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By R. L. Derick

The Orchard Valley Mine, a large underground coal mine located in western Colorado, experienced a major mine fire during an idled Sunday on June 1, 1986. This mine had extensive problems with spontaneous combustion near the coal outcrop. Spontaneous combustion has been determined to be the probable cause of that fire. Preparing for a mine emergency was an on-going task. Once the emergency occurred, much of the preparation work was implemented and aided in controlling the situation. Later, the successes and shortfalls that arose from that emergency were analyzed for future course of action. This paper summarizes the activity that led up to the major fire, the handling of that emergency, the lessons learned, and the changes implemented.

Jan 1, 1993

By Du Sichen, S. Seetharaman, Wei Liu

"The viscosities of two-phase mixtures are of great importance in the modelling of the fluid flow in metallurgical processes. For example, in steel making and refining, the intimate mixing of metal droplets in the slag phase requires a consideration of the effective viscosities for the mixture. The present work was aimed at an understanding the phenomena underlying the viscous flow in a two-phase mixture with widely differing viscosities.Emulsions of silicone oils of known viscosities (345mPa.S and 1010mPa.S at 293K) with small amounts of water evenly distributed in the same were prepared by subjecting the mixture to uniform stirring using a magnetic stirrer. The viscosities of these emulsions were measured at constant temperature by rotating cylinder method using Brookfield Digital Rheometer. The uniformity of the preparation of the emulsions was confirmed by the reproducibility of the results. Th7 measured viscosities were generally found to be independent of the torque under the experimental conditions so that the two-phase mixture could be considered as a Newtonian liquid. The variation of viscosities with temperature and the effect of addition of a surface-active substance were also studied in this work.The measured viscosities were found to be· higher than those of both pure water and silicone oil. The experimental viscosities were found to increase with increasing concentration of water. The influence of surface tension on the viscosities was examined by adding surfaceactive agent to the mixtures. The result is discussed and compared with theoretical models developed by Einstein, Taylor and Oldroyd."

Jan 1, 2000

By Richard Simon

This paper presents an ongoing study on the use of borehole breakouts to estimate in situ stresses at depth in a Canadian underground mine. Breakouts were identified using an acoustic televiewer (ATV) probe. Rock samples were tested in a laboratory to determine their failure curve. Breakout analyses were performed using a 2D failure criterion and a multiaxial failure criterion. Analyses were carried out using both short-term (peak) and long-term strengths (the latter considered here as being represented by the damage initiation threshold DIT). The analyses have shown that the use of the longterm strength and a multiaxial failure criterion leads to results that are more consistent with stress measurements performed in the field, in the vicinity of the mine.

Jun 1, 2012

By Kan Xing

This paper introduces common detrimental consequences to the environment from mining in the Beijing West Mining Area. For example, ongoing mining operations can cause the following environmental deterioration: rock burst, roof rises, roof falls and inrush (Pit dash for ward water). Post-closure, after minerals resources are exhausted, the following environmental issues may remain: landslides (collapse, and mud-rock flow), dropping or exhausted water tables, water pollution, desertification and soil erosion, water accumulation, Slay endanger, ground subsidence, and causal factors in seismic activity. This paper analyzes this wide range of environmental consequences of mining, and offers a theoretical foundation to underpin a corresponding management scheme.

Aug 1, 2013

By G. T. Lapidus, J. Trejo-Gallardo

A phenomenological model is presented for leaching silver from silver sulfide contained in mineral particles with ammoniacal thiosulfate solutions of copper in stirred reactors. Experimental results were used to adjust the kinetic parameters of the model, such as the reaction order and velocity. The incorporation of the cuprous sulfide-silver sulfide equilibrium at the reaction interface allowed the prediction of the conversion limits for different reagent concentrations. The information obtained from the reactor model was later integrated into a heap leaching simulation, whose results adequately describe tendencies observed in column tests, with respect to variations in copper and thiosulfate concentrations. Comp

Jan 1, 2005

By S. A. N. Sheya

The U.S. Bureau of Mines performed batch equilibrium contact experiments to examine the ability of activated coconut-shell carbon to adsorb various metal cyanide complexes. Tests were also conducted to determine the effect these cyanide complex impurities might have on the adsorption of gold by the activated carbon. Metal cyanide species included in the investigation were antimony, arsenic, cadmium, calcium, cobalt, gold, iron, mercury, nickel, silver, thallium, and zinc. Tests were made over a pH range of 6.4 to 12.5. The carbon exhibited a preference for gold adsorption over other metals present in solution. In the absence of gold, the metal cyanide complexes were adsorbed; adsorption generally decreased with increasing pH. However, calcium and thallium adsorptions increased with increasing pH, while arsenic and iron were not adsorbed at any pH.

Jan 1, 1989

By Todd M. Ruff

Current methods of inspecting wire rope for broken wires or excessive wear include visual inspection, physical measurements of rope diameter, and electromagnetic nondestructive testing (NDT). Visual inspection and physical measurement arc the least comprehensive methods. Electromagnetic NDT enables a more thorough assessment of the condition of a wire rope, but the repeatability, accuracy, and objectivity of this method can be improved. One means of achieving this goal is to use a computer to analyze the test data and determine the condition of the wire rope, including the presence of broken wires and corrosion, and the amount of wear. An off-the-shelf data acquisition and analysis system was tested in a U.S. Bureau of Mines laboratory using a continuous loop of wire rope containing fabricated flaws. The test rope was run through a commercially available NDT instrument. The output of the instrument, normally connected to a paper strip chart recorder, was digitized and analyzed with a personal computer. These initial tests were successful in showing that the use of a computer can improve current methods of NDT waveform collection and analysis.

Jan 1, 2010

By A. K. Bakshi

Slurry rheology affects autogenous grinding performance by changing the rock's breakage characteristics. In this study pilot scale batch autogenous grinding was carried out to observe the effect of viscosity on the breakage characteristics of the rocks (the media), and on the overall specific energy consumption. Clay/fines content, and temperature of the initial charge, were varied to alter the viscosity of the slurry. Results showed that at higher slurry viscosity, rocks became more difficult to break, resulting in an overall increase in the specific energy consumption of the mill. Also, it was observed that viscosity had a significant effect on the amount of critical size material present in the grinding circuit, where the critical size material is the material which is too large to be effectively ground in the mill, and too fine to act as grinding media.

Jan 1, 1996

By K. Osseo-Asare

It is possible to form a two-phase system in certain polymerlinorganic salt/water mixtures, such as those containing the polymer polyethylene glycol (PEG). Such aqueous biphase systems have many of the separation characteristics of conventional solvent? extraction systems, but are environmentally friendlier. Just like the well-known organic solvent/water two-phase system, the top polymer-rich phase is more hydrophobic. and the bottom salt-rich phase more hydrophilic. The partition of dispersed? particles is dependent on the interfacial interaction between the particles and the conjugate aqueous biphase solutions. In particular, the hydrophilic/hydrophobic properties of the surface determine the transfer of the dispersed particles into either the top (more hydrophilic) phase or the bottom (more hydrophobic) phase. Accordingly, differences in the surface chemistry of particles can be exploited to achieve selective separations. In this work, several approaches to separation control will be discussed. using pyrite (FeS2), alumina (AI203). hematite (Fe203), silica (Si02), and titania (Ti02) as model particulate materials. For metal sulfides, pH and redox potential can be used to alter the hydrophobicity/hydrophilicity of the particles. In ?the case of oxides. polymer adsorption and collector adsorption may be exploited to facilitate particle transfer.

Jan 1, 1999

By I. G. L. Sinclair

The Selbaie deposit is located in northern Quebec. It is comprised of three distinct, but genetically related, Cu-Zn-Ag ore bodies which also contain economically significant amounts of Au. The deposits are Archean in age and volcanogenic in origin. At Selbaie, ore microscopy has been employed to aid in planning of ore beneficiation methods and to monitor the ongoing performance of the concentrator. Examples of both types of study are described. Early in the life of the mine, excessive amounts of Zn appearing were found to be appearing in the Cu concentrate. Microscopic examination of concentrates showed that this was being caused by the presence of coatings of supergene chalcocite on sphalerite grains. Fine coatings of supergene galena and chalcopyrite were also observed on some sphalerite grains. The presence of Ag and Au in the ores makes an important contribution to the revenue of the mine. The various modes of occurrence and mineralogical relationship of these two metals are described and discussed. Monitoring of the ongoing concentrating process at selbaie is done by qua-litative and quantitative examination of products collected at various points along the circuit. Causes of such problems as excessive loss of metals to the tailings or inefficient recovery of individual metals, can often be identified and possible solutions proposed.

Jan 1, 1989

By Yuanbo Zhang, Yongbin Yang, Guanghui Li, Zhengwei Yu, Yufeng Guo, Tao Jiang, Xiaohui Fan, Youming Hu

"Composite agglomeration process (CAP), as an innovative method for preparing blast furnace burden, was developed and has been put into operation in China. CAP is different from traditional agglomeration processes of iron-bearing materials involving sintering and pelletizing. Compared to the traditional agglomeration processes, CAP is characterized by several strengths such as permission of diverse iron-bearing materials in production, obvious improvement of permeability in the feed bed, decreasing the fuel consumption and remarkably increasing the productivity of sintering machine. Furthermore, the use of the composite agglomerates prepared with CAP is capable of obviating the negative effects caused by the differences in quality of sinter and pellets on the operation of blast furnaces. This paper mainly presents an overview of the principle and applications of CAP.Development Background and Principle of CAPhe traditional agglomeration processes including sintering and pelletizing have been the two predominant methods for preparing ironmaking burden from iron-bearing materials. Sintering is a way for agglomeration by heating the coarser fine ores (general granularity 0~10mm). The mechanical strength of irregular porous sinter is obtained by the solidification of molten phase at high temperature process. It has been shown that the production of high basicity sinter (R=1.8~2.2) is characterized by low energy consumption and high efficiency compared to low basicity sintering. Meantime, the finished high basicity sinter is characterized by good mechanical strength and metallurgical performance. Pelletizing is another way for agglomeration by firing wet green pellets, which are balled from the fine grained iron ores or concentrates. Based on the differences of chemical compositions, the finished pellets can be divided into acidic oxidized pellets, fluxed pellets, magnesium-bearing pellets, and so on. The acidic oxidized pellets are the dominant products of modern pelletizing."

Jan 1, 2012

By Ljiljana Solujic

The need for the removal of mercury from the precious metals extraction circuits may be influenced by process, environmental, as well as by occupational hazard reasons. In these circuits mercury is mainly present as cyanide complexes. The effectiveness of any stabilization method will be influenced by the high thermodynamic stability mercury-cyano species exhibit in an aqueous solution. In this study, we have investigated the utility of the trisodium salt of trimmercapto-s-triazine (TMT) for precipitation of mercury from the corresponding cyano-complexes. The influence of pH molar ratio of TMT to Hg, coagulant and flocculant additions, excess of free cyanide, as well as the presence of other metal-cyano species on the effectiveness of mercury precipitation were investigated in detail. Also, a "teal world" precious metals mill effluent initially containing ~7 ug/mL (ppm) of Hg was treated and A was found that greater than 99.8% of the mercury was removed from the solution as am insoluble Hg/TMT complex.

Jan 1, 1996

By Xiang Yu

Hong Kong has a dense distribution of utility services laid under its road network. Utility undertakers frequently demand road openings to install new services and/or maintain existing ones. Road openings can cause troubles to the road network and negatively impact the public interest. Highways Department is responsible for managing road openings in Hong Kong under the Land (Miscellaneous Provisions) Ordinance. Highways Department has spent a lot of efforts to computerize excavation permit processing and utility management. The computerized system has gone through several generations and the current one is called the excavation permit management system (XPMS). On the one hand, the XPMS handles various excavation permit processing functions including permit application/approval/refusal/issuance/extension/termination, fees/costs, permit conditions, and permit period assessment; on the other hand, the XPMS accounts for some important utility management issues such as spatial check, coordination of multiple openings, traffic management, audit inspection, and defect liability. This paper discusses how the application, coordination, and other administrations of an excavation permit are eased by using the XPMS in Hong Kong. Background information such as the governing legal and regulatory framework, and Highways Department?s administrative structure is introduced. The system architecture and advantages of the XPMS are presented. The work procedures and various functions of the XPMS are studied in detail.

Aug 1, 2013

By Jun Lu

This paper presents the evaluation, enhancement and comparison of two hydraulic fracturing techniques which were employed to mitigate the impact of a massive sandstone channel on two successive longwall faces. The hydraulic fracturing technique and Longwall Visual Analysis (LVA) software were initially employed to mitigate the impact of thick, massive sandstoneroof during mining of longwall Panel 21. Improved longwall face conditions and productivity were observed as Panel 21 mined through the sandstone channel. However, moderate sandstone fractures and falls at the face were still present in areas where hydraulic fracture influence was not present. Such adverse conditions caused two to three weeks of production delays due to large face cavities, jammed face conveyor and subsequent face gluing. Based on the mining experience in Panel 21, and site-specific roof geology in Panel 22, a modified and more effective hydraulic fracturing program was employed. Fewer well-placed holes were drilled, and larger volume of water was pumped into each hole in order to propagate the individual horizontal pancake fractures over a larger area, thereby enhancing caving and relieving face pressure caused by overhang of the massive sandstone. Longwall Visual Analysis (LVA) software was also employed at Panel 22 to predict the cavity risk index and guide the longwall face crew in double-pulling shields behind the shearer drum. This helped to reduce the tip-to-face distance at the critical spots along the longwall face, which helped mitigate the formation of the roof cavities and failure of massive sandstone onto the face conveyor. Underground observations, face advance rate and face rock delay analysis confirmed that longwall face conditions and advance rate in Panel 22were significantly improved compared to those of Panel 21. Consequently, safety and productivity were improved.

Jan 1, 2014

By Henry Hu

In high pressure die casting processes, proper control of temperature die yields a high casting production rate and superior quality components, Die temperature is usually influenced by various die design and process parameters such as size and location of intemal water cooling lines, flow rates of cooling lines, and pouring temperature of molten metal. Among them, the cooling water flow rate plays a major role in controlling thermal pattern of the die_ In order to develop an effective control strategy, data of local die temperature must be collected and analyzed, In this study, a PC-based data acquisition and control system (DACS) for die temperature control has been designed, and established, The developed DACS has three input channels for temperature signals and one input channel for water flow rate signals, as well as one output channel for a water pump, and is capable of displaying data in both curve format and value format. Implementation of the DACS in a laboratory setup has also been attempted, It should be pointed out that more advanced control mechanisms can be potentially integrated into this system in future,

Jan 1, 2003

By Philippe De Donato, Odile Barres, Mukendi Kongolo, Stoyan Gaydardzhiev, David Bastin, Jean-Marie Kanda

The adsorption patterns of potassium amylxanthate on the surface of high purity malachite subjected to prior sulfidization with NaSH have been followed and elucidated. DRIFTS spectroscopy has been used to trace the associated physicochemical alterations as well as the chemical species present on the mineral surface. Varying the collector concentration from 5.10-4 to 1.10-2 mol/L has led to different degree of surface coverage of the alkyl groups and to formation of organometallic hydrophobic complexes of CuX or CuX - X2 type. The results reveal that the CuX complex formed on the malachite surface without sulfidizing agent is more unstable and prone to dissolution-precipitation phenomena. Based upon the constructed adsorption isotherms and upon the degree of statistical coverage, different zones of mineral-reagent interactions could be distinguished. They correspond respectively to the monolayer, bi-layer and tridimensional condensation domains. In each of the identified zones mono or double layer adsorption patterns of the collector are proposed leading respectively to formation of surface compounds with different degree of hydrophobicity. The results suggest that sulfidisation remains an important prerequisite in view achieving efficient flotation of the malachite from the studied copper ore.

Jan 1, 2014

By F. N. Kissell, R. J. Bielicki, J. H. Perkins

A sorption apparatus for measuring the equilibrium sorption isotherm and the rate of diffusion of methane from fine-sized coal was designed and constructed. Preliminary work that used Pittsburgh and Pocahontas No. 3 coal shows that the diffusion coefficient varies with pressure and that the fracture spacing in these two coals is substantially different.

Jan 1, 1972

By F. Habashi

Lead is an ancient metal. The alchemists related it to the planet Saturn. It was largely obtained by smelting galena which generally contains small quantities of silver. That is why the metallurgy of lead was closely related to that of silver and in some cases the ore was treated only for its silver content. It was also known during the Roman time that lead vapors were toxic. Lead has been produced exclusively by pryrometallurgical methods. Lead refining is a complex process because of the presence of deleterious impurities such as arsenic, antimony, and bismuth. In the nineteenth century lead played an important role as a material of construction in the manufacture of sulfuric acid. In the twentieth century tetraethyl lead was used exclusively as an anti-knock reagent. In recent years lead is mainly used for making batteries.

Jan 1, 2008

By W. K. Collins

Engineered Scavenger Compounds (ESCs), developed by the U.S. Bureau of Mines, are a novel class of compounds that can selectively recover a desired element from a solid or molten alloy. Lithium titanate (Li2Ti3O7 or L'20-3T'02) is being used as an ESC to recover lithium (Li) from Aluminum-Lithium (Al-Li) alloys. X-ray diffraction measurements have shown that lithium titanate undergoes a phase change from an orthorhombic structure to a hexagonal structure. This change is due to the incorporation of Li in the matrix of the material and the effect of temperature. Although both are metastable, the hexagonal phase that forms during the scavenging of Li from Al-Li alloys appears to be the more stable phase. Recovering Li from the ESC by electrodeposition does not cause the structure to revert to the orthorhombic phase. Both the orthorhombic and the hexagonal structures of Li2Ti3O7 have similar scavenging capacities for Li. This paper proposes a new mechanism for the phase transformation.

Jan 1, 1993

By Raymond M. Stateham

Climatic conditions are compared with roof fall occurrence from April 1, 1972, to December 31, 1975, by the Bureau of Mines. These comparisons indicate that humidity has a strong influence on roof fall occurrence rates. Cubic regression techniques are used to develop best fit curves. Statistical analysis of these curves indicate that both are sinusoidal and exhibit positive correlation with each other. The sine waves have a period of 1 year with maximum and minimum inflection points in August and February.

Jan 1, 1978