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By E. C. Tarpley, H. M. Cooper, R. F. Abernethy

"INTRODUCTION The float-and-sink test 5/6/ is generally the first test used in determining the washing characteristics of coal. The simplest form of the test is that of using one solution of such specific gravity that the test sample is separated into ""float"" and ""sink"" fractions. In practice, however, a series of solutions is used, and the sample is separated into a number of fractions of a definite specific-gravity range. Analyses of a series of fractions of this type are often referred to as the ""specific-gravity analysis,"" and are of great value in the selection, construction, and operation of commercial washing equipment.The test is rather simple to use, provided a number of conditions are recognized and as many as possible held constant, such as:1. In laboratory testing, two types of solution are available -Aqueous solutions of calcium and zinc chlorides.Mixtures of organic liquids such as carbon tetrachloride, benzene, gasoline, bromoform, etc.2. Absorption of the solution by the coal,3. Solvent action of the solution toward the coal.4. Constancy of specific gravity during the test is affected by temperature changes, dilution, and evaporation.5. Personal technique of the test, such as the time the coal is in the liquid, rate of adding the sample to the liquid, stirring, time of draining, etc.6. Moisture content of the coal as tested."

Dec 1, 1947

By J. Grogan

Leaching of galvanized steel coatings allows the steel substrate to be used as a zinc-free scrap source to steel and iron furnaces. In this study the behaviors of sulfuric acid leaching solutions are investigated. The ranked significance of the variables are shown to be acid concentration > temperature > zinc concentration. Examination of the leaching mechanism finds the rate-limiting step to be the cathodic hydrogen reduction reaction. This rate is not only influenced by acid concentration, but also by the hydrogen reduction exchange current density. Dezincing leaching rates are improved by taking advantage of the higher exchange current density of the iron substrate versus the zinc coating. This is accomplished in practice by increasing the exposed interfacial zinc:iron surface area through shredding. Also, a leach control mechanism is proposed through online monitoring of the zinc-iron couple mixed potential.

By D. C. DERINGER

METALLURGISTS and mill operators appreciate, in a general way, .the economic or commercial relationship between recovery and grade of product but few have correlated in detail fluctuating metal prices with the metallurgy. They know that many factors such as metal price, dedusiions for returning charge, transportation, percentage of metal in head ore, etc.; all affect the commercial relationship between recovery and grade of product. In practically every mill some one at some ' time has calculated the amount of recovery that can be sacrificed for each percentage increase in grade of concentrate and from this calculated ratio the commercial or ., economic tail has been established. Such a ratio finally becomes a well-entrenched rule by which the progress of the metallurgy is judged.. When once established, these-, ratios are but seldom corrected to changes of metal prices for each possible grade of concentrate that may be produced. The calculation is tedious when often repeated. Other methods have been suggested and used to correlate the commercial with the metallurgical phase. A factor .derived ,by multiplying the grade of concentrate by recovery is often used, but is of little importance because it does not possess a single commercial quantity. The percentage monetary recovery calculated by dividing the gross value of the ore into the net smelter return gives a good economic index and, is to be commended, but it is difficult to correlate exactly and quickly the work of each day on a commercial basis.

Jan 1, 1931

By Aaron Evans, Chu E. Ho, Tom Richards

"This paper describes an innovative case history of using jet grouting to form a groundwater cutoff wall at the interface of a cut-and-cover construction and an existing tunnel. The design of the jet grouting layout was complicated by the presence of a left-in-place bulkhead of unknown dimensions abandoned by previous construction of the existing tunnel. Jet grouting was performed through predrilled holes within the narrow space between the existing bulkhead sheeting and tunnel structure. A systematic sequence of primary and secondary jet grout elements of varying diameters and panel lengths was executed to achieve an effective groundwater barrier. A key challenge in the jet grout design was the impact of potential deviations due to shadowing effects of the left-in-place bulkhead sheeting and pre-formed jet grout columns, as well as overbreak concrete in adjacent secant pile walls. The flexibility of the jet grouting methodology enabled a wide range of operational parameter combinations to be performed, allowing column diameters to be adjusted based on actual field installation measurements. Special precaution was exercised when grouting at critical locations to avoid over-pressurization and damage to the existing tunnel structure.IntroductionThe 96th Street Station box for the new Second Avenue Subway Line in Manhattan, New York included a transition tunnel, which connected the station to an existing tunnel built in the early 1970s (Figure 1). The new station and transition tunnel were both constructed using the cut-and-cover technique with bottom-up sequence (Aksman et al. 2012, Grigson et al. 2016). The main station structure incorporated permanent diaphragm walls for most of its length, except for the southern segment where high rock levels were encountered and the station box was constructed within temporary secant pile walls socketed into the rock. The permanent diaphragm walls were also utilized for temporary excavation support (Ho and Hu 2014). At the northern end of the site, the new transition tunnel was constructed within temporary secant pile walls that extended from the station diaphragm walls to the existing tunnel at the tie-in location. A temporary traffic deck spanning 60ft across the secant pile and diaphragm walls along the full excavated length of the site allowed traffic to continue operating at street level while construction of the station and transition tunnel progressed below grade."

Jan 1, 2016

By Paul R. Kruesi

A patent-applied-for process has been developed in which zinc chloride is extracted by tributyl phosphate in kerosine, and stripped with ethylene glycol or ammoniated ethylene glycol. The anhydrous zinc chloride is precipitated from the glycol as the ammine and zinc chloride is prepared by thermal decomposition with recycle of ammonia. The process permits the production of high grade zinc from scraps and drosses. Its applicability to the recycling of zinc will be illustrated.

Jan 1, 1984

By KENNETH CITTISGHAM

During the year 1945, the total number of wells drilled in Ohio, including the. non¬productive wells, was 1034. For the 10-year period ending with 1945, the average completions per year were 1125, the least number being 910 in 1938, and the maximum 1561 in 1941. The proportion of dry holes in 1945 was 37 per cent?about the same as for the year 1944 but exceeding the 10-year average, which was 34 per cent. The number of oil wells completed exceeded the number drilled in 1944 by about 30 per cent, the average initial per well being the same in both years. Gas-well completions were approximately 10 per Cent less than in 1944, with the average initial per well about 5 per cent greater. The difference in number of oil and gas wells in the two years was in Berea and Clinton completions, as the number of oil wells increased about 30 per cent, owing to greater activity in the two sands named, while the number of gas wells decreased because of fewer completions therein.

Jan 1, 1946

By Behdeen Oraee, Amirhossein Bangian, Kazem Oraee

"Determination of the optimum design of chain pillars has a significant effect on the economics and safety of longwall operations. Most pillar design formulae are based on empirical methods and supplemented by local experience. They therefore lack versatility of application under different geotechnical conditions.In this paper, in order to illustrate the shortcomings of the above, a typical real coal pillar in Tabas coal mine has first been studied and the conventional formulae have been used to determine the optimum dimensions. The results show that a wide difference exists between the predicted and the real field data. The Oraee-Hosseini formula has then been applied to this mine in order to determine the optimum design. The results from this formula demonstrate a close fit between the theoretical VALUES (and those produced by laboratory tests and in practice. It is further demonstrated that the wide discrepancy between the results obtained from the two formulae is attributed to the dissimilarities between geotechnical conditions of Tabas and the original regions whose data were used to devise the empirical formulae.It is finally concluded that the application of numerical simulation methods and experimental equations together with engineering judgment used by the mining design engineer, will provide the most accurate design characteristics.INTRODUCTIONLongwall is an underground mining method which has a high rate of production capacity and mechanization ability. This mining method, which is appropriately applied for soft rock fiatlying bedded ore bodies, gradually became a widespread mining method amongst European coal mines at the beginning of the 19'h century. It was then applied in some of the U.S. coal mines with the development of self advancing support mechanisms in early 1960's (Oraee, 2001).Underground coal production around the world using Longwall mining method doubled during 1990s. The main reasons for this improvement were: the high level of mechanization, increased 10 safety, adequate design of panels, and well designed ventilation systems (Peng, 2006)."

Jan 1, 2010

By John G. McLain

OF all the zinc that the world consumed in 1936-'38 the United States took about 31 per cent, and almost 14 per cent of the world's zinc supply in that period was used for galvanizing purposes in the United States. Further examination of the statistics shows that about 71/2 per cent (147,500 tons in 1939) of the world zinc consumption goes into the galvanizing of sheets in the United States, which is what I am going to talk about in this paper. There is nothing especially new about galvanizing; in every year since 1921 somewhere between 41 and 49 per cent of the country's zinc consumption has been used for this purpose, and yet few people not specialists in its manufacture know much about how it is made. You take an iron or steel sheet and dip it in molten zinc and there you have a galvanized sheet-that about epitomizes popular knowledge of the subject even among engineers.

Jan 1, 1941

By R. Y. Wan

Acid ferric sulfate solution has been used for heap and dump leaching of low-grade chalcopyrite ores and is being considered as a possible lixiviant for the hydrometallurgical processing of copper sulfide concentrates. For many years, researchers have attempted to explain the leaching behavior of chalcopyrite, since the reaction rate kinetics are extremely slow and seem to be significantly influenced by the nature of the reaction product. A summary of conclusions drawn from reported literature on chalcopyrite leaching is found in the paper by Munoz, Miller, and Wadsworth(1) and more recently by Dutrizac.(2) Lowe(3) and Jones and Peters (4) attributed rate control to a surface reaction. Linge,(5) Dutrizac,(6) Bauer,(7) and researchers at the University of Utah(1,8) reported that the reaction rate is limited by transport in the chalcopyrite lattice or through the elemental sulfur reaction product layer. Munoz et al.(1) presented a model, derived from the Wagner theory of oxidation, which is based on the formation of a protective sulfur layer with rate control by electron transport through the insulating sulfur layer. By utilizing Wagner's parabolic oxidation relationships, (9) the following equation was obtained: [ ] where a is the fraction of CuFeS2 reacted at time t, pB is the molar density of CuFeS2, do is the initial diameter of the particle, e is the electronic charge, s is the total electrical conductivity of the sulfur layer, and ?G is the Gibbs free energy for the reaction:

Jan 1, 1984

By D. B. Gawthrop

"One of the properties of an explosive, of interest to the user, is its ability to transfer detonation across an air gap to another explosive charge. This Property is of particular importance with permissible explosives used in coal mines, since they are relatively insensitive to detonation when compared to many of the commercial dynamites used in metal mining.An essential characteristic of an explosive is that it shall always be sufficiently sensitive to propagate detonation completely. An insensitive explosive constitutes a hazard because of (1) the danger of drilling into unexploded portions of charges of explosives which have partially misfired, and (2) the likelihood of a low order of detonation, or the burning, of all or part of the charge in a hole prepared for blasting. The latter condition not only usually produces large volumes of poisonous gases, but it is particularly hazardous in gassy or dusty coal mines where explosions may result.The Bureau of Mines and manufacturers of explosives determine the sensitivity of explosives to detonation over an air gap by means of a [(halved-cartridge gap test,"" for which the ends of the cartridges of explosive exposed to one another, are cut off. Since in blasting, the crimped ends remain on the cartridges used, this investigation has been made to ascertain the effect of the crimped paper ends on the distance detonation is propagated over an air gap as compared with the propagation distances obtained when the crimped-paper ends are removed."

Nov 1, 1932

By J. R. Bridge, D. A. Vaughan

The phase diagram of the Zr-H system over the range 0 to 65 atomic pet was determined by high temperature X-ray diffraction methods. Results show a eutectoid between a zirconium and the hydride phase. The eutectoid temperature was established at 560±10°C with a eutectoid composition of 42*3 atomic pet H. The hydride phase of the lowest hydrogen content is stable only above the eutectoid temperature, but is formed and retained in a metastable state during reaction of zirconium with hydrogen at temperatures below 560°C. One hydride phase is indicated that exists over the composition range 55 to 65 atomic pet H. RECENT increase in the industrial importance of zirconium has stimulated several investigations of the reaction of zirconium with hydrogen. Review of the literature on interpretation of absorption isotherms' ' shows that attempts were made to relate the observations to the room temperature hydride phases reported by Hagg.3 However, more recently Schwartz and Mallett' reported the existence of a new hydride phase, isomorphous with the lower hydride in the Hf-H system described by Sidhu.4 This phase was found adjacent to the metal in a diffusion gradient sample. In addition to the new phase, Schwartz and Mallett reported on only two of the five hydrides found by Hagg. Gulbransen" confirmed the existence of only three hydrides of

Jan 1, 1957

By M. Leroux, S. R. Rao, J. A. Finch

"Poor Pb/Zn selectivity during Pb flotation in laboratory tests on a Mississippi Valley-type Pb/Zn ore was traced to a pH effect. In the pH range 9.5-11 sphalerite floated readily without copper activation. Compared to sphalerite flotation with copper activation this procedure gave equivalent selectivity but reduced flotation rate.Possible mechanisms of this sphalerite flotation without copper activation are discussed. Activation by Fe(OH) 2 is suggested, the Fe++ions being derived from superficial oxidation of pyrite in the ore.INTRODUCTIONGalena and sphalerite commonly occur together. The usual practice is to float galena first followed by the flotation of sphalerite after activation with copper (II) sulphate. If ores contain pyrite it is depressed by maintaining an alkaline pH (9- 10) and using NaCN as depressant.In flotation tests with a Pb/Zn ore from Polaris selective flotation of galena could not be achieved consistently as a considerable amount of sphalerite, even though unactivated, floated. A systematic study was carried out to determine the cause of this problem. This led to the unexpected finding that sphalerite floated in the alkaline pH range 9.5-11.0 without preactivation with Cuso 4 . This paper describes the results of this study and discusses a possible mechanism of the flotation of sphalerite."

Jan 1, 1987

By Fredy Rolando Castillo Peña

El presente trabajo describe el impacto de la crisis financiera mundial en la industria minera y su interrelación con la gestión de las comunidades circundantes al área de influencia de las operaciones mineras y del Estado a través de sus instituciones públicas y locales. Es decir, la crisis financiera internacional brinda a los empresarios mineros la oportunidad de replantear el enfoque tradicional de las acciones de RSE (Responsabilidad social empresarial) y así realizar una redistribución presupuestal adecuada e involucrada en una gestión efectiva con valores estratégicos en los líderes de la comunidad y del Estado.

Sep 14, 2009

By Rodríguez V. Raymundo E.

El presente trabajo describe la evaluación del uso de brocas tricónicas como herramientas principales de perforación en el yacimiento minero de Cerro Verde, Arequipa. La óptima utilización de esta herramienta representa el 30% de los costos totales de perforación, los cuales se ven reflejados en los factores de análisis a considerar para la superación de performances y las perspectivas que se aplicarán en el futuro para alcanzar mejores rendimientos y bajar los costos de perforación.

Oct 14, 1980

By Wilfred A. Lyons

El departamento geológico de una mina describe ilustraciones de mapas y y secciones transversales del yacimiento, como sus secciones longitudinales. En este sentido, el objetivo del texto señala el uso de las secciones longitudinales contorneadas donde se localizan los valores deseados, para luego unirse mediante isogradas, produciendo un gráfico simi lar al de un plano topográfico. Las principales secciones contorneadas son: las secciones longitudinales contorneadas de valores metalíferos, secciones longitudinales contorneadas de espesores de vetas, secciones longitudinales contorneadas mineralógicas, secciones longitudinales contorneadas de estructura de vetas, secciones longitudinales contorneadas de pares metalíferas, secciones longitudinales contorneadas combinadas, secciones longitudinales contorneadas de contenido metálico, así como se describen las inferencias de las secciones longitudinales contorneadas.

Aug 20, 1965

By J. P. Ibáñez

The uptake of copper from extremely dilute aqueous solutions by alginate in the form of protonated dry alginate beads was investigated. Barium was used to cross link the alginate forming the beads. The effect of various experimental parameters such as pH and metal ions concentration on the uptake of copper were studied. The uptake was strongly dependent on the Cu-bearing solution pH up to a value of 4.5. A removal of 100% o was achieved when the initial concentration of copper was as low as 8.0 mg/L. The maximum uptake, i, e., the loading capacity, was found to be 167 mg of copper per g of beads. The mechanism governing the removal of copper was found to be ion exchange between protons of the alginate beads and cupric ions of the solution. For this ion exchange process a molar ratio, d[H+]/d[Cu2+], of 2.0 was determined. EPMA-EDX analysis of the Cu-loaded beads showed a uniform distribution of the ions throughout the structure of the alginate, regardless the solution pH. This may suggest that this sorbent material is a porous ion exchanger having high permeability and capacity. The uptake of copper and of the heavy metals cadmium and zinc by this sorbent is compared.

Jan 1, 1999

By R. R. Hornor, Geo. M. Hunt

The purpose of this paper is to point out some of the benefits and economies to be derived by the better selection , preparation, storage , preservation and utilization of mine timber , and to give some specific information on certain wood preservatives and processes suitable for mine timber preservation . The paper is based largely upon data obtained by actual experimentation and service tests conducted by the U. S. Forest Products Laboratory , Madison, Wisconsin, on wood preservation , covering a period of many years , and upon a field survey during the past summer by one of the mining engineers of the U. S. Bureau of Mines of some of the principal mining districts of Michigan , South Dakota , Montana , and Idaho , in which he made a general ' study of mine timber in metal mines , particular attention "being given to timber decay ; the conditions under which it takes place most actively ; the measures , if any , that are being used to combat it; and, finally, the advantages that might be anticipated in the use of chemically treated timber to prevent decay and thus prolong its life .

Feb 1, 1922

By Clyde E. Williams

[As a results of work conducted during the past three years, the Northwest Experiment Station of the Bureau of Mines, in cooperation with the University of Washington at Seattle, Washington, has developed a process for the production of sponge iron. Commercial operation of this process in a 3 to 4-ton scale has been so satisfactory that its use on a large scale (20 to 100 tons per day) can be safely considered. Description of Process. The process consists in passing a mixture of iron ore and coal through a rotating kiln heated at one end to a temperature sufficient to convert iron oxide to metallic iron, discharging, cooling, and separating the sponge iron from the residual coke and silicious material on a magnetic separator. Both the coal and the ore should be crushed to peso as 6-meth scream, tans producing particles finer then 1/12 of an inch. Seventy-five parts of coal or other carbonaceous material arc charged with every 100 parts of ore), This large amount of coal is required in order to supply sufficient carbon to maintain a strongly reducing atmosphere in the charge, but may be reduced to about 65 parts per 100 parts of ore by recovering and using tae carbon that remains in the discharge product. Large-scale operation and refinements in furnace design should lower this ratio to perhaps 56 or 60 parts of coal to 100 parts of ore.]

Jan 1, 1924

By Roy L. Zuber

Identification and analysis of mining hazards involves the correlation of accident, injury and illness information from all segments of the mining industry. It would not be feasible to process the volume of data involved without substantial reliance upon a computerized information system similar to that maintained by the Health and Safety Analysis Center. Numerous statistical programs are applied to the computerized accident-injury-illness data base to identify those mining tasks and associated activities which are responsible for most of the injuries and occupational illnesses. These programs are used to flag those mining tasks or conditions at specific mines or segments of the mining industry where either a significant increase in the injury/illness trend has been reported or where the number of injuries/illnesses related to specific mining tasks or conditions are high. Upon identification of those mining hazards which warrant further analysis, a computerized search of the coded accident data is performed to correlate the predominant categories by cause of injury or illness, source of injury, nature of injury, type of accident, etc. From this correlation, those factors most common to the conditions responsible for the hazard may be identified. Based upon analyses of this form, recommendations are made regarding the appropriate engineering, training, and/or operational improvements necessary to alleviate the hazard. In addition to mining hazard analysis, the computerized data base also has application in the area of optimum resource allocation. Computer programs have been developed to assist management in allocating resources based upon organizational requirements and historical accident - injury trends.

Jan 1, 1983

By B. Tulu, D. Gearhart

A comprehensive monitoring program was conducted to measure the rock mass displacements, support response, and stress changes at a longwall tailgate entry in West Virginia. Monitoring was initiated a few days after development of the gateroad entries and continued during passage of the longwall panels on both sides of the entry. Monitoring included overcore stress measurements of the initial stress within the rock mass, changes in cable bolt loading, standing support pressure, roof deformation, rib deformation, stress changes in the coal pillar, and changes in the full three-dimensional stress tensor within the rock mass at six locations around the monitoring site. During the passage of the first longwall, stress measurements in the rock and coal detected minor changes in loading, while minor changes were detected in roof deformation. As a result of the relatively favorable stress and geological conditions, the support systems did not experience severe loading or rock deformation until the second panel approached within 30–50 ft of the instrumented locations. After reaching the peak loading at about two to three inches of roof sag, the cable bolts started to unload, and the load was transferred to the standing supports. The standing support system was able to maintain an adequate opening inby the shields to provide ventilation to the first crosscut inby the face, as designed. The results were used to calibrate modeled cable bolt response to field data and to validate numerical modeling procedures that have been developed to evaluate entry support systems. It is concluded that the support system was more than adequate to control the roof of the tailgate up to the longwall face location. The monitoring results have provided valuable data for the development and validation of support design strategies for longwall tailgate entries.

Jan 1, 2017