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By Martin B. Schranz

Copper sulfate pentahydrate is recovered from the spent etchant waste stream of a printed circuit board manufacturing facility by cooling crystallization. The fluidized bed crystallizer contains submerged cooling surfaces which are bathed in a stream of air. The air bubbles provide agitation which improve heat transfer, reduce fouling and maintain crystals in suspension. The recently patented apparatus (US 5,523,064) has advantages when compared to a conventional surface cooled crystallizer including capital cost, ease of operation and production of larger more uniform crystals

Jan 1, 1997

By Jian Ye

Recycling of aluminum scrap, such as Used Beverage Container (UBC) scrap is steadily increasing. In secondary remelting of such scrap, it is a common practice to use protective molten salt cover. An appropriate salt protects metal from oxidation, promotes coalescence of the suspended metal droplets, and separates clean metal from the oxide contamination. The molten salt also reacts with metal. This causes metal loss and change of resulting metal composition. In this paper, role of molten salt fluxes in melting of UBC scrap is discussed, and selection criteria for molten salt are provided.

Jan 1, 1995

By V. M. Sokolov, Jr. DuPlessis

The technology for recycling fine wastes, grinding sludges or swarf, and solids such as slag that contain a high content of metallic material needed improving. The objective was to produce a master alloy that met the tight requirements of the Western manufacturers and achieve improved yields of the valuable elements, nickel and cobalt, to over 90%. The alloys from the production of Alnico. magnets were chosen for this work. A process is proposed .that is able to recycle all kinds of Alnico wastes. This process is able to reduce all detrimental elements, which are contained in the wastes, to within acceptable levels. Molybdenum, if present, is an exception. Depending on the levels of contamination of undesirable elements different recycling strategies are proposed. The majority of the wastes can be recycled by melting and refining with a liquid slag layer using unique melting furnaces that are relatively unknown in Western nations. The proposed technologies allow the reelamation of over 95% of the cobalt and nickel from any kind of Alnico waste, and there are no limitations on the proportion of different kinds of wastes in the charge. The proposed processes and technologies could also be applied to the recycling of grindings, turnin

Jan 1, 2000

By Kazuhiro Asai

Nippon Mining and Metals Company has an annual indium production capacity of 30 tons at its Saganoseki smelter and refinery. Lately, indium content in the. zinc smelting dust, one of the main sources, has been on the decrease while the amount of impurity in it on the increase. The present process at Saganoseki does not permit efficient elimination of a large. amount of impurity. Therefore, studies were conducted to improve its recovery process. As a result, a new indium recovery process consisting of leaching, solvent extraction and electrowinning has been developed. The new process was tested at a pilot plant and satisfactory results were obtained. This new process is discussed in this paper.

Jan 1, 1995

By Thomas F. Hagelien, Stein Tore Johansen, Svend Graadahl

"The dross appearing at the surface of an aluminium melt consists, in addition to aluminium, of mainly oxide films but also other non metallic inclusions. The inclusion particles are often poorly wetted by the metal and accumulate at the metal surface. However, in impeller stirred reactors for melt refining stirring may be exceedingly strong and inclusions accumulated at the metal surface may be entrained into the bulk metal. Concerning inclusion removal, such effects may deteriorate the effectiveness of melt refining.In this paper we investigate the surface entrainment of buoyant particles in a water model of an impeller stirred refining reactor. Under varying operating conditions the particle concentration in the bulk liquid is measured by laser light attenuation. The observed entrainment of particles is explained theoretically and metallurgical consequences of the findings are discussed.IntroductionIn the modern cast house continuos metal refining and casting is well established. One of the most distinct advances in metal refining has been the introduction of degassers which introduce bubbles into the metal. The bubbles act to remove dissolved elements together with nonmetallic inclusions. In the most efficient degassers stirring by different kind of rotors is applied to increase mass transfer and inclusion removal. However, it has been known from experience in the cast house that for violent stirring the concentration of some types of inclusions may increase from inlet to outlet of the reactor. This phenomenon has so far been attributed to production of dross in the reactor due to oxidation of metal. Due to removal of inclusions by bubbles the dross layer inside the reactor must be expected to increase in thickness by time. The removed inclusions and produced oxides due to strong stirring is removed at regular interval by the operators of the degasser. However, a fundamental understanding of the phenomena which take place in and below the dross layer is lacking. In the present work we add buoyant particles to the surface of a refining reactor and investigate how these particles may be entrained and dispersed into the liquid depending on the flow conditions. Similar investigations for gas stirred ladles have been performed by Taniguchi et al [1] who found that below a critical gas flow rate all particles are trapped at the surface. Above the critical gas flowrate the surface velocity are sufficiently high to entrain the particles. In this situation it looks like all particles are ready for the melt and a balance between terminal velocity and turbulent dispersion determine the concentration in the liquid."

Jan 1, 1999

By Charles Washburn

The authors review mercury sources, and contaminant streams, with particular emphasis on mercury that is extracted from precious metal ores. The design and operation of both large and small mercury distillation facilities are detailed. The relevant properties and characteristics of mercury and mercury vapor are presented. Facility engineering with respect to industrial hygiene, area ventilation, and material handling is presented.

Jan 1, 2003

By Zhang Chuanfu

The fibrous nickel oxide powder was prepared by the method of chemical precipitation and pyrolysis, that is, the NiO precursor was firstly precipitated from nickel ions solution with addition of oxalate salt and then the final NiO powder was obtained by pyrolysis of the prucursor. The effects of the pH, reaction temperature, reactant concentration, addition of surfactant on the morphology of the precursor particles were investigated. The influences of the various conditions, including the temperature and time, the air flow and the speed of the temperature increase on the morphology, average size and specific surface area of the NiO particles were also addressed. The fibrous NiO particles with IOO~ 120 in axis/diameter ratio and 5.5 m2/g of the specific surface area may be produced under certain operation conditions by this process.

Jan 1, 2003

By C. D. Adams, R. T. Tuenge, C. N. King, J. A. Samuels, B. F. Espinoza, R. C. Dye, C. F. Schaus, D. C. Smith, N. M. Peachey

"Recently, doped calcium thiogallate (CaGa2S4) phosphors have been investigated for use in electroluminescent flat panel displays. The current technique used for the deposition of thin film calcium thiogallate is sputtering. Unfortunately, this requires a high temperature annealing process to provide the desired crystallinity of the phosphor. Recent efforts have focused on the possible use of metal-organic chemical vapor deposition (MOCVD) to produce the CaGa2S4 layer. The use of MOCVD provides an attractive alternative to sputtering since it does not require heating above the strain point temperatures of the glass substrates used for the display panels. To accomplish this, the deposition of both Ga2S3 and CaS is investigated as these compounds are intermediate steps in the development of the phosphor deposition. Uniform, crystalline films of both Ga2S3 and CaS were deposited and the process shows promise for successful deposition of the CaGa2S4 phosphor.IntroductionThe lack of a satisfactory blue phosphor having sufficiently high luminances at low power has hampered the development of high resolution flat panel displays. Recently, a new series of blue emitting materials have been investigated for use in thin film electroluminescent (TFEL) devices. l ,2,3 These phosphors are based on a series of alkaline earth thiogallate host materials of the form MGa2S4:RE where M can be either calcium, strontium, zinc, or barium and RE is a rare earth ion. A full-color VGA TFEL panel using CaGa2S4:Ce as the blue phosphor has recently been fabricated and tested. l This FPD provided a luminance of 10 cdlm2 at 60 Hz. The enhanced blue in this display allowed its color capabilities to approach those of the conventional CRT.The method of depositing the phosphor onto the display panels in these test devices has been sputtering. Unfortunately the phosphor as deposited does not possess the crystalline properties required for optimum luminance. The crystalline structure is achieved by subsequent annealing of the deposited material. Although this post deposition anneal provides the desired crystal structure, it occurs above the strain point temperature of ordinary glass. Consequently, the implementation of these phosphors requires the use of glasses capable of withstanding high temperatures, adding to the cost of the final display unit."

Jan 1, 1994

By E. S. Geskin, W. L. Chen, A. Vora

"This paper is concerned with the application of an abrasive waterjet for metal shaping. The waterjet cutting technology uses water compressed to the pressure up to 55,000 psia which is accelerated in a cylindric nozzle. Abrasive particles are then supplied into the water stream and accelerated by the water. Cutting occurs via the interaction between the water-particles stream and a workpiece that causes material erosion at the impingement zone. The mechanism of this interaction enables shaping of practically any material with a minimal effect on the metallurgy of subsurface. The motion of the jet penetrating through a material body is guided by a robotic arm. A waterjet cutter is becoming one of the principal tools for shaping titanium, super-alloys and other hard-to-machine metals and composites. The shaping, resulting from the waterjet cutter, is very similar to laser beam cutting. However, unlike laser processing, there is no damage to the subsurface structure.The presented work discusses the experimental study of cutting of titanium plates. The results of these experiments demonstrate the potential of the abrasive waterjet as a shaping tool. IntroductionOne of the main avenues in the development of metal shaping is the use of high energy beams as cutting tools (1,2). There are a number of advanced beam oriented material removal technologies, such as laser, electron beam, plasma and abrasive waterjet (AWJ) cutting. The advantages of AWJ cutting are well understood and documented (3-14). This technology has the potential of becoming the principal tool for netshaping and netsurfacing of parts. However, the use of AWJ is currently limited to cutting of hard-to-machine materials such as titanium, superalloys, glass, composites, etc. The cost of A W J cutting is much higher and the productivity is much lower than those of the thermal cutting. At the same time abrasive waterjet can be used for shaping any existing technological material from fabrics, plastics, aluminum to glass, composites, and diamonds. The material losses during AWJ shaping are minimal. The roughness and waveness of the surfaces generated during AWJ cutting are substantially less than those of the thermal cutting. Due to the size of the jet cross-section total force exerted by the jet on a workpiece does not exceed 30-50 newtons. This terminates the need in the use of complex fixture for material holding. Low applied forces and low surface temperature prevent the damage of metal subsurface in the course of cutting. The small size of the impingement area will determine the limited width of the kerf. Due to the size of kerf and unidirectional character of the water jet the formation of practically any metal contour is possible."

Jan 1, 1988

By Ray Y. Lin, Sunil G. Warrier

"Low cost processing of metal matrix composites is an essential requirement for this class of materials to be acceptable in commercial application. In an effort to reduce the cost of processing of metal matrix composites, an infrared pressureless liquid infiltration technique has been developed. The salient features of infrared infiltration are that it is rapid, simple and a low cost process. The rapid processing capability causes very little oxide formation on the alloy resulting in both improved wetting and flow characteristics and reduced oxygen contamination in the composite. Thus, vacuum is normally not required. Using infrared inflltration, aluminum and titanium matrix composites have been prepared under an ambient argon atmosphere. Reinforcements in these composites include carbon fibers, silicon carbide Nicalon fibers and Textron's SCS fibers. Microstructural and mechanical test results indicate that completely consolidated composites with good fiber distribution, limited interfacial reaction and high mechanical properties can be manufactured by this process. IntroductionAluminum and titanium matrix composites reinforced with ceramic reinforcements are strong candidates for numerous applications in the aerospace and automotive industries. Aluminum matrix composites are commonly fabricated by either solid state vacuum hot pressing, liquid state pressure infiltration or squeeze casting [1]. Although liquid state pressure infiltration and squeeze casting has significant advantages over solid state processes, the requirement for pressure makes these composites uneconomical for large scale industrial application. Titanium matrix composites are primarily fabricated by solid state diffusion bonding [2]. Pressureless liquid infiltration can significantly reduce the cost of fabrication in both the composite systems. However, during pressureless infiltration processes, several complications concerning the wetting characteristics and chemical compatibility arise."

Jan 1, 1994

By Martín Reyes

Iron concentration by ion flotation techniques, from sulfate solutions in presence of zinc was studied in a laboratory flotation column by continuous mode using a synthesized sand shell plate sparger, an anionic collector, promoters, and surfactant propylenglicol 400. Effects of experimental parameters, such as the concentration of reagent: potassium amyl xanthate and dithiophosphate, superficial gas velocity, and superficial liquid velocity were studied in terms of the recovery and enrichment of Fe (III). The results show that the iron elimination from the solution in the presence and absence of zinc (II) are of 59 % and 72 % respectively. The flotation efficiencies decrease with an increase of the concentration of xanthate and air flow rate. The best recovery was achieved, at Jg 0.1 cm/s, Jl 0.72 cm/s and a mixture of xanthate and dithiophosphate as promoter. It was also demonstrated that it is possible to selectively separate and concentrate iron (III) from solutions containing zinc. The behavior of iron ion flotation in a flotation column is reported in this research as a gas hold up, superficial gas velocity, bubble size and superficial bubbles area flux function. The results show that the extraction of aqueous ions of metal iron by ion flotation is strongly affected by: [C], Jg (cm/s), eg (%), Db (mm), Jl (cm/s), y Sb (s-1).

Jan 1, 2009

By F. Shen

Qualitative and quantitative results obtained during the physical modeling of the molten aluminum flow in a tundish using an aqueous system are presented. Surface tuft, free-surface powder and laser sheet visualization techniques were utilized for qualitative studies, whereas laser Doppler velocimetry was used to elucidate the 3-D flow regimes quantitatively. The results of the study are used for validation of the CFD codes, and to explore the effect of the alterations below the nozzle in order to: (1) decrease turbulence levels, and (2) collect the inclusions. Near the nozzle, the interaction of the impinging jet and the inclined walls gives rise to vortex structures. Downstream of the nozzle, two counter-rotating secondary cells diminish in strength. As flow turns through the bend, a separation region is created. The flow heading into the closed duct is seen to be nonsymmetric. A video tape highlighting the major findings is presented.

Jan 1, 1993

By Carl C. Nesbitt

A study was conducted to examine the treatment of metal-bearing effluents by precipitating the metals as sulfides and simultaneously collecting the particles by flotation. The precipitant was hydrogen sulfide gas which was introduced into a bench-scale column cell with air. The study included experiments of various flotation reagents and column configurations in treating solutions containing dissolved copper, lead, mercury, iron, zinc and cadmium. An acidic laboratory waste from a local copper operation was used to test the column with a solution containing several metals and arsenic. Precipitates were observed to form at the gas/liquid interface when the gas mixtures were rich in H2S. Copper, mercury, lead, and cadmium were precipitated from solution as sulfides to concentrations near detection limits. The flotation of these precipitates was enhanced with small amounts of S-7151 promoter from American Cyanamide Company and Dowfroth 1263 mixed with the feed. The recovery of the precipitates in this manner produced a smaller volume slurry which was easier to dewatering than a slurry produced by conventional precipitation techniques. The low pH and high oxidation-reduction potential in the cell from H2S addition was not conducive to form precipitates of iron, zinc or arsenic. However, these ions were precipitated as sulfides by raising the pH of the column discharge.

Jan 1, 1994

By André L. de Vegt

Soil and groundwater beneath a zinc production plant in The Netherlands are contaminated with metals and sulfate. To avoid contamination of nearby drinking water aquifers, a hydro-geological containment system and a biological treatment plant for the extracted ground water have been installed. Currently about 5000 m3/day of groundwater is extracted from a combination of 12 shallow and deep wells. Heavy metals and sulfate have to be removed from the extracted water before it can be discharged into a river. Several water treatment methods have been studied and pilot tested at the site. The preferred and selected process is based on the activity of sulfate reducing bacteria (SRB) and combines sulfate removal and heavy metal removal in one single installation. Anaerobic bacteria reduce sulfate to sulfide resulting in the precipitation of metal sulfides. Excess sulfide Is biologically converted to elemental sulfur. A full scale biological treatment system was started up in May 1992. Design, start-up, commissioning and operational experiences are reported in this paper. Concentrations of metals and sulfate in the SRB water treatment plant effluent are well within the limits set by the Dutch Authorities for discharge to surface water.

Jan 1, 1995

By C. Gasparrini

Mineralogy may be applied to the selection of appropriate separation techniques, as well as to assist in the evaluation of problems causing loss of metals and other economically important elements during plant processing. Mineralogic studies may thus help develop techniques to optimize metal recoveries. The present paper describes how such factors as the minerals in which the elements of interest are concentrated, their chemistry, the chemistry of the associated minerals, grain size and textural associations with other minerals in the ore, may affect decisions on separation techniques for the recovery of economic elements. A number of case studies are described in which the mineralogical observation of ore samples has revealed the cause of problems experienced in the extraction of select precious and base metals, or has been decisive in the choice of appropriate techniques for recovery.

Jan 1, 1981

Novel techniques were developed to obtain samples from and make measurements in the shaft of the flash furnace at the Kalgoorlie Nickel Smelter. The data obtained was used to validate mathematical models of the burners and the reaction shaft. Particle, gas and wall temperatures were measured along with the oxygen potential of the molten particles. Collected particles were characterised by sizing, chemical analysis and optical microscopy. The region of the shaft immediately beneath the burner where the rate of change was most rapid received special attention.

Jan 1, 1993

By Harrison Hodge

In the Bayer process for alumina production, between 2–35% Al2O3 is lost with bauxite residue due primarily to incomplete dissolution of aluminiumbearing minerals during caustic leaching or the precipitation of sodium alumino-silicate solids. The recovery of sodium and aluminium from the residue, and particularly from the contained sodium alumino-silicates, is becoming an increasingly critical issue from both an environmental and economic standpoint. Lime-soda residue sintering followed by selective leaching has been proposed as a method to recover sodium and alumina. The factors influencing the sintering mechanisms and kinetics, and the subsequent leaching have not been well described to date. In this study, the physical and chemical changes taking place during isothermal sintering of bauxite residue in air, particularly at short reaction times are investigated using scanning electron microscope (SEM) and X-ray diffraction (XRD). The impacts of these changes on the recovery of valuable materials are reported.

By Andressa A. Silva, Esperidiana A. B. Moura, Francisco R. Valenzuela-Diaz, Jorge N. Sales

This work aims to study the influence of the nanoclay Cloisite 20A incorporation on mechanical properties of ABS (acrylonitrile butadiene styrene). The incorporation of Cloisite 20A was made in two steps; firstly,a masterbatch was preparated and then, it was incorporated in ABS. The Cloisite 20A masterbatch using 40 % of nanoclay and 60 % of SAN (Styrene Acrylonitrile) was prepared in an adiabatic mill. After that, Cloisite 20A masterbarch at 1 and 5 % (wt) was added in ABS. The resulting nanocomposites were characterized by tensile tests and the correlation between properties was discussed.

Jan 1, 2015

By Mark Jolly, Nasim Soleimanian

"During the last 20 years CFD (Computational Fluid Dynamics) has been used as a tool to aid furnace designers and manufacturers to improve energy efficiency and effectiveness of glass furnaces. However as the models are maturing the effect of feeding equipment used to push the raw material into the furnace has not been included in the process models. This paper investigates the effects of batch pattern in the melt space caused by charging equipment on the energy efficiency of the furnace focusing on the melting zone. A simple batch patterns sensitivity study has been performed using purpose built software (Glass Furnace Model-GFM). It is concluded that in order to further reduce the energy consumption of the furnace it is necessary to model the batch charging process in more detail to find more opportunities for improvement.Introduction Glass manufacturing is a conservative industry which applies to all the four major segments (float glass, container glass, fiberglass, and specialty glasses). Risks due to the high capital investment, very long service life of the furnaces, and the demand for high performance and quality from the outset translates into evolutionary progress rather than revolutionary. The main problem facing glass manufacturers are the financial cost of manufacture, its impact on the environment, and mounting pressure imposed by the authorities for greener manufacturing and reduction in emissions.The main energy intensive activities involved in continuous glass manufacturing are: the need for high temperature to create and maintain the viscous flow, homogenisation of glass melt (melt residence time), and maintaining the two to achieve continuous output of glass at the right quality. The high temperature and long duration of homogenisation has resulted in the design oflarge furnaces, which have high energy consumption, low specific performance, and high C02 emissions. As an example in the container glass sector the most efficient furnace has a specific primary energy consumption of 3.8 GJ /tonne of glass at a level of 50% cullet in the batch. Even very small improvements in efficiency by optimising operation would have a high impact [1-14]. Given the conservative nature of the industry and the costs involved in experimental data gathering, CFD modeling of the process has been used extensively during last two decades to not only improve our understanding of the process but also as a tool in predicting possible optimisation windows, e.g. Glass Furnace Model ( GFM), a commercially available piece of software that has been developed to optimise furnace operation."

Jan 1, 2013

By J. Rajesh Kumar

The extraction equilibrium study of tetravalent platinum was carried out using tri-octyl/decyl amine (Alamine 336) and bis(2,4,4-trimethylpentyl) monothiophosphinic acid (Cyanex 302) in kerosene from hydrochloric acid media to investigate their extraction capacity, since they have different donor atoms, ?N? and ?S?. Their distribution equlibria were studied as a function of acid, extractant, diluents and temperature. The title metal shows the inverse behavior at higher acid concentrations. Extraction of tetravalent platinum increases with increase of extractant concentration. The plot of log D vs. log [Extractant], mol.L-1 is linear with slopes 1±0.3, indicating the association of one mole of extractant with the extracted metal species. Stripping of metal from the loaded organic (LO) with mineral acids and bases such as hydrochloric, sulphuric, nitric acids and ammonia, hydrogen peroxide, sodium hydroxide, thio- urea were studied. Regeneration and recycling capacity of Alamine 336/Cyanex 302 and extraction behavior of associated elements was also studied.

Jan 1, 2009