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By B. H. Sage, W. N. Lacey, W. M. Morris

The volumetric behavior of isobutane at temperatures below its critical temperature has been studied by several investigators. Seibert and Burrelll measured the vapor pressure of isobutane from the ice point to the critical temperature. Dana and co-workers2 determined among other thermodynamic quantities the density of the saturated liquid and the saturated gas and the vapor pressure from approximately 0 to 130 F. Sage and Lacey3 studied a number of the thermodynamic properties of this hydrocarbon from 70" to 250" F. The specific volume in the gas and liquid region was determined at pressures up to 3000 Ib. per sq. in.? throughout this temperature interval. In addition, the vapor pressures were measured at 30" intervals. These data taken together serve to establish the thermodynamic behavior of isobutane at temperatures between 0" and 250" F. with reasonable accuracy. However, apparently there are no data available at the higher temperatures. For this reason an investigation of the volumetric behavior of isobutane at temperatures between 100" and 460" F. was carried out with apparatus that has been described in another paper (p. 136, this volume). Materials The isobutane used in this investigation was obtained from the Philgas Division of the Phillips Petroleum Co. That company's special analysis upon this sample indicated it to contain less than 0.03 mol per cent of impurities. In order to avoid traces of noncondensable gases, this hydrocarbon material was subjected to two successive fractionations at a high reflux ratio in a column approximately 4 ft. long and % in. in diameter, which was packed with small glass rings. The middle portion of distillate from the first fractionation was used in the second fraction-ation and a portion of the overhead from this second distillation process was repeatedly condensed at liquid-air temperatures at a pressure only slightly above the sublimation pressure of isobutane at this temperature.

Jan 1, 1940

By Julian Kennedy Edgar

THINKING that it may prove of interest to the Institute, I have prepared a short account of the blowing in and subsequent working of the "A" furnace of the Edgar Thomson Steel Works. This furnace was built for the purpose of making spiegel, but has been started and is now running on Bessemer iron. The shape and size of the furnace are shown in the accompanying drawing. It will be seen that the section is formed of lines making very small angles with each other. In fact, an arc of a circle can be drawn, from the top to the tuyeres, which will nowhere deviate more than two inches from the lines given. In building, also, great pains were taken to gradually round the angles, so that the most careful observer, standing in the crucible and looking upward, could not tell at what points the slopes changed. It will also be seen that the widest part of the furnace is almost exactly midway between the bottom and the stock line, The flattest slope is maintained for 20 feet above the crucible, and is about 1 s inch to the foot from the perpendicular. The furnace is lined with small brick throughout, and has six tuyeres four inches in diameter, which project seven inches inside of crucible. There are three Siemens-Cowper-Cochrane stoves, each 15 feet in diameter by 50 feet high. Blast is furnished by an upright engine with 32-inch steam cylinder, 84-inch air cylinder, and 48-inch stroke. The steam cylinder has balanced poppet valves, working horizontally. The steam valves are worked by a Porter link-movement in order to obtain a variable cut-off. The exhaust valves are worked by a separate eccentric. It is intended to attach a governor to the cut-off, but at present it is set by hand. The steam cylinder is

Jan 1, 1880

By Gilbert Thiessen

The use of a pneumatic process for removing fine material (usually less than 48-mesh) is increasing in the preparation of stoker-size coal. The fine material, produced as a byproduct, is known as dedusting-plant dust. Since fusain is the most friable ingredient in bituminous coal (it may readily be rubbed to an impalpable powder with the fingers), it tends to accumulate in this byproduct. While studying the properties of cokes produced by blending Illinois coals with other materials, considerable quantities of fusain were required. Dedusting-plant dust suggested itself as a convenient supply. It became necessary, therefore, to determine how much fusain was contained in a measured sample of dust, how the fusain was distributed with respect to size and specific gravity in the sample, and whether or not it would be feasible or desirable further to concentrate or to recover the fusain from the dust before using it in the blends to be coked. The results obtained indicate the possibilities of production of a high-fusain material. Previous Work Lehmann and Stach have developed a processl,2 for separation of banded bituminous coals into their band ingredients by impact pulverization followed by screening or air separation. They found, as might be expected, that the fusain was concentrated in the very fine material. Prockat and Raute3 examined samples from dedusting plants operating in the Ruhr. They separated the dust into various screen sizes and determined the composition of each of these sizes in terms of the banded ingredients of the original coal. In the dusts examined by them, the finest material was always high in fusain, and most of the fusain contained in the original samples could be recovered from this fraction.

Jan 1, 1936

By Pierre J. Wauters, Eddy J. Jacques

Starting up a fan or modifying its setting point either by rotational speed variations or blade angle changes, obviously results in new ventilation conditions in the network, which is, of course, the object of the operation. However, since transient phenomena may then occur, particularly in complex networks, there may be a need to simulate these situations prior to any action. This is all the more true, if we are dealing with a multiple interactive fan sys- tem. Simulations with a transient model have shown that the flow in certain airways could be temporarily reversed due to the pres- sure variations that reach both its ends with a different time lag. This phenomenon may cause dangerous situations to occur in cases of fire or outburst of methane. It is also true that the air flow could be reversed in secondary and less powerful fans, while still rotating in the normal direction. The study and the experimental investigation of the extension of the reverse flow characteristic is therefore justified from two points of view : • a numerical simulation model for transient flow conditions must be capable of handling temporary reversed flows, and thus have appropriate fan characteristic curves available over the entire operating domain; • while operating fans, reversed flows should be avoided or at least reduced. Therefore, the design of start-up procedures or real time control algorithms should take these phenomena into account. A particular interesting application is the operating of two fans in parallel. In order to investigate experimentally the characteristic curves of a fan under reversed flow conditions a small scale model was built. This facility was designed in such a manner that it was possible to carry out experiments concerning flow reversions and to try out sequential start-up procedures for two fans in parallel.

Jan 1, 1997

By Robert Kinzie

WHEN Mr. Cameron, the President of the Santa Cruz Portland Cement Co., returned from Europe in 1929, he brought first-hand infor-mation about a very versatile type of hydraulic cement. It was not a new cement, many articles having been written about it in foreign journals, but in this country the record of this type of cement had been either neglected or minimized. Using local materials, and applying the information brought back by Mr. Cameron together with many data in numerous publications, the Santa Cruz Portland Cement Co. developed the Santa Cruz high-silica cement. This cement is manufactured by grinding with portland cement clinker a properly calcined mixture of siliceous material and lime. It has all the utility of portland cement, together with an increased resistance to the destructive action of many aggressive solutions. To explain the necessity for the development of a cement having these characteristics, the history of hydraulic binding materials may be reviewed briefly. The materials used as binding media by primitive people were mud, lime, gypsum and bitumin. Due to its utility, ease of preparation, and its common occurrence, lime was the most widely used. Fat lime, when used by itself or with an inert sand, hardened only on the outside surface, where the carbonate was formed by absorption of carbon dioxide from the air, while, the interior of the mortar remained soft. It was quite early discovered that the incorporation of proper siliceous material with the lime increased its ability to harden, and for this purpose various natural siliceous powders were used, such as puzzo-lana in Italy, trass in what is now Germany, and santorin in Greece. These powders reacted with the lime forming a permanent cement and rendered unnecessary the access of carbon dioxide to the mortar.

Jan 1, 1934

By Ting Luo, Hongmin Zhu, Kai Huang, Shuanglong Du, Tao Gui, Yifan Xiu

"Poplar cotton, a cellulosic material, was found to adsorb metals ions effectively. In the present study, the biosorption characteristics of Pb(II) onto poplar cotton, were evaluated as a function of pH, contact time, biomass dosage, initial concentration and temperature. Within the pH range investigated (1.0-6.0), the optimal pH value suitable for the uptake of Pb(II) was determined. The maximum adsorption capacity obtained from the Langmuir model is around 0.52mol kg for the poplar cotton sorbent. Equilibration is achieved in 60min for the studied concentrations. Results suggest that the poplar cotton can be directly used as an effective and low-cost biosorbent for removal of Pb(II) from aqueous solution.IntroductionHigh value utilization of various biowastes produced in agricultural, forestry, fishing industries, etc. have attracted great interest from many researchers [1], Biomass, due to its easy availability, great abundance, low cost, easy processing, eco-friendliness and biodegradability, has exhibited exciting potential for being used as raw materials for the preparation of many new hi-tech functional products [2]. For example, using biowastes to synthesize sorbents for application in the removal of toxic substances such as dyes [3], heavy metals from the waste water [4] or in the recovery of valuable metals [5] from the ore tailings and secondary metals resources has made great progress in last decade. In present study, poplar cotton, a kind of white light fluff of poplar trees, like that of dandelion, usually flying in the air each spring was tested as a biosorbent for the remove lead ions from the water. It may also provide some good ideas for new sorbent design. Lead, as one of the typical poisonous heavy metals, for its typical toxicity and extensive pollution, was chosen to test the adsorption behavior of poplar cotton in aqueous solutions."

Jan 1, 2012

By Julian Kennedy

THINKING that it may prove of interest to the Institute, 1 have prepared a short; account of the blowing in and subsequent working of the "A" furnace of the Edgar Thomson Steel Works. This furnace was built for the purpose of making spiegel, but has been started and is now running on Bessemer iron. The shape and size of the furnace are shown in the accompanying drawing. It will be seen that the section is formed of lines making very small angles with each other. In fact, an arc of a circle can be drawn, from the top to the tuyeres, which will nowhere deviate more than two inches from the lines given. In building, also, great pains were taken to gradually round the angles, so that the most careful observer, standing in the crucible and looking upward, could not tell at what points the slopes changed. It will also be seen that the widest part of the furnace is almost exactly midway between the bottom and the stock line. The flattest slope is maintained for 20 feet above the crucible, and is about 18 inch to the foot from the perpendicular. The furnace is lined with small brick throughout, and has six tuyeres four inches in diameter, which project seven inches inside of crucible. There are three Siemens-Cowper-Cochrane stoves, each 15 feet in diameter by 50 feet high. Blast is furnished by an upright engine with 32-inch steam cylinder, 84-inch air cylinder, and 48-inch stroke. The steam cylinder has balanced poppet valves, working horizontally. The steam valves are worked by a Porter link-movement in order to obtain a variable cut-off. The exhaust valves are worked by a separate eccentric. It is intended to attach a governor to the cut-off, but at present it is set by hand. The steam cylinder is

Jan 1, 1880

By Sidney L. Hansen

This report was written because of concerns of the possible error involved when stopping leakage is incorrectly assumed to be turbulent. It is common practice to use turbulent flow to characterize each airway branch for computer models of mine ventilation circuits. This report addresses computer methods to accurately model air-leakage paths. A graphical method is described for deriving the equations of leakage through stoppings. The significance of modeling leakage according to the proper flow regime (turbulent or laminar) is demonstrated by the following method. A hypothetical mine was developed to represent present-day conditions. The stoppings of the mine were chosen to leak according to laminar flow properties. The mine was represented by constructing two base models. One base model used turbulent leakage equations for each stopping, while allowing the corresponding resistances to vary. The other base model used the correct laminar leakage equations and held corresponding resistances constant. The mine circuit was then expanded to demonstrate future development. The expanded portion was designed with stoppings that were identical to those in the base mine. The mine in the future state was represented by two projection models. Each projection model was an extended version of its associated base model; one used turbulent leakage equations and one used laminar leakage equations for stoppings. The laminar projection was theoretically correct and is used as a basis for comparison of differences in airflow quantities. Rather than modeling every leakage path for stoppings, a more practical approach is also discussed. A good level of accuracy is maintained by combining leakage paths if the proper flow equations are used. This method was used on the hypothetical mine projection and the flows were very similar to the theoretical values.

Jan 1, 1989

SHELBY M. HARRISON,* New York, N. Y. (written discussion ?).¬Your secretary requested a brief description of the Russell Sage Foundation, in order that members of the Institute, if they should desire to avail themselves of it, would know what type of service is offered to them through our institution. The foundation was established in 1907 by the gift of Mrs. Russell Sage of $10,000,000 as a capital fund, the income of which is to be spent for the improvement of social and living conditions in the United States. One of the lines of activity which the foundation has felt would lead toward this end is the development and promotion of community surveys; and because the scope and methods followed in these surveys are very similar to the scope and method of much of the institution's work in general, an idea of its main activities can perhaps be given best by describing one of our surveys. Incidentally, it may be pointed out that antecedent to the survey stand at least two important facts: first, the recognition. that communities are active, not static forces, that they develop, that changes in. material and human relationships occur continuously, and that with them come new social and civic problems which must, in many cases, be diagnosed and prescribed for anew; and second, the reality of scientific advances along lines which make possible at least some measure of solution of the problems. Evidences of these changes are abundant; many of them are found in the rapid growth of cities in the last few decades. Villages in agricultural districts, places where everybody knew everybody else, where the pulpit had been long the chief or only influence molding public opinion, where the air was unclouded by the smoke from factory stacks, where the water supply was not affected by pollution, where sunlight and building

Jan 5, 1918

By A. E. H. Bergmann

INTRODUCTION The Sachtleben Chemie GmbH in Duisburg, a subsidiary of the Metallgesellschaft AG, operates a new sulfuric acid plant that employs fluid bed roasting of pyrite concentrates. The plant produces about 300,000 tons per year of pyrite cinders from the fluid bed roasting unit. The cinder product consists of 58 percent iron and is about 80 percent by weight smaller than 50 microns. This cinder product was found to be a competitive source material for the cement industry as the iron-containing additive. However, the extreme fineness of the cinder and its dusting tendency were undesirable and an agglomerating technique became necessary. In order to keep the price of agglomerated pyrite-cinders at a competitive level, the agglomerating method must be chosen such a way the capital and operating costs are low. Initial experiments were carried out on a laboratory scale to make an appropriate choice of the agglomerating method. Major goals of agglomerating the cinders were to improve the transportation, storage, and proportioning and metering properties. Minimum specifications are put on the size, size distribution and shape of the product. Criterion for handling is that a minimum of minus one mm. fines are produced after several handlings, while for storage, it is also desirable for the agglomerated product to survive several months in open air. Thermal agglomeration processes such as sintering one known to produce excellent products, but are by far too expensive for our application. For the same reason, granulation, balling, and pelletizing tests with addition of organic binding agents, such as tylose, starch, sulfite wash, molasses, etc. were not continued. The costs for the binding agent was considerable, which is probably due to the high pore volume of our cinders (35 %). Furthermore, the pellets or granules

Jan 1, 1977

By W. N. Lacey, B. H. Sage, W. M. Morris

The volumetric behavior of isobutane at temperatures below its critical temperature has been studied by several investigators. Seibert and Burrelll measured the vapor pressure of isobutane from the ice point to the critical temperature. Dana and co-workers2 determined among other thermodynamic quantities the density of the saturated liquid and the saturated gas and the vapor pressure from approximately 0 to 130 F. Sage and Lacey3 studied a number of the thermodynamic properties of this hydrocarbon from 70" to 250" F. The specific volume in the gas and liquid region was determined at pressures up to 3000 Ib. per sq. in.? throughout this temperature interval. In addition, the vapor pressures were measured at 30" intervals. These data taken together serve to establish the thermodynamic behavior of isobutane at temperatures between 0" and 250" F. with reasonable accuracy. However, apparently there are no data available at the higher temperatures. For this reason an investigation of the volumetric behavior of isobutane at temperatures between 100" and 460" F. was carried out with apparatus that has been described in another paper (p. 136, this volume). Materials The isobutane used in this investigation was obtained from the Philgas Division of the Phillips Petroleum Co. That company's special analysis upon this sample indicated it to contain less than 0.03 mol per cent of impurities. In order to avoid traces of noncondensable gases, this hydrocarbon material was subjected to two successive fractionations at a high reflux ratio in a column approximately 4 ft. long and % in. in diameter, which was packed with small glass rings. The middle portion of distillate from the first fractionation was used in the second fraction-ation and a portion of the overhead from this second distillation process was repeatedly condensed at liquid-air temperatures at a pressure only slightly above the sublimation pressure of isobutane at this temperature.

Jan 1, 1940

By Pentti Seppanen

The activities of Outokumpu Oy in the mining industry span all branches from prospecting to the production of refined metals and the manufacture of semifinished products. Products include copper, zinc, mercury, cadmium, nickel, cobalt, sulfur, gold, silver, iron ore, stainless steel, selenium, ferrochromium, lead and chromium concentrates, as well as chromite foundry sand. In addition, the activities of Outokumpu Oy extend to development and production of instruments, planning of industrial projects and instrumentation as well as the manufacture of specialized machines for ore concentration. The company now operates ten mines, eight of which are underground and all of which are in sulfide deposits except one. The fully automated monitoring and control of underground mine ventilation at the Pyhasalmi mine are an important technological contribution to the industry. Development work on the ventilation control was started in 1969, and since May 1973 it has operated in a fully automated computer-controlled mode. The Pyhasalmi mine has been in production since 1962, having begun as an open-pit operation. Development of underground mining began in 1967. The present annual production is one million tons all from underground mining. The underground mine is equipped with a main shaft and an auxiliary shaft, and two raises for ventilation. There is also a rampway from the surface to a depth of 500 m. The main shaft is for ore hoisting and the auxiliary shaft is used for waste-rock hoisting and for downcast ventilation. One of the raises is for downcast ventilation and the other is for upcast ventilation. The mining methods employed at Pyhasalmi are sublevel stoping with backfill, sublevel caving, and sublevel shrinkage stoping. Copper and zinc concentrates are produced. The Pyhasalmi mine is highly mechanized with about 4000 installed diesel horsepower underground. The maximum capacity of fresh air is 150 m3/s.

Jan 1, 1979

By Wenhua Wan, Jan M. Mutmansky

Many concerns have been expressed worldwide regarding the use of diesel equipment in underground mines due to the potential health risks associated with diesel particulate matter (DPM). In assessing the risk to the health of miners and designing control strategies for DPM, it is important to know the concentration of DPM in the working areas of a mine. In some mines, significant stratification occurs due to the characteristics of the diesel exhaust, affecting exposure and the ability to measure DPM concentrations accurately. This study outlines some of the concentration profile data obtained during sampling at three mines where diesels were employed. Mine #1 (a gold mine) employed large openings in which a diesel-powered roof bolter was used. Mines #2 and #3 are both room-and-pillar operations with varying conditions. Mine #2 is an experimental mine where two stationary diesels were utilized for sampling purposes, while Mine #3 is a traditional evaporite operation using two mobile diesel vehicles for section haulage. These field studies indicated that some level of stratification occurred in all the mines, but the stratification was not as pronounced in the case of Mine #2 due to the complex pattern of exhaust emissions generated by the vehicles. The stratification seemed to depend on the distance from the vehicle, the mine air velocity, whether the vehicles were moving or stationary, and whether the exhaust was diluted by equipment design features. The concentration of DPM was generally higher at samplers located near the roof and lower at samplers located near the floor. However, this was not found in all cases. This paper provides conclusions on how knowledge of stratification patterns can be utilized in sampling and control of DPM in mine atmospheres.

Jan 1, 1997

By Claude H. P. Lupis, John F. Elliott

The classic Siez~erts' technique has been employed to determine the solubility of oxygen in liquid pure silver and the effect on the oxygen solubility of solute metal additions to liquid silver. The results indicate that oxygen deviates slightly from Sieverts' law in pure silver as = 3.9. Gold, platinum, md palladium decrease the solubility of oxygen in silver. First-order free energy, enthalpy, md entropy interaction coefficients are determined from the data. An important aspect in the establishment of the formalisms to be applied to represent the thermody-namic behavior of components of solutions is the accuracy of the experimentally determined thermody-namic properties. Wagner developed the first-order free energy interaction coefficient.' Recent papers2'3 extend the treatment formally to other thermodynamic properties and define the second- and higher-order interaction coefficients. A current communication4 considers in some depth the requirements and limitations imposed because of experimental error on the use of several formalisms now under active consideration in the field. This communication reports the results of an experimental study of the behavior of oxygen in liquid silver alloys that was carried out concurrently with the development of Refs. 2 and 3 with the hope of providing sufficiently precise information so that enthalpy and entropy interaction coefficients could be determined. THE EXPERIMENTS The Sieverts technique was employed using an improved design of the reaction bulb over that developed originally by Humbert5 and subsequently improved by pehlke6 and Weinstein.7 The Vycor reaction bulb as shown in Fig. 1 was air-cooled and contained a port for the thermocouple angling off to one side and a vertical port for connections to the gas supply and

Jan 1, 1969

By Richard J. Gowen

THE FUTURE The environment in which we live appears to change so slowly that most of us are unaware that any change has occurred at all. As the years pass, we notice increasing smog in our cities, new variations in weather, the shifting landscape with changing populations, and subtle but ever present alterations in the quality of life. In considering the future of our environment, we find we must grapple with questions concerning the very future of life as we know it today. Questions of resources, technology, society, governance, and purpose. Let us focus on the future of our environment and, in particular, raise the question of who is responsible for the environment. We know that action, or lack of action, will clearly influence our future environment. It is fashionable to catalog the many short-sightedness of our forefathers in developing the technologies which support the style of living to which we have become accustomed. However, I shall struggle to resist the temptation to list the well known ills of our present environment. Rather, let us concentrate on the future in our consideration of the priority of the multitude of options proposed to relieve our current energy crisis. We have recently witnessed the dramatic effects of air pollution produced by Mount St. Helen's eruptions. In the state of South Dakota, we watched our blue skies turn hazy and felt our eyes sting with the presence of volcanic ash. We were appalled at the dramatic effects on the landscape, crops, transportation, and all aspects of life in communities immediately downwind of the volcanic eruption. But in a few weeks, life had returned to near normal on the earth's surface leaving the volcanic ash in the atmosphere to ultimately

Jan 1, 1983

By Gherman Pavlovich Nikonov

Results of preliminary research on the use of small diameter water jets at high pressure for cutting rocks has demonstrated the possibility of effective cutting of anthracite. Detailed research has, therefore, been conducted at the Skotchinsky Institute of Mining to study the dynamics and structure of the small water jets and the mechanism by which they cut coal. One of the objects of this research was to obtain data for the design of a machine for cutting rock, based on the same principles as that for cutting coal. The productivity of water jet mining machines depends on the hydro- dynamic parameters of the jet. Therefore, the research on small diameter water jets was directed, initially to a study of the nature of the variation of these parameters, and to obtain a profile of dynamic pressure distribution over the section of the jet. As has been confirmed previously, the required jet pressure (to cut coal) lies in the range of 100 to 500 atmospheres. These pressures were utilized for the research. The diameter of the nozzle was changed as ~follows; 0.97; 1.24; 1.5; 2.17; 2.87; and 3.57 mm. Graphs showing dynamic pressures for each nozzle diameter and varied axial dynamic pressure were obtained over distances ranging from 2 to 70 cm from the nozzle. One of the most important hydrodynamic parameters of a jet, closely related to the dynamics of jet disturbance in air, is the magnitude of the axial dynhmic pressure. A study of the variation in this pressure with increasing distance from the nozzle led to the separation of the jet into three specific parts, which differ from each other not only in the nature of the change in dynamic pressure, but also in structural properties.

Jan 1, 1971

By S. Murdock, R. L. Fleischer, H. W. Alter, J. E. Gingrich

The use of solid state track deters allows totally passive, integrating measurements of 222Rn (radon) or of 220Rn (thoron) plus radon. A track-detecting solid is placed in a holder that is closed by a selective membrane and exposed to the atmosphere of interest to produce an accurately time-averaged record over times of interest that range typically from a week to a year. By selection of the proper membranes, dosimetry can be done for radon or for the sum of radon and thoron. A different membrane is appropriate for measuring radon under humid conditions such as are found in the ground. Large numbers of measurements have been made with these systems both in the ground, where radon levels are high, and in indoor environments, where levels are orders of magnitude less. Calibrations have been carried out at both high and low concentrations of radon. New results in the air at the site of the Shirley Basin mine and mill give reproducible results with month-long integrating periods. The off-site background levels are in the range 0.7 to 1.0 pCi/l (26-37 Bq/m3). The average yearlong on-site level is 1.5 pCi/l (56 Bq/m3); at the mill it is 2.6 pCi/l (96 Bq/m3); and the level measured at the backhoe in the open pit mine is 3.9 pCi/l (144 Bq/m3). The region of significantly elevated radon levels is confined to a radius of 1.6 km of the mine and mill. All of the on-site radon concentrations are less than but comparable to the typical values found in the living areas of modern energy-efficient homes.

Jan 1, 1981

By Frank E. McCall, Michael A. Trevits, Fred Garcia

The U.S. Bureau of Mines investigated the influence of atmospheric pressure changes on methane gas migration through mine seals at a mine site located in the Pittsburgh Coalbed. The mine gained access to a coal reserve through part of an abandoned mine and constructed nine seals to isolate the extensive old workings from the active mine area. Underground problems were experienced when atmospheric pressure fell, causing methane gas to migrate around the seals and into the active workings. During mining operations, methane gas levels exceeded legal limits and coal production was halted until the ventilation system could be improved. When mining resumed with increased air flow, methane gas concentrations occasionally exceeded the legal limits and production had to be halted until the methane level fell within the mandated limit. To assist the ventilation system, a pressure relief borehole located in the abandoned workings near the mine seals was proposed. Preliminary estimates by a gob gas simulator (computer model) suggested that a 0.76 m (2.5 ft) diameter pressure relief borehole with an exhaust fan would be necessary to remove enough methane from the abandoned area so that the ventilation system could dilute the gas in the active workings. However, by monitoring methane gas emissions and seal pressure, during periods of low atmospheric pressure, the amount of methane gas that migrated into the active mine workings was calculated. Researchers then determined that a relief borehole, 20.3 cm (8-in) with an exhaust fan could remove at least twice the maximum measured volume of migrating methane gas. Because gas concentrations in the abandoned workings could potentially reach explosive limits, it was proposed that the mine eliminate the exhaust fan. Installation of the recommended borehole and enlarging two other ventilation boreholes located in the abandoned area reduced methane gas leakage through the seals by at least 63%.

Jan 1, 1995

By Robert A. Jankowski, Fred N. Kissell

Recent allegations about tampering of coal mine dust samples have led to suggestions that the coal industry needs a respirable dust compliance sampling method that is less subject to tampering. The sampler designs under consideration include fixed location monitors that could be mounted on a mining machine or located at a stationary location in the mine, and samplers that are worn, like the existing samplers. Fixed-point samplers have a design advantage, since samplers worn on the body will have size and weight limitations. On the other hand, in some cases there are respirable dust concentration gradients, which will dictate careful placement of a fixed-point sampler inlet to determine the exposure of workers. This study examined dust concentration-gradient data obtained by the Bureau of Mines and others over the last decade. As an example of spatial gradients at continuous miners, a fixed-point monitor located in front of the operators cab shows a higher dust concentration than a sampler located on the operator and reduced exposure when the sampling location is behind the operator cab. It may be necessary to use a sampling tube with a machine mounted monitor, to sample in the operators breathing zone in the cab to provide a more representative sample of the miners exposure. For face workers on longwalls or on continuous miner sections using remote control, the study shows significant dust level gradients and gradient variations between typical operator positions and mining machine locations. In addition, if fixed-point monitoring is used to monitor an area, vs the exposure of specific workers, dust control technologies currently employed to ensure reduced dust exposure such as the diversion of dust laden air away from the workers, or through the use of remote control of mining machinery may not indicate the same dust reduction obtained with current sampling techniques.

Jan 1, 1993

By Balesh W. Konda, Andrew B. Cecala, George W. Klinowski

Methane ignitions continue to be a major concern to the longwall mining industry. In spite of numerous advances in technology over the past decade, there has not been a measurable reduction in the number of longwall face ignitions. These ignitions will continue to be a problem as deeper and gassier seams are mined, as production rates are increased through numerous improvements in longwall mining equipment, and as the output of the workforce increases due to improved management-labor relations. It is necessary to know methane liberations, emissions, and flow patterns in order to effectively deal with it and to design control technology to reduce the occurrence of longwall face ignitions. A cooperative research project between the Bureau of Mines and the Canada Centre for Mineral and Energy Technology (CANMET) has been established to address longwall methane problems. The initial direction of this work was to look at methane flow patterns during the entire longwall mining process, and more specifically to examine and compare methane levels and flow patterns for advance and retreat methods of longwall mining. Both advance and retreat longwall mining is practiced in the Sydney coal fields in Nova Scotia. In 1986, a study was performed on advancing longwall panels at the Lingan Colliery, and a similar study was recently completed at the Phalen Colliery on a retreating panel. Methane monitors were placed at various locations along the face, intake, return, and bleeder airways. Handheld methane monitors were also used upstream and downstream of the shearer mining machine. This setup allowed a determination of methane sources on the longwall panels, including: liberation from cutting with the shearer mining machine, emissions from the coal seam along the face, emissions from the gob area, and methane already in the intake air. The results from both studies are reported and the differences between the two longwall mining methods compared.

Jan 1, 1989