Search Documents

By M. Noppé

"Dilution in underground coal operations can be underestimated by up to five times during Feasibility Studies, with disastrous economic consequences. Every 1% of stone waste introduced can reduce an in situ specific energy of 11,000 BTU/lb (25 MJ/kg) by some 110 BTU/lb (0.25 MJ/kg) and increases the abrasiveness of the run-of-mine coal. Where a wash plant is not in place, penalties imposed for not meeting contractual specifications alone can amount to some AU$1 million per year.This paper presents a method for monitoring, reporting and ultimately controlling dilution in an underground coal mining operation. The dilution trends before and after introducing the recommended controls in a continuous miner/longwall mine are presented over an eight year period. The additional information from such a dilution monitoring program can also be used to control mining horizons and plan longwall extraction heights across the face proactively, on a short-term scale with resulting improvements in productivity. INTRODUCTION Grade control, as practiced on any mine, is concerned with predicting routine quality and tonnage values for short- to medium-term mining operations, and the reconciliation of these predictions against “actual” results. For a longwall mine supplying steam coal, such routine parameters may include the proximate analyses, specific energy (SE), abrasiveness and sulphur, as well as float and sink analyses if the coal is beneficiated. In addition, grade control is concerned with identifying the mineable horizon (or horizons) in a selective-mining operation, together with monitoring how well these horizons have been extracted or adhered to. Close-spaced surface drilling can be costly for any mining venture, particularly for longwall mines operating in the deeper seams. For this reason, much of the data for short-term grade control requirements are acquired during actual bord-and-pillar development. The underground data are derived from so-called “channel” samples. These samples are cut or chipped from the coal seam, perpendicular to the mining horizon, with dimensions suitable for obtaining sufficient “representative” sample for analyses. For a 2m thick mining horizon, a channel sample 300 mm wide and 50 mm deep over the thickness of the horizon would provide some 4.5 kg of sample, sufficient for most of the necessary tests. To allow the information to be computer recorded, additional information such as seam thickness, sample co-ordinates, and the elevation of the seam (or horizon) roof or floor, may be required."

Jan 1, 2015

By PDF

The adsorption of ethoxylated sulfonates and nonionics of the same ethoxylation number?on a low-ash coal has been studied. The surfactant adsorption has been investigated as a function of concentration, pH, temperature and ionic strength for three homologues. Zeta potential of coal particles and surface tension of supernatants has been concurrently determined to eludicate the orientation of sudactant molecules on the coal surface as well as the mechanism of adsorption process. The adsorption data are utilized to calculate thermodynamic parameters such as the free energy of adsorption and isoteric heats of adsorption.

Jan 1, 1988

By A. Griffiths

The? use of hydrogen peroxide to detoxify gold mill waste waters containing cyanide and other toxic substances is already an established technology. Recent advances have extended the range of application of hydrogen peroxide treatment to include the removal of complex iron cyanides, the simultaneous removal of cyanide and toxic metals down to very low levels and treatment of barren bleeds, CIP' pulps and tailings pond discharges. Three treatment plants are described here. Each was installed at a gold mine in North America in 1987 and each illustrates a different application of hydrogen peroxide. The need for individual design of the detoxification plant to fit particular requirements is shown by the examples chosen.

Jan 1, 1988

By P. O. Lindahl

The U.S. Bureau of Mines initiated research to improve the safety and efficiency of transporting coal from deep underground mines using a balanced air-lift hydrohoist. A 50-m-high pilot-scale model was constructed and tested to evaluate the feasibility of hydraulically hoisting a coal-water slurry in a U-tube pipeline from the mine level to the surface with the assistance of compressed air. A prototype screw feeder is used to continuously compact and inject 5-cm or less run-of-mine coal into a pressurized 20-cm-diam pipeline. Production rates up to 40 metric tph at an airflow of 1.5 m3/min were achieved with the model, and coal size degradation was relatively minor. Modifications are in progress to achieve 100 tph at an airflow of 2.8 standard m3/min injected into the riser pipe. Pilot-scale results indicate that an air-lift hydrohoist system is a feasible, cost-effective alternative to conventional skip hoisting that can be installed in existing shafts or surface-drilled holes closer to the face area. Air-lift hydrohoisting offers advantages of infinitely adjustable slurry flow rates, reduced pressure at the point of coal injection, and flexible design that can be combined with hydraulic pumping. Proposed design changes are discussed for coal transport, mine layouts, ventilation, fire control, and escapeways using this system.

Jan 1, 1995

By R. G. Bradburn

The events which led to computer control of the grinding circuit at Brenda Mines are described, beginning with mill operating philosophy. High production rates are encouraged so that, despite severe upstream disturbances, a manual control method to meet this philosophy had developed. Unfortunately, due to the time interval between manual control adjustments, losses in production resulted. An analog control method was devised and, although superior to manual control in some situations, was found to suffer from several practical limitations. The data logging capabilities of a control computer seemed warranted. Circuit test- work combined with an analysis of operating data showed that (1) metallurgical personnel, at times could increase production rates by as much as 10 percent over that achieved by grinding operators, (2) the chosen data base required an increase of 2 percent or more to be statistically significant and (3) for a 2 percent increase there would be a significant rate of return of investment in a computer installation, Consequently one grinding circuit was fully instrumented, and a rented control computer was installed by Brenda personnel. Prior to installation, Brenda metallurgical and instrumentation personnel were trained in the use of the computer. An experimental program was devised with short and long term objectives. The short term objective was to develop a practical control strategy which would yield immediate production improvement. This goal has been met as described in this paper. Statistically significant increases in excess of 2 percent have been established. Work is being completed for the permanent installation of computer control on all four grinding circuits at the present time. Long term objectives are (1) off line analysis of the circuit using mathematical models of process units, (2) on line experiments to study alternative contol tactics, and (3) possible expansion of computer facilities to the crushing plant.

Jan 1, 1976

Australian underground coal mines predominately use the longwall method for coal extraction. In longwall mining at least two parallel roadways known as gateroads are mined to delineate the sides of the longwall block, a longwall installation face is then driven connecting the gateroads to enable the longwall mining equipment to be installed. Roadway development should ideally be ahead of the longwall so that the longwall equipment can be installed into the newly developed panel with minimal delay to coal production. A discrete event model of roadway development can help assess how a particular configuration may perform with high levels of variability and uncertainty in operations. One of the major delays associated with roadway development is caused by the shuttle car due to its cyclic stop-start nature. Shuttle car travelling paths and machine interactions are normally constraint by the mine?s roadway layout and mine safety issues. This paper presents simulations of shuttle car route options which can be considered at the design stage to minimize the cycle time of a shuttle car as part of a general roadway development simulation model developed using 3D Flexsim.

Feb 23, 2014

This paper presents the results of an investigation of the stability of the mass flow rates and average pellet size in the different streams of an industrial-scale balling circuit. The variables in this study include water content, drum speed and fresh feed rate. It was found that both the mass flow rates and pellet diameter are greatly disturbed when a change, positive or negative, in any of the variables takes place. For most of these disturbances to be damped don, a period of one hour or so is required. When a disturbance in the feed rate was made, the transient period extended to more than one and half hours (the duration of the experiment). It was observed that there is an interaction between the drum speed and moisture needed for producing an acceptable green ball product. The moisture content of the product pellets was found to be a function of the pellet size, with the larger pellets retaining a higher moisture content.

Jan 1, 1980

By Henry N. McCarl

The New England States form the most northeastern portion of the continental United States and include Connecticut, Rhode island, Massachusetts, Vermont, New Hampshire, and Maine. These states have an aggregate population of over 10.5 million people, and an average annual population rate increase of about 1.3%. A great deal of new construction is required each year to meet the increasing demand for new homes, roads, offices, factories, and warehouses. Yet, prices of construction materials such as blocks and concrete are generally higher in New England than in other well populated areas of the United States. This is an indication of local demand being somewhat greater than supply, an atmosphere conducive to new developments in the production of construction materials. One such field of development is the rapidly growing Lightweight Aggregate Industry. Recent construction in Boston has used a great deal of lightweight aggregate. New structures using lightweight aggregate in lightweight concrete include the following: M.I.T.'s 20-story Earth Science Center and 17-story Married Students Housing Project Prudential Life Insurance Center, West End Redevelopment Project at Charles River Park, Hotel Americana, and the British-owned 33-story office building at 50 Pearl Street.

Jan 1, 1964

By Charles S. Spirakis

The consistent occurrence of organic carbon early in the paragenesis of Mississippi Valley-type sulfide deposits suggests a genetic link between organic carbon and the sulfide ores. Reduction of sulfate in the mineralizing solution by organic carbon at the sites of mineralization is commonly proposed as the precipitation mechanism for these deposits, but inorganic sulfate reduction is too slow to be important to the chemistry of the ore zone, and bacteria, which catalyze sulfate reduction at low temperatures, are not known to survive at the temperatures of mineralization. Sulfate reduction with or without bacteria is not consistent with the sulfur Isotope evidence. Sulfur isotope studies also indicate that the derivation of sulfur from hydrocarbon at the sites of mineralization is unlikely. Organometallic complexing may be involved in the transport of metals, but no plausible mechanism for breaking these complexes at the sites of mineralization has been proposed. Reduction of partly oxidized sulfur species in the mineralizing solution by organic carbon at the sites of mineralization is a possibility which deserves further scrutiny.

Jan 1, 2013

By C. A. Fleming, K. W. Sarbutt, P. K. MacPhail

The SART process has been developed for Teck to treat bar­ren solution from the cyanidation/CIP process that has been developed for the Lobo-Marte project in Chile. The objective of the process is to recover cyanide in a form that is suitable for recycling to the leaching part of the process. The Marte and Lobo ore bodies require a dosage rate of about 2 kg/t NaCN, of which only 0.5 kg/t is truly consumed (as thiocyanate, cyanate and ferrocyanide species). The remaining -1.5 kg/t is present as cop­per cyanide (-1 kg/t) and free cyanide (-0.5 kg/t), and is poten­tially recoverable and recyclable. SART is an acronym that describes the unit operations in this cyanide recovery process; namely, .. Sulphidization .. Acidification .. Recycling of precipitate " Thickening of precipitate The basic chemistry has been applied previously, and has also been the subject of two patents (American Cyanamid Company, 1965, Potter et al., 1986). The process involves the conversion of all free and WAD cyanide in solution to hydrocyanic acid by acidification of the tailings solution to pH :s,4, and the conversion of all copper in solution to cuprous sulphide (synthetic chal­cocite) by the addition of a sulphide salt:

Jan 1, 1998

By P. W. King

The performance of the versatile McNally Wedag horizontal vibratory centrifuge for dewatering ultra fine 0.5 x 0.15 mm (28 x 100 mesh) material has proven to be success¬ful and the results presented herein will examine its capabilities in terms of capacity, solids capture, product moisture, effluent solids, and size analysis. Centrifugal dewatering of fine refuse has proven t to be another application for which this unit has performed exceptionally well.

Jan 1, 1985

By Leonidio Stegmiller

Since the petroleum crisis in 1973, charcoal1 is being considered one of the most important fuel for the Brazilian consumers, mainly for pellet's producers. In replacing fuel by charcoal mixed up with ore, obviously one of the first thing to be investigated is its influence in the product's quality. Special attention has been given to the metallurgical characteristics. This paper infocus the effect of increasing dosings of charcoal to the pellet's porosity and how other physical and metallurgical characteristics will be affected accordingly. This work was carried out using two different finesses of charcoal and dosing varied from 0.5 to 2.0%.

Jan 1, 1982

By E. D. Attanasi, M. W. Bultman, J. H. DeYoung

The 1987 recovery in the US mining industry permitted modest increases in exploration expenditures that year (Fig. 1). Favorable market conditions apparently allowed the gains to be sus¬tained in 1988. There was great uncer¬tainty early in the year as to whether world and US economic growth would be a casualty of the October 1987 worldwide stock market crash. By nearly all measures, the performance of the US minerals industry was strong¬. A weak US dollar and the strong growth of worldwide capital spending resulted in in¬creased US exports of con¬sumer and producer durable items as well as strong domes¬tic demand for metals. In fact, 1988 US steel industry exports reached levels not attained since the mid-1970s. It was re¬ported that steel industry labor productivity is now roughly twice the 1981 level. Among metals with signifi¬cant average nominal price increases in 1988 over 1987 levels were copper (43%), alu¬minum (52%0), and zinc (44%). Even though domestic copper production has grown since 1984 by 30% in mining and 24% in refining, em¬ployment in mining and milling is 4% below the 1984 level. Domestic unit costs are reported in the range of $1.10 to $1.33/kg (50 to 60 cents per lb). The US base metals industry is proba¬bly in its best cash position in many years. However, there has not been a large increase in exploration expendi¬tures. This is due mostly to the percep¬tion that worldwide capacity can easily be increased. Industry reports do show that "low cost" copper producers have been buying reserves from weaker com¬panies. The 1987 Society of Economic Ge¬ologists (SEG) survey of exploration activity indicated that 95 cents out of every exploration dollar spent by US and Canadian firms was for base and precious metals (Economic Geology, January 1989). Press reports, though, make it clear that most of that spending was targeted for precious metals. US claim staking data (Fig. 2) rein¬forces this suspicion. The apparent lag in new claim filings in Alaska and phe¬nomenal growth in filings in the lower 48 states suggests that exploration is directed at relatively low risk targets. In the conterminous 48, more than 40% of the new claims were made in Nevada, indicating an emphasis on gold (although even Nevada had some base metals exploration). Even with a price decline during 1988, the difference between the gold price and average global "cash" production cost of $7.30/g ($227 per oz) still leaves room for an attractive return (Northern Miner, 1988). Exploration plans and results Metals Economics Group (Halifax) indicated in its 1988 exploration survey that exploration expenditures by US and South African firms would be at about 1987 levels. It also reported that Canadian and Australian firms were ex¬pected to reduce their exploration spend¬ing significantly. Firms in both coun¬tries were caught in changes in tax laws. In Canada, the Mining Ex¬ploration Depletion Allow¬ance (MEDA) once permitted generous tax write-offs to in¬dividuals investing in miner¬als exploration. It was to be replaced in January 1989 with the Canadian Exploration In¬centives Program (CEIP). Although structured and ad¬ministered differently than MEDA, CEIP can provide an equivalent or possibly greater financial incentive for min¬eral exploration, for junior mining companies. In 1987, it is estimated that junior com¬panies accounted for two¬-thirds of the off-property (or grass roots) exploration ex¬penditures in Canada. Australia will revoke the tax exemption for gold in 1990. Australian operators, therfore, were expected to concentrate efforts on speeding up pro¬duction during 1988 and 1989. In 1988, Chile and Mali announced special efforts to attract gold explora¬tion by foreign companies. The Cana¬dian government continues to express concern about the write-off (and drawdown) of base metal reserves. Falconbridge did announce a new initiative to identify additional base metal reserves in the Sudbury district. Discoveries Gold deposits dominated discoveries

Jan 1, 1989

By Susan G. Bilhorn

A number of studies have been conducted in active and inactive mine environments using continuous monitoring and data acquisition systems to detect various parameters. In addition to the information obtained for research purposes, these monitoring systems can provide a means to remotely collect required information (such as radon daughter concentrations and air velocity) and control various conditions (such as fan operation and air door position) in numerous working sections of an active mine. Selection of detector locations and placement, which are critical to obtain the information and control desired while not inhibiting mine operations and influencing the detector readings, are covered in this paper.

Jan 1, 1984

By S. P. Brown, J. E. Worthington

Increasingly, exploration geology seems to be growing into a practice overly separated from production geology, yet the eventual purpose of exploration is a producing mine. To help in the search for new deposits, exploration "lessons" will be drawn from the papers given at the Fall AIME Applied Geology Symposium. In addition, examples will be re-emphasized to show how early observation of matters now routine to mine work (for example, hydrology, rock mechanics, oxidation state) can help increase the effectiveness of exploration.

Jan 1, 1992

By William G. Holroyd

In January 1992, the Office of the US Trade Representative announced that the People's Republic of China had agreed to protect US intellectual property, including computer software, sound recordings, agrichemicals and pharmaceuticals. Under the agreement, China will make significant improvements in its patent, copyright and trade-secret laws. Ambassador Carla A. Hills, the US trade representative, said "this agreement should create significant opportunities for US firms interested in marketing high valued-added products to China." Principal beneficiaries will include the agrichemical and computer industries, as well as pharmaceutical, entertainment. The agreement will safeguard these industries' intellectual property, stimulating new exports to China and helping to generate additional growth in the US. Refractory grade bauxite was included in the mineral category of the $1.5 billion of Chinese products on which the US government threatened to impose an immediate 100% trade tariff. Refractory bauxite is available from Guyana and Brazil at higher cost and in different grades. However, refractory brick manufacturers would have had little choice but to pass on the costs to their consumers. Although the United States and China are separated by political ideology and internal governing structures, this agreement recognizes the importance of a $19 billion trading relationship. Consequently, the renewal of China's most favored-nation trading status in the US congress in -June 1992 was all but assured. Many US companies doing business in China and Hong Kong have been quietly increasing their investments since 1989. These companies can now concentrate on developing sales to the domestic Chinese market. This market is expected to surpass 1.2 billion people in 1995 and approach 1.3 billion by the end of the century.

Jan 1, 1993

By R. A. Pimentel

Complying with reduced dust standards (i.e., less than 2.0 mg/m3) due to quartz levels that exceed 5 percent is presently a critical problem for many continuous mining sections. Results are presented of research which was performed to determine the factors causing high levels of respirable quartz dust and to identify the major contributors to operator exposure. It was found that the significant sources of quartz dust are the drilling of the roof and the mining of the roof, floor and rock bands. Both the miner and the bolter may be on a reduced standard, but compliance is easiest to achieve on the bolter for which improvements in maintenance and operator practices are usually sufficient. At the miner, the problem is more elusive. Research continues to identify operating and mining practices that contribute to the exposure..

Jan 1, 1985

By William E. Saegart

Copper has been mined in the Philippines since at least as early as the Ming dynasty (1368 A.D. to 1644 A. D.). The principal source areas of this early production were in Camarines Norte (Paracale), in the Mountain Province, which now boasts the largest number of Philippine porphyry copper deposits, in Masbate and in Surigao, The Spanish Era began in 1521. Although they were primarily interested in gold, the Spaniards operated several copper mines including the San Remigio mine on Panay and the Lepanto mine in northern Luzon, beginning in 1842 and 1865 respectively. Prior to World War II most of the Philippine copper production was supplied by these same two mines together with the Hixbar mine, Rapu Rapu Island which began operation in 1939. The Hixbar and San Remigio mines are cupriferous pyrite deposits and the Lepanto is a vein-¬form replacement deposit (Kinkel et al. ,I 1956). No significant copper production was derived from porphyry copper occurrences prior to world War II.

Jan 1, 1976

By Reginald E. Reid

Mining on Bureau of Land Management (BLM) administered lands is affected by Federal laws and regulations requiring the mining industry to plan for the environmental consequences of surface disturbance. Regardless of the requirements for obtaining a claim, permit, lease or contract to mine, a notice or a mining and reclamation plan will be submitted and an acceptable environmental document must be prepared prior to mining. A bond may be required based on the results of the environmental evaluation, public interest and the operator's past history of compliance. In several areas, Federal requirements are different from California's requirements under their Surface Mine and Reclamation Act (SMARA). Therefore, the BLM is negotiating with the State in order to work out problem areas of responsibility and duplication of effort.

Jan 1, 1984

By CAIJUN CHEN, MING ZHANG, ZHENWEI WU, FENG ZHOU, BOQUAN LI, XILIANG ZHANG, ZHOU PU

Traveling grate is a widely used process for iron ore pellet production; however, the thermal state of pellets in drying section is still unclear. In this study, the temperature distribution of drying section was investigated using computational fluid dynamics (CFD). Based on the calculated results of airflow velocity, space temperature distribution, and the temperature change of pellets, it concluded that there is a coupling effect in drying section in traveling grate. The gas with higher temperature in DDD transfers heat to UDD through the gap of the insulation board, and the temperature gradient of the pellet bed changed before reaching the insulation board. The characteristics of pellet bed expected to appear in DDD was displayed in UDD in advance. Moreover, a contrast experiment was conducted to verify the model.

Feb 1, 2021