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By T. Plikas, T. Porretta, M. Al-Dojayli, B. Pretorius, J. Woloshyn, H. Ghorbani

"Water-cooled ducts represent an integral part of high temperature off-gas systems in metallurgical processes. Typically, off-gas enters these ducts at significantly elevated temperatures; therefore, water cooling may be required to maintain the duct skin temperature within allowable design limits. These off-gases are typically of high mineral content that could lead to dust buildup, and there is a possibility of slag buildup / molten metal splashing. Therefore, dust cleaning provisions may be necessary in order to remove or minimize accretion on the duct wall, which could otherwise impact the water cooling and the system process efficiency. These ducts may have complex geometry and experience a wide range of loading, including gravity loads, water and gas pressures, cyclic thermal loading and dynamic impact forces. Consequently, the thermo-mechanical assessment of such water-cooled ducts is critical and requires consideration phenomena such as high temperature gradients, potential nucleate boiling, thermal ratcheting and fatigue failures. Such assessment is not comprehensively covered by design-by-rule design codes and guidelines due to its complexity. This paper presents a successful implementation example of design-by-analysis methodology to improve the design and extend the life of a water-cooled furnace transition duct using Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA).INTRODUCTION Water-cooling represents an important part of high temperature off-gas systems in metallurgical processes. Typical temperatures of the off-gas in the furnace uptake are in excess of 1400°C, and thus there is a need to maintain the water-cooled duct and jacket skin temperatures within their material allowable design limits. Water-cooled channels have been used effectively in arc furnace roof design (Sosonkin et al., 1972; Smolyarenko and Khainson, 1988) and other furnaces as well as in furnace fuming jackets (Scholey et al., 1994). The design of these systems was based on one-dimensional analysis to ensure sufficient cooling is available under extreme furnace conditions (Smolyarenko and Khainson, 1988; Scholey et al., 1994). With advancement in furnace and fuming system designs, water-cooled duct designs have become more complicated in geometry. Numerical techniques, such as three-dimensional fluid flow and heat transfer modeling, are therefore needed to more accurately calculate water velocity, temperature and convective heat transfer coefficients in the water-cooled channels (Haywood et al., 2002; Henning et al., 2010). This is of particular importance around geometric corners where stagnant water flow may lead to local nucleate boiling at the critical heat flux, causing hot spots (Bergman et al., 2011). High wall skin temperatures increase the risk of failures due to thermal stresses as well as increasing corrosion rates (Gelfi et al., 2012), leading to costly equipment downtime and potential safety risks."

Jan 1, 2017

By D. Stone, N. J. Aslin, W. Webb

In today's modem copper electro-refineries, increasingly higher average current densities are being employed. With these increases many refineries are approaching their limiting current density. The nearness of the average operating current density to the limiting current density has placed increasing emphasis on the need to maintain an even current distribution. This paper explores the importance of maintaining even current density and discusses the factors, processes and practices that are necessary to achieve and maintain high quality production at high operational intensity.

Jan 1, 2005

By Trevor Saldanha, Stephen Grano

A key uncertainty in flotation modelling is determining, a priori, the proportion of each mineral which will develop a certain rate constant for different feeds of variable liberation and hydrophobicity. First and foremost is the ability to predict the proportion of minerals that will not be recovered, even at very long flotation times, and which therefore report to the tailing stream as the non-floatable fraction (i.e., having a zero rate constant). Recent empirical evidence has shown there are at least two factors which contribute to heterogeneity in flotation rates and, in particular, the appearance of a non-floatable fraction - heterogeneity in the distribution of adsorbed collector amount on a particle-by-particle basis, even for the same liberated mineral in the same size fraction, and the existence of a critical contact angle below which the bubble-particle union is unstable. In this paper, inferred measures of the critical contact angle for liberated particles are compared with stability model calculations. This has demonstrated that the dependency of the critical contact angle with particle size and mineral specific gravity are explicable by bubble-particle stability considerations. This argument is further extended to the flotation behaviour of composite particles, as a function of liberation class, in which the wetting perimeter of the attached bubble on the composite particle surface is constrained by the presence of a surrounding hydrophilic domain for the case of simple binary composites. Reasons for the different flotation behaviour of composite particles having different textures, as noted in the literature, are also discussed in terms of the stability of the bubble-particle union.

Jan 1, 2014

By J. -P. Lempainen, K. Haavanlammi, K. Valkama

The Outotec nickel matte chloride leaching process is especially suitable for small capacity standalone nickel refineries. The matte is leached with hydrochloric acid and oxygen in multiple steps in atmospheric OKTOP® reactors. Oxygen feed prevents reductive conditions and hydrogen formation in the leaching process. A sufficiently high acid concentration keeps the iron dissolved in the solution. The iron is removed after leaching by precipitation and the pregnant leach solution continues to metals recovery. The metals recovery from the chloride solution is done by solvent extractions, where ammonia is used for pH control. Copper and nickel are stripped from the organic phases into sulphate solutions. Metals can be recovered from the purified solution by conventional electrowinning. Other alternatives are precipitation or hydrogen reduction processes. The ammonium chloride in the solvent extraction raffinate is regenerated into ammonia. The calcium chloride solution from ammonia regeneration is routed to acid regeneration where sulphuric acid is added and ultra-pure gypsum is precipitated. The hydrochloric acid solution from this step is recycled back to leaching. The process yields good overall metal recoveries and expensive

Jan 1, 2014

By Theodore Ineich

The “BIOMOre” project aims to prove the technical feasibility of indirect in situ bioleaching of sulfide minerals contained in a deep underground deposit, by bringing together the disciplines required to make a success. The underground location in Poland was provided by project partner KGHM inside an operating copper mine. Key components of this project were the design and construction of a pilot plant, and its operation in an underground environment. This project also included a ∼250 t (100 m3) fragmented rock reactor hydraulically connected to the pilot plant. The pilot plant consisted of several tanks and pumps, a fluidised bed ferric iron generating bioreactor containing immobilised acidophilic iron oxidation biomass, and all the required instrumentation and utilities. Before the bioleaching phase could start, the rock reactor had to be flushed continuously firstly with water to remove chloride salts that are corrosive and also harmful for the bacteria used in the bioreactor, and secondly, with sulfuric acid solution to react with the carbonates present in the ore matrix. This paper summarizes the design, construction, commissioning, and operation of the pilot plant.

By L. B. Pankratz

Enthalpies above 298° K were determined for AgCl to 1,400° K and for AgBr to 1,200° K by copper-block calorimetry. Before melting, both compounds showed an anomalous increase in enthalpy, an effect associated with lattice defect formation. Melting points and heats of fusion were determined to be AgCl, 730° K and 2,945 cal/mole; AgBr, 700° K and 2,030 cal/mole. The heat capacity of both melted substances decreased with increasing temperature over the entire liquid ranges investigated. Enthalpies above 298° K were tabulated at even temperatures along with derived entropy increments and heat capacity values. The results were combined with the known heats of formation and entropies at 29.8.15° K to obtain values of the heats and free energies of formation over the range 298.15° to 1,400° K for AgC1 and 298.15° to 1,200° K for AgBr.

Jan 1, 1970

By R. Karl Zipf, Z. T. Bieniawski

"SummaryAs part of an effort.to understand the mechanics of fine fragment formation in coal, which is important in studies of respirable dust due to mining, fracture toughness measurements and the strain energy density (SEO) theory were applied to calculate the crush zone size under a cutting tool in coal. This · zone is the major source of fine fragments in the 1 to 10 µm size range. The model used in these calculations is a boundary element program containing a failure criterion based on the SEO theory. The boundary element program calculates linear elastic stresses at numerous points in the coal material ahead of a cutting bit. These stresses arc then input to a subroutine called critical ftaw length and orientation (CFLO) which uses the SED theory to determine the CFLO for a small crack at the boundary element stress computation point. The extent of crushing is based on earlier postulates about . the role of inherent flaws in a fragmentation process. To form 1 to 10 µm fragments requires firstly a local stress strong enough to activate flaws with a characteristic length less than 1 to 10 µm and secondly, a flaw density sufficient to provide an average spacing between flaws also on the order of 1 to 10 µm. The locus of active lO µm ftaws represents the maximum possible extent of fine fragmentation in the 10 µm or less size range assuming that a sufficient inherent flaw density exists. The approach offers a first order approximation to the extent of crushing under a tool tip. The size and shape of the crush zone volume is affected by the attack angle and geometry of the tool.IntroductionFine fragment generation in the 1 to 10 µm size range under the action of a generic coal cutting tool may be explained on the basis of fracture mechanics which suggests two major sources of fine fragments: first in a crush zone near the tool tip and second by shear fracturing. along major macrocrack surfaces (Zipf and Bieniawski, 1988a). In this paper, fracture toughness measurements and the strain energy density theory are used to calculate the crush zone size. This zone represents the major source of fine fragments in the 1 to 10 µm size range and understanding the mechanical factors controlling its size represents a first step toward using fracture mechanics to characterize the ·tendency of various coals to produce undesirable fine fragments."

Aug 31, 1989

By D. W. Bacon

Plant process optimization programs are often costly, both in technical effort and loss of production. Evolutionary Operation or "EVOP" is a mode of plant operation consisting of controlled cyclical changes in process conditions by which information is provided concerning potential process improvements while both volume and quality uniformity in production are maintained. Its conceptual simplicity and low cost of utilization have led to successful adoption in a variety of industrial manufacturing operations. This paper is an expository account of basic EVOP theory, the problems encountered and the organization required in applying it to a processing plant. Illustrations are provided which indicate the payoff that can result.

Jan 1, 1967

By S. Bahrampour

One of the basic requirements for designing an optimized rock support for an underground opening is having reasonably enough geological information. It is often financially impractical to obtain detailed geological information about the rock surrounding the excavations. The geological and geotechnical information which are obtained during the construction phase are also usually inadequate and need periodic operation stoppage. Penn State University- J.H. Fletcher & Co. joint venture is to improve the existing instrumented roofbolter so that the 3D geological and geotechnical map of the rock mass surrounding the underground working can be generated real-time as the data is being collected. This information will also be used to design appropriate support for different sections of mines. In this paper, recent results in improving the performance of the measurement while drilling system will be discussed. Moreover, updates related to borehole probing methods for estimating the properties of the rock masses will be presented.

Feb 23, 2014

By E. Gock

Based on the scientific investigations on mechanochemical synthesis of metal sulphides from metals or metal compounds and sulphur or sulphur compounds, the article describes the industrial production of nanoscale metal sulphides. Special operational conditions such as inert atmosphere, size and type of the grinding balls, grinding time and specific energy input are taken into consideration. A system configuration for the manufacturing of sulphides at a capacity of 100 kg/h is presented.

Jan 1, 2014

By Leo Panian, Ryan Nagle, Priyanshu Singh, Gina Carlson, Wayne Magnusen

"This case study presents the design and construction of an integrated foundation and ground improvement solution utilizing deep soil mixing (DSM) and micropiles. 270 Brannan is a midrise office building in San Francisco that straddles the historic shoreline that was reclaimed in the 19th century. Subsurface conditions include shallow bedrock inland of the historic shoreline, and steeply dipping bedrock overlain by 60 feet of compressible deposits and liquefiable fill on the bay side. Project challenges included mitigating the liquefaction and lateral spreading hazards, addressing settlement concerns in the fill and the bay deposits, developing a cost-effective foundation support solution, assuring satisfactory seismic performance, and addressing construction restrictions with existing adjacent structures.DSM combined with micropiles was identified as the most cost-effective solution for the ground conditions. The DSM panels act both as a liquefaction mitigation mechanism and a foundation support system. Resistance to seismic overturning is provided by uplift-resisting micropiles. The DSM-micropile solution allows the use of efficient conventional spread footing foundations, integrating isolated micropile groups to anchor the shear walls. Successful installation of the system relied on a program of field testing to validate the design and conformance with the design criteria.INTRODUCTIONThe regular grid of surface streets within San Francisco’s South of Market (SOMA) district provides little evidence of the geotechnical complexities that lie below. In the late 1800s, sand dunes, bedrock hills, cliffs, marshes, and mud flats were flattened and filled, concealing their locations and characteristics. The 1906 San Francisco earthquake and fire leveled many buildings in SOMA; new buildings were built after 1906 – often on top of rubble and debris from the structures that came before. Locally, the combination of natural geology and historical interventions can produce complex subsurface conditions that vary dramatically over short distances. This is particularly true at locations where tidal mudflats once met bedrock hills at the shore of San Francisco Bay.This case study describes an integrated foundation and ground improvement system implemented for a multistory “Class A” office building at a complex SOMA urban infill site. The system utilizes cement deep soil mixing (DSM) in combination with spread footings and micropiles to address a range of design and construction issues, including liquefaction and lateral spreading mitigation; consistency of earthquake ground motions; shallow foundation support; seismic uplift resistance; and avoidance of loading adjacent basement walls. The system was implemented by a technically-sophisticated owner through a process that included constructive collaborations between the project geotechnical engineer, structural engineer, general contractor, and specialty foundation and ground improvement contractor(s). The system is designed to cost-effectively provide a high level of seismic performance."

Jan 1, 2017

By A. T. Yu

There are compelling reasons for us to look to our Country's Western coal. Despite its inherent low BTU content, Western coal's low sulphur content provides a near-ideal answer to satisfy our in- dependent goals of clean air and self-sufficiency in energy. Vast reserves, thick seams and amenability to low-cost strip mining serve as a powerful economic basis for its viability as a primary and dependable source of energy for the coming decades. A major consideration, the solution of which may not be quite obvious, is transportation cost. These abundant deposits are remote from the utilities of the heavily populated eastern regions of the United States (Figure 1). A Western coal mine in Montana is likely 1500 miles or more from an eastern power plant. The comparable distance to an eastern coal mine may be only 200 miles. Thus, the question is: How can the haulage cost of our Western coal be substantially reduced to an acceptable level? If resolved, western reserves of coal will be one of the key solutions to satisfying our Nation's energy needs.

Jan 1, 1975

By P J. Jacobs

FORACO is the third-largest global drilling services company, and recently celebrated its 50th anniversary. The company’s historical roots are in French-speaking West Africa, delivering hydrogeological drilling services to resource companies, villages and regional centres. Today, FORACO operates over 300 drill rigs in more than 20 countries.The Asia Pacific region of FORACO runs a fleet of 37 late model drilling rigs servicing the diamond drilling, reverse circulation, coal, coal seam gas and hydro drilling sectors.FORACO Australia has extensive experience delivering large diameter coring (LDC) samples to the resource community. In the past three years, the company has been involved in six 8? coring projects in a variety of geographies and geologies, including iron ore, coal and uranium. FORACO has developed proprietary equipment and techniques to deliver cost-effective LDC samples with outstanding core recovery.The FORACO LDC sampling system is hands free, with mechanised rod and corebarrel handing to minimise the risk of manual handling injuries. Sample volumes are six times PQ (the common industry standard for large core samples), with core recoveries consistently above 96 per cent in extremely difficult formations.Eight inch coring is a conventional coring system suited to hole depths up to 150 m. For deeper applications, FORACO has recently invested over $4 M in a 6? wireline coring system capable of achieving depths of 300 m.CITATION:Jacobs, P J, 2014. Large diameter core sampling, in Proceedings Sampling 2014 , pp 71–76 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 29, 2014

By H. R. Beard

The citrate process for sulfur dioxide emission control was developed in pursuit of the Bureau of Mines goal of minimizing the adverse environmental impact of mineral-processing operations. This publication describes the gas analysis procedures used during development of the process. The research required the capability to analyze SO2, H2S, CO, CO2, COS, volatile hydrocarbons, NO, NO2, O2, N2, and H2. The methods described include gas chromatography, electrochemical detection, infrared spectroscopy, and the use of a computer program to predict the product composition in complex reactions. Laboratory and pilot plant applications are discussed.

Jan 1, 1979

By Fedotov Pavel

One of the efficient means of ore disintegration during the processing is its volume breakage in such machines as roller-presses. Up to date neither the ore disintegration mechanism in roller-presses nor the reasons of their high efficiency are thoroughly investigated. In this work, the mathematical model of Finite Element Method of bad material disintegration in roller-press is discussed. The mechanism of the interparticle ore disintegration is traced.

Sep 1, 2012

By P. J. McDonough

The Bureau of Mines designed and tested a hardware-software system for measuring on-line corrosion rates of materials in a rod mill in operation. Currents ranging from 10-6 to 10-3 A and potentials in I-mV increments were converted to a digital signal. The digitized data were frequency-modulated and transmitted from a rotating ball mill to an FM receiver, where they were decoded by computer and then processed in real time using assembly language software. This design approach would allow accurate measurement and control of systems where signals of small amplitude and large ranges are present.

Jan 1, 1988

By Farzad Mohammadi, David Kratochvil, Patrick Littlejohn

"With more rigorous regulations being enacted in the mining industry, a need exists for cost effective and environmentally compliant technologies to remove selenium from mine impacted waters to ultra-low concentrations. Existing selenium treatment methods have high life cycle costs, introduce risks of acute fish toxicity, and produce biological waste residues that represent future liabilities. Furthermore, achieving selenium discharge limits of less than 4 ppb is a challenge for existing technologies. Selen-IX™ is a technology developed by BioteQ that selectively removes selenium from mine impacted waters to less than 1 ppb. The technology is purely physico-chemical and takes advantage of the basic principles of ion exchange and electrochemistry. Unlike conventional electrocoagulation that removes suspended solids and breaks emulsions or oxidizes heavy metals, the electrochemical process employed by Selen-IX™ relies on creating conditions where iron acts as a highly effective reducing reagent transforming selenium from a dissolved species into elemental selenium bound in a solid phase. The iron-selenium by-product of Selen-IX™ is an inorganic, non-hazardous and chemically stable solid. Due to their high iron content, the solids produced by Selen-IX™ are of interest to the steel making industry as a low cost feedstock. This offtake potential can not only reduce the life cycle cost of selenium removal by reducing disposal costs but more importantly, eliminate the risk of future environmental liabilities. In this paper, the basics of Selen-IX™ technology are presented along with results of successful piloting on streams from coal and copper-gold deposits.INTRODUCTIONVarious contaminants are released into mining wastewater during the extraction and processing of metals. One such contaminant is selenium. A naturally occurring element found in rocks and minerals, mining activities accelerate its release into the environment. Selenium in trace quantities is essential to all life forms but at higher concentrations it can be harmful, especially to aquatic life where selenium bioaccumulation can lead to reproductive deficiencies."

Jan 1, 2016

The Gosowong epithermal quartz-adularia vein, in the Halmahera magmatic arc, is a new discovery in an area of primary tropical rain forest with no history of gold mining or mineralization. The newly recognized mineral district also contains a number of other epithermal vein systems, two centres of porphyry Cu-Au mineralization, and a number of argillic and advanced argillic alteration zones that may be related to underlying mineralization. Gosowong was discovered and tested through the application of basic exploration techniques including drainage sampling, soil sampling, trenching, magnetics, IP, and diamond drilling. Lapse time from the initial reconnaissance discovery of a stream sediment anomaly to the release of inferred resource estimates of approximately 1.0m ounces was just over 3 years.

Jan 1, 1997

By U König, N Norberg

Traditionally, quality control of iron sinter has relied on time-consuming wet chemistry. However, the mineralogical composition that defines the physical properties, such as strength or reducibility, is not monitored.X-ray diffraction (XRD) analysis in combination with Rietveld quantification and statistical data evaluation using partial least squares regression (PLSR) has been successfully trialled to determine the mineralogical composition and process parameters such as the FeO (Fe2+) content and basicity of iron sinter within an analysis time of less than eight minutes per sample. The results were compared with wet chemistry data.PLSR does not require pure phases, crystal structures or complex modelling of peak shapes. The analysis is therefore easy to set up and ideal if only one property needs to be analysed. PLSR results show an accuracy for the FeO content of ±0.3 per cent for the samples analysed in this case study.Both the PLSR and Rietveld methods take the full XRD pattern into account and can be simultaneously applied on the same measurement. PLSR was found to be the more robust method if only FeO and basicity results are required. The Rietveld method helps to predict other parameters, such as the compression strength of the sinter, by monitoring all existing phases (eg larnite C2S or silico-ferrite of calcium and aluminium phases).CITATION:König, U and Norberg, N, 2015. Iron sinter process control using x-ray diffraction, in Proceedings Iron Ore 2015, pp 53–60 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By Neal Lee

Often the effects of wet boreholes are not taken into consideration when designing a blasting program to exhibit a certain amount of explosive energy per unit of rock such as design by powder factor, expressed in lbs./bcy (pounds explosives per bank cubic yard) or kg/bcm (kilograms per cubic meter), often the effects of wet holes are not considered. This paper examines different methods of loading wet holes and the effects they have on actual explosive quantities/unit of rock. In particular, we are looking at the amount of water trapped within the explosive column (bulk loading from the collar), or the annular space left void of explosives product around and between cartridges (wet-bags) with many of the current wet hole loading methods in use. We will focus on the effect this has on actual powder factor relative to “as designed” dry hole loading values, as well as the effect on performance of the explosives.

Jan 1, 2011