Search Documents

By J. T. Crawford

The purpose of this paper is two fold. It will: (1) examine leasing analysis as a project evaluation criterion, and (2) compare the cost of leasing with other methods of financing. The use of leasing has grown extensively in recent years as a method of obtaining equipment. The computer industry has been highly dependent upon leasing from its earliest days to dispurse its equipment to the customer, while airlines and railroads acquire large segments of their aircraft and rolling stock by leasing. Over the last few years the mining industry has leased haulage trucks, bulldozers and other equipment of similar nature.

Jan 1, 1974

By P. O. Ripley

Into this tumultuous twentieth century, every second, two new babies are born. This is 5,412 per hour, and 130,000 per day. Relentlessly, consistently, alarmingly, they add to the more than three billion human beings who already inhabit the earth. Every tick of tier clock brings with it a problem child, the problem of another mouth to feed, another body to clothe, another human being for whom to provide. On the other hand, medical science has achieved a postponement of death, considerably past the period of a few years ago. Thus, life expectancy has been increased and world population has increased accordingly. Darwin (4) writing in 1962, suggests "It is curious how long the world is taking to perceive that we are living in what is a fantastically abnormal period of history, and one which must inevitably end soon, The first warning note of a possible population explosion was given by Malthus in 1799". He suggested that population increases geometrical while production increases only arithmetically and that soon we would not be able to feed the rapidly increasing population.

Jan 1, 1966

By Edward S. Plotkin, Gary A. Almeraris, Thomas F. Peyton

The lining of the tunnel and shafts for a new section of New York City's- water system required extensive components to produce, deliver and place a continuous tunnel linning. The project placed approximately 153,000 CM (200,000 cy) of concrete for 5,340 M (17,520) of drill and blast 7.3 M (24 ft.) ID tunnel, located at depths of 152 M (500 ft.) to 213 M (700 ft.) . This section of tunnel will be connected to the surface water distribution system via four shafts of varying diameters ranging from 5.8 M (19 ft.) ID to 1.5 M (5 ft.) ID . All work was done beneath the streets of Manhattan under the rigid constraints of the City of New York and the Bureau of Water Supply regulations.

Jan 1, 1987

By George P. Demopoulos, Yan Zeng, Zhibao Li

Precipitated silica is marketed with a rising demand as reinforcing filler in the rubber industry and as a potential raw material for the synthesis of lithium-ion battery electrodes. Due to an awareness of the environmental impact of the existing processes for the production of precipitated silica, a green and sustainable process was proposed by using sodium bicarbonate (NaHCO3) as an alternative to sulfuric or hydrochloric acid in the precipitation reaction with sodium silicates. The use of NaHCO3 allows for better control of the supersaturation and pH to form silica with desired quality. Additionally, Na2CO3 solution as the process by-product is recyclable because it could be recovered to produce NaHCO3 by absorbing CO2. The solubility of sodium metasilicate nonahydrate (Na2SiO3·9H2O) in the Na-CO3-HCO3-OH-H2O system was measured using a dynamic method in the temperature range from 288.15 to 308.15 K. It is found that the solubility of Na2SiO3·9H2O decreases with increasing concentration of either Na2CO3 or NaOH over the investigated concentration range. With the aid of the OLI platform, a chemical model for the Na2SiO3-Na-CO3-HCO3-OH system was established with newly obtained interaction parameters of the Bromley-Zemaitis model by regression of experimental solubility data. The new model predicted the solubility of Na2SiO3·9H2O in multi-component systems with good agreement and was used to conduct a preliminary feasibility study of the new process.

Jan 1, 2015

By N. Parlee, V. C. Kashyap

The solubilities of nitrogen in liquid iron and liquid Fe-Ni, Fe-Mo, Fe-V, and Fe-Mo-V alloys were measured by the Sieverts method. Measurements were made at 1600° to 1800°C on binary alloys up to 20 pet Ni, 10 pet V, 10 pet Mo; and on ternary alloys containing 0 to 3 pet V with 0 to 5 pet Mo. The results on liquid iron confirm that Sieverts' law is obeyed in the range 50 to 750 mm pressure. The measured solubilities and their temperature coefficients are in general agreement with other modern authors. The logarithms of the activity coefficients of nitrogen in the binaries are approximately linear functions of the pet of alloying element. A method suggested by Wagner, Chipman, and others for predicting gas solubilities in complex alloys from solubility data on binaries was applied to the Fe-Mo-V alloys. Reasonably good agreement was obtained between calculated and experimental solubilities. NITROGEN'S solubility in liquid iron has been studied by a number of investigators. It is reasonably well established that the solubility of nitrogen follows Sieverts' law at least up to 1 atm partial pressure and that the solubility increases gradually with temperature. The solubility of nitrogen in Fe-X binary liquid systems has been investigated in only a few cases. Only the systems Fe-Cr,3-5, 7 Fe-V,3 Fe-Mn,3, 5 Fe-Ni,3, 5 Fe-Si,B, H Fe-C, L, H and Fe-P4 appear to have received any study. The only work on liquid Fe-V was done by Brick and Creevy.3 This was limited to 13.5 pet and 26.5 pet V, but no exact temperatures were recorded. No work whatsoever appears to have been done on liquid Fe-Mo alloys and even work on Fe-Ni alloys is rather scant. The work on liquid ternary systems is still more limited, and the only publication available appears to be that of Wentrup and Reif,7 who studied the Fe-Cr-Mn and Fe-Cr-Ni alloys. Rassbach, Saunders, and Harbrecht17 have reported work on the solubility of nitrogen in stainless steel but this was not a systematic study of any particular system. Commercial alloys usually contain several alloying elements. Thus, it often becomes important to be able to predict the nitrogen solubility in systems containing two or more added elements without the necessity of making measurements. Wagner,14 Chipman," Darken and Gurry," and Morris and Buehl 14 have suggested means by which this may be accomplished, and Langenberg14 has recently applied one of these methods to nitrogen solubility in complex liquid alloys. This paper reports the results of nitrogen solubility determinations on Fe-Ni, Fe-Mo, Fe-V, and Fe-Mo-V alloys and compares calculated and experimental solubilities in the ternary alloy. Attempted measurements on Fe-Cr alloys were not successful by the experimental method employed. Experimental Method The general method of solubility measurement was that of Sieverts.' The apparatus and procedure were essentially the same as used by Liang, Bever, and Floe."' The equipment consisted of a small vacuum furnace heated by a 6 kw induction unit, gas measuring apparatus, and a gas purification train. The crucibles used were Norton Alundum with alumina sand around them for insulation. The crucibles were charged with 100 to 200 g of material, about 180 g or nearly filling the crucible being found most satisfactory. Hot volumes were determined with argon and ranged from 95 to 130 cu cm (stp). Temperature measurements were made with a Leeds and Northrup optical pyrometer which was calibrated periodically against the melting point of iron in the same apparatus."-'* Good quality nitrogen, hydrogen, and argon gases were further purified and dried in standard purification trains. The sources of the high purity iron and other alloying elements used were as follows:

Jan 1, 1959

By C. G. Dunn, F. W. Daniels, M. J. Bolton

IN recent investigations1. a data on relative grain boundary energies in silicon iron have been obtained. The present investigation is a continuation of this work along similar lines for the purpose of obtaining additional information on boundary energies. One aim has been to extend the data for a (110) series, which was formerly studied,' to small differences in orientation, since a recent theory3,4 based on a dislocation model of grain boundaries predicts a E. ? (A-ln ? )* form of energy curve for small differences in orientation. Another aim has been to provide data for a (100) series—all grains having (100) planes parallel with the surface of sheet speci-mens—and to compare the results with the predicted form of energy curve. Finally, information on the nature of approach to equilibrium conditions was to be obtained through observations on the movements of grain boundaries. Recently published papers2,3,5 have treated the mathematical problem of expressing equilibrium conditions for grain boundaries for the general case when boundary energy depends upon boundary orientation. The equilibrium equations, which relate equilibrium angles and grain boundary -free energies, contain additional terms that express the variation of energy with boundary rotation. It has been necessary in the present investigation, however, to neglect these additional terms since no data for their evaluation were available. Dropping the additional terms leads to the following approximate equations which were used: E12/sin ?3 = E18/sin?2 =E28/sin?1 or those of the form: E28 + E13 cos ?3 + E12 cos ?2 = 0 Experimental Procedure Except for sample F1, all specimens were made from two lots of silicon iron called C and L respectively. The compositions of these are listed in table I. In the preparation of 12 three-grain specimens for the present investigation, a controlled grain growth technique, which has been described previously,' was used. After preparation, the specimens were notched at the boundaries to shorten them as a means of providing more rapid approach to equilibrium in the anneals. Initial grain boundary angles were determined from micrographs taken at X500. Seven anneals, totaling about two days at 1300°C and two to four days at 1400°C, were run in an atmosphere of pure dry argon as described in a previous paper.' Boundary changes generally could be followed without metallographic surface preparation, because thermal etching occurred during the anneals. These observations indicated angle changes of as much as 35" in some instances, with the major changes occurring during the first anneal. Annealing was discontinued when the angles reached stationary values. Fig. 1 gives a schematic diagram for purposes of defining crystallographic and boundary directions for three grains with common plane parallel with the sheet. Differences in orientations (expressed by A) are the angles between [00l] directions. They can be calculated with the aid of the ?'s. The grain boundary angles can be calculated from the w'S. Results Results are given in table 11. Types of crystal-lographic planes refer to those parallel with the sheet. Orientations are given in terms of [00l] direc-tions as shown in fig. 1. Except for grain 3 of specimen H6, which was unintentionally tilted 7" out of a (100) plane, all grains generally were within 1" or 2" of the plane specified. The directions of boundaries were measured generally to within 1" on both upper and lower surfaces, and the average direc- tions were determined for use in calculating the grain boundary angles. Variations in grain boundary directions refer to deviations from average directions. Boundaries near the junction point for all specimens generally were very close to perpendicu-

Jan 1, 1951

By Stephen C. Tadolini, John P. McDonnell

"High-strength cable bolts have been used for ground support in underground coal mines for many years. Cable bolts are routinely used as secondary ground support in numerous longwall gateroad support applications, areas that possibly experience the most severe conditions in current underground coal mining. Additionally, when mining ground conditions deteriorate, engineers oftentimes recommend cable supports as a principal solution because of the established credibility for successful ground control. Nevertheless, there is still a reluctance to utilize non-tensioned cable supports as an effective primary roof support alternative.This paper provides historical and recently documented examples of non-tensioned cable supports utilized as an effective primary ground support method in a western U.S. underground coal mine, and it will continue the technical discussion between the differences of various degrees of tension in cable supports with respect to ground behavior and reactions.INTRODUCTIONResin-grouted cable supports are widely used to support difficult ground conditions throughout the world. Through the use of innovative applications and configurations they have proven to be a major paradigm shift in roof support and ground control technology in the U.S. (Tadolini and Koch, 1993; McDonnell et al., 1995; Tadolini and Gallagher, 1994; Tadolini and Trackemas, 1994)Today, the basic cable bolt support consists of a high-strength steel cable installed in bore holes that range in diameter from 25 to 50 mm (1 to 2 in) depending on the strand size and drilling equipment. Cables are offered in both bright and galvanized, for corrosion protection, and range in capacity from about 30 to 60 tons. An example of a resin-grouted cable bolt and the key components is shown in Figure 1. The steel cables are flexible and the support length is not limited by the height of the opening. Lengths of up to 10 m (32 ft) have been supported with high pattern densities when standing supports were not operationally feasible. The most common lengths are 3 to 5 m (10 to 16 ft). An important physical characteristic is that PC-strand has an ASTM minimum elongation requirement of 4%. For comparison purposes, the ASTM 432-08 Standard Specifications for Roof and Rock Bolts and Accessories specifies elongation requirements for traditional roof bolts are a minimum of 12% for grade 40, 9% for grade 60, and 8% for grade 75 materials, respectively. Traditional roof bolts can stretch and elongate twice the length that cable bolts can, which makes design considerations challenging."

Jan 1, 2010

By O. W. Ellis

The writer has dealt with the effect of various methods of melting copper upon the gas content of the metal.' The copper referred to in his earlier paper was melted in the foundry both in the oil furnace and the electric furnace. As the metal did not measure up to conductivity standard, the term "casting copper" was applied to the material in the title of the paper. It was thought that some information in regard to the gases in a sample of overpoled copper might also be of interest, and through the courtesy of C. R. Stevens, superintendent of the copper mill of the West-inghouse Elec. & Mfg. Co., such a sample was obtained. The metal was chill-cast in the form of an ingot about 7 in. long, 2 1/2 in. deep (from the base to the raised surface of the ingot) and from 1 3/8 to 1 7/8 in. wide. A photograph of part of the ingot is shown in Fig. 1. The effect of over-poling on the surface of the metal is here quite clearly shown.

Jan 1, 1929

By O. W. Ellis

The writer has dealt with the effect of various methods of melting copper upon the gas content of the metal.' The copper referred to in his earlier paper was melted in the foundry both in the oil furnace and the electric furnace. As the metal did not measure up to conductivity standard, the term "casting copper" was applied to the material in the title of the paper. It was thought that some information in regard to the gases in a sample of overpoled copper might also be of interest, and through the courtesy of C. R. Stevens, superintendent of the copper mill of the West-inghouse Elec. & Mfg. Co., such a sample was obtained. The metal was chill-cast in the form of an ingot about 7 in. long, 2 1/2 in. deep (from the base to the raised surface of the ingot) and from 1 3/8 to 1 7/8 in. wide. A photograph of part of the ingot is shown in Fig. 1. The effect of over-poling on the surface of the metal is here quite clearly shown.

Jan 1, 1929

By T. V. Falkie

REMARKS OF DR. THOMAS V. FALKIE, DIRECTOR, BUREAU OF MINES, U.S. DEPARTMENT OF THE INTERIOR, BEFORE THE FALL MEETING OF THE SOCIETY OF MINING ENGINEERS, AIME, ACAPULCO, MEXICO, SEPTEMBER 23, 1974 This is a time of uncertainty on the world mineral scene. For some of the world's so-called "developed" countries, reserves and production of key minerals are running low. And, we have learned that the energy so essential in recovering and processing minerals can suddenly be in short supply. The prospects for a "no growth" situation in energy or mineral consumption are practically nil. Moreover, the world's economy is in flux, casting doubt on whether traditional mineral customers will continue to be able to buy, or for that matter, whether traditional suppliers of minerals will continue to sell. It is clear that the mineral situation is contributing to world inflationary pressures, which incidentally are most damaging to developing countries. So it is appropriate that SME members devote this session to the world mineral situation, and consider some of the opportunities and responsibilities that we will inevitably encounter as the future becomes the present. The opportunities, to me at least, are especially intriguing, I have the good fortune to be part of an organization that has an enormous capability and responsibility for dealing with mineral problems. The Interior Department's Bureaus, including the Bureau of Mines, have been around for a long time. They are. a prolific and reliable source of both mineral information and mineral technology.

Jan 1, 1974

By R. P. Smith

The diffusivity of carbon in iron, cobalt, and alloys of 89.7 and 79.3 wt pct Co has been determined by a decarburization method for the temperature range 850° to 1100°C. The Plots of log D us 1/T for the two Fe-Co alloys are linear through the region of the Curie temperature, showing that, unlike some cases of substitutional diffusion, carbon diffusion in these alloys is not affected by electron spin order. RECENT investigations1-' have shown that for substitutional diffusion in iron the change in diffusivity with temperature does not follow an Arrhenius equation, at temperatures near the Curie temperature. Data on the diffusivity of carbon in a iron5"9 indicate that this anomaly does not exist for interstitial diffusion; however, this has not been definitely established. Since cobalt and Fe-Co alloys, 80 to 100 pct Co, have Curie temperatures in a temperature range convenient for carbon-diffusion measurements they are suitable systems for studying the relation of interstitial diffusion and the Curie temperature. EXPERIMENTAL The carbon diffusivity, D, was determined by a decarburization method. The diffusion cylinders, made from small vacuum melts of electrolytic cobalt and plastiron, were about 0.76 cm diam and 6.3 cm long. A small amount of carbon was added to each melt to keep the oxygen content as low as possible. The cylinders were first treated with a hydrogen-3 pct water vapor mixture at 1100°C to constant weight, then carburized to the desired initial carbon content with a suitable CO-C02 gas mix-

Jan 1, 1964

By E. S. Fisher, L. C. R. Alfred

The elastic anisotropy factors, c4,/c6,, c3,/cll, and c12/cl,, for hcp metal crystals vary significantly among the dgferent unalloyed metals. Significant variations with temperature are also found. The effects of elastic anisotropy on the dislocation in an elastic continuum with hexagonal symmetry have been investigated by computing the elasticity factors for the self-energies of dislocations in fourteen different metals at various temperatures where the elastic moduli have been reported. For most of the metals the effects of the orientation of the Burgers vector, dislocation line, and glide plane are small and isotropic conditions can be assumed without significant error. Significant effects of anisotropy are, however, found in Cd, Zn, Co, Tl, Ti, and Zr. The elasticity factors have been applied in the calculations of dislocation line tensions, the repulsive forces between partial dislocations, and the Peierls-Nabarro dislocation widths. It is predicted that the increase in elastic anisotropy with temperature in titanium and zirconium makes edge dislocations with (a), (a + c), and (c) Burgers vectors unstable in basal, pyramidal, and prism planes, respectively. The probability of stacking faults forming by dissociation of Shockley partials in basal planes also decreases with increasing c4,/c6, ratio, when the stacking fault energy is greater than 50 ergs per sq cm. The widths of screw dislocations with b = (a) in titanium and zirconium increase very significantly in prism planes and decrease in basal planes as c4,/c6, increases. The effects of elastic anisotropy on various dislocation properties in cubic crystals have received considerable attention during the past few years. In the case of cubic symmetry the departure from isotropic elasticity depends entirely on the shear modulus ratio, A = 2c4,/(cl, —c12); i.e., the medium is elastically isotropic when A = 1. Foreman1 showed that an increase in the ratio A produces a systematic lowering of the dislocation self-energy for a given orientation and Poisson's ratio. ~eutonico~, has shown that large anisotropy can have a marked effect on the formation of stacking faults by the splitting of glissile dislocations in (111) planes of fcc and (112) planes of bcc crystals. ~iteK' made similar calculations for (110) planes of bcc metals. Both studies of bcc metals showed that the large A values encountered in the alkali metals tend to reduce the repulsive forces between Shockley partial dislocations. In fcc metals, however, A does not vary over the large range encountered in bcc metals; consequently, the effect of A on the forces between Shockley partials is masked somewhat by the differences in Poisson's ratio between metals. The effect of A on the line tension of a bowed out pinned dislocation has also been investigated for cubic crystals, first by dewit and Koehler5 and more recent- ly by Head.6 In both cases the line energy model is applied and the core energy is not taken into account, thus making the conclusions somewhat tenuous with regard to the physical interpretation. Nevertheless, the fact that a large A decreases the effective line tension is clearly evident and the tendency for large A to produce conditions that make a straight dislocation unstable (negative line tensions) also seem evident. Head, in fact, shows visual microscopic evidence that stable V-shaped dislocations occur in 0 brasse6 For hcp metals the definition of elastic anisotropy is more complex and, furthermore, significant deviations from an isotropic continuum are found among a number of real hcp metals, especially at higher temperatures. The present work was carried out to survey the effects of elastic anisotropy on the elasticity factors, K, that enter into the calculations of the stress fields around a dislocation core. Some isolated analytical calculations have previously been carried out for several hcp metals but they are restricted in the dislocation orientations and temperature.8'9 The present computations are based on single-crystal elastic moduli that have appeared in the literature and consider various orientations requiring numerical computations. The results are then applied to survey the effects of temperature on the dislocation line tension and dislocation splitting in hcp metals. PROCEDURE Anisotropy Factors. The degree of elastic anisotropy in hcp crystals cannot be described by a single parameter, such as the A ratio in cubic crystals. The following three ratios must be simultaneously equal to unity in order to have an elastically isotropic hexagonal crystal: The magnitudes of these ratios at several temperatures, as computed from the existing data for the elastic moduli of unalloyed hcp metals, are given in Table I. There are no cases of complete elastic isotropy, but the large anisotropy ratios encountered in the cubic alkali metals are also missing. There are, however, several significant differences among the hcp metals, the most notable being the relatively small A and B ratios in zinc and cadmium and the differences in the magnitudes and temperature dependences of A. It has been noted that the temperature dependence of A has a consistent relationship to the occurrence of the hcp — bcc tran~formation. For cadmium, zinc, magnesium, rhenium, and ruthenium, A is less than unity at 4'~ and, with exception for rhenium, decreases with increasing temperature. In the case of rhenium, A has essentially no temperature dependence between 923' and 1123"~, so that it is clear that A does not approach unity at higher temperatures. Cobalt is similar to the above-mentioned group of metals in that it also does

Jan 1, 1969

By A. M. Kivari

OPERATIONS at the cement plant of the Permanente Corporation, in the hills about 45 miles south of San Francisco and 12 miles west of San Jose, are interesting to the members because of the adoption of modern hydrometallurgical methods for handling and beneficiating raw materials. Closed-circuit grinding, classification, hydro-separation, flotation, agitation, and thickening are familiar terms at this cement plant. These methods make it possible to process refractory limestone into suitable materials for the manufacture of modern cements. Construction of the plant, having originally a design capacity of 7000 bbl. of cement per day, was started in June 1939, and the first clinker was ground on the following Christmas Day. At present the capacity is about 12,000 bbl. of finished cement per 24 hr., most of the production being low-heat cement.† About 3130 tons of limestone, 620 tons 0f clay and 100 tons of gypsum are required daily for this output. Occasionally iron oxide is added to the clay to obtain the desired composition. This, together with the gypsum, is purchased from outside sources. Up to the present time, the corporation has produced low-heat, normal, moderate heat, moderate-sulphate-resisting, high-early-strength, oil-well, modified-oil-well, and plastic cements. Most of the present production is for Shasta Dam, near Redding, Calif., the total demand being 5,800,000 bbl, of cement. Following are some of the cement requirements of the Shasta Dam specifications: [PERCENT Chemical composition: Loss in ignition2.25 Insoluble residue0.75 SO32.25 MgO5.00 Uncombined lime in clinker (CaO)1 .25 Percentage of iron oxide to alumina ratio1.5 Compound composition: Tricalcium silicate (3CaO.Si02)Not more than 3,5 Dicalcium silicate (2CaO.Si02)Not less than 40 and not more than 65 Tricalcium aluminate (3CaO.Al2O7)Not more than 7 Tetracalcium aluminoferrite (4CaO.A12O3.Fe203) Not more than 0 Fineness:] The average specific surface in the bin sampled shall be not less than 1800 sq. cm. per gram and no individual sample less than 1600 sq. centimeters. Compressive strength: The average compressive strength-in pounds per square inch of three mortar cubes composed of one part cement and 2.75 parts fine testing sand, by weight, shall be equal to or greater than the following:

Jan 1, 1941

By Anne C. Chinellato, Alejandra T. Soria, Nelida L. del Mastro, Amanda C. S. Pereiral, Esperidiana A. B. Moura, Anibal V. Abreu

"This work presents a comparative study of the thermo-mechanical and morphological properties of sugarcane bagasse fiber/HDPE composite treated with electron-beam and gamma radiation. The composite samples obtained by extrusion and injection molding processes were irradiated at 50 and 90 kGy using either a 1.5 MeV electron beam accelerator or gamma irradiator EMI-9, at room temperature in presence of air. The irradiated and non-irradiated samples were submitted to mechanical and MPI tests, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), sol-gel analysis and X-Rays Diffraction (XRD) and the correlation between their properties was discussed. Improvement of the bagasse fiber/HDPE composite properties, using electron-beam or gamma radiation, was found.IntroductionResidues of sugarcane bagasse fiber are widely produced in Latin America and other countries: in Southern Africa, Egypt, South-Eastern Asia, India, China, Australia, Cuba, among other producers, as by-products of the sugar and bioethanol industry. The sugarcane industry in Brazil and Uruguay is well established and expanding with large potential to increase the production of sugarcane bagasse in the next years [1-3]. Although the major portion of the bagasse is currently burnt for energy supply in the sugarcane industry, the disposal of this byproduct is still inefficient and, consequently, it is critical for agricu1ture profitability and environmental protection. Sugarcane bagasse is a lignocellu1ose fiber mainly constituted by around 46 % cellu1ose, containing hemicellu1ose, lignin, fat and waxes, silica and other elements [3, 4]. Studies have reported that sugarcane bagasse can be used to produce thermoplastic polymeric composites with excellent properties for many applications. [5-8]. Based on this survey, the transformation of bagasse into high quality industrial products, such as bagasse-polymer composites, can provide its more effective utilization."

Jan 1, 2012

By T. F. Tomb

Although the number of operating longwalls (approximately 100) has remained relatively constant over the last five years, longwall production levels have significantly increased and have in some cases more than doubled. As a result of the increase in production, control of respirable dust continues to be a problem. Therefore, the Mine Safety and Health Administration (MSHA), Pittsburgh Health Technology Center, Dust Division, initiated a study to investigate the availability and adequacy of technology for controlling dust on longwall mining operations. The study involved 23 longwall mining operations in three different Coal Mine Safety and Health Districts. Each operation was visited for a full shift. Respirable dust samples were collected on face personnel and at fixed locations along the face. Parameters in place to control dust were noted with special emphasis being placed on obtaining quantitative data relative to ventilation, headgate dust controls, cutting drum sprays, external machine sprays and cutting sequence. Attempts were made to correlate dust control parameters in place at the time of the visit to dust concentrations measured at the tail, on the tail shearer operator and to the average concentration of dust determined from averaging all the measurements from the occupations sampled. The parameters in place to control dust were also compared to the gamut of technology known to be available to control dust. This paper presents a discussion on the effectiveness of the parameters in place to control dust and on the availability of technology for the control of dust on longwall mining operations.

Jan 1, 1990

By H. S. Fleming

My original intention was to give a full account of Southern furnaces, ores and cokes; but, owing to the difficulty of getting reliable information, I confine this paper to a general description of the ores used in, and immediately around, Chattanooga. Mr. L. S. Colyar, Manager of the Rising Fawn furnace, wrote me in answer to an inquiry as to what ores they were using, " Below I give you analyses of the mixture of ore we have been using for the past seven or eight years. We haven't a complete analysis of any ores, but I will give them to you as I have them. Attalla Soft Rising Fawn Hard Rising Fawn Red Ore. Red Ore. Soft Ore. Iron,.... 50.60 38.48 46.82 Silica,. .. 11.69 7.32 22.69 Phosphorus,. .. 1.06 .319 .350 This is a fair average of all the ores we get in this section." The following analyses of Birmingham soft ore were received from the Morris Mining Co., of that place. No. 1. NO. 2. No. 3. No. 4. Iron.....51.60 54.88 51.04 51.20 Silica,. .. 19.32 10.60 17.32 17.08 Alumina,....19 .88 1.18 Phosphorus,. ..129 .287 .116 .464 Mine No. 1, second vein, shows: iron, 46.40; alumina, 4.92; phosphorus,.212; silica, 19.60. Mine No. 1, by analyses obtained from the Mary Pratt Furnace CO., shows: Iron. Silica. Fine red ore,.49.00 18.38 Lump red ore,...54.42 17.10 Bottom vein,.50.00 21.38 Bottom vein,.41.24 13.52 A lot of this ore delivered in Chattanooga gave : iron, 53.32; alumina, 2.10; phosphorus,.529; silica, 18.03.

Jan 1, 1887

By G. R. Palmer

The occurrence of mercury minerals in precious metal-bearing ores has long been noted. During cyanide leaching of these gold-silver ores, some mercury forms a soluble cyanide complex, which is present in the pregnant leach solution and passes through the process operations of the cyanidation mill. As a result, mercury is found on the electrowinning cell cathodes, on the stripped carbon before It is volatilized during carbon regeneration, or in theme tailings pond. The U.S. Department of the Interior's Bureau of Mines is examining the effectiveness of two ion-exchange resins to adsorb gold and/or mercury from a cyanide leach solution. The resins, Duolite A-7 and Ionac A-305, were contacted with leach solutions containing varying concentrations of mercury, gold, and silver. The resin A-7 reached a maximum mercury loading of 0.0165 lb Hg/ft3, and A-305 reached a maximum mercury capacity of greater than 0.44 lb Hg/ft3. Adsorption of gold by both A-7 and A-305 is influenced by the presence of additional ions in the solution.

Jan 1, 1984

By Catharine T. Fogg

The U.S. Bureau of Mines investigated the availability of platinum, palladium, and rhodium from 16 deposits in four market economy countries (MEC's). Major recoverable products include 164 Moz of platinum, 80 Moz of palladium, 13 Moz of rhodium, 24 Moz of ruthenium, 4 Moz of Iridium, 2 Moz of Osmium, and 10 Moz of gold. The 12 deposits in the Republic of South Africa are estimated to account for 96.7 pct of total recoverable platinum. The base-case scenario estimates the long-term cost of production including recovery of capital, but provides no return on the investment or O-pct discounted cash-flow rate of return (DCFROR). The total production costs in January 1990 U.S. dollars ranged from $325/oz to $1,288/oz of platinum compared to an average January 1990 price of $492/oz. Approximately 83 pct of total recoverable platinum was economic at a cost level of $4S0/oz or less. At the IS-pct DCFROR, only 26 pct of total recoverable platinum was economic. For platinum-group metals (PGM), attention has been focused on the ratios of the three primary metals: platinum, palladium, and rhodium. Sensitivity analyses were performed to determine the impact long-term rhodium price increases could have on the total cost of production for platinum and palladium.

Jan 1, 1993

By G. L. Finfinger, J. Cervik, L. J. Prosser

The Bureau of Mines has completed an underground degasification project in which an underground piping system was used to transport methane from the coalbed to the surface. In a 10-month period four horizontal holes were drilled to an average depth of 1,450 feet. All four holes were surveyed vertically and azimuthally. In 991 days of degasification, 255 MMcf of gas was drained from the coalbed. The underground piping system proved to be a safe and effective means of transporting methane from the coalbed to the surface.

Jan 1, 1981

By P. R. Jochens, A. A. Hejja

The effect of the reactivity of lime on desulphurization efficiency in the basic oxygen furnace by A. A. HEJJA,D. D. HOWAT, andP.R.jOCHENS Published in the Journal March 1973. DISCUSSION R. E. Leyman* The authors discuss in detail the effects of transport and storage at the steel plant on the reactivity of lime as measured by the DIN Reactivity Test. They attribute the deterioration in reactivity to the absorption of water vapour and carbon dioxide, but make no mention of the possible role of atmospheric sulphur dioxide in this respect. The significance of the mineralogical and surface characteristics of gold grains in the recovery process by C. E FEATHER and G. M. KOEN Published in the Journal February 1973. AUTHORS' REPLY TO DISCUSSION (Published in the Journal July 1973) H. P. Carlisle Mr Carlisle's questions and observations will be dealt with in the same order as they were raised. 1. How were the mass percentages of the grains determined from the sizes measured in polished section?

Jan 3, 1973