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By Pravin Mathur

"Praxair's CoJet® technology was introduced in 1997 to effectively inject chemical energy in electric arc furnaces. Coherent jets were invented as a revolutionary means of injecting oxygen and other gases into the EAF and into converters. Today, steel makers have widely accepted this concept in over 70 EAFs worldwide. Indeed, the whole industry has shifted to this new standard for chemical energy input in EAFs. CoJet® technology has also been implemented successfully in BOF converters.This paper will review the principles of coherent jets as applied to steelmaking. The key learnings garnered from several furnaces are also reviewed. In addition, while the CoJet® program has been widely accepted worldwide, based on steady feedback received from customers and the market place, several programs are underway in development and commercialization. These enhancements and new applications of CoJet® technology are also overviewed in the paper."

Jan 1, 2004

Spirals have become one of the most popular methods for treating fine coal. Unfortunately, spirals tend to produce an undesirably high specific gravity cut-point and often misplace significant amounts of coal and/or rock. In the present study, a process-engineering tool known as linear circuit analysis was used to identify problems with traditional spiral circuits and to suggest alternative configurations. These analyses indicate that a modified rougher-cleaner circuit incorporating a middlings recycle stream offers the best option for improving performance while maintaining a reasonable circulating load. In light of this finding, a full-scale test circuit was installed and evaluated at an existing preparation plant. Data obtained from the plant tests indicate that the new spiral circuit can simultaneously reduce cut-point and improve separation efficiency. Preliminary economic analyses show that the new circuit provides an attractive payback on the capital investment.

Jan 1, 1998

The U.S. Bureau of Mines evaluated water-jet-assisted longwall shearers in full-scale laboratory tests and underground. Both test programs showed that use of high-pressure water did little to reduce the shearer motor energy required to maintain a given cutting rate. However, three other major benefits were achieved with the use of water-jet-assisted cutting. At a pressure of 1,800 psi, respirable dust levels were reduced about 80 pct compared with the dust levels of the conventional water spray system operating at 340 psi. Operating at higher pressures required for water-jet assist also resulted in an increase in the average size of coal cut, which translates into a decrease in product fines. Finally, although no controlled measurements of bit wear as a function of water pressure were made, mine personnel reported that the shearer bits lasted longer when water-jet-assisted cutting was used.

Jan 1, 1989

By J. Avraamides

Some operational difficulties have been encountered in the transfer of carbon-in-pulp technology to Australian conditions. Many gold mines? are located in remote and arid areas where the available ground water is highly saline. There is a gradual depletion of free milling oxidised gold ore reserves resulting in the necessity to treat deeper primary sulphide .deposits which can be refractory. Some near-surface ore-bodies and tailing dumps are contaminated by natural vegetative matter which can interfere with the adsorption of gold from the cyanided pulp,. Advances which have been? made include potable water conservation in elution, a new type of regeneration kiln, inter-stage screens, alternative leaching systems transportable carbon-in-pulp plants and efficient open-cut mining methods. Academic and applied research is well supported by government and industry and the results are normally rapidly disseminated and put into practice by the gold mining industry.

Jan 1, 1989

By E J. Hancock, K H. B Chu

Failures within hard rock underground excavations have historically been defined by a depth of failure, estimated in the field or through individual measurements, with a simplified failure geometry; such as 1/3 span, cubic or paraboloid. This simplified shape, volume and mass of failure is typically used to estimate in situ demand as a simplified discrete point. However, the highly variable failure geometry indicates simplified methods to estimate the mass can be erroneous in comparison to high precision LiDAR scans. Advances in technology have enabled the accurate capture of failure geometry and allow a far more accurate analysis of failures to be completed. This case study investigates a number of real-life failures to accurately define the failure geometry, the distribution of the failure parameters and compares this to traditional methodologies. This paper also outlines a suggested means of standardising failure geometry parameters whilst accounting for their variability.

Nov 29, 2022

By H. Lachmund, R. Bruckhaus

At Dillinger Hüttenwerke/Germany steel production of grades for linepipe applications especially for sour service has a long tradition. The BOF process after replacement of the vessels is optimized by a newly developed lime addition model and variations in lance tip geometry. Equipped with three state-of-the-art VOD tank degassers metallurgical requirements of lowest contents of e. g. sulphur, nitrogen and hydrogen can be achieved. Three continuous casting machines of vertical bending type with solid core even improve already high levels of cleanliness. The vertical part corresponds to the metallurgical length of 12 to 15 m and therefore assures a maximum of cleanliness after solidification before bending. Slab thickness up to 400 mm can be produced with model controlled dynamic soft reduction. The accurate alignments of the casters assure minimized segregation and microporosity. Surface and internal cracks can be avoided by special cooling, bending and straightening strategies.

Jan 1, 2005

By Peter Sylvén, Darwin Morales

Despite being crucial for the smelting process, furnace tapping using oxygen lances has not been considered an operation that brings value. Therefore, these important tools have not seen a significant change in over 100 years. Problems related to the use of oxygen lances include: • Inaccurate tool: causing damages shortening the life of the taphole refractories. • Safety: extended exposure to the operator in an unsafe area of the furnace. • Cost: high oxygen consumption & high lance consumption. • Time consuming and frustrating to connect one lance to another. This paper will suggest a very good solution; new concept thermal lances. We will show how these provide an outstanding performance for a more efficient, faster and cost-effective furnace tapping operation. These new lances are very accurate tools that enable the operator to perform a more controlled operation; resulting in longer taphole life, fewer repairs and less down-time.

Jan 1, 2016

By Luke Meers

Roadway development rates in Australian underground coal mines are failing to keep pace with modern longwall systems and are unlikely to sustain further improvements in longwall productivity into the future unless step change improvements to roadway development equipment and practices are made. Bottlenecks which limit and constrain improved production and impact the safety of operators have been identified through a series of industry surveys, with the manual installation of strata support materials, consumables delivery, coal haulage and monorail installation being highlighted as major areas to improve development performance. This paper looks at research being carried out at the University of Wollongong in designing an integrated system approach for the fully automated handling and installing of development consumables, and the systems required to support these activities. A series of hard automation manipulation devices have been demonstrated in surface trials and the results indicate that rapid roadway development can be achieved.

Aug 1, 2013

By E. R. Bauer

Noise-induced hearing loss (NIHL) continues to be a concern of the mining industry. A new noise standard (30 CFR, Part 62) is aimed at reducing NIHL in mining through engineering and administrative noise controls. However, the difficulty and expense of implementing engineering controls can make administrative controls an attractive alternative for reducing worker noise exposure. Over the last three years, the National Institute for Occupational Safety and Health (NIOSH) has conducted worker noise exposure surveys in underground and surface coal mines and in coal preparation plants. The surveys revealed numerous possible administrative controls and an approach to implementation and analysis. The surveys have shown that worker dosimetry, time-motion studies and equipment noise profiling are important aspects of effectively utilizing administrative controls. A description of the approach for selecting, implementing and evaluating administrative controls and a list of possible administrative controls are reported.

Jan 1, 2007

By K Komori

Naoshima Smelter and Refinery has treated shredder residue and incinerator fly ash in Japan since 2003. As a highlight, a new incinerating and melting furnace, as well as fly ash washing treatment plant were newly constructed for pre-treatment of shredder residue and fly ash respectively, and the pre-treated materials are ultimately treated in the existing Mitsubishi continuous copper smelting and converting process line. Since wastes such as shredder residue tend to vary in size and in shape, and contain some chlorine, the installation of a new pre-treatment line was required. The combination of the new pre-treatment line with the existing Mitsubishi Continuous Copper Process line has created a highly efficient and environmentally friendly system for recovering and recycling of valuable metals that previously used to be sent to a landfill. This paper reviews the approach that Naoshima took to establish its current recycling business strategy.

Jan 1, 2007

By Eti Purwaningsih, Widi Astuti, Erik Prasetyo

Selective-reductive leaching of manganese from low-grade manganese ore using tannic acid as a reductant in acidic media was demonstrated by XRD, SEM-EDX characterization, and batch leaching studies at room temperature. The pH change in the liquid phase before and after leaching revealed that selectivity of manganese over iron was due to the hydrolysis of iron. The acidity in the liquid phase during leaching was dictated by two mechanisms: proton-consuming reaction (manganese oxide reduction by tannic acid) and proton-producing reaction (ferric ion reduction by tannic acid to produce ferrous ion). Based on the leaching studies, the more prevalent reaction between these two was determined by initial leaching conditions: tannic acid concentration, sulfuric acid concentration, liquid-solid ratio, temperatures, and agitation time. Kinetic studies revealed that maximum recovery was attained within 6-h agitation, which indicated a product layer diffusion process.

By V. V. Lodeischikov

This paper covers some problems of treatment of complex gold ores and concentrates containing copper, lead, zinc, antimony and uranium. All these metals may present in ores both as major and associated components. The paper suggests recommendations for early determination of relative value of the metals in ores, which largely contribute to the selection of concentration and metallurgical flow sheets. The focus of this work is on treatment of complex ores in gold plants. The metal extraction technologies used by such gold plants are typically aimed at maximum gold recovery. Therefore, production of base metals as by-products requires significant updating of the existing process flow sheets based on economic, environmental and other considerations. At the same time, cooperation between gold plants and base-metal plants is of great importance. This paper provides an overview of worldwide existing and innovative processes of base metals extraction from complex and refractory gold ores.

Jan 1, 2014

By Christoph Pichler

A special desulphurization slag accrues during the processing of iron ore to steel, which is needed to generate high quality steel. Sulphur removing is done by different technologies, but the most common one is the generation of a high sulphur containing slag by sulphur affine elements. Currently, this desulphurization slag is partly recycled, however, huge amounts are still dumped. To utilize this desulphurization slag for future purposes, a recycling process must be established. Therefore, first characterization of this material started some years ago at the Chair of Nonferrous Metallurgy, Montanuniversität Leoben. Subsequent trials in lab scale size were performed, also some investigations for different treatment steps were evaluated, starting with a parameter study in a hot stage microscope at various gas-atmospheres. Finally, the developed recycling process concept was verified in pilot scale trials to confirm the new recycling technology. Due to the successful treatment process, also a patent was applied.

By J. Robert Wells

The Bureau of Mines has developed a spectrochemical procedure for determining 19 impurity elements in high-purity titanium metal, titanium oxides, and titanium halides in which all samples are converted to titanium dioxide. Determination of these impurities was studied in the general concentration range of 0 to 1,000 p.p.m., but different determination limits were found for the various elements. The procedure is quantitative for 18 elements but semi-quantitative3 for beryllium and has an overall relative standard deviation of 15.8 percent. Two mixtures were used, one composed of graphite and lithium carbonate plus gallium oxide and the other of graphite and lithium carbonate plus germanium dioxide. Each mixture was blended mechanically with an equal weight of titanium dioxide. Lithium carbonate served as buffer-diluent. Gallium was the internal standard for 1 impurity element, germanium for 7, and titanium for the remaining 11.

Jan 1, 1962

By R. Padilla

A thermogravimetric study has been conducted to follow the decomposition and volatilization of arsenic from enargite concentrate in nitrogen and slightly oxidizing atmospheres. Temperature has a large effect on the rate of volatilization of arsenic. Fractional volatilization of arsenic as high as 98% were obtained in less than 60 min at 650°C in nitrogen atmosphere, while in slightly oxidizing atmosphere the same volatilization could be achieved in 30 min. It was found that arsenic volatilizes as sulfide in nitrogen atmosphere and as 4xture of sulfide and oxide in atmospheres containing 1% oxygen. By using the pore blocking and the first order kinetic models, apparent activation energies of 213 and 200 kJ/mol for the temperature range of 780 - 900 K and 205 and 184 kJ/mol for the temperature range of 900 - 985 K were determined for enargite and copper concentrate, respectively.

Jan 1, 1997

By A. R. Miller

A fuel cell locomotive incorporates the advantages of its competitors, namely catenary-electric and diesel-electric units, while avoiding their disadvantages. It possesses the environmental benefits, at the vehicle, of an electric locomotive but the higher overall energy efficiency and lower infrastructure costs of a diesel locomotive. The natural fuel for a fuel cell is hydrogen, which can be produced from many renewable sources or via nuclear energy, and thus a hydrogen-fuel cell locomotive will not depend on imported oil. Hydrogen produced from renewable primary energies or nuclear energy would provide a totally zero-emissions vehicle, that is, with zero carbon in the energy cycle. A project partnership among Vehicle Projects Inc of the USA, and South African partners Anglo American Platinum, Ltd, Trident South Africa, and Battery Electric, has designed and is launching a series of five prototype fuel cell-powered mine locomotives.

Jan 1, 2012

The importance of proper planning, preparation, and execution of a steady state sampling campaign for metallurgical plant assessment must not be underestimated. Careful planning can increase the amount and reliability of information from an optimum number of samples and fully utilize available plant data. It requires specification of the data required, determination of run duration sampling frequency, the selection, modification and testing of sample points and cutters, as well as organisation and briefing of plant and sampling personnel. Preparation immediately prior to sampling, the conduct of the sampling campaign itself and procedures to handle the collected samples and information are discussed. Cutter design, fabrication and use are described in detail, and typical sampling situations, for ball mills, classifiers, pipes, launders, flotation cells and thickeners are considered individually. Measurement of pulp flow rate can often resolve difficult mass balance problems, and discussion of convenient techniques is included.

Jan 1, 1976

By Huimin Lu, Zegao Sun, Zhijiang Gao

The traditional Ti6Al4V alloys were obtained by the smelting reduction of V-Ti bearing beach placer by rotary hearth furnace and aluminothermic reaction in laboratory. First, it gets he lp from combined rotary hearth furnace and grinding magnetic separation process to prepare titanium slag containing vanadium. In this study, a neural network model was used. The comparisons between experiment results and neural network simulation results show that genetic algorithm (GA)-based on back propagation (BP) method can predict the degree of reduction and separation of iron and slag with higher prediction accuracy. Then by aluminothermic reaction process, the optimized process parameters for Ti-V-Al alloys were searched. Al can deoxidize metal V and Ti from the metal oxides of artificial rutile containing vanadium. Finally, traditional Ti6Al4V alloy can be obtained by remelt and adjust the constituents.

Jan 1, 2016

By David J. T. Carson

"The metalliferous deposits of Vancouver Island have generally been assigned to the Mesozoic ""Coast Range Orogeny."" However, a metallogenic study by the writer has revealed that several important classes are early or middle Tertiary. Included are porphyry coppers, and gold-quartz, arsenic and copper-arsenic veins.The porphyry coppers and many gold-quartz veins are within and adjacent to Oligocene-Eocene quartz diorite intrusive complexes. Arsenic and copper-arsenic veins have a close spatial relationship to sills and laccoliths of Oligocene dacite porphyry which intrude the late Cretaceous Nanaimo Group.Other deposits of demonstrable Tertiary age include a molybdenum stockwork related to a relatively potassic Eocene plug and a few small copper-skarn occurrences. Some copper stockworks and a mercury deposit are probably also Tertiary.The copper deposits of previously recognized Tertiary age are those of the Sooke area that occur in Eocene basalts and Oligocene gabbros."

Jan 1, 1969

By S. Amira

In the last two decades, many new creep-resistant magnesium alloys have been developed for high temperatures applications. Their mechanical performance and corrosion behaviour were reported for various experimental conditions. However, these conditions often led to uneven comparison basis. In the present study the microstructure, mechanical properties and corrosion performance of four of these newly developed creep-resistant magnesium alloys were systematically compared. Specimens were obtained from experimental box-like components that were die-cast and thixocast in comparable conditions. Their mechanical and corrosion properties were compared using similar testing conditions. Results show that the creep resistance, strength and impact resistance of specimens are comparable but systematically lower compared to specimens cast under optimized conditions. The reduced concentration of elements such as Al, Ca, Sr and Ce lead to a decrease of the corrosion resistance of the magnesium alloys in 3.5% NaCI solution.

Jan 1, 2007