Search Documents

By G. Danko

Ventilation and refrigeration for mine climate modification, contributes significantly to the operating costs of a deep hot mine. Mine climate simulation programs can be used to minimize the impact of these costs. There are several computer codes available including CLIMSIM?, to assist in this work. Whichever simulation program is used, it is the mine ventilation engineer who must supply the input data. This paper raises and answers the following question, namely: what accuracy is required of the basic input parameters, in order for a certain precision to be obtained in the predicted air temperatures? In the first part of the paper a new approach is described to estimate the dry and wet bulb temperature of the airflow, either in a dry or wet roadway. The calculation procedure allows an arbitrary temperature change with time, using Duhamel's superposition solution. Matrix-vector representation is applied to simplify the computational structure. In the second part of the paper the sensitivities of the dry and wet bulb air temperatures are analyzed to the changes of the rock thermo-physical properties, the heat transfer coefficient and the wetness factor.

Jan 1, 1988

By A. J. Burger, F. L. D. Cloete

Tests indicated that effective recovery of pyrite from a coarse Witwatersrand quartzitic ore can be accomplished by intensified flotation in an air-sparged hydrocyclone. Air is fed through the porous cylindrical wall of the hydrocyclone into a swirling layer of slury. Hydrophobic particles are attached selectively to small air bubbles, which form a froth and are recovered through the overflow. Hydrophilic particles pass out in the underflow. A spigot in which flow is restricted by an orifice was found to be more successful in preventing blockage by wood chips than an annular opening between a pedestal and the cylinder wall. Pyrite recoveries of 85 to 93 per cent at grades of 35 to 40 per cent sulphur were obtained in the air-sparged hydroclone with residence times of about 1 second. Comparative tests in a batch flotation cell after 320 seconds yielded average recoveries of up to 96 per cent, but with a mean grade of 32,5 per cent sulphur. A high colector dosage of 120 g/t was required in the cyclone, compared with the 40 gft used in conventional operations. An air flowrate of about 150 I/min was adequate at a slury feed rate of 35l/min. Particle sizes between 38 and 106µm yielded the best flotation results.

Jan 1, 1988

By Charles F. Seemann

It is with considerable trepidation that I set out to defend "litigation" to Design Professionals (DPs), as a better method of resolving disputes than arbitration, in the light of my personal feeling that an increasing amount of America's productive process is being squandered in litigation. Newer methods of dispute resolution, particularly arbitration, are fashionable, and opponents of these schemes risk being viewed as cynical or self-serving. My quandary is heightened since for some smaller disputes, arbitration seems clearly the better choice. I must concede, for example, that when the cost of dispute resolution--i.e., the cost of the process (such as arbitrators fees, attorneys fees, etc.), plus the cost impact of the non-productivity of involved employees--approximates the amount of the dispute, controlling that cost may be as important as a correct resolution. This principle is particularly true for small disputes arising during the progress of a project; it is probably more cost-effective for all parties to resolve their disputes quickly than permitting the dispute to drag out.

Jan 1, 1988

By N. Panagiotopoulos

A low-grade (1.06% Ni, 0.06% Co) hematitic type lateritic ore from Triada, Euboea Island, Greece, has been leached with sulfuric acid at atmospheric pressure for the extraction of the contained Ni and Co values. The effect of various parameters, including reaction time and leaching temperature, acid strength, pulp density, etc., on Ni, Co extraction and Fe dissolution was determined. By leaching at 95°C for 4h with a 3N sulfuric acid solution at 25% pulp density, Ni and Co extractions were 82 and 75% respectively, and Fe co-dissolution 28%, yielding a pregnant solution containing 2.7 g/l Ni, 0.16 g/l Co, and 33 g/l Fe. Overall acid consumption was 850 kg/t ore (or 100 kg/kg Nil. Preheating of the laterites at 600°C before leaching resulted in much faster leaching kinetics for Ni, but the final extraction and acid consumption remained unaffected; Fe extraction was not influenced. Three-stage counter-current leaching at 9S°C, using 2N acid strength at each stage and 35% pulp density, reduced acid consumption to 350 kg/t ore (41 kg/kg Nil, and yielded 81% Ni recovery. Percolation leaching of -10 mm laterite at ambient temperature with 3N acid for 7 days resulted in 58% Ni extraction.

Jan 1, 1988

By A. L. Wilder

Coeur d'Alene Mines Corporation's newest precious metals property is located in the old Rochester Mining District approximately twenty-five miles northeast of Lovelock, Nevada. Built at an elevation in excess of 6 000 feet, the Coeur-Rochester gold silver heap leach property encountered cold weather operational problems typical of most northern Nevada heap leach properties, soon after the start-up of operations last fall. Due to the size of the heap area under leach at Rochester, it was decided that 1 the usual practice of spraying to an "ice field" and waiting for the spring thaw was impractical. Further, the delivery schedule for a solution heating system of the size required was unacceptable. Accordingly, Rochester personnel embarked on a program to seek out a leach solution distribution system that would enable an operation through the winter and yet be cost effective. The findings of this program were rather dramatic and, as a result, the whole perception of heap leach solution application at Rochester has changed forever.

Jan 1, 1988

By Liu Liching, Yan Hongjiu

"In China, the electromagnetic induction initiating system f or blasting engineering has been greatly developed in recent years. With this system, the total number of detonators that may be blasted in each round has been increased from 420 to 940 as a result of the invention of a powerful exploder, and the length of leg wires of a detonator has reached 12 metres. These developments make the new system suitable for blasting engineering of medium scale. Another attractive feature of this system is a set of testing instruments which have been invented that enable a final check of the system to be made before firing as in normal electric blasting. This paper reports on these developments.IntroductionThe initiating system for blasting explosives is one of the key factors to the success of blasting engineering, along with the progress of explosives and blasting technology. Today, we have initiating systems which may be divided into two groups: electric and non-electric. The earliest initiating system was non-electric. Many mines, as well as many projects where rock excavation was involved, were blasting non-electrically before the new nonelectric initiating system came into use in the 1970s. Electric and non-electric initiating systems are the two main initiating systems which are now being widely used, each having its advantages and disadvantages. In electric blasting, the blasting supplies and the blasting circuit can be checked before it is used or fired and, therefore, is regarded to be more reliable. In many large-scale blasting engineering where reliability of the initiation is of great concern, a checkable initiating system is preferable. The electric initiating system is not considered to be as safe as the non-electric initiating system due to its inability to choose proper ignition energy. Therefore, a non-electrical initiating system would be preferable where a hazard of stray currents or static electric energy exists. At this stage of development, one would say it would be advantageous to develop a new initiating system."

Jan 1, 1988

By Andrew F. McKown, Lewis L. Oriard

Advances in explosives engineering are moving forward in several different aspects. These include improvements and new development in explosives products, the application of these products to blasting technologies, and the study of the peripheral effects of the use of explosives, such as ground vibrations and airblast. Topics of special interest in the last several years include new explosives and detonators, cap timing, explosive casting, high-speed photography, perimeter and slope control, air decking and mathematical modeling of blasting processes.

Jan 1, 1988

[Determine how subsidence resulting from underground coal mining affects surface structures, and evaluate the usefulness s of the tiltmeter for monitoring foundation movement. Approach The Bureau of Mines is studying foundation response to mine subsidence in order to determine how subsidence-induced ground movements affect foundations in place directly above the mint. These investigations are essential if economic mitigation and repair techniques are to be made. In addition, commercially available tiltmeter are being evaluated (or use as a cost-effective monitoring technique. To study foundation response and to evaluate the tiltmeter system, full-scale model foundations were constructed, instrumented, and monitored for three years. Vertical and horizontal displacements, tilt magnitudes and directions, and observed damages were recorded. Displacements were compared with measured lilt to determine if the tiltmeter was tracking foundation response to subsidence, The Bureau developed a computer software package to aid in the reduction and analysis of the tiltmeter data.]

Jan 1, 1988

By P. L. Loyselle, B. D. Comilsen, D. H. Carlson, J. H. Johnson

"In-mine airborne particulate samples have been successfully collected and the relative amounts of diesel and coal determined using the Laser Raman Quantitative Analysis (LRQA) method. This method allows analysis of filters which have been collected by a method similar to that used to determine the airborne respirable dust concentration in us underground coal mines. Samples were taken near the feeder-breaker, on haulage vehicles, and in the returns. Sampling methodologies were developed for coal-only and diesel-only particulate reference samples with sufficient filter loading for the LRQA method. A statistical analysis of reproducibility has been carried out. Samples have been collected simultaneously at two locations using the LRQA and the size-selective sampling methods. Good agreement between the two methods has been found.INTRODUCTIONThe goal of this research has been to develop the Laser Raman Quantitative Analysis (LRQA) method to measure the composition of respirable particulate, i.e. the fractions of coal and of diesel particulate, in the mine ambient air. In earlier Bureau of Mines sponsored research, we successfully demonstrated that the LRQA method could be used to measure the fraction of Diesel Particulate Matter (DPM) in coal/diesel particulate mixtures which were prepared in the laboratory.(I) 'The immediate objective was to test and refine this LRQA method on samples collected in a diesel underground coal mine.Specific objectives required to meet this goal include:I) Develop in-mine sample collection methods which will insure sufficient particulate loading on filters for LRQA. ,2) Develop methodology for in-mine collection of reference samples (""coal-only"" and ""diesel-only"" filters) which arc required for quantitative LRQA. 3) Analyze precision and accuracy of the LRQA method. 4) Compare composition measurements with another analytical method, i.e. the University of Minnesota/Bureau of Mines size selective sampling Micro-Orifice Uniform Deposit Impactor (MOUDI) method.An advantage of the LRQA method is that it allows analysis of filters which have been collected by a method similar to that used to determine the respirable dust concentration in US underground coal mines. No new sampling instruments and techniques are required. Transfer of sample from collection substrate to analysis substrate is not necessary. Furthermore, other analyses can be made on the same sample since the technique is nondestructive."

Jan 1, 1988

By R. L. Grayson, S. S. Peng

"Research has been conducted during the past year on a study to correlate respirable coal mine dust characteristics with worker positions and coal seams. The first characteristic of respirable coal mine dust which has been addressed in the correlation study is respirable dust mass concentration. In fulfillment of this objective, two mines operating in different coal seams have been selected for respirable dust mass sampling on both longwall panels and continuous mining sections. At present, sampling has been completed on the longwall panel operating in the first mine, and one half of the planned sampling has been accomplished on the continuous mining section.The first mine sampled is operating in the Pittsburgh coal seam. The average mining height is approximately 78"" with an average of 8"" of bottom shale being mined. The mine is primarily a longwall mine, and continuous mining machines are used to support the longwall.Figure 1 shows the layout of the longwall panel which was sampled. Intake air is coursed via the track heading up to the headgate area. The air splits at the headgate. Approximately 20,000-30,000 cubic feet of air per minute (CFM) is used to ventilate the longwall face and about 5,000-10,000 CFM is routed down the belt entry. Substantial leakage across the gob was noted during the sampling period. An average of 1800 CFM per 100 feet of face leaked through the shields into the gob from #1 shield to #112 shield. A substantial amount of leakage also occurred between the #1 shield and the solid rib of the headgate development panel. The path of the air used to ventilate the panel is shown with arrows in Figure 1. Direction of air flow was opposite to the coal moving direction on the armored face conveyor.A double-drum ranging shearer is used on the face to cut a 30-inch web of coal. Normal practice is to cut from the tailgate to headgate with the leading drum raised and the tail drum lowered for cutting bottom. After reaching the headgate, the shearer is reversed and both drums are lowered for a clean-up pass. The last 40 feet of face on the tailgate is cut on the clean-up pass.The shearer is equipped with 2 banks of 4 water sprays each and 2 large sprays on the headgate end and 1 bank of 4 sprays on the tailgate end. Additionally, sprays are located above bits on the cutting drums. Actual cutting speed was approximately 14-18 feet per minute, depending on conditions.The cross sectional area for air flow on the face was approximately 60 square feet before a pass was mined and 80 square feet after a pass was mined but before the shields were advanced. The cross sectional area at the shearer was about 35 square feet.The condition of both the tailgate and headgate of the panel was good with no signs of significant roof problems. The roof conditions along the face during the sampling period were variable. At times, as much as 3 feet of drawslate fell from the roof for a span of as much as 40 shields. Generally, however, relatively local areas of falling roof were encoun-tered, usually limited to a 10-20 shield span when appearing.Ten days were spent gathering respirable dust samples on the longwall panel. Mine Safety Appliance (MSA) sampling units equipped with 10-mm nylon cyclones, pre-weighed MSA PVC filters, and constant-flow DuPont pumps were used to obtain thesamples. The pumps were calibrated at a 2 liters-per-minute flow rate. The 10-mm cyclone was selected for classifying total dust into the desired respirable fraction in order to obtain ""legally defined"" respirable dust samples for detailed physical characterization."

Jan 1, 1988

By C. J. Johnson, C. J. Bise

"The occurrence of Coal Worker's Pneumoconiosis (CWP) ·has been potentially linked with several characteristics of coal such as rank, volatility, percent content of ash and non-coal components, quartz content, and the presence of several trace elements. According to the National Research Council, numerous epidemiological Studies: indicate that the incidence of CWP varies significantly with the composition and/or the concentration of the coal mine dust.Although advances in dust suppression techniques have markedly reduced respirable dust levels in underground coal mines, the National Research Council has concluded that chemical characteristics of respirable dust from different coal seams should be studied. With this objective in mind, research has been conducted in underground coal mines located in the eastern and mid-western United States, and in the laboratory to characterize the elemental composition of mining-generated airborne dust and laboratory-generated dust derived from samples taken from these mines. The goal of the research is to determine if a relationship exists between mining-generated and laboratory-generated dust from the ·same mine. Results of this research will be presented. ,"

Jan 1, 1988

By K. H. Lee

The rate of beryllium dissolution from a low-grade ore was studied in sulfuric acid solutions. The effect of stirring speed, sulfuric acid concentration, particle size and temperature on the rate of dissolution of beryllium was established. The results of the study showed that the dissolution rate is independent of stirring speed within the range of 250-1000 rpm but depends on 1/2 power of the sulfuric acid concentration. The dissolution rate increases exponentially with decrease in particle size and the maximum attainable rate of extraction with respect to particle size is 6.6 x 10 mol dm min. The apparent activation energy (^E) for the dissolution reaction is 54.4 kJ/mol (13.0 kcal/mol). Based on this magnitude of the activation energy, it is concluded that a surface chemical reaction is the rate limiting step for the temperature range (70° -100°C) investigated.

Jan 1, 1988

By Krishna Nand

For assessing the safety of structures during underground explosions, ground particle velocity gives the best damage criteria, and 100 mm/see of ground particle velocity has been internationally accepted as the threshold value of safety (no damage). Results of extensive controlled underground explosion experiments conducted by the author to study the effects of ground vibrations on specially prepared concrete blocks, and also on low rise buildings and dams showed that no damage normally occurred when ground particle velocities were less than 100 mm/sec. Analysis of a large number of accelerograms from a dam site in India also indicated that no damage occurred to normal structures when integrated ground particle velocities were less than 100 mm/sec. Major damage in well built structures like a dam was noticed for ground particle velocity as high as about 350 mm/sec. These results are also generally substantiated from damage data obtained for various structures during other earthquakes, including Elcentro (1940), Taft (1952), Parkfield (1965), and San Fernando (1971). These studies, therefore, suggest that the damage criteria during underground explosions and earthquakes are similar; and 100 mm/see of ground particle velocity seems to be the general threshold value of safety (no damage) against ground vibrations.

Jan 1, 1988

Au airway hteat and moisture exchange .,Jgorithm is described which is generalised to suit most mining situations and can be run separately on a microcomputer or used within a network simulation. The main difference between this technique and other simplified methods is that a non-uniform boundary condition is allowed for. This permits radiative heat transfer between surfaces of different wetness in addition to evaporative and convective heat and mass transfer.

Jan 1, 1988

By M. M. Nash

Since the late 19th Century, scholars have been concerned about finding proper methods of managing business. The search seems to be taking us full-circle to the time and motion studies of Taylor (Horn, 1987). It wasn't until the late 1970's, however, that systematic investigations were made in the mining industry. One of the first was a study by Sanders, Patterson, and Peay (1976). That project explored the relationship of attitudes and safety. Peay, Atkin, and Goodman (1977, then reviewed the whole area of Organizational Development, including the so-called Rushton experiment.

Jan 1, 1988

By P. Koskinen

Outokumpu Oy has 30 years' experience in nickel production. It is mainly based on the technology developed within the company. The production chain starts from the mines reaching to the high-grade cathode nickel and the stainless steel manufacturing. As a multi-metal producer Outokumpu has the advantage to exploit from nickel raw materials also other valuable metals and intermediate products which can be processed at the company's various plants. The main source of nickel concentrate is nowadays the Enonkoski Mine started up in early 1986. It is the most modern mine in Finland being provided with the latest Finnish high-tech systems. Nickel concentrates are smelted at the Harjavalta Works using Outokumpu's internationally well-known flash smelting method. Also nickel containing residues and secondaries' are used as raw materials. The high-grade nickel matte from the smelter is then refined at the nickel refinery in a hydrometallurgical process, which was also developed by the company's own research staff. These processes have been continually improved and capacities gradually enlarged to 18 000 mtpy of cathode nickel. Besides plating, melting and superalloying purposes part of the nickel ends in stainless steel at the Tornio Works. The production was started in 1976 and has reached an established position on the European market.

Jan 1, 1988

By Frederick K. Allgaier

This report presents the final data from a 5-yr Bureau of Mines study designed to determine the surface subsidence characteristics resulting from longwall coal mining in a geologic environment common to the Western United States, It includes a description of the geologic setting of the study site, the mine plan, measurement techniques, and results of the monitoring program. Measured subsidence values were obtained over four adjacent longwall panels- Major subsidence characteristics such as longitudinal and transverse profiles, angles of draw, time-related subsidence development, and critical width are discussed. The maxima subsidence value of 5.8 ft was 68 pct of the mining thickness. The average angle of draw was 30°, Subsidence at the center of the first panel continued for 46 months following undermining. The lengths of the longwall panels precluded a definitive determination of the critical width and maximum possible subsidence.

Jan 1, 1988

By Peter G. Cooper

"During 1987, the feasibility of modernising the ER&S smelter at Port Kembla, NSW, Australia was studied. The selection of appropriate technologies to carry the smelter into the 21st century considered issues such as capital cost, existing infrastructure, feed mix, capacity, product quality, flexibility and potential for further development. Both hydrometallurgical and pyrometallurgical process schemes were considered. Some novel combinations were assessed but ultimately rejected. Final technology selections included proven smelting and anode furnace processes, pyrometallurgical slag cleaning and modifications to existing equipment. This process scheme balanced risk against development potential within the constraints imposed by the existing plant.BackgroundThe Electrolytic Refining and Smelting Company of Australia (ER&S) has operated a custom copper smelter at Port Kembla since 1908. Existing technology includes a sinter plant/blast furnace, three small Peirce Smith converters, two reverberatory anode furnaces and a conventional tankhouse. These process units were all installed prior to 1960 and have proven to be flexible enough to process the wide variety of domestic feed materials purchased by ER&S.However, by the early 1980s, threats to domestic concentrate supplies highlighted the need for major changes to reduce operating costs to world competitive levels. Various studies in the ensuing years failed to identify an economically attractive solution. Furthermore, pressures were increasing to improve the environmental performance of the smelter.During 1986 the options for redevelopment were again considered and by the end of 1987 technologies for the retrofit had been selected and a full feasibility study was completed."

Jan 1, 1988

By J. E. Rourke, O&apos

This paper describes the use of rock index property testing to obtain rock properties that a.re useful in the design and construction planning of an underground development for civil engineering or mining projects. The index properties discussed include (1) point load; (2) Schmidt hammer hardness; (3) abrasion hardness; and (4) total hardness. The first two index properties correlate to uniaxial compressive strength and Young's modulus. Discussions are given on the relationship to rock mass properties and the integrated use with semi-empirical, geotechnical design methods. The latter two properties correlate to construction performance parameters and some experience is cited. Examples of data are presented from an index testing program carried out on siltstone, sandstone and limestone rock core samples from a deep borehole drilled in the Paradox Basin of Utah for a nuclear waste repository site investigation.

Jan 1, 1988

By Hsi-keng Hu

"This paper deals with the flotability of stibnite and summarizes the major experiences and technological innovations of some typical practices of antimony sulfide ores in China. Experiences of cyanide-free and -less flotation of complex antimony sulfide ores and the application of the heavy media process to the preconcentration are described.Performance improvements obtained by innovations in operating techniques are also outlined and discussed. Technical innovations involve: (1) ramification roughing and differential-rate cleaning of stibnite-arsanopyrite ore; (2) the application of the new flotation reagent system; (3) process of separation flotation of Sb-Hg bulk concentrate; (4) extraction of gold from Au-Sb bulk concentrate; (5) flotation recovery of coarse stibnite particles.IntroductionChina is rich in natural resources of antimony and is one of the major antimony producers in the world. During the past several decades, a lot of research works have been done and many experiences in milling practices were gained, some of which are summarized briefly as follows.I. Heavy Media separation of Antimony sulfide Ore at Xikuangshan Hill, Hunan province (1)HMS as a technique of preconcentration of antimony ore has been performed more than ten years in China with good results.1. Ore characteristics The antimony ore of Xikuangshan belongs to the epithermal- metasomatic-filled doposit of antimony sulfide. Major minerals are stibnite (92.1%), antimony oxides (7.9%) and a small amount of pyrite and pyrrhotite; the gangue minerals are quartz, silicic limestone, calcite, hydrous kaolin, sericite, barite and others. The specific gravity of the ore is 2.8 and the specific gravity of stibnite and gangue are 4.6 and 2.654, respectively."

Jan 1, 1988