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By Lito C. Mejia

Diesel-powered equipment operating in a gassy underground mine could conceivably ingest a methane-air mixture from the mine atmosphere that could cause the diesel engine to overspeed, or exceed its rated speed. Engine overspeed, particularly if extreme (engine runaway), could result in personal injury, a possible mine explosion, and/or catastrophic engine failure. In this report, the Bureau of Mines reviews the literature on the potential hazards of methane-induced diesel engine overspeed. Also included are the Bureau's findings from consultations with representatives of the diesel engine industry to determine the specific engine behavior that could he expected under the overspeed condition. The report summarizes data on mine accidents involving methane, discusses results of tests on the compression ignition of methane in diesel engines, and examines fuel governors and intake-air-cutoff devices, two kinds of devices used to prevent overspeed. Analysis of the information gathered suggests that the conditions necessary to cause a diesel engine to overspeed uncontrollably are not likely to occur, particularly if the engine is equipped with flame-proofing devices. The available literature and lack of actual overspeed case histories suggest that the safety devices currently in use are sufficient to prevent diesel engine overspeed.

Jan 1, 1984

By Alexander Zamora Chávez

Dado que la planta concentradora de la Compañía Minera Milpo tiene una capacidad mínima de producción en los concentrados de plomo y zinc, es necesario mejorar la recuperación de plata y plomo a través del grado de moliendabilidad, la modificación en el circuito de flotación y la evaluación de los reactivos colectores. Asimismo se utilizó el método de diseño hexagonal para evaluar la dosificación de los colectores Aeroflat 225 y 242, optimizando la recuperación de plata y plomo. En ese sentido, el objeto del texto es describir las condiciones adecuadas para la recuperación de la plata y el plomo a través de las pruebas de laboratorio que determinan la moliendabilidad, así como la aplicación del diseño hexagonal en la optimización de la extracción de la plata y plomo en la planta concentradora de la mina Milpo.

Nov 24, 1986

By J de Witte

When used in suitable ground conditions, rock bolts can have advantages over other permanent tunnel lining solutions. Permanent rock bolts offer flexibility in tunnelling profile and rapid rock bolt installation can enable time and cost savings. There are also disadvantages when considering the suitability of rock bolts for permanent support installations. These generally concern achieving the specified durability requirement over the specified design life. By investigating alternate approaches to rock bolt installation, quality assurance (QA), monitoring and design life it may be possible to alleviate some of these concerns.The design and construction benefits that can be realised through the use of rock bolts are primarily related to reducing project program time. This time reduction could be realised if rock bolts are considered as a permanent solution, with the installation being completed as a part of the primary excavation cycle. Any reduction of the program could allow direct and indirect cost savings and in the case of a major project, allow the revenue stream to be realised earlier.Currently ambiguity exists where the treatment of rock bolts as permanent support components is inconsistent with that of (often identical) ground anchors, as utilised in stabilising cut and cover structures. The ground support design process, implementation and testing are generally similar, though the acceptance of rock bolts as long-term support elements is treated differently to ground anchors in technical specifications.This paper discusses some of the benefits available through the use of rock bolts. It offers different solutions to the concerns surrounding durability, including alternate approaches to installation, Quality Assurance practices and monitoring solutions. The selection of an alternate design life is also investigated as another means of alleviating concerns around long-term durability. The paper will also provide an indication of savings that could be expected through the use of rock bolts as part of a long-term support system.

Mar 8, 2011

By Martin J. Gavin

"Before discussing oil shales it may be well to consider briefly the conditions surrounding the petroleum industry in the United States, because these largely explain why so much interest is being manifested in oil shales. The United States is not only the greatest producer of petroleum in the world, its output amounting to about 65 per cent of the world's total production; but is also the world's greatest consumer, using more petroleum than it produces within its own borders. For the past four or five years it has been necessary to import oil at a continually increasing rate to make up the deficit between domestic production and domestic consumption. Experts who have made a close study of the future supply and demand for, crude petroleum are satisfied that under present production practice and with the development of possible undeveloped productive areas, the gap between domestic consumption and production will steadily .increase.As possible solutions for the impending domestic shortage of oil, various expedients are receiving attention. These may be grouped under three heads, as follows:(1) Temporary measures, such as curtailment of consumption, development of more efficient methods of production, and more efficient utilization of supplies of petroleum still available. It is unlikely that there will be any great curtailment in consumption of petroleum in the United States; rather, consumption will continue to increase unless a real shortage of oil actually forces curtailment of consumption. The other two possibilities mentioned deserve, and are resolving, serious thought. Much experimental work along these lines, some of which has already yielded excellent results, is being done. Obviously, however, any of these remedies are temporary ones only, so far as regards domestic production of petroleum."

Oct 1, 1920

By R C, K L. Rees, J S. J van Deventer

In contrast with previously published models for the carbon-in-pulp (CIP) process, the model proposed in this paper incorporates film transfer, intraparticle diffusion, simultaneous leaching, preg-robbing, the loading of multicomponent species, and the effects of fouling and changing cyanide levels. The rationale behind this comprehensive model is that changes in fouling and competitive adsorption along a CIP cascade affect the profiles of gold loading. As it is impossible to quantify all these non-ideal factors, a method is proposed whereby an imaginary species is postulated so as to combine all the competitive effects. A plant survey at the Telfer mine has shown that the mass loss due to a gravimetric analysis of the fouled carbon could be used directly to quantify this competitive effect. The degradation and consumption of cyanide along the Telfer CIP cascade enhance the loading of copper on to the carbon, which should be taken into account when modelling the gold profiles. It appeared that the effect of cyanide itself on the loading of gold was negligible compared with its effect on the copper. Evidently much more research is required on this topic in order to optimise CIP operations exposed to constantly changing conditions.

Jan 1, 1998

By Ann G. Kim

The U.S. Bureau of Mines mine fIre diagnostic methodology to locate and monitor fIres in abandoned mines and waste banks is based on the controlled sampling of the mine atmosphere to determine changes in the concentration of hydrocarbons desorbed from heated coal. To provide background data for this methodology, a laboratory study was conducted in which samples of coal and coal waste were heated under controlled conditions. Gas samples from the combustion furnace were analyzed for standard gases CO2 and CO and for the C1 to Cs hydrocarbons. In all tests, the concentration of desorbed hydrocarbons increased during heating and decreased during cooling. A dimensionless hydrocarbon ratio, Rl, was developed as the signature for heated coal. For bituminous coals, the value of Rl increases during heating of coal samples and decreases during cooling of the same samples. Generally, Rl values of 100 or more indicate coal sample temperatures of at least 100° C. The emission of higher molecular weight hydrocarbons from anthracite samples was very low, resulting in relatively low Rl values at all temperatures. Data from fIeld projects confIrmed these results.

Jan 1, 1991

By L. Yuan, J. H. Rowland, D. Bahrami, R. Thomas

Blasting is the main method of production in many non-coal underground mining operations and produces multiple toxic gases as a result. The Mine Safety and Health Administration (MSHA) requires mine operators to measure the level of toxic gases in mines as frequently as necessary to ensure they are below regulatory safety limits. The current practice uses portable gas monitors to check the concentrations of toxic gases after a fixed post-blast time. This paper studies the application of a gas monitoring system in the return entry of a limestone mine to determine a safe re-entry time. The National Institute for Occupational Safety and Health (NIOSH) conducted such a monitoring program in a limestone mine from September 2016 through May 2018. NIOSH/PMRD (Pittsburgh Mining Research Division) is endeavoring to develop workplace solutions to improve detection of and reduce the risk of hazardous conditions. This study showed that the use of gas monitoring in the return air can be a useful tool at the mine operator’s disposal to detect and reduce the risk of hazardous conditions and also to reliably estimate the re-entry time.

By Emre Karakaya, Niyazi Bilim

Boreholes are used for many purposes in mining operations, petroleum engineering, and construction works. Numerous factors affect the performance of drilling equipment. Researchers continue to work on the variable drilling parameters that can be adjusted in order to reach more efficient drilling operations. Penetration rate is an essential indicator in drillability analysis and estimating. This parameter is of great importance in mining projects. There are almost no models that can estimate the penetration rate for core drilling operations. Under the abovementioned circumstances, this paper focuses on developing models that allow estimating the penetration rate based on rock material properties. During the conduct of this study, drilling experiments under 11 different pressure forces were performed on 8 different rock units, and the equations which estimated the penetration rate depending on the physico-mechanical properties of the rock samples were derived. Experiments were carried out under different pressure forces to investigate the effect of the pressure force on the derived estimation models. The obtained results allowed deriving equations that ensured estimating the penetration rate based on the physico-mechanical properties of the rocks and the applied pressure force. Using these equations, the penetration rate in core drilling operations can be estimated.

Sep 30, 2020

By Ross T. McGillivray, David S. Graham, Dan A. Brown, Steven D. Dapp

"The Selmon Expressway includes an elevated structure extending across several miles of weathered karstic limestone geology, and represents a challenge for design because of the high variability of the material and the difficulty in characterizing the strength. The nature of the epikarst in this region of Tampa is such that variability can be extreme within distances of only a few feet. The weathered rock includes extremely soft soil infill within solution features on and within the formation. The limestone is so weathered that coring typically does not yield useful samples for strength testing, and in-situ Standard Penetration Testing (SPT) tests often encounter refusal blow counts. Thus the challenge for foundation design includes two components of reliability risks: the uncertainty associated with the ground conditions at a given foundation location plus the uncertainty associated with the foundation performance at a given location even when the stratigraphy is determined.This paper describes the design approach that has been implemented successfully for two projects at the Lee Roy Selmon Crosstown Expressway (LRS) in Tampa, Florida: the assessment and remediation of the reversible elevated lane (REL) foundations constructed in 2004, and the elevated expressways widening project constructed in 2012. Included in this design approach is a method developed for computing axial resistance in this local geology. Design for axial loading relies primarily on the development of side resistance, which was considered less subject to performance risks than base resistance. The calculation method incorporates a statistical analysis of SPT data, tempered by engineering judgment, to characterize stratigraphy at a given location into either soil, intermediate geomaterial (IGM) or rock.IntroductionThe subsurface stratigraphy of sites underlain by weathered limestone formations can be highly variable with respect to material layer thicknesses and strengths, even over short horizontal distances. This is the case for much of Florida, and particularly the Tampa area. These conditions present a challenging environment for the design of drilled foundations because of the need for a reliable determination of subsurface conditions at each foundation location, as they relate to the expected axial performance. Contributing factors include:"

Jan 1, 2015

By T. J. Langan, M. Ramajayam, T. Dorin

"6xxx-series Al alloys are the most commonly used alloys in the automotive industry as they have an appropriate balance of strength, corrosion resistance and formability. The main strengthening phase in these alloys is the ß’-Mg2Si precipitates. One opportunity to achieve stronger 6xxx-series Al alloys, without affecting corrosion and formability, is the use of Sc. The main challenge of using Sc in 6xxx-series lies in the heat treatment, which must be designed to allow for a fine precipitation of both Al3Sc and ß’-Mg2Si. In this work, two model alloys are used, an Al-Sc-Zr and an Al-Mg-Si-Cu-Sc-Zr, to explore the impact of the 6xxx-series key elements (Mg, Si and Cu) on the Al3Sc precipitates. Transmission electron microscopy and atom probe tomography are used to investigate the precipitates present in the microstructure after casting. We find that higher Si content results in the formation of dispersoids upon casting. The average composition of these dispersoids is (Al0.8,Si0.2)3 (Sc0.888,Zr0.024,Mg0.08,Cu0.008). A closer look at the solid solution reveals that most of the Sc and Zr is supersaturated after casting even in the presence of Mg, Si and Cu. We discuss the impact of these results on the design of a suitable heat treatment for 6xxx-series alloys with Sc.INTRODUCTION The most common strategy to strengthen aluminum (Al) alloys is by micro-alloying to form a fine distribution of precipitates (Gladman, 1999). Whilst precipitates enhance the strength, this is often done to the detriment of ductility and corrosion performance (Davis, 1999). The 6xxx-series Al alloys are heavily used in the automotive industry as they offer an appropriate balance of strength, ductility and corrosion resistance (W. S. Miller et al., 2000). The strength increment in these alloys comes from the formation of the ß’–Mg2Si and the quaternary Q’ phase (Chakrabarti & Laughlin, 2004; Polmear, St. John, Nie, & Qian, 2017). One opportunity to achieve stronger 6xxx-series alloys, whilst keeping good balance of corrosion resistance and formability, is the use of small additions of scandium (Sc). Sc is one of the most potent strengtheners in Al alloys (Dorin, Ramajayam, Vahid, & Langan, 2018; Røyset & Ryum, 2005). Most of the strengthening benefits from Sc come from the formation of fine Al3Sc dispersoids. The following strengthening mechanisms apply to Sc: 1) Solid solution strengthening, 2) precipitation hardening, 3) inhibiting recrystallization, 4) assisting nucleation of other strengthening phases (Dorin, Ramajayam, Lamb, & Langan, 2017). As compared to other dispersoid phases, Al3Sc dispersoids have good electrochemical compatibility with Al alloys and hence do not affect their corrosion resistance (Cavanaugh, Birbilis, Buchheit, & Bovard, 2007). The coarsening resistance of Al3Sc is often improved by adding zirconium (Zr), as it forms a Zr rich shell around Al3Sc which prevents Sc from moving across the interface."

Jan 1, 2018

By I. I. Maximov

The paper describes the results of studies performed with a view to develop an improved technology for processing high-grade massive and cupriferous ores of the Talnakh deposit, the main valuable components being nickel, copper and PGM. The studies? main task was production of nickel concentrate with nickel content of approx. 15%, nickel recovery being as high as possible. The studies were performed on two ore samples. One sample was a mix containing high-grade massive (78%) and cupriferous (22%) ores with nickel content of 1.93% and copper content of 3.6%; the other sample was a mix of high-grade ores with nickel content of 2.25% and copper content of 3.72%. Main ore minerals were copper sulfides ? chalcopyrite and cubanite, their total content being 10.5% ~ 11%, pentlandite (5.2% ~ 6.1%) and pyrrhotite (36.7% ~ 42.9%). Influence of grinding media on pentlandite and pyrrhotite separation results, achieved through combined use of triethylenetetramine (TETA) and sodium sulfite (SS), was also investigated. It is shown, that combined application of TETA/SS in the ratio of 1:2, permits to grind products in metal mill (mild steel) with metal balls (mild steel), achieving results that are similar to those achieved by means of grinding in inert grinding media with TETA/SS ratio of 1:1. Application of the developed technology provided for production of high-grade nickel concentrate with nickel content of 14.7% ~ 15.6%, nickel recovery being 76 % ~ 77%. Earlier experiments performed on the above mentioned ore mix permitted to produce nickel concentrate with nickel content of 10%, nickel recovery being 75.9%. Consequently, nickel content was increased by 4.7% ~ 5.6%, and a higher nickel recovery was achieved. The paper also describes metallurgical results related to nickel, copper and PGM with regard to all processing products.

Jan 1, 2014

By J. A. du Plessis, C. Dorfling

Selenium, tellurium and other precious metals (OPMs, namely Rh, Ru and Ir) dissolve in the final leaching stage of base metal refineries. Se and Te are typically removed from the copper sulphate leach solution by precipitation with sulphurous acid. Recovery of dissolved OPMs is desirable because it will reduce OPM inventory and losses. Thiourea is an effective OPM precipitation reagent, but yields insufficient Te removal. Copper is known to enhance Te precipitation when using sulphurous acid as precipitation reagent. The primary objective of this project was to evaluate whether simultaneous precipitation of Se, Te and OPMs using thiourea with metallic copper as precipitation reagents is possible. Batch precipitation tests were performed to evaluate the effect of temperature (50 – 70°C), thiourea addition (160 – 430% excess) and copper addition (2 – 8 g/L) on Se, Te and OPM precipitation. Increasing the temperature from 50°C to 70°C resulted in an average increase of 55.6 percentage points for Se precipitation and 13.5 – 23.5 percentage points for OPM precipitation. The copper addition did not have a significant impact on the precipitation behaviour. Increasing the thiourea addition increased the precipitation of Se and Te, especially when the copper addition was low; Rh and Ru precipitation also increased with up to 10 and 12 percentage points, respectively. Despite these observations, the precipitation of Se was significantly faster when no thiourea was added. It is not currently clear why thiourea appears to inhibit the Se precipitation by reaction with metallic copper. In general, Te precipitation was low (less than 30%) at the conditions investigated. Simultaneous precipitation of Se, Te and OPMs at temperatures below 80°C does not appear to be a viable option; a multiple stage operation for sequential removal of Se and Te with copper followed by OPM precipitation with thiourea would be required.

Jan 1, 2016

By Neall. George M.

No method of roof control yet devised has proven to be universally acceptable for the wide range of strata conditions experienced in U.S. coal mines. However, a relatively new innovation, the roof truss, has proven itself capable of preventing roof failures which both conventional and resin bolting could not. Presently, the economics of roof trusses are not favorable when compared to bolting due primarily to drilling and installation procedures, but this is expected to change with improved truss and equipment designs. To realize the full potential of this new method of roof control, design criteria are needed which can optimize the effect of the truss for varying strata conditions. A review of the literature reveals that some work has been conducted on the roof truss. 1 Gambrell and Haynes (1970) showed that the roof truss is superior to angled roofbolts installed through a header. Sheorey, Verma, and singh2 (1973) used statics to prove that the optimum angle of inclination should be greater than 450? However, to date, no systematic attempt has been made to establish design criteria. In this report, the problem was approached in three ways. First, model studies were performed to determine general trends of truss support as a function of a number of variables. This provided a better understanding of the support mechanism involved. Secondly, beam theory was employed to calculate the actual support capacity of a truss, realizing the many simplifications, assumptions, and shortcomings of this approach to such a complicated problem. Last, field testing will be utilized to test the hypotheses previously developed and provide hard data to further synthesize roof truss design criteria. Field testing has recently commenced and should be complete before mid 1977.

Jan 1, 1977

By J. H. Westbrook, R. W. Guard

The influence of a number of alloying additions on the structure and hardness of Ni3Al (?') has been studied. Three general effects have been observed.. solid-solution hardening, strain aging, and defect hardening arising from deviations from stoichiometry. The solid-solution hardening phenomena are complicated relative to binary terminal solid solutions due to the possibility of virtually independent substitution for the component elements and to the concomitant effects of strain aging. In many superior nickel-base high-temperature alloys the elevated temperature strength is attributable to the presence of a dispersion of Ni3A1 (?') in a solid-solution matrix. Examples of such alloys are Inconel X-550, Inco 713, Waspalloy, and Nimonic 80. It is, therefore, appropriate to seek a further understanding of the properties and alloying behavior of this compound. Ni3Al, the compound most rich in nickel in the nickel-aluminum binary system, was first detected by litakal but not established with certainty until the much later studies of Bradley and Taylor' and Alexander and Vaughan.3 More recently the mechanism of formation was clarified by Floyd4 who showed that Ni3Al is the product of a peritectic reaction at 1395°C between the melt and the compound NiAl in agreement with the original suggestion of Alexander and Vaughan.3 Ni3Al has the ordered face-centered-cubic or Cu3Au structure in which the nickel atoms occupy the face centers and the aluminum atoms the cube corners, a0 = 3.570A. Despite earlier reports to the contrary. the compound apparently remains ordered at least to 1000oC.5 It exists over a narrow range of compositions (-3 pct wide) whose limits and temperature dependencies thereof have been reviewed recently by Taylor and Floyd.' Most previous workers have found Ni3Al to be both hard and brittle7,8 although Maxwell and Grala8 obtained 2.5 to 6 pct tensile elongation at room temperature and Alexander and vaughan3 described the material as "hard and tough" on the basis of observations made while preparing metallographic specimens. In a recent study one of the present authors found that although considerable intergranu-lar brittleness was evident: individual grains of a coarse-grained inert atmosphere arc-melted specimen were readily deformable.l0 The same study also showed Ni3Al to have an anomalous temperature dependence of hardness in that such a curve exhibits a number of peaks between room temperature and 800°C which could not be associated with any microscopically observable precipitation reactions or polymorphic transformations. It was, therefore, proposed in the present study to elucidate the anomalous high-temperature strength behavior and to examine the solid-solution alloying of this compound and the effects of such alloying on hardness. Sample Preparation and Experimental Procedure-Samples, both of pure Ni,Al and of various alloyed solid solutions based on Ni3Al, were prepared by arc melting 100-g buttons in an inert atmosphere arc furnace. All buttons were heat treated for 4 hr at 1275oC and examined metallographically for homogeneity. Microstructures were typically homogeneous and single phase with ASTM grain size about 1 and unusually clean grain boundaries. Chemical analyses showed good correspondence (within a few tenths of a percent) with intended compositions. Microindentation hardness data were obtained from room temperature to 800°C in vacuo using a balanced-beam type loading system in an instrument to be described in detail elsewhere." In general a 100-g load, a loading rate of 1 mm per min and an indentation time of 15 sec were used. Various indenter materials were used according to the materials bein tested because of specimen-indenter interaction. Fl Measurements of the Vickers-type indentations were made at room temperature. Hardness-temperature curves were run at least twice on each sample to ensure that surface work-hardening effects had been eliminated." Precision lattice-parameter measurements were made on powder samples using a back-reflection

Jan 1, 1960

By Kenneth G. Skinner

The rapid growth of the metallurgical, chemical, and allied industries on the Pacific coast just prior to and during the war caused a sudden increase in the demand for refractories, which was the immediate cause of a revival in interest in refractory clays available on the Pacific coast, particularly in the Pacific Northwest. Population increases and shortage of shipping facilities caused an increase in the amount of various ceramic materials and products used and produced on the Pacific coast, with accompanying demand for information regarding sources of clay. In an effort to supply part of this information, the Bureau of Mines, in cooperation with the College of Mines, University of Washington, started a program in 1944 to test the refractory and other properties of clays from seven Pacific Northwest deposits that had been drilled and sampled as part of the Bureau of Mines alumina from clay investigation. Figure 1 shows the location of these deposits.

Jan 1, 1949

By Irving Hartmann

1. Under the conditions of the tests described herein, the proper use of an incombustible stemming plug of the type discussed prevented ignitions of gas in all tests during the firing of 21 single shots of permissible explosive in cool. In two tests with multiple blasting (four and five shots each) no ignitions resulted. 2. The results of a few tests in this investigation and of numerous tests made previously indicate that fire-clay stemming of the same weight as an incombustible plug provides about the same degree of protection as the plug against gas ignitions during blasting of coal by permissible explosives. 3. The hazard of gas ignition on firing charges of non-permissible 40-percent gelatin dynamite in coal was reduced but not eliminated when the shot holes were stemmed with one or two incombustible plugs or with an equivalent weight of fire clay. 4. On the basis of this investigation, the Bureau of Mines considers the proper use of incombustible stemming plugs of the design tested, under the conditions of the tests described in this paper, to be of equivalent safety as the same weight of fire-clay stemming. This report does not constitute approval or disapproval of the incombustible stemming plugs by the Bureau of Mines. 5. The test data indicate that misfired charges in shot holes stemmed with the incombustible stemming plug cannot be disposed of with certainty by the procedure recommended by the manufacturer. In this investigation the misfired charges failed to detonate in 30 percent of the trials.

Jan 1, 1950

By C. E. Julihn

In the past few years the advance of the Sunshine mine to national prominence as the chief silver-producing mine of the United States has revived interest in the area in which it is situated. Although this area lies between the great lead-Zinc-silver mines at Kellogg and those in the vicinity of Burke and Mullan it was generally presumed to be almost barren, as little ore had been found there until substantial ore bodies were developed on deep levels of the Sunshine mine. In early days it was called the "dry belt" because its ores were siliceous and contained little lead; but the classification of ores in smelting as wet or dry, although once customary, has long been obsolete The area will therefore be referred to in this paper as the silver belt of the Coeur d'Alene district because the value of its ore is due chiefly to silver, the current production of which is large, providing over 60 percent of the silver output of Idaho. Silver Belt - Its Limits and Character With a daily production of half a ten of silver or more from the Sunshine mine, the silver belt has become the scene of extensive exploration at many properties, and the outlook for its future seems promising enough to warrant the lively interest now being displayed in the area by the public.

Jan 1, 1936

By Kristopher John Shelswell

The work in this paper describes the theory, development and analysis of a computer model simulating a mine operation moving material using concurrent decline ramp truck haulage and skipping practices. This simulation was designed specifically to assess the performance of the truck haulage component and to expand on the scope and capabilities of traditional TKM fleet calculations. Haulage fleet simulation results were similar to TKM calculations for the lower to moderate production rate cases. However, comparisons of ramp-up and high production rate scenarios indicated that the simulation model was significantly more sensitive to operating practices and factors not accounted for by calculations derived when using a single TKM figure. Given the proper calibration of inputs and logic, the simulation model was additionally capable of providing information associated with general mine operations efficiency. Further benefits of the simulation model over a TKM approach included logistical assessments such as production schedule feasibility, productivity trade-off quantifications for proposed operating practices, and the validation of mine resource utilization scheduling. The simulation model was able to expand on traditional methods to approach planning and logistics by considering factors such as truck queuing, real-time traffic interactions, random events, and competition for resources on mine productivity.

May 1, 2013

By A. R. Taylor

This report describes the design, construction, and operation of a low temperature adiabatic calorimeter for measuring heat capacities of solids or liquids from 60° to 300° K. A brief discussion of the basic theory involved in chemical thermodynamics and the problems involved in obtaining accurate experimental data is presented. The operation of the calorimeter was tested by measuring the heat capacity of a sample of benzoic acid obtained from the National Bureau of Standards over a temperature range of 60° to 300° K. The measured heat capacity values of the benzoic acid compared favorably with similar values obtained by the Bureau of Standards, the maximum deviation being 0.5 percent. THEORY A brief discussion of the basic theory involved in chemical thermodynamics will illustrate the applications of heat capacity data and the problems involved in obtaining accurate experimental data.

Jan 1, 1962

By Yuexin Han, Wenbo Li, Xinran Zhu, Pengchao Li

A multi-stage fluidization magnetization roasting is a promising method to treat limonite ore. The dehydroxylation of limonite ore is a key reaction in the pre-heating stage. In this study, the dehydroxylation mechanism of limonite was studied in a laboratory fluidization roasting reactor. The samples were characterized using in situ X-ray diffraction, Fourier transform infrared spectroscopy, and simultaneous thermogravimetry and differential scanning calorimetry analysis. The phase transformation and kinetics analysis were studied. Results indicated that the dehydroxylation occurred at the temperature of 250–350 °C with the vanish of hydroxyl functional groups (-OH). The dehydroxylation kinetics followed the 2-D diffusion (Jander) reaction model G(α) = [1 − (1 − α)1/2]2, and the calculated activation energy was 113.43 kJ·mol−1. This study is conducive to exploiting limonite ore resources using magnetization roasting technology.

Nov 2, 2023