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By Gerrit V. R. Goodman, Charles D. Taylor

A technique was developed to determine the fraction of air recirculated from the scrubber exhaust toward the face and the fraction of gas captured by the scrubber. To determine these two values, a series of tests was required. In the first test, gas was released at the face area and concentrations measured at the scrubber exhaust. In the second test, gas was released directly into the scrubber with concentrations again measured in the scrubber exhaust. The simultaneous solution of two independent flow expressions gave values of recirculation and scrubber capture. A series of tests was conducted with various combinations of scrubber flow, curtain flow, setback distance, and machine location. Statistical analyses then were conducted to determine those factors which influenced the levels of scrubber recirculation and scrubber capture in a deep cut. INTRODUCTION As cutting depths increase, the trend is toward the use of blowing face ventilation systems. With these ventilation systems, the potential exists for recirculation between the scrubber exhaust and the intake air stream. One concern is that methane gas, having been removed from the face area, is subsequently recirculated back into the intake airflow. Under these conditions, methane-laden air could be substituted for fresh intake air, leading to increased methane concentrations at the face. There is currently no standard for recirculation between the scrubber and intake airflows. The implied understanding of the Mine Safety and Health Administration (MSHA) is, and has always been, that any recirculation of ventilation air is unacceptable. To minimize recirculation potential, MSHA suggests that operators maintain scrubber and curtain flows within 0.47 m3/sec (1000 cfm) of each other. Given that recirculation may occur in some circumstances, the question arises as to how much recirculation constitutes a hazard for the face workers. Unfortunately, there is currently insufficient information to answer this. Emphasis must instead be placed on means to quantify the amount of recirculation between the scrubber and face area. Methods must also be examined to control this phenomenon. This paper presents a technique for quantifying recirculation and scrubber capture levels in a blowing face ventilation system. Several ventilation parameters are investigated to determine their effects on these levels. DEVELOPMENT OF RECIRCULATION EXPRESSIONS One way to measure airflow quantities at a point near the face would be to measure the gas flow rate Qgas, and gas concentration c at that location. The airflow Qair, would be simply the ratio of these two values, Qair, = Qgas/c. Although gas concentration values, c, can be obtained easily with existing gas monitoring equipment, it is more difficult to obtain gas flow readings, Qgas, at specific locations. To obtain these values of Qgas, another method was needed. Previous work in this area was conducted by Kissell and Bielicki (1975). However, the calculations in their model assumed a constant gas concentration in the region around the continuous miner. In a deep cut, it is questionable that gas concentrations would remain constant or uniform around the mining machine. The technique presented here does not rely on this assumption. It instead assumes that the gas concentration in the scrubber exhaust remains constant. A quantity of gas released at the cutting face either flows into the scrubber inlets or bypasses the inlets and flows around the off-curtain side (in this example, the right side) of the continuous miner (Figure 1). The fraction of the face gas that flows

Jan 1, 1993

By Luis Garay, Felipe Montalvo, Jorge Poma, Jorge Gutierrez

Los sistemas de ventilación auxiliar en minería subterránea proveen de aire fresco a las zonas de producción, preparación y desarrollo. Estos sistemas de ventilación, quizás por su versatilidad, temporalidad y bajo coste de inversión no siempre son objeto de un análisis profundo para su dimensionamiento óptimo. Una muy común mala práctica en minería subterránea es no monitorear y reducir los consumos energéticos relacionados a los sistemas de ventilación auxiliar por considerarse de baja cuantía, sin embargo, existen estudios que demuestran que el coste económico que afrontan las corporaciones mineras en materia de ventilación auxiliar puede variar entre el 60 y 70 % de su consumo energético total de ventilación.

Sep 30, 2022

By Leonhard Weixler

The Bauer company was founded in 1790 by coppersmith Sebastian Bauer in Schrobenhausen, a small town north-west of Munich. The original workshop business carried out works including repairs to church roofs and brew kettles. Later the company expanded its operations to encompass water pipe installation, which it continued through to the 1980s. In addition to installing water pipes it then also began drilling wells, which were sometimes constructed using very simple methods, such as tripod frames (Figure 1).

Jan 1, 2011

By Xuling Chen, Yi Wang, Xiaohui Fan

"The current control method of grate-kiln iron ore oxide pellet production is lack of accuracy and normalization due to the limited detection conditions. Therefore, mathematical models of grate-kiln temperature field are presented. With calculation of gas-particle heat transfer as well as enthalpy changes of moisture evaporation and magnetite oxidation, the thermal history of pellets throughout grate-kiln process can be acquired and used for production status estimation. Taking the calculated results as well as detected data in production as inputs, process parameters such as running speed, fan opening and coal injection rate as adjusting objects, expert system for grate-kiln pellet production is outlined. And the preheating section dominated control strategy is explained. Results of production application show that the stability rate of gas temperature in gas hood of preheating section is increased from 91.0% to 94.2%, compressive strength and first grade rate of pellet are increased by 3.62% and 2.36%, respectively, while FeO content is 18.18% lower. Control guidance of this expert system can solve production anomalies effectively, stabilize grate-kiln iron ore oxide pellet production and improve pellet quality.IntroductionSteel industry in China has developed rapidly in recent years. China’s crude steel production in 2010 is nearly 627 million, which is 44.2% of the world total production. Burden with higher quality is demanded by enlargement and modernization of blast furnaces. And oxide pellet production has become a growing concern. In 2010, the total production of pellet in China is 110 million, and about 60% is produced by grate-kiln process."

Jan 1, 2012

By Robert E. Meredith, Thomas T. Campbell

An investigation was undertaken to examine the feasibility of employing low- temperature nonaqueous baths for electrodepositing some of the refractory metals of the ferroalloy group . To date , such metals as tungsten , molybdenum , and vanadium have been produced only by high - temperature processes that are technically difficult and sometimes cumbersome in operation . Deposition studies were performed in a wide variety of organic solvents , including amides , ammonia derivatives , ketones , polyhydroxy alcohols , and ethers . Compounds prepared and used as solutes included the chloride and bromide salts of vanadium , tungsten , and molybdenum . Studies were conducted over a temperature range of 20 ° to 200 ° C under inert atmosphere . Conductivity and current potential data were obtained for all baths that contained reasonable solute concentrations . Qualitative solubility data were obtained for compounds of ferroalloy metals in a variety of solvents . In general , all solutes showed low solubility in ethers and ketones but reasonable solubility ( in excess of 20 grams per liter ) in alcohols , amides , and ammonia derivatives . No successful metallic deposits that would encourage further study were obtained with any of the systems that were examined .

Jan 1, 1963

By M. T. McDonough

THE data relative to the effect of metal depth on slag volume was obtained from the operation on two acid electric furnaces in which heats of various sizes were produced. The furnaces used were of 3 and 5-ton rated capacity; the heats investigated ranged from 6 to 8 tons. Heats of 7 and 8 tons were made in the larger furnace; heats of 6 tons in the smaller one. Bath depths and diameters were measured on the furnaces when cold and each is accurate to one inch. Both the metal charge and the slag were weighed on a track scale accurate to ± 25 lb. All other components added to the furnace were weighed on a wheelbarrow scale accurate to ±5 lb.

Jan 1, 1947

By Kenneth L. Clifford

We have heard a lot during the recession about the mining industry now competing in a world market for sales of such commodities as copper, lead, zinc, molybdenum, iron ore, and phosphate. If the US mining industry is to survive, do we not have to reduce direct operating costs to a minimum? How significant is labor cost compared to consumables, electricity, fuel, maintenance, materials, and transportation? Ore grade is ultimately the dominant factor; but can we offset its dominance by improving productivity? Is the US mining industry perhaps only 25-30% as productive as it might be? What prevents the industry from being more productive? Can we retrofit older plants to be more productive or does it take a new plant with the largest equipment available for each unit operation? Present Productivity A copper industry study a few years ago covering 13 US copper concentrators ranging from about 10-45 kt/d (11,000-50,000 stpd) showed that productivity did not vary with capacity above 18 kt/d (20,000 stpd). Operating productivity varied significantly, however, from about 180-635 t/d (200-700 stpd) per operating hourly worker in most units, but one operation had 900 kt/d (1,000 stpd). Concentrators with more than 545 t/d (600 stpd) per hourly worker were in the 23 kt/d (25,000 stpd) or more category. Maintenance productivity covered about the same range, but most concentrators were in the 270¬635 t/d (300-700 stpd) per hourly maintenance worker. Again, one company stood well above others by exceeding 1 kt/d (1,100 stpd). Total hourly productivity ranged from 125-280 t/d (140-310 stpd) per hourly worker for most concentrators. The company with the most productive operation, however, was above 455 t/d (500 stpd). Salaried worker productivity for most operations was in the 725 t/d to 1.2 kt/d (800-1,300 stpd) per salaried worker range. The best operation was 2.2 kt/d (2,400 stpd). The end result is, of course, tons per day per total personnel. Most operations fell in the 110-220 t/d (120-240 stpd) range with the best operation at 400 t/d (440 stpd). This is the productivity definition that is most directly related to unit costs. Many of these operations have made some productivity progress

Jan 11, 1983

By John McDonald

THIS report is a continuation of an earlier one with a similar title,1 to which the reader is referred for such details of procedure as do not appear here. A brief summary will be given of the objects and methods of the research at this time. It was pointed out in the previous paper that properties of magnesium alloys, as re-ported by different workers, often differ. This was thought to be due to differences in the preparation of the specimens tested. The ideal way to compare alloys would be to prepare each of them in so many ways that reasonable assurance would exist that the best properties of each alloy had been developed. The alloys would then be com-pared on the basis of these properties. The treatment actually given the alloys of these studies is necessarily a compromise with completeness. Nevertheless, enough treatments have been given so that a con-siderable degree of assurance exists that the properties obtained are representative of the alloy as such, and not merely of the manner in which it was worked and heat-treated.

Jan 1, 1940

By Wenjun Duan, Qingbo Yu, Qin Qin, Junxiang Liu

In the study, the coke-oven gas (COG)-steam reforming process using hot blast furnace slag (BFS) as the heat carrier is explored for producing hydrogen and recovering high-grade waste heat of hot BFS. The method of the Gibbs energy minimization approach through Lagrange multiplier is adopted in the thermodynamic analysis of reforming process. The simulation is carried out to study the operation pressure, temperature and steam to carbon ratio (S/C) based on the chemical equilibrium calculations. The optimal operation conditions are determined to improve the yield and fraction of hydrogen in the COG-steam reforming process. The results suggest that the preferential operation conditions for COG-steam reforming process to produce hydrogen are achieved at 600ºC, 1.5MPa and S/C (5.0). Due to the CaO and other melts in BFS, CH4, CO and CO2 in COG are converted and removed efficiently, especially CO2. The hydrogen fraction reaches to 86.7% and its production is about 1.22mol with 1mol of the COG.

Jan 1, 2016

By R. Schaller, Ch. Karcher, A. Thess

"Electron beam evaporation of liquid metals is an innovative technology increasingly used in industry to produce very thin coatings of high purity. In this process the surface of a metal ingot, placed in a water-cooled copper crucible, is heated by bombarding it with a high-energy electron beam gun. The material melts, forming a free surface and eventually starting to evaporate. The rising vapor cloud condensates as a thin film on a moving substrate. The strong energy input at the free surface gives rise to vigorous thermos capillary and buoyancy driven convective motion within the melt, leading to unwelcome heat losses. This paper aims to show how these losses can be reduced by optimizing the geometry of the crucible and by using external magnetic fields. We present both experimental and numerical results.IntroductionElectron beam evaporation of liquid metals [l] is an innovative PVD-technology which is excellently suited for the industrial production of high-quality coatings. In this vacuum process a high-energy electron beam heats up the surface of a metal ingot. The ingot melts and forms a free surface. A schematic view of the arrangement is shown in Figure 1. When the temperature of the free surface exceeds the actual (pressure-dependent) saturation temperature of the ambient gas, the liquid starts to vaporize. The rising vapor cloud finally condensates on a moving substrate located at some distance above. To guarantee a superior quality of the coating the melt is typically confined in a water-cooled copper crucible. The intensive cooling is necessary to avoid chemical reactions between the melt and the crucible walls, that is, crucible materials and their reaction products are practically excluded from evaporation."

Jan 1, 1999

By Amos Bryant, Jesse Davis

This paper compares the predictions of the latest Institute of Makers of Explosives Safety Analysis for Risk (IMESAFR) model versus physical test data recovered from ISO-1 and ISO-2 tests in Woomera, SA. ISO-1 testing included placing 1054 kg (2324 lbs) of ANFO (ammonium nitrate-fuel oil) inside an ISO container on a flat bed truck. ISO-2 testing was identical except the NEW was 4000 kg (8818 lbs). The IMESAFR predictions are based on model runs using the best match available to the actual donor type involved in the test. This type of debris analysis is not the standard output of IMESAFR, as the program is designed to assess the probability of human fatality. However, all of the IMESAFR predictions presented were obtained from the use of the actual model equations and algorithms without adjustment. Test results from ISO-1 and ISO-2 will be presented as well as findings from the comparison between model results and actual explosive results from the ISO testing efforts.

Jan 1, 2010

By Geoffrey Purcell

Improvements which have been made in commericial flotation systems during the past fifty years have resulted more from trial and error methods in the mill than from research in the laboratory. Research has often provided explanations of why mill changes have improved the metallurgical process. Hopefully, in the next fifty years, changes in mill flowsheets will come about, primarily, as a result of research work. However, since minerals, in their infinite variety, cannot be reduced to a standard state, research on commercial ores will have only a local utility, and research on pure minerals will have little commercial application. What will emerge from research on pure systems are mechanisms of adsorption, and this in turn may throw some light on the very much more complex adsorption processes taking place in the pulps of commercial ores. Quartz, without a doubt, has been the subject of more research effort than any other mineral, but we are still a long way from completely understanding its behavior in flo¬tation. Hematite and calcite have received considerably less attention. Ores containing a mixture of all three minerals, however, are commercially important, and the iron deposits in Alabama have been extensively studied by the United States Bureau of Mines (1). The literature reveals no reports of research on synthetic mixtures of all three.

Jan 1, 1967

By L. Ekstrom, J. P. Dismukes

The homogeneity and microstrcture of zone-leveled Ge-Si alloys haw been investigated by sellera1 physical techniques and by metallography as a function of growth rate in the range 3 x 10 1x10 cm-sec', and as a system of alloy composition throughout the system. The temperature gradient at the solid-liquid interface was about 50 deg-cm-' Cellular or dendritic structures char-acteristic of constitutional supercooling were ob-served except at very slow growth rates, which ranged from about 2 x 10 cm -sec for Ge 1 sio alloy to about 2 X 10'5 cm-sec'1 for Ge .sSio.s alloy. Using a simple model similiar to that employed for dilute solid the dependence upon compo-sition over the entire system of the critical growth rate for the onset of constiutional supercooling was calculated, and was .found to he in good agreement with the experimental results. THE recent discovery of the low thermal conductivity of Ge-Si alloys' at high temperatures has revealed that these alloys have high efficiencies for thermoelectric-power generation.', Therefore, a reliable method was needed for the preparation of homogeneous samples required for definitive measurements throughout this alloy system. Due to the low diffusion rates in the solid alloys, the segregated samples obtained by quenching a melt are not readily homogenized by annealing.475 However. isothermal solidification from a melt of constant composition can produce uniform material. Of the available semiconductor crystal-growth procedures, the zone-leveling technique6 applied to a complete solid-solution alloy system by Wang and Alexander' and by others provides a simple method of doing this. In the present work, the homogeneity and microstructure of zone-leveled alloys have been correlated with growth conditions, and the conditions for preparing homogeneous Ge-Si alloys have been established. This has provided insight into the solidification process of alloy semiconductors. EXPERIMENTAL PROCEDURE Sample Preparation. The Ge-Si alloy phase diagram4 shown in Fig. l(a) consists of a complete series of solid solutions. The zone-leveling technique used to prepare most of the samples consists of moving a zone of liquidus composition (C1) through charge material of the corresponding solidus composition (C,), as is illustrated in Figs. l(b) and l(c). To prepare the charge materials, high-purity germanium and silicon were pulverized in a steel hammer mill, cleaned magnetically, and melted together to make uniform chill castings. The zone leveling was carried out in a resistance-heated furnace similar to that of Mitrenin et al.' shown in Fig. 2. However, a few specimens of high silicon content were prepared by the Czochralski technique. The growth rate ranged from 3.5 x X6 to 1.2 X 10~3 cm-sec-'. Temperature gradients in the solid and in the melt were determined by recording the temperature as the molten zone passed over a Pt-Pt 13 pct Rh thermocouple contained in a small

Jan 1, 1965

By Armin W. Stuedlein, Seth C. Reddy

In this study, factors affecting the reliability of augered cast-in-place (ACIP) piles under axial compression at the serviceability limit state are addressed using a simple probabilistic hyperbolic model and a database of load tests on ACIP piles in cohesion less soils. The aleatory and model uncertainty in a selected load-displacement model is statistically characterized, and is used to simulate representative random samples from the bivariate random vector of model parameters. A first-order reliability method (FORM) was used to determine the effect of sample size on the stability and uncertainty of the reliability index. Sample sizes greater than about 40 provided relatively consistent estimates of the reliability index; however, its uncertainty continued to decrease with increasing sample sizes. Additionally, the effect of slenderness ratio on the reliability of the serviceability limit state design was characterized and found to exhibit a significant effect on the probability of exceeding a specified displacement.

Jan 1, 2013

By N. Mohan, A. K. Biswas, V. Y. Sampat Kumar

At low sodium-oleate concentration, calcite flotation is substantially improved by the use of CO2 instead of air. Electrophoretic mobility measurements indicate that carbonation results in the accumulation o f positive charge on the calcite particles. This heightens adsorption of oleate anion, an effect confirmed by tracer-technique measurements. Fundamental insight is obtained as to how CO2 serves better as an activator than some mineral and organic acids, how oxalic acid acts as a depressor, and why the influence of Ca++ ions, liberated during carbonation, on flotation behavior of calcite is insignificant and sometimes adverse.

Jan 1, 1972

By Reinhardt Thiessen

This paper presents only the highlights of previous research on the paleobotany of coal. The accumulated material has become so vast that a comprehensive review of all findings relating to paleobotany would be far too long. The fact that coal is derived from plants is now so well-known that no further comment is required, but knowledge of the mode of transformation of plant substances into coal is not so general. The plant matter goes first through processes of semirottins-, maceration, and elimination of certain material to form peat, which is then further transformed into coal. The first stage has been termed the "biochemical process," because the more important changes take place under the influence of micro-organisms. Near the end of the biochemical action an unconsolidated peat is formed. The second or "dynamochemical process," caused by the addition of superincumbent rock strata such as sandstones and shales and application of additional pressure and possibly heat through mountain-building forces, results in the formation of higher-rank coals ranging from brown coal to anthracite. These stages in trans-formation of plant material to coal have been described in previous reports.4 The main object of this paper is to bring to the notice of paleobotanists the fact that coal contains an enormous amount of material in a remarkably good state of preservation. Although some of the coal-forming matter has lost its identity, much of the original structure is retained. A large proportion of the coal, therefore, particularly of common bright coals, comprises constituents or components that invariably have retained some of the original plant structure, and many of these structures may be assigned to certain plants. The identity of these plants and of the remains forms the subject of this paper.

Jan 1, 1941

Australia today is one of the leading countries in the fields associated with the mineral industry, an industry which accounts for over 50% of overseas income and revenue to government. This is no accident. In order to be competitive in what was recog- nised very early in the country's history as a highly profitable busi- ness, the Australian mineral industry (mining, extractive and refining metallurgy) has traditionally been very innovation con- scious, a characteristic which has been evident from the begin- ning of the industry or very nearly so: Australia's geographic isolation and the dispersion of the mineral industry over wide distances made an exchange of ideas difficult and often impossible. One needs only to look at the inaugural address given by Sir Henry Ayers, the first president of the then Australasian Insti- tute of Mining Engineers, in Adelaide on 4th April, 1892 (1) "There is probably no other pursuit which depends more on its productive development and profitable results than in the extent and application of the scientific and mechanical knowledge possessed and exercised by its manager." and "Having in view the value of the mining industry of Austral- asians, they should be urged to apply their best skill with all the scientific and mechanical knowledge obtainable to its future development."

Jan 1, 1988

By E. B. Kester

A study of the composition of the corresponding fractions of a primary and a high- temperature tar was undertaken to throw light on the net results of the pyrolysis of the primary products of coal decomposition in high-temperature coking practice, with reference both to total quantities of the chemically similar constituents and to their distribution throughout the boiling range. No exactly parallel investigations are on record. The distribution of substances in high-temperature tars, however, is fairly well understood. Such tars are more or less similar, for they consist of the more stable phenols, aromatic and olefinic compounds resulting from the pyrolytic decomposition of a wide variety of primary tar constituents. For example, from a typical distillation curve for high-temperature tar phenols4 it may be seen that the greatest portion of the phenols distills between 180° and 220° C., a fairly narrow range.

Jan 1, 1932

By B. Olson, V. A. Marple, D. J. Radet

"Gravitational forces have been found to be an important factor in defining the particle collection efficiency curve of inertial impactors for large particles. In general it was found that if the parameter G = gW /V 0 2 (g is the gravitational acceleration. w is the nozzle diameter and V 0 is the average fluid velocity at the nozzle throat) in greater than 10-3 the efficiency curve would shift to lower panicle sizes. No effect could be seen for lower values of G.IN'IRODUCTIONInertial impactors have long been used as classifiers for airborne particles. By proper design of the nozzles and flow rate it is possible to classify particles with a fairly sharp cut in the particle size range from approximately .02 µm to 50 µm. Because of inertial impactors wide usage they have been extensively studied calibrated and evaluated. Most of these studies have been experimental calibrations of single stages using monodisperse aerosol particles. However, due to impactor simplicity. i.e. a jet of particle laden air impinging upon a flat plate with large inertia particles crossing the streamlines and impacting upon the plate the impactor also lends itself to theoretical evaluation.The most comprehensive method for analyzing impactors theoretically is to use finite difference solutions to the Navier-Stokcs equations and solve for the velocity components and pressure at node points of a grid placed over the area of interest. Using iteration and relaxation techniques the value of the velocity vectors can be determined at these node points with good accuracy. Once the velocities arc known, theoretical particles of known size can be placed into the now field and their trajectories determined by analyzing their equation of motion using numerical methods.Rader and Marple (1985) have performed theoretical analysis on impactors and have included such factors as Ultra-Stoksian .drag and the physical diameter of the particle in their analysis. However, even with these· factors included, there appears to be discrepancy · between the experimental and theoretical results when the particle size is larger than approximately 4 or 5 µm. One possible reason for this discrepancy could be the effect of gravity on the particle as it passes through the impactor. Therefore, a program was initiated to study the effects of gravitational forces on the collection· efficiency of particles in impactors. The results of that study arc presented here."

Jan 1, 1990

By Paolo Heiniger

The aim of this paper is to present the operative solutions devised and then adopted to implement the underexcavation (soil extraction) of the Tower of Pisa, by means of soil extraction. The intervention has been performed by the Consorzio Progetto Torre di Pisa, a joint venture made of five qualified Italian companies (Trevi S.p.A. , Rodio S.p.A., Italsonda S.p.A., Ismes -Enel Hydro S.p.A., Bonifica S.p.A.), selected for their experience in the field of monitoring and restoration of monuments, structural design, foundation engineering and specialised works in underground conditions. Since 1991 the Consorzio has been charged with the specific task of implementing, within the contractual frame of a Concession, all the decisions made by the International Multidisciplinary Commission appointed by the Italian Government the previous year, with the aim at solving the «problem» of the Tower, strengthening the structure and stabilising its foundation. The Trevi Group, which is represented by Trevi S.p.A. in the above mentioned Consorzio, has given and is giving its direct and constant contribution and is engaged in supplying the special equipment to the operation and the drilling technology which has been successfully adopted to date.

Jan 1, 2000