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By M. Kinne

Catalyst preparation/ characterization Slightly modified DP (~Schumacher et al. Catal. Lett. 89, 109, 2003) CeO2 HAS 15 from Rhodia calcined in air for~ 2h BET: ~188m2/g, particles size: 5.7nm (TEM, XRD) + HAuCl4 at pH of 6.5-7, (>95% of the Au was deposited) ? Au/CeO2 (2.6wt% Au, ICP-AES) A new conditioning procedure was applied, including heating at low temperature in N2 and H2/N2 mixtures) Patent DE 10205873A1. Very small Au particles <2nm, for CO oxidation catalyst as Au/TiO2, Au/Fe2O3, and Au/Co2O3 Here Au particles size <3.5nm (XRD) Summary ? CO is nearly exclusively adsorbed on the Au particles ? Positive reaction orders of 0.5 are found for CO and H2O ? Ea= 40kJ/mol ? The catalyst is very active and stable ? During WGS reaction huge amounts of formates are formed and cover the surface ? The activity of the catalyst seems to be correlated with the formate species.

Oct 1, 2003

By P. N. Anyalebechi

Keywords: Aluminum alloy 3004, Solidification rate, Homogenization, Second phase particles The effects of the fineness of as-solidified cast microstructure and temperature on the response of aluminum alloy 3004 to homogenization heat treatment (a.k.a. preheat) have been investigated. The study was conducted at 538oC and 595oC on directionally solidified laboratory-size ingots with a range of solidification rate of 0.10oC/s to 29.4oC/s. Optical and electron microscopy, quantitative image analysis, electrical conductivity, and electron probe microanalysis were used to quantify the effects of the homogenization heat treatment on the microstructure of aluminum alloy 3004. In general, increase in fineness of as-cast microstructure and homogenization temperature enhances the a-transformation reaction, dissolution of Mg2Si, elimination of dendritic microsegregation, and dispersoid formation. The homogenization heat treatment reduces the average size of second phase particles in castings solidified at <1oC/s. However, in castings solidified at above 1oC /s, homogenization causes the coarsening of the second phase particles. Mn in solid solution is independent of homogenization heat treatment temperature.

Jan 1, 2005

By W. K. Katoto

The Tailings Leach Plant (TLP) of the Zambia Consolidated Copper Mines Ltd at Nchanga was commissioned in 1974 as the world&apos;s first largest successfully operated agitation leach SX-EW plant for copper production. The design, development and operation of the plant soon after commissioning termed as TLP stage II has been described by Holmes et al (1). In the initial phase the plant was designed to treat approximately 25,000 tonnes per day of current flotation tailings from the Nchanga Concentrator operations, and had a design capacity to produce 75,000 tonnes per annum of copper. Further expansion took place in 1986, and TLP stage III was successfully commissioned to treat an additional 20,000 -25,000 tonnes per day of large reserves (over 135m tonnes) of reclaimed tailings stockpiled since the early 1930&apos;s in four paddock type tailings dams (T01 to T04). The salient feature of TLP stage III expansion described by S K Mwenechanya et al (2 -3) was the installation of the world&apos;s largest Horizontal Belt Filter Plant with 26 filters each of 80 m2 filtration area.

Jan 1, 1996

By D. Mohapatra

The possibility of using 2,2,4-trimethyl-1,3-pentanediol dissolved in tetrachloromethane as extractant for boron recovery is discussed. The parameters optimized for this purpose are contact time, boron concentration in the aqueous phase, extractant concentration, equilibrium pH and phase ratio. NaOH is used as stripping agent for boron recovery from the loaded organic phase. Boron extraction is found to be a slow process (equilibrium time 20 minutes) compared to boron stripping, which is reasonably fast (equilibrium time 5 min). Maximum boron extraction is possible at a broad pH range from 1.0 to 6.0. Using 1.0M extractant concentration, a 1:1 phase ratio (organic: aqueous) and two stages, ~99% boron extraction is achieved. More than 97% boron stripping is possible using 0.5M NaOH at a 1:1 (organic: aqueous) phase ratio in two stages. Overall, a 95.6% boron recovery was achieved. Loss of solvent into the aqueous phase and co-extraction of Ca, Na and K into the organic phase at higher equilibrium pH are two major concerns in his process.

Jan 1, 2008

By Richard J. Mainiero, Michael J. Sapko, James H. Rowland III, Marcia L. Harris

All explosive materials produce a cloud of reaction products, the most toxic of which is nitrogen dioxide (NO2). In the study reported here, 4.5-kg (10-lb) charges of blasting agent confined in either thin-wall 10-cm (4-in) diameter galvanized pipe or 10-cm (4-in) schedule 80 seamless steel pipe were detonated in a closed chamber. The detonation gases were analyzed for NO2, nitric oxide (NO), ammonia (NH3), hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2), nitrogen (N2), oxygen (O2), and methane (CH4). Data were evaluated to determine the kinetics of the oxidation of NO to NO2. Analysis revealed that the only mechanism for NO loss for the conditions existing in the chamber was the reaction 2NO + O2 6 2 NO2. The rate constant was 2.08 @ 10-38 cm6 molecules-2 sec-1 for the rate equation -½d [NO]/dt = K @ [NO]2 @ [O2] for NO concentrations up to 100 ppm. The rate constant is in agreement with that recommended by Baulch, Drysdale, and Horne (1973).

By J Guo, K Williams, J Y. Guo, A W. Roberts, M Jones, B Chen

Numerical simulations using the discrete element method (DEM) were carried out to investigate the flow patterns and stress field redistribution at the hopper and feeder interface. The influences of different filling heights, belt speeds and clearances between the hopper bottom and feeder surface on feeder loads were studied. Meanwhile, experiments were conducted by utilising wedged plane-flow hoppers with different configurations and horizontal feeders with various clearances. The simulation results were compared with theoretical values and experimental measurements. In terms of the cases presented in this study, simulation results reveal good agreements with experimental observations regarding the flow pattern. Being similar to the theoretical values, the simulations provide close predictions on vertical feeder loads for steady flow states, but they may show significant overestimations for initial states. Additionally, suggestions are given for relevant simulation parameters based on the comparisons shown in this investigation.CITATION:Guo, J, Roberts, A W, Williams, K, Jones, M, Chen, B and Guo, Y J, 2017. Simulation investigation of flow patterns and feeder loads at hopper/feeder interface, in Proceedings Iron Ore 2017, pp 173–182 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017

By Ho-Sang Sohn

The kinetic study on desulfurization of copper matte by gas bubbling was designed under the presumptions of lower FeO activity and of no slag formation, Copper matte with 59% Cu and 22.6% S in weight was oxidized at 1523K by bubbling of Ar + O2 gas through a submerged nozzle. The effects of oxygen partial pressure and flow rate of gas on the oxidation rate of matte were discussed. The desulfurization rate and the evolution rate of SO2 gas of copper matte were significantly influenced by the oxygen partial pressure, but the dependence on gas flow rate was rather complicated. The desulfurization rate and evolution rate of SO2 gas of copper matte were described by the mass transfer rate through the gas film around the rising gas bubbles. Thermodynamic correlation equations between the partial pressure of gaseous species and matte composition were incorporated to the kinetic calculation, The present model shows that the reaction path starts to transiently cross over an isobar line of PSO2 to asymptotically approach to the particular isobar line drawn in a matte composition plane of %S and %O.

Jan 1, 2003

By R. B. Nourse

The depressed market for Ferrochrome worldwide has forced most producers in this industry to scale down production. Inevitably, many furnaces have been mothballed for prolonged periods, awaiting an upturn in the Ferrochrome market. In contrast, the Platinum industry is experiencing relative stability combined with good prices and they have been looking for cash cows to take advantage of these market conditions. It is, therefore, rather convenient that Platinum and Ferrochrome producers are virtually neighbours in the Bushveld complex of South Afiica, since there is an abundance of spare furnace capacity around (albeit for Ferrochrome). Against this backdrop, Pyromet Technologies (Pty) Ltd, who are currently designing a slag cleaning furnace for Anglo Platinum, was requested to perform pilot scale testwork on a 200kW furnace, in order to establish the suitability to process platinum concentrate and converter slag in a furnace designed for Ferrochrome. This paper provides an overview of the configuration, test conditions, operation and results achieved during the testwork. It also discusses the critical issues, such as refractory consumption, copper cooling and electrical parameters that need to be addressed when converting a Ferrochrome Smelter into a Sulphide Smelter.

Jan 1, 2002

By Oliver W. Marsden, John O. Marsden

This paper presents the results of a hypothetical case study that evaluates the potential transition of a large copper mining and extraction operation to 90% renewable energy. The case study considers three phases to accomplish such a transition; phase I considers installation of renewable power generation at the site to meet a portion of the current electric power needs, phase II considers conversion of diesel combustion mining equipment to electric equipment, and phase III considers implementation of renewable energy generation coupled with energy storage systems to provide approximately 90% of the total mine site energy requirements. The paper evaluates the results in the context of a range of purchased electric power unit costs ($0.065, $0.100, and $0.135/kWh) as well as various carbon tax scenarios ($0, $5.00, and $37.30/t CO2). While the case study is hypothetical and considers a range of assumptions, it clearly identifies a pathway to potentially economically viable transitions to a renewable energy platform for mining companies. This represents an approach that mining companies can use to help to meet emissions targets, as well as social responsibility and reporting requirements.

Jun 4, 2021

By J. O. Marsden

Parts I and II in this series of papers presented the chemistry of medium-temperature pressure leaching of copper sulfide concentrates and reviewed the metallurgical development of a process to effectively recover copper using medium-temperature pressure leaching and direct electrowinning (DEW). Part III reviewed the large-scale demonstration of the MT-DEW-SX process at Bagdad, Arizona. Key features of the process were the use of superfine grinding of the concentrate (to a P98 of 12 to 15 µm and a P80 of 6 to 7 µm), pressure leaching at 160ºC with 1,380 kPa (200 psig) oxygen overpressure, DEW to produce LME Grade A cathode, recycling some of the lean electrolyte to the pressure leaching step, and treatment of a lean electrolyte bleed by solution extraction (SX). Recycling of lean electrolyte provided all of the acid required to effectively dissolve copper and convert approximately 65% to 70% of the sulfide sulfur to elemental sulfur, resulting in an acid-autogenous process for pressure leaching. This paper (Part IV) discusses the development and design of a full-scale commercial application for the Morenci operation in Arizona.

Jan 1, 2007

By E N. Sajin

The final arsenic bearing waste products at the majority of metallurgical and chemical enterprises are cakes in which arsenic is present in the form of calcium arsenate. Burial of cakes demands construction of special burial sites and does not guarantee reliable protection from arsenic penetration into the ground and surface waters. Under laboratory conditions we developed technology for processing calcium arsenate cakes with obtaining low toxic products suitable for long-term storage, meeting environmental requirements. The investigations have shown that thermal processing of briquetted mixtures of cakes containing 15 - 20 per cent weight of pyrite under the temperature of 873 - 923¦K during 45 - 60 minutes gives briquettes sufficiently hard for transportation and long-term storage. Arsenic, under high sulphidisation temperature is bonded into low solubility non-volatile iron sulphide bearing compounds having chemical properties similar to the natural arsenic compounds. Solubility of the obtained products in neutral, acid and alkaline media was investigated during long period of time (three to 12 months). It was determined that arsenic content in the solutions did not exceed the norms for cultural and welfare basins and fish-ponds.

Jan 1, 2002

By Felix E. Mutschler

Alkaline rock-related precious metal deposits include: • orthomagmatic platinum group elements (PGE) ± gold (Au); • porphyry copper-silver-gold (Cu-Ag-Au, ±PGE); • epithermal Au-only, and Au-Ag-base metals; • submarine exhalative Kuroko-, Cyprus-, seamount- and Yellowjacket-type deposits; and • enigmatic deposits akin to Olympic Dam. Coeval epithermal deposits related to porphyry deposits suggest the two types represent separate immiscible fluids evolved in oxidized, CO2-rich alkaline magma chambers. Alkaline rock provinces develop above mantle hot-spots, but crustal structures control the final distribution of magmas and ore fluids. Prospecting guides for alkaline rock-related precious metal deposits include the presence of evolved alkaline rocks, pervasive K-metasomatic, redox and carbonatic alteration and low level Au (±Te, etc.) anomalies. Although alkaline igneous rocks crop out in less than 1 % of the area of the North American Cordillera and craton, alkaline rock-related ore deposits have produced nearly 13% of the total United States and Canadian lode gold production. Large (31-t or 1 million-oz) deposits are common (Fig. 1), and additional deposits and reserves are being discovered. New genetic models are evolving, making alkaline rock-related precious metal prospects attractive exploration targets.

Jan 1, 1991

By Maurizio Siepi, Bruno Vingiani, Claudio Asioli

"The article describes an emergency rehabilitation intervention executed at Buyo Dam, in Ivory Coast, to intercept a significant water seepage occurring through the foundation of this zoned earthfill retaining structure constructed in the late Seventies. To solve the problem, a 800 mm thick, 400 m long impervious cut-off wall (COW) was constructed on the right side of the embankment, operating from the dam crest and with the reservoir almost at its maximum level. The use of an innovative pre-mixed self-hardening grout, with a target hydraulic conductivity coefficient (k) lower than 10-9 m/s, was considered the only way to match the tight working schedule and the strict requirements for the filling material of the COW.Presentation of the Hydroelectric Scheme of BuyoThe hydroelectric scheme of Buyo, located at 6°14’28” N 7°20’45 W on the Sassandra River, in Ivory Coast (Figure 1), was built in the late Seventies for agriculture and power generation. With a reservoir of 8.3 billion m3 and an installed power capacity of 165 MW, enough to supply electricity to 111,000 homes, it represents an installation of great significance for this West African country."

Jan 1, 2016

By F Cesnik

The past few years has seen a concerted effort to improve the recovery of gold along with its co-product copper from the æhigh-gradeÆ Ridgeway concentrator at Newcrest Mining LtdÆs Cadia Valley Operations. A number of initiatives were identified and implemented, culminating in a sustained improvement in recovery of approximately three to four per cent for both metals. The key projects that contributed to this improvement included the installation of a 355 kW Metso stirred media detritor (SMD) to create a regrind circuit, installation of froth crowders on the scavenger circuit, installation of a Falcon SB2500SE gravity concentrator as part of the regrind circuit to improve gold recovered to bullion on-site and the optimisation of the grinding circuit to reduce the 80 per cent passing size (P80) of the primary grind from 160 to 121 ¦m for the same throughput via process control, cyclone and ball charge optimisation. This paper will focus on the supporting test work, where applicable, that was used as the design basis for the project, but more importantly the plant data before and after the changes to clearly identify the improvements to plant recovery.

Jan 1, 2007

By S. Vimalnath

The bioremediation capability of Pseudomonas aeruginosa cells was investigated for the biosorption of lead ions from aqueous solution. The various parameters such as pH, kinetics, biomass loading and concentration of lead affecting the biosorption process were studied. Complete bio removal of lead could be achieved for an initial concentration of 12.4 mg/L at pH 6.2, corresponding to typical industrial effluents. The biosorption isotherm followed Langmuirian behavior and the Gibbs free energy (?G) was determined to be-30.8 kJ/mole, indicative of chemisorption between the functional groups of the bacterial surface and lead. The biosorption kinetics adhered to a pseudo-second order model. The possible mechanisms of interaction of lead with the bacterial cells are discussed. A carbon paste electrode with a coating of biomass was developed for lead ion detection in aqueous solution using cyclic voltammetric technique. Concentrations of lead up to 5x10-5 M could be successfully detected using cyclic voltammetry, which could be improved to a detection limit of 1x10-8 M adopting differential pulse anodic stripping voltammetry (DPASV). Keywords: Pseudomonas aeruginosa, bioremediation, lead, voltammetry

Sep 1, 2012

By B Laidens, D Souza, W Bielefeldt

The CaO-MgO-SiO2-Al2O3 system, characterised by its intricate phases and thermodynamic properties, plays a pivotal role in steel secondary refining processes, encompassing desulfurisation, non-metallic inclusion capture, and refractory protection. Accurate predictions for diverse industrial applications, including metallurgy, ceramics, and materials science, are imperative. To address this challenge, a combination of machine learning techniques will be specifically applied to model the liquid fraction of the slag and the solid fraction of MgO. The development of an artificial intelligence (AI) system, leveraging various machine learning techniques, has gained momentum in this project. The focus of this work is on constructing an AI model, based on machine learning techniques, within the CaO-MgO-SiO2-Al2O3 system, utilising simulation results from FactSage™, version 8.1 (by GTT Technologies). The primary objective is to train the AI model using these simulation outputs to predict the percentage of liquid fraction and MgO saturation based on chemical composition parameters. The AI model will undergo training with a comprehensive data set of simulations within the CaOMgO- SiO2-Al2O3 system, covering a diverse range of compositional at 1873 K. These simulations, conducted through FactSage™ 8.1 software, provide a robust foundation for AI model training, ensuring generalisability and precise predictions for the liquid fraction of the slag and the solid fraction of MgO, the solid fraction of MgO in this case is determined by the difference between the total MgO and the MgO in the liquid fraction, so it is not the objective of this study to determine which phase of MgO is in the solid state.. The predictive capabilities of this AI model hold significant implications for process optimisation, quality control, and decision-making in CaO-MgO-SiO2-Al2O3- dependent industries. Precise estimations of the liquid fraction and MgO saturation empower researchers and engineers to enhance operational efficiency and quality. This paper explores the methodologies employed for AI model creation and training, achieved results in terms of prediction accuracy, and potential applications in the field. The development of this AI system signifies a notable advancement in utilising machine learning for better comprehension and control of complex chemical systems. Furthermore, to align the study with real-world steel production, we introduce FeO and MnO at concentrations of 2 per cent and 1 per cent at 1873 K, respectively, following the validation of model results using the CaO-MgO-SiO2-Al2O3 system. This adjustment aims to bring the study closer to the observed reality in steel mills globally.

Jun 19, 2024

By Marcus A. Grossmann

The Institute has established this lectureship to honor the memory of a great American metallurgist, one whose fame has continued long after his passing. As one scientist recently stated it, "All metallurgical texts gradually become outdated and outmoded, except those of the great Henry Marion Howe." It seems fitting, then, that, once every year, we shouId review, in his honor, some aspects of the science in which he was such a distinguished leader, and also discuss any new data that may help to clarify our concepts. It is my privilege, for which indeed I express the deepest appreciation to this Institute, to offer for consideration a few thoughts on the toughness and fracture of hardened steels. Before proceeding to the data, I wish to express my great indebtedness to many associates whose stimulating discussions, generous contributions of data and cooperation in experiments are gratefully acknowledged. (But I wish to absolve them of any blame that may arise from the way in which their discussions and data have been used!) First, Dr. Edgar C. Bain, Vice President, Carnegie-Illinois Steel Corporation, whose amiable but merciless criticisms and always constructive and thoughtful suggestions help unfailingly to guard against pitfalls. Then to associates at Gary Steel Works, especially Mr. H. B. Wishart, Mr. W. K. Smith and Mr. V. Elliott, for great assistance in securing data. Also to Col. C. H. Greenall, Director of Laboratories, Frankford Arsenal, and his metallurgical staff, including Messrs. J. K. Desmond, H. Markus, D. F. Armiento, H. Rosenthal and Henry George, for numerous data and illustrations. Further to Dr. J. R. Low and Dr. M. Asimow, for helpful discussions of effects of states of stress during deformation and rupture, to Mr. J. M. Hodge for discussions and data, to the staff of the U. S. Steel Corporation Research Laboratory for advice and data, and to the Metallurgical Staff at Duquesne Steel Works. The individual acknowledgments will also be found under illustrations. Acknowledgment is also due to Mr. S. C. Snyder for incredibly meticulous scrutiny of manuscript. To all of these, grateful thanks. Introduction The discussion to be offered here will deal with quench-hardened steels only, and may perhaps be considered under three headings: 1. It was found that, when ferrite was precipitated in the (prior austenite) grain boundaries of hardened steel, the notch-bar toughness was much less than in pieces fully hardened. The fracture took place in the ferrite, and the loss in toughness is attributed to the lower cohesive (cleavage) strength of the ferrite, as cornpared with martensite. 2. When notch-bar impact test pieces of quenched and tempered steels were examined as to their mode of fracture, it

Jan 1, 1947

By Marcus A. Grossmann

The Institute has established this lectureship to honor the memory of a great American metallurgist, one whose fame has continued long after his passing. As one scientist recently stated it, "All metallurgical texts gradually become outdated and outmoded, except those of the great Henry Marion Howe." It seems fitting, then, that, once every year, we shouId review, in his honor, some aspects of the science in which he was such a distinguished leader, and also discuss any new data that may help to clarify our concepts. It is my privilege, for which indeed I express the deepest appreciation to this Institute, to offer for consideration a few thoughts on the toughness and fracture of hardened steels. Before proceeding to the data, I wish to express my great indebtedness to many associates whose stimulating discussions, generous contributions of data and cooperation in experiments are gratefully acknowledged. (But I wish to absolve them of any blame that may arise from the way in which their discussions and data have been used!) First, Dr. Edgar C. Bain, Vice President, Carnegie-Illinois Steel Corporation, whose amiable but merciless criticisms and always constructive and thoughtful suggestions help unfailingly to guard against pitfalls. Then to associates at Gary Steel Works, especially Mr. H. B. Wishart, Mr. W. K. Smith and Mr. V. Elliott, for great assistance in securing data. Also to Col. C. H. Greenall, Director of Laboratories, Frankford Arsenal, and his metallurgical staff, including Messrs. J. K. Desmond, H. Markus, D. F. Armiento, H. Rosenthal and Henry George, for numerous data and illustrations. Further to Dr. J. R. Low and Dr. M. Asimow, for helpful discussions of effects of states of stress during deformation and rupture, to Mr. J. M. Hodge for discussions and data, to the staff of the U. S. Steel Corporation Research Laboratory for advice and data, and to the Metallurgical Staff at Duquesne Steel Works. The individual acknowledgments will also be found under illustrations. Acknowledgment is also due to Mr. S. C. Snyder for incredibly meticulous scrutiny of manuscript. To all of these, grateful thanks. Introduction The discussion to be offered here will deal with quench-hardened steels only, and may perhaps be considered under three headings: 1. It was found that, when ferrite was precipitated in the (prior austenite) grain boundaries of hardened steel, the notch-bar toughness was much less than in pieces fully hardened. The fracture took place in the ferrite, and the loss in toughness is attributed to the lower cohesive (cleavage) strength of the ferrite, as cornpared with martensite. 2. When notch-bar impact test pieces of quenched and tempered steels were examined as to their mode of fracture, it

Jan 1, 1947

By M. Abdellatif

"SynopsisCalcined basic nickel carbonate (BNC) concentrate was smelted in a pilotscale DC arc furnace to produce a nickel metal. The furnace was continuously operated for 12 days (24 hour/day), during which twelve different smelting conditions were investigated, with the major variables being reductant type and feed rate, flux composition and addition, and BNC feed rate.The 200 kW DC arc furnace was operated at power levels between 110 and 165 kW and at a total feed rate of 78 to 96 kg/h, resulting in an average slag and metal tapping temperature of about 1650°C. A total of 7.2 t of BNC were smelted, producing about 5.44 t of nickel metal and 2.94 t of slag. Nickel recoveries of 96.4% and higher were achieved, and the slag nickel content was as low as 0.1%. The major impurities in the metal were iron (mostly from oxygen lancing) and carbon. The calculated feed carry-over was less than 0.85% and the graphite electrode consumption was between 2.8–3.3 kg/MWh.IntroductionOne of the most distinctive advantages of DC open-arc smelting is the ability to process fine raw materials without any major issues with regard to the operability of the furnace, metal recovery, and metal quality. This has been demonstrated in Mintek’s DC arc pilot plant facilities over a period of about three decades (Curr et al., 1983). The materials that have been processed include laterite (Kotze, 2002), chromite fines (Curr et al., 1983), manganese fines (Lagendijk et al., 2010), PGM concentrates (Shaw et al., 2013), electric arc furnace (EAF) dust (Denton et al., 2005; Abdellatif, 2002a) and stainless steel (SS) dust (Denton et al., 2005; Abdellatif, 2002a; Goff and Denton, 2004), and petroleum fly ash (Abdellatif, 2002b). The top particle size of such materials can vary from a few millimetres (e.g. laterite) to micrometres (EAF and SS dust). Dusting, whether due to physical carryover of feed or to the arc side reactions, has been proven to be a non-issue. As such, the applications of DC open-arc furnaces have the potential to be extended to other raw materials such as particulate nickel oxide, which has a particle size much less than 100 µm.Nickel oxide is typically produced from laterite ore by sulphuric acid leaching, purification, and precipitation as basic nickel carbonate (BNC) (Rhamdhani, Jak, and Hayes, 2008) or as mixed hydroxide precipitate (MHP) (Mackenzie, Virnig, and Feather, 2006), and finally calcining at moderate temperatures (800–1200°C). The NiO product is very fine, with an average particle size in the range of 10–20 µm and a NiO content of more than 99%."

Jan 1, 2015

By P. T. Bissert, T. J. Lutz, J. A. Yonkey, G. T. Homce

"The National Institute for Occupational Safety and Health (NIOSH) has been researching refuge alternatives (RAs) since 2007. Refuge alternatives typically have built-in pressure relief valves (PRVs) to prevent the unit from reaching unsafe pressures. The Mine Safety and Health Administration (MSHA) requires that the PRVs vent the chamber at a maximum pressure of 1.25 kPa (0.18 psi, 5.0 in. H2O), or as specified by the manufacturer. To facilitate PRV testing, an instrumented benchtop test fixture was developed using an off-the-shelf centrifugal blower and ductwork. Relief pressures and flow characteristics were measured for three units: a modified PVC check valve, an off-the-shelf brass/cast iron butterfly check valve, and a commercially available valve that was designed specifically for one manufacturer’s steel pre-fabricated RA and has been adapted for use in built-in-place (BIP) RAs located at one mine. PRVs used in tent style RAs were not investigated. The units were tested with different modifications and configurations in order to check compliance with 30 CFR regulations. BACKGROUND The Mine Improvement and New Emergency Response Act of 2006 (Miner Act) (1) was enacted in the wake of three mine explosions/fires that claimed 19 lives that year. Intended to help improve underground coal mine accident preparedness, the MINER Act includes provisions that target mine safety issues in areas such as emergency response planning, adoption of new technology, training and education, and mine safety standards enforcement. Section 13 of the MINER Act specifically directed the National Institute for Occupational Safety and Health (NIOSH) to provide for research into the effectiveness and viability of refuge alternatives (RAs) for underground coal mines, and the Department of Labor to act on the results of such research as appropriate. These mandates culminated in the 2009 adoption of changes to 30 CFR mining health and safety regulations, requiring underground coal mines to provide mine emergency RAs and associated components, to provide a life-sustaining environment for persons trapped underground. Such RAs can be either self-contained mobile units or built-in-place (BIP) facilities. The regulatory changes also include provisions establishing requirements for the Mine Safety and Health Administration (MSHA) approval of RAs and their components, and among these provisions are numerous criteria for providing a safe breathable atmosphere under positive pressure within the RAs. One specific criterion for maintaining a safe RA atmosphere requires the inclusion of an air pressure relief valve that will activate at a maximum of 1.25 kPa (specified as 0.18 psi, or approximately 5.0 in H2O), or at a pressure as specified by the RA manufacturer, above mine atmospheric pressure in the RA (2)."

Jan 1, 2016