Search Documents

By Marco Antônio Siqueira Rodrigues

The possibilities for treating rinse waters fiom chromating bath by electrodialysis are discussed together with the possibilities of optimizing the treatment process for waste reduction and reuse of water and chemical products. An industrial effluent with 4600 ppm of Cr(VI), besides other metallic contamination, was used as work solution. This solution has been recirculated on an electrodialysis cell of three compartments, using exchange membranes Selemiom AMT and CMT. A migration of dichromate ions into the anodic compartment was obtained, so that an extraction of circa 99.9 % of Cr(VI) present on the solution was observed, resulting in water with a Cr(V[) concentration of 4 rnd. These results show that electrodialysis can be used to treat these effluents, and this water could be reused as rinse water. The solution of the anodic compartment, consisting at the beginning of the experiment of H2S04, 0.1 N, reached 7200 mg/l of Cr(VI). This concentrate could be reused on the chromating bath itself.

Jan 1, 1999

By Andrew B. Cecala

The U.S. Bureau of Mines has designed and evaluated total mill ventilation systems at two different mineral processing operations. Both systems have proven very effective at reducing respirable dust levels throughout the mill in a cost-effective manner. A 25,500-cfm system installed at a clay processing mill provided approximately 10 air changes per hour. This system reduced respirable dust concentrations by approximately 40 pct throughout the mill building. The second evaluation was performed at a silica sand operation. Tests were performed with 50,000 and 100,000 cfm of ventilation to the mill building, corresponding to 17 and 34 air changes per hour. Average mill-wide respirable dust reductions were 36 and 64 pct, respectively. Not only did these systems reduce respirable dust concentrations and increase visibility throughout the mills, they were also easy to install and required minimal maintenance. A total mill ventilation system provides a general purging of the mill air; the system should be viewed as a supplemental technique to assist other dust control systems in operation.

Jan 1, 2010

By Frederick W. Horton

With large deposits of low-grade molybdenum ore and a latent market for molybdenum, which with development might perhaps equal that for tungsten, the United States has for years made no pro- duction of molybdenum ore worthy of mention. In fact, during the decade previous to 1914, there was no output of molybdenum ore in this country except in 1905, 1906, and 1907, when a few small lots of molybdenite and wulfenite were marketed." To ascertain why this possible source of economic wealth should remain undeveloped, the United States Bureau of Mines undertook an investigation in 1914, with a view of assisting the establishment of a molybdenum industry in this country. A preliminary review of the situation showed the following conditions: Briefly there was a lack of any considerable demand for molyb- denum for the one known use that might consume any large tonnage of it, that is, for the manufacture to certain alloy steels to which molybdenum imparts properties roughly similar to those produced by tungsten. It was at once evident that the market for molybdenum in alloy steels must be developed, or that extensive new uses for the metal must be created, before the demand would be sufficient to war- rant any extensive mining of molybdenum ore. Investigation showed that one of the chief factors in retarding the development of any demand for molybdenum by the alloy-steel trade was that manufacturers who might use, or might investigate the possibilities of using, the metal were kept out of the market by the fear of not being able to obtain steady supplies. On the other hand, those who might be interested in the development of some of the extensive low-grade molybdenite or wulfenite deposits in this country were prevented from doing so by the small visible demand and the fear that any large production would glut the market. Owing to these conditions the mining of molybdenum has in the past been confined almost entirely to small-scale operations on high-grade streaks of molybdenite ore, and the methods of recovery have been limited largely to cobbing and hand picking.

Jan 1, 1916

By Joseph D. Davis

Selection of a suitable coal or coals for the manufacture of coke of desired quality with due consideration of the purpose for which the coke is intended requires careful thought, and often it will pay to go to consider able expense in testing such coals as may be available. In general it will always be possible to obtain a satisfactory coal or blend of coals for the particular purpose in view, but in some places the cost of transportation would be prohibitive. It may then be necessary to consider a coal or coals inferior in grade, rank, or both. At times, in fact, only one inferior coal may be available, when the problem becomes mainly one of selecting equipment and operating conditions best adapted to that coal, keeping in mind that the end product of the plant must compete with the imported product in the market the plant will serve. This applies particularly to new projects for which it is necessary to build a plant and start with a clean slate, so to speak. However, it will pay every coke-plant manager to employ a force to continually test the coals used and the coke produced to make sure that the quality is not changing appreciably. Furthermore, if the supply of coals used becomes exhausted it will be necessary to use other coals. Continual testing is particularly necessary at plants using borderline coals or blends, where slight changes in the composition or in operation of the ovens may render them dangerously expanding. In this connection it should be stated that control in the newer coke plants is considerably easier than for those built a decade or so ago, consequently in the new ovens a given operating program can be maintained more precisely. This point is important, because one of the main requirements of the coke user is uniformity in both physical and chemical characteristics. For example, any appreciable changes in the quality of coke delivered to the blast?-furnace operator will involve changes in operation if the best results are to be obtained. Such changes are expensive usually they take considerable time and involve production of inferior iron.

Jan 1, 1942

By G. D. Sandrock

The science and technology of roan temperature rechargeable metal hydrides began about 1969 with the discoveries that the intermetallic Compounds LaNi5 and TiFe could be, conveniently hydrided and dehydrided at roan temperature and modest H2 pressures. Subsequently, this lead to the development of a broad family of REE-containing AB5 hydrides and numerous applications that make use of the extraordinary H2-absorption and reaction-heat properties of these materials. Some of the applications include H2 storage, compression and separation, as well as heat pumping, heat to mechanical energy conversion and electric energy storage. This paper briefly reviews the fundamental phenomenology of metal hydrides, the history of the use of REE's in rechargeable metal hydrides, the practical engineering properties of these materials and the applications that have evolved around them. The rechargeable nickel metal hydride battery, a new vial alternative to NiCd cells, stands at the forefront of the applications.

Jan 1, 1992

By Shuan-cheng Gu

Roof bed separation often occurred due to the deformation incoordination of surrounding rock following the excavation of mine roadway. Bed separation has effect on the bolts, and the estimation of the influence will directly affect the safety of support systems. In this paper, the hyperbolic function model to analyze the load transfer mechanism on the bolts was simplified as the exponential function form for easy calculation. An elastic-plastic analysis model of the bolt loading occurred by the bed separation was established. And the development low that the bed separation affected to the bolt loading was discussed. According to the parameters analysis of different separation values and locations, the influence law of the bolt loading caused by roof bed separation was summarized. Finally, the effects of bed separation were considered for the bolting design, it was able to provide a reference to the anchorage design of stratified rock.

Aug 1, 2013

By Cem Şensöğüt, Özer Ören, Yaşar Kasap

The mining sector, which has an important place in terms of raw material and energy supply, is referred as a sector with one of the highest fatal accidents in comparison with other sectors. In this century, where occupational health and safety awareness has increased, it is important to review the past accident statistics and to determine the current deficiencies by using the information in the inventory. In this study, the Malmquist total factor productivity index (MPI) has been utilized to investigate the changes in the work accidents occurring in the Western Lignite Corporation (Turkey), where underground and surface production methods are applied, and to determine the measures to be taken. According to the results obtained, both the decrease in production amount and the increase in the number of accidents caused inefficiencies during the period in concern due to the expected 10-year economic life of the mechanized system operating in the underground production panel that came to an end in 2007 and the flooding took place in early 2017. Compared with the underground operations, it has been determined that production can be carried out at the appropriate scale despite the heavy working conditions encountered due to the changing climatic conditions and the progress of production in the surface operations.

By W. Dingley, G. R. Hoey

"AbstractWear of six types of grinding balls was compared with and without corrosion inhibition in grinding Ni-Cu sulphide and hematite ores in laboratory ball mills. Forged steel balls (Rc 60 to 65) and three types of white cast iron balls (Rc 50 to 65) were susceptible to corrosive wear and two types of stainless steel balls [AISI Type 440C (Rc 65) and AISI Type 302 is; 35)] were relatively immune. The relative wear rates of the five types of hard balls (Rc 50 to 65) were dependent on the corrosivity of the ore. Ranking of the hard balls with respect to wear resistance was consistent for the sulphide and hematite ores in the presence of corrosion inhibition, whereas their ranking was different for the two ores in the absence of inhibition.The electrochemical potential of the grinding balls was measured during grinding and was found to be a useful measurement for assessing the susceptibility of an alloy to corrosive wear. Reduction of ball wear for forged steel and white cast irons with corrosion inhibition was concomitant with a shift of ball potential to less active values. Ball potentials in the presence of inhibition were indicative of non-corroding metal surfaces.IntroductionA PREVIOUS STUDY by the authors (1) showed that corrosion inhibitors - sodium nitrite, sodium chromate and sodium metasilicate - reduced wear of forged steel grinding balls by up to 49% in grinding Ni-Cu sulphide ore. Although the mechanism of wear reduction was not elucidated, it was concluded that corrosion must play a significant role in the wear of grinding media. Remark and Wick (2) of Battelle Pacific Northwest Laboratories have also evaluated corrosion inhibitors for the reduction of metal wear using abrasive and n on- abrasive te sting procedures. Their research was sponsored by 16 companies throughout the world. Preliminary results indicated that anodic inhibitors prevent from one-fourth to one-half of the loss due to corrosion."

Jan 1, 1977

By Carlos Maurício F. Vieira, Lázaro A. Pizatto, Marcus Paulo Cardoso, Sergio Neves Monteiro, Joao Victor C. Nunes, Gustavo S. R. Matheus, Frederico M. Margem

The interest in composites with natural fibers is due, among other factors, to the growing worldwide concern with the preservation of environment and renewable raw materials. The natural fibers have many particular properties that make them an attractive alternative to traditional synthetic fibers. The advantages of using these fibers are: low cost, renewability, biodegradability, low toxicity, abundance and specific strength. The searching for new suitable, economically viable and technologically advanced materials justifies the accomplishment of this work that aims at comparing the mechanical behavior of polyester matrix composites with epoxy matrix composites reinforced with hemp fibers Izod impact tested. The specimens with dimensions: 10 63 12.7 mm, made in different volume fractions of fiber: 0–30 vol%. The samples were tested at PANTEC pendulum model XC-50 located at LAMAV/UENF. With this research was possible to analyse the mechanical properties of these two new materials.

Mar 1, 2018

By M. J. Pazuchanics

This U.S. Bureau of Mines report presents results from an ongoing investigation of the use of adaptive signal discriminating methods to distinguish between cutting coal and cutting mine rock. Bit-cutting forces and tool vibration were measured in the laboratory as a linear-cutting apparatus (LCA) made constant-depth cuts in coal, sandstone, and shale test specimens. A portion of the collected data has been analyzed and some preliminary results are given here. The influence of data bandwidth, data window size, number of signal features, and voting among classifiers on classification performance are noted. Results to date, based on ideal-cutting conditions and simple geologic materials, indicate that of the four classifiers tested there appears to be no single best classifier. Usually, classification accuracy showed slight improvement as the number of features considered for classification increased. The highest classification accuracies were achieved when voting was conducted among classifiers followed by voting among force components.

Jan 1, 1991

By Robert E. McIvor

"“Classification System Efficiency (CSE)” is a powerful, emerging tool that can be used to increase grinding circuit efficiency. It is defined as the percentage of the ball mill energy being used to grind target, oversize particles. The discovery, validation and current use of CSE, including how it was manipulated, are described through seven plant case studies. These resulted in efficiency improvements ranging from 3 to 30 percent, along with major reductions in over-grinding. The achievable CSE for any given circuit is described. This paper demonstrates both how, and how much, every plant can benefit from increasing grinding circuit CSE.DEFINITIONS: BALL MILL CIRCUIT “CLASSIFICATION SYSTEM EFFICIENCY (CSE)”, “EFFECTIVE MILL GRINDING POWER”: “WASTED/OVER-GRINDING MILL POWER”The closed ball mill circuit is shown in Figure 1. The extreme importance of the circulating load ratio in determining circuit productivity was demonstrated by Davis (1925) and re-published by Guadin (1939), as shown in Figure 2. The circuit production rate increases with increased circulating load ratio, rapidly so at first and continuing to increase more gradually with higher and higher values of circulating load ratio.The underlying cause of this relationship was seen when comparing the ball mill feed and product size distributions from two different ball mill circuits, one with a low circulating load ratio, and one with a high circulating load ratio (Figure 3). While the F80’s and P80’s of these two circuits were close to the same, the mill feed and discharge size distributions were quite different. The ball mill in the circuit with the higher circulating load ratio contained a substantially greater fraction of material coarser than the target P80, as indicated by the respective mill feed and discharge size distributions. This fraction represents the fraction of the mill power being expended on “coarse” (in this case, plus P80 size) material, or the circuit “classification system efficiency.” The “effective mill grinding power” is the total mill power multiplied by the CSE. The compliment of CSE, the remaining fraction of “fines” in the mill, is the fraction of the mill power being wasted, and spent on over-grinding of material already finer than the circuit target product size. This is the “wasted/over-grinding mill power”"

Jan 1, 2013

By G. E. Rennick

A siphon-type laboratory airlift well was designed and operated by the Bureau of Mines to study the concurrent flow of air and oil in small-diameter pipes. Glass flowstrings ranging from to 1 inch in diameter and from L4 to 64 feet in length were equipped with various-sized air-entry jets. Liquid holdup volumes were used to correlate vertical-flow data, and empirical equations for computing gas requirements were derived. The effect of flowstring length on flow efficiency, oil- and gas-production rates, and gas-oil ratios was relatively minor at all flowing pressures. Air-jet sizes and flowstring diameters, however, had a marked effect on flow efficiency and oil- and gas-production rates. The small air-jet sizes increased maximum flow efficiency and its associated flowing pressures but decreased oil- and gas-production rates. An increase in flowstring diameter increased maximum flow efficiency with its associated flowing pressure and also increased the production rates of oil and gas.

Jan 1, 1965

By Chang Wei, Zhigan Deng, Yizhao WANG, Cunxiong Li, Gang Fan, Xingbin Li

During the process of hematite precipitation, the transformation of Na jarosite convert into hematite has been studied in a batch reactor at different temperatures, ranging from 170°C to 200°C with 3h of the retention time in the presence of 30g/L Fe ( ) and 4g/L Na+. The composition of precipitation was seriously depended on the temperature, at 170°C hematite and sodium jarosite are the reaction products of iron precipitate, with an increasing in reaction temperature the sodium, sulfur content in precipitated decreased and sulfur mainly exist in forms of SO4 2-, and when temperature over 200°C hematite was the only phase in product. An increasing temperature was not only beneficial to iron precipitation, also conducive to jarosite conversion to form high quality hematite precipitate.

Jan 1, 2016

By Michel Dagbert

In the exploitation of porphyry-type deposits, the quality of the ore is mostly defined according to its grade. Besides the simplest distinction, ore-waste, several grade categories may exist and they correspond to the different ways in which the ore is further processed. At the time of mining the selection of the different categories is done from extensive information available from blast holes. But planning has to be done before this information is available and it is necessary for the geologist to forecast, from exploration and development data alone, the possible outcome of the selection done later on a block, a level, or the whole deposit and ultimately predict the ore reserves and value of the deposit. A good statement of this problem has been presented at the 1976 AIME annual meeting by Williamson and Hueller (1976). They have shown that, if the cut-off values are directly applied to the estimated grade of blocks, a gross overestimation of the recovered tonnage of ore (14%) will occur. This problem, now termed "the vanishing tons problem" (DaVid, 1977) seems to be common in many open-pit operations and it has been explained several times (DaVid, 1972; Huijbregts, 1975). In order to solve it l.Jilliamson and Mueller proposed a solution based on compiling masses and masses of blast hole data available from mined-out portions of the deposit. They derived empirical correction factors which provide for every block, given its estimated grade, the expected tonnage and average -grade of each category of material within that block. The purpose of our work is to repeat the same exercise but ignoring the blast holes data i.e. we want to derive the correction factors from the only DOH data. Doing this, we are more in the real conditions where the valuation of the mine and are reserve analysis has to be made before production actually starts. Two possible ways to achieve this goal will be investigated and the emphasis will be on recently

Jan 1, 1977

By Brian Hart, Stamen S. Dimov

"The naturally occurring carbonaceous material (CM) in gold bearing ores often exhibits strong-preg-robbing properties. It can adversely affect the process of gold recovery during the cyanidation due to its ability to adsorb, or preg-rob gold from the cyanide leach solution.Treatments of carbonaceous ores with chemical surfactants as blinding agents to limit preg-robbing have shown promising results but at the same time have demonstrated that, if not properly used, could have a strong detrimental effect on the gold recovery process. High dosages of surfactants used as passivating agents for carbonaceous matter could lead to unwanted partial passivation of the activated carbon added during the CIL process and severely impact the gold recovery. Optimal dosage for various surfactants would strongly depend on the ore mineralogy and the parameters of the pulp (temperature, pH, surface area and maturity of the carbonaceous material, etc).This paper describes an experimental study on the effectiveness of various commercially available blinding agents used to minimize the preg-robbing capacity of naturally occurring carbonaceous matter. The scope of the study was to: i) establish the optimum addition of blanking agent (surfactant) to minimize the preg-robbing capacity of the CM in the ore, and ii) establish maximum threshold amounts of blanking agents to be used before it negatively impacts the preg-robbing capacity of the activated carbon used in the CIL process. The study procedure involves standardized doping tests to evaluate the maximum preg-robbing capacity of treated CM, coupled with surface analysis with ToF-SIMS to monitor the presence and the degree of loading of these chemical surfactants on both the naturally occurring CM and the added activated carbon.INTRODUCTIONNaturally occurring carbonaceous material (CM) in gold bearing ores often exhibits strong-preg-robbing properties. Thus, it can adversely affect the process of gold recovery during cyanidation due to its ability to adsorb, or preg-rob gold from the cyanide leach solution. The preg-robbing properties of this naturally occurring carbonaceous matter can vary widely between ores, and within a single ore body (Dunne et al.,2013;Helm et al.,2009;Miller et al.,2005). The degree of preg-robbing related to the CM within an ore is defined by several parameters: total organic carbon (TOC) content, surface area, maturity (i.e., crystallinity) of the CM and the presence of various functional groups on the surface of the CM. Preg-robbing gold ores continue to be a significant challenge because of the lack of a single or universal solutions."

Jan 1, 2016

By Aaron Archer, James Parkes

This paper presents design considerations for the major underground elements of the pending BCRUA Phase 2 Raw Water Delivery System Project. These elements include two Lake Taps; an 8,800 LF, minimum 10-ft OD intake tunnel; a suction chamber with 6 Pump Shafts; a 30-ft diameter, 300-ft deep Main Shaft; a 2,600 LF Transmission Tunnel with 78-inch steel liner; and a 130-ft deep shaft on the Transmission Tunnel. The tunnels and shafts will be excavated through the Glen Rose limestone. The design development included consideration for technical requirements, easements, third party commitments, previous local project experience, and constructability based on contractor outreach.

Jun 13, 2021

By David White

Jan 1, 1925

By Manuel Gomez

This report presents prediction equations for eleven factors indicative of metallurgical coal quality which have been developed from data obtainable during exploration. Five coke strength parameters and six carbonization product yields have been predicted for coking coals having volatile matter contents in the range 16.3 to 42.1 percent, dry basis. The prediction models developed contain information from the proximate and ultimate analyses, the size consist, and the petrographic composition of coking coals carbonized in BM-AGA retorts at 800°, 900°, and 1,000°C. The equations reported have been evaluated with independent data derived from the 900°C carbonization of 33 binary blends. Present results show that metallurgical coal quality can be predicted ahead of mining. Capability to forecast coal quality is useful in mine planning and should provide basic information for optimization of blending and crushing techniques, leading to the production of uniform coke.

Jan 1, 1968

By Xuyang Liu, Xuewei Lv, Yu Zhang, Xiaolong Wu, Chunxin Li

Titanium nitride is a broad-spectrum specific functional material because of its many superior properties. Therefore, it is necessary to investigate synthesis methods of TiN and alloys containing TiN reinforcement. In the current study, with the increase of nitrogen gas pressure and the optimization of routine ball milling parameters, the conventional mechanical ball-milling method can be improved, the nanometers TiH2-TiN composite powder can be synthesized successfully in a shorter time. Nitrogen gas filled in ball mill jar in which the pressure was 0.6 MPa. TiH2 powder was milled under nitrogen atmosphere at a spinning rate of 250 rpm. The results show that the stable TiN is formed after grinding for 2.5 h according to the X-ray diffraction pattern. DSC (differential scanning calorimetry) curves also indicate that milled compound powder adsorbs certain nitrogen gas. The gas adsorbed in TiH2-TiN composite can exist stably below 200 °C.

Mar 1, 2017

By Z. Ruetz

Portable X-ray fluorescence (pXRF) analysis has been widely adopted in the geochemical and environmental field as a cost-saving alternative to standard analyses. This paper outlines the efficacy of a method for indirectly quantifying organic copper content in solvent extraction circuits via stripping of the chelated metal with concentrated sulfuric acid in a single contact and subsequent pXRF aqueous analysis. pXRF analysis is common within the mining industry but presents unique challenges with liquid analysis, the most prevalent of which are briefly discussed. This method was developed specifically for mining operations with regional constraints and limited resources. Providing an in-field alternative to flame atomic absorption spectrophotometry and inductively coupled plasma optical emission spectroscopy, this entirely mobile XRF analysis method produces consistent and accurate results within minutes and at a fraction of the cost.

Jan 1, 2023