitan Chicago area (Figure 1). Between September 1976 and September 1977, rock tunnel contracts having an estimated cost of approximately $420 million will be advertised. During the past six months, the Metropolitan Sanitary District of Greater Chicago (MSDGC) has awarded contracts for 16.5 miles of rock tunnels in diam of from 9 ft to 30 ft having a total bid price of $120,261,750. RECENT CONTRACT AWARDS Addison-Wilmette Tunnel $63,140,480 Upper Des Plaines #20 Tunnel 35,749,664 Upper Des Plaines #21 Tunnel 21,371,607 Addison-Wilmette Tunnel The first contract was advertised in September 1975. This contract, described as the Addison-Wilmette Tunnel, runs from Wilmette Harbor at Lake Michigan under the North Shore Channel to Addison Street in the City of Chicago, a distance of 10 miles. The contract calls for constructing approximately 27,750 linear ft of 30 ft ID and 24,020 linear ft of 22 ft ID unlined rock tunnels, excavation of two construction shafts, and the excavation of 32 drop shafts of various diam. Two hundred ninety-three companies were notified of this contract being advertised, 70 companies took out contract specifications and 3 companies ultimately submitted bids. The contract was awarded to a joint venture of:

Jan 1, 1976

By Joyce A. Ober

Strontium occurs commonly in nature, averaging 0.034% of all igneous rock; however, only two minerals, celestite and strontianite, contain strontium in sufficient quantities to make its recovery practical, and these minerals are found in sedimentary rocks. Of the two, only celestite has been found to occur in deposits of sufficient size to make development of mining facilities currently attractive. Celestite, the most common strontium mineral, consists primarily of strontium sulfate (SrSO,). Strontianite, the second most common mineral, consists primarily of strontium carbonate (Sr CO3). Strontianite would be the more useful of the two common minerals because strontium is used most commonly in the carbonate form, but few deposits have been discovered that are suitable for development. The physical properties of strontium ores are listed in [Table 1].

Jan 1, 1994

By Charles D. Litton

This report describes a smoke particle detector which utilizes a novel three electrode configuration and 5.0 [] source of Americium 241. The detector operates on the principle of diffusional charging by a region of unipolar molecular ions. The detector is sensitive to particle concentrations in the range of 10 to 5 20 ug/m3. The detector is intended for use primarily as an early warning fire detector but has the potential for other applications of particulate monitoring. In particular, this report adresses the potential use of the detector for monitoring diesel particulate matter (DPM). To assess the viability of this application, particle size data obtained from in-mine sampling of both DPM and dust were used to derive detector sensitivity functions for DPM and dust as a function of their mass concentrations only. These sensitivity functions are dependent upon the average diameters and size distributions of the DPM and dust. Using the derived sensitivity function for DPM, experiments were conducted in a ventilated tunnel where the true DPM mass concentrations, measured using a Tapered Element Oscillating Microbalance (TEOM) were compared to the mass concentrations calculated using the detector sensitivity function. The agreement between the two measurements was good, indicating that with additional experiments, coupled with in-mine evaluation of the detector, refinement of the device for use as a continuous monitor for DPM appears feasible.

Jan 1, 1989

By R. Frenette, A. W. Mo, H. A. Hamza

Fine particles present major technical and economic problems to those who deal with solid/liquid separation processes. In the coal industry the problem is compounded by the large amounts of produced fines such as those present in Western Canadian coals. Flocculants in the form of high molecular weight water soluble polymers are commonly considered an effective solution for the enhancement of the separation process. These reagents are relatively expensive especially when considering a low-price commodity such as coal. Optimization of the use of these reagents is therefore an operational necessity. Six polymers were evaluated as to their effectiveness in flocculating a fine coal tailing. Results were compared with those for a reference flocculant, in-use at that time in the washery. It was shown that, in general, flocculants significantly improve the solid/liquid separation process. The ranking of the flocculants as to their effectiveness in settling and filtration indicated that the best flocculants for settling were not necessarily the most effective for filtration. Flocculants that showed the best filtration improvement were generally cationic and those best for settling were anionic.

Jan 1, 1988