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By W. –E. Marx, M. Faber, R. Pollak, I. Astberg

INTRODUCTION Essentially three strategies are pursued in parallel for protecting the underground working force in mining against the consequences of methane ignitions which might lead to explosions: • Sufficient ventilation for avoiding the formation of explosive methane-air mixtures. • Avoiding sources of ignition caused possibly by electrical equipment or friction. • Structural explosion protection for limiting explosion propagation to the farthest-going extent for the case that methane is fired because of failing of the above preventive measures taken. The corresponding methods taken in mechanized roadheadings with point-attack roadheaders in German coalmining are subject of this paper. VENTILATION In ventilation of roadheading sites the following is to be considered in respect of methane control: • Sufficient air flows by volume being cycled to the heading face for diluting released methane to safe concentrations. • Sufficient local air velocities for effective mixing of methane and air in the whole heading site, in particular directly on the heading face and underneath the roof. Furthermore, ventilation needs to be laid out in a way that cut- ting does not result in health affecting dust exposure at any working place. Accordingly, the ventilation systems shown on Fig. 1 including primary and, if necessary, secondary auxiliary ventilation air ducts as well as dedusters, are used in roadheadings. This equipment is run according to the following principles: • If the roadheader is at standstill, the heading face is ventilated by the free air jet from the blowing duct closest to the face. In this operation phase the deduster is shut-down. • During cutting, the exhaust of the blowing air duct is automatically closed, and the deduster is taken into operation. The in- coming fresh air is now locally discharged via a lateral orifice, or distributed by Coanda-type ducts from the primary or secondary ventilation air duct. In this way, a stable dust wall not disturbed by the jet of the air duct is formed in front of the heading face. Only the ventilation air stream taken in by suction of the close-to-face deduster is passed through the inby zone of the heading face (over approx. 20 m). The clean exhaust of the deduster is dischayed to the roadway in some distance outby. Immediately at the heading face, methane accumulations possibly released by cutting are diluted by compressed-air jets from air-movers located near the roof which assure more rapid motion of the air without distuhing the dust wall. • In the zone of overlapping of primary and secondary duct and the deduster - that zone possibly is poorly ventilated during cutting - sufficient local air speed is assured by Coanda-type ducts or additional ventilation jets for avoiding methane accumulation. The regulations of the inspectorate specifies geometrical conditions to be met with these configurations of ventilation equipment. In-seam roadways are ventilated at rates > 0,5 m/s. For dedusters, present-day ventilation air flows are of 600-800 m+/ min. Ventilation monitoring and control is assured by units for measuring methane and ventilation air flows. If pre-set thresholds are exceeded or fallen short of, these measuring units shut-down - dependent on potential hazard - any not intrinsically safe electrical equipment in the roadheading, either totally or in limited zones. In addition, CO-measuring units near the roadway en- trance serve for early detection of mine fires. In spite of this ventilation layout and the equipment used and in spite of the water spray systems on the cutting head (discussed later in this paper) several cases of methane ignition and subsequent burning off (however, no explosions) have been recorded in the recent past. Therefore, the above-described ventilation is nowadays complemented in many cases by machine-mounted ventilation equipment for the immediate surroundings of the cutting head. Ventilation of the surroundings of the cutting head Investigations carried out subsequent to the above-mentioned gas ignitions have shown that the high ventilation air speed necessary for rapid dilution of methane could not permanently be arrived at in the following zones: • The direct zone of cutting, in particular during sumping. • The floor zone above the debris, predominantly below the cut- ting head. Accordingly, VOEST ALPINE-Bergtechnik, a producer of mining machinery, in cooperation with DMT developed for point- alttack roadheaders a novel machine-mounted ventilation equipment, the Jet-Block" (AERO SAFE Jet-Block) shown on Fig. 2. This system allows to ventilate the above-mentioned critical zones with high flow speeds. One AS Jet-Block is mounted on each side of the boom approx. 0.5 m behind the cutting head. The blocks discharge compressed-air jets with high energy from 10 nozzles per block into the hazardous zones (Fig. 3). Two nozzles of each jet block are tangentially oriented toward the upper circumference of the cutting head, the others are arranged fan-like with orientation to the heading face underneath the cutting head and the debris. The nozzle array of the blocks as well as the com-

Jan 1, 1997

By J. G. Speight

Laboratory studies indicate that autogenous heating of low-rank coal can be prevented by a prior treatment which involves immersing the coal for short (5-15 min.) periods in an inert liquid at temperatures between ~ 350° and 400°C. Such "carbonization" effectively reduces the accessible pore volume of the coal to levels at which heat generation through subsequent sorption of moisture and oxygen is too slow to cause significant temperature rises in a stockpile. In addition, this treatment also irreversibly removes most of the moisture held in the raw coal and raises its calorific value by as much as 10-12%.

Jan 1, 1973

By Claude Ferquson

MORE men are killed and injured in the metal mines of the United States from falls of rock and ore than from any other cause. Dan Harrington, of the U. S. Bureau of Mines, recently stated that "falls of men and material continue to take about 50 per cent of the lives annually lost in our mines (coal or metal) and this kind of accident is now and has been one of the most difficult to prevent." The fact that comparatively little has recently been written on this important subject for the benefit of the metal miner is the incentive for the present paper. Little will be said that will be new, but I hope to place fresh emphasis on certain well-known' principles' and to reiterate and stress previously stated rules so that the average experienced miner, as well as his buddy who may not be so experienced,' will sit up and take notice. It is not within the scope of this paper to discuss mining methods from the standpoint of safety and the prevention of accidents from falls of rock. It is up to the mine management to select the system of mining best suited to the character of the ore deposit and its wall conditions. This is something that the miner can do little about; although in many mines the management encourages the workmen to make suggestions that will improve existing

Jan 1, 1938

By Harry F. Weaver

WHEN 1 was assigned by the Director of the United States Bureau of Mines to present a paper at this annual meeting of the Mining Society of Nova Scotia, 1 was grateful, honoured, and elated to realize finally a life-long desire to see your beautiful land and visit with you who have the good fortune to live and work here. Naturally, in preparing for this important event, 1 wanted to give you something of special interest within the limits of the subject so I chose an area dose to my heart -the operation of our Federal coal mine inspection service, which has, as its fundamental purpose, the prevention of accidents in and around ?Coal mines. In 1957 the United States had 10,879 active coal mines scattered throughout 28 States and the Territory of Alaska. The production of coal for the year was about 515,472,000 tons, including 2.5,472,000 tons of anthracite and 490,000,000 tons of bituminous coal and Hgnite. Anthracite is mined principally in a comparatively small area of one State. AU the 28 States and the Territory produce bituminons coal and/or lignite. The beds mined range from 18 inches to more than 100 feet in thickness and from the horizontal to the perpendicular.

Jan 1, 1958

By A. J. Lanza

THE prevention of illness among the employees of the mining industry is especially important in view of the importance of the industry, the unsettled conditions of labor, which emphasize the economic necessity for conservation of labor, and for humanitarian reasons. The burden of chronic illness is altogether unwarranted and unnecessary. If the industry is to maintain its labor supply in an efficient manner and keep the standard high, it is essential that it make every effort to keep its labor in good physical condition. The basic principles underlying health conservation are the same for any industry, but they are here applied especially to the mining industry, and more particularly, perhaps, to metal mining, as it is with this phase of the industry that the writer is most familiar, and as it is conceded that metal mining presents more health hazards than coal mining. The first step in the prevention of illness lies in securing employees who are in sound health and free from organic disease. I do not mean that all men who go underground should be physically perfect, but they should be free from organic defects of the heart, lungs, and other organs, or from anatomical defects that would- markedly increase their liability to accident. The number of men working underground in mines in this country whose physical, condition totally unfits them for such work presents-a situation that should not be allowed to continue, and which I believe is 'not equalled in any other, industry in the country. There is but one way to secure men who come up to the required standard, . and that is by a thorough physical examination before employment. I am fully aware of the objections felt toward such a procedure by many employers and employees. There is much to he said on both sides, but to any one who is at all familiar with the mining industry as it is today in this country, and who approaches the matter with an unbiased mind, there can be absolutely no doubt as to the necessity for physical examination. As a purely logical proposition this is self-evident, but there remains the further necessity of placing physical examinations on such a

Jan 2, 1919

By C. Droun

"Low back pains account for about 13 per cent of all compensation claims made to the Quebec Workmen's Compensation Commission and cost the employers a sum exceeding ten million dollars. The frequency and cost of these health problems in Quebec metal mines are proportional to the provincial trends. An elaborate review of the literature on the causes, nature and prevention of low back pain is made in this presentation. A prevention program for low back pain has been designed in cooperation with a team of seven medical specialists and two physiotherapists for the Quebec metal mines. The program is especially designed for persons who have had low back pain, in order to prevent a recurrence, and for persons beginning to feel chronic difficulties. It is based on existing programs at the Hawthorne Plant of Western Electric Company and at Minnesota Mining and Manufacturing, but it requires a much different approach because of the nature of medical care available at the mining sites. The program is difficult because it involves a change of attitude for every employee and every supervisor. The program, so far, is beneficial because several men are now seriously engaged in an active program of reconditioning and because the problem of low back pain ie beginning to be seen from a new angle."

Jan 1, 1973

By Jian Yang

The mechanism of resulfurization in the desulfurization process with magnesium vapor produced in situ by aluminothermic reduction of magnesium oxide was clarified in the present work. The influences of various operating parameters on the resulfurization were studied and the methods that could prevent resulfurization were proposed. There are two kinds of mechanisms of resulfurization in the desulfurization process with magnesium. One is decomposition of the desulfurization product of MgS under the inert atmosphere. The other is oxidation of MgS under the oxidative atmosphere. Under the present experimental conditions, lowering operating temperature and oxygen partial pressure in the atmosphere could effectively prevent the resulfurization. Adding CaO onto the melt surface was an effective method for preventing the resulfurization due to transformation of the desulfurization product of MgS into the more stable compound of CaS. Since addition of the activated charcoal powders greatly decreased the transfer rate of oxygen in the atmosphere to the melt surface, it also reduced the resulfurization remarkably.

Jan 1, 2006

By G. Van Weert

Refractory ores and concentrates containing silver tend to form Ag-jarosite during autoclave oxidation. Silver extraction from the oxidation products is therefore low, unless a hot lime treatment step to decompose Ag-jarosite precedes cyanidation. Since silver iodide is very stable but soluble in cyanide solutions, the formation and decomposition of Ag-jarosite in the presence of iodine species was studied. Results indicate that Ag-jarosite formation could be prevented in favour of H3O-jarosite and AgI while oxidizing Ag2S under industrial autoclaving conditions, when the total iodine species to Ag mole ratio exceeded 5. Lower ratios gave proportionally more Ag-jarosite and less AgI. Under these conditions existing Ag-jarosite was also found to decompose in H30-jarosite and AgI.

Jan 1, 1993

By G. G. Lambert

The paper traces the pattern of spontaneous combustion in the workings of what was originally Hemsworth Colliery, but since July 1967 is now part of South Kirby Colliery. Examination is made of the Barnsley Seam sections and the part played by the top section of the seam as it comes in close proximity to the main seam. In this area of the colliery nine mechanised faces were set away between the years 1953 and 1968, every one "fired" at the pillar edge and six "fired" at the face line when production had ceased. The paper deals with the different preventative measures used, from sandbag walls, cement injections, spraying with polyurethane, until finally using Mandoseal as a sealant. Since the latter method was first used, the last three faces worked in this particular area were all salvaged completely, without any sign of a heating developing.

May 23, 1905

By P. E. Cavanagh

FOR THE PAST seven years Mr. W. Simpson, Chief Mechanical Inspector for the Nova Scotia Department of Mines, has carried out exhaustive field trials of non-destructive inspection equipment in the coal mines of that Province. This work has demonstrated the usefulness of a number of types of non-destructive inspection when used for periodic inspection of hoisting and haulage equipment in the coal mines of Nova Scotia. As a result, the Dominion Coal Company has instituted a programme of regular preventive maintenance inspection ?by a special staff of qualified and trained men. The purpose of this present paper is to describe how non-destructive testing techniques are used on ropes, axles, couplings, and other hoisting and haulage equipment, how these methods are being used in other industries, and the expected benefits from intelligent and properly organized use of these techniques in the coal mining industry.

Jan 1, 1956

By Wayne E. Tuomi

The mining industry is faced with a pressing problem; that is, to develop more efficient methods of extraction, handling and upgrading-techniques that will do the job faster and better than ever before. New techniques require new machines, or applications of new and improved materials that can be used to modify and improve existing machine and equipment designs. The traditional approach has been to increase productivity by increasing equipment size. Prognostication indicates that the trend toward larger equipment sizes and capacities will continue as one answer to the challenge imposed by future increases in mineral demands. But what is the limit on the continued growth of equipment size? Until about 1930, there was a very definite limit-a limit imposed by the strength of the steels and the power plants then available. The equipment engineer had come to an impasse: even though it was easily possible, for instance, to triple the size of a bucket, it had become impractical to correspondingly enlarge the boom, the counterweight, and the power plant.

Jan 3, 1967

By Marco Vinicio Guamán Alarcón

O modelo do Gradiente de Tensão (SG) e a Teoria da Distância Crítica (TCD) são usados para estimar o limite de fadiga de corpos de prova com entalhes alongados, e essas estimativas são testadas em C(T) modificados submetidos a tensões cíclicas de amplitude constante com uma razão de tensão R = 0.1. Os valores medidos são comparados com as previsões feitas por ambos os modelos. As previsões do modelo SG estiveram mais de acordo com os resultados experimentais. Também foi demonstrado que o modelo SG é quase equivalente à TCD no caso de entalhes com raios grandes, quando a TCD usa o método do ponto. Para o caso de entalhes afiados, os valores dos limites de fadiga previstos pela TCD são mais conservativos que os previstos pelo modelo SG.

Aug 17, 2017

By G. B. Gould

FROM the very inception of the price-control experiment in the bituminous-coal industry, the problem of price differentials was of major importance. In fact, assuming that there will be no legal or Govern- mental obstacles to price control, the successful maintenance of the present or any other method designed to control bituminous-coal prices will depend upon the discovery of some satisfactory way to determine these differentials in price, among: individual mines and groups of mines. Being of organic origin, bituminous coal is a commodity that presents an almost infinite variety of qualities. It is inevitable, therefore, that a work- able price-control system must attempt

Jan 1, 1935

By Nathan C. Rockwood

BASIC mineral commodities may be divided into two general classifications in their market or price characteristics. In one class are commodities sold on a world-wide basis, as gold, silver, nickel, asbestos and petroleum, and in the second are those produced and sold locally. Of course, no precise line of demarcation exists between the two; coal, for instance, belongs more or less in both. If there are enough producers of any commodity to prevent control of production by any one person or group, a free market then exists and the price in a buyer's market is determined by the most favored producer-meaning the producer, with the lowest production cost or the lowest cost of transportation, or both, to the particular market, or place of use. With minerals in the first classification, their high intrinsic value far outweighs the transportation cost and a uniform market price is accepted as an essential element in the economy of distribution. But with common minerals of small. intrinsic value and relatively high transportation costs, economists are reluctant to admit that a uniform price may also be an essential element in distribution.

Jan 1, 1940

By Walter J. Mead

By American tradition, if not by rational decision, publicly owned natural resources have been transferred to private industry for processing. The process of transfer requires specific determination of the price which the patentee, buyer, or lessee must pay to the government in exchange for the right to develop a resource, and selection of the patentee, buyer, or lessee from among several possible contestants. Pricing of natural resources owned by the government presents a set of problems quite different from ordinary commodity pricing. Natural resources in situ are not homogeneous commodities. Within any class of natural resources, specific leasable parcels will differ in value by reason of location and accessibility, as well as quality and quantity. Thus, there is no "going price;" every lease within a specific resource class will have a different value. To complicate further the pricing and buyer selection problems, competition may not be reliable. Natural-resource markets are characterized by oligopsony conditions. In a significant number of cases, as will be shown later, there has been only one bidder for a given lease, and in most lease sales the number of bidders is equal to or less than three. As a further complication, there is great uncertainty regarding the value of specific resources, even among the best-informed buyers, as well as within the leasing agency. In some instances, particularly with regard to oil and gas resources, there may be uncertainty about the presence of resources, as well as the quantity and quality of any resources contained in the tract offered for lease. In other cases, such as oil shale and some deep ocean minerals where new technologies are involved, the presence of the resource is clearly established. There may be a relatively high degree of knowledge about the quantity and quality of the resource, but there is great uncertainty concerning the cost of production. These problems in total make it difficult for the leasing agency to appraise accurately the resource to be leased, as well as for the potential bidder to calculate a bid price that will yield him a normal profit. The pricing goal of the federal government as the seller or lessee may be to capture the economic rent; that is, the price of a resource might equal its discounted present value. A required price substantially above this amount would either generate no bids, or, in the long run, would bankrupt the buyer. A price below this amount is a disguised subsidy to the lessee. A subsidy to mineral lessees, as to any other economic interest group, as a minimum should be justified by a clear showing of net external benefits from the economic activity. In the case of timber sales by the U.S. Forest Service, the Forest Service Handbook asserts that "the aim in national forest stumpage appraisal is to determine market value,"8 and "market value" is equated to "fair market value." Regarding minerals, there is no reference in legislation or regula-

Jan 1, 1976

By J. S. Roper

"IntroductionSNOW LAKE is situated in northern Manitoba at latitude 54° 55 and longitude 100°, 400 miles northwesterly of Winnipeg, 80 miles northeast of The Pas, 80 miles east of Flin Flon. A 38-mile road from Wekusko, on the Hudson's Bay railway, serves the community.The mine is located in and close to the southern edge of the Precambrian Shield in typical low-relief muskeg and lake country.The Howe Sound Exploration Company, Limited optioned the property from Nor Acme Gold Mines, Limited, after preliminary diamond drilling had outlined two orebodies of low-grade arsenical gold ore.Following the examination and study of geological data and of 50,000 feet of diamond-drill core, and metallurgical tests made during 1942 to 1945, a decision was made to develop the mine and build a 2 ,000-ton mill concurrently. This development has been described by G. C. Lipsey in a paper entitled The Development of a Mining Operation from Diamond-Drill Data which was published in the August. 1952, issue of Mining Engineering.Geological Features of the OrebodiesThe orebodies at Snow Lake occur in volcanic rocks of acid to basic composition and, to a lesser extent, in intrusive hornblendite. The hornblendite is a massive, uniform, .coarse-textured rock except in the immediate vicinity of the ore zone, where it becomes sheared and carbonatized. The acid volcanics have been converted to quartz-garnet-biotite gneiss, and the basic volcanics to amphibolite gneiss. Orebodies have been formed by the replacement of all three rock types."

Jan 1, 1955

By John B. Hastings

TEN miles from Hartsel, near Antelope springs, in Park county, Colorado, there is a large area of unconsolidated lake beds, which are interesting because at least a part of the lacustrine sands contains in the aggregate an immense amount of gold. During 1906, one of the arms of this dessicated lake was fairly well prospected with shafts and cuts by an Eastern company to test its value, as favorable amounts of gold had in some instances been found upon it. The claims of the company contain about 5,000 acres of the beds; but this is only a small portion of them, a south branch from a main body, which is at least 7 miles in diameter, with other and very wide lateral gulches, paralleling the one herein described on the east and west. A certain amount of digging and sampling was done in the outside areas; but the result was evidently unsatisfactory, since the work was discontinued. his section of Colorado has not been studied geologically, and the age of the ancient lake is unknown. It is probably Quaternary. I spent two weeks on the ground, in September and October, 1906, but was quite absorbed in the sampling. I looked, however, for terraces on the rim-rock and other evidences of movement and erosion, but did not find anything to denote an earlier age than the Quaternary. The granite rim-rock may be Archean; S. F. Emmons says that some of the granites in central Colorado are as old as that. The rim-rock as observed is a gray quartzose biotite-granite, except a small area in Sections 3 and 34, where it is a felsitic (?) breccia. The breccia is silicified by solfataric action at the corner near Shaft No. 7, in Section 34; but this action is older than the sands and does not extend to them. The shaft averaged 50c. per ton, more than twice as much as the rest.

Jan 5, 1908

By D. Collins, B. Pina, G. Snell

The conversion of moisture and ash free (maf) coal to pyridine solubles and gas was investigated in a microautoclave batch reactor. Two washed Kentucky coal samples (KY # 9 and KY #11) were studied in liquefaction solvents of various donor strength. The liquefaction solvent hydrogen donor strength was varied by changing the tetralin content of a mixed 1 -methylnaphthalene-tetralin mixture. Primary liquefaction conversions in excess of 90 wt% in 10 minutes of reaction time @ 700° K (427OC or 800°F) were achieved with liquefaction solvents of moderate donor strength, i.e. 40% tetralin. A modified irreversible first order rate expression (eq. 1) described the experimental data:

Jan 1, 1986

By John T. Ling

"This paper describes the operation of a rope haulage used as the main system of transportation in an underground coal mine. Prince Colliery, which is operated by the Cape Breton Development Corporation, has been in operation for 23 years and produces 1.2 million tonnes of coal annually. The mine extends a distance of 8000 metres under the Atlantic Ocean. All personnel and supplies are transported by means of an endless rope haulage system consisting of a train of rail cars that are operated by an electric engine on surface. The wire rope is 15 km long and weighs 63 tonnes. The system is believed to be the longest of its type used in an underground coal mine. The design of the system, safety features of the haulage, and problems encountered during the design and construction are described. IntroductionCoal has been mined commercially in Cape Breton, Nova Scotia since the 1800s. Several coal seams that are part of the Sydney coal fields, dip toward the north and northeast out under the Atlantic Ocean at angles between -4 and -15 degrees. Coal has been economically mined at depth in excess of 1200 m and more than 11 km from the coastline.Traditionally, single and double drum hoists have been used to haul the coal to the surface and also for transporting the workers and the materials required for mining up to 8 km. With the introduction of mechanized mining methods in the late 1960s, conveyor belts began to replace rope hoists for coal transportation. Improvements in hoisting system design also allowed for drums that could wind up to 6100 m of 32 mm wire rope in 15 layers.These hoists are commonly referred to as “drop hoists” because they take advantage of the gradient of the slope to assist in allowing the mine car train to reach the end of travel. The cars travel on steel rails and the rope is guided by rollers to reduce friction in the system."

Jan 1, 1999

By B. Hart, D. J. Miller, J. T. Francis, M. C. Biesinger, Smart. R. St. C.

Diagnosis of the surface chemical factors playing a part in flotation separation of a valuable sulfide phase requires measurement of the hydrophobic and hydrophilic species that are statistically different between the concentrate and tail streams. Time of flight secondary ion mass spectrometry (ToF-SIMS) can be used to identify sufficient particles of a specific mineral phase for reliable statistics determining a mean value for each species with 95% confidence intervals (1). Using the region of interest (ROI) facility in the Tof-SIMS software, a mass spectrum from each particle, at 1-2 monolayer sensitivity, is recorded and stored. This analysis is reported for a chalcopyrite / pyrite / sphalerite mineral mixture conditioned at pH 9 for 20 minutes in order to study transfer of copper from chalcopyrite via solution to the other two mineral surfaces since this mechanism can be responsible for their inadvertent flotation in copper recovery. Analysis from mineral selection based on specific ToF-SIMS signals (eg. Pb, Zn, Cu, Fe, Fe/Cu) indicated no statistical difference in the copper intensities on pyrite and sphalerite after this conditioning. Principal component analysis (PCA) of the ToF-SIMS imaging data identifies combinations of factors strongly correlated (positively or negatively) in images or spectra from mass spectra recorded at each of 256x256 pixels in a selected area of particles. PCA is a better method of selecting minerals due to multi-variable recognition. It has clearly separated a statistical difference in copper intensities between the sphalerite and pyrite phases. The method has been extended to samples from an operating plant again with excellent phase recognition and diagnostic surface chemistry.

Jan 1, 2004